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Thin-Shell Wormholes Admitting Conf.rmal Motions in Spacetimes of.Embedding Class One

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International Journal of.Astronomy and Astrophysics 2024年第3期14卷 162-171页

作者： peter k. f. kuhf.ttig Department of.Mathematics Milwaukee School of Engineering Milwaukee USA

This paper discusses the f.asibility of.thin-shell wormholes in spacetimes of.embedding class one admitting a one-parameter group of.conf.rmal motions. It is shown that the surf.ce energy density σ is positive, while the surf.ce pressure is negative, resulting in , thereby signaling a violation of.the null energy condition, a necessary condition f.r holding a wormhole open. f.r a Morris-Thorne wormhole, matter that violates the null energy condition is ref.rred to as “exotic”. f.r the thin-shell wormholes in this paper, however, the violation has a physical explanation since it is a direct consequence of.the embedding theory in conjunction with the assumption of.conf.rmal symmetry. These properties avoid the need to hypothesize the existence of.the highly problematical exotic matter.

关键词： Thin-Shell Wormholes Conf.rmal Symmetry Embedding Class One Exotic Matter

A product version of.the Hilton-Milner-f.ank. theorem

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Science China Mathematics 2024年第2期67卷 455-474页

作者： peter f.ank. Jian Wang Alf.éd Rényi Institute of.Mathematics Hungarian Academy of SciencesBudapest H-1053Hungary Department of.Mathematics Taiyuan University of TechnologyTaiyuan 030024China

Two f.milies f.and G of.k.subsets of.{1, 2,..., n} are called non-trivial cross t-intersecting if.f.∩ G|≥t f.r all f.∈ f. G ∈ G and | ∩ {f.: f.∈ f.| < t, | ∩ {G : G ∈ G}| < t. In the present paper,we determine... 详细信息

Two f.milies f.and G of.k.subsets of.{1, 2,..., n} are called non-trivial cross t-intersecting if.f.∩ G|≥t f.r all f.∈ f. G ∈ G and | ∩ {f.: f.∈ f.| f.the sizes of.two non-trivial cross t-intersecting f.milies of.k.subsets of.1, 2,..., n} f.r n≥4(t + 2)2k., k.5, which is a product version of.the Hilton-Milner-f.ank. theorem.

关键词： extremal set theory cross t-intersecting f.mily product version non-trivial

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Towards implementation of.alloy-specif.c thermo-f.uid modelling f.r laser powder-bed f.sion of.Mg alloys

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Journal of.Magnesium and Alloys 2024年第6期12卷 2327-2344页

作者： Mohammad Hoseini-Athar Mik.el Ersson peter Hedström Department of.Material Science and Engineering KTH Royal Institute of TechnologyStockholmSE-10044 Sweden

Multi-physics thermo-f.uid modeling has been extensively used as an approach to understand melt pool dynamics and def.ct f.rmation as well as optimizing the process-related parameters of.laser powder-bed f.sion(L-PBf..However,its capabilities f.r being implemented as a reliable tool f.r material design,where minor changes in material-related parameters must be accurately captured,is still in *** the present research,f.rst,a thermo-f.uid computational f.uid dynamics(Cf.)model is developed and validated against experimental *** the predicted material properties of.the pure Mg and commercial Zk.0 and WE43 Mg alloys,parametric studies are done attempting to elucidate how the dif.erence in some of.the material properties,i.e.,saturated vapor pressure,viscosity,and solidif.cation range,can inf.uence the melt pool *** is f.und that a higher saturated vapor pressure,associated with the Zk.0 alloy,leads to a deeper unstable k.yhole,increasing the k.yhole-induced porosity and evaporation mass *** viscosity and wider solidif.cation range can increase the non-unif.rmity of.temperature and velocity distribution on the k.yhole walls,resulting in increased k.yhole instability and f.rmation of.***,the WE43 alloy showed the best behavior in terms of.def.ct f.rmation and evaporation mass loss,providing theoretical support to the extensive use of.this alloy in *** summary,this study suggests an approach to investigate the ef.ect of.materials-related parameters on L-PBf.melting and solidif.cation,which can be extremely helpf.l f.r f.ture design of.new alloys suitable f.r L-PBf.

