Dongkai Shen^1,2,+, Qian Zhang¹, Yixuan Wang^1,*, Huiqing Ge^3,*, Zujin Luo^4,+

CMES-Computer Modeling in Engineering & Sciences, Vol.114, No.2, pp. 117-139, 2018, DOI:10.3970/cmes.2018.114.117

Abstract A pressure controlled mechanical ventilator with an automatic secretion clearance function can improve secretion clearance safely and efficiently. Studies on secretion clearance by pressure controlled systems show that these are suited for clinical applications. However, these studies are based on a single lung electric model and neglect the coupling between the two lungs. The research methods applied are too complex for the analysis of a multi-parameter system. In order to understand the functioning of the human respiratory system, this paper develops a dimensionless mathematical model of double-lung mechanical ventilation system with a secretion clearance function. More >

Chengquan Wang¹, Yonggang Shen^2,*, Yun Zou¹, Tianqi Li¹, Xiaoping Feng¹

CMES-Computer Modeling in Engineering & Sciences, Vol.114, No.1, pp. 75-93, 2018, DOI:10.3970/cmes.2018.114.075

Abstract The failure behavior of the precast prestressed concrete T girder was investigated by destructive test and finite-element analysis, and the mid-span deflection, girder stiffness and the variation of the cross section strain in the loading process were obtained, and the mechanical properties, mechanical behavior, elastic and plastic behavior and ultimate bearing capacity of T girder with large span were revealed. Furthermore, the relationship between the beam stiffness degradation, the neutral axis in cross-section, steel yielding and concrete cracking are investigated and analyzed. A method was proposed to predict the residual bearing capacity of a bridge More >

Qiang Tong¹, Qingwen Ren^{1, *}, Lei Shen ², Linfei Zhang ², Yin Yang³

CMES-Computer Modeling in Engineering & Sciences, Vol.114, No.1, pp. 33-58, 2018, DOI:10.3970/cmes.2018.114.033

Abstract In this article, the post-peak softening stage of the constitutive relation and the elastic stiffness degradation of concrete are investigated, and a highly reasonable constitutive relation curve is proposed. At the material level, the energy change in the concrete failure process is studied based on the different stress-strain curves of concrete under uniaxial tension and compression. The concrete failure criterion based on elastic strain energy density is deemed suitable and consistent with the experimental phenomena. The hysteresis phenomenon (lags behind the peak strength) is also discussed. At the structure level, the strength reduction method is More >

Lihua Wang^1,*, Zheng Zhong¹

CMES-Computer Modeling in Engineering & Sciences, Vol.114, No.1, pp. 1-18, 2018, DOI:10.3970/cmes.2018.114.001

Abstract A semi-analytical form of complex modal analysis is proposed for the time-variant dynamical problem of rotating pipe conveying fluid system. The complex mode superposition method is introduced for the dynamic analysis in the time and frequency domains, in which appropriate orthogonality conditions are constructed to decouple the time-variant equation of motion. Consequently, complex frequencies and modes of vibration are analytically formulated and the variations of frequencies and damping of the system are evaluated. Numerical time-variant example of rotating pipe conveying fluid illustrates the effectiveness and accuracy of this method. Furthermore, the proposed solution scheme is More >

Marco Götz^1,*, Ferenc Leichsenring¹, Thomas Kropp², Peter Müller², Tobias Falk², Wolfgang Graf¹, Michael Kaliske¹, Welf-Guntram Drossel²

CMES-Computer Modeling in Engineering & Sciences, Vol.117, No.3, pp. 387-423, 2018, DOI:10.31614/cmes.2018.04112

Abstract Numerical mechanical models used for design of structures and processes are very complex and high-dimensionally parametrised. The understanding of the model characteristics is of interest for engineering tasks and subsequently for an efficient design. Multiple analysis methods are known and available to gain insight into existing models. In this contribution, selected methods from various fields are applied to a real world mechanical engineering example of a currently developed clinching process. The selection of introduced methods comprises techniques of machine learning and data mining, in which the utilization is aiming at a decreased numerical effort. The More >

