• 전기학회논문지
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• 제61권6호
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• pp.851-858
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• 2012

In this paper, we design a seismic data acquisition system(SDAS) and implement it. This system is essential for development of a noble local earthquake disaster preventing system in population center. In the system, we choose a proper MEMS-type triaxial accelerometer as a sensor, and FPGA and ARM processor are used for implementing the system. In the SDAS, each module is realized by Verilog HDL and C Language. We carry out the ModelSim simulation to verify the performances of important modules. The simulation results show that the FPGA-based data acquisition module can guarantee an accurate time-synchronization for the measured data from each axis sensor. Moreover, the FPGA-ARM based embedded technology in system hardware design can reduce the system cost by the integration of data logger, communication sever, and facility control system. To evaluate the data acquisition performance of the SDAS, we perform experiments for real seismic signals with the exciter. Performances comparison between the acquired data of the SDAS and the reference sensor shows that the data acquisition performance of the SDAS is valid.

• 한국측량학회지
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• 제27권4호
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• pp.477-484
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• 2009

u-City 운영의 중심 역할을 담당하는 통합운영플랫폼은 유무선 통신망, 센서망을 연결하여 각종 센서 및 장치들을 수용하고, 다양한 정보를 통합적으로 수집 및 분석하며, 각종 인프라 요소들을 지능적으로 관제 운영한다. 본 연구에서는 u-City에서 통합운영플랫폼이 제공해야 할 서비스들을 공통응용 서비스, 운용관리 서비스 및 플랫폼 게이트웨이 서비스로 구분하고 각 서비스에 대한 세부 기능을 구성하고자 하였다. 이를 통해 구성된 세부 기능들은 상호간 정보 흐름 및 역할 정립을 통해 통합운영플랫폼의 서비스 기능을 명확히 할 것이며, 향후 서비스 기능 추가 및 수정에 따른 통합운영플랫폼의 기능 구성 참조 모델로 활용될 수 있을 것이다.

• 한국산업정보학회논문지
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• 제21권4호
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• pp.21-30
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• 2016

In a single-phase power factor correction (PFC), the standard cascaded control algorithm using a proportional-integral-derivative (PID) controller has two main drawbacks: an inability to track sinusoidal current reference and low harmonic compensation capability. These drawbacks cause poor power factor and high harmonics in grid current. To improve these drawbacks, this paper uses a proportional-integral-derivative-resonant (PIDR) controller which combines a type-III PID with proportional-resonant (PR) controllers in the PFC. Based on a small signal model of the PFC, the type-III PID controller was implemented taking into account the bandwidth and phase margin of the PFC system. To adopt the PR controllers, the spectrum of inductor current of the PFC was analyzed in frequency domain. The hybrid PIDR controller were simulated using PSCAD/EMTDC and implemented on a 3 kW PFC prototype hardware. The performance results of the hybrid PIDR controller were compared with those of an individual type-III PID controller. Both controllers were implemented successfully in the single-phase PFC. The total harmonic distortion of the proposed controller were much better than those of the individual type-III PID controller.

• The Journal of Asian Finance, Economics and Business
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• 제7권11호
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• pp.33-43
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• 2020

This study aims to investigate the importance of earnings quality as a determinant of companies' performance. It provides some empirical evidences from an emerging market, specifically from the Jordanian market. This study developed an econometric model for the effect of earnings quality on the companies' performance using empirical evidence. The study employs a panel data analysis method by using a sample of all Jordanian industrial public shareholding companies listed on Amman Stock Exchange (ASE) during 2010-2018. The results reveal that Return on Assets (ROA), Return on Equity (ROE), and Earnings Per Share (EPS) as proxies of company's performance are affected by the earnings quality. This provides the importance of positive earnings quality that eventually influences the companies' performance. The results of this study suggest that the higher control level on the managers' behavior and its outcome will have an effect on earnings quality, and thus the company's performance increases. As well as, high relevance of accounting information will improve earnings quality, and thus earnings quality with the interaction factors of the company's environment work on improving performance. As a conclusion, this study can work as a reference to assist standard setters, security analysts, regulators and other accounting-information users in appraising relation between the earnings quality and companies' performance.

• 설비공학논문집
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• 제14권2호
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• pp.153-160
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• 2002

As a way to assess the reliability of programs for building energy analysis, verification experiment and calculation of heating load are simultaneously conducted for a well-defined test space. Experimental conditions are carefully set to minimize uncertainties associated with radiation heating, air change, infiltration, and room-to-room interaction. Dyna- mic load calculations using TRNSYS, which are performed for two different computation domains, rely on the energy rate control that represents inherent load characteristics of a space. The predicted instantaneous heating load favorably simulates the overall behavior the measured one, though the latter fluctuates much more rapidly than the former Comparison of the accumulative load between the experiment and calculations shows a close agreement within an engineering tolerance, regardless of the computation model. It is deduced from such findings that the present experimental results along with weather information can serve as a set of reference data for validating load calculation softwares from the users'standpoint. In order to enhance the completeness of this work, a complementary study on the cooling load for the same test space is highly recommended.

