Relativistic fireworks     

Bertel Laurent  Per Carlqvist 《Astrophysics and Space Science》1991,181(2):211-235

We have studied a model of relativistic fireworks. In this model it is assumed that a series of explosions occur. In each explosion the fragments fly apart in arbitrary directions with a given velocity which is a parameter in the model.We have succeeded in obtaining an exact expression for the distribution of fragments in velocity space aftern explosions.We present an exact solution also in the limiting case of small velocity steps where the process turns into a diffusion in velocity space.The development in configuration space has been obtained through Monte-Carlo numerical simulations.The model has been applied to metagalactic cosmology. Although single explosions cannot reach the highest redshifts observed in the Hubble expansion the fireworks model offers a possibility to reach thesez-values in a few explosions.The model gives a density inhomogeneity of 20% over a tenth of the Hubble distance as seen from a typical position. Observations show a considerably greater irregular variation.The model gives a local velocity dispersion which is too great to comply with observations. A development of the model is suggested.  相似文献   

Geochemistry of Major Elements in a Pristine Boreal River System; Hydrological Compartments and Flow Paths     

J.?IngriEmail author  A.?Widerlund  M.?Land 《Aquatic Geochemistry》2005,11(1):57-88

Once or twice weekly, water sampling was undertaken for a two and a half year period in the Kalix River, northern Sweden. Soil water, groundwater, water in tributaries and mire water were also sampled at several occasions. Samples were filtered and analysed for major dissolved elements and TOC. Although only 5 of the bedrock in the Kalix River drainage basin is situated in the Caledonian mountains (mostly schist, with some outcrops of dolomite and limestone), the chemical composition of the river, at the river mouth, is clearly influenced by water from the mountain areas. High dissolved Ca/Mg ratios in June and July indicate a large influence of water from the mountain areas during summer. The dissolved Si/Mg ratio increases when water from the woodland (bedrock consisting of Precambrian granitoids) predominates during snowmelt in May, but the ratio is low during summer when water from the mountains is increased. However, the low Si concentrations in the mountain areas are probably not primarily the result of the different rocks but more a reflection of the less intense weathering of silicate minerals in the mountains. High Si/Mg ratios are closely related to high TOC. All the major dissolved elements, except TOC, are diluted by snowmelt in May. However, the dilution varies for different elements. Based on the interpretations of major element ratios the melt water discharge in May reflects two major compartments in the woodland; peatland areas and the upper section of the soil. During summer and autumn storm events in the woodland most of the storm water originated from peatland. High K/Mg ratios in the river in May are related to water discharge from the upper section of the till. Low S/Mg ratios in the river indicate an influence of mire water from the woodland both during melt water discharge in May and during increased water discharge in autumn. The Ca/Mg ratios in tributaries in the woodland are consistently lower during melt water discharge compared with values in August. The lower Ca/Mg ratio in May probably reflects water that has been in contact with the B-horizon in the till during spring flood. Data show that the TOC discharged during spring flood originates from two major compartments in the landscape, the upper soil profile and peatland. Storm discharge of TOC during the rest of the year originates mostly from peatland.  相似文献   

A Cosmological Explanation to the Pioneer Anomaly     

C.?Johan?MasreliezEmail author 《Astrophysics and Space Science》2005,299(1):83-108

An earlier paper introduced a new cosmological theory based on the proposition that all four metrical coefficients of space and time change with the cosmological expansion. Such a universal scale expansion would preserve the four-dimensional spacetime geometry and therefore by general relativity most physical relationships. In addition, if the scale expansion were exponential with time, all epochs would be equivalent. The theory resolves several outstanding problems with the standard model based on the Big Bang concept and better agrees with observations. Four independent observational programs support the SEC theory, which also provides an explanation to the Pioneer anomaly. A possible resolution to the recently discovered discrepancies between optical observations of the planets and their ephemerides is proposed.  相似文献   

Review of conditions for uses of the Bruun rule of erosion     

Per Bruun 《Coastal Engineering》1983,7(1):77-89

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Simulation of steady-state flow in three-dimensional fracture networks using the boundary-element method     

Allen M. Shapiro  Johan Andersson 《Advances in water resources》1985,8(3):106-110

An efficient method for simulating steady-state flow in three-dimensional fracture networks is formulated with the use of the boundary-element method. The host rock is considered to be impervious, and the fractures can be of any orientation and areal extent. The fractures are treated as surfaces where fluid movement is essentially two-dimensional. Fracture intersections are regarded as one-dimensional fluid conduits. Hence, the three-dimensional geometric characteristics of the fracture geometry is retained in solutions of coupled sets of one- and two-dimentional equations. Use of the boundary-element method to evaluate the fluid responses in the fractures precludes the need to internally discretize the areal extent of the fractures.  相似文献   

Platinum-group minerals from placers related to the Nizhni Tagil (Middle Urals, Russia) Uralian-Alaskan-type ultramafic complex: ore-mineralogy and study of silicate inclusions in (Pt, Fe) alloys   总被引：1，自引：0，他引：1  

