Pedestrian positioning system(PPS)using wearable inertial sensors has wide applications towards various emerging fields such as smart healthcare,emergency rescue,soldier positioning,etc.The performance of traditional ...Pedestrian positioning system(PPS)using wearable inertial sensors has wide applications towards various emerging fields such as smart healthcare,emergency rescue,soldier positioning,etc.The performance of traditional PPS is limited by the cumulative error of inertial sensors,complex motion modes of pedestrians,and the low robustness of the multi-sensor collaboration structure.This paper presents a hybrid pedestrian positioning system using the combination of wearable inertial sensors and ultrasonic ranging(H-PPS).A robust two nodes integration structure is developed to adaptively combine the motion data acquired from the single waist-mounted and foot-mounted node,and enhanced by a novel ellipsoid constraint model.In addition,a deep-learning-based walking speed estimator is proposed by considering all the motion features provided by different nodes,which effectively reduces the cumulative error originating from inertial sensors.Finally,a comprehensive data and model dual-driven model is presented to effectively combine the motion data provided by different sensor nodes and walking speed estimator,and multi-level constraints are extracted to further improve the performance of the overall system.Experimental results indicate that the proposed H-PPS significantly improves the performance of the single PPS and outperforms existing algorithms in accuracy index under complex indoor scenarios.展开更多
In the internet of battlefield things, ammunition is becoming networked and intelligent, which depends on location information. Therefore, this paper focuses on the self-organized network collaborative localization of...In the internet of battlefield things, ammunition is becoming networked and intelligent, which depends on location information. Therefore, this paper focuses on the self-organized network collaborative localization of munitions with an aerial three-dimensional(3D) highly-dynamic topographic structure under a satellite denied environment. As for aerial networked munitions, the measurement of munitions is objectively incomplete due to the degenerated and interrupted link of munitions. For this reason, a cluster-oriented collaborative localization method is put forward in this paper. Multidimensional scaling(MDS) was first integrated with a trilateration localization method(TLM) to construct a relative localization algorithm for determining the relative location of a mobile cluster network. The information related to relative velocity was then combined into a collaborative localization framework to devise a TLM-vMDS algorithm. Finally, an iterative refinement algorithm based on scaling by majorizing a complicated function(SMACOF) was employed to effectively eliminate the influence of incomplete link observation on localization accuracy. Compared with the currently available advanced algorithms, the proposed TLM-vMDS algorithm achieves higher localization accuracy and faster convergence for a cluster of extensively networked munitions, and also offers better numerical stability and robustness for highspeed motion models.展开更多
Absolute distance measurement is a fundamental technique in mobile and large-scale dimensional metrology.Dual-comb ranging is emerging as a powerful tool that exploits phase resolution and frequency accuracy for high-...Absolute distance measurement is a fundamental technique in mobile and large-scale dimensional metrology.Dual-comb ranging is emerging as a powerful tool that exploits phase resolution and frequency accuracy for high-precision and fast-rate distance measurement.Using two coherent frequency combs,dual-comb ranging allows time and phase response to be measured rapidly.It breaks through the limitations related to the responsive bandwidth,ambiguity range,and dynamic measurement characteristics of conventional ranging tools.This review introduces dual-comb ranging and summarizes the key techniques for realizing this ranging tool.As optical frequency comb technology progresses,dualcomb ranging shows promise for various professional applications.展开更多
Collimating lenses are an important component of laser ranging systems,and high overload environments severely affect the beam shaping effect of such lenses.This study proposes a buffer isolation method on the basis o...Collimating lenses are an important component of laser ranging systems,and high overload environments severely affect the beam shaping effect of such lenses.This study proposes a buffer isolation method on the basis of impact stress wave attenuation theory for collimating lens spacers,ANSYS finite element software was applied to simulate the high load dynamics of collimating lenses,and the buffer isolation performance of different materials and composite structures was compared and analysed.Optical simulation analysis of the collimating lenses under different buffer conditions was performed using ZEMAX software to study the mechanism by which a high overload affects the collimating lenses.High overload and optical shaping experiments based on theoretical analysis were further conducted.Results showed the superiority of butadiene rubber to polytetrafluoroethylene after application of 70000 g impact acceleration.The combination-gasket method was superior to the single-gasket method,and the sandwich combination-gasket method was superior to the double-layer combination-gasket method.展开更多
