In this paper, the Ground Penetrating Radar (GPR) method was used to characterize concrete tubes and steel/plastic tanks buried in IAG/USP test site. The microwave tomography was used to improve the GPR images, aiming...In this paper, the Ground Penetrating Radar (GPR) method was used to characterize concrete tubes and steel/plastic tanks buried in IAG/USP test site. The microwave tomography was used to improve the GPR images, aiming to retrieve the geometry of the targets. The numerical modeling studies also were done in order to predict the GPR results of the buried targets and to give more reliability to the results interpretation. The targets were installed in the first shallow geophysical test site of the Brazil located at Institute of Astronomy, Geophysics, and Atmospheric Science (IAG) of the University of S?o Paulo (USP). GPR profiles of 200 MHz (shielded bistatic antennas) were acquired along three lines containing concrete tubes and steel/plastic tanks buried in subsoil. The concrete tubes show a hyperbolic reflector for the top, and the vertical tube also presented a reflection on its bottom. The horizontal steel tanks were characterized by a strong GPR reflection on their top. The empty plastic tank shows a strong reflector for the top with normal polarity. On the other hand, the plastic tank filled with water shows a weaker reflector for its top characterized by the inverted polarity of GPR signal when compared with empty plastic tank. The plastic tank filled with water also went characterized by the strong reflection to its bottom, being a good indicative to interpret GPR data on target in subsoil with some types of fluid inside of tank. The results of polarity difference for the top of tank can be used as guide pattern to identify buried tank empty or filled with water. The application of microwave tomography to the GPR data permitted to determine the position and get a good identification of the edges of the targets studied. The numeric modeling presented a good accordance with real data reducing the ambiguities in interpretation of results. These results can be used as a reference, and they can be extrapolated for areas where there is no subsurface information.展开更多
Background:Floods and other extreme events have disastrous effects on wetland breeding birds.However,such events and their consequences are difficult to study due to their rarity and unpredictable occurrence.Methods:H...Background:Floods and other extreme events have disastrous effects on wetland breeding birds.However,such events and their consequences are difficult to study due to their rarity and unpredictable occurrence.Methods:Here we compared nest-sites chosen by Reed Parrotbills(Paradoxornis heudei) during June-August 2016 in Yongnianwa Wetlands,Hebei Province,China,before and after an extreme flooding event.Results:Twenty-three nests were identified before and 13 new nests after the flood.There was no significant difference in most nest-site characteristics,such as distance from the road,height of the reeds in which nests were built,or nest volume before or after the flood.However,nests after the flood were located significantly higher in the vegetation compared to before the flood(mean ± SE:1.17 ± 0.13 m vs.0.75 ± 0.26 m,p < 0.01).However,predation rate also increased significantly after the flood(67% vs.25%,p = 0.030).Conclusions:Our results suggested that Reed Parrotbills demonstrated behavioral plasticity in their nest-site selection.Thus,they appeared to increase the height of their nests in response to the drastically changing water levels in reed wetlands,to reduce the likelihood that their nests would be submerged again by flooding.However,predation rate also increased significantly after the flood,suggesting that the change in nest height to combat the threat of flooding made the nests more susceptible to other threats,such as predation.Animals' response to rare climatic events,such as flooding,may produce ecological traps if they make the animals more susceptible to other kinds of threats they are more likely to continue to encounter.展开更多
文摘In this paper, the Ground Penetrating Radar (GPR) method was used to characterize concrete tubes and steel/plastic tanks buried in IAG/USP test site. The microwave tomography was used to improve the GPR images, aiming to retrieve the geometry of the targets. The numerical modeling studies also were done in order to predict the GPR results of the buried targets and to give more reliability to the results interpretation. The targets were installed in the first shallow geophysical test site of the Brazil located at Institute of Astronomy, Geophysics, and Atmospheric Science (IAG) of the University of S?o Paulo (USP). GPR profiles of 200 MHz (shielded bistatic antennas) were acquired along three lines containing concrete tubes and steel/plastic tanks buried in subsoil. The concrete tubes show a hyperbolic reflector for the top, and the vertical tube also presented a reflection on its bottom. The horizontal steel tanks were characterized by a strong GPR reflection on their top. The empty plastic tank shows a strong reflector for the top with normal polarity. On the other hand, the plastic tank filled with water shows a weaker reflector for its top characterized by the inverted polarity of GPR signal when compared with empty plastic tank. The plastic tank filled with water also went characterized by the strong reflection to its bottom, being a good indicative to interpret GPR data on target in subsoil with some types of fluid inside of tank. The results of polarity difference for the top of tank can be used as guide pattern to identify buried tank empty or filled with water. The application of microwave tomography to the GPR data permitted to determine the position and get a good identification of the edges of the targets studied. The numeric modeling presented a good accordance with real data reducing the ambiguities in interpretation of results. These results can be used as a reference, and they can be extrapolated for areas where there is no subsurface information.
基金supported by the National Natural Science Foundation of China(Nos.31672303 to CY,31472013 and 31772453 to WL)
文摘Background:Floods and other extreme events have disastrous effects on wetland breeding birds.However,such events and their consequences are difficult to study due to their rarity and unpredictable occurrence.Methods:Here we compared nest-sites chosen by Reed Parrotbills(Paradoxornis heudei) during June-August 2016 in Yongnianwa Wetlands,Hebei Province,China,before and after an extreme flooding event.Results:Twenty-three nests were identified before and 13 new nests after the flood.There was no significant difference in most nest-site characteristics,such as distance from the road,height of the reeds in which nests were built,or nest volume before or after the flood.However,nests after the flood were located significantly higher in the vegetation compared to before the flood(mean ± SE:1.17 ± 0.13 m vs.0.75 ± 0.26 m,p < 0.01).However,predation rate also increased significantly after the flood(67% vs.25%,p = 0.030).Conclusions:Our results suggested that Reed Parrotbills demonstrated behavioral plasticity in their nest-site selection.Thus,they appeared to increase the height of their nests in response to the drastically changing water levels in reed wetlands,to reduce the likelihood that their nests would be submerged again by flooding.However,predation rate also increased significantly after the flood,suggesting that the change in nest height to combat the threat of flooding made the nests more susceptible to other threats,such as predation.Animals' response to rare climatic events,such as flooding,may produce ecological traps if they make the animals more susceptible to other kinds of threats they are more likely to continue to encounter.
