The Relationship Between Chromium Content and Erosion-Corrosion Resistance of Fe-Cr-C Alloy System

Hue, Nguyen Viet,Phuong, Doan Dinh,Tich, Nguyen Van,Binh, Hoang Thi 한국부식방식학회 2002 Corrosion Science and Technology Vol.31 No.1

In order to determine the influence of chromium on erosian-comsian coefficient of alloy in acid media, experiments were performed with chromium content in the range of 12-33% in different typical erosion-corrosion environments such as solution of sand, solution of sand with free acid in pH 2-7. The erosion-corrosion coefficient was evaluated by Apparatus for abrasion-corrosion testing. Wear coetr-icient, K, was calculated by formula: K=ΔMetalon/ΔMalloy Testing results were showed that the alloy with composition (%): Cr=28-30; C=1.8-2.0; Mn=2.5 - 3.0; is the optimum for manufacturing details resistant erosion-corrosion in media upto pH=2-3. This alloy is used successfully to produce details for sand-pumps, minerals processing cyclones.

Impacts of Perceived Security and Knowledge on Continuous Intention to Use Mobile Fintech Payment Services: An Empirical Study in Vietnam*

Dat Dinh NGUYEN,Thanh Duc NGUYEN,Trung Duc NGUYEN,Ha Viet NGUYEN 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.8

Stepping into the technological boom time, Vietnam has integrated into the trends of using Fintech applications as a new means of payment. This article evaluates the relationship between perceived security (including service security and platform security), knowledge, confirmation, perceived usefulness, satisfaction, attitude and lastly enterprise’s images regarding the service and continuous intention to use Fintech services. The survey results of 352 Vietnamese customers using Fintech services, reliability test and extended post-acceptance model (EPAM) which is based on PAM and ECT models. From the survey, we further found out that perceived security (BSS) has no direct impact on continued intention to use, while perceived security (BSS) has positive impact on confirmation (CON), similarly, perceived usefulness (PU) and user’s satisfaction (SES). Knowledge of the Mobile Fintech payment service (KNOW) has a positive impact on perceived security (BSS). Confirmation (CON) has a positive influence on perceived usefulness but in the meanwhile it has created a negative impact on user’s satisfaction (SES). From the survey it can also tell that user’s attitude (ATT) and enterprise image (IMG) both have a positive impact on continual intention to use Fintech services. From the research results, we also propose some recommendation to enhance the continual intention to use Fintech services in Vietnam.

Na-doped La_0.7Ca_0.3MnO₃ compounds exhibiting a large magnetocaloric effect near room temperature

Chi Linh, Dinh,Thi Ha, Nguyen,Huu Duc, Nguyen,Giang Nam, Le Huu,Bau, Le Viet,Manh An, Nguyen,Yu, Seong-Cho,Dang Thanh, Tran Elsevier 2018 PHYSICA B-CONDENSED MATTER - Vol.532 No.-

<P><B>Abstract</B></P> <P>In this work, we have investigated the magnetic properties and the magnetocaloric effect of La<SUB>0.7−x</SUB>Na<SUB>x</SUB>Ca<SUB>0.3</SUB>MnO<SUB>3</SUB> compounds, which were prepared by a conventional solid-state reaction technique. The Rietveld refinement results suggested that the samples are single phase belonging to an orthorhombic structure (space group <I>Pnma</I>). Analyzing temperature dependence of magnetization <I>M</I>(<I>T</I>) revealed that the Curie temperature (<I>T</I> <SUB>C</SUB>) increases with increasing Na content (<I>x</I>). Their <I>T</I> <SUB>C</SUB> value is found to be 260–298K for <I>x</I>=0.0–0.1, respectively. Base on <I>M</I>(<I>T</I>) data measured at different applied magnetic fields (<I>H</I>), temperature dependence of magnetic entropy change Δ<I>S</I> <SUB>m</SUB>(<I>T</I>) data for all the samples was calculated by using a phenomenological model. In the vicinity of <I>T</I> <SUB>C,</SUB> -Δ<I>S</I> <SUB>m</SUB>(<I>T</I>) curve reaches a maximum value (denoted as |Δ<I>S</I> <SUB>max</SUB>|), which gradually increases with increasing <I>H</I>. Under 12kOe, the value of |Δ<I>S</I> <SUB>max</SUB>| is in a range of 1.47–5.19J/kgK corresponding to the relative cooling power RCP=57.12–75.88J/kg. Applied the universal master curve method for the magnetic entropy change, we concluded that Na-doped in La<SUB>0.7−x</SUB>Na<SUB>x</SUB>Ca<SUB>0.3</SUB>MnO<SUB>3</SUB> compounds leads to modification the nature of the magnetic phase transition from the first- to the second-order.</P>

Preliminary study of doxycycline adsorption from aqueous solution on alkaline modified biochar derived from banana peel

