938 resultados para Automatic frequency control


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El cuestionamiento de las relaciones capitalistas de producción debe surgir a partir de su tendencia inherente a los desequilibrios y a la irracionalidad económica y no desde algún pre-juicio ideológico o político. En este contexto, la planificación económica se presenta como necesaria en la medida en que se requiera asegurar una autonomía humana de decisión con respecto a la distribución del ingreso, el acceso al empleo y la protección del medio ambiente. A partir de la constatación de este hecho, la planificación no sustituye a las relaciones mercantiles sino que cumple la función de garantizar una tendencia al equilibrio sobre la base de las relaciones mercantiles, lo que ningún automatismo del mercado puede garantizar. Se propone un principio de delimitación entre la planificación y la autonomía de las empresas (la reproducción de la vida humana), principio ampliable a la delimitación entre el Estado y las actividades de los grupos autónomos y de los mismos sujetos en general. Abstract The questioning of the capitalist relations of production must come from their inherent tendency to irrationality and economic imbalances and not from any ideological or political prejudice. In this context, economic planning is as necessary as it is required to ensure a human decision-making autonomy with respect to income distribution, access to employment and environmental protection. From the observation of this fact, planning is not a substitute for market relations but serves to ensure a tendency to balance on the basis of market relations, so no automatic of the market can guarantee. The article proposes a principle of demarcation between the planning and autonomy for enterprises (the reproduction of human life), expandable to top the demarcation between the state and the activities of autonomous groups and the same subjects in general.

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Erratum in: Low-frequency and common genetic variation in ischemic stroke: The METASTROKE collaboration. [Neurology. 2016]

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Idealized ocean models are known to develop intrinsic multidecadal oscillations of the meridional overturning circulation (MOC). Here we explore the role of ocean–atmosphere interactions on this low-frequency variability. We use a coupled ocean–atmosphere model set up in a flat-bottom aquaplanet geometry with two meridional boundaries. The model is run at three different horizontal resolutions (4°, 2° and 1°) in both the ocean and atmosphere. At all resolutions, the MOC exhibits spontaneous variability on multidecadal timescales in the range 30–40 years, associated with the propagation of large-scale baroclinic Rossby waves across the Atlantic-like basin. The unstable region of growth of these waves through the long wave limit of baroclinic instability shifts from the eastern boundary at coarse resolution to the western boundary at higher resolution. Increasing the horizontal resolution enhances both intrinsic atmospheric variability and ocean–atmosphere interactions. In particular, the simulated atmospheric annular mode becomes significantly correlated to the MOC variability at 1° resolution. An ocean-only simulation conducted for this specific case underscores the disruptive but not essential influence of air–sea interactions on the low-frequency variability. This study demonstrates that an atmospheric annular mode leading MOC changes by about 2 years (as found at 1° resolution) does not imply that the low-frequency variability originates from air–sea interactions.

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This thesis describes two separate projects. The first is a theoretical and experimental investigation of surface acoustic wave streaming in microfluidics. The second is the development of a novel acoustic glucose sensor. A separate abstract is given for each here. Optimization of acoustic streaming in microfluidic channels by SAWs Surface Acoustic Waves, (SAWs) actuated on flat piezoelectric substrates constitute a convenient and versatile tool for microfluidic manipulation due to the easy and versatile interfacing with microfluidic droplets and channels. The acoustic streaming effect can be exploited to drive fast streaming and pumping of fluids in microchannels and droplets (Shilton et al. 2014; Schmid et al. 2011), as well as size dependant sorting of particles in centrifugal flows and vortices (Franke et al. 2009; Rogers et al. 2010). Although the theory describing acoustic streaming by SAWs is well understood, very little attention has been paid to the optimisation of SAW streaming by the correct selection of frequency. In this thesis a finite element simulation of the fluid streaming in a microfluidic chamber due to a SAW beam was constructed and verified against micro-PIV measurements of the fluid flow in a fabricated device. It was found that there is an optimum frequency that generates the fastest streaming dependent on the height and width of the chamber. It is hoped this will serve as a design tool for those who want to optimally match SAW frequency with a particular microfluidic design. An acoustic glucose sensor Diabetes mellitus is a disease characterised by an inability to properly regulate blood glucose levels. In order to keep glucose levels under control some diabetics require regular injections of insulin. Continuous monitoring of glucose has been demonstrated to improve the management of diabetes (Zick et al. 2007; Heinemann & DeVries 2014), however there is a low patient uptake of continuous glucose monitoring systems due to the invasive nature of the current technology (Ramchandani et al. 2011). In this thesis a novel way of monitoring glucose levels is proposed which would use ultrasonic waves to ‘read’ a subcutaneous glucose sensitive-implant, which is only minimally invasive. The implant is an acoustic analogy of a Bragg stack with a ‘defect’ layer that acts as the sensing layer. A numerical study was performed on how the physical changes in the sensing layer can be deduced by monitoring the reflection amplitude spectrum of ultrasonic waves reflected from the implant. Coupled modes between the skin and the sensing layer were found to be a potential source of error and drift in the measurement. It was found that by increasing the number of layers in the stack that this could be minimized. A laboratory proof of concept system was developed using a glucose sensitive hydrogel as the sensing layer. It was possible to monitor the changing thickness and speed of sound of the hydrogel due to physiological relevant changes in glucose concentration.

