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Simulation, Validation and Implementation of a Control System for Uninterruptible Power Supply
No full textŠajā rakstā ir apskatīts nepārtrauktās barošanas bloka vadības sistēmas izveides algoritms. Tiek aprakstītas iespējas izveidot un pārbaudīt vadības sistēmu, neizmantojot spēka elementus. Ir doti modelēšanas rezultāti un to novērtējums
Simulation of a Simple Control Strategy for a Common 3x3 Matrix Converter
No full textŠajā darbā ir piedāvātas klasiskā matricveida spēka pārveidotāja modelēšans metodes. Tiek aprakstīta vienkārša vadības metode, ko var realizēt uz tabulu bāzes un vienkārši aprēķinu algoritmi. Ir apskatīta modelēšana gan MATLAB, gan precīzāka shematiskā modelēšana PSpice modelēšans vidē. Modelēšanas rezultāti apstiprina piedāvātās metodes lietderību
Implementation of Supercapacitors in Uninterruptible Power Supplies
No full textŠajā rakstā ir apskatīti nepārtrauktās barošanas bloki ar superkondensatoriem. Ir dots superkondensatoru un svina skābes akumulatoru salīdzinājums. Ir salīdzināti arī superkondensatoru un akumulatoru parametri. Ir apskatīti superkondensatoru izmantošans plusi un mīnusi. Eksperimentu rezultāti ar paaugstinošo pārveidotāju un akumulatoru baterijām un superkondensatoru kā enerģijas avotu ir doti
Indoor Air Quality in Nursery Schools in Latvia
No full textThe paper is devoted to the analysis of indoor air quality in Latvian nursery schools. In the
scope of this paper the main problems of indoor air quality in such institutions were identified
and possible solutions for the improvement of the existing situation were given. The paper
provides the results of monitoring on the specifics of indoor air quality in Latvian educational
institutions. It presents the results of the evaluation of the ventilation system’s operation in
different working regimes in Latvian climatic conditions
Reliability of Fatigue-Prone Airframe
No full textThis paper is a review and some development of previous authors works. On the base of p-set
function definition the solution of two airframe reliability problems are considered: the choice of both the specified maximum permitted life and inspection program for fatigue-prone airframe. The problems should be solved by processing of the lifetime test data. Instead of the use of confidence intervals for lifetime distribution parameters new approach based on the p-set function is offered. Then we do not need to solve the problem how to choose two values: confidence probability in conjunction with the required reliability. In fact we only need to know permissible probability of failure in service. For the case of approval test the minimax approach is offered. Some numerical examples are given
Combining Analytical and Simulation Approaches to Quantification of the Bullwhip Effect
No full textNowadays, effective and competitive company operation can be achieved through incorporating the concept of supply chain operation into company management. Inventory control, as a critical part of the supply chain management, becomes the second most frequent application area for simulation technique in logistics (after manufacturing). The dynamics of supply chain operation is characterised by the bullwhip effect that reflects an increase in demand variability while moving upwards the supply chain. The bullwhip effect can lead to holding an excessive inventory, insufficient capacities and high transportation costs. It is important to investigate the magnitude of this effect by quantifying it. This paper proposes an analytical model for the analysis and numerical evaluation of the bullwhip effect in supply chains. Simulation technique is used to validate the results obtained from the analytical model. Based on the validation results, the logic of the analytical model is examined, and some specifications of the analytical model are analysed and described
Synthesis of 2-(4’-Rbenzylidene)-4-aza-1,3-indandiones and Investigation of Isomerization around the Exocyclic Double Bond
No full text2-Benzylidene-4-aza-1,3-indanediones have been synthesized and their structures have been investigated by NMR spectroscopy and quantum chemistry in the AM1 approximation. It was established that rotation about the exocyclic C(2)=C(10) formal double bond occurs in chloroform solutions of these compounds. The energy characteristics of this process have been determined experimentally and estimated theoretically
Опыт международного сотрудничества в области имитационного моделирования
No full textVeikts vadošo starptautisko organizāciju imitācijas modelēšanas jomā aktivitāšu apskats, proti, apskatīta tādu organizāciju darbība, ka Eiropas Imitācijas modelēšanas biedrību federācija EUROSIM un Starptautiskā Modelēšanas un imitācijas biedrība SCS, ka arī vadošās Eiropas valstu nacionālās biedrības. Raksturota svarīgāko starptautisko konferenču imitācijas modelēšanas jomā tematika, tādu ka WSC, ECMS, I3M, EUROSIM Congress un INFORMS Annual Meeting, ka arī dota informācija par galvenajiem starptautiskiem žurnāliem šajā jomā
Polyisoprene – Nanostructured Carbon Composite – a Soft Pressure Sensor Alternative
No full textLatest related research shows natural polyisoprene – nanostructured carbon composite (PNCC) as a promising piezoresistive material for soft pressure sensors. The main advantages of PNCC over conventional sensors are exceptional sensitivity in finger pressure range and possibility to be embedded into soft structures. The current PNCC can be made when certain amount (usually percolative concentration) of high structure electroconductive filler is dispersed into elastomer matrix and vulcanized afterwards.
In this work we specify the percolation threshold for natural polyisoprene rubber filled with Degussa Printex XE2 extra electro-conductive high structure (nanostructured) carbon black, depending on methods of dispersing. After obtaining optimal composition we present a completely soft PNCC pressure sensor prototype, made using multi-gradient approach, when elementary layers with different filler concentration are cured together and forms uniform sensor body with integrated soft electrodes. Afterwards we couple it with simplified analog impulse counter. The prototype system elaborated could be used for counting of interface events between sensor and external environmental factor. If multiple sensor grid approach is used, it could be possible to estimate the distribution and intensity of the external pressure on soft, flat-like surface. These results could be evaluated as a step towards the artificial skin, capable to sense non-destructive interface of the external structure