Abstract: Microorganisms and their characteristic metabolisms seriously affect the service performance and service life of materials. To date, most studies have concentrated on the bacterial corrosion of materials and comparatively few have focused on the corrosion behavior and mechanisms fungi exhibit in atmospheric environments. Many fungi exist in the atmosphere and their activities significantly influence the corrosion of metals and coatings. In this paper, the relationship was reviewed between the biochemical characteristics of fungi and the corrosion behaviors of these materials, the effects of fungal corrosion behavior were discussed on metal and coating materials in atmospheric environments, and the mechanism of fungal corrosion was described. By contrasting the features of two types of corrosion, It was found that fungal corrosion mainly differ from bacterial corrosion with respect to their respective metabolites. Currently, most fungal corrosion research has been limited to phenomenal description and corrosion product analysis and has lacked any quantitative characterization of fungal metabolism and corrosion kinetics, which merits greater emphasis in future research.
Abstract: Rock-mass unloading often occurs during underground and slope engineering excavations. Here, rock-mass crack initiation and propagation during the excavation unloading progress was simulated using the extended finite element method (XFEM) in ABAQUS. Crack propagation and its influencing factors were studied and discussed after calculating the stress intensity factors at the crack tips, and by recording the crack's shape a dynamic evolution model was produced. The results show that the faster the unloading rate,the longer the crack,and the greater the crack dip angle, the easier the crack initiates. The normal stress on a crack surface decreases while shear stress increases during unloading, and that crack propagation is mainly controlled by shear stress. This is consistent with the theoretical analysis. The final shape of the modeled crack was also close to the result of the physical experiments, indicating the reliability of this study.
Abstract: To study the effect of specimen size on fracture parameters in Mode I fracture issue, a group of geometrically similar sandstone specimens were tested by three-point bending. The result shows that as the size of specimen increases, apparent tensile strength decreases and the apparent fracture toughness and length of the process zone increase. These three factors are a function of size. Based on these test results, equivalent linear elastic fracture mechanics (ELEFM) was used to calculate fracture parameters such as the length of the process zone in rock material. The fracture mechanism of sandstone was identified to be between the perfectly plastic and perfectly brittle limits and the effect of size on quasi-brittle material was shown. To verify the correctness of ELEFM, the length of the process zone was obtained by digital image correlation (DIC) test and the experimental and theoretical results were found to fit well.
Abstract: The sedimentary rule of tailings slurry has an important influence on dam structure. In this paper, the sediment formation characteristics and evolution law of tailings slurry were investigated through a unidimensional sedimentation experiment. The mesoscopic structure and stratigraphic classification of tailings sediment were discussed, the relationship between morphology and time was analyzed, and the electric double-layer theory was used to explain the influence of flocculation on the sedimentary characteristics. The experimental results show that, compared with sand particles, clay particles are smaller in size, contain more clay minerals and have better adsorption, and form a high-porosity flocculent structure in a liquid environment. With respect to the changes in the mesoscopic structure, tailings sediment can be divided into a water zone, flocculation zone, subsidence zone, and consolidation zone. The process of sedimentation can be divided into subsidence and consolidation stages along the time axis and the deposition time of the clayey tailings is about twice that of sandy tailings. The sedimentation time of the sandy tailings mainly depends on the free subsidence velocity of single particles, whereas the sedimentation process of clayey tailings can be described as a function of the interface level and time. This research findings lay a theoretical foundation for correlation research of the sedimentary process and mesoscopic structure, which provide a reference for the prediction of fine-grained tailings compression deformation.
Abstract: Paste made from high-sulfur tailings shows strength deterioration to different degrees and this can cause great changes in the quality of the filling body. The deterioration and degradation mechanism of high-sulfur paste with different sulfur contents was analyzed using XRD (X-ray diffraction) phase analysis and an ESEM. The results showed that sulfur tailings promoted the growth of early strength to a certain extent, but inhibited the development of later strength, and the greater the sulfur content, the more obvious the effect. In addition, sulfate produced by sulfide oxidation can promote the formation of expansive ettringite and gypsum. Meanwhile, the acidic environment caused decalcification of C-S-H and dissolution of CH, destroys the cementitious system and further promotes the degradation of the filling body. The crystal expansion strain and crack development process were analyzed using a pore calculation model. The linear development of elastic strain in swelling material was clarified.
