This proceedings contains the scientific contributions included in the program of the 6 th InternationalConference on Green Technology and Sustainable Development (GTSD2022), which was organized on July2930, 2022 in Nha Trang University, Khanh Hoa Province, Vietnam. The GTSD International Conferenceseries is a prestigious biannual event created to provide an international scientific research forum intechnologies and applications in the field of Green technology and Sustainable development in the Industrialrevolution 4.0. The areas of GTSD include but are not limited to energy engineering, environmentalengineering, education, digital transformation, new materials and solutions for sustainable development,advances in computational intelligence and their applications to the real world and so on.The conference is structurally organized in order to promote the active participation of all attendees andpresenters, via plenary presentation sessions, keynote addresses, interactive workshops and paneldiscussions, to find out how to further contribute to and solve various problems in life and manufacture. Theaim was to further increase the body of knowledge in this specific area by providing a forum to exchangeideas and discuss results.The program committee members of GTSD2022 come from various countries, and the 269 selected papers(out of more than 450 submitted papers) are from 27 countries and from 5 continents. This certainly attests tothe widespread and international importance of the theme of the conference. Each paper was carefullyreviewed on the basis of originality, novelty and rigorousness.We would like to take this opportunity to express our deep appreciation to all authors, participants, keynotespeakers, program committee members, session chairs, organizing committee members, steering committeemembers, as well as the organizers for their great efforts and contributions to making the GTSD2022successful, surging the global care about green technology research for sustainable development.
Trang 1PROCEEDINGS OF
TH 20226 INTERNATIONALCONFERENCE
ONGREENTECHNOLOGY
ANDSUSTAINABLEDEVELOPMENT
(GTSD)
VNUHCM PRESS
Trang 2Proceedings of
and Sustainable Development (GTSD)
July 29-30, 2022 - Nha Trang City, Vietnam
VNUHCM PRESS
Trang 4Table of Contents
Editors Preface viii GTSD2022 Organizing Committee ix
A Novel Mechanism Design following Augmented Objective with Flexible Energy Control 1
Xuan Phu Do and Van Chi Le
Evaluating Green Marketing Trending Determinants by a Text Mining Approach 5
Phan-Anh-Huy Nguyen
A Simple Synthesis of Antibacterial and Antifungal ZnO Nanorods 8
Khanh Son Trinh and Vinh Tien Nguyen
An Assessment of Complementary Energy of HPFRCs under Tension 15
Duy-Liem Nguyen, Tien-Tho Do, Thi-Ngoc-Han Vuong and H T Tai Nguyen
A Study of the Scavenging Process in a Two-stroke Free Piston Linear Engine at Low Velocity Using CFD and DPM 21
Nguyen Huynh Thi, Nguyen Van Trang, Huynh Thanh Cong, Dao Huu Huy, Huynh Van Loc, Truong Hoa Hiep, Ngo Duc Huy and Vo Bao Toan
Investigating the Relationship between Workers’ Needs and Commitments to Garment Enterprise 27
Tu Tran
Optimization of Aggregates in Concrete Brick with Recycled Materials from Stone 32
Nguyen Thang Xiem, Ho Minh Chau, Tran Doan Hung and Truong Thanh Chung
A Comparison on the Flexural Capacity and Dynamic Performance of a Reinforced Concrete Beam and a Steel Beam in a High-rise Building 36
Tham Hong Duong
Optimization Model for Biomass Supply Chain Planning: A Case Study in Mekong River Delta – Vietnam 44
Thi-Be-Oanh Cao, Duc Duy Nguyen, Thanh-Tuan Dang and Chia-Nan Wang
Developing a Digital Competence Performance Assessment Platform for University Students Based on the DigComp Framework 50
Anh Tho Mai, Thi Kim Oanh Duong and Anh Tuan Ngo
The Performance of Geonet Reinforced Straw Rolls as a Flexible Waterbreaker for Riverbank Protection 57
Minh-Duc Nguyen, Le-Nhat-Huy Nguyen and Tran-Phuong-Thao Hua
SSD21, Educational Toolbox for Static, Stability, and Dynamic Analysis of Frame 63
Truong Thanh Chung, Le Nguyen Anh Vu, Le Cong Lap and Nguyen Thang Xiem
Digital Competence of University Students: A Comparative Study at Three Universities in Vietnam 67
Anh Tho Mai, Quynh Trang Mai and Anh Tuan Ngo
Trang 5ii
Load Capacity Evaluation of Simple Reinforced Concrete Girder Bridges with Considering the Corrosion of Reinforcement and Concrete 75
Tran The Truyen, Tran Thu Minh, Nguyen Dac Duc, Tran Duc Manh and Nguyen Quoc Cuong
Effect of Biodegradable and Metallic Mordants on Dyeing Cotton Fabric with Spent Coffee Grounds 80
Tuan Anh Nguyen
The Importance of Green Technology for Sustainable Development Education: A Case Study at Lac Hong University 85
Nga Hong Thi Doan and Truong Van Nguyen
Unique Competitive Advantages of Vietnam’s Garment Industry in the Sustainable Development Trend 89
Quang-Tri Tran, Thanh-Nhan Nguyen, Tho Alang, Tuyet-Anh Truong, Kim-Chi Le and Nguyen Thi Le
Driving Factors of Green Economy for Smart Cities in the Context of Developing Countries 95
Tiep Nguyen, Nghia Hoai Nguyen, Leonie Hallo and Bao Van Pham
Impacts of Green Training on Green Competencies of Employees: Empirical Case of Industrial Manufacturers in Dong Nai Parks 101
Thanh-Lam Nguyen, Doan Thi Chuyen, Nguyen Thi Phuong Thao and Doan Van Ly
Mathematical Modelling of Combined Infrared and Heat Pump Drying of Squid 107
Pham Van Toan, Phan Nhu Quan, Nguyen Hay and Le Anh Duc
Improving the Tensile and Compressive Strength of Cement-Based Materials by Hybrid Electrospun Nanofibers 114
Tri N M Nguyen, Xuan Tung Nguyen, Thanh Toan Dao, Huy Q Nguyen and Jung J Kim
Controlling Crystal Morphology via Crystallization Processes, Cases Studied of KDP and Zinc Lactate 118
Tam Le-Minh, Cuong Nguyen Van and Venkata Subbarayudu Sistla
A Green Solution for Kitchen Waste Treatment Using Earthworm, Experimental and Mathematical Approaches 122
Tam Le-Minh, Phuong Pham Thi Hong and Nhu Vo Thi Thu
Effect of Reinforcement Corrosion on Crack Development in Concrete Under Load 127
Vo Van Nam and Tran The Truyen
Study on Synthesizing and Size Controlling of Silver Nanoparticles by Using a System of Two Protectants Trisodium Citrate and Polyvinylpyrrolidone 132
Hien Chuc Mai, Quynh Nguyen Thi Nhu, Thuan Hoang Duc, Du Cao Van, Cuong Ngo Van and Dung Duong Thi Ngoc
Study on Chemical Composition and In-vitro Biological Activities of Salvia officinalis L in Lamdong,
Vietnam 137
Thao Tran Thach, Cuong Ngo Van and Xuan Nguyen Bang
Dynamic Analysis of Plates under Moving Discontinuous Impulsive Load on Viscoelastic Foundation 141
The Tuan Nguyen and Trong Phuoc Nguyen
Trang 6Isolation and Quantitative Determination of Geniposide from Gardenia jasminoides Ellis Using
High-Performance Liquid Chromatography 147
Vo Thi Nga, Truong Thi Khanh Van and Bui Trung Huu
Oxygen-LPG Torch for Thermal Spraying 152
Ngo Thanh Binh, Le Van Canh and Pham Huy Dong
Predicting Land Use Change in Buon Ma Thuot City, Dak Lak Province by Integrating GIS and Markov Chain 158
Nguyen Thi Ngoc Quyen, Nguyen Thi Tinh Au, Nguyen Cong Tai Anh and Tran Thi Xuan Phan
Dissimilar Friction Stir Welded Lap-joint of Aluminum Alloy 6061 and 316 Stainless Steel 165
Huy Huu Ho, Hao Dinh Duong, Nam Hoai Quach, Thuyen Van Phi, and Tra Hung Tran
A Stochastic Half-Car Model for Vibration Analysis with Uncertain Parameters 169
Nguyen Van Thuan
Sources of Payment Risks to Contractors in the Vietnam Construction Industry 173
Duong Vuong, Thao Huynh and Phu Tran
Pharmacognostic Assessment of Polyscias Fruticosa Leaves in Vietnam 180
Dao Phan Thi Anh, Hue Ha Thi, Trang Le Vu Khanh, Thanh Le Duc, Huong Nguyen Thi Thu and Trieu Ly Hai
Alkali-Activated Slag/Sugarcane Bagasse Ash Pastes Cured in Room-Air Ambient and in Saturated Lime Water: A Study on the Compressive Strength and Shrinkage 185
Duc-Hien Le and My Ngoc-Tra Lam
Production Efficiency Improvement Using Value Stream Mapping with Simulation: A Case Study in Vietnam 191
Xuan-Quang Bach, Thanh-Tuan Dang and Chia-Nan Wang
Study on the Effect of Mixing Ratio of Biodiesel Fuel Made from Animal Fat on Exhaust Emissions of the Fishing Vessel’s Diesel Engines 199
Pham Dinh Trung, Mai Duc Nghia and Ho Duc Tuan
A Study on Mechanical Properties of Ca-Alginate Hydrogels 204
Thanh Tan Nguyen, Van Tron Tran, Long Nhut-Phi Nguyen and Nguyen Thi My Le
Mechanical Characteristics of PBT Based Blend 208
Hoang-Khang Lu, Ngoc Tran-Nhu Nguyen, Huy Huynh-Nhat Do, Van-Huong Hoang, Van-Thuc Nguyen, Nga Thi-Hong Pham, Van-Tron Tran, Long Nhut-Phi Nguyen and Thanh-Tan Nguyen
An Evaluation of Corporation Social Responsibility Performance for Vietnamese Contractors 213
Nguyen Van Minh, Ha Duy Khanh, Soo Yong Kim and Chu Viet Cuong
Local Waste Seeds as Organic-Based Coagulant Aids in Water and Wastewater Treatment 218
Nhung Thi-Tuyet Hoang, Anh Thi-Kim Tran and Luu Hong Quang
The Implementation of 5C’s in Online-Foreign Language Teaching for Vietnamese Students in the 4.0 Era 222
Chau Le Thi Bao, Nhu Vo Hoang Nhu and Nhi Ho Yen
Trang 7iv
Antibacterial Activity of Aqueous Extracts from Marine Sponges Found in Vietnam’s Sea 229
Huynh Nguyen Duy Bao and Nguyen Khac Bat
Digital Competence of University Students: Developing Information and Data Literacy for IT Students at Ho Chi Minh City University of Technology and Education 233
Anh Tho Mai and Quynh Trang Mai
A Simple Design Method for Piled Raft Foundations 239
Tong Nguyen, Nhat Nguyen Le Anh and Dat Nguyen Thanh
Evaluating Performance of Petroleum Industry Using Data Envelopment Analysis: A Case Study in Vietnam 247
Kristofer Neal C Imperial, Chia-Nan Wang, Thanh-Tuan Dang and Nguyen Ngoc Hiep
Fire Resistance Properties and Geopolymer Coating 254
Van Su Le, Van Vu Nguyen, Artem Sharko, Doan Hung Tran, Petr Louda, Piotr Los, Thang Xiem Nguyen, Stanislaw Mitura and Katarzyna Buczkowska
Effects of Intake Air Temperature on Power and Emission Characteristics of the HCCI Engine Fueled with the Blends of 15% Ethanol and 85% Petrol Fuels 259
Minh Xuan Le and Thanh Tuan Nguyen
Linear Viscoelastic Characterization of an SMA Mixture Using Dynamic Indirect Tensile Test 263
H T Tai Nguyen, Hong Ha Mai and Van Hien Nguyen
Effect of the Limestone Powder Content on the Properties of Alkali–Activated Slag Mortar 268
Tai Tran Thanh, Chung Pham Duy, Tu Nguyen Thanh and Hyug-Moon Kwon
The Educational Philosophy of Existentialism with the Development of Personalized Learning for Learners in Massive Open Online Courses (MOOCs) – The Case of Ho Chi Minh City University of Technology and Education 273
Thi Thao Tran, Tran Phuong Thao Hua and Thi Chu Tran
Transportation Infrastructure Strategy for Sustainable Development: A Case Study of Vietnam Mekong Delta 281
Le Thu Huyen
Study on Behaviour of Short Pile Groups in Soft Ground with Sand Leveling on a Small Scale Model Using Schneebeli Analogue Soil 286
Sy Hung Nguyen and Thi Phuong Huyen Tran
Research and Preparation of Thinking Strategies for Quality of Textile and Garment Products Manufactured in Vietnam 292
Nguyen Phuoc Son, Nguyen Ngoc Chau and Nguyen Thi Tuyet Trinh
Building Students’ Self-Reliant on Problem-Based Learning by Embedding Mind of Engineering Design Concept at HCMC University of Technology and Education 296
Trang 8Fabrication of Graphene Oxide from the Graphite Rod of a Disposed Battery 305
Huy-Binh Do, Hoang-Trung Huynh, Thien-Trang Nguyen, Van-Cuong Pham, Tien-Luat Nguyen, Anh-Vu Phan-Gia and Maria Merlyne De Souza
Design and Optimization of a Compliant Mechanism for Vibration-Assisted Drilling 309
Hai-Thanh Nguyen, Van-Khien Nguyen, Phan-Khanh-Tam Nguyen, Huy-Tuan Pham, Quang-Khoa Dang and Pham Son Minh
Eco-friendly Adsorbent Formulated from Rubber Shell Biochar to Remove Chromium (Cr(VI)) from Aqueous Solutions 313
Linh My Nguyen
A Study on the Effect of the Shape of the Center Rib on Thermal Resistance on the Dual-Layer channel Heat Sink 317
