Lean production system design for fishing net manufacturing using lean principles and simulation optimization

Value stream mapping (VSM) is a useful tool for describing the manufacturing state, especially for distinguishing between those activities that add value and those that do not. It can help in eliminating non-value activities and reducing the work in process (WIP) and thereby increase the service level. This research follows the guidelines for designing future state VSM. These guidelines consist of five factors which can be changed simply, without any investment. These five factors are (1) production unit; (2) pacemaker process; (3) number of batches; (4) production sequence; and (5) supermarket size. The five factors are applied to a fishing net manufacturing system. Using experimental design and a simulation optimizing tool, the five factors are optimized. The results show that the future state maps can increase service level and reduce WIP by at least 29.41% and 33.92% respectively. For the present study, the lean principles are innovatively adopted in solving a fishing net manufacturing system which is not a well-addressed problem in literature. In light of the promising empirical results, the proposed methodologies are also readily applicable to similar industries.     

Model repair — aligning process models to reality

Process mining techniques relate observed behavior (i.e., event logs) to modeled behavior (e.g., a BPMN model or a Petri net). Process models can be discovered from event logs and conformance checking techniques can be used to detect and diagnose differences between observed and modeled behavior. Existing process mining techniques can only uncover these differences, but the actual repair of the model is left to the user and is not supported. In this paper we investigate the problem of repairing a process model w.r.t. a log such that the resulting model can replay the log (i.e., conforms to it) and is as similar as possible to the original model. To solve the problem, we use an existing conformance checker that aligns the runs of the given process model to the traces in the log. Based on this information, we decompose the log into several sublogs of non-fitting subtraces. For each sublog, either a loop is discovered that can replay the sublog or a subprocess is derived that is then added to the original model at the appropriate location. The approach is implemented in the process mining toolkit ProM and has been validated on logs and models from several Dutch municipalities.     

Semantics for consistent activation in context-oriented systems

ContextContext-oriented programming languages provide dedicated programming abstractions to define behavioral adaptations and means to combine those adaptations dynamically according to sensed context changes. Some of these languages feature programming abstractions to explicitly define interaction dependencies among contexts. However, the semantics of context activation and the meaning of dependency relations have been described only informally, which in some cases has led to incorrect specifications, faulty implementations and inconsistent system behavior.ObjectiveWith the aim of avoiding faulty implementations and inconsistencies during system execution, this paper proposes both a formal and run-time model of contexts, context activation and context interaction.MethodAs a formal and computational basis, we introduce context Petri nets, a model based on Petri nets, which we found to match closely the structure of contexts in context-oriented systems. The operational semantics of Petri nets permits the modeling of run-time context activations. Existing Petri net analyses allow us to reason about system properties. As validation, we carried out small and medium-sized case studies.ResultsIn the cases explored, context Petri nets served effectively as underlying run-time model to ensure that declared context interaction constraints remain consistent during context manipulation. Moreover, context Petri nets enabled us to analyze certain properties regarding the activation state of particular contexts.ConclusionContext Petri nets thus proved to be appropriate to encode and manage the semantics of context activation, both formally and computationally, so as to preserve the consistency of context-oriented systems.     

马氏体-奥氏体复合钢复合层数对组织性能的影响

 开发更高性能的钢铁材料是促进“双碳”目标达成的有效途径之一。引入碳扩散是制备超高强度-高塑性复合钢的有效方法。在课题组前期研究基础上,利用真空热轧的方式制备不同层数的复合钢。通过增加层数,减小了复合钢内各层的厚度,复合钢在1 150 ℃热轧复合后继续保温过程,实现碳元素从高碳层向低碳层的扩散。利用扫描电子显微镜、FEI-透射电子显微镜及X射线衍射仪对组织及相组成进行了分析,利用电子探针显微分析仪测量了元素分配情况,并进行了硬度和拉伸性能测试。结果表明,随着层数的增加,复合钢内碳元素分布发生了明显的变化,马氏体层内部的碳含量逐渐升高,奥氏体层内部的碳含量逐渐降低,碳元素浓度差逐渐降低。同时,复合钢的屈服强度、抗拉强度和总伸长率呈现出先增加后降低的趋势。当复合钢内层数为9、11层时,其强度和塑性均超过单层马氏体钢;均匀伸长率随复合钢层数的增加而逐渐提高,15层复合钢取得了最大值(约10.1%)。9层复合钢获得了最佳的强度和塑性组合,与单层马氏体钢相比,抗拉强度(1 733 MPa)和伸长率(23.6%)分别提高了60 MPa和7.1%;同时其塑性也超过了单层奥氏体钢。此外,随着层数的增加,也导致奥氏体层比例逐渐提高,导致15层复合钢的强度低于单层马氏体钢的强度。     

