bluuebunny/crossref_metadata_2025 huggingface dataset:
A distributed graphics library system
Authors: Adelstein Frank , Richard Golden , Schwiebert Loren , Parent Rick , Singhal Mukesh
Published: November 2006

We present a set of library routines that allow easily parallelized graphics rendering routines that require no communication between each parallel task, such as ray‐tracing, to be run efficiently in an environment of distributed workstations. The presentation of the paper focuses on the problems encountered in implementing a distributed system under Unix and proposes solutions to each problem. Specifically, we discuss the challenges involved in overcoming the limits of communicating with a large number of processes in Unix and in providing fault tolerance when using sockets. Technical aspects of the implementation and some additional problems that were encountered are discussed. Finally, we compare the rendering times for a complex image with a renderer using the library and show that the library routines are able to exploit much of the existing parallelism. The library is presented using a graphics application, though the concepts are generic enough to be of use in designing any distributed system under Unix.
Visualizing program dependencies: An experimental study
Authors: Linos Panagiotis K. , Aubet Philippe , Dumas Laurent , Helleboid Yann , Lejeune Patricia , Tulula Philippe
Published: November 2006

This paper addresses the problem of visualizing program dependencies (i.e. entities and their relations). A code visualization tool that maintains a repository of structural and functional dependencies for C programs is described. Visualization of such dependencies is accomplished by using a presentation model which combines data and control flow information. Moreover, transformation mechanisms and partitioning techniques used by the tool provide the means for managing large graphical representations. The quantitative results from an experimental study using this tool indicate that the productivity of its users was increased and that the quality of changes made during a program modification exercise was improved. Furthermore, the qualitative results have shown that its presentation model, transformation mechanisms and partitioning techniques constitute a promising platform for the comprehension and maintenance of C programs. Finally, the outcome of an empirical evaluation of the tool and the enhancement of its functionality and user interface are also discussed in this paper.
Synthetic‐perturbation techniques for screening shared memory programs
Authors: Snelick Robert , Jájá Joseph , Kacker Raghu , Lyon Gordon
Published: November 2006

The synthetic‐perturbation screening (SPS) methodology is based on an empirical approach; SPS introduces artificial perturbations into the MIMD program and captures the effects of such perturbations by using the modern branch of statistics called design of experiments. SPS can provide the basis of a powerful tool for screening MIMD programs for performance bottlenecks. This technique is portable across machines and architectures, and scales extremely well on massively parallel processors. The purpose of this paper is to explain the general approach and to extend it to address specific features that are the main source of poor performance on the shared memory programming model. These include performance degradation due to load imbalance and insufficient parallelism, and overhead introduced by synchronizations and by accessing shared data structures. We illustrate the practicality of SPS by demonstrating its use on two very different case studies: a large image understanding benchmark and a parallel quicksort.
Experience realising a meta‐model for wide system understanding: The global system model
Authors: Freeman M. J. , Layzell P. J.
Published: November 2006

The Esprit DOCKET project seeks to reduce the problems associated with software maintenance through enhancing traditional, reverse engineering tools with other sources of knowledge, enabling mainters to produce more accurate system models. To produce accurate system models, knowledge about an information system, obtained from different sources, must be interpreted and integrated into a single model (known as the global system model in DOCKET). The definition and implementation of such a model involves the resolution of many issues. These include multiple views of a system at different levels of abstraction, handling inconsistency, incompleteness and system description evolution. This paper reports on the implementation of the Global System Model using the language SML. SML enabled design and implementation problems to be surmounted at a high level of abstraction and facilitated the rapid implementation and testing of the global system model, greatly reducing the effort required to implement it compared to more conventional facilities.
An interactive tool for design, simulation, verification, and synthesis of protocols
Authors: Chao Daniel Y. , Wang David T.
Published: November 2006

We have developed a user‐friendly CAD graphical tool for the design, verification, simulation, and synthesis of protocols based on an interactive tool for Petri net and state diagram designs. Special features of this tool are: the capability of modeling both control and data flows, reduction and analysis, simulation of network behavior and performance, coding (parametrized protocols and automatic implementation), synthesis (two party protocol and ordinary Petri nets), animation and flexible design. Since it is Petri‐net based, it allows simulation during all design phases and has extensive applications such as parallel debugging and simulation, expert systems, etc. Future enhancements of this tool are also discussed.
Parallel context‐sensitive compilation
Authors: Asthagiri Chandra R. , Potter Jerry L.
Published: November 2006

