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Quality checking of polymer modified bitumens in Slovenia
Marjan Tušar, Lidija Ržek, Mojca Ravnikar Turk, 2021, objavljeni znanstveni prispevek na konferenci

Povzetek: For many years the properties of bitumen have been determined based on mechanical tests as needle penetration, Ring&Ball and Fraass fracture temperature. For elastomer (styrene-butadiene-styrene) polymer modified bitumens these tests are not sufficient to show the important differences in bitumens. Elastic recovery and cohesion provide better insight, but rheological properties cannot be adequately described with conventional test. The requirements of the polymer modified bitumens (PmB) in Europe were defined in EN14023 in 2010 [1]. Since then several new tests were introduced in the research field and their procedures improved. In the European Standards Committee (CEN) TC 336, there is on-going work to develop performance related specifications. New laboratory test methods from American standards were adapted and transformed into EN standards (bitumen laboratory aging methods and rheological tests). These test methods are not yet employed in the cur-rent PmB European standard, however, the draft prEN 14023, April 2020 [2] suggests these new tests. In the recent years at ZAG Laboratory for asphalts and bitumen-based products long-term aging of bitumen by pressure aging vessel (PAV) and rheological tests were introduced. Traditional bitumen test methods are performed together with new rheological testse.g. Dynamic Shear Rheometer (DSR) testing, to characterize complex modulus and phase angle, and Multiple Stress Creep Recovery Test (MSCRT) in order to develop a preliminary data base on PmB’s, which are frequently used in Slovenia. The paper presents the current requirements for PmB’s in Slovenia and test results on PmB 45/80-65, original, laboratory aged and extracted from produced asphalt mixtures.
Ključne besede: polymer modified bitumen, recovered bitumen, laboratory ageing, dynamic shear rheometer, multiple stress creep recovery test
Objavljeno v DiRROS: 28.02.2024; Ogledov: 96; Prenosov: 64
.pdf Celotno besedilo (703,78 KB)
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Volumetric view on asphalt mixture
Marjan Tušar, Mojca Ravnikar Turk, Lidija Ržek, 2023, objavljeni znanstveni prispevek na konferenci

Povzetek: An asphalt layer consists of stone aggregates, binder and air voids. The content of air voids (Vmin and Vmax), the voids filled with bitumen (VFBmin and VFBmax), the content of air voids in stone aggregates (VMAmin and VMAmax) and volume content of bitumen (VBmin) should be determined for each type of asphalt mixture. The volumetric properties of asphalt layer listed above are important parameters for assessing the properties of asphalt and are usually first presented in the requirements for produced asphalt mixtures and built in asphalt layers. Visualization of volumetric properties is important for understanding the composition of the produced asphalt mixture. The most appropriate is a triangular representation of the volumetric requirements for three main components of asphalt layer (stone, bitumen and air).
Ključne besede: volumetric representation, asphalt mixture, void content, voids in aggregate
Objavljeno v DiRROS: 22.02.2024; Ogledov: 112; Prenosov: 51
.pdf Celotno besedilo (715,71 KB)
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Rheological behaviors of waste polyethylene modified asphalt binder : Statistical analysis of interlaboratory testing results
Di Wang, Andrea Baliello, Gustavo Pinheiro, Lily D. Poulikakos, Marjan Tušar, Kamilla Vasconcelos, Muhammad Rafiq Kakar, Laurent Porot, Emiliano Pasquini, Gaspare Giancontieri, Chiara Riccardi, Marco Pasetto, Davide Lo Presti, Augusto Cannone Falchetto, 2023, izvirni znanstveni članek

