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Structural Complexity Analysis of Information Systems Based on Petri Nets 被引量:3
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作者 王景光 甘仞初 《Journal of Beijing Institute of Technology》 EI CAS 1999年第4期416-423,共8页
Aim To present a quantitative method for structural complexity analysis and evaluation of information systems. Methods Based on Petri net modeling and analysis techniques and with the aid of mathematical tools in ge... Aim To present a quantitative method for structural complexity analysis and evaluation of information systems. Methods Based on Petri net modeling and analysis techniques and with the aid of mathematical tools in general net theory(GNT), a quantitative method for structure description and analysis of information systems was introduced. Results The structural complexity index and two related factors, i.e. element complexity factor and connection complexity factor were defined, and the relations between them and the parameters of the Petri net based model of the system were derived. Application example was presented. Conclusion The proposed method provides a theoretical basis for quantitative analysis and evaluation of the structural complexity and can be applied in the general planning and design processes of the information systems. 展开更多
关键词 information system Petri Nets structural complexity element complexity factor connection complexity factor
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Enhanced Structural Complexity Index:An Improved Index for Describing Forest Structural Complexity 被引量:1
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作者 Philip Beckschafer Philip Mundhenk +3 位作者 Christoph Kleinn Yinqiu Ji Douglas W.Yu Rhett D.Harrison 《Open Journal of Forestry》 2013年第1期23-29,共7页
The horizontal distribution of stems, stand density and the differentiation of tree dimensions are among the most important aspects of stand structure. An increasing complexity of stand structure is often linked to a ... The horizontal distribution of stems, stand density and the differentiation of tree dimensions are among the most important aspects of stand structure. An increasing complexity of stand structure is often linked to a higher number of species and to greater ecological stability. For quantification, the Structural Complexity Index (SCI) describes structural complexity by means of an area ratio of the surface that is generated by connecting the tree tops of neighbouring trees to form triangles to the surface that is covered by all triangles if projected on a flat plane. Here, we propose two ecologically relevant modifications of the SCI: The degree of mingling of tree attributes, quantified by a vector ruggedness measure, and a stem density term. We investigate how these two modifications influence index values. Data come from forest inventory field plots sampled along a disturbance gradient from heavily disturbed shrub land, through secondary regrowth to mature montane rainforest stands in Mengsong, Xishuangbanna,Yunnan,China. An application is described linking structural complexity, as described by the SCI and its modified versions, to changes in species composition of insect communities. The results of this study show that the Enhanced Structural Complexity Index (ESCI) can serve as a valuable tool for forest managers and ecologists for describing the structural complexity of forest stands and is particularly valuable for natural forests with a high degree of structural complexity. 展开更多
关键词 Forest Structure Index structural complexity Stem Map Species Composition NMDS
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The analysis of structural complexity of Piano Pieces "dedicated to Alice"
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作者 Junzhong ZHANG 《International Journal of Technology Management》 2014年第11期57-59,共3页
Beethoven is a famous German pianist, composer, and conductor, and he set the culmination of Western classical, created a romantic music camp precedent. The size of his music in general is very ambitious, mostly conce... Beethoven is a famous German pianist, composer, and conductor, and he set the culmination of Western classical, created a romantic music camp precedent. The size of his music in general is very ambitious, mostly concertos, symphonies, operas and other large works, technical approach and structure used is quite complex, people are left with a deep impression. But it works, while small piano pieces, also has music research value, "dedicated to Alice" is one of the few Beethoven piano pieces. This paper focuses on creative background "dedicated to Alice," this elaborate piano works by the complexity of the analysis of the structure of this work is that it reflects the author' s ideological soul to explore their musical value. 展开更多
