First-principles perturbative computation of dielectric and Born charge tensors in finite electric fields

We present a perturbative treatment of the response properties of insulating crystals under a dc bias field, and use this to study the effects of such bias fields on the Born effective charge tensor and dielectric tensor of insulators. We start out by expanding a variational field-dependent total-energy functional with respect to the electric field within the framework of density-functional perturbation theory. The second-order term in the expansion of the total energy is then minimized with respect to the first-order wave functions, from which the Born effective charge tensor and dielectric tensor are easily computed. We demonstrate an implementation of the method and perform illustrative calculations for the III-V semiconductors AlAs and GaAs under finite bias field

Converting water adsorption and capillary condensation in useable forces with simple porous inorganic thin films

This work reports an innovative humidity driven actuation concept based on Bangham effect using simple nanoporous sol-gel silica thin films as humidity responsive materials. Bilayer shaped actuators, consisting on a humidity-sensitive active nanostructured silica film deposited on a polymeric substrate (Kapton) were demonstrated as an original mean to convert water molecule adsorption and capillary condensation in useable mechanical work. Reversible silica surface energy modifications by water adsorption and the energy produced by the rigid silica film contraction, induced by water capillary condensation in mesopores, were finely controlled and used as the energy sources. The influence of the film nanostructure (microporosity, mesoporosity) and thickness, and of the polymeric support thickness, on the actuation force, on the movement speed, and on the amplitude of displacement are clearly evidenced and discussed. We show that the global mechanical response of such silica-based actuators can be easily adjusted to fabricate a humidity variation triggered tailor-made actuation systems. This first insight in hard ceramic stimulus responsive materials may open the door toward new generation of surface chemistry driven actuation systems.Comment: 17 pages, 7 figure

Using GIS to Assess Firearm Thefts, Recoveries and Crimes in Lincoln, Nebraska

Firearm use in the United States has long been of great concern and at the center of many debates. Most research, however, has either focused on the use of firearms in violent crimes or the availability of firearms compared to the violent crime rates. Few studies have focused on the theft of firearms or the relationships between stolen firearms and crime. Using seven years of data collected Lincoln, Nebraska Police Department, this thesis focuses on the geospatial dimensions of firearm thefts and recoveries. Specific attention is given to the relationship firearm thefts and recoveries have with gun-related crimes, violent crimes, and property crimes. Statistical analyses reveal that firearm thefts and recoveries show clear patterns of clustering. Firearm thefts are significantly related to gun-related crimes and property crimes while firearm recoveries are significantly related to gun-related crimes, violent crimes, and property crimes. Findings also reveal that the majority of firearms reported stolen in Lincoln are acquired by the thief in residential neighborhoods (between 70 and 80 percent). The average theft in Lincoln regardless of gang involvement was 1.9 firearms per theft, which is significantly lower than the average for gang involvement at 6.6 firearms per theft. Subsequent spatial analyses revealed a significant southwest directional movement of firearms stolen in relation to gang activity with a large number of firearms being recovered in Phoenix, Arizona. Statistically significant relationships were discovered to exist between gun-related and property crimes. Moreover, firearm recoveries, unlike thefts, were significantly related to violent crimes in addition to gun-related and property crimes. The results have important policy implications. They suggest that a greater amount of attention should be placed on the theft of firearms and their movement away from Lincoln. They also emphasize that gun owners need to put more effort into properly securing firearms in their residences and vehicles. Advisor: James W. Merchan

