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基于数字地形平滑和人工势场的无人机近地三维路径规划

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兵器装备工程学报 2024年第1期45卷 265-271页

作者：朱熠田辉郝向宇史涵意马文峰王聪陆军工程大学野战工程学院南京210007

根据无人机在地形跟随和地形规避任务中的特殊要求,提出了一种基于数字地形平滑技术的无人机三维飞行路径规划新方法。该方法包括以下2个步骤:第1步是通过访问SRTM数字地形模型,并设置安全高度、减少坡度和曲率等参数,对数字地形进行平... 详细信息

根据无人机在地形跟随和地形规避任务中的特殊要求,提出了一种基于数字地形平滑技术的无人机三维飞行路径规划新方法。该方法包括以下2个步骤:第1步是通过访问SRTM数字地形模型,并设置安全高度、减少坡度和曲率等参数,对数字地形进行平滑处理,生成一个安全的飞行表面。第2步在所获得的安全飞行表面的基础上,考虑了无人机的机动约束和威胁指标,设计了一种改进的向量场方法来搜索从给定起点到指定目的地的最优飞行路径。利用所设计三维路径规划仿真程序进行了仿真试验,仿真结果表明,所设计的路径规划方法可以在避开威胁源的情况下获得最佳的3D飞行路径,具有良好的可行性和有效性。

关键词：近地飞行 SRTM数字地形人工势场法三维路径规划

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面向单阶段目标检测的损失函数优化设计

电光与控制 2024年第3期31卷 86-93页

作者：刘龙哲刘刚徐红鹏权冰洁田慧河南科技大学信息工程学院河南洛阳471000

在基于深度学习的单阶段目标检测中,从交并比(IoU)出发的边界框回归损失对边界框位置关系变化敏感度不够,当预测框与真值框处于不同包含关系时,已有损失无法精确区分。针对上述问题,提出基于IoU的回归位置关系敏感度损失(RPIoU)。该损... 详细信息

在基于深度学习的单阶段目标检测中,从交并比(IoU)出发的边界框回归损失对边界框位置关系变化敏感度不够,当预测框与真值框处于不同包含关系时,已有损失无法精确区分。针对上述问题,提出基于IoU的回归位置关系敏感度损失(RPIoU)。该损失设计强化预测框和真值框相对位置关系的敏感度,首先在IoU后添加惩罚项,使两框角点无限靠近,解决中心点重合时IoU退化问题;其次引入非重叠区域面积与真值框面积比值为参数的指数函数作为惩罚项,解决损失无法区分预测框和真值框存在不同包含关系的问题,更精准地指导边框回归的位置;考虑到单阶段目标检测算法总损失各部分对于训练结果的贡献度不同,以平均精度均值(mAP)作为适应度函数,利用遗传算法对训练总损失进行优化,得到分类、回归、置信度损失的各自最佳权重。将设计的损失应用于单阶段目标检测算法YOLOv5,分别在可见光公开数据集VisDrone和自制红外飞机数据集上进行验证。在可见光公开数据集上的mAP达到0.447,比原始YOLOv5提升0.037;在红外飞机数据集的mAP达到0.966,比原始YOLOv5提升0.014。

关键词：标检测单阶段 IoU损失 RPIoU损失

Multi-disciplinary design optimization with fuzzy uncertainties and its application in hybrid rocket motor powered launch vehicle

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Chinese Journal of Aeronautics 2020年第5期33卷 1454-1467页

作者： Pengcheng WANG hui tian Hao ZHU Guobiao CAI School of Astronautics Beihang UniversityBeijing 100083China Key Laboratory of Spacecraft Design Optimization&Dynamic Simulation Technologies of Ministry of Education Beihang UniversityBeijing 100083China

In this paper,an Uncertainty-based Multi-disciplinary Design Optimization (UMDO)method combining with fuzzy theory and Multi-Discipline Feasible (MDF) method is developed for the conceptual design of a Hybrid Rocket Motor (HRM) powered Launch Vehicle (LV).In the method proposed,membership functions are used to represent the uncertain factors,the fuzzy statistical experiment is introduced to analyze the propagation of uncertainties,and means,standard deviations and credibility measures are used to delineate uncertain responses.A geometric programming problem is solved to verify the feasibility of the Fuzzy-based Multi-Discipline Feasible(F-MDF) method.A multi-disciplinary analysis of a three-stage HRM powered LV involving the disciplines of propulsion,structure,aerodynamics and trajectory is implemented,and the mathematical models corresponding to the F-MDF method and the MDF method are established.A two-phase optimization method is proposed for multi-disciplinary design optimization of the LV,including the orbital capacity optimization phase based on the Ziolkowski formula,and the scheme trajectory verification phase based on the 3-degree-of-freedom point trajectory *** correlation coefficients and the quadratic Response Surface Method (RSM) based on Latin Hypercube Sampling (LHS) are adopted for sensitive analysis of uncertain factors,and the Multi-Island Genetic Algorithm (MIGA) is adopted as the optimization *** results show that the F-MDF method is applicable in LV conceptual design,and the design with the F-MDF method is more reliable and robust than that with the MDF method.

