A FAMILY OF MODAL METHODS FOR COMPUTING EIGENVECTOR DERIVATIVES WITH REPEATED ROOTS

A family of modal methods for computing eigenvector derivatives with repeated roots are directly derived from the constraint generalized inverse technique which is originally formulated by Wang and Hu. Extensions are made to Akgun's method to allow treatment of eigensensitivity with repeated roots for general nondefective systems, and Bernard and Bronowicki's modal expansion approach is expanded to a family of modal methods.

The Cumulative Method for Multiplication and Division

This paper provides a method of the process of computation called the cumulative method, it is based upon repeated cumulative process. The cumulative method is being adapted to the purposes of computation, particularly multiplication and division. The operations of multiplication and division are represented by algebraic formulas. An advantage of the method is that the cumulative process can be performed on decimal numbers. The present paper aims to establish a basic and useful formula valid for the two fundamental arithmetic operations of multiplication and division. The new cumulative method proved to be more flexible and made it possible to extend the multiplication and division based on repeated addition/subtraction to decimal numbers.

Improved modal truncation method for eigensensitivity analysis of asymmetric matrix with repeated eigenvalues

An improved modal truncation method with arbitrarily high order accuracy is developed for calculating the second- and third-order eigenvalue derivatives and the first- and second-order eigenvector derivatives of an asymmetric and non-defective matrix with repeated eigenvalues. If the different eigenvalues λ1, λ2,……, λs of the matrix satisfy ｜λ1｜ ≤... ≤｜λr｜ and ｜λs｜ 〈｜〈s＋1｜ （s ≤r-l）, then associated with any eigenvalue λi （i≤ s）, the errors of the eigenvalue and eigenvector derivatives obtained by the qth-order approximate method are proportional to ｜λi｜/λs＋1｜q＋l, where the approximate method only uses the eigenpairs corresponding to λ1, λ2,……,λs A numerical example shows the validity of the approximate method. The numerical example also shows that in order to get the approximate solutions with the same order accuracy, a higher order method should be used for higher order eigenvalue and eigenvector derivatives.

Relationship between repeated triaxial test and Hamburg wheel tracking test on asphalt mixtures

Both the repeated triaxial test （RTT） and the Hamburg wheel tracking test （HWTT） are adopted to evaluate the high temperature performance of the stone mastic asphalt （SMA） and the mastic asphalt （MA）. The correlation of the permanent deformations of the MA and the correlation of the deformation developments of the SMA between the two tests are analyzed, respectively. Results show that both the two tests can effectively identify the high temperature performance of mixtures, and the correlation between the final results of the two tests as well as that between the deformation developments of the two tests are excellent with R20.9. In order to further prove the correlation, viscoelastic parameters estimated from the RTT results is used to simulate the rutting development in the HWTT slabs by the finite element method （FEM）. Results indicate that the correlation between the two tests is significant with errors less than 10%. It is suitable to predict the rutting development with the viscoelastic parameters obtained from the RTT.

Maximum Likelihood Estimation for the Pooled Repeated Partly Interval-Censored Observations Logistic Regression Model

Often in longitudinal studies, some subjects complete their follow-up visits, but others miss their visits due to various reasons. For those who miss follow-up visits, some of them might learn that the event of interest has already happened when they come back. In this case, not only are their event times interval-censored, but also their time-dependent measurements are incomplete. This problem was motivated by a national longitudinal survey of youth data. Maximum likelihood estimation (MLE) method based on expectation-maximization (EM) algorithm is used for parameter estimation. Then missing information principle is applied to estimate the variance-covariance matrix of the MLEs. Simulation studies demonstrate that the proposed method works well in terms of bias, standard error, and power for samples of moderate size. The national longitudinal survey of youth 1997 (NLSY97) data is analyzed for illustration.

A SIMPLE ITERATIVE PROCEDURE FOR FINDING ALL ZEROS OF A POLYNOMIAL WITHOUT REPEATED EVALUATION

In this note a simple iterative method for simultaneously finding all zeros of a polynomial is established.The method does not require repeated evaluation of the polynomial or its deriva-tives,and is globally convergent for quadratic polynomials.

