bluuebunny/crossref_metadata_2025 huggingface dataset:
Interference from endogenous antibodies in automated immunoassays: what laboratorians need to know
Authors: Ismail A A A
Published: July 2009

Full automation of laboratory procedures confers numerous advantages over semi-automated/manual tests because equipment, reagents and the computation of results are offered as an integrated package. Automation has allowed millions of immunoassay tests to be performed with good sensitivity and excellent precision but inaccuracy caused by interference from endogenous immunoglobulins/antibodies remained a problem (irrespective of the immunoassay’s format). Interference leading to a falsely high or low result affects a specific sample and may not be obvious despite the strictest laboratory control schemes. Reporting and interpreting such potentially erroneous data remained however the responsibility of the clinical laboratory despite the limited information supplied by their providers. The focus of this review is on highlighting the potential downside of current disjointed and blurred arrangement between the developers/providers of immunoassays, and the laboratorians responsible for providing these data to their clinical colleagues. These limitations can be addressed by drawing attention to the importance of the key fundamentals underpinning these immunologically based analyses which, if carefully considered, could help to formulate pragmatic strategies to reduce errors in immunoassays. In this review, the inherent fallibility of the binding reaction between an antigen and antibody will be reiterated. The difficulties in defining reaction rate kinetics in non-equilibrium automated assays, the potential clinical error rate and the need for minimising analytical error rate of these automated technologies will be highlighted.
Phosphaturic mesenchymal tumour-mixed connective tissue variant without oncogenic osteomalacia: Figure 1
Authors: Winters R , Bihlmeyer S , McCahill L , Cooper K
Published: July 2009

Phosphaturic mesenchymal tumour-mixed connective tissue variant is a rare tumour classically associated with oncogenic osteomalacia. This report describes two patients with this distinct tumour type but with no evidence of the paraneoplastic syndrome.
An improved method for constructing tissue microarrays from prostate needle biopsy specimens
Authors: McCarthy F , Fletcher A , Dennis N , Cummings C , O’Donnell H , Clark J , Flohr P , Vergis R , Jhavar S , Parker C , Cooper C S
Published: July 2009

Background:

Prostate cancer diagnosis is routinely made by the histopathological examination of formalin fixed needle biopsy specimens. Frequently this is the only cancer tissue available from the patient for the analysis of diagnostic and prognostic biomarkers. There is, therefore, an urgent need for methods that allow the high-throughput analysis of these biopsy samples using immunohistochemical (IHC) markers and fluorescence in situ hybridisation (FISH) analysis based markers.

Methods:

A method that allows the construction of tissue microarrays (TMAs) from diagnostic prostate needle biopsy cores has previously been reported. However, the technique only allows the production of low-density biopsy TMAs with a maximum of 20 cores per TMA. Here two methods are presented that allow the rapid and uniform production of biopsy TMAs containing between 54 and 72 biopsy cores. IHC and FISH techniques were used to detect biomarker status.

Results:

Biopsy TMAs were constructed from prostate needle biopsy specimens taken from 102 patients entered into an active surveillance trial and 201 patients in a radiotherapy trial. The detection rate for cancer in slices of these biopsy TMAs was 66% and 79% respectively. Slices of a biopsy TMA prepared from biopsies from active surveillance patients were used to detect multiple IHC markers and to scoreTMPRSS2-ERGfusion status in a FISH-based assay.

Conclusions:

The construction of biopsy TMAs provides an effective method for the multiplex analysis of IHC and FISH markers and for their assessment as prognostic biomarkers in the context of clinical trials.
Prognostic significance of neuron-associated protein expression in non-muscle-invasive urothelial bladder cancer
Authors: Mhawech-Fauceglia P , Ali L , Cheney R T , Groth J , Herrmann F R
Published: July 2009

Background:

Numerous novel genes have been identified in urothelial bladder cancer (UBC); genes including ninjurin, synuclein and neuropilin seem to be associated with invasive tumours and aggressive behaviour.

Aims:

To define the protein expression of these biomarkers and to reveal their prognostic value in a large series of superficial (pTa) and minimally invasive (pT1) cases of UBC with a long and adequate follow-up.

Methods:

Tissue microarray was done on 183 paraffin-embedded tumour tissues (pTa 81, pT1 102). Statistical analysis was performed to define the association between each of these biomarkers, clinical data and tumour outcomes.

Results:

There was a statistically significant association between synuclein expression and tumour stage (p = 0.029). Ninjurin expression was significantly associated with tumour progression in univariate analysis. Tumour grade seemed to have an independent value in predicting tumour recurrence and progression.

