Documents published in Scipedia

• Analysis of Airflow Uniformity in Pig Nurseries Using Duct Ventilation in Northeast China_prova_latex_2

  Z. Wu, K. Xu, Y. Chen, Y. Liu, M. Liu, J. Sánchez Pinedo

  Colección de pruebas Jesús Sánchez (2024). 4

  
  

  Abstract

  The problem of uneven ventilation in pig houses must be solved to effectively improve the winter environmental quality of pig nurseries in cold regions. In this study, the airflow field and airflow uneven coefficients of pig nurseries with duct ventilation were simulated and calculated using computational fluid dynamics, and compared with pig nurseries with different duct diameters, inlet and outlet air velocities and air supply angles. The average relative error between the simulated and measured values was 12 %. Comparison of simulation results and airflow uneven coefficients showed that the airflow uneven coefficients of the fences were reduced, and the airflow field was uniformly distributed with a duct diameter of 0.3 m , inlet and outlet air velocities of 1.5 and 2.0 \mathrm{~m} / \mathrm{s}, respectively, and an air supply angle of 45^{\circ }. These improvements resulted in a more homogeneous ventilation, which led to more uniform ventilation and contributed to discharging dirty air outdoors. Then the test pig nursery was modified based on the simulation and analysis results. Difference analyses were carried out between the control and the test pig nurseries. Comparative analyses showed the differences between the test data and the monitoring data were smaller, and the duct ventilation was more uniform, which was suitable for the healthy growth of piglets.

  Abstract
  The problem of uneven ventilation in pig houses must be solved to effectively improve the winter environmental quality of pig nurseries in cold regions. In this study, the [...]

  • 0
  •  read

• Analysis of Airflow Uniformity in Pig Nurseries Using Duct Ventilation in Northeast China_prova_latex

  Z. Wu, K. Xu, Y. Chen, Y. Liu, M. Liu, J. Sánchez Pinedo

  Colección de pruebas Jesús Sánchez (2024). 2

  
  

  Abstract

  The problem of uneven ventilation in pig houses must be solved to effectively improve the winter environmental quality of pig nurseries in cold regions. In this study, the airflow field and airflow uneven coefficients of pig nurseries with duct ventilation were simulated and calculated using computational fluid dynamics, and compared with pig nurseries with different duct diameters, inlet and outlet air velocities and air supply angles. The average relative error between the simulated and measured values was 12 %. Comparison of simulation results and airflow uneven coefficients showed that the airflow uneven coefficients of the fences were reduced, and the airflow field was uniformly distributed with a duct diameter of 0.3 m , inlet and outlet air velocities of 1.5 and 2.0 \mathrm{~m} / \mathrm{s}, respectively, and an air supply angle of 45^{\circ }. These improvements resulted in a more homogeneous ventilation, which led to more uniform ventilation and contributed to discharging dirty air outdoors. Then the test pig nursery was modified based on the simulation and analysis results. Difference analyses were carried out between the control and the test pig nurseries. Comparative analyses showed the differences between the test data and the monitoring data were smaller, and the duct ventilation was more uniform, which was suitable for the healthy growth of piglets.

  Abstract
  The problem of uneven ventilation in pig houses must be solved to effectively improve the winter environmental quality of pig nurseries in cold regions. In this study, the [...]

  • 0
  •  read

• Optimizing Convolutional Neural Network-Long Short-Term Memory Architecture with Additive Attention Mechanism for Stock Price Prediction

  B. Wu, Y. Qi, G. Fu

  Rev. int. métodos numér. cálc. diseño ing. (2024). Vol. Online First, 47

  
  

  Abstract

  Stock price fluctuations reflect market expectations for the economic situation and company profits. Accurately predicting stock prices has become a hot topic in academia. With the rapid development of artificial intelligence, many researchers are starting to use machine learning algorithms to predict stock prices. In this paper, a new time series prediction model, the combination of the convolutional neural network and long shortterm memory neural network with additive attention mechanism (CNNLSTM-AAM), is proposed for stock price prediction. It can combine the advantages of the convolutional neural network (CNN), the long shortterm memory (LSTM) neural network, and the additive attention mechanism (AAM), and better capture nonlinear features of time series data. In the simulation analysis, we select sample data of three stocks (Vanke A, Shanghai International Port Group, and China Merchants Bank) and three stock price indexes (China Securities 500 Index, Shanghai Stock Exchange 50 Index, and Growth Enterprise Index) in the Chinese stock market for comparative analysis, and use mean square error (MSE), mean absolute error (MAE), and mean absolute percentage error (MAPE) as the evaluation indexes. The CNN-LSTM-AAM model has the best prediction ability relative to the CNN and CNN-LSTM models. In addition, we also find that the prediction ability of the CNN-LSTM-AAM model for different stock data sets is different under the existing parameter conditions. For a specific dataset, the parameter conditions of the CNN-LSTM-AAM model need to be further adjusted to achieve the best prediction effect. Based on the above findings, the CNN-LSTM-AAM model has better performance and higher accuracy, and can provide credible decision-making basis and research methods for investors, financial institutions, and regulators.

