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Time-frequency feature extraction of newborn EEG seizure using SVD-based techniques

EURASIP JOURNAL ON APPLIED SIGNAL PROCESSING 2004年第16期2004卷 2544-2554页

作者： Hassanpour, H Mesbah, M Boashash, B Queensland Univ Technol Lab Signal Proc Res Brisbane Qld 4001 Australia

The nonstationary and multicomponent nature of newborn EEG seizures tends to increase the complexity of the seizure detection problem. In dealing with this type of problems, time-frequency-based techniques were shown to outperform classical techniques. This paper presents a new time-frequency-based EEG seizure detection technique. The technique uses an estimate of the distribution function of the singular vectors associated with the time-frequency distribution of an EEG epoch to characterise the patterns embedded in the signal. The estimated distribution functions related to seizure and nonseizure epochs were used to train a neural network to discriminate between seizure and nonseizure patterns.

关键词： detection time-frequency distribution singular value decomposition probability distribution function

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Comparison of Moment-Based Parameter Estimation Methods for Rayleigh-Stokes distribution of Wave Crests and Troughs

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INTERNATIONAL JOURNAL OF OFFSHORE AND POLAR ENGINEERING 2012年第3期22卷 200-208页

作者： Izadparast, Amir H. Niedzwecki, John M. SOFEC Inc Res & Dev Grp Houston TX USA Texas A&M Univ Zachry Dept Civil Engn College Stn TX USA

The Rayleigh-Stokes model has been widely applied to represent the probability distribution function of crests and troughs of weakly nonlinear random processes. In this study, the parameter estimates for the 3-parameter Rayleigh-Stokes probability distribution function model are obtained from application of 2 moment-based empirical parameter estimation methods, i.e. conventional method of moments and method of linear moments. Monte Carlo simulations are utilized to compare the performance of these parameter estimation approaches in estimating the parameters of the Rayleigh-Stokes distribution, and also to evaluate the uncertainty of the extreme statistics. Additionally, the effect of sample size on the uncertainty of the model statistics is evaluated. Finally, the Rayleigh-Stokes model is utilized to estimate the probability distribution function of disturbed wave crests beneath a mini-TLP, and the model performance is evaluated.

关键词： Rayleigh-Stokes model weakly nonlinear process probability distribution function method of moments method of linear moments

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Off-Line Signature Verification Based on Multi-Scale Local Structural Pattern

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INTERNATIONAL JOURNAL OF PATTERN RECOGNITION AND ARTIFICIAL INTELLIGENCE 2017年第6期31卷 1756010-1756010页

作者： Wen, Jing Fang, Bin Zhang, Liang Zhu, Yu Chongqing Univ Coll Comp Sci Chongqing 400030 Peoples R China Chengdu Univ Key Lab Pattern Recognit & Intelligent Informat P Inst Higher Educ Sichuan Prov Chengdu Peoples R China

The paper proposes a theoretically very simple, and effective multi-scale local structural patterns (MS-LSP) for off-line signature verification. The proposed strategy models the signature by probabilistically counting the distribution of each local structural pattern on multiple scales. This representation correlates with the writing style of an individual and depict the shape and structural information of signatures. Extensive experiments on two challenging databases (MCYT, GPDS960) show that the proposed approach achieves noticeably verification rates and it is expected to provide a powerful discriminative representation of the signature.

关键词： Off-line signature verification local structural pattern encoding feature probability distribution function Chi-square distance pattern recognition

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Translocation, Rejection and Trapping of Polyampholytes

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POLYMERS 2022年第4期14卷 797页

作者： Kim, Yeong-Beom Chae, Min-Kyung Park, Jeong-Man Johner, Albert Lee, Nam-Kyung Sejong Univ Dept Phys & Astron Seoul 05006 South Korea Catholic Univ Korea Dept Phys Bucheon 14662 South Korea Univ Strasbourg Inst Charles Sadron ICS CNRS Unistra F-67000 Strasbourg France

