Eksperimentalno modeliranje i numerička FE analiza procesa izvlačenja sa stanjenjem čeličnih traka

This paper deals with analysis of steel strip ironing using experimental modelling and numerical FE simulation. Since both approaches are complementary to each other, numerous results were obtained that enable complete analysis of the processes within deformation zone. Device for modelling of strip ironing has been developed for experimental testing. Die cone angle, holding force, contact friction conditions on the die and the punch side were varied, due to easily replaceable working elements of the device. Friction coefficient values used in numerical FE simulations were determined based on measured values of forces on die and punch, as well as forming load on machine. Experimentally obtained results were confirmed by FE analysis that provided additional information about physics of the process itself within deformation zone. Presented research results point to coherent influences of process factors on tensile wall stress values, which represents key indicator for efficiency of forming, resulting in recommendations for efficient process management.Rad se bavi analizom procesa izvlačenja sa stanjenjem čelične trake, primjenom eksperimentalnog modeliranja i numeričkih FE simulacija. Kako su oba pristupa komplementarna, dobiveno je mnoštvo rezultata za sveobuhvatnu analizu procesa u deformacijskoj zoni. Za potrebe eksperimentalnog modeliranja razvijen je uređaj za modeliranje procesa izvlačenja sa stanjenjem trake. Zahvaljujući lako izmjenjivim radnim elementima uređaja, varirane su vrijednosti kuta matrice, sile držanja, uvjeti kontaktnog trenja na strani izvlakača i matrice. Vrijednosti faktora trenja, korištenih u numeričkim FE simulacijama su određene na osnovu izmjerenih vrijednosti sila na matrici i izvlakaču, kao i ukupne sile na stroju. Eksperimentalno dobiveni rezultati potvrđeni su numeričkom FE analizom, pri čemu je ona dala dodatne informacije o samoj fizici procesa u deformacijskoj zoni. Prikazani rezultati istraživanja ukazuju na spregnute utjecaje analiziranih faktora procesa na iznos rasteznog naprezanja u stijenki matrice, koji predstavlja ključni pokazatelj uspješnosti obrade, iz kojih proizlaze preporuke za uspješno upravljanje procesom

Predictors of unfavourable outcome in aneurysmal subarachnoid haemorrhage

Background. Mortality rates following aneurysmal subarachnoid haemorrhage (aSAH) have decreased due to improvements in diagnoses and the management of complications, as well as early obliteration of the aneurysms. Neurogenic pulmonary oedema (NPO) is a clinical syndrome associated with an acute increase in intracranial pressure and a release of catecholamines into the circulation. This study investigated independent predictors of unfavourable outcomes (Glasgow Outcome Scores 1, 2 or 3) in patients with aSAH. Materials and methods. A total of 262 patients with aSAH (162 females) were included in this prospective study. Clinical characteristics were assessed, and electrocardiographic, serum cardiac and inflammatory biomarker measurements were recorded on admission. Outcomes were assessed three months after admission. Univariate and multivariate analyses of these data were used to predict unfavourable outcomes. Results. A total of 156 patients (59.54%) had unfavourable outcomes. Compared to those who had favourable outcomes, patients with unfavourable outcomes were significantly older (54.37 ± 10.56 vs. 49.13 ± 10.77 years; p < 0.001) and had more severe aSAHs (Hunt and Hess grades ≥ 3: 82.7% vs. 39.6%; p < 0.001). Patients with unfavourable outcomes were more likely to have NPO (10.3% vs. 2.8%; p = 0.023), hydrocephalus (34.0% vs. 20.8%; p = 0.02), and aneurysm reruptures (28.2% vs. 3.8%; p < 0.001).Independent predictors of an unfavourable outcome included Hunt and Hess grades ≥ 3 (odds ratio [OR], 4.291; 95% confidence interval [CI], 2.168–8.491; p < 0.001), increased systolic blood pressure on admission (OR, 1.020; 95% CI, 1.002–1.038; p = 0.03), increased heart rate (HR) on admission (OR, 1.024; 95% CI, 1.001–1.048; p = 0.04), and aneurysm rerupture (OR, 4.961; 95% CI, 1.461–16.845; p = 0.01).Conclusions. These findings suggest that aneurysm reruptures, as well as increased blood pressure and HR, are associated with unfavourable outcomes in patients with aSAH

