聚乙烯膜料老化抗裂模型试验研究

为研究解决渠道防渗聚乙烯(PE)膜料的冻融老化问题,依据薄膜理论对PE水压力变形及应力应变模型进行了数学推导.在室内冻融老化条件下对PE抗拉、抗裂性能分别进行了对比试验.研究表明,冻融老化100次循环后PE的性能均有所降低.用圆形中心变位模型模拟了PE冻融老化抗裂强度与鼓包高度关系曲线,经检验模拟曲线与观测曲线基本吻合.表明该模型可用于PE抗裂强度或变形计算,为PE应用于渠道防渗设计提供了理论依据.     

Anomalous dielectric behavior in nanocrystalline γ-Fe_2O_3

The measurements of electric capacities and dielectric loss angles for nanocrystalline γ-Fe₂O₃, under air and vacuum atmospheres have been conducted by using ac LRC method, and the conductivity and the polarization relaxation time have also been calculated from the frequency spectra of real and imaginary parts of the dielectric constants. The anomalous dielectric behavior implies the existence of two kinds of polarization mechanisms with different relaxation times, which are caused by the defects and the dangling bonds in the interfaces, respectively. The experimental and calculated results indicated that the polarization loss and the conductance loss are dominant in air atmosphere and vacuum, respectively.     

An electrochemical impedance spectroscopic study of the electronic and ionic transport properties of LiCoO2 cathode

The storage behavior and process of the first delithiation-lithiation of LiCoO2 cathode were investigated by electrochemical impedance spectroscopy(EIS). The electronic and ionic transport properties of LiCoO2 cathode along with variation of electrode potential were obtained in 1 mol·L?1 LiPF6-EC:DMC:DEC electrolyte solution. It was found that after 9 h storage of the LiCoO2 cathode in electrolyte solu-tions,a new arc appears in the medium frequency range in Nyquist plots of EIS,which increases with increasing the storage time. In the charge/discharge processes,the diameter of the new arc is reversi-bly changed with electrode potential. Such variation coincides well with the electrode potential de-pendence of electronic conductivity of the LiCoO2. Thus this new EIS feature is attributed to the change of electronic conductivity of LixCoO2 during storage of the LiCoO2 cathode in electrolyte solutions,as well as in processes of intercalation-deintercalationtion of lithium ions. It has been revealed that the reversible increase and decrease of the resistance of SEI film in charge-discharge processes can be also ascribed to the variation of electronic conductance of active materials of the LiCoO2 cathode.     

密闭空间爆后准静态气压及地运动分析

准静态气压参数和地运动速度参数是保证密闭空间爆炸作业安全开展的重要参考.通过获取某工程现场3次爆破后的实测地运动速度数据和准静态压力数据进行时频域分析,结果表明,不同比例药量下,质点振速时程曲线和频域曲线均具有一致性,随着爆心距增加,质点振速幅值减小,主要频段趋近低频段,比例药量仅对地运动速度幅值有影响,对频域分布及主频影响不大.不同质量沙墙对准静态气压峰值及衰减速度均有影响,沙墙质量越小,爆后准静态气压峰值越大,其衰减越快.     

Studies of the first lithiation of graphite materials by electrochemical impedance spectroscopy

Recently, lithium-ion batteries have attracted inten- sive research interests, especially with respect to the complex interfacial reactions between electrolyte and electrode. Carbonaceous materials are most widely em- ployed as negative materials for lith…     

一种新的常微分方程初值问题数值解法

有别于传统的常微分方程数值解法,从一个新的角度出发提供一套新的求解常微分方程初值问题的数值计算方法;通过对一阶常微分方程（组）、二阶常微分方程和Vander Pol方程的求解验证了方法的正确性,数值解与解析解相对误差小于0.5%.     

Analysis and Simulation for Planetary Gear Fault of Helicopter Based on Vibration Signal

Fault diagnosis for helicopter’s main gearbox based on vibration signals by experiments always requires high costs. To solve this problem,a helicopter’s planetary gear system is taken as an example. Firstly,a simulation model is established by McFadden,and analyzed under ideal condition. Then this model is developed and improved as the delay-time model of the vibration signal which determines the phase-change of sidebands when the system is running. The cause and change-rules of planetary gear system’s vibration signal are analyzed to establish the fault diagnosis model.At the same time,the vibration signal of fault condition is simulated and analyzed. This simulation method can provide a reference for fault monitoring and diagnosis for planetary gear system.     

A quantum algorithm that deletes marked states from an arbitrary database

We present a general quantum deletion algorithm that deletes M marked states from an N-item quantum database with arbitrary initial distribution. The general behavior of this algorithm is analyzed, and analytic result is given. When the number of marked states is no more than 3N/4 , this algorithm requires just a single query, and this achieves exponential speedup over classical algorithm.     

飞行器最优时滞反馈控制器设计

在设计飞行器最优反馈控制时,针对系统具有控制时滞的特性,采用连续状态变换思想,将具有时滞的控制系统转化为无时滞的控制系统,求使得无时滞控制系统性能指标最小的解,利用这个解去求原系统的状态函数,进而得到时滞反馈控制与状态变换后最优控制之间的关系,求出最优时滞反馈控制的增益。对某型无人直升机实验所得的悬停数据进行仿真验证,仿真结果证明了所提方法的有效性。     

2.5MV快沿电磁脉冲模拟器脉冲源故障状态模拟分析

利用电路模拟软件与实测波形,建立了2.5MV快沿电磁脉冲(EMP)模拟脉冲源等效电路模型.通过在电路模型中模拟绝缘薄弱环节,如Marx输出端、中储电容、中储开关与峰化电容间支撑绝缘子、峰化电容等位置,设置等效滑闪电路的方法,对模拟器脉冲源可能出现的绝缘故障进行了模拟分析.将模拟器调试阶段出现的故障波形与模拟结果进行比对,二者符合良好.试验结果证明,根据模拟故障波形并结合试验中出现的巨大声响、电源跳闸等物理现象及后续输出电压降低等情况,可以实现模拟器滑闪故障的准确定位,从而保证故障的及时发现与快速排除,提高装置运行可靠性.