Polyampholytes (PA) are a special class of polymers comprising both positive and negative monomers along their sequence. Most proteins have positive and negative residues and are PAs. Proteins have a well-defined sequence while synthetic PAs have a random charge sequence. We investigated the translocation behavior of random polyampholyte chains through a pore under the action of an electric field by means of Monte Carlo simulations. The simulations incorporated a realistic translocation potential profile along an extended asymmetric pore and translocation was studied for both directions of engagement. The study was conducted from the perspective of statistics for disordered systems. The translocation behavior (translocation vs. rejection) was recorded for all 2(20) sequences comprised of N = 20 charged monomers. The results were compared with those for 10(7) random sequences of N = 40 to better demonstrate asymptotic laws. At early times, rejection was mainly controlled by the charge sequence of the head part, but late translocation/rejection was governed by the escape from a trapped state over an antagonistic barrier built up along the sequence. The probability distribution of translocation times from all successful attempts revealed a power-law tail. At finite times, there was a population of trapped sequences that relaxed very slowly (logarithmically) with time. If a subensemble of sequences with prescribed net charge was considered the power-law decay was steeper for a more favorable net charge. Our findings were rationalized by theoretical arguments developed for long chains. We also provided operational criteria for the translocation behavior of a sequence, explaining the selection by the translocation process. From the perspective of protein translocation, our findings can help rationalize the behavior of intrinsically disordered proteins (IDPs), which can be modeled as polyampholytes. Most IDP sequences have a strong net charge favoring translocation. Even f

关键词： translocation polyampholytes drift-diffusion probability distribution function Monte Carlo simulation

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Concentration fluctuations and flammability of cryo-compressed hydrogen and methane jets

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FUEL 2024年第PartB期358卷

作者： Yao, Chenyi Ba, Qingxin Hecht, Ethan S. Christopher, David M. Li, Xuefang Shandong Univ Inst Thermal Sci & Technol Inst Adv Technol Jinan 250061 Peoples R China Shandong Univ Sch Mech Engn Jinan 250061 Peoples R China Sandia Natl Labs Combust Res Facil Livermore CA 94550 USA Tsinghua Univ Key Lab Thermal Sci & Power Engn Minist Educ Beijing 100084 Peoples R China Shandong Univ Shandong Engn Res Ctr High efficiency Energy Stora Sch Energy & Power Engn Jinan 250061 Peoples R China

Compressed hydrogen stored at cryogenic temperatures has a much higher density than room-temperature storage, which enables large-scale hydrogen storage and transport. An understanding of the release of cryogenic hydrogen from pressurized vessels is needed to evaluate the risk and safety concerns with the use of this fuel. The present work extends the analysis of previous experimental studies that measured the gas concentrations of cryo-compressed hydrogen jets and methane jets using a laser Raman scattering diagnostic system. Since the Raman signals are very small, a denoising algorithm was applied to significantly reduce the noise to enable statistical analysis of the data. The transient features of the turbulent jets were characterized by their concentration intermittencies and probability density functions (PDFs). A two-part PDF was developed to predict the bimodal features of the jet concentration distributions. Then, the flammability factors of the cryogenic jets were calculated based on the intermittency and the PDF.

关键词： Cryo-compressed jets Ignition probability Flammability factor probability distribution function Intermittency

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Stochastic Dynamic Analysis of an Offshore Wind Turbine Structure by the Path Integration Method

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ENERGIES 2019年第16期12卷 3051页

作者： Zhao, Yue Lian, Jijian Lian, Chong Dong, Xiaofeng Wang, Haijun Liu, Chunxi Jiang, Qi Wang, Pengwen Tianjin Univ State Key Lab Hydraul Engn Simulat & Safety 135 Yaguan Rd Tianjin 300350 Peoples R China PowerChina Huadong Engn Corp Ltd 201 Gaojiao Rd Hangzhou 311122 Zhejiang Peoples R China

