1,943 research outputs found
Receipt for Paid Advertisement, G. B. & J. H. Utter, Steam Job Printers, to Peleg Clarke Jr., August 3, 1868
Get PDFThis receipt, dated August 3, 1868, is for an advertisement with the Narragansett Weekly and The Sabbath recorder through the G.B. and J. H. Utter Steam Job Printers, purchased by Peleg Clarke, advertising as Executor for the estate of Benjamin Reynolds. The payment of $1.75 for a 1 inch 6 week advertisement was received by G. B. and J. H. Utter.https://scholarsjunction.msstate.edu/fvw-manuscripts-clarke/1068/thumbnail.jp
Dynamics of low anisotropy morphologies in directional solidification
No full textWe report experimental results on quasi-two-dimensional diffusion limited growth in directionally solidified succinonitrile with small amounts of poly(ethylene oxide), acetone, or camphor as a solute. Seaweed growth, or dense branching morphology, is selected by growing grains close to the {111} plane, where the in-plane surface tension is nearly isotropic. The observed growth morphologies are very sensitive to small anisotropies in surface tension caused by misorientations from the {111} plane. Different seaweed morphologies are found, including the degenerate, the stabilized, and the strongly tilted seaweeds. The degenerate seaweeds show a limited fractal scaling range and, with increased undercooling, suggests a transition from "fractal" to "compact" seaweed. Strongly tilted seaweeds demonstrate a significant twofold anisotropy. In addition, seaweed-dendrite transitions are observed in low anisotropy growth
Double Dendrite Growth in Solidification
No full textWe present experiments on the doublon growth morphology in directional solidification. Samples used are succinonitrile with small amounts of poly(ethylene oxide), acetone, or camphor as the solute. Doublons, or symmetry-broken dendrites, are generic diffusion-limited growth structures expected at large undercooling and low anisotropy. Low anisotropy growth is achieved by selecting a grain near the {111} plane leading to either seaweed (dense branching morphology) or doublon growth depending on experimental parameters. We find selection of doublons to be strongly dependent on solute concentration and sample orientation. Doublons are selected at low concentrations (low solutal undercooling) in contrast to the prediction of doublons at large thermal undercooling in pure materials. Doublons also exhibit preferred growth directions and changing the orientation of a specific doublonic grain changes the character and stability of the doublons. We observe transitions between seaweed and doublon growth with changes in concentration and sample orientation
Efficient Computation of Dynamic Stability Data with a Linearized Frequency Domain Solver.
No full textDetermination of aeroelastic stability boundaries for full aircraft configu-
rations by solving the time-accurate unsteady Reynolds-averaged Navier-Stokes (RANS)
equations is recognized as extremely computationally expensive or impractical. This is due
to the wide range of
flight conditions, frequencies, and structural deformation mode shapes
that must be examined to ensure a configuration is free from
flutter. Nonetheless there
is an increasing demand within the aerospace industry for accurate
utter analysis in the
transonic regime, which can only be satisfied with the use of high-fidelity RANS codes.
Hence we are motivated to seek a more efficient numerical method. By assuming that
perturbations to the
ow are small and harmonic, we can derive an efficient alternative
method by linearization of the RANS equations, a linearized frequency domain (LFD)
solver. With this approach the unsteady simulation reduces to a single non-linear steady
computation followed by a single linear simulation in the frequency-domain. This method
is not new, but has principally been applied to turbomachinery so far. The contribution
of this paper twofold: firstly to show that LFD is sufficiently accurate and reliable for
applications to aeroelastic problems that occur in external aerodynamics, and secondly to
demonstrate the speed-up that can be expected over full unsteady computations. Viscous
transonic analysis is carried out on complex geometries in three-dimensions. The results
show good agreement with full unsteady simulation and experiment, and a reduction in
computational costs up to one order of magnitude is demonstrated
Numerical flutter analysis of turbomachinery bladings based on time-linearized, time-spectral and time-accurate simulations
No full textWithin the European research project FUTURE a transonic compressor rotor has been evaluated with respect to its aeroelastic stability. Based on the identical computational mesh different numerical approaches of the DLR flow solver TRACE and the ONERA code elsA are compared in this paper: whereas a time-linearized method based on small time-harmonic perturbations of the steady flow field is chosen in TRACE, elsA uses a non-linear time-domain harmonic balance method in order to determine local
aerodynamic work entries and the corresponding global damping values for all inter-blade phase angles (IBPA).
