Scaling-up quantum heat engines efficiently via shortcuts to adiabaticity

The finite-time operation of a quantum heat engine that uses a single particle as a working medium generally increases the output power at the expense of inducing friction that lowers the cycle efficiency. We propose to scale up a quantum heat engine utilizing a many-particle working medium in combination with the use of shortcuts to adiabaticity to boost the nonadiabatic performance by eliminating quantum friction and reducing the cycle time. To this end, we first analyze the finite-time thermodynamics of a quantum Otto cycle implemented with a quantum fluid confined in a time-dependent harmonic trap. We show that nonadiabatic effects can be controlled and tailored to match the adiabatic performance using a variety of shortcuts to adiabaticity. As a result, the nonadiabatic dynamics of the scaled-up many-particle quantum heat engine exhibits no friction and the cycle can be run at maximum efficiency with a tunable output power. We demonstrate our results with a working medium consisting of particles with inverse-square pairwise interactions, that includes noninteracting and hard-core bosons as limiting cases.Comment: 15 pages, 3 figures; typo in Eq. (51) fixed. Feature paper in the Special Issue "Quantum Thermodynamics" edited by Prof. Dr. Ronnie Koslof

Quantitative Analysis of a Turbulent Wind Tunnel with Obstructions for use in Liquid Flame Spread Experiments

The research was done as part of an effort to develop alternative fire suppressant technologies for aircraft engine nacelles. The turbulent shear flow behind a surface mounted fence inside an open circuit wind tunnel was investigated experimentally. The tunnel test section was designed to be 2-D and exhibit flow qualities similar to those found in a typical engine nacelle. A 279 mm wide fuel pan was inserted approximately four fence heights downstream of the fence location. The fuel pan was filled using water to simulate fuel with a depth of 32 mm. Cold flow tests were done on different fence configurations with turbulent airflow. The average turbulence intensity in the stream wise direction was 12% at the forward edge of the pan and with no fence in place. The Reynolds number was 2 x 104 in the free stream and based on a fence height of 50.8 mm. Several fences were used to simulate general types of clutter elements. The height, length, degree of perforation, and distance to the fuel pan were all fence geometries that were tested. Measurements were taken of the 2-D flow field along the centerline of the test section using Particle Image Velocimetry (PIV). A separation region with strong reverse flow was found to exist above the pan and have flow characteristics that were largely sensitive to fence dimensions. It was also found that the results for different configurations can be collapsed using the appropriate non-dimensional parameters

Physical activity affects brain integrity in HIV+ individuals

Prior research has suggested benefits of aerobic physical activity (PA) on cognition and brain volumes in HIV uninfected (HIV−) individuals, however, few studies have explored the relationships between PA and brain integrity (cognition and structural brain volumes) in HIV-infected (HIV +) individuals. Seventy HIV + individuals underwent neuropsychological testing, structural neuroimaging, laboratory tests, and completed a PA questionnaire, recalling participation in walking, running, and jogging activities over the last year. A PA engagement score of weekly metabolic equivalent (MET) hr of activity was calculated using a compendium of PAs. HIV + individuals were classified as physically active (any energy expended above resting expenditure, n = 22) or sedentary (n = 48). Comparisons of neuropsychological performance, grouped by executive and motor domains, and brain volumes were completed between groups. Physically active and sedentary HIV + individuals had similar demographic and laboratory values, but the active group had higher education (14.0 vs. 12.6 years, p = .034). Physically active HIV + individuals performed better on executive (p = .040, unadjusted; p = .043, adjusted) but not motor function (p = .17). In addition, among the physically active group the amount of physical activity (METs) positively correlated with executive (Pearson’s r = 0.45, p = 0.035) but not motor (r = 0.21; p = .35) performance. In adjusted analyses the physically active HIV + individuals had larger putamen volumes (p = .019). A positive relationship exists between PA and brain integrity in HIV + individuals. Results from the present study emphasize the importance to conduct longitudinal interventional investigation to determine if PA improves brain integrity in HIV + individuals

H2 molecule in strong magnetic fields

The Pauli-Hamiltonian of a molecule with fixed nuclei in a strong constant magnetic field is asymptotic, in norm-resolvent sense, to an effective Hamiltonian which has the form of a multi-particle Schr\"odinger operator with interactions given by one-dimensional \delta-potentials. We study this effective Hamiltonian in the case of the H2 -molecule and establish existence of the ground state. We also show that the inter-nuclear equilibrium distance tends to 0 as the field-strength tends to infinity

Sources of American Law: An Introduction to Legal Research

At its most basic definition the practice of law comprises conducting research to find relevant rules of law and then applying those rules to the specific set of circumstances faced by a client. However, in American law, the legal rules to be applied derive from myriad sources, complicating the process and making legal research different from other sorts of research. This text introduces first-year law students to the new kind of research required to study and to practice law. It seeks to demystify the art of legal research by following a “Source and Process” approach. First, the text introduces students to the major sources of American law and describes the forms the various authorities traditionally took in print. After establishing this base, the text proceeds to instruct students on the methods they will most likely use in practice, namely electronic research techniques and the consultation of secondary sources. Sources of Law incorporates screencasts currently hosted on YouTube that actively demonstrate the processes described in the static text. Finally, the text illustrates how the different pieces come together in the legal research process. Sources of Law focuses on realistic goals for 1Ls to learn in a relatively small amount of instruction time, and so focuses mainly on the basics. It does introduce some advanced material so that 1Ls can recognize pieces of information they may encounter in research, but it does not fully cover researching materials outside the scope of the traditional 1L course. As such, it is best-suited for introductory legal research courses for 1Ls.https://uknowledge.uky.edu/lawfac_book/1003/thumbnail.jp

Practical Experience with State-of-the-Art Technologies in SCADA Systems

A Supervisory Control and Data Acquisition (SCADA) system is a powerful tool which, when implemented properly in irrigation districts, can lead to improved water delivery service to farms, more effective operations, reduced spill (and therefore reduced diversions), and in some cases a reduction in costs (less labor, less energy, etc.). However, widespread adoption of SCADA and automation technologies remains a technical and financial challenge for most irrigation districts. In spite of many good hardware and software products available on the market now, putting all the pieces together requires specialized expertise. Nevertheless, by following some straightforward strategies and rules of good practice, combined with advanced control techniques, even very complex automation systems have been successfully implemented. These implementation steps are briefly outlined with a focus on lessons learned. Updated implementation costs for typical system components are given to aid in project planning