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Magnetic Properties of a Rare-Earth Antiferromagnetic Nanoparticle Investigated with a Quantum Simulation Model

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Chinese Physics Letters 2011年第6期28卷 251-254页

作者： LIU Zhao-Sen Sechovský Vladimir Diviš martin Faculty of Mathematics and Physics Nanjing University of Information Science and TechnologyNanjing 210044 Department of Condensed Matter Physics Faculty of Mathematics and PhysicsCharles UniversityKe Karlovu 512116 Prague 2Czech Republic

A Usov-type quantum model based on a mean-field approximation is utilized to simulate the magnetic structure of an assumed rare-earth nanoparticle consisting of an antiferromagnetic core and a paramagnetic outer *** study the magnetic properties in the presence and absence of an external magnetic *** simulation results show that the magnetic moments in the core region orientate antiferromagnetically in zero external magnetic field;an applied magnetic field rotates all of the magnetic moments in the paramagnetic shell completely to the field direction,and turns those in the core(which tries to maintain its original antiferromagnetic structure)towards the orientation in some degree;and the paramagnetic shell does not have a strong influence on the magnetic configuration of the core.

关键词： field particle turns

Magnetic Orderings and Néel Temperature of TbNi2B2C

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Chinese Physics Letters 2009年第10期26卷 177-180页

作者：刘照森 Divis martin Sechovsky Vladimir Faculty of Mathematics and Physics Nanjing University of Information Science and Technology Nanjing 210044 Department of Condensed Matter Physics Faculty of Mathematics and Physics Charles University Ke Karlovu 5 121 16 Prague 2 Czech Republic

We employ a two-ion model to calculate the spontaneous magnetization and susceptibility of TbNi2B2C with the mean-field theory, and derive an analytic formula for the Néel temperature of the material with the perturbation theory. In both the cases, only the four lowest crystal-electric-field （CEF） states are taken into account as base functions. Our theoretical results are consistent with the experimental data, manifesting the strong effects of the low lying CEF states on the magnetic behaviors of the material and the suitability of the theoretical approach proposed here.

关键词： Condensed matter: electrical magnetic and optical

Negative Magnetoresistivity of ErBi and Its Crystal-Field Levels

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Chinese Physics Letters 2009年第1期26卷 268-271页

A theoretical approach is generalized and employed in this work to evaluate the magnetoresistivity of ErBi in external magnetic fields. The calculated results and theoretical analyses show that when an external magnetic field is applied in the z-direction, the magnetoresistivity can be reduced considerably due to the degeneracy lifting of the crystal-field levels. However, when the magnetic field is exerted along the x-axis, the magnetoresistivity will be increased because of the formations of new magnetic states of the Er ion and its transitions within and between these new states.

关键词： field emission molybdenum dioxide enhancement factor

Influence of individual tree characteristics,spatial structure and logging history on tree-related microhabitat occurrence in North American hardwood forests

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Forest Ecosystems 2021年第2期8卷 357-372页

作者： Maxence martin Patricia Raymond Yan Boucher Département des Sciences fondamentales Université du Québec à Chicoutimi555boul.de l’UniversitéChicoutimiQuébec G7H 2B1Canada Institut de la recherche sur les forêts Université du Québec en Abitibi-Témiscamingue445boul.de l’UniversitéRouyn-NorandaQuébec J9X 5E4Canada Centre d'étude de la forêt Université du Québec à MontréalP.O.Box 8888Centre-ville StationMontréalQuébec H3C 3P8Canada Direction de la recherche forestière Ministère des Forêtsde la Faune et des Parcs(MFFP)2700rue EinsteinQuébecQuébec G1P 3W8Canada

Background:Tree-related microhabitats(hereafter,"TreMs")are key components of forest biodiversity but they are still poorly known in North American hardwood *** spatial patterns of living trees bearing TreMs(hereafter,"TreM-trees")also remain to be *** logging practices can lead to a loss of TreM-trees and of their associated biodiversity,it is essential to identify the factors explaining TreM occurrence to better integrate them into forest *** therefore inventoried TreMs in 40.5-ha survey strips in northern hardwood forests in Quebec,Canada,while recording the spatial location of each *** strips were located in unmanaged oldgrowth forests,and 2 were in forests managed under selection *** 4 stands were dominated by sugar maple(Acer saccharum Marsh.)and American beech(Fagus grandifolia Ehrn.).Beech bark disease,an exotic pathology,was observed in all the ***:Large diameter at breast height and low tree vigor were the main characteristics explaining the presence of TreMs at the tree ***-trees presented slight spatial aggregation *** aggregates,however,were not well-defined and were generally constituted by a large number of trees bearing few different types of *** TreM classes(broken branch or top and woodpecker lodge)also presented a spatial *** practices had no significant effect on TreM *** bark disease increased the frequency of senescent *** impact of this pathology on TreMs was however mitigated by the small size of infected trees and probably by the short time elapsed since its ***:The factors explaining the presence and abundance of TreMs on trees has so far been little studied in North American hardwood *** results highlight that TreM-tree characteristics in the surveyed forests are consistent with those of previous studies conducted in other forest types and regions(e.g.,Europe or Northwestern America).To our knowledge,th

