Experimental characterization of heat transfer from an electrically heated thin filament

Thin filaments for use in glass, polymer, or textile industries are formed by extruding molten material through an orifice to form a continuous filament. These filaments are cooled rapidly from the melting temperature of the material to near room temperature. If this cooling occurs too rapidly or too slowly imperfections can develop in the filaments. These imperfections can decrease the overall quality and strength of the fiber sometimes leading to temporary production shutdowns caused by filament breakage.;Driven by the need to understand and control the cooling of thin filaments, research has been conducted to attempt to experimentally characterize the heat transfer experienced by a thin filament. For this study, a platinum filament was placed axially in a vertical wind tunnel and electrically heated. Forced convective air flowing over the stationary heated filament was used to simulate the heat transfer associated with a forming filament moving through still air. A computerized data acquisition system was utilized to collect information on the heat dissipated by the filament. These data in addition to freestream data were used to evaluate the heat transfer coefficient. Data were collected for 5 different filament diameters, 25.4, 38.5, 51, 63.5 and 76 microns for 5 different dynamic pressure settings, 0.0, 0.466, 0.931, 1.397, and 1.863 mm Hg over a temperature range of 400 K to 1100 K in increments of 100 K. These data were taken at a zero crossflow setting. The angle of the test filament with the freestream was altered producing a crossflow effect and the same data were recorded for 2.5°, 5° and 7° crossflow angles. From these data an empirical equation was developed for the heat transfer coefficient as a function of filament diameter, temperature difference between the filament and the freestream, freestream velocity and crossflow angle. When compared with the experimental data the empirical equation was accurate to approximately 11.5%

Being Virtuous and Prosperous: SRI’s Conflicting Goals

Can SRI be a means to make investors both virtuous and prosperous? This paper argues that there can be significant tensions between these goals, and that SRI (and indeed all investment) should not allow the pursuit of maximizing investment returns to prevail over an ethical agenda of promoting social and economic justice and environmental protection. The discourse on SRI has changed dramatically in recent years to the point where its capacity to promote social emancipation, sustainable development and other ethical goals is in jeopardy. Historically, SRI was a boutique sector of the market dominated by religious-based investors who sought to invest in accordance with the tenets of their faith. From the early 1970s, the aspirations of the SRI movement morphed significantly in the context of the divestment campaign against South Africa’s apartheid regime. No longer were social investors satisfied with just avoiding profit from immoral activities; instead, they also sought to change the behavior of others. Business case SRI is a problematic SRI benchmark for several reasons: often there is a countervailing business case for financing irresponsible activities, given the failure of markets to capture all social and environmental externalities; secondly, even if investors care about such concerns, there may be no means of financially quantifying their significance for investment purposes; and, thirdly, even if such factors can be financially quantified, they may be deemed to be such long-term financial costs or benefits that they become discounted and ignored. The ethics case for SRI and ethical business practices more generally takes the view that both investors and the companies they fund have ethical responsibilities that trump the pursuit of profit maximization. Ethical investment should be grounded on this foundation. However, it may not be enough. To keep ethical investment ethical will likely require institutionalizing new norms and governance standards, in such domains as reforming fiduciary duties and the internal governance of financial organizations. SRI’s own codes of conduct including the UNPRI have yet to demonstrate the robustness to move the financial community beyond business as usual

12.2-GHz methanol maser MMB follow-up catalogue - II. Longitude range 186 to 330 degrees

We present the second portion of a catalogue of 12.2-GHz methanol masers detected towards 6.7-GHz methanol masers observed in the unbiased Methanol Multibeam (MMB) Survey. Using the Parkes radio telescope we have targeted all 207 6.7-GHz methanol masers in the longitude range 186 to 330 degrees for 12.2-GHz counterparts. We report the detection of 83 12.2-GHz methanol masers, and one additional source which we suspect is thermal emission, equating to a detection rate of 40 per cent. Of the 83 maser detections, 39 are reported here for the first time. We discuss source properties, including variability and highlight a number of unusual sources. We present a list of 45 candidates that are likely to harbor methanol masers in the 107.0-GHz transition.Comment: Accepted MNRAS 19 July 201

