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Item Robust Solution of the Linear Servomechanism Problem(1974-09-01) Staats, P.W.; Pearson, J.B.This paper furnishes a complete solution to the problem of designing robust controllers for linear servomechanisms. The results complete the work begun in [1] in that arbirary exogenous signals are included in the problem formulation. Only constant exogenous signals were considered in [1]. ([1] "Robust solutions to linear multivariable control problems", J.B. Pearson, R.W. Shields, and P.W. Staats, Jr., Proceedings: 1974 Joint Automatic Control Conference, University of Texas, June 18-21, 1974, pp. 172-176, to appear IEEE Trans. A-C., Oct 1974.Item The Effect of Intersymbol Interference on the Performance of a Digital FM System(1974-10-20) Papantoni-Kazakos, P.; Paz, I.The error performance of a digital FM system is studied in the presence of additive Gaussian noise. The digital system considered is a conventional one employing a voltage-controlled oscillator as the modulator and a limiter-discriminator followed by a low-pass filter as the demodulator. The notion ofItem The Limiting Density of a Nonlinear System(1974-10-20) Papantoni-Kazakos, P.; Kazakos, D.The RC filter-hard limiter-RC filter nonlinear system shown in Fig. 1 is the subject of this paper. Because of computational difficulties implicated in the analysis of the above system, only its response to the zero mean Gaussian system input has been analytically investigated [2,3,5]. An approximate output density has also been found for nonzero mean Gaussian, while verified to be "close" to the real one for finite means [4]. In the present paper, a close form of the system output density is obtained when the input mean tends to infinity. for that, xi-upcrossing methods were used.Item Concentration of Binary FM Spectra(1974-11-20) Papantoni-Kazakos, P.; Kazakos, D.The spectrum of a digital FM signal can be considered as an indicator of the resistance of the signal to distortions caused by band-limitation. The study in this paper is oriented toward the design of a signaling pulses that will achieve a concentrated about the carrier frequency FM signal spectrum. Convenient spectrum expressions and general guarantees of optimality are found for FSK signals.Item A Mathematical Model of the Vagally Driven SA Nodal Pacemaker(1975-01-20) Greco, E.C.; Clark, Jr., J.W.A model is developed for the vagal control of SA nodal activity in the heart and consists essentially of a modified bonhoeffer-Van der Pol (BVP) model of the "free-running" SA node and a lumped model of the neural terminations in that region. The model is capable of mimicing both the driven transient behavior of the node in terms of pacemaker and inhibition curves, as well as steady-state entrainment phenomena. The model data also agrees very well with experimental data from dog experiments performed in our laboratory. The model is described by a set of nonlinear, third-order, ordinary differential equations and provides a relatively uncomplicated functional model of heart period changes due to vagal stimulation patterns.Item Analog Computer Simulation of Maximum Expiratory Flow Limitation(1975-01-20) Olender, Mark F.; Clark, Jr., J.W.; Stevens, P.M.This paper extends previous modeling work in our laboratory on the simulation of the panting maneuver executed in a body plethysmograph [Golden, et al. (1973)] to the simulation of a wider range of pulmonary function tests and, in particular, the maximum expiratory flow-volume (MEFV) curve. the simulation is implemented on an analog computer for ease of parameter manipulation; the effects of changes in several model parameters (such as large and small airway resistence, and airway and lung compliance on the MEFV curve are discussed. The model structure presented here is much simpler than the ventilatory sytem models of Fry (1968) and Pardaens, et al. (1972) and yet yields the same information in a diagnostic sense.Item Interferometric Studies of Mode Locked Nd3+: Glass Lasers(1975-03-20) Shah, Rajiv R.; Rabson, Thomas A.; Kim, Dae M.A general technique for measuring the electric field vector of the ultrashort pulses from mode locked laser systems is described. The technique is applied to perhaps the most difficult laser to analyze, the dye mode locked, Nd3+:glass laser whose pulses change rapidly in bandwidth and amplitude, are chirped, and can occur in quite short pulse trains. The results of these measurements indicate a rather rapid change in the phases between modes and a plot of the phase change as a function of mode frequency has been obtained.Item Solution of the Forward and Inverse Problems Associated with the Potential Field of a Single Active Fiber in a Volume Conductor(1975-04-20) Greco, E.C.; Clark, Jr., J.W.; Harman, T.L.A solution of Laplace's equation relating the transmembrane potential distribution of an active fiber in a volume conductor to its extracellular field distribution utilizing a Fourier transform method [4] has been reformulated as a one-dimensional linear filtering problem. Formulation of the solution in this manner allows the application of well-known techniques in linear system theory and optimal linear filtering thereby facilitating the solution for both the forward (from transmembrane to field potential distribution) and inverse (from field to transmembrane potential distribution) problems. The forward problem is shown to be a simple two-stage filtering process composed of a membrane and medium filter. In the inverse case the field potential distribution is considered in the presence of additive measurement noise and the best estimate in the least-mean-square sense will be obtained for the transmembrane potential distribution.Item An Identification Scheme for the Determination of Systemic Arterial Load Parameters(1975-04-20) Ling, R.Y.S.; Clark, Jr., J.W.; Srinivasan, R.; Cole, J.S.; Pruett, R.C.An identification scheme is developed for the determination of several parameters of a modified "Windkessel" model of the systemic arterial system for an individual patient undergoing cardiac catheterization. The scheme utilizes a modification of the well-known Prony method [10,11] as a "starter method" to determine good nominal values for the model parameters being varied. These values then serve as input to an iterative nonlinear least squares identification method (Marquardt method [14]) which then converges to final values of the parameters. Solution of the model equations with these parameter values yields the best fit of model generated and observed aortic and brachial artery pressures. This technique, coupled with a method for determining the mechanics of the left ventricle (e.g., the elastance concept [1-5]), permits the functional characterization of the hemodynamic properties of the left