A High Efficiency Active Rectifier for 6.78MHz Wireless Power Transfer Receiver with Bootstrapping Technique and All Digital Delay-Locked Loop

Nga, Truong Thi Kim,Park, Hyung-Gu,Lee, Kang-Yoon The Institute of Electronics and Information Engin 2014 IEIE Transactions on Smart Processing & Computing Vol.3 No.6

This paper presents a new rectifier with a bootstrapping technique to reduce the effective drop voltage. An all-digital delay locked loop (ADDLL) circuit was also applied to prevent the reverse leakage current. The proposed rectifier uses NMOS diode connected instead of PMOS to reduce the design size and improve the frequency respond. All the sub-circuits of ADDLL were designed with low power consumption to reduce the total power of the rectifier. The rectifier was implemented in CMOS $0.35{\mu}m$ technology. The peak power conversion efficiency was 76 % at an input frequency of 6.78MHz and a power level of 5W.

Power-saving mechanism with delay bound for Mobile WiMAX systems

Nga, D. T. T.,Lim, H. IET 2011 IET COMMUNICATIONS Vol.5 No.13

<P>In Mobile World Interoperability for Microwave Access (WiMAX), the power-saving mechanism (PSM), which operates alternately in sleep and awake modes, works to extend the lifetime of mobile stations (MSs), although it concurrently induces a medium access control (MAC) service data unit (SDU) response delay. In this study, the authors derive the analytical models for two of the most important performance metrics: the average power consumption and the average MAC SDU response delay of an MS in sleep mode. These metrics are given as a function of the sleep mode system parameters: initial sleep window <I>T</I><SUB>min</SUB> and final sleep window <I>T</I><SUB>max</SUB>. Based on these models, the authors show that a tradeoff relationship exists between them. The authors then propose an optimised power-saving mechanism (OPSM) that jointly determines the optimal <I>T</I><SUB>min</SUB> and <I>T</I><SUB>max</SUB> to minimise the power consumption under a given MAC SDU response delay constraint. Through both numerical analyses and subsequent simulations, the authors show that the OPSM effectively minimises the power consumption of an MS in its sleep mode while guaranteeing the MAC SDU response delay constraint.</P>

Performance evaluation and optimisation guidelines for the type II power-saving class of mobile world interoperability for microwave access

Nga, D. T. T.,Lim, H. IET 2012 IET communications Vol.6 No.14

<P>In Mobile World Interoperability for Microwave Access (also known as IEEE802.16e), a standard power-saving mechanism (PSM) that alternates between sleep and wake modes is adopted to extend the lifetime of mobile stations (MSs), but it simultaneously induces a medium access control (MAC) service data unit (SDU) response delay. The standard PSM defines three power-saving classes (PSCs), among which Type I is based on a binary-exponential increase in the sleep window, and Type II is based on a constant sleep window. Over the years, most studies have mainly focused on PSC Type I, while only a few have considered Type II. This study derives several analytical models of PSC Type II and evaluates the power consumption and MAC SDU response delay performance. Based on the derived models, an optimised power under delay-bound mechanism (OPDBM) is proposed to find the optimal initial sleep window parameter that minimises the power consumption of an MS while satisfying a given MAC SDU response delay constraint. Both numerical analysis and simulation experiments show that the OPDBM effectively minimises the power consumption of an MS while guaranteeing any imposed/required MAC SDU response delay constraint in a wide variety of environments.</P>

T–S Fuzzy-Model-Based Sliding-Mode Control for Surface-Mounted Permanent-Magnet Synchronous Motors Considering Uncertainties

Nga Thi-Thuy Vu,Dong-Young Yu,Han Ho Choi,Jin-Woo Jung IEEE 2013 IEEE transactions on industrial electronics Vol.60 No.10

<P>This paper presents a new sliding-mode control (SMC) scheme based on Takagi-Sugeno (T-S) fuzzy model for surface-mounted permanent-magnet synchronous motors (SPMSMs). First, a global T-S fuzzy model is given to represent the nonlinear dynamics of the SPMSM. The proposed T-S fuzzy-model-based sliding-mode controller considers motor parameter uncertainties and unknown external noises, so it is robust against motor parameter and load torque variations. Also, the linear matrix inequalities with feasible performance constraints are used to design both the sliding surface and the sliding-mode controller, and the stability of the proposed controller is analytically proven. In this paper, a simple sliding-mode observer is used to estimate load torque information. The proposed observer-based control scheme is implemented by using a Matlab/Simulink simulation tool and a prototype SPMSM drive with a TMS320F28335 DSP. Finally, simulations and experiments have been performed to justify that the proposed observer-based control strategy can guarantee a better performance (i.e., faster dynamic response, less steady-state error, more robustness, etc.) than the conventional observer-based nonfuzzy SMC scheme when there exist motor parameter uncertainties and unknown external disturbances.</P>

Graphium agamemnon Linnaeus (Lepidoptera: Papilionidae), a pest of soursop (Annona muricata Linnaeus), in Vietnam: Biology and a novel method of control

Nga Thi VU,Rod EASTWOOD,Chat Thi NGUYEN,Lam Van PHAM 한국곤충학회 2008 Entomological Research Vol.38 No.2

Few butterflies are pests of economic significance, but some may be locally destructive, such as the papilionid Graphium agamemnon Linnaeus, which is known to feed on the commercially important soursop (Annona muricata Linnaeus) in Vietnam. This paper documents the life history and ecology of G. agamemnonand investigates commonly used control measures in south-east Vietnam. A novel method of controllingG. agamemnon infestation is described. If soursop basal rootstock (Annona glabra Linnaeus) is encouraged to shoot during times of peak butterfly activity, ovipositing G. agamemnon females are preferentially attracted to the new growth where the resulting early stages may be easily detected and removed by hand.

