• Advances in aircraft and spacecraft science
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• 제9권1호
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• pp.59-68
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• 2022

The physical and mathematical foundations of the heat-shielding composite materials functioning under the conditions of aerodynamic heating of aircraft, as well as under the conditions of the point effect of high-energy radiation are considered. The problem of deformation of a thin shallow shell under the action of a local temperature field is approximately solved. Such problems arise, for example, in the case of local destruction of heat-protective coatings of aircraft shells. Then the aerodynamic heating acts directly on the load-bearing shell of the structure. Its destruction inevitably leads to the death of the entire aircraft. A methodology has been developed for the numerical solution of the entire complex problem on the basis of economical absolutely stable numerical methods. Multiple results of numerical simulation of the thermal state of the locally heated shallow shell under conditions of its thermal destruction at high temperatures have been obtained.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.250-255
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• 2004

In this paper, we established baseline information and insight on residual stress relief mechanism associated with furnaced and local PWHT(post weld heat treatment) operation. Based on FEM analysis results, we suggested that furnaced PWHT stress relief mechanism was based on creep relaxation and local PWHT stress relief mechanism involved complicated interactions between plasticity and creep. In case of furnaced PWHT, significant stress relaxation was occurred in the early stage of PWHT. In case of local PWHT, stress relaxation magnitude was increased as PWHT time increased. Finally, We have proposed that detailed furnaced and local PWHT procedure, and qualification criteria to support current codes of practices.

• 한국산학기술학회논문지
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• 제21권2호
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• pp.503-510
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• 2020

친환경 산악철도는 산악지역 환경보전을 위해 기존 급곡선·급경사 도로 위에 매립된 콘크리트 톱니 궤도에서 운행하게 된다. 폭이 좁은 도로 특성상 단선 구간이 많아지고, 교행에 따른 분기부가 많이 존재한다. 분기부에서 기존 선로전환기와 히팅장치는 중앙 톱니 궤도의 이동 공간 확보, 두터운 결빙의 신속히 제거 등이 불가하여 산악철도에 적용하기 곤란하다. 이런 문제 해결을 위해 궤도 블록 이동 선로전환기와 고주파유도 히팅장치를 개발하였다. 개발 선로전환기는 콘크리트 톱니궤도 블록을 유압 액튜에이터를 이용하여 이동시킴으로 선로를 전환할 수 있고, 크로싱의 결선부가 없어져서 탈선의 위험이 감소되며, 쇄정도 간편해진다. 히팅장치는 고주파 유도가열을 이용하여 발열 효율을 높임으로 톱니궤도의 두터운 결빙을 신속히 제거할 수 있다. 선로전환기와 히팅장치의 시작품을 제작하여 동작시험을 실시함으로 성능을 입증하였다. 히팅장치는 기존 방식에 비해 10배 이상 발열 효율이 있음을 확인하였다. 개발된 선로전환기와 히팅장치는 동절기 산악트램의 운행을 위한 필수 핵심기술로서, 산악철도의 안전성 및 효율을 높임으로 국내외 산악관광지의 산악철도 도입 확산에 기여할 수 있다. 또한 산악철도는 동절기 교통이 두절되는 지역주민들에게 교통기본권을 제공하고, 관광 활성화와 지역경제 발전 효과를 가져올 수 있다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.699-704
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• 2002

The pipe with a long-neck flange is widely used in power plants, chemical plants, and shipbuilding companies. New the pipe with a long-neck flange is manufactured by welding a thick flange to a pipe. But this long-neck flange pipe has some deflects in the welding region such as unfitting and local thermal fatigue, which weaken the strength around the neck of the flange. Moreover, after welding the flange, the contacting surfaces of the flange have to be machined flat. So, that is uneconomical. Therefore, to solve the above problems of the long-neck flange pipe, a new process, which has no defects around the flange neck, is required. In this study, three forming processes are suggested to get an enhanced long-neck flange. First suggested process consists of conical terming and flange forming. Second and third suggested processes consist of the bulging of a long pipe locally heated by induction coils and the flange forming. The differences between second and third suggestions are the thickness and local heating area of the pipe. That is, the thickness of the initial pipe of third suggestion is larger than that of the final product, and the local heating area is smaller than that of second suggestion. These three suggestions fur forming a long-neck flange are simulated by FE analyses with a commercial cede DEFORM 2D. Especially, the theoretical result of FE analysis on the first suggestion fur forming a long-neck flange is verified by the experiment with aluminum 6063 pipes. From the theoretical and experimental results, it is concluded that three suggested processes are very useful in order to manufacture the pipe with a long-neck flange without any deflects.

