First principles analysis of lattice dynamics for Fe-based superconductors and entropically-stabilized phases

Modern ab initio calculations are becoming an essential, complementary tool to inelastic x-ray scattering studies, where x-rays are scattered inelastically to resolve meV phonons. Calculations of the inelastic structure factor for any value of Q assist in both planning the experiment and analyzing the results. Moreover, differences between the measured data and theoretical calculations help identify important new physics driving the properties of novel correlated systems. We have used such calculations to better and more efficiently measure the phonon dispersion and elastic constants of several iron pnictide superconductors. This dissertation describes calculations and measurements at room temperature in the tetragonal phase of CaFe2As2 and LaFeAsO. In both cases, spin-polarized calculations imposing the antiferromagnetic order present in the low-temperature orthorhombic phase dramatically improves the agreement between theory and experiment. This is discussed in terms of the strong antiferromagnetic correlations that are known to persist in the tetragonal phase. In addition, we discuss a relatively new approach called self-consistent ab initio lattice dynamics (SCAILD), which goes beyond the harmonic approximation to include phonon-phonon interactions and produce a temperature-dependent phonon dispersion. We used this technique to study the HCP to BCC transition in beryllium

Hazard alerting and situational awareness in advanced air transport cockpits

Advances in avionics and display technology have significantly changed the cockpit environment in current 'glass cockpit' aircraft. Recent developments in display technology, on-board processing, data storage, and datalinked communications are likely to further alter the environment in second and third generation 'glass cockpit' aircraft. The interaction of advanced cockpit technology with human cognitive performance has been a major area of activity within the MIT Aeronautical Systems Laboratory. This paper presents an overview of the MIT Advanced Cockpit Simulation Facility. Several recent research projects are briefly reviewed and the most important results are summarized

An experimental study of the effects of automation on pilot situational awareness in the datalink ATC environment

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1992.Includes bibliographical references (leaf 111).by Edward C. Hahn.M.S

Supply-Chain Synchronization: Lessons from Hyundai Motor Company

One of the challenges of supply-chain management is developing ways to effectively integrate activities across organizations on the supply chain. Hyundai Motor Company developed mechanisms to coordinate production planning and scheduling activities among supply-chain members. Hyundai Motor\u27s production-and-sales-control (P/SC) department uses regularly scheduled cross-functional meetings and scheduling policies to coordinate supply-chain activities. When implementing this process, the P/SC department overcame structural, environ mental, and behavioral problems. Although Hyundai manage ment concedes that the process is not perfect, communication among supply-chain members has improved, and the P/SC group has successfully promoted mutual understanding and respect among functional areas. The primary benefit, ultimately, is improved customer satisfaction through better integration of functional activities

Implicit Category Priming Capacity

Past research has shown that accessing a memory allows faster subsequent access to the memory activated as well as to related information (priming). There has been much research devoted to implicit category priming (unintentional priming of a category of information), but this research has not determined the number of categories that can be implicitly primed simultaneously. The goal of the present quantitative study was to address that gap. Twenty participants (ages 27-54 years, M=44 years), who volunteered through an online participant pool, were presented with 2 tasks over the Internet. A scrambled phrase task implicitly primed 5 unrelated categories and a lexical decision (LD) task measured the priming (mean time between tasks = 42 seconds). Resulting primed and unprimed LD response latency distributions were strongly, positively skewed, which obscured individual priming effects. Gaussian parameters were extracted to overcome this skew, and the distributions were created for analysis. Dunnett\u27s multiple comparisons post-hoc test following a 1-way ANOVA showed that 2 of the 5 categories remained significantly primed. Follow-up research should determine the reliability of this value. This value, and its range (to be identified in follow-up studies) would provide a means for comparing lesson efficacy and teacher performance. The results of this research also replicate previous research demonstrating long-term implicit category priming

Computational and Experimental Evaluation of Actuating Shape Memory Polymer Foams in the Context of Aneurysm Treatment

Shape memory polymer foams may be used to treat vascular aneurysms through thermal actuation of the foam from a compacted to an expanded configuration within the aneurysm structure, thereby alleviating blood pressure on the weakened aneurysm walls and reducing potential for rupture. After delivery to the aneurysm site, fiber-delivered laser light absorbed by the foam structure is converted into thermal energy, and actuation of the foam results. Introduction of nonphysiological energy into the body during foam actuation necessitates an evaluation of potential thermal damage to nearby tissue. In the present investigation, the foam is idealized as a heat-dissipating, volumetrically static object centered in a straight tube of flowing water. Velocity profiles around the heat-dissipating device are acquired experimentally with particle image velocimetry. A computational fluid dynamics package is then used to predict the experimental velocity profiles and temperature distributions by numerical solution of the Navier-Stokes and energy equations, and agreement between the computational solution and experimental results is assessed. Discussion of this assessment, as well as several preliminary procedures leading up to the creation of the heat-dissipating device and critical analysis of the methods employed, is also given. PIV and CFD are found to be in reasonable agreement with one another. Using laser-induced fluorescence as a temperature measurement modality, which is discussed in the text insofar as the technique was attempted several times and failed, together with PIV and CFD provides a formidable array of techniques exists to characterize flow around a heated device

Study of the Effects of Changing Physiological Conditions on Dielectric Properties of Breast Tissues

This paper addresses the changes in the physical characteristics (temperature and water/blood content) of breast tissue under different physiological conditions. We examined ex vivo specimens of breast tissue excised at the time of surgery to study the effects of physiological conditions on dielectric properties. We observed that the dielectric properties strongly depend on tissue physiological state. When the biological tissues undergo physiological changes, such as those due to disease or those induced by external changes such as variations in the environmental temperature, the microscopic processes deviate from their normal state and impact the overall dielectric properties. This suggests that microwave imaging might be used to monitor the physiological conditions of the body