bluuebunny/crossref_metadata_2025 huggingface dataset:
Biogas Production Potential of Thermophilic Anaerobic Biodegradation of Organic Waste by a Microbial Consortium Identified with Metagenomics
Authors: Kabaivanova Lyudmila , Petrova Penka , Hubenov Venelin , Simeonov Ivan
Published: May 2022

Anaerobic digestion (AD) is a widespread biological process treating organic waste for green energy production. In this study, wheat straw and corn stalks without any harsh preliminary treatment were collected as a renewable source to be employed in a laboratory-scale digester to produce biogas/biomethane. Processes parameters of temperature, pH, total solids, volatile solid, concentration of volatile fatty acids (VFA), and cellulose concentration, were followed. The volume of biogas produced was measured. The impact of organic loading was stated, showing that the process at 55 °C tolerated a higher substrate load, up to 45 g/L. Further substrate increase did not lead to biogas accumulation increase, probably due to inhibition or mass transfer limitations. After a 12-day anaerobic digestion process, cumulative volumes of biogas yields were 4.78 L for 1 L of the bioreactor working volume with substrate loading 30 g/L of wheat straw, 7.39 L for 40 g/L and 8.22 L for 45 g/L. The degree of biodegradation was calculated to be 68.9%, 74% and 72%, respectively. A fast, effective process for biogas production was developed from native wheat straw, with the highest quantity of daily biogas production occurring between day 2 and day 5. Biomethane concentration in the biogas was 60%. An analysis of bacterial diversity by metagenomics revealed that more than one third of bacteria belonged to class Clostridia (32.9%), followed by Bacteroidia (21.5%), Betaproteobacteria (11.2%), Gammaproteobacteria (6.1%), and Alphaproteobacteria (5%). The most prominent genera among them were Proteiniphilum, Proteiniborus, and Pseudomonas. Archaeal share was 1.37% of the microflora in the thermophilic bioreactor, as the genera Methanocorpusculum, Methanobacterium, Methanomassiliicoccus, Methanoculleus, and Methanosarcina were the most abundant. A knowledge of the microbiome residing in the anaerobic digester can be further used for the development of more effective processes in conjunction with theidentified consortium.
Special Issue “Migraine and Headache in Children and Adolescents”
Authors: Genizi Jacob , Guidetti Vincenzo
Published: May 2022

Migraine in developmental age is a common pathology [...]
Study on Influencing Factors of High-Temperature Basic Characteristics of Iron Ore Powder and Optimization of Ore Blending
Authors: Yang Shuangping , Liu Haijin , Sun Haixing , Zhang Tiantian , Liu Shouman
Published: May 2022

In order to explore the reasonable ore blending of low-silicon magnetite in sintering, it I necessary to realize the efficient utilization of low-silicon ore, further reduce cost, and increase yield. In this study, based on the high-temperature basic characteristics of iron ore powder used in the experiment, sinter pot tests were carried out with different low-silicon ore ratios, and the microstructure of the sinter was observed by scanning electron microscopy (SEM) and energy spectrum analysis (EDS) to determine the optimal matching law of low-silicon ore. The result showed that SiO2, Al2O3, and burning loss in iron ore powder composition were positively correlated with its assimilation, whereas MgO and basicity R2 were negatively correlated with the assimilation of iron ore powder. When the ratio of low-silicon ore was not more than 35%, increasing the ratio of hematite improved the liquid production and increased the production of acicular calcium ferrite. Therefore, the optimization of ore blending based on assimilation can improve the quality of sinter and strengthen the sintering process. This study has certain reference significance for the industrial production of low-silica sintering.
Mechanical Properties of the New Generation RACE EVO and R-Motion Nickel–Titanium Instruments
Authors: Basturk Fatima Betul , Özyürek Taha , Uslu Gülşah , Gündoğar Mustafa
Published: May 2022

This study aimed to evaluate and compare the dynamic cyclic fatigue, torsional and bending resistance of two novel RACE EVO (FKG Dentaire SA, La Chaux de Fonds, Switzerland) and R-Motion (FKG) nickel–titanium instruments with traditional RaCe (FKG) instruments. RACE EVO, R-Motion and RaCe instruments with a size of 25 and taper of 0.06 were used. A dynamic cyclic fatigue test was used to assess the time to fracture. The fractured surfaces were further analyzed using scanning electron microscopy at ×350 and ×3000 magnifications. A torsional resistance test was performed to measure the maximum torsional strength and angle of rotation. Phase transformations with temperature were evaluated using differential scanning calorimetry. The results were statistically analyzed with a Kruskal–Wallis test at a 5% significance level. R-Motion had the highest time to fracture and the lowest torsional and bending resistance, whereas RaCe had the lowest time to fracture and the highest torsional and bending resistance (p < 0.05). In relation to the angle of rotation, RACE EVO instruments had the highest deformation capacity followed by R-Motion and RaCe instruments (p < 0.05). The greater cyclic fatigue resistance and lower torsional and bending resistance results indicate that the novel R-Motion and RACE EVO instruments are less rigid and more flexible than RaCe instruments.
Distribution of Hydrogen and Defects in the Zr/Nb Nanoscale Multilayer Coatings after Proton Irradiation
Authors: Laptev Roman , Stepanova Ekaterina , Pushilina Natalia , Svyatkin Leonid , Krotkevich Dmitriy , Lomygin Anton , Ognev Sergei , Siemek Krzysztof , Doroshkevich Aleksandr , Uglov Vladimir
Published: May 2022

