未知参数多项式相位信号的最优检测及性能

根据Neyman-Pearson(NP)准则,利用广义似然比检验方法,给出了未知参数多项式相位信号的最优检测器。在相位多项式次数分别为1或2时,周期图、chirp傅里叶变换检测即为对应的最优检测器。推导了检验统计量的概率密度函数以及虚警概率和检测概率,揭示了多项式相位信号检测中信号能量噪声比、信号参数空间中搜索点数、虚警概率和检测概率之间的关系。仿真结果验证了理论分析的有效性。     

非线性HVS边界提取算子

为对人眼视觉系统(human visual system以下简称HVS)的明暗分界感觉进行较准确的计算机模拟,根据HVS对光强度信号的非线性响应特征,作者对司明状态下的HVS边界感觉机制进行了细致研究,提出新的非线性算子,把该算子用于图像边界提取的计算机模拟,经试验验证,与人眼感觉符合较好.     

指数函数分解法的CPM非相干序列估计

连续相位调制本身所具有的高效频谱和功率利用率使得这种调制方式非常适合应用于无线通信环境中,但其解调的复杂度也随着记忆长度和进制数的增加呈指数增长。该文给出的非相干序列估计算法,通过将大量的参考信号分解成矢量形式,将信号间的相关运算转化为矢量乘法运算,可以有效地降低CPM解调器前端复杂度;在序列译码阶段,采用的是指数窗的截短方法,在不损失性能的前提下有效降低了解调器后端的复杂度。     

应用贪心算法的次最优MC-CDMA检测机(英文)

应用贪心算法提出了一种次最优ＭＣ－ＣＤＭＡ检测机。仿真结果表明，与传统检测机比较，它据有次最优的性能，但结构比最优检测机简单。     

Tracking Edges, Corners and Vertices in an Image

Abstract.  In a range of imaging problems, particularly those where the images are of man-made objects, edges join at points which comprise three or more distinct boundaries between textures. In such cases the set of edges in the plane forms what a mathematician would call a planar graph. Smooth edges in the graph meet one another at junctions, called 'vertices', the 'degrees' of which denote the respective numbers of edges that join there. Conventional image reconstruction methods do not always draw clear distinctions among different degrees of junction, however. In such cases the algorithm is, in a sense, too locally adaptive; it inserts junctions without checking more globally to determine whether another configuration might be more suitable. In this paper we suggest an alternative approach to edge reconstruction, which combines a junction classification step with an edge-tracking routine. The algorithm still makes its decisions locally, so that the method retains an adaptive character. However, the fact that it focuses specifically on estimating the degree of a junction means that it is relatively unlikely to insert multiple low-degree junctions when evidence in the data supports the existence of a single high-degree junction. Numerical and theoretical properties of the method are explored, and theoretical optimality is discussed. The technique is based on local least-squares, or local likelihood in the case of Gaussian data. This feature, and the fact that the algorithm takes a tracking approach which does not require analysis of the full spatial data set, mean that it is relatively simple to implement.     

应用神经网络粒子群算法的多用户检测

为了减少最优多有户检测器的计算复杂度,提出了一种融合粒子群优化算法和神经网络的神经网络粒子群优化算法,并设计了一种解决CDMA通信系统的多用户检测问题的新方法。该方法是把神经网络嵌入到粒子群优化算法的每一代中以改进算法性能。通过混合神经网络到PSO中,还可以加快PSO的收敛速度,减少计算复杂度。仿真结果证明了所设计的检测器无论抗多址干扰能力和抗远近效应能力都优于应用Hopfield神经网络、遗传算法和粒子群算法的多用户检测器。     

An analysis of pulsation periods of long period variable stars

Summary.  We report the results of a period change analysis of time series observations for 378 pulsating variable stars. The null hypothesis of no trend in expected periods is tested for each of the stars. The tests are non-parametric in that potential trends are estimated by local linear smoothers. Our testing methodology has some novel features. First, the null distribution of a test statistic is defined to be the distribution that results in repeated sampling from a population of stars. This distribution is estimated by means of a bootstrap algorithm that resamples from the collection of 378 stars. Bootstrapping in this way obviates the problem that the conditional sampling distribution of a statistic, given a particular star, may depend on unknown parameters of that star. Another novel feature of our test statistics is that one-sided cross-validation is used to choose the smoothing parameters of the local linear estimators on which they are based. It is shown that doing so results in tests that are tremendously more powerful than analogous tests that are based on the usual version of cross-validation. The positive false discovery rate method of Storey is used to account for the fact that we simultaneously test 378 hypotheses. We ultimately find that 56 of the 378 stars have changes in mean pulsation period that are significant when controlling the positive false discovery rate at the 5% level.     

Difficulties with estimating city-wide urban forest cover change from national, remotely-sensed tree canopy maps

Two datasets of percent urban tree canopy cover were compared. The first dataset was based on a 1991 AVHRR forest density map. The second was the US Geological Survey’s National Land Cover Database (NLCD) 2001 sub-pixel tree canopy. A comparison of these two tree canopy layers was conducted in 36 census designated places of western New York State. Reference data generated by photo-interpreting the tree cover on 1994 and 2002 orthoimages were compared on a city-wide basis to estimates of the tree cover derived from the AVHRR and NLCD tree canopy maps. Comparison of the AVHRR-based estimate with the 1994 photo-interpreted reference showed low accuracy and high variability. The comparison between the NLCD-derived estimate and 2002 photo-interpreted values had higher accuracy but shows a consistent under prediction bias for all tree cover values. In comparing the two photo-interpreted reference sets, little actual change was detected for this study region. Assessing change using differences between the imagery-based AVHRR and NLCD urban tree cover datasets is shown to lead to erroneous results.     

也说“求放心”说与百回本《西游记》大旨——兼与石钟扬先生商榷

自《西游记》于明代中后期问世以来，从心学角度探求作品之大旨成为《西游记》研究的主线，且在当代仍有广泛的影响。石钟扬先生提出谢肇淛“求放心”说有违《西游记》大旨的疑问，对于深入认识《西游记》有一定的启示意义，但在立论和证据方面存在着诸多偏颇，对心学与《西游记》的关系、“求放心之喻”的主题观似不能作彻底的否定。     

Testing with a nuisance parameter present only under the alternative: a score-based approach with application to segmented modelling

ABSTRACT

We introduce a score-type statistic to test for a non-zero regression coefficient when the relevant term involves a nuisance parameter present only under the alternative. Despite the non-regularity and complexity of the problem and unlike the previous approaches, the proposed test statistic does not require the nuisance to be estimated. It is simple to implement by relying on the conventional distributions, such as Normal or t, and it justified in the setting of probabilistic coherence. We focus on testing for the existence of a breakpoint in segmented regression, and illustrate the methodology with an analysis on data of DNA copy number aberrations and gene expression profiles from 97 breast cancer patients; moreover some simulations reveal that the proposed test is more powerful than its competitors previously discussed in literature.