Analysing the consequence of gas pipeline explosion safety impact
Nowadays, most of the analysis of the explosion of und erground gas pipeline consequences did not consider the tunnel's covering ground conditions. In this paper,the risk are analyzed w ith considering and without considering of covering rock layer of pipe problems, through the relevant modeling, application of M ATLAB software,carried out the simulation to the final blasting effect.And made a final disscion of the two kinds of simulation r esults respectively.
Pipeline two-dimensional impact location determination using time of arrival with instant phase (TOAIP) with piezoceramic transducer array
An impact event on a pipeline generates stress waves that travel along the pipeline, and the traveling stress waves can be easily detected by distributed piezoceramic transducers. To pinpoint impact location on a pipeline, the time of arrival (TOA) is commonly used and the envelope calculated by the Hilbert transform is an effective method to determine the TOA. However, the envelope used to extract the TOA depends on the manual selection of the trigger threshold. In fact, the instant phase, that changes regularly from -pi to pi as the stress wave travels, is an important characteristic parameter of the signal, and the TOA can be determined by the periodicity of the instant phase. However, this fact has been overlooked in calculating TOA in the literature. In this paper, a new method, time of arrival with instant phase (TOAIP), is developed to calculate the TOA without the need of manual selection of the threshold. Taking into account the non-stationarity of the signal and noise interference, short time window Fourier transform and band-pass filter are utilized to extract the useful signal, the TOA is then determined by using the instant phase which is based both the first zero-crossing point of signal and the periodicity of the phase. In general, most of the pipeline impact localization realize one-dimensional positioning along its length direction. Another novelty of this paper is the development of the two-dimensional impact location (TDIL) that can estimate the impact location information along both length and circumferential directions. Experimental studies based on pipeline with distributed lead zirconate titanate (PZT) transducers mounted on the surface of the pipeline are carried out in this research. Both of physical measurements and inversion results have verified the accuracy and reliability of TOAIP and TDIL on the pipeline.
Gill diseases of cultured salmonids in Ontario.
Between 1977 and 1981, the Fish Pathology Laboratory of the Ontario Veterinary College received 239 cases from trout farms of southern Ontario, 51 (21.3%) of which had diseased gills. Branchial lesions in 86.3% of these 51 cases were characterized by marked lamellar epithelial hyperplasia with epithelial hypertrophy and lamellar fusion. Filamentous bacteria were seen on the surface of the branchial filaments and lamellae in 68.6% of the cases. Our observations highlight the importance of gill diseases as a production problem of farmed salmonids in southern Ontario.