Search results for "velocity"
showing 10 items of 881 documents
Functional adaptation of sarcolemma to physical stress
2010
Effect of Ion Escape Velocity and Conversion Surface Material on H- Production
2011
According to generally accepted models surface production of negative ions depends on ion escape velocity and work function of the surface. We have conducted an experimental study addressing the role of the ion escape velocity on H− production. A converter‐type ion source at Los Alamos Neutron Science Center was employed for the experiment. The ion escape velocity was affected by varying the bias voltage of the converter electrode. It was observed that due to enhanced stripping of H− no direct gain of extracted beam current can be achieved by increasing the converter voltage. The conversion efficiency of H− was observed to vary with converter voltage and follow the existing theories in qual…
Estimation of the Time-Variant Velocity of a Single Walking Person in Two-Dimensional Non-Stationary Indoor Environments Using Radio-Frequency Techni…
2020
Accurate estimation of the time-variant (TV) velocity of moving persons/objects in indoor spaces is of crucial importance for numerous wireless indoor applications. This article introduces a novel iterative procedure to estimate the TV velocity, i.e., TV speed and TV angle-of-motion (AOM), of a single moving person in 2D indoor environments by using radio-frequency (RF) techniques. The indoor area is equipped with a distributed 2 × 2 multiple-input multiple-output (MIMO) system. The proposed method is divided into two parts. In the first part, we estimate the path gains and the instantaneous Doppler frequencies by fitting the exact spectrograms of the complex channel gains of a 2D no…
Experimental investigation on turbulent structures and sediment transport
2011
Role of vegetation on flow hydrodynamics and erosion processes
2011
ANALYSIS OF VELOCITY FIELD AND TURBULENCE CHARACTERISTICS OF FLOW IN A VEGETATED LABORATORY FLUME
2011
Vegetation altering hydrodynamic conditions of an open channel flow controls the exchanges of sediment, nutrients and contaminants. Thus, the knowledge of the hydraulic characteristics of flow over vegetation is very important to support the management of fluvial processes. But, the analysis of the hydrodynamic conditions is complex because vegetation is flexible in varying degrees and it oscillates in the flow changing position. Furthermore, because of temporal changing of roughness due to natural vegetative growth, the response of vegetation to the flow can change in time. Many theoretical and experimental investigations have been performed in order to analyze both the mean flow and turbu…
Experimental analysis of flow in a laboratory flume with flexible vegetation
2011
Log velocity profile and bottom displacement for a flow over a very flexible submerged canopy
2007
Management of shallow lagoons and salt marsh environments usually requires use of numerical models in order to understand the hydrodynamic characteristics of these basins. In order for these models to give reliable results one has to have good knowledge of the interaction between the flow and the aquatic vegetation, which strongly alters the hydrodynamic characteristics. Many experimental and theoretical studies are available in the technical literature, but, because of the very different vegetation and flow characteristics, they do not yet allow one to have a clear and general knowledge of the phenomena, in terms of both flow resistance and velocity distribution. The latter is very importa…
Numerical Simulations of the Flow Field of a Submerged Hydraulic Jump over Triangular Macroroughnesses
2021
The submerged hydraulic jump is a sudden change from the supercritical to subcritical flow, specified by strong turbulence, air entrainment and energy loss. Despite recent studies, hydraulic jump characteristics in smooth and rough beds, the turbulence, the mean velocity and the flow patterns in the cavity region of a submerged hydraulic jump in the rough beds, especially in the case of triangular macroroughnesses, are not completely understood. The objective of this paper was to numerically investigate via the FLOW-3D model the effects of triangular macroroughnesses on the characteristics of submerged jump, including the longitudinal profile of streamlines, flow patterns in the cavity regi…
Fractional calculus approach for the representation of power spectral densities and correlation functions in wind engineering
2010
The paper deals with the digital simulation of wind velocity samples by Fractional Spectral Moment function. It is shown that such a function represents a third useful way to characterize a stationary Gaussian stochastic process, alongside the power spectral density and the correlation function. The method is applied to wind velocity fields whose power spectra is given by the Kaimal’s, the Davenport’s and the Solari’s representation. It is shown that by constructing a digital filter whose coefficients are the fractional spectral moments, it is possible to simulate samples of the target process as superposition of Riesz fractional derivatives of Gaussian white noise processes.