bluuebunny/crossref_metadata_2025 huggingface dataset:
Maternal Responsiveness and Children's Achievement of Language Milestones
Authors: Tamis‐LeMonda Catherine S. , Bornstein Marc H. , Baumwell Lisa
Published: March 2003

This prospective longitudinal study examined the contribution of dimensions of maternal responsiveness (descriptions, play, imitations) to the timing of five milestones in children's (N= 40) early expressive language: first imitations, first words, 50 words in expressive language, combinatorial speech, and the use of language to talk about the past. Events‐History Analysis, a statistical technique that estimates the extent to which predictors influence the timing of events, was used. At 9 and 13 months, maternal responsiveness and children's activities (e.g., vocalizations, play) were coded from videotaped interactions of mother – child free play; information about children's language acquisition was obtained through biweekly interviews with mothers from 9 through 21 months. Maternal responsiveness at both ages predicted the timing of children's achieving language milestones over and above children's observed behaviors. Responsiveness at 13 months was a stronger predictor of the timing of language milestones than was responsiveness at 9 months, and certain dimensions of responsiveness were more predictive than others. The multidimensional nature of maternal responsiveness and specificity in mother – child language relations are discussed.
Early Reading Development in Children at Family Risk for Dyslexia
Authors: Pennington Bruce F. , Lefly Dianne L.
Published: March 2003

In a 3‐year longitudinal study, middle‐ to upper‐middle‐class preschool children at high family risk (HR group, N= 67) and low family risk (LR group, N= 57) for dyslexia (or reading disability, RD), were evaluated yearly from before kindergarten to the end of second grade. Both phonological processing and literacy skills were tested at each of four time points. Consistent with the well‐known familiarity of RD, 34% of the HR group compared with 6% of the LR group became RD. Participants who became RD showed deficits in both implicit and explicit phonological processing skills at all four time points, clearly indicating a broader phonological deficit than is often found at older ages. The predictors of literacy skill did not vary by risk group. Both risk groups underwent a similar developmental shift from letter‐name knowledge to phoneme awareness as the main predictor of later literacy skill. This shift, however, occurred 2 years later in the HR group. Familial risk was continuous rather than discrete because HR children who did not become RD performed worse than LR non‐RD children on some phonological and literacy measures. Finally, later RD could be predicted with moderate accuracy at age 5 years, with the strongest predictor being letter‐name knowledge.
Evidence That Children and Adolescents Have Internal Models of Peer Interactions That Are Gender Differentiated
Authors: Markovits Henry , Benenson Joyce , Dolenszky Eva
Published: March 2003

This study examined whether children's internal representations reflect gender differences that have been found in peer interactions. The dimensions examined were (1) preferences for dyadic or group situations, (2) whether children who are friends with a given target child are likely to be friends with each other, and (3) perceptions of the probability of knowing information about friends. Participants from preschool; grades 2, 6, 8, and 10; and college (N= 278) were asked questions about typical girls and boys. Results indicate that both girls and boys (1) rate typical boys as preferring group interactions more than do typical girls, a difference present as early as preschool; (2) rate typical boys as more likely than typical girls to be friends with one another if they are friends with the same target boy or gir,l respectively; and (3) rate typical girls as more likely than typical boys to know certain types of information about friends. These results are consistent with the existence of internal models of social interactions that are at least partially gender specific.
The Influence of Group Size on Children's Competitive Behavior
Authors: Benenson Joyce F. , Nicholson Catherine , Waite Angela , Roy Rosanne , Simpson Anna
Published: March 2003

The present research was designed to test the hypothesis that children would compete more in tetrads than in dyads. Twenty‐two pairs of male and 14 pairs of female target children (N= 72) played a competitive game in both tetrads and dyads. Consistent with the hypothesis, male target children competed more in tetrads than in dyads. This hypothesis was not supported for females, however. Analyses of the dynamics of tetrads and dyads further demonstrated that based on a global measure of smiling, the emotional atmosphere was less positive in tetrads than in dyads. The causes and consequences of interaction in different sized social groups are discussed.
Learning Words from Knowledgeable versus Ignorant Speakers: Links Between Preschoolers' Theory of Mind and Semantic Development
Authors: Sabbagh Mark A. , Baldwin Dare A.
Published: March 2003

