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21.
Pavel Voráček 《Astrophysics and Space Science》1982,81(1-2):85-94
Four situations are shown where the Schwarzschild metric cannot be used or is subject to unsurmountable problems. The first is the question of a metric useful for PPN-formalism checking different gravitational theories. The second problem occurs in connection with Mach's principle, when the flatness of the spacetime inside a massive hollow sphere is a generally accepted solution. The metrical discontinuity on the same spherical shell is a third problem. The fourth one is the anisotropy of the mass-energy of a test particle in the gravitational field. Three principles for solution are proposed:
- The space is not dilated, but rather contracted, in the gravitational field; then the measurement-rods are shorter and measured distances have greater magnitudes.
- The potential energy is to be related to a potential level where a stationary observer is placed and the general relativistic potential must be used.
- A new metric must be introduced which is distinct from the Schwarzschild metric, so that the space in the gravitational field is warped isotropically.
22.
In this initial study, we propose a new distance function D
V
involving heliocentric vectorial orbital elements. The function measures differences between: the orbital energies, the angular
momentums vectors and the Laplace vectors. In comparison with the widely used D
SH
criterion of Southworth and Hawkins, D
D
criterion of Drummond and their hybrid D
H
by Jopek, the new function contains one invariant with respect to the principal secular perturbation: the orbital energy.
The new function proved to be useful in the classification amongst the IAU2003 meteoroids which we searched for streams by
D
V
function and also using D
SH
and D
N
-function given by Valsecchi et al. For major streams, the results agree very well. For minor, and near-ecliptical streams
the results sometimes differ markedly. 相似文献
23.
Seasonal residence and counterurbanization: the role of second homes in population redistribution in Finland 总被引:1,自引:0,他引:1
Since the late twentieth century, many developed countries have experienced population deconcentration, labelled as counterurbanization. There has been an academic discussion on the meaning, validity and universality of this concept, drivers of counterurbanization and its impacts on rural areas. To date, research on counterurbanization mostly apply static and discrete definitions of residence, migration and population, which is an increasingly simplistic view in the contemporary reality of a growing multitude of forms of mobility, often related to dual residence. Particularly large-scale quantitative studies on counterurbanization are confined by existing statistical practices. This paper attempts to overcome this obstacle and describe the transformation of the settlement system in Finland acknowledging the role of second home mobility. To achieve this goal, it introduces two alternative measures of population, seasonal and average population, and analyses their spatial dynamics between the years 1990 and 2010 based on georeferenced grid statistical data. The study finds that although registered population has been concentrating during the period in analysis, seasonal population has been increasingly dispersed due to the growing number of second homes. It shows that the counterurbanization process, though not noticed by conventional statistics, does occur in Finland, manifested by seasonal rather than permanent moves. The article concludes that various forms of mobility should be taken into account when analysing the urban–rural population dynamics and transformations of settlement systems as well as in rural development planning. 相似文献
24.
Daniel H. Doctor E. Calvin Alexander Jr Metka Petrič Janja Kogovšek Janko Urbanc Sonja Lojen Willibald Stichler 《Hydrogeology Journal》2006,14(7):1171-1191
Karst aquifer components that contribute to the discharge of a water supply well in the Classical Karst (Kras) region (Italy/Slovenia) were quantitatively estimated during storm events. Results show that water released from storage within the epikarst may comprise as much as two-thirds of conduit flow in a karst aquifer following rainfall. Principal components analysis (PCA) and end-member mixing analysis (EMMA) were performed using major ion chemistry and the stable isotopes of water (δ18O, δ2H) and of dissolved inorganic carbon (δ13CDIC) to estimate mixing proportions among three sources: (1) allogenic river recharge, (2) autogenic recharge, and (3) an anthropogenic component stored within the epikarst. The sinking river most influences the chemical composition of the water-supply well under low-flow conditions; however, this proportion changes rapidly during recharge events. Autogenic recharge water, released from shallow storage in the epikarst, displaces the river water and is observed at the well within hours after the onset of precipitation. The autogenic recharge end member is the second largest component of the well chemistry, and its contribution increases with higher flow. An anthropogenic component derived from epikarstic storage also impacts the well under conditions of elevated hydraulic head, accounting for the majority of the chemical response at the well during the wettest conditions. 相似文献
25.
