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Добірка наукової літератури з теми "Pulse source of magnetic field"

Автор: Grafiati

Опубліковано: 30 травня 2022

Оновлено: 31 травня 2022

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Статті в журналах з теми "Pulse source of magnetic field"

Mamedov, N. V., A. S. Rohmanenkov, and A. A. Solodovnikov. "Magnetic field influence on the Penning discharge characteristics." Journal of Physics: Conference Series 2064, no. 1 (November 1, 2021): 012039. http://dx.doi.org/10.1088/1742-6596/2064/1/012039.

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Abstract In this work characteristics of pulsed penning ion source for miniature linear accelerators was investigated by experimental measurements and PIC (Particle-In-Cell) simulations. The paper presents dependences of the discharge current and extracted current on intensities of the uniform magnetic field for different pressure. Also, typical examples of the current pulse waveforms obtained by PIC simulation and experiment for different magnetic field are presented. The simulated electron and ion distributions inside discharge gap give qualitative explanation of the experimentally observed fluctuations in current pulses. These current fluctuations arise as a result of the violation of the electric field axial symmetry due to the electron spoke movement of the towards the anode.

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Zhang Jun, 张军, 靳振兴 Jin Zhenxing, 张点 Zhang Dian, 杨建华 Yang Jianhua, 舒挺 Shu Ting, 钟辉煌 Zhong Huihuang, and 周生岳 Zhou Shengyue. "4.8 MJ magnetic field excitation source using pulse width modulation technique." High Power Laser and Particle Beams 22, no. 6 (2010): 1323–26. http://dx.doi.org/10.3788/hplpb20102206.1323.

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DÖRR, M., D. ECKERT, H. ESCHRIG, F. FISCHER, P. FULDE, R. GROESSINGER, W. GRÜNBERGER, et al. "THE DRESDEN 100 T/10 ms PROJECT: A HIGH MAGNETIC FIELD FACILITY AT AN IR-FEL." International Journal of Modern Physics B 16, no. 20n22 (August 30, 2002): 3397. http://dx.doi.org/10.1142/s0217979202014541.

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We have proposed to build a 100 T/10 ms, 70 T/100 ms, 60 T/1 s pulsed field user facility with a 50 MJ capacitor bank at the Forschungszentrum Rossendorf near Dresden. This would provide the appealing possibility to have access to Zeeman energies in the energy range of the infrared free-electron-lasers (5 μm to 150 μm; 2 ps; cw; > 10 W) now under construction at the radiation source ELBE (superconducting electron linear accelerator; 40 MeV; 1 mA; 2 ps; cw) in Rossendorf. The work is accompanied by computer simulations of the planned coil systems, of the power supply, and by the development of high-strength conductors aiming at a tensile strength of about 1.5 GPa at σ ≈ σ Cu/2 (microcomposite CuAg alloys and Cu-steel macro compounds). With a view of gaining experience in the construction and operation of pulsed magnets, a pilot pulsed field laboratory was established at the Institute of Solid State and Materials Research Dresden (IFW Dresden). The laboratory includes short pulse magnets with peak field up to 60 T in a 24 mm bore and a rise time of about 10 ms (coil from NHMFL, Tallahassee), and a 40 T long pulse magnet with 24 mm bore and rise time of about 80 ms (coil from METIS, Leuven). The repetition rate of 20 min between pulses is limited by the cooling time of the coils. The coils are energized by a 1 MJ, 10 kV capacitor bank with some special features. With this set-up measurements of magnetization and magnetotransport on 4f-electron systems, for example RECu2, have been out in the temperature range of 1.5 to 300 K and at fields up to 52 T using high precision pick-up coils.

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Espina-Hernández, J. H., Roland Grössinger, Reiko Sato Turtelli, and J. M. Hallen. "A New Measuring System for Determining the Magnetic Viscosity in Permanent Magnets." Advanced Materials Research 68 (April 2009): 12–20. http://dx.doi.org/10.4028/www.scientific.net/amr.68.12.

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A new system for measuring magnetic viscosity in bulk hard magnetic materials base on a pulsed field method is presented. After the magnetizing field pulse, the stray field of the sample, which is proportional to the magnetic moment, is measured with a compensated set of two Hall probes. The set of Hall probes is driven with an AC voltage source and the Hall voltage is detected using a lock-in amplifier. By this method the system is able to measure the time dependence of the magnetization (viscosity). The magnetic viscosity coefficient (S) is obtained through a linear fitting of the magnetization decay versus ln t. Two typical Nd-Fe-B samples were measured and good agreement with the results from the traditional viscosity experiment was obtained.

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Fitak, Robert R., Eleanor M. Caves, and Sönke Johnsen. "Orientation in Pill Bugs: An Interdisciplinary Activity to Engage Students in Concepts of Biology, Physics & Circular Statistics." American Biology Teacher 80, no. 8 (October 1, 2018): 608–18. http://dx.doi.org/10.1525/abt.2018.80.8.608.

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We present a novel laboratory activity to introduce students to experimental approaches often used by biologists to study orientation in animals. We first provide an overview of the current understanding of magnetoreception – the ability of some organisms to sense magnetic fields. We then outline an exercise that uses common pill bugs (Armadillidium vulgare) to examine whether a pulsed magnetic field affects their directional preference. The first part of the experiment includes the construction and visual testing of a pulse magnetizer built using low-cost and easily obtainable materials. Afterward, students examine the orientation of pill bugs both before and after being subjected to a magnetic pulse. Finally, students analyze their results with circular statistics using the open-source R coding platform, providing them experience in coding languages and statistical analysis. The interdisciplinary and biophysical nature of this experiment engages students in concepts of electromagnetic induction, magnetism, animal behavior, and statistics.

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Abedi-Varaki, Mehdi. "Effect of obliquely external magnetic field on the intense laser pulse propagating in plasma medium." International Journal of Modern Physics B 34, no. 07 (March 11, 2020): 2050044. http://dx.doi.org/10.1142/s0217979220500447.

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In this paper, self-focusing of intense laser pulse propagating along the obliquely external magnetic field on the collisional magnetoactive plasma by using the perturbation theory have been studied. The wave equation describing the interaction of intense laser pulse with collisional magnetoactive plasma is derived. In addition, employing source-dependent expansion (SDE) method, the analysis of the laser spot-size is discussed. It is shown that with increasing of the angle in obliquely external magnetic field, the spot-size of laser pulse decreases and as a result laser pulse becomes more focused. Furthermore, it is concluded that the self-focusing quality of the laser pulse has been enhanced due to the presence of obliquely external magnetic field in the collisional magnetoactive plasma. Besides, it is seen that with increasing of [Formula: see text], the laser spot-size reduces and subsequently the self-focusing of the laser pulse in plasma enhances. Moreover, it is found that changing the collision effect in the magnetoactive plasma leads to increases of self-focusing properties.

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YANG, YANJU, CHUNLEI CHENG, WENYAO YANG, JIE LI, ZHENGFU CHENG, and XIAOYU ZHANG. "STUDY OF ACOUSTIC SOURCE EXCITED BY PULSED MAGNETIC FIELD." Journal of Mechanics in Medicine and Biology 21, no. 05 (April 14, 2021): 2140008. http://dx.doi.org/10.1142/s021951942140008x.

