bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Investigation of Outflow of Non-Metallic Inclusions during Steel Refining in the Ladle
Authors: Migas Piotr , Ślęzak Marta , Karbowniczek Mirosław , Szczęch Stanisław , Hornik Andrzej
Published: April 2022

The article presents the results of numerical simulations of liquid steel flow in the main steelmaking ladle. The paper analyses the mechanism of the outflow of non-metallic Al2O3 and MnS inclusions with diameters in the range of 4–27 µm. The simulations were performed with ANSYS Fluent software. In order to determine the shape and size of non-metallic inclusions formed in the main ladle during steel refining, the collected samples of liquid metal were analysed using a scanning microscope with SEM/EDS and LM (light microscopy). Simulation tests and calculations were carried out for the case of steel refining under the conditions of the Cognor SA HSJ Department in Stalowa Wola (Poland). The presented method of using simulation tests to optimize the technology of steel refining in the ladle is an example. The analysis of the results shows that the gas flow in the metal volume has the greatest impact on the outflow of non-metallic inclusions in the steelmaking ladle.
Investigation of the Reusability of a Polyurethane-Bound Noise-Absorbing Pavement in Terms of Reclaimed Asphalt Pavement
Authors: Faßbender Sabine , Oeser Markus
Published: April 2022

A key aspect of sustainable pavement construction is the use of environmentally-friendly designed pavement materials. These materials are characterized by the fact that they are renewable raw materials, require a low amount of energy during production and in the best case, are made from a high proportion of recyclable materials in order to reduce waste. A number of recent studies have demonstrated the recyclability of waste materials that can be very well utilized in road construction. This study describes the recycling of a new and innovative topcoat system that already contains recycled materials. However, the focus is on guaranteeing the mechanical performance of the innovative absorption layer where different portions of used material are added. Therefore, low-temperature behaviour, durability, fatigue and noise absorption are investigated in detail and it is concluded that their function is preserved. In order to investigate these characteristics, the impedance measuring tube, the uniaxial cyclic compression test (UCCT), the three point bending test (3PB), the uniaxial tension stress test (UTST) and the thermal stress restrained specimen test (TSRST) are used. However, the examined absorption material can be reused to build innovative roads.
Influence of Anticorrosive Pigment, Dry-Film Thickness and Conditioning Time on Protective Properties of Two-Component Epoxy Primer
Authors: Šolić Tomislav , Marić Dejan , Peko Ivan , Samardžić Ivan
Published: April 2022

The main protective properties of two-component epoxy coating are connected by the formation of a barrier of a certain thickness between the material and aggressive, environmentally induced reactants. Anticorrosive pigment is added to the coating in order to improve its protective effects. The conditioning time refers to the time interval required for the achievement of satisfactory cohesion bonds between the coating components, as well as a satisfactory adhesion force between the coating and the base material surface. This paper presents insights obtained after experimental research into the influence of input variables (the content of anticorrosive pigment in the coating, dry-film thickness, and conditioning time) on corrosion resistance. The specimens were kept in the aggressive atmosphere of a salt-spray test chamber within time intervals of 120, 240 and 480 h, where they were cyclically sprayed with a 5% sodium chloride (NaCl) solution, and then examined in laboratory conditions. Such a procedure imitated the aggressive conditions of a service environment. After exposure in the salt-spray test chamber, the specimens were tested to determine the protective properties of the coating and to evaluate damage occurring on the coating, with the purpose of assessing the coating quality in relation to the stated input variables. At all times, when the test samples were exposed to the salt chamber atmosphere, the anti-corrosion pigment content was found to have the greatest influence with the thickness of the dry coating film. The conditioning time was an influential factor to a lesser extent, and only in some observed cases. By analyzing the interactions of the input variables and the results obtained based on mathematical models and reaction surfaces, it was possible to define the most optimal values of the input parameters. For example, after 480 h of exposure in a salt chamber, notch corrosion of 0.6 mm was observed at a dry-film thickness of D1 and an anti-corrosion pigment content of 10%.
Shock-Induced Energy Release Performances of PTFE/Al/Oxide
Authors: Yuan Ying , Shi Dongfang , He Suo , Guo Huanguo , Zheng Yuanfeng , Zhang Yong , Wang Haifu
Published: April 2022

In recent years, polytetrafluoroethylene (PTFE)/aluminum (Al) energetic materials with high-energy density have attracted extensive attention and have broad application prospects, but the low-energy release efficiency restricts their application. In this paper, oxide, bismuth trioxide (Bi2O3) or molybdenum trioxide (MoO3) are introduced into PTFE/Al to improve the chemical reaction performance of energetic materials. The pressurization characteristics of PTFE/Al/oxide as pressure generators are compared and analyzed. The experiments show that the significantly optimized quasi-static pressure peak, impulse, and energy release efficiency (0.162 MPa, 10.177 s·kPa, and 0.74) are achieved for PTFE/Al by adding 30 wt.% Bi2O3. On the other hand, the optimal parameter obtained by adding 10% MoO3 is 0.147 MPa, 9.184 s·kPa, and 0.68. Further, the mechanism of enhancing the energy release performance of PTFE/Al through oxide is revealed. The mechanism analysis shows that the shock-induced energy release performance of PTFE/Al energetic material is affected by the intensity of the shock wave and the chemical reaction extent of the material under the corresponding intensity. The oxide to PTFE/Al increases the intensity of the shock wave in the material, but the chemical reaction extent of the material decreases under the corresponding intensity.
Structure, Properties, and Phase Transformations of Water Nanoconfined between Brucite-like Layers: The Role of Wall Surface Polarity
Authors: Tsukanov Alexey A. , Shilko Evgeny V. , Popov Mikhail
Published: April 2022

