Search results for "801"
showing 10 items of 1684 documents
Extension of the Applicability of Jäntti's Method to the Fast Calculation of Desorption Data
2000
The time for sorption measurements may be reduced substantially by measuring several values at short time intervals at the beginning of a kinetic curve and extrapolating them to the equilibrium value. The method used by Jäntti for simple adsorption processes has been extended to complicated processes described by a second-order differential equation. A simulated example is provided.
Do the mobile-rich get richer? Internet use, travelling and social differentiations in Finland
2014
This article investigates the daily travelling practices that are related to mobile-only, fixed-only and combined mobile/fixed use of the Internet, and the social differentiations that are related to these three ways of accessing the Internet. Survey data ( N = 612) collected from Finland in 2011 are analysed. The article shows that mobile-only Internet use is not associated with particularly diverse or frequent daily travelling practices, whereas combined mobile/fixed use is. Mobile-only Internet users are, in fact, in a relatively disadvantaged position – compared with other users, they are more typically unemployed and their household income is lower. The mobility of Internet access as …
Mobile Devices as Tools for Media and Communication Research: A Scoping Review on Collecting Self-report Data in Repeated Measurement Designs
2020
Mobile devices are deeply embedded in people’s everyday lives. On the one hand, this opens up a new field for media and communication research. On the other hand, the widespread diffusion allows fo...
Parenting in the digital era: Protective and risk parenting styles for traditional bullying and cyberbullying victimization
2019
Abstract This study analyzes the parenting styles that could act as risk or protective factors for bullying and cyberbullying victimization in Spain, considering the predisposition to aggression of the adolescents. The protective or risk effect of parenting styles for adolescents' related behavior such as antisocial behavior, school adjustment, and self-esteem was also analyzed. Study sample was 1109 adolescents aged between 12 and 17 years (49.96%, females, M = 13.88, SD = 1.38). A 4 × 2 × 2 × 2 MANOVA was applied for the outcome variables of bullying victimization (traditional bullying and cyberbullying), antisocial behavior, school adjustment, and self-esteem; with parenting style, predi…
Efficiency of a digital particle image velocimetry (DPIV) method for monitoring the surface velocity of hyper-concentrated flows
2018
Digital particle image velocimetry records high resolution images and allows the identification of the position of points in different time instants. This paper explores the efficiency of the digital image-technique for remote monitoring of surface velocity and discharge measurement in hyper-concentrated flow by the way of laboratory experiment. One of the challenges in the application of the image-technique is the evaluation of the error in estimating surface velocity. The error quantification is complex because it depends on many factors characterizing either the experimental conditions or/and the processing algorithm. In the present work, attention is devoted to the estimation error due …
Flow resistance law under equilibrium bed-load transport conditions
2018
Abstract The uniform flow resistance equation, in the form due to Manning or Darcy-Weisbach, is often applied to determine the stage-discharge relationship of a river cross-section. The application of this equation, namely the slope-area method, allows to indirectly measure by water level readings the corresponding river discharge. In this paper, a recently deduced flow resistance equation for open channel flow was tested during conditions of equilibrium bed-load transport. First the flow resistance equation was determined by dimensional analysis and applying the condition of incomplete self-similarity for the flow velocity profile. Then the analysis was developed by the following steps: (i…
Testing the USLE-M family of models at the Sparacia experimental site in south Italy
2017
The modified Universal Soil Loss Equation (USLE-M) was empirically deduced by a statistical analysis of the original data set of soil loss measurements used to derive the Universal Soil Loss Equation (USLE). The USLE-M, including the effect of runoffin the event rainfall-runofferosivity factor, is characterized by a better capacity to predict event soil loss. At first, in this paper, using the soil erosion representative variables of USLE-M and the reference condition adopted in the USLE, the dimensional analysis and the self-similarity theory are applied to theoretically deduce a multiplicative equation similar to the USLE-M. Then using the database of the Sparacia experimental site, the a…
Assessing flow resistance in gravel bed channels by dimensional analysis and self-similarity
2018
Abstract In this paper a new flow resistance equation for open channel flow, based on the integration of a power velocity profile, was tested for gravel bed channels. First this flow resistance equation, theoretically deduced by dimensional analysis and incomplete self-similarity condition, was reported. Then a relationship between the Γ function of the velocity profile, the channel slope and the Froude number was calibrated by the available laboratory measurements of flow velocity, water depth and bed slope carried out in 416 flume experimental runs with a gravel bed. Then the relationship for estimating Γ function and the theoretical resistance equation was tested by 83 independent flume …
Evaluating the Effects of Sediment Transport on Pipe Flow Resistance
2021
In this paper, the applicability of a theoretical flow resistance law to sediment-laden flow in pipes is tested. At first, the incomplete self-similarity (ISS) theory is applied to deduce the velocity profile and the corresponding flow resistance law. Then the available database of measurements carried out by clear water and sediment-laden flows with sediments having a quasi-uniform sediment size and three different values of the mean particle diameter Dm (0.88 mm, 0.41 mm and 0.30 mm) are used to calibrate the Γ parameter of the power-velocity profile. The fitting of the measured local velocity to the power distribution demonstrates that (i) for clear flow the exponent δ can be estimated b…
New Theoretical Solution of Stage-Discharge Relationship for Slit Weirs
2018
In this paper, the flow-process of a slit weir was analyzed on the basis of a theorem of dimensional analysis and incomplete selfsimilarity theory. The theoretically deduced stage-discharge formula then was calibrated using experimental data obtained for a ratio between the weir and the channel width, ranging from 0.05 to 0.25. The deduced stage-discharge relationship allowed measuring discharge values characterized by errors that, for 98% of the measured values, were less than or equal to 5%. The performance of the proposed theoreticalstage-discharge formula also was improved by introducing the Reynolds number (for 98.5% of the measured values the error was less than or equal to 5%, and th…