关键词： Fuzzy theory Hybrid Rocket Motor(HRM) Launch Vehicle(LV) Sensitive Analysis(SA) Uncertainty-based Multi-disciplinary Design Optimization(UMDO)

药物涂层球囊与普通球囊血管成形术治疗症状性颅内动脉粥样硬化性狭窄的安全性和预后对比研究

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中国卒中杂志 2024年第7期19卷 803-808页

作者：李彦江刘彤晖田惠孙岩张勇青岛大学附属医院神经介入科青岛266000 青岛大学附属医院介入手术室青岛266000

目的对比分析药物涂层球囊(drug-coated balloon,DCB)和普通球囊血管成形术治疗症状性颅内动脉粥样硬化性重度狭窄患者的安全性和预后。方法回顾性分析2020年3月-2022年4月在青岛大学附属医院进行治疗的症状性颅内动脉粥样硬化性重度狭... 详细信息

目的对比分析药物涂层球囊(drug-coated balloon,DCB)和普通球囊血管成形术治疗症状性颅内动脉粥样硬化性重度狭窄患者的安全性和预后。方法回顾性分析2020年3月-2022年4月在青岛大学附属医院进行治疗的症状性颅内动脉粥样硬化性重度狭窄患者,按照治疗方式的不同分为DCB组和普通球囊组。比较两组患者的一般临床资料、疗效和安全性终点,包括围手术期并发症、临床结局和影像随访结果。结果研究共纳入49例患者,其中DCB组30例,普通球囊组19例。两组的基线资料、围手术期并发症、术后6个月内再发卒中率、再狭窄率及死亡率差异均无统计学意义(P>0.05);6个月随访DCB组狭窄程度为14.50%(9.55%~23.42%),低于普通球囊组的30.00%(15.42%~37.61%),差异有统计学意义(P=0.027)。结论与普通球囊相比,DCB治疗症状性颅内动脉粥样硬化性重度狭窄是安全的,可以有效降低目标血管再狭窄的进展。

关键词：药物涂层球囊血管成形术颅内动脉粥样硬化缺血性卒中脑血管狭窄

Utilizing a new soil effective temperature scheme and archived satellite microwave brightness temperature data to estimate surface soil moisture in the Nagqu region, Tibetan Plateau of China

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Journal of Arid Land 2018年第1期10卷 84-100页

作者： tian hui Mudassar IQBAL Key Laboratory of Land Surface Process and Climate Change in Cold and Arid Regions Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China

Since the early 2000s, many satellite passive microwave brightness temperature （BT） archives, such as the Advanced Microwave Scanning Radiometer for the Earth Observing System （AMSR-E） BTs, have become the useful resources for assessing the changes in the surface and deep soil moistures over both arid and semi-arid regions. In this study, we used a new soil effective temperature （T scheme and the archived AMSR-E BTs to estimate surface soil moisture （SM） over the Nagqu region in the central Tibetan Plateau, China. The surface and deep soil temperatures required for the calculation of regional-scale T were obtained from outputs of the Community Land Model version 4.5 （CLM4.5）. In situ SM measurements at the CEOP-CAMP/Tibet （Coordinated Enhanced Observing Period Asia-Australia Monsoon Project on the Tibetan Plateau） experimental sites were used to validate the AMSR-E-based SM estimations at regional and single-site scales. Furthermore, the spatial distribution of monthly mean surface SM over the Nagqu region was obtained from 16 daytime AMSR-E BT observations in July 2004 over the Nagqu region. Results revealed that the AMSR-E-based surface SM estimations agreed well with the in situ-based surface SM measurements, with the root mean square error （RMSE） ranging from 0.042 to 0.066 m3/m3 and the coefficient of determination （R2） ranging from 0.71 to 0.92 during the nighttime and daytime. The regional surface soil water state map showed a clear spatial pattern related to the terrain. It indicated that the lower surface SM values occurred in the mountainous areas of the northern, mid-western and southeastern parts of Nagqu region, while the higher surface SM values appeared in the low elevation areas such as the Tongtian River Basin, Namco Lake and bog meadows in the central part of Nagqu region. Our analysis also showed that the new T^scheme does not require special fitting parameters or additional assumptions, which simplifies the data requirements for regional-scale ap

关键词： soil effective temperature archived AMSR-E brightness temperature CLM4.5 soil temperature output Cumulative Distribution Function (CDF) matching surface soil moisture Tibetan Plateau

Dynamic access clustering selecting mechanism based on Markov decision process for MANET

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The Journal of China Universities of Posts and Telecommunications 2007年第4期14卷 88-92页

作者： WANG Dao-yuan tian hui Wireless Technology Investigate Laboratory Beijing University of Posts and Telecommunications Beijing 100876 China

Clustering is an important method in the mobile Ad-hoc network（MANET）. As a result of their mobility, the cluster selection is inevitable for the mobile nodes during their roaming between the different clusters. In this study, based on the analysis of the cluster-selecting problem in the environment containing multiple clusters, which are overlaying and intercrossing, a novel dynamic selecting mechanism is proposed to resolve the dynamic selection optimization of roaming between the different clusters in MANET. This selecting mechanism is also based on the consideration of the stability of communication system, the communicating bandwidth, and the effect of cluster selecting on the communication and also in accordance with the Markov decision-making model.

