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Determination of pressure losses in hydraulic pipeline systems by considering temperature and pressure
Vladimir Savić, Darko Knežević, Darko Lovrec, Mitar Jocanović, Velibor Karanović, 2009, izvirni znanstveni članek

Opis: Generally accepted methods for calculating pressure losses within flat pipelines, as presented in literature and used in praxis, are based on the Reynolds number, which considers the viscosity and density of fluid, internal pipe friction coefficient, pipe geometry, and oil circulation velocity. Such an approach contains serious inconsequentiality. Namely, only nominal values for viscosity and density are considered in the calculation, which differs substantially from real conditions. It often leads to inaccurate calculations of pressure losses. A numerical model has been developed within the work prescribed in the paper, which takes into account actual changes in density and viscosity under the current oil pressure and temperature in order to overcome the above weaknesses of standard calculation procedures. Such an approach is novel and provides new capacity for an accurate pressure drop analysis of advanced hydraulic systems.
Ključne besede: tlačne izgube, ravne cevi, viskoznost, gostota, temperatura, pressure loss, float pipelines, viscosity, density, temeprature
Objavljeno: 11.08.2015; Ogledov: 491; Prenosov: 36
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A low bending loss multimode fiber transmission system
Denis Đonlagić, 2009, izvirni znanstveni članek

Opis: This paper presents a high bend tolerant multimode optical fiber transmission system that is compatible with standard 50 ìm graded index multimode fiber, interms of achievable bandwidth and interconnectivity losses. When the 10 loops of the proposed bend resistive multimode fiber were wrapped around a cylinder of 1.5 mm radius, bend losses below -0.2 dB were achieved in case of experimentally produced fiber. Furthermore, when the section of the proposed bend resistive fiber was inserted between two sections of a standard 50 ìm graded index multimode fiber, the total experimental measured loss proved to be below -0.15 dB.
Ključne besede: optical fiber transmission systems, bending loss, bend resistive multimode fiber, optical communications, fiber optics
Objavljeno: 31.05.2012; Ogledov: 1249; Prenosov: 62
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Experimental models of medium break loss of coolant accidents with and without steam generator tube rupture
Jure Marn, Marjan Delić, Leopold Škerget, 2003, izvirni znanstveni članek

Opis: This paper reports model experiments simulating medium break loss of coolant accidents, with and without steam generator tube rupture (SGTR), in pressurized water reactors. Apart from a significant influence on the pressure in the reactor coolant system in the early parts of the accident, SGTR generally has only a small effect on the pressures and temperatures during the accident. The initial reactor conditions are found to be more significant. Some results of preliminary numerical models are briefly presented and these are broadly in agreement with the experimental measurements.
Ključne besede: nuclear engineering, nuclear accidents, steam generator tube rupture, loss of coolant, medium break loss of coolant accident, computer program, Melcor, MELCOR computer code, integral test facility
Objavljeno: 01.06.2012; Ogledov: 868; Prenosov: 70
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Assessment of magnetic fluid losses out of magnetic properties measurement
Miloš Beković, Irena Ban, Anton Hamler, 2010, objavljeni znanstveni prispevek na konferenci

Opis: In this paper an improved measurement system for experimental assessment of magnetic fluid losses is presented. When fluid is exposed to AC magnetic field, three different losses mechanisms are active; relaxation, hysteresis and resonance mechanism. In this paper not individual contributions where studied but combine acting which can be determine as specific power losses (SPL). SPL of the sample is obtained for a variety of amplitudes and frequencies of magnetic field with presented method of measurement of field parameters where results revealed f H2 dependence for fixed temperature of the sample. Temperature dependence of SPL is examined with calorimetrical measurements, where heating of magnetic fluid at fixed value of applied field and various frequencies is examined and results revealed linearly decreasing temperature dependence.
Ključne besede: magnetic fluid loss, magentic field, hysteresis loop
Objavljeno: 30.06.2017; Ogledov: 366; Prenosov: 222
.pdf Celotno besedilo (495,15 KB)
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Effect of backfat loss during lactation on weaning-to-oestrus interval of sows at gonadotropin application
Dejan Škorjanc, Marko Hohler, Maksimiljan Brus, 2008, izvirni znanstveni članek

