Reliability Estimation of Open Source Software based Computational Systems

Software systems are progressively being deployed in many facets of human life. The implication of the failure of such systems, has an assorted impact on its customers. The fundamental aspect that supports a software system, is focus on quality. Reliability describes the ability of the system to function under specified environment for a specified period of time and is used to objectively measure the quality. Evaluation of reliability of a computing system involves computation of hardware and software reliability. Most of the earlier works were given focus on software reliability with no consideration for hardware parts or vice versa. However, a complete estimation of reliability of a computing system requires these two elements to be considered together, and thus demands a combined approach. The present work focuses on this and presents a model for evaluating the reliability of a computing system. The method involves identifying the failure data for hardware components, software components and building a model based on it, to predict the reliability. To develop such a model, focus is given to the systems based on Open Source Software, since there is an increasing trend towards its use and only a few studies were reported on the modeling and measurement of the reliability of such products. The present work includes a thorough study on the role of Free and Open Source Software, evaluation of reliability growth models, and is trying to present an integrated model for the prediction of reliability of a computational system. The developed model has been compared with existing models and its usefulness of is being discussed.

The Wrong Kind of Lean: Over-Commitment and Under-Represented Skills on Technology Teams

This paper reports on results from five companies in the aerospace and automotive industries to show that over-commitment of technical professionals and under-representation of key skills on technology development and transition teams seriously impairs team performance. The research finds that 40 percent of the projects studied were inadequately staffed, resulting in weaker team communications and alignment. Most importantly, the weak staffing on these teams is found to be associated with a doubling of project failure rate to reach full production. Those weakly staffed teams that did successfully insert technology into production systems were also much more likely than other teams to have development delays and late engineering changes. The conclusion suggests that the expense of project failure, delay and late engineering changes in these companies must greatly out-weigh the savings gained from reduced staffing costs, and that this problem is likely going to be found in other technology-intensive firms intent on seeing project budgets as a cost to be minimized rather than an investment to be maximized.

Preventive maintenance models with random maintenance quality

In real-world environments it is usually difficult to specify the quality of a preventive maintenance (PM) action precisely. This uncertainty makes it problematic to optimise maintenance policy.-This problem is tackled in this paper by assuming that the-quality of a PM action is a random variable following a probability distribution. Two frequently studied PM models, a failure rate PM model and an age reduction PM model, are investigated. The optimal PM policies are presented and optimised. Numerical examples are also given.

The price of risk in construction projects: contingency approximation model (CAM)

Little attention has been focussed on a precise definition and evaluation mechanism for project management risk specifically related to contractors. When bidding, contractors traditionally price risks using unsystematic approaches. The high business failure rate our industry records may indicate that the current unsystematic mechanisms contractors use for building up contingencies may be inadequate. The reluctance of some contractors to include a price for risk in their tenders when bidding for work competitively may also not be a useful approach. Here, instead, we first define the meaning of contractor contingency, and then we develop a facile quantitative technique that contractors can use to estimate a price for project risk. This model will help contractors analyse their exposure to project risks; and help them express the risk in monetary terms for management action. When bidding for work, they can decide how to allocate contingencies strategically in a way that balances risk and reward.

DGGE with genomic DNA: Suitable for detection of numerically important organisms but not for identification of the most abundant organisms

Identification of all important community members as well as of the numerically dominant members of a community are key aspects of microbial community analysis of bioreactor samples. A systematic study was conducted with artificial consortia to test whether denaturing gradient gel electrophoresis (DGCE) is a reliable technique to obtain such community data under conditions where results would not be affected by differences in DNA extraction efficiency from cells. A total of 27 consortia were established by mixing DNA extracted from Escherichia coli K12, Burkholderia cepacia and Stenotrophomonas maltophilia in different proportions. Concentrations of DNA of single organisms in the consortia were either 0.04, 0.4 or 4 ng/mu l. DGGE-PCR of genomic DNA with primer sets targeted at the V3 and V6-V8 regions of the 16S rDNA failed to detect the three community members in only 7% of consortia, but provided incorrect information about dominance or co-dominance for 85% and 89% of consortia with the primer sets for the V6-V8 and V3 regions, respectively. The high failure rate in detection of dominant B. cepacia with the primers for the V6-V8 region was attributable to a single nucleoticle primer mismatch in the target sequences of both, the forward and reverse primer. Amplification bias in PCR of E. coli and S. maltophilia for the V6-V8 region and for all three organisms for the V3 region occurred due to interference of genomic DNA in PCR-DGGE, since a nested PCR approach, where PCR-DGGE was started from mixtures of 16S rRNA genes of the organisms, provided correct information about the relative abundance of original DNA in the sample. Multiple bands were not observed in pure culture amplicons produced with the V6-V8 primer pair, but pure culture V3 DGGE profiles of E. coli, S. maltophilia and B. cepacia contained 5, 3 and 3 bands, respectively. These results demonstrate DGGE was suitable for identification of all important community members in the three-membered artificial consortium, but not for identification of the dominant organisms in this small community. Multiple DGGE bands obtained for single organisms with the V3 primer pair could greatly confound interpretation of DGGE profiles. (C) 2008 Elsevier Ltd. All rights reserved.

