bluuebunny/crossref_metadata_2025 huggingface dataset:
Multifunctional Polyhedral Oligomeric Silsesquioxane (POSS) Based Hybrid Porous Materials for CO2 Uptake and Iodine Adsorption
Authors: Gamal Mohamed Mohamed , Tsai Mei-Yin , Wang Chih-Feng , Huang Chih-Feng , Danko Martin , Dai Lizong , Chen Tao , Kuo Shiao-Wei
Published: January 2021

In this study, two different types of hybrid porous organic polymers (POPs), polyhedral oligomeric silsesquioxane tetraphenylpyrazine (POSS-TPP) and tetraphenylethene (POSS-TPE), were successfully synthesized through the Friedel−Crafts polymerization of tetraphenylpyrazine (TPP) and tetraphenylethene (TPE), respectively, with octavinylsilsesquioxane (OVS) as node building blocks, in the presence of anhydrous FeCl3 as a catalyst and 1,2-dichloroethane at 60 °C. Based on N2 adsorption and thermogravimetric analyses, the resulting hybrid porous materials displayed high surface areas (270 m2/g for POSS-TPP and 741 m2/g for POSS-TPE) and outstanding thermal stabilities. Furthermore, as-prepared POSS-TPP exhibited a high carbon dioxide capacity (1.63 mmol/g at 298 K and 2.88 mmol/g at 273 K) with an excellent high adsorption capacity for iodine, reaching up to 363 mg/g, compared with the POSS-TPE (309 mg/g).
Bacteria Adhesion of Textiles Influenced by Wettability and Pore Characteristics of Fibrous Substrates
Authors: Hemmatian Tahmineh , Lee Halim , Kim Jooyoun
Published: January 2021

Bacteria adhesion on the surface is an initial step to create biofouling, which may lead to a severe infection of living organisms and humans. This study is concerned with investigating the textile properties including wettability, porosity, total pore volume, and pore size in association with bacteria adhesion. As model bacteria, Gram-negative, rod-shaped Escherichia coli and the Gram-positive, spherical-shaped Staphylococcus aureus were used to analyze the adhesion tendency. Electrospun webs made from polystyrene and poly(lactic acid) were used as substrates, with modification of wettability by the plasma process using either O2 or C4F8 gas. The pore and morphological characteristics of fibrous webs were analyzed by the capillary flow porometer and scanning electron microscopy. The substrate’s wettability appeared to be the primary factor influencing the cell adhesion, where the hydrophilic surface resulted in considerably higher adhesion. The pore volume and the pore size, rather than the porosity itself, were other important factors affecting the bacteria adherence and retention. In addition, the compact spatial distribution of fibers limited the cell intrusion into the pores, reducing the total amount of adherence. Thus, superhydrophobic textiles with the reduced total pore volume and smaller pore size would circumvent the adhesion. The findings of this study provide informative discussion on the characteristics of fibrous webs affecting the bacteria adhesion, which can be used as a fundamental design guide of anti-biofouling textiles.
Electrospun Functional Nanofiber Membrane for Antibiotic Removal in Water: Review
Authors: Zhao Kun , Kang Shi-Xiong , Yang Yao-Yao , Yu Deng-Guang
Published: January 2021

As a new kind of water pollutant, antibiotics have encouraged researchers to develop new treatment technologies. Electrospun fiber membrane shows excellent benefits in antibiotic removal in water due to its advantages of large specific surface area, high porosity, good connectivity, easy surface modification and new functions. This review introduces the four aspects of electrospinning technology, namely, initial development history, working principle, influencing factors and process types. The preparation technologies of electrospun functional fiber membranes are then summarized. Finally, recent studies about antibiotic removal by electrospun functional fiber membrane are reviewed from three aspects, namely, adsorption, photocatalysis and biodegradation. Future research demand is also recommended.
A Novel Modeling Approach for Plastics Melting within a CFD-DEM Framework
Authors: Celik Alptekin , Bonten Christian , Togni Riccardo , Kloss Christoph , Goniva Christoph
Published: January 2021

Existing three-dimensional modeling approaches to single-screw extrusion can be classified according to the process sections. The discrete element method (DEM) allows describing solids transport in the feed section. The melt flow in the melt section can be calculated by means of computational fluid dynamics (CFD). However, the current state of the art only allows a separate consideration of the respective sections. A joint examination of the process sections still remains challenging. In this study, a novel modeling approach is presented, allowing a joint consideration of solids and melt transport and, beyond that, the formation of melt. For this purpose, the phase transition from the solid to liquid states is modeled for the first time within the framework CFDEMCoupling®, combining CFD and DEM by a novel melting model implemented in this study. In addition, a melting apparatus for the validation of the novel melting model is set up and put into operation. CFD-DEM simulations are carried out in order to calculate the melting rate and are compared to experimental results. A good agreement between the simulation and experimental results is found. From the findings, it can be assumed that the CFD-DEM simulation of single-screw extruder with a joint consideration of the feed and melt section is feasible.
Tannic-Acid-Cross-Linked and TiO2-Nanoparticle-Reinforced Chitosan-Based Nanocomposite Film
Authors: Roy Swarup , Zhai Lindong , Kim Hyun Chan , Pham Duc Hoa , Alrobei Hussein , Kim Jaehwan
Published: January 2021

