BURA Community:
http://bura.brunel.ac.uk/handle/2438/8620
Sun, 22 Oct 2017 00:01:48 GMT2017-10-22T00:01:48ZA doping-less junction-formation mechanism between n-silicon and an atomically thin boron layer
http://bura.brunel.ac.uk/handle/2438/15285
Title: A doping-less junction-formation mechanism between n-silicon and an atomically thin boron layer
Authors: Fang, C; Mohammadi, V; Nihtianov, S
Abstract: The interest in nanostruc
tures of silicon and its dopants has significantly increased. We report the
creation of an ultimately-shallow junction at the surface of n-type silicon with excellent electrical and
optical characteristics made by depositing an atomically thin boron layer at a relatively low temperature
where no doping of silicon is expected. The presented experimental results and simulations of the ab
initio quantum mechanics molecular dynamics prove that the structure of this new type of junction
differs from all other known rectifying junctions at this time. An analysis of the junction formation has
led to the conclusion that the chemical interaction between the surface atoms of crystalline silicon
and the first atomic layer of the as-deposited amorphous boron is the dominant factor leading to the
formation of a depletion zone in the crystalline silicon which originates from the surface. The simulation
results show a very strong electric field across the c-Si/a-B interface systems where the charge transfer
occurs mainly from the interface Si atoms to the neighboring B atoms. This electric field appears to
be responsible for the creation of a depletion zone in the n-silicon resulting in a rectifying junctionformation
between the n-silicon and the atomically thin boron layer.Sun, 01 Jan 2017 00:00:00 GMThttp://bura.brunel.ac.uk/handle/2438/152852017-01-01T00:00:00Z[FAV- 05/10/2017-Mash] Buckling curves for stainless steel tubular columns
http://bura.brunel.ac.uk/handle/2438/15279
Title: [FAV- 05/10/2017-Mash] Buckling curves for stainless steel tubular columns
Authors: Afshan, S; Zhao, O; Gardner, L
Abstract: Towards the development of more resilient and sustainable structures, interest in the use of high performance construction materials, such as stainless steels, has increased in recent years. Recent studies [1] have highlighted a number of deficiencies in the flexural buckling provisions given in Eurocode 3: Part 1.4 for the design of stainless steel compression members. Therefore, this study aims to investigate the effect of production route (cold-formed and hot-finished) and material grade (austenitic, duplex and ferritic) on the behaviour and design of stainless steel square and rectangular hollow section columns. Test data from the literature combined with numerical modelling data generated as part of this study are used to derive a series of buckling curves for the design of stainless steel columns. Reliability analysis in accordance with Annex D of EN 1990 has been carried out to show that the proposed buckling curves comply with the Eurocode reliability requirements.Sun, 01 Jan 2017 00:00:00 GMThttp://bura.brunel.ac.uk/handle/2438/152792017-01-01T00:00:00ZMathematical model of sulphate ion concentration in a closed cooling system of a power plant
http://bura.brunel.ac.uk/handle/2438/15276
Title: Mathematical model of sulphate ion concentration in a closed cooling system of a power plant
Authors: Paweł, R; Krzyżyńska, R; Szeliga, Z; Jouhara, H
Abstract: In commercial power plants, water is used in many processes and its physical and chemical properties
have a significant impact on the efficiency of energy and heat production as well as failure-free operation.
One of the largest consumers of water in a power unit is the cooling system consisting of condensers and
cooling towers. In cooling towers, the main mechanism for the decrease in temperature of the water is its
partial evaporation, which causes a gradual decrease in the amount of circulating water and, on the other
hand, a continuous increase in the concentration of chemical compounds in the closed system. Among
others, an uncontrolled increase in the sulphate ion concentration in cooling water may cause the corrosion
of the concrete parts of the hydraulic system as well as an increase in the deposition of calcium salts
on the surfaces of the heat exchangers, thereby worsening the heat exchange processes inside the condenser.
The daily demand for fresh water in power plants often reaches tens of thousands of cubic metres and
so the amount of wastewater released also has a significant influence on the environment. Therefore the
Polish Ministry of Environment and EU directives have introduced, from the beginning of 2016, new limits
on the physical and chemical parameters of wastewater released to natural reservoirs. Taking into
account the previous regulations, the authors present a mathematical model which allows the prediction
of the daily changes of the sulphate ion concentration in the circulating water in a condenser - cooling
tower closed cooling system and the calculation of the minimum wastewater flow rate fulfilling legal
restrictions.Sun, 01 Jan 2017 00:00:00 GMThttp://bura.brunel.ac.uk/handle/2438/152762017-01-01T00:00:00ZStatistical methods for the analysis of corrosion data for integrity assessments
http://bura.brunel.ac.uk/handle/2438/15275
Title: Statistical methods for the analysis of corrosion data for integrity assessments
Authors: Tan, Hwei-Yang
Abstract: In the oil and gas industry, statistical methods have been used for corrosion analysis for various asset systems such as pipelines, storage tanks, and so on. However, few industrial standards and guidelines provide comprehensive stepwise procedures for the usage of statistical approaches for corrosion analysis. For example, the UK HSE (2002) report “Guidelines for the use of statistics for analysis of sample inspection of corrosion” demonstrates how statistical methods can be used to evaluate corrosion samples, but the methods explained in the document are very basic and do not consider risk factors such as pressure, temperature, design, external factors and other factors for the analyses. Furthermore, often the industrial practice that uses linear approximation on localised corrosion such as pitting is considered inappropriate as pitting growth is not uniform. The aim of this research is to develop an approach that models the stochastic behaviour of localised corrosion and demonstrate how the influencing factors can be linked to the corrosion analyses, for predicting the remaining useful life of components in oil and gas plants. This research addresses a challenge in industry practice. Non-destructive testing (NDT) and inspection techniques have improved in recent years making more and more data available to asset operators. However, this means that these data need to be processed to extract meaningful information. Increasing computer power has enabled the use of statistics for such data processing. Statistical software such as R and OpenBUGS is available to users to explore new and pragmatic statistical methods (e.g. regression models and stochastic models) and fully use the available data in the field. In this thesis, we carry out extreme value analysis to determine maximum defect depth of an offshore conductor pipe and simulate the defect depth using geometric Brownian motion in Chapter 2. In Chapter 3, we introduce a Weibull density regression that is based on a gamma transformation proportional hazards model to analyse the corrosion data of piping deadlegs. The density regression model takes multiple influencing factors into account; this model can be used to extrapolate the corrosion density of inaccessible deadlegs with data available from other piping systems. In Chapter 4, we demonstrate how the corrosion prediction models in Chapters 2 and 3 could be used to predict the remaining useful life of these components. Chapter 1 sets the background to the techniques used, and Chapter 5 presents concluding remarks based on the application of the techniques.
Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonSun, 01 Jan 2017 00:00:00 GMThttp://bura.brunel.ac.uk/handle/2438/152752017-01-01T00:00:00Z