A non-LTE argon cascaded arc plasma is studied and modelled with the general plasma simulation program PLASIMO. The structure of PLASIMO is flexible and transparent, so that apart from the study given in the present paper several other multicomponent stationary plasmas in a wide pressure range (10 −3 to 1 bar), from local thermal equilibrium (LTE) to non-LTE, and with different energy coupling mechanisms can be simulated as well. The modular structure is divided into three main parts: the transport part which forms the heart of the model, the plasma configuration part, and the composition part. The latter two parts define the input parameters for the transport part and are controlled by the PLASIMO user. The three parts are again divided into separate modules. The strong modularity makes PLASIMO easy to handle and easy to adjust or expand. Results of PLASIMO applied on the cascaded arc are compared with experimental data and show reasonable agreement. The influence of the boundary conditions on the simulation results is discussed.
In order to improve the realism of our Plasimo computer model [1,2] in modelling multi-ion mixtures, we developed and implemented a self-consistent multicomponent diffusion model based on frictions. As presented, this diffusion model includes effects of the ambipolar electric field as well as any external electric fields. Moreover, it is comparatively easy to include other diffusion contributions. This model was shown to produce good and consistent results for both single and multi-ion mixtures.
We study a blood testing procedure for detecting viruses like HIV, HBV and HCV. In this procedure, blood samples go through two screening steps. The first test is ELISA (antibody Enzyme Linked Immuno-Sorbent Assay). The portions of blood which are found not contaminated in this first phase are tested in groups through PCR (Polymerase Chain Reaction). The ELISA test is less sensitive than the PCR test and the PCR tests are considerably more expensive. We model the two test phases of blood samples as services in two queues in series; service in the second queue is in batches, as PCR tests are done in groups. The fact that blood can only be used for transfusions until a certain expiration date leads, in the tandem queue, to the feature of customer impatience. Since the first queue basically is an infinite server queue, we mainly focus on the second queue, which in its most general form is an S-server M/G [k,K] /S + G queue, with batches of sizes which are bounded by k and K.Our objective is to maximize the expected profit of the system, which is composed of the amount earned for items which pass the test (and before their patience runs out), minus costs. This is done by an appropriate choice of the decision variables, namely, the batch sizes and the number of servers at the second service station. As will be seen, even the simplest version of the batch queue, the M/M [k,K] /1 + M queue, already gives rise to serious analytical complications for any batch size larger than 1. These complications are discussed in detail. In view of the fact that we aim to solve realistic optimization problems for blood screening procedures, these analytical complications force us to take recourse to either a numerical approach or approximations. We present a numerical solution for the queue length distribution in the M/M [k,K] /S +M queue and then formulate and solve several optimization problems. The power-series algorithm, which is a numerical-analytic method, is also discussed.
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