bluuebunny/crossref_metadata_2025 huggingface dataset:
Picosecond Pulsed Laser Deposition of Metals and Metal Oxides
Authors: Dikovska Anna , Atanasova Genoveva , Dilova Tina , Baeva Aleksandra , Avdeev Georgi , Atanasov Petar , Nedyalkov Nikolay
Published: September 2023

In this work, we present the fabrication of thin films/nanostructures of metals and metal oxides using picosecond laser ablation. Two sets of experiments were performed: the depositions were carried out in vacuum and in air at atmospheric pressure. The subjects of investigation were the noble metals Au and Pt and the metal oxides ZnO and TiO2. We studied and compared the phase composition, microstructure, morphology, and physicochemical state of the as-deposited samples’ surfaces in vacuum and in air. It was found that picosecond laser ablation performed in vacuum led to the fabrication of thin films with embedded and differently sized nanoparticles. The implementation of the same process in air at atmospheric pressure resulted in the fabrication of porous nanostructures composed of nanoparticles. The ablation of pure Pt metal in air led to the production of nanoparticles with an oxide shell. In addition, more defects were formed on the metal oxide surface when the samples were deposited in vacuum. Furthermore, the laser ablation process of pure Au metal in a picosecond regime in vacuum and in air was theoretically investigated using molecular dynamics simulation.
Nanoarchitectonics in Materials Science: Method for Everything in Materials Science
Authors: Ariga Katsuhiko , Fakhrullin Rawil
Published: September 2023

The history of mankind has been accompanied by the development of materials science [...]
Advanced Self-Healing Ceramics with Controlled Degradation and Repair by Chemical Reaction
Authors: Sekine Nobuhide , Nakao Wataru
Published: September 2023

Controlling the chemical reaction rate concerning degradation and repair is found to be important to design advanced self-healing ceramics. The recovery and degradation behaviors of strength and stiffness were investigated by exposing aqueous solutions of different pH and calcium ion concentrations to the introduced crack on typical self-healing ceramics dispersed with alumina cement as a self-healing agent. The chemical reaction of cement undergoes the following three stages: dissolution of components such as calcium ions, formation of a gel, and formation of final products. Experimental and thermodynamic assessments revealed that even under conditions where the final products are identical (thermodynamic equilibrium), kinetic effects (excessive dissolution of components or insufficient crystal formation) result in strength degradation rather than repair. It was also suggested that the repair function could be enhanced by controlling the nucleation site of the crystals.
Comparative Study on Micro-Grinding Performance of 2.5D Cf/SiCs, 2.5D SiCf/SiCs, and SiC Ceramics
Authors: Wen Quan , Li Yuanfeng , Gong Yadong
Published: September 2023

To investigate the micro-grinding process and performance of 2.5D Cf/SiC composites and 2.5D SiCf/SiC composites in depth, single-factor micro-grinding experiments were conducted by using SiC ceramics as a comparison. Differences in the material removal process, surface microstructure, surface roughness, and grinding force of the three materials under the same grinding parameters were comparatively analyzed. The results indicate that crack propagation is severe during the micro-grinding process of SiC ceramics. The ground surface is uneven, accompanied by pit defects and large surface roughness Ra. However, the presence of reinforcing fibers and interfaces in the two types of composites can inhibit crack propagation or change their extension directions. Therefore, their surfaces are smooth and flat after grinding, with small defects and low surface roughness Ra. In addition, the grinding processes of the two composites are both related to fiber orientation. There are differences in crack propagation paths and fiber fracture positions in the weft fiber layer and the radial fiber layer, which result in different forms of grinding defects. During micro-grinding, the real-time force signals of 2.5D Cf/SiC composites and 2.5D SiCf/SiC composites are relatively stable, while the signals of SiC ceramics have a large number of spikes. The average micro-grinding force of the three materials is: SiC ceramics > 2.5D SiCf/SiC composites > 2.5D Cf/SiC composites.
Metallographic Evaluation of Increased Susceptibility to Intermediate Embrittlement of Engine Valve Forgings Made of NCF 3015 High Nickel and Chromium Steel
Authors: Lachowicz Marzena M. , Zwierzchowski Maciej , Hawryluk Marek , Gronostajski Zbigniew , Janik Marta
Published: September 2023

This paper focused on determining the increased tendency of cracking after the die forging process of high nickel and chromium steel. The increase in carbon content in austenitic nickel–chromium steel promoted the tendency of valve forgings to forging intergranular crack on the valve head. Attention was paid to issues related to the chemical composition of the material to be considered when hot forming nickel–chromium steel components. Optical and scanning electron microscopies were used to examine the microstructure and fracture features of the samples removed from a fractured valve head. The embrittlement was due to microcavity formation at grain boundaries. Creep theory at grain boundaries was used to explain crack formation. The tensile behavior was interpreted from the evolution of the microstructure during deformation and referred to intermediate brittleness to explain the effect of carbon. It was found that the increased carbon content of the nickel–chromium steel and the strong undercooling observed at the edges of the valve head are factors that promote a reduction in grain boundary cohesion and enhance intermediate temperature embrittlement. Finally, it was found that the formation of a heterogeneous structure manifested by the presence of grain boundary M23C6-type carbides in the austenitic matrix was most likely related to the occurring brittleness.
Printing, Debinding and Sintering of 15-5PH Stainless Steel Components by Fused Deposition Modeling Additive Manufacturing
Authors: Chang Gaoyuan , Zhang Xiaoxun , Ma Fang , Zhang Cheng , Xu Luyang
Published: September 2023

