检索结果-内蒙古大学图书馆

The Probability Density Function Related to Shallow Cumulus Entrainment Rate and Its Influencing Factors in a Large-Eddy Simulation

引用

Advances in Atmospheric sciences 2024年第1期41卷 173-187页

作者： Lei ZHU Chunsong LU Xiaoqi XU Xin HE Junjun LI Shi LUO Yuan WANG Fan WANG Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)and Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration Nanjing University of Information Science and TechnologyNanjing 210044China Nanjing Joint Institute for Atmospheric Sciences Nanjing 210019China College of Aviation Meteorology Civil Aviation Flight University of ChinaGuanghan 618307China Collaborative Innovation Center for Western Ecological Safety Lanzhou UniversityLanzhou 730000China Department of Geography Hong Kong Baptist UniversityHong Kong SAR 999077China

The process of entrainment-mixing between cumulus clouds and the ambient air is important for the development of cumulus *** obtaining the entrainment rate(λ)is particularly important for its parameterization within the overall cumulus parameterization *** this study,an improved bulk-plume method is proposed by solving the equations of two conserved variables simultaneously to calculateλof cumulus clouds in a large-eddy *** results demonstrate that the improved bulk-plume method is more reliable than the traditional bulk-plume method,becauseλ,as calculated from the improved method,falls within the range ofλvalues obtained from the traditional method using different conserved *** probability density functions ofλfor all data,different times,and different heights can be well-fitted by a log-normal distribution,which supports the assumed stochastic entrainment process in previous *** analysis demonstrate that the relationship betweenλand the vertical velocity is better than other thermodynamic/dynamical properties;thus,the vertical velocity is recommended as the primary influencing factor for the parameterization ofλin the *** results of this study enhance the theoretical understanding ofλand its influencing factors and shed new light on the development ofλparameterization.

关键词： large-eddy simulation cumulus clouds entrainment rate probability density functions spatial and temporal distribution

来源：评论

学校读者我要写书评

暂无评论

The Challenges of Autonomous Unmanned Aerial System test and Evaluation

The Challenges of Autonomous Unmanned Aerial System Test and...

引用

2021 IEEE International Conference on Unmanned Systems, ICUS 2021

作者： Qi, Shengjun Wang, Feng Wu, Xinlong Aeronautical Science and Technology Simulation Key Laboratory Chinese Flight Test Establishment Xi'an China

ISBN: (纸本)9780738146577

With the development of artificial intelligence, computing and sensor technology, the autonomy of Unmanned Aerial System (UAS) has improved continually, but the autonomous capability levels vary. Hence, how to describe and evaluate autonomy of UAS scientifically and reasonably has become a hot topic in UAS test and evaluation area. In this paper, the developing status of research about autonomous UAS test and evaluation was reviewed. Then the concept meaning of UAS autonomy and the basic features of autonomy were analyzed comprehensively and systematically. Aiming at characteristics of UAS autonomy, the challenges of autonomous UAS test and evaluation were analyzed in depth from three aspects, autonomy levels, testing complexity and uncertainty and man-machine trust problem. Finally, according to current UAS testing methods and characteristics of autonomous UAS, the architecture of UAS autonomy test and evaluation, testing methods and contents were proposed, which would provide technical support for autonomous UAS test and evaluation. © 2021 IEEE.

关键词： Unmanned aerial vehicles (UAV)

来源：评论

学校读者我要写书评

暂无评论

An overview of large AI models and their applications

引用

Visual Intelligence 2024年第1期2卷 1-22页

作者： Tu, Xiaoguang He, Zhi Huang, Yi Zhang, Zhi-Hao Yang, Ming Zhao, Jian Civil Aviation Flight University of China College of Aviation Electronics and Electrical Guanghan 618307 China National Key Laboratory of Fundamental Science on Synthetic Vision Sichuan University Chengdu 610065 China Harbin Institute of Technology Harbin 150001 China EVOL Lab The Institute of AI (TeleAI) China Telecom Beijing 100033 China School of Artificial Intelligence Northwestern Polytechnical University Xi’an 710072 China

