The role of diffusion on the interface thickness in a ventilated filling box

We examine the role of diffusivity, whether molecular or turbulent, on the steady-state stratification in a ventilated filling box. The buoyancy-driven displacement ventilation model of Linden et al. (J. Fluid Mech., vol. 212, 1990, p. 309) predicts the formation of a two-layer stratification when a single plume is introduced into an enclosure with vents at the top and bottom. The model assumes that diffusion plays no role in the development of the ambient buoyancy stratification: diffusion is a slow process and the entrainment of ambient fluid into the plume from the diffuse interface will act to thin the interface resulting in a near discontinuity of density between the upper and lower layers. This prediction has been corroborated by small-scale salt bath experiments; however, full-scale measurements in ventilated rooms and complementary numerical simulations suggest an interface that is not sharp but rather smeared out over a finite thickness. For a given plume buoyancy flux, as the cross-sectional area of the enclosure increases the volume of fluid that must be entrained by the plume to maintain a sharp interface also increases. Therefore the balance between the diffusive thickening of the interface and plume-driven thinning favours a thicker interface. Conversely, the interface thickness decreases with increasing source buoyancy flux, although the dependence is relatively weak. Our analysis presents two models for predicting the interface thickness as a function of the enclosure height, base area, composite vent area, plume buoyancy flux and buoyancy diffusivity. Model results are compared with interface thickness measurements based on previously reported data. Positive qualitative and quantitative agreement is observed

Modelling Climate Change Impacts on Agriculture and Forestry with the Extended LTEM (Lincoln Trade and Environment Model)

In the land-based sectors, agricultural production generally is a source of carbon, while forestry may be thought to act as a sink. This paper focuses on new research examining the interaction of the two. The core of the research is the Lincoln Trade and Environment model (LTEM), a partial equilibrium model which links trade in NZ with the main trading countries overseas, through to production and associated environmental consequences . This paper reports on research expanding the model to include forestry from incorporating the capabilities of the Global Forest Products Model (GFPM) into the LTEM and hence producing an integrated model of agricultural and forestry land-uses for NZ and overseas. The paper extends the environmental modelling capabilities of the LTEM to include the impacts of climate change. The paper thereby reports on the development of a model of international trade that encompasses major agricultural commodities and forestry, complete with linkages and feedback with the environment and differentiated international markets. The paper then presents results of scenarios around changes in consumer behaviour and production using the new model.Environmental Economics and Policy,

Tetris is Hard, Even to Approximate

In the popular computer game of Tetris, the player is given a sequence of tetromino pieces and must pack them into a rectangular gameboard initially occupied by a given configuration of filled squares; any completely filled row of the gameboard is cleared and all pieces above it drop by one row. We prove that in the offline version of Tetris, it is NP-complete to maximize the number of cleared rows, maximize the number of tetrises (quadruples of rows simultaneously filled and cleared), minimize the maximum height of an occupied square, or maximize the number of pieces placed before the game ends. We furthermore show the extreme inapproximability of the first and last of these objectives to within a factor of p^(1-epsilon), when given a sequence of p pieces, and the inapproximability of the third objective to within a factor of (2 - epsilon), for any epsilon>0. Our results hold under several variations on the rules of Tetris, including different models of rotation, limitations on player agility, and restricted piece sets.Comment: 56 pages, 11 figure

Investigation of light scattering in highly reflecting pigmented coatings. Volume 3 - Monte Carlo and other statistical investigations Final report, 1 May 1963 - 30 Sep. 1966

Monte Carlo methods, Mie theory, and random walk and screen models for predicting reflective properties of paint film

