Influence of maintenance policies on multi-stage manufacturing systems in dynamic conditions

Manufacturing systems are subject to a degradation process that leads to machine failure if no action is taken. Machine failures reduce the performance of the manufacturing system with loss of profits. The research proposed here concerns the evaluation of the manufacturing system performance in dynamic conditions when different maintenance policies are implemented in a multi-machine manufacturing system controlled by multi-agent-architecture. There are two extreme maintenance policies that can be applied: no preventive maintenance, where action is taken on the failure state, and intensive preventive maintenance, which can eliminate unforeseen failures, but at a high cost. Dynamic policy maintenance is proposed to reduce the number of maintenance operations of the preventive policy. A discrete simulation environment has been developed in order to investigate the performance measures and the indexes of the costs of maintenance policies. The simulations have been conducted for several levels of mix, product demand and working time uncertainty. The simulation results show that the proposed approach leads to better performance for the manufacturing system and reduces the number of maintenance operations (cost index of the maintenance policy), except in the case of the mean time between failure, which is characterised by a very low standard deviation.     

A mathematical model of wound healing and subsequent scarring

Wound healing is a complex process involving the delicate interaction between elements that vary widely in nature and size scales, from the nanometre level, such as molecules, to cells measured in micrometres, and fibres with width and length measured on both scales. Hybrid approaches, where each species is represented by a model on an appropriate size scale, have received attention recently. In this study, we provide a review of earlier work on such hybrid models of wound healing. General models for each of the element types involved in dermal wound healing used in this research are described: cells, modelled as discrete individuals; chemicals, modelled as continua; and fibres, modelled with a novel tensorial representation. Techniques for integrating such disparate models are outlined. A six-species model (fibrin, collagen, macrophages, fibroblasts, transforming growth factor-β (TGF-β) and tissue plasminogen activator) of dermal wound healing is presented. The role of the cytokine TGF-β in the healing cascade is investigated using the model, along with its role in the degree of scarring in the healed tissue.     

数控加工仿真中的优化离散矢量模型

数控加工仿真是利用计算机模拟数控加工的过程。采用离散知音一法可以有较好的实时性和观察性。但在采用离散矢量法时，离散模型的建立对仿真的效果有很大的影响。而对于常用的彩和均匀离散方式建立起来的仿真模型，对仿真精度与仿真速度的要求无法同时得到满足，本文采用了一种基于非均匀离散的优化模型可以有效地解决此点不足，并将详细论述这种仿真模型的建立、数据更新及其显示等内容。     

Pluronic lecithin organogel of 5-aminosalicylic acid for wound healing

5-Aminosalicylic acid (5-ASA) is an aminosalicylate anti-inflammatory drug, which is also known as mesalazine or mesalamine. Currently employed in treating inflammatory bowel disease, ulcerative colitis, inflamed anus or rectum, and maintain remission in Crohn's disease. Evidence from the researchers highlighted its significant re-epithelization in allergic asthma, aphthous, and gastric ulcerative conditions. The objective of the study was to formulate the pluronic lecithin organogel (PLO) containing 5-ASA and evaluate its wound-healing ability in a full thickness excision wound rat model. The data obtained from in silico docking studies revealed 5-ASA is having an affinity towards the transforming growth factor-beta (TGF-β) specifically towards beta1. Among various formulations prepared (F1 to F8), F1, and F6 have shown a maximum in vitro drug release with optimum pH and viscosity. From MTT assay it was found that selected PLO formulations showed no toxicity and enhanced cell proliferation in HaCaT cell lines. In vivo wound-healing studies in albino Wistar rats has revealed that PLO accelerates wound closure and reepithelization to the statistically significant level on day 3 (p?相似文献   

Aerosol-based efficient delivery of telithromycin,a ketolide antimicrobial agent,to lung epithelial lining fluid and alveolar macrophages for treatment of respiratory infections

