64 research outputs found
Interfacial conduction in organic ferroelectric memory diodes
No full textSolution-processed memory diodes based on phase separated blends of ferroelectric and semiconducting polymers in the low resistance on-state operate similar to a vertical field-effect transistor at the pinch-off. Numerical simulations have shown that the performance of the diode is dominated by the conduction of charge carriers at the interface between the semiconductor and ferroelectric phases. Here, we present an unambiguous experimental demonstration of the charge injection process in the diodes. We employ a modified diode structure, wherein the electrode in contact with the semiconductor phase has been intentionally removed. Even in the absence of an electrical contact with the semiconductor phase, the diode still shows resistance switching. We provide numerical simulations that reproduce the experimentally measured I-V characteristics and therefore confirm interfacial conduction in the diodes. Furthermore, we discuss the implications of the proposed memory structure particularly in the performance of light-emitting diodes with built-in memory functionality, i.e., MEMOLEDs.Novel Aerospace Material
Role of Interface in Ferroelectric Polymer based Memory Diodes
No full textOrganic electronic devices have the potential to alter our everyday lives with their unique characteristics, such as flexibility, stretchability and low-cost. Among the envisioned devices are non-volatile memories for applications in contactless identification transponders and smart labels. This thesis investigates the operation of such a memory device that uses phase-separated blends of a ferroelectric and semiconducting polymer in a diode configuration. The blend film is composed of columns of semiconductor domains that run continuously through the ferroelectric polymer matrix from the bottom to the top electrode. Polarization of the ferroelectric polymer upon application of appropriate electric fields (greater than coercive field), leads to the modulation of the injection barrier at the metal-semiconductor contact.28 The diode exhibits a bistable rectifying current-voltage characteristic. Numerical models have been proposed to describe the device physics of the memory diodes.
This thesis provides a potential solution for ambient processing and operation of the memory diodes along with providing the experimental proof of the proposed operation mechanism of the memory diodes. Moreover, current driven memory devices have been demonstrated.
Based on tuneable injection barrier, MEMOLED, a light emitting diode with an inherent ferroelectric switch, has been demonstrated. The advantage of a built-in rectifying switch in the construction of the MEMOLED is to present a non-emissive OFF state and an emissive non-volatile ON state. However, the current efficiency is low as compared to that of pristine semiconductor polymer based OLEDs, and the retention time of the emissive state is short. Here, it is shown that charge trapping in the ferroelectric phase could be a possible reason for the lower performance of the MEMOLEDs. Finally, organic ferroelectric tunnel junctions, based on ultra-thin film of P(VDF-TrFE), with colossal tunneling electroresistance are demonstrated.viii, 90 Seite
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Using Response Generation Behaviors to Improve the Quality of Survey Data
No full textDespite their prevalent use, online surveys are vulnerable to data quality problems that may be attributed to several factors, including respondent induced measurement errors that cause discrepancies between respondent attributes and their responses. This research explores how a respondent’s response generation data manifests in their human computer interaction (HCI) device usage; and how these fine-grained HCI data may be used to identify poor-quality responses in online surveys. The larger goal of this research is to establish a structured set of guidelines to address the presence, impact, and appropriate mitigation for poor-quality survey responses. To this end, this dissertation provides a framework that utilizes individual characteristics, survey characteristics, as well as other external factors to determine one's response generation process and consequently the usefulness of that response.This dissertation establishes the prevalence of poor-quality responses in survey research and examines how behavioral differences between respondents exhibiting previously known undesirable behaviors may be used to detect poor-quality responses. ‘Essay One’ examines the presence of poor quality data among professional survey respondents and how HCI based behavioral data can be used to identify them. ‘Essay Two’ examines the same problem among another common participant pool, university students. ‘Essay Three’ alleviates typical Type I concerns in ‘Essay One’ and ‘Essay Two’ by examining whether specific undesirable behaviors exhibited by respondents while answering a question may be captured using appropriate metrics. The overall results obtained suggest that behavioral differences during the response generation process may be captured through HCI devices to create appropriate metrics that identify poor quality responses
