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991.
城市用水灰色动态预测模型的研究与应用 总被引:2,自引:0,他引:2
科学地预测城市用水量对拟定城市发展规模具有十分重要的意义。城市用水量受很多因素的影响,是一个充满灰色现象的“灰系统”。利用灰色系统理论建立动态GM(1,1)模型预测城市用水量。实例证明,模型能较好地拟合实测数据并具有较高的预测精度。 相似文献
992.
番茄的结构-功能模型 Ⅰ:基于有限态自动机的3D形态构建 总被引:1,自引:1,他引:1
根据番茄的形态结构特点及其演变规则,应用有限态自动机的数学理论,研究建立了番茄动态发展的随机结构模型。该模型建立在对番茄结构的宏观抽象和生理年龄(PHYAGE)与生长年龄(GA)这两个最重要的基本概念之上,利用“事件驱动”的状态转移机制模拟了番茄生长过程、分枝过程和死亡过程,其中利用了二项随机分布模拟番茄的动态生长,离散的Markov链用于模拟番茄的分枝模式。番茄的有限态自动机模型完成了对主茎上节间长度、果实个数以及叶子结构的随机模拟。并利用试验统计分析获得的参数结果,模拟出番茄在不同生长阶段的3D结构。该动态的番茄结构模型,为与生理生态模型进行接口建立互影响、互反馈的结构-功能模型打下了基础。 相似文献
993.
耕作、残茬及施肥管理对土壤有机质动态变化影响的情景分析 总被引:7,自引:0,他引:7
Based on data from 10-year field experiments on residue/fertilizer management in the dryland farming region of northern China, Century model was used to simulate the site-specific ecosystem dynamics through adjustment of the model's parameters, and the applicability of the model to propose soil organic carbon (SOC) management temporally and spatially, in cases such as of tillage/residue/fertilization management options, was identified v/a scenario analysis.Results between simulations and actual measurements were in close agreement when appropriate applications of stover,manure and inorganic fertilizer were combined. Simulations of extreme C/N ratios with added organic materials tended to underestimate the measured effects. Scenarios of changed tillage methods, residue practices and fertilization options showed potential to maintain and enhance SOC in the long run, while increasing inorganic N slowed down the SOC turnover rate but did not create a net C sink without any organic C input. The Century model simulation showed a good relationship between annual C inputs to the soil and the rate of C sequestration in the top 20 cm layer and provided quantitative estimations of changes in parameters crucial for sustainable land use and management. Conservation tillage practices for sustainable land use should be integrated with residue management and appreciable organic and inorganic fertilizer application, adapted according to the local residue resource, soil fertility and production conditions. At least 50% residue return into the soil was needed annually for maintenance of SOC balance, and manure amendment was important for enhancement of SOC in small crop-livestock systems in which crop residue land application was limited. 相似文献
994.
Astrid?P.?Vasquez James?L.?Regens James?T.?GunterEmail author 《Journal of Soils and Sediments》2004,4(3):151-156
Background and Goal A number of global events have generated intense scientific scrutiny and public concern of polychlorinated dibenzo-p-dioxins (dioxin). DIoxins have been associated with a range of adverse health effects. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is recognized as among the most dangerous of the dioxin compounds, and was a contaminant found In one of the
herbicides used for vegetation control during the Vietnam conflict: Agent Orange. As a result of purging spray systems and
leaking drums of Agent Orange concentrate, TCDD contamination occurred in the soils surrounding Hardstand 7 at Eglin Air Force
Base, Florida. This research uses a multimedia model to estimate the TCDD concentrations in surface soil around Hardstand
7 for a 70-year time Interval beginning with observed surface soil concentrations 1984.
Methods Hardstand 7 is a nearly 40-m circular concrete and asphalt aircraft parking area. The hardstand was used as a staging area
for spraying equipment used to disseminate herbicide In a test area called C-52A within EAFB. Concentrated herbicide was also
stored in 208-L barrels for use with the equipment, and later, for disposal. In 1984, a field investigation characterized
the extent of TCDD contamination in surface soils around Hardstand 7 using a radial sampling protocol. The 1984 observed concentrations
and locations was used in a multimedia model, CalTOX, as an initial source term concentrations and locations to estimate expected
concentrations during the subsequent 70-years.
