486 research outputs found
Development of a State-of-the-Art Dry Low NOx Gas Turbine Combustor for IGCC with CCS
The successful development of the coal-based integrated gasification combined cycle (IGCC) with carbon capture and storage (CCS) requires gas turbines capable of achieving dry low nitrogen oxide (NOx) combustion of hydrogen-rich syngas fuels for low emissions and high plant efficiency. This chapter describes the development of a “multi-cluster combustor” as a state-of-the-art dry low NOx combustor for hydrogen-rich syngas fuels. The combustor consists of multiple clusters of pairs of one fuel nozzle and one air hole that are installed coaxially. The essence of the design concept is the integration of two key technologies: rapid mixing of fuel and air for low NOx and flame lifting for flashback-resistant combustion. The combustor has been developed in three steps: burner development, combustor development, and feasibility demonstration for practical plants. The combustor was tested with a practical syngas fuel in a multi-can combustor configuration in an IGCC pilot plant in the final step. The combustor achieved the dry low NOx combustion of the syngas fuel in the pilot plant and the test results demonstrated the feasibility for achieving dry low NOx combustion of the syngas fuel in practical plants
Co-appearance of superconductivity and ferromagnetism in a CaRuO nanofilm crystal
By tuning the physical and chemical pressures of layered perovskite materials
we can realize the quantum states of both superconductors and insulators. By
reducing the thickness of a layered crystal to a nanometer level, a nanofilm
crystal can provide novel quantum states that have not previously been found in
bulk crystals. Here we report the realization of high-temperature
superconductivity in CaRuO nanofilm single crystals. CaRuO thin
film with the highest transition temperature (midpoint) of 64~K exhibits
zero resistance in electric transport measurements. The superconducting
critical current exhibited a logarithmic dependence on temperature and was
enhanced by an external magnetic field. Magnetic measurements revealed a
ferromagnetic transition at 180~K and diamagnetic magnetization due to
superconductivity. Our results suggest the co-appearance of superconductivity
and ferromagnetism in CaRuO nanofilm crystals. We also found that the
induced bias current and the tuned film thickness caused a
superconductor-insulator transition. The fabrication of micro-nanocrystals made
of layered material enables us to discuss rich superconducting phenomena in
ruthenates
A 24 GHz FM-CW Radar System for Detecting Closed Multiple Targets and Its Applications in Actual Scenes
This paper develops a 24 GHz band FM-CW radar system to detect closed multiple targets in a small displacement environment, and its performance is analyzed by computer simulation. The FM-CW radar system uses a differential detection method for removing any signals from background objects and uses a tunable FIR filtering in signal processing for detecting multiple targets. The differential detection method enables the correct detection of both the distance and small displacement at the same time for each target at the FM-CW radar according to the received signals. The basic performance of the FM-CW radar system is analyzed by computer simulation, and the distance and small displacement of a single target are measured in field experiments. The computer simulations are carried out for evaluating the proposed detection method with tunable FIR filtering for the FM-CW radar and for analyzing the performance according to the parameters in a closed multiple targets environment. The results of simulation show that our 24 GHz band FM-CW radar with the proposed detection method can effectively detect both the distance and the small displacement for each target in multiple moving targets environments. Moreover, we develop an IoT-based application for monitoring several targets at the same time in actual scenes
MOIRCS Deep Survey V: A Universal Relation for Stellar Mass and Surface Brightness of Galaxies
We present a universal linear correlation between the stellar mass and
surface brightness (SB) of galaxies at 0.3<z<3, using a deep K-band selected
catalog in the GOODS-North region. The correlation has a nearly constant slope,
independent of redshift and color of galaxies in the rest-z frame. Considering
unresolved compact galaxies, the tight correlation gives a lower boundary of SB
for a given stellar mass; lower SB galaxies are prohibited over the boundary.
