Focusing Ultrasonic Wave using Metamaterial-based Device with Cross Shape

Anh Hoang Vu,황영인,김학준,송성진 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.3

Focusing on the ultrasonic wave became a point of interest for many researchers in recent years. In this paper, we present the design of the acoustic metamaterials device with the broadband gradient index in the water medium, whose eective index of refraction can be controlled. The device consist of an organized array of cross shape unit cells, the focusing eect is obtained by controlling in the geometry parameters of cross shape and the arrangement between each unit cell in the device. The nite element numerical simulations were performed in the frequency domain to study the focusing eect of the structures at designed frequencies on the propagation of the ultrasonic wave and experiments also conducted using the same design with the simulations. The experiment results are in the good agreement with the simulation results which shows the applicability of this device for focusing ultrasonic wave.

Optimization-Based Fuzzy Energy Management Strategy for PEM Fuel Cell/Battery/Supercapacitor Hybrid Construction Excavator

Hoang Vu Dao,Xuan Dinh To,Hoai Vu Anh Truong,Tri-Cuong Do,Cong Minh Ho,Tri Dung Dang,안경관 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.4

Fuel cell hybrid electric construction equipment (FCHECE) is known as a promising solution to achieve the goal of energy saving and environment protection. Energy management strategy is a key technology of FCHECE, which splits the energy fl ow between power sources. This paper presents a novel optimal energy management strategy for a hybrid electric-powered hydraulic excavator system to enhance power performance, power sources lifespan, and fuel economy. As for the proposed powertrain configuration, fuel cell serves as a primary energy source, and supercapacitor and battery are considered as energy storages. The integration of supercapacitor and battery in fuel cell vehicle has advantages of improving power performance and storing the regenerative energy for future usage. An energy management strategy based on fuzzy logic control and a rule-based algorithm is proposed to effectively distribute the power between the three sources and reuse the regenerative energy. Furthermore, the parameters of the fuzzy logic system are optimized using the combination of a backtracking search algorithm which provides a good direction to the global optimal region and sequential dynamic programming as a local search method to fi ne-tune the optimal solution in order to reduce the hydrogen consumption and prolong the lifetime of the power sources. Simulation results show that the proposed energy management strategy enhances the vehicle performance, improves fuel economy of the FCHECE by 10.919%, increase battery and supercapacitor charge-sustaining capability as well as efficiency of the fuel cell system.

Tobacco Control Policies in Vietnam: Review on MPOWER Implementation Progress and Challenges

Hoang, Van Minh,Tran, Thu Ngan,Vu, Quynh Mai,Nguyen, Thi Tuyet My,Le, Hong Chung,Vu, Duy Kien,Tran, Tuan Anh,Nguyen, Bao Ngoc,Vu, Van Giap,Nguyen, Manh Cuong,Pham, Duc Manh,Kim, Bao Giang Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.no.sup1

In Vietnam, the WHO Framework Convention on Tobacco Control (WHO FCTC) took effect in March 2005 while MPOWER has been implemented since 2008. This paper describes the progress and challenges of implementation of the MPOWER package in Vietnam. We can report that, in term of monitoring, Vietnam is very active in the Global Tobacco Surveillance System, completing two rounds of the Global Adult Tobacco Survey (GATS) and three rounds of the Global Youth Tobacco Survey (GYTS). To protect people from tobacco smoke, Vietnam has issued and enforced a law requiring comprehensive smoking bans at workplaces and public places since 2013. Tobacco advertising and promotion are also prohibited with the exception of points of sale displays of tobacco products. Violations come in the form of promotion girls, corporate social responsibility activities from tobacco manufacturers and packages displayed by retail vendors. Vietnam is one of the 77 countries that require pictorial health warnings to be printed on cigarette packages to warn about the danger of tobacco and the warnings have been implemented effectively. Cigarette tax is 70% of factory price which is equal to less than 45% of retail price and much lower than the recommendation of WHO. However, Vietnam is one of the very few countries that require manufacturers and importers to make "compulsory contributions" at 1-2% of the factory price of cigarettes sold in Vietnam for the establishment of a Tobacco Control Fund (TCF). The TCF is being operated well. In 2015, 67 units of 63 provinces/cities, 22 ministries and political-social organizations and 6 hospitals received funding from TCF to implement a wide range of tobacco control activities. Cessation services have been starting with a a toll-free quit-line but need to be further strengthened. In conclusion, Vietnam has constantly put efforts into the tobacco control field with high commitment from the government, scientists and activists. Though several remarkable achievements have been gained, many challenges remain. To overcome those challenges, implementation strategies that take into account the contextual factors and social determinants of tobacco use in Vietnam are needed.

