Semitransparent organic solar cells(ST-OSCs)are promising for building-integrated photovoltaics,offering power generation,transparency and heat insulation.High performance ST-OSCs need sophisticated optical management...Semitransparent organic solar cells(ST-OSCs)are promising for building-integrated photovoltaics,offering power generation,transparency and heat insulation.High performance ST-OSCs need sophisticated optical management to balance the competing demands of power conversion efficiency(PCE)and average visible transmittance(AVT)for various applications.Here,a type of aperiodic band-pass filter(ABPF)made from LiF and ZnS are developed to selectively alter visible light transmission and near-infrared(NIR)reflection.This ABPF allows the active layers of ST-OSCs to re-harvest unabsorbed NIR photons,compensating for the loss of photocurrent caused by the high AVT of ST-OSCs.By carefully adjusting the thicknesses of individual layers within ABPFs,we can modulate their photonic bandgaps,enabling ST-OSCs to achieve multifunctional performance.ST-OSCs combined with the ABPF-1 demonstrate a remarkable light utilization efficiency(LUE)of 5.40%,a PCE of 14.21%and an AVT of 38.0%,which represent some of the highest values reported for ST-OSCs.Moreover,the ST-OSCs are equipped with excellent color neutrality and heat insulation functions.The ST-OSCs employing ABPF-2 exhibit a LUE of 4.78%,a color rendering index of 87.5 and an infrared rejection rate of 91.6%.This work offers an effective method for employing ABPFs in the creation of high-performance multifunctional ST-OSCs.展开更多
In order to filter signal effectively according to selective center frequency, a voltage-controlled dynamic band-pass filter with gain compensation was designed based on voltage-controlled gain wideband amplifier VCA8...In order to filter signal effectively according to selective center frequency, a voltage-controlled dynamic band-pass filter with gain compensation was designed based on voltage-controlled gain wideband amplifier VCA810. The transfer function of the filter was analyzed and gain compensation voltages were given through tests; besides, a system was designed, including the gain compensation circuit and the control voltage circuit, etc. Center frequency will change from 1 kHz to 20 kHz according to control voltage on condition that bandwidth of the filter remains constant. The designed system has the advantages of simple structure, low noise, stable performance and convenient adjustment.展开更多
We experimentally demonstrate an electrically triggered terahertz(THz) dual-band tunable band-pass filter based on Si_3 N_4–VO_2–Si_3 N_4 sandwich-structured hybrid metamaterials. The insulator–metal phase transiti...We experimentally demonstrate an electrically triggered terahertz(THz) dual-band tunable band-pass filter based on Si_3 N_4–VO_2–Si_3 N_4 sandwich-structured hybrid metamaterials. The insulator–metal phase transition of VO_2 film is induced by the Joule thermal effect of the top metal layer. The finite-integration-time-domain(FITD) method and finite element method(FEM) are used for numerical simulations. The sample is fabricated using a surface micromachining process,and characterized by a THz time-domain-spectrometer(TDS). When the bias current is 0.225 A, the intensity modulation depths at two central frequencies of 0.56 THz and 0.91 THz are about 81.7% and 81.3%, respectively. This novel design can achieve dynamically electric–thermo–optic modulation in the THz region, and has potential applications in the fields of THz communications, imaging, sensing, and astronomy exploration.展开更多
Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiatio...Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiation is required. In this work, a solar-blind filter is designed based on the concept of ＂transparent metal＂. The filter consisting of Al/SiO2 multilayers could exhibit a high transmission in the solar-blind wavelength region and a wide stopband extending from near-ultraviolet to infrared wavelength range. The central wavelength, bandwidth, Q factor, and rejection ratio of the passband are numerically studied as a function of individual layer thickness and multilayer period.展开更多
