Vulnerability assessment is a systematic process to identify security gaps in the design and evaluation of physical protection systems.Adversarial path planning is a widely used method for identifying potential vulner...Vulnerability assessment is a systematic process to identify security gaps in the design and evaluation of physical protection systems.Adversarial path planning is a widely used method for identifying potential vulnerabilities and threats to the security and resilience of critical infrastructures.However,achieving efficient path optimization in complex large-scale three-dimensional(3D)scenes remains a significant challenge for vulnerability assessment.This paper introduces a novel A^(*)-algorithmic framework for 3D security modeling and vulnerability assessment.Within this framework,the 3D facility models were first developed in 3ds Max and then incorporated into Unity for A^(*)heuristic pathfinding.The A^(*)-heuristic pathfinding algorithm was implemented with a geometric probability model to refine the detection and distance fields and achieve a rational approximation of the cost to reach the goal.An admissible heuristic is ensured by incorporating the minimum probability of detection(P_(D)^(min))and diagonal distance to estimate the heuristic function.The 3D A^(*)heuristic search was demonstrated using a hypothetical laboratory facility,where a comparison was also carried out between the A^(*)and Dijkstra algorithms for optimal path identification.Comparative results indicate that the proposed A^(*)-heuristic algorithm effectively identifies the most vulnerable adversarial pathfinding with high efficiency.Finally,the paper discusses hidden phenomena and open issues in efficient 3D pathfinding for security applications.展开更多
AIGaN/GaN HEMTs are investigated by numerical simulation from the self-consistent solution of Schr6dinger-Poisson-hydrodynamic （HD） systems. The influences of polarization charge and quantum effects are considered i...AIGaN/GaN HEMTs are investigated by numerical simulation from the self-consistent solution of Schr6dinger-Poisson-hydrodynamic （HD） systems. The influences of polarization charge and quantum effects are considered in this model. Then the two-dimensional conduction band and electron distribution, electron temperature characteristics, Id versus Vd and Id versus Vg, transfer characteristics and transconductance curves are obtained. Corresponding analysis and discussion based on the simulation results are subsequently given.展开更多
The epidermal growth factor receptor（EGFR）—tyrosine kinase inhibitors（TKIs） monotherapies have limited efficacy in the treatment of EGFR mutation-negative non-small cell lung cancers（NSCLCs）. In the present stu...The epidermal growth factor receptor（EGFR）—tyrosine kinase inhibitors（TKIs） monotherapies have limited efficacy in the treatment of EGFR mutation-negative non-small cell lung cancers（NSCLCs）. In the present study, we aimed to investigate the combined effect of erlotinib（ER） and cabozantinib（CAB） on NSCLC cell lines harboring wild-type EGFR and to optimize the dosage regimens using pharmacodynamic（PD） modeling and simulation. Therefore, we examined the combined effect of ER and CAB on cell viability, cloning, apoptosis induction, migration and growth dynamics in H1299 and A549 cells. PD modeling and simulation were also performed to quantitatively describe the H1299 cells growth dynamics and to optimize the dosage regimens as well. Our results showed that CAB effectively enhanced the sensitivity of both cell lines to ER. The PD models fitted the data well, and some important parameters were obtained. The exponential（λ_0） and linear（λ_1） growth rates of H1299 cells were 0.0241 h^（–1） and 360 cells？h^（–1）, respectively. The Emax of ER and CAB was 0.0091 h^（–1） and 0.0085 h^（–1）, and the EC50 was 0.812 μM and 1.16 μM, respectively. The synergistic effect observed in the experiments was further confirmed by the estimated combination index φ（1.37）,（95% confidence interval： 1.24–1.50）, obtained from PD modeling. Furthermore, the dosage regimens were optimized using simulations. In summary, both the experimental and modeling results demonstrated the synergistic interaction between ER and CAB in NSCLCs without EGFR mutations. Sequential combinations of ER and CAB provided an option for the therapy of the NSCLCs with wild-type EGFR, which would provide some references for preclinical study and translational research as well.展开更多
A deep understanding of crop-water eco-physiological relations is the basis for quantifying plant physiological responses to soil water stress. Pot experiments were conducted to investigate the winter wheat crop-water...A deep understanding of crop-water eco-physiological relations is the basis for quantifying plant physiological responses to soil water stress. Pot experiments were conducted to investigate the winter wheat crop-water relations under both drought and waterlogging conditions in two sequential growing seasons from 2000 to 2002, and then the data were used to develop and validate models simulating the responses of winter wheat growth to drought and waterlogging stress. The experiment consisted of four treatments, waterlogging (keep 1 to 2 cm water layer depth above soil surface), control (70%-80% field capacity), light drought (40%-50% field capacity) and severe drought (30%-40% field capacity) with six replicates at five stages in the 2000-2001 growth season. Three soil water content treatments (waterlogging, control and drought) with two replicates were designed in the 2001-2002 growth season. Waterlogging and control treatments are the same as in the 2000-2001 growth season. For the drought treatment, no water was supplied and the soil moisture decreased from field capacity to wilting point. Leaf net photosynthetic rate, transpiration rate, predawn leaf water potential, soil water potential, soil water content and dry matter weight of individual organs were measured. Based on crop-water eco-physiological relations, drought and waterlogging stress factors for winter wheat growth simulation model were put forward. Drought stress factors integrated soil water availability, the sensitivity of different development stages and the difference between physiological processes (such as photosynthesis, transpiration and partitioning). The quantification of waterlogging stress factor considered different crop species, soil water status, waterlogging days and sensitivity at different growth stages. Data sets from the pot experiments revealed favorable performance reliability for the simulation sub-models with the drought and waterlogging stress factors.展开更多
Six paddy soils of Shanghai, China, were studied after 120 days of anaerobicincubation at 25 deg C and 35 deg C. Four models, the effective accumulated temperature model, theone-component first-order exponential model...Six paddy soils of Shanghai, China, were studied after 120 days of anaerobicincubation at 25 deg C and 35 deg C. Four models, the effective accumulated temperature model, theone-component first-order exponential model (the one-pool model), the two-component first-orderexponential model (the two-pool model), and the two-component first-order plus zero-orderexponential model including a constant term (the special model), were fitted to the data of observedmineral-N during incubation using non-linear regression procedures. The two-pool model and thespecial model gave the best fits amongst the four models, and parameters in the special model weremore reasonable than those in the other three. Results showed that the special model gave a betterprediction of nitrogen mineralization under flooded conditions than the other three models.展开更多
Ultra-wideband(UWB)technology is a prospective technology for high-rate transmission and accurate localization in the future communication systems.State-of-art channel modeling approaches usually divide the UWB channe...Ultra-wideband(UWB)technology is a prospective technology for high-rate transmission and accurate localization in the future communication systems.State-of-art channel modeling approaches usually divide the UWB channel into several sub-band channels and model them independently.By considering frequency-dependent channel parameters,a novel analytical UWB channel model with continuous frequency response is proposed.The composite effect of all frequency components within the UWB channel on the channel impulse response(CIR)of delay domain is derived based on the continuous channel transfer function(CTF)of frequency domain.On this basis,a closed-form simulation model for UWB channels and geometry-based parameter calculation method are developed,which can guarantee the continuity of channel characteristics on the frequency domain and greatly reduce the simulation complexity.Finally,the proposed method is applied to generate UWB channel with 2 GHz bandwidth at sub-6GHz and millimeter wave(mmWave)bands,respectively.The channel measurements are also carried out to validate the proposed method.The simulated CIR and power gain are shown to be in good agreement with the measurement data.Moreover,the comparison results of power gain and Doppler power spectral density(DPSD)show that the proposed UWB channel model Received:Apr.23,2022 Revised:Jun.09,2022 Editor:Wei Fan achieves a good balance between the simulation accuracy and efficiency.展开更多
