Rattling vibration is an important noise source of gear-box. To controlthat noise, it is necessary to elaborate a mathematics-mechanical model on rattlinggears. In this paper, a rattling system modulated by noise was ...Rattling vibration is an important noise source of gear-box. To controlthat noise, it is necessary to elaborate a mathematics-mechanical model on rattlinggears. In this paper, a rattling system modulated by noise was investigated. Insteadof performing the very tedious numerical calculation, a discrete stochastic modeldescribed by three dimensional mean mapping was established by means of the NonGaussian closure technique. Through the example, the chaotic stochastic behaviormay be revealed. In comparison with deterministic model, the model developed inthis paper is more approximate to practice adn more available for acousticinvestigation, so that it is suggested to be applied to modeling on rattling vibration.展开更多
Grassland plays an important role in the global carbon cycle and climate regulation. However, there are still large uncertainties in grassland carbon pool and also its role in global carbon cycle due to the lack of me...Grassland plays an important role in the global carbon cycle and climate regulation. However, there are still large uncertainties in grassland carbon pool and also its role in global carbon cycle due to the lack of measured grassland biomass at regional scale or global scale with a unified survey method, particular for below-ground biomass. The present study, based on a total of 44 grassland sampling plots with 220 quadrats across Ningxia, investigated the characteristics of above-ground biomass （AGB）, below-ground biomass （BGB）, litter biomass （LB）, total biomass （TB） and root：shoot ratios （R：S） for six predominantly grassland types, and their relationships with climatic factors. AGB, BGB, LB and TB varied markedly across different grassland types, the median value ranging from 28.2-692.6 g m-2 for AGB, 130.4-2 036.6 g m-： for BGB, 9.2-82.3 g m2 for LB, and 168.0-2 681.3 g m-： for TB. R：S showed less variation with median values from 3.2 to 5.3 （excluding marshy meadow）. The different grassland types showed similar patterns of biomass allocation, with more than 70% BGB for all types. There is evidence of strong positive effects associated with mean annual precipitation （MAP） and negative effects associated with mean annual temperature （MAT） on AGB, BGB, and LB, although both factors have the opposite effect on R：S.展开更多
Studying the relationship between climate factors and soil organic carbon （SOC） is vitally important. However, how SOC responses to climate （temperature and precipitation） at cohesive extents is poorly studied. Tw...Studying the relationship between climate factors and soil organic carbon （SOC） is vitally important. However, how SOC responses to climate （temperature and precipitation） at cohesive extents is poorly studied. Two transects of approximately the same length （transect P and transect T） were selected to examine the variation of SOC content in relation to mean annual temperature （MAT） and mean annual precipitation （MAP）. The coefficients of partial correlation between SOC density and MAT （Rt） and MAP （Rp） were determined to quantify the relationships between SOC density and the two climate factors. The results indicated that for transect T, Rt was statistically significant once the extent level was greater than or equal to two fundamental extent units, while for transect P, Rp showed statistical significance only at extent levels which were greater than two fundamental extent traits. At the same extent levels but in different transects, Rts exhibited no zonal difference, but Rps did once the extent level was greater than two fundamental extent units. Therefore, to study the relationship between SOC density and different climate factors, different minimum extent levels should be ex- amined. The results of this paper could deepen the understanding of the impacts that SOC pool has on terrestrial ecosystem and global carbon cycling.展开更多
