Non-linear generation of acoustic noise in the IAR spacecraft

The requirement to produce high level acoustic noise fields with increasing accuracy in environmental test facilities dictates that a more precise understanding is required of the factors controlling nonlinear noise generation. Details are given of various nonlinear effects found in acoustic performance data taken from the IAR Spacecraft Acoustic Chamber. This type of data has enabled the IAR to test large spacecraft to relatively tight acoustic tolerances over a wide frequency range using manually set controls. An analog random noise automatic control system was available and modified to provide automatic selection of the chamber's spectral sound pressure levels. The automatic control system when used to complete a typical qualification test appeared to equal the accuracy of the manual system and had the added advantage that parallel spectra could be easily achieved during preset tests

A bibliography and survey of the vortex tube

A comprehensive bibliography of vortex tube publications is given together with a brief survey of the development of the vortex tube between 1931 and 1953

A note on the application of the vortex tube to ventilated suits

The vortex tube has no moving parts and its makes it an attractive form of refrigerator when a source of compressed air is available. The drawback is that this device has a low efficiency. The proposed application involves passing compressed air, from a jet engine, through a precooler and a vortex tube to the ventilated suit. Investigations show that the temperature of the air entering the ventilated suit is decreased as engine compression ratio and precooler efficiency are increased. Increase of the aircraft's forward speed will result in decreased cooling until a maxim= Mach number is reached above which the ventilated suit cooling requirement, of 115o F, can no longer be satisfied. The maximum permissible Mach number, for an aircraft flying at sea level under the maximum ambient tropical temperature of 45°C, has been calculated over a range of compression ratios, 3 - 15 and precooler efficiencies, 75 - 100 per cent. These results are plotted in figures 6 and 7. It is found that a practical application requires a precooler efficiency of not less than. 80. per cent

Vortex tube performance data sheets

Experiments to determine the effect of various operating and design parameters on the performance of a vortex tube are described in College of Aeronautics Note No. 30. The present note gives additional performance data on this tube and should be used as a supplement to Note No.30. These data sheets are intended as an aid to the estimation of the performance of vortex tubes and to the design of vortex tubes with given characteristics. In particular, the present note provides the optimum values of the vortex tube parameters which give maximum temperature drops. Figures 12-53 give temperature drop and cold mass flow ratio characteristics, figures 54-61 give the cold mass flow ratios at maximum temperature drop whilst figures 62-65 give the optimum inlet and cold outlet sizes for maximum temperature drop

On some aspects of the noise propagation from supersonic aircraft

The noise problem associated with an aircraft flying at supersonic speeds is shown to depend primarily on the shock wave pattern formed by the aircraft. The noise intensity received by a ground observer from a supersonic aircraft flying at high as well as low altitudes, is shown to be high although it is of a transient nature. Continues

Forested Wetland Mitigation: Developing Techniques to Restore Northern White-Cedar on Clay Settling Areas in Northern Michigan

When permitted activities degrade or destroy wetlands, mitigation is required by both state and federal laws (Michigan Environment, Great Lakes & Energy (EGLE) and Section 404 of the Clean Water Act). Forested wetlands are considered keystone ecosystems, but restoration of these systems is often limited by the environmental complexities and the slow growth of the long-lived tree species. Using a combination of greenhouse and field experiments, my research goal was to develop techniques to create northern white-cedar (Thuja occidentalis L.) forested wetlands in reclaimed/abandoned mining quarries. There are numerous environmental stressors in the inorganic sediments of reclaimed quarries including high moisture retention, low porosity, and lack of nutrients. I tested using soil amendments in full factorial treatments using: fertilizer (F), arbuscular mycorrhizae (AM), and organic matter. In addition to the soil amendment experiments, I also tested how seedling survival was influenced by soil moisture. Our results show that soil moisture had the greatest influence on survival in both the greenhouse and field trials. The addition of organic matter and AM improved seedling survival and growth while fertilizer decreased survival. My research indicates that the addition of organic matter and planting at the right water table levels are the best techniques to create forested wetlands in quarry sediments

Creativity and the measurement subclinical psychopathology in the general population: schizotypy, psychoticism, and hypomania

The aims of the study were to investigate the roles of well-known psychopathology measures in predicting creativity, to assess the concepts of a multitrait and single trait understanding, and to evaluate the role of latent measures of hypomania predicting creativity. Following the completion of a battery of questionnaires 203 participants completed 2 creative cognition tasks. Multivariate multiple regression analyses revealed significant effects for both schizotypy and the latent hypomania scales. Critically, these showed that some negatively (introvertive anhedonia, excitement, and social vitality) and others positively (impulsive nonconformity and mood volatility) predicted creativity. These findings suggest future avenues should evaluate the roles of mood, autonomy, and asociality in mediating the link between subclinical psychopathology and creativity. Further, research should both manipulate state and control trait mood when evaluating psychopathology and creativity

False-negative upper extremity ultrasound in the initial evaluation of patients with suspected subclavian vein thrombosis due to thoracic outlet syndrome (Paget-Schroetter syndrome)

OBJECTIVE: To assess the utilization and consequences of upper extremity Duplex ultrasound in the initial diagnostic evaluation of patients with suspected subclavian vein (SCV) thrombosis and venous thoracic outlet syndrome (VTOS). METHODS: A retrospective single-center review was conducted for patients that underwent primary surgical treatment for VTOS between 2008 and 2017, in whom an upper extremity ultrasound had been performed as the initial diagnostic test (n = 214). Clinical and treatment characteristics were compared between patients with positive and false-negative ultrasound studies. RESULTS: There were 122 men (57%) and 92 women (43%) that had presented with spontaneous idiopathic arm swelling, including 28 (13%) with proven pulmonary embolism, at a mean age of 30.7 ± 0.8 years (range 14-69). Upper extremity ultrasound had been performed 23.8 ± 12.2 days after the onset of symptoms, with confirmation of axillary-SCV thrombosis in 169 patients (79%) and negative results in 45 (21%). Of the false-negative ultrasound study reports, only 8 (18%) acknowledged limitations in visualizing the central SCV. Definitive diagnostic imaging (DDI) had been obtained by upper extremity venography in 175 (82%), computed tomography angiography in 24 (11%), and magnetic resonance angiography in 15 (7%), with 142 (66%) undergoing catheter-directed axillary-SCV thrombolysis. The mean interval between initial ultrasound and DDI was 48.9 ± 14.2 days with no significant difference between groups, but patients with a positive ultrasound were more likely to have DDI within 48 hours than those with a false-negative ultrasound (44% vs 24%; P = .02). At the time of surgical treatment, the SCV was widely patent following paraclavicular decompression and external venolysis alone in 74 patients (35%). Patch angioplasty was performed for focal SCV stenosis in 76 (36%) and bypass graft reconstruction for long-segment axillary-SCV occlusion in 63 (29%). Patients with false-negative initial ultrasound studies were significantly more likely to require SCV bypass reconstruction than those with a positive ultrasound (44% vs 25%; P = .02). CONCLUSIONS: Duplex ultrasound has significant limitations in the initial evaluation of patients with suspected SCV thrombosis, with false-negative results in 21% of patients with proven VTOS. This is rarely acknowledged in ultrasound reports, but false-negative ultrasound studies have the potential to delay definitive imaging, thrombolysis, and further treatment for VTOS. Initial false-negative ultrasound results are associated with progressive thrombus extension and a more frequent need for SCV bypass reconstruction at the time of surgical treatment