A method for allocating tolerances to exactly constrained assemblies is developed. The procedure is established as an optimization subject to constraints. The objective is to minimize the manufacturing cost of the assembly while respecting an acceptable level of performance. This method is particularly interesting for exactly constrained components that should be mass-produced. This thesis presents the different concepts used to develop the method. It describes exact constraint theory, manufacturing variations, optimization concepts, and the related mathematical tools. Then it explains how to relate these different topics in order to perform a tolerance allocation. The developed method is applied on two relevant exactly constrained examples: multi-fiber connectors, and kinematic coupling. Every time a mathematical model of the system and its corresponding manufacturing variations is established. Then an optimization procedure uses this model to minimize the manufacturing cost of the system while respecting its functional requirements. The results of the tolerance allocation are verified with Monte Carlo simulation.

A k-net of order n is an incidence structure consisting of n2 points and nk lines. Two lines are said to be parallel if they do not intersect. A k-net of order n satisfies the following four axioms: (i) every line contains n points; (ii) parallelism is an equivalence relation on the set of lines; (iii) there are k parallel classes, each consisting of n lines and (iv) any two non-parallel lines meet exactly once. A Latin square of order n is an n by n array of symbols in which each row and column contains each symbol exactly once. Two Latin squares L and M are said to be orthogonal if the n2 ordered pairs (Li,j , Mi,j ) are all distinct. A set of t mutual ly orthogonal Latin squares is a collection of Latin squares, necessarily of the same order, that are pairwise orthogonal. A k-net of order n is combinatorially equivalent to k − 2 mutually orthogonal Latin squares of order n. It is this equivalence that motivates much of the work in this thesis. One of the most important open questions in the study of Latin squares is: given an order n what is the maximum number of mutually orthogonal Latin squares of that order? This is a particularly interesting question when n is congruent to two modulo four. A code is constructed from a net by defining the characteristic vectors of lines to be generators of the code over the finite field F2 . Codes allow the structure of nets to be profitably explored using techniques from linear algebra. In this dissertation a framework is developed to study linear dependence in the code of the net N6 of order ten. A complete classification and combinatorial description of such dependencies is given. This classification could facilitate a computer search for a net or could be used in conjunction with more refined techniques to rule out the existence of these nets combinatorially. In more generality relations in 4-nets of order congruent to two modulo four are also characterized. One type of dependency determined algebraically is shown not to be combinatorially feasible in a net N6 of order ten. Some dependencies are shown to be related geometrically, allowing for a concise classification. Using a modification of the dimension argument first introduced by Dougherty [19] new upper bounds are established on the dimension of codes of nets of order congruent to two modulo four. New lower bounds on some of these dimensions are found using a combinatorial argument. Certain constraints on the dimension of a code of a net are shown to imply the existence of specific combinatorial structures in the net. The problem of packing points into lines in a prescribed way is related to packing problems in graphs and more general packing problems in combinatorics. This dissertation exploits the geometry of nets and symmetry of complete multipartite graphs and combinatorial designs to further unify these concepts in the context of the problems studied here.

Let v [greater than or equal to] k [greater than or equal to] 1 and lamda [greater than or equal to] 0 be integers and G be a graph with n vertices, m edges, and no multiple edges. A (v, k, lambda) block design is a collection Beta of k-subsets of a v-set X in which every unordered pair of elements in X is contained in exactly lambda of the subsets in Beta. A (G-decomposition, or (v, G, lambda) graph design, is a collection H1, H2, ..., Ht of subgraphs of Kv (the complete graph on v vertices) such that each edge of Kv is an edge of exactly lambda of the subgraphs Hi and each of the subgraphs Hi is isomorphic to G. A famous result by Wilson says that for a fixed graph G and integer lambda, there exists a (v, G, lambda) graph design for all sufficiently large integers v satisfying certain necessary conditions. In this thesis, we extend this result to include the case of loops in G. As a consequence, one obtains asymptotic existence of equireplicate graph designs for values of v satisfying certain necessary conditions, where a graph design is called equireplicate if each vertex of Kv occurs in the same number of subgraphs Hi of the decomposition.