Assuming that decomposition of organic matter in soils follows the first-order kinetics reaction, a computer model was developed to simulate soil organic matter dynamics. Organic matter in soils is divided up into two...Assuming that decomposition of organic matter in soils follows the first-order kinetics reaction, a computer model was developed to simulate soil organic matter dynamics. Organic matter in soils is divided up into two parts that include incorporated organic carbon from crop residues or other organic fertilizer and soil intrinsic carbon. The incorporated organic carbon was assumed to consist of two components, labile-C and resistant-C. The model was represented by a differential equation of dCt/dt = Kt × fr × fw × fs × ct (i = 1, r,S) and an integral equation of Cit = Cio × EXP(Ki × fT × fw × fs × t). Effect of soil parameters of temperature, moisture and texture on the decomposition was functioned by the fT, fw and fs, respectively. Data from laboratory incubation experiments were used to determine the first-order decay rate K, and the fraction of labile-C of crop residues by employing a nonlinear method. The values of K for the components of labile-C and resistant-C and the soil intrinsic carbon were evaluated to be 0.025,0.080 X 10-2 and 0.065 X 10-3d-1, respectively. The labile-C fraction of wheat straw, wheat roots, rice straw and rice roots were 0.50, 0.25, 0.40 and 0.20, respectively. These values are related to the initial residue carbon-to-nitrogen ratio (C/N) and lignin content.展开更多
Crop performance is determined by the combined effects of the genotype of the crop and the environmental conditions of the production system. This study was undertaken to develop a dynamic model for simulating environ...Crop performance is determined by the combined effects of the genotype of the crop and the environmental conditions of the production system. This study was undertaken to develop a dynamic model for simulating environmental （temperature and solar radiation） and N supply effects on fiber fineness, maturity and micronaire. Three different experiments involving genotypes, sowing dates, and N fertilization rates were conducted to support model development and model evaluation. The growth and development duration of fiber fineness, maturity, and micronaire were scaled by using physiological development time of secondary wall synthesis （PDT SWSP ）, which was determined based on the constant ratio of SWSP/ BMP. PTP （product of relative thermal effectiveness （RTE） and photosynthetically active radiation （PAR）, MJ m-2） and subtending leaf N content per unit area （N A , g m-2） and critical subtending leaf N content per unit area （CN A , g m-2） of cotton boll were calculated or simulated to evaluate effects of temperature and radiation, and N supply. Besides, the interactions among temperature, radiation and N supply were also explained by piecewise function. The overall performance of the model was calibrated and validated with independent data sets from three field experiments with two sowing dates, three or five flowering dates and three or four N fertilization rates for three subsequent years （2005, 2007, and 2009） at three ecological locations. The average RMSE and RE for fiber fineness, maturity, and micronaire predictions were 372 m g-1 and 5.0%, 0.11 m g-1 and 11.4%, 0.3 m g-1 and 12.3%, respectively, indicating a good fit between the simulated and observed data. It appears that the model can give a reliable prediction for fiber fineness, maturity and micronaire formation under various growing conditions.展开更多
A simulation model for phasic and phenological development of rice was developed using the scale of physiological development time, based on the ecophysiological development processes. The interaction of daily thermal...A simulation model for phasic and phenological development of rice was developed using the scale of physiological development time, based on the ecophysiological development processes. The interaction of daily thermal effectiveness, photoperiod effectiveness and intrinsic earliness(before heading), and basic filling duration factor(after heading)determined the daily physiological effectiveness, which accumulated to get physiological development time. The Beta and quadratic functions were used to describe daily thermal and photoperiod effectiveness, respectively. Five specific genetic parameters were added to adjust the genotypic differences in rice development so that all different varieties could reach the same physiological development time at a given development stage. The stages of seedling emergence, panicle initiation, heading, and maturity were validated using sowing dates under different ecological environments, with the RMSE of 1. 47, 5. 10, 4.58 and 3.37 days, respectively. The results showed that the model was not only explanatory and systematic but also accurate and applicable.展开更多
In this study, a regional air quality model system （RAQMS） was applied to investigate the spatial distributions and seasonal variations of atmospheric aerosols in 2006 over East Asia. Model validations demonstrated ...In this study, a regional air quality model system （RAQMS） was applied to investigate the spatial distributions and seasonal variations of atmospheric aerosols in 2006 over East Asia. Model validations demonstrated that RAQMS was able to reproduce the evolution processes of aerosol components reasonably well. Ground-level PM10 （particles with aerodynamic diameter ≤10 μm） concentrations were highest in spring and lowest in summer and were characterized by three maximum centers： the Taklimakan Desert （-1000 μg m^-3）, the Gobi Desert （-400 μg m^-3）, and the Huabei Plain （- 300 μg m^-3） of China. Vertically, high PM10 concentrations ranging from 100 μg m-3 to 250 μg m-3 occurred from the surface to an altitude of 6000 m at 30°-45°N in spring. In winter, the vertical gradient was so large that most aerosols were restricted in the boundary layer. Both sulfate and ammonium reached their highest concentrations in autumn, while nitrate reached its maximum level in winter. Black carbon and organic carbon aerosol concentrations reached maximums in winter. Soil dust were strongest in spring, whereas sea salt exerted the strongest influence on the coastal regions of eastern China in summer. The estimated burden of anthropogenic aerosols was largest in winter （1621 Gg） and smallest in summer （1040 Gg）. The sulfate burden accounted for -42% of the total anthropogenic aerosol burden. The dust burden was about twice the anthropogenic aerosol burden, implying the potentially important impacts of the natural aerosols on air quality and climate over East Asia.展开更多
OBJECTIVE To explain the high inter-individual variability and the frequency of exceeding the therapeutic reference range and the laboratory alert level of amisulpride,a popula⁃tion pharmacokinetic model in Chinese pa...OBJECTIVE To explain the high inter-individual variability and the frequency of exceeding the therapeutic reference range and the laboratory alert level of amisulpride,a popula⁃tion pharmacokinetic model in Chinese patients with schizophrenia was built based on therapeu⁃tic drug monitoring data to guide individualized therapy.METHODS Plasma concentration data(330 measurements from 121 patients)were ana⁃lyzed using a nonlinear mixed-effects model⁃ing approach with first-order conditional estima⁃tion with interaction(FOCE I).The concentra⁃tions of amisulpride were detected by HPLC-MS/MS.Age,weight,sex,combination medication history and renal function status were evaluated as main covariates.The model was internally val⁃idated using goodness-of-fit,bootstrap and nor⁃malized prediction distribution error.Recom⁃mended dosage regimens for patients with key covariates were estimated on the basis of Monte Carlo simulations and the established model.RESULTS A one-compartment model with first-order absorption and elimination was found to adequately characterize amisulpride concentra⁃tion in Chinese patients with schizophrenia.The population estimates of the apparent volume of distribution(V/F)and apparent clearance(CL/F)were 12.7 L and 1.12 L·h-1,respectively.Age sig⁃nificantly affected the clearance of amisulpride and the final model was as follow:CL/F=1.04×(AGE/32)-0.624(L·h-1).To avoid exceeding the lab⁃oratory alert level(640μg·L-1),the model-based simulation results showed that the recommended dose of amisulpride was no more than 600 mg per day for patients aged 60 years,800 mg per day for those aged 40 years and 1200 mg per day for those aged 20 years,respectively.CON⁃CLUSION Dosage optimization of amisulpride can be carried out according to age to reduce the risk of adverse reactions.The model can be used as a suitable tool for designing individual⁃ized therapy for Chinese patients with schizo⁃phrenia.展开更多
