Low energy positron diffraction from Cu(111): Importance of surface loss processes at large angles of incidence

Intensities of positrons specularly diffracted from Cu(111) were measured at the Brandeis positron beam facility and analyzed in the energy range 8eV40{degree}. 30 refs., 5 figs., 1 tab

Observation of Difference between Low-Energy Electron-Diffraction and Positron-Diffraction Structural Determination of the Cleavage Faces of CdSe

[[abstract]]Low-energy positron diffraction (LEPD) is used in conjunction with low-energy electron diffraction (LEED) to determine the relaxed atomic geometries of the CdSe cleavage surfaces. The LEPD analyses yield optimal fits at smaller top-layer perpendicular relaxations than LEED for both cleavage faces, and significantly better agreement between theoretical and experimental intensity profiles.[[fileno]]2030159010058[[department]]電機工程學

Characterization of roll bite heat transfers in hot steel strip rolling and their influence on roll thermal fatigue degradation

A temperature sensor with a thermocouple placed at ~0.5 mm from roll surface is used in hot rolling conditions to evaluate by inverse calculation heat transfers in the roll bite. Simulation analysis under industrial hot rolling conditions with short contact lengths (e.g. short contact times) and high rolling speeds (7 m./sec.) show that the temperature sensor + inverse analysis with a high acquisition frequency (> 1000 Hz) is capable to predict accurately (5 to 10 % error) the roll bite peak of temperature as well as the roll surface temperature evolution all around the roll rotation. However as heat flux is more sensitive to noise measurement, the peak of heat flux in the bite is under-estimated (20 % error) by the inverse calculation and thus the average roll bite heat flux is also interesting information from the sensor (these simulation results will be verified with an industrial trial that is being prepared). Rolling tests on a pilot mill with low rolling speeds (from 0.3 to 1.5 m./sec.) and strip reductions varying from 10 to 40 % have been performed with the temperature sensor. Analysis of the tests by inverse calculation show that at low speed (<0.5 m./sec.) and large contact lengths (reduction: 30 to 40%), the roll bite peak of heat flux reconstructed by inverse calculation is correct. At higher speeds (1.5 m./sec.) and smaller contact lengths (reduction: 10-20%), th