Two studies addressed whether children consider speakers' knowledge states when establishing initial word‐referent links. In Study 1, forty‐eight 3‐ and 4‐year‐olds were taught two novel words by a speaker who expressed either knowledge or ignorance about the words' referents. Children showed better word learning when the speaker was knowledgeable. In Study 2, forty‐eight 3‐ and 4‐year‐olds were taught two novel words by a speaker who expressed uncertainty about their referents. Whether the uncertainty truly reflected ignorance, however, differed across conditions. In one condition, the speaker said he made the object himself and thus, he was knowledgeable. In the other condition, the speaker stated that the object was made by a friend and thus, expressed ignorance about it. Four‐year‐olds learned better in the speaker‐made than in the friend‐made condition; 3‐year‐olds, however, showed relatively poor learning in both conditions. These findings suggest that theory‐of‐mind developments impact word learning.
Adolescents’ Working Models and Styles for Relationships with Parents, Friends, and Romantic Partners
Authors: Furman Wyndol , Simon Valerie A. , Shaffer Laura , Bouchey Heather A.
Published: March 2003

This study examined the links among adolescents’ representations of their relationships with parents, friends, and romantic partners. Sixty‐eight adolescents were interviewed three times to assess their working models for each of these types of relationships. Working models of friendships were related to working models of relationships with parents and romantic partners. Working models of relationships with parents and romantic partners were inconsistently related. A similar pattern of results was obtained for self‐report measures of relational styles for the three types of relationships. Perceived experiences were also related. Specifically, support in relationships with parents tended to be related to support in romantic relationships and friendships, but the latter two were unrelated. On the other hand, self and other controlling behaviors in friendships were related to corresponding behaviors in romantic relationships. Negative interactions in the three types of relationships also tended to be related. Taken together, the findings indicate that the representations of the three types of relationships are distinct, yet related. Discussion focuses on the nature of the links among the three.
Theory of Mind and Self‐Control: More than a Common Problem of Inhibition
Authors: Perner Josef , Lang Birgit , Kloo Daniela
Published: March 2003

This study tested the theory that advances on theory‐of‐mind tasks and on executive function tasks show a strong correlation because the typically used theory‐of‐mind tasks pose the same executive demands. In Experiment 1 with fifty‐six 3‐ to 6‐year‐old children, performance on the dimensional change card‐sorting task as an executive function task was correlated with performance on the usual false‐belief prediction task, r= .65, and the false‐belief explanation task, r= .65, as measures of theory‐of‐mind development. Because the explanation version of the false‐belief test is supposed to be free of the alleged executive demands inherent in the prediction version, the equally strong correlation with the executive function task suggests that this correlation cannot be due to common executive demands. In Experiment 2, the basic finding of Experiment 1 was replicated on another sample of 73 children, ages 3 to 5.5 years. The need for new theories to explain the developmental link between theory of mind and executive function development is discussed, and some existing candidates are evaluated.
Cultural Teaching: The Development of Teaching Skills in Maya Sibling Interactions
Authors: Maynard Ashley E.
Published: March 2003

Psychology has considered the development of learning, but the development of teaching in childhood has not been considered. The data presented in this article demonstrate that children develop teaching skills over the course of middle childhood. Seventy‐two Maya children (25 boys, 47 girls) ranging in age from 3 to 11 years (M= 6.8 years) were videotaped in sibling caretaking interactions with their 2‐year‐old brothers and sisters (18 boys, 18 girls). In the context of play, older siblings taught their younger siblings how to do everyday tasks such as washing and cooking. Ethnographic observations, discourse analyses, and quantification of discourse findings showed that children's teaching skills increased over the course of middle childhood. By the age of 4 years, children took responsibility for initiating teaching situations with their toddler siblings. By the age of 8 years, children were highly skilled in using talk combined with manual demonstrations, verbal feedback, explanations, and guiding the body of younger learners. Children's developing competence in teaching helped their younger siblings increase their participation in culturally important tasks.
Earned–Secure Attachment Status in Retrospect and Prospect
Authors: Roisman Glenn I. , Padrón Elena , Sroufe L. Alan , Egeland Byron
Published: March 2003

Past research with the Berkeley Adult Attachment Interview demonstrates that retrospectively defined earned–secures (who coherently describe negative childhood experiences) parent as effectively as do continuous–secures (who coherently describe positive childhood experiences), but manifest liabilities in the form of depressive symptomatology. This article presents data from a 23–year longitudinal study that replicate and extend prior research, testing a key premise that earned–secures so defined actually have a history of insecure attachments that change over time and/or endure consistently harsh or ineffective parenting in their youth. Discrepant with assumptions, retrospective earned–secures were not more likely than continuous–secures to have been anxiously attached in infancy and were observed in childhood and adolescence to have encountered among the most supportive and structured maternal parenting in a high–risk sample. Prospectively defined earned–secures (operationalized using participants’ infant attachment classifications) did indeed go on to have success in their close relationships, many without reporting relatively high levels of internalizing distress in adulthood.
Multidimensional Resilience in Urban Children Exposed to Community Violence
Authors: O’Donnell Deborah A. , Schwab–Stone Mary E. , Muyeed Adaline Z.
Published: March 2003

