• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.1
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• pp.1-8
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• 2019

In this study, a maximum power point tracking (MPPT) algorithm based on the perturb and observe (P&O) method with variable step size is proposed to improve the dynamic response characteristic of MPPT, using the existing P&O method. The proposed algorithm, which we verified by simulation and experiment, can track the maximum power point (MPP) through duty control and consisted of three operation modes, namely, constant voltage mode, fast mode, and variable step mode. When the insolation is constant, the voltage variation of the operating point at the MPP is reduced through the step size reduction of the duty in the variable step mode. Consequently, the vibration of the operating point is reduced, and the power generation efficiency is increased. When the insolation changes, the duty and the photovoltaic (PV) voltage are kept constant through the constant voltage mode. The operating point then rapidly tracks the new MPP through the fast-mode operation at the end of the insolation change. When the MPP is reached, the operation is changed to the variable step mode to reduce the duty step size and track the MPP. The validity of the proposed algorithm is verified by simulation and experiment of a PV system composed of a PV panel and a boost converter.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.217-224
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• 2003

ISO 14649 is a new interface (or language) standard for the CAD-CAM -CNC chain, currently under establishment by ISO TC184 SCI and SC4 . Upon completion, it will replace ISO 6983, so called M amp; G codes used for CNC since 1950' s. As the new language is being established, a new CNC controller called STEP-CNC (STEP­compliant CNC), capable of carrying out various intelligent tasks using the new language as an input, receives worldwide attention. In this paper, we present a distributed architecture for STEP-NC system based on the generic paradigm of STEP-NC. The STEP-NC system is consisted of 3 sub-systems: 1) CGS (Code Generation System), 2) CES (Code Edit System), and 3) ACS (Autonomous Control System). Also presented in this paper is algorithm for delta volume decomposition, a crucial algorithm for developing CGS. First method is based on the cutting tool and the second method is based on the turning features commonly used in the shop floor. An illustrative example is given to compare the two methods, and to illustrate usage scenario of the delta volume in the turning STEP- NC system under development.

• Journal of computational fluids engineering
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• v.15 no.4
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• pp.99-108
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• 2010

Fractional Step Methods(FSM) are popular in simulation of unsteady incompressible flow. In this study, we demonstrate that FSM, combined with a Volume-Of-Fluid method, can be further applied to simulation of multiphase flow. The interface between the fluids is constructed by the effective least squares volume-of-fluid interface reconstruction algorithm and advected by the velocity using the operator split advection algorithm. To verify our numerical methodology, our results are compared with other authors' numerical and experimental results for the benchmark problems, revealing excellent agreement. The present FSM sheds light on accurate simulation of turbulent multiphase flow which is found in many engineering applications.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.27-30
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• 2002

As computer capacity has been progressed continuously, the studies of the flow characteristics have been performing by the numerical methods actively. In this study, 3-dimensional unsteady incompressible Wavier-Stokes equation was solved by numerical method using the fractional step method with the fourth order compact pade' scheme to achieve high accuracy To validate the present code and algorithm, 3D flow-field around a cylinder was simulated. The drag coefficient and lift coefficient were computed and, then, compared with experiment. The present code will be tailored to LES simulation for more accurate turbulent flow analysis.

• 한국전산유체공학회:학술대회논문집
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• 2003.08a
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• pp.152-157
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• 2003

As computer capacity has been progressed continuously, the studies of the flow characteristics have been performing by the numerical methods actively. Recent numerical simulation has a tendency to require the higher-order accuracy in time, as well as in space. This tendency is more true in LES and acoustic noise simulation. In this study, 3-dimensional unsteady Incompressible Navier-Stokes equation was solved by numerical method using the fractional step method with the fourth order compact pade scheme to achieve high accuracy To validate the present code and algorithm, 3D flow-field around a cylinder was simulated. The drag coefficient and lift coefficient were computed and, then, compared with experiment. The present code will be tailored to LES simulation for more accurate turbulent flow analysis.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.06a
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• pp.49-54
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• 2006

During most of manufacturing processes of auto-body panels, the trimming line should be designed in advance prior to flanging. It is an important task to find a feasible trimming line to obtain a precise final part shape after flanging. This paper proposes a new fast method to find feasible trimming line based on one-step analysis. The basic idea of the one-step analysis is to seek for the nodal positions in the initial blank from the final part, and then the distribution of strain, stress and thickness in the final configuration can be calculated by comparing the nodal position in the initial blank sheet with the one of the final part. The one-step analysis method is able to predict the trimming line before flanging since the desired product shape after flanging can be defined from the final configuration and most of strain paths are simple during the flanging process. Finally, designers can obtain a discrete trimming line from the boundary of the developed meshes after one-step analysis and import it into CAD system in the early design stage. The proposed method has been successfully applied to two basic curve flanging processes demonstrating many advantages.

