R22、R134a在五级自动复叠制冷系统中的应用比较研究

对于多级自动复叠制冷系统,混合制冷剂的选取和组分配比具有很大的影响作用。分别采用R22/R23/R14/R740/R728和R134a/R23/R14/R740/R728两组混合制冷剂应用于五级自动复叠系统,对系统高温级制冷剂R22与R134a进行理论分析和对比实验研究,研究结果表明采用R134a更能有效控制系统排气温度,获取了更低的制冷温度。     

五级自动复叠制冷循环混合制冷剂特性分析与计算

根据已有的五级自动复叠循环系统,对两种制冷剂组合进行特性分析,并选择其中的组合R600a/R23/R14/R740/R728,同时进行制冷剂配比的模拟计算,并确定最终制冷剂的配比。     

101600例0～17岁人群末梢血锌元素参考值研究

为确定我国0～17岁不同年龄段健康人群末梢血锌参考值范围,采用BH 5100型多通道火焰原子吸收光谱仪检测了全国8省份101 600例0～17岁人群全血锌元素含量,用百分位数法确定末梢血锌元素参考值范围.结果表明,不同年龄段人群末梢血锌元素参考值范围分别是:0岁～,38.38～80.06 μmol/L;1岁～,47.7...     

同位素稀释液相色谱-串联质谱法测定动物性食品中的双酚A、壬基酚及辛基酚

建立了动物性食品肉、蛋和奶中双酚A、壬基酚和辛基酚的超高效液相色谱-串联质谱( UPLC-MS/MS)检测方法.比较了固相萃取法(SPE)和凝胶渗透色谱法(GPC)两种前处理技术,探讨了前处理过程中目标化合物背景污染的来源.最终采用乙酸乙酯-环己烷(1∶1,V/V)超声提取,经GPC净化后进行超高效液相色谱串联质谱分析.3种目标化合物的线性范围为0.25～1600 μg/L,相关系数R2＞ 0.999;对肉和鸡蛋样品,方法的定量限( LOQ)为0.2μg/kg;奶粉样品的LOQ为0.4 μg/kg.目标化合物在3个不同水平的加标回收率为85.9％～117.0％,RSD＜ 20％.应用本方法对市售动物性食品肉、蛋和奶进行了分析,壬基酚的检出率最高,含量为0.27～1357 μg/kg,此外还检出了双酚A.     

依据光谱研究闪电放电通道的半径及能量传输特性

利用无狭缝摄谱仪获得的云对地闪电回击过程的光谱, 结合同步辐射电场变化资料, 计算了闪电放电通道的温度、线电荷密度、通道的初始半径和扩张后的半径以及回击通道单位长度储存的能量. 结果与文献报道的其他方法得到的结果符合很好. 这些物理量的相关性分析表明: 电弧通道的初始半径主要取决于回击电流的持续时间; 通道温度越高, 半径越大; 通道初始半径、单位长度储存的能量与光谱总强度正相关, 通道单位长度储存的能量与初始半径的平方成正比. 关键词： 闪电放电通道 半径 能量 光谱总强度     

Polarization modulation in single-frequency He-Ne laser with an anisotropy feedback cavity

The polarization state is modulated by tilting birefringence component placed in the feedback external cavity.The variation of the polarization state in one period of modulation is found to be similar to sine wave.The periods become increasingly smaller.The maximum of variation in one period decreases against the rotated angle.The experimental phenomenon is subjected to the change of optical path and secondary reflection.The phenomenon is analyzed theoretically based on geometrical optics and crystal optics.High-accuracy measurements of absolute and relative angles can be realized based on the experimental phenomenon.The angle resolution is 0.1 arcsec in theory.     

Influences of polarization effect and p-region doping concentration on the photocurrent response of solar-blind p–i–n avalanche photodiodes

The influences of polarization and p-region doping concentration on the photocurrent response of Al0.4Ga0.6N/Al0.4Ga0.6N/Al0.65Ga0.35N p–i–n avalanche photodetector are studied in a wide range of reverse bias voltages.The simulation results indicate that the photocurrent under high inverse bias voltage decreases with the increase of polarization effect,but increases rapidly with the increase of effective doping concentration in p-type region.These phenomena are analyzed based on the calculations of the intensity and distribution of the electric field.A high p-region doping concentration in the p–i–n avalanche photodetector is shown to be important for the efficient compensation for the detrimental polarization-induced electrostatic field.     

Semi-classical theory and experimental research for polarization flipping in a single frequency laser with feedback effect

In this paper, we propose a semi-classical theory to successfully explain the polarization flipping in a single frequency laser. An experimental setup is built to verify this theory. The observed experimental phenomena are consistent with the theoretical analysis. We perform phase retardation measurements of birefringent components using this experimental system. The results show that the measurement repeatability is 0.12° and the measurement accuracy is 0.22 °.     

An Anomalous Gain Mechanism in GaN Schottky Barrier Ultraviolet Photodetectors

The gain mechanism in GaN Schottky barrier ultraviolet photodetectors is investigated by focused light beam. When the incident light illuminates the central region of the Schottky contact electrode, the responsiyity changes very little with the increase of reverse bias voltage. However, when the incident light illuminates the edge region of the electrode, the responsivity increases remarkably with the increase of reverse bias voltage, and the corresponding quantum efficiency could be even higher than 100%. It is proposed that the surface states near the edge of the electrode may lead to a reduction of effective Schottky barrier height and an enhancement of electron injection, resulting in the anomalous gain.     

基于偶氮化反应构筑无酶无试剂型过氧化氢传感器的研究

近年来,人们在临床诊断、化学医药、环境保护等领域对过氧化氢的测定开展了广泛研究~([1]).电化学方法测定H_2O_2具有方法简便、灵敏度高等优点.发展无酶无试剂型H_2O_2传感器是重要的研究方向之一~([2,3]).利用偶氮4-氨基苯硫酚(ATP)膜具有强的导电性,偶氮基可与硫堇(Th)进行偶联反应,从而在电极表面实现Th的共价固定,建立了新型无酶无试剂H_2O_2生物传感器.