• 한국수학교육학회지시리즈C:초등수학교육
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• 제22권1호
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• pp.13-27
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• 2019

초등 수학 교과서에서 모눈종이의 활용은 수와 연산, 도형, 측정 영역에서 사용하고, 이 중에서 도형 영역에서 가장 많이 사용하고 있다. 이러한 사용에도 불구하고 실제 초등 수학 교과서의 모눈종이를 활용한 수업 과정을 보면 모눈종이 사용에 따른 시행착오의 수정이나 보완이 어려워서 보다 효과적인 방안이 필요해보였다. 이에 본 연구에서는 한국과학창의재단(2017)의 '수학 수업용 교구 표준안'에서 제시한 교구 중에서 모눈종이보다 더 효과적인 모눈종이판 교구의 활용성을 설문 조사 하였다. 조사는 초등 수학 교과서에서 모눈종이를 활용하고 있는 차시별 학습주제 중에서 모눈종이와 모눈종이판에서 어느 것이 더 효과적인지를 교사들에게 조사한 후, 모눈종이판의 활용이 더 효과적인 학습주제의 성취기준을 찾아 분석하고, 영역별로 가장 효과적인 학습 주제의 구체적인 활동 과정을 제시하였다.

• 한국재료학회지
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• 제21권12호
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• pp.650-654
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• 2011

In this paper, the effects of conventional and newly developed elastomer modified underfill materials on the mechanical shock reliability of BGA board assembly were studied for application in mobile electronics. The mechanical shock reliability was evaluated through a three point dynamic bending test proposed by Motorola. The thermal properties of the underfills were measured by a DSC machine. Through the DSC results, the curing condition of the underfills was selected. Two types of underfills showed similar curing behavior. During the dynamic bending reliability test, the strain of the PCB was step increased from 0.2% to 1.5% until the failure circuit was detected at a 50 kHz sampling rate. The dynamic bending reliability of BGA board assembly using elastomer modified underfill was found to be superior to that of conventional underfill. From mechanical and microstructure analyses, the disturbance of crack propagation by the presence of submicron elastomer particles was considered to be mainly responsible for that result rather than the shear strength or elastic modulus of underfill joint.

• 한국산학기술학회논문지
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• 제10권9호
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• pp.2221-2226
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• 2009

본 논문에서는 태양전지를 기본 전력공급원으로 사용하는 대형건물용 옥외간판 LED 표식장치를 시스템을 구현하였다. 부하 발전 배터리 용량을 산정하고, 상용 예비전력을 도입한 계통연계형 태양광발전시스템을 설계하였다. 표식장치인 LED 부하에 대한 사전 휘도 시뮬레이션 및 균일성 검사를 거친 후, 이를 태양광발전시스템과 함께 설치하였다. 태양전지-LED 표식장치 현장 시험운영을 통하여 시스템의 신뢰성과 성능 및 제반 문제점을 파악하였다.

• 대한임베디드공학회논문지
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• 제9권2호
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• pp.101-107
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• 2014

Mobile robots use an environment map of its workspace to complete the surveillance task. However grid-based maps that are commonly used map format for mobile robot navigation use a large size of memory for accurate representation of environment. In this reason, grid-based maps are not suitable for path planning of mobile robots using embedded board. In this paper, we present the path planning algorithm that produce a secure path rapidly. The proposed approach utilizes a hybrid map that uses less memory than grid map and has same efficiency of a topological map. Experimental results show that the fast path planning uses only 1.5% of the time that a grid map based path planning requires. And the results show a secure path for mobile robot.

• 한국정보처리학회논문지
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• 제2권4호
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• pp.592-602
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• 1995

자동 배선 시스템의 배선영역 모델링 방법은 논-그리드(non-grid)와 그리드 방식 을 사용하고 있다. 본 논문에서는 라우팅 속도를 개선하기 위해 논-그리드와 그리드 방식을 혼합하여 자동 배선 시스템을 개발 하였다. 그리드방식은 PCB상에 전기적, 물 리적 요소들이 적다 할지라도 보드와 그리드의 크기에 제약을 받기 때문에 메모리가 많아지게 되어 자동 배선 속도를 감소시키는 단점을 가지고 있고, 논-그리드 방식은 shape-based 방식의 영역 처리방식을 사용하므로 메모리를 상당히 적게 소요된다. 그러므로 본 논문에서는 논-그리드 방식과 그리드 방식을 적용하여 초기 배선시에는 전자를 적용해 속도를 개선시켰고, 초기 배선시 연결되지 않은 배선은 후자를 적용해 서 완전한 배선이 이루어 질 수 있도록 하였다. 따라서, 본 시스템을 이와 같은 방식 을 이용하여 IBM 486DX2-66 컴퓨터의 Windows NT 환경하에서 Borland C＋＋로 개발하 였다.

