5,348 research outputs found
A high-order spectral deferred correction strategy for low Mach number flow with complex chemistry
We present a fourth-order finite-volume algorithm in space and time for low
Mach number reacting flow with detailed kinetics and transport. Our temporal
integration scheme is based on a multi-implicit spectral deferred correction
(MISDC) strategy that iteratively couples advection, diffusion, and reactions
evolving subject to a constraint. Our new approach overcomes a stability
limitation of our previous second-order method encountered when trying to
incorporate higher-order polynomial representations of the solution in time to
increase accuracy. We have developed a new iterative scheme that naturally fits
within our MISDC framework that allows us to simultaneously conserve mass and
energy while satisfying on the equation of state. We analyse the conditions for
which the iterative schemes are guaranteed to converge to the fixed point
solution. We present numerical examples illustrating the performance of the new
method on premixed hydrogen, methane, and dimethyl ether flames.Comment: 27 pages, 5 figure
NEMLink: Augmenting the Australian National Electricity Market transmission grid to facilitate increased wind turbine generation and its effect on transmission congestion
Hewson, MG ORCiD: 0000-0002-5212-3921This report’s primary aim is to investigate ‘The effect of increasing the number of wind turbine generators on transmission line congestion in the Australian National Electricity Market from 2014 to 2025’. The report is part of the research project titled ‘An investigation of the impacts of increased power supply to the national grid by wind generators on the Australian electricity industry’. The sensitivity analysis in this report uses simulations from the ‘Australian National Electricity Market (ANEM) model version 1.10’ 10’ (Wild, Bell & Foster 2015) to model the effect of five different levels of wind penetration on transmission congestion. The five levels of wind penetration span Scenarios A to E where Scenario A represents ‘no wind’ and Scenario E includes all the existing and planned wind power sufficient to meet Australia’s 20% 2020 41TWh Large Renewable Energy Target. Wild, Bell and Foster (2015) provide a comprehensive explanation of the both the ANEM model and the five levels of wind penetration
A Fourth-Order Adaptive Mesh Refinement Algorithm for the Multicomponent, Reacting Compressible Navier-Stokes Equations
In this paper we present a fourth-order in space and time block-structured
adaptive mesh refinement algorithm for the compressible multicomponent reacting
Navier-Stokes equations. The algorithm uses a finite volume approach that
incorporates a fourth-order discretization of the convective terms. The time
stepping algorithm is based on a multi-level spectral deferred corrections
method that enables explicit treatment of advection and diffusion coupled with
an implicit treatment of reactions. The temporal scheme is embedded in a
block-structured adaptive mesh refinement algorithm that includes subcycling in
time with spectral deferred correction sweeps applied on levels. Here we
present the details of the multi-level scheme paying particular attention to
the treatment of coarse-fine boundaries required to maintain fourth-order
accuracy in time. We then demonstrate the convergence properties of the
algorithm on several test cases including both nonreacting and reacting flows.
Finally we present simulations of a vitiated dimethyl ether jet in 2D and a
turbulent hydrogen jet in 3D, both with detailed kinetics and transport
Using inertial measurement units to quantify shoulder elevation after reverse total shoulder arthroplasty: a pilot study comparing goniometric measures captured clinically to inertial measures captured ‘in-the-wild’
Background: Reverse total shoulder arthroplasty (rTSA) is utilized for a variety of indications, but most commonly for patients with rotator cuff arthropathy. This procedure reduces pain, improves satisfaction, and increases clinically measured range of motion (ROM). However, traditional clinical ROM measurements captured via goniometer may not accurately represent ‘real-world’ utilization of ROM. In contrast, inertial measurement units (IMUs) are useful for establishing ROM outside the clinical setting. We sought to measure ‘real-world’ ROM after rTSA using IMUs.
Methods: A previously validated IMU-based method for continuously capturing shoulder elevation was used to assess 10 individuals receiving rTSA (1M, 82 ± 5 years) and compared to a previously captured 10 healthy individuals (4M, 69 ± 20 years) without shoulder dysfunction. Control subject data were previously collected over 1 week of continuous use. Patients undergoing rTSA donned sensors for 1 week pre-rTSA, 6 weeks at 3 months post-rTSA following clearance to perform active-independent ROM, and 1 week at 1 year and 2 years post-rTSA. Shoulder elevation was computed continuously each day. Daily continuous elevation was broken into 5° angle ‘bins’ (eg, 0-5°, 5-10°, etc.) and converted to percentage of the total day. IMU-based outcome measures were ROM binned percent (as described previously) and maximum/average elevation each week. Clinical goniometric ROM and patient-reported outcome measures were also captured.
