Composition and structure of extraction residue of direct coal liquefaction residue and recycle of active phase of iron catalyst

In order to solve the problem of iron source supply for large-scale direct liquefaction catalyst, and meanwhile realize the harmless separated-utilization of extraction residue from coal liquefaction, this paper conducted a research on the recovery of iron catalyst from extraction residue, and explored the feasibility of enriching recovery of iron catalyst by using physical magnetic separation method. Firstly, the characterization methods, such as particle size analysis, XRF, XRD, SEM, TG, SEM-EDX, were used to comprehensively characterize and analyze the physical and chemical properties of the extraction residue, and therefore determine the contents and existence forms of iron catalyst. From the results analysis, it can be seen that the extraction residue from industrial equipment is mainly composed of carbon in unreacted coal and residual carbon, volatile matter and ash, with uniform particle size and no agglomeration. The mass fraction of iron is 5.96%, and the iron species still exist as the active phase of paramagnetic Fe1−xS, which doped and coated by unreacted coal and residual asphalt, and uniformly mixed and distributed in the extracts with various elements such as Ca, Si, Al, O, etc. On this basis, four types of magnetic separation equipment were selected for magnetic separation enrichment under different magnetic field strengths, and the enriched samples were then used as catalysts for direct coal liquefaction reaction to investigate their performances in direct liquefaction reaction. The experimental results show that：On the one hand, the high gradient magnetic force generated by the wet vertical ring pulsating high gradient magnetic separator is applied to the magnetic catalyst fine powder. Together with using water as dispersion medium and washing medium, the fine separation of iron catalyst powder from extraction residue was realized more effectively. With the magnetic field strength of 640 000 A/m, the material enrichment rate of the iron-containing catalyst was 10.48%, and the mass fraction of iron was 11.37%, the extraction oil yield of high-pressure autoclave 41.96%, which was 7.17% higher than that without the catalyst, and 8.99% higher than that with the extraction residue. It can be mixed into fresh catalyst to achieve an effective reuse, to some extent solving the problem of catalyst iron source shortage

Quantitative Evaluation of Spatial Differentiation for Public Open Spaces in Urban Built-Up Areas by Assessing SDG 11.7: A Case of Deqing County

Urban public open spaces refer to open space between architectural structures in a city or urban agglomeration that is open for urban residents to conduct public exchanges and hold various activities. Sustainable Development Goal (SDG) 11.7 in the 2030 UN Agenda for Sustainable Development clearly states that the distribution characteristics of public open spaces are important indicators to measure the sustainable development of urban ecological society. In 2018, in order to implement the sustainable development agenda, China offered the example of Deqing to the world. Therefore, taking Deqing as an example, this paper uses geographic statistics and spatial analysis methods to quantitatively evaluate and visualize public open spaces in the built area in 2016 and analyzes the spatial pattern and relationship of the population. The results show that the public open spaces in the built-up area of Deqing have typical global and local spatial autocorrelation. The spatial pattern shows obvious differences in different parts of the built area and attributes of public open spaces. According to the results of correlation analysis, it can be seen that the decentralized characteristics of public open spaces have a significant relationship with the population agglomeration, and this correlation is also related to the types of public open spaces. The assessment results by SDG 11.7.1 indicate that the public open spaces in the built-up area of Deqing conform to the living needs of residents on the whole and have a humanized space design and good accessibility. However, the per capita public open spaces of towns and villages outside the built area are relatively low, and there is an imbalance in public open spaces. Therefore, more attention should be paid to constructing urban public open spaces fairly

The Influence of Sky View Factor on Daytime and Nighttime Urban Land Surface Temperature in Different Spatial-Temporal Scales: A Case Study of Beijing

Urban building morphology has a significant impact on the urban thermal environment (UTE). The sky view factor (SVF) is an important structure index of buildings and combines height and density attributes. These factors have impact on the land surface temperature (LST). Thus, it is crucial to analyze the relationship between SVF and LST in different spatial-temporal scales. Therefore, we tried to use a building vector database to calculate the SVF, and we used remote sensing thermal infrared band to retrieve LST. Then, we analyzed the influence between SVF and LST in different spatial and temporal scales, and we analyzed the seasonal variation, day–night variation, and the impact of building height and density of the SVF–LST relationship. We selected the core built-up area of Beijing as the study area and analyzed the SVF–LST relationship in four periods in 2018. The temporal experimental results indicated that LST is higher in the obscured areas than in the open areas at nighttime. In winter, the maximum mean LST is in the open areas. The spatial experimental results indicate that the SVF and LST relationship is different in the low SVF region, with 30 m and 90 m pixel scale in the daytime. This may be the shadow cooling effect around the buildings. In addition, we discussed the effects of building height and shading on the SVF–LST relationship, and the experimental results show that the average shading ratio is the largest at 0.38 in the mid-rise building area in winter

