差分变异本质粒子群的模糊熵图像分割

基本本质粒子群算法存在易陷入局部最优以及过早收敛的缺点。在基本本质粒子群算法的基础上,借鉴差分进化中利用差分量对种群进行变异操作的思想,提出了差分变异本质粒子群优化算法。结合图像模糊熵,得到了基于差分变异粒子群优化的模糊熵图像分割算法。算法利用差分变异本质粒子群来搜索使图像模糊熵最大的参数值,得到分割阈值对图像进行分割。通过与其它两种本质粒子群算法的分割结果比较表明该算法取得了令人满意的分割结果,算法运算时间很小,能够满足对煤尘浓度实时精确测量的要求。     

位山引黄灌区地下水超采区水的综合治理与保护

位山引黄灌区下游由于水资源环境差等原因，地下水严重超采．为求得水资源的良性循环，应采取对该区域水资源施行统一管理、引水补源和节约用水等措施。     

纳米技术在包装中的应用

简要介绍了纳米技术的相关概念,从包装材料及其工艺、包装机械、包装印刷、包装防伪等方面分析了纳米技术在包装中的应用.研究表明:纳米技术为包装的各个领域带来很多好处.越来越多的纳米包装将会出现在大家面前,同时也可能出现一些难以估计的负面影响.     

纳米技术在包装中的应用

简要介绍了纳米技术的相关概念，从包装材料及其工艺、包装机械、包装印刷、包装防伪等方面分析了纳米技术在包装中的应用。研究表明：纳米技术为包装的各个领域带来很多好处，越来越多的纳米包装将会出现在大家面前，同时也可能出现一些难以估计的负面影响。     

浅析电视频道包装的个性化

从频道包装的视觉识别角度来着重分析影响电视频道包装个性化的因素.通过案例、图示、对比的方式,详细论述了色彩配置、画面风格、运动方式、声音、字体,对电视频道包装个性化的影响.     

Determinants of extinction in the fossil record

The causes of mass extinctions and the nature of biological selectivity at extinction events are central questions in palaeobiology. It has long been recognized, however, that the amount of sedimentary rock available for sampling may bias perceptions of biodiversity and estimates of taxonomic rates of evolution. This problem has been particularly noted with respect to the principal mass extinctions. Here we use a new compilation of the amount of exposed marine sedimentary rock to predict how the observed fossil record of extinction would appear if the time series of true extinction rates were in fact smooth. Many features of the highly variable record of apparent extinction rates within marine animals can be predicted on the basis of temporal variation in the amount of exposed rock. Although this result is consistent with the possibility that a common geological cause determines both true extinction rates and the amount of exposed rock, it also supports the hypothesis that much of the observed short-term volatility in extinction rates is an artefact of variability in the stratigraphic record.