关键词 BEETHOVEN Piano Pieces "dedicated to Alice" complex structures
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The coordinated impact of forest internal structural complexity and tree species diversity on forest productivity across forest biomes
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作者 Qin Ma Yanjun Su +11 位作者 Tianyu Hu Lin Jiang Xiangcheng Mi Luxiang Lin Min Cao Xugao Wang Fei Lin Bojian Wang Zhenhua Sun Jin Wu Keping Ma Qinghua Guo 《Fundamental Research》 CAS CSCD 2024年第5期1185-1195,共11页
Forest structural complexity can mediate the light and water distribution within forest canopies,and has a direct impact on forest biodiversity and carbon storage capability.It is believed that increases in forest str... Forest structural complexity can mediate the light and water distribution within forest canopies,and has a direct impact on forest biodiversity and carbon storage capability.It is believed that increases in forest structural complexity can enhance tree species diversity and forest productivity,but inconsistent relationships among them have been reported.Here,we quantified forest structural complexity in three aspects(i.e.,horizontal,vertical,and internal structural complexity)from unmanned aerial vehicle light detection and ranging data,and investigated their correlations with tree species diversity and forest productivity by incorporating field measurements in three forest biomes with large latitude gradients in China.Our results show that internal structural complexity had a stronger correlation(correlation coefficient=0.85)with tree species richness than horizontal structural complexity(correlation coefficient=-0.16)and vertical structural complexity(correlation coefficient=0.61),and it was the only forest structural complexity attribute having significant correlations with both tree species richness and tree species evenness.A strong scale effect was observed in the correlations among forest structural complexity,tree species diversity,and forest productivity.Moreover,forest internal structural complexity had a tight positive coordinated contribution with tree species diversity to forest productivity through structure equation model analysis,while horizontal and vertical structural complexity attributes have insignificant or weaker coordinated effects than internal structural complexity,which indicated that the neglect of forest internal structural complexity might partially lead to the current inconsistent observations among forest structural complexity,tree species diversity,and forest productivity.The results of this study can provide a new angle to understand the observed inconsistent correlations among forest structural complexity,tree species diversity,and forest productivity. 展开更多
关键词 Internal structural complexity Horizontal structural complexity Vertical structural complexity Tree species diversity Forest productivity Lidar
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Static Requirement and Type's Complexity in the Diagnostics Phase
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《Journal of Civil Engineering and Architecture》 2012年第4期489-495,共7页
The preservation of a historical building, whatever its architectural and/or artistic value, is more successful when undertaken with a deep understanding of the building's history, development, materials and construc... The preservation of a historical building, whatever its architectural and/or artistic value, is more successful when undertaken with a deep understanding of the building's history, development, materials and construction techniques. The preliminary phase of any restoration intervention must start with data acquisition regarding the characteristics and conditions of the building, including a survey of significant alterations. In a great number of cases, restorations are not respectful of the building's static efficiency, so its static requirement is weakened. In fact, a very high percentage of instances in which a restoration effort results in building damage is attributable to such modification's indifference to the structural balance of a structure, as consolidated over time. This study focuses on the restoration intervention on two trilobate pillars that separate the central space from the presbytery in the Cathedral of Matera, located in southern Italy. Through the use of sonic tests - carried out despite the complexity of the shape of the building and constructive elements that characterize these pillars -- it was possible to show the effectiveness of the implemented intervention, highlighting critical points and weaknesses. The research aims to show how -- despite the complexity of some structural elements of a building -- in-depth knowledge of a structure's structure and history is essential to for the success of restoration interventions, which are respectful of a building's type and material peculiarities. 展开更多
