Fast-response Devices Research Articles

Optimization of the properties of nematic matrix suspended with subtle quantities of the nanoparticles for improved alignment and operating voltage

ABSTRACT The current study examines and reflects the effect of minute quantity of Diamond nanoparticles (DNPs) in the Nematic liquid crystal (NLC) matrix. A well structured and strategized study is performed in order to get a deep understanding about the interactions that might have taken place between the guests and the hosts. Our study professed a significant alteration in the number of parameters of guest-host system in comparison to the pure liquid crystal (LC) matrix that could be found extremely promising for the display devices and low-power switching machines. 0.05, 0.07 and 0.1 wt/wt% concentrations of the NPs incorporated in the LC matrix and the composites are prepared with the high precision weight measurement using electrical balance. Dielectric spectrum is catalogued for both the homogeneous and vertical alignments of sample cells. Threshold voltage and operating voltage are found to be significantly decreased for 0.05 wt/wt% composite. Response time for the prepared composites is profoundly abated which is a crucial factor for the fast response devices. Careful examination of pretilt angles is executed and an improvement in the alignment is found as one more perk of this study.

Semiconductor/Carbon Quantum Dot-based Hue Recognition Strategy for Point of Need Testing: A Review.

The requirement to establish novel methods for visual detection is attracting attention in many application fields of analytical chemistry, such as, healthcare, environment, agriculture, and food. The research around subjects like "point-of-need", "hue recognition", "paper-based sensor", "fluorescent sensor", etc. has been always aimed at the opportunity to manufacture convenient and fast-response devices to be used by non-specialists. It is possible to achieve economic rationality and technical simplicity for optical sensing toward target analytes through introduction of fluorescent semiconductor/carbon quantum dot (QD) and paper-based substrates. In this Review, the mechanisms of anthropic visual recognition and fluorescent visual assays, characteristics of semiconductor/carbon QDs and ratiometric fluorescence test paper, and strategies of semiconductor/carbon QD-based hue recognition are described. We cover latest progress in the development and application of point-of-need sensors for visual detection, which is based on a semiconductor/carbon quantum dot-based hue recognition strategy generated by ratiometric fluorescence technology.

Mosaic Charge Distribution-Based Sliding and Pressing Triboelectrification under Wavy Configuration

As high-voltage output and fast response devices, triboelectric nanogenerators (TENGs) are widely used for sensors with fast and high-sensitivity performance. As a primary electrical signal, the waveform output provides an accurate and rapid response to external stimulus parameters such as press and slide. Here, based on mosaic charging and residual charge theories, the contact charging principle of TENGs is further discussed. Moreover, a wavy structure is obtained in the vertical contact separation and lateral sliding modes to further study the influence of external parameters applied to TENGs, which thus helps further the understanding of the output waveforms. The experimental results show that wavy TENGs have output properties that are excellent compared to those of TENGs with flat structures, such as longer charging and discharging times and more complex waveforms. By researching the waveform in depth, our work will provide new prospects for application in various sensors of interactive wearable systems, intelligent robots, and optoelectronic devices based on TENGs.

Bottleneck Generator Identification and the Corresponding N-1 Frequency Security Constrained Intraday Generator Dispatch

Generators are typically dispatched in a preventive way to guarantee frequency stability in any single generator trip contingency. The largest generator outage is regarded as the severest by the conventional N-1 frequency security rule, since the contingency size is often the dominating factor in traditional systems. However, with the continuous integration of renewable energy sources and fast response devices (e.g., battery), the inertia and frequency response characteristics of generators become diversified. In such situations, the largest generator cannot be simply identified as the bottleneck generator for preventive dispatch, since the post-contingency frequency dynamic is determined by both the contingency size and the frequency response ability of the remaining system. In this paper, a system's frequency response ability (FRA) is quantitatively defined and derived as a function of system intrinsic parameters (e.g., system inertia, ramp rates of generators, load frequency relief coefficient, etc.). Then, the bottleneck generator can be identified through comparing the capacity of a unit with the maximum FRA of its corresponding remaining system. On this basis, an innovative N-1 frequency security constrained optimal intraday generator dispatch scheme is correspondingly established. Simulation results verify the superiority of the proposed method in both frequency security improvement and operation cost saving.

Two-Timescale Dynamic Energy and Reserve Dispatch With Wind Power and Energy Storage

The integration of volatile renewable resources and energy storage entails making dispatch decisions for conventional coal-fired units and fast-response devices in different timescales. This paper studies intraday dynamic energy-reserve dispatch following a two-timescale setting. The coarse timescale determines the hourly reference output and reserve allocation, which offers a sufficient backup for the fine-timescale operation; the fine timescale determines the adjustment of gas-fired units and energy storage system every 15 minutes in response to the actual wind power. A stochastic dynamic programming method is proposed to make decisions at the coarse timescale while guaranteeing the robust feasibility of the fast process via vertex scenarios of uncertainty set and bounding the state-of-charge intervals for energy storage; the fast-response actions at the fine timescale are updated using a truncated rolling-horizon optimization, which incorporates the cost-to-go functions calculated at the coarse timescale to prevent the fast decisions from being myopic. Case studies on the modified IEEE 5-bus system and 118-bus system validate the proposed framework.

