Accurate detection and picking of the P-phase onset time in noisy microseismic data from underground mines remains a big challenge. Reliable P-phase onset time picking is necessary for accurate source location needed ...Accurate detection and picking of the P-phase onset time in noisy microseismic data from underground mines remains a big challenge. Reliable P-phase onset time picking is necessary for accurate source location needed for planning and rescue operations in the event of failures. In this paper, a new technique based on the discrete stationary wavelet transform （DSWT）and higher order statist!cs, is proposed for processing noisy data from underground mines. The objectives of this method are to （1） Improve manual detection and tPicking of P-phase onset; and （ii） provide an automatic means of detecting and picking P-phase onset me accurately. The DSWT is first used to filter the signal over several scales. The manual P-phase onset detection and picking are then obtained by computing the signal energy across selected scales with frequency bands that capture the signal of interest. The automatic P-phase onset, on the other hand, is achieved by using skewness- and kurtosis-based criterion applied to selected scales in a time-frequency domain. The method was tested using synthetic and field data from an underground limestone mine. Results were compared with results obtained by using the short-term to long-term average （STA/LTA） ratio and that by Reference Ge et al. （2009）. The results show that the me!hod provides a more reliable estimate of the P-phase onset arrival than the STA]LTA method when the signal to noise ratio is very low. Also, the results obtained from the field data matched accurately with the results from Reference Ge et al. （2009）.展开更多
Capital structure denotes enterprises＇ form and proportion relation of various long-term funds source. The capital structure is the combination problem of the long-term funds about enterprise development and it is th...Capital structure denotes enterprises＇ form and proportion relation of various long-term funds source. The capital structure is the combination problem of the long-term funds about enterprise development and it is the quantity and proportion between every fund form. This paper analyzes the various factors which affect capital structural decision-making, and introduces capital structural optimization theory of the shelter benefit of tax revenue and bankruptcy cost balance. It studies the method and the evaluation criterion of capital structural optimization. And it constructs capital structural optimization model of coexistence condition of company＇s income tax and individual income tax. This will be very helpful for the rationality of enterprise capital structure.展开更多
The monthly changes in chlorophyll a, phytoplankton abundance and physicochemical parameters at two stations in Boka Kotorska Bay were investigated between 2003-2004. Nutrient salts varied widely, with maximum 3.65 μ...The monthly changes in chlorophyll a, phytoplankton abundance and physicochemical parameters at two stations in Boka Kotorska Bay were investigated between 2003-2004. Nutrient salts varied widely, with maximum 3.65 μmol.L^-1 for nitrates and 0.23 μmol.L^-1 for phosphate. Chlorophyll a concentration ranged from 0.25 to 7.63 mg·m^3 and the highest value was measured in winter period of year. It seems that reason for this is the land-based nutrient input into the coastal area here. According to chlorophyll a, nitrates and phosphates concentrations, the area could be oligomesotrophic to mesotrophic during winter.展开更多
Despite extensive research on various global waves in solar eruptions, debate continues on the intrinsic nature of them. In this work, we performed numerical experiments of the coronal mass ejection with emphases on t...Despite extensive research on various global waves in solar eruptions, debate continues on the intrinsic nature of them. In this work, we performed numerical experiments of the coronal mass ejection with emphases on the associated large-scale MHD waves. A fast-mode shock forms in front of the flux rope during the eruption with a dimming region following it, and the development of a three-component structure of the ejecta is observed. At the flank of the flux rope, the slow-mode shock and the velocity vortices are also invoked. The dependence of the eruption energetics on the strength of the background field and the coronal plasma density distribution is apparent： the stronger the background field is, and/or the lower the coronal plasma density is, the more energetic the eruption is. In the lower Alfven speed environment, the slow mode shock and the large scale velocity vortices may be the source of the EIT wave. In the high Alfvdn speed environment, on the other hand, the echo due to the reflection of the fast shock on the bottom boundary could be so strong that its interaction with the slow mode shock and the velocity vortices produces the second echo propagating downward and causing the secondary disturbance to the boundary surface. We suggest that this second echo, together with the slow shock and the velocity vortices, could constitute a possible candidate of the source for the EIT wave.展开更多
