检索结果-南通市图书馆

Earth and Planetary Physics 2022年第5期6卷 474-486页

作者： MoRan Liu Chen Zhou Ting Feng Xiang Wang zhengyu zhao Department of Space Physics School of Electronic InformationWuhan UniversityWuhan 430072China School of Computer Science and Information Engineering Hubei UniversityWuhan 430011China

Parametric decay instability(PDI)is an important process in ionospheric heating.This paper focuses on the frequency and wavevector matching condition in the initial PDI process,the subsequent cascade stage,and the generation of strong Langmuir turbulence.A more general numerical model is established based on Maxwell equations and plasma dynamic equations by coupling highfrequency electromagnetic waves to low-frequency waves via ponderomotive force.The primary PDI,cascade process,and strong Langmuir turbulence are excited in the simulation.The matching condition in the initial PDI stage and cascade process is verified.The result indicates that the cascade ion acoustic wave may induce or accelerate the formation of cavitons and lead to the wavenumber spectrum being more enhanced at 2k_(L)(where k_(L) is the primary Langmuir wavenumber).The wavenumber spectra develop from discrete to continuous spectra,which is attributed to the caviton collapse and strong Langmuir turbulence.

关键词： ionospheric electromagnetic propagation parametric decay instability cascade Langmuir turbulence

Modeling of kilometer-scale ionospheric irregularities at Mars

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Earth and Planetary Physics 2022年第2期6卷 213-217页

作者： ChunHua Jiang Rong Tian LeHui Wei GuoBin Yang zhengyu zhao School of Electronic Information Wuhan UniversityWuhan 430072China

Recently, kilometer-scale Martian ionospheric irregularities have been measured by the Mars Atmosphere and Volatile EvolutioN(MAVEN) mission(Fowler et al., 2020). In this study, we carried out a simulation of these irregularities, assuming a uniform Martian zonal neutral wind and a cosinusoidal perturbation of the plasma density as the seeding source. Results show that a vertical electric field shear could be induced by such a plasma density perturbation. We find that the vertical electric field shear causes a velocity shear of the plasma between the topside and bottomside ionosphere, which in turn is able to produce kilometer-scale ionospheric irregularities — irregularities of a smaller scale than were seen in previous simulations(Jiang CH et al., 2021). These kilometer-scale variations with altitude, in plasma density and magnetic field profiles, are comparable to the MAVEN observations.

关键词： Martian ionosphere ionospheric irregularities numerical simulation

Evidence of X-mode heating suppressing O-mode heating

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Earth and Planetary Physics 2020年第6期4卷 588-597页

作者： Ting Feng Chen Zhou Xiang Wang MoRan Liu zhengyu zhao Department of Space Physics School of Electronic InformationWuhan UniversityWuhan 430072China

In this study,we present three experiments carried out at the EISCAT(European Incoherent Scatter Scientific Association)heating facility on October 29 and 30,2015.The results from the first experiment showed overshoot during the O-mode heating period.The second experiment,which used cold-start X-mode heating,showed the generation of parametric decay instability,whereas overshoot was not observed.The third experiment used power-stepped X-mode heating with noticeable O-mode wave leakage.Parametric decay instability and oscillating two-stream instability were generated at the O-mode reflection height without the overshoot effect,which implies suppression of the thermal parametric instability with X-mode heating.We propose that the electron temperature increased because X-mode heating below the upper hybrid height decreased the growth rate of the thermal parametric instability.

关键词： ionospheric heating parametric decay instability thermal parametric instability overshoot suppression

Numerical simulation of the propagation of electromagnetic waves in ionospheric irregularities

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Earth and Planetary Physics 2020年第6期4卷 565-570页

作者： Chun Hua Jiang LeHui Wei GuoBin Yang Chen Zhou zhengyu zhao School of Electronic Information Wuhan UniversityWuhan 430072China

The characteristics of high-frequency(HF)electromagnetic(EM)wave propagation can be affected when EM waves propagate in the ionosphere.When ionospheric irregularities appear in the ionosphere,they can have a serious impact on the propagation of HF EM waves.In this study,the propagation of HF EM waves in ionospheric irregularities was investigated by numerical simulation.First,a twodimensional model of plasma bubbles was used to produce ionospheric irregularities in the ionosphere.A ray-tracing method was then utilized to simulate the propagation of HF radio waves in these ionospheric irregularities.Results showed that the propagation of HF radio waves in the ionosphere was more complex in ionospheric irregularities than without ionospheric irregularities.In addition,corresponding ionograms were synthesized by radio rays propagated in the ionosphere with these irregularities.The synthesized ionograms were then compared with the experimental ionograms recorded by an ionosonde.Results showed that spread F could be simulated on the ionograms when ionospheric irregularities occurred in the ionosphere.This result was consistent with the ionosonde observations.