Modeling and simulation have emerged as an indispensable approach to create numerical experiment platforms and study engineering systems.However,the increasingly complicated systems that engineers face today dramatica...Modeling and simulation have emerged as an indispensable approach to create numerical experiment platforms and study engineering systems.However,the increasingly complicated systems that engineers face today dramatically challenge state-of-the-art modeling and simulation approaches.Such complicated systems,which are composed of not only continuous states but also discrete events,and which contain complex dynamics across multiple timescales,are defined as generalized hybrid systems(GHSs)in this paper.As a representative GHS,megawatt power electronics(MPE)systems have been largely integrated into the modern power grid,but MPE simulation remains a bottleneck due to its unacceptable time cost and poor convergence.To address this challenge,this paper proposes the numerical convex lens approach to achieve state-discretized modeling and simulation of GHSs.This approach transforms conventional time-discretized passive simulations designed for pure-continuous systems into state-discretized selective simulations designed for GHSs.When this approach was applied to a largescale MPE-based renewable energy system,a 1000-fold increase in simulation speed was achieved,in comparison with existing software.Furthermore,the proposed approach uniquely enables the switching transient simulation of a largescale megawatt system with high accuracy,compared with experimental results,and with no convergence concerns.The numerical convex lens approach leads to the highly efficient simulation of intricate GHSs across multiple timescales,and thus significantly extends engineers’capability to study systems with numerical experiments.展开更多
Simulation models of heat and water transport have not been rigorously tested for the red soils of southern China. Based on the theory of nonisothermal water-heat coupled transfer, a simulation model, programmed in Vi...Simulation models of heat and water transport have not been rigorously tested for the red soils of southern China. Based on the theory of nonisothermal water-heat coupled transfer, a simulation model, programmed in Visual Basic 6.0, was developed to predict the coupled transfer of water and heat in hilly red soil. A series of soil column experiments for soil water and heat transfer, including soil columns with closed and evaporating top ends, were used to test the simulation model. Results showed that in the closed columns, the temporal and spatial distribution of moisture and heat could be very well predicted by the model, while in the evaporating columns, the simulated soil water contents were somewhat different from the observed ones. In the heat flow equation by Taylor and Lary (1964), the effect of soil water evaporation on the heat flow is not involved, which may be the main reason for the differences between simulated and observed results. The predicted temperatures were not in agreement with the observed one with thermal conductivities calculated by de Vries and Wierenga equations, so that it is suggested that Kh, soil heat conductivity, be multiplied by 8.0 for the first 6.5 h and by 1.2 later on. Sensitivity analysis of soil water and heat coefficients showed that the saturated hydraulic conductivity, KS, and the water diffusivity, D(θ), had great effects on soil water transport; the variation of soil porosity led to the difference of soil thermal properties, and accordingly changed temperature redistribution, which would affect water redistribution.展开更多
As the pivotal test equipment of aero-engines design,finalization,improvement,modification,etc.,the Altitude Ground Test Facilities(AGTF)plays an important role in the research and development of the aero-engines.With...As the pivotal test equipment of aero-engines design,finalization,improvement,modification,etc.,the Altitude Ground Test Facilities(AGTF)plays an important role in the research and development of the aero-engines.With the rapid development of advanced high-performance aeroengine,the increasing demand of high-altitude simulation test is driving AGTF to improve its test ability and level of automation and intelligence.The modeling method,simulation tool,and control technology are the key factors to support the improvement of the AGTF control system.The main purpose of this paper is to provide an overview of modeling methods,simulation tools,and control technologies in AGTF control system for future research.First,it reviews the evolution of AGTF in the world,from the early formative stage to integration stage.Then,the mathematical modeling method of AGTF for control application is overviewed.Furthermore,the simulation tools used in the AGTF control system are overviewed from numerical simulation to hardware-in-loop simulation and further to semi-physical simulation.Meanwhile,the control technologies used in the AGTF control system are summarized from single-variable control to multivariable integrated control,and from classical control theory to modern control theory.Finally,recommendations for future research are outlined.Therefore,this review article provides extensive literature information for the modeling,simulation,and control design of AGTF for control application.展开更多
Accurate acid placement constitutes a major concern in matrix stimulation because the acid tends to penetrate the zones of least resistance while leaving the low-permeability regions of the formation untreated.Degrada...Accurate acid placement constitutes a major concern in matrix stimulation because the acid tends to penetrate the zones of least resistance while leaving the low-permeability regions of the formation untreated.Degradable materials(fibers and solid particles)have recently shown a good capability as fluid diversion to overcome the issues related to matrix stimulation.Despite the success achieved in the recent acid stimulation jobs stemming from the use of some products that rely on fiber flocculation as the main diverting mechanism,it was observed that the volume of the base fluid and the loading of the particles are not optimized.The current industry lacks a scientific design guideline because the used methodology is based on experience or empirical studies in a particular area with a particular product.It is important then to understand the fundamentals of how acid diversion works in carbonates with different diverting mechanisms and diverters.Mathematical modeling and computer simulations are effective tools to develop this understanding and are efficiently applied to new product development,new applications of existing products or usage optimization.In this work,we develop a numerical model to study fiber dynamics in fluid flow.We employ a discrete element method in which the fibers are represented by multi-rigid-body systems of interconnected spheres.The discrete fiber model is coupled with a fluid flow solver to account for the inherent simultaneous interactions.The focus of the study is on the tendency for fibers to flocculate and bridge when interacting with suspending fluids and encountering restrictions that can be representative of fractures or wormholes in carbonates.The trends of the dynamic fiber behavior under various operating conditions including fiber loading,flow rate and fluid viscosity obtained from the numerical model show consistency with experimental observations.The present numerical investigation reveals that the bridging capability of the fiber–fluid system can be enhanced by increasing the fiber loading,selecting fibers with higher stiffness,reducing the injection flow rate,reducing the suspending fluid viscosity or increasing the attractive cohesive forces among fibers by using sticky fibers.展开更多
