期刊文献+
共找到131,198篇文章
< 1 2 250 >
每页显示 20 50 100
Clustering optimization strategy for cooperative positioning system aided by UAV 被引量:1
1
作者 Hongbo ZHAO Zeqi YIN Shan HU 《Chinese Journal of Aeronautics》 2025年第9期421-435,共15页
For multi-vehicle networks,Cooperative Positioning(CP)technique has become a promising way to enhance vehicle positioning accuracy.Especially,the CP performance could be further improved by introducing Sensor-Rich Veh... For multi-vehicle networks,Cooperative Positioning(CP)technique has become a promising way to enhance vehicle positioning accuracy.Especially,the CP performance could be further improved by introducing Sensor-Rich Vehicles(SRVs)into CP networks,which is called SRV-aided CP.However,the CP system may split into several sub-clusters that cannot be connected with each other in dense urban environments,in which the sub-clusters with few SRVs will suffer from degradation of CP performance.Since Unmanned Aerial Vehicles(UAVs)have been widely used to aid vehicular communications,we intend to utilize UAVs to assist sub-clusters in CP.In this paper,a UAV-aided CP network is constructed to fully utilize information from SRVs.First,the inter-node connection structure among the UAV and vehicles is designed to share available information from SRVs.After that,the clustering optimization strategy is proposed,in which the UAV cooperates with the high-precision sub-cluster to obtain available information from SRVs,and then broadcasts this positioning-related information to other low-precision sub-clusters.Finally,the Locally-Centralized Factor Graph Optimization(LC-FGO)algorithm is designed to fuse positioning information from cooperators.Simulation results indicate that the positioning accuracy of the CP system could be improved by fully utilizing positioning-related information from SRVs. 展开更多
关键词 Clustering optimization Cooperative positioning Locally-centralized FGO Networking wireless sensors Unmanned aerial vehicles Urban degradation environments
原文传递
High-precision spot centroid positioning of high-frame-rate short-wave infrared images for satellite laser communication
2
作者 FU Peng HE Dao-Gang +1 位作者 LIU Jun WANG Yue-Ming 《红外与毫米波学报》 北大核心 2025年第1期66-77,共12页
The accuracy of spot centroid positioning has a significant impact on the tracking accuracy of the system and the stability of the laser link construction.In satellite laser communication systems,the use of short-wave... The accuracy of spot centroid positioning has a significant impact on the tracking accuracy of the system and the stability of the laser link construction.In satellite laser communication systems,the use of short-wave infrared wavelengths as beacon light can reduce atmospheric absorption and signal attenuation.However,there are strong non-uniformity and blind pixels in the short-wave infrared image,which makes the image distorted and leads to the decrease of spot centroid positioning accuracy.Therefore,the high-precision localization of the spot centroid of the short-wave infrared images is of great research significance.A high-precision spot centroid positioning model for short-wave infrared is proposed to correct for non-uniformity and blind pixels in short-wave infrared images and quantify the localization errors caused by the two,further model-based localization error simulations are performed,and a novel spot centroid positioning payload for satellite laser communications has been designed using the latest 640×512 planar array InGaAs shortwave infrared detector.The experimental results show that the non-uniformity of the corrected image is reduced from 7%to 0.6%,the blind pixels rejection rate reaches 100%,the frame rate can be up to 2000 Hz,and the spot centroid localization accuracy is as high as 0.1 pixel point,which realizes high-precision spot centroid localization of high-frame-frequency short-wave infrared images. 展开更多
关键词 satellite laser communication spot centroid positioning short-wave infrared high frame rate NONUNIFORMITY
在线阅读 下载PDF
UAV clusters information geometry fusion positioning method with LEO satellite system
3
作者 Jiaqi LIU Yi ZHANG +3 位作者 Xingxing ZHU Chengkai Tang Zesheng DAN Yangyang LIU 《Chinese Journal of Aeronautics》 2025年第5期411-427,共17页
