A method for estimating edge length from flake dimensions: use and implications for technological change in the southern African MSA

This paper presents a method for estimating edge length from flake dimensions. Comparison of estimated values with data from measured flake edges demonstrates the robusticity of the method. Building on the work of Braun (Braun, D.R., 2005. Examining flake production strategies: examples from the Middle Paleolithic of Southwest Asia. Lithic Technology 30, 107–125; Braun, D.R., Harris, J.W.K., 2003. Technological developments in the Oldowan of Koobi Fora: innovative techniques of artifact analysis and new interpretations of Oldowan behavior, in Mora, R., de la Torre, I. (Eds.), Oldowan: Rather More than Smashing Stones. Treballs d’ Arqueologia 9, pp. 132–144) this estimate is used to generate an edge length to mass value for complete flakes—taken to be a proxy for flaking efficiency. It is shown that this value is useful in tracking the onset, variability and decline of a well known technological phase—the Howiesons Poort of South Africa. The results suggest that the Howiesons Poort was a time in which flaking efficiency was emphasised. Furthermore, comparison of upper limits of edge to mass values for different raw materials may provide an insight into changes in raw material selection.     

关于控制我国行政成本的思考

控制行政成本,提高行政效率,是实现行政管理体制改革的核心问题。要降低行政成本,必须注重行政成本宣传,强化行政成本意识;转变政府职能,控制政府机构规模;优化政府管理流程,提高工作效率;控制公务人员膨胀,规范职务消费行为;建立科学决策机制,提高领导决策水平;增强财政预算的刚性约束,健全财政预算管理机制;改革行政部门业绩考核方式,建立科学的绩效评估制度;健全社会监管体系,加大社会监督力度。     

接近与嫡系心智模式是旅行社增强竞争力的主要障碍

心智模决定人们的思维方式和行为习惯。章认为接近与嫡系不良心智模式是旅行社增强竞争力的主要障碍。旅行社应积极倡导学习与效益型的心智模式。     

Gas breakthrough experiments on fine-grained sedimentary rocks

The capillary sealing efficiency of fine‐grained sedimentary rocks has been investigated by gas breakthrough experiments on fully water saturated claystones and siltstones (Boom Clay from Belgium, Opalinus Clay from Switzerland and Tertiary mudstone from offshore Norway) of different lithological compositions. Sand contents of the samples were consistently below 12%, major clay minerals were illite and smectite. Porosities determined by mercury injection lay between 10 and 30% while specific surface areas determined by nitrogen adsorption (BET method) ranged from 20 to 48 m² g ^{? 1}. Total organic carbon contents were below 2%. Prior to the gas breakthrough experiments the absolute (single phase) permeability (k_abs) of the samples was determined by steady state flow tests with water or NaCl brine. The k_abs values ranged between 3 and 550 nDarcy (3 × 10^?21 and 5.5 × 10^?19 m²). The maximum effective permeability to the gas‐phase (k_eff) measured after gas breakthrough on initially water‐saturated samples extended from 0.01 nDarcy (1 × 10^?23 m²) up to 1100 nDarcy (1.1 × 10^?18 m²). The residual differential pressures after re‐imbibition of the water phase, referred to as the ‘minimum capillary displacement pressures’ (P_d), ranged from 0.06 to 6.7 MPa. During the re‐imbibition process the effective permeability to the gas phase decreases with decreasing differential pressure. The recorded permeability/pressure data were used to derive the pore size distribution (mostly between 8 and 60 nm) and the transport porosity of the conducting pore system (10^‐5–10^‐2%). Correlations could be established between (i) absolute permeability coefficients and the maximum effective permeability coefficients and (ii) effective or absolute permeability coefficients and capillary sealing efficiency. No correlation was found between the capillary displacement pressures determined from gas breakthrough experiments and those derived theoretically by mercury injection.     

Global finance and the German model: German corporations, market incentives, and the management of employer-sponsored pension institutions

Where there was a settled political geography of state power and responsibilities, the remarkable growth of global finance has put enormous pressure on national economic, political and social institutions. Furthermore, the looming crisis facing many continental European social security systems has raised many doubts about the long-term viability of the German model compared to its Anglo-American rivals. In this context, large German corporations have sought ways of sustaining their global competitiveness by, in part, restructuring their national and regional commitments. To illustrate, in this paper we concentrate on the nature and organization of German employer-sponsored pension institutions in relation to Anglo-American management practice. Two issues drive the analysis. One has to do with an emerging coalition between corporate management and shareholders with respect to the market value of the firm. The second issue has to do with the allocation of risk and uncertainty between the social partners when negotiating the financing and final value of promised retirement income. The institutional framework of collective decision-making common to many of Germany's largest firms is under pressure; three models of investment decision making relevant to pension assets and liabilities are used to illustrate this point. In doing so, we suggest that the German model is more fragile than commonly realized. We also suggest that Anglo-American management practices have penetrated and affected German corporate (national and regional) institutions and regulations. The social market lauded by advocates of stakeholder capitalism is changing rapidly, at least in the sphere of large firms and global finance.     

