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This article presents a trajectory design problem concerning the exploration of potentially hazardous near-Earth asteroids (PHAs) with reusable probes from cislunar space. A total of 20 probes, making round trips departing from and returning to a service space station in a lunar distant retrograde orbit, are expected to explore as many PHAs as possible by means of close flyby within a 10-year time window. The trajectory design problem was released in the 12th edition of China's Trajectory Optimization Competition on 20 August 2022, and a total of 10 sets of trajectory solutions were submitted. As the authors who proposed the competition problem, we present in this article the problem descriptions, trajectory analysis, and design, as well as an impressive trajectory solution in which a total of 105 PHAs are explored. It is concluded that taking advantage of reusable probes from cislunar space is a promising option to efficiently explore large numbers of PHAs. [ABSTRACT FROM AUTHOR]

In order to alleviate the increasingly serious traffic congestion problem in China, realize intelligent traffic control, and provide accurate and real-time traffic flow prediction data for traffic flow guidance and traffic travel, this paper designs a GPS-based vehicle trajectory fusion optimization deep model BN-LSTM-CNN which makes full use of the temporal and spatial correlation characteristics of dynamic traffic flow to improve the accuracy of short-term traffic flow prediction. The parameters of the historical GPS dynamic trajectory of the traffic network link are converted into a two-dimensional matrix image of time and space relationship. First, the spatial features are input to the CNN network, and the spatial dependence relationship between the links is mined, then the traffic flow time series modeling is performed with a four-layer ConvLSTM network, and the BN normalization layer is added to normalize the activation value of the previous layer on each batch, so that the model can obtain higher training accuracy and quickly complete the prediction of the traffic flow state in a certain period of time in the future. The experimental results show that the prediction model is fast to optimize, the prediction error is the smallest compared with other methods, and it can meet the real-time requirements of urban traffic control. [ABSTRACT FROM AUTHOR]

An improved non-dominated sorting genetic algorithm Ⅱ（NSGA-Ⅱ）for solving the large-scale optimization problem of trajectory planning in the strategic stage is designed. Under the framework of the classic NSGA-Ⅱ，an adaptive crossover operator and an adaptive mutation operator are used to accelerate the convergence speed of the algorithm and improve the quality of the solution，and an evaluation index to measure the pros and cons of the Pareto solution set is given. Considering the introduction of large-scale fourdimensional trajectories inevitably increases the complexity of the problem，this paper proposes an effective strategic conflict resolution model，which aims to minimize the number of potential conflicts and the cost of conflict resolution. Using 1 472 flights during peak hours of China’s air-route network for example verification，the proposed algorithm is compared with the classic NSGA-Ⅱ algorithm and MOEA/D. The experimental results show that the improved NSGA-Ⅱ algorithm has a better optimization effect，can effectively resolve the conflicts between aircraft and produce less trajectory amendment costs. [ABSTRACT FROM AUTHOR]

Rapid and responsive Earth observation satellites enable the evaluation of disaster risk, improve relief effectiveness, and reduce suffering and fatalities in the event of sudden disaster events. One promising method for responsive space satellites is orbital maneuvering. This article describes a multitree search framework for multisatellite responsiveness scheduling considering orbital maneuvering, where multiple ground targets are cooperatively observed by multiple observation satellites over a short period of time. Based on the traditional tree search, the proposed method constructs multiple trees and distributes all the targets to multiple satellites, allowing the observation sequence of a single satellite to be optimized. To apply the tree search algorithm, a tree node collection (TNC) composed of the corresponding nodes in multiple trees is used to represent the state of each satellite. Before the expansion phase, one specific node in the TNC is determined for later expansion. A beam search is then used to optimize the observation sequence. Ground-track adjustment techniques using impulse maneuver are considered for visiting a given target. The proposed framework is more effective than other algorithms and achieves a better performance than the previous best method in a typical multisatellite responsiveness scheduling scenario. [ABSTRACT FROM AUTHOR]

This report describes a study involving the design and optimization of Earth-Mars transfer trajectories with launch constraints by taking the Chinese Mars mission Tianwen-1 as a typical case. The trajectory characteristics of the mission are investigated, and the results indicate that the launch and transfer trajectories do not match at the injection point owing to the constraints on the launch site in China, the allowed range of the launch azimuth, and the launch vehicle's limited capability. Two strategies are presented to overcome these challenges. One involves performing a single deep space maneuver during the cruise, which was the option implemented in the Tianwen-1 mission. An alternative strategy involves skillfully utilizing a lunar gravity assist to efficiently change the velocity of the probe. Herein, the orbital elements, the velocity increments of the maneuvers, and the launch windows are analyzed for each strategy. The simulations were optimized by applying the particle swarm optimization algorithm under the patched conic model and by a local optimization algorithm under a high-fidelity model; the results indicate that both strategies are efficient for the investigated mission, and the velocity increment differences arising from the two models are small. The advantages and disadvantages of the two strategies are summarized. In general, the first strategy is more robust in design, but the second approach reduces the velocity increment. The method comprising the two strategies proposed in this paper has certain relevance for other similar space missions, especially in terms of dealing with launch constraints. [ABSTRACT FROM AUTHOR]