Van-Truc Nguyen,Thanh-Binh Nguyen,Thi-Dieu-Hien Vo,Nguyen Duy Dat,Thi-Kim Quyen Vo,Xuan Cuong Nguyen,Viet-Cuong Dinh,Thi-Ngoc-Chau Le,Thi-Giang-Huong Duong,Manh-Ha Bui,Xuan-Thanh Bui 대한환경공학회 2023 Environmental Engineering Research Vol.29 No.3

This study explores the adsorption of doxycycline (DOX) from aqueous solutions onto biochar derived from banana peel, which was prepared using a potassium hydroxide activation method (KOH-BPB). The biochar properties were characterized based on morphology, surface area (SBET of 710.241 ㎡ g<SUP>−1</SUP>), functional groups, and surface charge (pHPZC = 7.7). Parameters, including initial pH, DOX concentration, and ionic strength, that influenced the DOX adsorption capacity of KOH-BPB were examined. Adsorption equilibrium of DOX on KOH-BPB was assessed through four isothermal models: the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models. The obtained data were most compatible with the Langmuir model (R² = 0.9879). KOH-BPB has a maximum DOX absorption capacity of 121.95 mg g<SUP>-1</SUP> which exceeds that of many comparable absorbents. The maximum DOX removal was 96.7% at pH 6, a DOX concentration of 20 mg L<SUP>-1</SUP>, and a KOH-BPB dose of 1.0g L<SUP>-1</SUP>. These findings reveal that biochar from banana peel effectively removes antibiotic residues from water. This study provides a potential, low-cost, and environmentally friendly adsorbent.

Study on the Melting of the Defective Interstitial Alloys TaSi and WSi with BCC Structure

Nguyen Quang Hoc,Tran Dinh Cuong,Bui Duc Tinh,Le Hong Viet 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.8

The statistical moment method is used to study the melting of defective interstitial AB alloys, where A is the main element and B is an interstitial atom, with a body-centered-cubic (BCC) structure. The melting temperature of the AB alloy with defects is obtained from the temperature of absolute stability for the crystalline state and the equilibrium vacancy concentration. Numerical calculations are performed for the interstitial alloys TaSi and WSi. Our calculated results are in good agreement with other calculations.

Smoothed Group-Sparsity Iterative Hard Thresholding Recovery for Compressive Sensing of Color Image

Viet Anh Nguyen,Khanh Quoc Dinh,Chien Van Trinh,Younghyeon Park(박영현),Byeungwoo Jeon(전병우) 대한전자공학회 2014 전자공학회논문지 Vol.51 No.4

압축센싱은 성긴(Sparse) 또는 압축가능한(Compressible) 신호에 대해 Nyquist rate 미만의 샘플링으로도 신호 복원이 가능하다는 것을 수학적으로 증명한 새로운 패러다임의 신호 획득 방법이다. 단순한 신호 획득 과정을 이용하면서도, 동시에 우수한 압축센싱 복원 영상을 얻기 위한 많은 연구들이 수행되고 있다. 그러나, 에너지 분포 및 인간 시각 시스템 등 컬러 영상에 대한 기본적인 특성을 복원 과정에 활용한 기존 압축센싱 관련 연구는 많이 부족하다. 이러한 문제를 해결하기 위해, 본 논문에서는 컬러영상의 압축센싱 복원을 위한 평활 그룹-희소성 기반 반복적 경성 임계 알고리즘을 제안한다. 제안하는 방법은 그룹-희소성에 기반한 경성 임계치 적용과 프레임 기반 필터의 사용을 통해 영상의 변환 영역에 대한 희소성을 증대시키는 동시에 화소 영역의 평활 정도를 복원 과정에 활용할 수 있도록 한다. 또한, 그룹-희소화 경성 임계 과정은 자연 영상의 에너지 분포 및 인간 시각 시스템 특성에 따라 중요하다고 판단되는 RGB-그룹 계수들을 보전하도록 설계하였다. 실험 결과 객관적 화질 측면에서 제안방법이 대표적인 그룹-희소화 평활 복원 기법 보다 평균 PSNR이 최대 2.7dB 높은 것을 확인하였다. Compressive sensing is a new signal acquisition paradigm that enables sparse/compressible signal to be sampled under the Nyquist-rate. To fully benefit from its much simplified acquisition process, huge efforts have been made on improving the performance of compressive sensing recovery. However, concerning color images, compressive sensing recovery lacks in addressing image characteristics like energy distribution or human visual system. In order to overcome the problem, this paper proposes a new group-sparsity hard thresholding process by preserving some RGB-grouped coefficients important in both terms of energy and perceptual sensitivity. Moreover, a smoothed group-sparsity iterative hard thresholding algorithm for compressive sensing of color images is proposed by incorporating a frame-based filter with group-sparsity hard thresholding process. In this way, our proposed method not only pursues sparsity of image in transform domain but also pursues smoothness of image in spatial domain. Experimental results show average PSNR gains up to 2.7dB over the state-of-the-art group-sparsity smoothed recovery method.

