37,399 research outputs found
Some services of the Time and Frequency Division of the National Bureau of Standards
The Time and Frequency Division of the National Bureau of Standards (NBS) provides several services to the general public. The radio broadcasts of WWV, WWVH, and WWVB supply reliable, unambiguous time signals to many users. The NBS telephone time-of-day service attracts several hundreds of thousands of calls each year. Periodically, the NBS provides courses on specific topics relating to time and frequency technology. In addition to numerous technical papers published each year, the NBS has prepared the first volume of a comprehensive monograph on time and frequency. The results of research in the Time and Frequency Division of the NBS have had significant impact. An active TV time system capable of serving most of the U.S. currently awaits a ruling by the FCC on a petition filed last year on behalf of the NBS by the Department of Commerce. Three more recent developments are: (1) a TV frequency comparator (patent applied for); (2) a method to perform an independent (absolute) frequency evaluation of commercial cesium beam oscillators; and (3) a method of removing one source of frequency drift in commercial cesium beam oscillators
A school for humanity: Confronting division and trauma through lived values in Burundi
The Burundi American International Academy is an independent school in central Africa. It was established eight years ago expressly to generate potential leaders motivated to build peace, humanity and economic development in an impoverished country beset by political, ethnic, environmental and development challenges. The purpose of this research is to evaluate progress toward achieving the school’s aims to create such leaders through instilling and modelling the values of integrity, excellence, responsibility, passion, compassion and respect.
The study used qualitative approaches including semi-structured conversations, observations, video, questionnaires and follow-up interviews to provide data. Data was analysed using Grounded Theory to identify the characteristics of a model intended to deliver sustainable positive change in social processes through education.
Significant findings were that the school had developed a strong, united, persuasive and perhaps self-fulfilling narrative about its successes. This narrative shared between teachers, students, governors and parents, included convincing evidence of deep understanding of the relationship between values and action at macro and micro levels. The strong motivation among teachers and other adult participants towards sustaining its aims was reinforced by evidence of frequent values discussions and values-focussed in-service training.
Theory arising from grounded research led to discussion on staff training and curriculum coverage. This included suggestions on involving connections to the school’s humanitarian values and philosophy, cross-curricular approaches to Sustainable Development Goals and closer relations between the subject disciplines. Establishing inclusive values within a privileged minority in a divided and impoverished society and balancing charitable attitudes with aspirations to high status, were revealed as significant challenges for the school. While student admission to North American universities may result in losing of some promising future leaders, the school offers a globally transferrable example of how to establish and sustain a values-creating school
On the Symmetries of the Edgar-Ludwig Metric
The conformal Killing equations for the most general (non-plane wave)
conformally flat pure radiation field are solved to find the conformal Killing
vectors. As expected fifteen independent conformal Killing vectors exist, but
in general the metric admits no Killing or homothetic vectors. However for
certain special cases a one-dimensional group of homotheties or motions may
exist and in one very special case, overlooked by previous investigators, a
two-dimensional homethety group exists. No higher dimensional groups of motions
or homotheties are admitted by these metrics.Comment: Plain TeX, 7 pages, No figure
On the measurement of frequency and of its sample variance with high-resolution counters
A frequency counter measures the input frequency averaged over a
suitable time , versus the reference clock. High resolution is achieved
by interpolating the clock signal. Further increased resolution is obtained by
averaging multiple frequency measurements highly overlapped. In the presence of
additive white noise or white phase noise, the square uncertainty improves from
to .
Surprisingly, when a file of contiguous data is fed into the formula of the
two-sample (Allan) variance
of
the fractional frequency fluctuation , the result is the \emph{modified}
Allan variance mod . But if a sufficient number of contiguous
measures are averaged in order to get a longer and the data are fed into
the same formula, the results is the (non-modified) Allan variance. Of course
interpretation mistakes are around the corner if the counter internal process
is not well understood.Comment: 14 pages, 5 figures, 1 table, 18 reference
Health and cancer prevention: knowledge and beliefs of children and young people
Objective: To collect information from children and young people about their knowledge of and attitudes towards cancer and their understanding of health and health related behaviours to inform future health promotion work. Design: Questionnaire survey of 15-16 year olds, and interviews with play materials with 9-10 year old children. Setting: Six inner city, suburban, and rural schools. Subjects: 226 children aged 15-16 years and 100 aged 9-10 years. Main outcome measures: Knowledge about different types of cancer; beliefs about health; sources of information; quality of research data obtainable from young children about cancer and health. Results: Both samples knew most about lung cancer, but there was also some knowledge of breast and skin cancer and leukaemia. Smoking, together with pollution and other environmental factors, were seen as the dominant causes of cancer. Environmental factors were mentioned more often by the inner city samples. Television and the media were the most important sources of information. Young people were more worried about unemployment than about ill health. More than half the young people did not describe their health as good, and most said they did not have a healthy lifestyle. Children were able to provide detailed information about their knowledge and understanding by using drawings as well as interviews. Conclusions: Children and young people possess considerable knowledge about cancer, especially about lung cancer and smoking, and show considerable awareness of predominant health education messages. Despite this knowledge, many lead less than healthy lifestyles. Health is not seen as the most important goal in life by many young people; the circumstances in which many children and young people live are not experienced as health promoting
Unleashing the Power of Distributed CPU/GPU Architectures: Massive Astronomical Data Analysis and Visualization case study
Upcoming and future astronomy research facilities will systematically
generate terabyte-sized data sets moving astronomy into the Petascale data era.
While such facilities will provide astronomers with unprecedented levels of
accuracy and coverage, the increases in dataset size and dimensionality will
pose serious computational challenges for many current astronomy data analysis
and visualization tools. With such data sizes, even simple data analysis tasks
(e.g. calculating a histogram or computing data minimum/maximum) may not be
achievable without access to a supercomputing facility.
To effectively handle such dataset sizes, which exceed today's single machine
memory and processing limits, we present a framework that exploits the
distributed power of GPUs and many-core CPUs, with a goal of providing data
analysis and visualizing tasks as a service for astronomers. By mixing shared
and distributed memory architectures, our framework effectively utilizes the
underlying hardware infrastructure handling both batched and real-time data
analysis and visualization tasks. Offering such functionality as a service in a
"software as a service" manner will reduce the total cost of ownership, provide
an easy to use tool to the wider astronomical community, and enable a more
optimized utilization of the underlying hardware infrastructure.Comment: 4 Pages, 1 figures, To appear in the proceedings of ADASS XXI, ed.
P.Ballester and D.Egret, ASP Conf. Serie
The application of ERTS imagery to mapping snow cover in the western United States
The author has identified the following significant results. In much of the western United States a large part of the utilized water comes from accumulated mountain snowpacks; thus, accurate measurements of snow distributions are required for input to streamflow prediction models. The application of ERTS-1 imagery for mapping snow has been evaluated for two geographic areas, the Salt-Verde watershed in central Arizona and the southern Sierra Nevada in California. Techniques have been developed to identify snow and to differentiate between snow and cloud. The snow extent for these two drainage areas has been mapped from the MSS-5 (0.6 - 0.7 microns) imagery and compared with aerial survey snow charts, aircraft photography, and ground-based snow measurements. The results indicate that ERTS imagery has substantial practical applications for snow mapping. Snow extent can be mapped from ERTS-1 imagery in more detail than is depicted on aerial survey snow charts. Moreover, in Arizona and southern California cloud obscuration does not appear to be a serious deterrent to the use of satellite data for snow survey. The costs involved in deriving snow maps from ERTS-1 imagery appear to be very reasonable in comparison with existing data collection methods
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