Radiation damage is one of the significant factors limiting the operating time of many structural materials working under extreme conditions. One of the promising directions in the development of materials that are resistant to radiation damage and have improved physical and mechanical properties is the creation of nanoscale multilayer coatings (NMCs). The paper is devoted to the experimental comprehension of changes in the defect structure and mechanical properties of nanoscale multilayer coatings (NMCs) with alternating layers of Zr and Nb under irradiation. Series of Zr/Nb NMCs with different thicknesses of individual layers were fabricated by magnetron sputtering and subjected to H+ irradiation. The evolution of structure and phase states, as well as the defect state under proton irradiation, was studied using the methods of high-resolution transmission electron microscopy (HRTEM), X-ray diffraction analysis (XRD), glow discharge optical emission spectroscopy (GDOES), and positron annihilation spectroscopy (PAS). The layer-by-layer analysis of structural defects was carried out by Doppler broadening spectroscopy (DBS) using a variable-energy positron beam. To estimate the binding energy and the energy paths for the hydrogen diffusion in Zr/Nb NMCs, calculations from the first principles were used. When the thickness of individual layers is less than 25 nm, irradiation causes destruction of the interfaces, but there is no significant increase in the defect level, the S parameter (open volume defects amount) before and after irradiation is practically unchanged. After irradiation of NMC Zr/Nb with a thickness of layers 50 and 100 nm, the initial microstructure is retained, and the S parameter is significantly reduced. The GDOES data reveal the irregular H accumulation at the interface caused by significant differences in H diffusion barriers in the bulk of Zr and Nb multilayers as well as near the interface’s region.
Numerical Case Studies about Two-Dimensional CHS Joints with Symmetrical Full-Overlapped Top-Connection
Authors: Heinemann Patrick , Isopescu Dorina-Nicolina
Published: May 2022

Steel joints made out of circular hollow section profiles are used for many fields of applications, such as wide-span or representative halls for airports. By connecting two inclined pipes to a vertical third pipe, a ramified vertical column is created, where the node is the weakest point in the structure due to the geometrical heterogeneity. The current standards and Design Codes have limitations regarding the geometrical properties of hollow sections joints. However, the kind of steel joint presented in this paper is excluded in the current standards. This paper is about numerical FEA case studies of two-dimensional, circular hollow-section joints to figure out the resistance of atypical steel joints. In the first step, a small-scale model is generated to analyze the influence of the inclination. In the second step, the geometries of the different pipes are extended. The influence of the inclination angle and the stability of the joint are analyzed. It was discovered that the inclination angle between the three pipes has a large influence on the stresses and deflections at the node. By increasing the inclination angle, the maximum applied force can be increased. The extended members change the behavior and the stress distribution.
3D Modelling for Photonic Crystal Structure in Papilio maackii Wing Scales
Authors: Yang Shu , Wang Yingwen , Gao Weihong
Published: May 2022

As a typical representative of natural structural colors, the wings of butterflies living in different zones present colors due to different chromogenic mechanisms. In this work, Papilio maackii, a common species of butterfly living in China, was studied in order to clarify the photophysics of its wing scales. A FESEM was applied to observe the microstructure of the scales, and we found that they have a periodic photonic crystal structure. X-ray photoelectron spectroscopy was applied to clarify the wings’ chemical composition. Additionally, the optical properties of the scales were investigated using a UV-vis-NIR microspectrophotometer. Then, a simplified three-dimensional photonic crystal model was built according to the microstructure of the wing scales, and the plane-wave expansion method was used to calculate the band gap. The correlation between the calculated band gap and the practical reflective spectrum was also established for the wing scales of Papilio maackii.
Experimental Analysis of Aerodynamic Loads of Three-Bladed Rotor
Authors: Szmit Zofia , Kloda Lukasz , Kowalczuk Marcin , Stachyra Grzegorz , Warmiński Jerzy
Published: May 2022

The purpose of the current study is the experimental analysis of the dynamics and aerodynamic loads of a three-bladed rotor. The experimental tests focus on the rotation with three different angular velocities; for each angular speed, four different preset angles of beam have been studied. During the laboratory experiment, strain gauges, as well as high-speed cameras, have been used as the measurement system. The images from the high-speed cameras have been used to obtain aerodynamic loads in the form of polynomials, while the signals from strain gauges mounted on each beam allowed us to observe the synchronization phenomenon between beams.
Exploration of Zero-Valent Iron Stabilized Calcium–Silicate–Alginate Beads’ Catalytic Activity and Stability for Perchlorate Degradation
Authors: Jung Yu-Kyung , Narendra Kumar Alam Venugopal , Jeon Byong-Hun , Kim Eun Young , Yum Taewoo , Paeng Ki-Jung
Published: May 2022

