High-Frequency Fringing Fields Loss in Thick Rectangular and Round Wire Windings

This paper examines high-frequency losses of thick rectangular and round wire windings due to the fringing fields of an air-gap. It derives formulas for the losses and validates them numerically using the 2-D finite-element method (FEM). It also provides a procedure for including the effect of self and proximity fields in the loss calculations, using the principle of superposition and a one-dimensional model of self and proximity fields. The paper validates the latter procedure numerically, using a 2-D finite element model.      

低频电磁振动台非均匀气隙磁场优化设计

针对大行程低频电磁振动台气隙磁感应强度参数非线性导致振动激励信号产生失真的问题,在电磁振动台机电耦合模型分析基础上,采用电路等效原理建立大行程磁路简化数学模型,并基于Ansys Maxwell软件对气隙磁感应强度的非均匀分布特性进行仿真分析。基于连续混合整数非线性规划算法,分别仿真分析不同内磁轭母线轮廓及端面结构非线性参数对应的气隙磁感应强度分布特性,得到具有最小不均匀度的变气隙及变截面磁路最优解。仿真结果表明:变气隙和变截面结构分别将优化前25.95%的不均匀度降低到7.09%和2.70%,变截面结构具有更好的优化效果。设计的优化磁路结构可有效改善大行程低频电磁振动台气隙磁感应强度的非线性,降低输出振动信号的失真度,提高低频振动校准精度。     

Error in Insertion Loss Measurement Due to Multiple Reflections

A system error of a waveguide impedance bridge due to multiple reflections between the test section and the bridge circuit is analyzed. A principle and a method of making corrections to this system error are presented with actual numerical examples.     

地下列车移动荷载作用下隧道及自由场的动力响应解

针对地下列车运行引起的隧道和自由场上的振动响应问题,利用隧道-自由场动态相互作用系统在隧道轴线方向上的一致性或周期性,采用Fourier变换和Floquet变换等方法,在频率-波数域内推导了在移动荷载作用下隧道及自由场的动力响应解,此解把地下列车运行引起的动力响应问题归结到计算频率-波数域内的传递函数和频域内的移动外荷载的问题上,传递函数采用三维周期性有限元-边界元耦合的数值模型来计算,移动外荷载主要考虑为频域内轨道不平顺情况下的轮轨接触力.利用此动力响应解对北京地铁1号线东单站至建国门站区间的动力响应进行了计算,计算结果表明此方法具有良好的适用性.     

Decrease in Fullerene Productivity Due to Air Leakage in Carbon Arc Method

Fullerene productivity was investigated in the carbon arc discharge method when air was deliberately introduced into He-filled arc apparatus. Values of fullerene yield and production rate did not vary until the air leakage rate, denned as an increase in the ratio of air partial pressure relative to He pressure, was 0.2%/min. Fullerene productivity drastically decreased when the air leakage rate increased above 0.2%/min. Emission spectroscopic measurement of the arc plasma suggested the possibility that this decrease in productivity was related to an increase in the formation of carbon-air combined molecular species, e.g., CN, in the plasma.     

Decrease in Fullerene Productivity Due to Air Leakage in Carbon Arc Method

Abstract

Fullerene productivity was investigated in the carbon arc discharge method when air was deliberately introduced into He-filled arc apparatus. Values of fullerene yield and production rate did not vary until the air leakage rate, denned as an increase in the ratio of air partial pressure relative to He pressure, was 0.2%/min. Fullerene productivity drastically decreased when the air leakage rate increased above 0.2%/min. Emission spectroscopic measurement of the arc plasma suggested the possibility that this decrease in productivity was related to an increase in the formation of carbon-air combined molecular species, e.g., CN, in the plasma.     

