The atom-bond connectivity（ABC） index provides a good model for the stability of linear and branched alkanes as well as the strain energy of cycloalkanes,which is defined as ABC（G） =∑ uv∈E（G） √d u＋dv-2 dudv,...The atom-bond connectivity（ABC） index provides a good model for the stability of linear and branched alkanes as well as the strain energy of cycloalkanes,which is defined as ABC（G） =∑ uv∈E（G） √d u＋dv-2 dudv,where du denotes the degree of a vertex u in G.A chemical graph is a graph in which no vertex has degree greater than 4.In this paper,we obtain the sharp upper and lower bounds on ABC index of chemical bicyclic graphs.展开更多
Topological method was applied firstly to calculate the topological connectivity index of minerals (TCIM). The reciprocal of effective atomic refractivity of metal element in minerals was chosen as its valence. The re...Topological method was applied firstly to calculate the topological connectivity index of minerals (TCIM). The reciprocal of effective atomic refractivity of metal element in minerals was chosen as its valence. The reasonability of TCIM as an activity criterion was tested through comparison of TCIM with two kinds of electronegativity parameter, i.e. ionic percentage and energy criteria of Yang’s electronegativity, solubility product, energy criterion according to the generalized perturbation theory and adsorption of flotation reagents on the surface of minerals. The results indicated that TCIM is an effective structural parameter of minerals to study the structure activity relationship. In addition, different mineral is of different TCIM value, so TCIM brings about convenience in comparison of flotation activity for minerals.展开更多
Torrential processes are among the main actors responsible for sediment production and mobility in mountain catchments.For this reason,the understanding of preferential pathways for sediment routing has become a prior...Torrential processes are among the main actors responsible for sediment production and mobility in mountain catchments.For this reason,the understanding of preferential pathways for sediment routing has become a priority in hazard assessment and mitigation.In this context,the sediment Connectivity Index(IC)enables to analyse the existing linkage between sediment sources and the selected target(channel network or catchment outlet).The IC is a grid-based index that allows fast computation of sediment connectivity based on landscape information derived from a single Digital Terrain Model(DTM).The index computation is based on the log-ratio between an upslope and a downslope component,including information about drainage area,slope,terrain roughness,and distance to the analysis target(e.g.outlet).The output is a map that highlights the degree of structural connectivity of sediment pathways over analysed catchments.Until now,these maps are however rarely used to help defining debris-flow hazard maps,notably due to a lack of guidelines to interpret the IC spatial distribution.This paper proposes an exploitation procedure along profiles to extract more information from the analysis of mapped IC values.The methodology relies on the analysis of the IC and its component variables along the main channel profile,integrated with information about sediment budgeting derived from Difference of DEMs(DoD).The study of connectivity was applied in the unmanaged sub-catchment(without torrent control works)of the Rio Soial(Autonomous Province of Trento–NE Italy)to understanding the geomorphic evolution of the area after five debris flows(in ten years)and the related changes of sediment connectivity.Using a recent DTM as validation,we demonstrated how an IC analysis over the older DTM can help predicting geomorphic changes and associated hazards.The results show an IC aptitude to capture geomorphic trajectories,anticipate debris flow deposits in a specific channel location,and depict preferential routing pathways.展开更多
The atom-bond connectivity（ABC） index of a graph G, introduced by Estrada,Torres, Rodr′？guez and Gutman in 1998, is defined as the sum of the weights√1/di＋1/dj-2/didj of all edges vivj of G, where di denotes th...The atom-bond connectivity（ABC） index of a graph G, introduced by Estrada,Torres, Rodr′？guez and Gutman in 1998, is defined as the sum of the weights√1/di＋1/dj-2/didj of all edges vivj of G, where di denotes the degree of the vertex vi in G. In this paper, we give an upper bound of the ABC index of a two-tree G with n vertices, that is, ABC（G） ≤（2n- 4）√2/2＋√2n-4/n-1. We also determine the two-trees with the maximum and the second maximum ABC index.展开更多
Over the past six decades,the implementation of soil and water conservation measures has significantly reduced soil erosion and sediment yield on the Loess Plateau,China.However,while the overall reduction is well-doc...Over the past six decades,the implementation of soil and water conservation measures has significantly reduced soil erosion and sediment yield on the Loess Plateau,China.However,while the overall reduction is well-documented,the dynamic interplay between soil erosion potential and sediment connectivity,specifically how they spatially covary under land use/cover changes,remains insufficiently understood.To address this gap,this study established a model framework by integrating the revised universal soil loss equation(RUSLE),index of connectivity(IC),and sediment delivery ratio(SDR)to evaluate the spatio-temporal variations in soil erosion and sediment yield in the Hantaichuan Watershed,northern Loess Plateau,China,from 1995 to 2020 and to estimate the effects of land use/cover changes and check dam construction on sediment yield.The results revealed that the soil erosion in the Hantaichuan Watershed decreased by 43.90% from 1995 to 2020 and the sediment yield decreased by 69.28% under the combination of land use/cover changes and check dam construction.The IC and soil erosion(IC-SE)map revealed both the coupling and decoupling covariation relationships between sediment connectivity and soil erosion.By 2020,areas with high connectivity and high erosion(I-E)covered only 18.67% of the watershed,while contributed more than 40.00% to the total erosion.The I-E zones were mainly located in the central part of the watershed where aeolian sands derived from the Hobq Desert are concentrated and were identified as critical areas for soil and water conservation.This study provides support for priority management of watershed conservation measures as well as a valuable reference for future studies.展开更多
