冲击响应谱控制时域匹配的研究

衰减正弦作为小波,匹配冲击响应谱的缺点是,匹配的时域波形的末速度和末位移均无法保证为零,这在振动台上会产生二次过冲击。本语文给出一种迭代修正方法,可克服此种缺点。使用此方法研制的控制的实际应用表明给出的方法是有效的。     

气动锤头式冲击响应谱模拟方法研究

分析了目前常用的机械撞击式响应谱试验机的特点和存在的一些问题，设计了一种以压缩空气作为锤头动力的新型气动式冲击响应谱试验机，给出了锤头速度计算公式和响应谱最大值的估算方法，为大型产品的冲击响应谱试验提供了一种手段。     

冲击响应谱与经典冲击试验等效计算方法

产品即使在试验室里通过了经典冲击试验环境,在实际使用环境中还有损坏。因此简单采用经典冲击作为检测条件的试验规范已经不能满足使用需求。另外,试验中,给定的波形量级与脉宽往往超出电动振动台或冲击台的性能范围,阻碍了试验的顺利进行。基于等效冲击试验原理,采用冲击响应谱(SRS)代替经典冲击。运用改进的递归数字滤波法编制经典脉冲的冲击响应谱计算程序,实现了经典冲击与冲击响应谱的等效计算。算例和试验表明,方法合理可行。     

夹具连接方式对冲击响应谱模拟能力影响效应分析

文章介绍了夹具结构特性与冲击响应谱模拟试验能力之间的关系,通过典型夹具的有限元分析和试验验证的方式说明夹具连接方式对冲击响应谱模拟能力影响效应。结果表明,利用振动夹具进行冲击试验时,可以通过减少连接螺钉数量,提供冲击响应谱模拟能力。该方法可以为作为试验人员进行冲击响应谱试验的操作指导。     

对经典冲击和冲击响应谱的探讨

产品在生产、运输及使用过程中常面临各种冲击环境，容易引起产品质量和可靠性方面的诸多问题，因此在产品研制生产过程中需要进行冲击试验，本文对经典冲击和冲击响应谱试验进行原理分析，认为产品实际冲击环境非常复杂，应根据产品冲击环境的实测值和试验目的进行试验方法选择。最后根据两种试验方法的实际应用和相关标准的修订情况，提出了冲击响应谱在验证产品设计参数或可靠性等方面的优势，成为冲击试验的发展趋势。     

利用谐振板装置模拟冲击环境

通过对国外近年来发展起来的一种爆炸冲击模拟装置（即谐振板装置）的研究和分析，在现有条件的基础上设计了一种谐振板装置，并利用该装置进行了一系列的试验研究工作，主要研究了设备参数对冲击响应谱的影响。     

冲击台冲击波形的确定方法

本文对冲击台在冲击试验前,因测试冲击波形是否符合试验要求而所做的过多模拟测试,会导致试验效率较低、试验材料浪费等问题,在数据试验的基础上,运用泰勒公式和最小二乘法,将复杂的物理模型转化为若干个简单的数学模型,给出了一种冲击台的波形发生器的模拟选定和冲击台提升高度的确定方法,以确定冲击波形。测试数据表明,该方法建立的冲击波形的确定方法是可靠的。     

冲击响应谱规范试验室模拟述评

冲击响应谱试验已是航天产品必做的力学环境试验,本文介绍了目前试验室普遍使用的冲击响应谱模拟的手段,阐述了用电动振动台模拟和用机械式试验机模拟的差异,并对存在的差异进行了讨论。     

航天器冲击响应谱试验模拟方法概述

文章介绍了航天器冲击谱模拟试验技术的发展过程,对目前国内外应用较广的各类冲击试验方法进行了整理和分类,从典型脉冲模拟技术,振动试验系统模拟技术,机械碰撞模拟技术和火工品装置模拟技术四个主要方面,对各类冲击技术的特点及实现方式进行了着重的分析。通过对各方法的优缺点和适用范围进行比较,给经受不同冲击环境的航天器进行试验方法选择时提供了参考。     

对MIL-STD-810D/E中冲击与振动等效的说明

本文提供了扩大应用MIL-STD-810D/E(以下简称810D/E)中,方法516.3/516.4I-3.3节程序I(功能冲击)规定的冲击与振动等效分析的方法。程序I规定的等效仅适用于在规定频率范围内振动响应谱(VRS)超过冲击响应谱(SRS)的情况。本文用冲击响应谱超过振动响应谱时估计等效可能性的分析程序对810D/E进行了补充。使用Miner假设,将3σ极限以上的振动循环的潜在疲劳损伤与每个轴向冲击脉冲的潜在疲劳损伤进行了比较。文中还提供了一个例子。     

基于GJB150舰船冲击测量中零漂问题分析

舰船冲击试验为破坏性试验。由于冲击的持续时间短并且能量释放剧烈,在测试的过程中经常出现信号丢失、过载或零漂现象,极大的影响了测量数据的可靠性。通过对冲击测量过程中产生的零漂现象进行原因分析,从而提高测量信号的有效性。     

天然橡胶减震垫减震性能研究分析

采用相同结构的两种天然橡胶减震垫,进行了三种条件下的冲击试验和一种条件的振动试验,研究了减震材料硬度、产品质量对减震性能的影响.承受60g以上冲击时,使用该减震垫的产品经受的冲击能量可衰减50%以上,谐振频率在20Hz～40Hz的产品不宜使用该减震垫.     

