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141.
Igor Vrišer 《GeoJournal》1993,31(4):373-377
Agrarian economy on the territory of a new European state, ie Slovenia (the NW part of former Yugoslavia) has undergone substantial transformations over the past 150 years. The changes were particularly intense after World War II when the Yugoslav Communist Party came to power in former Yugoslavia. Under its influence an extensive redistribution of property (ie expropriations) was carried out, as well as reorientation of production and a thorough social transformation. After the independent state of Slovenia was established in 1991 (Slovenia, 1992) and the capitalist system was reintroduced, the agrarian economy of this area has had to face certain far-reaching problems which are crucial for the future development of the new state.  相似文献   
142.
哈萨克斯坦北部Kumdy-Kol金刚石矿床地质与变质金刚石成因   总被引:1,自引:0,他引:1  
哈萨克斯坦北部Kokchetav地区的Kumdy Kol金刚石矿床是世界上惟一的变质金刚石矿床。对该金刚石矿床成因以及相关岩石的诸多研究成果不仅深化了对超高压变质岩的研究 ,而且推动了大陆动力学研究的进展。在该金刚石矿床中找到的岩相学证据证明 ,该金刚石矿床的主要含矿岩石大理岩曾经在俯冲带中循环到 >2 4 0km的深部。文章在介绍Kokchetav变质金刚石矿床的地质特征和大地构造背景的基础上 ,讨论了该变质金刚石矿床的形成过程以及变质金刚石的成因。Kokchetav变质金刚石主要表现出蜂窝状或草莓状的特征外形。这种蜂窝状或草莓状金刚石是快速生长条件下结晶的结果。结合最近的研究成果 ,笔者认为Kokchetav金刚石矿床中金刚石的形成与深俯冲大理岩中的白云石分解作用密切相关。白云石分解反应形成文石和菱镁矿组合 ,菱镁矿继续分解形成金刚石 (MgCO3 =金刚石 +MgO +O2 )。基于这个认识 ,Kokchetav金刚石矿床中碳 (金刚石和石墨 )的来源应该是碳酸盐岩  相似文献   
143.
In view of increasing lead pollution (Pb2+) of coastal waters, the compensatory abilities of holothurians need to be assessed. The goal of the work is to clarify the functional and phenotypical differences between two types of phagocytes (P1 and P2) in Eupentacta fraudatrix exposed to Pb(NO3)2. It has been shown that 2 mg L?1 lead exposure for 48 h increases the number of P2 phagocytes as compared to P1 cells, does not significantly affect cell viability in both P1 and P2 phagocyte fractions, and significantly enhances chromatin condensation in P2 but not in P1 phagocytes. A lead concentration of 4 mg L?1 increases the number of P1 phagocytes compared to that of P2 type, and does not change cell viability and chromatin condensation in P1 phagocytes. In the P2 type, it decreases cell viability and does not influence the level of apoptosis. The protection against lead-induced apoptosis is apparently mediated by the activities of antioxidant enzymes, especially glutathione S-transferase. The differences in labeling cell surface receptors of P1 and P2 phagocytes by plant lectins also indicate the specific phenotypic properties of these cells. The results clarify the potential and GSH-dependent mechanisms of immune adaptation in holothurians that have been shortly exposed to lead at concentrations close to the maximum environmentally relevant level in coastal waters. Additionally, P1 and P2 phagocytes are first shown to have different functions and phenotypes during the response to lead, which indicates the complexity of the phagocytic system in holothurians and contributes to understanding the immunity evolution.  相似文献   
144.
Pulsars play a crucial astrophy sical role as highly energetic compact radio, X-ray and gammaray sources. Our previous works show that radio pulsars identified as pulsing gamma-ray sources by the Large Area Telescope(LAT) on board the Fermi Gamma-Ray Space Telescope have high values of magnetic field near the light cylinder, two-three orders of magnitude stronger compared with the magnetic fields of radio pulsars: log B_(lc)(G) are 3.60-3.95 and 1.75 correspondingly. Moreover,their losses of rotational energy are also three orders higher than the corresponding values for the main group of radio pulsars on average: log E(erg s~(-1)) = 35.37-35.53 and 32.64. The correlation between gammaray luminosities and radio luminosities is found. It allows us to select those objects from all sets of known radio pulsars that can be detected as gamma-ray pulsars with high probability. We provide a list of such radio pulsars and propose to search for gamma emission from these objects. On the other hand,the known catalog of gamma-ray pulsars contains some sources which are not currently identified as radio pulsars. Some of them have large values of gamma-ray luminosities and according to the obtained correlation, we can expect marked radio emission from these objects. We give the list of such pulsars and expected flux densities to search for radiation at frequencies 1400 and 111 MHz.  相似文献   
145.
Considering horizontally layered transversely isotropic media with vertical symmetry axis and all types of pure‐mode and converted waves we present a new wide‐angle series approximation for the kinematical characteristics of reflected waves: horizontal offset, intercept time, and total reflection traveltime as functions of horizontal slowness. The method is based on combining (gluing) both zero‐offset and (large) finite‐offset series coefficients. The horizontal slowness is bounded by the critical value, characterised by nearly horizontal propagation within the layer with the highest horizontal velocity. The suggested approximation uses five parameters to approximate the offset, six parameters to approximate the intercept time or the traveltime, and seven parameters to approximate any two or all three kinematical characteristics. Overall, the method is very accurate for pure‐mode compressional waves and shear waves polarised in the horizontal plane and for converted waves. The application of the method to pure‐mode shear waves polarised in the vertical plane is limited due to cusps and triplications. To demonstrate the high accuracy of the method, we consider a synthetic, multi‐layer model, and we plot the normalised errors with respect to numerical ray tracing.  相似文献   
146.