Effect of Tire Repeated Root Modal on Tire Modelling with Experimental Modal

The effect of tire repeated root modal（RRM）on tire modeling with an experimental modal is studied.Firstly,a radial tire with radial and tangential RRMs is tested and analyzed.By multi-point exciting of the radial tire,a multiple reference frequency domain method based on a least squares（LMS PolyMAX）algorithm is used to identify modal parameters.Then,modal stability diagram（MSD）,modal indication function（MIF）and modal assurance criteria（Auto-MAC）matrix are utilized to induce multiple inputs multiple outputs（MIMO）frequency response function（FRF）matrixes.The tests reveal that notable repeated roots exist in both radial and tangential response modes.Their modal frequencies and damping factors are approximately the same,the amplitudes of modal vectors are in the same order of magnitude,and the mode shapes are orthogonal.Based on the works mentioned,the method of trigonometric series modal shapes fitting is adopted,the effects of RRM model on tire modeling with a vertical experimental modal are discussed.The final results show that the effects of considering the RRM shapes are equivalent to the tire mode shapes depended on rotating the tire’s different exciting points during tire modeling,and since considering the RRM,the tire mode shapes can be unified and fixed during tire modeling.

Elastic Predictions of 3D Orthogonal Woven Composites Using Micro/meso-scale Repeated Unit Cell Models

This presentation predicts the elastic properties of three-dimensional(3D)orthogonal woven composite(3DOWC)by finite element analysis based on micro/meso repeated unit cell(RUC)models.First,the properties of fiber yarn are obtained by analysis on a micro-scale RUC model assuming fibers in a hexagonal distribution pattern in the polymer matrix.Then a full thickness meso-scale RUC model including weft yarns,warp yarns,Z-yarns and pure resin zones is established and full stiffness matrix of the 3DOWC including the in-plane and flexural constants are predicted.For thick 3DOWC with large number of weft,warp layers,an alternative analysis method is proposed in which an inner meso-RUC and a surface meso-RUC are established,respectively.Then the properties of 3DOWC are deduced based on laminate theory and properties of the inner and surface layers.The predicted results by the above two alternative methods are in good experimental agreement.

Analytical Solution for Plastic Responses of Metal Beams under Repeated Impacts Based on Membrane Factor Method

Marine structures are frequently subjected to repeated impact loadings,resulting in failure of the structures,even causing serious accidents.The analytical expressions of dimensionless permanent deflection and impact force of a metal beam based on maximal normal yield surface are derived by membrane factor method(MFM),then the results are compared with repeated impact tests.It can be found that the solutions based on MFM are between the upper and lower bounds,and very close to the results of the repeated impact tests,indicating the theoretical model proposed can predict the plastic responses of the metal beam accurately.What’s more,the influences of impact location and boundary condition on the dynamic responses of the beam subjected to repeated impacts are determined.Results show that,as the distance of impact location from the middle span of the beam increases,the permanent deflection decreases,while the impact force increases.Meanwhile,the influences of impact location enhance as the impact number increases.When the permanent deflection is smaller than the thickness,the effect of boundary condition on the plastic responses is significant.However,when the deflection is larger than the thickness,the beam will be like a string and only axial force works,resulting in little influence of boundary condition on the plastic responses of the beam.

重复注气压降法煤层渗透率模型与原位测试研究

煤层渗透率作为衡量瓦斯渗流与抽采难易程度的重要指标,对其进行准确测定具有重要意义。针对现有方法计算渗透率测试周期长、结果不稳定、模型不完善等问题,研究煤层渗透率的快速准确测定方法及相应的计算模型。基于煤层中气体径向不稳定流控制方程,结合不同压差下气体在煤层中的体积流量方程,建立可利用全区间压降数据测定煤层渗透率的注气压降计算模型。应用COMSOL数值模拟软件的达西渗流模块对模型进行求解,针对现场工程设计中可对压降曲线产生影响的测压气室长度进行单变量处理,根据模拟结果分析钻孔的测压气室长度可设计为2.0 m。根据数值模拟结果进行现场布置,搭建井下重复注气压降试验系统,结合煤层瓦斯赋存条件和巷道条件施工两组穿层钻孔,对2个测点分别注入两次高于煤层瓦斯压力的补偿气体进行渗透率原位测试,测试周期分别约为6 d和17 d,第2轮测试的注气压力高于第1轮。结合理论推导验证了注气压降过程中煤层瓦斯的雷诺数均处于线性达西渗流段,瓦斯在煤层中的渗流符合达西定律,满足计算模型的假设。与传统煤层渗透率计算方法进行了比较,结果表明:本方法和径向流量法的计算结果基本一致,可以满足实际工程需要。重复注气压降法的测试结果稳定可靠,具备快速测定的优点。

基于QCM液体密度响应模型测量油品含水率研究

油田开发中一直存在高含水率和低含水率测量不准确的问题,新型可再生的生物柴油,同样需要控制含水率以保证热值和稳定性。文中提出一种基于石英晶体微天平(QCM)液体密度响应模型的油品含水率测量方法,通过5组标准甘油溶液进行模型验证,结果表明,实验值与理论值的误差小于5%,并且在低含水量和高含水量2种情况下,误差幅度小于1%。重复性实验验证了模型的有效性。现场测量实验结果证实了模型的适用性。