The searching power of massively parallel associative computers is an under used and under investigated capability that can be used to facilitate software development. This paper describes the development of a context sensitive compiler for pattern‐matching languages using that searching power. The described compiler was implemented on the STARAN parallel computer and the compiled OPS5 programs were also executed on the STARAN obtaining an estimated throughput of 6000 rules per second. The described compilation of production rules into equivalent procedural rules is completely data parallel, with the degree of parallelism depending on the number of tokens in the program being compiled. During any one step of the context‐sensitive analysis, the entire program is processed in constant time.
Compiler‐assisted full checkpointing
Authors: Li Chung‐Chi Jim , Stewart Elliot M. , Fuchs W. Kent
Published: November 2006

This paper describes a compiler‐based approach to checkpointing for process recovery. The implementation is transparent to both the programmer and the hardware. The compiler‐generatedsparse potential checkpointcode maintains the desired checkpoint interval.Adaptive checkpointingreduces the size of the checkpoints.Trainingis used to select low‐cost, high‐coverage potential checkpoints. The problem of selecting potential checkpoints is shown to be NP‐complete, and a heuristic algorithm is introduced that determines a quick suboptimal solution. These compiler‐assisted checkpointing techniques have been implemented in a modified version of the GNU C (GCC) compiler. Experiments involving the modified version of the GCC compiler on a Sun SPARC workstation are summarized.
Distributed process creation within a shared data space framework
Authors: Robinson Patrick G. , Arthur James D.
Published: November 2006

This paper describes the design and implementation of a remote process instantiation mechanism which is consistent with the Linda paradigm and semantics of the EVAL operation, and which uses shared data space as the medium for passing process and environment parameters. The motivation for such an implementation stems from our effort to rehost a uniprocessor version of the Linda computational system to a network of workstations. The baseline version of the Linda system relies on the semantics of the UNIX fork() system call to create processes and to pass the proper execution parameters to them. In creating a distributed version of the Linda environment, two major issues are addressed: (1) how to instantiate a remote process that knows where, among several possibilities, to begin its execution, and (2) how to communicate the proper run‐time values of relevant variables to each new remote Linda process. Guiding our implementation was a desire to employ existing interprocess communication facilities, i.e. shared data space, to pass process creation and execution parameters.
An operating system independent WORM archival system
Authors: Russo Guido , Russo Stefano , Pirenne Benǒit
Published: November 2006

We describe the organization of a general purpose data archival system for Write‐Once, Read‐Many (WORM) optical disks. The system has been designed for large‐scale and long‐term data storage and retrieval. The archival system is independent of the operating system, flat, self‐consistent, does not use any write cache on magnetic disk, and allows the exploitation of auxiliary information on magnetic disk, which can be rebuilt immediately in case of a crash, to speed up file retrieval. A library in C language, called pODLIB, has been implemented as a portable interface to the archival system.
Adding graphics to a high‐level programming language
Authors: Jeffery Clinton L. , Griswold Ralph E. , Townsend Gregg M.
Published: November 2006

When graphics input/output capabilities are added to a programming language originally designed with a text stream input/output model, various design decisions affect the ease with which the graphics facilities are learned and used by applications programmers. In adding window system facilities to the Icon programming language, some design decisions were made very differently from the conventional wisdom, resulting in substantial benefits for programmers. In addition, some pre‐existing Icon language features have proved to be useful in graphics programming.
CBack: A simple tool for backtrack programming in C
Authors: Helsgaun Keld
Published: November 2006

Backtrack programming is such a powerful technique for problem solving that a number of languages, especially in the area of artificial intelligence, have built‐in facilities for backtrack programming. This paper describes CBack, a simple, but general tool for backtrack programming in the programming language C. The use of the tool is illustrated through examples of a tutorial nature. In addition to the usual depth‐first search strategy, CBack provides for the more general heuristic best‐first search strategy. The implementation of CBack is described in detail. The source code, shown in its full length, is entirely written in ANSI C and highly portable across diverse computer architectures and C compilers.
On tuning recursive procedures
Authors: Yehudai Amiram , Libedinsky Fernando
Published: November 2006

We propose a methodology of reducing the space requirements of recursive procedures without destroying their fundamental recursive structure. This technique is quite general, and seems to apply to most recursive procedures, particularly those dealing with recursive data structures. A recursive procedure is transformed into three procedures — a shell which is called from the outside, and has the same interface as the original, a recursive procedure with a minimum number of parameters, and no local variables, and a procedure that performs the operations but has no recursive calls. Our methodology was successfully employed in an implementation of a decision support system. The paper also includes results of experiments, in which space was reduced by a factor of up to seven, and run time was also improved.
Using protean for verifying a complex protocol — A case study
Authors: Lai R.
Published: November 2006