The interaction of water with confining surfaces is primarily governed by the wetting properties of the wall material—in particular, whether it is hydrophobic or hydrophilic. The hydrophobicity or hydrophilicity itself is determined primarily by the atomic structure and polarity of the surface groups. In the present work, we used molecular dynamics to study the structure and properties of nanoscale water layers confined between layered metal hydroxide surfaces with a brucite-like structure. The influence of the surface polarity of the confining material on the properties of nanoconfined water was studied in the pressure range of 0.1–10 GPa. This pressure range is relevant for many geodynamic phenomena, hydrocarbon recovery, contact spots of tribological systems, and heterogeneous materials under extreme mechanical loading. Two phase transitions were identified in water confined within 2 nm wide slit-shaped nanopores: (1) at p1 = 3.3–3.4 GPa, the liquid transforms to a solid phase with a hexagonal close-packed (HCP) crystal structure, and (2) at p2 = 6.7–7.1 GPa, a further transformation to face-centered cubic (FCC) crystals occurs. It was found that the behavior of the confined water radically changes when the partial charges (and, therefore, the surface polarity) are reduced. In this case, water transforms directly from the liquid phase to an FCC-like phase at 3.2–3.3 GPa. Numerical simulations enabled determination of the amount of hydrogen bonding and diffusivity of nanoconfined water, as well as the relationship between pressure and volumetric strain.
Effect of Laser Scanning Speed on the Microstructure and Mechanical Properties of Laser-Powder-Bed-Fused K418 Nickel-Based Alloy
Authors: Chen Zhen , Lu Yongxin , Luo Fan , Zhang Shuzhe , Wei Pei , Yao Sen , Wang Yongxin
Published: April 2022

Laser powder bed fusion (LPBF) is a powder-bed-based metal additive manufacturing process with multiple influencing parameters as well as multi-physics interaction. The laser scanning speed, which is one of the essential process parameters of the LPBF process, determines the microstructure and properties of the components by adjusting the instantaneous energy input of the molten pool. This work presents a comprehensive investigation of the effects of the laser scanning speed on the densification behavior, phase evolution, microstructure development, microhardness, and tensile properties of K418 alloy prepared by laser powder bed fusion. When the scanning speed is 800 mm/s, the microstructure of the material is dominated by cellular dendrite crystals, with coarse grains and some cracks in the melting tracks. When the scanning speed is increased to 1200 mm/s, a portion of the material undergoes a cellular dendrite–columnar crystal transition, the preferred orientation of the grains is primarily (001), and internal defects are significantly reduced. When the scanning speed is further increased to 1600 mm/s, columnar crystals become the main constituent grains, and the content of high-angle grain boundaries (HAGBs) within the microstructure increases, refining the grain size. However, the scanning speed is too fast, resulting in defects such as unmelted powder, and lowering the relative density. The experimental results show that by optimizing the laser scanning speed, the microhardness of the LPBF-ed K418 parts can be improved to 362.89 ± 5.01 HV, the tensile strength can be elevated to 1244.35 ± 99.12 MPa, and the elongation can be enhanced to 12.53 ± 1.79%. These findings could help determine the best scanning speed for producing K418 components with satisfactory microstructure and tensile properties via LPBF. In addition, since the LPBF process is largely not constrained and limited by the complexity of the geometric shape of the part, it is expected to manufacture sophisticated and complex structures with hollow, porous, mesh, thin-walled, special-shaped inner flow channels and other structures through the topology optimization design. However, due to the relatively narrow LPBF process window, this study will benefit from LPBF in producing a lightweight, complex, and low-cost K418 product, greatly improving its performance, and promoting the use of LPBF technology in the preparation of nickel-based superalloys.
Elucidating the Effects of Reaction Time on the Physicochemical Characterization of Valorized Synthesized Alumina
Authors: Bin Mokaizh Aiman A. , Shariffuddin Jun Haslinda , Baarimah Abdullah O. , Al-Fakih Amin , Mohamed Abdullah , Baarimah Salem O. , Al-Mekhlafi Al-Baraa Abdulrahman , Alenezi Hamoud , Olalere Olusegun Abayomi , Saeed Anwar Ameen Hezam
Published: April 2022