Micro-Hung-Son Dang and Thi-Anh-Tuyet Nguyen
Experimental Study of the Effect of Heat Input on Tensile Strength and Microstructure of the Weld using the Orbital TIG Welding Process 321
Thien Tran Ngoc, Ngoc-Huy Dinh, An-Duong Tra, Kha-Duy Doan, Binh-Minh Ngo and Anh-Duc Pham Duc
A Study of Customer Satisfaction in Online Food Delivery Service Quality During the Covid-19 Pandemic: Baemin’s Case Study 326
Hong-Xuyen Thi Ho, Ngoc-Tra Tran Thi and Ngoc-Anh Ha Thi
Controllable Green Synthesis and Morphological Properties of Gold Nanostar 332
P Quoc-Duy Huynh, Van-Dung Le, Chi-Hien Dang, Radek Fajgar, The-Ha Stuchlikova, Jiri Stuchlik and Thanh-Danh Nguyen
Isolation, Selection and Identification of the Probiotic Properties of Lactobacillus spp from Shrimp
Ponds in Nhon Trach, Dong Nai 336
Doan Thi Tuyet Le, Le Thi Thu Huong, Phan Pham, Pham Minh Thinh, Vo Thi Lan Chi, Nguyen Phuoc Trung, Huynh Minh Hieu and Do Minh Anh
Production of Cheese from Reconstituted Milk and Soy Milk with the Addition of Microbial Transglutaminase 340
Pham Thi Hoan and Trinh Khanh Son
Studying the Effect of Biodiesel Blend Ratios Derived from Rubber Seed Oil on the Technical Characteristics of Diesel Engines without Modifying the Structure by Simulation and Experiment 349
Nguyen Manh Cuong and Huynh Phuoc Son
Work from Home during the Covid-19 Pandemic: A Qualitative Research with Women Taking Care
of Young Children 355
Hien Phan Thi Thanh, Thuy Nguyen Thi Thanh and Tram Nguyen Thi Mai
Study on Determining the Freezing Mode of Frozen Fillet Bigeye Tuna (Thunnus obesus) 361
Dzung Tan Nguyen, Linh Khanh Thuy Do, Chuyen Van Hoang and Tuan Thanh Chau
Numerical Investigation of the Optimum Operating Condition in Magnetically Confined Plasma with Sheared Slab Ion-Temperature-Gradient Model 367
Thanh Tinh Tran
Trang 9vi
Using Brake and Engine Torque to Control Traction on Either Side of the Drive Wheel 371
Tan Tai Phan and Van Nhu Tran
Fatigue Life of Accelerated Corroded Steel Plate 377
Dao Duy Kien, Nguyen Thanh Hung, Nguyen Thi Thu Hao, Nguyen Van Hung and Haidang Phan
A Study on Ultrasonic Shear Horizontal Waves in Composite Structures 381
Duy Kien Dao, Hoang Ngoc Quy, Truong Giang Nguyen, Ductho Le, Hoai Nguyen and Haidang Phan
Designing and Modeling Pipe Welding Machine 385
Tuong Phuoc Tho, Phan Phuc Khang, Tran Thanh Nhon and Pham Phi Long
Investigation of the Mechanical Properties of Lightweight Geopolymer Concrete Using Keramzite as Coarse Aggregate 390
Kiet Tran Tuan, Duc Nguyen Phan, Tuan Le Anh, Khoa Nguyen Tan and An Huynh Thao
Researching and Improving the Registration and Treatment Process in Health Care Facility with Lean Principles and Ergonomics Standards 394
Minh-Tai Le
Application of Lean and Six Sigma Tools to Improve Productivity and Product Quality at Dien Quang Company, Vietnam 401
Minh Tai Le, Hoang Khang Lu and Nhat Huy Do Huynh
Hydrogen Plasma Annealed Gallium and Aluminum co-doped Zinc Oxide Films Applied in emissivity Glass 408
Low-Shang-Chou Chang, Yun-Che Tsai, Huang-Tian Chan, Jian-Liang Lai, Jian-Syun Wu and Wei-Min Wang
Study on Pectinase Production by Bacillus subtilis in Molasses and Its Application for Coffee
Fermentation 412
Ngan K Le, Duy Q Nguyen, Nhi Y Dinh and Phu H Le
Environmental Sustainability: Exploring Managers’ Attitudes and Behaviours at High-End Accommodation Businesses in Vietnam 417
Thanh-Nhan Nguyen, Quang-Tri Tran and Tho Alang
Research on Optimal Algorithms Using Experimental Planning to Improve Shoe Production Line Productivity 425
Minh Tai Le, Thi Cam Duyen Doan and Huynh Thao Vy Nguyen
Application of Multivariable Linear Regression Algorithm to Support Inventory Management 431
Trung Tin Ngo, Minh Tai Le, Nguyen Kim Thoa Vo and Thanh Nam Luong
Ethanol in Gasoline Fuel Blends: Experimental Investigation Effects on Exhaust Emission of the Homogeneous Charge Compression Ignition Engine 437
Minh Xuan Le and Thanh Tuan Nguyen
The Impact of the Industrial Revolution 4.0 on Logistics Businesses: A Case in Mekong Delta 441
Ngo Hong Ngoc and Huang Ying Yin
Trang 10Enhancement in Dielectric Constant of Poly Vinyl Alcohol by Loading of Strontium Titanate for Supercapacitor Applications 447
Anju Yadav, Dinesh Kumar Yadav, Khushbu Meena, Kiran Devat, Narendra Jakhar, Rajesh Sahu, S K Jain and Balram Tripathi
Free Vibration Analysis of Smart FG Porous Plates Reinforced by Graphene Platelets Using Isogeometric Approach 451
Lieu B Nguyen and Duc-Thien Pham
Free Vibration of MSGT Porous Metal Foam Microplates Using a Moving Kriging Meshfree Approach 459
P T Hung
Impacts of Adverse Weather on Mode Choice Behavior: A case study in Hanoi City, Vietnam 469
Binh Nguyen Mai, Thi Anh Hong Nguyen, Akimasa Fujiwara and Canh Do
Travel Behavior on Ground Access Mode Choices by Introducing a New City Air Terminal: A Case Study of Vientiane Airport, Laos 474
Komack Keochampa, Canh Do, Akimasa Fujiwara and Thi Anh Hong Nguyen
A Study of The Tensile Strength for The Mixing Ratio of Eva in Pa6/Eva Blends 482
Minh-Nhat Nguyen, Quy-Long Nguyen, Ngoc-Thien Tran, Vinh-Tien Nguyen and Minh The-Uyen Tran
Cytotoxicity of Isoxazole/Pyrazole Curcuminoids against Human Oral Epidermal Carcinoma-KB Cell Line 486
Hoang Minh Hao, Ho Dung Manh and Vo Thi Nga
Modeling of Flow Mixed with Polymers in Open Channel Flow: Application on the Blumenau River in Brazil 491
Walid Bouchenafa, Airton Hoenicke, Bruna Luiza Cunico, Huyen Xuan Dang-Vu and Trong Dang-Vu
Trang 11viii
Preface
This proceedings contains the scientific contributions included in the program of the 6th International Conference on Green Technology and Sustainable Development (GTSD2022), which was organized on July 29-30, 2022 in Nha Trang University, Khanh Hoa Province, Vietnam The GTSD International Conference series is a prestigious bi-annual event created to provide an international scientific research forum in technologies and applications in the field of Green technology and Sustainable development in the Industrial revolution 4.0 The areas of GTSD include but are not limited to energy engineering, environmental engineering, education, digital transformation, new materials and solutions for sustainable development, advances in computational intelligence and their applications to the real world and so on
The conference is structurally organized in order to promote the active participation of all attendees and presenters, via plenary presentation sessions, keynote addresses, interactive workshops and panel discussions, to find out how to further contribute to and solve various problems in life and manufacture The aim was to further increase the body of knowledge in this specific area by providing a forum to exchange ideas and discuss results
The program committee members of GTSD2022 come from various countries, and the 269 selected papers (out of more than 450 submitted papers) are from 27 countries and from 5 continents This certainly attests to the widespread and international importance of the theme of the conference Each paper was carefully reviewed on the basis of originality, novelty and rigorousness
We would like to take this opportunity to express our deep appreciation to all authors, participants, keynote speakers, program committee members, session chairs, organizing committee members, steering committee members, as well as the organizers for their great efforts and contributions to making the GTSD2022 successful, surging the global care about green technology research for sustainable development
On behalf of GTSD2022 Organizing Committee
Assoc.Prof Hoang An Quoc
General Co-Chair of GTSD2022
and
Dr Nguyen Vu Lan
Publication Chair of GTSD2022
Trang 12GTSD2022 Organizing Committee
General Chairs
A/Prof Le Hieu Giang, HCMUTE, Vietnam
A/Prof Trang Si Trung, NTU, Vietnam
Prof Nguyen Ngoc Thanh, WUST, Poland
Prof Wen-June Wang, NCU, Taiwan
Prof Yo-Ping Huang, NPU, Taiwan
Honorary Chairs
A/Prof Thai Ba Can, HCMUTE, Vietnam A/Prof Do Van Dung, HCMUTE, Vietnam A/Prof Ngo Van Thuyen, HCMUTE, Vietnam
Dr Khong Trung Thang, NTU, Vietnam
General Co-Chairs
Dr Quach Hoai Nam, NTU, Vietnam
A/Prof Hoang An Quoc, HCMUTE, Vietnam
Prof Huann-Ming Chou, KSU, Taiwan
Prof Chang-Ren Chen, KSU, Taiwan
A/Prof Nguyen Vu Quynh, LHU, Vietnam
A/Prof Nguyen Thanh Lam, LHU, Vietnam
Program Chairs
A/Prof Nguyen Truong Thinh, HCMUTE, Vietnam A/Prof Do Thanh Trung, HCMUTE, Vietnam A/Prof Nguyen Minh Tam, HCMUTE, Vietnam
Dr Huynh Phuoc Son, HCMUTE, Vietnam
Dr Tran Thi My Hanh, NTU, Vietnam
Dr Pham Thi Thu Thuy, NTU, Vietnam
Program and Steering Committee
Prof Nguyen Trung Kien, HUTECH, Vietnam
Prof Surya Narayan Panda, Chitkara Uni., India
Prof Arun Patil, SGU, India
Prof Sid Nair, VIT, Australia
Prof Pracha Yeunyongkul, RMUTL, Thailand
A/Prof Atul Sharma, RGIPT, India
A/Prof Truong N Luan Vu, HCMUTE, Vietnam
A/Prof Le Chi Kien, HCMUTE, Vietnam
A/Prof Bui Van Hong, HCMUTE, Vietnam
A/Prof Nguyen Tan Dung, HCMUTE, Vietnam
A/Prof Chau Dinh Thanh, HCMUTE, Vietnam
A/Prof Vo Viet Cuong, HCMUTE, Vietnam
A/Prof Truong Dinh Nhon, HCMUTE, Vietnam
A/Prof Duong Thi Kim Oanh, HCMUTE, Vietnam
A/Prof Trinh Khanh Son, HCMUTE, Vietnam
A/Prof Ngo Dang Nghia, NTU, Vietnam
Dr Irma Kunnari, HAMK, Finland
Dr Lisa Donaldson, DCU, Ireland
Dr Lai Jiang, KULEUVEN, Belgium
Dr Manoj Kumar Dash, IIITM Gwalior, India
Dr Le Minh Nhut, HCMUTE, Vietnam
Dr Nguyen Xuan Vien, HCMUTE, Vietnam
Dr Diep Phuong Chi, HCMUTE, Vietnam
Dr Huynh Van Vu, NTU, Vietnam
Dr Mai Thi Tuyet Nga, NTU, Vietnam
Dr Tran Quang Huy, NTU, Vietnam
Dr Jari Jussila, HAMK, Finland
Dr Phan Gia Anh Vu, HCMUTE, Vietnam
Dr Tran Vu Tu, HCMUTE, Vietnam
Dr Dang Quang Vang, HCMUTE, Vietnam
Dr Nguyen Khac Hieu, HCMUTE, Vietnam
Dr Vu Van Phong, HCMUTE, Vietnam
Publication Chairs
Dr Nguyen Vu Lan, HCMUTE, Vietnam
Media and Publicity Chairs
Chau Ngoc Thin, HCMUTE, Vietnam
Nguyen Van Nguyen, HCMUTE, Vietnam
Local Arrangement Chairs
Tran Nhat Tan, NTU, Vietnam
Vu Thi Thanh Thao, HCMUTE, Vietnam
Do Thi Ngoc Dung, HCMUTE, Vietnam Phung Phuong Thu Thuy, HCMUTE, Vietnam Nguyen Thi Minh Ngoc, HCMUTE, Vietnam Nguyen Thi Hoa, HCMUTE, Vietnam
Trang 14A Novel Mechanism Design following Augmented
Objective with Flexible Energy Control
Xuan Phu Do
Mechatronics and Sensor Systems Technology
Vietnamese German University
Binh Duong, Vietnam phu.dx@vgu.edu.vn
Abstract: This study presents a newly proposed theory for
design of augmented structure, especially in exoskeleton
design A general model is proposed with basic elements of a
featured actuator related to mechanism The calculation
theory is based on dynamical analysis with new modifications
to obtain general equations for design The new theory is
different from the conventional theory, which always
assumed that the analyzed structure was zero in a static state
The augmented theory has broken out the barrier of the
classical model with a new added element related to the
accumulated energy in the structure, especially in the
mechanical spring After formulating, antagonistic variable
stiffness mechanism is chosen to evaluate the proposed
analysis The simulation results show that the proposed
theory can meet the requirement in the design of new
augmented mechanism
Keywords: augmented mechanism, exoskeleton design,
general augmented mechanism, upper exoskeleton, lower
exoskeleton
I INTRODUCTION
Design of exoskeleton with low power consumption and
high efficacy is always the ultimate objective The main
design is to develop special calculation and modified
mechanisms based on the conventional structure such as beam
deflection Normally, the trials in design are always the safe
choice to guarantee the performance of the proposed structure
when manufacturing However, this also leads to unexpected
results that the efficiency of the structure is lower than the
desired values This study presents a new view of design
mechanism based on the dynamical parameters to overcome
