A non-contact low-frequency(LF)method of diagnosing the plasma surrounding a scaled model in a shock tube is proposed.This method utilizes the phase shift occurring after the transmission of an LF alternating magnetic...A non-contact low-frequency(LF)method of diagnosing the plasma surrounding a scaled model in a shock tube is proposed.This method utilizes the phase shift occurring after the transmission of an LF alternating magnetic field through the plasma to directly measure the ratio of the plasma loop average electron density to collision frequency.An equivalent circuit model is used to analyze the relationship of the phase shift of the magnetic field component of LF electromagnetic waves with the plasma electron density and collision frequency.The applicable range of the LF method on a given plasma scale is analyzed.The upper diagnostic limit for the ratio of the electron density(unit:m^(-3))to collision frequency(unit:Hz)exceeds 1×10^(11),enabling an electron density to exceed 1×10^(20)m^(-3)and a collision frequency to be less than 1 GHz.In this work,the feasibility of using the LF phase shift to implement the plasma diagnosis is also assessed.Diagnosis experiments on shock tube equipment are conducted by using both the electrostatic probe method and LF method.By comparing the diagnostic results of the two methods,the inversion results are relatively consistent with each other,thereby preliminarily verifying the feasibility of the LF method.The ratio of the electron density to the collision frequency has a relatively uniform distribution during the plasma stabilization.The LF diagnostic path is a loop around the model,which is suitable for diagnosing the plasma that surrounds the model.Finally,the causes of diagnostic discrepancy between the two methods are analyzed.The proposed method provides a new avenue for diagnosing high-density enveloping plasma.展开更多
A new error compensating five sample phase shifting algorithm which is insensitive to phase shift error is proposed to retrieve the phase distribution of a fringe pattern. It includes two steps. First, the linear ...A new error compensating five sample phase shifting algorithm which is insensitive to phase shift error is proposed to retrieve the phase distribution of a fringe pattern. It includes two steps. First, the linear phase shift error is estimated using four sample images. Then, the phase distribution is calculated with error corrected by using the phase shift error estimated in the first step. As the equations of error estimation and phase calculation are simple, this new algorithm is practical as well as effective. Computer simulations were carried out to verify the effectiveness of the algorithm. Results of two other well known error compensating algorithms are also presented, which show the new algorithm is the least sensitive to phase shift error.展开更多
Two phase extraction methods which are based separately on phase-stepping and shifting curve are mainly used in phase-sensitive imaging in gating interferometry to determine the x-ray phase shift induced by an object ...Two phase extraction methods which are based separately on phase-stepping and shifting curve are mainly used in phase-sensitive imaging in gating interferometry to determine the x-ray phase shift induced by an object in the beam. In this paper, the authors perform a full comparative analysis and present the main virtues and limitations of these two methods according to the theoretical analysis of the grating interferometry.展开更多
Based on the rotation transformation in phase space and the technique of integration within an ordered product of operators, the coherent state representation of the multimode phase shifting operator and one of its ne...Based on the rotation transformation in phase space and the technique of integration within an ordered product of operators, the coherent state representation of the multimode phase shifting operator and one of its new applications in quantum mechanics are given. It is proved that the coherent state is a natural language for describing the phase shifting operator or multimode phase shifting operator. The multimode phase shifting operator is also a useful tool to solve the dynamic problems of the mnltimode coordinate-momentum coupled harmonic oscillators. The exact energy spectra and eigenstates of such multimode coupled harmonic oscillators can be easily obtained by using the rnultimode phase shifting operator.展开更多
Reconfigurable intelligent surface(RIS)for wireless networks have drawn lots of attention in both academic and industry communities.RIS can dynamically control the phases of the reflection elements to send the signal ...Reconfigurable intelligent surface(RIS)for wireless networks have drawn lots of attention in both academic and industry communities.RIS can dynamically control the phases of the reflection elements to send the signal in the desired direction,thus it provides supplementary links for wireless networks.Most of prior works on RIS-aided wireless communication systems consider continuous phase shifts,but phase shifts of RIS are discrete in practical hardware.Thus we focus on the actual discrete phase shifts on RIS in this paper.Using the advanced deep reinforcement learning(DRL),we jointly optimize the transmit beamforming matrix from the discrete Fourier transform(DFT)codebook at the base station(BS)and the discrete phase shifts at the RIS to maximize the received signal-to-interference plus noise ratio(SINR).Unlike the traditional schemes usually using alternate optimization methods to solve the transmit beamforming and phase shifts,the DRL algorithm proposed in the paper can jointly design the transmit beamforming and phase shifts as the output of the DRL neural network.Numerical results indicate that the DRL proposed can dispose the complicated optimization problem with low computational complexity.展开更多
