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Hierarchically Distributed Optimization with a Flexible and Complexity-Reducing Algorithm

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Journal of Systems Science & Complexity 2024年

作者： LIANG Shu ZHANG Lei WEI Yiheng LIU Yemo 1.department of Control Science and engineering, Tongji university 2.Shanghai Research Institute for Intelligent Autonomous Systems 3.school of Mathematics, Southeast university 4.Beijing Aerospace Automatic Control Institute department of Control Science and engineering Tongji University Shanghai Research Institute for Intelligent Autonomous Systems school of Mathematics Southeast University Beijing Aerospace Automatic Control Institute

In this paper, the authors consider distributed convex optimization over hierarchical networks. The authors exploit the hierarchical architecture to design specialized distributed algorithms so that the complexity can be reduced compared with that of non-hierarchically distributed *** this end, the authors use local agents to process local functions in the same manner as other distributed algorithms that take advantage of multiple agents' computing resources. Moreover, the authors use pseudocenters to directly integrate lower-level agents' computation results in each iteration step and then share the outcomes through the higher-level network formed by pseudocenters. The authors prove that the complexity of the proposed algorithm exponentially decreases with respect to the total number of pseudocenters. To support the proposed decomposition-composition method for agents and pseudocenters, the authors develop a class of operators. These operators are generalizations of the widely-used subgradient based operator and the proximal operator and can be used in distributed convex optimization. Additionally, these operators are closed with respect to the addition and composition operations; thus, they are suitable to guide hierarchically distributed design and analysis. Furthermore,these operators make the algorithm flexible since agents with different local functions can adopt suitable operators to simplify their calculations. Finally, numerical examples also illustrate the effectiveness of the method.

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Chinese Guidelines for the Diagnosis and Management of Atrial Fibrillation

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Journal of Geriatric Cardiology 2024年第3期21卷 251-314页

作者： Chang-Sheng MA Shu-Lin WU Shao-Wen LIU Ya-Ling HAN Chinese Society of Cardiology Chinese Medical Association Heart Rhythm Committee of Chinese Society of biomedical engineering Beijing Anzhen Hospital Capital Medical University Guandong Provincial People’s Hospital Shanghai First People’s Hospital General Hospital of Northern Theater Command 不详

Atrial fibrillation(AF)is the most common sustained cardiac arrhythmia,significantly impacting patients’quality of life and increasing the risk of death,stroke,heart failure,and *** the past two decades,there have been significant breakthroughs in AF risk prediction and screening,stroke prevention,rhythm control,catheter ablation,and integrated *** this period,the scale,quality,and experience of AF management in China have greatly improved,providing a solid foundation for the development of guidelines for the diagnosis and management of *** further promote standardized AF management,and apply new technologies and concepts to clinical practice in a timely and comprehensive manner,the Chinese Society of Cardiology of the Chinese Medical Association and the Heart Rhythm Committee of the Chinese Society of biomedical engineering have jointly developed the Chinese Guidelines for the Diagnosis and Management of Atrial *** guidelines have comprehensively elaborated on various aspects of AF management and proposed the CHA2DS2-VASc-60 stroke risk score based on the characteristics of AF in the Asian *** guidelines have also reevaluated the clinical application of AF screening,emphasized the significance of early rhythm control,and highlighted the central role of catheter ablation in rhythm control.

关键词： prevention sustained diagnosis

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Analysis of finite-element-based methods for reducing the ill-posedness in the reconstruction of fluorescence molecular tomography

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Progress in Natural Science:Materials International 2009年第4期19卷 501-509页

作者： Zhun Xu, Jing Bai department of biomedical engineering, school of medicine, tsinghua university, Beijing 100084, China department of biomedical engineering School of Medicine Tsinghua University Beijing 100084 China

The major issue in reconstruction of optical imaging might be the ill-posedness of the problem. In this paper, four different algorithms, including singular value decomposition (SVD), the truncated SVD, Tikhonov regularization and adaptive regularization, are analyzed and applied for solving the matrix equation generated from diffuse equation based on finite-element method in fluorescence molecular tomography. Results illustrate the need for either imposition of regularization term or elimination of too small singular values in reducing the illposedness. The results also suggest that the adaptive-regularization method offers superior performance in the reconstruction among the four methods in most cases even if the initially selected regularization parameter is not optimal, thus providing the convenience for the reconstruction.

