Model tests on uplift capacity of double-belled pile influenced by distance between bells

To optimize the distance between the bells in pile design,this paper reports a series of small scale tests on the uplift capacity of double belled piles embedded in dry dense sand considering different bell space ratios.Finite element modelling is also performed to evaluate the range of soil failure around the piles during pile uplift displacement.Test results show that when bell space ratio is 6 or 8,the uplift capacity reaches the peak value.The upper bell bears more load than the lower one for the piles with bell space ratio less than 6,while the lower bell bears more load than the upper one for the piles with bell space ratio larger than 8.

Novel technique for cost reduction in mutation testing

Aimed at the problem of expensive costs in mutation testing which has hampered its wide use,a technique of introducing a test case selection into the process of mutation testing is proposed.For each mutant,a fixed number of test cases are selected to constrain the maximum allowable executions so as to reduce useless work.Test case selection largely depends on the degree of mutation.The mutation distance is an index describing the semantic difference between the original program and the mutated program.It represents the percentage of effective test cases in a test set,so it can be used to guide the selection of test cases.The bigger the mutation distance is,the easier it is that the mutant will be killed,so the corresponding number of effective test cases for this mutant is greater.Experimental results suggest that the technique can remarkably reduce execution costs without a significant loss of test effectiveness.

Energy distance的配对样本分布差异检验法

讨论了配对样本分布差异的检验问题,基于Energy distance的概念构造出了一种新的检验配对样本分布差异的检验统计量,该统计量具有U统计量形式,基于U统计量理论讨论了该检验统计量的大样本性质,导出了该检验统计量在零假设即配对变量同分布的情况下的渐近分布,最后采用bootstrap重抽样技术进行数值模拟说明该方法的有效性.本文提出的检验方法适用于任意有限维的具有有限一阶矩的随机向量.

Single Radar Measurement Method for Antiaircraft Projectile Miss Distance

To measure miss distance for antiaircraft projectile,a radial velocity identification and positioning method with a single radar is proposed. By analyzing the spatial resolution of multi-frequency ranging radar,the discrimination and testing model of this radar for multi-targets（ projectile and target） is established to analyze the systematic error of antiaircraft miss distance. Then through the aerial target flight test and contrast test with optical test equipment,the validity of the measurement method is verified. This newmethod has the potential to be used in the measurement of antiaircraft projectile miss distance.

Random-Like Testing of Very Large Scale Integration Circuit

A new approach to improve the test efficiency of random testing is presented in this paper. In conventional random testing, each test pattern is selected randomly regardless of the tests previously generated. This paper introduces the concept of random like testing. The method provided appears to have the same concepts as used in random testing,but actually takes an opposite way to it in order to improve the efficiency of random testing.In a random like testing sequence, the total distance among all test patterns is chosen to be maximal so that the fault sets detected by one test pattern are as different as possible from that detected by the tests previously applied. The procedure to construct a random like testing sequence (RLTS) is described in detail. Theorems to justify the effectiveness and usefulness of the procedure presented are developed. Experimental results on benchmark circuits as well as on other circuit are also given to evaluate the performance of the new approach.

Likelihood and Quadratic Distance Methods for the Generalized Asymmetric Laplace Distribution for Financial Data

Maximum likelihood (ML) estimation for the generalized asymmetric Laplace (GAL) distribution also known as Variance gamma using simplex direct search algorithms is investigated. In this paper, we use numerical direct search techniques for maximizing the log-likelihood to obtain ML estimators instead of using the traditional EM algorithm. The density function of the GAL is only continuous but not differentiable with respect to the parameters and the appearance of the Bessel function in the density make it difficult to obtain the asymptotic covariance matrix for the entire GAL family. Using M-estimation theory, the properties of the ML estimators are investigated in this paper. The ML estimators are shown to be consistent for the GAL family and their asymptotic normality can only be guaranteed for the asymmetric Laplace (AL) family. The asymptotic covariance matrix is obtained for the AL family and it completes the results obtained previously in the literature. For the general GAL model, alternative methods of inferences based on quadratic distances (QD) are proposed. The QD methods appear to be overall more efficient than likelihood methods infinite samples using sample sizes n ≤5000 and the range of parameters often encountered for financial data. The proposed methods only require that the moment generating function of the parametric model exists and has a closed form expression and can be used for other models.