Povzetek: This article investigated the effect of waste polyethylene (PE) on the modified asphalt binders’ rheological behavior from a statistical point of view. The interlaboratory testing results from the RILEM Technical Committee 279 Valorization of Waste and Secondary Materials for Roads Task Group 1 were used for this purpose. First, an unaged 70/100 penetration graded neat binder was selected as the reference material. Next, a single 5 % content of waste PE additives (PE-pellets and PE-shreds) was mixed with a 95 % neat binder to prepare two PE modified binders. Then, dynamic shear rheometer–based temperature-frequency sweep tests were performed over a wide range of temperatures and frequencies to evaluate the rheological properties of these three binders. Different rheological behaviors were observed in the isochronal plots at high temperatures. Based on a reproducibility precision requirement proposed for phase angle, 28°C was set as the transition temperature across the rheological behaviors. Next, according to the three rheological behaviors defined in a previous study by the authors, statistical analysis was introduced to identify sensitive rheological parameters and determine the thresholds. Results indicate that the phase angle measured above 28°C and 1.59 Hz can be used as a sensitive parameter to discriminate the three rheological behaviors of PE modified binders. The thresholds among different behaviors were also calculated as an example for phase angle measured at the highest common testing temperature of 70°C. Additional experimental evaluations on more types of PE modified binders, especially at intermediate and high temperatures, are recommended to better understand their influence on the rheological behavior of PE modified binders.
Ključne besede: bitumen, polietilen, reologija, medlaboratorijska primerjava
Objavljeno v DiRROS: 20.02.2024; Ogledov: 100; Prenosov: 44
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Rejuvenator obtained by pyrolysis of waste tires for use in asphalt mixtures with added reclaimed asphalt
Lidija Ržek, Mojca Ravnikar Turk, Marjan Tušar, 2022, samostojni znanstveni sestavek ali poglavje v monografski publikaciji

Povzetek: Although in recent years, big progress has been made in the field of recovering waste tires, they still represent an unwanted waste and their production is constantly increasing. We can use waste tires as a raw material for a new product. In our study, multiple liquid products were produced by pyrolysis of waste tires. After extensive testing of their properties, we selected the most suitable pyrolytic product for the purpose of rejuvenation. Rejuvenators are designed to soften the old, brittle and stiff aged bitumen in reclaimed asphalt. Bitumen with its viscoelastic characteristics is the most important component of asphalt and dictates its behaviour. Commonly bitumen, after adding rejuvenator, becomes less viscous, more ductile and its coating properties are restored. By using a pyrolytic rejuvenator, the proportion of reclaimed asphalt added to the asphalt mixture was increased. The reuse of reclaimed asphalt and waste tires means a reduction in waste material and is therefore important for the preservation of the environment and sustainable development.
Ključne besede: pyrolyse, rejuvenator, bitumen, reclaimed asphalt, waste tires
Objavljeno v DiRROS: 31.01.2024; Ogledov: 118; Prenosov: 50
.pdf Celotno besedilo (840,71 KB)
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Cysteine proteinase inhibitors stefin A and stefin B in operable carcinoma of the head and neck : Inhibitorji cisteinskih proteinaz stefin A in stefin B pri operabilnem karcinomu glave in vratu
Primož Strojan, Marjan Budihna, Alojz Šmid, Branka Svetic, Ivan Vrhovec, Janko Kos, Janez Škrk, 2002, izvirni znanstveni članek

Povzetek: Purpose. To evaluate the significance of cysteine proteinase inhibitors stefins (Stefs) A and B for a treatment decision and prognosis in operable squamous cell carcinoma of the head and neck (SCCHN). Patients and methods. Stefs A and B concentrations were determined immunobiochemically using ELISAs in cytosols prepared from the tumor and adjacent normal mucosa from 91 patients with operable SCCHN. The median follow-up period of patients alive atthe close-out date was 5.8 years (range, 5-9.3 years). Results. Stef A concentrations were significantly higher in tumor compared to normal mucosa (FM.05). When a subgroup with clinically palpable nodes) at presentation was taken into consideration (n=57), a significant difference in Stef A (P=0.03) and Stef B (P=0.02) concentrations between those with negative and positive necks, as determined on histopathological examination, was observed. On the univariate survival analysis, higher Stefsć concentrations turned to be prognostically advantageous. Stef A proved its independent prognostic significance also on multivariate setting. Conclusions. With the capability todifferentiate between the pN0- and pN+-stages of the disease in the patientsoriginally presented as node-positive, Stefs A and B could be useful markers when deciding on the extent of neck surgery. In addition, both Stefs proved to be reliable prognosticators for survival in patients with operable SCCHN.
Objavljeno v DiRROS: 31.01.2024; Ogledov: 119; Prenosov: 29
.pdf Celotno besedilo (114,91 KB)

