• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.10a
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• pp.231-237
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• 1994

컴퓨터의 눈부신 발달에 힙입어 실험 또는 해석적 방법으로 일반 구조물이나 기계구조물의 진동특성을 손쉽고 정확하게 파악하는 것이 가능하게 되었다. 그런데 최근의 산업현장은 지금까지의 정확한 구조해석에만 그치지 않고 이를 바탕으로 강도 개선, 재료 절감을 통한 원가절감, 중량 최소화 문제등의 차원에서 동적인 특성의 변경을 요구하고 있다. 이러한 문제는 그 중요성에도 불구하고 여전히 설계자의 경험이나 시행착오에 의존하고 있는 실정이다. 본 연구에서는 구조물 결합부분에 주목하여 동특성의 변경 문제를 해석하고자 하였다. 즉 거의 모든 구조물이 결합부를 가지고 있는데 결합부 특성을 정확히 파악할 수 없기 때문에 리벳이나 보울트나 어떤 특수한 형태 결합부가 구조물의 특성에 주는 영향을 예측하기 어렵다. 이러한 결합부이 특성을 알아내고 구조물 동특성 변경 및 개선안을 제시하는 최적설계를 위해 감도해석기법은 아주 유효하게 쓰일 수 있다. 한편 구조물의 대형화, 복잡화는 구조물 동특성 해석에 더욱 많은 계산시간과 용량이 큰 전자계산기를 필요로 하게 되었으며, 분계의 결합부위가 변경되거나 결합형태가 변했을 때 전계의 동특성을 다시 해석할 필요없이 분계만의 정보로부터 전계의 동특성을 알아낼 필요가 생겼다. 이러한 의미에서 구조물의 분계로부터 전계의 동특성을 해석을 위한 부분구조합성법이 대두되게 되었다. 본 연구에서는 이러한 감도해석과 부분구조합성법의 공통된 문제를 일치화하고자 하였다. 즉 감도해석기법을 이용하여 필요한 구조물의 동특성에 부합하는 결합부의 최적한 설계변수를 규명하였고 이렇게 구해진 결합부의 설계변수와 분계의 정보를 알고리즘이 비교적 간단하고 오차가 적은 축소임피던스 합성법에 적용하여 전계의 동특성을 해석함으로써 감도해석기법과 축소임피던스 합성법의 통합적용이 최적설계와 이에 따른 동특성 해석에 효과적인 방법임을 보이고자 하였다. 대상구조물은 구조물 결합의 기본적인 형태인 T형을 선택하였다. T형 구조물은 분계 A(16개의 사각요소)와 분계 B(8개의 사각요소)로 이루어져 있으며 두개의 스프링으로 결합되어 있다. 설계변수는 강성에 국한하였으며 결합부의 결합형태는 탄성결합과 강결합으로 하였다. 감도해석과 축소임피던스 합성법에 의해 구해진 고유진동수와 FRF를 상용 유한 요소 해석 패키지인 MSC/NASTRAN을 통하여 검증하여 이 연구의 타당성을 검토하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.8
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• pp.3625-3630
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• 2013

The modularization accomplished a big contribution in cost down and assembly-time shortening and the quality increase. But few improvements were made to this design largely due to the inflexibility of steel. In recent years, door modules made of PP-LFT material is manufactured using injection molding method. As a result, the plastic door modules allow more flexibility of door shape and become lighter. Warpage is generally large in the molded plastic door carrier plate due to the limitation of gate location and the fiber orientation. So after a few test injection the mold compensation processing for the improvement of an assembly characteristic. This research was performed to determine the factors that contribute to warpage for a injection-molded door carrier plate and presented differences in three mesh types of meshing method and its results. as a result we can improve process of tooling modification can reduce process of trial and error.

