Simulating methane emission from a Chinese rice field as influenced by fertilizer and water level     

Z. Yu  X. Shangguan  D. Pollard  E. J. Barron 《水文研究》2003,17(17):3485-3501

Natural and agricultural wetlands are considered to be the major sources of global atmospheric methane (CH₄). A one‐dimensional model was developed to simulate methane emission and used to examine the influence of various physical processes on the rate of methane emission. Three processes involved in the methane emission are implemented in the model: production, reoxidation and transport. Three transport pathways were considered: diffusion across water–air or soil–air interfaces, ebullition and diffusion through plants. These pathways are influenced by soil properties, plant growth, water‐table conditions, temperature and external inputs (e.g. fertilizer). The model was used to examine the seasonal variation of the methane emission at a rice field in Hunan, China, which was observed during a field experiment for consecutive (early and late) rice seasons in 1992. The observed seasonal variations of methane emission, and role of plants in transporting methane to the atmosphere, are captured by the model simulation. Further model applications were conducted to simulate effects of fertilizer and water‐level condition on the methane emission. The results indicate that unfermented organic fertilizer produces a higher methane emission rate than mineral fertilizer. The simulations with treatments of a deep‐water covering and constant moisture reduced the methane emission. The rice field study provides a framework for further development of the model towards simulations based on spatially distributed variables (e.g. water table, soil temperature and vegetation) at a regional scale. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

A 59-second period in the very high energy gamma-ray emission from the Geminga pulsar     

Yu. I. Neshpor  A. A. Stepanyan 《Astronomy Letters》2001,27(12):794-798

An analysis of our observations of the Geminga object with the GT-48 ground-based gamma-ray telescope has shown that its very-high-energy gamma-ray flux is modulated with a 59-s period. The 59-s period and its time derivative previously inferred from satellite data have been confirmed. According to our data, the period was 61.94 s in 1997 at MSD=50573. The statistical significance of this result is (1?4.5)×10^?4.  相似文献   

河外H_2O超脉泽辐射     

徐烨  蒋栋荣  郑兴武  俞志尧 《天文学进展》2001,(3)

介绍了近年来河外Ｈ２Ｏ超脉泽的主要观测结果。Ｈ２Ｏ超脉泽通常起源于活动星系核中央的拱核盘。它们主要寄生在 Ｓｅｒｆｅｒｔ ２星系或低电离核区。至今为止，已有２０个星系探测到Ｈ２Ｏ超脉泽。脉泽辐射的各向同性光度为１０～６０００Ｌ⊙。所有超脉泽星系显示出核的活动，显然，脉泽是由核活动所产生的射电和Ｘ射线光子或激波来抽运的。Ｈ２Ｏ超脉泽倾向存在于高倾斜度的星系，这使得沿视线上的分子柱密度增高，产生足够大的放大光深。最有可能产生Ｈ２Ｏ超脉泽辐射的星系应有一个包含着射电源的侧向的分子盘以及一个适当的抽运机制。  相似文献   

A Critical review of theoretical models of negatively polarized light scattered by atmosphereless solar system bodies     

Yu. G. Shkuratov  K. Muinonen  E. Bowell  K. Lumme  J. I. Peltoniemi  M. A. Kreslavsky  D. G. Stankevich  V. P. Tishkovetz  N. V. Opanasenko  L. Y. Melkumova 《Earth, Moon, and Planets》1994,65(3):201-246

About a dozen physical mechanisms and models aspire to explain the negative polarization of light scattered by atmosphereless celestial bodies. This is too large a number for the reliable interpretation of observational data. Through a comparative analysis of the models, our main goal is to answer the question: Does any one model have an advantage over the others? Our analysis is based on new laboratory polarimetric and photometric data as well as on theoretical results. We show that the widely used models due to Hopfield and Wolff cannot realistically explain the phase-angle dependence of the degree of polarization observed at small phase angles. The so-called interference or coherent backscattering mechanism is the most promising model. Models based on that mechanism use well-defined physical parameters to explain both negative polarization and the opposition effect. They are supported by laboratory experiments, particularly those showing enhancement of negative polarization with decreasing particle size down to the wavelength of light. According to the interference mechanism, pronounced negative branches of polarization, like those of C-class asteroids, may indicate a high degree of optical inhomogeneity of light-scattering surfaces at small scales. The mechanism also seems appropriate for treating the negative polarization and opposition effects of cometary dust comae, planetary rings, and the zodiacal light.  相似文献   

Corrections to the paper by M.Yu. Petukhov and Yu.V. Petukhov “Parametric generation of acoustic-gravity waves by Alfvén Waves in the solar atmosphere,” Astron. Lett. 28, 335 (2002)     

M. Yu. Petukhov  Yu. V. Petukhov 《Astronomy Letters》2003,29(9):640

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拉格朗日插值法在渔业资源评估上的应用     

陈文河  邵青 《广东海洋大学学报》2003,23(6):35-38

应用拉格朗日插值法拟合鱼类体长与体重之间的函数关系 ,使用计算机VB语言进行编写程序 ,与常用的线性回归法、Ricker法进行比较 ,得出体长与体重的关系式为Pn(x) =∑nk=0yklk(x)=∑nk=0(∏nj=0j≠kx-xjxk-xj)yk 。  相似文献   

智能照明系统在现代建筑照明中的应用研究   总被引：1，自引：0，他引：1  

陈丹 《成都信息工程学院学报》2007,22(6):735-738

在对传统照明系统和智能照明系统进行对比分析的基础上,剖析了智能照明系统的控制策略,并结合实际的工程应用,着重讨论了基于ABB I-Bus产品的智能照明控制系统的实现,结果表明该系统具有高效、便捷、节约能源等优点.同时,还对系统与建筑物楼宇自控系统问的系统集成方式进行了研究.  相似文献   

小杂鱼脱脂技术的研究     

陈培基  李来好  李刘冬  刁石强 《广东海洋大学学报》2003,23(6):21-26

以小杂鱼或低值鱼为原料 ,采用常温溶剂萃取法进行脱脂 ,研究了不同溶剂、溶剂混合比、流速和萃取时间对鱼类脱脂的影响。结果表明 ,在常温下用等体积的异丙醇和乙酸乙酯混合溶剂 ,以流速 4～ 8mL/min连续萃取 4～ 6h ,脱脂鱼肉的脂肪平均含量w为 0 .19%,脱脂率高达96 .2 6 %。该方法的溶剂损耗量为加热溶剂萃取法的 1/3倍。  相似文献   

桂西古侵蚀沉积间断面型金矿床(续载)     

陈开礼 《南方国土资源》2001,14(1):37-40

古侵蚀沉积间断面型金矿是桂西的主要金矿床类型。文章着重分析该类型金矿成矿地质条件 ,论述矿床成因及成矿机理 ,认为此类型金矿易采易冶 ,经济效益显著 ,建议加大开发力度。  相似文献   

我称道退耕还林,写这篇文章正是基于斯--退耕还林交响曲     

陈廷一 《国土资源》2005,(11):4-13

人类文明是需要付出代价的!当代中国退耕还林是生态恢复再造秀美山河的宏伟工程,也是一项惠及和影响子孙后代的文明工程.这项工程总投资3400亿元,工期10年（2000年至2010年）.它与三峡工程,青藏铁路,南水北调,西气东输,南电北输等工程一样举国瞩目.但是最体现农民利益、最受农民欢迎的当数共和国退耕还林工程.  相似文献