Flexible perovskite nanosheet-based photodetectors for ultraviolet communication applications

Ultraviolet (UV) photodetection has attracted much attention for applications like monitoring ozone holes and light communication. Although UV photodetectors based on conventional inorganic semiconductors have been widely investigated, fast response devices with high sensitivity remain needed for UV communication systems. This Letter reports on flexible ultrathin methylammonium lead bromide(MAPbBr3)-based UV photodetectors. In the UV regime, the response time reaches 3.3/4.0 μs, and the 3 dB bandwidth is 0.22 MHz. No current degradation is detected after repeated bending cycles, indicating the excellent mechanical flexibility and reliability of flexible high-speed UV photodetectors. Moreover, MAPbBr3 nanosheet-based photodetectors have been integrated into a UV communication system as signal receivers transmitting messages encrypted by international Morse codes. These results reveal the potential of ultrathin perovskite nanosheets in developing flexible optoelectronic devices for UV communications and related applications.

Создание гетероструктур зарощенного типа для СВЧ лазерных диодов

Comprehensive physical and technological studies on the creation of mesastripe structures with a channel in the substrate and subsequent burying of the structure with a layer of zinc selenide are carry out. Planarity of heterointerfaces between the substrate and epitaxial layers is studied by electron microscopy. The atomic structure of epitaxial layers GaInAsP/InP is studied by transmission electron microscopy. The profiles of epitaxial layers of the heterostructure are analyzed by secondary ion mass spectroscopy (SIMS). Layers with required composition of In0.78Ga0.22As0.68P0.32 corresponding to a laser wavelength of 1.3 μm are obtained. A technique for creating laser diodes with a channel in the substrate, including etching of mesastripe structure and burying with a layer of zinc selenide, is developed for the first time. This technique makes it possible to create laser diodes both with an optical confinement of laser emission and with a confinement of the current flow along the laser strip. Etching of p–n junction layers between laser strips and burying with zinc selenide on the surface of etched structure are developed for the first time. This technique made it possible to create heterostructures for laser diodes operating in the microwave range up to 10 GHz by liquid phase epitaxy (LPE). The ability to create and operate laser diodes in this design and technology is shown. The current–voltage characteristics, watt–ampere characteristics, and spectral characteristics of laser diodes are investigated. Russian technology for the creation of a microwave laser diode on a heterostructure with a channel in the substrate and repeated burying with zinc selenide is proposed. The prospects of using laser diodes of mesastripe structure with a channel in the substrate and buried with a layer of zinc selenide to create fast-response devices are shown.

Incorporación de Dispositivos FACTS en el Sistema Nacional Interconectado

Ante el desarrollo de los diferentes proyectos de generación hidrotérmicos y los actuales problemas de capacidad de la red de transmisión, resulta necesario evaluar los reforzamientos del sistema de transmisión del país, de acuerdo al crecimiento de la demanda y el ingreso de los nuevos proyectos de generación. CENACE con el fin de cumplir con su rol de suministrar energía al país bajo las mejores condiciones de economía y calidad, analizó, de manera conjunta con la empresa norteamericana Quanta Technology, la factibilidad de incluir en el sistema de transmisión, dispositivos de respuesta rápida que garanticen la calidad y continuidad del suministro eléctrico.
 En este trabajo, a través de un análisis de contingencias en estado estable, se realiza la caracterización del Sistema Nacional Interconectado para el año 2017, con lo que se logra identificar las contingencias más críticas para el sistema. Posteriormente, mediante un análisis dinámico resulta posible categorizar las contingencias asociadas con problemas de estabilidad de voltaje. Estas contingencias son evaluadas de forma individual para determinar el requerimiento de compensación reactiva dinámica en diferentes zonas del SNI.

PRIORITY PARAMETERS OF OPERATION MONITORING AND CONTROL OF TECHNOLOGIES OF VEGETABLE CROPS SEED PRODUCTION

Control of seed production of vegetable crops based on factor of quality is become the basis of modern management. There is a growing need in the fastresponse devices for determination of moisture and temperature in seeds and environment.

CdTe and CdZnTe semiconductor gamma detectors equipped with ohmic contacts

Semiconductor gamma detectors, equipped with ohmic contacts, are uniform and fast response devices that are not sensitive to hole trapping. Gamma generated charges flow within the detector bulk towards the ohmic contacts, and induce additional charge flow from the contacts towards them. The additional flow stems from the fundamental principles of Poisson and the continuity equations. Electrons flow from the negative contacts towards the holes and recombine with them, therefore, they overcome hole trapping. The ohmic contact effect transforms the detector into a single carrier device. Good quality ohmic contact detectors are achieved from a crystal grown by standard methods, that initially has too many traps, by adjustment of the Fermi level position within the forbidden band. The device design and its principle of operation are discussed.

Detectors for infrared free electron lasers

Research on IR free electron lasers is increasing rapidly. Although many of the detector requirements are similar to those for other IR sources, there is a special need for very fast response devices, and for imaging systems to obtain the beam profile. This paper reviews the available detectors and discusses the possible use of less conventional methods, such as submicrometre diameter Schottky diode rectifiers and the photon drag effect.