Total Minimal Dominating Signed Graph

Cartwright and Harary considered graphs in which vertices represent persons and the edges represent symmetric dyadic relations amongst persons each of which designated as being positive or negative according to whether the nature of the relationship is positive (friendly, like, etc.) or negative (hostile, dislike, etc.). Such a network S is called a signed graph. Signed graphs are much studied in literature because of their extensive use in modeling a variety socio-psychological process and also because of their interesting connections with many classical mathematical systems

A space odyssey

Space Tourism: opportunities and challenges of an emerging industr

Prediction of Microstructure for Heat Treatment Process in Dual Phase Steels using Cellular Automata

In this paper, a cellular automata method based model is proposed for simulating phase transformation kinetics of inter-critical heating of dual phase (DP) steel. This developed model deals with the kinetics of pearlite dissolution, ferrite transformation and austenite grain growth based on carbon diffusion process. The diffusion equation is discretized and solved by finite difference method (FDM) whereas austenite grain growth is controlled by transition rules applied in cellular automata algorithm. The model is operated in the temperature range of 730 0C to 890 0C for four different specimens of DP steel. This model predicts appropriately the microstructure and volume fraction of formed austenite during inter-critical heating of DP steel. In addition, this study shows that the presence of carbon and alloying elements enhances carbon equivalent of DP steel, helps in austenite formation

Synthesis, Characterization and Electrochemical Properties of Gold Nanomolecules

Chapter 1 gives a brief introduction to the field of gold nanomolecules. Various synthetic protocols and analytical techniques used through out this dissertation are discussed in detail. Size dependent properties of the gold nanomolecules are described. The structure of gold nanomolecules is explained based on the crystal structure of Au25(SCH2CH2Ph)18. The theoretical basis for the stability of the gold nanomolecules is explained using the super atom complex model and geometric parameters. Chapter 2 includes ligand exchange experiments on gold nanomolecules. Ligand exchange experiments are used to modify the monolayer of nanomolecules after synthesis. Ligand exchange reactions are monitored by mass spectrometry. Exploiting the mass difference of various ligands to monitor ligand exchange reactions is explained. Ligand exchange with dithiols is covered in this chapter. Interstaple vs intrastaple dithiol binding, optimum chain length for bidentate binding and effect on optical properties are studied in this project. Ligand exchange with other chalcogenide ligands like tellurides is discussed briefly. Chapter 3 covers the core size conversion reactions in gold nanomolecules. When gold nanomolecules are etched in excess thiols at elevated temperatures, some of the gold nanomolecules convert to a different size. Such change in core size is called core size conversion. Core size conversion in the larger and smaller sizes is studied in this project. Etching reactions are similar to ligand exchange except that they are more rigorous and performed at elevated temperatures. The use of core size conversion reactions as high yield synthetic protocols is explained. Some mechanistic details based on the mass spectrometric results are discussed. Chapter 4 covers the electrochemical properties of gold nanomolecules. The electrochemical behavior of gold nanomolecules is probed by voltammetry experiments. Cyclic voltammetry and differential pulse voltammetry are the primary techniques used for this purpose. The size dependence of electrochemical properties is demonstrated with different sizes. Solvent effects and the effect of alloying are also covered in detail. Chapter 5 covers mass spectrometry of gold nanomolecules. MALDI MS and ESI MS are the primary analytical techniques used to find the composition of gold nanomolecules. These techniques are increasingly used for studying synthesis, ligand exchange, alloying and fragmentation of gold nanomolecules. These techniques have several advantages and disadvantages for various applications. Applications of mass spectrometry tools for different applications are discussed with several case studies. Chapter 6 covers separation of gold nanomolecules by size exclusion chromatography. Size exclusion chromatography is the most efficient technique for separation of gold nanomolecules. Separation of different gold nanomolecules using size exclusion chromatography is described in this chapter. Advantages of size exclusion chromatography over conventional solvent fractionation techniques are demonstrated with examples. Chapter 7 highlights the contributions of this dissertation work to the field of gold nanomolecule research. Possible improvements and future directions of this research are presented

Learners’ educational aspirations in South Africa: The role of the home and the school

An extensive body of research exists on the background characteristics that predict learner achievement. However, in South Africa, little attention has been paid to the level of educational aspirations and the factors that shape the level of aspirations. Using a bio-ecological systems theory of development, we explored the role of gender, socio-economic status (determined by resources at home and school), parental involvement and school climate in determining educational aspirations. Using a nationally representative sample of 11,969 learners (females = 5,248; mean age = 15.7 years) from the Trends in International Mathematics and Science Study (TIMSS) and the statistical analysis technique of structural equation modelling (SEM), we investigated the relationships between parental involvement, school climate and learner educational aspirations. Our study showed that students from low socio-economic status (SES) homes and schools had lower educational aspirations. We also found positive relationships between both positive and negative school climate and learner aspirations. A surprising finding was that parental involvement did not have any influence on shaping learner aspirations. The findings indicate a need to improve educational resources at schools as well as the school climate, as schools matter for learners in low-income countries. Furthermore, it is important to inform learners of the requirements for tertiary education, so that they develop more realistic aspirations. Keywords: home resources; learner educational aspirations; parental involvement; school climate; school socio-economic statu

Investigational Analysis of Security Measures Effectiveness in Cloud Computing: A Study

In the modern era of business operation, the technical adoption of cloud services are high on rise by the large scale to small scale business establishment on various products and services. Needless to say that with the rise of adoption also gives birth to security concerns as cloud runs on common internet which are also used by trillions of internet-users. There are various means by which introducing a malicious program inside the cloud is not that complicated task for attacker. The various services providers as well as past researcher have introduced some of the potential security features which is claimed to be highly effective. However, accomplishing fail-proof security systems in cloud is never witnessed nor reported by any user or researcher, which clearly specifies that security problems do persist and are on exponential rise. Therefore, this paper discusses about the security issues in cloud supported by brief description of standard security models currently available in cloud. With extensive literatures on the existing security solutions, a significant research gap is explored in robust authentication system in cloud services. Keywords-component; Security, Cloud Computing,attacks, security model

How well do South African schools convert grade 8 achievement into matric outcomes?

School retention in South Africa and performance in the major school-leaving matric examination are characterised by significant inequalities on the basis of race and socio-economic status. In order to know at what point in the educational trajectory policy interventions and school improvement programmes will be most effective, it is necessary to trace the development of these educational inequalities to earlier phases of schooling and before. This paper reports on findings from a unique dataset that tracks individuals who participated in TIMSS in 2002 as grade 8 students to matric in 2006 and 2007. This permits an investigation into the extent to which educational inequalities are already evident by the eighth grade, and what if anything is achieved by secondary schools to reduce them. Several noteworthy findings emerge. The overall level of achievement, at both grade 8 and matric, differs widely across the historically different parts of the school system. There are also intriguing differences in the abilities of different parts of the system to convert grade 8 achievement into matric outcomes. What is clear is that inequalities in the cognitive ability of students at the outset of secondary school persist and that there is no observable evidence of a closing of these gaps by matric. This points to the importance of interventions prior to secondary school – at the primary school level and even at the level of early childhood development. Finally, it is also demonstrated that the decision to take mathematics in matric is characterised by a high degree of randomness within the historically black part of the school system. This points to the value of meaningful assessment practices and feedback to students, which serve as an important signal as to whether or not to choose mathematics as a matric subject.South Africa, Socio-economic Status, Education, Educational Achievement, Educational Inequality