Xem 1-20 trên 654 kết quả Magnetic
  • Từ trễ (tiếng Anh: magnetic hysteresis) là hiện tượng bất thuận nghịch giữa quá trình từ hóa và đảo từ ở các vật liệu sắt từ do khả năng giữ lại từ tính của các vật liệu sắt từ. Hiện tượng từ trễ là một đặc trưng quan trọng và dễ thấy nhất ở các chất sắt từ.

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  • Medicine is, fortunately, constantly evolving. Imaging diagnosis is no exception. Technical improvements guarantee further developments in diagnosis. Computed tomography (CT) and magnetic resonance imaging (MRI) have attained a recognized value in the diagnosis of the heart, which is continuing to increase. For this reason, we have now provided a separate chapter on diagnostic imaging of the heart. We have placed sectional CT images next to MR images of the heart to facilitate classification. We have limited ourselves to scans which are presently recognized as standard.

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  • Medicine is, fortunately, constantly evolving. Imaging diagnosis is no exception. Technical improvements guarantee further developments in diagnosis. Computed tomography (CT) and magnetic resonance imaging (MRI) have attained a recognized value in the diagnosis of the heart, which is continuing to increase. For this reason, we have now provided a separate chapter on diagnostic imaging of the heart. We have placed sectional CT images next to MR images of the heart to facilitate classification. We have limited ourselves to scans which are presently recognized as standard.

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  • Investigation of the magnetic properties of materials is very important, because magnetic phenomena have various scientific and technical applications. The macroscopic properties of matter are a manifestation of the microscopic properties of the atoms of which it is composed. The magnetic properties of materials may be very different for types of material, depending on their nature and structure.

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  • Since its first implementation by Lauterbur [1], Magnetic Resonance Imaging (MRI) has become an important noninvasive imaging modality. MRI has found a number of applications in the fields of biology, engineering, and material science. Because it provides unique contrast between soft tissues (which is generally superior to that of CT) and high spatial resolution, MRI has revolutionized diagnostic imaging in medical science. An important advantage of diagnostic MRI as compared to CT is that the former does not use ionizing radiation....

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  •  Some history:  Magnetic effects from natural magnets have been known for a long time. Recorded observations from the Greeks more than 2500 years ago.  The word magnetism comes from the Greek word for a certain type of stone (lodestone) containing iron oxide found in Magnesia, a district in northern Greece.  Properties of lodestones: could exert forces on similar stones and could impart this property (magnetize) to a piece of iron it touched.

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  • NMR is an experiment in which the resonance frequencies of nuclear magnetic systems are investigated. NMR always employs some form of magnetic field (usually a strong externally applied field B0) NMR is a form of both absorption and emission spectroscopy, in which resonant radiation is absorbed by an ensemble of nuclei in a sample, a process causing detectable emissions via a magnetically induced electromotive force.

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  • Magnetism often has a slight overtone of being mysterious. This is probably caused by the surprisingly strong forces between magnets which everybody can experience with magnetic toys, magnet boards, or similar objects. A strange effect is the unique ability of magnetic fields to penetrate many substances without any attenuation. Though the physical basis of magnetism is well explored, the outsider usually does not know very much about the details and sometimes tends to overestimate the real possibilities provided by magnetism.

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  • Mời các bạn cùng tham khảo nội dung cuốn sách "Magnet Funattract" dưới đây để nắm bắt được cách viết, cách phát âm các từ vựng: Force, friction, gravity, motion, repel, simple machine, work. Với các bạn bước đầu học tiếng Anh thì đây là tài liệu tham khảo hữu ích.

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  • In this contribution several topics concerning magnetic fields and overhead medium voltage power lines are reviewed: simple formulation to assess the magnetic field (MF) level; characterization of magnetic fields generated by typical three-phase and one-phase primary distribution lines, with balanced and unbalanced current; and main mitigation techniques, analysed in relation with typical reduction level obtained. Additional data concerning cost and performance of different solutions are also provided....

    doc31p powersystem 06-07-2010 62 5   Download

  • The field of magnetic nanostructures is now an exciting and central area of modern condensed matter science, which has recently led to the development of a major new direction in electronics – so called ‘spintronics’. This is a new approach in which the electron spin momentum plays an equal role to the electrical charge, and these radical ideas have galvanised the efforts of previously disparate research communities by offering the promise of surpassing the limits of conventional semiconductors. Clearly the world of magnetism has now entered electronics in a very fundamental manner.

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  •  NMR in solids, like solution-state, relies on the behavior of nuclear spin energy levels in a magnetic field. However, the interactions that affect NMR spectra act differently.  In liquids, molecules reorient and diffuse quickly, leading to narrow isotropic resonances.  In solids, the fixed orientation of individual crystallites leads to a range of resonance frequencies for anisotropic interactions.

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  • Tham khảo sách 'magnetic resonance imaging methods and biologic applications', y tế - sức khoẻ, y dược phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả

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  • Physical Phenomena at High Magnetic Fields-IV (PPHMF-IV) was the fourth conference sponsored by the National High Magnetic Field Laboratory (NHMFL). The previous conferences were held in May, 1991, 1995, and 1998. These meetings brought together experts in scientific research areas where high magnetic fields could make an important impact. PPHMF-III devoted substantial time to reviewing the state of many fields in regard to the role of high magnetic fields, such as semiconductors, heavy fermions, superconductivity, and molecular conductors.

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  • Normally, any ferromagnetic or ferrimagnetic material undergoes a transition to a paramagnetic state above its Curie temperature. Superparamagnetism is different from this standard transition since it occurs below the Curie temperature of the material. Superparamagnetism occurs in nanoparticles which are single domain. This is possible when their diameter is below 3–50 nm, depending on the materials.

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  • The concept of summerschools and workshops at the Kanzelho¨he Solar Observatory, Ka¨rnten, Austria, devoted to up-to-date topics in solar physics has been proven to be extremely successful, and thus in August/September 2003 the third combined summerschool and workshop was held there. This book contains the proceedings of the Summerschool and Workshop “Solar Magnetic Phenomena” held from 25 August to 5 September 2003 at the Solar Observatory Kanzelho¨he, which belongs to the Institute for Geophysics, Astrophysics and Meteorology of the University of Graz, Austria.

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  • Abstract The year 2008 marked the one hundredth anniversary of the observational discovery by George Ellery Hale of magnetic field in sunspots (Hale in Astrophys. J. 28:315–343, 1908). This observation, the first to suggest a direct link between the best-known variable features on the Sun and magnetism, started a line of research that has widened considerably over the last 100 years and is continuing today. Knowledge about all aspects of the Sun has increased in a remarkable way over the past few decades....

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  • This paper introduces a new analytical method for performing the output torque calculations of an interior permanent magnet synchronous motor (IPMSM) including both permanent magnet and reluctance torque components.

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  • Lecture Organic chemistry - Chapter 10: Nuclear magnetic resonance (NMR) spectroscopy. In this chapter, the following content will be discussed: What is spectroscopy? General spectrometer, the chemical shift δ, complex splitting patterns,...and other contents.

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  • The compounds of La1-xCaxMnO3- δ with x=0.46 and 0.50 occupy special positions in the phase diagram of La1-xCaxMnO3-δ system due to their interesting properties and charge-ordering phase transition. The samples were prepared by a solid-state reaction method. The XPD patterns show that the samples are of a single-phase orthorhombic-perovskite structure. The chemical compositions of the samples are investigated by EDS. The concentrations of oxygen and Mn3+; Mn4+ ions have been determined by dichromate method.

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