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971.
低雷诺数俯仰振荡翼型等离子体流动控制   总被引:2,自引:2,他引:0  
黄广靖  戴玉婷  杨超 《力学学报》2021,53(1):136-155
针对低雷诺数翼型气动性能差的特点, 通过介质阻挡放电(dielectric barrier discharge, DBD)等离子体激励控制的方法, 提高翼型低雷诺数下的气动特性,改善其流场结构. 采用二维准直接数值模拟方法求解非定常不可压Navier-Stokes方程,对具有俯仰运动的NACA0012翼型的低雷诺数流动展开数值模拟.同时将介质阻挡放电激励对流动的作用以彻体力源项的形式加入Navier-Stokes方程,通过数值模拟探究稳态DBD等离子体激励对俯仰振荡NACA0012翼型气动特性和流场特性的影响.为了进行流动控制, 分别在上下表面的前缘和后缘处安装DBD等离子体激励器,并提出四种激励器的开环控制策略,通过对比研究了这些控制策略在不同雷诺数、不同减缩频率以及激励位置下的控制效果.通过流场结构和动态压强分析了等离子体进行流场控制的机理. 结果表明,前缘DBD控制中控制策略B(负攻角时开启上表面激励器,正攻角时开启下表面激励器)效果最好,后缘DBD控制中控制策略C(逆时针旋转时开启上表面激励器,顺时针旋转时开启下表面激励器)效果最好,前缘DBD控制效果会随着减缩频率的增大而下降, 同时会导致阻力增大.而后缘DBD控制可以减小压差阻力, 优于前缘DBD控制,对于计算的所有减缩频率(5.01~11.82)都有较好的增升减阻效果.在不同雷诺数下, DBD控制的增升效果较为稳定, 而减阻效果随着雷诺数的降低而变差,这是由流体黏性效应增强导致的.   相似文献   
972.
A novel rapid transfer alignment algorithm for laser strapdown inertial navigation system (SINS) is studied. Transfer alignment have typically relied on velocity measurements from the master SINS as the source of alignment information, but lever arm error must be compensated accurately while velocity information is utilized, all most every quaternion based error model is nonlinear, so nonlinear filtering algorithms are need, suffering from computational complex and large error. Aim at these problems, a novel improved rapid transfer alignment algorithm formulation is presented, applying quaternion to built the process and measurement models, the improvement employs a special manipulation of the measurement equation results in a linear pseudo-measurement equation, thus the classical linear Kalman filter is employed to estimate the state, need not lever arm error compensation, results in the reduce of computational burden. Observability analysis of this new transfer alignment algorithm has been done based on the piece-wise constant system (PWCS) method, results show that the presented algorithm can accomplish the initial alignment task perfectly. A transfer alignment simulation system is also developed for the evaluation and analysis of the presented algorithm, simulation results are confirmed with the theoretical conclusion, which can achieve the transfer alignment accuracy about 1 mrad within 10 s.  相似文献   
973.
Controllable Goos–Hänchen shift of a light beam reflected from the colloidal ferrofluids is investigated by using the stationary-phase method. It is found that the Goos–Hänchen shift can be easily controlled by the local He factor and the volume factor. Using this scheme, the peak value, the peak position and the width of the Goos–Hänchen shift can all be controlled by adjusting the external magnetic field for a fixed configuration, which also provides a possibility for obtaining larger negative Goos–Hänchen shift by changing the external controlling field. Our results have potential applications in optical devices.  相似文献   
974.
ABSTRACT

A new catalytic kinetic fluorescent quenching method for the determination of trace gold(III) was investigated. The method was based on the catalytic effect of gold on oxidation of 3-(3′-methylphenyl)-5- (2′-arsenoxylphenylazo) rhodanine by hydrogen peroxide in potassium hydrogen phthalate–hydrochloric acid (pH = 3.4). Under the optimum conditions, the great decrease of fluorescence intensity has a linear relationship against the concentration of gold in the range of 0 to 12.0 µg·L?1 with a detection limit of 6.0 × 10?10g·L?1. The coexistent metal ions can be separated, and gold can be enriched by TBP resin of solid-phase extraction, which greatly improves the selectivity and sensitivity of the system. The method can be used to determine trace amounts of gold in ore samples successfully with satisfactory results.  相似文献   
975.
ABSTRACT

Optimized geometrical structure and harmonic vibration frequencies of prior synthesized (E)-3-phenyl-N-[4-(phenyl-amino) quinazoline-7-yl] acrylamide were computed by ab initio HF and DFT/B3LYP methods using both 6-31G* and 6-311G** basis sets and the Moller–Plesset second-order perturbation (MP2) method merely at the 6-31G* level. The infrared (IR) spectrum of the title compound has been measured in the range of 400–4000 cm?1. Complete vibrational assignments of the IR spectra were proposed. Moreover, the calculated wavenumbers of the title compound were compared with the experimental data. The correlation analyses indicate that good linearity relationships exist between the scaled theoretical vibration frequencies and the experimental values. Additionally, the atoms in molecules (AIM) method was applied to explore the possible intramolecular interactions in the title compound.  相似文献   
976.
