Modeling of Diffusion in Ellipsoidal Solids: A Comparative Study

Most food materials are usually measured in three mutually perpendicular dimensions (length, width, and thickness) and considered approximately as general ellipsoids. In this article, we briefly reviewed the available studies on how to deal with the diffusion problems in ellipsoidal solids. A three-dimensional (3-D) model was proposed to accurately represent the kernel geometry and rigorously interpret the diffusion phenomena. By the finite difference method, the numerical solution of the diffusion equation for kernels of different shape factors was obtained and compared with those predicted by the one-dimensional (sphere) model and two-dimensional (axi-symmetrical body) model. Meanwhile, the effectiveness of the latter two models was evaluated.     

通过宿主图像隐蔽传递双随机位相编码信息

本文基于图像隐藏和双随机位相编码技术提出了一种隐蔽传递信息的方法 ,可以把一幅或多幅需隐蔽传递的图像经双随机位相编码后隐藏在另一幅任意选取且足够大的宿主图像中。而在恢复隐蔽图像时 ,可直接对携带隐藏信息的融合图像进行处理 ,不需要利用原始宿主图像 ,且重构图像的质量较好 ,不受宿主图像的影响     

交联聚合物溶液与聚合物溶液的特性差异

采用光学显微摄影、动态光散射和核孔膜过滤等方法，研究了低浓度部分水解聚丙烯酰胺(HPAM)与柠檬酸铝(AlCit)形成的交联聚合物溶液(LPS)中交联聚合物线团(LPC)的形态、尺寸、变形性等特性。结果表明，LPC与聚合物线团(PC)相比，在形态、尺寸、变形性能等方面存在明显差异。干燥后的LPS样品中，LPC为球形，PC的形状不清晰。低于某一临界质量浓度(0．200～0．300g／1)时，LPC尺寸略小于PC；高于此浓度后，LPC的尺寸始终大于PC。HPAM／AlCit交联体系的临界质量浓度(0．280g／1)略高于聚合物溶液的临界交叠质量浓度(0．250g／1)。由于分子内的交联作用，与PC相比，LPC的剪切变形能力和水化变形能力有限，LPC较强的抗剪切变形特性使其具有特殊的封堵多孔介质的能力。     

弯曲河流三维数值模型

将平面正交曲线坐标系和垂向σ伸缩坐标系相结合,建立适合弯曲河流的三维水流数值模型。采用模式分裂技术将控制方程分解为外、内模式联合求解,方程的离散采用有限差分法。采用嘉陵江广元城区河段5个弯段内7个典型横断面地形、水位和流速资料对本文模型进行验证,模型成功地模拟出了水面横比降和弯道二次流,模拟结果与实测数据吻合较好。     

电扫描恒差比幅测向精度分析

电扫描多波束恒差比幅测向体制在现代雷达截获接收机中有着广泛应用。他是由微波开关依次快速接通各个天线，通过比较相邻天线接收通道上信号幅度的大小来实现测向的。文章首先以任两个相邻天线和全向参考天线接收及信号处理过程，详细推导了电扫描恒差比幅测向方程。然后以该方程为基础，根据该方程中各个观测量相互独立的特点，方位测量误差的均方根值可由测向方程的全微分求得，并将其作为电扫描恒差比幅测向的精度，由该精度公式可以看出，电扫描恒差比幅测向有很高的精度，并且在不同的角度上，其精度保持稳定。     

水面散热的焓差公式及其应用

我国现在所用的水面散热公式，包括蒸发散热、对流散热、辐射散热三部分，以此为基础建立的计算蒸发系数的通用公式是有缺陷的，其中不应包含水气温差。因为水气温差是对流散热的推动力，而蒸发散热只传质，不传热，只产生汽化潜热，所以不应有对流散热的成分。产生上述问题的原因是在实验中蒸发散热和对流散热是不可分的，本文将蒸发散热和对流散热合为一个公式，提出用焓差公式来整理试验资料，给出了以焓差为推动力的散热公式，使原有计算公式得到简化,更符合实际。     

Development of a laser wavefront sensor for measurement of discharges in air

A laser wavefront sensor of the Shack‐Hartmann type capable of simultaneous measurement at two wavelengths was constructed. The sensor uses a single optical path, and is suited for applications such as high‐voltage discharges in air, in which large insulation distances are necessary. The sensor was used to detect optical path differences due to an impulse discharge in air across a needle–plane electrode gap of gap length 17 mm. Optical path differences were measured at laser wavelengths of 532 and 1064 nm at 1.6 µs after insulation breakdown across the gap. From the difference in optical path differences at the two wavelengths, a line‐integrated electron density distribution in the direction perpendicular to the gap was obtained near the high‐voltage electrode. The distribution had a peak value of 1.4 × 10²⁰m^?2 and a full width at half maximum of 4.4 mm. Because of the coverage of a large observation area including the entire gap, the spatial resolution was 1.4 mm, which was inadequate to obtain the precise form of the electron density distribution. However, the results show the possibility of applying laser wavefront sensing to electron density measurement. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 10–17, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10247     

Gender-Typed Play and Amniotic Testosterone.

Sex differences in play are apparent in a number of mammalian species, including humans. Prenatal testosterone may contribute to these differences. The authors report the first attempt to correlate gender-typed play in a normative sample of humans with measurements of amniotic testosterone (aT). Testosterone was measured in the amniotic fluid of 53 children (31 boys and 22 girls). A strong sex difference was observed in aT and, at ages 4.75 to 5.8 years, on a modified version of the Child Game Participation Questionnaire. Hierarchical regression analyses on the entire group and within-sex correlations suggested that variations in aT did not contribute to individual differences in game participation as reported by the mother. A critique of explanations for this finding is presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

变形分数傅里叶变换双随机相位加密技术

提出变形分数傅里叶变换双随机相位编码技术。详细阐述了编码与解码的光学原理,由于变形分数傅里叶变换比分数傅里叶变换多两个分数傅里叶变换阶次,所以,变形分数傅里叶变换双随机相位编码技术比分数傅里叶变换双随机相位编码技术增加了两重密钥,进一步提高了系统的保密性能。并进行了计算机模拟验证,结果证明该原理是正确的。     

FDTD方法及其在多注电子光学系统研究中的应用

采用时域有限差分(FDTD)方法对L波段100 kW多注速调管的单个电子枪进行三维模拟计算,通过设置最小网格尺寸和发射时间间隔,得出的电流和导流系数与采用EGUN等软件计算的结果相一致,通过从MAFIA中导入三维磁场数据,模拟了位于径向不同位置处电子注通道的电子轨迹,研究发现在磁场均匀性较好的情况下,位于径向不同位置处的电子轨迹相差很小,同时讨论了如何减少模拟时间的问题.本文最后计算了多个注的电子枪,求得了电流值和导流系数,从中导入数据可以分段模拟多注速调管高频互作用段的注波互作用,以及收集极区域的电子发散.