bluuebunny/crossref_metadata_2025 huggingface dataset:
Expression of Structural Flavonoid Biosynthesis Genes in Dark-Blue and White Myrtle Berries (Myrtus communis L.)
Authors: Medda Silvia , Sanchez-Ballesta Maria Teresa , Romero Irene , Dessena Leonarda , Mulas Maurizio
Published: February 2021

Within the myrtle (Myrtus communis L.) species, different genotypes may produce dark-blue berries or white berries depending on the peel color upon ripening. One dark-blue cultivar and one white myrtle cultivar were used to study the molecular mechanisms underlying flavonoid biosynthesis. The relative expression levels of common (PAL, CHS, CHI, DFR and LDOX) and specific (FLS, ANR, LAR and UFGT) flavonoid genes were analyzed during fruit development by means of quantitative real-time polymerase chain reaction (RT-qPCR). Moreover, the anthocyanin content was determined, and it showed an increase with the ripening of the berries of the dark-blue cultivar. The results showed an increased transcript abundance of PAL, CHI, DFR, LDOX and UFGT gene expression in the dark-blue cultivar compared to the white one, as well as a strong positive correlation between the changes in gene expression and anthocyanin accumulation. The transcript levels of UFGT showed sharp increases at 150 and 180 days after full blooming (DAF) in the dark-blue cultivar, which corresponded with anthocyanin accumulation. However, ripening seemed to modulate the expression of genes implicated in flavonols (i.e., FLS) and flavan-3-ols (i.e., LAR and ANR) in different manners. However, whereas FLS transcript accumulation increased at the end of the ripening period in the dark-blue cultivar, LAR and ANR gene expression decreased in both cultivars.
Molecular Mechanisms of Anti-Melanogenic Gedunin Derived from Neem Tree (Azadirachta indica) Using B16F10 Mouse Melanoma Cells and Early-Stage Zebrafish
Authors: Jeon Hwang-Ju , Kim Kyeongnam , Kim Chaeeun , Kim Myoung-Jin , Kim Tae-Oh , Lee Sung-Eun
Published: February 2021

Melanogenesis represents a series of processes that produce melanin, a protective skin pigment (against ultraviolet rays), and determines human skin color. Chemicals reducing melanin production have always been in demand in the cosmetic market because of skincare interests, such as whitening. The main mechanism for inhibiting melanin production is the inhibition of tyrosinase (TYR), a key enzyme for melanogenesis. Here, we evaluated gedunin (Ged), a representative limonoid, for its anti-melanogenesis action. Melanin production in vitro was stimulated by alpha-melanocyte stimulating hormone (α-MSH) in B16F10 mouse melanoma cells. Ged reduced α-MSH-stimulated melanin production, inhibiting TYR activity and protein amount. We confirmed this result in vivo in a zebrafish model for melanogenesis. There was no sign of toxicity and malformation of zebrafish embryos during development in all treated concentrations. Ged reduced the number of produced zebrafish embryo pigment dots and melanin contents of embryos. The highly active concentration of Ged (100 µM) was much lower than the positive control, kojic acid (8 mM). Hence, Ged could be a fascinating candidate for anti-melanogenesis reagents.
Variation in Phenolic Chemistry in Zostera marina Seagrass along Environmental Gradients
Authors: Sævdal Dybsland Cecilie , Bekkby Trine , Hasle Enerstvedt Kjersti , Kvalheim Olav M. , Rinde Eli , Jordheim Monica
Published: February 2021

Chemical ecology has been suggested as a less time-consuming and more cost-efficient monitoring tool of seagrass ecosystems than traditional methods. Phenolic chemistry in Zostera marina samples was analyzed against latitude, sea depth, sample position within a seagrass meadow (periphery or center) and wave exposure. Multivariate data analysis showed that rosmarinic acid correlated moderately positively with depth, while the flavonoids had an overall strong negative correlation with increasing depth—possibly reflecting lack of stress-induced conditions with increasing depth, rather than a different response to light conditions. At a molecular level, the flavonoids were separated into two groups; one group is well described by the variables of depth and wave exposure, and the other group that was not well described by these variables—the latter may reflect biosynthetic dependencies or other unrevealed factors. A higher flavonoid/rosmarinic acid ratio was seen in the periphery of a seagrass meadow, while the contrary ratio was seen in the center. This may reflect higher plant stress in the periphery of a meadow, and the flavonoid/rosmarinic acid ratio may provide a possible molecular index of seagrass ecosystem health. Further studies are needed before the full potential of using variation in phenolic chemistry as a seagrass ecosystem monitoring tool is established.
Synthesis of a Biodegradable Polymer of Poly (Sodium Alginate/Ethyl Acrylate)
Authors: Flores-Hernández Cynthia G. , Cornejo-Villegas Maria de los Angeles , Moreno-Martell Abigail , Del Real Alicia
Published: February 2021