关键词： Fluorescence molecular tomography Reconstruction Ill-posedness The truncated SVD Adaptive regularization

Application of the wavelet transforms on axial strain calculation in ultrasound elastography

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Progress in Natural Science:Materials International 2006年第9期16卷 942-947页

作者： LUO Jianwen, BAI Jing and SHAO Jinhua (department of biomedical engineering, school of medicine, tsinghua university, Beijing 100084, China) department of biomedical engineering School of Medicine Tsinghua University Beijing 100084 China

In ultrasound elastography, the axial strain distribution within biological tissues is calculated as the numerical derivative (differentiation) of the estimated axial displacement field. Unfortunately, the numerical derivative is unstable because it can greatly amplify the noises, especially at high frequencies. This work focuses on the axial strain calculation from the estimated axial displacements using wavelet transforms (WTs), including continuous wavelet transforms (CWTs) and discrete wavelet transforms (DWTs). The feasibility of the WT-based method using the quadratic spline function is verified by computer simulations and some phantom data. Results indicate that the WT-based method can effectively reduce the noise amplification in axial strain calculation.

关键词： ultrasound elastography axial strain differentiation wavelet transforms.

Clinical practice guidelines for nutritional assessment and monitoring of adult ICU patients in China

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Journal of Intensive medicine 2024年第2期4卷 137-159页

作者： Xiangdong Guan Dechang Chen Yuan Xu Chinese Society of Critical Care medicine department of Critical Care medicine The First Affiliated Hospital of Sun Yat-sen UniversityGuangzhouChina department of Critical Care medicine Ruijin HospitalShanghai Jiao Tong University School of MedicineShanghaiChina department of Critical Care medicine Beijing Tsinghua Changgung HospitalBeijingChina 不详

The Chinese Society of Critical Care medicine(CSCCM)has developed clinical practice guidelines for nutrition assessment and monitoring for patients in adult intensive care units(ICUs)in *** guideline focuses on nutrition evaluation and metabolic monitoring to achieve optimal and personalized nutrition therapy for critically ill *** guideline was developed by experts in critical care medicine and evidence-based medicine methodology and was developed after a thorough review of the system and a summary of relevant trials or studies published from 2000 to July 2023.A total of 18 recommendations were formed and consensus was reached through discussions and reviews by expert groups in critical care medicine,parenteral and enteral nutrition,and *** recommendations are based on currently available evidence and cover several key fields,including screening and assessment,evaluation and assessment of enteral feeding intolerance,metabolic and nutritional measurement and monitoring during nutrition therapy,and organ function evaluation related to nutrition *** question was analyzed according to the Population,Intervention,Comparison,and Outcome(PICO)*** addition,interpretations were provided for four questions that did not reach a consensus but may have potential clinical and research *** plan is to update this nutrition assessment and monitoring guideline using the international guideline update method within 3–5 years.

关键词： Adults Critical illness Intensive care unit Nutriti on Nutriti on assessment and monitoring Guideline Recommendations Chinese Society of Critical Care medicine-Chinese Medical Association(CSCCM-CMA)

Right-and-left visual field stimulation:A frequency and space mixed coding method for SSVEP based brain-computer interface

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Science China(Information Sciences) 2011年第12期54卷 2512-2518页

作者： YAN Zheng, GAO XiaoRong & GAO ShangKai department of biomedical engineering, school of medicine, tsinghua university, Beijing 100084, China department of biomedical engineering School of Medicine Tsinghua University Beijing China

On the condition of using limited frequencies, fewer targets could be presented in brain-computer interface (BCI) based on steady-state visual evoked potentials (SSVEP). This paper proposes a novel coding method for SSVEP that, through a combination of frequency and spatial information, could increase the number of targets. Each target was composed of two flickers placed in the right-and-left visual fields. Given the role of the optic chiasm in the vision pathway, the two frequency components could be projected to contralateral occipital regions. Canonical correlation analysis (CCA) was utilized to detect the frequency components from the right or left visual cortex. Asymmetric index as a supplementary feature was also computed. Linear discriminant analysis (LDA) was used for target recognition. The attractive feature of this method is that it would substantially increase the number of targets. If the number of frequency was N, the method could present N times more targets than conventional SSVEP-based BCIs.

