Changing grading of soil: effect on critical states

Examples of situations are presented where the grading of a soil changes during its lifetime either by crushing of particles leading to an increase of fine material or by slow transport of fine particles with seepage leading to a decrease of fine material. Such grading changes influence the basic constitutive properties of the soil, in particular properties such as critical states which are dependent on the available range of densities of packing. Discrete element modelling is used to show the dependence of critical state conditions on grading and the way in which the particle assembly seeks out new critical state conditions as the grading changes.     

Strain analysis in Jurassic argillites of the Monte Sirino area (Lagonegro Zone,southern Apennines,Italy) and implications for deformation paths in pelitic rocks

Analysis of strain in Jurassic argillites forming part of the folded and thrusted sedimentary succession of the Lagonegro basin (southern Italian Apennines) has been carried out using ellipsoid-shaped reduction spots as strain markers. Most of the determined finite strain ellipsoids are of oblate type and show a peculiar distribution of the maximum extension direction (X), with maxima either subparallel or subperpendicular to the local fold axes. Using the strain matrix method, two different deformation histories have been considered to assist the interpretation of the observed finite strain pattern. A first deformation history involved vertical compaction followed by horizontal shortening (occurring by a combination of true tectonic strain and volume loss), whereby all strain is coaxial and there is no change in the intermediate axis of the strain ellipsoid. By this type of deformation sequence, which produces a deformation path where total strain moves from the oblate to the prolate strain field and back to the oblate field, prolate strain ellipsoids can be generated and may be recorded where tectonic deformation has not been large enough to reverse pretectonic compaction. This type of deformation history may be of local importance within the study area (i.e. it may characterize some fold hinge regions) and, more generally, is probably of limited occurrence in deformed pelitic rocks. A second deformation sequence considered the superposition of pre-tectonic compaction and tectonic strain consisting of initial layer-parallel shortening followed by layer-parallel shear (related to flexural folding). Also in this instance, volume change during tectonic deformation and tectonic plane strain have been assumed. For geologically reasonable amounts of volume loss due to compaction and of initial layer-parallel shortening, this type of deformation history is capable of producing a deformation path entirely lying within the oblate strain field, but still characterized by a changeover, during deformation, of the maximum extension axis (X) from a position parallel to the fold axis to one perpendicular to it. This type of deformation sequence may explain the main strain features observed in the study area, where most of the measured finite strain ellipsoids, determined from the limb regions of flexural folds, display an oblate shape, irrespective of the orientation of their maximum extension direction (X) with respect to the local structural trends. More generally, this type of deformation history provides a mechanism to account for the predominance of oblate strains in deformed pelitic rocks.     

金刚石中分子氢的赋存状态研究

金刚石中分子氢的定向红外光谱研究表明在垂直于(100),(110)和(111)三个方向上所测得分子氢的浓度是不相同的,且不同样品中的变化趋势也不同,即分子氢在金刚石中的定向性不明显;MNDO法计算结果显示分子氢在金刚石中的稳定程度大小关系依次为沿〈111〉定向的键心与反键心组合(a.b+b.c)〉六角体空隙(H)〉四面体空隙(T1)〉菱形中心(C1＝C2)〉四面体空隙(T2).     

合理设计岩屑规程保证正常钻进条件——金刚石钻进技术专题之一

论述了正常钻进的条件，提出了合理岩屑规程是保证正常钻进的关键和设计钻头的主要依据之一，讨论了岩屑规程与金刚石钻头唇面工作状态、孔底表面粗糙度和岩屑粒度的关系，提出了相应的建议。     

Spatialising the Melanesian Canarium industry: Understanding economic upgrading in an emerging industry among three Pacific small island states

This paper examines economic upgrading in the Canarium indicum (Canarium) nut industry in Vanuatu, the Solomon Islands and Papua New Guinea. Canarium is a tree that is indigenous to Melanesia, and has been the subject of several commercialisation attempts since 1988. The paper assesses the outcomes to various actors in the Canarium supply chain from attempts to upgrade industry products and processes by: (1) increasing the available resource in suitable locations; (2) improving nut products and processing techniques; (3) increasing actors’ knowledge and supply chain coordination; and (4) establishing product standards. A two-phase data generation process was implemented. Document analysis and participant observations of industry workshops initiated a set of four economic upgrading interventions that were adaptively implemented. A second stage of workshops and 76 interviews enabled outcomes to be assessed at the project’s end. Findings suggest that a small number of urban-based entrepreneurs benefit and subsequently are lead actors in industry development, but at the expense of benefits being distributed to a larger, more spatially disparate group of smallholder and small commercial growers. These economic upgrading outcomes are circumscribed by core-periphery relations in Pacific small island states and the scale of industry in each country. Thus, spatial inequalities are reproduced through the emerging Canarium industries. We argue that different routes to industry development are required in each country. Development initiatives that capitalise on the benefits of micro-enterprise clusters, joint action and regional institutional arrangements are proposed to overcome the impediments imposed by the particular geographies of Pacific island states.     