Perchlorate contamination in groundwater poses a serious threat to human health, owing to its interference with thyroid function. The high solubility and poor adsorption of perchlorate ions make perchlorate degradation a necessary technology in groundwater contaminant removal. Here, we demonstrate the perchlorate degradation by employing nano zero-valent iron (nZVI) embedded in biocompatible silica alginate hybrid beads fabricated using calcium chloride (1 wt%) as a crosslinker. The concentration of precursors (sodium alginate, sodium silicate) for bead formation was standardized by evaluating the thermal stability of beads prepared at different sodium silicate and alginate concentrations. Thermal degradation of silica alginate hybrid samples showed a stepwise weight loss during the thermal sweep, indicating different types of reactions that occur during the degradation process. The formation of the silica alginate hybrid structure was confirmed by FT-IR spectroscopy. Scanning electron microscopy (SEM) data revealed the surface morphology of silica alginate hybrid changes by varying sodium silicate and alginate concentrations. nZVI-loaded alginate–silicate polymer bead (nZVI-ASB) exhibited excellent perchlorate degradation efficiency by degrading 20 ppm of perchlorate within 4 h. Our study also showed the perchlorate degradation efficiency of nZVI-ASB is maximum at neutral pH conditions.
Effect of Polymer Drag Reducer on Rheological Properties of Rocket Kerosene Solutions
Authors: Guo Xiaodie , Chen Xuejiao , Zhou Wenjing , Wei Jinjia
Published: May 2022

Adding drag reduction agent (DRA) to rocket kerosene is an effective way to reduce the pipeline resistance of rocket kerosene transportation systems. However, so far, there have been few research reports on the effect of DRA on the rheological properties of rocket kerosene solution, especially from a microscopic perspective. In this study, coarse-grained molecular dynamics simulations were conducted to investigate the rheological properties of rocket kerosene solutions with DRAs of different chain lengths and concentrations. The results showed that the viscosity of DRA—kerosene solution is generally higher than that of pure kerosene at a low shear rate, while with an increase in shear rate, the viscosity of DRA—kerosene solution decreases rapidly and finally tends to become similar to that of pure kerosene. The shear viscosity of DRA—kerosene solution increases with an increase in chain length and concentration of polymers. Through observing the morphologic change of DRA molecules and analyzing the radius of gyration and the mean-squared end-to-end distance of polymers, it was confirmed that the rheological properties of DRA—kerosene solutions are strongly related to the degree of entanglement of polymer chains. The simulation results provide microscopic insights into the rheological behavior of DRA—kerosene solutions and clarify the intrinsic relation between the morphologic change of polymer molecules and the rheological properties of DRA—kerosene solutions.
Deformation Behavior, a Flow Stress Model Considering the Contribution of Strain and Processing Maps in the Isothermal Compression of a Near-α Ti–3.3Al–1.5Zr–1.2Mo–0.6Ni Titanium Alloy
Authors: Yu Weixin , Cao Junhui , Hou Shusen , Wang Guanglong , Li Yue , Lang Shaoting
Published: May 2022

In the present study, isothermal compression tests are conducted for a near-α Ti–3.3Al–1.5Zr–1.2Mo–0.6Ni titanium alloy at deformation temperatures ranging from 1073 K to 1293 K and strain rates ranging from 0.01 s−1 to 10 s−1 on a Gleeble-3500 thermomechanical compressor. The results show that, in the initial stage of the compression, the flow stress rapidly increases to a peak value because of elastic deformation, and then the alloy enters the plastic deformation stage and the flow stress slowly decreases with the increase in strain and tends to gradually stabilize. In the plastic deformation stage, the flow stress significantly decreases with the increase in the deformation temperature and the decrease in strain rate. A flow stress model considering the contribution of the strain is established, and the relative error between the calculated and the experimental values is 3.72%. The flow stress model has higher precision and can efficiently predict the flow behavior in the isothermal compression of the alloy. Furthermore, the processing map of the Ti–3.3Al–1.5Zr–1.2Mo–0.6Ni alloy is drawn. Based on the processing map, the influence of process parameters on power dissipation efficiency and stability parameters is analyzed, and the optimized hot working process parameters are pointed out.
Data-Driven Parameter Selection and Modeling for Concrete Carbonation
Authors: Duan Kangkang , Cao Shuangyin
Published: May 2022

Concrete carbonation is known as a stochastic process. Its uncertainties mainly result from parameters that are not considered in prediction models. Parameter selection, therefore, is important. In this paper, based on 8204 sets of data, statistical methods and machine learning techniques were applied to choose appropriate influence factors in terms of three aspects: (1) the correlation between factors and concrete carbonation; (2) factors’ influence on the uncertainties of carbonation depth; and (3) the correlation between factors. Both single parameters and parameter groups were evaluated quantitatively. The results showed that compressive strength had the highest correlation with carbonation depth and that using the aggregate–cement ratio as the parameter significantly reduced the dispersion of carbonation depth to a low level. Machine learning models manifested that selected parameter groups had a large potential in improving the performance of models with fewer parameters. This paper also developed machine learning carbonation models and simplified them to propose a practical model. The results showed that this concise model had a high accuracy on both accelerated and natural carbonation test datasets. For natural carbonation datasets, the mean absolute error of the practical model was 1.56 mm.
Prognostic Factors in Endodontic Surgery Using an Endoscope: A 1 Year Retrospective Cohort Study
Authors: Sukegawa Shintaro , Shimizu Rieko , Sukegawa Yuka , Hasegawa Kazuaki , Ono Sawako , Fujimura Ai , Yamamoto Izumi , Nakano Keisuke , Takabatake Kiyofumi , Kawai Hotaka , Nagatsuka Hitoshi , Furuki Yoshihiko
Published: May 2022

