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1.
根据 SPAC理论建立了一个冬小麦光合和蒸散的耦合模型。冬小麦 CO2 通量包括冠层光合、呼吸和土壤呼吸。冠层光合采用了 Farquhar光合作用生化模型 ,并通过冠层阻力的参数化将光合作用与蒸腾作用耦合起来。用涡度相关方法观测了 CO2通量 ,对模型进行了验证 ,结果显示模型可以较好地模拟 CO2 通量日变化过程。对模型的敏感性分析发现日间 CO2 通量最敏感的参数是初始量子效率。其次 ,CO2 通量对光响应曲线凸度、CO2 补偿点、凋萎点和叶面积指数的变化也有着较强的敏感性 ;夜间 CO2 通量敏感的参数是最适温度下 Rubisco催化能力和暗呼吸参数 相似文献
2.
用光合-蒸散耦合模型模拟冬小麦CO2通量的日变化 总被引:1,自引:0,他引:1
根据SPAC理论建立了一个冬小麦光合和蒸散的耦合模型.冬小麦CO2通量包括冠层光合、呼吸和土壤呼吸.冠层光合采用了Farquhar光合作用生化模型,并通过冠层阻力的参数化将光合作用与蒸腾作用耦合起来.用涡度相关方法观测了CO2通量,对模型进行了验证,结果显示模型可以较好地模拟CO2通量日变化过程.对模型的敏感性分析发现日间CO2通量最敏感的参数是初始量子效率.其次,CO2通量对光响应曲线凸度、CO2补偿点、凋萎点和叶面积指数的变化也有着较强的敏感性;夜间CO2通量敏感的参数是最适温度下Rubisco催化能力和暗呼吸参数. 相似文献
3.
A three-pool growth model of an individual Escherichia coli cell is described herein. The model is based on a previously developed chemically structured complex single cell growth model. The reduction in model complexity and the identification of the essential modes of motion, over the time scale of growth, is achieved by temporal decomposition and analysis of hierarchy in relaxation times. The three-pool model faithfully simulates the changes in cell size, cell shape, cell macromolecular composition, DNA initiation and termination periods, and the dependence of cell growth under abiotic glucose limitation. The predictions made by the reduced model compare favorably with both the experimental data and those of the full single cell model (SCM) without any parameter adjustments. The three-pool model has very few significant parameters and has the potential to find immediate practical use in bioreactor design and process control strategies. The model development illustrates the use of modal analysis to yield reduced physiologically realistic dynamic model of complex microbial system such as E. coll. 相似文献
4.
Dong K. Kim 《In vitro cellular & developmental biology. Animal》1997,33(4):289-293
Summary Doubling time has been widely used to represent the growth pattern of cells. A traditional method for finding the doubling
time is to apply gray-scaled cells, where the logarithmic transformed scale is used. As an alternative statistical method,
the log-linear model was recently proposed, for which actual cell numbers are used instead of the transformed gray-scaled
cells. In this paper, I extend the log-linear model and propose the extended log-linear model. This model is designed for
extra-Poisson variation, where the log-linear model produces the less appropriate estimate of the doubling time. Moreover,
I compare statistical properties of the gray-scaled method, the log-linear model, and the extended log-linear model. For this
purpose, I perform a Monte Carlo simulation study with three data-generating models: the additive error model, the multiplicative
error model, and the overdispersed Poisson model. From the simulation study, I found that the gray-scaled method highly depends
on the normality assumption of the gray-scaled cells; hence, this method is appropriate when the error model is multiplicative
with the log-normally distributed errors. However, it is less efficient for other types of error distributions, especially
when the error model is additive or the errors follow the Poisson distribution. The estimated standard error for the doubling
time is not accurate in this case. The log-linear model was found to be efficient when the errors follow the Poisson distribution
or nearly Poisson distribution. The efficiency of the log-linear model was decreased accordingly as the overdispersion increased,
compared to the extended log-linear model. When the error model is additive or multiplicative with Gamma-distributed errors,
the log-linear model is more efficient than the gray-scaled method. The extended log-linear model performs well overall for
all three data-generating models. The loss of efficiency of the extended log-linear model is observed only when the error
model is multiplicative with log-normally distributed errors, where the gray-scaled method is appropriate. However, the extended
log-linear model is more efficient than the log-linear model in this case. 相似文献
5.