Communication protocols used in the field have always suffered from failures. Some of these faults are the result of design errors; others are the result of implementation errors. These errors dramatically increase maintenance cost and decrease software reliability. The best time to maintain software is during its design stage. A formal approach to developing a protocol is deemed necessary to improve the quality of communication software and to reduce maintenance costs. Protocol verification plays a major role in achieving these objectives; a protocol is first specified formally and then this formal specification is analysed using a computer‐aided tool. PROTEAN is a software tool that verifies a protocol specified formally in Numerical Petri Nets. This paper describes the experience and practice of using PROTEAN to verify a complex protocol and then presents an evaluation of PROTEAN and its associated techniques in the light of protocol software development. The ISO FTAM protocol is used as a case study.
An approach to automatic display layout using combinatorial optimization algorithms
Authors: Lüders Peter , Ernst Rolf , Stille Stefan
Published: November 2006

The introduction of automatic display layout (ADL), i.e. the automatic placing and sizing of windows in a window‐oriented graphical user interface, is a major contribution towards an improved user interface. Our approach to ADL is to treat this problem as a combinatorial optimization problem. In this article we describe the concepts we used for implementing an experimental system which controls the computer screen contents and its layout. We give two examples of different standard applications into which we included ADL successfully, namely hypertext for a window layout problem and graph‐browser for a hierarchical graph layout problem within a particular window. The results show that automatic (and tool independent) display layout will be possible in the near future even in an interactive environment.
Using formalized temporal message‐flow diagrams
Authors: Citrin Wayne , Cockburn Alistair , Kanel Jurg Von , Hauser Rainer
Published: November 2006

Temporal message‐flow diagrams (TMFDs), alternatively called sequence charts, interaction diagrams, event traces, or actor diagrams, are illustrations of a system's global message‐passing activity over time, and a pictorial aid to understanding the system's behavior. They are widely used for requirements and documentation for network protocols and object‐oriented applications. We present a general formalism for TMFDs, describe a suite of tools we have designed that employs this formalism, and present our experiences with these tools. The formalism and tools described serve to support and broaden the use of TMFDs in developing communicating systems.
Preparation and Characterization of Annealed‐Enzymatically Hydrolyzed Tapioca Starch and the Utilization in Tableting
Authors: Tukomane Tuangporn , Leerapongnun Prakan , Shobsngob Sujin , Varavinit Saiyavit
Published: November 2006

Tapioca starch was annealed at 60°C for 90 min followed by hydrolysis with α‐amylase at 60°C at various lengths of time (30, 60 and 120 min) to obtain high‐crystalline starches. The reaction products were subjected to spray drying to obtain annealed–enzymatically hydrolyzed–spray dried tapioca starch (SANET) in the form of spherical agglomerated granules. The properties of SANET were compared with those of annealed–spray dried tapioca starch without enzymatic treatment (SANT) and native–spray dried tapioca starch (SNT). Scanning electron micrographs of the starch samples were used to study the morphological changes and to suggest the mode of enzyme attack during hydrolysis. The á‐amylase preferentially attacked the interior of the starch granules, leaving a deep round hole on the starch granule surface. It was found by X‐ray diffraction that both annealing and amylolysis did not alter the A type diffraction pattern. The% relative crystallinity of SANET was raised with increasing hydrolysis time and with decreasing amylose content. High performance size exclusion chromatography (HPSEC) demonstrated the decrease of the degree of polymerization (DP) of the amylose fraction of SANET after prolonged hydrolysis. For the utilization of SANET as tablet filler, it was directly compressed by a tablet compression machine at 4 kN to obtain tablets. The increased relative crystallinity of starch resulted in increased crushing strength and disintegration time, but in a decreased tablet friability.
Structured inspections of code
Authors: Van Emden Maarten H.
Published: November 2006

Cleanroom programming and code inspections independently provide evidence that it is more efficient to postpone the testing of code to a later stage than is usually done. This paper argues that an additional gain in quality and efficiency of development can be obtained by structuring inspections by means of an inspection protocol. The written part of such a protocol is prepared by the programmer before the inspection. It is modelled on Floyd's method for the verification of flowcharts. However, the protocol differs from Floyd's method in being applicable in practice. Structured inspections gain this advantage by not attempting to be a proof; they are no more than an articulation of existing forms of inspection. With the usual method of structured programming it may be difficult to prepare the inspection protol. On the other hand, ‘assertion‐driven programming’ (of which an example is included in this paper) not only facilitates protocol preparation, but also the coding itself.
Dynamic method for software test data generation
Authors: Korel Bogdan
Published: November 2006

Test data generation in program testing is the process of identifying a set of test data which satisfies a given testing criterion. Existing pathwise test data generators proceed by selecting program paths that satisfy the selected criterion and then generating program inputs for these paths. One of the problems with this approach is that unfeasible paths are often selected; as a result, significant computational effort can be wasted in analysing those paths. In this paper, an approach to test data generation, referred to as a dynamic approach for test data generation, is presented. In this approach, the path selection stage is eliminated. Test data are derived based on the actual execution of the program under test and function minimization methods. The approach starts by executing a program for an arbitrary program input. During program execution for each executed branch, a search procedure decides whether the execution should continue through the current branch or an alternative branch should be taken. If an undesirable execution flow is observed at the current branch, then a real‐valued function is associated with this branch, and function minimization search algorithms are used to locate values of input variables automatically, which will change the flow of execution at this branch.
Replay‐based debugging of occam programs
Authors: Cimitile A. , De Carlini U. , Villano U.
Published: November 2006

