Interference alignment for the MIMO interference channel

We study vector space interference alignment for the MIMO interference channel with no time or frequency diversity, and no symbol extensions. We prove both necessary and sufficient conditions for alignment. In particular, we characterize the feasibility of alignment for the symmetric three-user channel where all users transmit along d dimensions, all transmitters have M antennas and all receivers have N antennas, as well as feasibility of alignment for the fully symmetric (M=N) channel with an arbitrary number of users. An implication of our results is that the total degrees of freedom available in a K-user interference channel, using only spatial diversity from the multiple antennas, is at most 2. This is in sharp contrast to the K/2 degrees of freedom shown to be possible by Cadambe and Jafar with arbitrarily large time or frequency diversity. Moving beyond the question of feasibility, we additionally discuss computation of the number of solutions using Schubert calculus in cases where there are a finite number of solutions.Comment: 16 pages, 7 figures, final submitted versio

Tidal estimation in the Pacific with application to SEASAT altimetry

The techniques for computing the eigenfunctions of the velocity potential (Proudman functions) set out in Sanchez, et al. (1986) in relation to the Atlantic-Indian Oceans are here applied to the Pacific Ocean, using a 6x6 degree grid of 510 points (455 points for the associated stream functions). Normal modes are computed from the first Proudman functions and have natural periods from 43.9h downward. Tidal syntheses are derived from these modes by direct application of the (frictionless) dynamic equations and by least-squares fitting of Proudman functions to the dynamically interpolated tide-gauge data of Schwiderski (1983). The modes contributing the most energy to the principal harmonic tidal constituents are different in the two computations: their natural periods are typically in the range of 9 to 16h for semidiurnal, and 14 to 43h for diurnal tides. The rms of fit for the Proudman functions is, in all cases, better than the corresponding value for the same number of spherical harmonics

Surviving Higher Education: Retention & Persistence Through The Lens Of Psychological Survivorship

The purpose of this interpretative phenomenological study was to examine the lived experiences of students categorized as at-risk, non-traditional adult learners who persisted in pursuit of their higher education degree. These students demonstrated perseverance and grit when faced with challenges that might have caused them to drop out of school. The lived experiences of the participants are strongly linked to their identities as working professionals and adult-learners. Recent literature indicates that several theories and models have emerged on the concept of motivation as it relates to success in higher education. Research suggests that achievement is not solely based on cognitive abilities of the learner, but rather on the combination of cognitive ability and personality traits, such as grit and deliberate practice. In the past two decades, one of the most important innovations in the US higher education system has been the steady increase in distance education through online courses. The institution in this study is experiencing a similar trend in online learning enrollment growth coupled with student retention and persistence challenges. The students in this study have demonstrated the requisite grit and perseverance to succeed even in the face of adversity. Students in this study also exhibited a strong internal locus of control and all had strong support structures outside of their educational orbit

Tidal Prediction and Modern Time Scales

Modern time scales introduced since about 1950 and revised formulae for the mean lunar and solar longitudes are defined and compared with the formulae of Newcomb (1895) and Brown (1919), which still form the basis of current tide prediction practice. Changes in tidal arguments of order 0°.02 are identified, with a tendency to increase towards the 21st century. Small changes in potential amplitude and speed of some leading harmonic constituents from AD 1900 to 2000 are also noted. While all changes are small by tidal standards, it is recommended that the modern formulae be adopted by tidal authorities before discrepancies become noticeable. The modern formulae require at least an approximate correction for the difference between Dynamic or Ephemeris Time and Civil or Universal Time, which will probably exceed 1 minute before AD 2000

A Field Guide to Adaptation

Abstract: A Field Guide to Adaptation is a collection of satiric and elegiac poems, prose poems, and hybrid image/text poems, which explores various types of memory (personal, historical, cultural, and political), and human processes of memory (construction, interpretation, commodification, and loss)

Examining the Legal Consciousness of Residence Life Staff

Understanding the law has become an integral part of the work of higher education professionals, especially residence life staff. For decades, courts have contributed an increasingly important role in shaping the litigious nature of society at large and within higher education (Greenleaf, 1982). Barr and Associates (1988) noted the increasingly major influence of the law on campus life. Even in the mid-1990s, Gehring and Penney (1995) highlighted the critical need to understand legal issues for those professionals entering the field of higher education and student affairs. Since Olivas (2013) found that higher education law is a rapidly changing area in the field, knowledge of the law is critical to anyone in a professional position in higher education. [Discussion questions developed by Amelia King-Kostelac.

