螺栓拧紧方法及预紧力控制

石化、炼油企业装置上的静密封结构以螺栓法兰垫片连接系统为主,检修期间螺栓拧紧方法的选择和预紧力的正确控制对保证装置的安全运行至关重要。本文介绍了实际生产中常用的扭矩法、螺母转角法和液压拉伸法的基本原理,并给出了各种预紧力的控制方法及其所能达到的精度,对安装和维修有一定的指导意义。     

Entanglement Tightening and Stress Relaxation

The contribution of entanglements to the modulus of a time independent polymer is satisfactorily accounted for by the C₂/λ term in the Mooney-Rivlin equation. On the other hand, the role of entanglements in time dependent polymers is less evident and seems to give rise to a non-linear Mooney plot. A model is introduced which considers an entanglement as a topological knot that tightens with initial deformation and subsequently inhibits chain slippage. The observed maximum in a Mooney plot at small values of λ is predicted, and the experimental data of plasticised PVC polybutadiene and styrenebutadiene copolymer are fitted reasonably well.     

Tightening piecewise McCormick relaxations for bilinear problems

We address nonconvex bilinear problems where the main objective is the computation of a tight lower bound for the objective function to be minimized. This can be obtained through a mixed-integer linear programming formulation relying on the concept of piecewise McCormick relaxation. It works by dividing the domain of one of the variables in each bilinear term into a given number of partitions, while considering global bounds for the other. We now propose using partition-dependent bounds for the latter so as to further improve the quality of the relaxation. While it involves solving hundreds or even thousands of linear bound contracting problems in a pre-processing step, the benefit from having a tighter formulation more than compensates the additional computational time. Results for a set of water network design problems show that the new algorithm can lead to orders of magnitude reduction in the optimality gap compared to commercial solvers.     

风电紧固件的腐蚀与防护

风力发电作为替代世界传统能源的清洁能源之一,近几年来在我国发展迅猛。风电紧固件是实现发电机组装的最重要装配方式;由于其生存环境的特殊性已引起若干形态的腐蚀破坏,紧固件防腐技术的开发及应用已经成为当前重要课题。本文概括阐述了紧固件生存特点、腐蚀机理、常规防腐措施的局限性及风电紧固件防腐技术现状,并概括描述达克罗涂层的工作原理及优缺点。     

热塑性塑料和液体硅橡胶精密注射螺杆

2012年1月,汇集有约100家注塑厂商的Molding2012研讨会在美国佛罗里达州迈阿密举行。在为期两天半的研讨会上提出了医疗器械成型、液体硅橡胶（LSR）成型、微模塑、新兴技术、特种材料、能源管理、可持续发展和“绿色”模塑等27个主题。但是,总的来说这些主题相对集中于成型过程中怎样获得更佳的控制。两位演讲者在研讨会上提出了更为新颖的办法,用以提高加工热塑性塑料和液体硅橡胶制品的精密度。     

玻璃熔窑二次紧碹原因分析与实施

结合工作实践,分析了玻璃熔窑二次紧碹出现问题的原因,针对二次紧碹提出了整改措施,简要论述了采取措施后的效果。     

利用限位支架和冷紧法降低配管投资

介绍在化工装置的管道设计中合理地利用限位支架和冷紧法,既可降低配管耗材、节省投资,又能提高装置的安全性。     

有拧紧力矩复合材料单钉接头疲劳寿命预测

通过对有拧紧力矩复合材料单钉接头疲劳加载过程应力分析及材料三维疲劳失效准则损伤判定,并结合建立的疲劳加载材料退化模型、材料性能退化方法及复合材料接头最终失效判据,建立了基于三维累积损伤分析的层合板接头疲劳载荷作用下寿命预测方法。最后,对拉-拉疲劳载荷作用下有拧紧力矩层合板接头的疲劳寿命及破坏模式进行了模拟分析,并与试验结果进行了对比,结果表明,建立的寿命预测方法能够很好地预测有拧紧力矩复合材料单钉接头的寿命以及破坏模式。     

加强窑炉后期管理,延长窑炉运行周期

介绍用QC小组活动的方式和方法来加强玻璃窑炉的后期管理，达到延长窑炉运行周期、提高企业经济效益的目标。     

Tightening methods for continuous‐time mixed‐integer programming models for chemical production scheduling

