Thermal expansion of liquid Ti–6Al–4V measured by electrostatic levitation

The liquid density of Ti–6Al–4V was measured over a temperature range from 1661 to 1997 K that included undercooling by as much as 280 K. The sample was levitated in an electrostatic levitator and video imaging technique was used to capture the volume changes as a function of temperature. Over the temperature range the liquid density can be expressed by rholiq(T)=4123–0.254 (T–Tm) kg/m^3, where the melting temperature Tm is 1943 K. The corresponding volume expansion coefficient is alphaliq=6.05×10^–5 K^–1 near Tm

Minimizing convection effects to measure diffusion in liquid droplets during high-temperature electrostatic levitation

We present an approach to reduce the convective flow in an electrostatically levitated liquid droplet to such an extent that diffusion is the dominant mechanism for mass transport, thus enabling direct measurements of atomic diffusion in reactive liquids at elevated temperatures. Convection is minimized by containerless processing, and reducing temperature variations in the sample. The diffusion tracer is deposited in situ in the electrostatic levitation device used for containerless processing. Uniform noncontact heating of the sample is achieved by laser heating with multiple beams arranged symmetrically, e.g., in a tetrahedral geometry. The expected temperature variations and the resulting convection flows are estimated for a Zr-based glass-forming alloy. The analysis suggests that diffusion experiments are possible throughout the entire undercooled liquid temperature range of this alloy and, in microgravity, up to 50 K above the liquidus temperature

Suppressed Andreev Reflection at the Normal-Metal / Heavy-Fermion Superconductor CeCoIn5_5 Interface

Dynamic conductance spectra are taken from Au/CeCoIn$_5$ point contacts in the Sharvin limit along the (001) and (110) directions. Our conductance spectra, reproducibly obtained over wide ranges of temperature, constitute the cleanest data sets ever reported for HFSs. A signature for the emerging heavy-fermion liquid is evidenced by the development of the asymmetry in the background in the normal state. Below $T_c$, an enhancement of the sub-gap conductance arising from Andreev reflection is observed, with the magnitude of $\sim$ 13.3 % and $\sim$ 11.8 % for the (001) and the (110) point contacts, respectively, an order of magnitude smaller than those observed in conventional superconductors but consistent with those in other HFSs. Our zero-bias conductance data for the (001) point contacts are best fit with the extended BTK model using the d-wave order parameter. The fit to the full conductance curve of the (001) point contact indicates the strong coupling nature ($2\Delta/k_{B}T_c = 4.64$). However, our observed suppression of both the Andreev reflection signal and the energy gap indicates the failure of existing models. We provide possible directions for theoretical formulations of the electronic transport across an N/HFS interface. Several qualitative features observed in the (110) point contacts provide the first clear spectroscopic evidence for the $d_{x^2-y^2}$ symmetry.Comment: 13 pages, 7 figures, LaTeX, paper invited and submitted to SPIE Conference on Strongly Correlated Electron Materials: Physics and Nanoengineering, in San Diego, California, July 31 - August 4, 200

Sustainable seabed mining: guidelines and a new concept for Atlantis II Deep

The feasibility of exploiting seabed resources is subject to the engineering solutions, and economic prospects. Due to rising metal prices, predicted mineral scarcities and unequal allocations of resources in the world, vast research programmes on the exploration and exploitation of seabed minerals are presented in 1970s. Very few studies have been published after the 1980s, when predictions were not fulfilled. The attention grew back in the last decade with marine mineral mining being in research and commercial focus again and the first seabed mining license for massive sulphides being granted in Papua New Guinea’s Exclusive Economic Zone.Research on seabed exploitation and seabed mining is a complex transdisciplinary field that demands for further attention and development. Since the field links engineering, economics, environmental, legal and supply chain research, it demands for research from a systems point of view. This implies the application of a holistic sustainability framework of to analyse the feasibility of engineering systems. The research at hand aims to close this gap by developing such a framework and providing a review of seabed resources. Based on this review it identifies a significant potential for massive sulphides in inactive hydrothermal vents and sediments to solve global resource scarcities. The research aims to provide background on seabed exploitation and to apply a holistic systems engineering approach to develop general guidelines for sustainable seabed mining of polymetallic sulphides and a new concept and solutions for the Atlantis II Deep deposit in the Red Sea.The research methodology will start with acquiring a broader academic and industrial view on sustainable seabed mining through an online survey and expert interviews on seabed mining. In addition, the Nautilus Minerals case is reviewed for lessons learned and identification of challenges. Thereafter, a new concept for Atlantis II Deep is developed that based on a site specific assessment.The research undertaken in this study provides a new perspective regarding sustainable seabed mining. The main contributions of this research are the development of extensive guidelines for key issues in sustainable seabed mining as well as a new concept for seabed mining involving engineering systems, environmental risk mitigation, economic feasibility, logistics and legal aspects

Examining the protective effects of brand equity in the keepin\u27 it REAL substance use prevention curriculum