The extent to which parent, school, and peer support differentially affected multiple domains of resilience was examined among 2,600 sixth, eighth, and tenth graders from an urban public school system who took part in a comprehensive survey of high–risk and adaptive behaviors. Structural equation modeling was used to specify the relation among seven domains of resilience and parent, school, and peer support among children who had been victimized by community violence, those who had witnessed such violence, and a no–exposure control group. Results upheld the validity of a multidimensional conceptualization of childhood resilience, and indicated that although both parent and school support factors were significantly positively associated with resilience in children who had been exposed to community violence, peer support was negatively associated with resilience in the domains of substance abuse and school misconduct/ delinquency. These results were most robust among victimized children, followed by children who had witnessed violence. Implications for social policy and community violence research are discussed.
Racial Identity, Maternal Support, and Psychological Distress among African American Adolescents
Authors: Caldwell Cleopatra Howard , Zimmerman Marc A. , Bernat Debra Hilkene , Sellers Robert M. , Notaro Paul C.
Published: March 2003

This study investigated the role of racial identity and maternal support in reducing psychological distress among African American adolescents. Both direct and indirect influences of multiple dimensions of racial identity (i.e., centrality, private regard) and maternal support on perceived stress, depressive symptoms, and anxiety were examined among 521 African American twelfth graders. Findings indicated that maternal support was positively related to both centrality and private regard. Results provided little support for a direct association between racial identity or maternal support and depressive symptoms and anxiety within a multivariate context. Rather, the influences of racial identity attitudes and maternal support on these mental health outcomes were mediated by perceived stress. Further, the two racial identity attitudes were associated with perceived stress in different ways. Study findings suggest that the significance and meaning that African American adolescents attribute to being Black may be critical to their psychological well–being, and that maternal support and perceived stress are important considerations.
The Infant as Onlooker: Learning From Emotional Reactions Observed in a Television Scenario
Authors: Mumme Donna L. , Fernald Anne
Published: March 2003

Two studies investigated whether 10– and 12–month–olds can use televised emotional reactions to guide their behavior. Infants watched an actress orient toward 1 of 2 novel objects and react with neutral affect during baseline and with positive or negative affect during test. Infants then had 30 s to interact with the objects. In Study 1, 12–month–olds (N = 32) avoided the target object and showed increases in negative affect after observing the negative–emotion scenario. Twelve–month–olds’ responses to positive vs. neutral signals did not differ significantly. In Study 2, 10–month–olds (N = 32) attended to the televised presentations but showed no consistent changes in their object interactions or affect. Thus, 12–month–olds used social information presented on television and associated emotional signals with the intended target.
The Moderation of Adolescent–to–Peer Similarity in Tobacco and Alcohol Use by School Levels of Substance Use
Authors: Cleveland Harrington H. , Wiebe Richard P.
Published: March 2003

Using the National Longitudinal Study of Adolescent Health, this study examined the impact of school–level smoking and drinking on adolescent–peer similarity for smoking and drinking. Hierarchical linear modeling revealed that adolescent–peer similarity was significantly moderated by school–level substance use for both tobacco and alcohol use. For tobacco, similarity between adolescent and peer use increased from .18 in the lower quartile of tobacco–using schools to .44 in the upper quartile of tobacco–using schools. Corresponding similarities for alcohol use ranged from .25 to .34. These results suggest that schools with relatively few substance–using peers provide less opportunities for adolescents to pick niches that expose them to risk factors that correspond to their own substance–use behaviors.
Children's Suggestibility in Relation to their Understanding about Sources of Knowledge
Authors: Robinson E. J. , Whitcombe E. L.
Published: March 2003

In the experiments reported here, children chose either to maintain their initial belief about an object's identity or to accept the experimenter's contradicting suggestion. Both 3– to 4–year–olds and 4– to 5–year–olds were good at accepting the suggestion only when the experimenter was better informed than they were (implicit source monitoring). They were less accurate at recalling both their own and the experimenter's information access (explicit recall of experience), though they performed well above chance. Children were least accurate at reporting whether their final belief was based on what they were told or on what they experienced directly (explicit source monitoring). Contrasting results emerged when children decided between contradictory suggestions from two differentially informed adults: Three– to 4–year–olds were more accurate at reporting the knowledge source of the adult they believed than at deciding which suggestion was reliable. Decision making in this observation task may require reflective understanding akin to that required for explicit source judgments when the child participates in the task.
Life With (or Without) Father: The Benefits of Living With Two Biological Parents Depend on the Father's Antisocial Behavior
Authors: Jaffee Sara R. , Moffitt Terrie E. , Caspi Avshalom , Taylor Alan
Published: March 2003