Results: No differences existed between patient and healthy control demographics. While patients showed improvement in American Shoulder and Elbow Surgeon (ASES) score, pain score, and goniometric ROM, IMU-based average and maximum elevation were equal between control subjects and patients both pre- and post-rTSA. The percent of time spent above 90° was equal between cohorts pre-rTSA, rose significantly at 3 months post-rTSA, and returned to preoperative levels thereafter.
Discussion: Although pain, satisfaction, and ROM measured clinically may improve following rTSA, real-world utilization of improved ROM was not seen herein. Improvements during the acute rehabilitation phase may be transient, indicating longer or more specific rehabilitation protocols are necessary to see chronic improvements in post-rTSA movement patterns
Low C18 to C20 fatty acid elongase activity and limited conversion of stearidonic acid, 18:4(n-3), to eicosapentaenoic acid, 20:5(n-3), in a cell line from the turbot, Scophthalmus maximus
The TF cell line, derived from a top predatory, carnivorous marine teleost, the turbot (Scophthalmus maximus), is known to have a limited conversion of C18 to C20 polyunsaturated fatty acids (PUFA). To illuminate the underlying processes, we studied the conversions of stearidonic acid, 18:4(n-3), and its elongation product, 20:4(n-3), in TF cells and also in a cell line, AS, derived from Atlantic salmon (Salmo salar), by adding unlabelled (25 uM), U-14C (1 uM) or deuterated (d5; 25 uM) fatty acids. Stearidonic acid, 18:4(n-3), was metabolised to 20:5(n-3) in both cells lines, but more so in AS than in TF cells. Delta-5 desaturation was more active in TF cells than in AS cells, whereas C18 to C20 elongation was much reduced in TF as compared to AS cells. Only small amounts of docosahexaenoic acid (22:6(n-3)) were produced by both cell lines, although there was significant production of 22:5(n-3) in both cultures, especially when 20:4(n-3) was supplemented. We conclude that limited elongation of C18 to C20 fatty acids rather than limited fatty acyl Delta-5 desaturation accounts for the limited rate of conversion of 18:3(n-3) to 20:5(n-3) in the turbot cell line, as compared to the Atlantic salmon cell line. The results can account for the known differences in conversions of C18 to C20 PUFA by the turbot and the Atlantic salmon in vivo
A Sterile 20 Family Kinase and Its Co-factor CCM-3 Regulate Contractile Ring Proteins on Germline Intercellular Bridges
Germ cells in most animals are connected by intercellular bridges, actin-based rings that form stable cytoplasmic connections between cells promoting communication and coordination [1]. Moreover, these connections are required for fertility [1, 2]. Intercellular bridges are proposed to arise from stabilization of the cytokinetic ring during incomplete cytokinesis [1]. Paradoxically, proteins that promote closure of cytokinetic rings are enriched on stably open intercellular bridges [1, 3, 4]. Given this inconsistency, the mechanism of intercellular bridge stabilization is unclear. Here, we used the C. elegans germline as a model for identifying molecular mechanisms regulating intercellular bridges. We report that bridges are actually highly dynamic, changing size at precise times during germ cell development. We focused on the regulation of bridge stability by anillins, key regulators of cytokinetic rings and cytoplasmic bridges [1, 4-7]. We identified GCK-1, a conserved serine/threonine kinase [8], as a putative novel anillin interactor. GCK-1 works together with CCM-3, a known binding partner [9], to promote intercellular bridge stability and limit localization of both canonical anillin and non-muscle myosin II (NMM-II) to intercellular bridges. Additionally, we found that a shorter anillin, known to stabilize bridges [4, 7], also regulates NMM-II levels at bridges. Consistent with these results, negative regulators of NMM-II stabilize intercellular bridges in the Drosophila egg chamber [10, 11]. Together with our findings, this suggests that tuning of myosin levels is a conserved mechanism for the stabilization of intercellular bridges that can occur by diverse molecular mechanisms
Structure and Magnetic Fields in the Precessing Jet System SS433 III. Evolution of the Intrinsic Brightness of the Jets from a Deep Multi-Epoch VLA Campaign
We present a sequence of five deep observations of SS433 made over the summer
of 2007 using the VLA in the A configuration at 5 and 8 GHz. In this paper we
study the brightness profiles of the jets and their time evolution. We also
examine the spectral index distribution in the source. We find (as previously
reported from the analysis of a single earlier image) that the profiles of the
east and west jets are remarkably similar if projection and Doppler beaming are
taken into account. The sequence of five images allows us to disentangle the
evolution of brightness of individual pieces of jet from the variations of jet
power originating at the core. We find that the brightness of each piece of the
jet fades as an exponential function of age (or distance from the core),
exp(-tau/tau'), where tau is the age at emission and tau' = 55.9 +- 1.7 days.
