Rapid Growth Stage Research Articles

Study on the reconstruction in the crystallization process of mordenite

Abstract The crystallization process had a great influence on the structure and catalytic performance of zeolites. In this paper, a series of Mordenite were synthesized and the variation of structure, morphology, skeletal atoms and acid sites distribution during the crystallization process were systematically studied. The characterization results indicated that the crystallization process of Mordenite could be separated into three parts: amorphous stage, rapid growth stage and slow growth stage. The Mordenite crystals experienced a reconstruction process when the relative crystallinity was already high in the slow growth stage. The skeletal atoms and acid sites distribution gradually changed although the relatively crystallization almost stayed the same in the reconstruction process. Besides, some small Mordenite crystals dissolved while some crystal planes continued to grow, forming larger Mordenite crystals and more mesopores through crystal stacking. Al atoms located in the strong acid sites or 8 member-ring channels were more preferentially dissolved out and re-entered the weak acid sites position or the 12 member-ring channels.

Precipitation and Growth Simulation of γ′ Phase in Single Crystal Superalloy DD6 with Multiphase-Field Method and Explicit Nucleation Algorithm

The microstructure evolution of Ni-based superalloys during heat treatment is of great significance for obtaining better service performance. However, heat treatment experimentation is costly and time-consuming, and sometimes fails to reveal physical mechanisms well. In the present study, a multiphase-field model coupled with an explicit nucleation algorithm was established to simulate the precipitation and growth of γ′ phase in DD6 superalloy, which can be applied to a multicomponent elastic-inhomogeneous system. The PanNickel© database was used to calculate thermodynamic and kinetic data in multicomponent superalloys. First, the coupling method of multiphase-field model and explicit nucleation algorithm was introduced. The coupled model was used to simulate the precipitation of γ′ phase under isothermal and non-isothermal conditions. It was found that a unimodal microstructure was formed under isothermal conditions and there was a “soft impingement” phenomenon, while a bimodal distribution composed of cuboidal γ′ precipitates and fine secondary γ′ precipitates was formed during a cooling process of 25–125 °C/min. The effect of cooling rate was studied. Then, the chemical and elastic driving forces were analyzed. It was found that Al and Ta contributed most to the chemical driving force, while Re and W gathered at the γ/γ′ interface and inhibited the growth of γ′ phase. γ′ precipitates had a cuboidal shape under the influence of elastic driving force. Finally, the growth and coarsening process of γ′ phase was studied and compared with the well-known Lifshitz−Slyosov−Wagner (LSW) theory. The growth of γ′ phase can be divided into rapid growth, coarsening and quasi-static coarsening stages according to the simulation results, among which the coarsening stage is basically consistent with the LSW theory. The current model can be used to simulate the precipitation and growth of single crystal superalloys where multicomponent and elastic effects are considered.

Intelligent Resource Allocation for Video Analytics in Blockchain-Enabled Internet of Autonomous Vehicles With Edge Computing

Video surveillance in intelligent transportation systems (ITSs) is in the rapid growth stage, where video analytics is a potential technology to improve the safety of the Internet of Autonomous Vehicles (IoAV). However, massive video data transmission and computation-intensive video analytics bring an overwhelming burden for vehicular networks. Moreover, owing to the unstable network connection, the video data are not always reliable, which makes data sharing a lack of security and scalability in IoAV. In this work, we first propose a video analytics framework, where the multiaccess edge computing (MEC) and blockchain technologies are integrated into IoAV to optimize the transaction throughput of the blockchain system as well as reducing the latency of the MEC system. Furthermore, based on deep reinforcement learning, the joint optimization problem is modeled as a Markov decision process (MDP), and the asynchronous advantage actor–critic (A3C) algorithm is adopted to solve this problem. Simulation results demonstrate that our approach can fast converge and significantly improve the performance of blockchain-enabled IoAV with MEC.

