• 한국정밀공학회지
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• 제22권11호
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• pp.45-50
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• 2005

In this study, the casting/forging process was applied in manufacturing a low control arm, in order to prove that application of casting/forging process to Al6061 is likely to get the effect of light weight compared with existing steel products and to reduce the cost of materials. Firstly, In order to set up the optimum casting condition of the forging material, Al6061, casting experiments were carried out by controlling pouring temperature of the aluminum for casting, mold temperature, and pouring time. $700^{\circ}C$ pouring temperature, $300^{\circ}C$ mold temperature and 10-second pouring time were taken into account as the optimum casting conditions. With respect to a hot forging test, it is practiced on the basis of a temperature of materials, strain rate, and reduction rate so as to observe each microstructure and examine strain-stress curve simultaneously; examine tensile test and hardness test; eventually set up the optimum hot forging condition. A hot forging test, tensile test, hardness experiment, and microstructure observation were carried out on condition of $70\%$ reduction rate, $500^{\circ}C$ temperature of materials, and 1 strain rate. As a result of those experiments, 330MPa tensile strength, $16.4\%$ elongation, and 122.8Hv hardness were recorded. In oder to get a sound preform which has no unfitting cavity and less flash, two preforms were proposed on the basis of volume rate of the final product; the optimum volume rate of preform for the low control arm was $115\%$. In conclusion, it is confirmed that using the forging material rather than casting materials in casting/forging process is likely to get more superior mechanical properties. Compared with Al6061, performed by means of general forging, moreover, cast/forged Al6061 can not only stimulate productivity by reducing production processes, but cut down the cost of materials by reusing forging scraps.

• Journal of Biosystems Engineering
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• 제32권4호
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• pp.247-255
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• 2007

During the winter season in Korea, the relative humidity of greenhouse at night often exceeds 90% because air temperature inside the greenhouse is usually controlled using a heater with all of windows closed to minimize heat loss, thereby requiring the use of a dehumidifier that can maintain optimum humidity levels of $70{\sim}80%$ to provide a good growth condition of crops. Also, such a high humid condition can cause the development of a pest, such as insects, fungi or diseases. However, the use of most conventional dehumidifiers for low temperature dehumidification is limited because their performance is degraded due to frost accumulation on the evaporator coil. This study was carried out to develop a refrigeratory-based dehumidifier suitable for low temperature dehumidification in greenhouse cultivation. The developed dehumidifier consists of a condenser and an evaporator installed separately so that relative and absolute humidity levels can be reduced when air passed through the condenser and evaporator, respectively. The prototype dehumidifier showed a dehumidification capacity of $5{\sim}7kg/h$ when air with a temperature of $15{\sim}25^{\circ}C$ and a relative humidity of $70{\sim}95%$ came into the dehumidifier. Under the condition that either temperature or relative humidity was fixed, the amount of condensed water was proportional to the levels of both temperature and relative humidity.

• 한국표면공학회지
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• 제52권4호
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• pp.194-202
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• 2019

A systematic investigation was made on the influence of processing parameters such as gas composition and treatment temperature on the surface characteristics of hardened layers of low temperature plasma nitrided 316L Austenitic Stainless Steel. Various nitriding processes were conducted by changing temperature ($370^{\circ}C$ to $430^{\circ}C$) and changing $N_2$ percentage (10% to 25%) for 15 hours in the glow discharge environment of a gas mixture of $N_2$ and $H_2$ in a plasma nitriding system. In this process a constant pressure of 4 Torr was maintained. Increasing nitriding temperature from $370^{\circ}C$ to $430^{\circ}C$, increases the thickness of S phase layer and the surface hardness, and also makes an improvement in corrosion resistance, irrespective of nitrogen percent. On the other hand, increasing nitrogen percent from 10% to 25% at $430^{\circ}C$ decreases corrosion resistance although it increases the surface hardness and the thickness of S phase layer. Therefore, optimized condition was selected as nitriding temperature of $430^{\circ}C$ with 10% nitrogen, as at this condition, the treated sample showed better corrosion resistance. Moreover to further increase the thickness of S phase layer and surface hardness without compromising the corrosion behavior, further research was conducted by fixing the $N_2$ content at 10% with introducing various amount of $CH_4$ content from 0% to 5% in the nitriding atmosphere. The best treatment condition was determined as 10% $N_2$ and 5% $CH_4$ content at $430^{\circ}C$, where the thickness of S phase layer of about $17{\mu}m$ and a surface hardness of $980HV_{0.1}$ were obtained (before treatment $250HV_{0.1}$ hardness). This specimen also showed much higher pitting potential, i.e. better corrosion resistance, than specimens treated at different process conditions and the untreated one.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.1255-1260
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• 2006

This present study analyzed temperature depreciation ratio of window inside surface by KS F 2295 'Procedure for determining fenestration product condensation resistance values'. it estimated window indoor surface condensation due to variable environmental condition. Performance of condensation resistance by using temperature depreciation ratio until applied Low-e and Ar glazing improved about 45% from 24 mm clear. Temperature depreciation ratio by KS F 2295 considers analytic index of window condensation due to variable boundary condition.

