Investigation of Average Shear Stress in Natural Stream

Average shear stress is an important parameter for prediction of sediment transport,bank protection and other river engineering problems in natural streams. For this purposevelocity measurements were taken on Kızılırmak River sub branch, named Sarimsakli streamand Barsama station in center of Turkey. Acoustic Doppler Velocimeter (ADV) was used forthis purpose at six different periods and flow conditions. Nikuradse's equivalent sandroughnesses (ks) for each vertical along the wetted perimeter were determined using measuredvelocity distributions. Shear velocity (u*) and shear stress (meas) were determined thenaverage values were calculated for each flow condition. The commonly used one-dimensionalmean boundary shear stress equation at cross-section was re-arranged according to entropyparameter M and it reflects the real flow condition in natural stream

Modeliranje razdiobe napetosti smicanja u prirodnim malim vodotocima metodama mekog računanja

In this study, artificial neural networks (ANNs) and adaptive neuro-fuzzy inference system (ANFIS) were used to estimate shear stress distribution in streams. The methods were applied to the 145 field data gauged from four different sites on the Sarimsakli and Sosun streams in Turkey. The accuracy of the applied models was compared with the multiple-linear regression (MLR). The results showed that the ANNs and ANFIS models performed better than the MLR model in modeling shear stress distribution. The root mean square errors (RMSE) and mean absolute errors (MAE) of the MLR model were reduced by 47% and 50% using ANFIS model in estimating shear stress distribution in the test period, respectively. It is found that the best ANFIS model with RMSE of 3.85, MAE of 2.85 and determination coefficient (R2) of 0.921 in test period is superior to the MLR model with RMSE of 7.30, MAE of 5.75 and R2 of 0.794 in estimation of shear stress distribution, respectively.U ovoj studiji su za procjenu razdiobe napetosti smicanja u vodotocima korištene umjetne neuronske mreže (ANNs) i prilagodljivi neizraziti sustav zaključivanja (ANFIS). Metode su primijenjene na 145 nizova podataka prikupljenih na četiri različite postaje na vodotocima Sarimsakli i Sosun u Turskoj. Točnost primijenjenih modela uspoređena je s točnošću modela višestruke linearne regresije (MLR). Rezultati su pokazali da su oba modela (ANNs i ANFIS) bili bolji u modeliranju raspodjele napetosti smicanja od MLR modela. Pri korištenju ANFIS modela za procjenu raspodjele napetosti smicanja u testnom razdoblju srednje kvadratne pogreške (RMSE) i srednje apsolutne pogreške (MAE) su u odnosu na MLR model bile smanjene za 47%, odnosno 50%. Utvrđeno je da se za testno razdoblje najbolji ANFIS model, s RMSE = 3.85, MAE = 2.85 i koeficijentom određenosti R2 = 0.921, pokazao superiornim u procjeni napetosti smicanja u odnosu na MLR model, s RMSE = 7.30, MAE = 5.75 i R2 = 0.794

The role of oxidative stress and effect of alpha-lipoic acid in reexpansion pulmonary edema – an experimental study

Introduction: We investigated the role of oxidative stress in the pathogenesis of reexpansion pulmonary edema (RPE) and effect of alpha-lipoic acid (ALA) in the prevention of RPE

Protective efficiacy of taurine against pulmonary edema progression: experimental study

Re-expansion pulmonary edema (RPE) is an acute, rare and potentially lethal complication [1,2]. Its beginning is sudden and dramatic. The mechanism is not yet fully understood [1]. Some authors suggest that it may occur after rapid re-inflation of a collapsed lung [1]. It was reported by other authors that it may relate to surfactant depletion or may result from hypoxic capillary damage, leading to increased capillary permeability [1,3]. In RPE, unilateral lung injury is initiated by cytotoxic oxygen metabolites and temporally associated with an influx of polymorphonuclear neutrophils [1]. These toxic oxygen products are the results of re-oxygenation of a collapsed lung. Treatment of re-expansion pulmonary edema is basically preventive [4]

Protective efficiacy of taurine against pulmonary edema progression: experimental study

Re-expansion pulmonary edema (RPE) is an acute, rare and potentially lethal complication [1,2]. Its beginning is sudden and dramatic. The mechanism is not yet fully understood [1]. Some authors suggest that it may occur after rapid re-inflation of a collapsed lung [1]. It was reported by other authors that it may relate to surfactant depletion or may result from hypoxic capillary damage, leading to increased capillary permeability [1,3]. In RPE, unilateral lung injury is initiated by cytotoxic oxygen metabolites and temporally associated with an influx of polymorphonuclear neutrophils [1]. These toxic oxygen products are the results of re-oxygenation of a collapsed lung. Treatment of re-expansion pulmonary edema is basically preventive [4]

