Applying the Mahalanobis-Taguchi strategy for software defect diagnosis

The Mahalanobis-Taguchi (MT) strategy combines mathematical and statistical concepts like Mahalanobis distance, Gram-Schmidt orthogonalization and experimental designs to support diagnosis and decision-making based on multivariate data. The primary purpose is to develop a scale to measure the degree of abnormality of cases, compared to “normal” or “healthy” cases, i.e. a continuous scale from a set of binary classified cases. An optimal subset of variables for measuring abnormality is then selected and rules for future diagnosis are defined based on them and the measurement scale. This maps well to problems in software defect prediction based on a multivariate set of software metrics and attributes. In this paper, the MT strategy combined with a cluster analysis technique for determining the most appropriate training set, is described and applied to well-known datasets in order to evaluate the fault-proneness of software modules. The measurement scale resulting from the MT strategy is evaluated using ROC curves and shows that it is a promising technique for software defect diagnosis. It compares favorably to previously evaluated methods on a number of publically available data sets. The special characteristic of the MT strategy that it quantifies the level of abnormality can also stimulate and inform discussions with engineers and managers in different defect prediction situations.     

Modeling photon transport in fluorescent solar concentrators

Fluorescent solar concentrators (FSC) can concentrate light onto solar cells by trapping fluorescence through total internal reflection. In an ideal FSC, the major obstacle to efficient photon transport is the re‐absorption of the fluorescence emitted. In order to decompose the contribution of different photon flux streams within a FSC, the angular dependent re‐absorption probability is introduced and modeled in this paper. This is used to analyze the performance of different FSC configurations and is also compared with experimental results. To illustrate the application of the modeling, the collection efficiency of ideal devices has also been calculated from the re‐absorption probability and is shown to be useful for estimating non‐ideal losses such as those due to scattering or reflection from mirrors. The results also indicate that among the FSCs studied, the performance of those surrounded by four edge solar cells is close to ideal. The rapid optimization of FSCs has also been presented as another practical application of the models presented in this paper. © 2014 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons, Ltd.     

Growth and energy generation by Enterococcus faecium FAIR-E 198 during citrate metabolism

Citrate metabolism by Enterococcus faecium FAIR-E 198, isolated from Greek Feta cheese, was studied in various growth media containing citrate either in the presence of glucose, or as the sole carbon source, both under aerobic and anaerobic conditions. In de Man-Rogosa-Sharpe (MRS) broth with increasing citrate concentrations, cometabolism of citrate and glucose took place. Glucose was stoichiometrically converted into lactate, while citrate into acetate. Glucose consumption and biomass yield were enhanced with increasing initial citrate concentrations, even though maximum specific growth rate was not. When citrate was used as the sole carbon source in increasing initial concentrations, the main end product was acetate. Small amounts of lactate, formate, ethanol, and acetoin were also produced. In all cases, no significant differences were observed between aerobic and anaerobic conditions. However, when citrate was used as sole carbon source, formate production was favored in the absence of oxygen. The present work shows that E. faecium is able to utilize citrate in synthetic media, either in the presence of glucose or as the sole carbon source, resulting in energy production and the formation of aroma compounds.     

Less Impact Better Service (LIBS)

We discuss a new packet service paradigm, called “Less Impact Better Service” (LIBS). In simple terms, LIBS primarily schedules packets based on the delay they cause and cancels service differentiation policies when the cumulative delay due to prioritization becomes significant for non-prioritized packets. Based on LIBS, we evaluate different service policies that prioritize small packets using different service boundaries and we show that, by and large, LIBS satisfies better a number of applications with diverse demands in delay and throughput. We emphasize on Voice over IP applications, which are delay-sensitive but also utilize small packets and rates. Among other traditional performance measures, we also measure fairness in the context of LIBS, that is, we address the question whether the delay experienced per flow is proportional to the delay caused by that flow. We obtained very promising simulation results.     

General Reversibility

The first and the second author introduced reversible CCS (RCCS) in order to model concurrent computations where certain actions are allowed to be reversed. Here we show that the core of the construction can be analysed at an abstract level, yielding a theorem of pure category theory which underlies the previous results. This opens the way to several new examples; in particular we demonstrate an application to Petri nets.     

