Ordinary Network Research Articles

The use of a neural network for studying the relationship between air pollution and asthma-related emergency room visits

To establish the relationship between air pollution levels and bronchial asthma-associated emergency room (ER) visits, we adapted artificial network technology to conduct this study which focused on three different pollutants, sulphur dioxide, nitrogen oxide and ozone. The study population was comprised of adults presenting to the emergency room of a large metropolitan hospital in Israel during a 3-month period with acute exacerbation of bronchial asthma and who had a past history of intermittent airway disease compatible with bronchial asthma. The range of mean daily pollutants levels for the whole period were: O 3 = 15–26 μg m −3, NO x = 36–108 μg m −3, NO = 16–70 μg m −3, and SO 2 = 11–32 μg m −3. The data sets were composed of input air pollution levels and output ER visits. The first 126 data sets used for the training phase showed that maximal ER visits were mainly associated with the highest cumulative values of air pollution and mostly with nitrogen oxide. In phase two, an attempt was made to predict ER visits based on air pollution level in 49 data sets. The study findings demonstrated that ordinary network technology can be used for learning the effect of air pollution ER visits and, although limited in accuracy, to also predict future ER visits.

Routing scheme, permutation properties, and optical implementation of a four-shuffle-exchange-based Omega network

The routing scheme and some permutation properties of a four-shuffle-exchange-based Omega network are discussed. The corresponding optical setup, which is composed of 2-D phase spatial light modulators and calcite plates, is proposed and demonstrated through mapping the inputs to a 2-D array. Instead of one shuffle-exchange followed by one switching operation as in ordinary Omega networks, in our presented system, the shuffle interconnection embraced in the switches is accomplished simply by varying the switching structure of each stage. For the proposed polarization-optical modules, the system is compact in structure, efficient in performance, and insensitive to the environment. (C) 1997 Society of Photo-Optical Instrumentation Engineers.

BALANCED BISUBMODULAR SYSTEMS AND BIDIRECTED FLOWS

For a nonempty finite set V let 3^v be the set of all the ordered pairs of disjoint subset,s of V, i.e., 3^v := {(X, Y) | X, Y ⊆ V,X ∩ Y = ∅}. We define two operations, reduced union ⊔ and intersection ⊓, on 3^v as follows: for each (X_i,Y_i) ∈ 3^v (i = 1,2) (Y_l, Y_1) ⊔ (X_2, Y_2) = ((X_1 ∪ X_2) - (Y_1 ∪ Y_2), (Y_1 ∪ Y_2) - (X_1 ∪ X_2)), (X_1 , Y_1) ⊓ (X_2, Y_2) = (X_1 ∩ X_2, Y_1 ∩ Y_2). Also, for a {⊔, ⊓}-closed family F ⊆ 3^v a function f:F → R is called bisubmodular if for each (X_i , Y_i) ∈ F (i = 1, 2) we have f (X_1 ,Y_1) + f (X_2, Y_2) ≥ f((X_1, Y_1) ⊔ (X_2, Y_2)) + f ((X_1, Y_1) ⊓ (X_2, Y_2)). For a {⊔, ⊓}-closed family F ⊆ 3^V with (∅, ∅) ∈ F and a so-called bisubmodular function f : F → R on F with f(∅, ∅) = 0, the pair (F, f) is called a bisubmodular system on V. In this paper we consider two classes of bisubmodular systems which are closely related to base polyhedra. The first one is the class of balanced bisubmodular systems. We give a characterization of balanced bisubmodular systems and show that their associated polyhedra are the convex hulls of reflections of base polyhedra. The second one is that of cut functions of bidirected networks. It is shown that the polyhedron determined by the cut function of a bidirected network is the set of the boundaries of flows in the bidirected network and is a projection of a section of a base polyhedron of boundaries of an associated ordinary network.

