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NETLA를 이용한 이진 신경회로망의 기하학적인 학습방법
성상규,조현우,이기영,이준탁 동아대학교 정보기술연구소 2001 情報通信硏究所論文誌 Vol.9 No.1
This paper describes an optimal synthesis method of binary neural network(BNN) for an approximation problem of a circular region using a newly proposed learning algorithm[7]. Our object is to minimize the number of connections and neurons in hidden layer by using a Newly Expanded and Truncated Learning Algorithm(NETLA) for the multilayer BNN. The synthesis method in the NETLA is based on the extension principle of Expanded and Truncated Learning(ETL) and is based on Expanded Sum of Product (ESP) as one of the boolean expression techniques. And it has an ability to optimize the given BNN in the binary space without any iterative training as the conventional Error Back Propagation(EBP) algorithm[6]. If all the true and false patterns are only given, the connection weights and the threshold values can be immediately determined by an optimal synthesis method of the NETLA without any tedious learning. Futhermore, the number of the required neurons in hidden layer can be reduced and the fast learning of BNN can be realized. The superiority of this NETLA to other algorithms was proved by the approximation problem of one circular region.
GA-PID 제어기를 이용한 헬리콥터 시스템의 자세 제어
성상규,이준탁,박두환 한국마린엔지니어링학회 2004 한국마린엔지니어링학회지 Vol.28 No.4
The Helicopter system has a non-linearity and complexity. Futhermore, because of absence of its correct mathematical model. it is difficult to control accurately its attitudes for elevation angle and azimuth one. Therefore, we proposed a GA-PID control technique to control these angles efficiently. The proposed GA-PID controller can systematically generate optimal PID parameters by applying GA theory to a helicopter attitude control system. Through the computer simulation, the GA-PID technique shows better attitude control characteristic than traditional PID control technique.
Inconel 706의 열간단조 공정 중 재가열과 변형양에 따른 결정립 미세화에 대한 분석
성상규,강현준,이영선,이상용,이의종,제환일,신정호,윤은유 한국소성∙가공학회 2023 소성가공 : 한국소성가공학회지 Vol.32 No.5
To reduce the forming load due to the temperature drop, during the hot forging process, a reheating hot forging process design is required that to repeat heating and forging. However, if the critical strain required for recrystallization is not induced during forging and grain growth becomes dominant due to the reduction in dislocation density due to repeated heating, the mechanical properties may deteriorate. Therefore, in this study, Inconel 706 alloy was applied, and the grain refinement behavior was comparatively analyzed according to the number of reheating times and effective strain during reheating hot forging process. Reheating was carried out with a total compression rate of 40% up to 4 times. The Inconel 706 compression test specimens heated once showed finer grains as the effective strain increased due to the dynamic recrystallization phenomenon. However, as the number of heating increases, grain refinement was observed even in a low effective strain distribution of 0.43 due to static recrystallization during reheating. Moreover, grain growth occurs at a relatively low effective strain of 0.43 when the number of reheating is four or more. Therefore, it was effective to apply an effective strain of 0.43 or more during hot forging to Inconel 706 in order to induce crystallization through grain refinement and improve the properties of forged products. In addition, we could notice that up to three reheating times condition was appropriate to prevent grain growth and maintain fine grain size.
자동차 조향장치 부품 요크의 온간 밀폐 단조 적용을 위한 금형 응력 저감 설계 및 온간 단조품의 기계적 특성 분석
성상규,김기한,이영선,이상용,윤은유 한국소성∙가공학회 2022 소성가공 : 한국소성가공학회지 Vol.31 No.2
In this study, finite element analyses were performed by applying a stress ring and split die design to relieve the tensile stress acting on the die due to high surface pressure during warm-closed forging. The applied material was a yield-ratio-control-steel (YRCS). It was used without quenching or tempering after forging. In the case of stress rings design, the number of stress rings and the tolerance for shrink fit were different. Vertical and horizontal splits were applied for insert die split design. Case 5 die with three stress rings, 0.2 % shrink fit tolerance, and vertical split was selected as an effective die design for tensile stress reduction. Based on die stress reduction analyses, Case 5 die for warm-closed forging was produced and smooth forgeability was secured, making it possible to manufacture forging product of yoke with the required geometry. In addition, controlled cooling using warm forging heat was applied to secure mechanical properties of yokes. When oil cooling was used for direct controlled cooling after warm-closed forging, a relatively uniform Rockwell hardness distribution and high mechanical properties could be obtained.