提速对列车空调系统的影响

分析了列车提速对空调系统的不利影响，讨论了新风量计算应考虑的因素，并提出了改善空调系统性能的措施。     

优化修正入口边缘场四极质谱计离子光学特性的模拟计算

对一种具有优化修正入口边缘场的四极质谱计离子光学特性用相空间力学分析方法进行了模拟计算 ,给出了模拟计算的要点和结果分析。模拟结果与实验结果很好地一致 ,从而在理论上进一步证明了这种四极质谱计的可行性。     

空气和聚氨酯泡沫材料隔爆试验研究

在简要总结聚氨酯泡沫材料隔爆性能的基础上,介绍了硬质聚氨酯泡沫材料对冲击波的衰减规律.在空气和硬质聚氨酯泡沫材料的共同作用下,首先聚氨酯材料对冲击波进行衰减,穿过聚氨酯后空气介质又对冲击波进行二次衰减,冲击波的衰减就要复杂一些.对TNT和8701炸药(聚黑-2)采用升降法进行殉爆试验,在对试验定性分析的基础上,近似得出了空气和聚氨酯材料共同作用下的隔爆距离,以及当试验为临界条件时,紫铜药型罩对隔爆距离有较大的影响的结论.     

Generating Periodic Pulse Sequences of Nanosecond Spark Discharges in an Air Gap between Transparent Hydrogel Electrodes

Technical Physics Letters - Hydrogel electrodes transparent in the visible range have been used for the first time to generate periodic sequences of nanosecond pulsed spark discharges with current...     

Pulsed Eddy Current Technology: Characterizing Material Loss with Gap and Lift-off Variations

Abstract

Ownership costs of operational aircraft have increased steadily over the years. One of the major cost drivers is structural deterioration due to corrosion. Beyond the economics, finding and characterizing corrosion is essential for the continued airworthiness of aircraft fleets. To this end, the pulsed eddy current technique holds the potential of becoming the primary means of detecting corrosion in multilayered structures. Its wide-band frequency spectrum allows the determination of a large number of parameters, such as defect size and location. Pulsed eddy current is still considered an experimental nondestructive technique because of realistic inspection problems (e.g., probe tilting, protrusion of rivets, and thickness variations in adhesive and paint) have not been addressed in the past. Recent advances change this situation and allow pulsed eddy current to be a credible field technique.     

Pulsed Eddy Current Technology: Characterizing Material Loss with Gap and Lift-off Variations

Ownership costs of operational aircraft have increased steadily over the years. One of the major cost drivers is structural deterioration due to corrosion. Beyond the economics, finding and characterizing corrosion is essential for the continued airworthiness of aircraft fleets. To this end, the pulsed eddy current technique holds the potential of becoming the primary means of detecting corrosion in multilayered structures. Its wide-band frequency spectrum allows the determination of a large number of parameters, such as defect size and location. Pulsed eddy current is still considered an experimental nondestructive technique because of realistic inspection problems (e.g., probe tilting, protrusion of rivets, and thickness variations in adhesive and paint) have not been addressed in the past. Recent advances change this situation and allow pulsed eddy current to be a credible field technique.     

Role of the Dimerized Gap Due to Anion Ordering in the Quantized Hall Phases of Quasi-One Dimensional Organic Conductors

The electrical resistivities and magnetoresistances (MR) of a radical ion salt (EDO-TTFBr₂)₂FeCl₄ and its diamagnetic analogue (EDO-TTFBr₂)₂GaCl₄ are investigated under pressures. The resistivity of the FeCl₄ salt shows two anomalies due to the successive transitions of the π-electron layer, and another anomaly coming from the long-range magnetic ordering of the FeCl₄ layer. For the GaCl₄ salt negative MR is observed in the low-field region, suggesting a decrease of the SDW gap by applying the magnetic field. The MR of the FeCl₄ salt shows two abrupt increases, which proves the presence of field-induced successive transitions in the composite π-d spin system. The field dependence of the MR of this salt can be qualitatively explained based on the frustrated magnetic structure of π- and d-electron spins interacting with each other.     