The phase of cross-correlation function of two different normal modes contains source range information, which can be extracted by warping transform due to the dispersive characteristics of the shallow water waveguide...The phase of cross-correlation function of two different normal modes contains source range information, which can be extracted by warping transform due to the dispersive characteristics of the shallow water waveguide. The autocorrelation function of the received pressure or particle velocity contains both modal autocorrelation component(MAC) and modal cross-correlation component(MCC), with the former part usually treated as interference for source ranging. Because the real part of the vertical intensity flux(RPVIF) only contains MCC, a passive impulsive source ranging method based on the frequency warping transform of RPVIF with a single vector receiver in shallow water is presented. Using a waveguide-invariant-based frequency warping operator, the cross-correlation components of two different modes in the vertical intensity flux are warped into separable impulsive sequences, the time delays of which are subsequently used for source ranging. The advantages of source ranging based on warping the vertical intensity flux compared with warping the pressure autocorrelation function are pointed out, and the experiment results are also presented.展开更多
In this paper, a random access inter-satellite ranging(RAISR) system is designed. The ranging accuracy is optimized by an algorithm to greatly improve the ranging accuracy. This paper verifies the feasibility of the R...In this paper, a random access inter-satellite ranging(RAISR) system is designed. The ranging accuracy is optimized by an algorithm to greatly improve the ranging accuracy. This paper verifies the feasibility of the RAISR system through a series of theoretical analysis, numerical simulation, hardware system design and testing. The research work brings the solution to the design and accuracy optimization problem of the RAISR system,which eliminates the main error caused by the satellite dynamic characteristics and frequency source drift of the RAISR system.The accuracy of the measurement system has been significantly improved.展开更多
As an important station of International Laser Ranging Service(ILRS),Shanghai Astronomical Observatory(SHAO)has upgraded Satellite Laser Ranging(SLR)system with high repetition rate and achieved some technological pro...As an important station of International Laser Ranging Service(ILRS),Shanghai Astronomical Observatory(SHAO)has upgraded Satellite Laser Ranging(SLR)system with high repetition rate and achieved some technological progress,There are a lot of improvements for overall system performance,such as annual observation passes,measurement precision and quality of observation data.SLR technology with repetition rate of 10 kHz is accomplished firstly in China,and space debris laser ranging technology with200 Hz laser is promoted and proved to be more detective for weak echo,which lead to successful measurement for 40,000 km satellites and space debris within 3000 km.At the same time,SLR based on multi-telescopes and 1064 nm wavelength are planned to make a breakthrough of detection capabilities,and also to expand its application fields.These progresses will be introduced in this paper in detail.展开更多
As the complexity of space exploration missions augments,how to enhance the overall performance of communication,ranging or other functions has become a challengeable problem.Considering the integration of communicati...As the complexity of space exploration missions augments,how to enhance the overall performance of communication,ranging or other functions has become a challengeable problem.Considering the integration of communication and ranging,we present a bit-level composite signal for simultaneous ranging and communication.In this composite method,through a specially designed mapping scheme using low-weight codewords,the information sequence is converted to a sparse sequence which is then superimposed on the ranging code.For ranging,the correlation characteristics of the ranging code component can be maintained to calculate the transmitter-receiver distance.For communications,the sparse sequence can be extracted without interference by eliminating the ranging code component.Simulation results show that the proposed composite signal can support communication and ranging simultaneously with limited sacrifice of ranging performance,and the performance loss of ranging can be controlled and minimized by lowering the density of information sequences using different sparsification encoding methods.展开更多
