Because of its all-reflective layout based on the Fresnel double-mirror interference system, the newly developed Fourier transform imaging spectrometer has a very large spectral bandwidth ranged from a cut-off wavelen...Because of its all-reflective layout based on the Fresnel double-mirror interference system, the newly developed Fourier transform imaging spectrometer has a very large spectral bandwidth ranged from a cut-off wavelength (related to the cut-off wave number σ max ) to far infrared. According to the signal's symmetry and wide-band characteristics, a simple method that can efficiently weaken the low frequency noise in the reconstructed spectrum is presented. Also, according to the symmetry, the eigenvector method is applied to the reconstruction of the spectrum.展开更多
In this paper, a fast algorithm to reconstruct the spectrum of non-uniformly sampled signals is proposed. Compared with the original algorithm, the fast algorithm has a higher computational efficiency, especially when...In this paper, a fast algorithm to reconstruct the spectrum of non-uniformly sampled signals is proposed. Compared with the original algorithm, the fast algorithm has a higher computational efficiency, especially when sampling sequence is long. Particularly, a transformation matrix is built, and the reconstructed spectrum is perfectly synthesized from the spectrum of every sampling channel. The fast algorithm has solved efficiency issues of spectrum reconstruction algorithm, and making it possible for the actual application of spectrum reconstruction algorithm in multi-channel Synthetic Aperture Radar (SAR).展开更多
To study the spectrum reconstruction of the 20 MV X-ray generated by the Dragon-I linear induction accelerator, the Monte Carlo method is applied to simulate the attenuations of the X-ray in the attenuators of differe...To study the spectrum reconstruction of the 20 MV X-ray generated by the Dragon-I linear induction accelerator, the Monte Carlo method is applied to simulate the attenuations of the X-ray in the attenuators of different thicknesses and thus provide the transmission data. As is known, the spectrum estimation from transmission data is an ill-conditioned problem. The method based on iterative perturbations is employed to derive the X-ray spectra, where initial guesses are used to start the process. This algorithm takes into account not only the minimization of the differences between the measured and the calculated transmissions but also the smoothness feature of the spectrum function. In this work, various filter materials are put to use as the attenuator, and the condition for an accurate and robust solution of the X-ray spectrum calculation is demonstrated. The influences of the scattering photons within different intervals of emergence angle on the X-ray spectrum reconstruction are also analyzed.展开更多
This paper presents an experimental investigation into the runaway electron spectrum with a gas diode composed of a rough spherical cathode and plane anode under the excitation of a nanosecond-pulse generator in atmos...This paper presents an experimental investigation into the runaway electron spectrum with a gas diode composed of a rough spherical cathode and plane anode under the excitation of a nanosecond-pulse generator in atmospheric air.The runaway electron beams are measured by a collector covered with aluminum foil with a thickness from 0μm(mesh grid)to 50μm.The energy spectrum is calculated by an improved Tikhonov regularization called the maximum entropy method.The experimental results show that the transition state of the discharge consisted of multiple streamer channels stretched from the cathode with glow-like plasma uniformly distributed over the anode.The number of runaway electrons measured by the collector is in the order of 1010 in atmospheric pressure air with a gap spacing of 5 mm and applied voltages of70–130 kV.The cathode with a rough surface creates a more inhomogeneous electric field and larger emission site for the runaway electrons around the cathode,providing conditions for the coexistence of filamentary streamer and diffuse discharge.The reconstructed spectra show that the energy distribution of the runaway electrons presents a single-peak profile with energies from eU_(m/2)–2 eU_(m/3)(U_(m)is maximal voltage across the gap).展开更多
A new method which employs compressive sensing(CS) to reconstruct the sparse spectrum is designed and experimentally demonstrated. On the basis of CS theory, the simulation results indicate that the probability of rec...A new method which employs compressive sensing(CS) to reconstruct the sparse spectrum is designed and experimentally demonstrated. On the basis of CS theory, the simulation results indicate that the probability of reconstruction is high when the step of the sparsity adaptive matching pursuit algorithm is confirmed as 1. Contrastive analysis for four kinds of commonly used measurement matrices: part Hadamard, Bernoulli, Toeplitz and Circular matrix, has been conducted. The results illustrate that the part Hadamard matrix has better performance of reconstruction than the other matrices. The experimental system of the spectral compression reconstruction is mainly based on the digital micro-mirror device(DMD). The experimental results prove that CS can reconstruct sparse spectrum well under the condition of 50% sampling rate. The system error 0.0781 is obtained, which is defined by the average value of the 2-norm. Furthermore, the proposed method shows a dominant ability to discard redundancy.展开更多
A micro-spectrometer with phase modulation array is investigated in this paper. The vital component of this micro-spectrometer is a micro-interferometer array, which is built on a charge-coupled device (CCD) or a co...A micro-spectrometer with phase modulation array is investigated in this paper. The vital component of this micro-spectrometer is a micro-interferometer array, which is built on a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). Each element of micro-interferometer array is formed by polymethyl methacrylate (PMMA) grooves with different depth. When we illuminate the surface of the interferom- eter array, different interference intensity distribution would be formed at the bottom of each micro-interferom- eter. Optical power of this by the pixels of CCD substituted into a linear interferometer can be measured or CMOS. The data can be system. By solving the linear system with Tikhonov regularization method, spectrum of the incident beam can be reconstructed. Simulation results prove that the detection range of the spectrometer is a wide wavelength range covering from 300 to 1100 nm. Furthermore, the wavelength resolution of the device reaches picometer level. In comparison with conventional spectrometers, the novel spectrometer has distinct advan- tages of small size, low cost, high resolution, wide spectral measurement range, real-time measurement, and so on.展开更多
文摘Because of its all-reflective layout based on the Fresnel double-mirror interference system, the newly developed Fourier transform imaging spectrometer has a very large spectral bandwidth ranged from a cut-off wavelength (related to the cut-off wave number σ max ) to far infrared. According to the signal's symmetry and wide-band characteristics, a simple method that can efficiently weaken the low frequency noise in the reconstructed spectrum is presented. Also, according to the symmetry, the eigenvector method is applied to the reconstruction of the spectrum.
