Natural path planning using wavelet noise in static environment

In a constrained virtual environment, motion of a character has to be controlled with precision to avoid collisions. For modeling motion of a character representing some real‐life object, it is important to generate paths that look natural. A number of path planning algorithms have been introduced to solve real‐time path queries in an environment. However, in all such algorithms, a fixed path is returned always for the same start and goal positions in the environment. Recently, Perlin noise has been used to add variations to a path so that it appears more natural. However, because of pure random nature of Perlin noise function, often unnatural path occurs. In this paper, we present a new approach to natural path planning by adding wavelet noise to a path generated using subdivision‐based Corridor Map Method. Because wavelet noise is almost perfectly band limited and provides good details with minimal aliasing effects, the resulting path becomes smoother and more natural. Moreover, by appropriately choosing the levels of down/up sampling in the wavelet noise generation algorithm, frequency of wavelet noise can be adjusted. This serves as an effective tool in bringing variations in path as per the requirement. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of Scattering on THz Spectra of Granular Solids

Experimental studies of granular solids have shown that significant scattering effects restrict the accurate determination of material absorption in the terahertz (THz) region. The present work investigates the grain size dependent scattering contribution on the extinction spectra of Ammonium Nitrate, flour and salt between 0.2 to 1.2 THz using THz time-domain spectroscopy. The scattering contribution can be estimated by applying Mie theory for spherical grains. The approach essentially separates the independent contributions of true absorption and scattering losses and thus determines the total extinction for different grain sizes of various materials. The separation of the intrinsic material absorption from scattering losses shows that the frequency dependence in weakly absorbing materials is predominantly particle size dependent. Consequently, that range of THz frequencies cannot be used to differentiate granular solids having no intrinsic absorption.     

Secure data hiding scheme using shape generation algorithm: a key based approach

Data hiding in images has evolved as one of the trusted methods of secure data communication and numerous approaches have been introduced over the years using gray scale images as the cover media. Most of the methods are based on data hiding in least significant bit planes of cover images. Many such methods purely depend on data substitution algorithms by defining a pattern in which data is embedded. One can gain access to the secret data in a few attempts, if the algorithm is known. Keeping this in view several approaches based on secret keys have also been proposed by researchers. This paper proposes an efficient data embedding scheme using a key and an embedding pattern generated through midpoint circle generation algorithm. The pattern can be applied to a carrier that is mapped onto a grid/image. The cryptosystem uses the concept of steganography and is computationally light and secure. The secret-key is generated in such a way that Avalanche effect is ensured except in very rare cases. The proposed data embedding method is shown to be robust and highly secure while maintaining good hiding capacity and imperceptibility. It is applicable for data hiding in a generic grid that could be of pixels or bits.     

Delay-dependent stabilization of Lipschitz nonlinear systems

This work proposes an improvement over existing delay-dependent stabilization technique for linear systems having time-varying delays and norm-bounded uncertainties. The method is based on linear matrix inequalities (LMIs). Parameter tuning or iterative techniques are not required to get the required controller, if the proposed LMIs are satisfied. The method is also extended for systems having Lipschitz nonlinearities.