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Bi-dimension decomposed hidden Markov models for multi-person activity recognition

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第6期10卷 810-819页

作者： Wei-dong ZHANG Feng CHEN Wen-li xu Department of Automation Tsinghua University Beo'ing 100084 China

We present a novel model for recognizing long-term complex activities involving multiple persons. The proposed model, named ‘decomposed hidden Markov model’ (DHMM), combines spatial decomposition and hierarchical abstraction to capture multi-modal, long-term dependent and multi-scale characteristics of activities. Decomposition in space and time offers conceptual advantages of compaction and clarity, and greatly reduces the size of state space as well as the number of parameters. DHMMs are efficient even when the number of persons is variable. We also introduce an efficient approximation algorithm for inference and parameter estimation. Experiments on multi-person activities and multi-modal individual activities demonstrate that DHMMs are more efficient and reliable than familiar models, such as coupled HMMs, hierarchical HMMs, and multi-observation HMMs.

关键词： Multi-channel setting Hierarchical modeling Hidden Markov model Activity recognition

Development of Transition Metal Nitrides as Oxygen and Hydrogen Electrocatalysts

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Chinese Journal of Structural Chemistry 2022年第7期41卷 4-15页

作者： xuesheng Yan Daijie Deng Suqin Wu Henan li li xu Institute for Energy Research School of Chemistry and Chemical EngineeringKey Laboratory of ZhenjiangJiangsu UniversityZhenjiang 212013China

With the increasing demand for energy, various emerging energy storage/conversion technologies have gradually penetrated human life, providing numerous conveniences. The practical application efficiency is often affected by the slow kinetics of hydrogen or oxygen electrocatalytic reactions(hydrogen evolution and oxidation reactions, oxygen evolution and reduction reactions) among the emerging devices. Therefore, the researchers devote to finding cost-effective electrocatalysts. Non-noble metal catalysts have low cost and good catalytic activity, but poor stability, agglomeration, dissolution, and other problems will occur after a long cycle, such as transition metal oxides and carbides. Transition metal nitrides(TMNs) stand out among all kinds of non-noble metal catalysts because of the intrinsic platinum-like electrocatalytic activities, relatively high conductivity, and wide range of tunability. In this review, the applications of TMNs in electrocatalytic fields are summarized based on the number of metals contained in TMNs. The practical application potentials of TMNs in fuel cell, water splitting, zinc-air battery and other electrochemical energy storage/conversion devices are also listed. Finally, the design strategies and viewpoints of TMNs-based electrocatalyst are summarized. The potential challenges of TMNs-based electrocatalyst in the development of electrocatalytic energy devices in the future are prospected.

关键词： transition metal nitrides hydrogen oxygen improvement strategies electrocatalysts

Changes in leaf stomatal traits of different aged temperate forest stands

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Journal of Forestry Research 2021年第3期32卷 927-936页

作者： Qian li Jihua Hou Nianpeng He li xu Zihao Zhang Beijing Key Laboratory of Forest Resources and Ecosystem Processes Beijing Forestry UniversityBeijing 100083People’s Republic of China Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101People’s Republic of China College of Resources and Environment University of Chinese Academy of SciencesBeijingPeople’s Republic of China Key Laboratory of Vegetation Ecology Ministry of EducationNortheast Normal UniversityChangchunPeople’s Republic of China

Stomata control carbon and water vapor exchange between the leaves and the atmosphere,thus infl uencing photosynthesis and *** of forest patches with different stand ages are common in nature,however,information of which stomatal traits vary among these stands and how,remains ***,seven different aged forest stands(6,14,25,36,45,55,and 100 years)were selected in typical temperate,mixed broadleaf-conifer forests of northeast *** density,size and relative area of 624 species,including the same species in stands of different ages were *** density,size and relative area were distributed log-normally,differing across all species and plant functional *** density ranged from 4.2 to 1276.7 stomata mm^(–2),stomatal size ranged from 66.6 to 8315.7μm^(2),and stomatal relative area 0.1–93.3%.There was a significant negative relationship between density and size at the species and functional group levels,while the relative stomatal area was positively correlated with density and *** traits of dominant species were relatively stable across different stand ages but were significantly different for *** results suggest that stomatal traits remain relatively stable for dominant species in natural forests and therefore,spatial variation in stomatal traits across forest patches does not need to be incorporated in future ecological models.

