bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computational Geometry Education for Computer Graphics Students
Authors: Kolingerovà I. 
Published: September 2008

Abstract The paper surveys main features of computational geometry and presents the argument that a course oriented to applied computational geometry should be a part of the computer graphics curriculum, as it teaches effective algorithmic methods and helps to develop abstract thinking. Possible contents of the course and forms suitable and interesting for computer graphics students are discussed. The students' feedback on such a course has been mostly positive.
Improving Multipath Radiosity with Bundles of Parallel Lines
Authors: Martínez Roel , Sbert Mateu , Szirmay‐Kalos László 
Published: September 2008

AbstractMonte Carlo approaches use random lines to distribute the light power in the scene but the cost of creating a set of random single lines is very costly. In this paper, we present several software and hardware techniques in order to reduce the computational cost of the generation of random single lines by using bundles of parallel lines. The bundle of parallel lines is simulated with a general purpose polygon filling algorithm, like the painter's algorithm. We also present two graphics hardware implementations. The first approach uses two depth buffers in order to represent stochastically a bundle of parallel global lines. The second one uses multiple depth buffers and the aim is to exploit coherence between projection planes for each iteration. All algorithms were implemented with the multipath method.
Practical HDR Texture Compression
Authors: Munkberg J. , Clarberg P. , Hasselgren J. , Akenine‐Möller T. 
Published: September 2008

AbstractThe use of high dynamic range (HDR) textures in real‐time graphics applications can increase realism and provide a more vivid experience. However, the increased bandwidth and storage requirements for uncompressed HDR data can become a major bottleneck. Hence, several recent algorithms for HDR texture compression have been proposed. In this paper, we discuss several practical issues one has to confront in order to develop and implement HDR texture compression schemes. These include improved texture filtering and efficient offline compression. For compression, we describe how Procrustes analysis can be used to quickly match a predefined template shape against chrominance data. To reduce the cost of HDR texture filtering, we perform filtering prior to the colour transformation, and use a simple trick to reduce the incurred errors. We also introduce a number of novel compression modes, which can be combined with existing compression schemes, or used on their own.
Image‐Based Surface Compression
Authors: Ochotta Tilo , Saupe Dietmar 
Published: September 2008

AbstractWe present a generic framework for compression of densely sampled three‐dimensional (3D) surfaces in order to satisfy the increasing demand for storing large amounts of 3D content. We decompose a given surface into patches that are parameterized as elevation maps over planar domains and resampled on regular grids. The resulting shaped images are encoded using a state‐of‐the‐art wavelet image coder. We show that our method is not only applicable to mesh‐ and point‐based geometry, but also outperforms current surface encoders for both primitives.
Efficient CPU‐based Volume Ray Tracing Techniques
Authors: Marmitt Gerd , Friedrich Heiko , Slusallek Philipp 
Published: September 2008

AbstractRecent research on high‐performance ray tracing has achieved real‐time performance even for highly complex surface models already on a single PC. In this report, we provide an overview of techniques for extending real‐time ray tracing also to interactive volume rendering. We review fast rendering techniques for different volume representations and rendering modes in a variety of computing environments. The physically‐based rendering approach of ray tracing enables high image quality and allows for easily mixing surface, volume and other primitives in a scene, while fully accounting for all of their optical interactions. We present optimized implementations and discuss the use of upcoming high‐performance processors for volume ray tracing.
Calculating Compensation for Loss of Future Earnings: Estimating and using Work Life Expectancy
Authors: Butt Zoltan , Haberman Steven , Verrall Richard , Wass Victoria 
Published: September 2008

SummaryWhere personal injury results in displacement and/or continuing disability (or death), damages include an element of compensation for loss of future earnings. This is calculated with reference to the loss of future expected time in gainful employment. We estimate employment risks in the form of reductions to work life expectancies for the UK workforce by using data from the Labour Force Survey with the purpose of improving the accuracy of the calculation of future lifetime earnings. Work life expectancies and reduction factors are modelled within the framework of a multiple-state Markov process, conditional on age, sex, starting employment state, educational attainment and disability.
Estimating the Intensity of Conflict in Iraq
Authors: Nason Guy P. , Bailey Daniel 
Published: September 2008

SummarySince 2003 several Web sites have appeared that track the number of deaths of coalition personnel in the current Iraq conflict. The paper proposes the use of a recently developed multiscale variance stabilization method (the data-driven Haar–Fisz transform) to obtain good estimates of the mean intensity of deaths and demonstrates its statistical advantages over both the running mean (which is currently used on some Web sites) and also the Box–Cox transformation. The paper analyses both the number of deaths due to all causes and also due to hostile actions between June 2003 and March 2006. In both cases it appears that the marginal variance of both time series is an increasing function of the marginal mean. Further, although our estimates exhibit peaks that are related to local increases in intensity of conflict there appears to be a clear underlying increase in intensity of conflict during the conflict but with a decline and levelling off since June 2005. The paper also proposes a tentative inverse relationship between deaths due to non-hostile actions and deaths due to hostile actions.
Unemployed, Uneducated and Sick: The Effects of Socio-Economic Status on Health Duration in the European Union
Authors: Cooper D. , McCausland W. D. , Theodossiou I. 
Published: September 2008