Bond connectivity topological index S i based on chemical bonds was defined by using a matrix method.And S i is formed by atomic parameters such as the number of valence electrons,the number of the highest main quan...Bond connectivity topological index S i based on chemical bonds was defined by using a matrix method.And S i is formed by atomic parameters such as the number of valence electrons,the number of the highest main quantum of atoms and the bonding electrons and bond parameters such as the length of bonds,the electronegativity difference of bonding atoms.The molecular bond connectivity topological index S is composed of S i.The thermodynamic properties of saturated hydrocarbons,unsaturated hydrocarbons,oxygen organic,methane halide and transitional element compounds and the molecular bond connectivity topological index S have an optimal correlative relationship.展开更多
Mao'ershan region is representative in the natural secondary forested region of the eastern mountainous region, northeast China. The landscape nearest neighbor index and landscape connectivity index were calculate...Mao'ershan region is representative in the natural secondary forested region of the eastern mountainous region, northeast China. The landscape nearest neighbor index and landscape connectivity index were calculated with ARC/INFO software for Mao'ershan region. The spatial distribution of the landscape of the region was analyzed. The results showed that the landscape connectivity index of non-woodland was significantly higher than that of woodland. The landscape connectivity index of natural forest was nearly equal to zero, which means its fragmentation degree is high. The nearest neighbor index of plantation was lower than that of natural forest and non-forestland. Among the man-made forests, the distance index of the coniferous mixed plantation is the lowest, and its pattern is nearly glomeration. The landscape pattern of natural forest presented nearly random distribution. Among non-forest land, the distance index of cut blank was the lowest, and its pattern was also nearly glomeration. Keywords Landscape type - Landscape pattern - Nearest neighbor index - Landscape connectivity index - Natural secondary forest - Northeast China CLC number S759.92 Document code A Foundation item: This paper was supported by the Key Project of State Department of Science Technology (2002BA515B040).Biography: LI SHu-juan (1977), female. Lecture in Ocean University of China, Qingdao 266003, P. R. China.Responsible editor: Zhu Hong展开更多
According to the definitions of molecular connectivity and hyper-Wiener index, a novel set of hyper-Wiener indexes （Dn, ^mDn） were defined and named as condensed extended hyper-Wiener index, the potential usefulness...According to the definitions of molecular connectivity and hyper-Wiener index, a novel set of hyper-Wiener indexes （Dn, ^mDn） were defined and named as condensed extended hyper-Wiener index, the potential usefulness of which in QSAR/QSPR is evaluated by its correlation with a number of C3-C8 alkanes as well as by a favorable comparison with models based on molecular connectivity index and overall Wiener index.展开更多
For a connected simple graph G, the eccentricity ec（v） of a vertex v in G is the distance from v to a vertex farthest from v, and d（v） denotes the degree of a vertex v. The eccentric connectivity index of G, denot...For a connected simple graph G, the eccentricity ec（v） of a vertex v in G is the distance from v to a vertex farthest from v, and d（v） denotes the degree of a vertex v. The eccentric connectivity index of G, denoted by ξC（G）, is defined as ∑vЕV（G） d（v）ec（v）. In this paper, we will determine the graphs with maximal eccentric connectivity index among the connected graphs with n vertices and m edges（n ≤ m ≤ n ＋ 4）, and propose a conjecture on the graphs with maximal eccentric connectivity index and m edges （m ≥ n ＋ 5）. among the connected graphs with n vertices展开更多
Let G = (V,E) be a graph, where V(G) is a non-empty set of vertices and E(G) is a set of edges, e = uv∈E(G), d(u) is degree of vertex u. Then the first Zagreb polynomial and the first Zagreb index Zg<sub>1</...Let G = (V,E) be a graph, where V(G) is a non-empty set of vertices and E(G) is a set of edges, e = uv∈E(G), d(u) is degree of vertex u. Then the first Zagreb polynomial and the first Zagreb index Zg<sub>1</sub>(G,x) and Zg<sub>1</sub>(G) of the graph G are defined as Σ<sub>uv∈E(G)</sub>x<sup>(d<sub>u</sub>+d<sub>v</sub>)</sup> and Σ<sub>e=uv∈E(G)</sub>(d<sub>u</sub>+d<sub>v</sub>) respectively. Recently Ghorbani and Hosseinzadeh introduced the first Eccentric Zagreb index as Zg<sub>1</sub>*</sup>=Σ<sub>uv∈E(G)</sub>(ecc(v)+ecc(u)), that ecc(u) is the largest distance between u and any other vertex v of G. In this paper, we compute this new index (the first Eccentric Zagreb index or third Zagreb index) of an infinite family of linear Polycene parallelogram of benzenoid.展开更多
