Imperfect repair in degradation processes: A Kijima‐type approach

We consider a Wiener process with linear drift for degradation modeling. Regularly, maintenance actions are carried out which produce a reduction of the degradation level. In this paper, we consider the influence of such maintenance actions to the further development of the degradation process and the resulting lifetime distribution. A connection between virtual age in Kijima‐type models and degradation level in the underlying degradation process is developed. Furthermore, estimators for the process parameters as well as for the degree of repair are developed.     

Optimal warranty policies for systems with imperfect repair

We investigate a system whose basic warranty coverage is minimal repair up to a specified warranty length. An additional service is offered whereby first failure is restored up to the consumers’ chosen level of repair. The problem is studied under two system replacement strategies: periodic maintenance before and after warranty. It turns out that our model generalizes the model of Rinsaka and Sandoh [K. Rinsaka, H. Sandoh, A stochastic model with an additional warranty contract, Computers and Mathematics with Applications 51 (2006) 179–188] and the model of Yeh et al. [R.H. Yeh, M.Y. Chen, C.Y. Lin, Optimal periodic replacement policy for repairable products under free-repair warranty, European Journal of Operational Research 176 (2007) 1678–1686]. We derive the optimal maintenance period and optimal level of repair based on the structures of the cost function and failure rate function. We show that under certain assumptions, the optimal repair level for additional service is an increasing function of the replacement time. We provide numerical studies to verify some of our results.     

Organ Repair,Hemostasis, and In Vivo Bonding of Medical Devices by Aqueous Solutions of Nanoparticles

Sutures are traumatic to soft connective tissues, such as liver or lungs. Polymer tissue adhesives require complex in vivo control of polymerization or cross‐linking reactions and currently suffer from being toxic, weak, or inefficient within the wet conditions of the body. Herein, we demonstrate using Stöber silica or iron oxide nanoparticles that nanobridging, that is, adhesion by aqueous nanoparticle solutions, can be used in vivo in rats to achieve rapid and strong closure and healing of deep wounds in skin and liver. Nanoparticles were also used to fix polymer membranes to tissues even in the presence of blood flow, such as occurring after liver resection, yielding permanent hemostasis within a minute. Furthermore, medical devices and tissue engineering constructs were fixed to organs such as a beating heart. The simplicity, rapidity, and robustness of nanobridging bode well for clinical applications, surgery, and regenerative medicine.     

Improving Site‐Directed RNA Editing In Vitro and in Cell Culture by Chemical Modification of the GuideRNA

Adenosine‐to‐inosine deamination can be re‐addressed to user‐defined mRNAs by applying phosphothioate/2′‐methoxy‐modified guideRNAs. Dense chemical modification of the guideRNA clearly improves performance of the covalent conjugates inside the living cell. Furthermore, careful positioning of a few modifications controls editing selectivity in vitro and was exploited for the challenging repair of the Factor 5 Leiden missense mutation.     

Biodegradable thermogel as culture matrix of bone marrow mesenchymal stem cells for potential cartilage tissue engineering

Poly（lactide-co-glycolide）-poly（ethylene glycol）-poly（lactide-co-glycolide）（PLGA-PEG-PLGA） triblock copolymer was synthesized through the ring-opening polymerization of LA and GA with PEG as macroinitiator and stannous octoate as catalyst. The amphiphilic copolymer self-assembled into micelles in aqueous solutions, and formed hydrogels as the increase of temperature at relatively high concentrations（〉 15 wt%）. The favorable degradability of the hydrogel was confirmed by in vitro and in vivo degradation experiments. The good cellular and tissular compatibilities of the thermogel were demonstrated. The excellent adhesion and proliferation of bone marrow mesenchymal stem cells endowed PLGA-PEGPLGA thermogelling hydrogel with fascinating prospect for cartilage tissue engineering.     

GO法在固体激光器可靠性分析中的应用

对高功率半导体泵浦固体激光器(DPL)系统的可靠性进行了分析,根据GO法的原理构建了DPL系统的GO图;利用GO法计算公式,得到了系统故障率和平均无故障工作时间等重要可靠性指标。结果符合实验室经验值。最后分析了各部件的故障率的重要度,讨论了改善高功率DPL系统可靠性的措施,对系统的使用和维修等工作具有参考意义。     

A periodical replacement model based on cumulative repair‐cost limit

This paper considers a periodical replacement model based on a cumulative repair‐cost limit, whose concept uses the information of all repair costs to decide whether the system is repaired or replaced. The failures of the system can be divided into two types. One is minor failure that is assumed to be corrected by minimal repair, while the other is serious failure where the system is damaged completely. When a minor failure occurs, the corresponding repair cost is evaluated and minimal repair is then executed if this accumulated repair cost is less than a pre‐determined limit L, otherwise, the system is replaced by a new one. The system is also replaced at scheduled time T or at serious failure. Long‐run expected cost per unit time is formulated and the optimal period T* minimizing that cost is also verified to be finite and unique under some specific conditions. Copyright © 2007 John Wiley & Sons, Ltd.     

建筑施工高处坠落的原因及对策

高处坠落事故是建筑施工伤亡事故的主要原因之一,有效防止高处坠落事故对预防建筑施工安全事故有着十分重要的意义.本文针对建筑施工高处坠落事故现象,进行了原因分析,并提出预防高处坠落的具体措施.     

基于累积损伤过程的不完全预防维护决策

基于累积损伤过程研究旧系统的不完全预防维护策略,冲击服从非时齐Poisson过程,并产生随机的损伤量,损伤量是加法累加的.系统在累积损伤量达到k或系统运行年龄达到T时进行计划内预防维护.在两次计划内预防维护之间,当累积损伤量达到预定水平K (k K)时,对系统进行计划外维护,其费用高于计划内预防维护,利用再生过程理论得到单位时间维护成本,讨论在时齐Poisson过程下的时间预防维护策略与水平预防维护策略,同时给出算例.     

Automatic CAD model topology generation

Computer aided design (CAD) models often need to be processed due to the data translation issues and requirements of the downstream applications like computational field simulation, rapid prototyping, computer graphics, computational manufacturing, and real‐time rendering before they can be used. Automatic CAD model processing tools can significantly reduce the amount of time and cost associated with the manual processing. The topology generation algorithm, commonly known as CAD repairing/healing, is presented to detect commonly found geometrical and topological issues like cracks, gaps, overlaps, intersections, T‐connections, and no/invalid topology in the model, process them and build correct topological information. The present algorithm is based on the iterative vertex pair contraction and expansion operations called stitching and filling, respectively, to process the model accurately. Moreover, the topology generation algorithm can process manifold as well as non‐manifold models, which makes the procedure more general and flexible. In addition, a spatial data structure is used for searching and neighbour finding to process large models efficiently. In this way, the combination of generality, accuracy, and efficiency of this algorithm seems to be a significant improvement over existing techniques. Results are presented showing the effectiveness of the algorithm to process two‐ and three‐dimensional configurations. Copyright © 2006 John Wiley & Sons, Ltd.