Computing in a social context : gender difference in participation

The thesis reviews the literature relating to girls and computing within a framework which is structured around three specific questions. First, are there differences between girls and boys in their participation in class computing activities and/or in non-class computing activities? Second, do these differences in participation in computing activities have broader implications which justify the growing concern about the under-representation of girls? Third, wahy are girls under-represented in these activities? Although the available literature is predominantly descriptive, the underlying implicit theoretical model is essentially a social learning model. Girl's differential participation is attributed to learned attitudes towards computing rathan to differences between girls and boys in general ability. These attitudes, which stress the masculine, mathematical, technological aspects of computing are developed through modelling, direct experience, intrinsic and extrinsic reinforcement and generalisation from pre-existing, attitudes to related curriculum areas. In the literature it is implicitly assumed that these attitudes underlie girl's decisions to self-select out of computing activities. In this thesis predictions from a social learning model are complemented by predictions derived from expectancy-value, cognitive dissonance and self-perception theories. These are tested in three separate studies. Study one provides data from a pretest-posttest study of 24 children in a year four class learning BASIC. It examines pre- and posttest differences between girls and boys in computing experience, knowledge and achievement as well as the factors relating to computing achievement. Study two uses a pretest-posttest control group design to study the gender differences in the impact of the introduction of Logo into years 1, 3, 5 and 7 in both a coeducational and single-sex setting using a sample of 222 children from three schools. Study three utilises a larger sample of 1176 students, drawn from three secondary schools and five primary schools, enabling an evaluation of gender differences in relation to a wide range of class computing experiences and in a broader range of school contexts. The overall results are consistent across the three studies, supporting the contention that social factors, rather than ability differences influence girls' participation and achievement in computing. The more global theoretical framework, drawing on social learning, expectancy-value, cognitive dissonance and self-perception theories, provides a more adequate explanation of gender differences in participation than does any one of these models.

Sperm competition and offspring viability at hybridization in Australian tree frogs, Litoria peronii and L. tyleri

Hybridization between closely related species often leads to reduced viability or fertility of offspring. Complete failure of hybrid offspring (post-zygotic hybrid incompatibilities) may have an important role in maintaining the integrity of reproductive barriers between closely related species. We show elsewhere that in Peron's tree frog, Litoria peronii, males more closely related to a female sire more offspring in sperm competition with a less related rival male. Observations of rare 'phenotypic intermediate' males between L. peronii and the closely related L. tyleri made us suggest that these relatedness effects on siring success may be because of selection arising from risks of costly hybridization between the two species. Here, we test this hypothesis in an extensive sperm competition experiment, which shows that there is no effect of species identity on probability of fertilization in sperm competition trials controlling for sperm concentration and sperm viability. Instead, there was a close agreement between a male's siring success in isolation with a female and his siring success with the same female in competition with a rival male regardless of species identity. Offspring viability and survival, however, were strongly influenced by species identity. Over a 14-day period, hybrid offspring suffered increasing mortality and developed more malformations and an obvious inability to swim and right themselves, leading to compromised probability of survival. Thus, hybridization in these sympatric tree frogs does not compromise fertilization but has a strong impact on offspring viability and opportunity for reinforcement selection on mate choice for conspecific partners.

Status - based routing in baggage handling systems : searching verses learning

This study contributes to work in baggage handling system (BHS) control, specifically dynamic bag routing. Although studies in BHS agent-based control have examined the need for intelligent control, but there has not been an effort to explore the dynamic routing problem. As such, this study provides additional insight into how agents can learn to route in a BHS. This study describes a BHS status-based routing algorithm that applies learning methods to select criteria based on routing decisions. Although numerous studies have identified the need for dynamic routing, little analytic attention has been paid to intelligent agents for learning routing tables rather than manual creation of routing rules. We address this issue by demonstrating the ability of agents to learn how to route based on bag status, a robust method that is able to function in a variety of different BHS designs.