关键词： Habitat trees Wildlife habitat Northern hardwoods Old-growth forest Selection cutting Ecosystembased management Biodiversity indicators Conservation Forest management

Linear and angular momenta in tightly focused vortex segmented beams of light(Invited Paper)

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Chinese Optics Letters 2017年第3期15卷 7-11页

作者： martin Neugebauer Andrea Aiello Peter Banzer Max Planck Institute for the Science of Light Staudtstr. 2 Erlangen D-91058 Germany Institute of Optics Information and Photonics University Erlangen-Nuremberg Staudtstr. 7/B2 Erlangen D-91058 Germany

We investigate the linear momentum density of light, which can be decomposed into spin and orbital parts, in the complex three-dimensional field distributions of tightly focused vortex segmented beams. The chosen angular spectrum exhibits two spatially separated vortices of opposite charge and orthogonal circular polarization to generate phase vortices in a meridional plane of observation. In the vicinity of those vortices, regions of negative orbital linear momentum occur. Besides these phase vortices, the occurrence of transverse orbital angular momentum manifests in a vortex charge-dependent relative shift of the energy density and linear momentum density.

关键词： Invited Paper VSB Linear and angular momenta in tightly focused vortex segmented beams of light

Strength, deformability and permeability of kakiritic rocks from the Gotthard base tunnel

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第9期15卷 2224-2237页

作者： martin Vogelhuber Erich Pimentel Georgios Anagnostou ETH Zurich ZurichSwitzerland

The 57-km long,new Gotthard Base Tunnel(GBT)crosses over a 1.1-km long stretch containing kakirites,*** rocks which,depending on the degree of tectonisation,may exhibit severe squeezing behaviour upon tunnel *** tunnel stretch was already identified as a key problem in the early planning phase,necessitating intensive geological exploration and laboratory investigations over a 14-year period,including research and development in experimental *** laboratory investigations for the GBT provided not only a considerable amount of data about the geotechnical parameters of the kakirites,but also valuable information about their basic behaviour and the adequacy of various testing techniques for this type of ***,by using specially designed testing equipment and procedures,it was shown that,(1)conventional rock mechanics triaxial tests cannot provide reliable results for kakirites;(2)the kakirites obey the principle of effective stress in Terzaghi’s classical form and consequently it is indispensable to measure the pore pressure during triaxial testing,analogously to the consolidated drained(CD)and consolidated undrained(CU)tests in soil mechanics;(3)the effects of a possible loss of water and desaturation during sampling,transport,storage and preparation of specimens can be successfully mitigated by subjecting the specimens to flow-through before the actual triaxial testing;and,(4)CD tests on partially saturated specimens that are obtained by means of flow-through can provide reliable and reproducible *** saves a significant amount of time,allows a greater number of tests to be performed,and allows results to be obtained more quickly,which is particularly important for decision-making during tunnel advance.

关键词： Squeezing Pore pressure Triaxial testing

Reproductive biology of Gazella arabica: Predictors of offspring weight and short- and long-term offspring survival

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Current Zoology 2023年第6期69卷 643-653页

作者： Ryan A.martin Rudiger Riesch martin Plath Naif A.Al Hanoosh Torsten Wronski Department of Biology DeGrace HallCase Western Reserve UniversityClevelandOHUSA Department of Biological Sciences Centre for EcologyEvolution and BehaviourRoyal Holloway University of LondonEghamSurreyUK CEFE CNRSUniv MontpellierEPHEIRDMontpellierFrance College of Nursing of Ribeirao Preto University of Sao PauloAvenida Bandeirantes 390014040-902Brazil National Center for Wildlife King Khalid Wildlife Research CenterThumamahKingdom of Saudi Arabia Faculty of Science School of Biological and Environmental SciencesLiverpool John Moores UniversityLiverpoolUK

