نتایج جستجو برای: dust density

تعداد نتایج: 448715  

2006
S. Schnee T. Bethell

We have used a numerical simulation of a turbulent cloud to synthesize maps of the thermal emission from dust at a variety of far-IR and sub-mm wavelengths. The average column density and external radiation field in the simulation is well matched to clouds such as Perseus and Ophiuchus. We use pairs of single-wavelength emission maps to derive the dust color temperature and column density, and ...

2000
H. Ishimoto

We have used the relationship, consistent with observational data, between the radial dependence of the dust supply and the mass dependence of the number density distribution, to consider the parent bodies of interplanetary dust. We examine the number density distribution of the interplanetary dust within 5AU of the Sun on the ecliptic plane. For the model calculations, the number density equat...

2016
K. Quest M. Dutreix

Dust acoustic (or dust density) waves have been observed in many laboratory dusty plasmas. These low-frequency waves involve the dynamics of highly charged and massive dust grains, and can be excited by the flow of ions relative to dust. In this paper, we consider the nonlinear development of the dust acoustic instability, excited by thermal ion flow, in a collisional plasma containing dust wit...

Journal: :Environmental Health Perspectives 1986
C B Parnell D D Jones R D Rutherford K J Goforth

Physical properties of grain dust derived from five grain types (soybean, rice, corn, wheat, and sorghum) were measured and reported. The grain dusts were obtained from dust collection systems of terminal grain handling facilities and were assumed to be representative of grain dust generated during the handling process. The physical properties reported were as follows: particle size distributio...

Introduction: The determination of accurate dose distribution is an issue of fundamental importance in radiotherapy, especially with regard to the fact that the human body is a heterogeneous medium. Therefore, the present study aimed to analyze the density and isodose depth profiles of 6 MV beam in a SP34 slab-wooden dust (pine)-SP34 slab (SWS) heterogeneous phantom.  Materials and Methods: Th...

2011
Robert L. Merlino Jonathon R. Heinrich Su-Hyun Kim

The dust acoustic wave (DAW) is a very low frequency (tens of Hz) dust density wave in which the dust particles participate in the wave dynamics. The early experimental observations of DAWs showed that the wave was self-excited by a modest relative ion drift and grew to very high amplitudes (~100%). In the first part of this paper we describe experiments showing the self-steepening of nonlinear...

2017
Diana Powell Ruth Murray-Clay Hilke E. Schlichting

We present a novel method for determining the surface density of protoplanetary disks through consideration of disk ‘dust lines’ which indicate the observed disk radial scale at different observational wavelengths. This method relies on the assumption that the processes of particle growth and drift control the radial scale of the disk at late stages of disk evolution such that the lifetime of t...

2017
Isamu K. Onishi Minoru Sekiya

We investigate the effect of a radial pressure bump in a protoplanetary disk on planetesimal formation. We performed the two-dimensional numerical simulation of the dynamical interaction of solid particles and gas with an initially defined pressure bump under the assumption of axisymmetry. The aim of this work is to elucidate the effects of the stellar vertical gravity that were omitted in a pr...

حسین حکیمی‌پژوه, , سمیه کریمی , ,

In this paper, we investigated the effect of dipole-dipole interaction between the dust particles on the transverse oscillation of one dimensional dusty crystal. We used the Boltzmann distribution for the electrons and ions density and assumed that dust particles are negatively charged. The equation of motion for dust particles in this one dimensional chain was obtained. It is shown that the di...

2007
M. M. Abbas J. F. Spann A. C. LeClair J. C. Brasunas

Introduction: The lunar surface is covered with a thick layer of micron/sub-micron size dust grains formed by meteoritic impact over billions of years. The fine dust grains are levitated and transported on the lunar surface, as indicated by the transient dust clouds observed over the lunar horizon during the Apollo 17 mission [1-5] Theoretical models suggest that the dust grains on the lunar su...

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