Nonlinear chemical couplings in the tropospheric NO x -HO x gas phase chemistry     

J. Zimmermann  D. Poppe 《Journal of Atmospheric Chemistry》1993,17(2):141-155

A bifurcation phenomenon with relevance to atmospheric chemistry is discussed. The gasphase reactions in the troposphere exhibit two types of temporal evolution which are controlled by the strength of the source,Q, of nitric oxide, NO, via the nonlinear chemical coupling between the hydrogen oxides and nitrogen oxides chemistry. IfQ remains below a threshold value, all short-lived species, including NO, approach steady-state concentrations, while above the threshold bifurcation to another state with increasing (nonstationary) NO concentrations accompanied by a depletion of the OH and HO₂ abundances takes place.  相似文献   

POPULATION DYNAMICS AND PRODUCTION OF NEANTHES JAPONIC A (IZUKA)IN A SHRIMP POND   总被引：1，自引：0，他引：1  

丘建文  吴宝铃 《中国海洋湖沼学报》1993,11(4):360-367

During late February to mid-March, 1991, when mature N. japonica swarmed in the sea surface off Jimo County, Qingdao, seawater containing numerous early embryos was pumped into a nearby 2.7 ha. muddy-sand shrimp pond, where the embryos continued to develop. 800000 Penaeus chinensis seedlings were introduced into the pond on May 30, 1991. Monthly benthic samplings were carried out to determine the population dynamics and production of N. japonica in this atypical environ -ment.The density of N. japonica varied from 0 to 20400 ind./m2. The predation of P. chinensis was considered to be responsible for the mass mortality of N. japonica in June through July, when the worms were 2.2-3.3cm in length and lived in the top 2-4cm sediment. From August to September of 1991, the hottest period in the site, there was no substantial mortality of N. japonica as reported in earlier literature. This was explained by the deeper burrowing of the' worms that protected them from predation by shrimps.Monthly biomass ranged f  相似文献   

近代回归分析在交通调查分析建模中的应用     

杨仁  王冬根 《武汉大学学报(信息科学版)》1990,(3)

本文以出行发生量模型的建立为例,较为系统地讨论了近代回归分析中的自变量选择及回归诊断方法在交通调查分析建模中的应用。分析了在获取调查数据后,如何借助回归自变量选择方法来选择最佳自变量子集,以确定简捷的回归模型;文中应用回归诊断方法,讨论了修正回归模型、探测错误的调查数据的方法,从而为建立简捷、高精度的交通模型打下了基础。最后,作者提出了应用自变量选择及回归诊断方法建立出行发行量模型的一般步骤。  相似文献   

Modelling the effects of motion on primary production in the mixed layer of lakes     

John C. Patterson 《Aquatic Sciences - Research Across Boundaries》1991,53(2-3):218-238

A model of the time dependent relationship between productivity and light intensity following changes in light intensity is briefly described. The model incorporates two response timescales simulating initial response and photoinhibition, although additional timescales could easily be incorporated. The model is calibrated against one set of time dependent data, and applied to two simple models of motion in the upper mixed layer of a lake. The two models are: organised motion simulating Langmuir cells, and disorganised motion simulating the turbulent velocity field associated with surface wind stirring. The depth and therefore light histories for a number of photosynthesising particles are calculated by these models, and used by the productivity model to calculate mean productivities. The results show that the influence of the time dependent nature of the productivity relationship depends on the ratio of the mixed layer depth to the euphotic depth, and to a less extent, on the rate at which the particles circulate in the mixed layer.  相似文献   

The control of the production process of phytoplankton by the physical structure of the aquatic environment with special reference to its optical properties   总被引：2，自引：0，他引：2  

Barbara B. Prézelin  Max M. Tilzer  Oscar Schofield  Clivia Haese 《Aquatic Sciences - Research Across Boundaries》1991,53(2-3):136-186

This tutorial was designed for nonbiologists requiring an introduction to the nature and general timescales of phytoplankton responses to physical forcing in aquatic environments. As such, an effort was made to highlight biological markers which might assist in identifying, measuring and/or validating physical processes controlling the variability in the distribution, abundance, composition and activity of phytoplankton communities. Given the recent advances in environmental optics and remote sensing capabilities, a special emphasis was placed on the nature and utility of phytoplankton optical properties in current bio-optical modelling efforts to predict temporal and spatial variability in phytoplankton productivity and growth.  相似文献   