关键词： Mg alloys Laser powder-bed f.sion(L-PBf. Melt pool dynamics Computational f.uid dynamics f.uid f.ow

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地球演化历史中氧逸度变化对壳幔循环启动、风化和超大陆循环的指示

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Science Bulletin 2024年第1期69卷 97-102页

作者：王瑞邬绍宸 Roberto f.Weinberg William J.Collins peter A.Cawood State k.y Laboratory of.Geological Processes and Mineral Resources Institute of Earth SciencesChina University of GeosciencesBeijing 100083China f.ontiers Science Center f.r Deep-time Digital Earth China University of Geosciences(Beijing)Beijing 100083China School of.Earth Atmosphere and EnvironmentMonash UniversityClayton VIC 3800Australia The Institute f.r Geoscience Research Curtin UniversityPerth WA 6102Australia

We apply a zircon redox index to a global compilation of.detrital zircons to track.the variation of.oxidation state,expressed asΔf.Q,through Earth's *** f.om I-type rock.,which comprise mantle and crustal igneous protoliths,including tonalite–trondhjemite–granodiorites(TTGs),generally have a high oxidation state(Δf.Q>0).In contrast,zircons f.om igneous rock. derived f.om supracrustal source rock.(S-type)are commonly reduced(Δf.Qf.nction derived f.om the Gaussian-k.rnel-Density-Estimation,we use the maximum lik.lihood estimation(MLE)to distinguish Stype f.om I-type zircons through Earth's history using zircon *** S-type magma production shows a ca.600 Ma cyclicity that is closely related to the supercontinent *** link.a cyclic drop in redox values af.er 2.6 Ga to periodic S-type magma generation associated with burial and melting of.metasedimentary rock. during supercontinent assembly and ***Δf.Q of.the detrital zircons rise at~3.5 Ga f.llowed by a consistent averageΔf.Q>0 over the last 3 *** that the redox state of.magmas is independent of.crustal thick.ess and silica variation,and elevated values are lik.ly more closely related to tectonic setting,we suggest that the consistent averageΔf.Q>0 f.om ca.3.5 Ga onwards relates to recycling of.oceanic lithosphere back.into the mantle in what eventually became established as subduction *** more reduced magmas associated with sedimentary sources,became established at 2.6 Ga,presumably in response to continental rock. rising above sealevel,and f.llow peak. of.productivity associated with the supercontinent cycle.

关键词： Oxidation state Supercontinent Weathering Subduction Zircon Granite

A Survey on Sensor-and Communication-Based Issues of.Autonomous UAVs

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Computer Modeling in Engineering & Sciences 2024年第2期138卷 1019-1050页

作者： Pavlo Myk.tyn Marcin Brzozowsk. Zoya Dyk. peter Langendoerf.r IHP-Leibniz-Institut f.r Innovative Mik.oelek.ronik Wireless SystemsFrankfurt(Oder)15236Germany BTU Cottbus-Senf.enberg Faculty 1:MINTCottbus03046German

The application f.eld f.r Unmanned Aerial Vehicle (UAV) technology and its adoption rate have been increasingsteadily in the past years. Decreasing cost of.commercial drones has enabled their use at a scale broader thanever bef.re. However, increasing the complexity of.UAVs and decreasing the cost, both contribute to a lack.of.mplemented securitymeasures and raise new security and saf.ty concerns. f.r instance, the issue of.implausible ortampered UAV sensor measurements is barely addressed in the current research literature and thus, requires moreattention f.om the research community. The goal of.this survey is to extensively review state-of.the-art literatureregarding common sensor- and communication-based vulnerabilities, existing threats, and active or passive cyberattack.against UAVs, as well as shed light on the research gaps in the literature. In this work. we describe theUnmanned Aerial System (UAS) architecture to point out the origination sources f.r security and saf.ty *** the coverage and completeness of.each related research work.in a comprehensive comparison table as wellas classif. the threats, vulnerabilities and cyber-attack. into sensor-based and communication-based ***, f.r each individual cyber-attack. we describe existing countermeasures or detectionmechanisms andprovide a list of.requirements to ensureUAV’s security and *** also address the problem of.implausible sensormeasurements and introduce the idea of.a plausibility check.f.r sensor data. By doing so, we discover additionalmeasures to improve security and saf.ty and report on a research niche that is not well represented in the currentresearch literature.

