全部
图书
期刊
学位论文
会议论文
报纸
图片
视频
新闻
- A method for an efficiency and weight-optimised preliminary design of a hydrogen-powered fuel cell-based hybrid-electric propulsion system for aviation purposes
- 作者： Akkaya Mücahit Neumann Nicolai Peitsch Dieter 日期：2023-12-10 来源 ：CEAS Aeronautical Journal 文献类型 ：期刊 关键词：hybrid performance Optimisation Fuel electric aircraft design PEM preliminary cell
- 描述：There is a worldwide effort to advance the usage of zero-emission propulsion systems for aircraft. Due to their high thermodynamic efficiency and the fact that they produce no CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\textrm{CO}{2}$$\end{document} and NOx\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\textrm{NO}{x}$$\end{document} emissions, hydrogen-powered fuel cells are becoming increasingly popular for aviation purposes. However, fuel cell systems suffer from lower power density and higher cooling requirements when compared to conventional propulsion systems. Harnessing the high potential requires an optimised design of the whole propulsion system and its heat management system. This paper aims to present a method for the preliminary design and dimensioning of a fuel cell-based hybrid-electric propulsion system, which respects the limits of the heat management system and is weight and efficiency optimised. Thermodynamic models of the whole propulsion system are a crucial element to enable further investigations. Such a model has been developed, which is suitable for unsteady simulations of the propulsion and the heat management system performance of a short-range four-seater aircraft. A parameter study of the design parameters has been performed to display their impact on the system mass, the overall efficiency and the total hydrogen consumption. These results enable the identification of an overall optimised configuration. The study indicates that fuel cell-only configurations with an oversized fuel cell stack are beneficial for the analysed aircraft and flight mission.
- A load balancing method for avionics systems via artificial bee colony and simulated annealing algorithms
- 作者： Du Xiaoyan Du Chenglie Chen Jinchao Liu Yifan 日期：2023-12-29 来源 ：Soft Computing 文献类型 ：期刊 关键词：Artificial balancing Load bee colony systems Simulated annealing Avionics algorithm
- 描述：Avionics systems are a crucial part of aircraft, and the heterogeneity of resources also leads to load differentials within these systems. Inefficient load balancing technology faces the dual challenge of over-utilization and under-utilization of resources, which results in the decline of service performance (in the case of over-utilization) or the waste of resources (in the case of under-utilization). However, it is necessary to control avionics systems via an efficient load balancing method under time constraints and resource states. Therefore, this paper proposes a load balancing method for avionics systems using both artificial bee colony and simulated annealing algorithms. First, the load balancing model of avionics systems is established; this model can reflect the demands of the tasks for the resources in detail. Then, the load balancing of avionics systems is realized by artificial bee colony and simulated annealing algorithms, the hybrid algorithm not only retains the advantages of simple and easy implementation of ABC algorithm, but also utilizes the probability jump of SA algorithm to jump out of the local extreme and achieve the effect of global optimization. Finally, compared with the existing algorithms, the experimental results show that the algorithm proposed in this paper produces a good and stable load balance performance.
- A deep learning-based technique for firm classification and domain adaptation in land cover classification using time-series aerial images
- 作者： Kalita Indrajit Chakraborty Shounak Reddy Talla Giridhara Ganesh Roy Moumita 日期：2023-12-19 来源 ：Earth Science Informatics 文献类型 ：期刊 关键词：Convolutional Series images LSTMs Attention adaptation Time datasets mechanism Domain temporal multi
- 描述：In this manuscript, a novel framework has been presented for firm classification of a geographical area based on spatial as well as time-series analysis of multi-temporal very high resolution (VHR) satellite images. For this dual objective, an attention-based deep learning mechanism combined with the capabilities of convolutional-recurrent neural networks has been investigated for this purpose. The proposed classification strategy is introduced as ‘firm’ since it allows the classifier to assign only one class label to a multi-temporal image stack of co-registered images, as opposed to multiple. This technique ascertains the land-cover class by taking into consideration the geophysical changes on a landmass and thus outsmarting the conventional techniques relying on the visual interpretation of a single image. The attention mechanism focuses on the important portions of the image scene while the convolutional long short-term memory neural networks exploit the temporal dependencies on the time-series image scenes. Moreover, an adaptive land cover classification scheme, considering the features extracted from the proposed classification approach has been explored for more robust time-series based firm classification. To assess the performance of the proposed schemes, the experiments have been conducted on the two novels VHR multi-temporal land cover classification datasets. The investigated models have been shown to have the capacity to outperform the other state-of-the-art techniques under non-adaptive as well as adaptive scenarios using the multi-temporal images captured over disjoint geographical locations.