• Journal of Power Electronics
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• 제9권4호
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• pp.631-642
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• 2009

The sun is a useful reference direction because of its brightness relative to other astronomical objects and its relatively small apparent radius as viewed by spacecrafts near the Earth. Most satellites use solar power as a source of energy, and so need to make sure that solar panels are oriented correctly with respect to the sun. Also, some satellites have sensitive instruments that must not be exposed to direct sunlight. For all these reasons, sun sensors are important components in spacecraft attitude determination and control systems. To minimize components and structural mass, some components have multiple purposes. The solar cells will provide power and also be used as coarse sun sensors. A coarse Sun sensor is a low-cost attitude determination sensor suitable for a wide range of space missions. The sensor measures the sun angle in two orthogonal axes. The Sun sensor measures the sun angle in both azimuth and elevation. This paper presents the development of a model to determine the attitude of a small cube-shaped satellite in space relative to the sun's direction. This sensor helps small cube-shaped Pico satellites to perform accurate attitude determination without requiring additional hardware.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.495-498
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• 2010

본 시험장치는 가스터빈엔진의 이론적 열역학 계산을 실제 성능시험을 통해 비교해보고 관련 교육기관, 연구소 등에 가스터빈 엔진의 작동 원리와 구조에 대한 기초지식을 제공하도록 개발되었다. 추력 80lbf급 마이크로 터보제트 엔진을 대상으로 하여 NI DAQ(데이터 수집)장치와 LabVIEW 프로그램을 이용하여 실시간 계측되는 데이터와 기준 엔진 성능 시뮬레이션 데이터를 비교 할 수 있는 프로그램을 개발하였다.

• 조명전기설비학회논문지
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• 제25권5호
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• pp.22-33
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• 2011

An induction motor operated with a conventional direct self controller(DSC) shows a sluggish response during startup and under changes of torque command. Fuzzy logic controller(FLC) is used in conjection with DSC to minimize these problems. A FLC chooses the switching states based on a set of fuzzy variables. Flux position, error in flux magnitude and error in torque are used as fuzzy state variables. Fuzzy rules are determinated by observing the vector diagram of flux and currents. This paper proposes hybrid fuzzy controller for direct torque control(DTC) of induction motor drives. The speed controller is based on adaptive fuzzy learning controller(AFLC), which provide high dynamics performances both in transient and steady state response. Flux position, error in flux magnitude and error in torque are used as FLC state variables. The speed is estimated with model reference adaptive system(MRAS) based on artificial neural network(ANN) trained on-line by a back-propagation algorithm. This paper is controlled speed using hybrid fuzzy controller(HFC) and estimation of speed using ANN. The performance of the proposed induction motor drive with HFC controller and ANN is verified by analysis results at various operation conditions.

• 한국정보처리학회논문지
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• 제4권10호
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• pp.2453-2460
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• 1997

소프트웨어 개발방법에서 객체지향 분석방법은 많이 있고 계속적으로 새로운 기법이 소개되고 있다. 그러나 기존의 객체지향 분석방법에서는 정확한 객체의 식별과 확인이 어렵고 소프트웨어의 문제를 데이터에 근거해서 초기에 분해하기 때문에 상위 레벨의 제어 측면을 소홀히 하는 경향이 있다. 그 결과 사용자가 요구하는 소프트웨어에 대한 부정확한 이해와 분석오류를 낳는다. 따라서 본 논문에서는 이러한 문제점에 인식을 갖고 소프트웨어의 분석 단계에서 사용자의 요구가 충분히 반영될 수 있도록 객체모델의 메서드와 STD의 트랜지션 사이에 상호참조를 통해 완전성과 일관성을 검증할 수 있는 TOVERC를 설계하였다.

• Structural Engineering and Mechanics
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• 제76권4호
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• pp.435-449
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• 2020

This work presents the formulation of the isogeometric collocation method to solve the strong form equation of a unified and integrated approach of Reissner Mindlin plate theory (UI-RM). In this plate theory model, the total displacement is expressed in terms of bending and shear displacements. Rotations, curvatures, and shear strains are represented as the first, the second, and the third derivatives of the bending displacement, respectively. The proposed formulation is free from shear locking in the Kirchhoff limit and is equally applicable to thin and thick plates. The displacement field is approximated using the B-splines functions, and the strong form equation of the fourth-order is solved using the collocation approach. The convergence properties and accuracy are demonstrated with square plate problems of thin and thick plates with different boundary conditions. Two approaches are used for convergence tests, e.g., increasing the polynomial degree (NELT = 1×1 with p = 4, 5, 6, 7) and increasing the number of element (NELT = 1×1, 2×2, 3×3, 4×4 with p = 4) with the number of control variable (NCV) is used as a comparable equivalent variable. Compared with DKMQ element of a 64×64 mesh as the reference for all L/h, the problem analysis with isogeometric collocation on UI-RM plate theory exhibits satisfying results.