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721.
飞行器遥测数据是地面判断卫星在轨状态的唯一来源。异常检测有助于飞行器运行过程的视情动态决策,并能有效减少故障。然而,现有方法主要关注短时变化,难以有效识别集合异常模式。针对这一问题,提出了一种基于长时间尺度特性建模优化的飞行器遥测数据集合异常检测方法。首先,构建时序关联依赖模型,提取遥测数据片段中的高维时序规律并生成预测结果;然后,利用预测结果与观测数据之间的残差,构建统计模型,提取分布特征并形成异常检测判据;最后,利用迭代预测自动调整模型输入,提升集合异常检测的鲁棒性。通过实际飞行器姿态角数据的验证,结果表明,相比VAE-LSTM模型,异常片段的检出率提升了0.041,F1分数提升了0.039,证明了该方法在提高检测精度和降低漏检率方面的优势,为卫星视情运维提供可靠的基础数据支撑。 相似文献
722.
针对飞行器飞行试验中外测级间段数据缺失和精度不高的问题,提出了基于长短期记忆(long-short term memory,LSTM）网络的外测级间段数据预测方法。利用遥测视速度数据和外测融合数据建立LSTM网络回归模型,将外测级间段数据作为缺失数据进行预测插值,可将制导工具系统误差以及飞行器初始误差,包括遥外测时间对不准误差,一并利用回归网络表示,从而将遥测视速度数据作为网络输入,得到外测级间段的预测数据。试验数据处理结果证明,基于LSTM网络获得的外测级间段预测数据满足精度要求,所提方法具有实际应用价值。 相似文献
723.
V. M. Bogomol'nyi 《Measurement Techniques》2003,46(6):601-611
A physical-mathematical model is formulated and the conditions for the occurrence of self-excited oscillations of acoustoelectronic and piezoelectric transducers are determined. Resonance interaction of electromechanical transducers with a source of external electrical excitation is considered in the general case. It is shown, by analogy with mechanical oscillations, that it is best to use shock-vibration and recombination resonances to increase electromechanical coupling. 相似文献
724.
文章介绍了大房郢水库水文自动测报系统的组成、功能、运行情况、系统可靠性以及关键部分的保护措施. 相似文献
725.
张悦 《西北工业大学学报》1989,(3)
本文论述了数字码分多路传输的原理,提出了9路沃尔什码分数字多路复用系统的方案和原理逻辑电路,并进行了实验验证。特别对系统的关键与难点——沃尔什码组同步系统作了巧妙的设计。该系统对于需传被测参量较少的场合,是非常理想的传输设备。 相似文献
726.
《Journal of Great Lakes research》2023,49(2):515-530
Improvements in electronic tagging techniques provide new opportunities to gain insights into fish habitat selection and behaviours that have been difficult to capture using traditional assessment methods. However, data from acoustic telemetry studies in large freshwater systems may bias our understanding of fish habitat use and behaviour because of the typically low sampling frequency of transmitters as well as the limited spatial coverage and distribution of receivers in a waterbody. This study combined acoustic transmitters and pop-off data storage tags (pDSTs) on individual walleye in Lake Ontario to gain a better understanding of the feasibility and utility of double tagging a large nearshore freshwater fish. High frequency pDST data (every 2 s) revealed a novel diving behaviour by walleye which made repeated rapid dives beyond their standard daily depth range. Comparison of data from the two tag types showed that in this large freshwater system with low overall receiver coverage (∼4%), mean monthly and daily depth and temperature occupancy of walleye were similar, although many of the extreme values observed in the pDST data were not observed in the acoustic data. The accuracy of daily vertical distance travelled by walleye and summertime diving parameters was dependent on sampling frequency and only the pDST logging on a 2 s interval was able to provide reliable results. The results of this study show that novel insights can be gained, for fish large enough to handle the burden of multiples tags, ranging from spatial ecology to diving behaviours. 相似文献
727.