The COVID-19 pandemic and rising geopolitical tensions have severely disrupted global air transport,signifi-cantly impacting airport connectivity.This study analyzes the evolving patterns of global airport connectivit...The COVID-19 pandemic and rising geopolitical tensions have severely disrupted global air transport,signifi-cantly impacting airport connectivity.This study analyzes the evolving patterns of global airport connectivity in response to these overlapping crises.On top of using a refined Global Airport Connectivity Index(GACI)applied at quarterly intervals from 2019 to 2024,we develop an international GACI metric to evaluate changes and regional disparities across distinct stages of disruption and recovery.The findings reveal that,while global airport connectivity has largely returned to pre-pandemic levels,recovery trajectories varied markedly across regions due to different pandemic response strategies,vaccination timelines,and conflict-related airspace clo-sures.Specifically,the Middle East and North Africa experienced rapid recovery,whereas Northeast Asia and Eastern Europe lagged,hampered by prolonged border restrictions and geopolitical conflicts respectively.Furthermore,the results indicate that medium-sized and emerging international airports played a significant role in the overall market recovery.The study provides important insights into emerging structural shifts in the global air transport network,underscoring the necessity for adaptive,coordinated policies to enhance resilience against future disruptions.展开更多
Dendrimers are man-made polymeric macromolecules created from branching chains known as monomers. Topological indices (TIs) are molecular descriptors that define the structure and aid in establishing relationships wit...Dendrimers are man-made polymeric macromolecules created from branching chains known as monomers. Topological indices (TIs) are molecular descriptors that define the structure and aid in establishing relationships with various physicochemical properties such as volatility, density, melting point, and more. TIs are categorized according to their distance, spectrum, and degree. Within these TIs, topological descriptors based on connection numbers (CN) hold significant importance. In this article, we calculate the overall outcomes of Zagreb connection indices, including the inverse sum connection index (ISCI), geometric arithmetic connection index (GACI), harmonic connection index (HCI), atom bond connectivity connection index (ABCCI), hyper Zagreb connection index (HZCI), and symmetric division connection index (SDCI) for the polypropyleneimine anoctamin (PPIO) dendrimer and Poly(Propyl) Ether Imine (PPEI) dendrimers. PPIO dendrimers and PPEI dendrimers are a new class of versatile nanostructured materials capable of exhibiting extraordinary physicochemical properties, which are closely related to their intricate tree-like architecture. PPIO dendrimers (synthesized using polypropylene imine) are relatively biocompatible and show promise as drug carriers, mainly because their core is hydrophobic with a hydrophilic surface. The PPEI dendrimers are highly soluble in alcohols and water and offer the ability to introduce a versatile range of functionalities. Their controlled structure, stability and tunable surface functionalities make these dendrimers attract much attention in several fields like biomedical applications, catalysis and nanotechnology. Additionally, a comparative analysis is performed to validate the excellence of our generated graphical and numerical outcomes.展开更多
In this paper, we compute Atom-bond connectivity index, Fourth atom-bond connectivity index, Sum connectivity index, Randic connectivity index, Geometric-arithmetic connectivity index and Fifth geometric-arithmetic co...In this paper, we compute Atom-bond connectivity index, Fourth atom-bond connectivity index, Sum connectivity index, Randic connectivity index, Geometric-arithmetic connectivity index and Fifth geometric-arithmetic connectivity index of Dutch windmill graph.展开更多
Physical mechanisms and influencing factors on the effective stress coefficient for rock/soil-like porous materials are investigated, based on which equivalent connectivity index is proposed. The equivalent connectivi...Physical mechanisms and influencing factors on the effective stress coefficient for rock/soil-like porous materials are investigated, based on which equivalent connectivity index is proposed. The equivalent connectivity index, relying on the meso-scale structure of porous material and the property of liquid, denotes the connectivity of pores in Representative Element Area （REA）. If the conductivity of the porous material is anisotropic, the equivalent connectivity index is a second order tensor. Based on the basic theories of continuous mechanics and tensor analysis, relationship between area porosity and volumetric porosity of porous materials is deduced. Then a generalized expression, describing the relation between effective stress coefficient tensor and equivalent connectivity tensor of pores, is proposed, and the expression can be applied to isotropic media and also to anisotropic materials. Furthermore, evolution of porosity and equivalent connectivity index of the pore are studied in the strain space, and the method to determine the corresponding functions in expressions above is proposed using genetic algorithm and genetic programming. Two applications show that the results obtained by the method in this paper perfectly agree with the test data. This paper provides an important theoretical support to the coupled hydro-mechanical research.展开更多
