Molodtsov [8] introduced the concept of soft set as a new mathematical tool for dealing with uncertainties that is free from the difficulties that have troubled the usual theoretical approaches. In this paper we apply the notion of soft sets by Molodtsov to the theory of BCK-algebras. The notions of positive implicative soft ideals and positive implicative idealistic soft BCK-algebras are intro...

Computer algebra systems are a great help for mathematical research but sometimes unexpected errors in the software can also badly affect it. As an example, we show how we have detected an error of Mathematica computing determinants of matrices of integer numbers: not only it computes the determinants wrongly, but also it produces different results if one evaluates the same determinant twice. M...

This paper discusses Freudenthal’s didactical phenomenology for the mathematical structures related to measurement. Freudenthal starts with the set G of all objects having the attribute of weight, an attribute that is to be measured. He proposes two operations, the first one among the measurements themselves, called “addition”. Addition is interpreted in terms of the mental actions associated w...

Optimization problem for a structural acoustic model with controls governed by unbounded operators on the state space is considered. This type of controls arises naturally in the context of ”smart material technology”. The main result of the paper provides an optimal synthesis and solvability of associated nonstandard Riccati equations. It is shown that in spite of the unboundedness of control ...

Microsoft's Xbox and Sony's PlayStation overlay achievement and trophy systems onto their video games. Though these meta-game reward systems are growing in popularity, little research has examined whether players notice, use, or seek out these systems. In this study, game players participated in focus groups to discuss the advantages and disadvantages of meta-game reward systems. Participants d...

Experts may be modeled as managing the inductive dynamics of knowledge acquisition in the knowledge processes of society. Who becomes an expert may be modeled as a random process under the influence of strong positive feedback loops in the social mechanisms giving access to knowledge. These models have implications for the design of expert systems. 1 The Nature of Expertise Expert systems add a...

Growth – the change in number or size – and adaptation – the change in quality or structure – are key attributes of global processes in natural communities, society and economics (see, e.g., Hofbauer and Sigmund, 1988; Freedman, 1991; Young, 1993). In this paper we describe a model with explicit growth-adaptation feedbacks. We treat it in the form of an economic model of competition of two firm...

Impedance control facilitates the performance of tasks that involve contact with the environment. Two generic strategies for implementing impedance control have been described in the literature: the dynamic based approach [4] and the position based approach [7]. The second method has been introduced to eliminate the inherent sensitivity of the first method to the accuracy of the dynamic model. ...

In a companion paper (Nonlinear Impulsive Dynamical Systems. Part I: Stability and Dissipativity) Lyapunov and invariant set stability theorems and dissipativity theory were developed for non-linear impulsive dynamical systems. In this paper we build on these results to develop general stability criteria for feedback interconnections of non-linear impulsive systems. In addition, a uni®ed framew...