scholarly journals Improving bedload transport determination by grain-size fraction using the Swiss plate geophone recordings at the Erlenbach stream

2018 ◽  
Vol 40 ◽  
pp. 02009
Author(s):  
Dieter Rickenmann ◽  
Nicolas Steeb ◽  
Alexandre Badoux
Keyword(s):  
Grain Size ◽  
Size Fraction ◽  
Signal Amplitude ◽  
Original Method ◽  
Bedload Transport ◽  
Grain Sizes ◽  
Amplitude Histogram ◽  
Measured Characteristic ◽  
Improved Performance ◽  
Different Grain Size

Direct bedload samples were taken with a large metal basket at the steep Erlenbach stream in Switzerland. These measurements were compared with the signal of the Swiss impact plate geophone system to derive information about bedload transport. The so-called amplitude histogram (AH) method was developed in an earlier study to estimate the bedload flux for different grain-size classes at the Erlenbach. A new analysis of a larger set of measurements was made here to improve the performance of the AH method. The approach relies on an identification of the transported grain sizes through their dependency on the signal amplitude. As a new element we introduce here the impulse rate, which is found to affect the number of impulses recorded for each amplitude class. As compared to the original method, the new version of the AH method shows a slightly improved performance for total calculated bedload mass, and results in a clearly better agreement between calculated and measured characteristic grain sizes.

scholarly journals Characterization of mechanical properties of barium titanate ceramics with different grain sizes

2018 ◽  
Vol 36 (1) ◽  
pp. 151-156 ◽  
Author(s):  
Tomasz Trzepiecinski ◽  
Magdalena Gromada
Keyword(s):  
Grain Size ◽  
Compressive Strength ◽  
Barium Titanate ◽  
Testing Machine ◽  
Compression Tests ◽  
Grain Sizes ◽  
Average Grain Size ◽  
Uniaxial Testing ◽  
Different Grain Size ◽  
Titanate Ceramics

AbstractIn this paper, three BaTiO3 powders of various particle size distributions were obtained as a result of mechanical activation in the mixer mill. Green barium titanate pellets and cylindrical specimens were fabricated by both uniaxial and isostatic pressing methods. As a result of the application of different maximal sintering temperatures, the obtained materials were characterized by various average grain sizes: 0.8 μm, 20 μm and 31.0 μm. The basic properties of sintered pellets and cylinders were determined and the influence of materials average grain size on their Young’s modulus and compressive strength were determined through compression tests in a uniaxial testing machine, Zwick/Roell Z100. The elastic properties were similar for tested materials with a different grain size. However, the microstructure of BaTiO3 strongly influenced the compressive strength.

scholarly journals sedFlow – an efficient tool for simulating bedload transport, bed roughness, and longitudinal profile evolution in mountain streams

2014 ◽  
Vol 2 (2) ◽  
pp. 733-772 ◽  
Author(s):  
F. U. M. Heimann ◽  
D. Rickenmann ◽  
J. M. Turowski ◽  
J. W. Kirchner
Keyword(s):  
Grain Size ◽  
Size Fraction ◽  
Bedload Transport ◽  
Mountain Streams ◽  
Size Distributions ◽  
Roughness Effects ◽  
Efficient Tool ◽  
Transport Dynamics ◽  
Grain Size Distributions ◽  
Bed Roughness

Abstract. Especially in mountainuous environments, the prediction of sediment dynamics is important for managing natural hazards, assessing in-stream habitats, and understanding geomorphic evolution. We present the new modelling tool sedFlow for simulating fractional bedload transport dynamics in mountain streams. The model can deal with the effects of adverse slopes and uses state of the art approaches for quantifying macro-roughness effects in steep channels. Local grain size distributions are dynamically adjusted according to the transport dynamics of each grain size fraction. The tool sedFlow features fast calculations and straightforward pre- and postprocessing of simulation data. The model is provided together with its complete source code free of charge under the terms of the GNU General Public License (www.wsl.ch/sedFlow). Examples of the application of sedFlow are given in a companion article by Heimann et al. (2014).

scholarly journals sedFlow – a tool for simulating fractional bedload transport and longitudinal profile evolution in mountain streams

2015 ◽  
Vol 3 (1) ◽  
pp. 15-34 ◽  
Author(s):  
F. U. M. Heimann ◽  
D. Rickenmann ◽  
J. M. Turowski ◽  
J. W. Kirchner
Keyword(s):  
Grain Size ◽  
Size Fraction ◽  
Bedload Transport ◽  
Mountain Streams ◽  
Stream Channels ◽  
Roughness Effects ◽  
Current Application ◽  
Transport Dynamics ◽  
Climate Change Effects ◽  
Simulation Speed

