Complementary use of electrochemical testing techniques to study corrosion processes of HVOF Inconel 625, CoNiCrAIY and WCCoCr coatings

The purpose of coating is to get a blend of unique properties at low cost which is not possible from other manufacturing processes. High velocity oxygen fuel (HVOF) is one of the most commonly used thermal spraying processes to produce wear and corrosion resistant coatings. Alongside wear and corrosion resistant properties the HVOF thermally sprayed coating process also induces microstructural heterogeneities which decreased the corrosion resistant properties. Considerable research has been reported on corrosion testing of the HVOF sprayed coatings by using electrochemical techniques. Some electrochemical techniques give area average results whilst other allows the effect of different features to be determined. The complementary use of basic electrochemical techniques with more advance techniques is missing in most of the previous research. In this research work potentiodynamic polarization testing, electrochemical impedance spectroscopy and scanning electrochemical microscopy were used to see if the combined results could provide a broader picture of corrosion processes taking place at HVOF coatings. Three HVOF coatings of different microstructural complexity i.e. γ-phase Inconel 625, γ + β-phase CoNiCrAlY and WC-CoCr cermet coating were tested. Potentiodynamic polarization results gave overall current response of the applied potential which included the current responsible for chemical reaction and current for charging and discharging of the double layer. The general corrosion ranking of different materials was established by measuring corrosion potential, corrosion current density and passive current density from polarization curves. The analysis of the polarization curves revealed that without careful consideration of experimental details significant errors can be introduced. Improved procedures for potentiodynamic polarization testing were demonstrated by deliberately altering experimental parameters. The localized corrosion due to chloride ions and Cr-depleted regions was also studied by potentiodynamic polarization testing. The correlation between individual microstructural features and their electrochemical response was established by EIS including equivalent circuit modelling. The impedance spectroscopy results also revealed the electrochemical changes due to immersion time and polarization. The electrochemical activity at high resolution was studied by more sophisticated spatially resolved SECM. The SECM imaging and heterogeneous electron transfer rate constant studies in feedback mode pin point the regions of different electrochemical activity. The SECM imaging and SECM feedback approach curves at stainless steel and bulk Inconel showed negative feedback all over the surface. The Inconel 625 coating showed both positive and negative feedback from the surface. The positive feedback regions correspond to less electrochemically active and negative feedback regions correspond to electrochemically active regions. The comparison between SECM images and microscopy images confirmed that the splat boundaries were the most active regions in the HVOF Inconel 625 coating. The heterogeneous ET kinetic study determined higher rate constant values at positive feedback regions and lower rate constant values at negative feedback regions

Complementary use of electrochemical testing techniques to study corrosion processes of HVOF Inconel 625, CoNiCrAIY and WCCoCr coatings

The purpose of coating is to get a blend of unique properties at low cost which is not possible from other manufacturing processes. High velocity oxygen fuel (HVOF) is one of the most commonly used thermal spraying processes to produce wear and corrosion resistant coatings. Alongside wear and corrosion resistant properties the HVOF thermally sprayed coating process also induces microstructural heterogeneities which decreased the corrosion resistant properties. Considerable research has been reported on corrosion testing of the HVOF sprayed coatings by using electrochemical techniques. Some electrochemical techniques give area average results whilst other allows the effect of different features to be determined. The complementary use of basic electrochemical techniques with more advance techniques is missing in most of the previous research. In this research work potentiodynamic polarization testing, electrochemical impedance spectroscopy and scanning electrochemical microscopy were used to see if the combined results could provide a broader picture of corrosion processes taking place at HVOF coatings. Three HVOF coatings of different microstructural complexity i.e. γ-phase Inconel 625, γ + β-phase CoNiCrAlY and WC-CoCr cermet coating were tested. Potentiodynamic polarization results gave overall current response of the applied potential which included the current responsible for chemical reaction and current for charging and discharging of the double layer. The general corrosion ranking of different materials was established by measuring corrosion potential, corrosion current density and passive current density from polarization curves. The analysis of the polarization curves revealed that without careful consideration of experimental details significant errors can be introduced. Improved procedures for potentiodynamic polarization testing were demonstrated by deliberately altering experimental parameters. The localized corrosion due to chloride ions and Cr-depleted regions was also studied by potentiodynamic polarization testing. The correlation between individual microstructural features and their electrochemical response was established by EIS including equivalent circuit modelling. The impedance spectroscopy results also revealed the electrochemical changes due to immersion time and polarization. The electrochemical activity at high resolution was studied by more sophisticated spatially resolved SECM. The SECM imaging and heterogeneous electron transfer rate constant studies in feedback mode pin point the regions of different electrochemical activity. The SECM imaging and SECM feedback approach curves at stainless steel and bulk Inconel showed negative feedback all over the surface. The Inconel 625 coating showed both positive and negative feedback from the surface. The positive feedback regions correspond to less electrochemically active and negative feedback regions correspond to electrochemically active regions. The comparison between SECM images and microscopy images confirmed that the splat boundaries were the most active regions in the HVOF Inconel 625 coating. The heterogeneous ET kinetic study determined higher rate constant values at positive feedback regions and lower rate constant values at negative feedback regions