A method for computing unsupported roof distance in roadway advancement and its in-situ application

A reasonable unsupported roof distance(URD) when advancing underground coal mine roadways can contribute greatly to safe and rapid roadway development.A mechanical model of the roof,using the relationship between the roof stress distribution and URD,obtained by the difference method,and roof stability according to the in-situ roof stress and rock mass strength was developed.We subsequently designed a proper range of URD,developed a testing method of URD with the function of mining protection,evaluated roof stability through analyzing the test data and then determined a reasonable URD.Considering the factors of the geological conditions,the immediate roof stability and the efficiency of the labor arrangement system,the URD of the advancing roadway of 9802 working face in Zhangshuanglou coal mine was determined to be 6 m using the proposed method.The results show that,when a 2 m length of roadway was reinforced by temporary support and high pre-stressed bolt support after the roadway advancement of 6 m per cycle,the speed and the security of the roadway development can be achieved and the advance rate can reach more than 400 m per month.

油气管道组合缺陷漏磁检测信号数值模拟研究

为解决管道组合缺陷之间漏磁检测信号互相干扰,难以识别的问题,采用有限元方法建立仿真模型,研究管道内外、不同形状缺陷以及内外组合缺陷邻近情况下的漏磁场检测信号规律。研究结果表明:管道缺陷的漏磁检测信号在其轴向和径向分量上均存在显著差异;组合缺陷的检测信号存在相互干扰且具有一定的叠加性;当缺陷深度约为管壁厚的10%、25%、40%时,轴向信号干扰距离分别约为缺陷长度的1倍、2倍、3倍,径向信号干扰距离均约为长度的4倍,组合缺陷径向信号的互相干扰程度大于轴向信号,缺陷深度对轴向信号的影响大于径向信号。研究结果可为油气管道组合缺陷的识别提供理论依据。

金属预埋吊件剪切力学性能试验研究

为确定可行的金属预埋吊件(简称预埋吊件)剪切试验方法以及为安全系数提供可靠依据,对100、150mm两种不同边距的预埋吊件混凝土试件进行抗剪试验研究。研究预埋吊件的受剪力学性能,测量楔形体破坏角度,分析荷载-位移曲线,探究混凝土楔形体破坏的抗剪极限承载力与预埋吊件的物理特性之间的关系。结果表明:试验中所有预埋吊件均发生混凝土楔形体破坏,其角度与理想状态下的破坏角度接近;预埋吊件的直径、预埋到混凝土中的深度、预埋吊件轴心到剪力垂直边缘的距离与抗剪极限承载力之间均呈正相关。

基于动态阈值和差异性检验的自训练算法

针对自训练算法在迭代训练分类器的过程中存在难以有效选取高置信度样本以及误标记样本错误累积的问题,本文提出了基于动态阈值和差异性检验的自训练算法。引入样本的局部离群因子,据此剔除有标签样本中的离群点以及分类标注无标签样本,依据标注分批次处理无标签样本,以使模型更易选取到高置信度的无标签样本;根据新增伪标签样本的数量和对比隶属度的变化,设计一种动态隶属度阈值函数,提升高置信度样本的质量;定义密集距离度量样本间的差异性,分别计算伪标签样本与同类和不同类样本之间的密集距离之和,从而找出不确定度高的伪标签样本,并将此类样本并入下轮训练的无标签样本集中,缓解误标记样本错误累积的问题。实验结果表明,该算法在12个UCI基准数据集上均取得理想效果。

模拟短路试验核对变电所保护极性的方法探讨

近几年,因保护回路接线错误造成保护拒动、误动的事件频发。通过实际案例,从理论、实际多角度分析故障发生的原因,提出一种新型短路试验方法,并应用于实际验证其可靠性,以期为变配电设备运维、新线开通提供参考。

