Application of imaging techniques for characterizing MPI data

The Magnetic particle inspection (MPI) method is widely used in the industry for detecting surface or near surface flaws in ferromagnetic specimens. However, the attempts to quantify the physics underlying the method have been limited. This thesis is an effort to model the behavior of the magnetic particles under the influence of magnetic leakage fields. Imaging techniques are used to recreate the dynamics of the particles prior to their reaching an equilibrium around the flaw. The proposed approach has the capability to predict the time to equilibrium of the magnetic particles. Furthermore, the efficiency of the MPI method in terms of the fraction of the total number of particles around the flaw and the signal to noise ratio of the MPI image is predicted. The overall model can be used to obtain forward transfer functions between the flaw depth; and the time to equilibrium, efficiency and signal to noise ratio of the MPI image. Optimal experimental conditions for flaws of different depths are predicted

Modeling of combustion processes of stick propellants via combined Eulerian-Lagrangian approach

This research is motivated by the improved ballistic performance of large-caliber guns using stick propellant charges. A comprehensive theoretical model for predicting the flame spreading, combustion, and grain deformation phenomena of long, unslotted stick propellants is presented. The formulation is based upon a combined Eulerian-Lagrangian approach to simulate special characteristics of the two phase combustion process in a cartridge loaded with a bundle of sticks. The model considers five separate regions consisting of the internal perforation, the solid phase, the external interstitial gas phase, and two lumped parameter regions at either end of the stick bundle. For the external gas phase region, a set of transient one-dimensional fluid-dynamic equations using the Eulerian approach is obtained; governing equations for the stick propellants are formulated using the Lagrangian approach. The motion of a representative stick is derived by considering the forces acting on the entire propellant stick. The instantaneous temperature and stress fields in the stick propellant are modeled by considering the transient axisymmetric heat conduction equation and dynamic structural analysis

WHAT ARE THE DOMESTIC AND INTERNATIONAL DRIVERS OF AL-SHABAAB’S EVOLUTION? WHICH DRIVER(S) HAVE HAD THE MOST IMPACT ON THE GROUP'S EVOLUTION?

Al-Shabaab, a Somali-based militant group, has been destabilizing the Horn of Africa region since its formal emergence in 2006. While its initial attacks focused on Somalia and weakening the transitional government, the group has evolved into a transnational threat through cross-border attacks into Kenya and Uganda. Previous scholars have analyzed both domestic and transnational factors contributing to al-Shabaab’s evolution and endurance. To further contribute to understanding how the group has remained resilient, this thesis takes a unique approach in analyzing domestic and transnational drivers separately. To understand domestic drivers, I looked at country case studies to demonstrate how al-Shabaab leverages domestic challenges. To understand transnational drivers, I evaluated al-Shabaab’s activities crossing and transcending borders and how these have contributed to its expansion. Findings included that corruption has been the foundational challenge, both domestically and transnationally, exacerbating the effects of other drivers like ineffective counterterrorism policies and porous borders. Furthermore, the analysis revealed al-Shabaab’s inconsistent opportunistic use of ideology depending on the context. Finally, from a transnational perspective, al-Shabaab’s activities outside of Somalia can be divided into global and regional spheres of effort.Lieutenant Commander, United States NavyApproved for public release. Distribution is unlimited

Successful outcome of an ovarian ectopic pregnancy

Ovarian pregnancy is rare and a conspicuous variant of ectopic pregnancy and an accurate preoperative diagnosis is very challenging various advances in diagnostic modalities like Transvaginal ultrasonography has evolved in identifying an ovarian pregnancy. We report here one such case of 30 years old with severe lower abdominal pain and bleeding per vaginum following six weeks of amenorrhea confirmed as ovarian ectopic pregnancy consistent with Speigelberg’s criteria on ultrasonography. This case highlights the significance of 3D ultrasonography in the diagnosis. Histopathological report concluded it to be an ovarian ectopic pregnancy

SCISEAL: A CFD code for analysis of fluid dynamic forces in seals

A viewgraph presentation is made of the objectives, capabilities, and test results of the computer code SCISEAL. Currently, the seal code has: a finite volume, pressure-based integration scheme; colocated variables with strong conservation approach; high-order spatial differencing, up to third-order; up to second-order temporal differencing; a comprehensive set of boundary conditions; a variety of turbulence models and surface roughness treatment; moving grid formulation for arbitrary rotor whirl; rotor dynamic coefficients calculated by the circular whirl and numerical shaker methods; and small perturbation capabilities to handle centered and eccentric seals

Fixed Or Variable Rate Choice In The Commercial Bank Business Loan Market

We study the choice available to business borrowers and lenders between fixed rate and variable rate bank loans. Unlike previous studies that examine residential mortgage loans, this analysis examines commercial and industrial loans. Business loans differ in attributes from mortgage loans and hence provide an opportunity to test determinants of the mortgage loan choice decision for other loan types. The diversity of business loans also permits tests of any effect which lender size and borrower size may have on the choice decision. Using a continuous index of preferences for the variable rate commercial loan, we find that the determinants of the business loan choice decision are different from the determinants of the mortgage loan choice decision. In contrast to prior research, we find strong evidence contradicting the proposition that variable rate loans are merely a response to high and variable interest rates. Further, this the first study to reveal size as a determinant of loan choice. Larger banks and larger borrowers have a greater preference for variable rate loans. Our results combined with the consolidation occurring among banks leads to the conclusion that the observed shift to variable rate bank loans is not transitory, and poses a significant risk for businesses with asset returns uncorrelated with short-term loan rates