Electromagnetic holographic data are characterized by two modes, suggesting that image reconstruction requires a dual-mode sensitivity field as well. We analyze an electromagnetic holographic field based on tomography...Electromagnetic holographic data are characterized by two modes, suggesting that image reconstruction requires a dual-mode sensitivity field as well. We analyze an electromagnetic holographic field based on tomography theory and Radon inverse transform to derive the expression of the electromagnetic holographic sensitivity field （EMHSF）. Then, we apply the EMHSF calculated by using finite-element methods to flow simulations and holographic imaging. The results suggest that the EMHSF based on the partial derivative of radius of the complex electric potential φ is closely linked to the Radon inverse transform and encompasses the sensitivities of the amplitude and phase data. The flow images obtained with inversion using EMHSF better agree with the actual flow patterns. The EMHSF overcomes the limitations of traditional single-mode sensitivity fields.展开更多
For a Lorentzian invariant theory,the entanglement entropy should be a function of the domain of dependence of the subregion under consideration.More precisely,it should be a function of the domain of dependence and t...For a Lorentzian invariant theory,the entanglement entropy should be a function of the domain of dependence of the subregion under consideration.More precisely,it should be a function of the domain of dependence and the appropriate cut-off.In this study,we refine the concept of cut-off to make it applicable to timelike regions and assume that the usual entanglement entropy formula also applies to timelike intervals.Using the Rindler method,the timelike entanglement entropy can be regarded as the thermal entropy of the CFT after the Rindler transformation plus a constant,where c denotes the central charge.The gravitational dual of the‘covariant'timelike entanglement entropy is presented following this method.展开更多
Acoustic holographic method has been used in imaging,particle manipulation,material preparation and other fields.In acoustics,it is important to design the implementation of any acoustic wave formation surface[1-5].Tr...Acoustic holographic method has been used in imaging,particle manipulation,material preparation and other fields.In acoustics,it is important to design the implementation of any acoustic wave formation surface[1-5].Traditional methods use piezoelectric arrays to control any acoustic wave array.展开更多
This paper reviews the theoretical analysis of the imaging method and characteristic of the Nearfield Acoustical Holography (NAH). We present a new filtering method, least squares method for filtering with restraint, ...This paper reviews the theoretical analysis of the imaging method and characteristic of the Nearfield Acoustical Holography (NAH). We present a new filtering method, least squares method for filtering with restraint, which improves the stability of the reconstruction. The computer simulation experiment for the vibration and radiation of a round plate by means of the numerical method of NAH has been done and the effect of the new filtering method has been verified. The NAH imaging of radiation of a small loudspeaker using a scanning linear receiving array of 32 elements has been made and the preliminary results are given in the paper.展开更多
A method for fast and low bit-rate compression of digital holograms based on a new vector quantization （VQ） method known as the skip-dimension VQ （SDVQ） is proposed. Briefly, a complex hologram is converted into a...A method for fast and low bit-rate compression of digital holograms based on a new vector quantization （VQ） method known as the skip-dimension VQ （SDVQ） is proposed. Briefly, a complex hologram is converted into a real off-axis hologram, and partitioned into a set of image vectors. The image vectors are passed into a graphic processing unit （GPU）, and compressed through SDVQ into a set of code indices considerably smaller in data size than the source hologram. Experimental evaluation reveals that our scheme is capable of compressing a digital hologram to a compression ratio of over 500 times, in approximately 20-22 ms.展开更多
基金supported by the National Science and Technology Major Project(No.2011ZX05020-006)
文摘Electromagnetic holographic data are characterized by two modes, suggesting that image reconstruction requires a dual-mode sensitivity field as well. We analyze an electromagnetic holographic field based on tomography theory and Radon inverse transform to derive the expression of the electromagnetic holographic sensitivity field （EMHSF）. Then, we apply the EMHSF calculated by using finite-element methods to flow simulations and holographic imaging. The results suggest that the EMHSF based on the partial derivative of radius of the complex electric potential φ is closely linked to the Radon inverse transform and encompasses the sensitivities of the amplitude and phase data. The flow images obtained with inversion using EMHSF better agree with the actual flow patterns. The EMHSF overcomes the limitations of traditional single-mode sensitivity fields.
基金Supported partially by the National Natural Science Foundation of China (12175008)。
文摘For a Lorentzian invariant theory,the entanglement entropy should be a function of the domain of dependence of the subregion under consideration.More precisely,it should be a function of the domain of dependence and the appropriate cut-off.In this study,we refine the concept of cut-off to make it applicable to timelike regions and assume that the usual entanglement entropy formula also applies to timelike intervals.Using the Rindler method,the timelike entanglement entropy can be regarded as the thermal entropy of the CFT after the Rindler transformation plus a constant,where c denotes the central charge.The gravitational dual of the‘covariant'timelike entanglement entropy is presented following this method.
基金supported by the National Natural Science Foundation of China(Grant Nos.12025201,11521202,11890681,and 11522214)Calculations are supported by High-Performance Computing Platform of Peking University,China。
文摘Acoustic holographic method has been used in imaging,particle manipulation,material preparation and other fields.In acoustics,it is important to design the implementation of any acoustic wave formation surface[1-5].Traditional methods use piezoelectric arrays to control any acoustic wave array.
基金The project is supported by National Natural Science Foundation of China
文摘This paper reviews the theoretical analysis of the imaging method and characteristic of the Nearfield Acoustical Holography (NAH). We present a new filtering method, least squares method for filtering with restraint, which improves the stability of the reconstruction. The computer simulation experiment for the vibration and radiation of a round plate by means of the numerical method of NAH has been done and the effect of the new filtering method has been verified. The NAH imaging of radiation of a small loudspeaker using a scanning linear receiving array of 32 elements has been made and the preliminary results are given in the paper.
文摘A method for fast and low bit-rate compression of digital holograms based on a new vector quantization （VQ） method known as the skip-dimension VQ （SDVQ） is proposed. Briefly, a complex hologram is converted into a real off-axis hologram, and partitioned into a set of image vectors. The image vectors are passed into a graphic processing unit （GPU）, and compressed through SDVQ into a set of code indices considerably smaller in data size than the source hologram. Experimental evaluation reveals that our scheme is capable of compressing a digital hologram to a compression ratio of over 500 times, in approximately 20-22 ms.