Research on the Influence of FDI on Guangdong’s High-Quality Economic Development

With the transition of China's economy from the stage of rapid growth to the stage of high-quality development, the influence of the introduction of FDI on the high-quality development of regional economy has become more and more an issue to be discussed. This paper selects Guangdong Province as the frontier of China's reform and opening up. Combining with the new development concept of innovation, coordination, green, development and sharing, the high-quality development system of Guangdong's economy is constructed and the high-quality development index of Guangdong's economy is measured by entropy weight method. On this basis, empirical analysis of FDI on the quality of Guangdong province's economic development. Research shows that FDI can significantly promote the high-quality economic development of Guangdong, where technological progress and government intervention are important factors to promote the high-quality economic development of Guangdong, while industrial development hinders the high-quality economic development of Guangdong, urbanization has a positive role in promoting the high-quality economic development of Guangdong. However, the results were not significant. The results of quantile regression showed that for different levels of high-quality economic development, the promoting effect of FDI presented differences, specifically, with the improvement of the level of high-quality economic development, the promoting effect of FDI on high-quality economic development presented a gradual downward trend. Guangdong is in the important stage of the high-quality economic development to the objective and the role of FDI on Guangdong economy high-quality development, to distinguish the different economic development level of high-quality parts for the sensitivity of the FDI, specific aim ground is made science and Guangdong economy development stage of FDI into high-quality policy, to ensure high-quality economic growth is of great significance in Guangdong.

Study on dynamic mechanical properties of phosphate rock through experimental tests and mesoscale simulation

Dynamic characteristics of rock masses are an important part of the safety and stability analysis in rock mass engineering. The split Hopkinson pressure bar (SHPB) tests on the phosphate rock in Yichang are conducted, combined with the Split-desktop digital image method and mesoscopic discrete element method (DEM). Both macroscopic and mesoscopic characteristics of the phosphate rock have been studied from such perspectives as stress and strain, fractal characteristics of fragment size, and the spatial and temporal evolution of cracks. The research results show that the dynamic strength of the phosphate rock presents obvious strain rate effect, but the dynamic elasticity modulus is not so sensitive to the strain rate. There is a great correlation between the failure degree of rock specimens and the strain rate. The fractal characteristics of specimen fragments can be used to quantitatively evaluate the rock failure degree under impact loading. According to the characteristics of crack propagation, the rock failure process under the impact can be divided into four stages, namely the elastic crack-free stage, the crack initiation stage, the rapid crack growth stage, and the slow crack development stage. Moreover, with the increase of impact loading, micro-cracks are activated in large quantities. The specimens gradually change from the local damage mode to the axial splitting failure mode and to the crushing failure mode, and in this process, the number of tensile cracks takes an absolute advantage compared with the number of shear cracks.

Economic effects analysis of environmental regulation policy in the process of industrial structure upgrading: Evidence from Chinese provincial panel data

As Chinese economy enters the stage of high-quality development from the stage of rapid growth, the economic vitality that relies on the demographic dividend and capital dividend is gradually disappearing. In order to alleviate the downward pressure of the economy and explore a sustainable growth path, Chinese government is seeking to optimize industrial economic structure by strengthening environmental regulations. However, the effect of environmental regulation on the change of industrial structure has not been carefully examined yet. This study constructs a panel model and uses the panel data of 30 provinces in China from 2007 to 2016 to empirically test the economic effectiveness of environmental regulation policies on the upgrading of industrial structure. The results showed that diversified environmental regulation policies can accelerate change in regional industrial structure, and the positive effects of economic incentives and legislative monitoring of environmental regulation policies on the upgrading of industrial structure are significant. However, there are significant differences in the economic performance of environmental regulation policies among regions. The economic effectiveness of environmental regulation policies in the eastern region is better than that in the central and western regions, and the low level of environmental regulation in the central and western regions may trigger the “growth limit” problem. Therefore, in order for environmental regulation policies to better promote the upgrade of industrial structure and promote the high-quality development of the national economy, it is necessary to enrich environmental regulation policy tools, seek precise regulation in the field of the environment, build an environmental information service platform, promote supporting reform in key areas, and support the people's livelihood to alleviate transformation pressure.

Development Trend and Segmentation of the US Green Building Market: Corporate Perspective on Green Contractors and Design Firms

In the past decade, the architecture, engineering, and construction industry has witnessed increasing growth in the green building market and continues to expect a promising future. Although companies in the industry have played a significant role in developing the green building market, scarce studies have analyzed changes in the market from the perspectives of these corporations. Also, few studies classify green building companies by characteristics. To fill these gaps of knowledge, we explored the characteristics of the US green building market from a corporate perspective, specifically investigating green contractors and design firms. We first collected data of 464 top US green building companies identified by the Engineering News-Record over the past decade and explored the development trend of the green building market, based on the green revenue generated by these companies. We found that the general growth trend in the US green building market in the past decade could be divided into three stages: a rapid-growth stage (2000–2008), a steady-growth stage (2009–2013), and a maturity and transformation stage (2014–2016). We then categorized the 464 organizations into three groups with distinct characteristics by k-means cluster analysis techniques, including mature green building companies, sector-oriented green building companies, and primary-stage green building companies. This study provides the academic and practitioner communities with a holistic understanding of the development of the US green building market from the view of burgeoning companies. Corporate-level management systems and sustainable practices of the three clusters of green building companies also provide guidance for construction companies in the various stages of transformation towards sustainability to adopt different strategies.

