浅谈基于问题的创新性研究与教学

分析了基于问题的创新性研究和研究性教学的内涵,特别强调了如何提出科学问题的重要性以及应遵循的需求牵引、问题驱动和问题求解的科学研究特征。并且以信息化和网络化环境下多飞行器协同作战为实例,分析了多飞行器网络化协同控制的需求和特点,进而详细论述了如何分析问题和提出问题的详细过程,并说明了不同学科知识交叉和融合应用的重要性,便于领会如何在实际中提出问题并开展基于问题的创新性研究和研究性教学。     

细间距QFP组装技术探讨

细间距QFP的焊接技术发展到今天,遇到了一些新问题,如当无铅QFP和有铅焊料混装时,如何解决兼容性的问题,如何去除细间距QFP引脚上的氧化层,如何用激光焊接解决细间距QFP焊接的短路问题,如何用激光清洗的方法去除细间距QFP引脚之间的白色残留物,以及如何对印制板组件进行边界扫描测试等。详细介绍了解决这些问题的新工艺、新方法。实践证明,这些方法都是非常有效和切实可行的。     

小区物业管理系统安全平台的构建

随着现代化技术的发展和引入,智能化的小区物业管理系统进入了各个优质小区。如何保证系统在使用的过程中的安全问题成为了很多软件开发商和系统设计者要考虑的问题,如何构建一个物业系统安全平台是本文要讨论的主要问题。     

用提升方法设计M带LPPR-R滤波器组

本文研究了如何用提升方法构造M带PR-FIR滤波器组,并且考虑了一种特殊情形的线性相位(LinearPhase,LP)性质,及其优化设计问题,即如何转化为一个二次型优化问题.     

文物建筑的声学改造——清华大礼堂声学问题解决方案

简述了清华大礼堂声学问题的求解历史,以此为背景,详细说明了清华百年校庆之际对大礼堂的声学改造过程,如何克服声聚焦、颤动回声问题,如何解决混响时间过长问题,目的是为探索文物建筑的声学改造提供经验。     

地方高校双语教学模式研究

地方高校开展双语教学过程中,有许多问题要解决。本文对双语教师如何正确认识双语教学的本质和目标;如何改革教学方法与教学手段;如何合理选择教材和教学资源;如何建立健全双语教学管理机制,确定双语教学标准,认定双语教学师资,监控和评价双语教学效果,合理设置双语教学课程体系等问题进行了详细阐述。     

光电专业中复杂工程问题能力培养

针对光电信息科学与工程专业建设中的复杂工程问题设计困难的问题,从专业课程体系构建和专业核心课程中复杂工程问题的设计两个方面,分别从整体和局部进行了复杂工程问题体系的构建和具体示例,详细阐述了如何在专业建设和课程建设中如何开展学生解决复杂工程问题能力的培养问题,为专业认证和一流专业建设提供了有效保障.     

用lifting方法设计最优LPPR-FIR滤波器组

该文研究了如何用lifting方法构造线性相位完全重建有限脉冲响应(LPPR-FIR)滤波器组的优化设计问题,即如何转化为一个二次型优化问题.然后把该方法推广到M带FIR滤波器组,考虑在一种特殊情形中如何构造具有线性相位性质的M带PR-FIR滤波器组,最后列举了几个例子说明如何用lifting方法构造M带LPPR-FIR滤波器组。     

基于Astro工具的ASIC时序分析

在目前的ASIC设计中,时钟信号的质量对同步数字电路的影响越来越大。如何避免时序问题给电路造成的不利影响成为设计中的重要挑战。本文主要介绍了逻辑设计中值得注意的重要时序问题,以及如何克服这些问题。最后介绍了利用Astro工具进行时序分析的方法。     

物联网引领的食品安全检测系统设计

随着经济的发展,社会的进步,人类意识的提高,食品安全越来越被大众所密切关.人们的观念已经从如何吃得饱向如何吃得好、吃得安全转变.在日渐发达的信息社会下,食品安全形势更为严峻,食品安全问题成为人们心中重重的担忧,如何快速有效地解决食品安全问题是摆在所有人面前的重大问题之一.文章设计了一种物联网引领的食品安全监测系统,有效确保了食品供应链安全.     

Design of Biorthogonal Filter Banks Using a Multi-objective Genetic Algorithm for an Image Coding Scheme

In this paper, we present an optimization method based on a multi-objective Genetic Algorithm (GA) for the design of linear phase filter banks for an image coding scheme. To be effective, the filter banks should satisfy a number of desirable criteria related to such a scheme. Instead of imposing the entire PR condition as in conventional designs, we introduce flexibility in the design by relaxing the Perfect Reconstruction (PR) condition and defining a PR violation measure as an objective criterion to maintain near perfect reconstruction (N-PR) filter banks. Particularly in this work, the designed filter banks are near-orthogonal. This has been made possible by minimizing the deviation from the orthogonality in the optimization process. The optimization problem is formulated as a constrained multi-objective, and a modified Nondominated Sorting Genetic Algorithm NSGAII is proposed in this work to find the Pareto optimal solutions that achieve the best compromise between the different objective criteria. The experimental results show that the filter banks designed with the proposed method outperform significantly the 9/7 filter bank of JPEG2000 in most cases. Furthermore, the filter banks are near orthogonal. This is very helpful, especially where embedded coding is required.     

