Parameter uncertainty is a primary source of uncertainty in ocean ecosystem simulations.The deep chlorophyll maximum(DCM)is a ubiquitous ecological phenomenon in the ocean.Using a theoretical nutrients-phytoplankton m...Parameter uncertainty is a primary source of uncertainty in ocean ecosystem simulations.The deep chlorophyll maximum(DCM)is a ubiquitous ecological phenomenon in the ocean.Using a theoretical nutrients-phytoplankton model and the conditional nonlinear optimal perturbation approach related to parameters,we investigated the eff ects of parameter uncertainties on DCM simulations.First,the sensitivity of single parameter was analyzed.The sensitivity ranking of 10 parameters was obtained by analyzing the top four specifi cally.The most sensitive parameter(background turbidity)aff ects the light supply for DCM formation,whereas the other three parameters(nutrient content of phytoplankton,nutrient recycling coeffi cient,and vertical turbulent diff usivity)control nutrient supply.To explore the interactions among diff erent parameters,the sensitivity of multiple parameters was further studied by examining combinations of four parameters.The results show that background turbidity is replaced by the phytoplankton loss rate in the optimal parameter combination.In addition,we found that interactions among these parameters are responsible for such diff erences.Finally,we found that reducing the uncertainties of sensitive parameters could improve DCM simulations remarkably.Compared with the sensitive parameters identifi ed in the single parameter analysis,reducing parameter uncertainties in the optimal combination produced better model performance.This study shows the importance of nonlinear interactions among various parameters in identifying sensitive parameters.In the future,the conditional nonlinear optimal perturbation approach related to parameters,especially optimal parameter combinations,is expected to greatly improve DCM simulations in complex ecosystem models.展开更多
We present an incorporation of the kinetic Monte Carlo(kMC)simulation with the adjacency matrix(AM)method to investigate structural parameters of randomly branched polymers.The AMs of branched polymers are obtained by...We present an incorporation of the kinetic Monte Carlo(kMC)simulation with the adjacency matrix(AM)method to investigate structural parameters of randomly branched polymers.The AMs of branched polymers are obtained by the growth generation model,which is employed in the kMC simulation based on Gillespie’s algorithm.Of particular interest is the effect of the branched units on the relevant structural parameters.As an application in randomly hyperbranched polymers formed by AB_(2)type of monomers,average maximum span length,average length of sub-chains,number distribution of branched units,and meansquare radius of gyration are calculated.It is shown that the branched units can give rise to a significant effect on these physical quantities,whereby such a structure-property relationship can be employed to optimize reaction conditions and implement material designs.展开更多
Maximum rate of food consumption (C max) was determined for juvenile Sebastodes fuscescens (Houttuyn) at water temperature of 10, 15, 20 and 25℃. The relationships of C max to the body weight (W) at each temperature ...Maximum rate of food consumption (C max) was determined for juvenile Sebastodes fuscescens (Houttuyn) at water temperature of 10, 15, 20 and 25℃. The relationships of C max to the body weight (W) at each temperature were described by a power equation: lnC max = a + b lnW. Covariance analysis revealed significant interaction of the temperature and body weight. The relationship of adjusted C max to water temperature (T) was described by a quadratic equation: C max =-0.369 + 0.456T - 0.0117T 2. The optimal feeding temperature calculated from this equation was 19.5℃. The coefficients of the multiple regression estimation relating C max to body weight (W) and water temperature (T) were given in the Table 2.展开更多
Routine reliability index method, first order second moment (FOSM), may not ensure convergence of iteration when the performance function is strongly nonlinear. A modified method was proposed to calculate reliability ...Routine reliability index method, first order second moment (FOSM), may not ensure convergence of iteration when the performance function is strongly nonlinear. A modified method was proposed to calculate reliability index based on maximum entropy (MaxEnt) principle. To achieve this goal, the complicated iteration of first order second moment (FOSM) method was replaced by the calculation of entropy density function. Local convergence of Newton iteration method utilized to calculate entropy density function was proved, which ensured the convergence of iteration when calculating reliability index. To promote calculation efficiency, Newton down-hill algorithm was incorporated