The tribological behaviors of Cu-15Ni-8Sn/graphite composites with the graphite content of 38 vol.% against AISI321 stainless steel under dry-sliding, deionized water and sea water were investigated on a block-on-ring configuration. The results indicated that the friction coefficient was the lowest under dry-sliding, and the highest in deionized water. The wear rate decreased to reach the minimum value of 1.39×10-¹⁵ m³/(Nm) in sea water and in deionized water, it increased to the maximum value of 5.56×10-¹⁵ m³/(Nm). The deionized water hindered the formation of tribo-oxide layer and lubricating film, which resulted in the largest friction coefficient and wear rate. In sea water, however, the corrosion products comprised of oxides, hydroxides and chlorides were found on the worn surface, and the compacted layer composed of corrosion products and graphite played an important role in keeping the excellent wear resistance. It was elucidated that the tribological behaviors of Cu-15Ni-8Sn/graphite composite were powerful influenced by the friction environments.

Copper alloyed with various compositions of nickel and tin were cast into molds under argon atmosphere. The cast rods were homogenized, solution heat treated, followed by aging for different time duration. The specimens were characterized for microstructure and tested for microhardness and wear rate. A hybrid model with a linear function and radial basis function was developed to analyze the influence of nickel, tin, and aging time on the microhardness and tribological behavior of copper-nickel-sin alloy system. The results indicate that increase in the composition of nickel and tin increases the microhardness and decreases the wear rate of the alloy. The increase in the concentration of nickel and tin decreases the peak aging time of the alloy system.

This work is aimed to study the effect of boron on wear resistance of Fe-Cr-B alloys containing different boron contents (0 wt%, 5 wt%, 7 wt% and 9 wt%) from room temperature (RT) to 800 °C in order to explore their applications as high-temperature wear resistant mechanical parts. Additionally, the wear mechanism of alloys is evaluated. The tribological properties of alloys are systematically studied by using a ball-on-disc tribometer at 10 N and 0.20 m/s from RT to 800 °C sliding against Si₃N₄ ceramic ball. The boron element greatly improves the wear resistance of specimens as compared with that of unreinforced specimen. The friction coefficients of specimens decrease with increasing of testing temperature. The wear rates of Fe-Cr-B alloys decrease firstly and then raise with the increase of boron content. The specific wear rates of specimens with boron are 1/10 of the unreinforced specimen. Fe-21wt%Cr-7wt% B keeps the best tribological properties at high temperature.

The solidification microstructure, fracture morphologies, and mechanical properties of an Al-18Si alloy and alloys modified with Al-5Ti and Al-3P master alloys were investigated using an optical microscope, scanning electron microscope, and an electronic universal testing machine. The results show that additions of Al-5Ti and Al-3P have significant effects on the size and area fraction of the primary Si and the mechanical properties of the Al-18Si alloy. Compared to the Al-18Si alloy modified with 0.6 wt% Al-5Ti at 850 °C, when the Al-18Si alloy was modified with 0.3 wt% Al-5Ti and 0.5 wt% Al-3P at the same temperature, the average size of the primary Si decreased from 39 to 14 μm and the area fraction increased from 9.5% to 11.6%. The biggest influencing factor on the tensile strength and elongation of the Al-18Si alloy is the addition of Al-3P, followed by the modification temperature and the addition of Al-5Ti. At a modification temperature of 850 °C, the tensile strength and elongation of the Al-18Si alloy modified with 0.3 wt% Al-5Ti+0.5 wt% Al-3P increased by 19.6% and 88.6%, respectively compared to that of the Al-18Si alloy modified with 0.6 wt% Al-5Ti.