Abstract. Especially in mountainous environments, the prediction of sediment dynamics is important for managing natural hazards, assessing in-stream habitats and understanding geomorphic evolution. We present the new modelling tool {sedFlow} for simulating fractional bedload transport dynamics in mountain streams. sedFlow is a one-dimensional model that aims to realistically reproduce the total transport volumes and overall morphodynamic changes resulting from sediment transport events such as major floods. The model is intended for temporal scales from the individual event (several hours to few days) up to longer-term evolution of stream channels (several years). The envisaged spatial scale covers complete catchments at a spatial discretisation of several tens of metres to a few hundreds of metres. sedFlow can deal with the effects of streambeds that slope uphill in a downstream direction and uses recently proposed and tested approaches for quantifying macro-roughness effects in steep channels. sedFlow offers different options for bedload transport equations, flow-resistance relationships and other elements which can be selected to fit the current application in a particular catchment. Local grain-size distributions are dynamically adjusted according to the transport dynamics of each grain-size fraction. sedFlow features fast calculations and straightforward pre- and postprocessing of simulation data. The high simulation speed allows for simulations of several years, which can be used, e.g., to assess the long-term impact of river engineering works or climate change effects. In combination with the straightforward pre- and postprocessing, the fast calculations facilitate efficient workflows for the simulation of individual flood events, because the modeller gets the immediate results as direct feedback to the selected parameter inputs. The model is provided together with its complete source code free of charge under the terms of the GNU General Public License (GPL) (www.wsl.ch/sedFlow). Examples of the application of sedFlow are given in a companion article by Heimann et al. (2015).

Grain size characteristics of surface aeolian sands in the downwind margin of modern Mu Us Sandland

2020 ◽  
Author(s):  
Zhongyuan Wang ◽  
Yongqiu Wu
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Size Fraction ◽  
Boundary Line ◽  
Aeolian Sand ◽  
Different Grain Size ◽  
Morphologic Type ◽  
Aeolian Sands

<p>Desert (sandland) margin is the transition region from inner aeolian landforms  to other landforms outside, while it remains as an ambiguous conception in previous researches. Accurately delineating its boundary line and realizing the characteristics of the particle size distribution of surface aeolian sands in margin area can help us understand the formation of modern boundary of desert (sandland). In this research, the criteria of identification of the boundary were proposed and the boundary line was extracted quantitative. Then systematic analyses of grain size of aeolian sand in margin were conducted. Together with the morphologic type, activity and the geomorphological location of collected dunes, the factors controlled the particle-size distributions had also been analyzed. The results reveal the following: (1) There is notable difference in grain size characteristics of aeolian sand between inside and outside of Mu Us sandland. The outside samples are finer than inside. Additionally, the aeolian sand covering on loess is always more poorly sorted and with different grain size fraction composition. (2) The controlling factors on particle size distribution are different in different downwind margins. In southwest margin, the grain size characteristics of aeolian sand are influenced by time and degree of stabilization of sampled dune and locally topographic relief; From the estuary of Lu River to Yuxi River, sediment transport by wind is affected by topographic obstacles including both valley and loess gully. Meanwhile, the small dunefields in Loess Plateau outside of Mu Us sandland may originate from a local alluvial source; In northeast downwind margin, the grain size characteristics of aeolian sand covering on loess are determined by regional gully erosion after its deposition.</p>

A Novel Cell for Studying Ionic Transport in Powders During Compaction and Its Application to Lithium Silicate Glass Powder

2015 ◽  
Vol 229 (9) ◽  
Author(s):  
Dawid Murawski ◽  
Sebastian Roß ◽  
Harald Behrens
Keyword(s):  
Grain Size ◽  
Glass Powder ◽  
Size Fraction ◽  
Ionic Transport ◽  
Sample Volume ◽  
Lithium Silicate ◽  
Brittle Deformation ◽  
Material Surfaces ◽  
Different Grain Size ◽  
Grain Size Fractions

AbstractA new cell was developed to study the behavior of powders during axial compaction at temperatures up to 950 K and pressures up to 1 GPa. Electrical conductivity of the sample is measured by impedance spectroscopy. Change of sample volume can be simultaneously monitored using linear variable differential transducers. Flushing with gases allows pre-conditioning of material surfaces before compaction. The cell was tested with two different grain size fractions (60–150 μm and 200–250 μm) of lithium trisilicate glass in the brittle deformation range (315 K) and in the partially plastic deformation range (ca. 660 K). The DC conductivity increases linearly with pressure up to 750 MPa at about 660 K. Lower conductivity for the smaller grain size fraction under these conditions is attributed to higher shares of pores between the grains, acting as resistors.

scholarly journals Landscape Grain Effect in Yancheng Coastal Wetland and Its Response to Landscape Changes

2019 ◽  
Vol 16 (12) ◽  
pp. 2225 ◽  
Author(s):  
Peng Tian ◽  
Luodan Cao ◽  
Jialin Li ◽  
Ruiliang Pu ◽  
Xiaoli Shi ◽  
...  
Keyword(s):  
Grain Size ◽  
Landscape Pattern ◽  
Coastal Wetland ◽  
Diversity Index ◽  
Landscape Changes ◽  
Landscape Index ◽  
Strong Response ◽  
Artificial Wetlands ◽  
Grain Sizes ◽  
Different Grain Size

