The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Nongjian Tao - One of the best experts on this subject based on the ideXlab platform.
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Charge-Based Detection of Small Molecules by Plasmonic-Based Electrochemical Impedance Microscopy
Analytical chemistry, 2013Co-Authors: Christopher A. Macgriff, Shaopeng Wang, Peter Wiktor, Wei Wang, Xiaonan Shan, Nongjian TaoAbstract:Charge-based detection of small molecules is demonstrated by plasmonic-based electrochemical impedance microscopy (P-EIM). The dependence of surfAce plasmon resonance (SPR) on surfAce charge density is used to detect small molecules (60–120 Da) printed on a dextran-modified sensor surfAce. Local variations in charge density on an electrode surfAce are manifest in an optical SPR signal. The SPR response to an applied Ac potential measures the sensor surfAce impedance which is a function of the surfAce charge density. This optical signal is comprised of a dc and an Ac Component, and is measured with high spatial resolution. The dc element of the SPR signal represents conventional SPR imaging information. The amplitude and phase of local surfAce impedance is provided by the Ac Component. The phase signal of the small molecules is a function of their charge status, which is manipulated by the pH of a solution. Small molecules with positive, neutral, and negative charge are detected by P-EIM. This technique is...
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Electron transport in single molecules measured by a distance-modulation assisted break junction method.
Nano letters, 2008Co-Authors: Jilin Xia, Ismael Díez-pérez, Nongjian TaoAbstract:We describe a method to determine whether a measured current in a break junction is due to electron tunneling via spAce or conduction through a molecule bridged between two electrodes. By modulating the electrode separation, we monitor both the DC and the Ac Components of the current. The Ac Component indicates if a molecule is connected to the electrodes while the DC Component is the transport current through the molecule. This method allows us to remove the tunneling bAckground from conductance histograms and unambiguously measure the I−V charActeristic of single molecules. Furthermore, it provides valuable information about the electromechanical properties of single molecules.
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SurfAce impedance imaging technique.
Analytical chemistry, 2008Co-Authors: Kyle J. Foley, Xiaonan Shan, Nongjian TaoAbstract:We demonstrate here a surfAce impedance imaging technique based on sensitive dependence of surfAce plasmon resonance (SPR) on local surfAce charge density. By applying a potential modulation to a sensor surfAce, we are able to simultaneously obtain three images: the dc Component and the amplitude and phase of the Ac Component. The dc image measures local molecular binding Activity on the surfAce, as found in the conventional SPR imaging technique, and the Ac images are directly related to the local impedance of the surfAce. Our experimental data can be analyzed quantitatively in terms of the simple free electron gas model for the sensor surfAce and the Randles equivalent circuit model for interfAcial impedance.
Zhengyu Lu - One of the best experts on this subject based on the ideXlab platform.
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online updating of rotor time constant based on combined voltage and current mode flux observer for speed sensorless Ac drives
IEEE Transactions on Industrial Electronics, 2014Co-Authors: Kai Wang, Bin Chen, Guangtong Shen, Wenxi Yao, Kevin Lee, Zhengyu LuAbstract:The simultaneous online estimation algorithm of rotor time constant and rotor speed for a speed-sensorless induction mAchine is proposed. With a small signal injected to the flux command, the method can Accurately complete the online tuning of Tr over a wide range of speed estimation, including the rated speed and the very low speed of 1 Hz or even lower speeds under both no-load and loaded operations. Sensitivity of stator resistance error is studied, and the impAct of stator resistance error on this method is severely reduced by the closed-loop structure of combined voltage and current (UI) mode flux observer. The identification process only needs the Ac Component amplitude without considering Ac Component phase drifts; thus, the division by zero at the zero-crossing point is avoided, which greatly increases the AccurAcy. Furthermore, any differential integral operations or even a filter is not needed; hence, the computation is rather simple and time saving. Moreover, unlike other signal injection methods, there are no special requirements on the injected signal frequency. The AccurAcy and validity of the method has been verified by Matrix Laboratory simulation model. Further experimental results on a 2.2-kW 50-Hz 4-pole induction motor also show effectiveness of this proposed method.
Zdenek Peroutka - One of the best experts on this subject based on the ideXlab platform.
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IECON - Resolver motivated sensorless rotor position estimation of wound rotor synchronous motors with Kalman filter
IECON 2013 - 39th Annual Conference of the IEEE Industrial Electronics Society, 2013Co-Authors: David Uzel, Vaclav Smidl, Zdenek PeroutkaAbstract:This paper presents a novel estimation approAch to sensorless control of wound rotor synchronous motor drives. The proposed rotor position estimation strategy is motivated by principle function of a resolver and utilizes design similarity between the controlled motor and the resolver based rotor position sensor. The rotor circuit is fed by controlled three-phase bridge rectifier which produces an Ac Component of frequency of 300Hz in the rotor excitation (flux) current. This Ac Component of rotor excitation current can be understood like an injection signal. Its response on the stator is evaluated by simplified Kalman filter which estimates the rotor position. This paper describes physical principle and functionality of the proposed sensorless rotor position estimation technique and verifies the theoretical foundations by simulation and experimental results made on developed drive prototype of rated power of 10kW.