Metal FDM technology overcomes the problems of high cost, high energy consumption and high material requirements of traditional metal additive manufacturing by combining FDM and powder metallurgy and realizes the low-cost manufacturing of complex metal parts. In this work, 15-5PH stainless steel granules with a powder content of 90% and suitable for metal FDM were developed. The flowability and formability of the feedstock were investigated and the parts were printed. A two-step (solvent and thermal) debinding process is used to remove the binder from the green part. After being kept at 75 °C in cyclohexane for 24 h, the solvent debinding rate reached 98.7%. Following thermal debinding, the material’s weight decreased by slightly more than 10%. Sintering was conducted at 1300 °C, 1375 °C and 1390 °C in a hydrogen atmosphere. The results show that the shrinkage of the sintered components in the X-Y-Z direction remains quite consistent, with values ranging from 13.26% to 19.58% between 1300 °C and 1390 °C. After sintering at 1390 °C, the material exhibited a relative density of 95.83%, a hardness of 101.63 HRBW and a remarkable tensile strength of 770 MPa. This work realizes the production of metal parts using 15-5PH granules’ extrusion additive manufacturing, providing a method for the low-cost preparation of metal parts. And it provides a useful reference for the debinding and sintering process settings of metal FDM. In addition, it also enriches the selection range of materials for metal FDM.
Experimental Study on the Impact of Using FRP Sheets on the Axial Compressive Performance of Short-Circular Composite Columns
Authors: Liu Jie , Ma Deliang , Dong Feifei , Liu Zhongxiang
Published: September 2023

This paper conducts an experimental study on the axial compressive performance of FRP-steel-concrete composite columns. Nine short columns were produced and evaluated in the study, comprising of three concrete-filled steel tube reference columns and six FRP-steel-concrete composite columns, respectively denoted as “reference columns” and “composite columns”. Two categories of failure modes, including shear failure and waist drum, were observed from the experiments. The failure mode may trend toward waist drum from shear failure as more FRP layers were used. The number of FRP layers had a direct effect on the level of compressive strength attained, with a greater number of layers resulting in a greater increase in compressive strength. Moreover, a greater tensile strength and higher elastic modulus of CFRP sheets are more effective at improving the compressive stiffness of the columns. Finally, a four-stage confinement mechanism for FRP-wrapped steel tube concrete composite columns is proposed and discussed, through which the damage mechanisms of the composite structures are more rationally characterized.
Enhancing Tribo-Mechanical and Corrosion Properties of ADC 12 Alloy Composites through Marble Dust Reinforcement by Squeeze Casting Technique
Authors: Murugadoss Palanivendhan , Jeyaseelan Chandradass
Published: September 2023

This research intends to enhance the tribo-mechanical and corrosion properties of ADC 12 alloys by incorporating marble dust (MD) as a reinforcing element. Composites with varied MD concentrations (0–10 wt%) were fabricated using a squeeze casting process, addressing the limitations of conventional casting techniques. The microstructural analysis confirmed homogeneous MD dispersion within the ADC 12 matrix, facilitating an effective load transfer and solid interfacial bonding. As MD content increased, the experimental density decreased, while porosity increased from 1.22% to 3.97%. Remarkably, adding 4 wt% MD yielded a 20.41%, 17.63%, and 15.75% enhancement in hardness, tensile, and compression strength compared to the as-cast ADC 12. Incorporating MD particles facilitated Orowan strengthening and Hall–Petch strengthening mechanisms, contributing to the observed improvements. The wear rate was reduced by 18.33% with MD content, showing a 17.57% corrosion reduction at 72 h. These outcomes establish the synergistic benefits of ADC 12 squeeze casting with MD reinforcement, delivering superior tribo-mechanical and corrosion properties.
Micro-Injection Molding and Debinding Behavior of Hydroxyapatite/Zirconia Bi-Materials Fabricated by Two-Component Micro-Powder Injection Molding Process
Authors: Basir Al , Muhamad Norhamidi , Sulong Abu Bakar , Amin Muhammad bin Mohamed , Jamadon Nashrah Hani , Radzuan Nabilah Afiqah Mohd
Published: September 2023

