1,721,906 research outputs found
Vortex- and wake- induced vibrations in an array of cylinders
No full textFlow-induced vibration (FIV) is an important phenomenon, by which the flow around bluff bodies creates forces that excite vibration. When marine risers are designed in a tandem arrangement, two aspects of FIV including Vortex Induced Vibration (VIV) and Wake-Induced Vibration (WIV) are very important, resulting in strong vibrations and fatigue damage. In this thesis, the simultaneous effects of VIV and WIV are studied for the case of circular cylinders by means of Computational Fluid Dynamics (CFD) software ANSYS Fluent. An Arbitrary Lagrangian-Eulerian (ALE) formulation is applied on a deformable mesh needed for modelling a free vibrating cylinder. The response dynamics and wake interactions are addressed. Major aspects considered in the thesis include: the Reynolds number (Re), the mass-damping parameter, the degrees of freedom of a single cylinder and of a downstream cylinder and the combined effect of VIV and WIV.The current predictions focus on sub-critical Re flow so that turbulence models are applied using two-dimensional Reynolds Averaged Navier-Stokes (RANS) equations. Force coefficients are analysed based on pressure distribution and Strouhal number. The VIV and WIV response is analysed by considering oscillating amplitude, frequencies and motion trajectories.The work concentrates on FIV vibration in three main cases: a single circular cylinder, and a downstream cylinder in tandem and staggered arrangements. The cylinder was elastically mounted on a mass-spring-damper system, with 1 degree of freedom (dof), 1+1dof, 2 dof or 4 dof. The study results showed the cylinder’s vibration is strongly affected by the mass-damping ratio and reduced velocity. The coupling between inline and crossflow vibrations could increase the amplitude of motion dramatically compared to crossflow vibration only. The amplitude of vibration changes the wake pattern as well as the trajectory of the cylinder. The vibration in the inline direction on the downstream cylinder in the wake of the upstream one is remarkably high compared to the crossflow direction.With a 2 dof system, the simultaneous effects of VIV and WIV give rise to vibration in each direction with two natural frequencies. WIV can be observed in the low-frequency response of the cylinder, which is considerably larger than the high-frequency VIV response. The combination of these two components can result in vibrations of the cylinder with higher amplitudes compared to any single form of excitation. The trajectories of the cylinder with a 4 dof system are very chaotic
Graphene oxide-based degradation of metaldehyde: effective oxidation through a modified Fenton’s process
No full textA modified graphene oxide-based Fenton’s reaction has been investigated for the degradation of a challenging emerging contaminant which is not effectively removed in conventional water treatment. Metaldehyde, used as the challenge molecule in this study, is a common molluscicide that (like many highly soluble contaminants) has frequently breached European regulatory limits in surface waters. The new method involves graphene with higher hydrophilic characteristics (single-layer graphene oxide, SLGO) as a system that participates in a redox reaction with hydrogen peroxide and which can potentially stabilize the radical dotOH generated, which subsequently breaks down organic contaminants. The modified Fenton’s reaction has shown to be effective in degrading metaldehyde in natural waters (>92% removal), even at high contaminant concentrations (50 mg metaldehyde/L) and in the presence of high background organic matter and dissolved salts. The reaction is relatively pH insensitive. SLGO maintained its catalytic performance over 3 treatment cycles when immobilized. Its performance gradually decreased over time, reaching around 50% of starting performance on the 10th treatment cycle. X-ray photoelectron spectroscopy (XPS) analysis of modifications caused in SLGO by the oxidizing treatment indicated that the oxidation of Csingle bondC sp2 to carbonyl groups may be the cause of the decrease in performance. The proposed modified Fenton’s process has the potential to substitute traditional Fenton’s treatment although regeneration of the nanocarbon is required for its prolonged use
A participatory library model for university libraries
No full textThis research investigated the ways academic libraries are using social media and adopting participatory principles in their programs and services. Using the Grounded Theory method the research developed an empirically derived model for participatory libraries. The research revealed three core categories representing the participatory library: community, empowerment, and experience. The research provides library professionals, researchers and the library community, with a fresh perspective and holistic picture of the contemporary library. The findings can be used to guide the development of participatory libraries in Australia and internationally
Tensor Tomography of Stress-Induced Birefringence in Commercial Glasses
No full text1 online resource (PDF, 32 pages, includes illustrations)Garavito-Garzon, Carlos Andres; Micek, Catherine A.; Nguyen, Linh Viet; Seal, David C.; Sun, Huan; Trofimov, Evgeni; Allan, Douglas C.. (2009). Tensor Tomography of Stress-Induced Birefringence in Commercial Glasses. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/180400
Estimation and separation of linear frequency- modulated signals in wireless communications using time - frequency signal processing.
