提高高速公路沥青路面平整度的措施

优良的路面平整度能保证大量车辆经济、舒适、安全地通行,平整度好的路面,肯定会延长使用寿命,节约养护费用以及在路上通行的各种车辆的维修费用,不平整的纵向表面会引起较大的车轮动力,它将加速路面破坏,建设较平整的公路的经济效益是十分明显的。公路路面不平整的原因主要与路基和路面的施工有关,据此提出了改进路面平整度的措施和方法。     

Miniaturized wide‐band rat‐race coupler

New designs of wide‐band rat‐race couplers are proposed. The wide‐band operation is achieved with the use of the microstrip nonuniform transmission line sections for the branches of the conventional rat‐race coupler. The design formulas are developed using ABCD matrix and the even‐ and odd‐mode analysis. The theoretical analysis has been verified by measurements of the two manufactured wideband rat‐race couplers, one operate within 0.85–1.92 GHz and other within 1.55–3.55 GHz frequency range with the equal normalized characteristic impedance functions. For both fabricated couplers, the isolation parameter is better than 15 dB over a 77% relative bandwidth. Also, it is shown that the designed wide‐band rat‐race coupler can be realized in higher frequency bands with the fixed fractional bandwidth. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 675–681, 2013.     

一种电磁摆摆幅和周期的控制方法

针对2013年全国大学生电子设计竞赛J题要求,设计了一套基于单片机系统的电磁摆运动控制装置。通过控制底端位置对称的两个电磁铁的触发时机和脉冲强度实现了摆幅控制,通过控制摆锤周围磁感应强度实现了摆动周期控制。摆幅控制采用非均匀采样周期的积分分离PID控制算法,周期采用开环控制。实验结果表明,该控制方法取得了良好的稳态和动态性能。     

基于新型定子极面结构的开关磁阻电机转矩脉动抑制研究

为抑制开关磁阻电机(SRM)转矩脉动,提出了一种新型定子极面结构,将传统均匀气隙结构改成两段式的非均匀气隙结构。以一台11 k W、1 000 r/min、12/8极SRM为例,通过建立二维场路耦合时步有限元模型,对此类结构进行了验证与优化。结果表明:此类结构能够在保证电机效率基本不变的情况下,有效抑制转矩脉动,为进一步提升SRM的设计与运行水平,提供了有益的参考。     

工业汽轮机调节级部分进汽瞬态数值研究

针对采用喷嘴调节的汽轮机调节级效率和安全性问题,基于时均的N-S方程,采用六面体结构化网格和有限容积法,对某机组调节级内部流动进行了数值计算。给出了不同工况下调节级内部压力和速度分布图,分析了4阀开和3阀开工况下调节级内部流动。给出了动叶旋转一周扭矩的变化,并将非定常扭矩进行了傅里叶变换,得到了频谱图。研究结果表明,部分进汽使调节级内部流动不均匀,4阀开,动叶所承受最大瞬时扭矩是进汽弧段平均扭矩的2.2倍,3阀开,动叶所承受最大瞬时扭矩是进汽弧段平均扭矩的1.8倍,这可以为调节级动叶安全性校核提供参考;频谱图显示,动叶受到与转速相关的低频激振力;3阀开工况下调节级的效率比4阀开工况下降低7%。     

基于迭代NUFFT的不等距阵列天线低副瓣方向图综合

针对不等间距阵列天线的低副瓣方向图综合问题,提出了一种基于非均匀快速傅立叶变换(NUFFT)的迭代算法.通过严格的数学推导,建立非均匀离散傅立叶变换(NUDFT)与天线阵因子之间的对应关系,利用过采样FFT系数的线性组合来近似表达复指数函数进而实现NUFFT,最后通过插值和反复的迭代有效地抑制了阵列天线的最大副瓣电平.结合等间距阵列和不等间距阵列的算例,对比粒子群算法的优化结果,验证了该算法的有效性和高效性.     

偏心度与间隙比对轴流泵流动激励力的影响

叶轮偏心将会引起轴流泵叶轮顶部间隙沿周向不均匀,从而导致附加的流动激励和噪声.利用计算流体力学商业软件Fluent模拟不同偏心度和间隙比的轴流泵非定常流场,研究周向非均匀间隙对泵内压强脉动及叶轮激励力的影响.结果表明:壁面压强脉动强度并不是在最小间隙处达到最大,而是出现在偏离最小间隙处约30°~60°的方向,并随着间隙比增大,脉动强度最大值发生位置逐渐向最小间隙处靠拢;同时,偏心造成的非均匀叶顶间隙引起了轴频处的压强脉动,在间隙比为2.5%下偏心度从0%增加到60%,轴频处的压强脉动相对增量为661.54%;叶轮受到的径向激励力时均值与偏心度呈线性关系,其斜率与间隙比的平方根成正比.     

Measurement of Reactivity Effect and Thermal Neutron Flux in Non-uniformly Distributed Fuel Assemblies

A reactivity effect due to spatial variation of nuclear fuel concentration is an important problem for nuclear criticality safety in a reprocessing plant. As a method theoretically estimating this reactivity effect, the Goertzel's necessary condition is well known. To investigate this theoretical prediction, we have performed systematically a series of measurements of reactivity effect due to nonuniformity in the fuel distribution using a solid moderated core of the Kyoto University Critical Assembly. Thermal neutron flux distributions have been also measured using the activation method with gold wire. A nonuniform assembly was found to have an excess reactivity of 0.2%Δk/k when it had the same uranium mass as the uniform assembly was exactly critical. The fuel concentration of this nonuniform assembly was 40% higher in the center region than the uniform one. Moreover, the spatial distribution of reaction rate of gold wire due to thermal neutrons was flatter in this nonuniform assembly than in the uniform one, as expected by the Goertzel's condition.     

频变扩展重迭变换的快速算法

频变扩展重迭变换（FV-ELT）是一类具有灵活时频分辨率特性的非均匀滤波器组,适用于音频编码中时频映射处理部分。本文主要给出基于DCT-IV的FV-ELT快速算法,并给出复杂度计算公式。最后以几种典型滤波器组应用结构为例,给出了所需乘加运算次数。与直接计算模式相比,此快速算法能有效地降低FV-ELT的运算复杂度。     

Performance of Reservation in Call Admission Control Schemes for Code-Division Multiple Access Systems with Nonuniform Traffic Distribution Among Cells

In this paper, we propose the reservation type call admission control (CAC) scheme to resolve the intercell unbalanced traffic problem. Differently from a conventional CAC scheme where the system resource is fully allocated to the local users in the home cell, the proposed CAC scheme reserves a small portion of the system resource for new calls occurring in the neighboring cells instead of fully allowing the local users in the home cell to occupy the system resource. As a result, the proposed CAC scheme improves the overall call blocking probability when the traffic is nonuniformly distributed among cells. More specifically, the proposed CAC scheme improves the overall call blocking probability by 15% when one cell has 67% more traffic than its surrounding cells.