• 한국정밀공학회지
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• 제19권8호
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• pp.212-219
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• 2002

The pipe with a long-neck flange is widely used in power plants, chemical plants, and shipbuilding companies. Now the pipe with a long-neck flange is manufactured by welding a thick flange to a pipe. But this long-neck flange pipe has some defects in the welding region such as unfitting and local thermal fatigue, which weaken the strength around the neck of the flange. Moreover, after welding the flange, the contacting surfaces of the flange have to be machined flat. So, that is uneconomical. Therefore, to solve the above problems of the long-neck flange pipe, a new process, which has no defects around the flange neck, is required. In this study, three forming processes are suggested to get an enhanced long-neck flange. First suggested process consists of conical forming and flange forming. Second and third suggested processes consist of the bulging of a long pipe locally heated by induction coils and the flange forming. The differences between second and third suggestions are the thickness and local heating area of the pipe. That is, the thickness of the initial pipe of third suggestion is larger than that of the final product, and the local heating area is smaller than that of second suggestion. These three suggestions for forming a long-neck flange are simulated by FE analyses with a commercial code DEFORM 2D. Especially, the theoretical result of FE analysis on the first suggestion for forming a long-neck flange is verified by the experiment with aluminum 6063 pipes. From the theoretical and experimental results, it is concluded that three suggested processes are very useful in order to manufacture the pipe with a long-neck flange without any defects.

• 대한의용생체공학회:의공학회지
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• 제30권4호
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• pp.333-340
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• 2009

MR compatible coaxial-slot antenna for microwave hyperthermia was developed while its structure and size of each part were determined by computer simulation using finite element method(FEM). Its local heating performance was evaluated using tissue-mimic phantom and swine muscles. 2% agarose gel mixed with 6mM/$\ell$ $MnCl_2$ as a biological tissue-mimic phantom was heated by the proposed antenna driven by a 2.45GHz microwave generator. The temperature changes of the phantom were monitored using multi-channel digital thermometer at the distance of 0mm, 5mm, 10mm and 20mm from the tip center of the antenna. Also muscle tissue of swine was heated for 2 and 5minutes with 50W and 30W of microwave generator powers, respectively, to evaluate the local heating performance of the antenna. MRI compatibility was also verified by acquiring MR images and MR temperature map. MR signals were acquired from the agarose gel phantom using $T2^*$ GRE sequence with 1.5T clinical MRI scanner(Signa Echospeed, GE, Milwaukee, WI, U.S.A.) at Pusan Paik Hospital and were transferred to PC in order to reconstruct MR images and temperature map using proton resonance frequency(PRF) method and laboratory-developed phase unwrapping algorithm. Authors found that it has no severe distortion due to the antenna inserted into the phantom. Finally, we can conclude that the suggested coaxial-slot antenna has an excellent local heating performance for both of tissue-mimic phantom and swine muscle, and it is compatible to 1.5T MRI scanner.

• 한국자기학회지
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• 제23권3호
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• pp.110-116
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• 2013

본 논문에서는 전자기 결합 문제에 대한 효율적인 최적 설계를 위하여 샘플링 기반 민감도법을 제시하였다. 전자기 해석과 열/구조 해석 사이의 결합 특성에 무관하게 최적해를 도출하기 위하여 블랙박스 개념에 기초한 설계기법이 적용되었다. 현 설계점을 중심으로 초입방체 국부 영역에서 크리깅 근사모델을 생성하고 근사모델의 기저함수의 미분을 통하여 설계민감도 값을 도출하였다. 제안된 설계기법은 샘플링 기반 설계기법과 민감도 기반 설계기법의 장점만을 취한 혼합형 설계기법으로 열/구조 특성과 강성 결합된 전자기 문제의 최적 설계에도 적용이 가능하다. 제안된 방법은 비선형성이 강한 수학 예제 및 과도상태 해석이 요구되는 국부 유도가열용 코일 설계에 적용하여 그 정확성과 타당성을 검증하였다.