The landscape grain effect reflects the spatial heterogeneity of a landscape and it is used as a research core of landscape ecology. The landscape grain effect can be used to not only explore spatiotemporal variation characteristics of a landscape pattern, but also to disclose variation laws of ecological structures and functions of landscapes. In this study, the sensitivity of landscape pattern indexes to grain sizes 50–1000 m was studied based on landscape data in Yancheng Coastal Wetland acquired in 1991, 2000, 2008, and 2017. Response of the grain effect to landscape changes was analyzed and an optimal grain size for analysis in the study area was determined. Results indicated that: (1) among 27 indexes (12 in a class level and 15 in a landscape level), eight indexes were highly sensitive to grains, ten indexes presented moderate sensitivity, eight indexes presented low sensitivity, and one was unresponsive. It was shown that the area-margin index and the shape index were more sensitive to the different grain sizes. The aggregation index had some differences in the grain size change, and the diversity index had a low response degree to the grain size. (2) Landscape indexes showed six different responses to different grains, including slow reduced response, fast reduced and then slow reduced response, monotonically increased response, fluctuating reduced response, up-down responses, and stable response, which indicated that the landscape index was closely related to the spatial grain. (3) From 1991 to 2017, variation curves of the landscape grain size of different landscape types could be divided into four types: fluctuation rising type, fluctuation type, monotonous decreasing type, and monotonous rising type. Different grain size curves had different interpretations of landscape changes, but in general, Yancheng Coastal Wetland’s landscape tended to be fragmented and complicated, internal connectivity was weakened, and dominant landscape area was reduced. Natural wetlands were more sensitive to grain size effects than artificial wetlands. (4) The landscape index at the 50 m grain size had a strong response to different grain size changes, and the loss of landscape information was the smallest. Therefore, it was determined that the optimal landscape grain size in the study area was 50 m.

Influence of Grain Size to Resistivity Relaxation of La0.7Sr0.3MnO3 Nanoparticles

2015 ◽  
Vol 1123 ◽  
pp. 260-263
Author(s):  
Christian Fredy Naa ◽  
Didier Fasquelle ◽  
Manuel Mascot ◽  
Suprijadi ◽  
Sparisoma Viridi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Material ◽  
Grain Size ◽  
Sol Gel ◽  
Resistivity Ratio ◽  
Grain Sizes ◽  
Relaxation Measurements ◽  
Different Temperatures ◽  
Different Grain Size ◽  
The Magnetic Field

The resistivity relaxation in magnetic material is one of the important characteristics for reliable device operations. It also provides insight to the physics of magnetic material. Furthermore, this characteristic is related to the micro structural of the material. In this paper, the resistivity relax- ation of different grain sizes of La0.7Sr0.3MnO3(LSMO) nanoparticles has been studied. The LSMO nanoparticles was synthesized by sol-gel method and to obtain different grain size, the samples were sintered at different temperatures ranging from 800◦C to 1100◦C. The resistivity relaxation measurements were recorded for 500-1500s under the influence of magnetic field in range 25-110mT in room temperature. Under the influence of magnetic field, the resistivity of all samples were slowly de- creases as a function of time following logarithmic behavior. Moreover, no saturation was observed in the measurement time span. The resistivity ratio ρ(t)/ρ(0) as a function of time t was fitted by using logarithmic model. It is shown that resistivity relaxation depends on the grain size and the strength of the magnetic field.

scholarly journals Optimization of Aggregates Supply for Concrete Plants

2018 ◽  
Vol 64 (3) ◽  
pp. 99-110 ◽  
Author(s):  
A.K. Nicał
Keyword(s):  
Grain Size ◽  
Energy Consumption ◽  
Construction Industry ◽  
Size Fraction ◽  
Production Lines ◽  
Automated Production ◽  
Manufactured Products ◽  
Different Grain Size ◽  
Selection Of

AbstractOver the recent years, there is a growing interest in concrete prefabrication. Many of the currently operating concrete plants have implemented systems that increase the quality of manufactured products, have expanded highly automated production lines and have clearly reduced wastes and energy consumption. However, one of the problems often encountered in the construction industry is the inefficient organization of logistics processes. Proper shipments planning of aggregates consisting of the selection of their appropriate quantity and the aggregate stock, corresponding to the needs of concrete plants should contribute to lowering costs. Therefore, it is necessary to carry out the optimization, the aim of which is to minimize costs, as well as to maximize the fulfillment of the degree of expected needs of concrete plants. This paper presents a model that allows purchase strategy optimization of aggregates with different grain size fraction. For research purposes, three separate aggregate stocks and five different concrete plants are considered.

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