Bianchi Type I Anisotropic Magnetized Cosmological Model in General Relativity

Bianchi Type I magnetized Cosmological model for perfect fluid distribution is investigated. The magnetic field is due to an electric current produced along x-axis. The distribution consists of an electrically neutral perfect fluid with an infinite electrical conductivity. To get a determinate solution, a supplementary conditionA = BC between metric potentials is used. The behaviour of the model in presence and absence of magnetic field is also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

基于强度和延性的残余位移比谱及其影响因素分析

结构震后残余位移是抗震性能评估和地震损失评估的重要参数。文中针对理想弹塑性单自由度体系,采用与残余位移相关性最好的归一化参数定义残余位移比,通过动力时程分析建立统计平均的等延性残余位移比谱和等强度残余位移比谱,研究场地条件、延性系数及强度折减系数对等延性残余位移比谱和等强度残余位移比谱的影响,通过回归分析构建了等延性残余位移比谱和等强度残余位移比谱的预测方程。结果表明：残余位移与弹塑性谱位移的相关性较大,与弹性谱位移的相关性较小;软土场地下结构残余位移的评估需考虑场地条件的影响;残余位移比离散性受延性系数和强度折减系数影响显著。     

A ninth century earthquake-induced landslide and flood in the Kashmir Valley,and earthquake damage to Kashmir’s Medieval temples

An entry in the Tarikh-i-Hassan records that in 883 AD during the reign of King Avantivarman (855–883) an earthquake in Kashmir triggered a landslide that impounded the River Jhelum and flooded the Kashmir Valley. Kalhana’s Rajatarangini provides abundant details about how the ninth century engineer Suyya both cleared the natural dam, drained the valley and instituted numerous irrigation works. We identify the landslide(s) responsible for this Medieval flood and from twentieth century discharge statistics of the Jhelum calculate that it would have taken at least 2 years to flood the Kashmir Valley to near Anantnag. This presents a chronological difficulty, for the causal earthquake could not have occurred in the last 4 months of Avantivarman’s rule, and we conclude that it must have occurred much earlier, perhaps before the start of his reign. The flood occurred during a period of widespread temple building using massive uncemented limestone megablocks, capped by monolithic multi-ton roofs. Many of these magnificent temples, now in ruinous condition, are located close to the shores of the inferred Medieval flood level, suggesting that the transport of construction materials for these temples may have been ferried by barge from distant quarries. Historians and archaeologists have attributed the partial collapse of these temples to malicious damage by subsequent occupants of the valley, but the misalignment of blocks at lower levels within each edifice in recent earthquakes suggests that their lateral offsets are the result of jostling during prolonged shaking in historical earthquakes. From the serendipitous entrapment of datable materials beneath fallen blocks from Kashmir’s ninth century temples we can, in principle, identify the times of historical earthquakes. We chose the ruined Sugandhesa temple near Patan to test this hypothesis. Preliminary results indicate collapse in the tenth or eleventh century, and significant damage in 1885, with at least one intervening earthquake possibly in the seventieth century.     

Stability of rubble-mound breakwater using H50 wave height parameter

The prediction of rubble mound breakwaters' stability is one of the most important issues in coastal and maritime engineering. The stability of breakwaters strongly depends on the wave height. Therefore, selection of an appropriate wave height parameter is very vital in the prediction of stability number. In this study, H₅₀, the average of the 50 highest waves that reach the breakwater in its useful life, was used to predict the stability of the armor layer. First, H₅₀ was used instead of the significant wave height in the most recent stability formulas. It was found that this modification yields more accurate results. Then, for further improvement of the results, two formulas were developed using model tree.To develop the new formulas, two experimental data sets of irregular waves were used. Results indicated that the proposed formulas are more accurate than the previous ones for the prediction of the stability parameter. Finally, the proposed formulas were applied to regular waves and a wide range of damage levels and it was seen that the developed formulas are applicable in these cases as well.     