熟鸡肉中金黄色葡萄球菌生长预测模型的建立 总被引:2,自引:0,他引:2
【目的】研究不同浓度和不同温度条件下金黄色葡萄球菌接种在熟鸡肉中的生长情况,比较3种常见预测模型拟合的准确性,选择最适合的预测模型建立一级和二级模型,为进一步探讨建立三级模型提供数据基础。【方法】测定浓度为102、103和104 CFU/g的金黄色葡萄球菌接种在15-36°C熟鸡肉中的生长数据,使用Matlab软件分别建立修正的Gompertz、Logistic和Baranyi模型,通过比较残差和拟合度(RSS、AIC、RSE)选择最优模型,并且拟合出生长参数(迟滞期、最大比生长速率和最大细胞密度),在此基础上通过响应面方程建立二级模型。最后对模型的可靠性进行了内部和外部实验验证。【结果】36°C和29°C条件下,修正的Gompertz模型最适合;22°C和15°C条件下,最适合模型按接种浓度依次为修正的Gompertz、Logistic和Baranyi模型,综合考虑,最优模型选择修正的Gompertz模型。通过计算预测标准差(%SEP)、平方根误差(RMSE)、准确性因子(Af)和偏差因子(Bf)对建立的二级模型进行数学检验,检验结果均在可接受范围内。【结论】用修正的Gompertz方程和响应面方程建立的一、二级预测模型可以为建立三级模型提供有效、精确的基础。 相似文献
6.
基于北方农牧交错带主要作物马铃薯和油葵的叶片气孔导度、净光合速率和气象因子的平行观测数据,对常用气孔导度模型(Jarvis模型、Ball-Berry模型、Leuning模型和Medlyn模型)进行了适用性评价.结果表明:马铃薯的气孔导度与净光合速率呈现较强的线性关系,而油葵气孔导度与净光合速率的线性关系较弱.对于马铃薯气孔导度,Ball-Berry模型模拟效果最佳,Leuning模型和Medlyn模型次之,Jarvis模型模拟效果最差;各模型的模拟值与观测值的均方根误差(RMSE)分别为0.0331、0.0371、0.0456和0.0794 mol·m-2·s-1,归一化均方根误差(NRMSE)分别为26.8%、30.0%、36.9%和64.3%,拟合度(R2)分别为0.96、0.61、0.91和0.88.对于油葵的气孔导度,Jarvis模型模拟效果略好于Ball-Berry模型、Medlyn模型和Leuning模型,其RMSE分别为0.2221、0.2534、0.2547和0.2758 mol·m-2·s-1,NRMSE分别为40.3%、46.0%、46.2%和50.1%,R2分别为0.38、0.22、0.23和0.20.气象因子对气孔导度作用的通径分析表明,北方农牧交错带马铃薯和油葵气孔导度日变化主要受饱和水汽压差影响.模型评价结果表明用于油葵的气孔导度模型需要进一步改进. 相似文献
7.
The hydrologic model is the foundation of water resource management and planning. Conceptual model is the essential component of groundwater model. Due to limited understanding of natural hydrogeological conditions, the conceptual model is always constructed incompletely. Therefore, the uncertainty in the model's output is evitable when natural groundwater field is simulated by a single groundwater model. A synthetic groundwater model is built and regarded as the true model, and three alternative conceptual models are constructed by considering incomplete hydrogeological conditions. The outputs (groundwater budget terms from boundary conditions) of these groundwater models are analyzed statistically. The results show that when the conceptual model is closer to the true hydrogeological conditions, the distributions of outputs of the groundwater model are more concentrated on the true outputs. Therefore, the more reliable the structure of the conceptual model is, the more reliable the output of the groundwater model is. Moreover, the uncertainty caused by the conceptual model cannot be compensated by parameter uncertainty. 相似文献
8.
