In this paper,we focus on the recovery of piecewise sparse signals containing both fast-decaying and slow-decaying nonzero entries.In order to improve the performance of classic Orthogonal Matching Pursuit(OMP)and Gen...In this paper,we focus on the recovery of piecewise sparse signals containing both fast-decaying and slow-decaying nonzero entries.In order to improve the performance of classic Orthogonal Matching Pursuit(OMP)and Generalized Orthogonal Matching Pursuit(GOMP)algorithms for solving this problem,we propose the Piecewise Generalized Orthogonal Matching Pursuit(PGOMP)algorithm,by considering the mixed-decaying sparse signals as piecewise sparse signals with two components containing nonzero entries with different decay factors.The algorithm incorporates piecewise selection and deletion to retain the most significant entries according to the sparsity of each component.We provide a theoretical analysis based on the mutual coherence of the measurement matrix and the decay factors of the nonzero entries,establishing a sufficient condition for the PGOMP algorithm to select at least two correct indices in each iteration.Numerical simulations and an image decomposition experiment demonstrate that the proposed algorithm significantly improves the support recovery probability by effectively matching piecewise sparsity with decay factors.展开更多
[Objectives] To investigate the species diversity of wood-decaying fungi in karst regions of southwest China. [Methods] The karst core regions of southwest China, specifically Guizhou, Guangxi, and Yunnan, were invest...[Objectives] To investigate the species diversity of wood-decaying fungi in karst regions of southwest China. [Methods] The karst core regions of southwest China, specifically Guizhou, Guangxi, and Yunnan, were investigated for the first time to analyze the species diversity characteristics of wood-decaying fungi in this area. This analysis was conducted through a comprehensive 5-year field investigation and systematic identification process. [Results] The wood-decaying fungi exhibited a distinctive species composition and distribution pattern within karst habitats, encompassing significant groups such as Polyporaceae and Hymenochaetaceae. Furthermore, these fungi demonstrated varying functional characteristics across the two ecological types of standing tree decay and wood decay. It was observed that wood-decaying fungi had a significant impact on the material cycle within karst ecosystems by degrading lignin and cellulose. Furthermore, the distribution of species diversity was closely associated with the characteristics of karst geomorphology and the types of vegetation. [Conclusions] This study not only addresses the lack of background data regarding wood-decaying fungi resources in karst regions, but also elucidates the maintenance mechanisms of fragile ecosystems from the perspective of decomposers. It provides a scientific foundation for biodiversity conservation, the prevention and control of forest diseases, and sustainable ecological management in karst regions.展开更多
The anomalous behavior of the western Pacific subtropical high （WPSH） in E1 Nifio developing summer is studied based on the composite results of eight major E1 Nifio events during 1979-2013. It is shown that the WPS...The anomalous behavior of the western Pacific subtropical high （WPSH） in E1 Nifio developing summer is studied based on the composite results of eight major E1 Nifio events during 1979-2013. It is shown that the WPSH tends to retreat eastwards with weak intensity during the developing summer. The anomaly exhibits an intraseasonal variation with a weaker anomaly in June and July and a stronger anomaly in August, indicating that different underlying physical mechanisms may be responsible for the anomalous WPSH during early and late summer periods. In June and July, owing to the cold advection anomaly characterized as a weak northerly anomaly from high latitudes, geopotential height in East Asia is reduced and the WPSH tends to retreat eastwards slightly. By contrast, enhanced convection over the warm pool in August makes the atmosphere more sensitive to E1 Nifio forcing. Consequently, a cyclonic anomaly in the western Pacific is induced, which is consistent with the seasonal march of atmospheric circulation from July to August. Accordingly, geopotential height in the western Pacific is reduced significantly, and the WPSH tends to retreat eastwards remarkably in August. Different from the developing summer, geopotential height in the decaying summer over East Asia and the western Pacific tends to enhance and extend northwards from June to August consistently, reaching the maximum anomaly in August. Therefore, the seasonal march plays an important role in the WPSH anomaly for both the developing and decaying summer.展开更多
This study investigated the relationship be- tween the asymmetry in the duration of El Nifio and La Nina and the length of their decaying phases. The results suggested that the duration asymmetry comes from the long d...This study investigated the relationship be- tween the asymmetry in the duration of El Nifio and La Nina and the length of their decaying phases. The results suggested that the duration asymmetry comes from the long decaying ENSO cases rather than the short decaying ones. The evolutions of short decaying El Nino and La Nina are approximately a mirror image with a rapid decline in the following summer for the warm and cold events. However, a robust asymmetry was found in long decaying cases, with a prolonged and re-intensified La Nina in the following winter. The asymmetry for long decaying cases starts from the westward extension of the zonal wind anomalies in a mature winter, and is further contributed to by the air-sea interaction over the tropical Pacific in the following seasons.展开更多