This paper reports the use of the fast Fourier transform (FFT) in the direct Fourier transform method (DFM) in Computerized Tomography (CT) reconstruction. Phase corrections are needed in the CT reconstruction. In ord...This paper reports the use of the fast Fourier transform (FFT) in the direct Fourier transform method (DFM) in Computerized Tomography (CT) reconstruction. Phase corrections are needed in the CT reconstruction. In order to eliminate the image distortion from the basic DFM, Padding and band-pass filters are used in the improved DFM. Finally, some reconstructions from simulated projections and several experimental results are given.展开更多
We have designed and proposed the edge modes supported by graphene ribbons and the planar band-pass filter consist- ing of graphene ribbons coupled to a graphene ring resonator by using the finite-difference time-doma...We have designed and proposed the edge modes supported by graphene ribbons and the planar band-pass filter consist- ing of graphene ribbons coupled to a graphene ring resonator by using the finite-difference time-domain numerical method. Simulation results show that the edge modes improve the electromagnetic coupling between devices. This structure works as a novel, tunable mid-infrared band-pass filter. Our studies will benefit the fabrication of planar, ultra-compact nano-scale devices in the mid-infrared region. A power splitter consisting of two output ribbons that is useful in photonic integrated devices and circuits is also designed and simulated. These devices are useful for designing ultra-compact planar devices in photonic integrated circuits.展开更多
A surface mounted device （SMD） microwave ceramic band-pass filter for mobile communication with a new coupling structure is reported in this paper. In this filter, the external and internal coupling structures are f...A surface mounted device （SMD） microwave ceramic band-pass filter for mobile communication with a new coupling structure is reported in this paper. In this filter, the external and internal coupling structures are fabricated on an alumina substrate and both resonators and coupling structures are placed into a metal house to cut off its radiation. The relationship between the coupling structures and the performance of the filter is analyzed by high frequency structure software （HFSS） and the filter with a center frequency of 836.5 MHz, bandwidth of 40.0 MHz, pass-band ripple of 0.1 dB and insertion loss of 1.5 dB has been successfully designed and fabricated. The measured results show a good agreement with the simulation results.展开更多
This paper presents a planar microstrip wideband dual mode Band-Pass Filter(BPF) from 2 GHz to 3.4 GHz with a notched band at 2.62 GHz.The dual mode band-pass filter consists of a ring resonator with two quarter-wavel...This paper presents a planar microstrip wideband dual mode Band-Pass Filter(BPF) from 2 GHz to 3.4 GHz with a notched band at 2.62 GHz.The dual mode band-pass filter consists of a ring resonator with two quarter-wavelength open-circuited stubs at =90o and =0o,respectively.A square perturbation stub has been put at the corner of the ring resonator to increase the narrow stopbands and improve the performance of selectivity.By using a parallel-coupled feed line,a narrow notched band is introduced at the required frequency and its Fractional BandWidth(FBW) is about 5%.The proposed filter has a narrow notched band and a wide pass-band with a sharp cutoff frequency characteristic,the attenuation rate for the sharp cutoff frequency responses is 297.17 dB/GHz(cal-culated from 1.959 GHz with-34.43 dB to 2.065 GHz with-2.93 dB) and 228.10 dB/GHz(calculated from 3.395 GHz with-2.873 dB to 3.507 GHz with-28.42 dB).This filter has the advantages of good insertion loss in both operating bands and two rejections of greater than 16 dB in the range of 1.59 GHz to 1.99 GHz and 3.49 GHz to 3.98 GHz.Having been presented in this article,the measurement results agree well with the simulation results,which validates our idea.展开更多
A band-pass frequency selective surface(FSS) with polarization rotation property is proposed. The proposed polarization rotating FSS(PR-FSS) is a two-dimensional periodic structure, its unit cell is an antenna-filter-...A band-pass frequency selective surface(FSS) with polarization rotation property is proposed. The proposed polarization rotating FSS(PR-FSS) is a two-dimensional periodic structure, its unit cell is an antenna-filter-antenna(AFA) module,and the polarization directions of the upper and lower antennas in each AFA module are orthogonal to each other, so the PR-FSS can achieve frequency selection and 90 degrees polarization rotation at the same time. The numerical simulation demonstrate that the anticipated frequency selection and polarization rotation are realized by the PR-FSS in the frequency band from 8.84 GHz to 10.30 GHz with a relative bandwidth of 15.26%, and the maximum insertion loss in the pass band is only 0.17 d B. Finally, one effective experiment validation is carried out, a reasonable agreement is observed between the experimental and simulated results except for a slight deviation caused by fabrication error and measurement tolerance.展开更多
