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Hou Yanren Li Kaitai,

计算数学 , 2003,
Abstract: By taking example of the unsteady Navier-Stokes equation, a kind of postprocessing method for the standard Galerkin approximation, which is called one step Newton method for simplicity, is proposed by applying the idea of Newton iteration to unsteady problems. The analysis results show that this method can greatly improve the accuracy of the standard Galerkin approximation and the numerical experiments also indicate that it is a high performance method.
One-step alternating direction implicit FDTD algorithm
Liu Shao-Bin,Liu San-Qiu,

中国物理 B , 2004,
Abstract: In this paper, a novel unconditionally stable alternating direction implicit finite-different time-domain method (ADI-FDTD) called the one-step ADI-FDTD method is presented, where the calculation for one discrete time step is performed using only one procedure, but not the original two sub-updating procedures. Consequently, the proposed one-step ADI-FDTD methods have consumed less computer memory and computation resources and have been faster than the conventional ADI-FDTD methods. We analytically and numerically verified that the new algorithm is unconditionally stable and free from the Courant condition.
A Two-Step TOA Estimation Method for UWB Based Wireless Sensor Networks

WU Shao-Hua,ZHANG Nai-Tong,

软件学报 , 2007,
Abstract: In order to design a low-calculation and high-precision TOA (time of arrival) estimation algorithm for UWB (ultra wideband) based wireless sensor network (WSN), a two-step TOA estimation method which jointly employs energy-detection (ED) and match-filtering (MF) is proposed in this paper. Based on analyzing the principles of the two-step method, it is pointed out that the success rate of DP (direct path) block detection in the first step and the setting of MF-threshold-factor in the second step are the key issues that affect the performance of the method. Algorithm selection of the first step and setting of the energy integration interval, which are the two factors that affect the success rate of DP block detection, are discussed through simulations. The idea of DMR (DP to minimum energy sample ratio) based MF-threshold-factor selection is proposed, and the mathematical model of the relationship between DMRs and the optimal MF-threshold-factors are built. Results show that the proposed two-step method greatly outperforms the one-step energy-detection based non-coherent method, while largely decreases the computational complexity compared to the one-step match-filtering based coherent method, so that the two-step method is more appropriate for application to sensor nodes which need to be designed with low complexity and low power consumption.
One step preparation of AlON ceramics by aluminothermic reduction and nitridation

- , 2015,
Abstract: 以微米Al粉和纳米γ-Al????2??O????3??为原料,采用铝热还原氮化法在流动N????2??中进行了AlON陶瓷的一步反应烧结制备.结果表明,合成纯相AlON的最佳Al含量为11 wt%.在1650℃以下Al先和N????2??反应生成AlN,AlN再在1650℃以上与Al????2??O????3??通过固相反应生成AlON,并在1700℃制备了纯相的AlON,但此时块体中的AlON颗粒几乎没有出现烧结,在更高温度下才合并长大形成AlON陶瓷.煅烧温度较低时(≤1700℃),样品表面和内部的物相组成基本相同,但在高温下(≥1750℃)内部仍为纯相AlON而表层却被过度氮化出现AlN杂相.最后用热力学对该现象进行了分析.
AlON ceramics were prepared by one-step aluminothermic reduction and nitridation method using micron-sized Al and nanoscale γ-Al????2??O????3?? powders as the starting materials. The results showed the optimal Al content for single-phase AlON preparation was 11 wt%. At the temperature below 1650℃, AlN was primarily produced by direct Al nitridation. Then AlN reacted with Al????2??O????3?? forming AlON at above 1650℃. Single-phase AlON was synthesized at 1700℃, but the sintering among AlON particles was barely observed, which only occurred at higher temperature. For samples calcined at low temperature (≤1700℃), the phase compositions of both interiors and exteriors were basically the same. However, the interiors maintained pure AlON while the exteriors were over nitrided and AlN impurity appeared at high temperature (≥1750℃). Such phenomenon was analyzed with emphasis of thermodynamics
Damage Removal in GaN-LEDs by Two-Step Etching Technology

Song Yingping,Guo Xi,Ai Weiwei,Zhou Yueping,Shen Guangdi,

半导体学报 , 2006,
Abstract: A two-step etching technology is used and the optimized etching parameter is found by experiment to remove etching damage in GaN-LEDs.The PL intensity of the sample etched by ICP with a power of 750W is decreased a little.The thickness of the etch damage layer is less than 25nm.The forward turn-on voltage and reverse leakage current of the LED that was etched by the two-step etching technology are reduced noticeably.The EL intensity is increased,indicating that the leakage current and the rate of nonradiative recombination both decreased.The optical efficiency and device reliability are also improved.
Improvement in Anti-oxidation of Two-step Dipping Graphite with Different Solutions

