Evaluation of accelerated bridge construction methods and designs in the state of Iowa

Accelerated bridge construction (ABC) is the general term given to a variety of approaches aimed at reducing construction durations of bridge projects. Using these approaches on bridge projects introduces a number of advantages including reduced traffic disruption and increased safety. This thesis is comprised of two papers that focus on a number of ABC projects completed in the state of Iowa in the last decade. The first paper highlights the construction aspects of these projects and gives an evaluation of the projects based on criteria related to rapid construction and gives a comparison of the project cost to non-ABC projects. A road user cost analysis is also presented to demonstrate the cost benefit of decreased traffic disruption. The paper closes with a collection of lessons learned from the projects and a look into the future of ABC technologies. The second paper focuses on the design of accelerated bridge projects and the progression of the bridge elements and connection details over time. The paper includes an evaluation of the design of these bridges

Factors affecting the distribution of procurement awards for external analysis and management services.

Results of the analysis indicate that not-for-profit organizations suffer competitive disadvantages because of low levels of awareness, willingness, or ability. Statistical tests indicate that these competitive disadvantages are most likely to be observed in the "best-and-final" stage of the competition.Thus, even though the relative amounts within categories of nonexclusionary procurement methods awarded to for-profit and not-for-profit organizations will continue to be a function of behavioral and economic factors, political decisions will establish the parameters by which these behavioral and economic factors will affect the distribution of awards. The conclusion is that these political decisions discriminate against not-for-profit organizations in being eligible to participate in the procurement process and will continue to do so in the future in the absence of radical form.In addition to suffering competitive disadvantages when competition actually occurs, not-for-profit organizations are increasingly being excluded from the competitive process. The combined influence of small business set-asides and other exclusionary procurement methods for small business concerns has reduced the degree of competition substantially in the recent past between for-profit and not-for-profit organizations and will do so even more in the future. Taken to its extreme, this policy will have the effect of reducing not-for-profit participation in the procurement process to negligible proportions.This study is an analysis of factors affecting the distribution of contract (i.e., procurement) awards for "external analysis and management services"--management analysis, economic analysis, policy analysis, social research, management support, and the design, operation, and evaluation of social programs. The primary interests are: (1) the distribution of awards between for-profit and not-for-profit organizations, and (2) the impact upon this distribution of policies adopted by the Congress or the bureaucracy which have the effect of reducing the ability of one organizational type vis-a-vis another to compete effectively. The analysis utilizes data from a sample of contracts awarded by the U.S. Department of Housing and Urban Development (HUD) that indicate characteristics of the recipient organization, and to a lesser extent, characteristics of all organizations competing for awards

The Planet Nine Hypothesis

Over the course of the past two decades, observational surveys have unveiled the intricate orbital structure of the Kuiper Belt, a field of icy bodies orbiting the Sun beyond Neptune. In addition to a host of readily-predictable orbital behavior, the emerging census of trans-Neptunian objects displays dynamical phenomena that cannot be accounted for by interactions with the known eight-planet solar system alone. Specifically, explanations for the observed physical clustering of orbits with semi-major axes in excess of $\sim250\,$AU, the detachment of perihelia of select Kuiper belt objects from Neptune, as well as the dynamical origin of highly inclined/retrograde long-period orbits remain elusive within the context of the classical view of the solar system. This newly outlined dynamical architecture of the distant solar system points to the existence of a new planet with mass of $m_9\sim 5-10\,M_{\oplus}$, residing on a moderately inclined orbit ($i_9\sim15-25\deg$) with semi-major axis $a_9\sim 400 - 800\,$AU and eccentricity between $e_9 \sim 0.2 - 0.5$. This paper reviews the observational motivation, dynamical constraints, and prospects for detection of this proposed object known as Planet Nine.Comment: 92 pages, 28 figures, published in Physics Report

Employees, Firm Size and Profitability of U.S. Manufacturing Industries

We examine the relation between firm size and profitability within 109 SIC four-digit manufacturing industries. Depending on our measure of profitability, we find that profitability increases at a decreasing rate and eventually declines in up to 47 of our industries. No relation between profitability and size is found in up to 52 of our industries. These two categories account for 97 of our 109 industries. Profitability continues to increase as firms become larger in up to 11 industries. Hence, the relation between size and profitability is industry specific. But, regardless of the shape of the size profitability function, we find that profitability is negatively correlated with the number of employees for firms of a given size measured in terms of total assets and sales. These results are puzzling in the context of work by others who report that common stock returns are negatively correlated with size when size is measured by the market value of a company or with the work of those who argue that size is a proxy for risk. Interpreted against these works, our findings may mean that large firms earn excess returns, that small firms fail to earn their cost of capital, or that accounting returns simply behave differently than market returns with respect to firm size

The Origin of Universality in the Inner Edges of Planetary Systems

The characteristic orbital period of the inner-most objects within the galactic census of planetary and satellite systems appears to be nearly universal, with $P$ on the order of a few days. This paper presents a theoretical framework that provides a simple explanation for this phenomenon. By considering the interplay between disk accretion, magnetic field generation by convective dynamos, and Kelvin-Helmholtz contraction, we derive an expression for the magnetospheric truncation radius in astrophysical disks, and find that the corresponding orbital frequency is independent of the mass of the host body. Our analysis demonstrates that this characteristic frequency corresponds to a period of $P\sim3$ days, although intrinsic variations in system parameters are expected to introduce a factor of $\sim2-3$ spread in this result. Standard theory of orbital migration further suggests that planets should stabilize at an orbital period that exceeds disk truncation by a small margin. Cumulatively, our findings predict that the periods of close-in bodies should span $P\sim2-12$ days - a range that is consistent with observations.Comment: 9 pages, 4 figures, accepted to ApJ