John C. Lusth

Expert Systems and Diagnostic Expertise in the Mechanical and Electrical Domains

Current expert system technology tends to rely on the use of shallow empirically based experiential knowledge. With only this type of knowledge available, expert systems have been capable of reaching a high level of agreement with human experts in a limited area of expertise. However, due to the nature of their knowledge, such systems fall short of human expertise in many ways. The human diagnostic process is examined as it relates to the malfunction of mechanical and electrical devices. An expert system design is presented, called the integrated diagnostic model (IDM), that attempts to address some of the issues involved in bridging the gap between human and computer expertise. The IDM contains two different types of knowledge, one based on experience and one based on how the device to be diagnosed functions. These two types of knowledge are used together during a diagnostic session to determine what is wrong with the device. To demonstrate how the IDM works, an interaction with a prototype system that was built using the IDM is described; then research on extensions to the IDM is discussed.

A General Expert System Design for Diagnostic Problem Solving

Existing expert systems have a high percentage agreement with experts in a particular field in many situations. However, in many ways their overall behavior is not like that of a human expert. These areas include the inability to give flexible, functional explanations of their reasoning processes, and the failure to degrade gracefully when dealing with problems at the periphery of their knowledge. These two important shortcomings can be improved when the right knowledge is available to the system. This paper presents an expert system design, called the integrated diagnostic model (IDM), that integrates two sources of knowledge, a shallow, reasoning-oriented, experiential knowledge base and a deep, functionally oriented, physical knowledge base. To demonstrate the IDMs usefulness in the problem area of diagnosis and repair, an implementation in the mechanical domain is described.

LDC-1: a transportable, knowledge-based natural language processor for office environments

During the 1970s, a number of systems providing limited English-language processing capabilities were developed to permit computer access by casual or untrained users. The authors interest is in adapting and extending techniques developed for these systems, especially those used in database query systems and their own English-language programming language system (NLC), for use in office environments. This paper describes the layered domain class system LDC, a state-of-the-art natural language processor whose major goals are (1) to provide english-language retrieval capabilities for medium-sized office domains that have been stored on the computer as text-edited files, as opposed to more restrictive database structure; and (2) to eliminate the need to call in the system designer when extensions into new domains are desired, without sacrificing the depth or reliability of the interface. In this paper the authors (a) provide an overview of LDC, including sample inputs; (b) briefly discuss the role of each module of the system, with special attention to provisions for users to adapt the system to deal with new types of data; and (c) consider the relation of our system to other formal and natural language interfaces that are in use or under development. 77 references.

A characterization of important algorithms for quantum-dot cellular automata

Abstract Feature sizes in chip manufacturing are becoming so small that quantum mechanical behavior will soon have a deleterious effect on the function of devices. Quantum-dot cellular automata (QDCA) have been proposed as computing devices which are helped, rather than hindered, by the quantum behavior of electrons. QDCA compute by relaxing to a configuration of minimal energy. Previously, it has been shown that a quantum-dot device may not compute properly if all of its relaxed configurations are not equal in energy level. Such an automation is termed unbalanced . A necessary condition for an automaton to be balanced is that the number of distinguished configurations with minimum energy should equal the number of input combinations the automaton handles. Does an efficient algorithm for determining the number of distinguished ground states exist? If so, it will be difficult to find, as such an algorithm is shown to be NP-hard. Furthermore, the related problem of determining the minimum energy level of arbitrary automata is also shown to be NP-hard. These results have important implications for simulating and analyzing QDCA on conventional computers.

Quantum-dot cellular automata

There has been increasing concern in recent years that the limits of what can be achieved with current approaches to improving device performance will soon be reached. Quantum-dot cellular automata (QCA) have been proposed as a means of getting around these limitations. This paper reviews the work done concerning QCA to date. First, the QCA architecture is described along with a model used for calculating their properties. Next, the approach to computing with QCA by implementing QCA analogs to traditional logic devices will be discussed. Issues that affect the performance of these devices and the experimental work that has been done are summarized. Finally, some interesting QCA applications are reviewed.

Interpreting Artificial Neural Networks for Microwave Detection of Breast Cancer

This letter demonstrates the applicability of artificial neural networks (ANNs) to breast cancer detection. A simplified model of the breast containing a tumor was used to determine the scattering of electromagnetic waves in the microwave band. This data was used to train an ANN which was then tested on new data to predict the presence or absence of a tumor. Synthetic variation (noise) is added to the data to realistically model the breast.

A graph theoretic approach to quantum cellular design and analysis

In this article, graph theory is investigated as a tool for designing and analyzing quantum cellular automata (QCA). A method is presented for constructing graphs from an arbitrary automata. The constructed graphs are used to model both the static and dynamic states of QCA. Several fundamental theorems concerning the constructed graphs are presented relating QCA structure and behavior to graph colorings. Using these theorems, some simple QCA devices are analyzed and improvements, if applicable, are suggested.

Reduced cell switching in a mobile computing environment

With the huge growth and the market for laptop and palmtop computer purchases, a rapid increase of mobile usage in the Internet is expected. As mobile nodes move in a wireless computer network, a mobile node must determine when to switch its link-level point of attachment to the wired network. In this paper, we present six cell switching techniques and discuss their attributes. Specifically, we present the Late, Early, and Strong cell switching techniques and three variations of them. We then investigate the performance of these six techniques to discover the best method a mobile node should use to determine when to perform its re-attachment to the wired network.

Effect of corrosion on magnetic properties for FeMn and NiO spin valves

Spin-valve multilayer structures are promising candidates for next generation read heads in high-density magnetic recording applications. Two commonly used antiferromagnetic layers that exhibit effective pinning for spin valves are FeMn and NiO. Previously, the only corrosion studied of the two materials with respect to magnetic recording are concerned with immersing thin films into acidic and basic solutions. In a realistic corrosion study of spin valves constructed with these pinning materials, we find a high humidity environment is catastrophic to the FeMn spin valves, even with protective Ta capping layers. Scanning electron microscopy along with magnetic measurements on edge protected samples gives convincing evidence that edge effects seem to dominate. Protection of the edges with an epoxy film merely slows down the degradation. In contrast, NiO spin valves show remarkable resistance to corrosion. While magnetoresistance ratio decreases for FeMn spin valves with increased corrosion, coercivity remai...

Eliminating Non-Logical States from Linear Quantum-Dot-Cellular Automata

Abstract Quantum-dot-cellular automata are a method of computing with small numbers of electrons. The static shape of a particular automaton corresponds to a problem to be solved while the time-dependent evolution of the distribution of electrons within the automaton corresponds to a computation to solve the problem. The final distribution of electrons within the automaton represents a solution. The robustness of an automaton is characterized as the absolute energy difference between the lowest energy state and the first excited state. For computing IDENTITY, a basis for translating values across a larger system, it is shown that the robustness of the automaton can be improved dramatically by redesigning to eliminate non-logical states. By such redesign, the states that populate the energy levels between the logically correct answer and logically incorrect answers are prohibited, thereby increasing the energy gap between the ground state and the first excited state.