• Title/Summary/Keyword: Shift forward method

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Performance Evaluation of Islanding Detection Method by Phase Shifted Feed-Forward Voltage in Steady-State Grid Condition (전향보상 전압의 위상 변화를 통한 단독운전 검출 방법의 계통 정상 상태의 성능 평가)

  • Kim, Dong-Uk;Kim, Sungmin
    • The Transactions of the Korean Institute of Power Electronics
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    • v.23 no.6
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    • pp.373-380
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    • 2018
  • This study proposes a new islanding detection method that uses the phase shift of feed-forward voltage and evaluates the performance of an existing method and the proposed method when the grid frequency changes within the allowable range under steady-state conditions. The investigated existing method, which is slip mode frequency shift (SMS), uses current phase shift to detect islanding. The SMS method supplies reactive current to the grid under this condition, but the proposed method does not generate additional reactive power because it does not depend on the current control loop. The performance in steady-state grid condition is evaluated through simulations and experiments.

Effect of Blood Flow on Carotid and Vertebral Artery During Forward Shift on Head: Case Study (머리의 전방 이동이 경동맥과 추골동맥 혈류량의 변화에 미치는 영향: 사례연구)

  • Ko, Do-hoon;Kim, Han-il;Kim, Myung-joon
    • The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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    • v.21 no.1
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    • pp.43-47
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    • 2015
  • Background: The purpose of this study was to identify the effects of the blood flow on carotid and vertebral artery during the forward shift on head. Methods: A 20-year female healthy subject participated in this study. This study was set up the forward shift on head at the 3cm and 6cm in a shoulder midline (acromion). Measurement method were using duplex ultrasound with colour doppler imaging for the blood flow on carotid and vertebral artery. Results: Carotid artery was increased the blood flow and vertebral artery was decreased the blood flow during forward shift on head. Conclusions: These findings suggest that carotid and vertebral artery changes to the blood flow during forward shift on head. Therefore, we should be consider that hemodynamic factor when apply to the therapeutic exercise for patients of forward head posture.

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A Study on Efficiency Improvement of the Catenary-Pantograph Dynamic Interaction Analysis Program using Shift Forward Method (Shift Forward 방법을 이용한 가선계-판토그래프 동적 상호작용 해석 프로그램의 효율성 향상에 관한 연구)

  • Lee, Jin-Hee;Park, Tae-Won
    • Journal of the Korean Society for Railway
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    • v.15 no.6
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    • pp.572-578
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    • 2012
  • In the electric railway vehicles, securing stable current collection performance is an important factor which determines the quality of operation and the maximum speed. In order to predict such current collection performance, various analysis methods have been proposed for a long time. Also, investigations for improving the accuracy of the results and the efficiency of the analysis process have been performed. In this paper, a method for the efficiency improvement has been proposed. This method is based on the basic concept that the system equations of motion of a catenary numerical model include only interactive range with a pantograph. In this paper, an algorithm and generalized process for applying proposed method are introduced. Also, validity of the results and utility of the method was verified and studied.

Datuming by Wavefield Depth Extrapolation (파동장 외삽을 이용한 데이터밍)

  • Ji Jun
    • Geophysics and Geophysical Exploration
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    • v.1 no.2
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    • pp.116-126
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    • 1998
  • I present a datuming scheme for poststack data that uses wavefield depth extrapolation. The method I have developed allows the use of any depth extrapolation technique, such as phase-shift, split-step, and finite-difference extrapolation. I derive the datuming algorithms by transposing and taking the complex conjugate (i.e. taking adjoint) of the corresponding forward modeling operator, which does upward extrapolation from a flat surface to an irregular surface. The exact adjoint relation between the forward modeling operator and the datuming operator is demonstrated algebraically. Testing the poststack datuming algorithms with synthetic data, using several depth extrapolation algorithms, has shown that the method works well.

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Average SER Performance Analysis for Opportunistic Amplify-and-Forward Relay Systems (OAF 시스템의 정확한 심볼 오류 성능 분석)

  • Nam, Sang-Ho;Ko, Kyun-Byoung;Hong, Dae-Sik
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.49 no.4
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    • pp.1-8
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    • 2012
  • This paper presents a method for obtaining an exact average symbol error rate (ASER) of M-ary Phase Shift Keying (MPSK) for opportunistic amplify-and-forward (OAF) relay systems over Rayleigh fading channels. This is based on the relay selection probability when a relay is selected as the best one with respect to the received signal-to-noise ratio. We then derive the modified moment generating function (MGF) for OAF relay systems by taking the given relay selection probability into consideration. Based on the modified MGF, we derive the exact ASER which accurately explicates OAF relay system characteristics. Our results confirm that the derived ASER provides a tight upper bound for OAF relay systems.

