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Rodent burrow network dynamics under human-induced landscape transformation from desert to steppe in Kalmykian rangelands

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Integrative Zoology 2019年第4期14卷 410-420页

作者： Elena SURKova Sergey popov Andrey TCHABOVSKY A.N.Severtsov Institute of Ecology and Evolution Russian Academy of SciencesMoscowRussia Department of Vertebrate Zoology Lomonosov Moscow State UniversityMoscowRussia

Rodents play an important role in rangelands through the engineering of extensive burrow systems,which provides key habitats for many animal and plant *** have analyzed the long-term variation in the abundance and distribution of rodent burrows in grazing ecosystems of southern Russia(Kalmykia)under the landscape change from desert to steppe caused by the drastic reduction of livestock after the collapse of the USSR in the early *** conducted burrow surveys in the“desert”(1980)and“steppe”(2017)periods on 193-km *** found considerable changes in burrow abundance and distribution,as well as evidence of desert habitat fragmentation and isolation caused by the expansion of tall-grass *** of the open-dwelling diurnal ground squirrel(Spermophilus pygmaeus),the dominant and the keystone species during the“desert”period,almost completely disappeared from the rodent burrow network by 2017,indicating significant habitat *** contrast,the burrows of the folivorous social vole(Microtus socialis)which was rare in the 1980s,became abundant and ubiquitously *** burrow density of the desert-dwelling psammophilous midday gerbil(Meriones meridianus)decreased,while the distances between occupied patches increased,indicating desert habitat fragmentation and loss of population *** of the folivorous tamarisk gerbils(***)were recorded only sporadically in both 1980 and *** observed changes in the rodent burrow network,the key component of grazing ecosystems,correlate with rodent species ecology and can have long-term and important consequences for ecosystem functioning.

关键词： burrows fragmentation grazing impact keystone species rodents

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Adhesive wear and particle emission: Numerical approach based on asperity-free formulation of Rabinowicz criterion

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Friction 2018年第3期6卷 260-273页

作者： Valentin L.popov Roman POHRT Institute of Mechanics Technische Universit?t Berlin National Research Tomsk State University

In 1953 Archard formulated his general law of wear stating that the amount of worn material is proportional to the normal force and the sliding distance, and is inversely proportional to the hardness of the material. Five years later in 1958, Rabinowicz suggested a criterion determining the minimum size of wear particles. Both concepts became very popular due to their simplicity and robustness, but did not give thorough explanation of the mechanisms involved. It wasn't until almost 60 years later in 2016 that Aghababaei, Warner and Molinari(AWM) used quasi-molecular simulations to confirm the Rabinowicz criterion. One of the central quantities remained the "asperity size". Because real surfaces have roughness on many length scales, this size is often ill-defined. The present paper is devoted to two main points: First, we generalize the Rabinowicz-AWM criterion by introducing an "asperity-free" wear criterion, applicable even to fractal roughness. Second, we combine our generalized Rabinowicz criterion with the numerical contact mechanics of rough surfaces and formulate on this basis a deterministic wear model. We identify two types of wear: one leading to the formation of a modified topography which does not wear further and one showing continuously proceeding wear. In the latter case we observe regimes of least wear, mild wear and severe wear which have a clear microscopic interpretation. The worn volume in the region of mild wear occurs typically to be a power law of the normal force with an exponent not necessarily equal to one. The method provides the worn surface topography after an initial settling phase as well as the size distribution of wear particles. We analyse different laws of interface interaction and the corresponding wear laws. A comprehensive parameter study remains a task for future research.

关键词： adhesion plasticity wear Archard's law of wear Rabinowicz criterion wear particle emission surface topography boundary element method (BEM)

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Recovery of Brachiopod and Ammonoid Faunas Following the End-Permian Crisis:Additional Evidence from the Lower Triassic of the Russian Far East and Kazakhstan

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Journal of Earth Science 2014年第1期25卷 1-44页

作者： Yuri D Zakharov Alexander M popov Far Eastern Geological Institute Far Eastern BranchRussian Academy of Sciences

After the End-Permian mass extinction, ammonoids reached levels of taxonomic diver- sity higher than in the Changhsingian by the Dienerian Substage of the Induan. However, brachiopods exhibit a prolonged delay in recovery, and their taxonomic diversity had not recovered to Late Permian levels even by the Olenekian. The differential patterns of recovery between these two clades may reflect fundamental differences in physiology and behavior. Brachiopods were benthic organisms that were dependent on specific trophic sources, and their general reduction in size during the Early Triassic may have been a response to a relative paucity of food resources. In contrast, ammonoids were sluggish- nektic organisms that utilized a wider range of trophic sources and that suffered no comparable size decrease during the Early Triassic. Brachiopods may have been at a disadvantage also due to vulner- abilities associated with their larval stage, during which they had to locate a suitable substrate for set- tlement. In contrast, ammonoids had no larval stage and juveniles may have been dispersed widely into favorable habitats. These factors may account for differences in the relative success of ammonoids and brachiopods at high-latitude regions following the End-Permian mass extinction： ammonoids success- fully reeolonized the Boreal region during the Early Triassic whereas brachiopods did not.

