Shape optimization of pressure gradient microphones

Recently developed finite element computer programs were utilized to investigate the influence of the shape of a body on its scattering field with the aim of determining the optimal shape for a Pressure Gradient Microphone (PGM). Circular cylinders of various aspect ratios were evaluated to choose the length to diameter ratio best suited for a dual element PGM application. Alterations of the basic cylindrical shape by rounding the edges and recessing at the centerline were also studied. It was found that for a + or - 1 db deviation from a linear pressure gradient response, a circular cylinder of aspect ratio near 0.5 was most suitable, yielding a useful upper frequency corresponding to ka = 1.8. The maximum increase in this upper frequency limit obtained through a number of shape alterations was only about 20 percent. An initial experimental evaluation of a single element cylindrical PGM of aspect ratio 0.18 utilizing a piezoresistive type sensor was also performed and is compared to the analytical results

Effects of nozzle design on the noise from supersonic jets

The aeroacoustic supersonic performance of various internal nozzle geometries is evaluated for shock noise content over a wide range of nozzle pressure ratios. The noise emission of a Mach 1.5 and 2.0 convergent-divergent (C-D) nozzle is measured and compared to convergent nozzles. Comparisons are also made for a Mach 1.5 conical C-D nozzle and a porous plug nozzle. The Mach 1.5 conical C-D nozzle shows a small reduction in shock noise relative to the shock free case of the Mach 1.5 C-D nozzle. The Mach 1.5 C-D nozzle is found to have a wide operating nozzle pressure ratio range around its design point where shock noise remains unimportant compared to the jet mixing noise component. However it is found that the Mach 2 C-D nozzle shows no significant acoustic benefit relative to the convergent nozzle. Results from the porous plug nozzle indicate that shock noise may be completely eliminated, and the jet mixing noise reduced

Measurements of Mean Static Pressure and Far Field Acoustics of Shock Containing Supersonic Jets

The far field acoustic data base generated in studies of broadband shock noise from supersonic jets is presented. Both conical and contoured nozzles of exit Mach numbers 1.0, 1.5, and 2.0 were tested using unheated air at pressure ratios ranging from 1.9 to 14. Tests were performed both with and without screech suppression tabs. Overall sound pressure variations and representative 1/3-octave and narrowband spectra are presented. The mean static pressure measured within these jets is also surveyed

Air ambulance flights in northern Norway 2002-2008. Increased number of secondary fixed wing (FW) operations and more use of rotor wing (RW) transports

Air ambulance service in Norway has been upgraded during the last years. European regulations concerning pilots’ working time and new treatment guidelines/strategies have called for more resources. The objective was to describe and analyse the two supplementary air ambulance [fixed wing (FW) and rotor wing (RW)] alternatives’ activity during the study period (2002-2008). Furthermore we aimed to compare our findings with reports from other north European regions. This is a retrospective analysis. The air ambulance fleet’s activity according to the electronic patient record database of “Luftambulansetjenesten ANS” (LABAS) was analysed. The subject was the fleet’s operations in northern Norway, logistics, and patients handled. Type of flight, distances, frequency, and patients served were the main outcome measures. A significant increase (45%) in the use of RW and a shift in FW operations (less primary and more secondary) were revealed. The shift in FW operations reflected the centralisation of several health care services [i.e. percutaneous cardiac intervention (PCI), trauma, and cancer surgery] during the study period. Cardiovascular disease (CVD) and injuries were the main diagnoses and constituted half of all operations. CVD was the most common cause of FW operations and injuries of the RW ones. The number of air ambulance operations was 16 per 1,000 inhabitants. This was more frequent than in other north European regions. The use of air ambulances and especially RW was significantly increased during the study period. The change in secondary FW operations reflected centralisation of medical care. When health care services are centralised, air ambulance services must be adjusted to the new settings

Caffeine increases strength and power performance in resistance‐trained females during early follicular phase

The effects of 4 mg·kg‐1caffeine ingestion on strength and power were investigated for the first time, in resistance‐trained females during the early follicular phase utilizing a randomized, double‐blind, placebo‐controlled, crossover design. Fifteen females (29.8±4.0 years, 63.8±5.5 kg [mean±SD]) ingested caffeine or placebo 60 minutes before completing a test battery separated by 72 hours. One‐repetition maximum (1RM), repetitions to failure (RTF) at 60% of 1RM, were assessed in the squat and bench press. Maximal voluntary contraction torque (MVC) and rate of force development (RFD) were measured during isometric knee‐extensions, while utilizing interpolated twitch technique to measure voluntary muscle activation. Maximal power and jump height were assessed during countermovement jumps (CMJ). Caffeine metabolites were measured in plasma. Adverse effects were registered after each trial. Caffeine significantly improved squat (4.5±1.9%, effect size [ES]: 0.25) and bench press 1RM (3.3±1.4%, ES: 0.20), and squat (15.9±17.9%, ES: 0.31) and bench press RTF (9.8±13.6%, ES: 0.31), compared to placebo. MVC torque (4.6±7.3%, ES: 0.26), CMJ height (7.6±4.0%, ES: 0.50) and power (3.8±2.2%, ES: 0.24) were also significantly increased with caffeine. There were no differences in RFD or muscle activation. Plasma [caffeine] was significantly increased throughout the protocol and mild side‐effects of caffeine were experienced by only 3 participants. This study demonstrated that 4 mg·kg‐1 caffeine ingestion enhanced maximal strength, power and muscular endurance in resistance‐trained and caffeine‐habituated females during the early follicular phase, with few adverse effects. Female strength and power athletes may consider using this dose pre‐competition and ‐training as an effective ergogenic aid

Mathematical Modelling and Simulation of Magnetostrictive Materials by Comsol Multiphysics

Abstract: This paper presents the mathematical modeling for the analysis of the magnetostrictive materials, which describes the behaviour of the magnetomechanical coupling in a rod of magnetostrictive material and capturing it on Comsol© to have a predictive and detailed analysis. The simulation about the behaviour under harmonic excitation is done in this work

Air ambulance services in the Arctic 1999-2009 : a Norwegian study.

Air ambulance services in the Arctic have to deal with remote locations, long distances, rough weather conditions and seasonable darkness. Despite these challenges, the people living in the area expect a high quality of specialist health care. The objective of this study was to analyse the air ambulance operations performed in the Norwegian Arctic and study variations in diagnoses and flight patterns around the year. A retrospective analysis. All air ambulance operations performed during the time 1999 – 2009 period were analysed. The subjects were patients transported and flights performed. The primary outcome measures were patients’ diagnoses and task patterns around the year. A total of 345 patients were transported and 321 flights performed. Coronary heart and vascular disease, bone fractures and infections were the most common diagnoses. Most patients (85%) had NACA score 3 or 4. Half of all fractures occurred in April and August. Most patients were males (66%), and one fourth was not Norwegian. The median flying time (one way) was 3 h 33 m. Ten percent of the flights were delayed, and only 14% were performed between midnight and 8.00 AM. The period April to August was the busiest one (58% of operations). Norway has run a safe air ambulance service in the Arctic for the last 11 years. In the future more shipping and polar adventure operations may influence the need for air ambulances, especially during summer and autumn

Microscopic Structure of the Calcium Isotopes

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440