In recent years, large-scale artificial intelligence (AI) models have become a focal point in technology, attracting widespread attention and acclaim. Notable examples include Google’s BERT and OpenAI’s GPT, which have scaled their parameter sizes to hundreds of billions or even tens of trillions. This growth has been accompanied by a significant increase in the amount of training data, significantly improving the capabilities and performance of these models. Unlike previous reviews, this paper provides a comprehensive discussion of the algorithmic principles of large-scale AI models and their industrial applications from multiple perspectives. We first outline the evolutionary history of these models, highlighting milestone algorithms while exploring their underlying principles and core technologies. We then evaluate the challenges and limitations of large-scale AI models, including computational resource requirements, model parameter inflation, data privacy concerns, and specific issues related to multi-modal AI models, such as reliance on text-image pairs, inconsistencies in understanding and generation capabilities, and the lack of true “multi-modality”. Various industrial applications of these models are also presented. Finally, we discuss future trends, predicting further expansion of model scale and the development of cross-modal fusion. This study provides valuable insights to inform and inspire future future research and practice. © The Author(s) 2024.

关键词： Artificial intelligence GPT Large AI models Large language models

来源：评论

学校读者我要写书评

暂无评论

A Wideband Dual Layer Frequency Selective Surface Shielding Screen

A Wideband Dual Layer Frequency Selective Surface Shielding ...

引用

2022 International Applied Computational Electromagnetics Society Symposium, ACES-China 2022

作者： Bai, Zhendong Xu, Min Gao, Lu Liu, Jiaqi Beijing Institute of Space Long March Vehicle National Key Laboratory of Science and Technology on Test Ph Beijing China Army Aviation Institue Department of Aeronautical Engineering Beijing China

ISBN: (纸本)9781665452366

A dual layer polarization and incident angle insensitive frequency selective surface (FSS) with wideband feature for electromagnetic shielding is presented in this paper. A single layer FR4 dielectric substrate is attached both sides with periodic copper pattern. The front layer comprises of combined square and circle loop and the background layer comprises of combined circle loops and strips. The proposed FSS exhibits a 11.2 GHz ultra-wide stop band response from 4.3 to 15.5 GHz. Because of the symmetry of the structure, the FSS is polarization insensitive. Numerical computation validates the incident angles stability up to 60° in TE modes. © 2022 IEEE.

关键词： Frequency selective surfaces

来源：评论

学校读者我要写书评

暂无评论

An Incident Angle Insensitive Absorption Frequency Selective Surface

An Incident Angle Insensitive Absorption Frequency Selective...

引用

2022 International Applied Computational Electromagnetics Society Symposium, ACES-China 2022

作者： Bai, Zhendong Xu, Min Liu, Peng Gao, Lu Liu, Jiaqi Beijing Institute of Space Long March Vehicle National Key Laboratory of Science and Technology on Test Ph Beijing China Army Aviation Institue Department of Aeronautical Engineering Beijing China

ISBN: (纸本)9781665452366

In this paper, a novel angle insensitive frequency selective surface (FSS) is presented by combining the ring, square loop and cross to achieve better electromagnetic absorption performance. The unit cell consists of three layers, which are FSS, dielectric layer and patch substrate. The structure makes the reflections and transmission of the two sides not equal. The simulation results show that the proposed FSS provides absorption on several distinctive frequency bands ranging from C-band to K-band with maximum absorption of 99%. © 2022 IEEE.

关键词： Frequency selective surfaces

来源：评论

学校读者我要写书评

暂无评论

Image Segmentation Algorithm of Ischemic Stroke based on Wavelet Pooling Neural Network 2

Image Segmentation Algorithm of Ischemic Stroke based on Wav...

引用

2nd IEEE International Conference on Signal, Information and Data Processing, ICSIDP 2024

作者： Zhu, Huiyuan Zhai, Yao Wu, Jinghe Lu, Chuwei Zhang, Xianchao Li, Ruide Beijing Institute of Technology School of Cyberspace Science and Technology Beijing China College of Medicine Jiaxing University Provincial Key Laboratory of Multimodal Perceiving and Intelligent Systems Department of Nursing Jiaxing China Beijing Institute of Technology School of Information and Electronics Beijing China Aviation Industry Corporation of China Avic Xi' An Flight Automatic Control Research Institute Xi'an China Jiaxing University Provincial Key Laboratory of Multimodal Perceiving and Intelligent Systems Jiaxing China

