Optimization of Fixture Number in Large Thin-Walled Parts Assembly Based on IPSO

There are lots of researches on fixture layout optimization for large thin-walled parts.Current researches focus on the positioning problem,i.e.,optimizing the positions of a constant number of fixtures.However,how to determine the number of fixtures is ignored.In most cases,the number of fixtures located on large thin-walled parts is determined based on engineering experience,which leads to huge fixture number and extra waste.Therefore,this paper constructs an optimization model to minimize the number of fixtures.The constraints are set in the optimization model to ensure that the part deformation is within the surface profile tolerance.In addition,the assembly gap between two parts is also controlled.To conduct the optimization,this paper develops an improved particle swarm optimization(IPSO)algorithm by integrating the shrinkage factor and adaptive inertia weight.In the algorithm,particles are encoded according to the fixture position.Each dimension of the particle is assigned to a sub-region by constraining the optional position range of each fixture to improve the optimization efficiency.Finally,a case study on ship curved panel assembly is provided to prove that our method can optimize the number of fixtures while meeting the assembly quality requirements.This research proposes a method to optimize the number of fixtures,which can reduce the number of fixtures and achieve deformation control at the same time.

Development of Fixture Layout Optimization for Thin-Walled Parts:A Review

An increasing number of researchers have researched fixture layout optimization for thin-walled part assembly during the past decades.However,few papers systematically review these researches.By analyzing existing literature,this paper summarizes the process of fixture layout optimization and the methods applied.The process of optimization is made up of optimization objective setting,assembly variation/deformation modeling,and fixture layout optimization.This paper makes a review of the fixture layout for thin-walled parts according to these three steps.First,two different kinds of optimization objectives are introduced.Researchers usually consider in-plane variations or out-of-plane deformations when designing objectives.Then,modeling methods for assembly variation and deformation are divided into two categories:Mechanism-based and data-based methods.Several common methods are discussed respectively.After that,optimization algorithms are reviewed systematically.There are two kinds of optimization algorithms:Traditional nonlinear programming and heuristic algorithms.Finally,discussions on the current situation are provided.The research direction of fixture layout optimization in the future is discussed from three aspects:Objective setting,improving modeling accuracy and optimization algorithms.Also,a new research point for fixture layout optimization is discussed.This paper systematically reviews the research on fixture layout optimization for thin-walled parts,and provides a reference for future research in this field.

Meter-Scale Thin-Walled Structure with Lattice Infill for Fuel Tank Supporting Component of Satellite:Multiscale Design and Experimental Verification

Lightweight thin-walled structures with lattice infill are widely desired in satellite for their high stiffness-to-weight ratio and superior buckling strength resulting fromthe sandwich effect.Such structures can be fabricated bymetallic additive manufacturing technique,such as selective laser melting(SLM).However,the maximum dimensions of actual structures are usually in a sub-meter scale,which results in restrictions on their appliance in aerospace and other fields.In this work,a meter-scale thin-walled structure with lattice infill is designed for the fuel tank supporting component of the satellite by integrating a self-supporting lattice into the thickness optimization of the thin-wall.The designed structure is fabricated by SLM of AlSi10Mg and cold metal transfer welding technique.Quasi-static mechanical tests and vibration tests are both conducted to verify the mechanical strength of the designed large-scale lattice thin-walled structure.The experimental results indicate that themeter-scale thin-walled structure with lattice infill could meet the dimension and lightweight requirements of most spacecrafts.