Parallel programs are intrinsically non‐deterministic, and therefore the techniques of cyclical debugging that are commonly used for sequential programs are not suitable for parallel ones. This paper proposes a method to reproduce Occam program behaviour. Saving information on the timer values input by the program and the guards selected at run‐time on alternative commands allows program replay, i.e. it makes it possible to re‐execute the program deterministically with the same inputs following the same instruction path. This enables the software developer to use tools such as debuggers and intrusive monitors to help identify program faults. After discussing possible implementations of the proposed technique, IRD (an interactive replay debugger for Occam programs) is described. Finally, the use of the IRD in a sample debug session is presented as an example.
Using symbolic execution and data flow criteria to aid test data selection
Authors: Girgis Moheb R.
Published: November 2006

The utilization is described of a data flow path selection criterion in a symbolic execution system. The system automatically generates a subset of program paths according to a certain control flow criterion. This subset is called the ZOT‐subset, since it requires paths that traverse loops zero, one and two times. Experience indicates that traversing this subset of program paths is enough to cover most control flow and data flow components of the program. The problem with the ZOT‐subset is that it might contain, for large programs, a large number of paths. The number of paths in this subset can be reduced by concentrating on executable paths that cover vital components of programs such as data flow components. This object is achieved by employing a data flow path selection criterion in the system. The system symbolically executes the paths of the ZOT‐subset, and creates a system of branch conditions for each one. The user determines infeasible paths by checking the consistency of each system of conditions. The system selects feasible paths from the ZOT‐subset that cover the data flow criterion. Solving the systems of conditions of the selected paths provides the user with test data to fulfil the given data flow criterion.
Algebraic specifications and sequencing: A defect detection method
Authors: Olender Kurt M. , Bieman James M.
Published: November 2006

One class of program defects results from illegal sequences of otherwise legal operations in software implementations. Explicit statement of sequencing constraints, however, is not a common activity when specifying software even when using formal specification methods. This paper shows that constraints on program execution sequences can be derived directly from algebraic specifications. Results include heuristic methods for generating sequencing constraints and a generalization of these methods into automatable rules. The heuristics can be integrated into a specification methodology such as Larch. Engineers can use the generated sequencing constraints to detect sequencing defects in software even before dynamic testing begins. The method can be used to increase the reliability of software that is specified using algebraic methods.
Decision tables: Formalisation, validation, and verification
Authors: Murrell Stephen , Plant Robert
Published: November 2006

The decision table is one of the simplest representations of the rules underlying a systematic decision‐making process, and is especially valuable in the development of knowledge‐based systems. A two dimensional table links all relevant combinations of input conditions to the desired combinations of output actions in a very intuitive way. This simplicity belies the complex considerations involved in verifying, validating, formulating or interpreting this (or any other) representation of machine‐based knowledge. In this paper, the common styles of decision table representation are reviewed, a formulation of their meaning is presented, construction methods are reviewed, and an algorithm for ensuring consistency is suggested. The problems that may occur in imperfectly constructed tables are discussed, detection methods reviewed, and some implementation methods are presented.
Developing a sustained interest in science among urban minority youth
Authors: Basu Sreyashi Jhumki , Barton Angela Calabrese
Published: November 2006

This study draws upon qualitative case study to investigate the connections between the “funds of knowledge” that urban, high‐poverty students bring to science learning and the development of a sustained interest in science. We found that youth developed a sustained interest in science when: (1) their science experiences connected with how they envision their own futures; (2) learning environments supported the kinds of social relationships students valued; and (3) science activities supported students' sense of agency for enacting their views on the purpose of science. © 2006 Wiley Periodicals, Inc. J Res Sci Teach 44: 466–489, 2007
A novel technique for visualization of the normal and cleft fetal secondary palate: angled insonation and three‐dimensional ultrasound
Authors: Pilu G. , Segata M.
Published: November 2006

Objective

To evaluate the effectiveness of a novel approach to the visualization of the fetal secondary palate using three‐dimensional (3D) ultrasound.

Methods

Sonographic examinations were performed in normal fetuses and in one fetus with cleft lip and palate. To avoid acoustic shadowing from the alveolar ridge, the secondary palate was insonated at a 45° angle in the sagittal plane, and 3D ultrasound was used to reconstruct axial and coronal planes.