Focusing ultrasonic waves in a 2-D covered channel above the periodic array of Helmholtz resonators

Anh Hoang Vu,황영인,김학준,송성진 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.10

This paper presents the numerical simulation and experiments on focusing low-frequency ultrasonic waves in a 2-D covered channel above acoustic metamaterials composed of the periodic array of Helmholtz resonators, in which the refractive index can be in a negative value. The 2-D channel above the acoustic metamaterials is covered by a plate to limit the area affected by the negative refractive index metamaterials. Ultrasonic waves propagated in the 2-D covered channel are found to be highly dependent on input frequency and the designed Helmholtz resonator structure, where its negative refractive index causes the focusing phenomenon in this channel. From the numerical simulation and experiments, an amplitude focus spot is observed in the peak-to-peak of the time domain signal and frequency response at 125 kHz by mapping a pressure field in the 2-D covered channel. Different focal points with several input frequencies are also identified. Our research demonstrates the possibility of applying the designed lens based on acoustic metamaterials to improve the focusing effect in ultrasonic testing.

A Combination of Independent Component Analysis, Relative Wavelet Energy, and Support Vector Machine for Mental State Classification

Hoang-Anh T. Nguyen,Huy-Hoang Tran,Thang T. Vu,T.T. Quyen Bui 제어로봇시스템학회 2016 제어로봇시스템학회 국제학술대회 논문집 Vol.2016 No.10

Mental state classification is an important step for realizing a control system based on electroencephalography (EEG) signals which could benefit a lot of paralyzed people including the locked-in or Amyotrophic Lateral Sclerosis. Considering that EEG signals are nonstationary and often contaminated by various types of artifacts, classifying thoughts into correct mental states is not a trivial problem. In this work, our contribution is that we present and realize a novel model which integrates different techniques: Independent component analysis (ICA), relative wavelet energy, and support vector machine (SVM) for the same task. We applied our model to classify thoughts in two types of experiment whether with two or three mental states. The experimental results show that the presented model outperforms other models using Artificial Neural Network, K-Nearest Neighbors, etc.

Effect of Bleeding Dual Discharge Port on Aerodynamic Performance of a Single-stage Transonic Axial Compressor

Anh-Vu Co Tan,Van-Hoang Nguyen,Hoang-Quan Chu,Thai-Son Vu,Ky-Quang Pham,Anh-Tuan Nguyen,Tuong-Linh Nha 한국유체기계학회 2024 International journal of fluid machinery and syste Vol.17 No.2

An improvement of real-time polymerase chain reaction system based on probe modification is required for accurate detection of African swine fever virus in clinical samples in Vietnam

Tran Ha Thi Thanh,Dang Anh Kieu,Ly Duc Viet,Vu Hao Thi,Hoang Tuan Van,Nguyen Chinh Thi,Chu Nhu Thi,Nguyen Vinh The,Nguyen Huyen Thi,Truong Anh Duc,Pham Ngoc Thi,Dang Hoang Vu 아세아·태평양축산학회 2020 Animal Bioscience Vol.33 No.10

Objective: The rapid and reliable detection of the African swine fever virus (ASFV) plays an important role in emergency control and preventive measures of ASF. Some methods have been recommended by FAO/OIE to detect ASFV in clinical samples, including real-time polymerase chain reaction (PCR). However, mismatches in primer and probe binding regions may cause a false-negative result. Here, a slight modification in probe sequence has been conducted to improve the qualification of real-time PCR based on World Organization for Animal Health (OIE) protocol for accurate detection of ASFV in field samples in Vietnam. Methods: Seven positive confirmed samples (four samples have no mismatch, and three samples contained one mutation in probe binding sites) were used to establish novel real-time PCR with slightly modified probe (Y = C or T) in comparison with original probe recommended by OIE. Results: Both real-time PCRs using the OIE-recommended probe and novel modified probe can detect ASFV in clinical samples without mismatch in probe binding site. A high correlation of cycle quantification (Cq) values was observed in which Cq values obtained from both probes arranged from 22 to 25, suggesting that modified probe sequence does not impede the qualification of real-time PCR to detect ASFV in clinical samples. However, the samples with one mutation in probe binding sites were ASFV negative with OIE recommended probe but positive with our modified probe (Cq value ranked between 33.12-35.78). Conclusion: We demonstrated for the first time that a mismatch in probe binding regions caused a false negative result by OIE recommended real-time PCR, and a slightly modified probe is required to enhance the sensitivity and obtain an ASF accurate diagnosis in field samples in Vietnam.