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In magnetoacoustic tomography with magnetic induction and magnetically mediated thermoacoustic imaging, tissues are exposed to an alternating field, generating magnetoacoustic and thermoacoustic effects in the tissues. This study aimed to investigate the relationship between magnetoacoustic and thermoacoustic effects in a low-conductivity object put in a Gauss-pulsed alternating magnetic field. First, the derivations of the magnetic flux density and electric field strength induced by a Gauss-pulsed current flowing through the coil based on the theory of electromagnetic field were examined. Second, the analytical solution of the magnetic field was studied by simulation. To validate the accuracy of the analytical solution, the analytical solution and the numerical simulation of the magnetic flux density were compared. It shows that the analytical solution coincides with the numerical simulation well. Then, based on the theoretical analysis of the acoustic source generation, numerical studies were conducted to simulate pressures excited by magnetoacoustic and thermoacoustic effects in low-conductivity objects similar to tissues in the Gauss-pulsed magnetic field. The thermoacoustic effect played a leading role in low-conductivity objects placed in the Gauss-pulsed magnetic field, and the magnetoacoustic effect could be ignored. This study provided the theoretical basis for further research on magnetoacoustic tomography with magnetic induction and magnetically mediated thermoacoustic imaging for pathological tissues.

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Kondratenko, I. P., A. N. Karlov, and R. S. Kryshchuk. "CONTROL STRATEGIES TO ELIMINATE HARMONICS IN POWER GENERATION SYSTEMS BASED ON A DOUBLY-FED INDUCTION GENERATOR." Praci Institutu elektrodinamiki Nacionalanoi akademii nauk Ukraini, no. 61 (May 25, 2022): 5–12. http://dx.doi.org/10.15407/publishing2022.61.005.

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The action of high-density pulsed currents (109 A/m2) leads to the appearance of the electro-plastic effect in metal products. It is proposed to use magnetic pulse treatment of nonmagnetic plates by electromagnetic inductors with a U-shaped magnetic circuit for local flow pulsed currents in the nonmagnetic plates. The work aims to establish an influence of a ferromagnetic platform with nonlinear magnetic permeability on pulsed eddy currents and magnetic pressure of nonmagnetic metal plates with different electrical conductivity in modeling magnetic pulse treatment of welded joints to achieve the electro-plastic effect. Numerical simulation of pulsed electromagnetic fields by the finite element method is used. The current calculation in the inductor's winding is performed by solving the equations of the magnetic field and the electric circuit equations for a discrete-time interval. A power source is a capacitor that is charged to a specific voltage. To study the effect of the ferromagnetic platform on eddy currents and forces in a nonmagnetic plate with its different electrical conductivity, the same pulsed current in the inductor's winding is used. The dependence of amplitude values of eddy current density and magnetic pressure on the surfaces of nonmagnetic plates of different electrical conductivity is investigated. The influence of the presence and absence of a ferromagnetic platform and its electrical conductivity and magnetic permeability on the values of eddy currents and magnetic pressure in the nonmagnetic plate have been studied. Ref. 13, fig. 7, table.

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IZUMIDA, SHINJI, SHINGO ONO, ZHENLIN LIU, HIDEYUKI OHTAKE, and NOBUHIKO SARUKURA. "INTENSE THz-RADIATION SOURCES USING SEMICONDUCTORS IRRADIATED WITH FEMTOSECOND LASER PULSES IN A MAGNETIC FIELD." Journal of Nonlinear Optical Physics & Materials 08, no. 01 (March 1999): 71–87. http://dx.doi.org/10.1142/s0218863599000060.

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We report significant enhancement of THz radiation from InAs under magnetic field irradiated with femtosecond pulses. The THz-radiation power is significantly enhanced and reaches sub-mW level in a 1.7-T magnetic field with 1.5-W excitation power. The THz-radiation power is related almost quadratically both to the magnetic field and excitation laser power. Furthermore, the radiation spectrum is found to be controlled by the excitation pulsewidth, chirp direction of the excitation pulse, and the magnetic field. Additionally, we have demonstrated a new method to generate THz radiation from a saturable Bragg reflector in a magnetic field.

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Bespalov, Peter A., and Olga N. Savina. "Excitation of the main giant pulses from the Crab pulsar." Monthly Notices of the Royal Astronomical Society 498, no. 2 (August 20, 2020): 2864–70. http://dx.doi.org/10.1093/mnras/staa2520.

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ABSTRACT A model for the source of microwave main giant pulses (GPs) from the Crab pulsar is proposed and partly investigated. Pulse excitation takes place in a relativistic pair plasma with a strong magnetic field through the beam pulse amplifier (BPA) mechanism, in which short noise pulses of a certain type are amplified by energetic electrons at the Cherenkov resonance, even without strong anisotropy in the distribution function. The wave gain is shown to be as high as with an instability of hydrodynamic type, and wave escaping from the excitation region into the pulsar magnetosphere may not involve significant attenuation. The basic parameters of the source which explains the observed characteristics of the GP electromagnetic bursts have been analysed and are consistent with accepted ideas about physical conditions in the pulsar magnetosphere. The BPA mechanism explains the important properties of the GPs, such as the extremely short pulse duration (extreme nanoshots), the extremely high brightness temperature of the radiation source, the formation of radiation in a wide frequency range, and the possibility of radiation reaching the periphery of the pulsar magnetosphere.

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Більше джерел

Дисертації з теми "Pulse source of magnetic field"

Dias, André. "Development of a scanning MOKE system with a 10 T pulsed magnetic field source." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY099.

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Nous avons développé un système de mesure magnéto-optique à balayage basé sur l’Effet Kerr(MOKE). Le montage permet mesurer des cycles d'aimantation en balayant de larges surfaces (150 x 150 mm 2 ) sous un champ magnétique pulsé allant jusqu’à 10 T à température ambiante. Les champs magnétiques intenses sont produits par des bobines millimétriques (diamètre interne = 3 mm) connectées à un générateur de courant bipolaire pulsé. Nous avons pu démontrer que ce système présente un fort potentiel pour l'étude combinatoire de couches magnétiques dures. Pour cela, nous avons dressé grâce à notre système MOKE la carte 2D des courbes d’hystérèse pour des couches de SmCo et NdFeB élaborées par pulvérisation et présentant un gradient de composition et comparé avec des mesures de composition d'alliage (EDX) et l'analyse de la structure cristalline (XRD)
The aim of this PhD project is to study diamagnetic levitation at the micro-scale in a quantitative fashion and to explore its use for the precise positioning and controlled movement of micro/nano-objects. Diamagnetic materials will be prepared with controlled shape and size (µm-mm range). Micro-magnets will also be developed to levitate the diamagnetic objects or to levitate above diamagnetic surfaces. To complement the study, a fully automated scanning MOKE system will be developed in order to characterize the quality of our samples fabricated using the triode sputtering machine and applying techniques called micro magnetic transfer and micro flux concentrators. First simple micro-robotic devices will be designed, and hopefully tested

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Jenkins, Catherine A. (Catherine Ann) 1981. "Pulse-field actuation of collinear magnetic single crystals." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32717.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.
Includes bibliographical references (p. 33-34).
Ferromagnetic shape memory alloys (FSMAs) are a class of alloys that exhibits the shape memory effect, as in the alloy nickel-titanium, sometimes known as Nitinol. In FSMAs, though, the shape changes are not brought on just by changes in temperature or mechanical stresses, but can also be driven by the application of a relatively small magnetic field. The large strains exhibited by such materials are a result of the coexistence of several features, including a thermoelastic martensitic transition, and a ferromagnetic martensite (non-equilibrium, low-temperature) phase. The magnetocrystalline anisotropy must also be large, as seen in similar alloys such as iron-palladium (Fe₇₀Pd₃₀) [1]. Nickel-manganese-gallium is an FSMA that has shown up to 10% strain in certain orientations as an effect of unconstrained magnetic actuation [4]. To achieve cyclic actuation in FSMAs, the field-induced extension has conventionally been reversed by a compressive mechanical stress from a spring or field orthogonal to the actuating field. The use of a second FSMA crystal to provide the reset force was unreported. Collinear single crystals are shown here to be able to induce a 2.8% reset strain against one another when subjected alternately to individual pulsed magnetic fields in a custom designed and constructed apparatus. A setup of this type could be used in a bistable microswitch, linear motion actuator, or shutter controller where a low actuation stress is sufficient or the electrical contacts required to activate a piezoelectric device are undesirable.
by Catherine A. Jenkins.
S.B.