A chitosan-based nanocomposite film with tannic acid (TA) as a cross-linker and titanium dioxide nanoparticles (TiO2) as a reinforcing agent was developed with a solution casting technique. TA and TiO2 are biocompatible with chitosan, and this paper studied the synergistic effect of the cross-linker and the reinforcing agent. The addition of TA enhanced the ultraviolet blocking and mechanical properties of the chitosan-based nanocomposite film. The reinforcement of TiO2 in chitosan/TA further improved the nanocomposite film’s mechanical properties compared to the neat chitosan or chitosan/TA film. The thermal stability of the chitosan-based nanocomposite film was slightly enhanced, whereas the swelling ratio decreased. Interestingly, its water vapor barrier property was also significantly increased. The developed chitosan-based nanocomposite film showed potent antioxidant activity, and it is promising for active food packaging.
Morphology Evolution, Molecular Simulation, Electrical Properties, and Rheology of Carbon Nanotube/Polypropylene/Polystyrene Blend Nanocomposites: Effect of Molecular Interaction between Styrene-Butadiene Block Copolymer and Carbon Nanotube
Authors: Otero Navas Ivonne , Kamkar Milad , Arjmand Mohammad , Sundararaj Uttandaraman
Published: January 2021

This work studied the impact of three types of styrene-butadiene (SB and SBS) block copolymers on the morphology, electrical, and rheological properties of immiscible blends of polypropylene:polystyrene (PP:PS)/multi-walled carbon nanotubes (MWCNT) with a fixed blend ratio of 70:30 vol.%. The addition of block copolymers to PP:PS/MWCNT blend nanocomposites produced a decrease in the droplet size. MWCNTs, known to induce co-continuity in PP:PS blends, did not interfere with the copolymer migration to the interface and, thus, there was morphology refinement upon addition of the copolymers. Interestingly, the addition of the block copolymers decreased the electrical resistivity of the PP:PS/1.0 vol.% MWCNT system by 5 orders of magnitude (i.e., increase in electrical conductivity). This improvement was attributed to PS Droplets-PP-Copolymer-Micelle assemblies, which accumulated MWCNTs, and formed an integrated network for electrical conduction. Molecular simulation and solubility parameters were used to predict the MWCNT localization in the immiscible blend. The simulation results showed that diblock copolymers favorably interact with the nanotubes in comparison to the triblock copolymer, PP, and PS. However, the interaction between the copolymers and PP or PS is stronger than the interaction of the copolymers and MWCNTs. Hence, the addition of copolymer also changed the localization of MWCNT from PS to PS–PP–Micelles–Interface, as observed by TEM images. In addition, in the last step of this work, we investigated the effect of the addition of copolymers on inter- and intra-cycle viscoelastic behavior of the MWCNT incorporated polymer blends. It was found that addition of the copolymers not only affects the linear viscoelasticity (e.g., increase in the value of the storage modulus) but also dramatically impacts the nonlinear viscoelastic behavior under large deformations (e.g., higher distortion of Lissajous–Bowditch plots).]
Micro- and Nanocellulose in Polymer Composite Materials: A Review
Authors: Omran Abdoulhdi A. Borhana , Mohammed Abdulrahman A. B. A. , Sapuan S. M. , Ilyas R. A. , Asyraf M. R. M. , Rahimian Koloor Seyed Saeid , Petrů Michal
Published: January 2021

The high demand for plastic and polymeric materials which keeps rising every year makes them important industries, for which sustainability is a crucial aspect to be taken into account. Therefore, it becomes a requirement to makes it a clean and eco-friendly industry. Cellulose creates an excellent opportunity to minimize the effect of non-degradable materials by using it as a filler for either a synthesis matrix or a natural starch matrix. It is the primary substance in the walls of plant cells, helping plants to remain stiff and upright, and can be found in plant sources, agriculture waste, animals, and bacterial pellicle. In this review, we discussed the recent research development and studies in the field of biocomposites that focused on the techniques of extracting micro- and nanocellulose, treatment and modification of cellulose, classification, and applications of cellulose. In addition, this review paper looked inward on how the reinforcement of micro- and nanocellulose can yield a material with improved performance. This article featured the performances, limitations, and possible areas of improvement to fit into the broader range of engineering applications.
Adsorption Evaluation for the Removal of Nickel, Mercury, and Barium Ions from Single-Component and Mixtures of Aqueous Solutions by Using an Optimized Biobased Chitosan Derivative
Authors: Liakos Efstathios V. , Mone Mariza , Lambropoulou Dimitra A. , Bikiaris Dimitrios N. , Kyzas George Z.
Published: January 2021

In this experimental study, the use of 5-hydroxymethyl-furfural (HMF) organic compound as a grafting agent to chitosan natural polymer (CS) was examined. One optimized chitosan derivative was synthesized, and then tested (CS-HMF), in order to uptake nickel, mercury, and barium metal ions from single- and triple-component (multi-component) aqueous solutions. The characterization of the material before and after the metal uptake was achieved by scanning electron microscopy (SEM). The ability of the adsorption of CS-HMF was tested at pH = 6. The adjusting of temperature from 25 to 65 °C caused the increase in the adsorption capacity. The equilibrium data were fitted to the models of Langmuir and Freundlich, while the data from kinetic experiments were fitted to pseudo-1st and pseudo-2nd order models. The best fitting was achieved for the Langmuir model (higher R2). The adsorption capacity for nickel, mercury, and barium removal at 25 °C (single component) was 147, 107, and 64 (mg/g), respectively. However, the total adsorption capacity for the multi-component was 204 mg/g. A thermodynamic study was also done, and the values of ΔG0, ΔH0, and ΔS0 were evaluated.
Morphology and Structure Controls of Single-Atom Fe–N–C Catalysts Synthesized Using FePc Powders as the Precursor
Authors: Yan Ning , Liu Fan , Meng Xu , Qin Meng , Zhu Guangqi , Bu Luxia , Liu Zigeng , Wang Wei
Published: January 2021

