A whole-space transform formula of cylindrical wave functions for scattering problems

The theory of elastic wave scattering is a fundamental concept in the study of elastic dynamics and wave motion,and the wave function expansion technique has been widely used in many subjects.To supply the essential tools for solving wave scattering problems induced by an eccentric source or multi-sources as well as multi-scatters,a whole-space transform formula of cylindrical wave functions is presented and its applicability to some simple cases is demonstrated in this study.The transforms of wave functions in cylindrical coordinates can be classifi ed into two basic types: interior transform and exterior transform,and the existing Graf’s addition theorem is only suitable for the former.By performing a new replacement between the two coordinates,the exterior transform formula is fi rst deduced.It is then combined with Graf’s addition theorem to establish a whole-space transform formula.By using the whole-space transform formula,the scattering solutions by the sources outside and inside a cylindrical cavity are constructed as examples of its application.The effectiveness and advantages of the whole-space transform formula is illustrated by comparison with the approximate model based on a large cycle method.The whole-space transform formula presented herein can be used to perform the transform between two different cylindrical coordinates in the whole space.In addition,its concept and principle are universal and can be further extended to establish the coordinate transform formula of wave functions in other coordinate systems.

Global SH-wave propagation in a 2D whole Moon model using the parallel hybrid PSM/FDM method

We present numerical modeling of SH-wave propagation for the recently proposed whole Moon model and try to improve our understanding of lunar seismic wave propagation. We use a hybrid PSM/FDM method on staggered grids to solve the wave equations and implement the calculation on a parallel PC cluster to improve the computing efficiency. Features of global SH-wave propagation are firstly discussed for a 100-km shallow and900-km deep moonquakes, respectively. Effects of frequency range and lateral variation of crust thickness are then investigated with various models. Our synthetic waveforms are finally compared with observed Apollo data to show the features of wave propagation that were produced by our model and those not reproduced by our models. Our numerical modeling show that the low-velocity upper crust plays significant role in the development of reverberating wave trains. Increasing frequency enhances the strength and duration of the reverberations.Surface multiples dominate wavefields for shallow event.Core–mantle reflections can be clearly identified for deep event at low frequency. The layered whole Moon model and the low-velocity upper crust produce the reverberating wave trains following each phases consistent with observation. However, more realistic Moon model should be considered in order to explain the strong and slow decay scattering between various phases shown on observation data.

Global SH-wavefield calculation for a two-dimensional whole-Earth model with the parallel hybrid PSM/FDM algorithm

We present a parallel hybrid algorithm based on pseudospectral method （PSM） and finite difference method （FDM） for two-dimensional （2-D） global SH- wavefield simulation. The whole-Earth model is taken as a cross section of spherical Earth, and corresponding wave equations are defined in 2-D cylindrical coordinates. Spatial derivatives in the wave equations are approximated with efficient and high accuracy PSM in the lateral and high-order FDM in the radial direction on staggered grids. This algorithm allows us to divide the whole-Earth into sub-domains in radial direction and implement efficient parallel computing on PC cluster, while retains high accuracy and efficiency of PSM in lateral direction. A transformation of moment tensor between 3-D spherical Earth and our 2-D model was proposed to give corre- sponding moment tensor components used in 2-D modeling. Comparison of modeling results with those obtained by direct solution method shows very good accuracy of our algorithm. We also demonstrate its feasibility with a lateral heterogeneous whole-Earth model with localized velocity perturbation.