• 생물환경조절학회지
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• 제28권4호
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• pp.420-428
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• 2019

본 연구에서는 고설 딸기 관부(크라운부) 난방시스템을 전기 온수 보일러, 축열조, 순환 펌프, 관부난방 배관(백색 연질 PE관, 관경 16mm) 및 온도 제어반으로 구성하였다. 관부(크라운부) 난방의 경우 난방 배관을 딸기 관부에 최대한 밀착될 수 있도록 설치하고 배관 위치를 원예용 고정핀으로 고정하였다. 또한 관부 난방시스템의 에너지 효율을 증진하기 위해 축열조 온수 온도를 $20{\sim}23^{\circ}C$, 관부 온도를 $13{\sim}15^{\circ}C$로 관리하였다. 관부난방은 전기 온수보일러를 이용하여 $20{\sim}23^{\circ}C$의 온수를 축열조에 저장하고 순환펌프를 제어하기 위한 온도 센서를 딸기의 관부에 최대한 근접하여 설치하고 온도를 감지함으로써 관부(크라운부)를 집중적으로 난방하는 방식이다. 시험 온실의 난방 처리는 공간 난방 $4^{\circ}C$ + 관부난방(처리 1), 공간 난방 $8^{\circ}C$ (대조구), 공간 난방 $6^{\circ}C$ + 관부난방(처리 2)로 처리하였다. 각 난방처리는 온실 1동에 딸기를 980주를 심었으며, 재배방법은 표준재배법에 준해서 재배하였다. 난방 에너지 소비에 대한 비교시험은 2017년 11월 8일부터 2018년 3월 30일까지 수행되었다. 소비된 누적 전력량은 등유 사용량으로 환산하였고, 등유 소비량은 공간난방 $8^{\circ}C$(대조구)의 경우 1,320L(100%), 공간난방 $4^{\circ}C$ + 관부난방의 경우 928L(70.3%), 공간난방 $6^{\circ}C$ + 관부난방의 경우 1,161L (88%)로 계측되었다. 공간난방 $4^{\circ}C$ + 관부난방(처리 1) 및 공간난방 $6^{\circ}C$ + 관부난방(처리 2)은 $8^{\circ}C$ 공간난방(대조구)에 비해 생육 저하, 수확시기의 지연 등이 없이 비슷하게 딸기 수확이 가능하였으며, 29.7% 및 12%의 난방 에너지가 절감되는 것으로 분석되었다.

• 한국환경과학회지
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• 제29권4호
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• pp.339-349
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• 2020

This study aims to identify participating resident awareness of the improvements to forest carbon cycle villages created by the Korea Forest Service by introducing a system for district heating basedon forest biomass in mountainous areas. Hwacheon Forest Carbon Circulation village was established in Paroho-neureup village in Yuchon-ri, Hwacheon-gun between 2011 and 2013. However, its operation has not been smooth due to the increasing number of households rapidly leaving the district heating system. This study surveyed 76 households that participated in the district heating system using forest biomass in the early stages of the project. This includes households participating in the district heating system(participating households) and households not currently participating in the district heating system(withdrawal households) from September 2019. Surveys focused on the process of participating in forest carbon cycle village projects, and satisfaction in local heating and policy requirements. Of the 67 households, excepting those not allowed to participate in the survey due to death or having moved elsewhere, 36 households participated and 31 households the were in the process of leaving the village were also included. As a result, there was a significant difference between participating and exiting households in the motivation and satisfaction level of district heating. The results of this study are expects to reflect the importance of awareness of residents in the operation of the forest carbon cycle village. This will be utilized as an important dataset for improvement as a means to promote the re-entry if outgoing households. It will also help set the direction of the forest town revitalization project, utilizing forest biomass in the future.

• 한국분말재료학회지
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• 제12권2호
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• pp.131-135
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• 2005

7xxx series Al alloy has the most attractive properties including its excellent high specific strength, stress corrosion cracking and corrosion-resistance. However, in case of the Al-Zn system, the liquid phase has a transient aspect because of the high solid solubility of Zn in Al. Therefore, transient liquid phase sintering behavior was observed during the sintering process. And the amount of liquid and its duration were influenced by the process variables including heating rate and final sintering temperature. At high heating rates($100^{\circ}C/min$), the liquid fraction increased during sintering because diffusion was minimized and therefore local saturation could easily occur. The sintered density increased with increasing heating rate.