The micro-scale joining of two different materials using two-component micro-powder injection molding (2C-µPIM) is an intriguing technique. The formation of defects in bi-materials at different processing stages makes this technique challenging. This study presents the fabrication of defect-free bi-material micro-parts containing hydroxyapatite (HA) and 3 mol% yttria-stabilized zirconia (3YSZ) via 2C-µPIM. Critical powder volume concentrations (CPVCs) of 61.7 vol% and 47.1 vol% were obtained for the HA and 3YSZ powders, respectively. Based on the CPVCs, the optimal loadings for the HA and 3YSZ powders were selected as 60 vol% and 45 vol%, respectively. The HA and 3YSZ feedstocks were prepared by separately mixing the optimal powder contents with low-density polyethylene (LDPE) and palm stearin binders. The feedstocks displayed pseudoplastic behavior, and the lowest ranges of viscosity for the HA and 3YSZ at a temperature of 180 °C were 157.1–1392.5 Pa·s and 726.2–985.5 Pa·s, respectively. The feedstocks were injected to produce green HA/3YSZ micro-sized components. It was found that a solvent debinding temperature of 70 °C removed 60.6% of the palm stearin binder from the sample. In the thermal debinding stage, the open channels that formed in the bi-material sample’s solvent debound at 70 °C and contributed to the removal of 93 to 95% of the binder system. When the debound bi-materials were sintered at 1300 °C, the highest relative density of 96.3% was obtained. The sintering operation revealed a linear shrinkage between 13 and 17% in the sintered HA/3YSZ micro-parts.
Verification of Composite Beam Theory with Finite Element Model for Pretensioned Concrete Members with Prestressing FRP Tendons
Authors: Sha Xin , Davidson James S.
Published: September 2023

Composite beam theory was previously developed to establish an analytical solution for determining the transfer length of prestressed fiber-reinforced polymers (FRP) tendons in pretensioned concrete members. In the present study, a novel finite element (FE) modeling approach is proposed to provide further verification of the developed analytical method. The present FE model takes into account the friction coefficients obtained from pull-out tests on the FRP tendons and prestressed concrete members. Convergence analysis of two numerical simulations with different mesh densities is carried out as well. The results demonstrated that the transfer length predicted by the fine FE model with a friction coefficient of α = 0.3 for high pretension is in good agreement with the measured values and the analytical solutions. The consistency between the analytical solution and FE simulation not only further proves the reliability of composite beam theory but also demonstrates the importance of the bond–slip relationship in predicting the transfer length of pretensioned concrete members prestressed with FRP tendons.
Thermal Shock Behavior of Si3N4/BN Fibrous Monolithic Ceramics
Authors: Chen Qingqing , Zhang Yuan , Zhou Yu , Li Daxin , Ying Guobing
Published: September 2023

To develop materials suitable for aerospace applications, silicon nitride/boron nitride (Si3N4/BN) fibrous monolithic ceramics with varying BN contents were prepared. Employing analytical techniques such as XRD and SEM, coupled with mechanical testing equipment, the influence of BN concentration on the thermal shock resistance of Si3N4/BN fibrous monolithic ceramics was assessed. When the thermal shock differential is less than 800 °C, its residual flexural strength gradually decreases as the thermal shock differential increases. Conversely, when the differential exceeds 1000 °C, the residual flexural strength of the material increases. The residual strength of all samples reached its peak after undergoing a thermal shock assessment at a 1500 °C differential. When the BN mass fraction is 5 wt.%, the residual strength after a thermal shock at a temperature difference of 1500 °C is 387 ± 19 MPa, which is 124% higher than the original strength of the sample that did not undergo thermal shock (25 °C, 311 ± 18 MPa). The oxide layer formed on the thermal shock surface played a role in bridging defects introduced during material surface processing.
Crash Performance of Inward-Inverting Composite Tubes Filled with Foam: Experimentation and Simulation
Authors: Yu Pu , Yu Zhefeng , Zhou Xiang , Xu Wu
Published: September 2023

This study presents a novel shock absorber with an inward-inverting composite foam-filled tube. Under the compression of a pressing cap and the action of an internal inversion cap, the composite tube inverted inward. During the crushing, the fronds of the composite tube compacted the foam, thereby enhancing the energy absorption. Three types of foams were applied to the absorber, and a drop-weight impact test was performed to obtain the assessment parameters. The foam increased the specific energy absorption (SEA) of the composite tube to 103 kJ/kg. Finite-element simulation based on the user-defined material subroutine was performed for the initial failure and stable stages of the crushing, and a foam model was identified through the experimental data. The mean crush force from the simulation agreed with the experimental data, and the SEA maximum error was <7%, thus validating the crush simulation of the proposed shock absorber. The development of the damage modes of the plies was analyzed based on the simulation results, showing a good energy absorption mechanism of this shock absorber.
Highly Efficient SnIn4S8@ZnO Z-Scheme Heterojunction Photocatalyst for Methylene Blue Photodegradation
Authors: Luo Qiang , Sun Changlin , Zhao Juan , Cai Qizhou , Yao Shanshan
Published: September 2023

Building heterojunctions is a promising strategy for the achievement of highly efficient photocatalysis. Herein, a novel SnIn4S8@ZnO Z-scheme heterostructure with a tight contact interface was successfully constructed using a convenient two-step hydrothermal approach. The phase composition, morphology, specific surface area, as well as photophysical characteristics of SnIn4S8@ZnO were investigated through a series of characterization methods, respectively. Methylene blue (MB) was chosen as the target contaminant for photocatalytic degradation. In addition, the degradation process was fitted with pseudo-first-order kinetics. The as-prepared SnIn4S8@ZnO heterojunctions displayed excellent photocatalytic activities toward MB degradation. The optimized sample (ZS800), in which the molar ratio of ZnO to SnIn4S8 was 800, displayed the highest photodegradation efficiency toward MB (91%) after 20 min. Furthermore, the apparent rate constant of MB photodegradation using ZS800 (0.121 min−1) was 2.2 times that using ZnO (0.054 min−1). The improvement in photocatalytic activity could be ascribed to the efficient spatial separation of photoinduced charge carriers through a Z-scheme heterojunction with an intimate contact interface. The results in this paper bring a novel insight into constructing excellent ZnO-based photocatalytic systems for wastewater purification.
Metal Chalcogenide–Hydroxide Hybrids as an Emerging Family of Two-Dimensional Heterolayered Materials: An Early Review
Authors: Mikhlin Yuri , Likhatski Maxim , Borisov Roman , Karpov Denis , Vorobyev Sergey
Published: September 2023