This retrospective study clarified the success rate of endoscopic endodontic surgeries and identified predictors accounting for successful surgeries. In this retrospective study, 242 patients (90 males, 152 females) who underwent endoscopic endodontic surgery at a single general hospital and were diagnosed through follow-up one year later were included. Risk factors were categorized into attributes, general health, anatomy, and surgery. Then, the correlation coefficient was calculated for the success or failure of endodontic surgery for each variable, the odds ratio was calculated for the upper variable, and factors related to the surgical prognosis factor were identified. The success rate of endodontic surgery was 95.3%, showing that it was a highly predictable treatment. The top three correlation coefficients were post, age, and perilesional sclerotic signs. Among them, the presence of posts was the highest, compared with the odds ratio, which was 9.592. This retrospective study revealed the success rate and risk factors accounting for endoscopic endodontic surgeries. Among the selected clinical variables, the presence of posts was the most decisive risk factor determining the success of endodontic surgeries.
Mechanical and Tribological Properties of Ta-N and Ta-Al-N Coatings Deposited by Reactive High Power Impulse Magnetron Sputtering
Authors: Zin Valentina , Montagner Francesco , Deambrosis Silvia Maria , Mortalò Cecilia , Litti Lucio , Meneghetti Moreno , Miorin Enrico
Published: May 2022

In this article, the depositions and functional characterizations of Ta-N and Ta-Al-N coatings for protection purposes, grown by reactive high-power impulse magnetron sputtering onto silicon substrates, are described. Nitride films were grown while changing the substrate polarization voltage (i.e., the applied bias voltage) during the process. Moreover, the effects of adding Al to form a ternary system and the resulting variation of the coatings’ mechanical and tribological properties have been widely investigated by nanoindentation, scratch, and wear tests. Micro-Raman characterization has been applied to the wear tracks to explore the comprehensive tribo-environment and wear mechanism. Interestingly, Ta-Al-N films, despite significantly improved mechanical properties, show a premature failure with respect to Ta-N coatings. The wear mechanisms of Ta-N and Ta-Al-N systems were revealed to be very different. Indeed, Ta-Al-N films suffer higher oxidation phenomena during wear, with the formation of an oxidized surface tribofilm and a reduced wear resistance, while Ta-N coatings undergo plastic deformation at the wear surface, with a slightly adhesive effect.
Treasure on the Earth—Gold Nanoparticles and Their Biomedical Applications
Authors: Milan Justyna , Niemczyk Klaudia , Kus-Liśkiewicz Małgorzata
Published: May 2022

Recent advances in the synthesis of metal nanoparticles (NPs) have led to tremendous expansion of their potential applications in different fields, ranging from healthcare research to microelectronics and food packaging. Among the approaches for exploiting nanotechnology in medicine, gold nanomaterials in particular have been found as the most promising due to their unique advantages, such as in sensing, image enhancement, and as delivery agents. Although, the first scientific article on gold nanoparticles was presented in 1857 by Faraday, during the last few years, the progress in manufacturing these nanomaterials has taken an enormous step forward. Due to the nanoscale counterparts of gold, which exhibit distinct properties and functionality compared to bulk material, gold nanoparticles stand out, in particular, in therapy, imaging, detection, diagnostics, and precise drug delivery. This review summarizes the current state-of-the-art knowledge in terms of biomedical applications of gold nanoparticles. The application of AuNPs in the following aspects are discussed: (i) imaging and diagnosing of specific target; (ii) treatment and therapies using AuNPs; and (iii) drug delivery systems with gold nanomaterials as a carrier. Among the different approaches in medical imaging, here we either consider AuNPs as a contrast agent in computed tomography (CT), or as a particle used in optical imaging, instead of fluorophores. Moreover, their nontoxic feature, compared to the gadolinium-based contrast agents used in magnetic resonance imaging, are shown. The tunable size, shape, and functionality of gold nanoparticles make them great carriers for targeted delivery. Therefore, here, we summarize gold-based nanodrugs that are FDA approved. Finally, various approaches to treat the specific diseases using AuNPs are discussed, i.e., photothermal or photodynamic therapy, and immunotherapy.
Exploration of Carbon Dioxide Curing of Low Reactive Alkali-Activated Fly Ash
Authors: Harirchi Peyman , Yang Mijia
Published: May 2022

In this paper, the effect of carbon curing procedure on low reactive fly ash alkali-activated pastes was investigated. Specimens were cured with pure carbon dioxide (CO2) gas for different curing times under 4 bar pressure. Chemical and physical characteristics of the geopolymer pastes were obtained from mass monitoring, titration test, XRD, FTIR and TGA-DTG analyses. Regarding the test results, after three days of CO2 curing, the highest CO2uptake was obtained at 4.8 wt% of fly ash precursor, with carbon sequestration efficiency at 22.6%. The ratio of carbon dioxide absorbed as efflorescence to the total absorbed CO2 was measured. The results show that at early age, almost 50% of carbonated products appeared as efflorescence; however, by increasing the curing time, and after 3 days of curing, about 80% of carbon dioxide was stored in the matrix. It was found that, in all cases, carbonation curing was detrimental to the geopolymerization process due to a high amount of efflorescence and led to a reduction in the compressive strength. At 24 h and 3 days, the specimens showed a lower reduction in compressive strength in comparison to CO2 samples cured at 3 h, 6 h and 12 h. Regarding the XRD results, calcite was detected in the 24 h and 3 days specimens, which contributes to lower pore sizes due to a higher molar volume and production of silica gel that might participate in the polymerization processes and results in densified microstructures.
Study on the Ignition Mechanism of Inert Fuel Tank Subjected to High-Velocity Impact of Fragments
Authors: Liu Jian , An Fengjiang , Wu Cheng , Zhang Longhui , Zhang Yanxi , Li Yipeng
Published: May 2022