Understanding the origin of the high electrocatalytic activity of Fe–N–C electrocatalysts for oxygen reduction reaction is critical but still challenging for developing efficient sustainable nonprecious metal catalysts used in fuel cells. Although there are plenty of papers concerning the morphology on the surface Fe–N–C catalysts, there is very little work discussing how temperature and pressure control the growth of nanoparticles. In our lab, a unique organic vapor deposition technology was developed to investigate the effect of the temperature and pressure on catalysts. The results indicated that synthesized catalysts exhibited three kinds of morphology—nanorods, nanofibers, and nanogranules—corresponding to different synthesis processes. The growth of the crystal is the root cause of the difference in the surface morphology of the catalyst, which can reasonably explain the effect of the temperature and pressure. The oxygen reduction reaction current densities of the different catalysts at potential 0.88 V increased in the following order: FePc (1.04 mA/cm2) < Pt/C catalyst (1.54 mA/cm2) ≈ Fe–N–C-f catalyst (1.64 mA/cm2) < Fe–N–C-g catalyst (2.12 mA/cm2) < Fe–N–C-r catalyst (2.35 mA/cm2). By changing the morphology of the catalyst surface, this study proved that the higher performance of the catalysts can be obtained.
Analysis of Bubble Flow Mechanism and Characteristics in Gas–Liquid Cyclone Separator
Authors: Bai Yujie , Ji Hong , Liu Yaozhuo , Li Lei , Yang Shengqing
Published: January 2021

The separation of bubbles in a gas–liquid cyclone is complicated. A combination of numerical simulation and visual experimentation was considered apt to reveal the microscopic mechanisms of bubble flow. First of all, cyclones with different structures were numerically simulated. The calculation results show that the larger the diameter of the exhaust port, the better the bubble flow effect. When the exhaust port diameter was 24 mm, the gas discharge efficiency was 8% higher than that with an exhaust port diameter of 16 mm. The sequence of the bubble flow effect of a four-structure cyclone was obtained, and the gas discharge efficiency of the cyclone with a rectangular inlet was 7% higher than that of the trapezoidal inlet. Finally, a visual experimental platform was built to compare the rectangular inlet cyclone and spiral inlet cyclone with the best bubble flow effect. In accordance with the simulation numerical calculations, the bubble flow effect of the rectangular inlet cyclone was better than that of the spiral and trapezoid inlet cyclones, and the rectangular inlet in the middle was better. This article provides a specific theory and experience to guide further research on the separation mechanism, flow field characteristics and structurally optimal design of gas–liquid cyclones.
Evaluation of the Use of Recycled Vegetable Oil as a Collector Reagent in the Flotation of Copper Sulfide Minerals Using Seawater
Authors: Arcos Felipe , Uribe Lina
Published: January 2021

Considering sustainable mining, the use of seawater in mineral processing to replace conventional water is an attractive alternative, especially in cases where this resource is limited. However, the use of this aqueous medium generates a series of challenges; specifically, in the seawater flotation process, it is necessary to adapt traditional reagents to the aqueous medium or to propose new reagents that achieve better performance and are environmentally friendly. In this research, the technical feasibility of using recycled vegetable oil (RVO) as a collector of copper sulfide minerals in the flotation process using seawater was studied. The study considered the analysis of the metallurgical indexes when different concentrations of collector and foaming reagent were used, considering as collectors the RVO, potassium amyl xanthate (PAX) and mixtures of these, in addition to the methyl isobutyl carbinol (MIBC) as foaming agent. In addition, it was evidenced that the best metallurgical indexes were achieved using 40 g/t of RVO and 15 g/t of MIBC, which corresponded to an enrichment ratio of 6.29, a concentration ratio of 7.01, a copper recovery of 90.06% and a selectivity index with respect to pyrite of 4.03 and with respect to silica of 12.89. Finally, in relation to the study of the RVO and PAX collector mixtures, it was found that a mixture of 60 g/t of RVO and 40 g/t of PAX in the absence of foaming agent presented the best results in terms of copper recovery (98.66%) and the selectivity index with respect to pyrite (2.88) and silica (14.65), improving PAX selectivity and recovery compared to the use of RVO as the only collector. According to these results, it is possible to conclude that the addition of RVO improved the selectivity in the rougher flotation for copper sulfides in seawater. This could be an interesting opportunity for the industry to minimize the costs of the flotation process and generate a lower environmental impact.
On the Origins of the Hijrī Calendar: A Multi-Faceted Perspective Based on the Covenants of the Prophet and Specific Date Verification
Authors: Zein Ibrahim , El-Wakil Ahmed
Published: January 2021