into calculating entropy density function and Monte Carlo simulations (MCS) were performed to assess the efficiency of the presented method. Two numerical examples were presented to verify the validation of the presented method. Moreover, the execution and advantages of the presented method were explained. From Example 1, after seven times iteration, the proposed method is capable of calculating the reliability index when the performance function is strongly nonlinear and at the same time the proposed method can preserve the calculation accuracy; From Example 2, the reliability indices calculated using the proposed method, FOSM and MCS are 3.823 9, 3.813 0 and 3.827 6, respectively, and the according iteration times are 5, 36 and 10 6 , which shows that the presented method can improve calculation accuracy without increasing computational cost for the performance function of which the reliability index can be calculated using first order second moment (FOSM) method.展开更多
The westerly winds and East Asian summer monsoon play a leading role in climate change of southwestern North America and eastern Asia since the Last Glacial Maximum(LGM),respectively.Their convergence in arid and semi...The westerly winds and East Asian summer monsoon play a leading role in climate change of southwestern North America and eastern Asia since the Last Glacial Maximum(LGM),respectively.Their convergence in arid and semi-arid regions of the Asian continent(AAC)makes the regional climate change more complicated on the millennial-scale.There are still limitations in applying paleoclimate records and climate simulations of characteristic periods to investigate climate change patterns since the LGM in this region.In this study,we adopt two indexes indicating effective moisture and rely on a continuous simulation,a time slice simulation,and numerous paleoclimate records to comprehensively investigate the climate change modes and their driving mechanisms since the LGM in AAC.Results demonstrate a millennial-scale climate differentiation phenomenon and three climate change modes possibly occurring in AAC since the LGM.The western AAC largely controlled by the westerly winds is featured as wet climates during the LGM but relatively dry climates during the mid-Holocene(MH),coinciding with the climate change mode in southwestern North America.Conversely,dry conditions during the LGM and relatively wet conditions during the MH are reflected in eastern AAC governed by the East Asian summer monsoon,which leans to the climate change mode in eastern Asia.If climate change in central AAC is forced by the interaction of two circulations,it expresses wet conditions in both the LGM and MH,tending to a combination of the southwestern North American and eastern Asian modes.Precipitation and evaporation exert different intensities in influencing three climate modes of different periods.Furthermore,we identify the significant driving effects of greenhouse gases and ice sheets on westerly-dominated zones of AAC,while orbit-driven insolation on monsoon-dominated zones of AAC.展开更多
To investigate the effect of deep foundation pit excavation on the stability of retaining structure, a subway stationin the city of Jinan was selected as a project, and a FLAC3D-based three dimensional model was devel...To investigate the effect of deep foundation pit excavation on the stability of retaining structure, a subway stationin the city of Jinan was selected as a project, and a FLAC3D-based three dimensional model was developed fornumerical simulation. The horizontal displacement of the retaining structure, the axial force of the support, andthe vertical displacement of the column were studied and compared to the collected data from the field. The findingsindicate that when the foundation pit is excavated, the maximum deformation of the retaining structure progressivelydecreases from the top, the distortion of the retaining structure gradually rises, and the final maximumdeformation is around 17 meters deep. In each layer of support, the largest axial force support is located in thefirst reinforced concrete support;the uplift of the pit bottom caused by soil unloading plays a primary role in thevertical displacement of the column, and the column exhibits an upward trend under all construction conditions.When compared to the measured data, the generated findings are comparable and the fluctuation trend is extremelyconsistent. The findings of this article may give technical direction for the development of subway stationswith a comparable engineering basis.展开更多
