Abstract: Due to their sensitivity to a wide diversity of volatile gases, electronic noses are ideal instruments for measuring and monitoring odors and they are being applied in agricultural production testing, biological medicine detection, environmental monitoring, and food testing. An electronic nose (E-nose) utilizes a sensor array to provide a fingerprint response to a given odor, using pattern recognition software to identify and discriminate between odors. Each sensor in the array behaves like a receptor by responding to different odors to varying degrees. The changes are then transduced into electrical signals, which are preprocessed and conditioned before identification by a pattern recognition system. In this paper, recent electronic-nose systems and algorithms are reviewed which developed over the past two decades that have potential applications for detecting Chinese liquors, including brand identification, flavor detection, and the prediction of the ages. In addition, the technical design scheme and the application were detailed for the polymer quartz piezoelectric sensor E-nose.
Abstract: The calcite structure and the adsorption of water molecules as well as water molecule clusters on it were investigated using the CASTEP module, Materials Studio 6.1 based on the first principles of the density functional theory (DFT). Results indicate that the O site of calcite shows the highest activity in the reaction process, followed by the C and Ca sites; {1014} is the most stable cleavage plane, where the adsorption can occur between the water molecule and the Ca and O sites, and the O site shows a more stronger adsorption effect with the hydrogen bond formed through the H(H2O)-O(CaCO3) and H(H2O) -O(H2O) bonds. There are both hydrogen bonds between the water molecules, as well as the water molecules and calcite surface whose adsorption effects are mainly found to be the O site followed by the relative weaker Ca site.
Abstract: The effects of the combination of joint density and inclination on the strength and deformation characteristics of rocklike specimens containing open joints were studied by using uniaxial compression tests. The following conclusions were made:with the increase of joint inclination, the stress-strain curve changes from a multi-peak value to a single peak value and the brittleness of the specimen enhances, whereas the ductility of the specimen weakens. The influence of joint density on the unified peak strength is related to the size of joint inclination, and the effect of joint density on the unified modulus shows a "V" shape, namely, the unified elastic modulus first decreases and then increases with the increase of joint density. With the increase of joint inclination, the unified elastic modulus increases gradually and its maximum value, which achieves 70%-80% of the complete specimens' elastic modulus, appears at 90° of joint inclination. The joint inclination is the major influencing factor on the unified peak strength and the unified elastic modulus of the rock-like specimens containing many joints. Further analysis on the test results demonstrates that the transformation law of the relationship between the joint density or joint inclination and the stress-strain curve, as well as the unified peak strength and the unified elastic modulus, is related to the failure process of the specimen. The failure mode of the specimen can be classified into three categories:tension failure, shear failure, and mixed failure.
Abstract: To investigate the laws relating to the mole fraction of a component in a binary solution and its vapor pressure, the entropies of dissolution from the solid phase to the liquid phase of 48 typical compounds were assessed and the compounds were confirmed to not decompose during the phase transition processes. Under the condition where a compound also exists in a binary liquid melt, both of the components in the whole concentration range obey Raoult's law. Specifically, there is no such thing as an"activity"as defined by Lewis. The so-called "activity" is actually the balance mole fraction in the case where all components in the system are considered by comparing with the measured activity data for Mg-Si, Sb-In, and Fe-Mn binary systems. It is verified that the calculated equilibrated mole fraction represents the activity, thereby the binary metallic melts involve no activity. In addition, a general formula is deduced for the equilibrium mole fraction in the binary system in the case where the melt contains one intermetallic compound. In particular, the cases corresponding to A2B-type or AB-type intermetallic compounds were discussed. Finally, a broad sense Raoult's law was proposed that it is applicable in all three regions in binary solution divided by different temperatures:(I) the region corresponding to temperatures above the melting point of the component,(Ⅱ) the region corresponding to temperatures lower than the melting point of the pure component but greater than the liquidus temperature, and (Ⅲ) the region corresponding to temperatures lower than the liquidus temperature.
Abstract: To solve the high aluminum consumption problem in interstitial-free steel production in a steel plant, an aluminum consumption prediction model was established by mathematical statistics and BP neural networks. Compared with the multiple linear regression model, this model's result is more accurate. The influence of different smelting processes on aluminum consumption was analyzed, and the process parameters were optimized. The results show that the amount of aluminum consumption per ton of steel decreases 0.07 to 0.08 kg when the oxygen activity before RH or after decarbonization reduces by 0.005%. The effective utilization coefficient of aluminum-deoxidizing is from 70.31% to 80.35%; the aluminum consumption decreases about 0.1 kg when the temperature of steel before RH increases by 35 to 40℃. The heating utilization coefficient of aluminum thermal reaction is about 97.4%. When the blowing oxygen quantity is less than 100 m3 and greater than 100 m3, the ratio of oxygen reacting with aluminum is about 37.3% or about 74.6% respectively, and the aluminum consumption increases by 0.1 kg or 0.2 kg, respectively, with the blowing oxygen quantity increasing by 50 m3. After the process parameter optimization, the aluminum consumption decreases from 1.359 to 1.113 kg, which results in a decrease of 18.1%.