The existing Low-Earth-Orbit(LEO)positioning performance cannot meet the requirements of Unmanned Aerial Vehicle(UAV)clusters for high-precision real-time positioning in the Global Navigation Satellite System(GNSS)den... The existing Low-Earth-Orbit(LEO)positioning performance cannot meet the requirements of Unmanned Aerial Vehicle(UAV)clusters for high-precision real-time positioning in the Global Navigation Satellite System(GNSS)denial conditions.Therefore,this paper proposes a UAV Clusters Information Geometry Fusion Positioning(UC-IGFP)method using pseudoranges from the LEO satellites.A novel graph model for linking and computing between the UAV clusters and LEO satellites was established.By utilizing probability to describe the positional states of UAVs and sensor errors,the distributed multivariate Probability Fusion Cooperative Positioning(PF-CP)algorithm is proposed to achieve high-precision cooperative positioning and integration of the cluster.Criteria to select the centroid of the cluster were set.A new Kalman filter algorithm that is suitable for UAV clusters was designed based on the global benchmark and Riemann information geometry theory,which overcomes the discontinuity problem caused by the change of cluster centroids.Finally,the UC-IGFP method achieves the LEO continuous highprecision positioning of UAV clusters.The proposed method effectively addresses the positioning challenges caused by the strong direction of signal beams from LEO satellites and the insufficient constraint quantity of information sources at the edge nodes of the cluster.It significantly improves the accuracy and reliability of LEO-UAV cluster positioning.The results of comprehensive simulation experiments show that the proposed method has a 30.5%improvement in performance over the mainstream positioning methods,with a positioning error of 14.267 m. 展开更多
关键词 LEO positioning Information fusion UAVclusters Cooperative positioning Distributed
原文传递
Acetabular Component Positioning and Risk of Dislocation in Hip Arthroplasty: Is Lewinnek’s Safe Zone Truly Safe?
4
作者 Oliver Damiani Meyer Luis Henrique Zambra Wink +3 位作者 Walter Brandt Iserhard Carlos Roberto Schwartsmann Anthony Kerbes Yépez Leandro de Freitas Spinelli 《Open Journal of Orthopedics》 2025年第2期47-53,共7页
Objective: The present research aims to determine if adherence to the Lewinnek safe zone, when exclusively considered, constitutes a pivotal element for ensuring stability in the context of total hip arthroplasty. Thi... Objective: The present research aims to determine if adherence to the Lewinnek safe zone, when exclusively considered, constitutes a pivotal element for ensuring stability in the context of total hip arthroplasty. This is done by examining the acetabular placement in instances of hip dislocation after total hip arthroplasty (THA). Methodology: The authors searched 2653 patient records from 2015 to 2022 looking for patients who had total hip arthroplasty at our facility. For the analysis, 23 patients were culled from 64 individuals who exhibited post-THA dislocations, employing a stringent exclusion criterion, and the resultant acetabular angulation and anteversion were quantified utilizing PEEKMED software (Peek Health S.A., Portugal) upon radiographic evidence. Results: Within the operational timeframe, from the cohort of 2653 subjects, 64 presented with at least a singular incident of displacement. Post-exclusion criterion enforcement, 23 patients were eligible for inclusion. Of these, 10 patients conformed to the safe zone demarcated by Lewinnek for both inclination and anteversion angles, while 13 exhibited deviations from the prescribed anteversion and/or inclination benchmarks. Conclusion: Analysis of the 23 patients reveals that 13 did not confirm to be in the safe zone parameters for anteversion and/or inclination, whereas 10 were within the safe zone as per Lewinnek’s guidelines. This investigative review, corroborated by extant literature, suggests that the isolated consideration of the Lewinnek safe zone does not suffice as a solitary protective factor. It further posits that additional variables are equally critical as acetabular positioning and mandate individual assessment. 展开更多
关键词 Acetabular Component positioning DISLOCATION Hip Arthroplasty Lewinnek’s Safe Zone
暂未订购
A satellite observation data considered train positioning optimization method with RTK
5
作者 YUCHI Zhen-xin LI Wei +3 位作者 GAO Shi-juan CHEN Chun-yang HUANG Su-su JIANG Ji-xiong 《Journal of Central South University》 2025年第4期1548-1568,共21页
In this paper,a novel train positioning method considering satellite raw observation data was proposed,which aims to promote train positioning performance from an innovative perspective of the train satellite-based po... In this paper,a novel train positioning method considering satellite raw observation data was proposed,which aims to promote train positioning performance from an innovative perspective of the train satellite-based positioning error sources.The method focused on overcoming the abnormal observations in satellite observation data caused by railway environment rather than the positioning results.Specifically,the relative positioning experimental platform was built and the zero-baseline method was firstly employed to evaluate the carrier phase data quality,and then,GNSS combined observation models were adopted to construct the detection values,which were applied to judge abnormal-data through the dual-frequency observations.Further,ambiguity fixing optimization was investigated based on observation data selection in partly-blocked environments.The results show that the proposed method can effectively detect and address abnormal observations and improve positioning stability.Cycle slips and gross errors can be detected and identified based on dual-frequency global navigation satellite system data.After adopting the data selection strategy,the ambiguity fixing percentage was improved by 29.2%,and the standard deviation in the East,North,and Up components was enhanced by 12.7%,7.4%,and 12.5%,respectively.The proposed method can provide references for train positioning performance optimization in railway environments from the perspective of positioning error sources. 展开更多