Results

The secondary palate was successfully visualized in 10 of 15 normal fetuses, both in the axial and coronal planes. In the fetus with cleft lip and palate the lesion of the secondary palate was clearly demonstrated, particularly in the coronal plane.

Conclusion

Angled insonation and 3D ultrasound allow clear visualization of normal and cleft secondary palate. Copyright © 2006 ISUOG. Published by John Wiley & Sons, Ltd.
Motor planning: An architecture for specifying and controlling the behaviour of virtual actors
Authors: Zeltzer David , Johnson Michael B.
Published: November 2006

As virtual worlds become increasingly complex,task levelinteraction with virtual actors becomes correspondingly important. The control problem simply becomes unmanageable if we try to interact with synthetic agents at the wrong level of abstraction. However, it is not sufficient merely to implement a set of behaviours for a virtual actor; we require some mechanism for selecting and sequencing motor skills appropriate to the current behavioural goalsandthe states of other objects and actors in the virtual environment. In this paper we will describe a mechanism for linkingperceptionandactionto generate routine behaviours in a process we callmotor planning.We present our implementation of the skill network, in which motor skills are the nodes and the arcs represent inhibitory and excitatory connections, including extensions to this architecture based on recent work in robotics. We characterize the domain of motor planning, i.e. what kinds of behaviour can it account for, and when will it fail? We close with a discussion of the limits of our current implementation and work that remains to be done.
Inverse lagrangian dynamics for animating articulated models
Authors: Vasilonikolidakis Nickos , Clapworthy Gordon J.
Published: November 2006

This paper presents the application of inverse Lagrangian dynamics for the purpose of animating articulated models. The method orginates from mechanics and robotics and has been adapted to deal with branched kinematic chains and joints with multiple degrees of freedom. The method is then reformulated to calculate the ground reaction forces that apply to the body. The approach is direct and does not involve guesswork. The formulation has been implemented into a general animation system that is entirely interactive and supports the facility of simulating generic articulated models.
Automated lip‐sync: Background and techniques
Authors: Lewis John
Published: November 2006

The problem of creating mouth animation synchronized to recorded speech is discussed. Review of a model of speech sound generation indicates that the automatic derivation of mouth movement from a speech soundtrack is a tractable problem. Several automatic lip‐sync techniques are compared, and one method is described in detail. In this method a common speech synthesis method, linear prediction, is adapted to provide simple and accurate phoneme recognition. The recognized phonemes are associated with mouth positions to provide keyframes for computer animation of speech. Experience with this technique indicates that automatic lip‐sync can produce useful results.
Simulating the structure and dynamics of human hair: Modelling, rendering and animation
Authors: Rosenblum Robert E. , Carlson Wayne E. , Tripp Edwin
Published: November 2006

We develop and present a new approach to modelling the characteristics of human hair, considering not only its structure, but also the control of its motion and a technique for rendering it in a realistic form. The approach includes a system for interactively defining the global positioning of the strands of hair on the head. Special attention is paid to the self shadowing of the hair. A mass/spring/hinge system is used to control a single strand's position and orientation. We demonstrate that this approach results in a believable rendition of the hair and its dynamics.
Graphical displays of human strength data
Authors: Wei Susanna , Badler Norman I.
Published: November 2006

To facilitate the effective use of strength data in a human‐task simulation environment, we have developed graphical methods to display the multidimensional characteristics of strength data. We use human figures together with two and three dimensional graphical symbols, colours and animations to visualize the effects of different parameters on strength. These displays give a dynamic view of the effects of various parameters on strength, and illustrate safe and forbidden body postures (or regions) in terms of strength capabilities.
The virtual museum: Interactive 3D navigation of a multimedia database
Authors: Miller Gavin , Hoffert Eric , Chen Shenchang Eric , Patterson Elizabeth , Blackketter Dean , Rubin Steve , Applin Sally Ann , Yim Derrick , Hanan Jim
Published: November 2006

The Virtual Museum is an interactive, electronic museum where users can move from room to room, and select any exhibit in a room for more detailed examination. The exhibits in the museum are educational, encompassing topics such as medicine, plant growth, the environment, and space. To facilitate interaction with the museum, a new method for navigating through a prerendered 3D space, and interacting with objects in that space has been developed, called ‘virtual navigation’. Virtual navigation employs real‐time video decompression for the display of, and interaction with, high‐quality computer animation. In addition, a representation for 3D objects in animated sequences is used which permits pixel‐accurate, frame‐accurate object picking, so that a viewer can select any 3D object to trigger movement within the 3D space, to examine an exhibit in animated form, or to play a digital movie or soundtrack. The use of precomputed video permits 3D navigation in a realistic‐looking space, without requiring special‐purpose graphics hardware.
Computer animated visual translation from natural language to sign language
Authors: Lee Jintae , Kunii Tosiyasu L.
Published: November 2006

