bluuebunny/crossref_metadata_2025 huggingface dataset:
Pickering Emulsions Stabilized by Chitosan/Natural Acacia Gum Biopolymers: Effects of pH and Salt Concentrations
Authors: Adewunmi Ahmad A. , Mahboob Ahmad , Kamal Muhammad Shahzad , Sultan Abdullah
Published: December 2022

In this study, chitosan (CT) and naturally occurring acacia gum (AG) blends were employed as emulsifiers to form a series of emulsions developed from diesel and water. Effects of pH level (3, 5, 10, and 12) and various NaCl salt concentrations (0.25–1%) on the stability, viscosity, and interfacial properties of CT-(1%)/AG-(4%) stabilized Pickering emulsions were evaluated. Bottle test experiment results showed that the stability indexes of the CT/AG emulsions were similar under acidic (3 and 5) and alkaline (10 and 12) pH media. On the other hand, the effects of various NaCl concentrations on the stability of CT-(1%)/AG-(4%) emulsion demonstrated analogous behavior throughout. From all the NaCl concentrations and pH levels examined, viscosities of this emulsion decreased drastically with the increasing shear rate, indicating pseudoplastic fluid with shear thinning characteristics of these emulsions. The viscosity of CT-(1%)/AG-(4%) emulsion increased at a low shear rate and decreased with an increasing shear rate. The presence of NaCl salt and pH change in CT/AG solutions induced a transformation in the interfacial tension (IFT) at the diesel/water interface. Accordingly, the IFT values of diesel/water in the absence of NaCl/CT/AG (without emulsifier and salt) remained fairly constant for a period of 500 s, and its average IFT value was 26.16 mN/m. In the absence of salt, the addition of an emulsifier (CT-(1%)/AG-(4%)) reduced the IFT to 16.69 mN/m. When the salt was added, the IFT values were further reduced to 12.04 mN/m. At low pH, the IFT was higher (17.1 mN/M) compared to the value of the IFT (10.8 mN/M) at high pH. The results obtained will help understand the preparation and performance of such emulsions under different conditions especially relevant to oil field applications.
Numerical and Experimental Studies on the Improvement of Gas Chamber Structure during Gas-Assisted Extrusion
Authors: Liu Bin , Huang Xingyuan , Zhang Xiaohui , Ren Shaoyi , Lan Qiang , Luo Cheng
Published: December 2022

In the gas-assisted extrusion process, the melt inside the die is in a low-viscosity molten state, so the flow field of the gas cushion layer has a great effect on the cross-sectional shape of the micro-tube. Therefore, this study establishes the gas distribution chamber model of the gas-assisted die. Ansys Fluent software was used to simulate the gas flow field of the gas distribution chamber. The effect of the gas chamber structure on the size of the micro-tube was analyzed by the extrusion experiment. The research shows that the velocity unevenness coefficient of the gas outlet of the single gas chamber die is 11.8%, which is higher than that of the double gas chamber die. The use of a double gas chamber die can improve the stability of the gas cushion layer and the wall thickness non-uniformity of the micro-tube, which verifies the simulation results.
Density Functional Theory Analysis of the Copolymerization of Cyclopropenone with Ethylene Using a Palladium Catalyst
Authors: Zhang Chenggen , Yu Shuyuan , Wang Fei , Wang Fuping , Cao Jian , Zheng Huimin , Chen Xiaoyu , Ren Aijin
Published: December 2022

Density functional theory has been used to elucidate the mechanism of Pd copolymerization of cyclopropenone with ethylene. The results reveal that introducing ethylene and cyclopropenone to Pd catalyst is thermodynamically feasible and generates the α,β-unsaturated ketone unit (UnitA). Cis-mode insertion and Path A1a are the most favorable reaction routes for ethylene and cyclopropenone, respectively. Moreover, cyclopropenone decomposition can generate CO in situ without a catalyst or with a Pd catalyst. The Pd-catalyzed decomposition of cyclopropenone exhibits a lower reaction barrier (22.7 kcal/mol) than its direct decomposition. Our study demonstrates that incorporating CO into the Pd catalyst can generate the isolated ketone unit (UnitB). CO is formed first; thereafter, UnitB is generated. Therefore, the total energy barrier of UnitB generation, accounting for the CO barrier, is 22.7 kcal/mol, which is slightly lower than that of UnitA generation (24.0 kcal/mol). Additionally, the possibility of copolymerizing ethylene, cyclopropenone, and allyl acetate (AAc) has been investigated. The free energy and global reactivity index analyses indicate that the cyclopropenone introduction reaction is more favorable than the AAc insertion, which is consistent with the experimental results. Investigating the copolymerization mechanism will help to develop of a functionalization strategy for polyethylene polymers.
Composites Filled with Metal Organic Frameworks and Their Derivatives: Recent Developments in Flame Retardants
Authors: Lyu Ping , Hou Yongbo , Hu Jinhu , Liu Yanyan , Zhao Lingling , Feng Chao , Ma Yong , Wang Qin , Zhang Rui , Huang Weibo , Ma Mingliang
Published: December 2022

