Density-ratio-invariant mean-species profile of classical Rayleigh-Taylor mixing

Abstract CORONA 5 is a titanium alloy developed for applications in fracture-controlled aircraft components. Plane strain fracture toughnesses of 110,000 to 150,000 psi sq.rt. in. (120 to 165 MPa sq.rt. m) have been produced in this alloy at 135,00 psi (930 MPa) tensile strength through a variety of different process histories. The specific strength (strength/density ratio) is superior to that of the Ti-6A1-4V alloy. Resistance to fatigue crack propagation and resistance to chloride-stress-corrosion cracking are comparable to those of Ti-6A1-4V. This datasheet provides information on composition, physical properties, microstructure, elasticity, and tensile properties as well as fracture toughness and fatigue. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ti-70. Producer or source: Crucible Steel Company of America, Titanium Division.

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On the Transition from Homogeneous to Bubbling Fluidization

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19971698 ◽

1997 ◽

Vol 62 (11) ◽

pp. 1698-1709

Author(s):

Miloslav Hartman ◽

Zdeněk Beran ◽

Václav Veselý ◽

Karel Svoboda

Keyword(s):

Elastic Wave ◽

Froude Number ◽

Wave Velocity ◽

Density Ratio ◽

Elastic Wave Velocity ◽

Solid Density ◽

Archimedes Number ◽

Group A ◽

Experimental Findings

The onset of the aggregative mode of liquid-solid fluidization was explored. The experimental findings were interpreted by means of the dynamic (elastic) wave velocity and the voidage propagation (continuity) wave velocity. For widely different systems, the mapping of regimes has been presented in terms of the Archimedes number, the Froude number and the fluid-solid density ratio. The proposed diagram also depicts the typical Geldart's Group A particles fluidized with air.

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Compressive behaviours of octet-truss lattices

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406220913586 ◽

2020 ◽

Vol 234 (16) ◽

pp. 3257-3269 ◽

Cited By ~ 1

Author(s):

Yifan Li ◽

Huaiyuan Gu ◽

Martyn Pavier ◽

Harry Coules

Keyword(s):

Failure Modes ◽

Density Ratio ◽

Three Dimensional ◽

Compressive Load ◽

High Strength ◽

Detailed Comparison ◽

Compressive Response ◽

Beam Elements ◽

Structural Applications ◽

Octet Truss

Octet-truss lattice structures can be used for lightweight structural applications due to their high strength-to-density ratio. In this research, octet-truss lattice specimens were fabricated by stereolithography additive manufacturing with a photopolymer resin. The mechanical properties of this structure have been examined in three orthogonal orientations under the compressive load. Detailed comparison and description were carried out on deformation mechanisms and failure modes in different lattice orientations. Finite element models using both beam elements and three-dimensional solid elements were used to simulate the compressive response of this structure. Both the load reaction and collapse modes obtained in simulations were compared with test results. Our results indicate that three-dimensional continuum element models are required to accurately capture the behaviour of real trusses, taking into account the effects of finite-sized beams and joints.

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Conjugate Heat Transfer and Film Cooling of a Multi-Stage Cooling Scheme

Volume 10: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B, and C ◽

10.1115/imece2008-69138 ◽

2008 ◽

Author(s):

M. Ghorab ◽

S. I. Kim ◽

I. Hassan

Keyword(s):

Heat Transfer ◽

Film Cooling ◽

Gas Turbines ◽

Conjugate Heat Transfer ◽

Density Ratio ◽

Design Parameters ◽

Cooling Effectiveness ◽

Film Cooling Effectiveness ◽

Multi Stage ◽

Internal Gap

Cooling techniques play a key role in improving efficiency and power output of modern gas turbines. The conjugate technique of film and impingement cooling schemes is considered in this study. The Multi-Stage Cooling Scheme (MSCS) involves coolant passing from inside to outside turbine blade through two stages. The first stage; the coolant passes through first hole to internal gap where the impinging jet cools the external layer of the blade. Finally, the coolant passes through the internal gap to the second hole which has specific designed geometry for external film cooling. The effect of design parameters, such as, offset distance between two-stage holes, gap height, and inclination angle of the first hole, on upstream conjugate heat transfer rate and downstream film cooling effectiveness performance are investigated computationally. An Inconel 617 alloy with variable properties is selected for the solid material. The conjugate heat transfer and film cooling characteristics of MSCS are analyzed across blowing ratios of Br = 1 and 2 for density ratio, 2. This study presents upstream wall temperature distributions due to conjugate heat transfer for different gap design parameters. The maximum film cooling effectiveness with upstream conjugate heat transfer is less than adiabatic film cooling effectiveness by 24–34%. However, the full coverage of cooling effectiveness in spanwise direction can be obtained using internal cooling with conjugate heat transfer, whereas adiabatic film cooling effectiveness has narrow distribution.