SummaryWe employ a hazard function approach to estimate the effect of socio-economic and individual characteristics on the length of time that an individual remains in good health. The European Community Household Panel data set, for 13 European countries, for the years 1994–2002 is used. The study employs a relatively objective measure of physical health, the physical and mental health problems, illnesses and disabilities measure. The results show that socio-economic status does affect the likelihood of individuals entering bad health. In particular, unemployment experience increases and educational attainment decreases the probability that a person will cease to enjoy good health. Income effects are, however, somewhat weaker, being confined to a small number of countries and being mainly observed only for the highest income quartile. Age and gender effects are also found.
Two Sides to Every Story: Measuring Polarization and Inequality in the Distribution of Work
Authors: Gregg Paul , Wadsworth Jonathan 
Published: September 2008

SummaryIndividual- and household-based aggregate measures of joblessness can offer conflicting signals about labour market performance if work is unequally distributed. The paper introduces an index that can be used to measure both the extent and the sources of divergence between non-employment rates calculated at the two levels of aggregation. Built around a comparison of the actual household joblessness rate with that which would occur if work were equally distributed, the index conforms to basic axioms of consistency and can be decomposed and applied to any binary variable of interest measured at two different levels of aggregation. Applying these measures to data for Britain, we show that rising inequality in the distribution of work is mostly within group, largely unrelated to changes in size of household or the principal characteristics that are associated with individual joblessness.
Conflicting Evidence in a Bayesian Synthesis of Surveillance Data to Estimate Human Immunodeficiency Virus Prevalence
Authors: Presanis A. M. , De Angelis D. , Spiegelhalter D. J. , Seaman S. , Goubar A. , Ades A. E. 
Published: September 2008

SummaryInferential approaches based on the synthesis of diverse sources of evidence are increasingly employed in epidemiology as a means of exploiting all available information, perhaps from studies of differing designs. The application of the synthesis of evidence to real world problems generally leads to the formulation of probability models which are highly complex and for which there is a clear need for a well-defined iterative process of model criticism. This process should include an appraisal of model fit and the detection of inconsistent or conflicting evidence. The latter is especially relevant as, typically, multiple sources of data provide information on the same parameter. Detected conflicts need then to be resolved. We present a case-study of the detection and resolution of conflicting evidence, using as an illustration the estimation of the prevalence of human immunodeficiency virus (HIV) infection in England and Wales. We employ a Bayesian model to synthesize routine surveillance and survey data. The population aged 15–44 years is divided into mutually exclusive exposure groups. In each group g, we simultaneously estimate the proportion of the total population belonging to the group (ρ≫), the proportion of individuals infected with HIV (π≫) and the proportion of HIV positive individuals who are diagnosed (δ≫). The total number of HIV infections, both diagnosed and undiagnosed, is then estimated as a function of the parameters ρ≫, π≫ and δ≫. Model fit is assessed by examining the posterior mean deviance. Identification of the data items to which the model exhibits a lack of fit leads to the detection of conflicting evidence, one example of which is a conflict between census data and survey data over the size of the female Sub-Saharan African born population. This conflict arises from a naive interpretation of the representativeness of the survey data and is resolved by using two approaches: exclusion of data and expansion of the model to accommodate the bias.
Locally Dependent Latent Class Models with Covariates: An Application to Under-Age Drinking in the USA
Authors: Reboussin Beth A. , Ip Edward H. , Wolfson Mark 
Published: September 2008

SummaryUnder-age drinking is a long-standing public health problem in the USA and the identification of underage drinkers suffering alcohol-related problems has been difficult by using diagnostic criteria that were developed in adult populations. For this reason, it is important to characterize patterns of drinking in adolescents that are associated with alcohol-related problems. Latent class analysis is a statistical technique for explaining heterogeneity in individual response patterns in terms of a smaller number of classes. However, the latent class analysis assumption of local independence may not be appropriate when examining behavioural profiles and could have implications for statistical inference. In addition, if covariates are included in the model, non-differential measurement is also assumed. We propose a flexible set of models for local dependence and differential measurement that use easily interpretable odds ratio parameterizations while simultaneously fitting a marginal regression model for the latent class prevalences. Estimation is based on solving a set of second-order estimating equations. This approach requires only specification of the first two moments and allows for the choice of simple ‘working’ covariance structures. The method is illustrated by using data from a large-scale survey of under-age drinking. This new approach indicates the effectiveness of introducing local dependence and differential measurement into latent class models for selecting substantively interpretable models over more complex models that are deemed empirically superior.
Research Prioritization Based on Expected Value of Partial Perfect Information: A Case-Study on Interventions to Increase Uptake of Breast Cancer Screening
Authors: Welton N. J. , Ades A. E. , Caldwell D. M. , Peters T. J. 
Published: September 2008