Polymer matrix is vulnerable to fire hazards and needs to add flame retardants to enhance its performance and make its application scenarios more extensive. At this stage, it is more necessary to add multiple flame-retardant elements and build a multi-component synergistic system. Metal organic frameworks (MOFs) have been studied for nearly three decades since their introduction. MOFs are known for their structural advantages but have only been applied to flame-retardant polymers for a relatively short period of time. In this paper, we review the development of MOFs utilized as flame retardants and analyze the flame-retardant mechanisms in the gas phase and condensed phase from the original MOF materials, modified MOF composites, and MOF-derived composites as flame retardants, respectively. The effects of carbon-based materials, phosphorus-based materials, nitrogen-based materials, and biomass on the flame-retardant properties of polymers are discussed in the context of MOFs. The construction of MOF multi-structured flame retardants is also introduced, and a variety of MOF-based flame retardants with different morphologies are shown to broaden the ideas for subsequent research.
Wear Analysis of Tibial Inserts Made of Highly Cross-Linked Polyethylene Supplemented with Dodecyl Gallate before and after Accelerated Aging
Authors: Su Jian , Wang Jianjun , Yan Shitong , Zhang Min , Zhang Ningze , Luan Yichao , Cheng Cheng-Kung
Published: December 2022

The wear of the tibial insert is one of the primary factors leading to the failure of total knee arthroplasty. As materials age, their wear performance often degrades. Supplementing highly cross-linked polyethylene (HXLPE) with dodecyl gallate (DG) can improve the oxidation stability of tibial inserts for use in total knee arthroplasty (TKA). This study aimed to evaluate the wear resistance of HXLPE supplemented with DG (HXLPE-DG) tibial inserts before and after accelerated aging. HXLPE-DG tibial inserts were subjected to wear testing of up to 5 million loading cycles according to ISO 14243, and the resulting wear particles were analyzed according to ISO 17853. The wear rate, number, size, and shape of the wear particles were analyzed. The average wear rate of the unaged samples was 4.39 ± 0.75 mg/million cycles and was 3.22 ± 1.49 mg/million cycles for the aged samples. The unaged tibial inserts generated about 2.80 × 107 particles/mL following the wear test, but this was considerably lower for the aged samples at about 1.35 × 107 particles/mL. The average equivalent circle diameter (ECD) of the wear particles from the unaged samples was 0.13 μm (max: 0.80 μm; min: 0.04 μm), and it was 0.14 μm (max: 0.66 μm; min: 0.06 μm) from the aged samples. Moreover, 22.1% of the wear particles from the unaged samples had an aspect ratio (AR) of >4 (slender shape), while this was 15.4% for the aged samples. HXLPE-DG improves the wear performance of the material over time. HXLPE-DG is a novel material that has been demonstrated to have antiaging properties and high wear resistance, making it a promising candidate for use in TKA. Nevertheless, the results are preliminary and will be clarified in further studies.
Sunflower Oil as a Renewable Resource for Polyurethane Foams: Effects of Flame-Retardants
Authors: Asare Magdalene A. , Kote Prashant , Chaudhary Sahilkumar , de Souza Felipe M. , Gupta Ram K.
Published: December 2022

Currently, polyurethane (PU) manufacturers seek green alternatives for sustainable production. In this work, sunflower oil is studied as a replacement and converted to a reactive form through epoxidation and oxirane opening to produce rigid PU foams. Confirmatory tests such as Fourier-transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), and hydroxyl value among others were performed to characterize the synthesized polyol. Despite the versatility of rigid PU foams, they are highly flammable, which makes eco-friendly flame retardants (FRs) desired. Herein, expandable graphite (EG) and dimethyl methyl phosphonate (DMMP), both non-halogenated FR, were incorporated under different concentrations to prepare rigid PU foams. Their effects on the physio-mechanical and fire-quenching properties of the sunflower oil-based PU foams were elucidated. Thermogravimetric and compression analysis showed that these foams presented appreciable compressive strength along with good thermal stability. The closed-cell contents (CCC) were around 90% for the EG-containing foams and suffered a decrease at higher concentrations of DMMP to 72%. The burning test showed a decrease in the foam’s flammability as the neat foam had a burning time of 80 s whereas after the addition of 13.6 wt.% of EG and DMMP, separately, there was a decrease to 6 and 2 s, respectively. Hence, our research suggested that EG and DMMP could be a more viable alternative to halogen-based FR for PU foams. Additionally, the adoption of sunflower polyol yielded foams with results comparable to commercial ones.
DMA of TPU Films and the Modelling of Their Viscoelastic Properties for Noise Reduction in Jet Engines
Authors: Neubauer Moritz , Pohl Michael , Kucher Michael , Böhm Robert , Höschler Klaus , Modler Niels
Published: December 2022

Due to current developments in jet engine design, the acoustic performance of conventional acoustic liners needs to be improved with respect to lower frequency spectrums and broadband absorption. In this context, the present study aimed to determine the viscoelastic material properties of a thermoplastic polyurethane (TPU) film for targeted application in novel acoustic liners with integrated film material for enhanced noise reduction. Therefore, a dynamic mechanical analysis (DMA) was performed to determine these viscoelastic material properties. Based on the acquired data, the time-temperature shift (TTS) was applied to obtain the material’s temperature- and frequency-dependent mechanical properties. In this regard, the William-Landel-Ferry (WLF) method and an alternative polynomial approach determining the shift factors were investigated and compared. Furthermore, a generalized Maxwell model—so-called Prony-series—with and without pre-smoothing utilizing of a fractional rheological model was applied to approximate the measured storage and loss modulus and to provide a material model that can be used in finite element analyses. Finally, the results were discussed concerning the application of the films in acoustic liners under the conditions of a standard flight cycle and the applied loads. The present investigations thus provide a method for characterizing polymer materials, approximating their mechanical behavior for vibration applications at different ambient temperatures and enabling the identification of their operational limits during the application in acoustic liners.
Synthesis and Characterization of Hybrid Materials Derived from Conjugated Copolymers and Reduced Graphene Oxide
Authors: Lazanas Alexandros Ch. , Katsouras Athanasios , Spanos Michael , Manesi Gkreti-Maria , Moutsios Ioannis , Vashurkin Dmitry V. , Moschovas Dimitrios , Gioti Christina , Karakassides Michail A. , Gregoriou Vasilis G. , Ivanov Dimitri A. , Chochos Christos L. , Avgeropoulos Apostolos
Published: December 2022