There has been much speculation as to the type of calendar that was used by the pre-Islamic Arabs and the early Muslim community. The Hijrī calendar is said to have been adopted by ‘Umar b. al-Khaṭṭāb during his Caliphate despite evidence suggesting that it was instituted as soon as the Prophet emigrated to Madīnah. In this paper, we argue that a number of competing Arabian calendars existed up until 17 AH/AD 638, after which the Hijrī calendar was adopted as the definitive calendar of the Muslims. We propose that attempts at reconciling dates emanating from different calendars for major events in the Prophet’s life led to miscalculations which subsequently affected the chronology of the sīrah. This study ultimately argues that a purely lunar calendar was used by the pre-Islamic Arabs in parallel to a lunisolar calendar, and that specific dates reported in the covenants of the Prophet and in the historical works could shed new light in reconstructing the chronology of major events in the Prophet’s life.
Puritan Lecturers and Anglican Clergymen during the Early Years of the English Civil Wars
Authors: Chung Youngkwon
Published: January 2021

During the early years of the Civil Wars in England, from February 1642 to July 1643, Puritan parishioners in conjunction with the parliament in London set up approximately 150 divines as weekly preachers, or lecturers, in the city and the provinces. This was an exceptional activity surrounding lectureships including the high number of lecturer appointments made over the relatively brief space of time, especially considering the urgent necessity of making preparations for the looming war and fighting it as well. By examining a range of sources, this article seeks to demonstrate that the Puritan MPs and peers, in cooperation with their supporters from across the country, tactically employed the institutional device of weekly preaching, or lectureships, to neutralize the influence of Anglican clergymen perceived as royalists dissatisfied with the parliamentarian cause, and to bolster Puritan and pro-parliamentarian preaching during the critical years of 1642–1643. If successfully employed, the device of weekly lectureships would have significantly widened the base of support for the parliament during this crucial period when people began to take sides, prepared for war, and fought its first battles. Such a program of lectureships, no doubt, contributed to the increasing polarization of the religious and political climate of the country. More broadly, this study seeks to add to our understanding of an early phase of the conflict that eventually embroiled the entire British Isles in a decade of gruesome internecine warfare.
Negotiations of Science and Religion in Nordic Institutions: An Ethnographic Approach
Authors: Tiaynen-Qadir Tatiana , Qadir Ali , Vuolanto Pia , Hansen Petteri
Published: January 2021

This article explores how two seemingly contradictory global trends—scientific rationality and religious expressiveness—intersect and are negotiated in people’s lives in Nordic countries. We focus on Finland and Sweden, both countries with reputations of being highly secular and modernized welfare states. The article draws on our multi-sited ethnography in Finland and Sweden, including interviews with health practitioners, academics, and students identifying as Lutheran, Orthodox, Muslim, or anthroposophic. Building on new institutionalist World Society Theory, the article asks whether individuals perceive any conflict at the intersection of “science” and “religion”, and how they negotiate such a relationship while working or studying in universities and health clinics, prime sites of global secularism and scientific rationality. Our findings attest to people’s creative artistry while managing their religious identifications in a secular, Nordic, organizational culture in which religion is often constructed as old-fashioned or irrelevant. We identify and discuss three widespread modes of negotiation by which people discursively manage and account for the relationship between science and religion in their working space: segregation, estrangement, and incorporation. Such surprising similarities point to the effects of global institutionalized secularism and scientific rationality that shape the negotiation of people’s religious and spiritual identities, while also illustrating how local context must be factored into future, empirical research on discourses of science and religion.
The Sacramental Approach to the Sacred in Thomistic Perspective
Authors: Roszak Piotr
Published: January 2021

The main challenge of theology is the adequate manner of the transmission of what is sacred and belongs to the transcendent order by means of appropriate categories of immanent religious language. In history, there was a debate between the univocal and equivocal approach, but the main Christian rules of telling about the sacred were shaped by Thomas Aquinas, who proposed analogy as a fundamental tool: in the middle of similarity there is still great dissimilarity. From this perspective, the world is seen as sacramental, so all material reality refers to something more and further. In this way, the sacred has a transitory character. Nowadays, however, the naturalistic narrative dominates among many theories of the sacred. This paper will begin by dealing with several types of theological narrations about the sacred in Christian theology (metaphysical and historical, mediating and representative, etc.). Then it will go into characterizing the Thomistic storytelling and its hermeneutical rules. Finally, it will consider the role of imagination in transmitting the sacred (Chesterton, Lewis, McGrath) and how the new perception of the sacred—so visible in pilgrimages such as Camino de Santiago—can be integrated in a new thinking about the city of the future.
A Maximal Understanding of Sacrifice: Bataille, Richard Wagner, Pilgrimage and the Bayreuth Festival
Authors: Smith Philip , Stoll Florian
Published: January 2021

This paper calls for a broad conception of sacrifice to be developed as a resource for cultural sociology. It argues the term was framed too narrowly in the classical work of Hubert and Mauss. The later approach of Bataille permits a maximal understanding of sacrifice as non-utilitarian expenditures of money, energy, passion and effort directed towards the experience of transcendence. From this perspective, pilgrimage can be understood as a specific modality of sacrificial activity. This paper applies this understanding of sacrifice and pilgrimage to the annual Bayreuth “Wagner” Festival in Germany. Drawing on a multi-year mixed-methods study involving ethnography, semi-structured interviews and historical research, the article traces sacrificial expenditures at the level of individual festival attendees. These include financial costs, arduous travel, dedicated research of the artworks, and disciplines of the body. Some are lucky enough to experience transcendence in the form of deep emotional experience, and a sense of contact with sacred spaces and forces. Our study is intended as an exemplary paradigm case that can be drawn upon analogically by scholars. We suggest that other aspects of social experience, including many that are more ‘everyday’, can be understood through a maximal model of sacrifice and that a rigorous, wider comparative sociology could be developed using this tool.
Impact of COVID-19 Lockdown on the Fisheries Sector: A Case Study from Three Harbors in Western India
Authors: Avtar Ram , Singh Deepak , Umarhadi Deha Agus , Yunus Ali P. , Misra Prakhar , Desai Pranav N. , Kouser Asma , Kurniawan Tonni Agustiono , Phanindra KBVN
Published: January 2021

