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1.
Mingxuan Mao Li Zhang Qichang Duan O.J.K Oghorada Pan Duan Bei Hu 《International Journal of Green Energy》2017,14(8):694-702
The power-voltage (P-V) characteristic curves of a PV array are nonlinear and have multiple peaks under partially shaded conditions (PSCs). This paper proposes a novel maximum power point tracking (MPPT) method for a PV system with reduced steady-state oscillation based on a two-stage particle swarm optimization (PSO) algorithm. The grouping method of the shuffled frog leaping algorithm (SFLA) is incorporated in the basic PSO algorithm (PSO-SFLA), ensuring fast and accurate searching of the global extremum. An adaptive speed factor is also introduced into the improved PSO to further enhance its convergence speed. Test results show that the proposed method converges in less than half the time taken by the conventional PSO method, and the power is improved by 33% under the worst PSCs, which confirms the superiority of the proposed method over the standard PSO algorithm in terms of tracking speed and steady-state oscillations under different PSCs. 相似文献
2.
Peter?J.?ChristieEmail author Daniel?J.?Mennill Laurene?M.?Ratcliffe 《Behavioral ecology and sociobiology》2004,55(4):341-348
The fee-bee song of male black-capped chickadees (Poecile atricapillus) is considered a single-type song that singers transpose up and down a continuous frequency range. While the ability to shift song pitch in this species provides a mechanism for song matching as an aversive signal in male-male territorial song contests, the functional significance of this behaviour during the solo performances of males during the dawn chorus is unclear. We analysed the dawn chorus songs and singing behaviour of males whose winter-flock dominance status we determined. We used correlation analysis to show that pitch shifts were accompanied by changes to other fine structural characteristics in song, including temporal and relative amplitude parameters. We also found that songs of socially dominant males and songs of their most subordinate flockmates could be distinguished using these methods by the way they performed a between-note frequency measure accompanying pitch shifts. That is, a ratio measure of the internote frequency interval remained constant for songs of high-ranking birds despite changes in absolute pitch, while low-ranking males sang a smaller ratio as they shifted to higher absolute pitches. These findings identify previously unrecognised variation in the songs of black-capped chickadees. More importantly, they indicate a mechanism by which pitch shifting during the dawn chorus of black-capped chickadees could provide a reliable indicator of relative male quality.Communicated by I. Hartley 相似文献
3.
Stochastic dynamic programming (SDP) models predict that males singing to attract a mate should concentrate singing in what
has been termed the dawn chorus. This is because male birds should have a variable surplus of fat in the morning that can
be used to fuel singing, with the amount of fat available dependent upon such factors as his quality, foraging success and
risk of predation. In this manner, the dawn chorus can act as an indicator of male quality in the context of female mate choice.
We test a key prediction of SDP models of singing behaviour that males with greater fat levels should sing more. We conducted
an experiment where we recorded the dawn chorus of male silvereyes (Zosterops lateralis) on three consecutive days. Each male received supplementary food on the second day, which enabled us to sample his dawn
chorus before, during and after food supplementation. We also collected data on the effect of supplementary food on the body
mass of silvereyes. As predicted by SDP models, we found that silvereyes sang for a greater proportion of the time after receiving
supplementary food. Supplementary food also had a significant effect on the complexity of a male song, indicating that males
not only increased the quantity of their song but also the quality of their song when they received extra food. As the provision
of supplementary food significantly increased the mass of fed birds, our results support a causal link between male energy
reserves and his ability to perform the dawn chorus. 相似文献
4.
