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Apr 15, 2021

Progressive fragmentation and loss of natural forest habitat in one of the world’s biodiversity hotspots

Knowledge of the state of fragmentation and transformation of a forested landscape is crucial for proper planning and biodiversity conservation. Chile is one of the world’s biodiversity hotspots; within it is the Nahuelbuta mountain range, which is considered an area of high biodiversity value and intense anthropic pressure. Despite this, there is no precise information on the degree of transformation of its landscape and its conservation status. The objective of this work was to evaluate the state of the landscape and the spatio-temporal changes of the native forests in this mountain range. Using Landsat images from 1986 and 2011, thematic maps of land use were generated. A 33% loss of native forest in 25 years was observed, mainly associated to the substitution by forest plantations. Changes in the spatial patterns of land cover and land use reveal a profound transformation of the landscape and advanced fragmentation of forests. We discuss how these patterns of change threaten the persistence of several endemic species at high risk of extinction. If these anthropogenic processes continue, these species could face an increased risk of extinction.

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17

Apr 9, 2022

Sustainability study of medium-deep geothermal buried pipe for heat supply

In order to study the temperature change trend of the surrounding geotechnical soil during the operation and thermal recovery of the medium-deep geothermal buried pipe and the influence of the geotechnical soil on the operational stability of the vertical buried pipe after thermal recovery. Based on the data of geological stratum in Guanzhong area and the actual engineering application of medium-deep geothermal buried pipe heating system in Xi’an New Area, the influence law of medium-deep geothermal buried pipe heat exchanger on surrounding geotechnical soil is simulated and analyzed by FLUENT software. The results show that: after four months of heating operation, in the upper layer of the geotechnical soil, the reverse heat exchange zone appears due to the higher fluid temperature; in the lower layer of the geotechnical soil, the temperature decreases more with the increase of depth and shows a linear increase in the depth direction; without considering the groundwater seepage, after eight months of thermal recovery of the geotechnical soil after heating, the maximum temperature difference after recovery is 3.02 ℃, and the average temperature difference after recovery is 1.30 ℃ The maximum temperature difference after recovery was 3.02 ℃ and the average temperature difference after recovery was 1.30 ℃. The geotechnical thermal recovery temperature difference has no significant effect on the long-term operation of the buried pipe, and it can be operated continuously and stably for a long time. Practice shows that due to the influence of various factors such as stratigraphic structure, stratigraphic pressure, radioactive decay and stratigraphic thermal conductivity, the actual stratigraphic temperature below 2000m recovers rapidly without significant temperature decay, fully reflecting the characteristics of the Earth’s constant temperature body.

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8

Sept 10, 2021

Study on heat transfer characteristics of flow heat coupling of horizontal spiral tube heat exchanger

In view of the complex structural characteristics and special operating environment of the horizontal spiral tube heat exchanger of the shaft sealed nuclear main pump, the numerical simulation method of flow heat coupling is used to analyze the influence of the flow and temperature changes of the fluid on the shell side on the flow field and temperature field of the heat exchanger, explore the influence rules of the inlet parameters on the flow and heat transfer characteristics of the fluid in the heat exchanger, and analyze the enhanced heat transfer performance of the heat exchanger by using the relevant heat transfer criteria. The results show that the horizontal spiral tube fluid generates centrifugal force under the influence of curvature, forming a secondary flow which is different from the straight tube flow heat transfer, and the velocity distribution is concave arc, which will enhance the heat transfer efficiency of the heat exchanger; with the increase of shell side velocity, the degree of fluid disturbance and turbulence increases, while the pressure loss does not change significantly, and the heat transfer performance of the heat exchanger increases; under the given structure and size, the heat transfer performance curve of the heat exchanger shows that the increase of shell side flow and Reynolds number has a significant impact on the enhanced heat transfer of the spiral tube. In practical engineering applications, the heat transfer can be strengthened by appropriately increasing the shell side flow of the heat exchanger.

