检索结果-南通市图书馆

Journal of Traffic and Transportation Engineering(English Edition) 2019年第5期6卷 504-513页

作者： Bilin Han Harry Timmermans Urban Planning Group Eindhoven University of Technology

Organizing schedules and allocating time to different activities is always a challenge in dual-earner households,especially when they have children.Parents may need to link their schedule to those of their children to allow them escorting their children to school or to take care or be with their children at home.This paper reports the results of an analysis of the degree of synchronization of home departure and arrival times in dual earner households with children,where the degree of synchronization is defined as the gap between departure and arrival times of a parent and child.Using activity-travel diary data of different household members,a random parameters regression model is estimated to examine differences in time gaps in home departure and arrival times between parents and children as a function of gender,day of the week,age of the youngest child,and other socio-demographic characteristics.The results of the analysis provide insight into factors influencing the degree of synchronization and coordination of double activity-travel scheduling decisions in households with children.Findings indicate that gender,number of children in the household,age of the youngest child,travel within or outside peak hours,day of the week,transport mode used for the work commute and household income level significantly affect time gaps,especially arrival time gaps.

关键词： Home departure and arrival times Synchronization Time gap Dual-earner households Random parameters panel regression model

Obstacle-avoiding path planning for multiple autonomousunderwater vehicles with simultaneous arrival

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2019年第1期62卷 121-132页

作者： YAO Peng QI ShengBo College of Engineering Ocean University of China

This paper focuses on planning the obstacle-avoiding paths of multiple autonomous underwater vehicles(AUVs) in complex ocean environment, with the time coordination of simultaneous arrival. By imitating the nature phenomenon that river water avoids rocks and reaches the destination, the interfered fluid dynamical system(IFDS) is first presented to obtain the single-AUV path for obstacle avoidance, where the modulation matrix is calculated to quantify the influence of obstacles especially. Then the two-layer comprehensive adjustment to path length and voyage speed is utilized, aiming to achieve the simultaneous arrival at destination between multi-AUVs. By adjusting reactive parameters of IFDS, the former is to roughly ensure the intersection of AUVs' potential arrival time range to be non-null. On this basis, the latter adjusts each AUV's voyage speed finely using the consensus method with state predictor, which has faster convergence speed. If the multi-AUVs communication network is connected, the whole system will quickly converge to the consensus state, i.e., the estimated time of arrival(ETA) of each AUV tends to be equal. Finally, the simulation results verify the advantages of our proposed method.

关键词： autonomous underwater vehicles (AUVs) obstacle-avoiding paths simultaneous arrival interfered fluid dynamical system (IFDS) consensus method with state predictor

Dual-cavity beam arrival time monitor design for the Shanghai soft X-ray FEL facility

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2019年第5期30卷 14-21页

作者： Shan-Shan Cao Ren-Xian Yuan Jian Chen Yong-Bin Leng Shanghai Institute of Applied Physics Chinese Academy of Sciences University of Chinese Academy of Sciences

Free electron lasers provide high-power and ultrashort pulses with extreme brightness. In order to improve a facility's capabilities and explore the possibility of performing high-resolution time-resolved experiments, a beam arrival time resolution under 100 fs is required. In this article, a novel beam arrival time monitor(BAM)equipped with two cavities has been designed and a beam flight time measurement scheme based on the BAM prototype has been proposed to estimate phase jitter in the signal measurement system. The two BAM cavities work at different frequencies and the frequency difference is designed to be 35 MHz. Therefore, a self-mixing intermediate frequency signal can be generated using the two cavities. The measured beam flight time shows a temporal deviation of 37 fs(rms).

关键词： Beam arrival time monitor Dual-cavities Beam flight time Self-mixing

SIMULATION OF arrival TIME DISTRIBUTION OF SHOWER PARTICLES AT LARGE DISTANCES FROM CORE

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 1990年第3期33卷 299-307页

作者：戴宏跃笠原克昌 Institute of High Energy Physics Academia Sinica Beijing 100039 PRC Institute For Cosmic Ray Research University of Tokyo Japan

By a Monte Carlo simulation, the arrival time (delay time) distribution o?shower particles at large distance (>100 m) from the air shower core has been simulated.The characteristics of the distribution are expressed by three parameters. An approximate formula for the distribution has also been derived. The distribution is found depending strongly on the distance from the core, but almost independent of the age, zenith angle, primary energy, primary compositions. An apparent difference is seen in some cases in the distribution from event to event when the number of particles is small. This is only due to statistical fluctuation. Therefore it is important to take into account the experimental conditions in the comparison of the present results with experimental data.

关键词： cosmic ray extensive air shower Monte Carlo simulation arrival time distribution.

