共查询到10条相似文献,搜索用时 125 毫秒
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Ho-Young Kwon Sabine Grunwald Howard W. Beck Yunchul Jung Samira H. Daroub Timothy A. Lang Kelly T. Morgan 《Agricultural Water Management》2010,97(1):112-122
An ontology-based simulation (OntoSim) is a unique data modeling environment where soil–plant-nutrient processes are represented as database objects and the user-defined relationships among objects are used to generate computer code (Java) for running the simulation. The aim of this study was to model hydrologic processes of sugarcane-grown organic soils utilizing OntoSim in the Everglades Agricultural Area (EAA) of South Florida. This OntoSim-Sugarcane model describes the complex hydrology of sub-irrigation and open ditch drainage commonly used on Florida farms.Model calibration was conducted by (i) selecting rectangular farm water management units (<12 ha), which are encompassed with farm ditches, from two farms in the EAA, (ii) assembling all relevant input data including water tables (WT) recorded at the monitoring farm well of each unit, and (iii) optimizing the fits between the simulated and observed daily WT during two consecutive water years (WY). By calibrating two site-specific parameters – lateral saturated hydraulic conductivities of soil profiles and vertical saturated hydraulic conductivity of the underlying limestone bedrock – good agreement between simulated and observed daily WT was obtained (Nash–Sutcliffe efficiency coefficient >0.65; coefficient of residual mass <1%) within the units during WY96–97 (May 1995–April 1997). The validation of the model during subsequent WY98–99 at both units also showed Nash–Sutcliffe efficiency >0.55 and coefficient of residual mass <3%. It indicated that OntoSim-Sugarcane is able to simulate daily fluctuations of WT within the farm units and estimate lateral drainage/sub-irrigation and deep seepage that significantly contribute to the water balance at farms in the EAA. Thus, it can be a promising management tool to provide farmers with accurate assessment of water movement in this agricultural area. 相似文献
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H.M. Keener 《Agricultural Systems》1979,4(2):79-100
Energy equations for partitioning energy utilisation in the bovine animal were written and utilised in a dynamic simulation model of beef animal growth. Mathematical models for the rates of anabolism and catabolism of stored products in the animal's body are presented. Estimates of the parameters used in the models were developed using experimental results and an experimental feeding trial. Computer simulations of a growing beef animal were compared with independent experimental data. Results indicated that the developed model can estimate bovine growth performance and the rates and modes of heat production under varying thermal and nutrient environments. 相似文献
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《Agricultural Systems》2008,96(1-3):37-48
A modular approach to simulation modelling offers significant advantages for its application to agricultural and environmental questions, including re-use of model equations in different contexts and with different user-interfaces; configuration of model structures that are most appropriate to a given problem; and facilitation of collaboration between modelling teams. This paper describes the Common Modelling Protocol (CMP), a generic, open and platform-independent framework for modular simulation modelling that is in widespread use. The CMP is distinguished from existing simulation frameworks by taking an explicitly hierarchical view of the biophysical system being simulated and by representing continuous and discontinuous processes equally naturally. Modules of model logic are represented in the CMP by entities known as “components”. Each component may possess “properties” that convey the value of the quantities in its equations and “event handlers” that compute model logic. Low-level information-transfers in the CMP are carried out by means of a message-passing system. Co-ordinated sequences of messages carry out tasks such as initialization, exchange of variable values and the control of computation order. Extensible Markup Language (XML) is used in the protocol for tasks such as denoting data types, submitting simulations for execution and describing components to user-interface software. Examples are presented showing how the CMP can be used to couple modules developed by different teams and to configure a complex model structure. The choices and trade-offs encountered when building a framework for modular simulation are analyzed, using the CMP and other simulation frameworks as examples. The kinds of scientific issues that arise when the CMP is used to realize collaboration between modelling groups are discussed. 相似文献
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A simulation model of a lowland sheep system has been constructed. Biological components are modelled using state variables and flow equations, the variation between animals in a flock being simulated using random number generators. The model was validated against experimental results. Management rules were included to evaluate the effect of different management regimes on biological and economic output from the system and some example results are presented. 相似文献
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Farm management models often produce average crop shares over a number of years, whereas models from the natural sciences often require inputs of sequences of crops grown on a specific field over several years. In interdisciplinary modelling, this difference can be a relevant obstacle. To bridge this gap, an approach is presented that allows disaggregating results from farm management models to the level required by many natural science models. The approach presented includes two methodological innovations: first, minimum cross entropy is used to ensure a unique solution when modelling a linear programming model at the field level, even when objective and constraint coefficients are identical for different fields. Second, the use of a calibrated Markov chain approach allows the creation of land-use sequences that are closer to the linear programming model’s results than an unconditional stochastic simulation would be. The calibrated Markov chain makes use of a prior matrix of transition probabilities that can be empirically derived. Both simulations and analytical calculations with case study data show that the variances of the Markov chain approach are systematically lower than those yielded by a simple stochastic simulation approach. The approach introduced in this paper can improve the coupling of farm-level economic models with natural science models at the field level. 相似文献
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随着现代农业自动化水平的不断提高,更多具有自主作业能力的自动化农业机械被运用到了农业生产过程中,但农机需要精度较高的零部件与之匹配才能实现精准化作业。为了提高拖拉机零件的数控加工效率和精度,将UG软件引入到了零部件的数控加工工艺设计过程中,根据零部件的模型进行了工艺分析和参数确定,在确定好刀具和坐标系、加工工序及刀具走刀路径后,采用UG自动编程技术生成了加工代码,从而有效地提高了数控加工的效率和质量。为了验证方案的可行性,以拖拉机轴类的数控加工为例,对方案进行了可行性验证。验证结果表明:采用UG软件可以自动生成刀具的加工轨迹,并实现加工过程的仿真模拟,最后形成加工代码,证明在拖拉机零部件的数控加工过程中使用UG自动编程是可行的。 相似文献