Growth Boundary Research Articles

Improvement of strength and ductility synergy and the elimination of the yield point phenomenon of ultrafine-grained Mg–Al–Zn–Ag alloy sheet

Strength and ductility synergy in ultrafine-grained AZQ310 alloy sheet was successfully improved at the expense of grain boundary segregation via multi-pass rolling. Before rolling, the as-extruded alloy has high yield strength (TYS, 382 MPa) but poor elongation (4.1%) mainly due to the ultra-fine grains (414 nm) and the co-segregation of Al/Zn atoms at grain boundaries. More importantly, this non-equilibrium segregation dies away during the rolling process, and the sheet exhibits a tensile yield strength of 370 MPa, an ultimate strength of 422 MPa, and an elongation of 9.8% along the rolling direction after 5th pass rolling. The results show that the high strength-ductility synergy is mainly attributed to the ultra-fine grains and residual dislocations. Furthermore, it is surprising that the yield point phenomenon (YPP) prominently in as-extruded sample is weakened and finally eliminated in as-rolled sheets. Microstructure evolution in the room temperature tensile test manifests that the underlying reason for the YPP is the stress-induced grain growth and grain boundary segregation, which in turn expounds the difficulty in the refining of ultrafine-grained Mg alloys by traditional processing methods.

Conflicting interests between local governments and the European target of no net land take

To halt land take in Europe, the European Union set a “no net land take by 2050″ target in 2011. However, land take continues to occur in European countries, with recent studies suggesting that local decision-making is playing a major role in these land-use conversions. In this study, we investigated how urban growth boundaries (UGBs) are used by local governments to manage urban growth in Romania. A mixed-method approach was adopted, combining analysis of UGB changes over the past decade in all Romanian cities (N = 319) with a survey among representatives of local governments involved in land-use decision-making (N = 91 cities). The results showed that many cities have expanded their UGBs, despite population loss and sufficient undeveloped land within UGBs, showing that local government decisions conflict with policy targets at the European level. This is even the case when there is no physical need for land-take limits to be exceeded. We show that population dynamics and the extent of nature conservation areas significantly contribute to UGB changes, though these explain just a small fraction of all UGB changes. Furthermore, we identified a wide range of motivations among decision-makers regarding changing UGBs, including not only the fiscal system but also cities’ competitiveness and decisions about the long-term vision for development. We argue that policy innovations in urban containment should (i) aim to balance the interests of governments at different administrative levels, (ii) account for the particularities of each state member’s planning system, and (iii) allow for integrated and strategic city planning.

Multiple meanings and boundaries of growth in shrinking regions in East and North Finland

Growth stands out as a key development object in contemporary green economy policies. It is particularly interesting in the Nordic context such as in East and North Finland, where many regions are rich in natural resources, but also shrinking and lagging. Therefore, their regional development is simultaneously framed by an expected sustainability transition that alternates between green growth and degrowth agendas, and the socio-economic phenomenon of shrinkage. This article examines how growth is understood and framed among regional development actors, with special interest placed on different meanings, possible critics, and the boundaries of growth. The interviewed actors are positioned as intermediaries who possess special knowledge regarding regional development. The interviews show that the understanding of growth in this context requires various framings that combine global, regional, and local perspectives on sustainable development, as well as the burdens of shrinking and lagging regions balanced against cohesive and inclusive promises of green growth. The hegemonic frame is approached through a lens of green growth, yet the shrinking population remains in the background. Growth appears as a favoured means to tackle societal problems, which reflects a mission-oriented goal setting. Critical statements are directed at growth policies and funding instruments that do not seem to promote cohesive and inclusive growth. The clearest boundary for growth relates to nature, but it is far too early to make interpretations on an intentional degrowth agenda. From the regional actors’ perspective, setting boundaries for growth in a context of long-term shrinkage, sparse population, and extensive natural surroundings seems trivial. Handling the peripheries’ societal problems related to shrinkage and their struggle for resources appears as the more relevant mission that also requires growth in various forms.