关键词 structural complexity static requirements refurbishment interventions diagnosis phase CONSERVATION
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MEASURING STRUCTURE COMPLEXITY OF UML CLASS DIAGRAMS 被引量:6
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作者 Zhou Yuming Xu Baowen (Dept. of Computer Science & Eng., Southeast Univ., Nanjing 210096) (State Key Laboratory of Software Engineering, Wuhan University, Wuhan 430072) (Jiangsu Key Lab. of Computer Info. Proc. Tech., Soochow Univ., Suzhou 215006) 《Journal of Electronics(China)》 2003年第3期227-231,共5页
To provide system designer a valid measure to evaluate the structure complexityof class diagrams objectively, this letter first proposes a method to transform a class diagramsinto a weighted class dependence graph, th... To provide system designer a valid measure to evaluate the structure complexityof class diagrams objectively, this letter first proposes a method to transform a class diagramsinto a weighted class dependence graph, then presents a structure complexity measure for classdiagrams based on entropy distance. 展开更多
关键词 Class diagrams Structure complexity MEASURE Entropy distance DEPENDENCE
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A Method for Measuring the Structure Complexity of Web Application
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作者 MAO Cheng-ying LU Yan-sheng 《Wuhan University Journal of Natural Sciences》 EI CAS 2006年第1期143-150,共8页
The precise and effective measure results of Web applications not only facilitate good comprehension of them, but also benefit to the macro-management of software activities, such as testing, reverse engineering, reus... The precise and effective measure results of Web applications not only facilitate good comprehension of them, but also benefit to the macro-management of software activities, such as testing, reverse engineering, reuse, etc. The paper exploits some researches on measuring the structure complexity of Web application. Through a deep analysis of the configuration and objects' interactions of Web system, two conclusions have been drawn:① A generic Web application consists of static web page, dynamic page, component and database object; ② The main interactions have only three styles, that is static link, dynamic link and call/return relation. Based on analysis and modeling of the content of a Web page (static or dynamic), complexity measure methods of both control logic of script and nesting of HTML code are further discussed. In addition, two methods for measuring the complexity of inte〉page navigation are also addressed by modeling the inte〉page navigation behaviors of Web application via WNG graph. 展开更多
关键词 structure complexity measure DD graph HTree tree WNG graph
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Synthesis,Structural Characterization and Magnetic Properties of{[Gd(DMF)_(3)(DMSO)(H_(2)O)_(3)](μ-CN)(Fe)(CN)_(5)]}·2H_(2)O
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作者 CHEN Wen-Tong CAI Li-Zhen +4 位作者 WU A-Qing GUO Guo-Cong HUANG Jin-Shun DONG Zhen-Chao Akiyuki Matsushita 《无机化学学报》 SCIE CAS CSCD 北大核心 2004年第6期693-697,共5页
A new cyano-bridged Gadolinium^(Ⅲ)-Iron^(Ⅲ)complex{[Gd(DMF)_(3)(DMSO)(H_(2)O)_(3)]2H_(2)0(DMF=N,N·-dimethylformamide;DMSO=dimethylsulfoxidel}was synthesized by the grinding reaction method,.It crysta-]llizes in... A new cyano-bridged Gadolinium^(Ⅲ)-Iron^(Ⅲ)complex{[Gd(DMF)_(3)(DMSO)(H_(2)O)_(3)]2H_(2)0(DMF=N,N·-dimethylformamide;DMSO=dimethylsulfoxidel}was synthesized by the grinding reaction method,.It crysta-]llizes in the triclinic.,space group P1 with ceIl parameters:a=O.90363(2)nm,b=1.25078(3)nm,c=1.41303(1)nm,穋m^(-3),Z=2,Mr=756.72,F(000)=760,Ⅲ)and the approxi-mately oriented octahedrally sixfold-coordinated Fe(Ⅲ)are linked by a cyano-bridge group to construct a dinuclear compound.The{[Gd(DMF)_(3)(DMSO)(H_(2)O)_(3)](Ⅲ)-Fe(Ⅲ)interaction is antiferromagnetic.CCDC:223430. 展开更多
关键词 crystal structure cyano-bridged dinuclear complex hybrid prussian blue complex molecular magnet lanthanide mixed ligand complex
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Tree species identity and interaction determine vertical forest structure in young planted forests measured by terrestrial laser scanning
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作者 Mengxi Wang Lander Baeten +7 位作者 Frieke Van Coillie Kim Calders Kris Verheyen Quentin Ponette Haben Blondeel Bart Muys John Armston Hans Verbeeck 《Forest Ecosystems》 SCIE CSCD 2024年第3期266-275,共10页
