نتایج جستجو برای: velocity

تعداد نتایج: 141295  

2001
Héctor G. Arce

While observational evidence for the episodic nature of young stellar outflows continues to mount, existing numerical and theoretical models of molecular outflows assume they are formed by the interaction of a non-episodic wind from a young stellar object with an ambient cloud. In this Letter we estimate and discuss the effects of episodicity on the mass-velocity and position-velocity relations...

2012
Heynric Grotenhuis Wouter Stomp Jos J Westenberg Albert de Roos

Methods In 15 healthy volunteers (7 male; mean±SD age 19±6 years) pulmonary PWV was prospectively assessed between the proximal main pulmonary artery (MPA) and just before the first branching of the distal left pulmonary artery (LPA). One-directional through-plane velocity-encoded (VE) MRI using breath holds was used to assess the pulmonary flow at the levels of MPA and distal LPA with a tempor...

In this paper we have studied the effect of free convection on the heat transfer and flow through variable porous medium which is bounded by two vertical parallel porous plates. In this study it is assume that free stream velocity oscillates with time about a constant mean. Periodic temperature is considered in the moving plate. Effect of different parameters on mean flow velocity, Transient ve...

2004
ALEJANDRO ESQUIVEL

We use the results of magnetohydrodynamic (MHD) simulations to emulate spectroscopic observations and produce maps with variations of velocity centroids to study their scaling properties. In order to assess under which circumstances the scaling properties of the velocity field can be retrieved from velocity centroids, we compare two point statistics of velocity centroids with those of the under...

Journal: :فیزیک زمین و فضا 0
شهریار خاص احمدی موسسه ژئوفیزیک - دانشگاه تهران علی غلامی موسسه ژئوفیزیک - دانشگاه تهران

velocity analysis is one of the most important step in seismic data processing. it affects not only many processing steps directly and indirectly, but also is known as a primary interpretation of the data. however, it can also be assumed as one of the most time consuming processing step. the conventional velocity analysis method measures the energy amplitude along hyperbolic trajectories within...

Journal: :فیزیک زمین و فضا 0
مهرداد سلیمانی منفرد عضو هیات علمی علی خلیل زاده دانش آموخته کارشناسی ارشد/دانشگاه شاهرود

the conventional approach to seismic data analysis consists of two main steps: estimating seismic velocities, (the subsurface macro-model), and seismic imaging, (mapping of the reflected seismic energy to the reflector positions). the aim and the major challenge in the seismic data analysis is the construction of the best undistorted image. this challenge would be more problematic when geometri...

Journal: :فیزیک زمین و فضا 0
مریم خاکی فیروز کارشناس ارشد پردازش داده های لرزه ای، شرکت کدکم حمیدرضا سیاهکوهی دانشیار، گروه فیزیک زمین، مؤسسة ژئوفیزیک دانشگاه تهران

the stolt (f-k) migration algorithm is a direct (i.e. non-recursive) fourier-domain technique based on a change of variables (or equivalently, a mapping) that converts the input spectrum to the output spectrum. the algorithm is simple and efficient but limited to constant velocity. a v(z)(f-k) migration method, capable of very high accuracy for vertical variations of velocity, can be formulated...

Journal: :آب و خاک 0
سعید خدادوست سیوکی محمود نعمتی رضا استخر

introduction: for a velocity profile in turbulent flows, the flow conditions in the vicinity of the wall are described by logarithmic law of the wall. however, it has been extensively verified that the log-law does not apply in the outer region of the boundary layer. for example, in free surface flows, the law of the wall holds only for 20 percent of the flow depth from the wall. coles (1956) c...

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