• 한국기계가공학회지
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• 제18권10호
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• pp.93-98
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• 2019

Recently, with the development of the aerospace and automotive industries, the demand for high-melting-point materials has increased. However, high-melting-point materials are difficult to cut through conventional machining methods. Thermally assisted machining (TAM) is a method for improving the machinability by preheating the materials. A laser, the most commonly used device for TAM, has high efficiency through local preheating but is not sufficient for maintaining a high preheating temperature due to rapid cooling. However, the use of multi-heat sources can supplement the disadvantage of a single heat source. The high preheating temperature can be maintained with a wide and deep heat-affected zone (HAZ) by multi-heat sources. The purpose of this study is to analyze the preheating effects of multi-heat sources using laser plasma. Thermal analysis and preheating experiments were carried out. As a result, the high preheating effect of multi-heat sources compared with a single heat source was verified.

• 한국전기전자재료학회논문지
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• 제25권6호
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• pp.481-485
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• 2012

ZnO nanowires were synthesized by hydrothermal technique. Prepared synthesis aqueous solutions were preserved by preheating in autoclave type synthesis equipment with various preheating time of 1 h difference. ITO-coated corning glass substrates deposited with AZO seed layers were then inserted in the preheated synthesis aqueous solutions and ZnO nanowires were grown for 180 min at $90^{\circ}C$. Density, length and aspect ratio of the grown ZnO nanowires were investigated. Composition, structural and optical properties of the grown ZnO nanowires were analyzed. Characteristics of the ZnO nanowires were comparatively studied in relation with $Zn^{2+}$ ion concentration measured directly after the preheating of synthesis aqueous solution.

• 산업기술연구
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• 제23권A호
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• pp.29-33
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• 2003

This paper proposed methods of filament preheating to extend a fluorescent lamp life. The ballast for the fluorescent lamp can be classified into two main groups magnetics and electronics. The electronic ballast is lighter and smaller than the magnetic ballast and it can dim up and down. There are two ways to start the fluorescent lamp in the electronic ballast: rapid start and instant start. Also there are two methods of the driving inverter self excited oscillation and force excited oscillation. The rapid starting is different from the instant starting in that the rapid start is preheating the filament before the steady state. If there is a preheating process before the lamp ignition, the life of the fluorescent lamp can be increased. This paper presented the preheating methods for self excited oscillating system and force excited oscillating system.

• 한국식생활문화학회지
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• 제14권5호
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• pp.461-466
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• 1999

As a part of investigation to use sardine(Sardinops melanoslicta) more effectively as a food source, this study was undertaken the processing condition of rapid- and low salt-fermented liquefaction of sardine. To prepare rapid fermented products, the chopped whole sardine was added 8% NaCl and then preheating treatment at $40^{\circ}C,\;45^{\circ}C$ and $50^{\circ}C$ in the manufactured fermenter(180L) for 9 hrs, and then fermentation at $33^{\circ}C$ for 90 days. The chemical changes such as amino nitrogen(amino-N), volatile basic nitrogen(VBN), and histamine in the hydrolysates of fermented sardine were analyzed as well as viable cell count and organoleptic evaluation during fermentation to compare the quality between control and preheating samples. During fermenting, the amino-N in the hydrolysates increased rapidly during the first 30 days and slowly thereafter. The highest content of amino-N appeared at 75 days in control sample and $60{\sim}75$ days in preheating samples. The changes of VBN in the hydrolysates increased rapidly during first 15 days in control samples and 30 days in preheating samples. However they were generally low level in preheating samples. Histamine content in the hydrolysates of the control samples increased markedly after 15 days, but preheating samples were generally low level, and then $75{\sim}90$ days of fermentation reached to the maximum which was about $2.0{\sim}3.0$ times lower than that of control samples. As for the organoleptic flavor evaluation, the control and preheating at $40^{\circ}C$ samples were unpleasant odor after 15 and 60 days, respectively. But preheating at $45^{\circ}\;and\;50^{\circ}$ samples were fresh odor after 90 days fermentation.

