Recent enhancements to the GRIDGEN structured grid generation system

Significant enhancements are being implemented into the GRIDGEN3D, multiple block, structured grid generation software. Automatic, point-to-point, interblock connectivity will be possible through the addition of the domain entity to GRIDBLOCK's block construction process. Also, the unification of GRIDGEN2D and GRIDBLOCK has begun with the addition of edge grid point distribution capability to GRIDBLOCK. The geometric accuracy of surface grids and the ease with which databases may be obtained is being improved by adding support for standard computer-aided design formats (e.g., PATRAN Neutral and IGES files). Finally, volume grid quality was improved through addition of new SOR algorithm features and the new hybrid control function type to GRIDGEN3D

Institutional Repositories and the Role of Academic Libraries in Scholarly Communication

This paper explores the development of institutional repositories as a global phenomenon, comparing their objectives with the core principles of scholarly communication that have preserved and disseminated western knowledge for the past two centuries

Bar Beach (Beyond the Sea)

Two Australians have teamed up to produce the installation, Bar Beach (Beyond the Sea). Photo-based artist Allan Chawner collaborates with composer Andrew Chubb on this 3-channel video projection with original music. A sequence of still views, looking out over Bar Beach in the artists’ hometown of Newcastle, Australia, fades from one image to another in a 20-minute meditation on time, change and memory

Designing and Implementing an OVERFLOW Reader for ParaView and Comparing Performance Between Central Processing Units and Graphical Processing Units

In the Applied Aerosciences and CFD branch at Johnson Space Center, computational simulations are run that face many challenges. Two of which are the ability to customize software for specialized needs and the need to run simulations as fast as possible. There are many different tools that are used for running these simulations and each one has its own pros and cons. Once these simulations are run, there needs to be software capable of visualizing the results in an appealing manner. Some of this software is called open source, meaning that anyone can edit the source code to make modifications and distribute it to all other users in a future release. This is very useful, especially in this branch where many different tools are being used. File readers can be written to load any file format into a program, to ease the bridging from one tool to another. Programming such a reader requires knowledge of the file format that is being read as well as the equations necessary to obtain the derived values after loading. When running these CFD simulations, extremely large files are being loaded and having values being calculated. These simulations usually take a few hours to complete, even on the fastest machines. Graphics processing units (GPUs) are usually used to load the graphics for computers; however, in recent years, GPUs are being used for more generic applications because of the speed of these processors. Applications run on GPUs have been known to run up to forty times faster than they would on normal central processing units (CPUs). If these CFD programs are extended to run on GPUs, the amount of time they would require to complete would be much less. This would allow more simulations to be run in the same amount of time and possibly perform more complex computations

New low temperature techniques for electron thermometry and thermal isolation

Measuring electron temperature is an important method to understand the stability and coherence of a quantum circuit, since this variable describes how `quiet' the electronic environment is. In this thesis, the construction, calibration and operation of a quantum dot electron thermometer is demonstrated in two different cryostats. Compared to previous implementations of a quantum dot thermometer, the work presented here is unique in that it only requires a single gate connection to calibrate and operate, which simplifies the application of the device substantially. For the thermometer calibration, a physical model of the quantum-dot reservoir system was developed, which reveals information usually obtained from a stability diagram. Electron thermometry was successfully performed with the calibrated thermometer in a 1.0 K to 3.0 K range. With the fastest mode of operation the quantum dot thermometer was shown to have a sensitivity of 3.7±0.3 mK/√Hz at 1.3 K. This device provides a new versatile, sensitive and effective tool for monitoring electron temperature in nanoelectronic devices at cryogenic temperatures. Also in this thesis, several plastic solid-void structures were demonstrated to offer excellent thermal and structural properties at sub-Kelvin temperatures. Good low temperature insulators are extremely useful for support cryogenic components and sample environments without leaking unwanted heat. A structure fabricated from commercially available ABS LEGO elements was shown to be effective at thermally insulating two bodies at sub-Kelvin temperatures, with a thermal conductivity of κ = (8.7±0.3)×10-5 T1.75±0.02 Wm-1K-1. Similar scale 3D printed ABS and PLA gyroid structures were shown to also be effective as low-temperature insulators, having a thermal conductivity of κ = (3.07±0.05)×10-5T1.72±0.02 Wm-1K-1 and κ = 4.45±0.05)×10-5T1.64±0.02 Wm-1K-1, respectively. These samples demonstrate how low temperature insulation can be improved with readily available, fully customisable and affordable components

