153 research outputs found

    Nonlinear modelling of the seismic response of masonry structures: Calibration strategies

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    In this paper, a simple and practitioners-friendly calibration strategy to consistently link target panel-scale mechanical properties (that can be found in national standards) to model material-scale mechanical properties is presented. Simple masonry panel geometries, with various boundary conditions, are utilized to test numerical models and calibrate their mechanical properties. The calibration is successfully conducted through five different numerical models (most of them available in commercial software packages) suitable for nonlinear modelling of masonry structures, using nonlinear static analyses. Firstly, the panel stiffness calibration is performed, focusing the attention to the shear stiffness. Secondly, the panel strength calibration is conducted for several axial load ratios by attempts using as reference the target panel strength deduced by well-known analytical strength criteria. The results in terms of panel strength for the five different models show that this calibration strategy appears effective in obtaining model properties coherent with Italian National Standard and Eurocode. Open issues remain for the calibration of the post-peak response of masonry panels, which still appears highly conventional in the standards

    A methodology for the evaluation of morphology-based constitutive laws of corroded steel rebars

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    The assessment of degraded reinforced concrete (RC) existing structures is nowadays a topical problem since several ones have an age close to or higher than their design life. The degradation state of the structure needs to be properly assessed and included in the adopted numerical or analytical models. In this framework, rebars corrosion phenomena can modify the structural behavior of RC members, especially when the corrosive attack is localized in specific areas. As an example, in presence of localized concentrations of chlorides, pitting corrosion of the steel bars occurs, with a localized reduction of the bar section through pits. In this work, the results of a preliminary experimental survey performed on artificially corroded steel rebars are shown, to define an integrated methodology for the definition of material constitutive laws, accounting for morphological aspects of the corrosion phenomenon. A set of steel rebars, embedded in concrete prisms, have been artificially corroded with an accelerated process through electrolytic cells, to obtain local marked pits. The steel rebars have been extracted, cleaned, weighed and subjected to 3D scanning using two different techniques (one based on laser scanning and the other based on structured-light scanning) to evaluate the effective corrosion amount and morphology. Finally, tensile tests were carried out to evaluate the stress-strain curves and the values of yielding, ultimate strengths and elongation to fracture. The presented data and methodology can represent a useful reference for the definition of phenomenological constitutive laws for steel rebars affected by pitting corrosion

    Crecimiento del langostino blanco Litopenaeus vannamei cultivado bajo un sistema de siembra directa

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    El objetivo principal de la presente investigación fue determinar el crecimiento del langostino blanco cultivado en estanques de tierra bajo un sistema de siembra directa, utilizando las aguas de regadío,para lo cual se acondicionó 2 estanques de 1.196 m2,con densi- dades de 28.4 ind/m2 y 29.1 ind/m2, previa aclimatación de la poslarva, procedente de agua de mar, con 15 ups. Alimentados con balanceado, Nicovita, en formatos pre-cría, KR-1, KR-2, con 35% de proteína, con una frecuencia de alimentación 3 veces por día, utilizando 8 co- mederos por estanque.El peso promedio de siembra fue de 0.016 gr,la duración del periodo de cultivo en la etapa de engorde fue de 100 días de cultivo, obteniéndose pesos finales de 22.14 gr y 17.07 gr; con crecimientos promedio en gramos por semana de 1.70 y 1.42 para cada uno de los estanques respectivamente; los rendimientos en peso fueron de 1851.17 kg/ ha y de 1832.60 kg/ha, con sobrevivencias de 35.09% y 44.03% para cada estanque respecti- vamente,el ciclo de cultivo se desarrolló en la época de verano con temperaturas promedio entre 28.72° C y 34.63° C. Los valores promedio de oxígeno disuelto fluctuaron entre 5.11 ppm y 8.45 ppm. La alcalinidad estuvo entre 133.40 142.55 mg/l. La investigación demuestra que es posible alcanzar pesos superiores a los 15 gramos en 3 meses de cultivo

    Optimization of a high work function solution processed vanadium oxide hole-extracting layer for small molecule and polymer organic photovoltaic cells