关键词 train operation control system train positioning satellite positioning abnormal-data detection real-time kinematic positioning
在线阅读 下载PDF
A Base Station Deployment Algorithm for Wireless Positioning Considering Dynamic Obstacles
6
作者 Aiguo Li Yunfei Jia 《Computers, Materials & Continua》 2025年第3期4573-4591,共19页
In the context of security systems,adequate signal coverage is paramount for the communication between security personnel and the accurate positioning of personnel.Most studies focus on optimizing base station deploym... In the context of security systems,adequate signal coverage is paramount for the communication between security personnel and the accurate positioning of personnel.Most studies focus on optimizing base station deployment under the assumption of static obstacles,aiming to maximize the perception coverage of wireless RF(Radio Frequency)signals and reduce positioning blind spots.However,in practical security systems,obstacles are subject to change,necessitating the consideration of base station deployment in dynamic environments.Nevertheless,research in this area still needs to be conducted.This paper proposes a Dynamic Indoor Environment Beacon Deployment Algorithm(DIE-BDA)to address this problem.This algorithm considers the dynamic alterations in obstacle locations within the designated area.It determines the requisite number of base stations,the requisite time,and the area’s practical and overall signal coverage rates.The experimental results demonstrate that the algorithm can calculate the deployment strategy in 0.12 s following a change in obstacle positions.Experimental results show that the algorithm in this paper requires 0.12 s to compute the deployment strategy after the positions of obstacles change.With 13 base stations,it achieves an effective coverage rate of 93.5%and an overall coverage rate of 97.75%.The algorithm can rapidly compute a revised deployment strategy in response to changes in obstacle positions within security systems,thereby ensuring the efficacy of signal coverage. 展开更多
关键词 Wireless positioning base station deployment dynamic obstacles dynamic obstacle wireless positioning
在线阅读 下载PDF
Modeling and performance analysis of GNSS-based train positioning system with colored petri nets
7
作者 Shuting Chen Daohua Wu +1 位作者 Jiang Liu Siqi Wang 《High-Speed Railway》 2025年第3期175-184,共10页
Global Navigation Satellite System(GNSS)-based continuous and accurate train positioning is one of the key technologies for advanced train operations such as train virtual coupling.However,GNSS-based train positioning... Global Navigation Satellite System(GNSS)-based continuous and accurate train positioning is one of the key technologies for advanced train operations such as train virtual coupling.However,GNSS-based train positioning faces significant challenges in real-world scenarios due to environmental complexities and signal interferences.Considering this issue,this paper presents an approach for modeling and performance analysis of GNSS-based train positioning systems using Colored Petri Nets(CPNs).By systematically modeling the GNSS signal reception and processing process,the performance of the positioning system under various environment scenarios is evaluated.The system model integrates three types of interference signals(i.e.,Amplitude Modulation(AM)signals,Frequency Modulation(FM)signals,and pulse signals)while incorporating environmental factors such as terrain obstructions and tunnel shielding.Additionally,the Extended Kalman Filter(EKF)algorithm is employed to process GNSS observation data,providing accurate train position estimations.The simulation results demonstrate that signal interferences and complex environmental conditions significantly affect the GNSS-based positioning accuracy.This study offers a comprehensive framework for evaluating the performance of GNSS-based train positioning systems in different scenarios,highlighting critical factors that influence positioning accuracy and stability. 展开更多
关键词 GNSS-based train positioning positioning performance Environment scenario GNSS signal interference Colored petri Nets
在线阅读 下载PDF
A Biomimetic Stress Field Modulation Strategy Inspired by Scorpion Compound Slit Sensilla Enabled High-Accuracy and Low-Power Positioning Sensor for Identifying the Load Incident Angles
8
