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Search Results: 1 - 10 of 49288 matches for " Tuan Le Van "
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Full-Filling Subcarrier Power Allocation in OFDMA-Based Cognitive Radio Systems  [PDF]
Tuan Le Van, Hieu Dinh Chi, Kinh Nguyen Viet, Hieu Nguyen Thanh
Wireless Engineering and Technology (WET) , 2014, DOI: 10.4236/wet.2014.51002

When implementing an appropriate windowing, the interference from a Cognitive Radio (CR) system to licensed systems (primary users) will be significantly reduced. Consequently, power allocated to subcarriers can be increased, especially subcarriers having far spectral distance to primary user bands can be allocated full of its maximum possible power. In this paper, we propose a new class of sub-optimal subcarrier power allocation algorithm that significantly reduces complexity of OFDMA-based CR systems. Two sub-optimal proposals, called Pre-set Filling Range (PFR) and Maximum Filling Range (MFR) are studied. Investigations show that this new power allocating algorithm allows CR systems obtain high throughput while retaining low complexity.

Potential of Magnesium Chloride for Nutrient Rejection in Forward Osmosis  [PDF]
Yatnanta Padma Devia, Tsuyoshi Imai, Takaya Higuchi, Ariyo Kanno, Koichi Yamamoto, Masahiko Sekine, Tuan Van Le
Journal of Water Resource and Protection (JWARP) , 2015, DOI: 10.4236/jwarp.2015.79060
Abstract: Wastewater may contain high levels of the nutrients: nitrogen and phosphorus. Excessive release of nutrients to the environment can cause severe environmental problem such as eutrophication leading to algal blooms, oxygen deficiency, and fish kills. The forward osmosis (FO) could be a choice of treatment. FO process presents the results of using four kinds of variation in concentration of magnesium chloride (MgCl2) as draw solution and the two kinds of commercial membranes for nutrient rejection in the same cross flow velocity at 0.25 m/s and temperature at 25°C. Nutrients consisting of nitrogen (nitrite, nitrate, and ammonium) and phosphorus (phosphate) in feed solution were successfully rejected with an efficiency of mostly more 95%. The water flux in membrane HTI-NW achieved lower 7.55 - 9.61 L/m2·hr than in membrane HTI-ES that exceeds until 13.58 - 15.10 L/m2·hr. The reverse solute in membrane HTI-NW is seemly constant along all concentration of DS MgCl2 that the chloride diffusion is slightly higher than magnesium. In membrane HTI-ES, the reverse solute of chloride was almost three times than that of magnesium. The concentration of MgCl2 plays a significant role in rejecting nutrients by the Donnan’s potential and the diffusion constant in low and high concentration of DS, respectively.
Investigation the Dimensional Ratio Effect on the Resonant Properties of Piezoelectric Ceramic Disk  [PDF]
Vo Thanh Tung, Nguyen Trong Tinh, Truong Van Chuong, Nguyen Thi Mai H??ng, Dang Anh Tuan, Le Van Truyen
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.412202

In this work, the vibration characteristics of a piezoelectric ceramic disk with different dimensional ratio are studied by simulation method. Computational finite element modeling combined with the computational programs has allowed for the prediction of the effect, the change of diameter-to-thickness ratio on the resonant characteristics, the vibration modes as well as comparing the physic properties of piezoceramics. Three types of piezoelectric materials were chosen, piezoelectric materials (PZT) and Pb-free piezoelectric materials Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3(BZT-50BCT), BaTiO3 for research.

