• Proceedings of the KWS Conference
• /
• 2002.10a
• /
• pp.632-638
• /
• 2002

Electron beam (EB) and Gas tungsten arc (TIG) welds were performed on 12.7 mm thick Ti-6Al-4V plate (ASTM Titanium Grade 5). Charpy-V toughness and hardness, as well as, microstructure of the welds and penetration from the macrostructure were studied. It appears that by EB welding rather smaller $\beta$-grains than with TIG welding can be obtained. Next to the fusion line the $\beta$-grain size in the HAZ was 50 ${\mu}{\textrm}{m}$l while in the weld metal it was 150 ${\mu}{\textrm}{m}$. Charpy-V toughness of the EB weld metal was equal or even better to that of base metal, which shows that the $\alpha$-martensite per se is not particularly brittle if only the grain size is fine enough. This is similar to behavior of low carbon martensite in steel. The grain size was studied with light optical and scanning electron (SEM) microscopes. Thus for products, for products which can be manufactured automatically with very narrow fit, the EB welding of Ti-6Al-4V appears to yield satisfactory toughness without any complex post weld heat treatment. ill this study as in earlier studies the TIG welds gave lower toughness than that of the base material due to the higher heat input and slower cooling as compared to EB welding.

• 한국연소학회:학술대회논문집
• /
• 2012.11a
• /
• pp.119-122
• /
• 2012

Circulating fluided bed(CFB) furnace which can use a variety of low-grade fuels because of high heat capacity and good mixing characteristic in its furnace have turned out to be effective system. There is no many research to predict performance considering total boiler system with water-steam side. Most of performance prediction model have focused on hydrodynamics or chemical mechanism in furnace. so, This study is aimed to develop performance prediction model which consider water-steam side.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.12
• /
• pp.1343-1349
• /
• 2011

In this study, the power enhancement potential of a Rankine power cycle by transcritical operation was investigated by comparing the power of an HFC-134a subcritical cycle with that of an HFC-125 transcritical cycle, for a low-grade heat source with a temperature of about $100^{\circ}C$. For a fair comparison using different working fluids, each cycle was optimized by three design parameters from the viewpoint of power. In contrast to conventional approaches, the working fluid's heat transfer and pressure drop characteristics were considered in the present approach, with the aim of ensuring a more realistic comparison. The results showed that the HFC-125 transcritical cycle yields 9.4% more power than does the HFC-134a subcritical cycle under the simulation conditions considered in the present study.

• Journal of the Korean Society of Tobacco Science
• /
• v.7 no.1
• /
• pp.49-55
• /
• 1985

low grade leaves of flue-cured (N.C. 2326) and air-cured (Br 21) have been heated at $140^{\circ}C$ for 10 and 20 minutes, respectively. As heating duration increased, each contents of nicotine, total nitrogen, total sugar and free amino acid decreased in both leaves. The result obtained from this experiment are as following 1. Nicotine content decreased in both leaves. Heating for 10 and 20 minutes showed respectively nicotine decrease of 13.2% and 21.6% for Br 21 and 8.2% and 13.2% for N.C.2326. Decrease of total nitrogen and total sugar was inversely proportional to the heating duration. N.C. 2326 in the decrease out numbered Br.21 by the ratio 2: 1 for 10min.-heating, and 5:4 for 20 min.-heating. 3. Total free amino acid was decrease by 17.1% and 13.85 for N.C. 2326 and Br 21, respectively when heated for 10 min., and 25.6% and 26.5% respectively when heated for 20 min. When sucrose was added to Br 21, th decrease ratio of total free amino acid of Br.21 was increased. It is suggested that the addition of sucrose could promote the browning reaction in Br 21 leaves.

• Proceedings of the Petrological Society of Korea Conference
• /
• 2006.02a
• /
• pp.43-60
• /
• 2006

The Yeongnam Massif, one of Precambrian basements in Korean Peninsula, is characterized by widespread occurrence of low-pressure/high-temperature (LP/HT) schists and gneisses accompanying extensive anatexis and granitic magmatism. Metapelitic mineral assemblages define three progressive metamorphic zones pertinent to low-pressure facies series: cordierite, sillimanite and garnet zones with increasing temperature. Metamorphic grade ranges from lower amphibolite to lower granulite facies and metamorphic conditions reach ca. 750-800 C and 4-6 kbar in migmatitic gneisses. Migmatitic gneisses are prominent in the sillimanite and garnet zones. Textural and petrogenetic relationshipsin leucosome suggest that migmatitic gneiss is the product of anatexis of metasedimentary rocks. The migmatite formation during the prograde metamorphism is governed initially by fluid-present melting and subsequently by biotite-dehydration melting. The large amount of leucosomes in the sillimaniteand garnet zones can be explained by the fluid-present molting possibly triggered by an external supply of aqueous fluid. Field and geochronologic relationships between leucogranites and migmatitic gneisses further suggest that leucogranite has providedfluid and heat required for widespread migmatization.

