Water detection in jet fuel using a polymer optical fibre Bragg grating

Water is a common impurity of jet fuel, and can exist in three forms: dissolved in the fuel, as a suspension and as a distinct layer at the bottom of the fuel tank. Water cannot practically be eliminated from fuel but must be kept to a minimum as large quantities can cause engine problems, particularly when frozen, and the interface between water and fuel acts as a breeding ground for biological contaminants. The quantities of dissolved or suspended water are quite small, ranging from about 10 ppm to 150 ppm. This makes the measurement task difficult and there is currently a lack of a convenient, electrically passive system for water-in-fuel monitoring; instead the airlines rely on colorimetric spot tests or simply draining liquid from the bottom of fuel tanks. For all these reason, people have explored different ways to detect water in fuel, however all these approaches have problems, e.g. they may not be electrically passive or they may be sensitive to the refractive index of the fuel. In this paper, we present a simple, direct and sensitive approach involving the use of a polymer optical fibre Bragg grating to detect water in fuel. The principle is that poly(methyl methacrylate) (PMMA) can absorb moisture from its surroundings (up to 2% at 23 °C), leading to both a swelling of the material and an increase in refractive index with a consequent increase in the Bragg wavelength of a grating inscribed in the material.

Water detection in jet fuel using a polymer optical fibre Bragg grating

Water is a common impurity of jet fuel, and can exist in three forms: dissolved in the fuel, as a suspension and as a distinct layer at the bottom of the fuel tank. Water cannot practically be eliminated from fuel but must be kept to a minimum as large quantities can cause engine problems, particularly when frozen, and the interface between water and fuel acts as a breeding ground for biological contaminants. The quantities of dissolved or suspended water are quite small, ranging from about 10 ppm to 150 ppm. This makes the measurement task difficult and there is currently a lack of a convenient, electrically passive system for water-in-fuel monitoring; instead the airlines rely on colorimetric spot tests or simply draining liquid from the bottom of fuel tanks. For all these reason, people have explored different ways to detect water in fuel, however all these approaches have problems, e.g. they may not be electrically passive or they may be sensitive to the refractive index of the fuel. In this paper, we present a simple, direct and sensitive approach involving the use of a polymer optical fibre Bragg grating to detect water in fuel. The principle is that poly(methyl methacrylate) (PMMA) can absorb moisture from its surroundings (up to 2% at 23 °C), leading to both a swelling of the material and an increase in refractive index with a consequent increase in the Bragg wavelength of a grating inscribed in the material.

Surrogate-based analysis and optimization for the design of heat sinks with jet impingement

Heat sinks are widely used for cooling electronic devices and systems. Their thermal performance is usually determined by the material, shape, and size of the heat sink. With the assistance of computational fluid dynamics (CFD) and surrogate-based optimization, heat sinks can be designed and optimized to achieve a high level of performance. In this paper, the design and optimization of a plate-fin-type heat sink cooled by impingement jet is presented. The flow and thermal fields are simulated using the CFD simulation; the thermal resistance of the heat sink is then estimated. A Kriging surrogate model is developed to approximate the objective function (thermal resistance) as a function of design variables. Surrogate-based optimization is implemented by adaptively adding infill points based on an integrated strategy of the minimum value, the maximum mean square error approach, and the expected improvement approaches. The results show the influence of design variables on the thermal resistance and give the optimal heat sink with lowest thermal resistance for given jet impingement conditions.

Design Optimization of Submerged Jet Nozzles for Enhanced Mixing

The purpose of this thesis was to identify the optimal design parameters for a jet nozzle which obtains a local maximum shear stress while maximizing the average shear stress on the floor of a fluid filled system. This research examined how geometric parameters of a jet nozzle, such as the nozzle's angle, height, and orifice, influence the shear stress created on the bottom surface of a tank. Simulations were run using a Computational Fluid Dynamics (CFD) software package to determine shear stress values for a parameterized geometric domain including the jet nozzle. A response surface was created based on the shear stress values obtained from 112 simulated designs. A multi-objective optimization software utilized the response surface to generate designs with the best combination of parameters to achieve maximum shear stress and maximum average shear stress. The optimal configuration of parameters achieved larger shear stress values over a commercially available design.