Mechanical properties of composites based on unsaturated polyester resins obtained by chemical recycling of poly(ethylene terephthalate)

Composites based on unsaturated polyester (UPe) resins and fumed silica AEROSIL® RY 50, NY 50, RX 50 and NAX 50, as well as graphite, TiO2 or organically modified clay CLOISITE 30B were prepared in order to investigate the influence of reinforcing agents on the mechanical properties of composites. Unsaturated polyester resins were synthesized from maleic anhydride and products of glycolysis, obtained by depolymerization of poly(ethylene terephthalate) with dipropylene glycol (UPe1 resin) and triethylene glycol (UPe2 resin) in the presence of tetrabutyl titanate catalyst. The obtained unsaturated polyesters were characterized by FTIR spectroscopy, acid and hydroxyl values, and their mechanical properties were also examined. Significant increase of the tensile modulus, tensile strength and decrease of the elongation at break was observed for composites prepared after addition of 10 wt.% of graphite or 10 wt.% of TiO2 to the UPe resins, indicating strong interaction between matrix and filler particles. On the other hand, nanocomposites prepared using UPe2 and hydrophobically modified silica nanoparticles showed lower tensile strength and tensile modulus than polymer matrix. The presence of CLOISITE 30B had no significant influence on the mechanical properties of UPe1, while tensile strength and tensile modulus of UPe2 increased after adding 10 wt.% of clay.U ovom radu sintetisani su kompoziti na bazi nezasićenih poliestarskih (UPe) smola i SiO2 (AEROSIL®:RY 50, NY 50, RX 50 i NAX 50), grafita, TiO2 ili organski modifikovane gline CLOISITE 30B u cilju ispitivanja uticaja punioca na mehanička svojstva kompozita. Nezasićene poliestarske smole su sintetisane polazeći od anhidrida maleinske kiseline i proizvoda glikolize dobijenih depolimerizacijom poli(etilen-tereftalata) sa dipropilen glikolom (UPe1 smola) ili trietilen glikolom (UPe2 smola) u prisustvu katalizatora tetrabutil titanata. Sintetisane nezasićene poliestarske smole su ispitane primenom FTIR spektroskopije, određen im je kiselinski i hidroksilni broj i ispitana su njihova mehanička svojstva. Molarna masa srednja po brojnoj vrednosti sintetisanih nezasićenih poliestarskih smola je između 1620-1630 g mol-1. Moduli istezanja i zatezna čvrstoća kompozita pripremljenih dodavanjem 10 mas.% grafita ili TiO2 nezasićenim poliestarskim smolama su značajno porasli u odnosu na čiste poliestre, dok se izduženje pri kidanju smanjilo, što ukazuje na postojanje jakih interakcija između matrice i čestica punioca. Sa druge strane, nanokompoziti sintetisani korišćenjem UPe2 i modifikovanih nanočestica SiO2 su imali manju zateznu čvrstoću i module istezanja nego čista nezasićena poliestarska smola. Pokazano je da prisustvo gline CLOISITE 30B nema značajan uticaj na mehanička svojstva smole UPe1, dok su vrednosti modula istezanja i zatezne čvrstoće UPe2 porasle nakon dodavanja 10 mas.% gline

TDMA-Based Dual-Mode Communication for Mobile Wireless Sensor Networks

Small highly mobile robots, and in particular micro air vehicles (MAVs), are well suited to the task of exploring unknown indoor environments such as buildings and caves. Such a task imposes a number of requirements on the underlying communication infrastructure, with differing goals during various stages of the mission. This work addresses those requirements with a hybrid communications infrastructure consisting of a stationary mesh network along with the mobile nodes. The combined network operates in two independent modes, coupling a highly efficient, low duty cycle, low throughput mode for routing and persistent sensing with a burst mode for high data rate communication. By strategically distributing available frequency channels between the mobile agents and the stationary nodes, the overall network provides reliable long-term communication paths while maximizing data throughput when needed