This evolutionary model describes both the east and west jets equally well.
There is also significant variation (by a factor of at least five) in jet power
with birth epoch, with the east and west jets varying in synchrony. The lack of
deceleration between the scale of the optical Balmer line emission (10^15 cm)
and that of the radio emission (10^17 cm) requires that the jet material is
much denser than its surroundings. We find that the density ratio must exceed
300:1.Comment: 26 pages, 13 Figures, Accepted for publication in the Astrophysical
Journa
Structure and Magnetic Fields in the Precessing Jet System SS 433 II. Intrinsic Brightness of the Jets
Deep Very Large Array imaging of the binary X-ray source SS 433, sometimes
classified as a microquasar, has been used to study the intrinsic brightness
distribution and evolution of its radio jets. The intrinsic brightness of the
jets as a function of age at emission of the jet material tau is recovered by
removal of the Doppler boosting and projection effects. We find that
intrinsically the two jets are remarkably similar when compared for equal tau,
and that they are best described by Doppler boosting of the form D^{2+alpha},
as expected for continuous jets. The intrinsic brightnesses of the jets as
functions of age behave in complex ways. In the age range 60 < tau < 150 days,
the jet decays are best represented by exponential functions of tau, but linear
or power law functions are not statistically excluded. This is followed by a
region out to tau ~ 250 days during which the intrinsic brightness is
essentially constant. At later times the jet decay can be fit roughly as
exponential or power law functions of tau.Comment: 30 Pages, 11 Figures, Submitted to Ap
Wind speed and electricity demand correlation analysis in the Australian National Electricity Market: Determining wind turbine generators’ ability to meet electricity demand without energy storage
This paper analyses wind speed and electricity demand correlation to determine the ability of wind turbine generators to meet electricity demand in the Australian National Electricity Market (NEM) without the aid of energy storage. With the proposed increases in the number of windfarms to meet the Large-scale Renewable Energy Target (LRET), this correlation study is formative to identifying price and power stability issues and determining what transmission structure is required to best facilitate the absorption of wind power.
We calculate correlations between wind speed and electricity demand data for the years 2010 to 2012 using Weather Research & Forecasting Model (WRF 2015) wind speed data and Australian Energy Market Operator (AEMO) electricity demand data. We calculate state level correlations to identify potential bottlenecks in the interconnectors that link each state’s transmission network. The transmission lines within each state tend to be less of a constraint.
We find a small temporal increase in correlation between electricity demand and wind speed. This we attribute to an unwitting renewable energy portfolio effect with the increase in solar PV and solar water heating. Strengthening this portfolio effect is the decline in manufacturing that makes household domestic demand relatively larger. Comparing our study with an earlier correlation analysis by Bannister and Wallace (2011) tends to confirm our initial findings.
We find the most advantage from the lack of correlation between wind speed between the NEM’s peripheral states including Queensland, South Australia and Tasmania. Additionally, the correlation between electricity demand and wind speed is strongest between these states. Similarly, we find the most advantage from the lack of correlation between electricity demand in each of these states. The self-interest groups within Victoria and New South Wales and the transmission companies geographically contained within each state hinders the development of optimal interconnector capacity to maximise the benefit of wind power in the peripheral states and the NEM generally
- …