• Nuclear Engineering and Technology
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• 제52권9호
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• pp.2017-2024
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• 2020

In this study, a fractional order proportional integral derivative (FOPID) controller is designed to create the reference power trajectory and to conquer the uncertainties and external disturbances. A fractional nonlinear model was utilized to describe the nuclear reactor dynamic behaviour considering thermal-hydraulic effects. The controller parameters were tuned using optimization method in Matlab/Simulink. The FOPID controller was simulated using Matlab/Simulink and the controller performance was evaluated for Hard variation of the reference power and compared with that of integer order a proportional integral derivative (IOPID) controller by two models of fractional neutron point kinetic (FNPK) and classical neutron point kinetic (CNPK). Also, the FOPID controller robustness was appraised against the external disturbance and uncertainties. Simulation results showed that the FOPID controller has the faster response of the control attempt signal and the smaller tracking error with respect to the IOPID in tracking the reference power trajectory. In addition, the results demonstrated the ability of FOPID controller in disturbance rejection and exhibited the good robustness of controller against uncertainty.

• 대한기계학회논문집A
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• 제26권6호
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• pp.1127-1134
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• 2002

The present paper provides an engineering J estimation equation for surface cracked plates under combined bending and tension. The proposed equation is based on the reference stress approach, and the most relevant normalising loads to define the reference stress for accurate J estimations are given for surface cracked plates under combined bending and tension. Comparisons with J results from extensive 3-D FE analyses, covering a wide range of crack geometry, plate geometry and loading combination, show overall good agreement not only at the deepest point but also at arbitrary points along the crack front. for pure tension, agreement between the estimated J and the FE results is excellent, even at the surface point. On the other hand, for pure bending and combined bending and tension, the estimated J values become less accurate for locations close to the surface point. Thus the results in this paper will be useful to assess short-term fracture or low cycle fatigue of surface defects in plates under combined bending and tension.

• 한국주거학회:학술대회논문집
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• 한국주거학회 2009년 춘계학술발표대회 논문집
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• pp.355-360
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• 2009

Nowadays, the condition of overcrowded cities has raised a question which is insufficient land in cities, and has gotten worse because of the influx of the population continuously. It has rapidly constructed a skyscraper increasingly that the solution to secure a living space against these overcrowded cities until 2000, but these are already positioning itself as one of the new type of residence. The necessity of skyscraper as facilities of residence inside cities has be available both a solution for overcrowded cities and a meaning for a symbol of its represented a landmark. However, constructing skyscrapers indiscreetly can not guarantee dweller's life environment, and it contains risks unless design and facilities criteria are provided. Now, a skyscraper as a new substitute constituting a living space in the future for overcrowded cities deals with a systematic correlation between a city and construction. Therefore the aim of this study were to indicate a method for improvement of dweller's life environment at skyscraper through establishing a point of reference to inculcate them for a sustainable skyscraper from now on.

• 제어로봇시스템학회논문지
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• 제17권10호
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• pp.1029-1036
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• 2011

An energy-efficient reference walking trajectory generation algorithm is suggested utilizing allowable ZMP (Zero-Moment-Point) region, which maxmizes the energy efficiency for cyclic gaits, based on three-dimensional LIPM (Linear Inverted Pendulum Model) for biped robots. As observed in natural human walking, variable ZMP manipulation is suggested, in which ZMP moves within the allowable region to reduce the joint stress (i.e., rapid acceleration and deceleration of body), and hence to reduce the consumed energy. In addition, opimization of footstep planning is conducted to decide the optimal step-length and body height for a given forward mean velocity to minimize a suitable energy performance - amount of energy required to carry a unit weight a unit distance. In this planning, in order to ensure physically realizable walking trajectory, we also considered geometrical constraints, ZMP stability condition, friction constraint, and yawing moment constraint. Simulations are performed with a 12-DOF 3D biped robot model to verify the effectiveness of the proposed method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2009년도 정보 및 제어 심포지움 논문집
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• pp.350-353
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• 2009

The shielding enclosure is very essential device to test the electromagnetic wave power generated by various RF equipments. Some standards for the shielding enclosures were established to test them in right method. Generally, There are IEEE-STD-299 and MIL-STD-285 and NSA-65-6 of the method for measuring the effectiveness of shielding enclosures, the IEEE-STD-299 combined MIL-STD-285 and NSA-65-6 about the method for measuring shielding effectiveness(SE) about 1969 years, but, the measurement point of 299 proposal is many points(including shielding wall, seam, coner beat, shielding door, etc) and demand long time of measurement. To improve SE test method for shielding enclosures was studied and suggested to develop a proper test procedure. First, we measure reference level as frequency range and H/V polarization, secondly, measure leakage point, and finally, measure shield effect and calculate SE. Our method has a merit of the less measurement point than IEEE-STD-299, and shorten time than 299, and define representation SE of shielding enclosure effectively.

