Multiphonon-assisted anti-Stokes and Stokes fluorescence of triply ionized rare-earth ions

International Nuclear Information System (INIS)

Auzel, F.

1976-01-01

Experimental demonstration of multiphonon-assisted anti-Stokes and Stokes excitation of rare-earth ions (R 3+ ) in different hosts, that is, in a weak-coupling ion-lattice interaction case, is obtained. An exponential behavior of excitation probabilities with respect to energy difference between excitation and electronic line is found just as for multiphonon-assisted nonradiative decay and energy transfer. Exponential parameters α/sub As/ and α/sub S/ for anti-Stokes and Stokes excitation are measured and linked to the Miyakawa-Dexter α parameter for decay, leading to estimates for Pekar-Huang-Rhys coupling parameter S 0 of about 0.04, in agreement with values obtained from one-phonon spectra or nonradiative-decay measurements. A semiempirical formula is deduced to obtain α from only one parameter, an effective phonon energy

Incompressible Navier-Stokes and parabolized Navier-Stokes solution procedures and computational techniques

Science.gov (United States)

Rubin, S. G.

1982-01-01

Recent developments with finite-difference techniques are emphasized. The quotation marks reflect the fact that any finite discretization procedure can be included in this category. Many so-called finite element collocation and galerkin methods can be reproduced by appropriate forms of the differential equations and discretization formulas. Many of the difficulties encountered in early Navier-Stokes calculations were inherent not only in the choice of the different equations (accuracy), but also in the method of solution or choice of algorithm (convergence and stability, in the manner in which the dependent variables or discretized equations are related (coupling), in the manner that boundary conditions are applied, in the manner that the coordinate mesh is specified (grid generation), and finally, in recognizing that for many high Reynolds number flows not all contributions to the Navier-Stokes equations are necessarily of equal importance (parabolization, preferred direction, pressure interaction, asymptotic and mathematical character). It is these elements that are reviewed. Several Navier-Stokes and parabolized Navier-Stokes formulations are also presented.

Generalized Stokes eignefunctions: a new trial basis for the solution of incompressible Navier-Stokes equations

International Nuclear Information System (INIS)

Batcho, P.F.; Karniadakis, G.E.

1994-01-01

The present study focuses on the solution of the incompressible Navier-Stokes equations in general, non-separable domains, and employs a Galerkin projection of divergence-free vector functions as a trail basis. This basis is obtained from the solution of a generalized constrained Stokes eigen-problem in the domain of interest. Faster convergence can be achieved by constructing a singular Stokes eigen-problem in which the Stokes operator is modified to include a variable coefficient which vanishes at the domain boundaries. The convergence properties of such functions are advantageous in a least squares sense and are shown to produce significantly better approximations to the solution of the Navier-Stokes equations in post-critical states where unsteadiness characterizes the flowfield. Solutions for the eigen-systems are efficiently accomplished using a combined Lanczos-Uzawa algorithm and spectral element discretizations. Results are presented for different simulations using these global spectral trial basis on non-separable and multiply-connected domains. It is confirmed that faster convergence is obtained using the singular eigen-expansions in approximating stationary Navier-Stokes solutions in general domains. It is also shown that 100-mode expansions of time-dependent solutions based on the singular Stokes eigenfunctions are sufficient to accurately predict the dynamics of flows in such domains, including Hopf bifurcations, intermittency, and details of flow structures

Astronomical Research Using Virtual Observatories

Directory of Open Access Journals (Sweden)

M Tanaka

2010-01-01

Full Text Available The Virtual Observatory (VO for Astronomy is a framework that empowers astronomical research by providing standard methods to find, access, and utilize astronomical data archives distributed around the world. VO projects in the world have been strenuously developing VO software tools and/or portal systems. Interoperability among VO projects has been achieved with the VO standard protocols defined by the International Virtual Observatory Alliance (IVOA. As a result, VO technologies are now used in obtaining astronomical research results from a huge amount of data. We describe typical examples of astronomical research enabled by the astronomical VO, and describe how the VO technologies are used in the research.

FITSManager: Management of Personal Astronomical Data

Science.gov (United States)

Cui, Chenzhou; Fan, Dongwei; Zhao, Yongheng; Kembhavi, Ajit; He, Boliang; Cao, Zihuang; Li, Jian; Nandrekar, Deoyani

2011-07-01

With the increase of personal storage capacity, it is easy to find hundreds to thousands of FITS files in the personal computer of an astrophysicist. Because Flexible Image Transport System (FITS) is a professional data format initiated by astronomers and used mainly in the small community, data management toolkits for FITS files are very few. Astronomers need a powerful tool to help them manage their local astronomical data. Although Virtual Observatory (VO) is a network oriented astronomical research environment, its applications and related technologies provide useful solutions to enhance the management and utilization of astronomical data hosted in an astronomer's personal computer. FITSManager is such a tool to provide astronomers an efficient management and utilization of their local data, bringing VO to astronomers in a seamless and transparent way. FITSManager provides fruitful functions for FITS file management, like thumbnail, preview, type dependent icons, header keyword indexing and search, collaborated working with other tools and online services, and so on. The development of the FITSManager is an effort to fill the gap between management and analysis of astronomical data.

UKRVO Astronomical WEB Services

Directory of Open Access Journals (Sweden)

Mazhaev, O.E.

2017-01-01

Full Text Available Ukraine Virtual Observatory (UkrVO has been a member of the International Virtual Observatory Alliance (IVOA since 2011. The virtual observatory (VO is not a magic solution to all problems of data storing and processing, but it provides certain standards for building infrastructure of astronomical data center. The astronomical databases help data mining and offer to users an easy access to observation metadata, images within celestial sphere and results of image processing. The astronomical web services (AWS of UkrVO give to users handy tools for data selection from large astronomical catalogues for a relatively small region of interest in the sky. Examples of the AWS usage are showed.

Structuring Stokes correlation functions using vector-vortex beam

Science.gov (United States)

Kumar, Vijay; Anwar, Ali; Singh, R. P.

2018-01-01

Higher order statistical correlations of the optical vector speckle field, formed due to scattering of a vector-vortex beam, are explored. Here, we report on the experimental construction of the Stokes parameters covariance matrix, consisting of all possible spatial Stokes parameters correlation functions. We also propose and experimentally realize a new Stokes correlation functions called Stokes field auto correlation functions. It is observed that the Stokes correlation functions of the vector-vortex beam will be reflected in the respective Stokes correlation functions of the corresponding vector speckle field. The major advantage of proposing Stokes correlation functions is that the Stokes correlation function can be easily tuned by manipulating the polarization of vector-vortex beam used to generate vector speckle field and to get the phase information directly from the intensity measurements. Moreover, this approach leads to a complete experimental Stokes characterization of a broad range of random fields.

New Stokes' line in WKB theory

International Nuclear Information System (INIS)

Berk, H.L.; Nevins, W.M.; Roberts, K.V.

1982-01-01

The WKB theory for differential equations of arbitrary order or integral equations in one dimension is investigated. The rules previously stated for the construction of Stokes' lines for Nth-order differential equations, N> or =3, or integral equations are found to be incomplete because these rules lead to asymptotic forms of the solutions that depend on path. This paradox is resolved by the demonstration that new Stokes' lines can arise when previously defined Stokes' lines cross. A new formulation of the WKB problem is given to justify the new Stokes' lines. With the new Stokes' lines, the asymptotic forms can be shown to be independent of path. In addition, the WKB eigenvalue problem is formulated, and the global dispersion relation is shown to be a functional of loop integrals of the action

Effects of moderate pump and Stokes chirp on chirped-probe pulse femtosecond coherent anti-Stokes Raman scattering thermometry

KAUST Repository

Gu, Mingming; Satija, Aman; Lucht, Robert P.

2018-01-01

The effects of moderate levels of chirp in the pump and Stokes pulses on chirped-probe-pulse femtosecond coherent anti-Stokes Raman scattering (CPP fs CARS) were investigated. The frequency chirp in the pump and Stokes pulses was introduced

Astronomical Heritage in the National Culture

Science.gov (United States)

Harutyunian, H. A.; Mickaelian, A. M.; Parsamian, E. S.

2014-10-01

The book contains Proceedings of the Archaeoastronomical Meeting "Astronomical Heritage in the National Culture" Dedicated to Anania Shirakatsi's 1400th Anniversary and XI Annual Meeting of the Armenian Astronomical Society. It consists of 3 main sections: "Astronomical Heritage", "Anania Shirakatsi" and "Modern Astronomy", as well as Literature about Anania Shirakatsi is included. The book may be interesting for astronomers, historians, archaeologists, linguists, students and other readers.

