• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.229-235
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• 2011

This research aims todevelopa compression/absorption hybrid heat pump system using an $NH_3/H_2O$ as working fluid.The heatpump cycle is based on a combination of compression and absorption cycles. The cycle consists of two-stage compressors, absorbers, a desorber, a desuperheater, solution heat exchangers, a solution pump, a rectifier, and a liquid/vapor separator. The compression/absorption hybrid heat pump was designed to produce hot water above $90^{\circ}C$ using high-temperature glide during a two-phase heat transfer. Distinct characteristics of the nonlinear temperature profile should be considered to maximize the performance of the absorber. In this study, the performance of the absorber was investigated depending on the capacity, shape, and arrangementof the plate heat exchangers with regard tothe concentration and distribution at the inlet of the absorber.

• Journal of Life Science
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• v.20 no.9
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• pp.1345-1352
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• 2010

We investigated the effect of brown-rice vinegar (BRV) ingestion after strenuous Wingate tests on energy substrates during a 2 hr recovery period. For this, seven healthy male adolescents were chosen as subjects. They performed 3 Wingate tests to induce fatigue, after which they ingested brown-rice vinegar (BRV) drink and/or water as a control (CON) after 15 min of the test. Blood was obtained pre-exercise and 30 min, 60 min, and 120 min post-exercise, and blood glucose, lactate, free fatty acids, ammonia, and cortisol were analyzed. After 120 min of recovery period, the 4th Wingate test was conducted to calculate the power recovery ratio of the 3rd and 4th trials. Breathing frequency, oxygen saturation, and heart rate did not show significant changes. Blood glucose level was lower in CON than BRV after 120 min of recovery, and blood lactate and ammonia levels were lower in BRV at 60 and 120 min. The higher free fatty acids were found at 60 and 120 min in BRV. In addition, Wingate power recovery ratio of peak power and peak power/body weight was significantly higher in BRV compared to CON. These results suggested that BRV ingestion after strenuous exercise facilitates fatigue recovery. Therefore, BRV might be effectively used as an ergogenic aid for events in which competitors compete two or more times a day.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.233-238
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• 1981

A recirculating water system without filter bed was used for a high density experimental rearing of common carp, Cyprinus carpio, during the summer of 1981. Of the water system, 3 tanks were used for stocking each tank with 10,000, 20,000 and 30,000 common carp fingerlings which averaged 0.6 g. The water in the system was maintained in dark green colour by heavy growth of phytoplankton during the most period of the experiment. In this experiment, the best daily growth rate, $3.7\%$, was obtained from the 10,000 fish group followed by $2.8\%\;and\;3.0\%$ from the 20,000 and 30,000 fish groups respectively. Thus there was no significant difference between the latter two groups. Especially, notably high concentration of total ammonia, $5\sim7$ ppm ammonia-N, in the culture water appeared during the most experimental period, but this did not seem to have affected feeding and growth of the fish when the water was kept at heavy bloom. It was also obvious that the outbreak of columnaris disease was effectively depressed in this green water recirculating system compared to that in clarified recirculating system. One tank ($7m^2$) of this system was stocked with 446 common carp of intermediate size averaging 352.2 g and after 40 day rearing they grew to 486.3 g in average with a daily growth rate of $0.8\%$. This result was a little inferior to that reared in a tank of the clarified water system as control which showed $1.0\%$ daily growth rate. Therefore, before an initiation of the commercial production of fish in this method, further studies concerning the amount of ammonium with its effect on the fish under rearing in this system and the columnaris disease problem should be carried out.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.2
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• pp.198-203
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• 1989

