The Strangest Thing About Software

Although there are times when random search is dangerous and should be avoided, software analysis should start with random methods because they are so cheap, moving to the more complex methods only when random methods fail     

The effects of prior experience on the use of consumer products

Many products today are laden with a host of features which, for the majority of users, remain unused and often obscure the use of the simple features of use for which the product was devised (Norman in The design of everyday things. Basic Books, 2002; Keates and Clarkson in Countering design exclusion—an introduction to inclusive design. Springer, 2004). Since the cognitive capabilities of the marketed target group are largely not affected by age-related impairment, the intellectual demands of such products are frequently high (Rabbitt in Quart J Exp Psychol 46A(3):385–434, 1993). In addition, the age and technology generation of a product user will colour their expectations of the product interface and affect the range of skills they have available (Docampo in Technology generations handling complex User Interfaces. Ph. D. thesis, 2001). This paper addresses the issue of what features of products make them easy or difficult to learn to use, for the wider population as well as the older user, and whether and in what way individual prior experience affect the learning and use of a product design. To achieve the above, the interactions of users of varying ages and capabilities with two different everyday products were recorded in detail as they performed set tasks. Retrospective verbal protocols were then analysed using a category scheme based on an analysis of types of learning and cognition errors. This data was then compared with users’ performance on individual detailed experience questionnaires and a number of tests of general and specific cognitive capabilities. The principal finding was that similarity of prior experience to the usage situation was the main determinant of performance, although there was also some evidence for a gradual, age-related capability decline. Users of all ages adopted a means-end or trial and error interaction when faced with unfamiliar elements of the interaction. There was a strong technology generation effect such that older users were reluctant or unable to complete the required tasks for a digital camera.     

Estimating rate of occurrence of rare events with empirical bayes: A railway application

Classical approaches to estimating the rate of occurrence of events perform poorly when data are few. Maximum likelihood estimators result in overly optimistic point estimates of zero for situations where there have been no events. Alternative empirical-based approaches have been proposed based on median estimators or non-informative prior distributions. While these alternatives offer an improvement over point estimates of zero, they can be overly conservative. Empirical Bayes procedures offer an unbiased approach through pooling data across different hazards to support stronger statistical inference.This paper considers the application of Empirical Bayes to high consequence low-frequency events, where estimates are required for risk mitigation decision support such as as low as reasonably possible. A summary of empirical Bayes methods is given and the choices of estimation procedures to obtain interval estimates are discussed. The approaches illustrated within the case study are based on the estimation of the rate of occurrence of train derailments within the UK. The usefulness of empirical Bayes within this context is discussed.     

The Bayes linear approach to inference and decision-making for a reliability programme

In reliability modelling it is conventional to build sophisticated models of the probabilistic behaviour of the component lifetimes in a system in order to deduce information about the probabilistic behaviour of the system lifetime. Decision modelling of the reliability programme requires a priori, therefore, an even more sophisticated set of models in order to capture the evidence the decision maker believes may be obtained from different types of data acquisition.Bayes linear analysis is a methodology that uses expectation rather than probability as the fundamental expression of uncertainty. By working only with expected values, a simpler level of modelling is needed as compared to full probability models.In this paper we shall consider the Bayes linear approach to the estimation of a mean time to failure MTTF of a component. The model built will take account of the variance in our estimate of the MTTF, based on a variety of sources of information.     

3-D model-based frame interpolation for distributed video coding of static scenes.

This paper addresses the problem of side information extraction for distributed coding of videos captured by a camera moving in a 3-D static environment. Examples of targeted applications are augmented reality, remote-controlled robots operating in hazardous environments, or remote exploration by drones. It explores the benefits of the structure-from-motion paradigm for distributed coding of this type of video content. Two interpolation methods constrained by the scene geometry, based either on block matching along epipolar lines or on 3-D mesh fitting, are first developed. These techniques are based on a robust algorithm for sub-pel matching of feature points, which leads to semi-dense correspondences between key frames. However, their rate-distortion (RD) performances are limited by misalignments between the side information and the actual Wyner-Ziv (WZ) frames due to the assumption of linear motion between key frames. To cope with this problem, two feature point tracking techniques are introduced, which recover the camera parameters of the WZ frames. A first technique, in which the frames remain encoded separately, performs tracking at the decoder and leads to significant RD performance gains. A second technique further improves the RD performances by allowing a limited tracking at the encoder. As an additional benefit, statistics on tracks allow the encoder to adapt the key frame frequency to the video motion content.     

