数值模拟在建筑结构教学中的应用

建筑结构是建筑学专业学生的必修课程,教学大纲涵盖大量概念性知识和方法性知识.为了帮助学生在课堂上尽快进入课题情境,本文借助ANSYS结构有限元分析软件,将数值模拟引入建筑结构课程教学中,让学生直观看到构件和结构的受力特点和破坏形态,有助于启发学生的主动思维、提高课堂教学质量,实现“学习迁移”在教学中的正效应.     

An algorithm for astro-inertial navigation using CCD star sensors

A self-contained suite of astro-inertial navigation system is capable of autonomous mission and is operationally reliable. The typical astronavigation system (ANS) makes use of star-trackers, which are expensive and complex. To make the system cost effective and less complex, the star-tracker is replaced by a charge coupled device (CCD)-based star sensor, rigidly mounted on a strapdown inertial measurement unit (SIMU) of the system. This electro-optical star sensor is compact and easy to use with an ANS that utilizes efficient star identification techniques. This paper designs an algorithm that estimates axes misalignment angles of strapdown inertial navigation system (SINS) that makes stars' observations utilizing a CCD star sensor. Mathematical modeling of the suggested scheme was carried out and transformations between different frames were exercised. From the image projection geometry, stars' right ascensions and declinations, relative to the body frame, were estimated. Lastly, from the known stars' position vectors in mathematical platform and reference frames, axes misalignment matrix representing SINS attitude errors can be estimated employing the derived relationship.     

Improved Algorithm of Variable Bandwidth Kernel Particle Filter

Aiming at the large cost of calculating variable bandwidth kernel particle filter and the high complexity of its algorithm, a self-adiusting kernel function particle filter is presented. Kernel density estimation is facilitated to iterate and obtain new particle set. And the standard deviation of particle is introduced in the kernel bandwidth. According to the characteristics of particle distribution, the bandwidth is dynamically adjusted, and the particle distribution can thus be more close to the posterior probability density model of the system. Meanwhile, the kernel density is used to estimate the weight of updating particle and the system state. The simulation results show the feasibility and effectiveness of the proposed algorithm.     

外旋式电测粘度计的设计与计算

给出了一种通过静态电阻应变仪及外旋式粘度装置测量流体粘度的方法。由同步电动机带动外圆筒旋转剪切流体,从而将粘性力传递给内筒,内筒与圆轴相连。粘性力产生的扭矩使圆轴产生应变,在圆轴表面黏贴电阻应变片,通过合理组桥将应变显示在静态电阻应变仪上,根据应力应变关系计算出扭矩,从而计算出流体的动力粘度。     

永磁辅助式同步磁阻电机转矩预测控制方法

为了验证永磁磁阻电机具备宽调速域的优势,同时充分发挥永磁磁阻电机在弱磁运行时的输出转矩,提出了一种基于转矩预测控制的全速域控制方法。采用Ansys设计了一台永磁磁阻电机,并与Simulink联合仿真验证了方法的可行性。验证结果表明:转矩预测控制方法可以使电机在全速域获得良好的动态性能,同时永磁磁阻电机弱磁运行时依然具有优秀的转矩输出能力。     

复合材料构件模具材料选择模糊决策研究

为了实现复合材料构件模具材料的计算机辅助决策,在分析研究复合材料构件模具材料选择的知识和经验的基础上,运用加权多因素模糊模式识别技术,同时结合基于规则的推理（RBR）技术和权重动态调整技术,实现了具有一定自适应功能的复合材料构件模具材料选择模糊决策方法.实践表明,该决策方法能够很好地实现复合材料构件模具材料选用的快速智能化决策.     

基于DFT的水射流红外热像频域时空分析

基于二维离散傅里叶变换及空间频谱分析,对水射流湍流脉动的空间尺度进行了研究,得到了由红外辐射温度表征的被动标量湍流场在对流区、耗散区、惯性子区的特征空间尺度及其时间演化规律.对射流不同区域的关心点重新采样,得到湍流场中关心点的时间序列,利用一维离散傅里叶变换,分析了对流区大尺度涡中心、惯性子区小尺度涡中心、耗散区及射流轴心线上各关心点的湍流波动特征.计算了时间序列频谱的分形维数,研究了自由湍流不同尺度区间上述各关心点湍流脉动的分形特征.      

介质阻挡放电等离子体对压气机叶栅性能影响的实验

在压气机叶栅叶片两侧布置电极,对电极施加高压高频交流电产生等离子体,通过三孔探针测量栅后总压和速度的变化.实验中发现,流速低于20 m/s时,加电产生等离子体后,可显著改善栅后总压和速度分布;流速接近0 m/s时,等离子体仍会明显改变总压和速度的最小值;出现流动分离趋势后,等离子体无法抑制分离趋势;对分离区大小、分离涡强度的影响还需进一步的实验研究.      

OLEOPHOBIC AND HYDROPHOBIC FEATURE EXPERIMENTS OF FLUORINATED HIGH DENSITY POLYETHYLENE

The surface performances of directly fluorinated high density polyethylene （HDPE） are studied with Fourier transform infrared （FT-IR） spectra, scanning electron microscopy （SEM） and contact angle （CA） system. The SEM images show that there is a three-layer structure called the reaction, virgin and boundary layer structure. The depth of fluorinated layer is 5.75 ~m with 1 h fluorination time and 7.86 b~m with 2 h. The depths are 5.46 /~m and 5.07 /~m when fluorine density is 2G and 1~/0, respectively. CA indicates that the HDPE surface property becomes more hydrophobic with the increasing water contact angle from 78.5~ to 104.5~. Oleophobic and hydrophobic features of HDPE are identified by comparison of mass change experiments. It is shown that the in- crement rate of fluorinated HDPE is much lower than that of un-fluorinated HDPE filled in neither distilled water nor jet fuel.     

Is there an abnormal enhancement of atmospheric aerosol before the 2008 Wenchuan earthquake?

There are extensive reports of ionospheric disturbances before the great 2008 Wenchuan earthquake, which are possibly explained by seismogenic electric field hypotheses linked with the aerosols injected in atmosphere. This paper attempts to investigate the possible change of atmospheric aerosol optical depth (AOD) associated with this earthquake by using MODIS data from both Terra and Aqua satellites. The result shows a clear enhancement of AOD along the Longmenshan faults 7 days before the quake, which is 1 day and 4 days earlier than the reported negative and positive ionospheric disturbances, respectively, and is 1 day earlier than or quasi-synchronism with other reported atmospheric anomalies including air temperature, outgoing longwave radiation and relative humidity. Particularly, the spatial distribution of AOD enhancement is very local and it is correlated well with the active faults and surface ruptures. We suggest that this unique enhancement could be associated with the Lithosphere–Atmosphere–Ionosphere coupling process during the preparation of the Wenchuan earthquake.