PDQ: Parallel Distance Queries for deformable meshes

This paper presents a new algorithm to efficiently maintain Bounding-Volume Hierarchies (BVHs) for fast distance queries with deformable polygon meshes using multi-core architectures. The method involves inflating the bounding volumes in an efficient manner to guarantee the enclosure of the deformable model within the BVH at all times. This is done at low additional computation and memory cost without significantly degrading the quality of the BVH and also in a fashion that allows a simple parallel implementation. Additionally, to facilitate fast queries specifically for deforming meshes, we propose a novel algorithm for the bottom-up construction of BVHs that results in much faster distance queries.     

Sociomaterial actors in the assimilation gap: a case study of web service, management and IT-assimilation

This paper investigates the conditions for the assimilation of information systems (IS) and information technology (IT) in organizations and the influence of various actors in the organization and eBusiness context. To do so it draws on the literature on assimilation gap, sociomateriality and infrastructure together with a study of implementation and use of information and communication technology in and among organizations in a Swedish region. There were substantial investments in web infrastructure made on a regional level and the focus of this study is how the investments were transformed and assimilated in practices, relations and communication. Based on the empirical data from the case study, the paper extends the assimilation process into interplay among actors in organizations contexts. It describes organizations’ strategies for coping with their needs for information and the actors in these processes. Two categories of actors are identified, sensemaking and sensegiving actors, as most important in assimilation of IS/IT in organizations. A sociomaterial perspective gives guidance and a better understanding of the assimilation process in terms of knowledge and interpretative frames, and how assimilation involves identity construction and negotiations among sensemaking and sensegiving actors. The contribution of this paper is a better understanding of the context of assimilation and adaptation of IT in organizations’ business processes, and steps to be taken to improve readiness.     

Effect of Powder Processing and Sintering Conditions on the Microstructural,Thermal, and Mechanical Properties of Reticulated Zinc Oxide Ceramic Foams

Ceramic foams are made of zinc oxide using different amounts of Sb₂O₃ and Bi₂O₃ as sintering aids. The effect of a ball milling processing of the starting powders and the sintering temperature on the microstructure and the properties of the ZnO foams is investigated. The focus is set on the evolution of the secondary phases formed within the microstructure of ZnO. A determining effect is identified in the amount of an Al₂O₃ impurity which is introduced by abrasion of the milling vessels during ball milling. Alumina is partially dissolved in a spinel α–Zn₇Sb₂O₁₂ secondary phase which is stabilized by a reduction of the unit cell volume. Remaining Al₂O₃ is incorporated into zinc oxide under formation of a defect wurtzite phase. The phase evolution is a complex function of the content of sintering aids, the Al₂O₃ impurity level and the sintering temperature. The shrinkage during sintering and the porosity evolution are correlated to the phase composition within the ZnO material. The thermal conductivity and the compressive strength of the foams are determined, normalized with respect to their porosity, and correlated to the microstructure and phase composition of the ZnO strut material.     

Competence via the web

With the rapid growth and technical development of the internet, the interest in distributing education over the web has increased greatly during recent years. Educational systems and industry see the possibilities for more flexible and cost efficient solutions. At the same time, the internet industry is sensing a new market. The challenge lies in producing competence for the individual student through good teaching, while at the same time using technical solutions to create added value via the net. This article gives a short background to the new possibilities in distributed education over the internet, and discusses various factors for success in competence development efforts. The discussion focuses on the different aspects of educational design of web-based educational material.     

Form-Profiling of Optics Using the Geometry Measuring Machine and the M-48 CMM at NIST

We are developing an instrument, the Geometry Measuring Machine (GEMM), to measure the profile errors of aspheric and free form optical surfaces, with measurement uncertainties near 1 nm. Using GEMM, an optical profile is reconstructed from local curvatures of a surface, which are measured at points on the optic’s surface. We will describe a prototype version of GEMM, its repeatability with time, a measurements registry practice, and the calibration practice needed to make nanometer resolution comparisons with other instruments. Over three months, the repeatability of GEMM is 3 nm rms, and is based on the constancy of the measured profile of an elliptical mirror with a radius of curvature of about 83 m. As a demonstration of GEMM’s capabilities for curvature measurement, profiles of that same mirror were measured with GEMM and the NIST Moore M-48 coordinate measuring machine. Although the methods are far different, two reconstructed profiles differ by 22 nm peak-to-valley, or 6 nm rms. This comparability clearly demonstrates that with appropriate calibration, our prototype of the GEMM can measure complex-shaped optics.     

Surface damage induced by FIB milling and imaging of biological samples is controllable

Focused ion beam (FIB) techniques are among the most important tools for the nanostructuring of surfaces. We used the FIB/SEM (scanning electron microscope) for milling and imaging of digestive gland cells. The aim of our study was to document the interactions of FIB with the surface of the biological sample during FIB investigation, to identify the classes of artifacts, and to test procedures that could induce the quality of FIB milled sections by reducing the artifacts. The digestive gland cells were prepared for conventional SEM. During FIB/SEM operation we induced and enhanced artifacts. The results show that FIB operation on biological tissue affected the area of the sample where ion beam was rastering. We describe the FIB-induced surface major artifacts as a melting-like effect, sweating-like effect, morphological deformations, and gallium (Ga(+)) implantation. The FIB induced surface artifacts caused by incident Ga(+) ions were reduced by the application of a protective platinum strip on the surface exposed to the beam and by a suitable selection of operation protocol. We recommend the same sample preparation methods, FIB protocol for milling and imaging to be used also for other biological samples.     

Erosion—corrosion characteristics of a 2.25 Cr-1 Mo steel exposed at low particle velocities

The erosion-corrosion characteristics of a 2.25 Cr-1 Mo steel at low particle velocities and elevated temperatures were determined using a nozzle type laboratory erosion tester. The tests were performed with 180–360 μm angular alumina particles at 60° angle of impingement at low particle velocities of 2.6–8.2 m/s and in the temperature interval 20–600°C. The steel was tested both in the as-received condition as well as in two preoxidized conditions. The erosion-corrosion rate of the steel, both in the as-received and in the preoxidized conditions, was found to increase with increasing particle velocity. In contrast, the wastage rates were relatively independent of temperature in the temperature range investigated, the only exception being specimens exposed to the lowest particle velocity (2.6 m/s) at the very highest temperature, i.e. 600°C, which displayed a drastic increase in wastage. Specimens preoxidized at 700°C exhibited a somewhat higher erosion rate compared with non-preoxidized specimens and specimens preoxidized at 500°C. Microscopy revealed four different major wastage mechanisms, i.e. (i) plastic deformation, cracking and micro chipping of surface material of a size corresponding to the area impinged by eroding particles, (ii) chipping of somewhat larger oxide fragments (up to 10–15 μm in diameter), (iii) chipping or spalling of relatively large oxide fragments (up to 30–50 μm in diameter), and (iv) spalling along the steel-oxide interface or within an oxide layer due to cohesive failure, of larger (up to 500 μm in diameter) oxide layer fragments. In the present study extensive spalling was only observed for non-preoxidized specimens exposed to the lowest particle velocity (2.6 m/s) and the two highest specimen temperatures (550°C and 600°C).