Nguyen Bao

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Research and Design of an X-Band UHF Power Amplifier

Journal of the Russian Universities. Radioelectronics

Introduction. A method for designing power amplifiers for use in the transmitting channels of X-b... more Introduction. A method for designing power amplifiers for use in the transmitting channels of X-band transceiver modules is investigated. The design process was aimed at optimizing the relationship between the basic amplifier characteristics, including the operating frequency band, output power level, output linearity, high harmonics suppression, etc. Aim. Investigation of a method for designing an X-band UHF power amplifier, which is capable of optimizing the relationship between its main characteristics. Materials and methods. Theoretical calculations were combined with experimental studies into the design of a UHF power amplifier. The stages of the design process are described in detail, including major ideas, principal circuits, and strip circuits. Evaluations were conducted using the Keysight ADS high frequency circuit simulation tool. Results. A method for designing X-band UHF power amplifiers on the basis of a close combination of theory, simulation, and experimental adjus...

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Why is African Trade so Limited?

VNU JOURNAL OF ECONOMICS AND BUSINESS

This paper studies the determinants of the low participation of African countries to internationa... more This paper studies the determinants of the low participation of African countries to international trade. We point out the under-trading status of Africa, then we estimate a gravity equation in order to identify the determinants of trade in general. As we characterize the level of these explanatory variables in Africa as compared to the rest of the world, we identify the main variables behind the low participation of Africa to trade in general. Usual gravity factors play an important role, but we show that non-tariff measures and the quality of infrastructure and institutions are important. Import duties does not significantly impede African exports. We test the impact on African countries’ exports of a counterfactual scenario where infrastructure and institution variables in African countries are changed to the world average and conclude that the most important leverage effect to be expected from investment in infrastructure would be from mobile cellular telephone subscriptions. If...

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Optimizing Basement Construction Methods

International Journal of Research in Vocational Studies (IJRVOCAS), 2021

The underground part of SSG TOWER includes 4 basements, 4 basements at a height of -13.2m. Combin... more The underground part of SSG TOWER includes 4 basements, 4 basements at a height of -13.2m. Combined with the construction of 3m deep foundation, therefore, the minimum excavation depth is required to -16.2m. Due to the construction work in residential area, relatively ground, with large excavation depth and geology of the interaction area (clay layer up to 30m), the options for using diaphragm wall with drilled piles Small area, Laser piles or solier piles to make retaining walls during construction do not have that feature, so the author chooses the option of using reinforced concrete barrette walls for retaining walls during construction and as tunnel walls for this project. The semi-topdown construction method was chosen to ensure safety during construction because the excavation depth of the work is quite large and the geology of this area is quite weak. This measure completely solves the strut system because using the floor structure of the building to support this system has h...

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Study on Vietnam traffic accident situation via data of health sector

Journal of the Eastern Asia Society for Transportation Studies, 2011

The traffic accident database is the sole important source outside of traffic police that could h... more The traffic accident database is the sole important source outside of traffic police that could help effectively to understand the traffic safety situation. For right usage, this study has clarified its special feature such as better liability, difference of purpose, object and standard. The data of 2009 confirms the efforts to ensure the traffic safety so that the fatalities are under control, but the seriousness of traffic accident is very high. Especially, the study has proposed a methodology to find out the Correction Factor of the number of accident sufferer. Based on the corrected value, it could reconfirm that the number of injured published by traffic police is unrealistically low. It shows the underreporting level is about 63 times. It proved that the corrected data are quite in concordance with a rule from the Vietnamese Injury Pyramid that for each fatality, there are 58 injuries at difference seriousness.

Comparative Study on Vietnam Traffic Safety: The Existence of a 5-Years Cycle in Road Traffic Accidents Development

Journal of the Eastern Asia Society for Transportation Studies, 2010

This study has the aim to research on global tendency of road traffic safety development in the w... more This study has the aim to research on global tendency of road traffic safety development in the whole history of about 2 decades of Vietnam. For the great deficiency in the related traffic accidents data, it carries out a comparative analysis based on important relevant official legal documents which had great impact on the social life. Together with the more and more serious development of traffic accidents, it seems that there exists a hidden "5- years rule," by which for each 5 years, the traffic accidents become so critical that the authorities should re-intensify their efforts at a higher level in an attempt to control this big social problem, while the announced main approaches for traffic safety of Vietnam as “All people” and “Comprehensiveness” are basically not different with international well-known “4-E (Engineering, Enforcement, Education and Emergency)” and “Traffic Safety Stakeholders”.