the disadvantage Generally, a view of the existing
publications related to the content of this study is carried out
A design of a low-power stiffness mechanism was presented
in [1] The ideal variable stiffness mechanism with its
potential energy was analyzed based on many assumptions
related to the consumption value To use the internal energy
to control the exoskeleton mechanism’s movement was
presented in [2] The internal energy [2] was from the muscle
states of a human, and this value belonged to the physical
health of every person The disadvantage of the internal
energy is its unstable value and can be attacked by the working
environment As mentioned above, the theory of beam
deflection is main analysis in any research of design
mechanism The review of this analysis was presented in [3]
An extension of the research [2] was studied in [4] The
infinity energy in the calculation of the exoskeleton was
presented in [4] The analyzed theories [1,2,4] are different
from the conventional analysis [5] The result [5] was the
background to interpolate the efficient area of the stiffness
mechanism The metabolic cost was studied in [6] This issue
is one of the problems when controlling the mechanism and directly affects the structure’s functions [6] New modification
of the structure [1] was presented in [7] This modification [7] concentrated on improving the mechanical function of the spring at the knee exoskeleton In addition, the movement of the centroid point in the robotic mechanism was studied in [8] When designing the structure, the centroid point is also a part
of soft compliance calculation The stiffness of the above mechanisms is different from the application of smart material
as shown in [9-13] with the same objective in control the movement
From the above summarization, stiffness control is still a state-of-art issue when controlling and designing the structure However, the conventional theory does not fully view the affection of the initial energy in the designed model Hence it needs support from the controllers to fulfil the desired requirements This is also the main objective of this research which is shown in the next sections
II CONVENTIONAL AND PROPOSED THEORY
Figure 1 Suddenly energy at the first time of vibration control
There exists a phenomenon as shown in Fig 1 in any system at the first state The energy at this state is always larger than other positions and also affects the control system
To analyze the phenomenon, two specific models are chosen
in this study The conventional model of the design mechanism is shown in Fig 2 In this figure, three main mechanism elements are listed: motor, transmission, and dynamic functions The output of the mechanism includes force, stiffness In some particular cases, the output force can
be replaced by the output torque belonging to the objective control This model is also similar to the featured model of an exoskeleton The potential energy of the structure is defined
as follows [1]:
Trang 15Where, fi is the ith force of the structure with its
equilibrium l 0 and the length l i at ith position It is noted that
Eq.(1) is the general model for any mechanism The value p
is angular position, and the value x is the translational
position of the system
Figure 2 The first model of Antagonistic Variable Stiffness
Mechanism (AVSM) Energy (1) includes the internal and external energies
Normally, the internal energies are always assumed zero
value for all calculations This assumption is used in the
conventional model to neglect the complicated analysis, and
the obtained results are acceptable From definition (1), the
official dynamic parameters related to the movement are
Where, fIN is the input force, fOUT is the output force, and
kOUT is the output stiffness In Fig (1), the transmission
element is normally the mechanical spring-like model In
some exceptional cases, the element is the beam and the
activated actuators The condition for an ideal elastic element
Where, K is a symbolized translational position In the
proposed equation (3), the condition energy for an ideal
mechanism is different from the classical definition This is
from the characteristic of the manufactured elements always
remains an initial power inside its model The energy can be
seen as lower power, but it is complete affection to combine
the external energy This combination brings an unexpected
phenomenon in dynamic response at the first time to apply a
controller The power motor can be defined as follows:
Where, the values of w w1, 2,w3are found based on the
experiment data corresponding to acceleration, velocity, and
initial power of the system; P0is the initial power of the
motor (W) Eq.(4) is designed based on the assumption in
Eq.(3) Eq (4) also satisfies the phenomenon in the first time
of vibration control as shown in Fig 1 This phenomenon
always exists in any system, especially in suspension The variation of the energy also leads to the changing stiffness of the system as follows:
flexible calculation for design progress
III APPLICATION TO ANTAGONISTIC VARIABLE STIFFNESS MECHANISMS AND DISCUSSIONS
A First modification of AVSM
The potential energy of the first model of AVSM as shown in Fig 2 is given by:
1( , )3
This research is funded by Vietnam National Foundation for Science and
Technology Development (NAFOSTED) under grant number
107.02-2020.13 Corresponding author: Dr Xuan Phu Do
Trang 16B Second modification of AVSM
Figure 3 The second model of AVSM
The second mode of AVSM is shown in Fig 3 The
potential energy of the first model of AVSM as shown in Fig
3 is given by:
1( , , x ) , , x
2
Where, k is the input stiffness of the structure, p is the
angular position, l is the deflection of the spring length, x 1
and x 2 are the position of the first and the second springs The
input force and the output stiffness are determined as follows:
, ,, ,
k R x x , where is a constant related to the
proportionality of the force-deflection springs The input
force (14) can be written as follows:
The result (16) shows that the mechanism’s energy for
control is first order function with the input control and the
stiffness output This also points out that the movement is
independent when controlling
IV SIMULATION AND DISCUSSIONS
Simulation results of the first and the second AVSMs are
shown in Fig (4) and Fig (5) In the first model as shown in
Fig (4), the criterion for design follows the second-order
function of the input force and the output force This relation
is reflected clearly in Fig 4(a) It is shown that the increased
value of the output stiffness from 0 to 2 N/m corresponds to
the input force of approximately 100 N In this point, the
potential energy is nearly zero value However, the output
stiffness changes from 2 to 4 N/m with the potential energy 5
W as shown in Fig 4(b) It is remarked that the relation
between the input force and the potential energy is not linear
as shown in Fig 4(c) In Fig 4(c), it is shown that the
potential energy is not zero value if there exists internal energy of the structure as shown in Eq.(4)
The result of second AVSM is shown in Fig 5(a,b,c) The relation of the input force and the output stiffness is linear-like as shown in Fig 5(a) This response is from the connection of the first and the second mechanical springs as shown in Fig 3 The affection of the connection is also shown
in Fig 5(b) It is remarked that the values of the output stiffness are the actual value of the mechanical spring, which
is different from Fig 4 as the difference value when controlling The result in Fig 5(c) also points out that the potential energy will increase if there is internal energy in the structure
(a)
(b)
(c)
Figure 4 Result of the first AVSM: (a) input force versus output
stiffness, (b) potential energy versus output stiffness, (c) potential
energy versus input force
Trang 174
(a)
(b)
(c)
Figure 5 Result of the second AVSM: (a) input force versus
output stiffness, (b) potential energy versus output stiffness, (c)
potential energy versus input force
In this study, a new view of the stiffness mechanism is
presented This proposed theory is designed from the mutation
energy at the first time to control the system This theory also
modifies the traditional mechanism theory that the energy is
always approximate zero value The proposed theory also
presents equations related to the stiffness, input energy, and
output energy These equations point out that the energy
cannot assume the zero value related to the design of the
mechanism Two AVSM models are used to apply the
proposed theory The simulation and its results show that the
proposed theory can be developed to design the augmented
mechanism for supporting the movement of the upper limb
and lower limb The theory also gives a new view of design mechanisms when the energy and the stiffness of the system cannot be predicted
REFERENCES
[1] Vincent Chalvet, David J.Braun, “Criterion for the design of low-power variable stiffness mechanisms”, IEEE Transactions
on Robotics, vol 33, no 4, pp 1002-1010, 2017
[2] Amanda Sutrisno, David J.Braun, “How to run 50% faster without external energy”, Science Advances, vol 6, no 13, eaay1950, 2020
[3] Ke Wu, Gang Zheng, “A comprehensive static modeling methodology via beam theory for compliant mechanisms”, Mechanism and Machine Theory, vol 169, pp 104598, 2022
[4] Amanda Sutrisno, David J.Braun, “Enhancing mobility with quasi-passive variable stiffness exoskeletons”, IEEE Transactions on Neural Systems and Rehabilitation Engineering,vol 27, no 3, pp 487-496, 2019
[5] C.E.English, D.Russell, “Mechanics and stiffness limitations
of a variable stiffness actuator for use in prosthetic limbs”, Mechanism and Machine Theory, vol 34, pp 7-25, 1999
[6] Daniel F.N.Gordon, Christopher McGreavy, Andreas Christou, Sethu Vijayakumar, “Human-in-the-loop optimization of exoskeleton assistance via online simulation of metabolic cost”, IEEE Transactions on Robotics, pp 1-20, DOI: 10.1109/TRO.2021.3133137
[7] Sung Y.Kim, David J.Braun, “ Novel variable stiffness spring mechanism modulating stiffness independent of the energy stored by the spring”, 2021 IEEE/RSJ International Conference
on Intelligent Robots and Systems (IROS), pp 1-6, DOI: 10.1109/IROS51168.2021.9636339, 2021
[8] Qiang Huang, Chencheng Dong, Zhangguo Yu, Xuechao Chen, Qingqing Li, Huanzhong Chen, Huaxin Liu, “Resistant compliance control for biped robot inspired by humanlike behavior”, IEEE/ASME Transactions on Mechatronics, pp 1-
11, DOI: 10.1109/TMECH.2021.3139332, 2022
[9] Do Xuan Phu, Kruti Shah, Seung Bok Choi, “A new magnetorheological mount featured by changeable damping gaps using a moved-plate valve structure”, Smart Materials and Structures, vol 23, pp 125022, 2014
[10] D X Phu, S B Choi, Y S Lee, M S Han, “Design of a new engine mount for vertical and horizontal vibration control using magnetorheological fluid”, vol 23, pp 117001, 2014
[11] Do Xuan Phu, Seung Bok Choi, “Vibration control of a ship engine system using high-loaded magnetorheological mounts associated with a new direct fuzzy sliding mode controller”, vol 24, pp 025009, 2014
[12] Xuan Phu Do, Huy Ta Duc, Le Tran Huy Thang, Seung Bok Choi, Dalseong Yoon, “Design of a new inside multi-coil clutch for knee-exoskeleton structure based on Helmholtz phenomenon and magneto-rheological fluid”, Proceedings Volume 10598, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2018, 105983M,
2018, 105983M, 2018
Trang 18Evaluating Green Marketing Trending Determinants by a Text Mining Approach
Phan-Anh-Huy Nguyen
Faculty of Economics HCMC University of Technology and Education
Ho Chi Minh City, Vietnam huynpa@hcmute.edu.vn
Abstract: Green Marketing can also refer to the
production and marketing of goods based on environmentally
friendly products made from renewable materials This
