Numerical Study of Depressurization Rate during Blowdown Based on Lumped Model Analysis

To study the thermodynamic aspects of blowdown, the depressurization rate equation has been numerically solved. The equation, derived from macroscopic mass and energy balances in the pressure vessel, consisted of the energy and volumetric discharges terms multiplied by the decrease rate of residual coolant. By applying a dimensional analysis, dimensionless equations were obtained together with dimensionless parameters of blowdown. Blowdown calculations starting at typical BWR operating conditions indicated that the decrease rate of coolant increased for the liquid and two-phase mixture, and decreased for the vapor discharge. Further, the energy discharge term made a larger contribution to the depressurization rate in the case of vapor escape, while the volumetric discharge term did so in the case of liquid and two-phase mixture escape blowdowns. In the lumped model analyses, the averaged specific enthalpy and entropy of the residual coolant increased for the liquid discharge, remained almost constant for the two-phase mixture discharge, and decreased for the vapor discharge blowdown.     

Dimensional analysis for the heat transfer characteristics in the corrugated channels of plate heat exchangers

Using the Buckingham Pi theorem, this study derives dimensionless correlations to characterize the heat transfer performance of the corrugated channel in a plate heat exchanger. The experimental data are substituted into these correlations to identify the flow characteristics and channel geometry parameters with the most significant influence on the heat transfer performance. Simplified correlations by omitting the factors with less influence are then obtained. The results show that Nu_x is affected primarily by Re, R/D_h, x/D_h, and β. Neglecting the minor effect of factors on Nu_x, it is shown that Nu_m is determined primarily by Re, R/D_h and β.     

Characterization of uniform ultrathin layer for z-response measurements in three-dimensional section fluorescence microscopy

Layer‐by‐layer technique is used to adsorb a uniform ultrathin layer of fluorescently labelled polyelectrolytes on a glass cover slip. Due to their thickness, uniformity and fluorescence properties, these ultrathin layers may serve as a simple and applicable standard to directly measure the z‐response of different scanning optical microscopes. In this work we use ultrathin layers to measure the z‐response of confocal, two‐photon excitation and 4Pi laser scanning microscopes. Moreover, due to their uniformity over a wide region, i.e. cover slip surface, it is possible to quantify the z‐response of the system over a full field of view area. This property, coupled with a bright fluorescence signal, enables the use of polyelectrolyte layers for representation on sectioned imaging property charts: a very powerful method to characterize image formation properties and capabilities (z‐response, off‐axis aberration, spherical aberration, etc.) of a three‐dimensional scanning system. The sectioned imaging property charts method needs a through‐focus dataset taken from such ultrathin layers. Using a comparatively low illumination no significant bleaching occurs during the excitation process, so it is possible to achieve long‐term monitoring of the z‐response of the system. All the above mentioned properties make such ultrathin layers a suitable candidate for calibration and a powerful tool for real‐time evaluation of the optical sectioning capabilities of different three‐dimensional scanning systems especially when coupled to sectioned imaging property charts.     

(<Emphasis Type="Italic">S</Emphasis>)-2-Acetoxy-5-Undecanone,Female Sex Pheromone of the Raspberry Cane Midge, <Emphasis Type="Italic">Resseliella theobaldi</Emphasis> (Barnes)

The raspberry cane midge, Resseliella theobaldi, is a widespread pest of cultivated red raspberry in Europe. Pheromone-baited traps could provide a much-needed, accurate means to monitor the pest. Volatiles collected separately from virgin female and male midges were analyzed by gas chromatography (GC) coupled to mass spectrometry (MS) to reveal four female-specific components. In analyses by GC coupled to electroantennographic (EAG) recording from the antennae of a male midge, at least three of these components elicited responses. Based on its GC retention indices and mass spectrum, we propose that the major component is 2-acetoxy-5-undecanone and confirm this by synthesis of the racemic compound in seven steps and 63% yield from 4-pentenoic acid. The three minor components were each present at approximately 30% of the major component and were identified as 2-undecanone, (S)-2-acetoxyundecane, and (S)-2-undecanol by comparison of GC retention times and mass spectra with those of synthetic standards. GC analyses of the female-produced volatiles on an enantioselective column showed that only one enantiomer of 2-acetoxy-5-undecanone was present, and this was found to be the S-enantiomer by hydrolytic kinetic resolution of an epoxide intermediate in the synthesis and also by enantioselective hydrolysis of the racemic acetate with a lipase enzyme. The two enantiomers were also separated by high-performance liquid chromatography on an enantioselective column for field tests. In two field trapping tests, (S)-2-acetoxy-5-undecanone was highly attractive to male R. theobaldi; the R-enantiomer was not attractive. The racemic compound was just as attractive as the S-enantiomer, and addition of the three minor components in racemic form at two different loads did not affect catches. The pheromone could be dispensed from both rubber septa and polyethylene vials for at least 1 month under field conditions, but the former was preferred as it gave more uniform release. 2-Acetoxy-5-undecanone belongs to a new group of pheromone structures in the Cecidomyiidae, most others being mono- or diesters.     

