3,887 research outputs found
From urban to national heat island: The effect of anthropogenic heat output on climate change in high population industrial countries
The project presented here sought to determine whether changes in anthropogenic thermal emission can have a measurable effect on temperature at the national level, taking Japan and Great Britain as type examples. Using energy consumption as a proxy for thermal emission, strong correlations (mean r2 = 0.90 and 0.89, respectively) are found between national equivalent heat output (HO) and temperature above background levels Δt averaged over 5‐ to 8‐yr periods between 1965 and 2013, as opposed to weaker correlations for CMIP5 model temperatures above background levels Δmt (mean r2 = 0.52 and 0.10). It is clear that the fluctuations in Δt are better explained by energy consumption than by present climate models, and that energy consumption can contribute to climate change at the national level on these timescales
Origin of the Heavy Fermion Behavior in Ca_{2-x}Sr_{x}RuO_{4}: Roles of Coulomb Interaction and the Rotation of RuO_{6} octahedra
We study the electronic states for Ca_{2-x}Sr_{x}RuO_{4} in within the Gutzwiller approximation (GA) on the basis of the three-orbital
Hubbard model for the Ru t_{2g} orbitals. The main effects of the Ca
substitution are taken account as the changes of the hybridizations
between the Ru 4d and O 2p orbitals. Using the numerical minimization of the
energy obtained in the GA, we obtain the renormalization factor (RF) of the
kinetic energy and total RF, which estimates the inverse of the mass
enhancement, for three cases with the effective models of x=2 and 0.5 and a
special model. We find that the inverse of the total RF becomes the largest for
the case of x=0.5, and that the van Hove singularity, which is located on
(below) the Fermi level for the special model (the effective model of x=0.5),
plays a secondary role in enhancing the effective mass. Our calculation
suggests that the heavy fermion behavior around x=0.5 comes from the
cooperative effects between moderately strong Coulomb interaction compared to
the total bandwidth and the modification of the electronic structures due to
the rotation of RuO_{6} octahedra (i.e., the variation of the
hybridizations and the downward shift for the orbital). We propose
that moderately strong electron correlation and the orbital-dependent
modifications of the electronic structures due to the lattice distortions play
important roles in the electronic states for Ca_{2-x}Sr_{x}RuO_{4}.Comment: 16 pages, 13 figures, 1 table, accepted for publication in Physical
Review B; added the discussions both about the validity of the present
treatment and about Hund's metal in this allo
Branching mechanism of intergranular crack propagation in three dimensions
We investigate the process of slow intergranular crack propagation by the
finite element method model, and show that branching is induced by partial
arresting of crack front owing to the geometrical randomness of grain
boundaries. A possible scenario for branching instability of crack propagation
in disordered continuum medium is also discussed.Comment: 4 pages, submitted to Phys.Rev.E; v2:corrected typos v3: final
version to be publishe
Multiscale modeling of the moist-convective atmosphere — A review
AbstractMultiscale modeling of the moist-convective atmosphere is reviewed with an emphasis on the recently proposed approaches of unified parameterization and Quasi-3D (Q3D) Multiscale Modeling Framework (MMF). The cumulus parameterization problem, which was introduced to represent the multiscale effects of moist convection, has been one of the central issues in atmospheric modeling. After a review of the history of cumulus parameterization, it is pointed out that currently there are two families of atmospheric models with quite different formulations of model physics, one represented by the general circulation models (GCMs) and the other by the cloud-resolving models (CRMs). Ideally, these two families of models should be unified so that a continuous transition of model physics from one kind to the other takes place as the resolution changes. This paper discusses two possible routes to achieve the unification. ROUTE I unifies the cumulus parameterization in conventional GCMs and the cloud microphysics parameterization in CRMs. A key to construct such a unified parameterization is to reformulate the vertical eddy transport due to subgrid-scale moist convection in such a way that it vanishes when the resolution is sufficiently high. A preliminary design of the unified parameterization is presented with supporting evidence for its validity. ROUTE II for the unification follows the MMF approach based on a coupled GCM/CRM, originally known as the “super-parameterization”. The Q3D MMF is an attempt to broaden the applicability of the super-parameterization without necessarily using a fully three-dimensional CRM. This is accomplished using a network of cloud-resolving grids with gaps. The basic Q3D algorithm and highlights of preliminary results are reviewed. It is suggested that the hierarchy of future global models should form a “Multiscale Modeling Network (MMN)”, which combines these two routes. With this network, the horizontal resolution of the dynamics core and that of the physical processes can be individually and freely chosen without changing the formulation of model physics. Development of such a network will represent a new phase of the history of numerical modeling of the atmosphere that can be characterized by the keyword “unification”
Optimistic Managers & Their Influence on Productivity & Employee Engagement in a Technology Organization
The objective of this study is to investigate whether teams are more engaged and productive when led by an optimistic manager. Furthermore, we hypothesize that optimistic managers embody positive leadership—employing a strengths-based approach, maintaining a positive perspective, and frequently providing recognition and encouragement—which increases the engagement and productivity of their employees. In a cross-sectional study of 86 employees and 17 managers in an Information Technology (IT) organization, positive leadership correlated with employee optimism, engagement, and project performance. When we looked at a subset of this data prospectively, with 39 employees and 14 managers, manager optimism predicted project performance. Our data support the claim that positive leadership is correlated with employee engagement and performance, and further extends the importance of optimism in the workplace
Circularly-Polarized Light Emission from Semiconductor Planar Chiral Photonic Crystal
We proposed and demonstrated a scheme of surface emitting circularly
polarized light source by introducing strong imbalance between left- and
right-circularly polarized vacuum fields in an on-waveguide chiral grating
structure. We observed circularly polarized spontaneous emission from InAs
quantum dots embedded in the wave guide region of a GaAs-based structure.