Hydrogenated microcrystalline silicon (µc-Si:H) films were prepared on glass and silicon substrates by radio frequency magnetron sputtering at 100 °C using a mixture of argon (Ar) and hydrogen (H₂) gasses as precursor gas. The effects of the ratio of hydrogen flow (H₂/(Ar+H₂)%)) on the microstructure were evaluated. Results show that the microstructure, bonding structure, and surface morphology of the µc-Si:H films can be tailored based on the ratio of hydrogen flow. An amorphous to crystalline phase transition occurred when the ratio of hydrogen flow increased up to 50%. The crystallinity increased and tended to stabilize with the increase in ratio of hydrogen flow from 40% to 70%. The surface roughness of thin films increased, and total hydrogen content decreased as the ratio of hydrogen flow increased. All µc-Si:H films have a preferred (111) orientation, independent of the ratio of hydrogen flow. And the µc-Si:H films had a dense structure, which shows their excellent resistance to post-oxidation.

The constructed potential-pH diagrams of Li-Ni (Co, Mn)-H₂O system indicate that the LiNiO₂, LiCoO₂ and LiMnO₂ are thermodynamically stable in aqueous solution within the temperature range of 25-200 °C and the activity range of 0.01-1.00. A predominant co-region of LiNiO₂, LiCoO₂ and LiMnO₂ oxides (Li-Ni-Co-Mncomposite oxide) is found in the Li-Ni-Co-Mn-H₂O potential-pH diagrams, in which the co-precipitation region expands towards lower pH with rising temperature, indicating the enhanced possibility of synthesizing Li-Ni-Co-Mn composite oxide in aqueous solution. The experimental results prove that it is feasible to prepare the LiNi_0.5Co_0.2Mn_0.3O₂ cathode materials (NCM523) by an aqueous routine. The as-prepared lithiated precursor and NCM523 both inherit the spherical morphology of the hydroxide precursor and the obtained NCM523 has a hexagonal α-NaFeO₂ structure with good crystallinity. It is reasonable to conclude that the aqueous routine for preparing Ncm cathode materials is a promising method with the guidance of the reliable potential-pH diagrams to some extent.

According to the problems of short life and low strength of TiB₂ coating cathode for current technology in aluminium electrolysis industry, this work synthesized TiB₂-TiB/Ti gradient composite with TiB₂ coating and TiB whiskers in metallic Ti matrix by a electrolytic boronizing method based on similar density and thermal expansivity of the three materials. The phase composition and morphology of the cross-section were determined by X-ray diffraction (XRD), scanning electronic microscope (SEM) and X-ray energy dispersive spectrum (EDS). The results show that uniform TiB₂ layer with a thickness of 8-10 μm is continuously coated on the surface while the TiB whisker connected with TiB₂ layer was embedded dispersedly into the matrix. The TiB crystal whisker has a maximum length of about 220 μm. The growth rate of TiB₂ and TiB is enhanced by the strong reduction of B₄C. The novel gradient design of the composite helps to extend life and improve strength of the TiB₂ cathode in aluminium electrolysis.

In this study, we present the characterization of the carbon fibers recovered from the mechanochemical-enhanced recycling of carbon fiber reinforced fibers. The objectives of the study were to investigate the effect of our modified recycling method on the interfacial properties of recovered fibers. The reinforced plastics were recycled; the recycling efficiency was determined and the recovered fibers were sized using 1 wt% and 3 wt% concentration of (3-aminopropyl)triethoxysilane. We characterized the morphologies utilizing the electron spectroscopy for chemical analysis (ESCA), atomic force microscopy (AFM), FTIR-attenuated total reflection (ATR) spectroscopy and scanning electron microscopy (SEM). Although the surface of the fibers had no cracks, there was evidence of contaminations which affected the interfacial properties and the quality of the fibers. Results showed that the trends in the recovered and virgin fibers were similar with an increase in sizing concentration. The results highlighted the perspectives of increasing the quality of recovered fibers after the recycling process.