No full textSignal processing has been playing a key role in providing solutions to key problems encountered in communications, in general, and in wireless communications, in particular. Time-Frequency Signal Processing (TFSP) provides eective tools\ud
\ud
for analyzing nonstationary signals where the frequency content of signals varies in time as well as for analyzing linear time-varying systems. This research aimed at exploiting the advantages of TFSP, in dealing with nonstationary signals, into the fundamental issues of signal processing, namely the signal estimation and signal separation. In particular, it has investigated the problems of (i) the Instantaneous Frequency (IF) estimation of Linear Frequency-Modulated (LFM) signals corrupted in complex-valued zero-mean Multiplicative Noise (MN), and (ii) the Underdetermined Blind Source Separation (UBSS) of LFM signals, while focusing onto the fast-growing area of Wireless Communications (WCom).\ud
\ud
A common problem in the issue of signal estimation is the estimation of the frequency of Frequency-Modulated signals which are seen in many engineering and real-life applications. Accurate frequency estimation leads to accurate recovery of the true information. In some applications, the random amplitude modulation\ud
\ud
shows up when the medium is dispersive and/or when the assumption of point target is not valid; the original signal is considered to be corrupted by an MN process thus seriously aecting the recovery of the information-bearing frequency. The IF estimation of nonstationary signals corrupted by complex-valued zero-mean MN\ud
\ud
was investigated in this research. We have proposed a Second-Order Statistics approach,\ud
\ud
rather than a Higher-Order Statistics approach, for IF estimation using Time-Frequency Distributions (TFDs). The main assumption was that the autocorrelation function of the MN is real-valued but not necessarily positive (i.e. the spectrum of the MN is symmetric but does not necessary has the highest peak at zero frequency). The estimation performance was analyzed in terms of bias and variance, and compared between four dierent TFDs: Wigner-Ville Distribution, Spectrogram, Choi-Williams Distribution and Modified B Distribution. To further improve the estimation, we proposed to use the Multiple Signal Classification algorithm\ud
\ud
and showed its better performance. It was shown that the Modified B Distribution performance was the best for Signal-to-Noise Ratio less than 10dB.\ud
\ud
\ud
\ud
In the issue of signal separation, a new research direction called Blind Source Separation (BSS) has emerged over the last decade. BSS is a fundamental technique in array signal processing aiming at recovering unobserved signals or sources from observed mixtures exploiting only the assumption of mutual independence between the signals. The term "blind" indicates that neither the structure of the mixtures nor the source signals are known to the receivers. Applications of BSS are seen in, for example, radar and sonar, communications, speech processing, biomedical signal processing. In the case of nonstationary signals, a TF structure forcing\ud
\ud
approach was introduced by Belouchrani and Amin by defining the Spatial Time- Frequency Distribution (STFD), which combines both TF diversity and spatial diversity. The benefit of STFD in an environment of nonstationary signals is the direct exploitation of the information brought by the nonstationarity of the signals.\ud
\ud
A drawback of most BSS algorithms is that they fail to separate sources in situations where there are more sources than sensors, referred to as UBSS. The UBSS of nonstationary signals was investigated in this research. We have presented a new approach for blind separation of nonstationary sources using their TFDs. The\ud
\ud
separation algorithm is based on a vector clustering procedure that estimates the\ud
\ud
source TFDs by grouping together the TF points corresponding to "closely spaced"\ud
\ud
spatial directions. Simulations illustrate the performances of the proposed method for the underdetermined blind separation of FM signals. The method developed in this research represents a new research direction for solving the UBSS problem.\ud
\ud
The successful results obtained in the research development of the above two problems has led to a conclusion that TFSP is useful for WCom. Future research directions were also proposed
