Search results for "velocity"
showing 10 items of 881 documents
Seasonal and diel patterns of mayfly (Ephemeroptera) drift in Korge stream, Latvia
2009
A complex set of biotic and abiotic factors affects a drift. Mayfly drift has been extensively studied worldwide, but the manner in which the environmental factors interact is not completely clear. The aim of the present study was to characterise mayfly seasonal and diel drift patterns in relation to abiotic factors in a medium-sized lowland stream in Latvia. Drift samples were collected at three-hour intervals in a riffle section in May, August and September 2007. Distinct seasonal and diel patterns of the mayfly drift were observed in the Korge stream. These were not directly infuenced by primary hydraulic factors e.g. current velocity and discharge, but depended on the active growth peri…
On the variations of acoustic absorption peak with particle velocity in micro-perforated panels at high level of excitation.
2010
The acoustic behavior of micro-perforated panels (MPP) is studied theoretically and experimentally at high level of pressure excitation. A model based on Forcheimer's regime of flow velocity in the perforations is proposed. This model is valid at relatively high Reynolds numbers and low Mach numbers. The experimental method consists in measuring the acoustical pressure at three different positions in an impedance tube, the two measurement positions usually considered in an impedance tube and one measurement in the vicinity of the rear surface of the MPP. The impedance tube is equipped with a pressure driver instead of the usual loudspeaker and capable of delivering a high sound pressure lev…
Acoustic doppler velocity profiler for velocity and turbulence measurements in a large amplitude meandering flume
2008
Flow over deformed bed of a meandering laboratory channel is experimentally investigated. The velocity components have been obtained using an Ultrasonic Doppler Profiler (DOP2000) that measures the instantaneous flow velocity profile along the probe direction. In this work, some results obtained in peculiar sections along the channel are reported. A refined mesh of the measurement points has been used for each considered cross-section. The analysis of the collected data essentially confirms that when the aspect ratio is small the secondary circulation assumes great importance and, in accordance with previous findings, a second counter-rotating secondary circulation cell appears near the fre…
3d-Mapping Of Multiple Mirror Sources In A Room: A Two Channel Intensimetric Method.
2005
A large lecture theatre was analyzed by using a 3D intensimetric measurement method. Sweep signal providing the excitation of the environment was sent to an isotropic source. Sound intensity probe was positioned in some test points of the room and sound intensity vector decay was measured for each of them. The sound board of a PC was utilized to acquire couples of impulse responses for each sound intensity vector component. These signals were combined by using an algorithm implemented in Lab VIEW. Mirror sources were localized and visualized in a three-dimensional map for each measurement point. Resuls are presented as orthogonal projections and 3D-diagrams.
Active deformation in a sector of the Sicilian-Maghrebian Chain: new insights from integrated GNSS, structural high-resolution seismic reflection and…
2016
We document active deformation in a sector of the Sicilian Maghrebian Chain exposed in north Sicily and in its offshore prolongation on the basis of the integrated analysis of 1) time series of data collected by GNSS acquisition representing the change in the positions (X and Y) of permanent stations located in Palermo, Partinico, Prizzi, and Termini compared to the IGS station of Noto, 2) high-resolution (Sparker) single-channel reflection seismic data, 3) structural data, and 4) seismological data. The average values for the velocity vectors obtained for the Palermo, Partinico, Prizzi, and Termini Imerese stations are 4.55, 2.97, 2.96, and 2.15 mm/yr, respectively. The direction of the ve…
Effects of gait speed on stability of walking revealed by simulated response to tripping perturbation
2013
The objective of this work was to study stability of walking over a range of gait speeds by means of muscle-driven simulations. Fast walking has previously been related to high likelihood of falling due to tripping. Various measures of stability have shown different relationships between walking speed and stability. These measures may not be associated with tripping, so it is unclear whether the increase in likelihood of falling is explicable by an increase in instability. Here, stability with respect to a constant tripping perturbation was quantified as the immediate passive response of torso to the perturbation. Subject-specific muscle-driven simulations of eight young healthy subjects wa…
Exploring the reciprocal modulation of time and space in dancers and non-dancers.
2014
We explored whether time and space representations modulate each other in subjects that are trained to integrate time and space dimensions, i.e., professional dancers. A group of dancers, and one of non-dancers, underwent two different tasks employing identical stimuli. A first static central line could last one of three possible durations and could have one of three possible lengths. A second growing line appeared from the left or right of the screen and grew up toward the opposite direction at constant velocity. In the Spatial task, subjects encoded the length of the static line and stopped the growing line when it had reached half the length of the static one, regardless of time travel. …
Clinical-anamnestic and instrumental data in outpatients suffering from venous disease
1995
The authors studied 200 consecutive outpatients with symptoms due to venous disease of the lower limbs. All the patients underwent anamnestic, clinical and instrumental evaluation (c.w. Doppler velocimetry and strain-gauge plethysmography). The results of this study showed that some anamnestic and clinical data are significantly related to venous disease detected by instrumental techniques. The superficial and deep vein hypertension were, instead, correlated to oral contraceptive use.
Impact of insulin on microvascular blood flow and endothelial cell function in the postprandial state in patients with Type 1 diabetes.
2005
The aim of the present study was to investigate postprandial microvascular blood flow following a standardized test meal in nondiabetic subjects and in patients with Type 1 diabetes after regular insulin or insulin lispro. In this open-label, randomised cross-over study, 20 nondiabetic participants and 20 patients with Type 1 diabetes were enrolled. To valuate the postprandial time course of skin microvascular blood flow, laser Doppler flux (LDF) readings were obtained at baseline and every 30 min following a standardized test meal. Furthermore, the microvascular response to acetylcholine (Ach) was measured, and blood was collected for the measurement of serum insulin and blood glucose leve…
Microvascular skin blood flow following the ingestion of 75 g glucose in healthy individuals.
2009
It is expected that microvascular blood flow might be affected by blood glucose, blood insulin and C-peptide levels. In our investigation skin microvascular blood flow (LDF) was measured using laser doppler fluxometry at skin temperatures of 37 degrees C and 44 degrees C during a 75 g oral glucose load (OGT) or water in ten healthy volunteers (6 male, 4 female, age: 28.1+/-4.0) who had fasted overnight. The transcutaneous oxygen tension (tcPO2) was measured using a transcutaneous oxygen electrode at a temperature of 44 degrees C. The microvascular response to acetylcholine was investigated before the start of the ingestion period and after 30 minutes. In addition, the capillary blood cell v…