The performance of the Climate version of the Regional Eta-coordinate Model （CREM）, a regional climate model developed by State Key Laboratory of Numerical modeling for Atmospheric Science and Geophysical Fluid Dyna...The performance of the Climate version of the Regional Eta-coordinate Model （CREM）, a regional climate model developed by State Key Laboratory of Numerical modeling for Atmospheric Science and Geophysical Fluid Dynamics/Institute of Atmospheric Physics （LASG/IAP）, in simulating rainfall anomalies during the ENSO decaying summers from 1982 to 2002 was evalu- ated. The added value of rainfall simulation relative to reanalysis data and the sources of model bias were studied. Results showed that the model simulated rainfall anomalies moderately well. The model did well at capturing the above-normal rainfall along the Yangtze River valley （YRV） during E1 Nifio decaying summers and the below and above-normal rainfall centers along the YRV and the Huaihe River valley （HRV）, respectively, during La Nifia decaying summers. These features were not evident in rainfall products derived from the reanalysis, indicating that rainfall simulation did add value. The main limitations of the model were that the simulated rainfall anomalies along the YRV were far stronger and weaker in magnitude than the observations during E1 Nifio decaying summers and La Nifia decaying summers, respectively. The stronger magnitude above-normal rainfall during E1 Nifio decaying summers was due to a stronger northward transport of water vapor in the lower troposphere, mostly from moisture advection. An artificial, above-normal rainfall center was seen in the region north to 35°N, which was associated with stronger northward water vapor transport. Both lower tropospheric circulation bias and a wetter model atmosphere contributed to the bias caused by water vapor transport. There was a stronger southward water vapor transport from the southern boundary of the model during La Nifia decaying summers; less remaining water vapor caused anomalously weaker rainfall in the model as compared to observations.展开更多
The rigid-plastic assumption has greatly simplified the theoretical analysis of dynamic plastic response of structures.Within this framework,a common tool is the modal technique using approximate independent yield cri...The rigid-plastic assumption has greatly simplified the theoretical analysis of dynamic plastic response of structures.Within this framework,a common tool is the modal technique using approximate independent yield criteria,which leads to upper-and lower-bound solutions,but usually with poor accuracy.In this paper,by utilizing the membrane factor method(MFM),the large-deflection dynamic plastic response of square plates subjected to exponentially decaying pulse loading is analyzed by taking both the transient response phase and the exact yield criterion into account.Based on the combination of saturation analysis(SA)and MFM,the complete solutions and regressive formulae of saturated deflection and saturated impulse are obtained.As the dynamic behavior of plates under rectangular pulse loading serves as a benchmark of pulse-equivalent techniques,the large plastic deformation of square plates under short-duration rectangular pulse is also analyzed in detail.Moreover,by comparing the SA results of pulse-loaded square plates with different boundary conditions,it is found that the saturated deflection and saturated impulse of the fully clamped and simply supported square plates both increase linearly with the pulse amplitude,and the slopes are approximately the same,so the conversion between the SA quantities of plates with different boundary conditions can be easily achieved.展开更多
Direct numerical simulation of decaying homogeneous isotropic turbulence （DHIT） of a polymer solution is performed. In order to understand the polymer effect on turbulence or additive-turbulence interaction, we dire...Direct numerical simulation of decaying homogeneous isotropic turbulence （DHIT） of a polymer solution is performed. In order to understand the polymer effect on turbulence or additive-turbulence interaction, we directly investigate the influence of polymers on velocity gradient tensor including vorticity and strain. By visualizing vortex tubes and sheets, we observe a remarkable inhibition of vortex structures in an intermediate-scale field and a small-scale field but not for a large scale field in DHIT with polymers. The geometric study indicates a strong relevance among the vorticity vector, rate-of-strain tensor, and polymer conformation tensor. Joint probability density functions show that the polymer effect can increase ＂strain generation resistance＂ and ＂vorticity generation resistance＂, i.e., inhibit the generation of vortex sheets and tubes, ultimately leading to turbulence inhibition effects.展开更多
The performances of CMIP5 atmospheric general circulation models （AGCMs） in simulating the western North Pacific subtropical high （WNPSH） in El Nino decaying summers are examined in this study. Results show that m...The performances of CMIP5 atmospheric general circulation models （AGCMs） in simulating the western North Pacific subtropical high （WNPSH） in El Nino decaying summers are examined in this study. Results show that most models can reproduce the spatial pattern of both climatological and anomalous circulation associated with the WNPSH in El Nino decaying summers. Most CMIP5 AGCMs can capture the westward shift of the WNPSH in El Nino decaying summers compared with the climatological location. With respect to the sub-seasonal variation of the WNPSH, the performances of these AGCMs in reproducing the northward jump of the WNPSH are better than simulating the eastward retreat of the WNPSH from July to August. Twenty-one out of twenty-two （20 out of 22） models can reasonably reproduce the northward jump of the WNPSH in El Nino decaying summers （climatology）, while only 7 out of 22 （8 out of 22） AGCMs can reasonably reproduce the eastward retreat of the WNPSH in El Nino decaying summers （climatology）. In addition, there is a close connection between the climatological WNPSH location bias and that in El Nino decaying summers.展开更多
plane decaying leaves have been found capable of removing chromium and nickel ions from aqueous solutions. The removal efficiency depends upon the pH conditions, ions components and concentrations, and concentrations ...plane decaying leaves have been found capable of removing chromium and nickel ions from aqueous solutions. The removal efficiency depends upon the pH conditions, ions components and concentrations, and concentrations of leaves in media. The maximum removal for unique Cr6+ is about 7.5-8.0g/kg leaves at pH 4. 0, for unique Ni2+ about 2. 6g/kg at the region of PH5. 0-5.5. Under the described conditions nickel increases chromium uptake by plane decaying leaves from solution.展开更多