The COVID-19 related lockdowns have brought the planet to a standstill. It has severely shrunk the global economy in the year 2020, including India. The blue economy and especially the small-scale fisheries sector in India have dwindled due to disruptions in the fish catch, market, and supply chain. This research presents the applicability of satellite data to monitor the impact of COVID-19 related lockdown on the Indian fisheries sector. Three harbors namely Mangrol, Veraval, and Vankbara situated on the north-western coast of India were selected in this study based on characteristics like harbor’s age, administrative control, and availability of cloud-free satellite images. To analyze the impact of COVID in the fisheries sector, we utilized high-resolution PlanetScope data for monitoring and comparison of “area under fishing boats” during the pre-lockdown, lockdown, and post-lockdown phases. A support vector machine (SVM) classification algorithm was used to identify the area under the boats. The classification results were complemented with socio-economic data and ground-level information for understanding the impact of the pandemic on the three sites. During the peak of the lockdown, it was found that the “area under fishing boats” near the docks and those parked on the land area increased by 483%, 189%, and 826% at Mangrol, Veraval, and Vanakbara harbor, respectively. After phase-I of lockdown, the number of parked vessels decreased, yet those already moved out to the land area were not returned until the south-west monsoon was over. A quarter of the annual production is estimated to be lost at the three harbors due to lockdown. Our last observation (September 2020) result shows that regular fishing activity has already been re-established in all three locations. PlanetScope data with daily revisit time has a higher potential to be used in the future and can help policymakers in making informed decisions vis-à-vis the fishing industry during an emergency situation like COVID-19.
Impact of Monsoon-Transported Anthropogenic Aerosols and Sun-Glint on the Satellite-Derived Spectral Remote Sensing Reflectance in the Indian Ocean
Authors: Liu Rongjie , Zhang Jie , Cui Tingwei , Yu Haocheng
Published: January 2021

Spectral remote sensing reflectance (Rrs(λ), sr−1) is one of the most important products of ocean color satellite missions, where accuracy is essential for retrieval of in-water, bio-optical, and biogeochemical properties. For the Indian Ocean (IO), where Rrs(λ) accuracy has not been well documented, the quality of Rrs(λ) products from Moderate Resolution Imaging Spectroradiometer onboard both Terra (MODIS-Terra) and Aqua (MODIS-Aqua), and Visible Infrared Imaging Radiometer Suite onboard the Suomi National Polar-Orbiting Partnership spacecraft (VIIRS-NPP), is evaluated and inter-compared based on a quality assurance (QA) system, which can objectively grade each individual Rrs(λ) spectrum, with 1 for a perfect spectrum and 0 for an unusable spectrum. Taking the whole year of 2016 as an example, spatiotemporal pattern of Rrs(λ) quality in the Indian Ocean is characterized for the first time, and the underlying factors are elucidated. Specifically, QA analysis of the monthly Rrs(λ) over the IO indicates good quality with the average scores of 0.93 ± 0.02, 0.92 ± 0.02 and 0.92 ± 0.02 for VIIRS-NPP, MODIS-Aqua, and MODIS-Terra, respectively. Low-quality (~0.7) data are mainly found in the Bengal Bay (BB) from January to March, which can be attributed to the imperfect atmospheric correction due to anthropogenic absorptive aerosols transported by the northeasterly winter monsoon. Moreover, low-quality (~0.74) data are also found in the clear oligotrophic gyre zone (OZ) of the south IO in the second half of the year, possibly due to residual sun-glint contributions. These findings highlight the effects of monsoon-transported anthropogenic aerosols, and imperfect sun-glint removal on the Rrs(λ) quality. Further studies are advocated to improve the sun-glint correction in the oligotrophic gyre zone and aerosol correction in the complex ocean–atmosphere environment.
Climate Dynamics of the Spatiotemporal Changes of Vegetation NDVI in Northern China from 1982 to 2015
Authors: Sun Rui , Chen Shaohui , Su Hongbo
Published: January 2021