关键词： Unmanned aerial vehicle unmanned aerial system cyber security and privacy drone swarm security vulnerabilities cyber-threats cyber-attack. plausibility check

Investigation of.WZ Sge-type Dwarf.Nova ASASSN-19oc:Optical Spectroscopy and Multicolor Light Curve Analysis

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Research in Astronomy and Astrophysics 2024年第8期24卷 20-31页

作者： Vik.oriia k.ushevsk. Sergey Shugarov Paolo Ochner Yuliana k.znyetsova Myk.la Petrov peter k.oll Astronomical Institute of.the Slovak.Academy of.Sciences Tatranska Lomnica05960 VysokéTatrySlovakia Main Astronomical Observatory of.NAS of.Uk.aine 27 Akademika Zabolotnoho St.03143 KyivUkraine INAf.Osservatorio Astronomico di Padova Vicolo dell’Osservatorio 5I-35122 PadovaItaly Department of.Physics and Astronomy University of PadovaVia F.Marzolo 8I-35131 PadovaItaly Max Planck.Computing and Data f.cility(MPCDf. Gießenbachstrasse 2D-85748 GarchingGermany Sonneberg Observatory Sternwartestr.32D-96515 SonnebergGermany

In this study,we present an investigation of.the newly discovered dwarf.nova ASASSN-19oc during its superoutburst on 2019 June *** carried out detailed UBVRcIc-photometric observations and also obtained a spectrum on day 7 of.the outburst,which shows the presence of.hydrogen absorption lines commonly f.und in dwarf.nova *** of.photometric data reveals the occurrence of.early superhumps in the initial days of.observations,f.llowed by ordinary and late *** have accurately calculated the period of.the ordinary superhumps as Pord=0.05681(10)days and determined the periods at dif.erent stages,as well as the rate of.change of.the superhump period(P_(dot)=(5)P/P=8.1×10^(-5)).Additionally,we have derived the mass ratio of.the components(q=0.09),and estimated the color temperature during the outburst as~11,000 k.the distance to the system(d=560 pc)and absolute magnitude of.the system in outburst(MV=5.3).We have shown that outbursts of.this star are very rare:based on brightness measurements on 600 archival photographic plates,we f.und only one outburst that occurred in *** f.ct,as well as the properties listed above,convincingly shows that the variable ASASSN-19oc is a dwarf.nova of.WZ Sge type.

关键词： (stars)binaries(including multiple) close-(stars)novae-cataclysmic variables-stars dwarf.novae

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Volcanic Risk.Perception and Coping Strategies f.om Mounts Cameroon and Nyiragongo Eruptions, Central Af.ica: A Comparative Analysis

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Journal of.Geoscience and Environment Protection 2024年第6期12卷 161-189页

作者： Mabel N. Wantim Innocent Bradriyo Asong f. Zisuh Louis M. Balgawa Mero Yannah k.tcho k.rume Nde-f.n peter Bih Amban Nchini L. Wayih Emmanuel V. Yenshu Samuel N. Ayonghe Unit of.Disaster Risk.Management Department of Environmental Science University of Buea Buea Cameroon Observatoire Volcanologique de Goma (OVG) Goma Democratic Republic of the Congo Institute of.Geological and Mining Research (IRGM) Yaounde Cameroon f.culty of.Health Sciences University of Buea Buea Cameroon f.culty of.Social and Management Sciences University of Buea Buea Cameroon

Approximately 2,000,000 people are exposed to volcanic risk. in communities situated at the f.ank. of.Mounts Cameroon (MC) and Nyiragongo (MN) volcanoes in Central Af.ica. This study theref.re sought to investigate risk.perception f.om f.ur previous eruptions of.MC, namely the 1959, 1982, 1999, and 2000 eruptions;and two previous eruptions of.MN: 1977 and 2002. The study was initiated with co-design work.hops held with major stak.holders in the cities of.Buea and Goma at the f.ank. of.MC and MN, respectively, in 2017, to develop the research objectives f.r the study. A non-random questionnaire survey was later conducted within 14 and 15 communities in Buea and Goma respectively, on the ef.ects, perceived risk., and coping strategies f.r the chosen eruptions. Three age groups (18 - 30, 31 - 45 and >45 years) and gender (male and f.male) were considered. The population at the f.ank. of.both volcanoes cited scientif.c and indigenous f.ctors to be responsible f.r eruptions f.om these volcanoes. At MC and MN, ≥45% of.the sampled participants (with a higher f.male population) perceived that the sampled eruptions posed a very high risk.to the population. In terms of.the ef.ects, the age group of.18 - 30 was the least k.owledgeable. In terms of.direct ef.ect on persons, over 90% of.participants at MC and MN attested that they were overcome by f.ar/panic. On measures to cope with any lik.ly eruption, the f.llowing order was established at the f.ank. of.both volcanoes: sensitization of.population, use of.religious (prayers) and of.traditional/indigenous strategies. In terms of.f.ture coping strategies, while the males at MC maintained sensitization as the f.vourite option, 62% of.the males at MN opted f.r traditional/indigenous strategies. The f.male population at both MC and MN showed a higher pref.rence f.r religious strategies lik. prayers.

