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Energosistēmas modelēšanas pamati un īsslēguma procesu izpēte ETAP vidē
No full textŠis apraksts sniedz nepieciešamo informāciju par laboratorijas darba saturu (izvirzītiem mērķiem un uzdevumiem), norises kartību, pielaišanas un aizstāvēšanas prasībām, teorētisko un praktisko daļu un noformējums (pielikumā ir dota atskaites forma).
Laboratorijas darba apraksts ir speciāli izstrādāts Enerģētikas un elektrotehnikas bakalaura programmas studentiem disciplīnā - Elektriskās sistēmas II, lai pilnveidotu zināšanas par energosistēmas modelēšanas un pētīšanas iespējām.
Apraksts laboratorijas darbam ir brīvi pieejams, visas autortiesības pieder Rīgas Tehniskās universitātes Enerģētikas institūtam.
Piezīmes un novēlējumus metodisko norādījumu satura uzlabošanai lūdzam sūtīt autoriem uz elektronisko pastu, kas atrodas pielikumā
Effect of Holographic Grating Period on Its Relaxation in Amolecular Glassy Film
No full textDisordered materials are thermodynamically unstable and this instability manifests itself by
the relaxation of their structure. Relaxation phenomena in glasses and polymers have been studied
for a long time [1]. Holographic gratings (HG) recorded in relaxing photosensitive materials are
useful tools for relaxation studies [2]. Recently we have studied the effect of recording light
polarization on the HG relaxation [3]
Formation Mechanisms of Nano and Microcones by Laser Radiation on Surfaces of Si, Ge, and SiGe Crystals
No full textIn this work we study the mechanisms of laser radiation interaction with elementary semiconductors such as Si and Ge and their solid solution SiGe. As a result of this investigation, the mechanisms of nanocones and microcones formation on a surface of semiconductor were proposed. We have shown the possibility to control the size and the shape of cones both by the laser. The main reason for the formation of nanocones is the mechanical compressive stresses due to the atoms’ redistribution caused by the gradient of temperature induced by strongly absorbed laser radiation. According to our investigation, the nanocone formation mechanism in semiconductors is characterized by two stages. The first stage is characterized by formation of a p-n junction for elementary semiconductors or of a Ge/Si heterojunction for SiGe solid solution. The generation and redistribution of intrinsic point defects in elementary semiconductors and Ge atoms concentration on the irradiated surface of SiGe solid solution in temperature gradient field take place at this stage due to the thermogradient effect which is caused by strongly absorbed laser radiation. The second stage is characterized by formation of nanocones due to mechanical plastic deformation of the compressed Ge layer on Si. Moreover, a new 1D-graded band gap structure in elementary semiconductors due to quantum confinement effect was formed. For the formation of microcones Ni/Si structure was used. The mechanism of the formation of microcones is characterized by two stages as well. The first stage is the melting of Ni film after irradiation by laser beam and formation of Ni islands due to surface tension force. The second step is the melting of Ni and subsequent manifestations of Marangoni effect with the growth of microcones
Homo- and Hetero Structures Formation in Semiconductors by Laser Radiation: First Stage of Nanocones Formation
No full textHomo- and Hetero Structures Formation in Semiconductors by Laser Radiation: First Stage of Nanocones Formatio
Influence of Flexible Body Contact Deformation on the Linear Dimension Measurement Precision
No full textThe common measurement error when measuring the component geometrical dimensions using universal contact measurement instruments is caused by different factors, such as error of the measurement instrument, personal reading errors, effect of surface roughness on the measuring line deviation, influence of contact deformation measurement force, and others. The present article examines one of these factors, i.e. contact deformations under the influence of measurement force. To make precise measurements it is essential to find out the effect of roughness of measured components. High roughness creates additional measurement errors. It is particularly important in the measurement of thin components, flexible materials and films, as well as for components with nanocoating. Flexible bodies in the meaning of this article are components of different shape and sizes made of rubber or soft plastic.
This article studies principles of error formation based on the deformation of surface roughness and basic material
Surface Roughness 3D Parameters Calculations
No full textAt present surface roughness profile parameters are determined by standards. At the same time different exploitational properties of details are determined with the help of 3 dimensional image - microtopography (Fig. 1).
In microtopography surface roughness including nanocoatings is expressed by random field h (x, y) of two variables x, y - cartesian coordinates of surface point
An Assessment of the Potential and Finding the Optimal Method of Biowaste Treatment in Latvia
No full textThe paper presents the analysis of possibilities to utilize biowaste for biogas production in Latvia, including biogas production from landfill gas and biogas production from biowaste with the method of anaerobic digestion and composting. Analysis is based on selection of criteria and methodology for optimization of biowaste management and biogas production from biowaste, as well as on preliminary environmental and economic impact assessment
Coloured Petri Nets Based Simulation Scheme for Adaptive Bandwidth Management
No full textWe consider the problem of resource allocation for multiple classes of traffic in a substrate network with DaVinci architecture. According to DaVinci (Dynamically Adaptive Virtual Networks for a Customized Internet) approach a single physical network can support multiple traffic classes with different performance objectives by means of multiple virtual networks constructed over the physical one. In this context the problem of bandwidth allocation is a conditional maximization problem for the aggregate performance of all virtual networks. We describe Coloured Petri Nets (CPN) based models and present CPN based schemes for simulation of dynamically adaptive bandwidth allocation mechanisms proposed to support multiple traffics in a substrate network. The simulation study focuses on two traffic types: delay sensitive and throughput sensitive. Obtained simulation results demonstrate the achievement of dynamically adaptive bandwidth management strategies
Current Sensorless Control of Front-end Bidirectional AC/DC Converter Based on Half-bridge Topology
No full textElectrical grid modernization concept promotes the
use of DC subgrids in order to improve efficiency, minimizing
energy conversion count in the source-to-load chain. The present
paper discusses an average current sensorless control algorithm
for proposed bidirectional AC/DC converter, which is based on a
dual half-bridge topology with common neutral wire that is not
commutating during converter operation. The proposed current
sensorless control algorithm has been obtained analytically for
rectification, grid-tied and stand-alone inverter modes. The
average value of inductor current tracks the reference current
signal with constant switching frequency. Two control functions
for inductor’s discontinuous and continuous current modes have
been defined for each of the operation modes, and a sensorless
transition between DCM and CCM modes has been stated. The
proposed sensorless control algorithm has been also adapted for
use with LCL input filter. The results of simulation in the PSIM
software approved the analytical model, keeping the average
inductor current to follow the reference value in inductor
discontinuous and continuous conduction modes. Experimental
investigation of the proposed current control algorithm provided
similar results confirming the discussed theory