Aluminum waste-can management in Malaysia has recently become a serious environmental and public health issue, particularly in metropolitan areas. This has prompted the need to valorize these waste-cans into value-added products using the most economical and environmentally friendly techniques. In this study, the sol–gel technique was used to synthesize high-quality alumina from the aluminum waste-cans collected. From this method, the observed peaks of the synthesized alumina were identified as diaspore (α-AlO(OH)), boehmite (γ-AlO(OH)), aluminum oxide, or gamma-alumina (γ-Al2O3) crystalline structure and corundum. The morphological configuration, microstructure, and functional group properties of the synthesized alumina were evaluated. All the synthesized alumina exhibited a non-spherical shape and appeared to have hexagonal-like shape particles. Moreover, the XRD patterns of the synthesized alumina AL-6-30 and AL-12-30 exhibited a small angle (1–10°) with no XRD peak, which indicated a mesoporous pore structure with no long-range order. The overall results of γ-alumina synthesized from the aluminum waste-cans showed an optimal condition in producing a highly structured γ-alumina with excellent surface-area characteristics. The synthesized alumina exhibited stronger and highly crystalline functional characteristics almost comparable with the commercially available brands on the market.
Green-Engineered Cementitious Composite Production with High-Strength Synthetic Fiber and Aggregate Replacement
Authors: Fu Chaoshu , Chen Mingzhao , Guo Rongxin , Qi Rongqing
Published: April 2022

Engineered cementitious composites (ECCs) are potentially useful structural reinforcement and repair materials. However, owing to their high costs and carbon emissions, they are not used extensively. To control these carbon emissions and costs, recycled fly ash cenospheres (FACs) and high-strength polyethylene (PE) fibers are used here to explore the possibility of developing green lightweight ECCs (GLECCs). A series of experiments was conducted to test the physical and mechanical properties of the developed GLECC and to evaluate the possibility of developing an GLECC. The crack width development of the GLECC was also analyzed using the digital image correlation method. The experimental results indicate the following: (1) The increase in FAC content and the decrease in PE content worsened the performance of GLECCs, but the resulting GLECCs still had significant strain-hardening properties; (2) The performance and costs of GLECCs can be balanced by adjusting the amount of FAC and PE. The maximum amount of FACs attainable is 0.45 (FAC/binder), and the required amount of PE fibers can be reduced to 1%. As a result, the cost was reduced by 40% and the carbon emission was reduced by 36%, while the compressive strength was greater than 30 MPa, the tensile strength was greater than 3.5 MPa, and the tensile strain was nearly 3%. (3) The width of the crack was positively correlated with the FAC content and negatively correlated with the fiber content. In the 0.8% strain range, the average crack width can be controlled to within 100 μm and the maximum crack width can be controlled to within 150 μm, with the performance still meeting the requirements of many applications.
A PLLA Coating Does Not Affect the Insertion Pressure or Frictional Behavior of a CI Electrode Array at Higher Insertion Speeds
Authors: Dohr Dana , Wulf Katharina , Grabow Niels , Mlynski Robert , Schraven Sebastian P.
Published: April 2022

To prevent endocochlear insertion trauma, the development of drug delivery coatings in the field of CI electrodes has become an increasing focus of research. However, so far, the effect of a polymer coating of PLLA on the mechanical properties, such as the insertion pressure and friction of an electrode array, has not been investigated. In this study, the insertion pressure of a PLLA-coated, 31.5-mm long standard electrode array was examined during placement in a linear cochlear model. Additionally, the friction coefficients between a PLLA-coated electrode array and a tissue simulating the endocochlear lining were acquired. All data were obtained at different insertion speeds (0.1, 0.5, 1.0, 1.5, and 2.0 mm/s) and compared with those of an uncoated electrode array. It was shown that both the maximum insertion pressure generated in the linear model and the friction coefficient of the PLLA-coated electrode did not depend on the insertion speed. At higher insertion speeds above 1.0 mm/s, the insertion pressure (1.268 ± 0.032 mmHg) and the friction coefficient (0.40 ± 0.15) of the coated electrode array were similar to those of an uncoated array (1.252 ± 0.034 mmHg and 0.36 ± 0.15). The present study reveals that a PLLA coating on cochlear electrode arrays has a negligible effect on the electrode array insertion pressure and the friction when higher insertion speeds are used compared with an uncoated electrode array. Therefore, PLLA is a suitable material to be used as a coating for CI electrode arrays and can be considered for a potential drug delivery system.
A Comparison of Microtensile Bond Strength, Film Thickness, and Microhardness of Photo-Polymerized Luting Composites
Authors: El-Askary Farid , Hassanein Abdullah , Aboalazm Emad , Al-Haj Husain Nadin , Özcan Mutlu
Published: April 2022

The aim of this study was to evaluate the effect of CAD/CAM composite thickness on micro-tensile bond strength (µTBS), microhardness (HV), and film thickness (FT) of different luting composites. Composite blocks (6.8 mm × 6.8 mm) were divided into 12 groups according to: CAD/CAM thickness and luting composite. For each group, 21 rods (1 mm × 1 mm) were tested in tension at crosshead speed of 1 mm/min. Fracture modes were categorized as adhesive, mixed, and cohesive. Microhardness (n = 5/group) was assessed using microhardness tester. Film thickness (12-rods/group) was evaluated using a stereomicroscope (×40). Data were analyzed using the two-way ANOVA/Tukey’s HSD test (p = 0.05). Parameters “thickness”, “cement”, and “thickness x cement” showed significant difference on µTBS and HV (p < 0.05). At 2 mm, heated x-tra fil composite showed the highest µTBS (45.0 ± 8.5 MPa), while at 4 mm thickness, Grandio Flow revealed the lowest µTBS (33.3 ± 6.3 MPa). Adhesive, mixed, and cohesive failures were reported. The HV of all composites decreased when photo-polymerized through 4 mm thickness (p < 0.05). Regardless of CAD/CAM thickness, photo-polymerized composites can be successfully used for luting CAD/CAM composite.
A Comparative Analysis of Measured and Calculated Compressive Stresses of Magnetorheological Fluids under Unidirectional Compression and Constant Area
Authors: Bi Cheng , Wang Hongyun , Liu Wenfei , Wu Keqian
Published: April 2022

