检索结果-南通市图书馆

On the size of the intersection of two Lucas sequences of distinct type Ⅱ

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 2011年第7期54卷 1299-1316页

作者： cipu mihai MIGNOTTE Maurice TOGB Alain Institute of Mathematics of the Romanian Academy Bucharest RO-014700 Romania U. F. R. de Mathmatiques Universit de Strasbourg Strasbourg 67084 France Department of Mathematics Purdue University North Central Westville IN 46391 USA

Let a and b be positive integers, with a not perfect square and b > 1. Recently, He, Togband Walsh proved that the Diophantine equation x2-a((bk-1)/(b-1))2=1 has at most three solutions in positive integers. Moreover, they showed that if max{a,b} > 4.76·1051, then there are at most two positive integer solutions (x,k). In this paper, we sharpen their result by proving that this equation always has at most two solutions.

关键词： Diophantine equation exponential equation linear forms in logarithms

Dynamic event-triggered fault-tolerant cooperative resilient tracking control with prescribed performance for UAVs

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2024年第8期67卷 67-84页

作者： Rong YUAN Zhengcai AN Shuyi SHAO Mou CHEN mihai LUNGU College of Automation Engineering Nanjing University of Aeronautics and Astronautics Science and Technology on Electro-optic Control Laboratory Faculty of Electrical Engineering University of Craiova Aerospace Engineering Doctoral School University Politehnica of Bucharest

In this paper, a resilient tracking control scheme with cooperative collision avoidance performance is studied for the fixed-wing unmanned aerial vehicle(UAV) leader-follower formation in the presence of actuator failures and external disturbances. Firstly, based on the control objectives of UAV formation tracking and collision avoidance, the transformation tracking errors are obtained using the prescribed performance control technique. Next, a fault detection mechanism is introduced to determine if there is the actuator fault. Subsequently, the event-triggered resilient fault observers are designed based on a dynamic eventtriggered mechanism to estimate actuator faults. Furthermore, the prescribed performance functions and the H∞ performance index are employed to ensure the UAV formation collision-free and mitigate the impact of disturbances. Moreover, the resilient controller is designed to minimize the effect of the perturbations for the control gain and the fault observer gain on the system. The stability of the system is also proven through the Lyapunov stability analysis, and the controller gains are calculated by solving the linear matrix ***, the validity of the proposed control strategy is demonstrated by the simulation analysis.

关键词： UAV formation cooperative collision avoidance event-triggered fault observer prescribed performance resilient control

High temperature oxidation of inoculated high Si/SiMo ductile cast irons in air and combustion atmospheres

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

China Foundry 2024年第5期21卷 555-562页

作者： Iuliana Stan mihai Chisamera Robert Lascu Codrut Cariga Eduard Stefan Stelian Stan Denisa Anca Iulian Riposan National University of Science and Technology POLITEHNICA Bucharest Materials Science and Engineering Faculty313 Splaiul IndependenteiSector 6060042 BucharestRomania

The present work aims to investigate the effect of heating temperature(400,600 and 800°C)and inoculating elements(Ca,Ca-Ba,Ca-RE)on oxidation behavior of ductile irons containing 5.25%Si and 4.8%Si-2.3%Mo in dry air and combustion gas containing water vapour(natural gas burning).The oxidation is influenced by the gas atmosphere type,the iron alloying system,and the inoculating elements depending on the heating *** weight gain increases from 0.001%-0.1%(400°C)to 0.05%-0.70%(600°C)and up to 0.10%-2.15%(800°C).No particular effects of the considered influencing factors are found when heating at 400°C,while at 600°C,mainly the oxidation gas atmosphere type shows a visible *** the highest heating temperature of 800°C,a limited increase of the weight gain is found for dry air atmosphere(up to 0.25%),but it drastically increases for combustion atmospheres(0.65%-2.15%).The water vapour presence in the combustion atmosphere is an important oxidising factor at 600-800°*** alloying system appears to influence the oxidation behavior mainly at a heating temperature of 800°C in the combustion atmosphere,as evidenced by the lower weight gain in 5.25%silicon cast *** effects of inoculating elements increase with the heating temperature,with Ca and Ba-FeSi inoculation generally showing better *** inoculated with CaRE-FeSi exhibit a higher degree of *** results are in good relationship with the previous reported data:Ca-Ba-inoculation system appears to be better than simple Ca for improving the graphite parameters,while RE-bearing inoculant negatively affects the compactness degree of graphite particles in high-Si ductile *** the lower compactness degree is typical for graphite nodules in high-Si ductile irons,which negatively affects the oxidation resistance,it is necessary to employ specific metallurgical treatments to improve nodule ***,in particular,is a potential method to achieve this improvement.

