Second Order Suboptimal Power Allocation for MIMO-OFDM Based Cognitive Radio Systems

( Tien Hoa Nguyen ),( Thanh Hieu Nguyen ),( Van Duc Nguyen ),( Duyen Trung Ha ),( Guilllaume Gelle ),( Hyunseung Choo ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.8

This paper proposes an efficient and low complexity power-loading algorithm for MIMO-OFDM downlink based cognitive radio system that maximizes the sum rate of single secondary user (SU) under constraints on the tolerable interference thresholds between secondary user and primary user`s frequency bands and the total transmission power. Our suboptimal algorithm is based on the 2<sup>nd</sup> order interference tracking and nulling mechanism to allocate transmission power of the subcarriers among SU`s scheme. The performance of our proposed suboptimal scheme is compared with the performance of the classical power loading algorithms, e.g., water filling, 1^st order interference tracking, nulling, and other suboptimal schemes. Numerical results show that our algorithm has low complexity but obtains a higher channel capacity than that of some previous suboptimal algorithms in some scenarios. We dedicate also that for a given interference threshold, the 2^nd order interference tracking mechanism has dynamic number of nulling position instead fixed number of nulling position.

An efficient location-based pilot assignment in Cell-Free Massive MIMO

Nguyen Tien Hoa,Phan Lam Tung,Van Chien Trinh 한국통신학회 2023 ICT Express Vol.9 No.5

Cell-free Massive multiple-input multiple-output can offer many degrees of freedom for the high data rate and coverage probability. This network topology is one of the cutting-edge technologies potentially applied for next-generation wireless communications. In the canonical structure, however, each access point needs to accurately estimate the channel state information for the signal detection in the uplink and the precoding design in the downlink. Due to the finite lengths of coherence intervals, pilot contamination is one of the bottlenecks, reducing the data throughput of each user. We propose an efficient pilot assignment scheme called location-based pilot assignment (LPA) to overcome this limitation. It takes full advantage of the number of orthogonal pilot signals into account. The proposed algorithm divides the coverage area into smaller areas based on the number of users, where each area uses a subset of the pilot signals. Numerical results show that the proposed pilot assignment, LPA, offers good spectral efficiency to every users in the network with a tolerable computational complexity.

GNU Radio와 USRP 플랫폼을 이용한 OFDM및 COFDM 구현에 관한 연구

디엔 뉴옌 반(Dien Nguyen Van),투안 뉴옌 안(Tuan Nguyen Anh),티엔 호아 뉴옌(Tien Hoa Nguyen),반 둑 뉴옌(Van Duc Nguyen),노승환(Soonghwan Ro) 한국정보기술학회 2014 한국정보기술학회논문지 Vol.12 No.2

SDR allows users to adjust a system with its flexibility and re-configurability for any frequency band and different modulation of various physical parameters by using programmable hardware and software. In this paper, we implement an Orthogonal Frequency Division Multiplexing (OFDM) system with and without channel coding blocks based on Software-Defined Radio. Quadrature amplitude modulation QAM-16, convolutional encoder with block interleaving algorithm and hard decision Viterbi decoder are deployed for the implementation. Different scenarios have been implemented in real-time wireless transmission in order to evaluate the Packet Failure Rate (PFR). The results show that the introduction of channel coding reduces the PFR of transmitted data signals.

Isolation and Cytotoxic Potency of Endophytic Fungi Associated with Dysosma difformis, a Study for the Novel Resources of Podophyllotoxin

Hoa Thi Tran,Giang Thu Nguyen,Hong Ha Thi Nguyen,Huyen Thi Tran,Quang Hong Tran,Quang Ho Tran,Ngoc Thi Ninh,Phat Tien Do,Ha Hoang Chu,Ngoc Bich Pham 한국균학회 2022 Mycobiology Vol.50 No.5