Unidirectional compressive properties of magnetorheological (MR) fluids have been investigated under slow compression and constant area with different magnetic fields and different initial gap distances. Experimental tests of unidirectional compression were firstly carried out by using a commercial plate–plate rheometer. The theoretical model based on the continuous squeeze flow theory was developed to calculate the compressive stress. The comparisons between the measured and calculated compressive stresses of MR fluids were made. It showed that the compression resistance of the MR fluid in the magnetic field was much higher than that predicted by the theory. With the increasing magnetic flux density, the deviation between measured and calculated curves accelerated. Characteristics of the compressive stress variation with the reduction in gap distance have been analyzed. The structure strengthening effect induced by the chain structure aggregation in squeeze mode has been used to explain this deviation.
Fabrication and Characterization of Superhydrophobic Al-Based Surface Used for Finned-Tube Heat Exchangers
Authors: Li Ran , Wang Zanshe , Chen Meijuan , Li Zhang , Luo Xiaowei , Lu Weizhen , Gu Zhaolin
Published: April 2022

Enhancing the heat transfer performance of heat exchangers is one of the main methods to reduce energy consumption and carbon emissions in heating, ventilation, air-conditioning and refrigeration (HVAC&R) systems. Wettability modified surfaces developed gradually may help. This study aims to improve the performance of heat exchangers from the perspective of component materials. The facile and cost-effective fabrication method of superhydrophobic Al-based finned-tube heat exchangers with acid etching and stearic acid self-assembly was proposed and optimized in this study, so that the modified Al fins could achieve stronger wettability and durability. The effect of process parameters on the wettability of the Al fins was by response surface methodology (RSM) and variance analysis. Then, the modified fins were characterized by field-emission scanning electron microscopy (FE-SEM), 3D topography profiler, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR), respectively. The durability of the superhydrophobic fins was investigated by air exposure, corrosion resistance, and mechanical robustness experiments. The RSM and variance analysis demonstrated that a water contact angle (WCA) of 166.9° can be obtained with the etching time in 2 mol/L HCl solution of 10.5 min, the self-assembly time in the stearic acid ethanol solution of 48 h, and drying under 73.0 °C. The surface morphology showed suitable micro-nano structures with a mean roughness (Ra) of 467.58 nm and a maximum peak-to-valley vertical distance (Rt) of 4.095 μm. The chemical component demonstrated the self-assembly of an alkyl chain. The WCAs declined slightly in durability experiments, which showed the feasibility of the superhydrophobic heat exchangers under actual conditions.
Scanning Distance Influence on the Intraoral Scanning Accuracy—An In Vitro Study
Authors: Rotar Raul Nicolae , Faur Andrei Bogdan , Pop Daniel , Jivanescu Anca
Published: April 2022

Intraoral scanners (IOS) have reached a point where their impact in the dental office cannot be denied. The distance between the tip of the IOS and the preparation may have implications on the accuracy of the digital model. The objective of this study was to evaluate the differences in accuracy between digital impressions in the scenario of different scanning distances. Twenty consecutive scans were performed at five predetermined distances: 5 mm, 10 mm, 15 mm, 20 mm and 23 mm by a single operator. The scanning distance of 10 mm displayed the best accuracy with an overall trueness value of 23.05 μm and precision value of 4.2 μm. The drawn conclusion was that increased scanning distances can decrease the accuracy of a digital impression.
Performance of Nanocomposites of a Phase Change Material Formed by the Dispersion of MWCNT/TiO2 for Thermal Energy Storage Applications
Authors: AlOtaibi Maha , Alsuhybani Mohammed , Khayyat Maha , AlOtaibi Bandar
Published: April 2022

Thermal energy storage technology is an important topic, as it enables renewable energy technology to be available 24/7 and under different weather conditions. Phase changing materials (PCM) are key players in thermal energy storage, being the most economic among those available with adjustable thermal properties. Paraffin wax (PW) is one of the best materials used in industrial processes to enhance thermal storage. However, the low thermal conductivity of PW prevents its thermal application. In this study, we successfully modified PW based on multi-walled carbon nanotubes (MWCNT) with different concentrations of TiO2—3, 5 and 7 wt.%. The morphology of PCM and its relationship with the chemical structure and stability were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and Thermogravimetric analysis (TGA). As a result, the composites achieved a highest latent heat enthalpy of 176 J/g, in addition to enhanced thermal stability after 15 thermal cycles, and reliability, with a slight change in latent heat observed when using a differential scanning calorimeter (DSC). The thermal conductivity of the composites could significantly be enhanced by 100%. Compared to pure paraffin, the PCM composites developed in this study exhibited an excellent preference for thermal energy storage and possessed low cost, high reliability, and phase change properties.
The Wear Rate Forecast of MgO-C Materials Type MC95/10 in the Slag Spout Zone of an Oxygen Converter in Terms of the Bayesian Estimation
Authors: Zelik Wiesław , Sado Sebastian , Lech Ryszard
Published: April 2022

