• 융복합기술연구소 논문집
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• 제4권2호
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• pp.55-59
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• 2014

A cat is able to quickly recover balance from unstable posture. To observe the balance recovery procedure of the cat, an impulse is applied to the cat while walking on a narrow bridge. We find that it rotates its tail toward the falling direction. In our previous research, the balance recovery procedure is analyzed based on the law of the angular momentum conservation and then a key equation is derived to maintain the balance. However, it did not consider the gravity, so the performance is not good. In this paper, a new dynamic model is proposed using the Lagrangian mechanics. In the method, the gravity is included in the potential energy. Through the proposed dynamic model, controlling the balance of a walking robot is possible.

• 한국전자파학회논문지
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• 제14권10호
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• pp.1060-1070
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• 2003

국내 위성통신용 Ku/Ka 대역 파라볼라 안테나에 적용될 수 있는 삼중 사각 루프 슬롯 배열 형태인 새로운 주파수 선택 반사기 구조를 제시하였다. 본 논문에서 설계, 제작된 주파수 선택 반사기 구조는 다층 유전체인 하니콤 위에 삼중의 사각 루프 슬롯으로 구성되는 단위 소자가 평면에 2차원적으로 주기적인 배열 형태를 지닌다. 주파수 선택 반사기를 제작하여 측정한 결과 계산 결과와 일치되었으며, 요구되는 사양대로 14/12 GHz대 주파수에서는 입사파의 대부분이 투과되는 반면, 30/20 GHz대 주파수에서는 전반사가 일어남을 확인하였다.

• 천문학회보
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• 제37권1호
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• pp.76.1-76.1
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• 2012

One of the main challenges for future 21-cm observations is to remove foregrounds which are several orders of magnitude more intense than the HI signal. We propose a new technique for removing foregrounds of the redshifted 21-cm observations. We consider multi-frequency interferometer observations. We assume that the 21-cm signals in different frequency channels are uncorrelated and the foreground signals change slowly as a function of frequency. When we add the visibilities of all channels, the foreground signals increase roughly by a factor of N because they are highly correlated. However, the 21-cm signals increase by a factor of sqrt{N} because the signals in different channels contribute randomly. This enables us to obtain an accurate shape of the foreground angular power spectrum. Then, we obtain the 21-cm power spectrum by subtracting the foreground power spectrum obtained this way. We describe how to obtain the average power spectrum of the 21-cm signal.

• Journal of Mechanical Science and Technology
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• 제17권12호
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• pp.1977-1985
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• 2003

In the present study, the dynamic modelling of planar mechanisms that consist of a system of rigid bodies is carried out using point coordiantes. The system of rigid bodies is replaced by a dynamically equivalent constrained system of particles. Then for the resulting equivalent system of particles, the concepts of linear and angular momentums are used to generate the equations of motion without either introducing any rotational coordinates or distributing the external forces and force couples over the particles. For the open loop case, the equations of motion are generated recursively along the open chains. For the closed loop case, the system is transformed to open loops by cutting suitable kinematic joints with the addition of cut-joints kinematic constraints. An example of a multi-branch closed-loop system is chosen to demonstrate the generality and simplicity of the proposed method.

• International Journal of Precision Engineering and Manufacturing
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• 제1권2호
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• pp.115-123
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• 2000

We propose an extended version of multi-step algorithm of self-calibration of interferometric optical testing instruments. The key idea is to take wavefront measurements with near equal steps in that a slight angular offset is intentionally provided in part rotation. This generalized algorithm adopts least squares technique to determine the true azimuthal positions of part rotation and consequently eliminates calibration errors caused by rotation inaccuracy. In addition, the required numbers of part rotation is greatly reduced when higher order spatial frequency terms are of particular importance.

• Journal of information and communication convergence engineering
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• 제7권3호
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• pp.281-285
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• 2009

Mobile robot has various sensors for describing the external world. The ultrasonic sensor widely applied to the most mobile robot to detect the obstacle and environment owing to low cost, its easy to use. However, ultrasonic sensor has major problems: the uncertainty information of sensor, false readings caused by specular reflection, multi path effect, low angular resolution and sensitivity to changes in temperature and humidity. This paper describes a sensor system for map building of mobile robot. It was made of low cost PSD (Position Sensitive Detector) sensor array and high speed RISC MPU. PSD sensor is cost effective and light weighting but its output signal has many noises. We propose heuristic S/W filter to effectively remove these noises. The developed map building sensor system was equipped on a mobile robot and was compared with ultrasonic sensor through field test.

• 천문학회지
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• 제34권4호
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• pp.297-299
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• 2001

We have constructed the foundations to a series of theoretical diagnostic methods to probe the jet phenomenon in young stars as observed at various optical forbidden lines. We calculate and model in a self-consistent manner the physical and radiative processes which arise within an inner disk-wind driven magneto centrifugally from the circumstellar accretion disk of a young sun-like star. Comparing with real data taken at high angular resolution, our approach will provide the basis of systematic diagnostics for jets and their related young stellar objects, to attest the emission mechanisms of such phenomena. This work can help bring first-principle theoretical predictions to confront actual multi-wavelength observations, and will bridge the link between many very sophiscated numerical simulations and observational data. Analysis methods discussed here are immediately applicable to new high-resolution data obtained with HST and Adaptic Optics.

• 전자공학회논문지A
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• 제30A권11호
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• pp.1-10
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• 1993

A Study on New Digital In this paper, we propose a new Angular Form Carrier Recovery Loop(AFCR loop) for PSK modulation technique. AF CR loop includes detected angle symbol and Multi Level Hardlimiter. Using zero crossing DPLL, we model 1st 2nd AF CR loop, and also derive SCurve. In order to prove steady state operation of AF CR loop, we evaluate performance of this loop by Monte-Carlo and analytical simulation method. We also compare the performance of AF CR loop to that of other loop in terms of acquisition, S-Curve, and RMS jitter. From the comparison result, we verify that the performance of AF CR loop operates well in steady state.

• 조명전기설비학회논문지
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• 제24권9호
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• pp.26-35
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• 2010

The maximum output torque developed by the machine is dependent on the allowable current rating and maximum voltage that the inverter can supply to the machine. Therefore, to use the inverter capacity fully, it is desirable to use the control scheme considering the voltage and current limit condition, which can yield the maximum torque per ampere over the entire speed range. This controller is controlled speed and current using hybrid PI(HBPI) controller and estimation of speed using ANN. Also, this paper is proposed maximum torque control of induction motor using slip angular speed and current condition at widely speed range. The performance of the proposed induction motor drive with maximum torque control using HBPI controller is verified by analysis results at dynamic operation conditions.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2005년도 한국컴퓨터종합학술대회 논문집 Vol.32 No.1 (A)
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• pp.505-507
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• 2005

이 논문에서는 Wireless Network Mobility(NEMO) 환경하에서 지속적인 인터넷 연결성을 지원하고 또한 multi-angular routing 을 방지하여 최적화된 경로를 제공하기 위한 메커니즘을 제안한다. 이를 위해 각각의 NEMO 들은 parent-child 관계를 가지는 계층적 멀티 홉 NEMO 구조로 표현하고, 네트워크 이동성을 제공하기 필요한 최소한의 Mobile IPv6 Extension 에 대해서 설명한다. 또한 Wireless NEMO 환경하에서 hop by hop 터널링 기법을 이용한 최적화된 라우팅 동작에 대해 기술한다.