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A hybrid spectrum sharing approach in cognitive radio networks

2014 International Conference on Computing, Management and Telecommunications (ComManTel), 2014

In this paper, we propose a hybrid spectrum sharing approach in cognitive radio networks. If the ... more In this paper, we propose a hybrid spectrum sharing approach in cognitive radio networks. If the primary network satisfies the required quality of service (QoS), an underlay approach can be applied for the secondary network. Otherwise, the secondary network must help primary network obtain the QoS and hence it must operate on overlay mode. We also derive the closed-formed expressions of the outage probability for the secondary network over Rayleigh fading channels. Monte-Carlo simulations are then presented to verify our derivations.

Vận dụng cặp phạm trù nguyên nhân – kết quả phân tích vấn đề ô nhiễm môi trường ở Việt Nam

SCIENTIFIC JOURNAL OF TAN TRAO UNIVERSITY, 2020

Bảo vệ môi trường là một vấn đề trước mắt và có ý nghĩa to lớn cho sự phát triển bền vững và tươn... more Bảo vệ môi trường là một vấn đề trước mắt và có ý nghĩa to lớn cho sự phát triển bền vững và tương lai của nhân loại. Bài báo dựa trên mối quan hệ “nguyên nhân - kết quả”, tập trung vào phân tích các nguyên nhân gây suy thoái môi trường và chỉ ra các vấn đề tai hại do ô nhiễm môi trường. Kết quả nghiên cứu cho thấy rằng các yếu tố tự nhiên, sự thiếu ý thức của con người trong sản xuất và sinh hoạt, những tàn tích từ chiến tranh để lại chính những nguyên nhân chủ yếu gây ra ô nhiễm môi trường. Và theo quy luật, môi trường ô nhiễm sẽ tác động trở lại con người, chúng ta sẽ phải đứng trước các nguy cơ về sức khỏe, sự thiếu hụt tài nguyên, thiệt hại nặng về kinh tế, đất nước chậm phát triển. Từ đó, các giải pháp của vấn đề gây ra ô nhiễm môi trường có thể được đưa ra và thảo luận.

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Using DIRHB package to calculate the properties of some nuclei

Science and Technology Development Journal - Natural Sciences, 2020

In this work, the relativistic Hartree-Bogoliubov method is studied for calculating of nuclear pr... more In this work, the relativistic Hartree-Bogoliubov method is studied for calculating of nuclear properties such as binding energy per nucleon, charge radii, and single-particle energies of proton and neutron for some nuclei like O16, Ca40, Sn132 and Pb208. This method is the relativistic case of the Hartree-Fock-Bogoliubov method, which is a generalization of the Hartree-Fock method, and the method includes short-range correlations such as pairing force. In addition, the energy functional DD-ME2 is used to describe the effective interactions in equations of the relativistic Hartree-Bogoliubov method. The DIRHB package, which was written in Fortran, is utilized to calculate and get the results. The results are compared with experimental ones, except the single-particle energies of Ca40 due to the lack of data. The comparisons show well agreements between the calculation results and the experimental values of binding energy per nucleon as well as charge radii, for parameters of the DD-...

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Copulas and Markov processes

Illinois Journal of Mathematics, 1992

... Titre du document / Document title. Copulas and Markov processes. Auteur(s) / Author(s). DARS... more

Chemical constituents of Oldenlandia pinifolia and their antiproliferative activities

Natural product research, Jan 6, 2017

This study describes the chemical constituents of Oldenlandia pinifolia (Wall. Ex G. Don) Kuntze ... more This study describes the chemical constituents of Oldenlandia pinifolia (Wall. Ex G. Don) Kuntze (synonym Hedyotis pinifolia Wall. Ex G. Don) and discusses their anti-proliferative activities. Thirteen compounds were isolated from the n-hexane, ethyl acetate and n-butanol extracts of whole plants O. pinifolia by chromatography method. Their structures were elucidated using MS and NMR analysis and compared with reported data. They are three anthraquinones, a carotenoid, two triterpenes, four iridoid glycosides and three flavonoid glycosides. Among them, 2-methyl-1,4,6-trihydroxy-anthraquinone is a new one, and three compounds were found for the first time in this genus. MTT assay resulted that the n-butanol extract and four isolated compounds inhibited the proliferation of chronic myelogenous leukaemia cells. The results from Hoechst 33343 staining and caspase 3-inducing exhibited that those four tested compounds induced apoptosis and activated caspase 3 (p < 0.05). One of them, i...

