采样空间

In order to select optimal grid and good computation efficiency to recover the entire signal, aiming at the Ricker wavelet commonly used in forward modeling, we analyzed the alias and signal restoration problem in finite-difference method based on spatial sampling theorem and seismic wave traveling regulation in media with different velocity, to derive quantitative relationship among the modeling grid size, minimum velocity of model layer, and recovered main frequency of wavelet.

为了选择最佳的网格尺寸以及以最小的计算量完整地恢复出信号，针对地震波场正演模拟中经常使用的Ricker子波，根据空间采样定理和地震波在不同速度介质中的传播规律，分析了有限差分算法中的假频和信号恢复问题，推导出模拟网格尺寸、模型地层的最小速度和能够恢复的子波主频之间的近似定量关系，并用数值算例验证了这一关系。

At present, the speed of acquitting data already has reach above 100 MSa/s in Data Acquisition circuit card of the Virtual Oscillograph.

目前，应用于虚拟示波器的数据采集卡，其实时采样速率在百兆赫兹以上的已经出现，而且还有很大发展空间。

The algorithm first divides the scene into certain layers that do not intersect each other by light's frustums in light space, and generates one shadow map for each layer to ensure that any shadow map does not have the same sample points. Then a faster synthesizing scene shadow method, which avoids operations of pixel layer determination, is given to improve GPU's efficiency.

在光源空间中，利用光源视锥体将场景划分为不相交的多层区域，利用GPU为各层生成阴影图，以确保场景采样点不在多层阴影图中重复出现；同时给出了一种快速综合场景阴影效果的绘制方法，通过避免判断像素层次的操作提高了GPU的利用率。

A geostatistical method was put forward to analyse the spatial variability of combined heavy metal pollution in soils based on GIS. The spatial analysis showed a combined Cu and Cd pollution occurred in the research area, Cu was mainly concentrated in surface layer, but Cd had high concentrations in 0-60cm depth of soil profile. The correlation analysis revealed that the point source pollution was dominated by the pollution let-out of the smeltery.

研究首先建立了基于GIS的地统计学采样和分析方法的步骤，然后着重分析了土壤铜镉复合污染的空间变异特征和影响因素，发现研究区土壤铜镉复合污染为点源污染类型，铜在土壤中具有明显的表聚性，而镉容易迁移，在0-60cm的土层中均形成污染，同时土壤的复合污染已经在水稻籽粒中引起污染物超过食品食用标准。

Moreover, the same case library developed in the previous classification can be reused for time independent classification with satisfactory results.

利用CBR和模糊数学结合，并通过分层随机采样来控制案例在空间上的分布，以反映复杂环境所造成的光谱变化，由此解决遥感分类中的&同物异谱&现象。

The upland yellow-red soil as case, the automatic classification techniques for soil type and soil organic matter map at county scale (1:50,000) were developed based on knowledge classification rules and expert classified simulator; The relationship between physico-chemical properties of coastal saline soils and their hyperspectral reflectance were studied; The multi-temporal RS data were used to detect the land use in coastal soil region; The spatial variability and sampling strategy for coastal saline soils were researched.

以滨海盐碱土为对象，在国内系统的开展了盐碱土理化特性和地面土壤高光谱之间的关系研究，并利用不同时相遥感资料进行盐碱土地区农业土地利用制图，研究了盐碱土不同剖面土壤空间变异特性和高效采样策略。

The numerical results show that the simulation accuracy and efficiency are raised effectively by removing oversampling both in space and time domain.

一系列数值试验表明，该方法能够在保证模拟精度的同时，通过有效降低空间与时间维度上的过采样来显著提高弹性波模拟的效率。

For example, suppose we want to sample and quantize an ordinary television picture with a VGA video controller,so that it can be redisplayed without noticeable degradation.

数字图像通常占用存储空间很大，例如，要得到没有明显的质量下降的NTSC电视图像，数字化时就必须使用640×480×8/像素的矩阵，这样就需要307 200个8位像素，共2 457 600位，并且许多情况下还要求更精确的采样。

Digital pictures are often very large. For example, suppose we want to sample and quantize an ordinary television picture with a VGA video controller,so that it can be redisplayed without noticeable degradation. We must use a matrix of 640×480 pixels, where each pixel is

数字图像通常占用存储空间很大，例如，要得到没有明显的质量下降的NTSC电视图像，数字化时就必须使用640×480×8/像素的矩阵，这样就需要307 200个8位像素，共2 457 600位，并且许多情况下还要求更精确的采样。

By the time of its fall, most of the prisoners were writers who had written against the corruptions of the government.

到它被攻陷的时候，里面多数的犯人是写了反对政府贪污文章的作家。

The most obvious variation to ovum morphological character was that the color was changed from light green to sepiaceous in embryonic development, and all the ovums were almost hatched after 96h.

在胚胎发育过程中卵的形态特征最明显的变化是颜色从淡绿到深褐色，卵在发育96h后卵基本全部孵化。