近无损压缩算法在HOLTER系统中的应用研究

以单片机为主控器件的HOLTER(动态心电监护仪)系统的实时性和临床诊断的保真度要求都较高,这就要求使用于其上的压缩算法应简单高效且近无损,而目前针对此类设备的压缩算法虽然有较高的压缩率,但失真度和复杂度也较高。本文提出一种针对HOLTER系统的低复杂近无损预测算法,实验表明,该方法在保证一定压缩率的条件下,具有很好的实时性和保真度。     

Fidelity-guaranteed robustness enhancement of blind-detection watermarking schemes

Watermarking performance enhancement has always been a difficult task since the performance metrics of watermarking systems, i.e., fidelity, robustness, and payload size, inherently conflict with each other. Nowadays, most watermarking schemes hide payloads according to predefined rules or empirical perceptual models. Therefore, the performance of digital watermarking schemes can be determined only passively. In this study, a genetic algorithm-based framework for watermarking performance enhancement is proposed. Watermarked results having better robustness, guaranteed fidelity, and fixed payload size can be obtained. Existing blind-detection watermarking schemes can be improved significantly by incorporating the proposed framework. In addition, the proposed framework has many desirable advantages such as asymmetric embedding/detection overhead, easy integration with existing data-hiding schemes, and direct control over fidelity and robustness.     

频率域上的分形图象编码

研究了频率域上的分形图象编码，与空间域上的分形图象编码相比，它有两个突出的特点：分阶的亮度变换和几何变换的简化与合并。本文的理论分析和实验数据都表明，无论是在编码时间和压缩比方面，还是在解码的收敛性和图象保真度方面，频率域上的分形图象编码都要优于相应的空间域上的分形图象编码。     

Update strategies for kriging models used in variable fidelity optimization

Many optimization methods for simulation-based design rely on the sequential use of metamodels to reduce the associated computational burden. In particular, kriging models are frequently used in variable fidelity optimization. Nevertheless, such methods may become computationally inefficient when solving problems with large numbers of design variables and/or sampled data points due to the expensive process of optimizing the kriging model parameters in each iteration. One solution to this problem would be to replace the kriging models with traditional Taylor series response surface models. Kriging models, however, were shown to provide good approximations of computer simulations that incorporate larger amounts of data, resulting in better global accuracy. In this paper, a metamodel update management scheme (MUMS) is proposed to reduce the cost of using kriging models sequentially by updating the kriging model parameters only when they produce a poor approximation. The scheme uses the trust region ratio (TR-MUMS), which is a ratio that compares the approximation to the true model. Two demonstration problems are used to evaluate the proposed method: an internal combustion engine sizing problem and a control-augmented structural design problem. The results indicate that the TR-MUMS approach is very effective; on the demonstration problems, it reduced the number of likelihood evaluations by three orders of magnitude compared to using a global optimizer to find the kriging parameters in every iteration. It was also found that in trust region-based method, the kriging model parameters need not be updated using a global optimizer—local methods perform just as well in terms of providing a good approximation without affecting the overall convergence rate, which, in turn, results in a faster execution time.     

应用保真地震处理技术和层序地层学方法预测非构造圈闭

本文针对预测非构造圈闭这一油气勘探焦点问题,选择松辽盆地南部有利探区梨树断陷为研究区,采用保真地震处理技术对部分地震资料进行处理,首次应用层序地层学方法,综合地震、地质以及钻井资料,对区域沉积特征进行了剖析,将目的层划分为4个超层序和16个层序,确定了区域隐伏的湖底扇成因非构造圈闭,证明了保真地震处理技术与层序地层学方法的优越性和有效性。     

基于灰色理论的飞行模拟器逼真度评估

飞行模拟器的逼真度评估,先建立影响其逼真度各指标层次结构,确定评分等级标准.再确定评价指标权重、专家评分、定义评价样本矩阵、确定评价灰类及其灰色评价系数和灰色评价权向量与权矩阵、对相关参数作综合评价,计算其各指标权重值及逼真度评价值.对调查结果分析表明,得出评价结果与受训人员评价一致.     

移动数据传输安全性研究

在深入分析移动数据传输的基础上,重点研究数据传输的安全性。以具有数据采集功能的移动终端为研究对象,提出了较为合理的系统架构,综合考虑网络连通性、服务器状态、数据传输稳定性等多方面因素,保证了数据的安全传输。针对Wi-Fi、GPRS等连网方式,编程实现了网络自动连接、切换,保障了网络的连通性,对类似的工程有一定的指导意义。     

一种有效保真的等值线数字化方法

介绍了一种等值线数字化及简洁有效的保真方法.     

Fractal based ultra-wideband antenna development for wireless personal area communication applications

This paper presents a bandwidth enhanced, compact planar ultra-wideband antenna design for wireless personal area communication (WPAN) applications. The proposed antenna has fractal based geometry and is constructed using several iterations of a pentagon slot inside a circular metallic structure. The partial ground plane of the basic radiator is tapered, defected and a U slit is etched out from the microstrip feed to improve the −10 dB |S11| bandwidth. The proposed fractal based antenna has an impedance bandwidth from 2.9 GHz to 15 GHz with low profile configuration and is fabricated on FR4 substrate with dimensions of 32 mm × 32 mm × 1.6 mm. To authenticate the designed prototype, the antenna is fabricated and tested for impedance and radiation characteristics. The designed antenna has stable radiation characteristics in the operating band. Furthermore, the antenna is validated for its applicability in WPAN, by calculating fidelity factor through time domain analysis along with the transmission coefficient and group delay measurements.     

航天遥感图象压缩技术的最新发展

介绍了当今图象压缩技术的发展现状，以及航天遥感数据压缩技术的应用现状，探讨了上前各种图象压缩技术的特点，并说明了各种技术应用航天遥感的可能性，对将来我国航天遥感星载无损压缩，有损压缩以及地面数据压缩提出了建议。