关键词： electromagnetic waves ray tracing numerical simulation ionospheric irregularities ionogram

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基于多粒度语义融合的信息检索方法

计算机应用 2024年第6期44卷 1775-1780页

作者：赵征宇罗景涂新辉武汉科技大学计算机科学与技术学院武汉430065 华中师范大学计算机学院武汉430079

信息检索(IR)是一种通过特定的技术和方法组织、处理信息,以满足用户的信息需求的过程。近年来,基于预训练模型的稠密检索方法取得了巨大的成功;然而,这些方法只利用了文本和词语的向量表征计算查询与文档相关度,忽略了它们短语层面间... 详细信息

信息检索(IR)是一种通过特定的技术和方法组织、处理信息,以满足用户的信息需求的过程。近年来,基于预训练模型的稠密检索方法取得了巨大的成功;然而,这些方法只利用了文本和词语的向量表征计算查询与文档相关度,忽略了它们短语层面间的语义信息。针对该问题,提出一种名为MSIR(Multi-Scale IR)的IR方法。所提方法通过融合查询与文档中多种不同粒度的语义信息提高IR性能。首先,构建查询和文档中词语、短语和文本这3个粒度的语义单元;其次,利用预训练模型对这3个语义单元分别进行编码获得它们的语义表征;最后,利用语义表征计算查询和文档相关度。在Corvid-19、TREC2019和Robust04这3个不同大小的经典数据集上进行了对比实验。与ColBERT(ranking model based on Contextualized late interaction over BERT(Bidirectional Encoder Representation from Transformers))相比,MSIR在Robust04数据集的P@10、P@20、NDCG@10和NDCG@20指标上均实现了约8%的提升,同时在Corvid-19和TREC2019数据集上也取得了一定的改进。实验结果表明,MSIR能够成功融合多种语义粒度,提升检索精度。

关键词：语义融合信息检索稠密检索预训练模型文本检索

An Evaluation of Chinese Human-Computer Dialogue Technology

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Data Intelligence 2019年第2期1卷 187-200页

作者： zhengyu zhao Weinan Zhang Wanxiang Che Zhigang Chen Yibo Zhang Research Center for Social Computing and Information Retrieval Harbin Institute of TechnologyHarbin 150001China AI Research Institute IFLYTEK Co.Ltd.Hefei 230088China Huawei Technologies Co. Ltd.Shenzhen 518129China

The human-computer dialogue has recently attracted extensive attention from both academia and industry as an important branch in the field of artificial intelligence(AI).However,there are few studies on the evaluation of large-scale Chinese human-computer dialogue systems.In this paper,we introduce the Second Evaluation of Chinese Human-Computer Dialogue Technology,which focuses on the identification of a user’s intents and intelligent processing of intent words.The Evaluation consists of user intent classification(Task 1)and online testing of task-oriented dialogues(Task 2),the data sets of which are provided by iFLYTEK Corporation.The evaluation tasks and data sets are introduced in detail,and meanwhile,the evaluation results and the existing problems in the evaluation are discussed.

关键词： Chinese human-computer dialogue evaluation Evaluation data User intent classification Task-oriented dialogue

Characteristics of high frequency radio wave propagated in heated ionospheric regions

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Frontiers of Electrical and Electronic Engineering in China 2009年第2期4卷 205-209页

作者： Fang HE zhengyu zhao School of Electronic Information Wuhan UniversityWuhan 430072China

A two-dimensional Ohm heating theoretic model in the magnetizing ionosphere and a ray-tracing model in a discrete ionosphere background are used to analyze quantitatively the characteristics(mainly the Doppler shift and the phase shift)of the over-the-horizon radar(OTHR)wave,which propagates through the ionospheric region heated by high frequency radio wave.The simulation results about the Doppler and the phase shift are obtained within two minutes after the heater is on.Preliminary conclusions are given by comparing the numerical results with experimental data.