作者 Junqiu Zhang Yu Chen +11 位作者 Haoran Li Jiqi Gao Xiangbo Gu Jiachao Wu Xiaojing Qin Kejun Wang Bin Zhu Daobing Chen Tao Sun Jianhua Fan Zhiwu Han Luquan Ren 《Journal of Bionic Engineering》 2025年第2期727-738,共12页
Numerous arthropods evolve and optimize sensory systems, enabling them to effectively adapt complex and competitive habitats. Typically, scorpions can precisely perceive the prey location with the lowest metabolic rat... Numerous arthropods evolve and optimize sensory systems, enabling them to effectively adapt complex and competitive habitats. Typically, scorpions can precisely perceive the prey location with the lowest metabolic rate among invertebrates. This biological phenomenon contrasts sharply with engineered systems, which generally associates high accuracy with substantial energy consumption. Inspired by the Scorpion Compound Slit Sensilla (SCSS) with a stress field modulation strategy, a bionic positioning sensor with superior precision and minimal power consumption is developed for the first time, which utilizes the particular Minimum Positioning Units (MPUs) to efficiently locate vibration signals. The single MPU of the SCSS can recognize the direction of collinear loads by regulating the stress field distribution and further, the coupling action of three MPUs can realize all-angle vibration monitoring in plane. Experiments demonstrate that the bionic positioning sensor achieves 1.43 degrees of angle-error-free accuracy without additional energy supply. As a proof of concept, two bionic positioning sensors and machine learning algorithm are integrated to provide centimeter (cm)-accuracy target localization, ideally suited for the man-machine interaction. The novel design offers a new mechanism for the design of traditional positioning devices, improving precision and efficiency in both the meta-universe and real-world Internet-connected systems. 展开更多
关键词 Scorpion Compound Slit Sensilla(SCSS) Vibration Source Stress Field Modulation Strategy High-accuracy and low-power positioning Sensor Minimum positioning Unit(MPU)
在线阅读 下载PDF
A visual indoor positioning method with pedestrian interference suppression
9
作者 YANG Jiaqiang QIN Danyang +1 位作者 TANG Huapeng TAO Sili 《High Technology Letters》 2025年第2期184-193,共10页
Visual indoor positioning methods have the potential for widespread application in complex large-scale indoor environments,such as shopping centers and hospitals.However,during the visual positioning process,passing p... Visual indoor positioning methods have the potential for widespread application in complex large-scale indoor environments,such as shopping centers and hospitals.However,during the visual positioning process,passing pedestrians may cause occlusion in the visual image,leading to large deviations in the visual positioning results.Aiming at the problem of feature occlusion in visual images caused by pedestrians,this paper proposes a visual indoor positioning system that combines semantic segmentation and image restoration.The paper proposes a method called the fast image segmentation repair(FISR),which segments and rapidly repairs the selected image to eliminate the influence of pedestrians on image feature extraction and improve positioning accuracy.In addition,the paper proposes a method called local feature based bag-of-visual-words combined with high-level semantic information(LFHS)for image retrieval.LFHS uses both local features and high-level semantic information to obtain more comprehensive and accurate representations of image features.This approach improves the accuracy and robustness of image retrieval by harnessing the combined power of local features and high-level semantic information.Experimental results show that the proposed positioning method reduces the average positioning error by 0.35 m compared with NetVLAD and 0.49 m compared with MixVPR,significantly improving the performance of visual positioning technology. 展开更多
关键词 visual positioning disturbance of pedestrians image retrieval
在线阅读 下载PDF
Analysis and Countermeasures of Nursing Problems in the Placement of PICC Guided by Endocardial Electrocardiogram Positioning Technology
10
作者 Hui Chi Jing Xie 《Journal of Clinical and Nursing Research》 2025年第3期43-48,共6页
This study aimed to explore an effective nursing plan for peripherally inserted central catheter(PICC)placement guided by endocardial electrocardiogram(ECG)positioning technology and to analyze related nursing problem... This study aimed to explore an effective nursing plan for peripherally inserted central catheter(PICC)placement guided by endocardial electrocardiogram(ECG)positioning technology and to analyze related nursing problems and countermeasures.A total of 96 patients who underwent PICC placement using ECG-guided positioning technology in our hospital from January 2024 to December 2024 were selected and randomly divided into an experimental group(n=48)and a control group(n=48)using a random number table.The control group received routine basic nursing care,while the experimental group was provided with comprehensive high-quality nursing care.The results showed that the success rate of one-time catheter placement was significantly higher in the experimental group than in the control group(P<0.05),while the incidence of complications was notably lower in the experimental group(P<0.05).These findings suggest that comprehensive high-quality nursing care during PICC placement guided by ECG positioning technology can effectively enhance the success rate of catheter placement and reduce complications,indicating that this nursing approach is valuable for clinical promotion and application. 展开更多
