Responses of streamflow to vegetation and climate change in southwestern Australia

Southwestern Australia has experienced recent climate change, with an increase in air temperature of 0.6°C and a reduction in mean annual precipitation of -15% since 1970. Along with the warming and drying trends, dramatic declines of streamflow have occurred across the region. However, both forest mortality and an increase in leaf area index have been observed in the southwestern forest, suggesting varied responses of vegetation to climate change. In this study, 30 catchments were analyzed using the Mann-Kendall trend test, Pettitt’s change point test and the theoretical framework of the Budyko curve to study the rainfall-runoff relationship change, and effects of climate and land cover change on streamflow. A declining trend and relatively consistent change point (2000) of streamflow were found in most catchments, with 14 catchments showing significant declines (p < 0.05, -68.1% to -35.6%) over 1970-2000 and 2001-2015. Most of the catchments have been shifting towards a more water-limited climate condition since 2000. For the period of 1970 to 2015, the dynamic of vegetation attributes (land cover/use change and growth of vegetation) dominated the decrease of streamflow in about half the study catchments. In general, a coequal role of climate and vegetation on the decline in streamflow was found in the study, suggesting the importance of vegetation management on future water management and production. Precipitation is predicted to decline in the future; therefore, some forest management intervention is required to maintain forest growth and water supply in the southwest of Australia

Numerical approximation of the Euler-Poisson-Boltzmann model in the quasineutral limit

This paper analyzes various schemes for the Euler-Poisson-Boltzmann (EPB) model of plasma physics. This model consists of the pressureless gas dynamics equations coupled with the Poisson equation and where the Boltzmann relation relates the potential to the electron density. If the quasi-neutral assumption is made, the Poisson equation is replaced by the constraint of zero local charge and the model reduces to the Isothermal Compressible Euler (ICE) model. We compare a numerical strategy based on the EPB model to a strategy using a reformulation (called REPB formulation). The REPB scheme captures the quasi-neutral limit more accurately

Initial Vortex Densities after a Temperature Quench

We calculate the initial density of relativistic global vortices (strings) produced at a quench and contrast it with the predictions of Kibble and Zurek.Comment: Latex file, 8 pages, No figures. The text contains minor changes that elucidate the onset of classical behaviour more thoroughly. Also including the word temperature in the title makes the nature of the transition more explici

Preparation and characterization of diamond–silicon carbide–silicon composites by gaseous silicon vacuum infiltration process

Diamond–SiC–Si composites have been prepared using gaseous silicon vacuum infiltration. The evolution of the phases and microstructures of the composites have been analyzed using X-ray diffraction technique and scanning electron microscopy. It has been found that the diamond–SiC–Si composite is composed of β-SiC, diamond, and residual Si. The diamond particles were distributed homogeneously in the dense matrix of the composites. Besides, the effects of particle size and content of diamond on the properties of diamond–SiC–Si composites have been analyzed. The thermal conductivity of the composites increases with particle size and content of diamond. When the particle size and content of diamond are 300 µm and 80 wt %, respectively, the thermal conductivity of the composites approaches the value of 280 W·m⁻¹·K⁻¹.Проведен анализ эволюции фаз и микроструктуры композитов алмаз–SiC–Si, изготовленных с использованием процесса вакуумной инфильтрации газообразного кремния. Исследование выполнено с помощью дифракции рентгеновских лучей и сканирующей электронной микроскопии. Установлено, что композит алмаз–SiC–Si состоит из β-SiC, алмаза и остаточного Si. Алмазные частицы распределены однородно в плотной матрице композитов. Также проанализировано влияние размера частиц и содержания алмазов на свойства композитов алмаз–SiC–Si. Показано, что теплопроводность композитов возрастает с увеличением размера частиц и содержания алмазов. Теплопроводность композитов приближается к значению 280 Вт∙м⁻¹∙K⁻¹ при размере частиц и содержании алмаза 300 мкм и 80 % (по массе), соответственно.Проведено аналіз еволюції фаз і мікроструктури композитів алмаз–SiC–Si, виготовлених з використанням процесу вакуумної інфільтрації газоподібного кремнію. Дослідження виконано за допомогою дифракції рентгенівських променів і скануючої електронної мікроскопії. Встановлено, що композит алмаз–SiC–Si складається з β-SiC, алмазу і залишкового Si. Алмазні частки розподілені однорідно в щільній матриці композитів. Також проаналізовано вплив розміру частинок і вмісту алмазів на властивості композитів алмаз–SiC–Si. Показано, що теплопровідність композитів зростає зі збільшенням розміру частинок і вмісту алмазів. Теплопровідність композитів наближається до значення 280 Вт∙м⁻¹∙K⁻¹ при розмірі частинок і вмісту алмазу 300 мкм і 80 % (за масою) відповідно.This work was financially supported by the National Natural Science Foundation of China (grant no. 51102282) and Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province