关键词： ductile iron spheroidal graphite Si/SiMo oxidation air/combustion atmospheres FeSiCaMgRE treatment Ca,Ca-Ba,Ca-RE inoculation structure characteristics

Repeat-pass space-surface bistatic SAR tomography:accurate imaging and first experiment

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) 2024年第9期67卷 245-262页

作者： Zhiyang CHEN Yuanhao LI Cheng HU Shenglei WANG Xinpeng CHEN mihai DATCU Andrea Virgilio MONTI-GUARNIERI Radar Technology Research Institute School of Information and Electronics Beijing Institute of Technology Beijing Key Laboratory of Embedded Real-Time Information Processing Technology Beijing Institute of Technology Advanced Technology Research Institute Beijing Institute of Technology CEOSpace Tech University Politehnica of Bucharest Dipartimento di Elettronica Informazione e Bioingegneria Politecnico di Milano

Space-surface bistatic synthetic aperture radar(SS-BiSAR) offers an additional observation angle for monostatic spaceborne SAR, making it a promising technology for high-accuracy deformation retrieval technology in local regions. Repeat-pass SS-BiSAR tomography can accurately estimate the surfaces of buildings and steep areas, effectively removing terrain phases during deformation retrieving. However, inaccuracies in the orbital ephemeris can lead to image geometry distortion, reducing image pair coherence,introducing interferometric phase errors, and consequently deteriorating tomographic precision. This paper precisely models the image geometry distortion and interferometric phase error caused by repeat-pass ephemeris error. We propose an ephemeris correction method based on the chirp-Z transform to address these issues. Furthermore, we introduce an accurate tomography model to improve 3D reconstruction *** first SS-BiSAR tomography experiment, conducted using the Chinese Lutan-1 satellite, demonstrates that the correlation coefficient is improved by 0.16 after ephemeris error correction. Moreover, the density and precision of the tomographic point cloud are improved by 13.7% and 12.1%, respectively.

关键词： space-surface SAR tomography orbit error image distortion Lutan-1

End-Triassic storm deposits in the lacustrine Sichuan Basin and their driving mechanisms

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 Earth Sciences 2024年第7期67卷 2383-2400页

作者： Jianli ZENG Tingshan ZHANG mihai Emilian POPA Yongdong WANG Xi ZHANG Liqin LI Yuanyuan XU Ning LU Xiaoqing ZHANG School of Geoscience and Technology Southwest Petroleum University Chengdu 610500China Sichuan Key Laboratory of Natural Gas Geology Southwest Petroleum University Chengdu 610500China Faculty of Geology and Geophysics Doctoral Schoolof Geology Laboratory of Palaeontology University of Bucharest.Bucharest 010041Romania Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences Nanjing 210008China University of Chinese Academy of Sciences NanjingNanjing 210008China University of Chinese Academy of Sciences Beijing 100049China