A new model based on the theoretical work of Boudh-Hir and Mansoori was developed for prediction of surface tension of pure fluids. The new model has the advantage of not requiring densities in the calculation, and th...A new model based on the theoretical work of Boudh-Hir and Mansoori was developed for prediction of surface tension of pure fluids. The new model has the advantage of not requiring densities in the calculation, and the input parameters are critical temperature and connectivity indices. A total of 209 compounds covering a wide variety of substances were used to develop the model, and the overall correlative AAD is 4.21%. To test its predictive ability, the model is further used to predict the surface tension of 25 more compounds that were not included in the model development. The overall predictive AAD is 4.07%, which illustrates that the model is reliable. The model proposed is simple and easy to apply, with good predictive accuracy.展开更多
The thermodynamic relationships among aqueous solubility and molar volume (MV) , total molecular surface area (TSA) and molecular connectivity index (MCI) for highly hydrophobic chemicals. PCBs are established and dis...The thermodynamic relationships among aqueous solubility and molar volume (MV) , total molecular surface area (TSA) and molecular connectivity index (MCI) for highly hydrophobic chemicals. PCBs are established and discussed, respectively. Good linear relationships exist among In Cs and MV, TSA or MCI.展开更多
Based on quantitative structure-property relationship （QSPR） of organic compounds, the molecular connectivity indices of 21 phthalic acid ester compounds were extracted. Relationship between the physicochemical prop...Based on quantitative structure-property relationship （QSPR） of organic compounds, the molecular connectivity indices of 21 phthalic acid ester compounds were extracted. Relationship between the physicochemical properties （n-octanol/air partition coefficient, vapor pressure, water solubility） and the molecular connectivity indices of phthalic acid ester compounds have been established by multiple linear regression （MLR） method. The results showed that the zero-order valence connectivity index （0Xu） is the topology parameter which affects octanol/water partition coefficient and water solubility, and the topology parameter which affects vapor pressure is the first-order connectivity index （1X）. This indicated to a certain extent_that the molecular connectivity indices can be well used to express the quantitative relationship between the physicochemical properties and structure descriptions of phthalic acid ester compounds. The models constructed have good robustness and highly predictive capability.展开更多
The eccentricity of a vertex in a graph is the maximum distance from the vertex to any other vertex. Two structure topological indices: eccentric connectivity index and connective eccentricity index involving eccentri...The eccentricity of a vertex in a graph is the maximum distance from the vertex to any other vertex. Two structure topological indices: eccentric connectivity index and connective eccentricity index involving eccentricity have a wide range of applications in structure-activity relationships and pharmaceutical drug design etc. In this paper, we investigate the eccentric connectivity index and the connective eccentricity index of a (3, 6)-fullerene. We find a relation between the radius and the number of spokes of a (3, 6)-fullerene. Based on the relation, we give the computing formulas of the eccentric connectivity index and the connective eccentricity index of a (3, 6)-fullerene, respectively.展开更多
Prediction of antagonistic activity of <em>β</em>-carboline and its thirteen derivatives has been made using topological descriptors viz, connectivity index, and kappa shape index of different orders. For...Prediction of antagonistic activity of <em>β</em>-carboline and its thirteen derivatives has been made using topological descriptors viz, connectivity index, and kappa shape index of different orders. For evaluation of values of descriptor, molecular modeling and geometry optimization of all the compounds were carried out with CAChe Pro software by opting semiempirical PM3 method using MOPAC 2002. For prediction of activity multiple linear regression analysis (MLR) was performed. MLR analysis has been made by Project Leader Software associated with CAChe by using the above descriptors as independent variables and biological activity as dependent variables. We were performed leave-one-out methods and the result reflected a direct relationship between biological activity and connectivity index of zero order, while indirect relationship with connectivity index of second order and thus connectivity index is a reliable descriptor to predict the biological activity of <em>β</em>-carboline and its various derivatives.展开更多
Two typical provincial capitals （Nanjing and Zhengzhou） and two counties （Rugao and Yuanyang） in east （Jiangsu Province） and central （Henan Province） China were chosen respectively as the developed and less de...Two typical provincial capitals （Nanjing and Zhengzhou） and two counties （Rugao and Yuanyang） in east （Jiangsu Province） and central （Henan Province） China were chosen respectively as the developed and less developed comparative cases for pedodiversity and land use diversity correlative analysis by borrowing the recently better developed pedodiversity methodology. Land use classification was worked out using remote sensing images in three different periods （1986-1988, 2000-2001 and 2004-2006） for these studied case areas before the calculation of the constituent diversity index and spatial distribution diversity index modified after Shannon entropy in 2 kmx2 km grid scale of the soil and land use pattern