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1.
This article presents a conceptual framework for clarifying the network hypotheses embedded in policy theories and how they relate to macrolevel political institutions and microlevel political behavior. We then describe the role of statistical models of networks for testing these hypotheses, including the problem of operationalizing theoretical concepts with the parameters of statistical models. Examples from existing theories of the policy process and empirical research are provided and potential extensions are discussed.  相似文献   

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The Basilica of San Francesco in Assisi endured stronger earthquakes for centuries before 1997 earthquake, which generated the collapse of the two vaults. Experts blame as possible reasons of collapse the damage cumulated from previous earthquakes and/or the retrofitting made to the structure over its lifetime. This article presents the history of the retrofit interventions of the Basilica through the centuries, focusing mainly on the roof, which has been subjected to three major restorations through its life. It is shown using simple analytical models that the cumulative effects of the changes made to the roof of the Basilica affected the structure’s dynamic behavior in a negative manner, increasing the seismic loads on the existing structural members. In particular, the numerical results show that the 1958 roof intervention has stiffened the structure, redistributing the seismic loads on the façade and the transept. This overload might explain the collapse of the two Gothic vaults during 1997 earthquake.  相似文献   

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Basic properties of the production and trade system for sulfur in the North Atlantic sphere are studied. Oligopolistic competition produces a more stable system than polypoly. Occasional exceptions, difficult to anticipate theoretically, are possible, however. When subjected to realistic exogenous shocks in consumption (demand), the system is less stable than if the shocks appear in supply.  相似文献   

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Archaeologists construct sequence models to describe the operation of past activities such as production of stone tools. As developed in Japan, France, and North American, such models summarize processes, present intermediate steps, and link formally diverse materials. Some sequence models are teleological in that they present actions as predetermined patterns. Others can be considered evolutionary in that they describe results produced by selected interaction between conditions and variables. With separate strengths and different goals, both approaches to sequence modeling have archaeological utility.  相似文献   

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关于商代分封制的问题,学者有不同意见,有的学者认为商代存在分封制,也有的学者认为商代没有分封制,分封制是周代才确定的制度。  相似文献   

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A methodology is described for harnessing the power of supercomputer hardware to build an automated modeling system. The problems of applying this new approach to mathematical modeling in geography are discussed by reference to the design of better performing spatial interaction models. It is also possible that the results may provide clues about new theories and knowledge.  相似文献   

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This paper explores analytically the contemporary pottery‐making community of Pereruela (north‐west Spain) that produces cooking pots from a mixture of red clay and kaolin. Analyses by different techniques (XRF, NAA, XRD, SEM and petrography) showed an extremely high variability for cooking ware pottery produced in a single production centre, by the same technology and using local clays. The main source of chemical variation is related to the use of different red clays and the presence of non‐normally distributed inclusions of monazite. These two factors induce a high chemical variability, not only in the output of a single production centre, but even in the paste of a single pot, to an extent to which chemical compositions from one ‘workshop’, or even one ‘pot’, could be classified as having different provenances. The implications for the chemical characterization and for provenance studies of archaeological ceramics are addressed.  相似文献   

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Digital 3D modelling is increasingly common in archaeological recording, but building the models is only part of the story. Sharing and interacting with these digital representations is essential in fostering engagement and ensuring that research is relevant to the broader community. Projects and institutions understand that much of their communication and outreach now take place via digital platforms. However, archaeologists are faced with a variety of challenges when sharing 3D models of human remains online, including metadata curation, accessibility, openness, copyright as well as the ethical implications of sharing digital bioarchaeological data and long-term storage requirements. In this research, metadata from a collection of 3D models of human remains were extracted from SketchFab and analysed to understand how users share 3D models of human remains via online social platforms. The results were contrasted with a critical review of current ethical and technical guidelines, indicating potentially ethically compromising practices, particularly the lack of contextualising metadata for some models. This article proposes and discusses recommendations for developing more strategic approaches to the sharing of 3D data on human remains online, such as assessing and agreeing hosting, licensing and metadata management during project design. Frameworks are provided to support these approaches and make decisions on how to share data openly.  相似文献   

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杜旭宇 《攀登》2001,20(2):50-53
“后发优势”,实质上是由“时间差”而形成的一种“优势”。中国改革在时序安排上很好地考虑并利用了改革中的各种“时间差”,形成了一系列“后发优势”,大大简化了改革的难度,降低了改革的成本和风险,使得改革进展顺利并且取得很大的成功。  相似文献   

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本文通过对汉代铁官铭的系统研究,总结出铁官铭及职官的规律。同时根据铁官的省称与编号的规律,推论出未曾发现铁官铭的铁官作坊的职官形式,进而从具体作坊职官形式,推论汉代整个大铁官体系。  相似文献   

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The allocation of time by a part-time marketer between subsistence production and marketing links production and consumption decisions in a periodic marketing system. Distinctions between full- and part-time marketers are emphasized. The model of the part-time trader predicts changes in the time devoted to each activity and in outputs as relative prices change. Interpretations can be made regarding the amount of effort devoted to, and the rewards from, periodic marketing.  相似文献   

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我们基本上是通过对文本或文献的阅读,才可能重构关于历史时期的地理景观和地理知识,才可能理解历史时期地理景观与地理知识对于古人和今人的意义。因此本文考察了历史文本或文献中地理陈述与地理景观和地理知识之间的各种关系,以及当前对这些地理陈述的不同阅读方法。  相似文献   

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Cluster analysis has been pursued from a number of directions for identifying interesting relationships and patterns in spatial information. A major emphasis is currently on the development and refinement of optimization‐based clustering models for the purpose of exploring spatially referenced data. Within this context, two basic methods exist for identifying clusters that are most similar. An interesting feature of these two approaches is that one method approximates the relationships inherent in the other method. This is significant given that the approximation approach is invariably utilized for cluster detection in spatial and aspatial analysis. A number of spatial applications are investigated which highlight the differences in clusters produced by each model. This is an important contribution because the differences are in fact quite significant, yet these contrasts are not widely known or acknowledged.  相似文献   

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Interfacility Interaction in Models of Hub and Spoke Networks   总被引:3,自引:0,他引:3  
Providers of transportation services may reduce their average unit costs by bundling flows and channeling them between hubs (also known as concentrators or routers). The resulting facility locations are interdependent because of the flows between them. This paper analyzes mathematical models of hub systems in an effort to enhance understanding of the optimal location of interactive facilities. The paper examines the behavior of solutions to several alternative models that require the location of a hub at either of two similar locations. A model employing a concave cost function favors the assembly of flows, penalizes fractional facility locations, and produces local minima that have integer facilities.  相似文献   

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On the Use and Limitations of Trend Surface Models   总被引:1,自引:0,他引:1  
A lthough the technique of trend surface mapping has been developed in the main by geologists and geophysicists, its use has now diffused into a number of other fields including regional science, botany, meteorology, and geography. It would be wrong to be unduly critical of the pioneer applications of any technique, even where errors have been made, for there are few guidelines to help such explorers. On the other hand it is felt that trend surface methods are sufficiently well estab-lishd in geography for there to be a need for a more critical appraisal of the method, especially in view of some careless or even erroneous applications that have been made recently by geographers. This paper will highlight what are considered to be some of the more important limitations of trend surface models, and will point to one or two specifically geographical problems.  相似文献   

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