This paper presents a compact Ultra-Wideband （UWB） band-pass filter using a high-pass filter and a low-pass one, and the resonator with lumped elements. The structure of our proposed bandpass filter is very simple a...This paper presents a compact Ultra-Wideband （UWB） band-pass filter using a high-pass filter and a low-pass one, and the resonator with lumped elements. The structure of our proposed bandpass filter is very simple and the Defected Ground Structure（DGS） structure is used to get the low-pass filter characteristics. This proposed band-pass filter can be much smaller than a cascaded type filter. As a result of simulation, the insertion loss is less than 0.3 dB throughout the pass-band of 2.2 GHz- 10.6 GHz, while the return loss is more than 18 dB. And it has rejection level of 36 dB at GPS band.展开更多
The theoretical and experimental analyses of widening the differential group delay (DGD) dynamic range of degree of polarization(DOP)-based polarization mode dispersion monitor using a band-pass filter are presented....The theoretical and experimental analyses of widening the differential group delay (DGD) dynamic range of degree of polarization(DOP)-based polarization mode dispersion monitor using a band-pass filter are presented. The experiment shows that the maximum DGD monitoring range is widened up to ~6ps using band-pass filter. At the same time, DOP sensitivity has a little change. The experimental results are in accordance with the numerical ones.展开更多
An Electromagnetic Band Gap (EBG) loaded square waveguide Band-Pass Filter (BPF) is proposed in this paper. It’s simply composed by symmetrically loading periodical metal diaphragms on each wall of a square waveguide...An Electromagnetic Band Gap (EBG) loaded square waveguide Band-Pass Filter (BPF) is proposed in this paper. It’s simply composed by symmetrically loading periodical metal diaphragms on each wall of a square waveguide. The influences of insert sizes and loading periods on the overall BPF performances are analyzed. Experimental results agree well with those predicted. 6 GHz pass-band with insert loss less than 1 dB, 2.5 GHz stop-band and larger than 25 dB polarization isolation can be obtained. The BPF can be applied in dual-polarized waveguide-based antenna-feed systems.展开更多
A tunable dual-narrowband pass-band filter is designed. A one-dimensional photonic crystal （1D PC） is comprised of alternate dielectric layer and vacuum layer. Two quantum wells （QWs） as defects can be constructed...A tunable dual-narrowband pass-band filter is designed. A one-dimensional photonic crystal （1D PC） is comprised of alternate dielectric layer and vacuum layer. Two quantum wells （QWs） as defects can be constructed by sandwiching two plasma slabs symmetrically in the 1D PC, and a dual-narrowband pass-band filter is formed. The conventional finite- difference time-domain （FDTD） method and piecewise linear current density recursive convolution （PLCDRC）-FDTD method are applied to the dielectric and plasma, respectively. The simulation results illustrate that the dual-narrowband frequencies can be tuned by changing the plasma frequency. The pass band interval and the half-power bandwidths （-3-dB band widths） are related to the space interval between two QWs.展开更多
Fluctuation of pump power is one of the major sources of temporal and intensity noise in femtosecond fiber lasers.In this work,the transfer functions between the relative intensity noise(RIN)of the pump laser diode(LD...Fluctuation of pump power is one of the major sources of temporal and intensity noise in femtosecond fiber lasers.In this work,the transfer functions between the relative intensity noise(RIN)of the pump laser diode(LD)and the output RIN,between the RIN of the pump LD and timing jitter of femtosecond fiber lasers are systematically studied.It is demonstrated,for the first time to our knowledge,that the amplitude of the pump RIN transfer function can be effectively decreased by an intra-cavity narrow band-pass filter.In particular,for normal-dispersion lasers,the 3-d B bandwidth of the transfer function can also be narrowed by two-thirds,with a steeper falling edge.Furthermore,with the narrow band-pass filtering,the transfer function is almost independent of the net intra-cavity dispersion due to amplifier similariton formation.The proposed scheme can effectively isolate the pump-induced noise without the need of complex active pump LD control and intra-cavity dispersion management,thus providing an easy way for practical high-power,high-stability femtosecond fiber laser design and related high-precision applications outside the laboratory.