Marine resource exploitation and marine cargo transportation were increasingly frequent. Due to the impact of the marine environment, ships or platforms were affected. In this paper, a servo electric cylinder was used...Marine resource exploitation and marine cargo transportation were increasingly frequent. Due to the impact of the marine environment, ships or platforms were affected. In this paper, a servo electric cylinder was used as a wave compensation actuator to design a wave compensation system. The laser sensor was used to measure the displacement in the direction of the heave platform, and the obtained displacement was applied to the wave compensation in the heave direction to verify the feasibility of the compensation system.展开更多
The influence of the single photon laser altimeter range-gate width on the detection probability and ranging accuracy is discussed and analyzed,according to the LiDAR equation,single photon detection equation and the ...The influence of the single photon laser altimeter range-gate width on the detection probability and ranging accuracy is discussed and analyzed,according to the LiDAR equation,single photon detection equation and the Monte Carlo method to simulate the experiment.The simulated results show that the probability of detection is not affected by the range gate,while the probability of false alarm is relative to the gate width.When the gate width is 100 ns,the ranging accuracy can accord with the requirements of satellite laser altimeter.But when the range gate width exceeds 400 ns,ranging accuracy will decline sharply.The noise ratio will be more as long as the range gate to get larger,so the refined filtering algorithm during the data processing is important to extract the useful photons effectively.In order to ensure repeated observation of the same point for 25 times,we deduce the quantitative relation between the footprint size,footprint,and frequency repetition according to the parameters of ICESat-2.The related conclusions can provide some references for the design and the development of the domestic single photon laser altimetry satellite.展开更多
The sea-trial results indicate that the stable interference structure can be observed in low-frequency continuous spectra sound field.And the equation of the interference striation have been derived in light of the co...The sea-trial results indicate that the stable interference structure can be observed in low-frequency continuous spectra sound field.And the equation of the interference striation have been derived in light of the comcept of waveguide invariant, indicating that the striations are a family of quasi hyperbolas. The heading angle φ, waveguide invariant β and r0/v(r0 is the range of the closest point of approach and v is the navigating velocity of target) are estimated by using Hough transform for the image processing of the LOFARgram and bearing-time records. Four passive ranging algorithms based on double element or double array model are proposed. The simulation research shows that the first positioning algorithm should be adopted when the target heading angle is less than 10°; otherwise, the latter three algorithms are used to range, and the larger the heading angle is, the higher the positioning accuracy is. The relative ranging errors of the four methods are less than 10% under the simulation conditions used in this paper.展开更多
Waveguide invariant is widely used in underwater target passive ranging. In shallow water with uniform sound speed profile, the value of waveguide invariant is approximately a constant,while in shallow water with ther...Waveguide invariant is widely used in underwater target passive ranging. In shallow water with uniform sound speed profile, the value of waveguide invariant is approximately a constant,while in shallow water with thermocline, it varies in a wide range.The waveguide invariant distributions and striations in these two conditions are analyzed respectively. On the basis of wavenumber difference between reflected modes and refracted modes, a wavenumber-frequency domain filtering technique is proposed to separate the two groups of modes. The required relationship between array element space, total array length and target azimuth for effective application is discussed. Finally, the simulation results indicate that in shallow water with a thermocline, refracted modes can be effectively filtered out using the wavenumber-frequency domain filtering technique and the target's range is estimated accurately.展开更多
