bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption Properties for La(III), Ce(III), and Y(III) with Poly(6-acryloylamino-hexyl hydroxamic acid) Resin
Authors: Cao Xiaoyan , Zhou Chunjie , Wang Shuai , Man Ruilin
Published: December 2020

Using polyacrylic resin followed by the substitution reaction with 6-aminohexyl hydroxamic acid, poly(6-acryloylamino-hexyl hydroxamic acid) resin (PAMHA) was successfully synthesized. PAMHA, a spherical resin with the particle size of 0.4 mm, is a novel polyamide hydroxamic acid chelating resin containing acylamino and hydroxamic acid functional groups. A series of influences (pH, contact time, temperature, and the initial concentrations of rare earth ions) were investigated to determine the adsorption properties. The adsorption capacity for La(III), Ce(III), and Y(III) ions were 1.030, 0.962, and 1.450 mmol·g−1, respectively. Thermodynamic and kinetic studies were also carried out to show that the uptake of rare earth ions onto PAMHA fitted well the pseudo-second-order model and Langmuir isotherm, and the adsorption process was spontaneous endothermic. In addition, desorption of rare earth ions was achieved by using 2 mol·L−1 HNO3 and desorption efficiencies for La(III), Ce(III), and Y(III) ions were 98.4, 99.1, and 98.8%, respectively. Properties of PAMHA resin were characterized by scanning electron microscope (SEM), Fourier transform infrared spectrometry (FTIR), and X-ray photoelectron spectrometer (XPS). The results showed that there was coordination between the rare earth ions with PAMHA and rare metal ions were chemically adsorbed on the surface of the PAMHA.
Effect of Mixing Ratio of Oppositely Charged Block Copolymers on Polyion Complex Micelles for In Vivo Application
Authors: Nakamura Noriko , Mochida Yuki , Toh Kazuko , Fukushima Shigeto , Cabral Horacio , Anraku Yasutaka
Published: December 2020

Self-assembled supramolecular structures based on polyion complex (PIC) formation between oppositely charged polymers are attracting much attention for developing drug delivery systems able to endure harsh in vivo environments. As controlling polymer complexation provides an opportunity for engineering the assemblies, an improved understanding of the PIC formation will allow constructing assemblies with enhanced structural and functional capabilities. Here, we focused on the influence of the mixing charge ratio between block aniomers and catiomers on the physicochemical characteristics and in vivo biological performance of the resulting PIC micelles (PIC/m). Our results showed that by changing the mixing charge ratio, the structural state of the core was altered despite the sizes of PIC/m remaining almost the same. These structural variations greatly affected the stability of the PIC/m in the bloodstream after intravenous injection and determined their biodistribution.
Preparation of Alkaline Polyelectrolyte Membrane Based on Quaternary Ammonium Salt–Modified Cellulose and Its Application in Zn–Air Flexible Battery
Authors: You Xiang , Qiao Congde , Peng Dan , Liu Weiliang , Li Cong , Zhao Hui , Qi Hao , Cai Xiaoxia , Shao Yanqiu , Shi Xinhua
Published: December 2020

In this study, a type of alkaline solid polyelectrolyte (ASPE) membrane was developed via the introduction of microcrystalline cellulose (MCC) and its modified product (QMCC) into the polyvinyl alcohol (PVA) matrix. In this process, green NaOH/urea-based solvent was used to achieve a good dispersion of MCC in the PVA matrix; meanwhile, the OH− groups in the NaOH/urea-based solvent provided an alkaline environment for good ion conductivity. Compared to the MCC-incorporated ASPE, further improved conductivity was achieved when the MCC was modified with quantitative quaternary ammonium salt. TGA showed that the addition of QMCC improved the water retention of the matrix, which was beneficial to the OH− conduction in the system. Compared to the control (50 mS cm−1), a maximum conductivity of 238 mS cm−1 was obtained after the incorporation of QMCC in the PVA matrix. Moreover, the tensile strength of the polymer electrolyte were also significantly increased with the addition of QMCC. Finally, this developed ASPE membrane was used in assembling a flexible Zn–air battery and showed a promising potential in the development of flexible electronic devices.
Additive Manufacturing of Polyether Ether Ketone (PEEK) for Space Applications: A Nanosat Polymeric Structure
Authors: Rinaldi Marianna , Cecchini Federico , Pigliaru Lucia , Ghidini Tommaso , Lumaca Francesco , Nanni Francesca
Published: December 2020