• Journal of Welding and Joining
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• 제18권4호
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• pp.64-69
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• 2000

Reliability of PBGA(Plastic Ball Grid Array) package is very weak compared with normal plastic packages. The reliability are the lower resistance to popcorn cracking, which is reduced by moisture absorption in PCB(Printed Circuit Board). This paper adapts plasma treatment process and analyzes their effect. The contents of C and Cl decrease after plasma treatment but O, Ca and N relatively increase. The Plasma treatment to improve the adhesion between EMC(Epoxy Molding Compound) and PCB(solder mask). The degree of improvement was over 100% Max., which is depend on the properties of EMC. Ar+H$_2$as plasma gas show good result. There is a little difference in RF power and treatment time.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.524-527
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• 2000

In this paper, we have studied minimization of the burr which occurred after $\mu$-BGA(ball grid array) singulation process, singulation of the multilayer with a pulsed Nd:YAG(266, 532 nm) laser is used to cut the metal layer which doesn't well absorb laser beam. Especially, the photoresist and $N_2$blowing is effective to minimize of the surface demage and burr. In this experiment, the $N_2$ blowing reduces a laser energy loss by debris and suppress a surface oxidation. The SEM(scanning electron microscopes) and non-contact 3D inspector are used to measure cutting line-width and surface demage. The $\mu$-BGA singulation threshold energy is 75.0 J/cm$^2$at 30 ${\mu}{\textrm}{m}$/s scan speed.

• Journal of Power Electronics
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• 제13권6호
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• pp.1016-1023
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• 2013

Predictive current control offers the potential for achieving more precise current control with a minimum of distortion and harmonic noise. However, the predictive method is difficult to implement and has a greater computational burden. This paper introduces a theoretical analysis and experimental verification for an improved predictive current control technique applied to single phase grid connected voltage source inverters (VSI). The proposed technique has simple calculations. An ATmega1280 microcontroller board is used to implement the proposed technique for a simpler and cheaper control system. To enhance the current performance and to obtain a minimum of current THD, an improved tri-level PWM switching strategy is proposed. The proposed switching strategy uses six operation modes instead of four as in the traditional strategy. Simulation results are presented to demonstrate the system performance with the improved switching strategy and its effect on current performance. The presented experimental results verify that the proposed technique can be implemented using fixed point 8-bit microcontroller to obtain excellent results.

• JSTS:Journal of Semiconductor Technology and Science
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• 제12권3호
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• pp.320-330
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• 2012

In this paper, we investigate the power integrity of grid structures for power and ground distribution on printed circuit board (PCB). We propose the 2D transmission line method (TLM)-based model for efficient frequency-dependent impedance characterization and PCB-package-integrated circuit (IC) co-simulation. The model includes an equivalent circuit model of fringing capacitance and probing ports. The accuracy of the proposed grid model is verified with test structure measurements and 3D electromagnetic (EM) simulations. If the grid structures replace the plane structures in PCBs, they should provide effective shielding of the electromagnetic interference in mobile systems. An analytical model to predict the shielding effectiveness (SE) of the grid structures is proposed and verified with EM simulations.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 춘계학술대회 논문집
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• pp.440-445
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• 2007

This paper deals with assessment of risk component for electrical safety and investigation on the spot of computer room in elementary middle high school. The investigation was carried out side by side for floor, outlet, panel board, earth leakage circuit breaker at computer room In order to assess electrical safety at computer room, grounding simulator and power quality monitor have been used. Potential rise has been measured and analyzed for ground rod and grounding grid by using the simulator. Phase and neutral-line current have been monitored in real time. As a consequence, it is desirable for us to install conductive tile at floor of computer room Grounding grid had better than ground rod for electrical safety. Neutral-line current was produced by unbalanced phase current.