  Abstract
  Stock price fluctuations reflect market expectations for the economic situation and company profits. Accurately predicting stock prices has become a hot topic in academia. [...]

  • 0
  •  read

• A Numerical Study of the Impact of Bending and Torsional Stiffness on the Static Aeroelastic Characteristics of a Large Aspect Ratio Composite Wing

  S. qiao, F. Wang, P. Wang

  Rev. int. métodos numér. cálc. diseño ing. (2024). Vol. Online First, 46

  
  

  Abstract

  The bending and torsional stiffness influence structural deformation to varying degrees. Utilizing the coupled numerical method of Computational Fluid Dynamics and Computational Structural Dynamics (CFD/CSD), a comprehensive study was conducted on the impact of bending and torsional stiffness on the static aeroelastic behavior of a high-aspect-ratio wing, employing FLUENT software across diverse flight conditions. The study summarized this influence by comparing the computational outcomes. The results indicate that as the angle of attack rises, the lift increment diminishes gradually until the angle reaches 14 degrees, rendering the strategy of enhancing bending and torsional stiffness to gain more lift ineffective. Between 2 and 14 degrees of angle of attack, the lift difference between the scenarios decreases from 23.98% to 7.31%. At higher Mach numbers and lower angles of attack, augmenting wing stiffness significantly boosts wing lift. Optimal lift-to-drag characteristics are achieved at approximately 6 degrees of angle of attack. By averagely increasing the wing’s bending and torsional stiffness by 8.28% and 5.22%, respectively, the lift-to-drag characteristics can be enhanced by 5.27% at a low angle of attack of 0.75 Mach. The disparity in maximum deflection between the two stiffness wings is most pronounced at higher flight speeds and smaller angles of attack, with the opposite trend observed for the difference in maximum torsion angle. The key findings presented in this paper can expedite the integrated design of stiffness for this type of wing structure by providing vital technical insights.OPEN ACCESS Received: 24/07/2024 Accepted: 22/10/2024

  Abstract
  The bending and torsional stiffness influence structural deformation to varying degrees. Utilizing the coupled numerical method of Computational Fluid Dynamics and Computational [...]

  • 0
  •  read

• Analysis of Airflow Uniformity in Pig Nurseries Using Duct Ventilation in Northeast China_prova_word

  Z. Wu, K. Xu, Y. Chen, J. Sánchez Pinedo

  Colección de pruebas Jesús Sánchez (2024). 3

  
  

  Abstract

  The problem of uneven ventilation in pig houses must be solved to effectively improve the winter environmental quality of pig nurseries in cold regions. In this study, the airflow field and airflow uneven coefficients of pig nurseries with duct ventilation were simulated and calculated using computational fluid dynamics, and compared with pig nurseries with different duct diameters, inlet and outlet air velocities and air supply angles. The average relative error between the simulated and measured values was {| class="formulaSCP" style="width: 100%; text-align: center;" |- | 12\% |} . Comparison of simulation results and airflow uneven coefficients showed that the airflow uneven coefficients of the fences were reduced, and the airflow field was uniformly distributed with a duct diameter of 0.3 m , inlet and outlet air velocities of 1.5 and {| class="formulaSCP" style="width: 100%; text-align: center;" |- | 2.0\, m/s |} , respectively, and an air supply angle of {| class="formulaSCP" style="width: 100%; text-align: center;" |- | {45}^{\circ } |} . These improvements resulted in a more homogeneous ventilation, which led to more uniform ventilation and contributed to discharging dirty air outdoors. Then the test pig nursery was modified based on the simulation and analysis results. Difference analyses were carried out between the control and the test pig nurseries. Comparative analyses showed the differences between the test data and the monitoring data were smaller, and the duct ventilation was more uniform, which was suitable for the healthy growth of piglets.

  Abstract
  The problem of uneven ventilation in pig houses must be solved to effectively improve the winter environmental quality of pig nurseries in cold regions. In this study, the [...]

  • 0
  •  read

• Analysis of Airflow Uniformity in Pig Nurseries Using Duct Ventilation in Northeast China

  Z. Wu, K. Xu, Y. Chen, Y. Liu, M. Liu

  Rev. int. métodos numér. cálc. diseño ing. (2024). Vol. 40, (3), 39

  
  

  Abstract

  The problem of uneven ventilation in pig houses must be solved to effectively improve the winter environmental quality of pig nurseries in cold regions. In this study, the airflow field and airflow uneven coefficients of pig nurseries with duct ventilation were simulated and calculated using computational fluid dynamics, and compared with pig nurseries with different duct diameters, inlet and outlet air velocities and air supply angles. The average relative error between the simulated and measured values was 12%. Comparison of simulation results and airflow uneven coefficients showed that the airflow uneven coefficients of the fences were reduced, and the airflow field was uniformly distributed with a duct diameter of 0.3 m, inlet and outlet air velocities of 1.5 and 2.0 m/s, respectively, and an air supply angle of 45°. These improvements resulted in a more homogeneous ventilation, which led to more uniform ventilation and contributed to discharging dirty air outdoors. Then the test pig nursery was modified based on the simulation and analysis results. Difference analyses were carried out between the control and the test pig nurseries. Comparative analyses showed the differences between the test data and the monitoring data were smaller, and the duct ventilation was more uniform, which was suitable for the healthy growth of piglets.OPEN ACCESS Received: 19/07/2024 Accepted: 10/10/2024

  Abstract
  The problem of uneven ventilation in pig houses must be solved to effectively improve the winter environmental quality of pig nurseries in cold regions. In this study, the [...]