圆钢管型钢再生混凝土组合柱水平承载力计算方法研究

通过对11个圆钢管型钢再生混凝土组合柱进行低周反复荷载试验,分析再生粗骨料取代率、型钢截面形式、轴压比、型钢配钢率及圆钢管壁厚参数对组合柱水平承载力的影响规律;观察了组合柱的破坏形态及特征,研究了圆钢管、型钢翼缘及腹板应变的发展规律,分析了组合柱的地震破坏特征。研究表明,在水平地震作用下组合柱发生典型的压弯塑性铰破坏。在此基础上,结合现有规范提出了基于叠加原理的圆钢管型钢再生混凝土组合柱水平承载力计算方法。计算结果表明,其水平承载力计算值与试验值吻合度较好,能较为准确地预测组合柱的水平承载力。

基于IFM-KS模型的多层煤开采上覆岩层移动模型

双系煤层条件下的重复开采使得单层开采后已经趋于稳定的岩层再次“活化”,加剧了变形破坏的影响。因此,对煤层重复开采后引起的覆岩移动规律进行研究具有十分重要的意义。基于“力学模型+几何方法”融合的IFM-KS模型,提出了适用于多层开采条件下的岩层移动计算模型,揭示了煤层重复开采情况下岩层二次扰动后的移动变形规律。通过理论计算及UDEC数值计算方法验证了双系煤层开采情况岩层移动新模型的预测准确性。结果表明,理论计算的岩层位移结果与采用数值模拟得到的结果整体呈相同的沉降趋势,平均误差率约为15%。结合岩层移动模型计算结果,层间及上覆岩层空隙率的相关计算,与单层煤开采相比,双系煤层开采后造成的采空区空隙率变化剧烈,岩层破坏更加严重,上下采空区可通过裂隙沟通形成漏风通道。该计算模型能为类似采动件下岩层变形预计、采空区空隙率分布等提供一定的参考。

微量法检测石油产品闭口闪点的研究

闭口闪点是石油产品重要的安全性指标,可表示石油产品的蒸发性和判定是否混入轻馏分。比较详细地介绍了微量法检测石油产品闭口闪点的方法,并与传统的宾斯基-马丁闭口杯法进行了准确性、重复性、再现性的比较,结果表明:微量法的准确性、重复性、再现性更.好,而且微量法样品用量少、检测时间短,避免了宾斯基-马丁闭口杯法测量时的人为操作误差,提高了检测时的安全性,可以满足质检室的日常分析要求。

人工流产术后延伸护理对重复人工流产发生率的影响观察

目的 探讨人工流产术后延伸护理对重复人工流产发生率的影响。方法 选择2022年1月—2022年12月本院收治的200例人工流产术后患者为研究对象,采取随机数字表法分为对照组(n=100)和观察组(n=100)。术后,对照组予以常规护理,观察组给予延伸护理。比较两组患者的避孕知识掌握程度、避孕方式、重复人工流产、心理状态。结果 观察组避孕措施、保护女性生育力、人工流产知识掌握情况评分较对照组的评分更高(P<0.05)。观察组的避孕方式较对照组的更优(P<0.05)。观察组护理后3个月、6个月、12个月重复人工流产率较对照组更低(P<0.05);观察组的HAMA、HAMD评分降低幅度高于对照组(P<0.05)。结论 人工流产术后延伸护理可减少重复人工流产的发生,帮助患者更好地掌握避孕知识,值得推广应用。

转基因检测标准的方法验证工作研究

转基因检测标准为转基因食品的有效标识、科学监管、推广应用提供重要的技术支撑。方法验证工作是指实验室通过一定的科学方法,验证上述转基因检测标准在实验室现有的人员、设备、场地环境等条件下是否可得到令人满意的结果。方法验证工作直接影响到标准的实施和应用,但现有的转基因检测标准的验证方法,大部分只提供了方法验证的定义,缺乏具体的操作方案。从验证工作的仪器设备、试剂及标准物质、技术验证参数、环境要求等关键要素进行讨论,提出相应的验证工作建议,旨在为农业转基因实验室开展方法验证提供详细的技术指导,并为我国转基因标准体系的应用推广提供参考。

