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Finite element model updating of Canton Tower using regularization technique
Truong Thanh Chung,Chung Bang Yun,조수진,손훈 국제구조공학회 2012 Smart Structures and Systems, An International Jou Vol.10 No.5
This paper summarizes a study for the modal analysis and model updating conducted using the monitoring data obtained from the Canton Tower of 610 m tall, which was established as an international benchmark problem by the Hong Kong Polytechnic University. Modal properties of the tower were successfully identified using frequency domain decomposition and stochastic subspace identification methods. Finite element model updating using the measurement data was further performed to reduce the modal property differences between the measurements and those of the finite element model. Over-fitting during the model updating was avoided by using an optimization scheme with a regularization term.
Thanh Chung Truong,Jung Ryul Lee 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.4
In this paper, we study the laser-induced Lamb wave of plate-like structures with one side loaded by water using the ultrasonic propagation imager (UPI) system. The existent of Scholte wave mode at the solid-fluid interface is observed using the wavenumber-frequency spectrum. It is also shown that the S0 mode appears to be insignificantly affected by the water while the A0 mode is greatly diminished at low frequency range. The understanding of the effect of water to laser-induced Lamb wave is important for damage characterization of structures such as pipelines. Experiment was performed to detect damage of a plastic pipe structure with the ultrasonic wavenumber imaging (UWI) algorithm. The results showed that the UWI algorithm is robust and able to detect the damage regardless of the working condition of the pipe, with or without water inside.
Finite element model updating of Canton Tower using regularization technique
Truong, Thanh Chung,Cho, Soojin,Yun, Chung Bang,Sohn, Hoon Techno-Press 2012 Smart Structures and Systems, An International Jou Vol.10 No.4
This paper summarizes a study for the modal analysis and model updating conducted using the monitoring data obtained from the Canton Tower of 610 m tall, which was established as an international benchmark problem by the Hong Kong Polytechnic University. Modal properties of the tower were successfully identified using frequency domain decomposition and stochastic subspace identification methods. Finite element model updating using the measurement data was further performed to reduce the modal property differences between the measurements and those of the finite element model. Over-fitting during the model updating was avoided by using an optimization scheme with a regularization term.
Determinants of Operational Self-Sustainability of Microfinance Institutions in Vietnam
LE, Thanh Tam,DAO, Lan Phuong,DO, Ngoc Mai,TRUONG, Thi Hoai Linh,NGUYEN, Thi Thuy Duong,TRAN, Chung Thuy Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.10
The purpose of this paper is to investigate the determinants of the Operational Self-Sustainability (OSS) of Vietnamese microfinance institutions (MFIs). This research uses both qualitative and quantitative research methods: (i) qualitative research was via in-depth interviews with ten microfinance practitioners, policymakers and researchers; (ii) quantitative research was conducted by using panel data of 34 MFIs in the period 2011-2015 with binary logistics and OLS regressions. Results are as follows: (i) MFIs' OSS in Vietnam are mainly determined by five key factors: portfolio at risk (PAR>30), capital structure, gross loan portfolio, scope of activities and legal form; (ii) OSS are most affected by legal status (social organizations have better OSS than formal MFIs or programs/projects), location (MFIs focus in one province have higher OSS than working nationwide or just in one district), capital structure (MFIs with more equity proportion have higher OSS); (iii) surprisingly, average loan size per borrower and age of MFIs do not have statistically significant correlation with OSS. The key recommendations are: (i) MFIs should focus on its professionality and increase its equity; (ii) related stakeholders such as State Bank of Vietnam should promote the enabling ecosystem for microfinance development to enhance poverty reduction and economic development.