Z. Johan 《Mineralogy and Petrology》2006,87(1-2):1-30

Summary The study of platinum-group minerals (PGM) concentrates from the Nizhni Tagil placers related to the Soloviev Mountain (Gora Solovieva) Uralian-Alaskan-type intrusion revealed a predominance of (Pt, Fe) alloys over Ir-, and Os-bearing alloys. (Pt, Fe) alloys (“isoferroplatinum-type”) are interstitial with respect to chromite and show important variations in their chemical compositions, which are, however, falling within the experimentally determined stability field of isoferroplatinum. Tetraferroplatinum, enriched in Cu and Ni and tulameenite represent low-temperature mineral phases replacing (Pt, Fe) alloys. Alloys belonging to the Os–Ir–Ru ternary system have compositions corresponding to native osmium, iridium and ruthenium, respectively, and to rutheniridosmine. Osmium exsolutions appear in Ir-, and (Pt, Fe) alloys, and iridium exsolutions in (Pt, Fe) alloys. Laurite is a high-temperature phase included in native iridium and (Pt, Fe) alloys. Low-temperature PGM association comprises Ir-bearing sulpharsenides, including a phase (Ir, Os, Fe, Pt, Ru, Ni)₃(As, Sb)_0.85S, and a palladium antimonide Pd₂₀Sb₇. These two phases were previously unknown in nature. Furthermore, native palladium occurs in the studied concentrates. This low-temperature paragenesis indicates an interaction of Pt-, Os-, Ir- and Ru-bearing alloys with late fluids enriched in volatiles, As and Sb. The chromite composition is characterized by the predominance of Cr³⁺ → Fe³⁺ substitution like in other Uralian-Alaskan-type intrusions; that indicates a fO₂ variation during the chromite precipitation. Monomineralic inclusions of euhedral clinopyroxene and chromite crystals in (Pt, Fe) alloys were observed. Furthermore, (Pt, Fe) alloys contain polyphase silicate inclusions, which occupy the alloy negative crystals. Two types of silicate inclusions were recognized: (1) Low-pressure inclusions composed of amphibole, biotite, Jd-poor clinopyroxene, magnetite, apatite and glass; (2) High-pressure inclusions include: omphacitic clinopyroxene (up to 56 mol.% Jd), tremolite, muscovite, apatite, titanite and glass. In this case, the clinopyroxene is strongly zoned, revealing a pressure drop from about 25 to 5 kbar. The chemical composition of glass is corundum-normative and its H₂O content varies from about 12 to 15 wt.%. The composition of magmatic melts, from which the silicate inclusions have originated was estimated using EPMA and image analysis interpreted by stereology. Their compositions are close to those obtained experimentally by hydrous partial melting of upper mantle rocks. The interpretation of analytical data shows that magmatic melts entrapped by (Pt, Fe) alloys crystallized from about 1100 to 700 °C. The (Pt, Fe) alloys formed after the crystallization of chromite, clinopyroxene and albite. Consequently, the precipitation temperature of (Pt, Fe) alloys is estimated at about 900 °C. The significant pressure drop implies a decrease of volatile concentrations in the magmatic melt and the possible formation of a fluid phase, which might have generated, the precipitation of chromite and PGM.  相似文献   

Thermo-tectonic history of the Issyk-Kul basement (Kyrgyz Northern Tien Shan,Central Asia)     

Johan De Grave  Stijn Glorie  Mikhail M. Buslov  Daniel F. Stockli  Michael O. McWilliams  Vladislav Yu. Batalev  Peter Van den haute 《Gondwana Research》2013,23(3):998-1020

Lake Issyk-Kul occupies a large Late Mesozoic–Cenozoic intramontane basin between the mountain ranges of the Northern Kyrgyz Tien Shan. These ranges are often composed of granitoid basement that forms part of a complex mosaic assemblage of microcontinents and volcanic arcs. Several granites from the Terskey, Kungey, Trans-Ili and Zhetyzhol Ranges were dated with the zircon U/Pb method (SHRIMP, LA-ICP-MS) and yield concordant Late Ordovician–Silurian (~ 456–420 Ma) emplacement ages. These constrain the “Caledonian” accretion history of the Northern Kyrgyz Tien Shan in the amalgamated Palaeo-Kazakhstan continent. The ancestral Tien Shan orogen assembled in the Early Permian when final closure of the Turkestan Ocean ensued collision of Palaeo-Kazakhstan and Tarim. A Late Palaeozoic structural basement fabric formed and Middle–Late Permian post-collisional magmatism added to crustal growth of the Tien Shan. Permo‐Triassic cooling (~ 300–220 Ma) of the ancestral Tien Shan was unraveled using ⁴⁰Ar/³⁹Ar K-feldspar and titanite fission-track (FT) thermochronology on the Issyk-Kul granitoids. Apatite thermochronology (FT and U–Th–Sm/He) applied to the broader Issyk-Kul region elucidates the Meso-Cenozoic thermo-tectonic evolution and constrains several tectonic reactivation episodes in the Jurassic, Cretaceous and Cenozoic. Exhumation of the studied units occurred during a protracted period of intracontinental orogenesis, linked to far-field effects of Late Jurassic–Cretaceous accretion of peri-Gondwanan blocks from the Tethyan realm to Eurasian. Following a subsequent period of stability and peneplanation, incipient building of the modern Tien Shan orogen in Northern Kyrgyzstan started in the Oligocene according to our data. Intense basement cooling in distinct reactivated and fault-controlled sections of the Trans-Ili and Terskey Ranges finally pinpoint important Miocene–Pliocene (~ 22–5 Ma) exhumation of the Issyk-Kul basement. Late Cenozoic formation of the Tien Shan is associated with ongoing indentation of India into Eurasia and is a quintessential driving force for the reactivation of the entire Central Asian Orogenic Belt.  相似文献   

