农民工务工地非稳定性研究——以河南省33个村为例

农民工务工地非稳定性是农民工空间流动的重要表现形式之一。基于河南省33个村1091份调查问卷数据,采用务工地变动频率、务工地企业区域粘性指数和二元Logistic等指标和方法,对务工地非稳定性特征及影响因素进行研究。结果表明:农民工务工地非稳定性较大,行业之间存在较大差异,务工企业流动性较高,务工地企业区域粘性指数较小,区域流动成为农民工流动的基本特征。务工地非稳定性主要受到个人、家庭、村庄、务工地等多种经济和非经济因素、主观和客观因素的影响。     

一种古籍修复用纸伸缩性检测方法的探讨

补纸选配是古籍修复中的重要环节,但其伸缩性尚未引起足够重视。古籍修复补纸均为传统手工抄制,浸水后强度较低。按现行国家标准浸湿法检测补纸伸缩性时易产生撕裂、变形等问题,适用性较差。本研究探讨了一种古籍修复补纸的伸缩性检测方法——喷润法。利用水分检测仪对补纸相对含水量进行测定,从测量时间和可操作性的角度验证了该方法的可行性。通过十余种常用补纸的伸缩性检测结果发现,喷润法与浸湿法所得结果具有较好的一致性。随后探讨了古籍书叶伸缩性检测的适用性,并结合具体案例,建议在修复前分析古籍书叶与补纸的伸缩性匹配度。喷润法有效避免了补纸浸湿后的拉伸变形或破裂,既适用于古籍修复补纸,也适用于古籍书叶的无损检测,可为古籍修复策略的制定提供科学依据和参考。     

NOSTALGIA AND (PRE-)MODERNITY

This article argues that, in the fourteenth century, there was a wave of nostalgia that was provoked by extreme structural change: this was a moment of demographic catastrophe (with famine and plague), endemic warfare, economic fluctuation, intensified urbanization, and intellectual and spiritual novelties. Yet scholars from a range of disciplines have assumed that nostalgia and modernity are intimately connected. Given these framings of nostalgia as a modern phenomenon, this article seeks to explore the implications of premodern nostalgia. It begins by setting out the arguments for the intertwining of nostalgia and modernity. Some have argued that modernity brings a sense of rupture and that this produces nostalgia. Others, relatedly, have argued that modernity seems to speed up our experience of time and that this produces a nostalgia for a slower-paced and more predictable past. I juxtapose these arguments with evidence of fourteenth-century outpourings of nostalgia across a range of contexts in England, Italy, and France. I analyze examples of nostalgia in political contexts (both radical and reactionary), nostalgia for apparently lost economic orders, nostalgia for a lost set of chivalric values, and nostalgia for disrupted social orders. I then suggest that these fourteenth-century manifestations of nostalgia were actually produced by precisely the features of the period that are usually deemed to be exclusive to modernity: it was rapid, rupturing structural change that provoked nostalgic regret. Nostalgia, then, would seem to indicate that there are features of the fourteenth century that might be deemed modern. However, rather than simply trying to therefore push back the moment of the birth of modernity, I argue that nostalgia is indicative of the problems of periodization. The presence of nostalgia across epochs—these echoes across the webs of time—suggest that lines of periodization, birthing moments, need to be treated with extreme caution. And it is appropriate that such a reminder should come from a phenomenon such as nostalgia, which is, after all, about resonances and echoes across time—resonances that are amplified, distorted, whispered even, but that all challenge and complicate any straightforward sense of either linear or cyclical time.     

Causes and Consequences of Inequality in Egypt

This study presents an analysis of various facets of inequality in Egypt using a political economy approach to understand how inequalities are reproduced in the Egyptian economy. It examines the drivers of income and wealth inequality, and the impact of uneven taxation. The paper highlights how the mismeasurement of top incomes can skew the measurement of inequality, and shows how Egypt has one of the biggest wealth gaps in the world. It investigates educational, gender, and healthcare inequalities and how they are reproduced across generations. The paper also highlights the disparity between urban and rural areas, which further contributes to inequality. It assesses why economic growth in Egypt has had limited success in reducing poverty and inequality, and analyzes how state and military interference in markets hampers the growth of the private sector. The paper concludes by examining how inequality, combined with a number of challenges that Egypt is facing, including increased authoritarianism, climate change, demographic pressures, and water security will likely exacerbate many of the country’s socioeconomic and political problems. Overall, the study argues that inequality remains a key concern that, if left unaddressed, may lead to social unrest and instability in the long term.     

Sectoral diversification as insurance against economic instability

This paper examines the extent to which sectoral diversification can act as an insurance mechanism against fluctuations in regional gross value‐added growth rates. Portfolio theory is applied to the growth‐instability properties of German districts. Furthermore, a comprehensive diversification measure is defined. Stochastic Frontier Analysis is deployed in order to estimate whether diversification allows regions to achieve more efficient growth‐instability combinations. The results confirm that diversification does generate such effects. Spatial interactions do also play a role: The effects are less pronounced for regions whose economic performance is mainly driven by the surrounding regions.     