The objective of the study was to obtain a new biodegradable graft polymer by performing two chemical processes: first, a transesterification reaction between carboxylic acid’s salt and ethyl acrylate’s ester, followed by polymerization of the vinyl group from the ethyl acrylate monomer via free radicals. The copolymer’s FTIR shows an absence of ethyl bands, while the characteristic band of pyranose is maintained, which confirms the monomer’s graft. TGA analysis shows that sodium alginate had three decomposition temperatures: 103 °C due to dehydration, 212 °C associated with the destruction of glycosidic bonds, and 426 °C due to conversion of alginate into Na2CO3. The copolymer presents four processes at different temperatures, i.e., evaporation of alcohol at 65 °C, decomposition of ungrafted alginate at 220 °C, copolymer decomposition at 298 °C, and degradation of fragments into carbonate at 423 °C. The evaluation of the action of fungal growth on the copolymer was higher than 50%, which means it is an excellent material to be biodegraded.
Enhanced Thermal Insulation of the Hollow Glass Microsphere/Glass Fiber Fabric Textile Composite Material
Authors: Sun Jintao , Cai Fei , Tao Dongzhi , Ni Qingqing , Fu Yaqin
Published: February 2021

Glass fiber fabrics/hollow glass microspheres (HGM)–waterborne polyurethane (WPU) textile composites were prepared using glass fiber, WPU, and HGM as skeleton material, binder, and insulation filler, respectively, to study the effect of HGM on the thermal insulation performance of glass fiber fabrics. Scanning electron microscopy, Instron 3367 tensile test instrument, thermal constant analysis, and infrared thermal imaging were used to determine the cross-sectional morphology, mechanical property, thermal conductivity, and thermal insulation property, respectively, of the developed materials. The results show that the addition of HGM mixed in WPU significantly enhanced thermal insulation performance of the textile composite with the reduction of thermal conductivity of 45.2% when the volume ratio of HGM to WPU is 0.8 compared with that of material without HGM. The composite can achieve the thermal insulation effect with a temperature difference of 17.74 °C at the temperature field of 70 °C. Meanwhile, the tensile strength of the composite is improved from 14.16 to 22.14 MPa. With these results, it is confirmed that designing hollow glass microspheres (HGM) is an effective way to develop and enhance the high performance of insulation materials with an obvious lightweight of the bulk density reaching about 50%.
Preparation and Applications of Electrospun Optically Transparent Fibrous Membrane
Authors: Xiao Yanan , Luo Hao , Tang Rongxing , Hou Jiazi
Published: February 2021

The optically transparent electrospun fibrous membrane has been widely used in many fields due to its simple operation, flexible design, controllable structure, high specific surface area, high porosity, and unique excellent optical properties. This paper comprehensively summarizes the preparation methods and applications of an electrospun optically transparent fibrous membrane in view of the selection of raw materials and structure modulation during preparation. We start by the factors that affect transmittance among different materials and explain the light transmission mechanism of the fibrous membrane. This paper also provides an overview of the methods to fabricate a transparent nanofibrous membrane based on the electrospinning technology including direct electrospinning, solution treatment after electrospinning, heat treatment after electrospinning, and surface modification after electrospinning. It further summarizes the differences in the processes and mechanisms between different transparent fibrous membranes prepared by different methods. Additionally, we study the utilization of transparent as-spun membranes as flexible functional materials, namely alcohol dipstick, air purification, self-cleaning materials, biomedicine, sensors, energy and optoelectronics, oil–water separation, food packaging, anti-icing coating, and anti-corrosion materials. It demonstrates the high transparency of the nanofibers’ effects on the applications as well as upgrades the product performance.
Biodegradable Poly(butylene adipate-co-terephthalate) Antibacterial Nanocomposites Reinforced with MgO Nanoparticles
Authors: Wang Xionggang , Cui Lingna , Fan Shuhong , Li Xia , Liu Yuejun
Published: February 2021

Antibacterial packaging materials can reduce the microbial contamination of food surfaces. In this study, magnesium oxide (MgO) nanoparticles were synthesized and then coated with cetrimonium bromide (CTAB). CTAB-modified MgO (MgO@CTAB) was characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and thermogravimetric analysis. Then, different loadings of MgO@CTAB were mixed with poly(butylene adipate-co-terephthalate) (PBAT) by melt compounding. The results showed that the addition of MgO@CTAB deteriorated the thermal stability of PBAT due to MgO serving as a catalyst to promote the thermal degradation of PBAT. In addition, MgO@CTAB could serve as a nucleating agent to improve the crystallinity of PBAT. With the optimal 3 wt% of MgO@CTAB, the tensile strength of PBAT/MgO@CTAB increased from 26.66 to 29.90 MPa, with a slight enhancement in elongation at break. SEM observations and dynamical rheological measurements revealed that aggregation occurred when the content of MgO@CTAB exceeded 5 wt%. The presence of MgO@CTAB endowed PBAT with antibacterial properties. The bacterial inhibition zone increased with the increasing content of MgO@CTAB. In addition, MgO@CTAB had a better antibacterial efficiency against Gram-positive bacterial S. aureus than Gram-negative bacterial E. coli.
Hybrid Collagen Hydrogel/Chondroitin-4-Sulphate Fortified with Dermal Fibroblast Conditioned Medium for Skin Therapeutic Application
Authors: Maarof Manira , Mohd Nadzir Masrina , Sin Mun Lau , Fauzi Mh Busra , Chowdhury Shiplu Roy , Idrus Ruszymah Bt Hj , Lokanathan Yogeswaran
Published: February 2021

