620 research outputs found
Simulated Tip Rub Testing of Low-Density Metal Foam
Preliminary acoustic studies have indicated that low-density, open-cell, metal foams may be suitable acoustic liner material for noise suppression in high by-pass engines. Metal foam response under simulated tip rub conditions was studied to assess whether its durability would be sufficient for the foam to serve both as a rub strip above the rotor as well as an acoustic treatment. Samples represented four metal alloys, nominal cell dimensions ranging from 60 to 120 cells per inch (cpi), and relative densities ranging from 3.4 to 10 percent. The resulting rubbed surfaces were relatively smooth and the open cell structure of the foam was not adversely affected. Sample relative density appeared to have significant influence on the forces induced by the rub event. Acoustic responses of various surface preparations were measured using a normal incidence tube. The results of this study indicate that the foam s open-cell structure was retained after rubbing and that the acoustic absorption spectra variation was minimal
Modelling the impact of liner shipping network perturbations on container cargo routing: Southeast Asia to Europe application
Understanding how container routing stands to be impacted by different scenarios of liner shipping network perturbations such as natural disasters or new major infrastructure developments is of key importance for decision-making in the liner shipping industry. The variety of actors and processes within modern supply chains and the complexity of their relationships have previously led to the development of simulation-based models, whose application has been largely compromised by their dependency on extensive and often confidential sets of data. This study proposes the application of optimisation techniques less dependent on complex data sets in order to develop a quantitative framework to assess the impacts of disruptive events on liner shipping networks. We provide a categorization of liner network perturbations, differentiating between systemic and external and formulate a container assignment model that minimises routing costs extending previous implementations to allow feasible solutions when routing capacity is reduced below transport demand. We develop a base case network for the Southeast Asia to Europe liner shipping trade and review of accidents related to port disruptions for two scenarios of seismic and political conflict hazards. Numerical results identify alternative routing paths and costs in the aftermath of port disruptions scenarios and suggest higher vulnerability of intra-regional connectivity
An Overview of the Distributed Space Exploration Simulation (DSES) Project
This paper describes the Distributed Space Exploration Simulation (DSES) Project, a research and development collaboration between NASA centers which investigates technologies, and processes related to integrated, distributed simulation of complex space systems in support of NASA's Exploration Initiative. In particular, it describes the three major components of DSES: network infrastructure, software infrastructure and simulation development. With regard to network infrastructure, DSES is developing a Distributed Simulation Network for use by all NASA centers. With regard to software, DSES is developing software models, tools and procedures that streamline distributed simulation development and provide an interoperable infrastructure for agency-wide integrated simulation. Finally, with regard to simulation development, DSES is developing an integrated end-to-end simulation capability to support NASA development of new exploration spacecraft and missions. This paper presents the current status and plans for these three areas, including examples of specific simulations
Hadronic Parity Violation: a New View through the Looking Glass
Studies of the strangeness changing hadronic weak interaction have produced a
number of puzzles that have so far evaded a complete explanation within the
Standard Model. Their origin may lie either in dynamics peculiar to weak
interactions involving strange quarks or in more general aspects of the
interplay between strong and weak interactions. In principle, studies of the
strangeness conserving hadronic weak interaction using parity violating
hadronic and nuclear observables provide a complementary window on this
question. However, progress in this direction has been hampered by the lack of
a suitable theoretical framework for interpreting hadronic parity violation
measurements in a model-independent way. Recent work involving effective field
theory ideas has led to the formulation of such a framework while motivating
the development of a number of new hadronic parity violation experiments in
few-body systems. In this article, we review these recent developments and
discuss the prospects and opportunities for further experimental and
theoretical progress.Comment: Manuscript submitted to Annual Reviews of Nuclear and Particle
Scienc
Evaluation of alternative intersection treatments at rural crossroads using simulation software
Objective: Rural roads are characterised by hazardous roadsides and suboptimal geometry, yet allow for high travel speeds and unfavourable impact angles. In Victoria, 25% of persons seriously injured and 52% of fatalities occur on rural roads, with 30% occurring at intersections (Transport Accident Commision, 2016; Victorian Parliament Road Safety Committee 2002). In the USA, almost twice the number of traffic fatalities occur in rural areas than in urban areas, whilst accounting for less than half of all vehicle miles travelled and 21% of the population (NHTSA 2002). The choice of safety countermeasure is therefore paramount. Simulation software provides a cost-effective means of analysing alternative intersection treatments with a view to identifying their effectiveness in mitigating crashes. The aim of this research was to assess the safety benefits of four alternative intersection treatments using in-depth crash data with an advanced crash reconstruction process.
Method: Using a single serious injury real-world crash from the MUARC Enhanced Crash Investigation Study (ECIS, Fitzharris et al., 2015) and crash reconstruction software, an exemplar rural crash was reconstructed and validated against real-world data. The crash involved a passenger vehicle (EuroNCAP 5*) approaching from a minor road and failing to yield at a ‘give-way’ sign; the posted speed limit was 80 km/h. The vehicle was struck on the right/driver side by a rigid truck (B-vehicle; 1990) travelling on the major approach (100 km/h). The driver of the case vehicle was seriously injured. Four alternative intersection treatments appropriate for the crash site were constructed in CAD software (Rhinoceros V5): roundabout; rumble strips; a reduced speed limit and the combination of lower speed limit and rumbles to determine the reduction in crash forces in the presence of the countermeasures.