Quantitative assessment of the impact of groundwater depletion on phreatophytes in(hyper-)arid regions is key to sustainable groundwater management.However,a parsimonious model for predicting the response of phreatoph...Quantitative assessment of the impact of groundwater depletion on phreatophytes in(hyper-)arid regions is key to sustainable groundwater management.However,a parsimonious model for predicting the response of phreatophytes to a decrease of the water table is lacking.A variable saturated flow model,HYDRUS-1D,was used to numerically assess the influences of depth to the water table(DWT)and mean annual precipitation(MAP)on transpiration of groundwater-dependent vegetation in(hyper-)arid regions of northwest China.An exponential relationship is found for the normalized transpiration(a ratio of transpiration at a certain DWT to transpiration at 1 m depth,T_(a)^(*))with increasing DWT,while a positive linear relationship is identified between T_(a)^(*)and annual precipitation.Sensitivity analysis shows that the model is insensitive to parameters,such as saturated soil hydraulic conductivity and water stress parameters,indicated by an insignificant variation(less than 20%in most cases)under±50%changes of these parameters.Based on these two relationships,a universal model has been developed to predict the response of phreatophyte transpiration to groundwater drawdown for(hyper-)arid regions using MAP only.The estimated T_(a)^(*)from the model is reasonable by comparing with published measured values.展开更多
Synthetic aperture radar（SAR）image is severely affected by multiplicative speckle noise,which greatly complicates the edge detection.In this paper,by incorporating the discontinuityadaptive Markov random feld（DAMRF...Synthetic aperture radar（SAR）image is severely affected by multiplicative speckle noise,which greatly complicates the edge detection.In this paper,by incorporating the discontinuityadaptive Markov random feld（DAMRF）and maximum a posteriori（MAP）estimation criterion into edge detection,a Bayesian edge detector for SAR imagery is accordingly developed.In the proposed detector,the DAMRF is used as the a priori distribution of the local mean reflectivity,and a maximum a posteriori estimation of it is thus obtained by maximizing the posteriori energy using gradient-descent method.Four normalized ratios constructed in different directions are computed,based on which two edge strength maps（ESMs）are formed.The fnal edge detection result is achieved by fusing the results of two thresholded ESMs.The experimental results with synthetic and real SAR images show that the proposed detector could effciently detect edges in SAR images,and achieve better performance than two popular detectors in terms of Pratt＇s fgure of merit and visual evaluation in most cases.展开更多
For a Banach Space X Garcia-Falset introduced the coefficient R（X） and showed that if R（X） 〈 2 then X has a fixed point. In this paper, we define a mean non-expansive mapping T on X in the sense that ｜｜Tx - TY...For a Banach Space X Garcia-Falset introduced the coefficient R（X） and showed that if R（X） 〈 2 then X has a fixed point. In this paper, we define a mean non-expansive mapping T on X in the sense that ｜｜Tx - TY｜｜ ≤ a｜｜x - y｜｜ ＋ b｜｜x - Ty｜｜ for any x,y E X, where a,b ≥ 0, a ＋ b ≤ 1. We show that if R（X） 〈 1/1＋b then T has a fixed point in X.展开更多
Objective To test the following three hypotheses: ①plasma sodium concentration displays a 24-hour rhythm; ②the circadian rhythm of plasma sodium is disrupted in SHR fed a basal NaCl diet; ③high NaCl diet elevates ...Objective To test the following three hypotheses: ①plasma sodium concentration displays a 24-hour rhythm; ②the circadian rhythm of plasma sodium is disrupted in SHR fed a basal NaCl diet; ③high NaCl diet elevates plasma sodium concentration and may lead to an increase in mean arterial pressure (MAP) of SHR. Methods After having been instrumented with arterial catheter at 9 weeks of age, all rats (Spontaneously Hypertensive Rat, SHR; Wistar-Kyoto Rat, WKY) experienced two experimental protocols, the mean arterial pressure and heart rate were monitored and the blood samples also been analysed for sodium contents. Results On basal NaCl diet, plasma sodium concentrations in SHR were significantly higher than those of WKY at almost every time point measured and the plasma sodium concentration and MAP rhythms were in nearly opposite phases; on high NaCl diet, the MAP and plasma sodium rhythms were essentially opposite in WKY. In SHR, the plasma sodium rhythm was inversely related to the MAP rhythm. Conclusion Plasma sodium displays a significant circadian rhythm in rats. The high NaCl diet disrupts the normal plasma sodium circadian rhythm only in SHR.展开更多
