Fabrication of Planar Waveguide Chip for Splitting or Combining an Infrared Light Beam

Nguyen Thanh Binh,Nguyen Tat Thanh,Duong Thanh Trung,Nguyen Thanh Huong,Le Quoc Minh 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5

Based on hybrid materials of polymethamethyl acrylat, silica and zirconia (ASZ)/Titania (AST), some planar structures of optical power splitter/combiner type 1×N channels were designed and simulated for making masks by using computer software. Splitter chips were then fabricated by using the thin-film sol-gel technique and their structure was formed by using a direct photo-patterning method with UV light and a mask. A conformation of the waveguide was tested with an Alpha-Step IQ system. The waveguide properties of the splitter were measured with a 1550 nm laser source. The experimental results show that the light was transmitted through the chip with a total output efficiency of around 6% and was separated uniformly at the output channels. Based on hybrid materials of polymethamethyl acrylat, silica and zirconia (ASZ)/Titania (AST), some planar structures of optical power splitter/combiner type 1×N channels were designed and simulated for making masks by using computer software. Splitter chips were then fabricated by using the thin-film sol-gel technique and their structure was formed by using a direct photo-patterning method with UV light and a mask. A conformation of the waveguide was tested with an Alpha-Step IQ system. The waveguide properties of the splitter were measured with a 1550 nm laser source. The experimental results show that the light was transmitted through the chip with a total output efficiency of around 6% and was separated uniformly at the output channels.

A highly sensitive fluorescent chemosensor for simultaneous determination of Ag(I), Hg(II), and Cu(II) ions: Design, synthesis, characterization and application

Hien, Nguyen Khoa,Bao, Nguyen Chi,Ai Nhung, Nguyen Thi,Trung, Nguyen Tien,Nam, Pham Cam,Duong, Tran,Kim, Jong Seung,Quang, Duong Tuan Elsevier 2015 Dyes and pigments Vol.116 No.-

<P><B>Abstract</B></P> <P>A fluorescent chemosensor based on dimethylaminocinnamaldehyde-aminothiourea (DA) has been designed, synthesized, and applied with a combined theoretical and experimental study. The synthetic path, optimized molecular structure and characteristics of DA were carried out using the calculations at the B3LYP/LanL2DZ level of theory. The experimental investigations have a good agreement with the theoretical results. DA can be used as a chemosensor for simultaneous quantification of silver, copper, and mercury ions in aqueous solution at the ppb level. The stable geometric structures of the complexes between DA and Ag<SUP>+</SUP>, Hg<SUP>2+</SUP>, Cu<SUP>2+</SUP> with stoichiometry of 1:1, 2:1, and 2:1, have been found and investigated for electronic properties and fluorescence quenching phenomena by using Atoms in Molecules (AIM) and Natural Bond Orbitals (NBO) analyses.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A chemosensor has been studied with a combined theoretical and experimental study. </LI> <LI> Suitable for detecting trace amounts of Ag(I), Hg(II), Cu(II) ions at the ppb concentration level. </LI> <LI> High water solubility, simplicity, rapid analysis time, wide range of pH. </LI> <LI> The stable geometric structures of the complexes have been found and investigated. </LI> <LI> The fluorescence quenching of complexes is studied by using AIM and NBO analyses. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Thinning and drilling laser-assisted hatching in thawed embryo transfer: A randomized controlled trial

Le, Minh Tam,Nguyen, Thi Tam An,Nguyen, Thi Thai Thanh,Nguyen, Van Trung,Le, Dinh Duong,Nguyen, Vu Quoc Huy,Cao, Ngoc Thanh,Aints, Alar,Salumets, Andres The Korean Society for Reproductive Medicine 2018 Clinical and Experimental Reproductive Medicine Vol.45 No.3