Pham, Viet Hung,Dang, Thanh Truong,Hur, Seung Hyun,Kim, Eui Jung,Chung, Jin Suk American Chemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.5
<P>We report a simple, environmentally friendly approach for preparing highly conductive poly(methyl methacrylate)–reduced graphene oxide (PMMA-RGO) composites by self-assembly of positively charged PMMA latex particles and negatively charged graphene oxide sheets through electrostatic interactions, followed by hydrazine reduction. The PMMA latex was prepared by surfactant-free emulsion polymerization using a cationic free radical initiator, which created the positive charges on the surface of the PMMA particle. By mixing PMMA latex with a graphene oxide dispersion, positively charged PMMA particles easily assembled with negatively charged graphene oxide sheets through electrostatic interaction. The obtained PMMA-RGO exhibited excellent electrical properties with a percolation threshold as low as 0.16 vol % and an electrical conductivity of 64 S/m at only 2.7 vol %. Moreover, the thermomechanical properties of PMMA-RGO were also significantly improved. The storage modulus of PMMA-RGO increased by about 30% at 4.0 wt % RGO at room temperature while the glass transition temperature of PMMA-RGO increased 15 °C at only 0.5 wt % RGO.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-5/am300297j/production/images/medium/am-2012-00297j_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am300297j'>ACS Electronic Supporting Info</A></P>
Abbas, Syed Haider,Truong, Thanh Chung,Lee, Jung-Ryul Informa UK (Taylor Francis) 2017 Advanced composite materials Vol.26 No.suppl1
<P>This paper presents the implementation of an ultrasonic energy mapping (UEM) method in a field programmable gate array (FPGA)-based processing board. This method is integrated into an ultrasonic propagation imaging (UPI) system for real-field application. UEM method involves two-dimensional Fourier transform and wavenumber filtering to capture the energy scattering waves. Performing multi-dimensional Fourier transform in FPGA is a challenging task because it cannot fit into a single FPGA chip, and therefore, external memory is required to handle a large amount of data. The row-column decomposition method is used to perform 2D Fourier transform using two DDR3 SDRAM memories. Additionally, a source removal function is added into the system to highlight the damage when high energy at the source location occurs. The UPI system was applied for inspection of a composite wing box with impact damages. The UEM results showed that a damage of 20x20mm(2) was detected successfully in the presence of the source inside the scan area. Moreover, the UEM result is produced in less than 5 s for 57,600 points, which is practical for a real-world, non-destructive testing application.</P>
Van-Hoang Tran,Thanh-Huan Nguyen,Frédéric Plourde,Khanh-Duy Cong Do,Duy-Hung Chung,Cong-Truong Dinh,Gia-Diem Pham 한국유체기계학회 2023 International journal of fluid machinery and syste Vol.16 No.2
In order to increase turbine efficiency while retaining structural integrity, modern jet engines need an effective cooling system. Pin-fin arrays play a significant role in the internal cooling system of the turbine blade. In examining the efficacy of cooling techniques using pin-fins, the other papers focus on pin-fin configurations. In contrast, the current study is a step toward optimizing cooling cascade endwalls for better maneuvering and reservation of vortices, which leads to more considerable heat transfer near the endwalls. This study examines the flow field and heat transfer of roughed endwall in the pin-fin channel, including varieties with flat endwall and extruded endwall. The heat transfer of the channel and pressure drop properties of the extruded endwall case are quantitatively assessed to contrast with those of the flat endwalls scenario for an intake Reynolds number range of 7400 to 36000. The leading and trailing surfaces of the channel are divided into five streamwise regions to understand better how well the pin-fins and endwalls transmit heat. The results show that the new endwall construction significantly increases the high heat transfer zones around the pin-fins compared to the flat endwall scenario. In the meantime, the heat transfer of the channel to the pin-fins is enhanced by the modified endwall configuration. The redesigned endwall outperformed the basic case regarding the HTEI, rising by 15.9%. It is found that the friction factor of the new design is increased due to the narrowing channel. However, due to their much higher heat transfer capacity, the HTEI of extruded endwall is up to 41.5% higher than the HTEI of the channel with flat endwalls. These results demonstrate that the heat transfer properties of pin-fins can be significantly improved by optimizing endwall design.