Surface Integrity Evaluation of Brass CW614N after Impact of Acoustically Excited Pulsating Water Jet

AbstractPresented article is focused on surface integrity evaluation of brass CW614N form the sight of surface topography, structural changes in surface layers and strengthening character in subsurface layers after impact of acoustically excited pulsating water jet (PWJ). Surface topography was evaluated using optical profilometry. Structural changes in subsurface layer were observed based on mass material removal Δm [mg/s] and maximal depth of penetrance of PWJ hmax [mm]. Nano indentation measurement according to Berkovich were used to examination of strengthening character in subsurface layer. Disintegration of experimental samples was performed under constant technological conditions: hydraulic power of plunger pump Ph = 19kW; round nozzle diameter d = 1.6mm; feed speed rate v = 0.75mm/s; pressure of plunger pump p = 38MPa, stand-off distance of nozzle from target material z = 45mm; ultrasound frequency f = 20.29kHz and as variable factor was set power of ultrasound P on values 340, 360 and 380W. In terms of surface topography experimental investigation proved that PWJ under selected conditions is not suitable for precision machining. Evaluation of the surface characteristics indicates that the chemical composition has a significant effect on material weight loss Δm [mg/s] and a maximum depth of penetration of PWJ hmax [mm]. Evaluation of characteristics of subsurface layer was observed strengthened area with lower elasticity

Heavy Metals Contamination in Agricultural Soil and Rice in Tanzania: A Review

Research Article published by Science Publishing GroupHeavy metals contamination in agricultural soil is a potential environmental threat to the safety of agricultural food crops such as rice which is consumed by majority of Tanzanians. The aim of this review is to put together available information on sources of heavy metals, their extent of contamination in agricultural soil and in rice, the risk of exposure through rice consumption as well as the relationship between heavy metals contamination in agricultural soils and in rice in Tanzania. There are several methods of determining the concentrations of heavy metals in soils and in rice. These include Inductively Coupled Plasma Mass Spectrometer (ICP – MS) and Energy Dispersive X – ray Fluorescence spectrometer (EDXRF). It has been mostly reported that the extent of heavy metals contamination in agricultural soils is influenced by their closeness to mining or industrial areas. The use of river waters in mining areas or wastewater from industries for irrigation has been associated to increasing levels of heavy metals in agricultural soils. The elevated level of heavy metals in agricultural soils leads to their accumulation in crops especially rice which upon consumption poses health effects to human and the ecosystem at large. This review suggests the need for determining the extent of heavy metals contamination in agricultural soils around potential areas such as mining and to link this with exposure assessment on heavy metals through rice consumption in Tanzania. This information is necessary to establish the extent at which rice consumers in Tanzania are at risk of heavy metals exposure

Tambay tayo: Ang biruan sa barkada ng mga lalabintaunin

Ang isang lalabintaunin ay nasa napakahalagang yugto ng kanyang buhay sapagkat dito nakakaranas siya ng mga pagbabagong pisikal, sosyal at sikolohikal. Sa panahong ito nahuhubog ang malaking parte ng buhay ng isang indibidwal. Ang pag-aaral na ito ay nagbigay pokus sa biruan ng mga magkakabarkadang lalabintaunin at kung paano ito nakakaapekto sa kanilang debelopment. Para malaman kung papaano nakakaapekto ang biruan sa isang barkada nakisama at gumamit ng metodong pag-oobserba na may pakikilahok ang mga mananaliksik. Tatlong grupo ng magkakabarkada ang inobserbahan ng tatlo hanggang apat na beses. Ang mga datos ay kinalap sa pamamagitan ng paggawa ng field notes pagkatapos ng obserbasyon. Ang mga datos ay sinuri sa pamamagitan ng kwalitatibong pamamaraan. Ang mga magkakatulad na mga obserbasyon ay ipinagsama at sa mga nakalap ay nabuo ang mga temang nakita ng mga mananaliksik na sapat na makapagpapaliwanag sa pag-aaral. Ang mga resulta ay naglarawan sa silbi, epekto, laman at proseso ng biruan na nakakatulong sa pagdebelop ng isang lalabintaunin. Ayon din sa pag-aaral ang pagkakapikon ay naiiwasan at sa halip nagiging pangkatuwaan na lang sa mga magkakabarkada ang biruan dahil sa pagkakalapit nila sa isa\u27t-isa

Effect of pulsating water jet disintegration on hardness and elasticity modulus of austenitic stainless steel AISI 304L

The presented article is focused on the evaluation of mechanical properties of stainless steel disintegrated using an ultrasonically modulated pulsating water jet. The experimental procedure was performed using a nozzle with a circular orifice with an equivalent diameter of 1.6 mm. The mechanical properties evaluation was based on indentation elasticity modulus E-p and nano hardness H, which were measured using nanoindentation technique. Influence of ultrasonic power and plunger pressure change on disintegrated material was evaluated. Changes in mechanical properties in dependence on distance from the disintegrated surface were evaluated. Elasticity modulus and nano hardness change were observed below and on the sides of the disintegrated surfaces. Measurements were performed until the distance of 930 mu m. The indentation was carried in three series of 10 indents with 100 mu m spacing located below the affected area, next to the affected area and in the unaffected material. Results of experimental testing show changes of nano hardness (generally an appreciable decrease) and elasticity modulus (limited increase) of material under and to the side of the newly created surface.Web of Science1075-62730271