Finite time blow-up and breaking of solitary wind waves

The evolution of surface water waves in finite depth under wind forcing is reduced to an antidissipative Korteweg-de Vries-Burgers equation. We exhibit its solitary wave solution. Antidissipation accelerates and increases the amplitude of the solitary wave and leads to blow-up and breaking. Blow-up occurs in finite time for infinitely large asymptotic space so it is a nonlinear, dispersive, and antidissipative equivalent of the linear instability which occurs for infinite time. Due to antidissipation two given arbitrary and adjacent planes of constant phases of the solitary wave acquire different velocities and accelerations inducing breaking. Soliton breaking occurs in finite space in a time prior to the blow-up. We show that the theoretical growth in amplitude and the time of breaking are both testable in an existing experimental facility.

Geração de energia renovável em residências: aplicação de tecnologias existentes

Due to the high value of the bill that the Brazilian has been paying, one of the most expensive in the world, is becoming increasingly attractive the option for renewable energy in form of distributed micro and minigeneration. In other words, the renewable energy sources are becoming attractive not only because of environmental concerns, but also due to economic issues. This has become even more relevant and concrete after approval of rules by National Agency of Electric Energy (ANEEL) on 4/17/2012 (Normative Resolution n ° 482/2012 of 04/17/2012) aimed at reducing barriers to installation of small distributed generation, including microgeneration, with up to 100 kW of power, and minigeneration, 100 kW to 1 MW. The Normative Resolution n ° 482/2012 creates the Energy Clearing System, which allows consumers to install small generators in its consumer unit and exchange energy with the local distributor. The rule applies to generators that use renewable sources of energy (hydro, solar, biomass, wind and cogeneration qualified). In this context, this paper presents a technical and economic analysis of installing a residential microgenerating plant composed of photovoltaic cells, solar panels and small wind turbines

Estudo comparativo do desgaste de ferramentas cerâmicas de Al2O3 em relação às de B4C + TiB2

Due to the high value of the bill that the Brazilian has been paying, one of the most expensive in the world, is becoming increasingly attractive the option for renewable energy in form of distributed micro and minigeneration. In other words, the renewable energy sources are becoming attractive not only because of environmental concerns, but also due to economic issues. This has become even more relevant and concrete after approval of rules by National Agency of Electric Energy (ANEEL) on 4/17/2012 (Normative Resolution n ° 482/2012 of 04/17/2012) aimed at reducing barriers to installation of small distributed generation, including microgeneration, with up to 100 kW of power, and minigeneration, 100 kW to 1 MW. The Normative Resolution n ° 482/2012 creates the Energy Clearing System, which allows consumers to install small generators in its consumer unit and exchange energy with the local distributor. The rule applies to generators that use renewable sources of energy (hydro, solar, biomass, wind and cogeneration qualified). In this context, this paper presents a technical and economic analysis of installing a residential microgenerating plant composed of photovoltaic cells, solar panels and small wind turbines

Análise comparativa entre Brasil e Alemanha sobre autoprodução de energia elétrica residencial

The energy crisis has affected many countries. With the growing warning with the emission in the atmosphere and the lack of resources, the seek for sustainable sources for energy genaration have become even bigger. Some Countries, as Germany, started first in this journey, creating an incentive program to self-generation with renewable sources (wind, photovoltaics, biomass, etc.), giving priority for smaller plants. In Germany the program called EEG started in 2004. In Brazil, since the beggining of 2012, the self-generators did not know how they could be beneficted for self-generation, and self-generation didn't become commun in the country. However, with NR 482, of April 17th, 2012, the parameters were defined, and the self-generator could have a guideline. Therewith, studyies can be redirected for a better knowlegde of the conditions the self-generator will be sujected, in addition to Germany's case as reference to compare with Brazil's case. In this paper these studies are made, focused in wind power (wind turbines) and photovoltaic panels

Attraction of the sand fly Nyssomyia neivai (Diptera: Psychodidae) to chemical compounds in a wind tunnel

Background: Similar to other hematophagous insects, male and female sand flies must feed on plants to obtain sugar and, subsequently, energy to complete their life cycles. A large number of compounds emitted by plants may act as volatile signals to these insects. Primary alcohols have been detected in some plants, but in small amounts. In a previous report, the attractiveness of saturated primary alcohols with 7 to 9 carbons was evaluated for Lutzomyia longipalpis, the vector of American visceral leishmaniasis, with positive results.Methods: In the present study, a wide range of primary alcohols, 3 to 10 carbons, were tested to investigate their attractiveness to another sand fly species, Nyssomyia neivai, a putative vector of American cutaneous leishmaniasis. The mixture of compounds that induced the best sand fly response was also evaluated.Results: Of the eight compounds evaluated, hexanol and octanol elicited the best attractive responses for sand fly females.Conclusion: Phytochemicals may be an interesting source of search for new sand fly attractants.

