Reconfigurable time interval measurement circuit incorporating a programmable gain time difference amplifier

PhD ThesisAs further advances are made in semiconductor manufacturing technology the performance of circuits is continuously increasing. Unfortunately, as the technology node descends deeper into the nanometre region, achieving the potential performance gain is becoming more of a challenge; due not only to the effects of process variation but also to the reduced timing margins between signals within the circuit creating timing problems. Production Standard Automatic Test Equipment (ATE) is incapable of performing internal timing measurements due, first to the lack of accessibility and second to the overall timing accuracy of the tester which is grossly inadequate. To address these issue ‘on-chip’ time measurement circuits have been developed in a similar way that built in self-test (BIST) evolved for ‘on-chip’ logic testing. This thesis describes the design and analysis of three time amplifier circuits. The analysis undertaken considers the operational aspects related to gain and input dynamic range, together with the robustness of the circuits to the effects of process, voltage and temperature (PVT) variations. The design which had the best overall performance was subsequently compared to a benchmark design, which used the ‘buffer delay offset’ technique for time amplification, and showed a marked 6.5 times improvement on the dynamic range extending this from 40 ps to 300ps. The new design was also more robust to the effects of PVT variations. The new time amplifier design was further developed to include an adjustable gain capability which could be varied in steps of approximately 7.5 from 4 to 117. The time amplifier was then connected to a 32-stage tapped delay line to create a reconfigurable time measurement circuit with an adjustable resolution range from 15 down to 0.5 ps and a dynamic range from 480 down to 16 ps depending upon the gain setting. The overall footprint of the measurement circuit, together with its calibration module occupies an area of 0.026 mm2 The final circuit, overall, satisfied the main design criteria for ‘on-chip’ time measurement circuitry, namely, it has a wide dynamic range, high resolution, robust to the effects of PVT and has a small area overhead.Umm Al-Qura University

Nanoparticles/polysaccharide nanocomposites for water purification

The main objective of this study was to synthesise of nanocomposites made of nanoparticles and cellulose or cellulose derivatives for the use of these in water purification. A variety of different kinds of nanoparticles were synthesised using similar approaches. Chapters one and two contain a literature review, introduction and technical information about the instruments. Chapter three includes all the experimental methodologies that have been used in general, while more details are giving late as required. Then, five chapters are about the synthesis and characterisation of specified nanocomposites and in each of these five chapters, water remediation was attempted.In chapter four, spherical silver nanostructures were synthesised in aqueous media and attached to cellulose paper: an environmentally porous support. The general method of synthesis was based on attaching Ag+ ions in the cellulose substrate then reducing these ions with sodium borohydride, a mild reducing agent. Different reaction conditions were investigated, for example precursors concentration and use of a stabiliser. The silver/cellulose nanocomposite was characterised with different analytical techniques. Silver nanoparticles appear as face-centred cubic (fcc) crystals of pure metallic silver. The quantity of silver nanoparticles was proportional to the concentration of silver ions in the precursor solution. Additional stabilised cellulose had a non-negligible impact: the investigations showed that its presence of them enhances the amount of silver nanoparticles immobilised in the samples. Moreover, it does not change the morphology of silver nanoparticles, although it helps keep these nanoparticles dispersed.In chapter five, nanocomposites were fabricated by interacting dispersion of nanoparticles with a support. First, a yellow dispersion of silver nanoparticles was synthesised by a chemical reduction method. The resulting dispersion of silver nanoparticles was stabilised by electrostatic forces. Attention was focused on the effect of temperature and addition method during the reduction step. The morphology of nanoparticles was investigated by quantitative and qualitative analytical techniques. Silver nanoparticles were spherical with a size of 17 nm ± 5.6, and shown to adsorb light ~ 400 nm due to surface plasmon resonance (SPR). The colloidal silver nanoparticles were put in contact with cellulose triacetate to prepare the composites. The process of adsorption was controlled by varying the pH of the dispersion. The coverage of silver nanoparticles over a solid substrate was evaluated by ICP analysis and visual observation. pH has a great impact on the improvement of quantity of silver nanoparticles over the surface; a homogenous yellow coverage of silver nanoparticles over cellulose triacetate was obtained at higher pH. Positive antibacterial action was observed from the silver cellulose triacete nanocomposites against MRSA.In chapter six, the electrochemical-behaviour of silver cellulose nanocomposites was investigated in relation to various parameters, i.e., the concentration of silver nanoparticles, electrolytes and concentration of electrolyte. The stripping of silver cellulose nanocomposites may depend on the size of the nanoparticles and the coverage of silver nanoparticles in the sample. Small nanoparticles showed a very sharp oxidation peak. However, polydispersed nanoparticles had slow and complex redox pattern. The peak potential varied with change in the electrolyte. The oxidation of silver nanoparticles was very sensitive to chloride ions. PXRD patterns confirmed the formation of silver chloride and silver nitrate. Silver cellulose nanocomposites have great potential in water purification.In chapter seven, cobalt nanoparticles was prepared by two synthetic approaches. The first approach involved the preparation of aqueous dispersions of cobalt nanoparticles by reduction of metal salt using sodium borohydride. A number of procedure conditions were investigated such as the precursor’s concentration, reduction time and temperature. In the first approach, highly crystalline cobalt nanoparticles with some other compounds were produced after further decomposing. Changing temperature has an impact on the crystal structure. The second approach involved saturating the porous, absorptive substrate with an aqueous solution of cobalt salt and then reducing the metal salt using sodium borohydride or hydrogen gas to cobalt nanoparticles in situ on the substrate surface. Cellulose was used to inhibit aggregation and agglomeration of the cobalt nanoparticles. It was likely that chemical reduction using sodium borohydride formed a mixture of spherical crystal and amorphous cobalt nanoparticles. In contrast, reduction by hydrogen gas may produce spherical crystal cobalt nanoparticles Therefore, cellulose substrate and hydrogen gas have potential in green synthesis of cobalt cellulose nanocomposites. The potential for using cobalt nanoparticles in wastewater treatment and a medical setting is high as cobalt nanoparticles mainly showed good antibacterial action against all bacterial isolates tested with zone of inhibition sizes up to 15 mm.In chapter eight, the green synthesis of copper nanoparticles and copper cellulose nanocomposites was carried out using a simple reduction method. Mixtures of copper and copper oxide nanoparticles were synthesised by reduction of copper ions using sodium borohydride, in different reaction conditio ns: concentration, atmosphere, temperature and using a stabiliser. The natural substrate cellulose was used to stabilise the nanoparticles. The physicochemical properties of copper as free nanoparticles and as copper cellulose nanocomposites were investigated. PXRD was used to identify the structure of the copper nanoparticles and show the effect of reaction condition, i.e., concentration precursor on crystal structures. PXRD patterns, TEM images and UV-VIS display the impact of cellulose on nanoparticle size, i.e., the presence of cellulose reduces the size of copper nanoparticles formed. Copper cellulose nanocomposites and copper nanoparticles had only sufficient or limited antibacterial action. Increasing the concentration of copper nanoparticles in samples may improve antibacterial activity