The salutary effects of being raised by two married, biological parents depend on the quality of care parents can provide. Using data from an epidemiological sample of 1,116 5–year–old twin pairs and their parents, this study found that the less time fathers lived with their children, the more conduct problems their children had, but only if the fathers engaged in low levels of antisocial behavior. In contrast, when fathers engaged in high levels of antisocial behavior, the more time they lived with their children, the more conduct problems their children had. Behavioral genetic analyses showed that children who resided with antisocial fathers received a “double whammy” of genetic and environmental risk for conduct problems. Marriage may not be the answer to the problems faced by some children living in single–parent families unless their fathers can become reliable sources of emotional and economic support.
Parenting and Family Socialization Strategies and Children's Mental Health: Low–Income Mexican–American and Euro–American Mothers and Children
Authors: Hill Nancy E. , Bush Kevin R. , Roosa Mark W.
Published: March 2003

The extent to which current theories on family–related factors associated with children's depression and conduct problems are applicable to Mexican American children was examined among demographically comparable samples of low–income Mexican American (English and Spanish speaking) and Euro–American mothers and children. There were ethnic differences in mean levels of children's depression, maternal inconsistent discipline, and hostile control. In addition, there were differences across language within the Mexican American sample on levels of reported maternal inconsistent discipline and hostile control. The vast majority of relations between parenting and mental health were similar between Mexican Americans and Euro–Americans, suggesting that current theories do apply across ethnic groups. However, analyses across language within the Mexican American sample showed that language preference moderated the relation between maternal acceptance and children's conduct problems. Moreover, the relation between acceptance and hostile control differed across groups. These results are discussed in light of the relative influence of ethnicity and other contextual variables on parenting and children's mental health.
To Commit or Not to Commit: Modeling Agent Conversations for Action
Authors: Flores Roberto A. , Kremer Robert C.
Published: March 2003

Conversations are sequences of messages exchanged among interacting agents. For conversations to be meaningful, agents ought to follow commonly known specifications limiting the types of messages that can be exchanged at any point in the conversation. These specifications are usually implemented using conversation policies (which are rules of inference) or conversation protocols (which are predefined conversation templates). In this article we present a semantic model for specifying conversations using conversation policies. This model is based on the principles that the negotiation and uptake of shared social commitments entail the adoption of obligations to action, which indicate the actions that agents have agreed to perform. In the same way, obligations are retracted based on the negotiation to discharge their corresponding shared social commitments. Based on these principles, conversations are specified as interaction specifications that model the ideal sequencing of agent participations negotiating the execution of actions in a joint activity. These specifications not only specify the adoption and discharge of shared commitments and obligations during an activity, but also indicate the commitments and obligations that are required (as preconditions) or that outlive a joint activity (as postconditions). We model the Contract Net Protocol as an example of the specification of conversations in a joint activity.
Normal Computation for Discrete Surfaces in 3D Space
Authors: Thürmer Grit , Wüthrich Charles A.
Published: March 2003

Associating normal vectors to surfaces is essential for many rendering algorithms. We introduce a new method to compute normals on discrete surfaces in object space. Assuming that the surface separates space locally into two disjoint subsets, each of these subsets contains implicitly information about the surface inclination. Considering one of these subsets in a small neighbourhood of a surface point enables us to derive the surface normal from this set. We show that this leads to exact results for C1 continuous surfaces in R3. Furthermore, we show that good approximations can be obtained numerically by sampling the considered area. Finally, we derive a method for normal computation on surfaces in discrete space.
From Footprints to Animation
Authors: Van De Panne Michiel
Published: March 2003

A method of using footprints as a basis for generating animated locomotion is proposed. An optimization process is used to maximize the physical plausibility and perceived comfort of a motion which is constrained to match given footprint and timing information. The proposed method creates plausible walking, turning, leaping, and running motions for bipedal figures at interactive rates. Autonomous motions are generated using a planning algorithm which dynamically generates new footprints and the associated new motions.
Dithered Color Quantization
Authors: Buhmann J.M. , Fellner D.W. , Held M. , Ketterer J. , Puzicha J.
Published: March 2003

Image quantization and digital halftoning are fundamental problems in computer graphics, which arise when displaying high‐color images on non‐truecolor devices. Both steps are generally performed sequentially and, in most cases, independent of each other. Color quantization with a pixel‐wise defined distortion measure and the dithering process with its local neighborhood optimize different quality criteria or, frequently, follow a heuristic without reference to any quality measure.

