Melting of Mg2GeO4 under pressure

Melting point of germanate forsterite, Mg₂GeO₄, was raised by compression at the rate of 30°C/GPa. The triple point, at which three phases of olivine- and spinel-type solids and liquid coexisted, was fixed at 1950°C and 3.5GPa. Wen these results are combined with the thermodynamical data of forsterite, Mg₂SiO₄, it is estimated that the triple point of forsterite lies in a region ranging from 2700° to 3000°C in temperature and from 20 to 30GPa in pressure.     

Determination of the olivine-spinel transition in magnesium germanate (Mg2GeO4) up to 20 kilobars and 1300°C

Reversal experiments of the olivine-spinel transition in Mg₂GeO₄ up to 20 kbar indicate a reaction boundary with the formula P = 35 (T ? 805). Pressure (P) in bars and temperature (T) in degrees centigrade.     

High-pressure disproportionation of Co2SiO4 spinel and implications for Mg2SiO4 spinel

Co₂SiO₄ spinel has been found to disproportionate into its isochemically mixed oxides with rocksalt and rutile structures at pressures between 170 and 190 kbar and temperatures between 1400 and 1800°C in a diamond-anvil press. The exact disproportionation pressure is not certain due to transient increases in pressure during the local and rapid heating by a continuous YAG laser. The slope of the phase boundary between the spinel phase and the mixed oxides is calculated to be?33 ± 20bar/deg. This negative slope is consistent with the observed anomalously large entropy of CoO (relative to its isostructural oxides) in entropy vs.(MV)^?1/2 systematics, whereM is the formula weight andV the molar volume. The sign of the slope for a phase boundary in the disproportionation of spinel depends on the values of entropy of the rocksalt oxides as well as the inverse character exhibited in the spinel phases. The normal entropy of MgO suggests that the phase boundary for the disproportionation of Mg₂SiO₄ spinel has positive slope.     

High-pressure X-ray diffraction studies on β- and γ-Mg2SiO4

Pressure effects on the lattice parameters of β- and γ-Mg₂SiO₄ have been measured at room temperature and at pressures up to 100 kbar using a multi-anvil high-pressure X-ray diffraction apparatus. The volume changes (ΔV/V₀) at 90 kbar are 5.4 · 10^?2 and 4.2 · 10^?2 for β- and γ-Mg₂SiO₄, respectively. Isothermal bulk moduli at zero pressure have been calculated from least-square fits of the data to straight lines. They turn out to be 1.66 ± 0.4 and 2.13 ± 0.1 Mbar for β- and γ-Mg₂SiO₄, respectively. The α → γ transition obeys Wang's linear V_φ?ρ relation but the α → β transition does not.     

Enhancing the Sustainability of Household Fe0/Sand Filters by Using Bimetallics and MnO2

Filtration systems containing metallic iron as reactive medium (Fe⁰ beds) have been intensively used for water treatment during the last two decades. The sustainability of Fe⁰ beds is severely confined by two major factors: (i) reactivity loss as result of the formation of an oxide scale on Fe⁰ and (ii) permeability loss due to pore filling by generated iron corrosion products. Both factors are inherent to iron corrosion at pH > 4.5 and are common during the lifespan of a Fe⁰ bed. It is of great practical significance to improve the performance of Fe⁰ beds by properly addressing these key factors. Recent studies have shown that both reactivity loss and permeability loss could be addressed by mixing Fe⁰ and inert materials. For a non‐porous additive like quartz, the threshold value for the Fe⁰ volumetric proportion is 51%. Using the Fe⁰/quartz system as reference, this study theoretically discusses the possibility of (i) replacing Fe⁰ by bimetallic systems (e.g., Fe⁰/Cu⁰), or (ii) partially replacing quartz by a reactive metal oxide (MnO₂ or TiO₂) to improve the efficiency of Fe⁰ beds. Results confirmed the suitability of both tools for sustaining Fe⁰ bed performance. It is shown that using a Fe⁰:MnO₂ system with the volumetric proportion 51:49 will yield a filter with 40% residual porosity at Fe⁰ depletion (MnO₂ porosity 62%). This study improves Fe⁰ bed design and can be considered as a basis for further refinement and detailed research for efficient Fe⁰ filters.     

