Performability measure for acyclic Markovian models

AbstractContinuous-time Markov processes with a finite-state space are generally considered to model degradable fault-tolerant computer systems. The finite space is partitioned as ∪mi=1 Bi, where Bi stands for the set of states which corresponds to the configuration where the system has a performance level (or reward rate) equal to τi. The performability Yt is defined as the accumulated reward over a mission time [0, t]. In this paper, a renewal equation is established for the performability measure and solved for both “standard” and uniform acyclic models. Two closed form expressions for the performability measure are derived for the two types of models. Furthermore, an algorithm with a low polynomial computational complexity is presented and applied to a degradable computer system

Comment on "Performability analysis: a new algorithm"

The paper “Performability Analysis: A New Algorithm” describes an algorithm for computing the complementary distribution of the accumulated reward over an interval of time in a homogeneous Markov process. In this comment, we show that in two particular cases, one of which is quite frequent, small modifications of the algorithm may reduce significantly its storage complexity.Postprint (published version

Using Interval Constrained Petri Nets and Fuzzy Method for Regulation of Quality: The Case of Weight in Tobacco Factory

The existence of maximal durations drastically modifies the performance evaluation in Discrete Event Systems (DES). The same particularity may be found on systems where the associated constraints do not concern the time. For example weight measures, in chemical industry, are used in order to control the quantity of consumed raw materials. This parameter also takes a fundamental part in the product quality as the correct transformation process is based upon a given percentage of each essence. Weight regulation therefore increases the global productivity of the system by decreasing the quantity of rejected products. In this paper we present an approach based on mixing different characteristics theories, the fuzzy system and Petri net system to describe the behaviour. An industriel application on a tobacco manufacturing plant, where the critical parameter is the weight is presented as an illustration

Primary care management of diabetes in a low/middle income country: A multi-method, qualitative study of barriers and facilitators to care

<p>Abstract</p> <p>Background</p> <p>The management of patients with diabetes mellitus is complex. Some research has been done in developed countries to attempt to determine the factors that influence quality of care of patients with diabetes: Factors thus far postulated are usually categorised into patient, clinician and organisational factors. Our study sought to discover the main barriers and facilitators to care in the management of diabetes in primary care in a low/middle income country.</p> <p>Methods</p> <p>A qualitative study, based on reflexive ethnography using participant observation, semi-structured interviews of clinicians (10) and group interviews with paramedical staff (4) and patients (12) in three purposively sampled health centres, along with informal observation and discussions at over 50 other health centres throughout Tunisia. A content analysis of the data was performed.</p> <p>Results</p> <p>Over 400 potential barriers or facilitators to care of patients with diabetes in primary care in Tunisia emerged. Overall, the most common cited factor was the availability of medication at the health centre. Other frequently observed organisational factors were the existence of chronic disease clinics and clinicians workload. The most commonly mentioned health professional factor was doctor motivation. Frequently cited patient factors were financial issues, patient education and compliance and attendance issues. There were notable differences in the priority given to the various factors by the researcher, physicians, paramedical staff and the patients.</p> <p>Conclusion</p> <p>We have discovered a large number of potential barriers and facilitators to care that may potentially be influencing the care of patients with diabetes within primary care in Tunisia, a low/middle income country. An appreciation and understanding of these factors is essential in order to develop culturally appropriate interventions to improve the care of people with diabetes.</p

Constraints to Economic Development and Growth in the Middle East and North Africa

When comparing the speed and extent of economic development in different geographic regions of the world over the past 20 years, the under-average performance of Arab countries in general and Arab Mediterranean countries in particular is striking. This is despite an overall favorable geo-strategic situation at the crossroads of three continents, with excellent connections to sea and waterways and in direct proximity to the European Union, one of the world’s economic hubs. It is also despite the minor importance of negative factors such as a high-burden diseases or high levels of ethnic fractionalization. In this paper, I focus on identifying the most important constraints on Arab Mediterranean economic development. I use state-of-the-art econometric tools to quantify constraints that have been identified through economic theory and studies of the political economy characteristics of the region. The empirical results offer support for the central hypothesis that limited technological capacities and political economy structures are the primary constraints on economic development. With a view to international structural adjustment efforts, my findings imply that the limited success of the Euro-Mediterranean policy to stimulate the economic development of the Arab Mediterranean countries might be because structural adjustment efforts do not tackle—or at least do not sufficiently tackle— these constraints.Vergleicht man Geschwindigkeit und Umfang der wirtschaftlichen Entwicklung der verschiedenen Weltregionen in den vergangenen zwanzig Jahren, so fällt insbesondere das unterdurchschnittliche Abschneiden der arabischen Länder im Allgemeinen und der arabischen Mittlemeerländer im Besonderen ins Auge, und dies trotz einer insgesamt vorteilhaften geographischen Lage im Schnittpunkt dreier Kontinente mit exzellenten Anschlussmöglichkeiten an See- und Wasserwege, trotz der direkten Nachbarschaft zum Weltwirtschaftsdrehkreuz Europäische Union und trotz der relativ geringen Bedeutung wichtiger entwicklungshemmender Faktoren, beispielsweise ethnische Zersplitterung oder massive Ausbreitung von Krankheiten wie AIDS oder Malaria. In diesem Aufsatz wird versucht, von den unterschiedlichen Hemmfaktoren wirtschaftlicher Entwicklung, die in der wirtschaftstheoretischen Literatur und/oder in MENARegionalstudien diskutiert werden, diejenigen herauszuarbeiten, die wirtschaftliche Entwicklung am stärksten behindern oder möglicherweise stärker als andere. Dabei benutze ich modernste ökonometrische Verfahren, um den Einfluss der verschiedenen erklärenden Variablen zu quantifizieren. Die Ergebnisse stützen die Eingangshypothese, dass insbesondere mangelnde technologische Kapazitäten und Fähigkeiten sowie regionalspezifische politökonomische Strukturen die wirtschaftliche Entwicklung in den arabischen Mittelmeerländern behindern

Chile's export diversification since 1960: A free market miracle or mirage?

Conventional wisdom has proclaimed Chile's recent economic development a 'free market miracle'. In an examination of Chile's export diversification experience, this article departs from that view. By analysing the dynamics underlying the emergence of the salmon, fruit, forestry and wine sectors in Chile's export basket since the 1960s, the study sheds light on the crucial role of industrial policy in the process of capability accumulation that shapes new industries. The article undertakes a qualitative historical analysis of the scope and nature of policy interventions in each of the four sectors and conducts a quantitative policy evaluation using the difference-in-difference method. It finds that public institutions are essential in overcoming market failures inhibiting the emergence of new industries. Specifically, it shows that the government has a key role to play as a catalyst of human capital accumulation, as a venture capitalist, in trade promotion, and in ensuring 'national' sector reputation through a strong regulatory and quality control role. By elaborating on the dynamic process of structural transformation and capability accumulation, this article contributes to theoretical debates on the role of vertical policies in the emergence of new competitive sectors, and debates relating to static versus dynamic approaches to comparative advantage