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991.
The Graph-Theoretical Field Model provides a unifying approach for developing numerical models of field and continuum problems. The methodology examines the field problem from the first stages of conceptualization without recourse to the governing differential equations of the field problem; this is accomplished by deriving discrete statements of the physical laws which govern the field behaviour. There are generally three laws, and these are modelled by the “cutset equations”, the “circuit equations”, and the “terminal equations”. In order to establish these three sets of equations it is expedient first to spatially discretize the field in a manner similar to the finite difference method and then to associate a linear graph (denoted as the field graph) with the spatial discretization. The concept of “through” and “across” variables, which underlies the cutset and circuit equations respectively, enables one to define the graph in an unambiguous manner such that each “edge” of the graph identifies a pair of complementary variables. From a knowledge of the constitutive properties and the boundary conditions of the field it is possible to associate terminal equations with sets of edges. Since the resulting sets of equations represent the field equations, these equations provide the basis for a complete (but approximate) solution to the field or continuum problem. In fact, this system approach uses a two part model: one for the components and another for the interconnection pattern of the components which renders the formulation procedures totally independent of the solution procedure.This paper presents the theoretical basis of the model and several graph-theoretic formulations for steady-state problems. Examples from heat conduction and small- deformation elasticity are included. 相似文献
992.
Recently, March, Hooper, and Baum (1977) described a sample of 99 nonstudent elders in terms of their demographic characteristics and their attitudes toward lifelong learning. The sample was found to be well‐educated (mean years of education = 13.61, SD = 9.43), active in the community, well‐read, and fairly affluent. The majority demonstrated a quite open attitude toward the appropriateness of formal education in old age, but also felt that learning can be acquired outside the classroom: “living is learning.” The present study was undertaken to similarly describe a sample of elderly people enrolled in the University of Wisconsin guest student program, and to contrast these respondents with those in the earlier study. The student group was found to be significantly younger than the nonstudent group (mean = 70.78, SD = 7.21 vs. mean = 74.69, SD = 8.45; t = 2.87, p < .001). Although there is no difference in the mean years of education of the two groups, there is significantly greater variability in years of education in the student group (F = 10.98, p < .001), with 50.4% of the nonstudent group versus 21.6% of the student group having 12 years of education or less. Additionally, it was found that only 10 of the 139 student respondents did not have either personal or vicarious personal (through familial significant others) experience with higher education in youth. The respondents’ stated preference for class format and student group age is also summarized, and some implications for educational gerontology are discussed. 相似文献
993.
J. Mitchell Miller 《Journal of Criminal Justice Education》2013,24(3):323-324
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Exploratory activity was examined in 4 young baboons with the aim of investigating the type of spatial coding (purely geometric and/or by taking into account the identity of the object) used for the configuration of objects. Animals were individually tested in an outdoor enclosure for their exploratory reactions (contact time and order of spontaneous visits) to changes brought about to a configuration of different objects. Two kinds of spatial changes were made: a modification (1) of the shape of the configuration (by displacement of one object) and (2) of the spatial arrangement without changing the initial shape (exchanging the location of two objects). In the second experiment, the effect of a spatial modification of the global geometry constituted by four identical objects was investigated. Finally, in the third experiment, a substitution of a familiar object with a novel one was performed without changing the objects’ configuration. The baboons strongly reacted to geometrical modifications of the configuration. In contrast, they were less sensitive to modifications of local features that did not affect the initial spatial configuration. Analyses of spontaneous exploratory activities revealed two types of exploratory strategies (cyclic and back-and-forth). These data are discussed in relation to (1) the distinction between the encoding of geometric versus local spatial features and (2) the spatial function of exploratory activity. 相似文献
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