基于模糊数学和粒子群算法的边坡参数反分析

传统的利用边坡位移进行力学参数反分析的方法构造的目标函数较为简单.为了体现滑坡土体的不同性质,文中在传统优化方法的基础上,分析了滑坡体内部土体的位移特点,并将滑坡土体分为滑坡床、滑坡面和滑坡体3个类别.然后分别利用模糊数学和粒子群算法求得不同位置土体对3个类别的隶属度以及3个类别的位移权重,并根据土体的隶属度和3个类别...     

剩余压紧力条件下滑靴副的油膜特性及功耗

在考虑滑靴高速旋转时底面会形成热楔支承力的基础上,利用求解高次微分方程的研究方法建立了剩余压紧力状态下柱塞泵的滑靴底面的油膜模型,通过Matlab编程精确描述了剩余压紧力状态下滑靴油膜的动态特性,并以此为基础研究了滑靴的油膜厚度与负载、转速的关系,推导了滑靴高速运行所造成的功耗损失,同时分析了负载和转速变化对滑靴功耗损...     

两种基于苯并咪唑衍生物配体的新型铱(Ⅲ)配合物的合成及发光性能研究

合成了新型配体N-异丙基-2-苯基苯并咪唑(bi)和N-异丙基-2-(4-氟苯基)苯并咪唑(fbi),并用它们与三氯化铱和乙酰丙酮反应,制备了相应的环金属铱(Ⅲ)配合物发光材料(bi)2Ir(acac)和(fbi)2lr(acac)(acac=乙酰丙酮).对其结构用1H NMR和元素分析方法进行了表征,研究了配合物的UV-vis,荧光光谱及电化学性质.两种材料的最大发光波长分别位于514 nm和493nm.电化学研究表明,在苯环上引入氟原子后,配合物的HOMO和LUMO间能隙增大(分别为O.12 eV和0.15 eV),与最大发光波长蓝移结果吻合.     

山东省湿地面积变化及其生态价值分析

笔者利用三期中国湿地数据,首次定量化研究山东省湿地在1990年、2000年2008年间的变化趋势,并对生态价值变化进行分析.结果显示,山东省湿地自然湿地从1990到2008年减少达到1 966.48 km2,减幅达到37.58%,面积变化先急促后迟缓.山东省湿地生态系统服务功能价值从1990年的374.82亿元,到2000年减少到333.18亿元,然而到2008年增长到了 373.38亿元,先减少后增加,同湿地面积变化趋势一致,这在总量上的增长,完全是人工湿地的增长,自然湿地一直在减少.     

Zircon U-Pb ages of granites at Changba and Huangzhuguan in western Qinling and implications for source nature

Mesozoic granitoids are widespread in the Qinling-Dabie-Sulu orogenic belt. Precise U-Pb dating on these granitoids can reveal the evolution of the continental collision orogen and thus provide information on the nature of magma sources. This study presents zircon LA-ICP-MS U-Pb dating and whole-rock geochemical analyses for two intrusions at Changba and Huangzhuguan in western Qinling. Zircon U-Pb ages for central and marginal phases of the Huangzhuguang intrusion are 214±1 Ma and 213±3 Ma, respectively. Zircons from the Changba intrusion yield a dominant cluster with an U-Pb age of 213±2 Ma. Collectively, these ages are younger than ages of 220 to 240 Ma for ultrahigh-pressure metamorphism due to the continental collision between the South China Block and the North China Block, corresponding to syn-exhumation magmatism. Some inherited zircons occur in the Changba intrusion, yielding a weighted mean of ²⁰⁶Pb/²³⁸U ages at 757±14 Ma. This indicates that the Changba intrusion has the crustal source of mid-Neoproterozoic ages and a tectonic affinity to the South China Block. Geochemically, the two intrusuons are both rich in LILE and LREE but depleted in HFSE and HREE, similar to arc-type igneous rocks. The Huangzhuguang intrusion exhibits linear correlations between SiO₂ and the other major oxides, implying chemical evolution from a cognate magma source. It contains mafic enclaves, suggesting possible mixing of felsic-mafic magmas. The Changba granite is rich in Si and K but poor in Fe and Mg as well as has a high value of Fe*, suggesting strong differentiation of granitic magma. Therefore, the two intrusions were derived from the Late Triassic anatexis of the continental crust of different compositions in the northern margin of South China Block. This process may be coupled with exhumation of the subducted continental crust in the stage of late collision.     

