Modal strain energy-based updating procedure for damage detection: a numerical investigation

Quy Thue Nguyen,Ramazan Livaoğlu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.4

Structural health monitoring is used to control the health of regularly deteriorating special structures or those subjected to sudden loading. Damage localization and severity estimation are important goals of researchers. In this study, an existing modal strain energybased approach is enhanced by a proposed updating procedure to detect damage and estimate severity. Numerical validation is conducted on a cantilever beam and a portal frame. The updated results obtained using the suggested technique are better compared with those of the existing method. On the basis of only the fundamental mode shape, the updating technique can successfully localize damaged elements regardless of the complexity of damage scenarios, and it can estimate severity with acceptable accuracy levels as long as the modal data are free of noise or submerged in noise at low levels.

Export Performance and Stock Return: A Case of Fishery Firms Listing in Vietnam Stock Markets

Quy Thi VO 한국유통과학회 2019 The Journal of Asian Finance, Economics and Busine Vol.6 No.4

The research aims to study the relationship between export performance and stock return of Vietnamese fishery companies. To conduct this study, quarterly data was collected for period from 2010-2018 of 13 fishery companies listing in Ho Chi Minh Stock Exchange (HOSE) and Ha Noi Stock Exchange (HNX). The export performance was measured by export intensity, export growth and export market coverage. In addition, interest rate, exchange rate, GDP, firm size, profitability, and financial leverage were considered as the control variables in the research model. Panel data analysis with Generalized Least Squares model was employed to estimate the predictive regression. The findings indicated that export intensity and export growth have a significant and positive relationship with stock returns. However, export market coverage has not a significant relationship with stock return at the 0.05 level. Profitability, financial leverage, and exchange rate have a positive relationship, while interest rate and GDP have no relation to stock return at the 0.05 significance level. The findings imply that investors should consider the export intensity instead of export growth and export market coverage as selecting stock of fishery exports firms to invest; managers should increase export intensity to increase company’s stock price or firm market value.

A high-performance triode-type carbon nanotube field emitter for mass production

Quy, Nguyen Van,Hoa, Nguyen Duc,An, Myungchan,Cho, Yousuk,Kim, Dojin IOP Pub 2007 Nanotechnology Vol.18 No.34

<P>A triode-type field emission device based on carbon nanotubes (CNTs) synthesized on an anodic aluminum oxide (AAO) template was fabricated. For the improvement of device performance, in addition to the basic advantages of using AAO to obtain uniform CNTs with strong adhesion, several considerations were taken into account, including highly crystalline CNTs synthesized through thermal chemical vapor deposition (CVD) at 1200 °C, lowering the contact resistance with a Ti buffer layer and reducing the pixel size and gate-to-emitter distance. The triode-type field emitter showed a high current density of 20 mA cm<SUP>−2</SUP> and a low turn-on voltage of 16 V. The very high field enhancement factor of 1.6 × 10<SUP>6</SUP> cm<SUP>−1</SUP> confirmed the high efficiency of the triode structure in electron extraction.</P>

Improved electrocatalytic activity of electrodeposited Ni₃S₄ counter electrodes for dye- and quantum dot-sensitized solar cells

Quy, Vu Hong Vinh,Park, Jeong-Hyun,Kang, Soon-Hyung,Kim, Hyunsoo,Ahn, Kwang-Soon Elsevier 2019 Journal of industrial and engineering chemistry Vol.70 No.-

<P><B>Abstract</B></P> <P>Nickel sulfide (Ni<SUB>3</SUB>S<SUB>4</SUB>) films are deposited onto F-doped SnO<SUB>2</SUB> (FTO) substrates using a facile one-step potentiodynamic electrodeposition without any extra treatment. The potential sweep is between −0.9V and 0.7V (vs. Ag/AgCl) for 4–10 cycles. The series resistance is gradually reduced with increased Ni<SUB>3</SUB>S<SUB>4</SUB> film thickness, indicating the metallic conduction of the Ni<SUB>3</SUB>S<SUB>4</SUB> phase. The Ni<SUB>3</SUB>S<SUB>4</SUB> deposited for 8 cycles (denoted FTO/Ni<SUB>3</SUB>S<SUB>4</SUB>-8) exhibits full coverage on the FTO substrate, with 110nm thickness and a distinctive structure of porous and nanoscale interconnecting nanoparticular networks, which provide numerous electrochemical active sites to contact with electrolyte. The film not only exhibits prominent electrocatalytic activities but also shows excellent electrochemical stability in both polysulfide and iodide-based electrolytes compared to FTO/Pt. On the contrary, the FTO/Ni<SUB>3</SUB>S<SUB>4</SUB>-10 shows merged clusters, leading to more compact and less porous morphology, which reduced electrocatalytic activity. The quantum dot-sensitized solar cell (QD-SSC) fabricated using the FTO/Ni<SUB>3</SUB>S<SUB>4</SUB>-8 counter electrode (CE) exhibits power conversion efficiency (PCE) of 4.57%, short-circuit current (J<SUB>sc</SUB>) of 15.92mAcm<SUP>−2</SUP>, open-circuit voltage (V<SUB>oc</SUB>) of 0.545V, and fill factor (FF) of 52.63%. In addition, the dye-sensitized solar cell (D-SSC) using FTO/Ni<SUB>3</SUB>S<SUB>4</SUB>-8 CE achieves a PCE of 8.17%, J<SUB>sc</SUB> of 16.28mAcm<SUP>−2</SUP>,V<SUB>oc</SUB> of 0.735V, and FF of 68.34%. On the other hand, the PCEs of 2.56% and 7.58% are obtained for QD-SSC and D-SSC with Pt CE, respectively. We suggest that the electrodeposited Ni<SUB>3</SUB>S<SUB>4</SUB> should be promising electrocatalytic electrodes for various applications such as QD-SSCs, D-SSCs, supercapacitors, photoelectrochemical water-splitting cells, and batteries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ni<SUB>3</SUB>S<SUB>4</SUB> films were electrochemically synthesized on F-doped SnO<SUB>2</SUB> substrates. </LI> <LI> FTO/Ni<SUB>3</SUB>S<SUB>4</SUB> exhibited porous and nanoscale interconnecting nanoparticular networks. </LI> <LI> FTO/Ni<SUB>3</SUB>S<SUB>4</SUB> provided excellent electrocatalytic activity and numerous active sites. </LI> <LI> It led to significantly enhanced charge transfer and mass transport kinetics. </LI> <LI> FTO/Ni<SUB>3</SUB>S<SUB>4</SUB> CE showed better performance than Pt CE for both of QD-SSC and D-SSC. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Neural-Network-Based Low-Speed-Damping Controller for Stepper Motor With an FPGA