Objective: In frozen and thawed embryos, the zona pellucida (ZP) can be damaged due to hardening. Laser-assisted hatching (LAH) of embryos can increase the pregnancy rate. This study compared thinning and drilling of the ZP before frozen embryo transfer (FET). Methods: Patients were randomly allocated into two groups for LAH using thinning or drilling on day 2 after thawing. Twenty-five percent of the ZP circumference and 50% of the ZP thickness was removed in the thinning group, and a hole $40{\mu}m$ in diameter was made in the drilling group. Results: A total of 171 in vitro fertilization/intracytoplasmic sperm injection FET cycles, including 85 cycles with drilling LAH and 86 cycles with thinning LAH, were carried out. The thinning group had a similar ${\beta}$-human chorionic gonadotropin-positive rate (38.4% vs. 29.4%), implantation rate (16.5% vs. 14.4%), clinical pregnancy rate (36.0% vs. 25.9%), miscarriage rate (5.8% vs. 2.4%), ongoing pregnancy rate (30.2% vs. 23.5%), and multiple pregnancy rate (7.0% vs. 10.6%) to the drilling LAH group. There were no significant differences in pregnancy outcomes between subgroups defined based on age (older or younger than 35 years) or ZP thickness (greater or less than $17{\mu}m$) according to the LAH method. Conclusion: The present study demonstrated that partial ZP thinning or drilling resulted in similar outcomes in implantation and pregnancy rates using thawed embryos, irrespective of women's age or ZP thickness.

Spectral and Energy Efficiencies in Full-Duplex Wireless Information and Power Transfer

Nguyen, Van-Dinh,Duong, Trung Q.,Tuan, Hoang Duong,Shin, Oh-Soon,Poor, H. Vincent Institute of Electrical and Electronics Engineers 2017 IEEE Transactions on Communications Vol. No.

<P>A communication system is considered consisting of a full-duplex multiple-antenna base station (BS) and multiple single-antenna downlink users (DLUs) and single-antenna uplink users (ULUs), where the latter need to harvest energy for transmitting information to the BS. The communication is thus divided into two phases. In the first phase, the BS uses all available antennas for conveying information to DLUs and wireless energy to ULUs via information and energy beamforming, respectively. In the second phase, ULUs send their independent information to the BS using their harvested energy while the BS transmits the information to the DLUs. In both the phases, the communication is operated at the same time and over the same frequency band. The aim is to maximize the sum rate and energy efficiency under ULU achievable information throughput constraints by jointly optimizing beamforming and time allocation. The utility functions of interest are nonconcave and the involved constraints are nonconvex, so these problems are computationally troublesome. To address them, path-following algorithms are proposed to arrive at least at local optima. The proposed algorithms iteratively improve the objectives with convergence guaranteed. Simulation results demonstrate that they achieve rapid convergence and outperform conventional solutions.</P>

Low-Power Direct Conversion Transceiver for 915 MHz Band IEEE 802.15.4b Standard Based on 0.18 μm CMOS Technology

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.

PLANTATION ECONOMY OF FRENCH PEOPLE IN PROVINCE HA NAM FROM 1884 TO 1945 - SUGGESTIONS FOR VIETNAM TODAY

Duong Van Khoa,Mai Thi Tuyet,Nguyen Hai Trung 한국베트남학회 2019 베트남연구 Vol.17 No.2

Pandemics and Economic Complexity: A Cross-Country Analysis

Nguyen Dinh Trung,Duong Kim Thanh,Phung Huong Thi Thu,Ha Mai Quynh 한국국제경제학회 2024 International Economic Journal Vol.38 No.1

This paper is the first attempt to empirically examine the impact of pandemics on economic complexity in a cross-country setting. We employ a unique and recently developed measure of pandemic intensity, which is the World Pandemic Discussion Index. Using panel-corrected standard error regressions on a panel dataset of 90 countries from 1996 to 2019, we find that an increase in pandemic discussion could reduce economic complexity. Further heterogeneity tests show that this detrimental effect of pandemics only occurs in emerging and low-income countries, or in countries with low levels of institutional quality. By using mechanism analysis,wealso find that pandemics reduce economic complexity via deteriorating the quality of human capital. These findings are robust to a comprehensive battery of robustness and sensitivity checks. Overall, our paper could provide valuable implications for policy makers in devising measures to support the economic recovery process post-pandemics.