Reproductive traits are central to organismal fitness,and so the factors influencing patterns of reproduction and offspring survival are at the heart of *** use of breeding data collected over 16 years at the King Khalid Wildlife Research Centre in Saudi Arabia,we investigated the reproductive biology of Arabian gazelles Gazella *** survival was mainly a function of birth weight,with heavier offspring having higher survival rates than lighter ***,while sons were heavier than daughters,daughters had higher survival *** could not find evidence that giving birth to sons negatively impacts offspring weight in the following *** uncovered large narrow-sense heritability(h2)in offspring weight at birth,while maternal effects(m2)on birth weight were of lesser ***,maternal effects on offspring survival were strong until weaning age,while paternal effects dominated survival to sexual maturity and first *** propose that variation in maternal postnatal care might overshadow the effects of maternal inheritance of birth weights,while the overall strong heritability of weight at birth and the paternal effects on survival llustrates strong variance in sire fitness based on genetic quality,suggesting a role for sexual selectionbyfemalemate choiceinwildpopulations.

关键词： Arabian gazelles heritability life-history evolution offspring mortality sex differences ungulates

Novel green technology for wastewater treatment: Geo-material/geopolymer applications for heavy metal removal from aquatic media

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International Journal of Sediment Research 2023年第1期38卷 33-48页

作者： Nenad Grba Andre Baldermann martin Dietzel Department of Chemistry Biochemistry and Environmental Protection Faculty of Sciences University of Novi Sad Institute of Applied Geosciences and NAWI Graz Geocenter Graz University of Technology

The aim of this paper is to show the concise chemico-physical adsorbent performance of water purification systems utilizing geo-(e.g., allophane, clinoptilolite, and smectite) and bio-polymer materials(e.g.,chitosan or cellulose nanocomposite materials) and to propose an optimal ground-water remediation technique. The performance of geo-materials is evaluated based on the individual sorption and immobilization capacities for various priority substances and pollutants(e.g., lead, zinc, cadmium, copper,arsenic, and others), their availability, and cost-efficient use. A systematic assessment of the sorption potential of geo-materials in comparison to other available sorbents used for the removal of harmful aqueous metal ions is made through a literature review. This paper introduces novel sustainable technologies based on natural and tailored silicate-polymerized substances(geo-materials and geopolymers),and highlights their applicability in the treatment of water and solid matter contaminated by heavy metal ions. The advantages of geo-materials and geopolymers over other commercially available sorbents used for heavy metal ion removal from solution are presented through a literature review. Benefits and current challenges of geo-materials and geopolymers applications in water processing technologies and in environmental remediation are discussed, with recognition of their performance, individual sorption and immobilization capacities, availability, and cost-efficient use. The applications described here comprise:(i) the removal of heavy metal ions from contaminated water using in-situ remediation strategies;(ii) heavy metal ion immobilization through co-precipitation with silicate binders in underground stabilization and waste solidification scenarios; and(iii) a proposal for a new geo-material/geopolymer-based solidification and stabilization technology for efficient, sustainable, and simultaneous treatment of soil/sediment and groundwater at environmental hotspots.

关键词： Geo-materials Heavy metal ions Environmental protection Water treatment Clay minerals Sustainability

A Method of Characterizing Radio Signal Space for Wireless Device Localization

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Tsinghua Science and Technology 2015年第4期20卷 385-408页

作者： John-Austen Francisco Richard P.martin Department of Computer Science Rutgers University

In this work we present a novel approach for describing radio signal spaces for localization algorithms. We first introduce a new metric, the Discretely Distributed Log-H61der Metric （DDLHM）. The DDLHM is designed to characterize the type and degree of signal distortion relative to Iognormal signal-to-distance path models. We first show how the DDLHM can describe and discriminate distortions in an exhaustive set of synthetic signal spaces. We then determine a reduced set of maximally diagnostic distortion parameters. Using only 4% of the maximal set of DDLHMs, we found the reduced set matches with an acceptable degree of error 95% of the time. Using the synthetic reduced set, we characterized a variety of wireless localization algorithms＇ behaviors to attenuation, bias, and multipath. We found algorithms made much different tradeoffs between best case and average case error. We then use the DDLHM to identify distortion types in three different physical environments using measured 802.11 signal strengths, and predict the positioning performance of several localization algorithms. Our approach predicts average localization error to within 2 meters of the observed average error.

关键词： radio propgation 802.11 WiFi