Avorio d'ogni ragione: the supply of elephant ivory to northern Europe in the Gothic era

This article accounts for the hitherto unexplained increase in the availability of ivory in mid-thirteenth-century France through an alteration in the medieval trade routes that brought elephant tusks from Africa to northern Europe. A newly-opened passage through the Straits of Gibraltar allowed a small amount of luxury goods to be shipped together with bulk materials necessary to the flourishing textile industries of northern Europe.     

《报任安书》三题

文章讨论司马迁《报任安书》中的两个“不得已”与“曼辞以自饰”的意义以及与“从上雍”相关的结构分析问题。     

Satellite footprint to cultural lifelines: Sirius XM and the circulation of Canadian content

Satellite radio posed a new question for Canadian policy-makers: How to take advantage of a transnational radio service while ensuring cultural identity was not lost within channel offerings that are predominately American. Comparing the initial licensing of satellite radio in Canada (2005) to the merger of the services (2011) and the post-merger license renewal (2012) highlights a shift in the spatial understanding of satellite radio, from being determined by a satellite’s footprint to that of what I call ‘cultural lifelines,’ the various mobile devices and services that enable one to maintain connection to cultural content. Alongside shifting spatial considerations of satellite radio, Canadian content has increasingly been packaged as a brand or genre, catering to fragmented taste preferences and individual, mobile listening practices.     

Embodied bicycle commuters in a car world

As an initiative to increase cycling, bike to work (BTW) events emphasize a pragmatic approach in which people learn through sensory experience. Pragmatism contends that the lived experience of the commuter within fluid geographies of social and physical conditions informs commuting knowledge and behavior. I researched how bicyclists participate in the 2012 BTW event in Lake Tahoe (USA) and how these experiences facilitate the process of becoming bicycle commuters. My study included participant observations, interviews, video observations, and route mapping. I analyzed this data with thematic and narrative analyses. I find that the BTW event illuminates bicycling, a normally invisible practice in a car world, and creates temporary bicycle-friendly spaces that provide the embodied experience and knowledge of bicycle commuting within context. Through this lived experience, participants can break free from unconscious car-based patterns and become embodied bicycle commuters who engage in active renegotiations of their commuting practices.     

The role of the stress regime on microseismicity induced by overpressure and cooling in geologic carbon storage

Fluid injection in deep geological formations usually induces microseismicity. In particular, industrial‐scale injection of CO₂ may induce a large number of microseismic events. Since CO₂ is likely to reach the storage formation at a lower temperature than that corresponding to the geothermal gradient, both overpressure and cooling decrease the effective stresses and may induce microseismicity. Here, we investigate the effect of the stress regime on the effective stress evolution and fracture stability when injecting cold CO₂ through a horizontal well in a deep saline formation. Simulation results show that when only overpressure occurs, the vertical total stress remains practically constant, but the horizontal total stresses increase proportionally to overpressure. These hydro‐mechanical stress changes result in a slight improvement in fracture stability in normal faulting stress regimes because the decrease in deviatoric stress offsets the decrease in effective stresses produced by overpressure. However, fracture stability significantly decreases in reverse faulting stress regimes because the size of the Mohr circle increases in addition to being displaced towards failure conditions. Fracture stability also decreases in strike slip stress regimes because the Mohr circle maintains its size and is shifted towards the yield surface a magnitude equal to overpressure minus the increase in the horizontal total stresses. Additionally, cooling induces a thermal stress reduction in all directions, but larger in the out‐of‐plane direction. This stress anisotropy causes, apart from a displacement of the Mohr circle towards the yield surface, an increase in the size of the Mohr circle. These two effects decrease fracture stability, resulting in the strike slip being the least stable stress regime when cooling occurs, followed by the reverse faulting and the normal faulting stress regimes. Thus, characterizing the stress state is crucial to determine the maximum sustainable injection pressure and maximum temperature drop to safely inject CO₂.     

