scholarly journals Impact of rotation on the evolution of convective vortices in collapsing stars

2021 ◽  
Author(s):  
E Abdikamalov ◽  
T Foglizzo ◽  
O Mukazhanov
Keyword(s):  
Acoustic Wave ◽  
Stellar Collapse ◽  
Hydrodynamic Evolution ◽  
Speed Up ◽  
Wave Emission ◽  
The Impact ◽  
Convective Vortices ◽  
Radial Stretching ◽  
Acoustic Wave Emission ◽  
Hydrodynamics Equations

Abstract We study the impact of rotation on the hydrodynamic evolution of convective vortices during stellar collapse. Using linear hydrodynamics equations, we study the evolution of the vortices from their initial radii in convective shells down to smaller radii where they are expected to encounter the supernova shock. We find that the evolution of vortices is mainly governed by two effects: the acceleration of infall and the accompanying speed up of rotation. The former effect leads to the radial stretching of vortices, which limits the vortex velocities. The latter effect leads to the angular deformation of vortices in the direction of rotation, amplifying their non-radial velocity. We show that the radial velocities of the vortices are not significantly affected by rotation. We study acoustic wave emission and find that it is not sensitive to rotation. Finally, we analyze the impact of the corotation point and find that it has a small impact on the overall acoustic wave emission.

Audible acoustic wave emission in excimer laser interaction with materials

1996 ◽  
Vol 79 (5) ◽  
pp. 2186-2191 ◽  
Author(s):  
Y. F. Lu ◽  
M. H. Hong ◽  
S. J. Chua ◽  
B. S. Teo ◽  
T. S. Low
Keyword(s):  
Acoustic Wave ◽  
Excimer Laser ◽  
Laser Interaction ◽  
Wave Emission ◽  
Acoustic Wave Emission

scholarly journals Multiscale Boundary Element Method for Acoustic Wave Model

MATEMATIKA ◽  
2019 ◽  
Vol 35 (3) ◽  
Author(s):  
Nor Afifah Hanim Zulkefli ◽  
Yeak Su Hoe ◽  
Munira Ismail
Keyword(s):  
Boundary Element Method ◽  
Numerical Methods ◽  
Acoustic Wave ◽  
Boundary Element ◽  
Computational Efficiency ◽  
Large Scale ◽  
Wave Model ◽  
Large Scale Problems ◽  
Speed Up ◽  
Element Method

In numerical methods, boundary element method has been widely used to solve acoustic problems. However, it suffers from certain drawbacks in terms of computational efficiency. This prevents the boundary element method from being applied to large-scale problems. This paper presents proposal of a new multiscale technique, coupled with boundary element method to speed up numerical calculations. Numerical example is given to illustrate the efficiency of the proposed method. The solution of the proposed method has been validated with conventional boundary element method and the proposed method is indeed faster in computation.

IDENTIFICATION OF IMPACT FORCE ON THE GAS PIPE BASED ON ANALYSIS OF THE ACOUSTIC WAVE

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1039-1044 ◽  
Author(s):  
MIN-SOO KIM ◽  
SANG-KWON LEE ◽  
SUNG-JONG KIM
Keyword(s):  
Acoustic Wave ◽  
Cavity Mode ◽  
Impact Force ◽  
Correlation Technique ◽  
Frequency Method ◽  
Time Frequency ◽  
Long Time ◽  
Mode Characteristics ◽  
The Impact ◽  
The Waves

An acoustic wave signal measured on the gas pipe due to impact force is transfer to the far distance through the medium inside of duct. This signal is very complex since it includes the acoustic wave and solid wave. Acoustic wave is affected by the cavity mode inside of duct. The analysis of this acoustic wave gives information about the impact force. For the analysis of this signal, the correlation technique has been used for a long time. This method has a limitation for the application since the waves have dispersive and cavity mode characteristics for the flexible wave. In this paper, we present the time-frequency method for the identification of impact force and the location of impact on the gas pipe. The results give the useful information for the impact force and are applied to the analysis of leakage location of the gas pipe.