Abstract: Bioleaching is one of the most effective methods of extracting valuable elements from low-grade, refractory secondary copper sulfide. In this research, Acidithiobacillus ferrooxidans was used to leach refractory secondary copper sulfide from Fujian Province. The bioleaching microorganisms were added to the culture, domesticated, and column leaching experiments. These were based on different particle size ratios and carried out sequentially. Based on this experiments, the evolution disciplinarians of bacterial concentration, pH values and copper extraction rates were obtained at different stages. Using computed tomography (CT) technology, ore heap slumping inside the columns, cross section porosity evolution and leaching mechanisms were studied. The results indicate that bacterial concentration and pH values present trends that increase first and then stabilize. The proliferation of bacteria in the leaching columns is slower and the bacterial concentration is only 5×107 per mL after 480 h. During the leaching process, fine particles tend to move to the bottom of columns and the ore heap slump phenomenon appears. On the top surface of the column the porosity tends to be greater with increase rate of 6.65%, conversely, this tends to be smaller at the column bottom, and its decreases rate is 8.29%. The slump degree is proportional to the fines content; the minimum slump is 1.7 mm and the maximum 6.15 mm. Ore particle size is the key factor in the leaching process; column B (with particle size r < 1 mm accounted for 28.41% of whole ores quality) shows the best copper extraction rate of 47.23% after 480 h.
Abstract: To assure that compression on the rakes of a deep corn thickener does not stop mixing, an additional circular slurry system, which activates slurry all the time, is employed and running resistance is usually decreased. However, there is still uncertainty on how circular parameters affect underflow properties. This means that the design and application of such systems lack support from scientific theories. Hence, it is necessary to create a study on how circular parameters regulate underflow parameters. Analysis of the circular system mechanism shows that its effect can be divided into two parts and the effect of the system on underflow properties is clarified. In addition, the value of underflow concentration in thickeners is solved based on calculus and finally a mathematical model is produced, which simulates the regulation of underflow properties in thickeners. Using the model, the circular parameters of underflow in thickeners are verified. The experiment indicates that the solid concentration of underflow decreases with circular underflow initiation, then tends to stabilize. Also, the volume fraction of underflow increases in the range of 0.7% -2.2% with ascending circular flow and height. In addition, the time necessary for the solid concentration to stabilize is reversely affected by underflow flow and height. The regression function obtained from experimental statistics shows excellent performance in the model when designing and analyzing circular systems for thickeners.
Abstract: This paper optimized the synthesis conditions such as molar ratio, temperature and time by examining quartz recovery and the active content of quaternary ammonium. The reverse-flotation results using roast-magnetite separation of Jiugang iron show that a concentrate with a grade of 56.54% and a recovery rate of 77.33% are obtained using M-N as collector. At 5-30℃, the reverse flotation result is stable, as well as the low-temperature resistance is excellent. Selectivity of M-N is superior to the traditional collector dodecylamine and ether amines. The result of Zeta potential and infrared spectroscopy reveals that the successful separation effect of M-N is due to electrostatic adsorption and hydrogen bonding on quartz.
Abstract: Quaternary ammonium lignin was synthesized from rice straw after phenolization, crosslinking and amination. Its adsorption properties for AuCl4- were investigated. The adsorbent was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), thermogravimetric analysis and differential scanning calorimetry (TG-DSC). The effects of initial concentration of AuCl4-, concentration of hydrochloric acid and adsorption time on the effect of adsorption for AuCl4- were discussed. The results show that the quaternary ammonium lignin has excellent thermal stability and its surface is irregularly rough and porous. The maximum adsorption capacity is 3.27 mol·kg-1 when the concentration of hydrochloric acid is 0.5 mol·L-1, the initial concentration of AuCl4- is 6.0 mmol·L-1 and the adsorption time is 100 h. The equilibrium time of adsorption for AuCl4- is 360 min when the concentration of AuCl4- is 1 mmol·L-1, the concentration of hydrochloric acid is 0.5 mol·L-1. Moreover, AuCl4- was reduced to elemental gold by the phenolic hydroxyl group of the quaternary ammonium lignin through the analyses of XRD, SEM and FT-IR.