Chorusing males of the neotropical treefrog Hyla microcephala call in distinct bouts punctuated by periods of silence, a pattern known as unison bout singing. Schwartz (1991) previously tested and refuted the hypotheses that males periodically stop calling either because of a female preference for males that call cyclically, or because high ambient noise levels inhibit vocal activity. Males of H. microcephala are vocally responsive to the calls of other males, and during calling bouts their rate of note production can exceed 10,000 per hour. In natural choruses females preferentially pair with males that call at the higher rates. Because females can pair with males over many hours, males may stop calling periodically to save energy so they can continue to call for the entire period that females are available. We directly tested this energy conservation hypothesis by collecting samples of males early in the evening just after chorusing commenced and later when chorusing had ended for the night. Trunk muscles (internal and external oblique), which are responsible for the airflow associated with note production, were dissected, frozen, and their glycogen content measured. Data on calling behavior were obtained for late-evening samples. Individual calling behavior was not correlated with a males final glycogen level. In addition, many males ended their calling before glycogen reserves were exhausted, indicating that factors other than energy can determine when males finally stop chorusing, However, the biochemical assays supported the energy conservation hypothesis. Unless chorusing was punctuated by pauses, most males would have been unable to sustain high rates of calling for an entire evening without exhausting glycogen reserves in their trunk muscles. Because the time females pair with males is probably unpredictable to males, the ability to call for long periods may improve a males chances of mating. 相似文献
5.
Benjamin P. Smith Claudia Alcaraz Zini Janusz Pawliszyn Michael J. Tyler Yoji Hayasaka Brian Williams Elina Bastos Caramao 《Chemistry and Ecology》2000,17(3):215-225
Solid-phase microextraction (SPME) is an effective technique for studying frog volatile secretions. Its primary advantage is in its application to sampling live animals. the ability to sample an organism over an extended period allows changes in an individual's chemical signature to be determined. the presence of eucalyptol in the skin secretion of Ewing's tree frog, Litoria ewingi, was used to assess the effectiveness of SPME in sampling frog volatiles. Rapid sample times coupled with the polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre provided the best signal/noise ratio for the majority of frog volatiles analysed, and importantly resulted in the least amount of stress to the animals involved. 相似文献
6.
Loïc A. Hardouin Dominique Robert Vincent Bretagnolle 《Behavioral ecology and sociobiology》2008,62(12):1909-1918
The dawn chorus is a striking feature of spring mornings and a characteristic behaviour of many bird species, particularly
the passerines. Dawn singing has been considered a reliable signal of male quality for mate and rival assessment. Singing
is presumed to be relatively costly at dawn both because air temperatures are relatively low and because birds have not fed
overnight. Models of optimal daily routine predict the existence of a “dusk chorus” in nocturnal birds, although this prediction
has received little empirical attention. Nocturnal birds at dusk may be energy-limited because of a lack of daytime feeding,
and singing at dusk may thus ensure signal reliability. Here, we used an observational and experimental approach to study
vocal behaviour at dusk and dawn in a nocturnal raptor, the little owl Athene noctua. We assess whether male little owls adjust their vocal behaviour according to feeding stage (i.e. period of the night), ambient
air temperature and territorial context (i.e. spontaneous calling behaviour vs elicited calling by intrusion). Across different
temperatures, we find that both spontaneous vocal activity and inter-individual variability in call duration increased at
dusk, clearly indicating a dusk chorus phenomenon. Results from playback presentations suggest that food, rather than air
temperature, is likely to be more constraining at dusk. We discuss how comparing dusk and dawn choruses in nocturnal and diurnal
species can provide insights into both mechanistic and functional aspects of signalling behaviour. 相似文献
7.
Reinier M. Mann Ross V. Hyne Catherine B. Choung Scott. P. Wilson 《Environmental pollution (Barking, Essex : 1987)》2009,157(11):2903-2927
Agricultural landscapes, although often highly altered in nature, provide habitat for many species of amphibian. However, the persistence and health of amphibian populations are likely to be compromised by the escalating use of pesticides and other agricultural chemicals. This review examines some of the issues relating to exposure of amphibian populations to these chemicals and places emphasis on mechanisms of toxicity. Several mechanisms are highlighted, including those that may disrupt thyroid activity, retinoid pathways, and sexual differentiation. Special emphasis is also placed on the various interactions that may occur between different agro-chemicals and between chemicals and other environmental factors. We also examine the indirect effects on amphibian populations that occur when their surrounding pond communities are altered by chemicals. 相似文献
8.