A scheme to treat the singularity in global seismic wavefield simulation using pseudospectral method with staggered grids

The pseudospectral method has been applied to the simulation of seismic wave propagation in 2-D global Earth model. When a whole Earth model is considered, the center of the Earth is included in the model and then singularity arises at the center of the Earth where r=0 since the 1/r term appears in the wave equations. In this paper, we extended the global seismic wavefield simulation algorithm for regular grid mesh to staggered grid configuration and developed a scheme to solve the numerical problems associated with the above singularity for a 2-D global Earth model defined on staggered grid using pseudospectral method. This scheme uses a coordinate transformation at the center of the model, in which the field variables at the center are calculated in Cartesian coordinates from the values on the grids around the center. It allows wave propagation through the center and hence the wavefield at the center can be stably calculated. Validity and accuracy of the scheme was tested by compared with the discrete wavenumber method. This scheme could also be suitable for other numerical methods or models parameterized in cylindrical or spherical coordinates when singularity arises at the center of the model.

Experimental Investigation of Instantaneous Properties of Wave Slamming on the Plate

The purpose of this paper is to investigate the instantaneous properties of wave slanuning on the plate structure of an open structure. The advanced instantaneous measuring technique-Particle Image Velocimetry （PIV） is applied to acquire the instantaneous velocity field of wave slamming. From the cross-correlation analysis results of the images captured by the CCD camera, the flow fields of wave impacting on the structure are displayed visually, and the instantaneous whole- field fluid velocity vectors are obtained. The relation between the instantaneous peak impacting pressures and the instantaneous velocities of water particles is studied by probability analysis.

Effect of Short-Term Whole-Body Vibration Training on Metabolic Risk Factors, Inflammatory Markers, and Arterial Stiffness

To investigate the effect of aerobic exercise combined with whole-body vibration (WBV) training on metabolic syndrome risk, and inflammatory markers, and to compare its effects on arterial stiffness and several blood parameters related to metabolic syndrome with those of aerobic training alone. Thirty healthy participants were divided into 2 groups matched for age and body mass index (BMI). Fifteen subjects were assigned to the WBV group (WBV + aerobic training) and the other 15 to the control group (aerobic training only). All participants performed a treadmill exercise 3 days/week for 4 weeks, for 50 min after 30 min rest period. Exercise was performed at a heart rate (HR) corresponding to 60% of the HR at each individual’s maximum oxygen uptake (VO2max). Body weight and BMI after training were significantly lower than those before training in the WBV group (P < 0.01). Concerning arterial stiffness, the pulse-wave velocity after training was significantly lower than that before training in the WBV group (1048.7 ± 105.6 vs. 1008.4 ± 101.1 cm/s, P < 0.05). Meanwhile, the VO2max after training was significantly higher than that before training in the WBV group (47.7 ± 12.8 vs. 51.4 ± 14.1 mL·min-1·kg-1, P < 0.01). However, no significant differences were observed in any parameters before and after training in the control group. Our results suggest that aerobic exercise combined with WBV training may be effective in reducing arterial stiffness and improving cardiorespiratory fitness than aerobic training alone.

深远海多功能原油转驳船全船有限元分析

为实现深远海石油的安全高效运输,开发了具有全新船型的深远海多功能原油转驳船(Cargo Transfer Vessel,CTV)。根据原油转驳船工作海域的环境特点,使用有限元计算软件包Sesam,建立了有限元分析结构模型,采用了等效设计波方法对该类型船只进行频域水动力分析,并对主要负载进行长期预测,然后将波浪载荷施加于结构模型中进行强度校核。通过校核不同工况下原油转驳船的屈服强度、屈曲强度,并基于谱疲劳分析与子模型技术对易于产生疲劳破坏的节点进行疲劳分析,优化了船体设计结构。计算分析结果表明:原油转驳船的设计强度与疲劳寿命均满足DNV的规范要求,载荷下船体结构应力均低于320 MPa,具有足够的承载能力。通过添加水密补板,优化后的舷侧肋位处纵骨过梁孔有效提高了疲劳寿命,对后续系列船的设计与校核具有一定参考价值。