Detection of 6.7 GHz methanol absorption towards hot corinos

Methanol masers at 6.7 GHz have been found exclusively towards high-mass star forming regions. Recently, some Class 0 protostars have been found to display conditions similar to what are found in hot cores that are associated with massive star formation. These hot corino sources have densities, gas temperatures, and methanol abundances that are adequate for exciting strong 6.7 GHz maser emission. This raises the question of whether 6.7 GHz methanol masers can be found in both hot corinos and massive star forming regions, and if not, whether thermal methanol emission can be detected. We searched for the 6.7 GHz methanol line towards five hot corino sources in the Perseus region using the Arecibo radio telescope. To constrain the excitation conditions of methanol, we observed thermal submillimeter lines of methanol in the NGC1333-IRAS 4 region with the APEX telescope. We did not detect 6.7 GHz emission in any of the sources, but found absorption against the cosmic microwave background in NGC1333-IRAS 4A and NGC1333-IRAS 4B. Using a large velocity gradient analysis, we modeled the excitation of methanol over a wide range of physical parameters, and verify that the 6.7 GHz line is indeed strongly anti-inverted for densities lower than 10^6 cm^-3. We used the submillimeter observations of methanol to verify the predictions of our model for IRAS 4A by comparison with other CH3OH transitions. Our results indicate that the methanol observations from the APEX and Arecibo telescopes are consistent with dense (n ~ 10^6 cm^-3), cold (T ~ 15-30 K) gas. The lack of maser emission in hot corinos and low-mass protostellar objects in general may be due to densities that are much higher than the quenching density in the region where the radiation field is conducive to maser pumping.Comment: Accepted by A&

Multi-transition study and new detections of class II methanol masers

We have used the ATNF Mopra antenna and the SEST antenna to search in the directions of several class II methanol maser sources for emission from six methanol transitions in the frequency range 85-115 GHz. The transitions were selected from excitation studies as potential maser candidates. Methanol emission at one or more frequencies was detected from five of the maser sources, as well as from Orion KL. Although the lines are weak, we find evidence of maser origin for three new lines in G345.01+1.79, and possibly one new line in G9.62+0.20. The observations, together with published maser observations at other frequencies, are compared with methanol maser modelling for G345.01+1.79 and NGC6334F. We find that the majority of observations in both sources are consistent with a warm dust (175 K) pumping model at hydrogen density ~10^6 cm^-3 and methanol column density ~5 x 10^17 cm^-2. The substantial differences between the maser spectra in the two sources can be attributed to the geometry of the maser region.Comment: 13 pages, 6 figures, Accepted for publication in MNRA

The roles of the central executive and visuospatial storage in mental arithmetic: a comparison across strategies

Previous research has demonstrated that working memory plays an important role in arithmetic. Different arithmetical strategies rely on working memory to different extents-for example, verbal working memory has been found to be more important for procedural strategies, such as counting and decomposition, than for retrieval strategies. Surprisingly, given the close connection between spatial and mathematical skills, the role of visuospatial working memory has received less attention and is poorly understood. This study used a dual-task methodology to investigate the impact of a dynamic spatial n-back task (Experiment 1) and tasks loading the visuospatial sketchpad and central executive (Experiment 2) on adults' use of counting, decomposition, and direct retrieval strategies for addition. While Experiment 1 suggested that visuospatial working memory plays an important role in arithmetic, especially when counting, the results of Experiment 2 suggested this was primarily due to the domain-general executive demands of the n-back task. Taken together, these results suggest that maintaining visuospatial information in mind is required when adults solve addition arithmetic problems by any strategy but the role of domain-general executive resources is much greater than that of the visuospatial sketchpad. © 2013 The Author(s). Published by Taylor & Francis