Measurement Coding for Compressive Sensing of Color Images

Dinh, Khanh Quoc,Trinh, Chien Van,Nguyen, Viet Anh,Park, Younghyeon,Jeon, Byeungwoo The Institute of Electronics and Information Engin 2014 IEIE Transactions on Smart Processing & Computing Vol.3 No.1

From the perspective of reducing the sampling cost of color images at high resolution, block-based compressive sensing (CS) has attracted considerable attention as a promising alternative to conventional Nyquist/Shannon sampling. On the other hand, for storing/transmitting applications, CS requires a very efficient way of representing the measurement data in terms of data volume. This paper addresses this problem by developing a measurement-coding method with the proposed customized Huffman coding. In addition, by noting the difference in visual importance between the luma and chroma channels, this paper proposes measurement coding in YCbCr space rather than in conventional RGB color space for better rate allocation. Furthermore, as the proper use of the image property in pursuing smoothness improves the CS recovery, this paper proposes the integration of a low pass filter to the CS recovery of color images, which is the block-based ${\ell}_{20}$-norm minimization. The proposed coding scheme shows considerable gain compared to conventional measurement coding.

An Improved LEACH Routing Protocol for Energy-Efficiency of Wireless Sensor Networks

Nguyen Duy Tan,Longzhe Han,Nguyen Dinh Viet,Minho Jo 한국산학기술학회 2012 SmartCR Vol.2 No.5

A wireless sensor network (WSN) is a wireless network consisting of a base station (BS) and multiple micro-sensor nodes. The micro-sensor nodes run on batteries that are not recharged during the network’s lifetime. Therefore, prolonging WSN lifetime is a significant problem. There are some energy-efficient hierarchical routing protocols designed especially for WSNs, such as sensor protocols for information negotiation (SPIN), low-energy adaptive clustering hierarchy (LEACH) and LEACH-centralized (LEACH-C). In this article, we propose an improvement on the LEACH routing protocol to decrease energy consumption and prolong network lifetime. LEACHDistance Energy (LEACH-DE) selects a cluster head node not only by considering residual energy of the node greater than the average residual energy level of nodes in network, but also by examining the geometric distance between the candidate node to the BS as a key parameter. The results of simulation show our proposed algorithm outperforms LEACH and LEACH-C in terms of conserving energy and prolonging WSN lifetime.

Tracking Control of Omnidirectional Mobile Platform with Disturbance Using Differential Sliding Mode Controller

Viet-Tuan Dinh,김상봉,Hung Nguyen,신승목,김학경,변기식 한국정밀공학회 2012 International Journal of Precision Engineering and Vol.13 No.1

In this paper, a differential sliding mode tracking controller (DSMC) using voltage input is designed for trajectory tracking of the three-wheeled omnidirectional mobile platform (OMP) based on its dynamic modeling with disturbances. First, a tracking error vector is defined, and then a differential sliding surface vector is chosen. A control law is obtained by using Lyapunov direct method with backstepping technique. The control law stabilizes the sliding surface vector and makes the tracking error vector go to zero asymptotically. To implement the designed controllers, a control system is developed based on PIC microcontroller. A camera sensor and encoders are used. The simulation and experiment results are presented to illustrate effectiveness of the proposed controller.

Factors Affecting Employees' Organizational Commitment in Foreign Direct Investment Enterprises

NGUYEN, Thi Viet Nga,DO, Thanh Quang,DINH, Cong Hoang Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.10

This study aims to develop a research framework to investigate the factors affecting organizational commitment among employees who are working in Foreign Direct Investment (FDI) enterprises in Vietnam. The authors designed an online survey distributed to employees in FDI enterprises, collecting the data from 312 employees. All scales in this study are adopted from previous studies; tools employed include Cronbach's Alpha, Exploratory Factor Analysis, and Confirmatory Factor Analysis (CFA) to examine the internal consistency, reliability, dimensionality, and validity of each variable. Then, the structural equation modelling (SEM) was utilized in order to estimate path correlations between variables. Results indicate that the leadership style has the strongest effect on organizational commitment, followed by job satisfaction and working performance. Moreover, working performance and job satisfaction are also influenced by leadership style. However, there is no statistical evidence to show that job satisfaction has an impact on working performance. In addition, bootstrapping method is used to show the indirect effect of variables; results reveal that leadership style, though, does not have indirect effect on working performance via job satisfaction, but it indirectly affects organizational commitment throughout working performance. In other words, the study finds that working performance mediates the link between leadership style and organizational commitment.