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991.
David Simmonds 《Research in Transportation Economics》2011,31(1):2-11
In discussion of the modelling methods that can be used to assess the impacts of transport change on regional and local economies, “land-use/transport interaction (LUTI) models” are often referred to as if all such models were examples of a single, homogeneous commodity. The first and major purpose of this paper is to correct this impression by comparing and contrasting some key features of the main models or modelling packages in the LUTI tradition, particularly those which are generally recognized as constituting the current “state-of-the-art”, or at least the “state of practice”. One particular point within the comparison will be the differing use which is made (or not made) of spatial input-output models in the different approaches.The second purpose of the paper is (more briefly) to compare LUTI modelling with alternative approaches and in particular with spatial computable general equilibrium (SGCE) modelling. One of the common features to emerge from the preceding comparison is that LUTI modelling has been mainly concerned with predicting the location of fixed totals of jobs and of households under different transport scenarios. This is a general feature, even though in some cases these totals are directly fixed by the user whilst in other cases they are the results of long chains of calculations that are insensitive to transport scenarios; in a few cases, the total levels of economic activity are variable according to accessibility-related variables. In contrast, the use of SCGE modelling in testing the impact of transport proposals is very much concerned with the consequences for the total size of the economy in question, usually with a less detailed concern for the spatial distribution of impacts. This comparison leads to a discussion of whether LUTI modelling and SCGE modelling are mutually exclusive or whether some form of synthesis or integration between the two may be theoretically appropriate and/or practically desirable. The requirements of project appraisal - i.e., the assessment of benefits - are also considered. 相似文献
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Offshore jack-up rigs are often used for site exploration and oil well drilling. The footings of jack-up rigs are known as spudcan foundations. The risk of rapid uncontrolled penetration of spudcan in seabed (“punch-through”) exposes jack-ups to significant risk during installation in strong over weak layered seabeds. An example for this is a thin loose sand layer overlying a weaker stratum of clay. To prevent spudcans from “punch-through”, an in-situ measurement concept is suggested in this paper to control the installation process of spudcan foundations. First, three-dimensional finite element studies using a Coupled Eulerian–Lagrangian method are carried out to simulate the penetration process. The numerical results have been validated with existing analytical solutions and centrifuge model test data. Furthermore, parametric studies are carried out to quantify the influences of the sand thickness and shear strength of the clay on the bearing capacity of spudcans. Based on the numerical studies an idea for the development of an in-situ measurement concept is suggested to control the spudcan penetration process in-situ. 相似文献
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柴油机声振特性的研究已经成为现代柴油机技术的一个重要研究方向,在设计阶段了解和掌握柴油机振动噪声性能,基于仿真模型进行整机振动响应分析和噪声预测,对确保柴油机产品满足日益严格的振动噪声要求,提高其产品竞争力,具有十分重要的意义。以6L16/24型柴油机为研究对象,利用有限元/边界元方法对其声振特性进行了数值仿真. 相似文献