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Unsupervised Time Series Segmentation: A Survey on Recent Advances

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Computers, Materials & Continua 2024年第8期80卷 2657-2673页

作者： Chengyu Wang Xionglve Li Tongqing Zhou Zhiping cai College of Computer National University of Defense TechnologyChangsha410073China

Time series segmentation has attracted more interests in recent years,which aims to segment time series into different segments,each reflects a state of the monitored *** there have been many surveys on time series segmentation,most of them focus more on change point detection(CPD)methods and overlook the advances in boundary detection(BD)and state detection(SD)*** this paper,we categorize time series segmentation methods into CPD,BD,and SD methods,with a specific focus on recent advances in BD and SD *** the scope of BD and SD,we subdivide the methods based on their underlying models/techniques and focus on the milestones that have shaped the development trajectory of each *** a conclusion,we found that:(1)Existing methods failed to provide sufficient support for online working,with only a few methods supporting online deployment;(2)Most existing methods require the specification of parameters,which hinders their ability to work adaptively;(3)Existing SD methods do not attach importance to accurate detection of boundary points in evaluation,which may lead to limitations in boundary point *** highlight the ability to working online and adaptively as important attributes of segmentation methods,the boundary detection accuracy as a neglected metrics for SD methods.

关键词： Time series segmentation time series state detection boundary detection change point detection

A survey of geothermal power generation combined with renewable energy for low carbon emissions

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Clean Energy 2024年第3期8卷 138-146页

作者： Xuyang Liu Dongsheng cai Chiagoziem CUkwuoma Qi Huang Olusola Bamisile College of Nuclear Technology and Automation Engineering Chengdu University of TechnologyChengduSichuan P.R.China Electrical Engineering Department Southwest University of Science and TechnologyMaiyangSichuan P.R.China

At present,industrial development is heavily dependent on traditional fossil energy,which has had an increasingly serious impact on the *** and renewable energy has received extensive attention and its proportion in daily life has gradually *** a clean and renewable energy source that is not affected by changes in weather and seasons,geothermal energy has developed rapidly in recent years and has received increasing *** to reports,the total installed capacity of geothermal power generation in the world in 2020 was 15950 MW-an increase of~27%over *** the end of 2019,the total installed capacity for global geothermal direct use was 107727 MW-an increase of 52.0%compared with 2015;the total annual energy use was 1020887 TJ(283580 GWh)-an increase of 72.3%over *** the investigation of geothermal power generation technology in recent years,the characteristics and shortcomings of various power generation methods are *** the same time,this review analyzes the characteristics of geothermal energy and other renewable-energy(solar energy,water energy)coupling power generation,and analyzes the principles and characteristics of geothermal energy and various new-energy coupling power generation *** investigation and analysis,this review provides a complete understanding of various geothermal power generation technologies and provides insights into the future development direction.

关键词： geothermal power generation solar energy water energy combined power generation

Large-Scale Multi-Objective Optimization Algorithm Based on Weighted Overlapping Grouping of Decision Variables

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Computer Modeling in Engineering & Sciences 2024年第7期140卷 363-383页

作者： Liang Chen Jingbo Zhang Linjie Wu Xingjuan cai Yubin Xu Shanxi Key Laboratory of Big Data Analysis and Parallel Computing Taiyuan University of Science and TechnologyTaiyuan030024China School of State Key Laboratory of Novel Software Technology Nanjing UniversityNanjing210008China

The large-scale multi-objective optimization algorithm(LSMOA),based on the grouping of decision variables,is an advanced method for handling high-dimensional decision ***,in practical problems,the interaction among decision variables is intricate,leading to large group sizes and suboptimal optimization effects;hence a large-scale multi-objective optimization algorithm based on weighted overlapping grouping of decision variables(MOEAWOD)is proposed in this ***,the decision variables are perturbed and categorized into convergence and diversity variables;subsequently,the convergence variables are subdivided into groups based on the interactions among different decision *** the size of a group surpasses the set threshold,that group undergoes a process of weighting and overlapping ***,the interaction strength is evaluated based on the interaction frequency and number of objectives among various decision *** decision variable with the highest interaction in the group is identified and disregarded,and the remaining variables are then reclassified into ***,the decision variable with the strongest interaction is added to each *** minimizes the interactivity between different groups and maximizes the interactivity of decision variables within groups,which contributed to the optimized direction of convergence and diversity exploration with different *** was subjected to testing on 18 benchmark large-scale optimization problems,and the experimental results demonstrate the effectiveness of our *** with the other algorithms,our method is still at an advantage.

