Heat Transfer Mechanism In Particle-Laden Turbulent Shearless Flows

Particle-laden turbulent flows are one of the complex flow regimes involved in a wide range of environmental, industrial, biomedical and aeronautical applications. Recently the interest has included also the interaction between scalars and particles, and the complex scenario which arises from the interaction of particle finite inertia, temperature transport, and momentum and heat feedback of particles on the flow leads to a multi-scale and multi-physics phenomenon which is not yet fully understood. The present work aims to investigate the fluid-particle thermal interaction in turbulent mixing under one-way and two-way coupling regimes. A recent novel numerical framework has been used to investigate the impact of suspended sub-Kolmogorov inertial particles on heat transfer within the mixing layer which develops at the interface of two regions with different temperature in an isotropic turbulent flow. Temperature has been considered a passive scalar, advected by the solenoidal velocity field, and subject to the particle thermal feedback in the two-way regime. A self-similar stage always develops where all single-point statistics of the carrier fluid and the suspended particles collapse when properly re-scaled. We quantify the effect of particle inertial, parametrized through the Stokes and thermal Stokes numbers, on the heat transfer through the Nusselt number, defined as the ratio of the heat transfer to the thermal diffusion. A scale analysis will be presented. We show how the modulation of fluid temperature gradients due to the statistical alignments of the particle velocity and the local carrier flow temperature gradient field, impacts the overall heat transfer in the two-way coupling regime

Taming and Leveraging Directionality and Blockage in Millimeter Wave Communications

To cope with the challenge for high-rate data transmission, Millimeter Wave(mmWave) is one potential solution. The short wavelength unlatched the era of directional mobile communication. The semi-optical communication requires revolutionary thinking. To assist the research and evaluate various algorithms, we build a motion-sensitive mmWave testbed with two degrees of freedom for environmental sensing and general wireless communication.The first part of this thesis contains two approaches to maintain the connection in mmWave mobile communication. The first one seeks to solve the beam tracking problem using motion sensor within the mobile device. A tracking algorithm is given and integrated into the tracking protocol. Detailed experiments and numerical simulations compared several compensation schemes with optical benchmark and demonstrated the efficiency of overhead reduction. The second strategy attempts to mitigate intermittent connections during roaming is multi-connectivity. Taking advantage of properties of rateless erasure code, a fountain code type multi-connectivity mechanism is proposed to increase the link reliability with simplified backhaul mechanism. The simulation demonstrates the efficiency and robustness of our system design with a multi-link channel record.The second topic in this thesis explores various techniques in blockage mitigation. A fast hear-beat like channel with heavy blockage loss is identified in the mmWave Unmanned Aerial Vehicle (UAV) communication experiment due to the propeller blockage. These blockage patterns are detected through Holm\u27s procedure as a problem of multi-time series edge detection. To reduce the blockage effect, an adaptive modulation and coding scheme is designed. The simulation results show that it could greatly improve the throughput given appropriately predicted patterns. The last but not the least, the blockage of directional communication also appears as a blessing because the geometrical information and blockage event of ancillary signal paths can be utilized to predict the blockage timing for the current transmission path. A geometrical model and prediction algorithm are derived to resolve the blockage time and initiate active handovers. An experiment provides solid proof of multi-paths properties and the numeral simulation demonstrates the efficiency of the proposed algorithm

