原油含水率检测线圈传感器的优化

为了提高电磁电导法管外测量原油含水率线圈传感器的灵敏度,对影响灵敏度的关键参数--线圈传 感器的距离进行了优化设计。在保持最优频率和电流强度不变的情况下,首先,使用ANSYS进行电磁仿真,通过比较发射线圈和屏蔽线圈在管道内部产生的磁场强度大小确定了两线圈之间的最优距离为0.6 m;然后,利用 MATLAB从0. 1 m到1 m对接收线圈上的电压进行了数据计算,结果表明0. 6 m处的电压值最大,最优距离使原油 含水率的有用信号从0.1 m或1 m的0.03 μV提高到了0.6m的1.27 μV,使传感器的灵敏度提高了41倍;最后, 实际测试了两线圈距离从0.1 m至1 m接收线圈上多点电压值,实验结果表明0. 6 m处的电压值最大,进一步证明了 0. 6 m为两个线圈间的最优距离。     

Numerical and experimental studies of refrigerant circuitry of evaporator coils

This study attempts to analyze the performances of evaporator coils with complex refrigerant circuitry using a distributed simulation model, which has three elements: branch, tube and control volume. The governing equations for a control volume are presented in the paper together with the computer simulation procedure for branches, tubes and control volumes of a coil. The model predictions on four test coils are validated with experimental data collected under different airflow conditions using R134a as a refrigerant. Using this model, the heat transfer and fluid flow characteristics of the coils are studied. The study shows that while the thermal resistance of refrigerant side is comparable to that of airside, the coil comprehensive performance can be improved by changing the refrigerant mass velocity along the flow path. Compared with a common coil, using a complex refrigerant circuitry arrangement where the refrigerant circuits are properly branched or joined may reduce the heat transfer area by around 5% in coil design. A guideline is proposed for the refrigerant circuitry arrangements to improve the coil performance.     

Risk assessment for chemical pickling of metals contaminated by radioactive materials

In recent years, many cases of contamination of metal scraps by unwanted radioactive materials have occurred. Moreover, international organisations are evaluating the possibility to re-use or to recycle metals coming from nuclear power plants. The metal recycling industry has started to worry about radiation exposure of workers that could be in contact with contaminated metals during each manufacturing phase. Risks are strongly dependent on the radiation source features. The aim of this study is to perform risk assessment for workers involved in chemical pickling of steel coils. Monte Carlo simulations have been performed, using the MCNP package and considering coils contaminated with (60)Co, (137)Cs, (241)Am and (226)Ra. Under the most conservative conditions (coil contaminated with 1.0 kBq g(-1) of (60)Co), the dose assessment results lower than the European dose limit for the population (1 mSv y(-1)), considering a maximum number of 10 contaminated coils handled per year. The only exception concerns the case of (241)Am, for which internal contamination could be non- negligible and should be verified in the specific cases. In every case, radiation exposure risk for people standing at 50 m from the coil is widely <1 mSv y(-1).     

NMR detection with multiple solenoidal microcoils for continuous-flow capillary electrophoresis

Nuclear magnetic resonance (NMR) spectroscopy represents a promising on-line detector for capillary electrophoresis (CE). The inherent poor sensitivity of NMR mandates the use of NMR probes with the highest mass sensitivity, such as those containing solenoidal microcoils, for CE/NMR hyphenation. However, electrophoretic current degrades the resolution of NMR spectra obtained from solenoidal coils. A new method to avoid microcoil NMR spectral degradation during continuous-flow CE is demonstrated using a unique multiple solenoidal coil NMR probe. The electrophoretic flow from a single separation capillary is split into multiple outlets, each possessing its own NMR detection coil. While the CE electrophoretic flow is directed through one outlet, stopped-flow, high-resolution NMR spectra are obtained from the coil at the other outlet. The electrophoretic flow and NMR measurements are cycled between the outlets to allow a continuous CE separation with "stopped-flow" detection. As a new approach for improving multiple coil probe performance, the magnetic field homogeneity is automatically adjusted (via the shim coils of the magnet) for the active coil. The multiple microcoil CE/NMR coupling has been used to analyze a <3 nmole mixture of amines while obtaining between 1 and 2 Hz line width, demonstrating the ability to avoid electrophoretic current-induced line broadening.     

