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Biomedical subjects

Chongxun Zheng

Publications and source records attributed to Chongxun Zheng.

12 recordsLinked to original sources
PubMed2005

[Experimental study of excitation of peripheral nerves in transverse electric field stimulation].

The classical cable function has been used to represent the response of peripheral nerves stimulated by external parallel electric field. Experiments show that peripheral nerves can be activated by perpendicular electric field induced by magnetic pulses, indicating that the activation mechanism needs to be thoroughly investigated. Several excitation properties of peripheral nerves in transverse-field were explored in the present paper. With a human's median nerve in vivo, stimulation threshold, excitation position and the relation between excitation threshold and fiber's radius were studied. The relation between stimulation threshold and stimulation duration was researched with sciatic nerves from toad in vitro. The experimental results verify that the modified cable function is much efficient than the classical cable function. The research will improve the nerve magnetic stimulating technique and be beneficial to further application.

Animals↗
PubMed2005

[Digital watermarking for electroencephalogram compression].

In this paper, digital watermarking and EEG compression are introduced firstly, and then a number of digital watermarking methods are explored to resolve the problem of integrality and authenticity in EEG compression. At last, the current state of this technique inside and outside country is summarized and future endeavors are discussed.

Computer Security↗
PubMed2005

[Modeling for activating peripheral nerves by transverse electric field].

The classical cable function has been used to represent the response of peripheral nerves stimulated by external parallel electric field. It can not describe the excitation of peripheral nerves stimulated by perpendicular electric field. In this paper, responses of the nodes of Ranvier to transverse-field are deeply investigated by mathematic simulation and in-vitro experiments. The paper demonstrates that, under perpendicular electric field stimulation, the responses evoke a two-stage process including an initial polarization and the actual change of the transmembrane potential. It is the net inward current along a radial direction of the node of Ranvier that causes the peripheral nerve excitation. Based on the two-stage process, a novel model is introduced to describe peripheral nerves stimulated by transverse-field, and the classical cable function is modified. The new model and the improved cable function are verified by several in-vitro experiments. They can be used to represent peripheral nerves responses by arbitrary electric field stimulation.

Animals↗
PubMed2005

[Study on feature extraction of the sleep-multigraph].

Recording the sleep-multigraph is an important method for sleep monitoring and research. In this study, after the all-night sleep in six nights being monitored, the process of sleep is shown by EEG complexity and spectrum feature. It can provide a new path for estimating the sleep quality by sleep staging. Especially, the EEG complexity in different sleep stages is studied. The results indicate that the deeper the sleep, the smaller the EEG complexity of whole cortex. This is of significance to the study on sleep biopsychology.

Electroencephalography↗
PubMed2005

[Auto sleep staging and sleep quality estimation based on BP neural network].

To estimate the sleep quality, a 3-layer BP neural network was studied. The EEG complexity and the power spectrum of sleep-multigraph served as the input vector of the network . All-night sleep-stage scoring was performed. Then several parameters (sleep period, shallow sleep period, deep sleep period, REM period, ratio of the wakeful period and sleep one) were defined to estimate the sleep quality. The experiments revealed that the estimated sleep condition was the same as the subjects' impression. The data on six cases of all-night sleep show that this method is available to estimate the sleep quality.

Electroencephalography↗
PubMed2005

[A study on technology to identify human beings or animals in life-detector based on radar].

To determine whether a living object is human being or animal by detecting the respiration signal using the life-detector based on radar to penetrate the building or debris. To fully utilize the nonstationary character of the respiration signal, short time Fourier transform (STFT) is employed to get the signal's time-frequency representation. Singular value decomposition (SVD) is then used in the spectrogram to extract feature vector for pattern identification. Human beings and animals can be identified from the respiration sensed by the life-detector based on radar. Experimental results show that the method based on STFT and SVD is stable and efficient to differ from the human being and animal.