Endophytic fungi are promising sources for the production of podophyllotoxin-an important anticancer compound, replacing depleted medical plants. In this study, the endophytes asso- ciated with Dysosma difformis-an ethnomedicinal plant species were isolated to explore novel sources of podophyllotoxin. Fifty-three endophytic fungi were isolated and identified by morphological observation and ITS-based rDNA sequencing, assigning them to 27 genera in 3 divisions. Fusarium was found the most prevalent genus with a colonization frequency of 11.11%, followed by Trametes (9.26%) and Penicillium (7.41%). Phylogenetic trees were constructed for the endophytic fungi community in two collection sites, Ha Giang and Lai Chau, revealing the adaptation of the species to the specific tissues and habitats. Cytotoxic activity of endophytic fungal extracts was investigated on cancer cell lines such as SK-LU-1, HL-60, and HepG2, demonstrating strong anti-cancer activity of six isolates belonging to Penicillium, Trametes, Purpureocillium, Aspergillus, and Ganoderma with IC50 value of lower than 10 mg/mL. The presence of podophyllotoxin was indicated in Penicillium, Trametes, Aspergillus and for the first time in Purpureocillium and Ganoderma via high-performance liquid chromatography, which implied them as a potential source of this anti- cancer compound.

Multiple-degrees-of-freedom dielectric elastomer actuators for soft printable hexapod robot

Nguyen, Canh Toan,Phung, Hoa,Nguyen, Tien Dat,Jung, Hosang,Choi, Hyouk Ryeol Elsevier 2017 Sensors and actuators. A Physical Vol.267 No.-

<P><B>Abstract</B></P> <P>In this paper, we present the development of a printable hexapod walking robot driven by the multiple-degrees-of-freedom (multi-DOF) soft actuators based on dielectric elastomer. The multi-DOF soft actuators are employed to provide versatile movements including two translations and single rotation within a simple structure based on the antagonistic configuration of two elastomer membranes. The soft actuators demonstrate the potential of being used as a multifunctional joint to actuate the robot leg’s motion which biologically mimics the animal’s walking posture. The actuator performances are enhanced by developing the novel mixed silicone compound, Wacker P7670 and Nusil CF2-2186, and applying the optimized prestrain to the silicone-based actuator membranes. A theoretically and experimentally comprehensive study was carried out to investigate the soft actuators performances in terms of linear displacements, deflection angle, output force, torque, dynamic response, and load carrying capability. We successfully demonstrated the robot’s locomotion on the flat rigid surfaces with the forward and backward walking movements at an average speed of 3cm/s (about 12 body-lengths/min) using the alternating tripod walking gait of insects.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The application of the multiple-degrees-of-freedom (multi-DOF) soft actuators based on dielectric elastomer in driving the locomotion of a hexapod walking robot is presented in this paper. </LI> <LI> The actuator performances are significantly enhanced by replacing the synthetic elastomer with the novel mixed silicone compound, Wacker P7670 and Nusil CF2-2186, and applying the optimized prestrain to the silicone-based actuator membranes. </LI> <LI> The hexapod robot’s fabrication process is implemented using 3D printing technology which provides the lightweight, scalable, and easy-to-manufacture characteristic of the robot. </LI> <LI> A theoretically and experimentally comprehensive study is carried out to investigate the soft actuators performances in terms of linear displacements, deflection angle, output force, torque, dynamic response, and load carrying capability. </LI> <LI> The hexapod robot’s locomotion on flat rigid surfaces with the forward and backward walking movements at an average speed of 3cm/s (about 12 body-lengths/min) using the alternating tripod walking gait of insects is successfully demonstrated. </LI> </UL> </P>

Decentralized Dynamic Sub-Carrier Assignment for OFDMA-Based Adhoc and Cellular Networks

NGUYEN, Van-Duc,HAAS, Harald,KYAMAKYA, Kyandoghere,CHEDJOU, Jean-Chamerlain,NGUYEN, Tien-Hoa,YOON, Seokho,CHOO, Hyunseung The Institute of Electronics, Information and Comm 2009 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.92 No.12

