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The importance of using discounted cash flow methodology in techno-economic analyses of energy and chemical production plants
Zorka Novak-Pintarič, Zdravko Kravanja, 2017, izvirni znanstveni članek

Opis: This paper demonstrates the correct application of discounted cash flow methodology for evaluating and designing energy and chemical production plants. Such processes usually correspond to capital intensive long-term projects. Simple economic criteria, like the profit or production cost are insufficient for this type of decision making because they do not take into account the time value of money and underestimate the profitabilities of the evaluated plants. This paper shows that some of those criteria based on the discounted cash flows establish suitable compromises between long-term cash flow generation and profitability. As several alternative options are usually evaluated in parallel, it is shown how to rank mutually exclusive alternatives properly and how to select the best option from among them. Two large-scale case studies demonstrate that using discounted cash flow methodology can result in substantially different decisions than non-discounted criteria, however, these decisions are affected by several input parameters.
Ključne besede: discounted cash flow analysis, time value of money, net preset value, profitability, process
Objavljeno: 04.08.2017; Ogledov: 486; Prenosov: 324
.pdf Celotno besedilo (501,44 KB)
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Determination of penicillamine by batch and flow-injection potentiometry with AgI-based sensor
Njegomir Radić, Josipa Komljenović, Danilo Dobčnik, 2000, izvirni znanstveni članek

Opis: Potentiometric determination of penicillamine (pen) is described based on a batch experiment and flow-injection analysis (FIA) using a chemical sensor with AgI-based membrane. The membrane was prepared by pressing silver salts (AgI, Ag2S) and powdered Teflon. This membrane was incorporated in a multipurpose electrode body for batch measurements, and in a tabular flow-through sensor body for FIA measurements. For batch measurements, the equilibrium potentials recorded with continuous addition of standard penicillamine solution were considered in relation to ▫$lg(c_pen/mol L^-1)$▫. Linear response with slope of 60 mV was obtained in the concentration range from 2.5 x ▫$10^5$▫ mol ▫$L^1$▫ to 1.8 x ▫$10^-2$▫mol ▫$L-1$▫. In using the tubular sensor with a membrane of the same coposition for FIA measurements, the linear response with slope of 59 mV was recorded in the concentration range from 1 x ▫$10^4$▫ mol ▫$L^1$▫ to 1 x ▫$10^-1$▫ mol ▫$L^-1$▫. The response of the applied chemical sensor to penicillamine (designated also as RSH) is explained by the formation of sparingly soluble RSAg in the reaction solution and/or the exposed surface of the sensor. The solubility product ▫$K_s(RSAg)$▫ was determined using experimental values recorded both by batch measurements and by the continuous-flow experiment. The mean value obtained by different measurements and using a membrane of the same composition is ▫$K_s(RSAg)$▫ = (1.4+-0.1) x ▫$10^-20$▫ mol ▫$L-2$▫).
Ključne besede: analytical chemistry, batch potentiometry, flow-injection analysis, membrane electrode, tubular sensors, penicillamine
Objavljeno: 05.07.2017; Ogledov: 548; Prenosov: 66
.pdf Celotno besedilo (196,90 KB)
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Roundabout arm capacity determined by microsimulation and discrete functions technique
Tomaž Tollazzi, Matjaž Šraml, Tone Lerher, 2008, izvirni znanstveni članek