Computer animation and visualization can facilitate communication between the hearing impaired and those with normal speaking capabilities. This paper presents a model of a system that is capable of translating text from a natural language into animated sign language. Techniques have been developed to analyse language and transform it into sign language in a systematic way. A hand motion coding method as applied to the hand motion representation, and control has also been investigated. Two translation examples are also given to demonstrate the practicality of the system.
Physical simulation of land vehicles with obstacle avoidance and various terrain interactions
Authors: Jimenez Stéphane , Luciani Annie , Raoult Olivier
Published: November 2006

Programming the motions of an autonomous planetary robot moving in an hostile and hazardous environment is a complex task which requires both the construction of nominal motion plans and the anticipation as far as possible of the effects of the interactions existing between the vehicle and the terrain. In this paper we show how physical models and dynamic simulation tools can be used for amending and completing a nominal motion plan provided by a classical geometrical path planner. The purpose of our physical modeller‐simulator is to anticipate the dynamic behaviour of the vehicle while executing the nominal motion plan. Then the obtained simulation results can be used to assess and optimize the nominal motion plan. In the first part, we outline the physical models that have been used for modelling the different types of vehicle, of terrain and of vehicle‐surface interactions. Then we formulate the motion planning problem through the definition of two basic abstract constructions derived from physical model: the concept of generalized obstacle and the concept of physical target. We show with various examples how it is possible, when using this method, to solve the locomotion problem and the obstacle avoidance problem simultaneously and, furthermore, to provide the human operator with a true force feedback gestural control over the simulated robot.
Programming mechanical simulations
Authors: Kearney Joseph K. , Hansen Stuart , Cremer James F.
Published: November 2006

This paper examines the control of complex physical objects in simulation. We introduce a programming paradigm that allows a simulation to be treated as a multi‐level constraint solver. The control programmer is given the ability to specify constraints on the controlled response of mechanisms and to conditionally change these constraints dependent on the state of system. The approach facilitates the development of model‐based, event‐driven control programs. The usefulness of the paradigm is demonstrated through the simulation of a hopping robot.
Computation of global illumination in a participating medium by monte carlo simulation
Authors: Pattanaik S. N. , Mudur S. P.
Published: November 2006

This paper discusses techniques for the computation of global illumination in environments with a participating medium using a Monte Carlo simulation of the particle model of light. Efficient algorithms and data structures for tracking the particles inside the volume have been developed. The necessary equation for computing the illumination along any given direction has been derived for rendering a scene with a participating medium. A major issue in any Monte Carlo simulation is the uncertainty in the final simulation results. Various steps of the algorithm have been analysed to identify major sources of uncertainty. To reduce the uncertainty, suitable modifications to the simulation algorithm have been suggested using variance reduction methods of forced collision, absorption suppression and particle divergence. Some sample scenes showing the results of applying these methods are also included.
Animation through space and time based on a space deformation model
Authors: Bechmann Dominique , Dubreuil Nicolas
Published: November 2006

To animate deformable objects through time and space, a new technique that will be referred to as DOGMA is proposed here. It is well suited to animation for both interactive design and real‐time visualization.

The concept of animation primitives based on an extension to animation of the space deformation model is introduced. Animation primitives can be added to any geometrical modeller because they are independent of the underlying geometrical model of the animated objects. It encapsulates animation through space and time under a unique formalism. A local control of deformations both through space and time is easily specified. A direct manipulation of objects is provided. At any time, animated objects are continuously computed from their corresponding animation primitives. This dispenses with the necessity for major storage of the interpolation process. A fully interactive system offers an interactive environment which enables the user to animate deformable objects in real time.
Illusion—creating a mock reality
Authors: Stöβer Achim , Leister Wolfgang , Meyer Frerk
Published: November 2006

Photorealistic computer animation sequences have become more important in recent years in visualization and presentation techniques as well as in fine arts. Some aspects of creating a photorealistic computer animation are demonstrated by the following example of the film Illusion that was created by the computer graphics team at the University of Karlsruhe. An overview of modelling methods, some special effects and details on how to administrate a large computer animation project are presented.
A language for the classification and shading of multivariate volume data
Authors: Palmer Thomas C. , Simpson Edward V. , Smith William M.
Published: November 2006

A novel, language‐based interface to the specification of multivariate volume classification and shading algorithms has been implemented. The system facilitates experimentation by providing access to data relevant to volume classification and shading (scalars, gradients, and gradient magnitudes) in a C‐like language environment. The user writes code to calculate opacity and colour on a per voxel basis. The code is interpreted and compiled in a transparent fashion and then executed on a volume data‐set. The output is a volume primitive suitable for input to standard volume rendering algorithms.
Design and animation of volume density functions
Authors: Ebert David S.
Published: November 2006