Energetic exploitation from a hybrid PV-wind power micro-generation rural electrification

Hybrid system micro-generation integration of PV-wind power is presented by a form of energy in which problems resulting from variability in the intensity of wind and solar intensity are possible mitigation either by complementation between one source to another or the largest stability configured by the generate the system. Based on this context, this work aims to assessing the performance of a hybrid system PV-wind power energy small of a rural property for their electrification. The study has been developed at the Rural Laboratory Powering from Engineering Department of UNESP. In order to present this research, a hybrid system has been installed PV-wind power, composed of one 400Wp windmill and a 300 Wp PV-system. The results obtained allowed us to evaluate the solar and wind energy supplied ranked among 285 and 360 kWh electric power generated by the PV-wind power hybrid system stood between 25,5 and 31 kWh. At is to say achieving yield of approximately than 10% during one year observation period, i.e., it was concluded that the performance of the hybrid system depended essentially the energy received and generated by the PV-system and that there was complementation between generating wind power and PV-systems with regard to time of day and the annual seasons by confirming the technical feasibility of this kind system of micro-generation in small rural properties.

Active power reserve for frequency control provided by distributed generators in distribution networks

In a smart grid environment, attention should be paid not only to the power supplied to satisfy loads and system losses but also to the services necessary to provide security and stability to the system: the so-called ancillary services. As they are well known the benefits that distributed generation can bring to electrical systems and to the environment, in this work the possibility that active power reserve for frequency control could be provided by distributed generators (DGs) in an efficient and economical way is explored. The proposed methodology was tested using the IEEE 34-bus distribution test system. The results show improvements in the capacity of the system for this ancillary service and decrease in system losses and payments of the distribution system operator to the DGs.

The feasibility of using wind energy for rural populations lacking electric power in Brazil

In the wake of current global image involving environmental impacts, the use of wind power has had a remarkable growth in recent years as a technique for generating electricity. In fact, it is a source featuring strong dissemination of technology which provides decrease in costs and a greater access to low-income electricity. PROINFA (Incentive Program for Alternative Energy Sources) promotes a greater diffusion of new technologies for power generation, in particular wind-produced. Due to such a scenario on the exploitation of such energy source, current analysis discusses strategies for the development of domestic wind technology and the implications for electricity-lacking rural areas. Analysis shows a similar behavior between rural populations lacking electricity and the amount of potential energy available in the region. It is expected that this assay will contribute towards the establishment of public policies for wind-energy parks on rural farms in the North and Northeast regions of Brazil.

Nebraska Wind Power: A Comparitive Study of Knowledge and Attitudes

Abstract The goal of this project is to assess the knowledge and attitudes of Nebraskans on the issue of wind power. The point of this research is to learn whether the presence of wind power has a positive effect on a person’s knowledge about and attitudes toward wind power and wind turbines. Using mail surveys, qualitative and quantitative data were collected from the towns of Pierce and Ainsworth Nebraska. The surveys aided in seeing patterns of knowledge about wind power and wind turbines and positive and negative attitudes and major concerns regarding wind power.

The Evolution of Sonata Form in the Wind Music of W.A. Mozart

Mozart’s wind music occupies a rather small space in the overall scope of his compositional output, numbering a total of ten works. Yet when viewed in the larger context of Mozart’s life, the wind music was written over the span of nine years, encompassing a large period from his youth up to his last decade in Vienna. Ranging from the simple divertimenti (K. 166 and 186) through the Tafelmusik (K. 213, 240, 252, 253 and 270) and finally culminating in the three Serenades (K. 361, 375 and 388), the wind music demonstrates Mozart’s maturation in wind writing, and also serves to illustrate the evolution in his use of sonata forms.

A cyclic bipolar wind in the interacting binary V 393 Scorpii

V393 Scorpii is a double periodic variable characterized by a relatively stable non-orbital photometric cycle of 253 d. Mennickent et al. argue for the presence of a massive optically thick disc around the more massive B-type component and describe the evolutionary stage of the system. In this paper, we analyse the behaviour of the main spectroscopic optical lines during the long non-orbital photometric cycle. We study the radial velocity of the donor determining its orbital elements and find a small but significant orbital eccentricity (e = 0.04). The donor spectral features are modelled and removed from the spectrum at every observing epoch using the light-curve model given by Mennickent et al. We find that the line emission is larger during eclipses and mostly comes from a bipolar wind. We also find that the long cycle is explained in terms of a modulation of the wind strength; the wind has a larger line and continuum emissivity at the high state. We report the discovery of highly variable chromospheric emission in the donor, as revealed by the Doppler maps of the emission lines Mg II 4481 and C I 6588. We discuss notable and some novel spectroscopic features like discrete absorption components, especially visible at blue depressed O I 7773 absorption wings during the second half-cycle, Balmer double emission with V/R curves showing 'Z-type' and 'S-type' excursions around secondary and main eclipses, respectively, and H beta emission wings extending up to +/- 2000 km s(-1). We also discuss possible causes for these phenomena and for their modulations with the long cycle.

