Reconstruction method for jitter tolerant data acquisition system

A waveform digitizing system tolerant to deterministic jitter can be obtained by isolating the deterministic part of the jitter and calibrating the system to eliminate its effects. Calibration of the system can be made from measured nonuniform sampling times. It will be shown that this information allows reconstructing the signal at uniformly spaced sampling times. To reconstruct a signal from its nonuniform samples, we use the Shannon expansion combined with a time stretching/compressing method. Moreover, the reconstruction of a signal from a finite number of samples introduces a truncation error. We propose, using a windowing technique, to reduce the truncation error, which improves considerably the resolution, or the number of effective bits of an analog to digital conversion system.     

Partial semi-coarsening multigrid method based on the HOC scheme on nonuniform grids for the convection–diffusion problems

A partial semi-coarsening multigrid method based on the high-order compact (HOC) difference scheme on nonuniform grids is developed to solve the 2D convection–diffusion problems with boundary or internal layers. The significance of this study is that the multigrid method allows different number of grid points along different coordinate directions on nonuniform grids. Numerical experiments on some convection–diffusion problems with boundary or internal layers are conducted. They demonstrate that the partial semi-coarsening multigrid method combined with the HOC scheme on nonuniform grids, without losing the high-order accuracy, is very efficient and effective to decrease the computational cost by reducing the number of grid points along the direction which does not contain boundary or internal layers.     

A versatile pattern synthesis algorithm for circular antenna array

This article presents a versatile pattern synthesis algorithm for controlling the sidelobe level and nulling region for circular antenna arrays. Nonuniform fast Fourier transform using the min–max interpolation method is utilized to overcome the nonlinear feature of circular arrays. The major advantage of the proposed algorithm is low complexity, which is key for hardware implementation. Moreover, the proposed algorithm functions well in amplitude‐only pattern synthesis, which may be required for low‐cost array systems using attenuators instead of complete amplitude and phase adjustment modules. Additionally, element failure of antenna arrays can be minimized in practical operations by resynthesizing the pattern by using the remaining antennas to achieve satisfactory performance. Simulation results indicate the lower complexity and higher versatility of the proposed algorithm compared with the conventional methods.     

不均匀风速分布下翅片管换热器的优化分析与实验

风速分布对翅片管换热器性能影响较大。本文在换热器结构尺寸、空气进口状态一定的条件下,对三种典型风速分布时翅片管换热器的流程布置形式进行了仿真优化与实验研究。结果表明:在上三角和中三角两种风速分布形式下,优化后制冷量分别提高了10.3%、3%;对于上三角优化形式,高风速区是改善换热效果的重点区域;在制冷量相同的情况下,上三角优化形式使系统COP提高8%左右。搭建实验台对仿真结果进行了验证,表明模拟值和实验值相对误差均控制在5%以内。     

Wideband and low‐loss waveguides of nonuniform cross‐section

Waveguides of nonuniform cross‐section are introduced, analyzed and then their cross‐section is optimized to reach wideband and low‐loss waveguides. The waveguide cross‐section is defined as a Fourier series whose unknown coefficients are optimized using genetic algorithm to reach a proper cross‐section for waveguide. A verified finite difference method is used in analysis stage of optimization. The results show that optimum designed nonuniform cross‐section waveguides have lower conductor attenuation constant in comparison with double ridged waveguides of the same bandwidth. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:115–121, 2015.     

连续冶炼冶金焦工艺初探──(Ⅱ)特点和有待研究的问题

本文论述了连续混热式冶金焦炉炼焦新工艺的特点，对连续炼焦工艺几项预期指标与现有几种焦炉做了比较，并指出了连续炼焦工艺有待解决的问题。     

Numerical deembedding technique for planar discontinuities with periodically nonuniform feed lines

A numerical short‐open calibration technique is applied to deembedding of planar discontinuities with periodically perturbed nonuniform feed lines in the full‐wave method of moments (MoM) algorithm. Different from the other deembedding techniques that are based on the assumption of uniform feed lines, this proposed technique exhibits an unparalleled capability on modeling of planar circuits with nonuniform feed lines. To demonstrate this feature, the open and gap discontinuities are modeled under periodically nonuniform feed configuration, and the effective per‐unit‐length transmission parameters of slow‐wave and electromagnetic bandgap structures are extracted from the full‐wave MoM simulation. Two periodically nonuniform microstrip‐line resonator circuits are modeled and then confirmed by EM simulators and measurement. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

The Effects of Inhomogeneity and Adiabatic Dusty Charge Fluctuation on Solitary Waves

Using the perturbation method, the modified variable coefficient Kadomtsev-Petviashvili (MKP) equation governing nonlinear dust acoustic solitary waves is for the first time derived with the combined effects of adiabatic dust charge fluctuation and higher-order transverse perturbation in inhomogeneous dusty plasmas due to the spatial gradients of dust charge and plasma densities. The MKP equation is reduced to the standard Kadomtsev-Petviashvili (KP) equation. The numerical results show that inhomogeneity has strong influence on the nonlinear properties of dust acoustic solitary waves.     

WC-10%Co非均匀结构细晶合金的研究

本文采用抗弯强度检测仪、洛氏硬度计、SEM、体视显微镜等检测手段,研究了以超细晶WC-1.0%Co为基础,WC-1.0μm的添加量对WC-10%Co非均匀结构细晶合金组织和性能的影响。研究表明:WC-1.0μm添加量从27%、36%到45%(质量分数),都能形成晶粒度非均匀结构合金组织;非均匀结构合金的平均晶粒度、双晶平均尺寸随WC-1.0μm添加量的增加而增大,但细晶所占比例减少,而粗晶所占比例增加;随WC-1.0μm添加量的增加,合金矫顽磁力、抗弯强度、硬度降低,而断裂韧性有所提高;从切削试验和现场使用情况可知,WC-1.0μm的添加量为36%(质量分数)的合金切削性能最好。     

Investigation of nonuniformity in a liquid–solid fluidized bed with identical parallel channels

Previous work has demonstrated that multiphase flow through identical parallel channels and multiple cyclones can give rise to significant nonuniformity among the flow paths. This article presents results from a study where the distribution of voidage and flux through parallel channels in liquid–solid fluidized beds is investigated. Experiments and computational fluid dynamics simulations were performed with 1.2 mm glass beads fluidized by water where a cross baffle divided a 191 mm diameter column into four identical parallel channels. Voidages were measured by optical fiber probes. Simulations from a three‐dimensional unsteady‐state Eulerian–Eulerian model based on FLUENT software showed good agreement with the experimental results. Despite the symmetrical geometry of the system, the average voidage and particle velocities in one channel differed somewhat from those in the others. Increasing the superficial liquid velocity could increase voidage greatly and affect the degree of nonuniformity in the four channels. © 2009 American Institute of Chemical Engineers AIChE J, 2009