A designated centre for people with disabilities operated by Brothers of Charity Services Galway, Galway

LENUS (Irish Health Repository)

Murphy, Andrew W

2005-07-29

BACKGROUND: The aim of the SPHERE study is to design, implement and evaluate tailored practice and personal care plans to improve the process of care and objective clinical outcomes for patients with established coronary heart disease (CHD) in general practice across two different health systems on the island of Ireland. CHD is a common cause of death and a significant cause of morbidity in Ireland. Secondary prevention has been recommended as a key strategy for reducing levels of CHD mortality and general practice has been highlighted as an ideal setting for secondary prevention initiatives. Current indications suggest that there is considerable room for improvement in the provision of secondary prevention for patients with established heart disease on the island of Ireland. The review literature recommends structured programmes with continued support and follow-up of patients; the provision of training, tailored to practice needs of access to evidence of effectiveness of secondary prevention; structured recall programmes that also take account of individual practice needs; and patient-centred consultations accompanied by attention to disease management guidelines. METHODS: SPHERE is a cluster randomised controlled trial, with practice-level randomisation to intervention and control groups, recruiting 960 patients from 48 practices in three study centres (Belfast, Dublin and Galway). Primary outcomes are blood pressure, total cholesterol, physical and mental health status (SF-12) and hospital re-admissions. The intervention takes place over two years and data is collected at baseline, one-year and two-year follow-up. Data is obtained from medical charts, consultations with practitioners, and patient postal questionnaires. The SPHERE intervention involves the implementation of a structured systematic programme of care for patients with CHD attending general practice. It is a multi-faceted intervention that has been developed to respond to barriers and solutions to

On the Coupling of Incompressible Stokes or Navier–Stokes and Darcy Flows Through Porous Media

KAUST Repository

Girault, V.; Kanschat, G.; Riviè re, B.

2012-01-01

In this chapter, we present the theoretical analysis of coupled incompressible Navier-Stokes (or Stokes) flows and Darcy flows with the Beavers-Joseph-Saffman interface condition. We discuss alternative interface and porous media models. We review

Evaluation of micronozzle performance through DSMC, navier-stokes and coupled dsmc/navier-stokes approaches

NARCIS (Netherlands)

Torre, F. la; Kenjeres, S.; Kleijn, C.R.; Moerel, J.L.P.A.

2009-01-01

Both the particle based Direct Simulation Monte Carlo (DSMC) method and a compressible Navier-Stokes based continuum method are used to investigate the flow inside micronozzles and to predict the performance of such devices. For the Navier-Stokes approach, both slip and no-slip boundary conditions

Explanatory supplement to the astronomical almanac

CERN Document Server

Urban, Sean E

2013-01-01

The Explanatory Supplement to the Astronomical Almanac offers explanatory material, supplemental information and detailed descriptions of the computational models and algorithms used to produce The Astronomical Almanac, which is an annual publication prepared jointly by the US Naval Observatory and Her Majesty's Nautical Almanac Office in the UK. Like The Astronomical Almanac, The Explanatory Supplement provides detailed coverage of modern positional astronomy. Chapters are devoted to the celestial and terrestrial reference frames, orbital ephemerides, precession, nutation, Earth rotation, and coordinate transformations. These topics have undergone substantial revisions since the last edition was published. Astronomical positions are intertwined with timescales and relativity in The Astronomical Almanac, so related chapters are provided in The Explanatory Supplement. The Astronomical Almanac also includes information on lunar and solar eclipses, physical ephemerides of solar system bodies, and calendars, so T...

Astronomical Ecosystems

Science.gov (United States)

Neuenschwander, D. E.; Finkenbinder, L. R.

2004-05-01

Just as quetzals and jaguars require specific ecological habitats to survive, so too must planets occupy a tightly constrained astronomical habitat to support life as we know it. With this theme in mind we relate the transferable features of our elementary astronomy course, "The Astronomical Basis of Life on Earth." Over the last five years, in a team-taught course that features a spring break field trip to Costa Rica, we have introduced astronomy through "astronomical ecosystems," emphasizing astronomical constraints on the prospects for life on Earth. Life requires energy, chemical elements, and long timescales, and we emphasize how cosmological, astrophysical, and geological realities, through stabilities and catastrophes, create and eliminate niches for biological life. The linkage between astronomy and biology gets immediate and personal: for example, studies in solar energy production are followed by hikes in the forest to examine the light-gathering strategies of photosynthetic organisms; a lesson on tides is conducted while standing up to our necks in one on a Pacific beach. Further linkages between astronomy and the human timescale concerns of biological diversity, cultural diversity, and environmental sustainability are natural and direct. Our experience of teaching "astronomy as habitat" strongly influences our "Astronomy 101" course in Oklahoma as well. This "inverted astrobiology" seems to transform our student's outlook, from the universe being something "out there" into something "we're in!" We thank the SNU Science Alumni support group "The Catalysts," and the SNU Quetzal Education and Research Center, San Gerardo de Dota, Costa Rica, for their support.

Intrinsic character of Stokes matrices

Science.gov (United States)

Gagnon, Jean-François; Rousseau, Christiane

2017-02-01

Two germs of linear analytic differential systems x k + 1Y‧ = A (x) Y with a non-resonant irregular singularity are analytically equivalent if and only if they have the same eigenvalues and equivalent collections of Stokes matrices. The Stokes matrices are the transition matrices between sectors on which the system is analytically equivalent to its formal normal form. Each sector contains exactly one separating ray for each pair of eigenvalues. A rotation in S allows supposing that R+ lies in the intersection of two sectors. Reordering of the coordinates of Y allows ordering the real parts of the eigenvalues, thus yielding triangular Stokes matrices. However, the choice of the rotation in x is not canonical. In this paper we establish how the collection of Stokes matrices depends on this rotation, and hence on a chosen order of the projection of the eigenvalues on a line through the origin.

Choosing and using astronomical eyepieces

CERN Document Server

Paolini, William

2013-01-01

This valuable reference fills a number of needs in the field of astronomical eyepieces, including that of a buyer's guide, observer's field guide and technical desk reference. It documents the past market for eyepieces and its evolution right up to the present day. In addition to appealing to practical astronomers - and potentially saving them money - it is useful both as a historical reference and as a detailed review of the current market place for this bustling astronomical consumer product. What distinguishes this book from other publications on astronomy is the involvement of observers from all aspects of the astronomical community, and also the major manufacturers of equipment. It not only catalogs the technical aspects of the many modern eyepieces but also documents amateur observer reactions and impressions of their utility over the years, using many different eyepieces. Eyepieces are the most talked-about accessories and collectible items available to the amateur astronomer. No other item of equi...

A Radon Micro Study of Salthill, Galway

International Nuclear Information System (INIS)

Boyle-Tobin Ann

2006-01-01

This project presents a study of radon gas, when it enters from the ground into the built environment. In order to further inform the present body of knowledge on this potentially dangerous gas, a radon micro study is carried out in the area of Salthill, Galway. A total of 51 households are measured for radon. The results indicate a high variation in the levels recorded, with over a third of the houses measuring above the national safe standard of 200 becquerels per cubic meter, with a small percentage of houses exhibiting very high levels. The results are spatially analysed against the local geology, as radon is a by-product of the breakdown of uranium in rocks. Householders' knowledge and awareness of radon is explored to inform the reasons why more people are not testing their homes for radon, and not installing remedial measures when high levels are detected. The findings indicate significant gaps in householders' knowledge of radon. A certain complacency is noted, which may indicate that people still do not recognise a need to know about this invisible threat. As ways to encourage further testing and remediation levels are equally explored, the government is viewed to play a central role in these processes through partial state funding. Further evidence supports continued and more effective and widespread advertising of radon issues, through all types of media, with emphasis at local level. Incidents of lung cancer and lung disease of long term residents are recorded in an attempt to find out if there is a correlation between them. The results indicate no correlation; however, not all households could participate in this part of the survey as it was limited to long-term residents only

Korean Astronomical Calendar, Chiljeongsan

Science.gov (United States)

Lee, Eun Hee

In fifteenth century Korea, there was a grand project for the astronomical calendar and instrument making by the order of King Sejong 世宗 (1418-1450). During this period, many astronomical and calendrical books including Islamic sources in Chinese versions were imported from Ming 明 China, and corrected and researched by the court astronomers of Joseon 朝鮮 (1392-1910). Moreover, the astronomers and technicians of Korea frequently visited China to study astronomy and instrument making, and they brought back useful information in the form of new published books or specifications of instruments. As a result, a royal observatory equipped with 15 types of instrument was completed in 1438. Two types of calendar, Chiljeongsan Naepyeon 七政算內篇 and Chiljeongsan Oepyeon 七政算外篇, based on the Chinese and Islamic calendar systems, respectively, were published in 1444 with a number of calendrical editions such as corrections and example supplements (假令) including calculation methods and results for solar and lunar eclipses.

