Modified PROMETHEE Approach for Solving Multi-Criteria Location Problems with Complex Criteria Functions

The specific problem that occurs in multi-criteria decision-making (MCDM) processes is ranking a number of alternatives using complex criteria functions (the hierarchical structure of criteria) whose values must consider the impacts of all-important characteristics and parameters of alternatives. The problem becomes more complex by increasing the number of levels of sub-criteria functions (degree of decomposition). This paper proposes an extended procedure based on the mean values conversion of the net outranking flow of sub-criterion functions obtained by modified PROMETHEE methods. The actual value of criterion functions is used only at the last level, and transformed values of the net outranking flow for generating a final rank of alternatives are introduced at other levels. This procedure provides a more objective comparison of the impact of various individual criteria to rank the alternatives and easier making of unique solution, where the impact of decision-maker (DM) experience and subjective estimation is minimised in the selection. Applicability and practicability of the presented procedure for solving the selection problem of a logistics warehouse location are demonstrated in the analysis of a case study example

Energy Method in Efficient Estimation of Elastic Buckling Critical Load of Axially Loaded Three-Segment Stepped Column

This paper treats the elastic stability of three-segment stepped column that is subjected to axial concentrated compressive forces using the strain energy method. Efforts have been made to establish the methodology for the development of a model that is useful for quick, yet quite accurate, estimation of the elastic buckling critical load. By using the load, segments stiffness and lengths ratios, the dimensionless influence coefficient is defined for any combination of parameters. The diagrams of critical load based on geometric parameters variation are given. The results of analytical model are compared with numerical results obtained from finite element method. Within two investigation regimes, influences of bending stiffness and lengths variations are analyzed separately.Publishe

Analysis of the Influence of Large Diameter Bearing Support Structure Condition on Reliability in Operation

The causes of support structure deformation of the large diameter bearing arise from external loads and they are variable by the magnitude and point where load acts. By forming a model of bonds, on the basis of which would be performed a theoretical analysis of the interaction of revolving and non-revolving parts in construction and transport mechanization machines, with the variation of geometric values of supporting structure elements, could be obtained some parameters that have a dominant influence on the increasing of necessary support surface stiffness for bearing bond. Therefore, the deformation of support surface must be smaller than allowed value. In this way, will be separated a typical carrying structures which favorably effect on functionality of bonds. Also, we noticed the shortcomings of these structures that should be eliminated. The result of such research and analysis should enable the fulfillment of the demands which placed before of construction and transport mechanization machines, i.e. the better adaptability of the excavator running machine with the leaning surface, as well as the radial-axial bearing support surface deformation must be kept under the limits that allows the proper functioning of bonds.Publishe

Modeling of Arterial Stiffness using Variations of Pulse Transit Time

In this paper, a finite element (FE) modeling is used to model effects of the arterial stiffness on the different signal patterns of the pulse transit time (PTT). Several different breathing patterns of the three subjects are measured with PTT signal and corresponding finite element model of the straight elastic artery is applied. The computational fluid-structure model provides arterial elastic behavior and fitting procedure was applied in order to estimate Young's module of stiffness of the artery. It was found that approximately same elastic Young's module can be fitted for specific subject with different breathing patterns which validate this methodology for possible noninvasive determination of the arterial stiffness

Transient finite element modeling of functional electrical stimulation

Transcutaneous functional electrical stimulation is commonly used for strengthening muscle. However, transient effects during stimulation are not yet well explored. The effect of an amplitude change of the stimulation can be described by static model, but there is no differency for different pulse duration. The aim of this study is to present the finite element (FE) model of a transient electrical stimulation on the forearm. Discrete FE equations were derived by using a standard Galerkin procedure. Different tissue conductive and dielectric properties are fitted using least square method and trial and error analysis from experimental measurement. This study showed that FE modeling of electrical stimulation can give the spatial-temporal distribution of applied current in the forearm. Three different cases were modeled with the same geometry but with different input of the current pulse, in order to fit the tissue properties by using transient FE analysis. All three cases were compared with experimental measurements of intramuscular voltage on one volunteer