关键词： Lower Triassic South Primorye Kazakhstan brachiopod ammonoid biotic recovery.

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Prompt neutron emission in ^(250)No spontaneous fission associated with ground and isomeric state decays

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Chinese Physics C 2024年第6期48卷 112-117页

作者： R.S.Mukhin A.V.Isaev A.V.Andreev M.L.Chelnokov V.I.Chepigin H.M.Devaraja I.N.Izosimov A.A.Kuznetsova O.N.Malyshev A.G.Popeko Yu.A.popov A.Rahmatinejad B.Sailaubekov T.M.Shneidman E.A.Sokol A.I.Svirikhin M.S.Tezekbayeva M.A.Bychkov A.V.Yeremin O.Dorvaux B.Gall K.Kessaci K.Hauschild A.Lopez-Martens Joint Institute for Nuclear Research Dubna141980Russia Dubna State University Dubna141982Russia Institute of Nuclear Physics Almaty050032Kazakhstan L.N.Gumilyov Eurasian National University Astana010008Kazakhstan Kazan Federal University Kazan420008Russia Universitéde Strasbourg CNRSStrasbourg67000France IJCLab IN2P3-CNRSUniversitéParis-SaclayOrsay91400France

The complete-fusion reaction^(204)Pb(^(48)Ca,2n)^(250)No was used to study two activities of^(250)No with distinct half-lives.A total of 1357 events were observed in the SFiNx neutron detection *** average number of neutrons emitted per spontaneous fission of^(250)No was determined to be(4.1±0.1).The unusually symmetrical shape of the prompt neutron multiplicity distribution was restored and presented for the first *** tests were performed to compare the prompt neutron multiplicity distributions associated with the ground state and K-isomer state decays.

关键词： spontaneous fission prompt neutrons actinide

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Multiscale Modeling and Simulations of Flows in Naturally Fractured Karst Reservoirs

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Communications in Computational Physics 2009年第6期6卷 162-184页

作者： Peter popov Yalchin Efendiev Guan Qin Institute for Scientific Computation Texas A&M UniversityCollege StationTX 77843 Department of Mathematics Texas A&M UniversityCollege StationTX 77843

Modeling and numerical simulations of fractured,vuggy,porus media is a challenging problem which occurs frequently in reservoir *** problem is especially relevant in flow simulations of karst reservoirs where vugs and caves are embedded in a porous rock and are connected via fracture networks at multiple *** this paper we propose a unified approach to this problem by using the StokesBrinkman equations at the fine *** equations are capable of representing porous media such as rock as well as free flow regions(fractures,vugs,caves)in a single system of *** then consider upscaling these equations to a coarser *** cell problems,needed to compute coarse-scale permeability of Representative Element of Volume(REV)are discussed.A mixed finite element method is then used to solve the Stokes-Brinkman equation at the fine scale for a number of flow problems,representative for different types of vuggy *** is also performed by numerical solutions of Stokes-Brinkman cell problems in selected *** isolated vugs in porous matrix as well as vugs connected by fracture networks are analyzed by comparing fine-scale and coarse-scale flow *** different types of fracture networks,representative of short-and long-range fractures are studied *** is also shown that the Stokes-Brinkman equations can naturally be used to model additional physical effects pertaining to vugular media such as partial fracture with fill-in by some material and/or fluids with suspended solid particles.

关键词： Homogenization Stokes equation Brinkman equation porous media

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Experimental and Numerical Assessment of the Influence of Bottomhole Pressure Drawdown on Terrigenous Reservoir Permeability and Well Productivity

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Fluid Dynamics & Materials Processing 2023年第3期19卷 619-634页

作者： Sergey popov Sergey Chernyshov Evgeniy Gladkikh Oil and Gas Research Institute of Russian Academy of Science Moscow119333Russian Perm National Research Polytechnic University Perm614990Russian

During oil and gas fields development,a decrease in reservoir and bottomhole pressure has often a detrimental effect on reservoir properties,especially *** study presents the results of laboratory tests conducted to determine the response of terrigenous reservoir core-sample permeability to changes in the effective stresses and a decrease in the reservoir *** considered samples were exposed for a long time to a constant high effective stress for a more reliable assessment of the viscoplastic *** to these experiments,the decrease of the core samples permeability may reach 21%with a decrease in pressure by 9.5 MPa from the initial reservoir *** simulations have been also *** have been based on the finite element modeling of the near-wellbore zone of the terrigenous reservoir using poroelasticity *** simulation results show a limited decrease in reservoir permeability in the near-wellbore zone(by 17%,which can lead to a decrease in the well productivity by 13%).