Recent improvements in additive layer manufacturing (ALM) have provided new designs of geometrically complex structures with lighter materials and low processing costs. The use of additive manufacturing in spacecraft production is opening up many new possibilities in both design and fabrication, allowing for the reduction of the weight of the structure subsystems. In this aim, polymeric ALM structures can become a choice, in terms of lightweight and demisability, as far as good thermomechanical properties. Moreover, provided that fused-deposition modeling (FDM) is used, nanosats and other structures could be easily produced in space. However, the choice of the material is a crucial step of the process, as the final performance of the printed parts is strongly dependent on three pillars: design, material, and printing process. As a high-performance technopolymer, polyether ether ketone (PEEK) has been adopted to fabricate parts via ALM; however, the space compatibility of 3D-printed parts remains not demonstrated. This work aimed to realize a nanosat polymeric structure via FDM, including all the phases of the development process: thermomechanical design, raw material selection, printing process tuning, and manufacturing of a proof of concept of a technological model. The design phase includes the application of topology optimization to maximize mass saving and take full advantage of the ALM capability. 3D-printed parts were characterized via thermomechanical tests, outgassing tests of 3D-printed parts are reported confirming the outstanding performance of polyether ether ketone and its potential as a material for structural space application.
Influence of Density on Foam Collapse under Burning
Authors: Baguian Abdoul Fayçal , Ouiminga Salifou Koucka , Longuet Claire , Caro-Bretelle Anne-Sophie , Corn Stéphane , Bere Antoine , Sonnier Rodolphe
Published: December 2020

The fire behaviour of flexible polyurethane foams was studied using a cone calorimeter, with a special emphasis on the collapse step. Only one peak of heat release rate, ranging from 200 to 450 kW/m2, is observed for thin foams, depending on the foam density and the heat flux. On the contrary, heat release rate (HRR) curves exhibit two peaks for 10 cm-thick foams, the second one corresponding to the pool fire formed after foam collapse. In all cases, the collapse occurs at a constant rate through the whole thickness. The rate of the recession of the front was calculated using digital and infrared cameras. Interestingly, its value is relatively constant whatever the heat flux (especially between 25 and 35 kW/m2), probably because of the very low heat conductivity preventing heat transfer through the thickness. The rate increases for the lightest foam but the fraction of burnt polymer during collapse is constant. Therefore, the pool fire is more intense for the densest foam. A simple macroscopic model taking into account only the heat transfer into the foam leads to much lower front recession rates, evidencing that the collapse is piloted by the cell walls’ rigidity.
Fabrication of UV-Crosslinked Flexible Solid Polymer Electrolyte with PDMS for Li-Ion Batteries
Authors: Kalybekkyzy Sandugash , Kopzhassar Al-Farabi , Kahraman Memet Vezir , Mentbayeva Almagul , Bakenov Zhumabay
Published: December 2020

Conventional carbonate-based liquid electrolytes have safety issues related to their high flammability and easy leakage. Therefore, it is essential to develop alternative electrolytes for lithium-ion batteries (LIBs). As a potential candidate, solid-polymer electrolytes (SPEs) offer enhanced safety characteristics, while to be widely applied their performance still has to be improved. Here, we have prepared a series of UV-photocrosslinked flexible SPEs comprising poly(ethylene glycol) diacrylate (PEGDA), trimethylolpropane ethoxylate triacrylate (ETPTA), and lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) salt, with the addition of polydimethylsiloxane with acrylated terminal groups (acryl-PDMS) to diminish the crystallinity of the poly(ethylene glycol) chain. Polysiloxanes have gained interest for the fabrication of SPEs due to their unique features, such as decrement of glass transition temperature (Tg), and the ability to improve flexibility and facilitate lithium-ion transport. Freestanding, transparent SPEs with excellent flexibility and mechanical properties were achieved without any supporting backbone, despite the high content of lithium salt, which was enabled by their networked structure, the presence of polar functional groups, and their amorphous structure. The highest ionic conductivity for the developed cross-linked SPEs was 1.75 × 10−6 S cm−1 at room temperature and 1.07 × 10−4 S cm−1 at 80 °C. The SPEs demonstrated stable Li plating/stripping ability and excellent compatibility toward metallic lithium, and exhibited high electrochemical stability in a wide range of potentials, which enables application in high-voltage lithium-ion batteries.
Robust Effects of Graphene Oxide on Polyurethane/Tourmaline Nanocomposite Fiber
Authors: Zhang Yuanchi , Hu Jinlian
Published: December 2020

The use of energy therapy including tourmaline/negative ions has gained huge popularity due to their long-standing historical evidence in improving human health and the technology development. However, the limitations of tourmaline based polyurethane fibers including the unsatisfied mechanical properties and negative ions releasing performances hind their further applications for wearable energy therapy. In this study, graphene oxide was modified within the polyurethane/tourmaline nanocomposite and then the wet-spinning method was used to prepare the fibers. As expected, the results proved that polyurethane/tourmaline/graphene oxide fiber had enhanced Young’s modulus (8.4 MPa) and tensile stain at break (335%). In addition, the number of released negative ions from polyurethane/tourmaline/graphene oxide fiber was significantly improved 17 times and 1.6 times more than that of neat polyurethane fiber and polyurethane/tourmaline fiber, respectively. Moreover, the releasing number of negative ions was significantly decreased after being applying voltage. We envision that the proposed polyurethane/tourmaline/graphene oxide fiber will provide valuable insights into the development of the wearable energy products.
Polystyrene Biodegradation by Tenebrio molitor Larvae: Identification of Generated Substances Using a GC-MS Untargeted Screening Method
Authors: Tsochatzis Emmanouil , Lopes Joao , Gika Helen , Theodoridis Georgios
Published: December 2020

