• Title/Summary/Keyword: Phase Plane

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A Stability Analysis of the Magnetic Bearing System Subject to Sensor dislocation Error -Discussion on Nonlinear Magnetic Force Model- (센서의 설치 오차에 따른 자기베어링 지지 로터계의 안정도에 관한 연구 -비선형 자기력 모델에 대한 고찰-)

  • 정재일;김종원
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1996.11a
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    • pp.799-805
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    • 1996
  • In many cases, the magnetic farce model is linearized at the origin in designing the controller of a magnetic bearing system. However. this linear assumption is violated by the unmodeled nonlinear effect such as sensor dislocation and backup bearing dislocation. Therefore, a direct probe into the nonlinear magnetic force model in an active magnetic bearing system is necessary. To analyze the nonlinear magnetic force model of a magnetic bearing system, phase plot analysis which is to plot the numerical solution of the nonlinear equation in several initial points in the interested region is applied. Phase plot analysis is used to observe a nonlinear dynamic system qualitatively (not quantitatively). With this method, we can get much useful information of the nonlinear system. Among this information, a bifurcation graph that represents stability and locations of fixed points is essential. From the bifurcation graph, a stability criterion of magnetic bearing system is derived.

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Control and Modulation of Three to Asymmetrical Six-Phase Matrix Converters based on Space Vectors

  • Al-Hitmi, Mohammed A.;Rahman, Khaliqur;Iqbal, Atif;Al-Emadi, Nasser
    • Journal of Power Electronics
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    • v.19 no.2
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    • pp.475-486
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    • 2019
  • This paper proposes the modulation and control of a three-to-six-phase matrix converter with an asymmetrical six-phase output. The matrix converter (MC) outputs consist of two sets of three-phase spatially shifted by $30^0$, where the two sets have two isolated neutrals. The space vector approach is considered for the modeling and subsequent modulation of the three-to-six phase MC. The intelligent selection of voltage space vectors is made to synthesize the reference voltages and to obtain a sinusoidal output. The dwell times of selected voltage space vectors are adjusted in such a way that the effect of the second and the third auxiliary plane vectors (i.e., x1-y1, and x2-y2) are nullified. To achieve the maximum output voltage gain and to ensure that no reactive power is drawn from the utility supply, the input side power factor is maintained at unity. Nevertheless, the source side power factor is controllable. The modulation technique is implemented in dSPACE working in conjunction with a FPGA. Hardware results that validate the proposed control algorithm are discussed.

Optical security system for protection of personal identification information (개인신원정보 보호를 위한 광 보호 시스템)

  • 윤종수;도양회
    • Korean Journal of Optics and Photonics
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    • v.14 no.4
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    • pp.383-391
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    • 2003
  • A new optical security system for the protection of personal identification information is proposed. Personal identification information consisting of a pure face image and an identification number is used for verification and authentication. Image encryption is performed by a fully phase image encryption technique with two random phase masks located in the input and the Fourier plane of 4-f correlator. The personal information, however, can be leaked out in the decryption process. To cope with this possibility, the encrypted image itself is used in the identification process. An encrypted personal identification number is discriminated and recognized by using the proposed MMACE_p (multiplexed MACE_p) filter, and then authenticity of the personal information is verified by correlation of the face image using the optical wavelet matched filter (OWMF). MMACE_p filter is a synthetic filter with four MACE_p (minimum average correlation energy_phase encrypted) filters multiplexed in one filter plane to recognize 10 different encrypted-numbers at a time. OWMF can improve discrimination capability and SNR (signal to noise ratio). Computer simulations confirmed that the proposed security technique can be applied to the protection of personal identification information.

Analysis on Orbital Dynamics Operation Results of KOMPSAT-3 during Early Phase after Launch (다목적실용위성 3호 발사 후 초기 궤도 운영결과 분석)

  • Jung, Ok-Chul;Yim, Hyeonjeong;Chung, Dae-Won;Kim, Eun-Kyou;Kim, Hak-Jung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.41 no.4
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    • pp.319-326
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    • 2013
  • This paper describes the orbital dynamics operation results for the launch and early operations phase (LEOP) of KOMPSAT-3, which was successfully launched on May 18, 2012. At the initial phase, operational orbit determination was carried out using ground tracking data and GPS navigation solution. And, both in-plane and out-of plane maneuvers were executed in order to change the orbit from the injection orbit to the mission orbit. In addition, the accuracy of precise orbit determination was indirectly evaluated by overlapping method using GPS raw data of KOMPSAT-3 and international GNSS service data from worldwide-distributed ground stations. Currently, KOMPSAT-3 is operated in pre-defined mission orbit, and its various kinds of orbit data are generated and distributed to support the normal mission operations.

