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  • Articles  (18)
  • Springer  (10)
  • Oxford University Press  (7)
  • Institute of Physics (IOP)  (1)
  • Physics  (14)
  • Chemistry and Pharmacology  (4)
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  • Articles  (18)
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  • 1
    Electronic Resource
    Electronic Resource
    High molecular weight syndiotacticity-rich poly(vinyl alcohol) gel in aging process (2000)
    Springer
    Colloid & polymer science 278 (2000), S. 1198-1204 
    Details
    ISSN: 1435-1536
    Keywords: Key words Aging ; Poly(vinyl alcohol) ; Gel ; Syndiotacticity ; High molecular weight
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The properties of the aged gels of high molecular weight syndiotacticity-rich poly(vinyl alcohol)s (HMW S-PVAs) with different syndiotactic diad (s-diad) contents were investigated. HMW S-PVA gels with s-diad content of 61.5% and 58.2% showed the rapid increases of the syneresis and the turbidity from the early stage of aging time, which is ascribable to the phase separation, while that with s-diad content of 55.7% did not. From the morphological study, it was confirmed that the phase separation in HMW S-PVA gel with s-diad content of 61.5% occurred without the liquid-liquid phase separation in sol state, whereas both the liquid-liquid phase separation in sol state and the subsequent phase separation in gel state occurred in the case of HMW S-PVA gel with s-diad content of 58.2%. On the other hand, HMW S-PVA gel with s-diad content of 55.7% showed neither the liquid-liquid phase separation in sol state nor the phase separation in gel state in the long period of time. It was also confirmed from wide angle X-ray diffractogram that the crystallization was accompanied by the phase separation in gel state in the aging process of PVA gel. However, the crystallization was hindered by the fast network formation at the initial stage of time. Later the syndiotacticity promoted the crystallization. The tensile modulus of HMW S-PVA gel with higher syndiotacticity increased more significantly with time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960000387
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  • 2
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    Observation of reactor antineutrino disappearance using delayed neutron capture on hydrogen at RENO (2020)
    Springer
    Details
    Publication Date: 2020-04-01
    Print ISSN: 1126-6708
    Electronic ISSN: 1029-8479
    Topics: Physics
    Published by Springer
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  • 3
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    Supermassive black hole formation at high redshifts via direct collapse in a cosmological context (2015)
    Oxford University Press
    Details
    Publication Date: 2015-05-24
    Description: We study the early stage of the formation of seed supermassive black holes via direct collapse in dark matter (DM) haloes, in the cosmological context. We perform high-resolution zoom-in simulations of such collapse at high z . Using the adaptive mesh refinement code enzo , we resolve the formation and growth of a DM halo, until its virial temperature reaches ~10 4  K, atomic cooling turns on, and collapse ensues. We demonstrate that direct collapse proceeds in two stages, although they are not well separated. The first stage is triggered by the onset of atomic cooling, and leads to rapidly increasing accretion rate with radius, from $\dot{M}\sim 0.1\,\mathrm{M}_{\odot }\,{\rm yr^{-1}}$ at the halo virial radius to few M yr –1 , around the scale radius R s ~ 30 pc of the NFW DM density profile. The second stage of the collapse commences when the gas density takes precedence over the DM density. This is associated with the gas decoupling from the DM gravitational potential. The ensuing collapse approximates that of an isothermal sphere with $\dot{M}{(r)}\sim$  const. We confirm that the gas loses its angular momentum through non-axisymmetric perturbations and gravitational torques, to overcome the centrifugal barrier. During the course of the collapse, this angular momentum transfer process happens on nearly all spatial scales, and the angular momentum vector of the gas varies with position and time. Collapsing gas also exhibits supersonic turbulent motions which suppress gas fragmentation, and are characterized by density PDF consisting of a lognormal part and a high-density power-law tail.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 4
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    Supermassive black hole seed formation at high redshifts: long-term evolution of the direct collapse (2015)
    Oxford University Press
    Details
    Publication Date: 2015-12-18