Stochastic dynamic analysis of an offshore wind turbine (OWT) structure plays an important role in the structural safety evaluation and reliability assessment of the structure. In this paper, the OWT structure is simplified as a linear single-degree-of-freedom (SDOF) system and the corresponding joint probability density function (PDF) of the dynamic response is calculated by the implementation of the path integration (PI) method. Filtered Gaussian white noise, which is obtained from the utilization of a second-order filter, is considered as horizontal wind excitation and used to excite the SDOF system. Thus, the SDOF model and the second-order linear filter model constitute a four-dimensional dynamic system. Further, a detailed three-dimensional finite element model is applied to obtain the natural frequency of the OWT and the efficient PI method, which is modified based on the fast Fourier transform (FFT) convolution method, is also utilized to reduce the execution time to obtain the PDF of the response. Two important parameters of wind conditions, i.e., horizontal mean wind speed and turbulence standard deviation, are investigated to highlight the influences on the PDF of the dynamic response and the reliability of the OWT.

关键词： stochastic dynamic offshore wind turbine path integration FFT convolution probability distribution function

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Understanding Intensity-Duration-Frequency (IDF) Curves Using IMERG Sub-Hourly Precipitation against Dense Gauge Networks

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REMOTE SENSING 2022年第19期14卷 5032-5032页

作者： Lau, Alcely Behrangi, Ali Univ Arizona Dept Hydrol & Atmospher Sci Tucson AZ 85721 USA

The design storm derived from intensity-duration-frequency (IDF) curves is the main input for hydrologic analysis or hydraulic design for flood control. The regions with higher flood risks due to extreme precipitation are often deficient in precipitation gauges. This study presents a detailed evaluation of IDF curves derived using IMERG Final half-hourly precipitation (V06), fitted with the widely used CDFs: Gumbel and MLE, Gumbel and MM, Pearson 3, and GEV. As benchmarks and following the same method, we also derived IDF curves using areal average gridded precipitation constructed from two dense gauges networks over (1) the WegenerNET Feldbach region in the Alpine forelands of Austria and (2) the gauge network of the Walnut Gulch Experimental Watershed, in a semiarid region of the United States. In both regions, the frequency analysis for return periods between 2 and 100 years was based on half-hourly rainfall and compared at a grid-scale with a spatial resolution of IMERG, 0.1 degrees x 0.1 degrees lat/lon. The impact of order in which the gridded gauge-based precipitation average is performed within an IMERG grid was evaluated by computing two different Annual Maximum Series (AMS). In one, the average was computed before obtaining the AMS (AB-AMS), and in the other, the average was computed after obtaining the AMS for each gauge grid (AA-AMS) within the IMERG grid. The evaluation revealed that IMERG AMS agrees better with AB-AMS than AA-AMS for the two study regions. Lastly, it was found that the use of Gumbel distribution in calculating IMERG IDF curves results in better agreement with the ground truth than the use of the other three distributions studied here. The outcomes should provide valuable knowledge for the application of IMERG precipitation over regions with sparse gauges.

关键词： IDF curves remote sensing precipitation IMERG WegenerNET Walnut Gulch annual maximum series probability distribution function gridded precipitation areal average

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The optimal algorithm for eliminating nonlinear error in phase measurement profilometry based on global statistical phase feature function

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MEASUREMENT SCIENCE AND TECHNOLOGY 2024年第6期35卷 065020-065020页

作者： Zhu, Zhenmin Xu, Xiaokai Long, Wenqing He, Lifa Zhang, Jing Liu, Haoran Jiang, Jianru East China Jiaotong Univ Sch Elect & Elect Engn Nanchang 330013 Peoples R China Longnan Junya Elect Technol Co Ltd Ganzhou Jiangxi Peoples R China Xi An Jiao Tong Univ Faclty Elect & Informat Engn Xian Peoples R China

