Uniaxial compression and tension tests of anthracite and loading rate dependence of peak strength

The mechanical characteristics of coal under uniaxial compressive stress and uniaxial tensile stress are key factors in investigations of the stability of galleries and coal faces, and are vital considerations for the efficient design of coalmines, disaster prevention, and environmental preservation. These mechanical characteristics have long been a topic of research, but remain insufficiently understood. In this study we performed uniaxial compression tests and uniaxial tension tests on coal, with particular attention to two concerns. The first was to measure the loading rate dependence of the peak strength of coal. Coal shows high sample-to-sample scatter in strength; test methods that are successful in comparatively homogeneous rock types cannot be used for coal. We therefore used an alternative test method that was recently developed by the authors. Anthracite samples were subjected to alternating slow and fast strain rates. Measured variations in stress during this process were used to estimate the loading rate dependence of peak strength. The second objective was to obtain complete stress–strain curves for coal under uniaxial tensile stress. It is difficult to hold samples secure during a tensile test; consequently, such curves have yet to be obtained. This study presents a successful application of the authors' method to the analysis of coal samples, yielding a complete stress–strain curve under tensile stress. The two methods presented here hold promise for application not only to anthracite but also to a wide variety of coals. It is possible to derive the values of the constants used in constitutive equations from the obtained experimental results. Once these equations are determined, they can be incorporated into finite-element software to investigate various time-dependent behaviors of coal and aid in the efficient design of coalmines and the prevention of subsidence and mine disasters.     

A diatom‐inferred record of lake variability during the last 900 years in Lützow–Holm Bay,East Antarctica

Decadal–centennial‐scale climate variability in coastal Antarctica remains poorly understood due to the limited number of highly resolved, well‐dated records. We present a 900‐year, decadal‐scale reconstruction based on sedimentary diatoms from Lake Abi in Lützow–Holm Bay, East Antarctica. Hydrological change is inferred from diatom ecological preferences in conjunction with an existing regional training set and implies that lake water specific conductivity, depth and nitrogen availability are the key drivers of diatom assemblage change. Lake Abi underwent a series of subtle environmental changes related to these environmental variables, possibly driven by changes in catchment snow melt and the duration of seasonal ice cover. Ordination is used to trace the major patterns of change in the diatom community, with notable shifts identified between 470 and 400 and at ～350 cal a BP (where present = CE 1950). The frequency of environmental variability at Lake Abi is broadly consistent with a record of the Interdecadal Pacific Oscillation during the last millennium, but contrasts with the apparent climate stability elsewhere in eastern Antarctica. Further research is required to constrain the limnological and ecological responses of lakes in coastal Antarctica to obtain more rigorous palaeoclimate reconstructions from these sites of immense potential.     

The Rn content of groundwater in strata of the Plio-Pleistocene Osaka Group in the Sennan area, Japan

Studies on the ²²²Rn content of groundwater were conducted to obtain knowledge of its distribution in the geosphere just below ground surface and below the depth of 100 m in the Osaka Group (Plio-Pleistocene). Samples analyzed from ten bore holes within 10 m depth below land surface showed that a sandy layer contained groundwater with consistent radon concentrations except for a few locations where the variations in the water level were large due to precipitation and/or the water level was within 2 m of ground surface. The average ²²²Rn concentration in groundwater within 10 m of land surface was found to be approximately equal to $\text{1}\text{3}$ to $\text{3}\text{5}$ of the highest concentration found in groundwater from a well penetrating 100–200 m (420 pCi/l^?1).     

红阳煤田的岩煤层对比

采用岩相旋回法、标志层法和煤岩层组合特征等多种方法,对红阳煤田的岩煤层进行综合对比,认为该煤系沉积稳定,标志层明显,易于辨认及对比,岩性、岩相变化有一定规律可循,具有比较明显的旋回结构,煤层层位在旋回上有一定的分布规律,为一套海陆交互相滨海平原型沉积。     

Sedimentary environment of Late Carboniferous Tangjiatun Formation in Acheng of Heilongjiang

According to the lithological assemblages and elemental geochemistry of the measured Profile,the authors studied the sedimentary and tectonic environment of the Late Carboniferous Tangjiatun Formation ...     

X-ray Raman scattering for structural investigation of silica/silicate minerals

We have performed X-ray Raman scattering (XRS) measurements on the oxygen K and silicon L absorption edges of four silica minerals: α-quartz, α-cristobalite, coesite, and stishovite. We have also calculated the partial electron densities of states (DOSs) and compared these with the XRS spectra. This study demonstrates that the short-range structure around the atom of interest strongly influences the XRS spectral features. Importantly, the oxygen K-edge XRS spectra are found to reflect the p-orbital DOS while the silicon L-edge spectra reflect the s- and d-orbital DOSs, even when a product of a momentum transfer and a mean radius of a electron orbit (1s for oxygen and 2p for silicon), Qr, is close to or larger than unity. Building on this, calculations of the partial DOSs for other silica phases are presented, including ultra-high-pressure phases, which provide a good reference for further XRS study of silica and silicate minerals. XRS measurements should be performed on not only either of oxygen or silicon but also on many kinds of constituent elements to reveal the structural change of glasses/melts of silicates under extreme conditions.     

Molecular line mapping of the giant molecular cloud associated with RCW 106 – II. Column density and dynamical state of the clumps

We present a fully sampled C¹⁸O (1–0) map towards the southern giant molecular cloud (GMC) associated with the H  ii region RCW 106, and use it in combination with previous ¹³CO (1–0) mapping to estimate the gas column density as a function of position and velocity. We find localized regions of significant ¹³CO optical depth in the northern part of the cloud, with several of the high-opacity clouds in this region likely associated with a limb-brightened shell around the H  ii region G333.6−0.2. Optical depth corrections broaden the distribution of column densities in the cloud, yielding a lognormal distribution as predicted by simulations of turbulence. Decomposing the ¹³CO and C¹⁸O data cubes into clumps, we find relatively weak correlations between size and linewidth, and a more sensitive dependence of luminosity on size than would be predicted by a constant average column density. The clump mass spectrum has a slope near −1.7, consistent with previous studies. The most massive clumps appear to have gravitational binding energies well in excess of virial equilibrium; we discuss possible explanations, which include magnetic support and neglect of time-varying surface terms in the virial theorem. Unlike molecular clouds as a whole, the clumps within the RCW 106 GMC, while elongated, appear to show random orientations with respect to the Galactic plane.     

矿产资源潜力评价成果图空间数据库中属性数据质量检查探讨

属性数据是矿产资源潜力评价成果的重要组成部分,从某种意义上说,属性数据质量直接影响矿产资源潜力评价的效果。基于此认识,通过分析属性数据填写的原则、技术要求,提出了采取软件和人工两种方式检查属性数据质量的方法。