Study of Magnetic Field Inhomogeneity Due to Different Positional Deviations of a Permanent Magnet Guideway

This paper focuses on the magnetic field inhomogeneity at the rail gap due to five kinds of position deviations between two segments of permanent magnet guideway (PMG). PMG model is built by the finite element analysis software, and effectiveness of the model is proven by comparing the actual magnetic field with the calculated value. The influence of the magnetic field by the gap, horizontal displacement and vertical displacement was investigated. Kinetic characteristics of HTS maglev when it passes the rail gap are studied. The change of magnetic field at the rail gap is also studied in these cases: one PMG rotates relative to another PMG and the gap is not perpendicular to the direction of PMG. It is found that magnetic force between two PMGs will enlarge the position deviations. Finally, the methods are introduced for improving the homogeneity of magnetic field of PMG and then reducing the magnetic loss due to magnetic field inhomogeneity.     

General Formulas for the Average Magnetic Field at a Receiving Circular-Loop Antenna Placed Arbitrarily to a Radiating Loop

For testing the sensitivity of receivers having loop antennas, radiating and receiving loops have been located either coplanar or coaxial to each other. Theoretical analyses of the magnetic fields have been carried out for such alignments of loops. It is often necessary in the actual tests to estimate the effects of deviations from these ideal arrangements of the loops. In this paper, the radiating and receiving circular loops are located arbitrarily in direction, and a formula is derived to obtain the average normal component of the magnetic-field strength incident on the receiving loop using the Eulerian angles. The theory is applied to the design of a generator in which a rotating field is used as the standard field. In this case, the calculated values of the magnetic field are in agreement with the measured ones to within ±0.1 dB.     

The Spin Wave Gap and Switching Field in Thin Films with In-Plane Anisotropy

In this paper, we have calculated the spin wave gap and the angular dependence of magnetization reversal in a single-layer thin magnetic film that includes the strong perpendicular magnetic anisotropy and in-plane anisotropy. The film is assumed to be under the influence of the out-of-plane direction of the applied magnetic field at zero temperature. Using the quantum model, it is shown that the calculated equations present a nonzero spin wave gap at zero magnetic field which is strongly affected by anisotropies. The effects of the in-plane anisotropy and the role of the applied field were examined. We also discussed a simple theoretical model for the angular variation of switching field by using a quasi-classical argument. We used some constants in connection with experimental data which are reported for chromium telluride thin films grown by molecular beam epitaxy.     

Fresnel and Far-field Diffraction of a Truncated Elliptical Gaussian Beam Due to an Elliptical Aperture

Abstract

Using the Hopkins algorithm, expressions are derived for the intensity patterns, in both the Fresnel and far-field regions, associated with the diffraction of a plane-wave elliptical Gaussian beam truncated by an elliptical aperture. This is accomplished by evaluating the diffraction integral subject to the Fresnel approximation. Numerical results are presented that indicate how the truncation parameter affects the side-lobe level in the Fresnel and far-field regions.     

风道结构对自提冷冻冷藏柜空气流场和温度场的影响

风道结构的改变可有效改善自提冷冻柜内部气流组织和优化热环境性能。本文在自提冷冻冷藏柜有负载状态下,针对上送上回的送回风方式,改变风道结构,即轴流挡板角度(30°、45°、60°、90°)、背部送风孔板开孔方式(上疏下密的非均匀式开孔、下部集中式开孔、等间距式开孔)以及送风板开孔率(6%、8%、10%),建立10种模型并对比分析,选取最优结构模型。并将原始结构(挡板角度45°、集中开孔方式、开孔率6%)模拟与实测结果进行对比,验证了模型的正确性。数值模拟和实验验证结果显示,回风板角度60°时相比于原对照组45°的均匀性提高了23. 0%,非均匀开孔方式相比于集中式开孔速度均匀性提高了4. 8%,且开孔率为8%时比原6%的整体均匀性提高了5. 1%,因此在回风板角度α=60°,送风板非均匀式开孔、开孔率φ=8%时冷冻柜气流组织合理,热环境性能较为理想。