Ruohan Meng^1,2,*, Qi Cui^1,2, Chengsheng Yuan^1,2,3

CMES-Computer Modeling in Engineering & Sciences, Vol.117, No.3, pp. 425-454, 2018, DOI:10.31614/cmes.2018.04765

Abstract With the development of data science and technology, information security has been further concerned. In order to solve privacy problems such as personal privacy being peeped and copyright being infringed, information hiding algorithms has been developed. Image information hiding is to make use of the redundancy of the cover image to hide secret information in it. Ensuring that the stego image cannot be distinguished from the cover image, and sending secret information to receiver through the transmission of the stego image. At present, the model based on deep learning is also widely applied to the More >

Matthew D. Lindemer¹, Suresh G. Advani^2,*, Ajay K. Prasad²

CMES-Computer Modeling in Engineering & Sciences, Vol.117, No.3, pp. 527-553, 2018, DOI:10.31614/cmes.2018.00481

Abstract The lattice Boltzmann method (LBM) is used to simulate the growth of a solid-deposit on the walls of a circular tube resulting from a gas-to-solid reaction and precipitation process. This process is of particular interest for the design of reactors for the production of hydrogen by the heterogeneous hydrolysis of steam with Zn vapor in the Zn/ZnO thermochemical cycle. The solid deposit of ZnO product on the tube wall evolves in time according to the temporally- and axially-varying convective-diffusive transport and reaction of Zn vapor with steam on the solid surface. The LBM is well-suited… More >

Qianxin Wang^1,2,3, Chao Hu^1,2,*, Ya Mao^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.117, No.3, pp. 509-525, 2018, DOI:10.31614/cmes.2018.04098

Abstract Designing the optimal distribution of Global Navigation Satellite System (GNSS) ground stations is crucial for determining the satellite orbit, satellite clock and Earth Rotation Parameters (ERP) at a desired precision using a limited number of stations. In this work, a new criterion for the optimal GNSS station distribution for orbit and ERP determination is proposed, named the minimum Orbit and ERP Dilution of Precision Factor (OEDOP) criterion. To quickly identify the specific station locations for the optimal station distribution on a map, a method for the rapid determination of the selected station locations is developed,… More >

R. E. Jones^1,*, J. A. Templeton¹, C. M. Sanders¹, J. T. Ostien¹

CMES-Computer Modeling in Engineering & Sciences, Vol.117, No.3, pp. 309-342, 2018, DOI:10.31614/cmes.2018.04285

Abstract We use machine learning (ML) to infer stress and plastic flow rules using data from representative polycrystalline simulations. In particular, we use so-called deep (multilayer) neural networks (NN) to represent the two response functions. The ML process does not choose appropriate inputs or outputs, rather it is trained on selected inputs and output. Likewise, its discrimination of features is crucially connected to the chosen inputoutput map. Hence, we draw upon classical constitutive modeling to select inputs and enforce well-accepted symmetries and other properties. In the context of the results of numerous simulations, we discuss the More >

Michely Laís de Oliveira^1,*, Marcio Augusto Villela Pinto², Simone de Fátima Tomazzoni Gonçalves², Grazielli Vassoler Rutz³

CMES-Computer Modeling in Engineering & Sciences, Vol.117, No.2, pp. 251-270, 2018, DOI:10.31614/cmes.2018.04237

Abstract Studies of problems involving physical anisotropy are applied in sciences and engineering, for instance, when the thermal conductivity depends on the direction. In this study, the multigrid method was used in order to accelerate the convergence of the iterative methods used to solve this type of problem. The asymptotic convergence factor of the multigrid was determined empirically (computer aided) and also by employing local Fourier analysis (LFA). The mathematical model studied was the 2D anisotropic diffusion equation, in which ε > 0 was the coefficient of a nisotropy. The equation was discretized by the Finite… More >