关键词 Electrocardiogram-guided positioning technology PICC catheter placement Nursing care
暂未订购
Fuzzy boundary guidance and oriented Gaussian function-based anchor-free network for rail positioning in turnout sections
11
作者 TONG Shuzhen WANG Qing LU Xiaobo 《Journal of Southeast University(English Edition)》 2025年第3期356-365,共10页
Rail positioning is a critical step for detecting rail defects downstream.However,existing orientation-based detectors struggle to effectively manage rails with arbitrary inclinations and high aspect ratios,particular... Rail positioning is a critical step for detecting rail defects downstream.However,existing orientation-based detectors struggle to effectively manage rails with arbitrary inclinations and high aspect ratios,particularly in turnout sections.To address these challenges,a fuzzy boundary guidance and oriented Gaussian function-based anchor-free network termed the rail positioning network(RP-Net)is proposed for rail positioning in turnout sections.First,an oriented Gaussian function-based label generation strategy is introduced.This strategy produces smoother and more accu-rate label values by accounting for the specific aspect ratios and orientations of the rails.Second,a fuzzy boundary learning module is developed to enhance the network’s abil-ity to model the rail boundary regions effectively.Further-more,a boundary guidance module is developed to direct the network in fusing the features obtained from the downs-ampled network output with the boundary region features,which have been enhanced to contain more refined posi-tional and structural information.A local channel attention mechanism is integrated into this module to identify critical channels.Finally,experiments conducted on the tracking dataset show that the proposed RP-Net achieves high posi-tioning accuracy and demonstrates strong adaptability in complex scenarios. 展开更多
关键词 rail positioning label generation boundary guidance oriented object detection
在线阅读 下载PDF
Robotic System for Total Hip Arthroplasty Based on Self-Positioning and Grinding
12
作者 Jiacheng Liu Dongliang Wang +8 位作者 Binghao Yang Weibo Ning Jiaqi Zhu Jun Hu Zhun Fan Hongjiang Chen Ye Yuan Weijun Zhou Shuxing He 《Journal of Beijing Institute of Technology》 2025年第4期418-432,共15页
Total hip arthroplasty(THA)has limitations in grinding angles,prosthesis placements,and thickness variations.THA robotics offer promise but encounter challenges like manual control of the robotic arm for precise posit... Total hip arthroplasty(THA)has limitations in grinding angles,prosthesis placements,and thickness variations.THA robotics offer promise but encounter challenges like manual control of the robotic arm for precise positioning and potential over-grinding when controlled manually.This paper presents a THA surgical robot system with automatic positioning and automatic grinding and filing functions.It achieves precise positioning during the surgery by using the singular value decomposition of initial value screening and sliding mode control(SMC),and ensures uniformity,stability and controlled filing thickness through the designed end grinding and filing actuator system.It has been verified experimentally that the average position errors in the x,y,and z directions are 0.692 mm,0.512 mm,and 0.66 mm respectively,and the Euclidean distance error is 1.322 mm.The average angle error is less than 1.136°.The end effector can perform automatic grinding according to the predetermined planning value within the safe force threshold of 30 N.This THA surgical robot system can meet the requirements of the hip replacement surgery for the accuracy,driving ability and robustness of the system. 展开更多
关键词 total hip arthroplasty(THA) robotics system surgical positioning
在线阅读 下载PDF
Research on indoor positioning and navigating technology based on scale hierarchical visual image feature matching
13
作者 BIE Haoze QIN Danyang +1 位作者 YANG Jiaqiang LI Sitong 《High Technology Letters》 2025年第2期164-174,共11页
