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Seismic Demand Evaluation of Steel MRF Buildings with Simple and Detailed Connection Models
Kien Le-Trung,이기학,이재홍,이도형 한국강구조학회 2010 International Journal of Steel Structures Vol.10 No.1
A detailed connection model can take into account effects such as strength and stiffness degradation, pinching and brittle behavior while a simple one cannot. This study investigates the effects of using the detailed and simple connection models on the seismic behavior of steel moment resisting frame (MRF) buildings. The frame models designed by 1994 UBC and 2000IBC provisions involved the use of clear length dimensions of elements, panel zone models, and connection models subjected to suites of 20 accelerograms with 50/50, 10/50 and 2/50 hazard levels. The interstory drifts, column axial forces, and probability of building failure were investigated. The results show that the discrepancy of the building behaviors between using the detailed and simple connections became larger when the more severe seismic hazard levels and higher percentile values were considered. Therefore, the detailed connection models would be recommended to evaluate and predict seismic performance of steel MRF buildings.
Trung-Kien Nguyen,Viet-Hoang Le,Quoc-Hoang Duong,Seok-Kyun Han,Sang-Gug Lee,Nak-Seon Seong,Nae-Soo Kim,Cheol-Sig Pyo 한국전자통신연구원 2008 ETRI Journal Vol.30 No.1
This paper presents the experimental results of a lowpower low-cost RF transceiver for the 915 MHz band IEEE 802.15.4b standard. Low power and low cost are achieved by optimizing the transceiver architecture and circuit design techniques. The proposed transceiver shares the analog baseband section for both receive and transmit modes to reduce the silicon area. The RF transceiver consumes 11.2 mA in receive mode and 22.5 mA in transmit mode under a supply voltage of 1.8 V, in which 5 mA of quadrature voltage controlled oscillator is included. The proposed transceiver is implemented in a 0.18 μm CMOS process and occupies 10 mm2 of silicon area.
Trung Kien Vu,Manh Kha Hoang,Hung Lan Le 한국통신학회 2019 ICT Express Vol.5 No.2
In this paper, a specific type of incomplete data in Wi-Fi fingerprinting based indoor positioning systems (WF-IPS) is presented: censored and dropped mixture data. For fitting this type of data, a censored and dropped Gaussian Mixture Model (CD-GMM) was proposed. Further, an extended version of the Expectation-Maximization (EM) algorithm is developed for estimating parameters of this model. Simulation results demonstrate the effectiveness of the proposed method for parameter estimation.
Nguyen, Trung-Kien,Oh, Nam-Jin,Le, Viet-Hoang,Lee, Sang-Gug IEEE 2006 IEEE transactions on microwave theory and techniqu Vol.54 No.2
A low-power low flicker-noise receiver front-end for 915-MHz-band IEEE 802.15.4 standard in 0.18-μm CMOS technology is implemented. A power-constrained simultaneous noise and input matching low-noise amplifier (LNA) can be achieved by using a conventional inductive degeneration cascode amplifier with an extra gate-source capacitor. In combination with the LNA, a passive mixer showing low 1/f noise performance is adopted to convert the RF signal directly to the baseband signal. The measured results show a conversion gain of 30 dB and a noise figure of 3 dB with 1/f noise corner frequency of 30 kHz. Two-tone test measurements indicate -5-dBm input third-order intercept point and +45-dBm input second-order intercept point. The RF receiver front-end dissipates 2 mA from a 1.8-V supply.
Long, Le Ngoc,Thi, Pham Tan,Trung Kien, Pham,Trung, Pham Thanh,Ohtani, Masataka,Kumabe, Yoshitaka,Tanaka, Hirofumi,Ueda, Shigenori,Lee, Hyoyoung,Thang, Phan Bach,Khai, Tran Van Elsevier 2020 APPLIED SURFACE SCIENCE - Vol.504 No.-
<P><B>Abstract</B></P> <P>In this study, a novel hydrothermal route has been developed for the synthesis of MoS<SUB>2</SUB>/graphene composite with controllable structures, in which ammonium molybdatetetrahydrate, as-prepared graphene oxide (GO), and thioacetamide were used as staring materials. Effects of Mo<SUP>4+</SUP>-to-C precursor ratios and crystalline time on the structures, components and morphologies of MoS<SUB>2</SUB>/graphene were investigated. MoS<SUB>2</SUB>/graphene samples were characterized using XRD, FESEM, HRTEM, FTIR, Raman spectroscopy, HAADF-STEM/EDS, HXPES and electrical measurements. The results show that petal-like MoS<SUB>2</SUB> nanostructures with ultrathin petals (~1–10 layers) and coexistence of 1T- and 2H-MoS<SUB>2</SUB> phases can be synthesized on graphene surface in a short time (~2 h). Comparison of crystallization conditions, we found that the crystallization time had a significant effect on the size of the MoS<SUB>2</SUB> nanopetals. The shorter the reaction time is, the thinner the petal-like MoS<SUB>2</SUB> nanoscale is. On the other hand, by adjusting the ratios of Mo<SUP>4+</SUP>to C (denoted as: MoS<SUB>2</SUB>/C (1:2), MoS<SUB>2</SUB>/C (3:2), MoS<SUB>2</SUB>/C (2.5:1) and MoS<SUB>2</SUB>/C (3:1)), different MoS<SUB>2</SUB>/graphene architectures including “sandwich-liked”, “layer–by–layer” and “anchored” can be obtained. On the basis of these results, a possible growth mechanism of MoS<SUB>2</SUB>nanopetals on GO was proposed. Interestingly, the as-synthesized material depicts its memristive behavior through the Volt-Ampere characteristics, suggesting a potential application in logic memory devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel hydrothermal route has been developed for the synthesis of MoS<SUB>2</SUB>/graphene composite with controllable structures. </LI> <LI> The effects of Mo<SUP>4+</SUP>-to-C precursor ratios and crystalline time on properties of MoS<SUB>2</SUB>/graphene were investigated by FESEM, HRTEM, XRD, FTIR, Raman spectroscopy, HAADF-STEM/EDS and HXPES. </LI> <LI> The memristive properties of the MoS<SUB>2</SUB>/graphenenanocomposite were presented. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Low-Temperature Solution Process of Al-Doped ZnO Nanoflakes for Flexible Perovskite Solar Cells