Evaluation of effective material properties of composite materials using special FEM

In the present paper, a novel method using the special 2D finite element method (FEM) and the concept of equivalent homogeneous materials has been employed to evaluate the effective material properties of composites. Special 2D finite elements containing an internal defect or reinforcement have been well developed in order to greatly simplify the numerical modeling of composites. It can assure the high precision especially in the vicinity of defects or reinforcements in composite materials. Some numerical examples will be provided to demonstrate the validity and versatility of the proposed method by comparing the existing results from other literatures.

Mg-based metallic glass / titanium interpenetrating phase composite with high mechanical performance

We report an Mg-based metallic glass/titanium interpenetrating phase composite in which constituent phases form a homogeneously interconnected network. The porous titanium constrains shear bands propagation thoroughly and promotes shear bands branching and intersection subsequently. The homogeneous phase distribution promotes regularly distributed local shear deformation and leads to a uniform deformation for the composites. Moreover, the interpenetrating phase structure introduces a mutual-reinforcement between metallic glass and titanium. Therefore, the composite exhibits excellent mechanical performance with compressive fracture strength of 1783 MPa and fracture strain of 31%.

Project team trust in leadership and leader values

This international research showed that when senior leaders' values and behaviours were perceived as being congruent by project teams, there was enrichment of interpersonal relationships and a reinforcement of relational trust. Conversely, when leaders' values and behaviours were perceived as not congruent, they were considered to lack integrity and trustworthiness.

Sensitivity to motivational cues in attention-deficit / hyperactivity disorder

This thesis examined a prediction of Reinforcement Sensitivity Theory regarding the association between personality traits and motivated behaviour and, whether reward-and-punishment sensitivity is associated with Attention-deficit / Hyperactivity disorder (ADHD). Results supported the predicted association between personality and motivated behaviour, but not the predicted association between reward-and-punishment sensitivity and ADHD.

Leisure-time physical activity, inactivity and sedentary behaviours

Assesses the relationship between leisure-time physical activity and sedentary behaviours in two cross-sectional studies of adults. Behavioural choice theory was applied to gain a better understanding of people's time allocation in these behaviours. The findings show that preference, reinforcement, and barriers are potentially important factors to consider in the study of the increasing population prevalence of sedentary lifestyles.

A study on the thermodynamics of in situ MgAl2O4/Al MMC formation using amorphous silica sources

MgAl₂O₄ (spinel) is considered as a commercially important ceramic reinforcement in MMC fabrication because of the possible tailorable properties imparted with Al for many applications. Generally, any oxygen source, i.e., the dissolved oxygen, or pure oxygen atmosphere or atmospheric oxygen is sufficient for the formation of MgAl₂O₄ in Al–Mg alloy. Among all the reactive oxygen sources, the reactivity of SiO₂ with Al alloy is found to be higher. Amorphous silica is highly reactive in nature compared to crystalline silica. The present study has examined the thermodynamics of MgAl₂O₄ formation in Al–Mg alloy by amorphous silica sources with the aid of differential thermal analyzer (DTA) and the simulated experiments. The dissolution of Si and the formation of MgAl₂O₄ are detected as the endothermic peak and the immediate exothermic peak respectively in DTA curves and the presence of MgAl₂O₄ is confirmed by the XRD of the simulated sample. The MgO formed due to the oxidation of Mg in Al–Mg alloy has been found to influence the MgAl₂O₄ formation.

High-performance composite from epoxy and glass fibers : morphology, mechanical, dynamic mechanical, and thermal analysis

Diglycidyl ether of bisphenol-A type epoxy resin cured with diamino diphenyl sulfone was used as the matrix for fiber-reinforced composites to get improved mechanical and thermal properties for the resulting composites. E-glass fiber was used for fiber reinforcement. The morphology, tensile, flexural, impact, dynamic mechanical, and thermal properties of the composites were analyzed. The tensile, flexural, and impact properties showed dramatic improvement with the addition of glass fibers. Dynamic mechanical analysis was performed to obtain the Tg of the cured matrix as well as the composites. The improved thermal stability of the composites was clear from the thermogravimetric analysis. Scanning electron micrographs were taken to understand the interfacial adhesion between the fiber and the matrix. The values of mechanical properties were compared with modified epoxy resin composite system. Predictive models were applied using various equations to compare the mechanical data obtained theoretically and experimentally.