Maximum Power Point Tracking (MPPT) is an important process in Photovoltaic (PV) systems because of the need to extract maximum power from PV panels used in these systems. Without the ability to track and have PV pane...Maximum Power Point Tracking (MPPT) is an important process in Photovoltaic (PV) systems because of the need to extract maximum power from PV panels used in these systems. Without the ability to track and have PV panels operate at its maximum power point (MPP) entails power losses;resulting in high cost since more panels will be required to provide specified energy needs. To achieve high efficiency and low cost, MPPT has therefore become an imperative in PV systems. In this study, an MPP tracker is modeled using the IC algorithm and its behavior under rapidly changing environmental conditions of temperature and irradiation levels is investigated. This algorithm, based on knowledge of the variation of the conductance of PV cells and the operating point with respect to the voltage and current of the panel calculates the slope of the power characteristics to determine the MPP as the peak of the curve. A simple circuit model of the DC-DC boost converter connected to a PV panel is used in the simulation;and the output of the boost converter is fed through a 3-phase inverter to an electricity grid. The model was simulated and tested using MATLAB/Simulink. Simulation results show the effectiveness of the IC algorithm for tracking the MPP in PV systems operating under rapidly changing temperatures and irradiations with a settling time of 2 seconds.展开更多
Complete prior statistical information is currently required in the majority of statistical evaluations of complex models. The principle of maximum entropy is often utilized in this context to fill in the missing piec...Complete prior statistical information is currently required in the majority of statistical evaluations of complex models. The principle of maximum entropy is often utilized in this context to fill in the missing pieces of available information and is normally claimed to be fair and objective. A rarely discussed aspect is that it relies upon testable information, which is never known but estimated, i.e. results from processing of raw data. The subjective choice of this processing strongly affects the result. Less conventional posterior completion of information is equally accurate but is computationally superior to prior, as much less information enters the analysis. Our recently proposed methods of lean deterministic sampling are examples of very few approaches that actively promote the use of minimal incomplete prior information. The inherited subjective character of maximum entropy distributions and the often critical implications of prior and posterior completion of information are here discussed and illustrated, from a novel perspective of consistency, rationality, computational efficiency and realism.展开更多
Recently,a Schwarz crystal structure with curved grain boundaries(GBs)constrained by twin-boundary(TB)networks was discovered in nanocrystalline Cu through experiments and atomistic simulations.Nanocrystalline Cu with...Recently,a Schwarz crystal structure with curved grain boundaries(GBs)constrained by twin-boundary(TB)networks was discovered in nanocrystalline Cu through experiments and atomistic simulations.Nanocrystalline Cu with nanosized Schwarz crystals exhibited high strength and excellent thermal stability.However,the grainsize effect and associated deformation mechanisms of Schwarz nanocrystals remain unknown.Here,we performed large-scale atomistic simulations to investigate the deformation behaviors and grain-size effect of nanocrystalline Cu with Schwarz crystals.Our simulations showed that similar to regular nanocrystals,Schwarz nanocrystals exhibit a strengthening-softening transition with decreasing grain size.The critical grain size in Schwarz nanocrystals is smaller than that in regular nanocrystals,leading to a maximum strength higher than that of regular nanocrystals.Our simulations revealed that the softening in Schwarz nanocrystals mainly originates from TB migration(or detwinning)and annihilation of GBs,rather than GB-mediated processes(including GB migration,sliding and diffusion)dominating the softening in regular nanocrystals.Quantitative analyses of simulation data further showed that compared with those in regular nanocrystals,the GB-mediated processes in Schwarz nanocrystals are suppressed,which is related to the low volume fraction of amorphous-like GBs and constraints of TB networks.The smaller critical grain size arises from the suppression of GB-mediated processes.展开更多
In this paper, the glitching activity and process variations in the maximum power dissipation estimation of CMOS circuits are introduced. Given a circuit and the gate library, a new Genetic Algorithm (GA)-based techni...In this paper, the glitching activity and process variations in the maximum power dissipation estimation of CMOS circuits are introduced. Given a circuit and the gate library, a new Genetic Algorithm (GA)-based technique is developed to determine the maximum power dissipation from a statistical point of view. The simulation on 1SCAS-89 benchmarks shows that the ratio of the maximum power dissipation with glitching activity over the maximum power under zero-delay model ranges from 1.18 to 4.02. Compared with the traditional Monte Carlo-based technique, the new approach presented in this paper is more effective.展开更多