In order to improve the processing precision and shorten the hob manufacturing cycle of the face gear, a precision generating hobbing method for face gear with the assembly spherical hob is proposed. Firstly, the evolution of the cylindrical gear to spherical hob basic worm is analyzed, then the spherical hob basic worm is designed, thus the basic worm and spiral angle equation of spherical hob are obtained. Secondly, based on the design method of the existing hob, the development method of the assembly spherical hob is analyzed, the cutter tooth and the cutter substrate of the assembly hob are designed, and the whole assembly is finished. Thirdly, based on the need of face gear hobbing, a numerical control machine for gear hobbing is developed, and the equation of the face gear is obtained. Fourth, for reducing the face gear processing errors induced by equivalent installation errors, the error analysis model is established and the impacts of each error on the gear tooth surface are analyzed. Finally, the assembly spherical hob is manufactured and the gear hobbing test is completed. According to the measurement results, the processing parameters of face gear hobbing are modified, and the deviation of tooth surface is significantly reduced.

The phenomenon of heat accumulation and transportation in the composite materials is a very typical and critical issue during drilling process. In this study, a three-dimensional temperature field prediction model is proposed using finite difference method, based on the partly homogenization hypothesis of material, to predict temperature field in the process of drilling unidirectional carbon fiber/epoxy (C/E) composites. According to the drilling feed motion, drilling process is divided into four stages to study the temperature distributing characteristics. The results show that the temperature distribution predicted by numerical study has a good agreement with the experimental results. The temperature increases with increasing the drilling depth, and the burn phenomena is observed due to the heat accumulation, especially at the drill exit. Due to the fiber orientation, an elliptical shape of the temperature field along the direction is found for both numerical and experimental studies of C/E composites drilling process.

In this research, crashworthiness of polyurethane foam-filled tapered decagonal structures with different ratios of a/b=0, 0.25, 0.5, 0.75 and 1 was evaluated under axial and oblique impacts. These new designed structures contained inner and outer tapered tubes, and four stiffening plates connected them together. The parameter a/b corresponds to the inner tube side length to the outer tube one. In addition, the space between the inner and outer tubes was filled with polyurethane foam. After validating the finite element model generated in LS-DYNA using the results of experimental tests, crashworthiness indicators of SEA (specific energy absorption) and F_max (peak crushing force) were obtained for the studied structures. Based on the TOPSIS calculations, the semi-foam filled decagonal structure with the ratio of a/b=0.5 demonstrated the best crashworthiness capability among the studied ratios of a/b. Finally, optimum thicknesses (t₁ (thickness of the outer tube), t₂ (thickness of the inner tube), t₃ (thickness of the stiffening plates)) of the selected decagonal structure were obtained by adopting RBF (radial basis function) neural network and genetic algorithm.

Most existing network representation learning algorithms focus on network structures for learning. However, network structure is only one kind of view and feature for various networks, and it cannot fully reflect all characteristics of networks. In fact, network vertices usually contain rich text information, which can be well utilized to learn text-enhanced network representations. Meanwhile, Matrix-Forest Index (MFI) has shown its high effectiveness and stability in link prediction tasks compared with other algorithms of link prediction. Both MFI and Inductive Matrix Completion (IMC) are not well applied with algorithmic frameworks of typical representation learning methods. Therefore, we proposed a novel semi-supervised algorithm, tri-party deep network representation learning using inductive matrix completion (TDNR). Based on inductive matrix completion algorithm, TDNR incorporates text features, the link certainty degrees of existing edges and the future link probabilities of non-existing edges into network representations. The experimental results demonstrated that TFNR outperforms other baselines on three real-world datasets. The visualizations of TDNR show that proposed algorithm is more discriminative than other unsupervised approaches.

Aiming at the problem of small area human occlusion in gait recognition, a method based on generating adversarial image inpainting network was proposed which can generate a context consistent image for gait occlusion area. In order to reduce the effect of noise on feature extraction, the stacked automatic encoder with robustness was used. In order to improve the ability of gait classification, the sparse coding was used to express and classify the gait features. Experiments results showed the effectiveness of the proposed method in comparison with other state-of-the-art methods on the public databases CASIA-B and TUM-Gaid for gait recognition.