Purpose: The efficacy of aerosol-based delivery of telithromycin (TEL), as a model antimicrobial agent, for the treatment of respiratory infections was evaluated by comparison with oral administration. Method: The aerosol formulation (0.2 mg/kg) was administered to rat lungs using a Liquid MicroSprayer®. Results and discussion: The time courses of the concentration of TEL in lung epithelial lining fluid (ELF) and alveolar macrophages (AMs) following administration of an aerosol formulation to rat lungs were markedly higher than that following the administration of an oral formulation (50 mg/kg). The time course of the concentrations of TEL in plasma following administration of the aerosol formulation was markedly lower than that in ELF and AMs. These results indicate that the aerosol formulation is more effective in delivering TEL to ELF and AMs, compared to the oral formulation, despite a low dose and it avoids distribution of TEL to the blood. In addition, the antibacterial effects of TEL in ELF and AMs following administration of the aerosol formulation were estimated by pharmacokinetics/pharmacodynamics analysis. The concentrations of TEL in ELF and the AMs time curve/minimum inhibitory concentration of TEL ratio were markedly higher than the effective values. Conclusion: This study indicates that an antibiotic aerosol formulation may be an effective pulmonary drug delivery system for the treatment of respiratory infections.     

自动化集装箱码头运输系统配置的仿真优化

以新型自动化集装箱码头中间运输系统为研究对象,建立了自动化集装箱码头中间运输系统的仿真优化模型,并利用仿真优化方法搜索优化调度方案,最小化船舶靠岸后装卸作业的总时间和最大化各种设备的操作效率,优化模块使用遗传算法,整个程序使用C#语言编制.通过仿真计算表明能够非枚举地从所有可能的动态调度方案中搜到最佳方案:运输系统的设备利用率、系统作业时间,都得到了相应改善.     

水平圆筒型混合机中颗粒混合的离散模拟

采用离散模型模拟了水平圆筒型混合机中 10 0 0个颗粒混合的全过程 ,分析了颗粒流型的变化规律和混合曲线 ,得到了颗粒由相对静止到开始下滑的塌落过程 ,所得结果与已知实验结果符合很好 ,这有助于揭示混合机内部颗粒的运动规律     

密集到达下的预约决策的仿真研究

为了分析在密集到达情况下的预约决策的效果,研究针对不同场景的合理预约方式。通过现场调研及历史数据统计,选用9种预约规则,利用离散系统仿真设置分析了11组预约率与3种人数密集到达情况相结合的33种场景。以等待时间为评价指标汇总仿真实验数据,分析得到了预约规则−密集到达人数−预约率三者相关联的变化规律,以及在各场景下的最佳预约规则类型。针对密集到达下预约系统的设计,以及选择合理的预约规则等方面总结了规律并给出相应改善建议。     

Simulation of capacity and cost for the planning of future process chains

One of the most promising approaches in modern microelectronics is the introduction of 3D chip micro systems with through-silicon via (TSV) interconnections. A successful transfer of this technology from the scientific level up to the level of mass production is not least of all a matter of cost-effectiveness and profit, which is directly related to high productivity. The developed technologies therefore have to be feasible for effective mass production. In this paper we introduce a method for planning and evaluating costs in future process chains. This method goes beyond usual mostly Excel-supported solutions, as it is based on a discrete event simulation system. The simulation model is generically generated out of an XML process chain definition file and includes a sophisticated state model for machines. Multiple process scenarios are created with the help of a supporting software tool. These scenarios are investigated for achieving favourable equipment and process chain configurations as well as control strategies to support manufacturing ramp-ups.     

