Numerical studies of viscous stagnation point flows

A rapid finite-difference procedure for computing stagnation point flows at a given Reynolds number in terms of stream function and vorticity distributions is described. The method is illustrated for spherical and cylindrical curvature for Reynolds number ranges of 1 ≤ Re ≤ 400 and 4 ≤ Re ≤ 100 respectively. Predicted radial and angular velocity distributions in the frontal region are compared with results from numerical solutions of the full elliptic equations of motion. The use of a modified potential flow outer boundary condition reduces the region of numerical computation.     

遥望P2P——P2P到底是什么

要版权还是强调互联网技术的进步?Napster与世界影音”巨鳄”们持续不断的较量,把全球IT目光都吸引了过去。从此开始,P2P(peertopeer)堂而皇之地走到了台前,引来喧哗一片。     

Development of a Molecular Aptamer Beacon Applied to Magnetic-Assisted RNA Extraction for Detection of Dengue and Zika Viruses Using Clinical Samples

Limitations in the detection of cocirculating flaviviruses such as Dengue and Zika lead us to propose the use of aptameric capture of the viral RNA in combination with RT-PCR (APTA-RT-PCR). Aptamers were obtained via SELEX and next-generation sequencing, followed by colorimetric and fluorescent characterizations. An APTA-RT-PCR assay was developed, optimized, and tested against the viral RNAs in 108 serum samples. After selection, sequence APTAZC10 was designed as a bifunctional molecular beacon (APTAZC10-MB), exhibiting affinity for the viral targets. APTA-RT-PCR was able to detect Dengue and Zika RNA in 43% and 8% of samples, respectively. Our results indicate that APTAZC10-MB and APTA-RT-PCR will be useful to improve the detection of Dengue and Zika viruses in a fast molecular assay for the improvement of infectious disease surveillance.     

柴油机燃用不同比例菜籽油生物柴油和乙醇柴油的对比试验研究

在一台S195直喷柴油机上进行燃料燃烧对比试验,试验结果表明,燃用生物柴油和乙醇柴油会使柴油机的动力性有所下降,其中菜籽油生物柴油的动力性接近纯柴油燃料的动力性,乙醇柴油的动力性相对较差。生物柴油和乙醇柴油的油耗率都比纯柴油要高,生物柴油的油耗率要高于乙醇柴油。但随负荷的增大,这种差距呈下降趋势。生物柴油和乙醇柴油在较大工况范围都可以保持比纯柴油燃料较低的CO排放量。低负荷状态下改善不明显,甚至会增大;高负荷工况下,混合燃料的CO排放比纯柴油降低较多。绝大部分工况下,生物柴油和乙醇柴油燃料的HC排放都比纯柴油高。绝大部分工况下,生物柴油和乙醇柴油的NOx排放和碳烟排放都比纯柴油低,其中生物柴油的表现优于乙醇柴油。     

Human cytochrome P4502B6: interindividual hepatic expression, substrate specificity, and role in procarcinogen activation

In situ hybridization was combined with serotonin (5-hydroxytryptamine, 5-HT) or tyrosine hydroxylase immunocytochemistry and with Fluoro-Gold retrograde labeling of bulbo-spinal pathways in order to investigate the expression of GAP-43 mRNA in monoamine cell groups of the adult rat brain stem. Consistent with previous reports, GAP-43 mRNA was observed in serotonin and dopamine cell groups in the pons. In addition, GAP-43 expressing cells were observed in all the major monoamine cell groups in the medulla. Thus the B1, B2 and B3 serotonin cell groups all showed high GAP-43 expression in all contained many GAP-43 expressing serotonin cells with spinal cord projections. The A1, A2, A5 and A6 noradrenaline cell groups also showed high GAP-43 expression, although cells with spinal cord projections were largely restricted to the A5 group and A6 subcoeruleus region. In all areas, GAP-43 expressing cells with spinal cord projections were also observed which were not serotonergic or noradrenergic.     

