检索结果-南通市图书馆

Evolution of electron“zebra stripes”in the South Atlantic Anomaly:Initial observations from Macao Science Satellite-1

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2024年第11期67卷 3344-3353页

作者： LIU ying ZONG QiuGang zou Hong YE YuGuang SUN YiXin Institute of Space Physics and Applied Technology Peking UniversityBeijing 100871China State Key Laboratory of Lunar and Planetary Science Macao University of Science and TechnologyMacao 999078China

“Zebra stripes”denote banded structures characterized by periodic peaks and valleys in the spectrograms of energetic electrons in the Earth's inner radiation belt and slot *** contrast to previous investigations primarily grounded in equatorial observations,this study presents two events exhibiting the evolution of electron zebra stripes within the South Atlantic Anomaly,as observed from the Macao Scientific Satellite-1 in low Earth *** findings affirm that the structural and evolutionary features of zebra stripes in both events accord with the drift echo *** start time extrapolated from the electron spectrograms correlates with substorm onsets,consistent with prior ***,the duration of zebra stripe evolution during the event of June 5–6,2023,reaches an impressive 34.7 h,a markedly longer interval than findings from the Van Allen *** discrepancy suggests that the observed lifetime of electron zebra stripes may not inherently reflect natural limitations but could be constrained by instrumental *** results implicate that high-energy-resolution detectors have the potential to significantly enhance our capacity to scrutinize the dynamics of the radiation belt.

关键词： zebra stripe inner radiation belt energetic electron South Atlantic Anomaly Macao Science Satellite large-scale electric field

A preliminary investigation on the occurrence and distribution of antibiotic resistance genes in the Beijiang River, South China

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2013年第8期25卷 1656-1661页

作者： Zhenhao Ling ying Yang Yuanli Huang shichun zou Tiangang Luan School of Marine Sciences Sun Yat-sen University Department of Civil and Environmental Engineering Hong Kong Polytechnic University Environmental Biotechnology Lab Department of Civil Engineering The University of Hong Kong Guangzhou Quality Supervision and Testing Institute

The occurrence of antibiotic resistance genes （ARGs） was investigated and quantified in 20 water samples collected in the Beijiang River, South China. Sulfonamide- and tetracycline-resistant bacteria were present in 17 and 14 of the collected 20 samples. For sulfonamide ARGs, sulI and sulII were frequently observed in the Beijiang River. The levels of sulI were higher than sulII （p 〈 0.05）, with the mean values of （1.41 ± 1.12） × 10-2 and （1.58 ± 1.71） × 10-3 copies/16S rDNA, respectively. For tetracycline ARGs, tetG had the highest frequency, 100%, followed by tetA （85%）, tetO （85%）, tetC （70%）, tetX （60%）, tetM （40%） and tetQ （20%）, while tetE and tetS were not detected in all the samples from the Beijiang River. On the other hand, tetC had the highest concentration, ranging from 8.30 × 10-2 to 13.20 copies/16S rDNA. The poor correlation between ARGs and antibiotic concentrations revealed that the self-amplification and persistence of ARGs were the reasons that made ARGs exist in the water environment even though the antibiotic selecting pressure was absent. Because so few field measurements have been conducted for investigating the levels of ARGs in rivers in South China, this study provides an important insight on better understanding the occurrence and spread of ARGs in such an ecosystem.

关键词： antibiotic resistant genes Beijiang River South China

Swelling Process of Thin Polymer Film Studied via in situ Spectroscopic Ellipsometry

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2017年第5期33卷 833-838页

作者： XU Lin zou Zhiming ZHANG Huanhuan shi Tongfei Laboratory of Surface Physics and Chemistry Guizhou Education University Guiyang 550018 P. R. China Guangxi Key Laboratory of Electrochemical and Magneto-chemical Functional Materials College of Chemistry and Bioengineering Guilin University of Technology Guilin 541004 P. R. China State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun 130022 P R. China University of Chinese Academy of Sciences Beijing 100049 P. R. China

The swelling process of thin polystyrene films in quantity was studied in this paper using the in situ spec- troscopic ellipsometry. We systematically investigated the influence of film thickness on the swelling process of thin polystyrene films. The results show that in the case of high Mw polystyrene（Mw=400000）, the curve of the swelling degree as a function of time discloses that the relaxation of the long polymer chains accompanies the diffusion of acetone molecules, The swelling process is via the Fickian relaxation mechanism. Both the values of the equilibrium swelling degree and the diffusion coefficient of acetone molecules in the polystyrene film decrease as the film thick- ness reduces under confinement. However, in the case of lowMw PS（Mw=4100）, the dewetting process is so fast be- fore the equilibrium of swelling that the whole swelling process cannot be observed.

