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가상 고정물을 이용한 축 대칭 용접물의 용접 변형 해석 모델링 기법
이호진,이봉상,정인철,심덕남,Lee, Ho-Jin,Lee, Bong-Sang,Jung, In-Chul,Shim, Deog-Nam 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.2
Although two dimensional axi-symmetric modeling is useful for calculating the residual stresses of a cylindrical weldment such as a core barrel, this conventional axi-symmetric modeling can not express the behavior of shrinkage well in the locally heated weld zone. New technique of two dimensional axi-symmetric modeling using a virtual fixture is suggested to simulate the behavior of dimensional changes in the weld zone during the heating period of the welding. The virtual fixture in the model has a role to restrain the expansion of the high temperature heated region, which simulates equivalent intrinsic restraint effect of the weldment. In the restraint condition of the virtual fixture above the critical yield strength, the calculated shrinkages by using the suggested axi-symmetric model agreed well with those measured in a welded mock-up. The calculated residual stresses by using the suggested axi-symmetric model also agreed well with those calculated by using conventional axi-symmetric model which has beenused for calculating residual stresses in the weldment.
이호진,채왕병,정은수,Lee, H.J.,Chae, W.B.,Jeong, E.S. 대한설비공학회 1997 설비공학 논문집 Vol.9 No.2
Steady components and unsteady components of second-order velocity and temperature within pulse tube refrigerators were obtained. Second-order solutions were obtained from the first-order solutions of continuity, momentum and energy equations, assuming that the amplitude of the piston motion is small. The axial temperature gradient was considered in the analysis. The flow direction of the streaming was consistent with previous experimental observations. Effects of axial temperature gradient on secondary flow and second-order temperature were shown.
다중경로 환경에서 PMP기법을 이용한 음원의 위치 추정성능 향상
이호진,윤경식,신동훈,이균경,Lee, Ho Jin,Yoon, Kyung Sik,Shin, Dong Hoon,Lee, Kyun Kyung 한국군사과학기술학회 2014 한국군사과학기술학회지 Vol.17 No.2
Source localization is an important problem in the field of sonar and radar, etc. For the purpose of source localization, two or more spatially separated sensors are often used to measure the time difference of arrivals of a radiating source whose transmitted signal waveform is unknown. The NLS(Nonlinear Least Square) cost function with curve fitting method was proposed recently, which provide robust source localization performance by reducing estimation ambiguity. However, even this algorithm shows degraded performance in a multipath environment. To estimates source localization correctly, source localization algorithm that eliminate the effect of multipath signals is required. In this paper, PMP(Power Matching Procedure) is added to the algorithm, which provides improved source localization performance by properly cutting out the effect of multipath signals. Through simulation the performance of the proposed source localization algorithm is verified.
해석 해의 온도곡선을 이용한 템퍼비이드 용접공정 평가기술
이호진,이봉상,박광수,변진귀,정인철,Lee, Ho-Jin,Lee, Bong-Sang,Park, Kwang-Soo,Byeon, Jin-Gwi,Jung, In-Chul 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.5
Brittle microstructure created in a heat affected zone (HAZ) during the welding of low alloy steel can be eliminated by post-weld heat treatment (PWHT). If the PWHT is not possible during a repair welding, the controlled bead depositions of multi-pass welding should be applied to obtain tempering effect on the HAZ without PWHT. In order to anticipate and control the tempering effect during the temper bead welding, the definition of temperature curve obtained from the analytical solution was suggested in this research. Because the analytical solution for heat flow is expressed as a mathematical equation of weld parameters, it may be effective in anticipating the effect of each weld parameter on the tempering in HAZ during the successive bead depositions. The reheating effect by the successive bead layer on the brittle coarse grained HAZ formed by earlier bead deposition was estimated by comparing the overlapped distance between the temperature curves in the HAZ. Three layered weld specimens of SA508 base metal with A52 filler were prepared by controlling heat input ratio between layers. The tempering effect anticipated by using the overlapped distance between the temperature curves was verified by measuring the micro-hardness distribution in the HAZ of prepared specimens. The temperature curve obtained from analytical solution was expected as a good tool to find optimal temper bead welding conditions.