Background Whether mean arterial pressure(MAP)and pulse pressure(PP),two indicators of cerebral perfusion,could guide the selection of anti-hypertensive strategies after acute ischaemic stroke remains uncertain.Our st...Background Whether mean arterial pressure(MAP)and pulse pressure(PP),two indicators of cerebral perfusion,could guide the selection of anti-hypertensive strategies after acute ischaemic stroke remains uncertain.Our study was to explore the impact of early anti-hypertensive intervention on adverse clinical outcomes following ischaemic stroke stratified by the levels of MAP and PP based on the China Antihypertensive Trial in Acute Ischemic Stroke(CATIS).Methods The trial randomised 4071 acute ischaemic stroke patients with elevated systolic blood pressure(SBP)to receive anti-hypertensive treatment(targeting a 10%-25%reduction in SBP during the 24 hours postrandomisation,reaching a BP level<140/90 mm Hg in 7 days,further keeping these levels throughout hospitalisation)or discontinue anti-hypertensive treatment during hospitalisation.The primary outcome was death or major disability at 14 days or hospital discharge.Study outcomes were analysed by comparing the BP-lowering intervention group and control group,stratified by tertiles of MAP or PP levels.Results No significant difference was observed in the primary outcome between the intervention and control groups across all MAP(p=0.69 for homogeneity)and PP(p=0.78 for homogeneity)categories.The corresponding odds ratios(95%CIs)were 1.08(0.85-1.36),0.92(0.74-1.15)and 1.00(0.81-1.25)for participants with low,intermediate,and high MAP and were 0.99(0.79-1.25),1.06(0.84-1.34)and 0.95(0.77-1.18)for participants in PP subgroups,respectively.Furthermore,early anti-hypertensive intervention was not associated with secondary outcomes(including neurological deterioration,recurrent stroke,vascular events and all-cause mortality)by MAP and PP(all p>0.05).Conclusions Early anti-hypertensive therapy neither decreased nor increased the odds of major disability,mortality,recurrent stroke or vascular events in patients with acute ischaemic stroke regardless of different MAP and PP levels.展开更多
We prove that a surjective map(on the positive cones of unital C^(*)-algebras)preserves the minimum spectrum values of harmonic means if and only if it has a Jordan *-isomorphism extension to the whole algebra.We repr...We prove that a surjective map(on the positive cones of unital C^(*)-algebras)preserves the minimum spectrum values of harmonic means if and only if it has a Jordan *-isomorphism extension to the whole algebra.We represent weighted geometric mean preserving bijective maps on the positive cones of prime C^(*)-algebras in terms of Jordan *-isomorphisms of the algebras.We also characterize order isomorphisms and orthoisomorphisms of the projection lattice of the von Neumann algebra of all bounded linear operators on a Hilbert space,answering an open question arisen by Dye.Finally,we give a description for Fuglede-Kadison determinant preserving maps on the positive cone of a finite von Neumann algebra and improve Gaal and Nayak’s work on this topic.展开更多
文摘Rattling vibration is an important noise source of gear-box. To controlthat noise, it is necessary to elaborate a mathematics-mechanical model on rattlinggears. In this paper, a rattling system modulated by noise was investigated. Insteadof performing the very tedious numerical calculation, a discrete stochastic modeldescribed by three dimensional mean mapping was established by means of the NonGaussian closure technique. Through the example, the chaotic stochastic behaviormay be revealed. In comparison with deterministic model, the model developed inthis paper is more approximate to practice adn more available for acousticinvestigation, so that it is suggested to be applied to modeling on rattling vibration.
基金supported by the Strategic-Leader Sci-Tech Projects of Chinese Academy of Sciences(XDA05050403)the Important Direction Project of Innovation of Chinese Academy of Sciences(CAS)(KSCX1-YW-12)
文摘Grassland plays an important role in the global carbon cycle and climate regulation. However, there are still large uncertainties in grassland carbon pool and also its role in global carbon cycle due to the lack of measured grassland biomass at regional scale or global scale with a unified survey method, particular for below-ground biomass. The present study, based on a total of 44 grassland sampling plots with 220 quadrats across Ningxia, investigated the characteristics of above-ground biomass （AGB）, below-ground biomass （BGB）, litter biomass （LB）, total biomass （TB） and root：shoot ratios （R：S） for six predominantly grassland types, and their relationships with climatic factors. AGB, BGB, LB and TB varied markedly across different grassland types, the median value ranging from 28.2-692.6 g m-2 for AGB, 130.4-2 036.6 g m-： for BGB, 9.2-82.3 g m2 for LB, and 168.0-2 681.3 g m-： for TB. R：S showed less variation with median values from 3.2 to 5.3 （excluding marshy meadow）. The different grassland types showed similar patterns of biomass allocation, with more than 70% BGB for all types. There is evidence of strong positive effects associated with mean annual precipitation （MAP） and negative effects associated with mean annual temperature （MAT） on AGB, BGB, and LB, although both factors have the opposite effect on R：S.
