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Orbital Blocking Game Near Earth-Moon L1 Libration Point

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Space(Science & Technology) 2023年第1期3卷 660-674页

作者： Hongyu Han Zhaohui dang School of Astronautics Northwestern Polytechnical UniversityXi’an710072China National Key Laboratory of Aerospace Flight Dynamics Northwestern Polytechnical UniversityXi’an710072China

This paper explores the blocking capabilities of a spacecraft deployed near Earth-Moon L1 libration point against another spacecraft attempting lunar gravity assist,based on theΔV required for *** study demonstrates that a pursuer at L1 libration point can effectively block low-energy evaders with minimalΔV expenditure,creating a blockade against their use of gravity ***,blocking against high-energy evaders is relatively *** on Lyapunov orbits can execute blockades that L1 pursuers cannot,albeit with lower mission-capable *** paper discusses mission-capable rates for different Lyapunov orbits and evader energies,revealing that each Lyapunov orbit has its unique optimal blocking energy,decreasing as the Lyapunov orbit size *** addition,the paper proposes a strategy for evaders to bypass blockades by sacrificing a portion of theirΔV and verifies it *** analysis covers the cost and benefits of the L1 libration point-related blockade,the importance of the mission-capable rate,and the possibility of lunar-orbit *** findings provide insights for future research on orbital games in the Earth-Moon system and orbital blockade.

关键词： orbital Earth Orbital

Two-dimensional directional modulation with dual-mode vortex beam for security transmission

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Journal of Systems Engineering and Electronics 2022年第6期33卷 1108-1118页

作者： ZHU Changju SONG Maozhong dang Xiaoyu ZHU Qiuming College of Electronic Information Engineering Nanjing University of Aeronautics and AstronauticsNanjing 211106China

A two-dimensional directional modulation(DM)technology with dual-mode orbital angular momentum(OAM)beam is proposed for physical-layer security of the relay unmanned aerial vehicle(UAV)tracking *** elevation and azimuth of the vortex beam are modulated into the *** can form the digital waveform with the encoding *** the signal is direction-dependent,the modulated waveform is purposely distorted in other directions to offer a security *** concentric uniform circular arrays(UCAs)with different radii are excited to generate dual vortex beams with orthogonality for the composite signal,which can increase the demodulation *** to the phase propagation characteristics of vortex beam,the constellation at the desired azimuth angle will change continuously within a wavelength.A desired single antenna receiver can use the propagation phase compensation and an opposite helical phase factor for the signal demodulation in the desired *** show that the proposed OAM-DM scheme offers a security approach with direction sensitivity transmission.

关键词： directional modulation(DM) orbital angular momentum(OAM) physical-layer security directional sensitivity

Judicious training pattern for superior molecular reorganization energy prediction model

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Journal of Energy Chemistry 2023年第6期81卷 143-148,I0005页

作者： Xinxin Niu Yanfeng dang Yajing Sun Wenping Hu Tianjin Key Laboratory of Molecular Optoelectronic Sciences Department of ChemistrySchool of ScienceTianjin UniversityTianjin 300072China Joint School of National University of Singapore and Tianjin University Fuzhou 350207FujianChina

Reorganization energy(RE)is closely related to the charge transport properties and is one of the important parameters for screening novel organic semiconductors(OSCs).With the rise of data-driven technology,accurate and efficient machine learning(ML)models for high-throughput screening novel organic molecules play an important role in the boom of material *** different molecular descriptors and algorithms,we construct a reasonable algorithm framework with molecular graphs to describe the compositional structure,convolutional neural networks to extract material features,and subsequently embedded fully connected neural networks to establish the mapping between features and predicted *** our well-designed judicious training pattern about feature-guided stratified random sampling,we have obtained a high-precision and robust reorganization energy prediction model,which can be used as one of the important descriptors for rapid screening potential *** root-meansquare error(RMSE)and the squared Pearson correlation coefficient(R^(2))of this model are 2.6 me V and0.99,*** importantly,we confirm and emphasize that training pattern plays a crucial role in constructing supreme ML *** are calling for more attention to designing innovative judicious training patterns in addition to high-quality databases,efficient material feature engineering and algorithm framework construction.

