• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1177-1181
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• 2014

A 2D grid-like (4, 4)-connected topology coordination polymer, $[Co(BTA)_2(H_2O)_2]_n$ (1), where HBTA = 2-(1H-benzotriazol-1-yl)acetic acid, has been synthesized by hydrothermal method and characterized by single crystal X-ray diffraction, IR spectroscopy, elemental analysis and surface photovoltage spectroscopy (SPS). X-ray diffraction analyses indicated that 1 displays octahedral metal centers with secondary building units (SBUs) [$Co(BTA)_2(H_2O)_2$] bridged by the $BTA^-$ ligands. In the crystal, the 2D supramolecular architecture is further supported by $O-H{\cdots}O$, $O-H{\cdots}N$, $C-H{\cdots}O$ hydrogen bonds and ${\pi}{\cdots}{\pi}$ stacking interactions. The SPS of polymer 1 indicates that there are positive response bands in the range of 300-600 nm showing photo-electric conversion properties. There are good relationships between SPS and UV-Vis spectra.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.10
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• pp.999-1008
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• 2007

The spacer grid set is a component in the nuclear fuel assembly. The set supports the fuel rods safely. Therefore, the spacer grid set should have sufficient strength for the external impact forces such as earthquake. The fretting wear occurs between the spring of the fuel rod and the spacer grid due to flow-induced vibration. Conceptual design of the spacer grid set is performed based on the Independence Axiom of axiomatic design. Two functional requirements are defined for the impact load and the fretting wear, and corresponding design parameters are selected. The overall flow of design is defined according to the application of axiomatic design. Design for the impact load is carried out by using nonlinear dynamic analysis to determine the length of the dimple. Topology optimization is carried out to determine a new configuration of the spring. The fretting wear is reduced by shape optimization using the homology theory. The deformation of a structure is called homologous if a given geometrical relationship holds before, during, and after the deformation. In the design to reduce the fretting wear, the deformed shape of the spring should be the same as that of the fuel rod. This condition is transformed to a function and considered as a constraint in the shape optimization process. The fretting wear is expected to be reduced due to the homology constraint. The objective function is minimizing the maximum stress to allow a slight plastic deformation. Shape optimization results are confirmed through nonlinear static analysis.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.8
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• pp.1114-1122
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• 2018

In this paper, we propose a theoretical framework for provisioning marginal resources in wired and wireless computer networks which include Internet. In more detail, we propose a mathematical model for the upper bounds of marginal capacity in grid networks, where the resource is designed a priori by normal traffic estimation and marginal resource is prepared for unexpected events such as natural disasters and abrupt flash crowd in public affairs. To be specific, we propose a method to evaluate an upper bound for minimum marginal capacity for an arbitrary grid topology using the concept of a strong Roman domination number. To that purpose, we introduce a graph theory to model and analyze the characteristics of general grid structure networks. After that we propose a new tight upper bound for the strong Roman domination number. Via a numerical example, we show the validity of the proposition.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.2
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• pp.223-231
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• 1999

본 논문은 두 개의게이트웨이를 사용한 격자구저망에서 최적의 게이트웨이 위치 설정을 위한 알고리즘을 제안하고 원리를 유도하였다. 최적의 게이트웨이 위치란 격자구조망내 각 노드에서 게이트웨이까지의 평균 최소 링크 수를 가지는 위치로 정의한다. 두 개의 게이트웨이르 사용함으로써 망내의 신뢰도 향상 효과를 가져오며, 우회 경로로 인한 호차단 확률(call blocking probability)과 호설정시간(call setup time)을 최소화한다. 따라서 본 논문에서는 망의 성능을 향상시키기 위하여 두 개의 게이트웨이의 최적의 위치를 결정하는 Grid-Traverse 알고리즘을 제안하고 설정원리들을 유도하여 , 수학적 귀납법으로 이 원리들을 증명하였다.

• Advances in Computational Design
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• v.5 no.3
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• pp.277-289
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• 2020

This article describes the technology for constructing of a multiply-connected three-dimensional area's finite element representation. Representation of finite-element configuration of an area is described by a discrete set that consist of the number of nodes and elements of the finite-element grid, that are orderly set of nodes' coordinates and numbers of finite elements. Corresponding theorems are given, to prove the correctness of the solution method. The adequacy of multiply-connected area topology's finite element model is shown. The merging of subareas is based on the criterion of boundary nodes' coincidence by establishing a simple hierarchy of volumes, surfaces, lines and points. Renumbering nodes is carried out by the frontal method, where nodes located on the outer edges of the structure are used as the initial front.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.969-972
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• 2003

This paper deal with a necessary factors for design grid connected photovoltaic system with stand-alone operation, and show simulation results of individual functions and multi- operation according to utility condition. Generally, photovoltaic system have only one operation of either stand-alone or line interactive, and have a isolation transformer for electrical isolation from utility therefore it is bulky, weighty, and a high price system as compared with usefulness. In this paper, A topology and algorithm adequate for lightweight, high efficiency, low price, multi function is selected and inquired into the validity using simulation of variable conditions.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1317-1326
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• 2017

The cascaded H-bridge (CHB) multilevel converter is a promising topology for large-scale photovoltaic (PV) systems. The output voltage over-modulation derived by the inter-module active power imbalance is one of the key issues for CHB PV systems. This paper proposed a dynamic power distribution strategy to eliminate the over-modulation in a CHB PV system by suitably redistributing the reactive power among the inverter modules of the CHB PV system. The proposed strategy can effectively extend the operating region of the CHB PV system with a simple control algorithm and easy implementation. Simulation and experimental results carried out on a seven-level CHB grid-connected PV system are shown to validate the proposed strategy.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.329-332
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• 2005

Distributed generation (DG) systems fall in islanding operation when they still in operation even when the main grid is out of electric power Islanding operation is further classified into intentional islanding and unintentional islanding operations. In intentional islanding operation, the DG backs up critical loads while it separates from the main grid on islanding detection. Intentional islanding operation increases utilization of the DG system during the islanding operation. This paper proposes reasonal inverter topology and its control algorithm for seamless transfer of DG systems in intentional islanding operation.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.707-710
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• 2005

This paper presents a 3kW grid-connection photovoltaic power generation system and its topology. Photovoltaic system must provide the sinusoidal output voltage wave for unity power factor High frequency switching converters are becoming more popular because of several benefits which are essential in power conversion system. This paper introduces a high speed digital controller using TMS320F2812 DSP chip which can be used for high frequency switching converters. The experimental results of the proposed PWM Inverter demonstrates its high performance with unity input power factor having very low distorsion in input current waveforms and good dynamic characteristics at full load.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.787-798
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• 2013

This paper proposes a special power circuit topology and its corresponding control strategy for an energy recovery power accumulator battery pack testing system (PABPTS), which is particularly used in electric vehicles. Firstly, operation principle and related parameter design for the system are illustrated. Secondly, control strategy of the composite power converter for PABPTS is analyzed in detail. The improved scheme includes a high accuracy charge and discharge current closed loop. active power reference for the grid-side inverter is provided by the result of multiplication between battery pack terminal voltage and test current. Simulation and experimental results demonstrate that the proposed scheme could not only satisfy the requirements for PABPTS with wide-range current test, but also could recover the discharging energy to the power grid with high efficiency.