Tilted Bianchi Type I Models with Heat Conduction Filled with Disordered Radiations of Perfect Fluid in General Relativity

In this paper, we have investigated some tilted Bianchi Type I models with heat conduction filled with disordered radiation of perfect fluid. To get a determinate solution, we have assumed a condition A =(BC) ⁿ between metric potentials. Alternatively we have discussed the case A=(BC) ^1/3 for which tilted nature of the model is preserved. The various and geometrical features with singularities in the models are also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

An LRS Bianchi Type I Bulk Viscous Fluid String Cosmological Model in General Relativity

An LRS Bianchi type I string dust cosmological model with and without bulk viscosity following a method used by Letelier and Stachel, is investigated. To get a determine solution, it is assumed that σ∝θ whereσ is shear and θ is scalar of expansion and which leads to A =αBⁿ were n is a constant. The physical and geometrical aspects of the model are also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Magnetostatic stiff-fluid model of cylindrical symmetry in general relativity

We study the static stiff-fluid model for perfect fluid distributions in the presence of incident magnetic field. The magnetic field is surrounded by static stiff fluid of infinite electric conductivity and it is due to the electric current flowing along theZ-axis. The various physical and geometrical properties together with the state of model in absence of magnetic field are also discussed.     

Thermal stability of extended clusters in dravite: a combined EMP,SREF and FTIR study

A dravite from Yemen of near end-member composition was treated in air and hydrogen atmospheres at 600–900 °C to reveal changes in Mg and Al order over the octahedrally coordinated Y and Z sites, and to explore related changes in the characteristic vibrational bands in the principal (OH)-stretching frequency. Relevant information was obtained using electron microprobe analysis (EMPA), structural refinement (SREF) and polarized infrared (IR) single-crystal spectroscopy. Overall, the EMPA, SREF and IR data show that only minor changes occur during thermal treatment up to at least 800 °C, including variations in structural parameters, Mg–Al order–disorder and (OH)-stretching bands, indicating limited hydrogen loss. Untreated and treated dravite samples have very similar long-range and short-range atomic structures, which may be related to the occurrence of stable Al–Mg extended clusters around the O1 (=W) and O3 (=V) sites: ^W(F)–^Y(MgMgMg)–^V(OH)₃–^Z[AlAlAlAlAl(Al,Mg)]; ^W(OH)–^Y(MgMgAl)–^V(OH)₃–^Z[AlAlAlAlAl(Al,Mg)]; ^W(O^2–)–^Y(AlAlAl)–^V(OH)₃–^Z[AlAlAlAlAl(Al,Mg)]. These extended clusters remain stable to temperatures close to the observed start of decomposition (~900 °C).     

Melt inclusion constraints on petrogenesis of the 2014–2015 Holuhraun eruption,Iceland

The 2014–2015 Holuhraun eruption, on the Bárðarbunga volcanic system in central Iceland, was one of the best-monitored basaltic fissure eruptions that has ever occurred, and presents a unique opportunity to link petrological and geochemical data with geophysical observations during a major rifting episode. We present major and trace element analyses of melt inclusions and matrix glasses from a suite of ten samples collected over the course of the Holuhraun eruption. The diversity of trace element ratios such as La/Yb in Holuhraun melt inclusions reveals that the magma evolved via concurrent mixing and crystallization of diverse primary melts in the mid-crust. Using olivine–plagioclase–augite–melt (OPAM) barometry, we calculate that the Holuhraun carrier melt equilibrated at 2.1?±?0.7 kbar (7.5?±?2.5 km), which is in agreement with the depths of earthquakes (6?±?1 km) between Bárðarbunga central volcano and the eruption site in the days preceding eruption onset. Using the same approach, melt inclusions equilibrated at pressures between 0.5 and 8.0 kbar, with the most probable pressure being 3.2 kbar. Diffusion chronometry reveals minimum residence timescales of 1–12 days for melt inclusion-bearing macrocrysts in the Holuhraun carrier melt. By combining timescales of diffusive dehydration of melt inclusions with the calculated pressure of H₂O saturation for the Holuhraun magma, we calculate indicative magma ascent rates of 0.12–0.29 m s^?1. Our petrological and geochemical data are consistent with lateral magma transport from Bárðarbunga volcano to the eruption site in a shallow- to mid-crustal dyke, as has been suggested on the basis of seismic and geodetic datasets. This result is a significant step forward in reconciling petrological and geophysical interpretations of magma transport during volcano-tectonic episodes, and provides a critical framework for the interpretation of premonitory seismic and geodetic data in volcanically active regions.