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 Ca2_2RuO4_4 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 Ca$_2$RuO$_4$ nanofilm single crystals. Ca$_2$RuO$_4$ thin film with the highest transition temperature $T_c$ (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 Ca$_2$RuO$_4$ 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