Relative clauses(RCs)processing has been a hot issue in decades.Studies from head-initial languages have found that SRCs were easier to comprehend than ORCs,and many different models were constructed to account for SR...Relative clauses(RCs)processing has been a hot issue in decades.Studies from head-initial languages have found that SRCs were easier to comprehend than ORCs,and many different models were constructed to account for SRCs preference.Chinese are head-final languages and the head noun phrases are behind the internal-clause.Such a great difference in syntactic structure made Chinese to be the optimum material to test the models mentioned above.In the paper,two experiments were carried out using eye-movement tracking methods to explore the difficulty with RCs processing in mandarin,and results showed that:when the two noun phrases were both from animate category,SRCs were more difficult than ORCs,but when the noun phrases in the internal-relative-clause were inanimate and the noun phrases in the matrix were animate,the difficulties with SRCs were greatly reduced.Based on these findings,we hold that the linear syntactic distance between the gap and the filler was not the key reason to the difficulty with SRCs.On the contrary,the ambiguity in argument construction may be the most important.展开更多
In October, 1998, Ted Hughes, the great English poet and writer died of cancer at the age of 68. From 1957 to 1998, Hughes published numerous books of poetry and received various awards including the prestigious Whitb...In October, 1998, Ted Hughes, the great English poet and writer died of cancer at the age of 68. From 1957 to 1998, Hughes published numerous books of poetry and received various awards including the prestigious Whitbread Poetry Award. He was appointed Poet Laureate in 1984 and given Merit of Order shortly before his death. He was generally regarded, with Philip Larkin, as one of the two most important English poets since the Second展开更多
The solution of the current wind retrieval algorithm for scatterometers has several wind vector ambi-guities, due to the bi-harmonic relationship between normalized backscattering cross section and the relative wind d...The solution of the current wind retrieval algorithm for scatterometers has several wind vector ambi-guities, due to the bi-harmonic relationship between normalized backscattering cross section and the relative wind direction and the existence of the measurement error. In order to remove the ambiguities for a unique wind field, a circular median filter approach (CMF) is usually adopted. But under the con-dition for clustering distribution of the false ambiguities in some local areas, the CMF fails and thus engenders block ambiguities, which degrade the precision of the retrieved wind field. For such a situation, a technique of identification and removal of the block ambiguities is presented to further optimize the retrieved wind field after CMF. It is demonstrated in experiment that this technique can identify and remove most of the block ambiguities.展开更多
Shakespeare's Julius Caesar is remarkable for its rational mode as manifested in the use of language, style, action as well as its characterization. In this essay, I argue that the play is also striking with its n...Shakespeare's Julius Caesar is remarkable for its rational mode as manifested in the use of language, style, action as well as its characterization. In this essay, I argue that the play is also striking with its numerous(ir)rational ambiguities. The same Latin word, ratio, is at the root of two words that are often used to explain human behaviors: reason and rationality. The fi rst related ambiguity is organized around the confl ict between reason and passion. The other is related to rational choice, which is opposed to the diverse forms of irrationality. This paper argues that Julius Caesar challenges the idea that a rational actor is one who acts only for sufficient reasons, and the play also subverts the conventional understanding of reason and rationality.展开更多
The optical potential ambiguity is a long-standing problem in the analysis of elastic scattering data.For a specific collid-ing system,ambiguous potential families can lead to different behaviors in the nearside and f...The optical potential ambiguity is a long-standing problem in the analysis of elastic scattering data.For a specific collid-ing system,ambiguous potential families can lead to different behaviors in the nearside and farside scattering components.By contrast,the envelope method can decompose the experimental data into two components with negative and positive deflection angles,respectively.Hence,a question arises as to whether the comparison between the calculated nearside(or farside)component and the derived positive-deflection-angle(or negative-deflection-angle)component can help analyze the potential ambiguity problem.In this