ventricle and its systemic load for an individual patient.Item Optimal Choice of the Kernel Function for the Parzen Kernel-type Density Estimators(1975-04-20) Kazakos, D.Let Wp(2) be the Sobolev space of probability density functions f(X) whose first derivative is absolutely continuous and whose second derivative is in Lp(- ∞ ,+ ∞), for p ∈ [1, + ∞]. Using an upper bound to the mean square error for a fixed X E [f(X) - fn(X)0]2, found by G. Wahba, where fn(X) is the Parzen Kernel-type estimate of f(X), we find the finite support Kernel function K(X) that minimizes the said upper bound. The optimal Kernel funciton is: K(y) = (1+a-1) (2T)-1 [1-T-a |y|a], for |y|-1.Item Structural Controllability of Multi-Input Linear Systems(1975-05-20) Shields, R.W.; Pearson, J.B.This paper extends the results of Lin on structural controllability of single-input linear systems to multi-input linear systems. An interesting by-product of this extension is an applicaiton of "generic analysis" to the determination of the rank of a structured matrix. The algorithm for computing "generic" rank is applicable to various problems other than the controllability problem studied here.Item Moments and Error Expressions in Polynomial Minimum Mean Square Estimation(1975-05-20) Kazakos, D.; Papantoni-Kazakos, P.The mathematical complexity of the minimum mean square estimators made inevitable the consideration of suboptimal solutions, such as the linear minimum mean square estimators. The compromise between performance and complexity can be in general less serious if the estimator that will substitute the optimum one is polynomial. If the minimum mean square estimator happens to be equal to a polynomial one, the polynomial substitution does not involve any compromise with respect to performance. Balakrishnan [1] found a necessary and sufficient condition satisfied by the joint characteristic functions of observations and variable to be estimated, so that the m.m.s. estimiate is a polynomial. The equivalent relationships in this case were found in the present paper. A matrix expression of the error difference from two different m.m.s. polynomial estimators was also found. This form involves much fewer calculations than required for finding separately the two errors.Item On a Class of Minimum Energy Controls Related to Spline Functions(1975-07-20) Netravali, Arun N.; de Figueiredo, Rui J.P.The problem of determining a minimum energy control for a dynamically interconnected set of p single-input single-output finite-dimensional linear time-varying dynamical systems, for which the outputs are constrained to assume prescribed values at different points in time is considered. It is shown that the solution (optimal controller) is obtained by performing a linear operation on an appropriate vector-valued generalized interpolating spline.Item LM-g SPLINES(1975-07-20) de Figueiredo, Rui J.P.As an extension of the notion of an L-g spline, three mathematical structures called LM-g splines of types, I, II and II are introduced. (partial abstract)Item p-Efficient Estimators(1975-08-20) Papantoni-Kazakos, P.This paper is concerned with estimates of an unknown vector parameter S based on observations X. A generalized error autocorrelation matrix with components the error moments of order 2p, is defined. A lower bound for this matrix is found and the p-efficient P(X/S) statistics realizing it are determined. The cases of i) X and S real, ii) S scalar real, and iii) X real and S complex are examined.Item Robustness in Parameter Estimation(1975-10-20) Papantoni-Kazakos, P.Due to vagueness in the definition of robustness, there has been no natural transition between robust and nonparametric parameter estimators. In this work, qualitative ideas first expressed by Hampel [1] are extended in an effort to present a theory that unifies the nonparametric and robust concepts. Robustness is definied in a precise mathematical way that transists to nonparametricness naturally. As a result, some general constructive characteristics of robust estimators are studied.Item A Parallel Graph Algorithm for Finding Connected Components(1975-10-20) Hirschberg, D.S.A parallel program is presented that determines the connected components of an undirected graph in time 0(log2n) using n2 processors. It is assumed that the processors have access to common memory. Simultaneous access to the same location is permitted for fetch, but not store, instructions.Item Tagged Architectures and Protection: Message Systems(1975-10-20) Feustel, Edward A.Recent work in extensible programming languages and operating systems by Redell, Lampson, Hewitt, and others coupled with developments in distributed computer systems motivates a study in models of the implementation of protection on tagged architectures. an extension of the notions of message and actor as discussed in previous work provides and abstract framework which may lead to the development of a suitable virtual machine. We wish to show that such a system provides a good framework for representation and protection of types, data, and procedures.Item An Algorithm for Optimal Single Linear Feature Extraction from Several Gaussian Pattern Classes(1975-11-20) Starks, S.A.; de Figueiredo, Rui J.P.; Van Rooy, D.L.A computational algorithm is presented for the extraction of an optimal single linear feature from several Gaussian pattern classes. The algorithm minimizes the increase in the probability of misclassification in the transformed (feature) space. The general approach used in this procedure was developed in a recent paper by R.J.P. de Figueiredo. Numerical results on the application of this procedure to the remotely sensed data from the Purdue C1 flight line as well as LANDSAT data are presented. It was found that classification using the optimal single linear feature yielded a value for the probability of misclassification on the order of 30% less than that obtained by using the best single untransformed feature. Also, the optimal single linear feature gave performance results comparable to those obtained by using the two features which maximized the average divergence.Item Tagged Architecture and the Semantics Programming Languages: Extensible Types(1975-11-20) Feustel, Edward A.This research note suggests that before we design hardware or software for the task of problem solving, we re-evaluate the task of problem solving in terms of the linguistic constituents which will be required and the manner in which these linguistic constituents will be combined. Utilizing the principles of composition and abstraction-to-specifics, we conclude that all data and programs might be realized in a structured format called messages. We conclude with a few preliminary thoughts and questions as to how an architecture designed for such structured operands might be designed.