Storm deposits or tempestites are event sequences formed by storms,requiring at least a water temperature of 26.5℃.While inland lakes are unlikely to form storm deposits because of their limited width and water *** Upper Triassic Xujiahe Formation in the Sichuan Basin is a set of coal-bearing,clastic sequences with dominant sedimentary facies varying from braided river delta to lacustrine settings,with storm deposits widely *** the Zilanba of Guanyuan area,in situ tree trunks on a palaeosol surface in Member Vof the Xujiahe Formation provide new evidence of a storm *** fallen-down directions of nine in situ tree trunks were predominant in the NW direction,contrary to the palaeocurrent direction of the underlying strata,suggesting that the southeasterlies prevailed during the end-Triassic in the northern Sichuan *** mud clasts were frequently recorded in sandstones of the Xujiahe Formation,as well as in the Xindianzi *** mud clasts showed a rip-up or a plastic deformation with upside-down V-shapes,were capped on an erosional surface,showed no transport traces and were therefore interpreted as a storm lag *** megamonsoonal climate prevailed during the Late Triassic,although the megamonsoons themselves could not generate a storm deposition in the Xujiahe Formation due to its low maximum surface wind *** driving mechanism for generating storm deposits in the Xujiahe Formation is suggested to be tropical cyclones over the Tethys Ocean moving eastward,further landfalling on the western margin of the Sichuan *** of storm events in the circum-Tethys region show a widespread storm surge in low latitudes during the *** storm deposits at the top of the Xujiahe Formation represent a sedimentary response to the end-Triassic hyperthermal event.

关键词： Sichuan Basin End-Triassic Xujiahe Formation Storm deposits

Modular-integrative modeling: a new framework for building brain models that blend biological realism and functional performance

在线全文

学校读者我要写书评

暂无评论

National Science Review 2024年第5期11卷 13-16页

作者： Mario Senden Sacha J.van Albada Giovanni Pezzulo Egidio Falotico Ibrahim Hashim Alexander Kroner Anno C.Kurth Pablo Lanillos Vaishnavi Narayanan Cyriel Pennartz mihai A.Petrovici Lea Steffen Tonio Weidler Rainer Goebel Department of Cognitive Neuroscience Maastricht University Maastricht Brain Imaging Centre Maastricht University Institute of Neuroscience and Medicine(INM-6) and Institute for Advanced Simulation(IAS-6) and JARA-Institut Brain Structure-Function Relationships(INM-10) Jülich Research Center Institute of Zoology University of Cologne Institute of Cognitive Sciences and Technologies The Bio Robotics Institute Scuola Superiore Sant'Anna RWTH Aachen University Donders Institute for Brain Cognition and BehaviorRadboud University Cognitive and Systems Neuroscience Group Swammerdam Institute for Life Sciences University of Amsterdam Department of Physiology University of Bern FZI Research Center of Information Technology

To cope with the immense complexity of the brain, neuroscientific research often focuses on isolated brain structures or circumscribed perceptual, cognitive or motor functions [1]. This reductionist approach overlooks the intricate and multifaceted interplay among various structural and functional *** instance, even simple movements require the coordinated activation of numerous neuronal populations across multiple brain regions [2].

关键词： WORLD SURVEY PROJECTS

Exploring fs-laser irradiation damage subthreshold behavior of dielectric mirrors via electrical measurements

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

High Power Laser Science and Engineering 2024年第2期12卷 24-32页

作者： Petrisor Gabriel Bleotu Radu Udrea Alice Dumitru Olivier Uteza Maria-Diana mihai Dan Gh Matei Daniel Ursescu Stefan Irimiciuc Valentin Craciun Extreme Light Infrastructure-Nuclear Physics(ELI-NP) Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering(IFIN-HH)MagureleRomania Doctoral School of Physics University of BucharestMagureleRomania LULI-CNRS CEAUniversite SorbonneEcole PolytechniqueInstitut Polytechnique de ParisPalaiseau CEDEXFrance Apel Laser IlfovRomania Aix-Marseille University CNRSLP3 UMR 7341MarseilleFrance Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering(IFIN-HH) MagureleRomania University Politehnica of Bucharest BucharestRomania National Institute for Lasers Plasma and Radiation Physics MagureleRomania

