276 research outputs found
Thermionic charge transport in CMOS nano-transistors
We report on DC and microwave electrical transport measurements in
silicon-on-insulator CMOS nano-transistors at low and room temperature. At low
source-drain voltage, the DC current and RF response show signs of conductance
quantization. We attribute this to Coulomb blockade resulting from barriers
formed at the spacer-gate interfaces. We show that at high bias transport
occurs thermionically over the highest barrier: Transconductance traces
obtained from microwave scattering-parameter measurements at liquid helium and
room temperature is accurately fitted by a thermionic model. From the fits we
deduce the ratio of gate capacitance and quantum capacitance, as well as the
electron temperature
Unified linear response theory of quantum dot circuits
Modelling the electrical response of multi-level quantum systems at finite
frequency has been typically performed in the context of two incomplete
paradigms: (i) Input-output theory, which is valid at any frequency but
neglects dynamic losses, and (ii) semiclassical theory, which captures well
dynamic dissipation effects but is only accurate at low frequencies. Here, we
develop a unifying theory, valid for arbitrary frequencies, that captures the
non-unitary effects introduced by finite relaxation and dephasing. The theory
allows a multi-level system to be described by a universal small-signal
equivalent circuit model, a resonant RLC circuit, whose topology only depends
on the number of energy levels, which we apply here to the case of a charge
qubit in a double quantum dot. Our model will facilitate the design of hybrid
quantum-classical circuits and the simulation of qubit control and quantum
state readout
Reconfigurable Boolean Logic using Magnetic Single-Electron Transistors
We propose a novel hybrid single-electron device for reprogrammable low-power
logic operations, the magnetic single-electron transistor (MSET). The device
consists of an aluminium single-electron transistors with a GaMnAs magnetic
back-gate. Changing between different logic gate functions is realized by
reorienting the magnetic moments of the magnetic layer which induce a voltage
shift on the Coulomb blockade oscillations of the MSET. We show that we can
arbitrarily reprogram the function of the device from an n-type SET for
in-plane magnetization of the GaMnAs layer to p-type SET for out-of-plane
magnetization orientation. Moreover, we demonstrate a set of reprogrammable
Boolean gates and its logical complement at the single device level. Finally,
we propose two sets of reconfigurable binary gates using combinations of two
MSETs in a pull-down network
Experimental analysis of a coiled stirred tank containing a low cost PCM emulsion as a thermal energy storage system
This article presents the results of heat transfer coefficient and volumetric energy density measurements in an agitated tank containing a low-cost phase change material emulsion, heated by water flowing in a coil. For the stirring a three-stage impeller is placed in the central axis of a 46 l commercial tank. By measuring the temperature dependency on time and solving the transient enthalpy balance, the heat transfer coefficient between the helical coil and the agitated phase change material emulsion is determined, based on the impeller Reynolds number. The thermal energy storage efficiency has also been analysed. This phase change material emulsion shows a phase change temperature range between 30 and 50 °C. Its solid content is about 60% with an average size of 1 µm. The results have shown that the overall heat transfer coefficient is around 3.5–5.5 times higher when a stirring rate of 290–600 rpm is used. Furthermore, even at the lowest stirring rate, the thermal energy storage efficiency improves from 76-77%–100%, without detriment to the energy consumption of the stirrer
Internet of things (IoT) as sustainable development goals (SDG) enabling technology towards smart readiness indicators (SRI) for university buildings
Non-residential buildings contribute to around 20% of the total energy consumed in Europe. This consumption continues to increase globally. Smart building proposals (focused on Nearly Zero Energy Building (NZEB), air quality monitoring, energy saving with thermal comfort, etc.) were already necessary before 2020, and the pandemic has made this research and development area more essential. Furthermore, the need to meet the Sustainable Development Goals (SDG) and obtain technological solutions based on the Internet of Things (IoT) requires holistic contributions through real installations that serve as spaces for measuring, testing, study and research. This article proposes a “measure–analyse–decide and act” methodology to quantify the Smart Readiness Indicator (SRI) for university buildings as a reference environment for energy efficiency and COVID-19 prevention models. Two conceptual spaces (physical and digital) within two dimensions (users and infrastructures) are designated over an IoT three-level model (information acquisition, interoperable communication, and data-driven decision). An IoT ecosystem (sensoriZAR) was implemented as a proof-of-concept of a smart campus at the University of Zaragoza, Spain. Focused on CO2 and energy consumption monitoring, the results showed effectiveness through real installations, demonstrating the IoT potential as SDG-enabling technologies. These contributions allow not only experimental lab tests (from the authors’ expertise in several specialties of Industrial, Mechanical, Design, Thermal, Electrical, Electronic, Computer and Telecommunication Engineering) but also a reference model for direct application in academic works, research projects and institutional initiatives, extendable to professional environments, buildings and cities. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)