Concentration monitoring and performance of a migratory corrosion inhibitor in steel-reinforced concrete

Inhibitor concentration depth profiles for concrete samples treated with a proprietary migratory corrosion inhibitor (of the Cortec MCI range) are presented. The treated concrete was cored and these cores were then sectioned and crushed before being immersed in distilled water to extract the available inhibitor. The amine concentrations were quantified using an ammonium-sensing electrode and were then related to the inhibitor concentration present. The inhibitor examined, reported to contain a combination of volatile amines and amino carboxylate compounds, was found to readily diffuse through concrete. The inhibitor was subjected to a 5-year trial and found to be effective in suppressing corrosion of steel reinforcement in the presence of high chloride concentrations. The concentration profiles indicate that only relatively low concentrations of inhibitor were required to achieve inhibition in this case.

Simulation-based learning for control of complex conveyor networks

This research investigated the problem of path planning in complex conveyor networks. A reinforcement learning approach was applied to derive a control strategy for routing traffic. The derived strategy was verified in real world systems and was found to improve network performance by prioritising traffic flows and balancing network load.

Research contributions to development of particulate reinforced MMCs by theoretical and experimental studies

This thesis is a compilation of eighty publications on analytical, experimental and numerical studies on the mechanical, tribological and corrosion behaviour of metal matrix composites (MMCs). The models based on the interface between matrix and reinforcement behaviour help accurate prediction of density and locked up hysterysis-strain in the composites at elevated temperatures.

Self-assembled natural rubber/multi-walled carbon nanotube composites using latex compounding techniques

Functionalization of multi-walled carbon nanotubes (MWCNTs) plays an important role in eliminating nanotube aggregation for reinforcing polymeric materials. We prepared a new class of natural rubber (NR)/MWCNT composites by using latex compounding and self-assembly technique. The MWCNTs were functionalized with mixed acids (H2SO₄/HNO₃ = 3:1, volume ratio) and then assembled with poly (diallyldimethylammonium chloride) and latex particles. The Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy were used to investigate the assembling mechanism between latex particles and MWCNTs. It is found that MWCNTs are homogenously dispersed in the natural rubber (NR) latex as individual nanotubes since strong self-aggregation of MWCNTs has been greatly depressed with their surface functionalization. The well-dispersed MWCNTs produce a remarkable increase in the tensile strength of NR even when the amount of MWCNTs is only 1 wt.%. Dynamic mechanical analysis shows that the glass transition temperature of composites is higher and the inner-thermogenesis and thermal stability of NR/MWCNT composites are better, when compared to those of the pure NR. The marked improvement in these properties is largely due to the strong interfacial adhesion between the NR phase and MWCNTs. Functionalization of MWCNTs represents a potentially powerful technology for significant reinforcement of natural rubber materials.

Understanding children's sedentary behaviour : a qualitative study of the family home environment

Electronic media (EM) (television, electronic games and computer) use has been associated with overweight and obesity among children. Little is known about the time spent in sedentary behaviour (SB) among children within the family context. The aim of this study was to explore how the family home environment may influence children's electronic-based SB. Focus groups and family interviews were conducted with 11- to 12-year old children (n = 54) and their parents (n = 38) using a semi-structured discussion guide. Transcripts were analysed using a thematic content approach. A brief self-completed questionnaire was also used to measure leisure behaviour and electronic devices at home. Children incorporated both sedentary and physical activities into their weekly routine. Factors influencing children's EM use included parent and sibling modelling and reinforcement, personal cognitions, the physical home environment and household EM use rules and restrictions. Participants were not concerned about the excessive time children spent with EM. This under-recognition emerged as a personal influencing factor and was viewed as a major barrier to modifying children's electronic-based SB. Efforts to reduce SB in children should focus on the influencing factors that reciprocally interact within the family home. An emphasis on increasing awareness about the risks associated with spending excessive time in screen-based activities should be a priority when developing intervention strategies aimed at modifying the time children spend in SB.