Joint Information and Jamming Beamforming for Secrecy Rate Maximization in Cognitive Radio Networks

Nguyen, Van-Dinh,Duong, Trung Q.,Dobre, Octavia A.,Shin, Oh-Soon IEEE 2016 IEEE transactions on information forensics and sec Vol.11 No.11

<P>In this paper, we consider the secure beamforming design for an underlay cognitive radio multiple-input single-output broadcast channel in the presence of multiple passive eavesdroppers. Our goal is to design a jamming noise (JN) transmit strategy to maximize the secrecy rate of the secondary system. By utilizing the zero-forcing method to eliminate the interference caused by JN to the secondary user, we study the joint optimization of the information and JN beamforming for secrecy rate maximization of the secondary system while satisfying all the interference power constraints at the primary users, as well as the per-antenna power constraint at the secondary transmitter. For an optimal beamforming design, the original problem is a nonconvex program, which can be reformulated as a convex program by applying the rank relaxation method. To this end, we prove that the rank relaxation is tight and propose a barrier interior-point method to solve the resulting saddle point problem based on a duality result. To find the global optimal solution, we transform the considered problem into an unconstrained optimization problem. We then employ Broyden-Fletcher-Goldfarb-Shanno method to solve the resulting unconstrained problem, which helps reduce the complexity significantly, compared with the conventional methods. Simulation results show the fast convergence of the proposed algorithm and substantial performance improvements over the existing approaches.</P>

An Efficient Precoder Design for Multiuser MIMO Cognitive Radio Networks With Interference Constraints

Nguyen, Van-Dinh,Tran, Le-Nam,Duong, Trung Q.,Shin, Oh-Soon,Farrell, Ronan IEEE 2017 IEEE Transactions on Vehicular Technology VT Vol.66 No.5

<P>We consider a linear precoder design for an underlay cognitive radio multiple-input multiple-output (MIMO) broadcast channel, where the secondary system consisting of a secondary base station (BS) and a group of secondary users is allowed to share the same spectrum with the primary system. All the transceivers are equipped with multiple antennas, each of which has its own maximum power constraint. Assuming zero-forcing (ZF) method to eliminate the multiuser interference, we study the sum rate maximization problem for the secondary system subject to both per-antenna power constraints at the secondary BS and the interference power constraints at the primary users. The problem of interest differs from the ones studied previously that often assumed a sum power constraint and/or single antenna employed at either both the primary and secondary receivers or the primary receivers. To develop an efficient numerical algorithm, we first invoke the rank relaxation method to transform the considered problem into a convex–concave problem based on a downlink-uplink result. We then propose a barrier interior-point method to solve the resulting saddle point problem. In particular, in each iteration of the proposed method we find the Newton step by solving a system of discrete-time Sylvester equations, which help reduce the complexity significantly, compared to the conventional method. Simulation results are provided to demonstrate fast convergence and effectiveness of the proposed algorithm.</P>

Joint Fractional Time Allocation and Beamforming for Downlink Multiuser MISO Systems

Nguyen, Van-Dinh,Tuan, Hoang Duong,Duong, Trung Q.,Shin, Oh-Soon,Poor, H. Vincent IEEE 2017 IEEE communications letters Vol.21 No.12

<P>It is well known that the use of traditional transmit beamforming at a base station (BS) to manage interference in serving multiple users is effective only when the number of users is less than the number of transmit antennas at the BS. Non-orthogonal multiple access (NOMA) can improve the throughput of users with poorer channel conditions by compromising their own privacy, because other users with better channel conditions can decode the information of users with poorer channel conditions. NOMA still prefers that the number of users is less than the number of antennas at the BS transmitter. This letter resolves such issues by allocating separate fractional time slots for serving users with similar channel conditions. This enables the BS to serve more users within a time unit while the privacy of each user is preserved. The fractional times and beamforming vectors are jointly optimized to maximize the system’s throughput. An efficient path-following algorithm, which invokes a simple convex quadratic program at each iteration, is proposed for the solution of this challenging optimization problem. Numerical results confirm its versatility.</P>