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Coercivity mechanisms in nanostructured permanent magnets

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Chinese Physics B 2019年第7期28卷 1-13页

作者： G P Zhao l Zhao l C Shen J Zou l Qiu College of Physics and Electronic Engineering & Institute of Solid State Physics Sichuan Normal UniversityChengdu 610066 China State Key luboratory of Metastablc Materials Science and Technology Yunshnn University.Qinhuangdao 066004China Collaborative Innovation Center for Shunxi Advanced Permanent Materials and Technology Lint'en 041004 China

Coercivity mechanism in permanent magnets has been debated for many *** this paper, various models of the coercivity mechanism are classified and re-examined by the comparison and *** rotation and curling models can reveal the underlying reversal mechanism clearly based on isolated grains with elliptic *** contrast, the numerical methods consider inter-grain interactions while simulating the evolution of the spins and hysteresis loops with complicated ***, an exact simulation of magnetic reversal in permanent nanomagnets requires many meshes to mimic the thin domain wall *** and pinning are the two main coercivity mechanisms in permanent *** former signifies the beginning of the magnetic reversal, whilst the latter completes ***, it is proposed that the large difference between the intrinsic magnetic properties of the nucleation centers and those of the main phase can result in a large pinning field(self-pinning), which has the attributes of both traditional nucleation and *** a pinning explains the experimental data of permanent magnets very well, including the enhancement of the coercivity by the grain boundary pinning.

关键词： coercivity mechanism permanent nanomagnets self-pinning

A theoretical investigation of the band alignment of type-I direct band gap dilute nitride phosphide alloy of GaN_xAs_yP_(1-x-y)/GaP quantum wells on GaP substrates

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Chinese Physics B 2014年第7期23卷 640-644页

作者： O l nsal B Gnül M Temiz Department of Engineering Physics University of Gaziantep

The GaP-based dilute nitride direct band gap material Ga（NAsP） is gaining importance due to the monolithic integra- tion of laser diodes on Si microprocessors. The major advantage of this newly proposed laser material system is the small lattice mismatch between GaP and Si. However, the large threshold current density of these promising laser diodes on Si substrates shows that the carrier leakage plays an important role in Ga（NAsP）/GaP QW lasers. Therefore, it is necessary to investigate the band alignment in this laser material system. In this paper, we present a theoretical investigation to optimize the band alignment of type-I direct band gap GaNxAsyP1-x-y/GaP QWs on GaP substrates. We examine the effect of nitrogen （N） concentration on the band offset ratios and band offset energies. We also provide a comparison of the band alignment of type-I direct band gap GaNxAsyP1-x-y/GaP QWs with that of the GaNxAsyP1-x-y/Al2Ga1-2P QWs on GaP substrates. Our theoretical calculations indicate that the incorporations of N into the well and AI into the barrier improve the band alignment compared to that of the GaAsP/GaP QW laser heterostructures.

关键词： quantum well band alignment carrier confinement dilute nitride phosphide alloy

Exact Travelling Wave Solutions of Discrete Planar Velocity Boltzmann Models

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Chinese Physics letters 1997年第8期14卷 561-564页

作者： lÜ Xian-qing Department of Applied Mathematics Tsinghua UniversityBeijing 100084

By investigating the discrete planar Boltzmann models:the square 4-velocity and the hexagonal 6-velocity models,exact travelling wave solutions can be studied in a concise *** their exact travelling wave solutions can only be monotonic travelling *** conclusions of the precursors need *** suggests a general method for obtaining nontrivial exact solutions for the similar discrete Boltzmann equation.

关键词： equation. wave. travelling

Dynamic heating and thermal destruction conditions of quartz particles in polydisperse plasma flow of RF-ICP torch system

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Plasma Science and Technology 2020年第11期22卷 114-126页

作者： l MIAO Yu M GRISHIN Department of Thermophysics Moscow State Technical University N E BaumanMoscow 105005Russia