A unified view on lifetime distributions arising from selection mechanisms

In this paper, we formulate a flexible density function from the selection mechanism viewpoint (see, for example, Bayarri and DeGroot (1992) and Arellano-Valle et al. (2006)) which possesses nice biological and physical interpretations. The new density function contains as special cases many models that have been proposed recently in the literature. In constructing this model, we assume that the number of competing causes of the event of interest has a general discrete distribution characterized by its probability generating function. This function has an important role in the selection procedure as well as in computing the conditional personal cure rate. Finally, we illustrate how various models can be deduced as special cases of the proposed model. (C) 2011 Elsevier B.V. All rights reserved.

The complementary exponential power lifetime model

In this paper we propose a new lifetime distribution which can handle bathtub-shaped unimodal increasing and decreasing hazard rate functions The model has three parameters and generalizes the exponential power distribution proposed by Smith and Bain (1975) with the inclusion of an additional shape parameter The maximum likelihood estimation procedure is discussed A small-scale simulation study examines the performance of the likelihood ratio statistics under small and moderate sized samples Three real datasets Illustrate the methodology (C) 2010 Elsevier B V All rights reserved

The complementary exponential geometric distribution: Model, properties, and a comparison with its counterpart

In this paper, we proposed a new two-parameter lifetime distribution with increasing failure rate, the complementary exponential geometric distribution, which is complementary to the exponential geometric model proposed by Adamidis and Loukas (1998). The new distribution arises on a latent complementary risks scenario, in which the lifetime associated with a particular risk is not observable; rather, we observe only the maximum lifetime value among all risks. The properties of the proposed distribution are discussed, including a formal proof of its probability density function and explicit algebraic formulas for its reliability and failure rate functions, moments, including the mean and variance, variation coefficient, and modal value. The parameter estimation is based on the usual maximum likelihood approach. We report the results of a misspecification simulation study performed in order to assess the extent of misspecification errors when testing the exponential geometric distribution against our complementary one in the presence of different sample size and censoring percentage. The methodology is illustrated on four real datasets; we also make a comparison between both modeling approaches. (C) 2011 Elsevier B.V. All rights reserved.

Log-Burr XII regression models with censored data

In survival analysis applications, the failure rate function may frequently present a unimodal shape. In such case, the log-normal or log-logistic distributions are used. In this paper, we shall be concerned only with parametric forms, so a location-scale regression model based on the Burr XII distribution is proposed for modeling data with a unimodal failure rate function as an alternative to the log-logistic regression model. Assuming censored data, we consider a classic analysis, a Bayesian analysis and a jackknife estimator for the parameters of the proposed model. For different parameter settings, sample sizes and censoring percentages, various simulation studies are performed and compared to the performance of the log-logistic and log-Burr XII regression models. Besides, we use sensitivity analysis to detect influential or outlying observations, and residual analysis is used to check the assumptions in the model. Finally, we analyze a real data set under log-Buff XII regression models. (C) 2008 Published by Elsevier B.V.

A simple relation between the Leimkuhler curve and the mean residual life

In this paper, a simple relation between the Leimkuhler curve and the mean residual life is established. The result is illustrated with several models commonly used in informetrics, such as exponential, Pareto and lognormal. Finally, relationships with some other reliability concepts are also presented. (C) 2010 Elsevier Ltd. All rights reserved.

Reliability properties under a stopping time shift

Considering a series representation of a coherent system using a shift transform of the components lifetime T-i, at its critical level Y-i, we study two problems. First, under such a shift transform, we analyse the preservation properties of the non-parametric distribution classes and secondly the association preserving property of the components lifetime under such transformations. (c) 2007 Elsevier B.V. All rights reserved.

