多波段多极化成像雷达图象识别森林类型效果分析

要陕西省宜川县三北防护林地区获取的航天飞机成像雷达ＳＩＲ－Ｃ／Ｘ－ＳＡＲ数据为基础,进行了森林类型的识别与分类,区分出针叶林、阔叶林和混交林３种森林类型,并通过从ＳＩＲ－Ｃ／Ｘ－ＳＡＲ数据中提取这３种类型森林的后向散射系数,分析了多波段、多极化雷达在森林类型识别中的作用。     

网页制作课程的教学探讨

首先对网页制作课程的特点进行了介绍,进而介绍了如何提高学生学习网页制作课程的兴趣、多媒体网络教室在网页制作课程中的使用以及如何选择合理的教学内容等,其目的是提高网页制作课程的教学效果。     

Network effects as drivers of individual technology adoption: Analyzing adoption and diffusion of mobile communication services

Adoption research has largely ignored the dynamic impact of network effects on technology adoption and diffusion. For example, some technologies become more attractive the more social peers use them as well. But adoption at the same time increases the value for the peers and thereby their adoption decisions as well. Unfortunately, interdependencies like these make adoption and diffusion patterns very complex. Drawing on network effect theory, we develop an adoption and diffusion model that explicitly considers the role of direct and indirect network effects for individual technology adoption, using mobile commerce adoption as application example. By applying a simulation approach we can exemplify and analyze the fundamental adoption dynamics given rise to by network effects. We thereby propose a way of how to incorporate network effects into adoption research and disclose the role of the technology diffusion lifecycle for individual adoption.     

Cartesian product of compressible effect algebras

In the paper, we prove that is compatible with p}, the set of commutant of p, and , the projection commutant of a, are all normal sub-effect algebras of a compressible effect algebra E, and is a direct retraction on E} is a normal sub-effect algebra of an effect algebra E. Moreover, we answer an open question in Gudder’s (Rep Math Phys 54:93–114, 2004), Compressible effect algebras, Rep Math Phys, by showing that the cartesian product of an infinite number of E _i is a compressible effect algebra if and only if each E _i is a compressible effect algebra. This work was supported by the SF of Education Department of Shaanxi Province (Grant No. 07JK267), P. R. China.     

Streaming potential and electroviscous effect in heterogeneous microchannels

This communication presents a theoretical analysis of the streaming potential and the electroviscous effect on pressure-driven flow in heterogeneous microchannels. Compact formulae in terms of phenomenological coefficients are derived for the streaming potential and the apparent viscosity ratio in channels with surface charge variations perpendicular and parallel to the applied pressure gradient. In the latter case, the streaming potential per unit liquid flow in a multi-section channel is found to be simply the summation of that in each homogeneous section. The apparent viscosity ratio is a weighted average of each section where the hydrodynamic resistance serves as the weighting factor. The phenomenological coefficients are specified using electrokinetic flow analysis, through which the streaming potential and electroviscous effect in a two-section slit channel are examined. It is found that they both depend on the arrangement of surface heterogeneity in small microchannels. This dependence, however, gets weak in large microchannels, which is consistent with the prediction of thin double layer approximation.

Empirical Evaluation of User Models and User-Adapted Systems

Empirical evaluations are needed to determine which users are helped or hindered by user-adapted interaction in user modeling systems. A review of past UMUAI articles reveals insufficient empirical evaluations, but an encouraging upward trend. Rules of thumb for experimental design, useful tests for covariates, and common threats to experimental validity are presented. Reporting standards including effect size and power are proposed.     

宽带高效超声波传感器的研究

提出了一种新型的双层压电结构超声波传感器 ,借助于移相电容器的移相作用 ,改变各压电层的激励电压的幅值和相位 ,实现对传感器频率特性的控制 ,从而得到了具有宽频带高效率的超声波传感器 ,为研究宽带高效超声波传感器探索了一条新的途径     

多效蒸发系统优化设计目标函数的建立与求解

建立了带有冷凝水闪蒸的并流多效蒸发系统优化设计新模型。该模型以整个蒸发系统的年总费用（包括加热蒸汽年费用、真空系统年费用以及蒸发器和各辅助设备的年折旧维修费用等）最小为优化目标,以生蒸汽压力、冷凝器真空度及各效有效传热温度痉为决策变量,提出一种新算法——复合形法嵌套拉格朗日乘子法和矩阵法求最优解。算例表明,生蒸汽压力、冷凝器真空度、价格参数和冷凝水闪蒸对优化结果影响显著,按新模型优化设计比常规设计可节省年费用16％左右。新算法对初值要求不高、收敛稳定性好、收敛速度快。     

秸秆还田对农田生态系统及作物生长的影响

秸秆还用是利用秸秆的一种有效方式．大量试验表明,秸秆还田会对土壤产生多种作用：能改善土壤物理性状,降低土壤容重,增加孔隙度;能增加土壤微生物数量,增强生物和多数酶的活性;增加土壤有机质积累和养分含量;能改变土壤腐殖质组成及特性;影响作物生长发育,促进作物产量提高．其中,秸秆覆盖还田还具有蓄水保墒,调节地温和保持水土,抑制田间杂草等功能．总之,秸秆还田对农田具有良好的生态效应。     

水田施用涂层尿素对氮素挥发抑制效果的模拟试验

水田土壤施用涂层尿素抑制氮素挥发损失的研究结果表明,涂尿素素肥料在全层混施,8cm深施和表面撒施3种施肥方式下均有抑制NH3和NOx挥发损失的作用,涂层尿素与普通尿素相比,表面撒施降低氮素（NH3＋NOx)挥发损失率达32．8％,8cm深施降低氮素（NH3＋NOx)挥发失率达19．9％,全层混施降低氮素（NH3＋NOx)挥发损失率达6．9％。