• Journal of Power Electronics
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• 제16권6호
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• pp.2221-2230
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• 2016

Voltage and frequency stability issues occur in existing centralized power system due to the high penetration of renewable energy sources, which decrease grid absorptive capacity of them. The grid-connected inverter that mimics synchronous generator characteristics with inertia characteristic is beneficial to electric power system stability. This paper proposed a novel three-phase four-wire grid-connected inverter with an independent neutral line module that mimics synchronous generators. A mathematical model of the synchronous generator and operation principles of the synchronverter are introduced. The main circuit and control parameters design procedures are also provided in detail. A 10 kW prototype is built and tested for further verification. The primary frequency modulation and primary voltage regulation characteristics of the synchronous generator are emulated and automatically adjusted by the proposed circuit, which helps to supports the grid.

• Journal of Power Electronics
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• 제1권2호
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• pp.78-87
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• 2001

A new high-power step-up based on the two-module parallel-input (PISO) modular dual inductor-fed push-pull converter is proposed. The proposed converter is operated at a constant duty cycle and employs and auxiliary circuit to control the output voltage with a phase-shift between two modules. It shows a high efficiency due to the greatly reduced switch turn-off stress. It also shows a high and linear voltage conversion ratio, low current stress in the output capacitor, and fast control-to-output dynamics. The operation principles and the mathematical models of the proposed converter are presented. Features of the proposed converter are discussed in comparison with the two-module PISO modular dual inductor-fed push-pull converter. Also, experimental results from a 50kHz, 800W, 350 Vdc prototype with an input voltage range of 20-32 Vdc are provided to confirm the validity of the proposed converter. The new converter compares favorably with the conventional counterpart, and is considered well siuted to high-power step-up applications.

• 전력전자학회논문지
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• 제23권5호
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• pp.366-372
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• 2018

Three-port dual-active bridge (DAB) converter in a DC microgrid was studied due to its high power density and cost-effectiveness. The other advantages of DAB include galvanic isolation and bidirectional power conversion capability using simple control modulation. The three-port DAB converter consists of a three winding transformer and three bridges. The transformer has three phases, which means that the ports are coupled. Thus, the three-port DAB converter causes unwanted power flows when the load connected to each port changes. The basic operational principles of the three-port DAB converter are presented in this study. The decoupling control strategy of the independent port power transfer is presented with a mathematical power model to overcome the unexpected power flow problem. The validity of the proposed analysis and control strategy is verified with PSIM simulation and experiments using a 1-kW prototype power converter.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.48-52
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• 2001

In this paper presents an accurate AFM used that is free from the Z-directional distortion of a servo actuator is described. Two mathematical correction methods by the in-situ self-calibrationare employed in this AFM. One is the method by the integration, and the other is the method by inverse function of the calibration curve. The in situ self-calibration method by the integration, the derivative of the calibration curve function of the PZT actuator is calculated from the profile measurement data sets which are obtained by repeating measurements after a small Z-directional shift. Input displacement at each sampling point is approximately estimated first by using a straight calibration line. The derivative is integrated with reference to the approximate input to obtain the approximate calibration curve. Then the approximation of the input value of each sampling point is improved using the obtained calibration curve. Next the integral of the derivative is improved using the newly estimated input values. As a result of repeating these improving process, the calibration curve converges to the correct one, and the distortion of the AFM image can be corrected. In the in situ self-calibration through evaluating the inverse function of the calibration curve, the profile measurement data sets were used during the data processing technique. Principles and experimental results of the two methods are presented.

• Structural Engineering and Mechanics
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• 제12권6호
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• pp.685-698
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• 2001

In this paper, a general method for the automatic search for Strut-and-Tie (S&T) models representative of possible resistant mechanisms in reinforced concrete elements is proposed. The representativeness criterion here adopted is inspired to the principle of minimum strain energy and requires the consistency of the model with a reference stress field. In particular, a highly indeterminate pin-jointed framework of a given layout is generated within the assigned geometry of the concrete element and an optimum truss is found by the minimisation of a suitable objective function. Such a function allows us to search the optimum truss according to a reference stress field deduced through a F.E.A. and assumed as representative of the given continuum. The theoretical principles and the mathematical formulation of the method are firstly explained; the search for a S&T model suitable for the design of a deep beam shows the method capability in handling the reference stress path. Finally, since the analysis may consider the structure as linear-elastic or cracked and non-linear in both the component materials, it is shown how the proposed procedure allows us to verify the possibilities of activation of the design model, oriented to the serviceability condition and deduced in the linear elastic field, by following the evolution of the resistant mechanisms in the cracked non-linear field up to the structural failure.

