Design and optimization of coil structure based on the uniformity of core temperature field

Coil structure size parameters during electromagnetic induction heating affect the temperature field and heating rate of a carbon fiber-reinforced polymer (CFRP) shell. In this study, a finite element analysis model is established on the basis of a single-screw coil structure, and the influence of coil diameter, length, turns, and position relationship on the temperature field distribution and heating rate of the CFRP shell is studied. According to image entropy theory, the influence of coil structure size parameters on the uniformity of a temperature field distribution is analyzed. Furthermore, the accuracy of the coil structure size parameters with respect to temperature field variation is verified with a CFRP induction heating experiment. This study provides theoretical support and a verification method for the selection, design, and optimization of the coil structure size parameters of CFRP shells during induction heating.

     

Analysis of the practical force accuracy of electromagnet-based nanoindenters

Two important factors that influence the force accuracy of the electromagnet-based nanoindenters but have not yet attracted much attention are analyzed, and a more reasonable way to estimate the force accuracy is presented in this paper. MTS Nano Indenter®, with the characteristics of a coil suspended in a uniform magnetic field by two sets of springs acting as an actuator and force measuring unit, is used as an example. One of the two factors is the uniformity of the magnetic field. The other is the stiffness of the supporting spring. Consequently, the practical force accuracy varies considerably from test to test because it firmly depends on the working position of the coil and the displacement stroke. A reasonable estimated accuracy value is of the order of 10⁰ μN for typical indentation tests with a 10² nm indentation depth or a 10⁰ mN test force.     

低场核磁共振螺线管线圈的设计

在常规低场核磁共振(NMR)实验中,NMR响应的空间均匀度与螺线管收发线圈的尺寸、样品的大小以及采用的脉冲序列类型有关,根据这些条件可以确定具有给定射频(RF)场均匀度的线圈最小尺寸.考虑到螺线管匝数、线径等因素对信噪比的影响,对线圈的各项参数进行了优化,设计了具有最佳信噪比性能的螺线管线圈.     

Optimization of dimensions of a device for circular magnetization of cylindrical components. III. Investigation of circular field component generated by a one-layer toroidal coil

The effect of dimensions of a toroidal coil and the number of turns in the coil on the circular magnetic field component within the region limited by the inside axial sections of the turns has been studied. The configuration of this field has been determined. Optimal dimensions of the coil have been calculated. In order to obtain a higher amplitude of the circular field, one should use coils with smaller numbers of turns. In the inner region of a one-layer toroidal coil close to the turns, the peaks of the circular field diminish with the number of turns, but the number of points where the field intensity is maximal becomes larger, i.e., the field becomes more uniform. Methods of further increase in the circular component of the magnetic field have been suggested.     

Design and testing of a 1.5 Tesla double-tuned (H/P) RF surface coil with intrinsic geometric isolation

We analyse the isolation characteristics of axial and transverse field surface radio frequency coils, used to design a double-tuned surface coil composed by two coils, that combine proton (¹H) detection and localized spectra of phosphorous (³¹P). Several geometrical configurations were analysed, including circular loop and figure-of-eight coils, with the aim to optimize the isolation between the two channels. Our analysis shows that by using at least one transverse coil for the design of the double-tuned probe, it is possible to achieve a good intrinsic geometrical decoupling, without the need of additional decoupling circuits. On the basis of the experimental results, we have designed and built a 1.5 T double-tuned probe composed by a circular loop coil and a transverse field coil, with the external coil tuned at the ¹H frequency and the internal coil tuned at the ³¹P frequency, that shows a good intrinsic decoupling and signal-to-noise ratio.     

A theoretical and experimental study on transverse field radio frequency surface coils

We have analysed, theoretically and experimentally, transverse field RF surface coils comprising two parallel linear current elements (figure-of-eight, FO8). A quasi-static numerical integration of the Biot–Savart law was used to simulate the B₁ field distribution of FO8 coils comprising a range of coil diameters and linear element separations. RF coil prototypes, suitable for ¹H and ³¹P magnetic resonance imaging/spectroscopy at 1.5 T, that closely match the simulated models, were built and tested using workbench and MRI methods. A comparison with standard loop RF coils was made. Testing with phantoms showed a good agreement between the theoretical and experimental RF field distributions. Our findings should be useful to optimize the sensitivity and spatial selectivity of FO8 coils by a careful choice of the geometrical parameters. A number of applications where the use of FO8 RF coils could be of benefit are discussed, these include in vivo nuclear magnetic resonance imaging/spectroscopy.     

