Modified DS np Chart Using Generalized Multiple Dependent State Sampling under Time Truncated Life Test

This study presents the design of a modified attributed control chart based on a double sampling(DS)np chart applied in combination with generalized multiple dependent state(GMDS)sampling to monitor the mean life of the product based on the time truncated life test employing theWeibull distribution.The control chart developed supports the examination of the mean lifespan variation for a particular product in the process of manufacturing.Three control limit levels are used:the warning control limit,inner control limit,and outer control limit.Together,they enhance the capability for variation detection.A genetic algorithm can be used for optimization during the in-control process,whereby the optimal parameters can be established for the proposed control chart.The control chart performance is assessed using the average run length,while the influence of the model parameters upon the control chart solution is assessed via sensitivity analysis based on an orthogonal experimental design withmultiple linear regression.A comparative study was conducted based on the out-of-control average run length,in which the developed control chart offered greater sensitivity in the detection of process shifts while making use of smaller samples on average than is the case for existing control charts.Finally,to exhibit the utility of the developed control chart,this paper presents its application using simulated data with parameters drawn from the real set of data.

Surface effects on in-shoe plantar pressure and tibial impact during running

Purpose： This study aims to explore the effects of running on different surfaces on the characteristics of in-shoe plantar pressure and tibial acceleration. Methods： Thirteen male recreational runners were required to run at 12 km/h velocity on concrete, synthetic track, natural grass, a normal treadmill, and a treadmill equipped with an ethylene vinyl acetate （EVA） cushioning underlay （treadmill_EVA）, respectively. An in-shoe plantar pressure system and an accelerometer attached to the tibial tuberosity were used to record and analyze the characteristics of plantar pressure and tibial impact during running. Results： The results showed that there were no significant differences in the 1 st and 2nd peak plantar pressures （time of occurrence）, pressure-time integral, and peak pressure distribution for the concrete, synthetic, grass, and normal treadmill surfaces. No significant differences in peak positive acceleration were observed among the five tested surface conditions. Compared to the concrete surface, however, running on treadmillEVA showed a significant decrease in the 1st peak plantar pressure and the pressure time integral for the impact phase （p 〈 0.05）. These can be further ascribed to a reduced peak pressure observed at heel region （p 〈 0.05）. Conclusion： There may not be an inevitable relationship between the surface and the lower-limb impact in runners. It is, however, still noteworthy that the effects of different treadmill surfaces should be considered in the interpretation of plantar pressure performance and translation of such results to overground running.

复杂结构井旋转下套管数学模型建立与分析

随着复杂结构井钻井技术发展,井斜角和方位角随着井深复杂变化引起常规套管下入方式难度大,旋转下套管技术可有效解决套管下入的难题,但该方面的理论模拟分析报道较少,增加了旋转下套管技术应用的盲目性和低效性。综合运用软杆和刚杆模型的优点并考虑井眼轨迹对模型计算条件影响,建立了旋转下套管数学模型;结合实例井对比了大钩载荷和模拟的轴向应力,验证了模型的正确性;在此基础上,探讨了常规和不同旋转速度下套管的摩阻,并分析了不同摩阻系数条件下的摩阻分布特征。实例分析表明:相同井深下,旋转下套管摩阻小于常规下套管摩阻,并且旋转速度越快,下套管摩阻越小;当旋转速度分别为15 r/min和20 r/min时,井底处摩阻降低幅度分别为12.13%和19.17%;造斜率越大,摩阻越高,导致套管下入到指定深度难度加大;钻井液摩阻系数越大,套管下入难度越高;在井深1 401.5 m,裸眼段摩阻系数分别为0.21和0.29,常规下套管摩阻分别为46.51 kN和57.49 kN。该模型能准确预测下套管摩阻,对复杂结构井的套管下入具有指导意义。

空调及换气系统运行对室内PM_(2.5)净化效果的影响

为了研究室内空调与换气系统运行时空气净化器对室内空气的净化效果,采用试验研究和CFD模拟相结合的方法,研究了空调与换气系统运行对净化器将室内PM_(2.5)净化到ASHRAE规定的可接受室内空气质量的限值15μg/m^(3)的净化时间的影响。结果表明,净化器外加空调净化时间相比净化器单独运行时间缩短15.2%;净化器外加换气系统净化时间相比净化器单独运行时缩短了30.4%;三系统联合运行时的净化时间相比净化器单独运行时间缩短32.6%。结果可为研究空调与换气系统对空气净化器净化效果的贡献及室内空气净化方式提供参考。

