Mediating Power: Distance Learning Interfaces, Classroom Epistemology, and the Gaze

Distance learning's interfaces—from corresponding through the postal service to the televised talking head—have traditionally been designed from the top down, supporting banking models of learning or, in writing instruction, current-traditional rhetoric pedagogies. Due to temporal and spatial constraints, these interface designs often support (or encourage) one-way communication from the instructor to the student. Students mostly interact with the instructor by asking questions or submitting work, and they tend to have little correspondence with other peers. These methods clearly privilege the instructor's knowledge and evaluation. Furthermore, these interface designs empower the instructor to gaze upon the students and assess them—often not as a corporeal body but as a corpus of texts. Thus, each interface adopted for distance learning sets up a power dynamic in which the capability to share the roles of creating knowledge is juxtaposed with the instructor's capability to normalize the students and reify their own authority through their gaze. In this article we examine the traditional classroom interface through the correspondence course interface, the simulated classroom interface, and the synchronous video interface to raise questions about the infrastructures of distance learning and their implications for student learning.     

测量散射参数的交互换位双信号方法及其应用

叙述了外内向功率波复数比的测量方法,给出了散射参数测量的交互换位双信号测量线方法。用此方法测量了双栅ＧａＡｓＭＥＳＦＥＴ适用散射参数,并用它设计Ｓ波段混合集成双栅ＧａＡｓＭＥＳＦＥＴ可控增益放大器。测试结果与设计吻合。     

一种新型加工中心加工球面的研究

介绍一种采用 STEWART机构的新型加工中心 .对这种加工中心加工球面时各“腿”长度变化的规律进行了分析 .结果表明 :各“腿”长度呈正 (余 )弦规律变化 ,且其变化周期与幅度均相同 ;它们的变化曲线依次相差 1 2 0°到达峰顶 ,其顺序与加工球面上截面圆各点的逆时针顺序相互对应 .导出的各“腿”长度变化的公式可用于指导数控编程     

Estimating the altitude of aerosol plumes over the ocean from reflectance ratio measurements in the O2 A-band

A methodology is proposed to infer the altitude of aerosol plumes over the ocean from reflectance ratio measurements in the O₂ absorption A-band (759 to 770 nm). The reflectance ratio is defined as the ratio of the reflectance in a first spectral band, strongly attenuated by O₂ absorption, and the reflectance in a second spectral band, minimally attenuated. For a given surface reflectance, simple relations are established between the reflectance ratio and the altitude of an aerosol layer, as a function of atmospheric conditions and the geometry of observation. The expected accuracy for various aerosol loadings and models is first quantified using an accurate, high spectral resolution, radiative transfer model that fully accounts for interactions between scattering and absorption. The method is developed for POLDER and MERIS, satellite sensors with adequate spectral characteristics. The simulations show that the method is only accurate over dark surfaces when aerosol optical thickness at 765 nm is relatively large (> 0.3). In this case, the expected accuracy is on the order of ± 0.5 km or ± 0.2 km for POLDER or MERIS respectively. More accurate estimates are obtained with MERIS, since in this case the spectral reflectance ratio is more sensitive to aerosol altitude. However, a precise spectral calibration is needed for MERIS. The methodology is applied to MERIS and POLDER imagery acquired over marine surfaces. The estimated aerosol altitude is compared with in situ lidar profiles of backscattering coefficient measured during the AOPEX-2004 experiment for MERIS, or obtained with the space-borne lidar CALIOP for POLDER. The retrieved altitudes agree with lidar measurements in a manner consistent with theory. These comparisons demonstrate the potential of the differential absorption methodology for obtaining information on aerosol altitude over dark surfaces.     

Light scattering from anisotropic, randomly rough, perfectly conducting surfaces

An approach is introduced for performing rigorous numerical simulations of electromagnetic wave scattering from randomly rough, perfectly conducting surfaces. It is based on a surface integral technique, and consists of determining the unknown electric surface current densities from which the electromagnetic field everywhere can be determined. The method is used to study the scattering of a p-polarized beam from an anisotropic Gaussian, randomly rough, perfectly conducting surface. It is demonstrated that the surface anisotropy gives rise to interesting and pronounced signatures in the angular intensity distribution of the scattered light. The origins of these features are discussed.     

对老龄化背景下居住区活动场所的调查研究——以杭州市若干居住小区为例

以不同类型的居住小区活动场所为调研对象,归纳活动场所在老年人Et常生活交往、社区设施布置及环境规划等方面的不足,从总体模式和细节处理上提出对不同类型居住区在规划与建设上的对策,研究结果可供政府将适老社区改造纳入城市综合改造的政策制定参考,也可为今后社区开发中涉及中老年客户的地产项目提供理论支持。     

基于层次遗传算法的物流配送中心选址策略*

在考虑物流规划部门和客户双方利益的基础上,采用双层规划模型描述物流配送中心的选址问题。基于进化博弈与多目标优化的思想设计了层次遗传算法来求解该模型,通过两个遗传算法的交互迭代求解物流配送中心选址问题。最后通过算例验证了模型与算法的可行性。     

尘粒光电脉冲信号的采集与多道处理技术

在检测净化或超净化场所的含尘浓度和含粒粒度分布方面提出了一种全新的多道处理方法，依光的散射理论及威尔金线性放线法，使得尘粒粒度与通道地址之间确定了一种对应关系，从而给尘粒光电脉冲信号的实时处理带来了极大的方便。     

浸泡后多孔硅的结构及光致发光特性

用电化学腐蚀方法制备了多孔硅样品,在浸泡液中浸泡使其表层多孔层与样品分离,在样品表面形成了丰富的SiO2包裹纳米硅颗粒结构,研究了样品的光致发光(PL)特性.结果表明,与剥离前相比,表层多孔层剥离后PL谱的强度约有10倍的增幅,峰位主要在蓝紫光范围内.在300℃干氧中退火后,样品的发光强度下降为退火前的三分之一,随着退火温度的升高,发光强度有所增强.退火前后有不同的发光机理,退火前光激发主要在纳米硅内,然后在二氧化硅层中的发光中心辐射复合;退火后光激发和光辐射都发生在二氧化硅层中.