Residual lifetime prediction model of nonlinear accelerated degradation data with measurement error

For the product degradation process with random effect (RE), measurement error (ME) and nonlinearity in step-stress accelerated degradation test (SSADT), the nonlinear Wiener based degradation model with RE and ME is built. An analytical approximation to the probability density function (PDF) of the product's lifetime is derived in a closed form. The process and data of SSADT are analyzed to obtain the relation model of the observed data under each accelerated stress. The likelihood function for the population-based observed data is constructed. The population-based model parameters and its random coefficient prior values are estimated. According to the newly observed data of the target product in SSADT, an analytical approximation to the PDF of its residual lifetime (RL) is derived in accordance with its individual degradation characteristics. The parameter updating method based on Bayesian inference is applied to obtain the posterior value of random coefficient of the RL model. A numerical example by simulation is analyzed to verify the accuracy and advantage of the proposed model.

MODIFIED LAYER REMOVAL METHOD FOR MEASUREMENT OF RESIDUAL STRESS DISTRIBUTION IN THICK PRE-STRETCHED ALUMINUM PLATE

The integrated structure parts are widely used in aircraft. The distortion caused by residual stresses in thick pre-stretched aluminum plates during machining integrated parts is a common and serious problem. To predict and control the machining distortion, the residual stress distribution in the thick plate must be measured firstly. The modified removal method for measuring residual stress in thick pre-stretched aluminum plates is proposed and the stress-strain relation matrix is deduced by elasticity theory. The residual stress distribution in specimen of 7050T7451 plate is measured by using the method, and measurement results are analyzed and compared with data obtained by other methods. The method is effective to measure the residual stress.

Measurement and Analysis on Hardness and Residual Stress of Heavy Forging after Heat Treatment

The hardness and residual stress in the forging for cold roller during low temperature tempering,and the relationship of residual stress and cooling temperature of high temperature tempering for heavy forgings were studied.The stress relaxation constant at low temperature tempering and the elasto-plastisity inversion temperature at high temperature tempering were found.The results are of great importance to determine rational tempering cooling process of heavy forgings.

MLSI-RT: memorize LOS range measurements identified residual test location algorithm and performance analysis

The dominant error source of mobile terminal location in wireless sensor networks （WSNs） is the non-line-of-sight （NLOS） propagation error. Among the algorithms proposed to mitigate the influence of NLOS propagation error, residual test （RT） is an efficient one, however with high computational complexity （CC）. An improved algorithm that memorizes the light of sight （LOS） range measurements （RMs） identified memorize LOS range measurements identified residual test （MLSI-RT） is presented in this paper to address this problem. The MLSI-RT is based on the assumption that when all RMs are from LOS propagations, the normalized residual follows the central Chi-Square distribution while for NLOS cases it is non-central. This study can reduce the CC by more than 90%.

Situations and Countermeasures on Veterinary drug residues and Detection to Animal Material Food of Entry-Exit Trade

With the people's lives improving,the demands of livestock products on the import and export aspects were growing. Veterinary drug residues as the important factor which might influence animal products safety has become a major concern. In this paper,the status quo and inspection of the veterinary drug residue and the corresponding control measures were put forward.

Electromotive force measurements in liquid Ag-In-Pd lead-free alloys

Emf technique was employed to determine indium activities in the liquid Ag-In-Pd alloys using galvanic cells with yttria-stabilised-zirconia as solid electrolyte according to the scheme： kanthal/rhenium, Ag-In-Pd, In2O3 ｜ YSZ ｜ Ni, NiO, Pt. Composition and temperature measurement ranges were limited, because of very steep liquidus surface; 35 compositions for Xpd up to 0.3 were investigated and at temperatures from near-liquidus up to 1700 K. High temperature experiments required special moly furnace to be constructed with unique automatic gas supply system for fumace winding protective atmosphere. Emf readings were taken and recorded by automatic data acquisition system. Linear dependence of emf on temperature was observed for all compositions investigated, and results were approximated by straight line equa- tions. Then In activities were calculated using well-known relations and taking into account correction for thermoelectric power between kanthal and platinum. Results are to be used along with other existing data to perform assessment of the ternary system under accord.