超磁致伸缩换能器驱动磁场均匀性的研究

给出超磁致伸缩换能器驱动磁场均匀性概念后,论述了超磁致伸缩换能器驱动磁场宜用电磁感应强度表示。建立了ANSYS2D有限元模型,分析了超磁致伸缩棒、线圈长度、磁路闭合与否、补偿线圈等对磁场均匀性的影响,得出了明确的结论。该分析结果已经用于指导超磁致伸缩换能器的设计,取得良好的效果。     

Linear free vibration analysis of cross-ply laminated cylindrical helical springs

A linear free vibration analysis of symmetric cross-ply laminated cylindrical helical springs is performed based on the first-order shear deformation theory. Considering the rotary inertia, the shear and axial deformation effects, governing equations of symmetric laminated helical springs made of a linear, homogeneous, and orthotropic material are presented in a straightforward manner based on the classical beam theory. The free vibration equations consisting of 12 scalar ordinary differential equations are solved by the transfer matrix method. The overall transfer matrix of the helix is computed up to any desired accuracy. The soundness of the present results are verified with the reported values which were obtained theoretically and experimentally. After presenting the non-dimensional graphical forms of the free vibrational characteristics of (0°/90°/90°/0°) laminated helical spring made of graphite-epoxy material (AS4/3501-6) with fixed–fixed ends, a non-dimensional parametric study is worked out to examine the effects of the number of active turns, the shear modulus in the 1–2 plane (G₁₂), the ratio of the cylinder diameter to the thickness (D/d), and Young's moduli ratio in 1 and 2 directions (E₁/E₂) on the first six natural frequencies of a uniaxial composite helical spring with clamped-free, clamped-simple, and clamped–clamped ends.     

Optimization of dimensions of a device for circular magnetization of cylindrical components. IV. Investigation of circular magnetizing field generated by a multilayered toroidal coil

The effect of dimensions of a toroidal coil, the number of turns and layers in its winding on the circular field component generated in its inside volume defined by the inside axial sections of the turns has been investigated. The configuration of the field in this region has been calculated, and the principles of the design of magnetizing coils have been formulated. In order to obtain a higher circular field intensity in the region close to the turns, it is advisable to use multilayered windings. A fairly uniform circular field is generated in a local region if the winding is divided into equal sectors containing zones with turns of wire and gaps between them. In order to obtain a circular field component of a relatively high intensity and a constant sign over a wide sector of the inside volume, one should build a coil of several sections uniformly distributed over the frame perimeter.     

Application of response surface methodology in the optimization of laser treatment in buckypaper lighting for field emission displays

Carbon nanotube field emission backlight (CNT-BLU) is promising to replace traditional backlighting devices in liquid crystal display (LCD) industry. This study reports a laser irradiation process to enhance field emission properties of buckypaper, a thin sheet of high-loading carbon nanotube network. The scanning laser treated the selected region of buckypaper to activate CNT emitters. The improvement of phosphorescence luminance intensity, uniformity, and the reduction of turn-on field were achieved by adjusting machining parameters of laser power, laser lens motion speed, laser resolution, laser beam size, and pattern orientation. Design of experiment and response surface methodology provided ways to rapidly search the feasible laser parameter setting for processing buckypaper field emitters and improving field emission properties within fewer experimental runs. 2^5?1 Fractional fracotrial design presented the initial models of five repsponses. In addition, the face-centered central composite design is applied since the 2^5?1 factional factorial design showed curvature significance. It assisted to give the scientifical insight of the following conclusions. High-energy laser treatment damages and burns the CNTs into carbon oxide materials; furthermore, it loses the effective CNTs. Low-energy laser treatment performs CNT activation and produced low field emission performance. In this study, we succeeded to apply statistical analysis methods to understand the physics and mechanics of laser-activated buckypaper field emission and, furthermore, improve, optimize, and demonstrate performance by material selection, process development, and characterization.     

Improvement of dimensional uniformity on micro-dimple arrays generated by electrochemical micro-machining with an auxiliary electrode

Micro-dimples play an important role in improving the performance and reliability of mechanical systems. Through-mask electrochemical micro-machining (TMEMM) is a feasible alternative for generating micro-dimples. However, in TMEMM, the electrical field intensity at the edge is higher than that in other areas, which leads to poor dimensional uniformity of the micro-dimple arrays. In this paper, an auxiliary electrode with a positive potential was proposed to enhance the uniformity of distribution of the electrical field on the workpiece. Simulation results indicate that the auxiliary electrode with an appropriate potential is useful for improving the uniformity of the electrical field distribution. Experiments verify that with the potential of 10 V on the auxiliary electrode, the dimensional uniformity of the micro-dimple arrays was improved significantly, and the normalized dimensions of the arrays increased to 0.95. This approach is therefore effective in obtaining micro-dimple arrays with uniform dimensions.     

