• Interaction and multiscale mechanics
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• v.7 no.1
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• pp.543-561
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• 2014

We present a full energy and force formulation of the quasicontinuum method with non-local and local transition elements. Non-local transition elements are developed to transmit inhomogeneity from the atomistic to the continuum regions. Local transition elements are developed to resolve the mathematical mismatch between non-local atoms and the local continuum. The rationale behind these transition elements is provided by analyzing the energy and force transitions between atoms and continuum under the Cauchy-Born rule. We show that breakdown of the Cauchy-Born rule occurs for slaved atoms of local elements within the cutoff of non-local atoms. The inadequacy of the Cauchy-Born rule at the transition region naturally leads to the need of atomistic treatment of transition slaved and transition representative atoms. Such an atomistic treatment together with a full or cutoff sampling allows non-local transition elements containing these transition entities to transmit inhomogeneity. Different force formulations for transition representative atoms and pure local representative atoms allow the local transition elements to resolve non-local and local mismatches. The method presented herein is validated by force calculations in an unstressed perfect crystal as well as an unrelaxed grain boundary model. A nanoindentation simulation in 3D is conducted to demonstrate the accuracy and efficiency of the proposed method.

• Journal of Mechanical Science and Technology
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• v.15 no.11
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• pp.1499-1506
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• 2001

Various transition elements are used in general for the effective finite element analysis of complicated mechanical structures. In this paper, a solid-to-beam transition finite element, which can b e used for connecting a C1-continuity beam element to a continuum solid element, is proposed. The shape functions of the transition finite element are derived to meet the compatibility condition, and a transition element equation is formulated by the conventional finite element procedure. In order to show the effectiveness and convergence characteristics of the proposed transition element, numerical tests are performed for various examples. As a result of this study, following conclusions are obtained. (1) The proposed transition element, which meets the compatibility of the primary variables, exhibits excellent accuracy. (2) In case of using the proposed transition element, the number of nodes in the finite element model may be considerably reduced and the model construction becomes more convenient. (3) This formulation method can be applied to the usage of higher order elements.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.4
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• pp.356-366
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• 2022

This paper presents a mode transition method that applies frequency compensation technique of an LLC resonant converter for stable mode transition. LLC resonant converters used in various applications require high efficiency and high power density. However, because of circuit property, a wider voltage gain range equates to a greater circuit loss, so maintaining high efficiency at all voltage gain ranges is difficult. In this case, full bridge-half bridge mode transition method can be used, which maintains high efficiency even in a wide voltage gain range. However, this method causes damage to the circuit through overcurrent by the mode transition. This study analyzes the cause of the problem and proposes a mode transition method that applies frequency compensation technique to solve the problem. The proposed method verifies the stable transition through simulation analysis and experimental results.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.859-862
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• 1998

Many playback methods of MPEG-1 video were developed and are have beendeveloped now. But nomal playback method demands great time. In this paper we designed and implemented the scene transition playback method of the MPEG-1 video data. The previous studies of scene transition playback have used to the DC or edge information after decoding process of picture. In this paper, scene transition is detected by macroblock information from MPEG-1 compressed area, then decodes and playbacks the only scene transition picture. This MPEG-1 video player was implemented by decoding control. So it is possible to add special playback method to MPEG-1 video player. As the result, which is proposed in this paper the scene transition method can minimize to decoding calculation and decrease to playback time of the MPEG-1 video data.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.235-238
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• 2006

This paper is about the code that realizes the $e^N$-Method for boundary-layer transition prediction. The $e^N$-Method based on the linear stability theory is applied to predicting boundary-layer transition frequently. This paper deals with the construction of code, stability analysis and the calculation of N-factor. The results of transition prediction using the $e^N$-Method for flat plate/cone compressible boundary-layers are presented.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.2
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• pp.67-72
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• 2005

In conventional small signal stability analysis, system is assumed to be invariant and the state space equations are used to calculate the eigenvalues of state matrix. However, when a system contains switching elements such as FACTS devices, it becomes non-continuous system. In this case, a mathematically rigorous approach to system small signal stability analysis is by means of eigenvalue analysis of the system periodic transition matrix based on discrete system analysis method. In this paper, RCF(Resistive Companion Form) method is used to analyse small signal stability of a non-continuous system including switching elements. Applying the RCF method to the differential and integral equations of power system, generator, controllers and FACTS devices including switching elements should be modeled in the form of state transition equations. From this state transition matrix eigenvalues which are mapped to unit circle can be calculated.

• KIEE International Transactions on Power Engineering
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• v.5A no.4
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• pp.344-349
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• 2005

In conventional small signal stability analysis, the system is assumed to be invariant and the state space equations are used to calculate the eigenvalues of the state matrix. However, when a system contains switching elements such as FACTS equipments, it becomes a non-continuous system. In this case, a mathematically rigorous approach to system small signal stability analysis is performed by means of eigenvalue analysis of the system's periodic transition matrix based on the discrete system analysis method. In this paper, the RCF (Resistive Companion Form) method is used to analyze the small signal stability of a non-continuous system including switching elements. Applying the RCF method to the differential and integral equations of the power system, generator, controllers and FACTS equipments including switching devices should be modeled in the form of state transition equations. From this state transition matrix, eigenvalues that are mapped into unit circles can be computed precisely.

• The Transactions of the Korea Information Processing Society
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• v.7 no.8
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• pp.2520-2527
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• 2000

An improved transition density propagation method for power estimation is proposed. The power estimation for the zero delay model is a proper criteria for the.lower boutldlIry for power consumption. A transition propagation method, including the zero delay model as a lower boundary for power stimation was studied. However, there were some redundancy factors in the process of transition density propagation. Hence this paper will explore the transition density propagation behavior to eliminate the redundancy factors and present theirriprQved estimation methodology for the signal transition density. The experiments show that the proposed method has comparably better estimation accuracy than the conventional methods.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.12
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• pp.198-208
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• 1995

BiCMOS circuit consist of CMOS part which constructs logic function, and bipolar part which drives output load. Test to detect stuck-open faults in BiCMOS circuit is important, since these faults do sequential behavior and are represented as transition faults. In this paper, proposes a method for efficiently detecting transistor stuck-open faults in BiCMOS circuit by transforming them into slow-to=rise transition and slow-to-fall transition. In proposed method, BiCMOS circuit is transformed into equivalent gate-level circuit by dividing it into pull-up part which make output 1, and pull-down part which make output 0. Stuck-open faults in transistor are modelled as transition fault in input line of gate level circuit which is transformed from given circuit. Faults are detceted by using pull-up part gate level circuit when expected value is '01', or using pull-down part gate level circuit when expected value is '10'. By this method, transistor stuck-open faults in BiCMOS circuit are easily detected using conventional gate level test generation algorithm for transition fault.

• Journal of Internet Computing and Services
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• v.5 no.6
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• pp.59-66
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• 2004

In this paper, we propose a transmission rate prediction method of video data. The proposed method checks shot transition characteristics after dividing MPEG video data into a GoP unit and then uses Kalman filter. It used algorithm to detect shot transition information by high speed in compressed domain in order to check a correct shot transition of video data and classified into a abrupt shot transition type and a gradual shot transition type. Information to have been classifying is used as factors of Kalman filter and predicts a transmission rate of video data. Also, the proposed method decreased processing time with detecting shot transition and predicting a transmission rate of video data in compressed domain. It predicted a transmission rate with 96.2- 97.6% in the experiment that used three kinds of 911 1frames of different video data.