Abstract: The hot deformation behavior of 0Cr16Ni5Mo martensitic stainless steel with different nitrogen contents was studied on a Gleeble3800 thermal machine. The true strain-stress curves and deformed microstructures of the tested steels were investigated. The result shows that with an increase in nitrogen content, the stress increases and the recrystallized grain size reduces. Using the flow stress equation combined with Zener-Hollomon parameters, three constitutive equation models were established. Comparing the stress values from the constitutive equation models and the experiment, the hyperbolic sine model performed best. So, the constitutive equations for the tested steels were obtained by using the hyperbolic sine mode, with some improvements made during the calculation.
Abstract: Ceramic coatings were formed on 7050 aluminum alloy (AA7050) by microarc oxidation (MAO). Subsequently, scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS) were used to evaluate the microstructure of the coatings. The coatings consist of an outer porous layer made of Al2O3 and an inner dense layer made of sintered alumina and aluminum substrate. Furthermore, potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) were combined with slow strain rate tests (SSRT) to investigate the effect of microarc oxidation on the corrosion and stress corrosion cracking (SCC) of AA7050 in 3.5% NaCl solution. The corrosion on the surface of AA7050 and the corrosion rate and SCC decrease owing to the coatings on AA7050.
Abstract: The microstructure, structure, and cracking behavior of Q235-A strip iron oxide skin were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and a universal tensile testing machine. The results show that the composition of the iron oxide mainly consists of Fe3O4, Fe2O3, and Fe, together with small amount of FeO, the oxide layer has the same thickness all over, about 10 μm, the structure is dense, and the matrix is better connected. The tensile experiments show that with increasing strain, the increase in the number of cracks is at first slow, then fast, then slow again. When the strain reaches 0.05%, its iron oxide skin begins to crack; the number of cracks increases with increasing strain in the range 0.08% -0.10%. When the strain exceeds 0.10%, the crack number increases slowly, and when the strain exceeds 0.15%, the number of cracks stops grow.
Abstract: The traditional seeker optimization algorithm (SOA) uses three steps for an optimal search:calculating the search direction, searching the step length, and updating the individual position. Its shortcomings are the large amount of calculation required and weak communication between populations, which results in low speed optimization. To address these disadvantages, this paper offers the binomial crossover operator improved seeker optimization algorithm (BCOISOA) as an improvement. In terms of computational search step length, this paper adopts a random number and maximum function product judgment subgroup location so that global optimization computation speed can be improved. In terms of update location, this paper puts forward two crossover operators to strengthen the connection between the populations. This avoids premature convergence of the algorithm during the process of updating the search direction, caused by the local optimum, and achieves a fast and accurate optimal solution. This article usesthe BCOISOA-BP neural network algorithm for a two-phase grinding process to achieve a grind size online soft sensor. Compared with the SOA and PSO algorithms, the simulation result shows that the BCOISOA algorithm has the fastest convergence speed and highest precision. It therefore satisfies the requirements of grind size real-time detection.
Abstract: In process industries, such as metallurgy and chemistry, real procedure parameters usually possess high-dimensional nonlinear features. To solve the problem of outlier detection in complex high-dimensional data, the concept of a soft hyper-sphere is introduced in this paper. An original data set is projected into a high-dimensional feature space using a nonlinear kernel function, and the boundary of the soft hyper-sphere is determined within this feature space. To avoid a mass product quality incident, location information on the testing samples, which are projected into the feature space, is used to decide whether they are outliers. As an applied example, practical procedure data obtained from a type of auto steel product were tested. The results verify that the proposed outlier detection algorithm based on a soft hyper-sphere has a better ability for outlier detection in high-dimensional nonlinear data than tradional methods.
Abstract: To accurately locate hidden damage in welded joints, a metal magnetic memory (MMM) gradient model was present based on maximum likelihood estimation (MLE) optimized by particle swarm optimization (PSO). Tabular welded Q235 specimens were subjected to fatigue tensile experiments. Using electron microscope scanning and X-ray detection, it is found that MMM gradient K is sensitive to the location of early hidden damage and decreases with an increase in distance from it. A nonlinear function is then presented between the position parameter and the MMM gradient. MLE is introduced to establish the nonlinear objective function. Furthermore, considering the nonlinear objective function is easy to get into the local rather than the global extremum, the PSO is adopted to optimize the objective function for a global search ability. The results show the location error of the model is 3.48%, therefore MMM provides a new tool for the identification and accurate location of early hidden damage in welded joints.
