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 $p$-order hierarchical amplitudes $S_p$, in both real and redshift space. We compare our results with numerical simulations, focusing on the $\Omega=1$ 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 $\sigma_L$ 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 $\sigma$ 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 $\sigma \approx 1$, but provides a good fit to the \Lambda-CDM models for $\sigma$ 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 $t_3$ and the corresponding hierarchical amplitude $T_3$ of the divergence of the velocity field for arbitrary non-Gaussian initial conditions. We find that $T_3$ qualitatively resembles the corresponding hierarchical amplitude for the density field, $S_3$, 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 $S_3$ and $T_3$ with non-Gaussian initial conditions to evolved fields smoothed with a spherical tophat window function. We show that certain linear combinations, namely $S_3 + {1 \over 2} T_3$, $S_3 + T_3$, and $s_3 + t_3$, lead to expressions which are much simpler, for non-Gaussian initial conditions, than $S_3$ and $T_3$ (or $s_3$ and $t_3$) 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 $n=-1$, 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 $n=0$ power-law spectrum are also consistent. The observed topology is inconsistent with an initially Gaussian model that has $n=-2$, 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