An electromagnetic semi-active dynamic vibration absorber for thin-walled workpiece vibration suppression in mirror milling

As critical components of aircraft skins and rocket fuel storage tank shells,large thin-walled workpieces are susceptible to vibration and deformation during machining due to their weak local stiffness.To address these challenges,we propose a novel tunable electromagnetic semi-active dynamic vibration absorber(ESADVA),which integrates with a magnetic suction follower to form a followed ESADVA(follow-ESADVA)for mirror milling.This system combines a tunable magnet oscillator with a follower,enabling real-time vibration absorption and condition feedback throughout the milling process.Additionally,the device supports self-sensing and frequency adjustment by providing feedback to a linear actuator,which alters the distance between magnets.This resolves the traditional issue of being unable to directly monitor vibration at the machining point due to space constraints and tool interference.The frequency shift characteristics and vibration absorption performance are comprehensively investigated.Theoretical and experimental results demonstrate that the prototyped follow-ESADVA achieves frequency synchronization with the milling tool,resulting in a vibration suppression rate of approximately 47.57%.Moreover,the roughness of the machined surface decreases by18.95%,significantly enhancing the surface quality.The results of this work pave the way for higher-quality machined surfaces and a more stable mirror milling process.

Numerical Analysis of Cold-Formed Thin-Walled Steel Short Columns with Pitting Corrosion during Bridge Construction

Pitting corrosion is harmful during bridge construction,which will lead to uneven roughness of steel surfaces and reduce the thickness of steel.Hence,the effect of pitting corrosion on the mechanical properties of cold-formed thin-walled steel stub columns is studied,and the empirical formulas are established through regression fitting to predict the ultimate load of web and flange under pitting corrosion.In detail,the failure modes and load-displacement curves of specimens with different locations,area ratios,and depths are obtained through a large number of non-linear finite element analysis.As for the specimens with pitting corrosion on the web,all the specimens are subject to local buckling failure,and the failure mode will not change with pitting corrosion,but the failure location will change with pitting corrosion location;the size,location,and area ratio of pitting corrosion have little influence on the ultimate load of cold-formed thin-walled steel short columns,but the loss rate of pitting corrosion section area has a greater impact on the ultimate bearing capacity.As for the specimen with flange pitting corrosion,the location and area ratio of pitting corrosion have less influence on the ultimate load of cold-formed thin-walled steel short columns,and the section area loss rate has greater influence on the ultimate bearing capacity;the impact of web pitting corrosion on the ultimate load is greater than that of flange pitting corrosion under the same condition of pitting corrosion section area.The prediction formulas of limit load which are suitable for pitting corrosion of web and flange are established,which can provide a reference for performance evaluation of corroded cold-formed thin-walled steel.

Sensitivity of springback and section deformation to process parameters in rotary draw bending of thin-walled rectangular H96 brass tube

In order to study the effects of the process parameters on springback and section deformation, a sensitivity analysis model was established based on the combination use of the multi-parameter sensitivity analysis method and the springback/section deformation prediction finite element model, and by using this model the sensitivities of the springback and the section deformation to process parameters were analyzed and compared. The results show that the most sensitive process conditions for springback angle are the boost speed and the pressure of pressure die, and the most sensitive process condition for section deformation is the number of cores. When the clamp force, the boost speed and the pressure of pressure die are utilized to control section deformation, the effect of these process parameters on springback should be considered. When the process parameters are mainly used to control springback, the effect of these process parameters on the section deformation should be always considered.

VIBRATION IN HIGH-SPEED MILLING OF THIN-WALLED COMPONENTS

To investigate the vibration principle in machining thin-walled components, a dynamic model for end milling of flexible structures is built based on considering the variations in the dynamic chip thickness and the differences between up-milling and down-milling. Two milling experiments verify the model. Experimental results show that the model can predict the milling force and displacements simultaneously in the dynamic milling process.