更快速度下周期性短波不平顺引起的轮轨高频振动特性及控制限值

随着列车运行速度的不断加快,轮轨高频振动引起的车辆、轨道部件伤损问题更加突出,尤以周期性的短波不平顺最为常见。为了掌握轮轨高频振动自下而上的传递衰减规律以及制定合理的钢轨打磨策略,有必要针对车辆系统在高频激励条件下的耦合振动特性开展深入的理论研究。本文通过对大量实测数据的拟合,得到了更宽频段范围内的轨道高低不平顺谱拟合公式,并通过反演得到了0.002~100 m波长范围内的高低不平顺样本;在此基础上建立了高速动车组-轨道刚柔耦合动力学模型,其中对轮对、钢轨均考虑了弹性体振动模态,仿真分析了周期性短波不平顺引起的轮轨高频振动特性。结果表明,车辆各部件的振动频率分布范围为30~1390 Hz,且自下至上呈逐层衰减趋势。通过提取周期性短波不平顺幅值变化对轮轨相互作用的影响规律,进一步提出了适应400 km/h高速铁路的典型波长周期性短波不平顺的量化控制限值要求。

微机械电容式加速度计检测电路设计

通过对MEMS电容式加速度计的差分电容检测电路优缺点的比较,结合直流充放电检测方法和交流测量方法的优点,设计了微分检测电路,用方波作为载波。该电路由方波信号发生器、微分电路、全波整流电路和滤波电路组成。经试验验证:可检测到10-16F的差分电容,且其非线性度小于±1%FS,可作为MEMS电容式加速度计的后续处理电路。

短波近红外光谱的整粒小麦蛋白质PLS方法的定量分析

利用漫反射法获得的整粒小麦短波近红外光谱 (833～ 1111nm) ,采用化学计量学中的偏最小二乘法 (PLS)方法 ,选取不同的波长范围对光谱进行信息提取和分析 ,给出了不同因子数时PLS方法进行蛋白质分析的结果及其因子数与预测标准偏差平方和 (PRESS)关系曲线 ,确定了最佳回归因子数。并通过选取最佳回归因子和不同波段 ,对整粒小麦的蛋白质成分进行了定量分析 ,比较了不同波长范围对分析的影响 ,并从中获得了较好的预测结果 ,实验表明 ,合理选择光谱范围可减少非主要信息的干扰 ,并以此来提高成分分析精度的方法是切实可行的 。

面向地震烈度仪的现地地震动预测模型的构建与验证

利用初期P波预警参数构建现地地震动预测模型,使其在达到设定阈值时快速发出报警信息,是现地地震预警系统面临的一个关键问题,直接关系到发布信息的准确性和及时性。针对地震烈度仪基于微机电系统传感器记录到的数据质量较差,通过两次积分获取的位移存在较大偏差,会引起更多的误报和漏报,本文采用不同阶数(1—4阶)的巴特沃斯滤波器,分别构建了基于P波3 s和全P波段数据的位移幅值PD、速度幅值PV和加速度幅值PA与地震动峰值速度PGV和峰值加速度PGA的现地地震动预测模型,然后利用收集到的川滇示范预警网地震事件记录进行验证。结果表明,对于地震烈度仪微机电系统传感器的记录,采用1阶巴特沃斯滤波器处理、基于全P波段波形拟合获取到的PV与PGV的相关性和PA与PGA的相关性为两种最优现地地震动预测模型。具体应用时,应同时利用两种或两种以上的统计关系进行现地地震动预测,并将实际地震动观测值作为额外的判定条件,以降低误报率和漏报率。

粮食立筒仓弹性变形对卸料动压力的影响与计算

本文结合工程实践，通过对粮食立筒仓卸料时的贮料与筒仓壁的弹性变形及其传播对动态压力的影响计算，从理论上验证了混凝土筒仓在整体流动卸料状态下压力修正系数取值的适用性，并提出了钢板筒仓压力修正系数的合理取值，可作为工程设计及制定钢板筒仓设计规范的参考依据。

