Growth and structural properties of GaN films on flat and vicinal SiC(0001) substrates

Initial stage GaN growth by molecular-beam epitaxy (MBE) on SiC(0001) substrate is followed by in situ scanning tunneling microscopy. Comparison is made between growth on nominally flat and vicinal substrate surfaces and the results reveal characteristic differences between the two. Ex situ transmission electron microscopy (TEM) and X-ray diffraction (XRD) rocking curve measurements of the films show lower density of defects and better structural quality of the vicinal film. We suggest the improved structural quality of the vicinal film is related to the characteristic difference in its initial stage nucleation and coalescence proccsses than that of the flat film.

Assessing soil erosion rates on manually-tilled hillslopes in the Sichuan Hilly Basin using Cs-137 and Pb-210(ex) measurements

IEECAS SKLLQG

Measurements of bremsstrahlung spectra on SECRAL

The axial emitted bremsstrahlung spectra were measured on SECRAL (Superconducting ECR ion source with Advanced design in Lanzhou) using an HPGe detector. The spectral temperature T-spe was obtained from the linear fit of the spectra in the semi-log present. The evolution of T-spe with microwave power and magnetic field configuration is investigated in this paper.

Penning trap mass measurements on nobelium isotopes

The Penning trap mass spectrometer SHIPTRAP at GSI Darmstadt allows accurate mass measurements of radionuclides, produced in fusion-evaporation reactions and separated by the velocity filter SHIP from the primary beam. Recently, the masses of the three nobelium isotopes No252-254 were determined. These are the first direct mass measurements of transuranium elements, which provide new anchor points in this region. The heavy nuclides were produced in cold-fusion reactions by irradiating a PbS target with a Ca-48 beam, resulting in production rates of the nuclei of interest of about one atom per second. In combination with data from decay spectroscopy our results are used to perform a new atomic-mass evaluation in this region.

Experimental velocity measurements and effect of flow maldistribution on predicted permeator performances

The shell-side flow distribution of a parallel flow hollow-fiber gas permeator was characterized using a thermo-anemograph. The permeator has an internal diameter of 103 mm and contains 21000 fibers. The overall fiber packing fraction is 40.1%. Experimental results revealed that shell-side flow maldistributions exist in the operating conditions studied. The gas-flow velocity is the highest at the permeator center, but lowest near the shell wall. The effects of shell-side flow maldistribution on predicted permeator performances are discussed with a simple model. Model calculation results show that flow maldistributions can have considerable effect on permeation systems with relatively high separation factors and stage cuts. (C) 1998 Elsevier Science B.V.

Death on a road (Dem. 23.53)

Scholarly consensus holds that a law quoted in Demosthenes (23.53) permitted one to kill a highway robber who had lain in ambush and attacked one on a road. But the relevant phrase says nothing explicit about ambush. Modern interpretation derives from Harpocration and other ancient authorities. It is argued here that they were mistaken and that the phrase referred to those who inadvertently killed a fellow traveler while overtaking on a road.' The new interpretation may offer another way to think about the encounter between Oedipus and Laius.

Measurements and simulations of noise imposed on supercontinuum generated in microstructure fiber

We present experimental and theoretical investigations of the highly nonlinear and broadband noise that exists on supercontinuum spectra generated from launching femtosecond Ti:Sapphire pulses into microstructure fiber.

Amplitude noise on supercontinuum generated in microstructure fiber: Measurements and simulations

Supercontinua generated in microstructure fiber can exhibit significant excess amplitude noise. We present experimental and numerical studies of the origins of this excess noise and its dependence on the input laser pulse parameters.

Effect of machine dependence on wall failure property measurements, Jenike versus an annular shear tester

Annular, ring or torsional shear testers are commonly used in bulk solids handling research for the purpose of powder characterisation or equipment design. This paper reports from a DEFRA sponsored project which aims to develop an industrial powder flow-ability tester, (based on the annular shear tester) that is economic to buy and quick and easy to use in trained but unskilled hands. This paper compares the wall failure loci measured with an annular shear cell with measurements obtained using the accepted standard wall friction tester, the Jenike shear cell. These wall failure loci have been measured for several bulk solids which range from fine cohesive powders to free-flowing granular materials, on a stainless steel 304 2B wall surface.