Towards effective management protocols: A transnational review of the state-of-the-art of coronavirus disease 2019 (COVID-19) in Pakistan and the United Arab Emirates

Coronavirus disease 2019 (COVID-19) has proliferated rapidly in Pakistan, adversely affecting every province. The grave repercussions that the pandemic has elicited in Pakistan have evoked a dire need for drastic measures to be employed at both the governmental and provincial levels. Due to the inequitable appropriation of healthcare resources with respect to the various provinces, however, a stark contrast in terms of morbidity and mortality persists. Furthermore, considering that Pakistani citizens constitute a noteworthy proportion of expatriates residing in the United Arab Emirates (UAE) and the close proximity of the two countries, due consideration of the situation in the UAE is also warranted. We present a transnational review to delineate the current state-of-the-art in Pakistan and the United Arab Emirates and evaluate pragmatic management protocols that remain at the epicenter of a national healthcare conundrum

A multi-hop angular routing protocol for wireless sensor networks

In this article, we propose two new routing protocols for wireless sensor networks. First one is AM-DisCNT (angular multi-hop distance-based clustering network transmission) protocol which uses circular deployment of sensors (nodes) for uniform energy consumption in the network. The protocol operates in such a way that nodes with maximum residual energy are selected as cluster heads for each round. Second one is iAM-DisCNT (improved AM-DisCNT) protocol which exploits both mobile and static base stations for throughput maximization. Besides the proposition of routing protocols, iAM-DisCNT is provided with three mathematical models: two linear-programming-based models for information flow maximization and packet drop rate minimization and one model for calculating energy consumption of nodes. Graphical analysis for linear-programming-based mathematical formulation is also part of this work. Simulation results show that AM-DisCNT has 32% and iAM-DisCNT has 48% improved stability period as compared to LEACH (low-energy adaptive clustering hierarchy) and DEEC (distributed energy-efficient clustering) routing protocols. Similarly, throughput of AM-DisCNT and iAM-DisCNT is improved by 16% and 80%, respectively, in comparison with the counterpart schemes. © The Author(s) 2016

Digital Twin Concept, Method and Technical Framework for Smart Meters

Smart meters connect smart grid electricity suppliers and users. Smart meters have become a research hotspot as smart grid applications like demand response, power theft prevention, power quality monitoring, peak valley time of use prices, and peer-to-peer (P2P) energy trading have grown. But, as the carriers of these functions, smart meters have technical problems such as limited computing resources, difficulty in upgrading, and high costs, which to some extent restrict the further development of smart grid applications. To address these issues, this study offers a container-based digital twin (CDT) approach for smart meters, which not only increases the user-facing computing resources of smart meters but also simplifies and lowers the overall cost and technical complexity of meter changes. In order to further validate the effectiveness of this method in real-time applications on the smart grid user side, this article tested and analyzed the communication performance of the digital twin system in three areas: remote application services, peer-to-peer transactions, and real-time user request services. The experimental results show that the CDT method proposed in this paper meets the basic requirements of smart grid user-side applications for real-time communication. The container is deployed in the cloud, and the average time required to complete 100 P2P communications using our smart meter structure is less than 2.4 seconds, while the average time required for existing smart meter structures to complete the same number of P2P communications is 208 seconds. Finally, applications, the future development direction of the digital twin method, and technology architecture are projected

Kinetic and thermodynamic study of oxidative degradation of acid yellow 17 dye by Fenton-like process: Effect of HCO3−, CO32−, Cl− and SO42− on dye degradation