• Journal of Korean Society of Steel Construction
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• v.24 no.3
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• pp.313-323
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• 2012

The purpose of this study is to evaluate $CO_2$ reduction and the flexural performance of steel wire-integrated void deck plate slabs that were inserted in omega-shaped steel plates to reduce concrete and welded H-section beams. The void deck plate slab can secure the structure, not only reducing the weight of the building but it is also eco-friendly. Therefore, this study evaluated the flexural performance of the composite beam by conducting a monotonic loading test with the use of actuators. It quantitatively evaluated the $CO_2$ emission based on earlier studies. The main test parameters are the concrete thickness of upper slabs, and the interrupted width of the omega-shaped steel plate. The result of the test showed that the welded H-section beam applied steel wire-integrated void deck plate slabs that were inserted into the omega-shaped steel plate declined in flexural performance on the composite beam after reducing concrete volume. Likewise, it is effective in reducing $CO_2$.

• Solar Energy
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• v.16 no.2
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• pp.97-112
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• 1996

The purpose of research is to complement the circulating pump of gas boiler for the domestic and to develop a pump housing with internal three way valve: Housing and three way valve have been apart in the existing pump system. Based on the experimental result on can-typed circulating pump with existing housing, a new housing with internal three way valve was designed and manufactured. The performance of can-typed circulating pump with the new housing, and the performance of circulating pump of boiler system were tested. As a result ot the test, the new housing with internal three way valve has been excellent in respect of pump performance, weight and manufacturing cost. So It is expected to have an effect of import substitution.

• Journal of the Korean Institute of Landscape Architecture
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• v.37 no.5
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• pp.98-108
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• 2009

The purpose of this study is to analyze the characteristics of limited methods, economics and breeding appropriateness of native and imported ground cover plants in the methodology of a shallow soil rooftop garden. The new shallow soil rooftop gardening method uses a total of 13cm in soil thickness, including 4.5cm of top soil on a 7.5cm rock-wool-mat stacked onto a 1cm roll-type-draining plate. The total construction cost for each method of soil level within the design price standard for SEDUM BLOCK is 89,433won/$m^2$, and for DAKU is 92,550won/$m^2$. By comparing those two methods, the construction cost of the shallow soil artificial foundation methodology is 45,000won/$m^2$; this shows the new method is 50% less expensive than the existing method of shallow soil rooftop gardening. The experiment was executed on the rooftop of the Korean National Housing Corporation to ensure validity of the shallow soil artificial foundation planting, and the sample plants which were imported and grown now in native covering. A list investigating the growing plants was made of the cover rate in each plant class, both while alive and the dry plant weight. The native ground cover plants, Sedum kamtschaticum, Sedum middendorffianum, Allium senescens, Sedum sarmentosum, Aquilegia buergariana, and Caryopteris incana increased the cover rate, live weight and dry weight in the shallow soil artificial foundation method. Among the imported cover plants, Sedum sprium and Sedum reflexum, the cover rate increased and growth conditions improved. However, some species needed weed maintenance. After examination with the less expensive shallow soil artificial foundation method and growth analysis, it was found that rooftop gardens are a low-cost option and the growth of plants is great. This result shows the new method can contribute to the proliferation of rooftop gardens in urban settings.

• Korean Journal of Agricultural Science
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• v.15 no.2
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• pp.143-152
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• 1988

This study was conducted to obtain basic data which affected engine performance of the power tiller being widely used in the rural area. Among the various factors affected engine performance, only flywheel weight was considered as the major factor in this study. Fuel consumption ratio, motoring loss, torque, vibration and mechanical efficiency of the engine tested were measured and analyzed on the four levels of flywheel weight (32.2, 29.7, 26.4, 24.2 kg). The results obtained were as follows: 1. The maximum output of 6 and 7.5 kW engine was 7.43 kW and 7.85 kW respectively. When flywheel weight was reduced from 32.2 kg to 24.2 kg, output power of the engine was increased 0.27 kW in 6 kW engine and increased 0.39 kW in 7.5 kW engine. 2. The fuel consumption ratio was decreased from 300.8 to 296.8 g/kW-hr in 6 kW engine and decreased from 313.6 to 312.8 g/kW-hr in 7.5 kW engine when the flywheel weight was reduced from 32.2 kg to 24.2 kg. 3. The mechanical efficiencies of the engine was increased from 76.1 to 76.8% in 6 kW engine and increased from 76.7 to 77.0% in 7.5 kW engine when the flywheel weight was reduced from 32.2 kg to 24.2 kg. 4. When the flywheel weight was reduced from 32.2 kg to 24.2 kg, a tendency of a little decrease of vibration at X- and Z-axis in 6 kW engine and of a little increase of vibration at Y-axis in 6 kW engine and all directions in 7.5 kW engine was observed. 5. Motoring losses was decreased from 2.33 to l.76 kW in 6 kW engine and decreased from 2.46 to 1.84 kW in 7.5 kW engine when the flywheel weight was reduced from 32.2 kg to 24.2 kg. From the above results and the flywheel weight calculated theoretically, it was recommendable that the flywheel weight should be reduced about 7 kg in 6 kW engine and about 10 kg in 7.5 kW engine, respectively.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.250-251
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• 2023