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    We report a method of fabricating a high work function, solution processable vanadium oxide (V2Ox(sol)) hole-extracting layer. The atmospheric processing conditions of film preparation have a critical influence on the electronic structure and stoichiometry of the V2Ox(sol), with a direct impact on organic photovoltaic (OPV) cell performance. Combined Kelvin probe (KP) and ultraviolet photoemission spectroscopy (UPS) measurements reveal a high work function, n-type character for the thin films, analogous to previously reported thermally evaporated transition metal oxides. Additional states within the band gap of V2Ox(sol) are observed in the UPS spectra and are demonstrated using X-ray photoelectron spectroscopy (XPS) to be due to the substoichiometric nature of V2Ox(sol). The optimized V2Ox(sol) layer performance is compared directly to bare indium–tin oxide (ITO), poly(ethyleneoxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and thermally evaporated molybdenum oxide (MoOx) interfaces in both small molecule/fullerene and polymer/fullerene structures. OPV cells incorporating V2Ox(sol) are reported to achieve favorable initial cell performance and cell stability attributes

    Tungsten Oxide Nanorods Array and Nanobundle Prepared by Using Chemical Vapor Deposition Technique

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    Tungsten oxide (WO3) nanorods array prepared using chemical vapor deposition techniques was studied. The influence of oxygen gas concentration on the nanoscale tungsten oxide structure was observed; it was responsible for the stoichiometric and morphology variation from nanoscale particle to nanorods array. Experimental results also indicated that the deposition temperature was highly related to the morphology; the chemical structure, however, was stable. The evolution of the crystalline structure and surface morphology was analyzed by scanning electron microscopy, Raman spectra and X-ray diffraction approaches. The stoichiometric variation was indicated by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy

    Pramipexole effects on startle gating in rats and normal men

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    Dopamine D3 receptors regulate sensorimotor gating in rats, as evidenced by changes in prepulse inhibition (PPI) of startle after acute administration of D3 agonists and antagonists. In this study, we tested the effects of the D3-preferential agonist, pramipexole, on PPI in normal men and Sprague–Dawley rats. Acoustic startle and PPI were tested in clinically normal men, comparing the effects of placebo vs. 0.125 mg (n = 20) or placebo vs. 0.1875 mg (n = 20) pramipexole, in double blind, crossover designs. These measures were also tested in male Sprague–Dawley rats using a parallel design [vehicle vs. 0.1 mg/kg (n = 8), vehicle vs. 0.3 mg/kg (n = 8) or vehicle vs. 1.0 mg/kg pramipexole (n = 8)]. Autonomic and subjective measures of pramipexole effects and several personality instruments were also measured in humans. Pramipexole increased drowsiness and significantly increased PPI at 120-ms intervals in humans; the latter effect was not moderated by baseline PPI or personality scale scores. In rats, pramipexole causes a dose-dependent reduction in long-interval (120 ms) PPI, while low doses actually increased short-interval (10–20 ms) PPI. Effects of pramipexole on PPI in rats were independent of baseline PPI and changes in startle magnitude. The preferential D3 agonist pramipexole modifies PPI in humans and rats. Unlike indirect DA agonists and mixed D2/D3 agonists, pramipexole increases long-interval PPI in humans, in a manner that is independent of baseline PPI and personality measures. These findings are consistent with preclinical evidence for differences in the D2- and D3-mediated regulation of sensorimotor gating

    Private 5G Technology and Implementation Testing

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    69A3551747115/06-006NEC developed a Video Analytics implementation for traffic intersections using 5G technology. This implementation included both hardware infrastructure and software applications supporting 5G communications, which allows low latency and secure communications. The Virginia Tech Transportation Institute (VTTI) worked with NEC to facilitate the usage of a 3,400- to 3,500-MHz program experimental license band without SAS integration to successfully implement a private 5G deployment at the VTTI Smart Road intersection and data center. Specific use cases were developed to provide alerting mechanisms to both pedestrians and vehicles using cellular vehicle-to-everything/PC5 technology when approaching a traffic intersection and a dangerous situation is detected