Búsqueda y análisis de nuevos materiales PCM-TES de bajo coste
Este trabajo se centra en el almacenamiento de energía térmica mediante cambio de fasesólido‐líquido y sólido‐sólido. Los trabajos realizados hasta ahora respecto al almacenamientotérmico de energía mediante materiales de cambio de fase (PCM), demuestran que es viabletécnicamente para algunas aplicaciones. Sin embargo, el alto precio de los materiales hace quesu explotación comercial a gran escala no se haya producido hasta el momento. El objetivo esencontrar PCM de bajo coste a partir de residuos, subproductos o productos naturales. En elconcepto de bajo coste se incluye no sólo el bajo precio sino también un bajo impactoambiental por eso se incluyen productos naturales que pueden tener un precio elevado. Se habuscado en bases de datos de residuos, de Autorizaciones Ambientales Integradas y se hansolicitado muestras en distintos foros. Se han realizado pruebas a treinta sustanciasconseguidas (glicerinas de obtención de biodiesel, aceites usados, parafinas, subproductos defibras, aceites de pirólisis, yeso y aceites naturales) y hasta el momento se han obtenidoresultados interesantes para siete de ellas. Se está trabajando en la caracterización completade los materiales seleccionados que comprende entre otros: subenfriamiento, histéresis y ladeterminación de la conductividad térmica a partir de la difusividad térmica, capacidadcalorífica y densidad. El conocimiento de las magnitudes descritas es imprescindible paradiseñar y/o simular correctamente los sistemas en los que se incluyen estos materiales:cambios de volumen para diseñar su encapsulación o viscosidad para dimensionar las bombaspor ejemplo. Además se siguen buscando otras sustancias
Beyond-adiabatic Quantum Admittance of a Semiconductor Quantum Dot at High Frequencies: Rethinking Reflectometry as Polaron Dynamics
Semiconductor quantum dots operated dynamically are the basis of many quantum
technologies such as quantum sensors and computers. Hence, modelling their
electrical properties at microwave frequencies becomes essential to simulate
their performance in larger electronic circuits. Here, we develop a
self-consistent quantum master equation formalism to obtain the admittance of a
quantum dot tunnel-coupled to a charge reservoir under the effect of a coherent
photon bath. We find a general expression for the admittance that captures the
well-known semiclassical (thermal) limit, along with the transition to lifetime
and power broadening regimes due to the increased coupling to the reservoir and
amplitude of the photonic drive, respectively. Furthermore, we describe two new
photon-mediated regimes Floquet broadening, determined by the dressing of the
QD states, and broadening determined by photon loss in the system. Our results
provide a method to simulate the high-frequency behaviour of QDs in a wide
range of limits, describe past experiments, and propose novel explorations of
QD-photon interactions
Aplicación tecnológica de arcillas (acopios) de la sucesión superior de la formación Cerro Largo, Buenos Aires, Argentina
Based on mineralogical, physicochemical and technological characterization, the brownish and red clays of the upper pelitic succession of the Cerro Largo Formation, Sierras Bayas, Province of Buenos Aires, recently redefined as Olavarría Formation, composed of predominant illitic material, with impurities of quartz, calcite, siderite, hematite, goethite and pyrite, are suitable for red ceramic producís of low water absorption (15%). Preliminary controlled mixtures of the two varieties found (brownish and red), with different technological properties, constitute a better quality product than the ones obtained with the individual clays, wen with the addition of 3-5% bentonite.VI Reunión Argentina de Sedimentología - I Simposio de Arcilla realizado en
Bahía Blanca, Argentina los días 16 al 27 de mayo de 1996
Dispersively detected Pauli Spin-Blockade in a Silicon Nanowire Field-Effect Transistor
We report the dispersive readout of the spin state of a double quantum dot
formed at the corner states of a silicon nanowire field-effect transistor. Two
face-to-face top-gate electrodes allow us to independently tune the charge
occupation of the quantum dot system down to the few-electron limit. We measure
the charge stability of the double quantum dot in DC transport as well as
dispersively via in-situ gate-based radio frequency reflectometry, where one
top-gate electrode is connected to a resonator. The latter removes the need for
external charge sensors in quantum computing architectures and provides a
compact way to readout the dispersive shift caused by changes in the quantum
capacitance during interdot charge transitions. Here, we observe Pauli
spin-blockade in the high-frequency response of the circuit at finite magnetic
fields between singlet and triplet states. The blockade is lifted at higher
magnetic fields when intra-dot triplet states become the ground state
configuration. A lineshape analysis of the dispersive phase shift reveals
furthermore an intradot valley-orbit splitting of 145 eV.
Our results open up the possibility to operate compact CMOS technology as a
singlet-triplet qubit and make split-gate silicon nanowire architectures an
ideal candidate for the study of spin dynamics
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