Numerical simulation of turbulent mixing process of polydisperse quartz particle(particle size distribution in the range of 0.1-0.4 mm)flow with Ar and Ar-H2 plasma generated by radio frequency inductively coupled plasma(RF-ICP)torch has been *** approximate two-stage approach has been proposed to calculate the spatial-temporal distributions of temperature and resulting thermal stress in quartz particles during dynamic heating in polydisperse plasma *** influence of working gas compositions,particle size distributions,injection angle and flow rate of carrier gas on the thermal destruction conditions of quartz particles has been determined under different particle feed *** is found that all the solid quartz particles(0.1-0.4 mm)could be thermal destructed without overheating in RF-ICP torch system,when the hydrogen volume fraction in working gases is more than 1.5%-2%and particle feed rate is in a certain *** values of the maximum and minimum feed rates have been determined under different hydrogen volume *** optimal particle injection angle and flow rate of carrier gas is found around 50°-60°and 160-220 slpm,under which the value of maximum equivalent thermal stress in quartz particles is highest.

关键词： RF-ICP torch dynamic heating thermal destruction hydrogen volume fraction optimal injection conditions

Evaluating the impact of thermostat control strategies on the energy flexibility of residential buildings for space heating

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Building Simulation 2021年第5期14卷 1439-1452页

作者： Kun Zhang Michaël Kummert Department of Mechanical Engineering Polytechnique MontrealMontrealCanada

Buildings can be operated in an energy-flexible manner while respecting occupant thermal *** energy flexibility of building operations,both in time and quantity,can be harnessed by the electrical grid for load *** the context of smart grid and intelligent buildings,the concept of energy flexibility in buildings broadens the existing demand management thinking from the top-down one-way control to two-way *** paper,extending studies on thermostat controls of heating and air conditioning systems for demand response,evaluates the impact of different control schemes on the energy flexibility of residential *** control strategies,Model Predictive Control(MPC)and Rule-Based Control(RBC),are investigated for a space heating system using co-simulation *** indicators are introduced and adapted from the literature to assess the control performances of the *** results show that different flexibility indicators favour different control strategies in this case *** demand response events of four hours,the MPC strategy presents two to three times of flexible energy than that of *** also delivers 20%more of maximum power reduction during the events against *** RBC strategy,on the other hand,is twice of MPC for flexible energy *** evaluation work can be beneficial to guide the control system design of new buildings or control retrofits of existing buildings that consider better grid-building interactions for the future.

关键词： energy flexibility MPC grid-building interaction demand response

Annual survival and site fidelity of free-ranging white-tailed deer (Odocoileus virginianus): comparative demography before (1983- 1992) and after (1993-2005) spatial confinement

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Integrative Zoology 2014年第1期9卷 24-33页

作者： Stephen l.WEBB Kenneth l.GEE The Samuel Roberts Noble Foundation ArdmoreOklahoma USA

Survival and movement are important demographic variables influencing the dynamics of large herbivores with implications for management and evolution of life-history *** practices such as spatial con-finement and harvest regulation attempt to control survival and movement for the sustainability of harvested deer populations,but a paucity of long-term data exists on these management *** examined annual survival and site fidelity of free-ranging white-tailed deer(Odocoileus virginianus)over 10 years(1983-1992)to compare demographic parameters after spatial confinement(1993-2005).We used capture records(n=174;104 females,70 males),marked deer recaptures(n=42),and dead recoveries(n=68)to estimate sex-specif-ic,age-specific and time-specific *** found that annual female survival was 50%from 1983-1987 during a period of intense harvest,but increased to 93.7%after intense harvesting was *** to spa-tial confinement,annual survival of marked male deer averaged 36.7%-42.5%.After spatial confinement,annu-al survival increased on average for males(58%-99%)and females(77%-98%).Females showed high levels of site fidelity(>99%)prior to spatial confinement,whereas males showed much less site fidelity(≤4.5%for the 2 top-ranking models).During spatial confinement,the semi-impermeable fence effectively increased site fidelity of males(≥56%).These results stem from long-term study(23 years)of a large herbivore experiencing changes to life-history,resulting from changes in management that were applied to the population and aimed at altering population demographics,for sustainability of a harvestable population of deer.

