• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.4
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• pp.677-684
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• 2024

In this paper, the design method of a step-up DC-DC converter based on PWM control was studied for solar power system application. The operating principle of the switching mode step-up type DC-DC converter was analyzed and the basic design method was studied. For photovoltaic system application, an output voltage feedback control algorithm based on PWM control was developed to enable the converter's output voltage to follow the target voltage under variable input conditions. As a procedure to verify the effectiveness of the proposed algorithm, a prototype of a step-up DC-DC converter with a single feedback output voltage was designed and made by boosting the input voltage DC 10V to DC 30V. In experiments with prototypes, it was confirmed that the output voltage of the oscilloscope and LCD accurately followed the target output voltage. In the performance evaluation test, it was confirmed that the output voltage of the oscilloscope and LCD accurately followed the target output voltage by showing an error rate within 1 [%] of the reference voltage.

• Journal of Fisheries and Marine Sciences Education
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• v.24 no.5
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• pp.712-720
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• 2012

Recently, many problems related on shoreline response to spill oil were exposed again on a occasion of M/T Hebei spirit accident even though the weakness on the shoreline response system has been brought up since M/T Sea Prince oil spill accident. Therefore the establishment of shoreline response system that best suits our country is needed through considering the response system of well-developed country. The socioeconomic conflict between the persons concerned on the clean-up endpoints can be sharpened in Korea because the frequency of coastal use of our country is too high compared to other countries. Thus procedural justification, that is, how the clean-up endpoints be established is more important than what type of clean-up endpoints be used. In the present paper, we attempted to suggest a new manner on the decision making system for clean-up endpoints that best suits our country. The decision making system for clean-up endpoints need to be divided into two steps, that is, set-up step of clean-up endpoints criteria and decision step of clean-up endpoints. The decision making organization of local governments play a key role in case of set-up step of clean-up endpoints criteria, while the response command headquarters under Korean coast guard and decision making organization of local governments codecide whether the clean-up endpoints criteria is fits or not.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.4
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• pp.358-363
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• 2010

This paper proposes a step-by-step method of determining the parameters of equivalent circuit which is considered the no load losses for the single phase induction motor which has the starting winding. This method is comprised of three steps, and the stator resistance which is measured by the method of voltage drop is treated as constant and the stator and the rotor leakage reactances are assumed to be the same in every step. The test results of no load and locked rotor test are used in the 1st and 2nd step, and the ratings of name plate of the motor are needed in the 3rd step. In the 1st step, the traditional equivalent circuit parameters are directly calculated by no load and locked rotor conditions. In the next step, five nonlinear simultaneous equations for five unknown parameters can be set up by no load and locked rotor equivalent circuits. These equations are solved by using the initial parameters obtained by the 1st step parameters. In the final step, three nonlinear simultaneous equations for rotor winding resistance, leakage reactance and no load losses component resistance can be set up by equivalent circuit under the rated operation. Three parameters are solved by using the 2nd step parameters. Thus, equivalent circuit parameters are gradually refined step by step. The validity of the proposed method is evaluated by comparing the computed values obtained by the equivalent circuit parameters with the experimental values of the load test.

• Journal of The Korean Society of Integrative Medicine
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• v.10 no.4
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• pp.145-151
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• 2022

Purpose : Stroke patients exhibit abnormal walking patterns such as slow walking speed and asymmetrical walking values. The recovery of symmetrical walking in the stance phase using a treadmill means improvements in walking speed and asymmetrical walking. The purpose of this research was to investigate the effect of unilateral step treadmill training (USTT) on gait speed and the recovery of symmetrical walking in chronic stroke patients. Methods : Fifteen patients (11 men and 4 women) with chronic stroke participated in this study. The 10-meter walk test (10MWT) and GAITRite system were used to determine the intervention-related changes in gait speed and symmetrical walking values such as non-paretic step length (NSL), non-paretic step time (NST), paretic single-support time (PSST), step length asymmetry (SLA), and step time asymmetry (STA) after USTT. All participants completed USTT and underwent measurements at 3 different times: at pretest, posttest, and the follow-up test. Repeated-measures analysis of variance was used to compare walking speed and asymmetrical walking values. The statistical significance level was set at p<.05. Results : Walking speed by 10MWT (p<.05) showed significant improvements after USTT as follows: at pretest and posttest (p<.05), posttest and follow-up test (p<.05), and pretest and follow-up test (p<.05). Recovery of symmetrical walking patterns such as NSL (p<.05), NST (p<.05), and SLA (p<.05) were observed after USTT. However, no significant improvements were found in PSST (p>.05) and STA (p>.05) in symmetrical gait. Conclusion : This study suggests that USTT may have a positive effect on walking speed and symmetrical walking patterns in chronic stroke patients. Thus, this study contributes to the existing knowledge about the usefulness of USTT for the effective management of patients with chronic stroke. Further studies are needed to generalize these findings.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.3
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• pp.98-103
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• 2001

