The effect of dissolved oxygen in slurry on erosion-corrosion of En30B steel

Synergistic effect between corrosion and wear has been widely recognized in many tribo-corrosion systems. In most wet application conditions, dissolved oxygen (DO) is a controlling factor to the dynamics of corrosion process and is therefore expected to have significant impact on the tribo-corrosion performance of materials. In this study, the effect of DO (0 - 24 ppm) on erosion-corrosion behaviour of En30B low alloy steel has been investigated using a slurry pot erosion-corrosion test apparatus in a slurry containing 35wt% silica sand and 3.5% NaCl solution at 30°C and 45°C. The synergistic effect and its contributing components, i.e., erosion-enhanced corrosion and corrosion-enhanced erosion, have been measured/analysed. The total erosion-corrosion loss and synergy of the En30B steel increases with DO in the slurry, initially rapidly at DO levels below ~5 ppm and then less rapidly at the higher DO levels. The synergistic effect is mainly due to corrosion-enhanced erosion with negligible contributions from erosion-enhanced corrosion. Temperature has a significant effect on the total erosion-corrosion loss. Total erosion-corrosion was 34% higher at 45°C (in still air) than at 30°C. Mechanisms for the observed phenomena have been discussed based on the concept of corrosion-accelerated micro-crack propagation

Some thoughts on modelling abrasion-corrosion : wear by hard particles in corrosive environments

Wear by hard particles can involve abrasion or erosion and is one of the most severe forms of wear. When a corrosive environment is present, the material loss rate can be significantly increased due to interactions (synergy) between the mechanical and chemical/electrochemical actions. In developing strategies for mitigating such adverse synergistic effect, it is important to understand the complex effect of various parameters on material loss under given tribocorrosion conditions. In this paper, a model is presented for wear-corrosion synergy in abrasive wear by hard particles applicable to many conditions in both the marine renewable (abrasion by high concentrations of large sand particles on tidal turbines) and extractive metallurgy (abrasive wear in mineral extraction). The mechanical wear loss is modeled based on the grooving mechanism (micro-cutting/micro-ploughing). Wear-enhanced corrosion is calculated from the fresh surface areas generated by grooving and the corresponding transient corrosion current. The concept of “corrosion-degraded layer” on the worn surface is introduced to account for the corrosion-enhanced wear; within this corrosion-degraded layer, the material loss rate is higher under the same mechanical wear conditions than in the material that is unaffected by corrosion. Based on the model, the effect of wear conditions on synergy in hard particle wear-corrosion has been discussed. The relative thickness of the corrosion-degraded layer to the depth of hard particle penetration (grooving) in the mechanical wear is found to be an important parameter in determining the relative severity of synergy in different tribocorrosion systems. Good qualitative agreement has been observed between the predictions and published experimental results obtained from a range of abrasion-corrosion and erosion-corrosion lab testing

The Role of Mobile Phones in Governance-Driven Technology Exports in Sub-Saharan Africa

This study assesses how the mobile phone influences governance to improve information and communication technology (ICT) exports in Sub-Saharan Africa with data from 2000-2012. The empirical evidence is based on Generalised Method of Moments and three main governance concepts are used, namely: (i) institutional (comprising the rule of law and corruption-control); (ii) political (involving political stability/no violence and voice & accountability) and (iii) economic (including regulation quality and government effectiveness) governance. The following findings are established. First, there are positive net effects on ICT goods exports from independent interactions between mobile phones and ‘political stability’ ‘voice and accountability’ and corruption-control. Second, significant net effects are not apparent from independent interactions between mobile phones and government effectiveness, regulation quality and the rule of law. Theoretical and practical implications are discussed

The Role of Mobile Phones in Governance-Driven Technology Exports in Sub-Saharan Africa

This study assesses how the mobile phone influences governance to improve information and communication technology (ICT) exports in Sub-Saharan Africa with data from 2000-2012. The empirical evidence is based on Generalised Method of Moments and three main governance concepts are used, namely: (i) institutional (comprising the rule of law and corruption-control); (ii) political (involving political stability/no violence and voice & accountability) and (iii) economic (including regulation quality and government effectiveness) governance. The following findings are established. First, there are positive net effects on ICT goods exports from independent interactions between mobile phones and ‘political stability’ ‘voice and accountability’ and corruption-control. Second, significant net effects are not apparent from independent interactions between mobile phones and government effectiveness, regulation quality and the rule of law. Theoretical and practical implications are discussed

