• Applied Microscopy
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• 제25권3호
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• pp.99-107
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• 1995

The morphological changes of primary solid particles as a function of process time on hypereutectic Al-15.5wt%Si alloy during semi-solid state processing with a shear rate of $200s^{-1}$ are studied. In this alloy, it was observed that primary Si crystals are fragmented at the early stage of stirring and morphologies of primary Si crystals change from faceted to spherical during isothermal shearing for 60 minutes. To understand the role of Al dissolved in the primary Si crystal by shear stress at high temperature, lattice parameters of the primary Si crystals are determined as a variation of high order Laue zone(HOLZ) line positions measured from convergent beam electron diffraction(CBED) pattern. The lattice parameter of the primary Si crystal in the rheocast Al-15.5wt%Si alloy shows tensile strain of about 5 times greater than that of the gravity casting. Increase of the lattice parameter by rheocasting is due to the increased amount of Al dissolved in the primary Si crystal accelerated by shear stress at high temperature. The amounts of solute Al in the primary Si crystal are measured quantitatively by EPMA method to confirm the CBED analysis.

• Preventive Nutrition and Food Science
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• 제3권4호
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• pp.374-378
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• 1998

The objectives of this study are to determine the optimum process conditions of Korean beeswax and discuss the parameter of adsorption . Purification conditions, such as time, temperature and the type of adsorbents were investigated using the relationship between the properties of refined products and process conditions and theiptimum bleaching condition of Korean beeswax were determined for the first time. The various bleaching conditions were examined by observing the result of Lovibond color, photometric color, methods provided by the American Oil Chemists '(A.O.C.S).The iptimum bleaching temperature was 8$0^{\circ}C$ and the bleaching agents (5% of the weight of beeswax) which consisted of activated clay and activated carbon and a vacuum system were also necessary.

• Preventive Nutrition and Food Science
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• 제14권2호
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• pp.129-133
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• 2009

Salicornia herbacea is rich in natural minerals, dietary fibers, and potentially health-promoting phenolic compounds. In this paper, an experimental design was applied for the optimization of the ultrasound-assisted extraction of phenolic compounds from lyophilized Salicornia herbacea powder. The experiments were conducted in accordance with a five-level, three-variable central composite rotatable design (CCRD), and the effects of solvent concentration, extraction time, and extraction temperature were evaluated via response surface methodology (RSM). The optimal extraction conditions were as follows: ethanol concentration, 76.80%; extraction time, 20 min; and extraction temperature, $33.21^{\circ}C$; and the solvent concentration was the most significant parameter in this process, under which the predicted total phenolic content was 49.91 mg GAE/g sample.

• 한국수소및신에너지학회논문집
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• 제2권1호
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• pp.39-46
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• 1990

In order to improve the power of hydride heat pump, prototype heat pump was constructed using $Zr_{0.95}Ti_{0.05}Cr_{0.9}Fe_{1.1}$-$Zr_{0.9}Ti_{0.1}Cr_{0.6}Fe_{1.4}$ which had very good hydrogenation properties. The power changed with operating parameter such as cycle time, air flow rate, and temperature of hot air was investigated. The power shows maximum value with cycle time. The power increased with air flow rate and temperature of hot air. The power of the heat pump was $65-72 Kcal/Kg-alloy{\cdot}h$ under optimum operating condition, which was superior to that the system using $LaNi_{0.9}Al_{0.3}-MmNi_{4.15}Al_{0.66}Fe_{0.2}$ alloy pairs.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 B
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• pp.609-611
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• 1999

The purpose of this research is on figuring out the optimal PID parameter using critical gain and critical frequency that are obtained by relay feedback. The operating has been done under the condition that the least information about the object plant is given and also the operating is processed within the limit which dose not give rise to bad influence on the object plant. For simulation auto-tuning PID controller using relay feedback which also works on on-line at the same time is developed by the upper procedure. This algorithm is tried to apply to level-temperature control plant on a real time with PC Interface Card.

• 동력기계공학회지
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• 제19권3호
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• pp.48-54
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• 2015

This paper introduced a design method of soldering station that can control two types of soldering iron heater. At design time, to distinguish two types of soldering iron heater the voltage divider rule has been applied, and the distinguished resistor is inserted to handler of soldering iron to prevent misuse by users. And an algorithm to design a PID controllers is proposed. The proposed controllers parameter which can be easily realized, and are designed by using the input output data from systems, and have outstanding ability making the output response of nonlinear systems similar to the desired one. Temperature control experiments were performed to verify the ability of the suggested controller. As a result, suggested PID controller followed the desired ones, and one soldering station can control the various type of soldering irons in real time.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.88-93
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• 1998

The service life of tools in metal forming process is to a large extent limited by wear, fatigue fracture and plastic deformation. In warm forging processes wear is the predominant factor for operating lives of tools. To predict tool life by wear, Archard's wear model is generally applied. Usually hardness of die is considered to be a function of temperature in Archard's wear model. But hardness of die is a function of not only temperature but also operating time of die. To consider softening of die by repeated operations, it is necessary to express hardness of dies by a function of temperatures and operating time. By experiment of reheating of dies, die softening curves were obtained. Finally modified Archard's wear model in which hardness of die was expressed as a function of main tempering curve was proposed.

• 대한안전경영과학회지
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• 제10권4호
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• pp.121-126
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• 2008

The effect of $Al(OH)_3$ on physical, thermal, and retardant property of rubber was studied. It was analyzed by statistical experimental design method with one way array to confirm the effect of factors. Physical characteristics, thermal pyrolysis temperature, and combustion time were considered as the properties. The amount of $Al(OH)_3$ addition was chosen as significant parameter. As the result of ANOVA analysis, thermal pyrolysis temperature increased and combustion time decreased with increasing of $Al(OH)_3$.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.108-113
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• 2001

In this paper, the real-time prediction of high temperature creep strength and creep strength and creep life for nickel-based superalloy Udimet 720 (high-temperature and high-pressure gas turbine engine materials) was performed on round-bar type specimens under pure load at the temperatures of 538, 649 and 704$^{\circ}C$. The predictive equation of ISM creep has better reliability than that of LMP and LMP-ISM, and its reliability is getting better for long time creep prediction(10$^3$~10sup/5/ｈ).

• 한국환경과학회지
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• 제8권5호
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• pp.633-637
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• 1999

A series of meterological observation using automation weather station(AWS) carried out to investigate characteristics of nocturnal meteorological parameters for 16~17 June 1998 at Buljeongdong mountain slope, Kyungbuk. Dry temperature at valley was lower than mountain because of high lapse rate at valley, so the strong inversion layer occurrenced at mountain slope for nighttime. Contrary of dry temperature, relative humidity of valley was higher than mountain for nighttime. Wind speed at valley from sunset to next day morning was lower than mountain, but that of valley after sunrise was higher than mountain. Wind direction at valley for all observation time were southeasterlies(SE), that of mountain for nighttime were northeasterlies(NE) or northnorthwesterlies(NNW), and that of mountain after sunrise were irregular. Vapor pressure at valley for all observation time was higher mountain, particularly the difference was high for nighttime.