Round-robin differential phase shift （RRDPS） is a novel quantum key distribution protocol which can bound information leakage without monitoring signal disturbance. In this work, to decrease the effect of the vacuum...Round-robin differential phase shift （RRDPS） is a novel quantum key distribution protocol which can bound information leakage without monitoring signal disturbance. In this work, to decrease the effect of the vacuum component in a weak coherent pulses source, we employ a practical decoy-state scheme with heralded singlephoton source for the RRDPS protocol and analyze the performance of this method. In this scheme, only two decoy states are needed and the yields of single-photon state and multi-photon states, as well as the bit error rates of each photon states, can be estimated. The final key rate of this scheme is bounded and simulated over transmission distance. The results show that the two-decoy-state method with heralded single-photon source performs better than the two-decoy-state method with weak coherent pulses.展开更多
In this paper, we propose an encryption scheme based on phase-shifting digital interferometry. According to the original system framework, we add a random amplitude mask and replace the Fourier transform by the Fresne...In this paper, we propose an encryption scheme based on phase-shifting digital interferometry. According to the original system framework, we add a random amplitude mask and replace the Fourier transform by the Fresnel transform. We develop a mathematical model and give a discrete formula based on the scheme, which makes it easy to implement the scheme in computer programming. The experimental results show that the improved system has a better performance in security than the original encryption method. Moreover, it demonstrates a good capability of anti-noise and anti-shear robustness.展开更多
Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measure...Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector-camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.展开更多
A multiple-image encryption method based on two-step phase-shifting interferometry （PSI） and spatial multiplexing of a smooth compressed signal is proposed. In the encoding and encryption process, with the help of f...A multiple-image encryption method based on two-step phase-shifting interferometry （PSI） and spatial multiplexing of a smooth compressed signal is proposed. In the encoding and encryption process, with the help of four index matrices to store original pixel positions, all the pixels of four secret images are firstly reordered in an ascending order; then, the four reordered images are transformed by five-order Haar wavelet transform and performed sparseness operation. After Arnold transform and pixels sampling operation, one combined image can be grouped with the aid of compressive sensing （CS） and spatial multiplexing techniques. Finally, putting the combined image at the input plane of the PSI encryption scheme, only two interferograms ciphertexts can be obtained. During the decoding and decryption, utilizing all the secret key groups and index matrices keys, all the original secret images can be successfully decrypted by a wave-front retrieval algorithm of two-step PSI, spatial de-multiplexing, inverse Arnold transform, inverse discrete wavelet transform, and pixels reordering operation.展开更多
A method of single-shot phase-shifting digital holography with a photon-sieve-filtering telescope is proposed.Three copy images with different phases are first generated by use of a monofocal photon-sieve filter in Ke...A method of single-shot phase-shifting digital holography with a photon-sieve-filtering telescope is proposed.Three copy images with different phases are first generated by use of a monofocal photon-sieve filter in Kepler telescope,and then interfere with the reference plane wave by a beam combiner.The hologram is captured by a charge-coupled device(CCD)in one single exposure.The complex-valued amplitude of the test object can be reconstructed by three-step phase-shifting interferometry through three frames of extracted sub-interferograms from the single-exposure hologram.The principle and simulation experiments are carried out and verified the validity of our proposed method.This method can be applied for snapshot imaging and three-dimensional object construction.展开更多
