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Reviving the stalled shock by jittering jets in core collapse supernovae: jets from the standing accretion shock instability

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Research in Astronomy and Astrophysics 2019年第7期19卷 53-58页

作者： Noam Soker Department of Physics Technion – Israel Institute of Technology Guangdong technion israel institute of technology

I present a scenario by which an accretion flow with alternating angular momentum on to a newly born neutron star in a core collapse supernova(CCSN) efficiently amplifies magnetic fields and by that launches *** accretion flow of a collapsing core on to the newly born neutron star suffers spiral standing accretion shock instability(SASI).This instability leads to a stochastically variable angular momentum of the accreted gas,which in turn forms an accretion flow with alternating directions of the angular momentum,and hence alternating shear,at any given time.I study the shear in this alternating-shear sub-Keplerian inflow in published simulations,and present a new comparison with Keplerian accretion *** that comparison I argue that it might be as efficient as Keplerian accretion disks in amplifying magnetic fields by a dynamo.I suggest that although the average specific angular momentum of the accretion flow is small,namely,sub-Keplerian,this alternating-shear accretion flow can launch jets with varying directions,namely,jittering *** heating is an important ingredient in further energizing the *** jittering jets locally revive the stalled accretion shock in the momentarily polar directions,and by that they explode the star.I repeat again my call for a paradigm shift from a neutrino-driven explosion of CCSNe to a jet-driven explosion mechanism that is aided by neutrino heating.

关键词： stars jets-supernovae general-stars massive

Blast injury risks to humans within a military trench

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Defence technology（防务技术） 2024年第10期40卷 91-104页

作者： Idan E.Edri National Building Research institute Technion-Israel Institute of TechnologyTechnion CityHaifa 32000Israel

In land warfare,trenches serve as vital defensive fortifications,offering protection to soldiers while engaging in ***,despite their protective function,soldiers often sustain injuries within these *** lack of corresponding blast data alongside empirical injury reports presents a significant knowledge gap,particularly concerning the blast pressures propagating within trench spaces following nearby *** absence hinders the correlation between blast parameters,trench geometry,and reported injury cases,limiting our understanding of blast-related risks within *** paper addresses the critical aspect of blast propagation within trench systems,essential for evaluating potential blast injury risks to individuals within these *** advanced computational fluid dynamics(CFD)simulations,the study comprehensively investigates blast injury risks resulting from explosions near military *** a sophisticated computational model,the research analyzes the dynamic blast effects within trenches,considering both geometrical parameters and blast characteristics influenced by explosive weight and scaled *** numerical simulations yield valuable insights into the impact of these parameters on blast injury risks,particularly focusing on eardrum rupture,lung injury,and traumatic brain injury levels within the *** findings elucidate distinct patterns of high-risk zones,highlighting unique characteristics of internal explosions due to confinement and venting dynamics along the *** study underscores the significance of detailed numerical modeling in assessing blast injury risks and provides a novel knowledge base for understanding risks associated with explosives detonating near military *** insights gained contribute to enhancing safety measures in both military and civilian contexts exposed to blast events near trench structures.

关键词： Trench Blast Injury risk Eardrum rupture Lung injury Traumatic brain injury

Two-Phase Flow Patterns and Heat Transfer in Parallel Microchannels

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Journal of Thermal Science 2002年第4期11卷 353-358页

作者： AlainDegiovanni BenjaminRemy StephanéAndre Department of Mechanical Engineering Technion- Israel Institute of TechnologyDepartment of Mechanical Engineering Technion- Israel Institute of TechnologyDepartment of Mechanical Engineering Technion- Israel Institute of Technology

MicroChannel heat sinks with two-phase flow can satisfy the increasing heat removal requirements of modern micro electronic devices. One of the important aspects associated with two- phase flows in microchannels is to study the bubble behavior. However, in the literature most of the reports present data of only a single channel. This does not account for flow mixing and hydrodynamic instability that occurs in parallel microchannels, connected by common inlet and outlet collectors. In the present study, experiments were performed for air- water and steam- water flow in parallel triangular microchannels with a base of 200-300μ m. The experimental study is based on systematic measurements of temperature and flow pattern by infrared radiometry and high-speed digital video imaging. In air-water flow, different flow patterns were observed simultaneously in the various microchannels at a fixed values of water and gas flow rates. In steam-water flow, instability in uniformly heated microchannels was observed.