Sinkhole flooding above a shallow bedrock aquitard in an urbanizing community, central Tennessee, USA

In the aftermath of a storm on 6 February 2020, central Tennessee, USA flooded sinkholes were concentrated in places where two Late Ordovician aquitards are probably at or within ~10 m of the surface. The ~278 km2 study area is located ~35 km SE of central Nashville along the edge of Murfreesboro, a city of >153,000 that grew in population by ~40 % between 2010 and 2020. Within the study area, the largest amount of flooding happened within the ~12 km2 Shores Road focus area which includes the city boundary and is mostly within the city's urban growth boundary. Analysis of published geologic maps and stratigraphic observations reveals areas where bedrock aquitards are probably at or within ~10 m of the surface, and inundation was observed on 3 m cell size Dove multispectral satellite imagery on 8 February. The largest inundated areas were mapped with ~88 % accuracy through supervised classification of the 8 February scene. Of 1247 inundated features in the study area, 233 (~19 %) are in areas where the Pierce Limestone aquitard is at or within ~10 m of the surface, and this result is statistically significant at the p < 0.01 level because these areas comprise only 8 % of the study area. These 233 features account for ~27 % of the inundated area. If areas underlain by a second aquitard, the Lower Ridley Confining Layer, are included in the analysis, this approach explains ~69 % of the features and ~86 % of the inundated area. This result is also significant at the p < 0.01 level. Although many factors affect sinkhole formation and flooding in general, these results underscore the significance of shallow bedrock aquitards.

A Machine Learning Framework for Assessing Urban Growth of Cities and Suitability Analysis

Rural–urban immigration, regional wars, refugees, and natural disasters all bring to prominence the importance of studying urban growth. Increased urban growth rates are becoming a global phenomenon creating stress on agricultural land, spreading pollution, accelerating global warming, and increasing water run-off, which adds exponentially to pressure on natural resources and impacts climate change. Based on the integration of machine learning (ML) and geographic information system (GIS), we employed a framework to delineate future urban boundaries for future expansion and urban agglomerations. We developed it based on a Time Delay Neural Network (TDNN) that depends on equal time intervals of urban growth. Such an approach is used for the first time in urban growth as a predictive tool and is coupled with Land Suitability Analysis, which incorporates both qualitative and quantitative data to propose evaluated urban growth in the Greater Irbid Municipality, Jordan. The results show the recommended future spatial expansion and proposed results for the year 2025. The results show that urban growth is more prevalent in the eastern, northern, and southern areas and less in the west. The urban growth boundary map illustrates that the continuation of urban growth in these areas will slowly further encroach upon and diminish agricultural land. By means of suitability analysis, the results showed that 51% of the region is unsuitable for growth, 43% is moderately suitable and only 6% is suitable for growth. Based on TDNN methodology, which is an ML framework that is dependent on the growth of urban boundaries, we can track and predict the trend of urban spatial expansion and thus develop policies for protecting ecological and agricultural lands and optimizing and directing urban growth.

Prediction of Temperature Development of Concrete with Set-Controlling Admixture Based on a New Hydration Kinetics Model.

Temperature control is needed in the construction process of massive concrete and it can avoid the concrete cracks. Prediction of temperature development based on a hydration kinetics model can reduce the need for adiabatic temperature rise tests for concrete. However, the existing hydration kinetics model cannot accurately describe the hydration process of cement, thereby limiting the ability to further accurately predict the temperature rise of concrete based on the hydration kinetics model. This paper aims to establish a new hydration kinetics model, which is based on nucleation and growth model, and to predict the temperature development of concrete with set-controlling admixture based on this model. In this paper, the nucleation and growth of hydration products and the diffusion of free water by the modified boundary of nucleation and growth (BNG) model and the modified Fuji and Kondo's model are described. The relationship between nucleation rate and apparent activation energy and the relationship between effective diffusion coefficient and apparent activation energy are linear. However, the relationship between growth rate and apparent activation is exponential. Finally, the temperature development of concrete can be calculated by the hydration degree of the cement.