study,we conducted a trial application of the envelope method to the potential ambiguity problem.The envelope method was improved by including uncertainties in the experimental data.The colliding systems of 16O+28Si at 215.2 MeV and 12C+12C at 1016 MeV were considered in the analyses.For each colliding system,the angular distribution experimental data were described nearly equally well by two potential sets,one of which is“surface transpar-ent”and the other is refractive.The calculated angular distributions were decomposed into nearside and farside scattering components.Using the improved envelope method,the experimental data were decomposed into the positive-deflection-angle and negative-deflection-angle components,which were then compared with the calculated nearside and farside components.The capability of the envelope method to analyze the potential ambiguities was also discussed.展开更多
In this paper,we formulate the precoding problem of integrated sensing and communication(ISAC)waveform as a non-convex quadratically constrained quadratic programming(QCQP),in which the weighted sum of communication m...In this paper,we formulate the precoding problem of integrated sensing and communication(ISAC)waveform as a non-convex quadratically constrained quadratic programming(QCQP),in which the weighted sum of communication multi-user interference(MUI)and the gap between dual-use waveform and ideal radar waveform is minimized with peak-toaverage power ratio(PAPR)constraints.We propose an efficient algorithm based on alternating direction method of multipliers(ADMM),which is able to decouple multiple variables and provide a closed-form solution for each subproblem.In addition,to improve the sensing performance in both spatial and temporal domains,we propose a new criteria to design the ideal radar waveform,in which the beam pattern is made similar to the ideal one and the integrated sidelobe level of the ambiguity function in each target direction is minimized in the region of interest.The limited memory Broyden-Fletcher-Goldfarb-Shanno(LBFGS)algorithm is applied to the design of the ideal radar waveform which works as a reference in the design of the dual-function waveform.Numerical results indicate that the designed dual-function waveform is capable of offering good communication quality of service(QoS)and sensing performance.展开更多
In this paper,an antenna array composed of circular array and orthogonal linear array is proposed by using the design of long and short baseline“orthogonal linear array”and the circular array ambiguity resolution de...In this paper,an antenna array composed of circular array and orthogonal linear array is proposed by using the design of long and short baseline“orthogonal linear array”and the circular array ambiguity resolution design of multi-group baseline clustering.The effectiveness of the antenna array in this paper is verified by sufficient simulation and experiment.After the system deviation correction work,it is found that in the L/S/C/X frequency bands,the ambiguity resolution probability is high,and the phase difference system error between each channel is basically the same.The angle measurement error is less than 0.5°,and the positioning error is less than 2.5 km.Notably,as the center frequency increases,calibration consistency improves,and the calibration frequency points become applicable over a wider frequency range.At a center frequency of 11.5 GHz,the calibration frequency point bandwidth extends to 1200 MHz.This combined antenna array deployment holds significant promise for a wide range of applications in contemporary wireless communication systems.展开更多
BACKGROUND Asplenia-type heterotaxy syndrome(HS)is rare and refers to visceral malposition and dysmorphism.It is associated with a high infant mortality rate due to cardiac anomalies,and related digestive endoscopic i...BACKGROUND Asplenia-type heterotaxy syndrome(HS)is rare and refers to visceral malposition and dysmorphism.It is associated with a high infant mortality rate due to cardiac anomalies,and related digestive endoscopic interventions are poorly understood.With the improved long-term prognosis of these individuals after modern cardiac surgery,intra-abdominal anomalies have become increasingly significant.CASE SUMMARY Herein,we report successful endoscopic retrograde cholangiopancreatography(ERCP)in a 14-year-old male with asplenia-type HS that involved unique imaging findings and technical difficulties.His anatomic anomalies included complex congenital heart disease,midline liver placement,an absent spleen,a left-sided inferior vena cava,and dextroposition of the stomach and pancreas.He suffered from choledocholithiasis with obstructive jaundice,and the stone was successfully extracted with a basket following endoscopic papillary balloon dilation.CONCLUSION Although anatomic anomalies in HS increase the degree of technical difficulty when performing ERCP,they can be safely managed by experienced endosco-pists,as illustrated by the present case.Identifying these variations with imaging modalities and being aware of them before initiating an invasive intervention are crucial to preventing potential complications.展开更多
