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1.
In this paper, the frequency-dependent finite-difference time-domain (FDTD) method employing the piecewise linear recursive convolution (PLRC) scheme is applied to the numerical analysis of magnetized plasma with arbitrary magnetic declination. The PLRC-FDTD equations are derived in detail and are checked through practical examples. Excellent agreement between the numerical results and the exact analytical solutions is demonstrated.  相似文献   

2.
An additional coil between the plasma source and the mirror cell prefans incoming plasma to map it directly into the well-known twisted bow-tie shape and thus avoids reshaping drifts generated in conventional min-B mirror machines. This reduces vacuum chamber size requirements and eliminates any drift reshaping delay. Wound in series with the standard quadrupole loffe bar set, this dual-coil system features end connections which contribute no field on axis.  相似文献   

3.
A modified spiral imaging technique is presented, in which the conventional sinusoidal gradient waveforms are replaced by trapezoidal ones. In addition to allowing a reduced data acquisition time, the new waveforms circumvent specific hardware restrictions on the minimum scan repetition time.  相似文献   

4.
Knowledge discovery in databases is concerned with extracting useful information from databases, and the immune algorithm is a biological theory-based and globally searching algorithm. A specific immune algorithm is designed for discovering a few interesting, high-level prediction rules from databases, rather than discovering classification knowledge as usual in the literatures. Simulations show that this novel algorithm is able to improve the stability of the population, increase the holistic performance and make the rules extracted have higher precision.  相似文献   

5.
1 Introduction  Knowledgediscoveryindatabases (KDD)isconcernedwithextractingusefulinformationfromdatabases.Thetermdatamininghashistoricallybeenusedinthedatabasecommunityandinstatistics (ofteninthelatterwithnegativeconnotationstoindicateimproperdataanaly…  相似文献   

6.
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   

7.
Journal of Experimental and Theoretical Physics - In some magnets, despite the presence of a strong exchange interaction between magnetic ions, conventional magnetic ordering does not occur, but a...  相似文献   

8.
9.
一种新型的振荡场光化学传感器   总被引:2,自引:0,他引:2  
利用法布里珀罗振荡模构造了一种新型的光化学传感器。与传统的以表面等离子模和光导模为探针的迅衰场传感器不同 ,这种新型结构中被传感介质处于法布里珀罗腔的振荡场中 ,其能量在全部入射光能中的比重占得很大 ,使得这种传感器具有很高的灵敏度。实验证实这类传感器对葡萄糖溶液浓度和折射率的测量精度皆可达 10 - 5数量级以上  相似文献   

10.
一种新型的基于磁性液体的光纤Sagnac磁场传感器   总被引:2,自引:0,他引:2  
提出一种使用磁性液体的新型光纤Sagnac磁场传感器.磁性液体具有磁致可变双折射效应和二向色性,在外加磁场作用下,液体中的磁性纳米粒子沿磁场方向结链规则排列,形成各向异性.将其制成液体薄膜,放入具有一段保偏光纤的Sagnac环中,使光纤Saganc干涉仪的正弦形状干涉光谱可随外磁场变化.光纤中传输光垂直经过磁性液体薄膜...  相似文献   

11.
A hybrid metasurface realized by a double array of brass wires inserted into two high-permittivity dielectric slabs at both sides was used to perform a magnetic resonance spectroscopy experiment at a 1.5 T clinical magnetic resonance scanner. The metasurface coupled inductively to a transceive birdcage body coil located within the scanner’s bore. The metasurface demonstrated an enhancement of the signal-to-noise ratio of the magnetic resonance spectroscopy experiment in vitro. Up to a signal-to-noise ratio gain of 7.4 for choline and creatine spectral lines was observed in the presence of the metasurface compared to the body coil alone.  相似文献   

12.
Tumor segmentation from magnetic resonance imaging (MRI) is important for volume estimation and visualization of nasopharyngeal carcinoma (NPC). In some cases, segmentation using the general multispectral (GM) method often obtained poor results due to the high false positives caused by complex anatomic structures and serious overlap in feature space. In this study, a texture combined multispectral fuzzy clustering (TCMFC) segmentation algorithm was proposed. A texture measure of T1-weighted (T1) MR image was introduced by calculating the two-order central statistical information of every pixel within a window after the window convolution operation. The texture measure and the intensities in T1 and contrast-enhanced T1 images formed the new 3-D feature vector for fuzzy clustering implemented by semi-supervised fuzzy c-means (SFCM). Testing showed that by reducing the false positives significantly, the TCMFC method achieved improved segmentation results, compared with the GM method.  相似文献   

13.

