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751.
The availability of observed daily solar radiation (OSR) is restricted to recent years. Its estimation through different methods is necessary to develop long-term data sets for agricultural and environmental applications. The objective of this study was to analyze the impact of using generated daily solar radiation (GSR) on simulated growth and yield of cotton, maize, and peanut. Nine locations representing Georgia's major crop belt were selected. Daily weather data from the Georgia Automated Environmental Monitoring Network (AEMN), including solar radiation, maximum and minimum temperature, and precipitation, were duplicated. The OSR was removed from one set and then generated using a stochastic procedure. The Cropping System Models (CSM)-CROPGRO-Cotton, CERES-Maize, and CROPGRO-Peanut of the Decision Support System for Agrotechnology Transfer (DSSAT) v4 were used to simulate crop growth and yield at each location with both OSR and GSR and for rainfed and irrigated conditions. The statistical analysis included summary statistics, Pearson's coefficient of correlation, mean squared deviation (MSD) and its components, namely: squared bias (SB), squared difference between standard deviations (SDSD), lack of correlation weighted by the standard deviations (LCS), and regressions. Within locations, for the three crops under rainfed and irrigated conditions, GSR did not significantly affect simulated total evapotranspiration and aboveground biomass and yields. For the three crops, deviations of simulated water use and yields from GSR with respect to simulated water use and yields from OSR were lower for the rainfed than for the irrigated conditions. Yields from the CSM-CROPGRO-Cotton and -Peanut models had lower deviations than yields from the CSM-CERES-Maize model. LCS was the major component of the MSD suggesting that the extent of the difference between standard deviations of GSR and OSRG could affect the outputs of the crop models. Nevertheless, for most locations none of the MSD components of the GSR showed significant correlation with simulated yields and the overall performance of the models was not affected. It can be concluded based on the results of this study that GSR can be used as an input for crop model simulation models when OSR is not available. 相似文献
752.
A New Approach for the Flocculation Mechanism of Chitosan 总被引:2,自引:0,他引:2
A peak III/I ratio (peak) in pyrene-fluorescence spectrum was used to measure the polarity of microenvironment of chitosan adsorbing pyrene molecules. The authors detected the pyrene-fluorescence spectrum of chitosan with different degrees of deacetylation (DD) and determined the relationship between the flocculation of bentonite colloid and the peak of chitosan with a different molecular weight (MW) and DD. It can be concluded that MW rather than DD plays a key role in the flocculation and that bond bridging rather than charge neutralization dominates the flocculation with chitosan from a microenvironmental structure of view. 相似文献
753.
754.
起重机结构疲劳剩余寿命评估方法研究 总被引:3,自引:2,他引:3
针对机械结构的主要破坏形式——疲劳破坏,以桥式起重机焊接箱形主梁为研究对象,根据断裂力学Paris-Erdogan方程,结合Miner疲劳损伤累积理论,应用实验所得数据,推导出疲劳剩余寿命公式。采集不同类型,不同额定起重量起重机一段时间内相应起重量的工作次数数据,以模拟出危险点处相应的载荷谱。以VC++为开发平台,研制完成桥式起重机疲劳剩余寿命评估软件。该软件可模拟实现普通、铸造桥式起重机的疲劳剩余寿命估算,并与实验结果进行比较,表明具有较高的吻合性和实用性。 相似文献
755.
Influence of Social, Biophysical, and Managerial Conditions on Tourism Experiences Within the Great Barrier Reef World Heritage Area 总被引:1,自引:0,他引:1
N = 1475) traveling with tourism operations of different sizes who traveled to different sites completed surveys. Results indicated
that snorkelers who traveled with larger operations (more people and infrastructure) differed from those traveling with smaller
operations (few people and little on-site infrastructure) on benefits received and in the way that specific conditions influenced
their enjoyment. Benefits related to nature, escape, and family helped to define reef experiences. Conditions related to coral,
fish, and operator staff had a positive influence on the enjoyment of most visitors but, number of people on the trip and
site infrastructure may have the greatest potential as setting indicators. Data support the potential usefulness of visitor
input in applying the LAC concept to a marine environment where tourism and recreational uses are rapidly changing. 相似文献
756.
以上海某化工工业园区为目标区域,针对典型的大气VOCs污染过程,通过耦合高时间分辨率GC-MS在线监测、拉格朗日大气扩散模型、VOCs源谱及相似度分析等技术手段,开展了小尺度大气VOCs的精细化溯源.结果表明,针对敏感点监测到的VOCs高值时刻,拉格朗日大气扩散模型能够追踪主要的气团来向及企业潜在贡献,空间分辨率达到1... 相似文献
757.
758.
在加速腐蚀的基础上,通过对Q345铁塔材料的静强度和疲劳试验,研究了宁波地区大气腐蚀环境对Q345铁塔材料力学性能的影响。试验表明,5 a内的加速腐蚀对Q345镀锌材料静强度的影响可以忽略;Q345镀锌材料在当量腐蚀前4 a,腐蚀的形式为均匀腐蚀与点蚀共存;当量加速腐蚀1 a后的疲劳强度无显著降低;加速腐蚀3 a后疲劳强度降低6.2%;4 a后疲劳强度降低12.7%,对应在95%置信度和95%可靠度下的寿命则分别降低25%和46.5%;加速腐蚀第5年,由于均匀腐蚀的发生,削减了腐蚀坑深度,使得其对"腐蚀坑深度"敏感的疲劳强度与第4年相同。 相似文献
759.
760.
太阳光/硫掺杂TiO2体系对双酚A的氧化性能研究 总被引:1,自引:0,他引:1
利用小试试验研究了太阳光和硫(S)掺杂TiO2体系对水中双酚A(BPA)的降解效能及影响因素.结果表明,太阳光/S掺杂TiO2体系对纯水中BPA的去除效能较太阳光/TiO2体系显著提高,30 min时的去除率分别为79%和49%,且两体系对BPA的降解过程均很好地符合拟一级反应动力学模型;H2O2的投加量对两体系氧化BPA的性能均有显著的影响,但其最佳投加量不同(两体系的最佳H2O2浓度分别为20 mg/L和15 mg/L,太阳光/S掺杂TiO2比太阳光/TiO2体系高5 mg/L);较低的pH值有利于两体系中BPA的降解,pH为5.5时的反应速率常数比pH为8.5时高50%左右;腐殖酸会不同程度的降低两体系对BPA的降解速率,其影响均可以用二次方程来表示.此外,腐殖酸对太阳光/S掺杂TiO2体系的弱化作用要明显强于对太阳光/TiO2体系的,原因在于腐殖酸不仅会与BPA分子竞争.OH,而且会吸收部分可激发TiO2产生.OH的可见光. 相似文献