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Regulating wrinkling patterns by periodic surface stiffness in film-substrate structures

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Science China(Technological Sciences) 2019年第5期62卷 747-754页

作者： LI Bo ZENG ChongQing YIN SiFan FENG XiQiao Institute of Biomechanics and Medical Engineering AML Department of Engineering Mechanics Tsinghua University

Surface wrinkling of materials holds promise for important applications in diverse fields such as multifunctional surfaces and biomedical engineering. For these applications, it is of interest to attain various surface wrinkles with tunable wavelengths and amplitudes. Through a combination of experiments and numerical simulations, we here propose a method to regulate the wrinkling patterns in a film-substrate system by introducing periodic surface stiffness, which is generated through sequential specified ultraviolet-ozone(UVO) treatments. Both experiments and numerical simulations demonstrate that the proposed technique can produce various patterns with wide, tunable geometrical features and anisotropy. The effects of surface stiffness distribution, the exposure durations of UVO-treatments, and the loading biaxiality are examined on the generated surface patterns.

关键词： film-substrate system wrinkling surface patterns stiffness modification

Elevational patterns of abundant and rare bacterial diversity and composition in mountain streams in the southeast of the Tibetan Plateau

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Science China Earth Sciences 2019年第5期62卷 853-862页

作者： Keshao LIU TANDong YAO Yongqin LIU Baiqing XU Anyi HU Yuying CHEN Key Laboratory of Tibetan Environment Changes and Land Surface Processes Chinese Academy of Sciences University of Chinese Academy of Sciences CAS Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of Sciences Key Laboratory of Alpine Ecology and Biodiversity Chinese Academy of Sciences Key Laboratory of Urban Pollutant Conversion Institute of Urban Environment Chinese Academy of Sciences

Elevational gradients are powerful ‘natural laboratory' for testing the responses of microbes to geophysical influences. Microbial communities are normally composed of a few abundant and many rare taxa. Abundant and rare taxa play different ecological roles in kinds of environments, but how their diversity and composition patterns response to elevation gradients is still poorly elucidated. In this study, we investigated the elevational patterns of abundant and rare bacterial diversity and composition in a mountain stream from 712 to 3435 m at Gangrigabu Mountain on the Tibetan Plateau, China. Our results revealed abundant and rare bacteria had similar decreasing elevation trend of alpha diversity, and both of them showed a significant elevational distance-decay relationship. However, the turnover rate of the elevational distance-decay of rare bacteria was higher than that of abundant bacteria. The species-abundance distribution patterns of rare taxonomic composition were associated with the elevational gradient, while most of abundant bacterial clades did not display any relationships with *** results suggested that rare bacteria were more sensitive to changes in elevation gradient.

关键词： Rare bacteria Diversity patterns Elevation gradients Mountain stream

Fabrication of Polythiophene patterns through Blending of a Thermally Curable Polythiophene with Poly(methyl methacrylate) and Selective Thermal Curation

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Chinese Journal of Polymer Science 2017年第3期35卷 422-433页

作者： Mushtaque A.Memon Jin-hua Sun Hee-Tae Jung 闫寿科耿建新 State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical Technology Beijing 100029 China Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing 100190 China National Research Laboratory Department of Chemical and Biomolecular Engineering (BK-21) Korea Advanced Institute of Science and Technology 373-1 Guseong-dong Yuseong-gu Daejeon 305-701 Korea

In this study, we demonstrate a novel method for fabricating polythiophene patterns, i.e., cylindrical holes and cylinders, through blending of a thermally curable polythiophene carrying with tertiary ester groups(PT-tert-ESTER) and poly(methyl methacrylate)(PMMA), followed by thermal conversion of the PT-tert-ESTER to an insoluble polythiophene via low-temperature cleavage of the tertiary ester groups and removal of the PMMA component via ultraviolet degradation. We show that the surface polarity of substrates, the mass ratio of PT-tert-ESTER to PMMA in the blend solutions as well as the concentration of the blend solutions strongly influence the formation of the polythiophene patterns. Cylindrical holes are more readily formed on less polar substrates when a PT-tert-ESTER dominated blend solution is used, while cylinders are more readily formed on more polar substrates when a PMMA dominated blend solution is used. Moreover, the diameters of both the cylindrical holes and the cylinders decrease as the PT-tert-ESTER concentration is increased in the respective ranges of the PT-tert-ESTER/PMMA ratios where the patterns are formed. Grazing incident X-ray diffraction data have indicated that the patterning of the PT-tert-ESTER component in the blend films improves the crystallinity of PT-tert-ESTER as well as the molecular packing of the insoluble polythiophene in the resultant patterned polythiophene films.