The current strategy for rapid wound healing treatment involves combining a biomaterial and cell-secreted proteins or biomolecules. This study was aimed at characterizing 3-dimensional (3D) collagen hydrogels fortified with dermal fibroblast-conditioned medium (DFCM) as a readily available acellular skin substitute. Confluent fibroblasts were cultured with serum-free keratinocyte-specific medium (KM1 and KM2) and fibroblast-specific medium (FM) to obtain DFCM. Subsequently, the DFCM was mixed with collagen (Col) hydrogel and chondroitin-4-sulphate (C4S) to fabricate 3D constructs termed Col/C4S/DFCM-KM1, Col/C4S/DFCM-KM2, and Col/C4S/DFCM-FM. The constructs successfully formed soft, semi-solid and translucent hydrogels within 1 h of incubation at 37 °C with strength of <2.5 Newton (N). The Col/C4S/DFCM demonstrated significantly lower turbidity compared to the control groups. The Col/C4S/DFCM also showed a lower percentage of porosity (KM1: 35.15 ± 9.76%; KM2: 6.85 ± 1.60%; FM: 14.14 ± 7.65%) compared to the Col (105.14 ± 11.87%) and Col/C4S (143.44 ± 27.72%) constructs. There were no changes in both swelling and degradation among all constructs. Fourier transform infrared spectrometry showed that all groups consisted of oxygen–hydrogen bonds (O-H) and amide I, II, and III. In conclusion, the Col/C4S/DFCM constructs maintain the characteristics of native collagen and can synergistically deliver essential biomolecules for future use in skin therapeutic applications.
Study Analysis of Thermal, Dielectric, and Functional Characteristics of an Ethylene Polyethylene Diene Monomer Blended with End-of-Life Tire Microparticles Amounts
Authors: Marín-Genescà Marc , Mujal-Rosas Ramon , García-Amorós Jordi , Mudarra Miguel , Ramis Juan Xavier , Colom Fajula Xavier
Published: February 2021

The recycling and disposal of disused tires is a topic of great concern to today’s companies, researchers, and society in general. In this sense, our research aims to recycle end-of-life tires (GTRs) through the separation of the fraction of vulcanized rubber from the other compounds in order to later grind this fraction and separate it into lower particle sizes. Finally, we aim to incorporate these GTR particles as a filler of an ethylene-polyethylene-diene monomer (EPDM). The obtained composites with EPDM and GTR are tested (5%, 10%, 20%) comparing these values with neat EPDM as a control sample. Thermal tests such as differential calorimetry (DSC) and thermogravimetric analysis (TGA) as well as dielectric tests (DEA) are performed in order to characterize these materials and check their viability as dielectric or semiconductor, for industrial use. It is checked how the presence of GTR increases functional properties such as conductivity/permittivity. The influence of temperature (40 to 120 °C) and addition of GTR particles in electrical properties has also been analyzed. The dielectric behavior of these composites is fully characterized, analyzing the different types of relaxation with increasing frequency (10 mHz to 3 MHz), using the electric modulus, and Argand diagrams among other measures. The influence of GTR and temperature in the dielectric and thermal behavior of these materials has been analyzed, where CB of GTR creates interfacial polarization phenomena in the dielectric behavior of the composite and increases the permittivity (real and imaginary) as well as the conductivity. Finally, with these obtained properties, the possible application of EPDM/GTR composites as industrial dielectrics has been studied.
Utilization of Birch Bark as an Eco-Friendly Filler in Urea-Formaldehyde Adhesives for Plywood Manufacturing
Authors: Réh Roman , Krišťák Ľuboš , Sedliačik Ján , Bekhta Pavlo , Božiková Monika , Kunecová Daniela , Vozárová Vlasta , Tudor Eugenia Mariana , Antov Petar , Savov Viktor
Published: February 2021

The potential of using ground birch (Betula verrucosa Ehrh.) bark as an eco-friendly additive in urea-formaldehyde (UF) adhesives for plywood manufacturing was investigated in this work. Five-ply plywood panels were fabricated in the laboratory from beech (Fagus sylvatica L.) veneers bonded with UF adhesive formulations comprising three addition levels of birch bark (BB) as a filler (10%, 15%, and 20%). Two UF resin formulations filled with 10% and 20% wheat flour (WF) were used as reference samples. The mechanical properties (bending strength, modulus of elasticity and shear strength) of the laboratory-fabricated plywood panels, bonded with the addition of BB in the adhesive mixture, were evaluated and compared with the European standard requirements (EN 310 and EN 314-2). The mechanical strength of the plywood with the addition of BB in the adhesive mixture is acceptable and met the European standard requirements. Markedly, the positive effect of BB in the UF adhesive mixture on the reduction of formaldehyde emission from plywood panels was also confirmed. Initially, the most significant decrease in formaldehyde release (up to 14%) was measured for the plywood sample, produced with 15% BB. After four weeks, the decrease in formaldehyde was estimated up to 51% for the sample manufactured with 20% BB. The performed differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and derivative thermogravimetry (DTG), also confirmed the findings of the study. As this research demonstrated, BB as a waste or by-product of wood processing industry, can be efficiently utilized as an environmentally friendly, inexpensive alternative to WF as a filler in UF adhesive formulations for plywood manufacturing.
Different Effects of Albumin and Hydroxyethyl Starch on Low Molecular-Weight Solute Permeation through Sodium Hyaluronic Acid Solution
Authors: Tatara Tsuneo
Published: February 2021

