Research and development of an air-puff excitation system for lightweight structures

© 2019 International Group of Operational Modal Analysis. Lightweight, thin-walled structures appear in numerous engineering and natural structures. Due to their sensitivity, vibration excitation by, now traditional, contacting techniques, such as modally-tuned impact hammers or electrodynamic shakers, to investigate their dynamics is challenging since it typically adds substantial mass and/or stiffness at the excitation location. The research presented in this article, therefore, is intended to yield a system for the non-contact excitation of thin-walled structures through small, controlled blasts of air. An air-puff system, consisting of two fast-acting solenoid-controlled valves, a small air outlet nozzle and bespoke control software with a programmable valve control sequence, is researched and developed. The excitation impulse characteristics are investigated experimentally and described in detail for varying input control parameters. Ultimately, suitability of the system for the excitation of thin-walled structures is explored, for both a 3D-printed micro-satellite panel and a natural bee honeycomb, with promising results when compared to that of an impact hammer

Synthesis of new pseudo‐C‐nucleosides containing pyrazole rings in their structure

Synthetic approaches to new 4-(furanos-4-C-yl)-1H-pyrazole and 3-(furanos-4-C-yl)-1H-pyrazole derivatives are described, including its pyrazole-5-carboxylate derivative, which is a pyrazofurin analogue. Preparation of related 5-acetoxy-1-acetyl-1H-pyrazole, 5-acetoxy-1H-pyrazole-1-carboxylate, and 4,5-dihydro-1-phenyl-1H-pyrazol-5-one derivatives is also reported. The formation of the pyrazole rings was accomplished either by reaction of enones and of 1,3-diketones with N-nucleophiles or by ring closure of a diazoketone.info:eu-repo/semantics/publishedVersio

Parametric Model Order Reduction of Guided Ultrasonic Wave Propagation in Fiber Metal Laminates with Damage

This paper focuses on parametric model order reduction (PMOR) of guided ultrasonic wave propagation and its interaction with damage in a fiber metal laminate (FML). Structural health monitoring in FML seeks to detect, localize and characterize the damage with high accuracy and minimal use of sensors. This can be achieved by the inverse problem analysis approach, which employs the signal measurement data recorded by the embedded sensors in the structure. The inverse analysis requires us to solve the forward simulation of the underlying system several thousand times. These simulations are often exorbitantly expensive and trigger the need for improving their computational efficiency. A PMOR approach hinged on the proper orthogonal decomposition method is presented in this paper. An adaptive parameter sampling technique is established with the aid of a surrogate model to efficiently update the reduced-order basis in a greedy fashion. A numerical experiment is conducted to illustrate the parametric training of the reduced-order model. The results show that the reduced-order solution based on the PMOR approach is accurately complying with that of the high fidelity solution

Light suppression of nitrate reductase activity in seedling and young plant tissues

Light is often reported to enhance plant nitrate reductase (NR) activity; we have identified a context in which light strongly suppresses NR activity. In vitro NR activity measurements of laboratory-grown seedlings showed strong suppression of nitrate-induced NR activity in cotyledon, hypocotyl, and root tissues of Ipomoea hederacea (L.) Jacquin; robust NR activity accumulated in nitrate-induced tissues in the dark, but was absent or significantly reduced in tissues exposed to light during the incubation. The suppressive mechanism appears to act at a point after nitrate perception; tissues pre-incubated with nitrate in the light were potentiated and developed NR activity more rapidly than nitrate-induced tissues not so pre-exposed. Suppression was affected by moderate to low light levels under full-spectrum light sources and by single-wavelength red, green, and blue sources. The suppression phenomenon persisted in early (first through fourth) leaves of glasshouse plants grown in soil, and in artificially rejuvenated cotyledons. Collectively these observations suggest a link between light perception and NR regulation that remains to be fully characterized

Mediolateral Damping of an Overhead Body Weight Support System Assists Stability During Treadmill Walking

