• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제4권3호
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• pp.99-110
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• 2015

사물 인터넷(Internet-of-Things, IoT) 컴퓨팅은 무선 인터넷으로 다양한 디바이스를 연결하고 센서를 통해 획득한 사용자 주변 환경 정보를 이용하여 디바이스를 제어하는 여러 기술의 융합 기술이다. IoT 애플리케이션은 기존 소프트웨어와는 달리 다수 개의 IoT 디바이스와 협업을 통해 사용자에게 기능을 제공하고, 센서 네트워크, 통신 기술, 소프트웨어 공학 등 여러 기술들을 활용하여 설계된다. 그리고 최근에 소개된 신기술이기 때문에, 대부분의 연구는 시작 단계에 있다. 이런 이유로, IoT 애플리케이션 개발 프로젝트는 기존의 소프트웨어 개발 프로젝트에서 관찰되지 않은 기술적 이슈들이 발생할 수 있고, 기존의 프로젝트 수행 가이드라인을 그대로 적용하는 것이 제한되어 성공적으로 프로젝트를 수행하는 데 어려움이 따른다. 따라서 본 논문에서는 IoT 애플리케이션을 효율적으로 개발하기 위해, 프로젝트 준비 및 계획 단계와 설계 및 개발 단계로 구분하여 각 단계별로 기술적 이슈를 나열하고 효과적인 솔루션을 제시하고자 한다. 또한 IoT 디바이스 중 AR.Drone과 Sphero Ball을 활용한 애플리케이션 개발에서 본 논문의 솔루션에 대한 적용 및 활용 사례를 보여줌으로써, 연구의 실효성을 검증한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 추계학술대회 논문요약집
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• pp.24-24
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• 2003

For the elderly, achieving a close-to-normal ambulation is important for activities of daily life. Recent researches of SE(Silver Engineering) restoring physical ability would help the elderly by developing the advanced gait assisting devices and orthoses. For the applications using the advanced technologies, the gait characteristics of the elderly must be understood. However, a few studies were performed to investigate the physiological or pathological gaits. The purpose of this study is to provide the gait analysis data and also to investigate relationships between alignment of the lower limb, foot progression angle and knee joint moments in the healthy elderly. By participating a total of 20 healthy elderly persons in this study, the following facts were found: 1) Cadence showed 114.8 steps/min, gait speed showed 1.05 m/s, time per a stride showed 1.06 sec, time per a step showed 0.53 sec, single-supporting phase was 0.41 sec, double-supporting phase was 0.24 sec, stride length was 1.04m, Step length was 0.56m; 2) The maximum knee flexion angle through swing phase showed left 46.82$^{\circ}$, right 40.19$^{\circ}$ and the maximum knee extension angle showed left -1.32$^{\circ}$, right 2.01$^{\circ}$. Knee varus showed left 26.90$^{\circ}$, right 30.93$^{\circ}$; 3) The maximum knee flexion moment showed left 0.363 Nm/kg, right 0.464 Nm/kg, The maximum knee extension moment showed left 0.389 Nm/kg, right 0.463 Nm/kg. The maximum knee adduction moment showed left 0.332 Nm/kg, right 0.379 Nm/kg. The maximum internal rotational moment showed left 0.13 Nm/kg, right 0.140 Nm/kg; 4) The subjects who had varus alignment of the lower extremity had statistically higher in knee adduction moment in mid stance phase; and 5) The subjects who had large foot progression angle had statistically lower in knee adduction moment in late stance phase.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.158-163
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• 2005

Competitive electricity markets necessitate equitable methods for allocating transmission usage in order to set transmission usage charges and congestion charges in an unbiased and an open-accessed basis. So in competitive markets it is usually necessary to trace the contribution of each participant to line usage, congestion charges and transmission losses, and then to calculate charges based on these contributions. A UPFC offers flexible power system control, and has the powerful advantage of providing, simultaneously and independently, real-time control of voltage, impedance and phase angle, which are the basic power system parameters on which sys-tem performance depends. Therefore, UPFC can be used efficiently and flexibly to optimize line utilization and increase system capability and to enhance transmission stability and dampen system oscillations. In this paper, a mathematical approach to allocate the contributions of system users and UPFCs to transmission system usage is presented. The paper uses a dc-based load flow modeling of UPFC-inserted transmission lines in which the injection model of the UPFC is used. The relationships presented in the paper showed modified distribution factors that modeled impact of utilizing UPFCs on line flows and system usage. The derived relationships show how bus voltage angles are attributed to each of changes in generation, injections of UPFC, and changes in admittance matrix caused by inserting UPFCs in lines. The relationships derived are applied to two test systems. The results illustrate how transmission usage would be affected when UPFC is utilized. The relationships derived can be adopted for the purpose of allocating usage and payments to users of transmission network and owners of UPFCs used in the network. The relationships can be modified or extended for other control devices.

