An implicit marching method for the two-dimensional reduced Navier-Stokes equations at arbitrary mach number

An implicit marching procedure is developed from a parabolized form of the two-dimensional Navier-Stokes equations with allowance for chemical reaction in an effort to predict the flow in highly viscous chemical laser nozzles. The equations governing the fluid dynamics are linearized and solved as a coupled implicit system in a manner which requires no iteration and in which the pressure gradient for internal flows emerges directly as part of the solution without iteration. Accuracy and stability of the method are tested by computing the flow in the entrance region between parallel flat plates and comparing the results to analytical results as well as experimental data. Upon completion of these tests the procedure is used to predict the highly viscous chemically reacting flow in a laser nozzle and inlet duct.     

A two-parameter model for crack growth simulation by combined FEM–DBEM approach

This paper describes the application of a two-parameters crack growth model, based on the usage of two threshold material parameters (ΔK_th and K_max,th) and on the allowance for residual stresses, introduced at the crack tip by a fatigue load spectrum or by material plastic deformations. The coupled usage of finite element method (FEM) and dual boundary element method (DBEM) is proposed in order to take advantage of the main capabilities of the two methods.The procedure is validated by comparison with available experimental results, in order to assess its capability to predict the retardation phenomena, introduced by a variable load spectrum or by a plastic deformation introduced with a tool on the panel (indentation).In particular two different tests are made: the first test involve a CT specimen undergoing a load spectrum and the second one involve a dented panel undergoing a constant amplitude fatigue load. In both cases a satisfactory numerical–experimental correlation will be proved.The main advantages of the aforementioned procedure are: the simplicity of the crack growth law calibration (few constant amplitude tests are sufficient without the need for any non-physical calibration parameters), and the possibility to simulate residual stress effects on crack propagation with a simplified approach, based on linear elastic fracture mechanics.     

基于在线检测的叶片加工余量自适应优化方法

针对复合制造工艺背景下叶片毛坯形状复杂、余量分布不均的特点，提出基于加工中心在线检测的叶片装夹定位与余量优化方法。首先，根据叶片毛坯的工艺特性，建立了加工余量自适应优化的统一数学模型。然后，讨论了三类典型叶片包括无余量叶片、带余量叶片以及变形叶片组的定位与余量优化问题，并依次给出了适应不同约束条件的定位优化求解算法。最后，结合加工中心的在线检测方式，提出了叶片加工余量自适应优化的自动定位流程。算例分析结果表明，文中所提方法能够有效控制各种不同加工工艺制造的叶片毛坯的余量分布，使其自适应变化以满足实际工艺要求。     

The WKB Local Discontinuous Galerkin Method for the Simulation of Schrödinger Equation in a Resonant Tunneling Diode

In this paper, we develop a multiscale local discontinuous Galerkin (LDG) method to simulate the one-dimensional stationary Schrödinger-Poisson problem. The stationary Schrödinger equation is discretized by the WKB local discontinuous Galerkin (WKB-LDG) method, and the Poisson potential equation is discretized by the minimal dissipation LDG (MD-LDG) method. The WKB-LDG method we propose provides a significant reduction of both the computational cost and memory in solving the Schrödinger equation. Compared with traditional continuous finite element Galerkin methodology, the WKB-LDG method has the advantages of the DG methods including their flexibility in h-p adaptivity and allowance of complete discontinuity at element interfaces. Although not addressed in this paper, a major advantage of the WKB-LDG method is its feasibility for two-dimensional devices.     

微分求积法分析二维亚音速壁板的失稳问题

采用微分求积方法(简称DQ方法)研究了亚音速气流中二维壁板的失稳问题.运用特征值方法分析了壁板在不同边界条件下的失稳特性.结果表明:本方法可有效确定系统的失稳;两端简支和两端固支的壁板出现了发散失稳而未出现颤振失稳;固支—弹性支承的壁板系统出现了颤振失稳,颤振失稳动压与系统参数相关.     

