424 research outputs found
Microstructural Degeneracy associated with a Two-Point Correlation Function and its Information Content
Two-point correlation functions provide crucial yet incomplete
characterization of microstructures because different microstructures may have
the same correlation function. In an earlier Letter [Phys. Rev. Lett. 108,
080601 (2012)], we addressed the degeneracy question: What is the number of
microstructures compatible with a specified correlation function? We computed
this degeneracy, i.e., configurational entropy, in the framework of
reconstruction methods, which enabled us to map the problem to the
determination of ground-state degeneracies. Here, we provide a more
comprehensive presentation and additional results. Since the configuration
space of a reconstruction problem is a hypercube on which a Hamming distance is
defined, we can calculate analytically an energy profile corresponding to the
average energy of all microstructures at a given Hamming distance from a ground
state. The steepness of this profile is a measure of the roughness of the
energy landscape, which can be used as a proxy for ground-state degeneracy. The
relationship between roughness metric and ground-state degeneracy is calibrated
using a Monte Carlo algorithm for determining the degeneracy of a variety of
microstructures, including hard disks and Poisson point processes as well as
those with known degeneracies (single disks of various sizes and a particular
crystalline microstructure). We show that our results can be expressed in terms
of the information content of the two-point correlation functions. From this
perspective, the a priori condition for a reconstruction to be accurate is that
the information content, expressed in bits, should be comparable to the number
of pixels in the unknown microstructure. We provide a formula to calculate the
information content of any two-point correlation function, which makes our
results broadly applicable to any field in which correlation functions are
employed.Comment: Accepted for publication in Physical Review
Managing Climatic Risks to Combat Land Degradation and Enhance Food security: Key Information Needs
This paper discusses the key information needs to reduce the negative impacts of weather variability and climate change on land degradation and food security, and identifies the opportunities and barriers between the information and services needed. It suggests that vulnerability assessments based on a livelihood concept that includes climate information and key socio-economic variables can overcome the narrow focus of common one-dimensional vulnerability studies. Both current and future climatic risks can be managed better if there is appropriate policy and institutional support together with technological interventions to address the complexities of multiple risks that agriculture has to face. This would require effective partnerships among agencies dealing with meteorological and hydrological services, agricultural research, land degradation and food security issues. In addition a state-of-the-art infrastructure to measure, record, store and disseminate data on weather variables, and access to weather and seasonal climate forecasts at desired spatial and temporal scales would be needed
Qualitative assessment of the purity of multi-walled carbon nanotube samples using krypton adsorption
peer reviewedKrypton is a subcritical vapour at the nitrogen boiling temperature. As such, its adsorption on
crystalline surfaces leads to condensation steps, typical of type VI isotherms according to
IUPAC, while its adsorption on rough surfaces is BET-like. Based on this property of krypton
adsorption at 77 K, a methodology is proposed to determine the purity of carbon nanotubes
samples. The method is tested on model samples obtained by mixing mechanically purified
multi-walled carbon nanotubes with various amounts of the same catalyst as used for their
synthesis
Density of States for a Specified Correlation Function and the Energy Landscape
The degeneracy of two-phase disordered microstructures consistent with a
specified correlation function is analyzed by mapping it to a ground-state
degeneracy. We determine for the first time the associated density of states
via a Monte Carlo algorithm. Our results are described in terms of the
roughness of the energy landscape, defined on a hypercubic configuration space.
The use of a Hamming distance in this space enables us to define a roughness
metric, which is calculated from the correlation function alone and related
quantitatively to the structural degeneracy. This relation is validated for a
wide variety of disordered systems.Comment: Accepted for publication in Physical Review Letter
Inelastic Neutron Scattering Analysis with Time-Dependent Gaussian-Field Models
Converting neutron scattering data to real-space time-dependent structures
can only be achieved through suitable models, which is particularly challenging
for geometrically disordered structures. We address this problem by introducing
time-dependent clipped Gaussian field models. General expressions are derived
for all space- and time-correlation functions relevant to coherent inelastic
neutron scattering, for multiphase systems and arbitrary scattering contrasts.