Hyaluronic acid (HA), a high-molecular-weight linear polysaccharide, restricts solute transport through the interstitial space. Albumin and hydroxyethyl starch (HES) solutions are used to correct the decrease of blood volume during surgery, but may leak into the interstitial space under inflammation conditions. Given the possibility that the structure of HA may be affected by adjacent macromolecules, this study tested whether albumin and HES (Mw 130,000) exert different effects on solute permeation through sodium hyaluronic acid (NaHA: Mw 1.3 × 106) solution. To this end, permeation of Orange G, a synthetic azo dye (Mw 452), into NaHA solutions containing albumin or HES over time was assessed. The amount of time it took for the relative absorbance of Orange G to reach 0.3 (T0.3) was determined in each NaHA solution relative to the reference solution (i.e., colloid solution without NaHA). Relative T0.3 values of albumin were larger than those of HES for 0.1% NaHA solution (3.33 ± 0.69 vs. 1.16 ± 0.08, p = 0.006, n = 3) and 0.2% NaHA solution (1.95 ± 0.32 vs. 0.92 ± 0.27, p = 0.013, n = 3). This finding may help in the selection of an appropriate colloid solution to control drug delivery into the interstitial space of cancer tissue under inflammation conditions.
Axial and Radial Compression Behavior of Composite Rocket Launcher Developed by Robotized Filament Winding: Simulation and Experimental Validation
Authors: Mishra Rajesh , Behera Bijoy Kumar , Mukherjee Sayan , Petru Michal , Muller Miroslav
Published: February 2021

The principal objective of the work is to compare among carbon-glass filament wound epoxy matrix hybrid composites with a different fiber ratio made by robotized winding processes and optimize the geometry suitable for the Rocket Propelled Grenade Launcher. ANSYS based finite element analysis was used to predict the axial as well as radial compression behavior. Experimental samples were developed by a robot-controlled filament winding process that was incorporated with continuous resin impregnation. The experimental samples were evaluated for the corresponding compressional properties. Filament wound tubular composite structures were developed by changing the sequence of stacking of hoop layers and helical layers, and also by changing the angle of wind of the helical layers while keeping the sequence constant. The samples were developed from carbon and glass filaments with different carbon proportions (0%, 25%, 50%, 75%, and 100%) and impregnated with epoxy resin. The compressional properties of the tubular composites that were prepared by filament winding were compared with the predicted axial and radial compressional properties from computational modelling using the finite element model. A very high correlation and relatively small prediction error was obtained.
Comparative Study on Toughening Effect of PTS and PTK in Various Epoxy Resins
Authors: Kwon Woong , Han Minwoo , Kim Jongwon , Jeong Euigyung
Published: February 2021

This study investigated the toughening effect of in situ polytriazoleketone (PTK) and polytriazolesulfone (PTS) toughening agent when applied to various epoxy resins, such as diglycidyl ether of bisphenol A (DGEBA), diglycidyl ether of bisphenol F (DGEBF), and triglycidyl p-aminophenol (TGAP) with 3,3′-diaminodiphenylsulfone as a curing agent. The fracture toughness, tensile properties, and thermal properties of the prepared epoxy samples were evaluated and compared. When PTK was mixed with DGEBF, the fracture toughness was improved by 27% with 8.6% increased tensile strength compared to the untoughened DGEBF. When PTS was mixed with TGAP, the fracture toughness was improved by 51% without decreasing tensile properties compared to the untoughened TGAP. However, when PTK or PTS was mixed with other epoxy resins, the fracture toughness decreased or improved with decreasing tensile properties. This is attributed to the poor miscibility between the solid-state monomer of PTK (4,4′-bis(propynyloxy)benzophenone (PBP)) or PTS (4,4′-sulfonylbis(propynyloxy)benzene (SPB)) and the epoxy resin, resulting in the polymerization of low molecular weight PTK or PTS in epoxy resin. Therefore, the toughening effect of PTK or PTS can be maximized by the appropriate selection of epoxy resin based on the miscibility between PBP or SPB and the resin.
Machine Learning-Based Prediction of Selected Parameters of Commercial Biomass Pellets Using Line Scan Near Infrared-Hyperspectral Image
Authors: Pitak Lakkana , Laloon Kittipong , Wongpichet Seree , Sirisomboon Panmanas , Posom Jetsada
Published: February 2021

Biomass pellets are required as a source of energy because of their abundant and high energy. The rapid measurement of pellets is used to control the biomass quality during the production process. The objective of this work was to use near infrared (NIR) hyperspectral images for predicting the properties, i.e., fuel ratio (FR), volatile matter (VM), fixed carbon (FC), and ash content (A), of commercial biomass pellets. Models were developed using either full spectra or different spatial wavelengths, i.e., interval successive projections algorithm (iSPA) and interval genetic algorithm (iGA), wavelengths and different spectral preprocessing techniques. Their performances were then compared. The optimal model for predicting FR could be created with second derivative (D2) spectra with iSPA-100 wavelengths, while VM, FC, and A could be predicted using standard normal variate (SNV) spectra with iSPA-100 wavelengths. The models for predicting FR, VM, FC, and A provided R2 values of 0.75, 0.81, 0.82, and 0.87, respectively. Finally, the prediction of the biomass pellets’ properties under color distribution mapping was able to track pellet quality to control and monitor quality during the operation of the thermal conversion process and can be intuitively used for applications with screening.
Optimization Control on the Mixed Free-Surface-Pressurized Flow in a Hydropower Station
Authors: Wang Xinlong , Fan Honggang , Liu Bing
Published: February 2021