• 한국지진공학회논문집
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• 제14권2호
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• pp.75-84
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• 2010

원자력발전소에 설치되는 주요 전기기기들의 내부 부품을 내진검증하기 위해서는 캐비닛내부응답스펙트럼이 필요하고, 이는 캐비닛의 각 위치에서 정확한 지진응답을 구한 후에 생성이 가능하다. 반면에 대부분의 전기기기는 질량과 강성 분포가 복잡하기 때문에 해석적 방법에 의해 동적 분석을 수행하는 것이 어렵다. 이러한 여건을 감안하여 이 연구에서는 해석과 시험을 조합하여 기기의 지진응답을 예측하는 간편한 절차를 제안하였다. 제안된 절차는 먼저 충격시험을 통하여 규명된 실험모드특성을 이용하여 독립된 모드방정식을 구성하고, 이로부터 모드응답을 계산한 다음, 각 모드응답을 중첩함으로써 구조물의 지진응답을 예측한다. 제안된 절차의 신뢰성을 검증하기 위해서, 별도로 제작된 단순 강재 프레임 시편에 제안된 절차를 적용하여 지진응답을 예측하고, 이를 실제 진동대시험을 통하여 계측한 결과와 비교하였다. 이 연구를 통하여 충격시험에 의해 얻어진 실험모드특성을 이용하여 구조물의 지진응답을 비교적 정확하게 예측할 수 있음을 확인하였다.

• 대한수학교육학회지:수학교육학연구
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• 제11권2호
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• pp.273-289
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• 2001

Given that the culture of the mathematics classroom has been perceived as an important topic in mathematics education research, this paper deals with the construct of sociomathematical norms which can be used as an analytical tool in understanding classroom mathematical culture. This paper first reviews the theoretical foundations of the construct such as symbolic interactionism and ethnomethodology, and describes the actual classroom contexts in which social and sociomathematical norms were originally identified. This paper then provides a critical analysis of the previous studies with regard to sociomathematical norms. Whereas such studies analyze how sociomathematical norms become constituted and stabilized in the specific classroom contexts, they tend to briefly document sociomathematical norms mainly as a precursor to the detailed analysis of classroom mathematical practice. This paper reveals that the trend stems from the following two facts. First, the construct of sociomathematical norms evolved out of a classroom teaching experiment in which Cobb and his colleagues attempted to account for students' conceptual loaming as it occurred in the social context of an inquiry mathematics classroom. Second, the researchers' main role was to design instructional devices and sequences of specific mathematical content and to support the classroom teacher to foster students' mathematical learning using those sequences Given the limitations in terms of the utility of sociomathematical norms, this paper suggests the possibility of positioning the sociomathematical norms construct as more centrally reflecting the quality of students' mathematical engagement in collective classroom processes and predicting their conceptual teaming opportunities. This notion reflects the fact that the construct of sociomathematical norms is intended to capture the essence of the mathematical microculture established in a classroom community rather than its general social structure. The notion also allows us to see a teacher as promoting sociomathematical norms to the extent that she or he attends to concordance between the social processes of the classroom, and the characteristically mathematical ways of engaging. In this way, the construct of sociomathematical norms include, but in no ways needs to be limited to, teacher's mediation of mathematics discussions.

• 한국생활과학회지
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• 제15권2호
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• pp.209-225
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• 2006

The purpose of this study is to research the actual condition of environment and management of outdoor play at child care centers in Seoul, and to present a planning guideline for outdoor play environment. For this purpose, data were collected by a structured questionnaire and subjects were 164 directors of child care centers located in Seoul. The contents of the questionnaire were composed of general facts about the respondent and facility, environmental condition, managerial condition, and director's understanding about outdoor play. The data were then analyzed using the frequency, percentage, mean and crosstab. The major results have shown the following: 1) Most child care centers in Seoul had some space for outdoor play. 62% of them used front yard and 11 % a rooftop. 2) The space usually included fixed play instruments such as slide and complex unit structures, sand play area, and open area. It also had many natural elements as shrubs and earth. 3) 78% of the centers had a schedule for outdoor play. The schedule operates flexibly according to each center's own day schedule. Generally, a time for outdoor play was 21 to 30 minutes. 4) The directors of child care centers thought highly of outdoor play for it contributes to the balanced development of children. They answered that equipments and spaces, program devices, and teacher's understanding are some of the important factors for active outdoor play. 5) Most of them wanted wood-working area (construction activity area), water play area, and cages.

