Generalized Berreman's model of the elastic surface free energy of a nematic liquid crystal on a sawtoothed substrate

In this paper we present a generalization of Berreman's model for the elastic contribution to the surface free-energy density of a nematic liquid crystal in presence of a sawtooth substrate which favours homeotropic anchoring, as a function of the wavenumber of the surface structure $q$, the tilt angle $\alpha$ and the surface anchoring strength $w$. In addition to the previously reported non-analytic contribution proportional to $q\ln q$, due to the nucleation of disclination lines at the wedge bottoms and apexes of the substrate, the next-to-leading contribution is proportional to $q$ for a given substrate roughness, in agreement with Berreman's predictions. We characterise this term, finding that it has two contributions: the deviations of the nematic director field with respect to the corresponding to the isolated disclination lines, and their associated core free energies. Comparison with the results obtained from the Landau-de Gennes model shows that our model is quite accurate in the limit $wL>1$, when strong anchoring conditions are effectively achieved.Comment: 13 pages, 9 figures; revised version submitted to Phys. Rev.

The application of disaster management in Turkey from a comparative perspective: A proposal for a new model

Bu çalışma, 13-15 Eylül 2010 tarihleri arasında Algarve[Portekiz]’da düzenlenen 7. International Conference on Computer Simulation in Risk Analysis and Hazard Mitigation’da bildiri olarak sunulmuştur.This study examines the mutual relations between risk, risk society and types of disaster, after having defined risk and the risk society, then proceeding to analyze a range of disaster management models that are currently applied in Turkey and other countries. An empirical survey about the last major disaster that occurred in Turkey is carried out. Consequently, a new, effective and functional integrated disaster management model for Turkey is proposed. The term 'risk society' describes the inevitable new hazards produced by industrial society's process of development. The risk society brings not only hazards and risks that are not familiar and have not been faced before, but also prosperity and benefits for the members of the risk society. Natural and man-made disasters affect human beings more than in pre-industrial society and produce distinctive impacts on and changes in the psychological structure of urban society after disasters. The disaster management system applied in the risk society should be different from classical systems. While implementing a disaster management model, specific types of disaster that may occur in urban areas should be considered. The model should include swift response, efficiency and practicality. As a conclusion of all these studies, a new, effective disaster management model applicable to Turkey is proposed.Wessex Inst TechnolWit, Transact Ecol & Environ

Boundary element formulation for elastoplastic analysis of axisymmetric bodies

The complete formulation of B.E.M. applied to the analysis of axisymmetric bodies acting in the plastic range is presented in this paper. The concept of derivative of a singular integral given by Mikhlin has been used in order to calculate the stresses in internal points. Also a semianalytical approach is proposed to compute the matrix coefficients, presenting the way in which it can be done and the results obtained

Operation of a superconducting nanowire quantum interference device with mesoscopic leads

A theory describing the operation of a superconducting nanowire quantum interference device (NQUID) is presented. The device consists of a pair of thin-film superconducting leads connected by a pair of topologically parallel ultra-narrow superconducting wires. It exhibits intrinsic electrical resistance, due to thermally-activated dissipative fluctuations of the superconducting order parameter. Attention is given to the dependence of this resistance on the strength of an externally applied magnetic field aligned perpendicular to the leads, for lead dimensions such that there is essentially complete and uniform penetration of the leads by the magnetic field. This regime, in which at least one of the lead dimensions lies between the superconducting coherence and penetration lengths, is referred to as the mesoscopic regime. The magnetic field causes a pronounced oscillation of the device resistance, with a period not dominated by the Aharonov-Bohm effect through the area enclosed by the wires and the film edges but, rather, in terms of the geometry of the leads, in contrast to the well-known Little-Parks resistance of thin-walled superconducting cylinders. A theory, encompassing this phenomenology, is developed through extensions, to the setting of parallel superconducting wires, of the Ivanchenko-Zil'berman-Ambegaokar-Halperin theory for the case of short wires and the Langer-Ambegaokar-McCumber-Halperin theory for the case of longer wires. It is demonstrated that the NQUID acts as a probe of spatial variations in the superconducting order parameter.Comment: 20 pages, 18 figure

Prediction of hourly ozone concentrations with multiple regression and multilayer perceptron models

In this work ozone observations of an urban area of the east coast of the Iberian Peninsula, are analyzed. The data set contains measurements from five automatic air pollution monitoring stations (background suburban or traffic urban). The application of multiple linear regression and neural networks models is considered. These models forecast hourly ozone levels for short-term prediction intervals (1, 8, and 24 h in advance). The study period is 2010 2012. The input variables are meteorological observations, ozone and nitrogen oxides concentrations, and daily and weekly seasonal cycles. The performance criteria to evaluate the computations accuracy are the residual mean square error, the mean absolute error, and the correlation coefficient between observations and predictions. These criteria have better results for the 1-h and 24-h predictions in all the locations. The comparison of multiple linear regressions and multilayer perceptron networks indicates that the second approach allows to obtain more accurate forecast for the three prediction intervals.Capilla, C. (2016). Prediction of hourly ozone concentrations with multiple regression and multilayer perceptron models. International Journal of Sustainable Development and Planning. 11(4):558-565. doi:10.2495/SDP-V11-N4-558-565S55856511

Global wave loads on a damaged ship

A computational tool was applied based on a two dimensional linear method to predict the hydrodynamic loads for damaged ships. Experimental tests on a ship model have also been carried out to predict the hydrodynamic loads in various design conditions. The results of the theoretical method and experimental tests are compared to validate the theoretical method. The extreme wave induced loads have been calculated by short term prediction. For the loads in intact condition, the prediction with duration of 20 years at sea state 5 is used, while for loads in damaged conditions the prediction in 96 hours exposure time at sea 3 is used. The maximum values of the most probable extreme amplitudes of dynamic wave induced loads in damaged conditions are much less than those in intact condition because of the reduced time. An opening could change the distribution of not only stillwater bending moment but also wave-induced bending moment. It is observed that although some cross sections are not structurally damaged, the total loads acting on these cross sections after damage may be increased dramatically compared to the original design load in intact condition

Sensitivity Analysis and Optimization Using Energy Finite Element and Boundary Element Methods

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76597/1/AIAA-20811-196.pd

Computation of eigenmodes on a compact hyperbolic 3-space

Measurements of cosmic microwave background (CMB) anisotropy are ideal experiments for discovering the non-trivial global topology of the universe. To evaluate the CMB anisotropy in multiply-connected compact cosmological models, one needs to compute the eigenmodes of the Laplace-Beltrami operator. Using the direct boundary element method, we numerically obtain the low-lying eigenmodes on a compact hyperbolic 3-space called the Thurston manifold which is the second smallest in the known compact hyperbolic 3-manifolds. The computed eigenmodes are expanded in terms of eigenmodes on the unit three-dimensional pseudosphere. We numerically find that the expansion coefficients behave as Gaussian pseudo-random numbers for low-lying eigenmodes. The observed gaussianity in the CMB fluctuations can partially be attributed to the Gaussian pseudo-randomness of the expansion coefficients assuming that the Gaussian pseudo-randomness is the universal property of the compact hyperbolic spaces.Comment: 40 pages, 8 EPS figures; error estimation is included; accepted Classical and Quantum Gravit