Design of Time–Frequency Localized Filter Banks: Transforming Non-convex Problem into Convex Via Semidefinite Relaxation Technique

We present a method for designing optimal biorthogonal wavelet filter banks (FBs). Joint time–frequency localization of the filters has been chosen as the optimality criterion. The design of filter banks has been cast as a constrained optimization problem. We design the filter either with the objective of minimizing its frequency spread (variance) subject to the constraint of prescribed time spread or with the objective of minimizing the time spread subject to the fixed frequency spread. The optimization problems considered are inherently non-convex quadratic constrained optimization problems. The non-convex optimization problems have been transformed into convex semidefinite programs (SDPs) employing the semidefinite relaxation technique. The regularity constraints have also been incorporated along with perfect reconstruction constraints in the optimization problem. In certain cases, the relaxed SDPs are found to be tight. The zero duality gap leads to the global optimal solutions. The design examples demonstrate that reasonably smooth wavelets can be designed from the proposed filter banks. The optimal filter banks have been compared with popular filter banks such as Cohen–Daubechies–Feauveau biorthogonal wavelet FBs, time–frequency optimized half-band pair FBs and maximally flat half-band pair FBs. The performance of optimal filter banks has been found better in terms of joint time–frequency localization.     

一类冗余比为2的二维DFT调制滤波器组的设计

本文构建了一类冗余比为2的二维线性相位的双原型离散傅立叶变换（DFT）调制滤波器组。利用原型滤波器的多相位分解,推导出了该滤波器组的完全重构(PR)条件。基于该PR条件,我们将滤波器组的设计归结为一个关于原型滤波器的多相位分量的无约束优化问题。由于原型滤波器是线性相位的,多相位分量之间具有一定的关系,因此我们可以简化该优化问题。仿真结果验证了滤波器组PR条件的正确性。同时,仿真表明了优化算法的有效性,设计所得的滤波器组重构误差很小、频率特性较好,基本满足实际应用的需要。      

A direct approach to the design of QMF banks via frequency domainoptimization

This paper studies the design of quadrature mirror filter (QMF) banks via frequency domain optimization. A direct approach is adopted that gives the necessary and sufficient condition for perfect reconstruction (PR). While analysis filter banks are designed to achieve frequency domain specifications required for subband coding, synthesis filter banks are designed to minimize the reconstruction error in frequency domain. The criterion used to measure the reconstruction error is H_∞ or Chebyshev norm (sup-norm). State-space solutions are derived for the H_∞ optimization, and numerical algorithms are developed to obtain the optimal synthesis filter bank. Moreover, the asymptotic PR property is established for optimal H_∞ solution of the synthesis filter bank     

Design of 2D oversampled linear phase DFT modulated filter banks via modified Newton's method

In this paper, the structure of the 2D oversampled DFT modulated filter banks is analyzed and a spatial-domain condition of a filter bank without transfer function distortion is derived. Based upon the spatial-domain condition, a modified Newton's method is presented for fast design of 2D oversampled linear phase (LP) DFT modulated filter banks with nearly perfect reconstruction (NPR). We formulate the design problem into an unconstrained optimization with a fourth-order objective function, which is the weighted sum of the transfer function distortion of the filter bank and the stopband energy of the prototype filter (PF). The optimization is solved by the modified Newton's method, where each of iterations updates the PF by a set of linear equations. It is proved that the iteration process fast converges to a stationary point of the objective function. Compared with the existing methods, the new method is fast in computation and can design 2D filter banks with a large number of subbands.     

General analysis of two-band QMF banks

The two-channel perfect-reconstruction quadrature-mirror-filter banks (PR QMF banks) are analyzed in detail by assuming arbitrary analysis and synthesis filters. Solutions where the filters are FIR or IIR correspond to the fact that a certain function is monomial or nonmonomial, respectively. For the monomial case, the design problem is formulated as a nonlinear constrained optimization problem. The formulation is quite robust and is able to design various two-channel filter banks such as orthogonal and biorthogonal, arbitrary delay, linear-phase filter banks, to name a few. Same formulation is used for causal and stable PR IIR filter bank solutions     

On the optimality of nonunitary filter banks in subband coders

This paper investigates the energy compaction capabilities of nonunitary filter banks in subband coding. It is shown that nonunitary filter banks have larger coding gain than unitary filter banks because of the possibility of performing half-whitening in each channel. For long filter unit pulse responses, optimization of subband coding gain for stationary input signals results in a filter bank decomposition, where each channel works as an optimal open-loop DPCM system. We derive a formula giving the optimal filter response for each channel as a function of the input power spectral density (PSD). For shorter filter bank responses, good gain is obtained by suboptimal half-whitening responses, but the impact on the theoretical coding gain is still highly significant. Image coding examples demonstrate that better performance is achieved using nonunitary filter banks when the input images are in correspondence with the signal model.     

Theory and design of signal-adapted FIR paraunitary filter banks

We study the design of signal-adapted FIR paraunitary filter banks, using energy compaction as the adaptation criterion. We present some important properties that globally optimal solutions to this optimization problem satisfy. In particular, we show that the optimal filters in the first channel of the filter bank are spectral factors of the solution to a linear semi-infinite programming (SIP) problem. The remaining filters are related to the first through a matrix eigenvector decomposition. We discuss uniqueness and sensitivity issues. The SIP problem is solved using a discretization method and a standard simplex algorithm. We also show how regularity constraints may be incorporated into the design problem to obtain globally optimal (in the energy compaction sense) filter banks with specified regularity. We also consider a problem in which the polyphase matrix implementation of the filter bank is constrained to be DCT based. Such constraints may also be incorporated into our optimization algorithm; therefore, we are able to obtain globally optimal filter banks subject to regularity and/or computational complexity constraints. Numerous experiments are presented to illustrate the main features that distinguish adapted and nonadapted filters, as well as the effects of the various constraints. The conjecture that energy compaction and coding gain optimization are equivalent design criteria is shown not to hold for FIR filter banks