Influence of induction hardening parameters on the GS30Mn5 weld properties

This study examines parameters of post-weld heat treatment on the test specimens made of cast steel GS30Mn5. The welding is performed with shielded metal arc welding (SMAW) process. The aim is to obtain the surface without illicit cracks, with hardness ranging from 320 up to 400 HB. After induction heating, the specimens are cooled alternately with air and water. Decreased speed of quenching results in avoiding the occurrence of illicit splashes, while the hardness is maintained within the prescribed limits

The possibility of tribopair lifetime extending by welding of quenched and tempered stainless steel with quenched and tempered carbon steel

In the conditions of tribocorrosion wear, extending of parts lifetime could be achieved by using stainless steel,which is hardened to sufficiently high hardness. In the tribosystem bolt/ bushing shell/link plate of the bucket elevator transporter conveyor machine, the previously quenched and tempered martensitic stainless steel for bolts is hardened at ≈47 HRC and welded with the quenched and tempered high yield carbon steel for bolts. Additional material, based on Cr-Ni-Mo (18/8/6) is used. The microstructure and hardness of welded samples are tested. On the tensile tester, resistance of the welded joint is tested with a simulated experiment. Dimensional control of worn tribosystem elements was performed after six months of service

Quasiparticle spectra and excitons of organic molecules deposited on substrates: G0W0-BSE approach applied to benzene on graphene and metallic substrates

We present an alternative methodology for calculating the quasi-particle energy, energy loss, and optical spectra of a molecule deposited on graphene or a metallic substrate. To test the accuracy of the method it is first applied to the isolated benzene (C6H6) molecule. The quasiparticle energy levels and especially the energies of the benzene excitons (triplet, singlet, optically active and inactive) are in very good agreement with available experimental results. It is shown that the vicinity of the various substrates (pristine/doped graphene or (jellium) metal surface) reduces the quasiparticle HOMO-LUMO gap by an amount that slightly depends on the substrate type. This is consistent with the simple image theory predictions. It is even shown that the substrate does not change the energy of the excitons in the isolated molecule. We prove (in terms of simple image theory) that energies of the excitons are indeed influenced by two mechanisms which cancel each other. We demonstrate that the benzene singlet optically active (E1u) exciton couples to real electronic excitations in the substrate. This causes it substantial decay, such as {\Gamma} = 174 meV for pristine graphene and {\Gamma} = 362 meV for metal surfaces as the substrate. However, we find that doping graphene does not influence the E1u exciton decay rate.Comment: 16 pages, 14 figure

Influence of induction hardening parameters on the GS30Mn5 weld properties

This study examines parameters of post-weld heat treatment on the test specimens made of cast steel GS30Mn5. The welding is performed with shielded metal arc welding (SMAW) process. The aim is to obtain the surface without illicit cracks, with hardness ranging from 320 up to 400 HB. After induction heating, the specimens are cooled alternately with air and water. Decreased speed of quenching results in avoiding the occurrence of illicit splashes, while the hardness is maintained within the prescribed limits

TDDFT study of time-dependent and static screening in graphene

Time-dependent density functional theory (TDDFT) within the random phase approximation (RPA) is used to obtain the time evolution of the induced potential produce by the sudden formation of a C 1s core hole inside a graphene monolayer, and to show how the system reaches the equilibrium potential. The characteristic oscillations in the time-dependent screening potential are related to the excitations of π and σ + π plasmons as well as the low energy 2D plasmons in doped graphene. The equilibrium RPA screened potential is compared with the DFT effective potential, yielding good qualitative agreement. The self energy of a point charge near a graphene monolayer is shown to demonstrate an image potential type behavior, Ze/(z − z0), down to very short distances (4 a.u.) above the graphene layer. Both results are found to agree near quantitatively with the DFT ground state energy shift of a Li+ ion placed near a graphene monolayer.D.J.M. acknowledges financial support from the Spanish “Juan de la Cierva” program (JCI-2010-08156), MICINN (FIS2010-21282-C02-01), “Grupos Consolidados UPV/EHU del Gobierno Vasco” (IT-319-07), and ACI-Promociona (ACI2009-1036).Peer Reviewe

Occupational exposure to blood and body fluids among health-care workers in Serbia

© 2014 S. Karger AG, Basel. Objectives: The aim of this study was to examine the epidemiology of occupational accidents and self-reported attitude of health-care workers (HCWs) in Serbia. Subjects and Methods: A cross-sectional study was conducted among HCWs in selected departments of five tertiary care hospitals and in one secondary care hospital in February 2012. A previously developed self-administered questionnaire was provided to HCWs who had direct daily contact with patients. χ2 test and Student's t test were used for statistical analysis of the data. Results: Of the 1,441 potential participants, 983 (68.2%) completed the questionnaire: 655 (66.7%) were nurses/medical technicians, 243 (24.7%) were physicians and 85 (8.6%) were other personnel. Of the 983 participants, 291 (29.6%) HCWs had had at least one accident during the previous year and 106 (40.2%) of them reported it to the responsible person. The highest prevalence (68.6%) of accidents was among nurses/technicians (p = 0.001). Accidents occurred more often in large clinical centers (81.1%; p < 0.001) and in the clinical ward, intensive care unit and operating theater (p = 0.003) than in other departments. Seventy-six (13.1%) nurses/medical technicians had an accident during needle recapping (p < 0.001). Of all the HCWs, 550 (55.9%) were fully vaccinated, including significantly more doctors (154, 63.4%) than participants from other job categories (p < 0.001). Conclusion: There was a relatively high rate of accidents among HCWs in our hospitals, most commonly amongst nurses and staff working in clinical wards, intensive care units and operating theaters. The most common types of accidents were needlestick injuries and accidents due to improper handling of contaminated sharp devices or occuring while cleaning instruments or by coming into contact with blood through damaged skin or through the conjunctiva/mucous membranes