北京地区“环流－降水－谷物”系统的短期振动研究          下载免费PDF全文

黄嘉佑  张镡  颜明元 《应用气象学报》1994,(3)

文章用因子分析方法提取北京地区小麦气象产量主要特征及代表序列，并对该序列和北京地面气象要素的关系用交叉谱进行研究。发现它们在前期秋冬季中的４－６年的周期振荡（中心周期为４．５年）中有显著的相关，当前期秋季和冬季的降水量和气温在振荡中处于正距平时，当年的气象产量为丰年，反之为欠年；进一步对该序列与大气环流的静力和动力物理量之间关系研究发现它们在同样的周期振荡中有十分强烈的表现，尤其表现在与动力物理量上。研究结果进一步证实“环流－降水－谷物”系统的存在，并揭示在短期气候振动（４－６年）上的规律性。  相似文献   

The effect of gas-phase chemistry on aqueous-phase sulfur dioxide oxidation rates     

William R. Stockwell 《Journal of Atmospheric Chemistry》1994,19(3):317-329

The rates and mechanisms of both gas and liquid phase reactions for the oxidation of sulfur dioxide play an important role in the production of atmospheric acids and aerosol particles. Rhodeet al. (1981) concluded that sulfate production rates were highly non-linear functions of sulfur dioxide emission rates. Their modelling study used an HO _x termination mechanism for the HO—SO₂ reaction in the gas-phase. Stockwell and Calvert (1983) determined that one of the products of the overall reaction of HO with sulfur dioxide was an HO₂ radical. The National Research Council (1983) using a version of the Rhodeet al. (1981) model modified to include HO₂ production from the HO—SO₂ reaction concluded that sulfate production becomes much more linear with respect to reductions in sulfur dioxide emissions. However, the cause of this increased linearity was not explained by the National Research Council report. It is demonstrated that the increased linearity is due to the coupling of gas-phases and aqueous phase chemistry. The gas-phase sulfur dioxide oxidation mechanism has a very significant effect on hydrogen perodide production rates.  相似文献   

Aggregate resources: Production and environmental constraints     

R. Poulin  R. C. Pakalnis  K. Sinding 《Environmental Geology》1994,23(3):221-227

Aggregates are produced from sand and gravel deposits or from bedrock sources. Production sites are numerous to minimize transport and are more and more in a competing land use position. Urbanization, while creating a market, also sterilizes deposits and pressures producers to relocate further from populated areas. Regulating and permitting quarries is an issue in regions with growing populations. This regulatory environment may cause exploitation schemes to evolve towards greater recycling, importing, and marine production, for example. These changes may be entirely attributable to increased environmental constraints on producing operations and not on conventional mining constraints such as overburden, ore grade, and costs of operation.  相似文献   

A critical analysis of processes governing the nutrient profiles in the ocean     

R Ramesh  D Lal 《Journal of Earth System Science》1994,103(1):1-15

We have theoretically considered the problem of interpretation of nutrient profiles in the upper ocean (100–2000m). We compare the experimental depth profiles of nonconservative tracers, both stable and radioactive, with solutions of one-dimensional steady state transport equations of increasing complexity including situations not encountered in the real oceans. Apart from gaining insight into the nutrient transport processes, this analysis is useful in offering a way to obtain operational estimates of depth dependent/independent eddy diffusivity and dissolution fluxes in the ocean. These parameters are essential for estimating new production, total production and burial of carbon in the sediments.  相似文献   

叶县盐田探采结合井钻井工艺          下载免费PDF全文

王道乐 《探矿工程》1994,(3):44-46

针对叶县盐田的地质条件，上部无岩心钻进，采用大钻压、低转速、高泵压、大泵量喷射钻井的快速钻进技术；下部取心钻进，采用小钻压、高转速、低泵压、小泵量的取心钻进技术。采用防塌淡水泥浆与饱和盐水泥浆分别治理取得了较好的技术效果。  相似文献