• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.5-8
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• 2008

본 연구는 지난 연구에 이어서 핸드피스 터빈 형상에 따른 유동특성 및 성능을 수치해석을 이용하여 연구하였다. 정상상태 방법 중 하나인 프로즌 로터 방식을 이용하여 노즐 중심선과 터빈 로터사이의 여러 각도에 따라 계산하였다. 평평한 모양, 오목한 형상, 갈매기 모양 등 3가지 터빈 로터 형상의 특성을 분석하였다. 추가적으로, 가장 성능이 좋은 로터 모양에 있어서 다른 반사각으로 계산을 하였다.

• Animal cells and systems
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• 제6권1호
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• pp.65-68
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• 2002

Female genital morphology of Cryptocercus Kyebangensis is described, focusing on the structural features of ovipositors at each developmental stage. Ovipositor valves were the first genital structures to appear in female nymphs. The caudal margin of the 9th sternum was nearly straight in the 1st instars of both sexes, with a slight median notch, but was deeply concave in the female nymphs of the End instar. The 1st valve of ovipositor budded off from membranous fold between the 8th 8nd 9th sternum and a pair of the 2nd valve came from the 9th sternum. Separation of styli occurred in the female nymphs of the 8th or 9th instar. Some parts of the female genitalia were sclerotized after the final molt. Spermathecae were the fork type and leaned a little to the right in the middle line of the genital chamber from ventro-posterior view. The trace sealed with sclerite materials existed on the spermathecal opening. The genital segments (segments Ⅷ, IX, and X) were concealed completely by the 7th tergum and sternum posteriorly expanded. Terminal lobes which exist in the Blattidae were not observed in C. Kyebangensis. Instead, the apicolateral emargination existed on the terminal abdominal segment of C. Kyebangensis females.

• Archives of Plastic Surgery
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• 제33권3호
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• pp.379-382
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• 2006

Clinodactyly is defined as an angulation of a digit in the radio-ulnar plane. This anomaly can be congenital, dominantly inherited, or acquired due to trauma or inflammation. Although the deformity usually causes little functional impairment, correction is made because of cosmetic problems. Male subject, with polydactyly on thumb(Wassel's type VII) received first surgery at the age of one. And at the age of six, abnormal growth on the radial side of the first metacarpal bone and ulnar deviation of the distal phalanx of the thumb at the interphalangeal joint had developed. The authors used the growing bony segment from the first metacarpal bone as a bone graft for the correction of clinodactyly on thumb. Z-plasty incision was made on the concave(ulnar) side of thumb and a wedge osteotomy was made on the distal phalanx. The bone graft was inserted into the gap of the distal phalanx of the thumb and fixed it with K-wires. Deformity of the metacarpal bone and clinodactyly on thumb was corrected effectively without donor site morbidity with noticible growth of the grafted metacarpal bone 12 months after surgery.

• 한국결정성장학회지
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• 제9권4호
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• pp.402-416
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• 1999

The thermal distributions near the growth interface of 150nm CZ crystals were measured by three thermocouples installed at the center, middle (half radius) and edge (10nm from surface) of the crystals. The results show that larger growth rates produced smaller thermal gradients. This contradicts the widely used heat flux balance equation. Using this fact, it is confirmed in CZ crystals that the type of point defects created is determined by the value of the thermal gradient(G) near the interface during growth, as already reported for FZ crystals. Although depending on the growth systems the effective length of the thermal gradient for defect generation are varied, we defined the effective length as 10n,\m from th interface in this experiment. If the G is roughly smaller than 20C/cm, vacancy rich CZ crystals are produced. If G is larger than 25C/cm, the species of point defects changes dramatically from vacancies to interstitials. The experimental results after detaching FZ and CZ crystals from the melt show that growth interfaces are filled with vacancies. We propose that large G produces shrunk lattice spacing and in order to relax such lattice excess interstitials are necessary. Such interstitials recombine with vacancies which were generated at the growth interface, nest occupy interstitial sites and residuals aggregate themselves to make stacking faults and dislocation loops during cooling. The shape of the growth interface is also determined by te distributions of G across the interface. That is, the small G and the large G in the center induce concave and convex interfaces to the melts, respectively.

• 한국조경학회지
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• 제27권4호
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• pp.39-49
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• 1999

Urban streams have, recently, been straightened and widened to alleviate flooding problem. As a result, the stream have been modified inadvertently for ecological functions and microtopography. In this study, we investigated riparian vegetation and microtopography of the tributaries of Han River before and after the monsoon rain in summer. The purpose of this study was to relate the stream microtopography to the distribution of riparian vegetation. The stream microtopography was investigated for its scale and pattern. Vegetation was investigated from 131 plots by Braun-Blanquet method. The distribution of riparian vegetation was significantly correlated with the stream microtopography. Various herbaceous species occurred at stream bank slop, high terrace and channel side. However, at channel side and concave part of terrace where soils were in high moisture level, only a few wetland species were dominated. The complexity of the microtopography in the stream corridors led to heterogeneous riparian vegetation. The vegetation showed more stability against flooding at the stream corridors with natural and complex microtopography than at the urban-type stream corridors with simple topographical features. The results showed that the development of riparian vegetation was influenced by the changes in microtopography, which was primarily determined by the shape and characteristics of channel. It seemed that a close-to-nature river system would be restored more readily with an understanding of microtopographical features affecting the distribution of riparian vegetation.