关键词： Forest restoration Stomatal traits Stand age Plant functional groups Variation

Identification of Known and Novel PTCH Mutations in Both Syndromic and Non-syndromic Keratocystic Odontogenic Tumors

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International Journal of Oral Science 2009年第1期1卷 34-38页

作者： Shuang Pan li-li xu li-sha Sun Tie-jun li Department of Oral Pathology Peking University School and Hospital of Storaatology Beijing China

Aim To clarify the role of PTCH in patients with NBCCS- related and non-sydromic keratocystic odontogenic tumors. Methodology Mutation analysis was undertaken in 8 sporadic and 4 NBCCS-associated KCOTs. Results Four novel and two known mutations were identifled in 2 sporadic and 3 syndromic cases, two of which being germline mutations （c.2179delT, c.2824delC） and 4 somatic mutations （c.3162dupG, c.1362-1374dup, c.1012 C〉T, c.403C〉T）. Conclusion Our findings suggest that defects of PTCH are associated with the pathogenesis of syndromic as well as a subset of non-syndromic KCOTs.

关键词： keratocystic odontogenic tumor mutation,nevoid basal cell carcinoma syndrome PTCH

An Improved Method of Joint Inversion Using GPS and Gravity Observation Data

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Geo-Spatial Information Science 2005年第3期8卷 225-229页

作者： li Zhicai xu Caijun National Geomatics Center of China Haidian District Beijing China Key Laboratory of Geospace Environment and Geodesy Ministry of Eduction School of Geodesy and Geomatics Wuhan University Wuhan China

On the basis of the dislocation theory and gravity observation, a joint inversion model is presented with a fitting factor A scaling amplitudes between the gravity and GPS observation data. The test results show that the new joint model is better than that taking the scale factor ）, as a constant from the inversion result of MSE （mean square error）. In addition, the random cost method used in the inversion algorithm is revised and improved, which shows that the improved random cost method can easily get the local minimum value and greatly decrease the iteration steps.

关键词： joint inversion scale parameter random cost method

Nutrient coordination mechanism of tiger nut induced by rhizosphere soil nutrient variation in an arid area, China

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Journal of Arid Land 2023年第10期15卷 1216-1230页

作者： TAN Jin WU Xiuqin li Yaning SHI Jieyu li xu School of Soil and Water Conservation Beijing Forestry UniversityBeijing 100083China

Tiger nut is a bioenergy crop planted in arid areas of northern China to supply oil and adjust the planting ***,in the western region of Inner Mongolia Autonomous Region,China,less water resources have resulted in a scarcity of available farmland,which has posed a huge obstacle to planting tiger *** of tiger nut on marginal land can effectively solve this *** fully unlock the production potential of tiger nut on marginal land,it is crucial for managers to have comprehensive information on the adaptive mechanism and nutrient requirement of tiger nut in different growth *** study aims to explore these key information from the perspective of nutrient coordination strategy of tiger nut in different growth periods and their relationship with rhizosphere soil *** fertilization treatments including no fertilization(N:P(nitrogen:phosphorous)=0:0),traditional fertilization(N:P=15:15),and additional N fertilizer(N:P=60:15)were implemented on marginal land in the Dengkou *** and soil samples were collected in three growth periods,including stolon tillering period,tuber expanding period,and tuber mature *** no fertilization,there was a significant correlation between N and P contents of tiger nut roots and tubers and the same nutrients in the rhizosphere soil(Plization,there was a significant impact on the P content of tiger nut tubers(Plizer,the accumulation rate of N and P was faster in stolons than in tubers(Plimited availability of nutrients in the rhizosphere soil prompts tiger nut to increase the C:N ratio,improving N utilizat

关键词： tiger nut stoichiometry rhizosphere soil nitrogen addition marginal land

Speech perception in noise:Masking and unmasking

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Journal of Otology 2021年第2期16卷 109-119页