approach attracted many companies in recent years
Identifying the trending factors influencing green marketing
is a complicated task This paper proposed a novel
approach based on text mining techniques to figure out the
new determinants in green marketing activities The results
of this paper can be applied to enterprises in their selecting
business strategy development to boost their business
performance
Keywords: text mining, green marketing, marketing
strategy, data mining
I INTRODUCTION
Green marketing is an important topic in recent years
since more entrepreneurs focus on the environmental impacts
on society Furthermore, it is getting more concerns from
many organizations in the era of industrial revolution 4.0 In
current years, there are several studies investigating green
marketing issues in business [1 - 8] However, most of the
previous papers have not found the main themes which are
affected by green marketing Figuring out the trending
determinants is critically important to solve those problems
Therefore, this paper implemented a text mining approach in
order to help the organizations to have better conversations in
the new situation
The contributions of this study are as follows:
1) A new text mining approach is adopted to analyze the new
dataset
2) Four main themes with some related factors have been
discovered
3) The implications are proposed to support the business to
solve the green marketing issues
The remaining sections of the study are organized as follows:
in section 2, the reviews of related works are presented
Section 3 proposed the methodology Section 4 shows the
experimental results and implications
II LITERATURE REVIEW
Green marketing has been defined and analyzed in many
studies in recent years In [1], Peattie and Ken reported the
concepts of green marketing and its main features Dalton et
al drilled down about management techniques when
applying green marketing [2] In [3], Jain, Akansha, et al
used MCDM to select a suitable green marketing strategy under fuzzy environment Suki et al investigated the impacts
of corporate social responsibility on the links between green marketing concerns and consumer purchase intentions [4] Chung, Kuo Cheng reported the green marketing orientation
to achieve sustainable development in hospitality management [5] Mujahid, M., et al analyzed the link between green marketing and performance in small businesses [6] In [7], Mohd Noor et al tried to understand the consumers and green product purchase decision in Malaysia using a structural equation modeling-partial least square (sem-pls) approach In [8], Amaliana, Luthfatul, et al analyzed the consistency of bootstrap resampling in structural model with PLS-PM approach with the technology acceptance model to evaluate in green marketing management strategy In [9], Said, Syahnur, et al applied green marketing practice in purchasing decision home care product The results of the study showed that the attribute of environmentally friendly product design with the green label
is a variable that dominates the selections of consumers when purchasing the products Furthermore, preference attribute weight is having the smallest influence on making the purchasing decisions To the best of our knowledge, there is
a lack of paper applying text mining to figure out the trends
in green marking in recent years Hence, this paper proposed
a new approach to handle this issue by evaluating the green marketing determinants
A Dataset description
In this study, we use a dataset which is collected from
4000 related articles from newspapers recently The following keywords are used for the query to get access to the data: business, experience, data, analysis, technology, skills, work, management
B Text mining method
We use text mining software to visualize word cloud with co-occurrences of term extracted from the main text dataset
In this paper, we use topic modeling by co-word analysis The frequency of keywords is utilized to create the co-occurrences matrix and the clusters of related topics Then, the network visualization is also conducted to show the relationships between topics The algorithm is:
Step 1: Similarity Matrix construction From the co-occurrence matrix by normalizing the latter matrix, the similarity matrix is constructed on differences in the total number of occurrences
Trang 196
Step 2: Mapping technique:
The aim of mapping technique is to minimize a weighted
sum of distances between all pairs of items by the squared
Euclidean
Step 3: Translation, Rotation, and Reflection
The objective of three transformation techniques is to
transform the solution obtained for the optimization problem
Hence, it can create consistent results
The text mining results with discovered topics and
implications are described in this section
Figure 1 The word-cloud
From the resulting data in the word-cloud, it can be seen
that the keyword "Green" has been updated with a lot of tools,
maybe 5023 from green issues is seen as an issue that many
people care about and talk about The whole issue is updated
as “Marketing” with 2194 occurrences for marker work in
today's society is very important, especially the Green
Marketing trend Around the keywords when it comes to this
issue are: product, environment, consumer, company,
enterprise, energy, market and new
The keywords related to Green Marketing show that
consumers are interested in the company's environmentally
friendly products, affect the market, how is the energy
problem The keywords related to the issue show that
consumers are now interested in environmentally friendly
green products and new products or new energy sources to
help protect the environment, and companies should grasp
this green trend to influence the company's marketing to help
the company understand the market and develop better
The results obtained after performing data set analysis on
Green marketing appeared 4 main color clusters In each
cluster, there will be a particular factor that is larger than the
others because it appears more and has a strong association
with other clusters
Figure 2 Results for cluster 1 (red)
The factor “climate change” appears 134 times, although
it is not the factor with the highest frequency, it is an important factor that shows the relationship with other factors
in the same cluster 1 such as person, government, planet, effort This shows that climate change is an issue that the whole world needs to pay attention to Climate change will lead to many serious consequences for our planet, so people and governments are both working to limit and prevent climate change by saving resources, based on research and development technology to create new alternative energy
Figure 3 Results for cluster 2 (green)
The “market” element appears with the highest frequency
620 times among the elements in cluster2 It is not surprising that the element “market” appears a lot in the analysis results because the market is the place where marketing strategies are implemented In addition, in this cluster 2, we see the appearance of these factors such as strategy, research, firm (company), country, The appearance of these factors shows that if companies want to understand the market or dominate the market, it is essential to do research to analyze and come
up with appropriate strategies for each market in different countries and different families In a market where consumers are increasingly concerned about the environment, companies need to make changes in product strategies to meet consumer needs
Figure 4 Results for cluster 3 (blue)
Product is the element that appears the most with 1837 times and has many close links with factors inside and outside the cluster to create a strong linked system The reason that
Trang 20products are mentioned so many times in the topic of green
marketing is because plastic waste is currently a factor that
has a serious impact on the environment However, most of
the plastic waste discharged into the environment today
comes from product packaging, so in order to implement
green marketing campaigns, the first thing that needs to be
mentioned must be the change Product packaging becomes
more environmentally friendly
Through the links between product elements (product)
and factors inside and outside the cluster such as consumers,
technology, brands, strategies, etc., we see that brands should
start making changes to their products by applying new
technologies to research alternative materials in order to
change the product packaging to be more environmentally
friendly by capturing the green living trend that consumers
are aiming Certainly, this change will also consume time and
money of businesses, but if businesses have specific and
properly executed strategies, they will bring good results such
as gaining advantages in the market as well as building value
for the brand in the hearts of consumers
Figure 5 Results for cluster 4 (Yellow)
In this cluster, we focus on analyzing the green product
factor Like the analysis mentioned above, green product is a
trend in the current market However, creating green and
environmentally friendly products will cost many times
higher than conventional products Therefore, at present,
green and environmentally friendly products are still very
expensive compared to other common products That also
creates a huge impact on sales of green products Hence,
businesses need to have more strategies, learn to apply
technologies, and cooperate with suppliers to minimize the
cost of producing green products From there, it is possible to
optimize the price to compete in revenue with other
conventional products
V CONCLUSION
In this study, a novel text mining approach has been
implemented to find the green marketing trends There are
four main clusters which are the themes that have been
discovered From that, we have also analyzed the meanings
of each topic with some related determinants Then some business implications have been reported from the results The limitation of this research is the number of text documents in the dataset is not quite huge For future work,
we could get more data to solve some bias problems We could also apply sentiment techniques for implementing those tasks
[4] Suki, Norazah Mohd, Norbayah Mohd Suki, and Nur Shahirah Azman "Impacts of corporate social responsibility
on the links between green marketing awareness and consumer purchase intentions" Procedia Economics and Finance, vol 37, pp 262-268, 2016
[5] Chung, Kuo Cheng "Green marketing orientation: Achieving sustainable development in green hotel management" Journal of Hospitality Marketing & Management, vol 29.6, pp 722-738, 2020
[6] Mujahid, M., et al "Linking green marketing with performance: Environmental marketing model for small business" IOP Conference Series: Earth and Environmental Science vol 737 No 1 IOP Publishing, 2021
[7] Mohd Noor, Mohd Nazri, et al "Understanding consumers and green product purchase decision in Malaysia: a structural equation modeling-partial least square (sem-pls) approach" Asian Social Science , vol 12.9, pp 51-64, 2016
[8] Amaliana, Luthfatul, et al "The consistency of bootstrap resampling in structural model with PLS-PM approach: technology acceptance model in green marketing management strategy" IOP Conference Series: Earth and Environmental Science Vol 239 No 1 IOP Publishing,
2019
[9] Said, Syahnur, et al "Green Marketing Practice In Purchasing Decision Home Care Product" International Journal of Scientific & Technology Research, vol 9.06, pp 893-896,
Trang 218 Copyright © authors This work is licensed under a Creative Commons
Attribution-NonCommercial-NoDerivatives 4.0 International License
A Simple Synthesis of Antibacterial and Antifungal
ZnO Nanorods
Khanh Son Trinh
Faculty of Chemical and Food Technology
Ho Chi Minh City University of Technology and
Education
Ho Chi Minh City, Vietnam