Growth Giant Prawns (Macrobracium Rosenbergii) with Different Stock Densities on the Minapadi System: English

Minapadi is a fish rearing system in rice fields that is carried out with rice plants. This study aims to increase the income of farmers with high productivity of rice yields and increase the production of giant prawns. The method used is a Completely Randomized Design (CRD) experiment with 3 treatments and 3 replications. The treatments were: P1 = stocking density of 100 birds/plot, P2 = stocking density of 200 birds/plot, P3 = stocking density of 300 birds/plot. This research was conducted for 90 days. Parameters observed were rice productivity and growth. The results showed that the best treatment was P2 = stocking density of 200 birds/plot. by producing an average value of rice productivity of 5 kg/50 m2 and an average value of growth of giant prawns of 4.72%.   &nbsp

MITIGASI PERUBAHAN IKLIM MELALUI PENANAMAN MANGROVE DI DESA LHOK BUBON KECAMATAN SAMATIGA KABUPATEN ACEH BARAT

Mitigation of climate change is a business activity to reduce the risk of increasing greenhouse gas emissions in the atmosphere, gases can occur naturally in the environment and can also arise due to human activities. Mangroves are carbon-rich ecosystems and have an important role in climate regulation, namely by their ability to store large amounts of carbon as an effort to offset anthropogenic CO2 emissions. Mangrove ecosystems are able to store high carbon which is useful in reducing greenhouse gas emissions, mangrove ecosystems are also able to store carbon three to four times greater than ordinary tropical forests. The activity was carried out in Lhok Bubon Village, Samatiga District, West Aceh District. This activity was attended by the academic community of FPIK UTU with 50 participants. The method of implementing community service activities used was counseling and demonstration methods with students through planting 100 mangrove stems, namely Rhizopora sp. Protecting the mangrove ecosystem is our common awareness, especially students as the next generation of the nation, one of which is by not cutting down mangrove trees to be used as firewood or charcoal, opening up ponds and destroying the original habitat of mangrove ecosystems that can disrupt coastal aquatic biota. Students are given education (counseling) about the importance of conserving mangrove ecosystems from the threat of climate change mitigation. Students are very enthusiastic and active, it can be seen from the seriousness in participating in mangrove planting activities through discussions, questions and answers, and hands-on practice. Sustainability of a program like this is needed and efforts are made to become a routine program of gampong activities, NGO activities and also academic activities, because with sustainability it will be faster to see the results that have been expected together

Arsenic speciation in polychaetes (Annelida) and sediments from the intertidal mudflat of Sundarban mangrove wetland, India

This paper documents the concentration of total arsenic and individual arsenic species in four soft-bottom benthic polychaetes (Perenereis cultifera, Ganganereis sootai, Lumbrinereis notocirrata and Dendronereis arborifera) along with host sediments from Sundarban mangrove wetland, India. An additional six sites were considered exclusively for surface sediments for this purpose. Polychaetes were collected along with the host sediments and measured for their total arsenic content using inductively coupled plasma mass spectrometry. Arsenic concentrations in polychaete body tissues varied greatly, suggesting species-specific characteristics and inherent peculiarities in arsenic metabolism. Arsenic was generally present in polychaetes as arsenate (AsV ranges from 0.16 to 0.50 mg kg−1) or arsenite (AsIII ranges from 0.10 to 0.41 mg kg−1) (30–53 % as inorganic As) and dimethylarsinic acid (DMAV <1–25 %). Arsenobetaine (AB < 16 %), and PO4-arsenoriboside (8–48 %) were also detected as minor constituents, whilst monomethylarsonic acid (MAV) was not detected in any of the polychaetes. The highest total As (14.7 mg kg−1 dry wt) was observed in the polychaete D. arborifera collected from the vicinity of a sewage outfall in which the majority of As was present as an uncharacterised compound (10.3 mg kg−1 dry wt) eluted prior to AB. Host sediments ranged from 2.5 to 10.4 mg kg−1 of total As. This work supports the importance of speciation analysis of As, because of the ubiquitous occurrence of this metalloid in the environment, and its variable toxicity depending on chemical form. It is also the first work to report the composition of As species in polychaetes from the Indian Sundarban wetlands