Defragmenting the terms self-employed, entrepreneur and business owner

There is a growing belief from a range of sources that the only way forward economically is through the support and growth of entrepreneurial behaviour (Olaison, & Sørensen, 2014). Consequently, governments have been developing policies to facilitate entrepreneurship, universities have set up programmes to encourage entrepreneurship and organisations exist to support entrepreneurship (Rae and Woodier-Harris N, 2012; Anderson et al, 2014). Unfortunately, it is not clear exactly what entrepreneurial behaviour is and is not (Hunter, 2012). There are multiple theories on the nature of entrepreneurial behaviour (Shook, Priem, & McGee, 2003; Davidson, 2004; O’Gorman, 2015). This lack of clarity and disagreement causes confusion about the roles and actions of people who engage in entrepreneurial behaviour (Lyons, Lynn, & Bhaird, 2015). Part of the confusion lies in the way people who own operate businesses are defined. Traditionally people who work for themselves are seen as either self-employed, entrepreneurs or business owners. However, despite having different meanings, the terms are often used interchangeably (Parker, 2004; Hartog et al., 2010; Van Solinge, 2015), primarily for the purpose of convenience or simplicity. The interchangeable use of the terms in an environment, in which entrepreneurial behaviour is the favoured phenomenon, is likely to suppress important debates around the nature of entrepreneurial behaviour. This suppression is likely to divert the attention of policy makers and supporters away from important issues concerning the different roles, functions and needs of the self-employed, entrepreneurs or business owners. As a result, support that focuses on entrepreneurship could be at the expense of the other roles. Therefore, there is a need for academic research to seek clarity concerning the use of different terms used to describe people who work for themselves. The authors intend to present a discussion paper that aims to generate some clarity around what the terms self-employed, entrepreneur and business owner actually mean. The purpose of this study is to consolidate a number of notions, theories and concepts found in the literature concerning the definition, conceptualisation and characterisation of self-employed, entrepreneur and business owner. The intention is to identify both similarities or overlaps and distinct differences, in order construct a model that embraces self-employed, entrepreneur and business owner in a single structure

The Level of Awareness of Female Teachers of Students with Learning Disabilities with the Concepts of Sustainable Development and Their Application in Elementary Schools

