Results 1 - 10 of 4840
Results 1 - 10 of 4840. Search took: 0.024 seconds
|Sort by: date | relevance|
[en] Daily rainfall and temperature data of 158 weather stations in eight European countries and Iceland are investigated to set up a weekly cycle. The time series are divided into five time slices that are analyzed separately. As they depend strongly on the data availability, the significance of weekly cycles is generally higher for the past three time slices of 1931-1960, 1961-1990, and 1991-2005 compared to the two earlier analyzed time slices of 1871-1900 and 1901-1930. Precipitation does not follow any distinct significant weekly cycle. For temperature, however, significant weekly cycles exist in all analyzed countries. The weekly periodicities cannot be explained by random effects. A clear weekly signal is detected by means of a stationary block bootstrap approach. The cycles of temperature vary with the region and the time slice. However, they are found to be more stable for the last two time slices. For the dominant pattern of the weekly cycle in Germany, a coinciding significant weekly cycle of the large-scale circulation is detected for the time slice 1991-2005. In Germany, persistence can be observed for the weekday holding the minimum value of the temperature variables. The minimum is observed to occur on Saturday for the past two time slices. When judging from significant results exclusively, most other countries also show persistence for the past two time slices, except for the weekday with the maximum value of the temperature variables. This weekday either is Tuesday for Iceland and the UK or Wednesday for Sweden and Norway.
[en] Formation processes of caoline crust of weathering on garnites are accompanied with uranium evacuation (on the average 66%) and thorium (82%). Main uranium share in granites is related to accessor minerals, alterated biotite and intergranular sufures, in caoline crust of weathering - with caolinite, selvages of iron and titanium oxides and hydroxides. Two mechanisms of uranium extraction from accessor minerals exiting in parallel have been established: uranium transition to solution from edge parts of grains and microcracks and gradual solutions of minerals with transfer of all their components to the solution
[en] Asphalt is a sticky, black and highly viscous liquid or semi-solid that is presented in most crude petroleum and in some natural deposits. As is well known, asphalt has been the preferential choice in pavement construction since excellent utility of pavement, however, as other organic substances, it is also subjected to aging phenomena evolving with time. Asphalt aging is one of the principal factors causing deterioration of asphalt pavements. The photodegradation of asphalts must be considered in the study of the performance of asphalt pavement, especially in geographical regions where high solar radiation intensity occurs. It has an important influence in asphalt aging in tropical places as Brazil. Many methods have been applied to simulate aging of bitumen. It was just a simulation but not real aging asphalt. In this study we submitted the asphalt to the weather as sun and rain. Periodically, during 430 days, the XRD profiles were done and the results analyzed. The scattering measurements were carried out in 0-20 reflection geometry using a powder diffractometer Shimadzu XRD-6000. Scans were typically done from 8 deg to 28 deg every 0.05 deg. The parameters FWHM and peak centroid were analyzed. From 0 until 180 days the aging was faster. The peaks were marked and analyzed with the pass of time. The crystallinity of asphalt increase with weather exposition. Some angles of profiles changed the position indicating change of atomics plans. (author)
[en] A brief survey is made of previous methods that have been used to predict rainfall trends or drought spells in different parts of the earth. The basic methodologies or theoretical strategies used in these methods are compared with contents of a recent theory of Sun-Weather/Climate links (Njau, 1985a; 1985b; 1986; 1987a; 1987b; 1987c) which point towards the possibility of practical climatic predictions. It is shown that not only is the theoretical basis of each of these methodologies or strategies fully incorporated into the above-named theory, but also this theory may be used to develop a technique by which future monthly rainfall patterns can be predicted in further and finer details. We describe the latter technique and then illustrate its workability by means of predictions made on monthly rainfall patterns in some East African meteorological stations. (author). 43 refs, 11 figs, 2 tabs