591 research outputs found
Dependence of the Electroluminescence on the Spacer Layer Growth Temperature of Multilayer Quantum-Dot Laser Structures
Electroluminescence (EL) measurements have been performed on a set of In(Ga)As-GaAs quantum-dot (QD) structures with varying spacer layer growth temperature. At room temperature and low injection current, a superlinear dependence of the integrated EL intensity (IEL) on the injection current is observed. This superlinearity decreases as the spacer layer growth temperature increases and is attributed to a reduction in the amount of nonradiative recombination. Temperature-dependent IEL measurements show a reduction of the IEL with increasing temperature. Two thermally activated quenching processes, with activation energies of ˜ 157 meV and ˜ 320 meV, are deduced and these are attributed to the loss of electrons and holes from the QD ground state to the GaAs barriers. Our results demonstrate that growing the GaAs barriers at higher temperatures improves their quality, thereby increasing the radiative efficiency of the QD emission
Similarities in the architecture of the active sites of Ni-hydrogenases and Fe-hydrogenases detected by means of infrared spectroscopy
Similarities in the architecture of the active sites of Ni-hydrogenases and Fe-hydrogenases detected by means of infrared spectroscopy
Experimental study for local air/water flow structure of bubbly and slug flow regime
Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.A study for local hydraulic characteristics of water and air/steam mixture flow is a very challenging topic for advanced thermal hydraulic analysis code development. Recently, many researchers made efforts in the study of mechanistic feature related to the two phase dynamics such as an interfacial area transport model. The mechanistic study for the interfacial area needs a lot of understanding for the bubble/drop dynamics and flow propagation phenomena. To generate an experimental data base for a modeling, an air/water test was performed in this study. The facility has a cylindrical acryl test section of which the diameter and height are 80 mm and 10m, respectively. The major local parameters to be measured are the void fraction, bubble/liquid velocities, interfacial area concentration and bubble size. To investigate the transport phenomena of the twophase parameters, a local probe and an impedance void meter(IVM) are installed at three axial elevations of the test section. (L/D=12.2, 42.2, 100.7) The test range covers 0.5~2.8 m/s and 0.04~1.2 m/s of the superficial liquid and gas velocity, respectively, which corresponds to the bubbly and slug flow regimes. The system pressure conditions are 0.2~0.3 MPa at the L/D=12.2.dc201
Influence of season of birth, sex and paternal line on growth performance and carcass traits in pigs
Participants in the pig production industry focus on feed and feed additives to improve growth performance and meat quality of pigs. Consequently, the Rural Development Administration of the Republic of Korea produced a new paternal line to improve economic traits in pigs. However, there is an absence of information on pig traits with regard to season and sex, and a comparison between the new paternal line and past paternal lines. Therefore, the authors conducted this study to investigate the influence of season of birth, sex and paternal line on growth performance and carcass traits in pigs. A total of 2888 piglets ((Landrace × Yorkshire) × Darby Duroc (DD) or Chookjin Duroc (CD)) with an average age of three weeks were tested for 22 weeks during the four season of the year (spring 608 piglets, summer 404 piglets, autumn 576 piglets and winter 1300 piglets). The bodyweights (BW) of individual pig were recorded, and feed consumption was recorded at weeks 2, 12 and 22, to determine growth performance. At reaching market weight, backfat thickness was determined at the last rib area. Meat was graded according to the criteria of the slaughterhouse. There were no significant differences in growth performance and carcass traits between sexes. The CD line crossbred pig had a significant higher BW at 16 weeks, and higher carcass trait values at 22 weeks than the DD line. During weeks 8 to 16 the CD line crossbred pigs showed a tendency of an increased average daily gain (ADG) and gain : feed (G : F) ratio compared with the DD line. Furthermore, pigs born in spring had significant lower ADG, average daily feed intake (ADFI) and carcass trait values than born in the other seasons. In conclusion, the new paternal line (Chookjin Duroc) improved growth performance and carcass traits compare with the DD line.Keywords: sex, growth, terminal sire, meat quality, backfat thicknes
Regular black hole in three dimensions
We find a new black hole in three dimensional anti-de Sitter space by
introducing an anisotropic perfect fluid inspired by the noncommutative black
hole. This is a regular black hole with two horizons. We compare thermodynamics
of this black hole with that of non-rotating BTZ black hole. The first-law of
thermodynamics is not compatible with the Bekenstein-Hawking entropy.Comment: 15 pages, 16 figures, 3D noncommutative black hole included as Sec 4,
a version to appear in EPJ
Observational constraint on dynamical evolution of dark energy
We use the Constitution supernova, the baryon acoustic oscillation, the
cosmic microwave background, and the Hubble parameter data to analyze the
evolution property of dark energy. We obtain different results when we fit
different baryon acoustic oscillation data combined with the Constitution
supernova data to the Chevallier-Polarski-Linder model. We find that the
difference stems from the different values of . We also fit the
observational data to the model independent piecewise constant parametrization.
Four redshift bins with boundaries at , 0.53, 0.85 and 1.8 were chosen
for the piecewise constant parametrization of the equation of state parameter
of dark energy. We find no significant evidence for evolving .
With the addition of the Hubble parameter, the constraint on the equation of
state parameter at high redshift isimproved by 70%. The marginalization of the
nuisance parameter connected to the supernova distance modulus is discussed.Comment: revtex, 16 pages, 5 figures, V2: published versio
Future cosmological evolution in gravity using two equations of state parameters
We investigate the issues of future oscillations around the phantom divide
for gravity. For this purpose, we introduce two types of energy density
and pressure arisen from the -higher order curvature terms. One has the
conventional energy density and pressure even in the beginning of the Jordan
frame, whose continuity equation provides the native equation of state . On the other hand, the other has the different forms of energy density
and pressure which do not obviously satisfy the continuity equation. This needs
to introduce the effective equation of state to describe the
-fluid, in addition to the native equation of state .
We confirm that future oscillations around the phantom divide occur in
gravities by introducing two types of equations of state. Finally, we point out
that the singularity appears ar because the stability condition of
gravity violates.Comment: 23 pages, 10 figures, correcting typing mistake in titl
Melting behavior of ultrathin titanium nanowires
The thermal stability and melting behavior of ultrathin titanium nanowires
with multi-shell cylindrical structures are studied using molecular dynamic
simulation. The melting temperatures of titanium nanowires show remarkable
dependence on wire sizes and structures. For the nanowire thinner than 1.2 nm,
there is no clear characteristic of first-order phase transition during the
melting, implying a coexistence of solid and liquid phases due to finite size
effect. An interesting structural transformation from helical multi-shell
cylindrical to bulk-like rectangular is observed in the melting process of a
thicker hexagonal nanowire with 1.7 nm diameter.Comment: 4 pages, 4 figure
Equations of State in the Brans-Dicke cosmology
We investigate the Brans-Dicke (BD) theory with the potential as cosmological
model to explain the present accelerating universe. In this work, we consider
the BD field as a perfect fluid with the energy density and pressure in the
Jordan frame. Introducing the power-law potential and the interaction with the
cold dark matter, we obtain the phantom divide which is confirmed by the native
and effective equation of state. Also we can describe the metric gravity
with an appropriate potential, which shows a future crossing of phantom divide
in viable gravity models when employing the native and effective
equations of state.Comment: 23 pages, 7 figure
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