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Салам, Буссі. "Електромагнітно-акустичні перетворювачі для ультразвукового контролю металовиробів". Thesis, Національний технічний університет "Харківський політехнічний інститут", 2020. http://repository.kpi.kharkov.ua/handle/KhPI-Press/48184.

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Дисертація на здобуття наукового ступеня кандидата технічних наук (доктора філософії) за спеціальністю 05.11.13 «Прилади і методи контролю та визначення складу речовин» – Національний технічний університет «Харківський політехнічний інститут». Дисертація присвячена розробці нових ультразвукових електромагнітно-акустичних перетворювачів з джерелом імпульсного поляризуючого магнітного поля, методів підвищення чутливості контролю та діагностики металовиробів з використанням перетворювачів такого типу. Виконано аналітичний огляд та аналіз сучасних засобів і методів контролю та діагностики електромагнітно-акустичним методом [1–3] феромагнітних і електропровідних або тільки електропровідних виробів в умовах дії постійних та імпульсних поляризуючих магнітних полів з урахуванням наявності когерентних завад різного типу, технічного рівня сучасних електромагнітно – акустичних перетворювачів, схемотехнічних рішень засобів їх живлення, прийому з виробів ультразвукових імпульсів та їх обробки, визначення відомих переваг, недоліків та можливостей використання в дослідженнях і розробках. Визначені та обґрунтовані напрямки дисертаційного дослідження: розробка електромагнітно-акустичного перетворювача у вигляді спрощеної одновиткової моделі [4] джерела магнітного поляризуючого поля з феромагнітним осердям та високочастотною котушкою, яка розміщена між осердям та металовиробом; шляхом моделювання [5] розподілення індукції поляризуючого магнітного поля на торці осердя джерела магнітного поля та в поверхневому шарі як феромагнітного так і неферомагнітного металовиробу визначено особливості розташування високочастотної котушки індуктивності під джерелом магнітного поля для ефективного збудження зсувних ультразвукових імпульсів (в центральній частині торця феромагнітного осердя) або поздовжніх ультразвукових імпульсів (біля периферійної частини торця феромагнітного осердя) [6]. Збільшення кількості витків котушки намагнічування при наявності феромагнітного осердя призводить до значного збільшення часу перехідних процесів при включенні живлення імпульсного джерела поляризуючого магнітного поля і при його виключенні. В результаті час дії імпульсу живлення збільшується до 1 мс і більше, що призводить до збільшення сили притягування ЕМАП до феромагнітного виробу, додаткових втрат електроенергії, погіршенню температурного режиму перетворювача. Для зменшення часу дії імпульсу живлення джерела магнітного поля необхідно зменшувати кількість витків котушки намагнічування, але це призводить до зменшення величини магнітної індукції навіть при наявності феромагнітного осердя. В результаті раціонального вибору конструкції джерела магнітного поля встановлена необхідність виконання його котушки намагнічування плоскою двовіконною трьохвитковою і виготовляти з високоелектропровідного високотеплопровідного матеріалу [7-9]. Осердя повинно бути розміщено в вікнах котушки намагнічування тільки торцями. В результаті час дії імпульсу намагнічування зменшено до 200 мкс, що достатньо для контролю виробів товщиною до 300 мм. Високочастотна котушка індуктивності виконана з двома лінійними робочими ділянками, які розташовуються під вікнами котушки намагнічування [9]. При протилежних напрямках високочастотного струму в цих робочих ділянках в поверхневому шарі виробу збуджуються синфазні потужні імпульси зсувних ультразвукових хвиль. При цьому відношення збуджуваних амплітуд зсувних та поздовжніх імпульсів перевищує 30 дБ. Тобто когерентні імпульси поздовжніх хвиль при контролі луна методом практично не будуть впливати на результати діагностики феромагнітних виробів. Розроблені варіанти конструкцій електромагнітно-акустичних перетворювачів з одновитковими [7], двовитковими [8] та трьохвитковими [9] котушками намагнічування джерела імпульсного поляризуючого магнітного поля. При одновитковій котушці [7] перехідні процеси при включенні імпульсу живлення мінімальні. Проте необхідно збуджувати в котушці струм з силою в кілька кА, що ускладнює температурний режим перетворювача та апаратуру живлення. При трьохвитковій котушці [9] намагнічування амплітуда донних імпульсів по відношенню до амплітуди завад перевищує 24 дБ, що дозволяє проводити контроль та діагностику значної кількості металовиробів. При використанні шихтованого осердя [9] відношення амплітуд корисного сигналу і шуму збільшилося до 38 дБ, що дає можливість проводити ультразвуковий контроль лунаметодом. Розроблено метод [10 ] ультразвукового електромагнітно- акустичного контролю феромагнітних виробів, суть якого заключається в збудженні ультразвукових імпульсів шляхом формування в поверхневому шарі феромагнітного виробу двох рядом розташованих короткочасно намагнічених ділянок з протилежним напрямком векторів магнітної індукції поляризуючого поля, збудженні в намагнічених ділянках пакетних імпульсів електромагнітного поля з протилежно направленими векторами напруженості тривалістю в кілька періодів високої частоти заповнення, при цьому збудження імпульсів електромагнітного поля виконують в момент часу, який дорівнює часу перехідних процесів з встановлення робочої величини індукції поляризуючого магнітного поля, а прийом ультразвукових імпульсів відбитих з виробу виконується в період часу tпр, який визначається за виразом T – t1 – t2 – t3 < tпр = t1 + t2 + t3 + 2H/C, де Т – тривалість імпульсу намагнічування; t1 – час перехідних процесів з встановлення робочої величини індукції поляризуючого магнітного поля; t2 – час дії пакетного імпульсу електромагнітного поля; t3 – час затухаючих коливань в плоскій високочастотній котушці індуктивності; Н – товщина виробу або відстань в об’ємі виробу, які підлягають ультразвуковому контролю; С – швидкість поширення зсувних ультразвукових хвиль в матеріалі виробу. Встановлено [9] [9], що завади в феромагнітному осерді, обумовлені ефектом Баркгаузена та магнітострикційним перетворенням електромагнітної енергії в ультразвукову при збудженні ультразвукових імпульсів, практично виключаються за рахунок виготовлення осердя шихтованим, матеріал пластин осердя повинен мати низький коефіцієнт магнітострикційного перетворення, пластини осердя повинні бути орієнтовані перпендикулярно провідникам робочих ділянок плоскої високочастотної котушки індуктивності, а також заповненням щілин між пластинами осердя рідиною із значною густиною, наприклад гліцерином. Показано, що чутливість прямих ЕМА перетворювачів з імпульсним намагнічуванням при живленні розробленим генератором пакетних зондуючих високочастотних імпульсів [11 ] та прийомі малошумлячим підсилювачем [12 ] забезпечують виявлення плоскодонних відбивачів діаметром 3 мм і більше при частоті зондування 40 Гц, піковому високочастотному струмі 120 А, частоті зсувних лінійно поляризованих ультразвукових коливань 2,3 МГц, тривалості високочастотного пакетного імпульсу 6…7 періодів частоти заповнення, тривалості імпульсу намагнічування 200 мкс, густині струму намагнічування 600 А/мм2 та при зазорі між ЕМАП і виробом 0,2 мм [9] [9]. При цьому амплітуда луна імпульсу відбитого від дефекту по відношенню до амплітуди завад досягає 20 дБ. Розроблені ЕМАП захищені 2 патентами на корисну модель.
Thesis for a Candidate Degree in Engineering (Doctor of Philosophy), specialty 05.11.13 "Devices and methods of testing and determination of composition of substances" - National Technical University "Kharkiv Polytechnic Institute". The dissertation is devoted to development of new ultrasonic electromagnetic-acoustic transducers with a source of pulsed polarizing magnetic field, methods of sensitive testing and diagnostics of metalware with the use of transducers of this type. Analytical review and analysis of modern means and methods of testing and diagnostics via electromagnetic-acoustic method [1-3] of ferromagnetic and electrically conductive or strictly electrically conductive products under conditions of impact of constant and pulse polarizing magnetic fields taking into account the presence of coherent interferences of different types, technical level of modern electromagnetic circuits, means of their power supply, reception of ultrasonic pulses from metalware and their processing, determination of known advantages and disadvantages, and opportunities of their use in research and development. The direction of the research is defined and justified: development of electromagnetic-acoustic transducer in the form of a simplified single-wind coil model [4] of a source of a magnetic polarizing field with a ferromagnetic core and a high-frequency coil, which is located between the core and the sample; by modeling [5] the distribution of induction of polarizing magnetic field at the end face of the core of the magnetic field source and in the surface layer of both ferromagnetic and non-ferromagnetic metallurgy the features of the location of the high frequency coil of inductance under the magnetic field source are effectively determined for the effective excitation of shear ultrasonic pulses (near the peripheral end of the ferromagnetic core) [6]. The increase in number of winds of magnetization coil in presence of a ferromagnetic core leads to a significant increase in time of transients during the process of powering of a pulsed source of a polarizing magnetic field and during its switching off. As a result, the duration of the power pulse increases to 1 ms or more, which leads to an increase in the force of attraction of EMAP to the ferromagnetic product, additional losses of electricity, deterioration of temperature conditions of the transducer. To reduce the duration of powering pulse of magnetic field it is necessary to reduce the number of winds of the magnetizing coil, but this leads to a decrease in magnetic induction magnitude, even in presence of a ferromagnetic core. As a result of rational choice of the design of the magnetic field source, the flat coil of magnetization must be made with a two-window three-wind and made of high-conductive high-heat-conducting material [7-9]. The core should be placed in the windows of the magnet coil only by the ends. As a result, the action time of the magnetization pulse is reduced to 200 μs, which is sufficient for testing of samples up to 300 mm thick. The high-frequency inductor coil is made of two linear working sections that are located under the windows of the coil [9]. In opposite directions of high-frequency current in these working areas, in-phase powerful pulses of shear ultrasonic waves are excited in the surface layer of the product. The ratio of the excited amplitudes of the shear and longitudinal pulses exceeds 30 dB. That is, the coherent pulses of longitudinal waves in the testing of the moon by the method will practically not affect the results of the diagnosis of ferromagnetic products. Design variants of electromagnetic-acoustic transducers with one-wind [7], two-wind [8] and three-wind magnetization coils [9] of a source of a pulsed polarizing magnetic field are developed. With a single-coil [7], the transients are minimal when the power pulse is winded on. However, it is necessary to excite in the coil a current of several kA, which complicates the temperature conditions of the transducer and power equipment. With a three-coil [9] magnetization, the amplitude of the bottom pulses in relation to the amplitude of the interference exceeds 24 dB, which allows for testing and diagnostics of large variety of samples. When using the charge core [9], the ratio of amplitudes increased to 38 dB, which makes it possible to monitor the echo by the method. The method [10] of ultrasonic electromagnetic - acoustic testing of ferromagnetic products is developed. vectors of intensity with duration of several periods of high filling frequency, n and this excitation of the pulses of the electromagnetic field is performed at a time equal to the time of transients to establish the operating value of the induction of the polarizing magnetic field, and the reception of ultrasonic pulses reflected from the product is performed in the time period tпр, which is determined by the expression T – t1 – t2 – t3 < tпр = t1 + t2 + t3 + 2H/C, where T is the duration of the magnetization pulse; t1 is the time of transients to establish the working value of the induction of a polarizing magnetic field; t2 - time of packet pulse of electromagnetic field; t3 is the time of damping oscillations in the flat high frequency inductor; H is the thickness of the product or the distance in volume of the product to be ultrasound; C is the velocity of propagation of shear ultrasonic waves in the material of the product. It is established [9] that the interferences in the ferromagnetic core caused by the Barkhausen effect and magnetostrictive transformation of electromagnetic energy into ultrasound are practically excluded by production of the core blended, usage of the material of the core plates which has a low coefficient of magnetostrictive conversion, perpendicular core plates orientation in relation to the conductors of the working areas of the flat high-frequency inductor, as well as filling of the gaps between the plates with a high density fluid, such as glycerol. It is shown that the sensitivity of direct EMA transducers with pulse magnetization when powered by a batch high frequency probe pulse generator [11] and when receiving via a low noise amplifier [12] provide detection of flat-bottomed reflectors with a diameter of 3 mm or more, probe frequency of 40 Hz, peak high-frequency current of 120A, shear linearly polarized ultrasonic oscillations of 2.3 MHz, high frequency packet pulse duration 6…7 filling frequency periods, magnetization pulse duration 200 μs, magnetization current density of 600 A / mm2 and at the gap between the EMAP and the product of 0.2 mm [9]. The amplitude of the echo momentum reflected from the flaw in relation to the noise amplitude reaches 20 dB. The EMATs developed are protected with 2 utility model patents.

