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Comparative study of the accuracy of the PSM and Kogelnik models of diffraction in reflection and transmission holographic gratings
Get PDFCalculated diffractive efficiencies in the visible spectral band from lossless planar holographic gratings are studied using the PSM and Kogelnik models of diffraction for the case of the σ-polarization. The results are numerically compared with rigorous coupled wave calculations over a wide parameter space covering both transmission and reflection geometries. For most reflection gratings, the PSM model is shown to consistently provide a marginally superior estimation of the diffractive efficiency. This is particularly evident in a clearly superior description of the diffractive sideband structure for most gratings, both in terms of angle and wavelength. For the transmission grating, the PSM model continues to provide a relatively good description of diffraction at low permittivity modulations and lower incidence angles with respect to the grating plane normal. However, overall Kogelnik’s theory is shown to provide a somewhat superior estimation of diffractive efficiency and a clearly superior description of the diffractive side-band structure in the transmission case
Systematic Avocating
Get PDFFeeling obliged to undertake complex research tasks outside core working hours is a common occurrence in academia. Detailed and timely research projects are expected; the creation and defence of sufficient intervals within a crowded working schedule is one concern explored in this short version paper. Merely working longer hours fails to provide a satisfactory solution for individuals experiencing concerns of this nature. Personal effort and drive are utilised and requires the application of mental mustering and systematic procedures. The attitude to research work is treating the task as a hobby conceptualised as avocating. Whilst this provides a personal solution through immersion in the task, this approach should raise concerns for employers. The flexibility of grounded theory is evident and the freedom to draw on various bodies of knowledge provides fresh insight into a problem that occurs in organizations in many sectors experiencing multiple priorities. The application of the core category, systematic avocating, may prove beneficial
ACERemix: A Tool for Glitch Music Production and Performance
Get PDFIn this paper we discuss the use of a recently developed audio compression approach: Audio Compression Exploiting Repetition (ACER) as a compositional tool for glitch composition and remixing. ACER functions by repeating similar sections of audio where they occur in a file and discarding the repetitive data. Thresholds for similarity can be defined using this approach, allowing for various degrees of (dis)similarity between materials identified as 'repetitive'. Through our initial subjective evaluation of ACER, we unexpectedly discovered that the compression method produced musically interesting results on some materials with higher levels of compression. Whilst listeners demonstrate this level of loss of fidelity to be unacceptable for the purposes of compression, it shows potential as a performance or production tool. When applied to pop songs the predicable form of the music was disrupted, introducing moments of novelty, while retaining the songs quantized rhythmic structure. In this paper we propose the use of ACER as a suitable method for producing sonic materials for 'glitch' composition. We present the use of ACER for this purpose with regards to a variety of materials that may be suitable for glitch or electroacoustic composition and using ACER in several different ways to process and reproduce musical audio
Towards a Comprehensive Typology of Knowledge for Social Work and Alcohol
Get PDFThis article presents a theoretical model of knowledge acquisition by social workers with regards to alcohol, which formed the propositional element of a recently awarded doctoral thesis submission. It begins by briefly contextualising the relationship between alcohol and social work, the profession's response to the increasing sense of alcohol-related issues in workloads and calls for more effective intervention responses. In considering how this is often reflected in demands for social workers to receive more education about alcohol, it critically examines existing considerations of possible typologies of knowledge for social work, before encapsulating them within a model focusing on alcohol. The model suggests that any such typology is likely to be composed of multiple sources, including both codified and non-codified elements. It concludes by considerations of some of the implications for research approaches that could be used to gain a better understanding of these knowledge frameworks. In doing so it proposes that it is through these alternative considerations that more holistic understandings of social work knowledge will be established. Discussion of the implications of working within more inclusive knowledge frameworks, for social work education, policy, practice and research, are contained throughout the article
The Reframing of Methodology: Revisiting a PhD Study
Get PDFThe paper draws on a PhD study to explore some methodological dilemmas associated with the execution of qualitative research when framed within positivist study design. The PhD was linked to an externally funded research project which evaluated the implementation of a custody-based intervention in the secure estate. While the PhD was conceived as a qualitative study, informed by interpretivist methodology and associated epistemology, the wider funded study was informed by positivist tradition and used a quantitative method. This led to dilemmas of both practical and methodological nature. The author revisits her study's methodological position to review issues raised by the research design and suggests an alternative proposal informed methodologically by critical realism which may better serve the study's interests. In doing so, the paper suggests how revisiting previous research may assist us in gaining methodological understanding and allow us to reframe our future endeavours to more useful end