The impact of location services on people’s lives has grown significantly in the era of widespread smart device usage.Due to global navigation satellite system(GNSS)signal rejection,weak signal strength in indoor env... The impact of location services on people’s lives has grown significantly in the era of widespread smart device usage.Due to global navigation satellite system(GNSS)signal rejection,weak signal strength in indoor environments and radio signal interference caused by multiwall environments,which collectively lead to significant positioning errors,vision-based positioning has emerged as a crucial method in indoor positioning research.This paper introduces a scale hierarchical matching model to tackle challenges associated with large visual databases and high scene similarity,both of which will compromise matching accuracy and lead to prolonged positioning delays.The proposed model establishes an image feature database using GIST features and speeded up robust feature(SURF)in the offline stage.In the online stage,a positioning navigating algorithm is constructed based on Dijkstra’s path planning.Additionally,a corresponding Android application has been developed to facilitate visual positioning and navigation in indoor environments.Experimental results obtained in real indoor environments demonstrate that the proposed method significantly enhances positioning accuracy compared with similar algorithms,while effectively reducing time overhead.This improvement caters to the requirements for indoor positioning and navigation,thereby meeting user needs. 展开更多
关键词 visual feature scale hierarchy feature matching indoor positioning indoor navigation
在线阅读 下载PDF
Cooperative Positioning Method for Multi-unmanned Systems Based on Confidence Evaluation
14
作者 SHI Chenfa XIONG Zhi +3 位作者 WU Tianxu LI Qijie WANG Huiming ZHOU Haoyu 《Transactions of Nanjing University of Aeronautics and Astronautics》 2025年第S1期38-50,共13页
In order to solve the problem of limited computational resources of multi-unmanned systems airborne navigation platform,a distributed cooperative positioning method based on confidence evaluation is proposed.Firstly,t... In order to solve the problem of limited computational resources of multi-unmanned systems airborne navigation platform,a distributed cooperative positioning method based on confidence evaluation is proposed.Firstly,the impact of ranging error,priori information,spatial geometric configuration and adjacent nodes count on cooperative positioning performance are analyzed individually.Secondly,a confidence evaluation method for measurement information of adjacent nodes is designed according to the cooperative positioning principle,which comprehensively considers the coupling relationship between influencing factors.Finally,a distributed cooperative navigation filter based on inter-vehicle ranging is designed.Simulation studies show that confidence evaluation method proposed in this paper can effectively characterize the contribution of measurement information to positioning results,and positioning accuracy under the proposed method is improved by more than 15%compared with the traditional screening methods based on optimal geometric configuration and closest distance. 展开更多
关键词 confidence evaluation distributed architecture cooperative positioning dilution of precision multi-source fusion
在线阅读 下载PDF
Anti-spoofing performance analysis of typical GNSS-based railway train positioning schemes
15
作者 Siqi Wang Jiang Liu +3 位作者 Baigen Cai Jian Wang Debiao Lu Wei Jiang 《High-Speed Railway》 2025年第1期37-43,共7页
Global Navigation Satellite Systems(GNSSs)are vulnerable to both unintentional interference and intentional attacks,making it difficult to meet the stringent safety requirements of railway train control systems.The gr... Global Navigation Satellite Systems(GNSSs)are vulnerable to both unintentional interference and intentional attacks,making it difficult to meet the stringent safety requirements of railway train control systems.The growing threat to information security posed by spoofing attacks has received limited attention.This study investigates the impact of GNSS spoofing attacks on train positioning,emphasizing their detrimental effects on the accuracy and availability of train location report functions for train operation control.To explore the antispoofing performance of typical GNSS-based train positioning schemes,specific approaches,and system architectures are designed under two GNSS-alone and two GNSS-integrated train positioning schemes.Field data are utilized to establish spoofing attack scenarios for GNSS-based train positioning,with which the anti-spoofing capabilities of different train positioning schemes are evaluated.Experimental results indicate that under specific conditions,the GNSS-integrated positioning schemes demonstrate superior GNSS spoofing suppression capabilities.Results of the tests present valuable guidance for designers and manufacturers in developing more advanced and resilient train positioning solutions and equipment for the next generation of train control systems,thereby promoting the applications of GNSS technology in railway systems. 展开更多
