bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of the Hakimi method for solving the problem of placement of optimal crews of emergency commissioners
Authors: Lukoyanov V , Vorobyev A , Rassoha V 
Published: November 2019

Abstract
The urgency of the problem being investigated is due to the constant presence of traffic jams on the major cities streets caused by various traffic incidents, which dramatically reduce the traffic capacity of the roadway and impede an unhindered passage for road users. One of the ways to solve this problem is the institute of emergency commissioners, which currently does not fully perform the functions imposed on it. In particular, the late arrival at the crash site contributes to the appearance of traffic jam. The paper proposes a scientifically based approach to solving the problem of rational crew’s deployment of emergency commissioners in the urban area. The article materials may be useful for regulation of the services of emergency commissioners, the State Traffic Safety Inspectorate, and for coordinating their cooperation with insurance companies.
Increasing the shape accuracy of the hardened parts of the frame by technological methods
Authors: Makaruk A A , Pashkov A A , Samoylenko O V 
Published: November 2019

Abstract
Aluminum alloy parts of the aircraft’s power frame are usually ribbed longitudinally and transversely to increase rigidity. As a result, the cross-section of such parts is a complex complex shape in the form of a brand, channel, I-beam, etc. with straight and inclined shelves. In the manufacturing of parts in the process of both mechanical processing and subsequent impact hardening there is an undesirable deformation (leashes), which is expressed in the deviation from the plane and saber-like form. After milling, the leashes can be removed by local plastic deformation methods, such as rolling by rollers, or by pressing, and after hardening, mechanical treatment, including straightening by local plastic deformation methods, is not allowed by the industry standard technical procedure. Expansion of technological possibilities of manufacturing of low-rigid parts with application of technology of preventive deformation -introduction of pre-distortion of the form of a detail for compensation of the leashes arising on the subsequent strengthening operations by methods of surface plastic deformation.
Grinding of aluminum alloy panels after shot peen forming on contact type installations
Authors: Starodubtseva D A , Koltsov V P , Vinh L T 
Published: November 2019

Absract
One of the key technological processes of production of the airframe of an aircraft is the manufacture of large-sized contour forming details such as “panel” and “fuselage shell”. To date, the most promising method of obtaining the required aerodynamic shape of such parts is the method of shot peen forming. It consists of processing the outer surface of a part with a stream of fast-moving shots, because of which a specific profile of micro roughness stays on the surface, characterized by numerous prints of fraction of different diameter and depth [1-5]. The grinding of the flap wheel is part of the forming process and improve the quality of the original surface. For the formation of large-sized surfaces, the scientists of INRTU have developed and introduced in the conditions of the Irkutsk aviation plant a unique installation for the shot peen forming– grinding of UDF-4 with CNC system [6, 7]. The primary, and the main difference of domestic development from foreign counterparts, is the division of the forming operation into smaller stages for easier process control. The development and improvement of grinding technology requires the development of appropriate methods and special software for it, which enables to automate the processing process.
Studying the effect of surface conditioning on the corrosion performance of titanium dental implants
Authors: Masia N D E , Smit M , Mwamba A I , Moema J S 
Published: November 2019

Abstract
The biocompatibility of dental implants is dependent on good interaction between implant-human body tissue and a good osseointegration. The surface roughness plays an important role enhancing bone healing and promoting biomechanical properties at the bone/implant interface. The increase in surface roughness can simultaneously improve cell migration and attachment of an implant, and enhance the osseointegration process. However surface roughness has shown to be detrimental to corrosion, raising the need to achieve a balance between good osseointegration and corrosion performance. This study characterised the corrosion performance of commercially pure titanium grade 4 with different surface conditionings. Implants in the form of 15 mm discs and implant screws were tested in basic Ringers lactate solution of pH 5.5 at 37°C and in modified Ringers of pH 2. Corrosion tests included open circuit potential (OCP), potentiodynamic polarization test (PDP) and mass loss corrosion tests. Metallurgical characterisation showed that titanium Grade 4 consisted of equiaxed alpha (α-Ti) grains. The OCP test showed that the machined implants were nobler than the roughened implants. The corrosion rates obtained were very low, below 0.13 mm/y which is an acceptable corrosion rate for biomaterial design and application. Mass-loss tests showed that the alloys passivated regardless of the surface conditioning. The machined surface had a corrosion resistance higher than that of the roughened surface finish in all conditions.
Development of a mathematical equation describing the strain hardening behaviour of metastable AISI 301 austenitic stainless steel
Authors: Mukarati T W , Mostert R J , Siyasiya C W 
Published: November 2019