Nowadays, aircraft fuel tanks are protected by measures such as inerting, fire and explosion suppression, which significantly improve their ability to mitigate mechanical damage and prevent fire in the case of an accidental attack. In this study, an equivalent inert fuel tank with fire and explosion suppression was designed according to the vulnerabilities of a typical fighter. Then, a ballistic gun, a 37 mm gun and a two-stage light-gas gun were used to propel different fragments in tank damage experiments at different speeds (1400 m/s–2600 m/s). Experimental results show that the disassembly of a fuel tank is a prerequisite for igniting fuel. When the fragments hit the gas phase of the tank, the fuel tank was not disassembled and the fuel was not ignited. The calculation results show that the internal oxygen concentration was always lower than the limiting oxygen concentration (12%) before the fuel tank was disassembled. In addition, the minimum ignition speeds of inerted fragments with different masses as predicted by the ignition criterion when hitting the liquid fuel are consistent with the test results. This shows that increasing the mass of inert fragments will increase the minimum ignition speed and reduce the probability of ignition of the fuel. However, the implosion effect of the energetic fragments released about 3 times the chemical energy of its own kinetic energy, and the high-temperature and high-pressure products were very beneficial to the disintegration and ignition of the fuel tank compared to inert fragments.
The Effect of Ligature Type on Lateral Tooth Movement during Orthodontic Treatment with Lingual Appliances—An In Vitro Study
Authors: Reichardt Elisabeth , Decker Steffen , Dalstra Michel , Nalabothu Prasad , Steineck Markus , Fernandez Leandro , Verna Carlalberta
Published: May 2022

(1) Background: One of the most challenging parts in lingual orthodontics is the control and correction of the tip of anterior teeth, due to the occlusal open vertical slot of the incisors in lingual systems. The presented experimental in-vitro study was performed to determine the maximal tipping moment of the anterior teeth between two types of lingual brackets, the Incognito™ Appliance System (Incognito, TOP-Service, Bad Essen, Germany) and Tip-Bar™ system (Incognito, TOP-Service, Bad Essen, Germany). Furthermore, twelve different ligation methods and two different ligature materials were investigated. (2) Methods: The measurement was performed by assessing the stiffness and ultimate strength of the ligature in a uniaxial material testing machine (Instron, Norwood, MA, USA) using a 0.025 × 0.018 inch stainless steel wire. (3) The results showed that the highest precision for control tipping of anterior teeth was determined for the 0.010 inch Stainless Steel Tie (Pelz and Partner). Furthermore, the Tip-Bar™ brackets increased the maximal moment by 33.8% for elastic and steel ligatures. (4) Conclusions: The lateral tooth movement is highly dependent on the type of ligature and applied material during orthodontic treatment with lingual appliances. The use of 0.010 inch steel ligatures and the Tip-Bar™ bracket design results in better alignment in the anterior teeth segment.
Effect of Post-Fabricated Aging on Microstructure and Mechanical Properties in Underwater Friction Stir Additive Manufacturing of Al–Zn–Mg–Cu Alloy
Authors: Li Ying , He Changshu , Wei Jingxun , Zhang Zhiqiang , Tian Ni , Qin Gaowu , Zhao Xiang
Published: May 2022

The fabricated Al–Zn–Mg–Cu alloy build has low mechanical properties due to the dissolution of strengthening precipitates back into the matrix during friction stir additive manufacturing (FSAM). Post-fabricated aging was considered an effective approach to improve the mechanical performance of the build. In this study, various post-fabricated aging treatments were applied in the underwater FSAM of Al–7.5 Zn–1.85 Mg–1.3 Cu–0.135 Zr alloy. The effect of the post-fabricated aging on the microstructure, microhardness, and local tensile properties of the build was investigated. The results indicated that over-aging occurred in the low hardness zone (LHZ) of the build after artificial aging at 120 °C for 24 h as the high density of grain boundaries, subgrain boundaries, dislocations, and Al3Zr particles facilitated the precipitation. Low-temperature aging treatment can effectively avoid the over-aging problem. After aging at 100 °C for 48 h, the average microhardness value of the build reached 178 HV; the yield strength of the LHZ and high hardness zone (HHZ) was 453 MPa and 463 MPa, respectively; and the ultimate tensile strength of the LHZ and HHZ increased to 504 MPa and 523 MPa, respectively.
Mechanical and Electrical Properties of Rapid-Strength Reactive Powder Concrete with Assembly Unit of Sulphoaluminate Cement and Ordinary Portland Cement
Authors: Wang Hui , Cai Xin , Rao Chaomin , Wang Kewei , Wang Jianmin
Published: May 2022

