A Validated Model for the Zero Drift Due to Transformer Signals in Electromagnetic Flowmeters Operating With Electrolytic Conductors

In this paper, the author investigates theoretically the magnitudes of the zero offsets and the zero drifts originating from magnetic-flux linkage between the coils of the electromagnet and the loop formed by the electrode cables in an electromagnetic flowmeter for electrolytic conductors. The dependence of such zero offsets on the liquid properties, frequency of operation, etc., is explained. This dependence is used to predict the zero offsets expected in metering this liquid using phase-sensitive detection with the flowmeter tube described in this paper. Precautions needed in flowmeter design to minimize instrument offsets and zero drifts are explained. In the end, the proposed model was validated against the experimental data     

Rationality Analysis and Direct Parametrization of Generalized Offsets to Quadrics

In this paper, working over algebraically closed fields of characteristic zero, we present formal proofs for a complete analysis of the rationality of generalized offsets to all irreducible quadrics, and we show how to derive rational parametrizations of the offsets, when they are rational, from the parametrization of the original quadric. This is achieved by means of a surface, constructed without implicitizating, that is either linear in one variable or tubular. More precisely, we prove that generalized offsets to elliptic and hyperbolic paraboloids are rational, generalized offsets to parabolic cylinders are rational, and generalized offsets to hyperbolic cylinders are irreducible and not rational. Also we prove that generalized offsets to elliptic cylinders of revolution have two rational components, and that generalized offsets to non-revolution elliptic cylinders are irreducible and not rational. Furthermore, we state that generalized offsets to cones of revolution have two rational components and to non-revolution cones are irreducible and not rational. In addition, an offset to the sphere has two rational components and to an ellipsoid is rational. Finally, we prove that generalized offsets to one and two-sheeted hyperboloids are rational. Received: December 3, 1998; revised version: September 23, 1999     

Crystal chemistry of the NaZr2(PO4)3, NZP or CTP,structure family

The NaZr₂(PO₄)₃ type structure (abbreviated as NZP or CTP, CaTi₄(PO₄)₆), has emerged as a new family, which has extraordinary technological utility in three fields: fast-ion conductors, radwaste solidification and zero expansion ceramics. NZP or CTP is formed by an extraordinary range of discrete compositions and crystalline solutions. In this paper these compositions are classified according to their crystal chemical substitution scheme, and some uncommon trends in the systematic variation of their lattice parameters are shown. Some of the major trends are explained by correlation with the rotation of polyhedra in the structure.     

A method of calibrating magnetometers on a spinning spacecraft

This paper describes a procedure for quantifying and compensating for angular offsets and slow-varying drifts associated with a flux-gate magnetometer onboard a spinning spacecraft. Such magnetometers have been down on numerous spacecraft such as IMP-8, DE-1, and ISTP/GEOTAIL, and similar instruments are currently proposed to fly on the ISTP/WIND spacecraft. Consequently, slight geometric misalignment of the sensor from their chosen axes will create errors in the measured signal. These misalignments can be quantified using perturbation theory and compensated in the data analysis process. The technique is applicable to magnetometers on spinning spacecraft. Also, over long time periods, the magnetometer will develop slight drifts in the electronic components, and these too can be quantified in the data analysis process. A technique is discussed that quantifies and compensates for such perturbations from the measurements. The technique has been successfully applied for the last sixteen years to IMP-8 magnetometer data and more currently to the GEOTAIL magnetometer data, and can be applied in a general way to measurements from any magnetometer onboard a spinning spacecraft. Further improvements in the technique are also discussed     

Design of electrode array of inductance flowmeter

Multielectrode inductance flowmeters were brought forward toward coping with the problem of flow regime dependence of traditional inductance flowmeters. Design of the electrode array is of great importance in construction of a multielectrode inductance flowmeter. The number of electrodes and electrode size are two primary parameters of the array. In this paper, the governing equation of the multielectrode inductance flowmeter was solved using a finite difference method. The chord measurement method was employed to analyze the influences of both parameters on the estimation of mean flow velocity. Based on the quantitative calculation of the influences of the two parameters on measurement error, criteria for the design of the electrode array were presented.     

Superconductivity, Spin Density Wave and Field Induced Spin Density Wave versus anion ordering in the (TMTSF)2ClO4 salt

An effect of electron correlation is studied in an angular dependence of magnetoconductivity of quasi one-dimensional organic conductors. We investigate the effect of both quasi-particle’s lifetime and velocity due to the electron correlation near SDW in the magnetoconductivity. We found that the momentum dependence of lifetime strongly suppresses the one-dimensional axis magnetoconductivity at a magic angle θ=45°. On the other hand, the change of the momentum dependence of the velocity originating from the electron correlation enhances the interchain magnetoconductivity at θ=0°. These effects are explained from the momentum dependence of lifetime and velocity over the electron’s commensurate orbital on Fermi surface at the magic angles.     