In order to better study the dynamic characteristics and the control strategy of parafoil systems,considering the effect of flap deflection as the control mechanism and regarding the parafoil and the payload as a rigi...In order to better study the dynamic characteristics and the control strategy of parafoil systems,considering the effect of flap deflection as the control mechanism and regarding the parafoil and the payload as a rigid body,a six degrees-of-freedom(DOF)dynamic model of a parafoil system including three DOF for translational motion and three DOF for rotational motion,is established according to the K rchhoff motion equation.Since the flexible winged paafoil system flying at low altitude is more susceptibleto winds,the motion characteristics of the parafoil system Wth and Wthout winds are simulated and analyzed.Furthermore,the ardropm test is used to further verify the model.The comparison results show that the simulation trajectory roughly overlaps with the actual flight track.The horzontnl velocity of the simulation model is in good accordance with the airdrop test,with a deviation less than0.5m/s,while its simulated vertical velocity fuctuates slightly under the infuence of the wind,and shows a similar trend to the ardrop test.It is concludedthat the established model can well describe the characteristics of the parafoil system.展开更多
ABSTRACT Rainfall responses to doubled atmospheric carbon dioxide concentration were investigated through the analysis of two pairs of two-dimensional cloud-resolving model sensitivity experiments. One pair of experi...ABSTRACT Rainfall responses to doubled atmospheric carbon dioxide concentration were investigated through the analysis of two pairs of two-dimensional cloud-resolving model sensitivity experiments. One pair of experiments simulated pre-summer heavy rainfall over southern China around the summer solstice, whereas the other pair of experiments simulated tropical rainfall around the winter solstice. The analysis of the time and model domain mean heat budget revealed that the enhanced local atmospheric warming was associated with doubled carbon dioxide through the weakened infrared radiative cooling during the summer solstice. The weakened mean pre-summer rainfall corresponded to the weakened mean infrared radiative cooling. Doubled carbon dioxide increased the mean tropical atmospheric warming via the enhanced mean latent heat in correspondence with the strengthened mean infrared radiative cooling during the winter solstice. The enhanced mean tropical rainfall was associated with the increased mean latent heat.展开更多
The existence of clearance in the joints of mechanisms system is inevitable.The movements of the real mechanism are deflection from the ideal mechanism due to the clearances and the motion accuracy is decreased.The ef...The existence of clearance in the joints of mechanisms system is inevitable.The movements of the real mechanism are deflection from the ideal mechanism due to the clearances and the motion accuracy is decreased.The effects of the hinge clearance on the crank and rocker mechanism system are studied.The system dynamics equation with clearance is presented.The contact dynamics model is established using the nonlinear equivalent spring-damp model and the friction effect is considered by using Coulomb friction model.Then the models are incorporated into ADAMS,and based on the model,large numbers numeric simulations are made.The regularity of contact forces in clearance are studied in detail.And the effects of clearance size,clearance friction on the mechanism dynamics characteristic are analyzed.The simulation results can predict the effects of clearance on the mechanism dynamics characteristic preferably.展开更多
Multi-disciplinary virtual prototypes of complex products are increasingly and widely used in modern advanced manufactur- ing. How to effectively address the problems of unified modeling, composition and reuse based o...Multi-disciplinary virtual prototypes of complex products are increasingly and widely used in modern advanced manufactur- ing. How to effectively address the problems of unified modeling, composition and reuse based on the multi-disciplinary heteroge- neous models has brought great challenges to the modeling and simulation （M＆S） science and technology. This paper presents a top-level modeling theory based on the meta modeling framework （M2F） of the COllaborative SIMulation （COSlM） theory of virtual prototyping to solve the problems. Firstly the fundamental prin- ciples of the top-level modeling theory are decribed to expound the premise, assumptions, basic conventions and special require- ments in the description of complex heterogeneous systems. Next the formalized definitions for each factor in top level modeling are proposed and the hierarchical nature of them is illustrated. After demonstrating that they are self-closing, this paper divides the top- level modeling into two views, static structural graph and dynamic behavioral graph. Finally, a case study is discussed to demon- strate the feasibility of the theory.展开更多
A novel mathematical model for single particle slurry propylene polymerization rising heterogeneous Ziegler-Natta catalysts has been developed to describe the kinetic behavior, the molecular weight-distribution, the m...A novel mathematical model for single particle slurry propylene polymerization rising heterogeneous Ziegler-Natta catalysts has been developed to describe the kinetic behavior, the molecular weight-distribution, the monomer concentration, the degree of polymerization, the polydispersity index （PDI）, etc. This model provides a more valid mathematical description by accounting for the monomer diffusion phenomena at two levels as multigrai model counts, and obtains results that are more applicable to the conditions existing in most polymerizations of industrial interest. Considering that some models on the mesoscale phenomena are so complex that some existingmodeling aspects have to be simplified or even neglected to make the model convenient for use in interesting engineering studies, it is very important to put some effort into determining what sort of numerical analysis works bestfor these problems. For this reason, special attentionis.paid to these studies to explorean efficient algorithm usingadaptive grid-point spacing in a tlnlte-ditterence technique to tlgure out more practical mass transport models andconvection-diffusion models efficiently. The reasonable outcomes, as well as the significant computation time saving, have been achieved, thereby displaying the advantage of this calculation method.展开更多
基金supported by the fundings from 2024 Young Talents Program for Science and Technology Thinking Tanks(No.XMSB20240711041)2024 Student Research Program on Dynamic Simulation and Force-on-Force Exercise of Nuclear Security in 3D Interactive Environment Using Reinforcement Learning,Natural Science Foundation of Top Talent of SZTU(No.GDRC202407)+2 种基金Shenzhen Science and Technology Program(No.KCXFZ20240903092603005)Shenzhen Science and Technology Program(No.JCYJ20241202124703004)Shenzhen Science and Technology Program(No.KJZD20230923114117032)。
文摘Vulnerability assessment is a systematic process to identify security gaps in the design and evaluation of physical protection systems.Adversarial path planning is a widely used method for identifying potential vulnerabilities and threats to the security and resilience of critical infrastructures.However,achieving efficient path optimization in complex large-scale three-dimensional(3D)scenes remains a significant challenge for vulnerability assessment.This paper introduces a novel A^(*)-algorithmic framework for 3D security modeling and vulnerability assessment.Within this framework,the 3D facility models were first developed in 3ds Max and then incorporated into Unity for A^(*)heuristic pathfinding.The A^(*)-heuristic pathfinding algorithm was implemented with a geometric probability model to refine the detection and distance fields and achieve a rational approximation of the cost to reach the goal.An admissible heuristic is ensured by incorporating the minimum probability of detection(P_(D)^(min))and diagonal distance to estimate the heuristic function.The 3D A^(*)heuristic search was demonstrated using a hypothetical laboratory facility,where a comparison was also carried out between the A^(*)and Dijkstra algorithms for optimal path identification.Comparative results indicate that the proposed A^(*)-heuristic algorithm effectively identifies the most vulnerable adversarial pathfinding with high efficiency.Finally,the paper discusses hidden phenomena and open issues in efficient 3D pathfinding for security applications.
