• 전자공학회논문지
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• 제50권2호
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• pp.203-209
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• 2013

Digital Radiography(DR)는 film/screen(F/S)과 비교하여 넓은 계조와 높은 Detective Quantum Efficiency(DQE), Modulation Transfer function(MTF)를 바탕으로 화질의 개선과 저 선량으로 검사가 가능할 것으로 예상됐지만 기대와는 다르게 과노출이 Signal to Noise Ratio(SNR)향상을 가져 오면서 환자 피폭선량의 증가를 가져오게 되었으며 이는 Dose Creep이라는 개념으로 설명 된다. DR에서의 선량 증가 이유는 F/S의 촬영에서 사용했던 관전압(kVp)을 고정 적용하여 Auto Exposure Control(AEC)를 사용하기 때문에 과노출을 유발 할 수 있다. 이에 본 논문은 DR에서 적합한 일반촬영 방법을 제안하고자 관전압이 대조도에 주는 영향, 관전류(mA)변화에 따른 MTF 측정, 머리 모형을 촬영한 영상의 Peak Signal to Noise Ratio(PSNR) 측정을 통해 정량적 평가를 시행 하였다. 그 결과 관전압에 의한 대조도 변화는 후보정 이후 개선이 가능하며, 관전류에 의한 MTF 측정 결과 50%영역은 1.41~1.39 lp/mm, 10% 영역은 3.19~2.8 lp/mm로 관전류 변화에 따른 초점크기 변화는 영상의 해상력에 영향을 주지 않는다. 영상의 PSNR측정 결과는 관전압과 관전류가 증가 하여도 90kVp를 제외하고 30dB 이상으로 시각에 의한 영상의 차이를 인지하기 어렵다. 실험결과를 바탕으로 디지털 일반촬영에서 관전압은 80kVp 이상 100kVp이하, 관전류는 선예도와 상관 관계가 없으므로 선량과 조사시간을 단축 시킬 수 있는 방향으로 사용하기를 제안한다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.21-21
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• 2009

현장의 GMA 용접기는 일반적으로 용접기 본체로부터 와이어 송급장치까지의 거리가 약 50m 정도 떨어져 있고 송급장치로부터 토치까지의 거리는 약 3~5m 정도이다. 특히 국산 GMA 용접기의 와이어 송급장치는 DC 모터의 일종인 프린트모터를 사용하고 있으며 제어기는 오픈루프 제어를 하고 있다. 따라서 와이어 송급속도의 변동을 보상할 수 있는 어떤 수단도 장착되어 있지 않다. 또한 송급장치와 토치간 와이어를 안내하는 케이블 도관의 마찰 때문에 토치 끝단에서의 와이어 송급속도가 불규칙해질 수밖에 없다. 용접 시 와이어 송급속도의 순간적인 변동 때문에 용접부의 전류 파형이 매우 불규칙해지고 이 때문에 용융된 용적이 용융풀로 이행하지 못하고 스패터로 비산하는 현상을 발생시킨다. 본 연구에서는 이를 해결하고자 국산 SCR 용접기 및 인버터 용접기와 호환 가능한 디지털 제어형 와이어 송급장치와 Push-Pull 용접 토치를 개발하였다. 또한, 개발된 시스템을 이용하여 정 역 방향 제어기술을 적용하였고 아크 발생 시의 스패터 최소화 공정을 제안하였다. 실험은 SM490A 강재를 사용하여 BOP(Bead On Plate) 용접을 실행하였다. 용접 중 LabVIEW를 이용하여 아크 발생 초기 전류, 전압 그리고 와이어 송급속도를 측정하였고, 고속 카메라를 이용하여 용접현상을 분석하였다. 본 연구를 통해 아크 발생 초기의 스패터를 최소화하는 공정을 도출할 수 있었다. 용접공정 변수인 아크 발생 초기의 와이어 송급속도, 와이어의 역송급 진행거리 그리고 역송급 판단 시점의 용접 전류 값은 실험을 통해 얻을 수 있었다. 또한, 이 연구를 통해 개발된 시스템의 성능을 평가하였다.

