The Advertisement Calls and Distribution of Two Sympatric Species of \u3cem\u3eChiasmocleis\u3c/em\u3e (Méhely 1904) (Anura, Microhylidae, Gastrophryninae) from the Atlantic Forest

The advertisement calls of Chiasmocleis cordeiroi and C. crucis are described for populations from the municipalities of Igrapiúna and Camacan, respectively, state of Bahia, Brazil. Both calls consist of multipulsed notes produced in series. Differences between the two calls are: dominant frequency, higher in C. cordeiroi (range 4500-4898 Hz; C. crucis range 4069-4435 Hz); note rate, higher in C. cordeiroi (range 6.20--7.46 s/note; C. crucis range 5.17-5.59 s/note); pulse rate, higher in C. cordeiroi (151.82-194.83 s/note; C. crucis range 125.30- 142.12 s/note); and the structure of the modulation patterns of the notes. Moreover, the advertisement calls of C. crucis and C. cordeiroi are more similar than the calls of all syntopic congeners. Furthermore, the current distribution of both species was extended

Photosynthesis, stomatal conductance and leaf water potential in crabwood (Carapa guianensis)

Leaf water potential is one of the most important factors affecting stomatal functioning. The aim of this study was to assess the effect of variation in diurnal irradiance and vapour pressure deficit on photosynthesis (A), stomatal conductance (g s) and leaf water potential (psi) in Carapa guianensis (Aubl.). Data were collected from 07:00 to 17:00 h. Photosynthetic rates reached a maximum (2.5 µmol m-2 s-1) at 10:00 h, thereafter declined to a minimum of 1 µmol m-2 s-1 at 16:00 h. Stomatal conductance oscillated during the day, from 0.04 mol m-2 s-1 (at midday) to 0.02.mol.m-2.s-1 at the end of the afternoon. Leaf water potential was higher early in the morning (-0.3 MPa) and lower (-0.75 MPa) at mid-afternoon (14:30 -15:00 h). After reaching a minimum, psi increased up to -0.64 MPa at sunset. Photosynthetic rates increased linearly as a function of g s (P < 0.01). Also there was a positive relationship between psi and g s (P< 0.01). Photosynthetic rates declined during the day after reaching a peak early in the morning, which makes clear that environmental factors that influence psi greatly affect carbon assimilation of C. guianensis.O potencial hídrico da folha é um dos fatores mais importantes que afetam o funcionamento dos estômatos. O objetivo deste trabalho foi avaliar o efeito da variação diurna na irradiância e déficit de pressão de vapor (DPV) na fotossíntese (A), condutância estomática (g s) e potencial hídrico da folha (psi) em Carapa guianensis (Aubl.). Os dados foram coletados de 07:00 às 17:00 h. A taxa fotossintética atingiu um valor máximo (2,5 µmol m-2 s-1) às 10:00 h, depois declinou até atingir um mínimo de 1 µmolm-2 s-1 às 16:00 h. A condutância estomática oscilou durante o dia, de 0,04 molm-2s-1 (ao meio dia) para 0,02 molm-2s- 1 no final da tarde. O potencial hídrico da folha foi máximo nas primeiras horas do dia (-0,3 MPa) e mínimo (-0,75 MPa) no meio da tarde (14:30 a 15:00 h). Após ter alcançado um mínimo, o psi aumentou até -0,64 MPa no fim da tarde. A taxa fotossintética aumentou linearmente em função do g s (P < 0,01). Também houve uma relação positiva entre psi e g s (P < 0,01). A taxa fotossintética declinou durante o dia após ter alcançado um pico no início da manhã, demonstrando que os fatores ambientais que afetam o psi têm efeito significativo na assimilação do carbono de C. guianensis

A controlled filtering method for estimating harmonics of off-nominal frequencies

The increasing use of power electronics in power systems causes a high injection of harmonic components which can in turn interfere with utility equipment and customer loads. Therefore, the correct estimation and measurement of harmonics have become an important issue. If the power frequency of the signal is steady and near the nominal value, the discrete Fourier transform (DFT) can be used and good estimation performance is achieved. However, there are considerable power frequency variations on isolated systems such as shipboard power systems, micro-grids and smart-grids. When these variations occur there may be significant errors in the estimates using the DFT. In order to deal with this problem, this work presents a novel technique based on demodulation of the power line signal and subsequent filtering for harmonics estimation. The main features of the proposed harmonic estimation technique are: precise and accurate estimation of harmonics of off-nominal frequencies and fast estimation of harmonics (about two cycles of the fundamental component). Simulation results show that the proposed technique performs well in comparison with the DFT and can be a good candidate to replace it in cases where the power frequency is subject to considerable variations

Considerations on the aggregation of harmonics produced by large wind farms

One aspect of assessing the harmonics tolerated by a power system is the estimation of the aggregation or sum of harmonics arising from the various sources. The estimation of harmonics is not exact or uniform, since there will be unpredictable variations in either the non-linear sources and/or parameters of the system which affect the summation. The combination of a number of harmonic sources will generally lead to less than the arithmetic sum of the maximum values due to uncertainty of magnitude and phase angle. Hence the resulting summation is difficult to estimate accurately. In this paper the harmonic summation caused by large wind farms with harmonic sources is investigated. The work verifies, by computational simulations, the harmonic aggregation in the point of common coupling (peC) of a typical wind farm under study by the Brazilian Systems Operator. Results show that the harmonic summation estimates for different conditions. The results are also compared with the lEe 61400-21 recommended aggregation factors. The results indicate that aggregation of harmonics at the point of common coupling cannot be easily generalized. The topology of the wind farm, the type of electronic converter, the wind variations, the frequency range and the upstream supply system impedance play a very role in the determination of the aggregation coefficients

A new approach for harmonic summation using the methodology of IEC 61400-21

This work verifies, by computational simulations, the harmonic aggregation in the point of common coupling (PCC) of some electrical systems that feed wind turbines. Results show that the harmonic summation estimates using the IEC 61400-21 methodology may present significant errors. In this work, we analyze the IEC 61400-21 methodology and propose adjustments to improve the estimations. Using the proposed adjustments, we note that the errors in the estimates are significantly reduced

Considerations on the aggregation of harmonics produced by large wind farms

One aspect of assessing the harmonics tolerated by a power system is the estimation of the aggregation or sum of harmonics arising from the various sources. The estimation of harmonics is not exact or uniform, since there will be unpredictable variations in either the non-linear sources and/or parameters of the system which affect the summation. The combination of a number of harmonic sources will generally lead to less than the arithmetic sum of the maximum values due to uncertainty of magnitude and phase angle. Hence the resulting summation is difficult to estimate accurately. In this paper the harmonic summation caused by large wind farms with harmonic sources is investigated. The work verifies, by computational simulations, the harmonic aggregation in the point of common coupling (peC) of a typical wind farm under study by the Brazilian Systems Operator. Results show that the harmonic summation estimates for different conditions. The results are also compared with the lEe 61400-21 recommended aggregation factors. The results indicate that aggregation of harmonics at the point of common coupling cannot be easily generalized. The topology of the wind farm, the type of electronic converter, the wind variations, the frequency range and the upstream supply system impedance play a very role in the determination of the aggregation coefficients