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- Tin A. Nguyen, Walton A. Perkins, Thomas J. Laffey, Deanne Pecora
- IJCAI
- 1985

In t h i s paper we desor ibe a program t h a t v e r i f i e s t he oons is tenoy and completeness of exper t system knowledge bases whioh u t i l i z e t he Lookheed Expert System (LES) framework. The a l g o r i t h m s desor ibed here are not s p e c i f i c to LES and oan be a p p l i e d to most r u l e -based systems. The program, o a l l e d CHECK,… (More)

It is shown that a sufficient condition for a nonnegative real symmetric matrix to be completely positive is that the matrix is diagonally dominant.

- Thomas J. Laffey, Preston A. Cox, James L. Schmidt, Simon M. Kao, Jackson Y. Read
- AI Magazine
- 1988

complex applications such as satellite control, autonomy, and data analysis; the Pilot's Associate; autonomous vehicles; battle management; aerospace systems (for example, monitoring electric, power, propulsion, and life-support systems); communications network monitoring and control; robotics and vision systems; process control; financial advice (for… (More)

Dedicated to Hans Schneider on the occasion of his seventieth birthday. Abstract. Let A be an entrywise nonnegative n n matrix and let sk := trace (A) (k = 1;2; : : :). It is shown that if n is odd and s1 = 0, then (n 1)s4 s22. The result is applied to show that (3; 1 2 (1 p17); 2; 2) is not the spectrum of a nonnegative 5 5 matrix while (3; 1 2 (1 p 17);… (More)

We describe a computer program that implements an algorithm to verify the consistency and completeness of knowledge bases built for the Lockheed expert system (LES) shell. The algorithms described here are not specific to this particular shell and can be applied to many rule-based systems. The computer program, which we call CHECK, combines logical… (More)

- Layne T. Watson, Thomas J. Laffey, Robert M. Haralick
- Computer Vision, Graphics, and Image Processing
- 1985

We show that there exist real numbers λ1, λ2, . . . , λn that occur as the eigenvalues of an entry-wise nonnegative n-by-n matrix but do not occur as the eigenvalues of a symmetric nonnegative n-by-n matrix. This solves a problem posed by Boyle and Handelman, Hershkowitz, and others. In the process, recent work by Boyle and Handelman that solves the… (More)

- Thomas J. Laffey, Walton A. Perkins, Tin A. Nguyen
- IEEE Expert
- 1986

- Tin A. Nguyen, Walton A. Perkins, Thomas J. Laffey, Deanne Pecora
- AI Magazine
- 1987

Let F be a field, Mn(F ) the algebra of n × n matrices over F and A ∈ Mn(F ) with trace(A) = 0. The following facts are well-known (i) if A is not a scalar, then A is similar over F to a matrix with zero diagonal (ii) A = [P, Q] = PQ − QP for some P , Q ∈ Mn(F ). In this paper we consider the situation when F is replaced by the ring of integers Z. We show… (More)