Angular distribution of Z(0 power) bosons in Z+jet events at the square root of S = 7 TeV

For the first time, the Z0 boson angular distribution in the center-of-momentum frame is measured in proton-proton collisions at [special characters omitted] = 7 TeV at the CERN LHC. The data sample, recorded with the CMS detector, corresponds to an integrated luminosity of approximately 36 pb–1 . Events in which there is a Z0 and at least one jet, with a jet transverse momentum threshold of 20 GeV and absolute jet rapidity less than 2.4, are selected for the analysis. Only the Z0's muon decay channel is studied. Within experimental and theoretical uncertainties, the measured angular distribution is in agreement with next-to-leading order perturbative QCD predictions.

Influência do jet lag social em marcadores circadianos de atividade - repouso e cardíaco em estudantes de medicina

Studies reveal that in recent decades a decrease in sleep duration has occurred. Social commitments, such as work and school are often not aligned to the "biological time" of individuals. Added to this, there is a reduced force of zeitgeber caused by less exposure to daylight and larger exposure to evenings. This causes a chronic sleep debt that is offset in a free days. Indeed, a restriction and extent of sleep called "social Jet lag" occurs weekly. Sleep deprivation has been associated to obesity, cancer, and cardiovascular risk. It is suggested that the autonomic nervous system is a pathway that connects sleep problems to cardiovascular diseases. However, beyond the evidence demonstrated by studies using models of acute and controlled sleep deprivation, studies are needed to investigate the effects of chronic sleep deprivation as it occurs in the social jet lag. The aim of this study was to investigate the influence of social jet lag in circadian rest-activity markers and heart function in medical students. It is a cross-sectional, observational study conducted in the Laboratory of Neurobiology and Biological Rhythmicity (LNRB) at the Department of Physiology UFRN. Participated in the survey medical students enrolled in the 1st semester of their course at UFRN. Instruments for data collection: Munich Chronotype Questionnaire, Morningness Eveningness Questionnaire of Horne and Östberg, Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, Actimeter; Heart rate monitor. Analysed were descriptive variables of sleep, nonparametric (IV60, IS60, L5 and M10) and cardiac indexes of time domain, frequency (LF, HF LF / HF) and nonlinear (SD1, SD2, SD1 / SD2). Descriptive, comparative and correlative statistical analysis was performed with SPSS software version 20. 41 students participated in the study, 48.8% (20) females and 51.2% (21) males, 19.63 ± 2.07 years. The social jet lag had an average of 02: 39h ± 00:55h, 82.9% (34) with social jet lag ≥ 1h and there was a negative correlation with the Munich chronotype score indicating greater sleep deprivation in subjects prone to eveningness. Poor sleep quality was detected in 90.2% (37) (X2 = 26.56, p <0.001) and 56.1% (23) excessive daytime sleepiness (X2 = 0.61, p = 0.435). Significant differences were observed in the values of LFnu, HFnu and LF / HF between the groups of social jet lag <2h and ≥ 2h and correlation of the social jet lag with LFnu (rs = 0.354, p = 0.023), HFnu (rs = - 0.354 , p = 0.023) and LF / HF (r = 0.355, p = 0.023). There was also a negative association between IV60 and indexes in the time domain and non-linear. It is suggested that chronic sleep deprivation may be associated with increased sympathetic activation promoting greater cardiovascular risk.

