An accurate analysis of scalar quantization-based data hiding

This paper comes to fill a gap in watermarking theory, analyzing the exact performance of the scalar Costa scheme (SCS) facing additive Gaussian attacks when the usual approximation of high-resolution quantization is not valid, thus taking into account the host statistics. The analysis is focused on the assessment of the probability of error, showing new results, an although it is valid in a general scenario, its practical interest is increased when SCS is used in conjunction with the so-called spread-transform. The accomplished reformulation of the problem also permits to show that the achievable rate of SCS is never worse than that of classical spread-spectrum-based methods, as it was thought so far, and allows to establish interesting links with spread spectrum and the Improved Spread Spectrum method.     

A variational approach to magnetoelastic buckling problems for systems of superconducting tori

A variational principle for the magnetoelastic stability problem of superconductors is constructed. Independently, a pair of integral equations is derived, from which the initial and the perturbed field can be computed. The integral equations are solved for in-plane buckling of a slender pair of concentric tori, and out-of-plane buckling of a slender pair of equal coaxial tori. By using the variational principle, it is shown that both cases can become unstable when the currents on the two tori are equally directed, and the pertinent buckling values are calculated. The thus obtained buckling values are compared with the results of an alternative, mathematically less rigorous, method. A good correspondence between the two methods is found (at least as long as the two tori are not too near).     

Characterizing the surface contact behaviour of ceramics

The indentation hardness of four glass-bonded ceramics has been examined as a function of load and temperature, It has been observed that the relative hardness values may interchange depending on the temperature and load of testing. For each material there are two regimes of temperature dependence. A has been possible to qualitatively correlate the transition temperature with the composition of the glassy binder phase.     

Risk factors associated with recidivism among extrafamilial child molesters.

This study examined the predictive efficacy of 10 rationally derived, archivally coded variables for assessing reoffense risk among extrafamilial child molesters. Follow-up data on 111 child molesters who were discharged from the Massachusetts Treatment Center between 1960 and 1984 were used. Degree of sexual preoccupation with children, paraphilias, and number of prior sexual offenses predicted sexual recidivism. Juvenile and adult antisocial behavior, paraphilias, and low amount of contact with children predicted nonsexual victim-involved and violent recidivism. Area under the receiver-operating characteristic curves in all three analyses indicated discrimination that was substantially better than chance, ranging from .73 to .79. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Shear ductility and toughenability study of highly cross-linked epoxy/polyethersulphone

The objective of the present study was to determine whether the ductility and toughenability of a highly cross-linked epoxy resin, which has a high glass transition temperature, T _g, can be enhanced by the incorporation of a ductile thermoplastic resin. Diglycidyl ether of bisphenol-A (DGEBA) cured by diamino diphenyl sulphone (DDS) was used as the base resin. Polyethersulphone (PES) was used as the thermoplastic modifier. Fracture toughness and shear ductility tests were performed to characterize the materials. The fracture toughness of the DDS-cured epoxy was not enhanced by simply adding PES. However, in the presence of rubber particles as a third component, the toughness of the PES–rubber-modified epoxy was found to improve with increasing PES content. The toughening mechanisms were determined to be rubber cavitation, followed by plastic deformation of the matrix resin. It was also determined, through uniaxial compression tests, that the shear ductility of the DDS-cured epoxy was enhanced by the incorporation of PES. These results imply that the intrinsic ductility, which had been enhanced by the PES addition, was only activated under the stress state change due to the cavitation of the rubber particles. The availability of increasing matrix ductility seems to be responsible for the increase in toughness. This revised version was published online in November 2006 with corrections to the Cover Date.     

Mode coupling and equilibrium mode distribution conditions in plastic optical fibers

The equilibrium mode distribution (EMD) condition is critical for optical fiber measurements. In this letter, we examine the achievement of EMD condition inside plastic optical fibers (POF's) under different launch conditions. Our pulse broadening measurements of step-index (SI) POF's as a function of fiber length show that the EMD condition can readily be achieved in an SI POF much shorter than in glass optical fibers. The observation of the EMD condition was also independently verified using the far-field pattern technique.     

Injection mold flashing of liquid crystalline polymers

Thermotropic polyesters, such as Vectra (Hoechst Celanese), have excellent moldability for intricate parts that require high precision of form, such as electronic connectors. Two apparently contradictory aspects of molding behavior contribute to the moldability. On the one hand, the low viscosity of the liquid crystalline polymer (LCP) at high shear rates favors ease of filling molds that contain long, thin paths. On the other, parts molded from LCP have little or no flash to interfere with the functioning of the parts. There has apparently been little work on the rheological aspects of flash formation. An approximate analysis is made by considering that the flash is the result of melt being extruded from the mold cavity into a slit at the mold parting line. The driving force for the extrusion is the injection pressure. The flow is assumed to be isothermal until solidification occurs, at a time that depends on the thickness of the slit, on the thermal diffusivity of the melt, the melt and mold temperatures, and on the solidification temperature of the material. The viscosity is assumed to have power-law dependence on shear rate. It is found that when the aspect ratio (length to thickness) of the flash is small, its length is strongly dependent on the magnitude of the pressure drop at the contraction from the cavity to the slit. At the minimum pressure required to fill a mold, the flash length is predicted to be independent of the rheological and thermal properties of the melt, except for the power-law exponent. Differences in end correction can, however, account for different tendencies to flash at equal moldability. Comparison of the model with Richardson's analysis of freezing in a cavity suggests a correlation of the thermal properties of the melt with his parameter c, which is related to mold filling ability. Tests of the model and possible refinements are suggested.