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A Critical Study Of Total Bed Material Load Predictors

A Critical Study Of Total Bed Material Load Predictors

Applying the selected total bed material load predictors to the selected data, the values of total bed material load were computed and were compared with the observed values of total bed material load in order to assess the accuracy of selected ten total bed material load predictors. Thereafter, analysis of the results was made in three ways: (1) In first approach, the accuracy of each predictor was assessed by comparing the measured and computed values of total bed material load between a discrepancy ratio range of 0.5 to 2.0.The discrepancy ratio can be defined as the ratio of computed and measured values of total bed material load. Percentile scores of all the ten predictors considered in this study and authors' newly developed predictor in the discrepancy ratio range of 0.5 to 2.0 were computed [Table 2] to assess the accuracy of each predictor.

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Study on Characteristic of Bed Material and Bed Load Discharge in Sungai Jemberau, Tasik Chini

Study on Characteristic of Bed Material and Bed Load Discharge in Sungai Jemberau, Tasik Chini

In conclusion, the size and types of bed material were identified at Sungai Jemberau, Tasik Chini. The bed load discharge was evaluated using two different formulas which were Schoklitsch and Duboys equations. From the analysis of the results of each of the formula, Duboys can be used to predict bed load transport for Sungai Jemberau as it is suitable for uniform sediments with specific gravity that are varying from 1.25 to 4. The particle size range for the Duboys is between 0.01 – 4.0mm. This result also shows that Duboys gives a better and reliable prediction for bed load discharge and concentration at Sungai Jemberau. The bed load results predicted by Duboys equation shows that there were increasing value of bed load discharge happen in Sungai Jemberau after that area had facing a flooding situation. The size of bed material also increases from 2.75mm in 24 November 2016 to 4.2mm in 5 March 2017. After flood, Sungai Jemberau also becomes wider due to the erosion and riverbank failure at that area.

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Bedform migration in a mixed sand and cohesive clay intertidal environment and implications for bed material transport predictions

Bedform migration in a mixed sand and cohesive clay intertidal environment and implications for bed material transport predictions

Despite the above limitations, it has been shown that the bed mate- rial transport rates for the biologically active mixed sand-mud under fi eld conditions in the Dee Estuary were signi fi cantly reduced for bed cohesive clay fractions below 2.8 vol% and for EPS fractions below 0.05 wt%, due to physical and biological cohesion. This is below the 3 – 5% clay content found for the transition to a cohesion-dominated erod- ing bed (van Ledden et al., 2004), but above the EPS fraction (0.026%) found to stabilize wave ripples by Friend et al. (2008). These results have important implications for sediment transport modelling. Since the bed material transport rate depends on the strength of biological and physical cohesion, clean sand formulae should only be used if bed cohesive clay and EPS contents are close to zero. In addition, bed mate- rial transport reduced below the limit of detection, of the 3D-ARP, for bed cohesive clay content above about 2.8 vol%, in the present study. Eq. (11) can be used to estimate bed material transport rates for differ- ent bed cohesive clay contents below 2.8 vol%. The implications of this work for sediment transport modelling also extend to larger-scale geo- morphology and coastal engineering. For example, slowing down bedform migration at the unexpectedly low bed mud contents found in this study may add to the stability of nearshore environments and therefore in fl uence shoreline change, longshore sediment transport, in- tertidal channel switching, and other nearshore processes.

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Principal Longevity, Leadership Behaviors, and Student Academic Achievement

Principal Longevity, Leadership Behaviors, and Student Academic Achievement

Downstream fining of bed material is described well by an exponential model with R 2 = 0.74 (Figure 2.4). This model excludes the uppermost sample because it occurs before substantial coarse sediment inputs. Folk and Ward (1957) graphical arithmetic statistics (Bunte and Abt, 2001) were calculated and classified for bed material samples. The reach at site 8 is an infilled morphology characterized by a sand bed that was not sampled with a surface grid, thus it does not have statistics. Patches of gravel at sites 8a and 8b, approximately 150 and 250 meters upstream, were sampled. These samples reveal a local fining of surface bed material at this forced reach (Table 3.1, Figure 3.8). Nine sites were poorly sorted, two were moderately well sorted and one was moderate. Nine sites are fine skewed or very fine skewed, one site is very coarse skewed and only two sites is considered nearly symmetrical. Sites 1-7 are considered leptokurtic (i.e. more peaked than a normal distribution). Sites 8a, 9 and 10 are platykurtic (less peaked) and site 8b is mesokurtic (normal). Given these non-normal descriptive statistics, further statistical analysis of bed material grain sizes would require methods robust to non-normal distributions.