Les armes de jet d’Argilos : catalogue typologique

Quelques sites archéologiques comme Olympie, Stymphalos et Olynthe possèdent respectivement un répertoire faisant l’étude des armes de jet retrouvées durant une série de campagnes de fouilles archéologiques. Parmi ces indexes, figurent fréquemment des pointes de flèche, des balles de fronde et des saurotères (contrepoids de lance ou de javelot) provenant de différentes périodes historiques gréco-romaines. À travers les 20e et 21e siècle de notre ère, des spécialistes comme D. Robinson (1931), A. Snodgrass (1964), H. Baitinger (2001), C. Hagerman (2014) dédièrent une partie de leur expertise pour produire des synthèses sur ces objets jadis négligés. Ainsi, ils parvinrent à créer de grandes encyclopédies commentées composées de projectiles retrouvés en sol grec. À l’aide de ces bases de données, les archéologues militaires sont en mesure d’établir des datations et l’origine prétendue de certains types de projectiles. Jusqu’en 2015, les artéfacts militaires trouvés sur le site archéologique d’Argilos n’avaient jamais fait l’objet d’une étude de synthèse. D’abord, inspiré par de publications semblables, ces projectiles furent soumis à un inventaire sous forme de catalogue. Au total, deux types de balles de fronde en plomb, onze types de pointes de flèche et un type de saurotère furent identifiés. Finalement, ce nouveau contenu fut assujetti à des analyses comparatives avec d’autres sites archéologiques possédant des données similaires. Les conclusions découlant de ces analogies donnèrent naissance à la première typologie des armes de jet argilienne. Certes, les analyses se heurtèrent à certains obstacles, notamment à une compréhension de la quasi-inexistence d'une pointe de flèche typiquement "grecque" et à la confusion systématique quant à la distinction entre un saurotère et une pointe de javelot, voire possiblement un carreau de gastraphétès (une sorte d’arbalète imposante utilisée lors de sièges durant le 4e siècle av. J.-C.). En partie, ceci découle de l'historique d'échanges entre la Grèce et les autres peuples méditerranéens, balkaniques et orientaux. En outre, de nombreuses réformes militaires des périodes archaïque et classique provoquèrent une évolution constante sur les aspects stratégiques et les tactiques militaires. Considérant ces facteurs parmi tant d'autres et le fait qu'Argilos ait été une fondation grecque en territoire thraco-macédonien, la possibilité d'influence "étrangère" devient alors prépondérante sur la typologie des projectiles argiliens publiée dans le présent mémoire. Avec beaucoup d’espoir, nous croyons sans équivoque que ce travail de recherche contribuera grandement non seulement à l’histoire d’Argilos, mais aussi à l’étude des projectiles en Grèce du nord.

Evaluation of a ToF Camera for Remote Surveying of Underground Cavities Excavated by Jet Boring

Cigar Lake is a high-grade uranium deposit, located in northern Saskatchewan, Canada. In order to extract the uranium ore remotely, thus ensuring minimal radiation dose to workers and also to access the ore from stable ground, the Jet Boring System (JBS) was developed by Cameco Corporation. This system uses a high-powered water jet to remotely excavate cavities. Survey data is required to determine the final shape, volume, and location of the cavity for mine planning purposes and construction. This paper provides an overview of the challenges involved in remotely surveying a JBS-mined cavity and studies the potential use of a time-of-flight (ToF) camera for remote cavity surveying. It reports on data collected and analyzed from inside an experimental environment as well as on real data acquired on site from the Cigar Lake and Rabbit Lake mines.

