23,717 research outputs found
Análisis de la conductividad térmica y resistencia a compresión del hormigón en las estructuras termoactivas
En el presente trabajo se lleva a cabo el análisis del hormigón para su empleo como parte de las llamadas estructuras termoactivas. Se analizó la conductividad térmica de diferentes tipos de hormigón, así como su resistencia a compresión, y el reparto de temperaturas en el interior de una losa termoactiva de hormigón. Las estructuras termoactivas basan su funcionamiento en el aprovechamiento de la inercia térmica del hormigón para llevar a cabo el proceso de climatización de los edificios. Para ello se incorpora una serie de conductos, para transportar un fluido caloportador, en el interior de los elementos estructurales de hormigón armado de los edificios. Estos sistemas requieren temperaturas medias para su funcionamiento, por lo que permiten el aprovechamiento de energías renovables como la geotermia de baja entalpía. En el trabajo se llevó a cabo una campaña experimental de probetas de hormigón H-25, elaboradas con tres tipos de cemento diferentes (CEM I, CEM II y CEM III) combinados con dos tipos de árido (de origen calizo y origen silíceo) en el que se estudió por una parte la resistencia a compresión del hormigón, y por otra parte la conductividad térmica del hormigón en tres grados de humedad diferentes (0%, 50% y 100% de humedad). Los resultados obtenidos indicaron que las muestras elaboradas con cemento del tipo CEM I y árido calizo ofrecieron valores de resistencia a compresión superiores a las de las muestras elaboradas con cemento CEM II, CEM III y árido silíceo. Por otra parte, de los ensayos térmicos se obtuvieron valores de conductividad superiores en las muestras elaboradas con cemento CEM II, árido silíceo, y con un 100% de humedad. Del estudio de la resistencia del hormigón, y la conductividad térmica se puede concluir que el hormigón elaborado con cemento de tipo CEM II y árido silíceo resultó más adecuado para su empleo en los elementos estructurales de hormigón armado, siempre que los requerimientos estructurales no se vean comprometidos. Al contrario de lo que se esperaba, el empleo de cemento CEM III, de origen siderúrgico, no supuso el aumento de la conductividad térmica de las muestras de hormigón analizadas. Para el análisis del reparto de temperaturas en el interior de una losa termoactiva se realizó una muestra física de losa de hormigón con un sistema de tubos embebidos por los que se hizo circular el agua, y una serie de termopares en el interior del hormigón a diferentes profundidades de la cara exterior de la losa. En cada termopar se analizó el reparto de temperaturas con 3 temperaturas de agua diferentes (30ºC, 40ºC y 50ºC), combinadas con 2 supuestos de temperatura ambiente de la sala en la que se realizaron los ensayos: la temperatura preexistente y la temperatura ambiente aumentada hasta 28ºC mediante el empleo del sistema de aire acondicionado de la sala. Los resultados conseguidos mostraron que con una temperatura del agua de 30ºC el hormigón de la losa alcanza temperaturas más próximas a las del fluido caloportador que con temperaturas de 40ºC o 50ºC. Se comprobó que el estrato con temperaturas más estables de la losa se dio en los termopares más alejados de las tuberías y más próximos a la cara externa de la losa, y que el sistema alcanzó la estabilización de las temperaturas tras 9 horas aproximadamente de funcionamiento. Del análisis del reparto de temperaturas dentro del hormigón de una losa termoactiva se puede concluir que el sistema es apropiado para el empleo de temperaturas medias del fluido caloportador, que se consiguen temperaturas más estables en planos a una cierta distancia del sistema de tuberías, y que el sistema resulta más eficiente durante períodos largos de funcionamiento. ----------ABSTRACT---------- The aim of the project is to study the concrete used in reinforced concrete structures of thermally active building systems (TABS). To that purpose the thermal conductivity and compressive strength of different kinds of concrete samples were analized, as well as the distribution of temperatures inside a sample of thermally activated concrete slab. Thermally active structures are based on thermal inertia of concrete for being used as part of the heating and cooling systems of buildings. To this purpose, a system of pipes with heat transfer fluid is embedded into concrete structures for heating and cooling different parts of buildings. As low temperatures are required for these heating and cooling systems, renewable energies such as geothermal energy are successfully used for climate control of buildings. For this reason different specimens and testing procedures were proposed to study. On the one hand the compressive strength of concrete made with three different types of cement (CEM I, CEM II and CEM III) and two different kinds of aggregate (limestone and siliceous). On the other hand, thermal conductivity of concrete were also studied at three different levels of humidity (0%, 50% and 100% of humidity). Results from tests showed that specimens made of concrete with CEM I and limestone aggregate had a higher compressive strength, while conductivity tests showed that concrete made with cement CEM II, siliceous aggregate and humidity of 100% had higher values of conductivity than the other specimens. In conclusion, concrete made of cement type CEM II and siliceous aggregate improves the conductivity of concrete for its use on thermal active structures. Thermal conductivity is also improved by high levels of humidity in concrete. Contrary to the expectations, concrete specimens made of cement CEM III did not show higher thermal conductivity levels than concrete made of cement CEM I and CEM II. In order to analize the distribution of heat inside of the concrete of a thermally active concrete slab, a sample with embedded tubes with water and thermocouples was made. The