• 전자공학회논문지D
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• 제35D권12호
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• pp.1-11
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• 1998

고속펄스 전송을 위한 다중결합된 마이크로스트립 신호버스에서 제일 근접한 선로상에 유기되는 누화피크치를 최소화시키기 위해 선로자태를 합성시키는 방법을 제안하였다. 평행하게 배열된 데이터버스에서 구동선로로부터의 누화에너지는 가장 근접한 선로에 거의 집중되므로 반사파 제어를 위한 최적화기법을 통해 선로간의 평균간격을 늘리는 방법을 채택하였다. 입출력 파형예측을 위해 일반화된 S-행렬 기법을 적용하였으며 선로간의 평균간격을 늘리기 위해 합성된 다양한 형태의 비일정선로의 누화특성을 비교 분석하였다. 그 결과 펄스가 갖는 주파수 범위내에서 스펙트럼을 고르게 반사시키게 하는, dip을 갖는 쳬비셰프형 테이퍼가 입출력 파형의 보전성에 큰 영향을 주지 않는 범위내에서 누화피크치를 최소로 함을 볼 수 있었다.

• Structural Engineering and Mechanics
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• 제20권1호
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• pp.1-20
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• 2005

The present paper deals with the seismic response analysis and the evaluation of most likely failure modes for a water storage structure. For the stress analysis, a 3-D mathematical model has been adopted to represent the structure appropriately. The structure has been analyzed for both static and seismic loads. Seismic analysis has been carried out considering the hydrodynamic effects of the contained water. Based on the stress analyses results, the most likely failure modes viz. tensile cracking and compressive crushing of concrete for the various structural elements; caused by the seismic event have been investigated. Further an attempt has also been made to quantify the initial leakage rate and average emptying time for the structure during seismic event after evaluating the various crack parameters viz. crack-width and crack-spacing at the locations of interest. The results are presented with reference to peak ground acceleration (PGA) of the seismic event. It has been observed that, an increase in PGA would result in significant increase in stresses and crack width in the various structural members. Significant increase in initial leakage rate and decrease in average emptying time for the structure has also been observed with the increase in PGA.

• 터널과지하공간
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• 제32권6호
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• pp.386-396
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• 2022

로드헤더에 미치는 변수의 영향력을 분석하기 위해 픽커터 절삭시험 관련 참고문헌들을 조사하였고, 수록된 데이터들을 수집하였다. 입력 인자는 일축압축강도, 절삭 깊이, 절삭 간격, 받음각, 비틀림각, 출력 인자는 비에너지, 절삭력, 수직력으로 결정했다. 입력 인자와 출력 인자로 분류 후 실험계획법을 작성하였고 분산분석을 이용해 변수들에 대한 기여도를 조사하였다. 그 결과, 절삭력과 비에너지에 가장 큰 영향을 미치는 요인은 일축압축강도와 절삭 간격으로 분석되었다.

• 한국농공학회논문집
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• 제54권4호
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• pp.29-38
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• 2012

Drip irrigation is a affordable irrigation under structured cultivation. Drip irrigation system with high uniformity can be achieved through effective design, maintenance and management of irrigation systems. Nevertheless the design guidelines have not been established for the drip irrigation system products in domestic and imported considering cultivation method and greenhouse environment in Korea. The objectives of this study were to evaluate the performance of drip irrigation system with uniformity through an experiment. The experiment was conducted to study with nine different types of emitters produced in domestic and imported. Hazen-Williams coefficients were also estimated for the drip emitter through hydraulic simulation for design use. It was found that approximately 91.5 % for 10 cm emitter spacing and 96.2 % for 30 cm emitter spacing of statistical uniformity were observed in respectively. Average emission uniformity was decreased as the reduction of emitter spacing. The results would be used in the drip irrigation system design and guideline construction.

• 한국주조공학회지
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• 제31권4호
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• pp.191-197
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• 2011

Transparent organic materials have been frequently used as an analog of the solidifying metallic materials, because their transparency permits an in-situ observation of the microstructural development during solidification through optical microscopy. Pivalic acid (PVA)-ethanol system showing an anisotropic property in solid-liquid interfacial energy and interface kinetics was adopted in the present experiment, and the detailed experiments performed are as follows: (1) variation of dendrite tip temperature with growth velocity, (2) correlation between primary dendrite arm spacing (${\lambda}_1$) and the growth orientation away from the heat flow direction (tilt angle: ${\theta}$), (3) variation of dendrite tip radius (R) with growth velocity (V), (4) dendrite tip stability parameter (${\sigma}^*$) and its dependence on the concentration. Concerning the correlation between the dendrite tip temperature and growth velocity the present result is well suited to Hunt-Lu equation. As the tilt angle increases, the average primary dendrite spacing tends to increase.