展开更多
In response to the problem of traditional methods ignoring audio modality tampering, this study aims to explore an effective deep forgery video detection technique that improves detection precision and reliability by ...In response to the problem of traditional methods ignoring audio modality tampering, this study aims to explore an effective deep forgery video detection technique that improves detection precision and reliability by fusing lip images and audio signals. The main method used is lip-audio matching detection technology based on the Siamese neural network, combined with MFCC (Mel Frequency Cepstrum Coefficient) feature extraction of band-pass filters, an improved dual-branch Siamese network structure, and a two-stream network structure design. Firstly, the video stream is preprocessed to extract lip images, and the audio stream is preprocessed to extract MFCC features. Then, these features are processed separately through the two branches of the Siamese network. Finally, the model is trained and optimized through fully connected layers and loss functions. The experimental results show that the testing accuracy of the model in this study on the LRW (Lip Reading in the Wild) dataset reaches 92.3%;the recall rate is 94.3%;the F1 score is 93.3%, significantly better than the results of CNN (Convolutional Neural Networks) and LSTM (Long Short-Term Memory) models. In the validation of multi-resolution image streams, the highest accuracy of dual-resolution image streams reaches 94%. Band-pass filters can effectively improve the signal-to-noise ratio of deep forgery video detection when processing different types of audio signals. The real-time processing performance of the model is also excellent, and it achieves an average score of up to 5 in user research. These data demonstrate that the method proposed in this study can effectively fuse visual and audio information in deep forgery video detection, accurately identify inconsistencies between video and audio, and thus verify the effectiveness of lip-audio modality fusion technology in improving detection performance.展开更多
基金the financial support provided by the National Natural Science Foundation of China(22361132545,52273200,52473199)the Science and Technology Development Program of Jilin Province(20230101131JC)+1 种基金RSCF Grant(24-4300178)Ministry of Science and Higher Education of the Russian Federation(Contract No.075-00276-25-00)。
文摘Semitransparent organic solar cells(ST-OSCs)are promising for building-integrated photovoltaics,offering power generation,transparency and heat insulation.High performance ST-OSCs need sophisticated optical management to balance the competing demands of power conversion efficiency(PCE)and average visible transmittance(AVT)for various applications.Here,a type of aperiodic band-pass filter(ABPF)made from LiF and ZnS are developed to selectively alter visible light transmission and near-infrared(NIR)reflection.This ABPF allows the active layers of ST-OSCs to re-harvest unabsorbed NIR photons,compensating for the loss of photocurrent caused by the high AVT of ST-OSCs.By carefully adjusting the thicknesses of individual layers within ABPFs,we can modulate their photonic bandgaps,enabling ST-OSCs to achieve multifunctional performance.ST-OSCs combined with the ABPF-1 demonstrate a remarkable light utilization efficiency(LUE)of 5.40%,a PCE of 14.21%and an AVT of 38.0%,which represent some of the highest values reported for ST-OSCs.Moreover,the ST-OSCs are equipped with excellent color neutrality and heat insulation functions.The ST-OSCs employing ABPF-2 exhibit a LUE of 4.78%,a color rendering index of 87.5 and an infrared rejection rate of 91.6%.This work offers an effective method for employing ABPFs in the creation of high-performance multifunctional ST-OSCs.