A GC-MS method has been applied to screen and evaluate the generation of chemical compounds during the biodegradation of polystyrene (PS) with Tenebrio molitor larvae. Several resulting compounds have been identified, including trimers 2,4,6-triphenyl-1-hexene and 1,3,5-triphenylcyclohexane, the volatiles acetophenone and cumyl alcohol, and 2,4-di-tert butylphenol, a non-intentionally added substance (NIAS) present in the plastic material. The PS monomers styrene and α-methyl styrene were also identified in the extracts. Bioactive molecules present in the biomass of the studied insects were identified, such as the free fatty acids myristic, palmitic, and oleic acid. Undecanoic acid was also found, but in lower mass fractions. Finally, biochemically formatted amides resulting from their respective fatty acids were identified, namely tetradecanamide, hexadecanamide and oleamide. The formation of all these substances seems to suggest enzymatic and biochemical activity occurring during the biodegradation of PS, and their amounts varied throughout the experience. The overall degradation rate of PS resulted in a 13% rate, which highlights the potential of biorecycling using these insects.
Application of Glass Fiber and Carbon Fiber-Reinforced Thermoplastics in Face Guards
Authors: Wada Takahiro , Churei Hiroshi , Yokose Mako , Iwasaki Naohiko , Takahashi Hidekazu , Uo Motohiro
Published: December 2020

Face guards (FGs) are protectors that allow for the rapid and safe return of athletes who are to play after sustaining traumatic facial injuries and orbital fractures. Current FGs require significant thickness to achieve sufficient shock absorption abilities. However, their weight and thickness render the FGs uncomfortable and reduce the field of vision of the athlete, thus hindering their performance. Therefore, thin and lightweight FGs are required. We fabricated FGs using commercial glass fiber-reinforced thermoplastic (GFRTP) and carbon fiber-reinforced thermoplastic (CFRTP) resins to achieve these requirements and investigated their shock absorption abilities through impact testing. The results showed that an FG composed of CFRTP is thinner and lighter than a conventional FG and has sufficient shock absorption ability. The fabrication method of an FG comprising CFRTP is similar to the conventional method. FGs composed of commercial FRTPs exhibit adequate shock absorption abilities and are thinner and lower in weight as compared to conventional FGs.
Encapsulating MoO2 Nanocrystals into Flexible Carbon Nanofibers via Electrospinning for High-Performance Lithium Storage
Authors: Zhang Xinyu , Gao Mingzhen , Wang Wei , Liu Bing , Li Xianbo
Published: December 2020

Design and synthesis of flexible and self-supporting electrode materials in high-performance lithium storage is significant for applications in the field of smart wearable devices. Herein, flexible carbon nanofiber membranes with uniformly distributed molybdenum dioxide (MoO2) nanocrystals are fabricated by a needlefree electrospinning method combined with the subsequent carbonization process, which exhibits outstanding structural stability under abrasion and deformation. The as-fabricated lithium-ion batteries (LIBs) exhibit a high discharge of 450 mAh g−1 after 500 cycles at 2000 mA g−1 by using the MoO2/C nanofiber membrane as the self-supporting anode. Further, the nanofibers structure remains intact after 500 cycles, which reflects the excellent stability of the materials. This study provides a simple and effective method for the preparation of MoO2/C nanofiber materials, which can not only maintain its excellent electrochemical and physical properties, but also easily realize large-scale production. It is undoubtedly beneficial for the development of flexible LIBs and smart wearable devices.
Biocidal Polymers: Synthesis, Characterization and Antimicrobial Activity of Bis-Quaternary Onium Salts of Poly(aspartate-co-succinimide)
Authors: El-Newehy Mohamed H. , A. Meera Moydeen , Aldalbahi Ali K. , Thamer Badr M. , Mahmoud Yehia A.-G. , El-Hamshary Hany
Published: December 2020

Microbial multidrug resistance presents a real problem to human health. Therefore, water-soluble polymers based on poly(aspartate-co-succinimide) were synthesized via reaction of poly(aspartate-co-succinimide) with bis-quaternary ammonium or quaternary salts. The resultant copolymers were characterized by various techniques such as FTIR, TGA, 1HNMR, 13CNMR and elemental microanalysis. Antimicrobial activities of the new onium salts were investigated against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Salmonella typhi, and the fungi; Candida albicans,Aspergillus niger, Cryptococcus neoformans and Aspergillus flavus by agar diffusion method. Antimicrobial activity was studied in terms of inhibition zone diameters, in addition to the estimation of minimal inhibitory concentration (MIC) of the prepared compounds. A. niger and E. coli were the most affected microorganisms among the tested microorganisms with an inhibition zone of 19–21 (mm) in case of biocides, (V) and (VII). The obtained results showed that the quaternary onium salts have higher activity compared to the aspartate copolymer with MIC concentrations of 25 mg/mL for (VII) and (V) and 50 mg/mL for (VI) and (IV).
Promising Drug Delivery Approaches to Treat Microbial Infections in the Vagina: A Recent Update
Authors: Pandey Manisha , Choudhury Hira , Abdul-Aziz Azila , Bhattamisra Subrat Kumar , Gorain Bapi , Carine Teng , Wee Toong Tan , Yi Ngiam Jing , Win Yi Lim
Published: December 2020