Given a graph G, a K_3-decomposition of G, also called a triangle decomposition, is a set of subgraphs isomorphic to K_3 whose edges partition the edge set of G. Further, a rational K_3-decomposition of G is a non-negative rational weighting of the copies of K_3 in G such that the total weight on any edge of G equals one. In this thesis, we explore the problem of rational triangle decompositions of dense graphs. We start by considering necessary conditions for a rational triangle decomposition, which can be represented by facets of a convex cone generated by a certain incidence matrix. We identify several infinite families of these facets that represent meaningful obstructions to rational triangle decomposability of a graph. Further, we classify all facets on up to 9 vertices and check all 8-vertex graphs of degree at least four for rational triangle decomposability. As the study of graph decompositions is closely related to design theory, we also prove the existence of certain types of designs. We then explore sufficient conditions for rational triangle decomposability. A famous conjecture in the area due to Nash-Williams states that any sufficiently large graph (satisfying some divisibility conditions) with minimum degree at least 3/4v is K_3-decomposable; the same conjecture stands for rational K_3-decomposability (no divisibility conditions required). By perturbing and restricting the coverage matrix of a complete graph, we show that minimum degree of at least 22/23v is sufficient to guarantee that the given graph is rationally triangle decomposable. This density bound is a great improvement over the previously known results and is derived using estimates on the matrix norms and structures originating from association schemes. We also consider applications of rational triangle decompositions. The method we develop in the search for sufficient conditions provides an efficient way to generate certain sampling plans in statistical experimental design. Furthermore, rational graph decompositions serve as building blocks within certain design-theoretic proofs and we use them to prove that it is possible to complete partial designs given certain constraints. / Graduate / 0405

The aim of this study is to investigate how and in which form students come in contact with practical applications in the upper secondary school course Chemistry B. The study is based upon the assumption that all learning is situated in a social environment. The theoretical framework is the design theory perspective, which entails an assumption that the pedagogical tools affect the knowledge content. The empiric materials in the study are collected through three methods: textbook analysis, classroom observations and questionnaires. Two groups of students and their teachers were observed during a section of the relevant course. The textbook analysis focuses upon the same course section in the textbooks of the two groups and compares these books with the relevant section in a third textbook. In addition, the two student groups responded to a questionnaire on their attitudes toward the subject of chemistry subject linked to its applications at a society level. The study shows that there are significant differences between the strategies which teachers and textbooks use in order to present and visualise practical applications of chemical theory. The context strategy is based upon the students’ own surroundings and uses real life application as a tool for the presentation of the principles of chemistry. According to this strategy, the knowledge content should be organised in such a way that the chemical principles are used to explain our surroundings. The process and product strategy, on the other hand focuses upon a scientific approach, in which science as a process and scientific products are most important. With this strategy, applications are used to illustrate and exemplify the knowledge content. The conclusion of this study is that neither different forms of presentation nor the presence of practical applications affect the students' attitude towards the subject. Furthermore, practical applications are not a significant part of the students' learning strategies.

Accessibility in the landscape has gained increased attention in recent years, and the practice of Universal Design, rather than providing ‘accessible’ accommodations as separate, distinct elements within the landscape, attempts to address social issues such as segregation by proposing an integrated accessibility and design for a diverse society. However, while proposing integration, it can be criticized as designing to the lowest common denominator and clinging to the idea of a ‘disabled’ population which must be designed down to. It frequently fails to address the complexities arising from conflicts between the needs of individuals with different disabilities and lacks a theoretical framework which would place the philosophy’s ideals within a broader social and cultural context. The poststructural project is posited as such a theoretical framework, and a means for evaluating the principles of Universal Design along with the social and cultural beliefs upon which the accessibility issue rests. Poststructuralism is used to challenge the idea of separate ‘able’ / ‘disabled’ populations on the basis that this dichotomous opposition is based on limiting conceptions of disability and fails to acknowledge the complexities which comprise the diverse fabric of society. The project is explored here as an alternative means for advancing the ideals of Universal Design within the realm of landscape architecture. Using a matrix of poststructural practices, social concepts such as normality and disability are examined and ‘deconstructed.’ Ultimately a reconstruction of the paradigm, a Critically Integrated Design, is proposed based upon the reconceptualization and resituation of accessibility and social conditions. / Master of Landscape Architecture

