PAN-S光度法高选择性测定儿童指血铁

建立了一种快速、准确、高选择性测定指血铁的新方法。铁在pH 4 5HAc -NaAc介质中 ,与PAN -S作用生成红色配合物 ,吸光度与铁离子浓度成正比。该法线性范围 0～ 1 5× 1 0 4μmol·L-1,平均回收率为 99 5 % ,批内变异系数 (CV)和批间变异系数分别为 0 0 2 7与 0 0 39,与原子吸收法具有良好的相关性 ,y (本法 ) =1 0 1x (原子吸收法 ) -2 3,r =0 992 7,P >0 0 5。 6 2例健康儿童指血铁含量为 5 5 0 3～ 974 3μmol·L-1(x± 2S)。     

采用发射极非均匀指间距技术改善功率异质结双极晶体管热稳定性的研究

为了提高多发射极功率异质结双极晶体管的热稳定性,本文利用耦合热阻表征发射极指间距变化对发射极指间热耦合作用的影响,得到了耦合热阻与发射极指间距之间的变化关系,提出了发射极非均匀指间距技术.通过热电反馈模型对采用发射极非均匀指间距技术的功率HBT进行热稳定性分析,得到了多发射极指上的温度分布.结果表明,多发射极HBT在采用非均匀发射极指间距技术后,峰值温度明显下降,温度变化幅度更加平缓,有效地提高了器件的热稳定性. 关键词： 异质结双极晶体管 耦合热阻 指间距     

手掌静脉识别典型波长选择

目前的手掌静脉识别系统均采取主动光源来获取掌脉图像,光源波长的选择直接影响掌脉图像的清晰度与识别性能。典型的掌脉识别成像波长为760,850,890,940 nm,但没有指出哪种波长识别性能最佳。从两个角度解决此问题,从识别特征提取角度,建立了基于Fisher判别率的掌脉成像清晰度模型,对4种波长拍摄的掌脉清晰度进行比较;从特征匹配角度,以3种典型的生物特征识别算法对4种波长拍摄的掌脉图像进行识别性能比较。在包含4种波长共2400幅掌脉图像的自建图库中进行实验,模型选择和典型算法实验结果都表明,850 nm优于其他3种波长。证明了850 nm拍摄的掌脉图像的识别性能最佳。     

A comparative study of jet formation in nozzle‐ and nozzle‐less centrifugal spinning systems

Centrifugal spinning, a recently developed approach for ultra‐fine fiber production, has attracted much attention as compared with the electrospinning, due to its high yield, no solution polarity and high‐voltage electrostatic field requirements, etc. In this study, the jet formation process and spinning parameters on jet path are explored and compared in nozzle‐ and nozzle‐less centrifugal spinning systems. For nozzle‐less centrifugal spinning, fingers are formed at the front of thin liquid film due to the theory of Rayleigh–Taylor instability. We find that the lower solution concentration and higher rotational speed favor the formation of thinner and longer fingers. Then, the critical angular velocity and initial jet velocity for nozzle‐/nozzle‐less centrifugal spinning are obtained in accordance with the balance of centrifugal force, viscous force, and surface tension. When jet leaves the spinneret, it will undergo a series of motions including necking and whipping processes, and then, a steady spiral jet path is formed with its radius getting tighter. Finally, we experimentally study the effect of rotational speed and solution concentration on jet path, which shows that the higher rotational speed results in a larger radius of jet path while the solution concentration has little effect on it. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1547–1559     

三山岛金矿F3断裂带的水文地质工程地质特征及灾害防治

本文对三山岛金矿F3断裂带的构造、岩性和水动力学特征进行了研究,对矿坑开挖中的突水和坑道碎屑流的成因做了探讨,并在水文地质结构、水化学、水同位素及水文地热学的综合研究基础上,对未来的二期井下工程开挖中可能出现的工程地质问题进行了预测,提出了防治方案。     

振动工具传至手臂系统的能量

振动白指病(VWF)是手持振动工具操作工人的职业病,其发病率决定于从工具传入手中的总能量水平。本文介绍了传入手中的能量的计算方法,并结合对操作工人的实测结果加以比较。结论指出,在6.3～1000Hz范围以内,由风镐手柄传入手中的单位时间的功为1.57×10~2J·S~(-1),而由风镐凿子传入手中的单位时间的功则更多。     

Effect of small parameters on the structure of the front formed by unstable viscous-fluid displacement from a Hele-Shaw cell

The process of displacement of a viscous fluid from a Hele-Shaw cell consisting of two plates separated by a small gap is investigated. The front formed when the fluid is displaced from the cell by another, lower-viscosity fluid is unstable. The lower-viscosity fluid breaks through the layer of displaced fluid and forms channels called viscous fingers. As a result, a mixing zone occupied by both displaced and displacing fluids is formed. The structure of the unstable displacement front is investigated when the surface tension forces have no effect on the shape of the fingers. This situation is realized when a water-glycerin mixture is rapidly displaced from the cell by water. Equations taking the inertial and viscous forces acting in the plane of the plates into account are obtained by averaging the Navier-Stokes equations over the cell gap. Using the equations obtained the stability of a plane displacement front traveling in the direction of its normal and the stability of the lateral surfaces of the viscous fingers is investigated when the fluid velocities are parallel to the interface. From the solution for stability of the transverse displacement front it follows that the viscous forces acting in the plane of the plates determine the finger width (when there is no surface tension). Instability also develops in the flow on the longitudinal fluid interface. In this case the destabilizing factor is the inertial forces. Under the action of this instability the fingers, in their turn, lose stability and disintegrate into viscous bubbles.     

Passage to the limit in a chain of the muskat problems(II)

This paper is the continuation of the paper: “Passage to the limit in a chain of the Muskat problems(I)”. In spherically symmetric case one prove that for some class of initial data, generated by a chain of the Muskat problems, the solutions of smooth approximate problems converge to a weak solution of the Muskat problem. This weak solution can be regarded as interpretation of so-called finger phenomenon.     

The toxicity of hydroxylated and carboxylated multi-walled carbon nanotubes to human endothelial cells was not exacerbated by ER stress inducer

The toxicity of hydroxylated or carboxylated MWCNTs to human endothelial cells was modest, and the toxicity was not exacerbated by ER stress inducer.