Vertical forest structure is closely linked to multiple ecosystem characteristics,such as biodiversity,habitat,and productivity.Mixing tree species in planted forests has the potential to create diverse vertical fores... Vertical forest structure is closely linked to multiple ecosystem characteristics,such as biodiversity,habitat,and productivity.Mixing tree species in planted forests has the potential to create diverse vertical forest structures due to the different physiological and morphological traits of the composing tree species.However,the relative importance of species richness,species identity and species interactions for the variation in vertical forest structure remains unclear,mainly because traditional forest inventories do not observe vertical stand structure in detail.Terrestrial laser scanning(TLS),however,allows to study vertical forest structure in an unprecedented way.Therefore,we used TLS single scan data from 126 plots across three experimental planted forests of a largescale tree diversity experiment in Belgium to study the drivers of vertical forest structure.These plots were 9–11years old young pure and mixed forests,characterized by four levels of tree species richness ranging from monocultures to four-species mixtures,across twenty composition levels.We generated vertical plant profiles from the TLS data and derived six stand structural variables.Linear mixed models were used to test the effect of species richness on structural variables.Employing a hierarchical diversity interaction modelling framework,we further assessed species identity effect and various species interaction effects on the six stand structural variables.Our results showed that species richness did not significantly influence most of the stand structure variables,except for canopy height and foliage height diversity.Species identity on the other hand exhibited a significant impact on vertical forest structure across all sites.Species interaction effects were observed to be site-dependent due to varying site conditions and species pools,and rapidly growing tree species tend to dominate these interactions.Overall,our results highlighted the importance of considering both species identity and interaction effects in choosing suitable species combinations for forest management practices aimed at enhancing vertical forest structure. 展开更多
关键词 TreeDivNet FORBIO Stand structural complexity Terrestrial laser scanning Vertical forest structure Tree diversity Planted forests
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Additive manufacturing of pure copper via vat photopolymerization with slurry
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作者 An-liang YE Meng WANG +4 位作者 Yan-bin JIANG Xiao-zan WU Chao-qun PENG Jin HE Xiao-feng WANG 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2024年第12期3992-4004,共13页
Stereolithography(SLA)combined with a two-step post-processing method“oxidation−reduction”was developed to fabricate pure copper with high complexity.The copper slurries for SLA were prepared,and particularly the in... Stereolithography(SLA)combined with a two-step post-processing method“oxidation−reduction”was developed to fabricate pure copper with high complexity.The copper slurries for SLA were prepared,and particularly the influence of volume fraction of copper on the properties of copper slurries was investigated.In the two-step post-treatment process,organics were removed by oxidation and copper powder was oxidized simultaneously,and then the oxidized copper was reduced into highly reactive copper particles,improving the sintering activity of the copper green body and enhancing the relative density of the sintered part.The results show that curing depth of the copper slurries decreased with the increase of volume fraction of copper.The viscosity of the pure copper slurry rises exponentially as the volume fraction of copper exceeded 50%.The highest volume fraction of pure copper slurry for SLA is 55%.The specimens exhibited an increase in hardness and electrical conductivity with the increase of volume fraction of copper.Specifically,the maximum values of hardness and conductivity of samples with 55 vol.%copper were HV 52.7 and 57.1%(IACS),respectively. 展开更多
关键词 pure copper additive manufacturing STEREOLITHOGRAPHY complex structure parts copper slurry
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Modularized and Parametric Modeling Technology for Finite Element Simulations of Underground Engineering under Complicated Geological Conditions
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作者 Jiaqi Wu Li Zhuo +4 位作者 Jianliang Pei Yao Li Hongqiang Xie Jiaming Wu Huaizhong Liu 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第7期621-645,共25页