Directing at evaluation for qualifying rate in weaponry test,this article discusses firstly how field test information is flooded with lots of prior information.Then a fast Bayesian evaluation algorithm is presented b...Directing at evaluation for qualifying rate in weaponry test,this article discusses firstly how field test information is flooded with lots of prior information.Then a fast Bayesian evaluation algorithm is presented based on the elaborate analysis of prior information reliability and the second category of maximum likelihood.The example demonstrates that the algorithm presented in this article is better and more robust compared with classical evaluation algorithm for safe-or-failure test and normal Bayesian method,which can make the best of prior information.展开更多
基金Supported by the Qingdao National Laboratory for Marine Science and Technology(No.2016OPR0107)the National Natural Science Foundation of China(No.41806013)。
文摘Parameter uncertainty is a primary source of uncertainty in ocean ecosystem simulations.The deep chlorophyll maximum(DCM)is a ubiquitous ecological phenomenon in the ocean.Using a theoretical nutrients-phytoplankton model and the conditional nonlinear optimal perturbation approach related to parameters,we investigated the eff ects of parameter uncertainties on DCM simulations.First,the sensitivity of single parameter was analyzed.The sensitivity ranking of 10 parameters was obtained by analyzing the top four specifi cally.The most sensitive parameter(background turbidity)aff ects the light supply for DCM formation,whereas the other three parameters(nutrient content of phytoplankton,nutrient recycling coeffi cient,and vertical turbulent diff usivity)control nutrient supply.To explore the interactions among diff erent parameters,the sensitivity of multiple parameters was further studied by examining combinations of four parameters.The results show that background turbidity is replaced by the phytoplankton loss rate in the optimal parameter combination.In addition,we found that interactions among these parameters are responsible for such diff erences.Finally,we found that reducing the uncertainties of sensitive parameters could improve DCM simulations remarkably.Compared with the sensitive parameters identifi ed in the single parameter analysis,reducing parameter uncertainties in the optimal combination produced better model performance.This study shows the importance of nonlinear interactions among various parameters in identifying sensitive parameters.In the future,the conditional nonlinear optimal perturbation approach related to parameters,especially optimal parameter combinations,is expected to greatly improve DCM simulations in complex ecosystem models.
基金supported by the National Natural Science Foundation of China[grant numbers 41931181 and 42075048]the Youth Innovation Promotion Association of the Chinese Academy of Sciences[grant number 2022075]。
基金supported by the Central Guidance on Local Science and Technology Development Fund of Hebei Province (No.236Z7601G)the Interdisciplinary Research Program of Natural Science of Hebei University, China (No.DXK202112)。
文摘We present an incorporation of the kinetic Monte Carlo(kMC)simulation with the adjacency matrix(AM)method to investigate structural parameters of randomly branched polymers.The AMs of branched polymers are obtained by the growth generation model,which is employed in the kMC simulation based on Gillespie’s algorithm.Of particular interest is the effect of the branched units on the relevant structural parameters.As an application in randomly hyperbranched polymers formed by AB_(2)type of monomers,average maximum span length,average length of sub-chains,number distribution of branched units,and meansquare radius of gyration are calculated.It is shown that the branched units can give rise to a significant effect on these physical quantities,whereby such a structure-property relationship can be employed to optimize reaction conditions and implement material designs.
文摘Maximum rate of food consumption (C max) was determined for juvenile Sebastodes fuscescens (Houttuyn) at water temperature of 10, 15, 20 and 25℃. The relationships of C max to the body weight (W) at each temperature were described by a power equation: lnC max = a + b lnW. Covariance analysis revealed significant interaction of the temperature and body weight. The relationship of adjusted C max to water temperature (T) was described by a quadratic equation: C max =-0.369 + 0.456T - 0.0117T 2. The optimal feeding temperature calculated from this equation was 19.5℃. The coefficients of the multiple regression estimation relating C max to body weight (W) and water temperature (T) were given in the Table 2.
