Application of a reliability model generator to a pressure tank system

A number of mathematical modelling techniques exist which are used to measure the performance of a given system, by assessing each individual component within the system. This can be used to determine the failure frequency or probability of failure of the system. Software is available to undertake the task of analysing these mathematical models after an individual or group of individuals manually create the models. The process of generating these models is time consuming and reduces the impact of the model on the system design. One way to improve this would be to automatically generate the model. In this work the procedure to automatically construct a model, based on Petri nets, for systems undergoing a phased-mission is applied to a pressure tank system, undertaking a four phase mission

Automated generation of a reliability model for a system undertaking phased missions

There are various mathematical models available to assess the reliability of a given system, these models relate the performance of the system to the performance of the components of which it is comprised and can be used to determine the failure probability or failure frequency of the system in question. Currently there is software available to perform the mathematical analysis of the model but its construction, which is used as input to the software, is undertaken manually. This is quite a lengthy process and can limit the usefulness of the model. One way of improving this situation would be to automate the construction process. In this work a procedure is developed to automatically generate a reliability model, based upon Petri Nets, for a system undertaking a phased mission

Application of a reliability model generator to a pressure tank system

A number of mathematical modelling techniques exist which are used to measure the performance of a given system, by assessing each individual component within the system. This can be used to determine the failure frequency or probability of failure of the system. Software is available to undertake the task of analysing these mathematical models after an individual or group of individuals manually create the models. The process of generating these models is time consuming and reduces the impact of the model on the system design. One way to improve this would be to automatically generate the model. In this work the procedure to automatically construct a model, based on Petri nets, for systems undergoing a phased-mission is applied to a pressure tank system, undertaking a four phase mission

Automatic construction of a reliability model for a phased mission system

There are a number of mathematical modelling techniques available to determine the reliability of any system design, for example Fault Trees, Event Trees etc. These models relate the performance of the system to the performance of the components of which it is comprised and are generally quite difficult to construct. Once constructed the analysis of the models can be performed using commercially available software. This stage of the analysis is well developed and can be performed efficiently. The model construction however is a lengthy process and reduces the impact of the reliability study on the system design. One way of improving this situation would be to automate the construction process. In this work a procedure is developed to automatically generate a reliability model, based upon Petri Nets, for a system undertaking a phased mission

Reliability modelling of PEM fuel cells with hybrid Petri nets

In this paper, a novel model for dynamic reliability analysis of a PEM fuel cell system is developed using Modelica language in order to account for multi-state dynamics and aging. The modelling approach constitutes the combination of physical and stochastic sub-models with shared variables. The physical model consist of deterministic calculations of the system state described by variables such as temperature, pressure, mass flow rates and voltage output. Additionally, estimated component degradation rates are also taken into account. The non-deterministic model, on the other hand, is implemented with stochastic Petri nets which represent different events that can occur at random times during fuel cell lifetime. A case study of effects of a cooling system on fuel cell performance was investigated. Monte Carlo simulations of the process resulted in a distribution of system parameters, thus providing an estimate of best and worst scenarios of a fuel cell lifetime

Modeling of fluid flow in periodic cell with porous cylinder using a boundary element method

© 2016 Elsevier Ltd. All rights reserved.The problem of viscous incompressible flow past a periodic array of porous cylinders (a model of flow in an aerosol filter) is solved. The approximate periodic cell model of Kuwabara is used to formulate the fluid flow problem. The Stokes flow model is then adopted to model the flow outside the cylinder and the Darcy law of drag is applied to find the filtration velocity field inside the porous cylinder. The boundary value problems for biharmonic and Laplace equations for stream functions outside and inside the porous cylinder are solved using a boundary elements method. A good agreement of numerical and analytical models is shown. The analytical formulas for the integrals in the expressions for the stream function, vorticity and Cartesian velocity components are obtained. It is shown that the use of analytical integration gives considerable advantage in computing time

Influence of chronic L-DOPA treatment on immune response following allogeneic and xenogeneic graft in a rat model of Parkinson's disease

Although intrastriatal transplantation of fetal cells for the treatment of Parkinson’s disease had shown encouraging results in initial open-label clinical trials, subsequent double-blind studies reported more debatable outcomes. These studies highlighted the need for greater preclinical analysis of the parameters that may influence the success of cell therapy. While much of this has focused on the cells and location of the transplants, few have attempted to replicate potentially critical patient centered factors. Of particular relevance is that patients will be under continued L-DOPA treatment prior to and following transplantation, and that typically the grafts will not be immunologically compatible with the host. The aim of this study was therefore to determine the effect of chronic L-DOPA administered during different phases of the transplantation process on the survival and function of grafts with differing degrees of immunological compatibility. To that end, unilaterally 6-OHDA lesioned rats received sham surgery, allogeneic or xenogeneic transplants, while being treated with L-DOPA before and/or after transplantation. Irrespective of the L-DOPA treatment, dopaminergic grafts improved function and reduced the onset of L-DOPA induced dyskinesia. Importantly, although L-DOPA administered post transplantation was found to have no detrimental effect on graft survival, it did significantly promote the immune response around xenogeneic transplants, despite the administration of immunosuppressive treatment (cyclosporine). This study is the first to systematically examine the effect of L-DOPA on graft tolerance, which is dependent on the donor-host compatibility. These findings emphasize the importance of using animal models that adequately represent the patient paradigm

Systematic and detailed analysis of behavioural tests in the rat Middle Cerebral Artery Occlusion (MCAO) model of stroke: tests for long-term assessment

In order to test therapeutics, functional assessments are required. In pre-clinical stroke research, there is little consensus regarding the most appropriate behavioural tasks to assess deficits; especially when testing over extended times in milder models with short occlusion times and small lesion volumes. In this study we comprehensively assessed 16 different behavioural tests, with the aim of identifying those that show robust, reliable and stable deficits for up to 2 months. These tasks are regularly used in stroke research, as well as being useful for examining striatal dysfunction in models of Huntington’s and Parkinson’s disease. Two cohorts of male Wistar rats underwent the intraluminal filament model of MCAO (30min) and were imaged 24hrs later. This resulted in primarily subcortical infarcts, with a small amount of cortical damage. Animals were tested, along with sham and naïve groups at 24hrs, 7 days, and 1 and 2 months. Following behavioural testing, brains were processed and striatal neuronal counts were performed alongside measurements of total brain and white matter atrophy. The staircase, adjusting steps, rotarod and apomorphine induced rotations were the most reliable for assessing long-term deficits in the 30 min transient MCAO model of stroke