This paper is concerned with the minimizers of L^(2)-subcritical constraint variar tional problems with spatially decaying nonlinearities in a bounded domain Ω of R~N(N≥1).We prove that the problem admits minimizers...This paper is concerned with the minimizers of L^(2)-subcritical constraint variar tional problems with spatially decaying nonlinearities in a bounded domain Ω of R~N(N≥1).We prove that the problem admits minimizers for any M> 0.Moreover,the limiting behavior of minimizers as M→∞ is also analyzed rigorously.展开更多
In this paper,a one-dimension particle-in-cell(PIC)code(EDIPIC)is employed to simulate the parallel-plate ion extraction process under an externally applied electrostatic field,focusing on the analysis of the influe n...In this paper,a one-dimension particle-in-cell(PIC)code(EDIPIC)is employed to simulate the parallel-plate ion extraction process under an externally applied electrostatic field,focusing on the analysis of the influe nee of the initial electron temperature on the extracted ion fluxes to the metal plates during the ion extraction process.Compared with previously published results,the plasma oscillations on a timescale of the electron plasma period,and the excitation of the ion acoustic rarefaction waves resulting from the plasma oscillations originating from both the negative and positive electrodes,are studied for the first time.The modeling results show that both the negative and positive extractors can collect ions due to the plasma oscillations and the propagation of the ion acoustic rarefaction waves.With the in crease of the initial electron temperature achieved by keeping other parameters unchanged,on the one hand,both the ion speed and flux to the negative and positive plates increase,which leads to a significant decrease of the ion extraction time,while on the other hand,the ion flux to the positive plate after the formation of a Child-Langmuir sheath is much more sensitive to an increase of the initial electron temperature than that to the negative plate.The PIC simulation results provide a deeper physical understanding of the influence of the initial electron temperature on the characteristics of the entire ion extraction process in a decaying plasma.展开更多
The spatiotemporal evolutions of a one-dimensional collisionless decaying plasma bounded by two electrodes with an externally applied electrostatic field are studied by theoretical analyses and particle-in-cell(PIC)si...The spatiotemporal evolutions of a one-dimensional collisionless decaying plasma bounded by two electrodes with an externally applied electrostatic field are studied by theoretical analyses and particle-in-cell(PIC)simulations with the ion extraction process in a laser-induced plasma as the major research background.Based on the theoretical analyses,the transport process of the charged particles including electrons and ions can be divided into three stages:electron oscillation and ion matrix sheath extraction stage,sheath expansion and ion rarefaction wave propagation stage and the plasma collapse stage,and the corresponding criterion for each stage is also presented.Consequently,a complete analytical model is established for describing the ion extraction flux at each stage during the decaying of the laser-induced plasmas under an electrostatic field,which is also validated by the PIC modeling results.Based on this analytical model,influences of the key physical parameters,including the initial electron temperature and number density,plasma width and the externally applied electric voltage,on the ratio of the extracted ions are predicted.The calculated results show that a higher applied electric potential,smaller initial plasma number density and plasma width lead to a higher ratio of the extracted ions during the first stage;while in this stage,the initial electron temperature shows little effect on it.Meanwhile,more ions will be extracted before the plasma collapse once a higher electric potential is applied.The theoretical model presented in this paper is helpful not only for a deep understanding to the charged particle transport mechanisms for a bounded decaying plasma under an applied electrostatic field,but also for an optimization of the ion extraction process in practical applications.展开更多
A study on the potential response of exponentially decaying polarizing current of electrode was car- ried out.The appearance of critical point of the potential-time response of exponentially decaying current was ensur...A study on the potential response of exponentially decaying polarizing current of electrode was car- ried out.The appearance of critical point of the potential-time response of exponentially decaying current was ensured from theoretical analysis,and this is the theoretical foundation of the critical point method for the measurement of corrosion current of metals.The comparison of the corrosion currents measured by the critical point and static methods for the system of 321 stainless steel in 0.5N HCI+0.5N NaCI solution at static state shows that the results agree very well.Finally.the tran- sient corrosion currents of 321 stainless steel in 0.5N HCI+0.5N NaCl solution at different strain level are listed.展开更多
A direct numerical simulation is performed on 256~3 grids for decaying isotropic tur- bulence.The total kinematic energy,Taylor micro-scale,Taylor micro-scale Reynolds number and the velocity derivative skewness are c...A direct numerical simulation is performed on 256~3 grids for decaying isotropic tur- bulence.The total kinematic energy,Taylor micro-scale,Taylor micro-scale Reynolds number and the velocity derivative skewness are calculated.The snapshots of energy spectra and energy transfer spectra are plotted.These measurements verify the DIA predictions:decaying isotropic turbulence has the energy propagation and occupies the final decay periods.The skewness remains to some level with small variation even in the final decay period.展开更多
Decaying wood is a novel key factor required for biodiversity and function of a forest,as it provides a good account of substrate and habitats for various organisms.Herein,the bacterial diversity in decaying wood of B...Decaying wood is a novel key factor required for biodiversity and function of a forest,as it provides a good account of substrate and habitats for various organisms.Herein,the bacterial diversity in decaying wood of Betula platyphylla was discussed through high throughput sequencing.Our results showed that most of the obtained sequences belonged to the phyla Firmicutes,Proteobacteria,Bacteroidetes,Actinobacteria,Acidobacteria and Verrucomicrobia.Bacterial community compositions in samples with higher moisture content were obviously different than that with lower content,which could be reflected by richness estimators,diversity indices,and cluster and heatmap analysis.All three networks were non-random and possessed topological features of complex systems such as small-world and modularity features.However,these networks exhibited distinct topological features,indicating the potential ability of extensive cooperative and competitive interactions in the decayed wood microenvironments.Redundant analysis showed that most bacterial phyla were mainly distributed in highermoisture trunks.The obtained data will increase the knowledge of the complex bacterial diversity associated with dead wood,and lay a foundation for the bioconversion technology of plant cell walls using bacteria.展开更多