New Life for Astronomical Instruments of the Past at the Astronomical Observatory of Taras Shevchenko

Science.gov (United States)

Kazantseva, Liliya

2012-09-01

Astronomical instruments of the past are certainly valuable artifacts of the history of science and education. Like other collections of scientific equipment, they also demonstrate i) development of scientific and technical ideas, ii) technological features of the historical period, iii) professional features of artists or companies -- manufacturers, and iv) national and local specificity of production. However, astronomical instruments are also devices made for observations of rare phenomena -- solar eclipses, transits of planets of the solar disk, etc. Instruments used to study these rare events were very different for each event, since the science changed quickly between events. The Astronomical Observatory of Kyiv National Taras Shevchenko University has a collection of tools made by leading European and local shops from the early nineteenth century. These include tools for optically observing the first artificial Earth satellites, photography, chronometry, and meteorology. In addition, it has assembled a library of descriptions of astronomical instruments and makers'price-lists. Of particular interest are the large stationary tools that are still active in their pavilions. Almost every instrument has a long interesting history. Museification of astronomical instruments gives them a second life, expanding educational programs and tracing the development of astronomy in general and scientific institution and region in particular. It would be advisable to first create a regional database of these rare astronomical instruments (which is already being done in Ukraine), then a common global database. By combining all the historical information about astronomical instruments with the advantages of the Internet, you can show the full evolution of an astronomical instrument with all its features. Time is relentless, and much is destroyed, badly kept and thrown in the garbage. We need time to protect, capture, and tell about it.

Astronomical Instrumentation System Markup Language

Science.gov (United States)

Goldbaum, Jesse M.

2016-05-01

The Astronomical Instrumentation System Markup Language (AISML) is an Extensible Markup Language (XML) based file format for maintaining and exchanging information about astronomical instrumentation. The factors behind the need for an AISML are first discussed followed by the reasons why XML was chosen as the format. Next it's shown how XML also provides the framework for a more precise definition of an astronomical instrument and how these instruments can be combined to form an Astronomical Instrumentation System (AIS). AISML files for several instruments as well as one for a sample AIS are provided. The files demonstrate how AISML can be utilized for various tasks from web page generation and programming interface to instrument maintenance and quality management. The advantages of widespread adoption of AISML are discussed.

Approximate Stokes Drift Profiles in Deep Water

Science.gov (United States)

Breivik, Øyvind; Janssen, Peter A. E. M.; Bidlot, Jean-Raymond

2014-09-01

A deep-water approximation to the Stokes drift velocity profile is explored as an alternative to the monochromatic profile. The alternative profile investigated relies on the same two quantities required for the monochromatic profile, viz the Stokes transport and the surface Stokes drift velocity. Comparisons with parametric spectra and profiles under wave spectra from the ERA-Interim reanalysis and buoy observations reveal much better agreement than the monochromatic profile even for complex sea states. That the profile gives a closer match and a more correct shear has implications for ocean circulation models since the Coriolis-Stokes force depends on the magnitude and direction of the Stokes drift profile and Langmuir turbulence parameterizations depend sensitively on the shear of the profile. The alternative profile comes at no added numerical cost compared to the monochromatic profile.

On the Coupling of Incompressible Stokes or Navier–Stokes and Darcy Flows Through Porous Media

KAUST Repository

Girault, V.

2012-11-03

In this chapter, we present the theoretical analysis of coupled incompressible Navier-Stokes (or Stokes) flows and Darcy flows with the Beavers-Joseph-Saffman interface condition. We discuss alternative interface and porous media models. We review some finite element methods used by several authors in this coupling and present numerical experiments.

Amateur Astronomers: Secret Agents of EPO

Science.gov (United States)

Berendsen, M.; White, V.; Devore, E.; Reynolds, M.

2008-06-01

Amateur astronomers prime the public to be more interested, receptive, and excited about space science, missions, and programs. Through recent research and targeted programs, amateur astronomy outreach is being increasingly recognized by professional astronomers, educators, and other amateurs as a valued and important service. The Night Sky Network program, administered by the ASP, is the first nationwide research-based program specifically targeted to support outreach by amateur astronomers. This Network of trained and informed amateur astronomers can provide a stimulating introduction to your EPO programs as Network members share the night sky with families, students, and youth groups.

Stochastic 2-D Navier-Stokes Equation

International Nuclear Information System (INIS)

Menaldi, J.L.; Sritharan, S.S.

2002-01-01

In this paper we prove the existence and uniqueness of strong solutions for the stochastic Navier-Stokes equation in bounded and unbounded domains. These solutions are stochastic analogs of the classical Lions-Prodi solutions to the deterministic Navier-Stokes equation. Local monotonicity of the nonlinearity is exploited to obtain the solutions in a given probability space and this significantly improves the earlier techniques for obtaining strong solutions, which depended on pathwise solutions to the Navier-Stokes martingale problem where the probability space is also obtained as a part of the solution

Stokes Space in Direct-Detection Data Transmission Systems

DEFF Research Database (Denmark)

Estaran Tolosa, Jose Manuel; Lu, Xiaofeng; Zibar, Darko

2015-01-01

Stokes-based processing permits complete and phase-insensitive characterization of the field’s SOP, readily unlocking polarization diversity in transmission systems where DD is desired. We present an overview on Stokes notions and most recent achievements in this context.......Stokes-based processing permits complete and phase-insensitive characterization of the field’s SOP, readily unlocking polarization diversity in transmission systems where DD is desired. We present an overview on Stokes notions and most recent achievements in this context....

Origins of Stokes shift in PbS nanocrystals

KAUST Repository

Voznyy, Oleksandr

2017-10-27

Stokes shift, an energy difference between the excitonic absorption and emission, is a property of colloidal quantum dots (CQDs) typically ascribed to splitting between dark and bright excitons. In some materials, e.g., PbS, CuInS2, CdHgTe, a Stokes shift of up to 200 meV is observed, substantially larger than the estimates of dark-bright state splitting or vibronic relaxations. The shift origin remains highly debated, as contradictory signatures of both surface and bulk character were reported for the Stokes-shifted electronic state. Here we show that the energy transfer among CQDs in a polydispersed ensemble in solution suffices to explain the excess Stokes shift. This energy transfer is primarily due to CQD aggregation, and can be substantially eliminated by extreme dilution, higher-viscosity solvent, or better-dispersed colloids. Our findings highlight that ensemble polydispersity remains the primary source of the Stokes shift in CQDs in solution, propagating into the Stokes shift in films and the open-circuit voltage deficit in CQD solar cells. Improved synthetic control can bring notable advancements in CQD photovoltaics, and the Stokes shift continues to provide a sensitive and significant metric to monitor ensemble size distribution.

Contaminants in surface water and sediments near the Tynagh silver mine site, County Galway, Ireland

Energy Technology Data Exchange (ETDEWEB)

O' Neill, A. [School of Planning, Architecture and Civil Engineering, Queen' s University of Belfast, Belfast, Northern Ireland (United Kingdom); Phillips, D.H., E-mail: d.phillips@qub.ac.uk [School of Planning, Architecture and Civil Engineering, Queen' s University of Belfast, Belfast, Northern Ireland (United Kingdom); Bowen, J. [School of Planning, Architecture and Civil Engineering, Queen' s University of Belfast, Belfast, Northern Ireland (United Kingdom); Sen Gupta, B. [School of the Built Environment, Hariot-Watt University, Edinburgh, Scotland (United Kingdom)

2015-04-15

A former silver mine in Tynagh, Co. Galway, Ireland is one of the most contaminated mine sites in Europe with maximum concentrations of Zn, As, Pb, Mn, Ni, Cu, and Cd far exceeding guideline values for water and sediment. The aims of this research were to 1) further assess the contamination, particularly metals, in surface water and sediment around the site, and 2) determine if the contamination has increased 10 years after the Environmental Protection Agency Ireland (EPAI) identified off-site contamination. Site pH is alkaline to neutral because CaCO{sub 3}-rich sediment and rock material buffer the exposed acid generating sulphide-rich ore. When this study was compared to the previous EPAI study conducted 10 years earlier, it appeared that further weathering of exposed surface sediment had increased concentrations of As and other potentially toxic elements. Water samples from the tailings ponds and adjacent Barnacullia Stream had concentrations of Al, Cd, Mn, Zn and Pb above guideline values. Lead and Zn concentrations from the tailings pond sediment were 16 and 5 times higher, respectively, than concentrations reported 10 years earlier. Pb and Zn levels in most sediment samples exceeded the Expert Group (EGS) guidelines of 1000 and 5000 mg/kg, respectively. Arsenic concentrations were as high as 6238 mg/kg in the tailings ponds sediment, which is 62 and 862 times greater than the EGS and Canadian Soil Quality Guidelines (CSQG), respectively. Cadmium, Cu, Fe, Mn, Pb and Zn concentrations in water and sediment were above guideline values downstream of the site. Additionally, Fe, Mn and organic matter (OM) were strongly correlated and correlated to Zn, Pb, As, Cd, Cu and Ni in stream sediment. Therefore, the nearby Barnacullia Stream is also a significant pathway for contaminant transport to downstream areas. Further rehabilitation of the site may decrease the contamination around the area. - Highlights: • Tynagh silver mine in Co. Galway, Ireland is a source of