CICC 형태의 초전도 버스 선에서 냉각 및 자기장에 의한 응력 해석
이호진,남현일,김기백,홍계원,Lee, Ho-Jin,Nam, Hyeon-Il,Kim, Gi-Baek,Hong, Gye-Won 한국초전도저온공학회 2000 한국초전도저온공학회논문지 Vol.2 No.2
A CICC type superconducting bus-line electrically connecting a superconducting magnet to a power supply is cooled down to low temperature under the external magnetic field during operation. The thermal contraction during the cooling may be constrained by the supports which are installed to protect the bus-line from Lorenz magnetic forces. This constrained contraction causes thermal stresses in the bus-line to release thermal contraction. The minimum stress conditions in the bus-line may be optimized by controlling the supporting arrangement considering the thermal contraction and the external field. The analytical method to find optimal supports arrangement was suggested by using the beam theory, and numerical calculation using commercial code was performed to verify the suggested analytical optimization method.
이호진,정비오,Lee, Ho Jin,Jeong, Bi O 대한족부족관절학회 2021 대한족부족관절학회지 Vol.25 No.1
The open Broström procedure is considered the surgery of choice for treating chronic lateral ankle instability. The role of arthroscopy has gained popularity in the surgical treatment of chronic lateral ankle instability, partly for the ability to manage the intra-articular pathology combined with ankle instability. Arthroscopic techniques can be divided broadly into the arthroscopic-assisted Broström technique and arthroscopic all-inside ligament repair. The clinical results of these arthroscopic techniques are similar to open procedures. The arthroscopic technique may be an excellent alternative to the open Broström procedure in treating chronic lateral ankle instability when applying the appropriate indications.
이호진,현철,이상욱,Lee, Hojin,Hyun, Chul,Lee, Sangwook 한국정보통신학회 2020 한국정보통신학회논문지 Vol.24 No.1
본 논문에서는 미확인 우주물체를 감시하기 위해, 전자광학 관측 장비인 망원경 시스템의 관측 성능에 대한 M&S(Modeling & Simulation) 분석을 수행한다. 2개의 망원경 시스템을 활용한 미확인 우주물체 관측에 대한 운용개념을 고려하고, M&S 모델을 구성한다. 관측 운용개념을 바탕으로 초기궤도결정을 수행하여 추정궤도를 생성하고, 추정궤도에 대한 옵셋 보정을 수행하여 보정 주기에 따른 관측 성능을 분석한다. 본 논문의 M&S 분석 결과는 옵셋 보정 주기가 짧을수록 관측 성능이 높게 나타나며, 길어질수록 오차 보정 기회가 줄어들기 때문에 성능이 낮아짐을 보여준다. 그래서 미확인 우주물체 감시를 위한 망원경 시스템의 관측 성능을 높이기 위해서는 초기궤도 추정을 정밀화하거나 옵셋 보정을 지속적으로 수행할 수 있도록 하는 관측 시스템이 구성되어야 한다. In this paper, the observation performance of the electro-optical telescope system which surveils the unknown space objects, is analyzed by the Modeling & Simulation(M&S). The operation concept for the observation of the unknown space objects using two telescope systems is considered and the M&S models are constructed. Based on the operation concept for observing the unknown space objects, the estimated orbit is generated by Initial Orbit Determination(IOD) and the observation performance is analyzed according to the offset compensation cycle for the estimated orbit. The result of the M&S based analysis in this paper shows that the observation performance increases with the shorter offset compensation cycle, and decreases with the longer offset compensation cycle. Therefore, to improve the performance of the telescope system which surveils the unknown space objects, the observation system with accurate initial orbit determination or shorter offset compensation cycle should be designed and constructed.