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the advancement of the times, robotics technology is also developing rapidly. Some large enterprises in China use robots to work in manufacturing and handling positions, and also make robots more and more widely used. This paper focuses on the trajectory planning strategy for three-degree-of-freedom high-speed parallel manipulator of Delta robot in Cartesian space under high-speed operation handling, the point-to-point "door" type handling operation trajectory under the condition of ensuring control accuracy and increasing productivity in intelligent packaging is established based on the inverse kinematics model of the manipulator. The 4–3–3-4 degree polynomial interpolation is presented to control height of obstacle avoidance and trajectory length, on this basis, the mapping relationship between the motion features in operation space and those in joint space is established. Taking into account the complexity of trajectory optimization due to multiple constraints, in order to reduce the difficulty of trajectory optimization, it is necessary to ensure smoothness and constrains of angular displacement, angular velocity and angular acceleration of each joint in space, an improved particle swarm optimization algorithm is proposed to optimize trajectory running time of the 4–3–3-4 degree polynomial interpolation. The simulation results by using Matlab indicate that the accurate and stable time-optimal trajectory planning of 4–3–3-4 degree polynomial interpolation can be achieved by means of the improved particle swarm optimization algorithm. Compared with other trajectory planning algorithms, the proposed algorithm is easier to implement, which not only improves the local convergence of particle swarm optimization algorithm, achieves the time optimal trajectory planning of Delta robot, but also realizes the controllability of obstacle avoidance height, therefore which realizes the fast, accurate and safe operation in intelligent packaging. [ABSTRACT FROM AUTHOR]

Inspired by the widespread and increasing usage of natural gas, we study the power consumption minimization problem associated with natural gas pipeline transmission in gunbarrel networks with nonidentical compressors. To accurately and flexibly model both gas flow dynamics and compressor working domains, we formulate the problem as a dynamic programming problem. Then we propose an approximate solution approach based on state dimension reduction. We analyze the problem properties and characterize conditions under which optimality is not compromised by the proposed solution approach. Next, we conduct numerical experiments using two data sets based on real networks in China and a data set from the public library GasLib. Numerical results demonstrate that the proposed solution approach significantly reduces computation time without compromising optimality in most cases. Specifically, the proposed solution approach obtains optimal solutions more than a 100 times faster than the exhaustive search when gas pressures are discretized at 0.01 MPa. Further, the optimality gaps do not exceed 0.4%. [ABSTRACT FROM AUTHOR]

Increasing complexity due to a constantly growing number of target functions turns air traffic trajectory optimization into a multidimensional and nonlinear task that in turn necessitates a focus on the case-sensitive most important criteria. The criteria vary by continent and involve operational, economic, environmental, political, and social concerns. Furthermore, the requirements may alter for a single flight along its journey since air traffic is a transcontinental, segment-wise differently affected transportation mode. Tracked flight data allow for the observation and evaluation of large numbers of flights, as well as the extraction of criteria relevant to flight efficiency and to derive optimization strategies to improve it. In this study, flight track data of China and Europe were compared toward flight efficiency. We found major disparities in both continents' routing structures. Historical ADS-B data considered to be reference trajectories were assessed for flight efficiency while putting a dedicated focus on the vertical profile. Criteria to optimize vertical flight efficiency (VFE) were derived. Based on the findings, suggestions for improvement towards trajectories with minimum fuel are formulated. Different optimization strategies were tested to identify important input variables and, if possible, to determine differences between operation in China and in Europe. On average and in both regions, the influence of weather (e.g., wind speed and wind direction) exceeds the influence of aerodynamics (aircraft type, mass), as the weather-optimized vertical profile more often results in minimum fuel consumption than the aerodynamically optimized trajectory. Atmospheric conditions, network requirements, aircraft types and flight planning procedures are similar in China and Europe and only have a minor impact on flight efficiency during the cruise phase. In a multi-criteria trajectory optimization of the extracted reference trajectories considering the weather, operational constraints and prohibited areas, we found that in China, on average, just under 13 % fuel could be saved through optimal vertical and horizontal routing. In Europe, the figure is a good 10 % . Furthermore, we calculated a fuel-saving potential of 8 % in China and 3 % in Europe through vertical adjustments of the trajectory alone. The resultant reference trajectories will be used for further analysis to increase the efficiency of continental air traffic flows. [ABSTRACT FROM AUTHOR]