The influence of multi-photon pulses on practical differcBtial-phase-shift quantum key distribution （DPS-Qt（D） is analysed. We have estimated the information which Eve obtained by PNS （photon-number splitting） at...The influence of multi-photon pulses on practical differcBtial-phase-shift quantum key distribution （DPS-Qt（D） is analysed. We have estimated the information which Eve obtained by PNS （photon-number splitting） attack and BS （beam splitting） attack. The result indicates that the PNS attack and BS attack will not limit the transmission distance as long as we select an appropriate mean photon number. Also, the maximum mean photon number under BS attack in practical DPS-QKD system and the set of practical assumptions about Eve＇s capabilities are presented.展开更多
Although the phase-shift seismic processing method has characteristics of high accuracy, good stability, high efficiency, and high-dip imaging, it is not able to adapt to strong lateral velocity variation. To overcome...Although the phase-shift seismic processing method has characteristics of high accuracy, good stability, high efficiency, and high-dip imaging, it is not able to adapt to strong lateral velocity variation. To overcome this defect, a finite-difference method in the frequency-space domain is introduced in the migration process, because it can adapt to strong lateral velocity variation and the coefficient is optimized by a hybrid genetic and simulated annealing algorithm. The two measures improve the precision of the approximation dispersion equation. Thus, the imaging effect is improved for areas of high-dip structure and strong lateral velocity variation. The migration imaging of a 2-D SEG/EAGE salt dome model proves that a better imaging effect in these areas is achieved by optimized phase-shift migration operator plus a finite-difference method based on a hybrid genetic and simulated annealing algorithm. The method proposed in this paper is better than conventional methods in imaging of areas of high-dip angle and strong lateral velocity variation.展开更多
The behaviors of coupled oscillators, each of which has periodic motion with random natural frequency in the absence of coupling, are investigated when phase shifts are considered. In the system of coupled oscillators...The behaviors of coupled oscillators, each of which has periodic motion with random natural frequency in the absence of coupling, are investigated when phase shifts are considered. In the system of coupled oscillators, phase shifts are the same between different oscillators. Synchronization and synchronization transition are revealed with different phase shifts. Phase shifts play an important role for this kind of system. When the phase shift α〈 0.5π, the synchronization state can be attained by increasing the coupling, and the system cannot reach the synchronization state while α≥ 0.5π. A clear scaling between complete synchronization critical coupling strength Kpc and α - 0.5π is found.展开更多
We present the transmission spectra of light transmitting a metallic thin film perforated with differently shaped sub- wavelength hole arrays, which are calculated by a plane-wave-based transfer matrix method. We anal...We present the transmission spectra of light transmitting a metallic thin film perforated with differently shaped sub- wavelength hole arrays, which are calculated by a plane-wave-based transfer matrix method. We analyze the transmission peak positions and the phase-shift angles of different surface plasmon polariton （SPP） modes by using the microscopic theoretical model proposed by Haitao Liu and Philippe Lalanne [Liu Haitao, and Lalanne Philippe 2008 Nature 452 728], in which the phase shift properties of the SPPs scattered by the subwavelength hole arrays are considered. The results show that the transmission peak position and the minus phase shift angle of the SPP increase as the hole size increases. On the other hand, the effective dielectric constant of the metallic film can be deduced by the microscopic theoretical model.展开更多
Quantum key distribution is the art of sharing secret keys between two distant parties, and has attracted a lot of attention due to its unconditional security. Compared with other quantum key distribution protocols, t...Quantum key distribution is the art of sharing secret keys between two distant parties, and has attracted a lot of attention due to its unconditional security. Compared with other quantum key distribution protocols, the differential phase shift quantum key distribution protocol has higher efficiency and simpler apparatus. Unfortunately, the uncondi- tional security of differential phase shift quantum key distribution has not been proved. Utilizing the sharp continuity of the von Neuman entropy and some basic inequalities, we estimate the upper bound for the eavesdropper Eve＇s infor- mation. We then prove the lower bound for the security of the differential phase shift quantum key distribution protocol against a one-pulse attack with Devatak-Winter＇s secret key rate formula.展开更多
We investigate the co-propagation of a strong pump beam and a weak signal beam in lead glass, and find that the large phase shift of the strongly nonlocal spatial optical soliton （SNSOS） can be realized via cross-ph...We investigate the co-propagation of a strong pump beam and a weak signal beam in lead glass, and find that the large phase shift of the strongly nonlocal spatial optical soliton （SNSOS） can be realized via cross-phase modulation. The theoretical study suggests a synchronous propagation of the pump SNSOS and the signal SNSOS under the required initial condition. A π-phase shift of the signal SNSOS is experimentally obtained by changing the power of the pump SNSOS by about 13 mW around the soliton critical power, which agrees qualitatively with our theoretical prediction. The ratio of the phase shift rate of the signal SNSOS to that of the pump SNSOS shows a close match to the reciprocal of the ratio between their wavelengths.展开更多