Factors Influencing Participant Satisfaction with Free/Libre and Open Source Software Projects

The purpose of this research was to identify factors that affect participants’ satisfaction with their experience of a free/libre open source software (FLOSS) project. The research built on existing models of user satisfaction from the information systems literature, and also incorporated two characteristics of FLOSS projects first identified by Ye, Nakakoji, Yamamoto, and Kishida (2005), product openness and process openness. The central research question it answered was, What factors influence participant satisfaction with a free/libre and open source application software project? Richard Stallman’s reasons for setting up the GNU project and the Free Software Foundation arose from his frustration at being forced to be a passive user of software used for a Xerox printer. These suggest that being able to be an active participant in a FLOSS project is one factor that should be examined, and therefore the first sub-question this project answers is, What types of contributions do participants make to free/libre and open source software projects? Several studies have shown that the extent of participation in a FLOSS project varies from individual to individual, and this variation leads to the second sub-question, Do the factors that influence satisfaction vary for different types of participation? If so, in what way? A preliminary conceptual model of factors affecting participant satisfaction was developed, reflecting the key concepts identified in the literature. The main theoretical goal of this research was to test the model using empirical data. The research used a sequential, mixed methods approach. The first, qualitative stage involved reviewing documents from selected projects and interviewing a purposive sample of FLOSS project participants. The second, quantitative stage involved an online survey of FLOSS project participants, and the data gathered were used to test the conceptual model. The results of the first stage showed that participation in FLOSS projects was a more complex construct than previously reported in the literature. Seven distinct categories of activities were identified: • use; • interaction with code; • supporting the community; • outreach; • sponsorship; • management; and • governance. Four attributes that modified these categories were also identified: organisational focus, role formality, remuneration, and time commitment. Data from 154 responses to the online survey were used to test the model using stepwise multiple regression, which determined the effect of each of the variables on overall participant satisfaction. Moderated regression analysis was used to test the effects of three potential moderating variables. The results showed that that perceived system complexity had the largest effect, decreasing satisfaction if respondents perceived that the software was complex, while project openness and perceived developer communication quality accounted for the most variance in satisfaction. The main theoretical contribution of this research lies in its extension of satisfaction studies to FLOSS communities, showing that communication and openness are more important than in conventional software projects. Its practical contribution will help people involved in the management and governance of FLOSS projects to identify ways of increasing their participants’ satisfaction, which may in turn encourage them to contribute more

Automatic structured grid generation using Gridgen (some restrictions apply)

The authors have noticed in the recent grid generation literature an emphasis on the automation of structured grid generation. The motivation behind such work is clear; grid generation is easily the most despised task in the grid-analyze-visualize triad of computational analysis (CA). However, because grid generation is closely coupled to both the design and analysis software and because quantitative measures of grid quality are lacking, 'push button' grid generation usually results in a compromise between speed, control, and quality. Overt emphasis on automation obscures the substantive issues of providing users with flexible tools for generating and modifying high quality grids in a design environment. In support of this paper's tongue-in-cheek title, many features of the Gridgen software are described. Gridgen is by no stretch of the imagination an automatic grid generator. Despite this fact, the code does utilize many automation techniques that permit interesting regenerative features