Quy Ngoc Le,Jae-Wook Jeon IEEE 2010 IEEE transactions on industrial electronics Vol.57 No.9

<P>We present a low-speed-damping controller for a stepper motor using artificial neural networks (ANNs). This controller is designed to remove nonlinear disturbance at low speeds. The proposed controller improves the stepper motor performance at less than the resonance speed of the stepper motor system. Due to its ability to learn, the proposed controller can adapt to different resonant speed ranges without any identification process for system parameters. Conversely, we also introduce the implementation of an ANN-based controller, online backpropagation learning, and a microstep driver on a single field-programmable gate array. An implementation and experimental results are conducted to verify the feasibility and the effectiveness of the proposed controller.</P>

Electrodeposited MoS₂ as electrocatalytic counter electrode for quantum dot- and dye-sensitized solar cells

Quy, Vu Hong Vinh,Vijayakumar, Elayappan,Ho, Phuong,Park, Jeong-Hyun,Rajesh, John Anthuvan,Kwon, JongMyeong,Chae, Jiyoung,Kim, Jae-Hong,Kang, Soon-Hyung,Ahn, Kwang-Soon Elsevier 2018 ELECTROCHIMICA ACTA Vol.260 No.-

<P><B>Abstract</B></P> <P>Molybdenum disulfide (MoS<SUB>2</SUB>) films are electrochemically synthesized on F-doped SnO<SUB>2</SUB> (FTO) substrates using potentiostatic electrodeposition (ED) at a constant −1 V for 20–60 min. The MoS<SUB>2</SUB> is deposited according to island growth mode. As the ED time increases to 40 min, the clusters of MoS<SUB>2</SUB> nano particles enlarge and thicken, but maintain nanopores between the clusters. Additional increase in ED time (to 60 min) causes clusters to merge and make the film denser. Furthermore, this MoS<SUB>2</SUB> film exhibits cracks due to stress accumulated in the film. The film FTO/MoS<SUB>2</SUB> (40 min) shows significantly enhanced electrocatalytic activity compared to other films. This is because the FTO/MoS<SUB>2</SUB> (40 min) not only has more electrochemically active sites but also significantly facilitates charge transfer and mass transport. When it is employed as the counter electrode (CE) for quantum-dot and dye-sensitized solar cells (QD-SSC, D-SSC), the QD-SSC with FTO/MoS<SUB>2</SUB> (40 min) CE exhibits even higher overall energy conversion cell efficiency (3.69%) than that with Pt CE (2.16%). Moreover, the D-SSC with FTO/MoS<SUB>2</SUB> (40 min) CE exhibits cell efficiency (7.16%) similar to that with FTO/Pt CE (7.48%). This indicates that MoS<SUB>2</SUB> is a promising CE for all QD-SSCs and D-SSCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MoS<SUB>2</SUB> films were electrochemically synthesized on F-doped SnO<SUB>2</SUB> substrates. </LI> <LI> Change in electrodeposition time affected particle size and pore condition. </LI> <LI> FTO/MoS<SUB>2</SUB> -ED 40 min had better electrocatalytic activity and more active sites. </LI> <LI> FTO/MoS<SUB>2</SUB> -40 also showed much improved charge transfer and mass transport. </LI> <LI> FTO/MoS<SUB>2</SUB>-40 CEs in QD-SSC and D-SSC showed better efficiency than Pt CE. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