SummaryWe investigate whether Bayesian decision theory, in the form of expected value of partial perfect information (EVPPI) analysis, is a realistic and practical approach to research prioritization. We develop a simple cost-effectiveness analysis of breast cancer screening as a typical case-study, motivated by data from a cluster randomized 2 × 2 factorial trial of interventions to increase uptake. An EVPPI analysis is developed which shows that, on the basis of the evidence that was available beforehand, the trial was cost effective, but that after incorporating the results of the trial it would still be cost effective to carry out research that further reduced decision uncertainty. We identify key conceptual and technical issues: the relationship between the target interventions and the previous evidence, the distinction between variation and uncertainty and methods for correlated parameters. EVPPI methods have clear advantages over current methods of research prioritization, but we suggest that some specific sensitivity analyses are required before they can be used confidently in practice. These have limitations, and there is a need to develop robust methods to optimize research portfolios.
Impairment of nigrostriatal dopamine neurotransmission by manganese is mediated by pre‐synaptic mechanism(s): implications to manganese‐induced parkinsonism
Authors: Guilarte Tomás R. , Burton Neal C. , McGlothan Jennifer L. , Verina Tatyana , Zhou Yun , Alexander Mohab , Pham Luu , Griswold Michael , Wong Dean F. , Syversen Tore , Schneider Jay S. 
Published: September 2008

AbstractThe long‐term consequences of chronic manganese (Mn) exposure on neurological health is a topic of great concern to occupationally‐exposed workers and in populations exposed to moderate levels of Mn. We have performed a comprehensive assessment of Mn effects on dopamine (DA) synapse markers using positron emission tomography (PET) in the non‐human primate brain. Young male Cynomolgus macaques were given weekly i.v. injections of 3.3–5.0 mg Mn/kg (n = 4), 5.0–6.7 mg Mn/kg (n = 5), or 8.3–10.0 mg Mn/kg (n = 3) for 7–59 weeks and received PET studies of various DA synapse markers before (baseline) and at one or two time points during the course of Mn exposure. We report that amphetamine‐induced DA release measured by PET is markedly impaired in the striatum of Mn‐exposed animals. The effect of Mn on DA release was present in the absence of changes in markers of dopamine terminal integrity determined in post‐mortem brain tissue from the same animals. These findings provide compelling evidence that the effects of Mn on DA synapses in the striatum are mediated by inhibition of DA neurotransmission and are responsible for the motor deficits documented in these animals.
Caffeine protects against MPTP‐induced blood‐brain barrier dysfunction in mouse striatum
Authors: Chen Xuesong , Lan Xun , Roche Ian , Liu Rugao , Geiger Jonathan D. 
Published: September 2008

AbstractThe blood‐brain barrier (BBB) is important physiologically. Pathologically, BBB disruption has been implicated in a wide spectrum of neurological disorders including Parkinson’s disease (PD). Recent studies indicate that caffeine is protective against PD, but by poorly understood mechanisms. Using a MPTP neurotoxin model of PD we tested the hypothesis that the protective actions of caffeine were because of, at least in part, preventing MPTP‐induced BBB dysfunction. FVB mice were pre‐treated with caffeine (10 mg/kg, i.p.) or saline for 7 days prior to initiation of neurotoxin treatments; during the 7 days of neurotoxin treatment, caffeine or saline continued to be administered 10 min before each dose of MPTP (20 mg/kg, i.p.). Striatum (and for some studies hippocampus and cerebral cortex as well) were evaluated for BBB leakage, tight junction protein expression levels, integrity of dopaminergic neurons, and activation of astrocytes and microglia using immunostaining, immunoblotting and real‐time PCR techniques. We found that caffeine blocked MPTP‐induced decreases in numbers of tyrosine hydroxylase‐positive dopaminergic neurons, increases in leakage of Evan’s blue dye and FITC‐albumin in striatum but not in cerebral cortex or hippocampus, decreases in levels of the tight junction proteins occludin and ZO‐1, and increases in reactive gliosis. Our results suggest that caffeine might protect against PD and PD‐like features in animal models, in part, by stabilizing the BBB.
Development and testing of a generic sensor model for pushbroom satellite imagery
Authors: Weser Thomas , Rottensteiner Franz , Willneff Jochen , Poon Joanne , Fraser Clive S. 
Published: September 2008