were conducted and then a connection index was proposed to evaluate the relationship between soil and land use diversity. Results show that during the years from 1986 to 2006, the composition and spatial distribution of regional land use pattern had changed greatly. The agricultural land area of all the studied case areas decreased obviously in which Nanjing has the highest decrement of 895.98 km2 mainly into urban use while the other land use type area changes show the same trend. The connection index of four typical soil family types and typical urban land use types, i.e., urban construction land, transportation land and industrial and mining area all increased in this period. In the studied case areas, there is the highest soil constituent diversity in Zhengzhou at 0.779 while the simplest soil constituent diversity in Rugao at 0.582. Meanwhile we have higher land use diversity in the more urbanized Jiangsu Province than Henan Province, Nanjing is ranking the first that has been getting higher and higher in the three periods at 0.366 in 1986-1988, 0.483 in 2000-2001 and 0.545 in 2004-2006. Finally, the connection index figures to evaluate the relationship between soil and land use diversity of the studied areas were compared to show the similar phenomenon that this figure grows fastest in Nanjing followed by Zhengzhou and other places.展开更多
基金Supported by the National Natural Science Foundation of China(11071272,10831001,11171279,11101087)the Young Talent Foundation of Fuzhou University(XRC-1154)
文摘The atom-bond connectivity（ABC） index provides a good model for the stability of linear and branched alkanes as well as the strain energy of cycloalkanes,which is defined as ABC（G） =∑ uv∈E（G） √d u＋dv-2 dudv,where du denotes the degree of a vertex u in G.A chemical graph is a graph in which no vertex has degree greater than 4.In this paper,we obtain the sharp upper and lower bounds on ABC index of chemical bicyclic graphs.
文摘Topological method was applied firstly to calculate the topological connectivity index of minerals (TCIM). The reciprocal of effective atomic refractivity of metal element in minerals was chosen as its valence. The reasonability of TCIM as an activity criterion was tested through comparison of TCIM with two kinds of electronegativity parameter, i.e. ionic percentage and energy criteria of Yang’s electronegativity, solubility product, energy criterion according to the generalized perturbation theory and adsorption of flotation reagents on the surface of minerals. The results indicated that TCIM is an effective structural parameter of minerals to study the structure activity relationship. In addition, different mineral is of different TCIM value, so TCIM brings about convenience in comparison of flotation activity for minerals.
文摘Torrential processes are among the main actors responsible for sediment production and mobility in mountain catchments.For this reason,the understanding of preferential pathways for sediment routing has become a priority in hazard assessment and mitigation.In this context,the sediment Connectivity Index(IC)enables to analyse the existing linkage between sediment sources and the selected target(channel network or catchment outlet).The IC is a grid-based index that allows fast computation of sediment connectivity based on landscape information derived from a single Digital Terrain Model(DTM).The index computation is based on the log-ratio between an upslope and a downslope component,including information about drainage area,slope,terrain roughness,and distance to the analysis target(e.g.outlet).The output is a map that highlights the degree of structural connectivity of sediment pathways over analysed catchments.Until now,these maps are however rarely used to help defining debris-flow hazard maps,notably due to a lack of guidelines to interpret the IC spatial distribution.This paper proposes an exploitation procedure along profiles to extract more information from the analysis of mapped IC values.The methodology relies on the analysis of the IC and its component variables along the main channel profile,integrated with information about sediment budgeting derived from Difference of DEMs(DoD).The study of connectivity was applied in the unmanaged sub-catchment(without torrent control works)of the Rio Soial(Autonomous Province of Trento–NE Italy)to understanding the geomorphic evolution of the area after five debris flows(in ten years)and the related changes of sediment connectivity.Using a recent DTM as validation,we demonstrated how an IC analysis over the older DTM can help predicting geomorphic changes and associated hazards.The results show an IC aptitude to capture geomorphic trajectories,anticipate debris flow deposits in a specific channel location,and depict preferential routing pathways.
基金Supported by the National Natural Science Foundation of China(Grant Nos.6116400561440005+6 种基金11161037)the Program for Changjiang Scholars and Innovative Research Team in Universities(Grant No.IRT-15R40)Key Laboratory of Tibetan Information Processing of Ministry of Education of Chinathe Research Fund for the Chunhui Program of Ministry of Education of China(Grant No.Z2014022)the Nature Science Foundation of Qinghai Province(Grant Nos.2013-Z-Y172014-ZJ-9072014-ZJ-721)
文摘The atom-bond connectivity（ABC） index of a graph G, introduced by Estrada,Torres, Rodr′？guez and Gutman in 1998, is defined as the sum of the weights√1/di＋1/dj-2/didj of all edges vivj of G, where di denotes the degree of the vertex vi in G. In this paper, we give an upper bound of the ABC index of a two-tree G with n vertices, that is, ABC（G） ≤（2n- 4）√2/2＋√2n-4/n-1. We also determine the two-trees with the maximum and the second maximum ABC index.
