• 소성∙가공
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• 제20권2호
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• pp.132-139
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• 2011

Three dimensional simulations were performed for the deformation of a slab in a roller hearth type slab reheating furnace. The main objective of this study was to examine the deformation pattern of the slab due to the shadow effect, i.e., the temperature difference between the upper and lower slab surfaces, in particular, the variations of displacement and effective stress in the vertical direction. A commercially available FE code, ANSYS Workbench $12.1^{TM}$, was used in a fully coupled thermo-elasticity analysis. Several cases with different slab surface temperatures were selected for the simulations. For the sake of simplicity, the temperature environment inside the furnace was assumed to be homogeneous for the upper and lower faces of the slab. Two cases of with different slab width were selected as model geometry. The deformation patterns were computed and explained in terms of periodicity and symmetry. The results indicated that the shadow effect leads to a significant displacement in the vertical direction and, thereby, is one of the main reasons for the separation of the slab and its supports. These simulations also predicted that the deformation is more severe along the transverse direction than along the longitudinal direction.

• 소성∙가공
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• 제20권2호
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• pp.110-117
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• 2011

The purpose of this work is to develop of a press forming process for mobile phone battery cover as an alternative to the current manufacturing process by laser welding. This press forming process consists of a combination of bending, side pressing and side bending operations. The dimensional error for each process was investigated by finite element(FE) analysis and the Taguchi optimization method. The spreading of the cover width in the side pressing process was adjusted by modifying the blank shape with a notch. The over-bending method was adopted to compensate the spring-back which occurs after bending. Forming experiments were performed to verify the reliability of the developed press forming process. In addition, the strength of the product was evaluated to verify the suitability of the battery cover manufactured with this new press forming process. The results of the forming experiments indicate that the dimensional accuracy of the battery cover is within the required tolerance. The strength of the battery cover was evaluated to 547N which is larger than required strength of 400N.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.445-447
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• 1997

In this paper a remote monitoring and control system using Modem for UPS (Uninterruptible Power Supply) is proposed. The conventional remote monitoring system for UPS is used to local remote monitoring system by RS232 or RS485 communication code. But recently. the system is changed to wide remote monitoring and control system using Modem for quick analysis of errors, correction of errors, report of errors and other user-friendly functions. In this study, we designed and develope system which is able to control UPS an monitor errors, statuses, actual values transmitted from UPSs of each site.

• 음성과학
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• 제5권2호
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• pp.57-75
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• 1999

The purpose of this paper is to develop an English prosody training system using PC for Korean learners of English. The program is called Intonation Training Tool (ITT). It operates on DOS 5.0. The hardware for this program requires over IBM PC 386 with 4 MBytes main memory, SVGA (1 MByte or more) for graphic, soundblaster 16 and over 14 inch monitor size. The ITT program operates this way: the learners can listen as well as see the English teacher's stress and intonation patterns on the monitor. The learner practices the same patterns with a microphone. This program facilitates the learner's stress and intonation patterns to overlap the teacher's patterns. The learner can find his/her stress and intonation errors and correct these independently. This program is expected to be a highly efficient learning tool for Korean learners of English in their English prosody training in the English class without the aid of a native English speaker in the classroom.

• 소성∙가공
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• 제17권3호
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• pp.189-196
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• 2008

Alloy718 is the nickel-base super alloy well used as gas turbine components under severe operating conditions because of its high strength at high temperature and excellent creep resistance. In this study, a coupling bolt for the gas turbine component is manufactured by hot heading process instead of whole machining in order to improve the mechanical properties. Die shape for the hot heading has been designed by general design rule of hot forging and also optimal process condition has been investigated by finite element method. The initial billet temperature and the punch speed have been determined by $1150^{\circ}C$ and 600mm/s on the basis of finite element analysis, respectively. The coupling bolt has been manufactured by 200ton screw press and evaluated by experiment in order to investigate the mechanical properties. As a result of experiment, the mechanical properties such as hardness, tensile strength and creep behavior have been superior to those manufactured by machining.

• 대한기계학회논문집B
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• 제32권9호
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• pp.645-651
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• 2008

For a high speed train driving at 300 km/h, aero-acoustic noise is a dominant component among various noise sources. The aeroacoustic noise is mainly due to inter-coach spacings because discontinuities in the train surface significantly disturb turbulent flows. This often leads to the uncomfortableness of passengers. Interestingly, the aero-acoustic noise reduces with decreasing the mud-flap spacing of the inter-couch spacing. We perform numerical simulations to investigate flow characteristics around the inter-coach spacing. We model the inter-coach spacing as a simple 2-D cavity with flaps, and calculate the velocity and pressure field using two equation turbulence models, varying the flap spacing. The results show that a wider flap spacing develops a higher inflection point in mean velocity profiles over the cavity. It is likely that large eddies generated near the inflection point persist longer in the downstream since they are less affected by the wall. This probably induces the more aero-acoustic noises. The wider spacing also results in the larger pressure difference between the inside and outside of the cavity. This is also responsible for the increased noise since the large difference would cause a strong flow oscillations in and out of the cavity.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 추계학술대회
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• pp.349-350
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• 1996

Using FEM, we analyzed the stress changes on early osteonecrosis of femoral head as the necrotic area increases. A 3D FEM model of proximal femur was made from the CT scam data of fresh frozen adult proximal femur with the material properties from literature. The model consisted of 5994 elements and 5275 nodes. FE analyses were peformed using MSC/NASTRAN. At normal states, stress transmission is mainly along the primary compression trabeculae(PCT). Until 60% involvement of PCT with necrotic lesion, stress transmission is still along the remained PCT. When the PCT involvement is from 60% to 85%, stress transmission is along the PCT and margin of the necrotic lesion. When involvement is more than 85%, stress is mostly transferred to posterior part of femoral head.