结肠机器人无线能量传输系统的设计与实现

为使结肠机器人摆脱供电线缆,深入肠道内部,研制了一种无线供能装置．该装置基于电磁耦合原理,可在人体胃肠道区域产生固定频率的均匀交变磁场,并针对结肠机器人在人体内运动的功率要求、姿态与位置的不确定性及尺寸要求等,设计了合适的接收线圈模型．用不同股数的绕线制作了8种相同外形尺寸的接收线圈,比较各线圈的接收效率,最终选用10股绕线制成的线圈．实际搭建了为肠道机器人供能的无线能量传输系统,并验证了其可行性．     

Hydraulic behavior of forced-flow cooled superconducting coils for the large helical device

The large helical device (LHD) has been operated since 1998 and the 13th experimental campaign was conducted in 2009. Before final assembling, cool-down and excitation tests for the Inner Vertical (IV) field coil, which is one of the LHD poloidal field coils, were carried out in 1995. This coil, which consists of a cable-in-conduit conductor, (CICC) is cooled by the forced-flow of supercritical helium. During the tests of the IV coil, hydraulic characteristics, such as flow distribution among cooling channels and friction factors, were measured. In this paper, the consistency of the behavior of the IV coil will be presented and comparison with other fusion devices using superconducting coils will also be made at not only cryogenic temperatures but also at room temperature.     

ORPUS-1 - A pulsed superconducting solenoid

A recent series of reference designs for Tokamak Experimental Power Reactors (EPR's) has indicated that superconducting poloidal field (PF) coils will be necessary for successful operation of these devices. It would also be desirable to use superconducting PF coils in earlier tokamak fusion devices if such coils could be developed quickly enough. In this paper, the PF coil performance requirements are briefly reviewed and some implications for the coil design are developed. A small coil (stored energy 14 kJ) has been built using construction techniques similar to those which could be employed for PF coils. The coil has been charged at rates up to 2 T/sec. Both maximum field and charging rate were limited by available power supplies. Loss measurements were carried out during pulsed operation and data for hysteretic and eddy current loss are presented. The loss measurement system used allows considerable insight into the effects of conductor motion and training.     

Determining Basic Characteristics of Magnetic Induction Measures

Basic characteristics are determined for Helmholtz coils with particular nonoptimal dimensions. It is shown that such a coil can be used as part of a tester for instruments of V&E-METR type.     

Superconducting magnet development for fusion at JAERI

The development of superconducting magnets for fusion at the Japan Atomic Energy Research Institute (JAERI) is described. The objective of the project is the Fusion Experimental Reactor (FER) which will be constructed with superconducting toroidal and poloidal coils. For toroidal coils, JAERI has already developed the 8 T Japanese LCT coil and five other large coils (one NbTi and four Nb₃Sn coils, from 7 T to 11 T) for the Cluster Test Programme. For poloidal coils, JAERI has developed three 30–50 kA pulsed conductors. In addition to coil development, cryogenic technology and structural material development are also in progress.     

Development of design for large scale conductors and coils using MgB2 for superconducting magnetic energy storage device

MgB₂ wires are commercially available, and their superconducting characteristics have been continuously developed in the last decade. The relatively high critical temperature of these wires has attracted the attention of researchers, especially in the field of superconducting magnetic energy storage (SMES) coil applications in terms of its relatively high critical temperature, as it enables the use of liquid hydrogen for cooling the coils. The sensitivity of multi-filament MgB₂ wires to bending strain makes the design of large-scale conductors and coils for an SMES system technologically difficult, and the careful investigation of the applied strains during manufacturing is required. Two-conventional methods have been introduced for the fabrication of the coils: wind-and-react (W&R) and react-and-wind (R&W). These methods have been demonstrated to be suitable for the production of large-scale MgB₂ magnets to maximize the coil performance. The W&R and R&W methods have been successfully applied to the designs of conductors and coils, and small W&R test coil fabrication, as well as stability demonstrations are performed in this study. Our study is the first to demonstrate the feeding of hundreds of amperes of transport current using multifilamentary MgB₂ wires at around liquid hydrogen temperature in the practical background magnetic field of 2 T. The minimum quench energy and normal zone propagation velocity are also experimentally investigated for the protection of the actual coils for SMES application.     