17~45岁肥胖门诊患者的6分钟步行试验距离参考方程研究

背景 目前6分钟步行试验(6MWT)已经被广泛用于评估肥胖人群的运动能力,并为制订干预措施提供了参考依据。国外已有研究提出了其他人群的6MWT距离参考方程,但中国17~45岁且BMI≥30 kg/m^(2)肥胖受试者的6MWT距离参考方程研究较少。目的 为17~45岁门诊肥胖受试者制订6MWT距离参考方程,并评估其影响因素。方法 根据美国胸科学会指南,前瞻性选取2022年6月—2023年9月于江苏省苏北人民医院内分泌科肥胖门诊部就诊的143名年龄17~45岁且BMI≥30 kg/m^(2)的成年人(71名男性和72名女性),进行人体测量和6MWT。采用逐步多元回归模型建立6MWT距离参考方程,将新建立的6MWT距离参考方程与现有的预测方程进行比较。结果 143名受试者的平均6MWT距离为(506.1±49.8)m,其中男性平均6MWT距离为(515.7±50.1)m,大于女性的平均6MWT距离(496.6±47.9)m(P<0.05)。在年龄段17~23岁、24~30岁、31~37岁以及38~45岁中,男性与女性6MWT距离比较,差异均有统计学意义(P<0.05)。男性受试者的体质量、BMI、最大心率(HR_(max))、心率差(ΔHR)、腰围、舒张压差(ΔDBP)、Borg量表评分差(ΔBorg)与6MWT距离相关(P<0.05),女性受试者的体质量、BMI、腰围与6MWT距离相关(P<0.05)。以步进的方法将潜在的影响因素纳入多元线性回归方程中,最终建立6MWT距离参考公式:男性y=494.463+1.414×ΔHR-3.903×BMI+0.874×HR_(max),R^(2)=0.429,女性y=670.448+0.299×ΔHR-4.342×BMI-0.195×HR_(max),R^(2)=0.312。结论 17~45岁门诊肥胖受试者中,男性的平均6MWT距离长于女性,且在不同年龄段均有显著差异。男性的体质量、BMI、HR_(max)、ΔHR、腰围、ΔDBP、ΔBorg与6MWT距离相关,女性的体质量、BMI、腰围、ΔSBP与6MWT距离相关。通过多元线性回归分析,为男性和女性分别建立了预测6MWT距离的参考方程,这些公式可能为评估个体的体能水平提供有价值的参考。

冲击片雷管换能界面轴向距离能量耗散失效分析

为提高冲击片雷管作用的一致性和可靠性,针对因材料表面小型突起导致接触面不平整的装配问题,从换能界面能量耗散的角度对装配结构中两种轴向距离所产生的影响进行了探究。通过不同电压下的发火试验及感度试验,验证和分析两种轴向距离对冲击片雷管作用过程的影响。结果表明:加速膛-桥箔轴向距离会导致电爆能量的径向散失,进而影响了飞片冲击药柱端面能量的大小并引起聚酰亚胺薄膜的撕裂拉伸,随着轴向距离的持续增加,爆炸桥箔逐渐失效;加速膛-药柱轴向距离会影响飞片飞行的平稳程度以及撞击药柱速度,随着轴向距离增加,飞片飞行距离增长,到达药柱端面的速度降低且不一致,导致起爆药柱的稳定性降低,轴向距离应控制在0.3mm以内。

西北电网330 kV尖樊线人工短路试验中接地距离保护适应性分析

以风电为代表的新能源场站的故障特征对传统距离保护的附加阻抗产生了新的影响,导致保护性能降低。而现有距离保护适应性研究缺乏对单相接地故障场景的分析。为此,结合西北电网于尖樊线进行的2次人工短路试验数据,基于多种控制策略下的风电场故障特征,分析单相接地故障下接地距离保护附加阻抗系数,进而判断保护适应性。研究发现网侧保护附加阻抗系数较小,两侧电源故障电流对保护影响较小;而风电场侧保护附加阻抗系数较大,两侧电源故障电流对保护影响较大,导致保护拒动。

支流入汇对干流航道通航条件影响模拟研究

自然河流由于支流的汇入,在交汇区与干流相互混掺顶托,改变了原有的水流形态,形成复杂的水流结构,对内河船舶航运的操纵性和安全性均造成一定影响。采用数值模拟试验方法,基于分离式(MMG)水动力模型,系统地研究了不同交汇角、汇流比以及干支流河道宽度比情况下交汇区船舶通航条件,即船舶航行时的漂角和偏航距离因素,并以此为基础,基于Design-Export响应面分析软件,得出了无量纲化后的最大偏航距离与交汇角、汇流比以及干支流宽度比之间的响应函数。

基于空间视距的林区曲线道路行车舒适性研究

为提高林区曲线道路驾驶员行车安全性和舒适性,采用驾驶模拟试验办法,利用眼动和心率作为评价指标,从动态视角对林区曲线道路行车舒适性进行评价研究。基于空间视距理论建立5种不同空间视距的林区曲线道路场景,研究结果表明,驾驶员瞳孔直径变化率和心率增长率随着空间视距增大而不断减小,驾驶舒适性不断增大。考虑瞳孔直径变化率和心率增长率的最小空间视距值为101 m和89 m,得出瞳孔直径变化率和心率增长率的空间视距适宜值为128 m和132 m。

Distance-basedα-amylase biosensor fabricated with amylopectin-coated mesoporous membrane