关键词： MANET roam cluster selection effect

Oxygen vacancy O-terminated surface:The most exposed surface of hexagonal WO3(001)surface

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Chinese Chemical Letters 2020年第8期31卷 2095-2098页

作者： Feng hui tian Zhenze Liu Jin tian Yunfan Zhang Institute of Computational Science and Engineering State Key Laboratory of Bio-Fibers and Eco-Textiles&College of Chemistry and Chemical Engineering&College of Environmental Science and EngineeringQingdao UniversityQingdao 26607 JChina

It is known that exposed surface determines material’s ***3 is widely used in gas sensing and its working surface is proposed to control its ***,the working surface,or most exposed surface with detailed surface structure remain *** this paper,DFT calculation confirmed that oxygen vacancy O-terminated surface is the most exposed hexagonal WO3(001)surface,judging from competitive adsorption of CO and O2,working surface determination for CO sensing and comparison of oxygen vacancy formation ene rgies on different h-WO3(001)*** is found that DFT can be a useful alternate for exposed surface *** results provide new perspectives and performance explanations for material research.

关键词： Hexagonal WO3(001) Oxygen vacancy O-terminated surface Competitive adsorption Working surface Exposed surface determination theoretically

Numerical analysis of fuel regression rate distribution characteristics in hybrid rocket motors with different fuel types

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Science China(Technological Sciences) 2013年第7期56卷 1807-1817页

作者： LI Xintian tian hui CAI GuoBiao School of Astronautics Beihang University

This paper presents three-dimensional numerical simulations of the hybrid rocket motor with hydrogen peroxide (HP) and hy-droxyl terminated polybutadiene (HTPB) propellant combination and investigates the fuel regression rate distribution charac-teristics of different fuel types. The numerical models are established to couple the Navier-Stokes equations with turbulence,chemical reactions, solid fuel pyrolysis and solid-gas interfacial boundary conditions. Simulation results including the temper-ature contours and fuel regression rate distributions are presented for the tube, star and wagon wheel grains. The results demonstrate that the changing trends of the regression rate along the axis are similar for all kinds of fuel types, which decrease sharply near the leading edges of the fuels and then gradually increase with increasing axial locations. The regression rates of the star and wagon wheel grains show apparent three-dimensional characteristics, and they are higher in the regions of fuel surfaces near the central core oxidizer flow. The average regression rates increase as the oxidizer mass fluxes rise for all of the fuel types. However, under same oxidizer mass flux, the average regression rates of the star and wagon wheel grains are much larger than that of the tube grain due to their lower hydraulic diameters.

关键词： numerical analysis fuel regression rate hybrid rocket motor fuel types

Uncertainty analysis and probabilistic design optimization of hybrid rocket motors for manned lunar landing

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Science China(Technological Sciences) 2015年第7期58卷 1234-1241页

作者： ZHU Hao tian hui CAI GuoBiao BAO WeiMin School of Astronautics Beihang University China Aerospace Science and Technology Corporation

To obtain a conceptual design for a hybrid rocket motor(HRM)to be used as the Ascent Propulsion System in the Apollo lunar module,the deterministic design optimization(DDO)method is applied to the HRM *** on the results of an uncertainty analysis of HRMs,an uncertainty-based design optimization(UDO)method is also adopted to improve the design *** HRM design process,which is a multidisciplinary system,is analyzed,and a mathematical model for the system design is established to compute the motor performance from the input parameters,including the input variables and model *** input parameter uncertainties are quantified,and a sensitivity analysis of the model parameter uncertainties is conducted to identify the most important model parameter uncertainties for *** DDO and probabilistic UDO methods are applied to conceptual designs for an HRM to be used as a substitute for the liquid rocket motor(LRM)of the Ascent Propulsion *** conceptual design results show that HRMs have several advantages as an alternative to the LRM of the Ascent Propulsion System,including nontoxic propellant combination,small motor volume,and comparable functions,such as restarting and *** of the DDO and UDO results indicate that the UDO method achieves more robust and reliable optimal designs than the DDO *** probabilistic UDO method can be used to develop better conceptual designs for HRMs.

关键词： hybrid rocket motor deterministic design optimization uncertainty-based design optimization sensitivity analysis manned lunar landing