Constraint satisfaction problems (CSPs) provide a unified framework for studying a wide variety of computational problems naturally arising in combinatorics, artificial intelligence and database theory. To any finite domain D and any constraint language Γ (a finite set of relations over D), we associate the constraint satisfaction problem CSP(Γ): an instance of CSP(Γ) consists of a list of variables x1, x2,..., x n and a list of constraints of the form "(x 7, x2,..., x5) ∈ R" for some relation R in Γ. The goal is to determine whether the variables can be assigned values in D such that all constraints are simultaneously satisfied. The computational complexity of CSP(Γ) is entirely determined by the structure of the constraint language Γ and, thus, one wishes to identify classes of Γ such that CSP(Γ) belongs to a particular complexity class. / In recent years, logical and algebraic perspectives have been particularly successful in classifying CSPs. A major weapon in the arsenal of the logical perspective is the database-theory-inspired logic programming language called Datalog. A Datalog program can be used to solve a restricted class of CSPs by either accepting or rejecting a (suitably encoded) set of input constraints. Inspired by Dalmau's work on linear Datalog and Reingold's breakthrough that undirected graph connectivity is in logarithmic space, we use a new restriction of Datalog called symmetric Datalog to identify a class of CSPs solvable in logarithmic space. We establish that expressibility in symmetric Datalog is equivalent to expressibility in a specific restriction of second order logic called Symmetric Restricted Krom Monotone SNP that has already received attention for its close relationship with logarithmic space. / We also give a combinatorial description of a large class of CSPs lying in L by showing that they are definable in symmetric Datalog. The main result of this thesis is that directed st-connectivity and a closely related CSP cannot be defined in symmetric Datalog. Because undirected st-connectivity can be defined in symmetric Datalog, this result also sheds new light on the computational differences between the undirected and directed st-connectivity problems.

This research develops a food demand system model based on the Linear Almost Ideal Demand System (LA/AIDS). The major contribution of this research is that the opportunity cost of time on food cooking/cleaning up is modeled in the demand system. Different from the traditional one constraint demand, this two constraints LA/AIDS model better captures consumer behavior and attitude toward food choice –food at home (FAH), sugar sweetened beverage (SSB), food away from home (FAFH). Using Statistics Canada Food Expenditure Survey (FES) and General Social Survey-time use, a two sample two stage least square (2S2SLS) is an applied in the data estimation. The empirical results show most coefficient estimates and own price elasticities are significant. FAH and FAFH are found to be more price elastic compared to a one constraint model, and SSB is found to be more price inelastic. This research provides a new perspective to estimate potential food policies, such as, a tax on SSB, or a food tax on "junk food".

The tourism industry involves people with specific but different needs to be satisfied, whether one is able-bodied or has a disability. People with disabilities are a global phenomenon and research indicated that 600 million people in the world have some type of disability. Therefore the market for tourists with disabilities cannot be disregarded, for it can significantly contribute to a country's tourism receipts. To understand and effectively cater for the disability market, there are several aspects that the tourism industry should look at. This leads to the aim of this study viz. to determine what the barriers and constraints faced by people with disabilities are. In order to achieve this aim, a hundred questionnaires were distributed to various sectors of the tourism industry, for example the accommodation sector (hotels, guesthouses, Bed and Breakfasts), tour operators and travel agents. The study indicated that: *The tourism industry needs to adapt and promote “Tourism for All”. *The lack of available and accessible facilities, transport, accommodation and attractions have an impact on the travel patterns of tourists with disabilities. * Marketing should include information to tourists with disabilities. * To achieve this goal and server diverse tourists, a universal design needs to be included in the current and future developments of tourism products. Evaluation of existing facilities and tourist attraction need to take place in order to provide a quality service and experience to people with disabilities. * Government and local authorities have an important role to fulfil to ensure that a universal design be implemented in tourist attraction and facilities. The key aspect that the tourism industry need to know and remember is that if a person has a disability, it does not mean that he/she is unable to travel or does not want to travel. / Thesis (M.A. (Tourism))--Potchefstroom University for Christian Higher Education, 2003.

Essay 1: I examine sales of private firms to better understand the effect of relaxing financial constraints on firm value. My empirical tests exploit an exogenous shock to financial constraints caused by interstate bank branching deregulation. On a sample of 557 sales of private firms to public acquirers, I find that relaxed financial constraints lead to a statistically significant increase of 7.3% in valuation multiples of private targets. I also find a significant increase in private target valuation multiples benchmarked to public target valuation multiples. These effects are more pronounced for firms in the sample with below median annual sales. Acquirer returns are negatively impacted when financial constraints on private targets are relaxed. The evidence supports the prediction that relaxing financial constraints allows private targets to substitute bank credit for some of the financing benefits provided by acquirers and bargain for a higher valuation.