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Дисертація на здобуття вченого ступеня кандидата технічних наук за спеціальністю 05.11.13 – прилади і методи контролю та визначення складу речовин. Національний технічний університет «Харківський політехнічний інститут», Харків, 2020. В дисертаційній роботі вирішено актуальну науково-практичну задачу з розробки нових типів ЕМАП для ефективного ультразвукового контролю металовиробів. В роботі виконано комп’ютерне моделювання розподілу магнітних полів ЕМАП при імпульсному намагнічуванні феромагнітних та немагнітних виробів. Встановлені шляхи побудови перетворювачів з максимальною чутливістю. Розроблено метод збудження імпульсних пакетних ультразвукових імпульсів за рахунок послідовного в часі формування імпульсного магнітного та електромагнітного полів. Розроблено технічні рішення пригнічення когерентних завад в осерді та у виробі. Визначені геометричні та конструктивні параметри джерела імпульсного магнітного поля, що дало можливість збуджувати потужні синфазні пакетні імпульси високочастотних зсувних коливань в ОК. Показано, що чутливість прямих ЕМА перетворювачів з імпульсним намагнічуванням забезпечують виявлення плоскодонних відбивачів діаметром 3 мм і більше при частоті зондування 40 Гц, частоті зсувних лінійно поляризованих ультразвукових коливань 2,3 МГц, піковому струмі високочастотних пакетних імпульсів 120 А, тривалості пакетних високочастотних імпульсів струму в 6 періодів частоти заповнення, тривалості імпульсу намагнічування 200 мкс, щільності струму намагнічування 600 А/мм2 та при зазорі між ЕМАП і виробом 0,2 мм. При цьому амплітуда луна-імпульсу від дефекту по відношенню до амплітуди завад досягає 20 дБ, що дає можливість забезпечити якісну дефектоскопію металовиробів.
Thesis for a Candidate Degree in Engineering, specialty 05.11.13 – Devices and methods of testing and determination of composition of substances. National Technical University “Kharkiv Polytechnic Institute”, Kharkiv, 2020. A relevant scientific – practical problem on development of new types of EMAP for effective ultrasonic control of metal products is solved in the dissertation. Computer simulation of EMAT magnetic fields distribution in pulse magnetization of ferromagnetic and non-magnetic products is performed. Ways to build transducers with maximum sensitivity are established. The method of excitation of pulsed batch ultrasonic pulses due to the sequential formation of pulsed magnetic and electromagnetic fields is developed. Technical solutions for suppression of coherent interference in the core and in the product have been developed. The geometrical and structural parameters of pulsed magnetic field source were determined, which made it possible to excite powerful in-phase packet pulses of high-frequency shear oscillations in a sample. It is shown that the sensitivity of direct EMA transducers with pulse magnetization provide detection of flat-bottom reflectors with a diameter of 3 mm and more at a probing frequency of 40 Hz, a frequency of shear linearly polarized ultrasonic oscillations of 2.3 MHz, a peak current of high-frequency packet pulses of 120 A, duration of batch high frequency current pulses in 6 periods of filling frequency, magnetization pulse duration of 200 μs, magnetization current of 600 A and at the gap between EMAP and product of 0.2 mm.

