Mapping and measuring urban-rural inequalities in accessibility to social infrastructures

Equal access to social infrastructures is a fundamental prerequisite for sustainable development,but has long been a great challenge worldwide.Previous studies have primarily focused on the accessibility to social infras-tructures in urban areas across various scales,with less attention to rural areas,where inequality can be more severe.Particularly,few have investigated the disparities of accessibility to social infrastructures between urban and rural areas.Here,using the Changsha-Zhuzhou-Xiangtan urban agglomeration,China,as an example,we investigated the inequality of accessibility in both urban and rural areas,and further compared the urban-rural difference.Accessibility was measured by travel time of residents to infrastructures.We selected four types of social infrastructures including supermarkets,bus stops,primary schools,and health care,which were funda-mentally important to both urban and rural residents.We found large disparities in accessibility between urban and rural areas,ranging from 20 min to 2 h.Rural residents had to spend one to two more hours to bus stops than urban residents,and 20 min more to the other three types of infrastructures.Furthermore,accessibility to multiple infrastructures showed greater urban-rural differences.Rural residents in more than half of the towns had no access to any infrastructure within 15 min,while more than 60%of the urban residents could access to all infrastructures within 15 min.Our results revealed quantitative accessibility gap between urban and rural areas and underscored the necessity of social infrastructures planning to address such disparities.

Effect of granular shape on radial segregation in a two-dimensional drum

Granular segregation is widely observed in nature and industry.Most research has focused on segregation caused by differences in the size and density of spherical grains.However,due to the fact that grains typically have different shapes,the focus is shifting towards shape segregation.In this study,experiments are conducted by mixing cubic and spherical grains.The results indicate that spherical grains gather at the center and cubic grains are distributed around them,and the degree of segregation is low.Through experiments,a structured analysis of local regions is conducted to explain the inability to form stable segregation patterns with obviously different geometric shapes.Further,through simulations,the reasons for the central and peripheral distributions are explained by comparing velocities and the number of collisions of the grains in the flow layer.

Segregation of Mg-6Gd alloy under natural convection:From macro solute distribution to micro dendrite growth

Segregation is a serious defect in alloy ingots which severely deteriorates materials performance.The segregation defect in Mg-6Gd alloy is studied by coupling macro thermal-solutal-convection transport and micro dendrite growth.The macroscopic fluid dynamics and mass transfer equations are resolved to forecast the segregation behavior under conditions of continuous temperature variation during the solidification process.The numerical model is validated by testing double-diffusive natural convection in a closed square cavity.A phase field model is then applied to simulate the micro dendrite growth,using macro undercooling and liquid flow velocity as boundary conditions.Results show that the multiscale segregation behavior,including macro solute distribution and micro dendritic morphology,is strongly dependent on the temperature condition and the liquid convection,which provides guidance for reducing and eliminating the segregation defect.

Effect of casting process on the inner-wall band segregation of high-strength antisulfur pipes

Controlling inner-wall band segregation is one of the difficulties in the production of high-strength antisulfur pipes.Comparative tests were carried out on different casting processes(superheat,mold electromagnetic stirring,end electromagnetic stirring,casting speed and soft reduction)for the smelting of high-strength antisulfur pipes.The microstructures of continuous-casting billets and hot-rolled or tempered pipes were analyzed using a metallographic microscope and scanning electron microscope.The mechanism and evolution law regarding the inner-wall band segregation of high-strength antisulfur pipes were studied,and the influence of different casting processes was explored.

Towards designing high mechanical performance low-alloyed wrought magnesium alloys via grain boundary segregation strategy:A review

