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AR assistance for efficient dynamic target search

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Computational Visual Media 2023年第1期9卷 177-194页

作者： Zixiang Zhao Jian Wu Lili Wang State Key Laboratory of Virtual Reality Technology and Systems School of Computer Science and EngineeringBeihang UniversityBeijingChina

When searching for a dynamic target in an unknown real world scene,search efficiency is greatly reduced if users lack information about the spatial structure of the scene.Most target search studies,especially in robotics,focus on determining either the shortest path when the target’s position is known,or a strategy to find the target as quickly as possible when the target’s position is unknown.However,the target’s position is often known intermittently in the real world,e.g.,in the case of using surveillance cameras.Our goal is to help user find a dynamic target efficiently in the real world when the target’s position is intermittently known.In order to achieve this purpose,we have designed an AR guidance assistance system to provide optimal current directional guidance to users,based on searching a prediction graph.We assume that a certain number of depth cameras are fixed in a real scene to obtain dynamic target’s position.The system automatically analyzes all possible meetings between the user and the target,and generates optimal directional guidance to help the user catch up with the target.A user study was used to evaluate our method,and its results showed that compared to free search and a top-view method,our method significantly improves target search efficiency.

关键词： augmented reality(AR) search guidance

Structural characteristics of electrohydrodynamic jets induced by a blade-plane actuator subjected to highly non-uniform electric fields:Parametric investigation through the particle image velocimetry techniques

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High Voltage 2023年第1期8卷 183-195页

作者： Zelu Yan Christophe Louste Philippe Traoré Jian Wu jian'an Fang Logistics Engineering College Shanghai Maritime UniversityShanghaiChina Institut PPRIME Universitéde PoitiersPoitiersFrance Key Laboratory of Aerospace Thermophysics School of Energy Science and EngineeringHarbin Institute of TechnologyHarbinChina College of Information Science and Technology Donghua UniversityShanghaiChina

This study set out to systematically investigate the structural characteristics of plane electrohydrodynamic jets through the particle image velocimetry(PIV)techniques.Due to the wide range of applied voltages and electrode gaps under various experimental conditions,an assessment of the image quality and a statistical analysis of the velocity fields are first performed to ensure the validity of the PIV measurements,which were originally applied purely to fluid mechanics.The results indicate that the time interval between two consecutive images should be pre-adjusted to reduce the number of uncorrelated vector fields.Moreover,the minimum number of instantaneous fields should be achieved for an accurate calculation of the time-averaged fields.An equivalent electric field criterion adapted to the asymmetric electrode configuration is defined to find similarities in flow structures under different voltage and electrode gap conditions.As the applied electric field increases,three injection regimes are identified and the current increases almost linearly,indicating a large conduction current component.The decrease in charge density due to recombination proves to be relevant in all cases of this study.Analogous to the parametric analysis approach for classical jets and thermal plumes,the evolution of the coefficients of axial velocity,half-width and turbulence intensity are investigated.

关键词： plane particle blade

Seismic Hazard Analysis of China's Mainland Based on a New Seismicity Model

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International Journal of Disaster Risk Science 2023年第2期14卷 280-297页

作者： Weijin Xu Jian Wu Mengtan Gao Institute of Geophysics China Earthquake AdministrationBeijing100081China China Earthquake Disaster Prevention Center Beijing100029China

Based on the seismic source model in the Fifth Generation Seismic Ground Motion Parameters Zonation Map of China(FGSGMPZMC),a new seismic fault model,the new zonation of seismic risk areas(SRAs),and the estimation of seismicity rates for 2021-2030,this study constructed a new time-dependent seismic source model of China’s mainland,and used the probabilistic seismic hazard analysis method to calculate seismic hazard by selecting the ground motion models(GMMs)suitable for seismic sources in China.It also provided the probabilities of China’s mainland being affected by earthquakes of modified Mercalli intensity(MMI)Ⅵ,Ⅶ,Ⅷ,Ⅸ,and≥Ⅹin 2021-2030.The spatial pattern of seismic hazards presented in this article is similar to the pattern of the FGSGMPZMC,but shows more details.The seismic hazards in this study are higher than those in the FGSGMPZMC in the SRAs and fault zones that can produce large earthquakes.This indicates that the seismic source model construction in this study is scientific and reasonable.There are certain similarities between the results in this study and those of Rong et al.(2020)and Feng et al.(2020),but also disparities for specific sites due to differences in seismic source models,seismicity parameters,and GMMs.The results of seismic hazard may serve as parameter input for future seismic risk assessments.The hazard results can also be used as a basis for the formulation of earthquake prevention and mitigation policies for China’s mainland.