This paper attempts to analyze in detail the remote influence of the Indian Ocean Basin warming on the Northwest Pacific （NWP） during the year of decaying E1 Nifio. Observation data and the Fast Ocean- Atmosphere co...This paper attempts to analyze in detail the remote influence of the Indian Ocean Basin warming on the Northwest Pacific （NWP） during the year of decaying E1 Nifio. Observation data and the Fast Ocean- Atmosphere coupled Model 1.5 were used to investigate the triggering conditions under which the remote influence is formed between the positive sea surface temperature （SST） anomaly in the North Indian Ocean and the Anomalous Northwest Pacific anticyclone （ANWPA）. Our research show that it is only when there is a contributory background wind field over the Indian Ocean, i,e., when the Indian Summer Monsoon （ISM） reaches its peak, that the warmer SST anomaly in the North Indian Ocean incites significant easterly wind anomalies in the lower atmosphere of the Indo-West tropical Pacific. This then produces the remote influence on the ANWPA. Therefore, the SST anomaly in the North Indian Ocean might interfere with the prediction of the East Asia Summer Monsoon in the year of decaying E1 Nifio. Both the sustaining effect of local negative SST anomalies in the NWP, and the remote effect of positive SST anomalies in the North Indian Ocean on the ANWPA, should be considered in further research.展开更多
During the developing phase of central Pacific El Nio(CPEN), more frequent TC genesis over the northwest quadrant of the western North Pacific(WNP) is attributed to the horizontal shift of environmental vorticity fi...During the developing phase of central Pacific El Nio(CPEN), more frequent TC genesis over the northwest quadrant of the western North Pacific(WNP) is attributed to the horizontal shift of environmental vorticity field.Such a northwestward shift resembles the La Nia composite, even though factors that cause the shift differ(in the La Nia case the relative humidity effect is crucial). Greater reduction of TC frequency over WNP happened during the decaying phase of eastern Pacific El Nio(EPEN) than CPEN, due to the difference of the anomalous Philippine Sea anticyclone strength. The TC genesis exhibits an upward(downward) trend over the northern(southern) part of the WNP,which is linked to SST and associated circulation changes through local and remote effects.展开更多
Diagnostic analysis of the balance of kinetic energy (KE) is made for a decaying onland typoon, its external torrential rain area and environment. Results show that, besides low-level frictional dissipation as an ener...Diagnostic analysis of the balance of kinetic energy (KE) is made for a decaying onland typoon, its external torrential rain area and environment. Results show that, besides low-level frictional dissipation as an energy sink, upper-level horizontal export of KE is another important one for the typhoon. In its decaying KE grows in the external torrential rain area, and the KE production term Gk represents the chief energy source for the torrential rain. The growth of Gk is attributed to the development of the heavy rain and to the heating effect of released latent heat, and the external torrential rain owes its evolution to the exported KE from the strong windbelt in the east of the typhoon and the conversion of synoptic KE into mesoscale perturbation KE. The development of the torrential rain results in the KE feedback to its environment. The KE transfer from the typhoon to the external torrential rain area and then to the environmental region as a mechanism constitutes one of the causes for the rapid disintegration of the tempest.展开更多
Effects of addition of H2 gas in air DB discharge on its optical and electrical characteristics have been studied. Optical emission spectroscopy is used to investigate the effect of hydrogen admixing on the emission i...Effects of addition of H2 gas in air DB discharge on its optical and electrical characteristics have been studied. Optical emission spectroscopy is used to investigate the effect of hydrogen admixing on the emission intensity of the nitrogen second positive systems (300 - 420 nm) and the relative population density of states. An obvious decaying of the emission intensity of the nitrogen second positive bands with the introduction of H2 has been observed. It has been concluded that quenching of the nitrogen excited state is the responsible reason of this decaying. Mechanisms of excitation and ionization processes of nitrogen molecules in this mixture have been studied. Processes which are responsible for the decaying of the population density of have been reported. Addition of H2 to air improves the electrical characteristics of the DB discharge. An abrupt increasing in the electron density, reached about thirty fold at H2 flow rate of 3 L/min, as a result of increasing the ionization processes has been reported. The breakdown voltage of the discharge decreased from 1.87 kV to about 1.25 kV by the addition of H2 at flow rate of 3 L/min.展开更多