关键词： Thin polymer film Solvent swelling Dewetting

Flat-end tool orientation based on rotation-minimizing frame

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Advances in Manufacturing 2019年第3期7卷 257-269页

作者： Xiang zou Hon-Yuen Tam Hai-Yin Xu Ke shi School of Computer Science and Technology Huazhong University of Science and TechnologyWuhan 430074People's Republic of China College of Science and Engineering Department of Mechanical EngineeringCity University of Hong KongHong KongPeople's Republic of China

Well-designed tool orientation is crucial for the quality execution of five-axis machining with flat-end *** orientation can be specified in terms of tool inclination and tool tilt *** a given surface path,these aspects need to be specified for each cutter contact point along the path,because poor tool orientation choice can cause large axial acceleration of the machine tool,leading to inferior quality of the machined *** rotation-minimizing frame aims to reduce unnecessary frame rotation during *** concept has been adopted to develop tool orientation methods that allow variation in the inclination angle,the tilt angle,and both the inclination and tilt *** intention is to reduce unnecessary rotation of the tool frame as the tool follows a specified *** was conducted in the context of five-axis flat-end tool *** on these methods,tool orientation was planned along surface paths of a torus,sphere,and *** in tool orientation were always *** the perspective of reducing tool orientation changes and axial acceleration,it was demonstrated that simultaneous variation of the inclination and tilt angles based on rotation minimization provided the best results.

关键词： Five-axis machining Tool orientation Rotation-minimizing frame Numerical control

Event-triggered attitude tracking for rigid spacecraft

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2019年第12期62卷 178-193页

作者： Deheng CAI Hengguang zou Junzheng WANG Yuan HUANG Dawei shi State Key Laboratory of Intelligent Control and Decision of Complex Systems School of AutomationBeijing Institute of Technology China Academy of Space Technology

This study aims to investigate the problem of attitude control for a spacecraft with inertial uncertainties, external disturbances, and communication restrictions. An event-triggered active disturbance rejection control approach is proposed for attitude tracking of the spacecraft. An event-triggered mechanism is introduced together with an extended state observer to jointly monitor the system states and total disturbances. The observation error is proved to be uniformly bounded. Based on the proposed control scheme,the integrated tracking system is shown to be asymptotically stable, implying successful attitude tracking of the spacecraft for the desired motion. Numerical results illustrate the effectiveness of the control strategy in achieving satisfactory tracking performance with a reduced data-transmission cost.

关键词： spacecraft attitude tracking active disturbance rejection control event-triggered control extended state observer

The effect of interface roughness on the perpendicular exchange bias of NiO/CoPt/Pt stacking structure

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2021年第3期64卷 605-610页

作者： GAO ying HARUMOTO Takashi NAKAMURA Yoshio shi Ji Department of Materials Science and Engineering Tokyo Institute of Technology2-12-1OokayamaMeguro-kuTokyo 152-8550Japan

An orthogonal coupling structure of NiO/CoPt/Pt/glass with perpendicular exchange bias effect has been *** exchange bias is found to be strongly dependent on the interface roughness between NiO and CoPt *** conventional inverse proportionality of the exchange bias field with the ferromagnetic thickness is not applicable to this top-pinned stacking ***,an anomalous ferromagnetic thickness dependence of blocking temperature is also observed.A simulation on the basis of a spin configuration model with defects at the interface agrees well with the experimental *** findings suggest considerable contribution of the interface roughness to the perpendicular exchange bias.