Gibbs–Wulff optical vortex array

Optical vortex array (OVA) containing multiple optical vortices is an optimal candidate for applications of optical communications, complex manipulation of multi-particle systems, and mass-synchronous fabrication. However, the existing OVAs have not been constructed to respond to the application requirements, particularly for micro-/nanomaterial fabrication where the boundary, size, and stability need to be carefully considered. To address this issue, we propose a Gibbs–Wulff OVA (GWOVA) by analogizing the Gibbs–Wulff theorem in solid-state physics. Herein, the Gibbs–Wulff theorem is first generalized to OVA's generation as the condition to confine its growth boundary. The GWOVA, which possesses versatile structures and arrangement modes (simple- and close-packed modes), is successfully generated and grown. It exhibits high stability and perfect symmetry during growth and rotation, which satisfies the symmetric group of D2s. Owing to its stable structure and growth boundary conditions, the GWOVA has great potential for a wide range of applications, particularly in micro-/nanomaterial fabrication.

Dynamic Changes, Spatiotemporal Differences, and Ecological Effects of Impervious Surfaces in the Yellow River Basin, 1986–2020

Impervious surfaces (IS) are one of the most important components of the earth’s surface, and understanding how IS have expanded is vital. However, few studies on IS or urbanization have focused on the cradle of the Chinese nation—the Yellow River Basin (YRB). In this study, the Random Forest and Temporal Consistency Check methods were employed to generate long-term maps of IS in the YRB based on Landsat imagery. To explore the dynamics and differences in IS, we developed a spatiotemporal analysis and put forward regional comparisons between different research units of the YRB. We documented the remote sensing-based ecological index (RSEI) in multiple circular zones to discuss the ecological effects of the expansion of IS. The IS extraction strategy achieved excellent performance, with an average overall accuracy of 90.93% and kappa coefficient of 0.79. The statistical results demonstrated that the spatial extent of IS areas in the YRB increased to 18,287.36 km2 in 2020 which was seven times more than that in 1986, at rates of 166 km2/a during 1986–2001, 365 km2/a during 2001–2010, and 1044 km2/a during 2011–2020. Our results indicated that the expansion and densification of IS was slow in core urban areas with high initial IS fraction (ISF), significant in the suburban or rural areas with low initial ISF, and obvious but not significant in the exurb rural or depopulated areas with an initial ISF close to 0. The multiyear RSEI indicated that environmental quality of the YRB had improved with fluctuations. The ecological effects of the impervious expansion slightly differed in urban core areas versus outside these areas. When controlling the urban boundary, more attention should be paid to the rational distribution of ecologically important land. These results provide comprehensive information about IS expansion and can provide references for delineating urban growth boundaries.

Qualitative analysis of a time-delayed free boundary problem for tumor growth with Gibbs-Thomson relation in the presence of inhibitors

&lt;abstract&gt;&lt;p&gt;In this paper, we study a time-delayed free boundary of tumor growth with Gibbs-Thomson relation in the presence of inhibitors. The model consists of two reaction diffusion equations and an ordinary differential equation. The reaction diffusion equations describe the nutrient and inhibitor diffusion within tumors and take into account the Gibbs-Thomson relation at the outer boundary of the tumor. The tumor radius evolution is described by the ordinary differential equation. It is assumed that the regulatory apoptosis process takes longer than the natural apoptosis and proliferation processes. We first show the existence and uniqueness of the solution to the model. Next, we further demonstrate the existence of the stationary solutions and the asymptotic behavior of the stationary solutions when the blood vessel density is a constant. Finally, we further demonstrate the existence of the stationary solutions and the asymptotic behavior of the stationary solutions when the blood vessel density is bounded. The result implies that, under certain conditions, the tumor will probably become dormant or will finally disappear. The conclusions are illustrated by numerical computations.&lt;/p&gt;&lt;/abstract&gt;

