共查询到10条相似文献,搜索用时 74 毫秒
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Bradshaw John A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1978,6(2):166-171
An expression is developed in spherical harmonics for the magnetic field of a baseball coil. A simple dipole-layer model for the coil, and the computer program, MAFCO, yield comparable expansion coefficients, and give practically identical fields near the center of the baseball. 相似文献
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Two oscillatory systems representing nonferromagnetic conductors interacting with a high-frequency inhomogoneous magnetic field are examined. It is shown that there is a frequency range in which self-oscillations are excited. 相似文献
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为了充分利用超导线材的载流能力,需要精确计算超导线圈产生的最大磁场值,还需要明确最大磁场值所处的具体位置.其中,最大磁场点的位置主要由线圈的形状(径高比)决定.本文基于单积分法并通过MATLAB编程,将矩形截面线圈的径高比α和β参数化,计算分析线圈内壁边上和端面边上各点磁场的变化趋势.同时,利用电磁场有限元软件ANSYS,对矩形截面线圈的空间磁场进行仿真分析,得到线圈的内壁磁场系数、端面磁场系数和最大磁场系数随α和β的变化规律;进而,计算并寻找到了线圈截面上最大磁场点的位置和幅值.综合分析表明,线圈内壁边上的最大磁场点并不是始终位于内壁中点Bc处,而是可能偏离端点Be一小段距离的某点(a1,b-δ)处;线圈端面边上的最大磁场点一定不位于端点Be处,而是偏离端点Be一小段距离的某点(a1+δ,b)处.本文给出了线圈截面上最大磁场系数Kmc对应于线圈径高比(α,β)变化的等高曲线,矩形截面超导线圈最大磁场值可以通过计算内壁中点的磁场值与最... 相似文献
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单匝线圈在辐向磁场中的受力情况,很多教师都用纯数学方法(微元法)推导出其有效长度为线圈周长.文章用音频电流通过方形线圈,依次增加磁铁的个数让学生感觉音量的变化,并进一步合理外推出同样的结论.不仅能让学生体会基于实验合理外推这一科学的研究方法,还能让学生对扬声器的工作原理有清晰的认识. 相似文献
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Russian Physics Journal - 相似文献
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It is thought that the design of magnetic field modulation coils is one of the factors limiting enlargement of the sample
size in electron paramagnetic resonance (EPR) measurements. In this study, we miniaturized the magnetic field modulation coil
and combined it with a surface-coil-type resonator (SCR). The inductor of the SCR was a circular single-turn one-loop coil
(diameter, 1 mm), and the magnetic field modulation coil was a twin-loop coil consisting of two solenoid coils each made of
15 turns of copper wire on a cylindrical bobbin with an axial length of 3 mm and an elliptical cross section (major axis,
7 mm; minor axis, 3 mm). The former was located on the latter via a spacer (thickness, 3 mm) in such a way that the directions
of their axes coincided. Their combined size was about 10 mm wide, 10 mm deep, and 6 mm high. The transmission lines of the
SCR were set on resonance at about 700 MHz. EPR measurements of a phantom (comprising agar that included a nitroxide radical
and physiological saline solution), made with a miniaturized modulation coil combined with the SCR, exhibited a sensitivity
similar to that for the conventional method.
Authors' address: Hidekatsu Yokoyama, Department of Pharmaceutical Sciences, International University of Health and Welfare,
2600-1 Kitakanemaru, Ohtawara 324-8501, Japan 相似文献
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P. Kędzia T. Czechowski M. Baranowski J. Jurga E. Szcześniak 《Applied magnetic resonance》2013,44(5):605-618
In this paper we use a simple analysis based on properties of the axial field generated by symmetrical multipoles to reveal all possible distributions of two coaxial pairs of circular windings, which result in systems featuring zero octupole and 32 pole magnetic moments (six-order systems). Homogeneity of magnetic field of selected systems is analyzed. It has been found that one of the derived systems generates homogenous magnetic field whose volume is comparable to that yielded by the eight-order system. The influence of the current distribution and the windings placement on the field homogeneity is considered. The table, graphs and equations given in the paper facilitate the choice of the most appropriate design for a given problem. The systems presented may find applications in low field electron paramagnetic resonance imaging, some functional f-MRI (nuclear magnetic resonance imaging) and bioelectromagnetic experiments requiring the access to the working space from all directions. 相似文献