The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Hongguang Duan - One of the best experts on this subject based on the ideXlab platform.
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quantum Mechanical Wave packet dynamics at a conical intersection with strong vibrational dissipation
Journal of Physical Chemistry Letters, 2016Co-Authors: Hongguang Duan, Michael ThorwartAbstract:We derive a reduced model for the nonadiabatic quantum dynamics of an electronic Wave packet moving through a conical intersection in the presence of strong vibrational damping. Starting from the dissipative two-state two-model model, we transform the tuning and the coupling mode to the bath. The resulting quantum two-state model with two highly structured environments is solved numerically exactly in the regime of strong vibrational damping. We find negative cross peaks in the ultrafast optical 2D spectra as clear signatures of the conical intersection. They arise from secondary excitations of the Wave packet after having passed through the photophysical energy funnel. This feature is in agreement with recent transient absorption measurements of rhodopsin.
Michael Thorwart - One of the best experts on this subject based on the ideXlab platform.
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quantum Mechanical Wave packet dynamics at a conical intersection with strong vibrational dissipation
Journal of Physical Chemistry Letters, 2016Co-Authors: Hongguang Duan, Michael ThorwartAbstract:We derive a reduced model for the nonadiabatic quantum dynamics of an electronic Wave packet moving through a conical intersection in the presence of strong vibrational damping. Starting from the dissipative two-state two-model model, we transform the tuning and the coupling mode to the bath. The resulting quantum two-state model with two highly structured environments is solved numerically exactly in the regime of strong vibrational damping. We find negative cross peaks in the ultrafast optical 2D spectra as clear signatures of the conical intersection. They arise from secondary excitations of the Wave packet after having passed through the photophysical energy funnel. This feature is in agreement with recent transient absorption measurements of rhodopsin.
Torsten Söderström - One of the best experts on this subject based on the ideXlab platform.
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a Mechanical Wave diode using feedforward control for one way transmission of elastic extensional Waves
IEEE Transactions on Control Systems and Technology, 2007Co-Authors: Peter Nauclér, B Lundberg, Torsten SöderströmAbstract:This paper concerns the design and analysis of an active device capable of controlling Mechanical Waves. Its functionality is similar to that of a diode in an electrical network and, therefore, it is referred to as a Mechanical Wave diode. The aim is to block Waves in one direction in a Mechanical structure, while not affecting Waves travelling in the opposite direction. The device is based on feedforward control and its design is proposed on the basis of equations that describe elastic extensional Waves in bars. We present an ideal feedforward design which performs perfectly in the noise-free case. However, it has poor noise properties and is modified to be useful when measurement noise is present. Theoretical analysis and computer simulations show that the modified design is significantly less sensitive to such noise.
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Polynomial Feedforward Design Techniques for a Mechanical Wave Diode System
2007Co-Authors: Peter Nauclér, Torsten SöderströmAbstract:This paper considers feedforward control of extensional Waves in a bar. The system is designed to have properties analogous to those of an electrical diode and is therefore referred to as a Mechanical Wave diode. We present three different feedforward control strategies. Two of them relies on an ‘ideal’ design which is derived in the noise-free case, whereas the third is based on Wiener filtering theory. The control strategies are compared and evaluated for different signal models and in the presence of measurement noise. We show that the performance of the device is improved by using the (optimal) Wiener feedforward filter.
Shaozhen Song - One of the best experts on this subject based on the ideXlab platform.
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Air-coupled acoustic radiation force for non-contact generation of broadband Mechanical Waves in soft media.
Applied Physics Letters, 2016Co-Authors: Łukasz Ambrozinski, Ivan Pelivanov, Shaozhen Song, Soon Joon Yoon, David Li, Tueng T. Shen, Ruikang K. Wang, Matthew O'donnellAbstract:A non-contact method for efficient, non-invasive excitation of Mechanical Waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US Wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient Mechanical Wave in the transverse (lateral) direction. The type of Mechanical Wave is determined by boundary conditions. To prove this concept, a home-made 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm thick gelatin phantom mimicking soft biological tissue. A phase-sensitive (PhS)-optical coherence tomography system is used to track/image the Mechanical Wave. The reconstructed transient displacement of the Mechanical Wave in space and time demonstrates highly efficient generation, thus offering great promise for non-contact, non-invasive characterization of soft media, in general, and for elasticity measurements ...