In this study the preparation of hybrid materials based on reduced graphene oxide (rGO) and conjugated copolymers is reported. By tuning the number and arrangement of thiophenes in the main chain (indacenothiophene or indacenothienothiophene) and the nature of the polymer acceptor (difluoro benzothiadiazole or diketopyrrolopyrrole) semiconducting copolymers were synthesized through Stille aromatic coupling and characterized to determine their molecular characteristics. The graphene oxide was synthesized using the Staudenmaier method and was further modified to reduced graphene oxide prior to structural characterization. Various mixtures with different rGO quantities and conjugated copolymers were prepared to determine the optoelectronic, thermal and morphological properties. An increase in the maximum absorbance ranging from 3 to 6 nm for all hybrid materials irrespective of the rGO concentration, when compared to the pristine conjugated copolymers, was estimated through the UV-Vis spectroscopy indicating a differentiation on the optical properties. Through voltammetric experiments the oxidation and reduction potentials were determined and the calculated HOMO and LUMO levels revealed a decrease on the electrochemical energy gap for low rGO concentrations. The study indicates the potential of the hybrid materials consisting of graphene oxide and high band gap conjugated copolymers for applications related to organic solar cells.
Polyesters Incorporating Gallic Acid as Oxygen Scavenger in Biodegradable Packaging
Authors: Sonchaeng Uruchaya , Promsorn Juthathip , Bumbudsanpharoke Nattinee , Chonhenchob Vanee , Sablani Shyam S. , Harnkarnsujarit Nathdanai
Published: December 2022

Biodegradable polyesters polybutylene succinate (PBS) and polybutylene adipate-co-terephthalate (PBAT) were blended with gallic acid (GA) via cast extrusion to produce oxygen scavenging polymers. The effects of polyesters and GA contents (5 to 15%) on polymer/package properties were investigated. Increasing GA formed non-homogeneous microstructures and surface roughness due to immiscibility. GA had favorable interaction with PBAT than PBS, giving more homogeneous microstructures, reduced mechanical relaxation temperature, and modified X-ray diffraction and crystalline morphology of PBAT polymers. Non-homogenous dispersion of GA reduced mechanical properties and increased water vapor and oxygen permeability by two and seven folds, respectively. Increasing amounts of GA and higher humidity enhanced oxygen absorption capacity, which also depended on the dispersion characteristics of GA in the matrices. PBAT gave higher oxygen absorption than PBS due to better dispersion and higher reactive surface area. GA blended with PBAT and PBS increased oxygen scavenging activity as sustainable active food packaging using functional biodegradable polymers.
Hyperbranched Polyester Polyfumaratomaleate Doped with Gd(III) and Dy(III) Ions: Synthesis, Structure and Properties
Authors: Maksimov Aleksei , Vagapova Alina , Kutyreva Marianna , Kutyrev Gennadii
Published: December 2022

For the first time, metal–polymer complexes have been synthesized using hyperbranched polyester polyfumaratomaleate as a matrix, the structure of which has been established by 1H NMR, IR, electron spectroscopy, and elemental analysis methods. The formation of complexes with Gd(III) and Dy(III) ions involving fumarate and maleate groups of the polyester was proved by IR and electron spectroscopy methods. It was established that the structure of the coordination units has the form of a square antiprism. The compositions and conditional logarithms of the stability constants of the complexes were determined. It was established that complexation with lanthanide ions promotes emission enhancement in the ligand.
Evaluating the Mechanical and Tribological Properties of 3D Printed Polylactic-Acid (PLA) Green-Composite for Artificial Implant: Hip Joint Case Study
Authors: Fouly Ahmed , Assaifan Abdulaziz , Alnaser Ibrahim , Hussein Omar , Abdo Hany
Published: December 2022

Artificial implants are very essential for the disabled as they are utilized for bone and joint function in orthopedics. However, materials used in such implants suffer from restricted mechanical and tribological properties besides the difficulty of using such materials with complex structures. The current study works on developing a new polymer green composite that can be used for artificial implants and allow design flexibility through its usage with 3D printing technology. Therefore, a natural filler extracted from corn cob (CC) was prepared, mixed homogeneously with the Polylactic-acid (PLA), and passed through a complete process to produce a green composite filament suit 3D printer. The corn cob particles were incorporated with PLA with different weight fractions zero, 5%, 10%, 15%, and 20%. The physical, mechanical, and tribological properties of the PLA-CC composites were evaluated. 3D finite element models were constructed to evaluate the PLA-CC composites performance on a real condition implant, hip joints, and through the frictional process. Incorporating corn cob inside PLA revealed an enhancement in the hardness (10%), stiffness (6%), compression ultimate strength (12%), and wear resistance (150%) of the proposed PLA-CC composite. The finite element results of both models proved an enhancement in the load-carrying capacity of the composite. The finite element results came in line with the experimental results.
High-Efficiency Carbon Fiber Recovery Method and Characterization of Carbon FIBER-Reinforced Epoxy/4,4′-Diaminodiphenyl Sulfone Composites
Authors: Lee Yong-Min , Kim Kwan-Woo , Kim Byung-Joo
Published: December 2022