• Biomaterials and Biomechanics in Bioengineering
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• 제2권1호
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• pp.47-59
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• 2015

A bioactive and multifunctional elastin-like polymer (ELP) was produced by genetic engineering techniques to develop new artificial matrices with the ability to mimic the extracellular matrix (ECM). The basic composition of this ELP is a thermo- and pH-sensitive elastin pentapeptide which has been enriched with RGD-containing domains, the RGD loop of fibronectin, for recognition by integrin receptors on their sequence to promote efficient cell attachment. Hydrogels of this RGD-containing polymer were obtained by crosslinking with hexamethylene diisocyanate, a lysine-targeted crosslinker. These materials retain the "smart" nature and temperature-responsive character, and the desired mechanical behavior of the elastin-like polymer family. The influence of the degree of crosslinking on the morphology and properties of the matrices were tested by calorimetric techniques and scanning electron microscopy (SEM). Their mechanical behavior was studied by dynamical mechanical analysis (DMA). These results show the potential of these materials in biomedical applications, especially in the development of smart systems for tissue engineering.

• 생약학회지
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• 제45권3호
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• pp.209-213
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• 2014

The anti-melanogenic substance was isolated from the root of Angelica gigas Nakai by silica gel column chromatography, preparative HPLC and TLC. As a result of the structure analysis by mass, $^1H$-NMR, and $^{13}C$-NMR spectrometry, the compound was identified as demethylsuberosin. Demethylsuberosin reduced melanin contents of B16F1 melanoma cells in a dose-dependent manner and decreased to about 74% at a concentration $5{\mu}g/ml$. Demethylsuberosin inhibited the expression in microphthalmia associated transcription factor (MITF), tyrosinase, tyrosinase related protein-1 (TRP-1), and tyrosinase related protein-2 (TRP-2) in melanocytes. These results suggest that the whitening activity of demethylsuberosin may be due to the inhibition of the melanin synthesis by down-regulation of MITF, tyrosinase, TRP-1 and TRP-2 expression. Thus, our results provide evidence that demethylsuberosin might be useful as a potential skin-whitening agent.

• 한국축산시설환경학회지
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• 제13권2호
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• pp.113-120
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• 2007

본 시험은 근적외선분광법을 이용한 돈분뇨 액비의 질소, 인산, 칼리, 수분 및 유기물의 분석 가능성을 구명하고, 이를 활용한 분석기의 개발을 목적으로 수행하였으며, 그 결과는 다음과 같다. 1. 돈분뇨 액비시료는 $400{\sim}2,500nm$ 대역의 근적외선을 시료에 투과하여 측정하였으며, 동일시료에 대한 습식분석 결과, N, $P_2O_5,\;K_2O$, 수분 및 유기물 함량은 각각 1,555mg/l, 302mg/l, 240mg/l, 98.8%, 0.53%로 조사되었다. 2. 근적외선 분광광도법을 이용한 분석에서 N, $P_2O_5,\;K_2O$, 수분 및 유기물에 대한 RSQ ($r^2$, R, Coefficient of determination)는 각각 0.9190, 0.9749, 0.5046, 0.9883 및 0.9777이었고 SEC(Standard Error of Calibration)는 2.1649, 0.5019, 1.9252, 0.1180 및 0.0789였다. 3. 액비에 대한 이화학적 습식분석과 NIR 흡수스펙트럼 측정결과를 비교 분석하여 돈 분뇨 액비에 포함된 질소, 인산, 칼리, 수분 및 유기물 함량을 실시간으로 분석하고 액비 성분량을 자동 계산할 수 있는 알고리즘을 도입한 액비분석 프로그램을 작성하였다. 4. 액비 성분분석 시작기는 근적외선(NIR : Near InfraRed)을 받아들여 실시간으로 액비성분의 흡수율을 측정하는 광검출장치(NIR Spectrometer), 근적외선 Light Source로부터 나오는 빛을 반사시키는 반사경, 액비성분 분석용 시료를 넣어 측정하는 Cell Mount, $400{\sim}2,500nm$ 대역의 가시광선-근적외선을 방출하는 Tungsten halogen lamp, NIR Spectrometer와 Tungsten halogen lamp로 전압을 입력시켜 주는 Power Supply Module 및 전체를 Black Anodizing한 외형으로 구성되었다. 5. 실험결과, 칼리를 제외한 액비내 모든 성분이 광을 흡수하는 강도는 성분의 농도에 비례하였으며 원시 스펙트럼의 중첩 제거 및 빛의 산란보정을 통해 액비의 질소, 인산성분, 수분 및 유기물 함량을 측정하는데 효과적으로 이용할 수 있을 것으로 사료되며, 분광분석법을 이용한 액비성분 분석기 개발이 완료되면 현장에서 신속하고 정확한 분석이 가능할 것으로 판단된다.