Abstract

We present a scheme for interactive ray tracing of Bezier bicubicpatches using Newton iteration in this paper. We use a mixed hi-erarchy representation as the acceleration structure. This has abounding volume hierarchy above the patches and a fixed depthsubpatch tree below it. This helps reduce the number of ray-patchintersections that needs to be evaluated and provides good initial-ization for the iterative step, keeping the memory requirements low.We use Newton iteration on the generated list of ray patch intersec-tions in parallel. Our method can exploit the cores of the CPU andthe GPU with OpenMP on the CPU and CUDA on the GPU bysharing work between them according to their relative speeds. Adata parallel framework is used throughout starting with a list ofrays, which is transformed to a list of ray-patch intersections bytraversal and then to intersections and a list of secondary rays byroot finding. Shadow and reflection rays can be handled exactly inthe same manner as a result. We also show how our method ex-tends easily to generate soft shadows using area light sources andpath tracing by tracing a large number of rays per pixel. We rendera million pixel image of the Teapot model at 125 fps on a systemwith an Intel i7 920 and a Nvidia GTX580 for primary rays onlyand at about 65 fps with one pass of shadow and refection rays.

Abstract

Displays have seen much improvements over the years, withenhancements in spatial resolution and vertical refresh, etc.,to provide better and smoother visual experiences. Color in-tensity resolution, however, has not changed much over thepast few decades. Most displays are still limited to 8-bitsper channel. Simultaneously, much work has gone into cap-turing high dynamic range images. Mapping these directlyto current displays loses information that may be critical tomany applications. We present a way to enhance intensityresolution of a given display by mixing intensities over spa-tial or temporal domains. Our system sacrifices high verticalrefresh and spatial resolution in order to gain intensity res-olution. We present three ways to mix intensities: spatially,temporally and spatio-temporally. The systems produce in-between-intensities not present on the base display, whichare clearly distinguishable by the naked eye. We evaluateour systems using both a camera and human subjects, eval-uating whether they scale the intensity resolution and alsoensuring that the newly generated intensities follow the dis-play model

Abstract

Browsers of personal digital photographs all essentially fol-low the slide show paradigm, sequencing through the pho-tos in the order they are taken. A more engaging way tobrowse personal photographs, especially of a large space likea popular monument, should involve the geometric contextof the space. In this paper, we present ageometry directedphoto browserthat enables users to browse their personalpictures with the underlying geometry of the space to guidethe process. The browser uses a pre-computed package ofgeometric information about the monument for this task.The package is used to register a set of photographs takenby the user with the common geometric space of the monu-ment. This involves localizing the images to the monumentspace by computing the camera matrix corresponding to it.We use a state-of-the-art method for fast localization. Reg-istered photographs can be browsed using a visualizationmodule that shows them in the proper geometric contextwith respect to a point-based 3D model of the monument.We present the design of the geometry-directed browser anddemonstrate its utility for a few sequences of personal im-ages of well-known monuments. We believe personal photobrowsers can provide an enhanced sense of one’s own ex-perience with a monument using the underlying geometriccontext of the monument.

Abstract

: Density functional B3LYP method was used to investigate the preference of intra and intermolecular cyclizations of linear tripeptides containing tetrahydrofuran amino acids. Two distinct model pathways were conceived for the cyclization reaction and all possible transition states and intermediates were located. Analysis of the energetics indicate intermolecular cyclization being favored by both thermodynamic and kinetic control. Geometric and NBO analyses were performed to explain the trends obtained along both the reaction pathways. Conceptual density functional theory based reactive indices also show that reaction pathways leading to intermolecular cyclization of the tripeptides are relatively more facile compared to intramolecular cyclization.

Abstract

Theoretical justication for preferential heterochiral cyclic trimerization of 5- (aminoethyl)-2-furancarboxylic acid (AEFC) is attempted using density functional theory (DFT) calculations. Results from explicit solvent assisted reaction pathways indicate greater stability of heterochiral cyclic tripeptides over their homochiral counterparts, contrary to ndings from gas phase and implicit solvent phase results. Pathways explored at M06/6- 31G(d,p) and MP2/6-31G(d,p) levels of theory show kinetic preference for heterochiral cy- clization. Analysis of optimized geometries reveals existence of strong hydrogen bonding interactions in the solvated heterochiral tripeptides. Thus, the ability of the cyclic tripep- tides to form strong noncovalent interactions increases with conversion of stereochemistry at one of its chiral centers from homo to heterochiral conformation. The resulting change in molecular symmetry facilitates the interacting sites to reorient such that the peptide can in- teract with a nucleophile from both the faces. This is further substantiated by computed IR spectra, NBO and AIM data. Additionally, justication for the stability of heterochiral cyclic tripeptides comes from molecular electrostatic potential and electron density surfaces. These studies show clearly that for the kind of systems presented here, gas phase or implicit sol- vent phase studies are inadequate in explaining realistic situations. Calculations with solvent molecules, even if a few only, are necessary to substantiate experimental observations.

