Добірка наукової літератури з теми "Electromagnetic ejection"

This article first introduces the characteristics and disadvantages of traditional remote fire extinguishing technology and proposes a remote fire extinguishing system based on electromagnetic ejection. Based on the finite element analysis method and the grid matrix method, a seven-segment electromagnetic launcher model is designed. As the initial energy source, the capacitor can accelerate a 10 kg fire extinguishing bomb to 113 m/s with a range of 2 km. The results show that the electromagnetic catapult designed in this study can meet the needs of fire extinguishing bombs. This paper also designs the overall structure of the vehicle electromagnetic catapult remote fire extinguishing system, discusses its role in the field of firefighting, and prospects the future work.

Electromagnetic launching technology is one of the important application technologies in aerospace field in the future. It will change the way of rocket launching and even be applied to aerospace kinetic energy weapon system. Aiming at the characteristics of various bottom indicators, uncertain information probability and expert participation in the effectiveness evaluation system of aircraft electromagnetic ejection system, based on the index hierarchy model, the method of RIMER(rule-base inference methodology using the evidential reasoning) is used to evaluate the effectiveness, which provides some reference for the design and development of aircraft electromagnetic launching system.

Mergers of binary neutron stars and black hole–neutron star binaries are among the most promising sources for ground-based gravitational-wave (GW) detectors and are also high-energy astrophysical phenomena, as illustrated by the observations of GWs and electromagnetic (EM) waves in the event of GW170817. Mergers of these neutron star binaries are also the most promising sites for r-process nucleosynthesis. Numerical simulation in full general relativity (numerical relativity) is a unique approach to the theoretical prediction of the merger process, GWs emitted, mass ejection process, and resulting EM emission. We summarize the current understanding of the processes of neutron star mergers and subsequent mass ejection based on the results of the latest numerical-relativity simulations. We emphasize that the predictions of the numerical-relativity simulations agree broadly with the optical and IR observations of GW170817.

Abstract. The dynamics of nanometer-sized grains (nanodust) is strongly affected by electromagnetic forces. High-velocity nanodust was proposed as an explanation for the voltage bursts observed by STEREO. A study of nanodust dynamics based on a simple time-stationary model has shown that in the vicinity of the Sun the nanodust is trapped or, outside the trapped region, accelerated to high velocities. We investigate the nanodust dynamics for a time-dependent solar wind and magnetic field configuration in order to find out what happens to nanodust during a coronal mass ejection (CME). The plasma flow and the magnetic field during a CME are obtained by numerical simulations using a 3-D magnetohydrodynamic (MHD) code. The equations of motion for the nanodust particles are solved numerically, assuming that the particles are produced from larger bodies moving in near-circular Keplerian orbits within the circumsolar dust cloud. The charge-to-mass ratios for the nanodust particles are taken to be constant in time. The simulation is restricted to the region within 0.14 AU from the Sun. We find that about 35 % of nanodust particles escape from the computational domain during the CME, reaching very high speeds (up to 1000 km s−1). After the end of the CME the escape continues, but the particle velocities do not exceed 300 km s−1. About 30 % of all particles are trapped in bound non-Keplerian orbits with time-dependent perihelium and aphelium distances. Trapped particles are affected by plasma ion drag, which causes contraction of their orbits.

We quantified ventricular suction flow, volume, and pressure under hydrostatically zero source pressure for filling. A large-bore electromagnetic flow probe was placed in the valve-free mitral annulus of the dog heart that had been excised and was cross circulated with the left atrium widely opened. With the heart immersed in a blood pool, ventricular suction flow and transmural pressure were measured. After a rapid ejection flow [peak: 110 +/- 47 (SD) ml . s-1 . 100 g left ventricle-1] during systole, a slow suction flow (peak: 26 +/- 20 ml . s-1 . 100 g-1) occurred during diastole despite the zero source pressure for filling. Peak transmural pressure during ejection was 6 +/- 3 mmHg, and peak negative transmural pressure during suction was 2 +/- 1 mmHg. Suction volume, which was equal to ejection volume in steady state, was 8 +/- 3 ml/100 g left ventricle. Increases in paced heart rate markedly decreased suction volume by curtailing diastolic filling time. Epinephrine, propranolol, calcium, and verapamil variably changed suction volume, and these effects were primarily accounted for by the accompanied heart rate changes.