This paper describes the design and animation of volume density functions for creating images containing gases, solid textures and hypertextures. The development of functions for producing images and animations of gases is explained in detail. Procedures for modelling the geometry of various gases are described. Next, animation techniques for volume density functions are described and examples of the animation of these functions are presented, including steam rising from a teacup, wind effects, marble forming, and gas and liquid flow into an opening in a wall. Solid spaces are introduced as a unifying approach to describing and animating object attributes.
A simple approximation to rigid body dynamics for computer animation
Authors: Van Overveld C. W. A. M.
Published: November 2006

Recently, the dynamics of linked articulated rigid bodies has become a valuable tool for making realistic three‐dimensional computer animations. An exact treatment of rigid body dynamics, however, is based on rather non‐intuitive results from classical mechanics (e.g. the Euler equations for rotating bodies) and it relies heavily on sophisticated numerical schemes to solve (large) sets of coupled non‐linear algebraic and differential equations. As a result, articulated rigid bodies are not yet supported by most real‐time animation systems. This paper discusses an approach to rigid body dynamics which is based on (both conceptually and algorithmically much simpler) point mechanics; this gives rise to an asymptotically exact numerical scheme (NSI) which is useful in the context of real‐time animation, provided that the number of degrees of freedom of the simulated system is not too large. Based on NSI, a second scheme (NS2) is derived which is useful for approximating the motions of linked articulated rigid bodies; NS2 turns out to be sufficiently fast to give at least qualitative results in real‐time simulation. In general, the algorithm NS2 is not necessarily (asymptotically) exact, but a quantitative analysis shows that in the absence of reaction forces it conserves angular momentum.
Back‐face culling applied to collision detection of polyhedra
Authors: Vaněkčkek George
Published: November 2006

Back‐face culling is a preprocessing technique used in computer graphics to speed up the rendering of polyhedra. In this paper we show how this technique can be modified to reduce unnecessary checking of boundary elements in collison detection for a physical‐based simulation and animation systems. At each time step, we determinea prioriwhich faces cannot be part of the contact between two polyhedra and thus can be culled. In the computer graphics technique, the normal vector of a polygon is compared with the view direction. Here, the normal is compared to one or possibly several relative‐velocity vectors, and the face is culled when its motion is in the opposite direction of the normal vector.

We also give an algorithm that takes linear time in terms of the number of faces, and on the average eliminates half of the polygons. Owing to its low computational overhead, when it is used as a front end to a collision detection system, a noticeable improvement in performance can be achieved.
An articulated limb motion planner for optimized movement
Authors: Miller David P. , Parent Richard E.
Published: November 2006

Task level animation of articulated figures, such as the human body, requires the ability to generate collision‐free goal‐directed motion of individual limbs in the presence of obstacles. This paper describes a new articulated limb motion planner for goal‐directed point‐to‐point reaching motions. The produced motion avoids obstacles while optimizing an objective function.

This two‐phase algorithm uses heuristic guided Monte Carlo techniques to create a consistent underlying paradigm. The first phase consists of an existing potential field based random path planner which generates a population of candidate paths. This initial population is fed into the second phase, a genetic algorithm, which iteratively refines the population as it optimizes with respect to the objective function. The refinement process works on the principle ofpath coherency, the idea that a family of closely related collision‐free paths lies in the vicinity of a given collision‐free path.

This paper focuses on seven different optimization functions. Optimized trajectories produced by the new motion planner are compared to those generated solely by the random path planner. The presented algorithm is flexible in that a wide range of objective functions can be optimized. Applications of the algorithm include task level animation, ergonomics and robotics.
Object‐oriented motion abstraction
Authors: Erkan Bi̇ilge , Oüzüç Bülent
Published: November 2006

An important problem in the production of an animation sequence is the great amount of information necessary to control and specify the motion. Specification of complex animation sequences with a smaller amount of information is possible if they are built over some abstracted sequences. Abstraction supports dealing with complexity by structuring, so that the necessary features are made available while those that are not necessary are hidden. In our work, motion abstraction is used to build complex animation sequences with the help of object‐oriented concepts. A parametric key‐frame interpolation method is used for producing the in‐between frames of an animation sequence. The parameters that define the motion of a model, in our work, are position, orientation, size, shape and colour. Orientation transformations are implemented by unit quaternions.
A dynamic wrinkle model in facial animation and skin ageing
Authors: Wu Yin , Thalmann Nadia Magnenat , Thalmann Daniel
Published: November 2006

This paper describes a dynamic model to simulate expressive wrinkles in 3D facial animation and skin ageing. A skin surface is defined that can slide over an underlying layer, which constrains the surface by a spring force that simulates the connective fat tissue between them. Muscle masks are constructed to characterize the muscular contractions that provide the facial movement. Skin deformation is simulated through an elastic process assembled with visco and plastic units. By adjusting parameters for this physically based model, distinctive wrinkles for different faces can be generated.
Chemical and physical properties of isomeric glyceryl monoethers
Authors: Wood Randall , Snyder Fred
Published: November 2006