A retarding field energy analyzer（RFEA） is used to measure the time-averaged ion energy distributions（IEDs） on the substrate in both continuous wave（CW） and synchronous pulse modulated radio-frequency（RF） indu...A retarding field energy analyzer（RFEA） is used to measure the time-averaged ion energy distributions（IEDs） on the substrate in both continuous wave（CW） and synchronous pulse modulated radio-frequency（RF） inductively coupled Ar plasmas（ICPs）.The effects of the phase shift θ between the RF bias voltage and the RF source on the IED is investigated under various discharge conditions.It is found that as θ increases from 0 to π,the IED moves towards the low-energy side,and its energy width becomes narrower.In order to figure out the physical mechanism,the voltage waveforms on the substrate are also measured.The results show that as θ increases from 0 to π,the amplitude of the voltage waveform decreases and,meanwhile,the average sheath potential decreases as well.Specifically,the potential drop in the sheath on the substrate exhibits a maximum value at the same phase（i.e.,θ = 0） and a minimum value at the opposite phase（i.e.,θ = π）.Therefore,when ions traverse across the sheath region above the substrate,they obtain less energies at lower sheath potential drop,leading to lower ion energy.Besides,as θ increases from π to 2π,the IEDs and their energy widths change reversely.展开更多
A method to extract phase shifts and reconstruct the object wave in generalized phase-shifting interferometry(GPSI)is proposed.The phase distribution of a standard phase object and the least-square method are used to ...A method to extract phase shifts and reconstruct the object wave in generalized phase-shifting interferometry(GPSI)is proposed.The phase distribution of a standard phase object and the least-square method are used to extract phase shifts over a wide range from 0 to𝜌π.Consequently,the tested object wave can be further reconstructed with the extracted phase shifts.It is accurate and applicable for GPSI of any frame number𝑂(N𝑂≥2).Computer simulation has verified its feasibility and validity.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52107162 and 12202479)the Science and Technology Projects of Shaanxi Province,China(Grant Nos.2022CGBX-12 and 2022KXJ-57)the Science and Technology Projects of Xi’an City,China(Grant Nos.23KGDW0023-2022 and 23GXFW0011)。
文摘A non-contact low-frequency(LF)method of diagnosing the plasma surrounding a scaled model in a shock tube is proposed.This method utilizes the phase shift occurring after the transmission of an LF alternating magnetic field through the plasma to directly measure the ratio of the plasma loop average electron density to collision frequency.An equivalent circuit model is used to analyze the relationship of the phase shift of the magnetic field component of LF electromagnetic waves with the plasma electron density and collision frequency.The applicable range of the LF method on a given plasma scale is analyzed.The upper diagnostic limit for the ratio of the electron density(unit:m^(-3))to collision frequency(unit:Hz)exceeds 1×10^(11),enabling an electron density to exceed 1×10^(20)m^(-3)and a collision frequency to be less than 1 GHz.In this work,the feasibility of using the LF phase shift to implement the plasma diagnosis is also assessed.Diagnosis experiments on shock tube equipment are conducted by using both the electrostatic probe method and LF method.By comparing the diagnostic results of the two methods,the inversion results are relatively consistent with each other,thereby preliminarily verifying the feasibility of the LF method.The ratio of the electron density to the collision frequency has a relatively uniform distribution during the plasma stabilization.The LF diagnostic path is a loop around the model,which is suitable for diagnosing the plasma that surrounds the model.Finally,the causes of diagnostic discrepancy between the two methods are analyzed.The proposed method provides a new avenue for diagnosing high-density enveloping plasma.
文摘A new error compensating five sample phase shifting algorithm which is insensitive to phase shift error is proposed to retrieve the phase distribution of a fringe pattern. It includes two steps. First, the linear phase shift error is estimated using four sample images. Then, the phase distribution is calculated with error corrected by using the phase shift error estimated in the first step. As the equations of error estimation and phase calculation are simple, this new algorithm is practical as well as effective. Computer simulations were carried out to verify the effectiveness of the algorithm. Results of two other well known error compensating algorithms are also presented, which show the new algorithm is the least sensitive to phase shift error.
