FTSyn: a framework for automatic synthesis of fault-tolerance

In this paper, we present a software framework for adding fault-tolerance to existing finite-state programs. The input to our framework is a fault-intolerant program and a class of faults that perturbs the program. The output of our framework is a fault-tolerant version of the input program. Our framework provides (1) the first automated tool for the synthesis of fault-tolerant distributed programs, and (2) an extensible platform for researchers to develop a repository of heuristics that deal with the complexity of adding fault-tolerance to distributed programs. We also present a set of heuristics for polynomial-time addition of fault-tolerance to distributed programs. We have used this framework for automated synthesis of several fault-tolerant programs including a simplified version of an aircraft altitude switch, token ring, Byzantine agreement, and agreement in the presence of Byzantine and fail-stop faults. These examples illustrate that our framework can be used for synthesizing programs that tolerate different types of faults (process restarts, Byzantine and fail-stop) and programs that are subject to multiple faults (Byzantine and fail-stop) simultaneously. We have found our framework to be highly useful for pedagogical purposes, especially for teaching concepts of fault-tolerance, automatic program transformation, and the effect of heuristics.     

Development of a physical employment standard for a branch of the UK military

Abstract

A Physical Employment Standard (PES) was developed for the British Royal Air Force Regiment (RAF Regt). Twenty-nine RAF Regt personnel completed eight critical tasks wearing Combat Equipment Fighting Order (31.5?kg) while being monitored for physical and perceptual effort. A PES was developed using task simulations, measured on 61 incumbents. The resultant PES consists of: 1) a battlefield test involving task simulations: single lift and point-of-entry (psss/fail); timed elements (react to effective enemy fire and crawl) set at 95th performance percentile; casualty evacuation (CASEVAC) casualty drag and CASEVAC simulated stretcher carry completed without stopping. 2) a Multi Stage Fitness Test level 9.10 to assess aerobic fitness to complete a tactical advance to battle. The task-based PES should ensure RAF Regt personnel have a baseline level of fitness to perform and withstand the physical demands of critical tasks to at least a minimum acceptable standard.

Practitioner summary: A Physical Employment Standard (PES) was developed for the British RAF Regiment by measuring the physiological demands of critical tasks on a representative cohort of incumbent personnel. A task-based PES should ensure that only those candidates, irrespective of gender, race or disability, with the necessary physical attributes to succeed in training and beyond, are selected.     

APACS: a system for the automatic analysis and classification of conceptual patterns

Many existing inductive learning systems have been developed under the assumption that the learning tasks are performed in a noise-free environment. To cope with most real-world problems, it is important that a learning system be equipped with the capability to handle uncertainty. In this paper, we first identify the various sources of uncertainty that may be encountered in a noisy problem domain. Next, we present a method for the efficient acquisition of classification rules from training instances which may contain inconsistent, incorrect, or missing information. This algorithm consists of three phases: ( i ) the detection of inherent patterns in a set of noisy training data; ( ii ) the construction of classification rules based on these patterns; and ( iii ) the use of these rules to predict the class membership of an object. The method has been implemented in a system known as APACS (automatic pattern analysis and classification system). This system has been tested using both real-life and simulated data, and its performance is found to be superior to many existing systems in terms of efficiency and classification accuracy. Being able to handle uncertainty in the learning process, the proposed algorithm can be employed for applications in real-world problem domains involving noisy data.     

Laboratory work with automatic pipettes: a study on how pipetting affects the thumb

Abstract

The aim of this study was to assess the strain that is exerted on the thumb when working with automatic pipettes. The study consisted of three parts: a survey concerning stress-related symptoms in general and in the thumb in particlar, a study of the working conditions in the laboratory with the help of a video-film, and a power test. In the survey the Nordic Council of Ministers’ questionnaire and a newly developed questionnaire about the thumb were used. A usual and frequently carried out analysis that included several different methods of pipetting was filmed on video. The power test measured two things, the power that is necessary to press down the button of the pipette into different positions and the maximal strength when performing a movement in the same direction. It was shown that the strain on the thumb for a woman with weak muscular structures is unacceptably high. The symptoms increase with the amount of time spent with pipetting and with age. In addition, pipetting is done in a position where the thumb is not stable but nevertheless has to work to stabilize the grip around the pipette and to press down the button of the pipette. Therefore the muscles have to work both as mobilizing and stabilizing structures. It is concluded, therefore, that some form of automation ought to be taken into consideration if the amount of pipetting work tends to increase. The pipettes should be constructed with as little button resistance as possible and the handle should be designed to fit different hand sizes.     

Performability analysis of guarded-operation duration: a translation approach for reward model solutions

Performability measures are often defined for analyzing the worth of fault-tolerant systems whose performance is gracefully degradable. Accordingly, performability evaluation is inherently well suited for application of reward model solution techniques. On the other hand, the complexity of performability evaluation for solving engineering problems may prevent us from utilizing those techniques directly, suggesting the need for approaches that would enable us to exploit reward model solution techniques through problem transformation. In this paper, we present a performability modeling effort that analyzes the guarded-operation duration for onboard software upgrading. More specifically, we define a “performability index” Y that quantifies the extent to which the guarded operation with a duration φ reduces the expected total performance degradation. In order to solve for Y, we progressively translate its formulation until it becomes an aggregate of constituent measures conducive to efficient reward model solutions. Based on the reward-mapping-enabled intermediate model, we specify reward structures in the composite base model which is built on three stochastic activity network reward models. We describe the model-translation approach and show its feasibility for design-oriented performability modeling.     