基于Web of Science对土壤胶体影响重金属行为研究的计量分析

为全面了解土壤胶体影响重金属行为方向的研究现状和前沿动态,基于Web of Science(WoS)核心合集数据库,利用WoS自带分析工具、HistCite引文图谱分析软件、VOSviewer和Citespace可视化分析软件对1990—2021年间土壤胶体影响重金属行为的文献进行了计量分析。结果表明,在世界范围内该方向的发文量逐年稳步增长,我国相关研究起步较晚,但近些年呈现迅猛发展的势头。目前土壤胶体影响重金属行为研究发文量最多的国家和研究机构分别是美国和中国科学院,发文量最高的期刊为Environmental Science&Technology,主要研究学科为环境科学与生态学的交叉学科。关键词聚类分析显示“土壤胶体颗粒粒径分级与重金属的形态分布”、“土壤胶体的释放、沉积及对重金属的吸附作用”和“土壤胶体颗粒的迁移机制与迁移模型研究”为主要的研究主题,人工纳米颗粒在土壤中的行为、迁移转化以及生物有效性是现阶段的研究热点。利用场流分离技术结合单粒子电感耦合等离子体质谱等技术,探讨土壤胶体与人工纳米颗粒之间发生的复杂相互作用及其对人工纳米颗粒迁移归趋与环境命运的影响,是未来的主要研究方向。

基于Stacking融合模型的Web攻击检测方法

随着计算机技术与互联网技术的飞速发展,Web应用在人们的生产与生活中扮演着越来越重要的角色。但是在人们的日常生活与工作中带来了更多便捷的同时,却也带来了严重的安全隐患。在开发Web应用的过程中,大量不规范的新技术应用引入了很多的网站漏洞。攻击者可以利用Web应用开发过程中的漏洞发起攻击,当Web应用受到攻击时会造成严重的数据泄露和财产损失等安全问题,因此Web安全问题一直受到学术界和工业界的关注。超文本传输协议(HTTP)是一种在Web应用中广泛使用的应用层协议。随着HTTP协议的大量使用,在HTTP请求数据中包含了大量的实际入侵,针对HTTP请求数据进行Web攻击检测的研究也开始逐渐被研究人员所重视。本文提出了一种基于Stacking融合模型的Web攻击检测方法,针对每一条文本格式的HTTP请求数据,首先进行格式化处理得到既定的格式,结合使用Word2Vec方法和TextCNN模型将其转换成向量化表示形式;然后利用Stacking模型融合方法,将不同的子模型(使用配置不同尺寸过滤器的Text-CNN模型搭配不同的检测算法)进行融合搭建出Web攻击检测模型,与融合之前单独的子模型相比在准确率、召回率、F1值上都有所提升。本文所提出的Web攻击检测模型在公开数据集和真实环境数据上都取得了更加稳定的检测性能。

多维深度导向的Java Web模糊测试方法

随着Java Web的广泛应用,其安全问题日益突出。模糊测试作为一种有效的漏洞挖掘方法,目前已经被用于Java漏洞的检测。然而,由于Java Web应用代码规模庞大、业务逻辑复杂,现有的漏洞挖掘工具在模糊测试中存在随机性高、代码检测深度低的问题,导致漏洞挖掘的准确率较低。因此,文章提出基于多维深度导向的Java Web模糊测试方法。该方法使用Jimple作为待测Java Web应用字节码的三地址码中间表示,并生成代码对应的函数间调用图和函数内控制流图,在此基础上分析每个基本块的多维深度。同时,根据多维深度和模糊测试执行时间优化模糊测试指导策略,设计相应的输入结构解析策略、能量分配策略和变异算法调度策略,提升模糊测试的准确性。实验结果表明,相较于现有的模糊测试工具Peach和Kelinci,该方法能够在性能消耗较低的情况下取得更好的漏洞检测效果。

基于博弈的Web应用程序中访问控制漏洞检测方法

针对工业互联网中程序的访问控制策略隐藏在源码中难以提取,以及用户的访问操作难以触发所有访问路径而导致逻辑漏洞的通用化检测难以实现的问题,将博弈思想应用于访问控制逻辑漏洞检测中,通过分析不同参与者在Web应用程序中对资源页面的博弈结果来识别漏洞,使得不同用户的访问逻辑能被有针对性地获取。实验结果表明,所提方法在开源的11个程序中检测出31个漏洞,其中8个为未公开的漏洞,漏洞检测覆盖率均超过90%。