基金supported by the National Natural Science Foundation of China(42077076,42177323)the National Natural Science Foundation of China and Yellow River Water Science Research Joint Fund(U2243211).
文摘Over the past six decades,the implementation of soil and water conservation measures has significantly reduced soil erosion and sediment yield on the Loess Plateau,China.However,while the overall reduction is well-documented,the dynamic interplay between soil erosion potential and sediment connectivity,specifically how they spatially covary under land use/cover changes,remains insufficiently understood.To address this gap,this study established a model framework by integrating the revised universal soil loss equation(RUSLE),index of connectivity(IC),and sediment delivery ratio(SDR)to evaluate the spatio-temporal variations in soil erosion and sediment yield in the Hantaichuan Watershed,northern Loess Plateau,China,from 1995 to 2020 and to estimate the effects of land use/cover changes and check dam construction on sediment yield.The results revealed that the soil erosion in the Hantaichuan Watershed decreased by 43.90% from 1995 to 2020 and the sediment yield decreased by 69.28% under the combination of land use/cover changes and check dam construction.The IC and soil erosion(IC-SE)map revealed both the coupling and decoupling covariation relationships between sediment connectivity and soil erosion.By 2020,areas with high connectivity and high erosion(I-E)covered only 18.67% of the watershed,while contributed more than 40.00% to the total erosion.The I-E zones were mainly located in the central part of the watershed where aeolian sands derived from the Hobq Desert are concentrated and were identified as critical areas for soil and water conservation.This study provides support for priority management of watershed conservation measures as well as a valuable reference for future studies.
文摘Bond connectivity topological index S i based on chemical bonds was defined by using a matrix method.And S i is formed by atomic parameters such as the number of valence electrons,the number of the highest main quantum of atoms and the bonding electrons and bond parameters such as the length of bonds,the electronegativity difference of bonding atoms.The molecular bond connectivity topological index S is composed of S i.The thermodynamic properties of saturated hydrocarbons,unsaturated hydrocarbons,oxygen organic,methane halide and transitional element compounds and the molecular bond connectivity topological index S have an optimal correlative relationship.
基金This paper was supported by the Key Project of State Department of Science Technology (2002BA515B040).
文摘Mao'ershan region is representative in the natural secondary forested region of the eastern mountainous region, northeast China. The landscape nearest neighbor index and landscape connectivity index were calculated with ARC/INFO software for Mao'ershan region. The spatial distribution of the landscape of the region was analyzed. The results showed that the landscape connectivity index of non-woodland was significantly higher than that of woodland. The landscape connectivity index of natural forest was nearly equal to zero, which means its fragmentation degree is high. The nearest neighbor index of plantation was lower than that of natural forest and non-forestland. Among the man-made forests, the distance index of the coniferous mixed plantation is the lowest, and its pattern is nearly glomeration. The landscape pattern of natural forest presented nearly random distribution. Among non-forest land, the distance index of cut blank was the lowest, and its pattern was also nearly glomeration. Keywords Landscape type - Landscape pattern - Nearest neighbor index - Landscape connectivity index - Natural secondary forest - Northeast China CLC number S759.92 Document code A Foundation item: This paper was supported by the Key Project of State Department of Science Technology (2002BA515B040).Biography: LI SHu-juan (1977), female. Lecture in Ocean University of China, Qingdao 266003, P. R. China.Responsible editor: Zhu Hong
文摘According to the definitions of molecular connectivity and hyper-Wiener index, a novel set of hyper-Wiener indexes （Dn, ^mDn） were defined and named as condensed extended hyper-Wiener index, the potential usefulness of which in QSAR/QSPR is evaluated by its correlation with a number of C3-C8 alkanes as well as by a favorable comparison with models based on molecular connectivity index and overall Wiener index.
基金Supported by China Postdoctoral Science Foundation(2012M520815 and 2013T60411)the National Natural Science Foundation of China(11001089)
文摘For a connected simple graph G, the eccentricity ec（v） of a vertex v in G is the distance from v to a vertex farthest from v, and d（v） denotes the degree of a vertex v. The eccentric connectivity index of G, denoted by ξC（G）, is defined as ∑vЕV（G） d（v）ec（v）. In this paper, we will determine the graphs with maximal eccentric connectivity index among the connected graphs with n vertices and m edges（n ≤ m ≤ n ＋ 4）, and propose a conjecture on the graphs with maximal eccentric connectivity index and m edges （m ≥ n ＋ 5）. among the connected graphs with n vertices
文摘Let G = (V,E) be a graph, where V(G) is a non-empty set of vertices and E(G) is a set of edges, e = uv∈E(G), d(u) is degree of vertex u. Then the first Zagreb polynomial and the first Zagreb index Zg<sub>1</sub>(G,x) and Zg<sub>1</sub>(G) of the graph G are defined as Σ<sub>uv∈E(G)</sub>x<sup>(d<sub>u</sub>+d<sub>v</sub>)</sup> and Σ<sub>e=uv∈E(G)</sub>(d<sub>u</sub>+d<sub>v</sub>) respectively. Recently Ghorbani and Hosseinzadeh introduced the first Eccentric Zagreb index as Zg<sub>1</sub>*</sup>=Σ<sub>uv∈E(G)</sub>(ecc(v)+ecc(u)), that ecc(u) is the largest distance between u and any other vertex v of G. In this paper, we compute this new index (the first Eccentric Zagreb index or third Zagreb index) of an infinite family of linear Polycene parallelogram of benzenoid.