In this paper we propose a new method to simultaneously quantize and dither color images. The method is based on a rigorous cost‐function approach which optimizes a quality criterion derived from a generic model of human perception. A highly efficient algorithm for optimization based on a multiscale method is developed for the dithered color quantization cost function. The quality criterion and the optimization algorithms are evaluated on a representative set of artificial and real‐world images as well as on a collection of icons. A significant image quality improvement is observed compared to standard color reduction approaches.
An Efficient and Flexible Perception Pipeline for Autonomous Agents
Authors: Bordeux Christophe , Boulic Ronan , Thalmann Daniel
Published: March 2003

Agents in virtual environments require a combination of perception and action to behave in an autonomous way. We extend a software architecture for the management of actions blending, called AGENTlib, with a perception mechanism. The perception system provides a uniform interface to various techniques in the field of virtual perception, including synthetic vision, database access and perception persistency. We describe the framework we designed to efficiently filter valuable information from the scene and we address concerns about computation redundancy and data propagation through multiple filtering modules.
Improved Laplacian Smoothing of Noisy Surface Meshes
Authors: Vollmer J. , Mencl R. , Müller H.
Published: March 2003

This paper presents a technique for smoothing polygonal surface meshes that avoids the well‐known problem of deformation and shrinkage caused by many smoothing methods, like e.g. the Laplacian algorithm. The basic idea is to push the vertices of the smoothed mesh back towards their previous locations. This technique can be also used in order to smooth unstructured point sets, by reconstructing a surface mesh to which the smoothing technique is applied. The key observation is that a surface mesh which is not necessarily topologically correct, but which can efficiently be reconstructed, is sufficient for that purpose.
Partitioning and Handling Massive Models for Interactive Collision Detection
Authors: Wilson A. , Larsen E. , Manocha D. , Lin M. C.
Published: March 2003

We describe an approach for interactive collision detection and proximity computations on massive models composed of millions of geometric primitives. We address issues related to interactive data access and processing in a large geometric database, which may not fit into main memory of typical desktop workstations or computers. We present a new algorithm using overlap graphs for localizing the “regions of interest” within a massive model, thereby reducing runtime memory requirements. The overlap graph is computed off‐line, pre‐processed using graph partitioning algorithms, and modified on the fly as needed. At run time, we traverse localized sub‐graphs to check the corresponding geometry for proximity and pre‐fetch geometry and auxiliary data structures. To perform interactive proximity queries, we use bounding‐volume hierarchies and take advantage of spatial and temporal coherence. Based on the proposed algorithms, we have developed a system called IMMPACT and used it for interaction with a CAD model of a power plant consisting of over 15 million triangles. We are able to perform a number of proximity queries in real‐time on such a model. In terms of model complexity and application to large models, we have improved the performance of interactive collision detection and proximity computation algorithms by an order of magnitude.
Extending the CSG Tree. Warping, Blending and Boolean Operations in an Implicit Surface Modeling System
Authors: Wyvill Brian , Guy Andrew , Galin Eric
Published: March 2003

Automatic blending has characterized the major advantage of implicit surface modeling systems. Recently, the introduction of deformations based on space warping and Boolean operations between primitives has increased the usefulness of such systems. We propose a further enhancement which will extend the range of models that can be easily and intuitively defined with a skeletal implicit surface system. We describe a hierarchical method which allows arbitrary compositions of models that make use of blending, warping and Boolean operations. We call this structure the BlobTree. Blending and space warping are treated in the same way as union, difference and intersection, i.e. as nodes in the BlobTree. The traversal of the BlobTree is described along with two rendering algorithms; a polygonizer and a ray tracer. We present some examples of interesting models which can be made easily using our approach that would be very difficult to represent with conventional systems.
An Adaptive Spectral Rendering with a Perceptual Control
Authors: Claude Iehl Jean , Péroche Bernard
Published: March 2003

In this paper, we present a spectral rendering method based on a ray tracing algorithm and guided by a perceptual control of the error made. An adaptive representation of spectral data for light sources and materials is used and induces, for each pixel, the evaluation of an algebraic expression. For each visible wavelength, the computations of complex spread in refractive and dispersive materials, based on several photon maps, are locally restricted by an adaptive evaluation of the expression. This method allows to simulate high quality physically‐based pictures and, in particular, some specific phenomena like dispersion in transparent objects, scattered caustics,. . .
Reshaping the Coliseum in Rome: An Integrated Data Capture and Modeling Method at Heritage Sites
Authors: Gaiani Marco , Balzani Marcello , Uccelli Federico
Published: March 2003

The paper describes the process of building Internet‐transmittable, 3‐D digital virtual models of ancient heritage monuments from on‐site data, focusing especially on 3‐D dimensional data acquisition techniques and color processing methods. Section 1 considers project goals and the attendant problems; Section 2 provides a brief summary of state‐of‐the‐art experience and the technologies adopted by the Authors; Section 3 illustrates the key features of the 3‐D color data acquisition methods used as well as the shape and color processing pipeline; Section 4 describes the specific study conducted on single elements and faades of the Coliseum in Rome, while Section 6 outlines future work.
A Vector‐based Representation for Image Warping
Authors: Froumentin Max , Labrosse Frédéric , Willis Philip
Published: March 2003