Current design theory sets out many rules and guidelines for designers, but good design is still difficult to replicate. Often the design principles found in the manuals are misapplied, resulting in designs that (1) do not fulfill their purpose and (2) disrupt the clarity of information. This thesis will review and provide experimental data supporting a model of visual form/visual purpose connections based on the semiotic of C.S. Peirce. This model was first used by Amare and Manning (2005, 2006, 2007, 2008, 2009) to evaluate and explain both effective and ineffective visual information design. This thesis will extend their approach, reporting on the results of four experiments to test the aesthetic appeal and information retention from various visual designs. The four experiments presented in this thesis show that viewer's ability to recall information does not coincide with designs that they find the most visually stimulating or visually pleasing. High indicative contrasts allow for higher retention rate, but those contrasts do not necessarily conform to viewer's aesthetic preferences. Low indicative contrast options have a lower retention rate, but are preferred aesthetically by viewers. Peircean analysis accounts for this disconnect between usability and preference and can help designers find the balance that is needed between these competing purposes in visual information design.

Complexity and uncertainty have long been problems for organizations of all types. Organizational members do not do a very good job of dealing with the complexity and uncertainty as research shows that when faced with complex situations humans often turn to the same sources of information repeatedly (a practice that will eventually betray them), and/or reduce the amount of scanning that they do (Weick 1995; Boyd and Fulk 1996). Organizations often turn to information systems to help them deal with the complexity, but they often take a techno-centric view of knowledge that does not incorporate the human qualities needed for unstructured decisions (Malhotra 1997; Courtney 2001; Malhotra 2001). Additionally, there are times when the information systems that we are using may hinder the processes of dealing with the complexity (Weick and Meader 1993). Weick's (1995) concept of sensemaking is believed to help us to deal with this complexity. In his work with Meader (1993) he wonders what the effects of a sensemaking support system would have, but he does not have the answer because they state that it has not been asked. This dissertation answers the call of Weick and Meader as well as other scholars that have called for sensemaking and human intuition to be included in our information systems. This is accomplished by viewing sensemaking from an inquiring systems perspective (Churchman 1971) to develop a kernel theory that will be used in the context of design science to develop design requirements and principles for a sensemaking system. These design principles are then used to build an instantiation of the system in the form of SenseMan, a system designed to help a local government agency deal with complexity in the context of software updates. Finally the design is evaluated for its effectiveness in dealing with the complexity of in this context using both quantitative and qualitative methods.

No description available.

Good engineering practice requires designers to incorporate knowledge, processes and skills to produce a superior product. Each stage of the product realization process requires that the designer utilize available resources to make sound engineering decisions in a timely manner. Much of the research on engineering design has focused on formulating genera] models for the design process. However, it has been shown that these models are rarely used by engineers in practice. This dissertation advances the concept that useful design models must include methodologies that are particular to a given field or type of design. The inclusion of these knowledge-domain-dependent methodologies provides a complete framework for the greatest utility to the designer. This dissertation describes a general approach to engineering design and proposes a model for developing design assistance tools useful to the practicing designer. The methodology and the model are applied to the domain of cam mechanism design. The model describes the conceptual design process that begins with formulating objectives and establishing specifications and concludes with the actual synthesis of the cam profile. The design model is then incorporated into a comprehensive modular computer tool that is integrated with a PC-based CAD package. This dissertation contributes to both the field of engineering design and cam mechanism design. It provides a design model that incorporates a detailed methodology with information and analytical tools for design. By focusing on the knowledge domain of cam mechanism design it contributes to this field as well. Most prior research focused on techniques for synthesizing the cam profile and provided little assistance for the earlier stages of design. No previous tools have been developed that provide the scope of assistance presented in this dissertation. / Ph. D.