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Scouring of Pier under Clear-water Condition

Scouring of Pier under Clear-water Condition

The most common cause of bridge failures is from floods scouring bed material from around bridge foundations. Scour is the engineering term for the erosion caused by water of the soil surrounding a bridge foundation (piers and abutments). Scour is the removal of sediment around or near structures located in flowing water. It means the lowering of the riverbed level by water erosions such that there is a tendency to expose the foundations of a bridge. Scour occurs during the passage of high dischar ge, when the velocity of the stream exceeds the limiting velocity that can be withstood by the particles of the bed materials. It is an important hydraulic phenomenon from the point of view of construction of bridges. Scour depth is one of the most important factors for deciding the foundation levels of the bridge. Scour is the result of the erosive action of flowing water, excavating and carrying away material from the bed and banks of streams and from around the piers and abutments of bridges. Different materials scour at different rates. Loose granular soils are rapidly eroded by flowing water, while cohesive or cemented soils are more scour resistant. However, ultimate scour in cohesive or cemented soils can be as deep as scour in sand bed streams. Scour will reach its maximum depth in sand and gravel bed materials in hours; cohesive bed materials in days; glacial tills, sandstones and shale in months, lime stones in years. Many river bridges fail or are extremely damaged due to excessive local scouring during high floods. Excessive local scour occurs around bridge piers and abutments as a result of removal of bed material due to severe flow patterns surrounding the foundations (Yanmaz and Selamoglu, 2010). Since excessive scouring leads to considerable riverbed degradation, bridges should be designed to resist such unfavorable effects. In addition to proper design, bridges should be monitored periodically and existing scour criticality of them should be evaluated. Scour criticality of a bridge is assessed according to the level of scour with respect to the footing elevation of that bridge.

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Experimental Study of Effect of Bed Resistance on Velocity Profiles in Rectangular Channel

Experimental Study of Effect of Bed Resistance on Velocity Profiles in Rectangular Channel

not uniform due to the presence of free surface, the bed material of the channel, the discharge, the slope of the channel etc. A number of experiments have been done for three different bed materials with different discharges. The bed materials are the original bed material i.e. smooth iron bed, grass carpet and PVC. Velocity at different sections and different depths are taken with the help of pitot tube. From the experiment, it is found that the maximum velocity appears to occur at the free surface of the channel, and the average velocity for all the cases is coming almost 0.75 to 0.95 of the surface velocity.

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Evaluation of Wind-Induced Resuspension on the Performance of a Mine Tailings Storage Facility

Evaluation of Wind-Induced Resuspension on the Performance of a Mine Tailings Storage Facility

63 fetch length for that grid cell. Input parameters include cell coordinates, wind data, pond geometry, median grain size of bed material, critical shear stress of bed material, erosion test results, and sulphate production rate constants. From the analysis, a specific value of water cover depth is obtained for each square grid cell. The method is based on the premise that erosion and resuspension of bed sediment occur when the total bed shear stress induced by waves and return currents exceeds the critical shear stress of the bed material. Thus the bed shear stress contribution from return currents is not ignored. The required water cover depth is calculated by comparing the total bed shear stress and critical shear stress of the bed tailings In addition, the method can be used to estimate the concentration of resuspended sediments and sulphate concentrations in the water cover if the water cover depth is below the minimum required value. The Samad and Yanful (2005) approach can also provide optimal water cover depths that allow regulatory acceptable suspended solids or tailings concentrations. In this paper, the method of Samad and Yanful (2005) is used to investigate tailings resuspension at the Shebandowan tailings storage facility and the results are compared to field measured values. The minimum required water cover depth is calculated and compared with existing water cover depth to predict resuspension. The major limitation of the Samad and Yanful (2005) was found to be that it does not take into account sediment transportation and redeposition from one station to other station.