Magnetic and Magnetostrictive Properties of Amorphous Sm-Fe and Sm-Fe-B Thin Films

  • Choi, Y.S.;Lee, S.R.;Han, S.H.;Kim, H.J.;Lim, S.H.
    • Journal of Magnetics
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    • v.3 no.2
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    • pp.55-63
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    • 1998
  • Magnetic and magnetostrictive properties of amorphous Sm-Fe and Sm-Fe-B thin films are systematically investigated over a wide composition range from 14.1 to 71.7 at.% Sm. The films were fabricated by rf magnetron sputtering using a composite target composed of an Fe (or Fe-B) plate and Sm chips. The amount of B added ranges from 0.3 to 0.8 at. %. The microstructure, examined by X-ray diffraction, mainly consists of an amorphous phase in the intermediate Sm content range from 20 to 45 at.%. Together with an amorphous phase, crystalline phases of Fe and Sm also exist at low and high ends of the Sm content, respectively. Well-developed in-plane anisotropy is formed over the whole compositionrange, except for the low Sm content below 15 at.% and the high Sm content above 55 at %. As the Sm content increases, the saturation magnetization decreases linearly and the coercive force tends to increase, with the exception of the low Sm content where very large magnitudes of the saturation magnetization and the coercive force are observed due to the existence of the crystalline $\alpha$-Fe phase. The coercive force is affected rather substantially by the B addition, resulting in lower values of the coercive force in the practically important Sm content range of 30 to 40 at.%. Good magnetic softness indicated by well-developed in-plane anisotropy, a square-shaped hysteresis loop and a low magnitude of the coercive force results in good magnetostrictive characteristics in both Sm-Fe-B thin films. The magnetostrictive characteristics, particularly at low magnetic fields, are further improved by the addition of B; for example, at a magnetic field of 100 Oe, the magnitude of magnetostriction is -350 ppm in a Sm-Fe thin film and it is -470 ppm in a B containing Sm-Fe thin film.

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The Solid Phase Extraction of Phenol and Chlorophenols by the Chemically Modified Polymeric Adsorbents with Porphyrins

  • Jung, Min-Woo;Kim, Ki-Pal;Cho, Byung-Yun;Paeng, Insook R.;Lee, Dai-Woon;Park, Young-Hun;Paeng, Ki-Jung
    • Bulletin of the Korean Chemical Society
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    • v.27 no.1
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    • pp.77-81
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    • 2006
  • The commercially available Amberlite XAD-2 and XAD-4 resins were modified with macrocyclic protoporphyrin IX (PPIX) or tetrakis(p-carboxyphenyl) porphyrin (TCPP) to enhance the adsorption capacity for phenol and chlorophenols. The chemically modified polymeric adsorbents (XAD-2+PPIX, XAD-2+TCPP, XAD-4+PPIX, and XAD-4+TCPP) were applied to the solid phase extraction as an adsorbent material for the preconcentration of phenol and chlorophenols in environmental waters. Generally, the synthesized adsorbents showed higher recoveries than underivatized adsorbents, XAD-2 and XAD-4, without matrix interferences. Especially, XAD-4+PPIX showed more than 90% recoveries for all compounds used in this study including hydrophilic phenol. The major factor for the increase of the adsorption capacity was the increase of $\pi$-$\pi$ interaction between adsorbents and samples due to the introduction of the porphyrin molecule. However, the breakthrough volumes and recovery values of the XADs+TCPP columns were slightly decreased for the bulky chlorophenols such as TCP and PCP. Using molecular mechanics methods, the structures of TCPP and PPIX were compared with that of porphine, the parent molecule of porphyrin. Four bulky p-carboxyphenyl groups of TCPP were torsional each other, thus the molecular plane of TCPP were not on the same level. In conclusion, the decrease of breakthrough volumes and recovery values of XADs+TCPP columns for bulky phenols can be explained by the steric hindrance of the $\pi$-$\pi$ interaction between porphyrin plane and the phenols.

