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>

Photocatalytic removal of Rhodamine B in water using g-C3N4/MIL-53(Fe) material under LED visible light with persulfate activation

Nguyen Trung Dung,Nguyen Van Hiep,Manh B. Nguyen,Vu Dinh Thao,Nguyen Nhat Huy 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.10

Photocatalysis is usually considered as one of the most effective methods for treating non-biodegradable pollutants commonly found in textile wastewater. In this study, the photocatalyst of g-C3N4/MIL-53(Fe) was synthesized by the hydrothermal method and applied for the removal of Rhodamine B (RhB) in water. The photocatalytic material was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller analysis, UV-Vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. The results showed that the g-C3N4 doped MIL-53(Fe) with 97 wt% of MIL- 53(Fe) works effectively under visible light and the presence of oxidants (Na2S2O8). RhB removal efficiency can be more than 99% with 20mg/L of RhB, 300mg/L of catalyst, 200mg/L of Na2S2O8, and pH 3. In addition, the photocatalytic degradation mechanism of RhB with g-C3N4/MIL-53(Fe) was also proposed, which could be improved and studied for a wide range of applications in textile wastewater treatment.

Design, Synthesis and In Vitro Cytotoxic Activity Evaluation of New Mannich Bases

Bui, Trung Hieu,Le, Thi Thuy,Vu, Thu Thuy,Hoang, Xuan Tien,Luu, Van Chinh,Vu, Dinh Hoang,Tran, Khac Vu Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.5

A series of Novel Mannich bases has been synthesized and evaluated $in$ $vitro$ cytotoxic activity against the human hepatocellular carcinoma (HepG2), human lung carcinoma (SK-LU-1), and human breast cancer (MCF-7). Compound $\mathbf{9f}$ was found to be most potent against three cell lines with $IC_{50}$ values of 1.57, 1.16 and 1.21 ${\mu}g$/mL, respectively. In addition, compounds $\mathbf{9g}$, $\mathbf{10f}$ exhibited very significant activity against MCF-7 cell line with $IC_{50}$ values of 2.0 ${\mu}g$/mL.

Rapid and label-free detection of H5N1 virus using carbon nanotube network field effect transistor

Vu Van Thu,Phuong Dinh Tam,Phuong Trung Dung 한국물리학회 2013 Current Applied Physics Vol.13 No.7

DNA hybridization-based detection techniques are widely used in genetics, medicine, and drug discovery. However, the current techniques are usually based on labels and reagents that are time consuming and complex to implement. In this study, we report a label-free DNA sensor based on single-walled carbon nanotube field effect transistor (SWCNTFET) for selective DNA hybridization detection of H5N1 virus. A network of single-walled carbon nanotubes (SWCNTs) acts as the conductor channel. ProbeDNA sequences were adsorbed onto SWCNTs. The developed DNA sensor can effectively detect full-complementary DNA with concentration as low as 1.25 pM. The sensitivity of the DNA sensor reached approximately 0.28 nM/nA. The effect of the parameters, including DNA probe concentration, its complementary concentration,mismatched sequence, and hybridization time, on the sensor response was also studied. The results showed the potential application of the DNA sensor for medical, environmental, and epidemic detection.

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>

Enhancing PHY Security of Cooperative Cognitive Radio Multicast Communications

Nguyen, Van-Dinh,Duong, Trung Q.,Shin, Oh-Soon,Nallanathan, Arumugam,Karagiannidis, George K. IEEE 2017 IEEE transactions on cognitive communications and Vol.3 No.4

<P>In this paper, we propose a cooperative approach to improve the security of both primary and secondary systems in cognitive radio multicast communications. During their access to the frequency spectrum licensed to the primary users, the secondary unlicensed users assist the primary system in fortifying security by sending a jamming noise to the eavesdroppers, while simultaneously protect themselves from eavesdropping. The main objective of this paper is to maximize the secrecy rate of the secondary system, while adhering to all individual primary users’ secrecy rate constraints. In the case of active eavesdroppers and perfect channel state information (CSI) at the transceivers, the utility function of interest is nonconcave and the involved constraints are nonconvex, and thus, the optimal solutions are troublesome. To solve this problem, we propose an iterative algorithm to arrive at least to a local optimum of the original nonconvex problem. This algorithm is guaranteed to achieve a Karush–Kuhn–Tucker solution. Then, we extend the optimization approach to the case of passive eavesdroppers and imperfect CSI knowledge at the transceivers, where the constraints are transformed into a linear matrix inequality and convex constraints, in order to facilitate the optimal solution.</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>

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>

Visible light-driven photocatalytic degradation of doxycycline using ZnO/g-C₃N₄/biochar composite in aqueous solution

Nguyen Van Hung,Bui Thi Minh Nguyet,Nguyen Huu Nghi,Nguyen Minh Luon,Nguyen Ngoc Bich,Le Van Thanh Son,Nguyen Trung Kien,Dao Ngoc Nhiem,Nguyen Thanh Tuoi,Dinh Quang Khieu 대한환경공학회 2024 Environmental Engineering Research Vol.29 No.4

In the present work, ZnO/g-C₃N₄/biochar was prepared, and it was used for visible-light driven photocatalytic degradation of some colorants (methylene blue, rhodamine B, methyl orange) and some antibiotics (doxycycline, ciprofloxacin, amoxicilline). Biochar was prepared by pyrolysing Phragmites australis biomass. The ZnO/g-C₃N₄/biochar composite was synthesized with the alkaline hydrolysis method. The obtained materials were characterized by X-ray diffraction, scanning electron microscopy, transition electron microscopy, energy dispersive X-ray/elemental mapping, ultraviolet-visible-diffuse reflectance spectroscopy, photoluminescence spectroscopy, nitrogen adsorption/desorption isotherms and X-ray photoelectron spectroscopy. The results show that ZnO nanoparticles with a large surface area are highly dispersed on the g-C₃N₄ particle surface and biochar. The composite exhibits superior photocatalytic degradation ability toward doxycycline, a broad-spectrum antibiotic of the tetracycline compared with individual components (ZnO or g-C₃N₄) and satisfies stability after six treatment cycles. The kinetics and degradation mechanisms of doxycyline were also addressed. In addition, the present catalyst also exhibits the photocatalytic degradation of methylene blue, rhodamine B, methyl orange, ciprofloxacin and amoxicillin in visible-light regions.

A Study on the Poverty of Mountain People Depending on Forests

NGUYEN, Phuong Thi Minh,NGUYEN, Song Van,DO, Duc Tai,NGUYEN, Quynh Thi Thuy,DINH, Thanh Trung,NGUYEN, Hang Phan Thu Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.7

Livelihood capitals have a clear influence on livelihood development. As for the livelihood results, it has been pointed out in the analysis of the poor households that the ability of people to escape poverty depends especially on the access to livelihood capitals. This study aims to analyze the impacts of livelihood capital on poverty among mountain people who depend on forests through human capital, social capital, natural capital, physical capital and financial capital. This research employs the model of binary regression function. Independent variables x1, x2, …, xn are targets of livelihood strategy, vulnerability context, and livelihood capitals. These variables were selected to be included in the original model with dependent variable Y as poor and non-poor households. This study surveys households living in upland areas, near forests, and households of ethnic minorities. The results show that,out of the poor household rate, nearly 4% are newly-poor households or those falling back into poverty. Therefore, the government needs to pay more attention to this disadvantaged group and implements policies such as education and training policies, credit support policies, policies to support forest development, and payment for forest environmental services in the context of emerging countries like Vietnam.