关键词： Polythiophene patterns Cylindrical holes Cylinders Blending

Controllable and tunable plasma photonic crystals through a combination of photonic crystal and dielectric barrier discharge patterns

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Plasma Science and Technology 2023年第8期25卷 74-86页

作者：郭丽婷潘宇扬于广林王朝阳高匡雅范伟丽董丽芳 Department of Electrical Engineering Shanghai Jiao Tong UniversityShanghai 200240People's Republic of China Aviation Key Laboratory of Science and Technology on High Intensity Electromagnetic Environment Protection Anhui Province Key Laboratory of Aircraft Lightning ProtectionHefei 230031People's Republic of China

We report five types of patterns with square symmetry,including three novel types obtained by inserting a specially designed grid photonic crystal(PC)into a dielectric barrier discharge *** are studied using an intensified charge-coupled device camera and photomultiplier *** three novel types of patterns are a square pattern with one structure,a square superlattice pattern with four sublattices and a(1/4)K_(grid)(K_(grid)is the basic wave vector of the grid),and another square pattern with a complex inversion discharge *** the application viewpoint,the five types of patterns can be used as plasma photonic crystals(PPCs).Their band diagrams under a transverse-magnetic wave simulated by the finite element method show that there are a large number of band *** with the original PC with only a unidirectional band gap,the five types of PPCs have tunable and omnidirectional band gaps,which is very important in controlling the propagation of electromagnetic waves in the mm-wave *** experimental results enrich the pattern types in the dielectric barrier discharge system and provide a method for obtaining PPCs with symmetry controllability and bandgap tunability.

关键词： dielectric barrier discharge plasma photonic crystal patterns electromagnetic waves

Multi-scale regionalization based mining of spatio-temporal teleconnection patterns between anomalous sea and land climate events

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Journal of Central South University 2017年第10期24卷 2438-2448页

作者： XU Feng SHI Yan DENG Min GONG Jian-ya LIU Qi-liang JIN Rui Department of Geo-informatics Central South UniversityChangsha 410083China State Key Laboratory of Information Engineering in Surveying(Mapping&Remote Sensing Wuhan University)Wuhan 430079China Collaborative Innovation Center of Geospatial Technology Wuhan UniversityWuhan 430079China

Climate sequences can be applied to defining sensitive climate zones, and then the mining of spatio-temporal teleconnection patterns is useful for learning from the past and preparing for the future. However, scale-dependency in this kind of pattern is still not well handled by existing work. Therefore, in this study, the multi-scale regionalization is embedded into the spatio-temporal teleconnection pattern mining between anomalous sea and land climatic events. A modified scale-space clustering algorithm is first developed to group climate sequences into multi-scale climate zones. Then, scale variance analysis method is employed to identify climate zones at characteristic scales, indicating the main characteristics of geographical phenomena. Finally, by using the climate zones identified at characteristic scales, a time association rule mining algorithm based on sliding time windows is employed to discover spatio-temporal teleconnection patterns. Experiments on sea surface temperature, sea level pressure, land precipitation and land temperature datasets show that many patterns obtained by the multi-scale approach are coincident with prior knowledge, indicating that this method is effective and reasonable. In addition, some unknown teleconnection patterns discovered from the multi-scale approach can be further used to guide the prediction of land climate.

关键词： climate sequences anomalous climatic events spatio-temporal teleconnection patterns multi-scale regionalization

Compressed ghost imaging based on differential speckle patterns

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Chinese Physics B 2020年第2期29卷 294-300页

作者： Le Wang Shengmei Zhao Institute of Signal Processing and Transmission Nanjing University of Posts and Telecommunications(NUPT)Nanjing 210003China Key Laboratory of Broadband Wireless Communication and Sensor Network Technology(NUPT) Ministry of EducationNanjing 210003China

We propose a compressed ghost imaging scheme based on differential speckle patterns,named *** the scheme,a series of bucket detector signals are acquired when a series of random speckle patterns are employed to illuminate an unknown *** the differential speckle patterns(differential bucket detector signals)are obtained by taking the difference between present random speckle patterns(present bucket detector signals)and previous random speckle patterns(previous bucket detector signals).Finally,the image of object can be obtained directly by performing the compressed sensing algorithm on the differential speckle patterns and differential bucket detector *** experimental and simulated results reveal that CGI-DSP can improve the imaging quality and reduce the number of measurements comparing with the traditional compressed ghost imaging schemes because our scheme can remove the environmental illuminations efficiently.