We report here the degradation of AY-17 dye using Fenton-like process (H2O2/Fe3+). The maximum degradation (83%) of AY17 dye is achieved at pH 3 in 60 min, with optimum concentrations of AY 17 (0.06 mM), H2O2 (0.9 mM), and Fe2+ (0.06 mM). The scavenging effects of HCO3−, CO32−, Cl− and SO42− on dye degradation are also examined. The activation energy (Ea), activation enthalpy (rH*), and activation entropy (rS*) are calculated for the dye degradation using pseudo-first-order kinetics at various temperature.               KEY WORDS: Acid Yellow 17, H2O2/Fe3+, Fenton-like process, Oxidative degradation, Scavenging effects Bull. Chem. Soc. Ethiop. 2019, 33(2), 243-254.DOI: https://dx.doi.org/10.4314/bcse.v33i2.

Chronic inflammatory demyelinating polyneuropathy as a paraneoplastic manifestation of colorectal carcinoma: What do we know?

The pathogenesis of chronic inflammatory demyelinating polyneuropathy (CIDP) remains highly debated among experts. In recent times, literature has divulged a riveting yet plausible association between colorectal carcinoma and CIDP as its paraneoplastic ramification. Initially, research suggested that chronic inflammatory demyelinating polyneuropathy (CIDP) was caused solely by macrophages. However, recent studies have insinuated towards an alternative pathogenesis, one involving autoantibodies against paranodal junction proteins. These two distinct mechanisms are the primary contenders responsible for the development of CIDP, rendering it an elusive paraneoplastic manifestation of colorectal carcinoma.</p

Balanced Transmissions Based Trajectories of Mobile Sink in Homogeneous Wireless Sensor Networks

Mobile Sink (MS) based routing strategies have been widely investigated to prolong the lifetime of Wireless Sensor Networks (WSNs). In this paper, we propose two schemes for data gathering in WSNs: (i) MS moves on random paths in the network (RMS) and (ii) the trajectory of MS is defined (DMS). In both the schemes, the network field is logically divided into small squares. The center point of each partitioned area is the sojourn location of the MS. We present three linear programming based models: (i) to maximize network lifetime, (ii) to minimize path loss, and (iii) to minimize end to end delay. Moreover, a geometric model is proposed to avoid redundancy while collecting information from the network nodes. Simulation results show that our proposed schemes perform better than the selected existing schemes in terms of the selected performance metrics

Clinicopathological Profile and Surgical Treatment of Abdominal Tuberculosis: A Single Centre Experience in Northwestern Tanzania.

Abdominal tuberculosis continues to be a major public health problem worldwide and poses diagnostic and therapeutic challenges to general surgeons practicing in resource-limited countries. This study was conducted to describe the clinicopathological profile and outcome of surgical treatment of abdominal tuberculosis in our setting and compare with what is described in literature. A prospective descriptive study of patients who presented with abdominal tuberculosis was conducted at Bugando Medical Centre (BMC) in northwestern Tanzania from January 2006 to February 2012. Ethical approval to conduct the study was obtained from relevant authorities. Statistical data analysis was performed using SPSS version 17.0. Out of 256 patients enrolled in the study, males outnumbered females. The median age was 28 years (range = 16-68 years). The majority of patients (77.3%) had primary abdominal tuberculosis. A total of 127 (49.6%) patients presented with intestinal obstruction, 106 (41.4%) with peritonitis, 17 (6.6%) with abdominal masses and 6 (2.3%) patients with multiple fistulae in ano. Forty-eight (18.8%) patients were HIV positive. A total of 212 (82.8%) patients underwent surgical treatment for abdominal tuberculosis. Bands /adhesions (58.5%) were the most common operative findings. Ileo-caecal region was the most common bowel involved in 122 (57.5%) patients. Release of adhesions and bands was the most frequent surgical procedure performed in 58.5% of cases. Complication and mortality rates were 29.7% and 18.8% respectively. The overall median length of hospital stay was 32 days and was significantly longer in patients with complications (p < 0.001). Advanced age (age ≥ 65 years), co-morbid illness, late presentation, HIV positivity and CD4+ count < 200 cells/μl were statistically significantly associated with mortality (p < 0.0001). The follow up of patients were generally poor as only 37.5% of patients were available for follow up at twelve months after discharge. Abdominal tuberculosis constitutes a major public health problem in our environment and presents a diagnostic challenge requiring a high index of clinical suspicion. Early diagnosis, early anti-tuberculous therapy and surgical treatment of the associated complications are essential for survival