Elucidation of the evolutionary processes that constrain or facilitate adaptive divergence is a central goal in evolutionary biology, especially in non-model organisms. We tested whether changes in dynamics of gene flow (historical vs contemporary) caused population isolation and examined local adaptation in response to environmental selective forces in fragmented Rhododendron oldhamii populations. Variation in 26 expressed sequence tag-simple sequence repeat loci from 18 populations in Taiwan was investigated by examining patterns of genetic diversity, inbreeding, geographic structure, recent bottlenecks, and historical and contemporary gene flow. Selection associated with environmental variables was also examined. Bayesian clustering analysis revealed four regional population groups of north, central, south and southeast with significant genetic differentiation. Historical bottlenecks beginning 9168-13,092 years ago and ending 1584-3504 years ago were revealed by estimates using approximate Bayesian computation for all four regional samples analyzed. Recent migration within and across geographic regions was limited. However, major dispersal sources were found within geographic regions. Altitudinal clines of allelic frequencies of environmentally associated positively selected outliers were found, indicating adaptive divergence. Our results point to a transition from historical population connectivity toward contemporary population isolation and divergence on a regional scale. Spatial and temporal dispersal differences may have resulted in regional population divergence and local adaptation associated with environmental variables, which may have played roles as selective forces at a regional scale.
Microspeakers are key components of mobile devices in current consumer products; moreover, the user experience of multimedia products plays an essential role. The objective of this study was to investigate the acoustic performance of microspeakers in different enclosure parameters for mobile devices. Two methodologies are performed. The first model is an electro-mechano-acoustical model (EMA) of microspeaker along with distribution model of enclosure effect; the 2nd model, the details of diaphragms are taken into account in calculating the distribution models of microspeaker with enclosure parameters. They were combined and applied to determine microspeaker performance levels for mobile devices. Two methodologies show acceptable agreement with experimental results. The distribution model can well simulate the high frequency response than lumped model of microspeaker. The results can predict microspeaker system performance before industrial design and mechanism placement processes are executed.
This study provides a solution for the bass extension of a microspeaker system in a mobile device that involves using a resonant combination of a front chamber and a rectangular, long, pipe-shaped port. The efficient resonant coupling of the microspeaker system to the acoustic load in this structure enables a microspeaker with modest cone displacement to achieve a high sound pressure level (SPL) and bass extension below the resonance of the microspeaker in free air, and the total dimensions of the structure are minimized. A combination of electro-mechanic-acoustic and finite element methods was applied to determine the SPL and bass extension levels for mobile devices. Simulation results show acceptable agreement with experimental results. A suitable extended-range microspeaker system was applied in a 10 inch tablet. The audio frequency response could be extended from 630 to 300 Hz with the greatest loudness. As much as possible add low bound frequency extension to make the article more clear. Finally, five cases of parameter settings for the front chamber volume, rear chamber volume, rectangular pipe-shaped port, cross-sectional area, and opening area were studied. The results can be applied for optimizing a suitable extended-range microspeaker system.
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