Hydrocortisone vs Tocilizumab Effects on Cytokine Storm in Critically Ill Patients with COVID-19.

2020 ◽  
Author(s):  
Maria Vargas ◽  
Pasquale Buonanno ◽  
Carmine Iacovazzo ◽  
Gaetano Di Spigna ◽  
Daniela Spalletti ◽  
...  
Keyword(s):  
Critically Ill ◽  
Critically Ill Patients ◽  
Statistical Significance ◽  
Plasma Concentrations ◽  
Severe Pneumonia ◽  
Cytokine Storm ◽  
Tnf Α ◽  
Speed Up ◽  
The Impact ◽  
Late Stages

Abstract Introduction: Patients with severe pneumonia due COVID-19 are reported to have substantially lower lymphocyte counts and higher plasma concentrations of a number of inflammatory cytokines. In the late stages of COVID-19, cytokine storms are the mainly cause of disease progression and death. We performed a prospective observational study to evaluate the impact of tocilizumab and hydrocortisone on cytokine storm in critically ill patients with COVID-19.Methods: We included all adult patients with laboratory-confirmed COVID-19 infection and severe respiratory failure admitted to our ICU from March 10 to April 30. As therapeutic options, patients received tocilizumab od hydrocortisone. The primary end point was the evaluation of cytokine storm in terms of variation of the IL-6 and IL-6R, sgp130 and TNF-α concentrations during time to different treatment.Results: Eight patients received tocilizumab while 15 patients received hydrocortisone. IL-6 levels were lower in the hydrocortisone group with statistical significance was found at the days 2, 3, 8 and 9. The levels of IL-6R were lower during the days in the hydrocortisone group with statistical significance at days 1, 2, 3, 4, 5, 6, 8 and 10. Hydrocortisone group had higher levels of TNF-α at days 2, 3 and 4. The levels of sgo130 between tocilizumab and hydrocortisone groups were not statistically different during the days.Conclusions: In critically ill patients with severe COVID-19, the use of hydrocortisone allowed a better control of the cytokine storms, was further associated to less days of curarization, pronation and length of stay in ICU, and speed up the time to get negative RT-PCR swab.

scholarly journals Acoustic wave generation in collapsing massive stars with convective shells

2020 ◽  
Vol 493 (3) ◽  
pp. 3496-3512 ◽  
Author(s):  
Ernazar Abdikamalov ◽  
Thierry Foglizzo
Keyword(s):  
Acoustic Waves ◽  
Massive Stars ◽  
Core Collapse ◽  
Core Collapse Supernova ◽  
Stellar Collapse ◽  
Acoustic Wave Generation ◽  
Supernova Explosions ◽  
Accretion Shock ◽  
Stationary Background ◽  
Hydrodynamics Equations

ABSTRACT The convection that takes place in the innermost shells of massive stars plays an important role in the formation of core-collapse supernova explosions. Upon encountering the supernova shock, additional turbulence is generated, amplifying the explosion. In this work, we study how the convective perturbations evolve during the stellar collapse. Our main aim is to establish their physical properties right before they reach the supernova shock. To this end, we solve the linearized hydrodynamics equations perturbed on a stationary background flow. The latter is approximated by the spherical transonic Bondi accretion, while the convective perturbations are modelled as a combination of entropy and vorticity waves. We follow their evolution from large radii, where convective shells are initially located, down to small radii, where they are expected to encounter the accretion shock above the proto-neutron star. Considering typical vorticity perturbations with a Mach number ∼0.1 and entropy perturbations with magnitude ∼0.05kb/baryon, we find that the advection of these perturbations down to the shock generates acoustic waves with a relative amplitude $\delta {\rm p}/\gamma {\rm p} \lesssim 10{{\ \rm per\ cent}}$, in agreement with published numerical simulations. The velocity perturbations consist of contributions from acoustic and vorticity waves with values reaching ${\sim}10{{\ \rm per\ cent}}$ of the sound speed ahead of the shock. The perturbation amplitudes decrease with increasing ℓ and initial radii of the convective shells.