文摘In order to filter signal effectively according to selective center frequency, a voltage-controlled dynamic band-pass filter with gain compensation was designed based on voltage-controlled gain wideband amplifier VCA810. The transfer function of the filter was analyzed and gain compensation voltages were given through tests; besides, a system was designed, including the gain compensation circuit and the control voltage circuit, etc. Center frequency will change from 1 kHz to 20 kHz according to control voltage on condition that bandwidth of the filter remains constant. The designed system has the advantages of simple structure, low noise, stable performance and convenient adjustment.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574059,61565004,and 11774288)the National Technology Major Special Project,China(Grant No.2017ZX02101007-003)+2 种基金the Natural Science Foundation of Guangxi,China(Grant Nos.2015GXNSFDA139039 and2017GXNSFBA198116)the Foundation from Guangxi Key Laboratory of Automatic Detection Technology and Instrument,China(Grant No.YQ16101)the Innovation of Guangxi Graduate Education,China(Grant Nos.2018YJCX70,2018YJCX67,and 2018YJCX74)
文摘We experimentally demonstrate an electrically triggered terahertz(THz) dual-band tunable band-pass filter based on Si_3 N_4–VO_2–Si_3 N_4 sandwich-structured hybrid metamaterials. The insulator–metal phase transition of VO_2 film is induced by the Joule thermal effect of the top metal layer. The finite-integration-time-domain(FITD) method and finite element method(FEM) are used for numerical simulations. The sample is fabricated using a surface micromachining process,and characterized by a THz time-domain-spectrometer(TDS). When the bias current is 0.225 A, the intensity modulation depths at two central frequencies of 0.56 THz and 0.91 THz are about 81.7% and 81.3%, respectively. This novel design can achieve dynamically electric–thermo–optic modulation in the THz region, and has potential applications in the fields of THz communications, imaging, sensing, and astronomy exploration.
基金supported by the National Basic Research Program of China(Grant Nos.2010CB327504,2011CB922100,and 2011CB301900)the National NaturalScience Foundation of China(Grant Nos.60936004 and 11104130)+1 种基金the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK2011556 andBK2011050)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiation is required. In this work, a solar-blind filter is designed based on the concept of ＂transparent metal＂. The filter consisting of Al/SiO2 multilayers could exhibit a high transmission in the solar-blind wavelength region and a wide stopband extending from near-ultraviolet to infrared wavelength range. The central wavelength, bandwidth, Q factor, and rejection ratio of the passband are numerically studied as a function of individual layer thickness and multilayer period.
文摘This paper reports the use of the fast Fourier transform (FFT) in the direct Fourier transform method (DFM) in Computerized Tomography (CT) reconstruction. Phase corrections are needed in the CT reconstruction. In order to eliminate the image distortion from the basic DFM, Padding and band-pass filters are used in the improved DFM. Finally, some reconstructions from simulated projections and several experimental results are given.
文摘We have designed and proposed the edge modes supported by graphene ribbons and the planar band-pass filter consist- ing of graphene ribbons coupled to a graphene ring resonator by using the finite-difference time-domain numerical method. Simulation results show that the edge modes improve the electromagnetic coupling between devices. This structure works as a novel, tunable mid-infrared band-pass filter. Our studies will benefit the fabrication of planar, ultra-compact nano-scale devices in the mid-infrared region. A power splitter consisting of two output ribbons that is useful in photonic integrated devices and circuits is also designed and simulated. These devices are useful for designing ultra-compact planar devices in photonic integrated circuits.
基金Supported by Sino-British Excellent Youth Scholar Foundation (2005362)the Natural Science Foundation of Hubei Province (2008CDB315)
文摘A surface mounted device （SMD） microwave ceramic band-pass filter for mobile communication with a new coupling structure is reported in this paper. In this filter, the external and internal coupling structures are fabricated on an alumina substrate and both resonators and coupling structures are placed into a metal house to cut off its radiation. The relationship between the coupling structures and the performance of the filter is analyzed by high frequency structure software （HFSS） and the filter with a center frequency of 836.5 MHz, bandwidth of 40.0 MHz, pass-band ripple of 0.1 dB and insertion loss of 1.5 dB has been successfully designed and fabricated. The measured results show a good agreement with the simulation results.