With ultrafast laser systems reaching presently 10 PW peak power or operating at high repetition rates,research towards ensuring the long-term,trouble-free performance of all laser-exposed optical components is *** work is focused on providing insight into the optical material behavior at fluences below the standardized laser-induced damage threshold(LIDT)value by implementing a simultaneous dual analysis of surface emitted particles using a Langmuir probe(LP)and the target current(TC).HfO_(2) and ZrO_(2) thin films deposited on fused silica substrates by pulsed laser deposition at various O_(2) pressures for defect and stoichiometry control were irradiated by Gaussian,ultrashort laser pulses(800 nm,10 Hz,70 fs)in a wide range of *** TC and LP collected signals were in good agreement with the existing theoretical description of laser–matter interaction at an ultrashort time *** approach for an in situ LIDT monitoring system provides measurable signals for below-threshold irradiation conditions that indicate the endurance limit of the optical surfaces in the single-shot energy scanning *** LIDT value extracted from the LP-TC system is in line with the multipulse statistical analysis done with ISO 21254-2:2011(E).The implementation of the LP and TC as on-shot diagnostic tools for optical components will have a significant impact on the reliability of next-generation ultrafast and high-power laser systems.

关键词： HfO_(2) in situ detection Langmuir probe laser-induced damage threshold target current ZrO_(2)

在线全文

学校读者我要写书评

暂无评论

World Journal of Otorhinolaryngology-Head and Neck Surgery 2024年第2期10卷 97-104页

作者： mihai A.Bentan Evan R.Reiter Richard M.Costanzo Daniel H.Coelho Department of Otolaryngology-Head&Neck Surgery Virginia Commonwealth University School of MedicineRichmondVirginiaUSA

Objective:The aim of this study was to review findings from a large prospective national database of chemosensory disturbances associated with coronavirus disease 2019(COVID-19)*** Sources:The Virginia Commonwealth University Smell and Taste Center national database of COVID-19 chemosensory ***:A series of online surveys,first opened on April 10,2020,was made accessible nationwide to any adult with sudden chemosensory dysfunction since January *** received subsequent follow-up surveys 14 days,1 month,3 months,and 6 months after *** additional survey was sent to all participants on May 28,2022 to assess long-term *** pertaining to demographics,symptoms,comorbidities,treatments,and life impact was ***:Of 363 participants who reported complete smell recovery,51.2%recovered within 1 month,70%within 3 months,and 79%within 6 months,while 8.8%took over 1 year to completely *** all participants,7.5%had no smell *** predictors of recovery included age<40,male gender,and the presence of nasal *** predictors included difficulty breathing and prior head *** participants reported a decrease in quality of life and the presence of potential safety hazards associated with decreased smell ***:Most subjects with COVID-19-related chemosensory dysfunction recover,with the majority noting complete recovery within weeks of *** aged over 40 years and female gender were associated with lower rates of recovery.A considerable number of participants reported significant impact on quality of life and safety.

关键词： anosmia COVID-19 smell

Mechanical Properties of Collagen Biomimetic Films Formed in the Presence of Calcium,Silica and Chitosan

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2008年第2期5卷 149-158页

作者： mihai Chirita Medical Bioengineering Faculty Medicine and Pharmacy University "Gr.T.Popa"Iasi 7000115Romania

Using eucollagen solutions from ox hide, we cast collagen films to assess the influence of calcium and silica on the reconstitution of the fibrous structure of collagen. The tensile strength and the breaking elongation of the reconstituted collagen films were measured and analysed. Significant differences were observed between reconstituted collagen films with and without calcium and silica. The breaking elongation of the films obtained in the presence of silica was significantly greater, and the degradation was lower than other films of reconstituted collagen. Collagen and chitosan do not exist together as blends in nature, but the specific properties of each may be used to produce in biomimetic way man-made blends with biomedical applications, that confer unique structural, mechanical （detail） and in vivo properties.

关键词： modified collagen biomimetic films chitosan biomaterials biopolymers mechanical properties