A proposed expert system for word sense disambiguation: deductive ambiguity resolution based on data mining and forward chaining

One of the major issues in the process of machine translation is the problem of choosing the proper translation for a multi‐sense word referred to as word sense disambiguation (WSD). Two commonly used approaches to this problem are statistical and example‐based methods. In statistical methods, ambiguity resolution is mostly carried out by making use of some statistics extracted from previously translated documents or dual corpora of source and target languages. Example‐based methods follow a similar approach as they also make use of bilingual corpora. However, they perform the task of matching at run‐time (i.e. online matching). In this paper, by looking at the WSD problem from a different viewpoint, we propose a system, which consists of two main parts. The first part includes a data mining algorithm, which runs offline and extracts some useful knowledge about the co‐occurrences of the words. In this algorithm, each sentence is imagined as a transaction in Market Basket Data Analysis problem, and the words included in a sentence play the role of purchased items. The second part of the system is an expert system whose knowledge base consists of the set of association rules generated by the first part. Moreover, in order to deduce the correct senses of the words, we introduce an efficient algorithm based on forward chaining in order to be used in the inference engine of the proposed expert system. The encouraging performance of the system in terms of precision and recall as well as its efficiency will be analysed and discussed through a set of experiments.     

面向飞行器交会对接应用的载波相位差分技术研究

GNSS引导两飞行器交会对接的前提是实时可靠地估计相位模糊度。针对卫星和飞行器的高动态性所引发的频繁换星问题,提出一种实时递归相位模糊度估计方法。该算法能够有效处理失锁所造成的卫星起落现象,同时充分利用历史观测与当前观测方程中部分模糊度分量的关联性,使得模糊度估计的成功率对可见卫星数目的减少不敏感。为了验证该算法在空间飞行器对接中的精度和成功率,采用GPS模拟器仿真两飞行器近程导引段和最终逼近段的过程,应用新算法实时估计两飞行器间相对位置,精度达到亚厘米级水平,成功率在可见星数递减时依然渐进逼近100%。     

考虑换件维修代价的测试优化选择

测试优化选择是测试性设计工作的基础,保证选择的测试对被测系统具有较好的故障检测率和故障隔离率是测试优化选择的重要约束。从装备换件维修的角度,通过对故障模糊组分析,可知换件维修代价对测试选择结果具有重要影响。基于相关性矩阵,在分析装备换件维修对测试选择的影响基础上,以测试代价和维修代价最小为优化目标,以故障检测率、故障隔离率为约束,建立了考虑换件维修代价的数学模型,并采用混沌二进制粒子群算法求解。仿真实例结果表明,考虑换件维修代价的测试优化选择模型更加符合工程实际,选择结果更加准确和可靠。     

改进LMD及高阶模糊度函数的管道泄漏定位

针对天然气管道泄漏定位的问题,提出一种基于改进局域均值分解(LMD)及高阶模糊度函数的时延估计方法。该方法首先采用改进的LMD对声发射信号进行分解,获得多个PF分量,进而提出根据K-L散度的PF分量自动选择算法,获取含有主要泄漏信息的PF分量,在此基础上,研究了基于高阶模糊度函数计算声发射信号的时频参数,并通过时频分析获取特征频率的到达时间差,最后结合泄漏产生的广义声发射信号的传播速度完成对天然气管道泄漏的定位。实验结果表明,提出的方法能够进行定位且精度较直接相关法明显提高。     

幅相不一致对沃森-瓦特测向的影响及解决方法

针对沃森-瓦特测向处理中幅相不一致对定单向及测向准确度的影响问题,分析了定单向法则失效的原因,提出了针对参考通道输出信号的全相位校正方法.利用该方法获取的最优相位修正量对参考通道输出信号进行移相处理,使测向通道与参考通道输出信号之间的相位关系满足定单向法则的要求,提高了定单向方法的稳健性.通过对测向误差特性的分析,给出了因测向通道间幅相误差导致的测向误差表达式,提出了利用最小二乘法计算误差曲线的拟合参数,从而可实现利用有限区域内的测向误差测量数据对全方位测向误差的估计,提高测向的准确度.通过仿真验证了提出方法的有效性.     

多基线干涉仪解模糊算法

对辐射源进行无源定位常用的一种测向体制为多基线正交干涉仪体制。该体制设备在测向工作时,由于相位的周期性模糊问题会导致测向结果产生错误,即产生测向模糊。主要针对多基线干涉仪测向模糊问题进行分析,介绍了工程实现过程中常用的几种解模糊算法,通过仿真得出各种算法的在相同条件下的无模糊概率,并且给出了工程实现建议。     

Relationships among health perceptions vary depending on stage of readiness for colorectal cancer screening.

Objective: We explored whether relationships among health perceptions differ depending on individuals' stage of readiness for colorectal cancer screening (CRCS). Methods: Data from the National Cancer Institute's Health Information National Trends Survey (HINTS) were used to stage adults over 50 years of age (N = 2324) using a modified version of the Precaution Adoption Process Model (PAPM) staging algorithm. Health perceptions examined included perceived risk of cancer, worry about cancer, fatalism, and beliefs about ambiguity of cancer prevention recommendations. Results: Meaningful differences in patterns of relationships among health perceptions by stage were found. Conclusions: The nonlinear patterns that emerged indicate support for the role of these health perceptions in screening, the idea that behavioral readiness may moderate the relationship between important health perceptions, and the use of the stage construct in this context. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A parametric method for non-stationary interference suppression in direct sequence spread-spectrum systems

The problem of non-stationary interference suppression in direct sequence spread-spectrum (DS-SS) systems is considered. The phase of interference is approximated by a polynomial within the considered interval. According to the local polynomial Fourier transform (LPFT) principle, the received signal is dechirped by using the obtained phase approximation and the interference is, in turn, suppressed by excising the corrupted low-pass frequency band. For the estimation of polynomial coefficients, we use the product high-order ambiguity function (PHAF), known for its capability to successfully resolve components of a multicomponent polynomial-phase signal (PPS). The proposed method can suppress interferences with both polynomial and non-polynomial phase. In addition, it can suppress both monocomponent and multicomponent interferences. The simulations show that the proposed method outperforms time-frequency (TF) methods, that successfully deal with multicomponent interferences, in terms of the error probability and computational complexity.     

地面雷达数据处理系统设计

针对目前地面雷达数据处理中存在的目标多,机动性强,地面杂波强,虚警率高等问题,采用并设计了解速度模糊、点迹凝聚、航迹处理等算法,结合软件编程技术,对信号处理后的数据进行综合处理,经过雷达外场鉴定试验测试,数据处理使雷达的发现概率、虚警率、方位距离精度、速度分辨力等指标各提高了约十个百分点。     

星载SAR方位模糊研究

本文根据方位模糊产生机理详细分析了方位向成像处理参数、波长、方位方向图副瓣对方位模糊的影响.通过分析可知:方位分辨率相同时,低频段SAR系统模糊问题更严重,但可通过提高重频、压低方向图副瓣电平等方法可改善方位模糊,最后仿真验证了上述结论并给出改善方位模糊的设计考虑.