Results: The hypothetical scenarios demonstrate substantial reductions in impact force and different points of impact, resulting in a significantly lower injury severity for the struck driver. Speed limit reduction to 80 km/h on the main approach (from 100 km/h) in combination with rumble strips on both intersection approaches had the most favorable outcome with the crash avoided entirely, assuming speed compliance.
Discussion: The findings have implications for understanding the role of speed in crashes, and hence the design of effective countermeasures. Simulation software, validated using real-world data, provides a cost effective means of evaluating alternative intersection treatments for rural intersections. Scaled up, implementing these treatments would have significant safety benefits and reduce the road trauma currently associated with rural roads
Myeloid DAP12-associating lectin (MDL)-1 regulates synovial inflammation and bone erosion associated with autoimmune arthritis.
DNAX adaptor protein 12 (DAP12) is a trans-membrane adaptor molecule that transduces activating signals in NK and myeloid cells. Absence of functional Dap12 results in osteoclast defects and bone abnormalities. Because DAP12 has no extracelluar binding domains, it must pair with cell surface receptors for signal transduction. There are at least 15 known DAP12-associating cell surface receptors with distinct temporal and cell type-specific expression patterns. Our aim was to determine which receptors may be important in DAP12-associated bone pathologies. Here, we identify myeloid DAP12-associating lectin (MDL)-1 receptor (also known as CLEC5A) as a key regulator of synovial injury and bone erosion during autoimmune joint inflammation. Activation of MDL-1 leads to enhanced recruitment of inflammatory macrophages and neutrophils to the joint and promotes bone erosion. Functional blockade of MDL-1 receptor via Mdl1 deletion or treatment with MDL-1-Ig fusion protein reduces the clinical signs of autoimmune joint inflammation. These findings suggest that MDL-1 receptor may be a therapeutic target for treatment of immune-mediated skeletal disorders
Effects of 8-Week In-Season Contrast Strength Training Program on Measures of Athletic Performance and Lower-Limb Asymmetry in Male Youth Volleyball Players
Strength training using high and lower load such as contrast training (CST) seems to be beneficial as it addresses larger adaptive reserves in youth athletes. Therefore, the aim of this study was to investigate the effects of CST on dynamic balance (composite score during dynamic balance test (CS-YBT)), one repetition maximum lower-limb back squat (1RM), jumping performance (single-leg hop (SLH) or countermovement jump height (CMJ)), lower-limb asymmetry (predicted from the single-leg jump performance between two legs [ILA]) in elite youth male volleyball players. Thirty-one male youth volleyball players aged 14 years were randomly assigned to a CST group (n = 16) or a control group (n = 15). The tests were performed before and after 8 weeks of training. Significant group × time interactions was observed for CS-YBT [p < 0.001, η(p)(2) = 0.70], 1RM [p < 0.001, η(p)(2) = 0.95], SLH with right and left leg [p < 0.001, η(p)(2) = 0.69 and 0.51], CMJ [p < 0.001, η(p)(2) = 0.47]), whilst it was not notable in ILA [p < 0.294]. Post hoc tests showed that CST group demonstrated greater improvement in all of the dependent variables from medium to large effect size (for all p < 0.001). As a result, 8 weeks of CST twice a week can be an effective and efficient training along with volleyball training to improve skill-related fitness measures, except for lower-limb asymmetry in young volleyball players
Kepler Presearch Data Conditioning II - A Bayesian Approach to Systematic Error Correction
With the unprecedented photometric precision of the Kepler Spacecraft,
significant systematic and stochastic errors on transit signal levels are
observable in the Kepler photometric data. These errors, which include
discontinuities, outliers, systematic trends and other instrumental signatures,
obscure astrophysical signals. The Presearch Data Conditioning (PDC) module of
the Kepler data analysis pipeline tries to remove these errors while preserving
planet transits and other astrophysically interesting signals. The completely
new noise and stellar variability regime observed in Kepler data poses a
significant problem to standard cotrending methods such as SYSREM and TFA.
Variable stars are often of particular astrophysical interest so the
preservation of their signals is of significant importance to the astrophysical
community. We present a Bayesian Maximum A Posteriori (MAP) approach where a
subset of highly correlated and quiet stars is used to generate a cotrending
basis vector set which is in turn used to establish a range of "reasonable"
robust fit parameters. These robust fit parameters are then used to generate a
Bayesian Prior and a Bayesian Posterior Probability Distribution Function (PDF)
which when maximized finds the best fit that simultaneously removes systematic
effects while reducing the signal distortion and noise injection which commonly
afflicts simple least-squares (LS) fitting. A numerical and empirical approach
is taken where the Bayesian Prior PDFs are generated from fits to the light
curve distributions themselves.Comment: 43 pages, 21 figures, Submitted for publication in PASP. Also see
companion paper "Kepler Presearch Data Conditioning I - Architecture and
Algorithms for Error Correction in Kepler Light Curves" by Martin C. Stumpe,
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