Conclusion:

Tumours with strong synuclein expressions are more likely to be more advanced tumours (pT1). Tumours expressing ninjurin tend to progress slower than those with no ninjurin expressions. Synuclein and neuropilin failed to show any value in predicting tumour behaviour.
HOMOTOPY CLASSIFICATION OF NANOPHRASES IN TURAEV'S THEORY OF WORDS
Authors: FUKUNAGA TOMONORI
Published: July 2009

The purpose of this paper is to give the homotopy classification of nanophrases of length 2 with 4 letters. To do it we construct some new invariants of nanophrases γ and T. The invariant γ defined in this paper is an extension of the invariant γ for nanowords introduced by Turaev. The invariant T is a new invariant of nanophrases. As a corollary of these results, we give the classification of two-component pointed, ordered, oriented curves on surfaces with minimum crossing number less than or equal to 2.
VIRTUAL KNOT INVARIANTS FROM GROUP BIQUANDLES AND THEIR COCYCLES
Authors: CARTER J. SCOTT , SILVER DANIEL S. , WILLIAMS SUSAN G. , ELHAMDADI MOHAMED , SAITO MASAHICO
Published: July 2009

A group-theoretical method, via Wada's representations, is presented to distinguish Kishino's virtual knot from the unknot. Biquandles are constructed for any group using Wada's braid group representations. Cocycle invariants for these biquandles are studied. These invariants are applied to show the non-existence of Alexander numberings and checkerboard colorings.
FUNCTORS EXTENDING THE KAUFFMAN BRACKET
Authors: ARMSTRONG JOHN
Published: July 2009

In this article we extend evaluations of the Kauffman bracket on regular isotopy classes of knots and links to a variety of functors defined on the category [Formula: see text] of framed tangles. We show that many such functors exist, and that they correspond up to equivalence to bilinear forms on free, finitely-generated modules over commutative rings R.
THE PROJECTION STICK INDEX OF KNOTS
Authors: ADAMS COLIN , SHAYLER TODD
Published: July 2009

The stick index of a knot K is defined to be the least number of line segments needed to construct a polygonal embedding of K. We define the projection stick index of K to be the least number of line segments in any projection of a polygonal embedding of K. In this paper, we establish bounds on the projection stick index for various torus knots. We then show that the stick index of a (p, 2p + 1)-torus knot is 4p, and the projection stick index is 2p + 1. This provides examples of knots such that the projection stick index is one greater than half the stick index. We show that for all other torus knots for which the stick index is known, the projection stick index is larger than this. We conjecture that a projection stick index of half the stick index is unattainable for any knot.
ALEXANDER POLYNOMIALS AND ORDERS OF HOMOLOGY GROUPS OF BRANCHED COVERS OF KNOTS
Authors: KIM SE-GOO
Published: July 2009

Fox showed that the order of homology of a cyclic branched cover of a knot is determined by its Alexander polynomial. We find examples of knots with relatively prime Alexander polynomials such that the first homology groups of their q-fold cyclic branched covers are of the same order for every prime power q. Furthermore, we show that these knots are linearly independent in the knot concordance group using the polynomial splitting property of the Casson–Gordon–Gilmer invariants.
COMPUTING IN-SERVICE AIRCRAFT RELIABILITY
Authors: SAINTIS LAURENT , HUGUES EMMANUEL , BES CHRISTIAN , MONGEAU MARCEL
Published: July 2009

This paper deals with the modeling and computation of in-service aircraft reliability at the preliminary design stage. This problem is crucial for aircraft designers because it enables them to evaluate in-service interruption rates, in view of designing the system and of optimizing aircraft support. In the context of a sequence of flight cycles, standard reliability methods are not computationally conceivable with respect to industrial timing constraints. In this paper, first we construct the mathematical framework of in-service aircraft reliability. Second, we use this model in order to demonstrate recursive formulae linking the probabilities of the main failure events. Third, from these analytic developments, we derive relevent reliability bounds. We use these bounds to design an efficient algorithm to estimate operational interruption rate indicators. Finally, we show the usefulness of our approach on real-world cases provided by Airbus.
SOFTWARE RISK ANALYSIS
Authors: SCHNEIDEWIND NORMAN
Published: July 2009

There has been a lack of attention to the subject of risk management in the design and operation of software. This is strange because the risk to reliability is a critical problem in attempts to achieve a safe operation of the software. To address this problem, we evaluate existing models and introduce a new model for software risk prediction. The new model — cumulative failures gradient function — is based on the principles of neural networks. This metric identifiers the minimum test time required to achieve maximum improvement in software quality. We used three NASA Space Shuttle software systems in the evaluation of both existing and new models. The results showed that it was not possible to consistently rank these systems because the validity of the risk predictions varied depending on the risk model that was used. Therefore, the results suggest that it is advisable to use a variety of models to comprehensively evaluate the software risk.
DYNAMIC STIFFNESS MATRIX FOR FLEXURAL-TORSIONAL, LATERAL BUCKLING AND FREE VIBRATION ANALYSES OF MONO-SYMMETRIC THIN-WALLED COMPOSITE BEAMS
Authors: KIM NAM-IL , SHIN DONG KU
Published: July 2009