A new method of air ground ranging of airborne radar based on wavelet transform was proposed. The wavelet domain noise excision was applied as a post processing tool to reduce the white Gaussian noise appearing in the...A new method of air ground ranging of airborne radar based on wavelet transform was proposed. The wavelet domain noise excision was applied as a post processing tool to reduce the white Gaussian noise appearing in the radar echo. The wavelet approach overcomes the drawbacks of the traditional ranging method, thus considerably improving the accuracy and speed of air ground ranging. The whole algorithm was performed in frequency domain. It can take full advantage of the radar’s former hardware resource, such as FFT high speed processor. The simulation results demonstrate the validity of our new approach.展开更多
We utilize three parallel reservoir computers using semiconductor lasers with optical feedback and light injection to model radar probe signals with delays.Three radar probe signals are generated by driving lasers con...We utilize three parallel reservoir computers using semiconductor lasers with optical feedback and light injection to model radar probe signals with delays.Three radar probe signals are generated by driving lasers constructed by a threeelement laser array with self-feedback.The response lasers are implemented also by a three-element lase array with both delay-time feedback and optical injection,which are utilized as nonlinear nodes to realize the reservoirs.We show that each delayed radar probe signal can be predicted well and to synchronize with its corresponding trained reservoir,even when parameter mismatches exist between the response laser array and the driving laser array.Based on this,the three synchronous probe signals are utilized for ranging to three targets,respectively,using Hilbert transform.It is demonstrated that the relative errors for ranging can be very small and less than 0.6%.Our findings show that optical reservoir computing provides an effective way for applications of target ranging.展开更多
The range-velocity ambiguity caused by moving target influences on the ranging accuracy of a short-range millimeter wave radar greatly.A new method was presented in this paper to reduce the range-velocity ambiguity an...The range-velocity ambiguity caused by moving target influences on the ranging accuracy of a short-range millimeter wave radar greatly.A new method was presented in this paper to reduce the range-velocity ambiguity and improve the ranging accuracy by estimating parameters of the echo signal with fractional Fourier transform and self-correlation.And,a new quick searching algorithm was given also to increase the calculation speed.Compared to the Chinese remainder theorem method,the proposed method is excellent for its simplicity and reducing the computation complexity.The simulation results show its validity.展开更多
Satellite laser ranging(SLR)with higher repetition rate is the recent trend for its various advantages.Laser backscatter(coincidence between recently transmitted pulses and received pulses near the detector)is found t...Satellite laser ranging(SLR)with higher repetition rate is the recent trend for its various advantages.Laser backscatter(coincidence between recently transmitted pulses and received pulses near the detector)is found to be a constraint for the repetition rates higher than 20 kHz,due to,overlapping with photons returning from a satellite with the present constellation of most of the SLR systems.Such an overlap occurs at every 75 km satellite distance change at 2 kHz repetition rate,and remains for about 7.5 km;for a 20 kHz system however,it will occur after every 7.5 km and remains for 7.5 km,resulting in constant backscatter overlap e leaving no chance to avoid it.The resulting noise is 5 times more than before causing a serious problem in detection and lowers the signal to noise ratio of the overall SLR system.However,decreasing energy per shot at higher repetition rates e assuming a constant power laser e the resulting backscatter may decrease fractionally.展开更多
BACKGROUND Liver transplantation has evolved into a safe life-saving operation and remains the golden standard in the treatment of end stage liver disease.The main limiting factor in the application of liver transplan...BACKGROUND Liver transplantation has evolved into a safe life-saving operation and remains the golden standard in the treatment of end stage liver disease.The main limiting factor in the application of liver transplantation is graft shortage.Many strategies have been developed in order to alleviate graft shortage,such as living donor partial liver transplantation and split liver transplantation for adult and pediatric patients.In these strategies,liver volume assessment is of paramount importance,as size mismatch can have severe consequences in the success of liver transplantation.AIM To evaluate the safety,feasibility,and