Improving CubeSat downlink capacity with active phased array antennas

Master's Project (M.S.) University of Alaska Fairbanks, 2017Power budgets on small satellites are restricted by the limited surface area for solar panels. This limits the power available for radio communications, which constrains the downlink budget. The limited transmit power translates to low downlink data rates on small satellites. Antenna gain from directive antennas may be a power efficient way of improving the downlink budget, thereby increasing the downlink rate of small satellites. This project focuses on the design and development of a prototype low-power, electrically-steered S-band phased array RF front-end suitable for a CubeSat that could efficiently increase the EIRP, permitting higher data rates. A prototype of the array has been constructed and tested in an anechoic chamber. The four element array provides a minimum gain of 2.5 dB and average gain of 5 dB compared to a single patch antenna element with a 5W power envelope across a range of up to 60 degrees from broadside of the array

Discovery of kHz Fluctuations in Centaurus X-3: Evidence for Photon Bubble Oscillations (PBO) and Turbulence in a High Mass X-ray Binary Pulsar

We report the discovery of kHz fluctuations, including quasi-periodic oscillations (QPO) at ~330 Hz and ~760 Hz and a broadband kHz continuum in the power density spectrum of the high mass X-ray binary pulsar Centaurus X-3. These observations of Cen X-3 were carried out with the Rossi X-ray Timing Explorer (RXTE). The fluctuation spectrum is flat from mHz to a few Hz, then steepens to $f^{-2}$ behavior between a few Hz and ~100 Hz. Above a hundred Hz, the spectrum shows the QPO features, plus a flat continuum extending to ~1200 Hz and then falling out to ~1800 Hz. These results, which required the co-adding three days of observations of Cen X-3, are at least as fast as the fastest known variations in X-ray emission from an accreting compact object (kHz QPO in LMXB sources) and probably faster since extension to ~1800 Hz is indicated by the most likely parameterization of the data. Multi-dimensional radiation hydrodynamics simulations of optically thick plasma flow onto the magnetic poles of an accreting neutron star show that the fluctuations at frequencies above 100 Hz are consistent with photon bubble turbulence and oscillations (PBO) previously predicted to be observable in this source. For a polar cap opening angle of 0.25 radians, we show that the spectral form above 100 Hz is reproduced by the simulations, including the frequencies of the QPO and the relative power in the QPO and the kHz continuum. This has resulted in the first model-dependent measurement of the polar cap size of an X-ray pulsar.Comment: received ApJ: April 1, 1999 accepted ApJ: September 1, 199

Stocking Wilderness Lakes – There’s Something Fishy Going On?

The Wilderness Act of 1964 set aside lands to be managed and protected so as to preserve their natural conditions. Yet, many historically fishless lakes within designated wilderness continue to be stocked with native and non-native fish by state fish and game agencies in order to provide recreational fishing opportunities. This practice is controversial because stocking programs can compromise ecological and social values of Wilderness. Stocking is commonly accomplished without adequate cooperation and consultation between state and federal agencies. A better understanding of wilderness impacts from fish stocking, as well as improved cooperation between agencies may help balance opportunities for recreational fishing with wilderness values

Human-Centered Data Visualizations and Web Layouts for Life-Cycle Assessment Design Guides

User tests with 30 Dartmouth Engineering and STEM undergraduates were performed to investigate preferences toward a set of data visualizations and web layouts showing life-cycle assessment data and corresponding uncertainty. The data was collected and synthesized from academic papers, corporate manufacturers, and self-generated using the LCA software Sustainable Minds. A variety of visualizations were produced to accurately and aesthetically represent the data graphically, and especially understand how non-technical audiences interact with different displays of uncertainty, which is a key component of data visualization that is lacking from most LCA design guides. Web layouts were produced to present key information about the product and suggest sustainable design strategies in a digestible way end users.Ultimately, these learnings will be applied towards the creation of a free, user-friendly, online guide that provides useful recommendations for designers to reference when considering the assembly of products

