• 전자공학회논문지
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• 제50권7호
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• pp.286-291
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• 2013

홈 CATV 네트워크는 동축 케이블과 이상적인 특성을 만족하지 못하는 신호 분배기로 구성되며, 케이블 설치시 원치 않은 묶임이나 구부러짐 그리고 케이블 연결 부위의 문제점 등이 발생할 수 있다. 또한 케이블 커넥터의 배치에 따라 발생할 수도 있는 이러한 문제점은 신호 누설의 원인이 될 수 있고, 네트워크의 성능을 악화시키는 원인이 되기도 한다. 본 논문에서는 RG-59, RG-6 동축 케이블 등과 같은 차폐 케이블이나 신호 분배기 에서의 신호 누설 및 전파 문제를 분석하고, 이상적인 CATV 홈 네트워크 구축 방법을 설명한다.

• 한국기계가공학회지
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• 제14권1호
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• pp.29-35
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• 2015

In this study, a FEM analysis is undertaken of a rubber sleeve which is mounted onto a spreading mandrel so as to avoid marking the first wrappings of coils (known as the 'end-mark'), as occasionally occurs when a concentrated load is placed on the edge of a steel sheet, significantly reducing its quality. A commercial numerical package, ANSYS, was utilized to analyze the structural behavior of the rubber sleeve. In general, the strain of the sleeve increases as the thickness of the rubber layer (H) covering the tubes increases, thus also increasing the surface of the sleeve for a constant boundary condition, and decreasing the pitch (P) between each tube, resulting in an increase in the strain on the surface of the sleeve for all rubber thickness conditions tested here. In a comparison of two different materials, rubber and urethane, when H=3 mm and P=1.1D, the maximum total deformations in these cases are 0.12669 mm and 0.086623 mm, respectively.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.351-358
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• 2000

In a small centrifugal compressor system, a high-speed motor needs to be developed to drive impellers directly. Heat is generated by both electrical heating due to copper coil resistance and aerodynamic heating in the gap between the rotor and stator in a high-speed motor. Removal of the heat is essential to the design of such motors since most magnetic materials are brittle and can be easily fractured by the heat. In the present study the cooling flow fields and temperature distributions were analyzed by using computational fluid dynamics simulation for a high-speed motor which has air cooling system as well as water cooling system. In the analysis a conjugate heat transfer problem is solved by considering both convective heat transfer in the cooling system and conduction heat transfer in solid parts. Based on design drawings of a motor, air cooling system and water cooling system were analyzed to obtain temperature field and thus to check the coiling system performance. Also the cooling performance are studied for various flow rates of cooling air and water at the inlets.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.63-66
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• 1996

Cold rolling mill process in steel works uses stands of rolls to flatten a strip to a desired thichness. At Pohang Iron and Steel Company (POSCO) in Pohang, Korea, precalculation determines the mill settings before a strip actually enters the mill and is done by an outdated mathematical model. A corrective neural network model is proposed to improve the accuracy of the roll force prediction. Additional variables to be fed to the network include the chemical composition of the coil, its coiling temperature and the aggregated amount of processed strips of each roll. The network was trained using a standard backpropagation with 2,277 process data collected form POSCO from March 1995, then was tested on the unseen 200 data from the same period. The combined model reduced the prediction error by 55.4% on average.

• 한국정밀공학회지
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• 제20권9호
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• pp.126-134
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• 2003

This paper investigates the multi-pass wet wire drawing process considering the slip between the wire and the capstan. The production of fine wire through multi-pass wet wire drawing process would be impossible without backtension. The backtension is affected by many process parameters, such as slip, dies reduction, coiling number of wire at the capstan, machine reduction, characteristic of lubricant etc. Up to date, die design and dies pass schedule of multi-pass wet wire drawing process have been performed by trial and error of expert in the industrial field. In this study, an analysis program which can perform the analysis and considering the effect of slip at each capstan was developed. The effects of many important parameters (drawing force, backtension force, needed power, slip rate, slip velocity rate etc.) on multi-pass wet wire drawing process can be predicted by this developed program. It is possible to obtain the important basic data which can be used in the pass schedule of multi-pass wet wire drawing process by using this developed program.

• 제어로봇시스템학회논문지
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• 제5권6호
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• pp.714-723
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• 1999

This paper presents a short-term scheduling algorithm for the operation of steelmaking processes. The scope of the problem covers refining of the hot iron transferred form a blast furnace, ladle treatment, continuous casting, hot-rolling, and coiling for the final products that should satisfy the given demand. The processing time at each unit depends on how much the batch amount is treated, and te dedicated intermediate storage with finite capacity between the units is considered. Resource constraints and initial amount of each state are incorporated into the presented scheduling model for the algorithm of on-line scheduling. We propose amixed integer linear programming (MILP) model with two objectives for the scheduling. The first is to maximize the total profit while atisfying the due date constraint for each product. And the second is to minimize the total processing time, makespan, while satisfying the demand for each product. Especially, we observe the effect of penalizing the intermediate storage and the inventory level of the final product on the scheduling results.