Integrated sensing and communication(ISAC)is one of the main usage scenarios for 6G wireless networks.To most efficiently utilize the limited wireless resources,integrated super-resolution sensing and communication(IS...Integrated sensing and communication(ISAC)is one of the main usage scenarios for 6G wireless networks.To most efficiently utilize the limited wireless resources,integrated super-resolution sensing and communication(ISSAC)has been recently proposed to significantly improve sensing performance with super-resolution algorithms for ISAC systems,such as the Multiple Signal Classification(MUSIC)algorithm.However,traditional super-resolution sensing algorithms suffer from prohibitive computational complexity of orthogonal-frequency division multiplexing(OFDM)systems due to the large dimensions of the signals in the subcarrier and symbol domains.To address such issues,we propose a novel two-stage approach to reduce the computational complexity for super-resolution range estimation significantly.The key idea of the proposed scheme is to first uniformly decimate signals in the subcarrier domain so that the computational complexity is significantly reduced without missing any target in the range domain.However,the decimation operation may result in range ambiguity due to pseudo peaks,which is addressed by the second stage where the total collocated subcarrier data are used to verify the detected peaks.Compared with traditional MUSIC algorithms,the proposed scheme reduces computational complexity by two orders of magnitude,while maintaining the range resolution and unambiguity.Simulation results verify the effectiveness of the proposed scheme.展开更多
The translation of English language and literary works has always been crucial for cross-cultural communication.However,a key challenge in translating such works is the accurate communication of ambiguity,which refers...The translation of English language and literary works has always been crucial for cross-cultural communication.However,a key challenge in translating such works is the accurate communication of ambiguity,which refers to expressions deliberately used in English texts with unclear meanings.These expressions are often poetic and carry deep symbols and implications,adding a unique charm to literary works.This article explores the manifestations of ambiguity in English language and literature and the translation strategies that can be employed to optimize the translation of ambiguity in the English language and literature.展开更多
In this paper, we discuss the optimal insurance in the presence of background risk while the insured is ambiguity averse and there exists belief heterogeneity between the insured and the insurer. We give the optimal i...In this paper, we discuss the optimal insurance in the presence of background risk while the insured is ambiguity averse and there exists belief heterogeneity between the insured and the insurer. We give the optimal insurance contract when maxing the insured’s expected utility of his/her remaining wealth under the smooth ambiguity model and the heterogeneous belief form satisfying the MHR condition. We calculate the insurance premium by using generalized Wang’s premium and also introduce a series of stochastic orders proposed by [1] to describe the relationships among the insurable risk, background risk and ambiguity parameter. We obtain the deductible insurance is the optimal insurance while they meet specific dependence structures.展开更多
A method for integer ambiguity resolution in the global positioning system (GPS) multi-reference station network real time kinematic (RTK) is proposed. First, the barycenter of the triangle of reference stations f...A method for integer ambiguity resolution in the global positioning system (GPS) multi-reference station network real time kinematic (RTK) is proposed. First, the barycenter of the triangle of reference stations for ambiguity resolution is taken as a reference point. The satellite which has the largest elevation angle with the reference point is selected as a reference satellite. The parameters for constructing the weight matrix of carrier phase observation and the criteria for checking the correctness of integer ambiguity resolution of a network are obtained. Then, the wide ambiguity is calculated by a linear combination method of dualband observation. And the LI ambiguity is obtained by a nonionosphere combination method. The Kalman filter is introduced to refine the floating-point solution of ambiguity and estimate the real-time tropospheric delay. Finally, the cofactor matrix of ambiguity is de-correlated by Z-transformation to reduce the searching space of the integer ambiguity solution and improve the efficiency of the least-squares ambiguity decorrelation adjustment (LAMBDA) algorithm. The experimental results show that this method can reliably obtain the integer ambiguity solution among multi-reference stations with 40 epochs.展开更多
