检索结果-南通市图书馆

Shapes of the fastest fish and optimal underwater and floating hulls

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Theoretical & Applied Mechanics Letters 2022年第6期12卷 403-408页

作者： igor Nesteruk Institute of Hydromechanics National Academy of Sciences of UkraineNational Technical University of Ukraine“Igor Sikorsky Kyiv Polytechnic Institute”Ukraine

A streamlined shape of the best swimmers removes the boundary-layer separation and ensures a laminar flow *** fastest fish have a very sharp convex nose(rostrum),the purpose of which remains *** bodies of revolution similar to their shapes are analyzed in steady underwater and floating *** sources and sinks were located on the axis of symmetry and above the water surface to estimate the pressure on the body and the vertical velocities on the water *** was shown that the flow patterns on a special shaped body with concave nose has no stagnation points and ensure small values of the water surface *** fact allow diminishing the maximum pressure on the surface and wave *** shapes with the sharp concave nose and negative pressure gradients on their surface could be parts of the low drag underwater and floating hulls.

关键词： Drag reduction Wave drag Ship hulls optimization Unseparated shapes Water locomotion

Computational approaches to substrate-based cell motility

在线全文

学校读者我要写书评

暂无评论

npj Computational Materials 2016年第1期2卷 103-118页

作者： Falko Ziebert igor S Aranson Physikalisches Institut Albert-Ludwigs-Universität FreiburgFreiburgGermany Institut Charles Sadron CNRS-UPR22StrasbourgFrance Materials Science Division Argonne National LaboratoryArgonneILUSA Engineering Sciences and Applied Mathematics Northwestern UniversityEvanstonILUSA

Substrate-based crawling motility of eukaryotic cells is essential for many biological functions,both in developing and mature *** dysfunctions are involved in several life-threatening pathologies such as cancer and *** cells are also a natural realisation of active,self-propelled‘particles’,a popular research topic in nonequilibrium ***,from the materials perspective,assemblies of motile cells and evolving tissues constitute a class of adaptive self-healing materials that respond to the topography,elasticity and surface chemistry of the environment and react to external *** a comprehensive understanding of substrate-based cell motility remains elusive,progress has been achieved recently in its modelling on the whole-cell *** we survey the most recent advances in computational approaches to cell movement and demonstrate how these models improve our understanding of complex self-organised systems such as living cells.

关键词： motility healing metastasis

On character sums with determinants

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 Mathematics 2023年第12期66卷 2693-2714页

作者： Etienne Fouvry igor E.Shparlinski CNRS Laboratoire de Mathématiques d'OrsayUniversité Paris-SaclayOrsay 91405France School of Mathematics and Statistics University of New South WalesSydneyNSW 2052Australia

We estimate weighted character sums with determinants ad-bc of 2×2 matrices modulo a prime p with entries a,b,c and d vary ing over the interval [1,N].Our goal is to obtain non-trivial bounds for values of N as small as *** particular,we achieve this goal,with a power saving,for N≥p^(1/8+ε) with any fixed ε>0,which is very likely to be the best possible unless the celebrated Burgess bound is improved,By other techniques,we also treat more general sums but sometimes for larger values of N.

关键词： character sum determinant Burgess bound

Analytical model of 2D leakoff in waterflood-induced fractures

在线全文

学校读者我要写书评

暂无评论

Journal of Rock Mechanics and Geotechnical Engineering 2023年第7期15卷 1713-1733页

作者： igor Reznikov Dimitry Chuprakov Ilmir Bekerov Schlumberger Moscow Research MoscowRussia

Waterflood-induced fractures,also known as self-induced fractures,spontaneously form at injection wells during *** fractures propagate long distances through rock,allowing injected fluids to travel far away from a well,both within and outside the flooding ***,the me-chanics of waterflood-induced fracture propagation is similar to that of hydraulic fractures,which are intentionally created for reservoir *** models developed for hydraulic fractures can also be applied to waterflood-induced ***,waterflood-induced fractures are typically pumped with much larger volumes of water or brine and grow much longer in *** a result,fluid leakoff from waterflood fractures into the formation is more extensive and two-dimensional(2D),a characteristic that is often ignored in a majority of modern fracturing simulators,making their appli-cation to waterflood fractures *** this work,we revisit the problem of leakoff for long-growing waterflood-induced fractures and develop a new analytical model for fluid leakoff that provides improved predictions of fracture geometry and can be easily implemented in fracturing *** incorporate the developed solution into the classical Perkins-Kern-Nordgren(PKN)model of fracture growth,which shows that the choice of the Carter or a 2D leakoff model greatly impacts fracture ge-ometry at large *** conducted parametric study shows while a toughness-dominated regime af-fects fracture evolution,most of fracture lifetime occurs in a viscosity-and-leakoff-dominated *** also develop an asymptotic solution for a leakoff profile in the limiting case of 2D leakoff domination(~~M and~~K).Finally,we study 3D fracture growth and out-of-zone injection with three layers and a complex structure of *** study shows that ignoring the 2D leakoff during simulation results in a significant overestimation of fracture geometry *** present work,thus,plays an impor

关键词： Waterflooding Leakoff Analytical model Hydraulic fracturing Two-dimensional flow

Dynamical behavior of a mobile system with two degrees of freedom near the resonance

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2011年第1期27卷 7-17页

作者： Klaus Zimmermann igor Zeidis Faculty of Mechanical Engineering Technische Universitaet Ilmenau

The design of mobile robots that can move without wheels or legs is an important engineering and technological ***-propelling mechanisms consisting of a body that has contact with a rough surface and moveable internal masses are *** models of such systems are presented in this ***,a model of a vibration driven robot that moves along a rough horizontal plane with isotropic dry friction is *** is shown that by changing the off-resonance frequency detuning in sign,one can control the direction of motion of the *** addition,a locomotion system which moves in an environment with anisotropic viscous friction is *** all models,the method of averaging to obtain an algebraic equation for the steady-state＂average＂velocity of the system is used. Prototypes were constructed to compare the theoretical results with experimental ones.