Nam, SeongSik,Vu, Trung Kien,Le, Duc Thang,Oh, Ilwhan The Korean Electrochemical Society 2018 Journal of electrochemical science and technology Vol.9 No.2
Herein we report on the selective synthesis and direct growth of nanostructures using an aqueous chemical growth route. Specifically, Al-doped ZnO (AZO) nanoflakes (NFs) are vertically grown on indium tin oxide (ITO) coated flexible polyethylene terephthalate (PET) sheets at low temperature and ambient environment. The morphological, optical, and electrical properties of the NFs are investigated as a function of the Al content. Furthermore, these AZO-NFs are integrated into perovskite solar devices as the electron transport layer (ETL) and the fabricated devices are tested for photovoltaic performance. It was determined that the doping of AZO-NFs significantly increases the performance metrics of the solar cells, mainly by increasing the short-circuit current of the devices. The observed enhancement is primarily attributed to the improved conductivity of the doped AZO-NF, which facilitates charge separation and reduces recombination. Further, our flexible solar cells fabricated through this low temperature process demonstrate an acceptable reproducibility and stability when exposed to a mechanical bending test.
Development and validation of a pedestrian deformable finite element model
Tso-Liang Teng,Trung-Kien Le 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.8
Pedestrian protection has become an increasingly important consideration in vehicle crash safety. Pedestrian-vehicle crashes cause a significant number of pedestrian fatalities and injuries globally. Computer models are powerful tools for understanding how to reduce the severity of injuries in such crashes. Real-world studies of pedestrians provide an important source of information for evaluating pedestrian model dynamic performance and ability to reconstruct injurycausing events. This study describes the validation process of deformable pedestrian model using published postmortem human subject (PMHS) trajectory and head resultant velocity corridors, and demonstrates its applicability to pedestrian - vehicle impact research. We implemented the deformable pedestrian model using LS-DYNA finite element code. Based on PMHS data, the pedestrian model is used to validate the displacement trajectories of the head, pelvis, knee and foot. The finite element pedestrian model thus obtained can help assess the friendliness of vehicles with pedestrians in traffic crashes and assist in the future development of pedestrian safety technologies.
Micropropagation from root segments to improve seedling quality in Chinese foxglove crops
Thanh Loan Pham,Van Huy Nguyen,Thi Le Thu Hoang,Thi Tam Tien Ha,Trung Kien Tran,Xuan Duong Vu,Phi Bang Cao,Quang Trung Nguyen 한국식물생명공학회 2020 JOURNAL OF PLANT BIOTECHNOLOGY Vol.47 No.3
This is the first study to establish a complete protocol for micropropagation of Rehmannia glutinosa from root segments. The study involved investigating the effect of plant growth regulators on in vitro shoot regeneration and rooting and identifying substrates supporting survival and growth performance of ex vitro seedlings. A Murashige and Skoog (MS) medium containing 30 g/L sucrose for shoot induction and 0.2 mg/L indole-3-acetic acid (IAA), 1 mg/L 6-benzylaminopurine (BAP), and 1 g/L polyvinylpyrrolidone (PVP) for shoot multiplication resulted in the highest number of shoots per explant and shoot height. Applying a medium containing 0.5 mg/L IAA and 1 g/L PVP yielded optimal rooting of the shoots grown in vitro. Compost enriched with microbial inoculants and perlite enhanced seedling growth better than that with organic biofertilizer-free substrates (soil and sand). We recommend the continuous production of micropropagated R. glutinosa seedlings from root segments under the aforementioned conditions as a possible propagation technique for crops of this species.
Trajectory analyses of uncontrolled circular parachutes in random spatial wind fields
Thanh Dong Pham,Anh Tuan Nguyen,Vu Dan Thanh Le,Trung Kien Nguyen 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8
The present paper explores the trajectories of two uncontrolled circular parachute models which differ in size and mass in random spatial wind fields. The wind velocity components were generated through three-dimensional inverse fast Fourier transforms; and the correlations of the simulation data compared with the theoretical functions to confirm the accuracy of the wind model. The parachute systems are modelled as six-degrees-of-freedom rigid bodies, on which the aerodynamic forces and moments are applied. The dynamics model was validated before being used to study the drop trajectories of the parachute systems in spatial wind fields. Analyzing the drop trajectories and the impact point dispersion characteristics of the two parachute systems, the paper shows that the smaller one oscillates at a higher frequency and is affected more strongly by the wind. While descending at low altitude, there could be resonance between the dynamics of the larger parachute model and the wind turbulence. Moreover, it is found that the use of simplified vertical wind profiles, which include only the variation of the wind velocity against the altitude, may cause significant error in the simulation results.