Fast-hardening cement can be used to quickly repair concrete constructions. Characterizing mechanical properties by electrical properties is a promising method to evaluate the mechanical performance nondestructively. However, little attention has been paid to this area. In this paper, copper-coated fine-steel-fibers-reinforced reactive powder concrete (RPC) with compound cement was manufactured. The mass ratio of sulphoaluminate and ordinary Portland cement in the compound cement was 1:1. The influence of copper-coated fine steel fibers with the volume increasing from 0 to 3.0% by the total volume of RPC on the working performances (fluidity and setting time), mechanical properties (flexural strength and toughness, drying shrinkage rate and compressive strength) and electrical parameters (AC electrical resistance and AC impedance spectroscopy curves) was investigated. The electron microscope energy spectrum experiment was applied in analyzing the macro properties of RPC. The results exhibited that the increasing volume of steel fibers led to decreasing the fluidity and retarding the setting of RPC. The electrical resistance of RPC decreased in the form of a quartic function with the volume of steel fibers. The steel fibers volume of 1.5% was the percolation threshold value. The specimens cured for 28 days showed higher electrical resistance than the specimens cured for 1 day. The flexural or compressive strength of the specimens satisfied a specific functional relationship with the volume of steel fibers and electrical resistance. The addition of steel fibers led to improving the flexural toughness and decreasing the shrinkage rate. Furthermore, 3.0% steel fibers could improve the flexural toughness by 3.9 times and decrease the shrinkage to 88.3% of the specimens without steel fibers.
Preparation of Organic-Inorganic Coupling Phase Change Materials with Enhanced Thermal Storage Performance via Emulsion Polymerization
Authors: Lv Xifeng , Shen Xuehua , Zhang Luxiang , Wang Yazhou , Wang Fang
Published: May 2022

The serious phase separation in inorganic phase change materials, and easy leakage of organic phase change materials are the main obstacles to the practical batch application of phase change heat storage materials. To solve these problems, in this work, emulsion polymerization is introduced as the method for preparing organic-inorganic coupling phase change material (oic-PCM) with high heat storage performance using polyacrylamide (PAM) as the wall material and organic phase change material of cetyl alcohol as the core material, and diatomite is used as a supporting substrate to absorb inorganic sodium sulfate decahydrate (SSD). A differential scanning calorimeter (DSC), X-ray diffractometer (XRD), dust morphology and dispersion analyzer, and thermal conductivity tester were used to characterize the prepared organic-inorganic coupled phase change materials and investigate their performance. The research results show that when the mass fraction of cetyl alcohol is 68.97%, the mass fraction of emulsifier is 3.38%, and the mass fraction of sodium sulfate decahydrate/diatomite is 3.40%. The phase change latent heat of the organic-inorganic coupled phase change material is as high as 164.13 J/g, and the thermal conductivity reaches up to 0.2061 W/(m·k), which proves that the prepared organic-inorganic coupled phase change material has good heat storage performance, showing its good application prospects.
Bone Regeneration of Critical-Size Calvarial Defects in Rats Using Highly Pressed Nano-Apatite/Collagen Composites
Authors: Hatakeyama Wataru , Taira Masayuki , Sawada Tomofumi , Hoshi Miki , Hachinohe Yuki , Sato Hirotaka , Takafuji Kyoko , Kihara Hidemichi , Takemoto Shinji , Kondo Hisatomo
Published: May 2022

Osteo-conductive bone substitute materials are required in dentistry. In this study, highly pressed nano-hydroxyapatite/collagen (P-nHAP/COL) composites were formed by a hydraulic press. Critical-size bone defects (Φ = 6 mm) were made in the cranial bones of 10-week-old Wistar rats, in which P-nHAP/COL and pressed collagen (P-COL) specimens were implanted. Defect-only samples (DEF) were also prepared. After the rats had been nourished for 3 days, 4 weeks, or 8 weeks, ossification of the cranial defects of the rats was evaluated by micro-computed tomography (micro-CT) (n = 6 each). Animals were sacrificed at 8 weeks, followed by histological examination. On micro-CT, the opacity of the defect significantly increased with time after P-nHAP/COL implantation (between 3 days and 8 weeks, p < 0.05) due to active bone regeneration. In contrast, with P-COL and DEF, the opacity increased only slightly with time after implantation, indicating sluggish bone regeneration. Histological inspections of the defect zone implanted with P-nHAP/COL indicated the adherence of multinucleated giant cells (osteoclasts) to the implant with phagocytosis and fragmentation of P-nHAP/COL, whereas active bone formation occurred nearby. Fluorescent double staining indicated dynamic bone-formation activities. P-nHAP/COL is strongly osteo-conductive and could serve as a useful novel bone substitute material for future dental implant treatments.
Optoelectronic Properties of α-MoO3 Tuned by H Dopant in Different Concentration
Authors: Huang Xi , Xu Xin , Huang Jiawei , Zhang Zheyu , Gao Yujia , Lu Zhengli , Wu Zhenyuan , Luo Tian , Cai Yating , Qu Yating , Liu Pengyi , Hu Cuiying , Shi Tingting , Xie Weiguang
Published: May 2022

The optoelectronic properties of layered α-MoO3 are greatly limited due to its wide band gap and low carrier concentration. The insertion of hydrogen (H) can effectively tune the band structure and carrier concentration of MoO3. Herein, first-principles calculations were performed to unravel the physical mechanism of a H-doped α-MoO3 system. We found that the modulation of the electronic structure of H-doped MoO3 depends on the doping concentration and position of the H atoms. It was found that the band gap decreases at 8% doping concentration due to the strong coupling between Mo-4d and O-2p orbits when H atoms are inserted into the interlayer. More interestingly, the band gap decreases to an extreme due to the Mo-4d orbit when all the H atoms are inserted into the intralayer only, which has a remarkable effect on light absorption. Our research provides a comprehensive theoretical discussion on the mechanism of H-doped α-MoO3 from the doping positions and doping concentrations, and offers useful strategies on doping modulation of the photoelectric properties of layered transition metal oxides.
The Mechanical Behavior of a Screwless Morse Taper Implant–Abutment Connection: An In Vitro Study
Authors: Bagegni Aimen , Weihrauch Vincent , Vach Kirstin , Kohal Ralf
Published: May 2022