A method for image analysis, representation and re‐synthesis is introduced. Unlike other schemes it is not pixel based but rather represents a picture as vector data, from which an altered version of the original image can be rendered. Representing an image as vector data allows performing operations such as zooming, retouching or colourising, avoiding common problems associated with pixel image manipulation. This paper brings together methods from the areas of computer vision, image compositing and image based rendering to prove that this type of image representation is a step towards accurate and efficient image manipulation.
Motion Balance Filtering
Authors: Tak Seyoon , Song Oh‐young , Ko Hyeong‐Seok
Published: March 2003

This paper presents a new technique called motion balance filtering, which corrects an unbalanced motion to a balanced one while preserving the original motion characteristics as much as possible. Differently from previous approaches that deal only with the balance of static posture, we solve the problem of balancing a dynamic motion. We achieve dynamic balance by analyzing and controlling the trajectory of the zero moment point (ZMP). Our algorithm consists of three steps. First, it analyzes the ZMP trajectory to find out the duration in which dynamic balance is violated. Dynamic imbalance is identified by the ZMP trajectory segments lying out of the supporting area. Next, the algorithm modifies the ZMP trajectory by projecting it into the supporting area. Finally, it generates the balanced motion that satisfies the new ZMP constraint. This process is formulated as a constrained optimization problem so that the new motion resembles the original motion as much as possible. Experiments prove that our motion balance filtering algorithm is a useful method to add physical realism to a kinematically edited motion.
An Interactive Approach to Point Cloud Triangulation
Authors: Kobbelt Leif P. , Botsch Mario
Published: March 2003

We present an interactive system for the generation of high quality triangle meshes that allows us to handle hybrid geometry (point clouds, polygons,. . .) as input data. In order to be able to robustly process huge data sets, we exploit graphics hardware features like the raster manager and the z‐buffer for specific sub‐tasks in the overall procedure. By this we significantly accelerate the stitching of mesh patches and obtain an algorithm for sub‐sampling the data points in linear time. The target resolution and the triangle alignment in sub‐regions of the resulting mesh can be controlled by adjusting the screen resolution and viewing transformation. An intuitive user interface provides a flexible tool for application dependent optimization of the mesh.
Efficient Algorithms for Computing Conservative Portal Visibility Information
Authors: Jiménez W. F. H. , Esperança C. , Oliveira A. A. F.
Published: March 2003

The number of polygons in realistic architectural models is many more than can be rendered at interactive frame rates. Typically, however, due to occlusion by opaque surfaces (e.g., walls), only small fractions of such models are visible from most viewpoints. This fact is used in many popular methods for preprocessing visibility information which assume a scene model subdivided into convex cells connected through convex portals. These methods need to establish which cells or parts thereof are visible to a generalized observer located within each cell. The geometry of this information is termed a ‘visibility volume’ and its computation is usually quite complex. Conservative approximations of viewing volumes, however, are simpler and less expensive to compute. In this paper we present techniques and algorithms which permit the computation of conservative viewing volumes incrementally. In particular, we describe an algorithm for computing the viewing volumes for a given cell through a sequence of ‘m’ portals containing a total of ‘n’ edges in Omn time.
Wavelet Radiative Transfer and Surface Interaction
Authors: Lewis Robert R. , Fournier Alain
Published: March 2003

Recently, there has been considerable interest in the representation of radiance in terms of wavelet basis functions. We will present a coordinate system called Nusselt coordinates which, when combined with wavelets, considerably simplifies computation of radiative transport and surface interaction. It also provides straightforward computation of the physical quantities involved.

We show how to construct a discrete representation of the radiative transport operator Τ involving inner products of smoothing functions, discuss the possible numerical integration techniques, and present an application. We also show how surface interaction can be represented as a kind of matrix product of the wavelet projections of an incident radiance and a bidirectional reflectance distribution function (BRDF).
A Survey of 3D Solid Reconstruction from 2D Projection Line Drawings
Authors: Wang Weidong , Grinstein Georges G.
Published: March 2003

The reconstruction of a 3D object from its 2D projection(s) and its corresponding problem of 3D object recognition are two of the important research areas in the field of computer vision and artificial intelligence. Reconstruction involves determining the geometric and topological relationship of an object's atomic parts whereas recognition involves identifying an object by some form of template matching. Nagendra and Gujar1 gave a survey of several papers on reconstruction of 3D object from its 2D views. In this paper we present a taxonomy of 3D object reconstruction from 2D projection line drawings. We base the classification on the number of 2D views of the 3D solid object, the degree of user interaction necessary for correct reconstruction, and the internal representation used in the reconstruction process. We discuss the basic issues associated with this problem, review the relevant literature and present topics for future research.
A Theoretical Framework for Physically Based Rendering
Authors: Lafortune Eric P. , Willems Yves D.
Published: March 2003