The effect of cyanobacterial bloom decay on water quality and the complete degradation of cyanobacterial blooms in a short period were examined by an enclosure experiment in Gonghu Bay of Lake Taihu,China.Water qualit...The effect of cyanobacterial bloom decay on water quality and the complete degradation of cyanobacterial blooms in a short period were examined by an enclosure experiment in Gonghu Bay of Lake Taihu,China.Water quality parameters as well as taste and odor compounds during the breakdown of cyanobacterial blooms were measured.Results showed that the decay of cyanobacterial blooms caused anoxic water conditions,decreased pH,and increased nutrient loading to the lake water.The highest concentrations of dimethyl sulfide （DMS）,dimethyl trisulfide （DMTS）,and β-cyclocitral were observed in the anoxic water,at 62331.8,12413.3,and 1374.9 ng/L,respectively.2-Methylisoborneol was dominant during the live growth phase of cyanobacterial blooms,whereas DMS and DMTS were dominant during the decomposition phase.Dissolved oxygen,pH,and chlorophyll a were negatively correlated with DMS,DMTS,and β-cyclocitral,whereas total phosphorus,total nitrogen,and ammonium （NH4＋-N） were positively correlated with DMS,DMTS,β-cyclocitral,and β-ionone.The experimental results suggested that preventing the anaerobic decomposition of cyanobacterial blooms is an important strategy against the recurrence of a malodor crisis in Lake Taihu.展开更多
基金Supported by the National Key R&D Program of China(Grant No.2023YFA1009200)the National Natural Science Foundation of China(Grant Nos.12271079+1 种基金12494552)the Fundamental Research Funds for the Central Universities of China(Grant No.DUT24LAB127)。
文摘In this paper,we focus on the recovery of piecewise sparse signals containing both fast-decaying and slow-decaying nonzero entries.In order to improve the performance of classic Orthogonal Matching Pursuit(OMP)and Generalized Orthogonal Matching Pursuit(GOMP)algorithms for solving this problem,we propose the Piecewise Generalized Orthogonal Matching Pursuit(PGOMP)algorithm,by considering the mixed-decaying sparse signals as piecewise sparse signals with two components containing nonzero entries with different decay factors.The algorithm incorporates piecewise selection and deletion to retain the most significant entries according to the sparsity of each component.We provide a theoretical analysis based on the mutual coherence of the measurement matrix and the decay factors of the nonzero entries,establishing a sufficient condition for the PGOMP algorithm to select at least two correct indices in each iteration.Numerical simulations and an image decomposition experiment demonstrate that the proposed algorithm significantly improves the support recovery probability by effectively matching piecewise sparsity with decay factors.
基金Supported by National Natural Science Foundation of China(31900271,32160086)Key Technology Research for Identification of Toxic Fungi in Guizhou Province(GKHZC[2020]1Y065)+1 种基金Guizhou Grassroots Science Popularization Action Plan Project([2025]04)Study on Carbon Storage and Carbon Sink Value of Forest Vegetation in State-owned Shatang Forest Farms in Guangxi(2021KY02).
文摘[Objectives] To investigate the species diversity of wood-decaying fungi in karst regions of southwest China. [Methods] The karst core regions of southwest China, specifically Guizhou, Guangxi, and Yunnan, were investigated for the first time to analyze the species diversity characteristics of wood-decaying fungi in this area. This analysis was conducted through a comprehensive 5-year field investigation and systematic identification process. [Results] The wood-decaying fungi exhibited a distinctive species composition and distribution pattern within karst habitats, encompassing significant groups such as Polyporaceae and Hymenochaetaceae. Furthermore, these fungi demonstrated varying functional characteristics across the two ecological types of standing tree decay and wood decay. It was observed that wood-decaying fungi had a significant impact on the material cycle within karst ecosystems by degrading lignin and cellulose. Furthermore, the distribution of species diversity was closely associated with the characteristics of karst geomorphology and the types of vegetation. [Conclusions] This study not only addresses the lack of background data regarding wood-decaying fungi resources in karst regions, but also elucidates the maintenance mechanisms of fragile ecosystems from the perspective of decomposers. It provides a scientific foundation for biodiversity conservation, the prevention and control of forest diseases, and sustainable ecological management in karst regions.
基金supported by the National Science Foundation of China (Grant Nos. 41475052 and 41630530)
文摘The anomalous behavior of the western Pacific subtropical high （WPSH） in E1 Nifio developing summer is studied based on the composite results of eight major E1 Nifio events during 1979-2013. It is shown that the WPSH tends to retreat eastwards with weak intensity during the developing summer. The anomaly exhibits an intraseasonal variation with a weaker anomaly in June and July and a stronger anomaly in August, indicating that different underlying physical mechanisms may be responsible for the anomalous WPSH during early and late summer periods. In June and July, owing to the cold advection anomaly characterized as a weak northerly anomaly from high latitudes, geopotential height in East Asia is reduced and the WPSH tends to retreat eastwards slightly. By contrast, enhanced convection over the warm pool in August makes the atmosphere more sensitive to E1 Nifio forcing. Consequently, a cyclonic anomaly in the western Pacific is induced, which is consistent with the seasonal march of atmospheric circulation from July to August. Accordingly, geopotential height in the western Pacific is reduced significantly, and the WPSH tends to retreat eastwards remarkably in August. Different from the developing summer, geopotential height in the decaying summer over East Asia and the western Pacific tends to enhance and extend northwards from June to August consistently, reaching the maximum anomaly in August. Therefore, the seasonal march plays an important role in the WPSH anomaly for both the developing and decaying summer.
基金supported by the National Natural Science Foundation of China (Grant No. 41105046)
文摘This study investigated the relationship be- tween the asymmetry in the duration of El Nifio and La Nina and the length of their decaying phases. The results suggested that the duration asymmetry comes from the long decaying ENSO cases rather than the short decaying ones. The evolutions of short decaying El Nino and La Nina are approximately a mirror image with a rapid decline in the following summer for the warm and cold events. However, a robust asymmetry was found in long decaying cases, with a prolonged and re-intensified La Nina in the following winter. The asymmetry for long decaying cases starts from the westward extension of the zonal wind anomalies in a mature winter, and is further contributed to by the air-sea interaction over the tropical Pacific in the following seasons.