Abstract: The influence of Ti (mass fraction 0.10%) and the joint additions of Ti (mass fraction 0.11%) and V (mass fraction 0.20%) on the hot ductility of as-cast high manganese austenitic steels were studied using a Gleeble-3500 thermo-mechanical simulator over a temperature range of 700 to 1200℃. Fracture surfaces and particles precipitated at different testing temperatures were investigated via scanning electron microscopy (SEM) and X-ray energy dispersive spectrometry (EDS). The hot ductility curves as a function of temperature of high-Mn austenitic steels showed that Ti addition leads to loss of ductility in almost the entire testing temperature range. Moreover, the joint additions of Ti and V do not exhibit any improvement in the hot ductility, resulting in relatively poor hot ductility behavior. The phase diagrams of precipitates in Ti-and Ti-V-bearing high-Mn austenitic steels in the temperature range of 700 to 1600℃ were calculated via Thermo-Calc commercial software. The calculation results show that Ti(C,N) in Ti-bearing highMn steel precipitates at 1499℃, which is much higher than its liquidus temperature. This illustrates that Ti(C,N) particles form in the liquid steel. SEM-EDS results show that Ti(C,N) and (Ti,V) C particles form along the austenitic grain boundaries and the triple junction. These particles retard the occurrence of dynamic recrystallization and accelerate the extension of cracks near the grain boundaries.
Abstract: The P91 weld joint used in the experiment is re-tempered according to the heat treatment process. The effect of tempering times on its mechanical properties, including that at room temperature and high temperature, was then investigated in relation to the evolution of its microstructure using optical microscopy (OM), X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and tensile tests. Results indicate that the strength at room and high temperature of the heat affected zone increases first and then decreases with an increase in tempering times. In addition, the microstructure is still tempered sorbite that reserves the orientation of lath martensite, and the main phases are the α-Fe phase and Fe-Cr phase. After being tempered once, its high-temperature tensile strength reaches a maximum of 232.66 MPa. These improved mechanical properties relate to the dispersed distribution of niobium and vanadium carbonitride precipitate particles, dislocation tangles, and dense metastable dislocation networks. With the increase of tempering times, the distribution of Cr23C6 precipitates gradually undergoes a change from being isolated to displaying a continuous manner in the grain boundaries; this can embrittle the grain boundary and reduce the strength while improving toughness.
Abstract: The diffusion and accumulation behaviour of hydrogen in X70 pipeline steel were investigated via hydrogen permeation test, hydrogen diffusion simulation, and hydrogen content test technology in a simulated coal gas environment (4 MPa total pressure, 0.2 MPa hydrogen partial pressure). The mechanical properties of the X70 pipeline steel substrate and weld in a simulated coal gas environment were also analyzed through impact toughness test, crack propagation test, notch tensile test, and slow strain rate tensile test. Experimental results show that hydrogen absorbed on the X70 steel surface in a simulated coal gas environment spreads into the inside of the X70 steel, and the internal diffusion hydrogen mass fraction is 1.9×10-7 after reaching a steady state. Compared with the original performance in air, there is no decline in the impact performance, notched tensile and slow strain rate tensile strength, plasticity, and damage tolerance of the X70 pipeline steel substrate and weld in simulated coal gas. Results show that in a coal gas environment, X70 steel has a lower risk of hydrogen embrittlement.
Abstract: The stress corrosion cracking of 2024-T351 aluminum alloy was investigated by finite element simulation analysis, scanning electron microscopy/energy dispersive spectrometry, and X-ray photoelectron spectroscopy through SO2 mixed salt spray test. Results indicate that stress corrosion cracking initiates preferentially at the region of stress concentration of the C-ring top for 2024-T351 aluminum alloy. The morphologies of loose corrosion products change from fine rod-like and flocculent to plate-like. Secondary cracks form in the internal corrosion crack after 6 h, when the corrosion time increases to 480 h, and the fractures and cracks in the surface of the C-ring side penetrate the whole sample. The C-ring sample completely breaks after 720 h. The opening crack propagation is a mixed mode of transgranular and intergranular, while the main cracks extend along the normal of the C-ring and the secondary cracks extend mainly along the grain boundaries.