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Experimental and Numerical Approaches to Overtopping Levee Breach Effects in a River and Floodplain

Experimental and Numerical Approaches to Overtopping Levee Breach Effects in a River and Floodplain

The positions of the run are in a top, middle and below for the Run 1, Run 2 and Run 3, individually are depicts in Figure 5. The bed topographic pattern in river and levee section; and the floodplain are denoted by (a) and (b), respectively. After the beginning of overflow, an initial flow passes over the levee crest along with erosion on it near the floodplain, and afterwards, inundation water is spread over the floodplain with vertical erosion from the breach point. Then, the horizontal widening process starts by the collapse of the levee (Exp.R1). The more vertical erosion is observed on the levee section. Due to erosion in the levee as well as near the levee heel, a thalweg is formed along the flow direction from the river to the floodplain. Deposition pattern in the floodplain is smooth, because of coarse bed material, and it indicated that the flow is passes to the right-side direction in the floodplain (Exp.R1, Sim.R1).

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The Suitability of Typhoon Disaster  Reconstruction Work Planning—A Case  of Meizuolyu Stream in Taitung County

The Suitability of Typhoon Disaster Reconstruction Work Planning—A Case of Meizuolyu Stream in Taitung County

According to the longitudinal and lateral profile data obtained by the field survey and the surface particle size analysis of river bed material survey, HEC-RAS was used for hydrology mathematical calculation to review the allocation of all constructions. Based on the preliminary examination, the regulatory works constructed on the Meizuolyu stream could reach the preset goals preliminarily; the engineering of associated works in design could also take the influence of the engineering constructions on the ecology into consideration. However, some areas must be strengthened at present to avoid the recurrence of disasters. Suggestions on the improvement of the constructions in various sectors are giving below. The planning and design principles for future disaster pre- venting regulation works are also provided for reference.

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Local heat transfer coefficient around a
horizontal heating element in
gas-solid fluidized bed

Local heat transfer coefficient around a horizontal heating element in gas-solid fluidized bed

The key objectives of this work are to study the bubbling Gas-Solid fluidized bed in order to find the suitability of sand as a bed material in Gas-Solid fluidized bed and to find the local heat transfer coefficient around a horizontal heating element immersed horizontally in bubbling fluidized bed. An experiment has been carried out in a laboratory fluidized bed heat exchanger with atmospheric air as a fluidizing medium and silica sand of diameter 200μm, 350 μm and 500 μm diameter.

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Analysis of Flow Resistance for Different Bed Materials with Varying Discharge Experimentally in Open Channels

Analysis of Flow Resistance for Different Bed Materials with Varying Discharge Experimentally in Open Channels

In Ireland Limerinos Robert Manning in 1891 first introduced the Manning’s formula in his paper. In 1898, a paper was prepared in cooperation with the California Department of water resources for Geological Survey Water Supply for determination of Manning’s “n” for different bed roughness in open channel flow. Manning Coefficient was found by J. T in 1970 from measured bed roughness in natural channels. In 2002 Yen B. C. found that the flow in open channel is effected by the wall roughness of the channel, the cross sectional area as well as the roughness and viscosity of the bed material. In 2010, Francisco J.M. Simões did a lot of laboratory experiments and found that the total friction losses can be accurately predicted in natural channel with plane bed rather the sediments are transported in the channel. He introduced the resistance due to the flow viscous effects when the flow is turbulent and fully rough. Omid M. H. (2010) et al did a laboratory experiment and deduced some formula for friction factor in an alluvial channel. It is also shown in this paper that presence of bed load can reduce the friction factor as compared to the clear water flow. Ji-Sung KIM et.al in 2010, with the help of field measurements estimated Manning’s “n” for a gravel-bed river and also evaluated the various methods used for estimation of roughness coefficient. Ali1 Md Z. and Saib N. A. (2011) did a no. of laboratory experiments with different discharges and different bed materials to determine the affects of bed roughness in open channel flow. E. Retsinis et.al (2013) did a lot of laboratory experiment and concluded that the Manning’s “n” is not constant throughout the channel especially when the channel is having combined bed material.

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A Shear Reynolds Number Based Investigation Method of the Bed Load Transport in Large Rivers with Complex Morphodynamics

A Shear Reynolds Number Based Investigation Method of the Bed Load Transport in Large Rivers with Complex Morphodynamics

mm. The estimated local bed shear stress values increase with higher grain sizes, however, quite significant scattering of the points can be seen (Fig. 5). The green triangles refer to the sandy bed material samples, which were collected from the near-bank zones. Here, the bed material consists predominantly of silt and sand, gravel transport can be expected only during flood waves. The blue points originate from the side bars (e.g. bed material illustrated in Fig. 2). As it was introduced in chapter 2 and based on Fig. 2, the dominant grain size in the bed load is variable (both the sand and gravel can also dominate) and strongly flow dependent. Finally, the samples from the main channel are depicted by the red symbols. Based on the bed material analysis, only gravel transport can occur at this region of the channel, because the sand can be vanishingly found. But as the measurements indicate very stable bed surface, pure gravel transport can be expected.