ISBN: (纸本)9798331515669

Ischemic stroke is a high-risk brain disease that causes disability or death in adults worldwide. Rapid diagnosis and treatment, as well as segmentation of ischemic lesions from stroke medical images so that doctors can evaluate and develop treatment plans, are crucial to reducing brain damage. Currently, doctors' manual segmentation of lesions is time-consuming and labor-intensive and prone to missed or misdiagnosed diagnoses, delaying the best time for treatment. A well-trained neural network is considered as an effective aid for image segmentation tasks. However, in the traditional neural network down-sampling process, the pooling layer loses feature information, and the lost information significantly impacts the edge regions. While for medical images, edge regions are crucial features in the segmentation process. Therefore, to address the above issues, in this paper we improve upon the existing stroke lesion segmentation algorithm U-net, we design a segmentation network based on wavelet pooling and attention mechanisms. The network was tested on ISLES 2018 and ISLES 2022 datasets, and the Dice coefficient improved by 2.13% and 1.93% compared to baseline network, respectively. © 2024 IEEE.

关键词： Image segmentation

来源：评论

学校读者我要写书评

暂无评论

Robust Bipartite Consensus Tracking for Multi-Agent Systems under Acuator Faults 5

Robust Bipartite Consensus Tracking for Multi-Agent Systems ...

引用

5th IEEE International Conference on Electronics technology, ICET 2022

作者： Han, Chenglin Shi, Mengji Li, Rui Lu, Jiaqi Li, Zhiqiang Qin, Kaiyu University of Electronic Science and Technology of China School of Aeronautics and Astronautics Chengdu China Aircraft Swarm Intelligent Sensing and Cooperative Control Key Laboratory of Sichuan Province Chengdu China Civil Aviation Flight University of China Flight Technology College Chengdu China

ISBN: (纸本)9781665485081

This paper focuses on the robust bipartite consensus tracking problem of multi-agent systems under actuator faults. Both uncertainties and multiplicative actuator faults are considered in the system model. First, linearly parameterized neural networks are applied to approximate the uncertainty parts. Then, distributed adaptive update laws are designed for the unknown parameters and the actuator fault factors to guarantee the boundedness of estimation error. An adaptive bipartite consensus tracking control algorithm is proposed, which can solve the robust problem and suppress the uncertainties and actuator faults, simultaneously. Furthermore, numerical simulations are given to illustrate the effectiveness of the theoretical analysis. © 2022 IEEE.

关键词： Robust control

来源：评论

学校读者我要写书评

暂无评论

Study on strengthening mechanism of Al microalloying on softening behavior of Ti2AlNb/TA15 electron beam welding joint

引用

Materials science and Engineering: A 2025年 922卷

作者： Zhang, La Mei Chen, Guo Qing Wang, Hong Zhou Teng, Xin Yan Gan, Zhan Hua Zhu, Li Kuo Leng, Xue Song National Key Laboratory of Precision Welding & Joining of Materials and Structures Harbin Institute of Technology Harbin150001 China Chinese Flight Test Establishment Xi'an710089 China School of Materials Science and Engineering Harbin Institute of Technology Shenzhen518071 China

Electron beam welding (EBW) of Ti2AlNb and TA15 was experimented with and without an Al interlayer to analyze the effect of Al on the evolution of microstructure in the fusion zone (FZ) and its impact on joint performance. When welded without Al layer, significant softening occurred in the FZ with a microhardness of 250 HV, which was much lower than that of two base metals (BMs). The FZ was mainly composed of B2 phase which was softer than that of the O and α2 phase in Ti2AlNb BM as well as the α+β phase in TA15 BM. Furthermore, the weld was dominated by coarse columnar grains, which further resulted in the softening of the weld. The tensile strength of the joint at room temperature reached 914 MPa. Al element was introduced in subsequent experiments to improve the softening problem. Adding 50 μm thick Al layer could not completely improve the softening phenomenon, but the softening problem was solved with the 100 μm thick Al layer. When the thickness of Al layer was 50 μm, the main component phase of FZ changed to α′ martensite which was harder than B2 phase, and the microhardness increased by 30 HV. The tensile strength of the joint reached 946 MPa. The formation of the α2 (Ti3Al) phase in FZ during welding with 100 μm Al layer significantly enhanced its microhardness to 380 HV. And there was no obvious change in tensile strength when the softening problem was solved. All joints were fractured in the FZ. As the thickness of Al layer increased, the fracture mechanism gradually changed from quasi-dissociative fracture to brittle fracture. © 2024 Elsevier B.V.