Globally, the demand for carbon fiber-reinforced thermosetting plastics for various applications is increasing. As a result, the amount of waste from CFRPs is increasing every year, and the EU Council recommends recycling and reuse of CFRPs. Epoxy resin (EP) is used as a matrix for CFRPs, and amine hardeners are mainly used. However, no research has been conducted on recycling EP/4,4’-diaminodiphenyl sulfone (DDS)-based CFRP. In this study, the effect of steam and air pyrolysis conditions on the mechanical properties of re-cycled carbon fiber (r-CF) recovered from carbon fiber-reinforced thermosetting (epoxy/4,4′-diaminodiphenyl sulfone) plastics (CFRPs) was investigated. Steam pyrolysis enhanced resin degradation relative to N2. The tensile strength of the recovered r-CF was reduced by up to 35.12% due to oxidation by steam or air. However, the interfacial shear strength (IFSS) tended to increase by 9.18%, which is considered to be due to the increase in functional groups containing oxygen atoms and the roughness of the surface due to oxidation. The recycling of CFRP in both a steam and an air atmosphere caused a decrease in the tensile strength of r-CF. However, they were effective methods to recover r-CF that had a clean surface and increased IFSS.
Production of 3D Printed Bi-Layer and Tri-Layer Sandwich Scaffolds with Polycaprolactone and Poly (vinyl alcohol)-Metformin towards Diabetic Wound Healing
Authors: Harmanci Sena , Dutta Abir , Cesur Sumeyye , Sahin Ali , Gunduz Oguzhan , Kalaskar Deepak M. , Ustundag Cem Bulent
Published: December 2022

Type 2 diabetes mellitus (T2DM) is a chronic disease characterized by impaired insulin secretion, sensitivity, and hyperglycemia. Diabetic wounds are one of the significant complications of T2DM owing to its difficulty in normal healing, resulting in chronic wounds. In the present work, PCL/PVA, PCL/PVA/PCL, and metformin-loaded, PCL/PVA-Met and PCL/PVA-Met/PCL hybrid scaffolds with different designs were fabricated using 3D printing. The porosity and morphological analysis of 3D-printed scaffolds were performed using scanning electron microscopy (SEM). The scaffolds’ average pore sizes were between 63.6 ± 4.0 and 112.9 ± 3.0 μm. Molecular and chemical interactions between polymers and the drug were investigated with Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Mechanical, thermal, and degradation analysis of the scaffolds were undertaken to investigate the physico-chemical characteristics of the scaffolds. Owing to the structure, PCL/PVA/PCL sandwich scaffolds had lower degradation rates than the bi-layer scaffolds. The drug release of the metformin-loaded scaffolds was evaluated with UV spectrometry, and the biocompatibility of the scaffolds on fibroblast cells was determined by cell culture analysis. The drug release in the PCL/PVA-Met scaffold was sustained till six days, whereas in the PCL/PVA-Met/PCL, it continued for 31 days. In the study of drug release kinetics, PCL/PVA-Met and PCL/PVA-Met/PCL scaffolds showed the highest correlation coefficients (R2) values for the first-order release model at 0.8735 and 0.889, respectively. Since the layered structures in the literature are mainly obtained with the electrospun fiber structures, these biocompatible sandwich scaffolds, produced for the first time with 3D-printing technology, may offer an alternative to existing drug delivery systems and may be a promising candidate for enhancing diabetic wound healing.
Liquid Fraction Effect on Foam Flow through a Local Obstacle
Authors: Stennikova Oksana , Shmakova Natalia , Carrat Jean-Bastien , Ermanyuk Evgeny
Published: December 2022

An experimental study of quasi-two-dimensional liquid foams with varying liquid fractions is presented. Experiments are conducted in a Hele-Shaw cell with a local permeable obstacle placed in the center and filling 35, 60 and 78% of the cell gap. Foam velocity is calculated using a standard cross-correlation algorithm. Estimations of the liquid fraction of the foam are performed using a new simplified method based on a statistical analysis of foam cell structures. The pattern of the foam velocity field varies with increasing liquid fraction, responsible for significant variation of the foam’s rheology. The local permeability decreases with increasing obstacle height and liquid fraction. In case of high liquid fraction (5.8×10−2), the permeability coefficient tends to zero for obstacles filling more than 78% of the cell gap.
Biobased Castor Oil-Based Polyurethane Foams Grafted with Octadecylsilane-Modified Diatomite for Use as Eco-Friendly and Low-Cost Sorbents for Crude Oil Clean-Up Applications
Authors: Perera Helanka J. , Goyal Anjali , Alhassan Saeed M. , Banu Hussain
Published: December 2022