基金supported by the China-UK-Swiss Adapting to Climate Change in China(ACCC)Project-Climate Sciencethe Chinese Academy of Science Project under Grant KZCX2-YW-Q11-04
文摘The performance of the Climate version of the Regional Eta-coordinate Model （CREM）, a regional climate model developed by State Key Laboratory of Numerical modeling for Atmospheric Science and Geophysical Fluid Dynamics/Institute of Atmospheric Physics （LASG/IAP）, in simulating rainfall anomalies during the ENSO decaying summers from 1982 to 2002 was evalu- ated. The added value of rainfall simulation relative to reanalysis data and the sources of model bias were studied. Results showed that the model simulated rainfall anomalies moderately well. The model did well at capturing the above-normal rainfall along the Yangtze River valley （YRV） during E1 Nifio decaying summers and the below and above-normal rainfall centers along the YRV and the Huaihe River valley （HRV）, respectively, during La Nifia decaying summers. These features were not evident in rainfall products derived from the reanalysis, indicating that rainfall simulation did add value. The main limitations of the model were that the simulated rainfall anomalies along the YRV were far stronger and weaker in magnitude than the observations during E1 Nifio decaying summers and La Nifia decaying summers, respectively. The stronger magnitude above-normal rainfall during E1 Nifio decaying summers was due to a stronger northward transport of water vapor in the lower troposphere, mostly from moisture advection. An artificial, above-normal rainfall center was seen in the region north to 35°N, which was associated with stronger northward water vapor transport. Both lower tropospheric circulation bias and a wetter model atmosphere contributed to the bias caused by water vapor transport. There was a stronger southward water vapor transport from the southern boundary of the model during La Nifia decaying summers; less remaining water vapor caused anomalously weaker rainfall in the model as compared to observations.
基金the support of the Wuhan University of Technology start-up fund for Distinguished Professors(No.471-40120163)the China Scholarship Council(CSC).
文摘The rigid-plastic assumption has greatly simplified the theoretical analysis of dynamic plastic response of structures.Within this framework,a common tool is the modal technique using approximate independent yield criteria,which leads to upper-and lower-bound solutions,but usually with poor accuracy.In this paper,by utilizing the membrane factor method(MFM),the large-deflection dynamic plastic response of square plates subjected to exponentially decaying pulse loading is analyzed by taking both the transient response phase and the exact yield criterion into account.Based on the combination of saturation analysis(SA)and MFM,the complete solutions and regressive formulae of saturated deflection and saturated impulse are obtained.As the dynamic behavior of plates under rectangular pulse loading serves as a benchmark of pulse-equivalent techniques,the large plastic deformation of square plates under short-duration rectangular pulse is also analyzed in detail.Moreover,by comparing the SA results of pulse-loaded square plates with different boundary conditions,it is found that the saturated deflection and saturated impulse of the fully clamped and simply supported square plates both increase linearly with the pulse amplitude,and the slopes are approximately the same,so the conversion between the SA quantities of plates with different boundary conditions can be easily achieved.
基金supported by the National Natural Science Foundation of China (Grant No. 10872060)the Fundamental Research Funds for the Central Universities (Grant No. HIT.BRET2.2010008)
文摘Direct numerical simulation of decaying homogeneous isotropic turbulence （DHIT） of a polymer solution is performed. In order to understand the polymer effect on turbulence or additive-turbulence interaction, we directly investigate the influence of polymers on velocity gradient tensor including vorticity and strain. By visualizing vortex tubes and sheets, we observe a remarkable inhibition of vortex structures in an intermediate-scale field and a small-scale field but not for a large scale field in DHIT with polymers. The geometric study indicates a strong relevance among the vorticity vector, rate-of-strain tensor, and polymer conformation tensor. Joint probability density functions show that the polymer effect can increase ＂strain generation resistance＂ and ＂vorticity generation resistance＂, i.e., inhibit the generation of vortex sheets and tubes, ultimately leading to turbulence inhibition effects.
基金supported by the National Natural Science Foundation of China[grant numbers 41475052,41405058]China Postdoctoral Science Foundation[grant number 2015M571095]Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDA11010403]
文摘The performances of CMIP5 atmospheric general circulation models （AGCMs） in simulating the western North Pacific subtropical high （WNPSH） in El Nino decaying summers are examined in this study. Results show that most models can reproduce the spatial pattern of both climatological and anomalous circulation associated with the WNPSH in El Nino decaying summers. Most CMIP5 AGCMs can capture the westward shift of the WNPSH in El Nino decaying summers compared with the climatological location. With respect to the sub-seasonal variation of the WNPSH, the performances of these AGCMs in reproducing the northward jump of the WNPSH are better than simulating the eastward retreat of the WNPSH from July to August. Twenty-one out of twenty-two （20 out of 22） models can reasonably reproduce the northward jump of the WNPSH in El Nino decaying summers （climatology）, while only 7 out of 22 （8 out of 22） AGCMs can reasonably reproduce the eastward retreat of the WNPSH in El Nino decaying summers （climatology）. In addition, there is a close connection between the climatological WNPSH location bias and that in El Nino decaying summers.
文摘plane decaying leaves have been found capable of removing chromium and nickel ions from aqueous solutions. The removal efficiency depends upon the pH conditions, ions components and concentrations, and concentrations of leaves in media. The maximum removal for unique Cr6+ is about 7.5-8.0g/kg leaves at pH 4. 0, for unique Ni2+ about 2. 6g/kg at the region of PH5. 0-5.5. Under the described conditions nickel increases chromium uptake by plane decaying leaves from solution.
