Solitary-wave vortices in quadratic nonlinear media

We find families of vortex solitary waves in bulk quadratic nonlinear media under conditions for second-harmonic generation. We show that the vortex solitary waves are azimuthally unstable and that they decay into sets of stable spatial solitons. We calculate the growth rates of the azimuthal perturbations and show how those affect the pattern of output light. © 1998 Optical Society of AmericaPeer ReviewedPostprint (published version

Correlation Between The Use Of Games And Students' Motivation In Learning English

This research aims at analyzing correlation between the use of games and students' motivation. Quantitative method with correlation research design was used in this research. Its population consists of 65 students taken as research sample. Total sampling technique was applied in this research. Two independent variables correlated were the use of games as variable X and students' motivation as variable Y. Questionnaires used to collect data consisted of 40 items, in which 20 items related to the use of games and another 20 items concerning with students' motivation. The data were analyzed by applying computer program of SPSS (statistical package for social science) 18. Findings of the research indicate that the coefficient correlation (rxy) is 0.571, with the degree of freedom df = N-2 and the level of significance 0.05 or 5%. Value of r-table 0.244 indicates that the value of rxyis higher than rt (0.571 > 0.244). Thereby, alternative hypothesis (Ha) is accepted and null hypothesis (Ho) is rejected, so there is a significant correlation between the implementation of games and motivation of students at second semester of grade VIII. It means that the more often teachers use games the higher students motivation in learning English

A comparative study of difficulties in accounting preparation and judgement in agriculture using fair value and historical cost for biological assets valuation

Este estudio realiza un investigación empírica comparando las dificultades que se derivan de la utilización del valor razonable (VR) y del coste histórico (CH) en el sector agrícola. Se analiza también la fiabilidad de ambos métodos de valoración para la interpretación de la información y la toma de decisiones por parte de los agentes que actúan en el sector. Mediante un experimento realizado con estudiantes, agricultores y contables que operan en el sector agrícola, se halla que estos tienen más dificultades, cometen mayores errores e interpretan peor la información contable realizada a CH que la realizada a VR. Entrevistas en profundidad con agricultores y contables agrícolas desvelan prácticas contables defectuosas derivadas de la necesidad de aplicar el CH en el sector en España. Dadas las complejidades del cálculo del coste de los activos biológicos y el predominio de pequeñas explotaciones en el sector en los países occidentales avanzados, el estudio concluye que la contabilidad a VR constituye una mejoría de utilización y desarrollo de la contabilidad en el sector que la confeccionada a CH. Asimismo, el CH transmite una peor representación de la situación real de las explotaciones agrícolas.This paper presents empirical research comparing the accounting difficulties that arise from the use of two valuation methods for biological assets, fair value (FV) and historical cost (HC) accounting, in the agricultural sector. It also compares how reliable each valuation method is in the decision-making process of agents within the sector. By conducting an experiment with students, farmers, and accountants operating in the agricultural sector, we find that they have more difficulties, make larger miscalculations and make poorer judgements with HC accounting than with FV accounting. In-depth interviews uncover flawed accounting practices in the agricultural sector in Spain in order to meet HC accounting requirements. Given the complexities of cost calculation for biological assets and the predominance of small family business units in advanced Western countries, the study concludes that accounting can be more easily applied in the agricultural sector under FV than HC accounting, and that HC conveys a less accurate grasp of the real situation of a farm

Frequency Selective Surface with Two Quasi-Independent Notch Frequencies

A double-layer frequency selective surface (FSS) built on FR4 substrate exhibiting two notch frequencies in the 0–10-GHz range is introduced. Recently published examples demonstrate that further research needs to be undergone for obtaining separate tuning of the resulted notch frequencies. Thus, this issue is addressed in this paper: the notch frequencies can be quasi-independently set by appropriate values given to the geometrical parameters of the two metal patterns in the unit cells of the structure. The FSS behavior is stable with respect to the angle of incidence of impinging electromagnetic waves up to 45°, as proved by simulation and validated by experiments

Conmutacion totalmente optica de ondas guiadas en medios virefring.

A new kind of tunable all-optical guided-wave thresholding device using waveguides consisting of both birefringent linear media and isotropic nonlinear media is discussed. The behavior of the lower threshold with a suitable orientation of the crystal optical axis of the birefringent substrate, relative to the direction of propagation, is analyzed for TE-dominant guided wavesPeer ReviewedPostprint (published version

Empleo de isótopos ambientales para discernir la contaminación salina de la cuenca del río Llobregat

La formación geológica salina de la comarca del Bages(Barcelona) y su explotación minera en diferentes puntos de la cuenca del Llobregat, influyen en la salinización de los ríos Cardener y Llobregat. La cuenca potásica catalana presenta dos peculiaridades: la formación salina tiene un afloramiento en Cardona, y en algunas zonas las capas de mineral se encuentran cerca de la superficie pero sin aflorar. La geología del terreno puede influir en la salinidad de las aguas de la cuenca por contacto directo con los materiales salinos. La actividad minera de Cardona (cerrada en 1990), Suria,Balsareny y Sallent, genera en la producción del mineral un residuo salino que se acumula en el exterior de las minas formándose las escombreras salinas o «runams». Sus salessolubles se disuelven con la lluvia, y pueden llegar a las aguas superficiales y aguas subterráneas del entorno. El objetivo de este trabajo es evaluar las aportaciones salinas a la cuenca del río Llobregat, separando las de origen natural y las de procedencia antrópica, utilizando la composición isotópica del azufre y del oxigeno del sulfato disuelto en sus aguas. También se cuantifica el origen natural y antrópico de los cloruros que se aportan