Field experiment was conducted to find out the effect of lime materials application on yield, and chemical composition of Burley 21 in 1986. Lime materials and application rate were CaSO$_4$ : Ca 35kg/l0a. CaCO$_3$ : Ca 35kg/l0a and Liming: pH6.5. Contents of Ca and Mg in fresh or cured leaves were increased, but AI, Fe and Mn were decreased by applying lime materials. Yield were increased by applying lime materials. Among lime materials treatment, yield of limed and CaCO$_3$ plot were higher than that of CaSO$_4$ plot. Value per kg of cured leaves was not affected by applying lime materials. Cured leaves of CaSO$_4$ plot contained higher NH$_3$-nitrogen and alkalinity number of water insoluble ash than those of unlimed plot. Cured leaves of CaCO$_3$, plot contained higher alkalinity number of water soluble ash, insoluble ash and volatile neutral constituent, but lower protein-nitrogen and petroleum ether extracts than those of unlimed plot. Cured leaves of limed plot contained higher alkalinity number of water soluble and insoluble ash, NO$_3$-nitrogen and volatile neutral constituents, but lower protein -nitrogen, nicotine and petroleum ether extracts than those unlimed plot. Yield was increased, however leaf Quality in respect to chemical and organoleptic characteristics were not affected considerably by applying lime materials. Therefore, it suggests that controlling the soil pH about 6.5 by liming might be necessary for tobacco cultivation.

• Applied Chemistry for Engineering
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• v.33 no.2
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• pp.126-132
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• 2022

Alkaline fuel cells using liquid fuels such as hydrazine and ammonia are gaining great attention as a clean and renewable energy solution possibly owing to advantages such as excellent energy density, simple structure, compact size in fuel container, and ease of storage and transportation. However, common shortcomings including cathode flooding, fuel crossover, side yield reactions, and fuel security and toxicity are still challenging issues. Real time monitoring of fuel concentrations integrated into a fuel cell device can help improving fuel cell performance via predicting any loss of fuels used at a cathode for efficient energy production. There have been extensive research efforts made on developing real-time sensing platforms for hydrazine and ammonia. Among these, recent advancements in electrochemical sensors offering high sensitivity and selectivity, easy fabrication, and fast monitoring capability for analysis of hydrazine and ammonia concentrations will be introduced. In particular, research trend on the integration of metallic and metal oxide nanoparticles and also their hybrids with carbon-based nanomaterials into electrochemical sensing platforms for improvement in sensitivity and selectivity will be highlighted.

• Journal of the Korean Wood Science and Technology
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• v.33 no.3 s.131
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• pp.45-52
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• 2005

This research was performed to evaluate adsorption behavior of woody charcoals obtained from wood powder, fiber and bark of spruce (Abies sibirica Ledeb). The wood materials were carbonized at various temperatures for 1 hour using experimental rotary kiln without any inert gas. The adsorption capacity of iodine and toluene, specific surface area and removal efficiency of acetic acid and ammonia gas of those charcoals were measured. The higher was the temperature for carbonization, the lower yields of charcoals were. Ash content of bark charcoal was higher than that of wood powder charcoal or fiber charcoal. Elemental analysis of woody charcoal revealed that the content of carbon was gradually lincreased as carbonization temperature was higher. When carbonization temperature was higher, adsorption capacity of woody charcoals for iodine was much improved. Wood powder charcoal and fiber charcoal were more effective for iodine adsorption rather than bark charcoal. Capacity of toluene adsorption was the highest in the charcoal of $600^{\circ}C$. Charcoals produced at high temperature efficiently removed acetic acid gas, while charcoals carbonized at low temperature such as $400^{\circ}C$ were proper to remove ammonia gas. This difference may be explained that the acidity of charcoals depends on the carbonization temperature: charcoals of low temperature indicate acidic property, while those of high temperature turned to alkaline.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.729-736
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• 1997

For the recovery of industrial waste heat, a chemical heat transformer based on the reversible reaction between metal chlorides and ammonia gas was designed and a pilot scale unit of 1 kW-1hr was developed. A static calculation, which determined the amount of reacting materials and operating condition of system, and dynamic simulations were performed for the optimal design. The temperature and output power of generator in the system were varying with the amount of salt and heat exchange area. Optimum conditions such as the amount of salt-graphite, apparent density and size of mechanical unit were determined by the dynamic simulation for the system. According to the operating cycle of 4 stages, experimental results of temperature and output power were well agreed with the simulation values. This chemical heat transformer is turned out to be a very promising system for recovery of industrial waste heat because of its effective feature of lifting temperature.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.8 no.2
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• pp.73-84
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• 1975

The present study was conducted to evaluate the effects of oil spill from the wastewater of Yeosu Refinery on water quality of hard clam culture beds in Taein-Ri, Kwang Yang Bay. Wastewater and oil spill may reach to the culture beds in 6-8 hours by tidal current movement. Water quality is nearly normal as unpolluted sea water except the concentration of n-hexane extractive chemicals which shows higher than unpolluted sea water in period of September to October in 1973. It may be caused by wastewater of Yeosu Refinery.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.111-111
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• 2000