Towards a Java Subtyping Operad

The subtyping relation in Java exhibits self-similarity. The self-similarity in Java subtyping is interesting and intricate due to the existence of wildcard types and, accordingly, the existence of three subtyping rules for generic types: covariant subtyping, contravariant subtyping and invariant subtyping. Supporting bounded type variables also adds to the complexity of the subtyping relation in Java and in other generic nominally-typed OO languages such as C# and Scala. In this paper we explore defining an operad to model the construction of the subtyping relation in Java and in similar generic nominally-typed OO programming languages. Operads, from category theory, are frequently used to model self-similar phenomena. The Java subtyping operad, we hope, will shed more light on understanding the type systems of generic nominally-typed OO languages.Comment: 13 page

Hepatitis C virus screening practices and seropositivity among US veterans born during 1945 - 1965.

BACKGROUND: The Centers for Disease Control and Prevention (CDC) and the United States Preventive Services Task Force (USPSTF) recently augmented risk-based hepatitis C (HCV) screening guidelines with a recommendation to perform one-time screening in all persons born during 1945 - 1965, a birth cohort known to have a higher prevalence of HCV. We sought to estimate the proportion of veterans seen at the Atlanta VA Medical Center (AVAMC) who had ever been screened for HCV infection by birth year. METHODS: We used an administrative database of all veterans seen at the AVAMC between January 1, 2011 and December 31, 2011, and a laboratory generated list of all HCV antibody tests and HCV RNA viral loads that were performed at the AVAMC to determine receipt of screening and HCV antibody positivity. Odds ratios and 95% confidence intervals were estimated using SAS version 9.2 (SAS institute, Cary, North Carolina). RESULTS: HCV antibody testing had ever been performed on 48% (41,556) of the veterans seen in 2011; 10% of those tested had a positive antibody. Confirmatory viral loads were performed in 96% of those with a positive antibody screen. Those born during 1945 - 1965 were more likely to have a HCV antibody performed when compared with those born in other years (54% vs. 41%, odds ratio [OR] 1.70, 95% Confidence Interval [CI] 1.65-1.74). Among veterans ever tested for HCV antibody (n = 41,556), those born during 1945 - 1965 were 6 times more likely to have a positive HCV antibody (15% vs. 3%, OR 5.87, 95% CI 5.32-6.78), and 3 times more likely to have chronic HCV infection (76% vs. 50%, OR 3.25, 95% CI 2.65-4.00). CONCLUSIONS: Nearly half of the veterans seen in 2011 at the AVAMC had ever been tested for HCV infection. When examined by birth cohort, over half of the veterans born during 1945 - 1965 had been screened for HCV and 15% of those screened had a positive HCV antibody. Our findings confirm the increased prevalence of HCV infection in persons born during 1945 - 1965 as identified in the updated CDC and USPSTF recommendations

Factors affecting the performance of the Zn-Ce redox flow battery

The Hull Cell was used to investigate the impact of current density j on the morphology and uniformity of zinc electrodeposited from a 2.5 mol dm−3 Zn2+ solution in 1.5 mol dm−3 methanesulfonic acid at 40◦C onto carbon-composite surfaces. The range of the applied deposition current density used was between1 mA cm−2 and 100 mA cm−2. Good, robust deposits were obtained when j ≥ 10 mA cm2 whereas at j’s lower than this, patchy films formed due to the competing hydrogen evolution reaction (HER) on the bare carbon-composite surface. An understanding of these effects and its application in the redox flow battery enabled both the coulombic and cell potential efficiencies to be maintained at relatively high values, 90% and 69% respectively, indicating a successful inhibition of the HER on the fully formed Zn layer. Flow velocity at the low Reynolds number in the cell (Re <200) had little impact on the electrochemical cell performance. Depletion of the cerium species became an issue for long charge times