关键词： brian-computer interface (BCI) frequency-space mixed coding steady-state visual evoked potential (SSVEP)

Electric-stimulus rate encoding algorithm of Mandarin tonal information in cochlear implant

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Progress in Natural Science:Materials International 2006年第12期16卷 1315-1321页

作者： GUAN Tian~1, GONG Qin~1 and YE Datian~2**(1. department of biomedical engineering, tsinghua university, Beijing 100084, China 2. Research Center of biomedical engineering, Graduate school at Shenzhen, tsinghua university, Shenzhen 518055, China) department of biomedical engineering Tsinghua University Beijing 100084 China Research Center of biomedical engineering Graduate school Shenzhen Tsinghua University Shenzhen 518055 China

The modern multi-channel cochlear implants usually extract and encode the temporal envelope cues. This kind of algorithms can hardly satisfy the users who speak tonal languages, such as Mandarin. Many studies have tried to enhance the recognition ability of Mandarin through encoding tonal information and made suggestions to frequency-modulate the fixed pulse-rate carrier with the extracted tonal information based on the rate-pitch theory in electric hearing. However, how to encode and deliver the tonal information such as F_0by changing electric-stimulus rate has not got further study in clinical electric-stimulus mode. The present paper focuses on this matter by piecewise calculating the appreciable electric-stimulus rates. Then an electric-stimulus encoding algorithm of Mandarin tone is brought forward and testified through acoustic simulations. Such conclusion can be drawn that this algorithm of electric-stimulus rate could convey tonal information well and help to enhance the Mandarin speech recognition ability.

关键词： cochlear implant tone fundamental frequency electric-stimulus rate.

Improvement of the classification accuracy in discriminating diabetic retinopathy by multifocal electroretinogram analysis

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Progress in Natural Science:Materials International 2007年第8期17卷 913-918页

作者： Xu Jin~1 Hu Guangshu~(1**) Huang Houbin~2 (1.department of biomedical engineering,tsinghua university,Beijing 100084,China 2.department of Ophthalmology,General Hospital of Chinese PLA,Beijing 100853,China) department of biomedical engineering Tsinghua University Beijing 100084 China department of Ophthalmology General Hospital of Chinese PLA Beijing 100853 China

The multifocal electroretinogram (mfERG) is a newly developed electrophysiological *** this paper,a classifi- cation method is proposed for early diagnosis of the diabetic retinopathy using mfERG *** records were obtained from eyes of healthy individuals and patients with diabetes at different *** each mfERG record,103 local responses were *** value of each point on all the mfERG local responses was looked as one potential feature to classify the experimental *** sub- sets were selected from the feature space by comparing the inter-intra *** on the selected feature subset,Fisher's linear classi- fiers were *** the final classification decision of the record was made by voting all the classifiers' *** the method to classify all experimental subjects,very low error rates were *** crucial properties of the diabetic retinopathy classification method are also discussed.

关键词： diabetic retinopathy multifocal electroretinogram feature selection linear classifier

Simulation study and function analysis of the dynamic aortic valve

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Progress in Natural Science:Materials International 2006年第5期16卷 512-517页

作者： XIA Dongdong and BAI Jing (department of biomedical engineering, tsinghua university, Beijing 100084, China) department of biomedical engineering Tsinghua University Beijing 100084 China

The dynamic aortic valve (DAV) is a new left ventricular assist device, a micro-axial blood pump implemented at the position of the aortic valve, pumping blood from the left ventricle into the aortic artery. The present dynamic aortic valve operates at 7 different rotation speeds, ranging from 3000 r/min (speed 1) to 9000 r/min (speed 7). Because in vivo experiments need a lot of live animals and take a long period of time, modeling and simulation have been widely used to simulate and analyze hydra-dynamic property of the DAV and its assisting effects. With the measurements from the mock circulatory loop, a mathematic model of the DAV is established and embedded into the previously developed canine circulatory system. Using this model, the effect of the DAV on the failing heart at each rotation speed level is investigated. The vital cardiac variables are computed and compared with in vivo experimental results, which are in good agreement with an acceptable difference mostly 15%. The establishment of the DAV model and its simulation are useful for further improvement of the DAV device.

关键词： dynamic aortic valve mathematic model computer simulation.