• 대한기계학회논문집B
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• 제21권9호
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• pp.1115-1125
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• 1997

Experiments have been conducted to obtain local and average heat transfer coefficients associated with impingement of a row of circular, free surface-water jets on a constant heat flux surface. Nozzle arrays are a row of 3 jets (nozzle dia.=4.6 mm) and a row of 5 jets (nozzle dia.=3.6 mm), and the nozzle configuration is Reverse cone type revealed good performance in heat transfer. Nozzle-to-plate spacings ranging from 16 mm to 80 mm were investigated for two jet center to center spacings 25 mm and 37.5 mm in the jet velocity of 3 m/s (R $e_{D}$=27000) to 8 m/s (R $e_{D}$=70000). For a row of 3 jets and a row of 5 jets, the stagnation heat transfer of the central jet is lower than that of adjacent jets. In the wall jet region between jets, for small nozzle-to-plate spacing and large jet velocity, the local maximum in the Nusselt number was observed, however, for small jet velocity or large nozzle-to-plate spacing, the local maximum was not observed. Except for the condition of $V_{O}$=8 m/s and H/D=10, the average Nusselt number reveals the following ranking: a row of 5 jets, a row of 3 jets, single jet. For a row of 3 jet, the maximum average Nusselt number occurs at H/D=8 ~ 10, and for a row of 5 jets, it occurs at H/D=2 ~ 4. Compared with the single jet, enhancement of average heat transfer for a row of 3 jets is approximately 1.52 ~ 2.28 times, and 1.69 ~ 3.75 times for a row of 5 jets.ets.s.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.67-68
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• 2010

균열폭의 산정에 부착응력 및 균열간격 등 다양한 인자들이 영향을 미친다. EC2 및 MC90에서는 이러한 인자를 고려하여 최대 균열간격과 평균 변형률 차의 함수로서 균열폭을 제시하고 있다. 본 연구에서는 각 설계기준에 따라 균열폭을 예측하고 이를 실험결과와 비교, 분석하였다. 해석 결과 각 설계기준에 따른 균열폭 예측식은 실험값을 비교적 잘 예측하고 있음을 보여주었다.

• 한국산업융합학회 논문집
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• 제12권1호
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• pp.11-18
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• 2009

The air flow and heat transfer characteristics of an air jet impinging on a pedestal heat source has been investigated numerically to examine the effects of geometric parameters such as nozzle-to-pedestal spacing, nozzle diameter and pedestal size. Also, the parameters of Reynolds number, air jet power, supplied heat and thermal conductivity of pedestal have been studied to reveal how these affect the average Nusselt number. Hence, a two-dimensional turbulent model has been developed and adopted to simulate the fluid flow and heat transfer phenomena numerically. The results obtained from the model show that the nozzle-to-pedestal spacing, relative size of nozzle to pedestal and Reynolds number of air jet have a significant influence on the cooling characteristics of heated pedestal. Furthermore, some useful guidelines could be given to the application of cooling the heated pedestal.

• ETRI Journal
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• 제34권3호
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• pp.319-329
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• 2012

Closed-loop transmit diversity is considered an important technique for improving the link budget in the third generation and future wireless communication standards. This paper proposes several transmit diversity algorithms suitable for small wireless terminals and presents performance assessment in terms of average signal-to-noise ratio (SNR) and outage improvement, convergence, and complexity of operations. The algorithms presented herein are verified using data from measured indoor channels with variable antenna spacing and the results explained using measured radiation patterns for a two-element array. It is shown that for a two-element array, the best among the proposed techniques provides SNR improvement of about 3 dB in a tightly spaced array (inter-element spacing of 0.1 wavelength at 2 GHz) typical of small wireless devices. Additionally, these techniques are shown to perform significantly better than a single antenna device in an indoor channel considering realistic values of latency and propagation errors.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.501-508
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• 2002

The percentage of a mountainous district in our country is comparatively high but the concern for rock mass has been disregarded for a long time. Especially for rock slope, the most important factors are geometric characteristics and their shear strength parameter. In this paper, parametric studies are performed using the distinct element computer program UDEC-BB for rock slopes. Parameters adopted in this paper are joint angle, spacing, persistence, aperture and shear strength parameters (JRC, JCS, basic friction angle). To estimate slope stability, shear strength reduction method is used. The most important factors affecting rock slope stability are joint angle and spacing. The relationship between average displacement calculated by UDEC-BB and safe factor by shear strength reduction method is researched.