Comparative Study of the Ratio Spectra Derivative Spectrophotometry,Derivative Spectrophotometry and Vierordt's Method Appued to the Analysis of Lisinopril and Hydrochlorothiazide in Tablets

Abstract

Three new spectrophotometric methods are described for the determination of lisinopril and hydrochlorothiazide in their binary mixturer: First derivative spectrophotometry ratio spectra derivative and Vierordt's method. The procedures do not require any prior separation. In the derivative spectrophotometry, the dA/dλ values in the first derivative spectra of the mixture were measured at 269.6 nm for lisinopril and at 279.8 nm for hydrochlorothiazide. The calibration graphs were linear in the range 25.56–129.50 μg.ml^?1 for lisinopril and 10.60–139.80 μg.ml^?1 for hydrochlorothiazide. In ratio spectra derivative spectrophotometry, the calibration graphs for 15.68–129.50 μg.ml^?1 lisinopril and for 5.98–139.80 μg.ml^?1 hydrochlorothiazide were obtained by measuring the signals at 253.7 nm and 243.6 nm for lisinopril and at 280.1 nm and 270.8 nm for hydrochlorothiazide. In Vierordt's method, A¹ ₁ (1 %, 1 cm) values of lisinopril and hydrochlorothiazide were determined at 259.8 nm and 272.7 nm in the zero-order spectra. The quantity of both compounds were calculated by using the A¹ ₁ (1 %, 1cm) values. The methods were successfully applied to a pharmaceutical formulation for determination of both active compounds.     

Image denoising using trivariate prior model in nonsubsampled dual-tree complex contourlet transform domain and non-local means filter in spatial domain

Image denoising is always the basic problem of image processing, and the main challenge is how to effectively remove the noise and preserve the detailed information. This paper presents a new image denoising algorithm based on the combination of trivariate prior model in nonsubsampled dual-tree complex contourlet transformlet transform (NSDTCT) domain and non-local means filter (NLMF) in spatial domain. Firstly, NSDTCT is constructed by combining the dual-tree complex wavelet transform (DTCWT) and nonsubsampled directional filter banks (NSDFB). The noisy image is decomposed by using NSDTCT. Secondly, based on the correlation between the interscale and intrascale dependencies of NSDTCT coefficients, the distribution of the high frequency coefficients is modeled with the trivariate non-Gaussian distribution model. A nonlinear trivariate shrinkage function is derived in the framework of Bayesian theory, and then the denoised coefficients are obtained and inverse NSDTCT is performed to get the initial denoised image. Finally, NLMF is used to smooth the initial denoised image. Simulation experiment shows that our algorithm can obtain better performances than those outstanding denoising algorithms in terms of peak signal-to-noise ratio (PSNR), mean structural similarity (MSSIM) as well as visual quality.     

Effect of Opacity on the Solar Spectral Line of C I 165.7 nm by Escape Factor Treatment

In this article, we report that by using the intensity ratio of the (2-2) to (1-2) component of CI emission lines at about 165.7 nm, we determined the optical depth at the line center of the (2-2) component of CI emission lines by escape factor treatment. The optical depth at the line center of the (2-2) component is calculated to be 0.9998, which is a more reasonable value of solar spectral lines than the value that has been reported. The variation of the optical depth at the line center for different positions from the solar limb is discussed. Using the measured abundance of carbon and the results of ionization balance calculations, we estimate the electron density in the CI emitting region. The density of hydrogen is estimated in the CI emitting region by this method, and is testified to be a better value than the value that has been reported. This discussion will be significant in the analysis of opacity on the solar ultraviolet (UV) or extreme-ultraviolet (EUV) spectrum.     