中国地震科学实验场三维断层模型Web展示原型系统

活动断层的三维结构和模型是地震危险性研究的基础参数和重要数据。随着对接近真实形态的活动断层三维模型的应用需求不断增加,对这类模型数据的共享及研究的需求也日益增加。数据共享课题的一个重要议题是如何构建基于Web的三维断层模型展示平台,提高数据共享水平和用户体验。中国地震科学实验场(川滇地区)三维断层模型Web展示原型系统①是基于Arc GIS 10.6企业版的Web App Builder工具构建的一个实验性系统。该系统实现了基于Web GIS的三维展示系统的基本功能,并成功测试了更适用于地震行业标准的用户交互方式、基本功能、场景数据迁移方案和三维场景设计方案。场景数据从三维断层建模平台到GIS平台的迁移,是实现基于Web GIS三维展示系统的基础。场景中展示的三维数据采用与二维数据标准一致且视觉上融合度高的可视化方案。实践结果表明,三维数据从建模平台迁出后,应结合数据可视化方案,在属性层面上与二维数据相融合,以保证二维和三维数据在视觉上较好地融合。

基于主动探测的Web容器探测识别方法

随着工业互联网的飞速发展,各类Web容器的广泛使用呈现不断增长的趋势,然而,这也使得Web容器资产管理的问题变得更加复杂.随之而来的是诸多网络安全风险和潜在隐患,对于这些挑战,提升网络安全防御水平显得尤为迫切.为了解决这一问题,本文引入了一种新的基于主动探测的Web容器探测识别方法.在探测阶段,采用了一种先进的Web容器探针构建方法,通过此方法构建了Web容器探针.这个探针在识别阶段发挥关键作用,借助一种基于负载内容的Web容器识别方法,通过协议解码技术,实现了对Web容器的高度准确的识别.通过结合这两种先进的识别方法,成功识别了4种不同类型的Web容器,并且提升了精度,能够精确地区分这些Web容器的各个版本,总计实现了10个版本的准确识别.通过这种先进的主动探测方法,企业可以更好地了解和管理其Web容器资产,降低网络安全风险,并确保网络系统的稳定性和安全性.

基于Web of Science全球小麦低温逆境的研究态势分析

低温逆境已成为限制全球小麦稳产丰产与优质的主要农业气象灾害之一。为客观全面地了解全球小麦低温逆境领域的研究现状和发展趋势,基于Web of Science核心数据库中2000-2020年发表的以“小麦”和“低温”为研究主题的相关文献为数据源,利用CiteSpace可视化分析软件对检索到与主题密切相关的475篇文献从发文数量、发文国家、发文作者、研究机构、研究热点等方面进行统计分析。结果表明:自2000年以来,小麦低温逆境领域年发文数量总体呈波动上升趋势;以中国、美国和加拿大等国家为代表的农业大国均致力于该领域的研究;美国学者Skin⁃ner是该领域发文量最多的作者,与其他学者合作密切的有李向楠和Fowler;该领域文献多发表于《Molecular Genetics and Genomics》和《Annual Review of Plant Biology》等优质期刊上;俄罗斯科学院是该领域发文量最多的科研机构;耐低温小麦新品种培育、耐寒分子生物学研究以及提高小麦产质量等方面成为该领域的研究热点。

基于Web的数字化资源共享信息查询系统设计

数字化资源增多使得共享信息查询难度增加,为此,设计了基于Web的数字化资源共享信息查询系统。通过统一用户接口,实现数字化资源共享信息的交互和集成,构建查询系统管理平台。连接外部共享信息提供程序和服务执行个体,利用Web服务器的索引服务,完成信息局部查询。管理远程信息查询节点服务的请求,改变创建端点的新路由,防止信息丢失,结合语义相关优化系统,根据关键字的反向资源频次,获得辨识能力,实现数字化资源共享信息全局查询。实验结果表明,基于Web的信息查询系统的查询处理能力较强,能够提高查询准确率和查询效率。

