Instantaneous Global Navigation Satellite System(GNSS)attitude determination method which achieves real-time attitude determination using GNSS signal has been extensively studied,particularly the one using a priori at...Instantaneous Global Navigation Satellite System(GNSS)attitude determination method which achieves real-time attitude determination using GNSS signal has been extensively studied,particularly the one using a priori attitude information replacing the code measurements to enhance the successful rate for ambiguity resolution.However,there exists a key limitation that this method relies on considerable Monte Carlo sampling particles to construct the pdf of ambiguities,resulting in significant computational burdens.To address this limitation,this paper provides a rapid single-epoch GNSS attitude determination method based on a priori attitude information.It utilizes a second-order Taylor expansion to analytically estimate the covariance of the baseline conditioned on a priori attitude information.This is followed by deriving the float solution and covariance of ambiguities,which are then processed using the standard LAMBDA method for integer ambiguity resolution.Experimental results demonstrate that our method is both efficient and accurate,significantly reducing computational costs compared to previous methods,thereby enhancing its applicability for GNSS-based attitude determination.展开更多
With the rapid growth of socialmedia,the spread of fake news has become a growing problem,misleading the public and causing significant harm.As social media content is often composed of both images and text,the use of...With the rapid growth of socialmedia,the spread of fake news has become a growing problem,misleading the public and causing significant harm.As social media content is often composed of both images and text,the use of multimodal approaches for fake news detection has gained significant attention.To solve the problems existing in previous multi-modal fake news detection algorithms,such as insufficient feature extraction and insufficient use of semantic relations between modes,this paper proposes the MFFFND-Co(Multimodal Feature Fusion Fake News Detection with Co-Attention Block)model.First,the model deeply explores the textual content,image content,and frequency domain features.Then,it employs a Co-Attention mechanism for cross-modal fusion.Additionally,a semantic consistency detectionmodule is designed to quantify semantic deviations,thereby enhancing the performance of fake news detection.Experimentally verified on two commonly used datasets,Twitter and Weibo,the model achieved F1 scores of 90.0% and 94.0%,respectively,significantly outperforming the pre-modified MFFFND(Multimodal Feature Fusion Fake News Detection with Attention Block)model and surpassing other baseline models.This improves the accuracy of detecting fake information in artificial intelligence detection and engineering software detection.展开更多
This study was conducted retrospectively on a cohort of 68 patients with steroid 5α-reductase 2(SRD5A2)deficiency and 46,XY disorders of sex development(DSD).Whole-exon sequencing revealed 28 variants of SRD5A2,and f...This study was conducted retrospectively on a cohort of 68 patients with steroid 5α-reductase 2(SRD5A2)deficiency and 46,XY disorders of sex development(DSD).Whole-exon sequencing revealed 28 variants of SRD5A2,and further analysis identified seven novel mutants.The preponderance of variants was observed in exon 1 and exon 4,specifically within the nicotinamide adenine dinucleotide phosphate(NADPH)-binding region.Among the entire cohort,53 patients underwent initial surgery at Sichuan Provincial People’s Hospital(Chengdu,China).The external genitalia scores(EGS)of these participants varied from 2.0 to 11.0,with a mean of 6.8(standard deviation[s.d.]:2.5).Thirty patients consented to hormone testing.Their average testosterone-todihydrotestosterone(T/DHT)ratio was 49.3(s.d.:23.4).Genetic testing identified four patients with EGS scores between 6 and 9 as having this syndrome;and their T/DHT ratios were below the diagnostic threshold.Furthermore,assessments conducted using the crystal structure of human SRD5A2 have provided insights into the potential pathogenic mechanisms of these novel variants.These mechanisms include interference with NADPH binding(c.356G>C,c.365A>G,c.492C>G,and c.662T>G)and destabilization of the protein structure(c.727C>T).The c.446-1G>T and c.380delG variants were verified to result in large alterations in the transcripts.Seven novel variations were identified,and the variant database for the SRD5A2 gene was expanded.These findings contribute to the progress of diagnostic and therapeutic approaches for individuals with SRD5A2 deficiency.展开更多