Ordered Merkle Tree a Versatile Data-Structure for Security Kernels

Hidden undesired functionality is an unavoidable reality in any complex hardware or software component. Undesired functionality — deliberately introduced Trojan horses or accidentally introduced bugs — in any component of a system can be exploited by attackers to exert control over the system. This poses a serious security risk to systems — especially in the ever growing number of systems based on networks of computers. The approach adopted in this dissertation to secure systems seeks immunity from hidden functionality. Specifcally, if a minimal trusted computing base (TCB) for any system can be identifed, and if we can eliminate hidden functionality in the TCB, all desired assurances regarding the operation of the system can be guaranteed. More specifcally, the desired assurances are guaranteed even if undesired functionality may exist in every component of the system outside the TCB. A broad goal of this dissertation is to characterize the TCB for various systems as a set of functions executed by a trusted security kernel. Some constraints are deliberately imposed on the security kernel functionality to reduce the risk of hidden functionality inside the security kernel. In the security model adopted in this dissertation, any system is seen as an interconnection of subsystems, where each subsystem is associated with a security kernel. The security kernel for a subsystem performs only the bare minimal tasks required to assure the integrity of the tasks performed by the subsystem. Even while the security kernel functionality may be different for each system/subsystem, it is essential to identify reusable components of the functionality that are suitable for a wide range of systems. The contribution of the research is a versatile data-structure — Ordered Merkle Tree (OMT), which can act as the reusable component of various security kernels. The utility of OMT is illustrated by designing security kernels for subsystems participating in, 1) a remote fle storage system, 2) a generic content distribution system, 3) generic look-up servers, 4) mobile ad-hoc networks and 5) the Internet’s routing infrastructure based on the border gateway protocol (BGP)

Essays in Public and Nonprofit Financial Management

There are three primary goals of financial management: to help a firm weather environmental turbulence, to allow a firm to grow, and to make safe revenue choices to keep a firm operational. What is often disregarded in this discussion is organizational context. In this dissertation, I argue that we cannot manage finances in all organizations the same way. Organizational context matters for money management. Specifically, by organizational context I mean if a firm is a public, for-profit, or nonprofit entity. Organizational context shapes the winners and losers in resource distribution and hence fundamentally alters key expectations from various financial management tools and techniques. To demonstrate this, I address three questions related to each aspect of financial management. First, can fiscal slack help buffer budget shocks in public organizations? Second, does financial performance motivate risk taking in nonprofit, for innovation and growth? Finally, can revenue sourcing strategies affect key outcomes in decentralized public organizations? I use twenty years of data from over a thousand public school districts in Texas. I use ordinary least squares regression models with year fixed effects. First, I empirically demonstrate that fiscal slack alone cannot fully counterbalance the negative impact of 10 percent or greater budget shocks on aggregate district standardized test performance. However, districts with approximately 31.53 percent fund balance (unabsorbed fiscal slack) can reduce the negative impact of budget shocks more effectively than districts with minimum, or just 0.05 percent, fund balance. But the distinction of slack as an effective buffer in for-profits, in much less pronounced in public firms. Second, I offer a theoretical discussion of how an increase in financial performance may induce nonprofits to take more risks. This is in sharp contrast to their for-profit counterparts. Decline in financial performance is the key motivation for for-profit firms to innovate and take risks. But given the nondistribution constraint and the lack of profit motivation, when nonprofits are financially secure they would be induced to take more risk. Finally, I empirically investigate achievement gap based on income, a key outcome, in the highly decentralized US K-12 education system. Decentralization is expected to offer welfare enhancing opportunities, by allowing school policies to be tailored to small homogeneous student groups. I find that when more revenue is generated locally, more administrative decentralization can increase income-based achievement gap. Revenue source is less important in private organizations that actively seek to diversify revenue bases. These three separate conclusions together substantiate the key thesis that organizational context fundamentally alters outcomes and expectations from various money management choices in firms

2018-2019 Xavier University Undergraduate and Graduate University Catalog

https://www.exhibit.xavier.edu/coursecatalog/1269/thumbnail.jp

1996-1998 with 1997 revisions Xavier University College of Arts and Sciences, College of Business Administration, College of Social Sciences Course Catalog

https://www.exhibit.xavier.edu/coursecatalog/1139/thumbnail.jp

2017-2018 Xavier University Undergraduate and Graduate University Catalog

https://www.exhibit.xavier.edu/coursecatalog/1270/thumbnail.jp