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Three-component modelling of C-rich AGB star winds – V. Effects of frequency-dependent radiative transfer including drift★

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2714 ◽

2020 ◽

Vol 499 (2) ◽

pp. 1531-1560

Author(s):

Christer Sandin ◽

Lars Mattsson

Keyword(s):

Radiative Transfer ◽

Mass Loss ◽

Density Ratio ◽

Mie Scattering ◽

Speed Ratio ◽

Exponential Dependence ◽

Frequency Dependent ◽

Wind Velocities ◽

Drift Models ◽

Loss Rates

ABSTRACT Stellar winds of cool carbon stars enrich the interstellar medium with significant amounts of carbon and dust. We present a study of the influence of two-fluid flow on winds where we add descriptions of frequency-dependent radiative transfer (RT). Our radiation hydrodynamic models in addition include stellar pulsations, grain growth and ablation, gas-to-dust drift using one mean grain size, dust extinction based on both the small particle limit (SPL) and Mie scattering, and an accurate numerical scheme. We calculate models at high spatial resolution using 1024 gridpoints and solar metallicities at 319 frequencies, and we discern effects of drift by comparing drift models to non-drift models. Our results show differences of up to 1000 per cent in comparison to extant results. Mass-loss rates and wind velocities of drift models are typically, but not always, lower than in non-drift models. Differences are larger when Mie scattering is used instead of the SPL. Amongst other properties, the mass-loss rates of the gas and dust, dust-to-gas density ratio, and wind velocity show an exponential dependence on the dust-to-gas speed ratio. Yields of dust in the least massive winds increase by a factor 4 when drift is used. We find drift velocities in the range $10\!-\!67\, \mbox{km}\, \mbox{s}^{-1}$, which is drastically higher than in our earlier works that use grey RT. It is necessary to include an estimate of drift velocities to reproduce high yields of dust and low wind velocities.

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Waterfall Algorithm as a tool of investigation the geometrical features of granular porous media

Computational Particle Mechanics ◽

10.1007/s40571-021-00430-0 ◽

2021 ◽

Author(s):

Wojciech Sobieski

Keyword(s):

Particle Size ◽

Porous Media ◽

Lattice Boltzmann ◽

Granular Media ◽

Density Ratio ◽

Geometrical Features ◽

Granular Porous Media ◽

Collision Density ◽

Boltzmann Method ◽

The Impact

AbstractThe paper describes the so-called Waterfall Algorithm, which may be used to calculate a set of parameters characterising the spatial structure of granular porous media, such as shift ratio, collision density ratio, consolidation ratio, path length and minimum tortuosity. The study is performed for 1800 different two-dimensional random pore structures. In each geometry, 100 individual paths are calculated. The impact of porosity and the particle size on the above-mentioned parameters is investigated. It was stated in the paper, that the minimum tortuosity calculated by the Waterfall Algorithm cannot be used directly as a representative tortuosity of pore channels in the Kozeny or the Carman meaning. However, it may be used indirect by making the assumption that a unambiguous relationship between the representative tortuosity and the minimum tortuosity exists. It was also stated, that the new parameters defined in the present study are sensitive on the porosity and the particle size and may be therefore applied as indicators of the geometry structure of granular media. The Waterfall Algorithm is compared with other methods of determining the tortuosity: A-Star Algorithm, Path Searching Algorithm, Random Walk technique, Path Tracking Method and the methodology of calculating the hydraulic tortuosity based on the Lattice Boltzmann Method. A very short calculation time is the main advantage of the Waterfall Algorithm, what meant, that it may be applied in a very large granular porous media.