Surface flashover characteristics in liquid nitrogen for application of superconducting pancake coils

For the development of superconducting power apparatus, it is necessary to establish the dielectric technology in coolants like LN₂. Among the dielectric technology, surface flashover characteristics are studied with several simplified spacers at the structural aspects. Double pancake coil can apply to transformer and fault current limiter, etc. To design dielectric system of high temperature superconducting transformer consisting of double pancake coils, this study discusses an effective insulator composition. Circular shape insulator divided into two parts should be inserted between coils and the insulator should cover electric stresses concentrated at the circumference of the coils which are in the same section of double pancake coils facing each other.     

Analysis of a flux-coupling type superconductor fault current limiter with pancake coils

The characteristics of a flux-coupling type superconductor fault current limiter (SFCL) with pancake coils are investigated in this paper. The conventional double-wound non-inductive pancake coil used in AC power systems has an inevitable defect in Voltage Sourced Converter Based High Voltage DC (VSC-HVDC) power systems. Due to its special structure, flashover would occur easily during the fault in high voltage environment. Considering the shortcomings of conventional resistive SFCLs with non-inductive coils, a novel flux-coupling type SFCL with pancake coils is carried out. The module connections of pancake coils are performed. The electromagnetic field and force analysis of the module are contrasted under different parameters. To ensure proper operation of the module, the impedance of the module under representative operating conditions is calculated. Finally, the feasibility of the flux-coupling type SFCL in VSC-HVDC power systems is discussed.     

Magnetic field enhancement of high-Tc superconducting pancake coils by Mu metal sheets

High permeability ring-shaped mu metal sheets have been used to enhance magnetic fields in the bore of Bi-based high-T _c superconducting coils. The central magnetic fieldB ₀, generated by pancake coils placed between mu metal sheets, was measured at liquid nitrogen temperature 77 K. The increasing rate (IR) of the central magnetic fieldB ₀ for single pancake coils was from 15 to 63% by using a 0.1 mm thick mu metal sheet. IR was decreased when the originalB ₀ value increased. The thickness of mu metal sheets also affected IR. It was found that IR increased as the number of mu metal sheets was increased. In a test double-pancake coil IR reached 101%,B ₀ was enhanced from 902 to 1815 G, when the total thickness of mu metal sheets on the top and bottom surface of the coil was 2.0 mm. These results indicate that the well-designed high-permeability materials can significantly enhance the magnetic fields generated by high-T _c superconducting coils and magnets.     

Magnetic field enhancement of high-T c superconducting pancake coils by Mu metal sheets

High permeability ring-shaped mu metal sheets have been used to enhance magnetic fields in the bore of Bi-based high-T _c superconducting coils. The central magnetic fieldB ₀, generated by pancake coils placed between mu metal sheets, was measured at liquid nitrogen temperature 77 K. The increasing rate (IR) of the central magnetic fieldB ₀ for single pancake coils was from 15 to 63% by using a 0.1 mm thick mu metal sheet. IR was decreased when the originalB ₀ value increased. The thickness of mu metal sheets also affected IR. It was found that IR increased as the number of mu metal sheets was increased. In a test double-pancake coil IR reached 101%,B ₀ was enhanced from 902 to 1815 G, when the total thickness of mu metal sheets on the top and bottom surface of the coil was 2.0 mm. These results indicate that the well-designed high-permeability materials can significantly enhance the magnetic fields generated by high-T _c superconducting coils and magnets.     

Theoretical Analysis of AC Resistance in Coil Using Magnetoplated Wire

In this paper, we describe the ac resistance of a coil using a magnetoplated wire (MPW), which is prepared by circumferentially plating a copper wire with magnetic thin film. The $Q$ value of the MPW coil is higher than that of a coil using a copper wire without magnetic thin film plating (COW coil). High- $Q$ coils have lower loss and are required in various industrial fields. To further improve the $Q$-value characteristics of the MPW coil, it is necessary to theoretically analyze its ac resistance. We theoretically analyzed the ac resistance of coils generated by skin and proximity effects. The measured and calculated ac resistances of the MPW coil were in good agreement with a difference of 4%. In addition, the ac resistance generated by the proximity effect was reduced in the MPW coil, and was 50% of that in the COW coil.      

