Study made of interaction between sound fields and structural vibrations

Study analyzes structural vibrations and the interactions between them and sound fields. It outlines a conceptual framework to analyze the vibrations of systems and their interactions, incorporating the results of earlier studies and establishing a unified basis for continuing research

Analytical procedure for determining random load acting on a spacecraft due to a primary random load acting on an exterior structure Quarterly report no. 2, 1 Sep. - 30 Nov. 1965

Sound and vibration transmission in OGO SPACECRAFT shroud syste

The prediction and measurement of sound radiated by structures

Theories regarding the radiation of sound are reviewed and the implementation in strategies for explaining or measuring the sound produced by practical strucutres are discussed. Particular attention is given to those aspects that relate to the determination of the relative amounts of sound generated by various parts of a machine or structure, which can be very useful information for noise reduction efforts

Low-frequency noise reduction of spacecraft structures

Low frequency noise reduction of spacecraft structure

Storm‐time configuration of the inner magnetosphere: Lyon‐Fedder‐Mobarry MHD code, Tsyganenko model, and GOES observations

[1] We compare global magnetohydrodynamic (MHD) simulation results with an empirical model and observations to understand the magnetic field configuration and plasma distribution in the inner magnetosphere, especially during geomagnetic storms. The physics-based Lyon-Fedder-Mobarry (LFM) code simulates Earth\u27s magnetospheric topology and dynamics by solving the equations of ideal MHD. Quantitative comparisons of simulated events with observations reveal strengths and possible limitations and suggest ways to improve the LFM code. Here we present a case study that compares the LFM code to both a semiempirical magnetic field model and to geosynchronous measurements from GOES satellites. During a magnetic cloud event, the simulation and model predictions compare well qualitatively with observations, except during storm main phase. Quantitative statistical studies of the MHD simulation shows that MHD field lines are consistently under-stretched, especially during storm time (Dst \u3c −20 nT) on the nightside, a likely consequence of an insufficient representation of the inner magnetosphere current systems in ideal MHD. We discuss two approaches for improving the LFM result: increasing the simulation spatial resolution and coupling LFM with a ring current model based on drift physics (i.e., the Rice Convection Model (RCM)). We show that a higher spatial resolution LFM code better predicts geosynchronous magnetic fields (not only the average Bz component but also higher-frequency fluctuations driven by the solar wind). An early version of the LFM/RCM coupled code, which runs so far only for idealized events, yields a much-improved ring current, quantifiable by decreased field strengths at all local times compared to the LFM-only code

Electron Paramagnetic Resonance of Boron Acceptors in Isotopically Purified Silicon

The electron paramagnetic resonance (EPR) linewidths of B acceptors in Si are found to reduce dramatically in isotopically purified 28Si single crystals. Moreover, extremely narrow substructures in the EPR spectra are visible corresponding to either an enhancement or a reduction of the absorbed microwave on resonance. The origin of the substructures is attributed to a combination of simultaneous double excitation and spin relaxation in the four level spin system of the acceptors. A spin population model is developed which qualitatively describes the experimental results.Comment: 4 pages, 3 figure

Sensorization and intelligent systems in energetic sustainable environments

Sustainability is an important topic of discussion in our world. However, measuring sustainability and assessing behaviors is not always easy. Indeed, and in order to fulfill this goal, in this work it will be proposed a multi-agent based architecture to measure and assess sustainable indicators taken from a given environment. These evaluations will be based on past and present behaviors of the users and the particularities of the setting, leading to the evaluation of workable indicators such as gas emissions, energetic consumption and the users fitting with respect to the milieu. Special attention is given to user interaction and user attributes to calculate sustainable indicators for each type of structure, i.e., the aim of this scheme is to promote sustainability awareness and sustainable actions through the use of sustainable markers calculated in terms of the information gathered from the environment.The research presented is partially supported by a portuguese doctoral grant, SFRH/BD/78713/2011, issued by the Fundação da Ciência e Tecnologia (FCT) in Portugal

Componential coding in the condition monitoring of electrical machines Part 2: application to a conventional machine and a novel machine

This paper (Part 2) presents the practical application of componential coding, the principles of which were described in the accompanying Part 1 paper. Four major issues are addressed, including optimization of the neural network, assessment of the anomaly detection results, development of diagnostic approaches (based on the reconstruction error) and also benchmarking of componential coding with other techniques (including waveform measures, Fourier-based signal reconstruction and principal component analysis). This is achieved by applying componential coding to the data monitored from both a conventional induction motor and from a novel transverse flux motor. The results reveal that machine condition monitoring using componential coding is not only capable of detecting and then diagnosing anomalies but it also outperforms other conventional techniques in that it is able to separate very small and localized anomalies

Effect of aqueous polymer treatments on wood properties part 11: mechanical properties

Partially air-dried sapwood of sweetgum (Liquidambar styraciflua) and southern pine (Pinus spp.) was treated with either aqueous polyacrylate or aqueous dimethyloldihydroxyethyleneurea (DMDHEU) solutions. Tests for static bending, toughness, and hardness were conducted on matched treated and untreated pieces according to ASTM Standards. Properties of pine were not affected by treatment with the polyacrylate .. With sweetgum, the modulus of rupture and modulus of elasticity were reduced, while hardness was improved. For the DMDHEU treatment, reduction in property values for both species was related to curing temperature