- A Comparative Sentiment Analysis of Airline Customer Reviews Using Bidirectional Encoder Representations from Transformers (BERT) and Its Variants
- 作者： Zehong Li Chuyang Yang Chenyu Huang 日期：2023-12-23 来源 ：Mathematics 文献类型 ：期刊 关键词：sentiment natural Airline Analysis 62P25 Service processing language learning Machine customer
- 描述：The applications of artificial intelligence (AI) and natural language processing (NLP) have significantly empowered the safety and operational efficiency within the aviation sector for safer and more efficient operations. Airlines derive informed decisions to enhance operational efficiency and strategic planning through extensive contextual analysis of customer reviews and feedback from social media, such as Twitter and Facebook. However, this form of analytical endeavor is labor-intensive and time-consuming. Extensive studies have investigated NLP algorithms for sentiment analysis based on textual customer feedback, thereby underscoring the necessity for an in-depth investigation of transformer architecture-based NLP models. In this study, we conducted an exploration of the large language model BERT and three of its derivatives using an airline sentiment tweet dataset for downstream tasks. We further honed this fine-tuning by adjusting the hyperparameters, thus improving the model’s consistency and precision of outcomes. With RoBERTa distinctly emerging as the most precise and overall effective model in both the binary (96.97%) and tri-class (86.89%) sentiment classification tasks and persisting in outperforming others in the balanced dataset for tri-class sentiment classification, our results validate the BERT models’ application in analyzing airline industry customer sentiment. In addition, this study identifies the scope for improvement in future studies, such as investigating more systematic and balanced datasets, applying other large language models, and using novel fine-tuning approaches. Our study serves as a pivotal benchmark for future exploration in customer sentiment analysis, with implications that extend from the airline industry to broader transportation sectors, where customer feedback plays a crucial role.
- 9家航空公司宣布与去哪儿网暂停合作
- 作者： 暂无 日期：2016-12-22 来源 ：中国战略新兴产业 文献类型 ：期刊 关键词：航空公司 商务合作 暂停 东方航空 中国国航 旗舰店 南航
- 描述：截至1月5日晚,已有包括东方航空、中国国航在内的9家航空公司,宣布暂停与去哪儿网的商务合作,并关闭在去哪儿网的旗舰店。2015年的最后一天,海航、南航等多家航空公司也已宣布暂停与去哪儿网的合作。
- 9家公司入围美国航空航天局商业月球着陆器计划
- 作者： 暂无 日期：2019-07-05 来源 ：中国航天 文献类型 ：期刊 关键词：月球着陆器 航空航天局
- 描述：美国航空航天局(NASA)2018年11月29日宣布为其"商业月球有效载荷服务"(CLPS)计划选定了9家公司。这些公司未来将有资格拿到向月面运送有效载荷的合同,但并不保证一定会拿到合同。NASA将购买这些厂家商业月球着陆器上的空间,用于运送科学仪器和其他有效载荷。入围的公司是宇宙机器人技术公司、深空系统公司、德雷珀公司、萤火虫宇航公司、直觉机器公司、洛马航天公司、马斯滕空间系统公司、月球快递公司和超越轨道公司(Orbit Beyond)。中选的公司既有洛马这
- 9310航空齿轮真空渗碳热处理表面强化数值模拟及工艺参数优化
- 作者： 张治中 张银 胡云波 刘洲成 日期：2024-01-01 来源 ：重庆理工大学学报(自然科学) 文献类型 ：期刊 关键词：碳浓度 9310航空齿轮 工艺参数优化 真空渗碳 有效渗碳层
- 描述：9310航空齿轮真空渗碳热处理表面强化数值模拟及工艺参数优化
- 91部通用航空企业SMS建设研究
- 作者： 严风硕 牛夏蕾 日期：2018-04-09 来源 ：科技经济市场 文献类型 ：期刊 关键词：安全管理水平 91部通航企业 SMS建设
- 描述：为有效了解91部通用航空企业安全管理体系(SMS)建设过程中存在的缺陷和不足,提高我国91部通航企业安全管理水平,结合目前我国91部通航企业的运行特点和当前行业现状,分析了SMS在民航企业安全工作中的差异,梳理出目前我国91部通航企业SMS建设存在的问题,并针对问题提出相关完善建议,激发通航企业不断解决安全问题,完善安全机制、提高安全管理水平。
- 90后民航机务人员维修作风养成研究
- 作者： 温良 徐江华 邹长安 杨成军 严俊君 毛红军 日期：2019-07-05 来源 ：民航管理 文献类型 ：期刊 关键词：机务人员 航空公司
- 描述：研究背景及意义民航机务维修的基本作用是保持航空器的适航性、安全性和可靠性,保证航班正点,确保飞行安全,是构建民航强国的安全基石和根本保障。目前中国民航维修全行业从业人员117200人左右,近5年年均增长率6.9%。随着行业的快速发展及飞机的大量引进,维修行业对人才的需求将不断增加,预计2018年至2023年人员数量情况及每年的增量情况如图1。论文小组对全行业机务人员队伍进行了回顾,自2012年起,1990年及以后(以下简称"90后")出生的人员,
- 8月，国内民航旅客运输规模创今年最高
- 作者： 暂无 日期：2021-04-09 来源 ：空运商务 文献类型 ：期刊 关键词：国际航线 民航旅客运输 旅客运输量
- 描述：从9月15日举行的民航局新闻发布会上获悉,目前中国民航正呈现出稳健的恢复发展态势。从数据看,8月,全行业完成运输总周转量75.4亿吨公里,恢复至去年同期的65.4%,同比增速较2月提高39.3个百分点,其中,客运方面,本月共完成旅客运输量4553.9万人次,接近去年同期四分之三,同比增速较2月提高了58.9个百分点,其中,国内航空客运市场加快恢复,本月共完成4535.1万人次,已恢复至去年同期八