Environmental characteristics of hotspots of alcohol-related health incidents outside of the entertainment districts of Amsterdam     

Eleonore M. Veldhuizen  Johan Osté  Anton E. Kunst 《GeoJournal》2018,83(5):1053-1066

While hotspots of alcohol-related incidents have been associated with alcohol outlet density, few studies have considered other environmental factors. We aimed to characterise the environment of hotspots outside of outlet density areas in Amsterdam. Using geographical information systems, we identified hotspots of alcohol-related health incidents outside of outlet density areas based on the registry of alcohol related ambulance attendances. While quantitative data and methods were used to analyse victim profiles (including age, sex and home address) and temporal profiles (time of incident), we combined quantitative and qualitative information to develop environmental profiles of these hotspots. We identified 11 hotspots with 242 incidents outside outlet density areas. Results indicate substantial differences between incidents in these hotspots and incidents in high outlet density areas. Victims in these hotspots are older, more often male and live closer to the incident location compared to victims in high outlet density hotspots. Incidents are less likely to take place during the night and at weekends. In-depth analysis of four hotspots showed different combinations of contributing environmental factors, including (a) public parks bordering deprived neighbourhoods, (b) dance event facilities close to a traffic black spot, and (c) residential services for disadvantaged groups near ‘hang-outs’. The study shows that hotspots of alcohol-related incidents can arise outside outlet density areas at locations where several other environmental factors cluster, particularly in more deprived areas. Such hotspots can be addressed in urban planning and urban design.  相似文献   

The contribution of leading firms in environmental sustainability: dampening the detrimental effect of political capital ties     

Y. Hao  Y. Zhang  Q. Farooq 《International Journal of Environmental Science and Technology》2018,15(12):2581-2594

As a possible determinant of environmental sustainability, innovation management has grasped the attention of researchers. In the present research, we investigated the effect of political capital ties on firm’s contribution to environmental sustainability. We also examined how observed government support, an indicator of the inherent dependencies among political capital ties, moderates the effects of changes on innovation performance which plays a mediating role in the relationship of political capital ties and firm’s contribution in environmental sustainability. We got empirical data of 4807 listed firms of China (2010–2015) and diffused political capital ties to form a two-dimensional matrix on analysis of 36 interviews. Our study suggests that political capital dampens inputs for innovation resulting in a proliferation of innovation performance. This paper also guides that how moderation of enabling the effect of political capital ties is explained and measured through important dimensions of project initiation, high-tech accreditation and government subsidies in the context of government support.The present study also sheds light on new ways in which upper echelons theory, transaction cost and resource dependence theory can be integrated for more advanced research on political capital ties to evolve an optimal corporate strategy for environmental sustainability.  相似文献   

Flood frequency analysis of river swat using Log Pearson type 3, Generalized Extreme Value,Normal, and Gumbel Max distribution methods   总被引：1，自引：0，他引：1  

Muhammad Farooq  Muhammad Shafique  Muhammad Shahzad Khattak 《Arabian Journal of Geosciences》2018,11(9):216

In Pakistan, floods are among the most devastating and recurring natural hazards. Flood hazard assessment requires flood event magnitude and probability of occurrence. Flood frequency analysis is the most common technique used for the at-site estimation of flood recurrence magnitude. This paper evaluates four most commonly used distribution methods, i.e., Generalized Extreme Value (GEV), Log Pearson 3 (LP3), Gumbel Max, and Normal for the flood frequency and estimation of flood recurrence. Different hydrological stations data namely Khwazakhela, Chakdarra, Panjkora, and Munda Headwork located at Swat river was taken from Provincial Irrigation Department, Khyber Pakhtunkhwa. The analysis is done for 5-, 10-, 25-, 50-, and 100-year return periods by using annual maximum discharge data from 1980 to 2016 (37 yr). Three goodness-of-fit tests were applied to the fitted distributions, i.e., Kolmogorov–Smirnov, Anderson–Darling, and Chi-squared at 5% significance level. Results indicate that LP3 and GEV were ranked top two distributions at all locations while Gumbel Max and Normal were the least fitted having rank 3 and 4, respectively. Based on the goodness-of-fit ranking, LP3 was selected for the estimation of flood magnitude and return periods at Khwazakhela. Designed hydrographs based on probabilistic approach and flood 2010 hydrograph are presented for flood simulation.  相似文献