Dynamic performance of high speed solenoid valve with parallel coils

The methods of improving the dynamic performance of high speed on/off solenoid valve include increasing the magnetic force of armature and the slew rate of coil current, decreasing the mass and stroke of moving parts. The increase of magnetic force usually leads to the decrease of current slew rate, which could increase the delay time of the dynamic response of solenoid valve. Using a high voltage to drive coil can solve this contradiction, but a high driving voltage can also lead to more cost and a decrease of safety and reliability. In this paper, a new scheme of parallel coils is investigated, in which the single coil of solenoid is replaced by parallel coils with same ampere turns. Based on the mathematic model of high speed solenoid valve, the theoretical formula for the delay time of solenoid valve is deduced. Both the theoretical analysis and the dynamic simulation show that the effect of dividing a single coil into N parallel sub-coils is close to that of driving the single coil with N times of the original driving voltage as far as the delay time of solenoid valve is concerned. A specific test bench is designed to measure the dynamic performance of high speed on/off solenoid valve. The experimental results also prove that both the delay time and switching time of the solenoid valves can be decreased greatly by adopting the parallel coil scheme. This research presents a simple and practical method to improve the dynamic performance of high speed on/off solenoid valve.     

线性测微电感的精化

为提高测微电感传感器的测量精度,提出了基于赫姆霍兹线圈理论设计螺线管线圈的方法,改善了螺线管线圈内轴向上磁场的分布均匀性。首先,分析了螺线管线圈模型,建立了螺线管线圈参数与轴向磁场强度分布相互关系的广义函数模型。然后,通过线圈与磁芯的尺寸确定了系统轴向磁场强度分布函数模型,结合磁芯移动区间范围设置磁场均匀度最小误差目标函数,通过对目标函数寻优得到各螺线管线圈的各项参数。最后,搭建了测微电感传感器的测试系统,测试了传感器性能。实验结果表明:与传统线圈相比,改进型螺线管线圈在100μm测量范围内的线性度由0.46%提高到0.30%。实验显示通过对不同规格的螺线管线圈进行组合,可使得螺线管内轴向上磁场强度分布均匀,从而提高了测量精度。     

高世代平板显示光刻机照明系统中梯形视场的设计与仿真

针对大面积薄膜晶体管(TFT)液晶显示生产中的高世代光刻机(6代以上)照明系统改进,设计了一种新颖的梯形拼接照明视场方案。使用设置在微透镜阵列入瞳处的视场光阑阵列实现了梯形拼接照明视场,同时简化了系统设计。相较于以尼康平板液晶显示器(FPD)光刻机为代表的现有梯形拼接视场方案,提出的设计方案能减少投影物镜的热负担,同时在一定程度上提高照明系统的光能透过率。通过Lighttools建模分析,说明该设计方案能够实现梯形照明视场并且积分均匀性在1%以内,达到了设计预期效果。     

SAR of a birdcage coil with variable number of rungs at 300 MHz

The specific absorption rate produced in a rat’s brain phantom inside of quadrature birdcage coil as a function of the rung number was studied at 300 MHz. Electromagnetic field simulations and specific absorption rate and loss return responses were performed using a rat’s brain phantom weighing 100 mg. To assure optimal simulations and to evaluate coil performance, S-parameters were simulated and compared with experimentally data. Simulations showed that magnetic field uniformity improves and that electric field is increased with the number of rungs. Specific absorption rate and temperature values obtained from axial bi-dimensional maps increase as the number of rungs grows. These results corroborated very well with published data. A quadrature 16-rung birdcage coil was developed for comparison and phantom images were acquired to show its feasibility. The presented approach yields information on specific absorption rate allowing to previously develop RF coils and their possible effects on the biological sample.     