The use of screwless Morse taper implant–abutment connections (IAC) might facilitate the clinician’s work by eliminating the mechanical complications associated with the retention screw. The aim of this study is to evaluate the effect of artificial chewing on the long-term stability of screwless Morse taper IACs. Thirty-two implant abutments restored with an upper central incisor zirconia crown were used and divided into four groups according to the implant–abutment assembling manner (C1,H: screw retained (20 Ncm); C2: tapped; or C3: torqued (20 Ncm; the screws were removed before the dynamic loading)). All specimens were subjected to a cyclic loading (98 N) for 10 million chewing cycles. The survived samples were exposed to a pull-off force until failure/disassembling of the connection. All the samples revealed a 100% survival. Regarding the pull-off test, the screw-retained internal hexagonal IAC revealed significantly higher resistance to failure/disassembling (769.6 N) than screwless conical IACs (171.6 N–246 N) (p < 0.0001). The retention forces in the Morse taper groups were not significantly different (p > 0.05). The screw-retained hexagonal IAC showed the highest retention stability. The screw preload/retention in the conical IAC was lost over time in the group where the screws were kept in place during loading. Nevertheless, the screwless Morse taper IACs were stable for an extended service time and might represent a valid form of treatment for single-tooth replacement.
Object Detection via Gradient-Based Mask R-CNN Using Machine Learning Algorithms
Authors: Xavier Alphonse Inbaraj , Villavicencio Charlyn , Macrohon Julio Jerison , Jeng Jyh-Horng , Hsieh Jer-Guang
Published: May 2022

Object detection has received a lot of research attention in recent years because of its close association with video analysis and image interpretation. Detecting objects in images and videos is a fundamental task and considered as one of the most difficult problems in computer vision. Many machine learning and deep learning models have been proposed in the past to solve this issue. In the current scenario, the detection algorithm must calculate from beginning to end in the shortest amount of time possible. This paper proposes a method called GradCAM-MLRCNN that combines Gradient-weighted Class Activation Mapping++ (Grad-CAM++) for localization and Mask Regional Convolution Neural Network (Mask R-CNN) for object detection along with machine learning algorithms. In our proposed method, images are used to train the network, together with masks that shows where the objects are in the image. A bounding box is regressed around the region of interest in most localization networks. Furthermore, just like any classification task, the multi-class log loss is minimized during training. This model enhances the calculation time and speed, as well as the efficiency, which recognizes objects in images accurately by comparing state-of-the-art machine learning algorithms, such as decision tree, Gaussian algorithm, k-means clustering, k-nearest neighbor, and logistic regression. Among these methods, we found logistic regression performed well with an accuracy rate of 98.4%, recall rate of 99.6%, and precision rate of 97.3% with respect to ResNet 152 and VGG 19. Furthermore, we proved the goodness of fit of our proposed model using chi-square statistical method and demonstrated that our solution can achieve great precision while maintaining a fair recall level.
Machine Learning in Disaster Management: Recent Developments in Methods and Applications
Authors: Linardos Vasileios , Drakaki Maria , Tzionas Panagiotis , Karnavas Yannis
Published: May 2022

Recent years include the world’s hottest year, while they have been marked mainly, besides the COVID-19 pandemic, by climate-related disasters, based on data collected by the Emergency Events Database (EM-DAT). Besides the human losses, disasters cause significant and often catastrophic socioeconomic impacts, including economic losses. Recent developments in artificial intelligence (AI) and especially in machine learning (ML) and deep learning (DL) have been used to better cope with the severe and often catastrophic impacts of disasters. This paper aims to provide an overview of the research studies, presented since 2017, focusing on ML and DL developed methods for disaster management. In particular, focus has been given on studies in the areas of disaster and hazard prediction, risk and vulnerability assessment, disaster detection, early warning systems, disaster monitoring, damage assessment and post-disaster response as well as cases studies. Furthermore, some recently developed ML and DL applications for disaster management have been analyzed. A discussion of the findings is provided as well as directions for further research.
A Hybrid Recommendation System of Upcoming Movies Using Sentiment Analysis of YouTube Trailer Reviews
Authors: Sahu Sandipan , Kumar Raghvendra , MohdShafi Pathan , Shafi Jana , Kim SeongKi , Ijaz Muhammad Fazal
Published: May 2022