The derivation and validation of the practical operating equation for electromagnetic flowmeters: case of having an electrolytic conductor flowing through

In this paper, the practical operating equation for the electromagnetic flowmeter is derived for the case of having a circular pipe with an electrolytic conductor flowing through. It is assumed further that the magnetic field is uniform and the velocity profile is axisymmetric (assuming nonconducting walls). The derivation was done before by many authors to whom the author refer to in this paper, but the approach provided here is comprehensive and simple. To add to that, the solution for the electromagnetic flowmeter's operating equation illustrated in this paper is new and is provided using very simple mathematical concepts, eliminating the complexity of solutions provided by other authors in the past. In the end, the practical operating equation derived was validated using a new approach based on the finite element analysis and the moving stream method to estimate the error resulting from using this operating equation with the assumptions of having a uniform magnetic field and an axisymmetric velocity profile, which are difficult to achieve in practice. This error can be used in a dry calibration to estimate the error caused by variable flow characteristics.     

Influence of Wettability of the Channel Surface on the Readings of an Electromagnetic Flowmeter

The dependence of the readings of an electromagnetic flowmeter on the restructuring of the flow velocity profile in the flowmeter channel is discussed. The temporary instability of the flow profile caused by incomplete wetting of the Teflon surface of the channel by the liquid being measured is shown to be one cause of the changes in the flowmeter signal.     

基于高低压电源切换的双环恒流控制电磁流量计励磁控制系统

为了提高电磁流量计高频方波励磁性能,基于励磁恒流控制仿真分析,采用外环高低压电源切换和内环电流微调的双环励磁恒流控制方式,以保证电磁流量计高频方波励磁时一次仪表输出信号零点稳定、电源利用效率高。设计方波励磁控制系统,以实现高频方波精确励磁。仿真结果表明,高压源电压越高越有利于拓宽励磁频率范围。实验结果表明,系统在高频方波励磁时,励磁电流响应速度快且电磁流量计传感器输出信号零点稳定。     

Inductance calculation of twisted conductors by the broken line approximation

The mutual inductance between two skew straight thin conductors is obtained as a function of two vectors corresponding to two current carrying line segments. Based on the obtained analytical expressions for the mutual inductance, the versatile calculation method for the self- and mutual inductances of various twisted conductors is studied by means of the broken line or polygonal curve approximation. In particular, it is confirmed that this numerical calculation is consistent with the analytical calculation of the self- and mutual inductances for coaxial helical conductors for the asymptotic form of the long axial length. Furthermore, for the inductances of general twisted conductors, the similar asymptotic forms of the length dependence are obtained.     

Nanometer-level path-length control scheme for nulling interferometry

A method of stabilizing a dual-output rotational shearing inteferometer to the nanometer-level accuracy required for deep starlight nulling in planet searches is presented. In this approach one of the nulling beam combiner s two balanced outputs is used to control the other through a combination of external and internal path-length offsets. The path-length offsets sum to zero for the nulling output and to lambda/4 for the control, or the quadrature, output. In the quadrature output a 1-nm path-length error corresponds to a 1% output-power variation, thus allowing subnanometer control.     

结冰分裂导线舞动振幅分析

针对结冰分裂导线舞动问题,从功能的角度提出了一种舞动振幅的分析方法。导出了舞动振幅经历一个周期增量的表达式。所导出的舞动振幅增量的表达式说明了作用在结冰分裂导线上的气动力的各项在舞动振幅不同阶段的作用。得到的结论是:当舞动的振幅较小时,气动力中常数项与线性项的功是气动力总功中的主要部分;当舞动的振幅为中等时,气动力中常数项与线性项的功与非线性项的功在气动力总功中的比例相近;当舞动的振幅为较大时,气动力中非线性项的功在气动力总功中的比例大于常数项与线性项的功在气动力总功中的比例。     

A coupled finite-element, boundary-integral method for simulating ultrasonic flowmeters

Today's most popular technology of ultrasonic flow measurement is based on the transit-time principle. In this paper, a numerical simulation technique applicable to the analysis of transit-time flowmeters is presented. A flowmeter represents a large simulation problem that also requires computation of acoustic fields in moving media. For this purpose, a novel boundary integral method, the Helmholtz integral-ray tracing method (HIRM), is derived and validated. HIRM is applicable to acoustic radiation problems in arbitrary mean flows at low Mach numbers and significantly reduces the memory demands in comparison with the finite-element method (FEM). It relies on an approximate free-space Green's function which makes use of the ray tracing technique. For simulation of practical acoustic devices, a hybrid simulation scheme consisting of FEM and HIRM is proposed. The coupling of FEM and HIRM is facilitated by means of absorbing boundaries in combination with a new, reflection-free, acoustic-source formulation. Using the coupled FEM-HIRM scheme, a full three-dimensional (3-D) simulation of a complete transit-time flowmeter is performed for the first time. The obtained simulation results are in good agreement with measurements both at zero flow and under flow conditions.     

