41 research outputs found
Local Lagrangian Approximations for the Evolution of the Density Distribution Function in Large-Scale Structure
We examine local Lagrangian approximations for the gravitational evolution of
the density distribution function. In these approximations, the final density
at a Lagrangian point q at a time t is taken to be a function only of t and of
the initial density at the same Lagrangian point. A general expression is given
for the evolved density distribution function for such approximations, and we
show that the vertex generating function for a local Lagrangian mapping applied
to an initially Gaussian density field bears a simple relation to the mapping
itself. Using this result, we design a local Lagrangian mapping which
reproduces nearly exactly the hierarchical amplitudes given by perturbation
theory for gravitational evolution. When extended to smoothed density fields
and applied to Gaussian initial conditions, this mapping produces a final
density distribution function in excellent agreement with full numerical
simulations of gravitational clustering. We also examine the application of
these local Lagrangian approximations to non-Gaussian initial conditions.Comment: LaTeX, 22 pages, and 11 postscript figure
Negotiation Models for the European Energy Market – Heletel Fast Prototype
AbstractFor the purpose of the EU-DEEP project, a European co-funded project, which focuses on the European Energy market, a prototype was studied and developed for the management of resources that is based on transaction techniques. That is to say, the prototype examines all the possible cases and in order to make the decision, for the energy management system, which generator to use at a particular time depending from the result of negotiation with market terms using agent technologies between the energy managing system and the participating generator. The purpose of this study was to investigate the models of negotiation, the Software Agents with platforms as the JADE, as well as the requirements of the system and to develop a prototype and evaluate it
The Real and Redshift Space Density Distribution Function for Large-Scale Structure in the Spherical Collapse Approximation
We use the spherical collapse (SC) approximation to derive expressions for
the smoothed redshift-space probability distribution function (PDF), as well as
the -order hierarchical amplitudes , in both real and redshift space.
We compare our results with numerical simulations, focusing on the
standard CDM model, where redshift distortions are strongest. We find good
agreement between the SC predictions and the numerical PDF in real space even
for \sigma_L \simgt 1, where is the linearly-evolved rms
fluctuation on the smoothing scale. In redshift space, reasonable agreement is
possible only for \sigma_L \simlt 0.4. Numerical simulations also yield a
simple empirical relation between the real-space PDF and redshift-space PDF: we
find that for \sigma \simlt 1, the redshift space PDF, P[\delta_z], is, to a
good approximation, a simple rescaling of the real space PDF, P[\delta], i.e.,
P[\delta/\sigma] d[\delta/\sigma] = P[\delta_z/\sigma_z] d[\delta_z/\sigma_z],
where and \sigma_z are the real-space and redshift-space rms
fluctuations, respectively. This result applies well beyond the validity of
linear perturbation theory, and it is a good fit for both the standard CDM
model and the Lambda-CDM model. It breaks down for SCDM at ,
but provides a good fit to the \Lambda-CDM models for as large as 0.8.Comment: 9 pages, latex, 12 figures added (26 total), minor changes to
conclusions, to appear in MNRA
Human Factors in End-user Development of Marketing-IS: A Behavioral User Profiling Approach
AbstractMarketing-IS research has recently focused on the development of personalization systems that are based on the modeling of consumer behavior and consumer heterogeneity regarding their distinct needs and preferences. However, personalization approaches in the design and development stage of Marketing-IS have not been widely studied in the End-User Development (EUD) research area. The lack of such research studies results in the development of Marketing-IS tools that neglect the differences in the end-user behavior, and artifacts of low performance and reusability. Attempting to figure out how end-users can participate in the design and construction of Marketing-IS in an efficient way, research suggests the ‘construction’ of end- users behavioral profiles based on human factors. Recent evidence reveal that human factors such as gender and expertise level can influence and even determine the end-users’, behavior, and consequently performance, while end-users interact with EUD environments. This paper presents a methodological approach in which we identify different behavioral user-profiles, named ‘user-categories’ based on behavioural attributes derived by the human factors of gender and expertise level. The resulting user- categories can be applied in the modeling mechanism of adaptive EUD system environments. Such an approach is projected to implicitly assist the end-users in the enhancement of their performance during the development task of Marketing-I
TEORIJSKA PITANJA O INFORMACIJSKIM SUSTAVIMA RAČUNOVODSTVA OKOLIŠA U OBRAZOVNIM PROGRAMIMA ZA HOTELIJERSTVO
In a competitive environment the application of Information Technology Systems by tourism companies can increase future prosperity and financial growth. The purpose of this paper is to measure the natural assets and to calculate the environmental benefits, as well as, the associated costs, so as to include all the above in the financial statements (balance sheet and profit & loss account). It is crucial to point out that
the installation of a Green Accounting Information System requires evaluation of human assets (students and professors), availability of space, value the benefits, as well as, estimate the necessary installation costs.