L. Dai  H. Li  C. Liu  G. Su  S. Shan 《高压研究》2013,33(3):193-202
Electrical conductivities of pyroxenite were measured between frequencies of 10?1 and 106 Hz in a multi-anvil pressure apparatus using different solid buffers (Ni+NiO, Fe+Fe3O4, Fe+FeO and Mo+MoO2) to stabilize the partial pressure of oxygen. The temperature ranged from 1073 to 1423 K (800 to 1200 °C) and the pressure from 1.0 to 4.0 GPa. We observe that: (1) the electrical conductivity (σ) of pyroxenite depends on frequency; (2) σ tends to increase with rising temperature (T), and Log σ and 1/T obey a linear Arrhenius relationship; (3) under control of the buffer Fe+Fe3O4, σ tends to decrease with rising pressure, nevertheless the activation enthalpy tends to increase. For the first time we have obtained values for the activation energy and activation bulk volume of the main charge carriers, which are (1.60±0.07) eV and (0.05±0.03) cm3/mol, respectively; (4) for a given pressure and temperature, σ tends to rise with increased oxygen fugacity, whereas the activation enthalpy and preexponential factor tend to decrease; and (5) the behaviour of the electrical conductivity at high temperature and high pressure can be reasonably interpreted by assuming that small polarons provide the dominant conduction mechanism in the pyroxenite samples.  相似文献   
977.
谭叶  俞宇颖  戴诚达*  于继东  王青松  谭华 《物理学报》2013,62(3):36401-036401
在火炮上利用金属铋(Bi)直接撞击单晶LiF窗口, 开展了金属Bi反向碰撞的冲击加载-卸载实验研究, 实验采用激光位移干涉测试系统, 获得了金属Bi在11—16 GPa压力范围内完整的卸载粒子速度剖面. 实验结果结合特征线方法计算表明, 金属Bi经冲击加载进入体心立方相, 并在11—16 GPa冲击压力作用下发生了卸载熔化, 界面粒子速度剖面的卸载拐点, 对应着金属Bi经冲击加载后发生的卸载熔化, 而这一结论同Cox的理论计算及一维流体力学程序计算结果基本一致. 本文报道的金属Bi卸载波剖面解读技术, 对于认识冲击加载下其他相似材料相变具有实用价值.  相似文献   
978.
楔形盒染料掺杂胆甾相液晶激光器研究   总被引:1,自引:0,他引:1       下载免费PDF全文
岱钦  李勇  乌日娜  耿岳  全薇  李业秋  彭增辉  姚丽双 《物理学报》2013,62(4):44219-044219
设计制作了楔形盒掺杂激光染料PM580的胆甾相液晶器件, 研究了激光辐射行为. 在楔形液晶盒中出现了一系列与楔棱平行的向错线和不同规则形状的晶畴, 胆甾相液晶形成了平面态排列. 采用固体Nd:YAG倍频532 nm 波长激光作为抽运光, 获得调谐精度约1 nm, 调谐范围约17 nm的一维波长可调谐激光器. 楔形盒中, 液晶扭曲力与取向膜表面锚定力相互平衡的过程中胆甾相液晶螺距伸张, 光子禁带位置移动, 从而调谐光子禁带边沿出射激光波长. 关键词: 胆甾相液晶 楔形盒 激光辐射  相似文献   
979.
光子晶体光纤由于其灵活可调的色散特性用作色散补偿具有极大的应用潜力. 设计了一种色散补偿光子晶体光纤, 并运用频域有限差分法模拟了其色散特性,从理论上分析了其结构参数孔间距Λ和空气占空比d/Λ对该光子晶体光纤的色散系数的影响, 并且实际制备出了3种不同结构参数的光子晶体光纤. 通过对其色散曲线对比分析表明: 当光子晶体光纤孔间距在1 μm附近时, 其色散系数随着孔间距Λ和占空比d/Λ的增大而增加, 但对于孔间距Λ的变化比占空比d/Λ更为敏感, 并且随着孔间距Λ的增加,其对色散系数的影响能力逐渐减小. 设计并制备的光子晶体光纤在1550 nm处的色散系数为-241.5 ps·nm-1·km-1, 相对色散斜率为0.0018, 具有较好的色散补偿能力. 关键词: 色散 色散补偿 光子晶体光纤 结构参数  相似文献   
980.
Magnolol (MAG), a biphenolic neolignan, has various biological activities including antitumor effects. In this study, 15 MAG derivatives were semi-synthesized and evaluated for their in vitro anticancer activities. From these derivatives, compound 6a exhibited the best cytotoxic activity against four human cancer cell lines, with IC50 values ranging from 20.43 to 28.27 μM. Wound-healing and transwell assays showed that compound 6a significantly inhibited the migration and invasion of MDA-MB-231 cells. In addition, Western blotting experiments, performed using various concentrations of 6a, demonstrated that it downregulates the expression of HIF-1α, MMP-2, and MMP-9 in a concentration-dependent manner. Overall, these results suggest that substituting a benzyl group having F atoms substituted at the C2 position on MAG is a viable strategy for the structural optimization of MAG derivatives as anticancer agents.  相似文献   
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