Analytical solutions of the lattice Boltzmann BGK model

Analytical solutions of the two-dimensional triangular and square lattice Boltzmann BGK models have been obtained for the plane Poiseuille flow and the plane Couette flow. The analytical solutions are written in terms of the characteristic velocity of the flow, the single relaxation time , and the lattice spacing. The analytic solutions are the exact representation of these two flows without any approximation. Using the analytical solution, it is shown that in Poiseuille flow the bounce-back boundary condition introduces an error of first order in the lattice spacing. The boundary condition used by Kadanoffet al. in lattice gas automata to simulate Poiseuille flow is also considered for the triangular lattice Boltzmann BGK model. An analytical solution is obtained and used to show that the boundary condition introduces an error of second order in the lattice spacing.     

地空数据传输系统中单载波频域预均衡技术

在频率选择性瑞利慢衰落信道条件下,提出了一种适用于地空传输系统上行链路的单载波频域预均衡方法。在此基础上设计了预均衡系统模型,地面端将下行链路中的导频信号与本地导频信号对比进行信道状态估计,利用获得的信道状态信息对上行链路信号进行预均衡处理,然后在机载接收端对上行链路信号进行再均衡。基于迫零准则和最小均方误差准则,分析了该方法的信号处理流程,计算得到预均衡系数。通过仿真实验,对比分析了不同均衡方案的误码性能,结果表明:单独在地面发送端进行预均衡,会出现误码率平台效应;而预均衡之后在机载接收端进行再均衡的方法,在误码率为10-5的情况下,与采用线性均衡结构的传统单载波频域均衡方法相比有2~3dB的性能增益。     

U形渠道水跃的试验研究

从理论上推导了Ｕ形渠道的水跃方程。通过模型试验研究了Ｕ形渠道水跃的水流流态和流速分布,测量了跃前、跃后水深和水跃长度,提出了共轭水深、水跃长度和水跃消能率的计算公式。研究表明,Ｕ形渠道的水跃有良好的消能效果,其消能作用优于矩形渠道和梯形渠道,接近于三角形渠道。     

Effects of BaCl_2 on slow vacuolar ion channels on radish by patch-clamp

Effects of BaCl2 on slow vacuolar ion channels on radish by patch-clamp YANG Pin (杨 频) & ZHANG Liping (张丽平) Institute of Molecular Science, Shanxi University, Taiyuan 030006, China Correspondence should be addressed to Yang Pin (email: yangpin@sxu.edu.cn)     

探究苯与酸性高锰酸钾溶液的褪色反应

人教版高中教材《化学2》明确指出苯不能使酸性高锰酸钾溶液褪色。但在实验中多次发现苯与酸性高锰酸钾溶液混合后放置一段时间能够褪色。为探讨这一问题，设计了以光照或黑暗、加酸或不加酸为条件，利用紫外-可见分光光度计对放置不同时间后的混合液体进行测试，并对反应后生成的沉淀物进行XRD表征的实验方案。通过对实验数据的综合分析提出了苯与酸性高锰酸钾溶液褪色反应的可能反应机理。     

7,8-二氢-6,6-二甲基-7,8-环氧-6氢-吡喃[2,3-f]苯并-2,1,3-噁二唑的合成

本文给出了一条较好的制备7,8-二氢-6,6-二甲基-7,8环氧-6氢-吡喃[2,3-f]苯并-2,1,3-噁二唑的合成路线,即由对乙酰氨基苯酚经酯化、Fries重排、环合、还原、脱水、硝化、脱酰基、氧化、脱氧和催化环氧化等反应制得标题化合物,其结构经元素分析和光谱数据确证。     

A common method for the determination of several calcium channel blockers using an HPLC system with ultraviolet detection

We report a common HPLC method for the single or simultaneous determination of four calcium channel blockers (CCB), namely diltiazem (DTZ), verapamil (VER), nifedipine (NIF) and nitrendipine (NIT) and their active metabolites demetildiltiazem and deacetildiltiazem (MA and M1), norverapamil (NOR), and dehydronifedipine (DHN). DHN was first synthesised in our laboratory and different pH values of the mobil phase were subsequently prepared and tested for chromatographic separation. The detection system and the environmental light conditions were optimised. The best separations of all analytes were obtained using a C₁₈ column and a mobile phase of methanol, 0.04 M ammonium acetate, acetonitrile and triethylamine (2:2:1:0.04 v/v). Quantitation was performed using imipramine (IMI) as the internal standard. For DTZ and its metabolites (M1 and MA), the wavelength chosen was 237 nm; for VER and its metabolite NOR, it was 210 nm; and, finally for NIF and its metabolite DHN and NIT it was 216 nm. When a simultaneous analysis was carried out the wavelength was of 230 nm. The optimum pH were 7.90 and 7.10 when the separation of NIT and DTZ or VER and NIF were carried out, respectively, and 7.90 when a simultaneous separation was carried out. The detection limit of the assay was less than 8 ng ml⁻¹ for all compounds, with coefficients of variation less than 7% (for inter- and intra-day) over the concentration range of 1–1000 ng ml⁻¹. The retention times were less than 11 min. When NIF or NIT were studied, it was necessary to use a sodium vapour lamp in order to avoid the photodegradation which takes place under daylight conditions.     

Instrumental barriers in biological Fourier transform infrared spectroscopy

Biological applications of infrared spectroscopy have pressed for ever greater instrumental capabilities in terms of spectral sensitivity and quantitative exactness. Improved instrumentation has provided measurement of many vibrational modes in biological samples that previously were lost in noise. With highly optimized sampling conditions, useful measurements have been made with a peak-to-peak noise level less than 5 microabsorbance (5×10^–6 absorbance), at 0.5 cm^–1 resolution. However, optical and instrumental instabilities often result in sine waves that are not totally removed by the ratio of sample to reference. These often limit effective spectral sensitivity to 50 or 100 microabsorbance, peak-to-peak, and constitute a non-random noise. Non-atmospheric absorptions, especially one at 1959 cm^–1 with 0.8 cm^–1 band width (FWHM) are reported. The latter is due to a trace impurity in the KBr beam splitter substrate and compensator plate. Improvements in instrumentation and sampling conditions are expected to yield measurements of absorption bands as small as 50 microabsorbance with excellent signal/noise.     

Hall effects and entropy generation applications for peristaltic flow of modified hybrid nanofluid with electroosmosis phenomenon

The electroosmotic peristaltic flow of modified hybrid nanofluid in presence of entropy generation has been presented in this thermal model. The Hall impact and thermal radiation with help of nonlinear relations has also been used to modify the analysis. The assumed flow is considered due to a non-uniform trapped channel. The properties of modified hybrid nanofluid model are focused with interaction of three distinct types of nanoparticles namely copper ($Cu)$, silver ($Ag$) and aluminum oxide ($A{l}_2{O}_3).$ The mathematical modeling and significances of entropy generation and Bejan number are identified. With certain flow assumptions, the governing equations are attained for optimized peristaltic electroosmotic problem. Widely used assumptions of long wave length and low Reynolds number reduced the governing equations in ordinary differential equations. The ND solver is flowed for the solution process. The physical significant of results is observed by assigning the numerical values to parameters.