基金Supported by the National Natural Science Foundation of China (No. 51007040)
文摘This paper presents a planar microstrip wideband dual mode Band-Pass Filter(BPF) from 2 GHz to 3.4 GHz with a notched band at 2.62 GHz.The dual mode band-pass filter consists of a ring resonator with two quarter-wavelength open-circuited stubs at =90o and =0o,respectively.A square perturbation stub has been put at the corner of the ring resonator to increase the narrow stopbands and improve the performance of selectivity.By using a parallel-coupled feed line,a narrow notched band is introduced at the required frequency and its Fractional BandWidth(FBW) is about 5%.The proposed filter has a narrow notched band and a wide pass-band with a sharp cutoff frequency characteristic,the attenuation rate for the sharp cutoff frequency responses is 297.17 dB/GHz(cal-culated from 1.959 GHz with-34.43 dB to 2.065 GHz with-2.93 dB) and 228.10 dB/GHz(calculated from 3.395 GHz with-2.873 dB to 3.507 GHz with-28.42 dB).This filter has the advantages of good insertion loss in both operating bands and two rejections of greater than 16 dB in the range of 1.59 GHz to 1.99 GHz and 3.49 GHz to 3.98 GHz.Having been presented in this article,the measurement results agree well with the simulation results,which validates our idea.
基金supported by the National Natural Science Foundation of China (Grant No. 62072378)Xi’an Science and Technology Plan Project, China (Grant No. GXYD20.4)。
文摘A band-pass frequency selective surface(FSS) with polarization rotation property is proposed. The proposed polarization rotating FSS(PR-FSS) is a two-dimensional periodic structure, its unit cell is an antenna-filter-antenna(AFA) module,and the polarization directions of the upper and lower antennas in each AFA module are orthogonal to each other, so the PR-FSS can achieve frequency selection and 90 degrees polarization rotation at the same time. The numerical simulation demonstrate that the anticipated frequency selection and polarization rotation are realized by the PR-FSS in the frequency band from 8.84 GHz to 10.30 GHz with a relative bandwidth of 15.26%, and the maximum insertion loss in the pass band is only 0.17 d B. Finally, one effective experiment validation is carried out, a reasonable agreement is observed between the experimental and simulated results except for a slight deviation caused by fabrication error and measurement tolerance.
基金supported by the IT R&D program of MKE/ⅡTA:Study of technologies for improvingthe RF spectrum characteristics by using the meta-electromagnetic structure[2009-F-033-01]
文摘This paper presents a compact Ultra-Wideband （UWB） band-pass filter using a high-pass filter and a low-pass one, and the resonator with lumped elements. The structure of our proposed bandpass filter is very simple and the Defected Ground Structure（DGS） structure is used to get the low-pass filter characteristics. This proposed band-pass filter can be much smaller than a cascaded type filter. As a result of simulation, the insertion loss is less than 0.3 dB throughout the pass-band of 2.2 GHz- 10.6 GHz, while the return loss is more than 18 dB. And it has rejection level of 36 dB at GPS band.
基金National Natural Science Foundation of China(60377026)
文摘The theoretical and experimental analyses of widening the differential group delay (DGD) dynamic range of degree of polarization(DOP)-based polarization mode dispersion monitor using a band-pass filter are presented. The experiment shows that the maximum DGD monitoring range is widened up to ~6ps using band-pass filter. At the same time, DOP sensitivity has a little change. The experimental results are in accordance with the numerical ones.
文摘An Electromagnetic Band Gap (EBG) loaded square waveguide Band-Pass Filter (BPF) is proposed in this paper. It’s simply composed by symmetrically loading periodical metal diaphragms on each wall of a square waveguide. The influences of insert sizes and loading periods on the overall BPF performances are analyzed. Experimental results agree well with those predicted. 6 GHz pass-band with insert loss less than 1 dB, 2.5 GHz stop-band and larger than 25 dB polarization isolation can be obtained. The BPF can be applied in dual-polarized waveguide-based antenna-feed systems.