    Description: We use cosmological adaptive mesh refinement code enzo zoom-in simulations to study the long-term evolution of the collapsing gas within dark matter haloes at z . This direct collapse process is a leading candidate for rapid formation of supermassive black hole (SMBH) seeds. To circumvent the Courant condition at small radii, we apply the sink particle method, focusing on evolution on scales ~0.01–10 pc. The collapse proceeds in two stages, with the secondary runaway happening within the central 10 pc. The sink particles form when the collapsing gas requires additional refinement of the grid size at the highest refinement level. Their growth is negligible with the sole exception of the central seed which grows dramatically to M seed  ~ 2  x  10 6 M in ~2 Myr, confirming the feasibility of this path to the SMBH. The variability of angular momentum in the accreted gas results in the formation of two misaligned discs. Both discs lie within the Roche limit of the central seed. While the inner disc is geometrically thin and weakly asymmetric, the outer disc flares due to turbulent motions as a result of the massive inflow along a pair of penetrating filaments. The filamentary inflow determines the dominant Fourier modes in this disc – these modes have a non-self-gravitational origin. We do not confirm that m  = 1 is a dominant mode that drives the inflow in the presence of a central massive object. The overall configuration appears to be generic, and is expected to form when the central seed becomes sufficiently massive.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 5
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    Dust properties of Lyman-break galaxies in cosmological simulations (2014)
    Oxford University Press
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    Publication Date: 2014-03-21
    Description: Recent observations have indicated the existence of dust in high-redshift galaxies, however, the dust properties in them are still unknown. Here we present theoretical constraints on dust properties in Lyman-break galaxies (LBGs) at z  = 3 by post-processing a cosmological smoothed particle hydrodynamics simulation with radiative transfer calculations. We calculate the dust extinction in 2800 dark matter haloes using the metallicity information of individual gas particles in our simulation. We use only bright galaxies with rest-frame ultraviolet (UV) magnitude M 1700  〈 –20 mag, and study the dust size, dust-to-metal mass ratio, and dust composition. From the comparison of calculated colour excess between B and V band [i.e. E ( B  –  V )] and the observations, we constrain the typical dust size, and show that the best-fitting dust grain size is ~ 0.05 μm, which is consistent with the results of theoretical dust models for Type II supernova. Our simulation with the dust extinction effect can naturally reproduce the observed rest-frame UV luminosity function of LBGs at z  = 3 without assuming an ad hoc constant extinction value. In addition, in order to reproduce the observed mean E ( B  –  V ), we find that the dust-to-metal mass ratio needs to be similar to that of the local galaxies, and that the graphite dust is dominant or at least occupy half of dust mass.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 6
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    Parametric performance evaluation of a hydraulic centrifugal pump (2014)
    Institute of Physics (IOP)
    Details
    Publication Date: 2014-12-11
    Description: Parametric study of a hydraulic centrifugal pump with backward curved blades has been performed numerically using three-dimensional Reynolds-averaged Navier-Stokes equations. The shear stress transport turbulence model was used for analysis of turbulence. The finite volume method and an unstructured grid system were used for the numerical solution. The optimal grid system in the computational domain was selected through a grid dependency test. Tested parameters were related to the geometry of the impeller and volute: seven variables defining the hub and shroud contours and the blades angle of impeller, and two variables defining the inlet width and expansion angle of volute. The effects of these parameters on the hydrodynamic performance of the centrifugal pump have been investigated. It was found that the centrifugal water pump with the twisted blades has the enhancing efficiency compared to the straight blades pump.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 7
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    Cosmic Dawn (CoDa): the first radiation-hydrodynamics simulation of reionization and galaxy formation in the Local Universe (2016)
    Oxford University Press
    Details
    Publication Date: 2016-09-20
