This study was performed to investigate the spectral characteristics of micro-seismic signals observed during the rupture of coal. Coal rupture micro-seismic observations were obtained on a test system that included a...This study was performed to investigate the spectral characteristics of micro-seismic signals observed during the rupture of coal. Coal rupture micro-seismic observations were obtained on a test system that included an electro-hydraulic servo pressure tester controlled by a YAW microcomputer, a micro-seismic sensor, a loading system, and a signal collection system. The results show that the micro-seismic signal increases with increasing compressive stress at the beginning of coal rupture. The signal remains stable for a period at this stage. A large number of micro-seismic signals appear immediately before the main rupture event. The frequency of micro-seismic events reaches a maximum immediately after the coal ruptures. Micro-seismic signals were decomposed into several Intrinsic Mode Functions (IMF's) by the empirical mode decomposition (EMD) method using a Hilbert-Huang transform (HHT). The main fre- quency band of the micro-seismic signals was found to range from 10 to 100 Hz in the Hilbert energy spectrum and from marginal spectrum calculations. The advantage of applying an HHT is that this can extract the main features of the signal. This fact was confirmed by an HHT analysis of the coal micro-seis- mic signals that shows the technique is useful in the field of coal rupture.展开更多
Phenotypic plasticity is nearly universal among organisms, and evidence indicates that plasticity can exhibit additive genetic variation and respond to selection. These findings have important implications for our und...Phenotypic plasticity is nearly universal among organisms, and evidence indicates that plasticity can exhibit additive genetic variation and respond to selection. These findings have important implications for our understanding of how plasticity may be constrained and how its mechanistic structure may affect its evolution. Many life history trade-offs may be conceptua- lized as plastic traits, with individuals varying in their position along trade-off axes due to genetic differences, developmental plasticity, or short-term plasticity occurring throughout an individual＇s lifetime. Behavioral plasticity is key to understanding when organisms are likely to encounter trade-offs, whether those trade-offs can be mitigated, and how the tradc-offs affect the ecology and evolution of populations. In this review, we discuss hormonal and neural mechanisms that may influence how plastic behavioral traits are expressed and evolve. We also outline a classification of life history trade-offs and their mechanistic bases and discuss the currencies most likely to mediate each category of trade-off and bow they are tied to the mechanisms by which animals express their behaviors.展开更多
基金support for this work provided by the National Science and Technology Planning Project (No. 2009BAK54B03)the National Natural Science Foundation of China (No. 50834005)
文摘This study was performed to investigate the spectral characteristics of micro-seismic signals observed during the rupture of coal. Coal rupture micro-seismic observations were obtained on a test system that included an electro-hydraulic servo pressure tester controlled by a YAW microcomputer, a micro-seismic sensor, a loading system, and a signal collection system. The results show that the micro-seismic signal increases with increasing compressive stress at the beginning of coal rupture. The signal remains stable for a period at this stage. A large number of micro-seismic signals appear immediately before the main rupture event. The frequency of micro-seismic events reaches a maximum immediately after the coal ruptures. Micro-seismic signals were decomposed into several Intrinsic Mode Functions (IMF's) by the empirical mode decomposition (EMD) method using a Hilbert-Huang transform (HHT). The main fre- quency band of the micro-seismic signals was found to range from 10 to 100 Hz in the Hilbert energy spectrum and from marginal spectrum calculations. The advantage of applying an HHT is that this can extract the main features of the signal. This fact was confirmed by an HHT analysis of the coal micro-seis- mic signals that shows the technique is useful in the field of coal rupture.
文摘Phenotypic plasticity is nearly universal among organisms, and evidence indicates that plasticity can exhibit additive genetic variation and respond to selection. These findings have important implications for our understanding of how plasticity may be constrained and how its mechanistic structure may affect its evolution. Many life history trade-offs may be conceptua- lized as plastic traits, with individuals varying in their position along trade-off axes due to genetic differences, developmental plasticity, or short-term plasticity occurring throughout an individual＇s lifetime. Behavioral plasticity is key to understanding when organisms are likely to encounter trade-offs, whether those trade-offs can be mitigated, and how the tradc-offs affect the ecology and evolution of populations. In this review, we discuss hormonal and neural mechanisms that may influence how plastic behavioral traits are expressed and evolve. We also outline a classification of life history trade-offs and their mechanistic bases and discuss the currencies most likely to mediate each category of trade-off and bow they are tied to the mechanisms by which animals express their behaviors.