Phase Shift Analysis of 6Li Elastic Scattering on 12C and 28Si at Elab = 318 MeV

  • Kim, Yong Joo
    • New Physics: Sae Mulli
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    • v.68 no.12
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    • pp.1331-1337
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    • 2018
  • We present a three-parameter phase shift model whose form is the same as that of Coulombmodified Glauber model obtained from Gaussian nuclear densities. This model is applied to the $^6Li+^{12}C$ and the $^6Li+^{28}Si$ elastic scatterings at $E_{lab}=318MeV$. The calculated differential cross sections provide quite a satisfactory account of the experimental data. The diffractive oscillatory structures observed at forward angles can be explained as being due to the strong interference between the near-side and the far-side scattering amplitudes. The optical potentials for two systems are predicted by using the method of inversion. The calculated inversion potentials are found to be in fairly good agreements with the results determined from the optical model analysis in the surface regions around the strong absorption radius. We also investigate the effects of parameters in the three-parameter phase shift model on the elastic scattering cross sections.

Comparative Study on the Radiation Techniques for the Problem of Floating Body Motion with Forward Speed (전진 속도를 가지는 부유체 운동 문제에 대한 방사기법 비교 연구)

  • Oh, Seunghoon
    • Journal of the Society of Naval Architects of Korea
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    • v.56 no.5
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    • pp.396-409
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    • 2019
  • In this paper, a comparative study on the radiation techniques for the motion analysis of the three dimensional floating structure with the forward speed was carried out. The Sommerfeld radiation condition, the damping technique, and the point shift technique were used for the comparative study. Radiated wave patterns and hydrodynamic coefficients of the heave motion of floating structure with the forward speed were compared and analyzed. The characteristics and limitations of each radiation technique were analyzed through the calculation results. To overcome the limitations of conventional radiation techniques, the hybrid radiation technique combining the Sommerfeld radiation condition with the damping technique was proposed. It is confirmed that the proposed method, the Hybrid radiation technique, improves the limitation of the speed range and the dissipation of the wave of the conventional radiation technique. The motion analysis code of the three dimensional floating structure with the forward speed based on the Rankine source method with hybrid radiation technique was developed. In order to validate the developed code, hydrodynamic analyses were carried and compared with published experiments.

Layered Nonlinear feed-forward Sequence Generator (계층 구조의 비선형 피드포워드 수열 발생기)

  • 은유창;홍윤표;진석용;송홍엽
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.5C
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    • pp.595-600
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    • 2004
  • In this paper, we propose a new simple scheme of layered nonlinear feedforward logic (NLFFL) overlaid on a linear feedback shift resistor (LFSR) to generate pseudonoise sequences, which have good balance property and large linear complexity. This method guarantee noiselike statistics without any designed connection scheme e.g. Langford arrangement.

A Speed Control for the Reduction of the Shift Shocks in Electric Vehicles with a Two-Speed AMT

  • Kim, Young-Ki;Kim, Hag-Wone;Lee, In-Seok;Park, Sung-Min;Mok, Hyung-Soo
    • Journal of Power Electronics
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    • v.16 no.4
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    • pp.1355-1366
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    • 2016
  • In the present paper, a speed control algorithm with fast response characteristics is proposed to reduce the shift shock of medium/large-sized electric vehicles equipped with a two-speed AMT. Shift shocks, which are closely related with to the vehicles' ride comfort, occur due to the difference between the speed of the motor shaft and the load shaft when the gear is engaged. The proposed speed control method for shift shock reduction can quickly synchronize speeds occurring due to differences in the gear ratios during speed shifts in AMT systems by speed command feed-forward compensation and a state feedback controller. As a result, efficient shift results without any shift shock can be obtained. The proposed speed control method was applied to a 9 m- long medium- sized electric bus to demonstrate the validity through a simulated analysis and experiments.

Enhancement of Image Sharpness in X-ray Digital Tomosynthesis Using Self-Layer Subtraction Backprojection Method (관심 단층 제거 후 역투사법을 이용한 X-선 디지털 영상합성법에서의 단층영상 선명도 향상에 관한 연구)

  • Shon, Cheol-Soon;Cho, Min-Kook;Lim, Chang-Hwy;Cheong, Min-Ho;Kim, Ho-Kyung;Lee, Sung-Sik
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.1
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    • pp.8-14
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    • 2007
  • X-ray digital tomosynthesis is widely used in the nondestructive testing and evaluation, especially for the printed circuit boards (PCBs). In this study, we propose a simple method to reduce the blur artefact, frequently claimed in the conventional digital tomosynthesis based on SAA (shift-and-add) algorithm, and thus restore the image sharpness. The proposed method is basically based on the SAA, but has a correction procedure by finding blur artefacts from the forward-and back-projection for the firstly obtained, manipulated backprojection data. The manipulation is the replacement of the original data at the POI (plane-of-interest) by zeros. This method has been compared with the conventional SAA algorithm using the experimental measurements and Monte Carlo simulation for the designed PCB phantom. The comparison showed a much enhancement of sharpness in the images obtained from the proposed method.