Long‐chain saturated and mono‐ and diunsaturated 1‐ and 2‐glyceryl monoethers were synthesized by reacting 1,2‐isopropylidene and 1.3‐benzylidene glycerol potassium salts with alkyl halides in the preparation of the saturated monoethers, and with alkenyl‐p‐toluenesulfonates in the preparation of the unsaturated monoethers, followed by hydrolysis of the blocking groups with boric acid. The progress of the reaction was monitored by gasliquid chromatography (GLC) of the reaction mixture. The 2‐glyceryl ethers, with two exceptions, had not been prepared previously. Normal propyl and 3‐pentyl octadecyl ethers also were synthesized to aid in the interpretation of infrared (IR) and nuclear magnetic resonance (NMR) spectra. All the ethers prepared were purified by preparative thin‐layer chromatography (TLC) and crystallization. Their purity was found to be greater than 95%, as determined by TLC and GLC, supported by NMR and IR spectra. The isomeric 1‐ and 2‐glyceryl ethers were separated on Silica Gel G adsorbent layers impregnated with either sodium arsenite or boric acid and their TLC behavior interpreted, based on the polarity of the complexes formed. Melting point determinations indicated more than one polymorphic form. Comparison of IR and NMR spectra of the saturated and unsaturated isomeric glyceryl ethers, and various derivatives, demonstrated the applicability of these spectroscopy methods for characterization and structural determination, in addition to distinguishing between the two isomeric forms.
Structure of bovine milk fat triglycerides
Authors: Breckenridge W. C. , Kuksis A.
Published: November 2006

The triglycerides of bovine milk fat globules were isolated and separated into short, medium and long chain lengths by thin‐layer chromatography. The molecular weight distribution and the fatty acid composition of the component triglycerides was then separately determined by gas chromatography following argentation‐thin‐layer and preparative gas chromatography. Some 38 triglyceride types (28% of total), of which there could be up to 6 isomers, were specifically identified and quantitatively estimated. The quantitative estimates for the rest of the milk fat triglycerides were limited to much more complex glyceride groups. The results confirm the earlier claim that butyric and caproic acids occur in milk fat almost exclusively in combination with medium and long chain fatty acids.
The 9‐hexadecenoic and 11‐octadecenoic acid content of natural fats and oils
Authors: Kuemmel D. F. , Chapman L. R.
Published: November 2006

The monoenoic methyl esters from numerous fats and oils which contained appreciablecis‐9‐hexadecenoic acid (cis‐9‐16∶1) were isolated by liquid‐solid chromatography on silver nitrate‐silica gel. Analysis of the monoenes by packed and capillary column gas‐liquid chromatography showed that significant amounts ofcis‐11‐octadecenoic acid (cis‐11‐18∶1) were present in all samples. The amount ofcis‐11‐18∶1 found in the monoenoic methyl esters increased proportionally to logarithmic increases in thecis‐9‐16∶1 level. Most analyses reported in the literature also show this proportionality. This mathematical relationship suggests that chain elongation ofcis‐9‐16∶1 tocis‐11‐18∶1 is a biosynthetic pathway operative in a wide variety of species.
The structures of triglycerides from atherosclerotic plaques and other human tissues
Authors: Christie W. W. , Moore J. H. , Lorimer A. R. , Lawrie T. D. V.
Published: November 2006

Stereospecific analysis of trigly cerides isolated from human liver showed that these were much more asymmetric than the triglycerides from human adipose tissue. Heart muscle triglycerides were similar in structure to adipose tissue triglycerides. The triglycerides from aortic plaques were intermediate in structure between triglycerides of liver and adipose tissue.
Reactions of biological antioxidants: I. Fe(III)‐catalyzed reactions of lipid hydroperoxides with α‐tocopherol
Authors: Gruger E. H. , Tappel A. L.
Published: November 2006

Rates of α‐tocopherol oxidation were measured for free‐radical reactions produced by Fe(III)‐catalyzed dissociations of hydroperoxides. The kinetics were treated as first‐order in α‐tocopherol. The hydroperoxides were preformed from methyl linoleate, methyl linolenate, ethyl arachidonate, methyl eicosapentaenoate, and a fraction of polyunsaturated fatty esters of menhaden oil. The degree of unsaturation of the lipid hydroperoxides had little effect on the rates of α‐tocopherol oxidation. The rates of oxidation decrease with the concentration of water and increase with the acidity of the media. The pH data suggest a transition from one predominant mechanism to another, which may involve principally acid catalysis. A mechanism for α‐tocopherol oxidation is suggested.