基于树莓派B 微处理器的视频检测跟踪系统的实现

针对目前视频检测跟踪系统大多是在PC机上实现的现状,本文设计了一种基于树莓派B 微处理器的嵌入式检测跟踪系统,实现了视频检测跟踪系统的便携式小型化。在图像处理算法上本文采用帧间差分方法进行目标检测,通过形心标记进行目标跟踪。本系统采用基于Linux操作系统的树莓派B 微处理器进行算法移植,通过远程桌面连接工具或小型液晶显示器进行视频显示。实验结果表明,本系统可以很好的实现视频检测跟踪的基本功能。     

Near threshold vibrational excitation of molecules by positron impact: A projection operator approach

We report vibrational excitation (ν_i=0→ν_f=1) cross-sections for positron scattering by H₂ and model calculations for the (ν_i=0→ν_f=1) excitation of the C-C symmetric stretch mode of C₂H₂. The Feshbach projection operator formalism was employed to vibrationally resolve the fixed-nuclei phase shifts obtained with the Schwinger multichannel method. The near threshold behavior of H₂ and C₂H₂ significantly differ in the sense that no low lying singularity (either virtual or bound state) was found for the former, while a e⁺-acetylene virtual state was found at the equilibrium geometry (this virtual state becomes a bound state upon stretching the molecule). For C₂H₂, we also performed model calculations comparing excitation cross-sections arising from virtual (-iκ₀) and bound (+iκ₀) states symmetrically located around the origin of the complex momentum plane (i.e. having the same κ₀). The virtual state is seen to significantly couple to vibrations, and similar cross-sections were obtained for shallow bound and virtual states.     

PI度对LCD功耗电流的影响

从理论上计算了不同种类，不同厚度的ＰＩ对ＬＣＤ功耗电流的影响，从实验上比较了ＫＰＩ－３０３Ｂ和ＳＥ－２１７０在选用不同厚度时对功耗电流值的影响以及德国进口稀释剂ＮＭＰ和ＮＩＳＳＡＮ－ＰＩ专用稀释剂＊＊２１在配ＰＩ后对ＬＣＤ盒的功耗电流的影响，并对这种影响原因进行了解释，从而为ＰＩ材料的选用及相应的ＬＣＤ功耗电流控制标准的制定提供了一些有价值的实验和理论依据。     

Raspberry PI在课程设计中的应用

随着技术的不断提高,各种医疗仪器设备集成化、智能化的趋势也越来越明显,从而对毕业生的要求也越来越高.文中主要探讨了一种刚刚兴起的微型计算机-Raspberry PI,一种香烟盒大小的超小型电脑在课程设计中的应用.通过使用这种超小型计算机来进行简单项目的开发,来提高学生的动手能力与独立解决问题的能力,使学生时现代化医疗仪器的软硬件构成有一个较为深入的认识.     

基于四旋翼无人机的二次屏柜巡检系统

随着人们对于电力的需求量越来越大,相应的电力巡检的要求也越来越高。文中设计了基于四旋翼无人机的二次屏柜巡检系统。为解决无人机在室内GPS拒止问题,文中通过AprilTag算法配合传感器高度信息,实现无人机室内飞行路径规划功能、姿态矫正、自主飞行;在机载树莓派内存入任务程序,该程序将利用飞控和传感器实现对任务地点二维码的寻找和判断,并在达到指定点后执行拍摄任务;通过局域网将采集的图像传输到地面服务器,并输入到预先训练好的CNN网络模型中进行异常检测;依据识别结果判断二次屏柜是否工作正常,并将检测结果上传到显示平台。最终项目在贵州铜仁变电站室内二次屏柜现场测试成功。     

吹扫捕集-气质联用法检测树莓蒸馏酒中的挥发性成分*

树莓是一种种植适应性很强的新兴浆果,因其营养丰富、香味宜人、色泽诱人,目前种植面积日益扩大,发展迅猛。发酵果酒是树莓的一种主要的加工产品,其色泽鲜艳、香味浓郁,树莓蒸馏酒进一步富集了树莓发酵酒的挥发性风味成分,特点鲜明。采用吹扫捕集-气质联用方法对树莓蒸馏酒的特征性风味成分进行了分析检测,共检测确定了29种挥发性风味成分,其中乙缩醛,3-甲基-1-丁醇,乙酸乙酯,癸酸乙酯,2-甲基-1-丁醇等成分含量较高。乙缩醛、癸酸乙酯可作为树莓蒸馏酒的特征参考指标。