Low-alloyed magnesium(Mg)alloys have emerged as one of the most promising candidates for lightweight materials.However,their further application potential has been hampered by limitations such as low strength,poor plasticity at room temperature,and unsatisfactory formability.To address these challenges,grain refinement and grain structure control have been identified as crucial factors to achieving high performance in low-alloyed Mg alloys.An effective way for regulating grain structure is through grain boundary(GB)segregation.This review presents a comprehensive summary of the distribution criteria of segregated atoms and the effects of solute segregation on grain size and growth in Mg alloys.The analysis encompasses both single element segregation and multi-element co-segregation behavior,considering coherent interfaces and incoherent interfaces.Furthermore,we introduce the high mechanical performance low-alloyed wrought Mg alloys that utilize GB segregation and analyze the potential impact mechanisms through which GB segregation influences materials properties.Drawing upon these studies,we propose strategies for the design of high mechanical performance Mg alloys with desirable properties,including high strength,excellent ductility,and good formability,achieved through the implementation of GB segregation.The findings of this review contribute to advancing the understanding of grain boundary engineering in Mg alloys and provide valuable insights for future alloy design and optimization.

Solute atom segregation to I1 stacking fault and its bounding partial dislocations in a Mg–Bi alloy

Stacking faults(SFs)and the interaction between solute atoms and SFs in a Mg–Bi alloy are investigated using aberration-corrected scanning transmission electron microscopy.It is found that abundant I_(1)SFs are generated after cold rolling and are mainly distributed inside{1012}twins.After aging treatment,the formation of single-layer and three-layer Bi atom segregation in the vicinity of I_(1)fault are clearly observed.Bi segregation also occurs at the 1/6<2203>bounding Frank partial dislocation cores.The segregation behaviors in I_(1)fault and Frank dislocations are discussed and rationalized using first-principles calculations.

The occurrence,inheritance,and segregation of complex genomic structural variation in synthetic Brassica napus

"Synthetic"allopolyploids recreated by interspecific hybridization play an important role in providing novel genomic variation for crop improvement.Such synthetic allopolyploids often undergo rapid genomic structural variation(SV).However,how such SV arises,is inherited and fixed,and how it affects important traits,has rarely been comprehensively and quantitively studied in advanced generation synthetic lines.A better understanding of these processes will aid breeders in knowing how to best utilize synthetic allopolyploids in breeding programs.Here,we analyzed three genetic mapping populations(735 DH lines)derived from crosses between advanced synthetic and conventional Brassica napus(rapeseed)lines,using whole-genome sequencing to determine genome composition.We observed high tolerance of large structural variants,particularly toward the telomeres,and preferential selection for balanced homoeologous exchanges(duplication/deletion events between the A and C genomes resulting in retention of gene/chromosome dosage between homoeologous chromosome pairs),including stable events involving whole chromosomes("pseudoeuploidy").Given the experimental design(all three populations shared a common parent),we were able to observe that parental SV was regularly inherited,showed genetic hitchhiking effects on segregation,and was one of the major factors inducing adjacent novel and larger SV.Surprisingly,novel SV occurred at low frequencies with no significant impacts on observed fertility and yield-related traits in the advanced generation synthetic lines.However,incorporating genome-wide SV in linkage mapping explained significantly more genetic variance for traits.Our results provide a framework for detecting and understanding the occurrence and inheritance of genomic SV in breeding programs,and support the use of synthetic parents as an important source of novel trait variation.

No basalt accumulation and segregation atop the 660-km discontinuity beneath the Sea of Okhotsk

Recent seismic evidence shows that basalt accumulation is widespread in the mantle transition zone(MTZ),yet its ubiquity or sporadic nature remains uncertain.To investigate this phenomenon further,we characterized the velocity structure across the 660-km discontinuity that separates the upper mantle from the lower mantle beneath the Sea of Okhotsk by modeling the waveform of the S660P phase,a downgoing S wave converting into a P wave at the 660-km interface.These waves were excited by two regional>410-km-deep events and were recorded by stations in central Asia.Our findings showed no need to introduce velocity anomalies at the base of the MTZ to explain the S660P waveforms because the IASP91 model adequately reproduced the waveforms.This finding indicates that the basalt accumulation has not affected the bottom of the MTZ in the study area.Instead,this discontinuity is primarily controlled by temperature or water content variations,or both.Thus,we argue that the basalt accumulation at the base of the MTZ is sporadic,not ubiquitous,reflecting its heterogeneous distribution.