Active Source Seismic Identification and Automatic Picking of the P-wave First arrival Using a Convolutional Neural Network

在线全文

学校读者我要写书评

暂无评论

Earthquake Research in China 2019年第2期33卷 288-304页

作者： XU Zhen WANG Tao XU Shanhui WANG Baoshan FENG Xuping SHI Jing YANG Minghan Institute of Earth Exploration and Sensing(IEES) School of Earth Sciences and EngineeringNanjing UniversityNanjing 210046China Institute of Geophysics China Earthquake AdministrationBeijing 100081China School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China

In seismic data processing,picking of the P-wave first arrivals takes up plenty of time and labor,and its accuracy plays a key role in imaging seismic structures.Based on the convolution neural network(CNN),we propose a new method to pick up the P-wave first arrivals automatically.Emitted from MINI28 vibroseis in the Jingdezhen seismic experiment,the vertical component of seismic waveforms recorded by EPS 32-bit portable seismometers are used for manually picking up the first arrivals(a total of 7242).Based on these arrivals,we establish the training and testing sets,including 25,290 event samples and 710,616 noise samples(length of each sample:2 s).After 3,000 steps of training,we obtain a convergent CNN model,which can automatically classify seismic events and noise samples with high accuracy(>99%).With the trained CNN model,we scan continuous seismic records and take the maximum output(probability of a seismic event)as the P-wave first arrival time.Compared with STA/LTA(short time average/long time average),our method shows higher precision and stronger anti-noise ability,especially with the low SNR seismic data.This CNN method is of great significance for promoting the intellectualization of seismic data processing,improving the resolution of seismic imaging,and promoting the joint inversion of active and passive sources.

关键词： CNN Active source seismic identification First arrival picking Anti-noise ability

Weak signal direction of arrival estimation for colocated multiple-input multiple-output sonar array

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Acoustics 2019年第3期38卷 253-272页

作者： CHENG Xue WANG Yingmin School of Marine Science and Technology Northwestern Polytechnical UniversityXi'an 710072 Key Laboratory of Ocean Acoustics and Sensing(Northwestern Polytechnical University) Ministry of Industry and Information TechnologyXi'an 710072

In order to suppress the influence of symmetrical noise component on multiple-input multiple-output(MIMO)sonar’s direction of arrival(DOA)estimation under the condition of low signal-to-noise ratio,we propose a DOA estimation algorithm based on covariance matrix reconstruction method.Firstly,the noise field can be decomposed into symmetrical noise field and asymmetrical noise field.We utilize symmetry property of colored noise matrix and the feature that the imaginary part of covariance matrix has no relation with the symmetry noise to remove the real part of covariance matrix.This operation helps to suppress the influence of colored noise on DOA estimation accuracy.Based on the principle of the imaginary matrix part displacement and the dimension reduction transformation method,the real part of covariance matrix is reconstructed,which helps to suppress the bilateral spectrum interference.Thereafter,Toeplitz method is applied for the covariance matrix decorrelation amendment,and a noise subspace is formed by singular value decomposition(SVD).Finally,we can estimate the DOA of target signals.Both theoretical analysis results and numerical simulation results verify the symmetrical noise suppression performance of this algorithm,and the estimation performance of target azimuth is improved obviously.This method has the characteristics of lower operational complexity,higher degrees of freedom and stronger target resolution.

关键词： DOA Weak signal direction of arrival estimation for colocated multiple-input multiple-output sonar array

Taylor expansion MUSIC method for joint DOD and DOA estimation in a bistatic MIMO array

在线全文

学校读者我要写书评

暂无评论

Frontiers of Information Technology & Electronic Engineering 2019年第6期20卷 842-848页

作者： Wen-tao SHI Qun-fei ZHANG Cheng-bing HE Jing HAN School of Marine Science and Technology Northwestern Polytechnical University Xi'an 710072 China Science and Technology on Electronic Information Control Laboratory Chengdu 610041 China

We propose a Taylor expansion multiple signal classification(TE MUSIC) method for joint direction of departure(DOD) and direction of arrival(DOA) estimation in a bistatic multiple-input multiple-output(MIMO)array. First, using a Taylor expansion of the steering vector, a two-dimensional(2D) search in the conventional MUSIC method for MIMO arrays is reduced to a two-step one-dimensional(1D) search in the proposed TE MUSIC method. Second, DOAs of the targets can be achieved via Lagrange multiplier by a 1D search. Finally, substituting the DOA estimates into the 2D MUSIC spectrum function, DODs of the targets are obtained by another 1D search.Thus, the DOD and DOA estimates can be automatically paired. The performance of the proposed method is better than that of the MIMO ESPRIT method, and is similar to that of the 2D MUSIC method. Furthermore, due to the 1D search, the TE MUSIC method avoids the high computational complexity of the 2D MUSIC method. Simulation results are presented to show the effectiveness of the proposed method.

