• 대한수학회지
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• 제44권3호
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• pp.647-659
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• 2007

Relationships between the Ricci curvature and the squared mean curvature and between the shape operator associated with the mean curvature vector and the sectional curvature function for slant submanifolds of an S-space-form are proved, particularizing them to invariant and anti-invariant submanifolds tangent to the structure vector fields.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제9권4호
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• pp.261-268
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• 2009

In this paper we introduce stronger form of the notion of cover so-called p-cover which is more appropriate. According to this cover we introduce and study another type of compactness in L-fuzzy topology so-called $C^*$-compact and study some of its properties with some interrelation.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1519-1528
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• 2017

The paper proposes a well structured, component count waned single phase multilevel inverter (MLI) topology, which drives three different modules viz. Stipulation Based Sources Insertion (SBSI) module, Level Count Increasing (LCI) module and Inter-Linking H-Bridge (ILHB) module. The SBSI module confronts the number of basic sources needed in series/parallel to achieve required magnitude for any particular level. The LCI possesses an offsetting dc source and opuses to increase the number of levels and the ILHB module links the SBSI and LCI modules. A developed Hybrid Pulse Width Modulation (HPWM) strategy has PWM pulses for the switches of LCI module while the switches of the remaining two modules function at fundamental switching frequency. A fifteen level version of the proposed stipulation based sources insertion MLI (SBSIMLI) topology is simulated in MATLAB R2010a and a prototype of the similar specifications is constructed to validate the performance by experimental results. The comparison between the developed SBSIMLI topology and the competent topologies shows many interesting facts.

• Journal of Power Electronics
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• 제16권5호
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• pp.1706-1715
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• 2016

In this paper, a single phase modified switched-diode topology for both symmetrical and asymmetrical cascaded multilevel inverters is presented. It consists of a Modified Switched-Diode Unit (MSDU) and a Twin Source Two Switch Unit (TSTSU) to produce distinct positive voltage levels according to the operating modes. An additional H-bridge synthesizes a voltage waveform, where the voltage levels of either polarity have less Total Harmonic Distortion (THD). Higher-level inverters can be built by cascading MSDUs. A comparative analysis is done with other topologies. The proposed topology results in reductions in the number of power switches, losses, installation area, voltage stress and converter cost. The Nearest Level Control (NLC) technique is employed to generate the gating signals for the power switches. To verify the performance of the proposed structure, simulation results are carried out by a PSIM under both steady state and dynamic conditions. Experimental results are presented to validate the simulation results.

• 시스템엔지니어링학술지
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• 제20권spc1호
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• pp.90-96
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• 2024

In this paper, we propose a technique to model high resolution seafloor topography with 1m intervals using actual water depth data near the east coast of the Korea with 1.6km distance intervals. Using a feature point extraction algorithm that harris corner based on deep learning, the location of the center of seafloor mountain was calculated and the surrounding topology was modeled. The modeled high-resolution seafloor topography based on deep learning was verified within 1.1m mean error between the actual warder dept data. And average error that result of calculating based on deep learning was reduced by 54.4% compared to the case that deep learning was not applied. The proposed algorithm is expected to generate high resolution underwater topology for the entire Korean peninsula and be used to establish a path plan for autonomous navigation of underwater vehicle.

• Structural Engineering and Mechanics
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• 제34권5호
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• pp.581-595
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• 2010

This paper presents topology optimization of geometrically and materially nonlinear structures using a bi-directional evolutionary optimization (BESO) method. To maximum the stiffness of nonlinear structures under prescribed design load, the complementary work is selected as the objective function of the optimization. An optimal design can be obtained by gradually removing inefficient material and adding efficient ones. The proposed method can be applied to a series of geometrically and/or materially nonlinear structures. The results show considerable differences in topologies and stiffness of the optimal designs for linear and nonlinear structures. It is found that the optimal designs for nonlinear structures are much stiffer than those for linear structures when large design loads (which result in significantly nonlinear deformations) are applied.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2012년도 춘계학술발표대회
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• pp.590-593
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• 2012

