Modeling of Unsteady Laminar Flow Based on Steady Solution in Jetting Dispensing Process

Quoc Hung Nguyen,Seung-Bok Choi IEEE 2008 IEEE transactions on electronics packaging manufac Vol.31 No.2

<P>This paper proposes a new approach to model unsteady laminar flows of dispenser systems in the semiconductor packaging industry. The approach is based on the exact steady solution. After an overview of dispensing technology and historical modeling of the unsteady flows, a new modeling approach of the unsteady laminar flow in a circular pipe and annular duct is developed. From the proposed model, the modeling results of unsteady flow in an arbitrary circular pipe and annular duct are obtained and compared with the spectral solution. In addition, a comparative work between the proposed analytical dynamic model and the finite-element model is undertaken in order to demonstrate the effectiveness of the proposed modeling methodology.</P>

Robust Precoding and Postcoding for Multicell Multiuser Transmission using Imperfect CSI

Nguyen-Le, Hung,Nguyen-Duy-Nhat, Vien,Tang-Tan, Chien,Bao, Vo Nguyen Quoc The Korea Institute of Information and Commucation 2016 Journal of communications and networks Vol.18 No.5

This paper studies the problem of precoding and post-coding design for multicell multiuser downlink transmissions in the absence of perfect channel state information (CSI). Using statistical information of imperfect CSI, an iterative multiuser multicell transceiver design is formulated by minimizing the mean squared error (MSE) cost function of signal and leakage interference under per-base station power constraint (PBPC). The convergence of the iterative precoding and postcoding algorithm is verified by analytical and empirical results. The proposed precoding and postcoding algorithm offers a low computational complexity and robustness against CSI imperfection.

A new approach for dynamic modeling of an electrorheological damper using a lumped parameter method

Nguyen, Quoc-Hung,Choi, Seung-Bok Institute of Physics Publishing 2009 Smart materials & structures Vol.18 No.11

<P>This work proposes a new method for dynamic modeling of an electrorheological (ER) damper using a lumped parameter method. After describing the configuration and operating principle of the ER damper, quasi-static modeling of the damper is conducted on the basis of the Bingham model of ER fluid. Subsequently, the lumped parameter models of ER fluid flows in the damper are established and the integrated lumped model of the whole damper system is obtained by taking into account the dynamic motions of the annular duct, upper chamber, lower chamber and connecting pipe. In order to demonstrate the effectiveness of the proposed dynamic model, a comparative work between the simulation and the experiment is undertaken. This is performed under various piston motions with different excitation magnitudes and frequencies. In addition, the effect of ER fluid compressibility and initial pressure in the accumulator on the hysteresis of the ER damper is investigated. </P>

CT Imaging and 1D Computational Fluid Dynamics for Analysis of Structural and Functional Characteristics of Asthmatics with Fixed Airway Obstruction

Hung Quoc Nguyen,So Ri Kim,Kum Ju Chae,Gong Yong Jin,Sanghun Choi 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.5

Factors Affecting the Intention to Apply Management Accounting in Enterprises in Vietnam

NGUYEN, Hung Quoc,LE, Oanh Thi Tu Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.6

By applying behavioral intention theories and the theory of diffusion of innovation in organizations, this study identified several factors influencing the intention to apply management accounting in enterprises in Vietnam. Research data was collected from the questionnaire sent to Vietnamese enterprises in 2019, collecting 542 observations from accountants and directors. The data is, then, synthesized by excel file, conformity check, and processed by SPSS 20 software with descriptive statistics and multiple regression analysis. The results showed four factors that affect the intention to apply management accounting in enterprises in Vietnam: (1) Performance expectancy; (2) Effort expectancy; (3) Perceived trust; and (4) Subjective norms. The study pointed out that the above factors explain 60.618% of the variation of "intention to apply management accounting", in which, Subjective norms has the strongest impact (regression coefficient is 0.238). The findings also show that raising the awareness of managers and accountants about the role of management accounting, improving the qualifications and knowledge of accountants, and increasing the trust of managers about management accounting information are needed to increase the level of management accounting application in Vietnamese enterprises. The study also proposes recommendations to improve the effectiveness of management accounting for managers in operation and decision-making.

A License Plate Recognition System Based On SURF Algorithm

Nguyen Quoc Hung,A.A. Lensky,Jong Soo Lee 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8

The popularity and importance of intelligent transportation systems (ITS) are widely increasing. One of the big issue of the ITS system is an accurate late recognition feature. In this paper, we propose a novel license plate detection method based on the features [1] extracted from the speeded up robust features (SURF) algorithm. A “eatures dictionary”is constructed from the most frequent features and compared to a new input feature to find the appropriate license plate. A new detected feature is compared to the entire features in the dictionary to yield the distances between the feature and the features in the dictionary. The distances are used to estimate the probability density function. Moreover, the pattern matching framework utilizing the feature vectors and the dictionary are proposed. The final results of the experiment show that the average success rate is about 93 percent.