<P>In this paper, a novel decentralised dynamic sub-carrier assignment (DSA) algorithm for orthogonal frequency division multiple access (OFDMA)-based adhoc and cellular networks operating in time division duplexing (TDD) mode is proposed to solve the hidden and exposed node problem in media access control (MAC). This method reduces the co-channel interference (CCI), and thus increases the overall throughput of the network. Reduced CCI and increased throughput can be achieved, if time and frequency selectivity of the multi-path fading channel and the channel reciprocity offered by the TDD are fully exploited. The time and frequency selectivity of the channel are usually the main problem in mobile communication. However, in the context of channel assignment for OFDMA-based networks in TDD mode, the time and frequency selectivity of the channel are the key to reduce the interference. In the proposed channel assignment mechanism, several clusters of sub-carriers are assigned for data transmission between a transmitter and a receiver only if the corresponding channels of those sub-carriers linking this transmitter to potential victim receivers are deeply faded. In addition, the proposed algorithm works in a fully decentralised fashion and, therefore, it is able to effectively support ad hoc and multihop communication as well as network self-organisation. Numerical results show that the throughput obtained by the proposed approach for a given quality of service is higher than those of the conventional methods in any precondition of adhoc geographic scenario.</P>

Assessment of Left Ventricular Function and Regional Wall Motion by 256-Slice Dual-Source Coronary CT Angiography: A Comparison With 2D Transthoracic Echocardiography

Le Thi Thuy Lien,Nguyen Khoi Viet,Hoang Van Hoa,Phung Bao Ngoc,Nguyen Ngoc Trang,Vu Thi Kim Thoa,Nguyen Cong Tien,Phan Anh Phuong,Pham Minh Thong,Vu Dang Luu 아시아심장혈관영상의학회 2022 Cardiovascular Imaging Asia Vol.6 No.2

Objective: To compare left ventricular (LV) function, ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume (ESV), and regional wall motion analyzed in 256-slice dualsource coronary CT angiography (DSCT) with 2D transthoracic echocardiography (TTE). Materials and Methods: One hundred twelve patients suspected of coronary artery disease underwent DSCT and 2D-TTE within one week for LVEF, EDV, and ESV. The correlation between DSCT and 2D-TTE measurements was analyzed through linear regression and Bland- Altman analysis. Regional wall motion was visually scored with a 3-point scale (1, normal; 2, hypokinesia; 3, dysphagia, akinesia). Results: Average LVEF at 66.45%±1.27% (range 23%–85%) as determined on DSCT compared with 66.09%±1.01% (range 25%–84%) on 2D-TTE. LVEF exhibited a good correlation between DSCT and 2D-TTE (r=0.715; p<0.001). Good correlations between DSCT and 2D-TTE were demonstrated for LVEDV (r=0.732; p<0.001) and LVESV (r=0.841; p<0.001). Mean differences (±SD) of 1.78±24.10 mL (p<0.05) and 0.77±13.70 mL (p<0.05) were observed between DSCT and 2D-TTE for LVEDV and LVESV, respectively. LVEF was slightly overestimated with DSCT (0.52%±9.59%; p<0.05). Although the LVEF values calculated by DSCT and 2D-TTE were similar, EDV and ESV from DSCT were statistically higher than those from 2D-TTE (p<0.05). Agreement between DSCT and 2D-TTE in regional wall motion was 96.4%, κ=0.840. Conclusion: DSCT can provide comparable results to those using 2D-TTE for LV function (EF, EDV, and ESV) and regional wall motion assessment in a heterogeneous population.

LoRa 망에서 이중 홉 디코드-포워드 릴레이의 성능평가

노승환(Soong Hwan Ro),티엔 뉴옌 호아(Tien Nguyen Hoa) 한국통신학회 2022 한국통신학회 학술대회논문집 Vol.2022 No.2

이 연구에서는 LoRa 네트워크에서 이중 홉 디코딩-포워드의 성능 평가에 대한 성능평가를 하였다. 특히, 에지-ED(Edge-End Device)의 커버리지 확률(Pcov)과 스펙트럼 효율이 폐쇄형 표현식으로 계산되었다. 제안된 프레임워크를 기반으로 스펙트럼 효율과 커버리지 확률을 최대화하기 위한 에지-ED의 전송 전력과 함께 최적화하기 위한 릴레이 위치를 제안하였다.

