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11.
区域经济发展差异研究进展与展望   总被引:6,自引:1,他引:5  
区域经济发展差异研究一直是学者们关注的重点领域,且研究成果丰厚,主要集中在四个方面:区域经济发展差异的空间格局研究、时间演变研究、趋势预测研究和形成原因研究。但研究中还存在一些不足,针对问题,对区域经济发展差异研究提出了6个方面的展望:加强对欠发达区域经济发展差异研究、加强对边缘区经济发展差异研究、加强对城市及小尺度地域内部经济发展差异研究、加强对区域经济发展差异预测和预警研究、加强对区域经济发展差异动力机制研究、加强对区域经济发展差异对策研究。  相似文献   
12.
关于《左传》的记事终止时间,现在流行的《中国文学史》和《古代汉语》教材中存在两种不同的说法:一种认为迄于鲁哀公二十七年,即公元前468年;一种认为迄于鲁悼公四年,即公元前453年。结合《左传》一书的自身性质、编写体例、行文风格、古书通例等因素综合考察,鲁悼公四年和有关战国预言史料并不能作为记事终止时间的根据。《左传》的记事年代是和《春秋》大体一致的,最终止于鲁哀公二十七年,即公元前468年。但在流传过程中也间杂有一些战国史料。  相似文献   
13.
ABSTRACT

Despite the high vulnerability of historic structures to earthquakes, the approaches for evaluating seismic demand and capacity still appear inadequate and there is little consensus on the most appropriate assessment methods to use. To develop an improved knowledge on the seismic behavior of masonry structures and the reliability of analysis tools, two real-scale specimens were tested on a shake table, and several experts were invited to foresee failure mechanism and seismic capacity within a blind prediction test. Once unveiled, experimental results were simulated using multi-block dynamics, finite elements, or discrete elements. This article gathers the lessons learned and identifies issues requiring further attention. A combination of engineering judgment and numerical models may help to identify the collapse mechanism, which is as essential as it is challenging for the seismic assessment. To this purpose, discrete modeling approaches may lead to more reliable results than continuous ones. Even when the correct mechanism is identified, estimating the seismic capacity remains difficult, due to the complexity and randomness of the seismic response, and to the sensitivity of numerical tools to input variables. Simplified approaches based on rigid body dynamics, despite the considerable experience and engineering judgment required, provide as good results as do advanced simulations.  相似文献   
14.
This paper presents response spectral attenuation laws used in the new French Safety Rule, which is the reference for nuclear safety studies in France. Attenuation laws were derived from 965 horizontal and 485 vertical components from a two-step inversion method and accounts for geometrical spreading, anelastic attenuation and geological site condition. The datasets are mainly constituted of European strong motion records (83%) recently collected and homogeneously processed. In order to complete the distribution data beyond magnitude 6, a few American records were added, representing 17% of the datasets. The magnitude type and source-to-site distance definitions chosen to derive the laws are tested with respect to other definitions. These parametric tests induce a conservative law, for some magnitude and distance ranges of interest. The residual values between observed and predicted spectral accelerations are studied and do not exhibit any bias. The inferred laws are in good agreement with classical strong motion attenuation laws.  相似文献   
15.
The storage spaces within deeply buried Ordovician paleokarst reservoirs in the Tarim Basin are mostly secondary and characterized by strong heterogeneity and some degree of anisotropy. The types of fluids that fill the spaces within these reservoirs are of great importance for hydrocarbon exploration and exploitation. However, fluid identification from seismic data is often controversial in this area because the seismic velocity for this particular reservoir could be significantly influenced by many factors, including pore shapes, porosity, fluid types, and mineral contents. In this study, we employ the differential effective medium‐Gassmann rock physics model to interpret and discuss the characteristics of conventional karstic carbonate reservoirs in the Tarim Basin that are filled with different fluids (oil, gas, and water) using logging data and thus objectively build corresponding fluid identification criteria. These criteria are subsequently evaluated by amplitude versus offset (AVO) forward analysis based on typical logging data and further applied to ascertain the reservoir fluid types in two different areas in the Tarim Basin based on prestack inversion results. For conventional carbonate reservoirs, gas can be distinguished from heavy oil and water, but heavy oil and water are broadly similar on seismic data. For condensate carbonate reservoirs, water can be differentiated from light oil (i.e., condensates) and gas, but light oil and gas demonstrate substantial similarities in terms of their seismic responses. The predicted fluid results are in good agreement with the results of drilling and oil testing. In particular, modeling the seismically resolvable reservoirs in the carbonate strata in the Tarim Basin, which have needle‐ and sphere‐shaped storage spaces (pore aspect ratio > 0.3) and clay content that is lower than 5%, indicates that fluid properties could be properly evaluated if the porosity is larger than 5% for conventional carbonate reservoirs and >7% for condensate carbonate reservoirs.  相似文献   
16.