关键词： Terrigenous reservoir permeability core sample reservoir pressure bottomhole pressure drawdown effective stress well productivity

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Strength of adhesive contacts: Influence of contact geometry and material gradients

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Friction 2017年第3期5卷 308-325页

作者： Valentin L.popov Roman POHRT Qiang LI Institute of Mechanics Technische Universit(a)t Berlin Berlin 10623 GermanyNational Research Tomsk Polytechnic University Tomsk 634050 Russia Institute of Mechanics Technische Universit(a)t Berlin Berlin 10623 Germany

The strength of an adhesive contact between two bodies can strongly depend on the macroscopic and microscopic shape of the *** the past,the influence of roughness has been investigated ***,even in the presence of perfectly smooth surfaces,geometry can come into play in form of the macroscopic shape of the contacting *** we present numerical and experimental results for contacts of rigid punches with flat but oddly shaped face contacting a soft,adhesive *** it is carefully pulled off,we find that in contrast to circular shapes,detachment occurs not instantaneously but detachment fronts start at pointed comers and travel inwards,until the final configuration is reached which for macroscopically isotropic shapes is almost *** elongated indenters,the final shape resembles the original one with rounded *** describe the influence of the shape of the stamp both experimentally and *** simulations are performed using a new formulation of the boundary element method for simulation of adhesive contacts suggested by Pohrt and *** is based on a local,mesh dependent detachment criterion which is derived from the Griffith principle of balance of released elastic energy and the work of *** validation of the suggested method is made both by comparison with known analytical solutions and with *** method is applied for simulating the detachment of flat-ended indenters with square,triangle or rectangular shape of cross-section as well as shapes with various kinds of faults and to 'brushes'.The method is extended for describing power-law gradient media.

关键词： adhesion boundary element method (BEM) flat-ended indenters,gradient media

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Second-Order Invariant Domain Preserving ALE Approximation of Euler Equations

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Communications on Applied Mathematics and Computation 2023年第2期5卷 923-945页

作者： Jean-Luc Guermond Bojan popov Laura Saavedra Department of Mathematics Texas A&M UniversityCollege StationUSA Departamento de Matemática Aplicada a la Ingeniería Aeroespacial Universidad Politécnica de MadridMadridSpain

An invariant domain preserving arbitrary Lagrangian-Eulerian method for solving non-linear hyperbolic systems is *** numerical scheme is explicit in time and the approximation in space is done with continuous finite *** method is made invar-iant domain preserving for the Euler equations using convex limiting and is tested on vari-ous benchmarks.

关键词： Conservation equations Hyperbolic systems Arbitrary Lagrangian-Eulerian Moving meshes Invariant domains High-order method Convex limiting Finite element method

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Current self-limitation in a transverse nanosecond discharge with a slotted cathode

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Plasma Science and Technology 2017年第3期19卷 69-74页

作者： N A ASHURBEKOV K O IMINOV O A popov G S SHAKHSINOV Dagestan State University Faculty of Physics 43a Gadjieva Street Makhachkala 367002 Russia Moscow Power Engineering Institute Krasnokazal'mennaya 14 Moscow 111250 Russia

A high-voltage transverse pulsed nanosecond discharge with a slotted hollow cathode was found to be a source of high-energy （few kV） ribbon electron beams. Conditions for the formation and extinction of electron beams were experimentally studied in discharges in helium at pressures of 1-100 Torr. It was found that interaction of fast electrons with a non-uniform electric field near the slotted cathode led to limitation of the magnitude of the discharge current. A physical model was developed to describe the discharge current self-limitation that was in satisfactory agreement with the experimental results. Some technical solutions that are expected to increase the upper current limits in transverse nanosecond discharge are discussed.

关键词： nanosecond discharge electron beams upper current limitation slotted cathode

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Synchronous machine performance under geomagnetic disturbances

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High Voltage 2021年第5期6卷 894-903页

作者： Ilja Boguslawsky Nikolay Korovkin Victor popov Olga Sokolova Peter the Great St.Petersburg Polytechnic University St.PetersburgRussia Paul Scherrer Institute(PSI) VilligenSwitzerland

Geomagnetic disturbances(GMDs)are known to disturb power system equipment *** danger is associated with geomagnetically induced currents(GICs)occurring at the Earth's surface during *** do not endanger power system operation conditions by *** main challenge posed by GICs to power system states is the change in power system equipment operation conditions provoked by GIC *** primary avenue of blackout caused by GMDs is through power ***,in turn,can impair the operation of other power system equipment such as syn-chronous *** powerful synchronous machines are not designed and engineered to cope with the negative impacts of ***,the actual legal norms are inadequate in this *** the grid's resiliency to such an event is highly interesting to the *** physical processes in synchronous machine windings triggered by GICs and limitations brought to power grid operations are ***,the idea of the impact of GMDs on the power grid operation is *** analysis of the impact of GMDs on synchronous machines is performed in the second *** the end,the power system response under GMDs is studied.

关键词： geomagnetic Earth performance

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