Random walks on finitely structured transfinite networks

A general theory for random walks on transfinite networks whose ranks are arbitrary natural numbers is established herein. In such networks, nodes of higher ranks connect together transfinite networks of lower ranks. The probabilities for transitions through such nodes are obtained as extensions of the Nash-Williams rule for random walks on ordinary infinite networks. The analysis is based on the theory of transfinite electrical networks, but it requires that the transfinite network have a structure that generalizes local-finiteness for ordinary infinite networks. The shorting together of nodes of different ranks are allowed; this complicates transitions through such nodes but provides a considerably more general theory. It is shown that, with respect to any finite set of nodes of any ranks, a transfinite random walk can be represented by an irreducible reversible Makov chain, whose state space is that set of nodes.

Analyses of Possible Failure Mechanisms and Root Failure Causes in Power Plant Components Using Neural Networks and Structural Failure Database

This paper describes analyses of case studies on failure of structural components in power plants using hierarchical (multilayer) neural networks. Using selected test data about case studies stored in the structural failure database of a knowledge-based system, the network is trained: either to predict possible failure mechanisms like creep, overheating (OH), or overstressing (OS)-induced failure (network of Type A), or to classify a root failure cause of each case study into either a primary or secondary cause (network of Type B). In the present study, the primary root cause is defined as “manufacturing, material or design-induced causes,” while the secondary one as “not manufacturing, material or design-induced causes, e.g., failures due to operation or mal-operation.” An ordinary three-layer neural network employing the back propagation algorithm with the momentum method is utilized in this study. The results clearly show that the neural network is a powerful tool for analyzing case studies of failure in structural components. For example, the trained network of Type A predicts creep-induced failure in unknown case studies with an accuracy of 86 percent, while the network of Type B classifies root failure causes of unknown case studies with an accuracy of 88 percent. It should be noted that, due to a shortage of available case studies, an appropriate selection of case studies and input parameters to be used for network training was necessary in order to attain high accuracy. A collection of more case studies should, however, resolve this problem, and improve the accuracy of the analyses. An analysis module for case studies using the neural network has also been developed and successfully implemented in a knowledge-based system.

A unified domination approach for reliability analysis of networks with arbitrary logic in vertices

The concept of a probabilistic graph G has been used as a universal model for network reliability. Most of the literature on this subject concentrates on computing various reliability measures (such as k-terminal reliability or all-terminal reliability) which are the probability that vertices of G can communicate with other specified vertices. Primarily, this paper provides a common theoretical framework for addressing k-terminal reliability problems. To this end, it extends the model admitting vertex functions of G to be arbitrary monotone Boolean functions: in this case G is called a monotone (S,t)-graph. In such graphs the signal passability across a node is carried out in accordance with collections of signals delivered on the node inputs from other ones, the collections are subjected to some logic principle realized by a Boolean function. Monotone (S,t)-graphs include all known classes of directed multi-terminal network reliability models. The main result of this paper is the reliability expression for computing the probability of an acyclic monotone (S,t)-graph G being operational. The expression uses the local domination parameters introduced here. That reduces the system level of consideration to the element level, providing a unifying understanding of the combinatorial nature of some results based on the domination theory and developed earlier for ordinary networks.

A maximum principle for node voltages in finitely structured, transfinite, electrical networks

Transfinite electrical networks have unique finite-powered voltage-current regimes given in terms of branch voltages and branch currents, but they do not in general possess unique node voltages. However, if their structures are sufficiently restricted, those node voltages will exist and will satisfy a maximum principle much like that which holds for ordinary infinite electrical networks. The structure that is imposed in order to establish these results generalized the idea of local-finiteness. Other properties that do not hold in general for transfinite networks but do hold under the imposed structure are Kirchhoff's current laws for nodes of any ranks and the permissibility of connecting pure voltage sources to such nodes. This work lays the foundation for a theory of transfinite random walks, which will be the subject of a subsequent work.

HANDWRITTEN DIGIT RECOGNITION USING TWO-LAYER SELF-ORGANIZING MAPS

In this paper, we present a two-layer self-organizing neural network based method for handwritten digit recognition. The network consists of a base layer self-organizing map and a set of corresponding maps in the second layer. The input patterns are partitioned into subspace in the first layer. Patterns in a subspace are led to the second layer and a corresponding map is built according to the first layer performance. In the classification process, each pattern searches for several closest nodes from the base map and then it is classified into a specified class by determining the nearest model of the corresponding maps in the second layer. The new method yielded higher accuracy and faster performance than the ordinary self-organizing neural network.