The continuous mediums are divided into two kinds according to their geometrical configurations,the first one is related to Euclidian manifolds and the other one to Riemannian manifolds/surfaces in the point of view o...The continuous mediums are divided into two kinds according to their geometrical configurations,the first one is related to Euclidian manifolds and the other one to Riemannian manifolds/surfaces in the point of view of the modern geometry.Two kinds of finite deformation theories with respect to Euclidian and Riemannian manifolds have been developed in the present paper.Both kinds of theories include the definitions of initial and current physical and parametric configurations,deformation gradient tensors with properties,deformation descriptions,transport theories and governing equations of nature conservation laws.The essential property of the theory with respect to Euclidian manifolds is that the curvilinear coordinates corresponding to the current physical configurations include time explicitly through which the geometrically irregular and time varying physical configurations can be mapped in the diffeomorphism manner to the regular and fixed domains in the parametric space.It is quite essential to the study of the relationships between geometries and mechanics.The theory with respect to Riemannian manifolds provides the systemic ideas and methods to study the deformations of continuous mediums whose geometrical configurations can be considered as general surfaces.The essential property of the theory with respect to Riemannian manifolds is that the thickness variation of a patch of continuous medium is represented by the surface density and its governing equation is rigorously deduced.As some applications,wakes of cylinders with deformable boundaries on the plane,incompressible wakes of a circular cylinder on fixed surfaces and axisymmetric finite deformations of an elastic membrane are numerically studied.展开更多
Mountains imply enormous environmental variation, with alpine habitats entailing harsh environ- ments, especially for ectotherms such as lizards. This environmental variability also may imply variation in prey availab...Mountains imply enormous environmental variation, with alpine habitats entailing harsh environ- ments, especially for ectotherms such as lizards. This environmental variability also may imply variation in prey availability. However, little is known about how lizard trophic ecology varies with elevation. In this study, we analyze diet, prey availability, prey selection, and trophic niche width in the lacertid lizard Psammodromus algirus along a 2,200-m elevational gradient in the Sierra Nevada （SE Spain）. The analysis of fecal samples has shown that Orthoptera, Formicidae, Hemiptera, Coleoptera, and Araneae are the main prey, although, according to their abundance in pitfall traps, Formicidae and Coleoptera are rejected by the lizard whereas Orthoptera, Hemiptera, and Araneae are preferred. Prey abundance and diversity increase with elevation and diet subtly varies along with the elevational gradient. The consumption of Coleoptera increases with elevation probably as a consequence of the lizard foraging more in open areas while basking. The electivity for Araneae increases with elevation. Araneae are rejected in the lowlands--where they are rela- tively abundant--whereas, at high elevation, this lizard positively selects them, despite they being less abundant. The lizard trophic niche width expands with elevation due to concomitant greater prey diversity and hence this lizard feeds on more prey types in highlands. Although no sex difference in diet has been found, the trophic niche is broader in females than males. As a whole, alpine lizards show a trophic niche simitar to that found at lower elevat（ons, suggesting that P. algirus is well adapted to the harsh environment found in alpine areas.展开更多
文摘Accurate detection and picking of the P-phase onset time in noisy microseismic data from underground mines remains a big challenge. Reliable P-phase onset time picking is necessary for accurate source location needed for planning and rescue operations in the event of failures. In this paper, a new technique based on the discrete stationary wavelet transform （DSWT）and higher order statist!cs, is proposed for processing noisy data from underground mines. The objectives of this method are to （1） Improve manual detection and tPicking of P-phase onset; and （ii） provide an automatic means of detecting and picking P-phase onset me accurately. The DSWT is first used to filter the signal over several scales. The manual P-phase onset detection and picking are then obtained by computing the signal energy across selected scales with frequency bands that capture the signal of interest. The automatic P-phase onset, on the other hand, is achieved by using skewness- and kurtosis-based criterion applied to selected scales in a time-frequency domain. The method was tested using synthetic and field data from an underground limestone mine. Results were compared with results obtained by using the short-term to long-term average （STA/LTA） ratio and that by Reference Ge et al. （2009）. The results show that the me!hod provides a more reliable estimate of the P-phase onset arrival than the STA]LTA method when the signal to noise ratio is very low. Also, the results obtained from the field data matched accurately with the results from Reference Ge et al. （2009）.
文摘Capital structure denotes enterprises＇ form and proportion relation of various long-term funds source. The capital structure is the combination problem of the long-term funds about enterprise development and it is the quantity and proportion between every fund form. This paper analyzes the various factors which affect capital structural decision-making, and introduces capital structural optimization theory of the shelter benefit of tax revenue and bankruptcy cost balance. It studies the method and the evaluation criterion of capital structural optimization. And it constructs capital structural optimization model of coexistence condition of company＇s income tax and individual income tax. This will be very helpful for the rationality of enterprise capital structure.
文摘The monthly changes in chlorophyll a, phytoplankton abundance and physicochemical parameters at two stations in Boka Kotorska Bay were investigated between 2003-2004. Nutrient salts varied widely, with maximum 3.65 μmol.L^-1 for nitrates and 0.23 μmol.L^-1 for phosphate. Chlorophyll a concentration ranged from 0.25 to 7.63 mg·m^3 and the highest value was measured in winter period of year. It seems that reason for this is the land-based nutrient input into the coastal area here. According to chlorophyll a, nitrates and phosphates concentrations, the area could be oligomesotrophic to mesotrophic during winter.