Microwave modeling and validation in food thawing applications

Developing temperature fields in frozen cheese sauce undergoing microwave heating were simulated and measured. Two scenarios were investigated: a centric and offset placement on the rotating turntable. Numerical modeling was performed using a dedicated electromagnetic Finite Difference Time Domain (FDTD) module that was two-way coupled to the PHYSICA multiphysics package. Two meshes were used: the food material and container were meshed for the heat transfer and the microwave oven cavity and waveguide were meshed for the microwave field. Power densities obtained on the structured FDTD mesh were mapped onto the unstructured finite volume method mesh for each time-step/turntable position. On heating for each specified time-step the temperature field was mapped back onto the FDTD mesh and the electromagnetic properties were updated accordingly. Changes in thermal/electric properties associated with the phase transition were fully accounted for as well as heat losses from product to cavity. Detailed comparisons were carried out for the centric and offset placements, comparing experimental temperature profiles during microwave thawing with those obtained by numerical simulation.     

Software criticality analysis of COTS/SOUP

This paper describes the Software Criticality Analysis (SCA) approach that was developed to support the justification of using commercial off-the-shelf software (COTS) in a safety-related system. The primary objective of SCA is to assess the importance to safety of the software components within the COTS and to show there is segregation between software components with different safety importance. The approach taken was a combination of Hazops based on design documents and on a detailed analysis of the actual code (100 kloc). Considerable effort was spent on validation and ensuring the conservative nature of the results. The results from reverse engineering from the code showed that results based only on architecture and design documents would have been misleading.     

An Accelerated Genetic Algorithm

The standard Genetic Algorithm, originally inspired by natural evolution, has displayed its effectiveness in solving a wide variety of complex problems. This paper describes the use of the natural phenomenon known as the Baldwin effect (or cross-generational learning) as an enhancement to the standard Genetic Algorithm. This is implemented by using an artificial neural network to store aspects of the population's history. It also describes a method by which the negative side effects of a large elite sub-population can be counter-balanced by using an ageing coefficient in the fitness calculation.     

Oxidation of ferrocyanide by birnessite

The Fe-CN complexes ferrocyanide, [FeII(CN)6]4-, and ferricyanide, [FeIII(CN)6]3-, which are contaminants in soil and groundwater, form a redox couple, [FeII(CN)6]4- <==> [FeIII(CN)6]3- + e-, E(H) = 356 mV. We studied the oxidation of [FeII(CN)6]4- by birnessite, delta-MnIVO2, in batch experiments as influenced by [FeII(CN)6]4- concentration, pH, and reaction time. Additionally, stopped-flow experiments were carried out at five temperatures (10-30 degrees C) and four pH values (pH 4.1-5.3). In the batch experiments, [FeII(CN)6]4- was completely oxidized to [FeIII(CN)6]3-, and oxidation did neither depend on time for t > 2 min, nor on concentration (0.12-0.47 mM), nor on pH (pH 3.3-9.9). Lasting adsorption of Fe-CN complexes on the birnessite surface or precipitation of manganese ferricyanide were not detected. Manganous ions resulting from the reductive dissolution of birnessite did not precipitate as manganese oxide because an identical decrease of Mn solution concentrations was observed under air and under a N2 atmosphere. Two processes were detected by the stopped-flow experiments. The first rapid one with an activation energy of approximately 60 kJ mol(-1) was attributed to short-term adsorption and simultaneous oxidation of [FeII(CN)6]4- on the birnessite surface. The second slower process with an activation energy of approximately 20 kJ mol(-1) was attributed most probably to diffusion of the reaction product Mn2+ into the interior of the birnessite, which creates fresh reaction sites at the outer surface.