현재 인터넷은 하드웨어 종속적인 특징을 가지고 있어 급변하는 환경에 적응하기 힘들다. 이러한 제약사항은 관련 산업 발전을 더디게 하고 있다. 이와 같은 네트워크 환경에서 산업 발전을 위하여 네트워크 인프라에 유연성을 제공할 수 있는 기술의 개발이 필요하다. 그러한 문제를 해결하기 위해 오픈프로토콜인 OpenFlow의 Programmable Network의 특성을 이용하여 네트워크 가상화를 구현하였으며, 응용 서비스별 Virtual Network를 제공하는 방안에 대해 연구하였다. 이를 위하여 OpenFlow 기반의 Programmable Network를 구축하였으며, 동적으로 구성이 가능한 네트워크에서 가상화를 제공하기 위해 VNAPI를 개발하였다. 또한, VNAPI를 통하여 신뢰성 있고 효율적인 응용 서비스의 전달을 위하여 Virtual Network Topology에 대한 설계를 같이 수행하였다.

• 한국정보처리학회논문지
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• 제1권2호
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• pp.184-193
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• 1994

본 논문은 최소목(Minimum-weight Spanning Tree, MST)에 있어서 네트워크의 랭크 중 몇개가 삭제(또는 파괴) 또는 추가(또는 회복) 되었을 때, MST를 재구성하는 분산 알고리즘을 제안한다. 본 논문에서 제안한 알고리즘의 메세지 복잡도는 Ο(m＋n log(t＋f))이고, 이상시간 복잡도는 Ο(n＋n log(t＋f))가 되며, 여기서 n은 네트워크의 프로세서의 수이고 t(resp. f)는 추가되는 링크의 수(resp. 이전 MST의 삭제된 링크의 수)이다. 그래서 네트워크의 형태가 변형이 된 다음에 f=O이고 m=e일 경우에는 m=t＋n이 된다. 또한 본 논문의 마지막 부분에서는 링크의추가, 삭제와 마찬가지로 프로세서의 추가, 삭제되었을 경우의 알고리즘도 제안한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.361-366
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• 2012

In this paper, we propose the efficient technique that reduces the number of spot-welds and increases the structural rigidity by using the topology optimization technique. Eigen value analysis is used to evaluate the rigidity of the optimized model. As a first step, the topology optimization is performed to find optimal spot-weld distributions. In this study, the design objective is to maximize the weighted frequencies. The volume fractions of the weld components are used as design constraints, and also the densities of each element in the individual design space are used as design variables. And then, to consider the possibility of spot-weld failure, the contribution rate analysis was performed by using the orthogonal array method of DOE. The spot-welds in the rear panel part are reinforced according to estimation results of the contribution rate analysis. Finally, we obtained optimized spot-weld layout model which has the reduced number of spot-welds and the improved dynamic stiffness.

• Journal of Power Electronics
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• 제11권4호
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• pp.490-498
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• 2011

This paper presents a novel analysis, design, and implementation of a battery charging three-phase high frequency semi-controlled power converter feasible for plug-in hybrid electric vehicles. The main advantages of the proposed topology include high efficiency; due to lower power losses and reduced number of switching elements, high output power density realization, and reduced passive component ratings proportionally to the frequency. Additional advantages also include grid economic utilization by insuring unity power factor operation under different possible conditions and robustness since short-circuit through a leg is not possible. A high but acceptable total harmonic distortion of the generator currents is introduced in the proposed topology which can be viewed as a minor disadvantage when compared to traditional boost rectifiers. A hysteresis control algorithm is proposed to achieve lower current harmonic distortion for the rectifier operation. The rectifier topology concept, the principle of operation, and control scheme are presented. Additionally, a dc-dc converter is also employed in the rectifier-battery connection. Test results on 50-kHz power converter system are presented and discussed to confirm the effectiveness of the proposed topology for PHEV applications.