sontk@hcmute.edu.vn
Vinh Tien Nguyen
Faculty of Chemical and Food Technology
Ho Chi Minh City University of Technology and
Education
Ho Chi Minh City, Vietnam tiennv@hcmute.edu.vn
Abstract: ZnO nanorods were prepared by precipitation
method with Zn(CH3COO)2 as the precursor, NaOH as the
precipitating agent and soluble starch as the capping agent
X-ray diffraction analysis showed that the ZnO nanoparticles
(NPs) were structured in the wurtzite lattice with an average
crystallite size of 11.38 nm Field-emission scanning electron
microscopy coupled with energy-dispersive spectroscopy
showed that the material was mostly nanorods with an
average size of 28 nm UV-vis absorption spectra showed that
ZnO-NPs strongly absorb UV radiations The ZnO NRs
demonstrate typical dose-dependent antimicrobial activities
and inhibited Escherichia coli, Staphylococcus aureus, and
Salmonella sp 99.7, 99.96, and 100% respectively at 184
ppm ZnO-NPs At 553 ppm concentration, ZnO-NPs
demonstrated 100% inhibition for the three bacterial strains
Gram-positivity and Gram-negativity seemed to be
unimportant for the resistance of bacteria toward ZnO NRs
ZnO NRs at 14740 ppm showed a weak 98.2% growth
inhibition against the fungi Colletotrichum gloeosporioides
FESEM and EDS analyses showed that the cells of bacteria
were distorted and damaged when being in contact with ZnO
NRs in dispersion The fungal cells in these conditions turned
into spores and were also damaged The synthesized ZnO
NRs can find a wide range of applications as an antibacterial
and antifungal component in inks, paints, coatings,
cosmetics, and pharmaceutics
Keywords: ZnO nanoparticles, antibacterial, antifungal,
UV absorption, Staphylococcus aureus, Salmonella
I INTRODUCTION
In recent years, the synthesis and antimicrobial activities
of ZnO nanomaterials are gaining much attention due to their
low cost, chemical stability, biocompatibility and
biodegradability Recent research on ZnO nanomaterials
focused on green methods of their syntheses using natural
sources of reagents For example, plant extracts were used to
synthesize ZnO nanoparticles and their antibacterial activity
was tested on E.Coli, Streptococcus sp, Enterococcus sp, and
Klebsiella sp [1] Another study used the powder of leaves of
S multiflorus to prepare ZnO nanomaterials and tested their
antifungal activity on Aspergillus niger and Aspergillus flavus
[2] ZnO nanomaterials were also synthesized using
diethylene glycol and triethylene glycol and incorporated into
an antimicrobial film against Staphylococcus aureus and
Proteus vulgaris [3]
Most of the methods using natural sources such as plant
extracts are relatively complicated due to involving the extract
preparation and hence increasing the production costs In this study, we used a simple chemical method to prepare the ZnO nanoparticles (NPs) using inexpensive and commercially available reagents including zinc acetate as the precursor, sodium hydroxide as the precipitating agent, and soluble starch as the capping agent to control the size of NPs The produced ZnO NPs were then tested for antibacterial and antifungal activity against different species
II EXPERIMENTAL METHODS
A Synthesis and characterization of ZnO NPs
ZnO NPs were synthesized based on a reported method [4] Soluble starch (1.5 g) was completely dissolved in 250 mL
of distilled water by stirring at 90oC for 10 min After cooling the solution to room temperature, 5.4875 g of Zn(CH3COO)2.2H2O (0.025 mol) was added and stirred until complete dissolution After that, 250 mL of 0.2 M NaOH solution was added dropwise under continuous stirring The solution was then left stirred for 2 h to complete the reaction The reaction mixture was then filtered and the solid was washed with 3x 500 mL of distilled water and dried at 80oC The dried solid was then ground into a powder
UV-vis spectra were recorded using a UH5300 (Hitachi, Japan) spectrophotometer
X-ray diffraction spectra were recorded using a D8 Advance platform (Bruker, Germany) with = 0.15406 nm at
nm was the wavelength of the X-ray, K = 0.9 was a constant, and D (nm) was the crystallites size
Field Emission Scanning Electron Microscopy (FESEM) was conducted using an S–4800 (Hitachi, Japan) electron microscope Energy Dispersive Spectra (EDS) were recorded using a 7593-H spectrometer (Horiba, Japan) Before FESEM and EDS measurements, the ZnO sample was sputtered with
a thin layer of Pt to enhance the electrical conductivity of ZnO
B Antimicrobial tests of ZnO NPs
Antibacterial activity of ZnO NPs was evaluated based on
a reported method with some modifications [6] The E.coli
bacteria were first activated in a Nutrient Broth medium at
Trang 2237oC for 24 h The ZnO NPs were dispersed in a nutrient agar
medium with different concentrations from 0 to 737 ppm The
nutrient agar medium was poured into Petri dishes and when
the agar solidified, 100 l of the bacteria suspension was
spread on the surface of the agar The Petri dishes were then
incubated at 37oC for 24 h After that, the density of survived
bacteria was determined by counting the number of bacterial
colonies The antibacterial activity was calculated using the
formula
%inhibition=𝐴1 −𝐴2
𝐴1 × 100, where A1 was the bacterial density in the Petri dish without
ZnO NPs (CFU/mL), and A2 was the bacterial density in the
Petri dish with ZnO NPs (CFU/mL)
One-way Analysis of Variance (ANOVA) was conducted
to test the statistically significant difference between the
means with a confidence level of 95%
Antifungal activity of the ZnO NPs was evaluated using a
reported method [7] A PDA medium was autoclaved at 121oC
for 15 min and then ZnO NPs were added with different
concentrations from 0 to 14740 ppm The medium was poured
into Petri dishes and left for solidification The spores of the
fungi were then put in the centre of each Petri dish The size
of the fungal colony was measured every day The percent
inactivation was calculated using the following formula [8]:
Where So was the area of the fungal colony (cm2) in the
control Petri dish without ZnO NPs (cm2) and Ss was the area
of the fungal colony (cm2) in the Petri dish with ZnO NPs
(cm2)
To evaluate the effect of the presence of ZnO NPs on the
bacterial cells, the microorganisms were first activated (in
Nutrient Broth medium for bacteria and in Potato Dextrose
Broth medium for fungi) at 37oC for 24 h After that, 30 mL
of the bacteria suspension was added to 30 mL of a sterilised
Nutrient Broth medium containing ZnO NPs of 184 ppm for
bacteria and 3685 ppm for fungi After 24 h of stirring, the
bacterial cells were centrifuged at 2000 rcf for 30 min, put on
a silicon wafer and left for drying under ambient conditions
The morphology of the cells was observed using the FESEM
and EDS equipment which was used for ZnO NPs described
above [9]
In this reaction, zinc ions were first precipitated into Zn(OH)2 and then dissolved in the presence of excessive hydroxide ions:
Zn2+ + 2OH- → Zn(OH)2 Zn(OH)2 + 2OH- → Zn(OH)42- + 2H+
The complex was unstable and gradually turned into ZnO NPs according to the reaction [10]:
Zn(OH)42- → ZnO +H2O + 2OH- The presence of excessive OH- ions turned soluble starch into a negatively charged form and hence stabilized the ZnO NPs by interacting with the positively charged Zn ions in the ZnO crystallites [11]
A Characterization of ZnO NPs
XRD spectrum of the synthesized material (Figure 1) shows characteristic peaks with corresponding planes of ZnO: 31.8424o (100), 34.3866o (002), 36.2351o (101), 47.4113o (102), 56.605o (110), 62.9608o (103), and 68.0339o (112), which were also reported in another study [12] These peaks indicated the wurtzite structure of ZnO based on the standard JCPDS number 36–1451
Figure 1 XRD spectum of ZnO NPs
The peaks at 2θ of 33.5334o and 59.5205o belong to Zn(OH)2, according to JCPDS number 38–0356 [13] This result indicated that the temperature of 80oC was not high enough to fully convert Zn(OH)2 to ZnO
The crystallites sizes of ZnO NPs were calculated using the Debye – Scherrer equation for different XRD peaks The average of these sizes was 11.38 nm, which is close to the size
of the ZnO NPs determined from the SEM images
Figure 2 FESEM micrograph of ZnO NPs at 50 000 magnification (A) and frequency distribution of particle sizes from
the FESEM micrographs (B)
Trang 2310
Figure 2A shows that there were several shapes of ZnO
NPs, including nanorod, nanowire, and nanotube, with the
majority being nanorods The nanorod shape of ZnO NPs in
this study was due to the usage of precursor zinc acetate It
was shown that the acetate precursor of zinc produced mainly
nanorods, while the chloride and sulfate precursors produced
nanoprims [14] Besides, in this study we used dilute 0.1 M
solution of zinc ions, thus facilitating the formation of
nanorods instead of nanoplates [15]
Figure 2B shows that the sizes of nanorods ranged from 10
to 57 nm with an average of 27.7 nm This result demonstrated
that the soluble starch effectively protected the NPs from
aggregation and growing in diameter [16]
The Energy dispersive spectrum (Figure 3) shows that zinc and oxygen were the main elements in the synthesized material The presence of carbon and the higher atomic percentage of oxygen compared to zinc were possibly due to the presence of soluble starch absorbed on the surface of ZnO NPs Because the size of ZnO NPs was small, the surface interaction between the capping soluble starch and the ZnP was strong, therefore it was difficult to completely remove the soluble starch by washing with water The presence of Al was due to the aluminum holder of the ZnO sample and the presence of Pt was due to the platinum sputtering process before SEM and EDS measurements
Figure 3 EDS spectrum (left) and element composition (right) of the synthesized ZnO NPs
UV-vis spectrum of the ZnO NPs dispersion in water
(Figure 4) shows a broad absorption peak near 366 nm This
result is similar to that of another study that reported an
absorption band of ZnO NPs from 355 to 380 nm [17] The
strong absorption of UV radiations by ZnO NPs can have
several applications such as in sunscreens or anti-aging
coatings
B Antibacterial activity
Table 1 shows that a concentration of 185 ppm of ZnO
NPs inhibited at least 99.0% of the growth of the three
bacteria ZnO NPs exhibited a dose-dependent antibacterial
activity, which was also reported in other studies [18, 19] The
high antibacterial effect was due to ZnO NPs because an
equivalent amount of Zn(CH3COO)2 exhibited significantly
lower antibacterial activity [19]
Figure 4 UV-vis spectrum of the dispersion of synthesized ZnO
NPs in water
Table 1 shows that the antibacterial effect of ZnO NPs
against negative E.coli was lower than against positive S.aureus, similar to other reports [20-22] In Gram-
Gram-positive bacteria, the cell is protected by a thick peptidoglycan membrane composed of teichoic acid, lipoteichoic acid, and surface proteins, while in Gram-negative bacteria, the cell is protected by a membrane composed of lipopolysaccharide,
porins and a thin peptidoglycan layer [23] Although E.coli and Salmonella are both Gram-negative, E.coli is more resistant while Salmonella is less resistant than S.aureus to
ZnO NPs This result indicated that the Gram type of bacteria might not be a significant factor in their resistance toward ZnO
369 ppm
553 ppm
737 ppm
Trang 24Figure 5 Area growth of C gloeosporioides treated with ZnO NPs with different concentrations for 7 days
C Antifungal activity
Figure 5 shows that the fungi C gloeosporioides
continuously grew even in the presence of ZnO NPs
However, the presence of ZnO NPs significantly inhibited the
fungal growth in all 7 days of the experiment Increasing the
ZnO NPs concentration resulted in higher growth inhibition
After 7 days, with ZnO concentrations from 3685 to 14740