拆除爆破数值模拟研究进展

评述了数值模拟技术在拆除爆破中应用的重要性,回顾了拆除爆破数值模拟的主要方法,论述了各种方法的优缺点。结合工程应用实例介绍了笔者及团队研发的离散元框架内的网格实体模型。分析了当前拆除爆破数值模拟技术存在的主要问题,对拆除爆破数值模拟技术的进一步发展进行了展望。     

DFT的装配车间生产物流策略仿真与研究

针对某汽车部件的实际装配生产,运用离散事件仿真的方法对基于需求流动技术(DFT)的装配生产物流策略进行了研究.在分析该汽车部件装配生产流程的基础上,确定eM-Plant仿真软件中的建模对象与装配生产系统中实体对象的对应关系,使用面向对象的方法建立了相应的离散事件仿真模型.在模型中分别实施基于推式生产方式的物流策略和基于DFT的物流策略,以该汽车部件的平均日产量为绩效指标,比较了两种物流策略对装配生产的影响.     

Advances in Numerical Simulation of Demolition Blasting

The application of numerical simulation in demolition blasting was commented. The main methods of numerical simulation in demolition blasting were reviewed. The advantages and disadvantages of the numerical methods mentioned in this paper were also indicated, respectively. Furthermore, the 3D DEM model, which was developed by the author together with his group, was detailed illustrated. The existed problems in the current numerical simulation methods of demolition blasting were presented and the trend of the further development was finally forecasted.     

时效组织演化的计算机模拟理论与模型

总结了时效组织的计算机模拟研究,基于Cahm-Hillard的非经典转变理论,提出一种新的动力学模型,不同于以往的连续介质模型,为离散格点形式,可租用于时效过程的所有阶段,包括形核、长大、粗化等,模型还可描述原子有序化和相分离,并考虑到弹性能对形貌演化和粗化过程的影响,且体积分数的影响、沉淀颗粒间的相互作用也在方程中自动体现。     

Preparation,characterization, and in vivo evaluation of nano formulations of ferulic acid in diabetic wound healing

Diabetes mellitus is most common disorder characterize by hyperglycemia. Chronic hyperglycemia may lead to over production of free radicals thereby results in oxidative stress which impaired healing of wounds. Ferulic acid (FA) has been shown to have antidiabetic and antioxidant properties. The aim of the present study was to develop Ferulic acid nanoparticles and to study its hypoglycemic and wound healing activities. Ferulic acid-poly(lactic-co-glycolic acid) (FA-PLGA) nanoparticles were prepared by nano precipitation method. The prepared FA-PLGA nanoparticles had an average size of 240?nm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis showed the prepared FA-PLGA nanoparticles were spherical in shape. Drug encapsulation assay showed that 88.49% FA was encapsulated in PLGA. Carbopol 980 was used to formulate FA-PLGA nanoparticles loaded hydrogel. FA-loaded polymeric nanoparticles dispersion (oral administration) and FA-loaded polymeric nanoparticles based hydrogel (topical administration) treated wounds were found to epithelize faster as compared with diabetic wound control group. The hydroxyproline content increased significantly when compared with diabetic wound control. Therefore, the results indicate that FA significantly promotes wound healing in diabetic rats.     

回转窑内颗粒轴向混合运动的数值模拟

为了研究不同粒径颗粒在水平回转窑内轴向混合运动机理,采用离散元软件EDEM对窑内颗粒轴向混合过程进行数值模拟,引入颗粒接触数动态跟踪颗粒的混合过程,以大、小颗粒接触数来衡量颗粒间的混合程度。结果表明:活动层内颗粒的运动速度较大;小颗粒轴向运动的主要方式是透过大颗粒间的间隙向大颗粒群渗透。     

A model based approach to assess the performance of production systems in degraded mode

Nowadays production systems are asked to perform their activities in a high uncertainty environment and to guarantee their performance in this environment. Therefore, they are asked to master risks that are part of their daily activities, to maintain the performance which is considered as their key success factor. Risks may cause serious effects that threaten the production systems and degrade their performance. Nevertheless, we cannot estimate the degradation that a risk may cause to system performance, since risk analysis methods found in the literature do not allow simulating the behaviour of the system in degraded mode. In order to help production systems to assess their performance in risk situations, we propose in this paper a model-based approach that enables assessing the performance of production systems in degraded mode. Our approach is based on function, interaction, structure (FIS) modelling framework that enables modelling complex system and its failures. The resulting model is converted into an executable simulation model based on a new class of Petri Nets (PNs) called predicate-transition, prioritised, synchronous (PTPS) PN. The obtained simulation model is then executed in order to obtain performance indicators in degraded mode. This tool is used during the system design, in order to study the impact of risks on the designed production system performance. It is also used to study an existing production system in order to analyse and optimise its behaviour in degraded mode. In this article, we present our tool and apply it to a special case of production systems which is a hospital sterilisation system.     