Mapping the Properties of Geological Objects with Allowance for Anisotropy Based on the Simulation of the Deformation Transformation

The statement for the problem on mapping the properties of geological objects is considered. Examples of its solution with allowance for anisotropy based on modeling the deformation transformation of an initially isotropic space within the variational method for geological mapping are given. The problem is reduced to modifying the type of model conditions represented by partial differential equations using the Jacobian matrix corresponding to the coordinate transformation for the simulated deformation. The proposed approach is applicable to the solution of two-dimensional and three-dimensional problems of geological mapping taking into account both the homogeneous and locally varying space anisotropy of the properties of geological objects     

对抗型半监督光伏面板故障检测

目的 传统的光伏面板故障检测主要依靠人工巡检,效率低下且误检率很高,而流行的基于机器视觉的智能检测方法又面临缺少大量负样例造成故障检测模型准确性偏低的问题。针对上述问题,本文提出一种基于对抗训练的半监督异常检测模型,通过应用梯度中心化（gradient centralization,GC）和Smooth L1损失函数,使模型具有更好的准确性和鲁棒性。方法 通过构建半监督异常检测模型并定义目标函数,将正常的光伏面板图像作为正样例原图输入半监督异常检测模型进行模型训练。然后将待测光伏面板图像输入到训练好的半监督异常检测模型,生成该待测图像对应的重建图像。最后通过计算待测原图像与其重建图像隐空间向量之间的误差来判断该待测光伏面板是否存在异常。结果 本文以浙江某光伏电站采集的光伏面板为实验对象,将本文方法与Pre-trained VGG16（Visual Geometry Group 16-layer network）、AnoGAN （anomaly generative adversarial network）、GANomaly等方法进行比较,AUC （area under curve）分别提高了0.12、0.052和0.033。结论 实验结果证明,本文提出的基于生成对抗网络的半监督异常检测模型大幅提高了光伏面板故障检测的准确率。     

基于HoloLens的飞机维修远程指导系统

针对飞机维修人员在遭遇棘手维修问题时难以快速处理的问题,提出一种基于HoloLens的飞机维修远程指导系统;采用改进的$P算法,对标注手势点序列进行时间标记,通过对专家端手绘笔划的快速识别,同时结合HoloLens设备的空间感知能力进行三维模型标注的放置;这种新型的索引标注方式,减少了专家端从模型库中调用标注的时间;同时结合二维标注,通过对圈选坐标信息和深度信息获取,对重点维修部位进行标注;在佩戴HoloLens设备时提高了维修人员对专家给出的特定维修部位和重点维修流程的理解程度;对改进$P算法速率进行了实验,实验验证了本文所改进的$P算法提升了手势识别速率,同时二维标注点的准确性也得到了保障,证明了维修远程指导系统的可用性。     

Advanced methods for safe visualization on automotive displays

Camera Monitor Systems (CMSs), for example, for backup cameras or mirror replacements, become increasingly important and already cover safety aspects such as guaranteed latency and no frame freeze. Today's approaches deal only with supervision of the digital interface, LCD backlight, and power supply. This paper introduces methods for advanced safety monitoring of panel electronics and optical display output that aim to enable future CMS based automotive use cases. Our methods are based on correlation of physical measurements with predicted values derived from a corresponding display model. This model was made via calibration measurements and many test patterns. Correlation of the monitoring results with predicted values corresponds to the probability that the RGB data are shown as intended. This implies that an overlying system, an Automotive Safety Integrity Level (ASIL) Prepared Video Safety System (APVSS), ensures that only safety verified RGB data are provided to the panel electronics. In case of failures, our methods enable a safe system state, for example, by deactivating the panel. An additional challenge is to allow graceful degradations, a safe but slightly degraded image may provide a better customer experience compared with no information. We successfully verified our approach by a fully functional prototype and extensive evaluation towards “light‐to‐light” (camera to display output) supervision.     