ppm, the percent inhibition ranged from 82.8% to 98.2%,
which is similar to the results of 93% inhibition against C
gloeosporioides [24] and 84.5% inhibition against
Erythricium salmonicolor [8]
The high antifungal activity of ZnO NPs was due to the
small size of the synthesized material [25] The mechanism of
antifungal activity was found to be the formation of reactive
oxygen species with high oxidative activity, hence lead to the
alteration of membrane permeability and subsequent cell
death [26, 27]
We used FE-SEM and EDS methods to observe the
microbial cells without and with the presence of ZnO NPs in
the nutrient agar in the previous antimicrobial tests
D Morphology and elemental analysis of microbial cells after ZnO NPs treatments
Comparing sub-figures (A) and (B) in Figures 6, 7, and 8 shows that the bacterial cells were shrinkled and distorted after the treatment with ZnO NPs On the cells in sub-figures (B) there were white dots that contained 3-10% zinc atoms based
on the EDS analysis (data table not shown), which are similar
to other studies [28-31]
It was found that the dispersion of ZnO NPs in the nutrient medium produced reactive oxygen species (ROS) such as hydroxide, superoxide, and hydrogen peroxide [29] These ROS with high reactivity would then react with components
of bacterial cell walls including proteins, lipids, and DNA, hence leading to cell death Hydrogen peroxide penetrates the cell wall into the cell, while superoxide ions attack the cell [32, 33] Another antibacterial mechanism of ZnO NPs was the direct attachment of the NPs on the cell wall and subsequent interaction with the membrane components such as proteins and enzymes, which also lead to the dysfunction of the cells and their death [34]
Figure 6 E.coli cells before (A) and after (B) treating with 184 ppm of ZnO
Trang 2512
Figure 7 S.aureus cells before (A) and after (B) treating with 184 ppm of ZnO NPs
Figure 8 Salmonella cells before (A) and after (B) treating with 184 ppm of ZnO NPs
Before treating C.gloeosporioides with ZnO NPs, one can
easily find the fungal cell in the FESEM micrograph (Figure
9A) However, after treating the fungi with ZnO NPs for 24 h,
we found only their spores (Figure 9B), with the presence of approximately 6.5% zinc atoms on the surface
Figure 9 A cell of C gloeosporioides before ZnO NPs treatment (A) and a fungal spore after treating the cells with ZnO NPs (B)
The antifungal mechanism of ZnO NPs is different from
their antibacterial mechanism and is attributed to the attack of
Zn2+ ions on N-acetylglucosamine or β-1,3-D-glucan synthase
(FKs1p) [8] N-acetylglucosamine plays a vital role in the
synthesis of chitin, and β-1,3-D-glucan synthase takes part in the synthesis of β-1,3-D-glucan [35] Both chitin and β-1,3-D-glucan are important components in the structure of fungal cell walls [8]
Trang 26IV CONCLUSION
In this study, we synthesized ZnO NPs in the shape of
nanorods with sizes mostly lower than 60 nm due to the
capping role of soluble starch The ZnO NPs demonstrate a
dose-dependent antibacterial activity toward different bacteria
and fungi Gram-positivity and Gram-negativity seemed to be
unimportant for the resistance of bacteria toward ZnO NPs
FESEM and EDS analyses showed that the cells of bacteria
were distorted and damaged when being in contact with ZnO
NPs in dispersion The fungal cells in these conditions turned
into spores and were significantly inhibited With the low cost
of zinc acetate precursor and the ease in the synthesis of ZnO
NPs, the material can find a wide range of applications as an
antibacterial and antifungal component in inks, paints,
coatings, cosmetics, and pharmaceutics
ACKNOWLEDGEMENT
The authors acknowledge Ho Chi Minh City University of
Technology and Education for the facility and equipment
required for this study We thank Mr Nguyen Duc Manh
(student ID 15116030) and Mr Nguyen Quoc Tuan Anh
(student ID 15116002) for their helpful technical support
REFERENCES
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Trang 28An Assessment of Complementary Energy of
Ho Chi Minh City University of Technology and Education
Ho Chi Minh City, Vietnam thodt@hcmute.edu.vn
Thi-Ngoc-Han Vuong
Faculty of Civil Engineering
Ho Chi Minh City University of Technology and Education
Ho Chi Minh City, Vietnam hanvtn@hcmute.edu.vn
H T Tai Nguyen
Faculty of Civil Engineering
Ho Chi Minh City University of Technology and Education
Ho Chi Minh City, Vietnam tainht@hcmute.edu.vn
Abstract: This paper deals with the complementary
energy of HPFRCs under tension through an experimental
study The HPFRCs were prepared from an identity matrix
but with different fiber types or volume contents The fiber
used in this research is long twisted with a length of 30 mm
and a diameter of 0.3 mm There were four levels of fiber
volume content as follows: 0.5 vol.%, 1.0 vol.%, 1.5 vol.%
and 2.0 vol.% to investigate the effect of fiber volume content
on the energy parameters of HPFRCs The complementary
energies of the HPFRCs were evaluated and correlated to a
number of microcracks as the dosage of the fiber was
changed
Keywords: HPFRC, Complementary energy,
First-cracking, Post-First-cracking, Energy absorption capacity
High-performance fiber-reinforced concretes (HPFRCs)
have been classified as one of the sustainable construction
materials, which can enhance structure resistance and avoid
ruinous disasters [1-3] The term “high-performance” of
HPFRCs refers to strain-hardening behavior accompanied by
multiple micro-cracks This property can be identified with an
increase of stress after the first crack due to the crack-bridging
mechanism of reinforcing fibers, and consequently leads to
high strain capacity and large energy absorption capacity of
HPFRCs HPFRCs only produce strain-hardening behavior
with suitable fiber type/content mixed in the plain concrete
[1-5] The interfacial bond between the fiber and HPFRC matrix
is strongly dependent on fiber type/content, which will govern
the mechanical properties of HPFRCs
On the other hand, a strain hardening HPFRC with lower
crack spacing, is characterized as a more ductile material This
is because the fracture strain beyond the first crack is mainly
due to microcracks, which were generated during
strain-hardening [1-3] Complementary energy is defined as the area
above the stress versus strain response curve of a material The
ratio of complementary energy to the crack tip toughness of
the mortar concrete will represent the capability of producing
many microcracks, as illustrated in Fig 1 [6-10] It is clear that
complementary energy is a key engineering property of
HPFRCs that should be evaluated Based on the test data of
the previous studies of the first author [11,12], this paper
focuses on the effect of fiber content on the complementary
energy of HPFRCs, which has been not assessed yet Better
understanding mechanical properties of HPFRCs, including their complementary energy, is highly expected to widen the application of HPFRCs
scc
Hardening energy (G hd )
epc ecc
Multiple microcracks
Crack Localization
Complementary energy (CE)
to evaluate in the discussion part
- The elastic energy (named G el) is the zone under the stress versus strain relationship curve within the elastic stage and calculated using Eq (1) It characterizes the energy absorption capacity per unit volume during extending a tensile specimen from 0 to ecc
- The hardening energy (named G hd) is the zone below the stress versus strain relationship curve with the strain range from 0 to epc The Ghd indicates the energy absorption capacity per unit volume during extending a tensile specimen from 0 to epc, it can be derived using Eq (2)
- The crack tip toughness (named CT ) is the zone above
the stress versus strain relationship curve in the elastic stage and given using Eq (3) It is noted that this expression is
equivalent to the result obtained by Li et al [13] The CT
reveals the energy per unit volume can not be absorbed during extending a tensile specimen from 0 to ecc
Trang 2916
- The complementary energy (named CE ) is the area
above the stress versus strain relationship curve with the strain
range from 0 to epc [13,14] The CE represents the energy
per unit volume can not be absorbed during extending a tensile
specimen from 0 to epc, it can be derived using Eq (4)
0
( )
cc el
pc hd
e e e
It is noted that the Ghd and Gel are the true energies
absorbed by a tensile specimen under loading whereas the CE
and CT are the virtual energies only
A Materials and preparation of specimens
L mm d mm
Figure 2 Photo of the twisted fiber type in this research
Table 1 Composition and compressive strength of Mortar Matrix
Materials Weight ratio
Compressive strength (MPa) 89
Table 2 properties of six fiber types
Fiber type
(Notation)
Tensile strength (MPa)
Length (mm)/
Diameter (mm)
Density (g/cm 3 )
Long twisted
The HPFRCs used an identical mortar matrix, whose composition is provided in Table 1 according to weight ratio The partial materials are sand, fly ash, cement and silica fume, water and superplasticizer The amount of superplasticizer was 0.07 by weight ratio of the cementitious materials It is noted that the sand in the mixture plays an engineering role as coarse filler material whereas the fly ash and silica fume play
a role as fine filler materials to densify the concrete mixture The compressive strength of the mortar matrix using a cylindrical specimen with a size of 100×200 mm was 89 MPa
at 18-day age Table 2 provides the properties of long twisted fiber (T30/0.3) used in this research Photos of the fiber were presented in Fig 2
All constituent materials of HPFRC were blended using a 20-L laboratory mixer (Hobart type) Sand, fly ash, cement and silica fume were dry-mixed for about 10 min at first After dry-mixing, water and then superplasticizer were added
to the mixture and wet-mixed for about 10 min Because the plain mortar showed appropriate flow capability and, the steel fibers were gradually added to the mortar mixture by hand and further blended for 5 min After demolding, all specimens were cured in water at the temperature of 25oC for 14 days The detail of mixing work can be referred to in previous studies [11,12]
Hinge mechanism
Hinge mechanism
b) Experiment setup for direct tensile test
Figure 3 Tensile specimen detail and experimental setup
Trang 30Dog-bone-shaped specimens were used in the direct
tensile test The working section over the gauge length of 100
mm is rectangular with a dimension of 50 × 25 mm2 To
prevent failure beyond the gauge length, both specimen ends
were reinforced by employing steel wire meshes, as described
in Fig 3a All the prepared specimens were tested through a
universal testing machine (UTM) with
displacement-controlled loading The standard displacement rate of 1.0
mm/min was applied to the movable crosshead of the UTM
The data collecting rate during loading was 1 Hz The
specimen elongation under tension was measured by two
linear variable differential transformers (LVDTs), as shown in
Fig 3b Besides, the hinge mechanism was designed at both
specimens Response curves of tensile stress versus strain of the HPFRCs were built and their complementary energies were derived and evaluated
A Tensile responses of HPFRCs with different fiber contents
Fig 4 presents the direct tensile responses of the HPFRCs using the same fiber type T30/0.3 but fiber content varying from 0.5 to 2.0 vol.% As can be seen in Fig 5, all these HPFRCs also exhibit strain-hardening behaviors, although the fiber contents were significantly different
Figure 4 Tensile responses of HPFRCs with different fiber contents
Table 3 Tensile parameters with different fiber contents
cc
s(MPa)
0.28 (0.077)
4.86 (0.69) 1.0 (0.003) 0.016 (0.47) 2.56 (0.092) 0.52 (0.78) 7.48
(0.002)
3.41 (0.03)
0.49 (0.035)
9.99 (1.22)
(0.005)