This paper presents the elastic strain energy, the potential energy with the second order terms of finite rotations, and the kinetic energy with rotary inertia effect for thin-walled composite beams of mono-symmetric cross-section. The equations of motion and force-displacement relationships are derived from the energy principle and explicit expressions for displacement parameters are given based on power series expansions of displacement components. The exact dynamic stiffness matrix is determined using the force-displacement relationships. In addition, the finite element model based on Hermitian interpolation polynomial is developed. In order to verify the accuracy and validity of the formulation, numerical examples are solved and the solutions are compared with results from ABAQUS's shell elements, analytical solutions from previous researchers and the finite element solutions using the Hermitian beam elements. The influence of constant and linearly variable axial forces, fiber orientation, and boundary conditions on the vibration behavior of composite beam are also investigated.
A SYMPLECTIC ALGORITHM FOR THE STABILITY ANALYSIS OF NONLINEAR PARAMETRIC EXCITED SYSTEMS
Authors: YING Z. G. , Ni Y. Q. , CHEN Z. H.
Published: July 2009

A symplectic numerical approach to the stability analysis of nonlinear parametric excited systems with multi-degree-of-freedom is developed and the stability of a nonlinear vibration system depends on the dynamic behavior of its perturbation. The nonlinear parameter-varying differential equations for the perturbation motion are expressed in the form of Hamiltonian equations with time-varying Hamiltonian, and are converted further into the classical Hamiltonian equations with extended time-invariant Hamiltonian by augmenting the state variables. The solution to the augmented Hamiltonian equations has the symplectic structure in terms of the symplectic transformation. Then the difference equations of the symplectic Runge-Kutta algorithm with a sufficient condition are constructed, which is proved to preserve the intrinsic symplectic structure of the original solution. In particular, the symplectic Gauss-Runge-Kutta algorithm with stage 2 and order 4 is proposed and applied to the stability analysis of a nonlinear system. Unstable regions based on the nonlinear periodic-parameter perturbation equation are obtained by using the symplectic Gauss-Runge-Kutta algorithm, analytical solution method and non-symplectic conventional Runge-Kutta algorithm to verify the higher accuracy of the proposed algorithm. Unstable regions based on the nonlinear perturbation are given to illustrate the improvement over those based on the linear perturbation. The developed symplectic approach to the stability analysis can preserve the symplectic structure of the original system and is applicable to nonlinear parametric excited systems with multi-degree-of-freedom.
SIX DEGREE-OF-FREEDOM MICROVIBRATION HYBRID CONTROL SYSTEM FOR HIGH TECHNOLOGY FACILITIES
Authors: WANG YONG , LIU HONG-JUN
Published: July 2009

With the view to achieving a more perfect microvibration-free working environment for high technology equipment such as semiconductors and optical microscopes, the authors investigate the use of a 6-DOF microvibration hybrid control system to mitigate two types of vibration (ground motion and direct disturbance). This hybrid control system comprises a table, five air springs as passive mounts and eight magnetostrictive actuators as active control actuators. To facilitate the feedback control and performance evaluation of the hybrid control system based on the one-third octave band spectra with the absolute velocity being the target, the analytical model of a hybrid control system that incorporates magnetostrictive actuators is established in the absolute coordinates. The control performance of the platform with a hybrid control system is assessed by comparing with the case of the platform with a passive control system. Simulation results indicate that the proposed platform with hybrid control system for microvibration is superior to that with passive control system because of its higher control performance against ground motion and direct disturbance for a wide range of frequencies.
COMPARISON OF VIBRATION CHARACTERISTICS FOR POSTBUCKLED FGM PLATES WITH PIEZOELECTRIC FIBER REINFORCED COMPOSITE ACTUATORS
Authors: XIA XIAN-KUN , SHEN HUI-SHEN
Published: July 2009

Vibration analysis is carried out for compressively loaded and thermally loaded postbuckled functionally graded material (FGM) plates with piezoelectric fiber reinforced composite (PFRC) actuators. The temperature field is assumed to be uniformly distributed over the plate surface but it varies through the thickness. The electric field has a non-zero-valued component EZ. Material properties of the substrate FGM layer are assumed to be graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents. The material properties of both FGM and PFRC layers are assumed to be temperature-dependent. The formulations are based on a third order shear deformation plate theory and the general von Kármán-type equation that include thermo-piezoelectric effects. The numerical illustrations cover small- and large- amplitude vibration characteristics of postbuckled, mid-plane symmetric FGM plates with surface-bonded or embedded PFRC actuators under uniform and non-uniform temperature fields. The results for monolithic piezoelectric actuators, which is a special case in the present study, are compared with those of PFRC actuators. The results reveal that control voltage has a small effect on the vibration characteristics of the compressed postbuckled FGM plate with PFRC actuators but has a relatively large effect on the natural frequency of thermally postbuckled plates.
Edge-avoiding wavelets and their applications
Authors: Fattal Raanan
Published: July 2009

We propose a new family of second-generation wavelets constructed using a robust data-prediction lifting scheme. The support of these new wavelets is constructed based on the edge content of the image and avoids having pixels from both sides of an edge. Multi-resolution analysis, based on these new
edge-avoiding wavelets
, shows a better decorrelation of the data compared to common linear translation-invariant multi-resolution analyses. The reduced inter-scale correlation allows us to avoid halo artifacts in band-independent multi-scale processing without taking any special precautions. We thus achieve nonlinear data-dependent multi-scale edge-preserving image filtering and processing at computation times which are
linear
in the number of image pixels. The new wavelets encode, in their shape, the smoothness information of the image at every scale. We use this to derive a new edge-aware interpolation scheme that achieves results, previously computed by solving an inhomogeneous Laplace equation, through an
explicit
computation. We thus avoid the difficulties in solving large and poorly-conditioned systems of equations.