Range-azimuth imaging of ground targets via frequency-modulated continuous wave(FMCW)radar is crucial for effective target detection.However,when the pitch of the moving array constructed during motion exceeds the phy...Range-azimuth imaging of ground targets via frequency-modulated continuous wave(FMCW)radar is crucial for effective target detection.However,when the pitch of the moving array constructed during motion exceeds the physical array aperture,azimuth ambiguity occurs,making range-azimuth imaging on a moving platform challenging.To address this issue,we theoretically analyze azimuth ambiguity generation in sparse motion arrays and propose a dual-aperture adaptive processing(DAAP)method for suppressing azimuth ambiguity.This method combines spatial multiple-input multiple-output(MIMO)arrays with sparse motion arrays to achieve high-resolution range-azimuth imaging.In addition,an adaptive QR decomposition denoising method for sparse array signals based on iterative low-rank matrix approximation(LRMA)and regularized QR is proposed to preprocess sparse motion array signals.Simulations and experiments show that on a two-transmitter-four-receiver array,the signal-to-noise ratio(SNR)of the sparse motion array signal after noise suppression via adaptive QR decomposition can exceed 0 dB,and the azimuth ambiguity signal ratio(AASR)can be reduced to below-20 dB.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
Relative positioning is recognized as an important issue for vehicles in urban environments.Multi-vehicle Cooperative Positioning(CP)techniques which fuse the Global Navigation Satellite System(GNSS)and inter-vehicle ...Relative positioning is recognized as an important issue for vehicles in urban environments.Multi-vehicle Cooperative Positioning(CP)techniques which fuse the Global Navigation Satellite System(GNSS)and inter-vehicle ranging have attracted attention in improving the performance of baseline estimation between vehicles.However,current CP methods estimate the baselines separately and ignore the interactions among the positioning information of different baselines.These interactions are called’information coupling’.In this work,we propose a new multivehicle precise CP framework using the coupled information in the network based on the Carrier Differential GNSS(CDGNSS)and inter-vehicle ranging.We demonstrate the benefit of the coupled information by deriving the Cramer-Rao Lower Bound(CRLB)of the float estimation in CP.To fully use this coupled information,we propose a Whole-Net CP(WN-CP)method which consists of the Whole-Net Extended Kalman Filter(WN-EKF)as the float estimation filter,and the Partial Baseline Fixing(PBF)as the ambiguity resolution part.The WN-EKF fuses the measurements of all baselines simultaneously to improve the performance of float estimation,and the PBF strategy fixes the ambiguities of the one baseline to be estimated,instead of full ambiguity resolution,to reduce the computation load of ambiguity resolution.Field tests involving four vehicles were conducted in urban environments.The results show that the proposed WN-CP method can achieve better performance and meanwhile maintain a low computation load compared to the existing methods.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
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
BeiDou navigation satellite system with global coverage(BDS-3)has been fully operational since July 2020,currently providing the positioning,navigation and timing service together with regional BDS-2.In addition to th...BeiDou navigation satellite system with global coverage(BDS-3)has been fully operational since July 2020,currently providing the positioning,navigation and timing service together with regional BDS-2.In addition to the legacy signals of B1I and B3I,the BDS-3 also transmits several new signals such as BIC,B2a and B2b,which brings new opportunities for rapid ambiguity resolution(AR)of BDS precise point positioning(PPP).In this contribution,a multi-frequency(MF)rapid PPP-AR method with regional network augmentation was proposed.Firstly,BDS five-frequency observations were introduced into uncombined double-differenced models to retrieve regional augmentation corrections at the server.Thereafter,a cascade PPP-AR strategy using extra-wide-lane,wide-lane and narrow-lane ambiguity was employed at the user.Once ambiguities were fixed to integers,the phase correction accuracy could reach about 3 cm on average overall BDS frequencies in the network with inter-station distances of 100-200 km.Subsequently,the statistical results of seven-day simulated kinematic experiments showed that over 99% of epochs on average realized PPP-AR.Correspondingly,the positioning accuracy of the MF fixed solution reached 1.8,1.9,4.7 cm in the east,north and up components,respectively,improving by 5-15% compared with the dual-frequency scheme.Moreover,several vehicle-borne experiments under different urban scenarios were also conducted.Under an open-sky or a relatively open highway scene,the BDS-MF scheme similarly exhibited good performance,and over 98% of epochs achieved rapid PPP-AR with a positioning accuracy better than 3 cm.More encouragingly,for this BDS-challenged experiment with an average satellite number of 8.6,although only 72.06% of epochs were available due to serious signal blockages caused by overpass,tunnels or tall buildings,the horizontal positioning accuracy could still remain 7 cm on average.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