Herein we report the synthesis and characterization of novel castor oil-based polyurethane (PU) foam functionalized with octadecyltrichlorosilane (C18)-modified diatomaceous earth (DE) particles, exhibiting superior hydrophobicity and oil adsorption, and poor water absorption, for use in effective clean-up of crude oil spillage in water bodies. High-performance and low-cost sorbents have a tremendous attraction in oil spill clean-up applications. Recent studies have focused on the use of castor oil as a significant polyol that can be used as a biodegradable and eco-friendly raw material for the synthesis of PU. However, biobased in-house synthesis of foam modified with C18-DE particles has not yet been reported. This study involves the synthesis of PU using castor oil, further modification of castor oil-based PU using C18 silane, characterization studies and elucidation of oil adsorption capacity. The FTIR analysis confirmed the fusion of C18 silane particles inside the PU skeleton by adding the new functional group, and the XRD study signified the inclusion of crystalline peaks in amorphous pristine PU foam owing to the silane cross-link structure. Thermogravimetric analysis indicated improvement in thermal stability and high residual content after chemical modification with alkyl chain moieties. The SEM and EDX analyses showed the surface’s roughness and the incorporation of inorganic and organic elements into pristine PU foam. The contact angle analysis showed increased hydrophobicity of the modified PU foams treated with C18-DE particles. The oil absorption studies showed that the C18-DE-modified PU foam, in comparison with the unmodified one, exhibited a 2.91-fold increase in the oil adsorption capacity and a 3.44-fold decrease in the water absorbing nature. From these studies, it is understood that this novel foam can be considered as a potential candidate for cleaning up oil spillage on water bodies.
Structural Characterization and Glycosaminoglycan Impurities Analysis of Chondroitin Sulfate from Chinese Sturgeon
Authors: Zhao Mei , Qin Yong , Fan Ying , Wang Xu , Yi Haixin , Cui Xiaoyu , Li Fuchuan , Wang Wenshuang
Published: December 2022

Chinese sturgeon was an endangered cartilaginous fish. The success of artificial breeding has promoted it to a food fish and it is now beginning to provide a new source of cartilage for the extraction of chondroitin sulfate (CS). However, the structural characteristics of sturgeon CS from different tissues remain to be determined in more detail. In this study, CSs from the head, backbone, and fin cartilage of Chinese sturgeon were individually purified and characterized for the first time. The molecular weights, disaccharide compositions, and oligosaccharide sulfation patterns of these CSs are significantly different. Fin CS (SFCS), rich in GlcUAα1-3GalNAc(4S), has the biggest molecular weight (26.5 kDa). In contrast, head CS (SHCS) has a molecular weight of 21.0 kDa and is rich in GlcUAα1-3GalNAc(6S). Most features of backbone CS (SBCS) are between the former two. Other glycosaminoglycan impurities in these three sturgeon-derived CSs were lower than those in other common commercial CSs. All three CSs have no effect on the activity of thrombin or Factor Xa in the presence of antithrombin III. Hence, Chinese sturgeon cartilage is a potential source for the preparation of CSs with different features for food and pharmaceutical applications.
High Multi-Environmental Mechanical Stability and Adhesive Transparent Ionic Conductive Hydrogels Used as Smart Wearable Devices
Authors: Wu Yuxuan , Liu Jing , Chen Zhen , Chen Yujie , Chen Wenzheng , Li Hua , Liu Hezhou
Published: December 2022

Ionic conductive hydrogels used as flexible wearable sensor devices have attracted considerable attention because of their easy preparation, biocompatibility, and macro/micro mechanosensitive properties. However, developing an integrated conductive hydrogel that combines high mechanical stability, strong adhesion, and excellent mechanosensitive properties to meet practical requirements remains a great challenge owing to the incompatibility of properties. Herein, we prepare a multifunctional ionic conductive hydrogel by introducing high-modulus bacterial cellulose (BC) to form the skeleton of double networks, which exhibit great mechanical properties in both tensile (83.4 kPa, 1235.9% strain) and compressive (207.2 kPa, 79.9% strain) stress–strain tests. Besides, the fabricated hydrogels containing high-concentration Ca2+ show excellent anti-freezing (high ionic conductivities of 1.92 and 0.36 S/m at room temperature and −35 ∘C, respectively) properties. Furthermore, the sensing mechanism based on the conductive units and applied voltage are investigated to the benefit of the practical applications of prepared hydrogels. Therefore, the designed and fabricated hydrogels provide a novel strategy and can serve as candidates in the fields of sensors, ionic skins, and soft robots.
Strategies for Improved Wettability of Polyetheretherketone (PEEK) Polymers by Non-Equilibrium Plasma Treatment
Authors: Primc Gregor
Published: December 2022

Polyetheretherketone (PEEK) is the material of choice in several applications ranging from the automotive industry to medicine, but the surface properties are usually not adequate. A standard method for tailoring surface properties is the application of gaseous plasma. The surface finish depends enormously on the processing parameters. This article presents a review of strategies adapted for improved wettability and adhesion of PEEK. The kinetics of positively charged ions, neutral reactive plasma species, and vacuum ultraviolet radiation on the surface finish are analyzed, and synergies are stressed where appropriate. The reviewed articles are critically assessed regarding the plasma and surface kinetics, and the surface mechanisms are illustrated. The directions for obtaining optimal surface finish are provided together with the scientific explanation of the limitations of various approaches. Super-hydrophilic surface finish is achievable by treatment with a large dose of vacuum ultraviolet radiation in the presence of oxidizing gas. Bombardment with positively charged ions of kinetic energy between about 100 and 1000 eV also enable high wettability, but one should be aware of excessive heating when using the ions.
Structure and Properties of Epoxy Polysulfone Systems Modified with an Active Diluent
Authors: Petrova Tuyara V. , Tretyakov Ilya V. , Kireynov Alexey V. , Shapagin Alexey V. , Budylin Nikita Yu. , Alexeeva Olga V. , Beshtoev Betal Z. , Solodilov Vitaliy I. , Yurkov Gleb Yu. , Berlin Alexander Al.
Published: December 2022

