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排序方式: 共有95条查询结果,搜索用时 15 毫秒
1.
Marie-Laure Bgout Anras Jean Paul Lagardre 《Aquaculture (Amsterdam, Netherlands)》2004,240(1-4):175-186
An experiment was conducted to measure swimming activity of rainbow trout (254.0±33.7 g) held in outdoor tanks under three culture conditions with stocking density used to generate differences: 27 (Culture Density 1, CD1), 80 (CD2) and 136 kg m−3 (CD3). Fish were fed dry pellets at 1% of tank biomass from 9h00 to 13h00 with automatic feeders. Using acoustic telemetry, fish positions were monitored every 5 s during 48 h for nine fish (three in each treatment). Swimming behaviour was analysed in terms of trajectories: they varied between (i) holding position (high turning angles), (ii) chaotic trajectories (equal use of all turning angles) and (iii) circular swimming (average turning angle of 60°). Space utilisation differed for each culture condition: CD3 conditions induced a prolonged residence time in the central zone of the tank. Rainbow trout swimming activity patterns and levels differed depending on both day–night alternation and culture conditions. All fish reared at CD1 and one reared at CD2 were day-active. All the other fish showed high activity pattern variability and a higher swimming level was observed under CD3. These results illustrate that monitoring fish swimming activity is feasible even under high densities and provide relevant insights on fish activity which can lead to behavioural welfare indices in relation to constraints imposed by culture conditions. 相似文献
2.
Andrew S. Brierley Paul G. Fernandes Mark A. Brandon Frederick Armstrong Nicholas W. Millard Steven D. McPhail Peter Stevenson Miles Pebody James Perrett Mark Squires Douglas G. Bone Gwyn Griffiths 《Fisheries Research》2003,60(2-3):569-576
The autonomous underwater vehicle (AUV) Autosub-2 was deployed on eight missions ahead of RRS James Clark Ross in the northern Weddell Sea and in the Bransfield Strait, Southern Ocean, to assess avoidance of the research vessel by Antarctic krill Euphausia superba. The AUV was equipped with the same type of scientific echosounder as the research vessel (Simrad EK500 operating at 38 and 120 kHz) and measured the density of krill along transect acoustically (g m−2 wet mass) prior to the ship’s arrival. We hypothesised that if krill avoided the ship, perhaps in response to radiated noise, then the ship should detect less krill than the AUV which is known to have much lower noise levels than the ship. We were unable to detect any significant difference between the density of krill detected by the ship or the AUV, either at the transect level or at finer scales within transects. We conclude, therefore, that avoidance by krill of RRS James Clark Ross will not significantly bias acoustic estimates of krill abundance by this vessel. 相似文献
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A 2-year-old Quarter Horse filly was admitted to our facility with a two-day history of trauma caused by barbed wire on the front face of the right front limb fetlock joint. A septic arthritis was confirmed with the synovial fluid examination. The cytologic evaluation of synovial fluid showed 101,000 leukocytes/mm3, 90% neutrophils, and a total protein concentration of 4 g/dL. It was, therefore, decided to perform an arthroscopic lavage using an ultrasonic device with the tip inserted inside the synovial cavity to exploit the phenomenon of acoustic cavitation. After the removal of the synovial pannus, the probe was left to vibrate in the area near the visible penetrating wound inside the joint until three liters of saline was finished. Further studies are needed for understanding and applying this technology in different equine fields and with different bacterial species. However, these first results are promising for the efficacy of this innovative procedure. 相似文献
7.
Seepage from earthen irrigation canals represents substantial water loss in irrigation districts. Historically, the determination of canal seepage was accomplished using the inflow-outflow method with propeller and electromagnetic type flow meters. This method was difficult, time consuming, and limited by measurement device accuracy. In recent years, advances in technology have lead to the widespread use of Acoustic Doppler Current Profilers (ADCP) for discharge measurements in streams and rivers. Even though ADCP use has become widespread for stream discharges, studies to determine canal seepage using this new technology are limited. Using an ADCP, extensive field measurements were conducted in the Middle Rio Grande Conservancy District. This paper describes the ADCP measurement protocol used to measure irrigation canal seepage and presents predictive equations for determining canal seepage based on flow rate and canal geometry. 相似文献
8.
Rubber-modified epoxy resins have been employed as adhesive and matrix materials for glass and corbon-fiber composites. The
behavior of fracture around a crack tip for rubber-modified epoxy resin is investigated through the acoustic emission (AE)
analysis of compact tension specimens. Damage zone and rubber particles distributed around a crack tip were observed by a
polarized optical microscope and an atomic force microscope (AFM). The damage zone in front of pre-crack tip in rubber-modified
specimen (15 wt% rubber) began to form at about 13 % level of the fracture load and grew in size until 57 % load level. After
that, the crack propagated in a stick-slip manner. Based on time-frequency analysis of AE signals and microscopic observation
of damage zone, it was thought that AE signals with frequency bands of 0.15–0.20 MHz and 0.20–0.30 MHz were generated from
cavitation in the damage zone and crack propagation, respectively. 相似文献
9.
木材表面声发射信号源的三角形定位方法 总被引:1,自引:0,他引:1
为了确定木材表面声发射源的发生位置,首先采用高速采集设备设计了基于Lab VIEW的多通道声发射信号采集平台,并采用小波分析方法从原始声发射信号中析取有用信号;然后根据信号传播的时延差确定声发射信号在木材表面的平均传播速率;最后依据基于时差的三角形几何定位原理,提出木材表面声发射信号源定位方法,并通过铅芯模拟声发射源的测试试验加以验证。结果表明该方法能够以较高的精度确定木材表面声发射信号源位置。 相似文献
10.
J. Pinhas V. Soroker A. Hetzroni A. Mizrach M. Teicher J. Goldberger 《Computers and Electronics in Agriculture》2008,63(2):131-139
The red palm weevil (RPW) is a key pest of horticultural and ornamental palm species in Asia, the Middle East and the Mediterranean region, currently dispersing in Mediterranean European countries, endangering the landscape. The RPW larvae bore deep into palm crowns, trunks and offshoots, concealed from visual inspection until the palms are nearly dead. Traded palm trees are intensively transported between and within countries, spreading the pest worldwide. Consequently, an urgent need exists to identify and monitor concealed RPW larvae. Acoustic signals of boring RPW larvae can be recorded from the infested palms using off-the-shelf recording devices, but the resolution of the signals emitted by healthy palms is often difficult to discriminate. The purpose of this research was to develop a mathematical method to automatically detect acoustic activity of RPW in offshoots and implement it in a prototype setup. The methodology applied was similar to techniques used in the field of speech recognition, utilizing Vector quantization (VQ) or Gaussian mixture modeling (GMM). The algorithm successfully achieved detection ratios as high as 98.9%. The study shows that it is feasible to detect RPW sounds using the mathematical method of speech recognition and commercial recording devices, which could be utilized to monitor trade and transportation of offshoots. 相似文献