作者： Xianhui Wang li xu Communication Sciences and Disorders Ohio UniversityAthensOH45701USA

Speech perception is essential for daily *** noise or concurrent talkers,on the other hand,can make it challenging for listeners to track the target speech(i.e.,cocktail party problem).The present study reviews and compares existing findings on speech perception and unmasking in cocktail party listening environments in English and Mandarin *** review starts with an introduction section followed by related concepts of auditory *** next two sections review factors that release speech perception from masking in English and Mandarin Chinese,*** last section presents an overall summary of the findings with comparisons between the two *** research directions with respect to the difference in literature on the reviewed topic between the two languages are also discussed.

关键词： Speech perception Auditory masking Speech unmasking Cocktail party problems Mandarin Chinese

Electrochemical impedance spectroscopy study on the corrosion of the weld zone of 3Cr steel welded joints in CO_2 environments

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International Journal of Minerals,Metallurgy and Materials 2015年第5期22卷 500-508页

作者： li-ning xu Jin-yang Zhu Min-xu Lu Lei Zhang Wei Chang Corrosion and Protection Center Key Laboratory for Environmental Fracture (MOE) Institute for Advanced Materials and Technology University of Science and Technology Beijing CNOOC Research Institute

The welded joints of 3Cr pipeline steel were fabricated with commercial welding wire using the gas tungsten arc welding （GTAW） technique. Potentiodynamic polarization curves, linear polarization resistance （LPR）, electrochemical impedance spectroscopy （EIS）, scan- ning electron microscopy （SEM）, and energy-dispersive spectrometry （EDS） were used to investigate the corrosion resistance and the growth of a corrosion film on the weld zone （WZ）. The changes in electrochemical characteristics of the film were obtained through fitting of the EIS data. The results showed that the average corrosion rate of the WZ in CO2 environments first increased, then fluctuated, and finally de- creased gradually. The formation of the film on the WZ was divided into three stages： dynamic adsorption, incomplete-coverage layer forma- tion, and integral layer formation.

关键词： petroleum pipelines steel corrosion welded joints carbon dioxide electrochemical impedance spectroscopy

Silicon-mediated enantioselective synthesis of structurally diverseα-amino acid derivatives

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Science China Chemistry 2020年第8期63卷 1082-1090页

作者： Jun-Han Ma li li Yu-li Sun Zheng xu Xing-Feng Bai Ke-Fang Yang Jian Cao Yu-Ming Cui Guan-Wu Yin li-Wen xu Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education and Key Laboratory of Organosilicon Material Technology of Zhejiang ProvinceHangzhou Normal UniversityHangzhou 311121China State Key Laboratory for Oxo Synthesis and Selective Oxidation Suzhou Research Institute(SRI)and Lanzhou Institute of Chemical Physics(LICP)University of Chinese Academy of Sciences(UCAS)Lanzhou 730000China

The catalytic asymmetric synthesis of novel and chiral amino acid derivatives with unconventional chemo-,diastereo-,and enantio-selectivity remains a paramount *** we reported a novel protocol for the use of highly enantioselective copper-catalyzed cycloaddition ofα,β-unsaturated acylsilanes as a springboard reaction for the facile synthesis of structurally diversified pyrrolidines and complicatedα-amino esters by *** newly developed process could provide a wide range of synthetically useful acylsilane-substituted pyrrolidines(ASiP)in high yields and excellent diastereo-and enantioselectivities with Cu/(R)-XylBINAP complex as the *** the downstream desilylation transformation enables to expand the potntial applications of 1,3-dipolar cycloaddition in the construction of structurally unique amino acid derivatives,in which an unprecedented and concerted fluoride anion-promoted C–X(X=H,Si,N,C)bond cleavage occurred to the enantioselective construction of aldehyde-substituted pyrrolidines,linear cinnamaldehyde or alkene-substituted amino esters in high ee values.

关键词： (3+2)cycloaddition asymmetric catalysis acylsilane pyrrolidine amino aldehyde amino acids