The surrounding geological conditions and supporting structures of underground engineering are often updated during construction,and these updates require repeated numerical modeling.To improve the numerical modeling ... The surrounding geological conditions and supporting structures of underground engineering are often updated during construction,and these updates require repeated numerical modeling.To improve the numerical modeling efficiency of underground engineering,a modularized and parametric modeling cloud server is developed by using Python codes.The basic framework of the cloud server is as follows:input the modeling parameters into the web platform,implement Rhino software and FLAC3D software to model and run simulations in the cloud server,and return the simulation results to the web platform.The modeling program can automatically generate instructions that can run the modeling process in Rhino based on the input modeling parameters.The main modules of the modeling program include modeling the 3D geological structures,the underground engineering structures,and the supporting structures as well as meshing the geometric models.In particular,various cross-sections of underground caverns are crafted as parametricmodules in themodeling program.Themodularized and parametric modeling program is used for a finite element simulation of the underground powerhouse of the Shuangjiangkou Hydropower Station.This complicatedmodel is rapidly generated for the simulation,and the simulation results are reasonable.Thus,this modularized and parametric modeling program is applicable for three-dimensional finite element simulations and analyses. 展开更多
关键词 Underground engineering modularized and parametric modeling finite element method complex geological structure cloud modeling
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在复二维仿射锥上的完备余齐性一Kahler度量
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作者 关庄丹 梁梦翔 《Chinese Quarterly Journal of Mathematics》 2024年第2期200-220,共21页
In this paper,we revisit the Kahler structures on the affine quadrics M1={z_(1)^(2)+z_(2)^(2)+z_(3)^(2)=1}in the paper by Bo Yang and Fang-Yang Zheng.We found that the Kahler structures on the complex surface are more... In this paper,we revisit the Kahler structures on the affine quadrics M1={z_(1)^(2)+z_(2)^(2)+z_(3)^(2)=1}in the paper by Bo Yang and Fang-Yang Zheng.We found that the Kahler structures on the complex surface are more complicated than what they have thought.We shall also give some detail calculations and found that our results fit quite well with earlier papers of the first author,one of them with X.X.Chen. 展开更多
关键词 Affine quadrics Complex structure Kahler metrics Cohomogeneity one action
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Reversible Data Hiding Algorithm in Encrypted Images Based on Adaptive Median Edge Detection and Ciphertext-Policy Attribute-Based Encryption
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作者 Zongbao Jiang Minqing Zhang +2 位作者 Weina Dong Chao Jiang Fuqiang Di 《Computers, Materials & Continua》 SCIE EI 2024年第10期1123-1155,共33页
With the rapid advancement of cloud computing technology,reversible data hiding algorithms in encrypted images(RDH-EI)have developed into an important field of study concentrated on safeguarding privacy in distributed... With the rapid advancement of cloud computing technology,reversible data hiding algorithms in encrypted images(RDH-EI)have developed into an important field of study concentrated on safeguarding privacy in distributed cloud environments.However,existing algorithms often suffer from low embedding capacities and are inadequate for complex data access scenarios.To address these challenges,this paper proposes a novel reversible data hiding algorithm in encrypted images based on adaptive median edge detection(AMED)and ciphertext-policy attributebased encryption(CP-ABE).This proposed algorithm enhances the conventional median edge detection(MED)by incorporating dynamic variables to improve pixel prediction accuracy.The carrier image is subsequently reconstructed using the Huffman coding technique.Encrypted image generation is then achieved by encrypting the image based on system user attributes and data access rights,with the hierarchical embedding of the group’s secret data seamlessly integrated during the encryption process using the CP-ABE scheme.Ultimately,the encrypted image is transmitted to the data hider,enabling independent embedding of the secret data and resulting in the creation of the marked encrypted image.This approach allows only the receiver to extract the authorized group’s secret data,thereby enabling fine-grained,controlled access.Test results indicate that,in contrast to current algorithms,the method introduced here considerably improves the