He II lambda 4686 IN eta CARINAE: COLLAPSE OF THE WIND-WIND COLLISION REGION DURING PERIASTRON PASSAGE

The periodic spectroscopic events in eta Carinae are now well established and occur near the periastron passage of two massive stars in a very eccentric orbit. Several mechanisms have been proposed to explain the variations of different spectral features, such as an eclipse by the wind-wind collision (WWC) boundary, a shell ejection from the primary star or accretion of its wind onto the secondary. All of them have problems explaining all the observed phenomena. To better understand the nature of the cyclic events, we performed a dense monitoring of eta Carinae with five Southern telescopes during the 2009 low-excitation event, resulting in a set of data of unprecedented quality and sampling. The intrinsic luminosity of the He II lambda 4686 emission line (L similar to 310 L-circle dot) just before periastron reveals the presence of a very luminous transient source of extreme UV radiation emitted in the WWC region. Clumps in the primary's wind probably explain the flare-like behavior of both the X-ray and He II lambda 4686 light curves. After a short-lived minimum, He II lambda 4686 emission rises again to a new maximum, when X-rays are still absent or very weak. We interpret this as a collapse of the WWC onto the "surface" of the secondary star, switching off the hard X-ray source and diminishing the WWC shock cone. The recovery from this state is controlled by the momentum balance between the secondary's wind and the clumps in the primary's wind.

Nondetection Index of Anti-Islanding Passive Protection of Synchronous Distributed Generators

Synchronous distributed generators are prone to operate islanded after contingencies, which is usually not allowed due to safety and power-quality issues. Thus, there are several anti-islanding techniques; however, most of them present technical limitations so that they are likely to fail in certain situations. Therefore, it is important to quantify and determine whether the scheme under study is adequate or not. In this context, this paper proposes an index to evaluate the effectiveness of anti-islanding frequency-based relays commonly used to protect synchronous distributed generators. The method is based on the calculation of a numerical index that indicates the time period that the system is unprotected against islanding considering the global period of analysis. Although this index can precisely be calculated based on several electromagnetic transient simulations, a practical method is also proposed to calculate it directly from simple analytical formulas or lookup tables. The results have shown that the proposed approach can assist distribution engineers to assess and set anti-islanding protection schemes.

Generators of supersymmetric polynomials in positive characteristic

In Kantor and Trishin (1997) [3], Kantor and Trishin described the algebra of polynomial invariants of the adjoint representation of the Lie superalgebra gl(m vertical bar n) and a related algebra A, of what they called pseudosymmetric polynomials over an algebraically closed field K of characteristic zero. The algebra A(s) was investigated earlier by Stembridge (1985) who in [9] called the elements of A(s) supersymmetric polynomials and determined generators of A(s). The case of positive characteristic p of the ground field K has been recently investigated by La Scala and Zubkov (in press) in [6]. We extend their work and give a complete description of generators of polynomial invariants of the adjoint action of the general linear supergroup GL(m vertical bar n) and generators of A(s).

Changes in phytoplankton composition in response to tides, wind-induced mixing conditions, and freshwater outflows in an urbanised estuarine complex

Recent reports have shown an increase in potentially harmful phytoplankton in Santos bay (Southeastern Brazilian Coast), located in a highly urbanised estuarine complex. Prediction of blooms is, thus, essential but the phytoplankton community structure in very dynamic regions is difficult to determine. In the present work, we discriminate bloom forming microphytoplankton dominance and their relationship to physical and meteorological variables to look for patterns observed in different tides and seasons. Comparing 8 distinct situations, we found five scenarios of dominance that could be related to winds, tides and rainfall: i) Surfers, diatoms occurring during high surf zone energies; ii) Sinkers, represented by larger celled diatoms during spring tide, after periods of high precipitation rates; iii) Opportunistic mixers, composed of chain forming diatoms with small or elongate cells occurring during neap tides; iv) Local mixers, microplanktonic diatoms and dinoflagellates which occurred throughout the 298 sampling stations; and v) Mixotrophic dinoflagellates, after intense estuarine discharges. Results suggest alterations in the temporal patterns for some bloom-forming species, while others appeared in abundances above safe limits for public health. This approach can also illustrate possible impacts of changes in freshwater discharge in highly urbanised estuaries.