Oxidative Degradation of Orange II Dye in Water with Raw and Acid‐Treated ZnO,and MnO2

Commercial ZnO, MnO₂, and their acid‐treated forms were used as catalysts for oxidative degradation of Orange II dye in water. ZnO and MnO₂ were treated with 0.5, 0.75, or 1.0 N aqueous H₂SO₄. The acid treated oxides were found to be highly effective in bringing about degradation of Orange II in water. As much as 68.7% of the dye in an aqueous solution of 1 mg/L concentration could be degraded with untreated ZnO as the catalyst. The degradation increased to 79.5% with 1.0 N acid treated ZnO as the catalyst when the reaction was carried out at room temperature for 240 min. The catalytic activity was slightly affected by the solution pH in the range of 2.0–8.0. With MnO₂ as the catalyst, there was only 12.7% degradation of the dye, but this increased up to 100% when 0.5 N acid treated MnO₂ was used as the catalyst. It was found that a catalyst loading of 5.0 g/L of raw and acid‐treated ZnO and a loading of 0.5 g/L of raw and acid‐treated MnO₂ could bring about almost 100% degradation of Orange II in water in an interaction time of 240 min at room temperature.     

Trust-region based instantaneous optimal semi-active control of long-span spatially extended structures with MRF-04K damper

In the field of civil engineering, magnetorheological fluid （MRF） damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong earthquakes and high winds. In this paper, the MRF damper-based semi-active control system is applied to a long-span spatially extended structure and its feasibility is discussed. Meanwhile, a _trust-region method based instantaneous optimal semi-active control algorithm （TIOC） is proposed to improve the performance of the semi-active control system in a multiple damper situation. The proposed TIOC describes the control process as a bounded constraint optimization problem, in which an optimal semi- active control force vector is solved by the trust-region method in every control step to minimize the structural responses. A numerical example of a railway station roof structure installed with MRF-04K dampers is presented. First, a modified Bouc- Wen model is utilized to describe the behavior of the selected MRF-04K damper. Then, two semi-active control systems, including the well-known clipped-optimal controller and the proposed TIOC controller, are considered. Based on the characteristics of the long-span spatially extended structure, the performance of the control system is evaluated under uniform earthquake excitation and travelling-wave excitation with different apparent velocities. The simulation results indicate that the MR fluid damper-based semi-active control systems have the potential to mitigate the responses of full-scale long-span spatially extended structures under earthquake hazards. The superiority of the proposed TIOC controller is demonstrated by comparing its control effectiveness with the clipped-optimal controller for several different cases.     

Melting of the silica isotypes SiO 2, BeF 2 and GeO 2 at elevated pressures

The melting curves of the structural analogues SiO ₂, BeF ₂ and GeO ₂ have been studied at pressures ?40 kbar in a piston-cylinder apparatus. The initial slopes dT_m/dP of the β-quartz-liquid boundaries for SiO ₂ and BeF ₂ are ～35° while the slope of the rutile-liquid boundary for GeO ₂ is approximately 32°C/kbar. These large values of dT/dP reflect the unusually low entropies of fusion for these compounds in which strong structural similarities exist between the crystalline phases and the melt. Implications for the extended phase diagram of silica are discussed and it is concluded that either: (1) a maximum exists on the coesite melting curve, or (2) estimates of the melting temperature of stishovite need to be revised upwards.     

High-pressure phases of Co2GeO4, Ni2GeO4, Mn2GeO4 and MnGeO3: implications for the germanate-silicate modeling scheme and the Earth's mantle

In a diamond-anvil press coupled with YAG laser heating, the spinels of Co₂GeO₄ and Ni₂GeO₄ have been found to disproportionate into their isochemical oxide mixtures at about 250 kbar and 1400–1800°C in the same manner as their silicate analogues. At about the same P-T conditions MnGeO₃ transforms to the orthorhombic perovskite structure (space group Pbnm); the lattice parameters at room temperature and 1 bar are a₀ = 5.084 ± 0.002, b₀ = 5.214 ± 0.002, and c₀ = 7.323 ± 0.003Å with Z = 4 for the perovskite phase. The zero-pressure volume change associated with the ilmenite-perovskite phase transition in MnGeO₃ is ?6.6%. Mn₂GeO₄ disproportionates into a mixture of the perovskite phase of MnGeO₃ plus the rocksalt phase of MnO at P = 250kbar and T = 1400–1800°C. The concept of utilizing germanates as high-pressure models for silicates is valid in general. The results of this study support the previous conclusion that the lower mantle comprises predominantly the orthorhombic perovskite phase of ferromagnesian silicate.     