3.41 (0.27)
0.55 (0.013)
12.53 (0.36)
Note: The standard deviations are delivered within parentheses
Table 3 shows the tensile parameters of the HPFRCs using T30/0.3 type with different fiber contents, varying from 0.5 vol.% to 2.0 vol% The tensile parameters in Table 4 were averaged from three tested specimens for each series, the values in the brackets were standard deviations As presented
in Table 4, all the tensile parameters increased with the increase in fiber content The content of 2.0 vol.% generated the best performance in terms of scc, ecc, spc and epc
B Energy parameters of HPFRCs
Table 4 gives the results of four energy parameters of
HPFRCs, including CE , CT , Ghd and Gel of HPFRCs These results were averaged from three specimens tested for each series Fig 5 graphically displays the comparisons of the
Trang 3118
energy parameters of HPFRCs using different fiber contents
As can be seen in Fig 5, all the four energy parameters of
HPFRCs generally increased as fiber volume content
increased As the fiber volume content was changed from 0.5
to 2.0 vol.%, the range values of the energy parameters were
observed as follows: from 0.381 to 1.609 kJ/m2 for the CE ,
from 0.014 to 0.027 kJ/m2 for the CT , from 0.981 to 5.419
kJ/m2 for the Ghd, and from 0.019 to 0.051 kJ/m2 for the Gel
Regardless of fiber content, the CT was observed to be lower
than the Gel at the first crack At the post crack, the CE was
significantly lower than the Ghd This means the material
capability of HPFRCs was utilized significantly The ratio
Figure 5 Comparison of energy parameters of HPFRCs
Table 4 Energy parameters of HPFRCs
Fiber content
(vol.%)
CE
(kJ/m 2)
hd G
(kJ/m 2)
CT
(kJ/m 2)
el G
(kJ/m 2)
hd
G CE
el
G CT
0.5 0.381 0.981 0.014 0.019 2.6 1.3
1.0 0.579 3.324 0.014 0.027 5.7 1.9
1.5 0.862 4.086 0.018 0.049 4.7 2.8
2.0 1.609 5.419 0.027 0.051 3.4 1.8
Note: Definition of energy parameters can be referred to Fig.1
C Correlation between complementary energy and number
of microcracks in hardening stage of HPFRCs
As illustrated in Fig 1, multiple microcracks (N ) are cr
generated during the hardening stage According to Naaman [14], the average crack spacing (
av L
) of a strain hardening composite can be predicted using Eq (5) Eq (5) relates to a number of fibers within cross-section (Nf), which is possibly estimated using Eq (6) Finally, Ncr within the gauge length
of a tensile specimen can be obtained using Eq (7) Mathematically, Eq (7) describes a linear relationship between Ncr and fiber volume content (Vf)
of 1D, 2 for case of 2D, and 0.5 for the case of 1, 2 and 3D fiber orientation; Ag is the cross-section area of tensile specimens; L is the gauge length of tensile specimen; is the crack spacing factor, its value ranging from 1 to 2 It is highlighted that the author investigated the number of cracks using experiment only and did not calculate the number of cracks through theoretical equations proposed by Naaman Since the ratio of the complementary energy to the crack tip toughness (CE CT ) of a composite represents capability /
of producing multiple microcracks (
cr
N ), in this section, the
ratio CE CT was correlated to / N of HPFRCs, which were cr
Generally, as the ratio CE CT is higher than 1, the multiple /microcracks possibly occur in the composite Kanda and Li [15] stated that the conditions for surely producing multiple microcracks are ratio CE CT >2.7 and ratio / spc/scc>1.3
Trang 32Table 5 supplies the ratio CE CT and / N As shown in cr
Table V, the ratio CE CT increased with the increase in fiber /
content The value of CE CT was from 26.3 to 58.8 while /
the value of spc/scc was from 1.9 to 3.7 These ratios
completely satisfy the conditions according to Kanda and Li
[14] The value of N was observed from 2.00 to 16.67 cr
Table 5 Capability in producing multiple microcracks of HPFRCs
cr N
Figure 6 Photos of multiple microcracks of HPFRCs within
the gauge length
Figure 7 A linear relationship between ratio CE CT/ and
number of multiple microcracks of HPFRCs
Figure 8 A linear relationship between fiber content and
number of multiple microcracks of HPFRCs
A linear relationship was supposed in this study for ratio /
CE CT versus N and cr Vf versus
N response curve was performed in Fig 7 with the
regression function Eq (8) Similarly, the fiber volume content versus N response curve was shown in Fig 8 with cr
the regression function Eq (9) The regression functions are useful for the prediction work of microcrack number and ratio /
CE CT with a changed fiber volume content
- The complementary energy, crack tip toughness, and the ratio between them of HPFRCs clearly increased with increasing fiber volume content
- The hardening energy of HPFRCs was much higher than the complementary energy, regardless of fiber content This means the material capability in terms of energy absorption was utilized significantly Also, the elastic energy was higher than the crack tip toughness of HPFRCs
- Relationship of microcrack number versus ratio complementary energy to crack tip toughness as well as the relationship of microcrack number versus fiber volume content were analytically modelled based on the test result and regression analysis The regression functions are useful for the prediction work of microcrack number and complementary energy as the fiber volume content in HPFRCs is changed
ACKNOWLEDGMENT
This research was supported by Ho Chi Minh City University of Technology and Education, the authors are grateful to the sponsor The opinions expressed in this paper are those of the authors and do not necessarily reflect the views of the sponsor
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Trang 34A Study of the Scavenging Process in a Two-stroke Free Piston Linear Engine at Low Velocity Using CFD
and DPM
Nguyen Huynh Thi
Faculty of Vehicle and Energy
Engineering
Ho Chi Minh City University of
Technology and Education
Ho Chi Minh City, Vietnam
nguyenhuynhthi@tgu.edu.vn
Nguyen Van Trang
Faculty of Vehicle and Energy
Huynh Thanh Cong
Vietnam National University - Ho Chi
Minh City
Ho Chi Minh City, Vietnam htcong@hcmut.edu.vn
Dao Huu Huy
Faculty of Vehicle and Energy
Engineering
Ho Chi Minh City University of
Technology and Education
Ho Chi Minh City, Vietnam
dhhuy2310@gmail.com
Huynh Van Loc
Faculty of Industrial Engineering Tien Giang University
My Tho City, Vietnam
Truong Hoa Hiep
Faculty of Industrial Engineering Tien Giang University
My Tho City, Vietnam
Ngo Duc Huy
Faculty of Vehicle and Energy Engineering
Ho Chi Minh City University of Technology and
Education
Ho Chi Minh City, Vietnam
Vo Bao Toan
Faculty of Vehicle and Energy Engineering
Ho Chi Minh City University of Technology and
Education
Ho Chi Minh City, Vietnam
Abstract: A free-piston linear engine (FPLE) does not
use a crankshaft to control piston motion The gas exchange
and piston movement are closely related to each other and
directly affecting to the engine performance In this study, a
numerical simulation using Computational Fluid Dynamics
(CFD) and the Discrete Phase Model (DPM) has been
performed to investigate the scavenging process in a
two-stroke free piston linear engine during warm up The
characteristics of the reciprocating motion can be
determined based on the dynamics model and the piston
motion profiles are imported into commercial CFD software
(Ansys Fluent V.21) Both models have been applied the
initial conditions such as the velocity of the piston, piston
displacement, and inlet pressure to assess the effect of the
trapping efficiency The results show that the trapping
efficiency ±5% difference in the two models was able to
achieve at piston of 0.32 m/s – 1.25 m/s In addition, the
change in gas at each displacement position of the piston
and different inlet pressures is also shown through the
simulation results
Keywords: free piston linear engine, scavenge
efficiency, piston motion, Computational Fluid Dynamics
(CFD), Discrete Phase Model (DPM)
I INTRODUCTION
The free-piston engine generator (FPLE) is a linear
internal combustion engine that is removed the crank and
piston moves freely in the cylinder With the advantages of
compactness, high efficiency [1], variable compression ratio
should be suitable for many different fuels [2], reducing friction compared to conventional heat engines [3] Visibly, FPLE is a research trend to improve the performance of hybrid vehicles The FPLE considered in the present research is the two-stroke dual-piston type The piston assembly has a free linear motion between the top dead center (TDC) and bottoms dead center (BDC) and the piston assembly motion is controlled by gas and load forces acting upon it Cancelling the crank mechanism allows the piston
to move freely between the two cylinders, giving the engine the advantage of flexible characteristics, but also poses a challenge to the stability of the engine The destabilization here is controlling the position of TDC before the combustion process; different positions of TDC produce different end-compression pressure that affects the power of the engine There are so many related researches on the stability control of FPLE, and proposed various control methods [4-7] These studies focus only on controlling the motion of the piston Although considerable progress has been made, the way FPLE is controlled remains one of the problems preventing its commercialization Another factor
is the mass of air and fuel trapped inside the combustion chamber The trapped mixtures that are affected by the gas exchange process in there have scavenging process That can be key to realizing the engine's combustion efficiency and emissions potential [8] But the stability of gas exchange is unpredictable and difficult for measurement techniques
CFD (Computational Fluid Dynamics) is a very useful tool to analyze the exchange gas through the motion process
of FPLE as well as the scavenging process Blarigan et al.,
Trang 3522
at Sandia National Laboratories, studied the effects of
design parameters such as gas pressure in box, inlet
position, and tilt angle on scavenging efficiency and
trapping efficiency of FPLE through CFD [9] Their results
indicate that during the early stages of gas exchange, some
gas travels from the scavenging port to the exhaust port,
causing direct trapping losses Blarigan et al., at Sandia
National Laboratories They introduced a non-dimensionally
modeled piston movement configuration into the KIVA-3V,
simulating it to obtain the basic FPLE scavenging
performance with constant intake pressure using the model
CFD [10] The results show that a gas exchange system with
continuously low-rise pressure maximizes efficiency and
reduces unclean emissions In addition, several other studies
show that FPLE has a faster piston speed than a
conventional engine, which results in shorter gas exchange
duration of FPLE, lower scavenge efficiency but higher trap
efficiency [11-12]
The studies above show that the gas exchange process
has been simulated and optimized the effects of design
parameters to FPLE However, these studies omitted the gas
exchange in the start process of FPLE, this process usually
operates at low speed but must ensure the trapping
efficiency This study presents a CFD simulation to
investigate scavenging structure and parameters on the
FPLE gas exchange process The dimensional parameters
are chosen based on a prototype FPLE, the motion of the
free piston is built based on a dynamic model to calculate
the piston’s motion profiles In this study, the key
parameters such as displacement piston, operating
low-frequency and inlet pressure are inlet parameters Two
methods CFD and the Eulerian-Lagrangian discrete phase
model (DPM) are used to track the ratio of particles trapped
and escape from the cylinder then find out trapping
efficiency and compare the accuracy with each other