Using commercial amateur astronomical spectrographs

CERN Document Server

Hopkins, Jeffrey L

2014-01-01

Amateur astronomers interested in learning more about astronomical spectroscopy now have the guide they need. It provides detailed information about how to get started inexpensively with low-resolution spectroscopy, and then how to move on to more advanced  high-resolution spectroscopy. Uniquely, the instructions concentrate very much on the practical aspects of using commercially-available spectroscopes, rather than simply explaining how spectroscopes work. The book includes a clear explanation of the laboratory theory behind astronomical spectrographs, and goes on to extensively cover the practical application of astronomical spectroscopy in detail. Four popular and reasonably-priced commercially available diffraction grating spectrographs are used as examples. The first is a low-resolution transmission diffraction grating, the Star Analyser spectrograph. The second is an inexpensive fiber optic coupled bench spectrograph that can be used to learn more about spectroscopy. The third is a newcomer, the ALPY ...

The First Astronomical Observatory in Cluj-Napoca

Science.gov (United States)

Szenkovits, Ferenc

2008-09-01

One of the most important cities of Romania is Cluj-Napoca (Kolozsvár, Klausenburg). This is a traditional center of education, with many universities and high schools. From the second half of the 18th century the University of Cluj has its own Astronomical Observatory, serving for didactical activities and scientific researches. The famous astronomer Maximillian Hell was one of those Jesuits who put the base of this Astronomical Observatory. Our purpose is to offer a short history of the beginnings of this Astronomical Observatory.

Storing Astronomical Information on the Romanian Territory

Science.gov (United States)

Stavinschi, M.; Mioc, V.

2004-12-01

Romanian astronomy has a more than 2000-year old tradition, which is, however, little known abroad. The first known archive of astronomical information is the Dacian sanctuary at Sarmizegetusa Regia, erected in the first century AD, having similarities with that of Stonehenge. After a gap of more than 1000 years, more sources of astronomical information become available, mainly records of astronomical events. Monasteries were the safest storage places of these genuine archives. We present a classification of the ways of storing astronomical information, along with characteristic examples.

Effects of moderate pump and Stokes chirp on chirped-probe pulse femtosecond coherent anti-Stokes Raman scattering thermometry

KAUST Repository

Gu, Mingming

2018-01-08

The effects of moderate levels of chirp in the pump and Stokes pulses on chirped-probe-pulse femtosecond coherent anti-Stokes Raman scattering (CPP fs CARS) were investigated. The frequency chirp in the pump and Stokes pulses was introduced by placing SF11 glass disks with thicknesses of 10 mm or 20 mm in the optical path for these beams. The magnitude of the chirp in the probe beam was much greater and was induced by placing a 30-cm rod of SF10 glass in the beam path. The temperature measurements were performed in hydrogen/air non-premixed flames stabilized on a Hencken burner at equivalence ratios of 0.3, 0.5, 0.7, and 1.0. We performed measurements with no disks in pump and Stokes beam paths, and then with disks of 10 mm and 20 mm placed in both beam paths. The spectrum of the nonresonant background four-wave mixing signal narrowed considerably with increasing pump and Stokes chirp, while the resonant CARS signal was relatively unaffected. Consequently, the interference of the nonresonant background with the resonant CARS signal in the frequency-spread dephasing region of the spectrum was minimized. The increased rate of decay of the resonant CARS signal with increasing temperature was thus readily apparent. We have started to analyze the CPP fs CARS thermometry data and initial results indicate improved accuracy and precision are obtained due to moderate chirp in the pump and Stokes laser pulses.

Stokes line width

International Nuclear Information System (INIS)

Nikiskov, A.I.; Ritus, V.I.

1993-01-01

The concept of Stokes line width is introduced for the asymptotic expansions of functions near an essential singularity. Explicit expressions are found for functions (switching functions) that switch on the exponentially small terms for the Dawson integral, Airy function, and the gamma function. A different, more natural representation of a function, not associated with expansion in an asymptotic series, in the form of dominant and recessive terms is obtained by a special division of the contour integral which represents the function into contributions of higher and lower saddle points. This division leads to a narrower, natural Stokes line width and a switching function of an argument that depends on the topology of the lines of steepest descent from the saddle point

Astronomical Cybersketching

CERN Document Server

Grego, Peter

2009-01-01

Outlines the techniques involved in making observational sketches and more detailed 'scientific' drawings of a wide variety of astronomical subjects using modern digital equipment; primarily PDAs and tablet PCs. This book also discusses about choosing hardware and software

Astronomical Symbolism in Australian Aboriginal Rock Art

Science.gov (United States)

Norris, Ray P.; Hamacher, Duane W.

2011-05-01

Traditional Aboriginal Australian cultures include a significant astronomical component, perpetuated through oral tradition and ceremony. This knowledge has practical navigational and calendrical functions, and sometimes extends to a deep understanding of the motion of objects in the sky. Here we explore whether this astronomical tradition is reflected in the rock art of Aboriginal Australians. We find several plausible examples of depictions of astronomical figures and symbols, and also evidence that astronomical observations were used to set out stone arrangements. However, we recognise that the case is not yet strong enough to make an unequivocal statement, and describe our plans for further research.

Statistics in a Trilinear Interacting Stokes-Antistokes Boson System

Science.gov (United States)

Tänzler, W.; Schütte, F.-J.

The statistics of a system of four boson modes is treated with simultaneous Stokes-Antistokes interaction taking place. The time evolution is calculated in full quantum manner but in short time approximation. Mean photon numbers and correlations of second order are calculated. Antibunching can be found in the laser mode and in the system of Stokes and Antistokes mode.Translated AbstractStatistik in einem trilinear wechselwirkenden Stokes-Antistokes-BosonensystemDie Statistik eines Systems von vier Bosonenmoden mit gleichzeitiger Stokes-Antistokes-Wechselwirkung wird bei vollquantenphysikalischer Beschreibung in Kurzzeitnäherung untersucht. Mittlere Photonenzahlen und Korrelationen zweiter Ordnung werden berechnet. Dabei wird Antibunching sowohl in der Lasermode allein als auch im System aus Stokes- und Antistokesmode gefunden.

Unsteady Stokes equations: Some complete general solutions

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

homogeneous unsteady Stokes equations are examined. A necessary and sufficient condition for a divergence-free vector to represent the velocity field of a possible unsteady Stokes flow in the absence of body forces is derived. Keywords. Complete ...

The Victorian Amateur Astronomer: Independent Astronomical Research in Britain 1820-1920

Science.gov (United States)

Chapman, Allan

1999-01-01

This is the first book to look in detail at amateur astronomy in Victorian Britain. It deals with the technical issues that were active in Victorian astronomy, and reviews the problems of finance, patronage and the dissemination of scientific ideas. It also examines the relationship between the amateur and professional in Britain. It contains a wealth of previously unpublished biographical and anecdotal material, and an extended bibliography with notes incorporating much new scholarship. In The Victorian Amateur Astronomer, Allan Chapman shows that while on the continent astronomical research was lavishly supported by the state, in Britain such research was paid for out of the pockets of highly educated, wealthy gentlemen the so-called Grand Amateurs . It was these powerful individuals who commissioned the telescopes, built the observatories, ran the learned societies, and often stole discoveries from their state-employed colleagues abroad. In addition to the Grand Amateurs , Victorian Britain also contained many self-taught amateurs. Although they belonged to no learned societies, these people provide a barometer of the popularity of astronomy in that age. In the late 19th century, the comfortable middle classes clergymen, lawyers, physicians and retired military officers took to astronomy as a serious hobby. They formed societies which focused on observation, lectures and discussions, and it was through this medium that women first came to play a significant role in British astronomy. Readership: Undergraduate and postgraduate students studying the history of science or humanities, professional historians of science, engineering and technology, particularly those with an interest in astronomy, the development of astronomical ideas, scientific instrument makers, and amateur astronomers.