关键词： conservation deer fidelity mortality Odocoileus virginianus population dynamics

Influence of Functionalization on the Structural and Mechanical Properties of Graphene

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Computers, Materials & Continua 2017年第2期53卷 109-127页

作者： l.S.Melro l.R.Jensen Department of Materials and Production Aalborg UniversityAalborgDenmark Corresponding author:liliana@m-tech.aau.dk

Molecular dynamics simulations were applied in order to calculate the Young’s modulus of graphene functionalized with carboxyl,hydroxyl,carbonyl,hydrogen,methyl,and ethyl *** influence of the grafting density with percentages of 3,5,7,and 10%and the type of distribution as a single cluster or several small clusters were also *** results show that the elastic modulus is dependent on the type of functional *** increasing coverage density also evidenced a decrease of the Young’s modulus,and the organization of functional groups as single cluster showed a lesser impact than for several small ***,the bond length and angle distribution probability analyses reveal that lengths and angles are affected with increasing functionalization suggesting more out-of-plane displacements of the carbon atoms within the graphene structure.

关键词： Functionalization graphene molecular dynamics Young’s modulus structural properties

Incipient sexual isolation in laupala cerasina： Females discriminate population-level divergence in acoustic characters

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Current Zoology 2012年第3期58卷 416-425页

作者： Jaime l. GRACE Kerry l. SHAW Department of Biology University of Maryland College Park MD 20742 USA Department of Neurobiology and Behavior Cornel1 University Ithaca NY 14853 USA kls4@cornell.edu

Sexual selection by female choice can shape the evolution of male traits within populations, since the most attractive males experience an increase in fitness through elevated mating success. Speciation by sexual selection occurs when evolution in traits and preferences within populations causes differentiation among populations, such that females in alternative populations prefer sexual signals of their own population relative to others. Differentiated traits and preferences thereby play an active role in limiting gene flow between divergent populations. The effectiveness of differentiated preferences in maintaining differentiated male signals against the homogenizing effects of gene flow across populations will be limited by both the degree to which fe- males can discriminate against non-local males, and the breeding values of traits and preferences. Populations of the Hawaiian cricket laupala cerasina have diverged in pulse rate, a sexually selected male signal, and female acoustic preference for pulse rate. Gene flow between neighboring populations may be reduced if migrants from sexually diverged populations experience re- duced mating success. We show that females discriminate among divergent songs characteristic of neighboring populations, that differences among populations in song and preference breed true in a common environment, and that mean preferences for each population closely match the mean pulse rates. Divergence in preference was observed only between populations that also dif- fered in song. Along with a striking ability to discriminate slight differences in song, correlated evolution of song and preference within populations could be a mechanism that promotes assortative mating among populations, thereby reducing gene flow, and leading to speciation in laupala [Current Zoology 58 （3）： 416-425, 2012].

关键词： Sexual selection Phenotypic divergence Behavioral isolation Preference functions Speciation

Integrating small mammal community variables into aircraft–wildlife collision management plans at Namibian airports

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Integrative Zoology 2015年第6期10卷 515-530页

作者： Morgan l.HAUPTFlEISCH Nico l.AVENANT Department of Agriculture and Natural Resources Sciences Polytechnic of NamibiaWindhoekNamibia Department of Mammalogy National Museumand Centre for Environmental ManagementUniversity of the Free StateBloemfonteinSouth Africa

Understanding ecosystems within and around airports can help to determine the causes and possible mitigation measures for collisions between aircraft and *** mammal communities are an important component of the semi-arid savanna ecosystems of Namibia,its productivity and its ecosystem *** are also a major direct attractant for raptors at *** present study compared the abundance and diversity of small mammals between Namibia’s 2 main airport properties(Hosea Kutako International Airport and Eros Airport),and among areas of land used for various purposes surrounding the airports.A total of 2150 small mammals(3 orders,11 species)were captured over 4 trapping *** mammal abundance was significantly higher at the end of the growing season than during the non-growing *** grass mowing regimen in current management plans at the airports resulted in a significant reduction of small mammal abundance at Hosea Kutako during the non-growing season only,thus indicating that annual mowing is effective but insufficient to reduce the overall abundance of mammal prey species for *** mammal numbers were significantly higher at Hosea Kutako Airport compared to the cattle and game farming land surrounding the airport,while no differences in small mammal densities or diversity were found for areas with different land uses at and surrounding *** study suggests that the fence around Hosea Kutako provides a refuge for small mammals,resulting in higher *** also indicates that different surrounding land use practices result in altered ecosystem function and productivity,an important consideration when identifying wildlife attractants at airports.

关键词： airport ecosystems bird strike risk Namibia small mammal indicators