Abstract
The strain hardening behaviour of AISI 301 metastable austenite steel was analysed by evaluating tensile data against the empirical mathematical equations of Hollomon, Ludwik and Ludwigson. It was found that these equations were inadequate to model this TRIP steel with low stacking fault energy (SFE). It was found that the fraction of strain-induced martensite could be expressed as a sigmoidal function of the applied strain. The log-log plots of true stress and true plastic strain from 5% to εUTS performed with uniaxial isothermal tests at 30 °C were thereafter adequately fitted with a sigmoidal curve. The instantaneous strain hardening exponent was determined as the slope of the above-mentioned sigmoidal curve at a specific strain value. The strain hardening exponent and the rate of strain hardening dσ/dε) increases with deformation due to formation of strain-induced martensite to a maximum and thereafter decreases as the volume fraction of strain-induced martensite approximates saturation. The variation of the instantaneous strain hardening exponent as a function of plastic strain and the strength coefficient, K, at 30 °C was deduced. A high value of K, 1526MPa, was determined. A correlation between the extent of martensitic transformation and the value of the instantaneous strain hardening exponent was observed. This work is part of the project that seeks to develop a constitutive model describing the flow stress during plastic deformation as a function of both plastic strain and the resulting martensitic transformation at different temperatures and strain rates and which accounts for the isotropic hardening process.
SiC and Al surface cladding of Ti-6Al-4V for improved wear properties – The binary advantage
Authors: Okoli U O , Otunniyi I O , Adebiyi I D 
Published: November 2019

AbstractTi-6Al-4V enjoys high specific strength, toughness and excellent corrosion resistance, but suffers high friction coefficient, severe adhesive wear and sensitivity to fretting wear. Laser surface cladding is one of the surface modification techniques used for improving on these demerits. Using a 4.4Kw continuous wave Nd-YAG laser processor, the surface cladding of as received Ti-6Al-4V alloy was done with mixtures of SiC and Al powders in different ratios. The SiC powder can serve as reinforcing particles and helps improve surface wear properties in resulting surface metal matrix composite while aluminium improves on the wetting between the metal and the reinforcement SiC phase. The success of this, however, depends on the careful optimisation of the powder ratio, which dictates the resulting phases and microstructural evolutions. Study of the cladding with scanning electron microscope (energy dispersive spectroscopy), optical microscope and x-ray diffraction revealed formation of intermetallic phases such as AlSiTi2, Ti7Al5Si12, TiSi2, AlSi3Ti2, Al6Ti19, Ti2VAl, AlTi3, AlCTi2, Ti3SiC2and Ti5Si4, which should enhance micro-hardness and tribological properties of the surface relative to the bulk as-received alloy. 90:10 weight percentage ratio of SiC and Al powder mixture gave the best microhardness with a value of 1169.95 Hv, compared to 323.67 Hv of the as-received, and mass loss under abrasive wear tests was only 40% of the as received. The morphology obtained for the abraded surfaces is also indicative of this improvement. In carefully optimised proportions and laser condition, the binary combination of Al and SiC powders suffice for well improved Ti-6Al-4V surface properties.
Morphological characterization of recycled powder and microstructures of Ti-6Al-4V components synthesized by LENS additive manufacturing
Authors: Sibisi P N , Popoola A P I , Arthur N K K , Pityana S L , Popoola O M 
Published: November 2019