Opis: The paper demonstrates the influence of the multi-channel pedestrian flow on the actual capacity of a one-lane roundabout, using micro-simulation and discrete functions. The proposed model is based on the theory of the expected time gap between the units of pedestrian traffic flow, which have the priority when crossing the arm of the roundabout. The proposed model represents an upgrade of the previous research in the field of modelling traffic flows in the one-lane roundabout.Apart from the multi-channel pedestrian flow the disturbances caused by the circular traffic flow of motorised vehicles at the roundabout are also considered. In this way the model can better illustrate the real conditions in traffic. A simulation analysis has been performed on the roundabout arm at Koroška Street in Maribor. The results of the analysis have indicated a relatively high reserve of the actual throughput capacity for the main motorized traffic flow in the analysed roundabout arm. The presented model represents a practicable and adaptable tool for planning the roundabout capacity in practice and for the sensitivity analysis of individual variables on the throughput capacity of the roundabout.
Ključne besede: roundabouts, traffic flow analysis, micro-simulation modelling, capacity analysis
Objavljeno: 05.06.2017; Ogledov: 798; Prenosov: 73
.pdf Celotno besedilo (4,50 MB)
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On new approach to rheological modeling of an electrostatic ash and water - quadratic law
Primož Ternik, 2002, objavljeni znanstveni prispevek na konferenci

Opis: In the paper a new rheological model for an electrostatic ash and water mixture is proposed. The fundamental equation of the rheological model was used to determine the relationship between the shear stress and the shear rate as well as the equation of a velocity profile for the flow through a straight pipe. Experimental results obtained from a capillary viscometer were used as the basis to determine the parameters for the proposed model by the non-linear regression analysis. With the Quadratic law a numerical analysis of a mixture flow through a capillary pipe with the finite volume method was performed. The derived equations for the velocity profile, shear stress and shear rate were validated through a comparison of numerically obtained and theoretical results. Finally, the compariosn between the Quadratic and the Power law is presented.
Ključne besede: fluid mechanics, non-Newtonian fluids, mixture of electrofilter ash and water, flow in pipes, capillary pipes, rheological model, velocity profile, shear stress, finite volume method, numerical analysis, quadratic law, power law, mehanika fluidov
Objavljeno: 01.06.2012; Ogledov: 1677; Prenosov: 28
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Tungsten - tungsten trioxide electrodes for the long-term monitoring of corrosion processes in highly alkaline media and concrete-based materials
Mitja Kolar, Aleš Doliška, Franc Švegl, Kurt Kalcher, 2010, izvirni znanstveni članek

Opis: The determination of pH in highly alkaline solutions and concrete materials is extremely important for monitoring or predicting the corrosion processes of reinforced concrete structures and to follow the hydration process of Portland cement, fly-ash, micro silica and other materials used in concrete manufacturing. The corrosion of reinforced concrete structures and the hydration of pozzolanic materials are long-term processes, which means, that appropriate durable, and resilient pH electrodes are needed, for direct implantation regarding solid concrete bodies. The purpose of this work was to characterise the potentiometric and surface properties of tungsten electrodes after exposure to extreme alkaline solutions. The tungsten wire surface was activated at 800 °C for 30 min within an oxygen flow. The formation of homogenous and compact multiple layers of $WO_3$ crystals was observed using X-ray diffraction and scanning electron microscopy. X-ray diffraction of thosetungsten electrodes exposed to saturated calcium hydroxide solution or the pore-water of cement-based materials during 10 months, indicated partly dissolved $WO_3$. Two new compounds appeared on the electrodes surfaces; pure tungsten and $CaWO_4$. The presence of tungsten was affecting any potentiometric response in acidic pH region (2-5) but in pH 5-12 region the response still remained linear with a slope of 42 2 mV/pH unit. The $W/WO_3$ electrode was suitable for the long-term monitoring of corrosion processes in concrete-basedmaterials according to the pH changes as it has stable and repeatable responses to alkaline solutions (pH > 12). All the tested interferring ions had no significant influence on electrode potential. The $W/WO_3$ electrode is simple, robust, inexpensive, and temperature resistant and can be applied in potentiometric titrations as well as in batch and flow-injection analysis. The prepared electrode is a highly promising pH sensor for the monitoring of pH changes in highly alkaline capillary water of concrete.
Ključne besede: potentiometry, pH, tungsten - tungsten trioxide, pore water, concrete, flow-injection analysis
Objavljeno: 31.05.2012; Ogledov: 1816; Prenosov: 71
.pdf Celotno besedilo (1,67 MB)
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