Abstract The purpose of our study is to reach an understanding of the situation of unaccompanied refugee minors in school. Thus the study aims to investigate what sort of possibilities and limits they encounter when going through their school education. We have chosen a qualitative method and conducted interviews with four persons between the ages of 18 and 21 years. The result of the study shows that unaccompanied refugee minors experience numerous limitations and lesser possibilities than other students, which prevents their educational and social development. The limitations partly depend on the school personnels lack of knowledge about this target group, and partly on the difficulty of dealing with a new culture which is different from the students original culture.  An important conclusion that our study has shown is that the educational system has a great impact on how well the students manage to function in the new society later on.  Therefore it is of great importance that the teachers have access to competence development , since this is of substantial importance for the  unaccompanied refugee minors development and socialization. / Syftet med vår studie är att undersöka ensamkommande flyktingbarns situation i skolan, främst med avseende på de begränsningar och eventuella hinder som barnen möter under skolgången.  Det insamlade datamaterialet har analyserats med hjälp av en tematisk tolkande ansats, där framförallt begreppet socialisation varit vägledande i tolkningsprocessen. Resultatet visar att ensamkommande flyktingbarn upplever många begränsningar och färre möjligheter i skolan. Detta försvårar deras möjligheter till kunskapsutveckling och socialisation. De hinder som ensamkommande flyktingbarn brottas med kan i relation till en övergripande nivå ses som en konsekvens av omfattande begränsningar inom skolan som institution. Inom den svenska skolan råder brist på resurser av varierande slag. Det saknas kunskap och insyn i ensamkommande barns livssituationer, vilket i sin tur begränsar elevernas förutsättningar att smälta in i och socialiseras i de nya förhållandena. En viktig slutsats i vår studie är att skolan har stor påverkan på hur eleverna klarar sig senare i livet i det nya samhället. Det är således av stor vikt att lärarna har tillgång till kompetensutveckling, eftersom lärares kapacitet i mötet med eleverna i en förlängning får stor betydelse för ensamkommande flyktingbarns lärande och socialisation.

Despite evidence to support physically active and passive leisure as significant contributors to well-being, for working mothers, fitting leisure into an already busy schedule can be challenging. The purpose of this study was to examine the influence of perceived time constraints and self-determination for physically active and passive leisure on conflict between these two leisure domains and the influence of this conflict on well-being among physically active working mothers. A total of 66 women who were physically active, worked at least 30 hours per week outside the home and had at least one child living in the home, participated in the study. At baseline, the participants completed a basic intake assessment in addition to validated questionnaires to measure time constraints and motivation for physically active and passive leisure. A two-week period of electronic experience sampling followed to evaluate leisure engagement. A final set of measures to evaluate conflict between physically active and passive leisure over the two weeks, and general well-being were completed at the end of the experience sampling period. Results indicated that despite relatively high levels of satisfaction with time available for both physically active and passive leisure, perceived time constraints were associated with increased goal conflict as are non-self-determined motivation for physically active leisure and self-determined motivation for passive leisure. Controlling for engagement in physically active and passive leisure, well-being is negatively influenced by goal conflict. Recommendations are provided regarding areas for additional research to further our understanding of the impact of opposing motivational orientations on goal conflict including the incorporation of Vallerand’s Dualistic Model of Passion (Vallerand et al., 2003). From a practical standpoint, the implications of the study results for interventions designed to address general well-being in middle class working mothers through targeting factors related to time constraints and goal conflict are discussed.

Chinese international students are the largest group among international students in Canada. They play an important role in Canadian universities as well as in leisure research. The current study aims to reveal Chinese international students’ leisure experience, and to explore their leisure constraints and negotiation strategies in their everyday lives. The framework of leisure constraints negotiation (Jackson, 1993) was employed. Eight interviews with Chinese international students from the University of Manitoba were conducted to hear the stories about their leisure experiences. The constant comparative method was used to analyze the data. Chinese international students were found to be constrained intrapersonally, interpersonally, structurally, and culturally in their leisure. However, they were trying to be active by applying some negotiation strategies. The results of this study can not only benefit this group but also other international student groups by identifying their leisure preferences and constraints, and help leisure service providers to facilitate leisure activities on campus.

