Abstract not available

A measurement system has been developed for use on a light aircraft to measure the pressure distribution over the wing surfaces. The measurement system was developed as a low-cost alternative to existing advanced measurement systems. The system consisted of low profile, low cost pressure sensors that interfaced digitally with microcontrollers for data acquisition. The pressure sensors and microcontrollers were developed into self-contained sensor modules with all electronic components mounted on flexible circuit board that formed the base of the modules. Two types of module were developed; a module with a single pressure sensor and a module with a row of seven pressure sensors at fifteen millimetre spacing. The total cost of the sensor modules was approximately ninety dollars for a single sensor module and one hundred and forty dollars for the seven sensor module. Studies were carried out using numerical methods to predict the pressure distribution over a NACA2412 airfoil. The numerical studies were used to evaluate the effect of adding the sensor modules to the wing, and the effect of the sensor distribution on measured force coefficients. Numerical predictions were made using the XFOIL software package. This software was validated using the Hess-Smith inviscid panel method. Flight testing was carried out with the pressure distribution measurement system to confirm the operation of the system and to make preliminary measurements. The flight testing focused on the measurement of steady state pressure distributions for comparison with the numerical predictions. Good agreement was found between the measured pressure distributions and the XFOIL predictions. Integration of the pressure distributions enabled comparison of normal force, lift force and quarter chord moment coefficients. The measured force coefficients showed the expected trends with angle of attack although it was found that the limited number of sensor modules used caused large error in the quarter chord moment coefficient compared to the numerical predictions.

<p>The pressure-density relationship and the pressure distribution inside the compression chamber of a newly designed New Holland BB960 large square baler were studied for the baling of alfalfa, whole green barley, barley straw, and wheat straw. An analytical model was developed for the pressure distribution inside the compression chamber of the large square baler in the x-, y-, and z-directions by assuming isotropic linear elastic properties for forage materials. In order to validate this model, a tri-axial sensor was designed and used to measure the forces inside the compression chamber when whole green barley, barley straw, and wheat straw were baled. The experimental results proved that the developed analytical model for each of the tested forage materials had a good correlation with the experimental data with a reasonable coefficient of determination (0.95) and standard error (20.0 kPa). Test data were also used to develop an empirical model for the pressure distribution inside the compression chamber of the baler for each of the tested forage materials using least square method in regression analysis. These empirical models were simple equations which were only functions of the distance from the full extension point of the plunger along the compression chamber length.</p><p>Analytical and empirical models were also developed for the pressure-density relationship of the baler for baling alfalfa and barley straw. Results showed that bale density initially decreased with distance from the plunger, and then remained almost constant up to the end of the compression chamber. The developed empirical model for both alfalfa and barley straw was a combination of a quadratic and an exponential equation. In order to validate the developed models, field tests were performed by baling alfalfa and barley straw of different moisture contents, flake sizes, and load settings. The forces on the plunger arms were recorded by a data acquisition system. The actual bale bulk density was calculated by measuring the bale dimensions and weight. Results showed that both load setting and flake size had a significant effect on the plunger force. The plunger force increased with increased load setting and flake size. Comparing analytical and empirical models for bale density as a function of the pressure on the plunger showed that the trend of variation of density with pressure in both models was similar, but the rate of change was different. The variation rate of density with pressure in the analytical model was higher than that of the empirical model. The analytical model underestimated the bale density at low plunger pressures but showed more accurate prediction at higher pressures, while the empirical model accurately predicted the bale density at both low and high pressures. Some crop properties such as coefficient of friction and modulus of elasticity were determined for the development of the pressure distribution model. Results showed that static coefficient of friction of alfalfa on a polished steel surface was a quadratic function of material moisture content, while the relationship between the coefficient of friction of barley straw on a polished steel surface and material moisture content was best expressed by a linear equation. Results of this study also proved that modulus of elasticity of alfalfa and barley straw was constant for the density range encountered in the large square baler.</p>

