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321.
Zhou Daoqi 《Solar physics》1993,147(2):225-239
In this paper we suggest that penumbral filaments are a phenomenon of magnetohydrodynamic instability, developed in a stable and uniform magnetic field of sunspots during a dissipation process. We have solved local magnetohydrodynamic disturbance equations and have obtained the necessary condition for filament instability mode, that the ratio of filament length to width must be larger than the ratio of Alfvén speed to sound speed. We have also obtained correlations between two fluctuations from their phase difference. Although there are two correlations between the fluctuation of temperature (or filament intensity) and (1) the fluctuation of magnetic field, and (2) the fluctuation of the flow during the phases of developing and dissipating of the filament, we cannot distinguish whether the correlation is associated with the light filament or dark filament and we cannot decide whether the phase difference is 0° or 180° from tg() = 0. However, we can make a judgment: if the correlation is associated with a light filament during its development phase, it will be associated with a dark filament during its dissipation phase, andvice versa. In addition, there are no correlations between the fluctuations mentioned above for a stable filament, because the phase difference of the filament is changing with time.The phase differences of filaments are related to the existence of a gravitational field.  相似文献   
322.
农田土壤水分的随机模拟和预报   总被引:3,自引:0,他引:3  
  相似文献   
323.
3D spatial data model and simulating are the core of 3D GIS can be adopted in different domains. A data model based on Quasi Tri-Prism Volume (QTPV) has been proposed. QTPV definition and its special cases have been discussed. Using QTPV and its special cases, irregular natural geological bodies and regular subsurface engineering can be described efficiently. The proposed model is composed of five primitives and six objects. Data structures and topological relationship of the fives primitives and three objects describing stratigraphy are designed in detail Some schemes are designed for the QTPV modelling of stratigraphy and subsurface engineering according to modelling data. The model manipulation method of QTPV cutting by an arbitrary plane is discussed. Using VC 6.0 programming language integrated with SQL database and OpenGL graphic library under windows environment, a system prototype 3DGeoMV has been developed. The experiment result shows that the QTPV model is feasible and efficient in modelling subsurface engineering.  相似文献   
324.
The ecological environment in the East China Sea (ECS) and the Yellow Sea (YS) has changed significantly due to sea-level rising and the Kuroshio incursion since the last deglaciation. In this study, biomarker records of core F10B from the mud area southwest off Cheju Island (MSWCI) were generated to evaluate phytoplankton productivity and community structure changes in response to environmental evolution during the last 14 kyr. The contents of diatom, dinoflagellate and haptophyte biomarkers (brassicasterol, dinosterol and C37 alkenones) display similar trends, with increasing phytoplankton productivity during the last 14 kyr due to the increased influences of the Kuroshio, and especially due to the eddy-induced upwelling during the late Holocene. On the other hand, the contents of terrestrial biomarkers (C28 +C30 +C32 n-alkanols) and terrestrial organic matter (TOM) proxies (TMBR’ and BIT) all reveal decreasing TOM input into the area around the sampling site for the 14 kyr, mostly due to sea-level rising. Phytoplankton biomarker ratios reveal a shift from a haptophyte-dominated community at 6.2–2.5 kyr BP to a diatom-dominated community at 2.5–1.45 kyr BP, likely caused by a stronger cold eddy circulation system at 2.5–1.45 kyr BP in the MSWCI.  相似文献   
325.
本工程场地为欠固结厚层填土现状,为保证承台底不脱空,采用粉喷桩加固承台底欠固结填土,并在粉喷桩内施工静压桩的技术对策,这样既加固了填土,又提高了静压桩单桩承载力,获得了良好的效果。  相似文献   
326.
This study documents the variability of surface sensible and latent heat fluxes in five regions of China (Northwest China, the Tibetan Plateau, Northeast China, North China, and Southeast China) using the ERA-40 reanalysis for the years 1960–2000. The surface sensible and latent heat flux variations are remarkably different in Northwest and Southeast China. The seasonal variation of the surface sensible heat fluxes is largest in Northwest China and smallest in Southeast China. In contrast, the seasonal variation in latent heat flux is largest in Southeast China and smallest in Northwest China. The interdecadal variation of surface sensible and surface latent heat fluxes strongly depends on both the region and season. The trends in surface sensible and latent heat fluxes in all four seasons are mainly caused by variations in both the land–air temperature difference and in the specific humidity. There is also a limited contribution of wind speed in some regions, depending on the season.  相似文献   
327.
Abstract In this paper such minerais as apatite, zircon and biotite from granites were determined and analyzed by secondary ion mass spectrometry (SIMS) for their isotopic ages, REE composition, trace elements and volatile components with an attempt to shed light on the origin and formation environments of the Jinningian granites in the Yunnan sector of the Kangdian (Xikang- Yunnan) earth's axis. The results show that the apatites, zircons and biotites of different geneses possess different fingerprint characteristics. Some correlations have been found between trace elements and volatile components contained in the minerais from granties.  相似文献   
328.
东北北部冷暖旱涝趋势的初步研究   总被引:8,自引:2,他引:8  
根据1951~1999年黑龙江省代表站的历年逐月的气温、降水量资料,用计算趋势系数的方法,研究了东北北部冷暖旱涝趋势的问题。结果指出:进入90年代,东北北部夏季气温变暖现象更加显著;但过渡季节气温变暖的趋势已经结束;旱涝趋势的变化比冷暖趋势的变化更为复杂,具有不同的季节特征和地域特征。  相似文献   
329.
介绍一种IP传输方案。该方案通过地震数据IP传输及存储单元(ITU)、IP流多串口服务器完成,能实现单个台站与多个台网中心的Internet传输、单个台站与多个台网中心的专线传输、地震台网中心之间的Internet连接、远程数据下载及参数设置等多种传输方式,该传输方案具备实时性、可压缩性、多路服务、安全性、数据在线保存、传输费用低、操作简单等特点。  相似文献   
330.
Hydrogeochemical characteristics of central Jianghan Plain, China   总被引:2,自引:0,他引:2  
The central Jianghan Plain is the semi-closed basin in the middle reaches of Yangtze River. A total of 78 water samples targeting groundwater were collected from 75 sites in this study site, the area between Yangtze River and Han River, including rivers and lakes for temperature, pH, electrical conductivity (EC), total dissolved solids (TDS) and ion composition measurements. Correlation matrix was used to assess the geochemical and anthropogenic processes. The most confined groundwater was grouped into HCO3–Ca–Mg, while phreatic groundwater and surface water had a more diversified hydrochemistry. The spatial variation in overall water quality as well as comparison with WHO (World Health Organization) standards for drinking water is illustrated. Mn, As and NO3 ? concentrations were found to exceed the allowable limits for drinking water of WHO guidelines, and they also show remarkable spatial variations. Abnormally high nitrate concentration, up to 150–190 mg/l, was found only in phreatic groundwater, which suggested that the nitrate pollution might be caused by agricultural activities. The present study may be helpful in further studies concerning water quality issues in this area where groundwater is a vital source for drinking and other activities.  相似文献   
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