关键词： two-phase flow heat transfer microchannels dryout.

Point spread function estimation from projected speckle illumination

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Light(Science & Applications) 2015年第1期4卷 92-98页

作者： Nizan Meitav Erez N Ribak Shy Shoham Department of Biomedical Engineering Technion-Israel Institute of TechnologyTechnion CityHaifa 32000Israel Department of Physics Technion-Israel Institute of TechnologyTechnion CityHaifa 32000Israel

The resolution of an imaging apparatus is ideally limited by the diffraction properties of the light passing through the system aperture,but in many practical cases,inhomogeneities in the light propagating medium or imperfections in the optics degrade the image *** we introduce a powerful and practical new approach for estimating the point spread function(PSF)of an imaging system on the basis of PSF Estimation from Projected Speckle Illumination(PEPSI).PEPSI uses the fact that the speckles’phase randomness cancels the effects of the aberrations in the illumination path,thereby providing an objective pattern for measuring the deformation of the imaging *** this approach,both wide-field-of-view and local-PSF estimation can be obtained by calibration-free,single-speckle-pattern ***,we demonstrate the feasibility of using PEPSI estimates for resolution improvement in iterative maximum likelihood deconvolution.

关键词： deconvolution microscopy optical aberrations speckle pattern

Supernovae Ia in 2017:a long time delay from merger/accretion to explosion

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Science China(Physics,Mechanics & Astronomy) 2018年第4期61卷 7-16页

作者： Noam Soker Department of Physics Technion-lsrael Institute of TechnologyHaifa 32000Israel Guangdong technion israel institute of technology shantou 515063China

I use recent observational and theoretical studies of type Ia supernovae(SNe Ia) to further constrain the viable SN Ia scenarios and to argue that there must be a substantial time delay between the end of the merger of the white dwarf(WD) with a companion or the end of mass accretion on to the WD and its terminal explosion. This merger/accretion to explosion delay(MED) is required to allow the binary system to lead to a more or less spherical explosion and to prevent a pre-explosion ionizing radiation. Considering these recent results and the required MED, I conclude that the core degenerate scenario is somewhat more favorable over the other scenarios, followed by the double degenerate scenario. Although the single degenerate scenario is viable as well, it is less likely to account for common(normal) SN Ia. As all scenarios require substantial MED, the MED has turned from a disadvantage of the core degenerate scenario to a challenge that theory should overcome. I hope that the requirement for a MED will stimulate the discussion of the different SN Ia scenarios and the comparison of the scenarios to each other.

关键词： supernovae supernova remnants cataclysmic binaries binary and multiple stars

Variational approximation methods for long-range force transmission in biopolymer gels

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Chinese Physics B 2022年第10期31卷 429-435页

作者： Haiqin Wang Xinpeng Xu Physics Program Guangdong Technion-Israel Institute of Technology241 Daxue RoadShantou 515063China technion-israel institute of technology Haifa 320000Israel

The variational principle of minimum free energy(MFEVP) has been widely used in research of soft matter *** MFEVP can be used not only to derive equilibrium equations(including both bulk equations and boundary conditions),but also to develop direct variational methods(such as Ritz method) to find approximate solutions to these equilibrium equations. We apply these variational methods to study long-range force transmission in nonlinear elastic biopolymer *** is shown that the slow decay of cell-induced displacements measured experimentally for fibroblast spheroids in threedimensional fibrin gels can be well explained by variational approximations based on the three-chain model of biopolymer gels.

