白净
医学超声成像、生理系统的建模与仿真、远程医疗技术、红外医学成家、医学信息学等
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 姓名：白净
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学术头衔：
博士生导师， 国家杰出青年科学基金获得者， 教育部“新世纪优秀人才支持计划”入选者
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学科领域：
无线电物理
 研究兴趣：医学超声成像、生理系统的建模与仿真、远程医疗技术、红外医学成家、医学信息学等
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9
【期刊论文】Axial Strain Calculation Using a LowPass Digital Diﬀerentiator in Ultrasound Elastography
白净， Jianwen Luo; Student Member; IEEE; Jing Bai; Fellow; IEEE; Ping He; Senior Member; IEEE; and Kui Ying
IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL, VOL. 51, NO.9, SEPTMBER 2004，0001，（）：
1年11月30日
In ultrasound elastography, tissue axial strains are calculated from the gradient of the estimated axial displacements. However, the common diﬀerentiation operation ampliﬁes the noises in displacement estimation, especially at high frequencies. In this paper, a lowpass digital diﬀerentiator (LPDD) is proposed to calculate the axial strain from the estimated tissue displacement. Several LPDDs that have been well developed in the ﬁeld of digital signal processing are presented. The corresponding performances are compared qualitatively and quantitatively in computer simulations and in preliminary phantom and in vitro experiments. The results are consistent with the theoretical analysis of the LPDDs.

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【期刊论文】Computer simulation of the baroregulation in response to moderate dynamic exercise
白净， X. Li， J. Bai
Med. Biol. Eng. Comput., 2001, 39, 480487，0001，（）：
1年11月30日
A baroregulation model, based on a previous pulsatile nonlinear multielement ardiovascular model, is extended and used to study shortterm regulation mechanisms. Using this model, the responses of several cardiovascular variables to ifferent exercise levels are simulated and compared with the experimental data reported in the literature. The impact of physiological or pathological changes on the shortterm regulation of arterial pressure under the stimulus of moderate dynamic exercise is then studied. The simulation results indicate that baroreflex feedback plays a critical role in the shortterm regulation of arterial pressure. When the baroreflex gain decreases to onethird of the normal value, the response of the mean arterial pressure to moderate dynamic exercise and postexercise recovery time increases by factors of 1.7 and 2.3, respectively. Clinical data from 36 subjects (two groups: normal and hypertensive) are collected to validate the model. Computer simulations for the hypertensive group show that the elastic modulus of the arterial vessel wall is increased by 1.5 times, and peripheral resistance is increased by 1.3 times the normal value, and the baroreflex gain decreases from 0.55 (for the normal group) to 0.40. The simulation results for normal and hypertensive groups agree well with the clinical data.
Cardiovascular system， Shortterm regulation， Baroregulation， Autonomic nervous system， Hypertension

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【期刊论文】Multiple modeling in the study of interaction of hemodynamics and gas exchange
白净， Anqi Qiu， Jing Bai
Computers in Biology and Medicine 31(2001)5972，0001，（）：
1年11月30日
Circulation plays an important rule in gas exchange. Therefore, there is an interaction between circulation and gas exchange. To understand the dynamic e ect of these two physiological systems, a computer simulation model of hemodynamics and gas exchange is established in this work. This model includes two physiological systems, namely the respiratory and circulatory systems. It consists of ve parts: the model of gas transport, exchange and storage within the body, the multielement nonlinear mathematical model of human circulatory system, an alveolar ventilation controller, a cardiac output controller, and a controller of breathing frequency. Model simulations provide results consistent with both dynamic and steadystate responses under hypoxia. Simulation results can re ect the interaction of hemodynamics and gas exchange. Using this model, the changes of pulmonary arterial pressure and right ventricular pressure in high altitude are studied. The optimal mode of breathing extra oxygen using nasal prongs or a facial mask is studied. This model may provide a useful tool to study reaction of hypoxia and the oxygen inhalation mode under hypoxia environments.c 2000 Elsevier Science Ltd. All rights reserved.
Hemodynamics， Circulatory system， Respiratory system， Hypoxia， Pulmonary hypertension， Oxygen inhalation， Computer simulation， Physiological model