Spatial Distribution Pattern and Influencing Factors of Bed-and-breakfasts(B&Bs)from the Perspective of Urban-rural Differences:A Case Study of Jiaodong Peninsula,China

There are significant differences between urban and rural bed-and-breakfasts(B&Bs)in terms of customer positioning,economic strength and spatial carrier.Accurately identifying the differences in spatial characteristics and influencing factors of each type,is essential for creating urban and rural B&B agglomeration areas.This study used density-based spatial clustering of applications with noise(DBSCAN)and the multi-scale geographically weighted regression(MGWR)model to explore similarities and differences in the spatial distribution patterns and influencing factors for urban and rural B&Bs on the Jiaodong Peninsula of China from 2010 to 2022.The results showed that:1)both urban and rural B&Bs in Jiaodong Peninsula went through three stages:a slow start from 2010 to 2015,rapid development from 2015 to 2019,and hindered development from 2019 to 2022.However,urban B&Bs demonstrated a higher development speed and agglomeration intensity,leading to an increasingly evident trend of uneven development between the two sectors.2)The clustering scale of both urban and rural B&Bs continued to expand in terms of quantity and volume.Urban B&B clusters characterized by a limited number,but a higher likelihood of transitioning from low-level to high-level clusters.While the number of rural B&B clusters steadily increased over time,their clustering scale was comparatively lower than that of urban B&Bs,and they lacked the presence of high-level clustering.3)In terms of development direction,urban B&B clusters exhibited a relatively stable pattern and evolved into high-level clustering centers within the main urban areas.Conversely,rural B&Bs exhibited a more pronounced spatial diffusion effect,with clusters showing a trend of multi-center development along the coastline.4)Transport emerged as a common influencing factor for both urban and rural B&Bs,with the density of road network having the strongest explanatory power for their spatial distribution.In terms of differences,population agglomeration had a positive impact on the distribution of urban B&Bs and a negative effect on the distribution of rural B&Bs.Rural B&Bs clustering was more influenced by tourism resources compared with urban B&Bs,but increasing tourist stay duration remains an urgent issue to be addressed.The findings of this study could provide a more precise basis for government planning and management of urban and rural B&B agglomeration areas.

Development of Sustainable Urban-Rural Integration:Dongtan Case Study

The environmental impact issues,such as global warming and expansion of the urban zone,seem more serious and have become the biggest defining challenges of the 21st century.Climate change can lead to water shortages,desertification,land degradation,air pollution,rising sea levels,accelerated deforestation,and exacerbated economic pressures.Global urban growth greatly impacts changes in sociability,humanity,and the environment of the Earth.The human presence,especially in cities,seriously affects resource use and waste disposal,and they are consuming natural resources faster than the planet can sustain during urbanization,changing how people live.China,with a population of 1.3 billion,has seen tens of millions of people living in the countryside migrate to cities,especially megacities,since the 1980s.As a result of its decision to industrialize and urbanize to boost the economy,China has become the world’s second-largest consumer of energy.In recent years,China’s government has quickly recognized the lessons of“limits to growth”and has taken action by initiating the construction process in Dongtan,Shanghai,China.They are making efforts to build urban-rural integration communities to promote sustainable development.Based on a literature review focusing on Dongtan,research questions are raised according to the research objective:(1)What are the challenges of sustainable development in urban-rural integration?(2)What practices has Dongtan implemented for sustainable development,or how is sustainable development being applied to Dongtan?(3)What are the social,political,environmental,and economic concerns regarding the sustainable development of Dongtan?The sustainable urban-rural integration concerns the ecological,economic,environmental,and psychological aspects of urban-rural integration design and management.The overall objective is to promote sustainable development in economic,social,ecological,and spatial dimensions.It will be a liveable,complete community that makes economic,environmental,and social sense locally while also contributing to national and global sustainable development.It will serve as a compelling model for how to build sustainable urban-rural integration worldwide.