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Jiang, Yuxiang. "A Unipolar Pulse Electromagnetic Field Apparatus for Magnetic Therapy: Design, Simulation and Development." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37854.

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As a magnetic therapy apparatus with medical benefits, the Unipolar Pulse Electromagnetic Field (UPEMF) apparatus is presented to produce unipolar pulsed magnetic waveforms with an intensity, shape, and frequency that meet medical requirements. The unipolar pulse is the most significant advantage, as the implemented apparatus is considered to be the first improvement in Pulse Electromagnetic Fields (PEMFs). The magnetic field is generated by a specially designed electromagnetic unit. In this unit, an electromagnet is concentrated by a designed concentrator to strengthen the magnetic field at the north pole and weaken the field on the opposite end. An electromagnetic shield is adopted to eliminate the effects of the south pole but allow the output from the north pole. Excited by a designed pulsed waveform generator, the electromagnetic unit generates a strong alternating-current magnetic field. In my work, the detailed design and development of the electromagnetic unit for UPEMF are introduced, therein being modeled and tested using Finite Element Method simulations. The model is characterized mathematically in three parts: the concentrator, the electromagnetic shield, and the overall unit. The testing and performance measurements of the actual Unipolar Pulse Electromagnetic Field apparatus are achieved using a Gauss meter and oscilloscope.

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Forsberg, Andreas. "Spatial variation of radio frequency magnetic field exposure from clinical pulse sequences in 1.5T MRI." Thesis, Umeå universitet, Institutionen för fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-90391.

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Cell biological exposure studies in magnetic resonance imaging (MRI) environment, where a complex mixture of strong magnetic fields are present, have attracted considerable interest in recent years. The outcome of such studies might depend strongly on the conditions, for example exposure parameters and spatial variations of exposure. The aim of this thesis has been to give a detailed description of how the radio frequency (RF) magnetic field varies with position and sequence choice within an MRI bore from a patient perspective and to highlight the need of better consistency in future research. Method: A straightforward theoretical description on the contribution to the RF magnetic field from a birdcage coil is given. A one dimensional coaxial loop antenna has been used as a probe to measure spatial variations of the RF magnetic field in a 1.5T MRI scanner. An exposure matrix containing RF magnetic field strength (H1-field) amplitudes in three dimensions was constructed and used to study several clinical protocols and sequences. A qualified correspondence measurement was also made on a 3T MRI scanner. Results: Around isocenter, for a common field-of-view (FOV), changes in exposure conditions were small; however, rapid changes of exposure conditions occurred upon approaching the end rings. The dominating H1-field component switched from lying in the xy-plane to pointing the z-direction and was roughly 3 times larger than in isocenter. Practical difficulties indicate even larger differences at positions not measurable with the equipment at hand. The strongest H1-field component was 32.6 A/m at position (x,y,z)=(-24,8,24) cm from the isocenter. Conclusions: Machine parameters such as repetition time, echo time and flip angle have little to do with actual exposure. Specic absorption rate (SAR) values correlated well with the square of measured root-mean-square (RMS) values of the magnetic field (B1,RMS) but not with peak values of the magnetic field (B1,peak), indicating that peak values are not unlikely to be part of compromising factors in previous contradictory exposure research on genotoxicity. Furthermore exposure conditions depend strongly on position and unfavorable situations may occur in the periphery of the birdcage coil. Potentially elevated risks for conducting surfaces, for example arms or external fixations, in the proximity of the end rings, are proposed. Aside from spatial variation consideration on which type of geometry exposed cell-biological samples are placed in should be held since eddy currents, hot-spots and proper SAR depend on geometry. Conditions may vary considerably between in-vitro, ex-vivo and in-vivo studies since geometries of test tubes, petri dishes and humans differ.

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Liu, Jean. "Constraining the Source Distribution of Meltwater Pulse 1A Using Near- and Far-Field Sea-level Data." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/30241.

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Meltwater pulse 1A (MWP-1A) is the largest land ice melt event of the last deglaciation. In a period of no more than 340 years, between 14.65 and 14.31 ka (Dechamps et al, 2012), ~10% of the total deglacial sea-level rise occurred (Hanebuth et al, 2000; Peltier and Fairbanks, 2006; Deschamps et al, 2012), resulting in the highest reported rate of global mean sea-level rise in the geological record, which may have exceeded 4 m per century (Deschamps et al, 2012). Yet, the implications of MWP-1A for constraining the rates of the underlying processes and its role in the sequence of climate events during Termination 1 remain unclear due to the lack of information on its melt source distribution. While glacial isostatic adjustment (GIA) modelling experiments (Clark et al, 2002; Bassett et al, 2005; Deschamps et al, 2012) and recent assessments of ice-sheet histories (Carlson and Clark, 2012) suggest that at least 50% of the event may have come from Antarctica, other interpretations of Antarctic ice-extent and sea-level records suggest a substantially smaller (including zero) Antarctic contribution (Ackert et al, 2007; Mackintosh et al, 2011; Whitehouse et al, 2012). In this study, we show that after reassessments of local MWP-1A amplitudes at Barbados and Sunda Shelf based on the well-constrained timing derived from the Tahiti sea-level record (Deschamps et al, 2012), the sea-level data from Barbados, Sunda Shelf, and Tahiti do not provide as tight of a constraint on the Antarctic contribution as previously thought. We find that between 1 to 10 m sea-level equivalent (sle) could have melted from the Antarctic, compared to 7 to 15 m sle from previous analyses (Clark et al, 2002; Bassett et al, 2005; Deschamps et al, 2012). To better constrain the source of MWP-1A, we also consider sea-level data from Scotland (Shennan et al, 2000), which have, until now, been excluded from MWP-1A fingerprinting experiments because they are strongly influenced by local ice unloading. To overcome this, we isolate the elastic MWP-1A amplitude (i.e. fingerprint signal) at this location using a suite of models that provide optimal fits to the Scottish data, and thereby remove near-field contamination. Preliminary results show that the inclusion of these data leads to an improved MWP-1A source distribution constraint compared to that obtained using the far- and intermediate-field data alone.

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Eichel, Rüdiger-Albert. "New concepts in two-dimensional pulse electron paramagnetic resonance spectroscopy : resolution enhancement by magnetic field modulation /." Zürich : [s.n.], 2001. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=14394.

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Kurpad, Krishna Nagaraj. "Transmit field pattern control for high field magnetic resonance imaging with integrated RF current sources." Texas A&M University, 2004. http://hdl.handle.net/1969.1/2755.

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The primary design criterion for RF transmit coils for MRI is uniform transverse magnetic (B1) field. Currently, most high frequency transmit coils are designed as periodic, symmetric structures that are resonant at the imaging frequency, as determined by the static magnetic (B0) field strength. These coils are excited by one or more voltage sources. The distribution of currents on the coil elements or rungs is determined by the symmetry of the coil structure. At field strengths of 3T and above, electric properties such as the dielectric constant and conductivity of the load lead to B1 field inhomogeneity due to wavelength effects and perturbation of the coil current distribution from the ideal. The B1 field homogeneity under such conditions may be optimized by adjusting the amplitudes and phases of the currents on the rungs. However, such adjustments require independent control of current amplitudes and phases on each rung of the resonant coil. Due to both the strong coupling among the rungs of a resonant coil and the sensitivity to loading, such independent control would not be possible and B1 homogeneity optimization would involve a time consuming and impractical iterative procedure in the absence of exact knowledge of interactions among coil elements and between the coil and load. This dissertation is based on the work done towards the design and development of a RF current source that drives high amplitude RF current through an integrated array element. The arrangement is referred to as a current element. Independent control of current amplitude and phase on the current elements is demonstrated. A non-resonant coil structure consisting of current elements is implemented and B1 field pattern control is demonstrated. It is therefore demonstrated that this technology would enable effective B1 field optimization in the presence of lossy dielectric loads at high field strengths.