Oimahmad Rahmonov Tadeusz Szczypek Tadeusz Niedźwiedź Urszula Myga-Piątek Małgorzata Rahmonov Valerian A. Snytko 《Environmental Earth Sciences》2017,76(8):324
Detailed analyses were conducted of human impact on juniper forest landscapes occurring within the Zarafshan Range (Pamir-Alay). Juniperus seravschanica and J. semiglobosa belong to forest-forming species in Central Asia. At present, juniper forests all over Tajikistan are seriously threatened as a result of excessive logging and cattle grazing. The aim of this paper is to present juniper forest transformation as a result of human activities as well as the diversity of soil properties in the organic and humus horizons in the altitudinal system of soil zonation. Three groups of phytocoenoses were distinguished: those with a dominant share of Juniperus seravschanica; those with a dominant share of J. semiglobosa; and mixed. Associations with Juniperus seravschanica and J. semiglobosa feature several variants of phytocoenoses with dominant species: Artemisia lehmanniana, A. dracunculus, Eremurus olgae, Festuca sulcata, Ligularia thomsonii, Stipa turkestanica, Thymus seravschanicus, and Ziziphora pamiroalaica. The collected soil samples differ in their granulometric composition. Gravelly cobble fractions >2 mm are dominant; the share of sandy particles <2 mm is much lower (about 10–20%). Fraction 0.5–0.05 attains 35% on average. The Corg content of the soil varied from 0.26 to 11.40% in the humus horizon (A) and from 4.3 to 25% in the organic (O). Similar relationships were reported in the case of Ntot concentration. A clear relationship can be observed between concentrations of Corg and Ntot. Soil pH varied, ranging from very low acidic (pH 5.5) to neutral (pH 8.5). The content of available P varied; high concentrations were noted in organic (O) (40.46–211 mg kg?1) and mixed horizons (OA) (2.61–119 mg kg?1). Maximum accumulations of Pavail (1739.6 mg kg?1) and Ptot (9696 mg kg?1) were observed at a site heavily affected by intense grazing. Concentrations of Mgavail varied from 116 to 964 mg kg?1. Most of the analysed soil profiles lacked an organic horizon; only thin humus occurred. 相似文献
26.
Changes in water chemistry along the High Arctic fluvial–lacustrine system located in Wedel Jarlsberg Land in the SW Spitsbergen (Svalbard) were investigated during the summer season of 2010 and 2011. The newly formed river–lake system consists of three lakes connected with the Brattegg River. The first bathymetric measurements of these lakes were made by the authors in 2010. The Brattegg River catchment represents a partly glaciered Arctic water system. The studied lakes are characterized by low mineralization and temperature of water. The value of the electrolytic conductivity (EC) ranges from 30.2 to 50.5 μS cm?1 and the temperature of surface water from 1.5 to 7.8 °C. The temperature increase takes place downstream starting from Upper Lake to the outflow from Myrktjørna Lake. The waters of lakes have higher temperatures than the stream. The predominant ions are HCO3 ? (up to 16.5 mg L?1), Cl? (6.66–8.53 mg L?1), Ca2+ (2.40–4.45 mg L?1) and Na+ (2.65–3.36 mg L?1). The highest values of ammonium and DOC found in the lowest Myrktjørna Lake seem to be related to the presence of aquatic organisms and also birds. From the group of 10 analyzed microelements, increased concentrations of aluminum, up to almost 500 μg L?1, are present in the lakes’ water. Water isotopic composition ranges for δ18O and δ2H, from ?10.6 to ?10.9‰ and from ?70.8 to ?72.3‰, respectively. The vertical zonality of lake waters is manifested in a decrease in the temperature and increase in EC and chemical elements concentrations. 相似文献
27.
The reservoir, having a volume of 76 hm3, a surface area of 1001 ha and a maximum depth of 17 m, is divided by a dam into two parts. Half of the upper part with an area of 200 ha is densely covered by macrophytes (Elodea, Potamogeton). The three main tributaries with 2.6 m3/s on an average are highly polluted and show α-mesosaprobic conditions. The reservoir is investigated between September and March in its longitudinal section at eight stations. The organic load and the total solids show a total decrease by 60% and 66%, respectively, and 70% of this selfpurification occurs in the upper, separated part of the reservoir. In the same way, also the total nitrogen is reduced, whereas the total phosphorus is reduced already in the upper part of the reservoir by 71%, then decreasing to 21% in the second part of the reservoir. With phosphorus, besides the biological elimination obviously also precipitation by the dissolved iron occurs, the concentration of which is reduced by 44 or 76%, resp. The bacteriological load of water improved by two to three orders of magnitude. 相似文献
28.
29.
30.
The Pond of Dvorec, used for a final treatment of waste waters and at the same time for fish breeding, has been observed working in an assimilation and later on in a stabilization mode (SVOBODA and KOUBEK) . The data on the chemical composition and microbiological properties of its sediments are given. A comparative analysis of the stabilization pond sediments and the sediments of the second stabilization pond have shown a high purification function. An influence of temperature, aeration and thickness of the layer upon a microbial activity and a release of the substance into the water environment were verified in laboratory experiments. A higher layer of sediments can, above all at increased temperatures, negatively influence the water quality for fish breeding. After composting the drawn pond sediments can be recommended for the fertilization of an agricultural land in near surroundings. 相似文献