Absorption from Finite-size Microperforated Panels at Arbitrary Incidence Angles

A rigid microperforated panel combined with a finite-depth air space can absorb sound effectively. Various studies of these systems have been performed and it has been found that hole configuration and backing depth are the primary factors that determine their absorption. However, the effects of panel flexibility and the finite size of the supported membrane segments have not been considered as extensively. In this present work, a two-dimensional model for arbitrary incidence angles was used to predict the sound absorption of an infinite array of finite-size, flexible microperforated panels. The absorption of various microperforated panels was measured in standing wave tubes and compared to predictions to verify the model at normal incidence. The effects of two different types of backing spaces, i.e., segmented and unsegmented, were compared. It was found that the segmented backing space is approximately locally reacting: as a result, the absorption at low frequencies is larger than that for the unsegmented backing space case. It was also found that the absorption from an array of finite-size microperforated panels can be successfully predicted with a knowledge of the panel’s physical material properties (e.g., flexural stiffness, loss factor, and mass per unit area) and hole configuration (e.g., hole size, film thickness, and number of holes per unit area)

A survey of current and past Pediatric Infectious Diseases fellows regarding training

<p>Abstract</p> <p>Background</p> <p>The objectives of this study were to characterize the satisfaction of Pediatric Infectious Diseases fellows with their training and to understand how opinions about training have changed over time.</p> <p>Methods</p> <p>Anonymous survey studies were conducted with questions designed to include areas related to the 6 ACGME core competencies. Surveys for current fellows were distributed by fellowship directors, while surveys for graduates were mailed to all individuals with Pediatric Infectious Diseases certification.</p> <p>Results</p> <p>Response rates for current fellows and graduates were 50% and 52%, respectively. Most fellows (98%) and graduates (92%) perceived their overall training favorably. Training in most clinical care areas was rated favorably, however both groups perceived relative deficiencies in several areas. Current fellows rated their training in other competency areas (e.g., systems-based practice, research, and ethics) more favorably when compared to past graduates. Recent graduates perceived their training more favorably in many of these areas compared to past graduates.</p> <p>Conclusions</p> <p>Pediatric Infectious Diseases fellowship training is well regarded by the majority of current and past trainees. Views of current fellows reflect improved satisfaction with training in a variety of competency areas. Persistent deficiencies in clinical training likely reflect active barriers to education. Additional study is warranted to validate perceived deficiencies and to establish consensus on the importance of these areas to infectious diseases training.</p

Track A Basic Science

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138319/1/jia218438.pd