An Electronic System for the Tuning of Masers

The automatic tuning of frequency standards gives a method of removing drifts due to cavity pulling. The paper describes an apparatus designed primarily for tuning the hydrogen maser. The apparatus can also be used for tuning other masers such as the rubidium maser. The system incorporates several of the best features of similar devices previously described in the literature. It includes a digital averager which makes possible the use of a reference oscillator less stable than the maser to be tuned. It includes also a digital integrator, solving the usual problem of offsets in standard integrators. Frequency corrections are made either proportionally or by unit steps through a varactor coupled to the maser cavity. The electronics are made almost entirely with TTL digital integrated circuits (type 7400) for low cost, reliability, and availability. Results on the tuning of rubidium and hydrogen masers are given.     

Nonphysical Reverse Currents in Transient Finite-Element Magnetics Simulation

We are concerned with the simulation of low-frequency transient magnetic fields and currents in conductors as modeled by the vector diffusion equation. In particular, the key topic of this paper is the diffusion of fields and currents into a conductor due to a rapidly varying magnetic field in the surrounding air. As an example, an explosive magnetic flux compression generator may be designed to produce an exponentially increasing magnetic field in the in the air gap between armature and stator. As a second example, in a standard railgun the motion of the armature causes a rapidly increasing magnetic field in the air ahead of the armature, inducing currents in the rails ahead of the armature. It has been observed that for these types of transient magnetics problems finite-element simulations can produce nonphysical “reverse currents” in conductors, currents that are flowing in the wrong direction. In this paper the root cause of these nonphysical reverse currents is explained, and several mitigation strategies are discussed.      

导线覆冰脱落的数值模拟和参数分析

导线覆冰脱落产生的纵向不平衡张力会严重威胁到输电线路的安全。在塔线体系模型基础上利用冰单元的生死模拟导线覆脱冰,通过与以往的模型试验比较验证该模拟方法的适用性,进行建模参数的敏感性分析以确定合适的计算模型,最后进行导线脱冰的参数分析。计算结果表明,脱冰前输电塔的基底剪力和基底弯矩为零,脱冰后两者大幅增加,且越靠近脱冰档数据越大。当档距越大、覆冰越多、脱冰位置越靠中间和脱冰比例越大时,脱冰响应越显著;当导线的初始张力越大时,脱冰响应越小。     

特大口径电磁流量计的检定

特大口径电磁流量计是一种新型的大口径计量仪表。然而它的实施检定是制约其自身发展的关键因素。本讨论了用标准表法检定特大口径流量计的原理,分析了标准流量计的误差修正,以期找到一种用标准表法检定特大口径电磁流量计的理想方法。     

Numerical Modelling of AC Loss in Coated Conductors by Finite Element Software Using <Emphasis Type="Italic">H</Emphasis> Formulation

This paper proposes a practical and memory efficient method to model YBCO coated conductors by commercial finite element software. This method uses the H formulation to directly solve a magnetic field in a two-dimensional space. This model has been successfully used for bulk materials and thick wires, and is extended in this article to solve geometries with high aspect ratios such as coated conductors. The effect of mesh quality and order of element on the performance and accuracy of the model is discussed. A model using 2nd order single layer elements is chosen as the optimal setting for solving AC loss in coated conductors. Based on this setting, a series of simulations with the thickness of the tape varying from 1 μm (the actual thickness) to 120 μm have been performed to investigate the effect of artificially expanding tape thickness. The results obtained from our FEM model are compared with the classical analytical solutions. The discrepancies between the two are discussed and explained. The model proposed in this paper is able to give an accurate solution of AC loss for simple geometry (such as a single tape with expanded thickness) within just a few minutes. Even in the case of dealing with complex problems (such as a tape in its actual dimension or a stack of tapes under complicated magnetic conditions), the model would only require a few hours to solve the problems with excellent convergence properties.     

光纤流量计初探

基于光纤的性能优势和光纤传感器的发展前景，文章利用光的强度受流量调制的特性，在传统涡街流量传感器基础上，设计了一种光纤流量计。文章阐述了光纤微弯损耗机理和光纤涡街流量传感器的工作原理，在此基础上提出了光纤涡街流量计系统设计模型，并进行了光纤涡街流量计的稳定性分析。     

Calculation of propagation velocity of normal and superconducting regions in composite conductors

This paper describes the calculation of the velocity of propagation of normal (or superconducting) regions along compoiste conductors taking into account current sharing between superconductor and normal substrate. Different peculiarities in the dependence of velocity on the current are discussed and the results are compared with some experimental data.