Abstract: Emission information is crucial for air quality modeling and air quality management. In this study, a new approach based on the understanding of the relationship between emissions and measured pollutant concentrations has been proposed to estimate pollutant emissions and source contributions. The retrieval can be made with single point in-situ measurements combined with backward trajectory analyses. The method takes into consideration the effect of planetary boundary layer height on pollutant mixing and transport. It is independent of energy statistics and therefore can provide frequent updates on emission information. The spatial coverage can be further improved by using measurements from several sites and combining the derived emission fields. The method was applied to yield the source distributions of black carbon (BC) and CO in the North China Plain (NCP) using in-situ measurements from the HaChi (Haze in China) Campaign and to evaluate contributions from specific areas to local concentrations at the measurement site. Results show an emission field for the NCP that is comparable to the INTEX-B inventory can be retrieved and directly applied to quantify areal source contributions. Compared to emissions in 2006, increased CO and BC emissions were found. Uncertainty analyses show that in-situ measurements of CO and BC bear errors below 0.1 ppm and 12%, respectively. WRF model underestimates the PBLH under stable conditions. On average, an error of 1% in the modeled PBLH results in 1% variation in the derived emissions. The trajectory displacement errors are mostly within 1.5 times the grid size. [Copyright &y& Elsevier]

We used a revised dataset of the atmospheric CH mixing ratios that were continuously measured at Mount Waliguan Baseline Observatory of western China during 2002-2006 to study the temporal variations and the potential sources regions of ambient CH. Approximately 58% observed values were filtered as background data by applying a robust local regression mathematic procedure. The median, 10% and 90% percentiles of CH background mixing ratios were 1831.8, 1820.7 and 1843.5 ppb (10 mol mol), respectively; the atmospheric CH time series showed large variations with a fluctuation of 200 ppb (maximum minus minimum), but the background CH exhibited a much smaller variation (about 38 ppb), indicating strong impacts from local or regional sources and sinks. Ambient CH displayed significant diurnal variations in different seasons during 2002-2006, as was the combined result of changes of nearby sources/sinks and local meteorological circulation. The averaged CH seasonal cycle showed minimum in spring and winter, maximum in summer (from June to August), as is completely opposite to that observed at Mauna Loa and Niwot Ridge. The incongruous variation should be attributed to enhancing regional/local sources (e.g., herd) around the site as well as the dominant air flow from the polluted north/northeastern region (e.g., Xining and Lanzhou city) in summer. Another possible reason is, compared to Mauna Loa and Niwot Ridge, the photochemical reaction at Waliguan is weaker. An analysis of 5 d back-trajectory (500 hPa) showed that the episode of high CH mixing ratios was associated with advection from the heavily populated regions east or southeast (e.g., Xining and Lanzhou) of Waliguan and northwest of Qinghai via Ge'ermu urban area where growing industrial activities as well as crops residue burning provide large sources of CH, suggesting a large source area; the low values were observed most frequently when air masses originated from the sparsely populated Tibet and south of Qinghai and Xinjiang Uygur Autonomous Region (XUAR). Additionally, atmospheric CH would be enhanced when air masses originated from Ningxia and northwest of Gansu areas (mainly growing rice) along the Yellow river region, especially in summer, suggesting agriculture source of CH. Our study helps to accurately estimate sources and sinks of CH, and thus is significant for understanding greenhouse effect over a regional scale and predicting global change in future. [ABSTRACT FROM AUTHOR]

From 16th to 19th century there is an intensified intercommunion for the technology of artillery-making and applying for guns between West and China through introducing science and technology by Jesuits. During this transmission, western knowledge of ballistic was introduced and combined with traditional Chinese knowledge and experiences, and this was reflected with concentration in the military books of Late Ming and Early Qing. This paper especially differentiates and analyses the description for trajectory knowledge in military books during this period from the aspect of terminology. Through analyzing the descriptions about devices for aiming, ballistic curve, and explanation for flight, the paper manifests that China of Late Ming and Early Qing inherited qualitative description for traditional cast weapon with gun-powder, as well as absorbed western technology and theory for trajectory, hoping that it might be of help to reflect the development and the evolution of Chinese ballistics after the introduction of western ballistics into China since 16th century. [ABSTRACT FROM AUTHOR]

