• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.368-373
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• 2017

Control method for DACS with variable burning area is designed and the performance of the control method is analyzed by doing simulation at various conditions. DACS, which got solid propellant on board, is designed as end-burning type typically. End-burning type DACS has the merit of controlling pressure and thrust, but it discharges the combustion gas which does not using for getting thrust. Therefore, optimal design of propellant grain and burning area changes over time as a result. Variable burning area can be assumed as a disturbance and adaptive control method is useful for pressure control of DACS effected by disturbance.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.2
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• pp.240-247
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• 1983

Heritability of flowering date, length of main stem, weight of 100 grains and number of shells per square meter in peanut were high with low local variation. There was positive genotypic correlation between length of main stem and yield, No. of shells per square meter and matured seed ratio, No of shells per square meter and yield 100 grain weight and yield but was negative genotypic correlation between flowering date and yield. With the view of path-coefficients, length of main stem, number of shells per square meter showed highly direct effects at.. all locations.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.2
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• pp.154-158
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• 2013

Expansion joint has been utilized in many areas including automotive bellows for exhaust system. Usage of expansion joint has been increased due to its inherent flexibility and excellent anti-vibration property. Simple shape of expansion joint is modeled to understand the behavior of joint system. 27 design cases using 3 design factors with 3 levels are constructed by design of experiment. Each case is simulated to find the most influential design factors. Response for this study, maximum stress in the expansion joint, has been used to determine main design factors of joint. Among the 3 design factors, factor B has affected greatly a response in the formation of optimum shape of joint. Also, interaction factor, $A{\times}B$, has also showed its influence to the response of joint. This study showed that design of experiment combined with finite element analysis could be used in the design decision process effectively in the design of expansion joint.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.587-592
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• 2008

In order to investigate the performance of an internal heat exchanger for $CO_2$ refrigerant system, the experiment was performed. Four kinds of internal heat exchangers(IHX) were used. The effects on the IHX length, the number of tube, the operating condition and the type of IHX were investigated. With increasing of the IHX length, the capacity and efficiency increased. The pressure drop of the low-side was larger compared with that of the high-side. As the temperature of the gas cooler increased, the capacity and efficiency increased linearly. The operation condition of evaporator was suggested as two phase region rather than superheat region. The capacity and efficiency of the micro-channel was larger about 90% and 75% than those of the tube. But the pressure drop of the micro-channel was more larger, compared with that of the tube.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.204-204
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• 2019

국지성 호우의 증가로 인해 도시 지역의 내수침수피해가 빈번하게 발생하고 있다. 특히 배수의 흐름이 집중되는 저지대 지역과 노후화된 하수관거가 설치된 지역에서 특히 피해가 집중되고 있으며, 이는 도로 측면에 설치된 빗물받이와 같은 하수시설에서 원활하게 배수가 되지 않기 때문에 강우 발생시 도로표면에 노면수가 정체되어 피해가 발생하고 있다. 과거 도로 노면의 형상과 강우의 임계 지속시간을 고려한 적정 우수 유출량 산정에 관한 연구가 진행된 바 있으나, 현재 발생하는 국지성 호우의 형태나 강우강도의 변화에 따른 유출량의 변화가 발생하였으며, 도달시간 산정식에 따른 매개변수의 차이와 새로운 도달시간 산정식의 개발로 도달시간의 결과가 크게 차이가 날 수 있다. 따라서 도로의 침수피해를 막고 교통 안정을 유지하기 위해서는 도로 조건을 고려한 도로 입구 및 하수관의 적절한 설계 등 다양한 연구가 주기적으로 이루어져야 한다. 본 연구에서는 강우 유출 모델인 SWMM 모형과 계산식을 이용하여 도로 표면의 폭과 길이, 도로 종횡단의 변화량, 재 산정한 강우강도에 따른 유출량을 계산하였다. 도로 표면의 폭과 길이, 경사를 다양하게 입력하였으며, 또한 각 Case에 따라 최대 유출량을 생성하는 임계지속기간을 결정하고 다양한 도달시간 산정식의 결과와 비교하여 상관관계를 분석하였다. 분석결과 도달시간은 산정식의 매개변수에 따라 차이가 발생하였으며, 도로표면의 길이와 횡단경사에 크게 영향을 받는 것으로 분석되었으며, 횡단경사보다 종단경사가 클 경우 도달시간이 길어져 유량의 집중을 막는 효과가 있는 것으로 나타났다.