High-pressure studies of ferroelectric phases related to the earth and planetary interiors

To determine the effects of high-pressure constraints on the overall behaviour of ferroelectrics (FE) of both the perovskite “soft-mode” and hydrogen-bonded types, the authors have conducted dielectric property measurements to 5.5 GPa on single crystals and polycrystalline aggregates of several ferroelectrics (BaTiO₃, Pb(Zr,Ti)O₃, triglycine sulphate, Rochelle salt). The results of the experiments indicate: (1) dielectric hysteresis is possible in ferroelectrics which are under high-pressure conditions of deviatoric stresses and strains in which the FE phase forms part of a composite system; that is, under the conditions it would encounter if it formed part of a planetary interior; (2) the continued stability of these FE phases is not restricted to a particular polarization mechanism; (3) existing FE states, occurring as elastic and dielectric inhomogeneities, can persist to much higher pressures than expected on the basis of the pressure dependence of isolated and unconstrained FE crystals.     

Dynamics of structures with uplift and sliding

A structure incorporating the mechanism of sliding, as used in seismic isolation, along with the mechanism of uplift, but at a different elevation, is proposed to study the possible beneficial effects on the response of the structure, as compared to allowing partial base uplift only. A two-mass model of system uplift and sliding is established. The equations of motion for both the phase of full contact and the phase of base uplift are derived. The criteria governing the transformation of these two phases are given. Both the time history and the response spectrum results show that the structure with both uplift and sliding mechanisms is superior to that with only the uplift mechanism. Not only is the response of the structure lessened, but also the amount of uplift is greatly reduced because of the added sliding mechanism.     

Impact of Ca2+ and Mg2+ on the Removal of F− by Magnesium Potassium Phosphate

This study investigates the influence of Ca²⁺ and Mg²⁺ on the removal of F^? by magnesium potassium phosphate (MPP) from water. The kinetic experiments reveal that the F^? concentration decreased from 3.5 to 3.31 mg L^?1 in a single (F^?) system and to 1.45 mg L^?1 in a ternary system (F^?, Ca²⁺, and Mg²⁺) after 1 min, respectively. Thus, the F^? removal efficiencies are found to increase by about 53% with the co‐active effect of Ca²⁺ and Mg²⁺ in the solution. Moreover, Ca²⁺ and Mg²⁺ are almost completely removed in the F^?, Ca²⁺, and Mg²⁺ system. According to the pseudo‐first‐order modeling, the rate constants k for F^?, Ca²⁺, and Mg²⁺ are 0.00348, 0.0106, and 0.0159 min^?1 respectively; thus, Mg²⁺ > Ca²⁺ > F^?. In the ternary system, the removal efficiencies are 53.29–66.03% for F^?, 99.99–100% for Ca²⁺, and 87.21–95.19% for Mg²⁺ with initial pH 5–10. The removal efficiencies of F^? increases with increases in initial concentrations of F^?, Ca²⁺, and Mg²⁺. The removal of F^? is governed by two routes: 1) adsorption by electrostatic interactions and outer sphere surface complexation; 2) co‐precipitation with Ca₃(PO₄)₂, CaHPO₄, Mg₃(PO₄)₂, and Mg(OH)₂.     

On the interaction of rayleigh surface waves with structures

A two-dimensional soil-structure interaction analysis is carried out for transient Rayleigh surface waves that are incident on a structure. The structure is modelled by a three-degree of freedom rigid basemat to which is attached a flexible superstructure, modelled by a single mass-spring system. The structural responses to a given Rayleigh wave train are compared with those that would have been obtained if the free-field acceleration-time history had been applied as a normally incident body wave. The results clearly exhibit the [frequency filtering] effects of the rigid basemat on the incident Rayleigh waves. It is shown that, if seismic excitation of a structure is, in fact, due to Rayleigh surface waves, then an analysis assuming normally incident body waves can considerably over-estimate structural response, both at basemat level for horizontal and vertical motions and for vertical oscillations of the superstructure. However, in the examples considered here, relatively large rocking effects were induced by the Rayleigh waves, thus giving maximum horizontal accelerations in the superstructure that were of comparable magnitude for Rayleigh and normally incident body waves.     

Quantifying the seismic response of structures with flexible diaphragms

Floor diaphragm in-plane stiffness affects building response to horizontal ground accelerations. This paper describes a series of elastic and inelastic time history analyses of symmetric structures with different deformation types, configurations and heights to quantify these effects. It is shown that displacements of single storey elastically responding structures tend to be most significantly affected by diaphragm flexibility. Analyses of these structures were cross-verified by a closed-form mechanics-based formulation developed to describe the response. Simple relationships were proposed to allow designers to conservatively estimate the increase in peak in-plane displacement resulting from diaphragm flexibility. Copyright © 2012 John Wiley & Sons, Ltd.     