We demonstrate the effectiveness of the new wavelet basis for various computational photography applications such as multi-scale dynamic-range compression, edge-preserving smoothing and detail enhancement, and image colorization.
Modeling human color perception under extended luminance levels
Authors: Kim Min H. , Weyrich Tim , Kautz Jan
Published: July 2009

Display technology is advancing quickly with peak luminance increasing significantly, enabling high-dynamic-range displays. However, perceptual color appearance under extended luminance levels has not been studied, mainly due to the unavailability of psychophysical data. Therefore, we conduct a psychophysical study in order to acquire appearance data for many different luminance levels (up to 16,860 cd/m2) covering most of the dynamic range of the human visual system. These experimental data allow us to quantify human color perception under extended luminance levels, yielding a generalized color appearance model. Our proposed appearance model is efficient, accurate and invertible. It can be used to adapt the tone and color of images to different dynamic ranges for cross-media reproduction while maintaining appearance that is close to human perception.
An empirical BSSRDF model
Authors: Donner Craig , Lawrence Jason , Ramamoorthi Ravi , Hachisuka Toshiya , Jensen Henrik Wann , Nayar Shree
Published: July 2009

We present a new model of the homogeneous BSSRDF based on large-scale simulations. Our model captures the appearance of materials that are not accurately represented using existing single scattering models or multiple isotropic scattering models (e.g. the diffusion approximation). We use an analytic function to model the 2D hemispherical distribution of exitant light at a point on the surface, and a table of parameter values of this function computed at uniformly sampled locations over the remaining dimensions of the BSSRDF domain. This analytic function is expressed in elliptic coordinates and has six parameters which vary smoothly with surface position, incident angle, and the underlying optical properties of the material (albedo, mean free path length, phase function and the relative index of refraction). Our model agrees well with measured data, and is compact, requiring only 250MB to represent the full spatial- and angular-distribution of light across a wide spectrum of materials. In practice, rendering a single material requires only about 100KB to represent the BSSRDF.
SubEdit
Authors: Song Ying , Tong Xin , Pellacini Fabio , Peers Pieter
Published: July 2009

In this paper we present
SubEdit
, a representation for editing the BSSRDF of heterogeneous subsurface scattering acquired from real-world samples. Directly editing measured raw data is difficult due to the non-local impact of heterogeneous subsurface scattering on the appearance. Our
SubEdit
representation decouples these non-local effects into the product of two local scattering profiles defined at respectively the incident and outgoing surface locations. This allows users to directly manipulate the appearance of single surface locations and to robustly make selections. To further facilitate editing, we reparameterize the scattering profiles into the local appearance concepts of albedo, scattering range, and profile shape. Our method preserves the visual quality of the measured material after editing by maintaining the consistency of subsurface transport for all edits.
SubEdit
fits measured data well while remaining efficient enough to support interactive rendering and manipulation. We illustrate the suitability of
SubEdit
as a representation for editing by applying various complex modifications on a wide variety of measured heterogeneous subsurface scattering materials.
iWIRES
Authors: Gal Ran , Sorkine Olga , Mitra Niloy J. , Cohen-Or Daniel
Published: July 2009

Man-made objects are largely dominated by a few typical features that carry special characteristics and engineered meanings. State-of-the-art deformation tools fall short at preserving such characteristic features and global structure. We introduce iWIRES, a novel approach based on the argument that man-made models can be distilled using a few special 1D
wires
and their mutual relations. We hypothesize that maintaining the properties of such a small number of wires allows preserving the defining characteristics of the entire object. We introduce an
analyze-and-edit
approach, where prior to editing, we perform a light-weight analysis of the input shape to extract a descriptive set of wires. Analyzing the individual and mutual properties of the wires, and augmenting them with geometric attributes makes them intelligent and ready to be manipulated. Editing the object by modifying the intelligent wires leads to a powerful editing framework that retains the original design intent and object characteristics. We show numerous results of manipulation of man-made shapes using our editing technique.
Harmonic fluids
Authors: Zheng Changxi , James Doug L.
Published: July 2009

