• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.31-36
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• 1998

By using wind vectors observed by NSCAT and significant wave heights observed by TOPEX/POSEIDON and ERS-2 altimeters, one-dimensional fetch growth of wind waves Is investigated under conditions of strong wind and high waves of the East Asian winter monsoon. The evolution of fetch-limited wind waves can be observed by the altimeters along the ground tracks. The fetch is estimated by using vector wind field observed by NSCAT. The derived growth characteristics of wind waves are compared with empirical relationships between the non-dimensional fetch and significant wave height proposed by previous studies. Good agreement with the empirical fetch graph formula normalized by the friction velocity is discemible, while the formulas normalized by the wind speed at a height of 10 m tend to underestimate the wave height under such severe conditions of high wind and very long fetch.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.143-146
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• 1995

Due to the recent growth of die/mold machining industry, demands for the high-precision and the high0quality of die product are increasing rapidly. Free surfaces of die/mold are often manufactured using the ball-end milling process. It is difficult to find the cutting condition of the ball-end milling process due to the free form machining for the various tool paths on inclined surface.

• 한국해양공학회지
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• 제23권3호
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• pp.46-52
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• 2009

Nowadays, many components in automobile, aircraft, offshore structure and industry require lightness and high strength. However, since developments of advanced materials have limitations, it mainly is applying to method of surface hardening. This study offered research about camshaft that is one among engine important component. The material used in this study is 0.53% carbon steel as structure material of camshaft, splineshaft, coupling, pulley, driveshaft et cetera. Camshaft is processed using mainly carbon steel, and receives wear and fatigue by special quality high speed of parts. Therefore, camshaft need surface hardening to improve camshaft's fatigue life and increase durability of engine. This study compare to residual stress and martensite microstructure created by high frequency induction treatment, and these results lead to the conclusion of fatigue crack growth characteristics.

• 노동경제논집
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• 제37권4호
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• pp.25-57
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• 2014

산업별 자료에 기초하여 무역거래 자유화 확대가 고용조정의 속도와 고용의 임금탄력성에 미치는 효과를 분석한 결과, 고용조정 속도는 취업자 기준보다 피고용자 기준의 경우가 좀 더 빠르게 나타나며, 수입 비율이 높은 산업들에서 수출 비율이 높은 산업들에 비해서 좀 더 빠르게 나타난다. 또한 경제개방의 확대는 피고용자 기준으로 볼 때 고용조정 속도를 조금씩 느리게 만들고 있으며 이는 주로 수출 비율 상승에 의해 주도된다. 고용의 임금탄력성은 경제개방률이나 수출 비율이 높을수록 상승하여 '고용 없는 성장(jobless growth)'의 환경이 강화되고 있다.

• 응용통계연구
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• 제29권1호
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• pp.13-25
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• 2016

KTX 개통으로 예상되었던 파급효과로는 건설투자로 인한 생산 및 고용 확대와 항공, 고속버스, 철도 등 운송수단간 수요 대체효과를 들 수 있다. 이외에도 기업의 지방이전, 수도권 기능의 분산을 통한 국토의 균형 개발, 고속철도 이용에 따른 시간비용 절감, 승용차의 고속도로 이용 및 교통사고 감소로 인한 사회 경제적 비용 축소도 기대되었다. 또한 KTX역 중심의 관광 네트워크를 통한 지역 관광 여가 산업의 발전과 지역 문화 예술 인적 교류 활성화를 통한 삶의 질 향상도 예상되었다. 반면에 고속철도망 연결로 주변 중소도시의 업무기능, 노동력 및 구매력이 인근 대도시로 흡수되면서 지방상권이 위축되는 지역불균형 심화문제도 예측되었다. 이와 함께 인구 및 기업의 유출로 인한 지역경제 공동화 등의 부작용도 우려되었다. 본 연구는 KTX 개통을 통한 고속철도망 연결이 지역경제에 어떠한 영향을 미쳤는지를 알아보기 위해 진행되었다. 먼저 백화점 판매액 불변지수를 이용한 기본모형에 대한 분석에서는 임금소득, 주택매매가격지수, 그리고 회사채수익률이 모두 유의하였고, 기본모형에 추가로 고려된 KTX 이용인구비율도 백화점 판매액 불변지수의 변동에 유의미한 영향을 주는 것으로 나타났다. 또한 지역 소비유출 효과를 확인하기 위해서 지역별 타지역 의료기관이용률을 종속변수로 분석하였다. 분석 결과, 부산의 경우에만 KTX 이용인구비율과 타지역 의료기관이용률간에 유의한 관련성을 확인할 수 있었다. 대구의 경우에는 통계적으로 유의하지 않았다. KTX 이용 자료가 부족한 상황에서 KTX 개통에 따른 지역경제에 대한 영향을 구체적으로 파악하는데 한계가 있다. 그러나 KTX의 효과가 개통 초기보다는 다소 감소되었지만 지역경제 발전 효과 및 가능성은 여전히 확인할 수 있었다.

• 한국인구학
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• 제10권2호
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• pp.82-98
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• 1987

The urban population in Asia more than doubled between 1960 and 1985, growing by 3.0 percent per annum on average. Yet during that period, the proportion of the total population living in urban areas increased only from 21 to 27 percent. This seeming paradox is explained by the relatively high rates of rural population growth in Asia, which averaged 1.8 percent over the same period. The Republic of Korea has experienced the most rapid rate of urbanization in Asia during the past century. The proportion urban jumped from 28 percent in 1960 to 65 percent in 1985. There is a clear association between economic growth and the pace of urbanization in Asia. Currently natural increase accounts for about 60 percent of urban growth, but the speed of urbanization is projected to increase after 1990, and migration, reclassification and annexation will comprise about half of urban growth, Seoul is currently the fourth largest urban agglomeration in Asia, and its population is projected to be over 13 million by the end of the century. It is argued that policies to deconcentrate urban population will not be generally successful in Asia and that governments should attempt to manage the growth of large metropolitan areas more efficiently.