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【期刊论文】Simulation study of the Hemopump as a cardiac assist device
白净， X. Li， J. Bai， P. He
Med. Biol. Eng. Comput., 2002, 40, 344353，0001，（）：
1年11月30日
A dynamic model was developed for a Hemopump that withdraws blood from the left ventricle and discharges it to the aorta through a miniature axialflow pump. Incorporation of the Hemopump model in a previously established model for the canine circulatory system enabled the effects of the Hemopump on various haemodynamic variables of the circulatory system to be studied, and the benefit of the Hemopump to the failing heart was investigated. In addition, the influence of the physiological status of the right ventricle on the Hemopump performances was examined, and the synchronous and nonsynchronous operations of the Hemopump were compared. Results verified that the Hemopump assists the failing heart by increasing the oxygen supply, while reducing the oxygen consumption of the heart through a reduction in the workload of the left ventricle. These beneficial effects were enhanced when the pump' s rotation speed was increased. When pump speed was increased from 17 000 to 23 000 revolutions min 1, the oxygen supply increased 101%, and the oxygen consumption decreased 60%.However, when the pump rotation speed was too high, the inflow to the pump could be impaired and the pump performance could be negatively affected. Predications from the model were in good agreement with the results previously obtained in animal experiments and in vitro measurements.
Cardiac assist device， Computer simulation， Hemopump， Ischaemia

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【期刊论文】Properties of SavitzkyGolay digital differentiators
白净， Jianwen Luo a， Kui Ying a， Ping He b， Jing Bai a， *
Digital Signal Processing 15(2005)122136，0001，（）：
1年11月30日
The SavitzkyGolay (SG) filters are generally used for smoothing and differentiation in many fields. The properties of the SG smoothing filters have been well studied. However, the properties of the SG differentiation filters or SG digital differentiators (SGDD, for the first order differentiation) are not developed well somehow, although they have been widely used. In the paper, the properties of the SGDD are discussed in detail. The effects of the SGDD on a noisefree single Gaussian line and a noisefree Gaussian doublet are studied via simulation. The results indicate that the contrast and resolution loss of the SGDD depends on the ratio of the width of signal derivative and filter length. The linear SGDD is not preferable for preserving small details of signal derivative from this study. The cubic and quintic SGDD with the choice of appropriate filter length are recommended in order to maintain the resolution of signal derivative.
SavitzkyGolay， Digital differentiator， Differentiation， Property

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【期刊论文】Photon migration in turbid mediaA finiteelement solution for the most favorable path
白净
，0001，（）：
1年11月30日

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【期刊论文】Photon migration in turbid media: A finiteelement solution for the most favorable path
白净， Jun Zhou， Jing Bai
Opt. Eng. 41(10)10 (October 2002)，0001，（）：
1年11月30日
A better understanding of the fundamental principles of photon migration in highly scattering media is of great importance for developing new methods for disease diagnosis, imaging, and tomography. In this paper we present a mostfavorablepath approach to the problem of light propagation in turbid media, based on the diffusion equation. The most favorable path, on which photons will be found, can be obtained from the path of the net flux propagation. The diffusion intensity and the direction of the net flux can be calculated with the finiteelement method, which can deal with heterogeneous problems and frequencydomain problems within complex geometry, and can introduce boundary effects as well. Simulations were conducted for phantoms with different optical parameters and sourcedetector separations. Experiments have been performed to verify this new method. The most favorable path is found to be more sensitive to the sourcedetector separation and the absorption coefficient of the medium than to the scattering coefficient. The feasibility of using the theory in optical tomography for the recognition of objects hidden in turbid media is discussed.

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【期刊论文】Threshold selection by clustering gray levels of boundary
白净， Lisheng Wang *， Jing Bai
Pattern Recognition Letters 24(2003)19831999，0001，（）：
1年11月30日
In this paper, threshold selection is considered in the continuous image rather than in digital image. We prove that, for each given object within 2D image, its optimal threshold is determined by the mean of the gray values of the points lying on its continuous boundary. Thus, we try to deduce threshold from the gray values of the boundary rather from the gray values of the given discrete sampling points (pixels or edge pixels). By the scheme, we well overcome some disadvantages existing in the threshold methods based on the histogram of edge pixels. Besides, the proposed method has the ability to well handle the image whose histogram has very unequal peaks and broad valley. 2003 Elsevier Science B.V. All rights reserved.
Threshold selection， Clustering algorithm， Image segmentation

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【期刊论文】Spatial location weighted optimization scheme for DC optical tomography
白净
27 January 2002 Vol. 11, No.2 OPTICS EXPRESS 141，0001，（）：
1年11月30日
In this paper, a spatial location weighted gradientbased optimization scheme for reducing the computation burden and increasing the reconstruction precision is stated. The method applies to DC diffusionbased optical tomography, where otherwise the reconstruction suffers slow convergence. The inverse approach employs a weighted steepest descent method combined with a conjugate gradient method. A reverse differentiation method is used to efficiently derive the gradient. The reconstructionresults confirm that the spatial location weighted optimization method offers a more efficient approach to the DC optical imaging problem than unweighted method does.

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