State of the art on automatic road extraction for GIS update: a novel classification

This paper surveys the state of the art on automatic road extraction for GIS update from aerial and satellite imagery. It presents a bibliography of nearly 250 references related to this topic. The work includes main approaches on general methods of road network extraction and reconstruction, road tracking methods, morphological analysis, dynamic programming and snakes, methods multi-scale and multi-resolution, stereoscopic and multi-temporal analysis, hyper-spectral experiments, and other techniques for road extraction. Likewise, other approaches related in any way with the road extraction topic are also considered. Between them different papers on segmentation, vectorization, optimization, evaluation, semantic nets and neural networks, fusion techniques, fuzzy logic, and other methods are discussed. A novel classification of road extraction methods according to our criteria is included in order to provide a significant contribution to research in this topic.     

Fully polynomial time approximation scheme for the weighted flow-time minimization on a single machine with a fixed non-availability interval

In a recent paper [Theoretical Computer Science 363, 257–265], He, Zhong and Gu considered the non-resumable case of the scheduling problem with a fixed non-availability interval under the non-resumable scenario. They proposed a polynomial time approximation scheme (PTAS) to minimize the total completion time.In this paper, we propose a fully polynomial-time approximation scheme to minimize the total weighted completion time. The FPTAS has O(n²/ε²) time complexity, where n is the number of jobs and ε is the required error bound. The proposed FPTAS outperforms all the previous approximation algorithms designed for this problem and its running time is strongly polynomial.     

An automatic method for controlling the centre of gravity of a model

In many applications the location of the centre of gravity of a mechanical part is an important factor that a designer must consider. If it is not in a desired location, a part might not work properly, e.g. unbalanced force might be generated in a rotational part. After a part is modeled, its centre of gravity cannot be altered unless its external shape or internal mass distribution is changed. However, the external shape is usually constrained by other design considerations. In this paper, an algorithm is proposed for controlling the centre of gravity of a hollowed part. Using this algorithm, the location of the centre of gravity of a part is controlled by changing its internal mass distribution.     

MDWiZ: A platform for the automated translation of molecular dynamics simulations

A variety of popular molecular dynamics (MD) simulation packages were independently developed in the last decades to reach diverse scientific goals. However, such non-coordinated development of software, force fields, and analysis tools for molecular simulations gave rise to an array of software formats and arbitrary conventions for routine preparation and analysis of simulation input and output data. Different formats and/or parameter definitions are used at each stage of the modeling process despite largely contain redundant information between alternative software tools. Such Babel of languages that cannot be easily and univocally translated one into another poses one of the major technical obstacles to the preparation, translation, and comparison of molecular simulation data that users face on a daily basis. Here, we present the MDWiZ platform, a freely accessed online portal designed to aid the fast and reliable preparation and conversion of file formats that allows researchers to reproduce or generate data from MD simulations using different setups, including force fields and models with different underlying potential forms. The general structure of MDWiZ is presented, the features of version 1.0 are detailed, and an extensive validation based on GROMACS to LAMMPS conversion is presented. We believe that MDWiZ will be largely useful to the molecular dynamics community. Such fast format and force field exchange for a given system allows tailoring the chosen system to a given computer platform and/or taking advantage of a specific capabilities offered by different software engines.     

Fully Discrete Analysis of a Discontinuous Finite Element Method for the Keller-Segel Chemotaxis Model

This paper formulates and analyzes fully discrete schemes for the two-dimensional Keller-Segel chemotaxis model. The spatial discretization of the model is based on the discontinuous Galerkin methods and the temporal discretization is based either on Forward Euler or the second order explicit total variation diminishing (TVD) Runge-Kutta methods. We consider Cartesian grids and prove fully discrete error estimates for the proposed methods. Our proof is valid for pre-blow-up times since we assume boundedness of the exact solution.     

An algorithm for automatic checking of exercises in a dynamic geometry system: iGeom

One of the key issues in e-learning environments is the possibility of creating and evaluating exercises. However, the lack of tools supporting the authoring and automatic checking of exercises for specifics topics (e.g., geometry) drastically reduces advantages in the use of e-learning environments on a larger scale, as usually happens in Brazil. This paper describes an algorithm, and a tool based on it, designed for the authoring and automatic checking of geometry exercises. The algorithm dynamically compares the distances between the geometric objects of the student’s solution and the template’s solution, provided by the author of the exercise. Each solution is a geometric construction which is considered a function receiving geometric objects (input) and returning other geometric objects (output). Thus, for a given problem, if we know one function (construction) that solves the problem, we can compare it to any other function to check whether they are equivalent or not. Two functions are equivalent if, and only if, they have the same output when the same input is applied. If the student’s solution is equivalent to the template’s solution, then we consider the student’s solution as a correct solution. Our software utility provides both authoring and checking tools to work directly on the Internet, together with learning management systems. These tools are implemented using the dynamic geometry software, iGeom, which has been used in a geometry course since 2004 and has a successful track record in the classroom. Empowered with these new features, iGeom simplifies teachers’ tasks, solves non-trivial problems in student solutions and helps to increase student motivation by providing feedback in real time.