Abstract
Direct Metal Laser Deposition (DMLD) processes such as LENS are gaining ground in commercial manufacturing processes of functional end-products. This is attributed to this process being popularized as a sustainable technology with the potential to substitute the energy intensive, wasteful and environmentally unfriendly traditional techniques. However, during processing a significant fraction of the injected powders do not end up as part of the final component. The properties of these powders change due to heating resulting in coalescence and possible chemical reactions with the surrounding environment. A potential way to overcome this is by adopting an effective powder recycling procedure by which material use efficiency can be improved. Even so, these changes may have detrimental impact on the mechanical properties of the end-product. The objective of this paper is to investigate the effect of powder recycling on mechanical properties as a consequence of a change in powder characteristics. The potential for improving the LENS process by powder recycling process has been evaluated by comparatively studying the feedstock characteristics, i.e. morphology, particle size distribution and microstructure of powders in as received state and after laser exposure during repeated deposition cycles. Microstructures, micro-hardness and Density of the built samples were measured after the first deposition-normalization-reuse cycle. The results revealed a correlation between the powder characteristics and the properties of the corresponding built sample used for that specific deposition.
Tensile properties and microstructural characterization of additive manufactured, investment cast and wrought Ti6Al4V alloy
Authors: Beyl K , Mutombo K , Kloppers C P 
Published: November 2019

Abstract
This paper presents an evaluation of the tensile properties and microstructural characterization of Ti6Al4V alloy manufactured with three different processing routes; traditional wrought processing, investment cast and Laser Engineered Net Shaping (LENS). Tensile specimens were machined from each process and tensile tested at room temperature. Fractured specimens were characterized using light optical microscopy, stereo microscopy, microhardness and Scanning Electron Microscopy (SEM) to investigate the microstructural morphology and the structural hardness variation. The investment cast Ti6Al4V alloy microstructure revealed large equiaxed grains containing various orientated lamellar colonies. The additive manufactured microstructure revealed long columnar grains with Widmanstatten α’ martensite laths and retained β grain boundaries. While the wrought Ti6Al4V microstructure was observed as smaller equiaxed grains with large colonies of fine lamellar and transformed β. Additive manufactured specimens had higher yield strength, ultimate tensile strength and hardness compared to the investment cast and wrought manufactured specimens.
Preparation and microstructural characterization of the 60Al-40V master alloy
Authors: Mapoli T O , Annan K A , Siyasiya C W , Mutombo Kalenda 
Published: November 2019

AbstractThe present study focused on preparation and characterization of 60Al-40V master alloy which was produced via aluminothermic process. The study assessed the production in order to provide the optimum Al requirement for maximum recovery of the V. V2O5(Vanadium pentoxide) and Al metal were mixed in the proportion of producing 60Al-40V and Al2O3(slag) through an exothermic reaction. Microstructural analysis and phase identification were done using Optical Microscopy (OM), Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Spectroscopy (EDX) and X-Ray Diffraction (XRD) analyses. The XRD revealed diffraction peaks mainly of the Al3V phase and some peaks of slightly homogenized Al8V5intermetallic compounds. The chemical composition was found to be 65 ± 0.03 and 35 ± 0.03 wt. % Al and V respectively. Good agreement between the experimental results and the predicted phases using Thermo-Calc. Software was observed.
Development and characterization of porous Ti-Sn-SiC composite intended for biomedical application
Authors: Mathebula C R , Matizambuka W , Bolokang A S 
Published: November 2019

Abstract
Titanium-based materials have received great research interest this is mainly due to their promising specific strength, thermal stability, corrosion resistance, and biocompatibility. Porous titanium has been shown to exhibit desirable properties as biomedical materials. Ti-Sn-SiC composites of different compositions were synthesized through mixing Ti, Sn and SiC powders. The study was carried out by blending and cold-pressing followed by sintering at a 1400°C. Microstructures of the materials were studied using an optical microscope (OP) and scanning electron microscopy (SEM). To investigate structural development and phase transformation, x-ray diffraction (XRD) was performed. A porous Ti-Sn-SiC composite was achieved which is favorable for biomedical application.
Preparation and characterization of glass-ceramic composites from South African coal fly ash
Authors: Modiga A , Sosibo N , Singh N 
Published: November 2019