Literature suggests that although many information systems of environmental management have been developed, no significant progress was made on the growth of green accounting information systems due to the inherent difficulty for the monetary expression of environmental accumulated costs and related natural resources.U konkurentskom okruženju primjenom sustava informacijske tehnologije turistička poduzeća mogu jačati svoj budući prosperitet i financijski rast. Svrha je rada izmjerili prirodne vrijednosti, te izračunati ekološke koristi kao i pripadajuće troškove, a radi uključivanja istih u financijska izvješća (bilanca i račun dobiti i gubitka). Ključno je istaknuti da prilikom uvođenja informacijskih sustava računovodstva okoliša treba procijeniti ljudske potencijale (studenti i profesori) i raspoloži prostor, te utvrditi koristi sustava i odrediti troškove njegovog uvođenja. Iz literature se može zaključiti da, iako su izrađeni brojni informacijski sustavi za menadžment okoliša, nema značajnijeg napretka na širenju informacijskih sustava "zelenog" računovodstva zbog inherentne teškoće monetarnog izražavanja akumuliranih ekoloških troškova i s njima povezanih prirodnih resursa
Skewness of the Large-Scale Velocity Divergence from Non-Gaussian Initial Conditions
We compute the skewness and the corresponding hierarchical amplitude
of the divergence of the velocity field for arbitrary non-Gaussian
initial conditions. We find that qualitatively resembles the
corresponding hierarchical amplitude for the density field, , in that it
contains a term proportional to the initial skewness, which decays inversely as
the linear growth factor, plus a constant term which differs from the
corresponding Gaussian term by a complex function of the initial three- and
four- point functions. We extend the results for and with
non-Gaussian initial conditions to evolved fields smoothed with a spherical
tophat window function. We show that certain linear combinations, namely , , and , lead to expressions which are
much simpler, for non-Gaussian initial conditions, than and (or
and ) considered separately.Comment: 13 pages, latex, no figure
The Topology of Large Scale Structure in the 1.2 Jy IRAS Redshift Survey
We measure the topology (genus) of isodensity contour surfaces in volume
limited subsets of the 1.2 Jy IRAS redshift survey, for smoothing scales
\lambda=4\hmpc, 7\hmpc, and 12\hmpc. At 12\hmpc, the observed genus
curve has a symmetric form similar to that predicted for a Gaussian random
field. At the shorter smoothing lengths, the observed genus curve shows a
modest shift in the direction of an isolated cluster or ``meatball'' topology.
We use mock catalogs drawn from cosmological N-body simulations to investigate
the systematic biases that affect topology measurements in samples of this size
and to determine the full covariance matrix of the expected random errors. We
incorporate the error correlations into our evaluations of theoretical models,
obtaining both frequentist assessments of absolute goodness-of-fit and Bayesian
assessments of models' relative likelihoods. We compare the observed topology
of the 1.2 Jy survey to the predictions of dynamically evolved, unbiased,
gravitational instability models that have Gaussian initial conditions. The
model with an , power-law initial power spectrum achieves the best
overall agreement with the data, though models with a low-density cold dark
matter power spectrum and an power-law spectrum are also consistent. The
observed topology is inconsistent with an initially Gaussian model that has
, and it is strongly inconsistent with a Voronoi foam model, which has a
non-Gaussian, bubble topology.Comment: ApJ submitted, 39 pages, LaTeX(aasms4), 12 figures, 1 Tabl
An evaluation of websites quality factors in agro travel and ecotourism
Tourism is an information intensive industry and as a service industry, information is the most significant quality factor for the industry. E-tourism is part of electronic trade that includes the fastest
developing technologies that assist to the hospitality and tourism strategic planning and management. The aim of this paper is to analyze and compare the quality of 3 Internet sites and detecting their strong and weak points by analyzing quality into its constituent dimensions. Research was carried out by personal interviews
and via electronic mails to a sample of 413 persons and internet users, out of which 157 responded. Statistical analysis included simple and multiple comparisons ANOVA and t-tests. Research detected some medium quality ratings, as well as, some more positive evaluations of certain individual factors. The Internet sites that collected the highest ratings are Agrotravel (5.32), Guest inn (5.08) and Ecotourism (4.26). Elements considered important in all three web portals are the lack of interaction facilities and conversation sections and personalized options with user personal accounts. Emphasis must be paid on the design, information,
interaction and overall quality of a web site
Genus statistics using the Delaunay tessellation field estimation method: (I) tests with the Millennium Simulation and the SDSS DR7
We study the topology of cosmic large-scale structure through the genus
statistics, using galaxy catalogues generated from the Millennium Simulation
and observational data from the latest Sloan Digital Sky Survey Data Release
(SDSS DR7). We introduce a new method for constructing galaxy density fields
and for measuring the genus statistics of its isodensity surfaces. It is based
on a Delaunay tessellation field estimation (DTFE) technique that allows the
definition of a piece-wise continuous density field and the exact computation
of the topology of its polygonal isodensity contours, without introducing any
free numerical parameter. Besides this new approach, we also employ the
traditional approaches of smoothing the galaxy distribution with a Gaussian of
fixed width, or by adaptively smoothing with a kernel that encloses a constant
number of neighboring galaxies. Our results show that the Delaunay-based method
extracts the largest amount of topological information. Unlike the traditional
approach for genus statistics, it is able to discriminate between the different
theoretical galaxy catalogues analyzed here, both in real space and in redshift
space, even though they are based on the same underlying simulation model. In
particular, the DTFE approach detects with high confidence a discrepancy of one
of the semi-analytic models studied here compared with the SDSS data, while the
other models are found to be consistent.Comment: 14 pages, 9 figures, accepted by Ap