Cancellation of MRI Motion Artifact in Image Plane (촬상단면내의 MRI 체동 아티팩트의 제거)

  • Kim, Eung-Kyeu
    • Journal of KIISE:Software and Applications
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    • v.27 no.4
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    • pp.432-440
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    • 2000
  • In this study, a new algorithm for canceling MRI artifact due to translational motion in image plane is described. Unlike the conventional iterative phase retrieval algorithm, in which there is no guarantee for the convergence, a direct method for estimating the motion is presented. In previous approaches, the motions in the x(read out) direction and the y(phase encoding) direction are estimated simultaneously. However, the features of x and y directional motions are different from each other. By analyzing their features, each x and y directional motion is canceled by different algorithms in two steps. First, it is noticed that the x directional motion corresponds to a shift of the x directional spectrum of the MRI signal, and the non-zero area of the spectrum just corresponds to the projected area of the density function on the x-axis. So the motion is estimated by tracing the edges between non-zero area and zero area of the spectrum, and the x directional motion is canceled by shifting the spectrum in inverse direction. Next, the y directional motion is canceled by using a new constraint condition, with which the motion component and the true image component can be separated. This algorithm is shown to be effective by using a phantom image with simulated motion.

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Performance Analysis of Spiral Axicon Wavefront Coding Imaging System for Laser Protection

  • Haoqi Luo;Yangliang Li;Junyu Zhang;Hao Zhang;Yunlong Wu;Qing Ye
    • Current Optics and Photonics
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    • v.8 no.4
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    • pp.355-365
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    • 2024
  • Wavefront coding (WFC) imaging systems can redistribute the energy of an interference laser spot on an image plane sensor by wavefront phase modulation and reduce the peak intensity, realizing laser protection while maintaining imaging functionality by leveraging algorithmic post-processing. In this paper, a spiral axicon WFC imaging system is proposed, and the performance for laser protection is investigated by constructing a laser transmission model. An Airy disk on an image plane sensor is refactored into a symmetrical hollow ring by a spiral axicon phase mask, and the maximum intensity can be reduced to lower than 1% and single-pixel power to 1.2%. The spiral axicon phase mask exhibits strong robustness to the position of the interference laser source and can effectively reduce the risk of sensor damage for an almost arbitrary lase propagation distance. Moreover, we revealed that there is a sensor hazard distance for both conventional and WFC imaging systems where the maximum single-pixel power reaches a peak value under irradiation of a power-fixed laser source. Our findings can offer guidance for the anti-laser reinforcement design of photoelectric imaging systems, thereby enhancing the adaptability of imaging systems in a complex laser environment. The laser blinding-resistant imaging system has potential applications in security monitoring, autonomous driving, and intense-laser-pulse experiments.

Three Component Velocity Field Measurements of Turbulent Wake behind a Marine Propeller Using a Stereoscopic PIV Technique (Stereoscopic PIV 기법을 이용한 선박용 프로펠러 후류의 3차원 속도장 측정)

  • Lee, Sang-Joon;Paik, Nu-Geun;Yoon, Jong-Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.12
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    • pp.1716-1723
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    • 2003
  • A stereoscopic PIV(Particle Image Velocimetry) technique was employed to measure the 3 dimensional flow structure of turbulent wake behind a marine propeller with 5 blades. The out-of-plane velocity component was determined using two CCD cameras with the angular displacement configuration. Four hundred instantaneous velocity fields were measured for each of four different blade phases and ensemble averaged to investigate the spatial evolution of the propeller wake in the near-wake region from the trailing edge to one propeller diameter(D) downstream. The phase-averaged velocity fields show the potential wake and the viscous wake developed along the blade surfaces. Tip vortices were generated periodically and the slipstream contraction occurs in the near-wake region. The out-of-plane velocity component and strain rate have large values at the locations of tip and trailing vortices. As the flow goes downstream, the turbulence intensity, the strength of tip vortices and the magnitude of out-of-plane velocity component at trailing vortices are decreased due to viscous dissipation, turbulence diffusion and blade-to-blade interaction.

Identification on the Three-Dimensional Vortical Structures of Impeller Flow by a Multi-Plane Stereoscopic PIV Method (스테레오 PIV 기법에 의한 임펠러 와류유동의 3차원 구조측정)

  • Yoon, Sang-Youl;Kim, Kyung-Chun
    • Proceedings of the KSME Conference
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    • 2001.06e
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    • pp.690-695
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    • 2001
  • The three-dimensional spatial structures of impeller flow created by a six bladed Rushton turbine have identified based on the volumetric velocity information from multi-plane stereoscopic PIV measurements. A total of 10 planes with 2 mm space with a 50 mm by 64 mm size of the field of view were targeted. To reduce the depth of focus, we adopted an angle offset configuration which satisfied the Scheimpflug condition. The distortion compensation procedure was utilized during the in situ calibration. Phase-locked instantaneous data were ensemble averaged and interpolated in order to obtain mean 3-D, volumetric velocity fields on a 60 degree sector of a cylindrical ring volume enclosing the turbine blade. Using the equi-vorticity surface rendering, the spatial structure of the trailing vortices was clearly demonstrated. Detail flow characteristics of the radial jet reported in previous studies of mixer flows were easily identified.

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