An optimal host–microbiota interaction in the human vagina governs the reproductive health status of a woman. The marked depletion in the beneficial Lactobacillus sp. increases the risk of infection with sexually transmitted pathogens, resulting in gynaecological issues. Vaginal infections that are becoming increasingly prevalent, especially among women of reproductive age, require an effective concentration of antimicrobial drugs at the infectious sites for complete disease eradication. Thus, topical treatment is recommended as it allows direct therapeutic action, reduced drug doses and side effects, and self-insertion. However, the alterations in the physiological conditions of the vagina affect the effectiveness of vaginal drug delivery considerably. Conventional vaginal dosage forms are often linked to low retention time in the vagina and discomfort which significantly reduces patient compliance. The lack of optimal prevention and treatment approaches have contributed to the unacceptably high rate of recurrence for vaginal diseases. To combat these limitations, several novel approaches including nano-systems, mucoadhesive polymeric systems, and stimuli-responsive systems have been developed in recent years. This review discusses and summarises the recent research progress of these novel approaches for vaginal drug delivery against various vaginal diseases. An overview of the concept and challenges of vaginal infections, anatomy and physiology of the vagina, and barriers to vaginal drug delivery are also addressed.
Analysis of the Impact of Changes in Thermomechanical Properties of Polymer Materials on the Machining Process of Gears
Authors: Gnatowski Adam , Gołębski Rafał , Sikora Piotr
Published: December 2020

This paper presents an analysis of the impact of modification of thermomechanical properties of polymer materials on the process of gear wheel machining on a CNC machine tool. Polymer materials Tecaflon (PVDA) and polyethylene (PE) were used for processing. The materials underwent thermal modification i.e., annealing. Prepared samples (gear wheel dimensions Ø76.5 × 20 mm) were machined under the same conditions, only changing the feed rate parameter. A CNC milling machine of its own construction was used for machining with a horizontal numerical dividing attachment. The obtained gear wheels were tested using ZEISS GEAR PRO gear analyzes software. Deviations of the involute outline and the tooth line allowed classification of wheels in the 9th grade of accuracy. Machined teeth surfaces were examined for changes in the properties of surface layer, taking into account the influence of polymer material thermal modification on the surface condition. The samples were tested for mechanical properties (tensile strength) and thermomechanical properties (DSC and DMTA). The tests showed positive changes in material strength and significant improvements in PVDA Tecaflon after heat treatment.
The Self-Enforcing Starch–Gluten System—Strain–Dependent Effects of Yeast Metabolites on the Polymeric Matrix
Authors: Alpers Thekla , Tauscher Viviane , Steglich Thomas , Becker Thomas , Jekle Mario
Published: December 2020

The rheological behaviour of dough during the breadmaking process is strongly affected by the accumulation of yeast metabolites in the dough matrix. The impact of metabolites in yeasted dough-like concentrations on the rheology of dough has not been characterised yet for process-relevant deformation types and strain rates, nor has the effect of metabolites on strain hardening behaviour of dough been analysed. We used fundamental shear and elongational rheometry to study the impact of fermentation on the dough microstructure and functionality. Evaluating the influence of the main metabolites, the strongest impact was found for the presence of expanding gas cells due to the accumulation of the yeast metabolite CO2, which was shown to have a destabilising impact on the surrounding dough matrix. Throughout the fermentation process, the polymeric and entangled gluten microstructure was found to be degraded (−37.6% average vessel length, +37.5% end point rate). These microstructural changes were successfully linked to the changing rheological behaviour towards a highly mobile polymer system. An accelerated strain hardening behaviour (+32.5% SHI for yeasted dough) was promoted by the pre-extension of the gluten strands within the lamella around the gas cells. Further, a strain rate dependency was shown, as a lower strain hardening index was observed for slow extension processes. Fast extension seemed to influence the disruption of sterically interacting fragments, leading to entanglements and hindered extensibility.
A Three-Dimensional Numerical and Multi-Objective Optimal Design of Wavy Plate-Fins Heat Exchangers
Authors: Yu Chao , Xue Xiangyao , Shi Kui , Shao Mingzhen
Published: December 2020

This paper presents a method for optimizing wavy plate-fin heat exchangers accurately and efficiently. It combines CFD simulation, Radical Basis Functions (RBF) with multi-objective optimization to improve the performance. The optimization of the Colburn factor j and the friction coefficient f is regarded as a multi-objective optimization problem, due to the existence of two contradictory goals. The approximation model was obtained by Radical Basis Functions, and the shape of the heat exchanger was optimized by multi-objective genetic algorithm (MOGA). The optimization results showed that j increased by 17.62% and f decreased by 20.76%, indicating that the heat exchange efficiency was significantly enhanced and the fluid structure resistance reduced. Then, from the aspects of field synergy and tubulence energy, the performance advantage of the optimized structure was further confirmed.
Multi-Objective Coordinated Optimal Allocation of DG and EVCSs Based on the V2G Mode
Authors: Liu Lijun , Xie Feng , Huang Zonglong , Wang Mengqi
Published: December 2020

