The Effects of Wear upon the Axial Profile of a Grinding Wheel in the Construction of Innovative Grinding Wheels for Internal Cylindrical Grinding

The article describes the effects of wear upon the axial profile of a grinding wheel in the axial cylindrical grinding processes. This mechanism was used to develop a grinding wheel with zone diversified structure made of microcrystalline sintered corundum abrasive grains and vitrifies bond. Such a grinding wheel is characterized by the conical rough grinding zone that is made by grains of a relatively large size, and a cylindrical finish grinding zone with grains of a smaller size and can be used in the single-pass grinding processes. Investigative tests conducted using newly-developed grinding wheels were described. Investigations were operated in the single-pass internal cylindrical grinding process of 100Cr6 steel. A comparison of results obtained using a zone diversified structure grinding wheel, with reference to a grinding wheel with grains of one size, were given. The analysis provides the roughness of the grinded surface, the grinding power, as well as chosen indicators of grinding efficiency. Experimental results obtained with use of a zone-diversified grinding wheel, built from relatively cheap grains of microcrystalline sintered corundum, showed that it is possible to obtain large material removal rate up to approximately 24 mm3/s and high quality of machined surface (=0.16−0.39 μm)

Morphology of Near- and Semispherical Melted Chips after the Grinding Processes Using Sol-Gel Abrasives Based on SEM-Imaging and Analysis

Selected issues related to SEM-imaging and image analysis of spherical melted chips formed during the grinding process are presented and discussed. The general characteristics of this specific group of machining products are given. Chip formation phenomena, as well as their overall morphology, are presented using selected examples of near- and semispherical melted chips occurring singly or concentrated in clusters on the grinding wheel surface after the machining process. Observation of the spherical melted chips and acquisition of their images were carried out for grinding wheel active surfaces with microcrystalline sintered corundum abrasive grains SG™ after the internal cylindrical grinding process of a 100Cr6 steel and Titanium Grade 2® alloy by use of a scanning electron microscope, JEOL JSM-5500LV. Analysis of the obtained SEM micrographs was carried out by Image-Pro® Plus 5.0 software to determine the selected geometrical parameters describing the morphological features of the assessed chips

Relationship between pressure and output parameters in belt grinding of steels and nickel alloy

Belt grinding of flat surfaces of typical parts made of steel and alloys, such as grooves, shoulders, ends, and long workpieces, is a good alternative to milling. Several factors can influence the belt grinding process of flat surfaces of metals, such as cutting speed and pressure. In this work, the importance of pressure in the belt grinding was investigated in terms of technological and experimental aspects. The grinding experiments were performed on structural alloy steel 30KhGSN2/30KhGSNA, structural carbon steel AISI 1045, corrosion-resistant and heat-resistant stainless steel AISI 321, and heat-resistant nickel alloy KHN77TYuR. The performance of the grinding belt was investigated in terms of surface roughness, material removal rate (MRR), grinding belt wear, performance index. Estimated indicators of the belt grinding process were developed: cutting ability; reduced cutting ability for belt grinding of steels and heat-resistant alloy. It was found that with an increase in pressure p, the surface roughness of the processed surface Ra decreased while the tool wear and MRR increased. With a decrease in plasticity and difficulty of machinability, the roughness, material removal rate, reduced cutting capacity (Performance index), material removal decreased, and the tool wear increased. The obtained research results can be used by technologists when creating belt grinding operations for steels and alloys to ensure the required performance is met

Systematic review and meta-analysis appraising efficacy and safety of adrenaline for adult cardiopulmonary resuscitation

BACKGROUND: There is a beneficial effect of adrenaline during adult cardiopulmonary resuscitation (CPR) from cardiac arrest but there is also uncertainty about its safety and effectiveness. The aim of this study was to evaluate the use of adrenaline versus non-adrenaline CPR. METHODS: PubMed, ScienceDirect, Embase, CENTRAL (Cochrane Central Register of Controlled Trials) and Google Scholar databases were searched from their inception up to 1st July 2020. Two reviewers independently assessed eligibility and risk of bias, with conflicts resolved by a third reviewer. Risk ratio (RR) or mean difference of groups were calculated using fixed or random-effect models. RESULTS: Nineteen trials were identified. The use of adrenaline during CPR was associated with a significantly higher percentage of return of spontaneous circulation (ROSC) compared to non-adrenaline treatment (20.9% vs. 5.9%; RR = 1.87; 95% confidence interval [CI] 1.37-2.55; p < 0.001). The use of adrenaline in CPR was associated with ROSC at 19.4% and for non-adrenaline treatment - 4.3% (RR = 3.23; 95% CI 1.89-5.53; p < 0.001). Survival to discharge (or 30-day survival) when using adrenaline was 6.8% compared to non-adrenaline treatment (5.5%; RR = 0.99; 95% CI 0.76-1.30; p = 0.97). However, the use of adrenaline was associated with a worse neurological outcome (1.6% vs. 2.2%; RR = 0.57; 95% CI 0.42-0.78; p < 0.001). CONCLUSIONS: This review suggests that resuscitation with adrenaline is associated with the ROSC and survival to hospital discharge, but no higher effectiveness was observed at discharge with favorable neurological outcome. The analysis showed higher effectiveness of ROSC and survival to hospital discharge in non-shockable rhythms. But more multicenter randomized controlled trials are needed in the future

Monitoramento dos fluxos de gases de efeito estufa de plantio de pinus e mata nativa, Rio Negrinho, SC.

Resumo

Compositional Changes in Two Small Mammal Communities During Succession in Southeastern Virginia

Changes in the composition of two small mammal communities were studied during 8 and 9 years of ecological succession in southern Chesapeake. Virginia. Using monthly live-trapping on grids of similar size and history since their abandonment as agricultural fields, we learned that house mice were early colonists on one grid but not the other. Two species of herbivorous rodent and the granivorous eastern harvest mouse were numerically dominant on both grids across the study. Some species disappeared early on one grid but persisted to the end at the other. The two arboreal small mammals, golden and white-footed mice, were most predictable between sites, showing up at year 8, after significant woody elements were present on the grids. The greatest abundances of small mammals (and probably greatest total biomass too) were seen between years 4 and 6 of ecological succession

Enchytraeids (Oligochaeta, Enchytraeidae) as soil quality indicators in integrated systems in Paraná State.

Resumo

Enquitreídeos como indicadores de qualidade do solo em sistemas integrados de produção nos Campos Gerais, Paraná.

Resumo. FERTBIO 2014