Employer satisfaction with employees with a disability

Previous research that addressed determents of employer satisfaction with employees with a disability (EWDs) mainly targeted employers’ perceptions of workplace performance. This thesis used quantitative and qualitative approaches to examine perspectives of employers and disability employment service providers (DESPs) on the complex nature of employer satisfaction with EWDs within an ecological paradigm. Three studies were undertaken. The first analysed questionnaire ratings for 656 employers of workplace performance of EWDs. Analyses found: (1) employers rated EWDs lower than non-disabled employees (NDEs) on employer satisfaction and work performance; (2) determinants of employer satisfaction differed between EWDs and NDEs; (3) employers were more satisfied with EWDs than NDEs in relation to work performance; (4) lower comparative ratings on employer satisfaction for EWDs influenced future employment intentions toward people with a disability; (5) employers’ perceptions of job-match affected ratings on employer satisfaction and performance; (6) effects of job-match on employer satisfaction were direct and indirect, through work performance; and (7) variables representing job-match were relatively more important to employers’ decisions to hire and retain a person with a disability than variables representing Social Concerns and employer/management items. A theoretical model that depicted the influence of processes (job-match) and outcomes (work performance) on employer satisfaction with EWDs was supported. The second study analysed questionnaire ratings from 36 non-employers of EWDs. Findings indicated very similar responses between employers and non-employers of EWDs on experiences related to employer satisfaction with NDEs. Views about the relative importance of variable related to hiring and retaining a person with a disability suggested that generalising findings from the first study to all employers was reasonable. The third study analysed data from interviews with 50 employers and 40 DESPs; and questionnaire responses for 56 DESPs and 36 non-employers of EWDs. This study validated the importance of job-match to successful employment outcomes; suggesting DESPs were undervaluing their services to the employers. The study also showed that Bronfenbrenner’s Ecological Systems Theory provided a relevant framework with which to interpret complex information from different stakeholders, important to understanding employer satisfaction. In summary, employer satisfaction was shown to be a relative concept that varied with referent, and a developmental phenomenon that was influences by many factors operating and interacting at a number of ecological levels. Policies and practices to promote employer satisfaction with EWDs need co-ordinated approaches that recognise the influence of contexts internal and external to the workplace and the dynamic nature and interrelationships of characteristics within these contexts

Thought Experiment as an Interdisciplinary Pedagogy

The thesis of this paper is that thought experiments provide an especially powerful way to frame a class discussion. They work for students for the same reason that they have worked for great geniuses (such as Einstein) through the ages—namely, because they are interdisciplinary. Competing rationalist and empiricist accounts of how thought experiments work suggest that they will engage both rationally- and empirically-minded students. Examples of student responses to thought experiments confirm that they bring out interestingly diverse ways of thinking. Concern that interdisciplinary pedagogy makes genuine communication impossible has led some theorists to insist on a methodological pluralism that refuses to privilege any one approach. I argue however, that interdisciplinary instructors must ultimately ask students to incorporate their diverse perspectives into the discourse of the instructor’s discipline in order to ensure that their work is judged in accordance with a time-tested criterion of excellence

Language Planning for Adult Immigrant Integration: Critical Perspectives on Challenges for and Motivations of Immigrant Second Language Learners in Finland

Finland has experienced a notable rise in immigration over the past decades while also since 2000 the reasons for relocation have diversified. Generally, local language learning is seen as a critical factor in the integration of foreign language speaking immigrant populations in their host societies. Language planners in Finland place education in the local language as a priority in efforts to support and advance integration. However, the Finnish language garners comparatively little attention on the international stage and learning Finnish can present challenges for second language migrant learners. Despite programming and financial support for adult immigrant learners, insufficient language skills continue to be a barrier to integration. This thesis research aims to identify motivators and challenges of adult immigrant learners of the Finnish language in the Helsinki region through the lens of critical language planning. Opportunities to study and use Finnish language are discussed taking into account critical perspectives on traditional language planning, such as discrimination based on one’s ethnicity, gender or economic situation as well as the presence of a prominent language of wider communication. The informants are Finnish language learners, non-EU adult immigrants to Finland who have been residents for 4-15 years. They participate in narrative interviews that are analyzed and discussed on the backdrop of language planning for migrants in Finland. Participants’ accounts of their learning goals, motives and process, communicative experiences, and the role of English in Finland are examined along with the role of L2 learning in integration. The interview analyses indicate that skills in English in the absence of Finnish aptitude can be sufficient for economic and social integration in certain cases, while remaining a limiting factor in other sectors of life, for example civic engagement and flexibility in personal advancement. Finnish language skills are seen to be most pertinent for the economic integration of those not fluent in English, who do not have a higher or professional education or who otherwise have difficulty finding sufficient employment. Participants however describe difficulties finding opportunities to use what they have learned in practice due to social or economic circumstances and the role of English in communication. Informants’ experiences of language switch with Finnish speakers are seen as a discouraging barrier to practice and indicative of opposing language planning for internationalisation and integration. Further language planning for access to instruction and practice is seen to be advisable particularly for immigrants immersed in primarily English-speaking environments.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format