In this paper we introduce the concept of the global reflection distribution function which allows concise formulation of the global illumination problem. Unlike previous formulations it is not geared towards any specific algorithm. As an example of its versatility we derive a Monte Carlo rendering algorithm that seamlessly integrates the ideas of shooting and gathering power to create photorealistic images.
The Mesh Propagation Algorithm for Isosurface Construction
Authors: Howic C.T. , Blake E.H.
Published: March 2003

A new algorithm, Mesh Propagation, is presented for the generation of isosurfaces from three‐dimensional discrete data sets. While producing the same surface mesh as that generated by a corrected Marching Cubes algorithm, its characteristic is that it constructs an isosurface using connected strips of dynamically triangulated polygons. This compact data structure speeds up surface construction and reduces surface storage requirements. The surface can also be displayed more quickly, particularly where there is hardware support for rendering triangle strips.

With engineering as well as medical imaging applications in mind, the algorithm can be used with both irregular and rectilinear grids of data, the primitive volume elements need not be hexahedral only, and volumes of heterogeneous polyhedral elements are supported without traversal complications.

The algorithm propagates through the cells in the grid and uses the same lookup table topologies as Marching Cubes to determine patches of surface‐element intersection; additional tables are used for non‐hexahedral elements. The surface patches are dynamically coded into triangle strips which are then concatenated and linked to construct the surface. The data structures used for propagating through the volume overcome the topological ambiguities associated with table‐based methods of surface construction and no holes are generated in the final mesh.
The Layout Design Language: A Technique for Generating Layout Plans
Authors: Grimsdale R.L. , Chang C.W.
Published: March 2003

The work described in this paper arose from a requirement for a system to support the production of models for training simulator visual systems and other visualisation applications. To reduce the labour involved in generating such models, it was decided to develop a technique whereby models could be generated by a high‐leuel language. For these models there is a requirement to generate 2‐D plans showing, for example, the locations of roads and buildings, subsequently 3‐D models of the buildings are placed at the defined locations. The 2‐D plans can be created through the use of the Layout Design Language (LD‐Language). LD‐Language has been formulated particularly for designing urban area street plans.

The primitive elements of the LD‐Language, plots, are assembled into patterns which can be further combined into a layout plan, with some support provided by the system. The work reported has successfully demonstrated that a complex layout plan can be developed using this language.
A Three Dimensional Image Cache for Virtual Reality
Authors: Schaufler Gernot , Stürzlinger Wolfgang
Published: March 2003

Despite recent advances in rendering hardware, large and complex virtual environments cannot be displayed with a sufficiently highframe rate, because of limitations in the available rendering performance.

This paper presents a new approach of software accelerated rendering which draws from the concepts of impostors, hierarchical scene subdivision and levels of detail. So far software optimization in real‐time rendering has merely considered individual objects. This work is actually optimizing the rendering of the whole virtual environment by implementing a three dimensional image cache. It speeds up rendering for large portions of the scene by exploiting the coherence inherent in any smooth frame sequence.

The implementation of the three dimensional image cache is discussed and the savings in rendering load achievable on a suitable hardware platform are presented.
BOXTREE: A Hierarchical Representation for Surfaces in 3D
Authors: Barequet Gill , Chazelle Bernard , Guibas Leonidas J. , Mitchell Joseph S.B. , Tal Ayellet
Published: March 2003

We introduce the boxtree, a versatile data structure for representing triangulated or meshed surfaces in 3D. A boxtree is a hierarchical structure of nested boxes that supports efficient ray tracing and collision detection. It is simple and robust, and requires minimal space. In situations where storage is at a premium, boxtrees are effective alternatives to octrees and BSP trees. They are also more flexible and efficient than R‐trees, and nearly as simple to implement.
Democracy as Procedure and Democracy as Regime
Authors: Castoriadis Cornelius
Published: March 2003

In the intellectual confusion prevailing since the demise of Marxism and “marxism”, the attempt is made to define democracy as a matter of pure procedure, explicitly avoiding and condemning any reference to substantive objectives. It can easily be shown, however, that the idea of a purely procedural “democracy” is incoherent and self‐contradictory. No legal system whatsoever and no government can exist in the absence of substantive conditions which cannot be left to chance or to the workings of the “market” but must be posited as objectives of political activity. The confusion results from a deficient understanding of what makes a society and an empty idea of “freedom”. The objective of politics is not happiness, an affair to be left to the individuals, but it certainly is liberty understood as participation in the governance of the polity; it is also the pursuit of the common good, defined as the sum of the prerequisites and facilitations of individual autonomy depending on collective action, and as the realization of commonly agreed collective goals.
Women Directors: Selection, Acceptance and Benefits of Board Membership
Authors: Burke Ronald J.
Published: March 2003