Formation mechanism and criterion of linear segregation in ZL205A alloy

The experiments and numerical simulation were conducted for ZL205A aluminum alloy cylindrical shell casting. The formation mechanism of the linear segregation produced by the low pressure die casting (LPDC) process was investigated. And the heat transfer of the casting during solidification process was analyzed by simulation technique, resulting from the information of linear segregation obtained by plenty of experiments. The new linear segregation criterion was proposed through the simulation and experimental results. It was found that the melting metal with high Cu contents was feeding the crack shrinkage formed by the tearing under the effect of feeding pressure during the later solidification, which led to the formation of linear segregation. The control methods for the linear segregation were suggested based on the proposed mechanism. Finally, the criterion of linear segregation was confirmed by the production of the actual castings.

Effect of carbon and boron additions on segregation behavior of directionally solidified nickel-base superalloys with rhenium

The phase transformation temperature, segregation behavior of elements and as-cast microstructure were investigated in experimental nickel-base superalloys with different levels of carbon and boron. The results show that the liquidus temperature decreases gradually but the carbide solvus temperature increases obviously with increasing carbon addition. Minor boron addition to the alloy decreases the liquidus temperature, carbide solvus temperature and solidus temperature slightly. Apart from rhenium, the segregation coefficients of the elements alter insignificantly with the addition of carbon. The segregation behavior of rhenium, tungsten and tantalum become more severe with boron addition. The volume fraction and size of primary carbides increase with increasing carbon addition. The main morphology of the carbides is script-like in the alloys with carbon addition while the carbide sheets tend to be concentrated and coarse in the boron-containing alloys

Non-equilibrium grain-boundary segregation of Bi in Cu bicrystals

The observations of grain-boundary segregation of Bi in Cu bicrystals were analyzed. According to equilibrium grain boundary segregation （EGS） model and non-equilibrium grain-boundary segregation （NGS） model, respectively, the segregation kinetics of isothermal annealing at 500 ＆#176;C and that of isochronal annealing for 24 h of Bi in Cu bicrystals were investigated. By qualitative analysis and quantitative analysis, it is concluded that the grain-boundary segregation of Bi agrees well with the theory of NGS. Based on the kinetics model of NGS, some parameters that are useful to predicting and controlling the Bi-induced embrittlement in Cu alloys are calculated as follows：the diffusion coefficient of Bi-vacancy complexes Dc=7.8×10^-5exp[-1.46/（kT）];the apparent diffusion coefficient of Bi atoms Di^A=7.66×10^at＋bexp[–1.76/（kT）], where a=8.45×10^-8 and b=-13.37.

Microstructure evolution and segregation behavior of thixoformed Al-Cu-Mg-Mn alloy

A commercial wrought Al-Cu-Mg-Mn alloy（2024） was thixoformed based on the recrystallization and partial melting（RAP） route, and the microstructure evolution and segregation behavior during the indirect thixoforming process were studied. The results show that fine spheroidal microstructures can be obtained by partial remelting of commercial extruded 2024 alloys without additional thermomechanical processing. During the indirect thixoforming, the stress distribution can be optimized by increasing the thickness of base region. Under three-dimensional compression stress state, the microstructures are homogeneous among different regions with no evidence of liquid segregation and micro-porosities, and the grains in the columns are deformed plastically. The distribution of tensile mechanical properties is consistent with the microstructures. Moreover, the distribution of deformation mechanism was discussed, and a technical method for improving the stress distribution was proposed.

Segregation and diffusion behavior of niobium in a highly alloyed nickel-base superalloy

The segregation during solidification and high temperature diffusion during homogenization of niobium in a highly alloyed nickel-base superalloy were investigated.Niobium is seriously segregated into the interdendritic regions with segregation coefficient as high as 4.30.Various niobium-enriched phases including Laves phase,δ phase,（γ＋γ＇） eutectic,MC and M6C types of carbides precipitated in the interdendritic regions.The soluble temperature of niobium-enriched phases and the degree of dendritic segregation were determined by differential thermal analysis and homogenization treatments at varied temperatures and times.The calculation of elemental diffusion indicates that the diffusion rate of niobium increases remarkably with the homogenization temperature increasing,so that the annealing time can be effectively reduced.A three-step homogenization treatment technology without incipient melting was established to eliminate the segregation of niobium and to obtain a uniform microstructure.