关键词： Reorganization energy Graph convolutional neural network Stratified training pattern Machine learning

Deep learning models for spatial relation extraction in text

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Geo-Spatial Information Science 2023年第1期26卷 58-70页

作者： Kehan Wu Xueying Zhang Yulong dang Peng Ye Key Laboratory of Virtual Geographic Environment(Nanjing Normal University) Ministry of EducationNanjingChina Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application NanjingChina Urban Planning and Development Institute Yangzhou UniversityYangzhouChina College of Civil Science and Engineering Yangzhou UniversityYangzhouChina

Spatial relation extraction is the process of identifying geographic entities from text and determining their corresponding spatial *** spatial relation extraction mainly uses rule-based pattern matching,supervised learning-based or unsupervised learning-based ***,these methods suffer from poor time-sensitive,high labor cost and high dependence on large-scale *** the development of pre-trained language models greatly alleviating the shortcomings of traditional methods,supervised learning methods incorporating pre-trained language models have become the mainstream relation extraction *** extraction and joint extraction,as the two most dominant ideas of relation extraction,both have obtained good performance on different datasets,and whether to share the contextual information of entities and relations is the main differences between the two *** this paper,we compare the performance of two ideas oriented to spatial relation extraction based on Chinese corpus data in the field of geography and verify which method based on pre-trained language models is more suitable for Chinese spatial relation *** fine-tuned the hyperparameters of the two models to optimize the extraction accuracy before the comparison *** results of the comparison experiments show that pipeline extraction performs better than joint extraction of spatial relation extraction for Chinese text data with sentence granularity,because different tasks have different focus on contextual information,and it is difficult to take account into the needs of both tasks by sharing contextual *** addition,we further compare the performance of the two models with the rule-based template approach in extracting topological,directional and distance relations,summarize the shortcomings of this experiment and provide an outlook for future work.

关键词： Spatial relation extraction pre-trained language model pipeline extraction joint extraction

User space transformation in deep learning based recommendation

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Journal of Systems Engineering and Electronics 2020年第4期31卷 674-684页

作者： WU Caihua MA Jianchao ZHANG Xiuwei XIE dang Radar Non-Commissioned Officer School Air Force Early Warning AcademyWuhan 430345China

Deep learning based recommendation methods, such as the recurrent neural network based recommendation method(RNNRec) and the gated recurrent unit(GRU) based recommendation method(GRURec), are proposed to solve the problem of time heterogeneous feedback recommendation. These methods out-perform several state-of-the-art methods. However, in RNNRec and GRURec, action vectors and item vectors are shared among users. The different meanings of the same action for different users are not considered. Similarly, different user preference for the same item is also ignored. To address this problem, the models of RNNRec and GRURec are modified in this paper. In the proposed methods, action vectors and item vectors are transformed into the user space for each user firstly, and then the transformed vectors are fed into the original neural networks of RNNRec and GRURec. The transformed action vectors and item vectors represent the user specified meaning of actions and the preference for items, which makes the proposed method obtain more accurate recommendation results. The experimental results on two real-life datasets indicate that the proposed method outperforms RNNRec and GRURec as well as other state-of-the-art approaches in most cases.

关键词： recommender system collaborative filtering time heterogeneous feedback recurrent neural network gated recurrent unit(GRU) user space transformation

A parametric design method of nanosatellite close-range formation for on-orbit target inspection

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Chinese Journal of Aeronautics 2023年第10期36卷 194-209页

作者： Bohan JIAO Qinbo SUN Hongyu HAN Zhaohui dang School of Astronautics Northwestern Polytechnical UniversityXi’an 710072China

This paper proposes an efficient design method for nano satellites formation flying near a large space target to perform ultra-close inspection missions.A parametric model for periodic relative motion between two satellites is firstly proposed through a detailed analysis of the relative orbital *** is proved that the existing periodic solutions of satellite relative motion such as in-plane 2:1 elliptic and circular periodic relative orbits both belong to the ellipsoid family of periodic relative *** motion planes and their locations and orientations of the general periodic relative orbits are then determined as the analytic functions of the initial relative *** maximal and minimal distances from the relative orbit to the origin are further analytically calculated too.A formation design algorithm is then proposed for optimal observation of feature points of the target considering various requirements of collision avoidance and observable distance by using this parametric *** examples about target inspection are introduced to quantitively evaluate and verify the models and *** simulation results are well consistent with the theoretical predictions,showing that the design proposed can be potentially applied for future practical on-orbit service missions.