Abstract: Springback is regarded as one of the main defects that occur in sheet-metal forming processes. Therefore, improving its prediction accuracy, especially under highly nonlinear conditions, is important for researchers. In this paper, constitutive equations that consider the isotropic hardening, kinematic hardening, and distortional hardening are proposed for magnesium alloy sheet. The work hardening and springback behaviors of 0.8-mm-thick AZ31B magnesium alloy sheet were investigated and simulated. The AZ31B specimen was subjected to a bending process after the pre-tension deformation, which aided in the observation of its springback behavior under nonlinear loading paths. Simulations were conducted using ABAQUS-Explicit (Vumat) and ABAQUS-Implicit (Umat). Comparisons between the experimental and numerical results demonstrate the strong influence of the kinematic hardening on the springback prediction of magnesium alloy sheet.
Abstract: This paper is a contribution to the ductile fracture prediction by the proposal of a new uncoupled ductile fracture criterion. In the new criterion, two typical void deformation models were carefully considered, with the plastic strain increment regarded as a key impetus of the damage evolution and its accumulation. The new ductile fracture criterion was constructed with three model parameters with different physical meanings. A 3D ductile fracture surface model was obtained by transforming the proposed criterion from stress space to the space of stress triaxiality, Lode parameter, and fracture strain, and a parametric study was carried out to better understand their effects. To validate the performance of the new criterion, it was used to construct the 3D fracture surfaces of 5083-O aluminum alloy, TRIP690, and Docol 600DL (a dual-phase steel). Comparisons of the results with experimental observations indicate that the proposed criterion provides good prediction capability over a large range of stress states for various materials, with good flexibility and considerable accuracy.
Abstract: A prediction model for the very high cycle fatigue life for inclusion-fine granular area (FGA) -fisheye-induced failure was studied in this work. Combined with the experimental results of Cr-Ni-W alloy steel, a local crack initiation life model (LCIL) and an inclusion-FGA based crack initiation life model (IFCIL) were developed on the basis of the local stress-life method and the dislocation-energy method, respectively. Using the Tanaka-Mura model as a reference, the fitting results of LCIL and IFCIL models were analyzed. Based on the respective modeling of the small crack growth within the FGA and the long crack growth outside the FGA within the fisheye, the total life model involving crack initiation and growth was established. As a result, combined with the results of three crack initiation life models, the IFCIL model exhibits the highest prediction precision, and the predicted crack initiation life associated with the FGA size is nearly equivalent to the total life. Conversely, the crack growth life only occupies a fine fraction of the total life. Between the predicted and experimental results, the agreement is fairly good within the factor-of-two boundaries. In short, the established total life model can be effectively used to predict the very high cycle fatigue life for the inclusion-FGA-fisheye induced failure.
Abstract: A blast furnace lining mathematical model was established based on the inverse heat transfer problem. After determining the boundary conditions of the model, this inverse heat transfer problem is divided into three problems which are the direct problem, the sensitivity problem and the adjoint problem, and these were solved using the conjugate gradient method. The feasibility of this model was proved by the inversion results of different shape functions and then it was discussed that the initial guess shape and number of measurement points effect on the inversion results. The results show that the accuracy of the inverse solution is independent of the the initial guess shape, but the number of measurement points has some impact on these results, whereby the more points are measured, the better the curve features are captured. An accurate inverse solution can be obtained with fewer measurement points and an average relative error within 3%, even though the arrangement of more points can achieve a slightly better solution.
Abstract: The effects of structural dimensions such as central tube equivalent radius, branch tube equivalent radius, tube spacing, and tube length on the performance of a flat double-P type radiant tube were studied in this paper. The structural dimensions of the radiant tube and the positions of the burner nozzles were optimized using an orthogonal experimental program. It is shown that obvious influencing factors on the surface temperature difference of the radiant tube are tube spacing, central tube equivalent radius, tube length, and branch tube equivalent radius in turn. However, significant influencing factors on the radiant power of the radiant tube are tube length, central tube equivalent radius, tube spacing, and branch tube equivalent radius in order. When the size ratio of the upper to lower air nozzle is 7:3 and the size ratio of the left to right air nozzle is 9:1, the performance parameters of the radiation tube are the best. When the distance between the air and fuel gas nozzle is 50 mm and the air nozzle distance is 60 mm, the uneven coefficient of the radiation tube's surface temperature is the smallest at 0.058.
Abstract: In order to reveal the mechanical essence of the detecting principle of SI-FLAT flatness measurement systems, the mathematical model of the relationship between amplitude and residual stress was established, based on the theory of fluid-structure interaction vibration of thin plates. The terms of inertia and fluid pressure were introduced to the equilibrium equation in incompatible Föppl-von Kármán equations. The time variables were separated out from the velocity function of fluid, pressure function of fluid, deflection function of thin plates and stress potential function of thin plates with consideration of periodic aerodynamic load. Therefore, the partial differential equations aiming at steady state of SI-FLAT flatness measurement systems was obtained. Solving the equations by using the method of separation of variables, the mathematical relationship between amplitude and residual stress was established. Combined with measured residual stress, the distribution of actual amplitude of thin plates could be calculated by the Siemens'amplitude-residual stress model, which coincided with the amplitude calculated by the fluid-structure interaction vibration model. The influences of fluid velocity at air pump's inlet, detecting distance and excitation frequency on amplitude were analyzed by using the fluid-structure interaction vibration model, which provides a theoretical basis for application of SI-FLAT flatness measurement systems.