As an important part of a terrestrial ecosystem, vegetation plays an important role in the global carbon-water cycle and energy flow. Based on the Global Inventory Monitoring and Modeling System (GIMMS) third generation of Normalized Difference Vegetation Index (NDVI3g), meteorological station data, climate reanalysis data, and land cover data, this study analyzed the climate dynamics of the spatiotemporal variations of vegetation NDVI in northern China from 1982 to 2015. The results showed that growth season NDVI (NDVIgs) increased significantly at 0.006/10a (p < 0.01) in 1982–2015 on the regional scale. The period from 1982 to 2015 was divided into three periods: the NDVIgs increased by 0.026/10a (p < 0.01) in 1982–1990, decreased by −0.002/10a (p > 0.1) in 1990–2006, and then increased by 0.021/10a (p < 0.01) during 2006–2015. On the pixel scale, the increases in NDVIgs during 1982–2015, 1982–1990, 1990–2006, and 2006–2015 accounted for 74.64%, 85.34%, 48.14%, and 68.78% of the total area, respectively. In general, the dominant climate drivers of vegetation growth had gradually switched from solar radiation, temperature, and precipitation (1982–1990) to precipitation and temperature (1990–2015). For woodland, high coverage grassland, medium coverage grassland, low coverage grassland, the dominant climate drivers had changed from temperature and solar radiation, solar radiation and precipitation, precipitation and solar radiation, solar radiation to precipitation and solar radiation, precipitation, precipitation and temperature, temperature and precipitation. The areas controlled by precipitation increased significantly, mainly distributed in arid, sub-arid, and sub-humid areas. The dominant climate drivers for vegetation growth in the plateau climate zone or high-altitude area changed from solar radiation to temperature and precipitation, and then to temperature, while in cold temperate zone, changed from temperature to solar radiation. These results are helpful to understand the climate dynamics of vegetation growth, and have important guiding significance for vegetation protection and restoration in the context of global climate change.
Sensitivity Analysis of Bistatic Scattering for Soil Moisture Retrieval
Authors: Li Tingting , Hajnsek Irena , Chen Kun-Shan
Published: January 2021

Soil moisture is one of the vital environmental variables in the land–atmosphere cycle. A study of the sensitivity analysis of bistatic scattering coefficients from bare soil at the Ku-band is presented, with the aim of deepening our understanding of the bistatic scattering features and exploring its potential in soil moisture retrieval. First, a well-established advanced integral method was adopted for simulating the bistatic scattering response of bare soil. Secondly, a sensitivity index and a normalized weight quality index were proposed to evaluate the effect of soil moisture on the bistatic scattering coefficient in terms of polarization and angular diversity, and the combinations thereof. The results of single-polarized VV data show that the regions with the maximum sensitivity and high quality index, simultaneously, to soil moisture are in the forward off-specular direction. However, due to the effect of surface roughness and surface autocorrelation function (ACF), the single-polarized data have some limitations for soil moisture inversion. By contrast, the results of two different polarization combinations, as well as a dual-angular simulation of one transmitter and two receivers, show significant estimation benefits. It can be seen that they all provide better ACF suppression capabilities, larger high-sensitivity area, and higher quality indices compared to single-polarized estimation. In addition, dual polarization or dual angular combined measurement provides the possibility of retrieving soil moisture in backward regions. These results are expected to contribute to the design of future bistatic observation systems.
Evaluation of the ABI/GOES-16 SST Product in the Tropical and Southwestern Atlantic Ocean
Authors: Azevedo Mayna Helena , Rudorff Natália , Aravéquia José Antônio
Published: January 2021

Sea surface temperature (SST) is an essential climate variable used for ocean and weather monitoring and forecasting. The NOAA’s next generation geostationary satellite GOES-16 was declared operational at the east position (75°W) in December 2017, carrying onboard an Advanced Baseline Imager (ABI). The hyperspectral ABI sensor now allows SST estimates every 10–15 min at both day and nighttime, with advanced options for cloud screening and water vapor correction. In the present work, we compare the first operational ABI SST product (OSI SAF, 2018) with an in situ match-up database (MDB) across the Tropical and Southwestern Atlantic Ocean, off the Brazilian coast, throughout the year of 2018. The MDB was obtained from two long-term programs, i.e., PIRATA moored buoys (FOLTZ et al., 2016) and PNBoia moored and drifting buoys (MARINHA DO BRASIL, 2017). Separate comparisons were made for each data set, analyzing the uncertainties according to the program (i.e., buoy type and region), satellite SST quality level and influence of diurnal heating. We also compare the ABI product with the OSTIA analysis L4 SST (DONLON et al., 2012) to increment our analyses on the spatio-temporal biases within the study region. The results show that the OSI SAF ABI SST L3C has a mean bias (0.1 °C) and error (RMSE, 0.5 °C) within the GHRSST standards, with an exception being coastal waters off the southeast Brazilian coast (RMSE, 0.65 °C), which are subjected to sharp thermal fronts. The highest biases are for regions/seasons subjected to persistent cloud coverage and high water-vapor content, i.e., the Intertropical and South Atlantic Convergence Zones, as well as highly dynamic frontal zones, i.e., the Brazil Malvinas Confluence Zone, the Subtropical Front and coastal waters. The ABI SST product is suitable for operational use, and applications should explore more deeply the new set of information provided.
A Constrained Graph-Based Semi-Supervised Algorithm Combined with Particle Cooperation and Competition for Hyperspectral Image Classification
Authors: He Ziping , Xia Kewen , Li Tiejun , Zu Baokai , Yin Zhixian , Zhang Jiangnan
Published: January 2021

Semi-supervised learning (SSL) focuses on the way to improve learning efficiency through the use of labeled and unlabeled samples concurrently. However, recent research indicates that the classification performance might be deteriorated by the unlabeled samples. Here, we proposed a novel graph-based semi-supervised algorithm combined with particle cooperation and competition, which can improve the model performance effectively by using unlabeled samples. First, for the purpose of reducing the generation of label noise, we used an efficient constrained graph construction approach to calculate the affinity matrix, which is capable of constructing a highly correlated similarity relationship between the graph and the samples. Then, we introduced a particle competition and cooperation mechanism into label propagation, which could detect and re-label misclassified samples dynamically, thus stopping the propagation of wrong labels and allowing the overall model to obtain better classification performance by using predicted labeled samples. Finally, we applied the proposed model into hyperspectral image classification. The experiments used three real hyperspectral datasets to verify and evaluate the performance of our proposal. From the obtained results on three public datasets, our proposal shows great hyperspectral image classification performance when compared to traditional graph-based SSL algorithms.
Detection of Fire Smoke Plumes Based on Aerosol Scattering Using VIIRS Data over Global Fire-Prone Regions
Authors: Lu Xiaoman , Zhang Xiaoyang , Li Fangjun , Cochrane Mark A. , Ciren Pubu
Published: January 2021