基金Project supported by the Key Program of the National Natural Science Foundation of China(Grant Nos.10490194 and 10734070) the National Natural Science Foundation of China(Grant Nos.10504033,10774144 and 10979055)+2 种基金the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KJCX2-YW-N42)the National Basic Research Program of China (Grant No.2009CB930804)the National Outstanding Youth Fund(Grant No.10125523)
文摘Two phase extraction methods which are based separately on phase-stepping and shifting curve are mainly used in phase-sensitive imaging in gating interferometry to determine the x-ray phase shift induced by an object in the beam. In this paper, the authors perform a full comparative analysis and present the main virtues and limitations of these two methods according to the theoretical analysis of the grating interferometry.
基金Project supported by the Natural Science Foundation of Shandong Province of China (Grant No. Y2008A16)the Natural Science Foundation of Heze University of Shandong Province, China (Grant No. XY09WL01)
文摘Based on the rotation transformation in phase space and the technique of integration within an ordered product of operators, the coherent state representation of the multimode phase shifting operator and one of its new applications in quantum mechanics are given. It is proved that the coherent state is a natural language for describing the phase shifting operator or multimode phase shifting operator. The multimode phase shifting operator is also a useful tool to solve the dynamic problems of the mnltimode coordinate-momentum coupled harmonic oscillators. The exact energy spectra and eigenstates of such multimode coupled harmonic oscillators can be easily obtained by using the rnultimode phase shifting operator.
文摘Reconfigurable intelligent surface(RIS)for wireless networks have drawn lots of attention in both academic and industry communities.RIS can dynamically control the phases of the reflection elements to send the signal in the desired direction,thus it provides supplementary links for wireless networks.Most of prior works on RIS-aided wireless communication systems consider continuous phase shifts,but phase shifts of RIS are discrete in practical hardware.Thus we focus on the actual discrete phase shifts on RIS in this paper.Using the advanced deep reinforcement learning(DRL),we jointly optimize the transmit beamforming matrix from the discrete Fourier transform(DFT)codebook at the base station(BS)and the discrete phase shifts at the RIS to maximize the received signal-to-interference plus noise ratio(SINR).Unlike the traditional schemes usually using alternate optimization methods to solve the transmit beamforming and phase shifts,the DRL algorithm proposed in the paper can jointly design the transmit beamforming and phase shifts as the output of the DRL neural network.Numerical results indicate that the DRL proposed can dispose the complicated optimization problem with low computational complexity.
基金Supported by the National Basic Research Program of China under Grant No 2013CB338002the National Natural Science Foundation of China under Grant Nos 11304397 and 61505261
文摘Round-robin differential phase shift （RRDPS） is a novel quantum key distribution protocol which can bound information leakage without monitoring signal disturbance. In this work, to decrease the effect of the vacuum component in a weak coherent pulses source, we employ a practical decoy-state scheme with heralded singlephoton source for the RRDPS protocol and analyze the performance of this method. In this scheme, only two decoy states are needed and the yields of single-photon state and multi-photon states, as well as the bit error rates of each photon states, can be estimated. The final key rate of this scheme is bounded and simulated over transmission distance. The results show that the two-decoy-state method with heralded single-photon source performs better than the two-decoy-state method with weak coherent pulses.
基金supported by the National Basic Research Program of China(Grant No.2011CB302903)the National Natural Science Foundation of China(Grant Nos.61272084 and 61202004)the Key Project of Natural Science Research of Jiangsu University,China(Grant No.11KJA520002)
文摘In this paper, we propose an encryption scheme based on phase-shifting digital interferometry. According to the original system framework, we add a random amplitude mask and replace the Fourier transform by the Fresnel transform. We develop a mathematical model and give a discrete formula based on the scheme, which makes it easy to implement the scheme in computer programming. The experimental results show that the improved system has a better performance in security than the original encryption method. Moreover, it demonstrates a good capability of anti-noise and anti-shear robustness.
