The influence of heat input on the toughness and fracture mechanism of surface weld metal

© 2018 The Authors. Surface welding is a way to extend the exploitation life of damaged parts and constructions and the heat input has a major influence on the weldment properties. In this paper is shown the influence of the heat input on the toughness and the fracture mechanism of the surface welded joint. Surface welding of high carbon steel with self shielded wire was conducted with three different heat inputs (6kJ/cm, 10 kJ/cm and 16 kJ/cm). Total impact energy, crack initiation and crack propagation energy were estimated at room temperature, -20 o C and -40 o C. Fracture analysis of fractured surfaces was also conducted and it has been found that increasing of heat input leads to an increase of share of transgranular brittle fracture, what is in complete accordance with the obtained energy values. Based on all obtained results, the optimum value of heat input for welding procedure applied was defined

The effect of shielding gas composition on the toughness and crack growth parameters of AlMg4,5Mn weld metals

The experiment have been performed using samples of welded joints of the three components aluminium alloy AlMg4,5Mn. The welding was performed with GTAW in the shielded atmosphere of Ar+0,015N2, mixture of the inert gases Ar+50%He+0,015N2 and Ar+70%He+0,015N2. After welding has been completed, the metallographic tests, the tensile test and the tests of the hardness were performed. Also, the weld metal toughness was estimated, using the instrumental Charpy impact testing system, followed by estimating the crack initiation energy, crack growth energy and the fracture mechanics parameters. The goal was to establish the effects of shielding atmosphere composition on the mechanical properties and fracture mechanics parameters of weld metal

Outbreak of West Nile virus infection among humans in Serbia, August to October 2012

We describe the first reported outbreak of West Nile virus (WNV) infection in humans in Serbia in August to October 2012 and examine the association of various variables with encephalitis and fatal outcome. Enzyme-linked immunosorbent assay (ELISA) was used for detection of WNV-specific IgM and IgG antibodies in sera and cerebrospinal fluid. A total of 58 patients (mean age: 61 years; standard deviation: 15) were analysed: 44 were from Belgrade and its suburbs; 52 had neuroinvasive disease, of whom 8 had meningitis, while 44 had encephalitis. Acute flaccid paralysis developed in 13 of the patients with encephalitis. Age over 60 years and immunosuppression (including diabetes) were independently associated with the development of encephalitis in a multivariate analysis: odds ratio (OR): 44.8 (95% confidence interval (CI): 4.93-408.59); p=0.001 (age over 60 years); OR: 10.76 (95% CI: 1.06-109.65); p=0.045 (immunosuppression including diabetes). Respiratory failure requiring mechanical ventilation developed in 13 patients with encephalitis. A total of 35 patients had completely recovered by the time they were discharged; nine patients died. The presence of acute flaccid paralysis, consciousness impairment, respiratory failure and immunosuppression (without diabetes) were found to be associated with death in hospital in a univariate analysis (p lt 0.001, p=0.007, p lt 0.001 and p=0.010, respectively)

MANAGEMENT OF RECURRENT APHTHOUS STOMATITIS IN HIV

Introduction: Today, human immunodeficiency virus (HIV) infection is often health problem. People with HIV are living longer and more of them are seeking care for the oral complications of this disease. This is the reason why the management of HIV infection is regular in the dental and medical everyday practice. Although HIV-related recurrent aphthous stomatitis (RAS) constitute a small percentage of oral lesions they are one of the most painful conditions of the oral cavity. The aim: is to point out the therapeutic possibilities and health improvement in people with HIV. Conclusion: Once a diagnosis of RAS is reached, the choice of a specific treatment modality is individual and the potential side effects of drugs should always be taken into account. It is important to reduce pain and achieve a prolonged remission