机械应力刺激对体外肺腺癌细胞增殖的影响

通过FX-4000柔性基底加载系统研究了不同波形的周期性拉伸对人肺腺癌A549细胞株增殖的影响,应用Image—pro图像处理软件对A549细胞株在心形波、三角波及方波等拉伸应变下的增殖动力学变化进行了分析。实验结果表明：在collagenⅠ基底膜上,应变为0％～20％,频率为0．5Hz及1．0Hz,加载时间为2h时,与对照组比较,方波刺激组细胞生长明显受到抑制,三角波与心形波刺激组细胞增殖率无明显差异。研究表明：A549细胞株对体外的生理应变作出响应时,方波的抑制作用最佳,而拉伸频率的影响并不明显。     

Unravelling the anticancer efficacy of 10-oxo-7-epidocetaxel: in vitro and in vivo results

Purpose: To prepare 7-epidocetaxel (7ED) and 10-oxo-7-epidocetaxel (10-O-7ED) formulations as like marketed Taxotere® (TXT) injection and to screen them for in vitro and in vivo anticancer efficacy including their in vivo toxicity behavior.

Methods: The 7ED and 10-O-7ED formulations were screened for in vitro anti-proliferative, anti-metastatic and cell cycle arresting behaviors. Further, in vivo acute toxicity of TXT injection containing 10% of 7ED and 10-O-7ED separately and the therapeutic study of 10-O-7ED alone were studied in B16F10 experimental metastasis mouse model.

Results: 10-O-7ED caused significantly higher cytotoxicity after 48 and 72?h than 22?h study. 10-O-7ED showed significantly increased in vitro anti-metastatic activity than TXT. The TXT caused more arrest of cells at S phase, whereas 10-O-7ED arrested more at G2-M phase and vice versa at higher concentration. In vivo acute toxicity study revealed better therapeutic effect with reduced toxicity of TXT containing 10% 10-O-7ED than TXT alone. Similarly, the therapeutic study revealed significantly less number of surface metastatic nodules formation with 10-O-7ED treated group (107?±?49) (***p?<?.0001) than control group (348?±?56). Also, the control group showed significant weight loss at the end (20th day) of the experiment (*p?<?.05, p?=?.041) than 10-O-7ED treated group which showed about 4% increased mean group weight.

Conclusion: Our study revealed the significantly higher in vivo anti-metastatic behavior, with no toxicity, of 10-O-7ED. However, it is a preliminary observation being noticed but further investigations are needed to address the potential of 10-O-7ED in cancer treatment with mechanisms behind the improved therapeutic efficacy with no toxicity.     

人—飞机—环境系统模拟中数学模型的研究与分析

通过对人－飞－环境模拟仿真技术中人操作的数学模型及“人－飞机－环境”操纵系统的数学模型的研究,具体分析了人的传递函数模型,最佳控制模型,模糊控制模型的适应范围及优缺点,并在对、人－飞机－环境”操纵系统的数学模型,性能指标进行分析后,提出了确定驾驶员和飞机之间最佳匹配的“人－飞机－环境”操纵系统计算机模拟综合评估系统,从而使人们一开始设计飞机时就考虑驾驶员作用,养活主设计盲目性,缩短设计周期,尤其在目前,先进技术的广泛应用使 飞机出现一些非常常规的运动,故更需进行人－机闭环综合分析,才能到做各系统功能合理分配,充分发挥飞机的整体效能。