The Effectiveness of Financial Sources for Climate Change in Vietnam

Thi Nhung NGUYEN(Thi Nhung NGUYEN ),Minh Hoa NGUYEN(Minh Hoa NGUYEN ),Thi Phuong Anh VU(Thi Phuong Anh VU ),Thi Hoang Anh DO(Thi Hoang Anh DO ) 한국유통과학회 2023 The Journal of Asian Finance, Economics and Busine Vol.10 No.1

This research aims to give information about the current situation of five financial sources for climate change in Vietnam, including (i) the State budget used by ministries; (ii) the State budget used by provinces; (iii) Bilateral funds; (iv) Multilateral funds; and (v) Private funds, and then classify them in line with the effectiveness. The working paper’s secondary data on spending on CC-related activities, collected from reports of six ministries and 29 provinces, show that the State budget has been crucial in subsidizing CC-related activities in Vietnam. Moreover, domestic investment has accounted for a major part of the total expenditure of ministries and provinces for climate change. In addition, by using primary data collected from surveys sent to twelve experts from 5 groups, such as researchers, practical experts, managers of private funding organizations (such as banks and enterprises), managers of international funding organizations and beneficiaries, and then analyzing the data through the AHP method, the study shows that all climate finance sources in Vietnam are still not very effective. However, private sector funds are considered the most effective financial source for responding to climate change.

The Effect of Tax Planning on Firm Value: A Case Study in Vietnam

VU, Thu Anh Thi,LE, Vinh Hoang Korea Distribution Science Association 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.2

The purpose of this paper is to examine the effect of tax planning on firm value of the non-financial firms listed in Vietnam, moderated by the state ownership. In this paper, effective tax rate is used to measure the tax planning; the state ownership is measured by the percentage of state equity holdings, and the firm value is measured by Tobin's Q. The data research is collected from audited financial statements and other statistical documents of 513 firms in the period of 2015-2019, provided by The FiinGroup (Vietnam). According to that, this paper uses quantitative research methods for the panel data. Regression analysis with GLS shows that the tax planning has a negative effect on firm value. In more detail, the association is not a variable in its direction when state ownership takes the role of a moderator. That means, in the perspective of principal-principal conflict, government should improve institutional environment to prevent firms form breaking the rules, especially accounting standards and principles. Assets allocation in tangible assets or making use of large size advantage should be taken into account. In the long run, firms should concentrate on the deployment of resources and the experience of knowledgeable practitioners to produce effective results.

Factors Affecting the Internal Control System: A Case Study of Chemical Enterprises in Vietnam

Hoang Thanh NGO,Tung Dao NGUYEN,Nga Thuy Thi NGUYEN,Ha Ngoc DAO,Anh Phuong Tran VU 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.12

The article analyzes the impact of factors affecting the internal control system of chemical enterprises in Vietnam, providing more empirical evidence on factors affecting the system of internal control. Research data is collected in the form of face-to-face interviews and email interviews with managers and employees working in different positions, managers at all levels, chief accountants, and accountants of 52 chemical enterprises in Vietnam. The survey results collected 310 questionnaires. After eliminating the invalid questionnaires due to many blank cells, the authors chose to use 297 questionnaires. Quantitative research was carried out with SPSS 25 software. Research results show that Business Strategy, Organizational Structure, Organization’s perception of the instability of the external environment, and Organizational culture are the factors that positively affect the internal control system of chemical enterprises. This can be explained that, for chemical enterprises, Business strategy, Organizational structure, Organization’s perception of the instability of the external environment, and Good organizational culture will positively impact the internal control system of chemical enterprises. Based on the research results, the authors have proposed recommendations to enhance the effectiveness of the internal control system of chemical enterprises in Vietnam, thereby contributing to improving the performance of enterprises in the chemical Vietnamese.