Designing and Testing of A High-Temperature Particle Lift for Concentrating Solar Power Applications
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Schroeder, Nathaniel Robert↗
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Results for “shaker test”
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Quantification and prediction of error in MIMO tests
Dynamic testing of systems is most realistic of real-world conditions when multiple input and multiple output (MIMO) techniques are used. To replicate measured environmental conditions, a series of desired outputs (responses) on the system must be realized by inverting the frequency response functions (FRF) matrix for input estimation. System identification is dependent on the number of inputs and outputs, which affect the type of solutions. In input estimation, the auto spectra of the determined inputs are affected by both the auto spectra and cross spectra of the desired outputs. This research evaluates errors and investigates two sources in an experimental setting. The first significant error source is test-to-test variability in FRFs from system identification tests, quantified by magnitude variability from long-duration tests. The second significant error source is the realization of time histories from frequency domain inputs. The spectral content of the realized random process deviates from the desired content and is also quantified. The structure is a linear three-story frame fixed at the base; two inputs are provided uniaxially with the use of suspended electrodynamic shakers. The proposed model for error sources was found to be effective in predicting errors in a SISO (single-input single-output) and a square (2-input 2-output) MIMO test.
Yousef, Odey↗
Detecting isolated resonance curves using fixed frequency voltage control tests
Isolated resonance curves, or isolas, are resonance branches of the harmonically forced system that exist separately from the main nonlinear forced response curve, leading to excessive vibrations. Traditional stepped or swept sine simulations and tests rely on continuation along the frequency parameter, typically resulting in a jump phenomenon along the primary resonance branch, prior to the disconnected isola. The main objective of this research is to propose an approach to identify isolated resonance curves by performing continuation along the input amplitude that initializes the response from a low-amplitude solution in the linear regime. Furthermore, this is achieved with the open-loop fixed frequency voltage control method that continues along the shaker voltage parameter and measures the so-called S-curves, which are theoretically a continuous solution branch that connect to the isola. The methodology is demonstrated on a fixture-wing-pylon assembly with a vibro-impact nonlinearity localized in a pylon subcomponent attachment. Multi-harmonic balance simulations are deployed to compute both the nonlinear forced response curves and S-curves to demonstrate the isola detection strategy on a reduced-order finite element model of the nonlinear system. Swept sine and fixed frequency voltage control tests are then conducted on the physical structure to demonstrate the isola detection experimentally, revealing the existence of the large amplitude vibrations that are undetected in the forces levels and frequencies measured with traditional frequency sweeping.
Characterization and Analytical Technique↗
Estrogen depletion alters osteogenic differentiation and matrix production by osteoblasts in vitro
Highlights: • Estrogen depletion accelerates osteoblast differentiation in static culture. • Mechanical stimulation exacerbated the effects of estrogen depletion on osteoblast differentiation. • Estrogen depletion alters osteoblasts capacity to produce a good quality matrix. Recent studies have revealed that the effects of estrogen deficiency are not restricted to osteoclasts and bone resorption, but that bone matrix composition is altered and osteoblasts exhibit an impaired response to mechanical stimulation. In this study, we test the hypothesis that estrogen depletion alters osteogenic differentiation and matrix production by mechanically stimulated osteoblasts in vitro. MC3T3-E1 cells were pre-treated with estrogen for 14 days, after which estrogen was withdrawn or inhibited with Fulvestrant up to 14 days. Fluid shear stress (FSS) was applied using an orbital shaker. Under estrogen depletion in static culture, osteogenic marker (ALP) and gene expression (Runx2) were decreased at 2 and after 7 days of estrogen depletion, respectively. In addition, up to 7 day the inhibition of the estrogen receptor significantly decreased fibronectin expression (FN1) under static conditions. Under estrogen depletion and daily mechanical stimulation, changes in expression of Runx2 occurred earlier (4 days) and by 14 days, changes in matrix production (Col1a1) were reported. We propose that changes in osteoblast differentiation and impaired matrix production during estrogen depletion may contribute to the altered quality of the bone and act as a contributing factor to increased bone fragility in postmenopausal osteoporosis.
60 APPLIED LIFE SCIENCES↗