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Simultaneous determination of Bingham material parameters using a ball probe concrete rheometer
(2021-01-25)
A new evaluation method allowing direct determination of the Bingham parameters from ball probe rheometers. A non‐linear relationship between the direct measured variables and the material parameters is revealed through numerical parameter studies. The method was validated on two devices of the ball probe type with different dimensions. Comparison with other methods showed good agreement. It is pointed out how the evaluation method can be transferred to devices having other dimensions by performing a limited number ...
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Experimental investigations of viscoelastic and ferroelectric heating in PZT–5H
(2021-01-25)
This contribution focuses on the separation of two effects causing a temperature change in experiments with electrically loaded ferroelectrics. These materials are often subjected to cyclic loading, where viscoelasticity prevails at lower electric fields, whereas dissipative heating by domain switching governs the heating above the coercive field. Different frequencies and load amplitudes are investigated experimentally.
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Extension of Gap Bridgeability and Prevention of Oxide Lines in the Welding Seam through Application of Tools with Multi-Welding Pins
(2021-07-30)
Friction stir welding has become important in many areas of production and is increasingly used for joining aluminum components. For long welding seams, conventional tools with only one welding pin reach their technical limitations due to low gap bridgeability. When welding aluminum, the stirred in surface layers, such as oxides, lead to a decrease in static and dynamic strength since linear accumulations are formed in the welding seam. The aim of the present study is to increase the gap bridgeability using tools ...
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Introducing the Logarithmic finite element method: a geometrically exact planar Bernoulli beam element
(2016-09-15)
We propose a novel finite element formulation that significantly reduces the number of degrees of freedom necessary to obtain reasonably accurate approximations of the low-frequency component of the deformation in boundary-value problems. In contrast to the standard Ritz–Galerkin approach, the shape functions are defined on a Lie algebra—the logarithmic space—of the deformation function. We construct a deformation function based on an interpolation of transformations at the nodes of the finite element. In the case ...
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On the appearance of horseshoe chaos in a nonlinear hysteretic systems with negative stiffness
(2021-09-16)
The problem of inhibition of horseshoe chaos in a nonlinear hysteretic systems using negative stiffness is investigated in this paper. The Bouc–Wen model is used to describe the force produced by both the purely hysteretic and linear elastic springs. The analytical investigation of the Hamiltonian shows that the appearance of separatrix in the system is directly related to the parameters of the hysteretic forces. This means that the transverse intersection between the perturbed and unperturbed separatrix can be ...
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Willingness-to-Pay for District Heating from Renewables of Private Households in Germany
(2020-05-18)
Recent discussion about future energy production promotes the recovery of industrial heat as a potential solution to reduce carbon emissions. Experts call for an expansion of central heating by renewable energy systems to ensure a decarbonization of energy systems. In this context, district heating could play a significant role in city and district planning. Nonetheless, for private households, environmental aspects are only one factor amongst others as, e.g., capital costs, comfort and security. In this study, we ...
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A modification of a traditional Ethiopian maize store for solar powered ambient drying to reduce post-harvest losses
(2020-07-14)
A gombisa is a traditional Ethiopian structure widely used for maize storage over several months. It lacks adequate ventilation for timely moisture removal, which promotes mold development and aflatoxin production. In this study, a traditional gombisa was compared to one modified by installing a solar powered fan to provide forced ambient air ventilation during daytime. Approximately 900 kg of moist ear maize were loaded into each structure and samples from selected locations were weighed periodically to monitor ...
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Friction Stir Spot Welding with Additional Bonding of Thick Sheet Aluminum Joints
(2019-06-27)
The high-strength aluminum alloys offer great potential for realizing lightweight constructions in car body construction. However, the use of aluminum alloys increases the overall thickness of the material, which poses new challenges for potential joining processes. This paper examines a process combination of friction stir spot welding (FSSW) and bonding for 4 mm EN AW 6082-T6 sheets. For the investigations, adhesive or glass beads were applied between the joining components and then the sheets were welded using ...
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Agricultural Water Productivity-Based Hydro-Economic Modeling for Optimal Crop Pattern and Water Resources Planning in the Zarrine River Basin, Iran, in the Wake of Climate Change
(2018-10-30)
For water-stressed regions/countries, like Iran, improving the management of agricultural water-use in the wake of climate change and increasingly unsustainable demands is of utmost importance. One step further is then the maximization of the agricultural economic benefits, by properly adjusting the irrigated crop area pattern to optimally use the limited amount of water available. To that avail, a sequential hydro-economic model has been developed and applied to the agriculturally intensively used Zarrine River Basin ...
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Correction and Informed Regionalization of Precipitation Data in a High Mountainous Region (Upper Indus Basin) and Its Effect on SWAT-Modelled Discharge
(2018-11-01)
The current study applied a new approach for the interpolation and regionalization of observed precipitation series to a smaller spatial scale (0.125° by 0.125° grid) across the Upper Indus Basin (UIB), with appropriate adjustments for the orographic effect and changes in glacier storage. The approach is evaluated and validated through reverse hydrology, and is guided by observed flows and the available knowledge base. More specifically, the generated corrected precipitation data is validated by means of SWAT-modelled ...