鞋底硬度对人体足底压力分布与冲击力的影响研究

为探究不同鞋底硬度跑鞋对跑步、跳跃过程中人体足底压力分布与下肢冲击力的影响,设定了ShoreC 35、ShoreC 48、ShoreC 583种不同鞋底硬度的跑鞋,选择16名男性大学生作为试验对象,对人体主动落地与慢跑、快跑过程中的足底压力分布情况与冲击力特征进行收集与分析,以期为人体运动损伤防护与跑鞋的合理设计提供借鉴。结果表明,较软鞋底能够有效降低冲击峰值、降低足底压强,有利于避免潜在的冲击伤害并增强足部舒适感;慢跑状态下,鞋底硬度因素对最大负载率、到达最大负载率的时间产生了显著影响。快跑状态下,鞋底硬度因素对到达冲击力峰值时间、到达最大负载率的时间有显著影响。

直馏柴油加氢裂化生产化工原料及喷气燃料反应规律研究

分别考察了体积空速、反应压力以及裂化反应温度对直馏柴油加氢裂化产品分布及性质的影响。研究表明,在相同反应温度与压力的条件下,当裂化体积空速由0.50 h^(-1)升高到1.25 h^(-1)时,重石脑油芳潜由47.5%升高到55.8%,喷气燃料馏分烟点由26.0 mm降低至22.0 mm,>260℃柴油馏分BMCI由13.92增大到16.14。在反应温度与体积空速不变的条件下,当反应压力由6MPa提高至8MPa时,重石脑油芳潜由62.0%降低至54.5%,喷气燃料烟点由21.2 mm提高至23.7 mm,>260℃柴油馏分BMCI由16.13降低至14.63。当反应温度由375℃升高到385℃时,重石脑油芳潜由61.2%降低至57.5%,喷气燃料烟点由23.2 mm提高至25.5 mm,>260℃柴油馏分BMCI由22.27降低到16.95。因此,直馏柴油加氢裂化所产重石脑油馏分是优质的催化重整原料,>260℃柴油馏分可作为蒸汽裂解制乙烯原料,控制适当的反应条件,还可以生产出合格的3#喷气燃料。

基于MOD16和地面降水数据的大别山区农业干旱与气象干旱响应关系

利用2000—2020年大别山区气象观测资料和MODIS16A2资料,计算降水距平百分率(PA)和作物缺水指数(CWSI),研究农业干旱与气象干旱的时空分布特征,利用滞后相关分析探究二者的响应关系。结果表明:(1)大别山区降水存在显著时空分布不均匀性,西北少、东南多,且旱涝年的降水量差异大(最高达875 mm)。(2)大别山区东南部发生气象干旱事件的频率偏高(最高为66.67%),但干旱程度较轻;北部发生干旱频率较低(最低为38.1%),但易发生严重干旱。(3)大别山区农业干旱具有秋冬春季容易发生、北部更容易发生、海拔低处更容易发生的特征。(4)大别山区南部农业干旱对气象干旱在次月和第3个月响应程度最高,农业干旱比气象干旱更容易发生,持续时间更久,影响更大。

基于正态变换的变样本容量Shewhart比例控制图设计

为了提高Shewhart型比例控制图的监控效率,将其与变样本容量策略结合,提出一种新的比例控制图(VSS Shewhart-RZ*控制图)来监控二元正态变量之比。基于正态变换方法设计了新的比例统计量Z*,以消除样本容量变化对比例控制图设计及使用的不利影响。采用马尔科夫链方法计算了该控制图的平均运行长度和平均样本容量,给出该控制图的参数优化算法。通过仿真分析研究了该控制图的统计性能,并与Shewhart比例控制图进行比较,结果表明VSS Shewhart-RZ*控制图的性能明显优于传统固定样本容量Shewhart比例控制图。

归来庄金矿矿体和岩体中Au等成分的Runs检验及意义

Runs检验是研究序列分布规律的一种数学方法。用这种方法检验归来庄金矿和铜石杂岩体的某些成分,得出归来庄金矿TC30中Au的高品位值的出现不是随机的,而是具有集中出现的规律性;铜石杂岩体中SiO2和Au都是具有随机变化性,说明杂岩体没有明显的演化关系,不同岩体的形成时间先后对成矿元素Au的富集没有明显影响;杂岩体中Al2O3和TiO2比值在闪长玢岩和二长斑岩中无明显差异,说明二者为同源成因。