An improved method based on the Tikhonov regularization principle and the precisely known reference station coordinate is proposed to design the regularized matrix. The ill-conditioning of the normal matrix can be imp...An improved method based on the Tikhonov regularization principle and the precisely known reference station coordinate is proposed to design the regularized matrix. The ill-conditioning of the normal matrix can be improved by the regularized matrix. The relative floating ambiguity can be computed only by using the data of several epochs. Combined with the LAMBDA method, the new approach can correctly and quickly fix the integer ambiguity and the success rate is 100% in experiments. Through using measured data sets from four mediumlong baselines, the new method can obtain exact ambiguities only by the Ll-frequency data of three epochs. Compared with the existing methods, the improved method can solve the ambiguities of the medium-long baseline GPS network RTK only using L1-frequency GPS data.展开更多
For enhancing performances and increasing functions of PD radar, High PRF, medium PRF and low PRF are commonly applied into system ambiguity appeared in range and velocity in some PRF. Based on clustering, a slidin...For enhancing performances and increasing functions of PD radar, High PRF, medium PRF and low PRF are commonly applied into system ambiguity appeared in range and velocity in some PRF. Based on clustering, a sliding window correlator algorithm for resolving the radar object ambiguity in range and velocity is described. Slide window algorithm is a searching algorithm. The probability of ambiguity resolution for targets and the computational efficiency are discussed. The relations between the probability of ambiguity resolution of this algorithm and PRF, the range of interest, and the width of sliding window are analyzed. Simulational results are also given.展开更多
Azimuth ambiguities (ghost targets) discrimination is of great interest with the development of a synthet- ic aperture radar (SAR). And the azimuth ambiguities are often mistaken as actual targets and cause false ...Azimuth ambiguities (ghost targets) discrimination is of great interest with the development of a synthet- ic aperture radar (SAR). And the azimuth ambiguities are often mistaken as actual targets and cause false alarms. For actual targets, HV channel signals acquired by a fully polarimetric SAR are approximately equal to a VH channel in magnitude and phase, i.e., the reciprocity theorem applies, but shifted in phase about ±π for the first-order azimuth ambiguities. Exploiting this physical behavior, the real part of the product of the two cross-polarized channels, i.e. (SHVSVH), hereafter called A12r, is employed as a new parameter for a target detection at sea. Compared with other parameters, the contrast of A12r image between a target and the surrounding sea surface will be obviously increased when A12r image is processed by mean filtering algo- rithm. Here, in order to detect target with constant false-alarm rates (CFARs), an analytical expression for the probability density function (pdf) ofA12r is derived based on the complexWishart-distribution. Because a value of A12r is greater/less than 0 for real target/its azimuth ambiguities, the first-order azimuth ambiguities can be completely removed by this A12r-based CFAR technology. Experiments accomplished over C-band RADARSAT-2 fully polarimetric imageries confirm the validity.展开更多
文摘Relative clauses(RCs)processing has been a hot issue in decades.Studies from head-initial languages have found that SRCs were easier to comprehend than ORCs,and many different models were constructed to account for SRCs preference.Chinese are head-final languages and the head noun phrases are behind the internal-clause.Such a great difference in syntactic structure made Chinese to be the optimum material to test the models mentioned above.In the paper,two experiments were carried out using eye-movement tracking methods to explore the difficulty with RCs processing in mandarin,and results showed that:when the two noun phrases were both from animate category,SRCs were more difficult than ORCs,but when the noun phrases in the internal-relative-clause were inanimate and the noun phrases in the matrix were animate,the difficulties with SRCs were greatly reduced.Based on these findings,we hold that the linear syntactic distance between the gap and the filler was not the key reason to the difficulty with SRCs.On the contrary,the ambiguity in argument construction may be the most important.
