68 research outputs found

    Measurement and Modeling of Particle Radiation in Coal Flames

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    This work aims at developing a methodology that can provide information of in-flame particle radiation in industrial-scale flames. The method is based on a combination of experimental and modeling work. The experiments have been performed in the high-temperature zone of a 77 kWth swirling lignite flame. Spectral radiation, total radiative intensity, gas temperature, and gas composition were measured, and the radiative intensity in the furnace was modeled with an axisymmetric cylindrical radiation model using Mie theory for the particle properties and a statistical narrow-band model for the gas properties. The in-flame particle radiation was measured with a Fourier transform infrared (FTIR) spectrometer connected to a water-cooled probe via fiber optics. In the cross-section of the flame investigated, the particles were found to be the dominating source of radiation. Apart from giving information about particle radiation and temperature, the methodology can also provide estimates of the amount of soot radiation and the maximum contribution from soot radiation compared to the total particle radiation. In the center position in the flame, the maximum contribution from soot radiation was estimated to be less than 40% of the particle radiation. As a validation of the methodology, the modeled total radiative intensity was compared to the total intensity measured with a narrow angle radiometer and the agreement in the results was good, supporting the validity of the used approach

    Multimodal Communication in a Noisy Environment: A Case Study of the Bornean Rock Frog Staurois parvus

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    High background noise is an impediment to signal detection and perception. We report the use of multiple solutions to improve signal perception in the acoustic and visual modality by the Bornean rock frog, Staurois parvus. We discovered that vocal communication was not impaired by continuous abiotic background noise characterised by fast-flowing water. Males modified amplitude, pitch, repetition rate and duration of notes within their advertisement call. The difference in sound pressure between advertisement calls and background noise at the call dominant frequency of 5578 Hz was 8 dB, a difference sufficient for receiver detection. In addition, males used several visual signals to communicate with conspecifics with foot flagging and foot flashing being the most common and conspicuous visual displays, followed by arm waving, upright posture, crouching, and an open-mouth display. We used acoustic playback experiments to test the efficacy-based alerting signal hypothesis of multimodal communication. In support of the alerting hypothesis, we found that acoustic signals and foot flagging are functionally linked with advertisement calling preceding foot flagging. We conclude that S. parvus has solved the problem of continuous broadband low-frequency noise by both modifying its advertisement call in multiple ways and by using numerous visual signals. This is the first example of a frog using multiple acoustic and visual solutions to communicate in an environment characterised by continuous noise

    A New Species of Leptobrachium from the Kelabit Highland, Northwestern Borneo (Anura, Megophryidae)

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    Four species of endemic Leptobrachium are known from Borneo, two lowland species L. kanowitense and L. abbotti, a montane species L. montanum, and a highland species L. gunungense. Of these, both L. montanum and L. abotti were found to contain several cryptic species by recent molecular studies. The population from Bario, Kelabit Highland of Sarawak, is one such cryptic species and was once called Lineage 2 of L. abbotti. Our morphological survey on this population proved that it has characteristics distinct from all other congeners, and therefore, we describe the Bario population as a new species, Leptobrachium kantonishikawai sp. nov. The new species is distinguished from putative topotypes of L. montanum and L. abbotti, as well as from L. gunungense by having a grayish brown abdomen, usually vermiculated, although sometimes spotted or blotched with white, and some unique morphometric characteristics
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