• Journal of Microbiology and Biotechnology
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• 제9권5호
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• pp.548-553
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• 1999

A production of $\beta-Carotene$was attempted in a fed-batch culture of Blakeslea trispora by controlling both foam and dissolved oxygen in the presence of surfactant, Span 20. Results obtained from the shake flask cultures indicated that a high concentration of dissolved oxygen was needed for both cell growth and $\beta-Carotene$ synthesis, and the optimal concentration of glucose was found to be in the range of 50-100 g/l. In order to maintain the dissolved oxygen concentration level at higher than 50% of air saturation, pure oxygen was automatically sparged into the medium with air. Foam was controlled by bypassing air from the submerged aeration to the headspace in response to the foam that was caused by Span 20. High agitation speed was found to be detrimental to the cell growth due to shear damage, even though it provided sufficient dissolved oxygen. On the other hand, a low aeration speed caused stagnant regions in the fermentor because of improper mixing. Thus, for the fed-batch operation, agitation speed was increased gradually from 300 to 700 rpm to prevent cell damage at the initial stage of fermentation and to give efficient mixing for a viscous culture broth as the culture proceeded. By controlling dissolved oxygen and foam, a high concentration of $\beta-Carotene$otene (1,190 mg/l) was obtained in 6 days of the fed-batch culture of B. trispora with 2.5% of the dry cell weight, which was approximately 5 times higher than that of the batch cultures.

• 대한기계학회논문집B
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• 제29권2호
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• pp.169-179
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• 2005

Nucleate boiling experiments on heating surface of constant wall temperature were performed using R113 for almost saturated pool boiling conditions. A microscale heater array and Wheatstone bridge circuits were used to maintain a constant wall temperature condition of heating surface and to measure the heat flow rate with high temporal and spatial resolutions. Bubble images during the bubble growth were taken as 5000 frames per second using a high-speed CCD camera synchronized with the heat flow rate measurements. The bubble growth behavior was analyzed using the new dimensionless parameters for each growth regions to permit comparisons with previous experimental results at the same scale. We found that the new dimensionless parameters can describe the whole growth region as initial and later (thermal) respectively. The comparisons showed good agreement in the initial and thermal growth regions. In the initial growth region including surface tension controlled, transition and inertia controlled regions as divided by Robinson and Judd, the bubble growth rate showed that the bubble radius was proportional to $t^{2/3}$ regardless of working fluids and heating conditions. And in the thermal growth region as also called asymptotic region, the bubble showed a growth rate that was proportional to $t^{1/5}$, also. Those growth rates were slower than the growth rates proposed in previous analytical analyses. The required heat flow rate for the volume change of the observed bubble was estimated to be larger than the heat flow rate measured at the wall. Heat, which is different from the instantaneous heat supplied through the heating wall, can be estimated as being transferred through the interface between bubble and liquid even with saturated pool condition. This phenomenon under a saturated pool condition needs to be analyzed and the data from this study can supply the good experimental data with the precise boundary condition (constant wall temperature).

• Maxillofacial Plastic and Reconstructive Surgery
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• 제27권1호
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• pp.24-31
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• 2005

Recently, Platelet rich plasma(PRP) is commonly used because it is now well known that platelets have many functions beyond that of simple hemostasis in aspect of containing autogenous source of several growth factors. It could be responsible for increasing cell mitosis, increasing collagen production, recruiting other cells to the site of injury, initiating vascular ingrowth, and inducing cell differentiation, enhancing bone formation capacity and easily handling to clinician. However, in spite of these clinical advantages, still the theory behind the use of PRP is compelling. This study was to determine preparation techniques used to increase the concentration of platelets and growth factors are all crucial steps in early wound healing of bone graft which may lead to a more rapid and denser bone regenerate. 200 volunteers were sampled and PRP were prepared according to each evaluation item in this study. Higher concentration of platelets have been gained in double centrifugation. 2000 and 2500 rpm showed proper concentration of platelets at first centrifugation and 5000 rpm in second. Timing for 2 minutes was showed good concentration of platelets in high and low centrifugation speed. It was better concentration of platelets in 20 or 30 ml volume during centrifugation. In histomorphologic findings, degrnulated and high concentraion of platelets were found in low centrifugation speed.

• 한국정밀공학회지
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• 제27권8호
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• pp.28-34
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• 2010

Railway wheel and axle is the most critical components in railway system. A wheel and axle failure can cause a derailment with its attendant loss of life and property. The service conditions of railway vehicles have become severe in recent years due to a general increase in operating speeds. Therefore, more precise evaluate of wheelset strength and safety has been desired. Fracture mechanics characteristics such as dynamic fracture toughness, fatigue threshold and charpy impact energy with respect to the tread, plate, disc hole of wheel and the surface of press fitted axle are evaluated. This paper describes the difference of fracture toughness, fatigue crack growth and fatigue threshold at the locations of wheel and axle. The results show that the dynamic fracture toughness, $K_{ID}$, is obviously lower than static fracture toughness, $K_{IC}$ and the fracture mechanics characteristics are difference to the location of wheel tread and hole.