Article of the Year 2021
Influence of Data Splitting on Performance of Machine Learning Models in Prediction of Shear Strength of SoilRead the full article
Mathematical Problems in Engineering is a broad-based journal publishing results of rigorous engineering research across all disciplines, carried out using mathematical tools.
Chief Editor, Professor Guangming Xie, is currently a full professor of dynamics and control with the College of Engineering, Peking University. His research interests include complex system dynamics and control and intelligent and biomimetic robots.
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Timing Evaluation of Telecom Investment Decision under Demand Uncertainty
Under uncertain conditions, the problem of selecting investment timing for telecom network optimization and expansion projects is common in the investment practice of telecom operators. By examining the characteristics of the demand and price of the telecommunications industry, combined with historical data of the telecommunications industry, an exponential function relationship of prices meeting demand is proposed, and then an investment timing decision model under the condition of uncertain demand is established on this basis. Studies have shown that when the value of the investment project is 1.5634 times the investment cost, the value of the investment option is the largest, and this is the optimal investment opportunity. The value of the investment opportunity F(V), the value of the project V, the degree of demand uncertainty , and discount rate are positively correlated, and it is negatively correlated with the opportunity cost of delaying project investment and keeping investment options alive.
Application of Grey Deformation Prediction Model Optimized by Double Coefficient for Tailings Dam
As a nonuniform structure, tailings dam undergoes complex and chaotic nonlinear changes, under the joint influence of multiple dynamic or nondynamic factors. These changes make it difficult to predict the deformation of tailings dam accurately with a numerical model. To solve the problem, this paper proposes a grey deformation prediction model optimized by double coefficient (GDPM-DC). Unlike a single grey prediction model, the GDPM-DC does not mutate significantly but adapts well to specific scenarios. Besides, the model can smoothen and stabilize the original data and thus achieve accurate prediction of the deformation of tailings dam. The main results are as follows. The GDPM-DC made more accurate predictions than the traditional grey model (1, 1) (GM (1, 1)), the grey model based on logarithmic transformation (GM-LT), and the grey model optimized by weight coefficient (GM-WC). It significantly improved the overall prediction accuracy of the vertical and transverse deformations of the dam and controlled the relative error of the predicted seepage pressure to 2.79%–3.71%. Moreover, the model could forecast the trend component and random fluctuation component of seepage pressure effectively, fit the increasing trend in stages 1–3 and the decreasing trend in stages 3–9, and realize the quantitative prediction of deformation law for the operating tailings dam. The research results provide a meaningful reference for the instability analysis and safety management of tailings dam.
Unified Mathematical Model of Gear Train Analysis Based on State Space Method
The state space method of gear train analysis and the unified mathematical model of state space based gear train analysis are proposed in this paper. Firstly, the concept of basic gear train unit is defined, and the state transformation equation of basic gear train unit is established, which is applied to express the transformation rule of the basic gear train unit and the adjacency relationship between the units. Then, the gear train state space is formed based on the dual vectors including input state eigenvector and output state eigenvector, which describe the state characteristics of the gear train unit. The state space is established based on the mapping relationship among the input-output dual vectors, the state transformation matrix, and the gear train unit. Then the dual vector operation laws and mathematical operation methods in gear train state space are generated. Therefrom, a unified mathematical model based on the kinematic, statics, and structural characteristics of the gear train in the state space is established. Finally, the digital identification and automatic analysis of any complex gear train is realized. The fast comparison and analysis of a large number of gear train schemes is achievable in the scheme design stage.
Comparative Analysis of the Effect of Joule Heating and Slip Velocity on Unsteady Squeezing Nanofluid Flow
In this paper, we studied unsteady MHD nanofluid squeezing flow between two parallel plates considering the effect of Joule heating and thermal radiation. The governing equations in the form of partial differential equations (PDEs) are transformed into a system of ordinary differential equations (ODEs) with the help of similarity transformation. The obtained boundary value problem is solved analytically by optimal auxiliary function method (OAFM) and numerically by Runge–Kutta method of order 4 (RKMO4). The OAFM results are validated and compared to the results of RKMO4. The effects of physical parameters such as stretching parameter , Prandtl number , Eckert number Ec, magnetic number , volume friction electric parameter , and porous parameter on the velocity, temperature, and concentration profiles are discussed with the help of plots. Also, the skin friction and Nusselt numbers effects are discussed with the help of tabular data. As the plates move apart, the Nusselt number and the skin friction coefficient decline and the Prandtl number decreases the temperature profile, whereas the stretching and Eckert number increases causing to increase the temperature field.
Preparation of Ag@AgCl/GO Material with Efficient Visible-Light Photocatalytic Performance
Ag@AgCl/GO was prepared by chemical coupling, in-situ deposition of supported AgCl, and photoreduction. The morphology, structure, and surface area of the prepared Ag@AgCl/GO were characterized by SEM, TEM, FT-IR, Raman spectra, and BET. The optical properties of the photocatalyst were analyzed by PL and UV-Vis DRS, respectively. The surface electrical properties and degradation stability were evaluated by zeta potential measurement and cyclic catalytic degradation experiments, and the photocatalytic mechanism was proposed in detail based on the ESR test and trapping experiment. The results showed that Ag@AgCl nanoparticles were spherical and cluster distributed on the folded structure of GO. The prepared Ag@AgCl/GO had good adsorption performance and photocatalytic degradation stability. The material showed good visible light catalytic performance; especially, the degradation rates of cationic dyes RhB and MB were significantly higher than those of anionic dyes MO and CR, and their degradation processes were in line with the quasi-first-order reaction kinetics. Holes (h+) and superoxide radicals (·O2－) were the main active species for the degradation of RhB.
Communication Strategy of Urban Media Image Based on Global Discretization
With the advent of the era of global economic integration, more and more cities are involved in the increasingly fierce competition in the form of image dissemination in order to obtain better economic benefits. The choice of media for this city to carry out image communication has become an inevitable choice for the survival and development of the city. However, since the effect of the current urban media image dissemination is not too ideal, in order to promote the dissemination and development of urban media image, this study made use of global discretization, which is widely used, to study the urban media image dissemination strategy. The research results prove that it is very important to combine global discretization and urban media image for development. Because, the combination of the two can improve the dissemination efficiency and effectiveness of the city’s media image to the greatest extent, enhance the city’s global popularity and competitiveness, and drive a large flow of capital and high-quality talents to the city. In order to obtain greater economic benefits in the wave of global economic integration and to stand out in the increasingly competitive urban environment, a firm foothold is gained in the global economy.