The Effect of Sample Edge Conditions on Standing Wave Tube Measurements of Absorption and Transmission Loss

The acoustical properties of isotropic, elastic porous materials are now conventionally specified by a set of nine, frequency-independent macroscopic parameters: e.g., flow resistivity, tortuosity, viscous and thermal characteristic lengths, etc. When these properties are known, it is possible to predict the absorption performance of the material, for example, in arbitrary geometries. Conversely, it has become popular to infer the macroscopic parameters of porous materials by finding the set of parameters that results in an optimal match of measurements and prediction. The software packages FOAM-X and COMET/Trim, for example, offer inverse characterization features of this type. However, here it is shown that that it may not be possible to represent large and small diameter samples of the same material as measured in standing wave tubes by using a single set of parameters. In practice, measurements in standing wave tubes can be significantly affected by sample edge effects, particularly gaps around the sample resulting from minor damage of the sample during cutting. Here it will be illustrated that it is necessary to model the sample inhomogeneity resulting from edge damage if both large and small tube results are to be modelled by using a single, consistent set of parameters

Sound Radiation Control Resulting from Tire Structural Vibration

The objective here was to study the control of sound radiation resulting from the structural vibration of a tire excited at one point. First, the tire was modeled as an orthotropic shell by using finite elements and the effect of various tire material parameters on structural wave propagation and the associated sound radiation was estimated. The parameters that were effective at controlling structural wave propagation were then identified. In addition, the radiation field characteristics in the space surrounding a tire placed on a rigid ground were analyzed by using radiation mode analysis. Based on these analyses, a strategy for reducing the radiated sound levels by modifying the tire parameters from a base set was determined. An improved set of material parameters was identified that resulted in reduced sound radiation within a specified target frequency region. That reduction was achieved by an increase of treadband circumferential stiffness that was found to move the onset of longitudinal wave motion within the treadband into a higher frequency region. Secondly, flexural wave propagation was found to be mainly controlled by inflation pressure and cross-sectional treadband stiffness. By appropriate adjustment of these three parameters, it was found possible to substantially reduce sound radiation in a mid-frequency region

Influence of Tire Size and Shape on Sound Radiation from a Tire in the Mid-Frequency Region

In this research, the influence of tire size and shape on sound radiation in the mid-frequency region was studied. First, the relationship between the structural wave propagation characteristics of a tire excited at one point and its sound radiation was identified by using FE and BE analyses. Then, by using that relationship, the effect of modifying a tire’s aspect ratio, width and wheel diameter on its sound radiation between 300 Hz and 800 Hz was investigated. Finally, an optimization of the sound radiation was performed by modification of the tire structure and shape. It was found that most of a tire’s structural vibration does not contribute to sound radiation. In particular, the effective radiation was found to occur at the frequencies where low wave number components of the longitudinal wave and the flexural wave first appear. In addition, when the tire size and shape were modified, it was found that the flexural wave motion was controlled primarily by the tire cross-sectional length while the longitudinal wave motion was mainly affected by the treadband overall diameter

Validation of a Polyimide Foam Model for Use in Transmission Loss Applications

The work described in this paper was focused on the use of a new polyimide foam in a double wall sound transmission loss application. Recall that polyimide foams are functionally attractive, compared to polyurethane foams, for example, owing to their fire resistance. The foam considered here was found to have a flow resistivity that was too high for conventional acoustical applications, and as a result, it was processed by partial crushing to lower the flow resistivity into an acceptable range. Procedures for measuring the flow resistivity and Young s modulus of the material have been described, as was an inverse characterization procedure for estimating the remaining Biot parameters based on standing wave tube measurements of transmission loss and absorption coefficient. The inverse characterization was performed using a finite element model implementation of the Biot poro-elastic material theory. Those parameters were then used to predict the sound transmission loss of a double panel system lined with polyimide foam, and the predictions were compared with full-scale transmission loss measurements. The agreement between the two was reasonable, especially in the high and low frequency limits; however, it was found that the SEA model resulted in an under-prediction of the transmission loss in the mid-frequency range. Nonetheless, it was concluded that the performance of polyimide foam could be predicted using conventional poro-elastic material models and that polyimide foam may offer an attractive alternative to other double wall linings in certain situations: e.g., when fire resistance is a key issue. Future work will concentrate on reducing the density of the foam to values similar to those used in current aircraft sidewall treatments, and developing procedures to improve the performance of the foam in transmission loss applications