Rivers on territory of the Republic of Serbia can be separated to three sea drainage basins: Black, Adriatic and Aegean. Majority of rivers belong to the Black Sea drainage basin. The Danube is the most important river in Serbia and one of the most important rivers of Europe. All rivers investigated in this paper represent direct or indirect tributaries of the Danube River and as that, they are belonging to the Black Sea drainage basin. In this study, the water quality status and the spatial and temporal trends of seven major rivers in Serbia were assessed through the application of ten parameters of Water Quality Index. Ten year (2004–2013) public database of environmental data was used. Into considerations were taken differences between every river individually and difference between sample positions on every single river. Based on the chemical parameters of water quality, it can be seen that the biggest rivers in Serbia show different values of WQ parameters. The highest WQ value is measured on the Drina River, while the lowest value is measured on the Ju?na Morava and the Tisza River. Analyses of parameters per period of year show that there is a statistically significant difference between values during warm and cold periods.  相似文献   
147.
Kinematical characteristics of reflected waves in anisotropic elastic media play an important role in the seismic imaging workflow. Considering compressional and converted waves, we derive new, azimuthally dependent, slowness-domain approximations for the kinematical characteristics of reflected waves (radial and transverse offsets, intercept time and traveltime) for layered orthorhombic media with varying azimuth of the vertical symmetry planes. The proposed method can be considered an extension of the well-known ‘generalized moveout approximation’ in the slowness domain, from azimuthally isotropic to azimuthally anisotropic models. For each slowness azimuth, the approximations hold for a wide angle range, combining power series coefficients in the vicinity of both the normal-incidence ray and an additional wide-angle ray. We consider two cases for the wide-angle ray: a ‘critical slowness match’ and a ‘pre-critical slowness match’ studied in Parts I and II of this work, respectively. For the critical slowness match, the approximations are valid within the entire slowness range, up to the critical slowness. For the ‘pre-critical slowness match’, the approximations are valid only within the bounded slowness range; however, the accuracy within the defined range is higher. The critical slowness match is particularly effective when the subsurface model includes a dominant high-velocity layer where, for nearly critical slowness values, the propagation in this layer is almost horizontal. Comparing the approximated kinematical characteristics with those computed by numerical ray tracing, we demonstrate high accuracy.  相似文献   
148.
149.
The well‐known asymptotic fractional four‐parameter traveltime approximation and the five‐parameter generalised traveltime approximation in stratified multi‐layer transversely isotropic elastic media with a vertical axis of symmetry have been widely used for pure‐mode and converted waves. The first three parameters of these traveltime expansions are zero‐offset traveltime, normal moveout velocity, and quartic coefficient, ensuring high accuracy of traveltimes at short offsets. The additional parameter within the four‐parameter approximation is an effective horizontal velocity accounting for large offsets, which is important to avoid traveltime divergence at large offsets. The two additional parameters in the above‐mentioned five‐parameter approximation ensure higher accuracy up to a given large finite offset with an exact match at this offset. In this paper, we propose two alternative five‐parameter traveltime approximations, which can be considered extensions of the four‐parameter approximation and an alternative to the five‐parameter approximation previously mentioned. The first three short‐offset parameters are the same as before, but the two additional long‐offset parameters are different and have specific physical meaning. One of them describes the propagation in the high‐velocity layer of the overburden (nearly horizontal propagation in the case of very large offsets), and the other characterises the intercept time corresponding to the critical slowness that includes contributions of the lower velocity layers only. Unlike the above‐mentioned approximations, both of the proposed traveltime approximations converge to the theoretical (asymptotic) linear traveltime at the limit case of very large (“infinite”) offsets. Their accuracy for moderate to very large offsets, for quasi‐compressional waves, converted waves, and shear waves polarised in the horizontal plane, is extremely high in cases where the overburden model contains at least one layer with a dominant higher velocity compared with the other layers. We consider the implementation of the proposed traveltime approximations in all classes of problems in which the above‐mentioned approximations are used, such as reflection and diffraction analysis and imaging.  相似文献   
150.
This paper establishes a mechanical model of the stress distribution in front of the driving face during coal roadway excavation. Theoretical research shows that the stress state in the plastic zone of the driving face is consistent with the limit equilibrium equation, and the elastic zone is in accordance with the equilibrium equation based on elasticity mechanics. Based on this improved mechanical state solution model, different coal material constitutive hypotheses are used for the analysis. The width of the plastic zone calculated under the brittle-perfectly elastic model can reach 2–5 times the height of the roadway, and the stress concentration coefficient can reach two or more times. 3DEC numerical simulation software was used to simulate the stress distribution of the heading face. The results of the simulation are similar to those of the theoretical analysis. Compared with the elastic-perfectly plastic model, the calculated results of the brittle-perfectly elastic model are more consistent with the numerical simulation results. The heading face coal during roadway excavation shows obvious damage, and the strength characteristics of the coal decrease.  相似文献   
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