Colossal Tunneling Electroresistance in Co-Planar Polymer Ferroelectric Tunnel Junctions

Ferroelectric tunnel junctions (FTJs) are ideal resistance-switching devices due to their deterministic behavior and operation at low voltages. However, FTJs have remained mostly as a scientific curiosity due to three critical issues: lack of rectification in their current-voltage characteristic, small tunneling electroresistance (TER) effect, and absence of a straightforward lithography-based device fabrication method that would allow for their mass production. Co-planar FTJs that are fabricated using wafer-scale adhesion lithography technique are demonstrated, and a bi-stable rectifying behavior with colossal TER approaching 106% at room temperature is exhibited. The FTJs are based on poly(vinylidenefluoride-co-trifluoroethylene) [P(VDF-TrFE)], and employ asymmetric co-planar metallic electrodes separated by &lt;20 nm. The tunneling nature of the charge transport is corroborated using Simmons direct tunneling model. The present work is the first demonstration of functional FTJs manufactured via a scalable lithography-based nano-patterning technique and could pave the way to new and exciting memory device concepts.</p

Everyday concept detection in visual lifelogs: validation, relationships and trends

The Microsoft SenseCam is a small lightweight wearable camera used to passively capture photos and other sensor readings from a user's day-to-day activities. It can capture up to 3,000 images per day, equating to almost 1 million images per year. It is used to aid memory by creating a personal multimedia lifelog, or visual recording of the wearer's life. However the sheer volume of image data captured within a visual lifelog creates a number of challenges, particularly for locating relevant content. Within this work, we explore the applicability of semantic concept detection, a method often used within video retrieval, on the novel domain of visual lifelogs. A concept detector models the correspondence between low-level visual features and high-level semantic concepts (such as indoors, outdoors, people, buildings, etc.) using supervised machine learning. By doing so it determines the probability of a concept's presence. We apply detection of 27 everyday semantic concepts on a lifelog collection composed of 257,518 SenseCam images from 5 users. The results were then evaluated on a subset of 95,907 images, to determine the precision for detection of each semantic concept. We conduct further analysis on the temporal consistency, co-occurance and trends within the detected concepts to more extensively investigate the robustness of the detectors within this novel domain. We additionally present future applications of concept detection within the domain of lifelogging

Domain-Size-Dependent Residual Stress Governs the Phase-Transition and Photoluminescence Behavior of Methylammonium Lead Iodide

Methylammonium lead iodide (MAPbI3) perovskite has garnered significant interest as a versatile material for optoelectronic applications. The temperature-dependent photoluminescence (TDPL) and phase-transition behaviors revealed in previous studies have become standard indicators of defects, stability, charge carrier dynamics, and device performance. However, published reports abound with examples of irregular photoluminescence and phase-transition phenomena that are difficult to reconcile, posing major challenges in the correlation of those properties with the actual material state or with the subsequent device performance. In this paper, a unifying explanation for the seemingly inconsistent TDPL and phase-transition (orthorhombic-to-tetragonal) characteristics observed for MAPbI3 is presented. By investigating MAPbI3 perovskites with varying crystalline states, ranging from polycrystal to highly oriented crystal as well as single-crystals, key features in the TDPL and phase-transition behaviors are identified that are related to the extent of crystal domain-size-dependent residual stress and stem from the considerable volume difference (ΔV&nbsp;≈ 4.5%) between the primitive unit cells of the orthorhombic (at 80 K) and tetragonal phases (at 300 K) of MAPbI3. This fundamental connection is essential for understanding the photophysics and material processing of soft perovskites

SePCAR: A Secure and Privacy-Enhancing Protocol for Car Access Provision

Contains fulltext : 178466.pdf (preprint version ) (Closed access) Contains fulltext : 178466.pdf (Publisher’s version ) (Open Access)nul

Graph-Theoretic Generation of Assembly Plans - Part II: Problem Decomposition and Optimization Algorithms

Efficient generation of assembly plans has significant implications on manufacturing costs, however, the underlying mathematical problem is both theoretically and computationally intractable. In the previous paper (Part I), we developed a graph-theoretic framework for the general problem, and we described a constraint satisfaction construct that generates correct assembly precedence graphs given establishment conditions. In this paper, we develop additional components for the framework: a problem decomposition scheme which decomposes a general set of establishment conditions into generalized 2-SAT problems. After mapping these satisfiability problems into specialized decision graphs, we develop a branch-and-bound algorithm which generates optimal precedence graphs and optimal assembly plans from the decision graph. Our method generates assembly precedence graph(s) which satisfy two basic criteria: (i) All sequences defined by the precedence graph are feasible according to design specif..