An improved method to calculate the radio interference of a transmission line based on the flux-corrected transport and upstream finite element method

The radio interference (RI) from HVDC transmission lines can block communication systems. In this paper the RI of a HVDC transmission line has been analyzed by the superposition of the electromagnetic field generated by the corona current based on phase-model transformation, where the corona current can be solved by the flux-corrected transport and finite difference method combining the upstream finite element method for bipolar conductor model instead of corona cage or excitation function. Our calculated values for 0.5 MHz RI from the proposed method compare well with measured values from a 800 kV HVDC test line established in China. With this validation, we find that RI should increase with temperature, increase with altitude, and vary in a complex way with relative humidity. Therefore, the proposed method can be adopted in transmission lines design and electromagnetic environment evaluation.     

Restricted spectral accuracy analysis to identify the single correct organic compound elemental‐composition from Orbitrap accurate mass data lists obtained at very high resolution

Restricted spectral accuracy is applied to Orbitrap data (240 000 resolution at m/z 400) to more clearly break out the scoring and ranking of allowable elemental compositions (ECs) in a candidate list. The correct EC is usually top ranked and separated from other answers by 10 to 40% within the dimensionless 0 to 100% scale, providing a single, definitive EC. The A + 2 position (where A denotes the monoisotopic line position) is especially advantageous in restricted spectral accuracy. It has enough intensity and more complexity than (A + 1) fine lines and is like a fingerprint. Avoidance of coalescence phenomena and careful ion population control are essential.     

A numerical method for the determination of slip characteristics between the layers of a two-layer slurry flow

The observed phenomenon of slip between the layers of a flowing slurry is modelled mathematically by a finite-element-based numerical technique. This technique enables us to quantify variables such as the slip velocity and shear stress distribution at the interlayer boundary and the pressure drop within the flow domain.     

Generalized expressions of Green''s function for multiconductor strip lines

In this paper the generalized expressions of the Green's function for multicoductor strip lines are derived from a model of narrow charge source by means of the Fourier transformation. Because of using a charge source with finite width, these expressions, occuring as improper integrals of the second type, are convergent at all the points to be considered, which are, hence, most suitable for numerical calculation in the method of moments. In addition, these expressions may be extended to more complicated structures of strip lines without difficulty.     

涂无机富锌漆高强螺栓连接的滑移和松驰

为提高高强螺栓的防锈性能,往往采用在摩擦面上涂无机富锌漆的表面处理方法。本文以漆膜厚度和时间变化为参数,对高强螺栓的抗滑移系数及其预拉力的松驰现象进行了实验研究,并对摩擦型高强螺栓的承载力做出评价。     

热处理YT14硬质合金微观结构与性能的关系

用XRD分析了YT14硬质合金在常规烧结态和不同淬火温度的热处理态下粘结相的相组成以及WC相和(Ti,W)C固溶体相的微观应力,用EDX技术测定了Co粘结相成份,用TEM大量观察了合金的显微结构。结果表明,淬火处理使W、Ti原于在粘结相中的平均浓度增加,从而改善了粘结相的相组成;部分结晶较完整又有较大尺寸的WC晶粒边缘出现滑移台阶,降低了WC晶粒间的邻接度,减少了粘结相的平均自由程;回火处理降低了WC相和(Ti,W)C相的微观应力,使合金的性能进一步提高。     

任意凸曲面上匀称刚体的滚动转折与滑落

研究任意凸曲面上匀称刚体的滚动规律。给出刚体从纯滚动到滑滚动的转折点和刚体离开曲面时滑落点以及对应的质心速度的一般计算公式,并举几例作了计算和讨论。     

Suspended stripline on magnetized ferrite and anisotropic dielectric substrates

Suspended stripline on magnetized ferrite and anisotropic dielectric substrates are examined here. The spectral domain immittance approach was used for obtaining the dyadic Green's functions in the Fourier transform domain. Galerkin's method was used to obtain the dispersion characteristics of the dominant mode, and the curves for a few cases are shown as examples which could be used in designing isolators, phase shifters, and directional couplers.     

Linear stability diagrams for the shear flow of an Oldroyd-B fluid with slip along the fixed wall

We consider the time-dependent shear flow of an Oldroyd-B fluid with slip along the fixed wall. Slip is allowed by means of a generic slip equation predicting that the shear stress is a non-monotonic function of the velocity at the wall. The complete one-dimensional stability analysis to one-dimensional disturbances is carried out and the corresponding neutral stability diagrams are constructed. Asymptotic results for large values of the elasticity number and finite element calculations are also presented. The instability regimes are within or coincide with the negative-slope regime of the slip equation. The numerical calculations agree with the linear stability results when the size of the initial perturbation is small. Large perturbations may destabilize a linearly stable steady state, leading to a periodic solution. The period and the amplitude of the periodic solutions increase with elasticity. Received: 19 June 1997 Accepted: 22 September 1997     

Self-Excited Wind-Induced Vibrations and Limit Cycles in Bundled Conductors

Abstract. Wake-induced oscillations on bundled conductors of overhead transmission lines are investigated. These oscillations are due to the leeward conductor lying in the wake of the windward one. We consider a twin horizontal bundle of overhead lines. First of all, the critical wind velocity (bifurcation point) of incipient flutter is identified [3, 4]. A nonlinear analysis is adopted to investigate the post-bifurcational behaviour of the oscillations. Using, if necessary a reduction to the center manifold, and an additional normal form transformation we obtain amplitude equations which can be analyzed qualitatively with regard to the unfolding parameters.Sommario: Vengono studiate le oscillazioni indotte dal distacco di scia in fasci di conduttori di linee di trasmissione sospese. Queste oscillazioni sono presenti nel conduttore sottovento che giace nella scia del conduttore sopravvento. In particolare viene considerato il caso di una coppia di conduttori disposti orizzontalmente. Prima di tutto, viene identificata la velocità critica del vento (punto di biforcazione) dovuta al flutter incipiente [3, 4]. Viene utilizzata un'analisi non lineare al fine di valutare il comportamento post-biforcativo delle oscillazioni. Usando, se necessario, una riduzione alla varietà centrale e un'addizionale applicazione del metodo della forma normale, si ottengono equazioni nelle ampiezze che possono essere analizzate in modo qualitativo con riferimento ai parametri essenziali.