Порівняльне дослідження теплових та оптичних властивостей бінарних нанокомпозитів на основі PANI
No full textНанорозмірні матеріали та нанокомпозити, які складаються з металів, провідних полімерів, вуглецевих нанотрубок, використовуються у величезній кількості додатків завдяки своїм оптичним, механічним, тепловим та хімічним властивостям. Робота полягає у виготовленні нанокомпозитів
PANI/rGO і PANI/MWCNT та вивченні їх оптичних і теплових характеристик. У статті детально описано методологію синтезу та відповідне оптично-теплове дослідження нанокомпозитів PANI/rGO та
PANI/MWCNT з 8 ваг. % rGO/MWCNT у чистому PANI з використанням процесу хімічної окислювальної полімеризації in-situ. Для дослідження морфології поверхні синтезованих нанокомпозитів були
використані скануюча електронна мікроскопія (SEM) та інфрачервона спектроскопія з перетворенням
Фур'є (FTIR). Для вимірювання теплової стабільності нанокомпозитів PANI/rGO і PANI/MWCNT використовували термогравіметричний аналіз (TGA). Дослідження спектрофотометрії в УФ та видимій
областях спектру виявили зменшення значень ширини забороненої зони в конкретних нанокомпозитних зразках PANI/rGO (8 wt. %) через посилення взаємодії між rGO-легованим PANI при молекулярному з'єднанні та відповідними алотропами вуглецю. Дослідження показало, що зразки PANI/rGO
мають чудові структурні, теплові та оптичні характеристики, що робить їх придатними для досліджень і розробок у сфері накопичувачів енергії та її додатків.Nanoscale materials and nanocomposites composed of metals, conducting polymers, carbon nanotubes,
because of their optical, mechanical, thermal, and chemical properties, are used in a huge number of applications. Current work includes the fabrication of PANI/rGO, as well as PANI/MWCNT nanocomposites and
the study of their optical and thermal characteristics. The article describes in detail the methodology of
synthesis and relative optical and thermal study of PANI/MWCNT and PANI/rGO nanocomposites with
8 wt. % rGO/MWCNT in pure PANI using an in-situ chemical oxidation polymerization process. Scanning
electron microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy were used to investigate
the surface morphology of synthesized nanocomposites. Thermogravimetric analysis (TGA) was used to
measure the thermal stability of PANI/rGO and PANI/MWCNT nanocomposites. UV-Visible spectrophotometry studies revealed a decrease in band gap values in specific PANI/rGO (8 wt. %) nanocomposite
samples due to the enhanced significant interaction between rGO-doped PANI at molecular conjugation
and the corresponding carbon allotropes. The study showed that PANI/rGO specimens have excellent
structural, thermal, and optical characteristics, making them suitable for research and development in the
field of energy storage devices and their applications
Cell-Type-Specific Mitochondrial Quality Control in the Brain: A Plausible Mechanism of Neurodegeneration
No full textNeurodegeneration is an age-dependent progressive phenomenon with no defined cause. Aging is the main risk factor for neurodegenerative diseases. During aging, activated microglia undergo phenotypic alterations that can lead to neuroinflammation, which is a well-accepted event in the pathogenesis of neurodegenerative diseases. Several common mechanisms are shared by genetically or pathologically distinct neurodegenerative diseases, such as excitotoxicity, mitochondrial deficits and oxidative stress, protein misfolding and translational dysfunction, autophagy and microglia activation. Progressive loss of the neuronal population due to increased oxidative stress leads to neurodegenerative diseases, mostly due to the accumulation of dysfunctional mitochondria. Mitochondrial dysfunction and excessive neuroinflammatory responses are both sufficient to induce pathology in age-dependent neurodegeneration. Therefore, mitochondrial quality control is a key determinant for the health and survival of neuronal cells in the brain. Research has been primarily focused to demonstrate the significance of neuronal mitochondrial health, despite the important contributions of non-neuronal cells that constitute a significant portion of the brain volume. Moreover, mitochondrial morphology and function are distinctly diverse in different tissues; however, little is known about their molecular diversity among cell types. Mitochondrial dynamics and quality in different cell types markedly decide the fate of overall brain health; therefore, it is not justifiable to overlook non-neuronal cells and their significant and active contribution in facilitating overall neuronal health. In this review article, we aim to discuss the mitochondrial quality control of different cell types in the brain and how important and remarkable the diversity and highly synchronized connecting property of non-neuronal cells are in keeping the neurons healthy to control neurodegeneration
