Technical States Research Articles

Rough sets analysis of diagnostic capacity of vibroacoustic symptoms

The paper refers to the problem of diagnostic classification of mechanical objects using vibroacoustic symptoms. A new approach based on the rough sets theory is applied to evaluate the symptoms from the point of view of their diagnostic capacity, i.e., the quality of estimation of a technical state of a mechanical object. The approach enables reduction of the set of symptoms to a minimal subset ensuring a satisfactory estimation. The minimal subset is then used to create a classifier of a technical state. Particular attention is paid to a comparison of different methods of calculation of symptom limit values which divide domains of symptoms into intervals corresponding to classes of technical states. The analysed set of data concerns the technical state of rolling bearings installed in a laboratory stand. They are described by a set of symptoms which result from measurements of noise and vibration of bearing housings. The bearings are in good or bad technical states. The paper presents particular steps of the rough sets methodology and gives, as a final result, a classifier of a technical state of bearings based on a minimal subset of symptoms with the greatest diagnostic capacity.

Evaluation of vibroacoustic diagnostic symptoms by means of the rough sets theory

Vibroacoustic symptoms used in technical diagnostics of mechanical objects are considered. In particular, a comparison of different methods defining symptom limit values is carried out. Symptoms limit values divide domains of symptoms into intervals which correspond to classes of technical states of considered objects. A new approach based on the rough sets theory was employed to perform this comparison. In consequence, a method giving the best definition of symptom limit values, in the sense of the most accurate diagnosis of the objects, was found out. The diagnostic investigation was done on data from a set of rolling bearings. The data were collected in a real industrial environment. So, in addition, the obtained results were compared with results of a similar investigation done in laboratory conditions.

On sufficient-completeness and related properties of term rewriting systems

The decidability of the sufficient completeness property of equational specifications satisfying certain conditions is shown. In addition, the decidability of the related concept of quasi-reducibility of a term with respect to a set of rules is proved. Other results about irreducible ground terms of a term rewriting system also follow from a key technical lemma used in these decidability proofs; this technical lemma states that there is a finite bound on the substitutions of ground terms that need to be considered in order to check for a given term, whether the result obtained by any substitution of ground terms into the term is irreducible. These results are first shown for untyped systems and are subsequently extended to typed systems.

The Effect of Employee Stock Ownership Plans on Corporate Profits. Additional Comment

September, 1980 edition of Journal of Risk and Insurance includes an article by D. T. Livingston and James B. Henry entitled The Effect of Employee Stock Ownership Plans on Corporate Profits. article is exceptionally poor scholarship. It states a sweeping conclusion about Employee Stock Ownership Plans (ESOPs) without the benefit of having studied plans that are true ESOPs and without the benefit of examining critically important distinctions among the wide variety of plans that are legitimately called ESOPs. Moreover, even if the article had been examining true ESOPs and the necessary distinctions therein, the data presented in no way justify the conclusion that ESOPs have a negative effect on corporate profitability. 1. authors were apparently not studying ESOPs. technical appendix states that the plans studied were employee stock plans established before 1966. There is an enormous difference between an employee stock purchase plan and an ESOP, which is an employee stock ownership plan. Stock plans require employees to put up their own money to buy the stock, and typically own a very small percentage of their sponsoring company. ESOPs rarely involve employee contributions, in order to avoid securities registration problems, and frequently own all or at least a very major portion of their sponsoring company. It is an egregious error to confuse the two. Moreover, the dates of inception of the plans provide another clue that they are not really ESOPs. There were only a handful of ESOPs established before the concept became popularized in 1975, but all of the plans studied in the article were established at least nine years before that time. To criticize ESOPs when one has not studied ESOPs is utterly irresponsible. 2. article makes no attempt to distinguish among different types of employee ownership plans, despite the tremendous differences that exist between different categories of ESOP. Common sense indicates that the percentage of the company owned by its employees ought to have something to do with the ESOP's effect on productivity and profitability. That notion was borne out by the Conte & Tannenbaum study for the University of Michigan's Survey Research Center indi-