关键词 Railway train control Global navigation satellite system Train positioning Interference attack Anti-spoofing
在线阅读 下载PDF
Determining the natural vibration period of towering structure using GNSS precise point positioning
16
作者 WANG Zhiming WU Jizhong 《Journal of Southeast University(English Edition)》 2025年第2期199-206,共8页
This study explores the use of the Global Navigation Satellite System(GNSS)precise point positioning(PPP)technology to determine the natural vibration periods of towering structures through simulations and field testi... This study explores the use of the Global Navigation Satellite System(GNSS)precise point positioning(PPP)technology to determine the natural vibration periods of towering structures through simulations and field testing.During the simulation phase,a GNSS receiver captured vi-bration waveforms generated by a single-axis motion simulator based on preset signal parameters,analyzing how different satellite system configurations affect the efficiency of extracting vibration parameters.Subsequently,field tests were conducted on a high-rise steel singletube tower.The results indicate that in the simulation environment,no matter the PPP positioning data under single GPS or multisystem combination,the vibration frequency of singleaxis motion simulator can be accurately extracted after frequency do-main analysis,with multisystem setups providing more precise amplitude parameters.In the field test,the natural vibration periods of the main vibration modes of high-rise steel single-tube tower measured by PPP technology closely match the results of the first two modes derived from finite element analysis.The first mode period calculated by the em-pirical formula is approximately 6%higher than those determined through finite element analysis and PPP.This study demonstrates the potential of PPP for structural vibration analysis,offering significant benefits for assessing dynamic responses and monitoring the health of towering structures. 展开更多
关键词 towering structure natural vibration period precise point positioning frequency domain decomposition
在线阅读 下载PDF
Study on the Effect of Spot Size and Non-Linearity on PSD Positioning Accuracy
17
作者 WANG Zechuan ZHANG Zhenhua +3 位作者 CHENG Shaowei YANG Haima HUANG Bo LIU Jin 《Wuhan University Journal of Natural Sciences》 2025年第3期213-221,共9页
Position-sensitive detector(PSD)is widely used in precision measurement fields such as flatness detection,auto-collimator systems,and degrees of freedom testing.However,due to factors such as uneven surface resistance... Position-sensitive detector(PSD)is widely used in precision measurement fields such as flatness detection,auto-collimator systems,and degrees of freedom testing.However,due to factors such as uneven surface resistance and differences in electrode structures,the nonlinearity of PSD becomes increasingly severe as the photosensitive surface moves from the center toward the edges of the four electrodes.To address this issue,a PSD nonlinearity correction algorithm is proposed.The algorithm utilizes the particle swarm optimization(PSO)algorithm to determine the optimal weights and thresholds,providing better initial parameters for the back propagation(BP)neural network.The BP neural network then iterates continuously until the error conditions are met,completing the correction process.Furthermore,a PSD nonlinearity correction system was developed,and the influence of different spot sizes on PSD positioning accuracy was simulated based on the current equation under the Gaussian spot model.This validated the robustness of the correction algorithm under varying spot sizes.The results demonstrate that the overall optimized error is reduced by 84.51%,and for spot sizes smaller than 1 mm,the error reduction exceeds 93.89%.This method not only meets the measurement accuracy requirements but also extends the measurement range of PSD. 展开更多
关键词 position-sensitive detector particle swarm algorithm nonlinear optimization spot characteristics positioning accuracy
原文传递
Evaluation of reduction quality and implant positioning in intertrochanteric fracture fixation:A review of key radiographic parameters
18
作者 Matthias Wittauer Joseph Henry +3 位作者 Guillermo Sánchez-Rosenberg Anton Philip Lambers Christopher W Jones Piers J Yates 《World Journal of Orthopedics》 2025年第8期45-57,共13页