关键词： Decision variable grouping large-scale multi-objective optimization algorithms weighted overlapping grouping direction-guided evolution

Climate warming is significantly influenced by rising summer maximum temperatures: insights from tree-ring evidence of the Western Tianshan Mountains, China

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Journal of Forestry Research 2024年第5期35卷 47-59页

作者： Meng Ren Yu Liu Qiufang cai Qiang Li Huiming Song Changfeng Sun The State Key Laboratory of Loess and Quaternary Geology Institute of Earth EnvironmentChinese Academy of SciencesXi’an 710061People’s Republic of China Xi’an Institute for Innovative Earth Environment Research Xi’an 710061People’s Republic of China Institute of Desert Meteorology China Meteorological AdministrationÜrümqi 830002People’s Republic of China Center for Excellence in Quaternary Science and Global Change Chinese Academy of SciencesXi’an 710061People’s Republic of China School of Human Settlements and Civil Engineering Xi’an Jiaotong UniversityXi’an 710049People’s Republic of China Qingdao National Laboratory for Marine Science and Technology Qingdao 266237People’s Republic of China

As one of the regions most affected by global cli-mate warming,the Tianshan mountains has experienced sev-eral ecological crises,including retreating glaciers and water *** warming in these mountains is considered mainly to be caused by increases in minimum temperatures and winter temperatures,while the influence of maximum temperatures is *** this study,a 300-year tree-ring chronology developed from the Western Tianshan Moun-tains was used to reconstruct the summer(June-August)maximum temperature(T_(max6-8))variations from 1718 to *** reconstruction explained 53.1% of the variance in the observed T_(max6-8).Over the past 300 years,the T_(max6-8)reconstruction showed clear interannual and decadal *** was a significant warming trend(0.18°C/decade)after the 1950s,which was close to the increasing rates of the minimum and mean *** increase in maximum temperature was also present over the whole Tianshan mountains and its impact on climate warming has *** T_(max6-8) variations in the Western Tianshan mountains were influenced by frequent volcanic eruptions combined with the influence of solar activity and the sum-mer North Atlantic *** study reveals that cli-mate warming is significantly influenced by the increase in maximum temperatures and clarifies possible driving mech-anisms of temperature variations in the Western Tianshan mountains which should aid climate predictions.

关键词： Tree rings Western Tianshan mountains Temperature change Climate warming

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In situ and on-line monitoring of cadmium in soil pore water using an automatic sampling integrated electrochemical sensor

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Science China(Technological Sciences) 2024年第9期67卷 2894-2904页

作者： KUANG JiaJie WEN JunLin cai XiXi ZHOU LiHua YUAN Yong Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control School of Environmental Science and EngineeringInstitute of Environmental Health and Pollution ControlGuangdong University of TechnologyGuangzhou 510006China School of Biomedical and Pharmaceutical Sciences Guangdong University of TechnologyGuangzhou 510006China

Cadmium(Cd) contamination in soil pore water is the primary pathway for Cd uptake by food crops,such as rice(Oryza sativa L.),posing significant risks to both food safety and human *** study presents a novel soil pore water metal sensor(SPW-Msensor) for in situ and online monitoring of Cd in soil pore water(Cd_(pw)).The SPW-Msensor integrates an automated sampling device,comprising a Rhizon sampler and a reciprocating series pump with an independent dual plunger drive,along with a portable electrochemical sensor consisting of a screen-printed electrode,flow cell,and portable *** SPW-Msensor enables the detection of Cd within a linear range of 50 to 300 ppb while exhibiting high anti-interference ***,it demonstrates excellent repeatability(relative standard deviation values(RSDs)<3.6%) across 30 measurements conducted within a 2-h *** method exhibits good agreement with results obtained using the standard ICP-MS method(RSDs<5%).Additionally,this study establishes a positive correlation between Cd_(pw)detected by the SPW-Msensor and total Cd concentration(Cd_(total)) in the soil with an R^(2) value equal to *** acquired from the SPW-Msensor can be utilized for predicting Cd_(total)through partial least squares regression modeling,achieving model quality score(Q^(2)) of 0.69,adjusted R^(2) of 0.9345,and root mean square error(RMSE) of *** SPW-Msensor demonstrates real-time monitoring capabilities for assessing Cd levels in acidified *** SPW-Msensor offers an efficient approach for in-situ and continuous monitoring of Cd_(pw)that provides valuable insights applicable to environmental and agricultural domains.