Recent theoretical developments in economics distinguish between risk and ambiguity(Knightian uncertainty).Using state-of-the-art methods with intraday stock market data from February 1993 to February 2021,we derive f...Recent theoretical developments in economics distinguish between risk and ambiguity(Knightian uncertainty).Using state-of-the-art methods with intraday stock market data from February 1993 to February 2021,we derive financial ambiguity and empirically examine the effect of shocks to it on the price and volatility of crude oil.We provide evidence that ambiguity carries important information about future oil returns and volatility perceived by investors.We validate these results using Granger causality and in-sample and out-of-sample forecasting tests.Our findings reveal that financial ambiguity is a possible factor that explains future drops in oil prices and their increased variability.Our findings will benefit scholars and investors interested in how financial ambiguity shapes short-term oil prices.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
Crowdfunding provides a novel and potential way for innovative but risky new ventures to fund their new product development(NPD)projects.To help potential investors evaluate the projects and enhance the credibility of...Crowdfunding provides a novel and potential way for innovative but risky new ventures to fund their new product development(NPD)projects.To help potential investors evaluate the projects and enhance the credibility of disclosure,founders are struggling with how to phrase the project description.The rapidly growing cleantech crowdfunding projects provide an ideal context to study this issue.We collected information on cleantech crowdfunding projects and matched non-cleantech crowdfunding projects from Kickstarter.The sample period extends from January 2013 to October 2018.Using signaling research as a theoretical lens and a dictionary-based,computerized text mining method,we found that founders of high-quality cleantech crowdfunding projects could create a reliable signal of quality by providing a project description with a less ambiguous tone and thus boost the success of crowdfunding.Moreover,the signaling effectiveness of a less ambiguous tone is more pronounced in cleantech crowdfunding than in matched non-cleantech crowdfunding,suggesting that the marginal benefit of using a less ambiguous tone is larger when the industry information environment is noisier.Further evidence shows that the signaling effectiveness of a less ambiguous tone in cleantech crowdfunding could be strengthened by backers’endorsements.Our findings imply that tone ambiguity in project descriptions is related to founders’information-concealing behavior.Potential investors could search ambiguous words in project descriptions and just allocate their limited attention into projects with a low percentage of ambiguous words to avoid information overload.Founders of high-quality projects could boost crowdfunding success by using a less ambiguous tone to describe their projects.The marginal effect is larger when there is greater uncertainty about project prospects.展开更多
In the case of a medium-long baseline, for real-time kinematic (RTK) positioning, the fixed rate of integer ambiguity is low due to the distance between the base station and the observation station. Moreover, the atmo...In the case of a medium-long baseline, for real-time kinematic (RTK) positioning, the fixed rate of integer ambiguity is low due to the distance between the base station and the observation station. Moreover, the atmospheric delay after differential processing cannot be ignored. For correcting the residual atmospheric errors, we proposed a GPS/BDS/Galileo/GLONASS four-system fusion RTK positioning algorithm, which is based on the extended Kalman filter (EKF) algorithm. After realizing the spatio-temporal unification of multiple global navigation satellite systems (GNSSs), we introduced a parameter estimation of atmospheric errors based on the EKF model, using the least-squares integer ambiguity decorrelation adjustment (LAMBDA) to calculate the integer ambiguity. After conducting experiments for different baselines, the proposed RTK positioning algorithm can achieve centimeter-level positioning accuracy in the case of medium-long baselines. In addition, the time required to solve the fixed solution is shorter than that of the traditional RTK positioning algorithm.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
