Flight test results of the F-16 aircraft modified with the axisymmetric vectoring exhaust nozzle

The results of the envelope expansion phase of the F-16 Multi-Axis Thrust Vectoring (MATV) program are presented in viewgraph format. The objectives and test approach are presented followed by results of testing with the initial control law configuration. The revised flight control laws are discussed followed by test results with the revised control laws. Additional testing added to the program, nose chines, parameter identification maneuvers, and the extended range angle of attack cones are briefly discussed

Heavy-tailed distribution, GARCH models and the silver returns

After serving as a medium of exchange for the human society, silver is still widely used in our daily life. From the jewellery, electronic and electrical industries as well as medicine, optics, the power industry, automotive industry and many other industries, silver is still playing a very active role. In addition to the industrial usage, silver also serves as an investment tool for many financial institutions. Thus, it is crucial to develop effective quantitative risk management tool for those financial institutions. In this paper, we investigate the conditional heavy tails of daily silver spot returns under the GARCH framework. Our results indicate that that it is important to introduce heavy-tailed distributions to the GARCH framework and the normal reciprocal inverse Gaussian (NRIG) distribution, a newly-developed distribution, has the best empirical performance in capture the daily silver spot returns dynamics.peer-reviewe

Uptake of HIV testing among adolescents and associated adolescent-friendly services

Abstract Background HIV testing remains low among adolescents. Making public health services more adolescent-friendly is one strategy used to encourage testing. However, it remains unclear whether government-led initiatives have a meaningfully impact. Methods The current study is observational and utilizes two sources of data (health-facility and adolescent-level) from one round of data collection of an on-going, longitudinal impact evaluation of a pilot cash plus program targeting adolescents. This study linked data from adolescent surveys (n = 2191) to data collected from nearby government-run health facilities (n = 91) in two rural regions of Tanzania. We used log binomial regression models to estimate the association between specific adolescent-friendly health service (AFHS) characteristics and adolescents' uptake of 1) HIV testing and 2) visiting a health care facility in the past year for sexual and reproductive health (SRH) services. Results Most adolescents (67%) lived in a village with a health facility, and all offered HIV services. We find, however, that AFHS have not been fully implemented. For example, less than 40% of facilities reported that they had guidelines for adolescent care. Only 12% of facilities had a system in place for referral and follow-up with adolescent clients, yet this was an important predictor of both past-year HIV testing (RR = 1.28, p < 0.1) and SRH visits (RR = 1.44, p < 0.05). Less than half (44%) offered services for survivors of gender-based violence (GBV), a significant predictor of past-year HIV testing (RR = 1.20, p < 0.05) and SRH visits (RR = 1.41, p < 0.01) among sexually-active adolescents. Conclusions We find that national guidelines on AFHS have not been fully translated into practice at the local level. We highlight particular gaps in adolescent referral systems and GBV services. Scaling up these two essential services could encourage greater HIV testing among a high-risk population, in addition to providing much needed support for survivors of violence

A statistical approach to quantitative data validation focused on the assessment of students' perceptions about biotechnology

Student awareness levels are frequently used to evaluate the effectiveness of educational policies to promote scientific literacy. Over the last years several studies have been developed to assess students' perceptions towards science and technology, which usually rely on quantitative methods to achieve broad characterizations, and obtain quantifiable and comparable data. Although the usefulness of this information depends on its validity and reliability, validation is frequently neglected by researchers with limited background in statistics. In this context, we propose a guideline to implement a statistical approach to questionnaire validation, combining exploratory factor analysis and reliability analysis. The work focuses on the psychometric analysis of data provided by a questionnaire assessing 1196 elementary and high school students' perceptions about biotechnology. Procedural guidelines to enhance the efficiency of quantitative inquiry surveys are given, by discussing essential methodological aspects and relevant criteria to integrate theory into practice.The authors are grateful to all the participant teachers and students that contributed to gather the data presented and to Catarina L. Santos for useful comments and suggestions on the manuscript. Maria Joao Fonseca was supported by the FCT fellowship SFRH/BD/37389/2007 and this work was sponsored by a research grant (PTDC/AGR-PRO/111857/2009) from Fundacao para a Ciencia e Tecnologia (FCT, Portugal)