Liquefaction of sewage sludge (SS) in ethanol-water cosolvents is a promising process for the preparation of bio-oil/biochar products. Effect of the combined use of ethanol and water on the distribution/transformation behaviors of heavy metals (HMs) contained in raw SS is a key issue on the safety and cleanness of above liquefaction process, which is explored in this study. The results show that pure ethanol facilitates the migration of HMs into biochar products. Pure water yields lower percentages of HMs in mobile/bioavailable speciation. Compared with sole solvent treatment, ethanol-water cosolvent causes a random/average effect on the distribution/transformation behaviors of HMs. After liquefaction of SS in pure water, the contamination degree of HMs is mitigated from high level (25.8 (contamination factor)) in raw SS to considerable grade (13.4) in biochar and the ecological risk is mitigated from moderate risk (164.5 (risk index)) to low risk (78.8). Liquefaction of SS in pure ethanol makes no difference to the pollution characteristics of HMs. The combined use of ethanol and water presents similar immobilization effects on HMs to pure water treatment. The contamination factor and risk index of HMs in biochars obtained in ethanol-water cosolvent treatment are 13.1−14.6 (considerable grade) and 79.3−101.0 (low risk), respectively. In order to further control the pollution of HMs, it is preferentially suggested to improve the liquefaction process of SS in ethanol-water mixed solvents by introducing conventional lignocellulosic/algal biomass, also known as co-liquefaction treatment.

Micro-scale functionally graded material (FGM) pipes conveying fluid have many significant applications in engineering fields. In this work, the thermoelastic vibration of FGM fluid-conveying tubes in elastic medium is studied. Based on modified couple stress theory and Hamilton’s principle, the governing equation and boundary conditions are obtained. The differential quadrature method (DQM) is applied to investigating the thermoelastic vibration of the FGM pipes. The effect of temperature variation, scale effect of the microtubule, micro-fluid effect, material properties, elastic coefficient of elastic medium and outer radius on thermoelastic vibration of the FGM pipes conveying fluid are studied. The results show that in the condition of considering the scale effect and micro-fluid of the microtubule, the critical dimensionless velocity of the system is higher than that of the system which calculated using classical macroscopic model. The results also show that the variations of temperature, material properties, elastic coefficient and outer radius have significant influences on the first-order dimensionless natural frequency.

The study reveals analytically on the 3-dimensional viscous time-dependent gyrotactic bioconvection in swirling nanofluid flow past from a rotating disk. It is known that the deformation of the disk is along the radial direction. In addition to that Stefan blowing is considered. The Buongiorno nanofluid model is taken care of assuming the fluid to be dilute and we find Brownian motion and thermophoresis have dominant role on nanoscale unit. The primitive mass conservation equation, radial, tangential and axial momentum, heat, nano-particle concentration and micro-organism density function are developed in a cylindrical polar coordinate system with appropriate wall (disk surface) and free stream boundary conditions. This highly nonlinear, strongly coupled system of unsteady partial differential equations is normalized with the classical von Kármán and other transformations to render the boundary value problem into an ordinary differential system. The emerging 11th order system features an extensive range of dimensionless flow parameters, i.e., disk stretching rate, Brownian motion, thermophoresis, bioconvection Lewis number, unsteadiness parameter, ordinary Lewis number, Prandtl number, mass convective Biot number, Péclet number and Stefan blowing parameter. Solutions of the system are obtained with developed semi-analytical technique, i.e., Adomian decomposition method. Validation of the said problem is also conducted with earlier literature computed by Runge-Kutta shooting technique.