基金supported by the Research Grants Council of the Hong Kong Special Administrative Region,China(Nos.25202520,15214523)the Fundamental Research Funds for the Central Universities,China(No.YWF-22-L-805)。
文摘Instantaneous Global Navigation Satellite System(GNSS)attitude determination method which achieves real-time attitude determination using GNSS signal has been extensively studied,particularly the one using a priori attitude information replacing the code measurements to enhance the successful rate for ambiguity resolution.However,there exists a key limitation that this method relies on considerable Monte Carlo sampling particles to construct the pdf of ambiguities,resulting in significant computational burdens.To address this limitation,this paper provides a rapid single-epoch GNSS attitude determination method based on a priori attitude information.It utilizes a second-order Taylor expansion to analytically estimate the covariance of the baseline conditioned on a priori attitude information.This is followed by deriving the float solution and covariance of ambiguities,which are then processed using the standard LAMBDA method for integer ambiguity resolution.Experimental results demonstrate that our method is both efficient and accurate,significantly reducing computational costs compared to previous methods,thereby enhancing its applicability for GNSS-based attitude determination.
基金supported by Communication University of China(HG23035)partly supported by the Fundamental Research Funds for the Central Universities(CUC230A013).
文摘With the rapid growth of socialmedia,the spread of fake news has become a growing problem,misleading the public and causing significant harm.As social media content is often composed of both images and text,the use of multimodal approaches for fake news detection has gained significant attention.To solve the problems existing in previous multi-modal fake news detection algorithms,such as insufficient feature extraction and insufficient use of semantic relations between modes,this paper proposes the MFFFND-Co(Multimodal Feature Fusion Fake News Detection with Co-Attention Block)model.First,the model deeply explores the textual content,image content,and frequency domain features.Then,it employs a Co-Attention mechanism for cross-modal fusion.Additionally,a semantic consistency detectionmodule is designed to quantify semantic deviations,thereby enhancing the performance of fake news detection.Experimentally verified on two commonly used datasets,Twitter and Weibo,the model achieved F1 scores of 90.0% and 94.0%,respectively,significantly outperforming the pre-modified MFFFND(Multimodal Feature Fusion Fake News Detection with Attention Block)model and surpassing other baseline models.This improves the accuracy of detecting fake information in artificial intelligence detection and engineering software detection.
基金supported by the Sichuan Science and Technology Program(No.2022JDZH0029 to JYY)the Special Fund for Clinical Research and Translational Medicine from Chinese Academy of Medical Sciences(No.2022-I2M-C&T-B-117 to JYY)the Sichuan Key Research and Development Project from the Department of Science and Technology of Sichuan Province(No.2022YFS0237 to YMT).
文摘This study was conducted retrospectively on a cohort of 68 patients with steroid 5α-reductase 2(SRD5A2)deficiency and 46,XY disorders of sex development(DSD).Whole-exon sequencing revealed 28 variants of SRD5A2,and further analysis identified seven novel mutants.The preponderance of variants was observed in exon 1 and exon 4,specifically within the nicotinamide adenine dinucleotide phosphate(NADPH)-binding region.Among the entire cohort,53 patients underwent initial surgery at Sichuan Provincial People’s Hospital(Chengdu,China).The external genitalia scores(EGS)of these participants varied from 2.0 to 11.0,with a mean of 6.8(standard deviation[s.d.]:2.5).Thirty patients consented to hormone testing.Their average testosterone-todihydrotestosterone(T/DHT)ratio was 49.3(s.d.:23.4).Genetic testing identified four patients with EGS scores between 6 and 9 as having this syndrome;and their T/DHT ratios were below the diagnostic threshold.Furthermore,assessments conducted using the crystal structure of human SRD5A2 have provided insights into the potential pathogenic mechanisms of these novel variants.These mechanisms include interference with NADPH binding(c.356G>C,c.365A>G,c.492C>G,and c.662T>G)and destabilization of the protein structure(c.727C>T).The c.446-1G>T and c.380delG variants were verified to result in large alterations in the transcripts.Seven novel variations were identified,and the variant database for the SRD5A2 gene was expanded.These findings contribute to the progress of diagnostic and therapeutic approaches for individuals with SRD5A2 deficiency.
