以发光二极管为背光源的平板显示对人体非视觉的影响

针对以发光二极管为背光源的平板显示对人体生理节律等非视觉的影响,采用节律因子评价模型设计了实验系统.通过全空间平均辐射法,采用国际电工委员会标准中平均图像电平的节目画面,测量显示不同图像时以发光二极管为背光源的平板显示器光辐射的节律因子.结果发现:以发光二极管为背光源的平板显示器在显示白场和大部分彩色图像时的节律因子为5.0以上,其非视觉效应比普通照明要强得多,且与显示的图像内容密切相关;该平板显示器的光学辐射对人体生理节律等非视觉具有不可忽视的影响.     

Comparative Study on Heat Transfer Enhancement of Low Volume Concentration of Al2o3–Water and Carbon Nano-Tube–Water Nano-Fluids in Transition Regime Using Helical Screw Tape Inserts

This study reports the comparison of heat transfer and friction factor characteristics of helical screw inserts in Al₂O₃–water and carbon nano-tube–water nano-fluids through a straight pipe in transition regime with constant heat flux boundary condition. Experiments were carried out by using 0.15% volume concentration of Al₂O₃–water and carbon nano-tube–water nano-fluid with helical tape inserts of twist ratio, TR = 1.5, 2.5, and 3. The thermal performance of helical screw tape inserts with the carbon nano-tube–water nano-fluid is found -to be higher when compared to the Al₂O₃–water nano-fluid. In addition, the maximum enhancement in heat transfer was obtained for the carbon nano-tube–water nano-fluid with helical tape inserts of twist ratio 1.5. The increase in pressure drop of the Al₂O₃–water nano-fluid with helical screw tape inserts is found to be higher compared to the carbon nano-tube–water nano-fluid helical screw tape inserts at lower value of twist ratio.     

Effect of V cut in perforated twisted tape insert on heat transfer and fluid flow behavior of tube flow: An experimental study

ABSTRACT

Present study investigates the heat transfer and friction characteristics of heat exchanger tube fitted with perforated twisted tape (PTT) insert having V cuts. A copper tube of 1 m length and 0.032 m inner diameter is used as test section to collect the experimental data by varying the twist ratio of PTT from 2 to 6 for the Reynolds number range of 2,700–23,400. V cuts are introduced in the PTT and the V-cut relative pitch ratio is varied from 1 to 2. The maximum thermo-hydraulic performance parameter is found to be 1.58.     

Heat Transfer in a Tube Fitted with Vertical and Horizontal Wing-Cut Twisted Tapes

This article reports an experimental investigation on the heat transfer, friction factor, and thermal enhancement factor of a tube equipped with vertical wing-cut twisted tapes, horizontal wing-cut twisted tapes, and plain twisted tapes with twist ratios of y = 2.0, 4.4, and 6.0. The obtained results reveal that the heat transfer rate, friction factor, and thermal enhancement factor in the tube equipped with horizontal wing-cut twisted tapes are significantly higher than those in the tube fitted with vertical wing-cut twisted tapes, plain twisted tapes, and a plain tube. An empirical correlation is subsequently derived from the experimental results.     

Equations of state for solids under strong compression

Abstract

The historical and theoretical background for the different mathematical forms commonly used to represent equations of state (EOS) for solids is reviewed and some criteria are discussed which allow to select some specific forms, which are not only convenient mathematical forms but bring out the physical meaning of the data. Some examples are discussed with emphasis on recent experimental and theoretical data including noble gas solids, simple metals and a few metals with special “anomalies” to illustrate the differences involved in the use of different EOS forms and to point out the specific physical reasons for differences in specific EOS forms.     

Gd2(WO4)3: Eu纳米发光材料中黄昆因子和能量传递速率的实验获得

采用共沉淀法制备了不同Eu³⁺掺杂浓度的Gd₂(WO₄)₃纳米发光材料. 测量了纳米材料样品的X射线衍射谱(XRD) 和场发射扫描电镜, 对样品的结构和形貌进行了表征. 测量了各样品的发射光谱和激发光谱(声子边带光谱), 绘制了浓度猝灭曲线, 确定了最佳的掺杂浓度为20 mol%. 通过声子边带光谱计算了不同掺杂浓度样品的黄昆因子. 测量了不同浓度样品的荧光寿命, 利用Auzel模型对Eu^{3+ 5}D₀能级荧光寿命数据进行了拟合, 确定了⁵D₀能级的固有寿命和猝灭过程中生成的声子数. 本文还根据荧光寿命数据计算了Eu³⁺之间的能量传递速率, 确定了能量传递速率与浓度的关系. 关键词： 钨酸盐 3+')" href="#">Eu³⁺ 黄昆因子 能量传递速率     