embedding rate while preserving lossless image recovery.Specifically,the average maximum embedding rates for the(3,4)-threshold and(6,6)-threshold schemes reach 5.7853 bits per pixel(bpp)and 7.7781 bpp,respectively,across the BOSSbase,BOW-2,and USD databases.Furthermore,the algorithm facilitates permission-granting and joint-decryption capabilities.Additionally,this paper conducts a comprehensive examination of the algorithm’s robustness using metrics such as image correlation,information entropy,and number of pixel change rate(NPCR),confirming its high level of security.Overall,the algorithm can be applied in a multi-user and multi-level cloud service environment to realize the secure storage of carrier images and secret data. 展开更多
关键词 Ciphertext-policy attribute-based encryption complex data access structure reversible data hiding large embedding space
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Post-stack reverse-time migration using a finite difference method based on triangular grids 被引量:4
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作者 郭书娟 李振春 +3 位作者 孙小东 叶月明 滕厚华 李芳 《Applied Geophysics》 SCIE CSCD 2008年第2期115-120,共6页
Compared with other migration methods, reverse-time migration is based on a precise wave equation, not an approximation, and performs extrapolation in the depth domain rather than the time domain. It is highly accurat... Compared with other migration methods, reverse-time migration is based on a precise wave equation, not an approximation, and performs extrapolation in the depth domain rather than the time domain. It is highly accurate and not affected by strong subsurface structure complexity and horizontal velocity variations. The difference method based on triangular grids maintains the simplicity of the difference method and the precision of the finite element method. It can be used directly for forward modeling on models with complex top surfaces and migration without statics preprocessing. We apply a finite difference method based on triangular grids for post-stack reverse-time migration for the first time. Tests on model data verify that the combination of the two methods can achieve near-perfect results in application. 展开更多
关键词 reverse-time migration structural complexity triangular grids finite difference
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Discussion on the Complex Structure of Nilpotent Lie Groups Gk
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作者 Caiyu Du Yu Wang 《Open Journal of Applied Sciences》 2024年第6期1401-1411,共11页
Consider the real, simply-connected, connected, s-step nilpotent Lie group G endowed with a left-invariant, integrable almost complex structure J, which is nilpotent. Consider the simply-connected, connected nilpotent... Consider the real, simply-connected, connected, s-step nilpotent Lie group G endowed with a left-invariant, integrable almost complex structure J, which is nilpotent. Consider the simply-connected, connected nilpotent Lie group Gk, defined by the nilpotent Lie algebra g/ak, where g is the Lie algebra of G, and ak is an ideal of g. Then, J gives rise to an almost complex structure Jk on Gk. The main conclusion obtained is as follows: if the almost complex structure J of a nilpotent Lie group G is nilpotent, then J can give rise to a left-invariant integrable almost complex structure Jk on the nilpotent Lie group Gk, and Jk is also nilpotent. 展开更多
关键词 Almost Complex Structure Nilpotent Lie Group Nilpotent Lie Algebra
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Large-scale complex physical modeling and precisionanalysis 被引量:6
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作者 吴满生 狄帮让 +4 位作者 魏建新 梁向豪 周翼 刘依谋 孔昭举 《Applied Geophysics》 SCIE CSCD 2014年第2期245-251,255,共8页
Large-scale 3D physical models of complex structures can be used to simulate hydrocarbon exploration areas. The high-fidelity simulation of actual structures poses challenges to model building and quality control. Suc... Large-scale 3D physical models of complex structures can be used to simulate hydrocarbon exploration areas. The high-fidelity simulation of actual structures poses challenges to model building and quality control. Such models can be used to collect wideazimuth, multi-azimuth, and full-azimuth seismic data that can be used to verify various 3D processing and interpretation methods. Faced with nonideal imaging problems owing to the extensive complex surface conditions and subsurface structures in the oil-rich foreland basins of western China, we designed and built the KS physical model based on the complex subsurface structure. This is the largest and most complex 3D physical model built to date. The physical modeling technology advancements mainly involve 1) the model design method, 2) the model casting flow, and 3) data acquisition. A 3D velocity model of the physical model was obtained for the first time, and the model building precision was quantitatively analyzed. The absolute error was less than 3 mm, which satisfies the experimental requirements. The 3D velocity model obtained from 3D measurements of the model layers is the basis for testing various imaging methods. Furthermore, the model is considered a standard in seismic physical modeling technology. 展开更多