• 대한수학교육학회지:수학교육학연구
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• 제24권3호
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• pp.429-442
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• 2014

본 연구에서는 최근 우리나라에서 논의되고 있는 STEAM 교육에 대하여 등장 배경, 주요 주장, 교육 방안 등을 살펴보고, 수학교육학의 관점에서 STEAM 교육을 분석하고자 하였다. STEAM 교육에서 기본적으로 가정하는 창의, 소통, 내용융합, 배려라는 네 가지 핵심 역량 중 다른 것과 달리 내용융합에 대한 근거는 매우 미약하며, STEAM 교육의 주요 원리는 그 동안 수학교육학이나 창의성 교육과 관련하여 논의되어 온 것에 상당히 유사함을 알아보았다. 결론적으로 STEAM 교육을 너무 급진적으로 추구하는 것은 조심스러우며, 기존에 수학교육학 분야나 창의성 교육과 관련된 논의를 고려하여 보다 많은 기초 연구가 필요함을 주장하였다.

• 한국수학사학회지
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• 제19권2호
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• pp.89-100
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• 2006

현재 우리나라에는 다양한 목적과 특성을 지닌 여러 가지 형태의 대안학교가 있다. 대안학교에서의 수학교육이 일반학교의 수학교육과 같아서는 대안학교의 교육적 이념에 맞는 교육을 실시할 수 없다. 본 논문에서는 학교 부적응 학생들을 대상으로 하는 대안학교에서 이루어지는 수학교육의 문제점을 교육내용 교수방법 교육환경의 세 가지 측면에서 살펴보고, 대안학교 학생들에게 적합한 수학교육의 한 방법으로 수학사를 활용한 수학교육에 대하여 알아본다.

• 한국수학교육학회지시리즈C:초등수학교육
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• 제27권2호
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• pp.187-198
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• 2024

덧셈과 뺄셈, 곱셈과 나눗셈의 관계는 초등학교 2, 3학년 수학에서 명시적으로 제시된다. 그러나 이후 학습에서 이러한 관계는 더 이상 논의되지 않는다. 본 논문은 초등학교 수학 교과서에서 뺄셈과 나눗셈의 계산 방법을 살펴보고, 이를 바탕으로 아동들의 이해 수준에서 덧셈과 뺄셈, 곱셈과 나눗셈의 관계를 정당화하고 뺄셈과 나눗셈에 활용할 수 있는 문제 상황과 활동을 논의한다. 또한 아동들이 덧셈과 뺄셈, 곱셈과 나눗셈의 관계와 등식의 성질을 뺄셈과 나눗셈에 활용하여 얻을 수 있는 교육적 시사점을 도출한다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2024년도 춘계학술발표대회
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• pp.830-833
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• 2024

As Large Language Models (LLM) like OpenAI's ChatGPT[1] continue to grow in popularity, new applications and services are expected to emerge. This paper introduces an experimental study on a smart web-builder application assistance system that combines Computer Vision with GUI object recognition and the ChatGPT (LLM). First of all, the research strategy employed computer vision technology in conjunction with Microsoft's "ChatGPT for Robotics: Design Principles and Model Abilities"[2] design strategy. Additionally, this research explores the capabilities of Large Language Model like ChatGPT in various application design tasks, specifically in assisting with web-builder tasks. The study examines the ability of ChatGPT to synthesize code through both directed prompts and free-form conversation strategies. The researchers also explored ChatGPT's ability to perform various tasks within the builder domain, including functions and closure loop inferences, basic logical and mathematical reasoning. Overall, this research proposes an efficient way to perform various application system tasks by combining natural language commands with computer vision technology and LLM (ChatGPT). This approach allows for user interaction through natural language commands while building applications.

• 대한수학교육학회지:학교수학
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• 제7권4호
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• pp.391-402
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• 2005

도형의 무게중심에 대한 일반적인 고찰은 삼각형의 무게중심에 대한 오개념을 올바르게 이해하게 해 주며, 일반화와 특수화, 해의 존재성과 유일성, 실세계의 수학적 모델링, 공리적 방법론 등과 관련하여 교육적으로 유익한 논의를 유발시킨다 는 점에서 가치가 있다. 본 연구는 무게중심에 대한 오개념의 파악과 해소를 위한 수학적 분석을 제시했으며, 다각형의 무게중심을 구하는 학생들의 잘못된 전략을 분석하여 교육적인 시사점을 얻었다. 또한, 다각형 무게중심의 탐구과정에서 제기될 수 있는 논리적 문제를 밝히고 해결하였다.