With the vigorous promotion of new energy sources and the development of vehicle-to-grid (V2G) technology, the influence of the V2G mode should be considered in the joint optimal allocation of Distributed Generation (DG) and electric vehicle charging stations (EVCSs). The timing characteristics of the intermittent output of DG, conventional demand for load, and charging load of the electric vehicle (EV) are considered, as is its participation in grid interaction to examine the construction of typical scenarios and the EV cluster dispatching strategy. From the perspective of comprehensively planning the coordination of the distribution network, a DG-EVCSs bi-level joint planning model is established under the peak and valley price mechanism, with the sub-objectives of obtaining a comprehensive profit and high quality of voltage, curbing system load fluctuations, and satisfactorily charging the EV. An improved harmony particle swarm optimization algorithm is proposed to solve the bi-level model. The proposed method was tested on the IEEE-33 and the PG&E-69 (Pacific Gas and Electric Company) bus distribution systems, and the results show that the optimized configuration model that considers the V2G mode can improve the overall performance of the planning scheme, promote the use of clean energy, smoothen the load fluctuations of the system, and improve the quality of voltage and charging satisfaction of EV users.
Optimizing the Axial Resistance Profile of Submerged Hollow Fiber Membranes
Authors: Kuhn Michael , Briesen Heiko
Published: December 2020

Submerged hollow fiber membranes (SHFMs) are used for a wide variety of applications. Their applicability and their advantages, however, depend crucially on the prevailing hydrodynamics within single fibers. In this respect, the non-uniform distribution of transmembrane flux is a known problem related to inhomogeneous membrane fouling and disadvantages for cleaning. To address this problem, we propose an approach to homogenize transmembrane flux by varying the local membrane resistance using optimal control methods for the first time in SHFM research. Based on an established model, different scenarios are optimized, namely with different fiber lengths and inner radii. In addition, a double-end setup is explored. It is shown that the optimization goal is reached very well in all tested cases, which underlines the general validity of our strategy. Further uses and extensions of the optimization method are provided, as well as hints for the practical implementation of the suggested measures.
Advanced 3D Cell Culture Techniques in Micro-Bioreactors, Part II: Systems and Applications
Authors: Altmann Brigitte , Grün Christoph , Nies Cordula , Gottwald Eric
Published: December 2020

In this second part of our systematic review on the research area of 3D cell culture in micro-bioreactors we give a detailed description of the published work with regard to the existing micro-bioreactor types and their applications, and highlight important results gathered with the respective systems. As an interesting detail, we found that micro-bioreactors have already been used in SARS-CoV research prior to the SARS-CoV2 pandemic. As our literature research revealed a variety of 3D cell culture configurations in the examined bioreactor systems, we defined in review part one “complexity levels” by means of the corresponding 3D cell culture techniques applied in the systems. The definition of the complexity is thereby based on the knowledge that the spatial distribution of cell-extracellular matrix interactions and the spatial distribution of homologous and heterologous cell–cell contacts play an important role in modulating cell functions. Because at least one of these parameters can be assigned to the 3D cell culture techniques discussed in the present review, we structured the studies according to the complexity levels applied in the MBR systems.
Parameters of Sustainable Development: Case of Arctic Liquefied Natural Gas Projects
Authors: Cherepovitsyn Alexey , Evseeva Olga
Published: December 2020

Effective management of the social and economic development of the Arctic zone of the Russian Federation is today a significant scientific and practical task. It requires an integrated approach to meet the expectations of the state, business and society. The main drivers of growth for remote Arctic territories are large investment projects, which not only create production and sectorial results, but also stimulate the development of related sectors of the economy. Additionally, they contribute to the formation of modern infrastructure in the region and create conditions for the broad introduction of innovative technologies. The current problem with territorial development strategic planning is the assessment of the results that have been achieved. This includes approved lists of indicators that do not allow for a full assessment of the impact of the implemented projects. Assessment on the achievement of the region goals is also murky. This indicates a lack of consistency in regional development management. This article defines the importance of the indicators for an assessment of sustainable development management. The model of achieving external effects in project activities is described. The concept of sustainability of large-capacity complexes for the production of liquefied natural gas (LNG) is also formulated. Based on the needs of micro- and macro-environment projects, a list of indicators for assessing the sustainability of LNG projects has been proposed. On the basis of the proposed indicator list, a sustainability analysis of three Arctic LNG projects was carried out. Based on the example of LNG production, it was concluded that approaches to assessing the sustainable socio-economic development of the Arctic region and its industrial systems are interrelated, but there are differences between them.
Are Investors’ Attention and Uncertainty Aversion the Risk Factors for Stock Markets? International Evidence from the COVID-19 Crisis
Authors: Shear Falik , Ashraf Badar Nadeem , Sadaqat Mohsin
Published: December 2020