关键词： over-the-horizon radar(OTHR) wave characteristics Doppler shift phase shift

A detailed investigation of low latitude tweek atmospherics observed by the WHU ELF/VLF receiver:Ⅰ. Automatic detection and analysis method

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Earth and Planetary Physics 2020年第2期4卷 120-130页

作者： RuoXian Zhou XuDong Gu KeXin Yang GuangSheng Li BinBin Ni Juan Yi Long Chen FuTai zhao zhengyu zhao Qi Wang LiQing Zhou Department of Space Physics School of Electronic InformationWuhan UniversityWuhan 430072China State Key Laboratory of Space Weather Chinese Academy of SciencesBeijing 100190China

As a dispersive wave mode produced by lightning strokes, tweek atmospherics provide important hints of lower ionospheric(i.e., D-region) electron density. Based on data accumulation from the WHU ELF/VLF receiver system, we develop an automatic detection module in terms of the maximum-entropy-spectral-estimation(MESE) method to identify unambiguous instances of low latitude tweeks.We justify the feasibility of our procedure through a detailed analysis of the data observed at the Suizhou Station(31.57°N, 113.32°E) on17 February 2016. A total of 3961 tweeks were registered by visual inspection;the automatic detection method captured 4342 tweeks, of which 3361 were correct ones, producing a correctness percentage of 77.4%(= 3361/4342) and a false alarm rate of 22.6%(= 981/4342).A Short-Time Fourier Transformation(STFT) was also applied to trace the power spectral profiles of identified tweeks and to evaluate the tweek propagation distance. It is found that the fitting accuracy of the frequency–time curve and the relative difference of propagation distance between the two methods through the slope and through the intercept can be used to further improve the accuracy of automatic tweek identification. We suggest that our automatic tweek detection and analysis method therefore supplies a valuable means to investigate features of low latitude tweek atmospherics and associated ionospheric parameters comprehensively.

关键词： tweeks automatic detection WHU-VLF receiver

A detailed investigation of low latitude tweek atmospherics observed by the WHU ELF/VLF receiver:2.Occurrence features and associated ionospheric parameters

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Earth and Planetary Physics 2020年第3期4卷 238-245页

作者： Juan Yi XuDong Gu Wen Cheng XinYue Tang Long Chen BinBin Ni RuoXian Zhou zhengyu zhao Qi Wang LiQing Zhou Department of Space Physics School of Electronic InformationWuhan UniversityWuhan 430072China State Key Laboratory of Space Weather Chinese Academy of SciencesBeijing 100190China

As a companion paper to Zhou RX et al.(2020),this study describes application of the automatic detection and analysis module to identify all the tweek atmospherics detectible in the WHU ELF/VLF receiver data collected at Suizhou station during the period of 3 February through 29 February 2016.Detailed analysis of the identified low-latitude tweek events reveals that the occurrence rate varies considerably—from 800 to 6000 tweeks per day,and exhibits a strong diurnal and local time dependence,the peak occurring before local midnight.The diurnal variation of identified tweeks was similar to that of the lightning data obtained by the World-Wide Lightning Location Network(WWLLN)..Estimates of the propagation distance and ionospheric reflection height of tweek atmospherics suggest that the majority(~92%)of the low latitude tweeks originate from the lightning activity within a radius of 4000 km and that they are very likely to reflect from the lower ionospheric D-region at the height range of 75–85 km.At these lower ionospheric reflection altitudes,~74%of the corresponding electron densities from the tweek spectral measurements are within 24.5–27.5 cm^-3.The daily variation of estimated D-region electron densities in the considered period(February 2016)also exhibits a small overall increasing trend from early to later in the month.

关键词： ionospheric D-region electron density tweek atmospherics

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《针灸秘验》刺血疗法特色探析

光明中医 2024年第4期39卷 660-663页

作者：吴俊郿赵征宇成都中医药大学针灸推拿学院四川成都610075

通过研习彭静山《针灸秘验》刺血医案归纳总结刺血疗法的规律及特点。彭氏运用刺血疗法灵活多变,广泛用于泻热解毒、镇静止痛、化瘀消癥、急救研究、消肿利水等方面。个人特色鲜明,方式方法独特。此文拟从刺血工具、刺血部位、刺血出血... 详细信息

通过研习彭静山《针灸秘验》刺血医案归纳总结刺血疗法的规律及特点。彭氏运用刺血疗法灵活多变,广泛用于泻热解毒、镇静止痛、化瘀消癥、急救研究、消肿利水等方面。个人特色鲜明,方式方法独特。此文拟从刺血工具、刺血部位、刺血出血量、刺血适应证以及刺血特色5个方面进行阐发,力图挖掘《针灸秘验》刺血疗法运用规律,加深对彭静山传统刺血疗法的认识与理解,加强临床运用水平,以期更好地传承其学术思想。

关键词：《针灸秘验》刺血疗法彭静山