scholarly journals Changes in ice-shelf buttressing following the collapse of Larsen A Ice Shelf, Antarctica, and the resulting impact on tributaries

2016 ◽  
Vol 62 (235) ◽  
pp. 905-911 ◽  
Author(s):  
SAM ROYSTON ◽  
G. HILMAR GUDMUNDSSON
Keyword(s):  
Antarctic Peninsula ◽  
Surface Velocity ◽  
Ice Shelf ◽  
Mass Redistribution ◽  
Grounding Line ◽  
Modelling Studies ◽  
Speed Up ◽  
Stringent Test ◽  
The Antarctic ◽  
The Impact

ABSTRACTThe dominant mass-loss process on the Antarctic Peninsula has been ice-shelf collapse, including the Larsen A Ice Shelf in early 1995. Following this collapse, there was rapid speed up and thinning of its tributary glaciers. We model the impact of this ice-shelf collapse on upstream tributaries, and compare with observations using new datasets of surface velocity and ice thickness. Using a two-horizontal-dimension shallow shelf approximation model, we are able to replicate the observed large increase in surface velocity that occurred within Drygalski Glacier, Antarctic Peninsula. The model results show an instantaneous twofold increase in flux across the grounding line, caused solely from the reduction in backstress through ice shelf removal. This demonstrates the importance of ice-shelf buttressing for flow upstream of the grounding line and highlights the need to explicitly include lateral stresses when modelling real-world settings. We hypothesise that further increases in velocity and flux observed since the ice-shelf collapse result from transient mass redistribution effects. Reproducing these effects poses the next, more stringent test of glacier and ice-sheet modelling studies.

scholarly journals Research on the Energy Release Characteristics of Six Kinds of Reactive Materials

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3940 ◽  
Author(s):  
Xianwen Ran ◽  
Liangliang Ding ◽  
Jingyuan Zhou ◽  
Wenhui Tang
Keyword(s):  
Energy Release ◽  
The Self ◽  
Weight System ◽  
Test Device ◽  
Reactive Material ◽  
Reactive Materials ◽  
Release Test ◽  
Penetration Ability ◽  
Speed Up ◽  
The Impact

Currently, PTFE/Al is widely used in the reactive fragmentation warhead. However, for the same explosive yield, the reactive fragments usually have a smaller damage-radius than the inert fragments because PTFE/Al has a poor penetration ability and needs an impact-speed up to 1000 m/s to stimulate its chemical reaction. To enhance the damage power of reactive fragments, six kinds of reactive materials (PTFE/Al, PTFE/B, PTFE/Si, PTFE/Al/B, PTFE/Al/Si, and PTFE/Al/CuO) based on PTFE were designed and studied. Through the drop weight system and the self-designed energy release test device, qualitative and quantitative analysis of the energy release ability of six kinds of reactive materials were carried out. The qualitative analysis results indicate that the reactions of PTFE/B and PTFE/Si are weak under the impact of drop hammer with only a very weak fire light produced, while the reactions of PTFE/Al, PTFE/Al/B, PTFE/Al/Si, and PTFE/Al/CuO are relatively intense, and the reaction of PTFE/Al/Si is the most intense. Through the self-designed energy release test device, the energy release ability of the reactive material was quantitatively compared and analyzed. The results show that the energy release ability of the four formulations were as follows: PTFE/Al/Si > PTFE/Al/CuO > PTFE/Al/B > PTFE/Al. Therefore, it can be concluded that the PTFE/Al/Si formulation is a new reactive material with strong energy release ability, which can be a new choice for reactive fragment.

