The problem of convective stability in a medium containing settling heavy solid particles are discussed. A study is made of the stability of steady convective flow of a medium containing an additive between vertical plates heated to different temperatures. It is shown that the presence of settling solid particles has a significant stabilizing effect on convective stability.
The electron beam technological processes like electron beam welding, electron beam additive technologies, etc. depend strongly on the characteristics of the electron beam, generated by the electron gun. In this work the estimation of the 3D radial current density distribution using training, testing and validation of different artificial neural networks is considered. The model estimation is based on experimental measurements of the electron beam current distribution in three cross-sections of the beam at different distances from the magnetic lens of the electron gun. The estimated neural models with different structures are compared. Graphical user interface for the evaluation of the radial electron beam distribution in any cross-sections of the beam is developed.
This paper presents a comparison of three methods for any pump energy analysis. Each method is used for the analysis of three different water pumps from the conventional steam thermal power plant – two feed water pumps (FWP1 and FWP2) and condensate pump (CP). For each pump three essential types of mechanical power which defines all energy analysis methods are: delivered power from power producer, real (polytropic) power and ideal (isentropic) power. Method 1 which compares delivered and real (polytropic) power show the best performances, while Method 3 which compare delivered and ideal (isentropic) power should be avoided because it results with too high energy power loss and too low energy efficiency of any pump. Method 2 which compares real (polytropic) and ideal (isentropic) pump power can be used as a good compromise for the pump energy analysis in the most of the cases – its results are similar to results of Method 1.
A mathematical method of linear surrogate parametric synthesis of frame surface non-coaxial eddy current probes with a uniform eddy current density distribution in the testing object’s zone is proposed. The metamodel of a frame eddy current probe with a planar structure of the excitation system is constructed. Acceptable accuracy of the created metamodel is obtained by using the decomposition of the extremum search space and using associative neural networks. Examples of the synthesis of such excitation systems using modern metaheuristic stochastic algorithms for finding the global extremum are considered. The numerical results of the obtained solution and graphic illustrative material of the density distribution of the eddy currents on the surface in the testing object’s zone are given.
It is created computer model of wire extrusion process with Matlab. The model is verified by comparing the simulated results with experimental.
Thermal comfort and indoor air quality highly depend on proper design of Heating, Ventilation and Air Conditioned (HVAC) system. These system require large amounts of energy. Efficient use of energy leads to new concept design of HVAC systems. In this article, energy consumption in office building is analysed using Hourly Analysis Program (HAP) software. The aim of this research work is focused in estimation of office building energy consumption considering three different HVAC systems, respectively. Therefore, Variable Refrigerant Flow (VRF) system, HVAC 2-pipe and HVAC 4-pipe system were analysed with respect to energy consumption. A typical office building placed in Tirana, of 5000 m2 of total area is used for this study.
The aim of this work is the implementation of the virtual hybrid human body model Virthuman into the pedestrian traffic collision scenarios. The pedestrians are the most vulnerable traffic road users and they are exposed to a high risk and suffer with serious injuries and responsible for high number of death and injuries. The interest of the study of simulation of a car crash accident is motivated by the effort to decrease these numbers. The authors use a virtual model of the full human body called Virthuman here. This model was built based on combination of two modelling approaches, particularly multibody and finite element. Such method is call a hybrid approach and keeps advantages of both principles. The model was fully validated against published experimental data (particular body segment tests as well as full body tests) and was successfully used in the number of applications. The purpose of this paper is to present the model as a suitable tool for pedestrian collision modelling and injury risk assessment. Besides the description of the model, the examples of the application towards pedestrian safety are going to be presented here.
Motorcycle accidents with opposite vehicles are among the most difficult to reconstruct due to complicated kinematics and interactions between multiple participants. The Multi-Body System approach commonly applied in software packages as PC-Crash and Virtual-Crash, allows for proper reconstruction of the crash kinematics but did not take into account the full deformation of the vehicles and occupants. On the other hand, the Finite Element Method approach, especially the explicit formulation, used in the field of crashworthiness gives a way to describe the proper material behavior of the participant components during dynamic events. For the analysis of the accident, the full FEM approach becomes too complicated and time-consuming (both for preparation of the simulation and for the simulation run). The authors would like to propose a hybrid approach which couples and FEM and MBS models in VPS numerical environment (Pam-crash solver). This paper presents an analysis of the accident between the maxi-scooter and the opposite vehicle. As the representation of the PTW driver, a Virthuman hybrid human body model was used. This model in opposition to full FEM models allows the fast calculation of the simulation. Besides the kinematics of the accident, prescribed injury criteria were assessed on the human body model.