In this paper, we examine the impact of investors’ attention to COVID-19 on stock market returns and the moderating effect of national culture on this relationship. Using daily data from 34 countries over the period 23 January to 12 June 2020, and measuring investors’ attention with the Google search volume (GSV) of the word “coronavirus” for each country, we find that investors’ enhanced attention to the COVID-19 pandemic results in negative stock market returns. Further, measuring the national culture with the uncertainty avoidance index (the aspect of national culture which measures the cross-country differences in decision-making under stress and ambiguity), we find that the negative impact of investors’ attention on stock market returns is stronger in countries where investors possess higher uncertainty avoidance cultural values. Our findings imply that uncertainty avoidance cultural values of investors promote financial market instability amid the crisis.
Machine Learning in P&C Insurance: A Review for Pricing and Reserving
Authors: Blier-Wong Christopher , Cossette Hélène , Lamontagne Luc , Marceau Etienne
Published: December 2020

In the past 25 years, computer scientists and statisticians developed machine learning algorithms capable of modeling highly nonlinear transformations and interactions of input features. While actuaries use GLMs frequently in practice, only in the past few years have they begun studying these newer algorithms to tackle insurance-related tasks. In this work, we aim to review the applications of machine learning to the actuarial science field and present the current state of the art in ratemaking and reserving. We first give an overview of neural networks, then briefly outline applications of machine learning algorithms in actuarial science tasks. Finally, we summarize the future trends of machine learning for the insurance industry.
Global 3D Features of Error Variances of GPS Radio Occultation and Radiosonde Observations
Authors: Xu Xu , Zou Xiaolei
Published: December 2020

Global Positioning System (GPS) radio occultation (RO) and radiosonde (RS) observations are two major types of observations assimilated in numerical weather prediction (NWP) systems. Observation error variances are required input that determines the weightings given to observations in data assimilation. This study estimates the error variances of global GPS RO refractivity and bending angle and RS temperature and humidity observations at 521 selected RS stations using the three-cornered hat method with additional ERA-Interim reanalysis and Global Forecast System forecast data available from 1 January 2016 to 31 August 2019. The global distributions, of both RO and RS observation error variances, are analyzed in terms of vertical and latitudinal variations. Error variances of RO refractivity and bending angle and RS specific humidity in the lower troposphere, such as at 850 hPa (3.5 km impact height for the bending angle), all increase with decreasing latitude. The error variances of RO refractivity and bending angle and RS specific humidity can reach about 30 N-unit2, 3 × 10−6 rad2, and 2 (g kg−1)2, respectively. There is also a good symmetry of the error variances of both RO refractivity and bending angle with respect to the equator between the Northern and Southern Hemispheres at all vertical levels. In this study, we provide the mean error variances of refractivity and bending angle in every 5°-latitude band between the equator and 60°N, as well as every interval of 10 hPa pressure or 0.2 km impact height. The RS temperature error variance distribution differs from those of refractivity, bending angle, and humidity, which, at low latitudes, are smaller (less than 1 K2) than those in the midlatitudes (more than 3 K2). In the midlatitudes, the RS temperature error variances in North America are larger than those in East Asia and Europe, which may arise from different radiosonde types among the above three regions.
A Novel Urban Composition Index Based on Water-Impervious Surface-Pervious Surface (W-I-P) Model for Urban Compositions Mapping Using Landsat Imagery
Authors: Zhang Lihao , Tian Yugang , Liu Qingwei
Published: December 2020

Monitoring urban compositions spatially and temporally is a crucial issue for urban planning and management. Nowadays, remote sensing techniques have been widely applied for urban compositions extraction. Compared with other remote sensing techniques, spectral indices have significant advantages due to their parameter-free and easy implementation. However, existing indices cannot extract different urban compositions well, and some of them can only extract one composition with less attention to other urban compositions. In this study, based on the water- impervious surface-pervious surface (W-I-P) model, a novel urban composition index (UCI) was developed by analyzing the robust features from the global spectral samples. Additionally, a semi-empirical threshold of UCI was proposed to extract different urban compositions (water, impervious surface area and pervious surface area). Four cities of China were selected as study areas, Landsat-8 images and Google Earth images were used for quantitative analysis. Correlation analysis, separability analysis, and accuracy assessment were conducted among UCI and five other existed indices (single and multiple composition indices) at the urban and global scales. Results indicated that UCI had a stronger correlation with the ISA proportion and a higher separability between each urban composition. UCI also achieved the highest overall accuracy and Kappa coefficient in urban compositions extraction. The suggested semi-empirical threshold was also testified to be reliable and can be a reference for practical application. There is convincing evidence that UCI is a simple, efficient, and reliable index for urban compositions extraction.
High-Resolution Ionosphere Corrections for Single-Frequency Positioning
Authors: Goss Andreas , Hernández-Pajares Manuel , Schmidt Michael , Roma-Dollase David , Erdogan Eren , Seitz Florian
Published: December 2020