One-Step Electrodeposited Nickel Cobalt Sulfide Electrocatalyst for Quantum Dot-Sensitized Solar Cells

Quy, Vu Hong Vinh,Min, Bong-Ki,Kim, Jae-Hong,Kim, Hyunsoo,Rajesh, John Anthuvan,Ahn, Kwang-Soon The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.5

<P>This paper reports a new facile one-step cyclic voltammetry electrochemical co-depositing method to prepare a novel nickel cobalt sulfide (NiCo2S4) counter electrode (CE) on a FTO glass substrate as well as its promising application as an efficient CE in CdSe quantum dot-sensitized solar cells (QD-SSCs). The QD-SSCs fabricated using NiCo2S4 as a CE exhibited a significantly enhanced short circuit current and fill factor, resulting in a significantly improved overall energy conversion efficiency (3.67%) compared to those with the Pt (2.26%), CoS (2.70%) and NiS (2.56%) CEs under 1 sun illumination. This can be attributed to the significantly enhanced electrocatalytic activity and superior electrical conductivity of the NiCo2S4 and the excellent electrical contact at the electrodeposited NiCo2S4/FTO interface. (C) 2016 The Electrochemical Society. All rights reserved.</P>

Enhancing adsorption efficiencies of organic molecules through covalently bonded structures of magnetic carbon nanoparticles

Quy Son Luu,Uyen Thi Do,Dokyung Kim,Jiwon Kim,Donghyeok Jo,Quynh Thi Nguyen,Youngbok Lee 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.105 No.-

This study introduces a facile method for synthesizing covalently bonded magnetic carbon nanoparticles(MCNs) in which carboxylic acid-functionalized activated carbon nanospheres (ACN-COOH) are connectedwith amine-terminated iron oxide nanoparticles (NPs) (Fe3O4-NH2) via a carbodiimide crosslinkingreaction. The adsorption characteristics of the developed magnetic nanoparticles (ACN-Fe3O4) wereinvestigated using a standard cationic dye (methylene blue, MB). Two additional MCNs (multi-coreand core@shell structures) were also prepared, and their adsorption performances were extensively compared. The developed ACN-Fe3O4 material thoroughly utilizes the strengths of activated carbon and Fe3O4themselves, exhibiting large specific surface areas (708.4 m2/g) and strong magnetic properties(40.3 emu/g), resulting in high adsorption capacity (349.5 mg/g) and recycling efficiency (76 % of adsorptionperformance after four cycles). In addition, a study of the mechanism reveals that pore-filling processesare dominant with minor contributions from electrostatic interactions, p–p interactions, and n–p interactions. The developed covalently bonded magnetic carbon nanoparticles (ACN-Fe3O4) can thusbe considered as competent adsorbents with the potential to compensate for the drawbacks of contemporaryMCNs, such as, low adsorption capacity, and weak magnetic properties.

Autonomous Stair Climbing Algorithm for a Small Four-Tracked Robot

Quy-Hung Vu,Byeong-Sang Kim,Jae-Bok Song 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10

In outdoor environments, mobility, adaptability and reliability of a robot are more important than its speed and precise trajectory. From a practical point of view, tracked robots have an advantage over wheeled robots in outdoor applications. The tracked robot is frequently operated by using the remote controller, but the remote operation is not effective for all cases. To overcome some complex obstacles such as rocks or stairs, the information related to the robot posture is required. However, the sensor information is not intuitive to the user to control the robot. In this research, a multi-active crawler robot (MACbot) was developed and the autonomous stair climbing algorithm was implemented to deal with those problems. Various experiments show that the MACbot can climb the stair autonomously.

Combination of an inverse solution and an ANN for damage identification on high-rise buildings

Quy T. Nguyen,Ramazan Livaoğlu 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.28 No.3

Structural health monitoring (SHM) is currently applied to control regularly the health of high-rise buildings which have deteriorated after being subjected to a sudden loading. Damage detection at element levels of a structure consisting of an enormous number of elements becomes the main objective. In this study, the complicated problem is simplified by a two-step solution. Damaged storeys are preliminarily detected before a full damage scenario at an element level is achieved. In Step 1, to overcome the issues related to the huge number of degrees of freedom (DOFs), the full building is simplified to a beam-like system using the Guyan condensation technique. As the natural characteristics of the two lowest modes at the intact and a damaged stage are obtained, the eigenvalue problem based inverse solution is applied to approximately detect damaged storeys. Furthermore, an updating procedure that is proposed in this study effectively enhances the first prediction. In Step 2, an artificial neural network (ANN) model is designed to indicate damaged members on detected storeys using only the first three modal modes. Compared to other approaches applied to detect damages on high-rise buildings, the robustness of the proposed method is that the required number of lowest modal modes is two and three in Step 1 and Step 2 respectively. Furthermore, regardless of the extension of the building in the horizontal direction, only one lateral displacement of each storey is measured to detect damaged storeys in Step 1 and generally detect damaged elements in Step 2. For light and asymmetrical damage scenarios, two more vertical displacements should be considered to obtain accurate element-level detection. However, for all cases, the required number of DOFs is significantly lower than the full system.