Dislocation entangled mechanisms in cu-graphene nanocomposite fabricated by high-pressure sintering

Graphene reinforced Cu-based nanocomposite (Cu-Gr), synthesized using high-pressure forming (∼8 GPa) route at 300 °C, achieved 96% of relative density and 84% IACS improvement in electrical conductivity, along with a significant increase in hardness and Young's modulus up to ∼94 GPa. The structure and defects evolution of NC-Cu and Cu-Gr nanocomposites were investigated using nanoindentation approach, and then backed up computationally. Molecular dynamics (MD) simulations results are well agreed with experimental data, which significantly reveled that grain growth and grain boundary sliding (GBS) are dominant deformation mechanism involves grain boundary movement through dislocation motion, stacking faults (SFs) and twin boundary (TBs) formation, along with matrix failure through grain growth and GBS with an increase in loading, and subsequently bending (bow shape) processes.

On the steady state problem of the chemotaxis-consumption model with logistic growth and Dirichlet boundary condition for signal

This paper concerns the steady state problem for chemotaxis consumption system with logistic growth and constant concentration of chemoattractant on the boundary of the domain. We establish the existence of a non-constant positive solution to this problem. The uniqueness of this solution is obtained under the smallness assumption on the boundary data. Some qualitative properties of the solutions and numerical results are presented.

Evaluating the Melbourne Strategic Assessment—Elegant on process, currently failing on implementation

SummaryThis paper provides a critical analysis of the development and current outcomes of Australia's first endorsed strategic assessment under the Environment Protection and Biodiversity Conservation Act 1999, namely, the Melbourne Strategic Assessment. It covers progress towards protection of a number of Nationally Significant Species and Ecological Communities – most notably, the native grassland communities immediately adjacent to Melbourne's Urban Growth Boundary. The Commonwealth approval to protect biodiversity and allow urban development was made in 2010 and it aimed to achieve its outcomes by 2020. These outcomes included providing new land for homes, for new transport corridors, and for conservation of biodiversity. Natural Temperate Grassland (4,667 ha), Grassy Eucalypt Woodland (709 ha) and seven other Matters of National Environmental Significance will be impacted. Mitigation for this is establishment of 15,000 ha of grassland reserves, 1,200 ha of grassy woodland reserves, over 4,000 ha of other land zoned for conservation and 300 ha of wetland restoration. We conclude that the Melbourne Strategic Assessment has been a success in terms of the elegance and comprehensiveness of the approach, in cooperation between the levels of government, in the economic benefits, and in some aspects of social engagement of the agreement. However, the achievement of environmental outcomes must be currently considered a failure due to poor implementation. This failure includes not meeting the agreed 10 year deadline for land acquisition and management, poor monitoring and protection of set‐aside areas, and in reporting. We offer suggestions for how these current shortcomings could be overcome. These align well with the recommendations of the review of the Environment Protection and Biodiversity Conservation Act 1999 (The independent statutory review of the Act in 2020) and include the establishment of the proposed Office of Compliance and Enforcement, the adoption of National Environmental Standards and the reforms regarding the role of Indigenous Australians in strategic assessments. If these were adopted, we conclude that the strategic assessment approach should be more widely used because of the more holistic approach and efficiencies that it envisages compared with site by site approaches.

Certain Subclasses of Meromorphic Functions Involving Differential Operator

We obtain the coefficient estimates, extreme points, distortion and growth boundaries, radii of starlikeness, convexity, and close-to-convexity, according to the main purpose of this paper.

Wachstumskoalitionen und Wachstumskritiken in der Stadtentwicklung: Reurbanisierungs- und Zuwanderungspolitiken

In this paper, growth coalitions and growth critiques are examined by using the example of in-migration policies in the context of Jena case study. This is based on the following questions: Which local growth coalitions do exist with which growth goals? To what extent do growth boundaries lead to an expansion of local growth coalitions with the urban hinterland? What kind of growth-critical positions are there in urban politics and to what extent do they question growth policies? The paper particularly ties in with the theoretical discussion of post-growth planning and enriches it by an empirical reflection by examining forms of municipal growth scepticism as well as limits of regional cooperation. The results show that there is a distinct growth coalition in Jena, which pursues the goal of attracting skilled workers to secure economic growth. However, due to natural growth limits and the resistance of individual residents, in-migration policies are reaching their limits, so that intermunicipal cooperation in the urban region is being sought as a fallback solution. Explicit critiques of growth and a fundamental public discussion about growth policies, on the other hand, just begin to emerge.