关键词： Electron beam welding

来源：评论

学校读者我要写书评

暂无评论

Study on the thinning characteristics of aviation tubes during bending forming under boundary lubrication friction

引用

Journal of Manufacturing Processes 2025年 149卷 443-455页

作者： Yu Wu Zhineng Wang Jing Tian Renzhen Chen Weiming Lin Yaochen Lin Health Maintenance for Mechanical Equipment Key Lab Hunan University of Science and Technology Xiangtan 411201 China Liaoning Key Laboratory of Advanced Measurement and Test Technology for Aviation Propulsion System Shenyang Aerospace University Shenyang 110136 China Zhejiang King-Mazon Intelligent Manufacturing Corp. Ltd Lijiang 321400 China

The reduction of wall thickness during the bending forming process of aviation tubes is a common issue, particularly for large-diameter, thick-walled tubes. Under heavy load conditions, the lubrication state deteriorates, leading to a boundary lubrication state that complicates the prediction of wall thickness reduction. Current research on tube bending forming relies on Coulomb friction, which does not accurately reflect real-world conditions. Therefore, we propose a method for analysing tube thinning during bending forming that considers the friction characteristics of boundary lubrication. ABAQUS/VFRIC was employed to develop a dynamic friction model that considers contact pressure. Additionally, material hardness and RMS roughness were incorporated into the finite element simulation. Results show that as the tubing advances, the contact area between the pressure die and the tube changes and the friction between them generates a certain amount of compressive stress. An increase in contact pressure results in a higher friction coefficient, leading to a substantial rise in the tensile stress on the tube's exterior, further aggravating the thinning of the outer wall. In particular, stress concentrations and elevated strains resulting from boundary lubrication friction are especially pronounced at the 40° and 60° bending positions. In addition, increased RMS roughness and decreased material hardness contribute to more significant thinning effects. Experimental verification indicates that this dynamic friction model offers greater accuracy than the traditional Coulomb friction model in predicting wall thickness thinning, achieving a maximum error reduction to 3% and an accuracy enhancement of 7%. The findings provide theoretical support for process optimisation in aerospace manufacturing and establish a foundation for designing and implementing high-precision forming processes.

关键词： Bending forming Friction model Wall thinning

来源：评论

学校读者我要写书评

暂无评论

SLAM algorithm based on bounding box and deep continuity in dynamic scene

引用

International Journal of Wireless and Mobile Computing 2021年第4期21卷 349-364页

作者： Fang, Baofu Han, Xiumeng Wang, Zaijun Yuan, Xiaohui School of Computer Science and Information Engineering Intelligent Interconnected Systems Laboratory of Anhui Province Hefei University of Technology Anhui Hefei230009 China Key Laboratory of Flight Techniques and Flight Safety Civil Aviation Flight University of China Sichuan Guanghan618307 China Department of Computer Science and Engineering University of North Texas DentonTX311277 United States

To solve the problems of low positioning accuracy and poor robustness caused by the inability of Simultaneous Localisation and Mapping (SLAM) algorithm to deal with dynamic targets in dynamic scenes, a SLAM algorithm based on bounding box and depth continuity in dynamic scenes is proposed. Firstly, the pixel random search filling process is carried out in combination with the depth and the bounding box to obtain the pixel-level segmentation result of the prior dynamic target. Then, the dynamic features are screened to eliminate the influence of dynamic targets. According to the screening results, relative static features which can be used for posture optimisation are selected. Posture optimisation is carried out by combining the static features to obtain the optimised camera posture. All experimental results show that the proposed algorithm significantly improves the positioning accuracy and real-time performance of SLAM algorithm in complex dynamic scenes. Copyright © 2021 Inderscience Enterprises Ltd.

关键词： Mapping

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：