The openness of the future is rightly considered one of the qualifying aspects of the temporality of modern society. The open future, which does not yet exist in the present, implies radical unpredictability. This article discusses how, in the last few centuries, the resulting uncertainty has been managed with probabilistic tools that compute present information about the future in a controlled way. The probabilistic approach has always been plagued by three fundamental problems: performativity, the need for individualization, and the opacity of predictions. We contrast this approach with recent forms of algorithmic forecasting, which seem to turn these problems into resources and produce an innovative form of prediction. But can a predicted future still be an open future? We explore this specific contemporary modality of historical futures by examining the recent debate about the notion of actionability in precision medicine, which focuses on a form of individualized prediction that enables direct intervention in the future it predicts.  相似文献   
17.
Seismic reflection data as used in the oil industry is acquired and processed as multitrace data with source‐receiver offsets from a few hundred metres (short offset) to several kilometres (long offset). This set of data is referred to as ‘pre‐stack’. The traces are processed by velocity analysis, migration and stacking to yield a data volume of traces with ‘zero‐offset’. The signal‐to‐noise enhancement resulting from this approach is very significant. However, reflection amplitude changes in the pre‐stack domain may also be analysed to yield enhanced rock physics parameter estimates. Pre‐stack seismic data is widely used to predict lithology, reservoir quality and fluid distribution in exploration and production studies. Amplitude versus offset (AVO) data, especially anomalous signals, have been used for decades as indicators of hydrocarbon saturation and favourable reservoir development. Recently, enhanced quantification of these types of measurement, using seismic inversion techniques in the pre‐stack domain, have significantly enhanced the utility of such measurements. Using these techniques, for example, probability of the occurrence of hydrocarbons throughout the seismic data can be estimated, and as a consequence the many pre‐stack volumes acquired in a three‐dimensional (3D) can be survey, reduced to a single, more interpretable volume. The possibilities of 4D time lapse observation extend the measurements to changes in fluid content (and pressure) with time, and with obvious benefits in establishing the accuracy of dynamic reservoir models and improvements in field development planning. As an illustration, recent results from the Nelson Field (UK North Sea), are presented where we show the method by which probability volumes for oil sands may be calculated. The oil–sand probability volumes for three 3D seismic datasets acquired in 1990, 1997 and 2000 are compared and production effects in these data are demonstrated.  相似文献   
18.
This paper addresses the legendary total solar eclipse of 29 May 1919. Two British teams confirmed the light bending prediction by Albert Einstein: Charles R. Davidson and Andrew C. C. Crommelin in Sobral, Brazil and Arthur S. Eddington and Edwin T. Cottingham on the African island of Príncipe, then part of the Portuguese empire. By jointly analyzing the two astronomical expeditions supported by written and visual sources, I show how, despite extensive scholarship on this famous historical episode and the historiographical emphasis on the plural dimensions of knowledge construction, many human and non-human actors have been kept in the shadow of the eclipse. I do so by focusing on what I call knowledge from the periphery together with knowledge from below, grounded literally on how localities (sites) affect choices and events, and growing outward to encompass a wide range of participants. I show how the geopolitical status of the two nations where the observational sites were located, and specifically Portugal's condition of colonial power, affected main decisions and events, while highlighting the active role of participants, ranging from experts from the peripheries and those involved in the travels to local elites and anonymous peoples, some of whom contributed to the observation of totality.  相似文献   
19.
The need for public investment to address loss of biodiversity in agricultural landscapes is well recognised, yet there is little analysis of the likely benefits of land‐use change for regional biodiversity or the cost effectiveness of different investment options. We estimated benefits for biodiversity and cost effectiveness of different investment scenarios over 50 years for a farming area in south‐eastern Australia. Declines in biodiversity were predicted under status quo land use. Implementing actions in the investment scenarios improved biodiversity status only slightly, compared with status quo land use. Future biodiversity status differed little between biodiversity‐focused investment and salinity‐focused investment. Biodiversity status equalled or exceeded current status only for investment scenarios with much more extensive revegetation than in catchment targets. Cost effectiveness of biodiversity improvement varied greatly between investment strategies. Biodiversity improvement was more cost effective when investment to meet catchment targets was focused on revegetation for salinity management rather than on high conservation value areas, because of lower opportunity costs for salinity management. With enhanced investment, the cost effectiveness of biodiversity improvement was greater when actions were in high conservation areas. Although improvements in biodiversity were small under the changed farming system scenarios, their cost effectiveness was higher than the other investment scenarios. Regional scale improvements in biodiversity in farming areas will require increased stewardship payments or other economic incentives for landholders.  相似文献   
20.
历史必然性是唯物史观理论体系所要论证的核心问题之一。历史必然性思想具有重要的本体论和认识论依据,历史必然性与人的历史主动性有逻辑关联,历史必然性与偶然性之间存在着辩证统一的关系,强调历史必然性思想是人类推动社会进步的强大理论武器,在未来预测中具有重要的科学意义。  相似文献   
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