改进小波阈值算法在心电信号去噪中的应用

心电信号（ECG）在采集的过程中总是参杂着各种噪声,可利用小波变换基本原理和方法进行去噪处理。对小波多分辨率理论进行研究后,在分析Donoho的软、硬阈值去噪法的基础上,提出一种改进阈值函数量化方法,改进阈值函数能克服软、硬阈值存在的缺陷,运用MIT-BIH心电数据库进行验证,并对ECG 信号用不同方法去噪后的结果进行了分析比较。实验表明,改进阈值方法可以有效地去除不同噪声干扰,在信噪比指标上也明显优于常用的软、硬阈值去噪方法。     

小波熵在心电高频噪声处理和R波检测中应用

为了在滤除噪声的同时不丢失信号有用信息,将小波熵理论与小波阈值去噪方法综合起来,提出一种基于小波熵的自适应阈值去噪和R波峰值定位方法,对心电信号高频噪声不同信噪比情况做了去噪处理,并同小波熵最优阈值法做了对比分析,结果表明,本算法可以自适应地确定小波系数阈值,不需要直接处理大量的小波系数,且具有良好的滤波性能,尤其在噪声严重时,去噪和R波检测效果更优。最后对实测和数据库中46例数据都做了应用分析,表明本算法具有快速性、有效性和稳定性的特点。     

Optimal placements of replicas in a ring network with majority voting protocol

In a distributed database system, data replicas are placed at different locations to achieve high data availability in the presence of link failures. With a majority voting protocol, a location survives for read/write operations if and only if it is accessible to more than half of the replicas. The problem is to find out the optimal placements for a given number of data replicas in a ring network. When the number of replicas is odd, it was conjectured by Hu et al. [X.-D. Hu, X.-H. Jia, D.-Z. Du, D.-Y. Li, H.-J. Huang, Placement of data replicas for optimal data availability in ring networks, J. Parallel Distrib. Comput., 61 (2001) 1412–1424] that every uniform placement is optimal, which is proved by Shekhar and Wu later. However, when the number of replicas is even, it was pointed out by Hu et al. that uniform placements are not optimal and the optimal placement problem may be very complicated. In this paper, we study the optimal placement problem in a ring network with majority voting protocol and an even number of replicas, and give a complete characterization of optimal placements when the number of replicas is not too large compared with the number of locations.     

远程心电监护系统的测试用例设计

文中以远程心电监护系统的测试为例,阐述了如何灵活采用等价类划分等多种黑盒测试技术来设计测试用例,同时兼具考虑测试用例的复用性。     

Frequency estimation of a sinusoidal signal via a three-point interpolated DFT method with high image component interference rejection capability

This paper proposes a three-point Interpolated Discrete Fourier Transform (IpDFT) method for frequency estimation of a discrete-time sinusoidal signal. It is based on the maximum sidelobe decay (MSD) windows and is highly effective in rejecting the detrimental effect on the estimation accuracy due to the image component of the signal spectrum. This remarkable feature is achieved by using an analytical expression based on a suitable weighting of the three largest DFT spectrum samples. The proposed method provides good results when the effect of the spectral interference due to the image component dominates other estimation error sources. The accuracy of the proposed method and of other state-of-the-art methods such as the multi-point IpDFT methods and the four-parameter sine-fitting (4PSF) algorithm are compared through both computer simulations and experimental results in the case of ideal, noisy, and harmonically distorted sinusoids. A small number of acquired cycles is assumed in order to analyze situations in which the contribution from the image component interference is significant. The performed comparison shows that the proposed method outperforms the considered multi-point IpDFT methods when the Signal-to-Noise Ratio (SNR) is higher than 30 dB and the number of acquired cycles is enough small. The proposed method outperforms also the 4PSF algorithm when the frequency estimation error is dominated by harmonics rather than wideband noise.     

