Classification of order sixteen non-symplectic automorphisms on K3 surfaces

We classify K3 surfaces with non-symplectic automorphism of order 16 in full generality. We show that the fixed locus contains only rational curves and points and we completely classify the seven possible configurations. If the N\'eron-Severi group has rank 6, there are two possibilities and if its rank is 14, there are five possibilities. In particular if the action of the automorphism is trivial on the N\'eron-Severi group, then we show that its rank is six.Comment: 15 page

Development and Application of Novel Sodium Silicate Microcapsule-Based Self-Healing Oil Well Cement

A majority of well integrity problems originate from cracks of oil well cement. To address the crack issues, bespoke sodium silicate microcapsules were used in this study for introducing autonomous crack healing ability to oil well cement under high-temperature service conditions at 80 °C. Two types of sodium silicate microcapsule, which differed in their polyurea shell properties, were first evaluated on their suitability for use under the high temperature of 80 °C in the wellbore. Both types of microcapsules showed good thermal stability and survivability during mixing. The microcapsules with a more rigid shell were chosen over microcapsule with a more rubbery shell for further tests on the self-healing efficiency since the former had much less negative effect on the oil well cement strength. It was found that oil well cement itself showed very little healing capability when cured at 80 °C, but the addition of the microcapsules significantly promoted its self-healing performance. After healing for 7 days at 80 °C, the microcapsule-containing cement pastes achieved crack depth reduction up to ~58%, sorptivity coefficient reduction up to ~76%, and flexural strength regain up to ~27%. The microstructure analysis further confirmed the stability of microcapsules and their self-healing reactions upon cracking in the high temperature oil well cement system. These results provide a promising perspective for the development of self-healing microcapsule-based oil well cements

Three-year performance of in-situ mass stabilised contaminated site soils using MgO-bearing binders

This paper provides physical and chemical performances of mass stabilised organic and inorganic contaminated site soils using a new group of MgO-bearing binders over 3 years and evaluated the time-dependent performance during the 3 years. This study took place at a contaminated site in Castleford, UK in 2011, where MgO, ground granulated blastfurnace slag (GGBS) and Portland cement (PC) were mixed with the contaminated soils in a dry form using the ALLU mass mixing equipment. Soil cores were retrieved 40-day, 1-year and 3-year after the treatment. The core quality, strength, and the leaching properties were determined via physical observation, unconfined compressive strength (UCS) and batch leaching tests. After 3-year treatment, the UCS values of ALLU mixes were in the range of 50–250 kPa; the leachate concentrations of Cd, Pb, Cu and Zn (except Ni) in all mixes were lower than their drinking water standards; and the leachability of total organics was in the range of 10–105 mg/L. No apparent degradation of the mass stabilised materials after 3 years’ exposure to the field conditions was found. MgO-GGBS blends were found able to provide higher strength and less leachability of contaminants compared to PC and MgO-only mixes in mass stabilised soils

Strength and drying shrinkage of slag paste activated by sodium carbonate and reactive MgO

This paper investigates the potential of combining Na2CO3 and reactive MgO as a sustainable activator for ground granulated blastfurnace slag. Two very different reactivity MgOs were added at 5–10 % and the Na2CO3 content varied from 4% to 8% by the weight of slag. The strength and drying shrinkage of the activated slag pastes were tested up to 90 d. It was found that the optimum reactive MgO addition was 5% regardless of the MgO type and Na2CO3 content. MgO with the higher reactivity significantly increased the early strength of the paste but had almost no effect on the strength at 90 d. On the other hand, the effect of the lower reactivity MgO on the strength was more profound at later ages and low Na2CO3 dosage. In terms of drying shrinkage, increasing the Na2CO3 content from 4% to 6% caused a remarkable decrease of drying shrinkage while increasing it from 6% to 8% had negligible effect. X-ray diffraction and thermogravimetric analysis revealed that the major hydration products were calcium silicate hydrate gel and hydrotalcite-like phases, similar to those in conventional alkali-activated slag cements. There was also a large quantity of calcite formed especially in the 8% Na2CO3 pastes due to causticisation. It was concluded that the combination of reactive MgO and Na2CO3 could serve as a potential sustainable activator for slags.The first author is grateful to Cambridge Trust and China Scholarship Council (CSC) for sponsoring his Ph.D. studentship.This is the accepted manuscript for a paper published in Construction and Building Materials, Volume 81, 15 April 2015, Pages 58–65, doi:10.1016/j.conbuildmat.2015.01.08

Evaluation of novel reactive MgO activated slag binder for the immobilisation of lead and zinc.

Although Portland cement is the most widely used binder in the stabilisation/solidification (S/S) processes, slag-based binders have gained significant attention recently due to their economic and environmental merits. In the present study, a novel binder, reactive MgO activated slag, is compared with hydrated lime activated slag in the immobilisation of lead and zinc. A series of lead or zinc-doped pastes and mortars were prepared with metal to binder ratio from 0.25% to 1%. The hydration products and microstructure were studied by X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The major hydration products were calcium silicate hydrate and hydrotalcite-like phases. The unconfined compressive strength was measured up to 160 d. Findings show that lead had a slight influence on the strength of MgO-slag paste while zinc reduced the strength significantly as its concentration increased. Leachate results using the TCLP tests revealed that the immobilisation degree was dependent on the pH and reactive MgO activated slag showed an increased pH buffering capacity, and thus improved the immobilisation efficiency compared to lime activated slag. It was proposed that zinc was mainly immobilised within the structure of the hydrotalcite-like phases or in the form of calcium zincate, while lead was primarily precipitated as the hydroxide. It is concluded, therefore, that reactive MgO activated slag can serve as clinker-free alternative binder in the S/S process.The authors are grateful to Cambridge Trust and China Scholarship Council (CSC) for their financial help of the PhD studentship for the first author.This is the accepted manuscript version. The final version is published by Chemosphere here: http://dx.doi.org/10.1016/j.chemosphere.2014.07.027

