空群

特别是民间掠夺式采矿留下的采空区群，更是大小不一，形态各异，层位复杂。

Especially , many abandoned stopes left by folk plundering mining are in different size and distributed complicatedly .

最后就矿山具体存在的空区群，建立三维空区群模型进行稳定性分析。

Finally , an actual cavity group with three cavities under open-pit limit was modeled in3D to calculate its stability .

基于MATLAB的差分空时酉群码的仿真实现

Simulation Implementation of Differential Space-Time Unitary Group Code Based on MATLAB

随着码率的不断增加，酉空时码群中的各个星座点之间的乘积距离会变得越来越小，从而导致性能恶化。

With the increase of the code rate , the production distance between the constellation of the unitary group code decreases rapidly and deteriorates the performance of the system .

人们从矿产资源的开采中获得了巨大的经济效益，但同时，不科学的开采及民间的掠夺式滥采形成了复杂的采空区（群），从而极易引发各种地质灾害。

People benefit a lot economically from the exploitation of mineral resources , however , unscientific mining and civil predatory mining leads to formation of the complicated goaf ( group ), which can easily cause a variety of geological disasters .

主要研究内容归纳如下：首先，在MIMO系统中，针对广义分层空时码的群检测算法引起的分集增益损失问题，提出迭代群检测算法。

The main contributions of the thesis are summarized as follows . Firstly , iterative group detection algorithms are proposed to reduce the diversity loss of generalized layered space-time codes due to the group detection in MIMO systems .