The effect of large strains on ageing of a filled elastomer

Strain endurance experiments on a filled elastomer were performed at several temperatures. It was found that superimposed prestraining accelerated the ageing process. This process was caused by microstructural changes in the elastomer. In order to evaluate the mechanical properties of a filled elastomer it is necessary to take into consideration not only the ageing effects but also the loading history.     

High-temperature electrical conductivity of aluminium nitride

The electrical conductivity of hot-pressed polycrystalline aluminium nitride doped with oxygen and beryllium was measured as a function of temperature from 800 to 1200° C and over a range of nitrogen partial pressure from 10² to 10⁵ Pa. The effect of beryllium dopant, the independence of conductivity from nitrogen partial pressure, and the observed activation energy suggested extrinsic electronic species or aluminium vacancies as charge carriers. Polarization measurements made with one electrode blocking to ionic species indicated that the aluminium nitride with oxygen impurity was an extrinsic electronic conductor.     

High density recording with perpendicular Co-Cr-Nb media and ring heads

Effective double layer structure was investigated by adding Nb to the sputtering source of Co-Cr thin film perpendicular magnetic recording tapes. The output from the tapes was measured with a ring head through to the short wavelength, λ50=0.19 μm (D50=267KFRPI).     

Nonlinear load-deflection relation of toroidal shells subjected to axisymmetric compression between rigid plates

Utility of toroidal shells as shock absorbers for radioactive materials' shipping casks is discussed by carrying out numerical and experimental analyses. The static load-deflection relations under axisymmetric compression between rigid plates are presented.A simple elastic-plastic analytical method is first developed on the basis of an incremental Rayleigh-Ritz method by taking account of the large deflections and the continuous change of contact points. Meridional compression is neglected and the meridional curvature distribution is approximated by a trigonometric series. Strain-hardening material properties and axisymmetric deformation are also assumed. In order to provide data for comparison purposes, static compression tests were performed using six models of different shapes and dimensions made of 304-type stainless steel. Finally, the applicability of the numerical method developed in this paper is discussed.The mechanical behavior of toroidal shells is also discussed.     

Access-mode predictions for low-power cache design

An access-mode prediction technique based on cache hit and miss speculation for cache design-achieves minimal energy consumption. Using this method, cache accesses can be adaptively switched between the way-prediction and the phased accessing modes.     

The automated simulation of dynamic non-linearity to shot-peening mechanics

This paper gives an automated simulation of dynamic non-linearity to shot-peening mechanics. Three-dimensional constitutive material law expressed in the stress invariants is used along with the nonlinear analysis based on the concept of initial stress. Residual stresses, strains, displacements and plasticity can be calculated using information in Gauss integration points. The ultimate load is reached when the algorithm does not converge. The corresponding failure modes can be interpreted as those for which as state of equilibrium is no longer possible. The final results obtained the shakedown diagrams plotted in three dimensions. The history of these diagrams is self-explanatory.     

Deposition rate dependence of coercivity in vaccum evaporated CoCr films

Deposition rate dependence of perpendicular coercivity Hcl in Cocr evaporated films at the deposition rate ranging from 0.4nm/s to 400nm/s is studied. Hcl increases with decreasing deposition rate as well as with increasing substrate temperature. A High Hcl over 500 Oe, which has ever been obtained only at a substrate temperature over 250°C when deposition rate is high(400nm/s), is obtained at a substrate temperature of 150°C under deposition rate of 2nm/s. "Shoulder" in the hysteresis loop disappears as Hcl exceeds 400 Oe. Therefore to decrease the deposition rate and to increase the substrate temperature have the same effect on Hcl. Saturation magnetization of the films with the same Cr concentration increases with decreasing deposition rate, and it is suggested that the degree of Cr segregation increases with decreasing deposition rate. Hcl is independent of the background pressure when the relative pressure, the quotient of (background pressure/deposition rate), is between 2×10^-8and 5×10^-6torr/(nm/s). From the results above, it is clarified that the difference of deposition rate between vacuum evaporation and sputtering is one of the major reasons for the difference of Hcl between the two.     

Segregation in sputtered Co-Cr films

The segregation growth process in sputtered Co-Cr films is investigated by examining the effect of substrate temperature on the segregated microstructure and magnetic properties. In sputtered Co-25at%Cr films, segregation occurs below 560°C, and both the saturation magnetization and the perpendicular anisotropy constant show a maximum around a substrate temperature of 300°C, where a specific microstructure, called a CP (chrysanthemum-like pattern) structure, is observed. The results suggest that the CP structure becomes observable in the highly segregated state and generates high perpendicular anisotropy. A new segregation growth model is derived from the results of the CP structure observations. Using this model, it is possible to explain the continuous transition of the magnetization mode between the continuous and the particulate modes.     

Modeling of optical low coherence reflectometry recorded Braggreflectograms: evidence to a decisive role of Bragg spectral selectivity

This paper draws attention to the basic principles governing reflections in uniform Bragg reflectors (BR) when measured employing optical low coherence reflectometry (OLCR) technique. Using computations based on transfer matrix method (TMM), we first showed a strong spectral dependence of Bragg reflectograms on an OLCR probe spectrum. Later, this dependence is exploited to evaluate, for the first time, the coupling coefficient κ of a Bragg grating in a distributed Bragg reflector (DBR) laser on InP     

On rigorous transaction scheduling

The class of transaction scheduling mechanisms in which the transaction serialization order can be determined by controlling their commitment order, is defined. This class of transaction management mechanisms is important, because it simplifies transaction management in a multidatabase system environment. The notion of analogous execution and serialization orders of transactions is defined and the concept of strongly recoverable and rigorous execution schedules is introduced. It is then proven that rigorous schedulers always produce analogous execution and serialization orders. It is shown that the systems using the rigorous scheduling can be naturally incorporated in hierarchical transaction management mechanisms. It is proven that several previously proposed multidatabase transaction management mechanisms guarantee global serializability only if all participating databases systems produce rigorous schedules