一种外LET柔顺半铰的动力学建模与分析

对一种外LET柔顺半铰进行建模与动力学特性分析。采用斜率不连续的绝对节点坐标法（ANCF）建立了该柔顺半铰系统动力学方程；对外力作用下半铰中心线和外轮廓的运动变形进行仿真，与实验结果对比，证明了绝对节点坐标法对柔顺半铰动力学建模的有效性；进一步分析了半铰外形尺寸变化对其变形规律的影响。     

控制点CGCS2000坐标的联测及解求

CGCS2000坐标系是我国目前精度最高的坐标系,其推广使用具有重大意义。文中在安装并学习美国高精度GPS基线处理软件GAMIT软件基础上,以4个无坐标信息观测墩为例,进行观测数据采集与数据处理方案的设计,以期获取4个观测墩的CGCS2000坐标。最终结果表明,各质量指标均满足限差要求,且平差后最弱边中误差满足《工程测量规范》(GB50026-2007)三等工程控制网的要求。     

弯曲半径对凸曲面翻边成形及回弹影响的研究

影响曲面翻边成形回弹的因素主要有零件弯曲曲率半径R、凹模圆角半径r以及材料的厚度t,利用Dynaform软件重点模拟零件弯曲曲率半径R对压缩类翻边中的凸曲面直线翻边的成形回弹影响,得出了零件弯曲曲率半径R对曲面翻边的成形回弹影响规律。通过计算机数值模拟得到在R30mm、R45mm和R60mm 3种半径下的成形极限图以及回弹前、后的主应变分布图,并结合试验的结果,得到随着弯曲半径增大而成形的回弹有所改善的结论。     

The HLD Study of Surfactant Partitioning for Oilfield Corrosion Inhibitors

The partitioning of corrosion inhibitor (CI) products is a measure of their potential to protect oilfield pipelines. In this paper the hydrophilic–lipophilic deviation (HLD) model is first used to quantify their partitioning in terms of the characteristic curvature (C _c,act) of a series of anionic (alkoxylated phosphate esters) and cationic (alkoxylated amines, aromatic amines, imidazoline acetates and quaternary amines) actives. This parameter is expressed over a range of pHs within which pipeline corrosion occurs. The HLD model is next used to predict the partitioning of each active from water into toluene at increased salinities. Linear mixing rules are lastly used to predict the characteristic curvature of Product A (C _c,mix) as a function of the C _c,act of a subset of actives.     

Monitoring of degradation of porous silicon photonic crystals using digital photography

We report the monitoring of porous silicon (pSi) degradation in aqueous solutions using a consumer-grade digital camera. To facilitate optical monitoring, the pSi samples were prepared as one-dimensional photonic crystals (rugate filters) by electrochemical etching of highly doped p-type Si wafers using a periodic etch waveform. Two pSi formulations, representing chemistries relevant for self-reporting drug delivery applications, were tested: freshly etched pSi (fpSi) and fpSi coated with the biodegradable polymer chitosan (pSi-ch). Accelerated degradation of the samples in an ethanol-containing pH 10 aqueous basic buffer was monitored in situ by digital imaging with a consumer-grade digital camera with simultaneous optical reflectance spectrophotometric point measurements. As the nanostructured porous silicon matrix dissolved, a hypsochromic shift in the wavelength of the rugate reflectance peak resulted in visible color changes from red to green. While the H coordinate in the hue, saturation, and value (HSV) color space calculated using the as-acquired photographs was a good monitor of degradation at short times (t < 100 min), it was not a useful monitor of sample degradation at longer times since it was influenced by reflections of the broad spectral output of the lamp as well as from the narrow rugate reflectance band. A monotonic relationship was observed between the wavelength of the rugate reflectance peak and an H parameter value calculated from the average red-green-blue (RGB) values of each image by first independently normalizing each channel (R, G, and B) using their maximum and minimum value over the time course of the degradation process. Spectrophotometric measurements and digital image analysis using this H parameter gave consistent relative stabilities of the samples as fpSi > pSi-ch.