关键词 complex structure seismic physical modeling modeling construction ACQUISITION
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Analysis of complicated structure seismic wave fields 被引量:3
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作者 周辉 王尚旭 +1 位作者 李国发 沈金松 《Applied Geophysics》 SCIE CSCD 2010年第2期185-192,195,共9页
In western China seismic wave fields are very complicated and have low signal to noise ratio.In this paper,we focus on complex wave field research by forward modeling and indicate that density should not be ignored in... In western China seismic wave fields are very complicated and have low signal to noise ratio.In this paper,we focus on complex wave field research by forward modeling and indicate that density should not be ignored in wave field simulation if the subsurface physical properties are quite different.We use the acoustic wave equation with density in the staggered finite-difference method to simulate the wave fields.For this purpose a complicated geologic structural model with rugged surfaces,near-surface low-velocity layers,and high-velocity outcropping layers was designed.Based on the instantaneous wave field distribution,we analyzed the mechanism forming complex wave fields.The influence of low velocity layers on the wave field is very strong.A strong waveguide occurs between the top and base of a low velocity layer,producing multiples which penetrate into the earth and form strong complex wave fields in addition to reflections from subsurface interfaces.For verifying the correctness of the simulated wave fields,prestack depth migration was performed using different algorithms from the forward modeling.The structure revealed by the stacked migration profile is same as the known structure. 展开更多
关键词 Wave equation SIMULATION complex geological structure wave field analysis guided wave
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Sub-stand diameter distribution types vary along an old-growth Douglas-fir chronosequence into the horizontal diversification development stage 被引量:1
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作者 JeriLynn E.Peck Eric K.Zenner 《Journal of Forestry Research》 SCIE CAS CSCD 2023年第2期415-424,共10页
Managing mature Douglas-fir[Pseudotsuga menziesii(Mirb.)Franco]stands to emulate the structural complexity of natural old-growth forest requires identifying structural targets at the sub-stand level at which neighborh... Managing mature Douglas-fir[Pseudotsuga menziesii(Mirb.)Franco]stands to emulate the structural complexity of natural old-growth forest requires identifying structural targets at the sub-stand level at which neighborhood dynamics and patchy disturbance shape structure.We therefore sought to describe the archetypal shapes of predominant sub-stand diameter distribution types(DDTs)observed in natural tree neighborhoods in stands comprising a chronosequence(ca.120-450+yrs)encompassing mature,vertical diversification,and horizontal diversification development stages.The ten 1.0 ha stands are located in the southcentral Oregon Cascades,USA.Building on the known spatial position of each tree,natural tree neighborhoods were identified using the floating neighborhood approach based on spatial tessellation connecting neighboring trees at the first-(mean 61 m2)through fifth-(mean 2058 m2)order scales.Cluster analysis was then used to objectively identify the most predominant DDTs among the relative tree size distributions observed in the trans-scale neighborhoods within each stand.Repeated measures regression was used to classify each DDT to one of six observed archetypal shapes:negative exponential,unimodal,rotated sigmoid,bimodal,concave,or multi-modal.Only three of the 81 observed DDTs deviated by<10%from the stand average,while every stand had at least one DDT that deviated by>50%(maximum 83%).Within each stand,five to ten predominant DDTs were observed,which deviated from the stand average by 30-48%and were characterized by two to five different archetypal shapes.Consequently,in some stands the majority of tree neighborhoods were best characterized by a different shape from that assigned at the stand level.Deviation from the stand average increased from the youngest stand in the mature development stage through the middle stands in the