文摘AIGaN/GaN HEMTs are investigated by numerical simulation from the self-consistent solution of Schr6dinger-Poisson-hydrodynamic （HD） systems. The influences of polarization charge and quantum effects are considered in this model. Then the two-dimensional conduction band and electron distribution, electron temperature characteristics, Id versus Vd and Id versus Vg, transfer characteristics and transconductance curves are obtained. Corresponding analysis and discussion based on the simulation results are subsequently given.
基金National Natural Science Foundation of China(NSFC,Grant No.81273583)
文摘The epidermal growth factor receptor（EGFR）—tyrosine kinase inhibitors（TKIs） monotherapies have limited efficacy in the treatment of EGFR mutation-negative non-small cell lung cancers（NSCLCs）. In the present study, we aimed to investigate the combined effect of erlotinib（ER） and cabozantinib（CAB） on NSCLC cell lines harboring wild-type EGFR and to optimize the dosage regimens using pharmacodynamic（PD） modeling and simulation. Therefore, we examined the combined effect of ER and CAB on cell viability, cloning, apoptosis induction, migration and growth dynamics in H1299 and A549 cells. PD modeling and simulation were also performed to quantitatively describe the H1299 cells growth dynamics and to optimize the dosage regimens as well. Our results showed that CAB effectively enhanced the sensitivity of both cell lines to ER. The PD models fitted the data well, and some important parameters were obtained. The exponential（λ_0） and linear（λ_1） growth rates of H1299 cells were 0.0241 h^（–1） and 360 cells？h^（–1）, respectively. The Emax of ER and CAB was 0.0091 h^（–1） and 0.0085 h^（–1）, and the EC50 was 0.812 μM and 1.16 μM, respectively. The synergistic effect observed in the experiments was further confirmed by the estimated combination index φ（1.37）,（95% confidence interval： 1.24–1.50）, obtained from PD modeling. Furthermore, the dosage regimens were optimized using simulations. In summary, both the experimental and modeling results demonstrated the synergistic interaction between ER and CAB in NSCLCs without EGFR mutations. Sequential combinations of ER and CAB provided an option for the therapy of the NSCLCs with wild-type EGFR, which would provide some references for preclinical study and translational research as well.
基金Project supported by the National High Technology Research and Development Program of China (863 Program) (No. 2003AA209030) High Technology Research and Development Program of Jiangsu Province (No. BG2004320) the National Natural Science Foundation
文摘A deep understanding of crop-water eco-physiological relations is the basis for quantifying plant physiological responses to soil water stress. Pot experiments were conducted to investigate the winter wheat crop-water relations under both drought and waterlogging conditions in two sequential growing seasons from 2000 to 2002, and then the data were used to develop and validate models simulating the responses of winter wheat growth to drought and waterlogging stress. The experiment consisted of four treatments, waterlogging (keep 1 to 2 cm water layer depth above soil surface), control (70%-80% field capacity), light drought (40%-50% field capacity) and severe drought (30%-40% field capacity) with six replicates at five stages in the 2000-2001 growth season. Three soil water content treatments (waterlogging, control and drought) with two replicates were designed in the 2001-2002 growth season. Waterlogging and control treatments are the same as in the 2000-2001 growth season. For the drought treatment, no water was supplied and the soil moisture decreased from field capacity to wilting point. Leaf net photosynthetic rate, transpiration rate, predawn leaf water potential, soil water potential, soil water content and dry matter weight of individual organs were measured. Based on crop-water eco-physiological relations, drought and waterlogging stress factors for winter wheat growth simulation model were put forward. Drought stress factors integrated soil water availability, the sensitivity of different development stages and the difference between physiological processes (such as photosynthesis, transpiration and partitioning). The quantification of waterlogging stress factor considered different crop species, soil water status, waterlogging days and sensitivity at different growth stages. Data sets from the pot experiments revealed favorable performance reliability for the simulation sub-models with the drought and waterlogging stress factors.
基金Project supported by the National Key Basic Research Support Foundation (NKBRSF) of China (No. G199901881).
文摘Six paddy soils of Shanghai, China, were studied after 120 days of anaerobicincubation at 25 deg C and 35 deg C. Four models, the effective accumulated temperature model, theone-component first-order exponential model (the one-pool model), the two-component first-orderexponential model (the two-pool model), and the two-component first-order plus zero-orderexponential model including a constant term (the special model), were fitted to the data of observedmineral-N during incubation using non-linear regression procedures. The two-pool model and thespecial model gave the best fits amongst the four models, and parameters in the special model weremore reasonable than those in the other three. Results showed that the special model gave a betterprediction of nitrogen mineralization under flooded conditions than the other three models.
基金supported in part by the National Key Scientific Instrument and Equipment Development Project(No.61827801)in part by the National Natural Science Foundation of China(No.62271250)+2 种基金in part by Natural Science Foundation of Jiangsu Province(No.BK20211182)in part by the Key Technologies R&D Program of Jiangsu(Prospective and Key Technologies for Industry)under Grants BE2022067 and BE2022067-3in part by China Scholarship Council,and in part by Postgraduate Research&Practice Innovation Program of Jiangsu Province,No.KYCX220360.
