A Proposal for Error Handling in OpenMP

OpenMP has been focused in performance applied to numerical applications, but when we try to move this focus to other kind of applications, like Web servers, we detect one important lack. In these applications, performance is important, but reliability is even more important, and OpenMP does not have any recovery mechanism. In this paper we present a novel proposal to address this lack. In order to add error handling to OpenMP we propose some extensions to the current OpenMP specification. A directive and a clause are proposed, defining a scope for the error handling (where the error can occur) and specifying a behaviour for handling the specific errors. Some examples of use are presented, and we present also an evaluation showing the impact of this proposal in OpenMP applications. We show that this impact is low enough to consider the proposal worthwhile for OpenMP.     

Analysis of DNA content in supraglottic epidermoid carcinoma

DNA analysis by flow cytometry is considered to be of prognostic value in epidermoid carcinoma of the head and neck. However, few and contradictory studies have been made on laryngeal carcinomas. We studied 48 epidermoid carcinomas in patients subjected to horizontal supraglottic laryngectomy with a 5-year- followup. The technique described by Hedley for fixated and paraffin-embedded tumors was used. Thirteen tumors were excluded on the grounds of presenting variation coefficients in excess of 10. Of the 35 cases analyzed, 28 (80%) were diploid and seven (20%) aneuploid. No correlation was observed between tumor ploidy and patient survival, recurrence, or any of the histopathological variables studied.     

Comparing effectiveness and efficiency in technical specifications and maintenance optimization

Optimization of technical specification requirements and maintenance (TS&M) has been found interesting from the very beginning at Nuclear Power Plants (NPPs). However, the resolution of such a kind of optimization problem has been limited often to focus only on individual TS&M-related parameters (STI, AOT, PM frequency, etc.) and/or adopting an individual optimization criterion (availability, costs, plant risks, etc.). Nevertheless, a number of reasons exist (e.g. interaction, similar scope, etc.) that justify the interest to focus on the coordinated optimization of all of the relevant TS&M-related parameters based on multiple criteria.The purpose of this paper is on signifying benefits and improvement areas in performing the coordinated optimization of TS&M through reviewing the effectiveness and efficiency of common strategies for optimizing TS&M at system level. A case of application is provided for a stand-by safety-related system to demonstrate the basic procedure and to extract a number of conclusions and recommendations from the results achieved. Thus, it is concluded that the optimized values depend on the particular TS&M-related parameters being involved and the solutions with the largest benefit (minimum risk or minimum cost) are achieved when considering the simultaneous optimization of all of them, although increased computational resources are also required. Consequently, it is necessary to analyze not only the value reached but also the performance of the optimization procedure through effectiveness and efficiency measures which lead to recommendations on potential improvement areas.     

An Analysis of Internal Parameter Variations Effects on Nanoscaled Gates

The predicted deterioration of the component quality, due to the shrinking of components to near atomic scale, threatens the effectiveness and the applicability of conventional digital system design methodologies in the giga and tera-scale integration era. Three aggression sources support the previous statement: i) the increasing device parameter variability induced by the extreme reduction of the critical feature sizes and the intrinsic nature of new devices; ii) the intense and practically unpredictable internal noise; and iii) the large number of physical defects. This paper provides a detailed analysis of the noise and parameter variations effects on a basic processing gate. We derive formulas to calculate the expected value and the variance of the gate output under the effects of noise, threshold, and gain fluctuations. Using these expressions we also derive a cost-performance equation that evaluates the gate error probability from its parameter variability, noise, power, and area or redundance. The proposed model is generic for any computing gate in the current digital paradigm. To illustrate the model applicability we calculate the error probability curve for a 90 nm CMOS inverter showing that for this technology the noise is the main limiting factor. A tradeoff analysis of area-power-redundancy-reliability for nanogates is performed indicating that the use of nanoscale individual elements for fabricating gates in deep-nanoscale technologies may not be a viable option. The results clearly suggest that the use of redundant structures is necessary and that averaging structures with mid-high redundancy factors may constitute a reasonable solution for building reliable nanoscale gates.     

An approach to integrating surveillance and maintenance tasks to prevent the dominant failure causes of critical components

Surveillance requirements and maintenance activities in a nuclear power plant aim to preserve components' inherent reliability. Up to now, predictive and preventive maintenance mainly concerned plant staff, but the US Nuclear Regulatory Commission Maintenance Rule released in July 1991 will have significant impact on how nuclear power plants perform and document this maintenance. Reliability Centered Maintenance (RCM) is a systematic methodology to establish maintenance tasks for critical components in plant with a high degree of compliance with the goals of the Rule. RCM pursues the identification of applicable and efficient tasks to prevent these components from developing their dominant failure causes, and, in turn, towards achieving proper levels of components availability with low cost. In this paper, we present an approach for identifying the most suitable set of tasks to achieve this goal, which involves the integration of maintenance activities and surveillance requirements for each critical component based on the unavailability and cost associated with each individual task which is performed on it.     

Design optimization of a safety-instrumented system based on RAMS+C addressing IEC 61508 requirements and diverse redundancy

This paper presents the design optimization by a multi-objective genetic algorithm of a safety-instrumented system based on RAMS+C measures. This includes optimization of safety and reliability measures plus lifecycle cost. Diverse redundancy is implemented as an option for redundancy allocation, and special attention is paid to its effect on common cause failure and the overall system objectives. The requirements for safety integrity established by the standard IEC 61508 are addressed, as well as the modelling detail required for this purpose. The problem is about reliability and redundancy allocation with diversity for a series-parallel system. The objectives to optimize are the average probability of failure on demand, which represents the system safety integrity, Spurious Trip Rate and Lifecycle Cost. The overall method is illustrated with a practical example from the chemical industry: a safety function against high pressure and temperature for a chemical reactor. In order to implement diversity, each subsystem is given the option of three different technologies, each technology with different reliability and diagnostic coverage characteristics. Finally, the optimization with diversity is compared against optimization without diversity.     

Age-dependent reliability model considering effects of maintenance and working conditions

Nowadays, there is some doubt about building new nuclear power plants (NPPs). Instead, there is a growing interest in analyzing the possibility to extend current NPP operation, where life management programs play an important role. The evolution of the NPP safety depends on the evolution of the reliability of its safety components, which, in turn, is a function of their age along the NPP operational life. In this paper, a new age-dependent reliability model is presented, which includes parameters related to surveillance and maintenance effectiveness and working conditions of the equipment, both environmental and operational. This model may be used to support NPP life management and life extension programs, by improving or optimizing surveillance and maintenance tasks using risk and cost models based on such an age-dependent reliability model. The results of the sensitivity study in the example application show that the selection of the most appropriate maintenance strategy would directly depend on the previous parameters. Then, very important differences are expected to appear under certain circumstances, particularly, in comparison with other models that do not consider maintenance effectiveness and working conditions simultaneously.