Efficient three-level screening designs using weighing matrices

Screening is the first stage of many industrial experiments and is used to determine efficiently and effectively a small number of potential factors among a large number of factors which may affect a particular response. In a recent paper, Jones and Nachtsheim [A class of three-level designs for definitive screening in the presence of second-order effects. J. Qual. Technol. 2011;43:1–15] have given a class of three-level designs for screening in the presence of second-order effects using a variant of the coordinate exchange algorithm as it was given by Meyer and Nachtsheim [The coordinate-exchange algorithm for constructing exact optimal experimental designs. Technometrics 1995;37:60–69]. Xiao et al. [Constructing definitive screening designs using conference matrices. J. Qual. Technol. 2012;44:2–8] have used conference matrices to construct definitive screening designs with good properties. In this paper, we propose a method for the construction of efficient three-level screening designs based on weighing matrices and their complete foldover. This method can be considered as a generalization of the method proposed by Xiao et al. [Constructing definitive screening designs using conference matrices. J. Qual. Technol. 2012;44:2–8]. Many new orthogonal three-level screening designs are constructed and their properties are explored. These designs are highly D-efficient and provide uncorrelated estimates of main effects that are unbiased by any second-order effect. Our approach is relatively straightforward and no computer search is needed since our designs are constructed using known weighing matrices.     

Foldover Conference Designs for Screening Experiments

A conference matrix is a square matrix C with zeros on the diagonal and ±1s off the diagonal, such that C ^T C = CC ^T  = (n ? 1)I, where I is the identity matrix. Conference matrices are an important class of combinatorial designs due to their many applications in several fields of science, including statistical-experimental designs, telecommunications, elliptic geometry, and more. In this article, conference matrices and their full foldover design are combined together to obtain an alternative method for screening active factors in complicated problems. This method provides a model-independent estimate of the set of active factors and also gives a linearity test for the underlying model.     

Block-circulant matrices for constructing optimal Latin hypercube designs

Computer simulations are usually needed to study a complex physical process. In this paper, we propose new procedures for constructing orthogonal or low-correlation block-circulant Latin hypercube designs. The basic concept of these methods is to use vectors with a constant periodic autocorrelation function to obtain suitable block-circulant Latin hypercube designs. A general procedure for constructing orthogonal Latin hypercube designs with favorable properties and allowing run sizes being different from a power of 2 (or a power of 2 plus 1), is presented here for the first time. In addition, an expansion of the method is given for constructing Latin hypercube designs with low correlation. This expansion is useful when orthogonal Latin hypercube designs do not exist. The properties of the generated designs are further investigated. Some examples of the new designs, as generated by the proposed procedures, are tabulated. In addition, a brief comparison with the designs that appear in the literature is given.     

Control Attitudes and Perceptions of Drug use: An Exploratory Study

Control attitudes represent opinions about the formal or informal control of a behavior by society. This study investigates control attitudes toward drug use based on data from semistructured in-depth interviews. The analysis shows that control attitudes toward drug use consist of a normative component (philosophical principles) and a perceptive component (perceptions of harm and perceptions of immorality). In particular, control attitudes are shaped by combinations of (1) libertarian principles and perceptions of harm to others, (2) paternalistic principles and perceptions of self-harm, and (3) moralistic principles and perceptions of immorality. The implications of the results in the study of normative culture are discussed.     

Multicultural education in Cyprus: A pot of multicultural assimilation?

In this paper, we attempt to answer the question: "is the Cypriot educational system a melting pot of every alien civilization and a kettle of cultural assimilation that perpetuates biases, clichés, racist behaviours and cultivates the idea that the different have no place among us?" We closely examine the case of a girl from Iran in a Cypriot primary school, using naturalistic observation models of research. Through the analysis of two vignettes, we attempt to answer the question posed above. We simultaneously reflect critically on the situation of multicultural education in Cyprus, while presenting its prospects for the future.     

The Development Manager's Advisory System: A Knowledge-Based DSS Tool for Project Assessment*

This research investigates whether the knowledge-based decision support system (KBDSS) paradigm provides the necessary supporting structure and developmental framework for product development evaluation. To address the research questions posed in this study, it is necessary to develop and implement KBDSS's at specific decision points along the product development cycle. This paper describes the design, development, and implementation of a KBDSS to support a product development manager's decision concerning full-scale development of a new product. From the systems design perspective, this paper addresses the integration and innovative use of a variety of techniques for knowledge acquisition, modeling, and processing. The approach utilized obtains the benefits of normative modeling as well as the flexibility and developmental advantages of knowledge-based systems. Since its implementation, the system has been successfully used by a development manager to support his recommendation for an ongoing project. His complete satisfaction with this system served as the impetus for the design and development of a multi-expert system which was implemented at the strategic level.     

Forging a Multicultural Education Ethos in Cyprus: Reflections on policy and practice

Contemporary Cypriotic society is no longer homogeneous. Increasingly, Cypriots are coming into contact with people from different cultures. We also see this in Cypriotic schools. In this paper, we investigate educational reality as it effects foreign and repatriated pupils in Cyprus. We do this by means of an ethnographic study in which we focus on one particular primary school classroom. It is hoped that this research will serve as a stimulus for possible changes and reforms in the Cypriotic educational system. In this manner, the Cypriot system will be able to keep pace with international developments in this area of education.