Two-dimensional (2D) materials and phenomena attract huge attention in modern science. Herein, we introduce a family of layered materials inspired by the minerals valleriite and tochilinite, which are composed of alternating “incompatible”, and often incommensurate, quasi-atomic sheets of transition metal chalcogenide (sulfides and selenides of Fe, Fe-Cu and other metals) and hydroxide of Mg, Al, Fe, Li, etc., stacked via electrostatic interaction rather than van der Waals forces. We survey the data available on the composition and structure of the layered minerals, laboratory syntheses of such materials and the effect of reaction conditions on the phase purity, morphology and composition of the products. The spectroscopic results (Mössbauer, X-ray photoelectron, X-ray absorption, Raman, UV-vis, etc.), physical (electron, magnetic, optical and some others) characteristics, a specificity of thermal behavior of the materials are discussed. The family of superconductors (FeSe)·(Li,Fe)(OH) having a similar layered structure is briefly considered too. Finally, promising research directions and applications of the valleriite-type substances as a new class of prospective multifunctional 2D materials are outlined.
Research on Fatigue–Healing Performance of Asphalt Mixture Based on the Semicircular Bending Test
Authors: Wang Lijun , Cheng Peifeng , Zhao Qiang
Published: September 2023

In order to study the self-healing performance of macroscopic fractures of asphalt mixtures, semicircular bending (SCB) tests were used to test 90# base asphalt mixtures, SBS (Styrene–Butadiene–Styrene) modified asphalt mixtures, and SBS + CR (Chloroprene Rubber) composite modified asphalt mixtures. The F-H-F (the asphalt mixture specimen was fatigued for a certain number of times, then healed under certain conditions, and then fatigued until destroyed) test was carried out, and the fatigue life recovery rate of the fatigue test before and after healing was defined as the healing index (HI). The gray correlation analysis method was used to judge the influence degree of influencing factors on fatigue–healing according to the correlation index. The results show the type of asphalt has the most significant influence on the healing ability of the asphalt mixture. In the case of complete healing, the fatigue–healing performance of the SBS + CR composite modified asphalt mixture was the best, followed by the SBS-modified asphalt mixture, and 90# base asphalt. When the healing temperature is close to the softening point of asphalt, the healing performance of 90# base asphalt is better when the healing temperature is low. When the healing time is longer, the healing performance is better, and there is an optimal healing time. The healing index decreased with the increase in the degree of damage. When the degree of damage is too large, the asphalt mixture will be difficult to heal.
Complementary Methods for the Assessment of the Porosity of Laser Additive-Manufactured Titanium Alloy
Authors: Petrișor Silviu Mihai , Savin Adriana , Stanciu Mariana Domnica , Prevorovsky Zdenek , Soare Marian , Nový František , Steigmann Rozina
Published: September 2023

The method of making parts through additive manufacturing (AM) is becoming more and more widespread due to the possibility of the direct manufacturing of components with complex geometries. However, the technology’s capacity is limited by the appearance of micro-cracks/discontinuities during the layer-by-layer thermal process. The ultrasonic (US) method is often applied to detect and estimate the location and size of discontinuities in the metallic parts obtained by AM as well as to identify local deterioration in structures. The Ti6Al4V (Ti64) alloy prepared by AM needed to acquire a high-quality densification if remarkable mechanical properties were to be pursued. Ultrasonic instruments employ a different type of scanning for the studied samples, resulting in extremely detailed images comparable to X-rays. Automated non-destructive testing with special algorithms is widely used in the industry today. In general, this means that there is a trend towards automation and data sharing in various technological and production sectors, including the use of intelligent systems at the initial stage of production that can exclude defective construction materials, prevent the spread of defective products, and identify the causes of certain instances of damage. Placing the non-destructive testing on a completely new basis will create the possibility for a broader analysis of the primary data and thus will contribute to the improvement of both inspection reliability and consistency of the results. The paper aims to present the C-scan method, using ultrasonic images in amplitude or time-of-flight to emphasize discontinuities of Ti64 samples realized by laser powder-bed fusion (L-PBF) technology. The analysis of US maps offers the possibility of information correlation, mainly as to flaws in certain areas, as well as distribution of a specific flaw in the volume of the sample (flaws and pores). Final users can import C-scan results as ASCII files for further processing and comparison with other methods of analysis (e.g., non-linear elastic wave spectroscopy (NEWS), multi-frequency eddy current, and computer tomography), leading to specific results. The precision of the flight time measurement ensures the possibility of estimating the types of discontinuities, including volumetric ones, offering immediate results of the inspection. In situ monitoring allows the detection, characterization, and prediction of defects, which is suitable for robotics. Detailing the level of discontinuities at a certain location is extremely valuable for making maintenance and management decisions.
Low-CO2 Optimization Design of Quaternary Binder Containing Calcined Clay, Slag, and Limestone
Authors: Lin Run-Sheng , Liao Yongpang , Han Yi , Oh Seokhoon , Park Ki-Bong , Yang Hyun-Min , Wang Xiao-Yong , Yang Bo , Meng Li-Yi
Published: September 2023

