It meets some difficulties in the case of ultrasonic phased arrays testing for the nickel-based alloy welded joint, since the ultrasound will propagate with curvilinear paths in this kind anisotropic joint. Thus, it i...It meets some difficulties in the case of ultrasonic phased arrays testing for the nickel-based alloy welded joint, since the ultrasound will propagate with curvilinear paths in this kind anisotropic joint. Thus, it is hard to calculate the phased array time delays properly according to the traditional focusing approach, which is based on the assumption that the sound beam will propagate in straight lines. In order to focus the phased arrays beam in this kind anisotropic joint, we provide a modified focusing approach by combining the ray tracing method and the bisectional searching optimization. With the help of this focusing approach, the curved ray path connecting each element position in phased arrays to the expected focus point in weldments can be determined, so that it can be used to calculate the proper time delay and control the beam focusing in the anisotropic weldment. Furthermore, some experimental examinations are carried out to compare the focusing behaviors between the traditional and the modified focusing approach. It shows that the provided focusing approach is more accurate than the traditional method in the case of inspection on the nickel-based alloy weldments.展开更多
In recent years,optical phased arrays(OPAs)have attracted great interest for their potential applications in light detection and ranging(Li DAR),free-space optical communications(FSOs),holography,and so on.Photonic in...In recent years,optical phased arrays(OPAs)have attracted great interest for their potential applications in light detection and ranging(Li DAR),free-space optical communications(FSOs),holography,and so on.Photonic integrated circuits(PICs)provide solutions for further reducing the size,weight,power,and cost of OPAs.In this paper,we review the recent development of photonic integrated OPAs.We summarize the typical architecture of the integrated OPAs and their performance.We analyze the key components of OPAs and evaluate the figure of merit for OPAs.Various applications in Li DAR,FSO,imaging,biomedical sensing,and specialized beam generation are introduced.展开更多
A polarization-independent nonmechanical laser beam steering scheme is proposed to realize continuous two-dimensional(2 D) scanning with high efficiency, where the core components are two polarization-dependent devi...A polarization-independent nonmechanical laser beam steering scheme is proposed to realize continuous two-dimensional(2 D) scanning with high efficiency, where the core components are two polarization-dependent devices, which are called liquid crystal optical phased arrays(LC-OPAs). These two one-dimensional(1D) devices are orthogonally cascaded to work on the state of azimuthal and elevation steering, respectively. Properties of polarization independence as well as 2D beam steering are mathematically and experimentally verified with a good agreement. Based on the experimental setup, linearly polarized beams with different polarization angles are steered with high accuracy. The measured angular deviations are less than 5 μrad, which is on the same order of the accuracy of the measurement system. This polarization-independent 2 D laser beam steering scheme has potential application for nonmechanical laser communication, lidar, and other LC-based systems.展开更多
To cope with the time-varying and Dopper-broadened clutter in airborne phase array radars, it is required that the signal processing should be adaptive and two-dimensional both in time and in space. However, the optim...To cope with the time-varying and Dopper-broadened clutter in airborne phase array radars, it is required that the signal processing should be adaptive and two-dimensional both in time and in space. However, the optimum two-dimensional adaptive processing is hard to realize real-timely because it requires a large amount of computation. From the idea of approximating the clutter process by using an auto regressive process, a linear prediction approach is proposed to realize the adaptive space-time processing of airborne adaptive array signals. The research shows that the clutter process can be well approximated by a low-order AR process, so a low-order linear prediction receiver can get a sub-optimum performance at a very low expense. Besides, the low-order linear prediction receiver has additional degrees of freedom to cope with other colored noises and interferences. In consideration of the many advantages of the linear prediction receiver in both algorithms and realizations, it has a good prospect in its application to air borne adaptive array signal processing.展开更多
A mathematical simulating model of phased-array antenna in multifunction array radar has been approached in this paper, including the mathematical simulating model of plane phased-array pattern, the mathematical simul...A mathematical simulating model of phased-array antenna in multifunction array radar has been approached in this paper, including the mathematical simulating model of plane phased-array pattern, the mathematical simulating model of directionality factor, the mathematical simulating model of array factor, the mathematical simulating model of array element factor and the mathematical simulating model of beam steering.展开更多