文摘The COVID-19 pandemic and rising geopolitical tensions have severely disrupted global air transport,signifi-cantly impacting airport connectivity.This study analyzes the evolving patterns of global airport connectivity in response to these overlapping crises.On top of using a refined Global Airport Connectivity Index(GACI)applied at quarterly intervals from 2019 to 2024,we develop an international GACI metric to evaluate changes and regional disparities across distinct stages of disruption and recovery.The findings reveal that,while global airport connectivity has largely returned to pre-pandemic levels,recovery trajectories varied markedly across regions due to different pandemic response strategies,vaccination timelines,and conflict-related airspace clo-sures.Specifically,the Middle East and North Africa experienced rapid recovery,whereas Northeast Asia and Eastern Europe lagged,hampered by prolonged border restrictions and geopolitical conflicts respectively.Furthermore,the results indicate that medium-sized and emerging international airports played a significant role in the overall market recovery.The study provides important insights into emerging structural shifts in the global air transport network,underscoring the necessity for adaptive,coordinated policies to enhance resilience against future disruptions.
文摘Dendrimers are man-made polymeric macromolecules created from branching chains known as monomers. Topological indices (TIs) are molecular descriptors that define the structure and aid in establishing relationships with various physicochemical properties such as volatility, density, melting point, and more. TIs are categorized according to their distance, spectrum, and degree. Within these TIs, topological descriptors based on connection numbers (CN) hold significant importance. In this article, we calculate the overall outcomes of Zagreb connection indices, including the inverse sum connection index (ISCI), geometric arithmetic connection index (GACI), harmonic connection index (HCI), atom bond connectivity connection index (ABCCI), hyper Zagreb connection index (HZCI), and symmetric division connection index (SDCI) for the polypropyleneimine anoctamin (PPIO) dendrimer and Poly(Propyl) Ether Imine (PPEI) dendrimers. PPIO dendrimers and PPEI dendrimers are a new class of versatile nanostructured materials capable of exhibiting extraordinary physicochemical properties, which are closely related to their intricate tree-like architecture. PPIO dendrimers (synthesized using polypropylene imine) are relatively biocompatible and show promise as drug carriers, mainly because their core is hydrophobic with a hydrophilic surface. The PPEI dendrimers are highly soluble in alcohols and water and offer the ability to introduce a versatile range of functionalities. Their controlled structure, stability and tunable surface functionalities make these dendrimers attract much attention in several fields like biomedical applications, catalysis and nanotechnology. Additionally, a comparative analysis is performed to validate the excellence of our generated graphical and numerical outcomes.
文摘In this paper, we compute Atom-bond connectivity index, Fourth atom-bond connectivity index, Sum connectivity index, Randic connectivity index, Geometric-arithmetic connectivity index and Fifth geometric-arithmetic connectivity index of Dutch windmill graph.
基金supported by the Yalongjiang River Joint Fund by the National Natural Science Foundation of China(NSFC)Ertan Hydropower Development Company,LTD(Nos.50579091 and 50539090)+1 种基金NSFC(No.10772190)Major State Basic Research Project of China(No.2002CB412708)
文摘Physical mechanisms and influencing factors on the effective stress coefficient for rock/soil-like porous materials are investigated, based on which equivalent connectivity index is proposed. The equivalent connectivity index, relying on the meso-scale structure of porous material and the property of liquid, denotes the connectivity of pores in Representative Element Area （REA）. If the conductivity of the porous material is anisotropic, the equivalent connectivity index is a second order tensor. Based on the basic theories of continuous mechanics and tensor analysis, relationship between area porosity and volumetric porosity of porous materials is deduced. Then a generalized expression, describing the relation between effective stress coefficient tensor and equivalent connectivity tensor of pores, is proposed, and the expression can be applied to isotropic media and also to anisotropic materials. Furthermore, evolution of porosity and equivalent connectivity index of the pore are studied in the strain space, and the method to determine the corresponding functions in expressions above is proposed using genetic algorithm and genetic programming. Two applications show that the results obtained by the method in this paper perfectly agree with the test data. This paper provides an important theoretical support to the coupled hydro-mechanical research.