Using GIS to Assess Firearm Thefts, Recoveries and Crimes in Lincoln, Nebraska

Firearm use in the United States has long been of great concern and at the center of many debates. Most research, however, has either focused on the use of firearms in violent crimes or the availability of firearms compared to the violent crime rates. Few studies have focused on the theft of firearms or the relationships between stolen firearms and crime. Using seven years of data collected Lincoln, Nebraska Police Department, this thesis focuses on the geospatial dimensions of firearm thefts and recoveries. Specific attention is given to the relationship firearm thefts and recoveries have with gun-related crimes, violent crimes, and property crimes. Statistical analyses reveal that firearm thefts and recoveries show clear patterns of clustering. Firearm thefts are significantly related to gun-related crimes and property crimes while firearm recoveries are significantly related to gun-related crimes, violent crimes, and property crimes. Findings also reveal that the majority of firearms reported stolen in Lincoln are acquired by the thief in residential neighborhoods (between 70 and 80 percent). The average theft in Lincoln regardless of gang involvement was 1.9 firearms per theft, which is significantly lower than the average for gang involvement at 6.6 firearms per theft. Subsequent spatial analyses revealed a significant southwest directional movement of firearms stolen in relation to gang activity with a large number of firearms being recovered in Phoenix, Arizona. Statistically significant relationships were discovered to exist between gun-related and property crimes. Moreover, firearm recoveries, unlike thefts, were significantly related to violent crimes in addition to gun-related and property crimes. The results have important policy implications. They suggest that a greater amount of attention should be placed on the theft of firearms and their movement away from Lincoln. They also emphasize that gun owners need to put more effort into properly securing firearms in their residences and vehicles. Advisor: James W. Merchan

Development of a system for adsorption measurements in the 77 – 500 K and 1 – 100 bar range

Adsorption is a phenomenon present in various systems important to the field of cryogenics, having a great deal of relevance in the development of vibration-free coolers: these are crucial for the cooling of sensitive detectors, as they offer the possibility of using a sorption compressor, do not have moving parts and do not induce unwanted mechanical vibrations in the system, maintaining its sensibility and greatly minimizing wear due to use. In the context of an ESA-funded project for the development of such a cooler, a study on adequate adsorption materials to use for the non-mechanical cryogenic compressor present in the final system was required. Considering this, a system for measurement of adsorption properties in the range of its operating pressures and temperatures was needed and, independently, also useful in future adsorption studies the laboratory decides to perform. A brief historical and functional review of the adsorption phenomenon, its applications in cryogenics, and available and various methods for its measurement is made. The design and assembly of an adsorption measurement system, through the volumetric (also known as manometric) method, for temperatures in the 77 K to 500 K range and pressures up to 100 bar is detailed. Proof pressure tests were made to validate the design of the vessel, with positive results. Other pre-measurement tests, such as heating and cooling assays, void and dead volume measurements, empty-vessel measurements, were all carried out with an intention to validate and characterize the developed system. A LabVIEWTM interface for the control and automatic acquisition of the system parameters was developed and tested throughout the whole process. Results were taken using a sample of HKUST-1 (also known as Cu3(BTC)2 or BasoliteTM C300) and compared against the results from another group, as well as a partner laboratory, from both their theoretical simulations and their commercial gravimetric system

Single-layer economic model predictive control for periodic operation

In this paper we consider periodic optimal operation of constrained periodic linear systems. We propose an economic model predictive controller based on a single layer that unites dynamic real time optimization and control. The proposed controller guarantees closed-loop convergence to the optimal periodic trajectory that minimizes the average operation cost for a given economic criterion. A priori calculation of the optimal trajectory is not required and if the economic cost function is changed, recursive feasibility and convergence to the new periodic optimal trajectory is guaranteed. The results are demonstrated with two simulation examples, a four tank system, and a simplified model of a section of Barcelona's water distribution network.Peer ReviewedPostprint (author’s final draft

The Impact of Civilian Aggravating Factors on the Military Death Penalty (1984-2005): Another Chapter in the Resistance of the Armed Forces to the Civilianization of Military Justice

In 1984, the U.S. Armed Forces amended its capital punishment system for death eligible murder to bring it into compliance with Furman v. Georgia. Those amendments were modeled after death penalty legislation prevailing in over thirty states. After a brief period between 1986 and 1990, the charging decisions of commanders and the conviction and sentencing decisions of court martial members (jurors) transformed the military death penalty system into a dual system that treats two classes of death eligible murder quite differently. Since 1990, a member of the armed forces accused of a killing a commissioned officer or murder with a direct impact on the ability of military commanders to run an effective and disciplined military is significantly more likely to face a capital court martial and be sentenced to death than a similarly situated member accused of a murder connected to the military only fry the identity of the accused. This empirical study of charging and sentencing decisions in 104 death eligible military murders from 1984-2005 documents contemporary resistance to the civilianization of the military death penalty as manifest in charging and sentencing decisions. We conclude that a limitation of death eligible murder to those directly impacting military command and control could reduce the risk of arbitrariness in the administration of the military death penalty