Opis: A total of 984 primiparous and multiparous crossbred sows (Swedish Landrace × Large White) housed on a commercial pig farm were used to study the effect of the decrease in backfat thickness during lactation and the level of backfat at weaning on weaning-to-oestrus interval and conception rate of sows. Primiparous sows (n=213) received a single injection of 400 IU eCG + 200 IU hCG (PG600®, Intervet) at weaning and approximately 30 % of sows did not respond to the first treatment. First-farrowing sows produced significantly fewer live-born piglets, had markedly thinner backfat in late gestation, showed significant loss of backfat thickness during lactation and showed thinner backfat at weaning than sows with a greater number of parities. Primiparous sows with backfat thinner than 18 mm at weaning lost an average of 21 % of backfat during lactation and had a significantly longer weaning-to-oestrus interval (31.75 ± 2.22 days), even after a second treatment with PG600®, than both primiparous sows which responded to the first treatment (5.95 ± 0.16 days) and multiparous sows which were not treated (5.19 ± 0.12 days). The primiparous and multiparous sows with thicker backfat at farrowing also had thicker backfat at weaning (r=0.874 and r=0.938 for primiparous and multiparous sows, respectively). Sows with thicker backfat at weaning showed a shorter weaning-to-oestrus interval and this correlation was higher for primiparous than for multiparous sows (r=-0.192 and r=-0.100, respectively). Thicker backfat of the sows at weaning was moderately but significantly correlated with lower loss of backfat during lactation (r=-0.179 and r=-0.273 for primiparous and multiparous sows, respectively). The present study showed that monitoring of backfat thickness and loss of backfat during lactation represents a useful tool to decrease non-productive days and improve the efficiency of high-producing pig herds.
Ključne besede: sow, gilts, backfat thickness, backfat loss, weaning to oestrus interval, conception rate, PG600
Objavljeno: 20.07.2017; Ogledov: 394; Prenosov: 191
.pdf Celotno besedilo (185,14 KB)
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Impacts of different factors on seepage and land uplift due to compressed-air injection
Zang Yongge, Sun Dongmei, Feng Ping, Stephan Semprich, 2017, izvirni znanstveni članek

Opis: In this study, using an in-situ, air-flow test in Essen, the impacts of different factors on multiphase flow and land uplift during and after compressed-air injection were investigated using numerical simulations. A loosely coupled, two-phase flow and geo-mechanical modeling approach, linking two numerical codes (TOUGH2/EOS3 and FLAC3D) was employed to simulate the in-situ, air-flow test for comparing the simulated and measured results. As the compressed air is injected, it flows upwards and laterally, and the vertical effective stress near and above the injection zones decreases owing to the pore pressure increasing here, causing an expansion of the soil skeleton in the corresponding zones. The land uplift, induced mainly by support actions from lower deformed soils, is relevant to the distribution of the porosity increments in the soil interior, and it increases rapidly during air injection. After the compressed-air injection stops, the land uplift decreases gradually to zero due to the overpressure dissipation. With a combination of intensive rainfall, the land uplift is slightly greater near the borehole, but it is significantly greater at a distance from the borehole than the land uplift with no or low rainfall, but the air-injection rate remains almost unchanged due to the unchangeable pore pressure near the injection region. As the intrinsic permeability increases or the air entry pressure decreases in the injected strata, both the land uplift and the air injection rate increase, but the time required for the land uplift to become zero is slightly advanced with either a small permeability or a high air entry pressure.
Ključne besede: loosely coupled two-phase flow and geo-mechanical model, in-situ, air-flow test, compressed-air injection, multiphase flow, land uplift, air loss
Objavljeno: 18.06.2018; Ogledov: 241; Prenosov: 17
.pdf Celotno besedilo (1,75 MB)
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