• 한국철도학회논문집
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• 제2권3호
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• pp.1-8
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• 1999

In this paper, descibed was the derived algorithm for calculating contact point between wheel and rail and the developed method for rail modeling. The proposed methods use travelling distance to represent rail center line position vector and rail orientation with respect to Newtonian reference frame. The methods call be easily used ill multibody dynamic analysis. Two numerical examples are shown to verify the validity of the proposed methods.

• 한국정보과학회논문지:정보통신
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• 제37권6호
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• pp.489-493
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• 2010

래터레이션 기반 실내 위치 측위 기법은 단말기와 AP(Anchor Point) 사이의 거리 예측을 위하여 RSS(Received Signal Strength)를 주로 사용한다. 그러나 무선 신호는 시간과 공간에 따라 무작위로 변화하는 특성을 가지므로 RSS를 이용한 거리 예측에서 오류의 발생은 불가피하다. 단말기와 AP사이의 거리 예측 정확도는 단말기 위치 예측 정확도에 많은 영향을 미치게 되므로 기존 기법들은 이를 해결하기 위하여 다수의 AP를 사용하였다. 그러나 많은 실험 결과들은 다수의 AP 사용보다는 경로 손실 모델에 잘 부합하는 RSS 측정 값을 가진 AP 즉 기준 AP 만을 선택하여 이용하는 것이 위치 예측 정확도를 향상시킬 수 있는 방법임을 보였다. 따라서 본 논문에서는 실내 환경에서 단말기의 측위 정확도활 향상시키기 위한 기준 AP 선택 기법과 선택된 기준 AP들을 이용한 적응적 거리 예측 기법을 제안한다. 또한 실내 위치 측위 시스템을 구현하여 다양한 실험 환경에서의 실험함으로써 제안 기법의 타당성을 검증하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.17-25
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• 2001

This paper briefly describes the new engineering method, called the enhanced reference stress method, to estimate J (or $C^*$) for non-linear fracture mechanics analysis of defective components, recently proposed by authors. The proposed method offers significant advantages over existing methods in terms of its accuracy, simplicity and robustness. Examples of application of the proposed method to typical piping integrity problems such as through-wall cracked pipes under combined loading, and surface cracked pipes under internal pressure and bending are given. Excellent agreements between the FE J and $C^*$ results and those of the proposed method provide sufficient confidence in the use of the proposed method. One notable point is that the proposed method can be used to estimate J (or $C^*$) along the crack front of surface cracks. Moreover simplicity of the proposed method makes it easy to extend to more complex problems. Thus the proposed method is attractive to assess the significance of defects under practical situations.

• Spatial Information Research
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• 제15권3호
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• pp.301-310
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• 2007

현재 우리나라에는 전국에 약 21,000점의 측량용 국가기준점이 표석 형태로 매설되어 있으며, 대부분이 시통을 위해 산 정상에 매설되어 있어 일반인들의 사용과 접근이 어렵다. 최근 유비쿼터스 환경이 구축되어 감에 따라 위치정보 및 위치정보 기반의 정보를 일반인들에게 손쉽게 제공할 수 있는 서비스가 요구되고 있다. 본 연구에서는 RFID 태그와 2차원 바코드를 이용하여 위치정보를 손쉽게 제공할 수 있는 새로운 개념의 기준점 프로토타입을 제작하였다. 본 논문에서는 개발된 인텔리전트 기준점을 실용화하여 실제로 서비스하기 위해 필요한 사항에 대해 고려하여 보았으며, 실제 테스트를 통해 사용 가능성을 검증해보았다.

• Journal of Positioning, Navigation, and Timing
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• 제1권1호
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• pp.45-49
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• 2012

The flight performance evaluation of navigation system is very significant because the reliability of navigation data directly affect the safety of aircraft. Especially, the high-level navigation system such as DGPS/INS, need more precise flight performance evaluation method. The performance analysis is evaluated by comparing between the navigation system in aircraft and reference trajectory which is more precise than navigation system in aircraft. In order to verify DGPS/INS performance of m-level, the GPS receiver, which is capable post-processed Carrier-phase Differential GPS(CDGPS) method of cm-level, have to be used as reference system. The DGPS/INS is estimated the Center of Gravity (CG) point of aircraft to offer precise performance while the reference system is output the position of GPS antenna which is mounted on the outside of aircraft. Therefore, in order to more precise performance evaluation, it needs to compensate the lever arm and coordinates transformation. This paper use quaternion and Direct Cosine Matrix(DCM) methods as coordinate transformation matrix in lever arm compensation of CDGPS reference trajectory. And it compares NED errors of DCM and quaternion transformation in lever arm of reference trajectory via DGPS/INS result.