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Thermal Modelling of a Solar Air Heater for All Over the Year of Yazd Province

Thermal Modelling of a Solar Air Heater for All Over the Year of Yazd Province

48 packed double-pass solar air heaters with external recycle. The wire mesh packed solar air heater leads turbulence intensity and broaden the heat transfer area, so the heat transfer efficiency in enhanced. A comprehensive revisal of reported studies imply that the thermal performance of double pass solar air heaters with packed bed material in the upper channel increases as compared to solar air heater with packed bed material in lower channel and without packed bed [6]. Anil SinghYadav et al [12] discussed a detailed review of the experimental investigations in order to improve the heat transfer by the use of artificial roughness of various sizes, shapes and orientations in design of solar air heater. The use of artificial roughness to increase heat transfer on a surface in the duct is an effective technique.

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Catalytic fast pyrolysis of corn stover in a fluidized bed heated by hot flue gas: Physicochemical properties of bio-oil and its application

Catalytic fast pyrolysis of corn stover in a fluidized bed heated by hot flue gas: Physicochemical properties of bio-oil and its application

The effects of bed materials on bio-oil yield and heavy oil percentage in the whole bio-oil are shown in the Figure 4. The highest bio-oil yield of 43.3wt.% is obtained at 500°C when dolomite is used as bed material. The heavy oil percentage in the whole bio-oil first increases and then decreases with the rise of temperature. For a given temperature higher than 450°C, calcined dolomite gives the lowest heavy oil percentage compared with quartz sand and aluminous soil. It is well known that the formation of tar has adverse effects on bio-oil production and pyrolysis system. It usually adheres to the internal walls of the pipes and reactors and is difficult to be cleaned. Calcined dolomite is favorable for bio-oil production below 500°C. A great quantity of CaO-MgO complexes, which are formed via the calcination of dolomite, have a positive effect on the catalytic cracking of biomass tars, leading to the increase of bio-oil yield.

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Bed Agglomeration Behavior in a Bubbling Fluidized-Bed Combustor

Bed Agglomeration Behavior in a Bubbling Fluidized-Bed Combustor

Figure 3-2 displays the temperature-differential pressure (T-ΔP) curves for BFB of the silica sand particles with various amounts of KCl (0, 0.2, 0.4, and 0.6wt% w.r.t. the weight of sand particles). As shown in the Figure, each test may be generally divided into three zones: heating zone (0-75 min), soaking zone (75-175 min), and cooling zone (>175 min). As given in Figure 3-2 (a), in the blank tests (with pure silica sand), the ΔP remained constant in all zones, suggesting smooth fluidization of the bed material. On the other hand, it can be observed from the figure that the values of ΔP of the bed material containing KCl in the heating zone are higher than those in the blank tests likely due to an increase in the drag force caused by the friction force between the viscous particle bed and the BFB column wall during the heating period. In the soaking zone, however, a slight decrease in ΔP was observed in the presence of a small amount of KCl (0.2wt%), suggesting channeling or slight agglomeration of bed material due to the melting of the KCl at a temperature close to 800C. Whereas, a large drop in ΔP was recorded in the soaking zone of the bed material containing 0.4 and 0.6wt% of KCl, suggesting severe channeling or bed material agglomeration. Compared with other tests, the ΔP signals in the test with 0.4wt% KCl exhibited more fluctuation, which might be due to the formation of unstable and weak channels/agglomerates in the bed. With 0.6wt% KCl, the agglomerates formed could be stable and strong, resulting a large decrease in ΔP with less fluctuation. These results are in a good agreement with those reported by Montes et al. using KOH as the modeling compound operating at a lower temperature (~ 400C) [15].