The pallet, typically a form of tertiary packaging, is a flat structure used as a base for the unitization of goods in the supply chain. In addition, standard pallets such as T-11 and T-12 are used throughout the logistics industry to reduce the cost and enhance the efficiency of transportation. However, in the case of special cargo, it is impossible to handle such cargo using a standard pallet due to its size and weight, so many have developed and are now using their customized pallet. Therefore, this study suggests a pallet size optimization method to calculate the optimal pallet size, which minimizes the loss of space on a pallet. The main input features are the specifications and the storage quantity of each cargo, and the optimization method that has modified the Neighborhood Search Algorithm calculates the optimal pallet size. In order to verify the optimality of the developed algorithm, a comparative analysis has been conducted through simulation.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• v.11 no.2
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• pp.261-265
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• 2006

가. 젖소분을 이용하여 관행사육과 상자사육방식을 비교한 결과 단위면적당 3,000g(15${\times}$15${\times}$30,cm)으로 관행방식과 차이가 없었다. 나. 지렁이의 수직분포는 15cm이상에 대부분 분포하고 있었으나 관행방식은 0 ${\sim}$ 10cm에서 고르게 분포되어 있었으나 상자사육에서는 0 ${\sim}$ 5cm에 70%이상이 분포되어 기계화 채취에 적합한 것으로 판단되었다. 다. 분변토 분리 및 배출시험을 위하여 로드셀을 켈리브레이션 하였으며 이때 출력전압(v)과 중량과의 회귀관계는 Y = 0.004X + 1.0995로 나타났다. 라. 분변토 분리 및 배출 시험을 한 결과 축분처리상자를 개량전에는 분리 및 배출장치의 압축력이 평균 1.2kg/cm$^{2}$, 1.4kg/cm$^{2}$로 나타났으며 축분처리상자의 배출구를 1cm 높이고 폭을 10cm 줄여 개량후 배출장치의 압축력이 평균 0.6kg/cm$^{2}$, 0.5kg/cm$^{2}$로 압축력을 50%, 64%절감 시킬 수 있었다.

• Journal of Aquaculture
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• v.13 no.3
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• pp.239-244
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• 2000

To test survival growth of juvenile abalone, five different diet were constituted. Diet 1, the control, was constituted with white fish meal (15%), soybean meal (25%) and wheat flour (25%); diets 2,3 and 4 were constituted to replace each one of these ingradietns by supplementing Sargossum powder (upto 10 %) and the fifth one by Undularia powder. Survival of these abalones differed significantly. Diet 4 supported the fastest growth. There was no significant difference in the composition of these abalones hence Sargassum can be used as a substitute.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.6
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• pp.72-86
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• 2019

SpaceX is currently leading the global launch market with the successful launch and recovery of Falcon 9 v1.2 Block 5. SpaceX developed Merlin engine, a kerosene gas generator engine, and continuously upgraded the engine from Falcon 1 to Falcon Heavy to increase payload weight. SpaceX suffered a lot of failures early on, but with the help of NASA, it was possible to overcome many crises and develop vehicles. In addition, it successfully developed reusable vehicles, which drastically reduced operating costs. Subsequent launch vehicles in Korea also need to be developed with reference to SpaceX's development strategy.