A network model for arbitrarily oriented IDT structures

A network model approach for analyzing arbitrarily oriented short-circuited SAW grating structures is extended to include interdigital transducers (IDTs) that are also arbitrarily oriented. The IDT structure is divided into cells, each modelled by a sequence of mismatched transmission lines consisting of a metallized and unmetallized region. The model includes: the impedance difference between metallized and free regions, the reflection coefficient at the metallization upstep, the reflection coefficient at the downstep for a counterpropagating wave, all deduced from the Datta-Hunsinger perturbation formula; the velocity difference between the free and metallized regions obtained using SAW propagation calculation software for arbitrarily oriented multilayers; and the energy storage susceptance at each finger discontinuity. Since only ordinary network elements are combined in accordance with the IDT geometry, this model permits good physical insight into the structure's characteristics and allows simple procedures for finding high directivity orientations.

How to Analyze the Results of Linear Programs—Part 2: Price Interpretation

In the second part of a four-part series, I consider an exercise in analysis that arises in many applications: Why is the price of 〈some commodity〉 equal to 〈whatever its solution value〉? The ability to interpret dual prices in a linear programming solution is part of economic analysis, and the mathematical basis is as old as linear programming, itself. New approaches, however, go beyond the usual duality arguments in answering this question in more practical terms. One of these new approaches is path tracing, which seeks a portion of the linear program that accounts for the row's price by activity costs from sources to the row. In some cases this is a simple path in a network problem. More generally, in ordinary network terms, it can be a tree or involve embedded cycles, but it is regarded as a path in hypergraph terms.

Alternative Approaches in the Estimation of User Demand and Surplus of Rail Network

Although railway network in the metropolitan area should be remarkably improved, we have some difficulties to calibrate accurate effects by improved level of rail service and to identify the additional lines should be constructed. The purpose of this paper is to propose a new structure for Probit Model using variable covariance matrix and to establish user surplus indices based on random utility theory.Using Metropolitan Census Data which was conducted in 1990, the above model and indices had been briefly estimated to demonstrate the efficiency of our methods. The results indicate that route choice behavior in complexed railway network should be expressed by considering similarity among routes, and user benefit for ordinary network should be calibrated using expected value of maximum utility.

A two‐stage network with dual partial concentrators

AbstractA two‐stage rearrangeable broadcast network (called an ordinary network here) that has been studied recently has a partial concentrator on the input side. We extend this study to a network with two partial concentrators: one on the input side and the other on the output side. We first study the network as a connection network and derive conditions for its rearrangeability. We show that the conditions are tight in some cases. We then show that a particular construction that meets the rearrangeability conditions actually yields a broadcast network. © 1993 John Wiley & Sons, Inc.

Finding the shortest path in railroad systems using the super-network

The shortest path problem is discussed to develop an automatic control system of the railroad in a factory. The super-network is proposed and an algorithm is given to find the shortest path on the super-network. The super-network is useful to model the railroad system because it can represent important factors in finding paths which cannot be represented by an ordinary network. An example is also given to show how a railroad system can be modelled using a super-network and how the shortest path can be found by the proposed algorithm.

Fault location for transmission lines using inference model neural network

The authors propose a new fault location method that uses a neural network to analyze the distribution pattern of the ground wire current along the power line. This method is able to locate the fault section even for secondary power lines with complicated configurations. The method is based on the inference process, i.e., human experts will analyze the distribution pattern of the current amplitude and phase angle. In locating fault sections, higher precision than ordinary three-layer neural network or the expert system of previous development can be obtained. The proposed neural network comprises three sets of three-layer neural networks which follow the back-propagation learning procedure. The 1st and 2nd neural networks calculate the candidate-1 and candidate-2 for the fault section using current amplitude and phase angle distribution patterns, respectively. The 3rd neural network then performs final fault location using these candidates and a current amplitude distribution pattern. The results evaluated with all possible fault causes indicate that the new method is precise to as high as 98.4 percent even when the measured values differ by 30 percent from predicted ones with EMTP.