• The KSFM Journal of Fluid Machinery
• /
• v.18 no.4
• /
• pp.13-21
• /
• 2015

The system design of the Organic Rankine Cycle(ORC) is greatly influenced by the thermal properties such as the temperature or the thermal capacity of heat source. Typically waste heat, solar energy, geothermal energy, and so on are used as the heat source for the ORC. However, thermal energy supplying from these kinds of heat sources cannot be provided constantly. Hence, an experimental study was conducted to utilize fluctuating thermal energy efficiently. For this experiment, an impulse turbine and supersonic nozzles were applied and the supersonic nozzle was used to increase the velocity at the nozzle exit. In addition, these nozzles were used to adjust the mass flowrate depending on the amount of the supplied thermal energy. The experiment was conducted with maximum three nozzles due to the capacity of thermal energy. The experimented results were compared with the predicted results. The experiment showed that the useful output power could be producted from low-grade thermal energy as well as fluctuating thermal energy.

• Transactions of the Korean hydrogen and new energy society
• /
• v.26 no.3
• /
• pp.278-286
• /
• 2015

This paper presents the analytical results of the thermodynamic performance characteristics for a cogeneration system using regenerative organic Rankine cycle (ORC) driven by low-grade heat source. The combined heat and power cogeneration system consists of a regenerative superheated ORC and an additional process heater in a series circuit. Eight working fluids of R134a, R152a, propane, isobutane, butane, R245fa, R123, and isopentane are considered for the analysis. Special attention is paid to the effect of turbine inlet pressure on the system performance such as thermal input, net power and useful heat productions, electrical, thermal, and system efficiencies. The results show a significant effect of the turbine inlet pressure and selection of working fluid on the thermodynamic performance of the system.

• The KSFM Journal of Fluid Machinery
• /
• v.17 no.1
• /
• pp.12-21
• /
• 2014

An organic Rankine cycle was analyzed to work at the optimal operating point when the heat source is fluctuated. R245fa was adopted as a working fluid, and an axial-type turbine as expander on the cycle was designed to convert the heat energy to the electricity since the turbo-type expander works at off-design points better than the positive displacement-type expander. A supersonic nozzle was designed to increase the spouting velocity because a higher spouting velocity can produce more output power. They were designed by the method of characteristics for the operating fluid of R245fa. Three different cases, such as various spouting velocities, various inlet total temperatures, and various nozzle numbers, were studied. From these results, an optimal operating cycle can be designed with the organic Rankine cycle when the available heat source as renewable energy is low-grade temperature and fluctuated.

• Korean Journal of Materials Research
• /
• v.25 no.11
• /
• pp.607-611
• /
• 2015

The microstructural evolution of Grade 91 tempered martensite ferritic steels heat treated at $760{\sim}1000^{\circ}C$ for two hours was investigated using scanning electron microscopy(SEM), energy disperse spectroscopy(EDS), electron backscattered diffraction (EBSD), and transmission electron microscopy(TEM); a microhardness tester was also employed, with a focus on the grain and precipitate evolution process as well as on the main hardening element. It was found that an evolution of tempered martensite to ferrite($760{\sim}850^{\circ}C$), and to fresh martensite($900{\sim}1000^{\circ}C$), occurred with the increase of temperature. Simultaneously, the parabolic evolution characteristics of the low angle grain boundary(LAGB) increased with the increase of the heating temperature(highest fraction of LAGB at $925^{\circ}C$), indicating grain recovery upon intercritical heating. The main precipitate, $M_{23}C_6$, was found to be coarsened slightly at $760{\sim}850^{\circ}C$; it then dissolved at $850{\sim}1000^{\circ}C$. Besides this, $M_3C$ cementite was formed at $900{\sim}1000^{\circ}C$. Finally, the experimental results show that the hardness of the steel depended largely on the matrix structure, rather than on the precipitates, with the fresh martensite showing the highest hardness value.

• Journal of Life Science
• /
• v.22 no.11
• /
• pp.1523-1528
• /
• 2012

In a previous proteomic study, heat shock protein beta 1 (HSPB1) was detected as differentially expressed protein in longissimus thoracis between low (grade 3) and high (grade 1++) meat quality groups by 2DE gel electrophoresis. The present study investigated an association of HSPB1 expression at the level of gene and protein with Warner-Bratzler shear force (WBS) measured in 20 Hanwoo steers. An analysis of variance (ANOVA) between expression values and WBS showed that WBS was affected by HSPB1 expression (p<0.05). The expression (at both gene and protein level) of the HSPB1 was 2 times higher in the low WBS group than that in the high WBS group (p<0.01). This result suggests that the HSPB1 gene may be a candidate gene associated with tenderness in longissimus thoracis of Korean cattle.