关键词： ghost imaging compressed sensing differential speckle patterns differential bucket detector signals

Precipitation differences cause contrast patterns of glacier-melt water supplied discharge of two glacier basins between northern and southern Third Pole

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Science Bulletin 2019年第7期64卷 431-434页

作者： Ruzhen Yao Jiancheng Shi Aerospace Information Research Institute Chinese Academy of Sciences

In the Third Pole (TP) region, there are about 100,000 km2of glaciers [1], distributed mainly in the Tibetan Plateau and its surroundings. Glacier melt-water from these glaciers not only feeds rivers, such as the Indus, Brahmaputra, Ganges, Yellow and Yangtze, which finally reach the seas, but also feeds the rivers, such as the Tarim River, Heihe River and a lot of other rivers, which finally reach the arid areas or deserts. The Asian Water Tower [2]is, therefore, proposed to characterize the significance of the glaciers and glacier melt water at all the river heads in the TP, which is important water resource both for regulating seasonal water demands in the arid areas or deserts and for sea level rising. In addition, they also change the water cycle at a large scale [3].

关键词： TP Precipitation differences cause contrast patterns of glacier-melt water supplied discharge of two glacier basins between northern and southern Third Pole

Dominant Synoptic patterns and Their Relationships with PM2.5 Pollution in Winter over the Beijing–Tianjin–Hebei and Yangtze River Delta Regions in China

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Journal of Meteorological Research 2019年第4期33卷 765-776页

作者： Yuzhi LIU Bing WANG Qingzhe ZHU Run LUO Chuqiao WU Rui JIA Key Laboratory for Semi-Arid Climate Change of the Ministry of Education College of Atmospheric SciencesLanzhou UniversityLanzhou 730000 Meteorological Observatory Unit 95021 Yichang 441000

This paper concerns about the episodes of PM2.5 pollution that frequently occur in China in winter *** severity of PM2.5 pollution is strongly dependent on the synoptic-scale atmospheric *** combined PM2.5 concentration data and meteorological data with the Hybrid Single Particle Lagrangian Integrated Trajectory model(HYSPLIT4)to investigate the dominant synoptic patterns and their relationships with PM2.5 pollution over the Beijing–Tianjin–Hebei(BTH)and Yangtze River Delta(YRD)regions in the winters of 2014–*** transport of PM2.5 from the BTH to YRD regions was examined by using cluster analysis and *** is found that the level of PM2.5 pollution over the BTH region was higher than that over the YRD *** concentration of PM2.5 in the atmosphere was more closely related to meteorological factors over the BTH *** episodes of PM2.5 pollution over the BTH region in winter were related to weather patterns such as the rear of a high-pressure system approaching the sea,a high-pressure field,a saddle pressure field,and the leading edge of a cold *** contrast,PM2.5 pollution episodes in the YRD region in winter were mainly associated with the external transport of cold air,a high-pressure field,and a uniform pressure *** analysis shows that the trajectories of PM2.5 were significantly different under different weather ***2.5 would be transported from the BTH to the YRD within 48 h when the PM2.5 pollution episodes were associated with three different kinds of weather patterns:the rear of a highpressure system approaching the sea,the high-pressure field,and the leading edge of a cold front over the BTH *** suggests a possible method to predict PM2.5 pollution episodes based on synoptic-scale patterns.

关键词： PM2.5 pollution episodes synoptic patterns Beijing-Tianjin-Hebei (BTH) Yangtze River Delta (YRD)

Mining geographic episode association patterns of abnormal events in global earth science data

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Science China(Technological Sciences) 2008年第S1期51卷 155-164页

作者： WU TianShu,SONG GuoJie,MA XiuJun,XIE KunQing,GAO XiaoPing & JIN XingXing Key Laboratory of Machine Perception,Ministry of Education,and Department of Machine Intelligence,Peking University,Beijing 100871,China Key Laboratory of Machine Perception Ministry of Education and Department of Machine Intelligence Peking University Beijing China

Abnormal events in earth science have great influence on both the natural envi-ronment and the human society. Finding association patterns among these events has great significance. Because data in earth science has characteristics of mass,high dimension,spatial autocorrelation and time delay,existing mining technolo-gies cannot be directly used on it. We propose a RSNN (range-based searching nearest neighbors) spatial clustering algorithm to reduce the data size and auto-correlation. Based on the clustered data,we propose a GEAM (geographic episode association pattern mining) algorithm which can deal with events time lags and find interesting patterns with specific constraints,to mine the association patterns. We carried out experiments on global climate datasets and found many interesting association patterns. Some of the patterns are coincident with known knowledge in climate science,which indicates the correctness and feasibilities of our methods,and the others are unknown to us before,which will give new information to this research field.

关键词： abnormal events association patterns high dimensional clustering earth science data