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Snitka V.,Kaunas University of Technology | Mizariene V.,Kaunas University of Technology | Bruzaite I.,Vilnius Gediminas Technical University | Lendraitis V.,Kaunas Technical College | Rackaitis M.,Bridgestone
International Journal of Nanomanufacturing | Year: 2010

In this work, the porphyrin nanotubes were built by ionic self-assembly in acidic aqueous solution of two oppositely charged non-metal porphyrins, namely, the anionic meso-tetra (4-sulfonatophenyl) porphine dihydrochloride (TPPS 4) and cationic meso-tetra (4-pyridyl) porphine (T4MPyP). The electrostatic forces between these porphyrin blocks contribute to the formation of porphyrin aggregates in the form of nanosheets and nanotubes, enhance the structural stability of these nanostructures. The nanosheets thickness approximately varies in the range of 3-15 nm and the sheets diameter up to 1 micron. Using the TEM and SEM, it was revealed that the mechanism of nanotubes formation is based on the wrapping of nanosheets in multiwall cigar-like structures. The porphyrin nanotubes obtained are hollow structures with a length from 200 nm up to 1,000 nm and have a diameter in the range of 50-140 nm with 20-40 nm thick walls. TEM images confirm a hollow tubular structure of the aggregates. Copyright © 2010 Interscience Enterprises Ltd.


Fedaravicius A.,Kaunas University of Technology | Jonevicius V.,Vilnius Gediminas Technical University | Kilikevicius S.,Kaunas University of Technology | Paukstaitis L.,Kaunas University of Technology | Saulys P.,Kaunas Technical College
Transport | Year: 2011

One of the most important measures to reduce the cost of preparing mortar units is the use of mortar shooting trainers operating according to the 'shell in shell' principle that best meets the needs of military forces. When increasing the efficiency of using equipment for mortar shooting training and seeking to reduce their production costs, further research on external ballistics is strictly necessary in order to improve the structural parameters of mine imitators. With the help of finite element modelling techniques, this article investigates air flow over mortar mine imitators. In order to achieve the aim, a package of Mechanical Desktop Software was used for creating a dimensional model of mine imitator the model of which was imported into ANSYS CFX and a finite element numerical model was generated. Considering the literary sources of experimental studies, SST turbulence model generating the results closest to those of experimental research was selected. After modelling, air drag force influencing mine imitator and the drag coefficient at different air flow speed were established. © 2011 Vilnius Gediminas Technical University (VGTU) Press Technika.


Fedaravicius A.,Kaunas University of Technology | Kilikevicius S.,Kaunas University of Technology | Survila A.,Kaunas University of Technology | Saulys P.,Kaunas Technical College | Lendraitis V.,Kaunas Technical College
Mechanika | Year: 2011

The interaction processes of mine imitator and the soil surface are analysed in the research. With the application of LS-DYNA FEM code the interaction characteristics and parameters of the mine imitator and the soil were determined for the velocity values of 35, 45, and 52 m/s. Dynamical model of the interaction of the mine imitator and the soil was developed. Computer simulation of the interaction was performed using MATLAB 6 software and the results obtained were compared with the results of simulation obtained using LS-DYNA FEM code. The obtained results were successfully applied in practice.


Dauksys G.,Kaunas University of Technology | Dauksys G.,Kaunas Technical College | Jonaitis A.,Kaunas University of Technology | Gudzius S.,Kaunas University of Technology | Morkvenas A.,Kaunas University of Technology
Elektronika ir Elektrotechnika | Year: 2016

It is well known the use of on-line partial discharge (PD) measurements as an indicator of stator winding insulation condition. The scheduled PD measurements could be used as a test to evaluate the quality of the equipment. The test results could help to diagnose the insulation problems in motors and generators for corresponding action before failure occurs. Although a number of PD measurement methods exists, but the tests results of on operating rotating machines can be influenced by conditions such as humidity, temperature, terminal voltage, and load. This paper describes the development of PD imitation mathematical model in stator insulation. The experimental investigation with physical model was performed for adequacy assessment. The capacitive sensor was used for PD online monitoring.