Proanthocyanidin to prevent formation of the reexpansion pulmonary edema

<p>Abstract</p> <p>Background</p> <p>We aimed to investigate the preventive effect of Proanthocyanidine (PC) in the prevention of RPE formation.</p> <p>Methods</p> <p>Subjects were divided into four groups each containing 10 rats. In the Control Group (CG): RPE wasn't performed. Then subjects were followed up for three days and they were sacrificed after the follow up period. Samplings were made from tissues for measurement of biochemical and histopathologic parameters. In the Second Group (PCG): The same protocol as CG was applied, except the administration of PC to the subjects. In the third RPE Group (RPEG): Again the same protocol as CG was applied, but as a difference, RPE was performed. In the Treatment Group (TG): The same protocol as RPEG was applied except the administration of PC to the subjects.</p> <p>Results</p> <p>In RPEG group, the most important histopathological finding was severe pulmonary edema with alveolar damage and acute inflammatory cells. These findings were less in the TG group. RPE caused increased MDA levels, and decreased GPx, SOD and CAT activity significantly in lung tissue.</p> <p>Conclusion</p> <p>PC decreased MDA levels. Oxidative stress plays an important role in pathophysiology of RPE and PC treatment was shown to be useful to prevent formation of RPE.</p

Modeling velocity distributions in small streams using different neuro-fuzzy and neural computing techniques

Accurate estimation of velocity distribution in open channels or streams (especially in turbulent flow conditions) is very important and its measurement is very difficult because of spatio-temporal variation in velocity vectors. In the present study, velocity distribution in streams was estimated by two different artificial neural networks (ANN), ANN with conjugate gradient (ANN-CG) and ANN with Levenberg-Marquardt (ANN-LM), and two different adaptive neuro-fuzzy inference systems (ANFIS), ANFIS with grid partition (ANFIS-GP) and ANFIS with subtractive clustering (ANFIS-SC). The performance of the proposed models was compared with the multiple-linear regression (MLR) model. The comparison results revealed that the ANN-CG, ANN-LM, ANFIS-GP, and ANFIS-SC models performed better than the MLR model in estimating velocity distribution. Among the soft computing methods, the ANFIS-GP was observed to be better than the ANN-CG, ANN-LM, and ANFIS-SC models. The root mean square errors (RMSE) and mean absolute errors (MAE) of the MLR model were reduced by 69% and 72%, respectively, using the ANFIS-GP model to estimate velocity distribution in the test period

Smart Neighbor Scanning with Directional Antennas in 60 GHz Indoor Networks

The 60 GHz technology has an immense potential to provide wireless communication at multi-gigabit rates. At 60 GHz frequency band, severe attenuation of the signals can significantly degrade communication performance. To cope with the attenuation problem, directional antennas with high directive gains can be utilized. When network nodes use directional antennas, the neighbor discovery process becomes more complicated and time consuming. To reduce the neighbor discovery time, we propose a smart neighbor scanning algorithm in this paper. It is observed that the proposed strategy discovers 70% of the links 81% faster and 90% of the links 15% faster than random scanning strategy

Sector Scanning Attempts for Non-Isolation in Directional 60 GHz Networks

Large path losses of millimeter waves restrain the acceptance of 60 GHz technology in future networks. Directional antennas can be exploited in 60 GHz networks to mitigate the detrimental impact of fading. Employing fully directional antennas complicates the neighbor discovery process where each sector must be probed individually to discover neighbors located in that sector. In random scanning strategy, nodes select to-be-scanned sector randomly. In this letter, we analyze the minimum number of random sector scanning attempts during neighbor discovery process to have a non-isolated network. We present an analytical model to study the isolation probability defined as probability of having at least one isolated node in the network. Based on the isolation probability, we derive the minimum number of sector scanning attempts in a 60 GHz ad hoc network with arbitrary number of nodes. Although 60 GHz directional network is studied, this analysis is applicable to any directional wireless network

Investigation of flow properties in natural streams using the entropy concept

This paper examines the discharge and velocity distributions in natural open channel flows using the entropy theory. Flow measurements were carried out at four different cross-sections in central Turkey. The mean and maximum velocities at these stations exhibited a linear distribution and the entropy parameter was calculated to be M=1.31. Using this value, discharges for all flow conditions were calculated as a function of the measured maximum velocities (umax). It was observed that the umax/H and zmax/H ratios remained relatively constant when 0.2=y/T=0.8, especially for the wider channels. Using these constant values for each station, umax and zmax could be determined solely as a function of the water depth H. Although the calculated velocities were higher than those measured at some verticals, the entropy-based approach presents an attractive alternative to the traditional flow-measurement techniques for the determination of flow properties because of its simplicity and quick application