Abstract

Optimal control theory in combination with time-dependent quantum dynamics is employed to design laser pulses which can perform selective vibrational and rotational excitations in a heteronuclear diatomic system. We have applied the conjugate gradient method for the constrained optimization of a suitably designed functional incorporating the desired objectives and constraints. Laser pulses designed for several excitation processes of the HF molecule were able to achieve predefined dynamical goals with almost 100% yield.

Abstract

Theoretical insights into homo versus heterochiral cyclic trimerization of 5-(aminoethyl)-2-furancarboxylic acid (AEFC) are provided based on density functional theory (DFT) calculations[1]. A comparison of pathways leading to cyclic trimerization explored at M06/6-31G(d,p) and B3LYP/6-31G(d,p) levels of theory indicates signicance of the M06 functional in determining the barrier heights. Kinetic preference for heterochiral cyclization is clearly observed from results obtained at M06/6-31G(d,p) level of theory. Structure analysis of geometries reveals existence of strong hydrogen bonding interactions in the solvated heterochiral tripeptides. Further support comes from IR spectra, NBO and AIM calculations, molecular electrostatic potential and electron density surfaces. Our study shows that for the kind of systems, calculations with solvent molecules, even if a few only, are sucient to substantiate experimental observations. Further study on anion binding anity of the peptides has revealed that while both homo and heterochiral cyclic tripeptides show equal electronic energies of interaction for a uoride ion in gas phase, the homochiral cyclic tripeptide shows relatively larger electronic energy of interaction for chloride and bromide ions ( 4 kcal/mol) compared to that shown by heterochiral cyclic tripeptide. In solvent phase, the peptides possess anity for uoride and chloride ions only. While, heterochiral cyclic peptide shows slightly larger interaction for uoride ion, anity of homochiral peptide for chloride ion is slightly larger than its heterochiral counterpart. Though the heterochiral cyclic tripeptide of AEFC is a stable product with high yield, anion recognition propensities are comparable to that of homochiral cyclic tripeptide.

Abstract

t Interaction between metal nanoparticles and biomolecules is important from the view point of developing and designing biosensors. Studies on proline tagged with gold nanoclusters are reported here using density functional theory (DFT) calculations for its structural, electronic and bonding properties. Geometries of the complexes are optimized using the PBE1PBE functional and mixed basis set, i. e., 6-311++G for the amino acid and SDD for the gold clusters. Equilibrium configurations are analyzed in terms of interaction energies, molecular orbitals and charge density. The complexes associated with cluster composed of an odd number of Au atoms show higher stability. Marked decrease in the HOMO-LUMO gaps is observed on complexation. Major components of interaction between the two moieties are: the anchoring N-Au and O-Au bond; and the non covalent interactions between Au and N-H or O-H bonds. The electron affinities and vertical ionization potentials for all complexes are calculated. They show an increased value of electron affinity and ionization potential on complexation. Natural bond orbital (NBO) analysis reveals a charge transfer between the donor (proline) and acceptor (gold cluster). The results indicate that the nature of interaction between the two moieties is partially covalent. Our results will be useful for further experimental studies and may be important for future application

Abstract

In this paper we present a novel recognition approach that results in a 15% decrease in word error rate on heavily degraded Indian language document images. OCRs have considerably good performance on good quality documents, but fail easily in presence of degradations. Also, classical OCR approaches perform poorly over complex scripts such as those for Indian languages. We address these issues by proposing to recognize character n-gram images, which are basically groupings of consecutive character/component segments. Our approach is unique, since we use the character n-grams as a primitive for recognition rather than for postprocessing. By exploiting the additional context present in the character n-gram images, we enable better disambiguation between confusing characters in the recognition phase. The labels obtained from recognizing the constituent n-grams are then fused to obtain a label for the word that emitted them. Our method is inherently robust to degradations such as cuts and merges which are common in digital libraries of scanned documents. We also present a reliable and scalable scheme for recognizing character n-gram images. Tests on English and Malayalam document images show considerable improvement in recognition in the case of heavily degraded documents.

Abstract

This paper presents a Bag of Visual Words (BoVW) based approach to retrieve similar word images from a large database, efficiently and accurately. We show that a text retrieval system can be adapted to build a word image retrieval solution. This helps in achieving scalability. We demonstrate the method on more than 1 Million word images with a sub-second retrieval time. We validate the method on four Indian languages, and report a mean average precision of more than 0.75. We represent the word images as histogram of visual words present in the image. Visual words are quantized representation of local regions, and for this work, SIFT descriptors at interest points are used as feature vectors. To address the lack of spatial structure in the BoVW representation, we re-rank the retrieved list. This significantly improves the performance.