基于增强型龙格库塔优化算法的跳频序列设计

跳频技术具有优秀的抗干扰性能和多址组网性能,跳频序列(FHS)作为其关键,在设计时面临性能指标差、难以兼顾多指标的问题。提出一种基于增强型龙格库塔优化算法(ERUN)的跳频序列设计方法。利用跳频序列的汉明相关性、复杂度、均匀性和平均跳频间隔构建目标函数,建立适用于启发式优化算法的跳频序列设计模型。针对龙格库塔优化算法(RUN)在复杂优化问题上收敛速度慢、寻优精度差的问题,提出增强型龙格库塔优化算法。利用混沌反向学习机制提高初始种群质量,基于二次插值法得到更好的个体更新方向,并根据自适应t分布扰动帮助种群跳出局部最优。在6个基准测试函数和目标函数上的测试结果表明,与RUN的3个最新变体相比,ERUN具有更快的收敛速度和更高的解精度。将得到的跳频序列应用于跳频系统中,实验结果表明,该方法在固定干扰环境下误码率为4%左右,在变化干扰环境下误码率没有明显上升,展现出了较强的抗干扰能力和复杂环境适应能力。

加氢裂化装置原料轻质化对反应过程影响研究

在加氢裂化装置原料轻质化的背景下,考察了蜡油中掺炼不同比例直馏柴油对加氢裂化产品分布及产品性质的影响。当直馏柴油掺炼比例为45%(质量分数,下同)时,喷气燃料收率最高,达到26%。随着直馏柴油掺炼比例的增加,重石脑油的环烷烃、芳烃含量降低;喷气燃料烟点呈逐渐升高的趋势;尾油(大于260℃)的链烷烃含量呈逐渐升高的趋势,环烷烃、芳烃含量呈逐渐降低的趋势,BMCI值(芳烃指数)呈先升高后降低的趋势。当直馏柴油掺炼比例为75%时,喷气燃料烟点最高,为28.8 mm。以掺炼15%直馏柴油的蜡油为原料时,随着转化率的升高,尾油的BMCI值逐渐降低;当尾油收率为20%时,尾油的BMCI值低至7.2,链烷烃质量分数升至62.0%,环烷烃质量分数降至35.2%,芳烃质量分数仅为2.6%。

磁控管自由振荡带宽对其注入锁定带宽的影响研究

自由振荡磁控管的输出信号通常具有一定的带宽,而非理想的单频信号;文章研究了磁控管自由振荡输出带宽对其注入锁定的影响。从统计上认为自由振荡磁控管的输出频率服从正态分布,结合注入锁定理论,计算了磁控管在不同注入频率下的输出频谱。理论分析表明:当考虑自由振荡磁控管输出频谱具有一定带宽时,峰值频率牵引带宽将大于理想单频假设下的锁定带宽;随着自由振荡带宽的增加,峰值频率牵引带宽增加,锁定带宽减小。磁控管注入锁定实验结果表明:自由振荡带宽(3 dB)分别为0.375、1.049 MHz时,其锁定带宽分别为8.4、7.9 MHz,峰值频率牵引带宽分别为10.2、13.9 MHz,验证了理论的正确性。本研究发展了磁控管注入锁定理论。

工业园区分布式屋顶光伏发电运行研究

全球能源结构的转变推动了分布式光伏发电业务的规模化发展。在此背景下,文章从分布式光伏发电的发展现状和面临的挑战出发,分析了电网规划与投资、负荷消纳的复杂性、配电网络的控制难题以及维护与检修的挑战等,并提出针对性的解决方案和建议,以期为未来分布式光伏发电技术的优化和发展提供有益参考。

基于光纤通信的配电自动化终端电源运行状态监测方法

配电自动化终端数据量庞大且电磁干扰严重,导致监测结果的实时性和准确性不佳。因此,提出基于光纤通信的配电自动化终端电源运行状态监测方法设计。该方法通过光纤通信技术将采集到的配电自动化终端电源运行数据实时传输到监测中心,然后监测中心根据信息建立状态评价体系,实现配电自动化终端电源运行状态监测。仿真实验结果表明,该方法的监测结果能够准确反映实际值,且监测用时只需1.03min,证明该方法能够迅速获取终端电源的各项关键参数,精确监测配电自动化终端电源运行状态。

变压器并列运行时负荷分配比例与短路阻抗关系的分析

变压器并列运行需要考虑如何解决负荷分配随各变压器额定容量匹配的合理性问题,而短路阻抗是影响负荷分配比例的主要因素。介绍了变压器并列运行的优缺点及并列运行的理想条件,以两台变压器并列运行为例,分析了负荷分配比例与短路阻抗大小的关系。结果表明:额定容量不相等的两台变压器并列运行时,要尽可能保证其短路阻抗相等,使每台变压器所带的负荷根据各自的额定容量按比例进行分配;不能满足短路阻抗完全相等的条件时,额定容量较小的变压器短路阻抗应选择大一些,额定容量较大的变压器短路阻抗应选择小一些,使并列运行后的系统总传输容量大于两台变压器的额定容量之和,以提高系统运行的经济性和安全性。