The mixed free-surface-pressurized flow in the tailrace tunnel of a hydropower station has a great impact on the pressure, velocity, and operation stability of the power station. In the present work, a characteristic implicit method based on the upwind differencing and implicit finite difference scheme is used to solve the mixed free-surface-pressurized flow. The results of the characteristic implicit method agree well with the experimental results, which validates the accuracy of the method. Four factors that influence the amplitude of pressure fluctuation are analyzed and optimized, and the results show that the relative roughness can influence the maximum pressure in the tailrace tunnel. Additionally, the maximum pressure decreases with the increase of the tunnel’s relative roughness. When the surface relative roughness increases from 0.010 to 0.018, the maximum pressure can decrease by 4.33%. The maximum pressure in the tailrace tunnel can be effectively restrained by setting vent holes in the flat-topped tunnel section (tunnel (4)) and a vent hole at 81.25%L (L is the length of tunnel (4)), which can reduce the maximum pressure by 56.72%. Increasing the vent hole number can also reduce the maximum pressure of the mixed free-surface-pressurized flow in the tailrace tunnel. An optimal set of two ventilation holes 10 m in diameter at 93.75%L and 56.25%L is proposed, which can reduce the maximum pressure by 15.30% in comparison with the single vent case.
Key Challenges and Opportunities for an Effective Supply Chain System in the Catalyst Recycling Market–A Case Study of Poland
Authors: Generowicz Natalia , Kulczycka Joanna , Partyka Monika , Saługa Kamil
Published: February 2021

Increasing public awareness about low emission and stricter standards has a significant impact on the industry. The use of catalytic converters provides one of the solutions to the problem of lowering the amount of exhaust fumes. As most catalytic converters contain a combination of the three metals Pt, Pd and Rh, the manufacture of catalysts for automobiles is the largest sector of demand for and consumption of PGMs (platinum group metals). In Poland, the recycling system for catalysts is still in the development stage, but there is a significant trend of increase mainly due to EU policy on the circular economy. Due to frequent legal changes, the market is not fully transparent and the price for used catalysts can vary significantly. Therefore, apart from the recycling technology itself, it is important for the company to have a transparent method of testing the catalysts. The aim of this article was to identify the key opportunities and challenges to improving the catalyst recycling system in Poland. The organisational solutions have been analysed to show that an effective system could be implemented by creating a network between suppliers and customers with the use of good laboratory equipment and IT applications. The article defines the key opportunities and challenges such as the need to invest in an innovative laboratory and software for assessment of chemical composition and economic value of waste. A great opportunity for the development of this sector is the high demand for critical raw materials such as PGMs, which can be supported by research and development (R&D) projects.
Developing a Risk Model for Assessment and Control of the Spread of COVID-19
Authors: Issa Usama H. , Balabel Ashraf , Abdelhakeem Mohammed , Osman Medhat M. A.
Published: February 2021

Coronavirus disease 2019 (COVID-19) continues to spread rapidly all over the world challenging nearly all governments. The exact nature of COVID-19’s spread and risk factors for such a rapid spread are still imprecise as available data depend on confirmed cases only. This may result in an asymmetrically distributed burden among countries. There is an urgent need for developing a new technique or model to identify and analyze risk factors affecting such a spread. Fuzzy logic appears to be suitable for dealing with multi-risk groups with undefined data. The main purpose of this research was to develop a risk analysis model for COVID-19’s spread evaluation. Other objectives included identifying such risk factors aiming to find out reasons for such a fast spread. Nine risk groups were identified and 46 risk factors were categorized under these groups. The methodology in this study depended on identifying each risk factor by its probability of occurrence and its impact on viruses spreading. Many logical rules were used to support the proposed risk analysis model and represented the relation between probabilities and impacts as well as to connect other risk factors. The model was verified and applied in Saudi Arabia with further probable use in similar conditions. Based on the model results, it was found that (daily activities) and (home isolation) are considered groups with highest risk. On the other hand, many risk factors were categorized with high severity such as (poor social distance), (crowdedness) and (poor personal hygiene practices). It was demonstrated that the impact of COVID-19’s spread was found with a positive correlation with the risk factors’ impact, while there was no association between probability of occurrence and impact of the risk factors on COVID-19’s spread. Saudi Arabia’s quick actions have greatly reduced the impact of the risks affecting COVID-19’s spread. Finally, the new model can be applied easily in most countries to help decision makers in evaluating and controlling COVID-19’s spread.
Mapping and Characterization of Phenological Changes over Various Farming Systems in an Arid and Semi-Arid Region Using Multitemporal Moderate Spatial Resolution Data
Authors: Lebrini Youssef , Boudhar Abdelghani , Laamrani Ahmed , Htitiou Abdelaziz , Lionboui Hayat , Salhi Adil , Chehbouni Abdelghani , Benabdelouahab Tarik
Published: February 2021

