Research on aiming methods for small sample size shooting tests of two-dimensional trajectory correction fuse

The longitudinal dispersion of the projectile in shooting tests of two-dimensional trajectory corrections fused with fixed canards is extremely large that it sometimes exceeds the correction ability of the correction fuse actuator.The impact point easily deviates from the target,and thus the correction result cannot be readily evaluated.However,the cost of shooting tests is considerably high to conduct many tests for data collection.To address this issue,this study proposes an aiming method for shooting tests based on small sample size.The proposed method uses the Bootstrap method to expand the test data;repeatedly iterates and corrects the position of the simulated theoretical impact points through an improved compatibility test method;and dynamically adjusts the weight of the prior distribution of simulation results based on Kullback-Leibler divergence,which to some extent avoids the real data being"submerged"by the simulation data and achieves the fusion Bayesian estimation of the dispersion center.The experimental results show that when the simulation accuracy is sufficiently high,the proposed method yields a smaller mean-square deviation in estimating the dispersion center and higher shooting accuracy than those of the three comparison methods,which is more conducive to reflecting the effect of the control algorithm and facilitating test personnel to iterate their proposed structures and algorithms.;in addition,this study provides a knowledge base for further comprehensive studies in the future.

Cautionary Remarks When Testing Agreement between Two Raters for Continuous Scale Measurements: A Tutorial in Clinical Epidemiology with Implementation Using R

Background: When continuous scale measurements are available, agreements between two measuring devices are assessed both graphically and analytically. In clinical investigations, Bland and Altman proposed plotting subject-wise differences between raters against subject-wise averages. In order to scientifically assess agreement, Bartko recommended combining the graphical approach with the statistical analytic procedure suggested by Bradley and Blackwood. The advantage of using this approach is that it enables significance testing and sample size estimation. We noted that the direct use of the results of the regression is misleading and we provide a correction in this regard. Methods: Graphical and linear models are used to assess agreements for continuous scale measurements. We demonstrate that software linear regression results should not be readily used and we provided correct analytic procedures. The degrees of freedom of the F-statistics are incorrectly reported, and we propose methods to overcome this problem by introducing the correct analytic form of the F statistic. Methods for sample size estimation using R-functions are also given. Results: We believe that the tutorial and the R-codes are useful tools for testing and estimating agreement between two rating protocols for continuous scale measurements. The interested reader may use the codes and apply them to their available data when the issue of agreement between two raters is the subject of interest.

ANALYSIS OF SIZE EFFECT,SHEAR DEFORMATION AND DILATION IN DIRECT SHEAR TEST BASED ON GRADIENT- DEPENDENT PLASTICITY

The paper concerns the issue of size law,localized deformation and dilation or compaction due to shear localization. It is assumed that the shear localization initiates at the peak shear stress in the form of single shear band,and based on gradient-dependent plasticity,an analytical solution on size effect or snap-back is obtained. The results show that the post peak response becomes steeper and even exhibits snap-back with increasing of length. For small specimen,the relative shear displacement when specimen failure occurs is lower than that of larger specimen and the shear stress-relative displacement curve becomes steeper. The theoretical solution on non-uniformity of strains in shear band is obtained and evolution of the relative shear displacement is represented. By resorting to the linear relation between local plastic shear strain and local plastic volumetric strain,the dilation and compaction within shear band are analyzed. Relation between apparent shear strain and apparent normal strain and relation between shear displacement and vertical displacement are established.

Rolling Fatigue Test of Large-Sized UHPC Member for Cable Stayed Bridge

Recently, research strives to apply Ultra High Performance Concrete (UHPC) to large-sized structures owing to its remarkable mechanical performance and durability compared to normal concrete. The Korea Institute of Construction Technology proposed SuperBridge800, an edge girder type UHPC cable stayed bridge with central span of 800 m, through its detailed design. The bridge is designed to be erected through the connection of precast UHPC segments. The precast UHPC segment is monolithically composed of one ribbed deck slab and edge girders at each side. The connection between the precast segments is achieved by steel bars at the edge girders and by UHPC cast-in-place wet joint at the slab. Despite of the outstanding mechanical performance of UHPC, the fabrication of large-sized members is a difficult task since UHPC hardens faster than normal concrete and requires a special curing process. Therefore, the constructability of large-sized UHPC segment should be secured to achieve SuperBridge800. Besides, the performance of the connection between segments should also be guaranteed, especially in terms of the fatigue performance of the UHPC cast-in-place joint, which constitutes a weak point. To that goal, two half-scaled UHPC segments are manufactured and the constructability is examined by fabricating a large-sized UHPC member connected with respect to the design conditions. This study conducts rolling fatigue test on the so-fabricated large-sized UHPC member. Rolling fatigue test is carried out up to 2 million cycles considering actual vehicle load at each center and quarter points of the member. The test results confirm that the service limit state is satisfied.

