• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.185-190
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• 2007

For the successful design of heat exchangers, it is very important to understand local heat transfer characteristics on the circular cylinder of the cross flow heat exchangers. In this study, the heat exchanger using screen is developed to enhance heat transfer. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients in the heat exchanger. The experiments are performed for single circular tube, in-line array tube bank with and without heat transfer promoter. Local Nusselt numbers of single circular tube and tube bank with heat transfer promoter are investigated and compared to those of without heat transfer promoter.

• ETRI Journal
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• 제32권4호
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• pp.548-554
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• 2010

The transcutaneous energy transmission system (TETS) composed of a Class-E amplifier may operate at a state away from the optimum power transmission due to the load variation. By introducing the feedback-loop technique, the TETS can keep the optimum state with constant output voltage by adjusting the important design parameters, that is, the duty ratio and frequency of the driving signal and the supply voltage. The relations between these adjusted parameters and the load are investigated. The effectiveness of the feedback technique is validated through a design example with a variable load parameter. The experimental results show that the Class-E amplifier in the feedback loop can keep operating at the optimum state under the condition of up to 50 percent variation of the load value.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.603-607
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• 2009

About a Structure is performance external insulation is fundamantal performance for enrgy-saving. these day, most of residential structures have constructed by internal insulation method structure. The method structure internal insulation have construction and economical efficiency, but on the other hand, be generated heat loss by heat bridge especially, be generated loss heat-energy logical consequence in structure ondol. The external insulation structure method has a mert able to minimum to loss heat about heat-bridge. But the external insulation technique is unsatisfactory statues within the know-how and method of construction and materials compared with developed countries. The recently, the requirement of market related to the external insulation technique is resulted by the energy efficiency system, but it can lead to the lack of alternative technique In study on the korea type passive house building design for insulation block method of wall system has to experimental characteristic heat-energy of practice building. In result field-experimental, the heat-bridge appeared to characteristic spent heat-energy of blow 2L class and have a suffience performance it.

• 실천공학교육논문지
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• 제12권1호
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• pp.1-10
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• 2020

공압제어회로는 4차 산업혁명 시대에 공장 자동화를 구성하는 중요한 기본 요소이며 대학 수준에서 공압제어회로를 설계하고 제작하는 능력을 기르는 것은 매우 중요한 교육과정 중의 하나이다. 본 연구에서는 공압제어회로의 설계 및 제작 과목에 캡스톤 디자인 방법을 적용하기 위해 모둠별 협동학습을 도입하였다. 또한, 학생들의 학습 성취도를 살펴봄으로써 향후 이 결과를 바탕으로 실천공학 교육의 혁신에 기여 하고자 하였다. 공압제어회로 설계 및 제작에서 실험집단에는 모둠별 협동학습을 적용하고 비교집단은 전통적 강의법을 적용하여 해석 능력의 차이를 검정하였다. 모둠별 협동학습을 수행한 실험집단이 전통적인 강의로만 진행된 비교집단보다 학업 능력이 높게 나타났고 유의수준 p<0.05의 t-검정 결과에서도 두 집단간에 유의미한 차이가 있음을 확인하였다. 실험집단에는 13개의 설문조사 문항을 4개의 모둠별로 응답하게 하고 그 결과를 분석하였는데, 전체 평균 4.731의 높은 만족도를 나타내었다. 본 연구를 통하여 공압제어회로의 설계 및 제작 교과목은 통상적인 과목으로 운영할 때 보다 캡스톤 디자인 기법을 적용했을 때 학생들의 학습 성취도 향상에 매우 효과적이라는 결론을 얻었으며 향후 캡스톤 디자인의 교육과정 개발에 기초 자료로 활용될 수 있을 것으로 기대된다.

• Computers and Concrete
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• 제20권4호
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• pp.461-468
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• 2017

With the increasing demand in the production of concrete, there is a need for adopting a feasible, economical and sustainable technique to fulfill practical requirements. Self-Compacting Concrete (SCC) is one such technique which addresses the concrete industry in providing eco-friendly and cost effective concrete. The objective of the present study is to develop a mix design for SCC with Crushed Rock Fines (CRF) as fine aggregate based on the plastic viscosity of the mix and validate the same for its fresh and hardened properties. Effect of plastic viscosity on the fresh and hardened properties of SCC is also addressed in the present study. SCC mixes are made with binary and ternary blends of Fly Ash (FA) and Ground Granulated Blast Slag (GGBS) with varying percentages as a partial replacement to Ordinary Portland Cement (OPC). The proposed mix design is validated successfully with the experimental investigations. The results obtained, indicated that the fresh properties are best achieved for SCC mix with ternary blend followed by binary blend with GGBS, Fly Ash and mix with pure OPC. It is also observed that the replacement of sand with 100% CRF resulted in a workable and cohesive mix.

