• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.69-72
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• 1998

A study to identify the energized status of the 22.9kV underground power cable by the detection of vibration was reformed. We derived that there exists vibration at double the line frequency in live cables by electromagnetic force. The vibration can be picked up by accelerometer sensor. A prototype was tested on the underground distribution system in Chonan Station, KEPCO. The results are presented and suggest the applicability of the detecting device.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.106-113
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• 2004

Most of mechanical structures are composed of many substructures connected to one another by various types of mechanical joints. In automotive engineering, it is important to study these connected structures under various dynamic forces for the evaluations of fatigue life and stress concentration exactly. In this study, the dynamic response of vehicle structure to external forces is classified an inverse problem involving strains from the experiment and the analysis. The practical dynamic forces are determined by the combination of the analytical and experimental method with analyzed strain by quasi-static finite element analysis under unit force and with measured strain by a strain gage under driving load, respectively. In a stressed body, inter-molecular chemical bonds are failed beyond the certain magnitude. The failure of molecular structure in material is considered as a time process of which rate is determined by mechanical stress. That is, the failure of inter-molecular chemical bonds is the fatigue lift of material. This kinetic concept is expressed as lethargy coefficient. And S-N curve is obtained with the lethargy coefficient from quasi-static tensile test. Equivalent practical dynamic force is obtained from the identification of practical dynamic force for one loading point. Using the practical dynamic force and S-N curve, fatigue life of a window pillar is analyzed with FEM under the identified force by the procedure of above mentioned.

• 품질경영학회지
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• 제49권3호
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• pp.255-268
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• 2021

Purpose: We sought to understand why a high-speed rotating projectile featuring a fuze-and-body assembly sometimes exhibited airburst, and we intended to improve the flight stability by eliminating airburst. Methods: We performed characteristic factor analysis, structural mechanics modeling, and dynamic modeling and simulation; and we scheduled firing tests to discover the cause of airburst. We used a step-by-step procedure to analyze the reliability function for selecting the bonding force standard that prevents airburst. Results: The 00MM high-speed rotating projectile features a fuze bonded to a body assembly; the bonding sometimes can break on firing. The resulting contact force, vibration and roll damping during flight generated yaw. Flight became unstable; fuze operation triggered an airburst. Our reliability test improved the bonding force standard (the force was increased). When the bonding force was at least the minimum required, a firing test revealed that airburst/flight instability disappeared. Conclusion: Analysis and identification of the causes of flight instability and airburst render military training safer and enhance combat power. Ammunition must perform as designed. Our method can be used to set standards that improve the performances of similar types of ammunition.

• Structural Engineering and Mechanics
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• 제59권6호
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• pp.973-992
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• 2016

A direct and relatively simple method for controlling nodal displacements and/or internal bar forces has been developed for prestressable structural assemblies including complex elements ("macro-elements", e.g., the pantographic element), involving Matrix Condensation, in which structural matrices being built up from matrices of elementary elements. The method is aimed at static shape control of geometrically sensitive structures. The paper discusses identification of the most effective bars for actuation, without incurring violation in bar forces, and also with objective of minimal number of actuators or minimum actuation. The advantages of the method is that the changes for both force and displacement regimes are within a single formulation. The method can also be used for adjustment of bar forces to either reduce instances of high forces or increase low forces (e.g., in a cable nearing slack).

• 한국생산제조학회지
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• 제7권2호
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• pp.91-99
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• 1998

This paper presents a methodology for identifying the cutter runout geometry in end milling process. Cutter runout is common but undesirable phenomenon in multi-tooth machining because it introduces variable chip loading to insert which results in a accelerated tool wear. amplification of force variation and hence enlargement vibration amplitude From understanding of chip load change kinematics, the analytical cutting force convolution model was formulated as the angular domain convolution model was formulated as the angular domain convolution of three dynamic cutting force component functions. By virtue of the convolution integration property, the frequency domain expression of the local cutting forces and the chip width density of the cutter. Experimental study is presented to validate the analytical model. This study provides the in-process monitoring and compensation of dynamic cutter runout to improve machining tolerance and surface quality for industrial application.

• Smart Structures and Systems
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• 제23권3호
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• pp.263-278
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• 2019

Moving train load parameters, including train speed, axle spacing, gross train weight and axle weights, are identified based on strain-monitoring data. In this paper, according to influence line theory, the classic moving force identification method is enhanced to handle time-varying velocity of the train. First, the moments that the axles move through a set of fixed points are identified from a series of pulses extracted from the second derivative of the structural strain response. Subsequently, the train speed and axle spacing are identified. In addition, based on the fact that the integral area of the structural strain response is a constant under a unit force at a unit speed, the gross train weight can be obtained from the integral area of the measured strain response. Meanwhile, the corrected second derivative peak values, in which the effect of time-varying velocity is eliminated, are selected to distribute the gross train weight. Hence the axle weights could be identified. Afterwards, numerical simulations are employed to verify the proposed method and investigate the effect of the sampling frequency on the identification accuracy. Eventually, the method is verified using the real-time strain data of a continuous steel truss railway bridge. Results show that train speed, axle spacing and gross train weight can be accurately identified in the time domain. However, only the approximate values of the axle weights could be obtained with the updated method. The identified results can provide reliable reference for determining fatigue deterioration and predicting the remaining service life of railway bridges.