최근 질화물 반도체를 이용한 단파장 laser diode (LD)와 ultraviolet light emitting diode (LED)에 관한 관심의 증가로 인하여 AlGaN의 성장에 관한 연구가 많이 진행되고 있다. Metalorganic chemical vapor deposition (MOCVD)법을 이용한 AlGaN 성장에 있어서는 Al의 전구체로 널리 사용되고 있는 trimethylaluminum (TMAl)과 암모니아와의 기상에서의 adduct 형성을 억제하기 위하여 주로 저압에서 성장을 하거나 원료 가스의 유속을 증가시키는 방법으로 연구가 되고 있다. 또한, AlN의 경우 GaN보다 녹는점이 매우 높기 때문에 일반적으로 Al을 포함하는 질화물 반도체의 성장에 있어서는 GaN보다 녹는점이 매우 높기 때문에 일반적으로 Al을 포함하는 질화물 반도체의 성장에 있어서는 GaN 성장 시보다 높은 온도에서 성장이 이루어지고 있다. MOCND법을 이용하여 AlGaN를 성장시키는 대부분의 연구들은 100$0^{\circ}C$ 이상의 고온에서의 성장 온도가 AlGaN특성에 미치는 영향에 대한 것으로 국한되고 있다. 그러나, InGaN/GaN multiple quantum wells (MQWs) 구조의 LD나 LED를 성장시키는 경우 In의 desorption을 억제하기 위하여 MQWs층 위에 저온에서 AlGaN를 성장하는 데 있어서 AlGaN의 성장 온도를 500-102$0^{\circ}C$로 변화시키면서 AlGaN의 성장거동을 고찰하였다. GaN는 사파이어 기판을 수소분위기하에서 고온에서 가열한 후 저온에서 GaN를 이용한 핵생성층을 성장하고 102$0^{\circ}C$의 고온에서 1.2$\mu\textrm{m}$정도의 두께로 성장하였다. AlGaN는 고온에서 성장된 GaN 위에 200Torr의 성장기 압력 하에서 trimethylgallium (TMGa)과 TMAl의 유속을 각각 70 $\mu$mol/min 으로 고정한 후 성장온도만을 변화시키며 증착하였다. 성장 온도가 낮아짐에 따라 AlGaN의 표면거칠기가 증가하고, 결함과 관련된 포토루미네슨스가 현저히 증가하는 것이 관찰되었다. 그러나, 성장온도가 50$0^{\circ}C$정도로 낮아진 경우에 있어서는 표면 거칠기가 다시 감소하는 것이 관찰되었다. 이러한 현상은 저온에서 표면흡착원자의 거동에 제한이 따르기 때문으로 생각되어진다. 또한, 성장 온도가 낮아짐에 따라 AlGaN의 성장을 저해하기 때문으로 판단된다. 성장 온도 변화에 따라 성장된 V의 구조적 특성 및 표면 거칠기 변화를 관찰하여 AlGaN의 성장 거동을 논의하겠다.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.2
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• pp.204-210
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• 1989

Normally cultured, harvested and yellowed leaves of aromatic tobacco variety. KA 101 were sun-cured under conventional polyethylene film house, air-cured in burley curing barn, and bulk-cured at three temperatures of 40$^{\circ}C$, 50$^{\circ}C$ and 60$^{\circ}C$. respectively, to investigate the effects of curing conditions on quality and chemical properties of leaf tobacco. Air-cured leaves had the poorest quality by price with little difference between that of sun-cured and three bulk-cured ones. Air-cured leaves were higher in ammonia nitrogen, protein nitrogen, total nitrogen, ash content and pH, but lower in sugar content when it compared with those of sun-cured and three bulk-cured ones. The curing variables tested did not affect the content of pet. ether ext. and volatile organic acids. The content of pet. ether ext., volatile organic acids, and most of volatile neutrals tended to decrease or not to change as the bulk-curing temperature increased. A quality index, (volatile organic acids, mg/l00g+％ pet. ether ext.) / ％(ash+pH) x 10, was found to be most accurate and easy to apply for the quality evaluation of aromatic tobaccos.