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Shore, Robert Michael. "Improved description of Earth's external magnetic fields and their source regions using satellite data." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8935.

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In near-Earth space, highly spatio-temporally variant magnetic fields result from solar-terrestrial magnetic interaction. These near-Earth external fields currently represent the largest source of error in efforts to model the magnetic field produced in the Earth’s interior. Starting in 1999, the Decade of Geopotential Field Research (Friis-Christensen et al., 2009) has greatly increased the amount of available low-Earth orbit (LEO) satellite magnetic data. These data have driven many advances in field modelling, yet have highlighted that LEO measurements are particularly susceptible to contamination from external fields. This thesis presents a series of studies attempting to describe the external fields in more detail, in order that they can be more effectively separated from the internal fields in magnetic modelling efforts. A range of analysis methods, different for each study, are applied to satellite and ground-based observatory data. Mandea and Olsen’s (2006) method of estimating the secular variation (SV) of the internal field from satellite data via ‘Virtual Observatories’ (VOs) is applied to synthetic data from the upcoming Swarm constellation satellite mission of the European Space Agency. Beggan (2009) found VOs constructed from CHAMP satellite data to be contaminated with external field signals which appeared to have a significant local time (LT) dependence. I find that utilising the increased coverage of LT sectors offered by the Swarm constellation geometry does not significantly decrease the contamination. Following this surprising result I tested a wide range of methods aimed at reducing the VO contamination from each parameterised external field source region. In anticipation of future studies using real data, I used the results of the tests to provide a more complete description of the external field variations affecting analyses of geographically-fixed magnetic phenomena when using satellite data and spherical harmonic analysis (SHA). Ionospheric electric currents flowing at LEO altitudes are known to violate the assumption of measurements taken in a source-free space, required in SHA-based models of the magnetic field. In order to better describe the electromagnetic environment at LEO altitudes, I use data from the Ørsted and CHAMP satellites to calculate the current density from Amp`ere’s integral. Vector magnetic data from discrete overflights of the two satellites (at different altitudes) are rotated into the along-track frame to define the integral loop and its ‘surface area’, permitting estimation of the predominantly zonal current density flowing in the region between the two orbital paths. I designed selection criteria to extract geometrically-stable overflights spanning the range of LTs twice in the 6 years of mutually available satellite vector data. From these overflights I resolve current densities in the range 0:1 μA=m2, with the distribution of current largely matching the LT progression of the Appleton anomaly. I applied detailed tests to check for biases intrinsic to the method, and present results free of systematic errors. The results are compared with the predictions of the CTIP (Coupled Thermosphere-Ionosphere-Plasmasphere) model of ionospheric composition and temperature, showing a typically good spatiotemporal agreement. I find persistent current intensifications between geomagnetic latitudes of 30 and 50 in the post-midnight, pre-dawn sector, a region which has been previously considered to be relatively free of currents. External fields induce currents in the Earth’s conducting mantle, the magnetic fields of which add to the field measured at and above the Earth’s surface. The morphology of the long-period inducing field is poorly resolved on timescales of months to years, reducing the accuracy of mantle induction studies (a key part of the Swarm mission). I improve the description of its morphology via the method of Empirical Orthogonal Functions (EOFs), which I apply to over a decade of ground-based observatory data. EOFs provide a decomposition of the spatiotemporal structures contained in the magnetic field data, with partitions arising from the data themselves, overcoming the relatively simplistic assumptions made about the inducing field morphology in LT. The results of vector data EOF analyses are presented, but I rely primarily on scalar analyses which are more fitting for this study. I overcome the limitations of the irregular observatory distribution with a novel spatial weighting matrix, combining the output from multiple EOF analyses to greatly improve the data coverage in LT. I find that the seasonal variation of the inducing field is more important than the variation of the symmetric ring current on annual periods, and that dawn-dusk asymmetry should be accounted for to increase the accuracy of mantle conductivity estimates based on data covering the decadal timescales of the solar cycle.

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Книги з теми "Pulse source of magnetic field"

Cowan, M. Megagauss magnetic field generation and pulsed power applications. New York: Nova Science, 1994.

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Hurban, Jane. Does the pulse form affect the enhanced suggestibility from right hemispheric magnetic field stimulation? Sudbury, Ont: Laurentian University, Department of Psychology, 1996.

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W, Kahler Stephen, and United States. National Aeronautics and Space Administration., eds. Study of the source regions of coronal mass ejections using Yohkoh SXT data: Final report for--NASA grant NAGW-4578, period of performance--1 May 1995 - 30 April 1997. [Washington, DC: National Aeronautics and Space Administration, 1997.

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Maccabee, Paul J., and Vahe E. Amassian. Lessons learned from magnetic stimulation of physical models and peripheral nerve in vitro. Edited by Charles M. Epstein, Eric M. Wassermann, and Ulf Ziemann. Oxford University Press, 2012. http://dx.doi.org/10.1093/oxfordhb/9780198568926.013.0006.

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This article provides a conceptual framework, which contributes to the understanding of the mechanisms involved in brain stimulation. The relationship between the induced topographic electric field and specific sites and regions of nerve activation in the brain are still not precisely known. Nevertheless, there is much more specific information available concerning peripheral nerve and nerve root stimulation. In vitro studies provide insight into the different properties of monophasic versus polyphasic pulses. Studies of brain stimulation agree with the in vitro conclusion that the polyphasic pulse is more powerful than the monophasic pulse. The shape of the induced pulse may be a relevant clinical response factor in repetitive TMS.

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Epstein, Charles M. Electromagnetism. Edited by Charles M. Epstein, Eric M. Wassermann, and Ulf Ziemann. Oxford University Press, 2012. http://dx.doi.org/10.1093/oxfordhb/9780198568926.013.0001.

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This article elucidates on the concept of electromagnetism and electromagnetic induction with a view to explaining the theory of magnetic stimulation, used to cure diseases in human beings. Magnetic stimulation follows the principles of electromagnetism. A changing primary current induces secondary currents, which are called eddy currents, in the nearby conductors (human tissue in this case). The strength of the electric field is measured by its electromotive force (emf), which in turn, is measured in volts. The changing primary current also gives rise to an induced voltage in the primary loop itself. The essential circuitry of a magnetic stimulator is composed of three elements, the capacitor, inductance of the stimulation coil, and a switch to connect them. This article also explains the process of the energy flow system through the inductor-capacitor system, applying this principle to the biphasic TMS pulse.

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Classen, Joseph, and Katja Stefan. Changes in TMS Measures induced by repetitive TMS. Edited by Charles M. Epstein, Eric M. Wassermann, and Ulf Ziemann. Oxford University Press, 2012. http://dx.doi.org/10.1093/oxfordhb/9780198568926.013.0016.

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This article reviews several protocols of repetitive transcranial magnetic stimulation (rTMS)-induced plasticity. rTMS, when applied to the motor cortex or other cortical regions of the brain, may induce effects that outlast the stimulation period. The neural plasticity, which emerges as a result of such interventions, has been studied to gain insight into plasticity mechanisms of the brain. In two protocols the structure of rTMS trains is modified, informed by the knowledge of the physiological properties of the corticospinal system. Pulse configuration, stimulus frequency, stimulus intensity, the duration of the application period, and the total number of stimuli are some variables that have to be taken into account when reviewing the physiological effects of rTMS. This article also introduces the concept of patterned rTMS pulses and rTMS with ischemic nerve block. In addition, rTMS has raised considerable interest because of its therapeutic potential; however, much needs to be done in this field.

