Planning failure-censored constant-stress partially accelerated life test

This article deals with the case of the failure-censored constant-stress partially accelerated life test （CSPALT） for highly reliable materials or products assuming the Pareto distribution of the second kind. The maximum likelihood （ML） method is used to estimate the parameters of the CSPALT model. The performance of ML estimators is investigated via their mean square error. Also, the average confidence interval length （IL） and the associated co- verage probability （CP） are obtained. Moreover, optimum CSPALT plans that determine the optimal proportion of the test units al- located to each stress are developed. Such optimum test plans minimize the generalized asymptotic variance （GAV） of the ML estimators of the model parameters. For illustration, Monte Carlo simulation studies are given and a real life example is provided.

基于正交试验设计的改性污泥基生物炭制备研究

为了进一步提高污泥基生物炭的吸附能力,采用掺入特定比例硫酸的氯化锌作为活化剂开展污泥基生物炭制备研究,通过正交试验结果可见,不同制备条件对生物炭碘吸附值影响的比较为:碳化温度>活化剂硫酸掺入比>碳化时间>活化剂浓度;结合不同制备条件对产率影响,获得最佳制备条件组合为:碳化温度500℃、活化剂硫酸掺入比60%、碳化时间1 h、活化剂浓度3 mol/L。在该组合条件下制备的改性污泥基生物炭碘吸附值为516.68 mg/g,产率为70.25%。

沙漠腹地风积沙压实特性试验分析

塔克拉玛干沙漠腹地修建石油钻井平台地基,地基材料运距远且会破坏沙漠地区生态环境,考虑到因地制宜,采用沙漠地区丰富的风积沙资源作为地基填料,其压实特性是影响地基施工工艺及质量的关键因素。为了研究其压实特性,进行了标准重型击实实验、超重型击实试验。研究结果表明:该地区风积沙粒径主要分布在0.075~0.25mm之间,属于级配不良的细砂;风积沙的重型、超重型击实曲线均呈“双峰”型,在干燥状态及最佳含水率时均能达到最大干密度,室内风积沙击实试验推荐使用大击实筒;不同的击实方式会产生不同的试验结果,最大干密度应结合现场确定。

论轿厢重量设计对电梯运行的影响

通过列举两种轿厢由于重量设计不够在电梯安装、运行中出现的问题,分析因轿厢重量较轻而导致电梯曳引能力试验失败和减速停靠过程发生故障的原因,从而提出合理的轿厢重量设计可以保证电梯满足曳引能力试验要求和解除电梯减速停靠过程发生的故障。同时分析了加大轿厢重量设计的利弊,轿厢重量设计过大会加大电梯运行能量消耗,最后提出规范轿厢重量设计范围的必要性。

Optimal Design of Multiple Stresses Accelerated Life Test Plan Based on Transforming the Multiple Stresses to Single Stress

For planning optimum multiple stresses accelerated life test plans, a commonly followed guiding principle is that all parameters of the life-stress relationship should be estimated, and the number of the stress level combinations must be no less than the number of parameters of the life-stress relationship. However, the general objective of an accelerated life test（ALT） is to assess thep-th quantile of the product life distribution under normal stress. For this objective,estimating all model parameters is not necessary, and this will increase the cost of test. Based on the theoretical conclusion that the stress level combinations of the optimum multiple stresses ALT plan locate on a straight line through the origin of coordinate, it is proposed that a design idea of planning the optimum multiple stresses ALT plan through transforming the problem of designing an optimum multiple stresses ALT plan to designing an optimum single stress ALT plan. Moreover, a method of planning the optimum multiple stresses ALT plan which can avoid estimating all model parameters is established. An example shows that, the proposed plan which only has two stress level combinations could achieve an accuracy no less than the traditional plan, and save the test time and cost on one stress level combination at least; when the actual product life is less than the design value, even the deviation of the model initial parameters value is up to 20%, the variance of the estimation of thep-th quantile of the proposed plan is still smaller than the traditional plans approximately 25%. A design method is provided for planning the optimum multiple stresses ALT which uses the statistical optimum degenerate test plan as the optimum multiple stresses accelerated life test plan.

