Automated Classification of Transient Contamination in Stationary Acoustic Data

An automated procedure for the classification of transient contamination of stationary acoustic data is proposed and analyzed. The procedure requires the assumption that the stationary acoustic data of interest can be modeled as a band-limited, Gaussian random process. It also requires that the transient contamination be of higher variance than the acoustic data of interest. When these assumptions are satisfied, it is a blind separation procedure, aside from the initial input specifying how to subdivide the time series of interest. No a priori threshold criterion is required. Simulation results show that for a sufficient number of blocks, the method performs well, as long as the occasional false positive or false negative is acceptable. The effectiveness of the procedure is demonstrated with an application to experimental wind tunnel acoustic test data which are contaminated by hydrodynamic gusts

Space vehicle propulsion systems: Environmental space hazards

The hazards that exist in geolunar space which may degrade, disrupt, or terminate the performance of space-based LOX/LH2 rocket engines are evaluated. Accordingly, a summary of the open literature pertaining to the geolunar space hazards is provided. Approximately 350 citations and about 200 documents and abstracts were reviewed; the documents selected give current and quantitative detail. The methodology was to categorize the various space hazards in relation to their importance in specified regions of geolunar space. Additionally, the effect of the various space hazards in relation to spacecraft and their systems were investigated. It was found that further investigation of the literature would be required to assess the effects of these hazards on propulsion systems per se; in particular, possible degrading effects on exterior nozzle structure, directional gimbals, and internal combustion chamber integrity and geometry

Assessment of Unsteady Propagation Characteristics and Corrections in Aeroacoustic Wind Tunnels Using an Acoustic Pulse

Two types of aeroacoustic wind tunnel test section configurations have been tested in the NASA Langley Quiet Flow Facility. The first is a more traditional open-jet configuration, where test section flow passes unbounded through the facility anechoic chamber. The second is the more recent Kevlar wall configuration, where a tensioned Kevlar sheet bounds the test section flow from the facility anechoic chamber. For both configurations, acoustic instrumentation is in the surrounding quiescent space. Both configurations are evaluated with a laser-based pulsed acoustic source, which provides unique capability for assessing the facility unsteady acoustic propagation characteristics. Metrics based on the wander and spread of the pulses are evaluated and show that measurements using Kevlar walls experience dramatically reduced unsteady effects when compared to the open-jet configuration. This leads to a corresponding improvement in coherence between microphones with the Kevlar configuration. Corrections for magnitude and phase for propagation through Kevlar as compared to open-jet propagation are calculated. While limitations in the experimental setup make quantitative analysis difficult, qualitative analysis shows Kevlar magnitude corrections similar to those determined in previous literature. Directivity effects beyond those already present for open-jet configurations are minimal. Phase corrections relative to open-jet configurations are indeterminate within the limitations of the experiment, though data suggest such corrections are not extreme. The background noise produced by the Kevlar is found to be its one drawback when compared with the open-jet configuration, showing significantly greater levels at high frequencies

The Influence of Continuity of Nursing Care in the Acute Care Setting on Readiness for Discharge and Post-Discharge Return to Hospital

Background: Promoting continuity of nursing care has the potential to increase patient readiness for discharge, which has been associated with fewer readmissions and emergency department (ED) visits. The few studies that have examined nursing continuity during acute care hospitalizations did not focus on discharge or post-discharge outcomes.Objectives: The aim of this research study was to examine the association of continuity in nurse assignment to patients prior to hospital discharge with return to hospital (readmission and ED/Observation visits), including exploration of the mediating pathway through patient readiness for discharge and moderation effects of unit environment and unit nurse characteristics.Methods: In a sample of 18,203 adult, medical-surgical patients from 33 Magnet hospitals participating in a randomized clinical trial evaluating implementation of discharge readiness assessments, regression analysis with simultaneous equation modeling was used to evaluate the impact of nurse continuity on readmissions and ED/Observation visits within 30 days after hospital discharge and the mediating pathway through discharge readiness measured by patient self-report and nurse assessments. Moderating effects of unit environment and nursing characteristics were examined across quartiles of unit environment (nurse staffing hours per patient day) and unit nurse characteristics (education and experience). Analyses were adjusted for patient characteristics, hospital fixed effects, and clustering at the hospital level.Results: Continuous nurse assignment on the last 2 days of hospitalization was observed in 6,441 (35.4%) patient discharges and was associated with a 0.85 absolute percentage point (95% CI [-0.0166, -0.0004], p\u3c0.05) reduction (7.8% relative reduction) in readmissions. There was no significant association with ED/Observation visits. Sensitivity analysis revealed a stronger effect in patients with higher Elixhauser Comorbidity Indexes. Readiness for discharge was not a mediator of the effect of continuity on return to hospital. Unit characteristics were not associated with nursing continuity. No moderation effect was evident for unit environment and nurse characteristics. Discussion: Continuity of nurse assignment on the last 2 days of hospitalization can reduce readmissions. Staffing for continuity may benefit patients and health care systems, with greater benefits for high comorbidity patients. Nurse continuity should be a priority consideration in assigning acute care nurses to augment readmission reduction efforts

Electromagnetic Sensor Arrays— Experimental Studies

The objectives of this research program are to develop the theoretical models, design methodology, and technology needed for the optimum application of near-field electromagnetic sensor arrays in NDE and robot control. A basic requirement for this work is to be able to analyze and control the spatial-frequency content in the field configuration generated by the array. To aid in understanding how best to satisfy this requirement, initial efforts at SRI have focused on obtaining experimental measurements of the relative spatial distributions associated with the responses of eddy-current reflection probes to surface steps and surface-breaking rectangular slots in aluminum plates. This paper presents the results obtained using a commercial reflection probe (Nortec SPO-2065) and an SRI-constructed five-coil, air-core reflection probe to interrogate such surface discontinuities. The data obtained with the five-coil probe are then compared with the results of a theory for the spatial response of such a probe that has been developed at Stanford University [1]

Analysis of Turnability for a Three Terminal Microwave Network

Three-terminal microwave networks can be shown to exhibit qualities that would make them desirable to be used as multiple terminal devices. Using microwave theory, where instantaneous voltage is a function of position on the line, this situation will be examined. These devices use the interference principle of propagating waves as the basis of their characteristics. This investigation will probe a three- terminal microwave network with one input and two output. This configuration acts similar to a splitter where the outputs may be controlled. These three terminals, plus manipulation of the lengths of each side, actually makes this a four terminal device, much like a transistor with one source, one gate, and two drains. The three terminal network will be examined in a situation such that the lengths of two of the sides will be varied and the wavelength will be held constant. The power of the signal at each of the output terminals, along with reflected power will be recorded. By using a case where the total length of the ring is an integer number of wavelengths, two cases of behavior arise. One case exhibits qualities much like the Aharanov-Bohm effect. The other case has tendencies to reflect most of the incoming signal, except near equal length sides

Microwave NDE of Ceramics

The objective of this work is to evaluate the potential of microwave techniques for detecting, classifying, and determining the dimensions of inclusions and surface cracks in structural ceramics such as Si3N4. Experimental results that show the feasibility of detecting various types of inclusions and voids in Si3N4 have been obtained, and these results are reviewed. In addition, the question of the quantitative capability of microwave NDE for this application is discussed