基金Project supported by the Science and Technology Major Projects of Zhejiang Province,China(Grant No.2013C03043-5)
文摘Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector-camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61775121,61307003,61405122,and 11574311)Key R&D Program of Shandong Province,China(Grant No.2018GGX101002)+1 种基金the Natural Science Foundation of Shandong Province,China(Grant No.R2016FM03)the Fundamental Research Funds of Shandong University,China(Grant No.2015GN031)
文摘A multiple-image encryption method based on two-step phase-shifting interferometry （PSI） and spatial multiplexing of a smooth compressed signal is proposed. In the encoding and encryption process, with the help of four index matrices to store original pixel positions, all the pixels of four secret images are firstly reordered in an ascending order; then, the four reordered images are transformed by five-order Haar wavelet transform and performed sparseness operation. After Arnold transform and pixels sampling operation, one combined image can be grouped with the aid of compressive sensing （CS） and spatial multiplexing techniques. Finally, putting the combined image at the input plane of the PSI encryption scheme, only two interferograms ciphertexts can be obtained. During the decoding and decryption, utilizing all the secret key groups and index matrices keys, all the original secret images can be successfully decrypted by a wave-front retrieval algorithm of two-step PSI, spatial de-multiplexing, inverse Arnold transform, inverse discrete wavelet transform, and pixels reordering operation.
基金Project supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2017292)the National Natural Science Foundation of China(Grant No.61775222)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LQ16A050001)
文摘A method of single-shot phase-shifting digital holography with a photon-sieve-filtering telescope is proposed.Three copy images with different phases are first generated by use of a monofocal photon-sieve filter in Kepler telescope,and then interfere with the reference plane wave by a beam combiner.The hologram is captured by a charge-coupled device(CCD)in one single exposure.The complex-valued amplitude of the test object can be reconstructed by three-step phase-shifting interferometry through three frames of extracted sub-interferograms from the single-exposure hologram.The principle and simulation experiments are carried out and verified the validity of our proposed method.This method can be applied for snapshot imaging and three-dimensional object construction.
文摘The influence of multi-photon pulses on practical differcBtial-phase-shift quantum key distribution （DPS-Qt（D） is analysed. We have estimated the information which Eve obtained by PNS （photon-number splitting） attack and BS （beam splitting） attack. The result indicates that the PNS attack and BS attack will not limit the transmission distance as long as we select an appropriate mean photon number. Also, the maximum mean photon number under BS attack in practical DPS-QKD system and the set of practical assumptions about Eve＇s capabilities are presented.
基金the Open Fund(PLC201104)of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Chengdu University of Technology)the National Natural Science Foundation of China(No.61072073)the Key Project of Education Commission of Sichuan Province(No.10ZA072)
文摘Although the phase-shift seismic processing method has characteristics of high accuracy, good stability, high efficiency, and high-dip imaging, it is not able to adapt to strong lateral velocity variation. To overcome this defect, a finite-difference method in the frequency-space domain is introduced in the migration process, because it can adapt to strong lateral velocity variation and the coefficient is optimized by a hybrid genetic and simulated annealing algorithm. The two measures improve the precision of the approximation dispersion equation. Thus, the imaging effect is improved for areas of high-dip structure and strong lateral velocity variation. The migration imaging of a 2-D SEG/EAGE salt dome model proves that a better imaging effect in these areas is achieved by optimized phase-shift migration operator plus a finite-difference method based on a hybrid genetic and simulated annealing algorithm. The method proposed in this paper is better than conventional methods in imaging of areas of high-dip angle and strong lateral velocity variation.
基金Project supported in part by the National Natural Science Foundation of China (Grant No 10875011)the 973 Programme (Grant No 2007CB814805)the Foundation of Doctoral Training of China (Grant No 20060027009)
文摘The behaviors of coupled oscillators, each of which has periodic motion with random natural frequency in the absence of coupling, are investigated when phase shifts are considered. In the system of coupled oscillators, phase shifts are the same between different oscillators. Synchronization and synchronization transition are revealed with different phase shifts. Phase shifts play an important role for this kind of system. When the phase shift α〈 0.5π, the synchronization state can be attained by increasing the coupling, and the system cannot reach the synchronization state while α≥ 0.5π. A clear scaling between complete synchronization critical coupling strength Kpc and α - 0.5π is found.
