18420 research outputs found
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Application of Ireland-Claisen Rearrangement in the Total Syntheses of 4-Ethylidene Proline Containing Natural Products
No full textKokrūpniecības blakusproduktu saturoša polipropilēna hibrīdkompozītu fizikāli-mehāniskās īpašības
No full textDarbā ir izpētītas kokrūpniecības blakusproduktu (saplākšņa ražošanas atlikumu, piemēram, frēzskaidas) izmantošanas iespējas koksnes šķiedru saturošu termoplastisku polimēru (polipropilēns) kompozītu (KŠK) iegūšanai. Izpētītas kompozītu fizikāli-mehāniskās īpašības, tehnoloģiskās īpašības, kā arī noskaidrota KŠK ūdens izturība un mēģināts ar SEM pētījumu palīdzību noskaidrot kompozītu sagraušanas mehānismu
Systemic Soundness in Continuous Information Systems Engineering
No full textThe necessity to embrace frequent and hard to predict changes in the
businesses of enterprises has led to the need for continuous information systems
engineering in order to support the enterprises with appropriate information
services. Systems engineering prescribes a particular process of systems
development from well defined requirements to the verified and validated resulting
system. This process, even applied continuously, only partly can be followed in
information systems engineering. First, the information system is a socio-technical
system, therefore it is impossible to fully engineer it. Second, frequent changes in
information system can rapidly cause its deviation from the initial design even up
to losing its systemic properties to some extent. The paper claims that systemic
properties of information systems should be checked during continuous
information systems engineering to support viability of enterprises. The Viable
Systems Model and consideration of ecosystemic dependency are proposed as
means for assuring systemic soundness of engineered information systems
The Power Station Regime Management under Uncertainty
No full textThe topicality of the task of power systems regimes optimization is significantly improved under the conditions of market economy. Developing the tasks for optimization of the regimes of electrical stations and power systems the changing of the optimization criteria should be considered as a significant innovation. The power station regime optimization is stochastic, multi-dimensional, multi-parameter etc.; that is why such task optimization should be made with using games theory criterion as well Pareto principle. In this paper the optimization stochastic algorithm is synthesized and proved its operation feasibility for the station regime
High Density Polyuretane Foarms Obtained from Residues of PET Industry and Midified with Cloisite Type Nanoparticles
No full textUsing Penalty Function Method for Analysis of Dynamic Behaviour of Viscoelastic Materials
No full textThe present article investigates the application of the penalty function method in the analysis of
behaviour of viscoelastic materials, particularly silicon rubbers, under dynamic loading. To perform the analysis, the mathematical model of the object was chosen, and the Matlab code for the mathematical model was developed. The dynamic force was applied to the given model. To find the most precise element describing the behaviour of elastic material from some set of available alternatives, the penalty method, which replaces a constrained optimization problem by a series of unconstrained problems, was used
Structure, Micromechanical and Magnetic Properties of Polycarbonate Nanocomposites
No full textThe current study evaluates the applicability of polycarbonate (PC) for development of magnetic polymer nanocomposites with CoFe2O4 nanofiller, the amount of which was changed from 0 to 5 wt. %. Ethylene-vinyl acetate elastomer in the amount of 10 wt. % was added as toughener. Upon introduction of the magnetic filler a magnetic hysteresis loop was observed: at 5 wt.% of CoFe2O4 saturation magnetization of the nanocomposite was 2,2 emu/g, remanent magnetization was 0,8 emu/g and coercivity is 1200 G. Nanoindentation tests showed that nanofiller-reinforced samples maintain reasonable plasticity characterized by work of plastic indentation, while their modulus and hardness were improved by up to 14% and 20%, correspondingly. Structural study revealed clustering of the nanofiller at the contents above 2 wt.% that led to reduction of strengthening effect
Structure and Mechanical Behaviour of Binary Polyprpoylene / Thermoplastic Polyolefine Elastomer Blends
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Software Application in Analog Modeling of Spot Resistance Welding
No full textResearch is connected with elaboration of the calculating module VarWELD, using MS Excel software, for item-by-item examination of various combinations of variable parameters of spot resistance welding as well as analysis of possible solutions for managing the characteristics of the process. Mentioned examination is one of the main stages of analogue modeling. Analogue modeling is new perspective approach for modeling of welding processes, based on process investigation, using logical functions. Application of analogue modeling in investigation of welding process allows predicting the quality level of goal function of the modeling without testing. In result the outlays for receiving the optimal welding regimes, metallographic research of welding seams, joint quality control and other facilities, considerable lowered. The procedure of analogue modeling using calculating module VarWELD is offered. The effectiveness of analogue modeling using VarWELD is proven