Animals↗
PubMed2004

[Feature extraction and classification of EEG for mental tasks based on wavelet packet analysis].

This paper explores the use of wavelet packet analysis to extract features from spontaneous electroencephalogram (EEG) during three different mental tasks. Artifact-free EEG segments are transformed to multi-scale representations by dyadic wavelet packet decomposition channel by channel. Their feature vectors formed by energy values of different sub-spaces EEG components are used as inputs of a radial basis function network to test the classification accuracies of three task pairs. The results indicate that the classification accuracies of the wavelet packet analysis method are significantly better than those of autoregressive model method. Wavelet packet analysis would be a promising method to extract features from EEG signals.

Electroencephalography↗
PubMed2004

[Study on eliminating self-dithering interference of the system for non-contact detecting life parameters based on an adaptive algorithm].

The non-contact life parameters detecting systems can detect many important life parameters such as heartbeat and breathing at certain distance. In practice, the self-dithering interference of the system is produced by some factors; it makes the signal-to-noise ratio (SNR) of the recorded signal lower. This paper is discussed an adaptive technology based on a variable step-size LMS algorithm, which is used to eliminate the self-dithering interference of the system and hence to raise the SNR of the detecting signal. A method to obtain the reference signal by vibration sensor is brought forward and the optimum parameters settings are discussed. The results show that the reference signal is an integral part of output signal of the vibration sensor and has a relationship with the setting direction of the sensor. The conclusion is that the method is effective and feasible; also the algorithm is well convergent.

Algorithms↗
PubMed2003

[Application of power spectral entropy to the noninvasive detection of focal ischemic cerebral injury].

A model of SD rat focal ischemic cerebral injury is presented for use in noninvasively detecting both the extent and the location of focal ischemic cerebral injury. EEG signals of ischemic region and normal region are recorded from the moment before ischemia to 30 minutes after ischemia. Then the Power Spectral Entropy(PSE) analysis of EEG is performed. Results show that the PSE of EEG signals changes greatly as a result of focal ischemic cerebral injury. The PSE of EEG signal of ischemic region is less than that before ischemia as the ischemia lasts 15 minutes. The PSE of EEG signals of ischemic region is much less than that of normal region. These indicate that the power spectral entropy of EEG signal is a good index of focal ischemic cerebral injury and the method of power spectral entropy analysis is simple and effective.

Animals↗
PubMed2003

[Application of support vector machines to classification of blood cells].

The support vector machine (SVM) is a new learning technique based on the statistical learning theory. It was originally developed for two-class classification. In this paper, the SVM approach is extended to multi-class classification problems, a hierarchical SVM is applied to classify blood cells in different maturation stages from bone marrow. Based on stepwise decomposition, a hierarchical clustering method is presented to construct the architecture of the hierarchical (tree-like) SVM, then the optimal control parameters of SVM are determined by some criterion for each discriminant step. To verify the performances of classifiers, the SVM method is compared with three classical classifiers using 3-fold cross validation. The preliminary results indicate that the proposed method avoids the curse of dimensionality and has greater generalization. Thus, the method can improve the classification correctness for blood cells from bone marrow.

Algorithms↗
PubMed2002

[Study on automatic segmentation of color images applied to blood cells].

A hybrid segmentation algorithm is proposed for automatic segmentation of blood cell images based on adaptive multi-scale thresholding and seeded region growing techniques. Firstly, an adaptive and scale space filter (ASSF) is applied to image histogram and a scale space image is built. According to the properties of the scale space image, proper thresholds can be obtained to separate the nucleus from the original image and the white blood cells are located. Secondly, the local color similarity and global morphological criteria constrain seeded region growing in order to finish the segmentation of the cytoplasm. The detection accuracy of white blood cell is 98% and the segmentation accuracy based on the subjective evaluation is 93%. Test shows that this algorithm is effective for automatic segmentation of white blood cells.

Algorithms↗