Revisiting Fe-doped 8YSZ as the electrolyte of SOFC – From sintering to electrochemical performance

One of the main challenges in preparing a dense and ionic conductive yttria-stabilized zirconia (YSZ) solid electrolyte is its high sintering temperature. Iron has been suggested as an efficient additive for Yttria-stabilized Zirconia (YSZ) to reduce its sintering temperature with the least detrimental effect on ionic conductivity. In this study, a deeper exploration of the iron’s effect on the physical, microstructural, and electrical properties of YSZ was conducted. 8YSZ samples with different contents of Fe2O3 (0, 1, 3, 5, 7 mol%) were prepared by tape casting and sintered at 1200 °C and 1300 °C for 4 h. X-Ray diffraction (XRD) analysis, scanning electron microscopy (SEM), optical dilatometry, and electrochemical impedance spectroscopy (EIS) were performed. The results showed that iron does not affect the stability of the cubic phase structure. Estimating oxygen vacancy concentrations by EIS revealed that increasing Fe2O3 concentration resulted in decreamnet of oxygen vacancy concentrations at the space-charged layer and deteriorates the grain boundary conductivity. On the other hand, adding Fe2O3 led to grain growth and grain boundary length reduction which, as an opposite factor, reduced the destructive effect of grain boundary on conductivity. The maximum total ionic conductivity of 0.044 S/cm was achieved by adding 3 mol% of Fe2O3 to 8YSZ sintered at 1300 °C.

Urbanization and growth of Greater Kuala Lumpur: Issues and recommendations for urban growth management

This paper discusses the urban management challenges in the Greater Kuala Lumpur area. Before examining Greater Kuala Lumpur's economic and social environment, we will look at the factors that make it a competitive and fiscally sound entity. When considering urban development and redevelopment, we consider how proposed and ongoing projects, as well as plans, hierarchical links, and road networks, contributed to the increase. Because there is no urban growth boundary, land use change and rural encroachment, as well as environmental degradation and the impact of national economic projects on urban expansion, are both rapid and linear in the analysis. This paper also considers how to manage linear development that results in the creation of new suburbs. Finally, we propose strategies for achieving sustainable urban expansion and management by balancing the financial and governance capacities of Greater Kuala Lumpur local governments.

Modelling and Forecast of Future Growth for Shandong’s Small Industrial Towns: A Scenario-Based Interactive Approach

The industrial small-town development process in Shandong is influenced by the urban agglomeration strategy and the regional collaborative production, thereby resulting in a challenge of growth boundary planning. How to build a growth forecast decision support system to help small industrial towns maintain sustainable development with limited trial and error costs is an essential topic in the current research of small town-related fields. Empirical analysis reveals that the growth factors of small towns differ from the factors of cities due to the other-organization planning management system and self-organization construction activities that coexist in small towns. Besides, due to the size of small towns, the impact of policy changes in small towns is more significant than in cities. Furthermore, as part of the regional production chain, small industrial towns are most vulnerable to uncertain external disturbances. Therefore, it is necessary to formulate different development scenarios according to possible disturbances and output corresponding development forecasts. The research aims to build a decision-making support system for Shandong’s small-town planning based on an urban modeling approach using geographic information technology and scenario planning. Considering the mutually driving effects of the objective environment and subjective policies of Shandong’s industrial towns, as well as the corresponding dynamic mechanisms and comparing the theoretical basis and limitations of the different modeling approaches, this essay constructs a model system based on a mathematical model and a system dynamics model. It is also an interactive model accompanied by applicable rules and factors so that initial information and relevant development goals can be inputted into the model system to simulate the influence of different policies and identify the small industrial town growth scenarios.