temperature at each thermocouple was analized depending on the distance to the tube system, water temperature (30ºC, 40ºC and 50ºC) and two different options for room temperature: the preexisting temperature and 28ºC of temperature by using air conditioning. Results from this part of the study showed that temperatures of concrete during the working period were closer to water temperature when this was 30ºC rather than 40ºC or 50ºC. The temperatures of concrete were more stable closer to surface levels rather than closer levels to tubes. The temperatures of the system reached its maximum values after 9 hours of use aproimately. In conclusion to this part of the study, the system results more suitable for using medium value temperatures for water, the location of the tubes system should be at the middle plane of the slab for stable temperatures at the exterior surface of the slab, and that the use of the system is more effective for long operative periods
The growclusters Package for R
The growclusters package for R implements an enhanced version of k-means
clustering that allows discovery of local clusterings or partitions for a
collection of data sets that each draw their cluster means from a single,
global partition. The package contains functions to estimate a partition
structure for multivariate data. Estimation is performed under a penalized
optimization derived from Bayesian non-parametric formulations. This paper
describes some of the functions and capabilities of the growclusters package,
including the creation of R Shiny applications designed to visually illustrate
the operation and functionality of the growclusters package.Comment: 10 pages, 6 figures, paper presented at 2022 Joint Statistical
Meeting
iPulse: March 2023
Issues: March 2023 [Spring Week #5]: Finding a Job as an International Student; Needing Help is Ok; The Art of Pseudocide; Viva LatinoAmerica!; Travel to the Max; Covered in Crystals; Mascara Gate: The Latest Beauty Controversy March 2023 [Spring Week #6]: Strut Your Stuff; Working Through the Gloom; Making the Most Out of Your Money; To Read or Not to Read?; Local vs. Global; Queen Bey is Back and Better Than Ever; Delray\u27s Take on Latin Flavor; Fighting for Inclusivity in Fashion; Career Fair Week is Around the Cornerhttps://spiral.lynn.edu/studentnews/1271/thumbnail.jp
Insights into the single-particle composition, size, mixing state, and aspect ratio of freshly emitted mineral dust from field measurements in the Moroccan Sahara using electron microscopy
The chemical and morphological properties of mineral dust aerosols emitted by wind erosion from arid and semi-arid regions influence climate, ocean, and land ecosystems; air quality; and multiple socio-economic sectors. However, there is an incomplete understanding of the emitted dust particle size distribution (PSD) in terms of its constituent minerals that typically result from the fragmentation of soil aggregates during wind erosion. The emitted dust PSD affects the duration of particle transport and thus each mineral's global distribution, along with its specific effect upon climate. This lack of understanding is largely due to the scarcity of relevant in situ measurements in dust sources. To advance our understanding of the physicochemical properties of the emitted dust PSD, we present insights into the elemental composition and morphology of individual dust particles collected during the FRontiers in dust minerAloGical coMposition and its Effects upoN climaTe (FRAGMENT) field campaign in the Moroccan Sahara in September 2019. We analyzed more than 300 000 freshly emitted individual particles by performing offline analysis in the laboratory using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDX). Eight major particle-type classes were identified with clay minerals making up the majority of the analyzed particles both by number and mass, followed by quartz, whereas carbonates and feldspar contributed to a lesser extent. We provide an exhaustive analysis of the PSD and potential mixing state of different particle types, focusing largely on iron-rich (Fe oxide-hydroxides) and feldspar particles, which are key to the effects of dust upon radiation and clouds, respectively. Nearly pure or externally mixed Fe oxide-hydroxides are present mostly in diameters smaller than 2 µm, with the highest fraction below 1 µm at about 3.75 % abundance by mass. Fe oxide-hydroxides tend to be increasingly internally mixed with other minerals, especially clays, as particle size increases; i.e., the volume fraction of Fe oxide-hydroxides in aggregates decreases with particle size. Pure (externally mixed) feldspar represented 3.2 % of all the particles by mass, of which we estimated about a 10th to be K-feldspar. The externally mixed total feldspar and K-feldspar abundances are relatively invariant with particle size, in contrast to the increasing abundance of feldspar-like (internally mixed) aggregates with particle size with mass fractions ranging from 5 % to 18 %. We also found that overall the median aspect ratio is rather constant across particle size and mineral groups, although we obtain slightly higher aspect ratios for internally mixed particles. The detailed information on the composition of freshly emitted individual dust particles and quantitative analysis of their mixing state presented here can be used to constrain climate models including mineral species in their representation of the dust cycle.</p
Towards Reuse and Recycling of Lithium-ion Batteries: Tele-robotics for Disassembly of Electric Vehicle Batteries
Disassembly of electric vehicle batteries is a critical stage in recovery,
recycling and re-use of high-value battery materials, but is complicated by
limited standardisation, design complexity, compounded by uncertainty and
safety issues from varying end-of-life condition. Telerobotics presents an
avenue for semi-autonomous robotic disassembly that addresses these challenges.