Proposal of rectifier type superconducting fault current limiter with non-inductive reactor (SFCL)

A rectifier type superconducting fault current limiter (SFCL) with non-inductive reactor has been proposed. The concept behind this SFCL is the appearance of high impedance during non-superconducting state of the coil. In a hybrid bridge circuit, two superconducting coils connected in anti-parallel: a trigger coil and a limiting coil. Both the coils are magnetically coupled with each other and have same number of turns. There is almost zero flux inside the core and therefore the total inductance is small during normal operation. At fault time when the trigger coil current reaches to a certain level, the trigger coil changes from superconducting state to normal state. This super-to-normal transition of the trigger coil changes the current ratio of the coils and therefore the flux inside the reactor is no longer zero. So, the equivalent impedance of both the coils increased thus limits the fault current. We have carried out computer simulation using EMTDC and observed the results. A preliminary experiment has already been performed using copper wired reactor with simulated super-to-normal transition resistance and magnetic switches. Both the simulation and preliminary experiment shows good results. The advantage of using hybrid bridge circuit is that the SFCL can also be used as circuit breaker. Two separate bridge circuit can be used for both trigger coil and the limiter coil. In such a case, the trigger coil can be shutdown immediately after the fault to reduce heat and thus reduce the recovery time. Again, at the end of fault when the SFCL needs to re-enter to the grid, turning off the trigger circuit in the two-bridge configuration the inrush current can be reduced. This is because the current only flows through the limiting coil. Another advantage of this type of SFCL is that no voltage sag will appear during load increasing time as long as the load current stays below the trigger current level.     

Inductance Calculations for Noncoaxial Coils Using Bessel Functions

A relatively simple and general method for calculating the mutual inductance and self-inductance of both coaxial and noncoaxial cylindrical coils is given. For combinations of cylindrical coils, thin solenoids, pancake coils, and simple circular loops, the mutual inductance can be reduced to a one-dimensional integral of closed form expressions involving Bessel and related functions. Coaxial and noncoaxial cases differ only by the presence of an extra Bessel factor J ₀(sp) in the noncoaxial integral, where p is the perpendicular distance separating the coil axes and s is the variable of integration. The method is related to a recently given noncoaxial generalization of Ruby's formula for a nuclear radiation source and detector system, the analogy being close but not exact. In many cases, the Bessel function integral for the inductance can be easily evaluated directly using Maple or Mathematica. In other cases, it is better to transform the integral to a more numerically friendly form. A general analytical solution is presented for the inductance of two circular loops which lie in the same plane     

Optimized radiofrequency coils for increased signal-to-noise ratio in magnetic resonance microscopy

The signal-to-noise ratio (SNR) is a major obstacle to achieving increased resolution in magnetic resonance microscopy (MRM). The SNR considerations for MRM are presented, with particular attention to the role of judicious receiver coil design in maximizing sensitivity and limiting noise contributions both from the sample and the coil. We present a number of different coil configurations that have been optimized for particular applications of MRM in the biological sciences. An overview of the literature regarding derivations of the SNR for birdcage-configuration volume coils, inductively coupled surface coils, and surgically implanted coils is presented in a unified fashion. Microscopy coils designed to reduce the total volume of excitation, thus coupling more closely to a given region of interest, are discussed. The volume coil is presented in terms of its application to lung imaging in small animals at 2 T and imaging of stroke at 7 T. The performance of traditional surface coils is demonstrated by application to spinal cord imaging in the rat. Finally, implanted coils are examined, as used in studies of the carotid arteries. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 277–284, 1997     

Quench current improvement through shape modification of racetrack coil

Superconducting racetrack coils have different shapes from those of ordinary solenoid coils which have the same curvature along the windings. So they have different or worse performance from the viewpoint of quench characteristics due to the different structures. Racetrack coils also have round curvatures along their end portions; however, the main difference of their structures from solenoid coils exists in the straight portions. It is considered that the worse performance is due to the straight portions. In the round portions, there exists strong continuous constraint along the windings against the movement toward the perpendicular direction during coil excitation. On the contrary, in the straight portions, there is almost no constraining. As a result, especially in the case of dry magnet, they show even worse characteristics than solenoid counterparts.For the compensation of this worse performance, we proposed one idea to improve quench characteristics of racetrack coils. We manufactured one racetrack coil with an ordinary shape and the other with the proposed idea. By experiments we made sure that the proposed one had a higher quench current. Moreover, after we had made an application of the proposed idea to the four field coils of an actual 30 kVA superconducting generator, we could get very good output voltage and current waveforms.