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Resolver motivated sensorless rotor position estimation of wound rotor synchronous motors
2013 IEEE International Symposium on Industrial Electronics, 2013Co-Authors: David Uzel, Zdenek PeroutkaAbstract:This paper presents a novel approAch to sensorless control of wound rotor synchronous motor drives. The proposed rotor position estimation strategy is motivated by principle function of a resolver and utilizes design similarity between the controlled motor and the resolver based rotor position sensor. The rotor circuit is fed by controlled three-phase bridge rectifier which produces an Ac Component of frequency of 300Hz in the rotor excitation (flux) current. This Ac Component of rotor excitation current can be understood like an injection signal. Its response on the stator is evaluated by phase-lock-loop (PLL) which estimates the rotor position. This paper describes physical principle and functionality of the proposed sensorless rotor position estimation technique and verifies the theoretical foundations by simulation and experimental results made on developed drive prototype of rated power of 10kW.
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ISIE - Resolver motivated sensorless rotor position estimation of wound rotor synchronous motors
2013 IEEE International Symposium on Industrial Electronics, 2013Co-Authors: David Uzel, Zdenek PeroutkaAbstract:This paper presents a novel approAch to sensorless control of wound rotor synchronous motor drives. The proposed rotor position estimation strategy is motivated by principle function of a resolver and utilizes design similarity between the controlled motor and the resolver based rotor position sensor. The rotor circuit is fed by controlled three-phase bridge rectifier which produces an Ac Component of frequency of 300Hz in the rotor excitation (flux) current. This Ac Component of rotor excitation current can be understood like an injection signal. Its response on the stator is evaluated by phase-lock-loop (PLL) which estimates the rotor position. This paper describes physical principle and functionality of the proposed sensorless rotor position estimation technique and verifies the theoretical foundations by simulation and experimental results made on developed drive prototype of rated power of 10kW.
I. N. Askerzade - One of the best experts on this subject based on the ideXlab platform.
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Plasma frequency of the tunnel Josephson junctions with anharmonic current-phase relationship
Technical Physics Letters, 2007Co-Authors: I. N. AskerzadeAbstract:The effect of alternating current on the plasma frequency of a tunnel Josephson junction with anharmonic current-phase relationship under the conditions of simultaneous passage of direct (dc) and alternating (Ac) current has been studied. It is established that the presence of the Ac Component decreases, whereas the anharmonicity increases the plasma frequency of the tunnel Josephson junction.
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The effect of alternating current on the plasma frequency of the tunnel Josephson junctions
Technical Physics Letters, 2005Co-Authors: I. N. AskerzadeAbstract:The effect of alternating current on the plasma frequency of the tunnel Josephson junctions simultaneously carrying both direct (dc) and alternating (Ac) currents has been studied. The presence of the Ac Component leads to a decrease in the plasma frequency. An analytical expression describing the plasma frequency as a function of the Ac current amplitude is proposed. The obtained results agree with the recent experimental data on the properties of tunnel Josephson junctions.
Kai Wang - One of the best experts on this subject based on the ideXlab platform.
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online updating of rotor time constant based on combined voltage and current mode flux observer for speed sensorless Ac drives
IEEE Transactions on Industrial Electronics, 2014Co-Authors: Kai Wang, Bin Chen, Guangtong Shen, Wenxi Yao, Kevin Lee, Zhengyu LuAbstract:The simultaneous online estimation algorithm of rotor time constant and rotor speed for a speed-sensorless induction mAchine is proposed. With a small signal injected to the flux command, the method can Accurately complete the online tuning of Tr over a wide range of speed estimation, including the rated speed and the very low speed of 1 Hz or even lower speeds under both no-load and loaded operations. Sensitivity of stator resistance error is studied, and the impAct of stator resistance error on this method is severely reduced by the closed-loop structure of combined voltage and current (UI) mode flux observer. The identification process only needs the Ac Component amplitude without considering Ac Component phase drifts; thus, the division by zero at the zero-crossing point is avoided, which greatly increases the AccurAcy. Furthermore, any differential integral operations or even a filter is not needed; hence, the computation is rather simple and time saving. Moreover, unlike other signal injection methods, there are no special requirements on the injected signal frequency. The AccurAcy and validity of the method has been verified by Matrix Laboratory simulation model. Further experimental results on a 2.2-kW 50-Hz 4-pole induction motor also show effectiveness of this proposed method.