关键词： cadmium pore water electrochemical sensor in-situ monitoring soil

Nd^(3)+:YAG-Al_(2)O_(3) nanocrystalline transparent ceramics with high inflexion concentration quenching of Nd^(3+) prepared by amorphous crystallization

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Journal of Advanced Ceramics 2024年第8期13卷 1242-1253页

作者： Xiujuan Wan Guangfan Tan Liang cai Jie Fu Jianqiang Li Yingchun Zhang School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China State Key Laboratory of New Ceramics and Fine Processing School of Materials Science and EngineeringTsinghua UniversityBeijing 100080China State Key Lab for Mesoscience and Engineering Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China

Rare earth ion-doped Y_(3)Al_(5)O_(12)(YAG)-based transparent ceramics have been used as important laser gain media for a long time,yet the doping concentration of active ions is limited due to concentration quenching,wherein the inflexion concentration quenching of Nd^(3+)is recognized as 1.0 at%.In this work,YAG-Al_(2)O_(3) nanocrystalline transparent ceramics with a concentration of Nd^(3+)(O-5.0 at%)were fabricated via amorphous crystallization,and the crystal structure evolution,morphology,and optical properties were systematically investigated by differential scanning calorimetry(DSC),X-ray powder diffraction(XRD),transmission electron microscopy(TEM),magnetic resonation(MAS),nuclear magnetic resonation(NMR),and fluorescence *** doping of Nd^(3+)can promote the transition of Al[5]and Al[6]to Al[14],indicating improvements in the ability of the amorphous material to form Nd^(3+):Y_(2)O_(3)-Al_(2)O_(3) vitrified beads,and 1.5 at%Nd^(3+):YAG-Al_(2)O_(3) nanocrystalline transparent ceramics can be obtained by crystallization at 1050℃ with a matrix composed of YAG and concomitant δ-Al_(2)O_(3) and θ-Al_(2)O_(3).The nanocrystalline transparent ceramics show an internal transmitance of 89.56%at 1064 nm,and the strongest emission peak corresponds to the energy transfer from 4F_(3/2) to 4l_(11/2) of Nd^(3+)with a fluorescence lifetime of 231μs when pumped by an 808 nm ***,spectral broadening begins to occur,indicating the onset of concentration quenching,when the concentration of Nd^(3+)exceeds 1.5 at%,substantially higher than the 1.0 at% observed in YAG ***-Al_(2)O_(3) nanocrystalline transparent ceramics obtained by amorphous crystalization can be utilized as the matrix to increase the inflexion point of doping concentration quenching of Nd^(3+),and this material may have great potential as a laser gain medium.

关键词： Y_(3)Al_(5)O_(12)(YAG)-Al_(2)O_(3) nanocrystalline transparent ceramics laser gain medium Nd^(3+)

Experimental study on performance of spring damping support structure system for large deformation tunnel in soft rock

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Underground Space 2024年第2期15卷 221-243页

作者： Jinfeng Xu Xiongyao Xie Zhou Shi Wuqiang cai Dinglun Xu Chen Xu Department of Geotechnical Engineering College of Civil EngineeringTongji UniversityShanghai 200092China Key Laboratory of Geotechnical and Underground Engineering Ministry of EducationTongji UniversityShanghai 200092China Zhaotong City Zhaolu Expressway Investment and Development Co. ZhaotongYunnan Province 657000China Institute of Rock Mechanics Ningbo UniversityNingboZhejiang 315211China