研究昆虫杆状病毒流行病模拟模型,对确定基因工程改造杆状病毒的主攻方向,明确病毒病田间流行的机制与关键因素,以及制定生物防治策略,均具有重要的理论与实践意义.本研究研制了用于昆虫杆状病毒流行病模拟的数学模型和Java模拟软件,该模型包括描述种群动态的一个微分方程组,描述气温变化、作物生长及病毒动态的若干模型等.模拟软件用... 相似文献
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10.
In a stochastic simulation study of a dairy cattle population three multitrait models for estimation of genetic parameters and prediction of breeding values were compared. The first model was an approximate multitrait model using a two-step procedure. The first step was a single trait model for all traits. The solutions for fixed effects from these analyses were subtracted from the phenotypes. A multitrait model only containing an overall mean, an additive genetic and a residual term was applied on these preadjusted data. The second model was similar to the first model, but the multitrait model also contained a year effect. The third model was a full multitrait model. Genetic trends for total merit and for the individual traits in the breeding goal were compared for the three scenarios to rank the models. The full multitrait model gave the highest genetic response, but was not significantly better than the approximate multitrait model including a year effect. The inclusion of a year effect into the second step of the approximate multitrait model significantly improved the genetic trend for total merit. In this study, estimation of genetic parameters for breeding value estimation using models corresponding to the ones used for prediction of breeding values increased the accuracy on the breeding values and thereby the genetic progress. 相似文献
11.
A. A. Koshelev A. E. Bazhutina S. F. Pravdin K. S. Ushenin L. B. Katsnelson O. E. Solovyova 《Biophysics》2016,61(5):785-792
A modification of the mathematical model of the shape and fiber direction field of the left cardiac ventricle is presented. The model was developed based on the idea of nested spiral surfaces. The ventricle is composed of surfaces that model myocardial layers. Each layer is filled with curves corresponding to myocardial fibers. The tangents to these curves form the myofiber direction field. A modified spherical coordinate system is linked with the model left ventricle, where the ventricular boundaries are coordinate surfaces. The model is based on echocardiographic, computed-tomography, or magnetic-resonance-imaging data. For this purpose, four-chamber and two-chamber echocardiography views or sections along the long axis of the left ventricle from these tomographic data in several positions are approximated with a model profile. To construct a 3D model, we then interpolate model parameters by periodic cubic splines and the vector field of the tangents to the model fibers is calculated. For verification of the model, we used diffusion-tensor magneticresonance-imaging data of the human heart. 相似文献
12.
It is challenge in epidemiology to characterize the temperol aspect of exposure-disease association. The authors propose a stochastic model to deal with exposures that are time-dependent and exhibit susceptibility and latency effects. The model is applied to a retrospective cohort data on lung cancer mortality in the blackfoot disease endemic area in Taiwan. The authors compare the proposed model with the multistage model, the back-calculation model, the catalytic model, and the age-period-cohort models. 相似文献
13.
Hubertus V.M. Hamelers Annemiek ter Heijne Nienke Stein René A. RozendalCees J.N. Buisman 《Bioresource technology》2011,102(1):381-387
A kinetic model of the bio-anode was developed based on a simple representation of the underlying biochemical conversions as described by enzyme kinetics, and electron transfer reactions as described by the Butler-Volmer electron transfer kinetics. This Butler-Volmer-Monod model was well able to describe the measured bio-anode polarization curves. The Butler-Volmer-Monod model was compared to the Nernst-Monod model described the experimental data significantly better. The Butler-Volmer-Monod model has the Nernst-Monod model as its full electrochemically reversible limit. Contrary to the Nernst-Monod model, the Butler-Volmer-Monod model predicts zero current at equilibrium potential. Besides, the Butler-Volmer-Monod model predicts that the apparent Monod constant is dependent on anode potential, which was supported by experimental results. 相似文献
14.
