• 한국작물학회지
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• 제51권1호
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• pp.41-47
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• 2006

To understand the heading habit of recently developed 20 Korean rice cultivars, rice plants in a phytotron were exposed to different temperature: $22.5^{\circ}C(day\;27^{\circ}C/night\;18^{\circ}C),\;27.5^{\circ}C(day\;32^{\circ}C/night\;23^{\circ}C)$, and day-length conditions: 10, 12, 13, 14, 15 hours. Four rice cultivars (Sobibyeo, Juanbyeo, Ilpumbyeo and Shindongjinbyeo) showed relatively short Basic Vegetative Phase (BVP) of 17 to 18 days, while Dasanbyeo showed the longest (35 days) BVP, compared to other remaining 15 tested cultivars which exhibited 24 to 31 days of BVP. In this experiment, it was tried out to separate the eliminable vegetative phase into photosensitivity and thermo-sensitivity with two different pathways. Many tested cultivars, however, exhibited quite different responses under low temperature and / or long day-length conditions. Especially, Surabyeo and Juanbyeo were the most difficult cultivars to separate into photo- or thermo-sensitivity in that the eliminable vegetative phase of these two cultivars increased greatly only under low temperature $(22.5^{\circ}C)$ and long day-length (15 hr.) conditions. Regarding the heading response to temperatures, tested cultivars could be categorized into 2 groups. In 1st group of rice cultivars, the eliminable vegetative phase decreased almost equally as the temperature changed from $20.0^{\circ}C\rightarrow22.5^{\circ}C\rightarrow25.0^{\circ}C\rightarrow27.5^{\circ}C$. In contrast, the 2nd group of rice cultivars exhibited eliminable vegetative phase slowly decreasing when the temperature changed from $22.5^{\circ}C\rightarrow25.0^{\circ}C\rightarrow27.5^{\circ}C$, but rapidly decreasing when the mean temperature changed from $20.0^{\circ}C\;to\;22.5^{\circ}C$. All the cultivars belonged to 2nd group, the heading date would be very delayed if cool summer comes.

• 대한토목학회논문집
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• 제30권1D호
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• pp.71-77
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• 2010

본 연구는 독일의 WRITH사에서 개발된 장비로 수행한 TBM 수로터널 현장을 대상으로 TBM굴진(A), 커터 점검 및 교환(B), TBM 점검 및 급유(C), TBM 정비(D), 후속설비(E), 갱내보강(F), 운영교대(G), 광차(H)의 8개의 분석작업 항목별로 생산성 분석을 통한 효율성 개선 방안을 제시하였다. 제시된 결과를 가지고 각 항목별로 차지하는 손실시간을 추적하고, 이 손실시간을 제거하여 TBM 순굴진이 차지하는 시간과 백분율 그리고 월굴진장을 분석하였다. 또한, TBM운영 굴진율, 월평균굴진장(m), 순굴진율(%) 등을 외국현장의 TBM 운영 효율성의 비교 분석을 통한 상승예상 월평균 굴진장 추정과 독일의 WRITH사에서 표준치로 제시한 월평균 굴진장을 비교 분석하고, 5개의 수로터널현장 평균 암질의 압축강도 $675{\sim}1662kgf/cm^2$에서의 적정 TBM 순굴진장을 예측하였다.

• 소성∙가공
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• 제10권4호
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• pp.302-310
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• 2001

The twisting and extrusion process of the product with involute helical fin from the round billet is developed by the upper bound analysis. The twisting of extruded product is caused by the twisted inclined die surface connecting the die enterance section and the die exit section linearly. In the analysis, the internal shear surface is defined as the curved twisted plane from the twisting of die surface and the shear work is calculated by the consumption of shear energy. The increase rate of angular velocity is determined by the minimization of plastic work. The angular velocity of die exit can be controlled by the land length and the length of inclined die. The alular velocity assums to be increased linearly by the axial distance from the die enterance to the die exit. The results of the analysis show that the angular velocity of the extruded product increases with the die twisting angle, the reduction of area, and decreases with the die length, the friction constant.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 정보화시공 학술발표회
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• pp.61-78
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• 2001

Various kind of fiber optic gauge sensors are available that can be bonded to civil engineering structures such as bridges, dams, tunnels and pipelines. A new fiber optic long gauge has significant advantages over other fiber optic sensors. These gauges can vary in length from less than 10 cm up to 30 m and provide the structural engineer with accurate measurements of displacement. These displacements can be converted to strains by dividing the measurement by the long gauge length. Using new optical technology, the long gauge instrument developed by FOX-TEK can choose max. 30 meters of gauge length so as to measure the very early stress/strain correlation curve. And this gauge length to be extended up to 100 meter in 2002.