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Supply chains are ubiquitous in any commercial delivery systems. The exchange of goods and services, from different supply points to distinct destinations scattered along a given geographical area, requires the management of stocks and vehicles fleets in order to minimize costs while maintaining good quality services. Even if the operating conditions remain constant over a given time horizon, managing a supply chain is a very complex task. Its complexity increases exponentially with both the number of network nodes and the dynamical operational changes. Moreover, the management system must be adaptive in order to easily cope with several disturbances such as machinery and vehicles breakdowns or changes in demand. This work proposes the use of a model predictive control paradigm in order to tackle the above referred issues. The obtained simulation results suggest that this strategy promotes an easy tasks rescheduling in case of disturbances or anticipated changes in operating conditions. © Springer International Publishing Switzerland 2017

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This paper describes the application of a Brain Emotional Learning (BEL) controller to improve the response of a SDOF structural system under an earthquake excitation using a magnetorheological (MR) damper. The main goal is to study the performance of a BEL based semi-active control system to generate the control signal for a MR damper. The proposed approach consists of a two controllers: a primary controller based on a BEL algorithm that determines the desired damping force from the system response and a secondary controller that modifies the input current to the MR damper to generate a reference damping force. A parametric model of the damper is used to predict the damping force based on the piston motion and also the current input. A Simulink model of the structural system is developed to analyze the effectiveness of the semi-active controller. Finally, the numerical results are presented and discussed.

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Background: There are limited data concerning endoscopist-directed endoscopic retrograde cholangiopancreatography deep sedation. The aim of this study was to establish the safety and risk factors for difficult sedation in daily practice. Patients and methods: Hospital-based, frequency matched case-control study. All patients were identified from a database of 1,008 patients between 2014 and 2015. The cases were those with difficult sedations. This concept was defined based on the combination of the receipt of high-doses of midazolam or propofol, poor tolerance, use of reversal agents or sedation-related adverse events. The presence of different factors was evaluated to determine whether they predicted difficult sedation. Results: One-hundred and eighty-nine patients (63 cases, 126 controls) were included. Cases were classified in terms of high-dose requirements (n = 35, 55.56%), sedation-related adverse events (n = 14, 22.22%), the use of reversal agents (n = 13, 20.63%) and agitation/discomfort (n = 8, 12.7%). Concerning adverse events, the total rate was 1.39%, including clinically relevant hypoxemia (n = 11), severe hypotension (n = 2) and paradoxical reactions to midazolam (n = 1). The rate of hypoxemia was higher in patients under propofol combined with midazolam than in patients with propofol alone (2.56% vs. 0.8%, p < 0.001). Alcohol consumption (OR: 2.674 [CI 95%: 1.098-6.515], p = 0.030), opioid consumption (OR: 2.713 [CI 95%: 1.096-6.716], p = 0.031) and the consumption of other psychoactive drugs (OR: 2.015 [CI 95%: 1.017-3.991], p = 0.045) were confirmed to be independent risk factors for difficult sedation. Conclusions: Endoscopist-directed deep sedation during endoscopic retrograde cholangiopancreatography is safe. The presence of certain factors should be assessed before the procedure to identify patients who are high-risk for difficult sedation.