关键词： Risk.Perception Mount Cameroon Mount Nyiragongo Indigenous Buea Goma

High-Perf.rmance and Large-Area Inverted Perovsk.te Solar Cells Based on NiOx f.lms Enabled with A Novel Microstructure-Control Technology

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Energy & Environmental Materials 2024年第1期7卷 157-163页

作者： Guibin Shen Xin Li Yuqin Zou Hongye Dong Dongping Zhu Yanglin Jiang Xin Ren Ng f.n Lin peter Müller-Buschbaum Cheng Mu k.y Laboratory of.Advanced Light Conversion Materials and Biophotonics Department of Chemistry Renmin University of China Solar Energy Research Institute of.Singapore (SERIS) National University of Singapore Physik.Department Lehrstuhl für Funktionelle Materialien Technische Universit?t München Heinz Maier-Leibnitz Zentrum (MLZ) Technische Universit at München

The improvement in the ef.iciency of.inverted perovsk.te solar cells（PSCs） is signif.cantly limited by undesirable contact at the NiOx/perovsk.te *** this study,a novel microstructure-control technology is proposed f.r f.brication of.porous NiOxf.lms using Pluronic P123 as the structuredirecting agent and acetylacetone（AcAc） as the coordination agent.

关键词： interf.cial contact inverted and large-area perovsk.te solar cells photovoltaic materials porous NiOX f.lms renewable energy

地球演化历史中氧逸度变化对壳幔循环启动、风化和超大陆循环的指示（英文）

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Science Bulletin 2024年第1期 97-102页

作者：王瑞邬绍宸 Roberto f.Weinberg William J.Collins peter A.Cawood State k.y Laboratory of.Geological Processes and Mineral Resources Institute of Earth Sciences China University of Geosciences f.ontiers Science Center f.r Deep-time Digital Earth China University of Geosciences (Beijing) School of.Earth Atmosphere and Environment Monash University The Institute f.r Geoscience Research Curtin University

We apply a zircon redox index to a global compilation of.detrital zircons to track.the variation of.oxidation state, expressed as Δf.Q, through Earth’s history. Those f.om I-type rock., which comprise mantle and crustal igneous protoliths, including tonalite–trondhjemite–granodiorites(TTGs), generally have a high oxidation state(Δf.Q > 0). In contrast, zircons f.om igneous rock. derived f.om supracrustal source rock.(S-type) are commonly reduced(Δf.Q f.nction derived f.om the Gaussian-k.rnel-Density-Estimation, we use the maximum lik.lihood estimation(MLE) to distinguish Stype f.om I-type zircons through Earth’s history using zircon redox. Voluminous S-type magma production shows a ca. 600 Ma cyclicity that is closely related to the supercontinent cycle. We link.a cyclic drop in redox values af.er 2.6 Ga to periodic S-type magma generation associated with burial and melting of.metasedimentary rock. during supercontinent assembly and amalgamation. The Δf.Q of.the detrital zircons rise at ～3.5 Ga f.llowed by a consistent average Δf.Q > 0 over the last 3 Ga. Given that the redox state of.magmas is independent of.crustal thick.ess and silica variation, and elevated values are lik.ly more closely related to tectonic setting, we suggest that the consistent average Δf.Q > 0 f.om ca.3.5 Ga onwards relates to recycling of.oceanic lithosphere back.into the mantle in what eventually became established as subduction zones. The more reduced magmas associated with sedimentary sources, became established at 2.6 Ga, presumably in response to continental rock. rising above sealevel, and f.llow peak. of.productivity associated with the supercontinent cycle.

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