Ventilatory lung function in workers in the tobacco industry

U cilju odgovora na pitanje u kojoj su meri profesionalne nokse registrovane u duvanskoj industriji mogle uticati na stanje ventilacije pluća eksponiranih radnika sprovedena su ispitivanja u radnoj sredini i na radnicima. U radnoj sredini je izvršena analiza tehnološkog procesa rada, rezultata mikroklimatskih merenja, hemijskih štetnosti i zaprašenosti. Ispitivanje ventilacije pluća sprovedeno je na 95 radnika eksponirane grupe i 129 radnika kontrolne grupe. Rezultati analize radne sredine ukazuju na prisustvo duvanske prašine iznad maksimalno dopuštenih koncentracija. lspitivanja ventilacije pluća eksponiranih radnika su pokazala statistički značajno sniženje vrednosti nekih primenjenih testova kod nepušača ove grupe u odnosu na nepušače kontrolne grupe, što objašnjavamo delovanjem navedenih noksi na radnom mestu.A study was carried out to determine respiratory hazards to workers in tobacco manufacture. The investigations at the workplace included analysis of the work technology and measurements of chemical pollutants and dust concentrations in the work rooms. Ventilatory lung function tests were performed in 95 workers exposed to tobacco dust and in 129 control workers. Results of workplace analysis showed the presence of tobacco dust levels exceeding the maximum permissible concentrations. The values of some lung function tests for exposed workers non-smokers were significantly lower than for control workers non-smokers. They could be attributed to the effect of occupational noxae on the respiratory system

Optical studies of gap, hopping energies and the Anderson-Hubbard parameter in the zigzag-chain compound SrCuO2

We have investigated the electronic structure of the zigzag ladder (chain) compound SrCuO2 combining polarized optical absorption, reflection, photoreflectance and pseudo-dielectric function measurements with the model calculations. These measurements yield an energy gap of 1.42 eV (1.77 eV) at 300 K along (perpendicular) to the Cu-O chains. We have found that the lowest energy gap, the correlation gap, is temperature independent. The electronic structure of this oxide is calculated using both the local-spin-density-approximation with gradient correction method, and the tight-binding theory for the correlated electrons. The calculated density of electronic states for non-correlated and correlated electrons shows quasi-one-dimensional character. The correlation gap values of 1.42 eV (indirect transition) and 1.88 eV (direct transition) have been calculated with the electron hopping parameters t = 0.30 eV (along a chain), t_yz = 0.12 eV (between chains) and the Anderson-Hubbard repulsion on copper sites U= 2.0 eV. We concluded that SrCuO_2 belongs to the correlated-gap insulators.Comment: 24 pages, 8 figures, to be published in Phys.Rev.

The Two Dimensional Kondo Model with Rashba Spin-Orbit Coupling

We investigate the effect that Rashba spin-orbit coupling has on the low energy behaviour of a two dimensional magnetic impurity system. It is shown that the Kondo effect, the screening of the magnetic impurity at temperatures T < T_K, is robust against such spin-orbit coupling, despite the fact that the spin of the conduction electrons is no longer a conserved quantity. A proposal is made for how the spin-orbit coupling may change the value of the Kondo temperature T_K in such systems and the prospects of measuring this change are discussed. We conclude that many of the assumptions made in our analysis invalidate our results as applied to recent experiments in semi-conductor quantum dots but may apply to measurements made with magnetic atoms placed on metallic surfaces.Comment: 22 pages, 1 figure; reference update

Impact of Nitrogen and Phosphorus on Grain Yield in Winter Triticale Grown on Degraded Vertisol

The objectives of this study were to investigate: (1) the effects of fertilization, environment, and their interactions on the thousand grain weight (TGW), hectolitre weight (HW) and grain yield (GY) of winter triticale, and (2) the correlations between these traits in different environments. The invariable nitrogen (80 kg N ha(-1)), potassium (60 kg K2O ha(-1)) and two phosphorus (60 and 100 kg P(2)O(5)ha(-1)) doses were used in Kragujevac location in central Serbia. Nitrogen was applied individually and in combination with two phosphorus rates and one rate of potassium fertilizer. Eight fertilization treatment controls and N-80, P-60, P-100, N80P60K60, N80P100K60, N(80)P(60)and N(80)P(100)were examined during three growing seasons. The yield and quality of triticale significantly varied across years and treatments. The average yield of all treatments in the 2015 growing season was significantly greater than in the previous years (3.597 t ha(-1)). Combined usage of NPK fertilizer (80 kg N ha(-1), 100 kg P(2)O(5)ha(-1)and 60 kg K2O ha(-1)) represented the excellent base for optimum supply of major nutrients, resulting in maximum GY (4.0 t ha(-1)). Negative and significant correlation was found between grain GY and TGW (-0.392*) in 2015, and positive highly significant correlation were in 2013 (0.648*) and 2014 (0.493*). The positive effect over complete application of fertilizer is the result of a lower pH value of the soil, as well as the low content of available phosphorus and potassium in Vertisol soil type. Optimizing fertilization for maximum profitability is of great importance in the future triticale production in Pannonian Environments