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Purpose: The purpose of the paper is to predict the erosion rate of the components of centrifugal pump under certain operating condition to identify the maximum erosion area and to discuss the factors affecting them. This helps to optimize design and estimate service life. Design/methodology/approach: In the paper, the Eulerian–Lagrangian approach method coupled with the erosion model to investigate the mixed sand characteristics on erosion characteristics of centrifugal pump flow-through wall. The hydraulic performance and wear characteristics experiment of the pump is used to verify the accuracy of the numerical simulation. Findings: The blade erosion area mainly occurs near the blade inlet and the trailing edge of the pressure surface, the main erosion area of the impeller back shroud is near the outlet of the flow passage and the main erosion area of the volute is near the tongue and the I section. With the change of the average diameter and density of sand particles, the average erosion rate on different flow-through walls is positively correlated with the average mass concentration to a certain extent. However, for different sand shape factors, there is little correlation between the average erosion rate and the average mass concentration. In addition, compared with other erosion areas, the increase of average sand particle diameter and density has the greatest impact on the total erosion rate of blade pressure surface, while the shape of sand particles has a greater impact on the total erosion rate of each flow-through wall of centrifugal pump. Originality/value: In this work, according to the characteristics of the mixed distribution of different sand diameters in the Yellow River Basin, the erosion characteristics of centrifugal pumps used in the Yellow River Basin are studied. The numerical calculation method for predicting the wall erosion of centrifugal pump is established and compared with the experimental results. The results can provide reference for optimizing design and increasing service life. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to prepare a robust superhydrophobic coating on concrete substrate with remarkable chemical and mechanical durability through "all-covalent" strategy. Design/methodology/approach: Amino-modified silica nano/micro-particles were prepared through two synthetic steps. "All-covalent" strategy was introduced to prepare a robust superhydrophobic coating on concrete surface via a "all-in-one" dispersion and a simple spraying method. The successful construction of the products was confirmed by Fourier transform infrared spectroscopy, water contact angles (WCA), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). The concrete protective properties were verified by solution immersion test, pull-off test and rapid chloride migration coefficient test. The mechanical durability was tested by falling sand impact. Findings: Hierarchical structures combined with the low-surface-energy segments lead to typically superhydrophobic coating with a WCA of 156° and a sliding angle of 1.3°. The superhydrophobic coating prepared through "all-covalent" strategy not only improves chemical and mechanical durability but also achieves higher corrosion and wear resistance than the comparison sample prepared by physically blending strategy. More importantly, the robust superhydrophobic coating showed excellent adhesion and protective performance of concrete engineerings. Practical implications: This new "all-covalent" superhydrophobic coating could be applied as a concrete protective layer with properties of self-cleaning, anti-graffiti, etc. Originality/value: Introduction of both silica nanoparticles and silica microparticles to prepare a robust superhydrophobic coating on concrete surface through "all-covalent" strategy has not been systematically studied previously. [ABSTRACT FROM AUTHOR]

Purpose -- The purpose of this paper is to investigate the relationships between the magnitude of job offshoring and organizational contingencies, including total number of employees, multinationality, business diversification, and relevancy of business activities. Design/methodology/approach -- Previous studies on job offshoring were restricted in descriptive and prescriptive understanding of the phenomena. Utilizing secondary data, this paper provides empirical findings on the magnitude of job offshoring from an organizational contingency perspective. Findings -- The results indicate that larger and multinational firms tend to offshore a larger number of jobs, and less diversified firms tend to offshore a higher ratio of jobs. Also, firms that offshore their core business activities are more likely to move a higher ratio of jobs to offshore destinations. Research limitations/implications -- This paper reveals some of the key organizational factors that account for the magnitude of job offshoring within American firms. Practical implications -- The findings offer insights in what the government, the society, the workforce need to prepare for future changes and the globalization of business. Originality/value -- The paper offers empirical explanations of the magnitude of job offshoring. Various governmental, private, and international institutions may rely on the findings in making political, commercial, and social policies and decisions. [ABSTRACT FROM AUTHOR]