Beam shaping is required for semiconductor lasers to achieve high optical fiber coupling efficiency in many applications. But the positioning errors on optics may reduce beam shaping effects, and then lead to low optical fiber coupling efficiency. In this work, the positioning errors models for the single emitter laser diode beam shaping system are established. Moreover, the relationships between the errors and the beam shaping effect of each shapers are analysed. Subsequently, the relationship between the errors and the optical fiber coupling efficiency is analysed. The result shows that position errors in the Z axis direction on the fast axis collimator have the greatest influence on the shaping effect, followed by the position errors in the Z axis direction on the converging lens, which should be strictly suppressed in actual operation. Besides, the position errors have a significant influence on the optical fiber coupling efficiency and need to be avoided.

Multi-level inverters (MLIs) have become popular in different applications such as industrial power control systems and distributed generations. There are different forms of MLIs. The cascaded MLIs (CMLIs) have some special advantages among them such as more different output voltage levels using the same number of components and higher power quality. In this paper, a 27-level inverter switching algorithm considering total harmonic distortion (THD) minimization is investigated. Switching angles of the inverter switches are achieved by minimizing a THD-based objective function . In order to minimize the THD-based objective function, the hyper-spherical search (HSS) algorithm, as a novel optimization algorithm, is improved and the results of improved HSS (IHSS) are compared with HSS algorithm and other five evolutionary algorithms to show the advantages of IHSS algorithm.

A novel fault ride-through strategy for wind turbines, based on permanent magnet synchronous generator, has been proposed. The proposed strategy analytically formulates the reference current signals, disregarding grid fault type and utilizes the whole system capacity to inject the reactive current required by grid codes and deliver maximum possible active power to support grid frequency and avoid generation loss. All this has been reached by taking the grid-side converter’s phase current limit into account. The strategy is compatible with different countries’ grid codes and prevents pulsating active power injection, in an unbalanced grid condition. Model predictive current controller is applied to handling rapid transients. During faults, the energy storage system maintains DC-link voltage, which causes voltage fluctuations to be eliminated, significantly. A fault ride-through strategy was proposed for PMSG-based wind turbines, neglecting fault characteristics, second, reaching maximum possible grid support in faulty grid conditions, while avoiding over-current and third, considerable reduction in energy storage system size and power rating. Inspiring simulations have been carried out through MATLAB/SIMULINK to validate the feasibility and competency of the proposed fault ride-through method and efficiency of the entire control system.

Renewing warranty can provide customers with better service, and thus help manufacturers to gain market opportunities. In engineering practice, the cost for replacement is usually higher than the cost for maintenance, hence manufacturers often face huge challenge to reduce the warranty service cost. With consideration of the warranty deadline, we propose a two-stage optimization model for renewing warranty. In the first stage, a renewing warranty with deadline (RWD) policy is implemented, where the deadline represents the cumulative uptime threshold. When the cumulative uptime exceeds the deadline, the product will be minimally repaired and kept to the residual warranty period. When RWD is expired, the replacement warranty with limited repairs (RWLR) policy is applied. Under the free replacement and pro-rata warranty policy, the corresponding two-stage cost optimization model is established from the manufacturer’s perspective, the aim is to minimize the cost rate and obtain the optimal warranty period. A numerical example is provided to illustrate the validity of the proposed model, and the sensitivity analysis is also carried out.

Advanced driver-assistance systems such as Honda’s collision mitigation brake system (CMBS) can help achieve traffic safety. In this paper, the naturalistic driving study and a series of simulations are combined to better evaluate the performance of the CMBS in the Chinese traffic environment. First, because safety-critical situations can be diverse especially in the Chinese environment, the Chinese traffic-accident characteristics are analyzed according to accident statistics over the past 17 years. Next, 10 Chinese traffic-accident scenarios accounting for more than 80% of traffic accidents are selected. For each typical scenario, 353 representative cases are collected from the traffic-management department of Beijing. These real-world accident cases are then reconstructed by the traffic-accident-reconstruction software PC-Crash on the basis of accident-scene diagrams. This study also proposes a systematic analytical process for estimating the effectiveness of the technology using the co-simulation platform of PC-Crash and rateEFFECT, in which 176 simulations are analyzed in detail to assess the accident-avoidance performance of the CMBS. The overall collision-avoidance effectiveness reaches 82.4%, showing that the proposed approach is efficient for avoiding collisions, thereby enhancing traffic safety and improving traffic management.