文摘In this paper, a fast algorithm to reconstruct the spectrum of non-uniformly sampled signals is proposed. Compared with the original algorithm, the fast algorithm has a higher computational efficiency, especially when sampling sequence is long. Particularly, a transformation matrix is built, and the reconstructed spectrum is perfectly synthesized from the spectrum of every sampling channel. The fast algorithm has solved efficiency issues of spectrum reconstruction algorithm, and making it possible for the actual application of spectrum reconstruction algorithm in multi-channel Synthetic Aperture Radar (SAR).
文摘To study the spectrum reconstruction of the 20 MV X-ray generated by the Dragon-I linear induction accelerator, the Monte Carlo method is applied to simulate the attenuations of the X-ray in the attenuators of different thicknesses and thus provide the transmission data. As is known, the spectrum estimation from transmission data is an ill-conditioned problem. The method based on iterative perturbations is employed to derive the X-ray spectra, where initial guesses are used to start the process. This algorithm takes into account not only the minimization of the differences between the measured and the calculated transmissions but also the smoothness feature of the spectrum function. In this work, various filter materials are put to use as the attenuator, and the condition for an accurate and robust solution of the X-ray spectrum calculation is demonstrated. The influences of the scattering photons within different intervals of emergence angle on the X-ray spectrum reconstruction are also analyzed.
基金supported by the National Science Fund for Distinguished Young Scholars(Grant No.51925703)National Natural Science Foundation of China(Grant Nos.52022096 and 51907190)the Royal Society–Newton Advanced Fellowship,UK(Grant No.NAF\R2\192117)。
文摘This paper presents an experimental investigation into the runaway electron spectrum with a gas diode composed of a rough spherical cathode and plane anode under the excitation of a nanosecond-pulse generator in atmospheric air.The runaway electron beams are measured by a collector covered with aluminum foil with a thickness from 0μm(mesh grid)to 50μm.The energy spectrum is calculated by an improved Tikhonov regularization called the maximum entropy method.The experimental results show that the transition state of the discharge consisted of multiple streamer channels stretched from the cathode with glow-like plasma uniformly distributed over the anode.The number of runaway electrons measured by the collector is in the order of 1010 in atmospheric pressure air with a gap spacing of 5 mm and applied voltages of70–130 kV.The cathode with a rough surface creates a more inhomogeneous electric field and larger emission site for the runaway electrons around the cathode,providing conditions for the coexistence of filamentary streamer and diffuse discharge.The reconstructed spectra show that the energy distribution of the runaway electrons presents a single-peak profile with energies from eU_(m/2)–2 eU_(m/3)(U_(m)is maximal voltage across the gap).
基金supported by the National Natural Science Foundation of China(Nos.61002013 and 11504435)the Natural Science Foundation of Hubei Province(No.2014CFA051)+1 种基金the Key Technology R&D Program of Hubei Province(No.2015BCE048)the Fundamental Research Funds for the Central Universities,South-Central University for Nationalities(Nos.CZY13034,CZW15055 and CZP17026)
文摘A new method which employs compressive sensing(CS) to reconstruct the sparse spectrum is designed and experimentally demonstrated. On the basis of CS theory, the simulation results indicate that the probability of reconstruction is high when the step of the sparsity adaptive matching pursuit algorithm is confirmed as 1. Contrastive analysis for four kinds of commonly used measurement matrices: part Hadamard, Bernoulli, Toeplitz and Circular matrix, has been conducted. The results illustrate that the part Hadamard matrix has better performance of reconstruction than the other matrices. The experimental system of the spectral compression reconstruction is mainly based on the digital micro-mirror device(DMD). The experimental results prove that CS can reconstruct sparse spectrum well under the condition of 50% sampling rate. The system error 0.0781 is obtained, which is defined by the average value of the 2-norm. Furthermore, the proposed method shows a dominant ability to discard redundancy.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China (Grant Nos. 6110611, 51172110, 651372119 and 61377019), the National Basic Research Program of China (Nos. 2012CB933301 and 2009CB930600), the Research Fund of National Laboratory of Solid State Microstructure (No. M25008).
文摘A micro-spectrometer with phase modulation array is investigated in this paper. The vital component of this micro-spectrometer is a micro-interferometer array, which is built on a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). Each element of micro-interferometer array is formed by polymethyl methacrylate (PMMA) grooves with different depth. When we illuminate the surface of the interferom- eter array, different interference intensity distribution would be formed at the bottom of each micro-interferom- eter. Optical power of this by the pixels of CCD substituted into a linear interferometer can be measured or CMOS. The data can be system. By solving the linear system with Tikhonov regularization method, spectrum of the incident beam can be reconstructed. Simulation results prove that the detection range of the spectrometer is a wide wavelength range covering from 300 to 1100 nm. Furthermore, the wavelength resolution of the device reaches picometer level. In comparison with conventional spectrometers, the novel spectrometer has distinct advan- tages of small size, low cost, high resolution, wide spectral measurement range, real-time measurement, and so on.