Re-active Passive (RAP) Devices for Control of Noise Transmission through a Panel

Re-Active Passive (RAP) devices have been developed to control low frequency (200 Hz), reactive distributed vibration absorber) to cover the medium frequency range (75 to 250 Hz), and active control for controlling low frequencies (<200 Hz). The device was applied to control noise transmission through a panel mounted in a transmission loss test facility. Experimental results are presented for the bare panel, and combinations of passive treatment, reactive treatment, and active control. Results indicate that three RAP devices were able to increase the overall broadband (15-1000 Hz) transmission loss by 9.4 dB. These three devices added a total of 285 grams to the panel mass of 6.0 kg, or approximately 5%, not including control electronics

Experimental investigation of reversed flow in a compressor cascade

An experimental investigation of reversed flow performance characteristics in a compressor cascade was conducted. The purpose was to gain a fundamental understanding of reversed flow in a compressor blade cascade, and to determine the effects of stagger angle and angle of attack on the reversed flow behavior in the cascade. Tests were conducted at two blade configurations, one to simulate reversed flow in a compressor rotor and one to simulate reversed flow in a compressor inlet guide vane. Three stagger angles were tested for each configuration with an absolute angle of attack range from 70 to 130 degrees. The investigation included total and static pressure measurements upstream and downstream of the cascade as well as blade surface measurements. Aerodynamic performance parameters were presented for a reversed flow cascade. Comparison of corrected total pressure loss curves suggested that blade rows of a compressor subjected to reversed flow may be treated as nearly equal loss producers. A comparison was made between total pressure loss coefficients from this investigation and experimental compressor performance. The total pressure loss coefficients compared favorably in magnitude and curve shape.Master of Scienc

Active structural acoustic control of double panel systems including hierarchical control approaches

The general trends and principles of active structural acoustic control when applied to double panel systems are investigated to determine the respective advantages and limitations of this approach. Included is the application of a novel hierarchical control approach which may reduce the controller complexity and the collinearity issue for large order controllers. This research was initiated by an interest in studying the noise transmission path from the noise field generated by an advanced turboprop engine through the aircraft fuselage and the interior trim into the interior acoustic field which can be modeled as a double panel system. The system studied was a double panel model consisting of two rectangular, uniform, flat plates separated by a sealed air cavity, mounted in a transmission loss test facility and excited by an oblique acoustic plane wave. Piezoelectric control inputs were mounted directly on the double panel system incident or radiating plates. Error sensors were microphones placed in the acoustic free field. The cost function was defined as the total radiated sound power from the double panel system. The investigation was carried out analytically with experimental verification. Results of active structural acoustic control (ASAC) applied to double panel systems indicated that the best control performance was exhibited by a double panel system controlled by PZT control actuators mounted on a sandwich board radiating plate. The sandwich board radiating plate double panel system exhibits a decreased coupling of the incident and radiating plates and a lower modal density which results in increased uncontrolled and controlled transmission loss. Piezoelectric (PZT) control actuators should be mounted on the radiating plate of a double panel system which can couple into the radiating acoustic field better than actuators mounted on the incident plate. As expected, better control is achieved with more control actuators since a more distributed forcing function can be attained. However, for on-resonance excitation, the increased number of actuators decreases performance due to collinearity of the actuators which results in spillover. Results of the biologically inspired hierarchical (BIO) control algorithm indicated that significant performance increases over a one output channel controller were attained for all of the BIO methods while performance lagged compared to a full order controller with the same number of control channels. One advantage of the hierarchical control structure was the ability to avoid the collinearity issue when the degrees of freedom excited in the double panel system was less than the number of control channels. In this instance, the hierarchical structure exhibited less spillover than a fully adaptive LQOCT controller.Ph. D

Journal of the Acoustical Society of America

A multi-degree of freedom control approach, which is largely inspired by biological systems, is presented. Control inputs to a structure are achieved by multiple piezoelectric actuators. One actuator chosen as the ''master'' actuator is under the direction of the central, sophisticated controller. The other ''slave'' actuators derive their control inputs by localized, simple learning rules related to the behavior of their neighbor actuators including the ''master.'' Simulations on the control of the vibrational energy density of a harmonically excited simply supported beam demonstrate a significant improvement in control performance over a single actuator case, particularly for off-resonance frequencies. Thus high attenuations are achieved with a multiple degree of freedom actuator with a single main channel of control.Langley Research CenterUnited States. Office of Naval Researc

The association between a history of anxiety or depression and utilization of diagnostic imaging

Objective While prior research shows that mental illness is associated with lower utilization of screening imaging, little is known about how mental illness impacts use of diagnostic imaging, other than for screening. This study explores the association between a history of anxiety or depression in the prior year and utilization of diagnostic imaging. Methods Commercial and Medicare Advantage health plan claims from 2017 and 2018 from patients with plans from one national organization were extracted. Exclusions were made for patients without continuous plan enrollment. History of anxiety or depression was determined using 2017 claims, and downstream diagnostic imaging was determined using 2018 claims. Univariate associations were assessed with Chi-square tests. A matched sample was created using Coarsened Exact Matching, with history of mental illness serving as the treatment variable. Logistic regressions were used to calculate adjusted odds ratios, before and after matching, controlling for age, sex, urbanicity, local income, comorbidities, claims history, region, and health plan characteristics. Associations between mental illness and chest imaging, neuroimaging, and emergency department imaging were also evaluated. Results The sample included 2,381,851 patients before matching. Imaging was significantly more likely for patients with a history of anxiety (71.1% vs. 55.7%, P &lt; .001) and depression (73.2% vs. 55.3%, P &lt; .001). The adjusted odds of any imaging were 1.24 (95% confidence interval [CI]: 1.22–1.26) for patients with a history of anxiety, and 1.43 (CI: 1.41–1.45) for patients with a history of depression before matching, and 1.18 (CI: 1.16–1.20) for a history of anxiety and 1.33 (CI: 1.32–1.35) for a history of depression after matching. Adjusted analyses found significant, positive associations between mental illness and chest imaging, neuroimaging, and emergency department imaging both before and after matching. Discussion In contrast to prior findings on screening, anxiety and depression were associated with greater likelihood of diagnostic imaging within the population studied. </jats:sec

The association between a history of anxiety or depression and utilization of diagnostic imaging.

ObjectiveWhile prior research shows that mental illness is associated with lower utilization of screening imaging, little is known about how mental illness impacts use of diagnostic imaging, other than for screening. This study explores the association between a history of anxiety or depression in the prior year and utilization of diagnostic imaging.MethodsCommercial and Medicare Advantage health plan claims from 2017 and 2018 from patients with plans from one national organization were extracted. Exclusions were made for patients without continuous plan enrollment. History of anxiety or depression was determined using 2017 claims, and downstream diagnostic imaging was determined using 2018 claims. Univariate associations were assessed with Chi-square tests. A matched sample was created using Coarsened Exact Matching, with history of mental illness serving as the treatment variable. Logistic regressions were used to calculate adjusted odds ratios, before and after matching, controlling for age, sex, urbanicity, local income, comorbidities, claims history, region, and health plan characteristics. Associations between mental illness and chest imaging, neuroimaging, and emergency department imaging were also evaluated.ResultsThe sample included 2,381,851 patients before matching. Imaging was significantly more likely for patients with a history of anxiety (71.1% vs. 55.7%, P DiscussionIn contrast to prior findings on screening, anxiety and depression were associated with greater likelihood of diagnostic imaging within the population studied