211 research outputs found
Cognitive Resource Management In 5G Networks
The 4G LTE network offers a high speed connectivity that is predicated on the construction platform of the 3G network and relies on an Internet Protocol (IP) for data transmission and reception. This platform’s utility is quickly becoming exhausted as the frequency spectrum approaches maximum device connectivity capacity. To improve network capacity, we must expand the bandwidth that our devices operate on. To effectively carry out this task, a self-configurable network must be employed in the development of the 5g network. This article aims to explore the technologies which form the platform for the 5G network and the cognitive resource management devices which the network is contingent upon. Base Stations (BS); Artificial Intelligence (AI); Internet Protocol (IP)
Computational Fluid Dynamics in Congenital Heart Disease
Computational fluid dynamics has been applied to the design, refinement, and assessment of surgical procedures and medical devices. This tool calculates flow patterns and pressure changes within a virtual model of the cardiovascular system. In the field of paediatric cardiac surgery, computational fluid dynamics is being used to elucidate the optimal approach to staged reconstruction of specific defects and study the haemodynamics of the resulting anatomical configurations after reconstructive or palliative surgery. In this paper, we review the techniques and principal findings of computational fluid dynamics studies as applied to a few representative forms of congenital heart disease
La Modernización Agroindustrial y el Surgimiento de la Agroecología en México (1920-1960)
Mexican countryside was a field of dispute between two agro-productive models in the first half of the 20th century. As a result of demographic pressures and industrial and urban development projects promoted by the governments emerged from the Mexican Revolution, and later of the economic and geopolitical interests of the United States government and the Rockefeller Foundation, efforts were made to modernize the country's traditional agriculture through improved seeds, agrochemicals and agricultural machinery among other elements. Although in some regions of the country these components were quickly incorporated, in other parts they generated alert reactions and opposition due to the social, economic, environmental and even geopolitical risks and problems that were believed to be generated. And they also motivated the development of research to find alternatives to the mentioned components. We propose that, to the extent that these manifestations questioned the relevance of agro-industrial technologies and sought alternatives from an ecological perspective, they constitute fundamental antecedents in the history of Mexican agroecology.Las parcelas mexicanas fueron un campo de disputa entre dos modelos agroproductivos en la primera mitad del siglo XX. Resultado de las presiones demográficas y los proyectos de desarrollo industrial y urbano que impulsaron los gobiernos emanados de la Revolución Mexicana, y posteriormente de los intereses económicos y geopolíticos del gobierno estadounidense y la Fundación Rockefeller, se buscó modernizar la agricultura tradicional mediante semillas mejoradas, agroquímicos y maquinaria agrícola entre otros elementos. Si bien en algunas regiones del país dichos componentes fueron rápidamente incorporados, en otras partes generaron reacciones de alerta y oposición por los riesgos y problemas sociales, económicos, ambientales e incluso geopolíticos que se creía podían generar. Y motivaron también el desarrollo de investigaciones para encontrar alternativas a los componentes mencionados. Proponemos que, en la medida que dichas manifestaciones cuestionaron la pertinencia de las tecnologías agroindustriales y buscaron alternativas desde una perspectiva ecológica, constituyen antecedentes fundamentales en la historia de la agroecología mexicana.Las parcelas mexicanas fueron un campo de disputa entre dos modelos agroproductivos en la primera mitad del siglo XX. Resultado de las presiones demográficas y los proyectos de desarrollo industrial y urbano que impulsaron los gobiernos emanados de la Revolución Mexicana, y posteriormente de los intereses económicos y geopolíticos del gobierno estadounidense y la Fundación Rockefeller, se buscó modernizar la agricultura tradicional mediante semillas mejoradas, agroquímicos y maquinaria agrícola entre otros elementos. Si bien en algunas regiones del país dichos componentes fueron rápidamente incorporados, en otras partes generaron reacciones de alerta y oposición por los riesgos y problemas sociales, económicos, ambientales e incluso geopolíticos que se creía podían generar. Y motivaron también el desarrollo de investigaciones para encontrar alternativas a los componentes mencionados. Proponemos que, en la medida que dichas manifestaciones cuestionaron la pertinencia de las tecnologías agroindustriales y buscaron alternativas desde una perspectiva ecológica, constituyen antecedentes fundamentales en la historia de la agroecología mexicana
Threshold volatility models: forecasting performance
The aim of this paper is to compare the forecasting performance of competing
volatility models, in order to capture the asymmetric effect in the volatility.