Obtained degree of polarization reaches as large as 25% at room temperature.
Numerical calculation visualizes spatial profiles of the modification of vacuum
field modes inside the structure with strong circular anisotropy.Comment: REVTeX4.1, 6pages, 3figure
Toward unification of the multiscale modeling of the atmosphere
As far as the representation of deep moist convection is concerned, only two kinds of model physics are used at present: highly parameterized as in the conventional general circulation models (GCMs) and explicitly simulated as in the cloud-resolving models (CRMs). Ideally, these two kinds of model physics should be unified so that a continuous transition of model physics from one kind to the other takes place as the resolution changes. With such unification, the GCM can converge to a global CRM (GCRM) as the grid size is refined. This paper suggests two possible routes to achieve the unification. ROUTE I continues to follow the parameterization approach, but uses a unified parameterization that is applicable to any horizontal resolutions between those typically used by GCMs and CRMs. It is shown that a key to construct such a unified parameterization is to eliminate the assumption of small fractional area covered by convective clouds, which is commonly used in the conventional cumulus parameterizations either explicitly or implicitly. A preliminary design of the unified parameterization is presented, which demonstrates that such an assumption can be eliminated through a relatively minor modification of the existing mass-flux based parameterizations. Partial evaluations of the unified parameterization are also presented. ROUTE II follows the "multi-scale modeling framework (MMF)" approach, which takes advantage of explicit representation of deep moist convection and associated cloud-scale processes by CRMs. The Quasi-3-D (Q3-D) MMF is an attempt to broaden the applicability of MMF without necessarily using a fully three-dimensional CRM. This is accomplished using a network of cloud-resolving grids with large gaps. An outline of the Q3-D algorithm and highlights of preliminary results are reviewed
Direct observation of acoustic phonon mediated relaxation between coupled exciton states in a single quantum dot molecule
We probe acoustic phonon mediated relaxation between tunnel coupled exciton
states in an individual quantum dot molecule in which the inter-dot quantum
coupling and energy separation between exciton states is continuously tuned
using static electric field. Time resolved and temperature dependent optical
spectroscopy are used to probe inter-level relaxation around the point of
maximum coupling. The radiative lifetimes of the coupled excitonic states can
be tuned from ~2 ns to ~10 ns as the spatially direct and indirect character of
the wavefunction is varied by detuning from resonance. Acoustic phonon mediated
inter-level relaxation is shown to proceed over timescales comparable to the
direct exciton radiative lifetime, indicative of a relaxation bottleneck for
level spacings in the range $\Delta E\$ ~3-6 meV.Comment: 6 pages, 4 figures, submitted for publicatio
Electrospray ionization mass spectrometric observation of ligand exchange of zinc pyrithione with amino acids
ArticleRAPID COMMUNICATIONS IN MASS SPECTROMETRY. 23(14):2161-2166 (2009)journal articl
Optimistic Managers & Their Influence on Productivity & Employee Engagement in a Technology Organization
The objective of this study is to investigate whether teams are more engaged and productive when led by an optimistic manager. Furthermore, we hypothesize that optimistic managers embody positive leadership—employing a strengths-based approach, maintaining a positive perspective, and frequently providing recognition and encouragement—which increases the engagement and productivity of their employees. In a cross-sectional study of 86 employees and 17 managers in an Information Technology (IT) organization, positive leadership correlated with employee optimism, engagement, and project performance. When we looked at a subset of this data prospectively, with 39 employees and 14 managers, manager optimism predicted project performance. Our data support the claim that positive leadership is correlated with employee engagement and performance, and further extends the importance of optimism in the workplace
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