Abstract: Because of lower inductance and higher commutation frequency, caused by high-frequency current harmonics induced by the PWM control, super high speed permanent magnet brushless motors commonly face overheating of both the rotor and stator. For chopping directly at the inverter, the frequency should be increased to reduce the current harmonics. But for the 10 kW class motor drives used in the air compressors of fuel cell vehicles, the power switch devices currently do not fulfill the needs of switch frequency and power simultaneously. Therefore, it is not a good choice to regulate the speed by chopping at the inverter. Aimed at reducing losses in the stators and rotors, this paper presented the design of a pre-Buck square wave drive for reducing current harmonics. By optimizing the back electromotive force (EMF) filter circuit and commutation compensation angle, the operation range of sensorless control CAN was extended to 3000-100000 r·min-1. The key points encountered during the drive development were analyzed and solutions proposed. Finally, the excellent performance of the drive was demonstrated by experiment.
Abstract: Aimed at solving the problem of multi-component separation of actual vibration signals, here a new iterative decomposition method is proposed based on a generating differential equation (GDE) method. The first step is to estimate the instantaneous frequency and amplitude envelope of the original signals using GDE, then the frequency of the first component is obtained using a lowpass filter. Second, the original signal is passed through a high-pass filter to obtain the amplitude of the first component. Finally, the first component is subtracted from the original signal and the residual value, as the new money initial value, is decomposed in the next iteration. Compared with conventional methods, the proposed method is illustrated and verified by the simulation signals. When used for analysis of rolling bearing experimental signals, the results demonstrate that the approach is practical and effective.
Aimed at the problems of artificial direction matching features being too subjective to analyze magnetic matching suitability and deep architectural features that can't be extracted, a new matching suitability analysis method based on a convolutional neural network (CNN) is proposed. First, direction-matching-suitability feature maps in six typical directions are established using the Gabor filter's direction selection characteristics. Second, a CNN is designed to extract the deep direction features. The training parameters of the CNN are optimized with a hybrid particle swarm optimization (HPSO) algorithm. Finally, simulation experiments are conducted to verify the proposed method. Results show that the method can effectively avoid complicated calculations and blindness when artificially extracting direction features, and the direction-matching-suitability analysis for magnetic navigation can be achieved automatically. The method's analysis accuracy is higher than in the traditional BP neural network (BPNN) and support vector machine (SVM), and has practical implications for geomagnetic navigation and route planning.
Abstract: By using the hysteresis characteristics in the cognitive psychological characteristics of the elderly, combined with an affective computing model based on Gross cognitive reappraisal, this paper takes consideration of the influence of the hysteresis characteristics on individual emotional state transition. It then establishes a hysteresis factor, based on cognitive reappraisal parameters, to correct the cognitive reappraisal ability of current emotional states, then simulates and analyzes the revised affective computing model using MATLAB. This improves the hysteresis factor effectively and revises the affective computing model resulting in more natural and harmonious human-robot interaction. To achieve the trusted affective computing model, this paper combines an FPGA hardware platform with an AES cipher algorithm for elderly affective information encryption processing, to realize the data trust in the affective computing. In this study, all the hardware components were built in the FPGA chip EP4CE115F29C7 using SOPC technology, the logic program was wrote, and the AES cipher algorithm was implemented with combination of the hardware components, to realize real-time data transmission and security during the process of affective computing, and its trust was improved. Finally, the experimental results show that the affective computing model under hysteresis characteristics is highly consistent with true elderly emotion, and trusted computing encourages a positive emotional state in the elderly.
Abstract: In order to study seismic responses and collapse mode of a wind turbine tower under operational conditions, a wind turbine tower model was developed by the wind turbine design software FAST. The structural responses in idle condition and operational conditions were calculated and compared. The influences of different angles between wind and earthquake inputs on structural responses were investigated. A detailed finite element model of the same tower was developed with ABAQUS. Wind load effects induced by the blades were calculated by FAST simulations and were verified with the results estimated through the blade element theory. Elastic analysis results from the FAST model and the ABAQUS model were also compared for verification purposes. Tower collapse simulations were conducted under earthquake excitations using the ABAQUS model. Study results show that the case with a 90° angle between the wind and earthquake inputs is the most dangerous scenario that could occur for tower dynamic responses. Collapse simulations indicate that the plastic hinges are initiated from the bottom part of the tubular tower wall; later, they develop into the upper part of the structure too. The tower fails at the middle-upper part of the tower wall.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