This study examined views of women directors on criteria for their being selected, reasons for serving and benefits derived from their directorships. Data were collected from 280 women serving on Canadian corporate boards of directors using anonymous questionnaires. A successful career in traditional business organizations emerged as the major selection criteria. Personal contacts and visibility to male board members was essential. Company/industry interest and broadening skills and knowledge motivated women’s board service. Finally women board members reported considerable benefits from serving. Efforts to broaden the selection and nomination process to include more qualified women may benefit women, men and organizations.
A Taxonomy of Systems of Corporate Governance
Authors: Weimer Jeroen , Pape Joost
Published: March 2003

This paper argues that debate on corporate governance in an international context is hampered by the lack of a coherent framework. A taxonomy of systems of corporate governance is proposed as a remedy. The taxonomy is based upon eight characteristics: the prevailing concept of the firm, the board system, the salient stakeholders able to exert influence on managerial decision‐making, the importance of stock markets in the national economy, the presence or absence of an external market for corporate control, the ownership structure, the extent to which executive compensation is dependent on corporate performance, and the time horizon of economic relationships. Four types of systems of corporate governance emerge: the Anglo‐Saxon systems, the Germanic systems, the Latin systems and the Japanese system.
The Familiarity Threat and Auditor Independence
Authors: Hussey Roger
Published: March 2003

Although legally auditors are answerable to shareholders, considerable doubt has been cast on their independence from the directors of the company which is audited. Recently, increasing competition amongst auditors and the growing importance to fee income of non‐audit work has been identified as factors which may further erode this assumed independence. Another factor which has been implicit in many studies of auditor independence is the close nature of the relationship between the auditor and the directors of the company. This has been termed the ‘Familiarity Threat’.

This article, based on a questionnaire survey of UK finance directors, investigates three aspects of the auditor/director relationship where the ‘Familiarity Threat’ may be present. First is the appointment method and the characteristics which directors consider to be preferable in selecting an auditing firm. Secondly is the duration of the auditors’ appointment and the frequency of contact between the lead partner and the finance director. Finally, is the finance directors’ perception of the nature of the relationship they enjoy with the auditors. For each of these aspects the responses from finance directors from independent public limited companies are compared to those of private companies to ascertain whether the ‘Familiarity Threat’ is more prevalent where certain public responsibilities are not imposed. Where appropriate, the responses are also analysed by the finance directors’ opinions on the probity of non‐audit work to ascertain whether this is an important variable as claimed in the literature.

The analysis demonstrates that, although present directors are influential in the appointment process and the personal chemistry between the directors and auditors is the most important desirable characteristic, the finance directors of independent public limited companies would appear to be more aware of their responsibilities to shareholders. However, many relationships are long established with over 40% of both private and independent public limited companies in the survey retaining their auditors for over 10 years. As far as frequency of contact is concerned, public limited companies were visited more frequently by their auditors and this was unaffected by finance directors’ opinions on the probity of non‐audit work. Finally, approximately 75% of finance directors claimed to enjoy a professional and amicable relationship with their auditors and these responses are unaffected by the type of company or opinions on non‐audit work.

The article concludes that there is the potential for the ‘Familiarity Threat’ to be present in both private and independent public limited companies, but its influence may be exaggerated particularly in respect of non‐audit work. It recommends that if controls are to be introduced to ensure the threat is kept to a minimum it would be best to concentrate on the selection and appointment process and the duration of auditors’ term of office.
Corporate Governance: And the Bargaining Power of Developing Countries to Attract Foreign Investment
Authors: Rueda‐Sabater Enrique
Published: March 2003

Following the rapid growth of foreign investment flows in the 1980s and 1990s some countries that had been dependent on official aid are now (even after the recent financial crises) obtaining most of their external financing from private sources. But low‐income countries still receive little private capital flows. Arguing that corporate governance, broadly defined to include many business practices, is an important determinant of inward foreign investment this paper explores links between corporate Governance: And the ability of developing countries to attract foreign investment. It raises policy questions for developing countries and points to the need for complementary actions by government, businesses associations and institutional investors to promote corporate governance improvements.
Antecedents and Consequences of Corporate Governance Structures
Authors: Burton Peter
Published: March 2003

The paper uses organisation theory to seek an explanation for the relative uniformity of governance structures (as distinct from other aspects of organisational structure) in public companies in the UK and USA. It then reviews theoretical and empirical evidence of ways in which these structures affect company performance, and finds that conventional views about the benefits of independent governance structures are not strongly supported.
Whither Corporate Governance in the 21st Century?
Authors: Cassidy Denis
Published: March 2003

In this personal perspective on corporate governance, Denis Cassidy draws on his board‐level experiences, including his chairmanship of Liberty PLC., and Newcastle United PLC.