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Empirical Stochastic Model of Multi-GNSS Measurements

Sensors ◽

10.3390/s21134566 ◽

2021 ◽

Vol 21 (13) ◽

pp. 4566

Author(s):

Dominik Prochniewicz ◽

Kinga Wezka ◽

Joanna Kozuchowska

Keyword(s):

Stochastic Model ◽

Density Ratio ◽

Functional Model ◽

Optimal Solution ◽

Global Navigation Satellite Systems ◽

Unknown Parameters ◽

Short Baseline ◽

Stochastic Parameters ◽

Dependent Model ◽

The Impact

The stochastic model, together with the functional model, form the mathematical model of observation that enables the estimation of the unknown parameters. In Global Navigation Satellite Systems (GNSS), the stochastic model is an especially important element as it affects not only the accuracy of the positioning model solution, but also the reliability of the carrier-phase ambiguity resolution (AR). In this paper, we study in detail the stochastic modeling problem for Multi-GNSS positioning models, for which the standard approach used so far was to adopt stochastic parameters from the Global Positioning System (GPS). The aim of this work is to develop an individual, empirical stochastic model for each signal and each satellite block for GPS, GLONASS, Galileo and BeiDou systems. The realistic stochastic model is created in the form of a fully populated variance-covariance (VC) matrix that takes into account, in addition to the Carrier-to-Noise density Ratio (C/N0)-dependent variance function, also the cross- and time-correlations between the observations. The weekly measurements from a zero-length and very short baseline are utilized to derive stochastic parameters. The impact on the AR and solution accuracy is analyzed for different positioning scenarios using the modified Kalman Filter. Comparing the positioning results obtained for the created model with respect to the results for the standard elevation-dependent model allows to conclude that the individual empirical stochastic model increases the accuracy of positioning solution and the efficiency of AR. The optimal solution is achieved for four-system Multi-GNSS solution using fully populated empirical model individual for satellite blocks, which provides a 2% increase in the effectiveness of the AR (up to 100%), an increase in the number of solutions with errors below 5 mm by 37% and a reduction in the maximum error by 6 mm compared to the Multi-GNSS solution using the elevation-dependent model with neglected measurements correlations.

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Impact of seasonality and malaria control interventions on Anopheles density and species composition from three areas of Uganda with differing malaria endemicity

Malaria Journal ◽

10.1186/s12936-021-03675-5 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Henry Ddumba Mawejje ◽

Maxwell Kilama ◽

Simon P. Kigozi ◽

Alex K. Musiime ◽

Moses Kamya ◽

...

Keyword(s):

Species Composition ◽

Vector Control ◽

Malaria Control ◽

Mosquito Species ◽

Density Ratio ◽

Indoor Residual Spraying ◽

Sub Saharan Africa ◽

Malaria Vector Control ◽

Vector Density ◽

Llin Distribution

Abstract Background Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the malaria control interventions primarily responsible for reductions in transmission intensity across sub-Saharan Africa. These interventions, however, may have differential impact on Anopheles species composition and density. This study examined the changing pattern of Anopheles species in three areas of Uganda with markedly different transmission intensities and different levels of vector control. Methods From October 2011 to June 2016 mosquitoes were collected monthly using CDC light traps from 100 randomly selected households in three areas: Walukuba (low transmission), Kihihi (moderate transmission) and Nagongera (high transmission). LLINs were distributed in November 2013 in Walukuba and Nagongera and in June 2014 in Kihihi. IRS was implemented only in Nagongera, with three rounds of bendiocarb delivered between December 2014 and June 2015. Mosquito species were identified morphologically and by PCR (Polymerase Chain Reaction). Results In Walukuba, LLIN distribution was associated with a decline in Anopheles funestus vector density (0.07 vs 0.02 mosquitoes per house per night, density ratio [DR] 0.34, 95% CI: 0.18–0.65, p = 0.001), but not Anopheles gambiae sensu stricto (s.s.) nor Anopheles arabiensis. In Kihihi, over 98% of mosquitoes were An. gambiae s.s. and LLIN distribution was associated with a decline in An. gambiae s.s. vector density (4.00 vs 2.46, DR 0.68, 95% CI: 0.49–0.94, p = 0.02). In Nagongera, the combination of LLINs and multiple rounds of IRS was associated with almost complete elimination of An. gambiae s.s. (28.0 vs 0.17, DR 0.004, 95% CI: 0.002–0.009, p < 0.001), and An. funestus sensu lato (s.l.) (3.90 vs 0.006, DR 0.001, 95% CI: 0.0005–0.004, p < 0.001), with a less pronounced decline in An. arabiensis (9.18 vs 2.00, DR 0.15 95% CI: 0.07–0.33, p < 0.001). Conclusions LLIN distribution was associated with reductions in An. funestus s.l. in the lowest transmission site and An. gambiae s.s. in the moderate transmission site. In the highest transmission site, a combination of LLINs and multiple rounds of IRS was associated with the near collapse of An. gambiae s.s. and An. funestus s.l. Following IRS, An. arabiensis, a behaviourally resilient vector, became the predominant species, which may have implications for malaria vector control activities. Development of interventions targeted at outdoor biting remains a priority.