Efficient algorithms for checking the atomicity of a run of read and write operations

LetX ₁,...,X _c be variables shared by a number of processorsP ₁,...,P _q that operate in a totally asynchronous and wait-free manner. An operation by a processor is either a write to one of the variables or a read of the values ofall variables. Operations arenot assumed to be instantaneous and may arbitrarily overlap in time. A succession of possibly overlapping operationsa ₁,...,a _n (i.e., a run) is said to be atomic, if these operations can be serialized in a way compatible with any existing precedences among them and so that any read operation returns for each variable the value of the most recent — with respect to the serialization — write operation on this variable. This paper examines the complexity of the combinatorial problem of testing a run for atomicity. First, it is pointed out that when there is only one shared variable or when only one processor is allowed to write to each variable, known theorems lead to polynomial-time algorithms for checking the atomicity of a run (the variable of the time-complexity function is the number of operations in the run). It is then proved that checking atomicity has polynomial-time complexity in the general case of more than one variables and with all processors allowed to read and write each variable. For the proof, the atomicity problem is reduced to the problem of consecutive 1s in matrices. The reduction entails showing a combinatorial result that might be interesting on its own.The research of the first author was partially supported by the European Union ESPRIT Basic Research Projects ALCOM II (contract no. 7141) and Insight II (contract no. 6019).The research of the second author was carried out while he was a student at the University of Patras and also during subsequent visits of his to Patras.     

Continuous systemic secretion of a lysosomal enzyme by genetically modified mouse skin fibroblasts

Cholera toxin from Vibrio cholerae has been shown to increase the secretory immune response when given orally with some antigens in mice and rabbits. The present study was designed to determine if cholera toxin was also an effective mucosal adjuvant in chickens. Tetanus toxoid was chosen as a model antigen, and response was measured by enzyme-linked immunosorbent assays of intestinal excreta, bile samples, and serum samples. Chickens given 20 micrograms of tetanus toxoid had a significant suppression of response when 20 or 50 micrograms of cholera toxin was given. Chickens given 100 micrograms of tetanus toxoid appeared to be mucosally tolerant, but there was apparent abrogation of the mucosal tolerance when 20 or 50 micrograms of cholera toxin was given. Cholera toxin apparently failed as a mucosal adjuvant in chickens but may have some anti-mucosal tolerogenic effect.     

Collaborative work during interventional radiological procedures based on a multicast satellite-terrestrial network.

Collaboration is a key requirement in several contemporary interventional radiology procedures (IRPs). This work proposes a multicast hybrid satellite system capable of supporting advanced IRP collaboration, and evaluates its feasibility and applicability. Following a detailed IRP requirements study, we have developed a system which supports IRP collaboration through the employment of a hybrid satellite-terrestrial network, a prototype multicast version of wavelet based interactive communication system (WinVicos) application, and a partition aggregation and conditional coding (PACC) wavelet codec. A semistructured questionnaire was also used to receive evaluative feedback from collaborating participants. The departments of interventional radiology of University Hospital of Patras, Greece and of Charite Hospital of Berlin, Germany have been connected on the system. Eight interventional radiologists and a vascular surgeon participated periodically in three satellite-terrestrial "fully collaborative" IRPs (average time 90 min) of high complexity and in four terrestrial educational sessions with great success, evidenced by considerable improving the IRP outcomes (clinical and educational). In case of high complexity, where the simultaneous presence of remote interventional expert and/or surgeon is required, advanced collaboration among staff of geographically dispersed international centers is feasible via integration of existing networking and other technologies.     

Survival analysis on the duration of open source projects

ContextOpen source (FLOSS) project survivability is an important piece of information for many open source stakeholders. Coordinators of open source projects would like to know the chances for the survival of the projects they coordinate. Companies are also interested in knowing how viable a project is in order to either participate or invest in it, and volunteers want to contribute to vivid projects.ObjectiveThe purpose of this article is the application of survival analysis techniques for estimating the future development of a FLOSS project.MethodIn order to apply such approach, duration data regarding FLOSS projects from the FLOSSMETRICS (This work was partially supported by the European Community’s Sixth Framework Program under the Contract FP6-033982) database were collected. Such database contains metadata for thousands of FLOSS projects, derived from various forges. Subsequently, survival analysis methods were employed to predict the survivability of the projects, i.e. their probability of continuation in the future, by examining their duration, combined with other project characteristics such as their application domain and number of committers.ResultsIt was shown how probability of termination or continuation may be calculated and how a prediction model may be built to upraise project future. In addition, the benefit of adding more committers to FLOSS projects was quantified.ConclusionAnalysis results demonstrate the usefulness of the proposed framework for assessing the survival probability of a FLOSS project.