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Cisternvagona stiprības novērtējums pie daudzciklu slogojuma
No full textDarbā tiek izpildīts cisternvagona katla un rāmja nogurumizturības novērtējums. Aprēķini tika veikti ar galīgo elementu metodi. Dotā uzdevuma sarežģītības dēļ cisternvagona katls un rāmis tika aprēķināti atsevišķi. Cisternvagona katla kalpošanas termiņš tika novērtēts, ievērojot vertikālo un garenisko dinamisko slodžu iedarbību pie dažādiem balstīšanas apstākļiem uz vagona rāmja. Cisternvagona rāmja nogurumizturība tika novērtēta sānu šūpošanās (pie pārkraušanas) režīmā sliežu ceļa garenisko nelīdzenumu dēļ
Teaching Linear Algebra, Analytic Geometry and Basic Vector Calculus with Mathematica at Riga Technical University
No full textRakstā stāstīts par jaunu matemātikas mācīšanas moduli, pielietotu Rīgas Tehniskajā Universitātē, pirmā kursa studentiem mācot lineāro algebru, vektoru algebru un analītisko ģeometriju. Modulis satur trīs komponentes: lekcijas, praktiskās nodarbības un laboratorijas darbus. Laboratorijas darbi notiek katru otro nedēļu un satur to pašu vielu, kas tiek aplūkota lekcijās un praktiskajās nodarbībās. Rakstā apkopoti arī studentu aptaujas rezultāti par paketes Mathematica lietošanu matemātikas kursā
Leaching of Heavy Metals from Cement Based Mortars with Waste Additive
No full textBoth mechanical and chemical properties of mixtures containing different quantities of slag and fly ash from metallurgical industry were studied. Obtained data indicated that heavy metals are partly leached out. Additive of industrial waste larger than 10% decreases both bending as well as compressive strength
Photoluminescence of Self-Trapped Excitons in Boron Nitride Nanotubes
No full textThe excitation energy dependence and temperature dependence of photoluminescence from boron
nitride nanotubes and hexagonal BN powder samples are reported. The results are discussed within
a model attributing the broad 3.2 eV luminescence from these samples to self-trapped excitons in
the low-dimensional structures of BN nanotubes and of nano-arch surface reconstructions on h-BN
sheet edge faces in powder. An empirical model accounting for the unusual combination of excitation
and temperature dependence of photoluminescence seen in these measurements is suggested.
For the model to be consistent with the hypothesis of self-trapped excitons on BN nanotubes, it may
be necessary to show that the cores of multiwall nanotubes are selectively probed by light tuned
below the h-BN exciton
Photoluminescence of ZnO Nanostructure Formed by Laser Radiation
No full textThe possibility of formation of ZnO nanostructures in polyvinylalcohol matrix by powerful laser radiation is studied in this work
Comparison of Fixed Point Arithmetic Errors for the FPGA-Based CRAIMOT Basis Function Generators
No full textThis paper describes the mean square error (MSE) of basis function (BF) caused by the quantization of sine/cosine values. MSEs for all CRAIMOT BFs are equal. Additionally, MSEs are estimated for random signals synthesized by a limited number of weighted CRAIMOT BFs (partial sum). Maximal and minimal MSEs are given in dependence on the wordlength of sine/cosine former and the number of BFs used for synthesis. Synthesis error is independent of the number of BFs, practically constant. Errors are compared for two versions of FPGA implemented BF generator and synthesizer. Versions of mentioned devices differ by sine/cosine former blocks implemented using CORDIC and optimal linear interpolation algorithms. A CORDIC former ensures approximately twice better accuracy. A preliminary simulation has been conducted and it has proved the existence of optimal angles (optimal transforms) from the implementation point of view
Prognozēšana asins sagatavotājiestādēs
No full textprognozēšanas metožu pielietošana ir svarīga jebkuras nozares darbībai un attīstībai. Prognozēšanas mērķis ir samazināt nenoteiktību par objekta attīstību nākotnē
The Construction of Lyapunov-Krasovsky Quadratic Functional for Neutral Stochastic Differential Equations
No full textThe paper is devoted to method and algorithm of Lyapunov-Krasovsky quadratic functional
construction for exponential stability analysis of neutral type stochastic differential equation
Alternative Constructions of Bus Bars for 3x3 Matrix Converter in Integrated Drives
No full textŠajā rakstā tiek piedāvāta jauna kopņu konstrukcija matricveida spēka pārveidotājiem. Galvenais uzdevums ir atrast veidu kā pēc iespējas kompaktāk izveidot kopņu konstrukciju, lai to var izvietot asinhronajā mašīnā. Šajā rakstā ir apskatītas konstruktīvo risinājumu idejas. Sīkāki pētījumi elektromagnētiskās savietojamības un siltuma novades jomā tiks veikti nākotnē
Modelling of Non-Functional Requirements of Embedded Systems
No full textThis paper is devoted to modelling of non-functional requirements of embedded
systems. As the set of such major features authors select the following non-functional
requirements: asynchronism, synchronization, scheduling, time constraints and reliability.
The article discusses several aspects of these requirements in correspondence with
eliminations of their modelling and analysis facilities in the task of testing of embedded
systems. Authors present existent modelling methods for the specification of these
requirements and highlight four of them for further detailed examination