<p>The pressure-density relationship and the pressure distribution inside the compression chamber of a newly designed New Holland BB960 large square baler were studied for the baling of alfalfa, whole green barley, barley straw, and wheat straw. An analytical model was developed for the pressure distribution inside the compression chamber of the large square baler in the x-, y-, and z-directions by assuming isotropic linear elastic properties for forage materials. In order to validate this model, a tri-axial sensor was designed and used to measure the forces inside the compression chamber when whole green barley, barley straw, and wheat straw were baled. The experimental results proved that the developed analytical model for each of the tested forage materials had a good correlation with the experimental data with a reasonable coefficient of determination (0.95) and standard error (20.0 kPa). Test data were also used to develop an empirical model for the pressure distribution inside the compression chamber of the baler for each of the tested forage materials using least square method in regression analysis. These empirical models were simple equations which were only functions of the distance from the full extension point of the plunger along the compression chamber length.</p><p>Analytical and empirical models were also developed for the pressure-density relationship of the baler for baling alfalfa and barley straw. Results showed that bale density initially decreased with distance from the plunger, and then remained almost constant up to the end of the compression chamber. The developed empirical model for both alfalfa and barley straw was a combination of a quadratic and an exponential equation. In order to validate the developed models, field tests were performed by baling alfalfa and barley straw of different moisture contents, flake sizes, and load settings. The forces on the plunger arms were recorded by a data acquisition system. The actual bale bulk density was calculated by measuring the bale dimensions and weight. Results showed that both load setting and flake size had a significant effect on the plunger force. The plunger force increased with increased load setting and flake size. Comparing analytical and empirical models for bale density as a function of the pressure on the plunger showed that the trend of variation of density with pressure in both models was similar, but the rate of change was different. The variation rate of density with pressure in the analytical model was higher than that of the empirical model. The analytical model underestimated the bale density at low plunger pressures but showed more accurate prediction at higher pressures, while the empirical model accurately predicted the bale density at both low and high pressures. Some crop properties such as coefficient of friction and modulus of elasticity were determined for the development of the pressure distribution model. Results showed that static coefficient of friction of alfalfa on a polished steel surface was a quadratic function of material moisture content, while the relationship between the coefficient of friction of barley straw on a polished steel surface and material moisture content was best expressed by a linear equation. Results of this study also proved that modulus of elasticity of alfalfa and barley straw was constant for the density range encountered in the large square baler.</p>

Thesis (M. Soc. Sc.)--University of Hong Kong, 1987.

The aim of this study was to investigate the dynamic collapse of composite shells in a constant external pressure water environment that is representative of a naval underwater structure. Laminated carbon/epoxy composite shells with diameters of 1.735 in., wall thickness of 0.041 in, length-to-diameter ratios ranging for 2.8 to 12 and [55/-55/(90)3/-55/55] layup were collapsed in a custom pressure testing facility that provided a constant pressure water environment. Buckling was sudden, dynamic, led to failure and fragmentation of the shells; the whole event lasted only a couple of ms. The dynamic collapse of the shells was recorded using high-speed digital imaging and dynamic pressure sensors synchronized with the camera were used to monitor the emanating pressure waves. All shells buckled in mode 2 at pressure levels predicted by models adopted. Collapse led to a localization zone in the central section of the shells, approximately spanning on a 4D length for the longer ones, and shorter for the shorter shells. A single axial crack developed in the collapsing section, which propagated 2 to 4 diameters depending on the length of the specimen. The axial crack was located on the extrados for long shells, and on the intrados for shorter ones. Helical cracks initiated from the tips of the axial crack, propagated outwards, and were responsible for the collapse and fragmentation of the two outer sections. The receding walls of the central localizing zone caused a dynamic drop in pressure that lasted until the inward motion was arrested by contact. This was followed by a sharp, short duration positive pressure pulse associated with an outward expansion wave. The pressure pulse varied to some degree around the circumference with the highest peak occurring opposite the initial crack. The final result of such dynamic events was catastrophic failure and fragmentation of the shell into small shreds. / text

published_or_final_version / Public Administration / Master / Master of Public Administration

No description available.

The purpose of the study was to examine psychological and methodological factors which would predict the white coat effect (WCE). The WCE is defined as the difference (mm Hg) between ambulatory and office measured blood pressure (BP). Sixty three community volunteers participated in this study. Participants were divided into 3 Response style groups: (1) Office responders had ambulatory BP values which were lower than office BP, (2) Non responders showed a minimal difference between office and ambulatory BP, and (3) Home responders had significantly higher ambulatory BP compared to office BP. Participants were asked to have a series of BP readings taken by a physician, nurse and by themselves and participate in 24 hour ambulatory monitoring. State and trait self-report psychological measures were completed. Self measured BP was the most representative of ambulatory BP for the sample as a whole, and in particular for the Home responders. State anxiety, previously dismissed as mediating factor in the expression of the white coat effect, proved to discriminate between the groups. Office responders had significantly higher levels of state anxiety, directly related to BP measurements, compared to Home and Non responders. Habituation to the experience of having BP measured by a physician, and habituation of the anxiety prior to the BP measurement, was different among the three groups. Trait psychological variables did not distinguish group membership. Self measured systolic BP, state anxiety prior to self measured BP, habituation to physician measured BP and the anxiety preceding it, were entered as predictors variables in a discriminant function analyses. These variables were able to correctly classify group membership for 63% of the sample.

Thesis (M.S.)--University of Michigan, 1965.