The ceramic–carbon refractory lining of an oxygen converter is subjected to variable thermochemical stresses, causing a progressive loss of material over time, which is expressed in a decreasing residual thickness of the lining. The forecasting method using Bayesian statistics has become a valuable skill in steel production planning and is one of the main conditions constituting the appropriate organization of steel and refractories production. This paper presents examples of Bayesian modelling of the unit wear rate value of the refractory materials for the zone with the highest wear in the refractory lining of a converter. From the experience gained during long-term operation of a steel-producing oxygen converter, it was found that the value of the unit wear rate of the refractory material in the slag spout zone of the steel-producing oxygen converter is subjected to an a posteriori normal distribution, with the following parameters: mean value µ = 401.23 µ heat−1, standard deviation σ = 13.74 µm heat−1. The forecasted mean value of the unit wear rate of the MC95/10 refractories lined in the slag spout zone of the oxygen converter used for steel production, and which operates in intensive exploitation conditions, was equal to µ = 420 µm heat−1.
Assessment of Woodcrete Using Destructive and Non-Destructive Test Methods
Authors: Fadiel Ashraf A.M. , Abu-Lebdeh Taher , Petrescu Florian Ion T.
Published: April 2022

Utilizing solid wastes and industrial by-products as a partial replacement for raw materials has become an acceptable practice among researchers and scientists in the civil engineering field. Sawdust and wood shavings are not an exception; they are being used in concrete as a partial or total replacement for some of its constituents. The main goal of this research is to establish a relation between destructive and non-destructive testing for concrete containing wood shavings as a partial replacement of sand (woodcrete). With this type of material existing, thus the need to understand the behavior of such material becomes urgent and evokes the need to ease the process of the assessment and the evaluation of such materials and therefore provide more understanding of its behavior. In addition to the conventional concrete mix, five mixes of woodcrete were made by replacing fine aggregate by volume with wood shavings at different replacement levels varied from 5% to 50%. Cubic samples were tested at the age of 90 days using nondestructive tests (NDT), namely, rebound hammer test and ultrasonic pulse velocity test. Then, the specimens were tested using a conventional compressive test using a universal compression testing machine. Statistical analysis was performed to establish empirical relations between destructive and non-destructive results. The dynamic modulus of elasticity was calculated, and some formulas to estimate the (compressive) strength of woodcrete using NDT results were proposed and tested against experimental results and showed acceptable results.
Role of Eu2+ and Dy3+ Concentration in the Persistent Luminescence of Sr2MgSi2O7 Glass-Ceramics
Authors: Fernández-Rodríguez Laura , Balda Rolindes , Fernández Joaquín , Durán Alicia , Pascual María Jesús
Published: April 2022

In this study, glass-ceramics based on Sr2MgSi2O7 phosphor co-doped with Eu/Dy were obtained from the sintering and crystallisation of glass powders. The glasses were melted in a gas furnace to simulate an industrial process, and the dopant concentration was varied to optimise the luminescence persistence times. The doped parent glasses showed red emission under UV light excitation due to the doping of Eu3+ ions, while the corresponding glass-ceramics showed persistent blue emission corresponding to the presence of Eu2+ in the crystalline environment. The dopant concentration had a strong impact on the sintering/crystallisation kinetics affecting the final glass-ceramic microstructure. The microstructures and morphology of the crystals responsible for the blue emission were observed by scanning electron microscopy–cathodoluminescence. The composition of the crystallised phases and the distribution of rare-earth (RE) ions in the crystals and in the residual glassy phase were determined by X-ray diffraction and energy dispersive X-ray analysis. The emission and persistence of phosphorescence were studied by photoluminescence.
Dielectric Property and Breakdown Strength Performance of Long-Chain Branched Polypropylene for Metallized Film Capacitors
Authors: Xiao Meng , Zhang Mengdie , Liu Haoliang , Du Boxue , Qin Yawei
Published: April 2022

At high temperatures, the insulation performance of polypropylene (PP) decreases, making it challenging to meet the application requirements of metallized film capacitors. In this paper, the dielectric performance of PP is improved by long-chain branching modification and adding different kinds of nucleating agents. The added nucleating agents are organic phosphate nucleating agent (NA-21), sorbitol nucleating agent (DMDBS), rare earth nucleating agent (WBG-Ⅱ) and acylamino nucleating agent (TMB-5). The results show that the long-chain branches promote heterogeneous nucleation and inhibit the motion of molecular chains, thereby enhancing the dielectric properties at high temperatures. Nucleating agents modulate the crystalline morphology of long-chain branched polypropylene (LCBPP), which leads to a decrease in the mean free path of carriers and an increase in trap energy level and trap density. Therefore, the conductivity is reduced and the breakdown strength is improved. Among the added nucleating agents, NA-21 showed a significant improvement in the electrical properties of LCBPP films. At 125 °C, compared with PP, the breakdown strength of the modified film is increased by 26.3%, and the energy density is increased by 66.1%. This method provides a reference for improving the dielectric properties of PP.
Special Issue: Biomimetic Organic–Inorganic Composites
Authors: Dutour Sikirić Maja
Published: April 2022