Various dynamic models are introduced that enable one to add time-dependence to
any given spatial statistics, as captured e.g. by small-angle scattering. In a
first approach, the Gaussian field is decomposed into localised waves that are
allowed to fluctuate in time or to move, either ballistically or diffusively.
In a second approach, a dispersion relation is used to make the spectral
components of the field time-dependent. The various models lead to
qualitatively different dynamics, which can be discriminated by neutron
scattering. The methods of the paper are illustrated with oil/water
microemulsion studied by small-angle scattering and neutron spin-echo. All
available data - in both film and bulk contrasts, over the entire range of
and - are analyzed jointly with a single model. The analysis points to
static large-scale structure of the oil and water domains, while the interfaces
are subject to thermal fluctuations. The fluctuations have an amplitude around
6 nm and contribute to 30 % of the total interface area.Comment: The following article has been accepted by Journal of Chemical
Physics. After it is published, it will be found at
https://aip.scitation.org/journal/jcp
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Plant Mounds as Concentration and Stabilization Agents for Actinide Soil Contaminants in Nevada
Plant mounds or blow-sand mounds are accumulations of soil particles and plant debris around the base of shrubs and are common features in deserts in the southwestern United States. An important factor in their formation is that shrubs create surface roughness that causes wind-suspended particles to be deposited and resist further suspension. Shrub mounds occur in some plant communities on the Nevada Test Site, the Nevada Test and Training Range (NTTR), and Tonopah Test Range (TTR), including areas of surface soil contamination from past nuclear testing. In the 1970s as part of early studies to understand properties of actinides in the environment, the Nevada Applied Ecology Group (NAEG) examined the accumulation of isotopes of Pu, 241Am, and U in plant mounds at safety experiment and storage-transportation test sites of nuclear devices. Although aerial concentrations of these contaminants were highest in the intershrub or desert pavement areas, the concentration in mounds were higher than in equal volumes of intershrub or desert pavement soil. The NAEG studies found the ratio of contaminant concentration of actinides in soil to be greater (1.6 to 2.0) in shrub mounds than in the surrounding areas of desert pavement. At Project 57 on the NTTR, 17 percent of the area was covered in mounds while at Clean Slate III on the TTR, 32 percent of the area was covered in mounds. If equivalent volumes of contaminated soil were compared between mounds and desert pavement areas at these sites, then the former might contain as much as 34 and 62 percent of the contaminant inventory, respectively. Not accounting for radionuclides associated with shrub mounds would cause the inventory of contaminants and potential exposure to be underestimated. In addition, preservation of shrub mounds could be important part of long-term stewardship if these sites are closed by fencing and posting with administrative controls
Значение традиционных нравственно-эстетических ценностей в формировании духовного мира ребенка в произведениях Эмиля Амита
Предлагаемый вниманию материал посвящён значению традиционных нравственно-эстетических ценностей в формировании духовного мира подрастающего поколения. Обращение к испокон веков ценимым ценностям под пером автора обретает особое звучание.Пропонований увазі матеріал присвячений проблемі еволюції морального ідеалу в творчості Е.Аміт. Традиційні споконвічні ціності під пером автора набувають особливого звучання.The material which is proposed to you dedicated to a problem of the evolution of the moral ideal in the creation of A Rmit
Agrometeorological forecasting
Agrometeorological forecasting covers all aspects of forecasting in agrometeorology. Therefore, the scope of agrometeorological forecasting very largely coincides with the scope of agrometeorology itself. All on-farm and regional agrometeorological planning implies some form of impact forecasting, at least implicitly, so that decision-support tools and forecasting tools largely overlap.
In the current chapter, the focus is on crops, but attention is also be paid to sectors that are often neglected by the agrometeorologist, such as those occurring in plant and animal protection. In addition, the borders between meteorological forecasts for agriculture and agrometeorological forecasts are not always clear. Examples include the use of weather forecasts for farm operations such as spraying pesticides or deciding on trafficability in relation to adverse weather. Many forecast issues by various national institutions (weather, but also commodity prices or flood warnings) are vital to the farming community, but they do not constitute agrometeorological forecasts.
(Modified From the introduction of the chapter: Scope of agrometeorological forecasting)JRC.H.4-Monitoring Agricultural Resource
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