LncRNAs are regulated by chromatin states and affect the skeletal muscle cell differentiation.

ObjectiveThis study aims to clarify the mechanisms underlying transcriptional regulation and regulatory roles of lncRNAs in skeletal muscle cell differentiation.MethodsWe analysed the expression patterns of lncRNAs via time‐course RNA‐seq. Then, we further combined the ATAC‐seq and ChIP‐seq to investigate the governing mechanisms of transcriptional regulation of differentially expressed (DE) lncRNAs. Weighted correlation network analysis and GO analysis were conducted to identify the transcription factor (TF)‐lncRNA pairs related to skeletal muscle cell differentiation.ResultsWe identified 385 DE lncRNAs during C2C12 differentiation, the transcription of which is determined by chromatin states around their transcriptional start sites. The TF‐lncRNA correlation network showed substantially concordant changes in DE lncRNAs between C2C12 differentiation and satellite cell rapid growth stages. Moreover, the up‐regulated lncRNAs showed a significant decrease following the differentiation capacity of satellite cells, which gradually declines during skeletal muscle development. Notably, inhibition of the lncRNA Atcayos and Trp53cor1 led to the delayed differentiation of satellite cells. Those lncRNAs were significantly up‐regulated during the rapid growth stage of satellite cells (4‐6 weeks) and down‐regulated with reduced differentiation capacity (8‐12 weeks). It confirms that these lncRNAs are positively associated with myogenic differentiation of satellite cells during skeletal muscle development.ConclusionsThis study extends the understanding of mechanisms governing transcriptional regulation of lncRNAs and provides a foundation for exploring their functions in skeletal muscle cell differentiation.

Fast Food Consumption Behaviour among College Students- A Case Study in Tinsukia

An adequate diet is one which meets in full all the nutritional needs of the person.”- ( Leonard A. Maynard, 1959). An adequate diet protects against many chronic no communicable diseases, such as heart disease, diabetes and cancer (WHO report, 2020) and is also considered as an important element for building physical fitness and mental health of an individual. “But there have been small decline in the purchase of less healthy food products, which translated to a small reduction of total energy and sugar purchases taken home”. – (Nicholas Berger, et al, 2020). Recent studies conducted by different academicians and researchers consider that among all the stages of a person life, the stage of adolescent is considered as the stage of rapid growth of malnutrition. “Malnutrition in all its forms, including obesity, under nutrition, and other dietary risks, is the leading cause of poor health globally.”- (Boyd A Swinburn, et al, 2019) With rapid growth of urbanization and advancement of modern up to date technology the ways of living of many people has greatly changed. The effects of the changing lifestyles of the individuals have altered their food habit. Fast food generally refers to the food that is quickly prepared within a short interval. Consumption of fast food has drastically increased in India. People, specifically the adolescents love to eat fried and roasted food. It has been observed from many studies that people prefer fast food for convenience (Hesamedin Askari Majabadi, et al, 2016), taste (B. Narayan & M. Prabhu, 2015) and also for social interaction (M. S. Anitharaj, 2018) and also to attain pleasure. But in spite of huge demand of fast food from larger section of people of the society, but consumption of too much of fast food may result into cardiac disease or obesity. Strict supervision of fast food companies is required. (Hesamedin Askari Majabadi, et al, 2016)

Critical Percolation Threshold Restricts Late‐Summer Arctic Sea Ice Melt Pond Coverage

