Search results for "Velocity"

Color Doppler ultrasonography of the eye and orbit

1993

Color Doppler imaging is the recent development in ultrasonography that allows simultaneous two-dimensional structural imaging in Doppler evaluation of blood flow. With this technique, it is possible for the first time to indirectly display the fine orbital vessels such as the ophthalmic artery and its branches, the central retinal artery, the posterior ciliary artery, and the lacrimal artery. Also, the display of venous structures such as the superior ophthalmic vein, the vortex vein, and the central retinal vein is possible. In addition to the qualitative display of those vessels, the hemodynamics in those vessels can be quantitatively assessed by looking at the Doppler spectrum and deter…

Physical modelling of Czochralski crystal growth in horizontal magnetic field

2017

Abstract This study addresses experimentally the heat transfer, the temperature azimuthal non-uniformity and the onset of oscillations in a low temperature physical model of a medium-sized Czochralski crystal growth process with a strong horizontal magnetic field (HMF). It is observed that under certain conditions the integral heat flux may decrease with increasing magnetic field strength at the same time as the flow velocity increases. The azimuthal non-uniformity of the temperature field in the melt near the crystal model rim is only little influenced by its rotation rate outside of a narrow range where the centrifugal force balances the buoyant one. The flow oscillation onset has been ob…

Reliability of Hemodynamic Parameters Measured by a Novel Photoplethysmography Device

2011

Three channel photoplethysmography (PPG) signal pulse wave studies of the leg’s conduit arteries during rest conditions were performed. The obtained data of each channel showed similar values, proving arterial PPG as a reliable and repeatable method to assess arterial waveform parameters. A validation experiment was carried out by acquiring signals from three identical IR PPG sensors, which were placed on different sites over the leg’s conduit arteries during rest conditions. Coefficients of variation (CV) were calculated at a 95% confidence interval by comparing results of each subject during multiple attempts. This data processing leads us to certain criteria of improvements in our method…

Über die Verzweigung des Polyvinylacetats. III. Bestimmung des Verzweigungsgrades und reaktionskinetischer Konstanten durch Messung der Mittelwerte d…

1964

Eine Serie von 11 Polyvinylacetaten wurde unter konstanten Reaktionsbedingungen bis zu verschiedenen Umsatzen polymerisiert. An diesen Praparaten wurden osmotische Messungen und Streulichtmessungen durchgefuhrt. Die Messungen liefern das Zahlen- und das Gewichtsmittel der Polymeren. Aus der Anderung der Mittelwerte mit steigendem Umsatz werden die Ubertragungskonstante Cp zum Polymeren und die Wachstumskonstante kN der endstandigen Doppelbindung berechnet. Die erhaltenen Zahlenwerte sind fur 60°C: Cp = 1,8.10−4, kN/kW = 0,80. Unter Benutzung dieser Zahlenwerte wurde die Zahl der Verzweigungspunkte pro Polymermolekul als Funktion des Umsatzes berechnet. A series of 11 polyvinylacetates was p…

Shapes and oscillations of raindrops with reduced surface tensions: Measurements at the Mainz vertical wind tunnel

2013

Abstract Important characteristics of raindrops pertinent to fields in atmospheric sciences such as weather radar or pollution scavenging are drop shape, oscillation frequency and amplitude, as well as the internal circulation. Atmospheric raindrops are never pure water drops but contain additional components like aerosol particles and dissolved species. Surface active substances, when present, reduce the surface tension of raindrops and, thus, increase the drop deformation which in turn affects breakup and coalescence, pollutant scavenging, and, finally, the formation of precipitation. Experiments were performed at the Mainz vertical wind tunnel with raindrops freely suspended at their ter…

ADCP velocity profiles analisys in the Castellammare gulf

2009

Velocity profiles have been collected in three points within the Castellammare gulf at around 1500 m far from the coastline. This area is characterized by the presence of an aquaculture farm that positioned 5 floating cages in this zone. The impact of this activity on the environment strictly depends on the currents and water exchange. The general aim of this research is the characterization of the circulation characteristics of this area. The analysis of the free surface oscillations shows the typical behaviour of tide forcing, with high minima and maxima during the night, due to the higher moon attraction during these hours compared with the morning hours. A prevalent current direction fr…

On the Second Order Rational Difference Equation $$x_{n+1}=\beta +\frac{1}{x_n x_{n-1}}$$ x n + 1 = β + 1 x n x n - 1

2016

The author investigates the local and global stability character, the periodic nature, and the boundedness of solutions of the second-order rational difference equation $$x_{n+1}=\beta +\frac{1}{x_{n}x_{n-1}}, \quad n=0,1,\ldots ,$$ with parameter \(\beta \) and with arbitrary initial conditions such that the denominator is always positive. The main goal of the paper is to confirm Conjecture 8.1 and to solve Open Problem 8.2 stated by A.M. Amleh, E. Camouzis and G. Ladas in On the Dynamics of a Rational Difference Equations I (International Journal of Difference Equations, Volume 3, Number 1, 2008, pp.1–35).

The Variation of the Fractional Maximal Function of a Radial Function

2017

Abstract In this article, we study the regularity of the non-centered fractional maximal operator $M_{\beta}$. As the main result, we prove that there exists $C(n,\beta)$ such that if $q=n/(n-\beta)$ and $f$ is radial function, then $\|DM_{\beta}f\|_{L^{q}({\mathbb{R}^n})}\leq C(n,\beta)\|Df\|_{L^{1}({\mathbb{R}^n})}$. The corresponding result was previously known only if $n=1$ or $\beta=0$. Our proofs are almost free from one-dimensional arguments. Therefore, we believe that the new approach may be very useful when trying to extend the result for all $f\in W^{1,1}({\mathbb{R}^n})$.

Exploring parallel capabilities of an innovative numerical method for recovering image velocity vectors field

2010

In this paper an efficient method devoted to estimate the velocity vectors field is investigated. The method is based on a quasi-interpolant operator and involves a large amount of computation. The operations characterizing the computational scheme are ideal for parallel processing because they are local, regular and repetitive. Therefore, the spatial parallelism of the process is studied to rapidly proceed in the computation on distributed multiprocessor systems. The process has shown to be synchronous, with good task balancing and requiring a small amount of data transfer.

2019

This paper describes a single body-mounted sensor that integrates accelerometers, gyroscopes, compasses, barometers, a GPS receiver, and a methodology to process the data for biomechanical studies. The sensor and its data processing system can accurately compute the speed, acceleration, angular velocity, and angular orientation at an output rate of 400 Hz and has the ability to collect large volumes of ecologically-valid data. The system also segments steps and computes metrics for each step. We analyzed the sensitivity of these metrics to changing the start time of the gait cycle. Along with traditional metrics, such as cadence, speed, step length, and vertical oscillation, this system est…