基金Under the auspices of Strategic Priority Research Program-Climate Change:Carbon Budget and Related Issues of Chinese Academy of Sciences(No.XDA05050503)National Key Technology Research and Development Program of China(No.2013BAD11B00)National Natural Science Foundation of China(No.41301242)
文摘Studying the relationship between climate factors and soil organic carbon （SOC） is vitally important. However, how SOC responses to climate （temperature and precipitation） at cohesive extents is poorly studied. Two transects of approximately the same length （transect P and transect T） were selected to examine the variation of SOC content in relation to mean annual temperature （MAT） and mean annual precipitation （MAP）. The coefficients of partial correlation between SOC density and MAT （Rt） and MAP （Rp） were determined to quantify the relationships between SOC density and the two climate factors. The results indicated that for transect T, Rt was statistically significant once the extent level was greater than or equal to two fundamental extent units, while for transect P, Rp showed statistical significance only at extent levels which were greater than two fundamental extent traits. At the same extent levels but in different transects, Rts exhibited no zonal difference, but Rps did once the extent level was greater than two fundamental extent units. Therefore, to study the relationship between SOC density and different climate factors, different minimum extent levels should be ex- amined. The results of this paper could deepen the understanding of the impacts that SOC pool has on terrestrial ecosystem and global carbon cycling.
基金This research was funded by projects of the China Geological Survey(12120113104100 and DD20190351)National Natural Science Foundation of China(41877199)Shaanxi Science and Technology Department(2019TD-040,2021ZDLSF05-01).
文摘Quantitative assessment of the impact of groundwater depletion on phreatophytes in(hyper-)arid regions is key to sustainable groundwater management.However,a parsimonious model for predicting the response of phreatophytes to a decrease of the water table is lacking.A variable saturated flow model,HYDRUS-1D,was used to numerically assess the influences of depth to the water table(DWT)and mean annual precipitation(MAP)on transpiration of groundwater-dependent vegetation in(hyper-)arid regions of northwest China.An exponential relationship is found for the normalized transpiration(a ratio of transpiration at a certain DWT to transpiration at 1 m depth,T_(a)^(*))with increasing DWT,while a positive linear relationship is identified between T_(a)^(*)and annual precipitation.Sensitivity analysis shows that the model is insensitive to parameters,such as saturated soil hydraulic conductivity and water stress parameters,indicated by an insignificant variation(less than 20%in most cases)under±50%changes of these parameters.Based on these two relationships,a universal model has been developed to predict the response of phreatophyte transpiration to groundwater drawdown for(hyper-)arid regions using MAP only.The estimated T_(a)^(*)from the model is reasonable by comparing with published measured values.
基金supported National Natural Science Foundation of China (No.61102167)
文摘Synthetic aperture radar（SAR）image is severely affected by multiplicative speckle noise,which greatly complicates the edge detection.In this paper,by incorporating the discontinuityadaptive Markov random feld（DAMRF）and maximum a posteriori（MAP）estimation criterion into edge detection,a Bayesian edge detector for SAR imagery is accordingly developed.In the proposed detector,the DAMRF is used as the a priori distribution of the local mean reflectivity,and a maximum a posteriori estimation of it is thus obtained by maximizing the posteriori energy using gradient-descent method.Four normalized ratios constructed in different directions are computed,based on which two edge strength maps（ESMs）are formed.The fnal edge detection result is achieved by fusing the results of two thresholded ESMs.The experimental results with synthetic and real SAR images show that the proposed detector could effciently detect edges in SAR images,and achieve better performance than two popular detectors in terms of Pratt＇s fgure of merit and visual evaluation in most cases.
基金the National Natural Science Foundation of China(No.10461006)the Natural Science Foundation of Shandong Province(Y002A10)the Younger Foundation of Yantai University(SX05Z9)
文摘For a Banach Space X Garcia-Falset introduced the coefficient R（X） and showed that if R（X） 〈 2 then X has a fixed point. In this paper, we define a mean non-expansive mapping T on X in the sense that ｜｜Tx - TY｜｜ ≤ a｜｜x - y｜｜ ＋ b｜｜x - Ty｜｜ for any x,y E X, where a,b ≥ 0, a ＋ b ≤ 1. We show that if R（X） 〈 1/1＋b then T has a fixed point in X.