Optical Measurement System for Motion Characterization of Surface Mount Technology

Advanced testing methods for the dynamics of mechanical microdevices are necessary to develop reliable, marketable microelectromechanical systems. A system for measuring the nanometer motions of microscopic structures has been demonstrated. Stop-action images of a target have been obtained with computer microvision, microscopic interferometry, and stroboscopic illuminator. It can be developed for measuring the in-plane-rigid-body motions, surface shapes, out-of-plane motions and deformations of microstructures. A new algorithm of sub-pixel step length correlation template matching is proposed to extract the in-plane displacement from vision images. Hariharan five-step phase-shift interferometry algorithm and unwrapping algorithms are adopted to measure the out-of-plane motions. It is demonstrated that the system can measure the motions of solder wetting in surface mount technology(SMT).

U-shaped Vision Transformer and Its Application in Gear Pitting Measurement

Although convolutional neural networks have become the mainstream segmentation model,the locality of convolution makes them cannot well learn global and long-range semantic information.To further improve the performance of segmentation models,we propose U-shaped vision Transformer(UsViT),a model based on Transformer and convolution.Specifically,residual Transformer blocks are designed in the encoder of UsViT,which take advantages of residual network and Transformer backbone at the same time.What is more,transpositions in each Transformer layer achieve the information interaction between spatial locations and feature channels,enhancing the capability of feature learning.In the decoder,for enhancing receptive field,different dilation rates are introduced to each convolutional layer.In addition,residual connections are applied to make the information propagation smoother when training the model.We first verify the superiority of UsViT on automatic portrait matting public dataset,which achieves 90.43%accuracy(Acc),95.56%Dice similarity coefficient,and 94.66%Intersection over Union with relatively fewer parameters.Finally,UsViT is applied to gear pitting measurement in gear contact fatigue test,and the comparative results indicate that UsViT can improve the Acc of pitting detection.

Usage of Pesticides and Control Measures in Qujing City

[Objective] The aim was to investigate pesticide use in Qujing city and explore the control measures.[Method] Surveys were made on pesticide use by farmers in five vegetable bases in Qujing city by questionnaires to study pesticide use and existing problems by farmers.[Result] Some problems existed in pesticide use in Qujing,such as non-standard pesticide source,lower-recognition of pesticide and impacts of pesticide residues on environment,and without professional guidance.[Conclusion] The existing problems can be resolved by enhancing technical trainings of technicians or pesticide managers,strengthening pesticide promotion,and reinforcing examination of pesticide residues.

A review of welding residual stress test methods

Due to local uneven heating during the welding process,the residual stress of the structure after welding affects the reliability of it.In order to ensure the reliability,it is of great significance to test the residual stress distribution of the welded joint.It has always been the focus to find a simple and feasible method for residual stress testing to quickly and accurately obtain the residual stress distribution of welded joints.The mechanical measurement method has high measurement accuracy,convenient and easy operation,but it will cause certain damage to the components.Physical measurement method can avoid damage to components,but its test cost is usually high,and its measurement accuracy can also be affected by the material microstructure characteristics of welded components.Based on the advantages and disadvantages of these two residual stress test methods,a modal test method is proposed.This method is a non-destructive measurement method.Based on the mathematical relationship between the residual stress of the welded structure and the natural frequency(mathematical model),the natural frequency is measured through the modal test to calculate the residual stress quickly.However,it is difficult to establish a mathematical model with this method,and it is not suitable for realization.

Research progress of residual stress determination in magnesium alloys

With the research development of the magnesium alloys,the deformation or stress corrosion induced by residual stress(RS)attracted extensive interests in industry and research efforts extensive.However,there are relatively few studies on the RS of magnesium alloys in the world.The generation cause of RS in magnesium alloys was analyzed at first.Several methods of determinate the RS,including destructive methods(drilling hole,crack compliance,layer exfoliation etc.)and non-destructive methods(X-ray Diffraction,Neutron Diffraction,Short Wavelength X-ray Diffraction)were summarized.The factors that influence the measuring accuracy of XRD method were emphasized.The research trends of RS in magnesium alloys were put forward.

