The Search for Stem Cell in Human Breast Milk

Ph.DDOCTOR OF PHILOSOPH

Wideband propagation measurement system using spread spectrum signaling and TDRS

In this paper, a wideband propagation measurement system, which consisted of a ground-based transmitter, a mobile receiver, and a data acquisition system, was constructed. This system has been employed in a study of the characteristics of different propagation environments, such as urban, suburban and rural areas, by using a pseudonoise spreading sequence transmitted over NASA's Tracking and Data Relay Satellite System. The hardware and software tests showed that it met overall system requirements and it was very robust during a 3-month-long outdoor data collection experiment

Channel fading for mobile satellite communications using spread spectrum signaling and TDRSS

This paper will present some preliminary results from a propagation experiment which employed NASA's TDRSS and an 8 MHz chip rate spread spectrum signal. Channel fade statistics were measured and analyzed in 21 representative geographical locations covering urban/suburban, open plain, and forested areas. Cumulative distribution Functions (CDF's) of 12 individual locations are presented and classified based on location. Representative CDF's from each of these three types of terrain are summarized. These results are discussed, and the fade depths exceeded 10 percent of the time in three types of environments are tabulated. The spread spectrum fade statistics for tree-lined roads are compared with the Empirical Roadside Shadowing Model

Advanced S-Band studies using the TDRSS communications satellite

This report will describe the design, implementation, and results of a propagation experiment which used TDRSS to transmit spread signals at S-Band to an instrumented mobile receiver. The results consist of fade measurements and distribution functions in 21 environments across the Continental United States (CONUS). From these distribution functions, some idea may be gained about what system designers should expect for excess path loss in many mobile environments. Some of these results may be compared against similar measurements made with narrowband beacon measurements. Such comparisons provide insight into what gains the spread signaling system may or may not have in multipath and shadowing environments

Mass Reconstruction of Galaxy-scale Strong Gravitational Lenses Using a Broken Power-law Model

With mock strong gravitational lensing images, we investigate the performance of the broken power-law (BPL) model proposed by \citet{2020ApJ...892...62D} on the mass reconstruction of galaxy-scale lenses. An end-to-end test is carried out, including the creation of mock strong lensing images, the subtraction of lens light, and the reconstruction of lensed images, where the lenses are selected from the galaxies in the Illustris-1 simulation. We notice that, regardless of the adopted mass models (the BPL model or its special cases), the Einstein radius can be robustly determined from imaging data alone, and the median bias is typically less than $1\%$. Away from the Einstein radius, the lens mass distribution tends to be harder to measure, especially at radii where there are no lensed images detected. We find that, with rigid priors, the BPL model can clearly outperform the single power-law models by achieving $<5\%$ median bias on the radial convergence profile within the Einstein radius. As for the source light reconstructions, they are found to be sensitive to both lens light contamination and lens mass models, where the BPL model with rigid priors still performs best when there is no lens light contamination. We show that, by correcting for the projection effect, the BPL model can estimate the aperture and luminosity weighted line-of-sight velocity dispersions to an accuracy of $\sim6\%$ scatter. These results highlight the great potential of the BPL model in strong lensing related studies.Comment: Accepted for publication in ApJ, 24 pages, 13 figures, 2 table