Zemax-Based Optimum Structural Design of Probe of an Optical-Fiber Sensor

Bubble plumes are important during the process of air-sea exchange,and optical-fiber phase detection is a suitable way to observe bubble plumes entrained by breaking waves.This paper designs a new optical-fiber probe(OFP)made of sapphire to overcome the limitations of existing materials(e.g.,high brittleness,poor corrosion resistance,and narrow bandwidth)and thereby enhance the detection performance of the OFP by improving its structure.Based on total internal reflection and light refraction,a simulation model of the probe is established in the Zemax optical design software to optimize the probe tip and matching mode of the two probe tips.The results show that the optimum OFP tip is a conical sapphire one with a cone angle of 35°.Tests are then conducted on a bespoke OFP sensor,the results of which are consistent with those predicted theoretically.The simulation results lay the foundation for the integrated design of OFP sensors and the optimization of their internal optics.The findings could also be applied to OFPs with multiple tips.

Corrosion and optimum corrosion protection potential of friction stir welded 5083-O Al alloy for leisure ship

Electrochemical tests were undertaken to determine the optimum conditions in seawater for corrosion protection of friction stir-welded 5083-O Al alloy.Polarization trend observations show that the limiting potential that avoids the effects of hydrogen embrittlement is -1.6 V,corresponding to the crossover point between concentration polarization and activation polarization.However,the optimum protection potential is between -1.5 and -0.7 V since the current density at these values is low in the potentiostatic tests.When a galvanic cell is formed in the seawater,the welds exhibit electrochemically stable trends.Welded parts in galvanic tests with various area ratios are stable and have excellent anticorrosion characteristics.

基于正交设计方法的塑性混凝土优化配合比试验研究

笔者利用正交试验法进行塑性混凝土试验方案设计,并结合SPSS软件对试验结果进行变异数分析和Duncan多重比较,以此探讨了引气剂掺量、膨润土用量、水胶比三种因素对其性能评价指标的影响,找出满足各设计要求的最佳配合比。结果表明:对静力抗压弹模和抗压强度而言,因素的主次顺序是膨润土掺量、水胶比、引气剂掺量;膨润土用量、水胶比及引气剂掺量的提高对弹性有利,对抗压强度不利。对渗透系数来说,主次排序是水胶比、引气剂掺量、膨润土掺量;膨润土用量及水胶比的增加对抗渗性不利,引气剂掺量的增加对抗渗性有利。该方法找出引气剂掺量0.02%、膨润土用量60%、水胶比0.95的相对最佳配比,并通过了验证。

Sustainable fisheries in shallow lakes:an independent empirical test of the Chinese mitten crab yield model

Next to excessive nutrient loading,intensive aquaculture is one of the major anthropogenic impacts threatening lake ecosystems.In China,particularly in the shallow lakes of mid-lower Changjiang(Yangtze) River,continuous overstocking of the Chinese mitten crab(Eriocheir sinensis) could deteriorate water quality and exhaust natural resources.A series of crab yield models and a general optimum-stocking rate model have been established,which seek to benefit both crab culture and the environment.In this research,independent investigations were carried out to evaluate the crab yield models and modify the optimum-stocking model.Low percentage errors(average 47%,median 36%) between observed and calculated crab yields were obtained.Specific values were defined for adult crab body mass(135 g/ind.) and recapture rate(18%and 30%in lakes with submerged macrophyte biomass above and below 1 000 g/m^2)to modify the optimum-stocking model.Analysis based on the modified optimum-stocking model indicated that the actual stocking rates in most lakes were much higher than the calculated optimum-stocking rates.This implies that,for most lakes,the current stocking rates should be greatly reduced to maintain healthy lake ecosystems.

