6,748 research outputs found

    Effect of Large-Scale Structure on Multiply Imaged Sources

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    We study the effects of large-scale density fluctuations on strong gravitational lensing. Previous studies have focused mostly on weak lensing, since large-scale structure alone cannot produce multiple images. When a galaxy or cluster acts as a primary lens, however, we find that large-scale structure can produce asymmetric shear of the same order as the lens itself. Indeed, this may explain the origin of the large shear found in lens models in conflict with the small ellipticity of the observed galaxy light distributions. We show that large-scale structure changes the lens equation to the form of a generalized quadrupole lens, which affects lens reconstruction. Large-scale structure also changes the angular diameter distance at a given redshift. The precise value depends on the lens and source redshifts and on the large-scale structure power spectrum, but the induced 1σ1\sigma uncertainty in determinations of the Hubble constant from measurements of time delays is of order 510%5-10 \%. If observations of lensing can constrain the magnitude of the shear which is due to large-scale structure, it would provide a direct probe of the overall amplitude of mass fluctuations.Comment: Latex, 20 pages, 3 PostScript figures, to appear in ApJ Sept. 10, 1996, substantially revise

    Variations in attitudinal gender preferences for children across 50 less-developed countries

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    While a number of studies have examined gender preferences for children by studying behavioral measures, such as skewed sex ratios, sex imbalance in infant mortality, and sibling size/order; attitudinal measures have been analyzed less systematically. Using 50 Demographic and Health Surveys conducted between 2000 and 2008, this paper seeks to advance our understanding of gender preferences in developing countries by examining attitudinal measures cross-nationally. This study’s findings show that, while balance preference is the most common type of preference in the vast majority of countries, countries/regions vary in the prevalence of son and daughter preferences. A preference for sons is not always found; and, indeed, a preference for daughters is shown to prevail in many societies.comparative, cross-national, gender preferences for children

    Sharing, listening, learning and developing understandings of Kaupapa Māori research by engaging with two Māori communities involved in education.

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    This paper is a culmination of common understandings that were elicited from two pieces of research: ‘The Impact of the BHP New Zealand Steel Mining on the Tangata Whenua and the Environment’ and ‘The Impact of Maori Medium Education within a Mainstream Secondary School on the Lives of its Participants, in particular the Teachers, Caregivers and Students’. It was at the conclusion of each research project and as a consequence of informal conversations and discussions that this paper evolved. The paper discusses shared understandings in the context of Kaupapa Māori research methodology and key findings from the two research projects

    Longitudinal dynamics of liquid filled elastic shells

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    Longitudinal dynamics of liquid filled elastic shells - interaction liquid and elastic tank, liquid surface instability, and bubble dynamic

    “She didn’t ask me about my grandma”. Using process drama to explore issues of cultural exclusion and educational leadership.

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    Purpose – This purpose of this paper is to describe a collaborative project from the University of Waikato, Hamilton New Zealand, in which the authors used process drama to engage final year teaching students with complex issues of cultural diversity, enabling them to “grow into” different kinds of leadership positions in an imagined educational setting. The paper describes the project and makes a case for process drama as a means of providing opportunities for leadership and as a potent tool for learning about issues of social justice. Design/methodology/approach – The drama was based on a fictional scenario described by Hall and Bishop, where a beginner teacher (of European descent) unwittingly diminishes the experiences of Maori and other non-European children in her class. Using a three-phase process planning model and with facilitators in role alongside the students, the drama explored the scenario from all points of view. Students were encouraged to build empathy for the beginner teacher and for the children and also to explore the dilemma faced by the teacher's tutor in deciding whether, and how, to confront the teacher on the issue. Findings – Through the drama, students built a sense of empathy for all sides of the issue and engaged in deep thinking about the experience of cultural exclusion. The safety and distance provided by the drama “frame” spurred students to take leadership roles and “stand up” for issues of social justice. The authors suggest that through such dramas students gain skills and perspectives that they may carry into their professional lives. Research limitations/implications – The paper describes a small project, over one lesson with a specific group of students. More research is needed into the effectiveness of process drama as a sustained strategy for teacher education. Originality/value – This scenario explored in the drama has currency in Aotearoa New Zealand, where the population is increasingly culturally diverse, where underachievement of Maori students continues to be of concern, and where research has shown the centrality of teacher-student relations in raising educational achievement for Maori. The authors believe this paper makes a compelling case for the value of drama as a tool for student teachers to encounter social justice issues in a meaningful way, and suggest that the paper is a valuable contribution to more than one discipline, as it straddles the fields of professional practice and drama as pedagogy

    Modelling conjugate flow and heat transfer in a ventilated room for indoor thermal comfort assessment

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    Conjugate natural and forced convection heat transfers in a domestic model room of finite-thickness walls and a heat source have been numerically studied. A 2-D non-ventilated square model room with a heat source is investigated at first for conditions of Prandtl number Pr=0.7 and Grashof number Gr=107. Computational results are compared with already validated numerical predictions and good agreement has been achieved in terms of stream function and temperature distributions. The study continues to consider 3-D ventilated rectangular model room with a finite-thickness wall and a heat source, in order to evaluate flow and heat transfer characteristics. Key physical features such as temperature distributions in both solid wall and indoor air domains, and heat transfer performance have been quantified, analysed and compared. These results provide the correlations among room heating device arrangement, wall thickness effect, indoor thermal comfort level and energy consumption. It was found that the arrangements of heat source and window glazing had significant impact on the temperature field, and further analysis of wall thickness and thermal conductivity variations revealed the level of the comfort temperature within the occupied zone. It was also found that for an average U-value of 0.22 W/m2K, thermal energy loss through a thinner wall of 20 cm thickness is 53% higher and indoor thermal temperature is 4.6 °C lower, compared with those of a thicker wall of 40 cm thickness. The findings would be useful for the built environment thermal engineers in design and optimisation of domestic rooms with a heat source

    Numerical simulation of convective airflow in an empty room

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    Numerical simulation of airflow inside an empty room has been carried out for a forced convection, a natural convection and a mixed convection respectively, by using a computational fluid dynamics approach of solving the Reynolds-averaged Navier-Stokes fluid equations. Two-dimensional model was studied at first; focusing on the grid refinement, the mesh topology effect, and turbulence model influences. It was found that structured mesh results are in better agreement with available experimental measurements for all three scenarios. Further study using a three-dimensional model has shown very good agreements with test data at measuring points. Furthermore, present studies have revealed low-frequency flow unsteadiness by monitoring the time history of flow variables at measuring positions. This phenomenon has not yet reported and discussed in previous studies

    Notions of Gender: Rehabilitating Refugee Women in Partition’s Aftermath

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    This article seeks to recover the experience and agency of refugee women during the process of rehabilitation after Partition, focusing on technical training.2 It explores the ideas that underpinned the process of rehabilitating refugee women in the immediate years following the Partition of India in August 1947, within the Bombay state. This article contributes to attempts in the historiography to challenge conventional histories of Partition that have marginalised women and focuses on recovering the agency of refugee women in rebuilding and reshaping their lives.3 It will be argued that the Bombay state’s notions of gender shaped and informed the type and content of rehabilitation that unattached refugee women4 received. Whilst the state showed little evidence of any genuine concern regarding the welfare of refugee women, unofficial organisations designed and implemented various schemes to rehabilitate refugee women. This article will reveal the fraught and unequal relationship, between a relatively absent state, and these unofficial organisations
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