Results The results indicate that more than 94% of the TCDD observed in surface soils 1984 will remain after a 70-year period. Access
restrictions and remediation activities at the site eliminate bar verification of the CalTOX estimates. Conclusions. TCDD
is highly persistent in the soil medium and natural attenuation may not produce a significant decrease In soil concentrations.
Recommendation Active remediation actions may be required to prevent exposure to TCDD contamination surface soils. Verifying CalTOX concentration
estimates an Important step that should be performed, however, the, model provides an easy to use tool to estimate TCDD surface
soil contamination at herbicide storage or dispersion staging sites. 相似文献
995.
EPIC模型中土壤氮磷运转和作物营养的数学模拟 总被引:11,自引:0,他引:11
土壤侵蚀和生产力影响估算模型EPIC是国际上较有影响的水土资源管理和作物生产力评价动力学模型。本文简要介绍了EPIC模型中描述土壤氮磷养分运转与作物氮磷营养的基本原理及其主要数学方程。在作物和土壤微生物等生物因素,热量、降水等气候因素,施肥、灌溉和土壤耕作等管理因素的影响下,农田土壤氮素和磷素不断发生空间运移和形态转化。EPIC模型能够逐日定量描述土壤中氮磷养分的矿化与固定、硝化与反硝化、淋洗与挥发、流失与吸收、矿质磷循环、豆科作物固氮等运移、转化及作物吸收过程的变化速率和数量,揭示出土壤剖面氮磷运移、转化和作物营养的动态变化规律,可供农田土壤管理和作物营养定量评价研究中借鉴。 相似文献
996.
以往水土保持水文水资源效应研究所采取的方法均为水文法和水保法。由于这2种方法都不能系统地揭示水土保持对水循环影响的物理机制,并且采用的水资源评价口径只是单一的狭义水资源,使得研究成果不能真实反映水土保持的水文水资源效应。以狭义水资源和广义水资源为评价口径的基于物理机制的分布式水文模型则能克服水文法和水保法的严重弊端。评述分布式水文模型的研究进展;应用基于物理机制的分布式水文模型(WEP-L模型),以黄河流域的重点水土流失治理区——河口镇至龙门区间为例,对水土保持的水文水资源效应进行定量研究。结果表明:水土保持使广义水资源量增加72.6亿m3,增幅27.1%;使狭义水资源量减少9.0亿m3,减幅14.4%;使狭义水资源的构成发生了变化,即地表水资源量减小、不重复量和地下水资源量增加。 相似文献
997.
构建了集雨灌溉工程规划方案评价指标体系,提出了多层次灰色关联综合评价模型,对模型中的有关计算问题作了探讨。运用层次分析法合理地处理了各因子权重分配。最后通过工程实例说明了模型的应用。 相似文献
998.
Short-term gully retreat rates over rolling hill areas in black soil of Northeast China 总被引:1,自引:0,他引:1
Soil loss has become one severe problem in black soil areas of Northeast China after several decades of cultivation. Gully erosion is one of its main components. In this study, short-term gully retreat was monitored from 5 active gullies selected in representative black soil area during April 2002 to June 2004, using differential global positioning system (GPS). With the support of geographic information system (GIS), multitemporal digital elevation models (DEM) were constructed from the data collected by GPS and then used for further analysis. This presents a new method to compute the retreat rate of gully heads and the rate of soil losses caused by gully erosion. The results indicate that the average volumetric retreat rate was 729.1 m3 year− 1, corresponding with an average linear retreat rate of 6.2 m year− 1 in gully head and planimetric changes of 323.6 m2 year− 1 during the two monitored years, but more erosion took place during the second and third monitored period compared to the first. The erosion by freeze thawing and snowmelt accounts for a large percent. And this will be emphasized when rainfall is added in spring. If only considering the third monitored period, the conservatively estimated retreat rate by freeze thawing and snowmelt (i.e. before rainy season) may even reach 8.6 m year− 1 in gully head, with a volumetric rate of 120.9 m3 year− 1 and planimetric changes of 173.6 m2 year− 1. These results reveal that gully erosion is a great threat in the study area and conservation measures are urgently needed. Based on the analysis of multi-temporal DEM, one conceptual model for gully developing in black soil of Northeast China is proposed, which is supported by the data. 相似文献
999.
1000.