An epoxy resin modified with polysulfone (PSU) and active diluent furfuryl glycidyl ether (FGE) was studied. Triethanolaminotitanate (TEAT) and iso-methyltetrahydrophthalic anhydride (iso-MTHPA) were used as curing agents. It is shown that during the curing of initially homogeneous mixtures, heterogeneous structures are formed. The type of these structures depends on the concentration of active diluent and the type of hardener. The physico-mechanical properties of the hybrid matrices are determined by the structure formed. The maximum resistance to a growing crack is provided by structures with a thermoplastic-enriched matrix-interpenetrating structures. The main mechanism for increasing the energy of crack propagation is associated with the implementation of microplasticity of extended phases enriched in polysulfone and their involvement in the fracture process.
Theoretical Analysis of the Movement Law of Top Coal and Overburden in a Fully Mechanized Top-Coal Caving Face with a Large Mining Height
Authors: Li Li , Zhang Xiao , Luo Jianqiao , Hu Bin
Published: December 2022

In recent years, with the rapid development of equipment manufacturing and advances in the research on mine pressure and rock mechanics, large-mining-height comprehensive mechanized coal mining technology has become increasingly widely used in thick-seam mining. On this basis, because the free space extracted is several times that of layered mining, the occurrence of strong ground pressure caused by the violent movement of the basic roof and the low recovery rate of the top coal have become the main problems. In this study, Dong Liang Coal Mine was taken as the engineering background by which to study the three typical movement forms of the basic roof, and the critical fracture conditions of the three forms were obtained through theoretical calculations. The movement result state of the basic roof strata was taken as the different overlying boundary conditions of the top coal to simulate its impact on the recovery rate, to explore the interaction mechanism between the basic roof strata and the top coal, and for use as a theoretical basis to guide engineering practice to improve energy recovery rates and safety efficiency.
Numerical Investigation of Fracture Morphology Characteristics in Heterogeneous Reservoirs
Authors: Cao Yuling , He Qiangsheng , Liu Chuang
Published: December 2022

Highly heterogeneous glutenite reservoirs with large amounts of gravel and weak interfaces pose a great challenge to predicting the trajectory of hydraulic fractures during the fracturing process. Based on the phase field method, a fully coupled numerical model of hydraulic fracturing is established. This paper is devoted to investigating the variation in the overall expansion pattern of hydraulic fractures in reservoirs considering randomly distributed gravel and weak interfaces. The numerical results demonstrate that the existence of gravel and a weak interface could alter the extending paths of the hydraulic fractures as well as the value of critical bifurcation injection rate. As the fracture energy of the weak interface is large enough, the hydraulic fracture tends to cross the gravel and the weak interface between the rock matrix and the gravel, forming a planar fracture. Deflection and branching of the hydraulic fracture are more likely to occur in reservoirs containing large gravels. The presented results extend the understanding of fractures propagating in heterogeneous reservoirs.
Ubuntu Philosophy and Mandatory Measles Vaccinations for Children
Authors: Sarangarajan Ruach , Ewuoso Cornelius
Published: December 2022

This is a primarily normative paper that draws on the thinking about friendliness grounded in an Afro-communitarian (Ubuntu) philosophy to argue for measles vaccine mandates for children below 6 years old under the assumptions that measles vaccines are safe for children in this age group, are widely available, and that children in this age-group experiences two-tiered vulnerability. Suppose the ethic of friendliness grounded in this Afro-communitarian philosophy requires us to be friendly to those who are friendly and unfriendly to a proportional degree to those who fail to be friendly. In that case, we are justified in mandating parents and guardians to vaccinate their children. Studies must research the concrete forms that measles vaccine mandates can take in African contexts.
Visualizing the Invisible Body: Redefining Shanshui and the Human Body in the Daoist Context
Authors: Liu Ziyun
Published: December 2022

This paper addresses the “invisible body in shanshui paintings” by redefining the correlation between shanshui and the human body in the Daoist context. I argue that the human body is not invisible in shanshui painting—it is ever-present through the agency of the shanshui. The correlation will be unpacked in two aspects. Firstly, shanshui is ontologically connected and shares a “corporeal” affinity with the bodies of human beings. Secondly and more importantly, with the development of inner alchemy (neidan 內丹), shanshui and the human body are identified as representative of one another. Shanshui becomes the body through the lens of the unique concept of neijing 內景 (inner landscape). As the powerful and redemptive mediation between human beings and the Dao, shanshui reveals not only the inner body but also the mechanism of inner energies. Furthermore, it offers a solution to solve the Daoist anxiety over the body’s physical limitations by breaking down the constant confrontation and opposition between the “I” and the cosmos and reactivating one’s primordial dependency on nature. Shanshui painting, in this vein, transcends the mundane body and provides access to the sacred truth and reality of the Dao.
Resource Conservation as the Main Factor in Increasing the Resource Efficiency of Russian Gas Companies
Authors: Vazhenina Larisa , Magaril Elena , Mayburov Igor
Published: December 2022

