On a Bicriterion Server Allocation Problem for a Multidimensional Erlang Loss System

In this work an optimization problem on a classical elementary stochastic system system, modeled as an Erlang-B (M/M/x) loss system, is formulated by using a bicriteria approach. The problem is focused on the allocation of a given total of k servers to a number of groups of servers capable of carrying certain offered traffic processes assumed as Poissonian in nature. Two main objectives are present in this formulation. Firstly a criterion of equity in the grade of service, measured by the call blocking probabilities, entails that the absolute difference between the blocking probabilities experienced by the calls in the different service groups must be as small as possible. Secondly a criterion of system economic performance optimization requires the total traffic carried by the system, to be maximized. Relevant mathematical results characterizing the two objective functions and the set N of the non-dominated solutions, are presented. An algorithm for traveling on N based on the resolution of single criterion convex problems, using a Newton-Raphson method, is also proposed. In each iteration the two first derivatives of the Erlang-B function in the number of circuits (a difficult numerical problem) are calculated using a method earlier proposed. Some computational results are also presented

Equidade e eficiência na optimização de sistemas multidimensionais de Erlang-B

Doutoramento em MatemáticaFormula-se um problema de optimização relativo à afectação de servidores entre grupos funcionais de Erlang-B (M/M/n/0), que ocorre na modelação de sistemas de Teletráfego. Na prática, há normalmente dois objectivos a atingir no dimensionamento de tais sistemas: Maximizar o volume de tráfego transportado (minimizando o tráfego perdido pelo sistema global) e optimizar o grau de serviço (minimizando as probabilidades de bloqueio). Analisa-se o conflito potencial entre os dois objectivos e caracteriza-se o conjunto N das soluções não dominadas do problema. A abordagem do problema de optimização é antecedida de um estudo numérico (cálculo das derivadas da função de Erlang-B) e analítico (propriedades de convexidade do modelo). Estabelecem-se dois métodos numéricos de cálculo das derivadas parciais de primeira e segunda ordem na variável número de servidores (Método da Recursão Completa Generalizada e Método da Recursão Reduzida). Uma análise do erro propagado nessas recursões mostra a notável estabilidade numérica dos processos de cálculo. Extensos resultados computacionais mostram a grande eficiência dos métodos propostos, mesmo para valores elevados dos argumentos. No que toca às propriedades analíticas, estabelece-se o sinal das derivadas parciais de segunda ordem da função tráfego de transbordo num sistema de Erlang-B. A convexidade em cada uma das variáveis é demonstrada no sentido estrito e em todo o domínio, generalizando resultados já conhecidos. É proposto um algoritmo para percorrer N, que usa o método de Newton combinado com uma estratégia especial de determinação das restrições que estão activas em cada óptimo de Pareto.An optimization problem related to the server allocation between Erlang-B functional groups is formulated. This problem occurs in Teletraffic Systems modeling. In applied situations, the design of such a system usually involves two objectives: to minimize the overflow traffic of the global system and to minimize the blocking probabilities. The potential conflict between these objectives is shown and the set N of the non inferior solutions of the problem is characterized. An algorithm for traveling on N is given. This algorithm uses the Newtow- Raphson method together with a special strategy for determining the set of active restrictions for each Pareto optimal solution. Previously to the explanation of this optimization problem, a numerical and analytic study of the model, including the determination of the Erlang-B function derivatives and convexity properties is presented. Two methods are proposed for the numerical evaluation of the first and second order derivatives of the Erlang-B function: Complete Generalized Recursion Method and Reduced Recursion Method. A good numerical stability of both methods is ensured by including a detailed error analysis. Furthermore, extensive computations show the great efficiency of those methods even for high argument values. Concerning the analytic properties, the sign of the second order partial derivatives of the overflow traffic function is established and the strict convexity in each variables is shown

Relative stability of linear systems

In this paper we analyze the evolution of the relative error in the state oflinear systems subject to perturbations. For this purpose we introduce the propertyof relative stability. The relevance of this property is illustrated by means of a casestudy, namely the computation of the Erlang-B function, which is well-known inthe context of Queueing Theory

Stacked Denoising Autoencoders and Transfer Learning for Immunogold Particles Detection and Recognition

In this paper we present a system for the detection of immunogold particles and a Transfer Learning (TL) framework for the recognition of these immunogold particles. Immunogold particles are part of a high-magnification method for the selective localization of biological molecules at the subcellular level only visible through Electron Microscopy. The number of immunogold particles in the cell walls allows the assessment of the differences in their compositions providing a tool to analise the quality of different plants. For its quantization one requires a laborious manual labeling (or annotation) of images containing hundreds of particles. The system that is proposed in this paper can leverage significantly the burden of this manual task. For particle detection we use a LoG filter coupled with a SDA. In order to improve the recognition, we also study the applicability of TL settings for immunogold recognition. TL reuses the learning model of a source problem on other datasets (target problems) containing particles of different sizes. The proposed system was developed to solve a particular problem on maize cells, namely to determine the composition of cell wall ingrowths in endosperm transfer cells. This novel dataset as well as the code for reproducing our experiments is made publicly available. We determined that the LoG detector alone attained more than 84\% of accuracy with the F-measure. Developing immunogold recognition with TL also provided superior performance when compared with the baseline models augmenting the accuracy rates by 10\%

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Percutaneous closure of atrial septal defects. The role of transesophageal echocardiography

PURPOSE: Evaluation of the role of transesophageal echocardiography in percutaneous closure of atrial septal defects (ASD) with the Amplatzer septal occluder. METHODS: Patients were selected for percutaneous closure of ASD by transesophageal echocardiography (TEE), which was also used to monitor the procedure, helping to select the appropriate size of the Amplatzer device, to verify its position, and to access the immediate results of the procedure. During the follow-up, TEE was used to evaluate the presence and magnitude of residual shunt (RS), device position, and right cardiac chamber diameters. RESULTS: Twenty-two (40%) of a total of 55 studied patients were selected. Thirteen underwent Amplatzer device implantation, eight are still waiting for it, and one preferred the conventional surgical treatment. All procedures were successful, which was mainly due to proper patient selection. Six (23%) patients acutely developed RS, which spontaneously disapeared at the three-month follow-up examination in three patients. There was a significant reduction in the right ventricle diastolic diameter, from 27mm (average) to 24mm and 20mm, one and three months after the procedure, respectively (p<0.0076). CONCLUSION: With the aid of TEE, percutaneous closure of ASD can be successfully, safely, and effectively performed