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81.
许斌 《数字社区&智能家居》2013,(3):457-462
数据获取是现代网络应用中的重要组成部分,是几乎所有网络操作的前提。下载工具能够帮助用户更加便捷地获取网络资源。该文提出一个基于云存储的离线下载系统,系统保持离线下载原有特色与优点,并引入云存储解决系统存储空间不足和"秒杀"下载率不高的的问题,利用基于文件存储价值的存储更新策略提高云存储系统的存储效率。双机热备技术的引入,有效提高系统整体可靠性。 相似文献
82.
This paper proposes an improved semi-fragile speech watermarking scheme by quantization of linear prediction (LP) parameters, i.e., the inverse sine (IS) parameters. The spectral distortion due to watermark embedding is controlled to meet the ‘transparency’ criterion in speech coding. A modified bit allocation algorithm combined with watermarking is developed to determine the quantization step so that the ‘transparency’ requirement is satisfied. Due to the statistical nature, the LP coefficients estimated from the watermarked speech signal are different from the watermarked LP coefficients even in the absence of attacks. This effect is the cause of increase in decoding error and minimum authentication length. To tackle this problem, an Analysis by Synthesis (AbS) scheme is developed to reduce the difference between the estimated LP coefficients and the watermarked ones. The watermark detection threshold and minimum authentication length are then derived according to the probability of error and the signal to noise ratio (SNR) requirements. Experimental results show that the proposed AbS based method can effectively reduce the difference between the watermarked IS parameter and the extracted IS parameter when there is no attacks. In addition, the modified bit allocation algorithm can automatically find the appropriate quantization step used in the odd-even modulation so that the transparency requirement is satisfied. 相似文献
83.
Precision-oriented search results such as those typically returned by the major search engines are vulnerable to issues of polysemy. When the same term refers to different things, the dominant sense is preferred in the rankings of search results. In this paper, we propose a novel two-box technique in the context of Web search that utilizes contextual terms provided by users for query disambiguation, making it possible to prefer other senses without altering the original query. A prototype system, Bobo, has been implemented. In Bobo, contextual terms are used to capture domain knowledge from users, help estimate relevance of search results, and route them towards a user-intended domain. A vast advantage of Bobo is that a wide range of domain knowledge can be effectively utilized, where helpful contextual terms do not even need to co-occur with query terms on any page. We have extensively evaluated the performance of Bobo on benchmark datasets that demonstrates the utility and effectiveness of our approach. 相似文献
84.
85.
In this paper, we address the problem of fusing multi-focus images in dynamic scenes. The proposed approach consists of three main steps: first, the focus information of each source image obtained by morphological filtering is used to get the rough segmentation result which is one of the inputs of image matting. Then, image matting technique is applied to obtain the accurate focused region of each source image. Finally, the focused regions are combined together to construct the fused image. Through image matting, the proposed fusion algorithm combines the focus information and the correlations between nearby pixels together, and therefore tends to obtain more accurate fusion result. Experimental results demonstrate the superiority of the proposed method over traditional multi-focus image fusion methods, especially for those images in dynamic scenes. 相似文献
86.
Adaptive robust torque control of electric load simulator with strong position coupling disturbance 总被引:2,自引:0,他引:2
Xingjian Wang Shaoping Wang Bin Yao 《International Journal of Control, Automation and Systems》2013,11(2):325-332
Electric load simulator (ELS) is an important equipment to exert aerodynamic load to actuation system according to flight condition. The key issue of ELS is how to eliminate the influence of extra torque caused by actuation system, parametric uncertainties and uncertain nonlinearities. In order to overcome these difficulties, this paper proposes a powerful model-based adaptive robust torque control (ARTC) algorithm which transfers external disturbance elimination problem to a performance-oriented problem under uncertainties and nonlinearities. A discontinuous projection-based online parameter adaptation is employed to reduce the effect of various parameter uncertainties. Instead of discontinuous friction model, a continuous friction model based on smooth shape function is applied for friction compensation. The estimated velocity of actuator is utilized in ARTC controller for eliminating extra torque. The backstepping design via adaptive robust control Lyapunov function is employed to construct ARTC control law for ELS. Extensive comparative results indicate that the proposed ARTC controller is effective to achieve a guaranteed transient as well as final tracking accuracy in the presence of both parametric uncertainties and uncertain nonlinearities. 相似文献
87.
Hong Peng Bin Hu Fang Zheng Dangping Fan Wen Zhao Xuebin Chen Yongxia Yang Qingcui Cai 《Personal and Ubiquitous Computing》2013,17(7):1341-1347
There are a lot of studies on chronic stress assessment applying psychology instruments or hormones analysis. However, there are only few studies using electroencephalogram (EEG), which is a non-invasive method providing objective inspection on brain functioning. In this paper, we analyzed overall complexity and spectrum power of certain EEG bands (theta, alpha and beta) collected from two groups of human subjects—high stress versus moderate stress at prefrontal sites (Fp1, Fp2 and Fpz). The results showed that the differences of nonlinear features (C0, LZC, D2, L1 and RE) and linear features (power and alpha asymmetry score) between two groups are significant. C0, LZC and D2 significantly increased in stress group at Fp1 and Fp2, while L1 and RE significantly decreased. And those with chronic stress have higher left prefrontal power. Finally, we suggest that it may be effective to discriminate the high-stress people from moderate-stress people by EEG. 相似文献
88.
机械机电行业中大量使用设计软件制作的工程图纸,如何从这些图纸中有效和快速的获取其中的明细表信息是一个关键环节.本文针对目前明细表信息提取过程繁琐、效率不高的问题,通过对明细表信息提取方法的阐述,实现了从设计软件图纸中简洁、快速的读取信息的目标.在此基础上还可以把这些信息集成到一个软件中,以便实现和其他软件系统的集成. 相似文献
89.
基于电流场的水下高速数字通信方法及实现 总被引:1,自引:0,他引:1
在水下大容量传感器数据回收的应用中,针对水声通信传输速率低、时延长的缺点,提出了以电场作为信息载体的近距离高速通信方法。基于麦克斯韦方程组推导了该方法的数学模型,讨论了影响通信距离的几个因素。在理论分析的基础上,设计了一套基于数字信号处理器(DSP)的水下电场通信系统,并进行了实验验证。实验表明,该系统可实现近距离码元速率200kbit/s条件下的无误码通信。该通信方法与水下自主航行器(AUV)技术结合,可用于水下物理场监测数据的高效回收。 相似文献
90.