Purpose: This in vitro study aims to explore the effects of selective laser melting (SLM) process parameters on the accuracy of the intaglio surface of cobalt–chromium alloy (Co–Cr), commercially pure titanium (CP Ti) and titanium alloy (Ti–6Al–4V) maxillary removable partial denture (RPD) frameworks and optimize these process parameters. Design/methodology/approach: Maxillary RPD framework specimens designed on a benchmark model were built. The process parameters, including contour scan speed and laser power, infill scan speed and laser power, hatch space, build orientation and metallic powder type, were arranged through the Taguchi design. Three-dimensional deviations of the clasps area, connector area and overall area of maxillary RPD frameworks were analyzed by using root mean square (RMS) as a metric. One-way analyses of variance with the above RMSs as the dependent variable were carried out (α = 0.05). Findings: Maxillary RPD frameworks built horizontally had a more accurate intaglio surface than those built at other orientation angles; CP Ti or Ti–6Al–4V maxillary RPD frameworks had a more accurate intaglio surface than Co–Cr ones; the Maxillary RPD framework built with a higher infill scan speed and lower infill laser power had the more accurate intaglio surface than the one built with other levels of these two process parameters. Originality/value: A novel benchmark model for evaluating the accuracy of the intaglio surface of maxillary RPD frameworks manufactured by SLM is proposed. The accuracy of the intaglio surface of maxillary RPD frameworks can be improved by adjusting SLM process parameters. The optimal setting of process parameters concerning the accuracy of the intaglio surface of maxillary RPD frameworks was given. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to investigate the interfacial conductivity and corrosion resistance of the Ni–P/Ti4O7 composite coating that is deposited on a carbon steel substrate as bipolar plates for proton exchange membrane fuel cells. Design/methodology/approach: The Ni–P/Ti4O7 coating was prepared by electroless plating. Scanning electron microscopy, white light interference, energy dispersive spectrometry and X-ray diffraction were used, respectively, to study the surface morphology, chemical composition and phase composition of coated samples. Electrochemical impedance spectroscopy, potentiodynamic and potentiostatic polarization were used to test the electrochemical performance and corrosion behavior. The interfacial contact resistance (ICR) was measured via the standard method. Findings: The surface of the Ni–P/Ti4O7 coating is complete and dense and without obvious defects. The electrochemical test results show that the Ni–P/Ti4O7 coating provides better corrosion resistance than the Ni–P coating and substrate. Compared with the Ni–P coating, the ICR of the Ni–P/Ti4O7 coating is lower by about 82.7%. This is because the coating has more conductive contact points. The more exciting thing is that the ICR of the Ni–P/Ti4O7 coating only increases to 12.38 mΩ·cm2 after 5 h of polarization. Originality/value: This paper provides a method for achieving surface modification of metal bipolar plates. Introducing Ti4O7 particles in the Ni–P layer reduces the contact resistance before and after polarization while ensuring good corrosion resistance. [ABSTRACT FROM AUTHOR]

Purpose: Scholars have identified several predictors of learner satisfaction, but little research addresses the impact of intragroup conflict in a virtual learning context. The purpose of this paper is to investigate the potentially deleterious effects of perceived intragroup relationship conflict on virtual learners' intention to re-enroll. Design/methodology/approach: Data were systematically collected from virtual learners using an online questionnaire and then analyzed by multiple regression models. Findings: The results show that emotional expressiveness is an antecedent to perceived intragroup relationship conflict, and the relationship is moderated by individuals' perceived enjoyment of computer-mediated communication. Virtual learners with a higher emotional expressiveness (i.e. extraverts) experience higher perceived relationship conflict, which in turn, lowers their intention to re-enroll. Research limitations/implications: The study confirms the antecedent and consequence of perceived intragroup relationship conflict in a virtual learning context. Practical implications: Educational institutions and businesses may use three proposed strategies to deal with intragroup relationship conflict. Originality/value: The study contributes to the limited knowledge on how to effectively manage virtual learning interactions by educational institutions and businesses. [ABSTRACT FROM AUTHOR]