Identification and Evaluation of Urban Construction Waste with VHR Remote Sensing Using Multi-Feature Analysis and a Hierarchical Segmentation Method

With rapid urbanization, the disposal and management of urban construction waste have become the main concerns of urban management. The distribution of urban construction waste is characterized by its wide range, irregularity, and ease of confusion with the surrounding ground objects, such as bare soil, buildings, and vegetation. Therefore, it is difficult to extract and identify information related to urban construction waste by using the traditional single spectral feature analysis method due to the problem of spectral confusion between construction waste and the surrounding ground objects, especially in the context of very-high-resolution (VHR) remote sensing images. Considering the multi-feature analysis method for VHR remote sensing images, we propose an optimal method that combines morphological indexing and hierarchical segmentation to extract the information on urban construction waste in VHR images. By comparing the differences between construction waste and the surrounding ground objects in terms of the spectrum, geometry, texture, and other features, we selected an optimal feature subset to improve the separability of the construction waste and other objects; then, we established a classification model of knowledge rules to achieve the rapid and accurate extraction of construction waste information. We also chose two experimental areas of Beijing to validate our algorithm. By using construction waste separability quality evaluation indexes, the identification accuracy of construction waste in the two study areas was determined to be 96.6% and 96.2%, the separability indexes of the construction waste and buildings reached 1.000, and the separability indexes of the construction waste and vegetation reached 1.000 and 0.818. The experimental results show that our method can accurately identify the exposed construction waste and construction waste covered with a dust screen, and it can effectively solve the problem of spectral confusion between the construction waste and the bare soil, buildings, and vegetation

Evaluating the Influence of Different Layouts of Residential Buildings on the Urban Thermal Environment

Urban residential building layouts have an impact on air temperature and thermal comfort. Research has shown that poorly designed building layouts can lead to thermal discomfort. Thus, it is crucial to analyze the relationship between residential building layouts and air temperature. We used the ENVI-met 3D microclimate model to simulate six typical residential building layouts and explore the diurnal and seasonal variations in air temperature. In addition, we used the physiological equivalent temperature (PET) as the evaluation index for the thermal comfort of different building layouts. The diurnal results showed that the air temperature of the parallel layout rose faster and fell faster, and these changes were more significant in summer. The results of the air temperature classifications indicated that the frequency of low-air-temperature areas in the parallel layout is approximately 12% smaller than that of the enclosed and semi-enclosed layouts, and the high-air-temperature area frequency is 11% higher than that of the enclosed and semi-enclosed layouts in summer. In winter, the frequency of low-air-temperature areas in the parallel layout is approximately 7% smaller than that of the enclosed and semi-enclosed layouts, and the high-air-temperature area frequency is 5% higher than that of the enclosed and semi-enclosed layouts. In combination with the PET results, we found that the enclosed layout is the optimal configuration. Moreover, in some cases, increased building height and vegetation lead to a reduction in air temperature

Rapid Mapping and Annual Dynamic Evaluation of Quality of Urban Green Spaces on Google Earth Engine

In order to achieve the United Nations 2030 Sustainable Development Goals (SDGs) related to green spaces, monitoring dynamic urban green spaces (UGSs) in cities around the world is crucial. Continuous dynamic UGS mapping is challenged by large computation, time consumption, and energy consumption requirements. Therefore, a fast and automated workflow is needed to produce a high-precision UGS map. In this study, we proposed an automatic workflow to produce up-to-date UGS maps using Otsu’s algorithm, a Random Forest (RF) classifier, and the migrating training samples method in the Google Earth Engine (GEE) platform. We took the central urban area of Beijing, China, as the study area to validate this method, and we rapidly obtained an annual UGS map of the central urban area of Beijing from 2016 to 2020. The accuracy assessment results showed that the average overall accuracy (OA) and kappa coefficient (KC) were 96.47% and 94.25%, respectively. Additionally, we used six indicators to measure quality and temporal changes in the UGS spatial distribution between 2016 and 2020. In particular, we evaluated the quality of UGS using the urban greenness index (UGI) and Shannon’s diversity index (SHDI) at the pixel level. The experimental results indicate the following: (1) The UGSs in the center of Beijing increased by 48.62 km2 from 2016 to 2020, and the increase was mainly focused in Chaoyang, Fengtai, and Shijingshan Districts. (2) The average proportion of relatively high and above levels (UGI > 0.5) in six districts increased by 2.71% in the study area from 2016 to 2020, and this proportion peaked at 36.04% in 2018. However, our result revealed that the increase was non-linear during this assessment period. (3) Although there was no significant increase or decrease in SHDI values in the study area, the distribution of the SHDI displayed a noticeable fluctuation in the northwest, southwest, and northeast regions of the study area between 2016 and 2020. Furthermore, we discussed and analyzed the influence of population on the spatial distribution of UGSs. We found that three of the five cold spots were located in the east and southeast of Haidian District. Therefore, the proposed workflow could provide rapid mapping and dynamic evaluation of the quality of UGS

