Canonical representation of stationary quantum Gaussian processes

Stimulated by the quantum generalization of the canonical representation theory for Gaussian processes in \cite{AHH}, we first give the representations (not necessarily canonical) of two stationary Gaussian processes $X$ and $Y$ by means of white noises $q_t$ and $p_t$ with no assumptions on their commutator. We then assume that $q_t+ip_t$ annihilates the vacuum state and prove that the representations are the joint Boson Fock ones if and only if $X$ and $Y$ have a scalar commutator

Microscopic thickness determination of thin graphite films formed on SiC from quantized oscillation in reflectivity of low-energy electrons

Low-energy electron microscopy (LEEM) was used to measure the reflectivity of low-energy electrons from graphitized SiC(0001). The reflectivity shows distinct quantized oscillations as a function of the electron energy and graphite thickness. Conduction bands in thin graphite films form discrete energy levels whose wave vectors are normal to the surface. Resonance of the incident electrons with these quantized conduction band states enhances electrons to transmit through the film into the SiC substrate, resulting in dips in the reflectivity. The dip positions are well explained using tight-binding and first-principles calculations. The graphite thickness distribution can be determined microscopically from LEEM reflectivity measurements.Comment: 7 pages, 3 figure

A method using granulated coal ash for disposal of the sludge carried by tsunami

Large amounts of sludge and debris accumulated on agricultural and residential areas after the Great East\ud Japan Earthquake. Since the sludge carried by the Tsunami has high contents of unstable-form organic matter ???UFOM???\ud (burned at 300??C), this sludge is considered to be the origin of malodorous gas generation that affects human activities.\ud Therefore, disposal of the sludge plays an important role in the reconstruction effort. Previously, it is obvious that\ud granulated coal ash (GCA) comprised of silica (44%), calcium oxide (21%) and aluminum oxide (13%) improves the\ud organic condition of sewage sludge. For example, the generation of malodorous gases, e.g. hydrogen sulfide and\ud ammonia, was greatly reduced after mixing GCA with the sewage sludge. In this study, we aim to propose a method\ud using GCA to disposal the sludge carried by Tsunami. For this purpose, changes in organic conditions and malodorous\ud gas generation of the sludge after mixing GCA are investigated based on laboratory experiments. In the laboratory\ud experiments, the sludge was mixed with GCA, and then was burned at 200??C to 600??C (intervals of 100??C) in 4 hours at\ud each temperature step. Furthermore, other experiments were conducted to measure amounts of gas generated from the\ud sludge in the absence and the presence of GCA. It was found that ignition behaviors of the sludge with and without\ud GCA were different, namely, the ignition loss at 300??C of the sludge mixing with GCA was lower than that of the sludge\ud without mixing GCA. This ensures that organic conditions (e.g. decreases in amounts of UFOM) of the sludge changes\ud after mixing GCA. Moreover, it was also found that malodorous gases did not generate from the sludge mixing with\ud GCA, indicating that GCA affects the digestion process of organic matter. It is expected that our proposed method is\ud also useful for the capitalization of dredged soil and the development of lowland

Improved crystal-growth and emission gain-narrowing of thiophene/phenylene co-oligomers

ArticleADVANCED MATERIALS. 15(3): 213-217(2003)journal articl

Energetics and structure of the lower E region associated with sporadic E layer

The electron temperature (<I>T<sub>e</sub></I>), electron density (<I>N<sub>e</sub></I>), and two components of the electric field were measured from the height of 90 km to 150 km by one of the sounding rockets launched during the SEEK-2 campaign. The rocket went through sporadic E layer (<I>E<sub>s</sub></I>) at the height of 102 km–109 km during ascent and 99 km–108 km during decent, respectively. The energy density of thermal electrons calculated from <I>N<sub>e</sub></I> and <I>T<sub>e</sub></I> shows the broad maximum in the height range of 100–110 km, and it decreases towards the lower and higher altitudes, which implies that a heat source exists in the height region of 100 km–110 km. A 3-D picture of <I>E<sub>s</sub></I>, that was drawn by using <I>T<sub>e</sub></I>, <I>N<sub>e</sub></I>, and the electric field data, corresponded to the computer simulation; the main structure of <I>E<sub>s</sub></I> is projected to a higher altitude along the magnetic line of force, thus producing irregular structures of <I>T<sub>e</sub></I>, <I>N<sub>e</sub></I> and electric field in higher altitude

Multiscale Kinetic Monte-Carlo for Simulating Epitaxial Growth

We present a fast Monte-Carlo algorithm for simulating epitaxial surface growth, based on the continuous-time Monte-Carlo algorithm of Bortz, Kalos and Lebowitz. When simulating realistic growth regimes, much computational time is consumed by the relatively fast dynamics of the adatoms. Continuum and continuum-discrete hybrid methods have been developed to approach this issue; however in many situations, the density of adatoms is too low to efficiently and accurately simulate as a continuum. To solve the problem of fast adatom dynamics, we allow adatoms to take larger steps, effectively reducing the number of transitions required. We achieve nearly a factor of ten speed up, for growth at moderate temperatures and large D/F.Comment: 7 pages, 6 figures; revised text, accepted by PR

Integrated external cavity laser composed of spot-size converted LD and UV written grating in silica waveguides on Si

The authors report for the first time an external cavity laser composed of a spot-size converted LD and a UV written waveguide grating, both integrated on Si. The laser operates in a single mode with a side-mode suppression of 37 dB. The threshold current is 12 mA and the average thermal coefficient is as low as -1.7 GHz

A method for investigation of sediment retention in sandy tidal flats

Recently, coastal environmental engineers have made attempts to understand the role of sediment (particulate organic matter adsorbed on fine soil particles, diameter range 1???100 ??m) in subsurface environment which is considered to be related to the biodiversity of estuaries. Since the retention amount of sediment is one of important factors in considering the biodiversity, understanding sediment retention is vital to good management of the estuarine environment. In this study, laboratory experiments were conducted to propose a model for investigating the sediment retention based on variations of water head in a sand bed. Field observations were also conducted to verify the validity of the proposed model. From laboratory experiments, variations of water head in the sand bed could be represented by our proposed model with a maximum relative error of 3%. As the proposed model takes the porosity and the hydraulic conductivity of the sand bed into account, sediment retention in the sand bed can be evaluated on the basis of variances in the porosity and the hydraulic conductivity when variations of water heads at the boundary and in the sand bed are known. A method was proposed to measure variations of river water head and water head in a tidal flat. Furthermore, sand material of the tidal flat was sampled in order to determine the porosity and the hydraulic conductivity of the tidal flat. Based on the observation results, the variation of water head in the tidal flat could be reproduced by the proposed model when the porosity and the hydraulic conductivity of the tidal flat were applied into the model. In other words, the porosity and the hydraulic conductivity of the tidal flat can be predicted by the proposed model when variations of river water head and water head in the tidal flat are measured, leading to the understanding of sediment retention in the tidal flat from temporal changes in the porosity and the hydraulic conductivity