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A Frequency Domain Equalization Algorithm for Fast Time-Varying Fading Channels
Le-Nam Tran,Een-Kee Hong,Huaping Liu 한국통신학회 2009 Journal of communications and networks Vol.11 No.5
Conventional frequency domain equalization (FDE) schemes were originally devised for quasi-static channels. Thus, such equalization schemes could suffer from significant performance degradation in fast-fading channels. This paper proposes a frequency domain equalization algorithm to mitigate the effect of fast time-varying fading. First, a mathematical expression is derived to quantify the total interference resulting from the time variation of the channel. Then, the proposed approach attempts to eliminate the effect of time-variations of the channel. This cancellation allows efficient use of the classical FDE structures in fast time-varying fading environments, although they are built upon the quasi-static channel model. Simulation results of bit-error-rate performance are provided to demonstrate the effectiveness of the proposed algorithm.
Le-Phuc Nguyen,Yen Thi Hai Pham,Phuong Thuy Ngo,Tri Van Tran,Loc Vinh Tran,Nam Thi Hoai Le,Luong Huu Nguyen,Tung Thanh Dang,Duc Anh Nguyen,Marco Wenzel,David Hartmann,Karsten Gloe,Jan J. Weigand,Klaus 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.5
Acid leaching and a two-step solvent extraction procedure were developed to produce high purity mixture of La and Ce from iron-rich spent FCC catalyst discharged from Dzung Quat refinery (Vietnam). Acid leaching of the spent catalyst with 2M HNO3 and a solid-to-liquid ratio of 1/3 at 80 oC in 1 h dissolved almost 90% of La while 12% of Al and 25% of Fe were transferred to the leachate. The extraction of RE metals and main impurities such as Al and Fe by a mixture of di-2-ethylhexyl phosphoric acid (D2EHPA) and tributyl phosphate (TBP) was investigated. Experiments showed that it was necessary to remove Fe before extracting RE and the optimum extraction conditions for a high recovery of RE while 0% of Al extraction were pH1, contact time=10min, and D2EHPA/TBP volume ratio= 4 : 1. At these conditions, the extraction yields of La(III) and Ce(III) were 72% and 89%, respectively. A two-step solvent extraction was developed to achieve a high purity of RE mixture, which included (1) the removal of impurity Fe by 25% (v/v) diisooctyl phosphinic acid (DiOPA) in n-octane for 140 min, (2) the extraction of rare earths by a mixture of di-2-ethylhexyl phosphoric acid (D2EHPA) and tributyl phosphate (TBP) in n-octane for 10 min without the need for adjusting the pH of the leaching solution.
On the Precoder Design for Block Diagonalized MIMO Broadcast Channels
Tran, Le-Nam,Juntti, Markku,Hong, Een-Kee IEEE 2012 IEEE communications letters Vol.16 No.8
<P>Block diagonalization (BD) is a linear precoding technique for MIMO broadcast channels such that it completely eliminates the multiuser interference. Consequently, the precoder of a user must lie in the null space of a matrix composing of other users' channel matrices. In this way, the problem of the precoder design is closely related to finding a basis of the null space of the matrix, which can be computed by, e.g., the singular value decomposition (SVD). Recently, a generalized channel inversion (GCI) method was introduced as a low-complexity design for BD. The GCI-based precoder design is also shown to be optimal for BD. However, since the GCI-based design relies on the pseudo-inverse of a matrix, there are many settings, to which this method is not applicable. In this letter, we first provide a connection between the SVD- and GCI-based designs using the results from linear algebra. Then, from this connection, we propose a precoder design that is devised for the cases where the GCI-based method cannot handle.</P>
A Frequency Domain Equalization Algorithm for Fast Time-Varying Fading Channels
Tran, Le-Nam,Hong, Een-Kee,Liu, Huaping The Korea Institute of Information and Commucation 2009 Journal of communications and networks Vol.11 No.5
Conventional frequency domain equalization (FDE) schemes were originally devised for quasi-static channels. Thus, such equalization schemes could suffer from significant performance degradation in fast-fading channels. This paper proposes a frequency domain equalization algorithm to mitigate the effect of fast time-varying fading. First, a mathematical expression is derived to quantify the total interference resulting from the time variation of the channel. Then, the proposed approach attempts to eliminate the effect of time-variations of the channel. This cancellation allows efficient use of the classical FDE structures in fast time-varying fading environments, although they are built upon the quasi-static channel model. Simulation results of bit-error-rate performance are provided to demonstrate the effectiveness of the proposed algorithm.
The Impact of Financial Integration on Monetary Policy Independence: The Case of Vietnam
TRAN, Ha Hong,LE, Thao Phan Thi Dieu,NGUYEN, Vinh Thi Hong,LE, Dao Thi Anh,TRINH, Nam Hoang Korea Distribution Science Association 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.2
Along with the trend of financial globalization, Vietnam has undergone a process of increasing financial integration. The great capital inflow poses a problem for the monetary policy's ability to follow a planned target during the changes in the global financial markets. This paper aims to examine the impact of financial integration on monetary policy independence in Vietnam and investigate the role of foreign exchange reserves on this relationship. The research borrows from Mundell-Fleming's Trilemma theory. The results show that increasing financial integration reduces the independence of monetary policy in the short term, and foreign exchange reserves have not shown an apparent role in Vietnam. In addition, increasing exchange rate stability has a negative impact on the independence of monetary policy, but it has an impact on growing market confidence and partly supporting the management process of monetary policy in the short term. Therefore, in the long run, Vietnam needs to allow exchange rate flexibility more, but there should not be sudden changes; the size of foreign exchange reserves should be strengthened to facilitate the implementation of an independent monetary policy with an obvious impact in the context of an increasing scale of international capital flows in the future.
