共查询到20条相似文献，搜索用时 297 毫秒
1.
True bond graphs, which use effort and flow variables whose product is power, can in principle be used to describe all types of physical systems. However, many system models do not use power variables and yet can be represented usefully as pseudo bond graphs. Pseudo bond graphs have been used particularly for open systems in which it is convenient to consider control volumes or compartments with boundaries across which mass can flow. In this paper, we show how the bond graph methods used for conductive and convective heat transfer can be generalized to account for diffusion, convection, and accumulation of a variety of physical quantities and how pseudo bond graphs can aid in constructing and representing such models. These models are known in mathematical biology as “compartmental models” and it is a main contribution of this paper to show that the same pseudo bond graphs apply to thermofluid and physiological dynamic models. The bond graphs build in some conservation principles automatically and yet have the flexibility to incorporate general multiport laws when necessary. Thus the pseudo bond graphs can exhibit system structure as do other network graphs and are very general in nature. 相似文献
2.
Previous works have shown the usefulness of bond graphs for modeling and simulation of interacting lumped and distributed systems. Frequently, when damping is included in the model, the overall system is “stiff”, possessing widely disparate characteristic times. This makes simulation difficult and time consuming.Bond graphs are used here to represent the interacting lumped and modal dynamics of a system while treating the damping as an external forcing onto the system. By performing a second modal decomposition, a second bond graph model can be formulated where the damping can now be physically represented. The result is a total system model in which the characteristic times can be controlled through elimination of high frequency modes. 相似文献
3.
Bond graphs are an extremely useful modeling procedure for representing the actual energy exchange mechanisms of interacting dynamic systems. Governing state equations are straightforwardly obtained from the bond graph; however, for large structures, a restrictively large number of equations can result. A procedure is developed whereby the original equations are reduced to a form suitable for modal decomposition. The resulting modes are reinterpreted in bond graph form with the resulting model being an extremely accurate system representation while requiring only a fraction of the original number of equations. The procedure is demonstrated through example. 相似文献
4.
It is shown that reinvestment and inventory effects can be described in 0431 0368 bond-graph terms. The associated differential equations in price and order-flow 0431 0368 V variables are bilinear forms. These effects are the fundamental inertia and compliance 0431 0368 V 3 of economic bond graph theory. Properties of the components and example market 0431 0368 V 3 graphs are discussed. 相似文献
5.
Jean Buisson 《Journal of The Franklin Institute》1993,330(6)
Modelling and simulation of switching devices with bond graphs is a subject which has no totally satisfying solutions. In this paper, switching devices are represented by flow or effort sources, with a variable circuit topology at switching time. For the simulation, the usual method uses causality resistors to insure integral causality to energy storage elements. The choice of those resistors is quite arbitrary and can lead to stiff systems. We propose, for linear systems, an approach without such resistors. When components lose the integral causality, the order of the state vector changes, provoking the use of pulse variables. A solution is proposed to compute the amplitude of the pulse and the value of the new variables. 相似文献
6.
Hong Zhu Chuan Chen Li-Zhi Liao Michael K. Ng 《Journal of The Franklin Institute》2018,355(4):1819-1845
The core issue of multiple graphs clustering is to find clusters of vertices from graphs such that these clusters are well-separated in each graph and clusters are consistent across different graphs. The problem can be formulated as a multiple orthogonality constrained optimization model which can be shown to be a relaxation of a multiple graphs cut problem. The resulting optimization problem can be solved by a gradient flow iterative method. The convergence of the proposed iterative scheme can be established. Numerical examples are presented to demonstrate the effectiveness of the proposed method for solving multiple graphs clustering problems in terms of clustering accuracy and computational efficiency. 相似文献
7.
Each graph may be associated with a certain function called its generic form. If one knows the generic forms of given graphs, then one can easily determine the number of spanning trees in graphs obtained from a complete multi-graph either (1) by adding, or (2) by deleting the edges of disjoint copies of the given graphs. Our obejective here is to give a proof of a simple and useful relation between the generic forms of graphs that are complementary with respect to a complete multi-graph. 相似文献
8.
Mojeed O. Oyedeji Magdi S. Mahmoud Yuanqing Xia 《Journal of The Franklin Institute》2021,358(5):2826-2845
Multiagent systems are increasingly becoming popular among researchers spanning multiple fields of study. However, existing studies only models communication interaction between agents as either fixed or switching topologies described by crisp graphs supported by algebraic graph theories. In this paper, we propose an alternative approach to describing agent interactions using fuzzy graphs. Our approach is aimed at opening up new research avenues and defining new problems in coordination control especially in terms of dynamics between agents’ states, graph topologies and coordination objectives. This paper studies distributed coordination on fuzzy graphs where the edge-weights modeling network topologies are dependent on the states of the agents in the network. In hindsight, the network weights are adjustable based on the situational state of the agents. First, we introduce the concept of fuzzy graphs and give some distinguishing features from the crisp or fixed graphs. Next, we provide some membership functions to define the state-dependent weights and finally we use some simulations to demonstrate the convergence of the proposed consensus algorithms especially for cases where the agents are subject to system failures. 相似文献
9.
This paper deals with the problem of finding graphs (directed and undirected) maximizing the number of spanning trees among the regular graphs with the same number of nodes and edges. The approach is based on heuristic algorithms such as k-optimal and evolutionary. The emphasis is rather on checking whether these techniques are applicable to solving extremal graph problems than investigating generic structures of optimal graphs. For this reason circulant graphs, for which computationally effective tree counting formulas exist, are discussed first and then the results extended to cover the class of regular graphs. 相似文献
10.