An analysis of youth participation in athletics

School athletics has a significant impact on the development of youth. This study is an exploration of the differences between youth who participate in school athletics and those who do not. Specifically, the study examined youth academic performance and behavior referrals, and variables such as grade level, age, gender, and ethnicity. In addition, the study examined whether or not there was a relationship between participation in the school’s free or reduced lunch program and athletic participation. To determine the differences and relationships of youth that participate in school athletics and those who do not participate, an existing dataset of 4,078 students was used from a mid-sized Midwestern school district. The data was provided from a local nonprofit organization that gathers data from the school district and offers the data to other nonprofit organizations to measure participant outcomes. The study found that there was a significant difference between youth who participate in school athletics and those who do not based on academic performance (GPA), behavior referrals, age and grade level. The study found that there was a significant relationship between youth who participate in school athletics and those who do not based on participation in the school’s free or reduced lunch program and their ethnicity. There was no significant relationship between youth who participate in school athletics and those who do not based on gender. The results suggest that youth should be actively involved with school athletics because the findings have demonstrated to have a significant impact on the study participant’s GPA and behavior. A reason that this may occur is athletes may be held to a higher standard by their coaches because if they do not achieve a certain grade or they are misbehaving, then they may not be able to participate in athletics

Stimulus-invariant processing and spectrotemporal reverse correlation in primary auditory cortex

The spectrotemporal receptive field (STRF) provides a versatile and integrated, spectral and temporal, functional characterization of single cells in primary auditory cortex (AI). In this paper, we explore the origin of, and relationship between, different ways of measuring and analyzing an STRF. We demonstrate that STRFs measured using a spectrotemporally diverse array of broadband stimuli -- such as dynamic ripples, spectrotemporally white noise, and temporally orthogonal ripple combinations (TORCs) -- are very similar, confirming earlier findings that the STRF is a robust linear descriptor of the cell. We also present a new deterministic analysis framework that employs the Fourier series to describe the spectrotemporal modulations contained in the stimuli and responses. Additional insights into the STRF measurements, including the nature and interpretation of measurement errors, is presented using the Fourier transform, coupled to singular-value decomposition (SVD), and variability analyses including bootstrap. The results promote the utility of the STRF as a core functional descriptor of neurons in AI.Comment: 42 pages, 8 Figures; to appear in Journal of Computational Neuroscienc

Minimal Universal Extra Dimensions

Highly degenerate spectra associated with universal extra dimensions (UED) provide an interesting phenomenology not only from the point of view of cosmology and astrophysics, but also for colliders. We study these exotic signals for the simplest case, called minimal UED, where it is natural to find slow charged particles, displaced vertices, tracks with non-vanishing impact parameters, track kinks, and even vanishing charged tracks.Comment: 6 pages, 3 figures. Contributed to XXIII International Symposium on Lepton and Photon Interactions at High Energy, Aug 13-18, 2007, Daegu, Kore

Mapping a Course for Improved Student Learning: How Innovative Schools Systematically Use Student Performance Data to Guide Improvement

To be useful to teachers and school leaders, test data must provide more than just a destination. Student performance results must also provide guidance that informs educators that they are moving in the right direction, while providing interactive and recursive feedback for mid-course adjustments. In order for student performance data to be useful to teachers and school leaders, and to make it worthwhile for them to make the extensive efforts necessary to learn to interpret and act upon what they learn, data feedback systems must rely on multiple sources of data collected and analyzed at regular intervals. This report is about building better roadmaps for teachers and school leaders in order to guide their instructional decision-making. The data required for more precise decision-making come from systematically exploiting a variety of student performance data at both the individual classroom and school levels. Rather than just relying on one individual test to provide guidance, innovative school leaders are building more comprehensive systems of assessments that provide better interim information from multiple perspectives. Through more sophisticated data systems, teachers and school leaders can foster a more inquiryoriented approach that involves ongoing and sustained investigations into the kinds of teaching that produce more powerful student learning. In this report, we show how innovative teachers and school leaders are creatively using their data to help guide their strategic decisions. Through their examples, we develop and describe a theory of what a system of school data use might look like