    Description: Cosmic reionization by starlight from early galaxies affected their evolution, thereby impacting reionization itself. Star formation suppression, for example, may explain the observed underabundance of Local Group dwarfs relative to N -body predictions for cold dark matter. Reionization modelling requires simulating volumes large enough [~ (100 Mpc) 3 ] to sample reionization ‘patchiness’, while resolving millions of galaxy sources above ~10 8 M combining gravitational and gas dynamics with radiative transfer. Modelling the Local Group requires initial cosmological density fluctuations pre-selected to form the well-known structures of the Local Universe today. Cosmic Dawn (‘CoDa’) is the first such fully coupled, radiation-hydrodynamics simulation of reionization of the Local Universe. Our new hybrid CPU-GPU code, ramses-cudaton , performs hundreds of radiative transfer and ionization rate-solver timesteps on the GPUs for each hydro-gravity timestep on the CPUs. CoDa simulated (91Mpc) 3 with 4096 3 particles and cells, to redshift 4.23, on ORNL supercomputer Titan, utilizing 8192 cores and 8192 GPUs. Global reionization ended slightly later than observed. However, a simple temporal rescaling which brings the evolution of ionized fraction into agreement with observations also reconciles ionizing flux density, cosmic star formation history, CMB electron scattering optical depth and galaxy UV luminosity function with their observed values. Photoionization heating suppressed the star formation of haloes below ~2  x  10 9 M , decreasing the abundance of faint galaxies around M AB 1600  = [–10, –12]. For most of reionization, star formation was dominated by haloes between 10 10 –10 11 M , so low-mass halo suppression was not reflected by a distinct feature in the global star formation history. Intergalactic filaments display sheathed structures, with hot envelopes surrounding cooler cores, but do not self-shield, unlike regions denser than 100 〈〉.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 8
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    Spectromicroscopic study of plasma-treatment effect on InP-substrate-based silicon nitride and silicon oxide patterns (2004)
    Springer
    Details
    Publication Date: 2004-03-01
    Print ISSN: 0947-8396
    Electronic ISSN: 1432-0630
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 9
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    Galaxy simulation with dust formation and destruction (2017)
    Oxford University Press
    Details
    Publication Date: 2017-01-04
    Description: We perform smoothed particle hydrodynamics (SPH) simulations of an isolated galaxy with a new treatment for dust formation and destruction. To this aim, we treat dust and metal production self-consistently with star formation and supernova (SN) feedback. For dust, we consider a simplified model of grain size distribution by representing the entire range of grain sizes with large and small grains. We include dust production in stellar ejecta, dust destruction by SN shocks, grain growth by accretion and coagulation and grain disruption by shattering. We find that the assumption of fixed dust-to-metal mass ratio becomes no longer valid when the galaxy is older than 0.2 Gyr, at which point the grain growth by accretion starts to contribute to the non-linear rise of dust-to-gas ratio. As expected in our previous one-zone model, shattering triggers grain growth by accretion since it increases the total surface area of grains. Coagulation becomes significant when the galaxy age is greater than ~ 1 Gyr; at this epoch, the abundance of small grains becomes high enough to raise the coagulation rate of small grains. We further compare the radial profiles of dust-to-gas ratio $(\mathcal {D})$ and dust-to-metal ratio $(\mathcal {D}/Z$ , i.e. depletion) at various ages with observational data. We find that our simulations broadly reproduce the radial gradients of dust-to-gas ratio and depletion. In the early epoch ( 0.3 Gyr), the radial gradient of $\mathcal {D}$ follows the metallicity gradient with $\mathcal {D}/Z$ determined by the dust condensation efficiency in stellar ejecta, while the $\mathcal {D}$ gradient is steeper than the Z gradient at the later epochs because of grain growth by accretion. The framework developed in this paper is applicable to any SPH-based galaxy evolution simulations including cosmological ones.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 10
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    Magnetic trapping of strongly-magnetized Rydberg atoms (2006)
    Springer
    Details
    Publication Date: 2006-04-13
    Print ISSN: 1434-6060
    Electronic ISSN: 1434-6079
    Topics: Physics
    Published by Springer
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