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Riehl, Mark. TMS stimulator design. Edited by Charles M. Epstein, Eric M. Wassermann, and Ulf Ziemann. Oxford University Press, 2012. http://dx.doi.org/10.1093/oxfordhb/9780198568926.013.0003.

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Transcranial magnetic stimulators have progressed from basic implementations to integrated systems optimized for treatment of pathologies. This article reviews key factors of design of such clinically targeted systems, discussing design principles, procedure-specific features, and clinical safety requirements. A power source, a capacitor, and a high-power switch controlled by a processor form the basic stimulator. The fundamental operating mechanism of a TMS stimulator is to create a changing magnetic field that can induce a current in adjacent conductive material. The clinical TMS system must incorporate patient positioning, patient comfort, coil positioning features, and intuitive user controls and means of managing patient data to be a fully effective system. The most important safety risk with repetitive TMS reported in the literature is the risk of inducing seizure. Other safety considerations include proper use of human factor analysis to minimize improper operation, the biocompatibility of materials touching the patient, and addressing acoustic noise.

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T. Wave Phenomena. Courier Dover Publications, 2014.

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Частини книг з теми "Pulse source of magnetic field"

Kivelson, Margaret G., and David J. Southwood. "Magnetopause pressure pulses as a source of localized field-aligned currents in the magnetosphere." In Physics of Magnetic Flux Ropes, 619–25. Washington, D. C.: American Geophysical Union, 1990. http://dx.doi.org/10.1029/gm058p0619.

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Olevsky, Eugene A., and Dina V. Dudina. "Magnetic Pulse Compaction." In Field-Assisted Sintering, 293–313. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-76032-2_9.

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Dobre, A., and A. M. Morega. "Numerical Simulation In Magnetic Drug Targeting. Magnetic Field Source Optimization." In XII Mediterranean Conference on Medical and Biological Engineering and Computing 2010, 651–54. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-13039-7_164.

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Osinskaya, J. V., and A. V. Pokoev. "The Ageing of Beryllium Bronze in the Pulse Magnetic Field." In Defect and Diffusion Forum, 81–85. Stafa: Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/3-908451-55-8.81.

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Foss, Clive. "Recovery of Source Magnetization Direction from Magnetic Field Data." In Encyclopedia of Solid Earth Geophysics, 1–11. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-10475-7_265-1.

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Foss, Clive. "Recovery of Source Magnetization Direction from Magnetic Field Data." In Encyclopedia of Solid Earth Geophysics, 1310–19. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-58631-7_265.

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Richter, Aleš, Miroslav Bartoš, and Želmíra Ferková. "Physical Analysis of Pulse Low-Dynamic Magnetic Field Applied in Physiotherapy." In IFMBE Proceedings, 239–45. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-10-9023-3_43.

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Dester, Gary D., and Edward J. Rothwell. "Analysis of the Late-Time Transient Field Scattered by a Line Source Above a Grounded Dielectric Slab." In Ultra-Wideband Short-Pulse Electromagnetics 8, 195–202. New York, NY: Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-73046-2_26.

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Nolle, Eugen. "Determination of the Magnetic Stray Field with an Equivalent Source Model." In Process Modelling, 305–12. Berlin, Heidelberg: Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/978-3-642-60120-0_20.

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Thottappillil, R., M. A. Uman, and N. Theethayi. "TEM Field Structure of Electric and Magnetic Fields From a Semi-Infinite Vertical Thin-Wire Antenna Above a Conducting Plane." In Ultra-Wideband, Short-Pulse Electromagnetics 7, 33–40. New York, NY: Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-37731-5_4.

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Тези доповідей конференцій з теми "Pulse source of magnetic field"

CHERNYKH, E. V., V. E. FORTOV, K. V. GORBACHEV, E. V. NESTEROV, S. A. ROSCHUPKIN, and V. A. STROGANOV. "HIGH VOLTAGE PULSED MCG-BASED ENERGY SOURCE." In Proceedings of the VIIIth International Conference on Megagauss Magnetic Field Generation and Related Topics. WORLD SCIENTIFIC, 2004. http://dx.doi.org/10.1142/9789812702517_0078.

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Kraus, W., U. Fantz, D. Wünderlich, Yasuhiko Takeiri, and Katsuyoshi Tsumori. "Dependence of the Performance of the Long Pulse RF Driven Negative Ion Source on the Magnetic Filter Field." In SECOND INTERNATIONAL SYMPOSIUM ON NEGATIVE IONS, BEAMS AND SOURCES. AIP, 2011. http://dx.doi.org/10.1063/1.3637400.

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Ono, S., T. Tsukamoto, H. Ohtake, E. Kawahata, T. Yano, and N. Sarukura. "Optimum geometry of the THz-radiation source using femtosecond pulse irradiated InAs [100] in a magnetic field." In Conference on Lasers and Electro-Optics (CLEO 2000). Technical Digest. Postconference Edition. TOPS Vol.39. IEEE, 2000. http://dx.doi.org/10.1109/cleo.2000.907382.

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Egorychev, Boris T., Dmitry V. Avdeev, Viktor V. Avdoshin, Anatoly M. Buyko, Gennady I. Volkov, Aleksey M. Glybin, Andrey V. Ivanovsky, et al. "Investigation of Solid Quasi-Spherical Liner Implosion Using Diagnostic Test Stand and Helical Explosive Magnetic Generator as a Pulsed Power Source." In 2006 International Conference on Megagauss Magnetic Field Generation and Related Topics. IEEE, 2006. http://dx.doi.org/10.1109/megaguss.2006.4530666.

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Dolinskii, V. Yu, D. A. Ershov, A. P. Falin, S. F. Garanin, A. V. Garin, O. N. Petrushin, and Yu S. Shigaev. "Prospects for development of pulsed source with a yield 1014 DT-neutrons based on spherical DPF chamber." In 2018 16th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS). IEEE, 2018. http://dx.doi.org/10.1109/megagauss.2018.8722685.

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Duday, P. V., A. M. Glybin, B. T. Egorichev, V. A. Ivanov, A. I. Krayev, V. B. Kudel'kin, S. M. Polyushko, et al. "Powerful Pulsed Source with Adjustable Time of Current Rise on the Basis of Helical EMG and Explosive Opening Switch to Drive Solid Liners." In 2006 International Conference on Megagauss Magnetic Field Generation and Related Topics. IEEE, 2006. http://dx.doi.org/10.1109/megaguss.2006.4530700.

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Shkuratov, Sergey I., Evgueni F. Talantsev, Jason Baird, Larry L. Altgilbers, and Allen H. Stults. "New Concept for Constructing an Autonomous Completely Explosive Pulsed Power System: Transverse Shock Wave Ferromagnetic Primary Power Source and Loop Flux Compression Amplifier." In 2006 IEEE International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS). IEEE, 2006. http://dx.doi.org/10.1109/megaguss.2006.4530697.

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Zhang, Li, James A. Bain, Jian-Gang Zhu, Leon Abelmann, and Takahiro Onoue. "The Role of STM Tip Shape in Heat Assisted Magnetic Probe Recording on CONI/PT Film." In ASME 2004 3rd Integrated Nanosystems Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/nano2004-46057.

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A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. In this work, field emission current from a scanning tunneling microscope (STM) tip is used as the heating source. The tip is made of Ir/Pt alloy. Pulse voltages of 3–7 V with a duration of 500 ns were applied to a CoNi/Pt multilayered film. Written by a blunt tip (radius 1000 nm), marks are formed with a nearly uniform mark size of 170 nm when the pulse voltage is above 4 V. While sharp tip (radius 50 nm) writing achieves no mark. The emission area of our tip-sample system derived from an analytic expression for field emission current is approximately equal to the mark size, and is largely independent of pulse voltage. For the blunt tip, the emission region is almost the same as the mark size. While for the sharp tip, the initially formed mark is too small, so that the domain wall surface tension shrinks the mark and it crashes finally.