Furthermore, nonlinear reference solutions for the critical IBPA range will be provided by both codes using their classical time-marching schemes. In this context the difference in terms of computational effort between the fast linearized or harmonic balance methods and the classical nonlinear techniques shall be highlighted as well
Improved turbofan intake liner design and optimization
No full textIn modern turbofan engines, fan noise is one of the principle noise sources due to increased bypass ratio of the engines. Acoustic liners in the intake and bypass sections of the engine are effective in mitigating noise generated by the fan. They also play an important role in reducing fan blade instabilities by minimizing low-frequency acoustic reflections within the intake. Any damage on the lined surface has the potential to compromise the effectiveness of the liner; especially, its noise suppressing capabilities. The research presented in this thesis explores these areas on a much wider scale and aims to obtain an improved design of turbofan liners. The work performed ranges from developing an efficient strategy to optimize intake liners automatically to reduce both community noise and low-frequency acoustic reflections, to investigating the effects of liner damage and repair on the performance of zero-splice intake liners. Computational Aero-Acoustic (CAA) models have been used to predict radiated noise from a turbofan intake and the results have been validated against Rolls-Royce rig and engine test data. Adjustments have been made to the linear predictions to account for non-linear propagation effects which are significant at high fan speeds. Intake liners have been optimised to mitigate radiated noise in the far-field by using the CAA code within automated optimisation routines. The cumulative process time of these automated techniques seems to be within the acceptable limit by the industry. The acoustic effects of liner damage and repair on liner performance have been assessed by using analytical and computational prediction models. The effects of the extent and the location of the damage or the repaired surface on the overall performance of the liner is assessed. Some preliminary rules and guidelines have also been proposed in order to quantify the acoustic effects of the damage. The acoustic impact of different intake liners on low-frequency reflections have been investigated by using computational models. The results show that high resistance liners are more effective in minimizing acoustic reflections within the intake
Associations between diet quality and mental health in New Zealand adolescents
No full textFull text is available to authenticated members of The University of Auckland only.Background The diet quality of young people has deteriorated significantly over recent decades. Poor diet quality has previously been implicated in poor physical health outcomes, including obesity, heart disease, and diabetes. However, more recently, there has been an interest in the relationship between diet quality and mental health, especially depression. The alarmingly high prevalence of depression in adolescent populations presents a threat to the emotional, physical, and social wellbeing of young people. Therefore, examining the relationship between diet, a modifiable lifestyle factor, and depression may have implications for improving the mental health of young people. Aims and Objectives This study explored the relationship between diet quality and self-reported mental health in an ethnically diverse adolescent population. Specifically, two objectives were examined: - Cross-sectional analyses to determine if diet quality is associated with mental health; and - Prospective analyses to determine if diet quality predicts mental health over time. Method Data for the study was derived from baseline and follow-up measurements of the New Zealand arm of the Pacific Obesity Prevention in Communities (OPIC) study. Six high schools in the South Auckland region of New Zealand participated in the OPIC study. All students enrolled in years 9-13 of participating schools were eligible to take part. Data was available for 4249 students at baseline; 679 students also had one-year follow-up data. Responses from self-report dietary questionnaires were used to assess diet quality; healthy eating and unhealthy eating were assessed as two separate scales measuring various eating behaviours. Mental health was assessed by the emotional subscale of the PedsQL instrument. Results A significant cross-sectional relationship was identified between diet quality and mental health. Eating a healthy diet was associated with fewer depressive symptoms; eating an unhealthy diet was associated with more depressive symptoms. These relationships remained significant after controlling for age, ethnicity and gender. No significant relationships were observed between diet quality at baseline and mental health scores at one-year follow-up. Conclusions These findings suggest that diet quality is associated with mental health in adolescents; however, the relationship between the variables over time is ambiguous and requires further exploration
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