This study develops a practical methodology to assess the accuracy of multi-temporal change detection using a trajectory error matrix (TEM). In this error matrix one axis represents the land-cover change trajectory categories derived from single-date classified images, and the other represents the land-cover change trajectories identified from reference data. The overall accuracies of change trajectories and states of change/no-change are used as indices for accuracy assessment. As the number of possible land-cover change trajectories can be enormous, a practical processing flow for computing accuracy assessment indices has also been developed to avoid listing all possible change trajectories in the error matrix. A case study using this method was conducted to assess the accuracy of land-cover change over a period with five observations in a study area in China's arid zone. This method simplifies the process of estimating overall accuracy in the change trajectory analysis, and provides a more realistic and detailed assessment of the results of multi-temporal change detection using post-classification comparison methods. [ABSTRACT FROM AUTHOR]

Total gaseous mercury (TGM) and carbon monoxide (CO) were measured every 5min and hourly, respectively, in Seoul, Korea, from February 2005 through December 2006. The mean concentrations of TGM and CO were 3.44±2.13ngm−3 and 613±323ppbv, respectively. TGM and CO concentrations were highest during the winter and lowest during the summer. In total, 154 high TGM concentration events were identified: 86 were classified as long-range transport events and 68 were classified as local events. The TGM and CO concentrations were well correlated during all long-range transport events and were weakly correlated during local events. Five-day backward trajectory analysis for long-range transport events showed four potential source regions: China (79%), Japan (13%), the Yellow Sea (6%), and Russia (2%). Our results suggest that measured ΔTGM/ΔCO can be used to identify long-range transported mercury and to estimate mercury emissions from long-range transport. [Copyright &y& Elsevier]

Air traffic trajectory optimization is a complex, multidimensional and non-linear optimization problem and requires a firm focus on the essential criteria. The criteria cover operational, economical, environmental, political, and social factors and differ from continent to continent. Since air traffic is a transcontinental transport system, the criteria may also change during a single flight. Historic flight track data allow observation and assess real flights, to extract essential criteria and to derive optimization strategies to increase air traffic efficiency. Real flight track data from the Chinese and European air traffic show significant differences in the routing structure in both regions. For that reason, reference trajectories of historic ADS-B 24-h air traffic data in China and Europe have been extracted and analyzed regarding horizontal flight efficiency and the most restrictive criteria of trajectory optimization. We found that prohibited areas might be the most powerful reason to describe deviations from the great circle distance in the Chinese air traffic system. Atmospheric conditions, network requirements, aircraft types and flight planning procedures are similar in China and Europe and only have a minor impact on flight efficiency during the cruise phase. In a multi-criteria trajectory optimization of the extracted reference trajectories considering the weather, operational constraints and prohibited areas, we found that flown ground distances could be reduced by 255 km in the Chinese airspace and 2.3 km in the European airspace. The resultant reference trajectories can be used for further analysis to increase the efficiency of continental air traffic flows. [ABSTRACT FROM AUTHOR]

The Yuanba giant gas field in the Sichuan Basin produces from Upper Permian Changxing heterogeneous reef-shoal reservoirs. It is an ultradeep tight gas reservoir with burial depth of 7000 m. This paper proposes an integrated methodology incorporating the reservoir geology description, petrophysics characterization, seismic response analysis, forward seismic modeling, pseudo-acoustic inversion, and reservoir architecture imaging to identify the geologically complex reef-shoal reservoirs and predict the distribution of the producible reservoirs. The facies of reef cap, reef core, reef base and shoal are first identified based on observations and interpretations of cores, thin sections, mud logging, wireline logs, and formation microscanner images (FMIs). High-energy shoals, reef cores, and reef caps are the most favorable reservoir microfacies. Seismic responses of reef-shoal reservoirs are then investigated through forward modeling and well-seismic calibration. Four reef belts are identified based on seismic reflections and edge detection by seismic paleogeomorphologic features. Reservoir distribution and quantitative properties are predicted using the facies-controlled postattack seismic inversion technique through the correlation between reservoir properties and seismic attributes, which is aided by pseudo-gamma acoustic inversion to exclude the shale-bearing non-reservoir and pseudo-neutron acoustic inversion based on its good relationship with porosity. The reef reservoir thicknesses range from 10 m to 130 m, and the thickest reservoir is located in the northwestern Yuanba gas field. Finally, 3-D visualization is used to characterize the spatial variation of the interior architecture, connectivity, and distribution of a good reservoir in the reef system. The accuracy rate of prediction for reservoirs and non-reservoirs reaches 88% using this method. The technique has also been successfully used for the deployment of development wells and well trajectory optimization, and the rate of encountering the predicted reservoirs is 100%. This study provides a practical approach to identify and predict the tight carbonate gas reservoir with similar petrophysical responses of density and acoustic to non-reservoirs in the complex carbonate system. • The high energy dolomitic facies is the best reservoir in the ultra-deep giant Yuanba Gas Field. • The tight reef-shoal reservoir are successfully characterized using integrated method. • Pseudo-acoustic impedance inversion is an effective tool identifying the best reservoir body. [ABSTRACT FROM AUTHOR]