The implementation of nanoimprint lithography for the fabrication of patterned magnetic media

Advances in technology are having profound effects throughout society. This is no truer than in the way information is being stored. The primary form of information storage for at least the past millennium has been paper. Today, an ever increasing amount of information is being stored electronically. An increased demand for high-performance, low-cost information storage has been a major catalyst in increasing the popularity of hard drives. In 2002, two exabytes of original information was stored on hard drives. This is ten times the amount of all printed material in the world if it were converted to electronic files. To keep up with this demand, the capacity of hard drives has increased by at least 60% annually since 1991. The capacity has mainly increased by scaling down the relevant dimensions much in the same way that has been done with microprocessors. Scaling cannot indefinitely be used to increase the capacity of hard drives that employ longitudinal magnetic recording. Before long, the superparamagnetic effect will limit the achievable information capacity of hard drives using conventional recording. Therefore, new technologies will be needed. Perpendicular recording, one of several new technologies, will make its entrance into the market later this year in a hard drive designed by Toshiba for Apple\u27s iPod music player. It is said that the hard drive will have an areal bit density of 133 Gbits/in2. This is an increase of 75% over what is currently available today. However, the hard drive will still employ a continuous magnetic medium. Even greater densities can be achieved if the magnetic medium is physically patterned into isolated bits. This technology, known as patterned magnetic media, has the potential of achieving areal bit densities greater than 1 Tbit/in2. The challenge is finding a way to fabricate it. A high-throughput, low-cost pattern generation technology is needed. Research completed with nanoimprint lithography demonstrates that it can be used to fabricate patterned magnetic media. Several patterns of magnetic media were fabricated with densely packed sub-20-nm features that would produce an areal bit density of at least 258 Gbits/in2

From Caution to College: The Effects on Veterans with Self- Reported Trauma Symptoms Sharing their Experiences with the Campus Community

Over 900,000 veterans are using benefits for higher education today; the vast majority of them served in the Global War on Terrorism (GWOT). Over 25% of GWOT service members that have been treated by the Veterans Affairs (VA) are reported to have symptoms of posttraumatic stress or posttraumatic stress disorder (PTS/PTSD). PTS/PTSD negatively impacts student veterans’ abilities to navigate stressful environments such as college and university settings. The Veterans Embracing Transition (VET) Connect Program at San José State University (SJSU) is designed to connect veterans with non-veterans as peer educators. Five of the 13 VET Connect peer educators (38.5%) who were interviewed reported having symptoms of PTSD. Through their service as peer educators on and off campus, these participants demonstrated signs of healthy coping effects through sharing experiences and educating non-veterans of the struggles related to military culture, service, combat, and loss. This study was conducted in collaboration with Sophia Alcala. We worked on independent research questions and observations using data derived from the same larger study simultaneously under the supervision of Dr. Klaw

Computational polarimetric microwave imaging

We propose a polarimetric microwave imaging technique that exploits recent advances in computational imaging. We utilize a frequency-diverse cavity-backed metasurface, allowing us to demonstrate high-resolution polarimetric imaging using a single transceiver and frequency sweep over the operational microwave bandwidth. The frequency-diverse metasurface imager greatly simplifies the system architecture compared with active arrays and other conventional microwave imaging approaches. We further develop the theoretical framework for computational polarimetric imaging and validate the approach experimentally using a multi-modal leaky cavity. The scalar approximation for the interaction between the radiated waves and the target---often applied in microwave computational imaging schemes---is thus extended to retrieve the susceptibility tensors, and hence providing additional information about the targets. Computational polarimetry has relevance for existing systems in the field that extract polarimetric imagery, and particular for ground observation. A growing number of short-range microwave imaging applications can also notably benefit from computational polarimetry, particularly for imaging objects that are difficult to reconstruct when assuming scalar estimations.Comment: 17 pages, 15 figure

Coded apertures for x-ray scatter imaging

We examine coding strategies for coded aperture scatter imagers. Scatter imaging enables tomography of compact regions from snapshot measurements. We present coded aperture designs for pencil and fan beam geometries, and compare their singular value spectra with that of the Radon transform and selected volume tomography.We show that under dose constraints scatter imaging improves conditioning over alternative techniques, and that specially designed coded apertures enable snapshot 1D and 2

Computational Microwave Imaging Using 3D Printed Conductive Polymer Frequency-Diverse Metasurface Antennas

A frequency-diverse computational imaging system synthesized using three-dimensional (3D) printed frequency-diverse metasurface antennas is demonstrated. The 3D fabrication of the antennas is achieved using a combination of PolyLactic Acid (PLA) polymer material and conductive polymer material (Electrifi), circumventing the requirement for expensive and time-consuming conventional fabrication techniques, such as machine milling, photolithography and laser-etching. Using the 3D printed frequency- diverse metasurface antennas, a composite aperture is designed and simulated for imaging in the K-band frequency regime (17.5-26.5 GHz). The frequency-diverse system is capable of imaging by means of a simple frequency-sweep in an-all electronic manner, avoiding mechanical scanning and active circuit components. Using the synthesized system, microwave imaging of objects is achieved at the diffraction limit. It is also demonstrated that the conductivity of the Electrifi polymer material significantly affects the performance of the 3D printed antennas and therefore is a critical factor governing the fidelity of the reconstructed images.Comment: Original manuscript as submitted to IET Microwaves, Antennas & Propagation (2017). 17 pages, 8 figure

3D Visualization of MPDV Data

Author Institution: National Security Technologies, LLCSlides presented at the 7th Annual Photonic Doppler Velocimetry (PDV) Workshop held at Sandia National Laboratory, Albuquerque, New Mexico, October 22-23, 2012

Computational Polarimetric Microwave Imaging

We propose a polarimetric microwave imaging technique that exploits recent advances in computational imaging. We utilize a frequency-diverse cavity-backed metasurface, allowing us to demonstrate high-resolution polarimetric imaging using a single transceiver and frequency sweep over the operational microwave bandwidth. The frequency-diverse metasurface imager greatly simplifies the system architecture compared with active arrays and other conventional microwave imaging approaches. We further develop the theoretical framework for computational polarimetric imaging and validate the approach experimentally using a multi-modal leaky cavity. The scalar approximation for the interaction between the radiated waves and the target---often applied in microwave computational imaging schemes---is thus extended to retrieve the susceptibility tensors, and hence providing additional information about the targets. Computational polarimetry has relevance for existing systems in the field that extract polarimetric imagery, and particular for ground observation. A growing number of short-range microwave imaging applications can also notably benefit from computational polarimetry, particularly for imaging objects that are difficult to reconstruct when assuming scalar estimations.Comment: 17 pages, 15 figure