整舱浮筏隔振系统功率流理论与试验研究

采用FEM和SEA方法计算整舱浮筏隔振系统传递的功率流,初步分析整舱浮筏隔振系统功率流传递特性。用间接方法测量了整舱浮筏隔振系统的功率流传递,分析整舱浮筏功率流理论计算和试验结果之间的关系及功率流的传递规律,说明采用FEM+SEA方法计算整舱浮筏隔振系统的功率流隔振效果在工程上是可行的。

机载电源检测系统的设计

为了检测飞机通话系统、控制系统、导航系统等设备的供电电源,设计了一种机载电源检测系统.该系统主要由信号采集板和计算机构成.信号采集板主要由单片机89C51、A/D转换器、电压和电流互感器、精密全波整流电路等组成,其结构紧凑.计算机软件采用虚拟仪器软件LabWindows/CVI 6.0开发,通过串口与信号采集板进行通信,对电源的各项参数(电压、电流和频率)进行实时采集和动态监控.软件功能强大且人机界面友好.该系统实现了机载设备供电电源各项参数的动态在线监测和故障定位,具有检测实时、故障诊断准确等特点.

人体全身振动评价研究

阐述了BS 6841-1987、ISO 2631-1997、吸收功率法这几个国际上影响较大的全身振动评价方法。分析国际上振动评价方法的研究现状,总结国际上对人体振动响应特性的研究,表明人体对振动的响应十分复杂,频率加权系数与人体姿势、体重、振动幅值等因素有关,寻找更科学的振动评价方法是全身振动评价研究的方向。结合国内振动评价的现状,指出应尽快依据国际标准修订国家标准,并开展振动评价的基础工作,以制定适合中国人特点的振动评价方法。

强多次波和低信噪比资料处理

对具有多次波干扰的低信噪比三维地震资料在资料处理各个阶段使用多个模块逐步压制、去除多次波和提高信噪比。利用模型射线追踪,获得准确的偏移速度场进行三维一步法偏移,利用优势频率反褶积提高分辨率。

基桩可打性分析与全程动测监控理论在码头工程中的应用

如何避免预应力混凝土基桩在锤击施打过程中的桩身断裂、破损现象,如何制订经济、合理、高效的沉桩施工方案是摆在工程师面前的重要课题。利用可打性GRLWEAP分析和全程动测监控理论在湛江某码头工程中的成功应用实例,通过对可打性分析与沉桩过程中的测试结果进行对比分析研究,探讨基于波动理论基础的沉桩控制方法,旨在为工程沉桩施工及质量控制提供技术参考。

超声波预处理对全株青贮玉米品质的影响

为研究超声波预处理对全株青贮玉米品质的影响,设置空白对照组、超声处理组(5、10、15、20、25 min)和乳酸菌对照组进行青贮玉米品质研究。结果表明:15 min和20 min超声处理后,全株玉米青贮饲料感官评定属于优良级。与对照组相比,超声处理后饲料的pH和氨氮比分别降低7.71%和7.82%,乳酸和乙酸含量分别提高52.14%和97.22%,干物质、水溶性碳水化合物、粗脂肪和粗蛋白质含量分别提高6.31%、15.76%、19.65%和16.34%,中性洗涤纤维、酸性洗涤纤维和酸性洗涤木质素含量分别显著降低26.10%、22.44%和29.08%。综合以上指标,15~20 min超声处理能明显提高全株玉米的青贮质量。

下承式钢板梁整体稳定问题研究

用弹性稳定理论及弹塑性稳定理论 ,对下承式钢板梁的整体稳定问题进行了详细分析 ,由此说明了《铁路桥涵设计规范》( TBJ2 - 85 )附录

地裂缝地形条件下瑞雷波的传播特征

利用高精度交错网格有效差分技术,以及参数平均算子实现非水平地表条件下瑞雷波全波场模拟.针对地裂缝的特殊地形条件进行瑞雷波的传播模拟,从炮记录和频散曲线两个方面讨论其传播特征.实验表明:不均匀浅地表地形条件会对能量的分配以及波形的转换产生影响,在勘探时要尽量对其加以避让.