无线数传技术在远程心电监护系统中的应用

心脏病是严重威胁人类健康和生命的主要疾病之一.现有的远程心电监护系统存在难以充分释放医院的专业资源、服务范围有限等不足,将心电监护从医院扩展到家庭,实现远程监护具有非常重要的现实意义.本文讨论了利用无线数传技术实现远程心电数据采集的解决方案,使用PTR2000无线通信模块设计了便携式心电数据采集发送盒和心电数据接收转发器,实现了对病人心电数据的远程采集和传输,为通过宽带网实现病人心电数据的远程采集和传输创造了条件.     

无线数传技术在远程心电监护系统中的应用

1 IntroductionH eartdisease is one ofm ain diseases m enace hu-m an' s health. According to relevantinform ation, showin Am erica, Japan and Europe, death rate ofheartdis-ease is the firstin population diseases,hold the positionof third in place in china.…     

Evaluating the effectiveness of FDM in identifying important factors in a dynamic flowshop

Dynamic events such as machine breakdown and hot jobs may induce problems on the production system such as order delay, increasing machine load, and changing inventory level. Past studies of dynamic events often use traditional design of experiments (DOE) to analyze the effects of dynamic events on system's performance. The shortcoming of this approach is that the number of experimental runs conducted would become exponentially increased as the number of factors increased. This study tries to use frequency domain methodology (FDM) instead so as to detect the higher order effects and rank important factors in a few experimental runs. Spectrum analysis is used to comprehend the effects of different location of machine breakdown and different size of hot jobs on the system's performance of flowshops with different traffic (utilization) and stability (oscillation). This study finds that the important factors identified by the FDM analysis are the same as that of DOE. However, only in some cases can the rankings of important factors be the same for both approaches. The dissimilarity between rankings of important factors found by these two methods is further measured using Kendall tau distance.     

同步脉搏心电信号的非线性分析

对同步脉搏信号和心电信号进行处理,获取脉搏信号和心电信号的间期序列P R及R R;采用非线性动力学理论与方法,计算非线性特征参数最大Lyapunov指数和近似熵ApEn,并进行相关性分析。从而分析比较同步脉搏和心电信号的相关性。结果表明,同步脉搏信号和心电信号的非线性指标也具有较好的相关性。说明可以通过对人体脉搏波的分析了解人体心脏的搏动情况,为人体心血管疾病的预防和诊断提供一种新的途径和辅助手段。     

Determination of vitality from a non-invasive biomedical measurement for use in fingerprint scanners

Fingerprints are the oldest and most widely used biometrics for personal identification. Unfortunately, it is usually possible to deceive automatic fingerprint identification systems by presenting a well-duplicated synthetic or dismembered finger. This paper introduces one method to provide fingerprint vitality authentication in order to solve this problem. Detection of a perspiration pattern over the fingertip skin identifies the vitality of a fingerprint. Mapping the two-dimensional fingerprint images into one-dimensional signals, two ensembles of measures, namely static and dynamic measures, are derived for classification. Static patterns as well as temporal changes in dielectric mosaic structure of the skin, caused by perspiration, demonstrate themselves in these signals. Using these measures, this algorithm quantifies the sweating pattern and makes a final decision about vitality of the fingerprint by a neural network trained by examples.     

数字滤波器在实时滤除心电干扰中的设计与应用

在医疗电子中的心电(ECG)监护仪的设计中,针对心电信号的特殊信号和干扰频率范围,进行了分析,并且设计了一个基于零极点对消的简单整系数滤波器,该滤波器具有严格线性相位,稳定性能好,利用DSP汇编语言进行算法的实现,提高了计算速度,有效地滤除了干扰。     

Towards an accurate sleep apnea detection based on ECG signal: The quintessential of a wise feature selection

A wise feature selection from minute-to-minute Electrocardiogram (ECG) signal is a challenging task for many reasons, but mostly because of the promise of the accurate detection of clinical disorders, such as the sleep apnea. In this study, the ECG signal was modeled in order to obtain the Heart Rate Variability (HRV) and the ECG-Derived Respiration (EDR). Selected features techniques were used for benchmark with different classifiers such as Artificial Neural Networks (ANN) and Support Vector Machine(SVM), among others. The results evidence that the best accuracy was 82.12%, with a sensitivity and specificity of 88.41% and 72.29%, respectively. In addition, experiments revealed that a wise feature selection may improve the system accuracy. Therefore, the proposed model revealed to be reliable and simpler alternative to classical solutions for the sleep apnea detection, for example the ones based on the Polysomnography.     