The current study aimed to identify the level of familiarity of teachers with learning disabilities with the concepts of sustainable development and their application in the elementary schools in the Kingdom of Saudi Arabia. Learning disabilities in the concepts of sustainable development, and the second dimension is their application of these concepts in the primary stage, and the psychometric properties of validity and stability were verified, and the study sample consisted of (100) female teachers. The results found that there were no differences in the teachers’ knowledge of the concepts of sustainable development and their application in the primary stage due to the variable of experience, while it was found that there were differences due to the variable of academic qualification in favor of the higher qualification over the lower one. Generally, the total mean of the awareness and application for the age (from 1 to 5 years is 4.17) and the SD is 0.89, (from 5 to 10 years is 4.35) and the SD is 0.59, (from 10 to 15 years is 4.27) and the SD is 0.81, and (more than 15 years 13 is 4.37) and the SD is 0.52.The study came out with some recommendations, it is necessary to strengthen and encourage female teachers to maintain a high level of awareness and application of the concepts of sustainable development in schools for elementary school

A nationwide study on the knowledge, awareness, and practices towards COVID-19 in Saudi Arabia

Purpose: To investigate public knowledge, awareness and practice regarding COVID-19 in Saudi Arabia.Methods: A cross-sectional descriptive study was conducted, with a 16-item self-administered questionnaire. Data was collected using social media as the platform a day after the lockdown commenced in Saudi Arabia and data collection lasted from March 25 to April 25, 2020. Chi-square test was performed to determine the association between the variables.Results: The results showed that 96 % (n = 1505) of adults were aware of the clinical symptoms of COVID-19 and 57.9 % (n = 908) correctly identified that a stuffy nose and sneezing were less common in persons infected with the virus. A majority (95.4 %, n = 1495) agreed that there was no established therapeutic treatment for COVID-19. Further, 91.7 % (n = 1437) agreed that the virus could spread via respiratory droplets and only 46.2 % (n = 724) acknowledged that wearing face mask helped prevent transmission. The results also showed that 83.2 % (n = 1299) of the participants thought that visiting crowded places increased the likelihood of transmission.Conclusion: The findings of this study reveal that adults in Saudi Arabia are cognizant of COVID-19 and maintained good attitudes and practices regarding it. Furthermore, health education programs aimed at improving awareness of the disease and appropriate control measures will be beneficial in curbing the virus pandemic. Keywords: Saudi Arabia, Coronavirus, Pandemic, COVID-19, Flu, Symptom

Algorithms for the Construction of Constrained and Unconstrained Optimal Designs

Chapter 1 provides an introduction to the area of optimum experimental design for the linear regression design problem with parameter vector theta. This problem seeks to obtain a best inference for all or some of the components of theta by making the dispersion matrix of their estimates small in some sense. In this chapter we summarise the main criteria used for this purpose. Chapter 2 studies a class of multiplicative algorithms of the form Pi(r+1)=pi(r)(di,delta) / SigmaJipj(r)f(dj,delta) indexed by a function f(d,delta) which depends on the derivatives of the criterion &phis;(p) and a free parameter delta for solving problem (a). The performance of the algorithm is investigated in constructing D-optimal designs under optimal choices of the parameter delta, and in constructing c-optimal designs starting from difficult initial designs, using an optimal and fixed value of the parameter delta. The work for this chapter has appeared in Torsney and Alahmadi (1992). Chapter 3 considers the covariance and correlation criterion of problem(b). The only property we know of these criteria is homogeneity in the weights p of degree -2 and zero respectively. This type of criterion differs from the standard optimality criteria such as c-, D- and A-optimality criteria. It may have negative first partial derivatives. An explicit solution has been found for the optimal weights and the optimal value for the covariance criterion when the number of design points equals the number of parameters i.e J = k, while in the case when J > k we have explored a new version of the above algorithm for dealing with this type of problem. Chapters 4 and 5 are concerned with the solution of problem (c). In Chapter 4 we consider the case when the number of design points equals the number of the unknown parameters theta. In this case we find a class of designs which guarantees zero covariance. Zero covariance is guaranteed under a transformation of the design weights p to two or three sets of variables each of which forms a probability vector. We wish to maximise standard design criteria with respect to these weights. This yields an extension of problem (a) of Chapter 2 to that of maximising a criterion with respect to two probability vectors and we use a natural extension of the algorithm used for that problem. For the above mentioned results the efficiencies of the restricted optimal design under the zero covariance constraint relevant to the unrestricted optimal design has been calculated. Chapter 5 considers the case when the number of design points exceeds the number of the parameters. Using a Lagrangian approach, the problem is transformed to one of simultaneous maximisation of two functions of the same probability vector each of which is maximised at the same value of this vector and have a common maximum of zero. This yields another extension of problem (a). Chapter 6 summarises the results obtained in the preceding chapters as well as giving an indication of future work that could be done