The ionosphere is one of the main error sources in positioning and navigation; thus, information about the ionosphere is mandatory for precise modern Global Navigation Satellite System (GNSS) applications. The International GNSS Service (IGS) and its Ionosphere Associated Analysis Centers (IAAC) routinely provide ionospheric information in terms of global ionosphere maps (final GIM). Typically, these products are modeled using series expansion in terms of spherical harmonics (SHs) with a maximum degree of n=15 and are based on post processed observations from Global Navigation Satellite Systems (GNSS), as well as final satellite orbits. However, precise applications such as autonomous driving or precision agriculture require real-time (RT) information about the ionospheric electron content with high spectral and spatial resolution. Ionospheric RT-GIMs are disseminated via Ntrip protocol using the SSR VTEC message of the RTCM. This message can be streamed in RT, but it is limited for the dissemination of coefficients of SHs of lower degrees only. It allows the dissemination of SH coefficients up to a degree of n=16. This suits to most the SH models of the IAACs, but higher spectral degrees or models in terms of B-spline basis functions, voxels, splines and many more cannot be considered. In addition to the SHs, several alternative approaches, e.g., B-splines or Voxels, have proven to be appropriate basis functions for modeling the ionosphere with an enhanced resolution. Providing them using the SSR VTEC message requires a transfer to SHs. In this context, the following questions are discussed based on data of a B-spline model with high spectral resolution; (1) How can the B-spline model be transformed to SHs in order to fit to the RTCM requirements and (2) what is the loss of detail when the B-spline model is converted to SHs of degree of n=16? Furthermore, we discuss (3) what is the maximum necessary SH degree n to convert the given B-spline model and (4) how can the transformation be performed to make it applicable for real-time applications? For a final assessment, we perform both, the dSTEC analysis and a single-frequency positioning in kinematic mode, using the transformed GIMs for correcting the ionospheric delay. The assessment shows that the converted GIMs with degrees n≥30 coincide with the original B-spline model and improve the positioning accuracy significantly.
Impact of Topography and Rainfall Intensity on the Accuracy of IMERG Precipitation Estimates in an Arid Region
Authors: Mahmoud Mohammed T. , Mohammed Safa A. , Hamouda Mohamed A. , Mohamed Mohamed M.
Published: December 2020

The influence of topographical characteristics and rainfall intensity on the accuracy of satellite precipitation estimates is of importance to the adoption of satellite data for hydrological applications. This study evaluates the three GPM IMERG V05B products over the arid country of Saudi Arabia. Statistical indices quantifying the performance of IMERG products were calculated under three evaluation techniques: seasonal-based, topographical, and rainfall intensity-based. Results indicated that IMERG products have the capability to detect seasons with the highest precipitation values (spring) and seasons with the lowest precipitation (summer). Moreover, results showed that IMERG products performed well under various rainfall intensities, particularly under light rain, which is the most common rainfall in arid regions. Furthermore, IMERG products exhibited high detection accuracy over moderate elevations, whereas it had poor performance over coastal and mountainous regions. Overall, the results confirmed that the performance of the final-run product surpassed the near-real-time products in terms of consistency and errors. IMERG products can improve temporal resolution and play a significant role in filling data gaps in poorly gauged regions. However, due to the errors in IMERG products, it is recommended to use sub-daily rain gauge data in satellite calibration for better rainfall estimation over arid and semiarid regions.
Semi-Automatic Method for Early Detection of Xylella fastidiosa in Olive Trees Using UAV Multispectral Imagery and Geostatistical-Discriminant Analysis
Authors: Castrignanò Annamaria , Belmonte Antonella , Antelmi Ilaria , Quarto Ruggiero , Quarto Francesco , Shaddad Sameh , Sion Valentina , Muolo Maria Rita , Ranieri Nicola A. , Gadaleta Giovanni , Bartoccetti Edoardo , Riefolo Carmela , Ruggieri Sergio , Nigro Franco
Published: December 2020

Xylella fastidiosa subsp. pauca (Xfp) is one of the most dangerous plant pathogens in the world. Identified in 2013 in olive trees in south–eastern Italy, it is spreading to the Mediterranean countries. The bacterium is transmitted by insects that feed on sap, and causes rapid wilting in olive trees. The paper explores the use of Unmanned Aerial Vehicle (UAV) in combination with a multispectral radiometer for early detection of infection. The study was carried out in three olive groves in the Apulia region (Italy) and involved four drone flights from 2017 to 2019. To classify Xfp severity level in olive trees at an early stage, a combined method of geostatistics and discriminant analysis was implemented. The results of cross-validation for the non-parametric classification method were of overall accuracy = 0.69, mean error rate = 0.31, and for the early detection class of accuracy 0.77 and misclassification probability 0.23. The results are promising and encourage the application of UAV technology for the early detection of Xfp infection.
Structure-From-Motion Photogrammetry of Antarctic Historical Aerial Photographs in Conjunction with Ground Control Derived from Satellite Data
Authors: Child Sarah F. , Stearns Leigh A. , Girod Luc , Brecher Henry H.
Published: December 2020

A longer temporal scale of Antarctic observations is vital to better understanding glacier dynamics and improving ice sheet model projections. One underutilized data source that expands the temporal scale is aerial photography, specifically imagery collected prior to 1990. However, processing Antarctic historical aerial imagery using modern photogrammetry software is difficult, as it requires precise information about the data collection process and extensive in situ ground control is required. Often, the necessary orientation metadata for older aerial imagery is lost and in situ data collection in regions like Antarctica is extremely difficult to obtain, limiting the use of traditional photogrammetric methods. Here, we test an alternative methodology to generate elevations from historical Antarctic aerial imagery. Instead of relying on pre-existing ground control, we use structure-from-motion photogrammetry techniques to process the imagery with manually derived ground control from high-resolution satellite imagery. This case study is based on vertical aerial image sets collected over Byrd Glacier, East Antarctica in December 1978 and January 1979. Our results are the oldest, highest resolution digital elevation models (DEMs) ever generated for an Antarctic glacier. We use these DEMs to estimate glacier dynamics and show that surface elevation of Byrd Glacier has been constant for the past ∼40 years.
Individual Tree Diameter Estimation in Small-Scale Forest Inventory Using UAV Laser Scanning
Authors: Hao Yuanshuo , Widagdo Faris Rafi Almay , Liu Xin , Quan Ying , Dong Lihu , Li Fengri
Published: December 2020