Age differences and the acquisition of spatial knowledge in a three-dimensional environment: Evaluating the use of an overview map as a navigation aid

This study examined age differences in the use of an electronic three-dimensional (3D) environment, and how the age differences were affected by the use of an overview map as a navigation aid. Task performance and the subjects’ acquisition of configural knowledge of the 3D-environment were assessed. Impact of spatial ability and prior experience on these measurements were also investigated. One group of older subjects (n=24) and one group of younger subjects (n=24) participated. An overall hypothesis for the work presented here was that differences in learning to and performing navigational tasks in the physical world are similar in learning and performing navigational tasks in the virtual world. The results showed that the older participants needed more time to solve the tasks; and similar to navigation in the physical world, the older participants were less likely to create configural knowledge. It could not be established that older participants benefited more from an overview map as cognitive support than younger subjects, except in the subjective sense: the older users felt more secure when the map was there. The map seemed to have supported the older users in creating a feeling of where objects were located within the environment, but it did not make them more efficient. The results have implications for design; in particular, it brings up the difficult issue of balancing design goals such as efficiency in terms of time and functionality, against maintaining a sense of direction and location in navigational situations.     

The use of turnover rate as a passive surveillance indicator for potential low back disorders

Passive surveillance techniques which rely only on injury reporting to locate ergonomic problems within a facility may not be sensitive enough to identify all jobs that place a worker at risk of low back disorder. The current study examines whether turnover rate data provide useful input to a passive surveillance approach. It is hypothesized that the turnover of employees through individual jobs, when not attributable to differential pay scales within a facility, is likely to indicate the presence of ergonomic hazards associated with low back cumulative trauma disorders. This study used the database and multiple logistic regression model developed by Marras et al. (1993) to evaluate this hypothesis. Two data sets were evaluated with the model to determine whether jobs with turnover resemble those with a high historical risk of LB-CTD. The first data set contained trunk motion and workplace data from jobs in which there had been turnover but there were no incidents of LB-CTD. When comparing these data to truly low risk jobs (no LB-CTD incidents or turnover), the model yielded an odds ratio of 5·2. This moderate odds ratio indicates that many of the jobs with turnover have characteristics similar to those found in high LB-CTD risk jobs. The second data set included jobs with turnover and moderate LB-CTD incident rates. The model's resulting odds ratio of 11·0 indicates that jobs with moderate incident rates and turnover are very similar to jobs with a high LB-CTD risk. These results suggest that passive surveillance programs would be more sensitive if turnover rates were determined for each job within a facility and were used to supplement incident rate data.     

Evaluating the precision of eight spatial sampling schemes in estimating regional means of simulated yield for two crops

We compared the precision of simple random sampling (SimRS) and seven types of stratified random sampling (StrRS) schemes in estimating regional mean of water-limited yields for two crops (winter wheat and silage maize) that were simulated by fourteen crop models. We found that the precision gains of StrRS varied considerably across stratification methods and crop models. Precision gains for compact geographical stratification were positive, stable and consistent across crop models. Stratification with soil water holding capacity had very high precision gains for twelve models, but resulted in negative gains for two models. Increasing the sample size monotonously decreased the sampling errors for all the sampling schemes. We conclude that compact geographical stratification can modestly but consistently improve the precision in estimating regional mean yields. Using the most influential environmental variable for stratification can notably improve the sampling precision, especially when the sensitivity behavior of a crop model is known.     