Calculation grid and turbulence model for numerical simulating pressure fluctuations in a high-speed train tunnel are studied through the comparison analysis of numerical simulation and moving model test. Compared the waveforms and peak-peak values of pressure fluctuations between numerical simulation and moving model test, the structured grid and the SST k-ω turbulence model are selected for numerical simulating the process of high-speed train passing through the tunnel. The largest value of pressure wave amplitudes of numerical simulation and moving model test meet each other. And the locations of the largest value of the initial compression and expansion wave amplitude of numerical simulation are in agreement with that of moving model test. The calculated pressure at the measurement point fully conforms to the propagation law of compression and expansion waves in the tunnel.

The onset times of acoustic signals with spikes, heavy bodies and unclear takeoffs are difficult to be picked accurately by the automatic method at present. To deal with this problem, an improved joint method based on the discrete wavelet transform (DWT), modified energy ratio (MER) and Akaike information criterion (AIC) pickers, has been proposed in this study. First, the DWT is used to decompose the signal into various components. Then, the joint application of MER and AIC pickers is carried out to pick the initial onset times of all selected components, where the minimum AIC position ahead of MER onset time is regarded as the initial onset time. Last, the average for initial onset times of all selected components is calculated as the final onset time of this signal. This improved joint method is tested and validated by the acoustic signals with different signal to noise ratios (SNRs) and waveforms. The results show that the improved joint method is not affected by the variations of SNR, and the onset times picked by this method are always accurate in different SNRs. Moreover, the onset times of all acoustic signals with spikes, heavy bodies and unclear takeoffs can be accurately picked by the improved joint method. Compared to some other methods including MER, AIC, DWT-MER and DWT-AIC, the improved joint method has better SNR stabilities and waveform adaptabilities.

In spite of the good performance of the steel plate shear wall (SPSW) in recent earthquakes and experimental studies, the need for huge columns to surround the infill plate is a major shortcoming of the system. This shortcoming can be resolved by using semi-supported SPSW. The semi-supported SPSW has secondary columns that prevent the transfer of stress from the infill plate to the main columns. In spite of extensive experimental and numerical investigations on SPSWs, there are many ambiguities regarding the behavior of the semi-supported SPSW. Although stress in the columns is reduced, incomplete diagonal tension field action is formed in the infill plate that creates new problems. In this paper, a new type of semi-supported SPSW is presented in which the steel plate and the secondary columns are angled. The creation of the angle of the plate and the secondary column makes it possible to use the full capacity of the steel plate as well as the capacity of the secondary columns. Numerical results showed that the wall with a 60° angle has a favorable performance relative to the semi-supported wall. Moreover, with the 60° angle, stiffness, strength and energy absorption is increased. The angle of the secondary columns has little effect on the non-elastic stiffness. Nevertheless, using a wall with an angle of more than 90° can neutralize the wall’s behavior relative to conventional walls. Therefore, the wall with a 60° angle as an optimal angle is recommended.

The adaptive neuro-fuzzy inference systems (ANFIS) are widely used in the concrete technology. In this research, the compressive strength of light weight concrete was determined. To this end, the scoria percentage and curing day variables were used as the input parameters, and compressive strength and tensile strength were used as the output parameters. In addition, 100 patterns were used, 70% of which were used for training and 30% were used for testing. To assess the precision of the neuro-fuzzy system, it was compared using two linear regression models. The comparisons were carried out in the training and testing phases. Research results revealed that the neuro-fuzzy systems model offers more potential, flexibility, and precision than the statistical models.