The complex modern trends in the growth of the consumption of raw hydrocarbon materials around the world, and as a consequence their accelerated depletion, have forced oil and gas industry enterprises to identify progressive resource-saving methods and technologies. Such methods could enable the environmental and technological effects of production processes to be achieved under conditions of sustainable economic development and with a policy of balanced consumption and resource provision. This research is devoted to the improvement of the scientific and methodological foundations and the development of predictive and analytical tools for assessing the efficiency of resource use in gas industry enterprises. With the application of the proposed instruments, we carry out simulation modeling of the efficiency of natural gas production, processing and pipeline transportation companies. In the course of a comparative analysis of the efficiency indicators for Russian gas companies, a resource-efficient variant of their development is selected and the most promising business projects are identified. Three branch companies of the Russian gas industry are accepted as the objects of the research in this study. As a result of the conducted approbation process, it is revealed that the existing practice of assessing consumption and resource provision in companies in the industry, as well as the use of methods and approaches to resource conservation, does not have a single and complex character. The methodology proposed by the authors makes it possible to approach industry companies with the same set of indicators, systematize and calculate them, identify existing unused reserves for resource conservation and identify promising resource-efficient projects.
Development of a SEM-EDS-XRD Protocol for the Physicochemical and Automated Mineralogical Characterisation of Coal Dust Particles
Authors: Kamanzi Conchita , Becker Megan , Von Holdt Johanna , Broadhurst Jennifer
Published: December 2022

Exposure to coal dust from mining-related activities has historically been linked to several preventable but incurable respiratory diseases. Although the findings of numerous biological studies have determined that the physicochemical and mineralogical aspects of dust particles greatly influence both cytotoxic and proinflammatory pathways, robust datasets which quantitatively define these characteristics of coal dust remain limited. This study aims to develop a robust characterisation routine applicable for real-world coal dust, using an auto-SEM-EDS system. In doing so, the study addresses both the validation of the particle mineralogical scans and the quantification of a range of coal particle characteristics relevant to respiratory harm. The findings presented demonstrate the application of auto-SEM-EDS-XRD systems to analyse and report on the physicochemical and mineralogical characteristics of thousands of dust-sized particles. Furthermore, by mineralogically mapping the particles, parameters such as liberation, mineral association and elemental distribution can be computed to understand the relationships between elements and minerals in the particles, which have yet to be quantified by other studies.
Place Recognition with Memorable and Stable Cues for Loop Closure of Visual SLAM Systems
Authors: Islam Rafiqul , Habibullah Habibullah
Published: December 2022

Visual Place Recognition (VPR) is a fundamental yet challenging task in Visual Simultaneous Localization and Mapping (V-SLAM) problems. The VPR works as a subsystem of the V-SLAM. VPR is the task of retrieving images upon revisiting the same place in different conditions. The problem is even more difficult for agricultural and all-terrain autonomous mobile robots that work in different scenarios and weather conditions. Over the last few years, many state-of-the-art methods have been proposed to solve the limitations of existing VPR techniques. VPR using bag-of-words obtained from local features works well for a large-scale image retrieval problem. However, the aggregation of local features arbitrarily produces a large bag-of-words vector database, limits the capability of efficient feature learning, and aggregation and querying of candidate images. Moreover, aggregating arbitrary features is inefficient as not all local features equally contribute to long-term place recognition tasks. Therefore, a novel VPR architecture is proposed suitable for efficient place recognition with semantically meaningful local features and their 3D geometrical verifications. The proposed end-to-end architecture is fueled by a deep neural network, a bag-of-words database, and 3D geometrical verification for place recognition. This method is aware of meaningful and informative features of images for better scene understanding. Later, 3D geometrical information from the corresponding meaningful features is computed and utilised for verifying correct place recognition. The proposed method is tested on four well-known public datasets, and Micro Aerial Vehicle (MAV) recorded dataset for experimental validation from Victoria Park, Adelaide, Australia. The extensive experimental results considering standard evaluation metrics for VPR show that the proposed method produces superior performance than the available state-of-the-art methods.
Gecko-Inspired Adhesive Mechanisms and Adhesives for Robots—A Review
Authors: Sikdar Soumya , Rahman Md Hafizur , Siddaiah Arpith , Menezes Pradeep L.
Published: December 2022

Small living organisms such as lizards possess naturally built functional surface textures that enable them to walk or climb on versatile surface topographies. Bio-mimicking the surface characteristics of these geckos has enormous potential to improve the accessibility of modern robotics. Therefore, gecko-inspired adhesives have significant industrial applications, including robotic endoscopy, bio-medical cleaning, medical bandage tapes, rock climbing adhesives, tissue adhesives, etc. As a result, synthetic adhesives have been developed by researchers, in addition to dry fibrillary adhesives, elastomeric adhesives, electrostatic adhesives, and thermoplastic adhesives. All these adhesives represent significant contributions towards robotic grippers and gloves, depending on the nature of the application. However, these adhesives often exhibit limitations in the form of fouling, wear, and tear, which restrict their functionalities and load-carrying capabilities in the natural environment. Therefore, it is essential to summarize the state of the art attributes of contemporary studies to extend the ongoing work in this field. This review summarizes different adhesion mechanisms involving gecko-inspired adhesives and attempts to explain the parameters and limitations which have impacts on adhesion. Additionally, different novel adhesive fabrication techniques such as replica molding, 3D direct laser writing, dip transfer processing, fused deposition modeling, and digital light processing are encapsulated.
Airborne Kite Tether Force Estimation and Experimental Validation Using Analytical and Machine Learning Models for Coastal Regions
Authors: Castelino Roystan Vijay , Kashyap Yashwant , Kosmopoulos Panagiotis
Published: December 2022

