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61.
Christine Franke Thomas Frederichs Mark J. Dekkers 《Geophysical Journal International》2007,170(3):1053-1066
Low-temperature rock magnetic measurements have distinct diagnostic value. However, in most bulk marine sediments the concentration of ferrimagnetic and antiferromagnetic minerals is extremely low, so even sensitive instrumentation often responds to the paramagnetic contribution of the silicate matrix in the residual field of the magnetometer. Analysis of magnetic extracts is usually performed to solve the problems raised by low magnetic concentrations. Additionally magnetic extracts can be used for several other analyses, for example electron microscopy or X-ray diffraction. The magnetic extraction technique is generally sufficient for sediments dominated by magnetite. In this study however, we show that high-coercivity components are rather underrepresented in magnetic extracts of sediments with a more complex magnetic mineralogy. We test heavy liquid separation, using hydrophilic sodium polytungstenate solution Na6 [H2 W12 O40 ], to demonstrate the efficiencies of both concentration techniques. Low-temperature cycling of zero-field-cooled, field-cooled and saturation isothermal remanent magnetization acquired at room temperature was performed on dry bulk sediments, magnetic extracts, and heavy liquid separates of clay-rich pelagic sediments originating from the Equatorial Atlantic. The results of the thermomagnetic measurements clarify that magnetic extraction favours components with high spontaneous magnetization, such as magnetite and titanomagnetite. The heavy liquid separation is unbiased with respect to high- and low-coercive minerals, thus it represents the entire magnetic assemblage. 相似文献
62.
构建起双向耦合的液固两相流动旋涡动力学模型与数值方法;应用离散涡方法,计算非定常不稳定水流场;采用Lagrange方法模拟颗粒运动,颗粒对流体的反作用通过修正涡泡运动速度来实现。利用所建模型,计算了两种St数的泥沙粒子在圆柱绕流场中的运动。结果证明了液固两相流动中颗粒运动与旋涡存在着明确的相关结构:(1)当水沙混合物中的泥沙颗粒碰上旋涡时,泥沙颗粒被卷入旋涡中,被卷入旋涡中的泥沙颗粒在运动过程中始终分布于旋涡区;(2)均匀水沙混合物绕圆柱流动,由于流体流过圆柱时产生剧烈分离流动,使得在尾迹流内中等St数 (St~o (1))的泥沙颗粒从均匀水沙混合物中分离出来而往旋涡区聚集。 相似文献
63.
DT—1016型阴离子交换树脂分离富集金铂钯 总被引:17,自引:5,他引:17
研究了DT-1016型阴离子交换树脂对超痕量Au,Pt,Pd的吸附性能及条件。在0.025mol/L HCl介质中,流出速度为0.5-1.0mL/min时,Au,Pt和Pd的富集效果最佳,吸附率分别为99.72%,99.06%和97.95%,共存离子无显著性影响。用等离子体质谱测定标准物质中Au,Pt和Pd,其结果与标准值基本相符。检出限Au为0.27μg/L,Pt为0.40μg/L,Pd为0.19μg/L。对GBW 07294铂族元素国家标准物质进行精密度试验,RSD(n=8)Au为19.2%,Pt为28.1%,Pd为15.6%。 相似文献
64.
氯化钠存在下氯化亚锡—罗丹明B—水体系浮选分离铱 总被引:5,自引:1,他引:5
研究了Ir(Ⅲ)在NaCl存在下SnCl2-罗丹明B-水体系中的浮选行为,在1.0mol/L HCl介质中,Ir(Ⅲ)与Pd,Pt,Rh,Au同时被浮选,Ir(Ⅲ)的浮选率为99.2%,并与常见贱金属离子分离,被浮选分离的Ir可采用原子吸收法测定,结果与火试金分离富集法相符。精密度试验,相对标准偏差(RSD,n=5)<3%。 相似文献
65.
66.