《Information processing & management》2020,57(2):102054
Social networks and many other graphs are attributed, meaning that their nodes are labelled with textual information such as personal data, expertise or interests. In attributed graphs, a common data analysis task is to find subgraphs whose nodes contain a given set of keywords. In many applications, the size of the subgraph should be limited (i.e., a subgraph with thousands of nodes is not desired). In this work, we introduce the problem of compact attributed group (AG) discovery. Given a set of query keywords and a desired solution size, the task is to find subgraphs with the desired number of nodes, such that the nodes are closely connected and each node contains as many query keywords as possible. We prove that finding an optimal solution is NP-hard and we propose approximation algorithms with a guaranteed ratio of two. Since the number of qualifying AGs may be large, we also show how to find approximate top-k AGs with polynomial delay. Finally, we experimentally verify the effectiveness and efficiency of our techniques on real-world graphs. 相似文献
11.
由于图形提供了描述研究结果的一种简洁、有效的方式,科学家将其作为科学的显著特征。研究发现,通过增加对图形的应用,有助于科学的进步和各领域之间的有效交流。 相似文献
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13.
Bhatia等指出,Xu等对无向图中的边不相交Min-Min问题的NP-完全性证明并不成立.我们首先用一个反例指出Bhatia等对Xu等的NP-完全性证明的修正依然存在错误.基于一个从MAX-2SAT的归约,我们给出了一个无向图中边不相交Min-Min问题的NP-完全性的正确证明. 相似文献
14.
A new calculation is given for the number of spanning trees in a family of labelled graphs considered by Kleitman and Golden, and for a more general class of such graphs. 相似文献
15.
H. Atlan R. Panet S. Sidoroff J. Salomon G. Weisbuch 《Journal of The Franklin Institute》1979,308(3):297-308
Bond graphs are used in order to understand the mechanism of interaction of three important and inter-related processes of reticulocyte metabolism: potassium efflux through the cell membrane, ATP metabolism and protein synthesis. Experimental data relative to membrane mediated inhibition of this synthesis by potassium carriers, dicyclohexyl-18-crown-6 and valinomycin, are then fitted to dynamical equations suggested from the bond graphs. 相似文献
16.
This study involves the application of bond graphs to the generation of heat by cells in brown adipose tissue. In the first portion of this paper, data are presented to show the types of signals that can be measured at several sites in the system controlling thermogenesis—signals travelling from the brain to the tissue as well as signals over a feedback pathway from spinal cord temperature receptors back to the brain. Bond graphs are developed for several components of the system with an emphasis being placed on graphs describing the alternative mechanisms proposed for cellular energy conversion. The power flow is calculated using ENPORT for one mechanism for different values of plasma membrane resistance. 相似文献
17.
Samuel D. Bedrosian 《Journal of The Franklin Institute》1981,312(6):417-430
The properties of special pairs of tree counting polynomials that relate to a class of incomplete graphs and their complements are presented. These polynomial pairs are related by the previously defined binary complementing operation.In contrast with alternative graph representations, they offer the possibility of serving as a convenient signature for the specific configurations.In Part II, a new constructive procedure is presented for deriving these polynomials. It is shown that the new algorithmic approach facilities obtaining the polynomials for cases not readily obtained by use of generic factors of the basic subgraphs. 相似文献
18.
尚轶伦 《中国科学院研究生院学报》2012,29(1):12-16
考虑加权连通图上的简单连续时间马氏过程,每条边上赋权为马氏过程的转移速率,使得马氏过程混合时间最短的赋权问题称之为最快混合马氏过程问题(FMMP).我们证明FMMP在图自同构群的不变点集合中取到最优,并且在边传递图中解析地得到了最优解. 相似文献
19.
Components within micro-scale engineering systems are often at the limits of commercial miniaturization and this can cause unexpected behavior and variation in performance. As such, modelling and analysis of system robustness plays an important role in product development. Here, schematic bond graphs are used as a front end in a sensitivity analysis based strategy for modelling robustness in multi-physics micro-scale engineering systems. As an example, the analysis is applied to a behind-the-ear (BTE) hearing aid.By using bond graphs to model power flow through components within different physical domains of the hearing aid, a set of differential equations to describe the system dynamics is collated. Based on these equations, sensitivity analysis calculations are used to approximately model the nature and the sources of output uncertainty during system operation. These calculations represent a robustness evaluation of the current hearing aid design and offer a means of identifying potential for improved designs of multiphysics systems by way of key parameter identification. 相似文献
20.
《Information processing & management》2020,57(6):102309
Effectively detecting supportive knowledge of answers is a fundamental step towards automated question answering. While pre-trained semantic vectors for texts have enabled semantic computation for background-answer pairs, they are limited in representing structured knowledge relevant for question answering. Recent studies have shown interests in enrolling structured knowledge graphs for text processing, however, their focus was more on semantics than on graph structure. This study, by contrast, takes a special interest in exploring the structural patterns of knowledge graphs. Inspired by human cognitive processes, we propose novel methods of feature extraction for capturing the local and global structural information of knowledge graphs. These features not only exhibit good indicative power, but can also facilitate text analysis with explainable meanings. Moreover, aiming to better combine structural and semantic evidence for prediction, we propose a Neural Knowledge Graph Evaluator (NKGE) which showed superior performance over existing methods. Our contributions include a novel set of interpretable structural features and the effective NKGE for compatibility evaluation between knowledge graphs. The methods of feature extraction and the structural patterns indicated by the features may also provide insights for related studies in computational modeling and processing of knowledge. 相似文献