• Journal of Navigation and Port Research
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• v.32 no.8
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• pp.637-643
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• 2008

When planning outfall system, the first target cif design is to maximize initial dilution of discharge effluent. To achieve the target effectively, the characteristics of mixing phenomenon between ambient and discharged water should be analyzed. Especially the analysis at the Near-Field-Region(NFR) as initial dilution zone should be preceded. Usually, the initial behavior of effluent through outfall system is rising toward the surface due to mixing with ambient water for heat discharge and sinking toward the bottom due to the difference of density for brine discharge. After mixed with eddies accompanied by the ambient water, the plumes are showing the same density and internal current pattern by advection and diffusion. Until recently, lots of studies are being carried out for the optimum design of outfall system. but it is difficult to find any studies of heat and brine discharge at the same time. Therefore, this study is hoped to provide some basic data for optimum design of outfall system.

• Journal of Energy Engineering
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• v.25 no.1
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• pp.86-91
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• 2016

Convenient design guideline for Waveguide-below-cutoff (WBC) array is proposed to obtain the minimum waveguide length for electromagnetic pulse (EMP) shielding. The analysis includes circular, rectangular, and hexagonal WBC, determine the total length of the waveguide. When the unit side of rectangular WBC and the diagonal line of hexagonal WBC are given as 30 mm, the length of hexagonal WBC is 5 mm shorter than rectangular case with shielding effectiveness (SE) 80 dB. The length difference is deepened with SE of 100 dB, which shows approximately 30 mm shorter length for hexagonal case than others. In addition, hexagonal WBC requires much shorter length than circular WBC. In conclusion, hexagonal case is the most effective with respect to flow velocity and pressure loss for equivalent SE.

• Horticultural Science & Technology
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• v.18 no.6
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• pp.787-791
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• 2000

Lettuce seedlings used in this investigation of planting distance and labor-saving efficiency were first grown in 100-hole paper trays for 30 days. Seedling height for transplanting ranged from 3 cm to 6 cm and plants had 3 to 5 leaves. The beds prepared for transplanting were of the arched type and were 35-40 cm in width, 15-20 cm in bed height, and between-bed furrow width was 20 30 cm. Typical seedling planting depth with the transplanter was 4-5 cm, although depth was quite variable because of the irregularities of the ground. Total transplanting time with the transplanter varied from 2.6 to 2.7 hours per 10a, while it took 38.1 hours per 10a with conventional planting. It was critical that the condition of both the seedlings and the bed be adjusted to the transplanter before planting. Considering yield and inter-plant distance, optimal transplanter performance resulted with $60{\times}20cm$ or $60{\times}25cm$spacing, and the labor-saving efficiency using the transplanter was improved by over 93% of that of conventional planting by hand.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.11
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• pp.1131-1139
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• 2009

Combustion Instabilities are caused by a coupling between acoustic waves and unsteady heat release. They can be eliminated using passive controller such as a Helmholtz resonator. But, Helmholtz resonator is normally only effective over a narrow frequency range. In this work, Helmholtz resonator is applied for reducing the combustion oscillations and we vary the Helmholtz resonator volume using piston in oder to tune in the wide range of operating conditions. As the result, it is found that the dominant combustion oscillations can be largely reduced by optimizing the size of resonator volume. And, interesting relation for phase difference of dynamic pressure both combustor and the helmholtz resonator are presented in this paper. Also, we investigate semi-active control using Helmholtz equation and phase difference.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.27 no.1
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• pp.87-93
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• 1982

Dihaploid lines derived from the another of the $F_1$ of single cross, SC72 $\times$ Hicks (Nicotiana tabacum L.) were estimated the variation, heritablities, genetic correlations and path-co-efficients on agronomic characters and chemical compositions. Dinaploids exhibited reduced vigor and growth when comparecd with the mid-parent value but had increased nicotine contents, and the range of dihaploids characters were deviated more than that of their parents. Heritabilities of days to flowering, leaves per plant, nicotine. contents, leaf size and plant height appeared high value, and the yield, value per kg. and reducing sugar contents were low. There were positive genetic correlations between yield, and value per kg., leaf width, leaves per plant and reducing sugar contents and negative genetic correlations appeared between nicotine contents and the other characters except for index of leaf shape. Path-coefficient analysis of genotypic correlation coefficients showed that leaves per plant and leaf width lave a high direct effect, and plant height and days to flowering have a high indirect effect on yield, respectively.