基金supported by the National Natural Science Foundation of China under Grant 62301051.
文摘Range-azimuth imaging of ground targets via frequency-modulated continuous wave(FMCW)radar is crucial for effective target detection.However,when the pitch of the moving array constructed during motion exceeds the physical array aperture,azimuth ambiguity occurs,making range-azimuth imaging on a moving platform challenging.To address this issue,we theoretically analyze azimuth ambiguity generation in sparse motion arrays and propose a dual-aperture adaptive processing(DAAP)method for suppressing azimuth ambiguity.This method combines spatial multiple-input multiple-output(MIMO)arrays with sparse motion arrays to achieve high-resolution range-azimuth imaging.In addition,an adaptive QR decomposition denoising method for sparse array signals based on iterative low-rank matrix approximation(LRMA)and regularized QR is proposed to preprocess sparse motion array signals.Simulations and experiments show that on a two-transmitter-four-receiver array,the signal-to-noise ratio(SNR)of the sparse motion array signal after noise suppression via adaptive QR decomposition can exceed 0 dB,and the azimuth ambiguity signal ratio(AASR)can be reduced to below-20 dB.
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.
基金supported by the National Natural Science Foundation of China(No.61901015)。
文摘Relative positioning is recognized as an important issue for vehicles in urban environments.Multi-vehicle Cooperative Positioning(CP)techniques which fuse the Global Navigation Satellite System(GNSS)and inter-vehicle ranging have attracted attention in improving the performance of baseline estimation between vehicles.However,current CP methods estimate the baselines separately and ignore the interactions among the positioning information of different baselines.These interactions are called’information coupling’.In this work,we propose a new multivehicle precise CP framework using the coupled information in the network based on the Carrier Differential GNSS(CDGNSS)and inter-vehicle ranging.We demonstrate the benefit of the coupled information by deriving the Cramer-Rao Lower Bound(CRLB)of the float estimation in CP.To fully use this coupled information,we propose a Whole-Net CP(WN-CP)method which consists of the Whole-Net Extended Kalman Filter(WN-EKF)as the float estimation filter,and the Partial Baseline Fixing(PBF)as the ambiguity resolution part.The WN-EKF fuses the measurements of all baselines simultaneously to improve the performance of float estimation,and the PBF strategy fixes the ambiguities of the one baseline to be estimated,instead of full ambiguity resolution,to reduce the computation load of ambiguity resolution.Field tests involving four vehicles were conducted in urban environments.The results show that the proposed WN-CP method can achieve better performance and meanwhile maintain a low computation load compared to the existing methods.
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.
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[Grant 41774030,Grant 41974027 and Grant 41974029]the Hubei Province Natural Science Foundation of China[Grant 2018CFA081]+1 种基金the frontier project of basic application from Wuhan science and technology bureau[Grant 2019010701011395]the Sino-German mobility programme[Grant No.M-0054].