On the existence and exponential attractivity of a unique positive almost periodic solution to an impulsive hematopoiesis model with delays
Trinh Tuan Anh,Tran Van Nhung,Le Van Hien
Mathematics , 2015, DOI: 10.1007/s40306-015-0149-5
Abstract: In this paper, a generalized model of hematopoiesis with delays and impulses is considered. By employing the contraction mapping principle and a novel type of impulsive delay inequality, we prove the existence of a unique positive almost periodic solution of the model. It is also proved that, under the proposed conditions in this paper, the unique positive almost periodic solution is globally exponentially attractive. A numerical example is given to illustrate the effectiveness of the obtained results.
Periodic solutions and exponential stability for shunting inhibitory cellular neural networks with continuously distributed delays
Le Van Hien,Tran Thi Loan,Duong Anh Tuan
Electronic Journal of Differential Equations , 2008,
Abstract: In this paper, we consider a class of shunting inhibitory cellular neural networks with continuously distributed delays (SICNNs). The delays are unbounded and the activation function is not assumed to be bounded. Using the continuation theorems of coincidence degree theory, Lyapunov functional method, we obtain new sufficient conditions for the existence and local exponential stability of periodic solutions of (SICNNs). Numerical examples illustrated our results are given.
Neutrino decay and long base-line oscillation experiments
Vo Van Thuan,Nguyen Tuan Anh,Le Huu Thang
Physics , 2000,
Abstract: Considering neutrinos as time-like leptons one may estimate the three-body decay probability of muon neutrinos in long base-line accelerator experiments. In the extreme assumption of time-space symmetry the absolute value of the transcendent mass of a muon neutrino is equal to the rest mass of its bradyon partner which is, however, strongly suppressed in measurements using the weak interaction. This decay, neglecting small oscillations or other effects, leads to a strong dependence of the effect on the base-line distance. As a result, few hundred kilometre long baseline experiments might hardly see muon-like events. Total rates of electron-like events from three-body decay are calculated for K2K, MINOS and ICARUS. Shorter base-line experiments able to see clearly the effect of muon neutrino decay are very promissing component of long base-line projects.
Assessment of Radiation Dose Caused by Radioactive Gaseous Effluent Released from Nuclear Power Plant Ninh Thuan 1 under Scenario of Normal Working Conditions  [PDF]
Nguyen Tuan Khai, Do Xuan Anh, Le Dinh Cuong, Duong Duc Thang, Vuong Thu Bac, Nguyen Thi Thu Ha, Nguyen Quang Long, Trinh Van Giap, Nguyen Hao Quang
World Journal of Nuclear Science and Technology (WJNST) , 2015, DOI: 10.4236/wjnst.2015.53018
Abstract: Based on guides RG 1.109, RG 1.111 published by United States Nuclear Regulatory Commission (USNRC), our research concentrates in assessing radiation doses caused by radioactive substances released from the nuclear power plant (NPP) Ninh Thuan 1 under the scenario of normal operation using software package NRCDose72 provided by the USNRC. The database including the released radioactive nuclides, meteorology, terrain, population and agricultural production activities have been collected and processed to build the input data for the model calculation. The wind rose distribution obtained from the meteorological data in a five-year period from 2009-2013 showed that the radioactive nuclides released to environment spread in two main wind directions which are North East and South West. The X/Q (s/m3) and D/Q (s/m2) qualities which are, respectively, the ratio of activity concentration to release rate and that of deposition density of radioactive nuclides to release rate were calculated within an area of 80 km radius from the NPP site using XOQDOQ. Population doses were calculated using GASPAR. The XOQDOQ and GASPAR are two specific softwares in NRCDose72 package.
Structural Study on the Complex of Ortho-Ester Tetra Azophenylcalix[4]arene (TEAC) with Th(IV)
Tran Quang Hieu,Nguyen Ngoc Tuan,Le Ngoc Tu,Le Van Tan
International Journal of Chemistry , 2011, DOI: 10.5539/ijc.v3n2p97
Abstract: A new 1:1 complex between Ortho-Ester Tetra-Azophenylcalix[4]arene (TEAC) and Thorium(IV) was found in weakly acidic medium (pH =4-5), ?max = 520 nm, Beer’s law was obeyed in the range 2.5 ×10-6 – 2.5×10-5 mol.L-1 of Th(IV), the limit of detection was 1.0 × 10? 6 mol.L-1 and linear regression equation was determined to be: absorbance (A) = 0,248×C(10-5 mol.L-1) + 0,02 (R2 = 0,990, n =7). The FT-IR, HNMR, Raman spectroscopies were also used to provide the existence of this complex, and the Molecular Mechanics (MM) method in Arguslab software was applied to optimize the structure. The energy of the system, QEq charge, bond lengths and bond angles were also calculated by this program. Combining all data, the structure of complex TEAC - Th(IV) has been proposed.
Classification of Real Solvable Lie Algebras Whose Simply Connected Lie Groups Have Only Zero or Maximal Dimensional Coadjoint Orbits
Le Anh Vu,Ha Van Hieu,Nguyen Anh Tuan,Cao Tran Tu Hai,Nguyen Thi Mong Tuyen
Mathematics , 2015,
Abstract: In this paper we study a special subclass of real solvable Lie algebras having small dimensional or small codimensional derived ideal. It is well-known that the derived ideal of any Heisenberg Lie algebra is 1-dimensional and the derived ideal of the 4-dimensional real Diamond algebra is 1-codimensional. Moreover, all the coadjoint orbits of any Heisenberg Lie group as well as 4-dimensional real Diamond group are orbits of dimension zero or maximal dimension. In general, a (finite dimensional) real solvable Lie group is called an $MD$-group if its coadjoint orbits are zero-dimensional or maximal dimensional. The Lie algebra of an $MD$-group is called an $MD$-algebra and the class of all $MD$-algebras is called $MD$-class. Simulating the mentioned above characteristic of Heisenberg Lie algebras and 4-dimensional real Diamond algebra, we give a complete classification of $MD$-algebras having 1-dimensional or 1-codimensional derived ideals.
3D FE Analysis of Effect of Ground Subsidence and Piled Spacing on Ultimate Bearing Capacity of Piled Raft and Axial Force of Piles in Piled Raft  [PDF]
Tuan Van Tran, Makoto Kimura, Tirawat Boonyatee
Open Journal of Civil Engineering (OJCE) , 2012, DOI: 10.4236/ojce.2012.24027
Abstract: The effects of ground subsidence and piled spacing on axial force of piles in squared piled rafts were investigated using numerical analysis. Two cases of piled rafts in soft clay including case 1 (s = 2d) and case 2 (s = 4d) with s and d were piled spacing and piled diameter respectively were considered in this study. Undrained (without ground water pumping) and drained (with ground water pumping) conditions were applied in each case in order to evaluate variations of ultimate bearing capacity of piled raft and axial force of the piles in piled raft. The results showed that ultimate bearing capacity increased about 25% for undrained condition and about 32% for drained condition when piled spacing increased from 2d to 4d. In the same piled spacing, axial force of the piles increased about 9% for piled spacing of 2d and 7% for piled spacing of 4d when drained condition was applied. When piled spacing increased 2 times (2d to 4d), the axial force of piles increased about 7% for undrained condition and about 5% for drained condition.
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