Estimation of underdetermined mixing matrix based on support vector machine

In underdetermined blind source separation (BSS), a novel algorithm based on extended support vector machine (SVM) is proposed to estimate the mixing matrix in this paper, including the number of the active sources. Instead of traditional clustering algorithms, it mainly takes the modulus of observations and the number in each direction of arrival, without any prior knowledge about the sources except for sparsity, and it is not sensitive to the initial values. Simulations are given to illustrate availability and robustness of our algorithm.     

开孔泡沫金属动态力学性能及能量特性

泡沫金属材料在防护吸能领域有着重要的应用前景,深入研究泡沫金属及其相关结构的冲击力学性能十分必要。通过Φ50 mm的分离式霍普金森杆(split Hopkinson pressure bar, SHPB)装置对开孔泡沫金属Fe、Ni、Fe-Ni合金(50 mm×10 mm)进行动态冲击试验。试验分析了应变和应变率对其力学性能及吸能特性的影响,通过对其峰值应力、波动应力、理想吸能效率等参数的对比分析多种冲击速度下不同泡沫金属材料的抗压强度与吸能性,为建筑、航天等工程的使用提供理论基础。研究结果表明：高冲击速度下峰值应力增大且Fe-Ni合金抗压强度最高,不同材料泡沫金属均存在波动应力且压密阶段时间各不相同。应变率介于600～1 150时泡沫金属Ni吸能性最优,该区间外Fe-Ni合金更优。当应变率大于1 000时,Fe-Ni合金理想吸能效率增幅较大,相较于700时提高了48%、为最优理想吸能材料。     

一种低噪声高PSRR的LDO线性稳压器

介绍了 LDO线性稳压器的系统组成原理,分析了系统的电源电压抑制比(PSRR)以及噪声与电路结构的关系,在此基础上,对LDO的核心电路模块进行了设计,并基于0.5μm标准CMOS工艺,运用Cadence平台进行了模拟仿真和验证.测试结果表明:该LDO的PSRR最低约为-45 dB@1 MHz,最高约为-75 dB@217 Hz;输出电压噪声在10 Hz频率以下约为0.78 μV(P-P),在10 Hz至l00 kHz频率范围内约为0.1 μV(RMS),能满足低噪声和高PSRR应用的要求.     

在不同介质中均相及异相Diels-Alder反应的研究

Diels-Alder反应的定位选择性和立体选择性,近年很受注意,报道了许多研究结果.前线分子轨道理论很好地解释了众所周知的内型规则.但是,不同溶剂和添加物对于各种Diels-Alder反应的立体选择性都有不同的影响.Gonzalez和Holt在三元混合溶剂体系中,研究环戊二烯和甲基丙烯酸甲酯的环加成反应,发现当添加表面活     

Electrophysiological research of synapse formation from beginning to maturity

The development of synapses is an important question in neurobiology. We employ patchclamp technique to record MEPCs and EPCs of myoballs inXenopus cell culture. The rate of EPC/MEPC is related with synapses maturation. Accordingly, we define the mature synapses as those whose rate of presynaptic membrane ’ s EPC to MEPC is more than 8. The process of maturation needs about 2–5 h after neuntes contact with myoballs. We divide the development of synapses into three stages: young, developing and mature. The neurotransmitters stack gradually and increase by hundreds of times along with young synapses growing into maturity. So the process of synapses maturation should include presynaptic membrane specialization, postsynaptic membrane specialization and neurotransmitters stack.     

建设工程项目施工实施阶段的投资控制

建设工程投资控制，是指在投资决策阶段、设计阶段和实施阶段把工程投资控制在批准限额的管理措施。在实施阶段中的准备阶段准确地确定发包价款，做好答疑、评标询标；在施工阶段中严格控制设计变更程序、明确变更项目单价的原则，掌握好设计变更、索赔引起的合同价款调整以及招标过程中材料、设备暂定价的确定，是建设工程项目实施阶段投资控制的关键。     

Comparison of Drought-Resistance about Three Wild Rocky-Grasses

In this experiment, using the methods of drought-stress in the pot and PEG simulative drought-stress, three native rocky-slope grasses Pogonatherum panideum（Lam.） Hack, Erioophorum comosum nees and Cynodon dactylon cultivated in the pots were selected as materials to study their drought-resistance by analyzing the indexes such as the leaf area index, the drying roots accumulation, the holding water ability of leaf, the relative conductance of leaf, the soluble protein, chlorophyll. At the same time, by comparing with membership function value of each index, the order of each grass drought-resistance was decided. The results showed that the drought-resistance of Erioophorum comosum nees was stronger than Cynodon dactylon and drought-resistance of Cynodon dactylon was stronger than Pogonatherum panideum （Lam.） Hack. The purpose of the experimental results was to find theoretical foundations for selecting and cultivating native protecting-slope vegetations to adapt to rocky slopes.     

《工业锅炉》课堂教学的方法与体会

文章通过对《工业锅炉》课程教材的分析 ,针对性地提出了在《工业锅炉》教学过程中教学方法的重要性。     

矿用减速器性能试验台测控系统设计

应用直流电回馈技术和虚拟仪器技术研制了矿用减速器性能试验台,介绍了试验台的组成及其测控系统.该试验台大大地提高了矿用减速器试验台和试验过程的技术水平.     

数学分析课程教学改革的几点尝试

结合数学分析课程教学实际,探讨数学分析课程教学内容的处理和教学方法的更新以及师资队伍的建设。