Fluid sounds, such as splashing and pouring, are ubiquitous and familiar but we lack physically based algorithms to synthesize them in computer animation or interactive virtual environments. We propose a practical method for automatic procedural synthesis of synchronized harmonic bubble-based sounds from 3D fluid animations. To avoid audio-rate time-stepping of compressible fluids, we acoustically augment existing incompressible fluid solvers with particle-based models for bubble creation, vibration, advection, and radiation. Sound radiation from harmonic fluid vibrations is modeled using a time-varying linear superposition of bubble oscillators. We weight each oscillator by its bubble-to-ear acoustic transfer function, which is modeled as a discrete Green's function of the Helmholtz equation. To solve potentially millions of 3D Helmholtz problems, we propose a fast dual-domain multipole boundary-integral solver, with cost linear in the complexity of the fluid domain's boundary. Enhancements are proposed for robust evaluation, noise elimination, acceleration, and parallelization. Examples are provided for water drops, pouring, babbling, and splashing phenomena, often with thousands of acoustic bubbles, and hundreds of thousands of transfer function solves.
Moving gradients
Authors: Mahajan Dhruv , Huang Fu-Chung , Matusik Wojciech , Ramamoorthi Ravi , Belhumeur Peter
Published: July 2009

We describe a method for plausible interpolation of images, with a wide range of applications like temporal up-sampling for smooth playback of lower frame rate video, smooth view interpolation, and animation of still images. The method is based on the intuitive idea, that a given pixel in the interpolated frames traces out a
path
in the source images. Therefore, we simply move and copy pixel gradients from the input images along this path. A key innovation is to allow arbitrary (asymmetric)
transition points
, where the path moves from one image to the other. This flexible transition preserves the frequency content of the originals without ghosting or blurring, and maintains temporal coherence. Perhaps most importantly, our framework makes occlusion handling particularly simple. The transition points allow for matches away from the occluded regions, at any suitable point along the path. Indeed, occlusions do not need to be handled explicitly at all in our initial graph-cut optimization. Moreover, a simple comparison of computed path lengths
after
the optimization, allows us to robustly identify occluded regions, and compute the most plausible interpolation in those areas. Finally, we show that significant improvements are obtained by moving gradients and using Poisson reconstruction.
FlexiStickers
Authors: Tzur Yochay , Tal Ayellet
Published: July 2009

Texturing 3D models using casual images has gained importance in the last decade, with the advent of huge databases of images. We present a novel approach for performing this task, which manages to account for the 3D geometry of the photographed object. Our method overcomes the limitation of both the constrained-parameterization approach, which does not account for the photography effects, and the photogrammetric approach, which cannot handle arbitrary images. The key idea of our algorithm is to formulate the mapping estimation as a Moving-Least-Squares problem for recovering local camera parameters at each vertex. The algorithm is realized in aFlexiStickersapplication, which enables fast interactive texture mapping using a small number of constraints.
Direct trimming of NURBS surfaces on the GPU
Authors: Schollmeyer Andre , Fröhlich Bernd
Published: July 2009

This paper presents a highly efficient direct trimming technique for NURBS surfaces, which is applicable to tessellation-based rendering as well as ray tracing systems. The central idea is to split the trim curves into monotonic segments with respect to the two parameter dimensions of the surface patches. We use an optimized bisection method to classify a point with respect to each monotonic trim curve segment without performing an actual intersection test. Our hierarchical acceleration structure allows the use of a large number of such curve segments and performs the bisection method only for points contained in the bounding boxes of the curve segments.

We have integrated our novel point classification scheme into a GPU-based NURBS ray casting system and implemented the entire trimmed NURBS rendering algorithm in a single OpenGL GLSL shader. The shader can handle surfaces and trim curves of arbitrary degrees, which allows the use of original CAD data without incorporating any approximations. Performance data confirms that our trimming approach can deal with hundreds of thousands of trim curves at interactive rates. Our point classification scheme can be applied to other application domains dealing with complex curved regions including flood fills, font rendering and vector graphics mapped on arbitrary surfaces.
Enrichment textures for detailed cutting of shells
Authors: Kaufmann Peter , Martin Sebastian , Botsch Mario , Grinspun Eitan , Gross Markus
Published: July 2009

We present a method for simulating highly detailed cutting and fracturing of thin shells using low-resolution simulation meshes. Instead of refining or remeshing the underlying simulation domain to resolve complex cut paths, we adapt the extended finite element method (XFEM) and enrich our approximation by customdesigned basis functions, while keeping the simulation mesh unchanged. The enrichment functions are stored in
enrichment textures
, which allows for fracture and cutting discontinuities at a resolution much finer than the underlying mesh, similar to image textures for increased visual resolution. Furthermore, we propose
harmonic enrichment functions
to handle multiple, intersecting, arbitrarily shaped, progressive cuts per element in a simple and unified framework. Our underlying shell simulation is based on discontinuous Galerkin (DG) FEM, which relaxes the restrictive requirement of
C
1
continuous basis functions and thus allows for simpler,
C
0
continuous XFEM enrichment functions.
Numerical coarsening of inhomogeneous elastic materials
Authors: Kharevych Lily , Mullen Patrick , Owhadi Houman , Desbrun Mathieu
Published: July 2009