Abstract
Though fly ash in South Africa has mainly been utilized in the construction industry, a large portion of it is still discarded. Production of glass-ceramic composites through fly ash devitrification has gradually become one of the applications being examined internationally. This study reports the investigation of producing glass-ceramic composites from fly ash and varying quantities of beverage waste glass and magnesium oxide as main raw materials. Glasses were obtained by melting fly ash and its additives using an arc furnace. Based on their behaviour when subjected to differential thermal analysis, the glasses were then crystallised through a double-staged thermal treatment to form glass-ceramic composites. The composition and behaviour of the glass-ceramic composites were investigated using X-ray diffraction, Scanning Electron Microscopy, mechanical and chemical assessments. The crystal content in the glass-ceramic composites increased as the magnesium oxide content was increased. The desired diopside phase decreased with an increased magnesium oxide content and ultimately resulted in the formation of forsterite and anorthite as the major and second major phases respectively. The glass-ceramic composites with lesser amounts of magnesium oxide were chemically and thermally resistant and they also demonstrated high cold compressive strength.
Development of MgAl2O4grain refiner in Al in-situ composite through H3BO3addition
Authors: Chandramohan P , Olubambi P A , Raghu R , Obadele B A 
Published: November 2019

AbstractIn the present work, a novel approach has been made for synthesis of in-situ Magnesium Aluminate (MgAl2O4) particles in the Al-4Mg alloy by Boric Acid (H3BO3) precursor addition (1 wt %, 1.5 wt % and 2 wt %) during the casting process. The developed composite has been investigated for its microstructural characteristics and corrosion performance. Scanning Electron Microscopy and Energy Dispersive Spectroscopy examination revealed the formation of MgAl2O4 particles in the composite. Potentiodynamic polarization corrosion experiments were performed on the Al-4Mg/H3BO3 composite specimens (1 wt %, 1.5 wt % and 2 wt %) in three different medium (3.5 % Sodium Chloride-NaCl, 1 M Sulphuric Acid-H2SO4 and 1 M Hydrochloric Acid-HCl). Corrosion results showed that Al-4Mg/1.5 wt % H3BO3 composite specimen exhibited better corrosion resistance in 3.5 % NaCl, 1 M H2SO4 and 1 M HCl medium due to the significant grain refinement produced by MgAl2O4 particles. The developed composite with better corrosion properties can be utilized for marine and naval application.
First-principles studies on the structural, electronic and mechanical properties of L1o and L12 FexPt1-x alloys
Authors: Lethole N L , Chauke H R , Ngoepe P E 
Published: November 2019

Abstract
Bimetallic FexPt1-x alloys with the L10 and L12 structures have recently gained a lot of consideration in practical applications for solid-state devices, storage of ultra-high density magnetic data and biomedicine. This is due to their high magnetic and magnetocrystalline anisotropy, density, and coercivity. In order to gain knowledge on the structural, electronic and mechanical properties of the cubic and tetragonal FexPt1-x alloys, we have calculated their equilibrium lattice constants, density of states, and elastic constants at 0 K, employing first-principles calculations. The calculated equilibrium lattice constants were found to be in good agreement with the experimental data to within 3 %. All independent elastic constants satisfy the necessary stability conditions for both cubic and tetragonal systems, suggesting mechanical stability. The shear anisotropic factors predict that the tetragonal FexPt1-x crystals are highly anisotropic along the {001} plane than {100}. Moreover, the percentage of bulk (AB) and shear (AG) anisotropies revealed completely isotropic systems in the bulk and slightly anisotropic in shear modulus.
Surface morphology characterisation for parts produced by the high speed selective laser melting
Authors: Shange M , Yadroitsava I , Pityana S , Yadroitsev I , Bester D 
Published: November 2019