Progress of Research on Urban Growth Boundary and Its Implications in Chinese Studies Based on Bibliometric Analysis.

Urban sprawl is a development theme of cities all over the world, especially in developing countries with rapid urbanization, and the long-established rough and outward urban growth pattern has brought about a series of social and ecological problems. As an important tool in controlling urban sprawl in western countries, the urban growth boundary (UGB) has become one of the three major policy tools in the national spatial planning system since it was introduced into China. Combined with a bibliometric analysis, this literature review summarizes UGB studies on development and evolution, delimitation means, and implementation management and provides references for studying UGB adaptability in China. The results show that: (1) Originating from Howard's garden city concept, UGB studies have formed a relatively complete system of "theoretical basis, technical methods, supporting policies, and implementation management" through long-term empirical research in foreign countries. With a relatively late start in China, UGB research currently focuses on different situations between China and abroad and the adaptation of China's localization. (2) UGB delimitation mainly includes two aspects: forward expansion, which, from the urban development perspective, is mainly supported by cellular automata (CA) urban growth simulation; and reverse restriction, which, from the ecological protection perspective, is supported by ecological security pattern construction, ecological sensitivity evaluation, and land suitability evaluation. (3) Many foreign UGB implementations have different forms and more flexible and comprehensive corresponding supporting policies. However, the current state of research in China in this area is still insufficient. Against the background of the national spatial planning system reform, the findings of this review provide references for delineating UGB that considers ecological protection and urban development under the scenarios of planning, formulating a supporting mechanism for multi-subject participation and multi-party coordination, and establishing an adjustment system based on implementation effect evaluation.

Urban Growth Simulation Based on a Multi-Dimension Classification of Growth Types: Implications for China’s Territory Spatial Planning

One of the primary aims of China’s territory spatial planning is to control the urban sprawl of local municipals and prevent regional competition and the negative consequences on the environment—which emphasizes the top-down spatial regulation. Indeed, the traditional cellular automaton (CA) model still has limitations when applied to the whole administration area since it may ignore the differences among cities and towns. Thus, this paper proposed a CM-CA (clustering, multi-level logit regression, integrated with cellular automaton) framework to simulate urban growth boundaries for cities and towns simultaneously. The significant novelty of this framework is to integrate several urban growth modes for all cities and towns. We applied our approach to the city of Xi’an, China, and the results showed satisfactory simulation accuracy of a CM-CA model for multiple cities and towns, and the clusters’ effects contributed 74% of the land change variance. Our study provides technical support for urban growth boundary delineation in China’s spatial planning.

Urban Growth Boundaries Delineation under Multi-Objective Constraints from the Perspective of Humanism and Low-Carbon Concept

Urban growth boundaries (UGBs) play an important role in controlling urban sprawl and protecting natural ecosystems. Traditional methods mainly focus on the heterogeneity of regional resources and environment rather than residents’ behavioral activities. However, residents’ behavioral activities are one of the most important factors influencing urban spatial form. Fortunately, the emergence of big data, especially phone signaling data, provides alternative data sources to understand the dynamic resident behavior activity space, which is significant for people-oriented urban development. Therefore, we propose a novel framework for UGB delineation based on multi-source big data and multi-objective constraints, which emphasizes humanism and the low-carbon concept in urban expansion simulation. The multi-objective constraints are constructed from the evaluation of resident activity space expansion potential, the evaluation of urban construction suitability, the evaluation of ecological conservation importance, and the human survival materials limitation. We apply the framework to Ningbo, and the results show that the framework under multi-objective constraints from a people-oriented and low-carbon perspective is more reliable and comprehensive than that without constraints. The findings also show that the UGB delineation based on multi-source big data has higher accuracy and better performance. The conceptual and methodological advances of this study are also applicable to other cities to help UGBs delineation.