文摘In October, 1998, Ted Hughes, the great English poet and writer died of cancer at the age of 68. From 1957 to 1998, Hughes published numerous books of poetry and received various awards including the prestigious Whitbread Poetry Award. He was appointed Poet Laureate in 1984 and given Merit of Order shortly before his death. He was generally regarded, with Philip Larkin, as one of the two most important English poets since the Second
文摘The solution of the current wind retrieval algorithm for scatterometers has several wind vector ambi-guities, due to the bi-harmonic relationship between normalized backscattering cross section and the relative wind direction and the existence of the measurement error. In order to remove the ambiguities for a unique wind field, a circular median filter approach (CMF) is usually adopted. But under the con-dition for clustering distribution of the false ambiguities in some local areas, the CMF fails and thus engenders block ambiguities, which degrade the precision of the retrieved wind field. For such a situation, a technique of identification and removal of the block ambiguities is presented to further optimize the retrieved wind field after CMF. It is demonstrated in experiment that this technique can identify and remove most of the block ambiguities.
文摘Shakespeare's Julius Caesar is remarkable for its rational mode as manifested in the use of language, style, action as well as its characterization. In this essay, I argue that the play is also striking with its numerous(ir)rational ambiguities. The same Latin word, ratio, is at the root of two words that are often used to explain human behaviors: reason and rationality. The fi rst related ambiguity is organized around the confl ict between reason and passion. The other is related to rational choice, which is opposed to the diverse forms of irrationality. This paper argues that Julius Caesar challenges the idea that a rational actor is one who acts only for sufficient reasons, and the play also subverts the conventional understanding of reason and rationality.
基金This work was supported by the National Natural Science Foundation of China(Nos.12005047 and U1832105).
文摘The optical potential ambiguity is a long-standing problem in the analysis of elastic scattering data.For a specific collid-ing system,ambiguous potential families can lead to different behaviors in the nearside and farside scattering components.By contrast,the envelope method can decompose the experimental data into two components with negative and positive deflection angles,respectively.Hence,a question arises as to whether the comparison between the calculated nearside(or farside)component and the derived positive-deflection-angle(or negative-deflection-angle)component can help analyze the potential ambiguity problem.In this study,we conducted a trial application of the envelope method to the potential ambiguity problem.The envelope method was improved by including uncertainties in the experimental data.The colliding systems of 16O+28Si at 215.2 MeV and 12C+12C at 1016 MeV were considered in the analyses.For each colliding system,the angular distribution experimental data were described nearly equally well by two potential sets,one of which is“surface transpar-ent”and the other is refractive.The calculated angular distributions were decomposed into nearside and farside scattering components.Using the improved envelope method,the experimental data were decomposed into the positive-deflection-angle and negative-deflection-angle components,which were then compared with the calculated nearside and farside components.The capability of the envelope method to analyze the potential ambiguities was also discussed.
基金supported in part by the National Natural Science Foundation of China under Grant 62271142in part by the Key Research and Development Program of Jiangsu Province BE2023021+2 种基金in part by the Jiangsu Key Research and Development Program Project under Grant BE2023011-2in part by the Young Scholar Funding of Southeast Universityin part by the Fundamental Research Funds for the Central Universities 2242022k60001。
文摘In this paper,we formulate the precoding problem of integrated sensing and communication(ISAC)waveform as a non-convex quadratically constrained quadratic programming(QCQP),in which the weighted sum of communication multi-user interference(MUI)and the gap between dual-use waveform and ideal radar waveform is minimized with peak-toaverage power ratio(PAPR)constraints.We propose an efficient algorithm based on alternating direction method of multipliers(ADMM),which is able to decouple multiple variables and provide a closed-form solution for each subproblem.In addition,to improve the sensing performance in both spatial and temporal domains,we propose a new criteria to design the ideal radar waveform,in which the beam pattern is made similar to the ideal one and the integrated sidelobe level of the ambiguity function in each target direction is minimized in the region of interest.The limited memory Broyden-Fletcher-Goldfarb-Shanno(LBFGS)algorithm is applied to the design of the ideal radar waveform which works as a reference in the design of the dual-function waveform.Numerical results indicate that the designed dual-function waveform is capable of offering good communication quality of service(QoS)and sensing performance.
