急斜煤层矿压显现规律的研究

本文简述了国内外急斜煤层矿压研究的概况;介绍了对4个急斜煤层长壁工作面进行矿压观测所获得的结果及规律;为配合理论研究在实验室作了相似材料模拟、计算机摸拟;简述了对急斜煤层开采后围岩运动及破断规律研究所建立的两种假说。     

Multi-user performance analysis of differential frequency hopping system over Rayleigh-fading channel

A novel non-coherent detection scheme for differential frequency hopping （DFH） system is proposed in asynchronous multi-user environments over Rayleigh-fading channels. The synchronous and asyn- chronous multi-user performances of DFH with the conventional detection scheme and this novel detection scheme are analyzed, respectively. The performance results are validated with simulation. The results of analyses and simulations prove two conclusions. Firstly, the performance of asynchronous multi-user DFH system overcomes that of synchronous multi-user DFH system over Rayleigh-fading channel. Secondly, the novel detection scheme can achieve better performance than the conventional non-coherent detection scheme in asynchronous multi-user environments.     

银杏种仁中银杏酚酸的提取及组分研究

银杏酚酸是银杏种仁中的过敏原。笔者以单因素试验为基础,采用正交试验设计优化银杏酚酸的提取工艺,并通过HPLC对其组分进行分析。结果表明:影响银杏酚酸提取量的主次顺序是乙醇浓度、料液比、提取时间,最佳提取条件为乙醇体积分数85%、提取时间12 h,料液比1∶12.5,在此条件下得到的银杏酚酸主要有5种。验证性实验表明,在该条件下,银杏酚酸的提取量(PW)达到147.94μg/g,残留的银杏酚酸质量分数为2.19%,显著小于国际标准。     

Linearization learning method of BP neural networks

Feedforward multi-layer neural networks have very strong mapping capability that is based on the non-linearity of the activation function, however, the non-linearity of the activation function can cause the multiple local minima on the learning error-surfaces, which affect the learning rate and solving optimal weights. This paper proposes a learning method linearizing non-linearity of the activation function and discusses its merits and demerits theoretically. Supported by Wuhan Shenguang Project, the National Natural Science Foundation of China and the 863 High Techology Project Zhou Shaoqian: born in Mar. 1962,Ph. D graduate student     

顶煤破坏规律及合理顶煤厚度的研究

在现场实测及实验室相似模拟研究的基础上,建立弹性深梁力学模型,对顶煤破坏特征及其机理进行了研究,进而探讨了确定合理顶煤厚度的方法。     

On design of physical random access channel in high-speed railway LTE systems

For the uplink in the long-term evolution （LTE） systems, the physical random access channel （PRACH） adopts Zadoff-Chu （ZC） sequences as preamble sequences, and each user can choose a unique cyclic shift for user identification. In high-mobility scenario, the Doppler fre- quency shift raises up the false alarm probability by inducing the correlation peak offsetting at the receiver side. Traditional detection method utilizes multiple search win- dows for searching the potential uplink users. When the Doppler frequency shift is larger than the subcarrier spac- ing, the energy of correlation peak leaks outside the search window and increases the false alarm probability. In this paper, we present a novel design for PRACH preamble sequence for high-speed railway scenario. Through numerical observation, we find out that the offset of the correlation peaks only depends on the initial root sequence number and the length of ZC sequences. Therefore, the root number of ZC sequences should be carefully designed to generate a preamble sequence to fight against the Doppler frequency shift. Consequently, those offsets of the corre- lation peaks are concentrated within a single search win- dow, resulting in lower complexity of detection and lower probability of false alarm for random access in LTE uplink.     

广义Gibson地基内部作用线源荷载的基本解

针对广义Gibson地基在埋藏线源荷载作用下的静力学问题,通过将内源线荷载等效为在相同深度范围内连续的集中点荷载的累加,采用Hankel积分变换方法,再结合具体的边界条件,推导得到地基土体在内源点荷载作用下的Hankel变换域中的解,并利用Hankel逆变换将变换域内的解转换为物理域内的积分形式解。然后对该解沿深度方向积分求得了地基土体在三种沿深度分布线荷载作用下的竖向位移解,并对地基内部沿深度分布线源荷载作用下地基表面土体变形问题通过具体算例,运用数值积分计算方法,分析了地基土体的非均质性、荷载分布深度等因素对地基表面土体竖向位移的影响。结果表明:①地基土体的非均质性对地基表面竖向位移有较大影响,相对而言,线源荷载竖向分布深度及荷载分布形式对地表竖向位移的影响较小,且地表竖向位移主要受浅层荷载的影响;②荷载分布深度对地表位移的影响主要体现在土体非均质性较小情况下,且在荷载沿深度减小分布时最为显著。     

基于ECGP的企业数据集成研究

提出了一种基于ECGP的数据集成模型,克服了传统数据集成模型中数据源节点过多带来的集成效率低、数据节点管理混乱等不足.ECGP提供了一种对等节点的分层方法,将节点按照拓扑优先级聚集成簇,从普通对等节点中选出主干节点作为簇的中心和服务提供者.还提出了基于软件即服务(SaaS)的NUTS-Sync数据集成框架,并讨论了2种数据集成模式:同步集成模式;异步集成模式.应用案例验证了模型的可行性和有效性.     

梳棉机的混和作用及其与均匀作用的关系

本文主要从理论上探讨了梳棉机的混和作用及其与均匀作用的关系。从梳棉机的输入输出微分方程出发,推导了梳棉机的传递函数,通过z变换将系统离散化得到梳棉机的脉冲传递函数,z反变换得到差分方程。从差分方程的物理意义解释,可以定量地认识梳棉机的混和作用。定义了混和不匀率,根据线性系统理论对不同的喂入情况的混和效果作了进一步的分析。阐明了混和作用与均匀作用的区别和联系,从而对梳棉机的混和作用及其与均匀作用的关系有更为明确的认识。     

Performance analysis of FFH/BPSK system with partial band noise jamming and channel estimation error in high-mobility wireless communication scenarios

In this paper, we analyze the bit error ratio （BER） of fast frequency hopping （FFH） system with binary phase shift keying （BPSK） in high-mobility wireless channels. By taking into account partial band noise jam- ming and channel estimation errors as Gaussian noise, both of maximal-ratio combining （MRC） and equal-gain com- bining （EGC） schemes are considered, and exact analytical BER expressions for MRC and EGC schemes are obtained. Especially, a closed-form BER expression for the MRC scheme is also presented in high signal-to-noise ratio region. Analytical and simulation results demonstrate that, the FFH/BPSK schemes suffer from performance degra- dation in the presence of channel estimation errors. The worst case jamming factor is shown to be inversely pro- portional to the signal to jamming ratio. With properly designed frequency hopping schemes and channel estima- tion schemes, the performance improvement is also observed as compared with the traditional noncoherent FFH/BFSK system.