Evaluating the use of synchronous communication in two blended courses

Abstract Residential universities are increasingly integrating online interaction within courses in the form of synchronous online chats, asynchronous online discussions and access to interactive resources. This article evaluates the educational effectiveness of online chats within a Humanities postgraduate course and a final year Commerce course. We consider the roles of course design, group dynamics, and facilitation style in the successful use of online collaboration within primarily face‐to‐face courses, as well as the potential for online collaboration within a blended course design to facilitate more inclusive learning conversations than are possible with exclusively face‐to‐face interaction.     

Impulsive noise suppression in the case of frequency estimation by exploring signal sparsity

The frequency estimation problem is addressed in this work in the presence of impulsive noise. Two typical scenarios are considered; that is, the received data are assumed to be uniformly sampled, i.e., without data missing for the first case and data are randomly missed for the second case. The main objective of this work is to explore the signal sparsity in the frequency domain to perform frequency estimation under the impulsive noise. Therefore, to that end, a DFT-like matrix is created in which the frequency sparsity is provided. The missing measurements are modeled by a sparse representation as well, where missing samples are set to be zeros. Based on this model, the missing pattern represented by a vector is indeed sparse since it only contains zeros and ones. The impulsive noise is remodeled as a superposition of a unknown sparse vector and a Gaussian vector because of the impulsive nature of noise. By utilizing the sparse property of the vector, the impulsive noise can be treated as a unknown parameter and hence it can be canceled efficiently. By exploring the sparsity obtained, therefore, a joint estimation method is devised under optimization framework. It renders one to simultaneously estimate the frequency, noise, and the missing pattern. Numerical studies and an application to speech denoising indicate that the joint estimation method always offers precise and consistent performance when compared to the non-joint estimation approach.     

汉字编码输入法动态评测系统的设计和实现

论文首先介绍了汉字编码输入法的现状以及通用要求标准,提出了对汉字编码输入法进行科学评测的重要性和意义,描述了输入法动态评测系统的方法,指出了影响动态评测结果的因素,描述了系统的主要功能,详细介绍了动态评测子系统的设计和实现过程,并给出了详实的测试数据。介绍的汉字输入法评测系统,可以作为探讨国家有关标准和规范的辅助工具。对汉字编码发明者和输入系统设计人员而言,该评测系统有很高的使用价值,对建立科学的输入法评价体系而言,该评测系统也有十分积极的意义。     

Evaluating the perceived and estimated quality in use of Web 2.0 applications

Web 2.0 refers to a new generation of web applications where individuals are able to participate, collaborate, and share created artefacts. Despite the fact that Web 2.0 applications are widely used for both educational and professional purposes, a consolidated methodology for their evaluation is still not available. This paper presents and discusses the results of two empirical studies on the case of mind mapping and diagramming Web 2.0 applications. Both studies employed logging actual use method to measure the estimated quality in use, while the retrospective thinking aloud method and an online questionnaire were applied to assess the perceived quality in use. Achieved analytical results showed that the results of the estimated and the perceived quality in use match partially, which indicates that quality in use should be measured with both subjective and objective instruments. The work presented in this paper is the first step towards a comprehensive methodology for evaluating the quality in use of Web 2.0 applications. Consequently, the usage of the proposed quality in use model for other types of Web 2.0 applications as well as contexts of use needs to be investigated in order to draw generalizable conclusions.     

Evaluating the use of learning objects in Australian and New Zealand schools

The Le@rning Federation, an agency funded by Australian and New Zealand governments, initiated a Field Review project as the start of a long-term research study to evaluate the impact, application and effectiveness of the online digital content developed according to the learning object model. In terms of content, the pilot Field Review found that many learning objects provided stimulating and diverse learning experiences for students. It is one of the potential strengths of learning objects that they are able to provide new geographical experiences and simulate dangerous or expensive learning activities at low relative cost.