Morphological evolution of three‐dimensional chemical dissolution front in fluid‐saturated porous media: a numerical simulation approach

This paper is concerned with the morphological evolution of three‐dimensional chemical dissolution fronts that occur in fluid‐saturated porous media. A fully coupled system between porosity, pore‐fluid flow and reactive chemical species transport is considered to describe this phenomenon. Using the newly presented concept of the generalized dimensionless pore fluid pressure‐gradient, which can be used to represent the interaction between solute advection, solute diffusion, chemical kinetics and the shape factor of the soluble mineral, a theoretical criterion has been established to assess the likelihood of instability at a chemical dissolution front in the reactive transport system. To simulate the chemical dissolution front evolution in a three‐dimensional fluid‐saturated porous medium, a numerical procedure combining both the finite difference method and the finite element method has been proposed. As the problem belongs to a complex system science problem, a small randomly generated perturbation of porosity is added to the initial porosity of a three‐dimensional homogeneous domain to trigger instability of a planar chemical dissolution front during its propagation within the fluid‐saturated porous medium. To test the correctness and accuracy of the proposed numerical procedure, a three‐dimensional benchmark problem has been constructed and the related analytical solution has been derived. This enables using the proposed numerical procedure for simulating the morphological evolution of a three‐dimensional chemical dissolution front from a stable, planar state into an unstable, fingering state. The related numerical results demonstrate that the proposed numerical procedure is useful for, and capable of, simulating the morphological instability of a three‐dimensional chemical dissolution front within a fluid‐saturated porous medium.     

Pattern formation during healing of fluid-filled cracks: an analog experiment

The formation and subsequent healing of cracks and crack networks may control such diverse phenomena as the strengthening of fault zones between earthquakes, fluid migrations in the Earth's crust, or the transport of radioactive materials in nuclear waste disposal. An intriguing pattern-forming process can develop during healing of fluid-filled cracks, where pockets of fluid remain permanently trapped in the solid as the crack tip is displaced driven by surface energy. Here, we present the results of analog experiments in which a liquid was injected into a colloidal inorganic gel to obtain penny-shaped cracks that were subsequently allowed to close and heal under the driving effect of interfacial tension. Depending on the properties of the gel and the injected liquid, two modes of healing were obtained. In the first mode, the crack healed completely through a continuous process. The second mode of healing was discontinuous and was characterized by a 'zipper - like' closure of a front that moved along the crack perimeter, trapping fluid that may eventually form inclusions trapped in the solid. This instability occurred only when the velocity of the crack tip decreased to zero. Our experiments provide a cheap and simple analog to reveal how aligned arrays of fluid inclusions may be captured along preexisting fracture planes and how small amounts of fluids can be permanently trapped in solids, modifying irreversibly their material properties.     

Revisiting Settlement Contemporaneity and Exploring Stability and Instability: Case Studies from the Indus Civilization

ABSTRACT

“Map overestimation,” or “the contemporaneity problem,” derives from the assumption that settlements identified during surface surveys were occupied throughout individual periods. Inductive and simulation analysis have been used to ascertain the degree of contemporaneity in surface survey data sets, as variation in settlement location is critical for understanding population density and demography, which inform social, economic and political interpretations. This paper revisits the inductive approach to interrogating survey data developed by W. M. Sumner and the simulation model approach developed by R. E. Dewar to explore the survey data from two regions within South Asia’s Indus civilization. This analysis demonstrates the strengths and weaknesses of these approaches. It also highlights the variability in settlement systems in different areas within the Indus civilization and shows that consideration of stability and instability within settlement systems is an important factor when considering dynamics of resilience and sustainability.     

Finance is History!

A new sensitivity to the significance of historical experience has developed since the 2007 financial crisis. There are three possible ways of drawing on the past: as a source of advice on policies, of patterns of past evolution, of multiple possibilities. The best way of thinking about history is as a way of testing conventional hypotheses – particularly when those hypotheses are being used to create market opportunities (by making for false confidence; but also by engendering exaggerated despair).     

Role of Monitoring in Historical Building Restoration: The Case of Leaning Tower of Pisa

A short summary is presented of the studies and the actions of Committees appointed in past 50 years for the Tower of Pisa. The discussion first addresses the attempts carried out during the whole history of the Tower to measure its movements and the efforts made to understand the origin and causes of its inclination. A history of foundation rotation has been also deduced by means of a precise architectural survey, which has led to a diagnosis for the inclination and its increase in time. As a consequence, several hypotheses for its stabilization have been proposed. All the measures for leaning tower stabilization need the application of observational method for their implementation. The observational method is strictly based on a comprehensive monitoring system, both described in the second part of the paper. The aims are to stress the importance of a well-conceived monitoring system and to propose the extension of concept of monitoring to construction history details. The data and actions described are from the work carried out by committees appointed by Italian Government during the second half of 20th century, in particular by the committee chaired by Professor Jamiolkowski, appointed in 1991. The authors have collaborated with this committee since 1993, and they are still in charge of the monitoring and maintenance of the Tower of Pisa.