accuracy of light detection and ranging(LIDAR)3D photography in the prediction of whole liver graft volume and mass.METHODS Seven liver grafts procured for orthotopic liver transplantation from brain deceased donors were prospectively measured with an LIDAR handheld camera and their mass was calculated and compared to their actual weight.RESULTS The mean error of all measurements was 17.03 g(range 3.56-59.33 g).Statistical analysis of the data yielded a Pearson correlation coefficient index of 0.9968,indicating a strong correlation between the values and a Student’s t-test P value of 0.26.Mean accuracy of the measurements was calculated at 97.88%.CONCLUSION Our preliminary data indicate that LIDAR scanning of liver grafts is a safe,cost-effective,and feasible method of ex vivo determination of whole liver volume and mass.More data are needed to determine the precision and accuracy of this method.展开更多
基金supported by the National Natural Science Foundation of China under(Grant No.52175531)in part by the Science and Technology Research Program of Chongqing Municipal Education Commission under Grant(Grant Nos.KJQN202000605 and KJZD-M202000602)。
文摘Pedestrian positioning system(PPS)using wearable inertial sensors has wide applications towards various emerging fields such as smart healthcare,emergency rescue,soldier positioning,etc.The performance of traditional PPS is limited by the cumulative error of inertial sensors,complex motion modes of pedestrians,and the low robustness of the multi-sensor collaboration structure.This paper presents a hybrid pedestrian positioning system using the combination of wearable inertial sensors and ultrasonic ranging(H-PPS).A robust two nodes integration structure is developed to adaptively combine the motion data acquired from the single waist-mounted and foot-mounted node,and enhanced by a novel ellipsoid constraint model.In addition,a deep-learning-based walking speed estimator is proposed by considering all the motion features provided by different nodes,which effectively reduces the cumulative error originating from inertial sensors.Finally,a comprehensive data and model dual-driven model is presented to effectively combine the motion data provided by different sensor nodes and walking speed estimator,and multi-level constraints are extracted to further improve the performance of the overall system.Experimental results indicate that the proposed H-PPS significantly improves the performance of the single PPS and outperforms existing algorithms in accuracy index under complex indoor scenarios.
文摘In the internet of battlefield things, ammunition is becoming networked and intelligent, which depends on location information. Therefore, this paper focuses on the self-organized network collaborative localization of munitions with an aerial three-dimensional(3D) highly-dynamic topographic structure under a satellite denied environment. As for aerial networked munitions, the measurement of munitions is objectively incomplete due to the degenerated and interrupted link of munitions. For this reason, a cluster-oriented collaborative localization method is put forward in this paper. Multidimensional scaling(MDS) was first integrated with a trilateration localization method(TLM) to construct a relative localization algorithm for determining the relative location of a mobile cluster network. The information related to relative velocity was then combined into a collaborative localization framework to devise a TLM-vMDS algorithm. Finally, an iterative refinement algorithm based on scaling by majorizing a complicated function(SMACOF) was employed to effectively eliminate the influence of incomplete link observation on localization accuracy. Compared with the currently available advanced algorithms, the proposed TLM-vMDS algorithm achieves higher localization accuracy and faster convergence for a cluster of extensively networked munitions, and also offers better numerical stability and robustness for highspeed motion models.
基金the National Natural Science Foundation of China(61575105,61611140125)Beijing Natural Science Foundation(3182011)Shenzhen Fundamental Research Funding(JCYJ20170412171535171).
文摘Absolute distance measurement is a fundamental technique in mobile and large-scale dimensional metrology.Dual-comb ranging is emerging as a powerful tool that exploits phase resolution and frequency accuracy for high-precision and fast-rate distance measurement.Using two coherent frequency combs,dual-comb ranging allows time and phase response to be measured rapidly.It breaks through the limitations related to the responsive bandwidth,ambiguity range,and dynamic measurement characteristics of conventional ranging tools.This review introduces dual-comb ranging and summarizes the key techniques for realizing this ranging tool.As optical frequency comb technology progresses,dualcomb ranging shows promise for various professional applications.