基金Project supported by the National Basic Research Program of China(Grant No.2010CB23202)the National Natural Science Foundation of China(Grant No.10805006)
文摘We present the transmission spectra of light transmitting a metallic thin film perforated with differently shaped sub- wavelength hole arrays, which are calculated by a plane-wave-based transfer matrix method. We analyze the transmission peak positions and the phase-shift angles of different surface plasmon polariton （SPP） modes by using the microscopic theoretical model proposed by Haitao Liu and Philippe Lalanne [Liu Haitao, and Lalanne Philippe 2008 Nature 452 728], in which the phase shift properties of the SPPs scattered by the subwavelength hole arrays are considered. The results show that the transmission peak position and the minus phase shift angle of the SPP increase as the hole size increases. On the other hand, the effective dielectric constant of the metallic film can be deduced by the microscopic theoretical model.
基金supported by the National Fundamental Research Program of China (Grant No. 2006CB921900)National Natural Science Foundation of China (Grant Nos. 60537020 and 60621064)the Innovation Funds of the Chinese Academy of Sciences
文摘Quantum key distribution is the art of sharing secret keys between two distant parties, and has attracted a lot of attention due to its unconditional security. Compared with other quantum key distribution protocols, the differential phase shift quantum key distribution protocol has higher efficiency and simpler apparatus. Unfortunately, the uncondi- tional security of differential phase shift quantum key distribution has not been proved. Utilizing the sharp continuity of the von Neuman entropy and some basic inequalities, we estimate the upper bound for the eavesdropper Eve＇s infor- mation. We then prove the lower bound for the security of the differential phase shift quantum key distribution protocol against a one-pulse attack with Devatak-Winter＇s secret key rate formula.
基金Project supported by the National Natural Science Foundation of China(Grant No.11274125)
文摘We investigate the co-propagation of a strong pump beam and a weak signal beam in lead glass, and find that the large phase shift of the strongly nonlocal spatial optical soliton （SNSOS） can be realized via cross-phase modulation. The theoretical study suggests a synchronous propagation of the pump SNSOS and the signal SNSOS under the required initial condition. A π-phase shift of the signal SNSOS is experimentally obtained by changing the power of the pump SNSOS by about 13 mW around the soliton critical power, which agrees qualitatively with our theoretical prediction. The ratio of the phase shift rate of the signal SNSOS to that of the pump SNSOS shows a close match to the reciprocal of the ratio between their wavelengths.
基金Project supported by the Important National Science and Technology Specific Project,China(Grant No.2011ZX02403-001)the National Natural Science Foundation of China(Grand No.11675039)the Fundamental Research Funds for the Central Universities,China(Grand No.DUT16LK06)
文摘A retarding field energy analyzer（RFEA） is used to measure the time-averaged ion energy distributions（IEDs） on the substrate in both continuous wave（CW） and synchronous pulse modulated radio-frequency（RF） inductively coupled Ar plasmas（ICPs）.The effects of the phase shift θ between the RF bias voltage and the RF source on the IED is investigated under various discharge conditions.It is found that as θ increases from 0 to π,the IED moves towards the low-energy side,and its energy width becomes narrower.In order to figure out the physical mechanism,the voltage waveforms on the substrate are also measured.The results show that as θ increases from 0 to π,the amplitude of the voltage waveform decreases and,meanwhile,the average sheath potential decreases as well.Specifically,the potential drop in the sheath on the substrate exhibits a maximum value at the same phase（i.e.,θ = 0） and a minimum value at the opposite phase（i.e.,θ = π）.Therefore,when ions traverse across the sheath region above the substrate,they obtain less energies at lower sheath potential drop,leading to lower ion energy.Besides,as θ increases from π to 2π,the IEDs and their energy widths change reversely.
基金Supported by the National Natural Science Foundation of China under Grant No 61275014the Science and Technology Program of Shandong Province under Grant No 2011GGH20119the Natural Science Foundation of Shandong Province under Grant No ZR2011FQ011.
文摘A method to extract phase shifts and reconstruct the object wave in generalized phase-shifting interferometry(GPSI)is proposed.The phase distribution of a standard phase object and the least-square method are used to extract phase shifts over a wide range from 0 to𝜌π.Consequently,the tested object wave can be further reconstructed with the extracted phase shifts.It is accurate and applicable for GPSI of any frame number𝑂(N𝑂≥2).Computer simulation has verified its feasibility and validity.