The role of brucite, ground granulated blastfurnace slag, and magnesium silicates in the carbonation and performance of MgO cements

This study focuses on the enhancement of the technical and environmental performance of MgO cements through the inclusion of brucite, GGBS, talc and serpentine as partial MgO substitutes in concrete blocks. The influence of these additives on the microstructure, hydration, carbonation, and mechanical performance of blocks cured under natural and elevated CO2 conditions is presented. An optimum replacement level was determined for each composition via unconfined compressive strength (UCS), scanning electron microscopy (SEM), x-ray diffraction (XRD), thermogravimetric analysis (TGA) and acid digestion. Mixes subjected to accelerated carbonation indicated up to 100% carbonation in 7 days. Results highlight the suitability of each additive in replacing MgO without compromising performance.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.conbuildmat.2015.07.10

Alliance management capability and SMEs’ international expansion : The role of innovation pathways

Although alliance management capability (AMC) has been widely investigated as a firm-level performance driver, it is still unclear whether and how this distinctive type of relational capability can enhance small and medium-sized enterprises (SMEs) internationalization activity. By integrating the alliance capability literature and resource-based view (RBV), as well as using data collected from a sample comprising 248 SMEs in UK manufacturing industries, we address this gap by examining the mechanisms through which SMEs can expand their internationalization via collaboration. We found support for our contention that AMC enhances radical and incremental co-innovation in SMEs, culminating in the international expansion of these firms. Additionally, we reveal the moderating effects of alliance partner diversity on the AMC and co-innovation relationship. The results offer both theoretical and managerial insights, contributing to a better understanding of how SMEs can leverage AMC to drive their global expansion strategies.© 2023 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

Microfluidic fabrication of microcapsules tailored for self-healing in cementitious materials

Autonomic self-healing in cement-based infrastructure materials has recently emerged as a promising strategy for extending the service life of concrete infrastructure. Amongst the various self-healing systems being developed, the use of microcapsules has received significant attention partly because of its ease implementation. Up to date, microcapsules for self-healing applications have been mainly manufactured using bulk emulsifications polymerisation techniques. However this methodology raises concerns regarding shell dimensions and interfacial bonding. This study proposes for the first time the fabrication of microcapsules with tailored characteristics for mechanically triggered self-healing action in cement-based composites. For this, a microfluidic device was used to produce a double emulsion template for the formation of microcapsules, containing both aqueous and organic liquid core. In addition, a novel method has been proposed to functionalize the microcapsules' surface with hydrophilic groups in order to increase the interfacial bond with the cementitious host matrix. The core retention was studied using EDX and TGA, and their mechanical triggering was investigated via SEM of the microcapsules embedded in the cement paste. The results demonstrated the capability of microfluidics to produce microcapsules with liquid organic core, thin shell, hydrophilic surface and appropriate fracture strength for use in mechanically triggered self-healing of cementitious materials.CAPES (Brazilian funding) and EPSR

Graphene nanoplatelet reinforced concrete for self-sensing structures – A lifecycle assessment perspective

Concrete is the most widely used construction material, however, concrete structures often suffer from poor durability and require frequent inspections and repairs. Concrete production is also associated with high carbon emissions and the large-scale depletion of natural resources. Recently, the addition of graphene nanoplatelets (GNPs) in cementitious materials has shown a potential to improve the performance and instigate additional functionalities. However, there is limited understanding around the environmental effects from the production of GNP and its incorporation in concrete. This study has investigated, by means of a Life Cycle Assessment (LCA), the environmental impact of concrete reinforced with graphene nanoplatelets by focusing on the “cradle-to-gate” of GNP production and their incorporation in concrete. The production of 1 kg of G2NanPaste (GNPs product) is found to result in 0.17 kgCO2 equivalent units which is lower than Portland cement (0.86 kgCO2 eq). Ordinary Portland cement (CEM I) is 248 times more damaging than G2NanPaste in terms of global warming. The superplasticiser addition is found to have a greater environmental impact compared to G2NanPaste. The sensitivity analysis showed that if the addition of GNPs results in a 5% reduction of the Portland cement, the effect of the concrete mix on global warming can be reduced by 21%. This indicates that GNPs could be environmentally friendly if used as a supplement for some of the cement. The main aim of this paper is to perform the first LCA of the addition of graphene nanoplatelets in concrete. It is hoped that this work will pave the way for further research in this area.Costain Group plc

Defining Niger Delta Soils – Are They Laterites?

This is the final published version. It was first published by IISTE at http://www.iiste.org/Journals/index.php/CER/article/view/22179.The ambiguity of the use of the term ‘laterite’ to generally classify tropical soils especially for engineering purposes needed to be addressed. An attempt was made to analyze the silica-sesquioxide ratio of some Niger Delta soils to establish whether these soils which are formed in the tropic are indeed laterites. This ratio is used because it is generally accepted as a parameter in the classification and specification of laterites and can be measured with some degree of accuracy in the laboratory. This study revealed that these soils (except the ferralsols) which were soft when wet and significantly hard when air-dried could not be called laterite soils because of the high silica-sesquioxide ratios. It is envisaged that this study would help the engineers in the region to have a better understanding of the soils which are erroneously acclaimed and handled as laterite soils