基金National Natural Science Foundation of China(51605227)the Fundamental Research Funds for the Central Universities(NUST30915011303)。
文摘Collimating lenses are an important component of laser ranging systems,and high overload environments severely affect the beam shaping effect of such lenses.This study proposes a buffer isolation method on the basis of impact stress wave attenuation theory for collimating lens spacers,ANSYS finite element software was applied to simulate the high load dynamics of collimating lenses,and the buffer isolation performance of different materials and composite structures was compared and analysed.Optical simulation analysis of the collimating lenses under different buffer conditions was performed using ZEMAX software to study the mechanism by which a high overload affects the collimating lenses.High overload and optical shaping experiments based on theoretical analysis were further conducted.Results showed the superiority of butadiene rubber to polytetrafluoroethylene after application of 70000 g impact acceleration.The combination-gasket method was superior to the single-gasket method,and the sandwich combination-gasket method was superior to the double-layer combination-gasket method.
基金Project supported by the Frontier Science Research of Chinese Academy of Sciences(Grant No.QYZDY-SSW-SLH005)
文摘The phase of cross-correlation function of two different normal modes contains source range information, which can be extracted by warping transform due to the dispersive characteristics of the shallow water waveguide. The autocorrelation function of the received pressure or particle velocity contains both modal autocorrelation component(MAC) and modal cross-correlation component(MCC), with the former part usually treated as interference for source ranging. Because the real part of the vertical intensity flux(RPVIF) only contains MCC, a passive impulsive source ranging method based on the frequency warping transform of RPVIF with a single vector receiver in shallow water is presented. Using a waveguide-invariant-based frequency warping operator, the cross-correlation components of two different modes in the vertical intensity flux are warped into separable impulsive sequences, the time delays of which are subsequently used for source ranging. The advantages of source ranging based on warping the vertical intensity flux compared with warping the pressure autocorrelation function are pointed out, and the experiment results are also presented.
基金supported by the National Natural Science Foundation of China (61525403)。
文摘In this paper, a random access inter-satellite ranging(RAISR) system is designed. The ranging accuracy is optimized by an algorithm to greatly improve the ranging accuracy. This paper verifies the feasibility of the RAISR system through a series of theoretical analysis, numerical simulation, hardware system design and testing. The research work brings the solution to the design and accuracy optimization problem of the RAISR system,which eliminates the main error caused by the satellite dynamic characteristics and frequency source drift of the RAISR system.The accuracy of the measurement system has been significantly improved.
基金The National Natural Science Foundation (NSF) of China (U1631240 and 11503068)CAS Key Technology Talent Program
文摘As an important station of International Laser Ranging Service(ILRS),Shanghai Astronomical Observatory(SHAO)has upgraded Satellite Laser Ranging(SLR)system with high repetition rate and achieved some technological progress,There are a lot of improvements for overall system performance,such as annual observation passes,measurement precision and quality of observation data.SLR technology with repetition rate of 10 kHz is accomplished firstly in China,and space debris laser ranging technology with200 Hz laser is promoted and proved to be more detective for weak echo,which lead to successful measurement for 40,000 km satellites and space debris within 3000 km.At the same time,SLR based on multi-telescopes and 1064 nm wavelength are planned to make a breakthrough of detection capabilities,and also to expand its application fields.These progresses will be introduced in this paper in detail.
基金This work was supported in part by National Natural Science Foundation of China(61671324)the Director’s Funding from Pilot National Laboratory for Marine Science and Technology(Qingdao)(QNLM201712)Zhan Xu was supported in part by National Natural Science Foundation of China(61620106001).
文摘As the complexity of space exploration missions augments,how to enhance the overall performance of communication,ranging or other functions has become a challengeable problem.Considering the integration of communication and ranging,we present a bit-level composite signal for simultaneous ranging and communication.In this composite method,through a specially designed mapping scheme using low-weight codewords,the information sequence is converted to a sparse sequence which is then superimposed on the ranging code.For ranging,the correlation characteristics of the ranging code component can be maintained to calculate the transmitter-receiver distance.For communications,the sparse sequence can be extracted without interference by eliminating the ranging code component.Simulation results show that the proposed composite signal can support communication and ranging simultaneously with limited sacrifice of ranging performance,and the performance loss of ranging can be controlled and minimized by lowering the density of information sequences using different sparsification encoding methods.