Optimisation of garment design using fuzzy logic and sensory evaluation techniques

The ease allowance is an important criterion in garment design. It is often taken into account in the process of construction of garment patterns. However, the existing pattern generation methods cannot provide a suitable estimation of ease allowance, which is strongly related to wearer's body shapes and movements and used fabrics. They can only produce 2D patterns for fixed standard values of ease allowance. In this paper, we present a new method for optimizing the estimation of ease allowance of a garment using fuzzy logic and sensory evaluation. Based on the optimized values of ease allowance generated from fuzzy models related to different key body positions and different wearer's movements, we obtain an aggregated ease allowance using the OWA operator. This aggregated result can further improve the wearer's fitting perception of a garment and adjust the compromise between the style of garments and the fitting comfort sensation of wearers. The related weights of the OWA operator are determined according to designer's linguistic criteria on comfort and garment style. The effectiveness of our method has been validated in the design of trousers of jean type. It can be also applied for designing other types of garment.     

Low-contrast surface inspection of mura defects in liquid crystal displays using optical flow-based motion analysis

This paper proposes a machine vision scheme for mura defect detection in LCD manufacturing. Mura is a Japanese word for blemish, which typically shows brightness imperfections from its surroundings in the surface. It appears as a low-contrast region without clear edges. Traditional automatic visual inspection algorithms detect mura defects from individual still images. They neglect that a mura defect may not be visually sensed in the image from a stationary system. In this study, the LCD panel is assumed to move along a track. While the panel passes through a fixed camera, the light reflection from different angles can effectively enhance the mura defect in the low-contrast images. The mura detection problem is therefore treated as a motion analysis in image sequences using optical flow techniques. Since a LCD panel moves along a single direction, both two-dimensional and one-dimensional optical flow methods are developed. Three discriminative features based on flow magnitude, mean flow magnitude and flow density in the optical flow field are presented to extract the defective regions. Both real panel images and synthetic surface images are used to evaluate the efficacy of the proposed methods. Experimental results have shown that the proposed 1D optical flow method works as well as the 2D optical flow method to detect very low-contrast mura defects of small size, and achieves a high processing rate around 20 frames per second for images of size 200 × 200.     

破片对飞机壁板冲击损伤仿真研究

文章基于飞机战伤抢修资源需求仿真模型,建立了离散杆破片在击穿条件下的毁伤仿真情形。主要通过ANSYS前处理器构建三维有限元毁伤模型得出K文件,利用ANSYs／LS-DYNA查看和分析其仿真结果,从而得出离散杆的速度和靶板厚度对毁伤效应的影响。通过计算机仿真分析结果和终点效应击穿条件下的靶板损伤预测数学模型,来进行对比分析飞机壁板的毁伤效应,得到了基本一致的数据结果,结论为战场飞机快速评估提供了科学依据,也为飞机平时修理提供了参考。     

飞机铆接结构缺陷的远场涡流检测技术研究

飞机机身铆接结构中缺陷的检测评估是目前航空和无损检测领域中的研究难点.远场涡流检测技术因其不受集肤效应的限制从而可以实现对大厚度构件的检测.设计了一种激励线圈带多层屏蔽结构的传感器模型,在非磁性金属平板构件上实现了远场涡流现象.采用旋转式扫描的检测方法对铆接结构中缺陷进行检测,结果表明,检测线圈在经过缺陷正上方时其相位出现极小值,并且该极小值与缺陷深度之间存在线性关系,从而验证了将远场涡流检测技术应用于铆接结构中缺陷检测的可行性.     

A new repair–replace strategy for items sold with a two-dimensional warranty

For repairable items, the manufacturer has the option to either repair or replace a failed item that is returned under warranty. In this paper, we look at a new warranty servicing strategy for items sold with two-dimensional warranty where the failed item is replaced by a new one when it fails for the first time in a specified region of the warranty and all other failures are repaired minimally. The region is characterised by two parameters and we derive the optimal values for these to minimise the total expected warranty servicing cost. We compare the results with other repair–replace strategies reported in the literature.     