关键词： biopolymer gels cell-cell communications force transmission variational methods

Amplifying magnetic fields of a newly born neutron star by stochastic angular momentum accretion in core collapse supernovae

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Research in Astronomy and Astrophysics 2020年第2期20卷 94-100页

作者： Noam Soker Department of Physics technion Guangdong technion israel institute of technology

I present a novel mechanism to boost magnetic field amplification of newly born neutron stars in core collapse *** this mechanism,that operates in the jittering jets explosion mechanism and comes on top of the regular magnetic field amplification by turbulence,the accretion of stochastic angular momentum in core collapse supernovae forms a neutron star with strong initial magnetic fields but with a slow *** varying angular momentum of the accreted gas,which is unique to the jittering jets explosion mechanism,exerts a varying azimuthal shear on the magnetic fields of the accreted mass near the surface of the neutron ***,I argue,can form an amplifying effect which I term the stochastic omega(Sω) *** the common αω dynamo the rotation has constant direction and value,and hence supplies a constant azimuthal shear,while the convection has a stochastic *** the Sω dynamo the stochastic angular momentum is different from turbulence in that it operates on a large scale,and it is different from a regular rotational shear in being *** basic assumption is that because of the varying direction of the angular momentum axis from one accretion episode to the next,the rotational flow of an accretion episode stretches the magnetic fields that were amplified in the previous episode.I estimate the amplification factor of the Sω dynamo alone to be ≈ 10.I speculate that the Sω effect accounts for a recent finding that many neutron stars are born with strong magnetic fields.

关键词： stars:neutron stars:magnetic field (stars:)supernovae:general

Uplifted cool gas and heating by mixing in cooling flows

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Research in Astronomy and Astrophysics 2018年第7期18卷 73-80页

作者： Shlomi Hillel Noam Soker Department of Physics Technion-Israel Institute of TechnologyHaifa 32000 Guangdong technion israel institute of technology Shantou 515069China

We analyze our earlier three-dimensional hydrodynamical numerical simulation of jet-inflated bubbles in cooling flow clusters, and find that dense gas that was not heated by the jets＇ activity and that resides around the hot jet-inflated bubbles can be identified as uplifted gas as observed in some clusters. During the build up of the dense gas around the hot bubble, mixing of hot bubble gas with other regions of the intracluster medium （ICM） heats the ICM. The vortices that mix the ICM with the hot bubble gas also excite shock waves, sound waves and turbulence. Sound waves, shocks, turbulence and uplifted gas might be easier to detect than the mixing process and hence attract more attention, but we argue that the contributions of these processes to the heating of the ICM do not add up to the level of contribution of the mixing-heating process.

关键词： galaxies clusters intracluster medium

Photonic Floquet topological insulators in a fractal lattice

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Light(Science & Applications) 2020年第1期9卷 734-740页

作者： Zhaoju Yang Eran Lustig Yaakov Lumer Mordechai Segev Physics Department and Solid State institute Technion-Israel Institute of TechnologyHaifa 32000Israel

We present Floquet fractal topological insulators:photonic topological insulators in a fractal-dimensional lattice consisting of helical *** helical modulation induces an artificial gauge field and leads to a trivial-totopological phase *** quasi-energy spectrum shows the existence of topological edge states corresponding to real-space Chern number *** study the propagation of light along the outer edges of the fractal lattice and find that wavepackets move along the edges without penetrating into the bulk or backscattering even in the presence of *** a similar vein,we find that the inner edges of the fractal lattice also exhibit robust transport when the fractal is of sufficiently high ***,we find topological edge states that span the circumference of a hybrid half-fractal,half-honeycomb lattice,passing from the edge of the honeycomb lattice to the edge of the fractal structure virtually without scattering,despite the transition from two dimensions to a fractal *** system offers a realizable experimental platform to study topological fractals and provides new directions for exploring topological physics.

关键词： transition fractal topological