The infection of insect cells with baculovirus was described in a mathematical model as a part of the structured dynamic model describing whole animal cell metabolism. The model presented here is capable of simulating cell population dynamics, the concentrations of extracellular and intracellularviral components, and the heterologous product titers. The model describes the whole processes of viral infection and theeffect of the infection on the host cell metabolism. Dynamic simulation of the model in batch and fed-batch mode gave goodagreement between model predictions and experimental data. Optimum conditions for insect cell culture and viral infectionin batch and fed-batch culture were studied using the model. 相似文献
15.
Lake circulation and sediment transport in Lake Myvatn 总被引:1,自引:0,他引:1
Lake circulation and sediment transport in Lake Myvatn have been calculated using AQUASEA, a numerical model developed by Vatnaskil Consulting Engineers. The goal of the modelling was to calculate changes in sediment transport within the lake due to changes in lake bathymetry caused by diatomite mining. The model uses the Galerkin finite element method and consists of a hydrodynamic flow model and a transport-dispersion model. The flow model is based on the shallow water equations and the wave equation. The transport model is based on the conservation of mass for suspended sediment. The model was calibrated against measurements performed during the summer of 1992. These included measurements of water elevation, current velocity, wave height, and concentration of suspended sediment. After calibration, the model was run for different mining scenarios to determine their impact on the sediment transport in the lake. 相似文献
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17.
Leaf litter processing in aquatic systems: A two variable model 总被引:3,自引:3,他引:0
18.
Dr. Sadao Tomizawa 《Biometrical journal. Biometrische Zeitschrift》1987,29(1):45-55
For square contingency tables with ordered categories, Agresti (1983) considered the linear diagonals-parameter symmetry model. An extended model including that model is proposed which has only one more parameter than that model. The model also includes the conditional symmetry model considered by McCullagh (1978). Decompositions for the proposed model and Agresti's model are given. 相似文献
19.
F. Martínez-Martínez M.A. Lago M.J. Rupérez C. Monserrat 《Computer methods in biomechanics and biomedical engineering》2013,16(7):747-757
In this study, six biomechanical models for simulating lamb liver behaviour are presented. They are validated using similarity coefficients from Medical Image on reconstructed volumes from computerised tomography images. In particular, the Jaccard and Hausdorff coefficients are used. Loads of 20 and 40 g are applied to the livers and their deformation is simulated by means of the finite element method. The models used are a linear elastic model, a neo-Hookean model, a Mooney–Rivlin model, an Ogden model, a linear viscoelastic model and a viscohyperelastic model. The model that provided a behaviour that is closest to reality was the viscohyperelastic model, where the hyperelastic part was modelled with an Ogden model. 相似文献
20.
目的:对现有硝酸甘油型大鼠偏头痛模型不均一稳定缺点予以改进,探究更为合理、有效模型建立方法和特征指标。方法:采用雄性SD大鼠,分别使用硝酸甘油无水乙醇注射液和硝酸甘油混悬液,按照12 mg/kg、10 mg/kg、8 mg/kg剂量造模并观察记录其行为学变化。用ELISA法检测模型血清和脑组织5-HT变化,确定较为合理、可靠且均一的改良硝酸甘油偏头痛模型。结果:成功复制大鼠体偏头痛模型。使用硝酸甘油混悬液,皮下注射用量为10 mg/kg时模型效果较均一,造模后20~60 min之间有显著的行为学变化,出现抖身现象,并以倦怠结束。结论:与现有的偏头痛模型比较,最显著的改进之处在于使用硝酸甘油混悬液,延长了模型标志性行为动作的持续时间,以特定时间段内出现明确的行为变化作为观察指标,避免了剂型剂量和个体差异带来的模型效果差异,从而提高了模型的均一性。 相似文献