Book Reviews

Books reviewed:
Cyberspace: The World in WiresRob Kitchin
Mike Crang, Phil Crang and Jon May, (eds.) Virtual Geographies: Bodies, Space and Relations
Joanne P. Sharp, Paul Routledge, Chris Philo and Ronan Paddison, (eds.) Entanglements of Power: Geographies of domination/resistance
Steven Daniels, Humphrey Repton: Landscape Gardening and the Geography of Georgian England
David Harvey, Spaces of Hope
Robert J. Mayhew, Enlightenment geography: the political languages of British geography 1650-1850
Felix Driver, Geography Militant: Cultures of Exploration and Empire
Eric Sheppard and Trevor Barnes, (eds.) A Companion to Economic Geography
Gordon L. Clark, Maryann P. Feldman and Meric S. Gertler, (eds.) The Oxford Handbook of Economic Geography     

Stability of Slender Masonry Columns with Circular Cross-Section under Their Own Weight and Eccentric Vertical Load

This work concerns the stability of unreinforced masonry slender circular cross-sectional columns subjected to their own weight and eccentric vertical load. Cantilever columns are examined, considering that the material has infinitely linear elastic behavior in compression and has no tensile strength. For the analysis, an existing numerical model and solution procedure developed for the stability analysis of masonry elements with rectangular cross-section are utilized and adapted to the circular columns. For the instability of the columns, an appropriate criterion that relates the top lateral deflection to the intensity of the applied eccentric vertical load is employed. By considering a reference column, critical buckling load is obtained, behavior of the column interpreted and efficiency of the numerical model emphasized. Performing a nonlinear buckling analysis using a general purpose software on this reference column, obtained results are compared with those of the adapted procedure of the present study. Implementing parametric analyses on reference column, effects of the column slenderness, eccentricity of vertical load, elastic modulus, and self-weight on the buckling load are investigated. Presented calculation procedure provides a useful tool in order to calculate the critical loads or to check the stability of masonry circular columns.     

Phase‐field modeling of epitaxial growth of polycrystalline quartz veins in hydrothermal experiments

Mineral precipitation in an open fracture plays a crucial role in the evolution of fracture permeability in rocks, and the microstructural development and precipitation rates are closely linked to fluid composition, the kind of host rock as well as temperature and pressure. In this study, we develop a continuum thermodynamic model to understand polycrystalline growth of quartz aggregates from the rock surface. The adapted multiphase‐field model takes into consideration both the absolute growth rate as a function of the driving force of the reaction (free energy differences between solid and liquid phases), and the equilibrium crystal shape (Wulff shape). In addition, we realize the anisotropic shape of the quartz crystal by introducing relative growth rates of the facets. The missing parameters of the model, including surface energy and relative growth rates, are determined by detailed analysis of the crystal shapes and crystallographic orientation of polycrystalline quartz aggregates in veins synthesized in previous hydrothermal experiments. The growth simulations were carried out for a single crystal and for grain aggregates from a rock surface. The single crystal simulation reveals the importance of crystal facetting on the growth rate; for example, growth velocity in the c‐axis direction drops by a factor of ~9 when the faceting is complete. The textures produced by the polycrystal simulations are similar to those observed in the hydrothermal experiments, including the number of surviving grains and crystallographic preferred orientations as a function of the distance from the rock wall. Our model and the methods to define its parameters provide a basis for further investigation of fracture sealing under varying conditions.     

东亚经济危机与东亚发展模式新探

本文从三个方面论述了东亚经济发展模式。首先,从历史的角度分析了东亚经济发展模式的产生、特点及其局限性。然后,进一步指出在经济全球化和信息化加速发展新的历史条件下,东亚发展模式已不能适应时代发展的要求,东亚发展模式与这次东亚经济危机存在着内在的必然的联系。最后,对东亚经济发展模式的发展与变革提出了自己的观点。