城市变化多基态修正模型三维时空表达

为了减少时态地理信息系统的数据冗余、提高运行效率,该文在对比分析多种时空数据基态修正模型的基础上,选择了一种只存储几个基态和相应变化信息的多基态修正模型,并以德州市某地区为例进行三维时空数据组织,实现了城市变化的三维动态展现,达到了城市变化三维时空可视化表达的目的。     

Persistent alternate abundance states in the coral reef sea urchin Diadema savignyi: evidence of alternate attractors

Alternate attractors have been shown to exist in a variety of terrestrial and aquatic systems, e.g. temperate forests, savannas, shallow lakes, wetlands, coral reefs, kelp forests. The shift from one attractor to another, also referred to as a regime shift, is thought to occur when a system passes some critical threshold such that the trajectory of the system changes direction. Alternate attractors in population dynamics can also exist, leading to alternate stable states in the population abundance of a species. This study explored alternate attractors in the population dynamics of the Indo‐Pacific sea urchin Diadema savignyi and the potential underlying mechanisms that promote its bi‐stability. In Moorea, French Polynesia, the local abundance of D. savignyi, a functionally important herbivore in lagoon habitats, occurs in two states: (i) solitary individuals that occupy crevices in low densities and (ii) aggregations of tens to hundreds of individuals. These different states are temporally stable and are not explained by spatial differences in recruitment rates of juveniles. A field experiment revealed that the per capita mortality rate of adult D. savignyi was substantially lower at sites where urchins occurred in aggregations compared with sites at which they were solitary individuals. An additional experiment showed that per capita mortality decreased with increasing aggregation size. Individuals in high‐density aggregations, however, had significantly smaller test diameters than solitary individuals, indicating that individuals in aggregations may be food limited. Collectively, the evidence suggests that the two different local abundance states of D. savignyi result from negative feedback loops where high local density can be maintained by aggregative behavior that greatly reduces per capita risk of predation when the local number of adult sea urchins is sufficiently large; sites with few sea urchins remain at low density because individuals are more susceptible to predation when crevices are occupied but there are not enough individuals to form large aggregations. Thus, there may be alternate attractors in the population dynamics of D. savignyi that can produce either persistently low or high local population densities.     

东太平洋海隆13°N表层含金属沉积物物质组成与元素赋存状态

为了解不同类型含金属沉积物在物质组成和元素赋存状态的差异,对东太平洋海隆13°N洋中脊两侧表层含金属沉积物(站号:E271和E53)进行了矿物学、地球化学分析,顺序提取实验,并与前人对轴部表层沉积物(站号:17A-EPR-TVG1)的研究结果作了对比分析。研究结果表明, E271和E53是远端含金属沉积物,由非浮力热液羽状流中颗粒物沉降所形成的;17A-EPR-TVG1沉积物是近喷口含金属沉积物,由黑烟囱或者热液硫化物丘状体崩塌、堆积,或者由热液羽状流中Fe-Mn氧化物和硫化物快速沉淀而形成的,近喷口沉积物比远端沉积物更富集Fe、Cu和Zn等元素。元素在两种含金属沉积物中的赋存状态基本相同,除了Fe,Cu,Zn,Mo和稀土元素(REE)等元素在远端沉积物中主要存在于Fe-Mn氧化物相,在近喷口沉积物中主要在残留相中。远端沉积物中REE页岩标准化配分模式与海水相似,表明REE主要来自海水,而近喷口沉积物中REE配分模式与热液流体相似,说明REE以高温热液流体来源为主。相关研究结果加深了对热液沉积作用研究的认识。     

N掺杂SnO2材料光电性质的第一性原理研究

采用全电势线性缀加平面波(full potential linearized augmented plane wave method,简记为FP-LAPW)方法,基于密度泛函理论第一性原理计算分析N掺杂SnO₂材料,研究了在N替代O原子和N替代Sn原子情况下的电子态密度、电荷密度分布以及光学性质.研究表明N掺杂替代Sn较之N掺杂替代O原子的带隙要宽,都宽于SnO₂的本征带隙,且两种情况下N分别处于负氧化态和正氧化态,其介电函数谱也与带隙对应发生蓝移,从理论上指出     

Parameter analysis for gate metal—oxide—semiconductor structures of ion-implanted 4H silicon carbide metal—semiconductor field-effect transistors

From the theoretical analysis of the thermionic emission model of current--voltage characteristics, this paper extracts the parameters for the gate Schottky contact of two ion-implanted 4H-SiC metal--semiconductor field-effect transistors (sample A and sample B for three and four times multiple ion-implantation channel region respectively) fabricated in the experiment, including the ideality factor, the series resistance, the zero-field barrier height, the interface oxide capacitance, the interface state density distribution, the neutral level of interface states and the fixed space charge density. The methods to improve the interface of the ion-implanted Schottky contact are given at last.