基于Web of Science数据库的淀粉多酚相互作用研究的可视化分析

为了解淀粉多酚相互作用的研究现状和发展趋势,采用文献计量学方法,以Web of Science核心合集数据库出版日期为2010-01-01至2024-04-18的论文为研究对象,进行可视化分析,为相关学科的研究提供参考。结果显示:淀粉多酚相互作用研究领域的年发文量总体呈上升趋势;中国研究机构在该领域发文数量优势明显,但在影响力方面与新西兰、澳大利亚和西班牙等国的研究机构相比还有一定差距;该领域研究热点主要集中在食品科学技术与化学学科方向,但同时也展示出多学科交叉融合的发展趋势。消化、特性、相互作用、生物利用度、抗菌活性、分子对接、复合物、纳米颗粒、活性膜等方面是该领域的研究前沿。

Warm bending mechanism of extrados and intrados of large diameter thin-walled CP-Ti tubes

In order to develop the warming bending technology of the large diameter thin-walled（LDTW） commercial pure titanium alloy CP-Ti tubes, the warm bending mechanism of the extrados and intrados of LDTW CP-Ti tubes was researched. By EBSD analysis and Vickers hardness test, the changes of microstructure and strength of the tubes at different bending temperatures of 293, 423 and 573 K, were analyzed. The results show： 1） The extrados of the bent tube deforms mainly by slip, along with few twinning, and the preferred orientation is similar to that of the initial tube; the intrados of the bent tube experiences compression deformation mainly by {1 012} tensile twinning, and the twinning makes the preferred orientation of wall materials change sharply. 2） The Vickers hardness values of both the extrados and intrados of the samples after bending increase greatly; the Vickers hardness values of the intrados are much higher than those of the extrados, and Vickers hardness values of the RD-TD planes are always higher than those of the RD-LD planes, which are related to the different deformation mechanisms.

基于HTML5技术的移动Web前端设计

阐述HTML5的特性、优势、移动Web前端设计面临的挑战。分析HTML5在移动Web前端设计中的应用,包括响应式设计、用户体验优化、性能优化。HTML5技术可以有效提高移动Web应用质量。

五位一体课程思政融合路径设计与探索——以“Web标准网页设计”课程为例

当下高校课程思政融合教学工作面临着机遇与挑战,对高校课程思政工作提出了更高的要求。立足于Web标准网页设计、课程思政融入立德树人的逻辑分析以及Web标准网页设计专业课与课程思政有机融合的关系,从课程内容重构、课程思政脉络设计、显性课程思政教育、隐性课程思政教育、课程思政教学反思五位一体,对Web标准网页设计课程思政融合路径进行了设计与探索,以期推动高校课程思政融合工作落地落实,提升其实效性。最后,对Web标准网页设计五位一体课程思政融合教学实施成效进行了分析,效果显著。

基于TransMP模型的Web系统剩余寿命预测方法

针对当前软件剩余使用寿命预测方法忽略了多性能指标间所蕴涵寿命信息的问题,提出一种融合多性能指标Transformer(TransMP)模型的Web系统剩余寿命预测方法。首先,搭建内存故障型Web系统加速老化实验平台,创建包含内存使用量、响应时间和吞吐率性能指标的数据集;其次,考虑不同性能指标蕴涵老化特征信息的差异性,构造由多编码器-解码器组成的TransMP模型,将性能指标数据分别输入内存指标编码器、响应时间编码器和吞吐率编码器提取老化特征信息,再引入特征融合层进行信息融合;最后,将融合信息输入由掩码注意力-多头注意力结构构成的解码器,预测得到系统状态达到老化阈值的剩余寿命。实验结果表明,该Web系统剩余寿命预测方法与最优的SALSTM方法相比,均方根误差分别降低了12.0%、17.3%和13.2%,平均绝对误差分别降低了13.3%、21.0%和10.4%,证明了该方法的有效性。