Carbon and hydrogen isotopic compositions and their evolutions of gases generated by herbaceous swamp peat at different thermal maturity stages

Coalbed methane (CBM) accumulation models include continuous gas accumulation and staged gas accumulation.However,studied on the geochemical characteristics and indices to evaluate staged accumulation CBM are lacking.This study for the first time obtained the carbon and hydrogen isotopic compositions of methane and ethane generated at different evolution stages using thermal simulation of samples prepared by treating an herbaceous swamp peat at different temperatures.The results showed that the carbon isotopic compositions of methane and ethane were obviously affected by the thermal evolution level of the starting sample,while the hydrogen isotopic compositions were closely related to the maturity of gases.The carbon and hydrogen isotopic compositions of gases generated by coal-forming organic matter with Ro values from 1.2%,1.7%,2.4%,3.2% and 3.7% to 5.2% were determinated.The relationship between Ro values and the carbon and hydrogen isotopic compositions of gases generated by coal-forming organic matter at different evolution stages as well as the carbon or hydrogen isotopic relationships between methane and ethane were established.The results provide a scientific basis for studying the genesis of CBM generated at different maturity intervals and understanding the geochemical characteristics of staged accumulation CBM.These results were applied to a case study on CBM from the southern Qinshui basin,and it was found that the CBM accumulated after the Middle Jurassic and was characteristic of staged gas accumulation.This is consistent with the result of geological studies,and further showed that the results of thermal simulation experiments are very important for evaluating the genesis of natural CBM.     

A small difference in nuclear mass could make a big impact in the cosmos

In a recent paper [1] published in Physical Review Letters, scientists at the Institute of Modern Physics, Chinese Academy of Sciences, have reported their first results from the Cooler Storage Ring at the Heavy Ion Research Facility, a newly-constructed major scientific facility in Lanzhou, China. As a part of an international collaboration including colleagues from Europe, USA and Japan, they were able to identify in experiments the very     

Reverberation nulling and echo enhancement at low frequency using waveguide invariance

Based on the fact that the transfer function vector between a source receiver array and the dominant scatterer of boundary reverberation at a range can be obtained from the corresponding reverberations scattered from this range cell, a reverberation nulling concept using time reversal processing has been proposed. However, current reverberation nulling methods have certain limitations when applied into practice, which would null boundary reverberation and target echo simultaneously. As a solution, a passive reverberation nulling and echo enhancement method at low frequency using waveguide invariance is proposed in this paper. In this method, the reverberation subspace for the target range cell is not obtained directly from the return signals scattered by the target range cell but from the return signals scattered by a range cell located before the target using waveguide invariance, so as to suppress the reverberation embodied in the target echo by passive reverberation nulling. Besides, a range-dependent optimal weighting vector rather than conventional projector matrix is deduced to null the reverberation component meanwhile maximizing the target echo, thereby enhancing the echo-to-reverberation ratio furthest. Numerical simulations in typical range-independent shallow water environment demonstrate the efficacy and the improved performance of the proposed method for echo-to-reverberation enhancement.     

激光辐照移动平板温度场分布的有限元分析

基于热传导理论,采用有限元方法建立激光辐照无限长移动平板表面激发瞬态温度场的三维模型,用以研究移动平板上下表面瞬态温度场.考虑板材料的热物理参数依赖于温度、板表面的热辐射及对流等因素,计算了上述因素及移动速度对温度场的影响,并进一步讨论了激光半径对温度场的影响.数值结果表明:激光辐照移动平板后,在材料中将产生准稳态温度...     

基于智能体模拟的结构性疏散计划设计研究

展示了一个基于Agent模拟方法的框架方法,用于为危急中的复杂技术系统设计结构性的疏散计划.该计划利用复杂自适应系统的模拟方式,并采用基于智能体模拟的方法作为认知工具来设计整体系统的疏散方案.结构化的疏散计划应用文中提出的整体性技术框架,没有采用标准化的常规方法.提出了一个使疏散人群能够更加适应的调整危机时刻的紧急情况和减少无效疏散的建议性方案.本框架方法在一个典型的复杂自适应系统一地铁火灾中得到应用.