The astronomical tables of Giovanni Bianchini

CERN Document Server

Chabas, Jose

2009-01-01

This book describes and analyses, for the first time, the astronomical tables of Giovanni Bianchini of Ferrara (d. after 1469), explains their context, inserts them into an astronomical tradition that began in Toledo, and addresses their diffusion.

The Soviet center of astronomical data

International Nuclear Information System (INIS)

Dluzhnevskaya, O.B.

1982-01-01

On the basis of the current French-Soviet cooperation in science and technology, the Astronomical Council of the U.S.S.R. Academy of Sciences and the Strasbourg Center signed in 1977 an agreement on setting up the Soviet Center of Astronomical Data as its filial branch. The Soviet Center was created on the basis of a computation center at the Zvenigorod station of the Astronomical Council of the U.S.S.R. Academy of Sciences, which had already had considerable experience of working with stellar catalogues. In 1979 the Center was equipped with a EC-1033 computer. In 1978-1979 the Soviet Center of Astronomical Data (C.A.D.) received from Strasbourg 96 of the most important catalogues. By September 1981 the list of catalogues available at the Soviet Center has reached 140 catalogues some of which are described. (Auth.)

Atlas of Astronomical Discoveries

CERN Document Server

Schilling, Govert

2011-01-01

Four hundred years ago in Middelburg, in the Netherlands, the telescope was invented. The invention unleashed a revolution in the exploration of the universe. Galileo Galilei discovered mountains on the Moon, spots on the Sun, and moons around Jupiter. Christiaan Huygens saw details on Mars and rings around Saturn. William Herschel discovered a new planet and mapped binary stars and nebulae. Other astronomers determined the distances to stars, unraveled the structure of the Milky Way, and discovered the expansion of the universe. And, as telescopes became bigger and more powerful, astronomers delved deeper into the mysteries of the cosmos. In his Atlas of Astronomical Discoveries, astronomy journalist Govert Schilling tells the story of 400 years of telescopic astronomy. He looks at the 100 most important discoveries since the invention of the telescope. In his direct and accessible style, the author takes his readers on an exciting journey encompassing the highlights of four centuries of astronomy. Spectacul...

Care of astronomical telescopes and accessories a manual for the astronomical observer and amateur telescope maker

CERN Document Server

Pepin, M Barlow

2005-01-01

Commercially-made astronomical telescopes are better and less expensive than ever before, and their optical and mechanical performance can be superb. When a good-quality telescope fails to perform as well as it might, the reason is quite probably that it needs a little care and attention! Here is a complete guide for anyone who wants to understand more than just the basics of astronomical telescopes and accessories, and how to maintain them in the peak of condition. The latest on safely adjusting, cleaning, and maintaining your equipment is combined with thoroughly updated methods from the old masters. Here, too, are details of choosing new and used optics and accessories, along with enhancements you can make to extend their versatility and useful lifetime. This book is for you. Really. Looking after an astronomical telescope isn't only for the experts - although there are some things that only an expert should attempt - and every serious amateur astronomer will find invaluable information here, gleaned from ...

Reporting Astronomical Discoveries: Past, Now, and Future

Science.gov (United States)

Yamaoka, Hitoshi; Green, Daniel W. E.; Samus, Nikolai N.; West, Richard

2015-08-01

Many new astronomical objects have been discovered over the years by amateur astronomers, and this continues to be the case. They have traditionally reported them (as have professional astronomers) to the Central Bureau for Astronomical Telegrams (CBAT), which was established in the 19th century. This procedure has worked very well throughout the 20th century, moving under the umbrella of the newly established IAU in 1920. The discoverers have been honored by the formal announcement of their discoveries in the publications of the CBAT.In recent years, some professional research groups have established other ways of announcing their discoveries of explosive objects such as novae and supernovae; some do not now report their discoveries or spectroscopic confirmations of the transients to the CBAT, including often spectroscopic reports of objects posted to the CBAT "Transient Objects Confirmation Page" -- the highly successful TOCP webpage, which assigns official positional designations to new transients posted there by approved, registered users. This leads to a delay in formal announcements of discoveries by amateur astronomers in many cases, as well as inconsistent designations being put into use by individual groups. Amateur astronomers are feeling frustrated about this situation, and they hope that the IAU will help to settle the situation.We have proposed the new IAU commission NC-52, which will treat these phenomena in a continuation of Commission 6, through the CBAT. We hope to continuously support the reporting of the discoveries by amateur astronomers, as well as professional astronomers, who all deserve and desire proper recognition. Our strategy will maintain the firm trust between the amateur and professional astronomers, which is necessary for true collaboration. The plan is for the CBAT to work with collaborators to assure that discoveries posted on the TOCP are promptly designated and announced by the CBAT, even when confirmations are made elsewhere

Navier-Stokes equations an introduction with applications

CERN Document Server

Łukaszewicz, Grzegorz

2016-01-01

This volume is devoted to the study of the Navier–Stokes equations, providing a comprehensive reference for a range of applications: from students to engineers and mathematicians involved in research on fluid mechanics, dynamical systems, and mathematical modeling. Equipped with only a basic knowledge of calculus, functional analysis, and partial differential equations, the reader is introduced to the concept and applications of the Navier–Stokes equations through a series of fully self-contained chapters. Including lively illustrations that complement and elucidate the text, and a collection of exercises at the end of each chapter, this book is an indispensable, accessible, classroom-tested tool for teaching and understanding the Navier–Stokes equations. Incompressible Navier–Stokes equations describe the dynamic motion (flow) of incompressible fluid, the unknowns being the velocity and pressure as functions of location (space) and time variables. A solution to these equations predicts the behavior o...

On entanglement of light and Stokes parameters

International Nuclear Information System (INIS)

Żukowski, Marek; Laskowski, Wiesław; Wieśniak, Marcin

2016-01-01

We present a new approach to Stokes parameters, which enables one to see better non-classical properties of bright quantum light, and of undefined overall photon numbers. The crucial difference is as follows. The standard quantum optical Stokes parameters are averages of differences of intensities of light registered at the two exits of polarization analyzers, and one gets their normalized version by dividing them by the average total intensity. The new ones are averages of the registered normalized Stokes parameters, for the duration of the experiment. That is, we redefine each Stokes observable as the difference of photon number operators at the two exits of a polarizing beam splitter multiplied by the inverse of their sum. The vacuum eigenvalue of the operator is defined a zero. We show that with such an approach one can obtain more sensitive entanglement indicators based on polarization measurements. (paper)

On entanglement of light and Stokes parameters

Science.gov (United States)

Żukowski, Marek; Laskowski, Wiesław; Wieśniak, Marcin

2016-08-01

We present a new approach to Stokes parameters, which enables one to see better non-classical properties of bright quantum light, and of undefined overall photon numbers. The crucial difference is as follows. The standard quantum optical Stokes parameters are averages of differences of intensities of light registered at the two exits of polarization analyzers, and one gets their normalized version by dividing them by the average total intensity. The new ones are averages of the registered normalized Stokes parameters, for the duration of the experiment. That is, we redefine each Stokes observable as the difference of photon number operators at the two exits of a polarizing beam splitter multiplied by the inverse of their sum. The vacuum eigenvalue of the operator is defined a zero. We show that with such an approach one can obtain more sensitive entanglement indicators based on polarization measurements.

Adrian Stokes and the portrait of Melanie Klein.

Science.gov (United States)

Sayers, Janet

2015-08-01

This paper focuses on the offer by the art writer Adrian Stokes to commission and pay for a portrait of the psychoanalyst Melanie Klein by the artist William Coldstream. It details some of the precursors of this offer in Stokes's preceding involvement first with Klein and then with Coldstream; her response to this offer; and its outcome and aftermath in Stokes's subsequent writing about Klein and Coldstream. Copyright © 2015 Institute of Psychoanalysis.

Analyticity estimates for the Navier-Stokes equations

DEFF Research Database (Denmark)

Herbst, I.; Skibsted, Erik

We study spatial analyticity properties of solutions of the Navier-Stokes equation and obtain new growth rate estimates for the analyticity radius. We also study stability properties of strong global solutions of the Navier-Stokes equation with data in and prove a stability result...

Tecnologias assistivas para cegos: competências essenciais para promoção da saúde conforme Consenso de Galway

Directory of Open Access Journals (Sweden)

Luciana Vieira de Carvalho

2017-01-01

Full Text Available Objective: to identify the key competence domains defined in the Galway Consensus Conference Statement present in assistive technologies to promote the health of blind adults. Methods: integrative review carried out in the Latin American and Caribbean Health Sciences Literature, SCOPUS , Cumulative Index to Nursing and Allied Health Literature, and Medical Publications portal. After application of inclusion criteria, the sample consisted of 10 articles. Eight competencies for health promotion were analyzed: Catalyzing change, Leadership, Assessment of needs, Planning, Implementation, Advocacy, and Partnerships. Results: the competences Catalyzing change and Partnerships prevailed, present in all articles. No study approached the Leadership and Advocacy. Conclusion: the competences Catalyzing change, Assessment of needs, Planning, Implementation, Evaluation and Partnerships were observed in technologies for promoting the health of blind adults.

