2,972 research outputs found
Global design of analog cells using statistical optimization techniques
We present a methodology for automated sizing of analog cells using statistical optimization in a simulation based approach. This methodology enables us to design complex analog cells from scratch within reasonable CPU time. Three different specification types are covered: strong constraints on the electrical performance of the cells, weak constraints on this performance, and design objectives. A mathematical cost function is proposed and a bunch of heuristics is given to increase accuracy and reduce CPU time to minimize the cost function. A technique is also presented to yield designs with reduced variability in the performance parameters, under random variations of the transistor technological parameters. Several CMOS analog cells with complexity levels up to 48 transistors are designed for illustration. Measurements from fabricated prototypes demonstrate the suitability of the proposed methodology
Education transformation in learning communities
Con la descripción de esta experiencia hemos pretendido dar a conocer qué es una Comunidad de Aprendizaje y analizar cómo funciona la del CEIP Andalucía de Sevilla, además de promover la reflexión de prácticas educativas favorecedoras del éxito escolar y la participación de la comunidad. La puesta en marcha de Comunidades de Aprendizaje precisa la implicación de múltiples agentes educativos, procesos de cambio, la introducción de nuevos modelos organizativos en el centro, el desarrollo de nuevas metodologías en el aula, el cambio de concepción de lo qué es un centro público, etc…Analizamos el ámbito de acción metodológico con la propuesta de grupos interactivos de aprendizaje y metodología de trabajo por proyectos; el ámbito curricular con sugerencias para las áreas de Lengua y Educación Artística y el ámbito de participación con la formación de las familias.
Esta Comunidad de Aprendizaje ha incrementado los niveles de competencia curricular del alumnado y ha disminuido el absentismo escolar, dos aspectos claves en un contexto de marginación y exclusión social, además del trabajo colectivo y cooperativo de todo el claustro, voluntarios, asociaciones, instituciones y familias
Waste-based materials in residential house construction
Waste from the construction sector has been increasing considerably in recent years, making it urgent to find alternatives to this waste that will enable us to preserve the environment and ecosystems. Many studies demonstrate the viability of using this and other waste in the construction sector, such as wood, ashes, and plastics. This article presents a review of research works where residual materials have been applied in the construction sector. To achieve this objective, a total of 35 articles were reviewed, published in English-speaking journals between 2015 and 2023. This review shows that, although in recent years efforts have been made for the application of waste materials in the construction sector has been significant, however, there is still work to be done in the study of the behavior of these residual materials, such as the emission of greenhouse gases, as well as the importance of residual materials pretreatment to ensure compatibility with the rest of the components. Another important aspect is that most studies consider environmental aspects without taking into account social and economic issues surrounding them in the construction sector
A CMOS Imager for Time-of-Flight and Photon Counting Based on Single Photon Avalanche Diodes and In-Pixel Time-to-Digital Converters
The design of a CMOS image sensor based on single-photon
avalanche-diode (SPAD) array with in-pixel time-to-digital converter (TDC) is
presented. The architecture of the imager is thoroughly described with emphasis
on the characterization of the TDCs array. It is targeted for 3D image
reconstruction. Several techniques as fast quenching/recharge circuit with tunable
dead-time and time gated-operation are applied to reduce the noise and
the power consumption. The chip was fabricated in a 0.18 m standard CMOS
process and implements a double functionality: time-of-flight (ToF) estimation
and photon counting. The imager features a programmable time resolution of
the array of TDCs down to 145 ps. The measured accuracy of the minimum
time bin is lower than 1LSB DNL and 1.7 LSB INL. The TDC jitter over
the full dynamic range is less than 1 LSB.Peer reviewe
Geomorphological mapping of granite caves
[Abstract] The aim is to develop a mapping which represents the relief and the form (morphology) of granite caves and associated superficial structures
Ensayos de envejecimiento adaptados a la evaluación del alabastro de la restauración del Palacio Episcopal de Tarazona