AbstractDuring the summer, vast regions of Arctic sea ice are covered by meltwater ponds that significantly lower the ice reflectivity and accelerate melting. Ponds develop over the melt season through an initial rapid growth stage followed by drainage through macroscopic holes. Recent analysis of melt pond photographs indicates that late‐summer ponds exist near the critical percolation threshold, a special pond coverage fraction below which the ponds are largely disconnected and above which they are highly connected. Here, we show that the percolation threshold, a statistical property of ice topography, constrains pond evolution due to pond drainage through macroscopic holes. We show that it sets the approximate upper limit and scales pond coverage throughout its evolution after the beginning of drainage. Furthermore, we show that the rescaled pond coverage during drainage is a universal function of a single non‐dimensional parameter, η, roughly interpreted as the number of drainage holes per characteristic area of the surface. This universal curve allows us to formulate an equation for pond coverage time‐evolution during and after pond drainage that captures the dependence on environmental parameters and is supported by observations on undeformed first‐year ice. This equation reveals that pond coverage is highly sensitive to environmental parameters, suggesting that modeling uncertainties could be reduced by more directly parameterizing the ponds' natural parameter, η. Our work uncovers previously unrecognized constraints on melt pond physics and places ponds within a broader context of phase transitions and critical phenomena. Therefore, it holds promise for improving ice‐albedo parameterizations in large‐scale models.

Multi-omics analysis of cellular pathways involved in different rapid growth stages of moso bamboo.

Moso bamboo (Phyllostachys edulis (Carriere) J. Houzeau) is a rapidly growing grass of industrial and ecological importance. However, the molecular mechanisms of its remarkable growth are not well understood. In this study, we investigated the early-stage growth of moso bamboo shoots and defined three different growth stages based on histological and biochemical analyses, namely, starting of cell division (SD), rapid division (RD) and rapid elongation (RE). Further analyses on potentially relevant cellular pathways in these growth stages using multi-omics approaches such as transcriptomics and proteomics revealed the involvement of multiple cellular pathways, including DNA replication, repair and ribosome biogenesis. A total of 8045 differentially expressed genes (DEGs) and 1053 differentially expressed proteins (DEPs) were identified in our analyses. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses of detected DEGs identified several key biological pathways such as phytohormone metabolism, signal transduction, cell wall development and carbohydrate metabolism. The comparative analysis of proteins displayed that a total of 213 DEPs corresponded with DEGs and 3 significant expression profiles that could be promoting the fast growth of bamboo internodes. Moreover, protein-protein interaction network prediction analysis is suggestive of the involvement of five major proteins of signal transduction, DNA synthesis and RNA transcription, and may act as key elements responsible for the rapid shoot growth. Our work exploits multi-omics and bioinformatic approaches to unfurl the complexity of molecular networks involved in the rapid growth of moso bamboo and opens up questions related to the interactions between the functions played by individual molecular pathway.

Optimization of Application Conditions of Drag Reduction Agent in Product Oil Pipelines.

Drag reduction performance was studied with a rotating disk instrument in the laboratory, and experiments show that there is an initial rapid growth stage and stability stage for drag reduction ratio change. The higher the rotational speed, the larger the initial drag reduction ratio is; the larger the concentration, the shorter the drag reduction stabilization time is. Under high concentration and high speed, the drag reduction onset time is short. Because of the shear degradation, the Reynolds number should be taken into account during use. Through a comparison of diesel properties after adding agents with national standard, it is confirmed that drag reduction agents could be used in this pipeline.

Analysis of Cracking Development and Mechanical Characteristics of High-Filled Cut-and-Cover Tunnel

The cut-and-cover tunnel (CCT) construction scheme has led to the popularity of high-filled cut-and-cover tunnel (HFCCT). HFCCT possesses a backfilling height of 30–50 m. However, such a high soil column produces a large force on the structure and the structure is prone to crack, causing structural damage and difficulty in normal use. In order to provide a reference for the structural safety assessment of HFCCT, we conducted a similarity model test to study the variation law of the development of crack, displacement, and internal force of HFCCT with a coefficient of λ (the ratio of the backfilling height to the height of the cut-and-cover tunnel). In the test, a 1:20 similar scale CCT model with slope angle 70° and groove width ratio 1 was built using data from the HFCCT on the Lanyu Line. The backfilling process on site was simulated in a simulation box (360 cm long, 120 cm wide and 209 cm high). A numerical model was also built using PFC2D to verify the accuracy of the model test and further explain the crack formation mechanism of the HFCCT from a microscopic perspective. The results show that with the increase of the coefficient of λ, the bearing stage of the CCT can be roughly divided into three stages: steady growth stage, rapid growth stage, and accelerated growth stage. Furthermore, the development of cracks is closely related to the displacement and internal force of the CCT. The larger the displacement of the CCT, the greater the instability of the structure and the larger the ratio of the bending moment to the internal force, which causes the crack to develop faster.

