Limits of the cylindrical absorber design for a sodium receiver

The applicability of the cylindrical arrangement of vertical tube banks is evaluated for liquid sodium concentrating solar thermal receivers and compared with a molten salt reference case through a series of parametric studies. It is shown that sodium receivers experience less thermo-elastic stress load and can operate under higher flux which presents advantages in terms of size reduction and efficiency. While the cylindrical receiver configuration cannot reach the efficiency target of 91% in a high temperature configuration (480 °C to 640 °C), there is potential to improve efficiency by improving heliostat field optics. Flux limitations due to thermo-elastic stresses are less stringent due for sodium receivers due to the better heat transfer properties, and consequently better heliostat field optics would benefit sodium receiver concepts more than molten salts ones

Broadband sparse sensing : a polynomial matrix approach to co-prime and super nested arrays

Passively monitoring the spectrum for detection and localisation of radar sources is ever more fraught with difficulty due to the advent of low probability of intercept (LPI) radar technology. A key aspect of LPI radar waveform design are the spread spectrum modulation schemes; instead of concentrating power over a narrow-bandwidth, this power can be spread across a broad-bandwidth making the source difficult to detect using conventional ESM methods. Such sources prompt the need for new detection, and direction of arrival estimation methods. Moreover, broadband antennas and their subsequent processing systems are expensive in terms of both cost and power-forcing a real world feasible limit on the number of antennas in a system. In addition, a fine spacing is required for ambiguity free direction of arrival estimation of higher frequency sources while a wide aperture is required for sufficient resolution of lower frequency sources. In this paper we present a novel sparse broadband direction of arrival method based upon co-prime and super-nested array geometries, using polynomial matrix methods whereby a new virtual array is formed containing many more virtual elements than in the physical array

Polynomial root-MUSIC algorithm for efficient broadband direction of arrival estimation

The popular MUSIC algorithm has been recently extended to broadband scenarios through the use of polynomial matrix methods and polynomial eigenvalue decomposition algorithms, producing impressive results, at the cost of a high computational complexity. This is due to the heuristic angular search stage of the algorithm. Through the extension of the popular narrowband variant of the MUSIC algorithm, Root- MUSIC, we aim to significantly reduce the computational cost of spatio-spectral polynomial MUSIC algorithm by eliminating this searching requirement. The performance of both algorithms are analysed and compared, demonstrating a similar performance with a significant reduction in computation time

Markers of success: A study of twins' instructed second language acquisition

We examined the association between proficiency in instructed second language acquisition (ISLA) and previous bilingualism, starting age of ISLA, language anxiety and attitude. The analyses were conducted on 564 adolescent Australian twins. Additionally, by examining discrepancies within approximately 100 pairs of monozygotic twins, we sought to specifically identify the environmental effects related to attitude and anxiety on achievement (i.e. with genetic effects removed). We found a clear relationship between attitude towards language learning and proficiency in the second language. Furthermore, the analyses on the monozygotic twins point to the possibility that higher language anxiety is associated with higher proficiency. On the other hand, bilingualism and starting age of ISLA appear to be unrelated to proficiency in the language being learned.</p

Broadband direction of arrival estimation via spatial co-prime sampling and polynomial matrix methods

Direction of arrival estimation is a crucial aspect of many active and passive systems, including radar and electronic warfare applications. Spread spectrum modulation schemes are becoming ever more common in both Radar and Communications systems. Because such modulation spreads the signal energy in frequency and time, such sources prompt the need for new approaches for detection and location. Broadband antennas and their subsequent signal processing systems are expensive in terms of both cost and power consumption. This forces a limitation on the number of elements in a feasible real-world array. In this paper a novel co-prime broadband MUSIC based direction of arrival algorithm is presented. The main feature of the new method is that it aims to reduce the number of antenna elements for a given aperture by utilising a coprime sensing scheme applied to the problem of broadband direction finding via the polynomial MUSIC algorithm. Comparative results using simulated data show that the proposed co-prime polynomial MUSIC has comparable performance to those obtained using a uniform linear array method with an equivalent physical apertur

Taking a break: The effect of taking a vacation from Facebook and Instagram on subjective well-being

