Electromagnetic coupling effects on the cavity measurement of antenna efficiency

Electromagnetic coupling effects on the antenna in a conducting cavity are studied theoretically and experimentally. It is observed in experiments that at the resonant frequencies of the cavity, the input resistance of the antenna attains values two or three orders of magnitude higher than that at frequencies away from resonance. It is shown via theoretical analysis that the input resistance of the antenna measured at the resonant frequencies of the cavity is not merely the loss resistance desired in computing the antenna efficiency, but is actually the sum of the loss resistance of the antenna and the coupling resistance between the antenna and cavity. This coupling effect is demonstrated quantitatively by numerical computations for dipole and monopole antennas. The computational results for the input resistance are in agreement with the measured data. A method is proposed to avoid the cavity-antenna antiresonance in the measurement.     

Depth Sensing Using Geometrically Constrained Polarization Normals

Analyzing the polarimetric properties of reflected light is a potential source of shape information. However, it is well-known that polarimetric information contains fundamental shape ambiguities, leading to an underconstrained problem of recovering 3D geometry. To address this problem, we use additional geometric information, from coarse depth maps, to constrain the shape information from polarization cues. Our main contribution is a framework that combines surface normals from polarization (hereafter polarization normals) with an aligned depth map. The additional geometric constraints are used to mitigate physics-based artifacts, such as azimuthal ambiguity, refractive distortion and fronto-parallel signal degradation. We believe our work may have practical implications for optical engineering, demonstrating a new option for state-of-the-art 3D reconstruction.     

The spectrum of respiratory disease associated with exposure to metal working fluids

Occupational respiratory diseases have been reported following exposure to metal working fluids. We report a spectrum of respiratory illnesses occurring in an outbreak in 30 workers of an automobile parts engine manufacturing plant. Workers presented with respiratory complaints and, after clinical and laboratory evaluations, were classified as those having hypersensitivity pneumonitis, occupational asthma, or industrial bronchitis, or those without occupational lung disease. Hypersensitivity pneumonitis affected seven workers, with six exhibiting serum precipitins to Acinetobacter Iwoffii. Occupational asthma and industrial bronchitis affected 12 and six workers, respectively. Oil-mist exposures were below current recommendations. Gram-negative bacteria, but no fungi, Thermophiles, or Legionella, were identified. Although specific agents responsible for each individual case could not be identified, probably both specific sensitizing agents and non-specific irritants from metal working fluids, additives, or contaminants contributed to this spectrum of occupational respiratory illness.     

Development of A-scan ultrasound technique for measuring local particle concentration in slurry flows

The effects of solid particle concentration on hydraulic performance and wear need to be considered during the design of slurry transport equipment used in the petroleum and mining industries. The acoustic properties of slurry flows such as velocity, backscatter, and attenuation as a function of volume fraction of solid particles are examined in this study. An ultrasound A-mode imaging method is developed to obtain particle concentration in a flow of soda lime glass particles (diameter of 195 μm) and water slurry in a 0.0254 m diameter pipe. Based on the acoustic properties of the slurry, a technique is developed to measure local solid particle concentrations. The technique is used to obtain concentration profiles in homogeneous (vertical flow) and non-homogeneous (horizontal flow) slurry flows with solid particle concentrations ranging from 1 to 10% by volume using a window size of 0.159 cm. The profiles show average concentration within each window vs. distance from the transducer face. For horizontal flow, profiles are obtained for average flow velocities of 2.0, 3.0, and 3.5 m/s. The algorithm developed utilizes the power spectrum and attenuation measurements obtained from the homogeneous loop as calibration data in order to obtain concentration profiles in other (i.e. non-homogenous) flow regimes. A computational study using FLUENT is performed and a comparison is made with the experimental results. Reasonable agreement between the experimental and computational results is observed. The ultrasound technique has proven to be useful in characterizing slurry flows containing concentrations too high to be investigated using optical techniques.     

Particle sizing using particle imaging velocimetry for two-phase flows

The major factors influencing the successful measurement of particle size from Particle Imaging Velocimetry (PIV) image data are described. Components of a standard PIV system, a high resolution CCD camera and argon ion laser, are used to capture images of stationary particles. The image data are used to ascertain the limitations of estimating particle size. The effects of the Gaussian distributed intensity variation across the depth of the light sheet and the optical collection system's depth of field are investigated. These effects provide insight into designing a balanced illumination and collection optical system necessary to obtain constant particle size estimates, independent of their position within the light sheet. Using a ‘balanced’ optical set-up, monodisperse particle images are shown to be reproducible and predictable over a range of particle sizes and fields of view. Accuracy in the particle size estimates on the order of 9% are obtained consistently. It is also shown that size distributions in a mixture of polydisperse particles can be obtained with a maximum deviation of 10–20% from the true size distribution.     