A novel slow-down set waveform is proposed to improve the set performance and a 1 kb phase change random access memory chip fabricated with a 13nm CMOS technology is implemented to investigate the set performance by d...A novel slow-down set waveform is proposed to improve the set performance and a 1 kb phase change random access memory chip fabricated with a 13nm CMOS technology is implemented to investigate the set performance by different set programming strategies based on this new set pulse. The amplitude difference (I1 - I2) of the set pulse is proved to be a crucial parameter for set programming. We observe and analyze the cell characteristics with different I1 - I2 by means of thermal simulations and high-resolution transmission electron microscopy, which reveal that an incomplete set programming will occur when the proposed slow-down pulse is set with an improperly high I1 - I2. This will lead to an amorphous residue in the active region. We also discuss the programming method to avoid the set performance degradations.展开更多
We demonstrate a 7-bit photonic true-time-delay (TTD) system which uses an 8 × 8 micro-optical-electro- mechanical system (MOEMS) optical switch for phased array antennas (PAAs) beamforming applications. Th...We demonstrate a 7-bit photonic true-time-delay (TTD) system which uses an 8 × 8 micro-optical-electro- mechanical system (MOEMS) optical switch for phased array antennas (PAAs) beamforming applications. The switch controls the optical signal to pass by the fiber delay lines (FDLs) of different lengths. Different time delays between adjacent channels are obtained due to the chromatic dispersion of FDLs. Therefore, the system cannot be disturbed by the environment. The measured time delay responses are nearly linear with the wavelength spacing between optical carriers as well as the lengths of FDLs, which agrees well with the theoretical analysis.展开更多
The Indian buffet process(IBP)and phylogenetic Indian buffet process(pIBP)can be used as prior models to infer latent features in a data set.The theoretical properties of these models are under-explored,however,especi...The Indian buffet process(IBP)and phylogenetic Indian buffet process(pIBP)can be used as prior models to infer latent features in a data set.The theoretical properties of these models are under-explored,however,especially in high dimensional settings.In this paper,we show that under mild sparsity condition,the posterior distribution of the latent feature matrix,generated via IBP or pIBP priors,converges to the true latent feature matrix asymptotically.We derive the posterior convergence rate,referred to as the contraction rate.We show that the convergence results remain valid even when the dimensionality of the latent feature matrix increases with the sample size,therefore making the posterior inference valid in high dimensional settings.We demonstrate the theoretical results using computer simulation,in which the parallel-tempering Markov chain Monte Carlo method is applied to overcome computational hurdles.The practical utility of the derived properties is demonstrated by inferring the latent features in a reverse phase protein arrays(RPPA)dataset under the IBP prior model.展开更多
基金Acknowledgements This study was supported by National Natural Science Foundation of China (Grant No. 51105033, 50975028, 51175133 ) and State Key Laboratory of Advanced Welding and Joining.
文摘It meets some difficulties in the case of ultrasonic phased arrays testing for the nickel-based alloy welded joint, since the ultrasound will propagate with curvilinear paths in this kind anisotropic joint. Thus, it is hard to calculate the phased array time delays properly according to the traditional focusing approach, which is based on the assumption that the sound beam will propagate in straight lines. In order to focus the phased arrays beam in this kind anisotropic joint, we provide a modified focusing approach by combining the ray tracing method and the bisectional searching optimization. With the help of this focusing approach, the curved ray path connecting each element position in phased arrays to the expected focus point in weldments can be determined, so that it can be used to calculate the proper time delay and control the beam focusing in the anisotropic weldment. Furthermore, some experimental examinations are carried out to compare the focusing behaviors between the traditional and the modified focusing approach. It shows that the provided focusing approach is more accurate than the traditional method in the case of inspection on the nickel-based alloy weldments.
基金supported by the Key Research and Development Program of Hubei Province(No.2021BAA004)the Innovation Project of Optics Valley Laboratory(Nos.OVL2021BG004 and OVL2023ZD004)+1 种基金the National Natural Science Foundation of China(NSFC)(Nos.62125503,62261160388,and 62105115)the Natural Science Foundation of Hubei Province of China(No.2023AFA028)。
文摘In recent years,optical phased arrays(OPAs)have attracted great interest for their potential applications in light detection and ranging(Li DAR),free-space optical communications(FSOs),holography,and so on.Photonic integrated circuits(PICs)provide solutions for further reducing the size,weight,power,and cost of OPAs.In this paper,we review the recent development of photonic integrated OPAs.We summarize the typical architecture of the integrated OPAs and their performance.We analyze the key components of OPAs and evaluate the figure of merit for OPAs.Various applications in Li DAR,FSO,imaging,biomedical sensing,and specialized beam generation are introduced.