Abstract
Additive Manufacturing (AM) systems are unique in terms of fast production and lead time to market. South Africa has built the AM Laser Powder Bed Fusion (LPBF) machine called Aeroswift with the world’s largest build volume and highest speed. Surface roughness of LPBF parts depends on process-parameters. High surface roughness and deformations during processing limit the application of this technology for certain industrial applications that require high precision. This study characterises the surface roughness for self-supported parallelepipeds samples produced using the Aeroswift platform. Test artefact parallelepipeds were built with 0-90 degrees sloping angles with respect to the building direction. Surface roughness for the as-built samples was analysed using Mitutoyo SURFTEST SJ-210 system and Zeiss Smartzoom 5 digital microscope. It was found that roughness values were higher for the bottom surfaces (overhang part) compared to upward surfaces, as expected. This was attributed to the higher amount of attached partially melted powder particles that were observed on the downward surface. Absolute values of Ra and Rz versus scanning direction and slope angle were found and analysed.
Study on the microstructure of 2124 aluminum alloy subjected to stress assisted aging
Authors: Quan L W , Wang C C 
Published: November 2019

Abstract
The effect of a load on the microstructure of 2124 aluminum alloy was investigated by employing transmission electron microscopy. When the alloy was aged at 190°C under a load of 6.05 kg, the deformation was increased with the aging time prolonging. Meanwhile the length of Al2CuMg(S) phase was shorter than the length of S phase in the alloy without loading. At the same time, there was no preferential orientation effect on S phase or Genier Preston Bagaryatsky (GPB) zones.
Effect of Hypoxia on Embryo Development in Silkworm Eggs
Authors: Gong Jing , Zhang Yuhao , Yan Jiamin , Shang Shan , Gu Hanfei , Zhu Yong 
Published: November 2019

AbstractDiapause is a common phenomenon during which organisms suspend development to overcome difficult environmental conditions. The silkworm is a classical model for the study of egg diapause. Our previous study showed that gene expression is similar in silkworm eggs treated with hyperoxia or HCl. In the present study, to further explore the mechanism of diapause prevention, nondiapause eggs and hyperoxia-/HCl-activated diapause eggs were treated with hypoxia. Embryo morphology, hatching time, and reactive oxygen species (ROS) levels were analyzed across different developmental stages. The results showed that hypoxia may inhibit the embryonic development of silkworm eggs. The morphology of nondiapause eggs under hypoxia differed from that of nondiapause eggs under normoxia during embryonic development, which, in turn, was similar to that of diapause eggs. Meanwhile, the hatching time of nondiapause eggs under hypoxia was delayed significantly. Moreover, the ROS levels of nondiapause eggs changed under hypoxia, showing a pattern similar to that of diapause eggs. Interestingly, when activated diapause eggs were treated with hypoxia, some eggs hatched in the following spring. These results suggest that early embryogenesis is largely dependent on oxygen levels and that hypoxia may induce a diapause-like state in activated diapause eggs. Additionally, ROS levels may play a key role in diapause. Thus, this study provides valuable information on the mechanisms of diapause and diapause prevention in silkworms.
Determination of Bisphenol A by High-Performance Liquid Chromatography Based on Graphene Magnetic Dispersion Solid Phase Extraction
Authors: Li Xinghua , Li Shuang , Bai Jialei , Peng Yuan , Ning Baoan , Shi Hongmei , Kang Weijun , Zhou Huanying , Gao Zhixian 
Published: November 2019

Abstract
Bisphenol A (BPA), as one of the environmental endocrine disruptors, is extensively existing and threatening to human health. To evaluate the environmental exposure level and protect human from the hazard of BPA, a precise and sensitive method is established. In this work, Graphene@ Fe3O4 (G@Fe3O4) is prepared by chemical coprecipitation method as magnetic dispersion solid phase extraction (MDSPE) material. The rapid and specific detection method of BPA is carried out by high-performance liquid chromatography (HPLC). Properties of G@Fe3O4 are identified by the fourier infrared spectrum and scanning electron microscopy. Conditions of solid phase extraction are optimized. Under the optimal extraction conditions, G@Fe3O4 has perfect enrichment effect on BPA. There is a good linear relationship in the range of 5.0~1000.0 μg/L with the correlation coefficient of 0.9997. The detection limit is 0.1 μg/L. This method is applied to water samples successfully, and recoveries of BPA are between 88.19% and 99.56% (RSDs &lt; 3.00%). G@Fe3O4 was synthesized, which was used to extract BPA in water samples before HPLC analysis, and has shown perfect extraction ability toward BPA, which indicates that the determination method of BPA by HPLC based on graphene MDSPE is faster and more precise.