基金supported by the Graduate Education Innovation Funds(2022CXZZ088)at Central China Normal University in Chinasupported by the NSFC(12225106,11931012)the Fundamental Research Funds(CCNU22LJ002)for the Central Universities in China。
文摘This paper is concerned with the minimizers of L^(2)-subcritical constraint variar tional problems with spatially decaying nonlinearities in a bounded domain Ω of R~N(N≥1).We prove that the problem admits minimizers for any M> 0.Moreover,the limiting behavior of minimizers as M→∞ is also analyzed rigorously.
文摘In this paper,a one-dimension particle-in-cell(PIC)code(EDIPIC)is employed to simulate the parallel-plate ion extraction process under an externally applied electrostatic field,focusing on the analysis of the influe nee of the initial electron temperature on the extracted ion fluxes to the metal plates during the ion extraction process.Compared with previously published results,the plasma oscillations on a timescale of the electron plasma period,and the excitation of the ion acoustic rarefaction waves resulting from the plasma oscillations originating from both the negative and positive electrodes,are studied for the first time.The modeling results show that both the negative and positive extractors can collect ions due to the plasma oscillations and the propagation of the ion acoustic rarefaction waves.With the in crease of the initial electron temperature achieved by keeping other parameters unchanged,on the one hand,both the ion speed and flux to the negative and positive plates increase,which leads to a significant decrease of the ion extraction time,while on the other hand,the ion flux to the positive plate after the formation of a Child-Langmuir sheath is much more sensitive to an increase of the initial electron temperature than that to the negative plate.The PIC simulation results provide a deeper physical understanding of the influence of the initial electron temperature on the characteristics of the entire ion extraction process in a decaying plasma.
基金the National Natural Science Foundation of China(Grant No.11775128)。
文摘The spatiotemporal evolutions of a one-dimensional collisionless decaying plasma bounded by two electrodes with an externally applied electrostatic field are studied by theoretical analyses and particle-in-cell(PIC)simulations with the ion extraction process in a laser-induced plasma as the major research background.Based on the theoretical analyses,the transport process of the charged particles including electrons and ions can be divided into three stages:electron oscillation and ion matrix sheath extraction stage,sheath expansion and ion rarefaction wave propagation stage and the plasma collapse stage,and the corresponding criterion for each stage is also presented.Consequently,a complete analytical model is established for describing the ion extraction flux at each stage during the decaying of the laser-induced plasmas under an electrostatic field,which is also validated by the PIC modeling results.Based on this analytical model,influences of the key physical parameters,including the initial electron temperature and number density,plasma width and the externally applied electric voltage,on the ratio of the extracted ions are predicted.The calculated results show that a higher applied electric potential,smaller initial plasma number density and plasma width lead to a higher ratio of the extracted ions during the first stage;while in this stage,the initial electron temperature shows little effect on it.Meanwhile,more ions will be extracted before the plasma collapse once a higher electric potential is applied.The theoretical model presented in this paper is helpful not only for a deep understanding to the charged particle transport mechanisms for a bounded decaying plasma under an applied electrostatic field,but also for an optimization of the ion extraction process in practical applications.
文摘A study on the potential response of exponentially decaying polarizing current of electrode was car- ried out.The appearance of critical point of the potential-time response of exponentially decaying current was ensured from theoretical analysis,and this is the theoretical foundation of the critical point method for the measurement of corrosion current of metals.The comparison of the corrosion currents measured by the critical point and static methods for the system of 321 stainless steel in 0.5N HCI+0.5N NaCI solution at static state shows that the results agree very well.Finally.the tran- sient corrosion currents of 321 stainless steel in 0.5N HCI+0.5N NaCl solution at different strain level are listed.
文摘A direct numerical simulation is performed on 256~3 grids for decaying isotropic tur- bulence.The total kinematic energy,Taylor micro-scale,Taylor micro-scale Reynolds number and the velocity derivative skewness are calculated.The snapshots of energy spectra and energy transfer spectra are plotted.These measurements verify the DIA predictions:decaying isotropic turbulence has the energy propagation and occupies the final decay periods.The skewness remains to some level with small variation even in the final decay period.
基金This project was supported by the State Key Laboratory of Tree Genetics and Breeding(Northeast Forestry University),the Fundamental Research Funds for the Central Universities(No.2572017AA23).
文摘Decaying wood is a novel key factor required for biodiversity and function of a forest,as it provides a good account of substrate and habitats for various organisms.Herein,the bacterial diversity in decaying wood of Betula platyphylla was discussed through high throughput sequencing.Our results showed that most of the obtained sequences belonged to the phyla Firmicutes,Proteobacteria,Bacteroidetes,Actinobacteria,Acidobacteria and Verrucomicrobia.Bacterial community compositions in samples with higher moisture content were obviously different than that with lower content,which could be reflected by richness estimators,diversity indices,and cluster and heatmap analysis.All three networks were non-random and possessed topological features of complex systems such as small-world and modularity features.However,these networks exhibited distinct topological features,indicating the potential ability of extensive cooperative and competitive interactions in the decayed wood microenvironments.Redundant analysis showed that most bacterial phyla were mainly distributed in highermoisture trunks.The obtained data will increase the knowledge of the complex bacterial diversity associated with dead wood,and lay a foundation for the bioconversion technology of plant cell walls using bacteria.