ANALYSIS OF VARIANTS OF STRUCTURES OF BUILT-UP COLUMNS ON EXAMPLES OF COLUMNS FOR CRANE RUNWAYS

U ovom radu je prikazana višekriterijumska analiza za dve varijante izvođenja složenih dvodelnih štapova koji su izrađeni od standardnih U profila, sa ispunom od spojnih limova, pri čemu su posmatrani na primerima stubova dizaličnih staza. U ovom istraživanju, pored različitih kriterijuma stabilnosti, analizirani su i različiti slučajevi provere čvrstoće, kao i nosivost šava kod veze spojnih limova sa U profilima. Takođe, izvšena je i optimizacija potrebnog broja spojnih limova, kao i njihovih dimenzija, za obe varijante složenih štapova, pri čemu se posmatralo kako se menja broj ovih limova, kao i njihova masa, pri povećanju sile pritiska na stub dizalične staze. Za postupak analize i optimizacije primenjen je alat Solver, kao i EA algoritam, u Ms EXCEL softveru. Primena ovakvog postupka se pokazalo opravdanim, pre svega zbog same prirode problema i analize, pri čemu se vrlo brzo može doći do potrebnih parametara pri projektovanju ovih tipova struktura. Takođe, pokazano je kako se menja ukupna masa stuba dizalične staze, pri promeni sile pritiska, za jednu i drugu varijantu, kao i poređenje masa stubova ovih varijanti.Publishe

ANALYSIS OF CALCULATION METHODS APPLIED TO THE RINGS OF PORTAL CRANE

The paper deals with calculation methods which have been applied to circular rings of portal cranes having revolving columns. The first part of the paper includes theoretical analysis of the loads of circular rings and calculation methods, too. In the second part of the paper the theoretical results of the calculation have been checked by finite element method (FEM) and by calculation software. It has been proved that calculation results have a high level of conformity, which provides the possibility for theoretical analysis of influence of different parameters on the intensity of ring stress and ring deformation.Publishe

Primena metode konačnih razlika kod određivanja ugiba nosača kontinualno promenljivog poprečnog preseka

Amongst others, the deformation criterion is to be fulfilled in the process of steel structure design. Often, it can be more restrictive than the stress criterion. Although the stress state is within the permissible limit, excessive structure deformation can lead the additional load to emerge in the carrying structure and cause improper operation and shorter life of attached devices and equipment. For that reason, besides other requirements, the allowable deformation limits of the steel carrying structure are defined. The stress-strain analysis of the structure is usually conducted by utilization of finite element method (FEM) in the early phase of the design process. Alternatively, this paper shows the application procedure of the finite difference method (FDM) for the deflection determination on the simple elastically restrained cantilever beam with continuously varying box-like cross-section and linear change of section height. Dependence of the deflection on the design parameters is obtained through programming in MATLAB and the comparison is made with the results from the finite element model built in ANSYS. The results from both numerical approaches showed excellent compliance.Publishe

Aksijalno-radijalni ležaj kao segment veze okretne platforme sa nosećom konstrukcijom

The paper presents the connection of rotating platforms in building and transport machines depending on the type of driving mechanism. A special attention is paid to axial-radial bearings having big diameters made by prominent manufacturers. There are some necessary conditions which have to be met by supporting frames because working capacity of the bearings depends on them. Also, the law of distribution of load of moment of external forces is proposed because it provides identification of maximum load as a starting basis for further research on determination of optimal laws of distribution of acting forces which are caused by the moment of forces.Publishe

Prilog analizi krutosti ramova utovarno-istovarnih kolica pretovarnih mosnih dizalica

The paper analyzes the dependence of the stiffness of the support frames of the cranes with loading-unloading trolley on the change of geometrical parameters of the frames. The calculation model of the frames with transverse stiffness was formed because it additionally stiffens the supporting surface of the frames for connection with the axial-radial bearing. The relations of characteristic geometrical sizes of longitudinal and transverse elements were established, at which the necessary stiffness of the frames of loading-unloading trolley was achieved. Also, the variables and constants of geometric size were introduced, as well as the constant values of appropriate coefficients, the variation of which provides the possibility to form the optimal structure of the frames of loading-unloading trolley.Publishe