Blended cement is commonly used for producing sustainable concretes. This paper presents an experimental study and an optimization design of a low-CO2 quaternary binder containing calcined clay, slag, and limestone using the response surface method. First, a Box–Behnken design with three influencing factors and three levels was used for the combination design of the quaternary composite cement. The lower limit of the mineral admixtures was 0%. The upper limits of slag, calcined clay, and limestone powder were 30%, 20%, and 10%, respectively. The water-to-binder ratio (water/binder) was 0.5. Experimental works to examine workability and strength (at 3 and 28 days) were performed for the composite cement. The CO2 emissions were calculated considering binder compositions. A second-order polynomial regression was used to evaluate the experimental results. In addition, a low-CO2 optimization design was conducted for the composite cement using a composite desirability function. The objectives of the optimization design were the target 28-day strength (30, 35, 40, and 45 MPa), target workability (160 mm flow), and low CO2 emissions. The trends of the properties of optimal combinations were consistent with those in the test results. In summary, the proposed optimization design can be used for designing composite cement considering strength, workability, and ecological aspects.
CoxCrFeNiTi High-Entropy Alloys Prepared via Mechanical Alloying and Spark Plasma Sintering for Magnetron Sputtering Coatings
Authors: Manea Ciprian Alexandru , Geambazu Laura Elena , Tălpeanu Dorinel , Marinescu Virgil , Sbârcea Gabriela Beatrice , Pătroi Delia , Udrea Radu Mihail , Lungu Magdalena Valentina , Lucaci Mariana
Published: September 2023

The main objective of this study was to develop a high-entropy alloy (HEA) derived from the CoxCrFeNiTi HEA system (x = 0.5, 1) for protective coatings using the magnetron sputtering method. In order to produce the high-entropy alloy targets required for the magnetron sputtering process, mechanically alloyed metallic powders were consolidated via spark plasma sintering (SPS). The microstructural analysis results of the HEA mixture presented morphology changes after 30 h of alloying, with the particles presenting uniform polygonal shapes and dimensions. Subsequently, 316L stainless steel (SS) specimens were coated via magnetron sputtering, comparing their composition with that of the sputtering targets used for deposition to establish stoichiometry. Microstructural analyses of the SPSed HEAs revealed no defects and indicated a uniform elemental distribution across the surface. Furthermore, the CoCrFeNiTi equiatomic alloy exhibited a nearly stoichiometric composition, both in the coating and the sputtering target. The XRD analysis results indicated that amorphous coatings were obtained for both Co0.5CrFeNiTi and the CoCrFeNiTi HEA, and nanoindentation tests indicated that the CoCrFeNiTi HEA coating presented a hardness of 596 ± 22 HV, compared to the 570 ± 19 HV measured for Co0.5CrFeNiTi, suggesting an improved wear resistance.
Hybrid Machine-Learning-Based Prediction Model for the Peak Dilation Angle of Rock Discontinuities
Authors: Xie Shijie , Yao Rubing , Yan Yatao , Lin Hang , Zhang Peilei , Chen Yifan
Published: September 2023

The peak dilation angle is an important mechanical feature of rock discontinuities, which is significant in assessing the mechanical behaviour of rock masses. Previous studies have shown that the efficiency and accuracy of traditional experimental methods and analytical models in determining the shear dilation angle are not completely satisfactory. Machine learning methods are popular due to their efficient prediction of outcomes for multiple influencing factors. In this paper, a novel hybrid machine learning model is proposed for predicting the peak dilation angle. The model incorporates support vector regression (SVR) techniques as the primary prediction tools, augmented with the grid search optimization algorithm to enhance prediction performance and optimize hyperparameters. The proposed model was employed on eighty-nine datasets with six input variables encompassing morphology and mechanical property parameters. Comparative analysis is conducted between the proposed model, the original SVR model, and existing analytical models. The results show that the proposed model surpasses both the original SVR model and analytical models, with a coefficient of determination (R2) of 0.917 and a mean absolute percentage error (MAPE) of 4.5%. Additionally, the study also reveals that normal stress is the most influential mechanical property parameter affecting the peak dilation angle. Consequently, the proposed model was shown to be effective in predicting the peak dilation angle of rock discontinuities.
A Study of the Structure and Physicochemical Properties of the Mixed Basicity Iron Ore Sinter
Authors: Dmitriev Andrey N. , Vyaznikova Elena A. , Vitkina Galina Yu. , Karlina Antonina I.
Published: September 2023