基金Supported by the National Basic Research Program of China(973 Program)(Nos.2010CB428504,2012CB956002)the National Natural Science Foundation of China(Nos.40906005,41105059,41065005,GYHY201106017,GYHY201306027)the National Key Technology Research and Development Program(No.2009BAC51B01)
文摘This paper attempts to analyze in detail the remote influence of the Indian Ocean Basin warming on the Northwest Pacific （NWP） during the year of decaying E1 Nifio. Observation data and the Fast Ocean- Atmosphere coupled Model 1.5 were used to investigate the triggering conditions under which the remote influence is formed between the positive sea surface temperature （SST） anomaly in the North Indian Ocean and the Anomalous Northwest Pacific anticyclone （ANWPA）. Our research show that it is only when there is a contributory background wind field over the Indian Ocean, i,e., when the Indian Summer Monsoon （ISM） reaches its peak, that the warmer SST anomaly in the North Indian Ocean incites significant easterly wind anomalies in the lower atmosphere of the Indo-West tropical Pacific. This then produces the remote influence on the ANWPA. Therefore, the SST anomaly in the North Indian Ocean might interfere with the prediction of the East Asia Summer Monsoon in the year of decaying E1 Nifio. Both the sustaining effect of local negative SST anomalies in the NWP, and the remote effect of positive SST anomalies in the North Indian Ocean on the ANWPA, should be considered in further research.
基金MOST 103-2111-M-845-001NSF grant AGS-1106536+1 种基金ONR grant N00014-0810256International Pacific Research Center
文摘During the developing phase of central Pacific El Nio(CPEN), more frequent TC genesis over the northwest quadrant of the western North Pacific(WNP) is attributed to the horizontal shift of environmental vorticity field.Such a northwestward shift resembles the La Nia composite, even though factors that cause the shift differ(in the La Nia case the relative humidity effect is crucial). Greater reduction of TC frequency over WNP happened during the decaying phase of eastern Pacific El Nio(EPEN) than CPEN, due to the difference of the anomalous Philippine Sea anticyclone strength. The TC genesis exhibits an upward(downward) trend over the northern(southern) part of the WNP,which is linked to SST and associated circulation changes through local and remote effects.
文摘Diagnostic analysis of the balance of kinetic energy (KE) is made for a decaying onland typoon, its external torrential rain area and environment. Results show that, besides low-level frictional dissipation as an energy sink, upper-level horizontal export of KE is another important one for the typhoon. In its decaying KE grows in the external torrential rain area, and the KE production term Gk represents the chief energy source for the torrential rain. The growth of Gk is attributed to the development of the heavy rain and to the heating effect of released latent heat, and the external torrential rain owes its evolution to the exported KE from the strong windbelt in the east of the typhoon and the conversion of synoptic KE into mesoscale perturbation KE. The development of the torrential rain results in the KE feedback to its environment. The KE transfer from the typhoon to the external torrential rain area and then to the environmental region as a mechanism constitutes one of the causes for the rapid disintegration of the tempest.
文摘Effects of addition of H2 gas in air DB discharge on its optical and electrical characteristics have been studied. Optical emission spectroscopy is used to investigate the effect of hydrogen admixing on the emission intensity of the nitrogen second positive systems (300 - 420 nm) and the relative population density of states. An obvious decaying of the emission intensity of the nitrogen second positive bands with the introduction of H2 has been observed. It has been concluded that quenching of the nitrogen excited state is the responsible reason of this decaying. Mechanisms of excitation and ionization processes of nitrogen molecules in this mixture have been studied. Processes which are responsible for the decaying of the population density of have been reported. Addition of H2 to air improves the electrical characteristics of the DB discharge. An abrupt increasing in the electron density, reached about thirty fold at H2 flow rate of 3 L/min, as a result of increasing the ionization processes has been reported. The breakdown voltage of the discharge decreased from 1.87 kV to about 1.25 kV by the addition of H2 at flow rate of 3 L/min.
基金supported by the National Water Pollution Control and Management Technology Major Project(No.2012ZX07101-010)the State Key Laboratory of Freshwater Ecology and Biotechnology(No.2011FBZ07)
文摘The effect of cyanobacterial bloom decay on water quality and the complete degradation of cyanobacterial blooms in a short period were examined by an enclosure experiment in Gonghu Bay of Lake Taihu,China.Water quality parameters as well as taste and odor compounds during the breakdown of cyanobacterial blooms were measured.Results showed that the decay of cyanobacterial blooms caused anoxic water conditions,decreased pH,and increased nutrient loading to the lake water.The highest concentrations of dimethyl sulfide （DMS）,dimethyl trisulfide （DMTS）,and β-cyclocitral were observed in the anoxic water,at 62331.8,12413.3,and 1374.9 ng/L,respectively.2-Methylisoborneol was dominant during the live growth phase of cyanobacterial blooms,whereas DMS and DMTS were dominant during the decomposition phase.Dissolved oxygen,pH,and chlorophyll a were negatively correlated with DMS,DMTS,and β-cyclocitral,whereas total phosphorus,total nitrogen,and ammonium （NH4＋-N） were positively correlated with DMS,DMTS,β-cyclocitral,and β-ionone.The experimental results suggested that preventing the anaerobic decomposition of cyanobacterial blooms is an important strategy against the recurrence of a malodor crisis in Lake Taihu.