像散椭圆高斯光束的M2因子矩阵的理论与实验研究

对像散椭圆高斯光束, 传统的M²因子测量采用M_x²和M_y²来描述光束质量. 当光束绕z轴旋转, M_x²和M_y²会随之变化, 单纯采用M_x²和M_y²来评价激光光束质量并不唯一. 为此采用了像散椭圆高斯光束的M²因子矩阵, 理论推导出了在同一坐标系下光场绕z轴旋转不同角度后的M²因子矩阵, 找出了光场旋转前后的M²因子矩阵元的不变量关系. 数值模拟、 实验测量得到M²因子矩阵主对角元随光斑旋转角度的变化轨迹曲线, 及反对角元随旋转角度的变化规律. 理论推导与实验结果相符. 结果表明, 像散椭圆高斯光束在主方向上时M_x²与M_y²之和最小; 在其他方向上的M_x², M_y²之和大于在主方向上的M_x², M_y²之和; 反对角元随旋转角度呈周期变化, 在主方向上为零. 关键词： M²因子矩阵')" href="#">M²因子矩阵 像散椭圆高斯光束 实验测量 矩阵光学     

A revised many-body potential energy function for the description of the H3O+(H2O)n clusters

A revised potential energy function that has been fitted to the latest set of Kebarle and coworkers [1982, J. Am. chem. Soc, 104, 1462] entropy and enthalpy measurements at T = 300 K is presented. The model assumes a rigid hydronium unit and accounts for all orders of many-body interactions explicitly. The difference with the older function that had been based on earlier measurements by Kebarle and co-workers [1972, J. Am. chem. Soc, 94, 7627; 1967, J. Am. chem. Soc, 89, 6393] is that more compact clusters are generated. We have studied the structural properties of water clusters in the size range 5–80 at T = 250 K within the framework of the (μPT) Grand Canonical ensemble. Clusters with sizes less than about 10 water molecules consist of a four-coordinated first shell, where the fourth water molecule is hydrogen bonded to the oxygen atom of the hydronium ion. The hydration number goes through a minimum value ～1.6, for a cluster size around 50, and it starts increasing again with further cluster growth, to ～2.5 for a cluster size of 250 water molecules, which is the largest cluster examined. On the other hand the water molecule coordination number shows a monotonic increase with cluster size. In small clusters, less than 10, water molecules prefer to be arranged in a chain-like fashion; at sizes around 50, tri-coordinated clathrate-like structures dominate whereas with further size increase the coordination number eventually levels off to the experimental bulk value, at 4.6.     

Natural radionuclide concentrations in soils around Baoji coal-fired power plant,China

Radionuclides are released together with fly ash from the coal-fired power plant and thus add to the natural radiation. Fifty soil samples were collected around the Baoji coal-fired power plant from 25 locations and the natural radionuclide concentrations were determined by a gamma ray spectrometric system. The results show that the activity concentrations in soil samples range from 12.54 to 40.18 Bq kg^?1, 38.02 to 72.55 Bq kg^?1 and 498.02 to 1126.98 Bq kg^?1 for ²²⁶Ra, ²³²Th and ⁴⁰K with the mean values of 27.35, 52.66 and 764.72 Bq kg^?1, respectively. In order to evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity (Ra_eq), the absorbed dose rate (D) and the annual effective dose rate have been calculated and compared with the internationally approved values. The radium equivalent activity in all the soil samples is lower than the safe limit set in the Organization for Economic Cooperation and Development report (370 Bq kg^?1). The average value of the calculated dose rates is higher than the global average value 55 nGy h^?1, and the calculated annual effective dose rate is significantly lower than the average annual external effective dose rate (460 μSv y^?1) of the normal background radiation.     

Space-angle distribution of the reflected charged particles adjusted for spin calculations

The efficiency of the proposed method of solution for the spin-considered highly anisotropic multiple scattering problem is based, following optics, upon the admission that the complete solution of the vectorial transport equation boundary problem is the superposition of the anisotropic and smooth parts, calculated separately. We use a vectorial small angle modification of the spherical harmonics method to evaluate the anisotropic part and the vectorial discrete ordinates method to obtain a smooth one. Some calculation examples for reflected radiation are given.