AFFECTION OF SIZE-DISTRIBUTION TESTING APPARATUS ON DETERMINED RESULTS

This paper comprehensively analyzes every factor affecting the medium sedimentating measurement of poivder size distribution, and based on this, selects the optimum condition. Three size testing apparatus are used for a-Al2O3 powder measurements and the measured results are analyzed and compared with each other by unary linear regression method.

ON RELATION BETWEEN SIZE DEVIATION OF RAW SILK AND TESTING-LENGTH

Based on the auto- corrclation coefficient model.we gave an expression ofsize deviation of raw silk when testing- length is equal to a fraction for the unitlength,and discussed how the ratio of the size deviatinons by different testing-length fluctuates with the pseudo- cycle.Using these results as a basis,weexamined how the size deviation with the continuous property of raw silk sizechanges when changing the testing- length from 450 m to ll2.5m.Then weexamined the problem of quality control of raw silk.

Sample Size Determination and Statistical Hypothesis Testing for Core Centration in Press Coated Tablets

A novel statistical approach to evaluate the manufacturing quality of press coated tablets in terms of the centering of their core is presented. We also provide a formula to determine the necessary sample size. This approach is applied to real data.

最大熵试验法对切割器功能可靠性的评估

针对切割器设计裕度大且刺激能量服从正态分布的特点,提出采用最大熵试验法对切割器的功能可靠性进行评估。以某型切割器为实例,通过临界药量摸底试验、升降法试验及成败型试验对其功能可靠性进行了评估。结果表明:运用最大熵试验法,采用46个试验样本即可完成切割器在置信度γ=0.95下,可靠性指标不小于0.999 995的可靠性评估试验,为航天火工装置(尤其是切割器)的小样本量高可靠性评估提供了技术途径。

“z值评价-风险评估-技术核验”统计评价模型用于低样本量能力验证——以水质监测为例

为解决低样本量下的能力验证z比分数评价结果可能偏离参加者真实能力水平的问题,建立了“z值评价-风险评估-技术核验”统计评价模型,以“一带一路”共建国家“水中铁和氟化物的检测”国际能力验证项目为例进行了验证。结果显示:样本量为14家(低样本量)、指定值与样本真值相对误差的绝对值大于4%时,铁检测项目获得“满意”评价结果的14家参加者中,5家存在数据“不准确”中/高风险;氟化物检测项目获得“满意”评价结果的11家参加者中,7家存在数据“不准确”中/高风险。技术核验反映出的突出问题是参加者未按照检测方法的要求实施质量控制措施,标准曲线绘制、试剂配制、关键仪器参数设置记录缺失,原始记录可追溯性较差。由此证实了数据风险点的存在,同时也印证了该统计评价模型的可靠性和必要性。

基于近红外光谱技术苹果尺寸差异对糖度模型适用性的影响

为消除水果自身尺寸差异对其糖度预测模型的不利影响,进一步提高水果分选模型精度,应用近红外光谱在线检测装置采集不同果径苹果的近红外光谱,对光谱进行多种预处理后,分别建立苹果可溶性固形物的偏最小二乘法模型,再用苹果果径75~85mm组中的建模集预测苹果果径分别为65~75、85~95mm组中的预测集样品,最后用果径组65~75、75~85、85~95 mm中的建模集和预测集,分别作为混合苹果尺寸糖度预测模型的建模集和预测集,并利用特征光谱选择算法对模型进行简化,建立苹果糖度通用预测模型。结果显示:与建模集和预测集果径不同时所建立的苹果糖度预测模型最优组相比,其相关系数Rp由0.805提高至0.943,预测集均方根误差值RMSEP由0.778减小至0.480,RPD由0.96增加至3.05,再对建立的通用模型进行简化,可以降低苹果尺寸对苹果糖度模型的影响,提高模型预测性能。