Design of Thermostable Nanogel Systems for Use in the White Tiger Basement Reservoir to Increase the Effectiveness of Crude Oil Production

Nguyen Phuong Tung,Nguyen Thi Phuong Phong,Nguyen Hoang Duy,Nguyen Quoc Hung 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5

This research was conducted to experimentally screen the suitability of acrylamido-2- methylpropane sulfonic acid-acrylamide (AMPS-AM) copolymer-based nanogels for using as sealants to shut-off water channels in the high-temperature and high-salinity reservoir conditions of the White Tiger oil feld. Via in situ intercalative free-radical copolymerization, nanogels have been prepared from montmorillonite-alkyl ammonium clay, AMPS and AM. Two primary compositions of nanogel systems were chosen. A mixture of hexamethylenetetramine (HMTA)/phenyl acetate (PhAc) was used as a crosslinking system. The results obtained from screening the gel properties by using the bottle test method, the test under nitrogen pressure and core ooding under imitated reservoir conditions show that the NANOSEAL-1 and the NANOSEAL-2 nanogels can well satisfy the VietsovPetro (VSP) technical requirements for water isolation materials. This research was conducted to experimentally screen the suitability of acrylamido-2- methylpropane sulfonic acid-acrylamide (AMPS-AM) copolymer-based nanogels for using as sealants to shut-off water channels in the high-temperature and high-salinity reservoir conditions of the White Tiger oil feld. Via in situ intercalative free-radical copolymerization, nanogels have been prepared from montmorillonite-alkyl ammonium clay, AMPS and AM. Two primary compositions of nanogel systems were chosen. A mixture of hexamethylenetetramine (HMTA)/phenyl acetate (PhAc) was used as a crosslinking system. The results obtained from screening the gel properties by using the bottle test method, the test under nitrogen pressure and core ooding under imitated reservoir conditions show that the NANOSEAL-1 and the NANOSEAL-2 nanogels can well satisfy the VietsovPetro (VSP) technical requirements for water isolation materials.

Dynamic modeling of an electrorheological damper considering the unsteady behavior of electrorheological fluid flow

Nguyen, Quoc-Hung,Choi, Seung-Bok Institute of Physics Publishing 2009 Smart materials & structures Vol.18 No.5

<P>In this study, dynamic modeling of an electrorheological (ER) damper is performed considering the unsteady behaviors of ER fluid flow through the annular duct of the damper. After describing the configuration of the ER damper, quasi-static modeling of the damper is conducted on the basis of the Bingham model of ER fluid. The pressure drop of the unsteady ER fluid flow through the annular duct between the electrodes of the damper with a known variation of flow rate is then obtained by solving the momentum equation of the ER fluid flow using the Laplace transform technique. Based on the proposed unsteady flow solution, the simulated results are obtained and compared with measured ones in order to evaluate the effectiveness of the proposed model. In addition, in order to reduce the computation load, a simplified solution of the dynamic damping force is proposed with validation. </P>

Geometry optimization of MR valves constrained in a specific volume using the finite element method

Nguyen, Quoc-Hung,Han, Young-Min,Choi, Seung-Bok,Wereley, Norman M Institute of Physics Publishing 2007 Smart materials & structures Vol.16 No.6

<P>This paper presents the geometric optimal design of magnetorheological (MR) valves in order to improve valve performance, such as pressure drop. The optimization problem is to find the optimal geometric dimensions of MR valves constrained in a specific volume. After describing the configuration of MR valves, their pressure drops are investigated on the basis of the Bingham model of an MR fluid. Then, the valve ratio, which is an objective function, is derived by considering the field-dependent (controllable) and viscous (uncontrollable) pressure drops of the MR valves. Subsequently, the optimization procedure using a golden-section algorithm and a local quadratic fitting technique is constructed via a commercial finite element method (FEM) parametric design language. From the constructed optimization tool, optimal solutions of the MR valves, which are constrained in a specific cylindrical volume defined by its radius and height, are calculated and compared with analytical ones. In addition, several different types of MR valves are optimized in the same specific volume and results are presented. </P>

Simulation of non-dilute fibre suspensions using RBF-based macro–micro multiscale method

Hung Quoc Nguyen,Canh-Dung Tran 한국유변학회 2022 Korea-Australia rheology journal Vol.34 No.1

The multiscale stochastic simulation method based on the marriage of the Brownian Configuration Field (BCF) and the Radial Basis Function mesh-free approximation for dilute fibre suspensions by our group, is further developed to simulate non-dilute fibre suspensions. For the present approach, the macro and micro processes proceeded at each time step are linked to each other by a fibre contributed stress formula associated with the used kinetic model. Due to the feature of non-dilute fibre suspensions, the interaction between fibres is introduced into the evolution equation to determine fibre configurations using the BCF method. The fibre stresses are then determined based on the fibre configuration fields using the Phan–Thien–Graham model. The efficiency of the simulation method is demonstrated by the analysis of the two challenging problems, the axisymmetric contraction and expansion flows, for a range of the fibre concentration from semi-dilute to concentrated regimes. Results evidenced by numerical experiments show that the present method would be potential in analysing and simulating various suspensions in food and medical industries.