Heat and Moisture Transfer in Wet Sand Exposed to Solar Radiation—Models and Experiments Concerning Buried Objects

One promising method of locating buried objects, such as land mines, is to use optical systems for detecting contrasts in surface temperature. With enhanced knowledge about the interacting physical processes behind these temperature contrasts, it is possible to improve detection precision. In such a context, moisture movement in the soil and moisture evaporation from the surface have been found to be of particular interest. This study was based on indoor experiments on wet and dry sand exposed to radiation from a solar panel. Simulations of heat and moisture transfer conducted with a one-dimensional model are also presented for the experiments. The calculations were successful in accurately predicting surface temperatures for both wet and dry sand, making it possible to predict surface temperatures under different conditions. These findings will contribute to increasing the probability of successful detection of buried objects under real conditions using optical methods.     

Interfacial Dipoles and Radiated Energy

Electric dipoles radiate an electromagnetic field into their surroundings. The electric and magnetic fields from a point source or from linear dipoles have components parallel to a spherical surface but also a radial component. In most investigations on radiated fields, only the part of the electric field that is parallel to a spherical surface is taken into account. The argument is that only that component contributes to the radiated energy. Here we show that the phase front in the lower half space is not a spherical surface and hence, the radial components contribute to radiated energy. We show differences in radiation patterns for point electric dipoles and linear dipoles, either modeled as perfectly conducting wires or as resistively loaded wires. Our primary interest lies with improving image resolution through processing of Ground-Penetrating Radar data. Here the emphasis lies with understanding the radiation characteristics of linear dipoles that can be incorporated with image processing algorithms. The model uses a thin-wire approximation for the transmitter antenna. The solution to the discrete system of equations is solved, incorporating interaction between the interface, using a CGFFT scheme including symmetrization and a newly developed preconditioning operator. We look at the electric and magnetic fields as well as the time-averaged Poynting vector radiation patterns in the E-plane and H-plane of the transmitting antenna. The results show that the radial component of the radiated electric and magnetic field is not negligible, even at distances more than seven wavelengths away from the antennas.     

变速铣削的试验研究

通过试验考证了变速铣削的减振效果和机床电机电流的波动幅度，试验结果表明，变速铣削同样具有明显的减振效果。机床电机电流虽有波动，但波动幅度不大，不会影响电机的正常使用，变速铣削具有良好的应用前景。     

同步辐射晶体单色器晶体热应变的模拟与实验结果的比较

报道了同步辐射装置光束线关键部件之一的晶体单色器晶体热应变的ANSYS有限元模拟结果,并与实验结果进行了比对,模拟结果在实验误差范围(约士15%)内与实验数据符合,证明了模拟结果的可靠性.     

Water and Radiation Effect on Sweet Sorghum Productivity

Suitability of sweet sorghum in Greece, where irrigation supply during crop development is limited as rainfall is scarce and evapotranspiration loss is high, is examined in relation with radiation availability. A two-year field experiment was conducted, in central Greece, imposing four soil water regimes via different irrigation treatments: (1) Highly irrigated, (2) Highly irrigated till anthesis when irrigation stopped, (3) Medium irrigated, and (4) Low irrigated. It was found that above-ground dry biomass production from non-water-stressed sweet sorghum plants suggests a high productivity potential among C₄ crops. Under water shortage, radiation use efficiency may be significantly lower. Radiation use efficiency seems to be linearly related to water consumption. Stressed plants (probably except severely stressed) seem to use available water more efficiently than unstressed plants. The slope of the line relating dry matter produced and water evapotranspired increases the sooner the stress is sensed. Yield reduction resulting from post-anthesis irrigation stopage is very little. High water use efficiency values tend to be related with low radiation use efficiency values.     

THERMAL RADIATION EFFECTS ON THE COMBUSTION BEHAVIOR OF POROUS CHAR PARTICLES

The effects of thermal radiation on the pseudosteady state and transient behavior of porous char particles exposed to an oxygen containing environment are investigated. The numerical simulation results show that particles that do not interchange radiant energy with their environment are characterized by wider ambient temperature regions where multiple steady states exist, higher combustion rates, and lower burning times     

同步辐射x射线光刻制作深亚微米T形栅

x射线光刻非常适合用于深亚微米T形栅的制作,这是因为它的高分辨率、大的曝光视场和高的生产效率足以满足MMIC制造工艺的要求。本文中我们首先对我们的x射线掩模制造工艺进行介绍,然后论述了一种用于制造深亚微米T形栅的两层胶工艺,介绍了所取得的一些研究结果,最后对国内的深亚微米光刻现状进行了简要分析。     

超导体核辐射探测器的探测原理

一、引言对于某些核辐射探测器,降低它们的工作温度便可得到较好的探测器性能,例如硅和锗探测器,当工作温度为77K时,能量分辨可提高很多。一些金属和它们的氧化物在极低温度下成为超导体,利用这种超导现象有可能得到性能极好的探测器,也有可能比现在已实用的半导体(?)测器的能量分辨要提高一个量级。高分辨测量有可能在许多领域内得到应用。关于在极低温度下((?)IK)对超导体核辐射探测器已有一些评论,这里仅介绍超导体核辐射探测器的探测原理。     

加载单极子天线的时域辐射特性

基本的单极子天线由于其本身的特社会在天线内部对馈入的信号进行多次反射，严重,制约着它的辐射性能。采用时域有限差分法对比计算了加载与非加载单极子天线的时域辐射特性。计算结果表明，加载是改善单极子天线时域辐射性能的最佳选择，但需要以牺牲辐射效率为代价。     

计算抛物面天线支杆对方向图影响的简化方法

本文基于物理光学球面波展开法，提出一种计算抛物面天线支杆对其方向图影响的简化方法，文中导出了计入支杆散射的天线辐射方向图的解析表达式，并给出了支杆对其方向图旁瓣电平影响的计算实例，数值结果表明，本文所提出的新方法不仅计算结果精度高，而且所需计算机容量小，运算速度快，可应用于天线工程设计。