We propose an approach for efficiently simulating elastic objects made of non-homogeneous, non-isotropic materials. Based on recent developments in homogenization theory, a methodology is introduced to approximate a deformable object made of arbitrary fine structures of various linear elastic materials with a dynamicallysimilar coarse model. This numerical coarsening of the material properties allows for simulation of fine, heterogeneous structures on very coarse grids while capturing the proper dynamics of the original dynamical system, thus saving orders of magnitude in computational time. Examples including inhomogeneous and/or anisotropic materials can be realistically simulated in realtime with a numerically-coarsened model made of a few mesh elements.
Preserving topology and elasticity for embedded deformable models
Authors: Nesme Matthieu , Kry Paul G. , Jeřábková Lenka , Faure François
Published: July 2009

In this paper we introduce a new approach for the embedding of linear elastic deformable models. Our technique results in significant improvements in the efficient physically based simulation of highly detailed objects. First, our embedding takes into account topological details, that is, disconnected parts that fall into the same coarse element are simulated independently. Second, we account for the varying material properties by computing stiffness and interpolation functions for coarse elements which accurately approximate the behaviour of the embedded material. Finally, we also take into account empty space in the coarse embeddings, which provides a better simulation of the boundary. The result is a straightforward approach to simulating complex deformable models with the ease and speed associated with a coarse regular embedding, and with a quality of detail that would only be possible at much finer resolution.
Self-organizing tree models for image synthesis
Authors: Palubicki Wojciech , Horel Kipp , Longay Steven , Runions Adam , Lane Brendan , Měch Radomír , Prusinkiewicz Przemyslaw
Published: July 2009

We present a method for generating realistic models of temperate-climate trees and shrubs. This method is based on the biological hypothesis that the form of a developing tree emerges from a self-organizing process dominated by the competition of buds and branches for light or space, and regulated by internal signaling mechanisms. Simulations of this process robustly generate a wide range of realistic trees and bushes. The generated forms can be controlled with a variety of interactive techniques, including procedural brushes, sketching, and editing operations such as pruning and bending of branches. We illustrate the usefulness and versatility of the proposed method with diverse tree models, forest scenes, animations of tree development, and examples of combined interactive-procedural tree modeling.
Dextrous manipulation from a grasping pose
Authors: Liu C. Karen
Published: July 2009

This paper introduces an optimization-based approach to synthesizing hand manipulations from a starting grasping pose. We describe an automatic method that takes as input an initial grasping pose and partial object trajectory, and produces as output physically plausible hand animation that effects the desired manipulation. In response to different dynamic situations during manipulation, our algorithm can generate a range of possible hand manipulations including changes in joint configurations, changes in contact points, and changes in the grasping force. Formulating hand manipulation as an optimization problem is key to our algorithm's ability to generate a large repertoire of hand motions from limited user input. We introduce an objective function that accentuates the detailed hand motion and contacts adjustment. Furthermore, we describe an optimization method that solves for hand motion and contacts efficiently while taking into account long-term planning of contact forces. Our algorithm does not require any tuning of parameters, nor does it require any prescribed hand motion sequences.
Performance-based control interface for character animation
Authors: Ishigaki Satoru , White Timothy , Zordan Victor B. , Liu C. Karen
Published: July 2009

Most game interfaces today are largely symbolic, translating simplified input such as keystrokes into the choreography of full-body character movement. In this paper, we describe a system that directly uses human motion performance to provide a radically different, and much more expressive interface for controlling virtual characters. Our system takes a data feed from a motion capture system as input, and in real-time translates the performance into corresponding actions in a virtual world. The difficulty with such an approach arises from the need to manage the discrepancy between the real and virtual world, leading to two important subproblems 1) recognizing the user's intention, and 2) simulating the appropriate action based on the intention and virtual context. We solve this issue by first enabling the virtual world's designer to specify possible activities in terms of prominent features of the world along with associated motion clips depicting interactions. We then integrate the prerecorded motions with online performance and dynamic simulation to synthesize seamless interaction of the virtual character in a simulated virtual world. The result is a flexible interface through which a user can make freeform control choices while the resulting character motion maintains both physical realism and the user's personal style.
Detail preserving continuum simulation of straight hair
Authors: McAdams Aleka , Selle Andrew , Ward Kelly , Sifakis Eftychios , Teran Joseph
Published: July 2009

Hair simulation remains one of the most challenging aspects of creating virtual characters. Most research focuses on handling the massive geometric complexity of hundreds of thousands of interacting hairs. This is accomplished either by using brute force simulation or by reducing degrees of freedom with guide hairs. This paper presents a hybrid Eulerian/Lagrangian approach to handling both self and body collisions with hair efficiently while still maintaining detail. Bulk interactions and hair volume preservation is handled efficiently and effectively with a FLIP based fluid solver while intricate hair-hair interaction is handled with Lagrangian self-collisions. Thus the method has the efficiency of continuum/guide based hair models with the high detail of Lagrangian self-collision approaches.
Generating photo manipulation tutorials by demonstration
Authors: Grabler Floraine , Agrawala Maneesh , Li Wilmot , Dontcheva Mira , Igarashi Takeo
Published: July 2009