We focus on examining the relative out-of-sample forecasting ability of the models
(SETAR-TGARCH and SETAR-THSV), which contain the introduction of regimes
based on thresholds in the mean equation and volatility equation, compared to the
GARCH model and SV model. For each model, we consider two cases: Gaussian and
t-Student measurement noise distribution. An important problem when evaluating
the predictive ability of volatility models is that the “true” underlying process is
not observable and thus a proxy must be defined for the unobservable volatility. To
attain our proposal, the proxy volatility measure and the loss function must also be
decided to ensure a correct ranking of models.
Our empirical application suggests the following results: when time series include
leverage effects on the mean, the introduction of threshold in the mean and variance
equations produces more accurate predictions. If the leverage in the mean is not
important, then the SVt is flexible enough to beat the threshold models.Peer ReviewedPostprint (published version
Threshold volatily models: forecasting performance
The aim of this paper is to compare the forecasting performance of competing
volatility models, in order to capture the asymmetric effect in the volatility.
We focus on examining the relative out-of-sample forecasting ability of the models
(SETAR-TGARCH and SETAR-THSV), which contain the introduction of regimes based on thresholds in the mean equation and volatility equation, compared to the GARCH model and SV model. For each model, we consider two cases: Gaussian and t-Student measurement noise distribution. An important problem when evaluating the predictive ability of volatility models is that the “true” underlying process is not observable and thus a proxy must be defined for the unobservable volatility. To attain our proposal, the proxy volatility measure and the loss function must also be decided to ensure a correct ranking of models.
Our empirical application suggests the following results: when time series include
leverage effects on the mean, the introduction of threshold in the mean and variance equations produces more accurate predictions. If the leverage in the mean is not important, then the SVt is flexible enough to beat the threshold models.Postprint (published version
Computational Analysis of Hybrid Norwood Circulation with Distal Aortic Arch Obstruction and Reverse Blalock-Taussig Shunt
BACKGROUND: The hemodynamics characteristics of the hybrid Norwood (HN) procedure differ from those of the conventional Norwood and are not fully understood. We present a multi-scale model of HN circulation to understand local hemodynamics and effects of aortic arch stenosis and a reverse Blalock-Taussig shunt (RBTS) on coronary and carotid perfusion. METHODS: Four 3-dimensional models of four HN anatomic variants were developed, with and without 90% distal preductal arch stenosis and with and without a 4-mm RBTS. A lumped parameter model of the circulation was coupled to a local 3-dimensional computational fluid dynamics model. Outputs from the lumped parameter model provided waveform boundary conditions for the computational fluid dynamics model. RESULTS: A 90% distal arch stenosis reduced pressure and net flow-rate through the coronary and carotid arteries by 30%. Addition of the RBTS completely restored pressure and flow rate to baseline in these vessels. Zones of flow stagnation, flow reversal, and recirculation in the presence of stenosis were rendered more orderly by addition of the RBTS. In the absence of stenosis, presence of the shunt resulted in extensive zones of disturbed flow within the RBTS and arch. CONCLUSIONS: We found that a 4-mm × 21-mm RBTS completely compensated for the effects of a 90% discrete stenosis of the distal aortic arch in the HN. Placed preventatively, the RBTS and arch displayed zones with thrombogenic potential showing recirculation and stagnation that persist for a substantial fraction of the cardiac cycle, indicating that anticoagulation should be considered with a prophylactic RBTS
The pattern of brittle deformation in Central America for an assessment of the seismo-tectonic framework
A seismo-tectonic map depicting the principal structural elements of the northern Central American region has been meticulously crafted to characterize the tectonic setting and the individual seismo-tectonic structures of this area. This region is subject to heightened seismic activity, with a large number of medium-high Magnitude occurrences transpiring annually. This map is presented alongside an informative dataset wherein fault trace
locations, geometry and kinematics descriptors and other available metadata have been stored. Therefore, the map offers a detailed and up-to-date depiction of the brittle deformation across the region, serving as a valuable resource for a comprehensive assessment of the seismo-tectonic framework. Moreover, the map and its accompanying database summarize fault characteristics for seismic hazard analysts and for civil protection workers, proving to be useful instruments in pinpointing areas where urgent fault research should be conducted from a seismic risk standpoint