文摘Ultra-wideband(UWB)technology is a prospective technology for high-rate transmission and accurate localization in the future communication systems.State-of-art channel modeling approaches usually divide the UWB channel into several sub-band channels and model them independently.By considering frequency-dependent channel parameters,a novel analytical UWB channel model with continuous frequency response is proposed.The composite effect of all frequency components within the UWB channel on the channel impulse response(CIR)of delay domain is derived based on the continuous channel transfer function(CTF)of frequency domain.On this basis,a closed-form simulation model for UWB channels and geometry-based parameter calculation method are developed,which can guarantee the continuity of channel characteristics on the frequency domain and greatly reduce the simulation complexity.Finally,the proposed method is applied to generate UWB channel with 2 GHz bandwidth at sub-6GHz and millimeter wave(mmWave)bands,respectively.The channel measurements are also carried out to validate the proposed method.The simulated CIR and power gain are shown to be in good agreement with the measurement data.Moreover,the comparison results of power gain and Doppler power spectral density(DPSD)show that the proposed UWB channel model Received:Apr.23,2022 Revised:Jun.09,2022 Editor:Wei Fan achieves a good balance between the simulation accuracy and efficiency.
基金supported by the Hundred Talents Program,the Chinese Academy of Sciences and the Natural Science Foundation of China(No.30030090,39830220)
文摘Assuming that decomposition of organic matter in soils follows the first-order kinetics reaction, a computer model was developed to simulate soil organic matter dynamics. Organic matter in soils is divided up into two parts that include incorporated organic carbon from crop residues or other organic fertilizer and soil intrinsic carbon. The incorporated organic carbon was assumed to consist of two components, labile-C and resistant-C. The model was represented by a differential equation of dCt/dt = Kt × fr × fw × fs × ct (i = 1, r,S) and an integral equation of Cit = Cio × EXP(Ki × fT × fw × fs × t). Effect of soil parameters of temperature, moisture and texture on the decomposition was functioned by the fT, fw and fs, respectively. Data from laboratory incubation experiments were used to determine the first-order decay rate K, and the fraction of labile-C of crop residues by employing a nonlinear method. The values of K for the components of labile-C and resistant-C and the soil intrinsic carbon were evaluated to be 0.025,0.080 X 10-2 and 0.065 X 10-3d-1, respectively. The labile-C fraction of wheat straw, wheat roots, rice straw and rice roots were 0.50, 0.25, 0.40 and 0.20, respectively. These values are related to the initial residue carbon-to-nitrogen ratio (C/N) and lignin content.
基金funded by the National Natural Science Foundation of China (30771277 and 30771279)
文摘Crop performance is determined by the combined effects of the genotype of the crop and the environmental conditions of the production system. This study was undertaken to develop a dynamic model for simulating environmental （temperature and solar radiation） and N supply effects on fiber fineness, maturity and micronaire. Three different experiments involving genotypes, sowing dates, and N fertilization rates were conducted to support model development and model evaluation. The growth and development duration of fiber fineness, maturity, and micronaire were scaled by using physiological development time of secondary wall synthesis （PDT SWSP ）, which was determined based on the constant ratio of SWSP/ BMP. PTP （product of relative thermal effectiveness （RTE） and photosynthetically active radiation （PAR）, MJ m-2） and subtending leaf N content per unit area （N A , g m-2） and critical subtending leaf N content per unit area （CN A , g m-2） of cotton boll were calculated or simulated to evaluate effects of temperature and radiation, and N supply. Besides, the interactions among temperature, radiation and N supply were also explained by piecewise function. The overall performance of the model was calibrated and validated with independent data sets from three field experiments with two sowing dates, three or five flowering dates and three or four N fertilization rates for three subsequent years （2005, 2007, and 2009） at three ecological locations. The average RMSE and RE for fiber fineness, maturity, and micronaire predictions were 372 m g-1 and 5.0%, 0.11 m g-1 and 11.4%, 0.3 m g-1 and 12.3%, respectively, indicating a good fit between the simulated and observed data. It appears that the model can give a reliable prediction for fiber fineness, maturity and micronaire formation under various growing conditions.
基金supported by the National Natura1 Science Foundation of China(30030090)the National 863 Program,China(2001AA245041)
文摘A simulation model for phasic and phenological development of rice was developed using the scale of physiological development time, based on the ecophysiological development processes. The interaction of daily thermal effectiveness, photoperiod effectiveness and intrinsic earliness(before heading), and basic filling duration factor(after heading)determined the daily physiological effectiveness, which accumulated to get physiological development time. The Beta and quadratic functions were used to describe daily thermal and photoperiod effectiveness, respectively. Five specific genetic parameters were added to adjust the genotypic differences in rice development so that all different varieties could reach the same physiological development time at a given development stage. The stages of seedling emergence, panicle initiation, heading, and maturity were validated using sowing dates under different ecological environments, with the RMSE of 1. 47, 5. 10, 4.58 and 3.37 days, respectively. The results showed that the model was not only explanatory and systematic but also accurate and applicable.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-Q11-03)the "Strategic Priority Research Program" of the Chinese Academy of Sciences (Grant No. XDA05100502)+2 种基金the National 973 Project of China (Grant No. 2010CB950804)the National Natural Science Foundation of China (GrantNo. 41075106)the Hundred Talents Program of the Chinese Academy of Sciences
文摘In this study, a regional air quality model system （RAQMS） was applied to investigate the spatial distributions and seasonal variations of atmospheric aerosols in 2006 over East Asia. Model validations demonstrated that RAQMS was able to reproduce the evolution processes of aerosol components reasonably well. Ground-level PM10 （particles with aerodynamic diameter ≤10 μm） concentrations were highest in spring and lowest in summer and were characterized by three maximum centers： the Taklimakan Desert （-1000 μg m^-3）, the Gobi Desert （-400 μg m^-3）, and the Huabei Plain （- 300 μg m^-3） of China. Vertically, high PM10 concentrations ranging from 100 μg m-3 to 250 μg m-3 occurred from the surface to an altitude of 6000 m at 30°-45°N in spring. In winter, the vertical gradient was so large that most aerosols were restricted in the boundary layer. Both sulfate and ammonium reached their highest concentrations in autumn, while nitrate reached its maximum level in winter. Black carbon and organic carbon aerosol concentrations reached maximums in winter. Soil dust were strongest in spring, whereas sea salt exerted the strongest influence on the coastal regions of eastern China in summer. The estimated burden of anthropogenic aerosols was largest in winter （1621 Gg） and smallest in summer （1040 Gg）. The sulfate burden accounted for -42% of the total anthropogenic aerosol burden. The dust burden was about twice the anthropogenic aerosol burden, implying the potentially important impacts of the natural aerosols on air quality and climate over East Asia.