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9

Sept 21, 2022

A social-ecological perspective for emerging cities: The case of Corniche promenade, “urban majlis” of Doha

In the past decade, the capital city of Doha of the State of Qatar has experienced rapid urban expansion and other changes due to globalization, which has caused (i) the loss of a compact urban pattern, (ii) landscape fragmentation, and (iii) deficiency of green spaces. Therefore, as envisioned by Qatar National Vision 2030 (QNV-2030), the State of Qatar plans to invest substantial funds into the urban regeneration of the built environment, along with the development of large areas of public parks as a means of promoting more sustainable urban development and enhancing city residents’ well-being. Accessibility contributes to the usability of public facilities on the part of the neighborhood community, thus enhancing city dwellers’ well-being. Nonetheless, the authors argue, the urban network along Doha’s Corniche promenade, the dominant open public space and the spine of the city, lacks connectivity at various scales of space. Therefore, this research study aimed to assess the existing conditions of Doha’s Corniche and recommend strategies for implementing its integration into the newly emerging city’s urban fabric. The findings, revealed through a network-analysis investigation based on graph theory, allowed us to generate a framework for shaping open public spaces, promoting higher living standards through a green network system planned at the city scale. The proposed framework addresses social-ecological challenges of distinctive open public spaces and helps define an approach for (i) tailoring the accessibility of open public spaces to their surroundings, and (ii) enhancing city dwellers’ well-being.

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9

Dec 23, 2021

Preparation of PbTiO3-CdS nanocomposite material and its microstructure and photocatalytic properties

In order to explore the influence of the ferroelectric surface on the structure and properties of semiconductor oxides, the growth of CdS nanocrystals was regulated and controlled by taking single-crystal perovskite PbTiO₃ nanosheets as the substrate through a simple hydrothermal method. Through composition design, a series of PbTiO₃-CdS nanocomposite materials with different loading concentrations were prepared, and their microstructure and photocatalytic properties were systematically analyzed. Studies show that in the prepared product, CdS nanoparticles selectively grow on the surfaces of PbTiO₃ nanosheets, and their morphology is affected by the exposed surfaces of PbTiO₃ nanosheets. There is a clear interface between the PbTiO₃ substrate and CdS nanoparticles. The concentration of the initial reactant and the time of hydrothermal reaction also significantly affect the crystal morphology of CdS. Photocatalysis studies have shown that the prepared PbTiO₃-CdS nanocomposite material has a significant degradation effect on 10 mg/L of Rhodamine B aqueous solution. The degradation efficiency rises with the increase of CdS loading concentration. When degrading 10 mg/L Rhodamine B aqueous solution, the PbTiO₃-CdS sample with a mass fraction of 3% can reach a degradation rate of 72% within 120 min.

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15

May 24, 2022

Urban livability and contextual uncertainties: An assessment of livability through the lens of urban dwellers in Guwahati, India

The frenetic pace of urban growth in India has caused major concerns regarding the quality of urban livability. Thus, constructing livable cities has become a major goal for new urbanization in India. But urban livability as a behavioral function of the interaction between urban environment and individual characteristics is still understudied. Therefore, to enhance urban livability and construct people-oriented livable cities, this research study aimed to understand the perception of the residents of Guwahati, India, on urban livability and its determinants. Following the notion of uncertain geographic context problem (UGCoP), the current study developed an appropriate conceptual and methodological framework that evaluated the residents’ satisfaction with urban livability and the effect of its dimensions using statistical methods, which were exploratory factor analysis, structural equation modeling and Spearman’s rank correlation. The empirical results of the study indicate that residents’ mean satisfaction with the city’s livable condition is above dissatisfaction level (2.735) and the four examined dimensions have a positive influence upon residents’ satisfaction with urban livability. Additionally, different socio-economic attributes also exert significant effects on the overall satisfaction with urban livability. Therefore, this study is a practical example and model reference for enhancing urban livability in India, particularly for fast-growing cities.

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