Important advances in modeling chemical production scheduling problems have been made in recent years, yet effective solution methods are still required. We use an algorithm that uses process network and customer demand information to formulate powerful valid inequalities that substantially improve the solution process. In particular, we extend the ideas recently developed for discrete‐time formulations to continuous‐time models and show that these tightening methods lead to a significant decrease in computational time, up to more than three orders of magnitude for some instances. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4461–4467, 2013     

Inhibiting Invasion into Human Bladder Carcinoma 5637 Cells with Diallyl Trisulfide by Inhibiting Matrix Metalloproteinase Activities and Tightening Tight Junctions

Diallyl trisulfide (DATS), an organosulfur compound in garlic, possesses pronounced anti-cancer potential. However, the anti-invasive mechanism of this compound in human bladder carcinoma is not fully understood. In this study, we evaluated the anti-invasive effects of DATS on a human bladder carcinoma (5637) cell line and investigated the underlying mechanism. The results indicated that DATS suppressed migration and invasion of 5637 cells by reducing the activities and expression of matrix metalloproteinase (MMP)-2 and MMP-9 at both the protein and mRNA levels. DATS treatment up-regulated expression of tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 in 5637 cells. The inhibitory effects of DATS on invasiveness were associated with an increase in transepithelial electrical resistance and repression of the levels of claudin family members. Although further studies are needed, our data demonstrate that DATS exhibits anti-invasive effects in 5637 cells by down-regulating the activity of tight junctions and MMPs. DATS may have future utility in clinical applications for treating bladder cancer.     

一种全新的控制方案简介

随着工业的各个领域陆续向大型化方向的发展,对自动化控制的要求越来越高,而各种自控系统也因此得到了快速发展。我们熟知的DCS系统和PLC系统每年都在大量地装备于各种自动化系统工程中。由于用户对电控、仪控一体化及管理控制一体化的需求,也由于信息技术的发展和高集成度控制系统的需求,加上PC机技术的日臻完善普及使其性能价格比日益提高,为一种全新的自控系统方案──PC－based Control的快速发展提供了非常有利的条件和广阔的市场前景,为众多用户提供了除DCS和PLC以外的另一种自控系统方案。 PC－based Control,顾名思…     

调节阀噪音的控制方法

通过分析调节阀噪音的几种来源,指出阻塞流引起的闪蒸和气蚀是产生流体动力学噪音的根源。利用图形分析了阻塞流引起闪蒸和气蚀的机理,详述闪蒸和气蚀工况调节阀噪音的各种控制方法。     

距离控制技术在电梯控制系统的应用

以艾默生CT EV3100电梯专用变频器为例介绍距离控制技术在电梯控制系统中的应用。结合距离控制技术及电梯逻辑控制的基本原理,确定了选型,进行了相关参数设置,并分析了系统应用过程中的实际问题。     

复配釜温度控制系统的DMC-PID控制

针对常规PID控制策略在复配釜內化学反应的吸热升温阶段和放热保温阶段的转折处难以取得满意控制效果的问题,提出了利用多变量动态矩阵控制(DMC)算法实现对设定温度的跟踪控制.进一步引入了DMC-PID控制策略,以改善系统的控制性能,实现了对设定温度的有效跟踪控制.最后通过试验研究,验证了本文方法的有效性.     

涂料生产中的计量和称重控制

主要论述涂料生产中计量和称重的控制方式和组成。     

分布式控制系统控制策略与回路组态方法的对比研究

介绍分布式控制系统的几种有代表性的回路组态方法，包括：数字调节器的POL语言编程法、集散控制系统（DCS）的填表法以及现场总线控制系统（FCS）的图形功能块连接法等，并揭示出其内部实现机理。同时，对三种系统结构中采用的输入／输出补偿、自适应控制功能以及各种变形的或先进的PID控制算法及其实现技术作了综合对比研究。最后指出：未来过程控制的发展将更多地依赖于新的控制概念和策略。     

控制回路中气动调节阀的选用

介绍了气动调节阀选择的几个因素。根据化工生产的工艺条件,选择合适的调节阀结构和类型;根据工艺对象,选择合适的流量特性;根据工艺参数,计算流量系数,选择阀的口径;根据工艺要求,选择材料和辅助装置。     

串级调速

我公司为5000t／d预分解熟料生产线,采用北京紫御湾科技有限公司设计的全数字机组串级调速系统,对部分风机进行了节能技术改造,效果明显。现将机组串级调速介绍如下。