A GIS Approach to Model Sediment Reduction Susceptibility of Mixed Sand and Gravel Beaches

The morphological form of mixed sand and gravel beaches is distinct, and the process/response system and complex dynamics of these beaches are not well understood. Process response models developed for pure sand or gravel beaches cannot be directly applied to these beaches. The Canterbury Bight coastline is apparently abundantly supplied with sediments from large rivers and coastal alluvial cliffs, but a large part of this coastline is experiencing long-term erosion. Sediment budget models provide little evidence to suggest sediments are stored within this system. Current sediment budget models inadequately quantify and account for the processes responsible for the patterns of erosion and accretion of this coastline. We outline a new method to extrapolate from laboratory experiments to the field using a geographical information system approach to model sediment reduction susceptibility for the Canterbury Bight. Sediment samples from ten representative sites were tumbled in a concrete mixer for an equivalent distance of 40 km. From the textural mixture and weight loss over 40 km tumbling, we applied regression techniques to generate a predictive equation for Sediment Reduction Susceptibility (SRS). We used Inverse Distance Weighting (IDW) to extrapolate the results from fifty-five sites with data on textural sediment composition to field locations with no data along the Canterbury Bight, creating a continuous sediment reductions susceptibility surface. Isolines of regular SRS intervals were then derived from the continuous surface to create a contour map of sediment reductions susceptibility for the Canterbury Bight. Results highlighted the variability in SRS along this coastline.     

温度冲击试验设备实现途径及热负荷分析

结合试验指标要求，对温度冲击试验设备实现途径进行分析比较，选择两箱式作为试验设备的实现方式；对设备组成结构及制冷、加热流程进行阐述，并对温度冲击试验过程中两种制冷状态下的热负荷进行了分析计算。     

COLD-SHOCK RESISTANCE TO LARGEMOUTH BASS,BLUEGILL, AND CHANNEL CATFISH1

ABSTRACT: Juvenile specimens of largemouth bass, bluegill, and channel catfish were tested to determine their ability to withstand abrupt temperature decreases simulating the environmental impact from a sudden shutdown of a nuclear reactor during the winter. Temperature reductions were administered over 2-hour and 24-hour periods to assess the importance of the rate of temperature change and hence the mitigative value of having a holding pond with a one-day retention time between the proposed cooling tower discharge and the receiving stream. Temperature decreases administered over a 2-hour period resulted in much greater mortality than decreases of the same magnitude administered over a 24-hour period. Thus, the value of a pond for mitigation from cold shock was substantiated. Results also indicated that adherence to the U.S. EPA temperature criteria for freshwater fish should provide adequate protection from cold shock.     

A Comparison of On-site Hunters,Sportsmen and the General Public about Recreational Rates and Future Land Use Preferences for the Savannah River Site

Management of ecosystems has been improved both by our understanding of how ecosystems function, as well as by what people consider to be suitable future land uses. This is particularly true with contaminated lands where decisions must be made about clean-up and future land use. In this paper I synthesize several surveys of public recreational rates and preferences for future land use of the Savannah River Site (SRS), a Department of Energy (DoE) facility located in South Carolina. Four groups of people were interviewed: on-site hunters; sportsmen; local residents attending an event near Aiken, South Carolina; and the general public attending a festival in Columbia, South Carolina. The general public that engaged in recreational activities averaged 20 days/ year or more for hunting and fishing, while sportsmen averaged over 50 days/year. All four groups rated maintaining SRS as a National Environmental Research Park (NERP) and using it for recreation as the highest preferred land uses. The general public rated hiking and camping higher than hunting and fishing, while sportsmen rated hunting higher than hiking and camping. All groups rated using SRS for homes as the lowest, or second lowest, preferred land use. There was disagreement on the ratings for industrial development, with people living closer to the site rating it higher than the general South Carolina population. These data can be used by local planners and managers in decision making regarding clean-up levels and future land use. The relative unanimity of views for cleaning up DoE sites, continued use of the site as a NERP and increased recreational use suggests that different groups of people share similar preferences for future use of SRS, and provides a useful paradigm for considering future land use decisions at other DoE sites nationwide. The relatively low ranking for housing and factories suggests that clean-up levels could be geared to future land use, such as recreation, which are less stringent than residential levels.     

Multi-stage sampling for large scale natural resources surveys: a case study of rice and waterfowl

Large-scale sample surveys to estimate abundance and distribution of organisms and their habitats are increasingly important in ecological studies. Multi-stage sampling (MSS) is especially suited to large-scale surveys because of the natural clustering of resources. To illustrate an application, we: (1) designed a stratified MSS to estimate late autumn abundance (kg/ha) of rice seeds in harvested fields as food for waterfowl wintering in the Mississippi Alluvial Valley (MAV); (2) investigated options for improving the MSS design; and (3) compared statistical and cost efficiency of MSS to simulated simple random sampling (SRS). During 2000-2002, we sampled 25-35 landowners per year, 1 or 2 fields per landowner per year, and measured seed mass in 10 soil cores collected within each field. Analysis of variance components and costs for each stage of the survey design indicated that collecting 10 soil cores per field was near the optimum of 11-15, whereas sampling >1 field per landowner provided few benefits because data from fields within landowners were highly correlated. Coefficients of variation (CV) of annual estimates of rice abundance ranged from 0.23 to 0.31 and were limited by variation among landowners and the number of landowners sampled. Design effects representing the statistical efficiency of MSS relative to SRS ranged from 3.2 to 9.0, and simulations indicated SRS would cost, on average, 1.4 times more than MSS because clustering of sample units in MSS decreased travel costs. We recommend MSS as a potential sampling strategy for large-scale natural resource surveys and specifically for future surveys of the availability of rice as food for waterfowl in the MAV and similar areas.