Purpose Sand production is a challenging issue during hydrocarbon production in the oil and gas industry. This paper aims to investigate one sand production process, i.e. transient sand production, using a novel bonded particle lattice Boltzmann method. This mesoscopic technique provides a unique insight into complicated sand erosion process during oil exploitation.Design/methodology/approach The mesoscopic fluid-particle coupling is directly approached by the immersed moving boundary method in the framework of lattice Boltzmann method. Bonded particle method is used for resolving the deformation of solid. The onset of grain erosion of rocks, which are modelled by a bonded particle model, is realised by breaking the bonds simulating cementation when the tension or tangential force exceeds critical values.Findings It is proved that the complex fluid–solid interaction occurring at the pore/grain level can be well captured by the immersed moving boundary scheme in the framework of the lattice Boltzmann method. It is found that when the drawdown happens at the wellbore cavity, the tensile failure area appears at the edge of the cavity. Then, the tensile failure area gradually propagates inward, and the solid particles at the tensile failure area become fluidised because of large drag forces. Subsequently, some eroded particles are washed out. This numerical investigation is demonstrated through comparison with the experimental results. In addition, through breaking the cementation, which is simulated by bond models, between bonded particles, the transient particle erosion process is successfully captured.Originality/value A novel bonded particle lattice Boltzmann method is used to investigate the sand production problem at the grain level. It is proved that the complex fluid–solid interaction occurring at the pore/grain level can be well captured by the immersed moving boundary scheme in the framework of the lattice Boltzmann method. Through breaking the cementation, which is simulated by bond models, between bonded particles, the transient particle erosion process is successfully captured. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to use cone-beam computed tomography (CBCT) and computer-aided design/3D printing technology to design and fabricate a drill guide template for access cavity preparation of permanent molars, and conduct a preliminary evaluation of its effectiveness.Design/methodology/approach CBCT scans were performed on two permanent maxillary first molars extracted due to periodontitis. Based on the scans, guide templates of access cavities were designed. The angle of the guiding cylinders was determined based on the direction of the long axis of the tooth. A 3D resin printer with high resolution was used to print the guide templates. The printed guide templates were used by a dentist with specialized clinical experience to perform access cavity preparation in a dental simulator. Then the prepared access cavities were scanned again by CBCT, and scan data were compared to the design data.Findings The 3D printed drill guide template had a close fit with the extracted tooth fit. The access cavity prepared using the guide template enabled the removal of the pulp chamber roof, and formed a straight-line access. Points were selected for measurement at regularly spaced intervals of 0.5 mm along the side wall of the access cavity. The mean deviation between the actual access cavities of the two permanent maxillary first molars and the designed cavities was less than 0.1 mm, with a maximum deviation of about 0.5 mm, showing a good conformance between the actual cavity and the designed cavity.Originality/value A drill guide template was designed and fabricated by 3D printing technology, which easily guided burs to complete the access cavity preparation work forming an ideal cavity shape with satisfying accuracy, and thus may reduce the complications during pulp chamber entry. [ABSTRACT FROM AUTHOR]

Purpose The use of removable complete dentures is a selectable restorative procedure for edentulous patients. To improve the fabrication quality and efficiency of removable complete dentures, this paper aims to introduce a new method to fabricate customized wax complete dentures with additive manufacturing. This process uses complementary digital technologies, and allows faster and better manufacture of complete dentures.Design/methodology/approach In the study, a dental scanner was used to obtain surface data from edentulous casts and rims made by the dentist. A parameterized three-dimensional graphic database of artificial teeth was pre-established. Specialized computer-aided design software was used to set up the artificial dentition and design the esthetic gingiva and base plate. A selective laser sintering machine was used to transfer the data from stereolithography files into a wax base plate with location holes for each artificial tooth.Findings Under this method, a set of wax base plates with 28 location holes available for the placement of the artificial teeth were designed and fabricated within 6 h. The try-in wax dentures fitted the patient’s mouth well, besides occlusion relationships. Then, the occlusion relationships can be adjusted manually to achieve a balanced centric occlusion.Originality/value This method can be used to design and fabricate wax try-in removable complete dentures semi-automatically and rapidly; however, the algorithm for the occlusion contact design needs to be improved. [ABSTRACT FROM AUTHOR]

Purpose – Three test platforms for long-term continuous loading are adopted to test the actuator prototypes of the 500-meter aperture spherical radio telescope (FAST). However, the wire ropes that are the key components of these platforms often break during testing. The purpose of this paper is to present an effective dimension design method for these wire ropes. This method is based on fatigue reliability theory. Design/methodology/approach – Three types of stresses are introduced into the total stress model of the wire rope according to the complicated stress conditions. The fatigue strength of the ropes is also discussed in this paper. Then, the total stress model and the results of fatigue strength analysis are applied to set the optimization function for these wire ropes. Subsequently, this optimization function is used to calculate the reliability of previously developed wire ropes in relation to the actuator test platform. Findings – The wire rope is unreliable, which is a finding that corresponds to those of previous tests. Upon drawing the optimal curve from the optimization function (whose optimal objective is the wire diameter), a wire rope is optimized for the FAST actuator test platforms. Finally, this optimized rope is used on the new actuator test platform. No fracture phenomenon has been detected in tests conducted over the past six months. Originality/value – The fatigue reliability theory-based optimization function for wire ropes can be adopted for the universal dimension design of other wire ropes. [ABSTRACT FROM AUTHOR]