文摘In this paper,an antenna array composed of circular array and orthogonal linear array is proposed by using the design of long and short baseline“orthogonal linear array”and the circular array ambiguity resolution design of multi-group baseline clustering.The effectiveness of the antenna array in this paper is verified by sufficient simulation and experiment.After the system deviation correction work,it is found that in the L/S/C/X frequency bands,the ambiguity resolution probability is high,and the phase difference system error between each channel is basically the same.The angle measurement error is less than 0.5°,and the positioning error is less than 2.5 km.Notably,as the center frequency increases,calibration consistency improves,and the calibration frequency points become applicable over a wider frequency range.At a center frequency of 11.5 GHz,the calibration frequency point bandwidth extends to 1200 MHz.This combined antenna array deployment holds significant promise for a wide range of applications in contemporary wireless communication systems.
文摘BACKGROUND Asplenia-type heterotaxy syndrome(HS)is rare and refers to visceral malposition and dysmorphism.It is associated with a high infant mortality rate due to cardiac anomalies,and related digestive endoscopic interventions are poorly understood.With the improved long-term prognosis of these individuals after modern cardiac surgery,intra-abdominal anomalies have become increasingly significant.CASE SUMMARY Herein,we report successful endoscopic retrograde cholangiopancreatography(ERCP)in a 14-year-old male with asplenia-type HS that involved unique imaging findings and technical difficulties.His anatomic anomalies included complex congenital heart disease,midline liver placement,an absent spleen,a left-sided inferior vena cava,and dextroposition of the stomach and pancreas.He suffered from choledocholithiasis with obstructive jaundice,and the stone was successfully extracted with a basket following endoscopic papillary balloon dilation.CONCLUSION Although anatomic anomalies in HS increase the degree of technical difficulty when performing ERCP,they can be safely managed by experienced endosco-pists,as illustrated by the present case.Identifying these variations with imaging modalities and being aware of them before initiating an invasive intervention are crucial to preventing potential complications.
基金supported by the National Natural Science Foundation of China under Grant No.62071114.
文摘Integrated sensing and communication(ISAC)is one of the main usage scenarios for 6G wireless networks.To most efficiently utilize the limited wireless resources,integrated super-resolution sensing and communication(ISSAC)has been recently proposed to significantly improve sensing performance with super-resolution algorithms for ISAC systems,such as the Multiple Signal Classification(MUSIC)algorithm.However,traditional super-resolution sensing algorithms suffer from prohibitive computational complexity of orthogonal-frequency division multiplexing(OFDM)systems due to the large dimensions of the signals in the subcarrier and symbol domains.To address such issues,we propose a novel two-stage approach to reduce the computational complexity for super-resolution range estimation significantly.The key idea of the proposed scheme is to first uniformly decimate signals in the subcarrier domain so that the computational complexity is significantly reduced without missing any target in the range domain.However,the decimation operation may result in range ambiguity due to pseudo peaks,which is addressed by the second stage where the total collocated subcarrier data are used to verify the detected peaks.Compared with traditional MUSIC algorithms,the proposed scheme reduces computational complexity by two orders of magnitude,while maintaining the range resolution and unambiguity.Simulation results verify the effectiveness of the proposed scheme.
文摘The translation of English language and literary works has always been crucial for cross-cultural communication.However,a key challenge in translating such works is the accurate communication of ambiguity,which refers to expressions deliberately used in English texts with unclear meanings.These expressions are often poetic and carry deep symbols and implications,adding a unique charm to literary works.This article explores the manifestations of ambiguity in English language and literature and the translation strategies that can be employed to optimize the translation of ambiguity in the English language and literature.