基金Project(50978112) supported by the National Natural Science Foundation of China
文摘Routine reliability index method, first order second moment (FOSM), may not ensure convergence of iteration when the performance function is strongly nonlinear. A modified method was proposed to calculate reliability index based on maximum entropy (MaxEnt) principle. To achieve this goal, the complicated iteration of first order second moment (FOSM) method was replaced by the calculation of entropy density function. Local convergence of Newton iteration method utilized to calculate entropy density function was proved, which ensured the convergence of iteration when calculating reliability index. To promote calculation efficiency, Newton down-hill algorithm was incorporated into calculating entropy density function and Monte Carlo simulations (MCS) were performed to assess the efficiency of the presented method. Two numerical examples were presented to verify the validation of the presented method. Moreover, the execution and advantages of the presented method were explained. From Example 1, after seven times iteration, the proposed method is capable of calculating the reliability index when the performance function is strongly nonlinear and at the same time the proposed method can preserve the calculation accuracy; From Example 2, the reliability indices calculated using the proposed method, FOSM and MCS are 3.823 9, 3.813 0 and 3.827 6, respectively, and the according iteration times are 5, 36 and 10 6 , which shows that the presented method can improve calculation accuracy without increasing computational cost for the performance function of which the reliability index can be calculated using first order second moment (FOSM) method.
基金The National Natural Science Foundation of China,No.42077415,No.41822708The Second Tibetan Plateau Scientific Expedition and Research Program(STEP),No.2019QZKK0202+2 种基金The National Key Research and Development Program of China,No.2019YFC0507401The Strategic Priority Research Program of Chinese Academy of Sciences,No.XDA20100102The 111 Project,No.BP0618001。
文摘The westerly winds and East Asian summer monsoon play a leading role in climate change of southwestern North America and eastern Asia since the Last Glacial Maximum(LGM),respectively.Their convergence in arid and semi-arid regions of the Asian continent(AAC)makes the regional climate change more complicated on the millennial-scale.There are still limitations in applying paleoclimate records and climate simulations of characteristic periods to investigate climate change patterns since the LGM in this region.In this study,we adopt two indexes indicating effective moisture and rely on a continuous simulation,a time slice simulation,and numerous paleoclimate records to comprehensively investigate the climate change modes and their driving mechanisms since the LGM in AAC.Results demonstrate a millennial-scale climate differentiation phenomenon and three climate change modes possibly occurring in AAC since the LGM.The western AAC largely controlled by the westerly winds is featured as wet climates during the LGM but relatively dry climates during the mid-Holocene(MH),coinciding with the climate change mode in southwestern North America.Conversely,dry conditions during the LGM and relatively wet conditions during the MH are reflected in eastern AAC governed by the East Asian summer monsoon,which leans to the climate change mode in eastern Asia.If climate change in central AAC is forced by the interaction of two circulations,it expresses wet conditions in both the LGM and MH,tending to a combination of the southwestern North American and eastern Asian modes.Precipitation and evaporation exert different intensities in influencing three climate modes of different periods.Furthermore,we identify the significant driving effects of greenhouse gases and ice sheets on westerly-dominated zones of AAC,while orbit-driven insolation on monsoon-dominated zones of AAC.
基金supported by the National Natural Science Foundation of China(51774199).
文摘To investigate the effect of deep foundation pit excavation on the stability of retaining structure, a subway stationin the city of Jinan was selected as a project, and a FLAC3D-based three dimensional model was developed fornumerical simulation. The horizontal displacement of the retaining structure, the axial force of the support, andthe vertical displacement of the column were studied and compared to the collected data from the field. The findingsindicate that when the foundation pit is excavated, the maximum deformation of the retaining structure progressivelydecreases from the top, the distortion of the retaining structure gradually rises, and the final maximumdeformation is around 17 meters deep. In each layer of support, the largest axial force support is located in thefirst reinforced concrete support;the uplift of the pit bottom caused by soil unloading plays a primary role in thevertical displacement of the column, and the column exhibits an upward trend under all construction conditions.When compared to the measured data, the generated findings are comparable and the fluctuation trend is extremelyconsistent. The findings of this article may give technical direction for the development of subway stationswith a comparable engineering basis.
