scispace - formally typeset
Search or ask a question
Topic

Radius

About: Radius is a research topic. Over the lifetime, 20599 publications have been published within this topic receiving 413557 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: In this article, a solution for the radius of the vapor bubble as a function of time is obtained which is valid for sufficiently large radius, since the radius at which it becomes valid is near the lower limit of experimental observation.
Abstract: The growth of a vapor bubble in a superheated liquid is controlled by three factors: the inertia of the liquid, the surface tension, and the vapor pressure. As the bubble grows, evaporation takes place at the bubble boundary, and the temperature and vapor pressure in the bubble are thereby decreased. The heat inflow requirement of evaporation, however, depends on the rate of bubble growth, so that the dynamic problem is linked with a heat diffusion problem. Since the heat diffusion problem has been solved, a quantitative formulation of the dynamic problem can be given. A solution for the radius of the vapor bubble as a function of time is obtained which is valid for sufficiently large radius. This asymptotic solution covers the range of physical interest since the radius at which it becomes valid is near the lower limit of experimental observation. It shows the strong effect of heat diffusion on the rate of bubble growth. Comparison of the predicted radius‐time behavior is made with experimental observations in superheated water, and very good agreement is found.

771 citations

Journal ArticleDOI
TL;DR: In this paper, the mass and radius of the isolated 205.53 Hz millisecond pulsar PSR J0030+0451 were estimated using a Bayesian inference approach to analyze its energy-dependent thermal X-ray waveform, which was observed using the Neutron Star Interior Composition Explorer (NICER).
Abstract: Neutron stars are not only of astrophysical interest, but are also of great interest to nuclear physicists because their attributes can be used to determine the properties of the dense matter in their cores. One of the most informative approaches for determining the equation of state (EoS) of this dense matter is to measure both a star’s equatorial circumferential radius R e and its gravitational mass M. Here we report estimates of the mass and radius of the isolated 205.53 Hz millisecond pulsar PSR J0030+0451 obtained using a Bayesian inference approach to analyze its energy-dependent thermal X-ray waveform, which was observed using the Neutron Star Interior Composition Explorer (NICER). This approach is thought to be less subject to systematic errors than other approaches for estimating neutron star radii. We explored a variety of emission patterns on the stellar surface. Our best-fit model has three oval, uniform-temperature emitting spots and provides an excellent description of the pulse waveform observed using NICER. The radius and mass estimates given by this model are km and (68%). The independent analysis reported in the companion paper by Riley et al. explores different emitting spot models, but finds spot shapes and locations and estimates of R e and M that are consistent with those found in this work. We show that our measurements of R e and M for PSR J0030+0451 improve the astrophysical constraints on the EoS of cold, catalyzed matter above nuclear saturation density.

758 citations

Journal ArticleDOI
TL;DR: In this article, a double-slot antenna placed on hemispherical lenses with varying extension lengths was investigated and the theoretical results were presented in terms of extension-length/radius and radius/ lambda, and therefore result in universal design curves for silicon lenses of different diameters and at different frequencies.
Abstract: Far-field patterns and Gaussian-beam coupling efficiencies are investigated for a double-slot antenna placed on hemispherical lenses with varying extension lengths. The radiation patterns of a double-slot antenna on a silicon dielectric lens are computed using ray-tracing inside the dielectric lens and electric and magnetic field integration on the spherical dielectric surface. The measured radiation patterns at 246 GHz and Gaussian-beam coupling efficiencies show good agreement with theory. The theoretical results are presented in terms of extension-length/radius and radius/ lambda , and therefore result in universal design curves for silicon lenses of different diameters and at different frequencies. The theoretical and experimental results indicate that for single units, there exists a wide range of extension lengths which result in high Gaussian-coupling efficiencies (50-60%) to moderately high f 's. These Gaussian-coupling efficiencies can be increased to 80-90 degrees % with the use of a lambda /sub m//4 matching-cap layer. For imaging array applications with high packing densities, an extension-length/radius of 0.38 to 0.39 (depending on frequency) will result in peak directivity and a corresponding Gaussian-coupling efficiency 15-20% lower than for single units. >

754 citations

Journal ArticleDOI
04 Dec 1948-Nature
TL;DR: In this paper, it was claimed that the observed isotropy of the cosmic rays incident on the earth is simply a consequence of a magnetic field assumed to exist in interstellar space, and the basis for this claim is that a single particle of energy n and charge e is deflected through an appreciable angle after travelling a distance d across a magnetic magnetic field of intensity H, provided n equal to 1010 eV., e equal to the electronic charge (4·77 × 10-10 E.G.U.), and d equal to radius of the galaxy (∽3
Abstract: IT is important to decide whether or not the main sources of the cosmic ray particles are external to our galaxy. An external source seems, at first sight, to be established by the observed isotropy of the cosmic rays incident on the earth. But it has been claimed by a number of authors that this isotropy is simply a consequence of a magnetic field assumed to exist in interstellar space. The basis for this claim is that a single particle of energy n and charge e is deflected through an appreciable angle after travelling a distance d across a magnetic field of intensity H, provided For n equal to 1010 eV., e equal to the electronic charge (4·77 × 10-10 E.S.U.), and d equal to the radius of the galaxy (∽3 × 1022 cm.), the necessary value of H is about 10-15 gauss. This value may be compared with the average interstellar field of about 10-20 gauss that would result if (i) every star possessed a magnetic moment equal to the commonly quoted magnetic moment for the sun (∽ 1·5 × 1034 C.G.S.) ; (ii) the stellar magnetic dipoles were all aligned parallel to each other.

749 citations

Journal ArticleDOI
TL;DR: In this article, a comprehensive set of convergence tests are presented to explore the role of various numerical parameters on the equilibrium structure of a simulated dark matter halo, and two independent, state-of-the-art, multi-stepping, parallel N-body codes: PKDGRAV and GADGET.
Abstract: We present a comprehensive set of convergence tests which explore the role of various numerical parameters on the equilibrium structure of a simulated dark matter halo. We report results obtained with two independent, state-of-the-art, multi-stepping, parallel N-body codes: PKDGRAV and GADGET. We find that convergent mass profiles can be obtained for suitable choices of the gravitational softening, timestep, force accuracy, initial redshift, and particle number. For softenings chosen so that particle discreteness effects are negligible, convergence in the circular velocity is obtained at radii where the following conditions are satisfied: (i) the timestep is much shorter than the local orbital timescale; (ii) accelerations do not exceed a characteristic acceleration imprinted by the gravitational softening; and (iii) enough particles are enclosed so that the collisional relaxation timescale is longer than the age of the universe. The most stringent requirement for convergence is typically that imposed on the particle number by the collisional relaxation criterion, which implies that in order to estimate accurate circular velocities at radii where the density contrast may reach $\sim 10^6$, the region must enclose of order 3000 particles (or more than a few times $10^6$ within the virial radius). Applying these criteria to a galaxy-sized $\Lambda$CDM halo, we find that the spherically-averaged density profile becomes progressively shallower from the virial radius inwards, reaching a logarithmic slope shallower than -1.2 at the innermost resolved point, $r \sim 0.005 r_{200}$, with little evidence for convergence to a power-law behaviour in the inner regions.

738 citations


Network Information
Related Topics (5)
Magnetic field
167.5K papers, 2.3M citations
85% related
Scattering
152.3K papers, 3M citations
85% related
Particle
96.5K papers, 1.9M citations
82% related
Excited state
102.2K papers, 2.2M citations
82% related
Dark matter
41.5K papers, 1.5M citations
81% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202215
2021638
2020696
2019778
2018722
2017617