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This document is the Argo quality control manual for Dissolved oxygen concentration. It describes two levels of quality control: • The first level is the real-time system that performs a set of agreed automatic checks. • Adjustment in real-time can also be performed and the real-time system can evaluate quality flags for adjusted fields • The second level is the delayed-mode quality control system.

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In April 2017, CMEMS plans to launch the WAVES NRT products. This document is focused in the automatic RTQC of the collected wave data. The validation procedure includes the delayed mode quality control of the data and will be specified in another guideline. To perform any kind of quality control to wave data, first it’s necessary to know the nature of the measurements and the analysis performed to those measurements to obtain the wave parameters. For that reason next chapter is dedicated to show the usual wave analysis and the different parameters and estimators obtained.

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Dissertação de Mestrado, Ciências da Linguagem, Faculdade de Ciências Humanas e Sociais, Universidade do Algarve, 2014

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Although electrical neurostimulation has been proposed as an alternative treatment for drug-resistant cases of epilepsy, current procedures such as deep brain stimulation, vagus, and trigeminal nerve stimulation are effective only in a fraction of the patients. Here we demonstrate a closed loop brain-machine interface that delivers electrical stimulation to the dorsal column (DCS) of the spinal cord to suppress epileptic seizures. Rats were implanted with cortical recording microelectrodes and spinal cord stimulating electrodes, and then injected with pentylenetetrazole to induce seizures. Seizures were detected in real time from cortical local field potentials, after which DCS was applied. This method decreased seizure episode frequency by 44% and seizure duration by 38%. We argue that the therapeutic effect of DCS is related to modulation of cortical theta waves, and propose that this closed-loop interface has the potential to become an effective and semi-invasive treatment for refractory epilepsy and other neurological disorders.

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Size and shape tuneable ZnO nanostructures were prepared by a low frequency ultrasound (42 kHz) route using various organic solvents as the reaction media. The crystalline nature, lattice parameters and microstructural parameters such as microstrain, stress and energy density of the prepared ZnO nanostructures were revealed through X-ray diffraction (XRD) analysis. The organic solvents influenced the size and morphology of the ZnO nanostructures, and interesting morphological changes involving a spherical to triangular shaped transition were observed. The visible emission properties and lattice vibrational characteristics of the nanostructures were drastically modified by the changes in size and shape. Raman spectral measurements revealed the presence of multiphonon processes in the ZnO nanostructures. The intensity of the visible emission band was found to vary with the size and morphology of the structures. The strongest visible emission band corresponded to the structure with the largest surface/volume ratio and could be attributed to surface oxygen vacancies. The control over the size and morphology of ZnO nanostructures has been presented as a means of determining the intensity of the visible emission band

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Background: Azoospermia is the medical condition of a man not having any measurable level of sperm in his semen. Follicle stimulating hormone (FSH) is a member of the glycoprotein hormone family that plays an important role in human reproduction because of its essential role in normal spermatogenesis. Various Single Nucleotide Polymorphisms (SNPs) have been reported within FSH receptor (FSHR) gene that may affect the receptor function. Objective: The present study aimed to investigate the correlation between two FSHR SNPs at positions A919G, A2039G, and susceptibility to azoospermia in a group of Iranian azoospermic men. The association between FSH levels within the sera and A919G and A2039G alleles and genotypes were also investigated. Materials and Methods: This case control study was performed on 212 men with azoospermia (126 non-obstructive and 86 obstructive) and 200 healthy Iranian men. Two FSHR gene SNPs were genotyped using PCR-RFLP method. The relationship between FSH levels within the sera and A919G and A2039G alleles and genotypes were also investigated. Results: Statistical analysis indicated that at A919G position, AA genotype and A allele were more frequent in obstructive azoospermia cases compared to non- obstructive or normal men (p=0.001). Regarding A2039G polymorphisms, no significant difference was observed between both azoospermia groups and the controls. The mean level of serum FSH was higher in the non-obstructive men compared to the obstructive patients (23.8 versus 13.8, respectively, p= 0.04). Conclusion: The results of the present study indicated that the genetic polymorphisms in the FSHR gene might increase the susceptibility to azoospermia in Iranian men.