Scattering Computations from Canonical Geometries and Their Accuracy

An overview of the computation of electromagnetic scattering is presented. Issues of solution convergence and future work in error analysis is also discussed

Creating a Multiracial Lesson Plan

The purpose of this project is to teach students about multiracial identity issues. Multiracial populations in the U.S. continue to grow and it’s important for educators to address the needs of these students. A 5-E multiracial literature lesson plan was created for second grade that incorporates KWL and Text-to-World teaching strategies. A second grade class were read two children’s picture books, each featuring a biracial protagonist, and were asked to discuss and evaluate the content and commonalities of these stories. Students recorded what they learned in this lesson in their KWL’s. The results reveal that some students understood the problems multiracial students face, while others learned about individual aspects of the cultures represented in the stories

The relationship between upper mantle anisotropic structures beneath California, transpression, and absolute plate motions

We calculated SKS splitting parameters for the California Integrated Seismic Network. In southern California, we also estimated splitting in the upper 100 km using azimuthal anisotropy determined from surface waves. The inferred splitting from surface waves in the mantle lithosphere is small (on average < 0.2 s) compared with SKS splitting (1.5 s) and obtains a maximum value (0.5 s) in the transpressive region of the Big Bend, south of, and aligned with, the San Andreas Fault (SAF). In contrast, the SKS splitting is approximately E-W and is relatively uniform spatially either side of the Big Bend of the SAF. These differences suggest that most of the SKS splitting is generated much deeper (down to 300–400 km) than previously thought, probably in the asthenosphere. Fast directions align with absolute plate motions (APM) in northern and southeastern California but not in southwestern California. We interpret the parallelism with APM as indicating the SKS anisotropy is caused by cumulative drag of the asthenosphere by the overlying plates. The discrepancy in southwestern California arises from the diffuse boundary there compared to the north, where relative plate motion has concentrated near the SAF system. In southern California the relative motion originated offshore in the Borderlands and gradually transitioned onshore to the SAF system. This has given rise to smaller displacement across the SAF (160–180 km) compared with central and northern California (400–500 km). Thus, in southwestern California the inherited anisotropy, from prior North American APM, has not yet been overprinted by Pacific APM

Online Human-Bot Interactions: Detection, Estimation, and Characterization

Increasing evidence suggests that a growing amount of social media content is generated by autonomous entities known as social bots. In this work we present a framework to detect such entities on Twitter. We leverage more than a thousand features extracted from public data and meta-data about users: friends, tweet content and sentiment, network patterns, and activity time series. We benchmark the classification framework by using a publicly available dataset of Twitter bots. This training data is enriched by a manually annotated collection of active Twitter users that include both humans and bots of varying sophistication. Our models yield high accuracy and agreement with each other and can detect bots of different nature. Our estimates suggest that between 9% and 15% of active Twitter accounts are bots. Characterizing ties among accounts, we observe that simple bots tend to interact with bots that exhibit more human-like behaviors. Analysis of content flows reveals retweet and mention strategies adopted by bots to interact with different target groups. Using clustering analysis, we characterize several subclasses of accounts, including spammers, self promoters, and accounts that post content from connected applications.Comment: Accepted paper for ICWSM'17, 10 pages, 8 figures, 1 tabl

Micromachined submicrometer photodiode for scanning probe microscopy

Journal ArticleA submicrometer photodiode probe with a sub-50 nanometer tip radius has been developed for optical surface characterization on a nanometer scale. The nanoprobe is built to detect subwavelength optical intensity variations in the near field of an illuminated surface. The probe consists of an Al-Si Schottky diode constructed near the end of a micromachined pyramidal silicon tip. The process for batch fabrication of the nanoprobes is described. Electrical and optical characterization measurements of the nanoprobe are presented. The diode has a submicrometer optically sensitive area with a 150 fW sensitivity

Nanometer scale absorption spectroscopy by near-field photodetection optical microscopy

Journal ArticleNear-field photodetection optical microscopy (NPOM) is a fundamentally new approach to near-field optical microscopy. This scanning probe technique uses a nanometer-scale photodiode detector which absorbs optical power directly as it is scanned in the near field of an illuminated sample surface. We have applied NPOM to measure the visible absorption spectrum of dye molecules embedded in a single 300 nm polystyrene sphere. The near-field absorption spectrum is obtained by measuring the NPOM probe photocurrent while the wavelength of the illumination pump beam is scanned from 450 to 800 nm. Peaks are identified at 567, 608, and 657 nm in the near-field spectrum of the single-dyed polystyrene sphere. These peak positions are in good agreement with far-field absorption measurements performed on many dyed polystyrene spheres

Micromachined submicrometer photodiode for scanning probe microscopy

Journal ArticleA submicrometer photodiode probe with a sub-50 nanometer tip radius has been developed for optical surface characterization on a nanometer scale. The nanoprobe is built to detect subwavelength optical intensity variations in the near field of an illuminated surface. The probe consists of an Al-Si Schottky diode constructed near the end of a micromachined pyramidal silicon tip. The process for batch fabrication of the nanoprobes is described. Electrical and optical characterization measurements of the nanoprobe are presented. The diode has a submicrometer optically sensitive area with a 150 fW sensitivity