文摘OBJECTIVE To explain the high inter-individual variability and the frequency of exceeding the therapeutic reference range and the laboratory alert level of amisulpride,a popula⁃tion pharmacokinetic model in Chinese patients with schizophrenia was built based on therapeu⁃tic drug monitoring data to guide individualized therapy.METHODS Plasma concentration data(330 measurements from 121 patients)were ana⁃lyzed using a nonlinear mixed-effects model⁃ing approach with first-order conditional estima⁃tion with interaction(FOCE I).The concentra⁃tions of amisulpride were detected by HPLC-MS/MS.Age,weight,sex,combination medication history and renal function status were evaluated as main covariates.The model was internally val⁃idated using goodness-of-fit,bootstrap and nor⁃malized prediction distribution error.Recom⁃mended dosage regimens for patients with key covariates were estimated on the basis of Monte Carlo simulations and the established model.RESULTS A one-compartment model with first-order absorption and elimination was found to adequately characterize amisulpride concentra⁃tion in Chinese patients with schizophrenia.The population estimates of the apparent volume of distribution(V/F)and apparent clearance(CL/F)were 12.7 L and 1.12 L·h-1,respectively.Age sig⁃nificantly affected the clearance of amisulpride and the final model was as follow:CL/F=1.04×(AGE/32)-0.624(L·h-1).To avoid exceeding the lab⁃oratory alert level(640μg·L-1),the model-based simulation results showed that the recommended dose of amisulpride was no more than 600 mg per day for patients aged 60 years,800 mg per day for those aged 40 years and 1200 mg per day for those aged 20 years,respectively.CON⁃CLUSION Dosage optimization of amisulpride can be carried out according to age to reduce the risk of adverse reactions.The model can be used as a suitable tool for designing individual⁃ized therapy for Chinese patients with schizo⁃phrenia.
基金the Major Program of National Natural Science Foundation of China(51490683).
文摘Modeling and simulation have emerged as an indispensable approach to create numerical experiment platforms and study engineering systems.However,the increasingly complicated systems that engineers face today dramatically challenge state-of-the-art modeling and simulation approaches.Such complicated systems,which are composed of not only continuous states but also discrete events,and which contain complex dynamics across multiple timescales,are defined as generalized hybrid systems(GHSs)in this paper.As a representative GHS,megawatt power electronics(MPE)systems have been largely integrated into the modern power grid,but MPE simulation remains a bottleneck due to its unacceptable time cost and poor convergence.To address this challenge,this paper proposes the numerical convex lens approach to achieve state-discretized modeling and simulation of GHSs.This approach transforms conventional time-discretized passive simulations designed for pure-continuous systems into state-discretized selective simulations designed for GHSs.When this approach was applied to a largescale MPE-based renewable energy system,a 1000-fold increase in simulation speed was achieved,in comparison with existing software.Furthermore,the proposed approach uniquely enables the switching transient simulation of a largescale megawatt system with high accuracy,compared with experimental results,and with no convergence concerns.The numerical convex lens approach leads to the highly efficient simulation of intricate GHSs across multiple timescales,and thus significantly extends engineers’capability to study systems with numerical experiments.
基金Project supported by the National Natural Science Foundation ofChina (No. 40171047) and the Doctoral Foundation of NationalEducation Ministry China
文摘Simulation models of heat and water transport have not been rigorously tested for the red soils of southern China. Based on the theory of nonisothermal water-heat coupled transfer, a simulation model, programmed in Visual Basic 6.0, was developed to predict the coupled transfer of water and heat in hilly red soil. A series of soil column experiments for soil water and heat transfer, including soil columns with closed and evaporating top ends, were used to test the simulation model. Results showed that in the closed columns, the temporal and spatial distribution of moisture and heat could be very well predicted by the model, while in the evaporating columns, the simulated soil water contents were somewhat different from the observed ones. In the heat flow equation by Taylor and Lary (1964), the effect of soil water evaporation on the heat flow is not involved, which may be the main reason for the differences between simulated and observed results. The predicted temperatures were not in agreement with the observed one with thermal conductivities calculated by de Vries and Wierenga equations, so that it is suggested that Kh, soil heat conductivity, be multiplied by 8.0 for the first 6.5 h and by 1.2 later on. Sensitivity analysis of soil water and heat coefficients showed that the saturated hydraulic conductivity, KS, and the water diffusivity, D(θ), had great effects on soil water transport; the variation of soil porosity led to the difference of soil thermal properties, and accordingly changed temperature redistribution, which would affect water redistribution.
基金This study was co-supported by the National Science and Technology Major Project,China(No.J2019-V-0010-0104)Zhejiang Provincial Natural Science Foundation of China(No.LQ23E060007).
文摘As the pivotal test equipment of aero-engines design,finalization,improvement,modification,etc.,the Altitude Ground Test Facilities(AGTF)plays an important role in the research and development of the aero-engines.With the rapid development of advanced high-performance aeroengine,the increasing demand of high-altitude simulation test is driving AGTF to improve its test ability and level of automation and intelligence.The modeling method,simulation tool,and control technology are the key factors to support the improvement of the AGTF control system.The main purpose of this paper is to provide an overview of modeling methods,simulation tools,and control technologies in AGTF control system for future research.First,it reviews the evolution of AGTF in the world,from the early formative stage to integration stage.Then,the mathematical modeling method of AGTF for control application is overviewed.Furthermore,the simulation tools used in the AGTF control system are overviewed from numerical simulation to hardware-in-loop simulation and further to semi-physical simulation.Meanwhile,the control technologies used in the AGTF control system are summarized from single-variable control to multivariable integrated control,and from classical control theory to modern control theory.Finally,recommendations for future research are outlined.Therefore,this review article provides extensive literature information for the modeling,simulation,and control design of AGTF for control application.