In this article, a novel semi-analytical algorithm for calculating backward-pumped Raman amplifier is proposed. The algorithm does not need iteration and can greatly save computational time. Simulation results for Raman amplifiers with 25 km, 50 km, and 100 km fibers show that the accuracy of the method is quite satisfying in comparison with the shooting algorithm and the deviation is within 0.02 dB.  相似文献   

14.
单幅图像的去雾新算法   总被引:2,自引:1,他引:2  
提出了一种基于单幅图像的去雾新算法.首先把图像归一化后从RGB彩色空间转换到HSI彩色空间,对色调分量运用四叉树分割法进行分割图像;分割后图像的每一局部小方块可以认为具有相同的场景深度,从而可以对每一局部小方块估计出空气光.然后再对亮度分量运用雾天图像光学模型,从雾的物理特性上去除雾对图像的影响.最后再对图像的饱和度分量进行校正,得到复原后的图像.该算法的主要优点是速度快,且不仅可以应用于彩色图像,也可以适用于灰度图像.通过该算法与其它几种算法的实验结果进行分析和比较,表明该算法能有效恢复出清晰图像.  相似文献   

15.
In this article, a novel semi-analytical algorithm for calculating backward-pumped Raman amplifier is proposed. The algorithm does not need iteration and can greatly save computational time. Simulation results for Raman amplifiers with 25 km, 50 km, and 100 km fibers show that the accuracy of the method is quite satisfying in comparison with the shooting algorithm and the deviation is within 0.02 dB.  相似文献   

16.
Combination of two-dimensional nuclear magnetic resonance (2-D NMR) correlation maps and a simple three-component model are proposed here to identify the structural composition of porous media. Homogeneous magnetic field and field with constant gradient of a novel Halbach sensor are employed for respective relaxation and diffusion measurements. NMR results are compared and confirmed with independent measurements on a scanning electron microscope and by energy dispersive spectrometer methods.  相似文献   

17.
Using the nonequilibrium Green's function technique, we investigate the Kondo effect in the quantum dot with perpendicular magnetic fields, in which one is the Zeeman splitting lies in the z-direction and the other is the spin flip points at the x-direction. It is found whatever one or two magnetic fields are applied, the local density of states (LDOS) will split into two peaks. The positions of two Kondo resonance peaks are determined by Zeeman energy △ when J = 0, and by √△^2+J^2 when J≠0.  相似文献   

18.
祁翔 《物理通报》2007,(10):23-25
在《物理学教程》中有这样一道习题:半径为R的木球上均匀绕有密集的细导线,线圈平面彼此平行,且以单层线圈覆盖住半个球面,设线圈的总匝数为N.通过线圈的电流为I.求球心O处的磁感强度.  相似文献   

19.
The understanding of the physical processes that occur below the threshold of protein thermal denaturation is of fundamental importance. In this thermal region proteins undergo a reversible folding/unfolding process whose evolution depends upon temperature and time. When the kinetics of the folding is altered, the specific biological activity of the protein is altered as well and aggregation phenomena usually intervene. The most important role in driving these processes is played by the solvent and water is certainly the solvent par excellence. It is well known that proteins become biologically active with no less than a water monolayer covering their surface. The knowledge of the physical properties of this monolayer is of basic importance to prevent folding alterations. We present a proton Nuclear Magnetic Resonance study at very high resolution of the thermodynamic properties of lysozyme hydration water as a function of temperature and time in the thermal region of the reversible denaturation.  相似文献   

20.
We describe a mid-infrared Laser Magnetic Resonance (LMR) spectrometer which is based on a cryomagnet and a sealed-off CO-laser. Faraday rotation combined with a multireflection cell is used for polarization sensitive detection of molecular radical ions. Experimental details and first spectroscopic examples are given.  相似文献   

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