To study the influence of sinter basicity on the microstructure, phase composition, and physicochemical and metallurgical properties, samples of agglomerates with different basicities were sintered and investigated. A comprehensive study of the structure, composition, chemical, and metallurgical properties of the sinter was conducted, and the optimum values for these properties were determined. The results of the mineralogical transformations that occurred during the sintering process are also presented. The magnetite contained in the concentrate partially dissolves in the silicate component and flux during agglomeration, forming a complex silicate SFCA with the general formula M14O20 (M–Ca, Si, Al, and Mg), which is the binder of the ore phases of the agglomerate. The proportion of ferrosilicates of calcium and aluminum in the sinter depends on the basicity of the sinter charge, and the morphology of the SFCA phase depends on the cooling rate of the sinter. The more CaO in the sinter charge, the more SFCA phase is formed in the sinter, and slow cooling results in the growth of large lamellar and dendritic SFCA phases.
An Extension of Strict Almost Contractions Employing Control Function and Binary Relation with Applications to Boundary Value Problems
Authors: Filali Doaa , Akram Mohammad , Dilshad Mohammad
Published: September 2023

This article comprises some fixed point results for Boyd–Wong-type strict almost contractions using locally L-transitive binary relations. We provide several examples to illustrate our findings. On applying our results, we determine a unique solution of a special boundary value problem.
A Min-Plus Algebra System Theory for Traffic Networks
Authors: Farhi Nadir
Published: September 2023

In this article, we introduce a comprehensive system theory based on the min-plus algebra of 2×2 matrices of functions. This novel approach enables the algebraic construction of traffic networks and the analytical derivation of performance bounds for such networks. We use the term “traffic networks” or “congestion networks” to refer to networks where high densities of transported particles lead to flow drops, as commonly observed in road networks. Initially, we present a model for a segment or section of a link within the network and demonstrate that the dynamics can be expressed linearly within the min-plus algebra. Subsequently, we formulate the linear system using the min-plus algebra of 2×2 matrices of functions. By deriving the impulse response of the system, we establish its interpretation as a service guarantee, considering the traffic system as a server. Furthermore, we define a concatenation operator that allows for the combination of two segment systems, demonstrating that multiple segments can be algebraically linked to form a larger network. We also introduce a feedback operator within this system theory, enabling the modeling of closed systems. Lastly, we extend this theoretical framework to encompass two-dimensional systems, where nodes within the network are also taken into account in addition to the links. We present a model for a controlled node and provide insights into other potential two-dimensional models, along with directions for further extensions and research.
Neural Network-Driven Sensorless Speed Control of EV Drive Using PMSM
Authors: Mohan Harshit , Agrawal Gopal , Jately Vibhu , Sharma Abhishek , Azzopardi Brian
Published: September 2023

To reduce pollution and energy consumption, particularly in the automotive industry, energy saving is the main concern, and hence, Electric vehicles (EVs) are getting significantly more attention than vehicles with internal combustion engines (IC engines). Electric motors used in Electric Vehicles (EVs) must have high efficiency for maximum utilization of the energy from the batteries or fuel cells. Also, these motors must be compact, lightweight, less expensive and very easily recycled. Further, to obtain better dynamic performance, various motor control strategies are used to control the speed of the motor. And to have increased reliability, sensorless speed control techniques that offer sufficiently high performance are used. The sensorless speed control techniques are largely divided into three groups: state observer methods, indirect measurement methods and saliency-based methods. Generally, the state observer uses back emf or flux linkage to estimate the speed of the motor. Since the back emf is directly proportional to the rotor speed, at low-speed back emf based method will give poor performance. The current-based Model Reference Adaptive System (MRAS) model is also popular for estimating low speed; however, assessments deteriorate during high performance applications such as EV. This paper presents an artificial neural network (ANN)-deployed sensorless speed control of permanent magnet synchronous motor (PMSM) drive used in EVs. In this paper, the estimation of speed using the current-based MRAS model is discussed and compared with the proposed ANN-based controller, which shows significant improvement in the performance of EV motor drives. The MATLAB simulation and experimental results are presented to validate the proposed algorithm.
Wave Propagation and Stability Analysis for Ostrovsky and Symmetric Regularized Long-Wave Equations
Authors: Kaplan Melike , Alqahtani Rubayyi T. , Alharthi Nadiyah Hussain
Published: September 2023

This work focuses on the propagation of waves on the water’s surface, which can be described via different mathematical models. Here, we apply the generalized exponential rational function method (GERFM) to several nonlinear models of surface wave propagation to identify their multiple solitary wave structures. We provide stability analysis and graphical representations for the considered models. Additionally, this paper compares the results obtained in this work and existing solutions for the considered models in the literature. The effectiveness and potency of the utilized approach are demonstrated, indicating their applicability to a broad range of nonlinear partial differential equations in physical phenomena.
On the Chromatic Number of Some (P3 ∪ P2)-Free Graphs
Authors: Li Rui , Li Jinfeng , Wu Di
Published: September 2023

Let G be a graph. We denote the chromatic (clique) number of G by χ(G)(ω(G)). In this paper, we prove that (i) χ(G)≤2ω(G) if G is (P3∪P2, kite)-free, (ii) χ(G)≤ω2(G) if G is (P3∪P2, hammer)-free, (iii) χ(G)≤3ω2(G)+ω(G)2 if G is (P3∪P2,C5)-free. Furthermore, we also discuss the chromatic number of (P3∪P2,K4)-Free Graphs.
Distribution of Eigenvalues and Upper Bounds of the Spread of Interval Matrices
Authors: Liao Wenshi , Long Pujun
Published: September 2023