• KIEAE Journal
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• 제15권4호
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• pp.29-35
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• 2015

Purpose: Double skin facade is a representative advantageous passive technology of building skin in the aspect of energy saving and environment improvement, reduces heat loss with buffer space in winter season and enhances indoor air and comfort of residents by activating natural ventilation in mid-season. However, in summer season, temperature increase in the intermediate space due to solar energy from exterior transparent skin could be a potential problem; also, relatively weak buoyancy of air caused by low density difference between double-skin facade could increase cooling load as air of intermediate space in high temperature hangs. However, proof data is insufficient to objectify such phenomenon. Method: In this study, researchers surveyed air temperature of intermediate space and airflow and diagnosed its cause targeting on applied multistory facade in the building which gives thermal uncomfort to residents. Also, the researchers produced Solar-air heat transfer coefficient meter, measured thermal boundary condition of double-skin facade, and presented the result of measurement as an objectified verification material regarding overheating phenomenon in the intermediate space of double-skin facade in summer season. Result: Inefficient condition was verified that total heat increases and overheating due to insufficient natural ventilation in multistory facade. In addition, logic behind preceding research was objectified and verified regarding high temperature phenomenon in the intermediate space which could increase cooling load in summer season.

• 한국표면공학회지
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• 제25권4호
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• pp.189-206
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• 1992

The effect of activation and electroless nickel plating conditions on contact properties was investi-gated for selective electroless nickel plating of Si wafers in order to obtain an optimum condition of con-tact hole filling. According to RCA prosess, p-type silicon (100) surface was cleaned out and activated. The effects of temperature, DMAB concentration, time, and strirring were investigated for activation of p-type Si(100) surface. The optimal activation condition was 0.2M HF, 1mM PdCl2, 2mM EDTA,$ 70^{\circ}C$, and 90sec under ultrasonic vibration. In electroless nickel plating, the effect of temperature, DMAB concentra-tion, pH, and plating time were studied. The optimal plating condition found was 0.10M NiSO4.H2O, 0.11M Citrate, pH 6.8, $60^{\circ}C$, 30minutes. The contact resistance of films was comparatively low. It took 30minutes to obtain 1$\mu\textrm{m}$ thick film with 8mM DMAB concentration. The film surface roughness was improved with decreasing temperature and decreasing pH of the plating solution. The best quality of the film was obtained at the condition of temperature $60^{\circ}C$ and pH 6.0. The micro-vickers hardness of film was about 800Hv. Plating rate of nickel on the hole pattern was slower than that of nickel on the line pattern.

• Journal of Plant Biology
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• 제17권4호
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• pp.31-37
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• 1974

Seedlings of Nongbaek representing strong cold tolerant variety of rice plant, Jinheung of medium variety and Tongil of weak variety were used respectively for the present study. These seedlings were water cultured in phytotron which maintained at the daytime and night temperature of 30-$25^{\circ}C$, 20-2$0^{\circ}C$, 20-15$^{\circ}C$ and 15-1$0^{\circ}C$. The growth rate of plant height, tillering rate, increase in dry weight and absorption pattern of important mineral nutrients at their early growth stage under each temperature conditions were observed. Generally, it appeared that Nongbaek was more active in the growth of plant height than Jinheung, and Jinheung was more active than Tongil under low temperature condition. The tillering rate of these three varieties was equally rapid while it was decreased in the order of weak cold tolerant variety, such as Tongil, Jinheung and Nongbaek as the temperature declined gradually. The dry weigh tincreasing curve showed almost the same pattern in the varieties at the treatment of each temperature. Under low temperature conditions, Nongbaek showed higher absorption rate of N per dry weight and higher absorption amount of per plant body, Jinheung followed and Tongil was the lowest. The absorption amount of P2O5 increased in the top part compared with the roots as temperature rose and decreased as temperature declined. There seemed to be no difference of absorption among the varieties which have different cold tolerance each other. Under low temperature the absorption rate of K per dry weight was high, as a whole, especially Nongbaek was markedly higher than the other two. The absorption rate of Ca, Mg and Fe was also equally high in all varieties under low temperature and Nongbaek showed a more absorptive tendency in the absorption amount under low temperature.

• 한국분무공학회지
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• 제9권1호
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• pp.15-20
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• 2004

The post injection effect to enhance aftertreatment devices' performance is essential to meet future stringent emission standards by controlling exhaust gas temperature and emission pollutants. The test has been made with commercial common rail diesel engine by post injection manipulation, to optimize exhaust gas temperature while guarantee low fuel penalty. The optimization was done at 1500, 2000 and 2500[rpm] for 2, 4[bar] condition which show low exhaust gas temperature. The main purpose of this test is dedicated to understand mechanism of exhaust gas temperature rise while optimizing

• 한국환경과학회지
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• 제19권1호
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• pp.105-114
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• 2010

The objective of the paper is to experimentally investigate the compressive strength of the concrete incorporating fly ash. Ordinary Portland cement(OPC). Water to binder ratio(W/B) ranging from 30% to 60% and curing temperature ranging from $-10^{\circ}{\sim}65^{\circ}C$ were also adopted for experimental parameters. Fly ash was replaced by 30% of cement contents. According to the results, strength development of concrete contained with fly ash is lower than that of plain concrete in low temperature at early age and maturity. In high curing temperature, the concrete with fly ash has higher strength development than that of low temperature regardless of the elapse of age and maturity. Fly ash can have much effect on the strength development of concrete at the condition of mass concrete, hot weather concreting and the concrete products for the steam curing.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 추계학술발표회요약집
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• pp.263-263
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• 2002