Properties and asymptotic behavior of solutions of some problems of one-dimensional motion of a viscous barotropic gas

Mathematical Notes, 1994

The qualitative theory of quasilinear equations of motion of a viscous compressible gas attracts ... more

Towards highly scalable pregel-based graph processing platform with x10

Proceedings of the 22nd International Conference on World Wide Web, 2013

Many practical computing problems concern large graph. Standard problems include web graph analys... more Many practical computing problems concern large graph. Standard problems include web graph analysis and social networks analysis like Facebook, Twitter. The scale of these graph poses challenge to their efficient processing. To efficiently process large-scale graph, we create X-Pregel, a graph processing system based on Google's Computing Pregel model [1], by using the state-of-the-art PGAS programming language X10. We do not purely implement Google Pregel by using X10 language, but we also introduce two new features that do not exists in the original model to optimize the performance : (1) an optimization to reduce the number of messages which is exchanged among workers, (2) a dynamic re-partitioning scheme that effectively reassign vertices to different workers during the computation. Our performance evaluation demonstrates that our optimization method of sending messages achieves up to 200% speed up on Pagerank by reducing the network I/O to 10 times in comparison with the default method of sending messages when processing SCALE20 Kronecker graph [2](vertices = 1,048,576, edges = 33,554,432). It also demonstrates that our system processes large graph faster than prior implementation of Pregel such as GPS [3](stands for graph processing system) and Giraph[4].

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Pedogenic Processes and Chemical Properties of Acid Sulfate Soils in the Northwestern Area of Mekong Delta, Vietnam

한국토양비료학회 학술발표회 초록집, Jun 1, 2014

On the stability of the characterization of double-composed random variables

Acta Mathematica Vietnamica, 1995

On the characterizations and their stabilities of the composed random variables by constant-regression

Multihop Decode-and-Forward Relay Networks: Secrecy Analysis and Relay Position Optimization

REV Journal on Electronics and Communications, 2012

Relay communication has advantages over direct transmission in terms of secrecy capacity. In this... more Relay communication has advantages over direct transmission in terms of secrecy capacity. In this paper, the performance of secrecy, offered by multihop decode-and-forward relaying, is investigated and compared to its counterpart in direct transmission. Three key performance measures are derived over Rayleigh fading channels: probability of non-zero secrecy capacity, secure outage probability and secrecy capacity, which are valid for an arbitrary number of hops. Based on the tractable form of the probability of non-zero secrecy capacity, the optimization problem of trusty relay replacement is also studied. Numerical results indicate that a proper relay replacement can increase the network security without extra network resources. The correctness of analytical results is confirmed by using a MATLAB-based independent simulation model.

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Tissue culture approaches for the selection of aluminium-tolerantCitrusspecies in the Mekong Delta of Vietnam

The Journal of Horticultural Science and Biotechnology, 2004

Summary The selection of aluminium-tolerant lines of two orange cultivars Citrus aurantium ‘Amarg... more Summary The selection of aluminium-tolerant lines of two orange cultivars Citrus aurantium ‘Amargo’ and C. sinensis ‘Pineapple’ was conducted using three types of explant: calli, embryos and plantlets. It was possible to select Al-tolerant callus lines of both cultivars using two different techniques using stagnant or shaken liquid medium. Two types of Al-tolerant calli were detected: surviving and recovered calli. At the embryo level, among three Al-tolerant lines of cv. ‘Amargo’, two lines tolerated Al-levels between 400–1000 μM, while one line died. Among three tested lines of cv. ‘Pineapple’ one line tolerated 400 μM Al, whereas the other two died. Results also showed differences in Al-tolerance at the callus and embryo levels. Testing of the selected lines of both cultivars at the plantlet level indicated that the two selected lines of ‘Amargo’, and the one line of ‘Pineapple’ were stable and tolerant at Al concentrations between 400–1000 μM.

A Study on the Status of Sediment Surrounding Lam Thao Fertilizers and Chemicals Joint-Stock Company

Performance Analysis for Selection Decode-and-Forward Relay Networks with Differential Modulation over Rayleigh Fading Channels

This paper offers performance analysis of selection decode and forward (DF) networks with differe... more This paper offers performance analysis of selection decode and forward (DF) networks with differential modulation/demodulation for an arbitrary number of relays in independent but not identically distributed Rayleigh fading channels. We have shown that the selection DF protocol with differential modulation can achieve full diversity in both independent identically distributed (i.i.d.) and independent but not identically distributed (i.n.d.) Rayleigh fading channels, and the performance loss due to using non-coherent detection is not substantial. Furthermore, we study the impact of combining techniques on the performance of the system by comparing a system that uses selection combining (SC) to one that uses maximum ratio combining (MRC). Simulations are performed and show that they match exactly with analytic ones in high SNR regime.

Vo Nguyen Quoc Bao, Nguyen Linh Trung, and Mérouane Debbah, “Relay Selection Scheme for Dual-hop Networks under Security Constraints with Multiple Eavesdroppers", IEEE Transaction on Wireless Communications, 10/2013, accepted

IEEE Transactions on Wireless Communications

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