    Smart Work Zone System

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    69A3551747115/VTTI-00-036In the previous Safe-D project 04-104, a prototype wearable Personal Protective Equipment vest that accurately localizes, monitors, and predicts potential collisions between work zone (WZ) workers and passing motorists was developed and demonstrated. The system also notifies the worker when they\u2019re about to depart geo-fenced safe areas within WZs. While the design supported a successful functional demonstration, additional design iteration was required to simplify, ruggedize, and reduce per unit costs to increase the likelihood of broader adoption. In addition, two new useful components were identified that support a more effective deployment package. One of these components is a Base Station that provides an edge computing environment for alert algorithm processing, consolidates communications of individual worker positions via a 4G link to a cloud computing environment, and can be coupled with a local roadside unit to support the broadcast of WZ information to connected and automated vehicles. The second component is a Smart Cone device that was added to help automatically define safe area boundaries and improve communications reliability between workers and the Base Station. This entire package was developed to support a broader scale deployment of the technology by the Virginia Department of Transportation

    Effect of apomorphine on cognitive performance and sensorimotor gating in humans

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    Contains fulltext : 88792.pdf (publisher's version ) (Closed access)INTRODUCTION: Dysfunction of brain dopamine systems is involved in various neuropsychiatric disorders. Challenge studies with dopamine receptor agonists have been performed to assess dopamine receptor functioning, classically using the release of growth hormone (GH) from the hindbrain as primary outcome measure. The objective of the current study was to assess dopamine receptor functioning at the forebrain level. METHODS: Fifteen healthy male volunteers received apomorphine sublingually (2 mg), subcutaneously (0.005 mg/kg), and placebo in a balanced, double-blind, cross-over design. Outcome measures were plasma GH levels, performance on an AX continuous performance test, and prepulse inhibition of the acoustic startle. The relation between central outcome measures and apomorphine levels observed in plasma and calculated in the brain was modeled using a two-compartmental pharmacokinetic-pharmacodynamic analysis. RESULTS: After administration of apomorphine, plasma GH increased and performance on the AX continuous performance test deteriorated, particularly in participants with low baseline performance. Apomorphine disrupted prepulse inhibition (PPI) on high-intensity (85 dB) prepulse trials and improved PPI on low intensity (75 dB) prepulse trials, particularly in participants with low baseline PPI. High cognitive performance at baseline was associated with reduced baseline sensorimotor gating. Neurophysiological measures correlated best with calculated brain apomorphine levels after subcutaneous administration. CONCLUSION: The apomorphine challenge test appears a useful tool to assess dopamine receptor functioning at the forebrain level. Modulation of the effect of apomorphine by baseline performance levels may be explained by an inverted U-shape relation between prefrontal dopamine functioning and cognitive performance, and mesolimbic dopamine functioning and sensorimotor gating. Future apomorphine challenge tests preferentially use multiple outcome measures, after subcutaneous administration of apomorphine.1 januari 201

    Study protocol for the multicentre cohorts of Zika virus infection in pregnant women, infants, and acute clinical cases in Latin America and the Caribbean: The ZIKAlliance consortium

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    Background: The European Commission (EC) Horizon 2020 (H2020)-funded ZIKAlliance Consortium designed a multicentre study including pregnant women (PW), children (CH) and natural history (NH) cohorts. Clinical sites were selected over a wide geographic range within Latin America and the Caribbean, taking into account the dynamic course of the ZIKV epidemic. Methods: Recruitment to the PW cohort will take place in antenatal care clinics. PW will be enrolled regardless of symptoms and followed over the course of pregnancy, approximately every 4 weeks. PW will be revisited at delivery (or after miscarriage/abortion) to assess birth outcomes, including microcephaly and other congenital abnormalities according to the evolving definition of congenital Zika syndrome (CZS). After birth, children will be followed for 2 years in the CH cohort. Follow-up visits are scheduled at ages 1-3, 4-6, 12, and 24 months to assess neurocognitive and developmental milestones. In addition, a NH cohort for the characterization of symptomatic rash/fever illness was designed, including follow-up to capture persisting health problems. Blood, urine, and other biological materials will be collected, and tested for ZIKV and other relevant arboviral diseases (dengue, chikungunya, yellow fever) using RT-PCR or serological methods. A virtual, decentralized biobank will be created. Reciprocal clinical monitoring has been established between partner sites. Substudies of ZIKV seroprevalence, transmissio
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