MONODISPERSE DROPLET GENERATION BY SPONTANEOUS CONDENSATION OF STEAM FLOW IN NOZZLES

Spontaneous Condensation (also called homogeneous Condensation)of steam flow in one dimensional nozzle has been numerically modeled. The classical (Frenkel and Volmer) and Deich's nucleation theories were used. Unlike the classical theory, Deich's theory also accounts for the critical droplet size dependence upon the expansion rate in the nozzle. Pressure ratio, mean droplet size and droplet size distributions were obtained along the axial length for various nozzles. Comparisons with experimental data were made. The agreement between the numerical results and the experimental data was good. Both theories predicted the pressure ratio properly but the classical theory tended to underestimate the droplet sizes. Deich's theory is preferred for analyzing and designing new nozzles. The classical theory cannot be used for obtaining a correlation for surface tension ratio, thereby limiting its usage for new nozzles. Effects of Inlet conditions and nozzle expansion rates on mean droplet size and droplet size distributions were examined. The spontaneous condensation process results in relatively monodisperse droplets. The numerical model and the results are discussed in this paper.     

LDV MEASUREMENTS OF SOLID-LIQUID SLURRY FLOW USING REFRACTIVE INDEX MATCHING TECHNIQUE

A refractive index matched facility for studying solid-liquid slurry flow was developed. The refractive index matching of the solid and liquid facilitates the use of non-intrusive—laser velocimetry to measure solid and liquid velocities for slurries with solid concentrations as high as 50 percent by volume. Silica gel and sodium iodide solution in water were used us the refractive index matched solid and liquid respectively. Tests were conducted on solid liquid slurry with 5 percent solid concentration by volume in the Reynolds number range of 700 to 8000. The Reynolds number ranges for the four flow regimes, stationary bed, saltation, heterogeneous and homogeneous flow were identified. It was shown that signal processing technique utilizing histograms and signal amplitude discrimination can be used to discriminate between liquid and solid velocities. The details of the facility and the results of the tests conducted on the slurry are discussed in this paper.     

Transgenic approaches to define the functional role of dual site phospholamban phosphorylation

Phospholamban is a critical regulator of the sarcoplasmic reticulum Ca2+-ATPase activity and myocardial contractility. Phosphorylation of phospholamban occurs on both Ser16 and Thr17 during isoproterenol stimulation. To determine the physiological significance of dual site phospholamban phosphorylation, we generated transgenic models expressing either wild-type or the Ser16 --> Ala mutant phospholamban in the cardiac compartment of the phospholamban knockout mice. Transgenic lines with similar levels of mutant or wild-type phospholamban were studied in parallel. Langendorff perfusion indicated that the basal hyperdynamic cardiac function of the knockout mouse was reversed to the same extent by reinsertion of either wild-type or mutant phospholamban. However, isoproterenol stimulation was associated with much lower responses in the contractile parameters of mutant phospholamban compared with wild-type hearts. These attenuated responses were due to lack of phosphorylation of mutant phospholamban, assessed in 32P labeling perfusion experiments. The lack of phospholamban phosphorylation in vivo was not due to conversion of Ser16 to Ala, since the mutated phospholamban form could serve as substrate for the calcium-calmodulin-dependent protein kinase in vitro. These findings indicate that phosphorylation of Ser16 is a prerequisite for Thr17 phosphorylation in phospholamban, and prevention of phosphoserine formation results in attenuation of the beta-agonist stimulatory responses in the mammalian heart.     

Cardiac-specific overexpression of mouse cardiac calsequestrin is associated with depressed cardiovascular function and hypertrophy in transgenic mice

Calsequestrin is a high capacity Ca2+-binding protein in the sarcoplasmic reticulum (SR) lumen. To elucidate the functional role of calsequestrin in vivo, transgenic mice were generated that overexpressed mouse cardiac calsequestrin in the heart. Overexpression (20-fold) of calsequestrin was associated with cardiac hypertrophy and induction of a fetal gene expression program. Isolated transgenic cardiomyocytes exhibited diminished shortening fraction (46%), shortening rate (60%), and relengthening rate (60%). The Ca2+ transient amplitude was also depressed (45%), although the SR Ca2+ storage capacity was augmented, as suggested by caffeine application studies. These alterations were associated with a decrease in L-type Ca2+ current density and prolongation of this channel's inactivation kinetics without changes in Na+-Ca2+ exchanger current density. Furthermore, there were increases in protein levels of SR Ca2+-ATPase, phospholamban, and calreticulin and decreases in FKBP12, without alterations in ryanodine receptor, junctin, and triadin levels in transgenic hearts. Left ventricular function analysis in Langendorff perfused hearts and closed-chest anesthetized mice also indicated depressed rates of contraction and relaxation of transgenic hearts. These findings suggest that calsequestrin overexpression is associated with increases in SR Ca2+ capacity, but decreases in Ca2+-induced SR Ca2+ release, leading to depressed contractility in the mammalian heart.     

Void fraction and pressure drop in two phase stratified flow

A procedure for computing the void-fraction and pressure drop in two-phase stratified flow over the whole range of flows from turbulent-turbulent to laminar-laminar, has been put forth. The results are in excellent agreement with those of previous investigators in flow situations where data are available. Simple curve fits of the theoretical results have been developed to compute the required quantities, as functions of the Lockhart - Martinelli parameters.