A survey of the application of Web 2.0 in Australasian university libraries
No full textPurpose: This paper aims to provide an overall picture of the application of Web 2.0 technologies in Australasian university libraries. The focus of the research was what types of Web 2.0 technologies were applied in such libraries as well as their purposes and features.\ud
\ud
Design/methodology/approach: Content analysis was used in terms of quantitative approach. A checklist as the main research instrument was developed based on other checklists and questionnaires, and synthesized ideas from literature. Data were collected by accessing all Australasian university library web sites within two weeks. Then, Microsoft Excel was utilized as a main tool to synthesize and analyze data, and present results.\ud
\ud
Findings: At least two‐thirds of Australasian university libraries deployed one or more Web 2.0 technologies. Only four Web 2.0 technologies were used for specific purposes and with some basic features. The general Web 2.0 application indexes were still low as the mean application index was 12 points and the highest index was 37 points (out of 100).\ud
\ud
Research limitations/implications: A combination of content analysis with survey and/or interview may enable future researchers to analyze other aspects (e.g. the application of internal wikis or the use of instant messaging for reference services) of Web 2.0 that a single method of content analysis could not gain.\ud
\ud
Originality/value: This unique study explores the application of Web 2.0 in a wide scope including any Australasian university libraries that deployed any types of Web 2.0 technologies. This study is useful for Australasian university libraries in evaluating/deploying Web 2.0. Library managers, librarians and other university libraries may also find this helpful once they want to implement such technologies in their libraries
The synthesis of zinc ferrite spinel: Determination of pH value in the co-precipitation step
No full textZinc ferrite (ZnFe2O4) nanomaterial can be facilely and conveniently synthesized via the co-precipitation method from aqueous Zn2+ and Fe3+ salt solutions using sodium hydroxide as the precipitant. However, zinc hydroxide is amphoteric and can be soluble at low and high pH values; therefore, the study on pH for simultaneous precipitation of Fe3+ and Zn2+ to achieve pure ZnFe2O4 spinel is essential. In the present study, we elaborate a theoretical equation expressing the relationship between the zinc concentration in complex formation and pH value in the co-precipitation step. Since then, we synthesized ZnFe2O4 spinel and analyzed the products via various techniques such as thermoanalysis (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Vis spectra to investigate the appropriate pH for simultaneous precipitation of Fe3+ and Zn2+. The results indicate that in a wide range of pH values, from 7 to 12, ZnFe2O4 single-phase spinel ferrite structure is formed after calcination of the precipitate at 800 degrees C, the average particle sizes (SEM, nm) of ZnFe2O4 samples are in the range of 59.5 nm-85.5 nm (but is non-linear change), and their bandgap values are similar, around 1.96 eV. However, the unwanted appearance of alpha-Fe2O3 phase, the shifting in peak position and the decrease in intensity in the XRD pattern of the spinel products synthesized at pH of 6 and 13, respectively, reflect that the stoichiometric ratio of Zn2+ to Fe3+ in the spinel products is not achieved to 1:2. Such results provide a fundamental basis for choosing the appropriate pH in synthesizing ZnFe2O4 nanoparticles with orientationally structural and optical characteristics.
Volunteers and the new tort law reform
No full textThe volunteer protection legislation in each Australian jurisdiction makes considerable changes to the law of civil liabil-ity. Advocates for volunteer protection from third party liability were quite successful in having their issue accepted by all governments in the race to provide relief from the insurance crisis. However, there are a number of provisions that can be improved now that there is time for reflection. This article outlines a number of reforms to the legislation to pro-vide better outcomes for volunteers, community organisations and persons injured through negligence
- …