• 대한금속재료학회지
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• 제47권11호
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• pp.728-733
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• 2009

Cu based amorphous ($Cu_{54}Zr_{22}Ti_{18}Ni_{6}$) powders were deposited onto Al 6061 substrates by cold spray process with different powder preheating temperatures (below glass transition temperature: $350^{\circ}C$, near glass transition temperature: $430^{\circ}C$ and near crystallization temperature: $500^{\circ}C$). The microstructure and macroscopic properties (hardness, wear and corrosion) of Cu based amorphous coating layers were also investigated. X-ray diffraction results showed that cold sprayed Cu based amorphous coating layers of $300{\sim}350{\mu}m$ thickness could be well manufactured regardless of powder preheating temperature. Porosity measurements revealed that the coating layers of $430^{\circ}C$ and $500^{\circ}C$ preheating temperature conditions had lower porosity contents (0.88%, 0.93%) than that of the $350^{\circ}C$ preheating condition (4.87%). Hardness was measured as 374.8 Hv ($350^{\circ}C$), 436.3 Hv ($430^{\circ}C$) and 455.4 Hv ($500^{\circ}C$) for the Cu based amorphous coating layers, respectively. The results of the suga test for the wear resistance property also corresponded well to the hardness results. The critical anodic current density ($i_{c}$) according to powder preheating temperature conditions of $430^{\circ}C$, $500^{\circ}C$ was lower than that of the sample preheated at $350^{\circ}C$, respectively. The higher hardness, wear and corrosion resistances of the preheating conditions of near $T_{g}$ and $T_{x}$, compared to the properties of below $T_{g}$, could be well explained by the lower porosity of coating layer.

• 한국정밀공학회지
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• 제32권12호
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• pp.1017-1021
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• 2015

Induction heating has been applied to the preheating process in various industrial fields. It has been used as a simple device structure, limiting the heating zone through controlled variables, and free-welding positions. It would be helpful to weld thick plates with arc welding such as GMAW. The induction heating process is well suited to this process. In this study, in order to find suitable induction heating parameters, a simulation was conducted with multi physics S/W. Three kinds of material were heated by induction coils designed specially for thick plate. Consequently, steel and nimonic alloy were the most efficient materials for preheating by induction. It can be concluded that the induction heating process is a good method for preheating the thick plate.

• 한국정밀공학회지
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• 제32권2호
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• pp.173-178
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• 2015

Laser-assisted machining (LAM) is an effective machining method for processing difficult-to-cut materials. Prediction and estimation of preheating effect of the LAM is difficult because of moving heat source. So it is necessary to study the preheating effect of the laser heat source irradiated on the curved surfaces of workpieces of various shape. In this paper, thermal analysis of the LAM for 3-dimentional workpiece with cylindrical shape was performed. The results of this analysis can be applied to obtain the optimal preheating method and path for LAM of 3-dimensional workpiece.

• 한국산업융합학회 논문집
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• 제12권3호
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• pp.163-169
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• 2009

A preheating module for domestic heating facility will increase a energy efficiency. That collects the wasted heat of exhaust gas and saves the energy. So a heating load is decreased because of a preheating that has a heating energy. Using of a preheating module, a boiler can reduce frequent operation of a burner. So it is increased persistence, decreased discharging noxious gases. Therefore we will intend to develop a heating facility that is a convenient system for the saving energy.

• 동아시아식생활학회지
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• 제6권3호
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• pp.325-333
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• 1996

Potato slices were dipped in calcium choreide ar chitosan solutions or and preheated in each of these solutions. In order to prevent the quality deterioration while they were refrigerated for 4 weeks at 5$^{\circ}C$ Changes in degree of browning and other quality factors were determined while they were refrigerated for 4 weeks at 5$^{\circ}C$ During refrigeration, L values were decreased and optical density (A420) were increased. But L values were increased and A420 were decreased by dipping or preheating. The contents of vitamin C were decreased. however, the loss of vitmin C were the lowest in calcium chloride treaed potato slices(CaPS). And there were no combined effects of dipping and preheating during refrigeration. However, protein content of CaPS increased but that of other treated potato slices were decreased compared to that of control. With respect to changes in other physicochemical qualit, pH increased in chitosan treated potato slices(ChPS) and loss of weight was the lowest in combined with preheating. From these results, it was considered that the shelf-life of potato slices could be increased by dipping or-and preheating.

• 한국약용작물학회지
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• 제8권2호
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• pp.146-150
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• 2000

수삼의 증삼전 열처리로 홍삼중의 추출가능 물질은 물추출물 뿐만 아니라 60%주정 수용액 추출물의 양을 근본적으로 다량 생성시켜 추출수율을 높였다. 또한 갈색도가 증진되었으며, 전분질을 함량을 저하시켜 추출물중 원심분리박의 대부분을 차지하고 있는 전분을 감소시키므로써 이의 제거를 위한 원심분리기 등 고가의 공정 단축이 가능할 수 있다. 증삼 전 예열 적정온도는 $70^{\circ}C$에서 60분이 적합하였으며 증삼시간에 따라서는 엑스추출율의 차이가 크지 않았다. 예열 조건별 물 추출물 엑스의 향미 비교에서 향과 맛 모두 당의 특성 향미가 증진됨을 나타냈다.