混合载波系统高阶计算分集方法

面向多载波系统的分集方案对于通信技术的发展而言至关重要,针对混合载波系统设计分数域四分量计算分集(fractional domain four-component computation diversity,FDFC-CD)方法,利用分数傅里叶信号含有多个时频分量的特点提高混合载波系统的分集性能,并基于多分量扩展的计算分集方法存在能量分布不均匀的背景,提出高阶计算分集方法,并进行了相应的仿真验证。针对高阶分数域四分量计算分集数据块内部部分点位相关性过高的问题,提出了基于数据块反转的能量平均化策略。仿真结果表明,高阶计算分集可以使系统比特误码率得以降低,且分集阶数越高,降低效果越好,其阶数选择受限于系统资源、链路衰减和接收机灵敏度。能量平均化策略的提出完善了高阶计算分集方法,二者结合良好,分集效果得到了进一步提高。

多元表征,实现高阶计算思维发展

表征就是把数学客观对象的外在形式(实物、模型、图像、文字、符号等外在表征)与学生内在心理编码(言语码、心象码、整合码等内在表征)进行交互对应,构建意义,而多元化的表征可以有效实现数学知识的多元建构、数学技能的多元训练、数学经验的多元积累。多元的表征之间相互递进,实现数学计算思维的高阶发展。要注重内在表征的多元化外化呈现,使数学计算思维可视、可感、可具体表达,最终抽象为高阶计算思维。

高职数学中有关高阶行列式的解法探讨

线性代数是高职计算机类等专业必学的内容之一,对于高职学生来讲,本章内容所需要的基础知识不是很多,对于一些简单的计算只要有初中的数学基础就足够了,但是对于某些复杂的高阶列式,需要一些技巧才能求出,本文主要根据其特点采用多种解法去计算。

HOS AND GA BASED INTERFERENCE REJECTION IN DS SS COMMUNICATION SYSTEMS

A new interference rejection filter based on Higher Order Statistics (HOS) and Genetic Algorithm (GA) is introduced. The advantages over the adaptive filters based on secondorder statistics or gradient algorithm are shown through computer simulation.

AN ELIMINATION ALGORITHM OF EXTREME VALUES FOR INTEGRATED TRISPECTRUM

In this paper, an algorithm for eliminating extreme values and reducing the estimation variance of an integrated trispectrum under low signal-to-noise ratio and short data sample conditions is presented. An analysis of the results of simulations using this algorithm and comparison with the conventional power spectrum and integrated trispectrum methods are presented.

基于YOLOv3模型的高阶目标检测方法

目标检测是计算机视觉的重要分支,目前基于深度学习的目标检测算法相较于传统目标检测算法在检测精度和检测时间上虽能略胜一筹,但其难以同时兼顾检测速度与检测精度,因此针对这一问题提出了改进YOLOv3后的Mul-YOLO目标检测网络。Mul-YOLO目标检测网络利用Haar小波进行数据预处理,将图像信息的低频特征在不同分辨率下层层分解,用以获得水平方向、垂直方向以及斜对角方向上的高频特征,进而利用高频特征记录的相应特征信息,减小被检测目标在几何状态变化、光照变化和背景变化下对检测精度带来的负面影响。在特征层上采样、卷积和拼接的过程中融入高阶计算,由此增强在有限的感受野内的特征表述能力,使得训练网络更加关注映射特征的显著性信息,增强了图像的分辨率,有效地减少了数据集训练过程中由连续的卷积和池化带来的信息丢失问题。在PASCAL VOC数据集下的实验结果表明,本文提出的Mul-YOLO目标检测模型相较于传统目标检测模型有了明显的改进,比如相较于Faster R-CNN ResNet提取特征的方法,mAP提高了8.97%,并且单张图片的检测时间提高了172 ms。与YOLOv3提取特征的方法相比,其mAP提高了33.48%,达到了检测精度与检测时间同时相得益彰的目的,综合其他比较结果,本文方法的有效性可以有效地得以验证。

Validation of a RANS transition model using a high-order weighted compact nonlinear scheme

A modified transition model is given based on the shear stress transport (SST) turbulence model and an intermittency transport equation. The energy gradient term in the original model is replaced by flow strain rate to saving computational costs. The model employs local variables only, and then it can be conveniently implemented in modern computational fluid dynamics codes. The fifth-order weighted compact nonlinear scheme and the fourth-order staggered scheme are applied to discrete the governing equations for the purpose of minimizing discretization errors, so as to mitigate the confusion between numerical errors and transition model errors. The high-order package is compared with a second-order TVD method on simulating the transitional flow of a flat plate. Numerical results indicate that the high-order package give better grid convergence property than that of the second-order method. Validation of the transition model is performed for transitional flows ranging from low speed to hypersonic speed.

Higher-Order Schwarz-Pick Estimates for Holomorphic Self-mappings on Classical Domains

In this paper, Schwarz-Pick estimates for high order FrSchet derivatives of holo- morphic self-mappings on classical domains are presented. Moreover, the obtained result can deduce the early work on Sc：hwarz-Pick estimates of higher-order partial derivatives for bounded holomorphic functions on classical domains.

Error Bounds for Uniform Asymptotic Expansions-Modified Bessel Function of Purely Imaginary Order

The authors modify a method of Olde Daalhuis and Temme for representing the remainder and coefficients in Airy-type expansions of integrals.By using a class of rational functions,they express these quantities in terms of Cauchy-type integrals;these expressions are natural generalizations of integral representations of the coe?cients and the remainders in the Taylor expansions of analytic functions.By using the new representation,a computable error bound for the remainder in the uniform asymptotic expansion of the modified Bessel function of purely imaginary order is derived.

A perspective on high-order methods in computational fluid dynamics

There has been an intensive international effort to develop high-order Computational Fluid Dynamics(CFD) methods into design tools in aerospace engineering during the last one and half decades. These methods offer the potential to significantly improve solution accuracy and efficiency for vortex dominated turbulent flows. Enough progresses have been made in algorithm development, mesh generation and parallel computing that these methods are on the verge of being applied in a production design environment. Since many review papers have been written on the subject, I decide to offer a personal perspective on the state-of-the-art in high-order CFD methods and the challenges that must be overcome.

Strichartz estimates for parabolic equations with higher order differential operators

The present paper first obtains Strichartz estimates for parabolic equations with nonnegative elliptic operators of order 2m by using both the abstract Strichartz estimates of Keel-Tao and the Hardy-LittlewoodSobolev inequality. Some conclusions can be viewed as the improvements of the previously known ones. Furthermore, an endpoint homogeneous Strichartz estimates on BMOx(Rn) and a parabolic homogeneous Strichartz estimate are proved. Meanwhile, the Strichartz estimates to the Sobolev spaces and Besov spaces are generalized. Secondly, the local well-posedness and small global well-posedness of the Cauchy problem for the semilinear parabolic equations with elliptic operators of order 2m, which has a potential V(t, x) satisfying appropriate integrable conditions, are established. Finally, the local and global existence and uniqueness of regular solutions in spatial variables for the higher order elliptic Navier-Stokes system with initial data in Lr(Rn) is proved.