Effects of solid solution alloying on creep deformation of aluminum

The effects of solid solution alloying on the creep-rupture properties, deformation characteristics, ductility, and fracture of pure aluminum were studied by means of creep-rupture tests on polished specimens of three alloys each of Al-Cu (0.24, 0.79, and 2.05 pct Cu), Al-Zn (4.93, 9.89, and 19.78 pct Zn), and Al-Mg (0.94, 1.92, and 5.10 pct Mg) at 500°, 700°, and 900°F.     

Parameter tuning or default values? An empirical investigation in search-based software engineering

Many software engineering problems have been addressed with search algorithms. Search algorithms usually depend on several parameters (e.g., population size and crossover rate in genetic algorithms), and the choice of these parameters can have an impact on the performance of the algorithm. It has been formally proven in the No Free Lunch theorem that it is impossible to tune a search algorithm such that it will have optimal settings for all possible problems. So, how to properly set the parameters of a search algorithm for a given software engineering problem? In this paper, we carry out the largest empirical analysis so far on parameter tuning in search-based software engineering. More than one million experiments were carried out and statistically analyzed in the context of test data generation for object-oriented software using the EvoSuite tool. Results show that tuning does indeed have impact on the performance of a search algorithm. But, at least in the context of test data generation, it does not seem easy to find good settings that significantly outperform the “default” values suggested in the literature. This has very practical value for both researchers (e.g., when different techniques are compared) and practitioners. Using “default” values is a reasonable and justified choice, whereas parameter tuning is a long and expensive process that might or might not pay off in the end.     

An Investigation of Information Systems Interoperability in UK Universities: Findings and Recommendations

This article reports on the key findings and implications of the Joint Information Systems Committee (JISC)-funded Online Catalogue and Repository Interoperability Study (OCRIS), a 3-month project which investigated the interoperability of Online Public Access Catalogues (OPACs) and Institutional Repositories (IRs) within UK universities. A series of detailed recommendations enumerate some of the ways in which they might begin to develop and support an interoperable systems landscape to the benefit of all key stakeholders.

The project combined quantitative and qualitative research methods including an online questionnaire distributed to staff within 85 universities, desk research, and two case studies conducted at the Universities of Cambridge and Glasgow.     

Interfacing remote transaction services using UPnP

Transaction execution in mobile environments needs to be flexible, not only to support typical mobile computing characteristics, like movement, disconnections and limited resources, but also to support the variety of transactional properties that might be required by different applications. Existing models for mobile transaction management solve different aspects of transaction execution, but are not flexible enough to solve all required aspects. Instead of designing a new transaction model, we propose a middleware (MobileTSe) which utilize existing transaction models to handle various requirements for mobile transaction execution. This paper presents an approach for flexible transaction processing in mobile applications, and describes how MobileTSe makes transaction services with different properties available on mobile units. We suggest a solution with transaction service discovery and control using UPnP.     

The Visual Computing of Projector‐Camera Systems

This article focuses on real‐time image correction techniques that enable projector‐camera systems to display images onto screens that are not optimized for projections, such as geometrically complex, coloured and textured surfaces. It reviews hardware‐accelerated methods like pixel‐precise geometric warping, radiometric compensation, multi‐focal projection and the correction of general light modulation effects. Online and offline calibration as well as invisible coding methods are explained. Novel attempts in super‐resolution, high‐dynamic range and high‐speed projection are discussed. These techniques open a variety of new applications for projection displays. Some of them will also be presented in this report.     

Efficient parallel implementation of iterative reconstruction algorithms for electron tomography

Electron tomography (ET) combines electron microscopy and the principles of tomographic imaging in order to reconstruct the three-dimensional structure of complex biological specimens at molecular resolution. Weighted back-projection (WBP) has long been the method of choice since the reconstructions are very fast. It is well known that iterative methods produce better images, but at a very costly time penalty. In this work, it is shown that efficient parallel implementations of iterative methods, based primarily on data decomposition, can speed up such methods to an extent that they become viable alternatives to WBP. Precomputation of the coefficient matrix has also turned out to be important to substantially improve the performance regardless of the number of processors used. Matrix precomputation has made it possible to speed up the block-iterative component averaging (BICAV) algorithm, which has been studied before in the context of computerized tomography (CT) and ET, by a factor of more than 3.7. Component-averaged row projections (CARP) is a recently introduced block-parallel algorithm, which was shown to be a robust method for solving sparse systems arising from partial differential equations. It is shown that this algorithm is also suitable for single-axis ET, and is advantageous over BICAV both in terms of runtime and image quality. The experiments were carried out on several datasets of ET of various sizes, using the blob model for representing the reconstructed object.     

Robust outdoor visual localization using a three‐dimensional‐edge map

Visual localization systems that are practical for autonomous vehicles in outdoor industrial applications must perform reliably in a wide range of conditions. Changing outdoor conditions cause difficulty by drastically altering the information available in the camera images. To confront the problem, we have developed a visual localization system that uses a surveyed three‐dimensional (3D)‐edge map of permanent structures in the environment. The map has the invariant properties necessary to achieve long‐term robust operation. Previous 3D‐edge map localization systems usually maintain a single pose hypothesis, making it difficult to initialize without an accurate prior pose estimate and also making them susceptible to misalignment with unmapped edges detected in the camera image. A multihypothesis particle filter is employed here to perform the initialization procedure with significant uncertainty in the vehicle's initial pose. A novel observation function for the particle filter is developed and evaluated against two existing functions. The new function is shown to further improve the abilities of the particle filter to converge given a very coarse estimate of the vehicle's initial pose. An intelligent exposure control algorithm is also developed that improves the quality of the pertinent information in the image. Results gathered over an entire sunny day and also during rainy weather illustrate that the localization system can operate in a wide range of outdoor conditions. The conclusion is that an invariant map, a robust multihypothesis localization algorithm, and an intelligent exposure control algorithm all combine to enable reliable visual localization through challenging outdoor conditions. © 2009 Wiley Periodicals, Inc.     

Generalized nonimaging compound elliptical and compound hyperbolic luminaire designs for pair-overlap illumination applications

Generalized nonimaging compound elliptical luminaires (CEL's) and compound hyperbolic luminaires (CHL's) are developed for pair-overlap illumination applications. A comprehensive analysis of CEL's and CHL's is presented. This includes the possibility of reflector truncation, as well as the extreme direction that spans the full range from positive to negative. Negative extreme direction devices have been overlooked in earlier studies and are shown to be well suited to illumination problems for which large cutoff angles are required. Flux maps can be calculated analytically without the need for computer ray tracing. It is demonstrated that, for a broad range of cutoff angles, adjacent pairs of CEL's and CHL's can generate highly uniform far-field illuminance while maintaining maximal lighting efficiency and excellent glare control. The trade-off between luminaire compactness and flux homogeneity is also illustrated. For V troughs, being a special case of CHL's and being well suited to simple, inexpensive fabri ation, we identify geometries that closely approach the performance characteristics of the optimized CEL's and CHL's.