Growth stage-dependent responses of carbon fixation process of alpine grasslands to climate change over the Tibetan Plateau, China

Alpine grassland ecosystem on the Tibetan Plateau (TP) is highly sensitive to climate change and plays a critical role in terrestrial carbon cycle. However, the long-term responses of alpine grassland ecosystem carbon fluxes to climate change at different growth stages and their controlling mechanisms have not been well understood. In this study, we quantified the spatial and temporal variations of gross primary productivity (GPP) and net ecosystem productivity (NEP) of alpine grassland ecosystems from 1982 to 2015 based on an improved Biome-BGC model, and then we examined how different climate factors (i.e., soil moisture, temperature, vapor pressure deficit (VPD), and solar shortwave radiation) affected GPP and NEP dynamics at different growth stages (i.e., the early rapid growth, physiological maturity, and senescence stages) using partial correlation analysis. Furthermore, the relative contributions of different climate factors on GPP and NEP dynamics were also analyzed using path analysis model. The results showed that both GPP and NEP of alpine grassland ecosystems increased significantly during the past 34 years, and the responses of GPP and NEP to climate change and their dominant climate factors significantly varied at different growth stages. Specifically, temperature severely limited the productivity of most alpine grasslands at all growth stages, and soil moisture played an increasingly important role in vegetation carbon fixation before senescence stage, while the effects of VPD and solar shortwave radiation on vegetation carbon fixation were relatively weak. Our study suggested that a finer temporal scale (e.g., the growth stage basis) should be considered to reveal the complex relationships between climate change and the variations of ecosystem carbon fluxes, which could provide a new sight to understand the mechanisms of terrestrial ecosystem's responses to global climate change.

Study on creep characteristics of unsaturated sericite schist residual soils

Sericite schist is an extremely soft rock, which is characterized by obvious rheological properties and large creep deformation. The residual soil of Sericite schist is in unsaturated state for most of the time. When encountering water, it interacts with water, which has a great influence on its strength. In this paper, one dimension and three axis creep tests of Sericite schist residual soil are carried out by using unsaturated quadruple consolidation apparatus and unsaturated triaxial creep apparatus. The results show that the creep process of the residual soil can be divided into three stages: rapid growth stage, slow growth stage and stable stage. The creep deformation of triaxial test is larger than that of one dimension.

High-quality Economic Growth under the Influence of Technological Innovation Preference in China: A Numerical Simulation from the Government Financial Perspective

China's economy has been transitioning from labor-driven and capital-driven at a stage of rapid growth to innovation-driven at a stage of high-quality development. In this paper, government's “technological innovation preference” (TIP) is introduced into the traditional neoclassical economic growth model which is Ramsey-Cass-Koopmans (RCK), as a factor affecting the utility of endogenous growth model with capital accumulation and technological innovation. Assumed that the government fiscal revenue is used for public and research spending, through which we can examine its impact on high-quality economic growth and transmission mechanism, as well as how TIP influences on the economy. Results indicate that the tax rates and the growth rates would be raised, while the proportion of public spending would fall if TIP enhanced by the government. Furthermore, though steady-state output level may be lower in short term, however, it may also achieve high-quality growth in long run.

Expression of cellulose synthase-like genes in two phenotypically distinct flax (Linum usitatissimum L.) subspecies

Cellulose synthase-like (CSL) genes encode glycosyltransferases thought to be involved in the biosynthesis of cell wall non-cellulosic polysaccharides; however, the exact function is not established yet for many of them. We performed a bioinformatics search of CSL genes in the flax genome, their phylogenetic analysis and evaluated expression of CSL genes in the course of plant development and in various plant parts. Quantitative RT-PCR was used to examine expression of CSL genes in several fiber-containing samples of two flax subspecies at seedlings, rapid growth and budding stages. One of the studied subspecies is fiber flax (cultivar Blakit) that was developed to produce high-quality fiber and another one is dehiscent flax that is not used for fiber production. Our study has revealed that the LusCSLD3 and LusCSLG3.2/3.3 genes were highly expressed in all studied samples and their expression was comparable with the expression of cellulose synthase genes involved in secondary cell wall development (LusCESA4 and LusCESA7-B) at rapid growth and budding stages. LusCSLB4 gene had a strong expression in seedling samples only. We have found that LusCSL gene expression profiles from the two phenotypically distinct flax subspecies are more different at the seedling stage than at the later developmental stages—expression of LusCSL was higher in fiber flax Blakit at the seedling stage as compared to dehiscent flax. Analysis of data from RNA-Seq experiments performed on various parts of flax plants revealed that LusCSLG with unknown substrate activity could be a specific glycosyltransferase involved in the synthesis of a non-cellulosic polysaccharide composing the fiber cell wall. Our findings lay the foundation for the understanding of the fiber cell-wall biogenesis and suggest characteristic features of this process in the cultivated flax.