The distribution of eigenvalues and the upper bounds for the spread of interval matrices are significant in various fields of mathematics and applied sciences, including linear algebra, numerical analysis, control theory, and combinatorial optimization. We present the distribution of eigenvalues within interval matrices and determine upper bounds for their spread using Geršgorin’s theorem. Specifically, through an equality for the variance of a discrete random variable, we derive upper bounds for the spread of symmetric interval matrices. Finally, we give three numerical examples to illustrate the effectiveness of our results.
Nonlinear Functional Observer Design for Robot Manipulators
Authors: Dao Hoang Vu , Nguyen Manh Hung , Ahn Kyoung Kwan
Published: September 2023

In this paper, a nonlinear functional observer (NFO) is first proposed for the control design of robot manipulators under model uncertainties, external disturbances, and a lack of joint velocity information. In principle, the proposed NFO can estimate not only lumped disturbances and uncertainties but also unmeasurable joint velocities, which are then fed back into the main controller. Compared to the well-known ESO design, the proposed NFO has a simpler structure, more accurate estimations, and less computational effort, and consequently, it is easier for practical implementation. Moreover, unnecessary observations of joint displacements are avoided when compared to the well-known extended state observer (ESO). Based on the Lyapunov theory, globally uniformly ultimately bounded estimation performance is guaranteed by the proposed NFO. Consequently, it is theoretically proven that the estimation performances of the NFO are better than those of the ESO. Simulations with a two-degree-of-freedom (2-DOF) robot manipulator are conducted to verify the effectiveness of the proposed algorithm in terms of not only the estimation performance but also the closed-loop control performance.
Balancing the Average Weighted Completion Times in Large-Scale Two-Agent Scheduling Problems: An Evolutionary-Type Computational Study
Authors: Avolio Matteo
Published: September 2023

The problem of balancing the average weighted completion times of two classes of jobs is an NP-hard scheduling problem that was very recently introduced in the literature. Interpreted as a cooperative-type two-agent single-machine problem, its applications are in various practical contexts such as in logistics for balancing the delivery times, in manufacturing for balancing the assembly lines and in services for balancing the waiting times of groups of people. The only solution technique currently existing in the literature is a Lagrangian heuristic, based on solving a finite number of successive linear assignment problems, whose dimension depends on the total number of jobs. Since the Lagrangian approach has not appeared to be particularly suitable for solving large-scale problems, to overcome this drawback, we propose to face the problem by means of a genetic algorithm. Differently from the Lagrangian heuristic, our approach is found to be effective also for large instances (up to 2000 jobs), as confirmed by numerical experiments.
Adaptive Synthesized Control for Solving the Optimal Control Problem
Authors: Diveev Askhat , Shmalko Elizaveta
Published: September 2023

The development of artificial intelligence systems assumes that a machine can independently generate an algorithm of actions or a control system to solve the tasks. To do this, the machine must have a formal description of the problem and possess computational methods for solving it. This article deals with the problem of optimal control, which is the main task in the development of control systems, insofar as all systems being developed must be optimal from the point of view of a certain criterion. However, there are certain difficulties in implementing the resulting optimal control modes. This paper considers an extended formulation of the optimal control problem, which implies the creation of such systems that would have the necessary properties for its practical implementation. To solve it, an adaptive synthesized optimal control approach based on the use of numerical methods of machine learning is proposed. Such control moves the control object, optimally changing the position of the stable equilibrium point in the presence of some initial position uncertainty. As a result, from all possible synthesized controls, one is chosen that is less sensitive to changes in the initial state. As an example, the optimal control problem of a quadcopter with complex phase constraints is considered. To solve this problem, according to the proposed approach, the control synthesis problem is firstly solved to obtain a stable equilibrium point in the state space using a machine learning method of symbolic regression. After that, optimal positions of the stable equilibrium point are searched using a particle swarm optimization algorithm using the source functional from the initial optimal control problem statement. It is shown that such an approach allows for generating the control system automatically by computer, basing this on the formal statement of the problem and then directly implementing it onboard as far as the stabilization system has already been introduced.
MOR-SLAM: A New Visual SLAM System for Indoor Dynamic Environments Based on Mask Restoration
Authors: Yao Chengzhi , Ding Lei , Lan Yonghong
Published: September 2023