Background Body weight support systems with three or more degrees of freedom (3-DoF) are permissive and safe environments that provide unloading and allow unrestricted movement in any direction. This enables training of walking and balance control at an early stage in rehabilitation. Transparent systems generate a support force vector that is near vertical at all positions in the workspace to only minimally interfere with natural movement patterns. Patients with impaired balance, however, may benefit from additional mediolateral support that can be adjusted according to their capacity. An elegant solution for providing balance support might be by rendering viscous damping along the mediolateral axis via the software controller. Before use with patients, we evaluated if control-rendered mediolateral damping evokes the desired stability enhancement in able-bodied individuals. Methods A transparent, cable-driven robotic body weight support system (FLOAT) was used to provide transparent body weight support with and without mediolateral damping to 21 able-bodied volunteers while walking at preferred gait velocity on a treadmill. Stability metrics reflecting resistance to small and large perturbations were derived from walking kinematics and compared between conditions and to free walking. Results Compared to free walking, the application of body weight support per-se resulted in gait alterations typically associated with body weight support, namely increased step length and swing phase. Frontal plane dynamic stability, measured by kinematic variability and nonlinear dynamics of the center of mass, was increased under body weight support, indicating reduced balance requirements in both damped and undamped support conditions. Adding damping to the body weight support resulted in a greater increase of frontal plane stability. Conclusion Adding mediolateral damping to 3-DoF body weight support systems is an effective method of increasing frontal plane stability during walking in able-bodied participants. Building on these results, adjustable mediolateral damping could enable therapists to select combinations of unloading and stability specifically for each patient and to adapt this in a task specific manner. This could extend the impact of transparent 3-DoF body weight support systems, enabling training of gait and active balance from an early time point onwards in the rehabilitation process for a wide range of mobility activities of daily life

A new dihydroxysterol from the marine phytoplankton Diacronema sp.

Diacronema sp. was cultured and its sterols were separated by column chromatography on silica gel. The new sterol 24-ethyl-4α-methyl-cholestane-3,20-diol (1) was characterised by NMR and MS spectrometry, as well as (22E)-24-ethyl-4α-methyl-5α-cholest-22-en-3β-ol (2) and β-sitosterol, the major components of the sterol fractions. Neither the biosynthetic origin of the new dihydroxysterol nor its role in the biochemistry of Diacronema is known.info:eu-repo/semantics/publishedVersio

A novel pentacyclic triterpene from Leontodon filii

A novel oleanene triterpenetetrol was isolated from the chloroform extract of the aerial parts of Leontodon filii. Its structure was shown to be 2β,3β,15α,21β-olean-12-ene-2,3,15,21-tetrol by chemical and spectroscopic methods. The fungicidal efficacy of the chloroform and methanol extracts of the plant was also evaluated, a protective effect being found against Plasmopara viticola, Botrytis cinerea, particularly powerful against Pyricularia oryzae.info:eu-repo/semantics/publishedVersio

Damage Identification in Fiber Metal Laminates using Bayesian Analysis with Model Order Reduction

Fiber metal laminates (FML) are composite structures consisting of metals and fiber reinforced plastics (FRP) which have experienced an increasing interest as the choice of materials in aerospace and automobile industries. Due to a sophisticated built up of the material, not only the design and production of such structures is challenging but also its damage detection. This research work focuses on damage identification in FML with guided ultrasonic waves (GUW) through an inverse approach based on the Bayesian paradigm. As the Bayesian inference approach involves multiple queries of the underlying system, a parameterized reduced-order model (ROM) is used to closely approximate the solution with considerably less computational cost. The signals measured by the embedded sensors and the ROM forecasts are employed for the localization and characterization of damage in FML. In this paper, a Markov Chain Monte-Carlo (MCMC) based Metropolis-Hastings (MH) algorithm and an Ensemble Kalman filtering (EnKF) technique are deployed to identify the damage. Numerical tests illustrate the approaches and the results are compared in regard to accuracy and efficiency. It is found that both methods are successful in multivariate characterization of the damage with a high accuracy and were also able to quantify their associated uncertainties. The EnKF distinguishes itself with the MCMC-MH algorithm in the matter of computational efficiency. In this application of identifying the damage, the EnKF is approximately thrice faster than the MCMC-MH

Liquid chromatography–diode array detection–electrospray ionisation mass spectrometry/nuclear magnetic resonance analyses of the anti-hyperglycemic flavonoid extract of Genista tenera Structure elucidation of a flavonoid-C-glycoside

The anti-hyperglycemic flavonoid extract obtained from Genista tenera was first studied by liquid chromatography (LC)–diode array detection (DAD) which showed the presence of two major compounds. One of them was identified as genistein-7-O-glucoside. Luteolin-7-O-glucoside was detected as a minor constituent, while luteolin-7,3′-di-O-glucoside and rutin were found in trace amounts. LC–DAD–ESI–MS and NMR were used to confirm the structure of these compounds and allowed the elucidation of the structure of the unknown major compound, which is the flavonoid 5,7,4′-trihydroxyisoflavone-8-C-glucoside.info:eu-repo/semantics/publishedVersio