We present a demonstration-based system for automatically generating succinct step-by-step visual tutorials of photo manipulations. An author first demonstrates the manipulation using an instrumented version of GIMP that records all changes in interface and application state. From the example recording, our system automatically generates tutorials that illustrate the manipulation using images, text, and annotations. It leverages automated image labeling (recognition of facial features and outdoor scene structures in our implementation) to generate more precise text descriptions of many of the steps in the tutorials. A user study comparing our automatically generated tutorials to hand-designed tutorials and screen-capture video recordings finds that users are 20--44% faster and make 60--95% fewer errors using our tutorials. While our system focuses on tutorial generation, we also present some initial work on generating content-dependent macros that use image recognition to automatically transfer selection operations from the example image used in the demonstration to new target images. While our macros are limited to transferring selection operations we demonstrate automatic transfer of several common retouching techniques including eye recoloring, whitening teeth and sunset enhancement.
Video SnapCut
Authors: Bai Xue , Wang Jue , Simons David , Sapiro Guillermo
Published: July 2009

Although tremendous success has been achieved for interactive object cutout in still images, accurately extracting dynamic objects in video remains a very challenging problem. Previous video cutout systems present two major limitations: (1) reliance on global statistics, thus lacking the ability to deal with complex and diverse scenes; and (2) treating segmentation as a global optimization, thus lacking a practical workflow that can guarantee the convergence of the systems to the desired results.

We present
Video SnapCut
, a robust video object cutout system that significantly advances the state-of-the-art. In our system segmentation is achieved by the collaboration of a set of local classifiers, each adaptively integrating multiple local image features. We show how this segmentation paradigm naturally supports local user editing and propagates them across time. The object cutout system is completed with a novel coherent video matting technique. A comprehensive evaluation and comparison is presented, demonstrating the effectiveness of the proposed system at achieving high quality results, as well as the robustness of the system against various types of inputs.
Curve skeleton extraction from incomplete point cloud
Authors: Tagliasacchi Andrea , Zhang Hao , Cohen-Or Daniel
Published: July 2009

We present an algorithm for curve skeleton extraction from imperfect point clouds where large portions of the data may be missing. Our construction is primarily based on a novel notion of generalized
rotational symmetry axis
(ROSA) of an oriented point set. Specifically, given a subset
S
of oriented points, we introduce a variational definition for an oriented point that is most rotationally symmetric with respect to
S
. Our formulation effectively utilizes normal information to compensate for the missing data and leads to robust curve skeleton computation over regions of a shape that are generally cylindrical. We present an iterative algorithm via planar cuts to compute the ROSA of a point cloud. This is complemented by special handling of non-cylindrical joint regions to obtain a centered, topologically clean, and complete 1D skeleton. We demonstrate that quality curve skeletons can be extracted from a variety of shapes captured by incomplete point clouds. Finally, we show how our algorithm assists in shape completion under these challenges by developing a skeleton-driven point cloud completion scheme.
A benchmark for 3D mesh segmentation
Authors: Chen Xiaobai , Golovinskiy Aleksey , Funkhouser Thomas
Published: July 2009

This paper describes a benchmark for evaluation of 3D mesh segmentation salgorithms. The benchmark comprises a data set with 4,300 manually generated segmentations for 380 surface meshes of 19 different object categories, and it includes software for analyzing 11 geometric properties of segmentations and producing 4 quantitative metrics for comparison of segmentations. The paper investigates the design decisions made in building the benchmark, analyzes properties of human-generated and computer-generated segmentations, and provides quantitative comparisons of 7 recently published mesh segmentation algorithms. Our results suggest that people are remarkably consistent in the way that they segment most 3D surface meshes, that no one automatic segmentation algorithm is better than the others for all types of objects, and that algorithms based on non-local shape features seem to produce segmentations that most closely resemble ones made by humans.
Cyclic plain-weaving on polygonal mesh surfaces with graph rotation systems
Authors: Akleman Ergun , Chen Jianer , Xing Qing , Gross Jonathan L.
Published: July 2009

In this paper, we show how to create plain-weaving over an arbitrary surface. To create a plain-weaving on a surface, we need to create cycles that cross other cycles (or themselves) by alternatingly going over and under. We use the fact that it is possible to create such cycles, starting from any given manifold-mesh surface by simply twisting every edge of the manifold mesh. We have developed a new method that converts plain-weaving cycles to 3D thread structures. Using this method, it is possible to cover a surface without large gaps between threads by controlling the sizes of the gaps. We have developed a system that converts any manifold mesh to a plain-woven object, by interactively controlling the shapes of the threads with a set of parameters. We have demonstrated that by using this system, we can create a wide variety of plain-weaving patterns, some of which may not have been seen before.
Capacity-constrained point distributions
Authors: Balzer Michael , Schlömer Thomas , Deussen Oliver
Published: July 2009