关键词： perpendicular exchange bias interface roughness FM thickness blocking temperature

PosFuzz:augmenting greybox fuzzing with effective position distribution

在线全文

学校读者我要写书评

暂无评论

Cybersecurity 2023年第4期6卷 123-143页

作者： Yanyan zou Wei zou JiaCheng Zhao Nanyu Zhong Yu Zhang Ji shi Wei Huo Institute of Information Engineering Chinese Academy of SciencesBeijingChina School of Cyber Security University of Chinese Academy of SciencesBeijingChina State Key Lab of Processors Institute of Computing TechnologyChinese Academy of SciencesBeijingChina Key Laboratory of Network Assessment Technology Chinese Academy of SciencesBeijingChina Beijing Key Laboratory of Network Security and Protection Technology BeijingChina Zhongguancun Laboratory BeijingChina

Mutation-based greybox fuzzing has been one of the most prevalent techniques for security vulnerability discovery and a great deal of research work has been proposed to improve both its efficiency and ***-based greybox fuzzing generates input cases by mutating the input seed,i.e.,applying a sequence of mutation operators to randomly selected mutation positions of the ***,existing fruitful research work focuses on scheduling mutation operators,leaving the schedule of mutation positions as an overlooked aspect of fuzzing *** paper proposes a novel greybox fuzzing method,PosFuzz,that statistically schedules mutation positions based on their historical *** makes use of a concept of effective position distribution to represent the semantics of the input and to guide the *** first utilizes Good-Turing frequency estimation to calculate an effective position distribution for each mutation *** then leverages two sampling methods in different mutating stages to select the positions from the *** have implemented PosFuzz on top of AFL,AFLFast and MOPT,called Pos-AFL,-AFLFast and-MOPT respectively,and evaluated them on the UNIFUZZ benchmark(20 widely used open source programs)and LAVA-M *** result shows that,under the same testing time budget,the Pos-AFL,-AFLFast and-MOPT outperform their counterparts in code coverage and vulnerability discovery *** with AFL,AFLFast,and MOPT,PosFuzz gets 21%more edge coverage and finds 133%more paths on *** also triggers 275%more unique bugs on average.

关键词： Greybox fuzzing Mutation position Mutation operator Code coverage Vulnerability discovery

Perspective on synthesis of high-energy-density fuels:From petroleum to coal-based pathway

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2021年第7期34卷 83-91页

作者： Chengxiang shi Jisheng Xu Lun Pan Xiangwen Zhang Ji-Jun zou Key Laboratory for Green Chemical Technology of the Ministry of Education School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China Collaborative Innovative Center of Chemical Science and Engineering(Tianjin) Tianjin 300072China

High-energy–density(HED)fuel is specifically pivotal to improve the performance of volume-limited *** widely used HED fuels composed of polycyclic hydrocarbons are mainly synthesized from petroleum *** order to ensure abundant supply,alternative resources such as coal should be ***,we summarize the synthesis methods and properties of typical HED fuels by using petroleum-derived cyclopentadiene(CPD)as key feedstock through dimerization,cycloaddition,hydrogenation and isomerization/photoisomerization reactions,and then propose a blueprint for synthesizing HED fuels from *** method to produce CPD from coal is analyzed and feasibility is demonstrated according to theoretical calculations and reported *** review provides a novel route for synthesis of HED fuels from coal.

关键词： High-energy-density Fuel Alkane Petroleum Cyclopentadiene Coal

Triplet excitation dynamics of β-carotene studied in three solvents by ns flash photolysis spectroscopy

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2017年第1期28卷 83-88页

作者： ying Jia ying shi Peng Wang Jian-Ping Zhang Department of Chemistry Renmin University of China Beijing 100872 China

Upon anthracene-sensitizing, triplet excitation dynamics of β-carotene（β-Car） were studied in nhexane, in methanol, and in acetonitrile, respectively, by ns flash photolysis spectroscopy. In n-hexane,only the bleaching of the ground state absorption（GSB） and the excitation triplet（^3Car＊） absorption were observed, and there were no cationic species detected. In both methanol and acetonitrile, similar excitation dynamics were observed, i.e.,^3Car＊ having a similar lifetime to that in n-hexane, and the immediate generation of the cation dehydrodimer（^#[Car]2^＋） upon excitation following transformation into the radical cation Car＊^＋, since Car＊^＋ has much longer lifetime in acetonitrile than in methanol. The results prove that both solvent and carotenoid structure determine the triplet excitation mechanism.

关键词： β-Carotene Triplet excitation dynamics Solvent effect ns Flash photolysis