Álvaro Michelena José Aveleira-Mata Esteban Jove Martín Bayón-Gutiérrez Paulo Novais Oscar Fontenla Romero José Luis Calvo-Rolle Héctor Aláiz-Moretón 《Expert Systems》2024,41(2):e13263
One of the most common attacks is man-in-the-middle (MitM) which, due to its complex behaviour, is difficult to detect by traditional cyber-attack detection systems. MitM attacks on internet of things systems take advantage of special features of the protocols and cause system disruptions, making them invisible to legitimate elements. In this work, an intrusion detection system (IDS), where intelligent models can be deployed, is the approach to detect this type of attack considering network alterations. Therefore, this paper presents a novel method to develop the intelligent model used by the IDS, being this method based on a hybrid process. The first stage of the process implements a feature extraction method, while the second one applies different supervised classification techniques, both over a message queuing telemetry transport (MQTT) dataset compiled by authors in previous works. The contribution shows excellent performance for any compared classification methods. Likewise, the best results are obtained using the method with the highest computational cost. Thanks to this, a functional IDS will be able to prevent MQTT attacks. 相似文献
728.
Philip M. Harrison Taylor Ward Dirk A. Algera Brad Culling Ted Euchner Alf Leake James A. Crossman Steven J. Cooke Michael Power 《河流研究与利用》2020,36(7):1033-1045
Potadromous salmonids that reside in hydropower reservoirs often have a high recreational and conservation value. However, the potential seasonal turbine entrainment vulnerability patterns of potadromous salmonids are not well understood. Here, we use acoustic telemetry to test the hypothesis that adults of two species of the Salvelinus genus (bull trout and lake trout) differ in their seasonal patterns of entrainment and entrainment vulnerability over a 2‐year period. Our results show that while both species were entrained at similarly low annual rates (~1%), these two salmonids differed in their patterns of forebay residency and proximity, with implications for entrainment risk. Bull trout occupied the forebay at low rates across all seasons, with no clear seasonal pattern of forebay proximity. In contrast, lake trout displayed a strongly seasonal pattern of entrainment vulnerability with a distinct movement away from the forebay during the summer, and a large increase in forebay proximity and use in the winter and spring. These findings provide a novel species‐specific demonstration of the potential entrainment vulnerability of lake trout. The seasonal patterns of entrainment vulnerability seen in previous bull trout studies, where bull trout occupied top pelagic predator niches, were not replicated in our study where bull trout occur in sympatry with another top pelagic predator. These findings, which indicate that species composition plays an important role determining entrainment vulnerability, have important implications for the conservation of indigenous lake trout and bull trout populations, and together highlight the need for a site‐specific approach to entrainment quantification. 相似文献
729.
Hoa Van Nguyen Michael Chesser Lian Pin Koh S. Hamid Rezatofighi Damith C. Ranasinghe 《野外机器人技术杂志》2019,36(3):617-635
Autonomous aerial robots provide new possibilities to study the habitats and behaviors of endangered species through the efficient gathering of location information at temporal and spatial granularities not possible with traditional manual survey methods. We present a novel autonomous aerial vehicle system—TrackerBots—to track and localize multiple radio‐tagged animals. The simplicity of measuring the received signal strength indicator (RSSI) values of very high frequency (VHF) radio‐collars commonly used in the field is exploited to realize a low‐cost and lightweight tracking platform suitable for integration with unmanned aerial vehicles (UAVs). Due to uncertainty and the nonlinearity of the system based on RSSI measurements, our tracking and planning approaches integrate a particle filter for tracking and localizing and a partially observable Markov decision process for dynamic path planning. This approach allows autonomous navigation of a UAV in a direction of maximum information gain to locate multiple mobile animals and reduce exploration time and, consequently, conserve on‐board battery power. We also employ the concept of search termination criteria to maximize the number of located animals within power constraints of the aerial system. We validated our real‐time and online approach through both extensive simulations and field experiments with five VHF radio‐tags on a grassland plain. 相似文献
730.