The Impact of Exchange Rate on Exports and Imports: Empirical Evidence from Vietnam

Nga Hong NGUYEN,Hat Dang NGUYEN,Loan Thi Kim VO,Cuong Quoc Khanh TRAN 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.5

The exchange rate is considered a tool improving the volume of exports and reducing imports. This paper aims to determine the impact of the exchange rate on exports and imports between Vietnam and the United States in the context of the trade war. The research uses Autoregressive Distributed Lag (ARDL) and Nonlinear Autoregressive Distributed Lag (NARDL) Model in the time-series data from 2010:1 to 2020:9. The ARDL’s results support that real exchange rate impact on export and import volumes, but less than the trade war. The trade war helps trade balance increase 0.35%, while the exchange rate increases trade balance 0.191% when the Vietnamese currency devalues 1% in the long run. In the short term, the real exchange rate makes the trade balance decrease. Therefore, the J curve exists between Vietnam and the U.S. The NARDL expresses that the exchange rate is asymmetric both in the short term and the long term. The findings of this study point to two important elements. Firstly, the exchange rate plays a minor role in exports and imports. Secondly, trade war plays a vital role in increasing exports and imports volume between two countries, and the J curve exists between the two countries.

10 Gbps/ch Full-Duplex Optical Link Using a Single-Fiber Channel for Signal Transmission

Nga, Nguyen T. H.,Sangirov, Jamshid,Gwan-Chong Joo,Byueng-Su Yoo,Ukaegbu, Ikechi A.,Tae-Woo Lee,Mu-Hee Cho,Hyo-Hoon Park IEEE 2014 IEEE photonics technology letters Vol.26 No.6

<P>A 10 Gbps/ch full-duplex (simultaneous bidirectional) optical link utilizing two optical subassembly (OSA) transceiver (TRx) modules and two wavelengths, 850 and 1060 nm, for sending and receiving optical signals through a single fiber channel in a fiber array is demonstrated. Each of the OSA TRx modules consists of transmitter/receiver chips, optical fibers embedded in a V-grooved silicon substrate, two 45 ° mirrors formed in fibers, and three silicon optical benches for mounting vertical-cavity surface-emitting lasers, photodiodes (PDs), and monitoring PDs. Mirror-1 in the fiber is coated with a wavelength-filtering layer to reflect transmitted light and pass through received light. Mirror-2 deflects received light to the PD. Two OSA TRx modules were applied in an end-to-end quad small form-factor pluggable optical link for 40-Gbps operation. This optical link showed good performance with clear eye-diagrams and a BER of at <;10<SUP>-12</SUP> Gbps/ch with -8-dBm input power.</P>

The assessment of potential hepatotoxicity using high content screening assaysbased on primary human hepatocytes and HepG2

Nga Thi Thu Tham,Seok Jin Kang,Hee Yi,Young Il Park,Hwan Goo Kang,Hyun Ok Ku 대한수의학회 2017 대한수의학회 학술대회발표집 Vol.2017 No.-

High-content analysis of in vitro hepatocyte injury induced by various hepatotoxicants

Nga T. T. Tham,황소련,방지현,이희수,박영일,강석진,강환구,김용상,구현옥 대한수의학회 2019 Journal of Veterinary Science Vol.20 No.1

In vitro prediction of hepatotoxicity can enhance the performance of non-clinical animal testing for identifying chemical hazards. In this study, we assessed high-content analysis (HCA) using multi-parameter cell-based assays as an in vitro hepatotoxicity testing model using various hepatotoxicants and human hepatocytes such as HepG2 cells and human primary hepatocytes (hPHs). Both hepatocyte types were exposed separately to multiple doses of ten hepatotoxicants associated with liver injury whose mechanisms of action have been described. HCA data were obtained using fluorescence probes for nuclear size (Hoechst), mitochondrial membrane potential (TMRM), cytosolic free calcium (Fluo-4AM), and lipid peroxidation (BODIPY). Cellular alterations were observed in response to all hepatotoxicants tested. The most sensitive parameter was TMRM, with high sensitivity at a low dose, next was BODIPY, followed by Fluo-4AM. HCA data from HepG2 cells and hPHs were generally concordant, although some inconsistencies were noted. Both hepatocyte types showed mild or severe mitochondrial impairment and lipid peroxidation in response to several hepatotoxicants. The results demonstrate that the application of HCA to in vitro hepatotoxicity testing enables more efficient hazard identification, and further, they suggest that certain parameters could serve as sensitive endpoints for predicting the hepatotoxic potential of chemical compounds.

The role of Patent on Foreign Direct Investment: Evidence in Vietnam

Nga Thi PHAM,Huong Thi Thu PHAM 한국유통과학회 2020 유통과학연구 Vol.18 No.6

Purpose: In the period of international integration, how is the implementation of intellectual property regulation in developing countries? Do intellectual property rights help attract more Foreign direct investment (FDI)? This study aims to show the effect of intellectual property rights, reflect in the number of patent registered (Patent distribution into two components: Patent_residents and Patent_non-residents) on FDI attraction in Vietnam. Research design, data and methodology: Using Autoregressive distributed lag (ARDL) model for the data collected from 1990 to 2018 with EViews version 9 software. Conclusions: The results indicate that the number of patent protection has a positive effect on FDI in both short term and long term. In particular, only patent registration of foreign individuals and organizations has a significant positive effect on attracting FDI, while that of Vietnamese patents is not statistically significant. From the results of this study, we provide some recommendations to help attract FDI based on raising awareness of intellectual property rights: Increase international cooperation for innovation to learn and encourage patent; Improve the capac ity of inventing as well as the ability to register patents of Vietnamese people; Government agencies are tasked to support a nd review registration procedures; Encouraging patent registration based on the patent