文摘Objective To test the following three hypotheses: ①plasma sodium concentration displays a 24-hour rhythm; ②the circadian rhythm of plasma sodium is disrupted in SHR fed a basal NaCl diet; ③high NaCl diet elevates plasma sodium concentration and may lead to an increase in mean arterial pressure (MAP) of SHR. Methods After having been instrumented with arterial catheter at 9 weeks of age, all rats (Spontaneously Hypertensive Rat, SHR; Wistar-Kyoto Rat, WKY) experienced two experimental protocols, the mean arterial pressure and heart rate were monitored and the blood samples also been analysed for sodium contents. Results On basal NaCl diet, plasma sodium concentrations in SHR were significantly higher than those of WKY at almost every time point measured and the plasma sodium concentration and MAP rhythms were in nearly opposite phases; on high NaCl diet, the MAP and plasma sodium rhythms were essentially opposite in WKY. In SHR, the plasma sodium rhythm was inversely related to the MAP rhythm. Conclusion Plasma sodium displays a significant circadian rhythm in rats. The high NaCl diet disrupts the normal plasma sodium circadian rhythm only in SHR.
基金funded by a Project of the Priority Academic Program Development of Jiangsu Higher Education Institutions(Grant no-NA)Project of MOE Key Laboratory of Geriatric Diseases and Immunology(JYN202406)+1 种基金Interdisciplinary Basic Frontier Innovation Program of Suzhou Medical College of Soochow University(YXY2302013)National Natural Science Foundation of China(82273706 and 82220108001).
文摘Background Whether mean arterial pressure(MAP)and pulse pressure(PP),two indicators of cerebral perfusion,could guide the selection of anti-hypertensive strategies after acute ischaemic stroke remains uncertain.Our study was to explore the impact of early anti-hypertensive intervention on adverse clinical outcomes following ischaemic stroke stratified by the levels of MAP and PP based on the China Antihypertensive Trial in Acute Ischemic Stroke(CATIS).Methods The trial randomised 4071 acute ischaemic stroke patients with elevated systolic blood pressure(SBP)to receive anti-hypertensive treatment(targeting a 10%-25%reduction in SBP during the 24 hours postrandomisation,reaching a BP level<140/90 mm Hg in 7 days,further keeping these levels throughout hospitalisation)or discontinue anti-hypertensive treatment during hospitalisation.The primary outcome was death or major disability at 14 days or hospital discharge.Study outcomes were analysed by comparing the BP-lowering intervention group and control group,stratified by tertiles of MAP or PP levels.Results No significant difference was observed in the primary outcome between the intervention and control groups across all MAP(p=0.69 for homogeneity)and PP(p=0.78 for homogeneity)categories.The corresponding odds ratios(95%CIs)were 1.08(0.85-1.36),0.92(0.74-1.15)and 1.00(0.81-1.25)for participants with low,intermediate,and high MAP and were 0.99(0.79-1.25),1.06(0.84-1.34)and 0.95(0.77-1.18)for participants in PP subgroups,respectively.Furthermore,early anti-hypertensive intervention was not associated with secondary outcomes(including neurological deterioration,recurrent stroke,vascular events and all-cause mortality)by MAP and PP(all p>0.05).Conclusions Early anti-hypertensive therapy neither decreased nor increased the odds of major disability,mortality,recurrent stroke or vascular events in patients with acute ischaemic stroke regardless of different MAP and PP levels.
基金supported by Louisiana Christian University Carolyn and Adams Dawson Professorship Fund(2206251515302)the second named author was supported by the NSFC(Grant No.11101220)the Fundamental Research Funds for the Central Universities(Grant No.96172373)。
文摘We prove that a surjective map(on the positive cones of unital C^(*)-algebras)preserves the minimum spectrum values of harmonic means if and only if it has a Jordan *-isomorphism extension to the whole algebra.We represent weighted geometric mean preserving bijective maps on the positive cones of prime C^(*)-algebras in terms of Jordan *-isomorphisms of the algebras.We also characterize order isomorphisms and orthoisomorphisms of the projection lattice of the von Neumann algebra of all bounded linear operators on a Hilbert space,answering an open question arisen by Dye.Finally,we give a description for Fuglede-Kadison determinant preserving maps on the positive cone of a finite von Neumann algebra and improve Gaal and Nayak’s work on this topic.
