LATVIAN JOURNAL of PHYSICS and
TECHNICAL SCIENCES
Nr. 2-2009
Viba J., Shtals L., Eiduks M.
Energy extraction from air or water by vibrations
Survilo J.
Compensation for non-uniformity in a meshed electrical network
Levins N., Orlova S., Pugačevs V., Kamoliņš E.
Optimization of the tooth zone of an axial inductor machine based on analysis of magnetic fields
Barkāns J., Žalostība D.
Climate as a result of the Earth heat reflection
Bobrovs V., Jelinskis J., Ivanovs G., Lauks G.
Research of traffic management in FTTX optical communication systems
Rozite G., Murashov A.
PC card for scientific data acquisition in laser vibrometry, seismic measurements and electrochemical impedance spectroscopy
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LATVIAN JOURNAL of PHYSICS and
TECHNICAL SCIENCES
ENERGY EXTRACTION FROM AIR OR WATER BY VIBRATIONS
J. Viba, L. Shtals, M. Eiduks
Riga Technical University, Institute of Mechanics,
6 Ezermalas Str., Riga, LV 1006, LATVIA e-mail: janis.viba@rtu.lv
The paper considers the possibility to derive energy from air or water in a non-traditional way
(without using rotating equipment). For this purpose, the authors studied variations in the additional area of a vibrating object in a definite sequence found as the solution of an optimisation problem. In the work, stably moving mechatronic systems were synthesised and modelled, whose control is very simple (not requiring calibration), being a function of the changing sign of phase coordinates.
COMPENSATION FOR NON-UNIFORMITY IN A MESHED ELECTRICAL NETWORK a
J. Survilo
Riga Technical University,
1 Kronvalda Blvd., LV-1010, Riga, LATVIA
Non-uniform electrical networks (meshed included), providing more reliable supply of electric energy to consumers, have greater losses than uniform ones. To upgrade such a network by reducing losses, special measures are provided, which should be done at the least cost. An effective measure of the kind would be introduction of opposing voltage or complementary reactances in some branches of the network. In this case, to determine the required parameters, a non-uniform meshed network should be disintegrated into separate cells – closed loops with equivalent node loads, which are the sum of node loads and the flows not belonging to a given cell.
Then the circulating power of all cells is calculated, and the cell with the maximum circulating power is selected to be upgraded. For this purpose, in this cell the pre-defined opposing voltage or complementary reactance is brought. If the total power loss in the network after the first step of upgrading is not satisfactory, a next similar step should be taken, and a next cell singled out for upgrading. Such cell upgrading should be continued until the total losses stop decreasing.
OPTIMIZATION OF THE TOOTH ZONE OF AN AXIAL INDUCTOR MACHINE BASED
ON ANALYSIS OF MAGNETIC FIELD
N. Levin, S. Orlova, V. Pugachov
Institute of Physical Energetics,
21 Aizkraukles Str., Riga, LV-1006, LATVIA
E. Kamolins
Riga Technical University,
1 Kalku Str., Riga, LV-1658, LATVIA
Possibilities to optimize the tooth zone geometry are considered for the inductor machine whose magnetic field is not plane-parallel. It is proposed to reduce the 3D-problem at the field investigation to a two-dimensional one. Based on the solution obtained and the following analysis of the objective function a more optimal design has been found for axial inductor generators of the
2ГВ.13.У1 type employed in the railway transport.
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LATVIAN JOURNAL of PHYSICS and
TECHNICAL SCIENCES
CLIMATE AS A RESULT OF THE EARTH HEAT REFLECTION
J. Barkāns, D. Žalostība
Riga Technical University, the Institute of Power Engineering,
1 Kronvalda Blvd., Riga LV-1010, LATVIA diana@eef.rtu.lv
The authors show that the mean global temperature – and, therefore, climate – is determined mainly by the reflected portion of the total heat received from the Sun. The heat reflected directly by infra-red radiation is insufficient for maintenance of the temperature necessary for the Earth life, since it is limited by absorption windows created by green-house gases (mainly water molecules). The deficient heat is transported by a strong vertical convective air stream – a component of the total air circulation. This heat – limited only by Newton’s law – is delivered to the upper troposphere layers not containing water molecules, from where it is dissipated, practically unlimitedly, at the infra-red radiation wavelengths corresponding to cooled media. The convection, in compliance with Newton’s law, creates a negative feedback, which stabilizes the processes of temperature changes on the Earth reducing them by half.
RESEARCH OF TRAFFIC MANAGEMENT IN FTTX OPTICAL COMMUNICATION
SYSTEMS
V. Bobrovs, J. Jelinskis, G. Ivanovs, G. Lauks
Institute of Telecommunications, Riga Technical University,
12 Āzenes Str., Rīga, LV-1048, LATVIA
The paper presents an overview of widely accepted passive optical networks (PONs), and provides the results of comparative OPTSIM simulation for PON technological facilities involving optical layers, with the aim to reveal fiber-to-the-x (FTTx) technologic solutions. Traffic load is simulated over a PON optical layer using the OPNET Modeler to determine potential advantages and drawbacks of the proposed FTTx solution with PON elements in the access networks. The authors show that the optimal transmission speed for PON FTTx would lie in the range 1.25–5.0 Gbit/s with a standard PON architecture, which could be raised to 10 Gbit/s, however in this case we have to change the end user’s equipment. In standards that specify the PON’s functionality two distances: 10 km and 20 km are indicated. Our simulation shows that, after upgrading the receiver electrical filter, 10 Gbit/s transmissions over 40 km could be reached.
PC CARD FOR SCIENTIFIC DATA ACQUISITION IN LASER VIBROMETRY, SEISMIC
MEASUREMENTS AND ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY
G. Rozite, A. Murashov
Institute of Physical Energetics,
21 Aizkraukles Str., Riga, LV-1006, LATVIA gunars59@inbox.lv
The most commercially available data acquisition cards have either low resolution (<16-bits) or are made on audio codec (ADC) chips, with a very poor DC accuracy (although a 24-bit resolution),
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LATVIAN JOURNAL of PHYSICS and
TECHNICAL SCIENCES and are not applicable in the cases when high dynamic range and low noises are required, especially in the 0.1-10 Hz region. In the paper, a new concept of a high-resolution auto-ranging
10V – 10mV PC card for demanding scientists is presented. The card supports plugging remote amplifiers/ conditioners as well as remote power sources and biasing. Such unique features of the card make it applicable for a wide range of scientific tasks, e.g. in laser interferometers, lock-in amplifiers, for spectrum measurements, phase demodulation, statistical deconvolution, etc. The architecture proposed by the authors is flexible, because most of the tasks are done in digital signal processing (DSP), while the analog part is realized on the 4 th
order ADS1254 super-high resolution delta-sigma ADC, which became available as late as in 2008. The authors discuss the functionality of the proposed card and consider the implementation details. The concept has been created as a result of multiple cross-correlated user requirements. The proposed hardware concept is royaltyfree and can be employed under the GNU public license; however, the firmware should be commercial to promote development effort.
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