文摘Accurate acid placement constitutes a major concern in matrix stimulation because the acid tends to penetrate the zones of least resistance while leaving the low-permeability regions of the formation untreated.Degradable materials(fibers and solid particles)have recently shown a good capability as fluid diversion to overcome the issues related to matrix stimulation.Despite the success achieved in the recent acid stimulation jobs stemming from the use of some products that rely on fiber flocculation as the main diverting mechanism,it was observed that the volume of the base fluid and the loading of the particles are not optimized.The current industry lacks a scientific design guideline because the used methodology is based on experience or empirical studies in a particular area with a particular product.It is important then to understand the fundamentals of how acid diversion works in carbonates with different diverting mechanisms and diverters.Mathematical modeling and computer simulations are effective tools to develop this understanding and are efficiently applied to new product development,new applications of existing products or usage optimization.In this work,we develop a numerical model to study fiber dynamics in fluid flow.We employ a discrete element method in which the fibers are represented by multi-rigid-body systems of interconnected spheres.The discrete fiber model is coupled with a fluid flow solver to account for the inherent simultaneous interactions.The focus of the study is on the tendency for fibers to flocculate and bridge when interacting with suspending fluids and encountering restrictions that can be representative of fractures or wormholes in carbonates.The trends of the dynamic fiber behavior under various operating conditions including fiber loading,flow rate and fluid viscosity obtained from the numerical model show consistency with experimental observations.The present numerical investigation reveals that the bridging capability of the fiber–fluid system can be enhanced by increasing the fiber loading,selecting fibers with higher stiffness,reducing the injection flow rate,reducing the suspending fluid viscosity or increasing the attractive cohesive forces among fibers by using sticky fibers.
基金The National Natural Science Foundation of China(No.61273138,61573197)the National Key Technology R&D Program(No.2015BAK06B04)+1 种基金the Key Fund of Tianjin(No.14JCZDJC39300)the Key Technologies R&D Program of Tianjin(No.14ZCZDSF00022)
文摘In order to better study the dynamic characteristics and the control strategy of parafoil systems,considering the effect of flap deflection as the control mechanism and regarding the parafoil and the payload as a rigid body,a six degrees-of-freedom(DOF)dynamic model of a parafoil system including three DOF for translational motion and three DOF for rotational motion,is established according to the K rchhoff motion equation.Since the flexible winged paafoil system flying at low altitude is more susceptibleto winds,the motion characteristics of the parafoil system Wth and Wthout winds are simulated and analyzed.Furthermore,the ardropm test is used to further verify the model.The comparison results show that the simulation trajectory roughly overlaps with the actual flight track.The horzontnl velocity of the simulation model is in good accordance with the airdrop test,with a deviation less than0.5m/s,while its simulated vertical velocity fuctuates slightly under the infuence of the wind,and shows a similar trend to the ardrop test.It is concludedthat the established model can well describe the characteristics of the parafoil system.
基金supported by 985 Program of Zhejiang University under Grant No.188020+193432602/215National Natural Science Foundation of China (Grant No.41175047)+3 种基金the R&D Special Fund for Public Welfare Industry by the Ministry of Finance and the Ministry of Science and Technology (Grant Nos.GYHY201006014 and 20100503310)the Basic Research Project of the State Key Laboratory of Severe Weather (12011LAS-B14)supported by the National Key Basic Research and Development Project of China under Grant Nos.2013CB430103 and 2011CB403405the National Natural Science Foundation of China under Grant Nos.41375058 and 41175065
文摘ABSTRACT Rainfall responses to doubled atmospheric carbon dioxide concentration were investigated through the analysis of two pairs of two-dimensional cloud-resolving model sensitivity experiments. One pair of experiments simulated pre-summer heavy rainfall over southern China around the summer solstice, whereas the other pair of experiments simulated tropical rainfall around the winter solstice. The analysis of the time and model domain mean heat budget revealed that the enhanced local atmospheric warming was associated with doubled carbon dioxide through the weakened infrared radiative cooling during the summer solstice. The weakened mean pre-summer rainfall corresponded to the weakened mean infrared radiative cooling. Doubled carbon dioxide increased the mean tropical atmospheric warming via the enhanced mean latent heat in correspondence with the strengthened mean infrared radiative cooling during the winter solstice. The enhanced mean tropical rainfall was associated with the increased mean latent heat.
基金Sponsored by Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT0520)
文摘The existence of clearance in the joints of mechanisms system is inevitable.The movements of the real mechanism are deflection from the ideal mechanism due to the clearances and the motion accuracy is decreased.The effects of the hinge clearance on the crank and rocker mechanism system are studied.The system dynamics equation with clearance is presented.The contact dynamics model is established using the nonlinear equivalent spring-damp model and the friction effect is considered by using Coulomb friction model.Then the models are incorporated into ADAMS,and based on the model,large numbers numeric simulations are made.The regularity of contact forces in clearance are studied in detail.And the effects of clearance size,clearance friction on the mechanism dynamics characteristic are analyzed.The simulation results can predict the effects of clearance on the mechanism dynamics characteristic preferably.
基金supported by the National High Technology Research and Development Program (863 Program) (2011AA040502).
文摘Multi-disciplinary virtual prototypes of complex products are increasingly and widely used in modern advanced manufactur- ing. How to effectively address the problems of unified modeling, composition and reuse based on the multi-disciplinary heteroge- neous models has brought great challenges to the modeling and simulation （M＆S） science and technology. This paper presents a top-level modeling theory based on the meta modeling framework （M2F） of the COllaborative SIMulation （COSlM） theory of virtual prototyping to solve the problems. Firstly the fundamental prin- ciples of the top-level modeling theory are decribed to expound the premise, assumptions, basic conventions and special require- ments in the description of complex heterogeneous systems. Next the formalized definitions for each factor in top level modeling are proposed and the hierarchical nature of them is illustrated. After demonstrating that they are self-closing, this paper divides the top- level modeling into two views, static structural graph and dynamic behavioral graph. Finally, a case study is discussed to demon- strate the feasibility of the theory.
基金Supported by the National High Technology Development Program of China （No.2006AA05Z226）, Natural Science Foundation of Zhejiang Province （No.Y105370）, National HI-TECH Industrialization Program of China （No.2004-2080）, and Science Fund for Distinguished Young Scholars of Zhejiang University （No. 111000-581645）.
文摘A novel mathematical model for single particle slurry propylene polymerization rising heterogeneous Ziegler-Natta catalysts has been developed to describe the kinetic behavior, the molecular weight-distribution, the monomer concentration, the degree of polymerization, the polydispersity index （PDI）, etc. This model provides a more valid mathematical description by accounting for the monomer diffusion phenomena at two levels as multigrai model counts, and obtains results that are more applicable to the conditions existing in most polymerizations of industrial interest. Considering that some models on the mesoscale phenomena are so complex that some existingmodeling aspects have to be simplified or even neglected to make the model convenient for use in interesting engineering studies, it is very important to put some effort into determining what sort of numerical analysis works bestfor these problems. For this reason, special attentionis.paid to these studies to explorean efficient algorithm usingadaptive grid-point spacing in a tlnlte-ditterence technique to tlgure out more practical mass transport models andconvection-diffusion models efficiently. The reasonable outcomes, as well as the significant computation time saving, have been achieved, thereby displaying the advantage of this calculation method.