文摘Marine resource exploitation and marine cargo transportation were increasingly frequent. Due to the impact of the marine environment, ships or platforms were affected. In this paper, a servo electric cylinder was used as a wave compensation actuator to design a wave compensation system. The laser sensor was used to measure the displacement in the direction of the heave platform, and the obtained displacement was applied to the wave compensation in the heave direction to verify the feasibility of the compensation system.
基金National Natural Science Foundation of China(No.41871382)Open Foundation of the Key Laboratory of Space Active Opto-electronics Technologyand Chinese Academy of Sciences(No.2018-ZDKF-1)。
文摘The influence of the single photon laser altimeter range-gate width on the detection probability and ranging accuracy is discussed and analyzed,according to the LiDAR equation,single photon detection equation and the Monte Carlo method to simulate the experiment.The simulated results show that the probability of detection is not affected by the range gate,while the probability of false alarm is relative to the gate width.When the gate width is 100 ns,the ranging accuracy can accord with the requirements of satellite laser altimeter.But when the range gate width exceeds 400 ns,ranging accuracy will decline sharply.The noise ratio will be more as long as the range gate to get larger,so the refined filtering algorithm during the data processing is important to extract the useful photons effectively.In order to ensure repeated observation of the same point for 25 times,we deduce the quantitative relation between the footprint size,footprint,and frequency repetition according to the parameters of ICESat-2.The related conclusions can provide some references for the design and the development of the domestic single photon laser altimetry satellite.
基金Sponsored by the Science and Technology Foundation of State Key Laboratory of Underwater Acoustic Technology(9140C2001010801,9140C2002100802)the Foundation for Basic Research of Harbin Engineering University(HEUFT07072)
文摘The sea-trial results indicate that the stable interference structure can be observed in low-frequency continuous spectra sound field.And the equation of the interference striation have been derived in light of the comcept of waveguide invariant, indicating that the striations are a family of quasi hyperbolas. The heading angle φ, waveguide invariant β and r0/v(r0 is the range of the closest point of approach and v is the navigating velocity of target) are estimated by using Hough transform for the image processing of the LOFARgram and bearing-time records. Four passive ranging algorithms based on double element or double array model are proposed. The simulation research shows that the first positioning algorithm should be adopted when the target heading angle is less than 10°; otherwise, the latter three algorithms are used to range, and the larger the heading angle is, the higher the positioning accuracy is. The relative ranging errors of the four methods are less than 10% under the simulation conditions used in this paper.
基金supported by the National Natural Science Foundation of China(1137407261371171)
文摘Waveguide invariant is widely used in underwater target passive ranging. In shallow water with uniform sound speed profile, the value of waveguide invariant is approximately a constant,while in shallow water with thermocline, it varies in a wide range.The waveguide invariant distributions and striations in these two conditions are analyzed respectively. On the basis of wavenumber difference between reflected modes and refracted modes, a wavenumber-frequency domain filtering technique is proposed to separate the two groups of modes. The required relationship between array element space, total array length and target azimuth for effective application is discussed. Finally, the simulation results indicate that in shallow water with a thermocline, refracted modes can be effectively filtered out using the wavenumber-frequency domain filtering technique and the target's range is estimated accurately.
文摘A new method of air ground ranging of airborne radar based on wavelet transform was proposed. The wavelet domain noise excision was applied as a post processing tool to reduce the white Gaussian noise appearing in the radar echo. The wavelet approach overcomes the drawbacks of the traditional ranging method, thus considerably improving the accuracy and speed of air ground ranging. The whole algorithm was performed in frequency domain. It can take full advantage of the radar’s former hardware resource, such as FFT high speed processor. The simulation results demonstrate the validity of our new approach.
