Various large-area growth methods for two-dimensional transition metal dichalcogenides have been developed recently for future electronic and photonic applications. However, they have not yet been employed for synthesizing active pixel image sensors. Here, we report on an active pixel image sensor array with a bilayer MoS2 film prepared via a two-step large-area growth method. The active pixel of image sensor is composed of 2D MoS2 switching transistors and 2D MoS2 phototransistors. The maximum photoresponsivity (Rph) of the bilayer MoS2 phototransistors in an 8 × 8 active pixel image sensor array is statistically measured as high as 119.16 A W−1. With the aid of computational modeling, we find that the main mechanism for the high Rph of the bilayer MoS2 phototransistor is a photo-gating effect by the holes trapped at subgap states. The image-sensing characteristics of the bilayer MoS2 active pixel image sensor array are successfully investigated using light stencil projection.
Abstract-In this paper we study how to reduce energy consumption in large-scale sensor networks which systematically sample a spatio-temporal field. We begin by formulating a distributed compression problem subject to aggregation (energy) costs to a single sink. We show that the optimal solution is greedy and based on ordering sensors according to their aggregation costs-typically related to proximity-and, perhaps surprisingly, it is independent of the distribution of data sources. Next we consider a simplified hierarchical model for a sensor network including multiple sinks, compressors/aggregation nodes and sensors. Using a reasonable metric for energy cost, we show that the optimal organization of devices is associated with a Johnson-Mehl tessellation induced by their locations. Drawing on techniques from stochastic geometry, we analyze the energy savings that optimal hierarchies provide relative to previously proposed organizations based on proximity, i.e., associated Voronoi tessellations. Our analysis and simulations show that an optimal organization of aggregation/compression can yield 8-28% energy savings depending on the compression ratio.
Purpose: To evaluate current patient demographics and surgical outcomes from a large series of 733 surgically treated orbital fractures from an ophthalmologist’s perspective. Methods: We reviewed the medical records of 733 patients with orbital fracture, who were treated surgically by one of the authors at Gil Hospital, Gachon University, from May 2000 until September 2007. Data regarding patient demographics, signs and symptoms at presentation, cause of injury, nature of fracture, associated ocular and nonocular injury, surgical outcome and complications were collected. Results: Male patients outnumbered female patients, and blowout fracture occurred most frequently between the ages of 20 and 29 years (mean age 30.7 years). Violent assault was the leading cause of the fractures, followed by fall/slip and traffic accidents. Common signs and symptoms were periorbital ecchymosis, ocular motility restriction, diplopia and enophthalmos. In the pediatric group, diplopia and ocular motility restriction were the most common. Subconjunctival hemorrhage, hyphema and commotio retinae were the most commonly associated ocular injuries. As for the location of fractures, medial wall fractures were the most common, followed by fractures of the inferior wall, and both medial and inferior walls, in order. The most common type of fracture was the ‘comminuted’ one. In the pediatric group, the percentage of trapdoor-type fracture was higher than in the adult group. Forty-four percent of the patients had diplopia preoperatively and 8.7% postoperatively. The average measurement of difference in the enophthalmos (≧2 mm) patient population was improved from 2.62 (±SD 0.9) to 1.73 (±SD 1.3) after surgery. Ocular motility restriction was preoperatively noted in 297 patients (40.5%), and only 18 patients (2.5%) showed restriction after surgery. Conclusion: Young male individuals are at the highest risk for orbital fractures. There are marked differences in the clinical symptomatology and findings between pediatric and adult orbital fractures. Diplopia, enophthalmos and ocular motility restriction improved by repair of fracture.
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