The Impact Of Air-Flow Separation On The Drag Of The Sea Surface 总被引:2,自引:1,他引:2
An approach that allows assessment ofthe impact of air-flow separation (AFS) fromwave breaking fronts on the sea-surface drag is presented. Wave breaking fronts are modelled by the discontinuities of the sea-surface slope. It is assumedthat the dynamics of the AFS from wave breaking crests is similar to thatfrom the backward facing step. The form drag supported by an individualbreaker is described by the action of the pressure drop distributed alongthe forward face of the breaking front. The total stress due to the AFS isobtained as a sum of contributions from breaking fronts of different scales.Outside the breaking fronts the drag of the sea surface is supported by theviscous surface stress and the wave-induced stress. To calculate the stressdue to the AFS and the wave-induced stress a physical model of the wind-wavespectrum is used. Together with the model of the air flow described in termsof surface stresses it forms a self-consistent dynamical system for the seasurface-atmosphere where the air flow and wind waves are strongly coupled.Model calculations of the drag coefficient agree with measurements. It is shownthat the dimensionless Charnock parameter (roughness length normalized onthe square of the friction velocity and the acceleration of gravity)increases with the increase of the wind speed in agreement with fieldmeasurements. The stress due to the AFS normalized on the square of thefriction velocity is proportional to the cube of wind speed. At low windsthe viscous surface stress dominates the drag. The role of the form drag,which is the sum of the stress due to the AFS and the wave-induced stress, isnegligible. At moderate and high winds the form drag dominates. At windspeeds higher than 10 m s-1 the stress supported by the AFS becomescomparable to the wave-induced stress and supports up to 50% of the totalstress. 相似文献
67.
G. J. Redhammer G. Roth W. Paulus G. André W. Lottermoser G. Amthauer W. Treutmann B. Koppelhuber-Bitschnau 《Physics and Chemistry of Minerals》2001,28(5):337-346
Single crystals of Li-aegirine LiFe3+Si2O6 were synthesized at 1573?K and 3?GPa, and a polycrystalline sample suitable for neutron diffraction was produced by ceramic sintering at 1223?K. LiFe3+Si2O6 is monoclinic, space group C2/c, a=9.6641(2)?Å, b= 8.6612(3)?Å, c=5.2924(2)?Å, β=110.12(1)° at 300?K as refined from powder neutron data. At 229?K Li-aegirine undergoes a phase transition from C2/c to P21 /c. This is indicated by strong discontinuities in the temperature variation of the lattice parameters, especially for the monoclinic angle β and by the appearance of Bragg reflections (hkl) with h+k≠2n. In the low-temperature form two non-equivalent Si-sites with 〈SiA–O〉=1.622?Å and 〈SiB–O〉=1.624?Å at 100?K are present. The bridging angles of the SiO4 tetrahedra O3–O3–O3 are 192.55(8)° and 160.02(9)° at 100?K in the two independent tetrahedral chains in space group P21 /c, whereas it is 180.83(9)° at 300?K in the high-temperature C2/c phase, i.e. the chains are nearly fully expanded. Upon the phase transition the Li-coordination changes from six to five. At 100?K four Li–O bond lengths lie within 2.072(4)–2.172(3)?Å, the fifth Li–O bond length is 2.356(4)?Å, whereas the Li–O3?A bond lengths amount to 2.796(4)?Å. From 57Fe Mössbauer spectroscopic measurements between 80 and 500?K the structural phase transition is characterized by a small discontinuity of the quadrupole splitting. Temperature-dependent neutron powder diffraction experiments show first occurrence of magnetic reflections at 16.5?K in good agreement with the point of inflection in the temperature-dependent magnetization of LiFe3+Si2O6. Distinct preordering phenomena can be observed up to 35?K. At the magnetic phase transition the unit cell parameters exhibit a pronounced magneto-striction of the lattice. Below T N Li-aegirine shows a collinear antiferromagnetic structure. From our neutron powder diffraction experiments we extract a collinear antiferromagnetic spin arrangement within the a–c plane. 相似文献
68.
研究了大孔膦酸树脂对毒砂中主、次和痕量元素的吸附行为及洗脱条件,结合巯基棉和TBP柱分离技术,建立了两个分离流程。在J-A1160型多道直读光谱仪上实现了毒砂单矿物中包括主量元素Fe和As在内的20个元素测定。主量元素As和Fe的相对标准偏差(n为5~10)分别为1.03%和0.9%,其它元素在5%~11%范围。流程经实际试样分析验证,结果与化学法相符。 相似文献
69.
70.