Nondestructive test of weld residual stresses by acoustoelastic technique

The fundamentals of acoustoelastic theory and the principle of acoustoelastic nondestructive stress analysis related ultrasonic test Instrument for weld residual stresses are described. The weld residual stress distribution in butt-welded joints was measured by the acoustoelastic stress analysis, which uses the pulse echo overlap method to measure the speed difference in ultrasonic shear waves polarized in principal directions, and a new method of evaluating the material anisotropy is proposed. The results indicate that the anisotropic coefficient of the welded metal is much greater than that of the parent metal. the longitudinal residual stress distributions measured by the acoustoelastic technique are coincident with those obtained by the theoretical analysis, and the measuring accuracy is much greater than that obtained by the resistance strain gauge.

Three-Dimensional Thermo-Elastic-Plastic Finite Element Method Modeling for Predicting Weld-Induced Residual Stresses and Distortions in Steel Stiffened-Plate Structures

The objective of the present paper is to develop nonlinear finite element method models for predicting the weld-induced initial deflection and residual stress of plating in steel stiffened-plate structures. For this purpose, three-dimensional thermo-elastic-plastic finite element method computations are performed with varying plate thickness and weld bead length (leg length) in welded plate panels, the latter being associated with weld heat input. The finite element models are verified by a comparison with experimental database which was obtained by the authors in separate studies with full scale measurements. It is concluded that the nonlinear finite element method models developed in the present paper are very accurate in terms of predicting the weld-induced initial imperfections of steel stiffened plate structures. Details of the numerical computations together with test database are documented.

Clinical study of standard residual liver volume and transient elastography in predicting poor prognosis of patients after hemihepatectomy

BACKGROUND Liver cancer resection,especially in patients with hemihepatectomy or extended hemihepatectomy,often leads to poor prognosis,such as liver insufficiency and even liver failure and death,because the standard residual liver volume(SRLV)cannot be fully compensated after surgery.AIM To explore the risk factors of poor prognosis after hemihepatectomy for hepatocellular carcinoma and evaluate the application value of related prognostic approaches.METHODS The clinical data of 35 patients with primary liver cancer in Nantong Third People's Hospital from February 2016 to July 2020 were retrospectively analyzed.The receiver operating characteristic curve was created using medcac19.0.4 to compare the critical values of the SRLV in different stages of liver fibrosis after hemihepatectomy with those of liver dysfunction after hemihepatectomy.It was constructed by combining the Child-Pugh score to evaluate its application value in predicting liver function compensation.RESULTS The liver stiffness measure(LSM)value and SRLV were associated with liver dysfunction after hemihepatectomy.Logistic regression analysis showed that an LSM value≥25 kPa[odds ratio(OR)=6.254,P<0.05]and SRLV≤0.290 L/m^(2)(OR=5.686,P<0.05)were independent risk factors for postoperative liver dysfunction.The accuracy of the new liver reserve evaluation model for predicting postoperative liver function was higher than that of the Child-Pugh score(P<0.05).CONCLUSION SRLV and LSM values can be used to evaluate the safety of hemihepatectomy.The new liver reserve evaluation model has good application potential in the evaluation of liver reserve function after hemihepatectomy.

A KIND OF GENERAL INFLUENCE MEASURE ON THE LINEAR WEIGHTED REGRESSION

The linear weighted regression model is one of the models studied in many articles in recent years. Some further problems, such as disturbation, influence measure and estimate efficiency, have been discussed in this paper on the basis of the regression diagnosties. The partial conclusions of this paper are the extension of the familiar concepts in the regression diagnosties theory[2' 3,7] because they are representative of this kind of model.