According to the convergence confinement theory,it is an effective measure to control the large deformation of high ground stress in fractured soft rock tunnels by using yielding *** yielding support can be classified as either radial or circumferential yielding *** yielding support is achieved by transforming radial displacement into circumferential tangential closure without compromising the support capacity of the primary lining support *** on this,and inspired by the design principle of dampers,a yielding support structure system with spring damping elements as its core was developed,based on the connection characteristics of steel arches in highway tunnel,which can provide increasing support resistance in the yielding deformation *** the mechanical properties of spring damping elements were obtained through indoor axial pressure and flexural *** addition,according to these results with numerical calculations,the yielding support structure system with embedded spring damping elements can reduce the internal force of the support structure by approximately 10%and increase the area of the plastic zone of the surrounding rock by 11.23%,which can fully utilize the self-bearing capacity of surrounding rock and verify the effectiveness of circumferential yielding ***,the spring damping support structure system was designed with reference to the construction process of the tunnel excavated by drilling and blasting method,and the transformation of the spring damping element to spring damping support structure was *** on field test results,surrounding ground pressure for the yielding support optimization scheme was reduced by 40%and more evenly distributed,resulting in the successful application and a reduction in the construction cost of large deformation tunnels in soft rock.

关键词： Soft rock Highway tunnel Convergence confinement method Circumferential yielding support with spring damping element Numerical calculations Field test

Landslide Displacement Prediction Based on Time Series and PSO-BP Model in Three Georges Reservoir, China

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Journal of Earth Science 2024年第3期35卷 1079-1082页

作者： Dexiang Gao Kou Li Yuncheng cai Tao Wen School of Geosciences Yangtze UniversityWuhan 430100China School of Science Yunnan Agricultural UniversityKunming 650201China

0 INTRODUCTION Landslides are one of the most frequent geological disasters in the world(Wen et al.,2020;Froude and Petley,2018),which have occurred frequently and widely distributed in China for a long *** landslides are essentially a complex multidimensional nonlinear dynamic system affected by its own geological conditions and external factors(Ma et al.,2021;Wang et al.,2019),including geotechnical characteristics,hydrogeology,geomorphologic conditions,climate,and weathering(Ma et al.,2020).The interaction of these factors makes the change of landslide displacement random,fuzzy and variable(Park and Michalowski,2017),and also brings great difficulties to the landslide displacement prediction(Ma et al.,2018).

关键词： landslide Landslide weathering

Skin-inspired interface modification strategy toward a structurefunction integrated hybrid smart fabric system with self-powered sensing property for versatile applications

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Nano Research 2024年第9期17卷 8200-8208页

作者： Xiang Cheng Teng Chen De Gong Pengcheng Ma Bo Chen Jun cai Aerospace Information Research Institute Chinese Academy of SciencesBeijing 100190China School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China Beijing U-Precision Tech Co. Ltd.Beijing 100176China University of Chinese Academy of Sciences Beijing 100049China

Fabric-based composites with superior mechanical properties and excellent perceptive function are highly ***,it remains a huge challenge to attain structure-function integration,especially for hybrid fabric ***,a skin-inspired interface modification strategy is proposed toward this target by constructing a hybrid smart fabric system consisting of two types of smart fabrics:carbon nanotube(CNT)/MXene-modified aramid fabrics and zinc oxide nanorod(ZnO NR)-modified carbon *** on that,flexible piezoelectric pressure sensors with skin-like hierarchical perception interfaces are fabricated,which demonstrate superb sensitivity of 2.39 V·kPa^(-1)and are capable of various wearable monitoring ***,the interface-modified hybrid fabric reinforced plastics can also be fabricated,which are proven to possess 13.6%higher tensile strength,10.1%elastic *** impressively,their average energy absorption can be improved by 111.9%,accompanied with inherent damage alert *** offers a paradigm to fabricate structure-function integrated hybrid smart fabric composites for the smart clothing and intelligent aerial vehicles.

关键词： hybrid fabrics interface modification piezoelectric pressure sensors self-diagnostic composites structure-function integration