  • 0
  •  read

• Word de prueba

  J. Sánchez Pinedo

  Colección de pruebas Jesús Sánchez (2024). 1

  
  

  • 0
  •  read

• Research on the Effects of Pit Excavation on Adjacent Existing Subway Tunnel Structures Based on the FEM-DEM Coupling Method

  D. Meng, W. Lei, J. Han, H. Li, Y. Huang

  Rev. int. métodos numér. cálc. diseño ing. (2024). Vol. 40, (3), 43

  
  

  Abstract

  With the swift advancement of underground space development, large deep excavation projects above subway stations are becoming more common. This study employs the Finite element method-Discrete element method (FEM-DEM) coupling method to examine the effects of excavation on the structure of nearby subway tunnels. First, the f lexible triaxial compression test was conducted using the FEM-DEM coupling method to acquire the macroscopic mechanical characteristics of various soil layers. Based on this, the ground particle model was developed using the particle size scaling method, the underground continuous wall support was constructed via the FEM-DEM coupling method, and the tunnel model was established using particles arranged circularly. The study shows that with the excavation, the particles at the bottom of the foundation start to heave upward, with the maximum uplift displacement being approximately 10 mm. Throughout the excavation process, substantial changes occur in the contact force chain within the pit, with notable stress release at the pit bottom. Moreover, the porosity at the pit bottom gradually increases, and the vertical stress decreases; the stress decreased by 75% compared to before excavation, primarily due to stress release during excavation. Lastly, a focused analysis was conducted on the tunnel deformation during excavation. Throughout the foundation pit excavation, the tunnel’s displacement mainly took place within the excavation area, and its vertical displacement increased as the excavation depth increased, with a maximum displacement of approximately 0.5 mm. Analysis of particle displacement at various locations in the tunnel revealed that particles closest to the foundation pit bottom experienced the greatest displacement, whereas those farther away had relatively smaller displacements. The findings offer crucial theoretical support for the design and implementation of excavation projects.

  Abstract
  With the swift advancement of underground space development, large deep excavation projects above subway stations are becoming more common. This study employs the Finite element [...]

  • 0
  •  read

• Control-Relevant Identification of the Unstable Inertial Systems

  I. Cojuhari

  Rev. int. métodos numér. cálc. diseño ing. (2024). Vol. 40, (3), 40

  
  

  Abstract

  Nowadays, with the rise of computing power, control-relevant identification methods have gained attention in various industrial applications, incorporating the requirements for control design into the process of system identification. Mathematical identification of stable linear dynamical systems is a widely studied problem in the literature, and it is prevalently performed in open-loop structures that may lead to high-order models suitable for control system design with imposed control objectives. However, in the case of unstable systems identification can become a challenge task, and usually is performed using closed-loop identification techniques. This paper presents the control-relevant identification approach for two kinds of unstable processes. The contribution focuses on establishing a well-fitted identified model by using a strategy that involves collecting data from the closed-loop system’s operation with a proportional controller when the system achieves an underdamped step response. In addition, a proportional-integral-derivative (PID) controller for each process was synthesized using maximal stability degree method. Concerning identification, the simulation results were compared with those of the genetic algorithm and offered better model estimation than the genetic algorithm. On the other hand, it is also demonstrated that the designed control algorithm offered a high degree of stability to the system and is more reliable in stabilizing the behavior of the unstable system than the genetic algorithm and the parametric optimization method.

  Abstract
  Nowadays, with the rise of computing power, control-relevant identification methods have gained attention in various industrial applications, incorporating the requirements [...]

  • 0
  •  read

• Effects of radar absorption materials application on stealth performance of inlet based on risk theory

  S. Liu, Z. Guo, L. Chen

  Rev. int. métodos numér. cálc. diseño ing. (2024). Vol. 40, (3), 42

  
  

  Abstract

  One significant technical measure to reduce the forward radar cross section (RCS) of the aircraft was to design the inlet into an S-shape. Additionally, the application of radar-absorbing material (RAM) can further decrease the RCS of the air intake which approach enhances the stealth capabilities of the aircraft. Nevertheless, the use of RAM will simultaneously increase the inherent weight of the air intake. The electromagnetic scattering characteristics of Sshaped inlets without RAM coating and seven coating schemes are calculated by numerical simulation. The risk theory was employed to assess the impact of the coating RAM on the radar cross-section. The simulation results indicate that coating RAM can further reduce the forward average RCS value. Compared to the full coating scheme the S-shaped inlets with RAM on the intake region can achieve 90% of the RCS reduction effect and cut down approximately forty percent of the coating.

  Abstract
  One significant technical measure to reduce the forward radar cross section (RCS) of the aircraft was to design the inlet into an S-shape. Additionally, the application of [...]

  • 0
  •  read