Throughout history, the welfare and prosperity of civilizations have depended on the development of novel, more advanced materials [...]
Compressive and Flexural Strength of 3D-Printed and Conventional Resins Designated for Interim Fixed Dental Prostheses: An In Vitro Comparison
Authors: Pantea Mihaela , Ciocoiu Robert Cătălin , Greabu Maria , Ripszky Totan Alexandra , Imre Marina , Țâncu Ana Maria Cristina , Sfeatcu Ruxandra , Spînu Tudor Claudiu , Ilinca Radu , Petre Alexandru Eugen
Published: April 2022

A provisionalization sequence is essential for obtaining a predictable final prosthetic outcome. An assessment of the mechanical behavior of interim prosthetic materials could orient clinicians towards selecting an appropriate material for each clinical case. The aim of this study was to comparatively evaluate the mechanical behavior—with compressive and three-point flexural tests—of certain 3D-printed and conventional resins used to obtain interim fixed dental prostheses. Four interim resin materials were investigated: two 3D-printed resins and two conventional resins (an auto-polymerized resin and a pressure/heat-cured acrylic resin). Cylindrically shaped samples (25 × 25 mm/diameter × height) were obtained for the compression tests and bar-shaped samples (80 × 20 × 5 mm/length × width × thickness) were produced for the flexural tests, observing the producers’ recommendations. The resulting 40 resin samples were subjected to mechanical tests using a universal testing machine. Additionally, a fractographic analysis of failed samples in bending was performed. The results showed that the additive manufactured samples exhibited higher elastic moduli (2.4 ± 0.02 GPa and 2.6 ± 0.18 GPa) than the conventional samples (1.3 ± 0.19 GPa and 1.3 ± 0.38 GPa), as well as a higher average bending strength (141 ± 17 MPa and 143 ± 15 MPa) when compared to the conventional samples (88 ± 10 MPa and 76 ± 7 MPa); the results also suggested that the materials were more homogenous when produced via additive manufacturing.
Extended Continuous Cooling Transformation (CCT) Diagrams Determination for Additive Manufacturing Deposited Steels
Authors: Halmešová Kristýna , Procházka Radek , Koukolíková Martina , Džugan Jan , Konopík Pavel , Bucki Tomasz
Published: April 2022

Continuous cooling transformation (CCT) diagrams are widely used when heat treating steels and represent which type of phase will occur in a material as it is cooled at different cooling rates. CCT diagrams are constructed on the basis of dilatometry measurements on relatively small testing samples (cylindrical shape with diameter of 4mm and length of 11 mm in this study). The main aim of this work was to demonstrate the possibility of evaluating the tensile test properties using mini-tensile tests from miniature volumes (1.4 × 10−7 m3 for one sample) subsequent to determination of the CCT diagram and to extend a standard CCT diagram with information about strength, ductility and the estimated value of the work-hardening coefficient. Mini-tensile tests (MTT) were recently developed due to the low availability of experimental material and have already been successfully used for local mechanical property characterization of metals. CCT diagrams were constructed for 42CrMo4 steel prepared by the laser-directed energy deposition (L-DED) process, for commercially available 42CrMo4 steel conventionally manufactured (for comparison of traditional processing and AM preparation) and for H13 tool steel deposited by the selective laser melting (SLM) process.
Predictive Modeling of Compression Strength of Waste PET/SCM Blended Cementitious Grout Using Gene Expression Programming
Authors: Khan Kaffayatullah , Jalal Fazal , Iqbal Mudassir , Khan Muhammad , Amin Muhammad , Al-Faiad Majdi
Published: April 2022

The central aim of this study is to evaluate the effect of polyethylene terephthalate (PET) alongside two supplementary cementitious materials (SCMs)—i.e., fly ash (FA) and silica fume (SF)—on the 28-day compressive strength (CS28d) of cementitious grouts by using. For the gene expression programming (GEP) approach, a total of 156 samples were prepared in the laboratory using variable percentages of PET and SCM (0–10%, each). To achieve the best hyper parameter setting of the optimized GEP model, 10 trials were undertaken by varying the genetic parameters while observing the models’ performance in terms of statistical indices, i.e., correlation coefficient (R), root mean squared error (RMSE), mean absolute error (MAE), comparison of regression slopes, and predicted to experimental ratios (ρ). Sensitivity analysis and parametric study were performed on the best GEP model (obtained at; chromosomes = 50, head size = 9, and genes = 3) to evaluate the effect of contributing input parameters. The sensitivity analysis showed that: CS7d (30.47%) > CS1d (28.89%) > SCM (18.88%) > Flow (18.53%) > PET (3.23%). The finally selected GEP model exhibited optimal statistical indices (R = 0.977 and 0.975, RMSE = 2.423 and 2.531, MAE = 1.918 and 2.055) for training and validation datasets, respectively. The role of PET/SCM has no negative influence on the CS28d of cementitious grouts, which renders the PET a suitable alternative toward achieving sustainable and green concrete. Hence, the simple mathematical expression of GEP is efficacious, which leads to saving time and reducing labor costs of testing in civil engineering projects.
Mechanical, Physico-Chemical and Morphological Characterization of Energy Optimised Furnace (EOF) Steel Slag as Coarse Aggregate in Concrete
Authors: Masilamani Arivoli , Ramalingam Malathy , Kathirvel Parthiban , Murali Gunasekaran , Vatin Nikolai Ivanovich
Published: April 2022

