Wavelength-Dependent Transient Characteristics Caused by Gain Saturation in Highly Nonlinear Fiber-Based Raman Amplifiers

We have investigated the transient characteristics of discrete Raman Amplifiers and found that the response time caused by gain saturation is dependent upon the wavelength, which corresponds to the effective length of the pump light.     

Back-to-back correlations of high-p(T) hadrons in relativistic heavy-ion collisions

We investigate the suppression factor and the azimuthal correlation function for high p(T) hadrons in central Au+Au collisions at sqrt[s(NN)]=200 GeV by using a dynamical model in which hydrodynamics is combined with explicitly traveling jets. We study the effects of parton energy loss in a hot medium, intrinsic k(T) of partons in a nucleus, and p (perpendicular) broadening of jets on the back-to-back correlations of high p(T) hadrons. Parton energy loss is found to be a dominant effect on the reduction of the awayside peaks in the correlation function.     

Analysis of one-and two-particle spectra at RHIC based on a hydrodynamical model

We calculate the one-particle hadronic spectra and correlation functions of pions based on a hydrodynamical model. Parameters in the model are so chosen that the one-particle spectra reproduce experimental results of √s= 130 AGeV Au + Au collisions at RHIC. Based on the numerical solution, we discuss the space-time evolution of the fluid. Two-pion correlation functions are also discussed. Our numerical solution suggests the formation of the quark-gluon plasma with large volume and low net baryon density.     

Effect of solute atoms on fracture toughness in dilute magnesium alloys

The effect of alloying elements on the toughness and the fracture behaviour was investigated on seven kinds of Mg-0.3?at.% X (X?=?Ag, Al, Ca, Pb, Sn, Y and Zn) alloys with a grain size of 3–5?μm. The fracture toughness and fracture behaviour in magnesium alloys were closely related to the segregation energy. The Mg–Al and –Zn alloys that had small segregation energy showed high toughness and ductile fracture in most regions, while the Mg–Ca alloy with large segregation energy exhibited low toughness and intergranular fracture. These different tendencies resulted from solute segregation at grain boundaries (GBs). The change in the lattice parameter ratio was the influential material parameter regardless of whether the GB embrittlement was for enhancement or suppression.     

Asymmetric oxidation of sulfides under solvent-free or highly concentrated conditions

The aluminium(salalen) complex was found to be an efficient catalyst for the asymmetric oxidation of sulfides under solvent-free or highly concentrated conditions, in which an only 0.002-0.01 mol% catalyst loading was sufficient to obtain optically active sulfoxides in high yield with high enantioselectivity.     

Lipase‐Catalyzed Transesterification of Polyesters to Ester Copolymers

Lipase‐catalyzed intermolecular transesterification between two different polyesters has been carried out using in toluene. The transesterification of poly(ε‐caprolactone) (PCL) and (1,4‐butylene adipate) took place via catalysis of lipase from Candida antarctica to give an ester copolymer. ¹³C NMR analysis showed that the resulting polymer was not a mixture of the starting polyesters, but a copolymer consisting of both units. The reaction temperature and solvent amount greatly affected the microstructure of the ester copolymer. Under appropriate conditions, the random copolymer was formed. The enzymatic transesterification has been monitored by size exclusion chromatography (SEC) and ¹³C NMR. Ester copolymers were enzymatically obtained from PCL and other poly(α,ω‐alkylene dicarboxylate)s and their microstructure depended on the polyester structure.     

Effects of severe plastic deformation on the corrosion behavior of aluminum alloys

Effects of severe plastic deformation on the corrosion behaviors of Al alloys containing precipitates have been investigated. Al and its alloys were severely deformed by equal-channel angular pressing (ECAP) processes and the corrosion behaviors of the Al alloys were evaluated by means of potentiodynamic polarization in a neutral buffer solution containing 0.002 M chloride ion. Introduction of huge plastic deformation to both of Al-5.4 wt% Ni and Al-5 wt% Cu alloys increased pitting potential. In contrast, ECAP treatment of 4N pure Al resulted in a decrease in open circuit potential, slight increase of passive current and shift of pitting potential to the negative direction. The influence of the change in microstructures caused by severe plastic deformation was investigated. Contribution to the Fall Meeting of the European Materials Research Society, Symposium D: 9th International Symposium on Electrochemical/Chemical Reactivity of Metastable Materials, Warsaw, 17th-21st September, 2007     

One-dimensional shock wave interaction with rubber and low-porosity foam

One-dimensional interaction between a planar shock wave and a rubber or low-porosity foam is investigated experimentally and numerically. The considered polyurethane foam is of high density (ρ _c=290 kg/m³) and lowporosity (ϕ=0.76), and this corresponds to an intermediate condition between rubber and high-porosity foam. Stress-strain relations for the low-porosity foam are investigated by machine tests, which show larger deformation against compressive force and higher non-linearity in stress-strain curve as compared with rubber. Also the low-porosity foam shows a hysteresis cycle. Experiments on shock wave-foam interactions are conducted by using a shock tube. Experimental time history of the surface stress of the foam at the end of the shock tube does not show shock type stress increase, but continuous excessive stress rise can be seen, and then dumping vibration approaching to gas dynamic pressure of the reflected shock wave is followed, and the highest stress amounts about 3∼4 times of the pressure after the reflected gas dynamic shock wave. Interactive motions of gas and the low-porosity foam are analyzed using the Lagrangean coordinates system. An elastic model for a low-porosity foam is assumed to be a single elastic material with the measured stress-strain relation. Results of numerical simulations are compared with the shock tube experiments, which show essentially same stress variations with experimental results.     

Selective appearance of ϵ-martensitic transformation and dynamic strain aging in Fe–Mn–C austenitic steels

The influence of stress-induced ε-martensitic transformation on the serrated flow behavior associated with dynamic strain aging was investigated. The ε-martensitic transformation was controlled by changing the deformation temperature and adding Si to Fe–17Mn–xSi–0.3?C alloys. The addition of Si promoted the ε-martensitic transformation, and suppressed the slip deformation due to solution hardening. The initiation of serrations around room temperature was delayed by the promotion of ε-martensitic transformation which initiated plastic deformation. The critical stress for the occurrence of serrations and the critical stress for the occurrence of slip deformation were found to have a linear relationship.