A compound class of Weibull and power series distributions

In this paper we introduce the Weibull power series (WPS) class of distributions which is obtained by compounding Weibull and power series distributions where the compounding procedure follows same way that was previously carried out by Adamidis and Loukas (1998) This new class of distributions has as a particular case the two-parameter exponential power series (EPS) class of distributions (Chahkandi and Gawk 2009) which contains several lifetime models such as exponential geometric (Adamidis and Loukas 1998) exponential Poisson (Kus 2007) and exponential logarithmic (Tahmasbi and Rezaei 2008) distributions The hazard function of our class can be increasing decreasing and upside down bathtub shaped among others while the hazard function of an EPS distribution is only decreasing We obtain several properties of the WPS distributions such as moments order statistics estimation by maximum likelihood and inference for a large sample Furthermore the EM algorithm is also used to determine the maximum likelihood estimates of the parameters and we discuss maximum entropy characterizations under suitable constraints Special distributions are studied in some detail Applications to two real data sets are given to show the flexibility and potentiality of the new class of distributions (C) 2010 Elsevier B V All rights reserved

O planejamento e o gerenciamento econômico-financeiros como instrumentos de redução da mortalidade das micro e pequenas empresas - estudo de caso: Restaurante Buongustaio

O presente estudo objetivou identificar as principais causas da mortalidade das micro e pequenas empresas brasileiras e como os instrumentos de planejamento e gerenciamento econômico-financeiros podem reduzir esta mortalidade. Foi realizada pesquisa bibliográfica sobre as micro e pequenas empresas (MPE) em que se identificaram: as definições, as principais características, a importância, as principais necessidades e dificuldades, a taxa de mortalidade e os fatores de mortalidade desse segmento de empresas. Dessa forma, verificou-se que as MPE têm grande importância na economia e sociedade brasileiras. A maioria expressiva (98%) das empresas brasileiras é classificada como MPE, sendo elas responsáveis por 43% da oferta de empregos e por quase a metade de toda a receita e valor da produção do país. O trabalho abordou pesquisas mostrando que as taxas médias de mortalidade das empresas brasileiras são significativas e preocupantes, podendo atingir índices próximos a 60% somente no primeiro ano de sua constituição, em alguns Estados do Brasil. Este fenômeno não pode ser atribuído a um fator isoladamente, mas a um conjunto de fatores ambientais, técnicos, administrativos e outros mais que, combinados, podem ampliar os riscos de fechamento das x empresas. No entanto, grande parte dos estudos aponta problemas de origem financeira como um dos principais fatores condicionantes da mortalidade das MPE. As necessidades mais prementes nas MPE, identificadas na pesquisa bibliográfica, foram: instrumentos de planejamento e gestão, treinamento especializado, capital de giro, crédito a taxas compatíveis com a rentabilidade e formalização dos processos. A pesquisa principal do trabalho é o estudo de caso abordando a experiência vivencial de implantação, planejamento, gerenciamento e controle do Restaurante Buongustaio em Brasília, nos seus 10 meses iniciais de funcionamento. Foram abordadas as principais dificuldades, problemas enfrentados e soluções envolvendo planejamento, gestão, recursos humanos, capital de giro e atendimento a clientes, dentre outros. o estudo de caso possibilitou a aferição de vários conceitos e conteúdos abordados na pesquisa bibliográfica e conclui-se que a utilização dos instrumentos de planejamento e gerenciamento econômico-financeiros, como: plano de negócios, análise econômico-financeira, gerenciamento do fluxo de caixa e de capital de giro, fornece importante contribuição para a sobrevivência e crescimento da micro e pequena empresa, reduzindo o seu risco de falência ou mortalidade prematura.

Análise crítica do sistema de franquias no Brasil

Este estudo procura investigar a atual situação do sistema de franquias no Brasil e propiciar uma maior compreensão das razões que levaram franqueados a desligarem-se de suas redes de franquias. Em primeiro lugar, apresenta-se um referencial teórico. Em seguida, são apresentados os resultados de uma pesquisa exploratória, baseada no Estudo de Casos, realizada junto a onze ex-franqueados de diferentes redes de franquias. Objetiva-se identificar os fatores que geraram a insatisfação com a franquia e os principais motivos de desligamento da rede. Por fim, são apresentadas as limitações e contribuições do estudo, bem como sugestões para estudos futuros.

Educação de jovens e adultos na cidade do Natal: uma reflexão sobre sucesso e insucesso

This essay proposes to research the success and failure in Education for Youth and Adults (known as EJA), based on the approval, failure and evasion rates in public schools belonging to the city of Natal, RN. Reflecting upon the reasons why some pupils from this program were dropping out of school while others kept on studying was a necessity. Therefore, we seek to know these subjects and their school environment. In the search this data, we set off by approaching the EJA politics, going through a historical path, highlighting significant facts to Brazilian and Natal history. While bringing together the pieces of information for this essay, we were lead to the State and City Education Department, in search of approval, failure and evasion rates from the year 2009. Based on these rates, two schools have been chosen: the first with a high failure rate and the second with a failure rate lower than the city average. The schools work was researched throughout the year 2010, through interviews with pupils, teachers, managers and employees; school files analysis; the analysis of files the establish the rules for EJA programs in the city of Natal. Nethertheless, this essay points to inner and outer factors which might come to contribute to the failure or success of pupils from the researched schools, emphasizing that the difference between those are in the team work present in the school with low failure rate