DENG Ya-li,ZHANG Xiao-meng,WEI Lian-qi,YE Shu-feng,CHEN Yun-fa,

过程工程学报 , 2012,
Abstract: A two-step dipping method was used to treat graphite with two solutions for improving its oxidation resistance.One dipping solution was mainly composed of magnesium chloride,aluminum hydroxide,phosphoric acid and another one borax,sodium tripolyphosphate,titanium dioxide.The composition and structure and mass change of the dipped graphite were analyzed by SEM,TG-DTA and XRD.The results showed that the mass loss of dipped graphite sample was less than 10% in air at 1150℃ for 1 h and the oxidation resistance was increased by 60% compared with untreated blank sample.The treated sample had flat surface,compact structure and clear edge after high temperature treatment,which was different from blank sample.The two kinds of dipping solution in high temperature formed glass polymer which was attached on the surface and pores of graphite,playing the role of oxidation resistance.
One-step Estimation for Varying Coefficient Models with Unknown Functions of Different Degrees of Smoothness

Tang Qingguo,Wang Jinde,

数学物理学报(A辑) , 2008,
Abstract: An one-step estimation method is proposed to estimate all the unknown functions in varying coefficient models, of which the degrees of smoothness may be different from each other. In one-step estimation approach, the local estimators of all the unknown functions and their derivatives can be obtained by only one minimization operation. The asymptotic properties of the estimators, including bias, variance and asymptotic distribution, are derived. It is shown that all the one-step estimators achieve the optimal convergence rates.
Reduction of proximity effect in fabricating nanometer-spaced nanopillars by two-step exposure

Zhang Yang,Zhang Renping,Han Weihu,Liu Jian,Yang Xiang,Wang Ying,Li Chian Chiu,Yang Fuhua,

半导体学报 , 2009,
Abstract: A two-step exposure method to effectively reduce the proximity effect in fabricating nanometer-spaced nanopillars is presented. In this method, nanopillar patterns on poly-methylmethacrylate (PMMA) were partly cross-linked in the first-step exposure. After development, PMMA between nanopillar patterns was removed, and hence the proximity effect would not take place there in the subsequent exposure. In the second-step exposure, PMMA masks were completely cross-linked to achieve good resistance in inductively coupled plasma etching. Accurate pattern transfer of rows of nanopillars with spacing down to 40 nm was realized on a silicon-on-insulator substrate.
Study of two step construction method of installing the box girder first and then installing the truss members of Dongting Lake railway cable-stayed bridge

, YANG Yi, YI Lunxiong

- , 2018,
Abstract: 针对洞庭湖铁路斜拉桥的结构特点,提出先箱后桁两步拼装的新方法,并对该法提出2个施工方案并进行有限元模拟和对比分析,定量研究箱、桁由于施工不同步引起的变形不协调问题。根据计算结果推荐方案2,该方案能将箱、桁变形的不协调控制在螺栓与螺栓孔间隙的可调范围内,而且可以在桥面上多点分段拼装主桁杆件以加快施工进度。该方案已被成功应用于该桥的施工并取得了很好的效果。
According to the structure characteristics of Dongting Lake railway cable-stayed bridge, a new method of two-step construction was proposed, in which the box girder was fabricated first and then the steel trusses were installed on the box girder deck. This method not only overcomes the shortages of separate installation, such as too many components and too heavy aerial work on the site, but also overcomes the shortcomings of segment installation such as large size and large weight of the segment, too many splice joints, and difficulties of installation, hoisting and transfer of the segment. Two plans of the new method were presented, and their construction processes were simulated. The nonconforming deformation of the box girder and the truss bars were studied quantitatively using finite element method. According to the results, plan 2 was recommended, which can control the nonconforming deformation of the box girder and the truss bars within the adjustable range of the gap between the bolt and the bolt hole. Furthermore, the installation of the truss bars upon the box girder can be divided into many parts along the length of the bridge. In these parts, the truss bars can be installed at the same time to speed up the construction process. Plan 2 has been recommended and successfully used in the construction of the bridge and obtained excellent results
Study on the Stability and Numerical Error of the Four-Stages Split-Step FDTD Method Including Lumped Inductors
Yong-Dan Kong;Qing-Xin Chu;Rong-Lin Li
PIER B , 2012, DOI: 10.2528/PIERB12062008
Abstract: The stability and numerical error of the extended four-stages split-step finite-difference time-domain (SS4-FDTD) method including lumped inductors are systematically studied. In particular, three different formulations for the lumped inductor are analyzed: the explicit, the semi-implicit, and the implicit schemes. Then, the numerical stability of the extended SS4-FDTD method is analyzed by using the von Neumann method, and the results show that the proposed method is unconditionally-stable in the semi-implicit and the implicit schemes, whereas it is conditionally stable in the explicit scheme, which its stability is related to both the mesh size and the values of the element. Moreover, the analysis of the numerical error of the extended SS4-FDTD is studied, which is based on the Norton equivalent circuit. Theoretical results show that: 1) the numerical impedance is a pure imaginary for the explicit scheme; 2) the numerical equivalent circuit of the lumped inductor is an inductor in parallel with a resistor for the semi-implicit and implicit schemes. Finally, a simple microstrip circuit including a lumped inductor is simulated to demonstrate the validity of the theoretical results.
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