关键词： Bistatic multiple-input multiple-output array Direction of departurc Direction of arrival Multiple signal classification Taylor expansion Computational complexity

Interindividual variation and consistency of migratory behavior in the Eurasian woodcock

在线全文

学校读者我要写书评

暂无评论

Current Zoology 2020年第2期66卷 155-163页

作者： Alessandro TEDESCHI Michele SORRENTI Michele BOTTAZZO Mario SPAGNESI Ibon TELLETXEA Ruben IBANEZ Nicola TORMEN Federico DE PASCALIS Laura GUIDOLIN Diego RUBOLINI Associazione"Amici di Scolopax" Via Roma57Mugnano del CardinaleAVI-83027Italy Federazione Italiana della Caccia Ufficio Avifauna MigratoriaVia Salaria 298/ARoma1-00199Italy Veneto Agricoltura Viale dell’Universita 14LegnaroP D1-35020Italy Ekoclub International Via per Volano 45Volano di CodigoroFE1-44020Italy Club de Cazadores de Becada Avda.Schulz 84 dchaGijonE-33208Spain Dipartimento di Biologia Universita degli Studi di PadovaVia U.Bassi 58/bPadova1-35131Italy Dipartimento di Scienze e Politiche Ambientali Universita degli Studi di Milanovia Celoria 26Milano1-20133Italy

Diverse spatio-temporal aspects of avian migration rely on relatively rigid endogenous programs.However,flexibility in migratory behavior may allow effective coping with unpredictable variation in ecological conditions that can occur during migration.We aimed at characterizing inter-and intraindividual variation of migratory behavior in a forest-dwelling wader species,the Eurasian woodcock Scolopax rusticola,focusing on spatio-temporal consistency across repeated migration episodes.By satellite-tracking birds from their wintering sites along the Italian peninsula to their breeding areas,we disclosed a remarkable variability in migration distances,with some birds flying more than 6,000 km to Central Asian breeding grounds(up to 101°E).Prebreeding migration was faster and of shorter duration than postbreeding migration.Birds moving over longer distances migrated faster during prebreeding migration,and those breeding at northernmost latitudes left their wintering areas earlier.Moreover,birds making longer migrations departed earlier from their breeding sites.Breeding site fidelity was very high,whereas fidelity to wintering areas increased with age.Migration routes were significantly consistent,both among repeated migration episodes and between pre-and postbreeding migration.Prebreeding migration departure date was not significantly repeatable,whereas arrival date to the breeding areas was highly repeatable.Hence,interindividual variation in migratory behavior of woodcocks was mostly explained by the location of the breeding areas,and spatial consistency was relatively large through the entire annual cycle.Flexibility in prebreeding migration departure date may suggest that environmental effects have a larger influence on temporal than on spatial aspects of migratory behavior.

关键词： arrival date breeding latitude flexibility repeatability satellite tracking wading birds

Relocation of the M8.0 Wenchuan earthquake and its aftershock sequence

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Earth Sciences 2008年第12期51卷 1703-1711页

作者： HUANG Yuan WU JianPing ZHANG TianZhong ZHANG DongNing Institute of Geophysics China Earthquake AdministrationBeijing 100081China

We relocated M8.0 Wenchuan earthquake and 2706 aftershocks with M≥2.0 using double-difference algorithm and obtained relocations of 2553 events. To reduce the influence of lateral variation in crustal and upper mantle velocity structure, we used different velocity models for the east and west side of Longmenshan fault zone. In the relocation process, we added seismic data from portable seismic sta-tions close to the shocks to constrain focal depths. The precisions in E-W, N-S, and U-D directions after relocation are 0.6, 0.7, and 2.5 km respectively. The relocation results show that the aftershock epi-centers of Wenchuan earthquake were distributed in NE-SW direction, with a total length of about 330 km. The aftershocks were concentrated on the west side of the central fault of Longmenshan fault zone, excluding those on the north of Qingchuan, which obviously deviated from the surface fault and passed through Pingwu-Qingchuan fault in the north. The dominant focal depths of the aftershocks are between 5 and 20 km, the average depth is 13.3 km, and the depth of the relocated main shock is 16.0 km. The depth profile reveals that focal depth distribution in some of the areas is characterized by high-angle westward dipping. The rupture mode of the main shock features reverse faulting in the south, with a large strike-slip component in the north.

关键词： Wenchuan earthquake Longmenshan fault zone earthquake relocation regional velocity model first arrival

Joint frequency, 2D AOA and polarization estimation using fourth-order cumulants

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2000年第3期43卷 297-303页

作者：王建英陈天琪 University of Electronic Science and Technology of China Chengdu 610054 China

Based on fourth-order cumulant and ESPRIT algorithm, a novel joint frequency, two-dimensional angle of arrival (2D AOA) and the polarization estimation method of incoming multiple independent spatial narrow-band non-Gaussian signals in arbitrary Gaussian noise environment are proposed . The array is composed of crossed dipoles parallel to the coordinate axes. The crossed dipole positions are arbitrarily distributed. Computer simulation confirms its feasibility.

关键词： frequency two-dimensional angles of arrival polarization ESPRIT fourth-order cumulant.