This paper presents the numerical analysis of piezoelectric devices using three-dimensional finite element analysis. The characteristic of piezoelectric transducer, such as mechanical displacement and electrical are analyzed and the validity is confirmed by experiments Applying the finite element routine to a piezoelectric transformer, the resonance features electrical impedance. the ratio of step-up voltage and vibration mode of piezoelectric transformer are calculated numerically By using three-dimensional finite element method effects of width variation to resonance features, electrical input impedance and the voltage step-up ratio for a piezoelectric transformer, can be considered in design procedure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.103-103
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• 2009

In this study, in order to develop high power piezoelectric transformer, we compared the piezoelectric transformers dimension. The basic composition of piezoelectric ceramics is ternary $0.01Pb(Ni_{1/3}Nb_{2/3})O_3-0.08Pb(Mn_{1/3}Nb_{2/3})O_3-0.91Pb(Zr_{0.505}Ti_{0.495})O_3$. The voltage step up ratio of piezoelectric transformer showed the maximum value at the near of 81 kHz and increased according to the increase of load resistance.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.809-819
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• 2017

In this paper, a new coupled inductor DC-DC converter with a high step-up voltage gain is proposed. It is developed from a clamp-mode coupled-inductor boost converter by incorporating an additional capacitor and diode. The proposed converter is able to achieve the higher voltage gain, while still retaining the switch voltage clamp property of its predecessor. In the paper, operation and analysis of the proposed converter are described. Experimental results from a prototype converter are presented to verify the validity of the analysis. The prototype circuit attains the highest efficiency of 92.8%.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.189-197
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• 2017

This paper elaborates two novel proposed topologies (type-I and type-II) of the high step-up DC-DC converter using switched inductor and voltage multiplier cell. The advantages of these proposed topologies are the less voltage stress on semiconductor devices, low device count, high power conversion efficiency, high switch utilization factor and high diode utilization factor. We analyze the Type-II topologies operating principle and mathematical analysis in detail in continuous conduction mode. High-intensity discharge lamp for the automotive application can use the derived topologies. The proposed converters give better performance when compared to the existing types. Also, it is found that the proposed type-II converter has relatively higher voltage gain compared to the type-I converter. A 40 W, 12 V input voltage and 72 V output voltage has developed for the type-II converter and the performances are validated.

• Culinary science and hospitality research
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• v.6 no.3
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• pp.425-442
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• 2000

The main purpose of this study is to propose that Beverage sales should be step-up in Family Restaurant. To achieve the purpose of this study theoretical and empirical approaches were used. In review of theoretical background, basic concepts and characteristics of beverage were studied. For empirical study, three Family Restaurant in Korea was selected and analyzed the beverage sales which classified to Liquor, Beer Wine and Non-alcoholic beverage. Based on it, I suggest a plan of beverage sales step-up of Family Restaurant as follow. First, keep the appropriate valance of the whole item: non-alcohol and alcohol item. Second, develop the menu should be effect beverage sales. Third, through the promotion and event the restaurant should derive the customer to purchasing behavior. Fourth. server can accommodate and offer the information of food and beverage menu that can evoke the customer's attention.

• Journal of Families and Better Life
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• v.28 no.4
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• pp.103-115
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• 2010

This study approached the leisure with the step of life cycle, analyzing the process of leisure career and leisure development in individual life. The leisure life cycle leads the other related studies by examining the concepts of continuity, change, leisure socialization, and leisure career. It also analyzes the patterns and the structures of the use of life time, using '2004 Time Use Survey' from the Korea National Statistical Office. As a result, this study suggests new 3 steps of leisure life cycle: participating and expanding stages, selective and concentrating stage, and continuing and absorbed stage. These steps set up the goal of leisure program by the periods. They also can help setting the direction of leisure activities, and can be used as basic data that can make up the leisure activity program models step by step. Moreover, the development of model can be used as valuable information to draw up the plans that can prepare for aging society and demand the support of policy.