Kargaudas V.,Kaunas University of Technology | Zmuida M.,Kaunas University of Technology | Zmuida M.,Kaunas Technical College
Mechanika | Year: 2012

Vibrations of elastic plate and compressible fluid are investigated. Compressibility of the fluid influences eigenmodes and to some degree eigenfrequencies also, while density of the fluid eigenfrequencies changes more than eigenmodes. Calculations of steel plate vibrations in water and wood plate vibrations in air are presented, influence of the water and the air compressibility discussed. Interaction of plate eigenmodes in vacuum is represented by hydrodynamic matrix, entries of which depend on sound wave speed in fluid. Eigenmodes of the plate in vacuum and eigenmodes in incompressible fluid can be applied as base functions of the investigation, but the set of eigenmodes of the plate in compressible fluid does not form a set of complete orthogonal base functions.


Dauksys G.,Kaunas University of Technology | Dauksys G.,Kaunas Technical College | Jonaitis A.,Kaunas University of Technology
Elektronika ir Elektrotechnika | Year: 2013

The solid insulations of electrical equipment are perpetually affected by various duration overvoltages. Electric stress of insulation depends on its thickness and amplitude of applied voltage. The damaged solid insulation may also influence characteristic parameters of partial discharges. The characteristic parameters of solid insulation quality should be permanently evaluated. Partial discharge monitoring provides reliable information necessary for basic maintenance of stator windings of motors and generators. Submitted paper deals with partial discharge measurements in stator windings during the increasing of applied voltage.


Gecys S.,Kaunas University of Technology | Smolskas P.,Kaunas Technical College | Zmuida M.,Kaunas Technical College
Elektronika ir Elektrotechnika | Year: 2010

The design methodology of conventional induction motors is not suitable for the borehole motors due to specific and extraordinary operating conditions. The parametrical method synthesis for small power solid rotor and copper-cage solid rotor induction motors is developed, taking into account the specific operating peculiarities and limiting factors. The main construction coefficients and change limit related parameters of the equivalent circuit for the design of the borehole motors, applying the parametrical synthesis principles, are determined, considering the maximum transmitted active power through the supply circuit to the motor. The calculations of equivalent circuit parameters, characteristics, applying the proposed parametrical method synthesis and tests, are carried out. This confirms reliable operation in the concrete supply circuit.


Dauksys G.,Kaunas Technical College | Dauksys G.,Kaunas University of Technology | Gvozdas V.,Kaunas University of Technology
6th International Conference on Electrical and Control Technologies, ECT 2011 | Year: 2011

High voltage insulation is loosing its quality during the operation of high voltage machines and generators. Degrading high voltage stator insulation is the main reason for sudden breakdown of stator windings. Partial discharge measurements can reveal a lot of defects in stator windings of high voltage rotating machines with operating voltage 6 kV. Partial discharge monitoring provides reliable information necessary for basic maintenance of stator windings of motors and generators. Submitted paper deals with partial discharge measurements in stator windings during the increasing of applied voltage.


Valatka P.,Kaunas University of Technology | Sucila V.,Kaunas University of Technology | Dauksys G.,Kaunas University of Technology | Dauksys G.,Kaunas Technical College
Elektronika ir Elektrotechnika | Year: 2010

The solid insulations of electrical equipment are perpetually affected by various duration overvoltages and overcurrents. Depending on its duration, the overvoltage event can be transient-a voltage spike, or permanent, leading to a power surge. They all directly affect the insulation. Electric stress of insulation depends on its thickness and amplitude of applied voltage. The damaged solid insulation may also influence characteristic parameters of partial discharges. In the following paper there are discussed the voltage influence on partial discharge characteristic parameters in the solid insulation. Partial discharge values in different size and shapes of solid insulation defects under different voltage influence are evaluated.


Augutis V.,Kaunas University of Technology | Saunoris M.,Kaunas University of Technology | Saunoris M.,Kaunas Technical College
Journal of Vibroengineering | Year: 2010

Surface roughness is an important parameter for evaluating the quality of material surfaces. It affects the tribological and optical properties of the materials. The paper proposes a new method for estimation of surface roughness, which is based on measurement of high frequency vibrations that are generated when air flow interacts with the surface of a solid body. It was determined that intensity of high frequency vibrations depends on surface roughness. Sandpapers with different magnitudes of surface roughness were used for the experimental study. © Vibroengineering. Journal of Vibroengineering.

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