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场站是气田集输的枢纽,也是高风险存在和集中的场所。本论文采用重大事故后果模拟分析法建立天然气泄漏速率估算模型、蒸气云爆炸模型,并以陕北某一天然气场站为例,借助Risk System软件对天然气泄漏速率和泄漏量以及蒸气云爆炸最大事故进行数值模拟。模拟分析结果有助于对天然气场站可能发生的各种事故进行风险评价,也有助于对各类风险大的危险危害因素提出对应的安全对策措施,确保安全生产。 相似文献
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The computational method of Large-Eddy Simulations has been used to study the weak, neutrally stable drainage flow within
tree canopies. The computational results show that a secondary velocity maximum that resembles a jet is formed within the
canopy under the nocturnal flow conditions. This jet-like flow is important in the analysis and measurements of the net ecosystem-atmosphere
exchange (NEE) for carbon dioxide (CO2). A uniformly distributed, plane source was placed within the canopy in order to simulate the nocturnal production of CO2. The NEE is calculated as the sum of the integration of the rate of change of the concentration of CO2 over the computational domain, the vertical turbulent flux measured directly by eddy-covariance (EC) method, and the advection
terms, which are not taken into account in the EC method. Numerical results of the velocity and concentration fields, within
and above the canopy, are presented and their impact on the CO2 transport is investigated in detail. The computational results show that 15–20% of NEE is drained out by the advection process
under the canopy. The results also show that the turbulent fluctuations in the lateral direction are also significant and
may result in 2–5% CO2 transport. 相似文献
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SPACSYS: Integration of a 3D root architecture component to carbon, nitrogen and water cycling—Model description 总被引:1,自引:0,他引:1
L. Wu M.B. McGechan N. McRoberts J.A. Baddeley C.A. Watson 《Ecological modelling》2007,200(3-4):343-359
It is an ongoing challenge to develop and demonstrate management practices that increase the sustainability of agricultural systems. Soil carbon and nitrogen dynamics directly affect soil quality, crop productivity and environmental impacts. Root systems are central to the acquisition of water and nutrients by plants, but are also a major pathway for the inputs of carbon and nutrients to soil. The complexity of both biotic and abiotic interactions, combined with stochastic changes in root architecture, makes it difficult to understand below-ground dynamics on the basis of experimentation alone. The integration of dynamic models of above-ground growth, three-dimensional root system demography, and interactions between plants and the environment, into one single model is a major challenge because of the complexity of the systems.In order to understand the interaction between a plant and the environment, it is advantageous to develop a model framework to integrate submodels that simulate various plant and environmental components. The objective of this paper is to outline a mechanistic and process-based model, which is capable of simulating interactions among environmental conditions around plants, plant growth and development, nitrogen and carbon cycles, with a three-dimensional root system submodel as an interface.The model presented in this paper is a mixed dimensional, multi-layer, field scale, weather-driven and daily time-step dynamic simulation model. The current version includes a plant growth and development component, a nitrogen cycling component, a carbon cycling component, plus a soil water component that includes representation of water flow to field drains as well as downwards through the soil layers, together with a heat transfer component. The components themselves and linkage among components are designed using object-oriented techniques, which makes the model robust, understandable and reusable. The components are implemented in the C++ programming language, and inputs and outputs of all components are organised as a database in either Microsoft® SQL Server 2000, Access 2000 or MySQL5.0. Root architecture is visualised by using the OpenGL graphics system. Preliminary validation with two separate experimental datasets shows that the model can reasonably simulate root systems, nitrogen cycling, water movement and plant growth. 相似文献
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Earlier rice phenology as a result of climate change can increase the risk of cold damage during reproductive growth in northern Japan 总被引:1,自引:0,他引:1
Hiroyuki Shimono 《Agriculture, ecosystems & environment》2011,144(1):201-207
The present study analyzed the impact of earlier rice phenology as a result of climate change on the risk of cold damage during reproductive growth using the historical temperature record from 1961 to 2010 at four locations in northern Japan. During this period, heading date has become 0.7-1.9 days earlier per 10 years. Air temperatures during the booting stage (6-15 days before heading) decreased by 0.18 °C per 10 years even though the air temperature on a given calendar date has increased slightly. The estimated potential yield losses caused by cold damage have increased since the start of the study period. Thus, the advance in phonological events as a result of global warming is likely to increase the risk of future yield losses, and this has important implications for future adaptation strategies (breeding new cultivars and changing crop management strategies) to reduce the risk of cold damage. 相似文献