文摘In this paper, we discuss the optimal insurance in the presence of background risk while the insured is ambiguity averse and there exists belief heterogeneity between the insured and the insurer. We give the optimal insurance contract when maxing the insured’s expected utility of his/her remaining wealth under the smooth ambiguity model and the heterogeneous belief form satisfying the MHR condition. We calculate the insurance premium by using generalized Wang’s premium and also introduce a series of stochastic orders proposed by [1] to describe the relationships among the insurable risk, background risk and ambiguity parameter. We obtain the deductible insurance is the optimal insurance while they meet specific dependence structures.
基金The National Key Technology R&D Program of Chinaduring the11th Five-Year Plan Period (No2008BAJ11B05)
文摘A method for integer ambiguity resolution in the global positioning system (GPS) multi-reference station network real time kinematic (RTK) is proposed. First, the barycenter of the triangle of reference stations for ambiguity resolution is taken as a reference point. The satellite which has the largest elevation angle with the reference point is selected as a reference satellite. The parameters for constructing the weight matrix of carrier phase observation and the criteria for checking the correctness of integer ambiguity resolution of a network are obtained. Then, the wide ambiguity is calculated by a linear combination method of dualband observation. And the LI ambiguity is obtained by a nonionosphere combination method. The Kalman filter is introduced to refine the floating-point solution of ambiguity and estimate the real-time tropospheric delay. Finally, the cofactor matrix of ambiguity is de-correlated by Z-transformation to reduce the searching space of the integer ambiguity solution and improve the efficiency of the least-squares ambiguity decorrelation adjustment (LAMBDA) algorithm. The experimental results show that this method can reliably obtain the integer ambiguity solution among multi-reference stations with 40 epochs.
文摘An improved method based on the Tikhonov regularization principle and the precisely known reference station coordinate is proposed to design the regularized matrix. The ill-conditioning of the normal matrix can be improved by the regularized matrix. The relative floating ambiguity can be computed only by using the data of several epochs. Combined with the LAMBDA method, the new approach can correctly and quickly fix the integer ambiguity and the success rate is 100% in experiments. Through using measured data sets from four mediumlong baselines, the new method can obtain exact ambiguities only by the Ll-frequency data of three epochs. Compared with the existing methods, the improved method can solve the ambiguities of the medium-long baseline GPS network RTK only using L1-frequency GPS data.
文摘For enhancing performances and increasing functions of PD radar, High PRF, medium PRF and low PRF are commonly applied into system ambiguity appeared in range and velocity in some PRF. Based on clustering, a sliding window correlator algorithm for resolving the radar object ambiguity in range and velocity is described. Slide window algorithm is a searching algorithm. The probability of ambiguity resolution for targets and the computational efficiency are discussed. The relations between the probability of ambiguity resolution of this algorithm and PRF, the range of interest, and the width of sliding window are analyzed. Simulational results are also given.
基金The National Natural Science Foundation of China under contract Nos 41376179 and 41106153
文摘Azimuth ambiguities (ghost targets) discrimination is of great interest with the development of a synthet- ic aperture radar (SAR). And the azimuth ambiguities are often mistaken as actual targets and cause false alarms. For actual targets, HV channel signals acquired by a fully polarimetric SAR are approximately equal to a VH channel in magnitude and phase, i.e., the reciprocity theorem applies, but shifted in phase about ±π for the first-order azimuth ambiguities. Exploiting this physical behavior, the real part of the product of the two cross-polarized channels, i.e. (SHVSVH), hereafter called A12r, is employed as a new parameter for a target detection at sea. Compared with other parameters, the contrast of A12r image between a target and the surrounding sea surface will be obviously increased when A12r image is processed by mean filtering algo- rithm. Here, in order to detect target with constant false-alarm rates (CFARs), an analytical expression for the probability density function (pdf) ofA12r is derived based on the complexWishart-distribution. Because a value of A12r is greater/less than 0 for real target/its azimuth ambiguities, the first-order azimuth ambiguities can be completely removed by this A12r-based CFAR technology. Experiments accomplished over C-band RADARSAT-2 fully polarimetric imageries confirm the validity.