关键词： Ellipsoid family Formation flying Nanosatellite Periodic relative orbit Target tracking and inspection

HMvisor: dynamic hybrid memory management for virtual machines

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Science China(Information Sciences) 2021年第9期64卷 74-89页

作者： dang YANG Haikun LIU Hai JIN Yu ZHANG National Engineering Research Center for Big Data Technology and System Services Computing Technology and System Lab Cluster and Grid Computing LabSchool of Computer Science and Technology Huazhong University of Science and Technology

Emerging non-volatile memory(NVM) technologies promise high density, low cost and dynamic random access memory(DRAM)-like performance, at the expense of limited write endurance and high write energy consumption. It is more practical to use NVM combining with the traditional DRAM. However, the hybrid memory management such as page migration becomes more challenging in a virtualization environment because virtual machines(VMs) are unaware of the memory heterogeneity. In this paper, we propose HMvisor, a hypervisor and VM coordinated hybrid memory management mechanism to better utilize DRAM and NVM resources. HMvisor exposes the memory heterogeneity to VMs by mapping virtual NUMA nodes to different physical NUMA nodes. We propose a lightweight and efficient page migration mechanism by decoupling page hotness tracking from page migration. HMvisor performs those operations in the hypervisor and VMs separately, without disrupting the execution of VMs. We also propose a memory resource trading policy to adjust the capacity of DRAM and NVM for each VM, with the monetary cost unchanged. We implement our prototype system based on QEMU/KVM and evaluate it with several benchmarks. Experimental results show that HMvisor can reduce 50% of write traffic to NVM with less than 5% performance overhead. Moreover, the hybrid memory adjustment scheme in HMvisor can significantly improve application performance by up to 30×.

关键词： hypervisor virtual machine non-volatile memory hybrid memory management

Further Results on Overlarge Sets of Kirkman Triple Systems

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Acta Mathematica Sinica,English Series 2009年第3期25卷 419-434页

作者： Lan dang YUAN Qing De KANG College of Career Technology Hebei Normal University Shijiazhuang 050031 P. R. China Institute of Mathematics Hebei Normal University Shijiazhuang 050016 P. R. China

In this paper, we introduce a new concept -- overlarge sets of generalized Kirkman systems （OLGKS）, research the relation between it and OLKTS, and obtain some new results for OLKTS. The main conclusion is： If there exist both an OLKF（6^k） and a 3-OLGKS（6^k-1,4） for all k ∈{6,7,...,40}／{8,17,21,22,25,26}, then there exists an OLKTS（v） for any v ≡ 3 （mod 6）, v ≠ 21. As well, we obtain the following result： There exists an OLKTS（6u ＋ 3） for u = 2^2n-1 - 1, 7^n, 31^n, 127^n, 4^r25^s, where n ≥ 1,r＋s≥ 1.

关键词： Kirkman frame Kirkman triple system overlarge set (2 1)-resolvable Steiner quadruplesystem

An Improved Kalman Filter Positioning Method in NLOS Environment

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China Communications 2019年第12期16卷 84-99页

作者： Zhanjun Hao Beibei Li Xiaochao dang College of Computer Science and Engineering Northwest Normal UniversityLanzhou 730070China Gansu Province Internet of Things Engineering Research Center Lanzhou 730070China

In the precision positioning system, NLOS(Non Line of Sight) propagation and clock synchronization error caused by multiple base stations are the main reasons for reducing the reliability of communication and positioning accuracy. So, in the NLOS environment, it has an important role to eliminate the clock synchronization problem in the positioning system. In order to solve this problem, this paper proposes an improved Kalman filter localization method NLOS-K(Non Line of Sight-Kalman filter). First, the maximum likelihood estimation algorithm is used to iterate. Then, the Kalman filter algorithm is implemented and the Kalman gain matrix is redefined. The clock drift is compensated so that the clock between the master and slave base stations remains synchronized. The experimental results show that in the non-lineof-sight environment, compared with other algorithms, the positioning accuracy error of the improved algorithm is about 5 cm, and the accuracy compared with other algorithms is 97%. In addition, the influence of bandwidth and spectral density on the method is analyzed, and the accuracy and stability of positioning are improved as a whole.

关键词： NLOS clock synchronization Kalman filtering maximum likelihood estimation spectral density