Unmanned aerial vehicle laser scanning (UAVLS) systems present a relatively new means of remote sensing and are increasingly applied in the field of forest ecology and management. However, one of the most essential parameters in forest inventory, tree diameter at breast height (DBH), cannot be directly extracted from aerial point cloud data due to the limitations of scanning angle and canopy obstruction. Therefore, in this study DBH-UAVLS point cloud estimation models were established using a generalized nonlinear mixed-effects (NLME) model. The experiments were conducted using Larix olgensis as the subject species, and a total of 8364 correctly delineated trees from UAVLS data within 118 plots across 11 sites were used for DBH modeling. Both tree- and plot-level metrics were obtained using light detection and ranging (LiDAR) and were used as the models’ independent predictors. The results indicated that the addition of site-level random effects significantly improved the model fitting. Compared with nonparametric modeling approaches (random forest and k-nearest neighbors) and uni- or multivariable weighted nonlinear least square regression through leave-one-site-out cross-validation, the NLME model with local calibration achieved the lowest root mean square error (RMSE) values (1.94 cm) and the most stable prediction across different sites. Using the site in a random-effects model improved the transferability of LiDAR-based DBH estimation. The best linear unbiased predictor (BLUP), used to conduct local model calibration, led to an improvement in the models’ performance as the number of field measurements increased. The research provides a baseline for unmanned aerial vehicle (UAV) small-scale forest inventories and might be a reasonable alternative for operational forestry.
Damage Assessment of Rice Crop after Toluene Exposure Based on the Vegetation Index (VI) and UAV Multispectral Imagery
Authors: Kim Hyewon , Kim Woojung , Kim Sang Don
Published: December 2020

Chemical spill accidents lead to environmental problems, especially for plants. Plant vegetation assessment is necessary after a chemical accident; however, conventional methods can be inaccurate and time-consuming. This study used the vegetation index (VI) extracted from unmanned aerial vehicle (UAV) multispectral imagery for crop damage assessment after chemical exposure. The chemical accident simulations were conducted by exposure of rice at five growth stages to four levels of toluene. The VI was measured at five days after damage and 67 days after planting. Physiological characteristics (chlorophyll content and grain yield) were also measured. As a result, the mean normalized difference VI (NDVI) of toluene-exposed rice was significantly decreased with respect to toluene exposure concentration increases at most growth stages. Recovery after toluene exposure was lower in rice exposed to higher concentrations at the earlier growth stages. The chlorophyll content and grain yield were also decreased after toluene exposure with respect to increasing toluene concentrations and showed positive correlations with the NDVI. It indicates that the NDVI is capable of reflecting the plant response to chemical exposure. Thus, the results demonstrated that the VI based on UAV multispectral imagery is feasible as an alternative for crop monitoring, damage assessment after chemical exposure, and yield prediction.
Fish-Inspired Task Allocation Algorithm for Multiple Unmanned Aerial Vehicles in Search and Rescue Missions
Authors: Alhaqbani Amjaad , Kurdi Heba , Youcef-Toumi Kamal
Published: December 2020

The challenge concerning the optimal allocation of tasks across multiple unmanned aerial vehicles (multi-UAVs) has significantly spurred research interest due to its contribution to the success of various fleet missions. This challenge becomes more complex in time-constrained missions, particularly if they are conducted in hostile environments, such as search and rescue (SAR) missions. In this study, a novel fish-inspired algorithm for multi-UAV missions (FIAM) for task allocation is proposed, which was inspired by the adaptive schooling and foraging behaviors of fish. FIAM shows that UAVs in an SAR mission can be similarly programmed to aggregate in groups to swiftly survey disaster areas and rescue-discovered survivors. FIAM’s performance was compared with three long-standing multi-UAV task allocation (MUTA) paradigms, namely, opportunistic task allocation scheme (OTA), auction-based scheme, and ant-colony optimization (ACO). Furthermore, the proposed algorithm was also compared with the recently proposed locust-inspired algorithm for MUTA problem (LIAM). The experimental results demonstrated FIAM’s abilities to maintain a steady running time and a decreasing mean rescue time with a substantially increasing percentage of rescued survivors. For instance, FIAM successfully rescued 100% of the survivors with merely 16 UAVs, for scenarios of no more than eight survivors, whereas LIAM, Auction, ACO and OTA rescued a maximum of 75%, 50%, 35% and 35%, respectively, for the same scenarios. This superiority of FIAM performance was maintained under a different fleet size and number of survivors, demonstrating the approach’s flexibility and scalability.