The origins of cosmic dust: A study of dust in galactic supernova remnants

This thesis investigates the question of whether supernovae (SNe) are important contributors of dust to the interstellar medium (ISM). Using far-infrared (FIR) observations of 190 supernova remnants (SNRs) covered by the Herschel Infrared Galactic Plane Survey (HiGal), we augment the current sample of dusty SNRs with an additional 38 from which dust emission is newly detected. This gives a 21 per cent detection rate of dust within SNRs in the Galactic Plane, although this is expected to be a lower limit given confusion with the ISM in this region. The majority of detected SNRs are young (less than 5 kyr), as expected since these objects tend to be more compact and have higher surface brightness, making them more easily detected above the level of the ISM. Nevertheless, we expand the age range of SNRs containing dust to roughly 100 kyr. Of our detections, 13 are from core collapse (CC) and 2 from Type Ia SNe (24 are of unknown type). Consistent with previous observations and theoretical models, we find that dust detected within the Type Ia SNRs is not expected to be of ejecta origin, but is more likely to have been swept up from the ISM. It is likely that many of our other detections are also dominated by ISM, although there are several objects within which we expect that the FIR emission originates from freshly formed ejecta material, including G350.1-0.3. We make new discoveries of ejecta dust within pulsar wind nebulae (PWNe) associated with three SNRs: G11.2-0.3, G21.5-0.9, and Kes 75. Using point process mapping (PPMAP) to analyse the FIR emission indicates the presence of dust within each object with temperatures between 20 and 40 K, and a PWN dust mass of 0.34 +/- 0.14 solar mass, 0.29 +/- 0.08 solar mass, 0.51 +/- 0.13 solar mass for G11, G21, and Kes 75 respectively. This suggests that SNe are important contributors of dust to the ISM, and PWNe in particular may play an important role in this. Although some of this dust may yet to be destroyed, there is evidence that the reverse shock has already reached the centre of G11, leaving behind a considerable mass of surviving dust. We use PPMAP further in an attempt to examine the dust properties, by studying the emissivity index, beta. The signal-to-noise in the longer wavebands is too low to constrain b for G11 or Kes 75; however, we find some evidence of a variation in the dust properties of ejecta dust within G21 (beta = 1.4 +/- 0.5), compared with that of the surrounding ISM (beta = 1.8 +/- 0.1). We study the dust within 11 of the other detected SNRs which are in regions with limited ISM variation, making background subtraction and thus dust analysis possible. By producing temperature maps, using their 24 – 70 micron flux ratios, we reveal the presence of warm dust (25 - 40 K) within all of these objects. For the objects with associated distance estimates, this analysis gives dust masses of between 0.2 and 340 solar mass, some of which are extremely large compared to the typical combined mass of freshly formed and swept up material. It is most likely that, despite careful background subtraction, the largest of these masses are overestimated due to contaminating ISM, which reduces the average dust temperature. As the dust mass is highly sensitive to even small changes in the estimated temperature, ISM confusion is the largest barrier to overcome when analysing the dust content of SNRs within the Galactic Plane. We detect a region of dust coincident with a strange radio source at the centre of G351.2-0.1. Previous studies have suggested that this could a PWN, or simply an unrelated HII region; we therefore attempt to determine its nature using FIR observations. Its spectral energy distribution (SED) suggests that the region consists of two dust components: (3.9 +/- 0.4) x 10^(-6) solar mass of warm dust with a temperature of 242 +/- 7 K, and 0.18 solar mass of cool dust with a temperature of 45.8 K. The temperature of the dust is higher than typical for a HII region, although not unheard of, and when considering the IR colours the emission from the core is consistent with either a HII region or SNR. We therefore cannot rule out either option based only on the IR emission, and the G351.2 core could be either an unrelated HII region, or a PWN with a considerable dust mass. A large region of dust was detected within a very unusual object known as the Tornado, G357.7-0.1. This is an object with a very uncertain past, which, it has been suggested, could have been formed by a SN or an X-ray binary. We detect FIR emission from multiple components of the Tornado: a filamentary structure within the tail region, peaks within the head, and an unrelated HII region dubbed the ‘eye’. Using PPMAP we reveal complex dust structures within the Tornado head and tail with temperatures between 15 and 61 K, and a total dust mass for the head of 16.7 solar mass. Within the head there is clear variation in the IR emission: an IR peak is detected to the north-west where the head is thought to be expanding into dense molecular material, and there is IR emission along radio filaments found towards the east. Comparing the IR and IR - radio colours highlights a variation in the emission from the two regions, suggesting that the dust properties or heat processes are different. When considering the nature of the Tornado, the head can be explained by a SNR aged between 2 and 8 kyr, with a large mass of dust swept up from the dense surrounding material. However, the tail is bizarre and more difficult to explain with a SN origin. We find it unlikely that it was formed by a progenitor prior to exploding. The structures in the tail could have been formed by jets from an X-ray binary, and we propose that the Tornado is similar to the W50 - SS 433 system, in which the jets of an X-ray binary plough into the SNR shell. This thesis has found a considerable dust mass contained within numerous Galactic SNRs, with several examples of newly detected ejecta dust. In particular, PWNe seem to be significant in the search for dusty SNRs. These findings suggest that SNe are important contributors of dust to the ISM