Electrostatic harmonic Langmuir waves are virtual modes excited in weakly turbulent plasmas, first observed in early laboratory beam-plasma experiments as well as in rocket-borne active experiments in space. However, their unequivocal presence was confirmed through computer simulated experiments and subsequently theoretically explained. The peculiarity of harmonic Langmuir waves is that while their existence requires nonlinear response, their excitation mechanism and subsequent early time evolution are governed by essentially linear process. One of the unresolved theoretical issues regards the role of nonlinear wave-particle interaction process over longer evolution time period. Another outstanding issue is that existing theories for these modes are limited to one-dimensional space. The present paper carries out two dimensional theoretical analysis of fundamental and (first) harmonic Langmuir waves for the first time. The result shows that harmonic Langmuir wave is essentially governed by (quasi)linear process and that nonlinear wave-particle interaction plays no significant role in the time evolution of the wave spectrum. The numerical solutions of the two-dimensional wave spectra for fundamental and harmonic Langmuir waves are also found to be consistent with those obtained by direct particle-in-cell simulation method reported in the literature.

Education systems are undergoing transformations in order to adapt their curriculum to develop skills that are required of professional from courses that have design disciplines. Also increasingly evident is the need for a transdisciplinary teaching that involves collaboration among different disciplines of the same science. In this context, this article focuses, by the case study of synthetic diamond particles, on the integration among Descriptive Geometry, Technical Drawing, Materials and Processes disciplines with the aid of CAD systems. Through this integration and a transdisciplinary teaching, it is possible to correlate the knowledge that involves three-dimensional modeling, the projection of objects and analysis of the geometric shape. The generated models represent an innovative feature for the process of teaching and learning in the disciplines that involve the design as it provides an effective contact between the student and the object of study through, the manufacturing experience and the concrete three-dimensional experience.

A recent paper [Ziebell et al., Phys. Plasmas 21, 010701 (2014)] discusses a new type of radiation emission process for plasmas in a state of quasi-equilibrium between the particles and enhanced Langmuir turbulence. Such a system may be an example of the so-called “turbulent quasi-equilibrium.” In the present paper, it is shown on the basis of electromagnetic weak turbulence theory that an initial thermal equilibrium state (i.e., only electrostatic fluctuations and Maxwellian particle distributions) transitions toward the turbulent quasi-equilibrium state with enhanced electromagnetic radiation spectrum, thus demonstrating that the turbulent quasi-equilibrium discussed in the above paper correctly describes the weakly turbulent plasma dynamically interacting with electromagnetic fluctuations, while maintaining a dynamical steady-state in the average sense.

Here we present a theoretical study on the main properties of Fractionally Integrated Exponential Generalized Autoregressive Conditional Heteroskedastic (FIEGARCH) processes. We analyze the conditions for the existence, the invertibility, the stationarity and the ergodicity of these processes. We prove that, if {Xt}t∈Z is a FIEGARCH(p,d,q) process then, under mild conditions, {ln(Xt2)}t∈Z is an ARFIMA(q,d,0) with correlated innovations, that is, an autoregressive fractionally integrated moving average process. The convergence order for the polynomial coefficients that describes the volatility is presented and results related to the spectral representation and to the covariance structure of both processes {ln(Xt2)}t∈Z and {ln(σt2)}t∈Z are discussed. Expressions for the kurtosis and the asymmetry measures for any stationary FIEGARCH(p,d,q) process are also derived. The h-step ahead forecast for the processes {Xt}t∈Z, {ln(σt2)}t∈Z and {ln(Xt2)}t∈Z are given with their respective mean square error of forecast. The work also presents a Monte Carlo simulation study showing how to generate, estimate and forecast based on six different FIEGARCH models. The forecasting performance of six models belonging to the class of autoregressive conditional heteroskedastic models (namely, ARCH-type models) and radial basis models is compared through an empirical application to Brazilian stock market exchange index.

Resumo:

Este artigo discute que, embora o volume da população seja um aspecto relevante a se considerar na relação entre população e ambiente, existem outros fatores que podem ser ainda mais importantes. Na perspectiva demográfica, elementos como a composição e distribuição espacial da população são fundamentais. Em termos ambientais, o estilo de desenvolvimento e o nível de consumo são decisivos. O Brasil vive um momento de transições flagrantes. Por um lado, existe a transição demográfica (queda nas taxas de mortalidade e natalidade), marcada pelo rápido declínio na taxa de fecundidade total, de cerca de 6 filhos por mulher, em 1960, para menos de 2 filhos, em 2010. Por outro lado, há uma transição de consumo, discutida neste trabalho tendo como referência a melhoria da situação econômica do país e o aumento do consumo de água, que é causado tanto pela expansão do sistema de abastecimento em áreas urbanas quanto pela tendência de aumento do gasto per capita. Assim, enquanto houve uma redução significativa das taxas de crescimento populacional, o consumo de água apresentou tendência de aumento, como resultado de alterações nos padrões de acesso e níveis de consumo.

Abstract:

In this paper we discuss that, although the volume of the population is an important aspect to be considered in the relationship between population and environment, there are other factors that may be even more important. From a demographic perspective, for example, details such as composition and spatial distribution of the population are essential. In environmental terms, the style of development and level of consumption are crucial. Brazil is going through a time of important transitions. On the one hand, the demographic transition (decreased levels of mortality and birth rates), is characterized by the rapid decline in total fertility rate, from about 6 children per woman in the 1960s to fewer than 2 children per woman in the late 2000s. On the other hand, there is a consumption transition also in course, discussed here in the relationship between improving the economic situation and increased water consumption, which is caused by the expansion of the supply system in urban areas and by the trend toward growing per capita consumption. Thus, while there has been a significant decrease in population growth rates, water consumption tends to increase as the result of changes in access patterns and consumption levels.

Resumen:

Este artículo discute que, aunque el volumen de la población sea un aspecto relevante a considerar en la relación entre población y ambiente, hay otros factores que pueden ser todavía más importantes. Desde la perspectiva demográfica, elementos como la composición y distribución espacial de la población son fundamentales. En lo que concierne al medio ambiente, el estilo de desarrollo y el nivel de consumo son decisivos. Brasil vive un momento de marcadas transiciones. Por un lado, existe la transición demográfica (baja en las tasas de mortalidad y natalidad), marcada por el rápido descenso en la tasa de fecundidad total, de cerca de 6 hijos por mujer, en 1960, para menos de 2 hijos, en 2010. Por otro lado, hay una transición de consumo, que se discute en este trabajo teniendo como referencia la mejora de la situación económica del país y el aumento del consumo de agua, que es ocasionado tanto por la expansión del sistema de abastecimiento en áreas urbanas como por la tendencia de aumento del gasto per cápita. De este modo, mientras hubo una reducción significativa de las tasas de crecimiento poblacional, el consumo de agua presentó una tendencia de aumento, como resultado de alteraciones en los estándares de acceso y niveles de consumo.