Development and Validation Study of the Internet Overuse Screening Questionnaire

Objective: Concerns over behavioral and emotional problems caused by excessive internet usage have been developed. This study intended to develop and a standardize questionnaire that can efficiently identify at-risk internet users through their internet usage habits. Methods: Participants (n=158) were recruited at six I-will-centers located in Seoul, South Korea. From the initial 36 questionnaire item pool, 28 preliminary items were selected through expert evaluation and panel discussions. The construct validity, internal consistency, and concurrent validity were examined. We also conducted Receiver Operating Curve (ROC) analysis to assess diagnostic ability of the Internet Overuse Screening-Questionnaire (IOS-Q). Results: The exploratory factor analysis yielded a five factor structure. Four factors with 17 items remained after items that had unclear factor loading were removed. The Cronbach’s alpha for the IOS-Q total score was 0.91, and test-retest reliability was 0.72. The correlation between Young’s internet addiction scale and K-scale supported concurrent validity. ROC analysis showed that the IOS-Q has superior diagnostic ability with the Area Under the Curve of 0.87. At the cut-off point of 25.5, the sensitivity was 0.93 and specificity was 0.86. Conclusion: Overall, this study supports the use of IOS-Q for internet addiction research and for screening high-risk individuals

Contagious Aggregation: Transmittable Protein Aggregation in Cellular Communities Initiated by Synthetic Cells

© 2021 American Chemical Society. All rights reserved.Aggregation of amyloidogenic proteins causing neurodegenerative diseases is an uncontrollable and contagious process that is often associated with lipid membranes in a highly complex physiological environment. Although several approaches using natural cells and membrane models have been reported, systematic investigations focusing on the association with the membranes are highly challenging, mostly because of the lack of proper molecular tools. Here, we report a new supramolecular approach using a synthetic cell system capable of controlling the initiation of protein aggregation and mimicking various conditions of lipid membranes, thereby enabling systematic investigations of membrane-dependent effects on protein aggregation by visualization. Extending this strategy through concurrent use of synthetic cells and natural cells, we demonstrate the potential of this approach for systematic and in-depth studies on interrogating inter- and intracellularly transmittable protein aggregation. Thus, this new approach offers opportunities for gaining insights into the pathological implications of contagious protein aggregation associated with membranes for neurotoxicity.11Nsciescopu

Contagious Aggregation: Transmittable Protein Aggregation in Cellular Communities Initiated by Synthetic Cells

Aggregation of amyloidogenic proteins causing neurodegenerative diseases is an uncontrollable and contagious process that is often associated with lipid membranes in a highly complex physiological environment. Although several approaches using natural cells and membrane models have been reported, systematic investigations focusing on the association with the membranes are highly challenging, mostly because of the lack of proper molecular tools. Here, we report a new supramolecular approach using a synthetic cell system capable of controlling the initiation of protein aggregation and mimicking various conditions of lipid membranes, thereby enabling systematic investigations of membrane-dependent effects on protein aggregation by visualization. Extending this strategy through concurrent use of synthetic cells and natural cells, we demonstrate the potential of this approach for systematic and in-depth studies on interrogating inter- and intracellularly transmittable protein aggregation. Thus, this new approach offers opportunities for gaining insights into the pathological implications of contagious protein aggregation associated with membranes for neurotoxicity. © 2022 American Chemical Society. All rights reserved.11Nsciescopu