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Thermo-mechanical Analysis of RVLH for APR1400 during a Severe Accident

Thermo-mechanical Analysis of RVLH for APR1400 during a Severe Accident

Coupled thermo-mechanical analysis was performed to investigate possibility and timescale of the failure. 2D axisymmetric finite element model was adopted based on APR1400 design data with relevant material properties such as heat convection coefficient of water, elastic-plastic strain data, and experimental data for creep. The thermal analysis model was iteratively refined to make thermal gradient contour line and element mesh boundary coincide so that bands of element mesh can be assigned to proper material properties for thermal stress analysis according to the result of thermal transient analysis. The objective of this paper is to develop the analysis method of the RVLH for APR1400 with thermo-mechanical analysis using FEM (Finite Elements Method) tools in case of core-melted severe accident condition, and investigate the creep behaviour in such case. The timescale of the creep failure can provide delay margin of emergency measures to mitigate the severe accident.

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Preliminary Study of Fluidization Curves in Polydisperse Beds Formed by a Binary Mixture of Raphanus sativus L  Husk and Sand

Preliminary Study of Fluidization Curves in Polydisperse Beds Formed by a Binary Mixture of Raphanus sativus L Husk and Sand

In the process of fluidization containing Pinus and Eucalyptus, Genehr [5] observed the formation of preferential paths, which caused an abrupt drop in the fluid load loss already in the mixture containing 50% biomass and 50% sand. This state makes the fluidization process impossible, so that a very large velocity of the upward fluid is required for the preferred paths to be undone. In this state of fluidization, however, the transport of part of the biomass out of the bed oc- curs, causing the system to lose efficiency. During the fluidization of the Rapha- nus sativus L. the mixture containing 70% of biomass presents a low formation of preferred paths, which contributes to the fluidization process occurring with a higher proportion of biomass, provoking an increase in the fluidization efficien- cy.

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Bovine Bone Charcoal as Support Material for Immobilization of Bacillus firmus Strain 37 and Production of Cyclomaltodextrin Glucanotransferase by Batch Fermentation in a Fluidized Bed

Bovine Bone Charcoal as Support Material for Immobilization of Bacillus firmus Strain 37 and Production of Cyclomaltodextrin Glucanotransferase by Batch Fermentation in a Fluidized Bed

The process described in the present work uses air supplementation in a flui- dized bed reactor containing Bacillus firmus strain 37 immobilized on active bovine bone charcoal, to produce by batch fermentation the enzyme CGTase (cyclomaltodextrin-glucanotransferase). Three different aeration rates were evaluated. The maximum CGTase activity was achieved after 120 hours of fermentation with aeration rate of 2 vvm and was equal to 2.48 U/mL. When 0.5 and 1 vvm were used the enzymatic activities achieved 1.1 and 0.57 U/mL, respectively. Bovine bone charcoal was characterized in terms of surface area, pore size and volume. To the best of our knowledge, the immobilization of microorganism cells in bovine bone charcoal for CGTase production has not been reported in the literature. Our results showed that fluidized bed reactor allows retaining high concentration of biomass, improving biomass-substrate contact and operation at low residence times, which resulted in improved en- zyme production. Therefore, the process as proposed has great potential for industrial development.

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Increasing of the heat and mass transfer 
		processes efficiency with the application of non uniform fluidization

Increasing of the heat and mass transfer processes efficiency with the application of non uniform fluidization

The calculated data show the convergence with the experimental data. The correlation coefficients are R=0.943 and =0.956 that confirms the adequacy of the model of the dynamics of the temperature field change during granulation from heterogeneous liquid systems in the fluidized bed with the use of conical dispersant and allows to determine temperature for implementation of stable kinetics of the process.

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A FACILE SYNTHESIS OF TRIAZOLOQUINAZOLINONE DERIVATIVES AS POTENTIAL Α GLUCOSIDASE INHIBITORS

A FACILE SYNTHESIS OF TRIAZOLOQUINAZOLINONE DERIVATIVES AS POTENTIAL Α GLUCOSIDASE INHIBITORS

atmosphere. The reaction mixture was allowed to stir at 100 °C for 12 h. The reaction progress was monitored by TLC. After completion of starting material. The reaction mixture was dissolved in ethyl acetate (50 mL) and filtered through celite bed, filtrate was concentrated under reduced pressure and crude compound was purified by column chromatography using (100-200 mesh silica gel) and desired product was eluted with 15% ethyl acetate in hexane to get pure compound tert-butyl (2-methyl-4-oxo-3-(pyridin-3- ylmethyl)-3,4-dihydroquinazolin-6-yl)carbamate(2c) as a white solid. Yield (2.5 g, 90.1%); R f (50% EtOAc in n-hexane) = 0.6; 1 H NMR (300 MHz, DMSO-d 6 ) δ 9.74 (s, 1H), 8.54 (d, J

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