Model-based sensitivity analysis of IaaS cloud availability

The increasing shift of various critical services towards Infrastructure-as-a-Service (IaaS) cloud data centers (CDCs) creates a need for analyzing CDCs’ availability, which is affected by various factors including repair policy and system parameters. This paper aims to apply analytical modeling and sensitivity analysis techniques to investigate the impact of these factors on the availability of a large-scale IaaS CDC, which (1) consists of active and two kinds of standby physical machines (PMs), (2) allows PM moving among active and two kinds of standby PM pools, and (3) allows active and two kinds of standby PMs to have different mean repair times. Two repair policies are considered: (P1) all pools share a repair station and (P2) each pool uses its own repair station. We develop monolithic availability models for each repair policy by using Stochastic Reward Nets and also develop the corresponding scalable two-level models in order to overcome the monolithic model''s limitations, caused by the large-scale feature of a CDC and the complicated interactions among CDC components. We also explore how to apply differential sensitivity analysis technique to conduct parametric sensitivity analysis in the case of interacting sub-models. Numerical results of monolithic models and simulation results are used to verify the approximate accuracy of interacting sub-models, which are further applied to examine the sensitivity of the large-scale CDC availability with respect to repair policy and system parameters

Localized electronic states and photoemission superconducting condensate in Bi2_{2}Sr2_{2}Ca1_{1}Cu2_{2}O8+x_{8+x}

We present the first detailed angle-resolved photoemission evidence that there are two types of carriers that contribute to the photoemission superconducting condensate in $Bi_{2}Sr_{2}Ca_{1}Cu_{2}O_{8+x}$. Our data indicate that both itinerant and somewhat localized normal state carriers can contribute to the formation of Cooper pairs.Comment: APS_Revtex, 11 pages, including 3 figures, available upon request. UW-Madison preprint#

Magnetic second harmonic generation at the Co2MnSi/AlO x interface

Copyright © 2008 American Institute of PhysicsWe have studied magnetic second harmonic generation (MSHG) at the Co2MnSi/AlOx interface. The variation of the MSHG intensity was consistent with the nonvanishing components of the nonlinear susceptibility tensor expected for the (001) cubic surface. The difference in the MSHG asymmetry, the MSHG anisotropy, is found to have maximum value at an annealing temperature of 450 °C, for which similar samples have previously been found to show optimum L21 site ordering and maximum tunnel magnetoresistance

A model for microinstability destabilization and enhanced transport in the presence of shielded 3-D magnetic perturbations

A mechanism is presented that suggests shielded 3-D magnetic perturbations can destabilize microinstabilities and enhance the associated anomalous transport. Using local 3-D equilibrium theory, shaped tokamak equilibria with small 3-D deformations are constructed. In the vicinity of rational magnetic surfaces, the infinite-n ideal MHD ballooning stability boundary is strongly perturbed by the 3-D modulations of the local magnetic shear associated with the presence of nearresonant Pfirsch-Schluter currents. These currents are driven by 3-D components of the magnetic field spectrum even when there is no resonant radial component. The infinite-n ideal ballooning stability boundary is often used as a proxy for the onset of virulent kinetic ballooning modes (KBM) and associated stiff transport. These results suggest that the achievable pressure gradient may be lowered in the vicinity of low order rational surfaces when 3-D magnetic perturbations are applied. This mechanism may provide an explanation for the observed reduction in the peak pressure gradient at the top of the edge pedestal during experiments where edge localized modes have been completely suppressed by applied 3-D magnetic fields

Seasonal timing for estimating carbon mitigation in revegetation of abandoned agricultural land with high spatial resolution remote sensing

Dryland salinity is a major land management issue globally, and results in the abandonment of farmland. Revegetation with halophytic shrub species such as Atriplex nummularia for carbon mitigation may be a viable option but to generate carbon credits ongoing monitoring and verification is required. This study investigated the utility of high-resolution airborne images (Digital Multi Spectral Imagery (DMSI)) obtained in two seasons to estimate carbon stocks at the plant- and stand-scale. Pixel-scale vegetation indices, sub-pixel fractional green vegetation cover for individual plants, and estimates of the fractional coverage of the grazing plants within entire plots, were extracted from the high-resolution images. Carbon stocks were correlated with both canopy coverage (R2: 0.76-0.89) and spectral-based vegetation indices (R2: 0.77-0.89) with or without the use of the near-infrared spectral band. Indices derived from the dry season image showed a stronger correlation with field measurements of carbon than those derived from the green season image. These results show that in semi-arid environments it is better to estimate saltbush biomass with remote sensing data in the dry season to exclude the effect of pasture, even without the refinement provided by a vegetation classification. The approach of using canopy cover to refine estimates of carbon yield has broader application in shrublands and woodlands

Collective modes of asymmetric nuclear matter in Quantum HadroDynamics

We discuss a fully relativistic Landau Fermi liquid theory based on the Quantum Hadro-Dynamics ($QHD$) effective field picture of Nuclear Matter ({\it NM}). From the linearized kinetic equations we get the dispersion relations of the propagating collective modes. We focus our attention on the dynamical effects of the interplay between scalar and vector channel contributions. A beautiful ``mirror'' structure in the form of the dynamical response in the isoscalar/isovector degree of freedom is revealed, with a complete parallelism in the role respectively played by the compressibility and the symmetry energy. All that strongly supports the introduction of an explicit coupling to the scalar-isovector channel of the nucleon-nucleon interaction. In particular we study the influence of this coupling (to a $\delta$-meson-like effective field) on the collective response of asymmetric nuclear matter ($ANM$). Interesting contributions are found on the propagation of isovector-like modes at normal density and on an expected smooth transition to isoscalar-like oscillations at high baryon density. Important ``chemical'' effects on the neutron-proton structure of the mode are shown. For dilute $ANM$ we have the isospin distillation mechanism of the unstable isoscalar-like oscillations, while at high baryon density we predict an almost pure neutron wave structure of the propagating sounds.Comment: 18 pages (LATEX), 8 Postscript figures, uses "epsfig