The relationship between Tourism and Internet

Sen, M.; Yapici, F. (2011). The relationship between Tourism and Internet. Universitat Politècnica de València. http://hdl.handle.net/10251/12229Archivo delegad

Higher Education Student's Behaviors as Avatars in a Web based Course in Second Life

AbstractApplications of virtual learning environments in higher education have gained particular attention both from educators and higher education institutions in recent years. In this respect, Second Life (SL) environments are the prime example of three dimensional multi-user environments which are low in cost and which offer a high value in terms of learning. In this study, a group of seventeen students from the faculty of education participated in a course, in which a part of their class activity was carried out in a SL environment. This paper describes the construction of a SL course environment that students enrolled in and summarizes the results of observations in this virtual classroom such as student's behavior and interaction

Atomistic simulations to micro-mechanisms of adhesion in automotive applications

This study aimed at depicting atomistic and microstructural aspects of adhesion and friction that appear in different automotive applications and manufacturing processes using atomistic simulations coupled with tribological tests and surface characterization experiments. Thin films that form at the contact interfaces due to chemical reactions and coatings that are developed to mitigate or enhance adhesion were studied in detail. The adhesion and friction experiments conducted on diamond-like carbon (DLC) coatings against Al indicated that F incorporation into DLC decreased the coefficient of friction (COF) by 30% -with respect to H-DLC that is known to have low COF and anti-adhesion properties against Al- to 0.14 owing to formation of repulsive F-F interactions at the sliding interface as shown by density functional theory (DFT) calculations. F atoms transferred to the Al surface with an increase in the contact pressure, and this F transfer led to the formation of a stable AlF3 compound at the Al surface as confirmed by XPS and cross-sectional FIB-TEM. The incorporation of Si and O in a F-containing DLC resulted in humidity independent low COF of 0.08 due to the hydration effect of the Si-O-Si chains in the carbonaceous tribolayers that resulted in repulsive OH-OH interactions at the contact interface. At high temperatures, adhesion of Al was found to be enhanced as a result of superplastic oxide fibers on the Al surface. Molecular dynamics (MD) simulations of tensile deformation of Al nanowires in oxygen carried out with ReaxFF showed that native oxide of Al has an oxygen deficient, low density structure and in O 2 , the oxygen diffusion in amorphous oxide healed the broken Al-O bonds during applied strain and resulted in the superplasticity. The oxide shell also provided nucleation sites for dislocations in Al crystal. In fuel cell applications, where low Pt/carbon adhesion is causing durability problems, spin-polarized DFT showed that metals with unfilled d orbitals increase the Pt/graphene interface strength from 0.009 J/m 2 to above 0.5 J/m 2 . Ir, Os, Ru, Rh and Re were the most effective modifiers, as they distributed their electronic charges evenly between Pt and graphene surfaces

Effects of Sodium Metabisulphide Treatment and Modified Atmosphere Packaging on Cold Storage of Carrots

The aim of this study was to investigate the effects of sodium metabisulphide (SMBS) treatment and modified atmosphere packaging (MAP) on the quality of ‘Nanco F1’ variety of Nantes group carrots grown in Kırıkhan during cold storage. Harvested carrots were placed in imperforated bag, and/or MAP and applied SMBS (dose of 1%) after washing with tap water for 3 minutes and stored at 0±0.5 °C and 90±5.0% relative humidity for 5 months and analyzed every month. In addition, carrots were kept at 20±0.5 ºC and 75±5.0 % relative humidity for 7 days in order to study its shelf life. The weight loss, carrot color (L* and h°), appearance (1-9), rooting and sprouting rate, rooting and sprouting degree, incidence of fungal decay, physiological disorders, carrot firmness, total soluble solid content, pH value, titratable acid content and taste (1-9) were determined during shelf life and storage. According to the findings, weight loss in imperforated bag was higher than MAP treatments during storage. It was determined that using ImPBTW (imperforated bag and washing with tap water) and ImPBTW + SMBS treatments, ‘Nanco F1’ type carrots could be kept at 0 °C for 3 months and 85-90% relative humidity without any quality deterioration. It was also determined that using MAPTW (modified atmosphere packaging and washing with tap water) + SMBS treatment, ‘Nanco F1’ type carrots could be stored for 4 months and using MAPTW treatment, they could be stored for 5 months at 0 °C and 85-90% relative humidity without losing much of the quality for local and distant markets. Also, it was found that SMBS treatments were not sufficient to prevent rooting and sprouting

Evolutionary optimization of a charge transfer ionic potential model for Ta/Ta-oxide hetero-interfaces

Tantalum, tantalum oxide and their hetero-interfaces are of tremendous technological interest in several applications spanning electronics, thermal management, catalysis and biochemistry. For example, local oxygen stoichiometry variation in TaOx memristors comprising of metallic (Ta) and insulating oxide (Ta2O5) have been shown to result in fast switching on the sub-nanosecond timescale over a billion cycles, relevant to neuromorphic computation. Despite its broad importance, an atomistic scale understanding of oxygen stoichiometry variation across Ta/TaOx hetero-interfaces, such as during early stages of oxidation and oxide growth, is not well understood. This is mainly due to the lack of a variable charge interatomic potential model for tantalum oxides that can accurately describe the ionic interactions in the metallic (Ta) and oxide (TaOx) environment as well as at their interfaces. To address this challenge, we introduce a charge transfer ionic potential (CTIP) model for Ta/Ta-oxide system by training against lattice parameters, cohesive energies, equations of state, and elastic properties of various experimentally observed Ta2O5 polymorphs. The best set of CTIP parameters are determined by employing a single-objective global optimization scheme driven by genetic algorithms followed by local Simplex optimization. Our newly developed CTIP potential accurately predicts structure, thermodynamics, energetic ordering of polymorphs, as well as elastic and surface properties of both Ta and Ta2O5, in excellent agreement with DFT calculations and experiments. We employ our newly parameterized CTIP potential to investigate the early stages of oxidation of Ta at different temperatures and atomic/molecular nature of the oxidizing species

Comparing optimization strategies for force field parameterization

Classical molecular dynamics (MD) simulations enable modeling of materials and examination of microscopic details that are not accessible experimentally. The predictive capability of MD relies on the force field (FF) used to describe interatomic interactions. FF parameters are typically determined to reproduce selected material properties computed from density functional theory (DFT) and/or measured experimentally. A common practice in parameterizing FFs is to use least-squares local minimization algorithms. Genetic algorithms (GAs) have also been demonstrated as a viable global optimization approach, even for complex FFs. However, an understanding of the relative effectiveness and efficiency of different optimization techniques for the determination of FF parameters is still lacking. In this work, we evaluate various FF parameter optimization schemes, using as example a training data set calculated from DFT for different polymorphs of Ir$O_2$. The Morse functional form is chosen for the pairwise interactions and the optimization of the parameters against the training data is carried out using (1) multi-start local optimization algorithms: Simplex, Levenberg-Marquardt, and POUNDERS, (2) single-objective GA, and (3) multi-objective GA. Using random search as a baseline, we compare the algorithms in terms of reaching the lowest error, and number of function evaluations. We also compare the effectiveness of different approaches for FF parameterization using a test data set with known ground truth (i.e generated from a specific Morse FF). We find that the performance of optimization approaches differs when using the Test data vs. the DFT data. Overall, this study provides insight for selecting a suitable optimization method for FF parameterization, which in turn can enable more accurate prediction of material properties and chemical phenomena