An astronomical murder?

Science.gov (United States)

Belenkiy, Ari

2010-04-01

Ari Belenkiy examines the murder of Hypatia of Alexandria, wondering whether problems with astronomical observations and the date of Easter led to her becoming a casualty of fifth-century political intrigue.

Observation of correlated anti-Stokes emissions by multiwave mixing in sodium vapor

International Nuclear Information System (INIS)

Motomura, Koji; Tsukamoto, Mayumi; Wakiyama, Akira; Harada, Ken-ichi; Mitsunaga, Masaharu

2005-01-01

We study experimentally nonlinear optical processes in which Stokes and anti-Stokes fields build up under strong, resonant, counterpropagating pump laser excitation in atomic sodium vapor. We find that, at some pump frequency, two off-axis anti-Stokes emissions propagating along reflection-symmetric directions are strongly temporally correlated, with a correlation time of 0.5 μs and a correlation range of 1 mrad. It is shown by the numerical analysis based on six-wave mixing process involving pump, Stokes, and anti-Stokes waves in the forward and the backward directions that such correlated anti-Stokes emissions are possible when the medium is opaque for the Stokes field and transparent for the anti-Stokes field. Possibilities of quantum correlation for entangled photon generation using this system are discussed

Finding Hidden Treasures: Investigations in US Astronomical Plate Archives

Czech Academy of Sciences Publication Activity Database

Hudec, René; Hudec, L.

2013-01-01

Roč. 53, č. 1 (2013), s. 23-26 ISSN 1210-2709 R&D Projects: GA ČR GA205/08/1207 Institutional support: RVO:67985815 Keywords : astronomical data archives * astronomical photography * astronomical photographic archives Subject RIV: BH - Optics, Masers, Lasers

Astronomía en la cultura

Science.gov (United States)

López, A.; Giménez Benitez, S.; Fernández, L.

La Astronomía en la Cultura es el estudio interdisciplinario a nivel global de la astronomía prehistórica, antigua y tradicional, en el marco de su contexto cultural. Esta disciplina abarca cualquier tipo de estudios o líneas de investigación en que se relacione a la astronomía con las ciencias humanas o sociales. En ella se incluyen tanto fuentes escritas, relatos orales como fuentes arqueológicas, abarcando entre otros, los siguientes temas: calendarios, observación práctica, cultos y mitos, representación simbólica de eventos, conceptos y objetos astronómicos, orientación astronómica de tumbas, templos, santuarios y centros urbanos, cosmología tradicional y la aplicación ceremonial de tradiciones astronómicas, la propia historia de la astronomía y la etnoastronomía (Krupp, 1989) (Iwaniszewski, 1994). En nuestro trabajo abordamos la historia y situación actual de esta disciplina, sus métodos y sus relaciones con otras áreas de investigación.

Astronomical Image and Data Analysis

CERN Document Server

Starck, J.-L

2006-01-01

With information and scale as central themes, this comprehensive survey explains how to handle real problems in astronomical data analysis using a modern arsenal of powerful techniques. It treats those innovative methods of image, signal, and data processing that are proving to be both effective and widely relevant. The authors are leaders in this rapidly developing field and draw upon decades of experience. They have been playing leading roles in international projects such as the Virtual Observatory and the Grid. The book addresses not only students and professional astronomers and astrophysicists, but also serious amateur astronomers and specialists in earth observation, medical imaging, and data mining. The coverage includes chapters or appendices on: detection and filtering; image compression; multichannel, multiscale, and catalog data analytical methods; wavelets transforms, Picard iteration, and software tools. This second edition of Starck and Murtagh's highly appreciated reference again deals with to...

The amateur astronomer

CERN Document Server

Moore, Patrick

2006-01-01

Introduces astronomy and amateur observing together. This edition includes photographs and illustrations. The comprehensive appendices provide hints and tips, as well as data for every aspect of amateur astronomy. This work is useful for amateur astronomers

From Petrov-Einstein to Navier-Stokes

Science.gov (United States)

Lysov, Vyacheslav

The fluid/gravity correspondence relates solutions of the incompressible Navier-Stokes equation to metrics which solve the Einstein equations. We propose propose two possible approaches to establish this correspondence: perturbative expansion for shear modes and large mean curvature expansion for algebraically special metrics. We show by explicit construction that for every solution of the incompressible Navier-Stokes equation in p+1 dimensions, there is an associated "dual" solution of the vacuum Einstein equations in p+2 dimensions. The dual geometry has an intrinsically flat time-like boundary segment whose extrinsic curvature is given by the stress tensor of the Navier-Stokes fluid. We consider a "near-horizon" limit in which hypersurface becomes highly accelerated. The near-horizon expansion in gravity is shown to be mathematically equivalent to the hydrodynamic expansion in fluid dynamics, and the Einstein equation reduces to the incompressible Navier-Stokes equation. It is shown that imposing a Petrov type I condition on the hypersurface geometry reduces the degrees of freedom in the extrinsic curvature to those of a fluid. Moreover, expanding around a limit in which the mean curvature of the embedding diverges, the leading-order Einstein constraint equations on hypersurface are shown to reduce to the non-linear incompressible Navier-Stokes equation for a fluid moving in hypersurface. We extend the fluid/gravity correspondence to include the magnetohydrodynamics/gravity correspondence, which translates solutions of the equations of magnetohydrodynamics (describing charged fluids) into geometries that satisfy the Einstein-Maxwell equations. We present an explicit example of this new correspondence in the context of flat Minkowski space. We show that a perturbative deformation of the Rindler wedge satisfies the Einstein-Maxwell equations provided that the parameters appearing in the expansion, which we interpret as fluid fields, satisfy the

Approximate Stokes Drift Profiles and their use in Ocean Modelling

Science.gov (United States)

Breivik, Oyvind; Bidlot, Jea-Raymond; Janssen, Peter A. E. M.; Mogensen, Kristian

2016-04-01

Deep-water approximations to the Stokes drift velocity profile are explored as alternatives to the monochromatic profile. The alternative profiles investigated rely on the same two quantities required for the monochromatic profile, viz the Stokes transport and the surface Stokes drift velocity. Comparisons against parametric spectra and profiles under wave spectra from the ERA-Interim reanalysis and buoy observations reveal much better agreement than the monochromatic profile even for complex sea states. That the profiles give a closer match and a more correct shear has implications for ocean circulation models since the Coriolis-Stokes force depends on the magnitude and direction of the Stokes drift profile and Langmuir turbulence parameterizations depend sensitively on the shear of the profile. Of the two Stokes drift profiles explored here, the profile based on the Phillips spectrum is by far the best. In particular, the shear near the surface is almost identical to that influenced by the f-5 tail of spectral wave models. The NEMO general circulation ocean model was recently extended to incorporate the Stokes-Coriolis force along with two other wave-related effects. The ECWMF coupled atmosphere-wave-ocean ensemble forecast system now includes these wave effects in the ocean model component (NEMO).

A change in fault-plane orientation between foreshocks and aftershocks of the Galway Lake earthquake, ML = 5.2, 1975, Mojave desert, California

Science.gov (United States)

Fuis, G.S.; Lindh, A.G.