基金supported by the National Basic Research Program of China (Grant No. 2011CB811403)the National Natural Science Foundation of China (Grant No. 10873030)+3 种基金the Chinese Academy of Sciences (Grant No. 2009J2-34)the CMA (Grant No. GYHY201106011)NASA (Grant No. NNX11AB61G)the Smithsonian Institution Sprague Endowment Fund during FY10
文摘Despite extensive research on various global waves in solar eruptions, debate continues on the intrinsic nature of them. In this work, we performed numerical experiments of the coronal mass ejection with emphases on the associated large-scale MHD waves. A fast-mode shock forms in front of the flux rope during the eruption with a dimming region following it, and the development of a three-component structure of the ejecta is observed. At the flank of the flux rope, the slow-mode shock and the velocity vortices are also invoked. The dependence of the eruption energetics on the strength of the background field and the coronal plasma density distribution is apparent： the stronger the background field is, and/or the lower the coronal plasma density is, the more energetic the eruption is. In the lower Alfven speed environment, the slow mode shock and the large scale velocity vortices may be the source of the EIT wave. In the high Alfvdn speed environment, on the other hand, the echo due to the reflection of the fast shock on the bottom boundary could be so strong that its interaction with the slow mode shock and the velocity vortices produces the second echo propagating downward and causing the secondary disturbance to the boundary surface. We suggest that this second echo, together with the slow shock and the velocity vortices, could constitute a possible candidate of the source for the EIT wave.
基金supported by the National Nature Science Foundation of China (Grant Nos. 11172069 and 10872051)some key project of education reforms issued by the Shanghai Municipal Education Commission (2011)
文摘The continuous mediums are divided into two kinds according to their geometrical configurations,the first one is related to Euclidian manifolds and the other one to Riemannian manifolds/surfaces in the point of view of the modern geometry.Two kinds of finite deformation theories with respect to Euclidian and Riemannian manifolds have been developed in the present paper.Both kinds of theories include the definitions of initial and current physical and parametric configurations,deformation gradient tensors with properties,deformation descriptions,transport theories and governing equations of nature conservation laws.The essential property of the theory with respect to Euclidian manifolds is that the curvilinear coordinates corresponding to the current physical configurations include time explicitly through which the geometrically irregular and time varying physical configurations can be mapped in the diffeomorphism manner to the regular and fixed domains in the parametric space.It is quite essential to the study of the relationships between geometries and mechanics.The theory with respect to Riemannian manifolds provides the systemic ideas and methods to study the deformations of continuous mediums whose geometrical configurations can be considered as general surfaces.The essential property of the theory with respect to Riemannian manifolds is that the thickness variation of a patch of continuous medium is represented by the surface density and its governing equation is rigorously deduced.As some applications,wakes of cylinders with deformable boundaries on the plane,incompressible wakes of a circular cylinder on fixed surfaces and axisymmetric finite deformations of an elastic membrane are numerically studied.
文摘Mountains imply enormous environmental variation, with alpine habitats entailing harsh environ- ments, especially for ectotherms such as lizards. This environmental variability also may imply variation in prey availability. However, little is known about how lizard trophic ecology varies with elevation. In this study, we analyze diet, prey availability, prey selection, and trophic niche width in the lacertid lizard Psammodromus algirus along a 2,200-m elevational gradient in the Sierra Nevada （SE Spain）. The analysis of fecal samples has shown that Orthoptera, Formicidae, Hemiptera, Coleoptera, and Araneae are the main prey, although, according to their abundance in pitfall traps, Formicidae and Coleoptera are rejected by the lizard whereas Orthoptera, Hemiptera, and Araneae are preferred. Prey abundance and diversity increase with elevation and diet subtly varies along with the elevational gradient. The consumption of Coleoptera increases with elevation probably as a consequence of the lizard foraging more in open areas while basking. The electivity for Araneae increases with elevation. Araneae are rejected in the lowlands--where they are rela- tively abundant--whereas, at high elevation, this lizard positively selects them, despite they being less abundant. The lizard trophic niche width expands with elevation due to concomitant greater prey diversity and hence this lizard feeds on more prey types in highlands. Although no sex difference in diet has been found, the trophic niche is broader in females than males. As a whole, alpine lizards show a trophic niche simitar to that found at lower elevat（ons, suggesting that P. algirus is well adapted to the harsh environment found in alpine areas.
