论长江中游地区新石器时代晚期的生计经济与人口压力

长江中游地区新石器时代晚期的主要生计方式是稻作农业,因渔猎所占比重不同而又可细分为山地型与平原型。水田稻作农业具有集约化程度高,产出也较高的特点。稻田耕作系统的形成与维护需要大量劳力,从而刺激人口迅速增长,结果造成人口压力。自然环境的数次波动更加剧了这种压力。因人口压力而引发的移民、战争和社会重组等,成为推动初期社会复杂化进程的主要原因。     

Carbon dioxide controlled earthquake distribution pattern in the NW Bohemian swarm earthquake region,western Eger Rift,Czech Republic – gas migration in the crystalline basement

The ascent of magmatic carbon dioxide in the western Eger (Oh?e) Rift is interlinked with the fault systems of the Variscian basement. In the Cheb Basin, the minimum CO₂ flux is about 160 m³ h^?1, with a diminishing trend towards the north and ceasing in the main epicentral area of the Northwest Bohemian swarm earthquakes. The ascending CO₂ forms Ca‐Mg‐HCO₃ type waters by leaching of cations from the fault planes and creates clay minerals, such as kaolinite, as alteration products on affected fault planes. These mineral reactions result in fault weakness and in hydraulically interconnected fault network. This leads to a decrease in the friction coefficient of the Coulomb failure stress (CFS) and to fault creep as stress build‐up cannot occur in the weak segments. At the transition zone in the north of the Cheb Basin, between areas of weak, fluid conductive faults and areas of locked faults with frictional strength, fluid pressure can increase resulting in stress build‐up. This can trigger strike‐slip swarm earthquakes. Fault creep or movements in weak segments may support a stress build‐up in the transition area by transmitting fluid pressure pulses. Additionally to fluid‐driven triggering models, it is important to consider that fluids ascending along faults are CO₂‐supersaturated thus intensifying the effect of fluid flow. The enforced flow of CO₂‐supersaturated fluids in the transitional zone from high to low permeability segments through narrowings triggers gas exsolution and may generate pressure fluctuations. Phase separation starts according to the phase behaviour of CO₂‐H₂O systems in the seismically active depths of NW Bohemia and may explain the vertical distribution of the seismicity. Changes in the size of the fluid transport channels in the fault systems caused, or superimposed, by fault movements, can produce fluid pressure increases or pulses, which are the precondition for triggering fluid‐induced swarm earthquakes.     

Fluid effect on hydraulic fracture propagation behavior: a comparison between water and supercritical CO2‐like fluid

The initiation of hydraulic fractures during fluid injection in deep formations can be either engineered or induced unintentionally. Upon injection of CO₂, the pore fluids in deep formations can be changed from oil/saline water to CO₂ or CO₂ dominated. The type of fluid is important not only because the fluid must fracture the rock, but also because rocks saturated with different pore fluids behave differently. We investigated the influence of fluid properties on fracture propagation behavior by using the cohesive zone model in conjunction with a poroelasticity model. Simulation results indicate that the pore pressure fields are very different for different pore fluids even when the initial field conditions and injection schemes (rate and time) are kept the same. Low viscosity fluids with properties of supercritical CO₂ will create relatively thin and much shorter fractures in comparison with fluids exhibiting properties of water under similar injection schemes. Two significant times are recognized during fracture propagation: the time at which a crack ceases opening and the later time point at which a crack ceases propagating. These times are very different for different fluids. Both fluid compressibility and viscosity influence fracture propagation, with viscosity being the more important property. Viscosity can greatly affect hydraulic conductivity and the leak‐off coefficient. This analysis assumes the in‐situ pore fluid and injected fluid are the same and the pore space is 100% saturated by that fluid at the beginning of the simulation.     

Chloride ion concentrations during the compression of rocks to extract pore water

Pore water needs to be extracted from rocks with low permeabilities to allow the major ion concentrations in the pore water to be estimated. Compressing a rock is the most widely used method of extracting the pore water. However, ion concentrations have been found to change during compression in previous studies, and the mechanisms involved in such ion concentration changes have not yet been fully assessed. In this study, two natural rocks and four artificially prepared samples were compressed, and changes in the chloride ion (Cl^?) concentrations as the compression pressure increased were investigated. Mechanisms that could have caused the changes observed were then assessed. The Cl^? concentrations in squeezed water decreased as the pressure increased if the sample contained a significant amount of smectite. The strong dependence of Cl^? concentration on the amount of smectite indicated that smectite played an important role in decreasing the Cl^? concentration. The dilution of the pore water with interlayer water from the smectite appeared to be the dominant mechanism involved in the decrease in Cl^? concentration found in a Kunigel‐V1 sample, because dilution of the pore water with interlayer water quantitatively explained the decrease in the Cl^? concentration. The filter effect caused by the anion exclusion effect did not appear to be a dominant mechanisms in our case. However, Cl^? concentration decrease found in natural rocks could not be fully explained by dilution with interlayer water, so other mechanisms must be involved the phenomenon in natural rocks.     