The tourism industry involves people with specific but different needs to be satisfied, whether one is able-bodied or has a disability. People with disabilities are a global phenomenon and research indicated that 600 million people in the world have some type of disability. Therefore the market for tourists with disabilities cannot be disregarded, for it can significantly contribute to a country's tourism receipts. To understand and effectively cater for the disability market, there are several aspects that the tourism industry should look at. This leads to the aim of this study viz. to determine what the barriers and constraints faced by people with disabilities are. In order to achieve this aim, a hundred questionnaires were distributed to various sectors of the tourism industry, for example the accommodation sector (hotels, guesthouses, Bed and Breakfasts), tour operators and travel agents. The study indicated that: *The tourism industry needs to adapt and promote “Tourism for All”. *The lack of available and accessible facilities, transport, accommodation and attractions have an impact on the travel patterns of tourists with disabilities. * Marketing should include information to tourists with disabilities. * To achieve this goal and server diverse tourists, a universal design needs to be included in the current and future developments of tourism products. Evaluation of existing facilities and tourist attraction need to take place in order to provide a quality service and experience to people with disabilities. * Government and local authorities have an important role to fulfil to ensure that a universal design be implemented in tourist attraction and facilities. The key aspect that the tourism industry need to know and remember is that if a person has a disability, it does not mean that he/she is unable to travel or does not want to travel. / Thesis (M.A. (Tourism))--Potchefstroom University for Christian Higher Education, 2003.

There is a noticeable decline in physical activity participation during transitions, including moving between levels of education (Bray & Born, 2004; Gyursick, Bray & Brittain, 2004; Bray & Kwan, 2007). Despite its importance, little is known about the process of successful transitions and how it impacts physical activity behaviour for university students. A way to further understand the transition process is to explore the leisure constraints and the constraints negotiation process for these young adults. The purpose of this study was to examine physically active leisure for young adults, who were successful at continuing their participation in physical activity during their transition into university. Students were recruited from randomly selected 2nd and 3rd year general courses and invited to participate in a semi-structured, one on one interview with the researcher. Fourteen semi-structured interviews were conducted with second to fourth year university students at a mid-size western Canadian university. Their narratives explored students’ beliefs, constraints, and constraint negotiation strategies they used to stay physically active, in a variety of individual and team sport physical activities. The participants were categorized into four categories, based on their participation level, and an in-depth analysis of narratives was done for each participant category. These profiles are rated on a continuum that determined whether they were more or less active than before, and on the types of the activities they pursued. The comparison and the placement into the particular categories were determined by what type of activities they are doing at university. The students reported having both positive orientation and an identity that was associated with their active behaviour. Physical activity was noted as a higher priority in their lives. Their current student environment and student lifestyle was an enabler for physically active behaviours. Students described feeling constrained, in some aspects of their behaviour, but because physical activity was a higher priority, they were able to successfully negotiate those constraints. A key theme that emerged from these stories was enjoyment, but for two separate reasons; the social aspect and a challenge aspect. These aspects were found in the same activity or different activity, depending on the interests of the participant. However, it is important that the individual understand why they participate in physical activity and the outcome(s) they seek. This will help the student continue their physical activity behaviour during transitions, into post-secondary education and through other life course stages. / Graduate

Computer models of the geometry of the real world have a tendency to assume that the shapes and positions of objects can be described exactly. However, real surfaces are subject to irregularities such as bumps and undulations and so do not have perfect, mathematically definable forms. Engineers recognise this fact and so assign tolerance specifications to their designs. This thesis develops a representation of geometric tolerance and uncertainty in assemblies of rigid parts. Geometric tolerances are defined by tolerance zones which are regions in which the real surface must lie. Parts in an assembly can slop about and so their positions are uncertain. Toleranced parts and assemblies of toleranced parts are represented by networks of tolerance zones and datums. Each arc in the network represents a relationship implied by the tolerance specification or by a contact between the parts. It is shown how all geometric constraints can be converted to an algebraic form. Useful results can be obtained from the network of tolerance zones and datums. For example it is possible to determine whether the parts of an assembly can be guaranteed to fit together. It is also possible to determine the maximum slop that could occur in the assembly assuming that the parts satisfy the tolerance specification. Two applications of this work are (1) tolerance checking during design and (2) analysis of uncertainty build-up in a robot assembly plan. I n the former, a designer could check a proposed tolerance specification to make sure that certain design requirements are satisfied. In the latter, knowledge of manufacturing tolerances of parts being manipulated can be used to determine the constraints on the positions of the parts when they are in contact with other parts.