An improved primal simplex variant for pure processing networks

In processing networks, ordinary network constraints are supplemented by proportional flow restrictions on arcs entering or leaving some nodes. This paper describes a new primal partitioning algorithm for solving pure processing networks using a working basis of variable dimension. In testing against MPSX/370 on a class of randomly generated problems, a FORTRAN implementation of this algorithm was found to be an order-of-magnitude faster. Besides indicating the use of our methods in stand-alone fashion, the computational results also demonstrate the desirability of using these methods as a high-level module in a mathematical programming system.

The Forms of Collective Racial Violence

Explanations for collective racial violence in America and Britain can be classified into three: communal disorder, political contention and class struggle. The first portrays rioting as the expressive acts of aggrieved but disorganized groups, the second as instrumental action by new contenders for political power and the third as authentic class rebellion based upon socially cohesive communities. The areas of disagreement between these three are examined and their different judgements about the character of the violence is assessed. Contrary to the concerns of much empirical research, the primary dispute is over the capability for collective action which ordinary social networks accord oppressed groups. The different approaches either devalue or exaggerate the type of collective action which can be organized on the basis of informal contacts. As a consequence they fail to recognize the occurrence of a fourth type of riot, civil resistance, and incorrectly assess the powerless position which some disadvantaged minorities occupy.

Preemptive Scheduling of Uniform Machines by Ordinary Network Flow Techniques

We consider the problem of scheduling n jobs, each with a specific processing requirement, release time and due date on m uniform parallel machines. It is shown that a feasible schedule can be obtained by determining the maximum flow in a network, thus permitting the use of standard network flow codes. Using a specialized maximum flow procedure, the complexity reduces to O(tn3) operations when t is the number of distinct machine types. Previous algorithms solve the feasibility problem in O((m + log n)(m2n3 + n4)) operations. In addition to the feasibility problem, we describe algorithms for the maximum lateness criterion. Here we develop a bound which compares even more favorably to the best previous bound. We also show how other criteria with respect to the amount of work completed on each job prior to its due date or the amount of work scheduled in each of a sequence of periods can be optimized by similar path augmenting techniques.

Computer-aided algebraic analysis of systematic errors in a composite microwave system

A program package is presented which performs complex, algebraic calculations of the systematic errors on the signals in a composite microwave system caused by errors of the subcomponents (i.e., unwanted leakages and reflections). Since the errors of the subcomponents are small the resulting systematic errors on the signals can be described by a multidimensional Taylor series expansion in the errors of the subcomponents, i.e., as a sum of terms each of which is a product of a numerical (complex) factor, a number of small factors (component errors given algebraic names), and a number of large factors (transmission/reflections for the ideal subcomponents given algebraic names). In addition to ordinary linear networks, the computer programs can be used for calculating the output signals from linear mixers in algebraic form.

Impedance Transformation and Matching for Lumped Complex Load with Nonuniform Transmission Line

New nonuniform transmission-linematching networks for a class of lumped complex loads are presented. A parabolic (or reciprocal parabolic) tapered transmission line, whose exact equivalent circuit is represented by a mixed lumped and distributed circuit, can transform the lumped series RC (or parallel RL) loads into different lumped impedances which are more convenient than the original load impedances for ordinary matching network design. Simple design procedures are described and useful design charts are given. Also, numerical examples are shown including experimental verification.

800-MHz band land mobile telephone system—Overall view

The 800-MHz band land mobile telephone system which is going into service in Tokyo and other major cities is described. This system is characterized by 1) an ordered array of cells which allows each radio channel to be reused by spacing at an appropriate coordination distance in a wide service area (cellular system), 2) development of a new higher frequency band, and 3) a fully automatic exchange system integrated with the ordinary telephone network. Field tests have been carried out in the Tokyo metropolitan area since 1975 and have now been brought to a successful completion.