基金the National Natural Science Foundation of China(Grant No.62075168)Guang Dong Basic and Applied Basic Research Foundation(Grant No.2020A1515011088)Special Project in Key Fields of Guangdong Provincial Department of Education of China(Grant No.2020ZDZX3052 and 2019KZDZX1025)。
文摘We utilize three parallel reservoir computers using semiconductor lasers with optical feedback and light injection to model radar probe signals with delays.Three radar probe signals are generated by driving lasers constructed by a threeelement laser array with self-feedback.The response lasers are implemented also by a three-element lase array with both delay-time feedback and optical injection,which are utilized as nonlinear nodes to realize the reservoirs.We show that each delayed radar probe signal can be predicted well and to synchronize with its corresponding trained reservoir,even when parameter mismatches exist between the response laser array and the driving laser array.Based on this,the three synchronous probe signals are utilized for ranging to three targets,respectively,using Hilbert transform.It is demonstrated that the relative errors for ranging can be very small and less than 0.6%.Our findings show that optical reservoir computing provides an effective way for applications of target ranging.
基金Sponsored by the NUST Research Fundation(2010ZYTS030)the Specialized Research Fundation for the Doctoral Program of Higher Education(20093219120018)
文摘The range-velocity ambiguity caused by moving target influences on the ranging accuracy of a short-range millimeter wave radar greatly.A new method was presented in this paper to reduce the range-velocity ambiguity and improve the ranging accuracy by estimating parameters of the echo signal with fractional Fourier transform and self-correlation.And,a new quick searching algorithm was given also to increase the calculation speed.Compared to the Chinese remainder theorem method,the proposed method is excellent for its simplicity and reducing the computation complexity.The simulation results show its validity.
基金the Austrian Academy of Science for providing a placement and Higher education commission of Pakistan to fund this study
文摘Satellite laser ranging(SLR)with higher repetition rate is the recent trend for its various advantages.Laser backscatter(coincidence between recently transmitted pulses and received pulses near the detector)is found to be a constraint for the repetition rates higher than 20 kHz,due to,overlapping with photons returning from a satellite with the present constellation of most of the SLR systems.Such an overlap occurs at every 75 km satellite distance change at 2 kHz repetition rate,and remains for about 7.5 km;for a 20 kHz system however,it will occur after every 7.5 km and remains for 7.5 km,resulting in constant backscatter overlap e leaving no chance to avoid it.The resulting noise is 5 times more than before causing a serious problem in detection and lowers the signal to noise ratio of the overall SLR system.However,decreasing energy per shot at higher repetition rates e assuming a constant power laser e the resulting backscatter may decrease fractionally.
基金the European Union and Greek national funds through the Operational Program Competitiveness,Entrepreneurship and Innovation,No.T1EDK-03599.
文摘BACKGROUND Liver transplantation has evolved into a safe life-saving operation and remains the golden standard in the treatment of end stage liver disease.The main limiting factor in the application of liver transplantation is graft shortage.Many strategies have been developed in order to alleviate graft shortage,such as living donor partial liver transplantation and split liver transplantation for adult and pediatric patients.In these strategies,liver volume assessment is of paramount importance,as size mismatch can have severe consequences in the success of liver transplantation.AIM To evaluate the safety,feasibility,and accuracy of light detection and ranging(LIDAR)3D photography in the prediction of whole liver graft volume and mass.METHODS Seven liver grafts procured for orthotopic liver transplantation from brain deceased donors were prospectively measured with an LIDAR handheld camera and their mass was calculated and compared to their actual weight.RESULTS The mean error of all measurements was 17.03 g(range 3.56-59.33 g).Statistical analysis of the data yielded a Pearson correlation coefficient index of 0.9968,indicating a strong correlation between the values and a Student’s t-test P value of 0.26.Mean accuracy of the measurements was calculated at 97.88%.CONCLUSION Our preliminary data indicate that LIDAR scanning of liver grafts is a safe,cost-effective,and feasible method of ex vivo determination of whole liver volume and mass.More data are needed to determine the precision and accuracy of this method.