The universal slope suggests that the stellar mass in galaxies was build up
over their cosmic histories in a similar manner irrelevant to galaxy mass, as
oppose to the scenario that massive galaxies mainly accumulated their stellar
mass by major merging. In contrast, SB shows a strong dependence on redshift
for a given stellar mass. It evolves as (1+z)^(-2.0~-0.8), in addition to
dimming as (1+z)^4 by the cosmological expansion effect. The brightening
depends on galaxy color and stellar mass. The blue population (rest-frame
U-V<0), which is dominated by young and star-forming galaxies, evolves as
~(1+z)^(-0.8 +-0.3) in the rest-V band. On the other hand, the red population
(U-V>0) and the massive galaxies (M_*>10^(10)M_sun) shows stronger brightening,
(1+z)^(-1.5+-0.1). Based on the comparison with galaxy evolution models, we
find that the phenomena are well explained by the pure luminosity evolution of
galaxies out to z~3.Comment: 10 pages, 9 figures. Accepted for publication in Ap
MOIRCS Deep Survey. X. Evolution of Quiescent Galaxies as a Function of Stellar Mass at 0.5<z<2.5
We study the evolution of quiescent galaxies at 0.5<z<2.5 as a function of
stellar mass, using very deep NIR imaging data taken with the Multi-Object
Infrared Camera and Spectrograph on the Subaru Telescope in the GOODS-North
region. The deep NIR data allow us to construct a stellar mass-limited sample
of quiescent galaxies down to ~10^{10} Msun even at z~2 for the first time. We
selected quiescent galaxies with age/tau>6 by performing SED fitting of the
multi broad-band photometry from the U to Spitzer 5.8um bands with the
population synthesis model of Bruzual & Charlot (2003) where exponentially
decaying star formation histories are assumed. The number density of quiescent
galaxies increases by a factor of ~3 from 1.0<z<1.5 to 0.5<z<1.0, and by a
factor of ~10 from 1.5<z<2.5 to 0.5<z<1.0, while that of star-forming galaxies
with age/tau<4 increases only by factors of ~2 and ~3 in the same redshift
ranges. At 0.5<z<2.5, the low-mass slope of the stellar mass function of
quiescent galaxies is alpha ~ 0 -- 0.6, which is significantly flatter than
those of star-forming galaxies (alpha ~ -1.3 -- -1.5). As a result, the
fraction of quiescent galaxies in the overall galaxy population increases with
stellar mass in the redshift range. The fraction of quiescent galaxies at
10^{11}-10^{11.5} Msun increases from ~20-30% at z~2 to ~40-60% at z~0.75,
while that at 10^{10}-10^{10.5} Msun increases from <~ 5% to ~15% in the same
redshift range. These results could suggest that the quenching of star
formation had been more effective in more massive galaxies at 1<~z<~2. Such a
mass-dependent quenching could explain the rapid increase of the number density
of ~M* galaxies relative to lower-mass galaxies at z >~ 1-1.5.Comment: 12 pages, 7 figures, accepted for publication in PASJ (Subaru special
issue). Updated to accepted versio
Thermoelectric Properties of Combustion-Synthesized Lanthanum-Doped Strontium Titanate
The possibility of combustion synthesis of perovskite-oxide thermoelectric materials with the attendant saving of energy and time and without deterioration in the thermoelectric properties was investigated by evaluating the thermoelectric properties of lanthanum-doped strontium titanate (Sr 1Àx La x TiO 3 , 0 x 0:1). The materials were successfully combustion synthesized and spark plasma sintered with 98.0-99.6% of true density, and their thermoelectric properties were evaluated from room temperature to 850 K. The optimal lanthanum doping amount ratio x in the considered temperature range was from 0.06 to 0.08, in which Sr 0:92 La 0:08 TiO 3 sample showed the maximum ZT of 0.22 at 800 K. This value was close to the highest recorded ZT at the same temperature up to now, and the ZT of most samples are higher than those synthesized by the conventional solid state reaction method. Thus, combustion synthesis is promising for producing perovskite-oxide thermoelectric materials for high-temperature application
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