Historical perception as a complementary framework for understanding the usability of mobile computers

This paper suggests a social-psychological framework for understanding the usability of mobile computers. This framework complements and extends extant sociological explanations of mobile computing. Sociological explanations satisfy principles of pragmatism and ubiquity in judging the usability of mobile computers. The paper argues that sociological explanations are inadequate, and draws upon the historical epistemology of perception to propose social-psychological explanations to complement them. By this epistemology, a user’s perception is deemed as a mode of action that is mediated by historical or functional representations. These issues are illustrated in an empirical case of the use of personal digital assistants (PDAs) in hospitals of the British National Health Service. The historical epistemology of perception suggests the principle of representation to complement the existing principles of ubiquity and pragmatism. This suggestion is derived from an analysis of the complementation between the user’s perception, work and movement which are conscious actions enacted concurrently during the use of mobile computers. Implications for the implementation and evaluation of mobile computing projects are provided.     

Empirical comparison of three metrics suites for fault prediction in packages of object-oriented systems: A case study of Eclipse

Packages are important high-level organizational units for large object-oriented systems. Package-level metrics characterize the attributes of packages such as size, complexity, and coupling. There is a need for empirical evidence to support the collection of these metrics and using them as early indicators of some important external software quality attributes. In this paper, three suites of package-level metrics (Martin, MOOD and CK) are evaluated and compared empirically in predicting the number of pre-release faults and the number of post-release faults in packages. Eclipse, one of the largest open source systems, is used as a case study. The results indicate that the prediction models that are based on Martin suite are more accurate than those that are based on MOOD and CK suites across releases of Eclipse.     

Detection and characterization of defects using GMR probes and artificial neural networks

This work presents an eddy-current testing system based on a giant magnetoresistive (GMR) sensing device. Non-destructive tests in aluminum plates are applied in order to extract information about possible defects: cracks, holes and other mechanical damages. Eddy-current testing (ECT) presents major benefits such as low cost, high checking speed, robustness and high sensitivity to large classes of defects. Coil based architecture probes or coil-magnetoresistive probes are usually used in ECT. In our application the GMR sensor is used to detect a magnetic field component parallel to a plate surface, when an excitation field perpendicular to the plate is imposed. A neural network processing architecture, including a multilayer perceptron and a competitive neural network, is used to classify defects using the output amplitude of the eddy-current probe (ECP) and its operation frequency. The crack detection, classification and estimation of the geometrical characteristics, for different classes of defects, are described in the paper.     

Structural and properties of nanocrystalline WO3/TiO2-based humidity sensors elements prepared by high energy activation

Nanocrystalline WO₃/TiO₂-based powders have been prepared by the high energy activation method with WO₃ concentration ranging from 1 to 10 mol%. The samples were thermal treated in a microwave oven at 600 °C for 20 min and their structural and micro-structural characteristics were evaluated by X-ray diffraction, Raman spectroscopy, EXAFS measurements at the Ti K-edge, and transmission electron microscopy. Nitrogen adsorption isotherms and H₂ Temperature Programmed Reduction were also carried out for physical characterization. The crystallite and particle mean sizes ranged from 30 to 40 nm and from 100 to 190 nm, respectively. Good sensor response was obtained for samples with at least 5 mol% WO₃ activated for at least 80 min. Ceramics heat-treated in microwave oven for 20 min have shown similar sensor response as those prepared in conventional oven for 120 min, which is highly cost effective. These results indicate that WO₃/TiO₂ ceramics can be used as a humidity sensor element.     

A new transparent Bio-MEMS for uni-axial single cell stretching

A novel, completely transparent bio-MEMS (bio-Micro Electro Mechanical System) device has been devised and manufactured using finite element analysis (FEA) and micro-fabrication techniques. The device has been designed to be used for testing the mechanical properties of single living cells, it is versatile and suitable for coupling with other analysis techniques. Furthermore, being completely transparent, it can be used with either transmission or reflection microscopes. The transparent bio-MEMS is based on a silicon dioxide?Csilicon nitride structure and, since the main goal is to test living cells, it is meant to work in a liquid environment and allow for cell stretching. Sensors for cell deformation and for platform displacement are also present and the required sensitivity for single cell analyses is granted. The device will moreover allow the recording of the stress?Cstrain curve for single living cells.     

Reliability and validity of an ergonomics-related Job Factors Questionnaire

Musculoskeletal disorders are an important cause of work disability and absenteeism. Specific job factors or tasks may increase the likelihood of developing work-related musculoskeletal disorders. The purpose of the present study was to translate and adapt a Job Factors Questionnaire for the Brazilian–Portuguese language and evaluate its psychometric properties. A cross-cultural adaptation was performed according to an internationally recommended methodology involving translation, synthesis, back-translation, revision by an expert committee, and pre-testing. The psychometric properties were evaluated by administering the questionnaire to 148 employees at two companies involved in the assembly and fabrication of metal products. The reliability of the questionnaire was assessed by measuring the temporal stability through a test–retest design. Construct validity was assessed using the known-groups technique and by comparing workers responses with findings from the Nordic Questionnaire. Reliability was determined to be satisfactory based on Intraclass Correlation Coefficients ranging from 0.54 to 0.73. Construct validity analysis demonstrated a significant difference (p ≤ 0.02) between production and office workers on answers to 10 questionnaire items, and a significant difference (p ≤ 0.01) on the scores of the adapted questionnaire between subjects that indicated presence or absence of musculoskeletal symptoms. The results indicated that the adapted version of the questionnaire had psychometric properties that were acceptable for use in occupational studies involving workers that speak Brazilian–Portuguese.

Relevance to industry

The present study provides results of a cross-cultural adaptation process and a psychometric properties analysis of an instrument that verifies workers' perception of job factors that may lead to work-related pain and discomfort.     

Surface mesh regeneration considering curvatures

This work describes an automatic algorithm for unstructured mesh regeneration on arbitrarily shaped three-dimensional surfaces. The arbitrary surface may be: a triangulated mesh, a set of points, or an analytical surface (such as a collection of NURBS patches). To be generic, the algorithm works directly in Cartesian coordinates, as opposed to generating the mesh in parametric space, which might not be available in all the cases. In addition, the algorithm requires the implementation of three generic functions that abstractly represent the supporting surface. The first, given a point location, returns the desired characteristic size of a triangular element at this position. The second method, given the current edge in the boundary-contraction algorithm, locates the ideal apex point that forms a triangle with this edge. And the third method, given a point in space and a projection direction, returns the closest point on the geometrical supporting surface. This work also describes the implementation of these three methods to re-mesh an existing triangulated mesh that might present regions of high curvature. In this implementation, the only information about the surface geometry is a set of triangles. In order to test the efficiency of the proposed algorithm of surface mesh generation and implementation of the three abstract methods, results of performance and quality of generated triangular element examples are presented.     

Aggregation in hub location problems

Because of their widespread use in real-world transportation situations, hub location models have been extensively studied in the last two decades. Many types of hub location problems are NP-hard and remain unmanageable when the number of nodes exceeds 200. We present a way to tackle large-sized problems using aggregation, explore the resulting error, and show how to reduce it. Furthermore, we develop a heuristic based on aggregation for k-hub center problems and present computational results.