In a digital fringe projection structured light system, the nonlinear phase error is generated by the gamma effect of both the projector, camera, and other electronic devices. One of the existing nonlinear correction methods is active correction by projecting ideal fringes as far as possible, and the other is passive compensation after capturing aberrant fringes. The former has higher accuracy but needs to capture a large number of fringe patterns, while the latter does not need many fringe patterns, but is not only greatly affected by random noise and out-of-focus effects, but also has poor accuracy. In this paper, an optimal algorithm for eliminating nonlinear error based on global statistical phase feature function (GSPF) is proposed. The phase distribution can be estimated from the difference between the global cumulative distribution function (CDF) and the normalized (CDF). For an ideal fringe pattern without nonlinear error and a fringe pattern with nonlinear error, the region wrapped by the x-axis normalized CDF is much smaller than the region wrapped by the x-axis global CDF, and the larger the nonlinear error is, the larger the difference between the two is. Therefore, the GSPF can be used for nonlinear error correction. Then the optimal nonlinear error correction is performed based on the minimum difference between the compensated phase entropy and the ideal phase entropy. The method does not require too many steps of phase-shifting, and only three fringe patterns are needed to realize accurate and robust correction. Experimental results show that the method is fast, highly accurate and robust. Using this technique, high accuracy measurements can be achieved with the traditional three-step phase-shifting algorithm.

关键词： three- dimensional measurement nonlinear correction probability distribution function

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Efficiency evaluation of the microgrid for selection of common bus using copula function-based efficiency curves of the converters

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SUSTAINABLE ENERGY TECHNOLOGIES AND ASSESSMENTS 2021年 48卷

作者： Tahir, Hira Lee, Jae-Suk Kim, Rae-Young Hanyang Univ Dept Elect & Biomed Engn Seoul 04763 South Korea Univ Engn & Technol Dept Elect Engn Lahore 54890 Pakistan

Due to the increase in load growth, construction of renewable energy-based microgrids (MG) has been seen as the most economical and viable solution in the recent past. It leads to the need for feasibility investigation at the planning and design stage for appropriate selection of common bus (CB) type. One of the critical factors to determine the suitable CB is efficiency analysis. This paper proposes an efficiency evaluation method by using the copula function-based efficiency curves of the converters. The degree of association between percentage loading and efficiency of the converters is defined using best-fitted copula estimation, and a large number of iterations are performed using Monte Carlo simulations to generate the efficiency for each time instant. A variety of scenarios are simulated to determine when and which type of CB is most favourable. The efficiency of the MG is strongly dependent on the converter efficiency, number of converters in the MG, and seasonal variations, both in generation and load demand. The results indicate that DC CB has superior performance with the net efficiency gain ranging from 8.26% to 5.63% in all scenarios considered in this study. Moreover, DC CB is most advantageous in the MG with the DC load only. It will bring greater advantages in the future with the continuous development of renewable energy-based MGs and the increasing penetration of DC loads.

关键词： AC Vs. DC Common bus Copula function Efficiency Microgrid probability distribution function

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Analysis of sea ice parameters for the design of an offshore wind farm in the Bohai Sea

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OCEAN ENGINEERING 2021年 239卷 109902-109902页

作者： Wang, Anliang Tang, Maoning Zhao, Qian Liu, Yu Li, Baohui Shi, Yunying Sui, Junpeng Natl Marine Environm Forecasting Ctr Marine Disaster Forecasting & Warning Div Beijing 100081 Peoples R China

Offshore wind power has gained much attention as a clean and renewable source of energy. In cold regions, offshore wind farms (OWFs) face many challenges due to sea ice cover. In response to these challenges, this paper establishes a scheme to evaluate sea ice parameters for the design of wind power projects. We have successfully applied this scheme to the OWF in the Bohai Sea. The scheme is based on data from sea ice satellite images, operational forecasting systems and field tests. The ice period, joint probability distribution function of ice velocity and thickness, and return period (RP) of thickness are investigated. Moreover, we determine the air temperature relationship between the OWF and Laizhou city. Then, the effective ice temperature is calculated for the OWF based on the air temperature. Combining the RPs of ice temperature and thickness, we compute the RPs of bending and compression strengths, which are two key parameters for the ice load design of wind turbine towers. Our scheme is feasible to implement and can provide complete sea ice information for OWFs from the stages of design and construction to operation.

关键词： Sea ice Offshore wind farm Bohai Sea probability distribution function Return period

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