文摘BeiDou navigation satellite system with global coverage(BDS-3)has been fully operational since July 2020,currently providing the positioning,navigation and timing service together with regional BDS-2.In addition to the legacy signals of B1I and B3I,the BDS-3 also transmits several new signals such as BIC,B2a and B2b,which brings new opportunities for rapid ambiguity resolution(AR)of BDS precise point positioning(PPP).In this contribution,a multi-frequency(MF)rapid PPP-AR method with regional network augmentation was proposed.Firstly,BDS five-frequency observations were introduced into uncombined double-differenced models to retrieve regional augmentation corrections at the server.Thereafter,a cascade PPP-AR strategy using extra-wide-lane,wide-lane and narrow-lane ambiguity was employed at the user.Once ambiguities were fixed to integers,the phase correction accuracy could reach about 3 cm on average overall BDS frequencies in the network with inter-station distances of 100-200 km.Subsequently,the statistical results of seven-day simulated kinematic experiments showed that over 99% of epochs on average realized PPP-AR.Correspondingly,the positioning accuracy of the MF fixed solution reached 1.8,1.9,4.7 cm in the east,north and up components,respectively,improving by 5-15% compared with the dual-frequency scheme.Moreover,several vehicle-borne experiments under different urban scenarios were also conducted.Under an open-sky or a relatively open highway scene,the BDS-MF scheme similarly exhibited good performance,and over 98% of epochs achieved rapid PPP-AR with a positioning accuracy better than 3 cm.More encouragingly,for this BDS-challenged experiment with an average satellite number of 8.6,although only 72.06% of epochs were available due to serious signal blockages caused by overpass,tunnels or tall buildings,the horizontal positioning accuracy could still remain 7 cm on average.
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Recent theoretical developments in economics distinguish between risk and ambiguity(Knightian uncertainty).Using state-of-the-art methods with intraday stock market data from February 1993 to February 2021,we derive financial ambiguity and empirically examine the effect of shocks to it on the price and volatility of crude oil.We provide evidence that ambiguity carries important information about future oil returns and volatility perceived by investors.We validate these results using Granger causality and in-sample and out-of-sample forecasting tests.Our findings reveal that financial ambiguity is a possible factor that explains future drops in oil prices and their increased variability.Our findings will benefit scholars and investors interested in how financial ambiguity shapes short-term oil prices.
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.
基金the financial support from the National Natural Science Foundation of China(72073063,71673133).
文摘Crowdfunding provides a novel and potential way for innovative but risky new ventures to fund their new product development(NPD)projects.To help potential investors evaluate the projects and enhance the credibility of disclosure,founders are struggling with how to phrase the project description.The rapidly growing cleantech crowdfunding projects provide an ideal context to study this issue.We collected information on cleantech crowdfunding projects and matched non-cleantech crowdfunding projects from Kickstarter.The sample period extends from January 2013 to October 2018.Using signaling research as a theoretical lens and a dictionary-based,computerized text mining method,we found that founders of high-quality cleantech crowdfunding projects could create a reliable signal of quality by providing a project description with a less ambiguous tone and thus boost the success of crowdfunding.Moreover,the signaling effectiveness of a less ambiguous tone is more pronounced in cleantech crowdfunding than in matched non-cleantech crowdfunding,suggesting that the marginal benefit of using a less ambiguous tone is larger when the industry information environment is noisier.Further evidence shows that the signaling effectiveness of a less ambiguous tone in cleantech crowdfunding could be strengthened by backers’endorsements.Our findings imply that tone ambiguity in project descriptions is related to founders’information-concealing behavior.Potential investors could search ambiguous words in project descriptions and just allocate their limited attention into projects with a low percentage of ambiguous words to avoid information overload.Founders of high-quality projects could boost crowdfunding success by using a less ambiguous tone to describe their projects.The marginal effect is larger when there is greater uncertainty about project prospects.
文摘In the case of a medium-long baseline, for real-time kinematic (RTK) positioning, the fixed rate of integer ambiguity is low due to the distance between the base station and the observation station. Moreover, the atmospheric delay after differential processing cannot be ignored. For correcting the residual atmospheric errors, we proposed a GPS/BDS/Galileo/GLONASS four-system fusion RTK positioning algorithm, which is based on the extended Kalman filter (EKF) algorithm. After realizing the spatio-temporal unification of multiple global navigation satellite systems (GNSSs), we introduced a parameter estimation of atmospheric errors based on the EKF model, using the least-squares integer ambiguity decorrelation adjustment (LAMBDA) to calculate the integer ambiguity. After conducting experiments for different baselines, the proposed RTK positioning algorithm can achieve centimeter-level positioning accuracy in the case of medium-long baselines. In addition, the time required to solve the fixed solution is shorter than that of the traditional RTK positioning algorithm.
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.