• 소성∙가공
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• 제20권3호
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• pp.193-205
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• 2011

Because of its rustproof property, stainless steel is widely used in kitchen appliances, building materials, electronics, chemical plants and automobile exhausts. In addition, the utilization of stainless steel for fuel cell application is growing. As the demand for this material increases, it is necessary to study the basic properties of stainless steel such as corrosion resistance, heat transfer, formability, cutting or shearing ability and weldability. In this article, the mechanical properties, formability and press forming performance of stainless steel are reviewed. Since temperature and strain rate affect the press forming performance of STS304(austenitic) stainless steel, the influence of these parameters on the plastic behavior should be investigated. Moreover, measures for the prevention of ridging of STS430(ferritic) and delayed fracture of STS430, which respectively appear during and after press forming, should be considered. Recently, stainless steel sheets with a thickness lower than 0.2 mm have been widely used in applications for mobile phone, digital camera and fuel cell separator. Therefore, there is a growing interest of studying the grain size effect and plasticity at the crystal scale in order to understand the anisotropic behavior and micro forming ability of thin sheets. This review paper was written with the objective of helping engineers and researchers to understand the forming characteristics of stainless steel and to establish standards in plastic forming techniques.

• Journal of Multimedia Information System
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• 제7권3호
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• pp.231-238
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• 2020

This work presents a fully analog baseline wander tracking and removal circuitry using high-pass filter (HPF) based R-peak detection and quadratic interpolation that does not require digital post processing, thus suitable for compact and low power long-term ECG monitoring devices. The proposed method can effectively track and remove baseline wander in ECG waveforms corrupted by various motion artifacts, whereas minimizing the loss of essential features including the QRS-Complex. The key component for tracking the baseline wander is down sampling the moving average of the corrupted ECG waveform followed by quadratic interpolation, where the R-peak samples that distort the baseline tracking are excluded from the moving average by using a HPF based approach. The proposed circuit is designed using CMOS 0.18-㎛ technology (1.8V supply) with power consumption of 19.1 ㎼ and estimated area of 15.5 ㎟ using a 4^th order HPF and quadratic interpolation. Results show SNR improvement of 10 dB after removing the baseline wander from the corrupted ECG waveform.

• Transactions on Control, Automation and Systems Engineering
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• 제3권3호
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• pp.146-151
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• 2001

Optical disk drive has excellent advantage of random accessibility of which performance is measured by access time. However, due to the increased rotational velocity of the disk and constraints of mechanical structure, two-stage seek algorithm which executes coarse and fine seeks sequentially has been adopted in most commercial optical disk drives. Although the laser spot is moved to a target track by a single seek operation, the limited operation range of the fine actuator restricts the application of the fine seek algorithm below a few hundreds of tracks. Especially, excessive movement of the objective lens causes a failure in generation of track-cross pulse and results in an unstable seek operation. In this paper, a new control algorithm for extending the fine seek range is proposed with an appropriate control structure. The coarse actuator is utilized to reduce the misalignment between the objective lens and the laser beam axis, and the fine actuator is controlled to follow the reference velocity trajectory. The proposed algorithm is applied to a CD-ROM drive to show its feasibility and some experimental results are presented.

• Transactions on Electrical and Electronic Materials
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• 제15권3호
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• pp.149-154
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• 2014

A new CMOS analog design methodology using an independently optimized self-cascode (SC) is proposed. This idea is based on the concept of the dual-workfunction-gate MOSFETs, which are equivalent to SC structures. The channel length of the source-side MOSFET is optimized, to give higher transconductance ($g_m$) and output resistance ($r_{out}$). The highest $g_m$ and $r_{out}$ of the SC structures are obtained by independently optimizing the channel length ratio of the SC MOSFETs, which is a critical design parameter. An operational amplifier (OPAMP) with the proposed design methodology using a standard digital $0.18-{\mu}m$ CMOS technology was designed and fabricated, to provide better performance. Independently $g_m$ and $r_{out}$ optimized SC MOSFETs were used in the differential input and output stages, respectively. The measured DC gain of the fabricated OPAMP with the proposed design methodology was approximately 18 dB higher, than that of the conventional OPAMP.

• 패션비즈니스
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• 제7권6호
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• pp.21-31
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• 2003

The CLI(Consumer Life Information) is a new study to unite and create new values recognizing the importance of knowledge and information in information-oriented society based on domestic science and digital technology. The objective of this research is to define academic identity of consuming science and CLI, to analyze the theory, styles, manners, psychology and the concept of consumption, which is the base of consuming life, and to present the direction of CLI with tasks and three major axises of CLI. Nowadays, international order demands new paradigms from human beings. Especially, vision and creation of the values are settled as methodological ways considering the economic power. The CLI should be on the same horizon adjusting social change of pointing values and quality in consuming patterns of diversity and variety. Therefore, I would suggest the ways for the CLI to head for as follows. First, it is to perceive the 3 major Axises & Task of CLI. Second, it is to develope service (experiencing goods) and goods that can lead consuming lives. Third, it is to study merchandising strategy, to create new signs and symbols of goods, and to collaborate of R & D(reseach and developement) and Business. Fourth, it is to head for globalization. Consequantly, this study will be helpful to establish the theory of relationship between producer and consumer in fashion business included research and developments of qualitative goods.

