Optimum Power Controller for Random Number Generator in the Crypto Module of Ubiquitous Computing Environment

Abstract. Critical cryptography applications require the production of an unpredictable and unbiased stream of binary data derived from a fundamental noise mechanism, which is quite difficult to create with a stable random bit stream, as required for statistical randomness, when using a random generator with only a hardware component. However, since all electronic systems are influenced by a finite bandwidth, 1/f noise, and other non-random influences, perfect randomness cannot be preserved by any practical system. Thus, when generating random numbers using an electronic circuit, a low-power white noise signal is amplified, then sampled at a constant sampling frequency. Yet, it is quite difficult to create an unbiased and stable random bit stream, as required for statistical randomness, when using a random generator with only a hardware component and in especially it has occur the drift phenomena of input power. Therefore if the randomness of output bit stream is beyond limits range, it is applied the regulation of input power range to take the output bit stream, through the evaluation of randomness by constant period of output bit stream. Accordingly, this paper proposes a method for stabilizing the input power of a random number generator using optimum power control mechanism in crypto module hardware. As such, the proposed scheme is designed to reduce the statistical property of a biased bit stream and optimize the input power to a random number generator engine in crypto module engine for ubiquitous computing

Physicochemical aspects of particle breakthrough in granular media filtration

textGranular media filtration is used almost universally to remove particles from drinking water, and is usually the last particle removal process in water treatment plants. Therefore, superb particle removal efficiency is needed during this process to ensure a high quality of drinking water. However, particle breakthrough can occur by either the breakoff of previously captured particles (or flocs) or the direct passage of some influent particles through the filter. It is hypothesized that there are physicochemical differences among the particles, such that better destabilized particles are caught in a filter, while others that are not so well destabilized are allowed through. To investigate these differences, the zeta potential distribution (ZPD) and particle size distribution of effluent samples after filtration were analyzed. Filtration experiments were performed in a laboratory-scale filter using spherical glass beads with diameter of 0.55 mm as collectors. A single type of particle suspension (Min-U-Sil 5, nearly pure SiO2) and three different destabilization methods (pH control, alum and polymer destabilization) were utilized. The operating conditions were similar to those of standard media filtration practice: a filtration velocity of 5 m/h. More favorable particles, i.e., particles with smaller surface charge, were well attached to the collectors especially during the early stage of filtration when surface charge of particles and collectors were both negative. This selective attachment of the lower charged particles caused the ZPD of the effluent to move to a more negative range. On the other hand, the ZPD of effluent did not keep moving from less negative to more negative during the later stages of filtration, and this result was thought to be caused by two reasons: ripening effects and detachment of flocs. At the same time, to assess the possibility of particle detachment during the normal filtration, a hydraulic shock load (20% increase of flow rate) was applied after 4 hours of normal filtration. Less favorable particles, i.e., particles with larger surface charge, were easily detached during the hydraulic shock load. Therefore, proper particle destabilization before filtration is crucial for maximum particle removal as well as minimum particle breakthrough.Civil, Architectural, and Environmental Engineerin

Interpretation of surficial shear crack propagation mechanisms in bending for Zn or AlSi coated hot press forming steels

The bending angle at the peak load is regarded as the most important parameter for evaluating bending properties of hot-press-forming (HPF) steels. However, it is not a mechanics-based parameter for the bending criterion, and the data interpretation is difficult because bending criteria in relation with microstructures and associated bending mechanisms have not been verified yet. In this study, effects of coating and baking treatments on bending angles at the peak load of three kinds of 1470 MPa-grade HPF steels were investigated by interrupted three-point bending tests coupled with direct microstructural observation. According to direct observations of sequential cracking processes of V-shaped crack (V-crack), bending procedures were classified into four stages: (1) formation of small V-crack, (2) increase in number and size of V-cracks, (3) initiation of shear-crack propagation from the V-crack tip, and (4) further propagation and opening of the shear crack. The minimum bending angle required for initiating the shear-crack propagation from the V-crack tip was defined as a critical angle, which meant the boundary between the 2nd and 3rd stages. The present bending behavior related with critical bending angle and V-cracking could be interpreted similarly by the fracture-mechanics concept, i.e., the initiation of shear-crack propagation.11Ysciescopu

Effects of untransformed ferrite on Charpy impact toughness in 1.8-GPa-grade hot-press-forming steel sheets

Hot press forming (HPF) steel sheets are austenitized, press-formed, and rapidly cooled to obtain a martensitic microstructure with an ultra-high strength. When they are insufficiently austenitized, their microstructures might contain a small amount of untransformed ferrite, which can deteriorate impact toughness as well as strength, but its causes and relevant fracture mechanisms have not been clearly verified yet. In this study, thus, 1.8-GPa-grade HPF sheets were austenitized at various temperature and time, and their tensile and Charpy impact test results were analyzed in relation with untransformed ferrite and its effect on fracture mechanisms. In the HPF sheets containing the untransformed ferrite, voids were formed mostly at ferrite/martensite interfaces, and were grown and propagated linearly to form a cleavage crack, whereas deformation bands were well developed without voids or cracks in the non-ferrite-containing sheets. The highly localized strains accommodated in the soft ferrite made ferrite/martensite interfaces or ferrite itself work as fracture initiation sites, which led to the brittle fracture and consequently to the deterioration of impact energy. This result can provide an important idea for optimization of austenitization conditions demanded for ultra-high strength and excellent impact toughness in HPF applications.114sciescopu

Effect of untransformed Ferrite on Charpy Impact Properties of Hot-Press-Forming Steels

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