改良式子宫下段切口外下缘娩头法在重复剖宫产术中的临床应用

目的:探究改良式子宫下段切口外下缘娩头法在重复剖宫产术中的临床应用效果。方法:选取2023年1—7月九江市妇幼保健院妇产科收治的重复剖宫产孕妇80例作为研究对象,按照随机数字表法分为研究组(40例)和对照组(40例)。对照组采用常规剖宫产娩头法,研究组采用改良式子宫下段切口外下缘娩头法。比较两组临床效果。结果:研究组剖宫产手术时间、切开子宫至胎头娩出时间及产后住院时间均短于对照组,产妇不良事件发生率低于对照组(P<0.05)。研究组新生儿不良事件发生率与对照组相比,差异无统计学意义(P>0.05)。研究组产后出血量少于对照组,新生儿Apgar评分高于对照组(P<0.05)。结论:对于重复剖宫产临床分娩,改良式子宫下段切口外下缘娩头法能够有效降低产后不良结局的发生风险性,同时可以改善产妇围手术期指标,促进术后恢复与母婴健康。

木结构榫卯节点抗震性能及加固试验分析

不同类型榫卯节点的加固方式应根据其具体破坏模式来选择,为探究不同加固方式与榫卯节点类型的适宜性,采用多阶屈曲阻尼器、伸臂式金属阻尼器、钢条分别对透榫节点、燕尾榫节点、半榫节点进行加固,通过开展加固与未加固榫卯节点低周反复荷载试验,并对比分析了榫卯节点的破坏特征、水平承载力、刚度和耗能能力.试验结果表明:各加固方式均能有效抑制节点拔榫、增加节点耗能、提升节点最大承载力和刚度等抗震性能指标,但各加固方式效率及对节点性能影响差异明显.其中,多阶屈曲阻尼器、伸臂式金属阻尼器和钢条加固节点的最大承载能力较未加固节点分别提高了46.7%、496%、203%;加固节点的初始刚度分别提高了14.5%、426%、221%;多阶屈曲阻尼器可显著增强透榫节点的耗能能力且对其承载力和初始刚度影响有限;伸臂式金属阻尼器可大幅提升燕尾榫节点的初始刚度和最大承载力,有效避免出现榫颈和榫角断裂;钢条加固方式在有效抑制半榫节点的拔榫的同时能有效提升节点刚度和承载力.可见,不同类型榫卯节点应根据性能需求选用适宜的加固方式并对加固参数进行合理化设计.

利用水平分割法计算给定串中的所有Maximal(NE/SNE) Repeats

提出一种利用给定符号串x[1…n]的后缀数组和最长公共前缀数组求x所有最大重复的新方法水平分割法.通过对x的最大不可扩展重复和最大超级不可扩展重复所有可能出现的位置以及判定条件的提炼,分别给出仅由x的后缀数组和最长公共前缀数组求x的所有最大重复、最大不可扩展重复和最大超级不可扩展重复的算法.该算法克服了除后缀数组和最长公共前缀数组外,还需利用其他辅助数组的缺陷,降低了空间开销,且时间复杂度没有增加,并可以在对最长公共前缀数组仅进行一次扫描的情况下求出给定串的所有最大重复、最大不可扩展重复和最大超级不可扩展重复.

基于位移逆有理Krylov子空间算法的频率域可控源电磁快速正演

本文开发了一种双重复极点位移逆(SAI)有理Krylov子空间算法,实现了频率域可控源电磁法(CSEM)多频电磁场值的快速计算.在有理Krylov子空间算法中,极点选择是保障CSEM正演精度的关键,单重复极点有理Krylov子空间算法在频率域可控源电磁法应用最为广泛,但其缺点在于正演计算频段范围有限,增加极点个数能够获取更宽频段响应.为此,立足于有理Krylov子空间基本理论,推导了多重复极点位移逆算法Rayleigh商一阶秩修改公式,并利用该模型降阶算法开展了可控源电磁法正演模拟.另外,本文利用粒子群算法求解多极点收敛率函数,可以快速获取最优多极点,从而确保正演模拟精度.相比于单重复极点,多重复极点位移逆算法会增加极点计算时间,但能在更宽的频率范围内准确计算电磁场值.根据频率范围选定合适的极点后,该方法仅需要求解与极点数相同的多个线性方程组,通过场源项和系数矩阵求得有理Krylov子空间,再将正演算子投影到有理Krylov子空间中,显著降低正演算子的自由度,提高多频正演的计算效率.设计了均匀半空间和块状异常模型,并开展了算法测试,计算结果表明:在保证精度的情况下,相比于常规矢量有限元算法,单重复极点、双重复极点位移逆模型降阶算法的加速比超过10倍以上;双重复极点位移逆模型降阶算法总体计算精度要优于相应的单重复极点算法,且具有更宽的计算频带.