• 한국자동차공학회논문집
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• 제14권2호
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• pp.166-173
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• 2006

This study investigates a heavy duty diesel engine with swept vol. 12.6L, 4cycle-OHC type to verify the effects of the performance and exhaust gas emission according to the variable specifications of both swirl ratio and flow coefficient in inlet port, combustion bowl and fuel injection system. To meet the high BMEP and stringent exhaust emission standard, a turbocharger with wastegate and an intercooler were installed in the engine. Helical port, major design parameters for combustion chamber and electronic fuel injection pump with 1,000bar were reviewed and applied. Confirmation tests were also performed to meet the target value, $NO_x$ 5.0g/kWh and PM 0.1g/kWh of Euro3 exhaust emission legislation. The results of this study show that not only is it effective to use a relatively bigger bowl size for controlling rapid burning condition due to the decreased in-bowl swirl, but also to use a concave cam with double injection rates to decrease $NO_x$.

• 한국가시화정보학회지
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• 제18권2호
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• pp.10-17
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• 2020

The curvature of wound boundaries has been identified as a key modulator that determines a type of force responsible for cell migration. While several studies report how certain curvatures of the boundary correlate with the rate at which the wound closes, it remains unclear how these curvatures are spatiotemporally formed to regulate the healing process. We investigated the dynamic changes in the boundary curvatures by visualizing cell migration patterns. Locally, cells at the convex boundary continuously move forward with transmitting kinetic responses behind to the cells away from the boundary, and cells at the concave boundary exhibit dramatic contracting motion, like a purse-string, when they accumulate enough negative curvatures to gain the thrust toward the void. Globally, the dynamics of boundary geometries are controlled by the diffusive flow of cells driven by the density gradient between the wound area and the cell layer.

• 한국자동차공학회논문집
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• 제8권5호
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• pp.78-85
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• 2000

This study is to develop the diesel engine which has 6 cylinder natural aspiration direct injection type of 7.4$\ell$ with high performance, low emissions and low fuel consumption Finally the developed engine meets Korean `98 exhaust emission regulation for the city bus of heavy duty diesel engine by optimizing the various combustion parameters affecting performance and exhaust emissions. Combustion parameters are the swirl ratio of intake ports, the profile of injection pump`s cam affecting injection pressure, the design features of piston bowl of injection pump`s cam affecting injection pressure, the design features of piston bowl of combustion chamber and injector`s hole size. Through experimental analysis, various combustion parameters are optimized and the results are as follows; the swirl ratio is 2.20, the profile of injection pump`s cam is concave and re-entrant ratio, inner diameter of piston bowl and hole diameter of injector is 0.88,$\psi$64.0mm and $\psi$0.25mm respectively.

• 산업경영시스템학회지
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• 제41권1호
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• pp.110-117
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• 2018

Machines and facilities are physically or chemically degenerated by continuous usage. One of the results of this degeneration is the process mean shift. By the result of degeneration, non-conforming products and malfunction of machine occur. Therefore a periodic preventive resetting the process is necessary. This type of preventive action is called 'preventive maintenance policy.' Preventive maintenance presupposes that the preventive (resetting the process) cost is smaller than the cost of failure caused by the malfunction of machine. The process mean shift problem is a field of preventive maintenance. This field deals the interrelationship between the quality cost and the process resetting cost before machine breaks down. Quality cost is the sum of the non-conforming item cost and quality loss cost. Quality loss cost is due to the deviation between the quality characteristics from the target value. Under the process mean shift, the quality cost is increasing continuously whereas the process resetting cost is constant value. The objective function is total costs per unit wear, the decision variables are the wear limit (resetting period) and the initial process mean. Comparing the previous studies, we set the process variance as an increasing concave function and set the quality loss function as Cpm+ simultaneously. In the Cpm+, loss function has different cost coefficients according to the direction of the quality characteristics from target value. A numerical example is presented.

• 한국주조공학회지
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• 제14권1호
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• pp.28-34
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• 1994

Metallurgical-grade polycrystalline silicon was directionally solidified at growth rates of $0.2{\sim}1.0mm/min$ by using split type, reusable graphite molds which were coated with $Si_3N_4$ powder. The resultant grain sizes of the silicon ingots and the shapes of the solid/liquid(S/L) interfaces were investigated. X-ray diffraction was used to determine the preferred orientation in each of the silicon ingots. The impurity content of the silicon was analyzed and the resistivities of the ingots were measured. During the growth of an ingot, the shape of the S/L interface was concave to the silicon melt, and the resistivity decreased. The presence of Al which can be acting as a carrier, is thought to be the main factor causing such a decrease in resistivity. When a growth rate of 0.2㎜/min was used, the preferred orientation was found to be (111).