Experimental Research on Residual Stress in Surface of Silicon Nitride Ceramic Balls

The influence of the residual stress in surface of ceramic balls on the fatigue life is large, because the life of silicon nitride ball bearings is more sensitive to the load acted on the bearings than the life of all-steel ball bearings. In this paper, the influence of thermal stress produced in sintering and mechanical stress formed in lapping process on residual stress in surface of silicon nitride ceramic balls was discussed. The residual compress stress will be formed in the surface of silicon nitride ceramic balls after sintering. The residual tensile stress will be formed in surface of silicon nitride ceramic balls in lapping process, and the size of abrasive particle is smaller, such trend is stronger. In this paper the residual stress was measured by the xylometric measurement in which the material in surface was peeled with lapping. The distribution of residual stress in surface can be calculated with the variation in specific volume. The technological parameter with which the material was peeled by lapping was given, for minimizing the extra influence of the residual stress forming in peeling on the original residual stress in surface, the abrasive particle size would not be too small and the load impressed would not be too large. Some experimental researches on residual stress in surface of silicon nitride ceramic balls were made. The surface of silicon nitride ceramic balls presented residual compressive stress after sintering and the influence of the ball size on the residual stress is feeble. It is expected that the size of ball blank is same for achieving the same residual compressive stress in surface on balls after final machining. In lapping process, the surface of silicon nitride ceramic balls presented residual tensile stress, the larger the load which is impressed on single ball, the larger the amplitude of residual tensile stress is; the smaller the abrasive particle, the stronger the trend of plastic deformation is and the larger the amplitude of residual tensile stress is.

Representation of residual stress symbol in the technical product documentation

A representation of residual stress graphic symbols in technical product documents is studied.The residual stress state of the product can be annotated in the technical product documents such as design drawings,process documents,test reports,papers and monographs.The composition of residual stress and the design of basic symbols,measurement method symbols,relief method symbols and state symbols of residual stress,and the representation of annotation for residual stress in documents are introduced.Residual stress symbol can be used in the design,manufacturing,inspection and service for the residual stress state requirements of the products in the mechanical manufacturing industry,as well as in light industry,daily necessities and other related industries.

A New Approach for Measuring Shareholder Value Creation

This paper introduces a new approach for measuring shareholder value creation （called adjusted economic profit （EP）） which combines the advantages of both EP and APV （adjusted present value） methods. In particular, the shareholder value creation over a period is derived as the sum of two components： the EP relating purely to the operations of the company and the EP generated each period due to the tax benefit that arises from debt financing. We consider our results to be important for analysts and decision makers involved in appraising business performance or making investment decisions and HR professionals as well.

嫦娥4/5号月球探测器VLBI观测数据质量分析

在中国探月工程(China’s Lunar Exploration Program,CLEP)中,甚长基线干涉测量技术(very long baseline interferometry,VLBI)具有重要作用。为获得月球探测器的准确定位、实现精确的测定轨功能并以此在探测器飞行过程中完成轨道修正,需要利用VLBI测站对月球探测器进行实时观测。首先以均值(arithmetic mean,AM)以及标准差(standard deviation,STD)作为主要的精度指标,对来源于上海天文台的嫦娥4号探测器、中继星以及嫦娥5号探测器的VLBI实测数据进行总观测时段的数据稳定性分析,并基于嫦娥4号探测器同时段S、X双频段观测,着重进行该探测器不同频率各项数据的质量分析;然后对探测器各工作时段分别进行时延、时延率测量形式误差以及残差分析,了解各时段探测器运动情况与数据变化的相关性。结果表明,3类探测器中,嫦娥4号的实测精度最高,达到1 ns量级;嫦娥5号的观测稳定性优于其他两类探测器;不同地面站对探测器的观测精度有所差异,并且在探测器不同的工作时段,实测数据表现出不同特征。

电气设备剩余电压测试仪校准方法

分析了电气设备剩余电压测试仪基本原理,提出一种基于标准阻容网络法对剩余电压测试仪剩余电压幅值和延迟时间参数进行校准的方法。结合交流标准电阻器和电容器等效模型,分析了标准电阻时间常数和标准电容损耗因数对校准结果的影响,推导了校准时剩余电压和延迟时间标准值的计算方法。采用1 MΩ交流标准电阻和1μF标准电容器组成的电路网络对剩余电压测试仪进行了校准,结果表明标准阻容网络法可满足该仪器的校准。对测量结果进行了不确定度分析,剩余电压幅值测量不确定度为1.1%,延迟时间测量不确定度为1.2%,主要不确定度分量为标准电容器损耗因数的影响。