卢氏膨胀岩湿胀软化特性研究

为研究卢氏膨胀岩湿胀软化特性,开展了膨胀性试验和常规三轴试验。并将泡水前后的膨胀岩进行扫描电子显微镜(SEM)试验和氮气吸附(NA)试验。为充分考虑膨胀岩内部颗粒之间的胶结作用和原始结构,试验样品采用原状膨胀岩。试验研究结果表明:膨胀岩吸水膨胀具有明显的各向异性,轴向膨胀率大于径向膨胀率且在1.5倍左右;随着相对含水率的增加,峰值强度呈先快速降低再缓慢降低的变化趋势,弹性模量和黏聚力呈增加趋势;在围压保持不变的情况下,随着含水率的增加,膨胀岩破坏形式由张拉破坏、张剪破坏向剪切破坏转变,并且膨胀岩破坏时表面裂缝增多。微观试验结果显示,泡水后膨胀岩微观结构裂隙比泡水前增多,孔隙发育明显,这是膨胀岩软化的根本原因。     

The spectroscopic and interferometric orbit of Gliese 150.2

We determined the spectroscopic-interferometric orbit of the binary red dwarf Gliese 150.2 with a period of 13.84 yr and a semimajor axis of 0.257 arcsec. Based on the orbital elements and on accurate measurements of the magnitude difference at several wavelengths, we estimated the spectral types and masses of the components (K0 V and M0 V, 0.79 and 0.55M _⊙) and the dynamical parallax of the binary (40.4 mas).     

Geochemistry, mineralogy, and technological properties of the main Stephanian (Carboniferous) coal seams from the Puertollano Basin, Spain

This study is focused on the occurrence and distribution of mineral matter and major and trace elements in the high volatile bituminous coal from Puertollano (south-central Spain). The relationship between ash behaviour and inorganic composition, as well as the possible formation of fouling and slagging deposits in boilers during the conversion process, were investigated. The Puertollano coals do not exhibit plastic properties, despite their rank, probably because of their high ash and inertinite contents.The Puertollano coal has medium to low total S content (0.48% to 1.63% db, with a mean of 1.0% db) and is characterised by relatively high contents of Si, Pb, Sb, and Cs. Some elements such as As, Cd, Co, Cr, Cu, Ge, Li, Mn, Ni, W, and Zn are also present in relatively high contents. The enrichment in a number of heavy metals could be attributed to the common sulphide ores occurring near the Puertollano coal deposit.The following trace elements affinities are deduced: (a) sulphide affinity: As, Co, Cd, Cu, Ni, Sb, Tl, and Zn; (b) aluminum–silicate affinity: K, Ti, B, Co, Cr, Cs, Cu Ga, Hf, Li, Nb, Rb, Sn, Ta, Th, V, Zr, and LREE; (c) Carbonate affinity: Ca, Mg, Mn, and B; (d) organic affinity: B.The very high Si levels and the anomalous enrichment in Cs, Ge, Pb, Sb, and Zn shown by the Puertollano coals account for the high contents of these elements in the Puertollano fly ash when compared with the other Spanish coal fly ashes.The chemical composition of the high temperature ash (HTA) is consistent with the trend shown by the ash fusion temperatures (AFT) and also with the predictive indices related to slagging and fouling propensities. Thus, the ash fusion temperatures increase with high values of Al₂O₃ as well as with the decrease in Fe₂O₃, CaO, and MgO.     

SURFACE ROUGHNESS EVOLUTION OF SOILS CONTAINING ROCK FRAGMENTS

Soil surface roughness is a dynamic property which determines, to a large extent, erosion and infiltration rates. Although soils containing rock fragments are widespread in the Mediterranean region, the effect of the latter on surface roughness evolution is yet poorly understood. Therefore, laboratory experiments were conducted in order to investigate the effect of rock fragment content, rock fragment size and initial moisture content of the fine earth on the evolution of interrill surface roughness during simulated rainfall. Surface elevations of simulated plough layers along transects of 50 cm length were measured before and after simulated rainfall (totalling 192.5 mm, I = 70 mm h⁻¹) with a laser microreliefmeter. The results were used to investigate whether systematic variations in interrill surface roughness along stony hillslopes in southeastern Spain could be attributed to rock fragment cover and rock fragment size. Soil surface elevations were measured along the contour lines (50 cm long transects) with a contact microreliefmeter. Roughness was expressed by two parameters related to the height and frequency of roughness elements, respectively: standard deviation of de-trended surface elevations (random roughness: RR), and correlation length (L) derived from exponential fits of the autocorrelation functions. The frequently used assumption that surface roughness (RR) of cultivated topsoils decreases exponentially with cumulative rain is not valid for soil surfaces covered by rock fragments. The RR of soils containing small rock fragments (1.7–2.7 cm) increased with cumulative rainfall after an initial decrease during the first 17.5 mm of rainfall. For soils containing large rock fragments (7.7 cm), RR increased with rainfall above a threshold rock fragment content by mass of 52 per cent. For a given rainfall application, RR increased non-linearly with rock fragment content. The correlation length for soils containing small rock fragments decreases with rock fragment content and is significantly lower than for soils with large rock fragments. Soils covered with small rock fragments (large RR and small L) are thus well protected against raindrop impact by a water film in the depressions between the rock fragments. On abandoned agricultural fields along hillslopes in southeastern Spain, rock fragments cover increases non-linearly with slope owing to selective erosion of finer particles on steep slopes. The increase of surface cover by large rock fragments (>25 mm) is even more pronounced. The simultaneous increase of rock fragment cover and rock fragment size with slope explains the non-linear increase of RR with slope. These relationships differ for soils covered by platy misaschists and those covered with cubic andesites. The variations in correlation length along the hillslopes are not clear, probably owing to a simultaneous increase in rock fragment cover and rock fragment size. These findings may provide a better prediction of soil surface roughness of interrill areas covered by rock fragments using slope angle and lithology.     