有机朗肯循环中滚动活塞式膨胀机膨胀比最优化研究

针对容积式膨胀机出口压力与冷凝器内背压不同导致不可逆损失现象的存在,改进并设计了可变膨胀比的滚动活塞式膨胀机,并分析其工作原理。以R245fa为工质,研究了蒸发器内有机工质无过热、膨胀机无泄漏条件下,系统参数变化对膨胀机最佳膨胀比的影响。结果表明:膨胀机的最佳膨胀比受膨胀机效率的影响很小,而受发生温度和冷凝温度的影响较大,蒸发温度越高,最佳膨胀比越大,冷凝温度越高,最佳膨胀比越小,当系统某参数变化时,可以通过调节系统的其他参数使膨胀机处于最佳膨胀比下运行。为膨胀机膨胀比的设计和运行工况的选择提供参考依据。     

微型燃气轮机生物质气燃烧实验台设计

本研究以现有的微型燃气轮机为原型,设计了单喷嘴生物质气燃烧实验台并具体介绍了实验台的系统、重要组成模块、测量参数和方法以及实验台的主要作用。本实验台能够实现关键流动参数测量、PIV流场测量、燃烧温度场测量和尾气排放测量等。实验室条件下,对微型燃气轮机燃烧室进行研究,得出的结论可应用于燃烧室流场结构分析、喷嘴的改型、火焰稳定性、排放控制、燃料组分改变对燃烧性能的影响以及相关的燃烧技术研究。     

考虑冷气掺混的重型燃气轮机变工况运行的精细建模及特性分析

为了研究全工况下燃气轮机内部运行参数及其所具有的特性规律,以PG9351FA燃机为分析对象,建立具有冷气掺混的重型燃气轮机变工况运行精细模型。该模型采用半经验公式对燃机冷却空气掺混量进行估算,充分考虑了冷气掺混对透平性能的影响,以及马赫数、攻角对透平变工况运行时造成的气流参数变化及速度损失的修正。结果显示:所建模型的精度有所提高,利用其计算所得结果与厂家提供数据相比,数据误差可控制在±0.4%以内,可用于预估燃机在部分负荷工况下的运行特性。应用模型分析了透平背压变动对透平膨胀比分配、排气温度及输出功率(出功)的影响,得到了透平内部气体流动参数和性能参数以及分级特性规律,其结果更真实地反映了机组在特定运行策略是的全工况特性规律。     

耦合喷射制冷的微燃机CCHP系统设计及性能分析

考虑到微燃机在夏季高温环境下性能下降导致CCHP(冷热电三联产系统)运行偏离设计工况,本文提出了利用CCHP系统烟气余热进行喷射制冷,并利用该冷量对微燃机进气进行冷却的研究思路。理论计算发现:以青岛为例,在夏季工况下,对微燃机进气进行冷却可以提高出力16.4%,提高发电效率7.5%左右;对比微燃机进气冷却前后,CCHP系统一次能源效率可提高25%左右,而系统一次能源节约率可提高3%~10%;同时系统单位发电量的CO_2排放量可降低约37%。因此,在夏季高温季节对微燃机进行进气冷却可以改善微燃机和CCHP系统运行性能。     

火力发电厂阀门泄漏故障声发射检测系统研究

阀门是火力发电厂重要的辅助设备之一,针对目前火力发电厂无法实现阀门内部泄漏故障有效检测的问题,结合LabVIEW软件编程特点和阀门泄漏故障检测要求,开发设计了阀门泄漏故障声发射在线监测系统。该系统由硬件和软件两部分组成,硬件系统采用了工业便携式计算机设计方案,使整套检测系统携带方便、拆卸简单灵活;软件系统则针对阀门泄漏声发射信号特点,设置了特定的状态检测指标,可实现阀门泄漏率的定量诊断和分等级报警。本研究检测试验表明:阀门泄漏故障声发射在线监测系统可以迅速捕捉到阀门泄漏故障,并可实现阀门泄漏率的定量诊断。