用于空间碎片清除的高功率激光器（英文）

虽然人类的太空活动已经考虑了尽量减少空间碎片的措施,但近地轨道碎片的数量仍呈指数增长,特别是中小型碎片的现有数量已对在轨卫星构成了实质性的威胁。作为具有较高期待的消除碎片办法,用地基DF激光器和空基Nd∶YAG激光器消除碎片的方案令人关注,它们可以以低成本和非破坏性的方式清除空间轨道的危险碎片。本文介绍了使用平均功率为100 kW的高功率、高重复频率P-P Nd∶YAG激光器和平均功率约为1.5 MW的DF激光器来保护在轨飞行器和清除直径为1～10 cm空间轨道危险碎片涉及的相关工作。     

Experimental gravity induced coexistence curve of methyl fluoride near the critical point

Abstract

The top part of the coexistence curve of methyl fluoride in the critical region has been determined first by direct observation of the disappearance of the meniscus of the fluid situated in a high-pressure light scattering cell and subsequently from the measured maximum depolarization ratio of an appreciable number of isochores close to the critical point. The experimental data obtained from direct observations yield a coexistence curve which nearly coincides with that found recently from pVT measurements. However, the data obtained from light scattering experiments describe a gravity induced coexistence curve which lies above the previous one and which shows a minimum at the critical point. The complete experimental data have been used to evaluate the critical parameters p_c, ρ_c and T_c and the critical exponent β.     

Effect of pressure on optical and electrical properties of tungsten diselenide single crystals

Optical absorption spectra of tungsten diselenide (WSe₂) single crystals subjected to different values of pressure (0, 2, 4 and 6 GPa) were obtained in the spectral range 700–1450 nm with the help of a UV–VIS–NIR spectrophotometer. The spectra were thoroughly analyzed in the absorption edge region for obtaining direct as well as indirect band gaps in this material. The high temperature resistivity and thermoelectric power on WSe₂ single crystals at various pressures were also studied. The results and their implications are discussed in the article.     

Tm3+,Yb3+共掺钨酸钙多晶材料的上转换发光及荧光温度特性

采用高温固相法制备了Tm³⁺,Yb³共掺CaWO₄多晶材料. 980 nm二极管激光器激发下,在可见区获得了¹G₄→³H₆,¹G₄→³H₄,³H₂,³H₃→³H₆ 跃迁产生的上转换荧光. 讨论了Yb³⁺ 离子浓度的变化对Tm³⁺ 的上转换发光强度的影响,同时根据荧光强度比的方法研究了689 和705 nm 红色上转换荧光在313–773 K 范围内的温度特性. 结果表明：基于Tm³⁺,Yb³⁺ 共掺CaWO₄ 多晶材料的红色上转换荧光可以实现温度监测,其测温的最大灵敏度值为5.7×10^-4 K^-1,相应的测量温度为458 K. 关键词： 上转换发光 3+')" href="#">Tm³⁺ 钨酸钙 荧光温度传感     

大功率单脉冲超声信号发生器的设计

为了提高探伤深度,实现混凝土大坝等散射强介质的超声检测,本文提出了一种成本低,小体积,结构简单的大功率单脉冲超声信号发生器,并给出了原理电路设计。所述装置利用控制电容充放电经脉冲变压器产生瞬时高压脉冲的新思路,克服了过去由于信号幅度限制功率上不去的困难。经实验验证该装置与现有的单脉冲信号发生器相比,探伤深度得到了很大提高,可用于混凝土结构构建的超声探伤。     

功率MOSFET的负偏置温度不稳定性效应中的平衡现象

通过对功率金属氧化物半导体场效应晶体管在静态应力下的负偏置温度不稳定性的实验研究, 发现器件参数的退化随时间的关系遵循反应扩散模型所描述的幂函数关系, 并且在不同栅压应力下, 实验结果中均可观察到平台阶段的出现. 基于反应扩散理论的模型进行了仿真研究, 通过仿真结果分析和验证了此平台阶段对应于反应平衡阶段, 并且解释了栅压应力导致平台阶段持续时间不同的原因. 关键词： 功率金属氧化物半导体场效应晶体管 负偏置温度不稳定性 反应扩散模型     

考虑自热效应的互连线功耗优化模型

基于互连线的分布式功耗模型,考虑自热效应的同时采用非均匀互连线结构,提出了一种基于延时、带宽、面积、最小线宽和最小线间距约束的互连动态功耗优化模型.分别在90和65 nm互补金属氧化物半导体工艺节点下验证了功耗优化模型的有效性,在工艺约束下同时不牺牲延时、带宽和面积所提模型能够降低高达35％互连线功耗.该模型适用于片上网络构架中大型互连路由结构和时钟网络优化设计.