• 인간식물환경학회지
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• 제22권5호
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• pp.525-539
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• 2019

Much research has been conducted on user behavior by taking surveys and interviews to plan the green space effectively. However, there is a limitation in understanding detailed user characteristics such as personalities and values. This study applied the Persona-based Scenario Method (PSM) to Hongneung Experimental Forest to understand the detailed needs and behaviors of the users in the forest recreation area. The PSM is a user experience modeling technique, which tries to understand the users by describing the type of users as real people. This study 1) extracts the factors of visitor recreation activities in Hongneung Experimental Forest based on the results of the survey, 2) develops user personas based on the results of survey and comes up with activity factors, and 3) designs user scenarios. As a result of applying the PSM, 64 factors of visitor activities were derived from the observation survey in 14 sites of Hongneung Experimental Forest and 25 key factors of visitor activities were chosen through observer's brainstorming. Second, three types of personas were developed considering the key factors and the results of user characteristics with quantitative and qualitative analysis. Lastly, context scenarios were designed by applying the key factors of visitor recreation activities to the persona model. We identified the design problems of the space and design requirements through the scenarios. This study has significance in that it takes an approach from the user perspective and was applied to the forest recreation area, which was mainly used in product design. The developed personas could be used for deriving design elements and setting the direction for planning considering detailed needs, behaviors and characteristics of users.

• 전기전자학회논문지
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• 제26권4호
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• pp.553-559
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• 2022

본 논문에서는 cascode GaN FET의 하프 브릿지 구성에서 오실레이션 억제를 위한 RC 스너버 회로 설계 기술을 분석한다. 대표적인 WBG 소자인 cascode GaN FET는 우수한 고속 스위칭 특성이 우수하다. 다만, 이러한 고속 스위칭 특성으로 인하여 false turn-off 문제가 야기되며, 이를 억제하기 위해 RC 스너버 회로가 필수적이다. 따라서, 일반적으로 많이 사용되는 실험 기반의 선정 기법과 근궤적법을 이용한 분석 기법을 비교한다. 일반적인 방법의 경우 실험적 경험을 바탕으로 오실레이션 억제 성능이 만족될 때까지 지속적인 회로 변경이 필요하다. 하지만, 근궤적 기법의 경우 비진동 R-C 맵을 기반으로 초기값을 설정 할 수 있다. 이러한 설계 기술에 따른 성능을 비교하기 위해 모의실험과 실제 더블 펄스 회로 구성을 통한 실험을 진행하였다.

• 한국군사과학기술학회지
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• 제15권2호
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• pp.130-137
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• 2012

In this paper, a post-analysis of cooling system for infrared(IR) window was performed based on heating experiment of IR window system. We applied the same experimental conditions to analysis, and then validated the analysis technique by comparing numerical and experimental results. For an analysis software, we used a professional heat/fluid analysis program and the numerical and experimental results were in fairly good agreement. We investigated the effect of thermal transfer between the frame and IR window and also a cooling efficiency between fluid and structure in order to determine the proper parameters for the analysis. In this study, 100 % thermal transfer between the frame and IR window and 30 % cooling efficiency between fluid and structure have been proposed, which can be used in the future conceptual design and analysis of similar IR windows.

• 한국유체기계학회 논문집
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• 제2권3호
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• pp.17-23
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• 1999

In the present numerical analysis, investigation of the effect of blade loadings from design shape on the slip factor variation was studied. Both the Eckardt radial bladed impeller and the backswept impeller were analyzed. In addition, a new design of the blade profile was arbitrarily attempted to generate a center-loading pattern in the original backswept impeller. Three dimensional compressible Navier-Stokes flow analysis with the Baldwin-Lomax turbulence model was applied to get the numerical slip factor at each impeller exit plane using the mass-averaging technique. The numerical slip (actors are in good agreement with the experimental ones and the Wiesner's slip factors deviate further from the numerical and experimental ones in both backswept impellers. Deviation angles and meridional channel loadings are found in no relation with the trend of change of the slip factor. Blade-to-blade loadings in midspan location are, however, found to have a direct relationship, especially at the sections where maximum loadings we to be expected. That information can be utilized in establishing an improved expression for slip factors in the future.

• 한국연소학회지
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• 제15권3호
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• pp.40-47
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• 2010

Calorific value of mixed gas, like liquefied natural gas (LNG), is strongly depends on its compositions which are affected by the mining place and producing time. The variation in calorific value have an direct influence on the combustion characteristics and performances of boiler, burner, vehicle, power plants etc. Thus, developing experimental method to measure exact calorific value is becoming an issue in the related industrial fields. Flame calorimeter is developed to get calorific value at the dynamic equilibrium state using electric substitution method. Refrigerant-11 carries heat from combustor and/or heater to the Peltier elements which pumped it out to the cooling water. It is found out that error in the measured calorific value of methane is 2.86% compared with the theoretical one. Developed design technique and the experimental data will be applied to design the national standard gas calorific value measuring apparatus.