基金supported by the National Science Foundation of China(NSFC)(Nos.61405029,91438108,and61231012)the Shanghai Aerospace Science and Technology(SAST)(No.2015087)
文摘A polarization-independent nonmechanical laser beam steering scheme is proposed to realize continuous two-dimensional(2 D) scanning with high efficiency, where the core components are two polarization-dependent devices, which are called liquid crystal optical phased arrays(LC-OPAs). These two one-dimensional(1D) devices are orthogonally cascaded to work on the state of azimuthal and elevation steering, respectively. Properties of polarization independence as well as 2D beam steering are mathematically and experimentally verified with a good agreement. Based on the experimental setup, linearly polarized beams with different polarization angles are steered with high accuracy. The measured angular deviations are less than 5 μrad, which is on the same order of the accuracy of the measurement system. This polarization-independent 2 D laser beam steering scheme has potential application for nonmechanical laser communication, lidar, and other LC-based systems.
文摘To cope with the time-varying and Dopper-broadened clutter in airborne phase array radars, it is required that the signal processing should be adaptive and two-dimensional both in time and in space. However, the optimum two-dimensional adaptive processing is hard to realize real-timely because it requires a large amount of computation. From the idea of approximating the clutter process by using an auto regressive process, a linear prediction approach is proposed to realize the adaptive space-time processing of airborne adaptive array signals. The research shows that the clutter process can be well approximated by a low-order AR process, so a low-order linear prediction receiver can get a sub-optimum performance at a very low expense. Besides, the low-order linear prediction receiver has additional degrees of freedom to cope with other colored noises and interferences. In consideration of the many advantages of the linear prediction receiver in both algorithms and realizations, it has a good prospect in its application to air borne adaptive array signal processing.
文摘A mathematical simulating model of phased-array antenna in multifunction array radar has been approached in this paper, including the mathematical simulating model of plane phased-array pattern, the mathematical simulating model of directionality factor, the mathematical simulating model of array factor, the mathematical simulating model of array element factor and the mathematical simulating model of beam steering.
基金Supported by the Strategic Priority Research Program of Chinese Academy of Sciences under Grant No XDA09020402the National Key Basic Research Program of China under Grant Nos 2013CBA01900,2010CB934300,2011CBA00607,and 2011CB932804+2 种基金the National Integrate Circuit Research Program of China under Grant No 2009ZX02023-003the National Natural Science Foundation of China under Grant Nos 61176122,61106001,61261160500,and 61376006the Science and Technology Council of Shanghai under Grant Nos 12nm0503701,13DZ2295700,12QA1403900,and 13ZR1447200
文摘A novel slow-down set waveform is proposed to improve the set performance and a 1 kb phase change random access memory chip fabricated with a 13nm CMOS technology is implemented to investigate the set performance by different set programming strategies based on this new set pulse. The amplitude difference (I1 - I2) of the set pulse is proved to be a crucial parameter for set programming. We observe and analyze the cell characteristics with different I1 - I2 by means of thermal simulations and high-resolution transmission electron microscopy, which reveal that an incomplete set programming will occur when the proposed slow-down pulse is set with an improperly high I1 - I2. This will lead to an amorphous residue in the active region. We also discuss the programming method to avoid the set performance degradations.
基金supported by the Subsidized Projecton Aerospace Technology Innovation Foundation of China Aerospace Science and Technology Corporationthe National Natural Science Foundation of China(No. 10778713 and 60736002)
文摘We demonstrate a 7-bit photonic true-time-delay (TTD) system which uses an 8 × 8 micro-optical-electro- mechanical system (MOEMS) optical switch for phased array antennas (PAAs) beamforming applications. The switch controls the optical signal to pass by the fiber delay lines (FDLs) of different lengths. Different time delays between adjacent channels are obtained due to the chromatic dispersion of FDLs. Therefore, the system cannot be disturbed by the environment. The measured time delay responses are nearly linear with the wavelength spacing between optical carriers as well as the lengths of FDLs, which agrees well with the theoretical analysis.
文摘The Indian buffet process(IBP)and phylogenetic Indian buffet process(pIBP)can be used as prior models to infer latent features in a data set.The theoretical properties of these models are under-explored,however,especially in high dimensional settings.In this paper,we show that under mild sparsity condition,the posterior distribution of the latent feature matrix,generated via IBP or pIBP priors,converges to the true latent feature matrix asymptotically.We derive the posterior convergence rate,referred to as the contraction rate.We show that the convergence results remain valid even when the dimensionality of the latent feature matrix increases with the sample size,therefore making the posterior inference valid in high dimensional settings.We demonstrate the theoretical results using computer simulation,in which the parallel-tempering Markov chain Monte Carlo method is applied to overcome computational hurdles.The practical utility of the derived properties is demonstrated by inferring the latent features in a reverse phase protein arrays(RPPA)dataset under the IBP prior model.