Design, synthesis and evaluation of novel <i>N</i>-hydroxybenzamides/<i>N</i>-hydroxypropenamides incorporating quinazolin-4(3<i>H</i>)-ones as histone deacetylase inhibitors and antitumor agents

Hieu, Doan Thanh,Anh, Duong Tien,Tuan, Nguyen Minh,Hai, Pham-The,Huong, Le-Thi-Thu,Kim, Jisung,Kang, Jong Soon,Vu, Tran Khac,Dung, Phan Thi Phuong,Han, Sang-Bae,Nam, Nguyen-Hai,Hoa, Nguyen-Dang Elsevier 2018 Bioorganic chemistry Vol.76 No.-

<P><B>Abstract</B></P> <P>In our search for novel small molecules targeting histone deacetylases, we have designed and synthesized several series of novel <I>N</I>-hydroxybenzamides/<I>N</I>-hydroxypropenamides incorporating quinazolin-4(3<I>H</I>)-ones (<B>4a-h</B>, <B>8a-d, 10a-d)</B>. Biological evaluation showed that these hydroxamic acids were generally cytotoxic against three human cancer cell lines (SW620, colon; <I>PC</I>-3, prostate; NCI-H23, lung cancer). It was found that the <I>N</I>-hydroxypropenamides (<B>10a-d)</B> were the most potent, both in term of HDAC inhibition and cytotoxicity. Several compounds, e.g. <B>4e</B>, <B>8b-c</B>, and <B>10a-c</B>, displayed up to 4-fold more potent than SAHA (suberoylanilide hydroxamic acid, vorinostat) in term of cytotoxicity. These compounds also comparably inhibited HDACs with IC<SUB>50</SUB> values in sub-micromolar range. Docking experiments on HDAC2 isozyme revealed some important features contributing to the inhibitory activity of synthesized compounds, especially for propenamide analogues. Importantly, the free binding energy computed was found to have high quantitative correlation (<I>R</I> <SUP>2</SUP> ∼ 95%) with experimental results.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel quinazolin-4(3H)-one-based <I>N</I>-hydroxybenzamides/<I>N</I>-hydroxypropenamides were synthesized. </LI> <LI> The <I>N</I>-hydroxybenzamides/<I>N</I>-hydroxypropenamides exhibited potent HDAC inhibition. </LI> <LI> The <I>N</I>-hydroxybenzamides/<I>N</I>-hydroxypropenamides exhibited good cytotoxicity. </LI> <LI> Docking studies and ADMET estimation were carried out. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Two series of novel, simple <I>N</I>-hydroxybenzamides/<I>N</I>-hydroxypropenamides incorporating quinolin-4(3H)-one (<B>4a-h</B>, <B>8a-d, 10a-d</B>) were designed and synthesized. Biological evaluation showed that these benzamides/propenamides potently inhibited HDAC with IC<SUB>50</SUB> values in sub-micromolar range. A number of compounds also exhibited cytotoxicity up to 4-fold more potent than SAHA, a positive control.</P> <P>[DISPLAY OMISSION]</P>

The Effect of Technology Spillover on Business Efficiency: A Case Study in Vietnam

Mai Lan PHUNG,Vu Hiep HOANG,Thi Thanh Huyen NGUYEN,Thi Thanh Van PHAM,Viet Tien TRAN,Van Hoa HOANG 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.5

The main objective of this study is to examine the interactive effect of technology spillover channels on business efficiency within the case study of manufacturing industry of Vietnam during the period from 2012 to 2018. The research model was developed with business efficiency as dependent variable and the relevant factors affecting the technology spillover capacity as independent variables. With a sample of 2,776 cross-sectional enterprises, panel data analysis approach was adopted to estimate the impact of technology spillover issue. Different spillover channels were also included in the analysis to enhance the empirical result. The study reveals that technology spillovers positively influence manufacturing business efficiency, in which horizontal spillover channel produces negative impact and vertical spillover channel, creates positive impact. Several factors that negatively affect the technology spillover capacity of businesses could be mentioned such as limited skills and experiences of workers, methods of implementing R&D, and the existence of FDI enterprises. Meanwhile, the rise of other factors related to joint-venture activities can help to increase the technology spillover capacity of businesses. In addition, skill and experience transfer makes a partial impact since this variable only positively affect the vertical spillover channel and provide no evidence of impact regarding horizontal spillover channel model.