• 디자인학연구
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• 제14권2호
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• pp.217-224
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• 2001

본 연구는 디자인 실무와 교육에서 전개되는 아이디어 스케치 과정을 인지적 그래픽 사고(Graphic Thinking)의 과정으로 보고, 인지적 사고 과정에서 시각적 디자인 사고의 과정의 고찰과 함께 이에 투입되는 언어/시각 정보의 영향을 실험/분석하였다. 실험방법으로 디자인 프로젝트를 설정하여 이의 프로토콜 분석을 시행하였으며, 그 결과를 SAS 통계시스템의 T-Test 분석을 하였다. 연구결과로서, 첫째로, 그래픽 사고는 추상적 /구체적 영역과 개념적/ 지각적 영역 사이에서 언어/ 시각 정보의 인지적 사고과정에 의해 진행되는 것으로 설명될 수 있으며, 둘째로, LCD 태블릿은 펜과 종이를 대체할 수 있는 적절한 장치임을 확인하였다. 셋째로, 컨셉 디자인 단계에서는 언어/ 시각 디자인 정보의 유형에 따른 영향에서 유의적인 차이가 있음을 확인하지 못하였다. 즉, 그래픽 사고과정에서 그래픽 이미지, 지각이미지, 그리고 정신 이미지가 복합적으로 작용되고 있음을 확인해주는 결과로 볼 수 있다. 금후 실험을 다각화하여 연구를 보완할 경우, 디자인 사고의 시각화 과정에 대한 보다 일반화된 이론 체계가 세워질 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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• pp.216-218
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• 2001

The transformer role is very important in power system operation and control; also its price is very expensive. Therefore many kinds of the efforts for transformer protection have been executed. So for as, current differential relay(87) has been mainly used for transformer protection. But current differential relaying method has several troubles as followings. Differential current can be occurred by transformers inrush current between winding1 and winding2 of transformer when transformer is initially energized. Also harmonic restrained element used in current differential relaying method is one of the causes of relays mal-operation because recently harmonics in power system gradually increase by power switching devices(SVC, FACTS, DSC, etc). Therefore many kinds of effort have been executed to solve the trouble of current differential relay and one of them is method using ratio of increment of flux linkages(RIFL) of the primary and secondary windings. This paper introduces a novel protective relay for power transformers using RIFL of the primary and secondary windings. Novel protective relay successfully discriminates between transformer internal faults and normal operation conditions including inrush and this paper includes real time test results using RTDS(Real Time Digital Simulator) for novel protective relay. A novel protective relay was designed using the TMS320C32 digital signal processor and consisted of DSP module. A/D converter module, DI/DO module, MMI interface module and LCD display module and developed by Xelpower co., Ltd.

• 전기학회논문지
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• 제67권8호
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• pp.994-1001
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• 2018

In this paper, to studied about future power system construction using PSS / E-Python API. Python-based future system automatical construction methods and modeling of renewable sources. it confirmed the stability of the powert system for each renewable area by calculating the weighted short circuit ratio (WSCR) index. it calculated the short circuit ratio (SCR) and selected the transmission line linkage scenario to improve the stability of vulnerable areas. it confirmed the WSCR index improvement through the selected transmission line linkage of scenario, and analyzed the stability of the renewable power system applying the scenario. It describes Facts and Shunt devices adjustment for the load flow convergence. It describes the stable methed of the bus voltage through the transformer Ratio Tap adjustment. By performing PSS/E ASCC using the Python it was performed three-phase short circuit fault capacity analysis, it is confirmed whether excess of the fault current circuit breaker capacity. In order to contingency accident analysis, it have described the generation of one or two line list of each areas using the Python. The list is used to contingency analysis and describe the soluted of the transmission line overload through comparison before and after adding the scenario line.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1471-1481
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• 2014

This paper presents the new power dissipation model of individual switching device in a high-level modular multilevel converter (MMC), which can be mostly used in voltage sourced converter (VSC) based high-voltage direct current (HVDC) system and flexible AC transmission system (FACTS). Also, the voltage balancing method based on sorting algorithm is newly proposed to advance the MMC functionalities by effectively adjusting switching variations of the sub-module (SM). The proposed power dissipation model does not fully calculate the average power dissipation for numerous switching devices in an arm module. Instead, it estimates the power dissipation of every switching element based on the inherent operational principle of SM in MMC. In other words, the power dissipation is computed in every single switching event by using the polynomial curve fitting model with minimum computational efforts and high accuracy, which are required to manage the large number of SMs. After estimating the value of power dissipation, the thermal condition of every switching element is considered in the case of external disturbance. Then, the arm modeling for high-level MMC and its control scheme is implemented with the electromagnetic transient simulation program. Finally, the case study for applying to the MMC based HVDC system is carried out to select the appropriate insulated-gate bipolar transistor (IGBT) module in a steady-state, as well as to estimate the proper thermal condition of every switching element in a transient state.