This article demonstrates the results of experimental research one of the pulsators. Its main difference from others is a pneumatic electromagnetic pulsator in combination with a collector. Therefore, this article describes in detail the process of studying the pulsator. The planned experiment was carried out on by Factorial experiments with multiple factors. The influence of factors (the ripple frequency n, the milk ejection q and the ratio between strokes t/T) on the vacuum pressure in the inter wall chamber of teat cups was studied. The regression equation of the dependence response criterion on factors is modeled. This dependence is demonstrated graphically. Also there is a contour graph which is for more detailed information.

This Bachelor Thesis is done within the project SCRAP (SCattering of Radar Waves on Aerosols in Plasmas), which aims to investigate the role of microparticles in the mesosphere. A sounding rocket is to be launched in spring of 2015 containing the experiment. The rocket will eject two free falling units (FFUs) which each subsequently releases a cloud of conductive microparticles into the mesosphere. The particle cloud will interact with the surrounding plasma and can thereafter be observed indirectly by using radar backscattering. In this project two different aspects of the microparticles have been studied. The first one is the way electromagnetic radiation is scattered on them, where known solutions to simplified versions of the problem are adapted in a simple computer program. The second part deals with the particle release mechanism for the FFU. Three different release techniques have been evaluated mainly on the amount of particle agglomeration caused by the releasing. The results show that the method called gunpowder approach has advantages over the others in a number of ways, including the particle dust capacity and the particle separation.