Kelvin-Helmholtz instability in solar chromospheric jets: theory and observation

Using data obtained by the high-resolution CRisp Imaging SpectroPolarimeter instrument on the Swedish 1 m Solar Telescope, we investigate the dynamics and stability of quiet-Sun chromospheric jets observed at the disk center. Small-scale features, such as rapid redshifted and blueshifted excursions, appearing as high-peed jets in the wings of the Hα line, are characterized by short lifetimes and rapid fading without any descending behavior. To study the theoretical aspects of their stability without considering their formation mechanism, we model chromospheric jets as twisted magnetic flux tubes moving along their axis, and use the ideal linear incompressible magnetohydrodynamic approximation to derive the governing dispersion equation. Analytical solutions of the dispersion equation indicate that this type of jet is unstable to Kelvin–Helmholtz instability (KHI), with a very short (few seconds) instability growth time at high upflow speeds. The generated vortices and unresolved turbulent flows associated with the KHI could be observed as a broadening of chromospheric spectral lines. Analysis of the Hα line profiles shows that the detected structures have enhanced line widths with respect to the background. We also investigate the stability of a larger-scale Hα jet that was ejected along the line of sight. Vortex-like features, rapidly developing around the jet’s boundary, are considered as evidence of the KHI. The analysis of the energy equation in the partially ionized plasma shows that ion–neutral collisions may lead to fast heating of the KH vortices over timescales comparable to the lifetime of chromospheric jets.

Modeling of Turbulent Natural Gas and Biogas Flames of the Delft Jet-in-Hot-Coflow Burner: Effects of Coflow Temperature, Fuel Temperature and Fuel Composition on the Flame Lift-Off Height

The structure of a turbulent non-premixed flame of a biogas fuel in a hot and diluted coflow mimicking moderate and intense low dilution (MILD) combustion is studied numerically. Biogas fuel is obtained by dilution of Dutch natural gas (DNG) with CO2. The results of biogas combustion are compared with those of DNG combustion in the Delft Jet-in-Hot-Coflow (DJHC) burner. New experimental measurements of lift-off height and of velocity and temperature statistics have been made to provide a database for evaluating the capability of numerical methods in predicting the flame structure. Compared to the lift-off height of the DNG flame, addition of 30 % carbon dioxide to the fuel increases the lift-off height by less than 15 %. Numerical simulations are conducted by solving the RANS equations using Reynolds stress model (RSM) as turbulence model in combination with EDC (Eddy Dissipation Concept) and transported probability density function (PDF) as turbulence-chemistry interaction models. The DRM19 reduced mechanism is used as chemical kinetics with the EDC model. A tabulated chemistry model based on the Flamelet Generated Manifold (FGM) is adopted in the PDF method. The table describes a non-adiabatic three stream mixing problem between fuel, coflow and ambient air based on igniting counterflow diffusion flamelets. The results show that the EDC/DRM19 and PDF/FGM models predict the experimentally observed decreasing trend of lift-off height with increase of the coflow temperature. Although more detailed chemistry is used with EDC, the temperature fluctuations at the coflow inlet (approximately 100K) cannot be included resulting in a significant overprediction of the flame temperature. Only the PDF modeling results with temperature fluctuations predict the correct mean temperature profiles of the biogas case and compare well with the experimental temperature distributions.

Elliptical dust growth in astrophysical plasmas

Elongated dust grains exist in astrophysical plasmas. Anisotropic growth of elliptical dust grains, via plasma deposition, occurs if the deposited ions are non-inertial. In reality the extent of such growth depends upon the initial kinetic energy of the ions and the magnitude of the electric field in the sheath. Simulations of the dynamics of the ions in the sheath are reported, showing how elliptical growth is related to the initial eccentricity and size of the seed relative to the sheath length. Consequences for the eventual fate of elliptical dust are then discussed.

Analytical and Experimental Investigation of an Ammonia/Air Opposed Reacting Jet

The point-by-point properties of an ammonia/air opposed-reacting-jet flowfield are described by solving the governing partial differential elliptic equations. Analytical descriptions of the reacting flowfield are compared to experimentally measured profiles of temperature and composition. Calculated distributions of stream function, temperature and fuel mole fraction are also presented. © 1972, Taylor & Francis Group, LLC. All rights reserved.

Jet o campero set

Fondo Margaritainés Restrepo

Instrumentation studies for plasma jet and hypersonic wind tunnel,

"This research was supported by the McDonnell Aircraft Corporation under Contract no. 6140-20 P.O. 7S4899-R."