液压支架立柱防冲吸能构件优化仿真及压溃实验研究

液压支架作为煤炭开采主要支护设备,经常受到冲击地压影响,防冲吸能构件起到保护液压支架作用,为获得更大的初始支反力峰值与吸能量、更小的支反力分散度,对吸能构件参数细化并通过ABAQUS有限元软件进行吸能构件的建模与压溃冲击仿真,获取吸能构件的吸能性能及屈曲变形形态,验证最优尺寸的吸能性能;对比吸能构件平均支反力的预测数据与有限元仿真数据,误差在15%以内,最优尺寸构件的平均支反力模型预测误差为−3.40%,验证吸能构件预测模型所预测数据较为准确;搭建吸能构件压溃实验台,选择5种加载速度,以准静态压溃方式对定制加工的吸能构件进行轴向加载压溃实验,实验结果表明:不同加载速度轴向压溃实验,支反力波动基本一致,最大初始支反力峰值为2253.52 kN,最大支反力标准差为206.23 kN,最小初始支反力峰值为2096.26 kN,最小支反力标准差为189.83 kN,初始支反力峰值的平均值为2149.32 kN,支反力标准差平均值为196.77 kN;不同压溃速度下的轴向压溃实验数据与吸能构件有限元仿真数据对比,初始支反力峰值、支反力标准差的相对误差分别为5.6%、11.07%;对最优尺寸吸能构件通过预测模型法、有限元仿真法、压溃实验法三种方法进行吸能性能分析,预测模型法的平均支反力为1879.7 kN,有限元仿真法的平均支反力为1945.9 kN,压溃实验法平均支反力为1919.8 kN,预测模型误差3.41%,压溃实验误差−1.3%,通过3种方法的数据验证结果,证明了吸能构件分析方法的可靠性和可行性。

Detecting Climate Change Trend, Size, and Change Point Date on Annual Maximum Time Series Rainfall Data for Warri, Nigeria

The study focused on the detection of indicators of climate change in 24-hourly annual maximum series (AMS) rainfall data collected for 36 years (1982-2017) for Warri Township, using different statistical methods yielded a statistically insignificant positive mild trend. The IMD and MCIMD downscaled model’s time series data respectively produced MK statistics varying from 1.403 to 1.4729, and 1.403 to 1.463 which were less than the critical Z-value of 1.96. Also, the slope magnitude obtained showed a mild increasing trend in variation from 0.0189 to 0.3713, and 0.0175 to 0.5426, with the rate of change in rainfall intensity at 24 hours duration as 0.4536 and 0.42 mm/hr.year (4.536 and 4.2 mm/decade) for the IMD and the MCIMD time series data, respectively. The trend change point date occurred in the year 2000 from the distribution-free CUSUM test with the trend maintaining a significant and steady increase from 2010 to 2015. Thus, this study established the existence of a trend, which is an indication of a changing climate, and satisfied the condition for rainfall Non-stationary intensity-duration-frequency (NS-IDF) modeling required for infrastructural design for combating flooding events.

小比尺条形基础承载力模型试验的尺寸效应研究

开展小比尺模型试验是土力学承载力研究中的重要方法,但小比尺模型的尺寸效应会影响试验的定量结果,导致小比尺试验一般仅能用于定性研究。在饱和砂土地基中开展了20组条形基础承载力的小比尺模型试验,通过改变基础尺寸、埋深以及砂土的密实度研究承载力的变化,进而引入离散元分析方法,采用抗转动模型模拟砂土颗粒的力学行为,对条形基础承载力试验进行模拟,从微观角度揭示小比尺模型试验尺寸效应的来源和对宏观承载力的影响规律。研究结果表明,饱和砂土地基密实度与基础埋深越大,小比尺实试验的尺寸效应越明显,尺寸效应的产生是应力水平变化、破坏模式改变以及渐进破坏程度综合作用的结果。

装配整体式梁柱节点的抗震性能对比研究

目的 研究预制柱纵筋间距放大后装配整体式T型节点和十字型节点的抗震性能,为工程设计提供依据。方法 对5个足尺梁柱节点试件进行低周往复荷载试验,通过对比各试件的滞回曲线、骨架曲线和位移延性等,研究了节点类型、柱纵筋间距和轴压比对梁柱节点抗震性能的影响。结果 装配式节点均发生梁端弯曲破坏,预制柱和节点核心区未见明显破坏,破坏主要是预制梁端底部纵筋屈服和梁端底部混凝土压碎脱落;楼板加强了叠合梁的抗负弯矩能力,叠合梁上部现浇混凝土和预制混凝土交界面出现明显的水平剪切裂缝;柱纵筋间距放大后,与对比试件相比,T型节点的承载力提高了9.2%,十字型节点的承载力提高了1.3%。结论 柱纵筋间距放大试件的延性和耗能能力与对比试件相差不大,柱纵筋间距放大对梁柱节点的抗震性能影响不大;十字型节点和T型节点位移延性系数相差不大。

