Dynamic deformation behavior of ultrafine-grained low-carbon steels fabricated by equal-channel angular pressing

The dynamic deformation behavior of ultrafine-grained low-carbon steels fabricated by equal-channel angular pressing (ECAP) was investigated in this study. Dynamic torsional tests, using a torsional Kolsky bar, were conducted on four steel specimens, two of which were annealed at 480 °C after ECAP, and then the test data were compared in terms of microstructures, tensile properties, and adiabatic shear-band formation. The equal-channel angular pressed specimen consisted of very fine, equiaxed grains of 0.2 to 0.3 μm in size, which were slightly coarsened after annealing. The dynamic torsional test results indicated that maximum shear stress decreased with increasing annealing time, whereas fracture shear strain increased. Some adiabatic shear bands were observed at the gage center of the dynamically deformed torsional specimen. Their width was smaller in the equal-channel angular pressed specimen than in the 1-hour-annealed specimen, but they were not found in the 24-hour-annealed specimen. Ultrafine, equiaxed grains of 0.05 to 0.2 μm in size were formed inside the adiabatic shear band, and their boundaries had characteristics of high-angle grain boundaries. These phenomena were explained by dynamic recrystallization due to a highly localized plastic strain and temperature rise during dynamic deformation.     

Changes in physicochemical properties and gaseous emissions of composting swine manure amended with alum and zeolite

Ammonia emissions from composted swine manure and the resulting physicochemical changes were monitored to determine the effectiveness of adding alum and zeolite during the composting process, as well as the most effective addition method. The two amendments reduced ammonia emissions 85?C92%, with the finished compost retaining three-fold more NH ₄ ⁺ -N than the unamended control. The addition of zeolite sequestered 44% of the retained NH ₄ ⁺ -N at zeolite exchange sites. The addition of amendments did not appear to significantly affect microbial activity, because the patterns of CO₂ emissions, total organic carbon (TOC) reduction, and the ratio of humic acid to TOC of amended and unamended composts were very similar. The final respiration rates and Solvita? maturity index indicated that the finished compost was well matured and aged. Alum has a high potential to reduce ammonia emissions and concomitantly enhance fertilizer N value. Zeolite further reduces ammonia emissions, and improves fertilizer quality, by serving as a slow-release N source.     

Router architecture evaluation for security network

This paper presents and evaluates router architectures for security networks. Through extensive simulations, the DAMQWR and PD-CB router architecture is shown to best support true fully adaptive routing capability of deadlock recovery schemes while maximizing network performance (102 % higher throughput and 86 % lower network latency than other architectures). Therefore, this router architecture can build a more stable security network by providing a higher network performance.     

Eleutheroside E,an active compound from Eleutherococcus senticosus,regulates adipogenesis in 3T3-L1 cells

In this study, we investigated the anti-adipogenic effects of Eleutherococcus senticosus and its active compounds in vitro to examine new functions. We first analyzed the active compounds in E. senticosus growing in Korea using HPLC and found that the concentration of eleutheroside B and E was higher in stems and roots than in other plant parts. There were no significant (p<0.05) differences in eleutheroside concentration between plant ages. Anti-adipogenic effects of E. senticosus on lipid accumulation in 3T3-L1 cells were examined. Extracts of stems and roots more effectively inhibited lipid accumulation in 3T3-L1 cells than extracts of other plant parts. Eleutheroside E was responsible for the pharmacological anti-adipogenic effects via regulation of the mTOR pathway. This is the first report of an anti-adipogenic effect of E. senticosus and the active compound eleutheroside E.     

Microstructure and thermal properties of dysprosium and thulium co-doped barium titanate ceramics for high performance multilayer ceramic capacitors

The co-doping characteristics on microstructure and thermal properties of barium titanate (BaTiO₃) were investigated to elucidate formation of core-shell structure by dysprosium (Dy) and thulium (Tm) addition in the BaTiO₃-Dy₂O₃-Tm₂O₃ system. The dielectrics co-doped with 0.7 mol% Dy₂O₃ and 0.3 mol% Tm₂O₃ had the dielectric constant up to 2200 as a function of temperature, which was 30% higher than that of specimen containing only Tm₂O₃ at the room temperature. It could be explained by the fact that the increase of Dy₂O₃ addition contributed to the improvement of dielectric constant. On the other hand, the rapid diffusion rate of Dy³⁺ ions in BaTiO₃ showed an adverse effect on temperature stability caused by destruction of core-shell. As the compensation for shell expansion in BaTiO₃, the reinforcement of the core-shell structure through the addition of Tm₂O₃ was confirmed by TEM-EDS analysis and attributed the temperature coefficient of capacitance (TCC) in a reliability condition (−55 °C to 125 °C, △C = ±15% or less). The enhanced electrical properties and temperature stability could be deduced from the generation of electrons and the formation core-shell structure in co-doped BaTiO₃ system respectively.     

Seismic analysis of semi-gravity RC cantilever retaining wall with TDA backfill

The seismic behavior of Tire Derived Aggregate (TDA) used as backfill material of 6.10 m high retaining walls was investigated based on nonlinear time-history Finite Element Analysis (FEA). The retaining walls were semi-gravity reinforced concrete cantilever type. In the backfill, a 2.74 m thick conventional soil layer was placed over a 3.06 m thick TDA layer. For comparison purpose, a conventional all soil-backfill model was also developed, and the analysis results from the two models under the Northridge and Takatori earthquakes were compared. The FEA results showed that both models did not experience major damage in the backfill under the Northridge earthquake. However, under the Takatori earthquake, the TDA-backfill model developed substantially large displacement in the retaining walls and in the backfill compared with the soil-backfill model. Regions of large plastic strain were mainly formed in the TDA layer, and the soil over the TDA layer did not experience such large plastic strain, suggesting less damage than the soil-backfill model. In addition, the acceleration on the backfill surface of the TDA-backfill model decreased substantially compared with the soil-backfill model. If an acceleration sensitive structure is placed on the surface of the backfill, the TDA backfill may induce less damage to it.     

Characteristics and economic evaluation of a CO2-capturing repowering system with oxy-fuel combustion for utilizing exhaust gas of molten carbonate fuel cell (MCFC)

A scale of 2.4 MW molten carbonate fuel cell (MCFC) was taken to construct a high-efficiency and economic power generation system without CO₂ emission for utilizing its exhaust gas. A conventional steam turbine power generation system (STPS) is evaluated and the net generated power (NGP) is estimated to be only 131 kW and the STPS is not economically feasible. A CO₂-caputuring repowering system is proposed, where low temperature steam produced at heat recovery steam generator (HRSG) by using the MCFC exhaust gas is utilized as a main working fluid of a gas turbine, and the temperature of the steam is raised by combusting fuel in a combustor by using pure oxygen, not the air. It is estimated that NGP of the proposed system is 253 kW, and CO₂ reduction amount is 583 t-CO₂/y, compared to 302 t-CO₂/y for the STPS and that the proposed system becomes economically feasible if a CO₂ emission credit higher than 20 $/t-CO₂ can be granted. It is also estimated, when its turbine inlet temperature is increased from 850 °C to 1000 °C, CO₂-capturing is not cost-consuming but becomes to be profitable, owing to improved power generation characteristics.