Smoke from fires significantly influences climate, weather, and human health. Fire smoke is traditionally detected using an aerosol index calculated from spectral contrast changes. However, such methods usually miss thin smoke plumes. It also remains challenging to accurately separate smoke plumes from dust, clouds, and bright surfaces. To improve smoke plume detections, this paper presents a new scattering-based smoke detection algorithm (SSDA) depending mainly on visible and infrared imaging radiometer suite (VIIRS) blue and green bands. The SSDA is established based on the theory of Mie scattering that occurs when the diameter of an atmospheric particulate is similar to the wavelength of the scattered light. Thus, smoke commonly causes Mie scattering in VIIRS blue and green bands because of the close correspondence between smoke particulate diameters and the blue/green band wavelengths. For developing the SSDA, training samples were selected from global fire-prone regions in North America, South America, Africa, Indonesia, Siberia, and Australia. The SSDA performance was evaluated against the VIIRS aerosol detection product and smoke detections from the ultraviolet aerosol index using manually labeled fire smoke plumes as a benchmark. Results show that the SSDA smoke detections are superior to existing products due chiefly to the improved ability of the algorithm to detect thin smoke and separate fire smoke from other surface types. Moreover, the SSDA smoke distribution pattern exhibits a high spatial correlation with the global fire density map, suggesting that SSDA is capable of detecting smoke plumes of fires in near real-time across the globe.
Random Forests for Landslide Prediction in Tsengwen River Watershed, Central Taiwan
Authors: Cheng Youg-Sin , Yu Teng-To , Son Nguyen-Thanh
Published: January 2021

Landslides have been identified as one of the costliest and deadliest natural disasters, causing tremendous damage to humans and societies. Information regarding the spatial extent of landslides is thus important to allow officials to devise successful strategies to mitigate landslide hazards. This study aims to develop a machine-learning approach for predicting landslide areas in the Tsengwen River Watershed (TRW), which is one of the most landslide-prone areas in Central Taiwan. Various spatial datasets were collected from 2009 to 2015 to derive 36 predictive variables used for landslide modeling with random forests (RF). The results of landslide prediction, compared with ground reference data, indicated an overall accuracy of 91.4% and Kappa coefficient of 0.83, respectively. The findings achieved from estimates of predictor importance also indicated to officials that the land-use/land-cover (LULC) type, distance to previous landslides, distance to roads, bank erosion, annual groundwater recharge, geological line density, aspect, and slope are the most influential factors that trigger landslides in the study region.
Cascade Object Detection and Remote Sensing Object Detection Method Based on Trainable Activation Function
Authors: Shivappriya S. N. , Priyadarsini M. Jasmine Pemeena , Stateczny Andrzej , Puttamadappa C. , Parameshachari B. D.
Published: January 2021

Object detection is an important process in surveillance system to locate objects and it is considered as major application in computer vision. The Convolution Neural Network (CNN) based models have been developed by many researchers for object detection to achieve higher performance. However, existing models have some limitations such as overfitting problem and lower efficiency in small object detection. Object detection in remote sensing hasthe limitations of low efficiency in detecting small object and the existing methods have poor localization. Cascade Object Detection methods have been applied to increase the learning process of the detection model. In this research, the Additive Activation Function (AAF) is applied in a Faster Region based CNN (RCNN) for object detection. The proposed AAF-Faster RCNN method has the advantage of better convergence and clear bounding variance. The Fourier Series and Linear Combination of activation function are used to update the loss function. The Microsoft (MS) COCO datasets and Pascal VOC 2007/2012 are used to evaluate the performance of the AAF-Faster RCNN model. The proposed AAF-Faster RCNN is also analyzed for small object detection in the benchmark dataset. The analysis shows that the proposed AAF-Faster RCNN model has higher efficiency than state-of-art Pay Attention to Them (PAT) model in object detection. To evaluate the performance of AAF-Faster RCNN method of object detection in remote sensing, the NWPU VHR-10 remote sensing data set is used to test the proposed method. The AAF-Faster RCNN model has mean Average Precision (mAP) of 83.1% and existing PAT-SSD512 method has the 81.7%mAP in Pascal VOC 2007 dataset.
Impacts of the Tropical Cyclone Idai in Mozambique: A Multi-Temporal Landsat Satellite Imagery Analysis
Authors: Charrua Alberto Bento , Padmanaban Rajchandar , Cabral Pedro , Bandeira Salomão , Romeiras Maria M.
Published: January 2021