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Acute Effects of Work Rest Interval Duration of 3 HIIT Protocols on Cycling Power in Trained Young Adults

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18084225 ◽

2021 ◽

Vol 18 (8) ◽

pp. 4225

Author(s):

José Manuel García-De Frutos ◽

Fco. Javier Orquín-Castrillón ◽

Pablo Jorge Marcos-Pardo ◽

Jacobo Á. Rubio-Arias ◽

Alejandro Martínez-Rodríguez

Keyword(s):

Density Ratio ◽

Lactate Concentration ◽

Interval Training ◽

Exercise Duration ◽

Similar Amount ◽

Rest Interval ◽

High Intensity Interval Training ◽

Active Recovery ◽

Acute Responses ◽

High Intensity Interval

High-Intensity Interval Training (HIIT) is described as a succession of short duration and maximum or near-maximum intensity efforts, alternated by recovery periods during which exercise continues at a lower intensity (active recovery) or is interrupted (passive recovery). Our objective was to evaluate the acute responses of three HIIT protocols of different work/rest interval times over the total time of the session, with self-selectable load and up to exhaustion, “all out”.The sample was composed of 22 male participants (n = 22) between 19 and 24 years old. The HIIT protocol consisted of one of the three HIIT protocols, of 30, 60 and 90 s density ratio 1:1 and with passive rest, with a total exercise duration of 10 min. The test was performed in a cycloergometer set in workload mode independent of the pedaling frequency. The comparison of the three HIIT protocols shows that the duration of the work/rest intervals, starting from 30 s of work, in the cycloergometer, there are no significant differences in the levels of lactate concentration in the blood, nor in the heart rate, since a similar amount is obtained in the three protocols. The percentage of maximum power developed reached in each HIIT protocol is related to the duration of the working intervals.

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Conditioning and PPP processing of smartphone GNSS measurements in realistic environments

Satellite Navigation ◽

10.1186/s43020-021-00042-2 ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Ganga Shinghal ◽

Sunil Bisnath

Keyword(s):

Single Point ◽

A Priori ◽

Density Ratio ◽

Satellite System ◽

Quality Parameters ◽

Urban Environments ◽

Dual Frequency ◽

Missing Measurements ◽

Data Gaps ◽

Point Positioning

AbstractSmartphones typically compute position using duty-cycled Global Navigation Satellite System (GNSS) L1 code measurements and Single Point Positioning (SPP) processing with the aid of cellular and other measurements. This internal positioning solution has an accuracy of several tens to hundreds of meters in realistic environments (handheld, vehicle dashboard, suburban, urban forested, etc.). With the advent of multi-constellation, dual-frequency GNSS chips in smartphones, along with the ability to extract raw code and carrier-phase measurements, it is possible to use Precise Point Positioning (PPP) to improve positioning without any additional equipment. This research analyses GNSS measurement quality parameters from a Xiaomi MI 8 dual-frequency smartphone in varied, realistic environments. In such environments, the system suffers from frequent phase loss-of-lock leading to data gaps. The smartphone measurements have low and irregular carrier-to-noise (C/N0) density ratio and high multipath, which leads to poor or no positioning solution. These problems are addressed by implementing a prediction technique for data gaps and a C/N0-based stochastic model for assigning realistic a priori weights to the observables in the PPP processing engine. Using these conditioning techniques, there is a 64% decrease in the horizontal positioning Root Mean Square (RMS) error and 100% positioning solution availability in sub-urban environments tested. The horizontal and 3D RMS were 20 cm and 30 cm respectively in a static open-sky environment and the horizontal RMS for the realistic kinematic scenario was 7 m with the phone on the dashboard of the car, using the SwiftNav Piksi Real-Time Kinematic (RTK) solution as reference. The PPP solution, computed using the YorkU PPP engine, also had a 5–10% percentage point more availability than the RTK solution, computed using RTKLIB software, since missing measurements in the logged file cause epoch rejection and a non-continuous solution, a problem which is solved by prediction for the PPP solution. The internal unaided positioning solution of the phone obtained from the logged NMEA (The National Marine Electronics Association) file was computed using point positioning with the aid of measurements from internal sensors. The PPP solution was 80% more accurate than the internal solution which had periodic drifts due to non-continuous computation of solution.

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