海胆状氧化锌/羰基铁粉核壳结构复合粒子的抗氧化及吸波性能

针对羰基铁粉吸收剂在温度较高时易被氧化的问题,采用水热法制备了氧化锌包覆羰基铁粉核壳结构复合粒子,并分别将羰基铁粉和氧化锌/羰基铁粉核壳粒子与石蜡混合,制备复合材料。结果表明,氧化锌纳米棒致密的包覆在羰基铁粉颗粒表面形成海胆状核壳结构复合粒子,正是这种结构将羰基铁粉颗粒与空气隔绝,使得复合粒子的抗氧化性能得到显著改善。与羰基铁粉复合吸波材料相比,氧化锌/羰基铁粉核壳粒子的复合材料吸收峰稍向低频移动,反射损耗小于-5 d B的带宽几乎保持不变,在不改变电磁吸波性能的前提下,提高了羰基铁粉粒子的使用温度。     

部分线性回归模型变窗宽一步局部M-估计

讨论了部分线性回归模型的变窗宽一步局部M-估计.用一步局部M-估计给出未知函数的估计,用平均方法给出参数估计.进一步通过两个引理证明一步M-估计的渐近正态性.所提出的方法继承了局部多项式的优点并且克服了最小二乘法缺乏稳健性的缺点.     

变系数联立模型的局部线性广义矩变窗宽估计

在随机设计条件下,提出了一类变系数联立模型,运用局部线性广义矩变窗宽估计,对模型的变系数进行了估计,研究了估计量的大样本性质.利用概率论中大数定律和中心极限定理,证明了估计量的大样本性质,局部线性广义矩变窗宽估计具有相合性和渐进正态性.     

A hybrid descent method for solving a convex constrained optimization problem with applications

The purpose of this paper is to introduce a hybrid descent algorithm for finding a common point in fixed‐point sets of quasi‐nonexpansive mappings and solution sets of variational inequality problems. In the framework of Hilbert spaces, the strong convergence of the hybrid descent algorithm is established. Numerical experiments for the bandwidth allocation, which demonstrate the effectiveness, performance, and convergence of the proposed algorithm, are provided.     

Four-dimensional scheduling for uplink dynamic bandwidth allocation in OFDM-PON

Orthogonal frequency division multiplexing passive optical network (OFDM-PON) has been considered a promising access solution to meet the variable bandwidth demand. In this paper, a novel scheduling for dynamic bandwidth allocation (DBA) at medium access control (MAC) layer is proposed for uplink transmission of OFDM-PON. In order to utilize the bandwidth efficiently, scheduling in four dimensions is adopted in the proposed DBA algorithm. Four dimensions stand for frequency domains, time domains, modulation formats and power allocations. The algorithm is quite flexible. Simulation results and analysis show that the proposed algorithm can efficiently utilize the OFDM bandwidth and make the system highly energy-efficient.     

基于周期极化化学计量比掺氧化镁钽酸锂晶体的高效率、单程、连续外腔倍频

利用长度为20mm的周期极化化学计量比掺氧化镁钽酸锂晶体（PP-MgO: SLT），实现了转换效率为11.8%的单程连续外腔准相位匹配（QPM）倍频，此时1064nm基频光的输入功率为7.69W，获得的532nm倍频光的输出功率为905mW。实验中可以发现，在不同的基频光聚焦条件和输入功率下，对应最大倍频输出的晶体温控炉的设定温度也要随之改变。此外，对允许角和允许温度也进行了研究，实验结果和理论结果符合的很好。     

The optimum bandwidth of chirp signals in ultrasonic applications

A new formula for the pulse-compression ratio achievable with linear FM pulses (chirp signals) in ultrasonic applications is derived. The calculations take into account the frequently omitted effects of the transfer function of an ultrasonic transducer. For a squared-cosine type transducer spectrum, the optimum chirp signal bandwidth is 1.14 times the 6 dB bandwidth of the transducer. The pulse-compression ratio is 2.24 dB lower than in the case of an ideal broadband transducer. Measurements show a close agreement with the presented theory.     

The Influence of Window Parameters on the Transmission Characteristics of Millimeter Waves

This work reports about the influence of some window parameters, such as the mechanical tolerance of disk thickness, the variation of distance between two disks, and the frequency drift during gyrotron operation on the transmission characteristics of millimeter waves. Detailed calculations of the transmission characteristics for a single-disk gyrotron window and frequency tunable double-disk plasma fusion torus windows have been performed. The geometry of the window units has been optimized in order to obtain a suitable transmission characteristic, i.e. power reflection less than –20 dB within a frequency bandwidth of about 1 GHz around the chosen frequencies.     

带宽等于最小度的图的最小边数

本文对带宽等于最小度的图的边数极值问题进行了研究,主要结果如下:对任意给定的正整数n及r(r相似文献   

The Hilbert Kernel Regression Estimate

Let (X, Y) be an ^d× -valued regression pair, whereXhas a density andYis bounded. Ifni.i.d. samples are drawn from this distribution, the Nadaraya–Watson kernel regression estimate in ^dwith Hilbert kernelK(x)=1/x^dis shown to converge weakly for all such regression pairs. We also show that strong convergence cannot be obtained. This is particularly interesting as this regression estimate does not have a smoothing parameter.