Pore pressure evolution and fluid flow during visco‐elastic single‐layer buckle folding

Pore pressure and fluid flow during the deformational history of geologic structures are directly influenced by tectonic deformation events. In this contribution, 2D plane strain finite element analysis is used to study the influence of different permeability distributions on the pore pressure field and associated flow regimes during the evolution of visco‐elastic single‐layer buckle folds. The buckling‐induced fluid flow regimes indicate that flow directions and, to a lesser degree, their magnitudes vary significantly throughout the deformation and as a function of the stratigraphic permeability distribution. The modelling results suggest that the volumetric strain and the permeability distribution significantly affect the resulting flow regime at different stages of fold development. For homogeneous permeability models (k > 10^?21 m²), low strain results in a mostly pervasive fluid flow regime and is in agreement with previous studies. For larger strain conditions, fluid focusing occurs in the buckling layer towards the top of the fold hinge. For low permeabilities (<10^?21 m²), local focused flow regimes inside the buckling layer emerge throughout the deformation history. For models featuring a low‐permeability layer embedded in a high‐permeability matrix or sandwiched between high‐permeability layers, focused flow regimes inside the folded layer result throughout the deformation history, but with significant differences in the flow vectors of the surrounding layers. Fluid flow vectors induced by the fold can result in different, even reversed, directions depending on the amount of strain. In summary, fluid flow regimes during single‐layer buckling can change from pervasive to focused and fluid flow vectors can be opposite at different strain levels, that is the flow vectors change significantly through time. Thus, a complete understanding of fluid flow regimes associated with single‐layer buckle folds requires consideration of the complete deformation history of the fold.     

The ballistics of seventeenth century musket balls

ABSTRACT

This paper investigates the firing of seventeenth Century musket balls. Prior to this research, the main concerns with making range predictions were associated with the deformed shape of the musket balls affecting their drag coefficient and therefore their distance to ground impact. However, the distance due to bounce and roll after initial impact has been unknown. In this work, the distance travelled after the first ground impact greatly exceeded expectations, with the musket balls approximately doubling the distance to their final resting positions. From these findings the initial factors thought to have had high relevance to the final resting position of the musket ball (velocity variation and drag co-efficient) become less significant and factors such as ground hardness become more prominent. The knowledge gained during this investigation will allow more accurate information to be obtained on the firing positions of opposing forces during conflicts in the English Civil War.     

Geomorphology and the sand and gravel industry of west Central Scotland

The countryside around towns is under increasing pressure for development as a result of the centrifugal forces which have characterised the capitalist urbanisation process in the post‐war era. Conflict between pro‐growth and anti‐growth interests is now endemic in many peri‐urban areas. This paper identifies the principal agents involved in the production of the built environment in the urban fringe and presents a detailed analysis of how divergent interests interact to determine the nature of the fringe environment. The research informs academic debate on rural land conversion and provides guidance for decision‐makers charged with management of the urban fringe.     

档案库房空气净化的研究

为解决大面积库房的空气净化问题,利用中央空调设备的送回风循环系统,采用灭菌型空气净化专利技术对库房空气净化处理。研究结果证明,被测环境中有害气体组分明显下降,霉菌菌落均有减少。对调节空气和改善库房内的空气质量起到了良好效果。     

The effect of pore size on cementation in porous rocks

Halite cementation in porous sandstone from the Lower Triassic Bunter Formation in North‐West Germany has been studied using measurements of porosity and permeability, before and after salt extraction, as well as from petrographic observations. The results show that in cemented sandstones there is a clear tendency for the larger pores to be halite‐filled while the smaller pores, which are responsible for the residual porosity, are left empty. Observations on cemented ‘pin‐stripe’ aeolian sandstones, in which laminations of fine and coarser sand grains alternate on a millimetre scale, indicate that this selective cementation is not due to differences in the brine composition in the pores. The implication, which is also supported by other observations, is that fluids in small pores can maintain a higher supersaturation with respect to crystallization.     

Prehistoric hunting pressure estimated by the age composition of excavated sika deer (Cervus Nippon) using the annual layer of tooth cement

Age of excavated sika deer was determined not only by the cement-annuli method but also by the observation method to avoid unnecessary destruction of archaeological materials. The observation method is based on tooth replacement, wear index and the appearance of cervical lines on the molar teeth. Stepwise discriminant analysis was used to establish a criterion for the age determination of excavated mandibles. Then the annulation method was carried out for well-preserved specimens older than 3–5 years. The age composition of excavated deer mandibles seems to have changed through the Jomon Period. Age composition at the Torihama sites (the Early Jomon Period) was characterized by an abundance of aged individuals, showing a close similarity with that of the recent deer population under protected conditions. Deer from the Kidosaku and Yahagi sites (the Late Jomon Period) and the SambuUbayama site (the Latest Jomon Period) were composed mainly of deer younger than 5 years, which seems to correspond to that of the recent hunted population living under natural conditions in Hokkaido. These data suggest that the hunting pressure increased during the Late and Latest Jomon Periods and compares with the pressures on recent hunted populations of sika deer.