Speckle noise appears when coherent illumination is employed, as for example Laser, Synthetic Aperture Radar (SAR), Sonar, Magnetic Resonance, X-ray and Ultrasound imagery. Backscattered echoes from the randomly distributed scatterers in the microscopic structure of the medium are the origin of speckle phenomenon, which characterizes coherent imaging with a granular appearance. It can be shown that speckle noise is of multiplicative nature, strongly correlated and more importantly, with non-Gaussian statistics. These characteristics differ greatly from the traditional assumption of white additive Gaussian noise, often taken in image segmentation, filtering, and in general, image processing; which leads to reduction of the methods effectiveness for final image information extraction; therefore, this kind of noise severely impairs human and machine ability to image interpretation. Statistical modeling is of particular relevance when dealing with speckled data in order to obtain efficient image processing algorithms; but, additionally, clinical ultrasound imaging systems employ nonlinear signal processing to reduce the dynamic range of the input echo signal to match the smaller dynamic range of the display device and to emphasize objects with weak backscatter. This reduction in dynamic range is normally achieved through a logarithmic amplifier i.e. logarithmic compression, which selectively compresses large input signals. This kind of nonlinear compression totally changes the statistics of the input envelope signal; and, a closed form expression for the density function of the logarithmic transformed data is usually hard to derive. This thesis is concerned with the statistical distributions of the Log-compressed amplitude signal in coherent imagery, and its main objective is to develop a general statistical model for log-compressed ultrasound B-scan images. The developed model is adapted, making the pertinent physical analogies, from the multiplicative model in Synthetic Aperture Radar (SAR) context. It is shown that the proposed model can successfully describe log-compressed data generated from different models proposed in the specialized ultrasound image processing literature. Also, the model is successfully applied to model in-vivo echo-cardiographic (ultrasound) B-scan images. Necessary theorems are established to account for a rigorous mathematical proof of the validity and generality of the model. Additionally, a physical interpretation of the parameters is given, and the connections between the generalized central limit theorems, the multiplicative model and the compound representations approaches for the different models proposed up-to-date, are established. It is shown that the log-amplifier parameters are included as model parameters and all the model parameters are estimated using moments and maximum likelihood methods. Finally, three applications are developed: speckle noise identification and filtering; segmentation of in vivo echo-cardiographic (ultrasound) B-scan images and a novel approach for heart ejection fraction evaluation
El ruido Speckle aparece cuando se utilizan sistemas de iluminación coherente, como por ejemplo Láser, Radar de Apertura Sintética (SAR), Sonar, Resonancia Magnética, rayos X y ultrasonidos. Los ecos dispersados por los centros dispersores distribuidos al azar en la estructura microscópica del medio son el origen de este fenómeno, que caracteriza las imágenes coherentes con un aspecto granular. Se puede demostrar que el ruido Speckle es de carácter multiplicativo, fuertemente correlacionados y lo más importante, con estadística no Gaussiana. Estas características son muy diferentes de la suposición tradicional de ruido aditivo gaussiano blanco, a menudo asumida en la segmentación de imágenes, filtrado, y en general, en el procesamiento de imágenes; lo cual se traduce en la reducción de la eficacia de los métodos para la extracción de información de la imagen final. La modelización estadística es de particular relevancia cuando se trata con datos Speckle, a fin de obtener algoritmos de procesamiento de imágenes eficientes. Además, el procesamiento no lineal de señales empleado en sistemas clínicos de imágenes por ultrasonido para reducir el rango dinámico de la señal de eco de entrada de manera que coincida con el rango dinámico más pequeño del dispositivo de visualización y resaltar así los objetos con dispersión más débil, modifica radicalmente la estadística de los datos. Esta reducción en el rango dinámico se logra normalmente a través de un amplificador logarítmico es decir, la compresión logarítmica, que comprime selectivamente las señales de entrada y una forma analítica para la expresión de la función de densidad de los datos transformados logarítmicamente es por lo general difícil de derivar. Esta tesis se centra en las distribuciones estadísticas de la amplitud de la señal comprimida logarítmicamente en las imágenes coherentes, y su principal objetivo es el desarrollo de un modelo estadístico general para las imágenes por ultrasonido comprimidas logarítmicamente en modo-B. El modelo desarrollado se adaptó, realizando las analogías físicas relevantes, del modelo multiplicativo en radares de apertura sintética (SAR). El Modelo propuesto puede describir correctamente los datos comprimidos logarítmicamente a partir datos generados con los diferentes modelos propuestos en la literatura especializada en procesamiento de imágenes por ultrasonido. Además, el modelo se aplica con éxito para modelar ecocardiografías en vivo. Se enuncian y demuestran los teoremas necesarios para dar cuenta de una demostración matemática rigurosa de la validez y generalidad del modelo. Además, se da una interpretación física de los parámetros y se establecen las conexiones entre el teorema central del límite generalizado, el modelo multiplicativo y la composición de distribuciones para los diferentes modelos propuestos hasta a la fecha. Se demuestra además que los parámetros del amplificador logarítmico se incluyen dentro de los parámetros del modelo y se estiman usando los métodos estándar de momentos y máxima verosimilitud. Por último, tres aplicaciones se desarrollan: filtrado de ruido Speckle, segmentación de ecocardiografías y un nuevo enfoque para la evaluación de la fracción de eyección cardiaca.

