title: Fabrication, microstructure, mechanical, and electrochemical properties of NiMnFeCu high entropy alloy from elemental powders

authors: Kumar, Ashok

subjects: high entropy alloys

abstract: Transition metal based high entropy alloys (HEAs) are often used in electrocatalytic (water electrolysis) applications due to the synergistic effect operating among its constituent elements and unpaired electrons in d orbitals of the concerned metal. In this study, a low cost NiMnFeCu high entropy alloy was successfully synthesised using the combined techniques of mechanical milling (MA) and vacuum sintering. X‐ray diffraction was used to analyse the phase composition, optical microscopy, and scanning electron microscopy were used to characterise the fabricated material’s microstructure and chemical homogeneity, thermal, and mechanical properties were tested using the differential scanning calorimetry method and a universal testing machine, respectively. Electrochemical workstation was used to carry out preliminary electrochemical studies such as linear sweep voltammetry (LSV), cyclic voltammetry (CV) and chronoamperometry. The results showed that the as‐ sintered NiMnFeCu HEA possessed a single‐ phase FCC structure. The HEA NiMnFeCu sintered at 1050 °C (S4) and 1000 °C (S2) with a holding time of 2 h showed a yield strength of 516.3 MPa and 389.8 MPa, respectively, and the micro‐hardness values were measured to be 233.45 ± 9 HV and 198.7 ± 8 HV, respectively. Preliminary electrochemical studies proved that the alloy sintered at 1000 °C (S2) with a holding time of 2 h exhibited excellent electrocatalytic properties with a measured overpotential of 322 mV at 10 mA cm⁻² at 100 cycles of CV and good stability for 10 h when compared to state‐of‐the‐art electrocatalytic materials IrO₂ and RuO₂ This suggested that the HEA NiMnFeCu fabricated under the condition S2 could potentially be used for industrial‐scale water electrolysis as it possesses permissible mechanical and good electrochemical properties.

text: Fabrication, microstructure, mechanical, and electrochemical properties of NiMnFeCu high entropy alloy from elemental powders Transition metal based high entropy alloys (HEAs) are often used in electrocatalytic (water electrolysis) applications due to the synergistic effect operating among its constituent elements and unpaired electrons in d orbitals of the concerned metal. In this study, a low cost NiMnFeCu high entropy alloy was successfully synthesised using the combined techniques of mechanical milling (MA) and vacuum sintering. X‐ray diffraction was used to analyse the phase composition, optical microscopy, and scanning electron microscopy were used to characterise the fabricated material’s microstructure and chemical homogeneity, thermal, and mechanical properties were tested using the differential scanning calorimetry method and a universal testing machine, respectively. Electrochemical workstation was used to carry out preliminary electrochemical studies such as linear sweep voltammetry (LSV), cyclic voltammetry (CV) and chronoamperometry. The results showed that the as‐ sintered NiMnFeCu HEA possessed a single‐ phase FCC structure. The HEA NiMnFeCu sintered at 1050 °C (S4) and 1000 °C (S2) with a holding time of 2 h showed a yield strength of 516.3 MPa and 389.8 MPa, respectively, and the micro‐hardness values were measured to be 233.45 ± 9 HV and 198.7 ± 8 HV, respectively. Preliminary electrochemical studies proved that the alloy sintered at 1000 °C (S2) with a holding time of 2 h exhibited excellent electrocatalytic properties with a measured overpotential of 322 mV at 10 mA cm⁻² at 100 cycles of CV and good stability for 10 h when compared to state‐of‐the‐art electrocatalytic materials IrO₂ and RuO₂ This suggested that the HEA NiMnFeCu fabricated under the condition S2 could potentially be used for industrial‐scale water electrolysis as it possesses permissible mechanical and good electrochemical properties.

year: 2022

title: Tie-breaking in Hoeffding trees

authors: Holmes, Geoffrey

subjects: computer science

abstract: A thorough examination of the performance of Hoeffding trees, state-of-the-art in classification for data streams, on a range of datasets reveals that tie breaking, an essential but supposedly rare procedure, is employed much more than expected. Testing with a lightweight method for handling continuous attributes, we find that the excessive invocation of tie breaking causes performance to degrade significantly on complex and noisy data. Investigating ways to reduce the number of tie breaks, we propose an adaptive method that overcomes the problem while not significantly affecting performance on simpler datasets.

text: Tie-breaking in Hoeffding trees A thorough examination of the performance of Hoeffding trees, state-of-the-art in classification for data streams, on a range of datasets reveals that tie breaking, an essential but supposedly rare procedure, is employed much more than expected. Testing with a lightweight method for handling continuous attributes, we find that the excessive invocation of tie breaking causes performance to degrade significantly on complex and noisy data. Investigating ways to reduce the number of tie breaks, we propose an adaptive method that overcomes the problem while not significantly affecting performance on simpler datasets.

year: 2005

title: Kei moenga - Tārā i te ārero. Lest it be severed from the tongue

authors: Bailey, Iraia Thompson

subjects: te reo Māori

abstract: Tūwharetoa are a distinctive tribal group who are located within the central North Island. With a proud and celebrated history, Tūwharetoa evolved through out time to become a complex and unique tribe, containing a number of sub tribes, each with its own authority, structure and land holdings. However, like all Māori, Tūwharetoa were greatly affected by the impact of European colonisation. In particular the unique language and customs of Tūwharetoa where savaged by the policy of assimilation and the introduction of a new language and its cultural beliefs. Presently the traditional language of Tūwharetoa is in a perilous state, and regardless of the many Māori language initiatives that have been established over the past few decades, the special language of Tūwharetoa is declining. This thesis is concerned with understanding the reasons why the traditional language of Tūwharetoa finds itself in this position, while also assessing the initatives implemented by Tūwharetoa to rectify this situation. Furthermore this study will look to create a possible pathway forward for Tūwharetoa to support the regeneration and revitalisation of the language. Ultimately this thesis will propose a framework bedded within language planning theory, supported by a kaupapa Māori research methodology and founded within the beliefs of Tūwharetoa, to see the return of te reo Māori as the main form of communication for the people of Tūwharetoa, and as a clear marker of our identity and uniqueness.

text: Kei moenga - Tārā i te ārero. Lest it be severed from the tongue Tūwharetoa are a distinctive tribal group who are located within the central North Island. With a proud and celebrated history, Tūwharetoa evolved through out time to become a complex and unique tribe, containing a number of sub tribes, each with its own authority, structure and land holdings. However, like all Māori, Tūwharetoa were greatly affected by the impact of European colonisation. In particular the unique language and customs of Tūwharetoa where savaged by the policy of assimilation and the introduction of a new language and its cultural beliefs. Presently the traditional language of Tūwharetoa is in a perilous state, and regardless of the many Māori language initiatives that have been established over the past few decades, the special language of Tūwharetoa is declining. This thesis is concerned with understanding the reasons why the traditional language of Tūwharetoa finds itself in this position, while also assessing the initatives implemented by Tūwharetoa to rectify this situation. Furthermore this study will look to create a possible pathway forward for Tūwharetoa to support the regeneration and revitalisation of the language. Ultimately this thesis will propose a framework bedded within language planning theory, supported by a kaupapa Māori research methodology and founded within the beliefs of Tūwharetoa, to see the return of te reo Māori as the main form of communication for the people of Tūwharetoa, and as a clear marker of our identity and uniqueness.

year: 2013