• 동력기계공학회지
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• 제5권2호
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• pp.36-42
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• 2001

This paper deals with finite element analyses of residual stresses causing popping up which are induced in micromachining processes of a microaccelerometer sensors. The paddle of the micro accelerometer sensor is designed symmetric with respect to the direction of the beam. After heating the tunnel gap up to 100 degree and get it through the cooling process and the additional beam up to 80 degree and get it through the cooling process. We learn the thermal internal stresses of each shape and compare the results with each other, after heating the tunnel gap up to 400 degree during the Pt deposition process. Finally we find the optimal shape which is able to minimize the internal stresses of microaccelerometer sensor. We want to seek after the real cause of this pop up phenomenon and diminish this by change manufacturing processes of microaccelerometer sensor by electrostatic force.

• 소성∙가공
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• 제12권5호
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• pp.457-464
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• 2003

In the powder compact melting technique, proper precursor fabrication is very important because density distribution after foaming and foamability are determined during precursor fabrication process. The fabrication of the precursor has to be performed very carefully because any residual porosity or other defects will lead to poor results in further processing. In order to evaluate the effect of the compaction parameters on the kinetics of the foaming process, a series of experiments were performed. In this study, aluminium foams with a closed cell structure were fabricated by using both the powder compact method and the induction heating process. A proper induction coil was designed to obtain a uniform temperature distribution over the entire cross sectional area of precursor. To establish the foamable precursor fabrication conditions, effects of process parameters such as the titanium hydride content (0.3∼1.5 wt.%), pressing pressure of the foamable precursor (50∼150kN) on the pore morphology were investigated.

• 한국주조공학회지
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• 제35권6호
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• pp.141-146
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• 2015

Aluminum-based hybrid parts were fabricated through a compound casting process with Al or Cu inserts which can be used for applications requiring high conductivity. Because the interface stability between the insert and the aluminum matrix is important, the effects of process variables on the interfacial adhesion strength were investigated. Additions of Cu and Mg to Al melt were found to enhance the adhesion strength, though the melt fluidity was slightly deteriorated when a small amount of Mg was added. An isothermal heating process after casting further improved the strength. However AlCu intermetallic compounds formed and their thickness increased during the heating process. As a result, deterioration in the interfacial adhesion strength was observed after an excessive annealing treatment.

• Advances in concrete construction
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• 제10권3호
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• pp.247-256
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• 2020

In this paper the possibility of using different regression models to predict the mechanical properties of limestone concrete after exposure to high temperatures, based on the results of non-destructive techniques, that could be easily used in-situ, is discussed. Extensive experimental work was carried out on limestone concrete mixtures, that differed in the water to cement (w/c) ratio, the type of cement and the quantity of superplasticizer added. After standard curing, the specimens were exposed to various high temperature levels, i.e., 200℃, 400℃, 600℃ or 800℃. Before heating, the reference mechanical properties of the concrete were determined at ambient temperature. After the heating process, the specimens were cooled naturally to ambient temperature and tested using non-destructive techniques. Among the mechanical properties of the specimens after heating, known also as the residual mechanical properties, the residual modulus of elasticity, compressive and flexural strengths were determined. The results show that residual modulus of elasticity, compressive and flexural strengths can be reliably predicted using an artificial neural network approach based on ultrasonic pulse velocity, residual surface strength, some mixture parameters and maximal temperature reached in concrete during heating.

• 대한가정학회지
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• 제17권3호
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• pp.45-52
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• 1979

The study was an attempt to compare the Korean home-made sesame oil (sample A) with the market goods in Korean (sample B) and in Japan (sample C) for their flavor and cooking after an hour heating. And there were 5 spices used green onion , garlic, ginger, black pepper and red pepper in heating process of the sesame oil. The results obtained were as follows : 1) On the chemical changes of AV, IV, SV, TBAV, and the appearence of color and viscosity , it was supposed that the changes were showed merely more by the heating than the heating of the spices addition. Among the spices garlic was noticed to change greatly in comparison with the other spices. And A was showed to change a little respectively at color , SV, which B, C changed more. 2) Through the sensory examination there was not of significant effect in the strength and acceptability after an hours heating between sample A, B and C. 3) Basic aroma component of the fresh sesame oil and the heating in the carbonyl fraction were analyzed and indentified by G L C. N-hexanal, n -heptanal , n-octanal etc were increased by means of the heating , sample b remarkably more than A.