Freezing and melting behaviors of H2O‐NaCl‐CaCl2 solutions in fused silica capillaries and glass‐sandwiched films: implications for fluid inclusion studies

Fluid inclusions of the H₂O‐NaCl‐CaCl₂ system are notorious for their metastable behavior during cooling and heating processes, which can render microthermometric measurement impossible or difficult and interpretation of the results ambiguous. This study addresses these problems through detailed microscopic examination of synthetic solutions during cooling and warming runs, development of methods to enhance nucleation of hydrates, and comparison of microthermometric results with different degrees of metastability with values predicted for stable conditions. Synthetic H₂O‐NaCl‐CaCl₂ solutions with different NaCl/(NaCl + CaCl₂) ratios were prepared and loaded in fused silica capillaries and glass‐sandwiched films for microthermometric studies; pure solutions were used with the capillaries to simulate fluid inclusions, whereas alumina powder was added in the solutions to facilitate ice and hydrate crystallization in the sandwiched samples. The phase changes observed and the microthermometric data obtained in this study have led to the following conclusions that have important implications for fluid inclusion studies: (i) most H₂O‐NaCl‐CaCl₂ inclusions that appear to be completely frozen in the first cooling run to ?185°C actually contain large amounts of residual solution, as also reported in some previous studies; (ii) inability of H₂O‐NaCl‐CaCl₂ inclusions to freeze completely may be related to their composition (low NaCl/(NaCl + CaCl₂) ratios) and lack of solid particles; (iii) crystallization of hydrates, which is important for cryogenic Raman spectroscopic studies of fluid inclusion composition, can be greatly enhanced by finding an optimum combination of cooling and warming rates and temperatures; and (iv) even if an inclusion is not completely frozen, the melting temperatures of hydrohalite and ice are still valid for estimating the fluid composition.     

为了平等而不平等——从学校向工农开门看新中国的教育平等努力(1949—1965)

中国共产党自成立起就把争取工农群众受教育权利和受教育机会作为己任。新中国人民民主专政政权的建立,使广大人民获得了平等的受教育权,但是长期以来工农教育劣势却不是自然而然就能改变的。学校向工农开门就是中国共产党为增加工农受教育机会、实现真正的教育平等而做出的一种努力。在实践中,虽然采取了各种优先照顾工农青年、工农子女入学的措施,但是工农入学机会尤其是高等学校入学机会却一直不能与其他群体相比肩。于是,1958年以后学校向工农开门力度进一步加大,并且随着阶级路线的贯彻,一些"剥削阶级"子女接受高等教育机会受到限制。这就使新中国教育平等的价值追求呈现"为了平等而不平等"的特点。     

北洋政府的侨资政策及其评价

民国北洋政府时期是华侨回国投资兴办实业蓬勃发展的阶段。这与海外华侨资本的迅猛增强密切相关 ,同时也与这一时期积极的工商政策与侨资政策有着直接的联系。北洋政府的侨资政策不仅继承了晚清积极引进侨资的政策 ,而且有所发展 ,有所创新 ,并收到了一定的成效     

景德镇御窑遗址出土青花绣墩的考古修复新方法研究

景德镇御窑遗址出土的15世纪中叶青花方胜纹绣墩,体量较大,器形特殊,出土时破损和缺失严重,修复难度较大。本研究通过分析传统考古修复中石膏作为补配材料的局限性,利用3D扫描打印的优势,设计采用新颖的高强度透明树脂取代传统修复补缺材料,并且结合特制的加固装置完成对大型青花绣墩的考古修复,满足了后期研究与展览的需要。本研究提出了具有一定实践意义的3D打印补配大件异形陶瓷器的修复技术路线。     

30年来国际“贸易-交通-旅游”(3T)互动的统计分析

经济全球化背景下,国际"贸易-交通-旅游"(3T)互动日益增强。采用1982-2011年时间序列数据,分析国际贸易、交通和旅游总量的发展历程,从进、出口分量视角考察三者相关关系,运用最小二乘法构建回归方程。结果发现:①30年来国际贸易、交通和旅游的发展呈持续增长态势。国际贸易和旅游日益重要。②国际贸易、交通和旅游增长过程具有同步性,表现为波动周期同涨同落。③所构建的回归方程决断系数R²均在0.99以上,国际贸易、交通和旅游存在显著相关性。国际货运与国际贸易,国际客运与国际旅游之间具有确定、直接的因果关系;国际贸易与国际旅游的因果性尚待探究。