Changing land use patterns is of great importance in environmental studies and critical for land use management decision making over farming systems in arid and semi-arid regions. Unfortunately, ground data scarcity or inadequacy in many regions can cause large uncertainties in the characterization of phenological changes in arid and semi-arid regions, which can hamper tailored decision making towards best agricultural management practices. Alternatively, state-of-the-art methods for phenological metrics’ extraction and long time-series analysis techniques of multispectral remote sensing imagery provide a viable solution. In this context, this study aims to characterize the changes over farming systems through trend analysis. To this end, four farming systems (fallow, rainfed, irrigated annual, and irrigated perennial) in arid areas of Morocco were studied based on four phenological metrics (PhM) (i.e., great integral, start, end, and length of the season). These were derived from large Moderate resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) time-series using both a machine learning algorithm and a pixel-based change analysis method. Results showed that during the last twenty-year period (i.e., 2000–2019), a significant dynamism of the plant cover was linked to the behavior of farmers who tend to cultivate intensively and to invest in high-income crops. More specifically, a relevant variability in fallow and rainfed areas, closely linked to the weather conditions, was found. In addition, significant lag trends of the start (−6 days) and end (+3 days) were found, which indicate that the length of the season was related to the spatiotemporal variability of rainfall. This study has also highlighted the potential of multitemporal moderate spatial resolution data to accurately monitor agriculture and better manage land resources. In the meantime, for operationally implementing the use of such work in the field, we believe that it is essential consider the perceptions, opinions, and mutual benefits of farmers and stakeholders to improve strategies and synergies whilst ensuring food, welfare, and sustainability.
Rice Mapping and Growth Monitoring Based on Time Series GF-6 Images and Red-Edge Bands
Authors: Jiang Xueqin , Fang Shenghui , Huang Xia , Liu Yanghua , Guo Linlin
Published: February 2021

Accurate rice mapping and growth monitoring are of great significance for ensuring food security and agricultural sustainable development. Remote sensing (RS), as an efficient observation technology, is expected to be useful for rice mapping and growth monitoring. Due to the fragmented distribution of paddy fields and the undulating terrain in Southern China, it is very difficult in rice mapping. Moreover, there are many crops with the same growth period as rice, resulting in low accuracy of rice mapping. We proposed a red-edge decision tree (REDT) method based on the combination of time series GF-6 images and red-edge bands to solve this problem. The red-edge integral and red-edge vegetation index integral were computed by using two red-edge bands derived from GF-6 images to construct the REDT. Meanwhile, the conventional method based on time series normalized difference vegetation index (NDVI), normalized difference water index (NDWI), enhanced vegetation index (EVI) (NNE) was employed to compare the effectiveness of rice mapping. The results indicated that the overall accuracy and Kappa coefficient of REDT ranged from 91%–94% and 0.82–0.87, improving about 7% and 0.15 compared with the NNE method. This proved that the proposed technology was able to efficiently solve the problem of rice mapping on a large scale and regions with fragmented landscapes. Additionally, two red-edge bands of GF-6 images were applied to monitor rice growth. It concluded that the two red-edge bands played different roles in rice growth monitoring. The red-edge bands of GF-6 images were superior in rice mapping and growth monitoring. Further study needs to develop more vegetation indices (VIs) related to the red-edge to make the best use of red-edge characteristics in precision agriculture.
Assessing Sponge Cities Performance at City Scale Using Remotely Sensed LULC Changes: Case Study Nanjing
Authors: Liu Xiaolong , Fu Dafang , Zevenbergen Chris , Busker Tim , Yu Meixiu
Published: February 2021

As a result of high-density urbanization and climate change, both the frequency and intensity of extreme urban rainfall are increasing. Drainage systems are not designed to cope with this increase, and as a result, floods are becoming more common in cities, particularly in the rapidly growing cities of China. To better cope with more frequent and severe urban flooding and to improve the water quality of stormwater runoff, the Chinese government launched the national Sponge City Construction (SCC) program in 2014. The current SCC design standards and guidelines are based on static values (e.g., return periods, rainfall intensities, and volume capture ratio (VCR)). They do not fully acknowledge the large differences in climate conditions across the country and assume that the hydraulic conditions will not change over time. This stationary approach stems from the traditional engineering approach designed for grey infrastructure (following a “one size fits all” approach). The purpose of this study was to develop a methodology to assess the VCR baseline (before construction in the pre-development stage) and changes in VCR (difference between the VCR of the pre- and post-development stage). The VCR of the post-development stage is one of the required indicators of the Assessment Standard for Sponge Cities Effects to evaluate SCC projects. In this study, the VCR was derived from remote-sensing-based land use land cover (LULC) change analysis, applying an unsupervised classification algorithm on different Landsat images from 1985 to 2015. A visualization method (based upon Sankey chart, which depicts the flows and their proportions of components) and a novel and practical partitioning method for built-up regions were developed to visualize and quantify the states and change flows of LULC. On the basis of these findings, we proposed a new indicator, referred to as VCRa-L, in order to assess the changes in urban hydrology after SCC construction. This study employed the city of Nanjing as a case study and analyzed detailed information on how LULC changes over time of built-up areas. The surface area of the urban and built-up areas of Nanjing quadrupled from 11% in 1985 to 44% in 2015. In the same period, neither the entire city nor its subregions reached the VCR target of 80%. The proposed new methodology aims to support national, regional, and city governments to identify and prioritize where to invest and implement SCC measures more effectively in cities across China.
Fractal and Multifractal Characteristics of Lineaments in the Qianhe Graben and Its Tectonic Significance Using Remote Sensing Images
Authors: Liu Zhiheng , Han Ling , Du Chengyan , Cao Hongye , Guo Jianhua , Wang Haiyang
Published: February 2021

