多媒体教室人机环境研究——河南理工大学多媒体教室研究

进入信息时代,作为一种新型的教育形式和现代化的教学手段,多媒体技术在给教育行业带来了新的机遇的同时也暴露了在多媒体教室建设上存在的诸多问题。本文主要从人-机-环境的角度出发,以河南理工大学多媒体教室为素材,通过对多媒体教室的物理环境分析、师生交流软环境等调研,探讨多媒体教室的硬件环境的改良建设的途径。     

Robust L2–L∞ control for uncertain singular systems with time-varying delay

We study the problem of L₂–L_∞ control for a class of uncertain singular systems with time-delay and norm-bounded parameter uncertainties in this paper. A new delay-dependent robust stability criterion is obtained in terms of linear matrix inequalities (LMIs). Based on this criterion, a state feedback controller is designed to guarantee that the closed-loop system is regular, impulse free and stable with a prescribed L₂–L_∞ performance satis?ed for all admissible parameter uncertainties. A simulation example is included to illustrate the e?ectiveness of the proposed method.     

Computer simulation on reliability of retention index with FDG–PET and optimization of dual-time-point imaging protocol

The inherent noise in positron emission tomography (PET) leads to the instability of quantitative indicators, which may affct the diagnostic accuracy for diffrentiating malignant and benign lesions in the management of lung cancer. In this paper, the reliability of retention index (RI) is systematically investigated by using computer simulation for the dual-time-point imaging protocol. The area under the receiver operating characteristic (ROC) curve is used to evaluate the optimal protocol. Results demonstrate that the reliability of RI is a?ected by several factors including noise level, lesion type, and imaging schedule. The RIs with small absolute values su?er from worse reliability than those larger ones. The results of ROC curves show that over delayed second scan cannot help to improve the diagnostic performance further, while an early ?rst scan is expected. The method of optimization based on ROC analysis can be easily extended to comprise as many lesions as possible.     

以非课程教育培养大学生创新实践能力的探索与思考

文章研究了培养大学生创新实践能力的机制问题．在仔细分析大学生创新实践能力的构成的基础上,提出培养大学生创新实践能力的主要工作内容,并针对这些工作内容,提出应建立相应的平台以保障工作内容顺利开展．     

内蒙古阿拉善地区沙米自然分布格局特征研究

本文根据野外调查的样地资料,应用方差/均值比率法、聚集指数、平均拥挤度、聚块性指数、Green指数和负二项分布的聚集强度等方法,研究了内蒙古阿拉善左旗境内的沙米种群的分布格局并分析格局形成的原因.结果表明:沙米的分布格局属于聚集分布,但其在不同类型地域的聚集强度有差异.     

流媒体通信控制策略研究

介绍了一种新的基于缓冲区管理的网络拥塞控制方法,该控制方法通过监测网络状态变化和客户端缓冲区状态,动态调整服务器端的发送速率,能够有效提高服务质量．结果表明该方法在流媒体网络传输中能够取得很好的效果．     

中国的空间探测及其科学内涵

文章回顾了人类探索空间的历史,特别是中国人对空间的探索历史;并分析了自人类进入空间时代以后探索空间的历程。通过对这一系列活动的分析,探讨了人类在空间探测活动中的动机及其科学内涵,进而对中国今后空间探测活动的战略科学目标展开讨论,并简要介绍了中国4个空间探测计划及其科学目标。     

TH65100卧式加工中心立柱模态分析与优化设计

研究了TH65100卧式加工中心立柱的结构设计和分析系统。利用Pro/Engineer和Ansys软件分别作为设计系统和分析系统,利用数据交换接口,对立柱进行三维实体建模与模态分析。得到了立柱的模态分析结果,并对比了2种筋板优化方法。取得了既减轻机身重量,又提高强度和刚度的显著效果,为结构的合理设计与改造提供了可靠的理论依据。     

山区高速公路岩体边坡稳定性处理技术

在分析岩体边坡稳定性的基础上,建立受非均布线形荷载作用的地基力学模型,应用叠加原理推导出岩体表面在上述荷载作用下,预应力锚索-地梁结构中垂直于梁轴线的平面内的地基中深z处的应力和位移计算公式,为研究预应力锚索-地梁结构在岩体中传递规律提供了理论基础.并以湖南省常张高速公路K123＋160-K123＋369边坡为实验区域,现场实验得出在对锚索施加预应力后,锚索预应力通过地梁传递给被加固的岩土体,其传递方式在垂直于地梁轴线的平面内是以梁轴线与该平面的交点为端点的近似橢圆的等值面形式由内向外呈逐渐衰减趋势分布的.藉此证明预应力锚索-地梁结构在山区高速公路岩体边坡中是一种可靠的处理技术.     

Structure of a beta1-adrenergic G-protein-coupled receptor

G-protein-coupled receptors have a major role in transmembrane signalling in most eukaryotes and many are important drug targets. Here we report the 2.7 A resolution crystal structure of a beta(1)-adrenergic receptor in complex with the high-affinity antagonist cyanopindolol. The modified turkey (Meleagris gallopavo) receptor was selected to be in its antagonist conformation and its thermostability improved by earlier limited mutagenesis. The ligand-binding pocket comprises 15 side chains from amino acid residues in 4 transmembrane alpha-helices and extracellular loop 2. This loop defines the entrance of the ligand-binding pocket and is stabilized by two disulphide bonds and a sodium ion. Binding of cyanopindolol to the beta(1)-adrenergic receptor and binding of carazolol to the beta(2)-adrenergic receptor involve similar interactions. A short well-defined helix in cytoplasmic loop 2, not observed in either rhodopsin or the beta(2)-adrenergic receptor, directly interacts by means of a tyrosine with the highly conserved DRY motif at the end of helix 3 that is essential for receptor activation.