• Journal of the korean society of oceanography
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• 제33권1-2호
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• pp.8-17
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• 1998

Paleoceanographic history of the East Sea is reconstructed based on several environmental parameters (coarse fraction content, planktonic foraminifera/benthic foraminifera ratio, fragmentation and assemblages of planktonic foraminifera, and coiling ratio of Neogloboquadrina pa-chyderma, etc,) of the late Quaternary sediments obtained from the Ulleung Basin. N. pa-chydeyma and Globigerina bulloides are dominant species (greater than 90% in abundance)among the total planktonic foraminifera assemblages in the late Quaternary sediments. The benthic foraminifera rarely occurred throughout the cores. Sinistrally-coiled specimens of N. pa-chyderma representing cold water temperature are observed more abundantly than dextrally-coil-ed ones. In addition, the sinistrally-coiled N, pachydeyma showed more the amount at the lower part of the cores than at the upper part suggesting the restriction of the Tsushima Warm Current into the East Sea during glacial period. G. bulloides, a species representative of upwelling condition, shows more abundant occurrence in the sediments of Core 941013 than those of Core 941006. This implies that Core 941013 is more influenced by upwelling than Core 941006. The upper part of the two cores contain more fragmentation of planktonic foraminifera suggesting significant dissolution by corrosive bottom wafer. Ascending CCD also played an important role for the absence of planktonic foraminifera at the upper part of the cores.

• 소성∙가공
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• 제15권8호
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• pp.603-608
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• 2006

The main purpose of the present study has been placed on investigating the mechanical properties and microstructures of C-Si-Mn-V steels for cold forming manufactured by controlled rolling and cooling technology. The steels were manufactured in electric arc furnace (EAF) and casted to $160{\times}160mm$ billet. The billets were reheated in walking beam furnace and rolled to coil, the stocks were rolled by Controlled Rolling and Cooling Technology (CRCT), so rolled at low temperature by water spraying applied in rolling stage and acceleratly cooled before coiling. Rolled coils were cold drawed to the degree of 16%, 27% of area reduction respectively without heat treatment. Microstructual observation, tensile test, compression test and charpy impact tests were conducted. The mechanical properties of the steels were changed by area reduction of cold drawing and it is founded that there are optimum level of cold drawing to minimize compression stress for these steels. From the result of this study, it is conformed that $80kg_{f}/mm^{2},\;90kg_{f}/mm^{2}$ grade high strength microalloyed steel for cold forming are developed by accelerated cooling and optimum cold drawing.

• Journal of Korean Neurosurgical Society
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• 제44권3호
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• pp.178-181
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• 2008

Although endovascular intervention is the first-line treatment of intracranial aneurysm, intraprocedural rupture or extravasation is still an endangering event. We describe two interesting cases of extravasation during embolotherapy for ruptured peripheral cerebral pseudoaneurysms. Two male patients were admitted after development of sudden headache with presentation of intracerebral and subarachnoid hemorrhage, respectively. Initial angiographic assessment failed to uncover any aneurysmal dilatation in both patients. Two weeks afterwards, catheter angiography revealed aneurysms each in the peripheral middle cerebral artery and anterior inferior cerebellar artery. Under a general anesthesia, endovascular embolization was attempted without systemic heparinization. In each case, sudden extravasation was noted around the aneurysm during manual injection of contrast after microcatheter navigation. Immediate computed tomographic scan showed a large amount of contrast collection within the brain, but they tolerated and made an unremarkable recovery thereafter. Intraprocedural extravasation is an endangering event and needs prompt management, however proximal plugging with coil deployment can be sufficient alternative, if one confronts with peripheral pseudoaneurysm. Peculiar angiographic features are deemed attributable to extremely fragile, porous vascular wall of the pseudoaneurysm. Accordingly, it should be noted that extreme caution being needed to handle such a friable vascular lesion.

• 대한기계학회논문집A
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• 제25권2호
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• pp.330-337
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• 2001

Wire drawing process of the high carbon steel with a high speed is usually conducted at room temperature using a number of passes or reductions through consequently located dies. In multi-stage drawing process, temperature rise in each pass affects the mechanical properties of final product such as bend, twist and tensile strength. Also, this temperature rise during the deformation is the reason that the wire in drawing process is broken by the embrittlement due to rapid strain aging effect. This paper presents the estimation of the wire temperature for the multi-stage wire drawing process. Using the proposed calculation method of wire temperature, temperature rise at deformation zone as well as temperature drop in block considering the heat transfer between the block and wire were calculated. As these calculated wire temperatures were applied to the real industrial fields, it was known that the calculated results were in a good agreement with the measured wire temperature.