Deterministic learning of completely resonant nonlinear wave systems with Dirichlet boundary conditions

In this paper, we investigate the approximation of completely resonant nonlinear wave systems via deterministic learning. The plants are distributed parameter systems (DPS) describing homogeneous and isotropic elastic vibrating strings with fixed endpoints. The purpose of the paper is to approximate the infinite-dimensional dynamics, rather than the parameters of the wave systems. To solve the problem, the wave systems are first transformed into finite-dimensional dynamical systems described by ordinary differential equation (ODE). The properties of the finite-dimensional systems, including the convergence of the solution, as well as the dominance of partial system dynamics according to point-wise measurements, are analyzed. Based on the properties, second, by using the deterministic learning algorithm, an approximately accurate neural network (NN) approximation of the the finite-dimensional system dynamics is achieved in a local region along the recurrent trajectories. Simulation studies are included to demonstrate the effectiveness of the proposed approach.     

基于剪切带扩展法的海底斜坡稳定性分析

简介剪切带扩展法（SBP）的原理及其在海底滑坡稳定性分析的应用;以舟山六横岛典型海底斜坡为分析案例,开展基于高斯函数的SBP和极限平衡法（LEM）斜坡稳定性对比分析研究;进行SBP输入参数对剪切带扩展系数R的敏感度分析. 研究结果显示,对于斜坡剪切带破坏长度,当剪切带扩展系数R不大于1时,LEM与SBP得到的滑坡滑裂面区域一致,当R大于1时,SBP计算得到的最终滑动区域比LEM计算得到的区域大;在斜坡发生滑动破坏区域SBP比LEM计算得到的安全系数低;地震影响因素和土体特征位移对R的影响较大.     

Crack initiation and propagation induced by inclusions in a nickel-base P/M superalloy under fatigue load

1 IntroductionRecently the key components in advanced aircraftengines are widely made of nickel-base P/M super-alloy. However, non-metallic inclusions are intro-duced into this material during powder metallurgyprocessing. In industry, although many method…     

热处理对Ti-Al-Sn-Zr-Mo-Si-X系合金性能的影响

研究了热处理对3种Ti-Al-Sn-zr-Mo-Si-X（X为ⅤB，ⅥB族一种或几种元素）系合金（A、B、C）室温拉伸性能的影响，对优化合金的热处理制度及优选热处理制度下3种合金的疲劳裂纹扩展行为也进行了探讨。结果表明，优选热处理制度下A、C合金的裂纹扩展速率差别不大，B合金560℃时效处理后，裂纹扩展速率比540℃时效处理的小。在相同热处理制度下，比较3种合金裂纹扩展速率的结果表明，IgΔK在1．2～1．5范围内B合金的抗疲劳裂纹扩展性能较优。     

应变速率对中碳低温贝氏体钢强塑性的影响

摘要：为探索低温贝氏体钢的断裂行为,研究应变速率对低温贝氏体钢TRIP效应的影响,采用不同应变速率的拉伸试验对低温贝氏体钢的强塑性进行研究。利用扫描电镜（SEM）、透射电镜（TEM）及X射线衍射（XRD）等试验方法对低温贝氏体钢的微观组织、断口形貌及裂纹走向进行表征。结果表明,随着应变速率的提高,试验钢的屈服强度由771MPa上升至806MPa,抗拉强度由1554MPa上升至1606MPa,断后伸长率由13.5%下降至9.0%。主要原因是高应变速率拉伸引发的绝热温升抑制了残余奥氏体的马氏体相变,对试验钢塑性造成负面影响。     

A fatigue-life prediction methodology for notched aluminum-magnesium alloy in gulf seawater environment

Local-strain and linear-elastic fracture-mechanics (LEFM) methodologies have been investigated for prediction of the corrosion-fatigue life of notched components of specially developed Al-2.5Mg alloys exposed to Arabian Gulf seawater environment. Corrosion-fatigue crack initiation life estimates were obtained using strain-life relationships; corrosion-fatigue crack propagation life estimates were obtained using LEFM relationships. The total corrosion-fatigue life was considered to be the sum of the crack initiation and crack propagation lives. Estimated corrosion-fatigue lives were compared with experimentally obtained corrosion-fatigue life data using center-notched specimens of three types of Al-2.5Mg alloys (containing different amounts of chromium) exposed to Arabian Gulf seawater environment. Two notch geometries, a circular notch (K _t= 2.42) and an elliptical notch (K _t= 4.2), were investigated. Good corrosion-fatigue life predictions can be obtained using local-strain and LEFM methodologies by determining the relevant material constants via a few simple fatigue tests on smooth specimens and a few crack-growth-rate tests in the environment at the frequency of interest.     

Enhanced extraction of isoflavones from Korean soybean by ultrasonic wave

The amounts of isoflavones extracted from Korean soybean by various ultrasonic waves were compared using 60% aqueous ethanol solution. The effect on extraction yield of variations in solvent composition, temperature, and extraction time was investigated. The experimental results confirmed that ultrasonic waves are a desirable method to extract isoflavones from Korean soybean. The highest yield of aglycone isoflavones was obtained by ultrasonic waves with a frequency of 20 KHz and an extraction time of 10 min, which produced yields of glycoside and aglycone isoflavones three-fold greater than those by dipping method.     

Analytical ray tracing system: Introducing art, a C-library designed for seismic applications

Ray tracing technique is an important tool not only to forward but also for inverse problems in Geophysics, which most of the seismic processing steps depend on. However, implementing ray tracing codes can be very time consuming. This article presents a computer library to trace rays in 2.5D media composed by a stack of layers. The velocity profile inside each layer is such that the eikonal equation can be analytically solved. Therefore, the ray tracing within such profile is made fast and accurate. The great advantage of an analytical ray tracing library is the numerical precision of the quantities computed and the fast execution of the implemented codes. Even though ray tracing programs exist for a long time, for example the seis88 package by ?ervený, most of those programs use a numerical approach to compute the ray. Regardless of the fact that numerical methods can solve more general problems, the analytical ones could be part of a more sophisticated simulation process, where the ray tracing time is completely relevant. We demonstrate the feasibility of our codes using several examples (Miqueles et al., 2013)  [1]. The library can also be used for other applications besides seismic, e.g., optics and tomography.     

Investigating dependencies in software requirements for change propagation analysis

ContextThe dependencies between individual requirements have an important influence on software engineering activities e.g., project planning, architecture design, and change impact analysis. Although dozens of requirement dependency types were suggested in the literature from different points of interest, there still lacks an evaluation of the applicability of these dependency types in requirements engineering.ObjectiveUnderstanding the effect of these requirement dependencies to software engineering activities is useful but not trivial. In this study, we aimed to first investigate whether the existing dependency types are useful in practise, in particular for change propagation analysis, and then suggest improvements for dependency classification and definition.MethodWe conducted a case study that evaluated the usefulness and applicability of two well-known generic dependency models covering 25 dependency types. The case study was conducted in a real-world industry project with three participants who offered different perspectives.ResultsOur initial evaluation found that there exist a number of overlapping and/or ambiguous dependency types among the current models; five dependency types are particularly useful in change propagation analysis; and practitioners with different backgrounds possess various viewpoints on change propagation. To improve the state-of-the-art, a new dependency model is proposed to tackle the problems identified from the case study and the related literature. The new model classifies dependencies into intrinsic and additional dependencies on the top level, and suggests nine dependency types with precise definitions as its initial set.ConclusionsOur case study provides insights into requirement dependencies and their effects on change propagation analysis for both research and practise. The resulting new dependency model needs further evaluation and improvement.