基金supported by the Aviation Science Foundation(Key Project 20121852030)Jiangsu Provincial Natural Science Foundation,China(Grant No.BK2011727)the Open Research Program in Jiangsu Provincial Key Laboratory of Meteorological Observation and Information Processing,China(Grant No.KDXS1207)
文摘A tunable dual-narrowband pass-band filter is designed. A one-dimensional photonic crystal （1D PC） is comprised of alternate dielectric layer and vacuum layer. Two quantum wells （QWs） as defects can be constructed by sandwiching two plasma slabs symmetrically in the 1D PC, and a dual-narrowband pass-band filter is formed. The conventional finite- difference time-domain （FDTD） method and piecewise linear current density recursive convolution （PLCDRC）-FDTD method are applied to the dielectric and plasma, respectively. The simulation results illustrate that the dual-narrowband frequencies can be tuned by changing the plasma frequency. The pass band interval and the half-power bandwidths （-3-dB band widths） are related to the space interval between two QWs.
基金funded by the National Science and Technology Innovation Special Zone Program of ChinaIndependent Innovation Project of China Academy of Space Technology+1 种基金Science and Technology Innovation Research and Development Project of China Aerospace Science and Technology CorporationNational Natural Science Foundation of China (No. 61675150)
文摘Fluctuation of pump power is one of the major sources of temporal and intensity noise in femtosecond fiber lasers.In this work,the transfer functions between the relative intensity noise(RIN)of the pump laser diode(LD)and the output RIN,between the RIN of the pump LD and timing jitter of femtosecond fiber lasers are systematically studied.It is demonstrated,for the first time to our knowledge,that the amplitude of the pump RIN transfer function can be effectively decreased by an intra-cavity narrow band-pass filter.In particular,for normal-dispersion lasers,the 3-d B bandwidth of the transfer function can also be narrowed by two-thirds,with a steeper falling edge.Furthermore,with the narrow band-pass filtering,the transfer function is almost independent of the net intra-cavity dispersion due to amplifier similariton formation.The proposed scheme can effectively isolate the pump-induced noise without the need of complex active pump LD control and intra-cavity dispersion management,thus providing an easy way for practical high-power,high-stability femtosecond fiber laser design and related high-precision applications outside the laboratory.
文摘In response to the problem of traditional methods ignoring audio modality tampering, this study aims to explore an effective deep forgery video detection technique that improves detection precision and reliability by fusing lip images and audio signals. The main method used is lip-audio matching detection technology based on the Siamese neural network, combined with MFCC (Mel Frequency Cepstrum Coefficient) feature extraction of band-pass filters, an improved dual-branch Siamese network structure, and a two-stream network structure design. Firstly, the video stream is preprocessed to extract lip images, and the audio stream is preprocessed to extract MFCC features. Then, these features are processed separately through the two branches of the Siamese network. Finally, the model is trained and optimized through fully connected layers and loss functions. The experimental results show that the testing accuracy of the model in this study on the LRW (Lip Reading in the Wild) dataset reaches 92.3%;the recall rate is 94.3%;the F1 score is 93.3%, significantly better than the results of CNN (Convolutional Neural Networks) and LSTM (Long Short-Term Memory) models. In the validation of multi-resolution image streams, the highest accuracy of dual-resolution image streams reaches 94%. Band-pass filters can effectively improve the signal-to-noise ratio of deep forgery video detection when processing different types of audio signals. The real-time processing performance of the model is also excellent, and it achieves an average score of up to 5 in user research. These data demonstrate that the method proposed in this study can effectively fuse visual and audio information in deep forgery video detection, accurately identify inconsistencies between video and audio, and thus verify the effectiveness of lip-audio modality fusion technology in improving detection performance.