鼠笼弹性支承干摩擦减振试验研究和参数识别

针对鼠笼弹性支承干摩擦阻尼器减振机理和摩擦参数不确定问题,提出了基于双线性梁单元简化模型的两步参数识别方法。基于梁单元弯曲理论和有限元分析,开展刚度分析并提出鼠笼弯曲刚度经验计算公式,相比传统理论公式误差更小,为参数识别提供初值条件。建立了鼠笼弹性支承干摩擦试验台,改变鼠笼端面接触压力,开展了鼠笼弹性支承扫频试验,得到了表征界面能量耗散特性的黏滞-滑移特性曲线和最佳正压力。基于鼠笼弹性支承黏滞-滑移曲线,采用遗传算法开展了梁单元与双线性弹簧单元两步参数识别,开展了参数识别结果验证和误差分析。试验结果表明,双线性梁单元简化模型迟滞曲线面积误差在10%以内,相比三维有限元模型,计算时间缩短了92.34%。该模型可为鼠笼弹性支承干摩擦减振设计提供一种高效的简化计算模型。

求解物流配送中心选址问题的改进鸽群算法

为了提高鸽群优化算法求解物流配送中心选址问题的优化效果,减少物流配送成本,提出了一种改进的鸽群优化算法。该算法在基础鸽群优化算法上,引入灰狼优化算法在寻优过程中的捕食策略,能够有效地提高鸽群优化算法的局部搜索能力、增强算法的寻优性能。由函数测试实验可得,该算法在求解测试函数最优值上具有寻优速度快、收敛精度高的特点。最后,将其应用到求解物流配送中心选址问题中,实验结果表明:改进的鸽群优化算法更适合求解高维物流配送中心选址问题。

具有竞争风险的步进应力加速寿命试验的最优设计和Bayes估计

讨论了渐进II型截尾数据中具有竞争风险的步进应力加速寿命试验的最优试验设计和参数估计.通过假定产品寿命服从Weibull分布,尺度参数对数是应力水平的线性函数基础上,利用KH模型采用极大似然方法和Bayes方法对模型参数进行了点估计和区间估计,而最优试验设计是使尺度参数对数的极大似然估计值在正常应力水平下的渐进方差达到最小.最后进行了仿真研究,结果显示提出的估计量具有良好的稳健性和有效性.

高速列车A286螺栓螺纹滚压工艺多目标优化

采用正交试验方法对螺栓螺纹滚压工艺参数进行优化,会存在精度差、效率低等问题。同时,通过试验来探究螺纹滚压表面质量与螺栓疲劳寿命之间关系的相关研究较少。针对某型A286高温合金螺纹紧固件难以满足高速列车所需疲劳寿命要求的问题,以高速列车用螺纹紧固件为研究对象,对螺纹滚压工艺参数进行了多目标优化。首先,选取了对螺纹滚压质量具有显著影响的工艺参数(滚丝轮旋转速度、进给速度和滚压精整时间)作为优化目标,选用最大等效应力和最大损伤作为评价指标,设计了正交试验;然后,采用基于Vague模糊集的螺纹滚压工艺参数多目标优化方法,对螺纹滚压工艺参数进行了寻优;最后,通过模糊集优化确定了螺纹滚压最佳工艺参数,并采用仿真试验与疲劳寿命试验的方式,对上述优化结果的准确性进行了验证。实验结果表明:滚丝轮转速16 r/min、滚丝轮进给速度3 mm/s和精整时间1 s为最佳工艺参数;参数优化后,螺栓的疲劳寿命同比提高了9%。研究结果表明:采用Vague模糊集优化螺纹滚压工艺参数的方法是有效的,并且具有一定的优越性,可以为厂家的生产优化提供理论依据。