• 한국식품영양과학회지
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• 제25권6호
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• pp.951-957
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• 1996

당근, 쪽파, 시금치와 같은 채소류에 대한 데치기 실험에서 데치기 시간은 전자레인지 CCT가 빨랐으며, 색도 및 절단강도 변화에서는 데치기 처리로 명암도, 적녹도, 황청도, 절단 강도가 대조구에 비하여 감소하였으며 그 감소 폭은 전자레인지 CCT의 경우가 적었다. 미세구조 관찰에서는 전자레인지 CCT가 NCCT보다 조직 구조가 덜 파괴하는 것으로 나타났으며, vitamin C 함량에서도 전자레인지 CCT가 손실이 적었다.

• 동력기계공학회지
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• 제20권5호
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• pp.46-51
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• 2016

The TMCP steel has expanded in the marine structure during manufacturing process because of its excellent weld-ability and impact toughness. In the case of merchant ships, coverage of TMCP steel has been used widely on over DH36 Classifications material. The line heating process is applied to the outer surface of the steel plate for the shipbuilding. In this study, We compared between TMCP and normalizing steel for shipbuilding by analyzing some basic data through performing the natural cooling after the line heating. The experimental results show the angular misalignment changes in line heating. Heated surface of normalizing steel material expanded to $-0.3^{\circ}$ and reduced to $+0.2^{\circ}$ after cooling. And during cooling at $194^{\circ}C$ for 1,500 seconds, Angular Misalignment began from - direction to + direction, passed the critical point to the default at 2,200 seconds and did not take place any more at $103^{\circ}C$ after the 2,700 seconds. Angular Misalignment results of TMCP steels and Normalizing steel material show same angular misalignment lasted 1,200 seconds, TMCP steel has given more expansion and contraction angle which is $0.2^{\circ}$ than that of the Normalizing steel. Length difference between expansion and contraction is about 0.3 mm.

• 대한조선학회논문집
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• 제39권2호
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• pp.45-51
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• 2002

선체는 많은 다중곡(compound curvature)을 가진 판들로 이루어져 있으며 이러한 판들을 가공하기 위해서, 조선소에서는 선상 가열(line heating) 방법이 널리 이용되어 왔다. 선상 가열법에서 가열선을 결정하는 방법으로 지금까지는 기하 변형해석을 이용하여 가열선을 제시하여 왔다. 그러나 기하해석으로 구한 가열선에 대한 역학적 검증이 이루어지지 않고 있으며 여러 가열선 중 어떤 가공선을 선택할 것인가에 대한 연구도 이루어지지 않고 있다. 본 논문에서는 기하해석을 통해 판의 가열정보를 얻었을 때 이를 역학적으로 검증하여 실제로 판에 가열정보대로 가공을 하였을 때 나타날 수 있는 판의 거동을 예측하였다. 또한 본 논문에서는 적정 가열선을 찾는 전체 과정을 제시하였다. 가공정보로부터 예측된 가공형상을 구한 후 목적형상과 비교하여 가공형상이 목적형상의 오차범위 내에 존재할 때까지 가열선의 조정변수를 변화시켜 적절한 가공정보를 획득하였다.

• 건축역사연구
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• 제30권6호
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• pp.33-44
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• 2021

The traditional Korean heating system ondol, one of the most important characteristics of Korean architecture, still remains as hydronic floor heating. Various studies have been conducted on the modernization of ondol, but the process of introducing the hydronic floor heating has not been seriously studied so far. Therefore, this paper aims to demonstrate how the hydronic floor heating had been introduced to Korea, taking the 1950s and 1960s Haengchon, Jongam, and Mapo Apartments for example - these three are regarded as the first Korean apartment houses after the Korean War. While Western advanced construction technology was imported for these apartments, various methods of modernizing ondol were also considered. What was remarkable in these attempts is that hydronic floor heating first appeared in Mapo 1st Apartment in 1962, because this is the universal heating method in the present Korea. This fact signifies that the traditional principle of floor heating has been maintained, and it would also be meaningful in terms of architectural exchanges between East and West, if considered along with Wright's application of the Korean heating principle to his houses since 1930s.

• 센서학회지
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• 제22권1호
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• pp.89-94
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• 2013

In this paper, we developed a beam of MEMS probe card using a BeCu sheet. Silicon wafer thickness of $400{\mu}m$ was fabricated by using deep reactive ion etching (RIE) process. After forming through silicon via (TSV), the silicon wafer was bonded with BeCu sheet by soldering process. We made BeCu beam stress-free owing to removing internal stress by using joule heating. BeCu beam was fused by using joule heating caused by high current. The fabricated BeCu beam measured length of 1.75 mm and width of 0.44 mm, and thickness of $15{\mu}m$. We measured fusing current as a function of the cutting planes. Maximum current was 5.98 A at cutting plane of $150{\mu}m^2$. The proposed low-cost and simple fabrication process is applicable for producing MEMS probe beam.