高校大科学设施推动高端装备制造业创新研究——以环境与载荷耦合全尺寸试验为例

大科学设施是推动前沿基础科学发展和技术创新的重要条件支撑,越来越多的高校承担了大科学设施的建设运行任务。重大工程材料服役安全研究评价设施通过研制开发能够实现真实服役工况的、复杂环境与载荷耦合的全尺寸试验装置,积极面向高端装备制造开展复杂工况下服役性能试验,对相关学科融合发展,以及国产高端装备制造的材料选型、新材料应用、设计优化和可靠性评价等方面发挥了不可替代的推动作用,在核心技术研发与产品验证等环节中加速国产化进程,是直接面向国民经济主战场的大科学设施。该文在总结环境与载荷耦合全尺寸试验技术创新的基础上,分析了大科学设施服务高端装备制造产业的实际案例。

不同尺寸HMX基压装装药的烤燃特性

为了研究装药尺寸对压装装药烤燃特性的影响,针对HMX基压装装药,建立了压装装药烤燃过程的计算模型,利用Fluent软件对不同装药尺寸的烤燃样弹进行了数值模拟,计算了不同升温速率下装药尺寸对压装装药点火位置、响应温度和响应时间的影响规律。结果表明:在同一升温速率下,HMX基压装炸药装药长径比为1.0时,装药中心响应温度均为最高;装药长径比大于1.0时,装药中心点火温度均随长径比的增加而降低;当长径比增大到一定程度时,装药中心的响应温度趋于恒值。装药的点火位置由升温速率和装药尺寸共同决定,且装药端面与曲面的传热量之比与长径比的平方成反比。当升温缓慢或长径比较小时,装药的点火位置位于装药中心;当升温速率较高且长径比较大时,装药的点火位置逐渐远离装药中心。

刚性弹侵彻缩比实验尺寸效应分析

侵彻缩比实验的弹体尺寸效应是影响实验结果应用的重要因素。为提高缩比实验结果换算至原型的准确性,通过刚性弹对岩石介质侵彻深度理论公式的分析,阐明了引起尺寸效应的主要因素,给出了侵彻深度公式中弹径系数等关键参数的实验确定方法,进一步给出了模型弹实验结果换算至原型弹的理论与方法。结果表明,对于率相关材料,应变率会导致尺寸效应;对于率无关材料,缩比本身也会导致尺寸效应,其本质是由于介质破坏发展存在尺寸效应。缩比越小,尺寸效应越明显。尺寸效应还与靶体材料本身性质以及原型弹口径有关。对于缩比为0.1的实验,安全起见可取弹径系数为1.3。控制尺寸效应的材料参数可通过2组不同缩比的侵彻实验得到。

硅橡胶压缩永久变形性能的研究进展

综述了硅橡胶压缩永久变形性能的研究进展,主要介绍了基胶、填料、助剂、试样尺寸及测试环境等对压缩永久变形测试结果的影响,并展望了低压缩永久变形硅橡胶的研究方向。

磨粒环境下超高分子量聚乙烯的摩擦学行为研究

井下装备的密封结构极易受到钻井液中颗粒的侵蚀而发生磨粒磨损最终导致密封失效,明确颗粒对密封件的损伤机理是提升密封性能延长密封寿命的关键.本研究中通过配置含二氧化硅颗粒的膨润土基液建立井下的磨粒环境,以常用于制作密封件的超高分子量聚乙烯(UHMWPE)材料作为研究对象,采用正交试验法研究颗粒浓度和尺寸对材料磨粒磨损行为的影响关系.正交试验分析结果表明:颗粒尺寸对UHMWPE摩擦学行为的影响程度显著高于颗粒浓度.在不同颗粒尺寸环境中对摩擦过程中的摩擦系数、材料磨损量和磨损形貌的变化行为展开分析时发现,摩擦副的摩擦系数和磨损量均表现出随着颗粒尺寸增加而逐渐增加的趋势,磨损状态逐渐恶化.此外,材料的表面磨损形态随颗粒尺寸的变化表现出“颗粒尺寸效应”.研究结果揭示了UHMWPE的磨粒磨损机理,为材料的工程应用和井下密封结构的设计提供了参考.

车门材料及结构轻量化研究

为了实现车门轻量化,文中综合了材料轻量化和结构轻量化两种方式。首先,建立车门有限元模型,根据企业标准选取车门上扭转刚度工况、下扭转刚度工况及车门侧向弯曲刚度工况进行了分析。其次,为车门主要构件选择轻金属材料,建立正交试验并进行分析,在同时考虑质量、成本和刚度的基础上,获得车门最佳材料组合。最后,对多材料车门模型进行尺寸优化,实现轻质多材料车门结构设计。新车门成本不高于原车门成本,刚度满足企业标准,同时车门自身总质量减小了44.6%。