• 대한토목학회논문집
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• 제29권1A호
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• pp.9-18
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• 2009

본 논문은 외부 긴장된 텐던의 장력추정에 대한 차분진화기법의 적용을 소개한다. 제안된 차분진화 알고리즘의 SI기법은 기존의 구배 기반의 최적화 기법과는 다르게 전역해 탐색이 가능하다. 수치실험은 인식변수에 대한 사전정보 없이도, 제안된 차분진화기법이 외부긴장 텐던의 정확한 장력 추정뿐 아니라 유효공칭직경 추정이 가능하여 1%미만의 추정 오차를 갖는 유용한 기법임을 보여준다. 또한 긴장력 손실 유무의 사용 상태를 고려한 축소실험 모델 실험을 이용하여 제안된 기법의 타당성이 실험적으로 검증되었다. 실험의 결과는 긴장력 손실과 무관하게 정확한 장력 추정과 유효공칭직경의 추정뿐 아니라 실험 모델의 감쇠비까지 추정되어 제안된 기법이 적합하고, 효과적인 방법임을 보여준다. 유효공칭 직경의 2% 추정 오차는 실제 꼬여진 단면을 갖는 텐던의 직경과 충실단면을 갖는 FE 모델의 직경의 차이 때문이다. 마지막으로, 기존이론과의 비교 분석으로 제안된 차분진화 기법의 정확성과 우월성이 검증되었다.

• 한국구조물진단유지관리공학회 논문집
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• 제13권5호통권57호
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• pp.109-120
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• 2009

본 논문은 외부 긴장된 긴장재의 손실 긴장력 추정에 대한 새로운 방법을 소개한다. 제안된 방법은 HGA과 FEM이 조합된 시스템 인식 기법으로 외부긴장된 긴장재의 손실된 긴장력이 추정된다. 제안된 기법의 인식변수로는 외부긴장 긴장재의 긴장력, 유효공칭직경, 단위길이당 질량과 레일리 감쇠 계수가 사용되었다. 첫째로 감쇠의 효과가 적용된 유한요소 모델 시스템을 모형화되고, 시스템 인식변수를 반복적으로 추정하는 역해석 기법을 이용하여 인식하게 된다. 마지막으로 3번의 수치실험을 통하여, 제안기법의 수치적 타당성 여부가 확인된다. 이때, 레일리 감쇠 계수를 제외한 인식변수들의 오차는 1%미만으로 인식된다.

• International Journal of Computer Science & Network Security
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• 제22권7호
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• pp.252-258
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• 2022

Ukraine has a significant in quantity and unique in quality parameters, in particular, the level of education, a resource - the labor force, which, along with natural resources, can serve as the basis for economic growth and the achievement of sustainable development goals. The study is aimed at a thorough identification of the main factors influencing the formation and use of the labor force in Ukraine, including by comparing with the indicators of the EU countries, before the start of the active phase of military aggression by the Russian Federation. It was found that until February 24, 2022, there were negative trends in the change in the quantitative and qualitative indicators of the labor force due to the demographic crisis, the transformation of the national economy and shortcomings in state regulation of labor market development processes. The military actions not only exacerbated pre-existing problems, but also led to the emergence of new ones. A significant number of refugees and internally displaced persons, with the termination of the activities of half of the economic entities, provoked a sharp increase in real unemployment and a decrease in wages. The specific problem of the labor market of Ukraine - the "labor crisis", which has and will have a significant impact on the labor force, is carefully considered.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.319-320
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• 2002

Numerical simulation of chip formation during high speed machining requires knowing the friction at tool/chip interface. This parameter is hardly identified and generally the loadings (temperature, force) during the identification are not similar to those encountered during machining. Thus, Coulomb friction identified with pin-on-disc device is often used to conduct numerical simulation. The used of this technique cannot leads to good numerical results of chip formation compared to the experimental tests especially in the case of low uncut chip thickness. In this contribution, we propose a new method to evaluate the friction at tool/chip interface. In fact several Coulomb friction parameters are identified corresponding to several parts of the cutting tool. Experimental tests have been conducted allowed us to determinate both the level and the distribution of the Coulomb friction. Experimental results are also compared to the results of orthogonal cutting simulation. We show that this technique allows predicting accuracy results of chip formation.