On the MMSE‐based multiuser millimeter wave MIMO hybrid precoding design

A hybrid MMSE‐based precoder and combiner design with low complexity is studied in this paper for both the downlink and uplink multiuser millimeter wave MIMO systems. At first, according to the underlying channel knowledge, the phases of the RF precoder and combiner are manipulated by using the MMSE criterion. On the basis of the MMSE‐based analog precoder design, the MMSE‐based digital baseband precoder can be readily derived. Thus, this method combines the advantage of using the MMSE precoding and phase extraction technique to obtain a reasonable solution. The proposed hybrid precoding design will be examined in both the uplink and downlink multiuser MIMO systems. Numerical results are presented to show that the proposed MMSE‐based hybrid precoding design is capable of attaining superior performance in terms of both the spectral efficiency and energy efficiency over the existing designs. Moreover, we will show that the MMSE‐based design can be readily extended to the multiuser millimeter wave MISO systems when only statistical channel state information is available.     

基于分形和岩心核磁共振的流体相对渗透率计算方法

流体的相对渗透率一般通过稳态、非稳态相渗实验或毛细管压力拟合法得到,但由于实验条件及时间的限制,相渗实验难以实现较大规模的应用。用分形理论推导了核磁共振测井横向弛豫时间(T2,NMR)与电阻率增大率的关系,根据渗流场和电流场的互等性并结合Brooks-Corey/Burdine方程得到相对渗透率与核磁共振横向弛豫时间的关系。实验数据及模型分析表明,由核磁共振横向弛豫时间计算的润湿相相对渗透率与实测值十分吻合,精度较高;由于未考虑非润湿相束缚饱和度的影响,模型计算的非润湿相相对渗透率与实测结果相差较大。     

Stripline-fed cylindrical slot antennas

A rigorous method of moments solutions for a stripline-fed cylindrical slot antenna is presented. The effects of the feeding parameters on the input impedance and far-field pattern are discussed. It is found that a cylindrical slot antenna can be matched to a 50-Ω stripline by displacing the slot from the axis of the feedline. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 33–41, 1998.     

Theoretical and experimental studies of a microstrip antenna with two parasitic patches

The variations of the dimensions and locations of two stacked parasitic elements on the input impedance SWR bandwidth and radiation patterns of aperture-coupled rectangular microstrip antennas are analyzed. It is found that the SWR bandwidth can be improved by selecting appropriate sizes and locations of the parasitic patches. A 45% bandwidth of patch antennas was attained for SWR≤2.2. Experimental results are obtained to verify the theory. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 49–55, 1998.     

A meshless solution of two-dimensional unsteady flow

The boundary element method (BEM) is a very useful numerical method for groundwater flow models. Particularly, this method was used to solve problems in homogeneous domains. However, it presents even greater difficulties than the other numerical methods when coping with non-homogeneities which are so characteristic in the groundwater hydraulics. Recently, meshless method which is based on a local boundary integral approach is introduced. It uses distributed nodal points, covering the domain. These points can be randomly spread over the domain. Every node is surrounded by a simple surface centered at the collocation point and the boundary integral equation is written on this local boundary. The unknown variables, in the local sub-domains, are approximated by some of the interpolation method. In this paper the combination of radial basis functions and the dual reciprocity method is used to solve the time-dependent groundwater flow.     

Fracture mechanics analysis of geometrically nonlinear shear deformable plates

This paper presents boundary integral equations for fracture mechanics analysis of geometrically nonlinear shear deformable plates. A radial basis function and dual reciprocity method are utilized to evaluate the derivative terms and the domain integrals that appear in the formulations, respectively. Numerical examples of the clamped and simply supported plates containing a center crack subjected to uniform transversal loadings are presented. Displacement extrapolation technique is used to compute the stress intensity factors (SIFs). Stress intensity factors of mode I for plate bending and membrane problems are presented. The normalized stress intensity factors in membrane significantly increase after few increments of the load while the normalized stress intensity factors in bending decrease. Less displacement and rotational constraints in cracked plates under uniform transversal loadings will raise the stress intensity factors. The bending stress intensity factors of a central crack in clamped square plate were found to be the highest values compared to those for clamped non-square plates.     

Shape design sensitivity and optimization for two-temperature generalized magneto-thermoelastic problems using time-domain DRBEM

The main purpose of this article is to propose an e?cient shape optimization technique based on the time-domain dual reciprocity boundary element method (DRBEM) to solve the two-temperature generalized magneto-thermoelastic problems. An implicit differentiation method was used to compute the shape design sensitivity of an approximate DRBEM solution with respect to design variables. The feasible direction method was suggested and implemented for use with the golden-section search technique for minimizing the weight objective function while satisfying all constraints. The optimum shape design of a square plate with a hole is used as the numerical example to verify the accuracy of the proposed technique.     

Generalized Theory of Thermoelastic Diffusion for Anisotropic Media

The equations of generalized thermoelastic diffusion, based on the theory of Lord and Shulman with one relaxation time, are given in anisotropic media. A variational principle for the governing equations is obtained. Then we show that the variational principle can be used to obtain a uniqueness theorem under suitable conditions. A reciprocity theorem for these equations is given. The obtained results are valid for some special cases that can be deduced from our generalized model.     

双路闭环谐振式微光学陀螺

通过建模仿真,从改善陀螺输出带宽以及提高互易性噪声抑制能力出发,对单路闭环谐振式微光学陀螺(R-MOG)和双路闭环R-MOG进行了分析研究。相比于单路闭环R-MOG,双路闭环R-MOG在抑制互易性噪声的同时,能较好地改善输出带宽,并进一步提高陀螺系统的线性度。在此基础上,搭建了双路闭环R-MOG的实验系统,并进行了陀螺零偏稳定性以及输出响应特性测试。实验结果表明,陀螺1h的零偏稳定性为0.53°/s,在±1000°/s转速范围内,陀螺系统的线性度为99.995%。     

微波铁氧体开关互易性的讨论

提出了Y 结型铁氧体开关能够在不改变控制信号的情况下实现收发双向传输的解决办法;应用传输矩阵对差相移 型铁氧体开关的工作原理和互易性进行了详细的讨论,得出了差相移误差和开关隔离度、互易性的关系,对铁氧体开关 的研制具有指导意义。