Manganese olivine II: point defect relaxation

To investigate the point defect chemistry and the kinetic properties of manganese olivine Mn₂SiO₄, the point defect relaxation time (τ) characterizing the rate of re-equilibration of electrical conductivity following a change in oxygen fugacity was measured for single crystals oriented for electrical conduction along the [010] direction. The experiments were carried out at temperatures T = 1173–1473 K and oxygen fugacities with the MnSiO₃ activity controlled at unity. The value of τ, which ranges from 130 to 1463 s, increases with decreasing temperature. At 1273 K, the value of τ in the regime is a factor of ∼1.8 smaller than that in the regime. The point defect relaxation time was used to calculate the chemical diffusivity (). Values of lie in the range 2.2× 10^{− 10} − 2.5×10^{− 9} m²/s. For the regime, a semi-log plot of vs 1/T yields a concave downward curve. Based on these results combined with those from Part I of this work for the point defect structure and electrical conductivity in Mn-olivine, it is proposed that the relaxation rate of electrical conduction is determined by the coupled diffusion of manganese vacancies and electron holes which rate-control the relaxation process at low and high temperatures, respectively. Deconvolution of the curve into two straight-line segments yields values for the mobilities and the diffusivities for Mn vacancies and electron holes. These results, combined with the measured electrical conductivity data, were used to calculate the concentrations of Mn vacancies and electron holes. These results in conjunction with those published for other transition-metal silicate olivines reveal the following: The mobility of electron holes in Mn-olivine is about two orders of magnitude smaller than that in Fe-olivine and is somewhat larger than that in (Mg_0.9Fe_0.1)-olivine. The mobilities of metal vacancies in these three olivines are similar both in magnitude and in temperature dependence. The concentrations of the majority point defects are the highest in Fe-olivine crystals and the lowest in Co-olivine crystals, while those in Mn-olivine and (Mg_0.9Fe_0.1)-olivine crystals lie in between. The deviation from stoichiometry in the cation sublattice for a transition-metal silicate olivine is about two orders of magnitude lower than that for the corresponding transition-metal oxide. Received: 10 January 1996 / Revised, accepted: 29 May 1997     

兰州-民和盆地红古城组的建立及其地质学意义

兰州—民和盆地下白垩统地层,出露良好,厚度较大,自下而上可建立８个非正式的岩石地层单位（岩组）。红古城组位于下白垩统上部的第七岩组。该组以剖面连续、出露甚好、顶底清楚、厚度不大而与上、下地层显著不同,具独特的岩性、岩相特征。虽然岩性、岩相在横向上变化较快,但顶、底界线都具良好的标志层,在盆地内可以广泛追索和对比。该组岩石地层单位的正式建立,不仅便于区内地层的划分与对比,而且对盆内层序地层、岩相分析、构造演化的研究都具重要意义。     

具有自动峰值保持功能的双数显表的设计方案

本文向读者介绍一种高精度,低成本,具有自动峰值保持功能,且同时显示峰值和瞬时值两种状态数显表的设计实现方案。     

利用X衍射进行砼质量事故分析

本文针对某工程砼质量事故,利用Ｘ衍射分析出砼矿物组成,判定出这次砼质量事故主要是由于水泥中石膏掺量过多而造成的。     

深部剪切形变带对浅源地震的控制--立交模式有限元的模拟计算

本文在“立交模式”的基础上,用三维粘弹有限元方法计算了几个简化的地质体模型,讨论了地壳下部的蠕滑断层对浅部断层活动的影响和对浅部应力场的调整和控制过程。结果表明,深部断层的蠕滑作用可使浅部应力场增强,井使得在特定方向,特定走向的断层内的应力加速积累或松弛。据此,本文解释了地震震中沿直线的迁移问题,同时也讨论了大地震原地重复发生的力学机制。     

Gamma-ray and microwave evidence for two phases of acceleration in solar flares

Relativistic electrons in large solar flares produce gamma-ray continuum by bremsstrahlung and microwave emission by gyrosynchrotron radiation. Using observations of the 1972, August 4 flare, we evaluate in detail the electron spectrum and the physical properties (density, magnetic field, size, and temperature) of the common emitting region of these radiations. We also obtain information on energetic protons in this flare by using gamma-ray lines. From the electron spectrum, the proton-to-electron ratio, and the time dependences of the microwave emission, the 2.2 MeV line and the gamma-ray continuum, we conclude that in large solar flares relativistic electrons and energetic nuclei are accelerated by a mechanism which is different from the mechanism which accelerates 100 keV electrons in flares.Research supported by NASA Grant 21-002-316 at the University of Maryland, College Park.     