• The Journal of the Convergence on Culture Technology
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• v.5 no.4
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• pp.283-288
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• 2019

In order to overcome the students' lack of information and experience, we developed a content planning tree that utilizes a decision tree. The content planning tree consists of a tree trunk creation step in which students select a theme and a story to develop, a parent branch generation step for selecting a category that can be developed based on the story, a child branch generation step for selecting the interesting "effect" method of producing the content effectively, a leaf generation step for selecting a multimedia expression 'element' to be visualized. The educational model was applied to game planning design and information visualization lectures, and provides examples of the categories, effects, and elements used in each lecture. The model was used for 145 team projects and the efficiency was confirmed by a step-by-step learning process.

• Toxicological Research
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• v.16 no.4
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• pp.317-323
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• 2000

The immunosuppressive effects of thirty nine chemicals chosen by their potential toxicity were evaluated using a three-step testing method. The immunotoxicity test method developed in this study consisted of three simple assays of lymphoproliferation, mixed leukocyte response, and interleukin (IL)-2 production. The first step was mitogen-induced proliferation assay. Ten chemicals showed the inhibitory effects on the mitogen (lipopolysaccharide or concanavalin A)-induced proliferation in dose-dependent manners. The second step was mixed lymphocyte response. This step crosschecked the growth-suppressive effects detected at the first step. All of 10 chemicals, which showed suppression of lymphoproliferation, also exhibited the suppressive effects on the mixed lymphocyte response in the similar range of chemical concentration. The third step was planned to determine whether or not this growth suppression was mediated through an early activation of T-cell, which could be represented with IL-2 production. Six out of 10 chemicals decreased the interleukin-2 production in the similar concentration range used in the step 1 and 2. These results suggest that those 6 chemicals might have their targets on the signal transduction path-way toward the IL-2 production. In the meantime the other 4 chemicals might have their targets after the IL-2 production signal. Taken all together, the three-step test would be simple, fast, and efficient to deter-mine whether or not the chemical has immunosuppressive effects.

• Journal of Korean Society of Rural Planning
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• v.19 no.3
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• pp.107-116
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• 2013

In this study, it provides the diagnostic index for the rural landscape formation. For the development of diagnostic index, this study first analyzed documents and papers on the landscape formation. Landscape types are also classified by their function and then landscape index was developed by AHP method. Classification system was categorized as three steps: 2 items for 1st step, 10 items for 2nd step, and 20 items(criteria) for 3rd step. In the survey of weighting values with AHP method, the analysis result for the first step showed that rural village landscape is more important than landscape around the village by approximately 20%. In the second step, residence is rated as the most important, followed by village tree planting, and then farmland around the rural villages, greenery, and water environment. In the third step, the feng shui is rated as the most important, followed by tree planting, village forest, culture, and history. While vehicle maintenance, village alleys and pedestrian facilities are rated lower. In index of the around the village, weighting value for index of the farm land and skyline has the highest value. While species richness, water quality and water resources were rated relatively low. In the future, the rural landscapes diagnosis index will be applied to measure the level of the rural villages landscapes and it is expected to propose political support for the landscapes formation.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.13-16
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• 2005

It would be desirable to have methods for specific problems, which have low communication costs compared to the computation costs, and in specific applications, algorithms need to be developed and mapped onto parallel computer architectures. Main memory access for shared memory system or global communication in message passing system deteriorate the computation speed. In this paper, it is found that the m-step generalization of the block Lanczos method enhances parallel properties by forming m simultaneous search direction vector blocks. QR factorization, which lowers the speed on parallel computers, is not necessary in the m-step block Lanczos method. The m-step method has the minimized synchronization points, which resulted in the minimized global communications compared to the standard methods.