GIS-Based Analysis of Railway's Origin/Destination Path-Selecting Behavior

This study aims to analyze a railway's OD path-selecting behavior with microsimulation analysis in big cities. In big cities, railway networks often consist of lines belonging to several different companies, making railway OD path-selecting behavior very complex. Usually, the second or third nearest stations are used instead of the nearest station. This study takes buildings rather than zones as origins or destinations for simulating railway path-selecting behavior. First, in the GIS database, we consider whether the destinations are within walking distance of their origins. Then we modify the map-based railway network with GIS to make it represent the real urban railway network more clearly. Then, from all the available stations for each building, and all the paths between the origin and destination stations, the one involving the shortest distance is the one used.     

Numerical Prediction of Seepage and Seismic Behavior of Unsaturated Fill Slope

This paper presents a case study on a numerical prediction of the seepage and seismic behaviors of an unsaturated fill slope. In this study, the numerical prediction is performed with a dynamic three-phase (soil, water and air) coupled analysis based on porous media theory and constitutive models. The weak forms of three governing equations, momentum balance equations of the overall three-phase material and mass and the momentum balance equations of the pore fluids (water and air), are implemented in a finite element model. The discretized equations are solved by the fully implicit method and the skeleton stress is also implicitly integrated. The in-situ observation at the target fill slope of the case study has been ongoing since 2006. First, distributions of water saturation in the fill slope are simulated by performing seepage analyses to reproduce the in-situ ground water level in the fill slope. Second, seismic responses of the fill slope during two past earthquakes are simulated, and the numerical method is validated by comparing observed acceleration records and numerical one. Finally, seismic responses of the fill slope during a future scenario earthquake are predicted under different moisture conditions of unsaturated fill. As a result, the following findings were obtained. 1) The shape of the ground water level was partially reproduced from the quite dry fill slope element by using virtual constant precipitation. However, the observation results of moisture distribution above the ground water level were not reproduced. 2) In the validation analyses after two earthquakes, the numerical method reproduced the positions of peak frequency of acceleration Fourier spectra. 3) The numerical results clearly showed that frequency characteristics of the seismic response and the residual displacement of the fill slope were affected by the initial distribution of the degree of saturation in the fill ground.     

Biodegradation of phenolic environmental pollutants by a surfactant-laccase complex in organic media

Oxidative degradation of phenolic environmental pollutants in organic media was investigated using a laccase complexed with surfactants. The catalytic activity of the surfactant-laccase complex in isooctane was markedly enhanced by appropriately adjusting the water content of the reaction medium using reverse micelles. The surfactant-laccase complex showed little activity towards the oxidative reaction of bisphenol A in water-saturated isooctane (i.e., 0.0055% [v/v] water) while effectively catalyzed the same reaction in isooctane containing 4% (v/v) water, which is over the maximum water solubility. The latter system was homogeneous and was only achieved by the aid of reverse micelles. With respect to the oxidation of bisphenol A, two products, 4-isopropylphenol and 4-isopropenylphenol, were identified by gas chromatography-mass spectrometry (GC-MS) analyses, indicating the oxidative degradation of the bis-phenolic structure of bisphenol A. We also found that the surfactant-laccase complex turned out to handle other environmental pollutants, chlorophenols, by the simultaneous addition of water and a redox mediator into the reaction medium using reverse micelles.     

Surface failure mode evaluation of pure AlN and AlN with Al<Subscript>2</Subscript>O<Subscript>3</Subscript>(0.1 <Emphasis Type="Italic">μ</Emphasis>m) oxide layer by microscratch testing

The surface scratch resistance, damage evolution and damage detection during microscratching of pure AlN and AlN with an Al₂O₃ oxide layer (∼0.1 μm) were investigated. The microscratch experiments were performed in a progressive load-ramped mode where the load was linearly increased from 0 to 3 N as the scratch progressed with a loading rate of 0.2 N/min. The experiments resulted to two different failure mechanisms; Ductile scratching and fracture dominated scratching. In the case of pure AlN, inconsistent different kinds of damages were found to initiate at low critical load measured as 0.30 N. This critical load was also found to decrease with increasing the surface roughness, material density and grain size of AlN. In the case of pure AlN with an Al₂O₃ oxide layer, the critical load for crack initiation was measured as 0.45 N, higher than pure AlN. This critical load was found to generate uniform discontinuous chipping. The distance between these defects decreased and the failure mode gradually transformed to continuous chipping as the scratch progressed. The surface modification of AlN with the use of an Al₂O₃ oxide layer was found to improve the tribological properties of AlN.     

Temperature dependence of bistable InGaAsP/InP lasers

An increase of hysteresis current width in bistable lasers with two or three sections was observed at higher temperatures. A rate equation analysis was performed where both carrier density dependence on lifetime and the bleaching of saturable absorption by the spontaneous emission were taken into account. We show that the increased loss of injected carriers due to Auger recombination process causes the increase in the hysteresis width. A small-signal stability analysis for the switch-off point revealed that increased coupling between carriers in the gain and absorption regions, through the absorption of superradiant emission, has the effect of raising the switch-off point to higher current levels. It was shown experimentally that, without changing the temperature, the current hysteresis width can be controlled by adjusting the current distribution in three sections.     

Transverse shear effect in a bimodulus plate

This paper concerns the bending analysis of a bimodulus elastic plate whose stress-strain relation is expressed by two straight lines with a slope discontinuity at the origin. An energy formulation of the problem is made, taking into account a transverse shear deformation. A method of numerical solution is presented for cylindrical bending of a plate.     

Double Charge Polarity Switching in Sb-Doped SnSe with Switchable Substitution Sites

Tin mono-selenide (SnSe) is one of the most promising thermoelectric materials; however, it experiences difficulty in controlling the carrier polarity, which is inevitable for realizing p-n homojunction devices. Herein, double switching of charge polarity in (Sn_1−xSb_x)Se by varying x is reported; pure SnSe shows p-type conduction, whereas the polarity of (Sn_1−xSb_x)Se switches to n-type conduction for 0.005 < x < 0.05, and then re-switches to p-type conduction for x > 0.05. The major Sb substitution site switches from the Se (Sb_Se) to Sn site (Sb_Sn) with increasing x. Sb_Sn (Sb³⁺ at Sn²⁺) works as a donor, but Sb_Se (Sb³⁻ at Se²⁻) does not produce a hole because of the Sb–Sb dimer formation. The mechanism of double polarity switching is explained by native p-type conduction in pure SnSe due to Sn-vacancy formation, whereas (Sn_1−xSb_x)Se exhibits n-type behavior due to conduction through the Sb_Se impurity band formed above the valence band maximum, and finally re-switches to weak p-type, where the Fermi level approaches the midgap level between the Sb_Se band and conduction band minimum. Clarification of the Sb doping mechanism will provide a crucial guide for developing more sophisticated doping routes for SnSe and high-performance energy-related devices.     

Effects of Grain Size of Hot-Pressed Silicon Nitride on Contact Damage Morphology and Residual Strength

Effects of the grain size of hot-pressed Si₃N₄ on contact damage morphology and residual strength were studied using the elastic/plastic indentation method with a spherical indenter. The contact damage, initially formed with increasing indentation load, was Hertzian cracks in the Si₃N₄ consisting of fine grains (mean grain size: 0.2 μm). In the coarser-grained Si₃N₄ (mean grain size: 0.8 μm), there was a damage texture, consisting of grain-sized microcracks. The residual strength was degraded at a load slightly higher than the critical load for contact damage formation. The strength degradation was not caused by contact damage but the residual stress formed around the impressions.