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Ryzhkov, Sergei V., and Andrey V. Anikeev. "Improved Regimes in High Pressure Magnetic Discharges." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22212.

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Field-Reversed Configuration (FRC) [1] and Gas-Dynamic Trap (GDT) [2] represent compact system, which is a special magnetic geometry for plasma confinement. Theoretical and experimental study of gas-dynamic regimes with high energy content is carried out. The approach to a high beta (β is the ratio of plasma pressure to magnetic pressure) magnetic systems assumed different regimes of plasma with beta > 0.5 that is proper to compact devices such as tori and mirror traps. Both FRC and GDT traps are axial symmetric configurations, has open field lines and poloidal magnetic field only. Last experimental results on GDT have shown the possibility to build the stationary system with high beta. Analysis of the global energy and particle balance together with the Monte-Carlo equilibrium modelling allowed to conclude that two-component plasma confined in a steady-state regime. The characteristic plasma lifetimes are 4 to 5 times less then the experiment duration. A peripheral gas-puff near the mirror region enabled to maintain the radial profile of background plasma during the all neutral beam injection (NBI) pulse. This report is focused mainly on ambipolar effect and the possibility of further increasing the fast ion energy content and β. Improved gas-dynamic regimes in high pressure magnetic discharges and microinstabilities arising are described. Synthesized hot ion plasmoid (SHIP) experiment in the compact mirror section attached to the GDT central cell and the scheme of compact tori (FRC formation) for the compact mirror cell of GDT device are presented. Fusion prospects (reactor, neutron source, material studies) of such systems with high-energy (fast) particles [3, 4] and hybrid FRC + GDT scheme proposed by author from Bauman Moscow State Technical University (BMSTU) are discussed.

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Ono, Shingo, Hiroshi Takahashi, Alex Quema, Gilbert Diwa, Hidetoshi Murakami, Nobuhiko Sarukura, and Michael Hasselbeck. "High frequency component of terahertz-radiation spectrum enhanced by using an excitation source with short pulse duration on an n-type InAs immersed in magnetic field." In Optical Terahertz Science and Technology. Washington, D.C.: OSA, 2005. http://dx.doi.org/10.1364/otst.2005.me5.

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Звіти організацій з теми "Pulse source of magnetic field"

Tilak, Anup S., Douglas J. Basarab, Herbert A. Leupold, II Potenziani, and Ernest. Magnetic Field Source for Bi-Chambered Electron Beam Devices. Fort Belvoir, VA: Defense Technical Information Center, November 1992. http://dx.doi.org/10.21236/ada261316.

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Meitzler, C. R. Magnetic field of a toroidal volume H sup minus source. Office of Scientific and Technical Information (OSTI), September 1989. http://dx.doi.org/10.2172/5481261.

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Holmes, John J. Boundary Conditions for Magnetic Field Gradients Inside a Source-Free Volume. Fort Belvoir, VA: Defense Technical Information Center, April 1999. http://dx.doi.org/10.21236/ada362760.

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J Selvaggi, S Salon, and O Kwon CVK Chari. A General Method for Calculating the External Magnetic Field from a Cylindrical Magnetic Source using Toroidal Functions. Office of Scientific and Technical Information (OSTI), February 2006. http://dx.doi.org/10.2172/881294.

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S.J. Zweben, D.S. Darrow, P.W. Ross, J.L. Lowrance, and G. Renda. Measurement of the Internal Magnetic Field of Plasmas using an Alpha Particle Source. Office of Scientific and Technical Information (OSTI), May 2004. http://dx.doi.org/10.2172/827999.

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Nikolic, L. Modelling the magnetic field of the solar corona with potential-field source-surface and Schatten current sheet models. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2017. http://dx.doi.org/10.4095/300826.

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Raitses, Y., Smirnov A., and N. J. Fisch. Comment on "Effects of Magnetic Field Gradient on Ion Beam Current in Cylindrical Hall Ion Source. Office of Scientific and Technical Information (OSTI), August 2008. http://dx.doi.org/10.2172/938977.

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Kaganovich, I. D., E. A. Startsev, A. B. Sefkow, and R. C. Davidson. Controlling Charge and Current Neutralization of an Ion Beam Pulse in a Background Plasma by Application of a Small Solenoidal Magnetic Field. Office of Scientific and Technical Information (OSTI), August 2007. http://dx.doi.org/10.2172/961895.

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Hart, Carl R., and Gregory W. Lyons. A Measurement System for the Study of Nonlinear Propagation Through Arrays of Scatterers. Engineer Research and Development Center (U.S.), November 2020. http://dx.doi.org/10.21079/11681/38621.

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Various experimental challenges exist in measuring the spatial and temporal field of a nonlinear acoustic pulse propagating through an array of scatterers. Probe interference and undesirable high-frequency response plague typical approaches with acoustic microphones, which are also limited to resolving the pressure field at a single position. Measurements made with optical methods do not have such drawbacks, and schlieren measurements are particularly well suited to measuring both the spatial and temporal evolution of nonlinear pulse propagation in an array of scatterers. Herein, a measurement system is described based on a z-type schlieren setup, which is suitable for measuring axisymmetric phenomena and visualizing weak shock propagation. In order to reduce directivity and initiate nearly spherically-symmetric propagation, laser induced breakdown serves as the source for the nonlinear pulse. A key component of the schlieren system is a standard schliere, which allows quantitative schlieren measurements to be performed. Sizing of the standard schliere is aided by generating estimates of the expected light refraction from the nonlinear pulse, by way of the forward Abel transform. Finally, considerations for experimental sequencing, image capture, and a reconfigurable rod array designed to minimize spurious wave interactions are specified. 15.

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Johra, Hicham. Performance overview of caloric heat pumps: magnetocaloric, elastocaloric, electrocaloric and barocaloric systems. Department of the Built Environment, Aalborg University, January 2022. http://dx.doi.org/10.54337/aau467469997.

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Heat pumps are an excellent solution to supply heating and cooling for indoor space conditioning and domestic hot water production. Conventional heat pumps are typically electrically driven and operate with a vapour-compression thermodynamic cycle of refrigerant fluid to transfer heat from a cold source to a warmer sink. This mature technology is cost-effective and achieves appreciable coefficients of performance (COP). The heat pump market demand is driven up by the urge to improve the energy efficiency of building heating systems coupled with the increase of global cooling needs for air-conditioning. Unfortunately, the refrigerants used in current conventional heat pumps can have a large greenhouse or ozone-depletion effect. Alternative gaseous refrigerants have been identified but they present some issues regarding toxicity, flammability, explosivity, low energy efficiency or high cost. However, several non-vapour-compression heat pump technologies have been invented and could be promising alternatives to conventional systems, with potential for higher COP and without the aforementioned refrigerant drawbacks. Among those, the systems based on the so-called “caloric effects” of solid-state refrigerants are gaining large attention. These caloric effects are characterized by a phase transition varying entropy in the material, resulting in a large adiabatic temperature change. This phase transition is induced by a variation of a specific external field applied to the solid refrigerant. Therefore, the magnetocaloric, elastocaloric, electrocaloric and barocaloric effects are adiabatic temperature changes in specific materials when varying the magnetic field, uniaxial mechanical stress, electrical field or hydrostatic pressure, respectively. Heat pump cycle can be built from these caloric effects and several heating/cooling prototypes were developed and tested over the last few decades. Although not a mature technology yet, some of these caloric systems are well suited to become new efficient and sustainable solutions for indoor space conditioning and domestic hot water production. This technical report (and the paper to which this report is supplementary materials) aims to raise awareness in the building community about these innovative caloric systems. It sheds some light on the recent progress in that field and compares the performance of caloric systems with that of conventional vapour-compression heat pumps for building applications.

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