1979-01-01

A marked change is observed in P/SV amplitude ratios, measured at station TPC, from foreshocks to aftershocks of the Galway Lake earthquake. This change is interpreted to be the result of a change in fault-plane orientation occurring between foreshocks and aftershocks. The Galway Lake earthquake, ML= 5.2, occurred on June 1, 1975. The first-motion fault-plane solutions for the main shock and most foreshocks and aftershocks indicate chiefly right-lateral strike-slip on NNW-striking planes that dip steeply, 70-90??, to the WSW. The main event was preceded by nine located foreshocks, ranging in magnitude from 1.9 to 3.4, over a period of 12 weeks, starting on March 9, 1975. All of the foreshocks form a tight cluster approximately 1 km in diameter. This cluster includes the main shock. Aftershocks are distributed over a 6-km-long fault zone, but only those that occurred inside the foreshock cluster are used in this study. Seismograms recorded at TPC (?? = 61 km), PEC (?? = 93 km), and CSP (?? = 83 km) are the data used here. The seismograms recorded at TPC show very consistent P/SV amplitude ratios for foreshocks. For aftershocks the P/SV ratios are scattered, but generally quite different from foreshock ratios. Most of the scatter for the aftershocks is confined to the two days following the main shock. Thereafter, however, the P/SV ratios are consistently half as large as for foreshocks. More subtle (and questionable) changes in the P/SV ratios are observed at PEC and CSP. Using theoretical P/SV amplitude ratios, one can reproduce the observations at TPC, PEC and CSP by invoking a 5-12?? counterclockwise change in fault strike between foreshocks and aftershocks. This interpretation is not unique, but it fits the data better than invoking, for example, changes in dip or slip angle. First-motion data cannot resolve this small change, but they permit it. Attenuation changes would appear to be ruled out by the fact that changes in the amplitude ratios, PTPC/PPEC and ptpc

Boundary Shape Control of the Navier-Stokes Equations and Applications

Institute of Scientific and Technical Information of China (English)

Kaitai LI; Jian SU; Aixiang HUANG

2010-01-01

In this paper,the geometrical design for the blade's surface(s)in an impeller or for the profile of an aircraft,is modeled from the mathematical point of view by a boundary shape control problem for the Navier-Stokes equations.The objective function is the sum of a global dissipative function and the power of the fluid.The control variables are the geometry of the boundary and the state equations are the Navier-Stokes equations.The Euler-Lagrange equations of the optimal control problem are derived,which are an elliptic boundary value system of fourth order,coupled with the Navier-Stokes equations.The authors also prove the existence of the solution of the optimal control problem,the existence of the solution of the Navier-Stokes equations with mixed boundary conditions,the weak continuity of the solution of the Navier-Stokes equations with respect to the geometry shape of the blade's surface and the existence of solutions of the equations for the G(a)teaux derivative of the solution of the Navier-Stokes equations with respect to the geometry of the boundary.

3D Topology optimization of Stokes flow problems

DEFF Research Database (Denmark)

Gersborg-Hansen, Allan; Dammann, Bernd

of energy efficient devices for 2D Stokes flow. Creeping flow problems are described by the Stokes equations which model very viscous fluids at macro scales or ordinary fluids at very small scales. The latter gives the motivation for topology optimization problems based on the Stokes equations being a model......The present talk is concerned with the application of topology optimization to creeping flow problems in 3D. This research is driven by the fact that topology optimization has proven very successful as a tool in academic and industrial design problems. Success stories are reported from such diverse...

Observatory Sponsoring Astronomical Image Contest

Science.gov (United States)

2005-05-01

Forget the headphones you saw in the Warner Brothers thriller Contact, as well as the guttural throbs emanating from loudspeakers at the Very Large Array in that 1997 movie. In real life, radio telescopes aren't used for "listening" to anything - just like visible-light telescopes, they are used primarily to make images of astronomical objects. Now, the National Radio Astronomy Observatory (NRAO) wants to encourage astronomers to use radio-telescope data to make truly compelling images, and is offering cash prizes to winners of a new image contest. Radio Galaxy Fornax A Radio Galaxy Fornax A Radio-optical composite image of giant elliptical galaxy NGC 1316, showing the galaxy (center), a smaller companion galaxy being cannibalized by NGC 1316, and the resulting "lobes" (orange) of radio emission caused by jets of particles spewed from the core of the giant galaxy Click on image for more detail and images CREDIT: Fomalont et al., NRAO/AUI/NSF "Astronomy is a very visual science, and our radio telescopes are capable of producing excellent images. We're sponsoring this contest to encourage astronomers to make the extra effort to turn good images into truly spectacular ones," said NRAO Director Fred K.Y. Lo. The contest, offering a grand prize of $1,000, was announced at the American Astronomical Society's meeting in Minneapolis, Minnesota. The image contest is part of a broader NRAO effort to make radio astronomical data and images easily accessible and widely available to scientists, students, teachers, the general public, news media and science-education professionals. That effort includes an expanded image gallery on the observatory's Web site. "We're not only adding new radio-astronomy images to our online gallery, but we're also improving the organization and accessibility of the images," said Mark Adams, head of education and public outreach (EPO) at NRAO. "Our long-term goal is to make the NRAO Image Gallery an international resource for radio astronomy imagery

Strong plasma shock structures based on the Navier--Stokes equations

International Nuclear Information System (INIS)

Abe, K.

1975-01-01

The structure of a plasma collisional shock wave is examined on the basis of the Navier--Stokes equations and simultaneously on the basis of the Fokker--Planck equation. The resultant structures are compared to check the validity of the Navier--Stokes equations applied to the structures of strong shock waves. The Navier--Stokes equations give quite correct structures for weak shock waves. For the strong shock waves, the detailed structures obtained from the Navier--Stokes equations differ from the results of the Fokker--Planck equation, but the shock thicknesses of the two shock waves are in relatively close agreement

Cosmological field theory for observational astronomers

International Nuclear Information System (INIS)

Zel'Dovich, Y.B.

1987-01-01

Theories of the very early Universe that use scalar fields (i.e., the so-called inflationary models of the Universe) have now come into wide use. The inflationary universe approach may perhaps solve some of the most difficult enigmas about the Universe as a whole. The inflationary universe forms a good bridge between the quantum theory of the birth of the Universe (which is still in the initial stages of development) and the standard hot Big Bang theory (which is well established, at least qualitatively). Therefore, an understanding of the basic ideas of inflation is a must for astronomers interested in the broad picture of the science. Astronomers are mathematically oriented enough (via celestial mechanics, electromagnetic theory, magnetohydrodynamics, nuclear reactions,etc.) that there is no negative attitude towards formulae in general. What the astronomer lacks is a knowledge of recent developments in particle physics and field theory. The astronomer should not be blamed for this, because these branches of physics are developing in a very peculiar fashion: some subfields of it are progressing comparatively slowly, with experimental verifications at each and every step, while other subfields progress rapidly

Astronomical Books and Charts in the Book of Bibliographie Coreenne

Science.gov (United States)

Lee, Ki-Won; Yang, Hong-Jin; Park, Myeong-Gu

2008-06-01

We investigate astronomical materials listed in the book of Bibliographie Coréenne written by Maurice Courant. He classified ancient Korean books into nine Divisions (?) and thirty six Classes (?), and published them as three volumes (ranging from 1894 to 1896) and one supplement (in 1901). In total, 3,821 books including astronomical ones are listed together with information on physical size, possessional place, bibliographical note, and so forth. Although this book is an essential one in the field of Korea bibliography and contains many astronomical materials such as Cheon-Mun-Ryu-Cho ????, Si-Heon-Seo ??????, and Cheon-Sang-Yeol-Cha-Bun-Ya-Ji-Do ????????, it has not been well known to the public nor to astronomical society. Of 3,821 catalogues, we found that about 50 Items (?) are related to astronomy or astrology, and verified that most ! of them are located in the Kyujanggak Royal Library ???. We also found an unknown astronomical chart, Hon-Cheon-Chong-Seong-Yeol-Cha-Bun-Ya-Ji-Do ??????????. Because those astronomical materials are not well known to international astronomical community and there have been few studies on the materials in Korea, we here introduce and review them, particularly with the astronomical viewpoint.

150th Anniversary of the Astronomical Observatory Library of Sciences

Science.gov (United States)

Solntseva, T.

The scientific library of the Astronomical observatory of Kyiv Taras Shevchenko University is one of the oldest ones of such a type in Ukraine. Our Astronomical Observatory and its scientific library will celebrate 150th anniversary of their foundation. 900 volumes of duplicates of Olbers' private library underlay our library. These ones were acquired by Russian Academy of Sciences for Poulkovo observatory in 1841 but according to Struve's order were transmitted to Kyiv Saint Volodymyr University. These books are of great value. There are works edited during Copernicus', Kepler's, Galilei's, Newton's, Descartes' lifetime. Our library contains more than 100000 units of storage - monographs, periodical astronomical editions from the first (Astronomische Nachrichten, Astronomical journal, Monthly Notices etc.), editions of the majority of the astronomical observatories and institutions of the world, unique astronomical atlases and maps

Heading in the Right Direction? Investigating Walkability in Galway City, Ireland

Directory of Open Access Journals (Sweden)

Mike Hynes

2018-04-01

Full Text Available As cities and towns worldwide strive to improve quality of life for citizens, debates centred on mobility are at the forefront of transportation policy thinking and urban design and planning. The automobile radically transformed cities, not always for the better, and the transport paradigm espoused over previous decades has primarily focussed on cars. This is still largely evident, driven by policymakers and key decisionmakers using forecasting and transportation and economic models that justify such car-centric planning. However, it is now clear that this approach of increasing automobility is unsustainable. Urban planners across the world are coming to a similar conclusion; they are better off with fewer cars, and a new vision is required, which sees people embracing active and sustainable transportation and sharing public space, information, and new innovative services to make cities more attractive and liveable. Walkability is the measure of how pleasant an area is for walking. By promoting and encouraging people to walk more, we achieve the benefits of better personal health and safer, more convivial neighbourhoods and communities. Making cities more walkable involves incorporating features into urban landscapes that make walking an agreeable experience and bringing a range of necessary and interesting destinations within walking distances of homes and workplaces. Using data from the Mobilities and Liveability in Galway project, this paper seeks a richer understanding of issues relating to existing topographies of walkability and the barriers and pressures that exist with regards to the further development of walking in the city—a healthy and pleasurable way of getting about.