• 대한산업공학회지
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• 제28권2호
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• pp.128-138
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• 2002

In this paper, we address how to reduce the length of tool retraction in a zigzag pocket machining. Tool retraction, in a zigzag pocket machining, is a non-cutting operation in which the tool moves to any remaining regions for machining. We developed an algorithm of generating tool retraction length in convex or concave polygonal shapes including islands. In the algorithm, we consider concave areas of cutting direction in the polygonal shape. Considering concave areas of cutting direction, the polygonal shape is decomposed to subregions which do not need any tool retraction. Using the proposed algorithm, we calculated the shortest length of tool retraction in cutting direction. Examples are shown to verify the validity of the algorithm.

• 조명전기설비학회논문지
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• 제24권12호
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• pp.164-170
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• 2010

For the surge currents like lightning or ground fault currents containing high frequency components which cause the electromagnetic interferences for the electronic devices and communication equipment, the grounding impedances give the significantly composite characteristics which are dependent on the frequency of surge currents. In this paper, the analytical model and method for determining the optimal length of the newly developed coaxial type carbon ground electrode which has a little fluctuation in grounding impedance with frequency. The length of minimizing the fluctuation of grounding impedance by changing frequency from 100[Hz] to 1[MHz] was determined, and the validity of this proposed method was confirmed by comparing with the simulated and measured data.

• 대한수학회지
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• 제38권4호
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• pp.807-842
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• 2001

This paper summarizes recent development of analytical and algorithmical results for stationary FIFO queues with multiple Markovian arrival streams, where service time distributions are general and they may differ for different arrival streams. While this kind of queues naturally arises in considering queues with a superposition of independent phase-type arrivals, the conventional approach based on the queue length dynamics (i.e., M/G/1 pradigm) is not applicable to this kind of queues. On the contrary, the workload process has a Markovian property, so that it is analytically tractable. This paper first reviews the results for the stationary distributions of the amount of work-in-system, actual waiting time and sojourn time, all of which were obtained in the last six years by the author. Further this paper shows an alternative approach, recently developed by the author, to analyze the joint queue length distribution based on the waiting time distribution. An emphasis is placed on how to construct a numerically feasible recursion to compute the stationary queue length mass function.

• 한국분무공학회지
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• 제6권3호
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• pp.17-22
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• 2001

Recently LPG engine is developed to fulfill such new requirements as improved fuel efficiency in additional to further reduced exhaust emission. This experimental study is conducted to analyze spray characteristics for pintle type injector used in a LPLi (Liquid Phase LPG injection) engine. Since spray parameters including penetration length and spray angle make a role to design injector and engine intake system, spray visualization experiment is performed under atmosphere ambient and charging condition using Mie scattering method. From the experimental result under various LPG formation, the increased propane component decreases penetration length because boiling point of propane is lower than butane. To simulate intake charging condition in MPI engine, spray visualization is performed under high pressure condition. As a result, as ambient pressure is increased from atmosphere to 3.0 bar, penetration length is decreased. However, as ambient pressure is increased from atmosphere to 3.0 bar, spray angle is increased.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.125-128
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• 2005

Recently new materials, such as fiber reinforced polymer(FRP) and other composite materials are being applied in reinforcing plate or plate or prestressing cables of concrete structures. Although these new materials themselves show the excellent durability and high strength, the bond behaviour between concrete surface and FRP is not well recognized. Therefore, this paper propose a evaluation method for effective bond length between fiber reinforced polymer(FRP) and concrete. To develop the evaluation method, this paper presents a review of current evaluation methods for effective bond length. These methods are compared by single face test, expose merits and demerits. And based on them, new evaluation method was developed. Finally, the new method was compared with existing methods to verify a adequateness for evaluation of effective bond length.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.454-457
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• 2006

This study presents a strut-and-tie model for the development of headed bars in an exterior beam-column joint with transverse reinforcements. The tensile force of a headed bar is considered to be developed by head bearing together with bond along a bonded length as a partial embedment length. The model requires construction of struts with biaxially compressed nodal zones for head bearing and fan-shaped stress fields against neighboring nodal zones for bond stresses along the bonded length. Due to the existence of transverse reinforcements, the fan-shaped stress fields are divided into direct and indirect fan-shaped stress fields. A required development length and head size of a headed bar can be optimally designed by adjusting a proportion between a bond contribution and bearing contribution.