Simulation Analysis of the Cooling Effect of Urban Water Bodies on the Local Thermal Environment

Urban water bodies have a cooling effect and alter the local urban thermal environment. However, current research is unclear regarding the relationships between factors such as the spatial density, area proportion, and distribution pattern of water bodies and the cooling effect of water on the local thermal environment. To clarify these relationships, it is critical to quantify and evaluate the influence these factors have on the cooling effect of water in the urban landscape. Therefore, we analyzed the cooling effect of different water bodies on the local thermal environment at the microscale by comparing their area proportions and distribution patterns using numerical simulations. Furthermore, we analyzed the day–night variation in the cooling effect of urban water bodies with different areas and distribution patterns. We used the area proportion, separation index (SI), and landscape shape index (LSI) to indicate the layouts of water bodies. The results showed that the cooling effect of a water body was higher during the day than at night. These results also showed that area proportion and LSI were positively correlated with the water body’s cooling effect. However, the efficiency of the cooling effect gradually decreased with increasing area proportion. When the LSI increased, more areas within the region displayed larger cooling effect values, but the uniformity of the regional cooling diminished. Additional results showed that the cooling effect had no significant positive correlation with SI. A moderate SI could enhance the uniformity of the cooling effect in the region and link the cooling effect between water patches

Simulation Analysis of the Cooling Effect of Urban Water Bodies on the Local Thermal Environment

Urban water bodies have a cooling effect and alter the local urban thermal environment. However, current research is unclear regarding the relationships between factors such as the spatial density, area proportion, and distribution pattern of water bodies and the cooling effect of water on the local thermal environment. To clarify these relationships, it is critical to quantify and evaluate the influence these factors have on the cooling effect of water in the urban landscape. Therefore, we analyzed the cooling effect of different water bodies on the local thermal environment at the microscale by comparing their area proportions and distribution patterns using numerical simulations. Furthermore, we analyzed the day–night variation in the cooling effect of urban water bodies with different areas and distribution patterns. We used the area proportion, separation index (SI), and landscape shape index (LSI) to indicate the layouts of water bodies. The results showed that the cooling effect of a water body was higher during the day than at night. These results also showed that area proportion and LSI were positively correlated with the water body’s cooling effect. However, the efficiency of the cooling effect gradually decreased with increasing area proportion. When the LSI increased, more areas within the region displayed larger cooling effect values, but the uniformity of the regional cooling diminished. Additional results showed that the cooling effect had no significant positive correlation with SI. A moderate SI could enhance the uniformity of the cooling effect in the region and link the cooling effect between water patches

Flex-LCC: A New Grid-Forming HVDC Rectifier for Collecting Large-Scale Renewable Energy

A new grid-forming (GFM) high-voltage direct current (HVdc) rectifier, named flexible line-commutated converter (Flex-LCC), is proposed in this article to collect the power generated by large-scale islanded or weak-grid-supported renewable energy systems. The Flex-LCC uses a series-connected hybrid valve based on the LCC and full-bridge modular multilevel converter (FBMMC), and adopts a new control. As a result, the Flex-LCC works as a GFM rectifier and retains the same dc voltage and power carrying capacity, dc fault clearing, and power reversal functions as an LCC. Particularly, the Flex-LCC has three salient features: the control of the Flex-LCC is decoupled from the LCC part's firing angle, the internal reactive power allocation is flexible, and the valve-side ac voltage of the FBMMC part has a wide operation range due to the decoupling of dc-port voltage and capacitor voltage. These bring reduced interharmonics, enhanced stability, and a smaller capacity boundary to the FBMMC part for the Flex-LCC. Furthermore, utilizing the reasonable design for the actual capacity and valve-side ac voltage of the FBMMC, the Flex-LCC can effectively balance cost, footprint, and weight, and match the current-carrying capacity between the series-connected LCC and FBMMC. The topology, control, characteristics, and design of the Flex-LCC are analyzed in detail in this article. Simulations and experiments validate the theory

Factores determinantes del número de relaciones bancarias

En este trabajo se analizan las variables determinantes del número de relaciones bancarias que contratan las empresas, utilizando el análisis logit y la regresión binomial negativa. Además de las variables utilizadas en estudios previos (dimensión empresarial, endeudamiento, edad y rentabilidad), se incorpora el uso de la banca electrónica. Los resultados muestran que las empresas de mayor tamaño, más jóvenes y más endeudadas mantienen un mayor número de relaciones bancarias. Por el contrario, no se puede confirmar la relación entre rentabilidad y número de entidades financieras con las que trabaja la empresa. En lo que respecta a la influencia de las TIC en el número de relaciones bancarias, los resultados obtenidos indican que las empresas que más utilizan la banca electrónica tienden a trabajar con un menor número de entidades financieras