Summation and decomposition of principal stresses in the crust

InthecompilationofWorldStressMap,9%ofdatacomesfromovercoringandhydraulicfracturingmeas-urement,23%fromboreholebreakingoff,63%fromearthquakefocalmechanism,and5%fromyounggeo-logicalinvestigation(Zoback,etal,1989).Onlyovercoringandhydraulicfracturingcanprovideboththeorienta-tionandmagnitudeofthehorizontalstress,allothermethodscanonlyprovidetheorientation,butnothemagni-tudeofthestresses.Althoughsomeresearcherstriedtoestimatemagnitudesofstressesinearthquakemechanismresearchbasedonsomeadditionalass…     

High-pressure inclusions in tholeiitic basalt and the range of lherzolite-bearing magmas in the Tasmanian volcanic province

Spinel-lherzolite xenoliths have been found in olivine tholeiite near Andover in the Tasmanian Tertiary volcanic province. They show a high-pressure mineralogy of predominant olivine (Mg₉₀), with aluminous enstatite (Mg₉₀) and lesser aluminous diopside and chrome-bearing spinel, and resemble lherzolite xenoliths commonly found in undersaturated lavas. Such xenoliths are unusual in tholeiitic basalts and the occurrence directly attests to a mantle origin for at least some tholeiitic magmas.The lherzolites are accompanied by doleritic and pyroxenitic xenoliths and by olivine, orthopyroxene, clinopyroxene and plagioclase xenocrysts. If near-liquidus phases are represented amongst the xenocrysts, then the magnesian number of the host basalt and its xenocryst assemblage provisionally suggest a magma derived by more than 15–20% partial melting of mantle peridotite, before commencing xenocryst crystallisation at pressures between 8–13 kbar.With this new record, lherzolite-bearing lavas in Tasmania now cover an extremely wide compositional range, extending from highly undersaturated olivine melilitite to olivine tholeiite. They also include a considerable number of fractionated alkaline rocks that are only sparsely reported in the literature as lherzolite hosts. This latter group contains representatives of a previously suggested but unestablished alkaline fractionation series based on olivine nephelinite, viz. calcic olivine nephelinite → sodic olivine nephelinite → potassi-sodic olivine nephelinite → mafic nepheline benmoreite → mafic phonolite.Lherzolite and megacryst-bearing lavas are relatively more abundant in peripheral parts to the main basalt sequences in Tasmania. This suggests that they developed in fringing zones of less intense mantle melting which enhanced stagnation and fractionation of magmas within the mantle before eruption. Calculated crustal thicknesses under these areas suggest that the magmas were generated at pressures exceeding 6–11 kbar, with the Andover tholeiitic magma exceeding 9 kbar.     

ETNA和K2数字强震仪电话拨号通讯中的若干问题

针对中国地震局"十五"数字强震动项目中,美国Kinemetrics公司的ETNA或K2数字强震仪拨号通讯中的电缆连接、仪器通讯速率选择、Modem的选用和参数设定,以及通讯软件使用中的若干问题进行了讨论,给出一些实现正常通讯的设置、配置和使用方法,特别是通过对多种Modem配置的反复试验,总结一些能够顺利进行拨号通讯的配置.     

Seismic imaging of complex structures with the CO-CDS stack method

Various seismic imaging methods are introduced to resolve some of the possible ambiguities of seismic interpretation in complex structures. Reducing dependency of imaging techniques on velocity or using diffraction energy for imaging more structural details are the main topics of the imaging research. In this study, we try to improve the seismic image quality in semi-complex structures by combining the common reflection surface (CRS) method with a diffraction based scheme in the common-offset domain. Previously introduced partial CRS and common offset CRS methods exhibited reliable performance in imaging complex media. Here, we were looking for stable and efficient solutions, preserving advantages of the previous methods. Herewith, the proposed operator fits better to diffractions than to reflections. Therefore, we call it the commonoffset common diffraction surface stack (CO CDS). In a previous study, improvement of the quality of seismic image by the CRS method was achieved by combination of the CDS method with the partial CRS. This resulted in the introduction of the partial CDS. Initially, in this study, the common-offset CRS traveltime equation was modified to the common-offset CDS. The hypothetical shot reflector experiment in the CRS method was changed to shot diffraction point experiment. In the introduced operator, two wavefront curvatures, observed at receivers positions, are set equal in order to satisfy the diffraction condition. In the proposed method, we search for accurate attribute sets for each considered offset individually, and then form a new operator by four coherent attributes. Application of the common- offset CDS method on synthetic and field data shows more details of the geological structures with higher quality, while preserving continuity of reflection events. The proposed method is, however, more expensive than the partial and common offset CRS for large dataset.