关键词： China’s mainland New seismicity model Probabilistic seismic hazard analysis(PSHA) Seismic fault model Seismic risk areas

ELF-EM Signal Processing While Drilling Based on Human-Computer Interaction Combined Algorithm

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China Communications 2023年第6期20卷 178-198页

作者： Fukai Li Jian Wu jian Chen Huaiyun Peng Yehuo Fan School of Telecommunications Engineering Xidian UniversityXi’an 710071China National Key Laboratory of Electromagnetic Environment China Research Institute of Radiowave PropagationQingdao 266107China

In the electromagnetic wave measurement while drilling(EM MWD), the extra low frequency electromagnetic wave(ELF-EM) below 20Hz was usually chosen as the carrier because of its transmission characteristics in the formation. However, as the drilling depth increases, the electromagnetic wave signals received on the ground gradually weaken, becoming lower than a certain signal-to-noise ratio(SNR)and making it impossible to be decoded or transmitted.The attenuation of electromagnetic wave in the formation is definitely one of the causes, but what matters more is the influence of environment noise at the well site, especially the in-band interference noise and random noise. Targeting at the out-of-band noise, the bandpass filter, which is invalid to the in-band noise,can be used to eliminate the noise out of the carrier’s main band. To cope with the question, an algorithm based on the human-computer interaction detection(HCID) was proposed in this paper that improves the SNR of ELF-EM signals, with the effective transmission distance of EM MWD increased. In this paper,the validity of the proposed HCID algorithm was verified through communication processing performance simulation and field data comparison, thus providing a reference for engineers and technicians in this field.Theoretical analysis and experimental data verification show that the combined algorithm decodes effectively under the in-band interference noise of-80d B SNR and in-band random noise of-17d B SNR.

关键词： measurement while drilling ELF-EM Inband noise HCID transmission distance

Dielectric permittivity of dusty plasma in the Earth's mesosphere

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Earth and Planetary Physics 2021年第1期5卷 117-120页

作者： Hui Li Jian Wu National Key Laboratory of Electromagnetic Environment(LEME) China Research Institute of Radio Wave PropagationQingdao 266109China

This paper deals with the dielectric permittivity of dusty plasma in the earth’s mesosphere.We give expressions for the complex dielectric permittivity of dusty plasma,taking into account the effects of the dust charging process and magnetic field.We discuss the dielectric permittivity of dusty plasma in several cases,such as high frequency approximation,parallel propagation in MF/HF band,and effects of plasma movement.Finally,the expressions are employed to study the phenomenon of radar echoes from the polar summer mesosphere.We report that dielectric permittivity caused by the dust charging process gives a radar cross section proportional to ω–4 and produces a number density of charged dust that agrees with measurements of mesopheric radar echoes.

关键词： dusty plasma dielectric permittivity polar summer mesosphere

Low-degree toroidal modes from the Sumatra-Andaman event observed by superconducting gravimeters

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Geodesy and Geodynamics 2019年第6期10卷 477-484页

作者： Chuang Xu Hangtao Yu Guangyu jian Shiqi Deng Boyang Zhou Yihao wu Department of Surveying Engineering School of Civil and Transportation EngineeringGuangdong University of TechnologyNo.100 Waihuan Xi RoadGuangzhou 510006China State Key Laboratory of Geodesy and Earth’s Dynamics Institute of Geodesy and GeophysicsChinese Academy of SciencesNo.340 Xu Dong AvenueWuhan 430077China State Key Laboratory of Information Engineering in Surveying Mapping and Remote SensingWuhan UniversityWuhan 430079China School of Earth Science and Engineering Hohai UniversityNanjing 210098China

The complex frequencies of the low-degree toroidal modes are helpful in constraining the mantle structure.In the early years,the traditional method to detect the low-degree toroidal modes is seismic approach,which is primarily limited by the horizontal noise of seismometers.Recently,it has been proved that gravity method is competitive.Therefore,we re-estimated or newly estimated the complex frequencies of the toroidal modes below 1.5 mHz excited by the 2004 Sumatra-Andaman event using gravity method in this paper.The results show that(1)The quality factors of0 T5-0 T9 and1 T2-1 T3 are estimated from superconducting gravity data for the first time;(2)The estimated frequencies and quality factors for0 T2-0 T9 and1 T2-1 T3 are consistent with those provided by previous publications,which verifies the correctness and effectiveness of our estimations;(3)The maximum difference of frequencies between our results and those from CPREM is on the order of 0.01 mHz and the maximum difference of quality factors is at the level of 10.

关键词： Low-degree toroidal modes Superconducting gravity data Complex frequency Quality factor

Incoherent scatter radar (ISR) observations of high-frequency enhanced ion and plasma lines induced by X/O mode pumping around the critical altitude

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Earth and Planetary Physics 2022年第4期6卷 305-312页

作者： Jun wu Jian Wu IHaggstrom Tong Xu ZhengWen Xu YanLi Hu National Key Laboratory of Electromagnetic Environment China Research Institute of Radio Wave PropagationBeijing 102206China European Incoherent Scatter Scientific Association(EISCAT) KirunaSE-98192Sweden

Analysis of Incoherent Scatter Radar(ISR)data collected during an experiment involving alternating O/X mode pumping reveals that the high-frequency enhanced ion line(HFIL)and plasma line(HFPL)did not appear immediately after the onset of pumping,but were delayed by a few seconds.By examining the initial behaviors of the ion line,plasma line,and electron temperature,as well as ionosphere conditions,we find that(1)the HFIL and HFPL were delayed not only in the X mode pumping but also in the O mode pumping and(2)the HFIL was not observed prior to enhancement of the electron temperature.Our analysis suggests that(1)leakage of the X mode to the O mode pumping may not be ignored and(2)spatiotemporal uncertainties and spatiotemporal variations in the profiles of ion mass and electron density may have played important roles in the apparent failure of the Bragg condition to apply;(3)nevertheless,the absence of parametric decay instability(PDI)cannot be ruled out,due to our inability to match conditions caused by the spatiotemporal uncertainties.