While branding appears to be an effective health prevention strategy, it is less clear how successful brands have protective effects. To better understand the role of branding in health prevention and promotion, it is necessary to examine how the persuasive mechanisms of branding function in health campaigns (e.g., modeling socially desirable behaviors). Using a cross-sectional data (N = 709), the current study uncovered the mechanisms explaining branding\u27s effects on adolescent substance use in a school-based substance use intervention, keepin\u27 it REAL (kiR) curriculum. Consistent with our predictions, a confirmatory factor analysis suggested that kiR brand equity had a higher-order, multidimensional factor structure. In addition, a path analysis revealed that brand equity affected adolescent substance use directly and through the predicted social cognitive processes including refusal efficacy and resistance skills. Thus it is concluded that kiR brand equity serves as a protective factor for adolescent substance use. Practical implications, research limitations and future directions are discussed

A Mixed-Methods Exploration of the Relationship Between Crime and Community Gardens: A Case Study of Seattle’s P-Patches from 1996 to 2006

Urban community gardens have been shown to have positive affects social capital, yet like many public spaces, are open to negative activities like crime. Contrary to this idea, most of the literature has indicated that urban green spaces are associated with a reduction in crime. This study utilized a mixed-methods research design to explore the hypothesis that areas around Seattle’s “P-Patch” community gardens are associated with a reduction in crime. We employed spatio-temporal GIS (Geographic Information Systems) analyses, statistical analyses, and qualitative interviews with gardeners. Yearly violent and property crime rates for 132 census tracts in Seattle, locations of 84 P-Patches were mapped, and changes in crime and garden establishment from 1996 to 2006 were observed. Correlations were conducted on socio-demographic, crime, and P-Patch variables. Interviews with four gardeners were conducted and qualitatively analyzed for common themes. Geographic visualization showed interesting patterns in crime and P-Patch establishment in South Seattle in particular, but outcomes of the correlation between P-Patch and crime variables were inconclusive. Qualitative interviews with gardeners provided a fuller account of the overall changes in Seattle crime, gardeners’ perceptions of neighborhood safety, and its relation to the development of urban community spaces such as P-Patches

A Mixed-Methods Exploration of the Relationship Between Crime and Community Gardens: A Case Study of Seattle’s P-Patches from 1996 to 2006

Urban community gardens have been shown to have positive affects social capital, yet like many public spaces, are open to negative activities like crime. Contrary to this idea, most of the literature has indicated that urban green spaces are associated with a reduction in crime. This study utilized a mixed-methods research design to explore the hypothesis that areas around Seattle’s “P-Patch” community gardens are associated with a reduction in crime. We employed spatio-temporal GIS (Geographic Information Systems) analyses, statistical analyses, and qualitative interviews with gardeners. Yearly violent and property crime rates for 132 census tracts in Seattle, locations of 84 P-Patches were mapped, and changes in crime and garden establishment from 1996 to 2006 were observed. Correlations were conducted on socio-demographic, crime, and P-Patch variables. Interviews with four gardeners were conducted and qualitatively analyzed for common themes. Geographic visualization showed interesting patterns in crime and P-Patch establishment in South Seattle in particular, but outcomes of the correlation between P-Patch and crime variables were inconclusive. Qualitative interviews with gardeners provided a fuller account of the overall changes in Seattle crime, gardeners’ perceptions of neighborhood safety, and its relation to the development of urban community spaces such as P-Patches.Faculty Sponsor: Jin-Kyu Jun

Enhanced temperature uniformity by tetrahedral laser heating

emperature profile on a spherical sample that is heated by laser beams in various geometries while processed in vacuum is analyzed. Sample heating by one or four laser beams was considered. An analytical expression was derived for directional sample heating cases. It suggests an enhanced temperature uniformity over the samples when heated with four diffuse laser beams arranged in a tetrahedral geometry. This was experimentally verified by heating a spherical stainless steel sample by laser beams. Both the calculated and experimentally determined temperature variations over the sample suggest that use of diffuse four beams arranged in tetrahedral geometry would be effective in reducing temperature variation to within 1 K. The enhancement in the temperature uniformity for four diffuse beams arranged in a tetrahedral geometry by a factor of 50 over a single focused beam is promising to accurately measure of thermophysical properties. This drastic improvement in temperature uniformity might even enable atomic diffusion measurements in the undercooled liquid states of the bulk glass forming alloys since Marangoni and gravity driven convection will be substantially reduced

Consequences of the partial restoration of chiral symmetry in AdS/QCD

Chiral symmetry is an essential concept in understanding QCD at low energy. We treat the chiral condensate, which measures the spontaneous breaking of chiral symmetry, as a free parameter to investigate the effect of partially restored chiral symmetry on the physical quantities in the frame work of an AdS/QCD model. We observe an interesting scaling behavior among the nucleon mass, pion decay constant and chiral condensate. We propose a phenomenological way to introduce the temperature dependence of a physical quantity in the AdS/QCD model with the thermal AdS metric.Comment: 11 pages, 6 figure