However, it is suggested that quality and realism of the user's haptic
interactions with the environment is important for precise, contact-rich and
safety-critical tasks. To investigate this proposition, we demonstrate the
disassembly of a Nissan Leaf 2011 module stack as a basis for a comparative
study between a traditional asymmetric haptic-'cobot' master-slave framework
and identical master and slave cobots based on task completion time and success
rate metrics. We demonstrate across a range of disassembly tasks a time
reduction of 22%-57% is achieved using identical cobots, yet this improvement
arises chiefly from an expanded workspace and 1:1 positional mapping, and
suffers a 10-30% reduction in first attempt success rate. For unbolting and
grasping, the realism of force feedback was comparatively less important than
directional information encoded in the interaction, however, 1:1 force mapping
strengthened environmental tactile cues for vacuum pick-and-place and contact
cutting tasks.Comment: 21 pages, 12 figures, Submitted to Frontiers in Robotics and AI;
Human-Robot Interactio
Self-Supervised Scene Dynamic Recovery from Rolling Shutter Images and Events
Scene Dynamic Recovery (SDR) by inverting distorted Rolling Shutter (RS)
images to an undistorted high frame-rate Global Shutter (GS) video is a
severely ill-posed problem, particularly when prior knowledge about
camera/object motions is unavailable. Commonly used artificial assumptions on
motion linearity and data-specific characteristics, regarding the temporal
dynamics information embedded in the RS scanlines, are prone to producing
sub-optimal solutions in real-world scenarios. To address this challenge, we
propose an event-based RS2GS framework within a self-supervised learning
paradigm that leverages the extremely high temporal resolution of event cameras
to provide accurate inter/intra-frame information. % In this paper, we propose
to leverage the event camera to provide inter/intra-frame information as the
emitted events have an extremely high temporal resolution and learn an
event-based RS2GS network within a self-supervised learning framework, where
real-world events and RS images can be exploited to alleviate the performance
degradation caused by the domain gap between the synthesized and real data.
Specifically, an Event-based Inter/intra-frame Compensator (E-IC) is proposed
to predict the per-pixel dynamic between arbitrary time intervals, including
the temporal transition and spatial translation. Exploring connections in terms
of RS-RS, RS-GS, and GS-RS, we explicitly formulate mutual constraints with the
proposed E-IC, resulting in supervisions without ground-truth GS images.
Extensive evaluations over synthetic and real datasets demonstrate that the
proposed method achieves state-of-the-art and shows remarkable performance for
event-based RS2GS inversion in real-world scenarios. The dataset and code are
available at https://w3un.github.io/selfunroll/
A Decision Support System for Economic Viability and Environmental Impact Assessment of Vertical Farms
Vertical farming (VF) is the practice of growing crops or animals using the vertical dimension via multi-tier racks or vertically inclined surfaces. In this thesis, I focus on the emerging industry of plant-specific VF. Vertical plant farming (VPF) is a promising and relatively novel practice that can be conducted in buildings with environmental control and artificial lighting. However, the nascent sector has experienced challenges in economic viability, standardisation, and environmental sustainability. Practitioners and academics call for a comprehensive financial analysis of VPF, but efforts are stifled by a lack of valid and available data.
A review of economic estimation and horticultural software identifies a need for a decision support system (DSS) that facilitates risk-empowered business planning for vertical farmers. This thesis proposes an open-source DSS framework to evaluate business sustainability through financial risk and environmental impact assessments. Data from the literature, alongside lessons learned from industry practitioners, would be centralised in the proposed DSS using imprecise data techniques. These techniques have been applied in engineering but are seldom used in financial forecasting. This could benefit complex sectors which only have scarce data to predict business viability.
To begin the execution of the DSS framework, VPF practitioners were interviewed using a mixed-methods approach. Learnings from over 19 shuttered and operational VPF projects provide insights into the barriers inhibiting scalability and identifying risks to form a risk taxonomy. Labour was the most commonly reported top challenge. Therefore, research was conducted to explore lean principles to improve productivity.
A probabilistic model representing a spectrum of variables and their associated uncertainty was built according to the DSS framework to evaluate the financial risk for VF projects. This enabled flexible computation without precise production or financial data to improve economic estimation accuracy. The model assessed two VPF cases (one in the UK and another in Japan), demonstrating the first risk and uncertainty quantification of VPF business models in the literature. The results highlighted measures to improve economic viability and the viability of the UK and Japan case.
The environmental impact assessment model was developed, allowing VPF operators to evaluate their carbon footprint compared to traditional agriculture using life-cycle assessment. I explore strategies for net-zero carbon production through sensitivity analysis. Renewable energies, especially solar, geothermal, and tidal power, show promise for reducing the carbon emissions of indoor VPF. Results show that renewably-powered VPF can reduce carbon emissions compared to field-based agriculture when considering the land-use change.
The drivers for DSS adoption have been researched, showing a pathway of compliance and design thinking to overcome the ‘problem of implementation’ and enable commercialisation. Further work is suggested to standardise VF equipment, collect benchmarking data, and characterise risks. This work will reduce risk and uncertainty and accelerate the sector’s emergence
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