MULTICARRIER DS—CDMA WITH ADAPTIVE MODULATION AND POWER ALLOCATION

Adaptive modulation and power allocation is introduced into the multicarrier DSCDMA system to improve the system performance and bandwidth efficiency.First,the system design appropriate for adaptive modulation and power allocation is given,then the algorithm of adaptive modulation and power allocation is applied.Simulation results demonstrate great performance improvement compared with the fixed modulated one.     

Exchange-correlation errors at harmonic and anharmonic orders: the case of bulk Cu

As an aid towards improving the treatment of exchange and correlation effects in electronic structure calculations, it is desirable to have a clear picture of the errors introduced by currently popular approximate exchange-correlation functionals. We have performed ab initio density functional theory and density functional perturbation theory calculations to investigate the thermal properties of bulk Cu, using both the local density approximation (LDA) and the generalized gradient approximation (GGA). Thermal effects are treated within the quasiharmonic approximation. We find that the LDA and GGA errors for anharmonic quantities are an order of magnitude smaller than for harmonic quantities; we argue that this might be a general feature. We also obtain much closer agreement with experiment than earlier, more approximate calculations.     

Electronic properties of magnetically doped nanotubes

Effect of doping of carbon nanotubes by magnetic transition metal atoms has been considered in this paper. In the case of semiconducting tubes, it was found that the system has zero magnetization, whereas in metallic tubes the valence electrons of the tube screen the magnetization of the dopants: the coupling to the tube is usually antiferromagnetic (except for Cr).     

Computational analysis of thin coating layer failure using a cohesive model and gradient plasticity

Thermal barrier coatings (TBC) are widely used to prevent transient high temperature attack and allow components high durability. Due to strong inhomogeneous material properties the TBC failure often initiates near the interface between the brittle oxide layer and the ductile substrate. A reliable prediction of the TBC failure requires detailed information about the crack tip field and the consequent fracture criteria. In the present paper both cohesive model and gradient plasticity are used to simulate the failure process and to study interdependence of the interface stress distribution with the specific fracture energies. Computations confirm that combination of the two models is able to simulate different failure mechanisms in the TBC system. The computational model has the potential to give a realistic prediction of the crack propagation process.     

φ90mm低铬铸球开裂失效分析

φ90mm低铬铸球在做落球试验中过早出现开裂现象。将该铸球材质进行化学成分分析、力学性能测定及金相组织观察。分析结果表明，该铸球的材料中夹杂物含量较高，其硬度值又偏高，铸球内部又存在严重缩松及其铸态组织中存在大量奥氏体转变产物，致使铸球在落球试验中过早开裂。经过工艺措施的改进，解决了铸球出现过早开裂的现象。     

A New Measure of Misfit for Covariance Structure Models

Various fit indices exist in structural equation models. Most of these indices are related to the noncentrality parameter (NCP) of the chi-square distribution that the involved test statistic is implicitly assumed to follow. Existing literature suggests that few statistics can be well approximated by chi-square distributions. The meaning of the NCP is not clear when the behavior of the statistic cannot be described by a chi-square distribution. In this paper we define a new measure of model misfit (MMM) as the difference between the expected values of a statistic under the alternative and null hypotheses. This definition does not need to assume that the population covariance matrix is in the vicinity of the proposed model, nor does it need for the test statistic to follow any distribution of a known form. The MMM does not necessarily equal the discrepancy between the model and the population covariance matrix as has been assumed in existing literature. Bootstrap approaches to estimating the MMM and a related quantity are developed. An algorithm for obtaining bootstrap confidence intervals of the MMM is constructed. Examples with practical data sets contrast several measures of model misfit. The quantile-quantile plot is used to illustrate the unrealistic nature of chi-square distribution assumptions under either the null or an alternative hypothesis in practice.

     

闪光灯泵浦Nd3+:GGG激光特性研究

用闪光灯泵浦掺钕钆镓石榴石(Nd^3 ：GGG)激光晶体，研究了脉冲宽度0．5ms、1ms、1．5ms和2ms的放电泵浦下激光输出，实验获得了1．92J的最大激光能量．     

重复压裂气井产能模拟研究

由于重复压裂气井原有裂缝的失效程度难以评价。导致重复压裂气井的产能预测常常有很大的误差。为此，根据重复压裂气井的压前产量和舍水率，拟合了原有裂缝的有效率，在考虑新裂缝和原有裂缝共同作用的情况下，建立了气、水两相平面二维的裂缝-油藏数学模型，通过对模型的数值求解，对重复压裂气井进行了产能评价。研究表明，在考虑新、老裂缝共同作用下的产能评价方法，能更为准确地预测重复压裂后的生产动态情况，对压裂时机的确定、压后经济效益的预测都具有重要的指导意义。     

塔里木盆地雅—轮地区断层封堵性研究

塔里木盆地雅—轮地区大部分圈闭及油气藏的形成与断裂作用密切相关,对断层封堵性的综合研究已成为该地区油气勘探的重要因素。应用地质定性分析、Allen剖面分析及断层涂抹量计算等方法,通过对研究区4个典型断层封堵油气藏的系统解剖研究,建立雅—轮地区断裂封堵性评价标准,对雅—轮地区断层的封堵性进行综合评价。雅—轮地区断层整体封堵效果良好,断层在圈闭形成和油气聚集过程中起着重要的控制作用,形成一系列沿断层带状分布的油气藏。亚南断裂的封堵效果东部要优于西部,下部要优于上部。轮台断裂在不同部位、不同深度均存在着不同的封堵性能,封堵非均质性明显,总体显示断裂东部地区(也根附近)的封堵性要好于西部雅南地区。