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Optical analogues have been suggested as a means to explore systems that are described by general relativity. We show an optical analogue of the Schrödinger-Newton equation applied to the specific study of rotating boson stars.
This work investigates the efficacy of “coplanar shielding,” in which copper shields are oriented concentric and coplanar to the RF coils rather than implemented as a full ground plane behind them. Following FDTD simulations to determine optimal shielding parameters, two coil geometries were constructed: a circular loop surface coil and a half-volume five-element receive array. Each was evaluated...
The simulated studies showing the effect of DC bias lines on an aperture coupled reconfigurable pixelated patch antenna for CLAS applications is presented. The simulations show significant deterioration in S11 and gain for all operating modes when copper bias wires are introduced. A solution utilizing very high sheet resistance bias lines in place of copper traces is proposed.
Colleges and universities in the U. S. spend anaverage of $1.10 per square foot (ft2) on electricity and 18ȼ/ft2 onnatural gas annually. In a typical college or university classroombuilding, lighting represents 31 percent and space heatingaccounts for 28 percent of total energy use, making those systemsthe best targets for energy savings [1]. This study utilizes fiveyears of data enlisting...
Water is required for the survival and development of all life but needs significant amounts of energy to access, treat and transport the resource for utilization. Rising population growth has increased water demand, resulting in increased stress on our limited water and energy sources. A systems approach is necessary to address this challenge and to develop an alternative solution that fully integrates...
We describe a project to develop new medium-energy gamma-ray instrumentation by constructing and flying a balloon-borne Compton telescope using advanced scintillator materials combined with silicon photomultiplier readouts. There is a need in high-energy astronomy for a medium-energy gamma-ray mission covering the energy range from approximately 0.4–20 MeV to follow the success of the COMPTEL instrument...
Multi-channel receivers are commonplace in MRI, but very few of these receivers are capable of operating over a broad enough bandwidth to accommodate nuclei other than 1H. While this is fine for imaging, the recent surge in interest in in vivo NMR has created a need for receive arrays to improve the often-poor sensitivity of other nuclei. However, the development of these arrays has been slowed by...
The field of computing is rapidly developing, requiring a strong and diverse labor force. The current work assessed the relationship between Lesbian, Gay, Bisexual, Transgender, and Queer (LGBTQ) students' sense of belonging in computing and thoughts about leaving the field. The results of two studies indicated that among undergraduate students (Study 1) and graduate students (Study 2), thoughts about...
NMR is a widely used technique for analysising the structure of matter, however the signals produced can be of very poor quality even with the averaging of hundreds or thousands of individual scans. It has therefore become common practice to use a restoration algorithm to improve the signal and remove degradation effects such as line broadening or blurring caused by the NMR instrument itself. The...
In early 2013, Marshall Space Flight Center's upper management chartered a diverse team for a six-week “sprint” to speculate (in a disciplined manner) and paint (with broad brush strokes) a picture of how earth, space, and public/private entities might be operating and relating to each other… in the year 2100. Two 12-person groups of civil servants, one with members having 15 years or less of NASA...
We study the nonlinear interaction between two non-collinear light beams that carry orbital angular momentum (OAM). Theory and experiments highlight the presence of new phase matching conditions in the presence of OAM.
We trap and rotate particles using a perfect vortex beam with integer or fractional topological charges. A linear relationship is observed between the rotation speed and orbital angular momentum content of the beam.
Understanding of Plasma Surface Interactions (PSI) and the selection of suitable plasma facing materials are critical areas for current tokamak experiments and future D-T burning facilities including ITER and FNSF. In support of PSI studies, DIII-D uses the Divertor Materials Evaluation System (DiMES), which contains a removable probe where material samples can be exposed to as few as a single well-characterized...
Higher strength main magnets and more demanding pulse sequences have driven interest in parallel excitation systems. Parallel transmit array coils need to be decoupled to be used effectively. Ultra-low output impedance power amplifiers have been proposed as a possible solution for this. They provide decoupling in a manner analogous to low input impedance preamplifiers. Chu et al suggest a tuning method...
Parallel transmit technology for magnetic resonance imaging can mitigate the challenges with the transmit field (B1) inhomogeneity and capture the increased signal-to-noise ratio benefit at high field strengths. Most of the available parallel transmit systems use conventional amplifier architectures with array coils that employ complex decoupling methods to isolate the individual elements. Current...
Bloch-Siegert B1 mapping for multiple-channel parallel excitation systems usually produces noisy estimates in low intensity regions. Methods that use linear combinations of multiple coils have been proposed to mitigate this problem. However, little work has been done to optimize these coil combinations to improve the signal-to-noise ratio of B1 mapping in a robust way. In this paper, we propose a...
MANETS are used in a variety of applications today ranging from military communications networks to emergency response team networks. Their dynamic network topology is one of the greatest strength in employing MANETS, but invites many opportunities for cyber security attacks as computational power for these systems is always a viable resource. This paper documents a study where a MATLAB simulation...
This paper documents a performance analysis of using CUDA in MATLAB to simulate the magnetic field generated by current running through a wire using the Biot-Savart law. It was found that the number of threads executing in a CUDA kernel varies the execution time linearly and the number of threads per block should be set to a power of 2 to optimize performance during runtime.
The objective of this research is to assess the sustainability of various renewable energy technologies, ranging from small solar panels to utility-scale wind farms. While potential environmental impacts associated with these technologies are broad, the focus here is greenhouse gas (GHG) emissions and freshwater withdrawal. GHG impacts are global in nature; however, for freshwater consumption the...
Insight into brain development and organization can be gained by computing correlations between structural and functional measures in parcellated cortex. Partial correlations can often reduce ambiguity in correlation data by identifying those pairs of regions whose similarity cannot be explained by the influence of other regions with which they may both interact. Consequently a graph with edges indicating...
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