Cette thèse se concentre sur la thématique de l'éjection électromagnétique appliquée dans le cadre de l'industrie du recyclage des métaux. L'objectif de celle-ci est la modélisation et la réalisation d'une architecture de conversion d'énergie permettant la réalisation de cette éjection. Le champ magnétique variable généré est utilisé afin de séparer d'un flux de déchets les matériaux métalliques non ferromagnétique tel que l'aluminium ou le cuivre par le biais d'une force de Laplace engendrée par la conjonction entre le champ magnétique crée et le champ magnétique induit par les courants de Foucault dans les matériaux conducteurs. L'architecture développée se compose de plusieurs éléments: un redresseur, un onduleur et un inducteur. La partie redresseur, à large plage de fonctionnement connectée sur le réseau d'alimentation triphasée permet d'obtenir une tension continu réglable et assure un prélèvement sinusoïdale de courant en phase avec la tension. La partie onduleur, permet de contrôler la puissance transmise, en adaptant l'amplitude et la fréquence du courant traversant la dernière partie du système que forme l'inducteur, responsable de la création du champ magnétique alternatif. Le choix du redresseur s'est porté sur la structure classique du redresseur abaisseur de tension de type Buck en raison de la faible impédance de l'inducteur utilisé. Bien que cette structure permette d'abaisser la tension triphasée, sa plage de fonctionnement peut être facilement augmentée sans l'ajout de composant passif. Le contrôle classique de ce redresseur ne se base que sur ses grandeurs de sorties ce qui peut engendrer des oscillations non contrôlées causées par la mise en résonance du filtre LC d'entrée excité par les harmoniques générés par les commutations des transistors. Nous avons proposé dans cette thèse une nouvelle méthode de contrôle qui traite à la fois de ses grandeurs d'entrée et de sortie et qui permet de contrôler les éventuelles oscillations du filtre LC d'entrée tout en bénéficiant d'une meilleure réponse dynamique lorsque le système est soumis à un échelon de charge. Cette méthode de contrôle se base sur les propriétés de platitude des systèmes différentielles, ainsi elle ne dépend pas du point de fonctionnement et garantit la stabilité large signal du système. Le choix de l'onduleur monophasé s'est porté sur une structure en pont complet permettant l'application de trois niveaux de tension et un large choix de contrôle de l'amplitude, de la forme et de la fréquence du courant traversant l'inducteur. Différents contrôle de ce convertisseur ont été étudiés et comparés. Ceux-ci permettent de faire varier la puissance injectée dans l'inducteur, ont un impact sur le contenu harmonique du courant le traversant et sur les contraintes des différents composants du système. Une modélisation de l'inducteur ainsi qu'une estimation de la valeur du champ magnétique nécessaire à l'éjection est effectuée. Les différentes méthodes proposées sont validées par des résultats de simulations numérique mais également par le biais de tests expérimentaux réalisés sur le système complet
This thesis focuses on the subject of electromagnetic ejection applied in the context of the metal recycling industry. The aim of this thesis is the modeling and the development of an architecture of energy conversion allowing the realization of this ejection. The generated variable magnetic field is used to separate non-ferromagnetic metallic materials such as aluminum or copper from a waste stream by means of a Laplace force generated by the conjunction between the magnetic field created and the magnetic field induced by the eddy currents in the conductive materials.The developed architecture is composed of several elements: a rectifier, an inverter and an inductor. The rectifier part with a wide operating range connected to the three-phase grid network allows to obtain an adjustable DC voltage and ensures a sinusoidal current in phase with the voltage. The inverter part allows to control the transferred power, by adjusting the amplitude and frequency of the current flowing through the last part of the system represented by the inductor, responsible for the generation of the variable magnetic field.The rectifier is based on the classical Buck rectifier structure because of the low impedance of the inductor used. Although this structure allows to lower the three-phase grid voltage, its operating range can be easily increased without the addition of passive components. The classical control of this rectifier is based only on its output variables which can lead to uncontrolled oscillations caused by the resonance of the lightly damped input LC filter excited by the harmonics generated by the switching of transistors. In this thesis, we proposed a new control method that deals with both its input and output variables and that allows both to control the oscillations of the input LC filter while obtaining a better dynamic response when the system is subjected to a load step. This control method is based on the flatness properties of differential systems, so it does not depend on the operating point and guarantees the large signal stability of the system.The single-phase inverter is based on a full bridge structure allowing the application of three voltage levels and a wide choice of control of the amplitude, shape and frequency of the current flowing through the inductor. Different controls of this converter have been studied and compared. These allow to vary the power injected in the inductor, have an impact on the harmonic content of the current flowing through it and on the constraints of the different components of the system.A modeling of the inductor as well as an estimation of the value of the magnetic field necessary for the ejection is carried out. The different methods proposed are verified by numerical simulations but also by experimental tests performed on the whole system