II MODELING AND SIMULATION
A Dynamic model
The mechanical forces acting on the piston include the
gas force in the left and right cylinder, mechanical friction
and inertia force, and traction of the actuator Piston
dynamics can be determined by Newton II's law
P cyl , P cyr is the pressure in the left and right cylinders; S
is the area of the piston crown F f is the friction force, m is
the mass of the translator, d 2 x/dt 2 is the acceleration of the
piston, F sl , F sr are respectively the spring forces in the left
and right Fst the force is received from the starting device
The velocity of piston is calculated by the equation:
In the actual model, the initial speed V0 is based on
the mechanical starter Fig 1 This speed is hindered by the
spring forces on the left or right The piston velocity of the
BDC to TDC form is determined by:
V = V0 − 𝐹.𝑡
Figure 1 A prototype of two-stroke free piston engine [15]
1- Cylinder 1; 2- Activation mechanism; 3- Compressor;
4-Carburetor, 5- Compressed air chamber; 6-Cylinder 2
B CFD model
The piston model and main parameters of FPLE are shown in Fig 2 and Table 1 The parameter of the FPLE is imported into commercial CFD software Ansys Fluent v.21
to define the calculating surfaces and volumes as well as to generate the mesh Then there is the meshing process, the cylinder mesh is generated in a multi-zone method, and the others have generated the mesh in the sweep method The velocity of the piston is calculated by a program written in Microsoft Visual C++ before importing it into the Ansys software as an input database, the input database is a user-defined function (UDF) In the dynamic mesh, the layering
is used to add or remove layers of cells according to the piston position In addition, the dynamic mesh changes according to the piston position to change the compression ratio, pressure The position of the piston can be changed step by step with a step of 0.5mm, from which it is possible
to control the pressure at the end of the compression stroke
in different locations
In order to investigate the effects of intake pressure on the scavenging process and the pressure at the end compression, the inlet pressures are adjusted from 1.05bar to 1.2bar; initial speeds are 0.32m/s and 1.25m/s The inlet and outlet temperatures are set at 300 K during the simulation process The inlet mixture is assumed to be an ideal gas In addition, the 𝑘 − 𝜀 turbulent model is employed to capture turbulence Input parameters are provided for the computational fluid dynamic (CFD) model to calculate the trapping efficiency In two-stroke, the trapping efficiency is defined as follows [13]:
t= mass of delivered fresh charge retained in cylinder
mass of delivered fresh charge through all scavenging ports
Trang 36Figure 2 a) Parameter of the FPLE, b) Computational mesh of the
Inlet pressure Pin (bar) 1.05 - 1.25bar
Inlet temperature Tin (K) 300K
The discrete Phase Model (DPM) is used to
co-track particles’ motion DPM is based on a
Euler-Lagrangian framework, the forces such as viscous drag, lift
force acting on the particles along their trajectories and
stochastic behaviour of the turbulent flow are taken into
account Based on tracking the particles throw discrete
phases in boundary areas to escape, trap and reflect Escape
condition is assumed in the inlet and outlet ports, the trap
condition is considered the cylinder and reflects condition is
being a wall of intake and exhaust pipes Fig 3 To shorten
the computational time and the approach become much
simpler, assumptions in particle motion calculations will be
simplified: all particles have the same size, and the flow
around the particles and particle-particle interaction is
neglected in the simulation In the Lagrangian reference
frame, the trajectory is predicted by integrating the force
balance on each individual particle and can be written as
where F is an additional acceleration (force/unit particle
mass) term; is the particle density and p is the continuum
phase density; u is the local fluid phase velocity and up is the
velocity of the particle phase, respectively; g is the gravity
of the particle The first item on the right is the drag force
per unit particle mass, r is the droplet or particle relaxation
time The initial parameters of the particle such as velocity,
mass flow inlet… similar to the CFD model; the trap
efficiency in the DPM is replaced by the number of
particles The trapping efficiency is defined: as the number
of particles entering the cylinder divided by the number of particles supplied from the scavenging ports
Figure 3 DPM calculation model III RESULTS AND DISCUSSION
A CFD simulation results
Pressure changes at the inlet port and open/closed position affect the scavenging process At an initial speed of 0.32m/s, the initial pressure gradually increases from 1.05bar to 1.2bar Trapping efficiency is increased but not significantly since the mass flow in/out of the cylinder is almost stable Fig 4 When the piston is close to fully closing the inlet, the mass flow drops suddenly at the 3.5 mm position and at the 4mm position the scavenge port fully close At 1.05bar pressure due to high mass flow at the scavenge port but at the exhaust mass flow no significant difference with the case other so trapping efficiency still tends to increase; at 1.1bar pressure due to mass flow at the scavenge port low but high mass flow at exhaust port making the exhaust port high so trapping efficiency still tends to reduce The flow velocity at the exhaust port is based on the flow velocity at inlet port, the flow velocity at the higher inlet the higher exhaust The results of the flow velocity simulation De = 0mm; De =2mm; De =3.5mm at 1.05bar Fig 6 and the rest of the cases are shown in Fig 7
Figure 4 Trapping efficiency from 1.05bar to 1.25bar
4045505560
1.05 bar 1.1 bar 1.15 bar 1.2 bar
Trang 3724
Figure 5 Mass flow versus piston displacement at piston speed
0.32m/s
Figure 6 Velocity Streamline at A) De = 0mm; B) De = 2mm; C)
De = 3.5mm with initial pressure = 1.05 bar and initial velocity of
piston = 0.32m/s
Figure 7 Flow velocity versus piston displacement at piston speed
of 0.32m/s When increasing the speed to 1.25m/s the trapping
efficiency increases at 1.05bar pressure, more mass flows
into the cylinder and out to the cylinder roughly equal to the
other pressure curves Through the two results, the speed of
0.32m/s still gives trapping efficiency higher than 1.25m/s,
the reason is a lot of new charge going out of the exhaust
port but new charge into cylinder low, as shown in the mass
flow Fig 8 and the velocity simulation De = 0mm; De
=2mm; De =3.5mm at 1.05bar Fig 9, the rest of the cases
are shown in Fig 10
Figure 8 Mass flow versus piston displacement at piston speed
1.25m/s
Figure 9 Velocity Streamline at A) De = 0mm; B) De = 2mm; C)
De = 3.5mm with initial pressure = 1.05bar and initial velocity of
in the cylinder, the number of trapped particles corresponds
to the amount that is lost through the exhaust port and trapped due to the obstruction of the piston wall at the scavenging ports Fig 12
Trang 38Figure 11 Trapping efficiency from 1.05 bar to 1.25 bar (DPM)
Figure 12 A) Particle residence time at De = 0mm, B) Particle
residence time at De = 4mm, C) Particle residence time at De =
6mm With a low piston speed of 0.32m/s, the amount of
particles trapped in the cylinder is high and stable When the
scavenging ports are completely closed, the number of
trapped particles is reduced, causing large air escape
through the exhaust port Fig 13 With a piston speed of
1.25m/s, the fast-closing time of the scavenging ports causes
the number of particles not to catch up to the cylinder, but
the number of particles retained is higher due to the
fast-closing time of the exhaust port Fig 14 However, at
0.32m/s the trapping efficiency is still higher
Figure 13 Amount of particle versus piston displacement at piston
ACKNOWLEDGMENT
This work belongs to the project grant No:
B2019-SPK-08 funded by Ministry of Education and Training, and hosted by Ho Chi Minh City University of Technology and Education, Vietnam
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Trang 40Investigating the Relationship between Workers’
Needs and Commitments to Garment Enterprise
Tu Tran
Faculty of Fashion and Tourism
Ho Chi Minh City University of Technology and Education
Ho Chi Minh City, Vietnam camtuspkt@hcmute.edu.vn
Abstract: This paper analyzes the relationship between
workers’ needs and commitments to garment enterprises
Data are collected from the direct survey through the
questionnaire will determine the level of satisfaction of
garment workers’ needs based on the Hierarchy of Needs
(Maslow, 1943), and the commitment between the worker
and the garment enterprise Then, through statistical analysis
to review and test the influence of each factor on worker
commitment to the enterprise The research results show that
factors affecting workers’ commitment to garment
enterprises include: social needs; physiological needs related
to business policies and the lives of workers; safety and
respect needs
Keywords: needs of garment workers, commitments with
garment enterprises, social needs, physiological needs, safety
and respect needs
I INTRODUCTION
From the beginning of 2021 until now, textile and garment
enterprises have prospered in terms of orders and export
markets, so the need to recruit more workers is quite large
However, many businesses are currently facing difficulties in
recruiting and facing a shortage of human resources [1]
In the report on the recruitment demand for mid-and
senior-level personnel in the Vietnamese market in the first
quarter of this year, Navigos Search Company stated that the
effectiveness of Free Trade Agreements (FTAs), especially
EVFTA (FTAs) Vietnam - EU), although it has not been able
to offset the decrease in export turnover caused by Covid-19,
it has brought significant effects in increasing export orders
for textile and garment enterprises in Vietnam Besides, the
tense situation in Myanmar has caused more orders to flow to
Vietnam, leading to an increase in demand for positions in the
textile and garment industry These advantages have helped
recruitment demand in the textile industry increase by 50-60%
over the same period in 2020, especially for middle and senior
management positions However, according to the Vietnam
Textile and Apparel Association (Vitas), after the 2020 labor
cuts, the textile and garment industries are now struggling to
re-hire because of workers who have returned to their
hometowns or online selling [1]
In the labor structure of the garment industry, workers
account for the highest proportion and the job-hopping rate is
also high This study is conducted to help understand the
factors affecting the commitment between workers and
garment enterprises by surveying workers about their needs
and level of engagement with their company With the data obtained from the survey and through processing and analyzing statistical data, it is hoped that the research results will provide managers with a deeper insight into the factors that connect employees and businesses Thereby drawing out several measures and recommendations to help the manager have better human resource management policies to connect workers with their company, and improve labor fluctuations
in the garment enterprises
1 The scale of satisfaction of needs
Maslow's hierarchy of needs (Maslow, 1943) [2] is a motivational theory in psychology comprising a five-tier model of human needs, often depicted as hierarchical levels within a pyramid
From the bottom of the hierarchy upwards, the needs are: physiological (food and clothing), safety (job security), love and belonging needs (friendship), esteem, and self-actualization (presented in figure 1)
Figure 1 Maslow's hierarchy of needs (1943)