vertical diversification stage to the oldest stands in the horizontal diversification stage.The complexity of DDT shapes tended to increase along the chronosequence(from negative exponential and uniform toward concave and multi-modal),with shape richness highest mid-sequence and evenness peaking in the oldest stands.The high diversity of sub-stand structural complexity reduces the utility of standlevel diameter distributions as old-growth restoration targets.However,the presence in early-sequence stands of sub-stand diameter distributions common to later-sequence stands may facilitate active management at the neighborhood level to promote future old-growth condition.Restoration of substand diameter structures would likely require combining spatial perspectives,such as by augmenting tree-level croptree management with diameter distribution targets for the resulting tree neighborhoods. 展开更多
关键词 Diameter distribution type Floating neighborhood Restoration silviculture Small-scale structural complexity
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Evolutionary Trend and Asymmetric Evolution of Living Things 被引量:1
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作者 李易洲 《Agricultural Science & Technology》 CAS 2009年第6期7-10,39,共5页
The evolutionary trend of organisms, which often evolved from a simpler structure to a more complex structure, is a mystery. It seems that the later living things appeared on the earth, the more complex their structur... The evolutionary trend of organisms, which often evolved from a simpler structure to a more complex structure, is a mystery. It seems that the later living things appeared on the earth, the more complex their structures were. This study pointed out that the evolutionary trend of organisms was the result of the organisms' asymmetric evolution-the phenomenon which the partition of the more complex structure was actually larger than that of the simpler structure on the same evolutionary platform of organisms, it explained the cause of the asymmetric evolution and listed much important evidence for organisms' asymmetric evolution. 展开更多
关键词 Bio-system Simple structure Complex structure Asymmetry-evolution
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Taxonomic and community composition of epigeal arthropods in monoculture and mixed tree species plantations in a deciduous forest of Ghana
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作者 Frederick Gyasi Damptey Emmanuel Opuni-Frimpong +5 位作者 Collins Ayine Nsor James Addai Daniel Kwame Debrah Benjamin Schnerch Felicity Bentsi-Enchill Henn Korjus 《Journal of Forestry Research》 SCIE CAS CSCD 2023年第3期641-653,共13页
Tropical forests provide several ecosystem services and functions and support approximately two-thirds of the world’s biodiversity but are seriously threatened by deforestation.Approaches to counteract this menace ha... Tropical forests provide several ecosystem services and functions and support approximately two-thirds of the world’s biodiversity but are seriously threatened by deforestation.Approaches to counteract this menace have revolved around aff orestation with several or a single tree species.We thus investigated how plantation forests with either a single or several tree species infl uenced arthropod taxonomic and community composition using pitfall traps to sample selected groups of epigeal arthropods(Araneae,Coleoptera,Orthoptera and Hymenoptera)and with environmental variables assessed simultaneously.Our results revealed 54 taxonomic groups with signifi cantly higher taxonomic richness,activity density,and diversity in the mixed stands than in the monoculture stands.The significant differences in community composition were mainly driven by families including Lycosidae,Formicidae,Staphylinidae,Scotylidae,Hydrophilidae,Gryllidae and Scarabaeidae and were explained by distinct habitat characteristics(canopy openness,litter depth,deadwood volume,and tree height).While the diverse tree communities and heterogeneous vegetation structure off ered food and habitat resources for diverse arthropod groups,the allelopathic nature coupled with homogenous stand characteristics of the Tectona grandis stands in the monoculture suppressed the growth of understorey vegetation that could otherwise serve as food and habitat resources for arthropods,which might have led to limited activities and diversity of arthropods in the monoculture plantation stands.The fi ndings thus highlight the need to promote mixed tree plantations in degraded tropical areas,especially when restoring biodiversity is the prime management focus. 展开更多
关键词 Arthropod community Forest plantations structural complexity Tree diversity Tropical deforestation
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