Fenites associated with carbonatite complexes : a review

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Carbonatites and alkaline-silicate rocks are the most important sources of rare earth elements (REE) and niobium (Nb), both of which are metals imperative to technological advancement and associated with high risks of supply interruption. Cooling and crystallizing carbonatitic and alkaline melts expel multiple pulses of alkali-rich aqueous fluids which metasomatize the surrounding country rocks, forming fenites during a process called fenitization. These alkalis and volatiles are original constituents of the magma that are not recorded in the carbonatite rock, and therefore fenites should not be dismissed during the description of a carbonatite system. This paper reviews the existing literature, focusing on 17 worldwide carbonatite complexes whose attributes are used to discuss the main features and processes of fenitization. Although many attempts have been made in the literature to categorize and name fenites, it is recommended that the IUGS metamorphic nomenclature be used to describe predominant mineralogy and textures. Complexing anions greatly enhance the solubility of REE and Nb in these fenitizing fluids, mobilizing them into the surrounding country rock, and precipitating REE- and Nb-enriched micro-mineral assemblages. As such, fenites have significant potential to be used as an exploration tool to find mineralized intrusions in a similar way alteration patterns are used in other ore systems, such as porphyry copper deposits. Strong trends have been identified between the presence of more complex veining textures, mineralogy and brecciation in fenites with intermediate stage Nb-enriched and later stage REE enriched magmas. However, compiling this evidence has also highlighted large gaps in the literature relating to fenitization. These need to be addressed before fenite can be used as a comprehensive and effective exploration tool.This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant No 689909

Effect of different curing method for coconut shell concrete

A study on flexural strength of Coconut Shell Concrete(CSC) by different type of curing method. The concrete produced by using 25% of coconut shell in coarse aggregates satisfies the minimum necessities of concrete. CSC has superior workability because of the smooth surface on one side of the shells. The impact resistance of CSC is high when compared with conventional concrete. Curing is the maintaining of a satisfactory moisture content and temperature in concrete during its early stage so that desired properties may develop. The strength and durability of concrete will be fully achieved if the concrete sample pass through the curing process. This study is focused on flexural strength of CSC which varies by different type of curing method. Two types of concrete mix were chosen for this study which is CSC and Normal Concrete(NC). The mixture of concrete poured in 24 mould as simple beam and pass through two type curing methods for 7 days and 28 days. Flexural tests were carried out to determine the flexural strength using simple beam specimens. It was observed that when CSC pass through two types of curing method, flexural strengths are comparable in between two curing methods. It was observed that when coconut shells as aggregate in proportions of 25% was used in CSC, flexural strengths comparable to that of NC can be obtained

Security system for ad-hoc wireless networks based on generic secure objects

As computing devices and wireless connectivity become ubiquitous, new usage scenarios emerge, where wireless communication links between mobile devices are established in an ad-hoc manner. The resulting wireless ad-hoc networks differ from classical computer networks in a number of ways, lack of permanent access to the global network and heterogeneous structure being some of them. Therefore, security services and mechanisms that have been designed for classical computer networks are not always the optimal solution in an ad-hoc network environment. The research is focused on analyzing how standard security services that are available in classical networks can be provided in an ad-hoc wireless network environment. The goal is to design a security system optimized for operation in ad-hoc wireless networks that provides the same security services – authentication, access control, data confidentiality and integrity, non-repudiation – currently available in classic wired networks. The first part of the thesis is the design and implementation of a security platform based on generic secure objects. The flexible and modular nature of this platform makes it suitable for deployment on devices that form ad-hoc networks – ranging from Java-enabled phones to PDAs and laptops. We then investigate the problems that appear when implementing in ad-hoc networks some of the security technologies that are standard building blocks of secure systems in classical computer networks. Two such technologies have been found to present problems, namely the areas of certification and access control. In a series of articles, we have described the problems that appear and devised solutions to them by designing protocols, techniques and extensions to standards that are optimized for usage in the ad-hoc network environment. These techniques, together with the functionality provided by the underlying security platform, are used to implement all standard security services – confidentiality, authentication, access control, non repudiation and integrity, allowing to integrate ad-hoc networks into the existing security infrastructure.QC 2010100