The heat balance on the sea surface in the mature phase of 1982/83 El Nino event

Using the air-sea data set of January, 1983 (the mature phase of the 1982/83 El Nino event), the net radiation on the sea surface, the fluxes of the latent and the sensible heat from ocean to the atmosphere and the net heat gain of the sea surface are calculated over the Indian and the Pacific Oceans for the domain of 35°N-35°S and 45°E-75°W. The results indicate that the upward transfer of the latent and the sensible heat fluxes over the winter hemisphere is larger than that over the summer hemisphere. The sensible heat over the tropical mid Pacific in the Southern Hemisphere is transported from the atmosphere to the ocean, though its magnitude is rather small. The latent heat flux gained by the air over the eastern Pacific is less than the mean value of the normal year. The net radiation, on which the cloud amount has considerable impact, is essentially zonally distributed. Moreover, the sea surface temperature (SST) has a very good correlation with the net radiation, the region of warm SST coinci     

Manganese olivine I: Electrical conductivity

To investigate the point defect chemistry and the kinetic properties of manganese olivine Mn₂SiO₄, electrical conductivity () of single crystals was measured along either the [100] or the [010] direction. The experiments were carried out at temperatures T=850–1200 °C and oxygen fugacities atm under both Mn oxide (MO) buffered and MnSiO₃ (MS) buffered conditions. Under the same thermodynamic conditions, charge transport along [100] is 2.5–3.0 times faster than along [010]. At high oxygen fugacities, the electrical conductivity of samples buffered against MS is 1.6 times larger than that of samples buffered against MO; while at low oxygen fugacities, the electrical conductivity is nearly identical for the two buffer cases. The dependencies of electrical conductivity on oxygen fugacity and temperature are essentially the same for conduction along the [100] and [010] directions, as well as for samples coexisting with a solid-state buffer of either MO or MS. Hence, it is proposed that the same conduction mechanisms operate for samples of either orientation in contact with either solid-state buffer.The electrical conductivity data lie on concave upward curves on a log-log plot of vs , giving rise to two regimes with different oxygen fugacity exponents. In the low- regime , the exponent, m, is 0, the MnSiO₃-activity exponent, q, is 0, and the activation energy, Q, is 45 kJ/mol. In the high regime 10^{ - 7} {\text{atm}}} \right)$$ " align="middle" border="0"> , m=1/6, q=1/4–1/3, and Q=45 and 200 kJ/mol for T<1100 °c=" and=">T>1100 °C, respectively.     

菲律宾东部沿岸流

根据1986～1989年间9～10月中国科学院海洋研究所“科学一号”船在菲律宾东部海域获得的CTD调查资料,分析了菲律宾东部沿岸流。分析得出,菲律宾东部沿岸流是一支每年都存在的南向流,除个别海域外,流速均小于20cm/s,是一支较弱的流。但这支流有一明显特征,除在该流源地外,最大流速值是在200m水层或者更深的地方。它的最大宽度约为200km,主要水体集中在700m以浅的水层。我们认为岸形影响是该支流形成的主要原因。     

Relation of ice conditions to climate change in the Bohai Sea of China

1NTRODUcrIONThe bohai As is a seasonally ice-covered sea and is located in the lowest latitudes (37' -4l'N), where sea ice occurs. The bohai ffea is nearly enclosed by land in the south, the northand the west, and only connects to the Huanghai ffea through the bohai Strait in the east.The width of the strait is abeut l06 km. The boai ffea is very shallow basin with the meandepth of l8 m and the maximum depth of 78 m. The topography of the sea bottom and thecoastal regions has an importan…