Milena Jovanović

Changes in the Volatile Profile of the Artemisia lobelii All. During Prolonged Plant Material Storage

Abstract Chemical composition of the essential oil hydrodistilled from the Artemisia lobelii All., after a storage period of seven years, was studied by GC and GC/MS and compared with the chemical composition of the oil obtained right after drying the same plant material. Although two leading constituents of the compared oils were camphor and 1,8-cineole (36.6% and 17.9% in the oil distilled directly after plant material drying and 17.8% and 11.0% in the oil obtained after prolonged storage, respectively), significant decrease in the oil yield (from 0.17% to 0.09%) and increase in the number of components (from 26 to 120) during plant material storage was observed. These changes in the oil content and composition are most probably influenced by the evaporation of the volatile constituents from the plant material during storage, and by the chemical transformations of the plant native metabolites.

Testing of Level of Vibration and Parameters of Bearings in Industrial Fan

Climate chambers are a complex system of electromechanical components used for conditioning of air for providing comfort and projected parameters of temperature, humidity, velocity and air cleanliness in the area. In this paper is presented examination of the fan unit company Flaktwoods GJLB-5-071, 17.95 kW, n=1450 rpm, with a multi-functional device Vibrotest 60, the Danish manufacturer Bruel & Kjaer, for diagnostic of parameters of vibration and condition of bearing. The measured parameters are related to: - levels of vibrations (including measurement points on the motor and on the fan) in the directions of coordinate axes, according to ISO 10816-1. - parameters of condition of bearing through the index of bearing condition BCU (Bearing Conditions Unit) and BCS (Bearing Spectrum Conditions) - analysis of the characteristic frequency of vibration in the spectrum, presented by FFT (Fast Fourier Transformation).

Vibration Analysis of Insufficiently Repaired Well Pump - A Case Study

Vibration analysis of the repaired well pump is to determine whether vibrations occur due to an insufficient pump repair or due to some new malfunction that happened after the repair. This paper presents vibration analysis of well pump as well as the applied corrections in order to lower the vibration levels. Vibration measurement of well pump is conducted on measurement points defined by standard ISO 10816-1.

Vibration Analysis of the Boiler Supply Air Fan—A Case Study

The air supply fan is an important element for boiler operation, responsible for providing the necessary air flow with respect to the combustion process demands. Vibration measurements of the boiler fan were conducted on measurement points defined by standard ISO 10816-1. Vibration measurements were done with Bruel&Kjaer Vibrotest 60, vibration analyzer and offline data acquisition device. The measured parameters are related to: levels of vibrations, parameters of condition of bearing BCU (Bearing Conditions Unit) and BCS (Bearing Spectrum Conditions), analysis of the characteristic frequency of vibrations is presented on FFT Spectrum diagrams. Based on the analysis the main conclusion is: measured vibrations are high and fan is in the field of unstable work.

Simulation of hybrid electrical vehicle for two different driving modes

Original scientific paper This paper shows an example of computer simulation of hybrid vehicle in two different driving modes. This example shows multiple areas of operation of a simulated hybrid electric vehicle. The hybrid electric vehicle is of combined type, similar to Toyota Prius cars. This hybrid electric vehicle has two types of driving power: the electric motor and the internal combustion (IC) engine, to increase the level of efficiency of driving assembly and to reduce air pollution. A hybrid electric vehicle combines the advantages of electric motor drive (no pollution and high available power at low speeds) and the advantages of IC engine (high dynamic performances and little pollution at high speeds). In the simulation of a hybrid electric vehicle SimPowerSystemsTM and SimDrivelineTM (MATLAB) were used.