The traditional Simultaneous Localization and Mapping (SLAM) systems are based on the strong static assumption, and their performance will degrade significantly due to the presence of dynamic objects located in dynamic environments. To decrease the effects of the dynamic objects, based on the ORB-SLAM2 system, a novel dynamic semantic SLAM system called MOR-SLAM is presented using a mask repair method, which can accurately detect dynamic objects and realize high-precision positioning and tracking of the system in dynamic indoor environments. First, an instance segmentation module is added to the front end of ORB-SLAM2 to distinguish dynamic and static objects in the environment and obtain a preliminary mask. Next, to overcome the under-segmentation problem in instance segmentation, a new mask inpainting model is proposed to ensure that the integrity of object masks, which repairs large objects and small objects in the image with the depth value fusion method and morphological method, respectively. Then, a reliable basic matrix can be obtained based on the above-repaired mask. Finally, the potential dynamic feature points in the environment are detected and removed through the reliable basic matrix, and the remaining static feature points are input into the tracking module of the system to realize the high-precision positioning and tracking in dynamic environments. The experiments on the public TUM dataset show that, compared with ORB-SLAM2, the MOR-SLAM improves the absolute trajectory accuracy by 95.55%. In addition, compared with DynaSLAM and DS-SLAM on the high-dynamic sequences (fr3/w/rpy and fr3/w/static), the MOR-SLAM improves the absolute trajectory accuracy by 15.20% and 59.71%, respectively.
Low-Frequency Electrical Conductivity of Trabecular Bone: Insights from In Silico Modeling
Authors: Cervantes María José , Basiuk Lucas O. , González-Suárez Ana , Carlevaro C. Manuel , Irastorza Ramiro M.
Published: September 2023

Background: The electrical conductivity of trabecular bone at 100 kHz has recently been reported as a good predictor of bone volume fraction. However, quantifying its relationship with free water (or physiological solution) content and the conductivities of its constituents is still difficult. Methods: In this contribution, in silico models inspired by microCT images of trabecular bovine samples were used to build realistic geometries. The finite element method was applied to solve the electrical problem and to robustly fit the conductivity of the constituents to the literature data. The obtained effective electrical conductivity was compared with the Bruggeman three-medium mixture model using a physiological solution, bone marrow and a bone matrix. Results: The values for the physiological solution plus bone marrow (together as one material) and the bone matrix that best captured the bone volume fraction in the two-medium finite element model were σps+bm = 298.4 mS/m and σb = 21.0 mS/m, respectively. Additionally, relatively good results were obtained with the three-medium Bruggeman mixture model, with σbm= 103 mS/m, σb= 21.0 mS/m and σps= 1200 mS/m. Simple linear relationships between the proportions of constituents depending on bone volume fraction were tested. Degree of anisotropy and fractal dimension do not show detectable changes in effective conductivity. Conclusions: These results provided some useful findings for simulation purposes. First, a higher value for the electrical conductivity of bone marrow has to be used in order to obtain similar values to those of experimental published data. Second, anisotropy is not detectable with conductivity measurements for small trabecular samples (5 mm cube). Finally, the simulations presented here showed relatively good fitting of the Bruggeman mixture model, which would potentially account for the free water content and could rescale the model for whole-bone electrical simulations.
Certain Properties of Harmonic Functions Defined by a Second-Order Differential Inequality
Authors: Breaz Daniel , Durmuş Abdullah , Yalçın Sibel , Cotirla Luminita-Ioana , Bayram Hasan
Published: September 2023

The Theory of Complex Functions has been studied by many scientists and its application area has become a very wide subject. Harmonic functions play a crucial role in various fields of mathematics, physics, engineering, and other scientific disciplines. Of course, the main reason for maintaining this popularity is that it has an interdisciplinary field of application. This makes this subject important not only for those who work in pure mathematics, but also in fields with a deep-rooted history, such as engineering, physics, and software development. In this study, we will examine a subclass of Harmonic functions in the Theory of Geometric Functions. We will give some definitions necessary for this. Then, we will define a new subclass of complex-valued harmonic functions, and their coefficient relations, growth estimates, radius of univalency, radius of starlikeness and radius of convexity of this class are investigated. In addition, it is shown that this class is closed under convolution of its members.
Some New Estimates of Hermite–Hadamard Inequalities for Harmonical cr-h-Convex Functions via Generalized Fractional Integral Operator on Set-Valued Mappings
Authors: Almalki Yahya , Afzal Waqar
Published: September 2023

The application of fractional calculus to interval analysis is vital for the precise derivation of integral inequalities on set-valued mappings. The objective of this article is to reformulated the well-known Hermite–Hadamard inequality into various new variants via fractional integral operator (Riemann–Liouville) and generalize the various previously published results on set-valued mappings via center and radius order relations using harmonical h-convex functions. First, using these notions, we developed the Hermite–Hadamard (H–H) inequality, and then constructed some product form of these inequalities for harmonically convex functions. Moreover, to demonstrate the correctness of these results, we constructed some interesting non-trivial examples.
Spectrum of One-Dimensional Potential Perturbed by a Small Convolution Operator: General Structure
Authors: Borisov D. I. , Piatnitski A. L. , Zhizhina E. A.
Published: September 2023

We consider an operator of multiplication by a complex-valued potential in L2(R), to which we add a convolution operator multiplied by a small parameter. The convolution kernel is supposed to be an element of L1(R), while the potential is a Fourier image of some function from the same space. The considered operator is not supposed to be self-adjoint. We find the essential spectrum of such an operator in an explicit form. We show that the entire spectrum is located in a thin neighbourhood of the spectrum of the multiplication operator. Our main result states that in some fixed neighbourhood of a typical part of the spectrum of the non-perturbed operator, there are no eigenvalues and no points of the residual spectrum of the perturbed one. As a consequence, we conclude that the point and residual spectrum can emerge only in vicinities of certain thresholds in the spectrum of the non-perturbed operator. We also provide simple sufficient conditions ensuring that the considered operator has no residual spectrum at all.