Movies are one of the integral components of our everyday entertainment. In today’s world, people prefer to watch movies on their personal devices. Many movies are available on all popular Over the Top (OTT) platforms. Multiple new movies are released onto these platforms every day. The recommendation system is beneficial for guiding the user to a choice from among the overloaded contents. Most of the research on these recommendation systems has been conducted based on existing movies. We need a recommendation system for forthcoming movies in order to help viewers make a personalized decision regarding which upcoming new movies to watch. In this article, we have proposed a framework combining sentiment analysis and a hybrid recommendation system for recommending movies that are not yet released, but the trailer has been released. In the first module, we extracted comments about the movie trailer from the official YouTube channel for Netflix, computed the overall sentiment, and predicted the rating of the upcoming movies. Next, in the second module, our proposed hybrid recommendation system produced a list of preferred upcoming movies for individual users. In the third module, we finally were able to offer recommendations regarding potentially popular forthcoming movies to the user, according to their personal preferences. This method fuses the predicted rating and preferred list of upcoming movies from modules one and two. This study used publicly available data from The Movie Database (TMDb). We also created a dataset of new movies by randomly selecting a list of one hundred movies released between 2020 and 2021 on Netflix. Our experimental results established that the predicted rating of unreleased movies had the lowest error. Additionally, we showed that the proposed hybrid recommendation system recommends movies according to the user’s preferences and potentially promising forthcoming movies.
HIFA-LPR: High-Frequency Augmented License Plate Recognition in Low-Quality Legacy Conditions via Gradual End-to-End Learning
Authors: Lee Sung-Jin , Yun Jun-Seok , Lee Eung Joo , Yoo Seok Bong
Published: May 2022

Scene text detection and recognition, such as automatic license plate recognition, is a technology utilized in various applications. Although numerous studies have been conducted to improve recognition accuracy, accuracy decreases when low-quality legacy license plate images are input into a recognition module due to low image quality and a lack of resolution. To obtain better recognition accuracy, this study proposes a high-frequency augmented license plate recognition model in which the super-resolution module and the license plate recognition module are integrated and trained collaboratively via a proposed gradual end-to-end learning-based optimization. To optimally train our model, we propose a holistic feature extraction method that effectively prevents generating grid patterns from the super-resolved image during the training process. Moreover, to exploit high-frequency information that affects the performance of license plate recognition, we propose a license plate recognition module based on high-frequency augmentation. Furthermore, we propose a gradual end-to-end learning process based on weight freezing with three steps. Our three-step methodological approach can properly optimize each module to provide robust recognition performance. The experimental results show that our model is superior to existing approaches in low-quality legacy conditions on UFPR and Greek vehicle datasets.
The Kp,q-Compactness and Kp,q-Null Sequences, and the KKp,q-Approximation Property for Banach Spaces
Authors: Kim Ju Myung
Published: May 2022

Let Kp,q (1≤p,q≤∞ with 1/p+1/q≥1) be the ideal of (p,q)-compact operators. This paper investigates the compactness and null sequences via Kp,q, and an approximation property of the ideal of Kp,q-compact operators.
Multimedia Applications Processing and Computation Resource Allocation in MEC-Assisted SIoT Systems with DVS
Authors: Li Xianwei , Chen Guolong , Zhao Liang , Wei Bo
Published: May 2022

Due to the advancements of information technologies and the Internet of Things (IoT), the number of distributed sensors and IoT devices in the social IoT (SIoT) systems is proliferating. This has led to various multimedia applications, face recognition and augmented reality (AR). These applications are computation-intensive and delay-sensitive and have become popular in our daily life. However, IoT devices are well-known for their constrained computational resources, which hinders the execution of these applications. Mobile edge computing (MEC) has appeared and been deemed a prospective paradigm to solve this issue. Migrating the applications of IoT devices to be executed in the edge cloud can not only provide computational resources to process these applications but also lower the transmission latency between the IoT devices and the edge cloud. In this paper, computation resource allocation and multimedia applications offloading in MEC-assisted SIoT systems are investigated. We aim to optimize the resource allocation and application offloading by jointly minimizing the execution latency of multimedia applications and the consumed energy of IoT devices. The studied problem is a formulation of the total computation overhead minimization problem by optimizing the computational resources in the edge servers. Besides, as the technology of dynamic voltage scaling (DVS) can offer more flexibility for the MEC system design, we incorporate it into the application offloading. Since the studied problem is a mixed-integer nonlinear programming (MINP) problem, an efficient method is proposed to address it. By comparing with the baseline schemes, the theoretic analysis and simulation results demonstrate that the proposed multimedia applications offloading method can improve the performances of MEC-assisted SIoT systems for the most part.
Multiple Periodic Solutions for Odd Perturbations of the Discrete Relativistic Operator
Authors: Jebelean Petru , Şerban Călin
Published: May 2022

We obtain the existence of multiple pairs of periodic solutions for difference equations of type −Δ(Δu(n − 1)1 − |Δu(n − 1)|2)=λg(u(n))(n∈Z), where g:R→R is a continuous odd function with anticoercive primitive, and λ>0 is a real parameter. The approach is variational and relies on the critical point theory for convex, lower semicontinuous perturbations of C1-functionals.
Event-Triggered Consensus Control of Nonlinear Strict Feedback Multi-Agent Systems
Authors: Zhuang Jiaojiao , Li Zhenxing , Hou Zongxiang , Yang Chengdong
Published: May 2022

In this paper, we investigate the event-triggered consensus problems of nonlinear strict feedback MASs under directed graph. Based on the high-gain control technique, we firstly give a state-based event-triggered consensus algorithm and prove that Zeno behavior can be excluded. When the full state information is unavailable, a high-gain observer is given to estimate state information of each agent and an observer-based algorithm is developed. Finally, we give an example to verify the effectiveness of both state-based and observer-based event-triggered consensus algorithms.