基于JADE与特征提取的正交/非正交空时分组码盲识别

针对非协作多输入多输出通信系统中正交空时分组码(orthogonal space-time block codes, OSTBC)与非正交空时分组码(non-orthogonal space-time block code, NOSTBC)的盲识别问题,提出结合特征值矩阵联合近似对角化(joint approximate diagonalization of eigenvalue matrix, JADE)与特征提取的盲识别方法。首先将接收信号转换为盲源分离问题中的线性瞬时混合模型,然后利用JADE算法估计出该模型的虚拟信道矩阵,根据该信道矩阵的相关矩阵为数量矩阵的特点,从相关矩阵中提取特征参数,利用此特征参数识别OSTBC与NOSTBC。仿真结果表明,在较低信噪比以及不同的调制模式下,所提方法均可有效识别出OSTBC与NOSTBC。     

Forecasting Forward Defaults with the Discrete‐Time Hazard Model

For predicting forward default probabilities of firms, the discrete‐time forward hazard model (DFHM) is proposed. We derive maximum likelihood estimates for the parameters in DFHM. To improve its predictive power in practice, we also consider an extension of DFHM by replacing its constant coefficients of firm‐specific predictors with smooth functions of macroeconomic variables. The resulting model is called the discrete‐time varying‐coefficient forward hazard model (DVFHM). Through local maximum likelihood analysis, DVFHM is shown to be a reliable and flexible model for forward default prediction. We use real panel datasets to illustrate these two models. Using an expanding rolling window approach, our empirical results confirm that DVFHM has better and more robust out‐of‐sample performance on forward default prediction than DFHM, in the sense of yielding more accurate predicted numbers of defaults and predicted survival times. Thus DVFHM is a useful alternative for studying forward default losses in portfolios. Copyright © 2013 John Wiley & Sons, Ltd.     

A genome-wide association study identifies new susceptibility loci for non-cardia gastric cancer at 3q13.31 and 5p13.1

Gastric cancer, including the cardia and non-cardia types, is the second leading cause of cancer-related deaths worldwide. To identify genetic risk variants for non-cardia gastric cancer, we performed a genome-wide association study in 3,279 individuals (1,006 with non-cardia gastric cancer and 2,273 controls) of Chinese descent. We replicated significant associations in an additional 6,897 subjects (3,288 with non-cardia gastric cancer and 3,609 controls). We identified two new susceptibility loci for non-cardia gastric cancer at 5p13.1 (rs13361707 in the region including PTGER4 and PRKAA1; odds ratio (OR) = 1.41; P = 7.6 × 10(-29)) and 3q13.31 (rs9841504 in ZBTB20; OR = 0.76; P = 1.7 × 10(-9)). Imputation analyses also confirmed previously reported associations of rs2294008 and rs2976392 on 8q24, rs4072037 on 1q22 and rs13042395 on 20p13 with non-cardia gastric cancer susceptibility in the Han Chinese population.     

Anomalous self-optimization of sulfate ions for boosted oxygen evolution reaction

Broadly,the oxygen evolution reaction(OER)has been deeply understood as a significant part of energy conversion and storage.Nevertheless,the anions in the OER c...     

降雨诱发泥石流危险性动态评价

为了建立更为客观且评价精度更高的泥石流危险性评价模型,深入分析泥石流危险性的影响因素,运用层次分析法构建了不同降雨工况下动态权重系统,结合模糊综合评价法实现了对苏峪口泥石流危险性动态评价。结果表明：随着降雨强度变化,指标权重呈现非线性动态变化特征,研究区泥石流危险性对各危险等级的隶属度不断变化,表现为随着降雨量增大,危险性逐级升高。分析认为所提出的泥石流危险性动态评价方法在考虑降雨指标取值变化对评价结果影响的基础上,兼顾了指标权重对降雨工况的响应,评价结果相对传统方法更为精准,也更符合客观实际。     

基于栅格法的人字齿有限元接触精确建模方法

提出了一种基于栅格法的人字齿有限元接触精确建模方法,将栅格法-27分法加密模板扩展到齿面局部加密建模中,根据单元间的节点连通关系建立编号索引矩阵,并以索引值判别过渡单元的加密模式;提出编号轮转算法将待加密单元节点重新编号,并结合节点映射算法修正齿面加密节点坐标;给出了保证节点几何精度、网格密度及质量的参数化精确建模流程．应用提出的精确建模方法对一对人字齿轮进行了有限元建模,分析了人字渐开线齿面的接触应力分布状态,并与赫兹接触理论对比验证了精确建模方法的正确性,为齿轮的加强接触分析提供有效的建模方法．     

MnF2吸收光谱的理论解释

通过对Ｍｎ＾２＋的实验值进行半经验的拟合,得到了它的３ｄ电子波函数,并利用晶体场理论中的点电荷模型,计算也ＭｎＦ２晶体的吸收光谱,计算结果与实验值吻合很好。     

超低碳冷轧薄板单向拉伸过程变形机理

通过对超低碳ＩＦ钢冷轧薄钢板拉伸过程中不同变形程度的测试与扫描电镜的观察,研究了其表面形貌及组织的变化规律．探讨了超低碳钢韧性断裂中内部孔洞形成机理,并指出超低碳钢中的微孔洞不是主要由夹杂物或第二相粒子产生,而是因为位错的滑移、集聚,在原有损伤处形成．     

染料脱色菌群的分离及对红色偶氮染料的脱色研究

从印染厂废水池的污泥中分离筛选到一组染料脱色菌群。研究了该脱色菌群在不同温度、pH 值、培养时间、需氧与否和是否含有机物的条件下对红色偶氮染料的脱色情况。试验结果表明,脱色菌群对外界条件无严格要求,适应范围广。但在pH 为9.0 ,温度为30 ℃,培养时间为72h,厌氧和含有机物的条件下对染料有较好的脱色效果     

截干萌在银杏叶用园培养中的应用机理

研究了截干萌对银杏高生长,单叶干重、单株叶产量和黄酮含量的影响,结果表明：（１）第一次截干后,银杏高生长量比对照高,第二次截干后,距地３０ｃｍ截干的处理高生长也超过对照,约为对照的１２７％;（２）截干后,银杏单叶干重显著高于对照;（３）第一次截干后,银杏单株一显著对照,第二次截干后,３０ｃｍ截干高度的处理单株叶产量约为对照的１１２％,且随截干高度的增加,单株叶产量有随着增加的趋势;（４）截干后,银