Coronal Mass Ejections (CMEs) and solar flares are energetic events taking place at the Sun that can affect the space weather or the near-Earth environment by the release of vast quantities of electromagnetic radiation and charged particles. Solar active regions are the areas where most flares and CMEs originate. Studying the associations among sunspot groups, flares, filaments, and CMEs is helpful in understanding the possible cause and effect relationships between these events and features. Forecasting space weather in a timely manner is important for protecting technological systems and human life on earth and in space. The research presented in this thesis introduces novel, fully computerised, machine learning-based decision rules and models that can be used within a system design for automated space weather forecasting. The system design in this work consists of three stages: (1) designing computer tools to find the associations among sunspot groups, flares, filaments, and CMEs (2) applying machine learning algorithms to the associations¿ datasets and (3) studying the evolution patterns of sunspot groups using time-series methods. Machine learning algorithms are used to provide computerised learning rules and models that enable the system to provide automated prediction of CMEs, flares, and evolution patterns of sunspot groups. These numerical rules are extracted from the characteristics, associations, and time-series analysis of the available historical solar data. The training of machine learning algorithms is based on data sets created by investigating the associations among sunspots, filaments, flares, and CMEs. Evolution patterns of sunspot areas and McIntosh classifications are analysed using a statistical machine learning method, namely the Hidden Markov Model (HMM).

Coronal Mass Ejections (CMEs) and solar flares are energetic events taking place at the Sun that can affect the space weather or the near-Earth environment by the release of vast quantities of electromagnetic radiation and charged particles. Solar active regions are the areas where most flares and CMEs originate. Studying the associations among sunspot groups, flares, filaments, and CMEs is helpful in understanding the possible cause and effect relationships between these events and features. Forecasting space weather in a timely manner is important for protecting technological systems and human life on earth and in space. The research presented in this thesis introduces novel, fully computerised, machine learning-based decision rules and models that can be used within a system design for automated space weather forecasting. The system design in this work consists of three stages: (1) designing computer tools to find the associations among sunspot groups, flares, filaments, and CMEs (2) applying machine learning algorithms to the associations' datasets and (3) studying the evolution patterns of sunspot groups using time-series methods. Machine learning algorithms are used to provide computerised learning rules and models that enable the system to provide automated prediction of CMEs, flares, and evolution patterns of sunspot groups. These numerical rules are extracted from the characteristics, associations, and time-series analysis of the available historical solar data. The training of machine learning algorithms is based on data sets created by investigating the associations among sunspots, filaments, flares, and CMEs. Evolution patterns of sunspot areas and McIntosh classifications are analysed using a statistical machine learning method, namely the Hidden Markov Model (HMM).

With the rapid development of artificial intelligence technology, intelligent projectile is gradually becoming an indispensable weapon in modern high-tech war. Small low-cost intelligent projectile has the advantages of good concealment, strong mobility and high combat efficiency cost ratio [1-2]. The development of intelligent projectile is an important link in the process of carrying out combat tasks, which directly determines whether the aircraft can take off smoothly [3]. Small low-cost intelligent projectile must meet two conditions: (1) have a certain high orbit speed to maintain aircraft stability; (2) In order to meet the demand of low cost, the impact overload borne by the guiding head, communication module and other components of projectile is limited, that is, the launching process of projectile must have low overload characteristics. Scholars from various countries have developed extensive and indepth research on the ejection methods of small projectiles, including high-pressure gas ejection [4], electromagnetic ejection [5], rocket assisted ejection [6], artillery direct launch [7] and ejection launch [8].According to the low overload ejection requirements of a small low cost intelligent projectile, a method was proposed to realise low overload ejection of the small projectile by using propellant gas based on the high-low pressure launching theory. The interior ballistic mathematical model of the projectile ejection was established and the numerical simulation was finished. Based on the simulation result, a low overload ejection device for propellant gas was designed. With this device, an ejection experiment study of the small intelligent projectile was carried out. The test results indicate that while the impact overload of the projectile is less than 60g ， the velocity the projectile leaving the barrel is more than 45m/s. The experimental results show that it is feasible to realize low overload ejection of small projectile by using propellant gas. The simulation results agree well with the test . The mathematical model can describe the projectile ejection process well. The research work provides theoretical and experimental basis for realizing low overload ejection process of small low cost intelligent projectile by using propellant gas.