Wind power can significantly contribute to the transition from fossil fuels to renewable energies. Airborne Wind Energy (AWE) technology is one of the approaches to tapping the power of high-altitude wind. The main purpose of a ground-based kite power system is to estimate the tether force for autonomous operations. The tether force of a particular kite depends on the wind velocity and the kite’s orientation to the wind vector in the figure-eight trajectory. In this paper, we present an experimental measurement of the pulling force of an Airush Lithium 12 m2 kite with a constant tether length of 24 m in a coastal region. We obtain the position and orientation data of the kite from the sensors mounted on the kite. The flight dynamics of the kite are studied using multiple field tests under steady and turbulent wind conditions. We propose a physical model (PM) using Artificial Neural Network (ANN) and Long Short-Term Memory (LSTM) deep neural network algorithms to estimate the tether force in the experimental validation. The performance study using the root mean square error (RMSE) method shows that the LSTM model performs better, with overall error values of 126 N and 168 N under steady and turbulent wind conditions.
High-Resolution Deformation Monitoring from DInSAR: Implications for Geohazards and Ground Stability in the Metropolitan Area of Santiago, Chile
Authors: Orellana Felipe , Moreno Marcos , Yáñez Gonzalo
Published: December 2022

Large urban areas are vulnerable to various geological hazards and anthropogenic activities that affect ground stability—a key factor in structural performance, such as buildings and infrastructure, in an inherently expanding context. Time series data from synthetic aperture radar (SAR) satellites make it possible to identify small rates of motion over large areas of the Earth’s surface with high spatial resolution, which is key to detecting high-deformation areas. Santiago de Chile’s metropolitan region comprises a large Andean foothills basin in one of the most seismically active subduction zones worldwide. The Santiago basin and its surroundings are prone to megathrust and shallow crustal earthquakes, landslides, and constant anthropogenic effects, such as the overexploitation of groundwater and land use modification, all of which constantly affect the ground stability. Here, we recorded ground deformations in the Santiago basin using a multi-temporal differential interferometric synthetic aperture radar (DInSAR) from Sentinel 1, obtaining high-resolution ground motion rates between 2018 and 2021. GNSS stations show a constant regional uplift in the metropolitan area (~10 mm/year); meanwhile, DInSAR allows for the identification of areas with anomalous local subsistence (rates < −15 mm/year) and mountain sectors with landslides with unprecedented detail. Ground deformation patterns vary depending on factors such as soil type, basin geometry, and soil/soil heterogeneities. Thus, the areas with high subsidence rates are concentrated in sectors with fine sedimentary cover and a depressing shallow water table as well as in cropping areas with excess water withdrawal. There is no evidence of detectable movement on the San Ramon Fault (the major quaternary fault in the metropolitan area) over the observational period. Our results highlight the mechanical control of the sediment characteristics of the basin and the impact of anthropogenic processes on ground stability. These results are essential to assess the stability of the Santiago basin and contribute to future infrastructure development and hazard management in highly populated areas.
DiTBN: Detail Injection-Based Two-Branch Network for Pansharpening of Remote Sensing Images
Authors: Wang Wenqing , Zhou Zhiqiang , Zhang Xiaoqiao , Lv Tu , Liu Han , Liang Lili
Published: December 2022

Pansharpening is one of the main research topics in the field of remote sensing image processing. In pansharpening, the spectral information from a low spatial resolution multispectral (LRMS) image and the spatial information from a high spatial resolution panchromatic (PAN) image are integrated to obtain a high spatial resolution multispectral (HRMS) image. As a prerequisite for the application of LRMS and PAN images, pansharpening has received extensive attention from researchers, and many pansharpening methods based on convolutional neural networks (CNN) have been proposed. However, most CNN-based methods regard pansharpening as a super-resolution reconstruction problem, which may not make full use of the feature information in two types of source images. Inspired by the PanNet model, this paper proposes a detail injection-based two-branch network (DiTBN) for pansharpening. In order to obtain the most abundant spatial detail features, a two-branch network is designed to extract features from the high-frequency component of the PAN image and the multispectral image. Moreover, the feature information provided by source images is reused in the network to further improve information utilization. In order to avoid the training difficulty for a real dataset, a new loss function is introduced to enhance the spectral and spatial consistency between the fused HRMS image and the input images. Experiments on different datasets show that the proposed method achieves excellent performance in both qualitative and quantitative evaluations as compared with several advanced pansharpening methods.
Editorial for the Special Issue “Advances of Remote Sensing in the Analysis of the Spatial and Temporal Variability of Land Surface”
Authors: Lanfredi Maria , Coluzzi Rosa , Imbrenda Vito , Simoniello Tiziana
Published: December 2022

Land systems have taken a central role in major environmental/climatic issues of the Anthropocene, as they are the result of interacting natural and anthropic processes that are crucial for life on Earth [...]