大坝小流量渗流量仪的优化设计及其应用

大坝渗流量直接反映了大坝结构体内的安全状况,因此渗流量监测数据的准确性、长期稳定性及可靠性对大坝安全显得尤为重要。根据调研及前期研制出的大坝小流量渗流量计在实际工程应用中出现的问题,对其进行了优化设计。通过旋转测量容器的设计方式实现了测量与引流分离,不仅简化了仪器结构、降低了仪器成本,而且解决了水流侵蚀及渗水析出物影响下,很多容积法自动化监测设备可靠性不高和在不大量雍高排水沟水位的情况下,容积法自动化监测设备很难布置的难题;通过增加防浪管和溢流板等防浪设计和液位开关的优化设计,提高了仪器的测量精度,为大坝渗流量监测提供了更为准确的数据依据;增加了复位功能,攻克了仪器正在运行过程中,突然断电,复电后仪器无法继续进行测量的问题,增加了仪器的可靠性,具有更为广阔的适应性;仪器采用零阀门设计,解决了因泥沙进入阀门导致阀门被卡死或无法完全关闭,出现测量不正常或无法测量的问题,提高了仪器的长期稳定性及可靠性差,另外,增加了自清洁装置,降低了仪器的维护工作量,增加了仪器适应性。通过厂内性能测试和在四个水电站的实际应用,证明了优化后的仪器具有测量精度高,可靠性及长期稳定性好,结构简单,方便现场安装等优点,为大坝渗流量监测提供了可靠的保障。

壳牌TAT固定球阀的优化设计

介绍了根据荷兰壳牌(SHELL)球阀技术规范MESC SPE/77-130设计固定球阀的特殊结构特点,壳牌SHELL设计确认型式试验规范MESC SPE/77-300的要求。基于产品TAT型式试验过程出现的问题对影响试验结果的关键部件进行分析,提出TAT固定球阀的结构优化设计。

击实试验的数据处理及对比分析

在水利工程建设施工中,填筑土料在碾压施工前均要做击实试验,以试验结果的最大干密度和最优含水率作为土料碾压质量控制的基本指标。有时在施工现场还要针对不同的土类进行抽样检验,保证其碾压控制指标的合理性。为能够快速处理击实试验结果数据,依据Excel提供的强大图表和内置函数功能,结合实际工程项目的土料击实试验,详细描述几种击实试验数据的处理方法及对比分析。

室内土工击实试验影响因素分析

介绍了土工室内击实试验的原理,对影响击实试验结果的主要因素进行了分析,另外还阐述了土工室内击实试验在工程中的应用。

茶籽多糖提取工艺的研究

以乙醇为溶剂对影响茶籽粕中多糖的提取因素进行了实验分析 ,在单因素实验的基础上 ,通过正交实验得出优化后的提取工艺条件为 :料液比为 1∶12 (W/V) ,乙醇浓度为 5 5 % ,提取温度为 5 5℃ ,提取时间为 3.0h ,茶籽多糖的得率和纯度分别为 6 .92 %和 78.74 %。

二项式分布场合加速退化零失效可靠性验证试验

对于长寿命高可靠产品,采用零失效可靠性验证试验需要大量的时间或者样本。为了缩短试验时间,建立了一种在二项式分布场合下基于性能退化数据的加速退化零失效可靠性验证试验方法。首先从加速退化模型和测量数据估计样品在规定时间内的退化量及其方差,然后在使用方风险和可用试验样本量的约束下,对试验费用进行优化,得到了最优的试验方案,并给出了单个样品停止试验的判定规则。最后通过一个实例证实了该方法能有效地缩短试验时间。灵敏度分析表明,在规定时间内退化量的预估值对试验方案的优化结果影响较大。

综合应力加速寿命试验方案优化设计理论与方法

针对综合应力加速寿命试验设计问题,就恒定应力加速寿命试验方法。在应用均匀正交试验理论确定了试验应力组合方式和试验次数的基础上,根据所提出的加速寿命试验方案优化设计的准则和方法,以产品在正常工作应力水平时寿命估计值的方差最小为目标,以各加速因子试验应力水平和各次试验试样分配比例为设计变量,应用极大似然估计理论,建立综合应力加速寿命试验方案优化设计的数学模型。对航天电连接器的综合应力加速寿命试验方案优化设计的结果表明,经过优化以后的试验方案不仅可以提高试验数据的估计精度、减少试验次数,而且还可以在相同置信度下减少试验所需的样本数量,并能够缩短试验时间。