Assessing the Reliability of Stryd 27 for Variable Speed Running
Wearable technology is beneficial when it comes to tracking and optimizing performance. The Stryd 27 is a wearable footpod marketed as being more responsive in measuring power during running than the previous version (Stryd 25). However, the reliability of this newer device to return consistent values has not been determined. PURPOSE: This study aimed to observe whether Stryd 27 gives reliable metrics during variable speed running. METHODS: Sixteen participants (N = 16; 50% female; height = 174.1 ± 8.1 cm; mass = 73.0 ± 12.4 kg) were recruited, each equipped with two Stryd 27 footpods (updated to the same software version) affixed to the shoelaces of their running shoes. The researchers recorded data using the Stryd app on a mobile device that was connected to the Stryd 27 via Bluetooth. Recording on both devices were started and stopped at the same time. Each participant completed two, 10-minute runs on an indoor track. The initial run was used to establish a baseline. Following a 5-minute rest period, participants proceeded with the second run, during which they alternated between faster and slower intervals. The pace for these intervals was set to be 20% faster and 20% slower than what each participant’s average pace was during the first run. Reliability of power, cadence, form power, ground contact time (GCT), vertical oscillation (VO), leg spring stiffness (LSS), and stride length during the interval run was determined using coefficient of variation (CV) and intraclass correlation coefficient (ICC), with CV0.70 (p \u3c 0.05) being considered evidence of reliability. RESULTS: Reliability data are shown in Table 1. The following measures were found to be reliable: power, cadence, form power, GCC, and VO. The measures of LSS and stride length were not found to be reliable. CONCLUSION: Runners using the new Stryd 27 can have confidence that most measures return reliable values (power, cadence, form power, GCT, and VO). Unfortunately, two measures were observed to not meet the threshold for reliability (LSS and stride length). Athletes interested in these measures should be cautious when interpreting their data
Copper: Synthesis Techniques in Nanoscale and Powerful Application as an Antimicrobial Agent
Nanosized metal particles show specific physical and chemical properties that allow the creation of new composites materials, which are important for multiple applications in biology and medicine such as infections control. Metal nanoparticles, mainly copper, exhibit excellent inhibitory effect on Gram-positive and Gram-negative bacteria; therefore the exploration about the efficient, economical, and friendly environmental technics to synthesize inorganic nanoparticles is imperative. In this work a brief overview of the several methods is made including the comparison of the methods, mainly between sonochemical, microwave, and chemical routes. It allows determining the optimal parameters and technical conditions to synthesize copper nanoparticles with physical and chemical properties suitable for the oral bacterial inhibition
Stryd 25 vs. Stryd 27: Comparing Running Metrics Between a Predecessor and “The Next Gen Stryd”
Wearable technology has claimed the top spot in the Worldwide Survey of Fitness Trends in all but two years since 2016. A popular wearable among runners is the Stryd power meter. The company markets its latest model, the Stryd 27, as 5x more responsive in measuring running power. Yet, it is unclear whether the new model performs differently than its predecessor. PURPOSE: This study aimed to compare running metrics of the Stryd 25 and Stryd 27 in self-paced and interval runs. METHODS: Participants consented (N = 16; 50% female; height = 174.1 ± 8.1 centimeters [cm]; mass = 73.0 ± 12.4 kilograms) and were equipped with the Stryd 25 and Stryd 27, attached randomly to the left and right shoelaces. Each Stryd was paired with a separate mobile device using the Stryd app. Researchers started and stopped recording on each Stryd simultaneously. Participants ran for 10 minutes at a self-selected pace counterclockwise around an indoor track (10 laps/mile) before resting for five minutes. Then participants ran 10 more minutes, alternating between fast and slow intervals: 120 seconds (s) × 2, 60 s × 2, 30 s × 4, and 15 s × 8. Fast and slow intervals were 20% faster and 20% slower, respectively, than the participant’s mean pace of the first run. The Stryd app recorded power in watts (W), cadence in steps per minute (spm), vertical oscillation (VO) in cm, and stride length in meters (m). Four independent t-tests were run to compare these measurements between the two Stryd models for the self-paced and interval runs. The alpha level was .05, and the effect size was Cohen’s d (0.2 small, 0.5 medium, 0.8 large). RESULTS: See Table 1. CONCLUSION: Four running metrics were statistically similar between the Stryd 25 and Stryd 27 during two indoor runs. Runners using the predecessor indoors can be confident it returns similar data to the newest model
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