Endemic Severe Fever with Thrombocytopenia Syndrome, Vietnam
Tran, Xuan Chuong,Yun, Yeojun,Van An, Le,Kim, So-Hee,Thao, Nguyen T. Phuong,Man, Phan Kim C.,Yoo, Jeong Rae,Heo, Sang Taek,Cho, Nam-Hyuk,Lee, Keun Hwa U.S. Department of Health and Human Services * Cen 2019 Emerging Infectious Diseases Vol.25 No.5
Tran, Duy Thanh,Hoa, Van Hien,Tuan, Le Huu,Kim, Nam Hoon,Lee, Joong Hee Elsevier 2018 Biosensors & bioelectronics Vol.119 No.-
<P><B>Abstract</B></P> <P>A three-dimensional hierarchical nanohybrid based on Cu-Au bimetallic nanocrystals integrated carbon nanotube arrays vertically grown on carbon spheres was successfully developed as an active platform for sensing application. Such nanohybrid can provide abundant active sites and act as an exceptional platform for immobilizing highly dense and well-dispersed carcinoembryonic antibody (anti-CEA) to sensitively detect CEA, an emerging biomarker of various cancer diseases. Due to the unique nanoarchitecture with altered electronic structure of Cu-Au bimetallic catalyst and enhanced interactions between components, such nanohybrid based biosensor demonstrated excellent electrochemical performance towards CEA detection with great sensitivity, wide linear detection range (0.025–25 ng/mL), very low limit of detection (0.5 pg/mL), and good selectivity. The results imply that this sensor has great potential to offer essential information for cancer diagnosis and management with great clinical importance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A 3D hierarchical Cu-Au nanocrystal integrated CNTs was grown on carbon sphere. </LI> <LI> The hybrid showed a wide linear detection range (0.025–25 ng/mL) and low detection limit (0.5 pg/mL). </LI> <LI> The hybrid showed good reproducibility and accurate detection of CEA in human serum. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Switching and Electrical Memory Effect in the Colossal Permittivity Material La2NiO4+δ
Le Van Hong,Tran Dang Thanh,Dao Nguyen Hoai Nam,,Nguyen Xuan Phuc 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
La2NiO4+δ ceramic samples were manufactured by using a solid state reaction method. The crystalline structural, magnetic and dielectric properties of the material were recorded and analyzed. A dielectric resonance, which is thought to be associated with the multiferroic behavior of the material, was observed at frequencies below 1 MHz. The I/V characteristics were easured on a capacitor-like structure, which exhibited resistance and capacitance switching when opposite voltage pulses of about 2.5 volts with a duration time of 500 ms were applied. The maximum ratios of the changes in the resistance and the capacitance were estimated to be of about 50 % and 35 % at room temperature, respectively. The electrical switching was reversible, with resistive states remaining for a rather long time. The observed capacitance switching and memory effects provide evidence for the presence of charge transfer and accumulation in the material.
Tran Thi Huyen,Ha Phuong Trang,Nguyen Thi-Ngan,Bui Dinh-Thanh,Le Pham Tan Quoc,Trinh Ngoc Nam 한국수산과학회 2023 Fisheries and Aquatic Sciences Vol.26 No.3
The thermolabile haemolysin (tlh) of Vibrio parahaemolyticus (Vptlh) from V. parahaemolyticus is a multiple-function enzyme, initially describes as a haemolytic factor activated by lecithin and phospholipase A2 enzymatic activity (Shinoda, 1991; Vazquez-Morado, 2021; Yanagase et al., 1970). Until now, the tlh structure has hypothesized including N-terminal and C-terminal domain, but what domain of the Vptlh structure does the haemolytic activity has not been refined yet. In this study, a 450-bp VpTLH nucleotide sequence of the entire Vptlh gene encoded the C-terminal domain cloned firstly to examine its responsibility in the activity of the Vptlh. The C-terminal domain fused with a 6-His-tag named the His-tag-VpC-terminal domain was expressed successfully in soluble form in the BL21 (DE3) PlysS cell. Remarkably, both expression and purification results confirmed a high agreement in the molecular weight of the His-tag-VpC-terminal domain was 47 kDa. This work showed the His-tag-VpC-terminal domain lysed the erythrocyte membranes in the blood agar and the phosphate buffered saline (0.9%) media without adding the lecithin substrate of the phospholipase enzyme. Haemolysis occurred at all tested diluted concentrations of His-tag-VpC-terminal domain (p < 0.05), providing evidence for the independent haemolytic activity of the His-tag-VpC-terminal domain. The content of 100 μg of the His-tag-VpC-terminal domain brought the highest haemolytic activity of 80% compared to that in the three remaining contents. Significantly, the His-tag-VpC-terminal domain demonstrated not to involve the phospholipase activity in Luria-Bertani agar supplemented with 1% (vol/vol) egg yolk emulsion. All results proved the vital responsibility of the His-tag-VpC-terminal domain in causing the haemolytic activity without the required activation by the phospholipase enzyme. Raw extracts of Phellinus igniarus and Phellinus pipi at 10–1 mg/mL inhibited the haemolytic activity of the His-tag-VpC-terminal domain from 67.7% to 87.42%, respectively. Hence applying the His-tag-VpC-terminal domain as a simple biological material to evaluate quickly potential derivatives against the Vptlh in vivo conditions will accessible and more advantageous than using the whole of the Vptlh.