Varazdin University of Applied science

Varaždin, Croatia

Varazdin University of Applied science

Varaždin, Croatia

Time filter

Source Type

Runje B.,University of Zagreb | Medic S.,Karlovac University of Applied science | Kondic Z.,Varazdin University of Applied science | Alar Z.,University of Zagreb | Tunjic D.,TUV Croatia d.o.o
Tehnicki Vjesnik | Year: 2012

This article focuses onto the process of fire-resistant coating production. That process belongs to the class of processes, considered statistically, which have only one, lower specification limit. Such processes are interesting in that they usually do not have the accompanied normal distribution. In order to bring the process under control, we monitored the fire-resistant coating production using the x-R control chart. The process capability analysis was applied on one set of data analyzed using three different methods. In the first method the data were approximated using the 3-parameter Weibull distribution. In the second method, data were transformed using the Johnson transformation while in the third method, applied for the purpose of comparison of sets, data were approximated with normal distribution. In the accompanied experiment, the thickness of the fire-resistance coating was measured on seven steel girders. The results have been analyzed using the trial version of the Minitab software package. Using the Monte Carlo method, numerical simulations were performed in order to estimate the uncertainty of measurements of coating thickness.


Stepanic J.,University of Zagreb | Medic S.,Karlovac University of Applied science | Kondic Z.,Varazdin University of Applied science
Tehnicki Vjesnik | Year: 2012

If a dimensional measurement on an object is to be performed during its non-perturbed motion, a specific approach is needed. In this article we consider length measurement of an object based on photographs of the object during its unperturbed motion. The main obstacle for determining measured length is the parallax which is generated as a convolution of contributions occurring in different parts of a measuring system. The quantitative expressions for the parallax are derived, and applied onto processing of the photos. As a result, we derive in a closed form the algorithm for quantitative estimates of the precisely measured length and accompanied standard deviation.


Medic S.,Karlovac University of Applied science | Kondic Z.,Varazdin University of Applied science | Runje B.,University of Zagreb
Tehnicki Vjesnik | Year: 2012

The Laboratory for Precise Measurement of Length, which is at the same time the Croatian National Laboratory for Length (in text Laboratory) takes part in CIPMMRA(Comité International des Poids et Mesures, Mutual Recognition Arrangement) comparisons of length standards, which include line scales as very important standards of length.When the results reported in the comparisons, it is necessary to state the estimated measurement uncertainty. Recently, the Monte Carlo simulations (MCS) have been increasingly applied in the field of estimation measurement uncertainties. The paper presents validation of the realised measurement uncertainty by GUM method in process of precise line scales calibration using the MCS method. The MCS method is based on random number generation from the probability density functions for each input value and forming of experimental probability density function of the output value. Also, the paper presents obtained results of the international comparison measurement which representing a real validation of the device and evaluated measurement uncertainty.


Runje B.,University of Zagreb | Markovic M.,University of Zagreb | Lisjak D.,University of Zagreb | Medic S.,Karlovac University of Applied science | Kondic Z.,Varazdin University of Applied science
Tehnicki Vjesnik | Year: 2013

In accordance with the applicable standards, this paper describes the demands for flatness of measurement tables. The paper has elaborated methods of measurement and a more detailed method of measuring flatness deviation with the use of an electronic level. Mathematical model has been described and an integrated computer model for processing, axonometric and topographic representation of the results of measuring deviations from flatness in the process of measuring with electronic level has been developed. The established mathematical model and developed software solution have been experimentally validated.


Mihalic T.,University of Zagreb | Medic S.,Karlovac University of Applied science | Kondic Z.,Varazdin University of Applied science
Tehnicki Vjesnik | Year: 2013

The improvements of the characteristics of centrifugal pump were investigated in this work experimentally and with computational fluid dynamics (CFD) analysis of the influence of adding vortex rotor to centrifugal one. The idea behind that improvement is in creating the so-called coherent structures of eddies and turbulence in the peripheral area of the vortex rotor mounted at the back side of centrifugal rotor. Research on the energy transformations in the centrifugal vortex pump in this work was carried out using control volume method for simulations of the flow in the centrifugal and the centrifugal vortex pump, and also by taking measurements of relevant parameters that describe the performance of pumps at their physical models. The measurement results were used as experimental validation and verification of numerical simulations; in contrast, flow visualization derived from the numerical simulation was used to interpret measurements. In deriving that experimental procedure, special care was taken with the flow measurements. The reason for this is in the fact that the flow measurements had the biggest influence on the overall measurement uncertainty. However, flow measurements were the most demanding with regard to experiment design and in taking the measurement readings. This experimental - CFD research made it possible to undertake an assessment of vortex rotor contribution on the head of centrifugal vortex pump. The influence of the vortex rotor on the efficiency of the centrifugal vortex pump was studied in contrast to the efficiency of a centrifugal pump with the same geometry. An analysis of the structure of flow was conducted in order to better understand the energy transformations that are the result of interaction between vortex rotor and the flow from the channels of centrifugal part of centrifugal vortex rotor.

Loading Varazdin University of Applied science collaborators
Loading Varazdin University of Applied science collaborators