Paper-based biosensors are widely employed in point-of-care testing(POCT)due to their convenience,portability,low cost,and ease of use.This study reports an integrated distance-based paper biosensor fabricated with a mesoporous membrane coated with stimuli-responsive polymer.The detection ofα-amylase(AMY)using amylopectin-coated mesoporous membrane is demonstrated as an example.After introducing the AMY solution,it is observed that the aqueous solution flows along the paper strip due to AMY-catalyzed hydrolysis of amylopectin.The flow distance is proportional to the concentration of AMY with a detection limit as low as 4 mU/mL.In addition,the detection of AMY is demonstrated in human serum.Furthermore,the inhibitory effect of acarbose on AMY is evaluated.This reagent-free and disposable biosensor allows single-step rapid detection of the analyte.This approach is very promising for the development of user-friendly,equipment-free,and cost-effective biosensors with remarkable sensitivity and excellent selectivity for disease diagnosis and hypoglycemic drug screening.

基于平板电脑的距离自适应视功能自测方案的研究

目的构建基于平板电脑的距离自适应视功能自测系统,并分析其精确性。方法基于配有摄像头的平板电脑,使用ArUco技术识别2 m范围内的二维码以进行实时测距,构建距离自适应的集视力(普通视标视力和不同对比度高通视标视力)、调节幅度和中心5°视野测定一体化的视觉功能检测系统。共纳入健康受试者22例(44眼)完成视功能检查,其中6名受试者在四种距离(1 m、1.25 m、1.6 m、2 m)分别完成视力测试,并在足矫和–3.00D欠矫模拟调节不足状态下分别完成调节幅度测试。比较程序读数距离和空间中二维码距平板屏幕实际距离;比较在不同距离的同种视标的视力测试结果一致性;分析足矫及欠矫状态下调节幅度的变化,并使用ICC法评估其可重复性;分析视野测试结果的对比敏感度阈值及有效性。结果实际距离与程序读数距离具有良好的一致性水平。相同对比度高通视标视力测试在不同距离的测试结果无显著差异(P>0.05),100%普通视标视力在0.9~1.1m距离范围内与其他距离结果存在显著差异(P<0.001)。测量3次调节幅度的ICC值为0.861(P<0.001);欠矫状态下的调节幅度较足矫状态更低,变化具有统计学差异(P<0.05)。双眼视野对比度阈值的上边缘值均值为16.92%,程序能正确识别视野缺损。结论本研究构建了一种基于平板电脑的距离自适应视功能自测系统,可在2 m内实时精准测距,根据距离自动调节初始视标的大小以精确呈现视标,进行视力、调节幅度及中心5°视野检测。该系统不受固定距离限制并且具有更高的检验效能,可应用于空间狭小且不能固定距离的空间站的视功能检测。

抛投防汛石沿坡面滑滚落距影响因素研究

为论证抛投时防汛石沿坡面滑滚的落距影响因素,基于黄河下游顺坝区沿岸坡抛投工况,建立理想情况下日常根石除险加固的抛投防汛石模型,推导考虑流速、水深、河堤坡度、边坡粗糙度的理论公式,通过水槽试验对理论分析结果进行验证比较,找出不同形状防汛石的抛投落距规律。结果表明:水流流速越大,抛投水深越深,河堤坡度越缓,边坡粗糙度越大,则防汛石的落距越大;不同形状的防汛石抛投落距不同,在其他因素相同的情况下,四棱台的落距最小,为最佳形状。利用钢筋混凝土外壳和沙石芯制作大体积新型复合材料防汛石,在黄河下游进行现场抛投试验,其落距与推算结果比较吻合。

基于静力触探试验及土工参数的黏性土空间变异性研究

自相关距离是进行岩土参数空间变异性分析的重要参数。基于浙江嘉兴某黏性土场地的246组静力触探试验(CPT)及18个钻孔取土室内土工试验,采用平均跨距法、递推空间法、曲线极限法计算了基于侧壁摩阻力f_(s)、锥尖阻力q_(c)和其他土工参数的自相关距离,分析了不同方法、不同参数计算垂直和水平自相关距离的优劣。研究表明:递推空间法的计算结果异常值少且变异系数较小,是研究区场地土体自相关距离的最优计算方法;基于f_(s)、q_(c)算得的自相关距离较为接近,垂直和水平自相关距离分别约为2 m和19 m,但不同土工参数计算得到的结果存在一定的差异。本研究获得了嘉兴黏性土自相关距离的典型值,为土体参数的空间变异性研究提供了基础,对该地区岩土工程的勘探点位布设、随机场的建立及后续可靠度分析具有重要的指导意义。