The Central Region of Mozambique (Sofala Province) bordering on the active cyclone area of the southwestern Indian Ocean has been particularly affected by climate hazards. The Cyclone Idai, which hit the region in March 2019 with strong winds causing extensive flooding and a massive loss of life, was the strongest recorded tropical cyclone in the Southern Hemisphere. The aim of this study was to use pre- and post-cyclone Idai Landsat satellite images to analyze temporal changes in Land Use and Land Cover (LULC) across the Sofala Province. Specifically, we aimed—(i) to quantify and map the changes in LULC between 2012 and 2019; (ii) to investigate the correlation between the distance to Idai’s trajectory and the degree of vegetation damage, and (iii) to determine the damage caused by Idai on different LULC. We used Landsat 7 and 8 images (with 30 m resolution) taken during the month of April for the 8-year period. The April Average Normalized Difference Vegetation Index (NDVI) over the aforementioned period (2012–2018, pre-cyclone) was compared with the values of April 2019 (post-cyclone). The results showed a decreasing trend of the productivity (NDVI 0.5 to 0.8) and an abrupt decrease after the cyclone. The most devastated land use classes were dense vegetation (decreased by 59%), followed by wetland vegetation (−57%) and shrub land (−56%). The least damaged areas were barren land (−23%), barren vegetation (−27%), and grassland and dambos (−27%). The Northeastern, Central and Southern regions of Sofala were the most devastated areas. The Pearson Correlation Coefficient between the relative vegetation change activity after Idai (NDVI%) and the distance to Idai’s trajectory was 0.95 (R-square 0.91), suggesting a strong positive linear correlation. Our study also indicated that the LULC type (vegetation physiognomy) might have influenced the degree of LULC damage. This study provides new insights for the management and conservation of natural habitats threatened by climate hazards and human factors and might accelerate ongoing recovery processes in the Sofala Province.
Assessment of Near-Real-Time Satellite Precipitation Products from GSMaP in Monitoring Rainfall Variations over Taiwan
Authors: Huang Wan-Ru , Liu Pin-Yi , Hsu Jie , Li Xiuzhen , Deng Liping
Published: January 2021

This study assessed four near-real-time satellite precipitation products (NRT SPPs) of Global Satellite Mapping of Precipitation (GSMaP)—NRT v6 (hereafter NRT6), NRT v7 (hereafter NRT7), Gauge-NRT v6 (hereafter GNRT6), and Gauge-NRT v7 (hereafter GNRT7)— in representing the daily and monthly rainfall variations over Taiwan, an island with complex terrain. The GNRT products are the gauge-adjusted version of NRT products. Evaluations for warm (May–October) and cold months (November–April) were conducted from May 2017 to April 2020. By using observations from more than 400 surface gauges in Taiwan as a reference, our evaluations showed that GNRT products had a greater error than NRT products in underestimating the monthly mean rainfall, especially during the warm months. Among SPPs, NRT7 performed best in quantitative monthly mean rainfall estimation; however, when examining the daily scale, GNRT6 and GNRT7 were superior, particularly for monitoring stronger (i.e., more intense) rainfall events during warm and cold months, respectively. Spatially, the major improvement from NRT6 to GNRT6 (from NRT7 to GNRT7) in monitoring stronger rainfall events over southwestern Taiwan was revealed during warm (cold) months. From NRT6 to NRT7, the improvement in daily rainfall estimation primarily occurred over southwestern and northwestern Taiwan during the warm and cold months, respectively. Possible explanations for the differences between the ability of SPPs are attributed to the algorithms used in SPPs. These findings highlight that different NRT SPPs of GSMaP should be used for studying or monitoring the rainfall variations over Taiwan for different purposes (e.g., warning of floods in different seasons, studying monthly or daily precipitation features in different seasons, etc.).
Mapping the Lithological Features and Ore-Controlling Structures Related to Ni–Cu Mineralization in the Eastern Tian Shan, NW China from ASTER Data
Authors: Zheng Shuo , An Yanfei , Shi Pilong , Zhao Tian
Published: January 2021

The study of lithological features and tectonic evolution related to mineralization in the eastern Tian Shan is crucial for understanding the ore-controlling mechanism. In this paper, the lithological features and ore-controlling structure of the Huangshan Ni–Cu ore belt in the eastern Tian Shan are documented using advanced spaceborne thermal emission and reflection radiometer (ASTER) multispectral data based on spectral image processing algorithms, mineral indices and directional filter technology. Our results show that the algorithms of b2/b1, b6/b7 and b4/b8 from ASTER visible and near-infrared (VNIR)- shortwave infrared (SWIR) bands and of mafic index (MI), carbonate index (CI) and silica index (SI) from thermal infrared (TIR) bands are helpful to extract regional pyroxenite, external foliated gabbro bearing Ni–Cu ore bodies as well as the country rocks in the study area. The detailed interpretations and analyses of the geometrical feature of fault system and intrusive facies suggest that the Ni–Cu metallogenic belts are related to Carboniferous arc intrusive rocks and Permian wrench tectonics locating at the intersection of EW- and NEE-striking dextral strike-slip fault system, and the emplacement at the releasing bends in the southern margin of Kanggur Fault obviously controlled by secondary faults orthogonal or oblique to the Kanggur Fault in the post-collision extensional environment. Therefore, the ASTER data-based approach to map lithological features and ore-controlling structures related to the Ni–Cu mineralization are well performed. Moreover, a 3D geodynamic sketch map proposes that the strike-slip movement of Kanggur Fault in Huangshan-Kanggur Shear Zone (HKSZ) during early Permian controlled the migration and emplacement of three mafic/ultramafic intrusions bearing Ni–Cu derived from partial mantle melting and also favored CO2-rich fluids leaking to the participation of metallogenic processes.