An analysis of the surface quality of AA5182 at different testing temperatures
Get PDFThe mechanical behaviour of the commercial aluminium alloys EN AW-5182, EN AW-6016 and EN AW-7021 is investigated at temperatures ranging from 298 to 77 K and strain rates from 1.7 × 10__ to 6.6 × 10_ s-1. A device which allows testing at cryogenic temperatures is developed and demonstrated, where the specimens are subject to uniaxial tensile loads. The influence of a solution heat treatment for precipitation hardenable alloys is shown. The strain hardening coefficient is determined and mapped in terms of the experimentally investigated uniform elongation. The experimental data of tested aluminium alloys are compared with EN AW-1050A-H14, which is used as a reference. The effect of the Portevin-LeChatelier (PLC) effect on ductility and strength is discussed. The Ludwik relationship is adapted to describe materials showing a PLC-effect
Cadmium Telluride Solar Cells on Ultrathin Glass for Space Applications
Get PDFThis paper details the preliminary findings of a study to achieve a durable thin film CdTe photovoltaic device structure onto ultra-thin space qualified cover glass. An aluminium doped zinc oxide (AZO) transparent conducting oxide (TCO) was deposited directly onto cover glass using metal organic chemical vapour deposition (MOCVD). The AZO demonstrated a low sheet resistance of 10 Ω/□ and high optical transparency of 85% as well as an excellent adherence and environmental stability. Preliminary deposition of the photovoltaic layers onto the AZO on cover glass, by MOCVD, showed the possibility of such a structure yielding a device conversion efficiency of 7.2 %. High series resistance (10 Ω.cm2) and low Voc (586 mV) were identified as the limiting factors when compared to the authors platform process on indium tin oxide (ITO) coated aluminosilicate. The coverage of the Cd1-xZnxS window layer along with the front contacting of the device was shown to be the major cause of the low efficiency. Further deposition of the AZO/CdTe employing an oxygen plasma cleaning step to the cover glass and evaporated gold front contacts significantly improved the device performance. A best conversion efficiency of 10.2 % with series resistance improved to 4.4 Ω.cm2 and open circuit voltage (Voc) up to 667 mV and good adhesion has demonstrated for the first time direct deposition of CdTe solar cells onto 100 μm thick space qualified cover glass
A comparative study of properties of starches from Irish potato (Solanum tuberosum) and sweet potato (Ipomea batatas) grown in Nigeria
No full textStarch isolated from Irish and sweet potatoes grown in Nigeria were characterized. The starch granules of Irish potato were larger (13.39–47.00 µm) and showed a wider range of size distribution than sweet potato (2.00–25.86 µm). There was significant difference (p < 0.05) in the moisture, nitrogen, fat, phosphorus, and amylose contents of the starches. Irish potato starch had a lower gelatinization peak temperature (64.2°C) than sweet potato starch (74.9°C) and exhibited higher swelling power and amylose leaching, lower pasting temperature, higher peak and lower setback viscosities. The shear stress–shear rate profiles indicated the starch pastes were non-Newtonian and could best be fitted to the Herschel–Bulkley model. Sweet potato starch paste exhibited a higher storage modulus than Irish potato starch paste. Irish potato starch paste showed significantly (p < 0.05) higher paste clarity and lower retrogradation than sweet potato. The starch properties dictate their food applications
Easter Eggs: Hidden Tracks and Messages in Musical Mediums
Get PDF‘Easter eggs’ are hidden components that can be found in computer software and various other media including music. In this paper the concept is explained, and various examples are discussed from a variety of mediums including analogue and digital audio formats. Through this discussion, the purpose of including easter eggs in musical mediums is considered. We propose that easter eggs can serve to provide comic amusement within a work, but can also serve to support the artistic message of the artwork.Concealing easter eggs in music is partly dependent on the properties of the chosen medium; vinyl records may use techniques such as double grooves, while digital formats such as CD may feature hidden tracks that follow long periods of empty space. Approaches such as these and others are discussed. Lastly, we discuss some software components we have developed ourselves in Max/MSP, which facilitate the production of easter eggs by performing certain sequences of notes, or as a result of time-based events. We therefore argue that computer music performances present unique opportunities for the incorporation of easter eggs. These may occur to the surprise of audiences, performers and composers, and may support the artistic purpose of compositions as a whole
Design and Performance Study of a Dual-Element Multiband Printed Monopole Antenna Array for MIMO Terminals
Get PDFThis letter presents a study on linearly polarized compact multiband multiple-input-multiple-output (MIMO) antenna system for small mobile terminals. The MIMO antenna system consists of two symmetric printed monopole antennas with edge-to-edge separation of 0.097 λ 0 at 900 MHz. Each antenna element has a capacitive feed and is composed of two twisted lines, a parasitic loop, and a shorting trip that generate five resonant modes around 900, 1800, 2100, 3500, and 5400 MHz, covering GSM850/900, DCS, PCS, UMTS, WLAN, and WiMAX frequency bands. Two inverted-L shaped branches and a rectangular slot with one circular end, etched on the ground plane, were introduced to improve the isolation between antenna elements. The isolation achieved is higher than 15 dB in the lower band and 20 dB in the upper bands, leading to an envelope correlation coefficient of less than 0.025. The simulated performance of the designed antenna system has been verified in the experiment