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Cerebral hyperperfusion syndrome after carotid angioplasty
Zoran Miloševič, Bojana Žvan, Marjan Zaletel, Miloš Šurlan, 2002, objavljeni znanstveni prispevek na konferenci

Povzetek: Background. Cerebral hyperperfusion syndrome after carotid endarterectomy is an uncommon but well-de- fined entity. There are only few reports of "hyperperfusion injury" following carotid angioplasty. Case report. We report an unstable arterial hypertension and high grade carotid stenosis in a 58-year-old, right-handed woman. After a stroke in the territory of middle cerebral artery carotid angioplasty was per- formed in the patient. Among riskfactors, the long lasting arterial hypertension was the most pronounced. Immediately after the procedure, the patient was stable without any additionalneurologic deficit. The sec- ond day, the patient had an epileptic seizure and CT revealed a small haemorrhage in the left frontal lobe. Conclusions. The combination of a high grade carotid stenosis and unstable arterial pressure is probably an important prognostic factor in the pathogenesis of hyperperfusion syndrome.
Objavljeno v DiRROS: 31.01.2024; Ogledov: 93; Prenosov: 31
.pdf Celotno besedilo (347,68 KB)

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Carotid angioplasty with cerebral protection
Zoran Miloševič, Bojana Žvan, Marjan Zaletel, Miloš Šurlan, 2002, izvirni znanstveni članek

Povzetek: Background. Carotid endarterectomy (CF.A) is widely used in the management of high-rade carotid stenosis: It is a surgical procedure requiring general anaesthesia and is suitable only for lesions located at or close to the carotid bifurcation. It may develop complications, such as stroke, death, cranial nerve palsies, wound haematoma and cardiac complications. The risk of complications is increased in patients with recurrent carotid artery stenosis following CEA, in subjects undergoing radiotherapy to the neck, and in patients with cardiopulmonary disease. The drawbacks of CEA have led physicians to search for alternative treatment options. Carotid angioplasty and stenting (CAS) is less invasive than CEA. The method is particularly suitable for the treatment of recurrent stenosis after previous CEA and distalinternal artery stenosis, which is inaccessible for CEA. CAS does not cause cranial nerve palsies. Moreover, it does not require general anaesthesiaand causes lower morbidity and mortality in patients with severe cardiopulmonary disease. The complications of CAS include stroke due to distalimmobilisation of a plaque or thrombus dislodged during the procedure, abrupt vessel occlusion due to thrombosis, dissection or vasospasm, and restenosis due to intmal hyperplasia. CAS is a relatively new procedure; therefore, it is essential to establish its efficacy and safety before it is introduced widely into clinical practice. Patients and methods. In Slovenia, we have also started with carotid angioplasty by the study: Slovenian Carotid Angioplasty Study (SCAS). We performed CAS in 17 patients (12 males and 5 females) aged from 69 to 82 years. All patients were symptomatic with stenosisgreater than 70 %. 10 patients suffered transient ischemic attacks, 4 patients minor strokes and 3 patients amaurosis fugax. (Abstract truncated at 2000 characters)
Objavljeno v DiRROS: 31.01.2024; Ogledov: 120; Prenosov: 27
.pdf Celotno besedilo (116,39 KB)

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