An exploration of the relationship between educational background and the coaching behaviours and practice activities of professional youth soccer coaches

This paper is closed access until 12 December 2019.Background and purpose: Despite the proliferation in recent years of higher education establishments offering tertiary-level study in the field of sports coaching, there is a lack of research into the impact of such courses on coaching practice. The behaviours employed and activities used by coaches during practice sessions is an area where one might expect to see such impact, indeed certain studies have tentatively noted the educational qualifications of coaches and suggested that this may play a role in the application of behaviours more aligned with player learning. The purpose of this study was therefore to compare youth soccer coaches with and without tertiary-level qualifications, examining their coaching behaviours and practice activities. Method: The participants were 10 male professional youth soccer coaches aged 24–55 with an average of 13 years coaching experience. Five of the coaches had completed undergraduate degree courses related to sport coaching. All of the coaches worked with players aged under 9 to under 18 in the youth academy of an English professional soccer club. Systematic observation of coach behaviour and practice activities was carried out using the Coach Analysis and Intervention System (Cushion et al. 2012), while follow-up interviews were used to elicit the coaches’ perceptions of, and rationale for, their behaviour. Findings: The observation data showed that graduate coaches used significantly more divergent questioning than non-graduate coaches, while the interview data revealed a general trend for graduate coaches to show greater self-awareness of behaviours and changes in behaviour between practice types. Graduate coaches also provided more comprehensive rationales, for example, seeing silence as a means of facilitating player decision-making as well as for observation. In contrast to previous research, sessions featured a higher proportion of playing form than training form activities and at over 20% of session duration, the ‘other’ practice state was a prominent feature of contact time with players. While some coaches saw ‘other’ as wasted time, graduate coaches identified this as an opportunity for group discussion and social interaction. The study adds to existing data about coach behaviours and practice activities, providing evidence that education background may indeed influence coaching practice

Heavy-tailed distribution, GARCH models and the silver returns

After serving as a medium of exchange for the human society, silver is still widely used in our daily life. From the jewellery, electronic and electrical industries as well as medicine, optics, the power industry, automotive industry and many other industries, silver is still playing a very active role. In addition to the industrial usage, silver also serves as an investment tool for many financial institutions. Thus, it is crucial to develop effective quantitative risk management tool for those financial institutions. In this paper, we investigate the conditional heavy tails of daily silver spot returns under the GARCH framework. Our results indicate that that it is important to introduce heavy-tailed distributions to the GARCH framework and the normal reciprocal inverse Gaussian (NRIG) distribution, a newly-developed distribution, has the best empirical performance in capture the daily silver spot returns dynamics

Distribution of 3-Isobutyl-2-methoxypyrazine across Rachis Components of Vitis vinifera Shiraz and Cabernet Sauvignon

Rootstock can significantly alter the concentration of methoxypyrazines (MPs) in the bunch stem (rachis) of Vitis vinifera L. cv. Cabernet Sauvignon and Shiraz, which has implications for winemaking and wine style. The distribution of MPs across the rachis is an important consideration, but such information was not available. This study aimed to address this research question by comparing MP concentrations in different rachis components throughout grape maturation and in the absence of ambient light. Shiraz and Cabernet Sauvignon bunches were sampled throughout development, segmented into four components (peduncle, top rachis, bottom rachis, and pedicel), and 3-isobutyl-2-methoxypyrazine (IBMP) was quantified in each. For both cultivars, IBMP showed a negative correlation with grape maturity, with concentrations in pedicel at harvest being significantly higher than other rachis components. Additionally, light exclusion significantly increased IBMP concentrations in all rachis segments. The concentration of IBMP varied significantly between different rachis components. The greatest concentrations were measured in the pedicel, which also contributed the largest proportion among the components to total rachis by weight. Due to elevated IBMP concentrations in rachis and the difficulties in excluding matter other than grape from a fermentor, the presence of pedicel during fermentation could produce Shiraz and Cabernet Sauvignon wines with higher concentrations of MPs, thereby potentially increasing vegetal sensory characteristics