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Strategies to improve phase-stability of ultrafast swept source optical coherence tomography for single shot imaging of transient Mechanical Waves at 16 kHz frame rate
Applied Physics Letters, 2016Co-Authors: Shaozhen Song, Ivan Pelivanov, Tueng T. Shen, Matthew O'donnell, Bao-yu Hsieh, Ruikang K. WangAbstract:We present single-shot phase-sensitive imaging of propagating Mechanical Waves within tissue, enabled by an ultrafast optical coherence tomography (OCT) system powered by a 1.628 MHz Fourier domain mode-locked (FDML) swept laser source. We propose a practical strategy for phase-sensitive measurement by comparing the phases between adjacent OCT B-scans, where the B-scan contains a number of A-scans equaling an integer number of FDML buffers. With this approach, we show that micro-strain fields can be mapped with ∼3.0 nm sensitivity at ∼16 000 fps. The system's capabilities are demonstrated on porcine cornea by imaging Mechanical Wave propagation launched by a pulsed UV laser beam, promising non-contact, real-time, and high-resolution optical coherence elastography.
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tracking Mechanical Wave propagation within tissue using phase sensitive optical coherence tomography motion artifact and its compensation
Journal of Biomedical Optics, 2013Co-Authors: Shaozhen Song, Zhihong Huang, Ruikang K. WangAbstract:We describe theoretical and experimental investigations of motion artifacts that can arise in the detection of shear Wave propagating within tissue with phase-sensitive optical coherence tomography. We find that the motion artifact is a combined product of sample surface motion and refractive index difference between sample and air, which cannot be neglected when estimating the tissue motion within tissue. A method of compensating the motion artifact is demonstrated, the results of which emphasize the need for surface motion compensation when measuring the Mechanical response for elastography or other biomedical applications.
Ruikang K. Wang - One of the best experts on this subject based on the ideXlab platform.
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Air-coupled acoustic radiation force for non-contact generation of broadband Mechanical Waves in soft media.
Applied Physics Letters, 2016Co-Authors: Łukasz Ambrozinski, Ivan Pelivanov, Shaozhen Song, Soon Joon Yoon, David Li, Tueng T. Shen, Ruikang K. Wang, Matthew O'donnellAbstract:A non-contact method for efficient, non-invasive excitation of Mechanical Waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US Wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient Mechanical Wave in the transverse (lateral) direction. The type of Mechanical Wave is determined by boundary conditions. To prove this concept, a home-made 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm thick gelatin phantom mimicking soft biological tissue. A phase-sensitive (PhS)-optical coherence tomography system is used to track/image the Mechanical Wave. The reconstructed transient displacement of the Mechanical Wave in space and time demonstrates highly efficient generation, thus offering great promise for non-contact, non-invasive characterization of soft media, in general, and for elasticity measurements ...
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Strategies to improve phase-stability of ultrafast swept source optical coherence tomography for single shot imaging of transient Mechanical Waves at 16 kHz frame rate
Applied Physics Letters, 2016Co-Authors: Shaozhen Song, Ivan Pelivanov, Tueng T. Shen, Matthew O'donnell, Bao-yu Hsieh, Ruikang K. WangAbstract:We present single-shot phase-sensitive imaging of propagating Mechanical Waves within tissue, enabled by an ultrafast optical coherence tomography (OCT) system powered by a 1.628 MHz Fourier domain mode-locked (FDML) swept laser source. We propose a practical strategy for phase-sensitive measurement by comparing the phases between adjacent OCT B-scans, where the B-scan contains a number of A-scans equaling an integer number of FDML buffers. With this approach, we show that micro-strain fields can be mapped with ∼3.0 nm sensitivity at ∼16 000 fps. The system's capabilities are demonstrated on porcine cornea by imaging Mechanical Wave propagation launched by a pulsed UV laser beam, promising non-contact, real-time, and high-resolution optical coherence elastography.
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tracking Mechanical Wave propagation within tissue using phase sensitive optical coherence tomography motion artifact and its compensation
Journal of Biomedical Optics, 2013Co-Authors: Shaozhen Song, Zhihong Huang, Ruikang K. WangAbstract:We describe theoretical and experimental investigations of motion artifacts that can arise in the detection of shear Wave propagating within tissue with phase-sensitive optical coherence tomography. We find that the motion artifact is a combined product of sample surface motion and refractive index difference between sample and air, which cannot be neglected when estimating the tissue motion within tissue. A method of compensating the motion artifact is demonstrated, the results of which emphasize the need for surface motion compensation when measuring the Mechanical response for elastography or other biomedical applications.