Analysis of Mechanical Strength and Failure Morphology of Prefabricated Closed Cracked Rock Mass Under Uniaxial Compression

In order to obtain the mechanical strength and failure characteristics of fractured rock masses with prefabricated closed crack, Based on the indoor uniaxial compression test, the parameters of the prefabricated closed crack specimens were calibrated. The PFC3D software was used to perform the uniaxial compression simulation test on the prefabricated closed crack rock-like material. The change rules of mechanical parameters of fractured specimens with different prefabricated closed cracks and the failure morphology of rock specimens were obtained. The results showed that: most of the parameters such as elastic modulus, secant modulus, deformation modulus, peak strength and peak strain of the specimen showed a downward trend with the increase of crack diameter and inclination. Among all the parameters, the change of crack inclination angle and diameter had the greatest impact on the Peak strength, and the least influence on Secant modulus; Micro cracks mainly occurred around the prefabricated crack, and when the diameter of prefabricated cracks was small, micro cracks outside the prefabricated cracks were more likely to appear; With the increase of crack diameter and inclination angle, the stress at the moment when the first micro crack appears first decreased and then increased; The growth process of the number of micro cracks had gone through three stages: the stage of no micro cracks, the stage of unstable growth of micro cracks and the stage of rapid growth of micro crack.

Oil charging model and controlling factors revealed by an online nuclear magnetic resonance (NMR) system

It is very difficult to simulate the charging process of crude oil under experimental conditions due to the low porosity and permeability of tight sandstone. However, simulations are important for revealing the mechanism of formation of tight oil and the oil-water distribution characteristics, as well as for enhancing the oil recovery efficiency. In this study, we established a new method, called nuclear magnetic resonance coupling displacement (NMR-DP), to simulate the tight oil charging process online. The NMR-DP method has the advantages of high precision, velocity, recyclability, and the ability to reflect the distribution of fluids in the micropores of a tight rock.We conducted a simulation experiment, involving the charging of crude oil into eight sandstone samples from Gaotaizi (in the Qijia-Longhupao area of the Songliao Basin). The results of this experiment were combined with those of microscopic measurements conducted on the pore structure (i.e., nuclear magnetic resonance, nitrogen adsorption, high-pressure and rate-controlled mercury injections, and micron-computed tomography). In this way, we clarified the charging process and its controlling factors (e.g., physical properties and wettability) and established a tight oil charging model. The results indicate that the oil charging saturation was controlled by several factors, including the charging pressure, physical properties, pore throat structure, and mineral composition of the rock. A smaller radius of the pore throat corresponded to a lower oil charging saturation and higher starting pressure gradient. The lower the content of clay and carbonate minerals, and the higher the content of feldspar mineral, the higher the oil saturation. Oil mainly occurred in the larger pores, while residual water mainly occurred in the smaller pores. The charging process was divided into four stages: an exponential rapid growth stage, a logarithmic slow-growth stage, a linear slow-growth stage, and a quasi-stationary stage. The method established in this paper is expected to be helpful for analyzing the distribution law of oil and water in tight sandstone areas, thereby aiding in the prediction of sweet spots and development of tight oil.

Dynamics of coastal aquaculture ponds in Vietnam from 1990 to 2015 using Landsat data

It is important to know coastal aquaculture distribution and dynamics for aquaculture sustainability and offshore ocean protection in coastal countries. Vietnam is one of the largest in Asia in aquaculture yield, and thus it is of great significance to map spatial-temporal changes of costal aquaculture for sustainable aquaculture and offshore environment protection in Vietnam. In this study, based on Landsat images from 1990 to 2015, we used object-oriented and decision trees to extract coastal aquaculture ponds, and then analyzed the spatial and temporal distribution and evolution of coastal aquaculture area in Vietnam. The results showed that: 1) the method proposed could effectively extract coastal aquaculture ponds with an overall accuracy of 86%; 2) Vietnam’s coastal aquaculture ponds were unevenly distributed and greatly different, and mainly distributed in the Mekong River Delta and Red River Delta, accounting for about 87%; 3) the development of Vietnam’s coastal aquaculture ponds can be divided into two main stages, including rapid growth stage before 2010 and slow growth after 2010. This study can provide support for making aquaculture policy and coastal environment protection in Vietnam.