The distribution and characteristics of geological lineaments in areas with active faulting are vital for providing a basis for regional tectonic identification and analyzing the tectonic significance. Here, we extracted the lineaments in the Qianhe Graben, an active mountainous area on the southwest margin of Ordos Block, China, by using the tensor voting algorithm after comparing them with the segment tracing algorithm (STA) and LINE algorithm in PCI Geomatica Software. The main results show that (1) the lineaments in this area are mostly induced by the active fault events with the main trending of NW–SE, (2) the box dimensions of all lineaments, NW–SE trending lineaments, and NE–SW trending lineaments are 1.60, 1.48, and 1.44 (R2 > 0.9), respectively, indicating that the faults exhibit statistical self-similarity, and (3) the lineaments have multifractal characteristics according to the mass index τ(q), generalized fractal dimension D(q), fractal width (Δα = 2.25), fractal spectrum shape (f(α) is a unimodal left-hook curve), and spectrum width (Δf = 1.21). These results are related to the tectonic activity in this area, where a higher tectonic activity leads to more lineaments being produced and a higher fractal dimension. All of these results suggest that such insights can be beneficial for providing potential targets in reconstructing the tectonic structure of the area and trends of plate movement.
Localization of the Chang’e-5 Lander Using Radio-Tracking and Image-Based Methods
Authors: Wang Jia , Zhang Yu , Di Kaichang , Chen Ming , Duan Jianfeng , Kong Jing , Xie Jianfeng , Liu Zhaoqin , Wan Wenhui , Rong Zhifei , Liu Bin , Peng Man , Wang Yexin
Published: February 2021

Chang’e-5, China’s first unmanned lunar sample-return mission, was successfully landed in Northern Oceanus Procellarum on 1 December 2020. Determining the lander location precisely and timely is critical for both engineering operations and subsequent scientific research. Localization of the lander was performed using radio-tracking and image-based methods. The lander location was determined to be (51.92°W, 43.06°N) by both methods. Other localization results were compared for cross-validation. The localization results greatly contributed to the planning of the ascender lifting off from the lander and subsequent maneuvers, and they will contribute to scientific analysis of the returned samples and in situ acquired data.
Continuity Enhancement Method for Real-Time PPP Based on Zero-Baseline Constraint of Multi-Receiver
Authors: Yang Fuxin , Zheng Chuanlei , Li Hui , Li Liang , Zhang Jie , Zhao Lin
Published: February 2021

Continuity is one of the metrics that characterize the required navigation performance of global navigation satellite system (GNSS)-based applications. Data outage due to receiver failure is one of the reasons for continuity loss. Although a multi-receiver configuration can maintain position solutions in case a receiver has data outage, the initialization of the receiver will also cause continuous high-precision positioning performance loss. To maintain continuous high-precision positioning performance of real-time precise point positioning (RT-PPP), we proposed a continuity enhancement method for RT-PPP based on zero-baseline constraint of multi-receiver. On the one hand, the mean time to repair (MTTR) of the multi-receiver configuration is improved to maintain continuous position solutions. On the other hand, the zero-baseline constraint of multi-receiver including between-satellite single-differenced (BSSD) ambiguities, zenith troposphere wet delay (ZWD), and their suitable stochastic models are constructed to achieve instantaneous initialization of back-up receiver. Through static and kinematic experiments based on real data, the effectiveness and robustness of proposed method are evaluated comprehensively. The experiment results show that the relationship including BSSD ambiguities and ZWD between receivers can be determined reliably based on zero-baseline constraint, and the instantaneous initialization can be achieved without high-precision positioning continuity loss in the multi-receiver RT-PPP processing.
A First Approach to Aerosol Classification Using Space-Borne Measurement Data: Machine Learning-Based Algorithm and Evaluation
Authors: Choi Wonei , Lee Hanlim , Park Jeonghyeon
Published: February 2021

A new method was developed for classifying aerosol types involving a machine-learning approach to the use of satellite data. An Aerosol Robotic NETwork (AERONET)-based aerosol-type dataset was used as a target variable in a random forest (RF) model. The contributions of satellite input variables to the RF-based model were quantified to determine an optimal set of input variables. The new method, based on inputs of satellite variables, allows the classification of seven aerosol types: pure dust, dust-dominant mixed, pollution-dominant mixed aerosols, and pollution aerosols (strongly, moderately, weakly, and non-absorbing). The performance of the model was statistically evaluated using AERONET data excluded from the model training dataset. Model accuracy for classifying the seven aerosol types was 59%, improving to 72% for four types (pure dust, dust-dominant mixed, strongly absorbing, and non-absorbing). The performance of the model was evaluated against an earlier aerosol classification method based on the wavelength dependence of single-scattering albedo (SSA) and fine-mode-fraction values from AERONET. Typical wavelength dependences of SSA for individual aerosol types are consistent with those obtained for aerosol types by the new method. This study demonstrates that an RF-based model is capable of satellite aerosol classification with sensitivity to the contribution of non-spherical particles.
Increasing Shape Bias to Improve the Precision of Center Pivot Irrigation System Detection
Authors: Tang Jiwen , Zhang Zheng , Zhao Lijun , Tang Ping
Published: February 2021