Laser Cutting of Small Diameter Nitinol Tube

2012 ◽  
Vol 729 ◽  
pp. 460-463
Author(s):  
Péter Nagy ◽  
János Dobránszky
Keyword(s):  
Laser Cutting ◽  
Applied Pressure ◽  
Small Diameter ◽  
Cutting Parameters ◽  
Development Project ◽  
Raw Material ◽  
Speed Up ◽  
Inner Diameter ◽  
Ar Gas ◽  
The Impact

In this article the complex research and development project of the laser cutting micromachining of nitinol alloys are shown. The laser cutting parameters of the 1.04 mm inner diameter and 0.1 mm wall thickness nitinol tubes are also shown. The laser cutting parameters of micromachining and the cut surface of nitinol tubes are summarized when 3 mJ pulse energy, 0.02 ms pulse duration, 6 bar Ar gas pressure, 3000 Hz frequency, 10 mm/s rotation speed and 5 mm/s2 speed-up were used. The effect of the laser cutting to the raw material is characterized by microstructural and micromechanical examinations. A detailed description is given of the energy input by laser beam machining. The pulse and the impact of the applied pressure parameters of the gas to the raw material are also shown.

scholarly journals Pre-Earthquake and Coseismic Ionosphere Disturbances of the Mw 6.6 Lushan Earthquake on 20 April 2013 Monitored by CMONOC

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 216 ◽  
Author(s):  
Shi ◽  
Liu ◽  
Guo ◽  
Liu ◽  
You ◽  
...  
Keyword(s):  
Acoustic Wave ◽  
Propagation Velocity ◽  
Ionospheric Disturbance ◽  
Lower Thermosphere ◽  
Propagation Speed ◽  
Lushan Earthquake ◽  
Electron Content ◽  
Terrestrial Environment ◽  
Total Electron ◽  
The Impact

In order to study the coupling relationship between large earthquakes and the ionosphere, the techniques of ionosphere data acquisition were refined by the Crustal Movement Observation Network of China (CMONOC) to detect the pre-earthquake ionospheric abnormal and coseismic ionospheric disturbances (CID) of the Mw 6.6 Lushan earthquake on 20 April 2013. Based on the regional ionosphere maps (RIMs) derived from the Global Positioning System (GPS) observations of CMONOC, the ionospheric local effects near the epicenter of the Lushan earthquake one month prior to the shock were analyzed. The results show that the total electron content (TEC) anomalies appeared 12–14 (6–8 April), 19 (1 April), and 25–27 (24–26 March) days prior to the Lushan earthquake, which are defined as periods 1, 2, and 3, respectively. Multi-indices including the ring current index (Dst), geomagnetic planetary (Kp) index, wind plasma speed (Vsw) index, F10.7, and solar flares were utilized to represent the solar–terrestrial environment in different scales and eliminate the effects of solar and geomagnetic activities on the ionosphere. After the interference of solar–terrestrial activity and the diurnal variation in the lower thermosphere were excluded, the TEC variations with obvious equatorial ionospheric anomaly (EIA) in period-1 were considered to be related to the Lushan earthquake. We further retrieved precise slant TECs (STECs) near the epicenter to study the coseismic ionospheric disturbance (CID). The results show that there was clear STEC disturbance occurring within half an hour after the Lushan earthquake, and the CID propagation distance was less than the impact radius of the Lushan earthquake (689 km). The shell models with different altitudes were adopted to analyze the propagation speed of the CID. It is found that at the F2-layer with the altitude of 277 km, which had a CID horizontal propagation velocity of 0.84 ± 0.03 km/s, was in accordance with the acoustic wave propagation velocity. The calculated velocity acoustic wave from the epicenter to the ionospheric pierce points of this shell model was about 0.53 ± 0.03km/s, which was also consistent with its actual velocity within the altitude of 0–277 km. Affected by the geomagnetic field, the CID mainly propagated along the southeast direction at the azimuth of 190°, which was almost parallel to the local magnetic line.

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