Social Networking Sites (SNS) such as Facebook and Instagram have relocated a large portion of people's social lives online, but can be intrusive and create social disturbances. Many people therefore consider taking an "SNS vacation." We investigated the effects of a one-week vacation from both Facebook and Instagram on subjective well-being, and whether this would vary for passive or active SNS users. Usage amount was measured objectively, using RescueTime software, to circumvent issues of self-report. Usage style was identified at pre-test, and SNS users with a more active or more passive usage style were assigned in equal numbers to the conditions of one-week SNS vacation (n = 40) or no SNS vacation (n = 38). Subjective well-being (life satisfaction, positive affect, and negative affect) was measured before and after the vacation period. At pre-test, more active SNS use was found to correlate positively with life satisfaction and positive affect, whereas more passive SNS use correlated positively with life satisfaction, but not positive affect. Surprisingly, at post-test the SNS vacation resulted in lower positive affect for active users and had no significant effects for passive users. This result is contrary to popular expectation, and indicates that SNS usage can be beneficial for active users. We suggest that SNS users should be educated in the benefits of an active usage style and that future research should consider the possibility of SNS addiction among more active users

Genetic and Environmental Influences on Literacy and Numeracy in Australian School Children

Each year, Australian students in Grades 3, 5, 7, and 9 sit nationwide tests in literacy and numeracy. These tests inform government, principals, and parents about student, school, and state performance in five domains: reading, spelling, grammar and punctuation, writing, and numeracy. As such, the results of these tests are of wide interest for diverse reasons depending on the stakeholder in question. In this thesis I examine the influence of genes and the environment on individual differences in performance on these tests. Using longitudinal data collected from a large sample of Australian twins and their siblings.&#13; Initially, as a test of validity, I compared the performance of large-scale reading tests against three literacy tests in comprehension, word reading and vocabulary individually administered to twins in Grade 3. The individually administered tests accounted for a substantial amount of the variance in the large-scale reading tests. Additionally, they were preferentially related, both genetically and environmentally, to large-scale reading tests compared to large-scale numeracy tests, confirming that large-scale school reading tests measure, at least in part, the literacy skills tapped by individual tests considered “gold-standard” in testing.&#13; In the second paper, I examined the extent to which genes and the environment contributed to variation in and covariation among the five domains in each grade. Averaged across domains and grade, genetic factors explained 60%, shared environment 10%, and unique environment 30% of the variation. Independent pathway models showed similar genetic and environmental structures at each grade with approximately one third to one half of the variation in each domain due to genes that influenced all domains.&#13; In the third paper, I explored the genetic and environmental influences on stability and growth in each of the domains. Stability in performance was primary due to genes. For growth, reading followed a compensatory growth pattern, and variation in growth was due to the genes that also influenced differences in performance at initial testing. By contrast, growth in numeracy was principally influenced by unique environmental factors. These results suggest individual differences in growth of reading are primarily due to a genetically influenced developmental delay in the acquisition of necessary skills, while for numeracy, differences are due to environmental influences, such as different teachers or interests.&#13; In the fourth paper, I tested if family or school SES moderated heritability of performance. Genetic influence was substantial and stable across all levels of family and school SES, with some evidence of a stronger influence of the shared environment when SES was lower, particularly for Grade 3 literacy. A final chapter presents a discussion summarising the principal findings, their implications, and their limitations

The Etiology of Individual Differences in Second Language Acquisition in Australian School Students: A Behavior‐Genetic Study

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/93553/1/j.1467-9922.2012.00718.x.pd

Individual Differences and Heritability of Thinking Styles and Working Memory Capacity: A Dual-process Perspective

Dual process theories propose that human decision-making involves the interplay of two distinct information processing systems, or modes of thinking: rational (logical) and experiential (intuitive). Previous research shows that individuals differ in their preferred modes of thinking and that these preferences for rationality and/or experientiality are believed to be predictive of a range of behaviours. Moreover, preference for rational thinking is believed to be intimately linked with working memory capacity (WMC). Three studies reported in this thesis investigated thinking styles, their relationship to WMC, their heritability and the extent to which they were associated with reasoning and decision-making performance across a range of tasks

Genetic and Environmental Influences on Perceived Social Support: Differences by Sex and Relationship

Previous research has shown that self-reports of the amount of social support are heritable. Using the Kessler perceived social support (KPSS) measure, we explored sex differences in the genetic and environmental contributions to individual differences. We did this separately for subscales that captured the perceived support from different members of the network (spouse, twin, children, parents, relatives, friends and confidant). Our sample comprised 7059 male, female and opposite-sex twin pairs aged 18−95 years from the Australian Twin Registry. We found tentative support for different genetic mechanisms in males and females for support from friends and the average KPSS score of all subscales, but otherwise, there are no sex differences. For each subscale alone, the additive genetic (A) and unique environment (E) effects were significant. By contrast, the covariation among the subscales was explained - in roughly equal parts - by A, E and the common environment, with effects of different support constellations plausibly accounting for the latter. A single genetic and common environment factor accounted for between half and three-quarters of the variance across the subscales in both males and females, suggesting little heterogeneity in the genetic and environmental etiology of the different support sources