用于胃肠道机器人的C型组合式无线能量发射线圈的设计与实验

现有适用于胃肠道机器人的无线能量传输系统的能量传输效率低、接收功率低且接收能量的位置均匀性差,无法满足功能复杂的新型胃肠道机器人的能量需求。本文提出了一种新型C型组合式发射线圈结构,通过有限元仿真分析供能单元组的磁感应强度大小和位置均匀性,确定供能单元组中线圈对间距的实验优化范围。最后搭建实验平台,优化供能单元组中线圈对间距,通过系统的能量传输效率、接收功率以及接收功率的位置均匀度对设计进行评估与验证。实验结果表明：当线圈对间距为150 mm时,中心位置的接收功率为1 165.34 mW,系统的能量传输效率为6.08%。系统的平均功率约为1 100 mW,平均能量传输效率达6%以上,接收功率的平均位置均匀度达94%。新型C型结构磁芯以及采用同一时刻只有一个供能单元组工作的组合式线圈结构,极大地改善了系统的接收功率与能量传输效率,并有较高的接收能量的位置均匀性。     

Evaluation of a Linear Self-Scanned Photodiode Array Detector for Direct Detection of 6-8 Kev X-Rays

ABSTRACT

The performance of a commercially available 1-dimensional x-ray detector based on a directly bombarded self-scanned photo-diode array has been evaluated for x-rays in the 6-8 KeV range. The detector consists of a linear array of 1024 pixels, each approximately 25 μm wide by 2000 μm tall. Modifications to allow cooling to -55°C, which is required for long x-ray exposures, are described. The signal yield is 0.63 ADC counts/Fe⁵⁵ x-ray, resulting in a detective quantum efficiency greater than 0.5 for doses over a range of 10 to 10⁴ x-rays per pixel per scan when operated at -55°C. The resolution is about 3 pixels (75 μm FWHM) and the response with respect to dose is linear up to 1.5 x 10⁴ x-rays integrated per pixel per scan. There is some non-linearity at doses below about 1000 x-rays/pixel/scan. The detector has very little geometric distortion. The uncorrected uniformity of response of the individual pixels (field flatness) is good to about 2%. However, the variation in responsiveness is stable and a field flatness calibration can be readily used to correct the uniformity of response.     

传感器内部磁场分布对磁弹索力传感器性能的影响

为了掌握磁弹索力传感器中磁场分布特点及其对传感器性能的影响,为磁弹索力传感器的设计提供参考,在讨论磁弹索力传感原理基础上,结合磁弹索力传感器结构原理分析磁弹索力传感器内部激励磁场及退磁场分布特点;在同样激励线圈的磁场条件下,通过改变感应线圈长度模拟内部磁场分布的均匀性变化情况,从而对传感器输出与应力关系进行对比性的仿真计算;并按照理论仿真思路,进行实验验证;实验结果表明:磁场均匀性从75％降低到25％时,传感器灵敏度从0.026 9 mV/MPa降低到0.021 9 mV/MPa,重复性误差从0.228％增加到0.734％,与理论仿真定性相符合.     

A study on the annealing characteristics of BAF for cold rolled steel strip

The cold spot temperature control system for BAF (Batch Annealing Furnace) has been established in order to reduce energy consumption to improve productivity and to stabilize the properties of products. We improved material quality, increased output, and decreased the annealing cost and homogeneous distribution of cold spot temperature in BAF. The introduction of H₂ instead of N₂ as atmospheric gas, combined with high convection in BAF, has resulted in a considerable increase in furnace efficiency and material quality. By the low density, high diffusibility, and reducing character of H₂, a better heat transfer resulting in uniform material temperature and improved coil surface can be achieved. The results in this study are as follows: Heating time is reduced to one half by increasing the inflow rate of atmospheric gas and changing of atmospheric gas component from HN_x(H₂: 5 %, N₂: 95%) to Ax(₂: 75%, N₂: 25%) gas. The annealing cycle time is also reduced to 2.7 times. In the case of HNx BAF the cold spot moved to the center after 32 hours of heating, while in the case of H₂ BAF it moved from the one-third position of the B coli inside to the center juster after 12 hours of heating, resulting from a heat transfer increase to the radius direction. The temperature in this part is higher than any other parts when cooling. Soaking time at batch annealing cycle is decided by input coil width, and the time for quality homogenization of 1219 mm width coil must be longer by 2.0 hours than that of 914 mm width coil with the same coil weight at H₂ BAF, however, it is necessary to make 2.5 hours longer at HNx BAF.     

Optimization of Dimensions of a Device for Circular Magnetization of Cylindrical Components. V. Circular Field Component in One Sector of Toroidal Coil

Analytical expressions for calculating the distribution of the circular magnetic field component generated by a coil shaped as a toroid sector have been obtained. The field distribution has been analyzed for different parameters of a toroidal coil divided into sectors. The maximal circular component of magnetic field is generated in a limited region in space by a coil composed of different sectors containing turns wound in several layers on top of one another. The field intensity depends on the sectorial angle, its inside and outside radius, and the number of layers in the winding. The sectorial angle corresponding to the maximal circular component depends on the radius-vector of the observation point.