• 융합신호처리학회논문지
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• 제9권3호
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• pp.224-229
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• 2008

In the paper, a new Constraint algorithm is proposed to solve the fan-in problem occurred in the encoding circuitry of an ADC. The Flash ADC architecture uses a Double-Base Number System(DBNS). The DBNS has been known to represent the Multidimensional Logarithmic Number System (MDLNS) used for implementing the multiplier accumulator architecture of FIR filter in Digital Signal Processing (DSP) applications. The authors use the DBNS with the base 2 and 3 in designing ADC encoder circuits, which is called as Double Base Integer Encoder(DBIE). A symmetric map is analyzed first, and then asymmetric map is followed to provide addition ready DBNS for DSP circuitry. The simulation results of the DBIE circuits in 6-bit and 8-bit ADC show the effectiveness of the Constraint algorithm with $0.18{\mu}m$ CMOS technology. The DBIE yields faster processing speed compared to the speed of Fat Tree Encoder (FAT) circuits by 17% at more power consumption by 39%.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제24권3호
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• pp.137-173
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• 2021

Research and national standards, such as the Next Generation Science Standards (NGSS) in the United States, promote the development and implementation of K-12 interdisciplinary curricula integrating the disciplines of science, technology, engineering, mathematics, and computer science (STEM+CS). However, little research has explored how teachers provide epistemic support in interdisciplinary contexts or the factors that inform teachers' epistemic support in STEM+CS activities. The goal of this paper is to articulate how interdisciplinary instruction complicates epistemic knowledge and resources needed for teachers' instructional decision-making. Toward these ends, this paper builds upon existing models of teachers' instructional decision-making in individual STEM+CS disciplines to highlight specific challenges and opportunities of interdisciplinary approaches on classroom epistemic supports. First, we offer considerations as to how teachers can provide epistemic support for students to engage in disciplinary practices across mathematics, science, engineering, and computer science. We then support these considerations using examples from our studies in elementary classrooms using integrated STEM+CS curriculum materials. We focus on an elementary school context, as elementary teachers necessarily integrate disciplines as part of their teaching practice when enacting NGSS-aligned curricula. Further, we argue that as STEM+CS interdisciplinary curricula in the form of NGSS-aligned, project-based units become more prevalent in elementary settings, careful attention and support needs to be given to help teachers not only engage their students in disciplinary practices across STEM+CS disciplines, but also to understand why and how these disciplinary practices should be used. Implications include recommendations for the design of professional learning experiences and curriculum materials.

• 한국콘텐츠학회논문지
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• 제14권7호
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• pp.518-528
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• 2014

본 연구는 서울시 강남구 U-street에 설치된 L.E.D 미디어 폴(Media pole)이라는 통합형 가로시설물이 보행 만족도에 어떠한 영향을 미치는지 분석하는 것이 주요 목적이다. 이를 위해 가로시설물로서 미디어폴의 구성요소를 보행자 관점에서 탐색적으로 살펴보고 이를 바탕으로 요인분석을 실시하였다. 요인분석을 통해 제1요인은 '심미 상징성'요인으로 명명하였고, 제2요인은 '형태 조형성', 제3요인은 '접근 연속성'으로 분석하였다. 제4요인은 '감각 전달성', 제5요인은 '정보 매체성'으로 명명하였다. 요인분석은 이용자 관점에서 사례대상지 보행자에 대한 행태관찰과 심층면접(In-depth Interview)을 실시하였고, 33개 예비변수를 도출하였다. 도출된 예비요인을 전문가 F.G.I(Focus Group Interview)를 통해 최종적으로 요인분석에서 사용할 20개 예비변수를 선정하였다. 요인분석을 통해 선정된 5개의 독립변수와 보행자의 만족도를 종속변수로 다중회귀분석을 실시한 결과 강남대로 U-street에 설치된 미디어 폴이 보행자의 보행만족도에 미치는 영향 중 통계학적 유의미한 영향요소는 '심미 상징성'요인으로 분석되었다. U-street에서 미디어 폴은 보행자에게 심미적 감성과 상징성으로 새로운 보행체험에 기여하고 있는 것으로 판단된다. 향후 이용자 편의성을 기반으로한 정보매체로서의 접근성을 강화하고 활용 가능한 콘텐츠 다양화를 유도해야할 것이다. IT 기반형 멀티미디어 매체인 미디어폴은 융합하는 가로환경과 융합하여 보행자에게 새로운 경험을 제공하여 보행활성화에 새로운 수단으로서의 가능성을 시사하고 있다.