The advanced condition of deterioration of the column’s bases of the courtyard of the Bishop’s Palace of Tarazona (Spain) built in the middle of 16th century required its restoration with Aragonese alabaster. Thus, adapted ageing tests were developed to simulate the environmental conditions in which the stones were and will be exposed. These tests were thermal fatigue by temperature variations, acid rain and water stagnation by immersion tests and a combination of both agents of decay. The results indicated that alabaster did not experimented deformation after thermal fatigue but a progressive dehydration to bassanite. This process entailed an increase of porosity and consequently a loss of structural properties. The dissolution was measured as a lineal weight and volume loss while porosity and capillary uptake remained stable. The conclusions of this study establish the importance of restoration protocols to maintain the alabaster integrity when used and exposed to rainwater and insolation.Las basas deterioradas de las columnas del patio del Palacio Episcopal de Tarazona (España), construido a mediados del siglo XVI, fueron restauradas con alabastro aragonés. Por lo tanto, se han desarrollado pruebas de envejecimiento adaptadas para simular las condiciones ambientales en las que las piedras estaban y estarán expuestas, fatiga térmica por variaciones de temperatura, lluvia ácida, inmersión en agua y una combinación de agentes de deterioro. Los resultados indican que el alabastro no experimentó deformación después de la fatiga térmica, sino una progresiva deshidratación a bassanita, lo cual implica un aumento de porosidad y una pérdida de propiedades estructurales. La disolución se midió como una pérdida lineal de peso y volumen, mientras que la porosidad y el ascenso capilar se mantuvieron estables. Se desprende la importancia de adoptar protocolos de restauración para mantener la integridad del alabastro cuando se expone al agua de lluvia e insolación
A high dynamic range image sensor with linear response based on asynchronous event detection
This paper investigates the potential of an image
sensor that combines event-based asynchronous outputs with
conventional integration of photocurrents. Pixels voltages can
be read out following a traditional approach with a source
follower and analog-to-digital converter. Furthermore, pixels
have circuitry to implement Pulse Density Modulation (PDM)
sending out pulses with a frequency that is proportional to the
photocurrent. Both read-out approaches operate simultaneously.
Their information is combined to render high dynamic range
images. In this paper, we explain the new vision sensor concept
and we develop a theoretical analysis of the expected performance
in standard AMS 0.18mm HV technology. Moreover, we provide
a description of the vision sensor architecture and its main blocksPeer reviewe
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A QPSK 110-Gb/s Polarization-Diversity MIMO Wireless Link with a 220-255 GHz Tunable LO in a SiGe HBT Technology
In this article, a polarization-diversity technique multiple-input multiple-output (MIMO) is demonstrated to double the spectral efficiency of a line-of-sight quadrature phase-shift keying (QPSK) wireless link at 220-255 GHz with a pair of highly integrated single-chip transmitter (TX) and receiver (RX) front-end modules in 0.13-µ {m SiGe HBT technology ( fTmax=350 /550 GHz) exploiting only a low-cost wire-bonded chip-on-board packaging solution for high-speed baseband (BB) signals. Both TX and RX chips accommodate two independent fundamentally operated direct-conversion in-phase and quadrature (IQ) paths with separately tunable on-chip multiplier-based ( × 16 ) local oscillator (LO) generation paths driven from a single external highly stable 13.75-16-GHz frequency synthesizer. On the RX side, a mixer-first architecture is implemented to improve the symmetry between upper and lower sidebands (USB and LSB) at the cost of an increased noise figure (NF), whereas, on the TX chip, each upconversion mixer is followed by a gain-bandwidth (BW)-limited four-stage power amplifier (PA) to support the link budget at a meter distance. Next, two independent IQ data streams from the upconversion/downconversion paths on each chip are directed to a common lens-coupled broadband on-chip slot antenna system. This way, two orthogonal circular polarizations [left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP)] can be transmitted with sufficient isolation for link operation without the need for a high-speed depolarizer in the BB for any relative orientation between TX and RX modules. The antenna combined with a 9-mm diameter Si-lens provides a directivity of 23.5-27 dBi at 210-270 GHz for each of the modules. This, along with a peak radiated power of 7.5 dBm/ch from the TX module, and the cascaded conversion gain (CG)/single sideband (SSB) NF of 18/18 dB/ch for the RX module followed by a broadband amplifier (PSPL5882) from Tektronix allowed successful transmission of two independent QPSK data streams with an aggregate speed of 110 and 80 Gb/s over 1 and 2 m, respectively, at 230 GHz with a board-level limited channel BB bandwidth (BW) of 13.5 GHz. © 1963-2012 IEEE
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