文摘Maximum Power Point Tracking (MPPT) is an important process in Photovoltaic (PV) systems because of the need to extract maximum power from PV panels used in these systems. Without the ability to track and have PV panels operate at its maximum power point (MPP) entails power losses;resulting in high cost since more panels will be required to provide specified energy needs. To achieve high efficiency and low cost, MPPT has therefore become an imperative in PV systems. In this study, an MPP tracker is modeled using the IC algorithm and its behavior under rapidly changing environmental conditions of temperature and irradiation levels is investigated. This algorithm, based on knowledge of the variation of the conductance of PV cells and the operating point with respect to the voltage and current of the panel calculates the slope of the power characteristics to determine the MPP as the peak of the curve. A simple circuit model of the DC-DC boost converter connected to a PV panel is used in the simulation;and the output of the boost converter is fed through a 3-phase inverter to an electricity grid. The model was simulated and tested using MATLAB/Simulink. Simulation results show the effectiveness of the IC algorithm for tracking the MPP in PV systems operating under rapidly changing temperatures and irradiations with a settling time of 2 seconds.
文摘Complete prior statistical information is currently required in the majority of statistical evaluations of complex models. The principle of maximum entropy is often utilized in this context to fill in the missing pieces of available information and is normally claimed to be fair and objective. A rarely discussed aspect is that it relies upon testable information, which is never known but estimated, i.e. results from processing of raw data. The subjective choice of this processing strongly affects the result. Less conventional posterior completion of information is equally accurate but is computationally superior to prior, as much less information enters the analysis. Our recently proposed methods of lean deterministic sampling are examples of very few approaches that actively promote the use of minimal incomplete prior information. The inherited subjective character of maximum entropy distributions and the often critical implications of prior and posterior completion of information are here discussed and illustrated, from a novel perspective of consistency, rationality, computational efficiency and realism.
基金the financial support from National Natural Science Foundation of China (Grants Nos.12325203,91963117,and 11921002)。
文摘Recently,a Schwarz crystal structure with curved grain boundaries(GBs)constrained by twin-boundary(TB)networks was discovered in nanocrystalline Cu through experiments and atomistic simulations.Nanocrystalline Cu with nanosized Schwarz crystals exhibited high strength and excellent thermal stability.However,the grainsize effect and associated deformation mechanisms of Schwarz nanocrystals remain unknown.Here,we performed large-scale atomistic simulations to investigate the deformation behaviors and grain-size effect of nanocrystalline Cu with Schwarz crystals.Our simulations showed that similar to regular nanocrystals,Schwarz nanocrystals exhibit a strengthening-softening transition with decreasing grain size.The critical grain size in Schwarz nanocrystals is smaller than that in regular nanocrystals,leading to a maximum strength higher than that of regular nanocrystals.Our simulations revealed that the softening in Schwarz nanocrystals mainly originates from TB migration(or detwinning)and annihilation of GBs,rather than GB-mediated processes(including GB migration,sliding and diffusion)dominating the softening in regular nanocrystals.Quantitative analyses of simulation data further showed that compared with those in regular nanocrystals,the GB-mediated processes in Schwarz nanocrystals are suppressed,which is related to the low volume fraction of amorphous-like GBs and constraints of TB networks.The smaller critical grain size arises from the suppression of GB-mediated processes.
基金Supported by NSF of the United States under contract 5978 East Asia and Pacific Program 9602485
文摘In this paper, the glitching activity and process variations in the maximum power dissipation estimation of CMOS circuits are introduced. Given a circuit and the gate library, a new Genetic Algorithm (GA)-based technique is developed to determine the maximum power dissipation from a statistical point of view. The simulation on 1SCAS-89 benchmarks shows that the ratio of the maximum power dissipation with glitching activity over the maximum power under zero-delay model ranges from 1.18 to 4.02. Compared with the traditional Monte Carlo-based technique, the new approach presented in this paper is more effective.
基金the National Defense Research Foundation of China(No.4010203010401)
文摘Directing at evaluation for qualifying rate in weaponry test,this article discusses firstly how field test information is flooded with lots of prior information.Then a fast Bayesian evaluation algorithm is presented based on the elaborate analysis of prior information reliability and the second category of maximum likelihood.The example demonstrates that the algorithm presented in this article is better and more robust compared with classical evaluation algorithm for safe-or-failure test and normal Bayesian method,which can make the best of prior information.