Frog call intensities and sound propagation in the South American temperate forest region 总被引:3,自引:0,他引:3
Sound pressure levels and the spectral structure of the advertisement calls of five species of frogs from the South American
temperate austral forest were analyzed. Males of Eupsophus emiliopugini, Batrachyla antartandica and B. leptopus call from the ground in bogs, while males of Hylorina sylvatica and Pleurodema thaul call from the water surface in marshes. Calling males of the species from bogs and marshes spaced at average distances that
were shorter and longer than 2 m, respectively. The properties of these habitats for sound propagation were evaluated by broadcasting
pure tones, broadband noise and tape-recorded advertisement calls of the three species from bogs and of H. sylvatica. Excess attenuation and spectral degradation were higher for calls broadcast in bogs than in the marsh. The calls of B.␣antartandica and B. leptopus, with dominant frequencies of about 2 kHz, were more affected than those of E.␣emiliopugini and H. sylvatica, with dominant frequencies below 1.5 kHz. These results show the lack of an optimal relationship between properties of habitats
for sound transmission and the spectral structure of these anuran calls. Body size imposes an important constraint on call
spectra and propagation, which frogs counteract by distribution patterns and auditory capabilities.
Received: 18 April 1997 / Accepted after revision: 15 February 1998 相似文献
9.
Benjamin P. Smith Claudia Alcaraz Zini Janusz Pawliszyn Michael J. Tyler Yoji Hayasaka Brian Williams 《Chemistry and Ecology》2013,29(3):215-225
Solid-phase microextraction (SPME) is an effective technique for studying frog volatile secretions. Its primary advantage is in its application to sampling live animals. the ability to sample an organism over an extended period allows changes in an individual's chemical signature to be determined. the presence of eucalyptol in the skin secretion of Ewing's tree frog, Litoria ewingi, was used to assess the effectiveness of SPME in sampling frog volatiles. Rapid sample times coupled with the polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre provided the best signal/noise ratio for the majority of frog volatiles analysed, and importantly resulted in the least amount of stress to the animals involved. 相似文献
10.
Bioaccumulation, maternal transfer and elimination of polybrominated diphenyl ethers in wild frogs 总被引:1,自引:0,他引:1
Liu PY Du GD Zhao YX Mu YS Zhang AQ Qin ZF Zhang XY Yan SS Li Y Wei RG Qin XF Yang YJ 《Chemosphere》2011,84(7):972-978
To investigate bioaccumulation, maternal transfer and elimination of polybrominated diphenyl ethers (PBDEs) in amphibians, we collected adult frogs (Rana limnocharis) from a rice field in an e-waste recycling site in China. We found that ∑PBDEs in the whole frogs and various tissues (brain, liver, testis and egg) ranged from 17.10 to 141.11 ng g−1 wet weight. Various tissues exhibited a similar PBDE congener profile, which was characterized by intermediate brominated congeners (BDE-99 and BDE-153) as the largest contributors, with less lower brominated congeners (BDE-28 and BDE-47) and higher brominated congeners (BDE-209). The maternal transfer capacity of PBDEs declined with the increase in bromine numbers of PBDE congeners. We suggest that the bromine atom number (the molecular size, to some degree) might be a determining factor for the maternal transport of a PBDE congener rather than Kow (Octanol-Water partition coefficient), which expresses a compound’s lipophilicity. ∑PBDEs concentrations in frogs decreased over time during a depuration period of 54 days when these wild frogs were brought to the lab from the e-waste recycling site. The half-life of ∑PBDEs was 35 days, with about 14 days for BDE-47, and 36 and 81 days for BDE-99 and BDE-153, respectively. The data shows that the elimination of PBDEs has no essential difference from aquatic and terrestrial species. 相似文献