This research tests energy optimised furnace (EOF) steel slag as substitution for natural coarse aggregate in concrete. Steel slag’s usefulness as a substitute for natural coarse aggregate in concrete is the primary goal of this research. According to IS:2386-1963, the characterization of EOF steel slag, as coarse, is done by examining the shape and size of a particle, mechanical properties, physical properties, soundness, and alkali-aggregate reactivity. Tests for detection of staining material in steel slag and hardness of inter-facial transition zone in hardened cement paste were also carried out. The chemical analysis of the steel slag reveals the stability of oxides present in the steel slag. Microstructural characterization by SEM (scanning electron microscope) analysis of steel slag aggregate was also employed to support the characterization and XRD analysis, and it was found that the EOF steel slag is crystalline. The digital image processing technique (DIP) is adopted to study the shape indices, circularity, sphericity, shape factor, and roundness of natural and EOF steel slag aggregate. According to the characterization and strength investigation, steel slag aggregate outperforms natural coarse aggregate.
Practical Obstacle-Overcoming Robot with a Heterogeneous Sensing System: Design and Experiments
Authors: Huang Yuanhao , Meng Ruifeng , Yu Jingyang , Zhao Ziqi , Zhang Xinyu
Published: April 2022

It is challenging for robots to improve their ability to pass through unstructured environments while maximizing motion performance in cities and factories. This paper presents an omnidirectional deformable wheeled robot based on a heterogeneous sensing system. We presented a novel structure with dual swing arms and six wheels. Moreover, the heterogeneous sensing system can perceive critical environmental data, such as friction and temperature, to assist the robot in executing different functions. In addition, a top-down ‘Order–Decision–Behaviour’ overall motion strategy is proposed based on the data acquisition. The strategy combines the key condition parameters with a kinetic model to integrate the robot’s movement, overcoming of obstacles, and mode switching. The robot is flexible and fast in moving mode and can overcome obstacles safely, reliably, and simply. This study describes the robot’s design, strategy, simulation, and experiments. Motion performance and strategy were investigated and evaluated in field environments.
Developing a Novel Fully Automated Concept to Produce Bowden Cables for the Automotive Industry
Authors: Sousa Vitor Fernando Crespim , Silva Francisco José Gomes da , Campilho Raul Duarte Salgueiral Gomes , Pinto Arnaldo Guedes , Ferreira Luís Pinto , Martins Nuno
Published: April 2022

The automotive industry is one of the driving forces of the global industry; thus, it is a very competitive sector which creates a constant need for process improvement, regarding productivity, quality, and flexibility. Automation has proven to be a viable solution for these production problems, with the rising adoption of these automated system by companies that try to design and implement more flexible systems, while reducing costs and improving process quality. Furthermore, the use of automation reduces the manpower factor and its associated variability. In the present work, a new concept for a Bowden cable production process is presented by employing the design science research (DSR) methodology. The project starts with the analysis of the previous production concept, determining possible problems and improvements, as well as setting objectives/requirements for a possible new concept/equipment. This information was used to develop a new automated Bowden cable production equipment, implementing several changes to the old concept and filling a gap in the literature in this field. The developed system was implemented and tested. A considerable reduction in cycle time was registered by 25%, which resulted in an increase of 30% in process productivity.
Assembly of Compliant Structures with Autonomous Industrial Mobile Manipulators (AIMM) Using an End Effector with Active Deformation Compensation for the Assembly of Flaps
Authors: Neitmann Maximilian , Rothe Tom , Kappel Erik , Hühne Christian
Published: April 2022

Composite structures in aeroplanes are often thin-walled and lightweight, resulting in significant compliance, which presents a handling and assembly challenge due to the associated part deformations. In order to counteract these deformations, the parts are held in their specified geometry using stiff and correspondingly heavy fixtures or jigs. Mobile industrial robots are very versatile and widely used in industrial volume production, but they are limited in their payload capacity. High-rate production of large aerospace modules requires highly automated flexible assembly processes. The approach presented in this paper is to combine mobile units with lightweight assembly jigs that have the capability of deformation compensation. The subject of the study is a high-rate assembly process for flap modules using an Autonomous Industrial Mobile Manipulator (AIMM) and a lightweight end effector. The end effector has a shape compensation function, implemented by an integrated Stewart platform, which enables the compensation of manufacturing tolerances as well as gravity effects. The compensation function is used in a closed loop and counteracts shape deviations by appropriate fixture shape adjustments. The paper reports on the conceptual design of the assembly scenario, the design of the end effector, its realization and the successful experimental demonstration at 1:1 scale.
A New Trajectory Tracking Control Method for Fully Electrically Driven Quadruped Robot
Authors: You Yulong , Yang Zhong , Zou Teng’an , Sui Yaoyu , Xu Changliang , Zhang Chi , Xu Hao , Zhang Zhao , Han Jiaming
Published: April 2022

