International Journal of Automation and Power Engineering
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Open Access journal
ISSN (Print) 2161-6442 - ISSN (Online) 2161-5055
Published by Science and Engineering Publishing Company [49 journals]
- Design of Portable ECG Monitoring System Based on LM4F120H5QR
Abstract: Design of Portable ECG Monitoring System Based on LM4F120H5QR
Author Shengqian MaXiaoyong NiMei Qi
The ECG acquisition circuit in the market now exists such defects as having complex structure , large size, high power consumption and overpriced, so to design a portable ECG monitor without the above mentioned disadvantages is urgently needed. The monitor designed by this paper uses ARM Cortex-M4 core processor LM4F120H5QR, and selects ADAS1000-3 as signal acquisition unit to reduce the amplification processing of ECG signals, in order to have a long period of ECG monitoring, the SD card is used as the storage medium. To realize the multi task processing and application management, the RT-Thread operating system is adopted. The digital signal processing technology is implemented by programming to replace the hardware filtering processing, which can save the circuit board size and reduce the power consumption. At the same time,the use of GPRS module for remote data transmission with PC monitoring interface can help doctors a remote diagnosis. Slave computer displays the collected ECG signal waveform and information on Colour LCD screen. After the comprehensive simulations and prototype tests, the results show that the system can achieve the success of the ECG signal acquisition, processing, storage, display and remote transmission. That’s the instrument has a good prospect.
- Robust Speaker Verification Using Improved PNCC Based on GMM-UBM
Abstract: Robust Speaker Verification Using Improved PNCC Based on GMM-UBM
Author XinXing JingBingwei XiangHaiYan YangPing Zho
Focused on the issue that the robustness of traditional Mel Frequency Cepstral Coefficient (MFCC) feature degrades drastically in speaker verification in noisy environments, a kind of suitable extraction method for low SNR environments based on Gaussian Mixture Model-Universal Background Model (GMM-UBM) and improved Power Normalized Cepstral Coefficient (PNCC) is proposed. First, the PNCC feature is extracted after the Voice Activity Detection (VAD), which uses long term analysis to remove the effect of background noise. Then, Cepstral Mean Variance Normalization (CMVN), Feature Warping and other methods are used to improve PNCC. Finally, GMM-UBM-MAP is set as the baseline system for speaker verification test with TIMIT speech database, the robustness of four different features (MFCC, GFCC, PNCC and improved PNCC) are analyzed and compared in different noisy conditions. The experimental results indicate that MFCC has achieved the highest recognition rate under the environment of clean speech. By mixing the test speech with sine noises, the improved PNCC is more robust against different low-SNR noises than other original features and its Equal Error Rate (EER) reduce significantly in low-SNR noise environments.
- In Vitro Estimation of Initial Stability of a Cementless Stem Made of
Shape Memory Alloy
Abstract: In Vitro Estimation of Initial Stability of a Cementless Stem Made of Shape Memory Alloy
Author Masaru HigaTakuya TuchihashiTomoki JonoshitaMasayoshi AboSatoshi Kakuna
The success of total hip arthroplasty (THA) in improving joint function and reducing pain is regarded as one of the great achievements of modern medicine. For a cementless THA stem, however, lack of initial stability leads to thigh pain and eventual loosening of the stem because of a loss of bone integration on the stem surface or continuous bone resorption around the stem. Obtaining adequate initial stability is one of the important factors for good short-term and long-term clinical outcomes. While most of the cementless stems are made of either cobalt-chrome-molybdenum (CoCrMb) or titanium-aluminum-vanadium (TiAlV) alloys, we have focused on an expandable cementless stem utilizing nickel-titanium (Ni-Ti) shape memory alloy (SMA). In this study, the expandable stem with SMA was evaluated in vitro, specifically testing to determine if the stem is able to achieve rigid initial stability in a medullary cavity under cyclic loadings. The proposed stem has Ni-Ti SMA expandable blades on the stem surfaces. For shape memorization, the SMA was restrained at an expanded shape under appropriate thermo-mechanical treatments. At the time of implantation into bone, the SMA with a contracted shape was kept below the martensite transformation temperature. After implantation, the SMA blades undergo reverse transformation due to body temperature, accompanied by a change from the contracted shape to the expanded shapes. The shape change results in a residual pressure between the bone and the stem. In mechanical tests, the stem with SMA showed better initial stability, in terms of relative micromotions at the stem-bone interface, under cyclic loadings. After 120 loadings, micromotion of 11 m was observed on the stem with SMA, while the micromotion on the stem without SMA was 122 m. Use of an expandable stem utilizing SMA is effective enough for rigid initial stability.