关键词： Incoherent Scatter Radar(ISR) ion line plasma line active ionosphere X/O mode

Comparisons of urban-related warming in Beijing using different methods to calculate the daily mean temperature

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Science China Earth Sciences 2019年第4期62卷 693-702页

作者： Deming ZHAO Jian Wu CAS Key Laboratory of Regional Climate-Environment for Temperate East Asia Institute of Atmospheric PhysicsChinese Academy of Sciences Department of Atmospheric Science Yunnan University

To evaluate the contribution of urban surface expansion to regional warming using different methods to calculate the daily mean surface air temperature(SAT), satellite-based images displaying urban surface expansion over the past 37 years(1980–2016) across China were collected for use in nested numerical experiments using the weather research and forecasting(WRF) regional climate model. The contribution of urban surface expansion to urban-related warming was determined using the daily mean SAT averages based on four time records each day(00, 06, 12, and 18 h UTC, T_4) and averages of the SAT maximum(Tmax) and minimum(Tmin)(Txn). The contribution of urban surface expansion to urban-related warming(relative value) in Beijing was 0.110°C per decade(22.8% of total warming) for T_4 and 0.094°C per decade(20.2%) for Txn. The values obtained when using T_4 were larger than those obtained when using Txn. Differences in the urban-related warming calculated using T_4 and Txncould be attributed to the smaller changing trends in Txnin the urban-surface expansion experiment, which resulted from a large changing trend in Tminand a much smaller changing trend in Tmax. The changes in the diurnal cycle of the energy budget due to urban surface expansion induced changes in the diurnal cycle of SAT, as evidenced by the four time records each day, as well as Tmaxand Tmin. This was especially true for periods of intense urban surface expansion, although the annual mean SAT calculated using Txnwas larger than that calculated using T_4. The increase in impervious area(walls, streets, etc.) due to urban surface expansion, as well as the widespread use of building materials with a large heat capacity resulted in a marked increase in ground heat flux in the daytime. This restricted the increase in SAT in the daytime, but promoted it at night. The increases in SAT due to urban surface expansion were not symmetrical, being smaller in the daytime and larger at night.

关键词： Urban surface expansion Surface air temperature Daily mean temperature Changing trend Urban-related warming

Research on Anthropomorphic Obstacle Avoidance Trajectory Planning for Adaptive Driving Scenarios Based on Inverse Reinforcement Learning Theory

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Engineering 2024年第2期33卷 133-145页

作者： Jian Wu Yang Yan Yulong Liu Yahui Liu School of Mechanical and Automotive Engineering Liaocheng UniversityLiaocheng 252000China 2 School of Vehicle and Mobility Tsinghua UniversityBeijing 100084China

The forward design of trajectory planning strategies requires preset trajectory optimization functions,resulting in poor adaptability of the strategy and an inability to accurately generate obstacle avoidance trajectories that conform to real driver behavior habits.In addition,owing to the strong time-varying dynamic characteristics of obstacle avoidance scenarios,it is necessary to design numerous trajectory optimization functions and adjust the corresponding parameters.Therefore,an anthropomorphic obstacle-avoidance trajectory planning strategy for adaptive driving scenarios is proposed.First,numerous expert-demonstrated trajectories are extracted from the HighD natural driving dataset.Subsequently,a trajectory expectation feature-matching algorithm is proposed that uses maximum entropy inverse reinforcement learning theory to learn the extracted expert-demonstrated trajectories and achieve automatic acquisition of the optimization function of the expert-demonstrated trajectory.Furthermore,a mapping model is constructed by combining the key driving scenario information that affects vehicle obstacle avoidance with the weight of the optimization function,and an anthropomorphic obstacle avoidance trajectory planning strategy for adaptive driving scenarios is proposed.Finally,the proposed strategy is verified based on real driving scenarios.The results show that the strategy can adjust the weight distribution of the trajectory optimization function in real time according to the“emergency degree”of obstacle avoidance and the state of the vehicle.Moreover,this strategy can generate anthropomorphic trajectories that are similar to expert-demonstrated trajectories,effectively improving the adaptability and acceptability of trajectories in driving scenarios.

关键词： Obstacle avoidance trajectory planning Inverse reinforcement theory Anthropomorphic Adaptive driving scenarios