We present a new general-purpose method for optimizing existing point sets. The resulting distributions possess high-quality blue noise characteristics and adapt precisely to given density functions. Our method is similar to the commonly used Lloyd's method while avoiding its drawbacks. We achieve our results by utilizing the concept of capacity, which for each point is determined by the area of its Voronoi region weighted with an underlying density function. We demand that each point has the same capacity. In combination with a dedicated optimization algorithm, this capacity constraint enforces that each point obtains equal importance in the distribution. Our method can be used as a drop-in replacement for Lloyd's method, and combines enhancement of blue noise characteristics and density function adaptation in one operation.
Interactive simulation of surgical needle insertion and steering
Authors: Chentanez Nuttapong , Alterovitz Ron , Ritchie Daniel , Cho Lita , Hauser Kris K. , Goldberg Ken , Shewchuk Jonathan R. , O'Brien James F.
Published: July 2009

We present algorithms for simulating and visualizing the insertion and steering of needles through deformable tissues for surgical training and planning. Needle insertion is an essential component of many clinical procedures such as biopsies, injections, neurosurgery, and brachytherapy cancer treatment. The success of these procedures depends on accurate guidance of the needle tip to a clinical target while avoiding vital tissues. Needle insertion deforms body tissues, making accurate placement difficult. Our interactive needle insertion simulator models the coupling between a steerable needle and deformable tissue. We introduce (1) a novel algorithm for local remeshing that quickly enforces the conformity of a tetrahedral mesh to a curvilinear needle path, enabling accurate computation of contact forces, (2) an efficient method for coupling a 3D finite element simulation with a 1D inextensible rod with stick-slip friction, and (3) optimizations that reduce the computation time for physically based simulations. We can realistically and interactively simulate needle insertion into a prostate mesh of 13,375 tetrahedra and 2,763 vertices at a 25 Hz frame rate on an 8-core 3.0 GHz Intel Xeon PC. The simulation models prostate brachytherapy with needles of varying stiffness, steering needles around obstacles, and supports motion planning for robotic needle insertion. We evaluate the accuracy of the simulation by comparing against real-world experiments in which flexible, steerable needles were inserted into gel tissue phantoms.
An efficient GPU-based approach for interactive global illumination
Authors: Wang Rui , Wang Rui , Zhou Kun , Pan Minghao , Bao Hujun
Published: July 2009

This paper presents a GPU-based method for interactive global illumination that integrates complex effects such as multi-bounce indirect lighting, glossy reflections, caustics, and arbitrary specular paths. Our method builds upon scattered data sampling and interpolation on the GPU. We start with raytraced shading points and partition them into coherent shading clusters using adaptive seeding followed by k-means. At each cluster center we apply final gather to evaluate its incident irradiance using GPU-based photon mapping. We approximate the entire photon tree as a compact illumination cut, thus reducing the final gather cost for each ray. The sampled irradiance values are then interpolated at all shading points to produce rendering. Our method exploits the spatial coherence of illumination to reduce sampling cost. We sample sparsely and the distribution of sample points conforms with the underlying illumination changes. Therefore our method is both fast and preserves high rendering quality. Although the same property has been exploited by previous caching and adaptive sampling methods, these methods typically require sequential computation of sample points, making them ill-suited for the GPU. In contrast, we select sample points adaptively in a single pass, enabling parallel computation. As a result, our algorithm runs entirely on the GPU, achieving interactive rates for scenes with complex illumination effects.
Single scattering in refractive media with triangle mesh boundaries
Authors: Walter Bruce , Zhao Shuang , Holzschuch Nicolas , Bala Kavita
Published: July 2009

Light scattering in refractive media is an important optical phenomenon for computer graphics. While recent research has focused on multiple scattering, there has been less work on accurate solutions for single or low-order scattering. Refraction through a complex boundary allows a single external source to be visible in multiple directions internally with different strengths; these are hard to find with existing techniques. This paper presents techniques to quickly find paths that connect points inside and outside a medium while obeying the laws of refraction. We introduce: a half-vector based formulation to support the most common geometric representation, triangles with interpolated normals; hierarchical pruning to scale to triangular meshes; and, both a solver with strong accuracy guarantees, and a faster method that is empirically accurate. A GPU version achieves interactive frame rates in several examples.
Frequency analysis and sheared reconstruction for rendering motion blur
Authors: Egan Kevin , Tseng Yu-Ting , Holzschuch Nicolas , Durand Frédo , Ramamoorthi Ravi
Published: July 2009

Motion blur is crucial for high-quality rendering, but is also very expensive. Our first contribution is a frequency analysis of motion-blurred scenes, including moving objects, specular reflections, and shadows. We show that motion induces a shear in the frequency domain, and that the spectrum of moving scenes can be approximated by a wedge. This allows us to compute adaptive space-time sampling rates, to accelerate rendering. For uniform velocities and standard axis-aligned reconstruction, we show that the product of spatial and temporal bandlimits or sampling rates is constant, independent of velocity. Our second contribution is a novel sheared reconstruction filter that is aligned to the first-order direction of motion and enables even lower sampling rates. We present a rendering algorithm that computes a sheared reconstruction filter per pixel, without any intermediate Fourier representation. This often permits synthesis of motion-blurred images with far fewer rendering samples than standard techniques require.