To improve the accuracy of tracking the trunk center-of-mass (CoM) trajectory and foot-end trajectory in a fully electrically driven quadruped robot, an efficient and practical new trajectory tracking control method is designed. The proposed trajectory tracking method is mainly divided into trunk balance controller (TBC) and swing leg controller (SLC). In TBC, a quadruped robot dynamics model is developed to find the optimal foot-end force that follows the trunk CoM trajectory based on the model predictive control (MPC) principle. In SLC, the Bessel curve is planned as the desired trajectory at the foot-end, while the desired trajectory is tracked by a virtual spring-damping element driving the foot-end, meanwhile, the radial basis function neural network (RBFNN) is applied for supervisory control to improve the control performance for the system. The experimental results show that the control method can modify the robot’s foot-end trajectory tracking effect, so that the stability error can be eliminated and the robustness of the controller can be improved, meanwhile, the linear and circular trajectory for CoM can be tracked accurately and quickly.
Assessing the Effect of Interimplant Distance and Angle on Different Impression Techniques
Authors: Albayrak Berkman , Korkmaz İsmail Hakkı , Wee Alvin G. , Sukotjo Cortino , Bayındır Funda
Published: April 2022

We aimed to evaluate the trueness of digital and conventional impression techniques based on different angles and distances between implants and the deviation caused by the angle and distance parameters varying between implants. Eight implants were placed in a polyurethane edentulous mandibular model at different angles and distances. After obtaining a 3-dimensional (3D) reference model by using an optical scanner, the model was scanned with three intraoral scanners: Cerec Omnicam (DO), Trios 3 (DT), and Carestream 3500 (DC). Then, the master casts obtained from the conventional impressions (C) were also digitized, and all impression data were imported into reverse engineering software to be compared with the 3D reference model. Distance and angle measurements between adjacent implants were performed, and the data were analyzed with ANOVA–Tukey and Kruskal Wallis tests. The significance level was accepted as p < 0.05. While DT and C groups gave the best results for high interimplant distances, the trueness of intraoral scanners was found to be superior to the conventional method between closer implants. At higher angulations, the angular trueness of C group was found to be significantly lower. At short distances, digital groups showed superiority, and the trueness of conventional impression decreased with higher angulations.
YOLO-GD: A Deep Learning-Based Object Detection Algorithm for Empty-Dish Recycling Robots
Authors: Yue Xuebin , Li Hengyi , Shimizu Masao , Kawamura Sadao , Meng Lin
Published: April 2022

Due to the workforce shortage caused by the declining birth rate and aging population, robotics is one of the solutions to replace humans and overcome this urgent problem. This paper introduces a deep learning-based object detection algorithm for empty-dish recycling robots to automatically recycle dishes in restaurants and canteens, etc. In detail, a lightweight object detection model YOLO-GD (Ghost Net and Depthwise convolution) is proposed for detecting dishes in images such as cups, chopsticks, bowls, towels, etc., and an image processing-based catch point calculation is designed for extracting the catch point coordinates of the different-type dishes. The coordinates are used to recycle the target dishes by controlling the robot arm. Jetson Nano is equipped on the robot as a computer module, and the YOLO-GD model is also quantized by TensorRT for improving the performance. The experimental results demonstrate that the YOLO-GD model is only 1/5 size of the state-of-the-art model YOLOv4, and the mAP of YOLO-GD achieves 97.38%, 3.41% higher than YOLOv4. After quantization, the YOLO-GD model decreases the inference time per image from 207.92 ms to 32.75 ms, and the mAP is 97.42%, which is slightly higher than the model without quantization. Through the proposed image processing method, the catch points of various types of dishes are effectively extracted. The functions of empty-dish recycling are realized and will lead to further development toward practical use.
Add-On Type Data-Driven Ripple-Free Dual-Rate Control Design Based on the Null Space of Steady-State Step Responses
Authors: Sato Takao , Yasui Ryota , Kawaguchi Natsuki
Published: April 2022

In the present study, a data-driven ripple-free design is proposed for a dual-rate sampled-data control system in which the sampling interval of the plant output is longer than the holding interval of the control input. The objective of the present study is to improve the steady-state intersample response without changing the sampled response and without using the plant model. To achieve the objective directly from controlled data, an add-on input based on the null space of steady-state step responses to an existing control system is used. The open-loop or closed-loop system to obtain the step response is assumed to be stable. In the present study, a two-degree-of-freedom design is given that redesigns the intersample output response independently of the steady-state sampled output response. In a numerical example, the proposed method is applied to a linear time-invariant single-input single-output stable system, where intersample ripples are eliminated using the add-on input that is independent of the existing sample output response in steady state.
Influence of Fit Clearance and Tightening Torque on Contact Characteristics of Spindle–Grinding Wheel Flange Interface
Authors: Yuan Qianqian , Zhu Yongsheng , Yan Ke , Zhang Xinzhuo
Published: April 2022

The spindle and grinding wheel flange (GWF) adopt double positioning of a tapered surface and end face. Due to the processing quality, the contact state of the spindle–GWF interface cannot be determined accurately. Based on the theory of finite element and the Yoshimura integral method, an analysis method for the contact stiffness of the spindle–GWF interface was established. In addition, the effects of the spindle–GWF interface’s original clearance and tightening torque on the contact pressure, final contact state and contact stiffness of the spindle–GWF interface were investigated and experimentally verified. It was found that the final contact state of the spindle–GWF changed when the tightening torque increased, especially when the original contact state was tapered contact, and the final contact state changed significantly after assembly. The contact pressure and contact stiffness of the spindle–GWF interface are increased by increasing the tightening torque. The radial stiffness is more affected by the end clearance variation compared to the axial and angular stiffness. When the original contact state is tapered contact, the radial stiffness of the interface is at maximum in three contact states. This research provides theoretical guidance for GWF assembly on gear-grinding machines.