AbstractA new generic pushbroom sensor model for high‐resolution satellite images in which the orbit and attitudes are modelled by splines is presented. Direct observations for the satellite orbits and attitudes provided in imagery metadata files are used to determine the parameters of these splines. As such observations are contaminated by systematic errors, the new sensor model also incorporates error correction for the orbit and attitude angles. Camera model parameter definitions and file formats generally differ between satellite pushbroom scanners, and the system image‐ to object‐space transformation models are not always compatible with a sensor model based on the familiar perspective model applied in photogrammetry. In order to make the new sensor model applicable to a large number of satellite imaging systems, these vendor‐specific definitions are first mapped to the definitions of the new sensor model during data import. This is illustrated for QuickBird, SPOT 5 and ALOS PRISM imagery. The model has been extensively tested using imagery from these same three satellites, over test sites in Melbourne and Bhutan. The tests have shown that the new sensor model can produce georeferencing accuracy of 1 pixel and better when biases in orbit and attitude data are compensated.
Potential accuracy of image orientation of small satellites: a case study of CHRIS/Proba data
Authors: Shaker Ahmed , Nichol Janet E. , Wong Man Sing 
Published: September 2008

AbstractThe new technology of small satellites (microsatellites) opens a new era in satellite observation of the earth. Small satellites such as ESA’s Project for On‐Board Autonomy (Proba), launched on 22nd October 2001, are of interest due to their low cost, flexibility of positioning, and capability for multiangular scanning in both across‐track and along‐track directions. Proba’s Compact High Resolution Imaging Spectrometer (CHRIS) provides multidirectional, as well as hyperspectral, data at 18 m resolution and is supplied mainly to the scientific community for experimental environmental applications. This research evaluates the use of various empirical mathematical models for small satellite orientation and terrain modelling using the multidirectional viewing capabilities of CHRIS data. Geometric correction and co‐registration of multiangle images is essential for their use for data extraction. Ideally, rigorous mathematical models should be formulated which precisely describe the satellite motion and represent the relationship between the image and the object spaces. The use of rigorous mathematical models has not been fully investigated using CHRIS/Proba data, because the satellite information provided is not adequate for rigorous sensor modelling. In this paper, several alternative empirical models are tested for the orientation and 3D geopositioning of CHRIS sensor images. The images used in this study cover extremely mountainous terrain in central Hong Kong. A set of five images from CHRIS/Proba taken in December 2005 from different angles are used to test the applicability of different forms of the empirical models for 3D geopositioning. The accuracy of the models is tested for different numbers and distribution of ground control points (GCPs) using different combinations of observation angles and base‐to‐height ratios. The results obtained show high integrity of the models used for CHRIS/Proba image orientation. In some cases, accuracy better than 2 pixels can be achieved using a modest number of GCPs.
Analysis of Cartosat‐1 images regarding image quality, 3D point measurement and DSM generation
Authors: Baltsavias Emmanuel , Kocaman Sultan , Wolff Kirsten 
Published: September 2008

AbstractThe Institute of Geodesy and Photogrammetry (IGP) at ETH Zurich is participating in the Cartosat‐1 evaluation programme, a common initiative of ISRO (India) and ISPRS. Within this programme various test sites with reference data have been established and Cartosat‐1 images have been acquired over these sites. Here, investigations at the Rome (Italy) and Maussane‐les‐Alpilles (France) test sites are reported. First, radiometric problems encountered with the images and pre‐processing for their improvement are reported. Examples are shown, together with pre‐processing methods that can be employed in order to improve image quality, aimed especially at automatic generation of a digital surface model (DSM) with fewer blunders and more matched points. Then, georeferencing is discussed and the 3D point measurement accuracy that can be achieved is introduced, as well as problems encountered with the rational polynomial coefficients (RPCs). The georeferencing results were produced using various options regarding image pre‐processing, the mathematical model used for georeferencing, the number and distribution of ground control points (GCPs) and the GCP image mensuration methods. The best results led to a planimetric and height accuracy (RMSE) of about 1·3 m. Use of an affine transformation after the RPCs, with about six well‐distributed GCPs transferred with matching to the second image, is suggested. Finally, the results of automatic DSM generation using the SAT‐PP program package developed at the IGP are presented. Various DSMs were generated with 10 m grid spacing. The results were checked visually and were also compared to the reference data provided. In the best case, the accuracy achieved is about 2·7 m without any manual editing, in spite of a 3‐year difference between the matching and reference DSMs. Although some aspects regarding image quality and RPC generation could be improved, Cartosat‐1 is a useful sensor for mapping and especially for the generation of DSMs. However, owing to its poor absolute geolocation accuracy, Cartosat‐1 cannot be used for the generation of a global DSM without GCPs.