Analysis on dynamic tensile extrusion behavior of UFG OFHC Cu

Dynamic tensile extrusion (DTE) tests with the strain rate order of similar to 10(5) s(-1) were conducted on coarse grained (CG) Cu and ultrafine grained (UFG) Cu. ECAP of 16 passes with route B-c was employed to fabricate UFG Cu. DTE tests were carried out by launching the sphere samples to the conical extrusion die at a speed of similar to 475 m/sec in a vacuumed gas gun system. UFG Cu was fragmented into 3 pieces and showed a DTE elongation of similar to 340%. CG Cu exhibited a larger DTE elongation of similar to 490% with fragmentation of 4 pieces. During DTE tests, dynamic recrystallization occurred in UFG Cu, but not in CG Cu. In order to examine the DTE behavior of CG Cu and UFG Cu under very high strain rates, a numerical analysis was undertaken by using a commercial finite element code (LS-DYNA 2D axis-symmetric model) with the Johnson - Cook model. The numerical analysis correctly predicted fragmentation and DTE elongation of CG Cu. But, the experimental DTE elongation of UFG Cu was much smaller than that predicted by the numerical analysis. This difference is discussed in terms of microstructural evolution of UFG Cu during DTE tests.111Ysciescopu

Investigation on 2007 abnormal wave occured at the West coast of Korea

Swell-type unexpected waves occurred along western coast of Korean at March, 2007 and it caused several deaths and heavy economic loss. Available field measurement data are collected to investigate this event, numerical model is setup to reproduce this unknown waves. We found several 1-min interval tidal elevation and sea level pressure (SLP) data along the western coast of Korea and analyzed it using wavelet technique. The wavelet power spectrum for sea water level anomalies is computed using the Morlet mother function. The high wave energy is occurred between 8 and 16 minutes during 0???2 KST 31 March 2007, and the sudden pressure jump of 3???5 hPa occurred simultaneously with high wave energy event. The numerical experiments of the abnormal wave were performed using 2-dimensional shallow water wave model (COMCOT), and air pressure forcing is made from the variation of SLP field and pressure jump from weather charts. We assume the air pressure jump of around 5 hPa is moving from Shandong of China to west coast of Korea. The sea water level by the travel of SLP field was changed all over west coast of Korea with low frequency and SLP field was not considered an original forcing of the abnormal wave. The sea level under the forcing of air pressure jump was obviously amplified by the Proudman resonant effect and it can reproduce the 2007 abnormal wave qualitatively

Research on sea level rise due to global warming in the Nortwestern Pacific using a non-Boussinesq numerical model

To study the seawater volume change due to the warming of the oceans, this work adapts the Modular\ud Ocean Model Version 4 (MOM4) oceanic general circulation model, which does not consider the Boussinesq\ud approximation, to regional model. Simulation data of Climate Model 2.1 (CM2.1), the Hadley Center Coupled Climate\ud Model 3 (HADCM3), and the Model for Interdisciplinary Research on Climate 3.2 (MIROC3.2), provided by the\ud Intergovernmental Panel on Climate Change (IPCC), were used as initial and boundary values, and the Special Report\ud on Emissions Scenarios (SRES) A1B and B1 were selected as the global warming scenarios. The Northwestern Pacific\ud region, which includes Korea, was selected as the study area, and the Yellow Sea, which has a complex coastline, was\ud expressed in detail by increasing the resolution. The average values of the results for the three experiments include a\ud temperature/sea level increase of approximately 3 ??C/35 cm from 2000 to 2100 in SRES A1B, and approximately 2 ??C\ud /27 cm in SRES B1. The East Sea experienced a larger change owing to the steric effect and showed a larger influence\ud resulting from density changes as the temperature of the Tsushima Warm Current, which passes through the Korea\ud Strait, increased. The result of the study that directly considered the steric effect predicted a higher sea level rise than\ud that of indirect computation because the indirectly computed dynamic height was eliminated; sea level rise in a shallow\ud area cannot be computed, and the unchanged volume serves as undersea pressure. Moreover, the Kuroshio Current,\ud which is a major current in the Northwestern Pacific, showed a decrease in transport as global warming progressed.\ud Despite the differences between models, a decrease of 4???5 SV in transport was observed for 2100; however, there was\ud no notable change in the transport of the Tsushima Warm Current

Time and Amplitude of Afterpulse Measured with a Large Size Photomultiplier Tube

We have studied the afterpulse of a hemispherical photomultiplier tube for an upcoming reactor neutrino experiment. The timing, the amplitude, and the rate of the afterpulse for a 10 inch photomultiplier tube were measured with a 400 MHz FADC up to 16 \ms time window after the initial signal generated by an LED light pulse. The time and amplitude correlation of the afterpulse shows several distinctive groups. We describe the dependencies of the afterpulse on the applied high voltage and the amplitude of the main light pulse. The present data could shed light upon the general mechanism of the afterpulse.Comment: 11 figure

Carbon Nanotubes as Nanoelectromechanical Systems

We theoretically study the interplay between electrical and mechanical properties of suspended, doubly clamped carbon nanotubes in which charging effects dominate. In this geometry, the capacitance between the nanotube and the gate(s) depends on the distance between them. This dependence modifies the usual Coulomb models and we show that it needs to be incorporated to capture the physics of the problem correctly. We find that the tube position changes in discrete steps every time an electron tunnels onto it. Edges of Coulomb diamonds acquire a (small) curvature. We also show that bistability in the tube position occurs and that tunneling of an electron onto the tube drastically modifies the quantized eigenmodes of the tube. Experimental verification of these predictions is possible in suspended tubes of sub-micron length.Comment: 8 pages, 5 eps figures included. Major changes; new material adde

Tracking Performance of the Scintillating Fiber Detector in the K2K Experiment

The K2K long-baseline neutrino oscillation experiment uses a Scintillating Fiber Detector (SciFi) to reconstruct charged particles produced in neutrino interactions in the near detector. We describe the track reconstruction algorithm and the performance of the SciFi after three years of operation.Comment: 24pages,18 figures, and 1 table. Preprint submitted to NI