Stiffness-oriented performance indices defined on two-dimensional manifold for 6-DOF industrial robot

In this paper, the modeling of the stiffness of a 6-DOF industrial robot is introduced, and two different stiffness-oriented performance indices are compared to improve the two-dimensional manifold. In previous study, the two-dimensional manifold is applied to simplify the workspace for error compensation to avoid the curse of dimensionality. Stiffness is one of the most concerned factors in robotic machining to reduce the deflection at the end of robot arm, which makes a stiffness-oriented manifold is quite essential in the actual application. An improved two-dimensional index is presented based on the Frobenius-condition-number of translational compliance matrix to avoid the ill-conditions of manipulator. The superiority of the improved index over the previous one is theoretically proved with several propositions in matrix theory. The simulations performed with sample points on a panel surface imply that the ill-conditions of robot can be effectively avoided. The results of contrast experiments conducted on KUKA robot show that the improved still ensure the accuracy of positioning in robotic machining.     

Two-dimensional substring indexing

As databases have expanded in scope to storing string data (XML documents, product catalogs), it has become increasingly important to search databases based on matching substrings, often on multiple, correlated dimensions. While string B-trees are I/O optimal in one dimension, no index structure with non-trivial query bounds is known for two-dimensional substring indexing. In this paper, we present a technique for two-dimensional substring indexing based on a reduction to the geometric problem of identifying common colors in two ranges containing colored points. We develop an I/O efficient algorithm for solving the common colors problem, and use it to obtain an I/O efficient (poly-logarithmic query time) algorithm for the two-dimensional substring indexing problem. Our techniques result in a family of secondary memory index structures that trade space for time, with no loss of accuracy.     

Application of folded plate analysis to bending,buckling and vibration of multilayer orthotropic sandwich beams and panels

A unified analysis method based on two-dimensional elasticity theory is outlined for evaluation of bending, buckling and vibration of multilayer orthotropic sandwich beams and panels. The effects of initial geometric imperfections are included. It is shown that beams or panels deforming under conditions of plain stress or plane strain may be treated as special instances of folded-plate structures using computer programs which are now widely available. Examples are given, including evaluation of stress contours in a sandwich panel under patch load and analysis of overall and local (face-wrinkling) buckling modes in sandwich panels with stiff and soft cores.     

破片侵彻飞机机翼壁板的应急修理有限元分析

针对飞机机翼壁板遭受导弹破片侵彻后的应急修理问题,以某飞机机翼受损壁板为例,采用全机有限元模型对其铆接修理进行强度计算．计算模型中补片的单元类型采用壳单元,铆钉用梁单元．结果表明,在铆钉钉距、排距和边距一定的情况下,铆钉排数与修理后的承载能力有对应关系．该对应关系为战场上合理制定应急修理方案提供理论参考．     

A two-dimensional lattice Boltzmann model for uniform channel flows

In this paper a novel two-dimensional lattice Boltzmann model (LBM) is developed for uniform channel flows. The axial velocity is solved from a momentum diffusion equation over the cross-sectional plane. An extrapolation boundary condition is also introduced to enhance the no-slip boundary in the momentum equation. This boundary treatment can also be applied to LBM simulations of other diffusion processes. The algorithm and boundary treatment are validated by simulations of steady Poiseuille and pulsatile Womersley flows in circular pipes. The numerical convergence and accuracy are comparable to those of existing models. Moreover, comparison with general three-dimensional lattice Boltzmann simulations demonstrates the advantages of our two-dimensional model, including lower computational resource requirements (memory and time), easier boundary treatment for arbitrary cross-sectional shapes, and no velocity constraint. These features are attractive for practical applications with uniform channel flows.