Intertrochanteric fractures,prevalent among older adults,pose significant clinical challenges due to high morbidity,mortality,and complication rates.Despite advancements in surgical methods and implant technology,one-... Intertrochanteric fractures,prevalent among older adults,pose significant clinical challenges due to high morbidity,mortality,and complication rates.Despite advancements in surgical methods and implant technology,one-year mortality remains between 20%and 30%,with up to 20%of survivors requiring revision surgery due to mechanical complications.Accurate fracture reduction and precise implant positioning are critical determinants of successful outcomes.This review synthesizes current literature on key radiographic parameters essential for evaluating fracture reduction quality and implant placement in intertrochanteric fracture fixation.Standardized intraoperative imaging techniques,such as correct anteroposterior and lateral fluoroscopic views,are fundamental for identifying malalignment.Important radiographic measures include the neck shaft angle,greater trochanter orthogonal line,anterior cortical line,and calcar displacement assessment.Reduction quality indices,notably the Baumgaertner and Chang Reduction Quality Criteria,provide reliable frameworks for predicting mechanical complications.Additionally,implant positioning parameters—including tip-apex distance,Calcar-referenced tip-apex distance,Cleveland zones,and Parker’s ratio index—are discussed as predictors of mechanical complications.Enhanced understanding and application of these radiographic criteria can improve surgical precision,reduce complications,and ultimately optimize patient outcomes in intertrochanteric fracture management. 展开更多
关键词 Intertrochanteric fractures Hip Cephalomedullary nail Reduction quality Implant positioning Complications Radiographic assessment
暂未订购
Time bias compensation model considering multi-layer sound speed perturbation for underwater acoustic positioning
19
作者 Yuanxi Yang Shengqiu Zhang Shuqiang Xue 《Acta Oceanologica Sinica》 2025年第2期104-113,共10页
Spatio-temporal variation of sound speed,in seafloor geodetic precise positioning,can always be attributed to the time error.Firstly,this paper analyzes the existing error compensation model,i.e.,the time ratio model,... Spatio-temporal variation of sound speed,in seafloor geodetic precise positioning,can always be attributed to the time error.Firstly,this paper analyzes the existing error compensation model,i.e.,the time ratio model,which is expressed by the recorded time multiplying a ratio coefficient.And then a time split model is proposed by expressing the acoustic ray traveling time as the recorded time pluses a perturbation time error.The theoretical differences between the proposed time bias compensation model and the time ratio model are analyzed.Under the new framework,sound speed perturbation models with optimal single-layer spatial gradient and multi-layer spatial gradients are developed to compensate for sound speed error in the complex cases.Numerical computation shows that the simple time split model keeps the same accuracy as some complicated models while considering the distribution of random error.Furthermore,multi-layer model can improve the positioning accuracy without putting the pressure on parametrization. 展开更多
关键词 seafloor geodesy underwater positioning GNSS-acoustic sound speed error resilient observation model
在线阅读 下载PDF
Positioning error prediction and compensation for the multi-boom working mechanism of a drilling jumbo
20
作者 Yuming CUI Songyong LIU +2 位作者 Zhengqiang SHU Zhenli LV Lie LI 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 2025年第1期66-77,共12页
A rock-drilling jumbo is the main piece of tunneling equipment used in the energy and infrastructure industries in various countries.The positioning accuracy of its drilling boom greatly affects tunneling efficiency a... A rock-drilling jumbo is the main piece of tunneling equipment used in the energy and infrastructure industries in various countries.The positioning accuracy of its drilling boom greatly affects tunneling efficiency and section-forming quality of mine roadways and engineering tunnels.In order to improve the drilling-positioning accuracy of a three-boom drilling jumbo,we established a kinematics model of the multi-degree-of-freedom(multi-DOF)multi-boom system,using the improved Denavit-Hartenberg(D-H)method,and obtained the mapping relationship between the end position and the amount of motion of each joint.The error of the inverse kinematics calculation for the drilling boom is estimated by an analytical method and a global search algorithm based on particle swarm optimization(PSO)for a straight blasting hole and an inclined blasting hole.On this basis,we propose a back-propagation(BP)neural network optimized by an improved sparrow search algorithm(ISSA)to predict the positioning error of the drilling booms of a three-boom drilling jumbo.In order to verify the accuracy of the proposed error compensation model,we built an automatic-control test platform for the boom,and carried out a positioning error compensation test on the boom.The results show that the average drilling-positioning error was reduced from 9.79 to 5.92 cm,and the error was reduced by 39.5%.Therefore,the proposed method effectively reduces the positioning error of the drilling boom,and improves the accuracy and efficiency of rock drilling. 展开更多
关键词 Multi-boom rock-drilling jumbo Kinematic model Neural network optimization positioning error prediction
原文传递
上一页 1 2 250 下一页 到第
使用帮助 返回顶部