COMPUTER SIMULATION OF GRAIN BOUNDARY SEGREGATION BEHAVIOR AND MECHANISMS OF STRENGTHENING OF Mg IN Ni-BASED SUPERALLOYS

This paper used EAM and static relaxation method to simulate the grain boundary segregation behavior of Mg in Ni-based superalloys. The results offer a better understanding in the strengthening mechanism of Mg addition in superalloys. The segregation of Mg increases the grain boundary cohesive bond and the vacancy formation energy, and decreases the mobility of grain boundary dislocation. It results in the retardation of creep voids initiation and growth.

Radial mixing and segregation of granular bed bi-dispersed both in particle size and density within horizontal rotating drum

Taking simultaneous variations in both particle volume and density into account, the radial mixing and segregation of binary granular bed in a rotating drum half loaded were investigated by a 3D discrete element method. Then, based on the competition theory of condensation and percolation, radial segregation due to differences in particle volume and/or density was analyzed. The results show that if either percolation effect induced by volume difference or condensation effect induced by density difference dominates in the active layer of moving bed, separation will occur. Controlling the volume ratio or density ratio of the two types of particles can achieve an equilibrium state between percolation and condensation, and then homogenous mixture can be obtained. When the percolation balances with the condensation, the relationship between volume ratioand density ratiopresents nearly a power function. Scaling up a rotating drum will not affect the mixing degree of the granular bed so long as the volume ratio and density ratio are predefined.

A Novel Segregation Distortion in Intraspecific Population of Asian Cotton(Gossypium arboretum L.)Detected by Molecular Markers

The segregation ratio of markers in an F2 population derived from Rudongjijiaoyaguo （Rdjjyg） and Zhongmian971 （Zm971） was studied using 3 morphological markers, 20 SSR markers, and ll SRAP markers. Totally, 24 markers （77.42%） showed a distorted segregation and all of them skewed toward the female genotype, which was peculiar in recent cotton research. All the three types of SSR markers and SRAP marker showed distorted segregation, but the morphological markers （Purple stem, Okra leaf, and Red spot color） were normally segregated. This indicated that such a novel segregation distortion phenomenon resulted from interior genetic factors, The allele frequency and the distribution of different genotype frequencies in the F2 population were analyzed in codominant markers, to find out factors attributed to distorted segregation. Most of them implied distorted allele frequency, but it was normal genotype frequency, which showed that these markers were influenced at the gamete level.

Effect of atomic structure on migration characteristic and solute segregation of ordered domain interfaces formed in Ni_(75)Al_xV_(25-x)

Based on the microscopic phase-field model, ordered domain interfaces formed between D022 （Ni3V） phases along [001] direction in Ni75AlxV25-x alloys were simulated, and the effects of atomic structure on the migration characteristic and solute segregation of interfaces were studied. It is found that the migration ability is related to the atomic structure of interfaces, and three kinds of interfaces can migrate except the interface （001）//（002） which has the characteristic of L12 （Ni3Al） structure. V atoms jump to the nearest neighbor site and substitute for Ni, and vice versa. Because of the site selectivity behaviors of jumping atoms, the number of jumping atoms during the migration is the least and the jumping distance of atoms is the shortest among all possible modes, and the atomic structures of interfaces are unchanged before and after the migration. The preferences and degree of segregation or depletion of alloy elements are also related to the atomic structure of interface.

Conservation-minded Urban Green Space System Planning in the Urban-rural Integration

Environmental and ecological problems in the urban-rural integration were analyzed, characteristics of urban green space system introduced, such as excellent landscape eco-structure, distinctive historical and humanistic features, and diversified natural landscape resources, and also challenges pointed out. Evolution, overall spatial structure and conservation concept of conservation-minded urban green space system planning were elaborated, on the basis of which the evaluation system of conservation-minded urban green space system was studied, and it was proposed that mutual relationship between impact factors of compound value and qualitative evaluation factors should be taken into consideration as a whole in evaluating conservation effects of green space system. Quantitative evaluation indexes and qualitative evaluation measures were analyzed, an objective and precise evaluation system for the conservation-minded urban green space system was established by combining qualitative and quantitative analysis to improve ecological environment during the urbanization, and fully show planning concepts of conservation-minded green space system.