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This model differs from previous works in that the electrical conductivity (and the current profile) is approximated in a more realistic way (parabolic instead of flat profile). The magnetohydrodynamic equations in an electrostatic approximation serve as the starting point of the theory. The effects of the external axial magnetic field, current profile, arc current and arc column radius on the helical instabilities of arcs were numerically studied. Numerical results show that the short wavelength perturbation can be stabilized by positive direction magnetic field, whereas the long wavelength perturbation can be stabilized by reverse magnetic field when the current profile is the uniform distribution. In the short wavelength perturbation case, the effect of positive direction magnetic field on the arc stability is very small when the current profile has a parabolic distribution. However, its stabilizing effect is enhanced for the long wavelength perturbation. The intermediate and long wavelength perturbation can also be stabilized by reverse magnetic field. The low current is beneficial for stabilizing arcs.  相似文献
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The bending deformation of an elastic beam with eccentrically embedded shape memory alloy (SMA) wires under the activation of electrical current has been investigated. A procedure, which accounts for the effect of transient heat transfer and gives rise to the beam bending responding to prescribed input electrical current profile is used for analysis. It is found that influences of ambient temperature, electric current intensity and prestrain of SMA on the bending deformation of beam are significant.  相似文献
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周亦军  彭东立 《声学技术》2012,31(2):179-183
宽带声学多普勒流速剖面仪(Broadband Acoustic Doppler Current Profile,BBADCP)通过接收海洋体积混响信号进行频偏估计,体积散射模型的准确性决定了理论仿真的正确性。针对BBADCP的信号模型特点,建立了散射体单元散射叠加效应的海洋体积回波时空特性及散射模型,推导了叠加噪声后散射回波的具体表达式。通过散射回波的离散化,把各参数(幅度、频率、调制)分离开来,单独考虑各参数对测速精度的影响。利用复协方差算法对水流流速进行估计,分析了信噪比、水流流速、紊流效应等因素对BBADCP流速估计的影响,验证了体积散射模型的正确性。  相似文献
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The ANTARES Neutrino Telescope was completed in May 2008 and is the first operational Neutrino Telescope in the Mediterranean Sea. The main purpose of the detector is to perform neutrino astronomy and the apparatus also offers facilities for marine and Earth sciences. This paper describes the design, the construction and the installation of the telescope in the deep sea, offshore from Toulon in France. An illustration of the detector performance is given.  相似文献
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黄雄飞  苑秉成  陈喜 《声学技术》2008,27(3):323-327
宽带声学多普勒海流剖面仪采用重复相位编码信号和复协方差方法进行频移量的估计.具有较高的测速精度,但是在测速上具有速度模糊,在不改变原有的系统结构的基础上对宽带多普勒海流剖面仪的信号处理方法进行改进,提出采用回波自相关的第一个旁瓣的位置解决测速模糊的方法,并推导了计算公式。最后进行了数字计算和仿真。结果证明了这种方法的正确性和可行性。  相似文献
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讨论了利用声相关流速剖面仪进行深水散射层观测的可行性。结合声相关流速剖面仪垂直发射编码调制信号、多阵元接收的特点以及测量流剖面三维速度的优势,提出利用回波强度和垂向速度两种方法对深水散射层进行观测。在23kHz声相关流速剖面仪工程样机海试数据的基础上,利用这两种观测方法对DSL进行了观测。观测结果表明:利用声相关流速剖面仪可以直观地观测深水散射层的分布及运动规律,这两种观测方法是实际可行的。  相似文献
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宽带声学多普勒流速剖面仪通过处理水下体积回波信号进行流速估计,回波模型的准确度决定了理论仿真的正确性.针对回波的散射特性,通过分析水层回波信号的时空关系,提出一种球面散射水层回波模型,并利用坐标旋转方法推导出该水层回波解析式.相比其他方法,该模型解析式充分体现了散射体模型形状对回波的作用,更加接近实际情况.对该模型下回波信号进行频谱和自相关特性分析,采用复相关算法估算流速.通过与实测数据进行对比,结果证明了该回波信号模型与解析式的正确性.  相似文献
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