Irrigation is indispensable in agriculture. Center pivot irrigation systems are popular means of irrigation since they are water-efficient and labor-saving. Monitoring center pivot irrigation systems provides important information for the understanding of agricultural production, water resources consumption and environmental change. Deep learning has become an effective approach for object detection and semantic segmentation. Recent studies have shown that convolutional neural networks (CNNs) are prone to be texture-biased rather than shape-biased, and increasing shape bias can improve the robustness and performance of CNNs. In this study, a simple yet effective method was proposed to increase shape bias in object detection networks to improve the precision of center pivot irrigation system detection. We extracted edge images of training samples and integrated them into the training data to increase shape bias in the networks. With the proposed shape increasing training scheme, we evaluated and compared PVANET and YOLOv4. Experiments with the images in Mato Grosso have shown that both PVANET and YOLOv4 achieved improved performance, which demonstrated the validity of the proposed method.
A Knowledge-Based Auxiliary Channel STAP for Target Detection in Shipborne HFSWR
Authors: Guo Liang , Deng Weibo , Yao Di , Yang Qiang , Ye Lei , Zhang Xin
Published: February 2021

The broadened first-order sea clutter in shipborne high frequency surface wave radar (HFSWR), which will mask the targets with low radial velocity, is a kind of classical space–time coupled clutter. Space–time adaptive processing (STAP) has been proven to be an effective clutter suppression algorithm for space-time coupled clutter. To further improve the efficiency of clutter suppression, a STAP method based on a generalized sidelobe canceller (GSC) structure, named as the auxiliary channel STAP, was introduced into shipborne HFSWR. To obtain precise clutter information for the clutter covariance matrix (CCM) estimation, an approach based on the prior knowledge to auxiliary channel selection is proposed. Auxiliary channels are selected along the clutter ridge of the first-order sea clutter, whose distribution can be determined by the system parameters and regarded as pre-knowledge. To deal with the heterogeneity of the spreading first-order sea clutter, an innovative training samples selection approach according to the Riemannian distance is presented. The range cells that had shorter Riemannian distances to the cell under test (CUT) were chosen as training samples. Experimental results with measured data verified the effectiveness of the proposed algorithm, and the comparison with the existing clutter suppression algorithms showed the superiority of the algorithm.
Effects of Differences in Structure from Motion Software on Image Processing of Unmanned Aerial Vehicle Photography and Estimation of Crown Area and Tree Height in Forests
Authors: Kameyama Shohei , Sugiura Katsuaki
Published: February 2021

This study examines the effects of differences in structure from motion (SfM) software on image processing of aerial images by unmanned aerial vehicles (UAV) and the resulting estimations of tree height and tree crown area. There were 20 flight conditions for the UAV aerial images, which were a combination of five conditions for flight altitude, two conditions for overlap, and two conditions for side overlap. Images were then processed using three SfM programs (Terra Mapper, PhotoScan, and Pix4Dmapper). The tree height and tree crown area were determined, and the SfM programs were compared based on the estimations. The number of densified point clouds for PhotoScan (160 × 105 to 50 × 105) was large compared to the two other two SfM programs. The estimated values of crown area and tree height by each SfM were compared via Bonferroni multiple comparisons (statistical significance level set at p < 0.05). The estimated values of canopy area showed statistically significant differences (p < 0.05) in 14 flight conditions for Terra Mapper and PhotoScan, 16 flight conditions for Terra Mapper and Pix4Dmapper, and 11 flight conditions for PhotoScan and Pix4Dmappers. In addition, the estimated values of tree height showed statistically significant differences (p < 0.05) in 15 flight conditions for Terra Mapper and PhotoScan, 19 flight conditions for Terra Mapper and Pix4Dmapper, and 20 flight conditions for PhotoScan and Pix4Dmapper. The statistically significant difference (p < 0.05) between the estimated value and measured value of each SfM was confirmed under 18 conditions for Terra Mapper, 20 conditions for PhotoScan, and 13 conditions for Pix4D. Moreover, the RMSE and rRMSE values of the estimated tree height were 5–6 m and 20–28%, respectively. Although the estimation accuracy of any SfM was low, the estimated tree height by Pix4D in many flight conditions had smaller RMSE values than the other software. As statistically significant differences were found between the SfMs in many flight conditions, we conclude that there were differences in the estimates of crown area and tree height depending on the SfM used. In addition, Pix4Dmapper is suitable for estimating forest information, such as tree height, and PhotoScan is suitable for detailed monitoring of disaster areas.
Optical Flow Estimation by Matching Time Surface with Event-Based Cameras
Authors: Nagata Jun , Sekikawa Yusuke , Aoki Yoshimitsu
Published: February 2021

In this work, we propose a novel method of estimating optical flow from event-based cameras by matching the time surface of events. The proposed loss function measures the timestamp consistency between the time surface formed by the latest timestamp of each pixel and the one that is slightly shifted in time. This makes it possible to estimate dense optical flows with high accuracy without restoring luminance or additional sensor information. In the experiment, we show that the gradient was more correct and the loss landscape was more stable than the variance loss in the motion compensation approach. In addition, we show that the optical flow can be estimated with high accuracy by optimization with L1 smoothness regularization using publicly available datasets.