Colossal Tunneling Electroresistance in Co-Planar Polymer Ferroelectric Tunnel Junctions
No full textFerroelectric 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 <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
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Factors Affecting Compliance with Alerts in the Context of Healthcare-related Emergencies
No full textThis study is a conceptual replication of the study by Han et al. (2015) in which the authors evaluated factors affecting students’ compliance with emergency instructions during campus emergencies. The current study focused on broader public health-related emergencies using eight scenarios evaluated by Amazon Mechanical Turk (AMT) participants. Analysis on the aggregated data showed that subjective norm and trust in information quality positively affected intention to comply with instructions, consistent with the original study. Three follow up analyses provide more nuanced results. First, an abridged dataset was created by filtering out participants whose reasons for non-immediate compliance weren\u27t related to verifying information and then complying. Analysis on this dataset showed that subjective norm no longer positively affected intention to comply. Second, scenarios used in the study were grouped by characteristics such as development speed, frequency, and area affected, and the analysis was redone. Factors affecting intention to comply immediately changed based on the characteristic, with subjective norm positively affected intention to comply in slow-developing scenarios, scenarios that affect at a limited area, and commonly occurring scenarios, while trust in information quality affects the other scenarios. Third, recall of information from the notification was collected from participants and analyzed. Results show that participants who chose to comply immediately recalled more information than others. Our replication study shows some support for the original conclusions; however, the broader setting and more nuanced analyses show also differences between both studies
Indian Agriculture in the New Economic Regime, 1971-2003: Empirics based on the Cobb Douglas Production Function
No full textThis paper reviews the trends in Indian Agriculture before and after the introduction of the economic reforms, and the advent of WTO regime. We employ the Cobb Douglas Production Function using the OLS specification to investigate the determinants of agricultural gross domestic product for the period 1970-71 to 2002-03, during pre and post-economic reforms to document the impact of policy change (post-1992) and India’s membership of the WTO (post-1995). Our empirical findings reveal that Indian agriculture sector has witnessed Decreasing Returns to Scale after the introduction of economic reforms, indicating that the input availability is under strain during the same period.Agriculture Gross Domestic Product, WTO, Economic Reforms, Trends, Determinants, Returns to Scale, Cobb Douglas Production Function, India
Thinking Fast or slow? Understanding Answering Behavior Using Dual-Process Theory through Mouse Cursor Movements
No full textUsers’ underlying cognitive states govern their behaviors online. For instance, an extreme cognitive burden during live system use would negatively influence important user behaviors such as using the system and purchasing a product. Thus, inferring the user's cognitive state has practical significance for the commercialized systems. We use Dual-Process Theory to explain how the mouse cursor movements can be an effective measure of cognitive load. In an experimental study with five hundred and thirty-four subjects, we induced cognitive burden then monitored mouse cursor movements when the participants answered questions in an online survey. We found that participants' mouse cursor movements slow down when they are engaged in cognitively demanding tasks. With the newly derived measures, we were able to infer the state of heightened cognitive load with an overall accuracy of 70.22%. The results enable researchers to measure users' cognitive load with more granularity and present a new, theoretically sound method to assess the user's cognitive state
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