关键词： Dynamics Friction Resonance Vibrationdriven systems

Output feedback control with disturbancecompensation in nonlinear MIMO systems undermeasurement noises

在线全文

学校读者我要写书评

暂无评论

Journal of Control and Decision 2022年第1期9卷 35-44页

作者： igor Furtat Pavel Gushchin Institute for Problems of Mechanical Engineering of the Russian Academy of Sciences(IPME RAS) St.-PetersburgRussia

A novel output feedback control law with disturbance compensation for nonlinear multiinputmulti-output (MIMO) time-invariant systems under measurement noises is proposed. Thedesigned control law, based on the noise and disturbance estimations, ensures the accuracy insteady state depending on the disturbance, only one component of noise vector and its firstderivatives. Therefore, the proposed algorithm is efficient under noises with large *** conditions in terms of linear matrix inequalities (LMIs) provide a practical exponentialstability of the closed-loop system. The simulations illustrate an efficiency of the proposedmethod compared with some existing ones.

关键词： Nonlinear system disturbance measurement noise compensation S-procedure LMI

Development of a two-stage virtual impactor for the generation of micrometer-scale monodisperse aerosols

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Particuology 2024年第12期95卷 189-197页

作者： Jun-Hyung Lim igor Kim Se-Jin Yook School of Mechanical Engineering Hanyang UniversitySeoul04763Republic of Korea

Monodisperse particles are useful across a wide range of industrial applications,such as LCD displays,solar cells and rechargeable batteries,due to their uniformly small ***,generating high volumes of monodisperse particles remains *** this study,it was aimed to generate mono-disperse aerosols by classifying micrometer-scale solid aerosol particles within a narrow size ***,a new particle-size classification device with two virtual impactors connected in series and clean air cores was *** first-stage virtual impactor had a slightly larger cutoff size than the second-stage,and the major flow discharged from the first-stage was directed to the *** target particle size range was altered by changing the nozzle sizes in the first and second stages or by adjusting the flow ***,the classification performance of the two-stage virtual impactor was simulated and validated through an experiment using Arizona test *** implemented combi-nations of cutoff sizes for the first and second stages were 3.0 and 2.0μm,3.9 and 2.7μm,or 6.7 and 4.8μ*** a result,monodisperse aerosol particles were classified at a geometric standard deviation of 1.04-1.14 and a particle size range of 2-6.7μ*** two-stage virtual impactor developed herein may be useful for various research and performance evaluations,as it can classify micrometer-scale solid particle aerosols that exhibit high monodispersity.

关键词： Virtual impactor Clean air core Dust collection efficiency Monodispersity

Release the iron: does the infection of magnetotactic bacteria by phages play a role in making iron available in aquatic environments?

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Oceanology and Limnology 2021年第6期39卷 2063-2069页

作者： igor TAVEIRA Dennis ABAZYLINSKI Fernanda ABREU Instituto de Microbiologia Paulo de Góes Departamento de Microbiologia GeralUniversidade Federal do Rio de JaneiroRio de Janeiro 21941-902Brazil School of Life Sciences University of Nevada at Las VegasLas Vegas 94720USA

Magnetotactic bacteria(MTB)are ubiquitous prokaryotes that orient along magnetic field lines due to magnetosomes’biomineralization within the *** structures are ferrimagnetic organelles that impart a magnetic moment to the *** succeed in producing magnetosomes,MTB accumulate iron in(i)cytoplasm;(ⅱ)magnetosomes;and(ⅲ)nearby the *** has already been estimated that a single MTB has an iron content of 10 to 100-fold higher than Escherichia *** are the most abundant entity in oceans and are known for controlling nutrient flow such as carbon and nitrogen by viral shunt and *** current work addresses the putative role of phages that infect MTB on the iron biogeochemical *** phage infection in MTB hosts cause a biogenic iron fertilization-like event in localized microenvironments?Are phages critical players in driving magnetosome biomineralization genes(BGs)horizontal transfer?Further investigation of those events,including frequency of occurrence,is necessary to fully comprehend MTB’s effect on iron cycling in aqueous environments.

关键词： horizontal gene transfer iron biogeochemical cycle magnetotactic bacteria magnetosome biomineralization genes phages

Phase preservation of orbital angular momentum of light in multiple scattering environment

在线全文

学校读者我要写书评

暂无评论

Light(Science & Applications) 2024年第10期13卷 2263-2275页

作者： igor Meglinski Ivan Lopushenko Anton Sdobnov Alexander Bykov College of Engineering and Physical Sciences Aston UniversityBirmingham B47ETUK Optoelectronics and Measurement Techniques University of OuluOulu FI-90014Finland

Recent advancements in wavefront shaping techniques have facilitated the study of complex structured light’s propagation with orbital angular momentum(OAM)within various *** introduction of spiral phase modulation to the Laguerre–Gaussian(LG)beam during its paraxial propagation is facilitated by the negative gradient of the medium’s refractive index change over time,leading to a notable increase in the rate of phase twist,effectively observed as phase retardation of the *** approach attains remarkable sensitivity to even the slightest variations in the medium’s refractive index(∼10^(−6)).The phase memory of OAM is revealed as the ability of twisted light to preserve the initial helical phase even propagating through the turbid tissue-like multiple scattering *** results confirm fascinating opportunities for exploiting OAM light in biomedical applications,*** as non-invasive trans-cutaneous glucose diagnosis and optical communication through biological tissues and other optically dense media.

关键词： scattering momentum light