祁连山北阿拉善地体特征及其大地构造演化

祁连山北阿拉善地块在大地构造位置上处于中亚造山带、塔里木板块、祁连山-秦岭造山带和华北板块之间.阿拉善地体在太古代-元古代作为一个相对独立的小地体发育, 其结晶基底岩性与塔里木板块、华北板块存在一定程度差异.受加里东构造运动影响, 板块与地体表现为南聚北散特点; 在中奥陶世早期阿拉善地体与华北板块拼为一体, 进入板块整体演化阶段.中海西构造运动期, 北部早二叠世古亚洲洋关闭, 发育新增地壳, 形成北缘沟弧盆体系; 晚海西构造运动期, 阿拉善地体向南俯冲, 祁连山洋关闭, 地壳增生, 阿拉善地体与塔里木板块、华北板块焊接在一起.新特提斯构造运动对其影响巨大, 南缘表现为"左旋"走滑, 北缘表现为"右旋"走滑, 古生代所形成构造带均受到新生代北东向构造的强烈改造.阿拉善地体频繁的构造运动, 致使其南北部相对稳定的燕山期所形成的煤系中小盆地群(阿拉善-银额盆地群、北山盆地群、河西走廊盆地群、祁连山东部盆地群、祁连山西部盆地群、阿尔金盆地群、柴达木周缘盆地群), 也相应发生快速沉降与快速抬升过程, 后期均遭受强烈改造与破坏, 不仅造就烃源岩欠发育, 就是造成储集层致密, 总体不利于油气的生成、运移、聚集成藏, 油气勘探前景欠佳.     

Retrieval of aerosol optical properties over a vegetation surface using multi-angular,multi-spectral,and polarized data

An algorithm to retrieve aerosol optical properties using multi-angular,multi-spectral,and polarized data without a priori knowledge of the land surface was developed.In the algorithm,the surface polarized reflectance was estimated by eliminating the atmospheric scattering from measured polarized reflectance at 1640 nm.A lookup table （LUT） and an iterative method were adopted in the algorithm to retrieve the aerosol optical thickness （AOT,at 665 nm） and the （A）ngstr（o）m exponent （computed between the AOTs at 665 and 865 nm）.Experiments were performed in Tianjin to verify the algorithm.Data were provided by a newly developed airborne instrument,the Advanced Atmosphere Multi-angle Polarization Radiometer （AMPR）.The AMPR measurements over the target field agreed well with the nearby ground-based sun photometer.An algorithm based on Research Scanning Polarimeter （RSP） measurements was introduced to validate the observational measurements along a flight path over Tianjin.The retrievals were consistent between the two algorithms.The AMPR algorithm shows potential in retrieving aerosol optical properties over a vegetation surface.     

Negative differential resistance behaviour in N-doped crossed graphene nanoribbons

By using first-principles calculations and nonequilibrium Green's function technique, we study elastic transport properties of crossed graphene nanoribbons. The results show that the electronic transport properties of molecular junctions can be modulated by doped atoms. Negative differential resistance (NDR) behaviour can be observed in a certain bias region, when crossed graphene nanoribbons are doped with nitrogen atoms at the shoulder, but it cannot be observed for pristine crossed graphene nanoribbons at low biases. A mechanism for the negative differential resistance behaviour is suggested.     

Distribution of caesium-137 in soils across a hillslope hollow

The distribution of soil ¹³⁷Cs in relation to selected soil and landform properties was studied across a 16 ha hillslope hollow in the Hunter valley, New South Wales, Australia. The hillslope was used as grazing for cattle. Caesium-137 was not significantly related to the amount of sand, silt, or clay, the bulk density, the organic matter content, the slope angle or the relative distance downslope. However, ¹³⁷Cs was significantly related to the thickness of the soil A horizon. Spatial variations in ¹³⁷Cs were compared with topographic units and a six-element hillslope model, but there was little correspondence. It was thought that the effects of microtopography could have masked potential interrelationships between ¹³⁷Cs and broader scale landform parameters.     

Inelastic constitutive properties and shear localization in Tennessee marble

The inelastic response of Tennessee marble is modelled by an elastic plastic constitutive relation that includes pressure dependence of yield, strain‐softening and inelastic volume strain (dilatancy). Data from 12 axisymmetric compression tests at confining pressures from 0 to 100 MPa are used to determine the dependence of the yield function and plastic potential, which are different, on the first and second stress invariants and the accumulated inelastic shear strain. Because the data requires that the strain at peak stress depends on the mean stress, the locus of peak stresses is neither a yield surface nor a failure envelope, as is often assumed. Based on the constitutive model and Rudnicki and Rice criterion, localization is not predicted to occur in axisymmetric compression although faulting is observed in the tests. The discrepancy is likely due to the overly stiff response of a smooth yield surface model to abrupt changes in the pattern of straining. The constitutive model determined from the axisymmetric compression data describes well the variation of the in‐plane stress observed in a plane strain experiment. The out‐of‐plane stress is not modelled well, apparently because the inelastic normal strain in this direction is overpredicted. In plane strain, localization is predicted to occur close to peak stress, in good agreement with the experiment. Observation of localization on the rising portion of the stress–strain curve in plane strain does not, however, indicate prepeak localization. Because of the rapid increase of mean stress in plane strain, the stress–strain curve can be rising while the shear stress versus shear strain curve at constant mean stress is falling (negative hardening modulus). Copyright © 2001 John Wiley & Sons, Ltd.