Distributed Collaborative Response Surface Method for Mechanical Dynamic Assembly Reliability Design

Because of the randomness of many impact factors influencing the dynamic assembly relationship of complex machinery, the reliability analysis of dynamic assembly relationship needs to be accomplished considering the randomness from a probabilistic perspective. To improve the accuracy and efficiency of dynamic assembly relationship reliability analysis, the mechanical dynamic assembly reliability（MDAR） theory and a distributed collaborative response surface method（DCRSM） are proposed. The mathematic model of DCRSM is established based on the quadratic response surface function, and verified by the assembly relationship reliability analysis of aeroengine high pressure turbine（HPT） blade-tip radial running clearance（BTRRC）. Through the comparison of the DCRSM, traditional response surface method（RSM） and Monte Carlo Method（MCM）, the results show that the DCRSM is not able to accomplish the computational task which is impossible for the other methods when the number of simulation is more than 100 000 times, but also the computational precision for the DCRSM is basically consistent with the MCM and improved by 0.40-4.63% to the RSM, furthermore, the computational efficiency of DCRSM is up to about 188 times of the MCM and 55 times of the RSM under 10000 times simulations. The DCRSM is demonstrated to be a feasible and effective approach for markedly improving the computational efficiency and accuracy of MDAR analysis. Thus, the proposed research provides the promising theory and method for the MDAR design and optimization, and opens a novel research direction of probabilistic analysis for developing the high-performance and high-reliability of aeroengine.

Application of Maximum Entropy Distribution to the Statistical Properties of Wave Groups

The new distributions of the statistics of wave groups based on the maximum entropy principle are presented. The maximum entropy distributions appear to be superior to conventional distributions when applied to a limited amount of information. Its applications to the wave group properties show the effectiveness of the maximum entropy distribution. FFF filtering method is employed to obtain the wave envelope fast and efficiently. Comparisons of both the maximum entropy distribution and the distribution of Longuet-Higgins （1984） with the laboratory wind-wave data show that the former gives a better fit.

Distributed collaborative extremum response surface method for mechanical dynamic assembly reliability analysis

To make the dynamic assembly reliability analysis more effective for complex machinery of multi-object multi-discipline(MOMD),distributed collaborative extremum response surface method(DCERSM)was proposed based on extremum response surface method(ERSM).Firstly,the basic theories of the ERSM and DCERSM were investigated,and the strengths of DCERSM were proved theoretically.Secondly,the mathematical model of the DCERSM was established based upon extremum response surface function(ERSF).Finally,this model was applied to the reliability analysis of blade-tip radial running clearance(BTRRC)of an aeroengine high pressure turbine(HPT)to verify its advantages.The results show that the DCERSM can not only reshape the possibility of the reliability analysis for the complex turbo machinery,but also greatly improve the computational speed,save the computational time and improve the computational efficiency while keeping the accuracy.Thus,the DCERSM is verified to be feasible and effective in the dynamic assembly reliability(DAR)analysis of complex machinery.Moreover,this method offers an useful insight for designing and optimizing the dynamic reliability of complex machinery.

Control charts for the Pareto distribution

The Pareto distribution plays an important role in various areas of research. In this paper, the average run length （ARL） unbiased control charts, which monitor the shape and threshold parameters of the Pareto distribution respectively, are proposed when the incontrol parameters are known. The effects of parameter estimation on the performance of the proposed control charts are also studied. Results show that the control charts with the estimated parameters are not suitable to be used in the known parameter case, thus the ARL-unbiased control charts for the shape and threshold parameters with the desired ARLo, which consider the variability of the parameter estimates, are further developed. The performance of the proposed control charts is investigated in terms of the ARL. Finally, an example is given to illustrate the proposed control charts.

Numerical Procedures for Calculating the Probabilities of Recurrent Runs

Run count statistics serve a central role in tests of non-randomness of stochastic processes of interest to a wide range of disciplines within the physical sciences, social sciences, business and finance, and other endeavors involving intrinsic uncertainty. To carry out such tests, it is often necessary to calculate two kinds of run count probabilities: 1) the probability that a certain number of trials results in a specified multiple occurrence of an event, or 2) the probability that a specified number of occurrences of an event take place within a fixed number of trials. The use of appropriate generating functions provides a systematic procedure for obtaining the distribution functions of these probabilities. This paper examines relationships among the generating functions applicable to recurrent runs and discusses methods, employing symbolic mathematical software, for implementing numerical extraction of probabilities. In addition, the asymptotic form of the cumulative distribution function is derived, which allows accurate runs statistics to be obtained for sequences of trials so large that computation times for extraction of this information from the generating functions could be impractically long.