基金Supported by the National Natural Science Foundation of China (No. 20106001) the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions of China, the Trans-century Training Programme Foundation for the Talen
文摘A new model based on the theoretical work of Boudh-Hir and Mansoori was developed for prediction of surface tension of pure fluids. The new model has the advantage of not requiring densities in the calculation, and the input parameters are critical temperature and connectivity indices. A total of 209 compounds covering a wide variety of substances were used to develop the model, and the overall correlative AAD is 4.21%. To test its predictive ability, the model is further used to predict the surface tension of 25 more compounds that were not included in the model development. The overall predictive AAD is 4.07%, which illustrates that the model is reliable. The model proposed is simple and easy to apply, with good predictive accuracy.
文摘The thermodynamic relationships among aqueous solubility and molar volume (MV) , total molecular surface area (TSA) and molecular connectivity index (MCI) for highly hydrophobic chemicals. PCBs are established and discussed, respectively. Good linear relationships exist among In Cs and MV, TSA or MCI.
基金Supported by the Natural Science Foundation of Zhejiang Province(LY12B07013,LY12C03009)Public Technology Research Project(Analysis and Measurement)of Zhejiang Province(2013C37098)Science and Technology Project of Zhejiang Province(2009C33163)
文摘Based on quantitative structure-property relationship （QSPR） of organic compounds, the molecular connectivity indices of 21 phthalic acid ester compounds were extracted. Relationship between the physicochemical properties （n-octanol/air partition coefficient, vapor pressure, water solubility） and the molecular connectivity indices of phthalic acid ester compounds have been established by multiple linear regression （MLR） method. The results showed that the zero-order valence connectivity index （0Xu） is the topology parameter which affects octanol/water partition coefficient and water solubility, and the topology parameter which affects vapor pressure is the first-order connectivity index （1X）. This indicated to a certain extent_that the molecular connectivity indices can be well used to express the quantitative relationship between the physicochemical properties and structure descriptions of phthalic acid ester compounds. The models constructed have good robustness and highly predictive capability.
文摘The eccentricity of a vertex in a graph is the maximum distance from the vertex to any other vertex. Two structure topological indices: eccentric connectivity index and connective eccentricity index involving eccentricity have a wide range of applications in structure-activity relationships and pharmaceutical drug design etc. In this paper, we investigate the eccentric connectivity index and the connective eccentricity index of a (3, 6)-fullerene. We find a relation between the radius and the number of spokes of a (3, 6)-fullerene. Based on the relation, we give the computing formulas of the eccentric connectivity index and the connective eccentricity index of a (3, 6)-fullerene, respectively.
文摘Prediction of antagonistic activity of <em>β</em>-carboline and its thirteen derivatives has been made using topological descriptors viz, connectivity index, and kappa shape index of different orders. For evaluation of values of descriptor, molecular modeling and geometry optimization of all the compounds were carried out with CAChe Pro software by opting semiempirical PM3 method using MOPAC 2002. For prediction of activity multiple linear regression analysis (MLR) was performed. MLR analysis has been made by Project Leader Software associated with CAChe by using the above descriptors as independent variables and biological activity as dependent variables. We were performed leave-one-out methods and the result reflected a direct relationship between biological activity and connectivity index of zero order, while indirect relationship with connectivity index of second order and thus connectivity index is a reliable descriptor to predict the biological activity of <em>β</em>-carboline and its various derivatives.
基金National Natural Science Foundation of China, No.41171177
文摘Two typical provincial capitals （Nanjing and Zhengzhou） and two counties （Rugao and Yuanyang） in east （Jiangsu Province） and central （Henan Province） China were chosen respectively as the developed and less developed comparative cases for pedodiversity and land use diversity correlative analysis by borrowing the recently better developed pedodiversity methodology. Land use classification was worked out using remote sensing images in three different periods （1986-1988, 2000-2001 and 2004-2006） for these studied case areas before the calculation of the constituent diversity index and spatial distribution diversity index modified after Shannon entropy in 2 kmx2 km grid scale of the soil and land use pattern were conducted and then a connection index was proposed to evaluate the relationship between soil and land use diversity. Results show that during the years from 1986 to 2006, the composition and spatial distribution of regional land use pattern had changed greatly. The agricultural land area of all the studied case areas decreased obviously in which Nanjing has the highest decrement of 895.98 km2 mainly into urban use while the other land use type area changes show the same trend. The connection index of four typical soil family types and typical urban land use types, i.e., urban construction land, transportation land and industrial and mining area all increased in this period. In the studied case areas, there is the highest soil constituent diversity in Zhengzhou at 0.779 while the simplest soil constituent diversity in Rugao at 0.582. Meanwhile we have higher land use diversity in the more urbanized Jiangsu Province than Henan Province, Nanjing is ranking the first that has been getting higher and higher in the three periods at 0.366 in 1986-1988, 0.483 in 2000-2001 and 0.545 in 2004-2006. Finally, the connection index figures to evaluate the relationship between soil and land use diversity of the studied areas were compared to show the similar phenomenon that this figure grows fastest in Nanjing followed by Zhengzhou and other places.
