Further analysis of the effects of baffles on combustion instability

A computerized analytical model, developed to predict the effects of baffles on combustion instability, was modified in an effort to improve the ability to properly predict stability effects. The model was modified: (1) to replace a single spatially-averaged response factor by separate values for each baffle compartment; (2) to calculate the axial component of the acoustic energy flux, and (3) to permit analysis of traveling waves in a thin annular chamber. Allowance for separate average response factors in each baffle compartment was found to significantly affect the predicted results. With this modification, an optimum baffle length was predicted which gave maximum stability

Analysis of the effects of baffles on combustion instability

An analytical model has been developed for predicting the effects of baffles on combustion instability. This model has been developed by coupling an acoustic analysis of the wave motion within baffled chambers with a model for the oscillatory combustion response of a propellant droplet developed by Heidmann. A computer program was developed for numerical solution of the resultant coupled equations. Diagnostic calculations were made to determine the reasons for the improper prediction. These calculations showed that the chosen method of representing the combustion response was a very poor approximation. At the end of the program, attempts were made to minimize this effect but the model still improperly predicts the stability trends. Therefore, it is recommended that additional analysis be done with an improved approximation

Analysis of combustion instability in liquid propellant engines with or without acoustic cavities

Analytical studies have been made of the relative combustion stability of various propellant combinations when used with hardware configurations representative of current design practices and with or without acoustic cavities. Two combustion instability models, a Priem-type model and a modification of the Northern Research and Engineering (NREC) instability model, were used to predict the variation in engine stability with changes in operating conditions, hardware characteristics or propellant combination, exclusive of acoustic cavity effects. The NREC model was developed for turbojet engines but is applicable to liquid propellant engines. A steady-state combustion model was used to predict the needed input for the instability models. In addition, preliminary development was completed on a new model to predict the influence of an acoustic cavity with specific allowance for the effects the nozzle, steady flow and combustion

Propulsion and Space Vehicle Systems Analysis Program Tensor I, volume I Technical report no. 341

Computer program for space vehicle and propulsion systems analysi

Becoming Skilled in Doing What\u27s Appropriate: The Nonreflective Rationality of Ethical Expertise

An Interview with Hubert Dreyfus, Department of Philosophy, University of California, Berkeley

MEASURING THE IMPACT AND RELEVANCE OF FEEDBACK ON THE TREATMENT EXPERIENCE

Despite decades of research, the key components of effective psychotherapy continue to be debated. Evidence-based practice has gained prominence and there is increasing demand from managed care and other payees that specific behavioral health problems be treated with psychotherapy interventions or techniques whose efficacy is supported by research. However, research conducted over the past decade suggests that no one counseling model or intervention reliably produces superior results and that there exists common or contextual features of all counseling that are most predictive of therapeutic outcome. This study explored whether routinely administered limited participant feedback provided to therapists at an Army Substance Abuse Outpatient Treatment Program improved treatment outcomes for participants who provided feedback on their functioning at weekly intervals using the 4-item Outcome Rating Scale (ORS). Subjects were 300 active-duty male and female soldiers randomized into a feedback group (N = 150) and a control group (N = 150). Eighteen Department of the Army civilian therapists participated by providing group psychotherapy to the participants.The study design intentionally did not proscribe therapists' behavior; the only change in the regular treatment process was therapists' knowledge of weekly progress graphs derived from ORS results for participants in the feedback condition. As predicted, participants whose therapists received weekly feedback showed both better treatment attendance and treatment outcomes than did participants where feedback was not provided to therapists. The results suggest that instead of limiting measurement of treatment outcome to the end of treatment (traditional efficacy studies), therapists' access to systematic feedback from the client's perspective of the treatment experience throughout the treatment experience can have a significant positive influence on the course of treatment itself. Results further emphasize the need for additional outcome-based research

Scanning Electron Microscopy of the Surface of Human Duodenum in Patients With and Without Duodenal Ulcer Disease

Endoscopic biopsy specimens of normal human duodenum from patients with duodenal ulcer disease were studied by light microscopy and by scanning electron microscopy. For scanning, the tissue was dried by the critical point-drying technique. SEM criteria for both normal and abnormal duodenal surfaces were determined. SEM evidence for the presence of tuft cells similar to those found on the surface of rat duodenum was found in both the normal and abnormal human material. Although other reports have described the favorable effects of carbenoxolone sodium treatment on duodenal ulcer disease, our SEM studies of four patients found that this treatment had no effect on the duodenal surface

Influence of Grazing on Soil Microbial Communities on a Mixed Grass Prairie Ecosystem

The grazing of ungulates is the predominant use for much of the world\u27s semiarid rangelands. Grazing these lands can result in significant changes not only in the vegetation community but also in the soil physical, chemical and biological properties. Changes in soil physical and chemical properties and the plant community can potentially lead to changes in soil microbial communities which may have long-term ramifications for nutrient cycling and carbon (C) sequestration. The objective of this research was to ascertain the influence of three long-term grazing treatments on soil microbial communities