Abstract: Due to the effect of the modulation part, the energy diffuses around the surrounding area of dominating frequencies and diminishes the readability of the time-frequency representation when short-time Fourier transform (STFT) is used to process nonstationary signals. However, when the instantaneous frequency slowly changes or is constant, the effect is small and can even be neglected. Thus, the time-frequency representations have high-energy concentration. Based on this feature, a novel method called iterative generalized short-time Fourier transform (IG-STFT) was proposed, which improved the readability of the time-frequency representation. First, the stationary mono-components are separated using iterative generalized demodulation. Then, the time-frequency representations of each mono-component are acquired using STFT. Finally, the time-frequency representation of the original signal is obtained according to the analysis results of STFT and the phase function. The analysis results of a planetary gearbox simulation signal and experimental signals verify the effectiveness of this method for analyzing nonstationary signals and diagnosing gear faults.
Abstract: To identify the unmeasurable parameters of a shell transfer arm, a virtual prototype of the shell transfer arm was built, and the built virtual prototype is regard as the source of the sample data. Considering the continuity and smoothness properties of the sample data, features of the curves were extracted by functional data analysis and functional principal component analysis, and the features and unknown parameters were used to train the extreme learning machine (ELM). At the meantime, the weight connecting the input layer and hidden layer and the threshold of the hidden nodes were optimized by particle swarm optimization (PSO) to improve the identification accuracy and generalization performance of ELM. At last, the presented method was verified by simulation data and test data. The identification results of the simulation data show that the optimized ELM has higher identification accuracy and better generalization performance. Also, the presented method is proved to be feasible and effective by comparing the real angular velocity and the angular velocity from the virtual prototype with respect to the test data identification results.
Abstract: To remedy the low convergence rate and low optimization accuracy of the artificial fish swarm algorithm (AFSA), an improved artificial fish swarm algorithm (IAFSA) was proposed. In the improved algorithm, the artificial fish could adjust the vision and step and form a balance between the local search and global search by identifying the actual condition. Furthermore, when the artificial fish in the foraging behavior does not find a better position than the current location, it steps forward to the optimal artificial fish by introducing the guide behavior to improved algorithm. The results indicate that the improved algorithm has advantages such as convergence rate, optimization accuracy, and anti local extremum value. The improved algorithm was applied to the system identification with the time-delay model. This algorithm can obtain a precise mathematical model of the controlled object and acquire great identification accuracy in the case of external interference.
Abstract: With the availability of a large number of sharing models, model search and task design would be an extremely complex project in the global navigation satellite system (GNSS) -distributed simulation environment (GDSE). For improving the efficiency of model search and task design, a real-time intelligent recommendation method was designed for GDSE. Based on the characteristics of the simulation model, the incidence relation and interface shape of the model were defined in the method and a conditional frequent pattern tree (FP-tree) structure was designed to further improve the retrieval efficiency. The effect of the conditional FP-tree structure was proved theoretically. Then, the calculation method of the model incidence relation degree was proposed and derived based on the Bayesian statistical method. The entire processing of the intelligent recommendation method was designed for implementing it in GDSE. Hence, to check the effect of the real-time intelligent recommendation method, it was implemented in GDSE. Compared with the simulation result of the traditional recommendation method, the model intelligent recommendation method is proved to have a shorter running time and a high accuracy on simulation model recommendation. The computing capability and real-time performance are proved through the simulation. It is demonstrated that the intelligent recommendation method is efficient and flexible for GDSE.
Abstract: The billet design problem (BDP) in seamless steel tube production is to assign order tubes to billets under process constraints. Because of the batch rule in practical production, each order has a minimum weight of tubes assigned to any billet. Meanwhile, as the number of tubes assigned to a billet must be an integer, the weight of tubes assigned to any billet is not continuous in its domain. Thus, the BDP discussed herein is more difficult to solve than the slab design and bin packing problems. In this study, a multi-objective mix-integer programming model was built based on a generalized description of the BDP, which is proved to be non-deterministic polynomial (NP) hard. For the case with single billet size wherein two objectives in the model are equivalent, a simplified model was set up and the lower bound of the objective could be found. Further, a two-stage heuristic algorithm based on greedy strategy was proposed to solve the problem. Finally, using computational results, it was proved that the algorithm is effective and efficient in solving the BDP.
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