Tip loss correction for actuator / Navier Stokes computations

DEFF Research Database (Denmark)

Shen, Wen Zhong; Sørensen, Jens Nørkær; Mikkelsen, Robert Flemming

2004-01-01

The new tip loss correction, initially developed for ID BEM computations [1], is now extended to 2D Actuator Disc / Navier-Stokes (AD/NS) computations and 3D Actuator Line / Navier-Stokes (AL/NS) computations. As shown in the paper, the tip loss correction is an important and necessary step...

Choosing and using astronomical filters

CERN Document Server

Griffiths, Martin

2014-01-01

As a casual read through any of the major amateur astronomical magazines will demonstrate, there are filters available for all aspects of optical astronomy. This book provides a ready resource on the use of the following filters, among others, for observational astronomy or for imaging: Light pollution filters Planetary filters Solar filters Neutral density filters for Moon observation Deep-sky filters, for such objects as galaxies, nebulae and more Deep-sky objects can be imaged in much greater detail than was possible many years ago. Amateur astronomers can take

The impact of the National Treatment Purchase Fund on numbers of core urology training cases at University Hospital Galway.

LENUS (Irish Health Repository)

Harney, T J

2011-06-01

Since the National Treatment Purchase Fund (NTPF) scheme was introduced in 2002, public patients waiting longer than three months for investigations and treatment are offered care in the private medical sector. Our aim was to assess the impact of the NTPF scheme on the number of training cases performed at University Hospital Galway (UHG). The number and type of urological procedures performed in the private medical sector under the NTFP scheme in 2008 were obtained from the UHG waiting list office. The number of these procedures performed on public patients by trainees at UHG in 2008 was determined retrospectively by reviewing theatre records. A significant number of core urology procedures were performed in the private sector via the NTPF scheme. Cancer centre designation and implementation of the EWTD will also place further pressures on urological training opportunities in Ireland.

On a theorem of Cattabriga related to Stokes equations

International Nuclear Information System (INIS)

Georgescu, V.

1978-01-01

We study the ''generalized Stokes boundary value problem'', which is a (generalization of a) linearized version of Navier-Stokes equations and we show the existence and unicity of the weak solution. It is known that these results can be used to prove the existence of weak (local) solutions to the Navier-Stokes equations. However, we are mainly interested in the method of proving it will be seen how easy the result follows from some general theorems about differential forms on a Riemannian manifold. (author)

The Classical Version of Stokes' Theorem Revisited

DEFF Research Database (Denmark)

Markvorsen, Steen

2005-01-01

Using only fairly simple and elementary considerations - essentially from first year undergraduate mathematics - we prove that the classical Stokes' theorem for any given surface and vector field in $\\mathbb{R}^{3}$ follows from an application of Gauss' divergence theorem to a suitable modification...... of the vector field in a tubular shell around the given surface. The intuitive appeal of the divergence theorem is thus applied to bootstrap a corresponding intuition for Stokes' theorem. The two stated classical theorems are (like the fundamental theorem of calculus) nothing but shadows of the general version...... to above. Our proof that Stokes' theorem follows from Gauss' divergence theorem goes via a well known and often used exercise, which simply relates the concepts of divergence and curl on the local differential level. The rest of the paper uses only integration in $1$, $2$, and $3$ variables together...

Synthesis and inversion of Stokes spectral profiles. Thesis

International Nuclear Information System (INIS)

Murphy, G.A.

1990-01-01

Observations of Stokes spectral profiles enable the magnetic fields on the Sun's surface to be determined. Inversion is the process whereby the profiles are reduced to magnetic field vectors. One of the most robust, accurate and rapid methods available for inversion uses the least-squares fitting of analytical Stokes profiles. As this technique is suitable for the automated reduction of large sets of data, it has been adopted for use with the Advanced Stokes Polarimeter, presently under development. The limitations of inversion by analytical profile fitting have not been firmly established. Confident analysis of magnet field vectors depends upon the precise interpretation of reduced data. In this work, a framework is introduced which allows such an assessment to be made. The magnetofluid-static sunspot models presented here provide a self-consistent range of physical conditions similar to those in sunspots. Inversion can then be carried out on Stokes profiles synthesized from these known realistic conditions. The capabilities of an inversion technique can be evaluated by comparison between the models and the deduced values

Solutions of Navier-Stokes Equation with Coriolis Force

Directory of Open Access Journals (Sweden)

Sunggeun Lee

2017-01-01

Full Text Available We investigate the Navier-Stokes equation in the presence of Coriolis force in this article. First, the vortex equation with the Coriolis effect is discussed. It turns out that the vorticity can be generated due to a rotation coming from the Coriolis effect, Ω. In both steady state and two-dimensional flow, the vorticity vector ω gets shifted by the amount of -2Ω. Second, we consider the specific expression of the velocity vector of the Navier-Stokes equation in two dimensions. For the two-dimensional potential flow v→=∇→ϕ, the equation satisfied by ϕ is independent of Ω. The remaining Navier-Stokes equation reduces to the nonlinear partial differential equations with respect to the velocity and the corresponding exact solution is obtained. Finally, the steady convective diffusion equation is considered for the concentration c and can be solved with the help of Navier-Stokes equation for two-dimensional potential flow. The convective diffusion equation can be solved in three dimensions with a simple choice of c.

Incompressible Navier-Stokes equations. Theory and practice

Energy Technology Data Exchange (ETDEWEB)

Gjesdal, T.

1996-12-31

This paper contains notes from a seminar presented at the Dept. of Mathematics in the University of Bergen, Norway, Oct. 1996. It first introduces the theory of existence and uniqueness of solutions to the incompressible Navier-Stokes equation and defines a well-posed initial-boundary value problem. It then discusses different methods for solving numerically the Navier-Stokes equations in velocity-pressure formulation. The emphasis is on pressure correction methods. 19 refs.

Serbian Astronomers in Science Citation Index in the XX Century

Science.gov (United States)

Dimitrijevic, Milan S.

The book is written paralelly in Serbian and English. The presence of works of Serbian astronomers and works in astronomical journals published by other Serbian scientists, in Science Citation Index within the period from 1945 up to the end of 2000, has been analyzed. Also is presented the list of 38 papers which had some influence on the development of astronomy in the twentieth century. A review of the development of astronomy in Serbia in the last century is given as well. Particular attention is payed to the Astronomical Observatory, the principal astronomical institution in Serbia, where it is one of the oldest scientific organizations and the only autonomous astronomical institute. Its past development forms an important part of the history of science and culture in these regions. In the book is also considered and the history of the university teaching of astronomy in Serbia after the second world war. First of all the development of the Chair of Astronomy at the Faculty of Mathematics in Belgrade, but also the teaching of astronomy at University in Novi Sad, Ni and Kragujevac is discussed. In addition to professional Astronomy, well developed in Serbia is also the amateur Astronomy. In the review is first of all included the largest and the oldest organization of amateur-astronomers in Serbia, founded in 1934. Besides, here are the Astronomical Society "Novi Sad", ADNOS and Research Station "Petnica". In Valjevo, within the framework of the Society of researchers "Vladimir Mandic - Manda", there is active also the Astronomical Group. In Kragujevac, on the roof of the Institute of Physics of the Faculty of Sciences, there is the "Belerofont" Observatory. In Ni, at the close of the sixties and the start of the seventies, there was operating a branch of the Astronomical Society "Rudjer Bokovic", while at the Faculty of Philosophy there existed in the period 1976-1980 the "Astro-Geophysical Society". In the year 1996 there was founded Astronomical Society

Abnormal anti-Stokes Raman emission as a coherent anti-Stokes Raman scattering-like process in disordered media

International Nuclear Information System (INIS)

Baltog, Ioan; Baibarac, Mihaela; Smaranda, Ion; Lefrant, Serge

2011-01-01

In this paper, we demonstrate that, by continuous single beam excitation, one can generate an abnormal anti-Stokes Raman emission (AASRE) whose properties are similar to a coherent anti-Stokes Raman scattering (CARS). The effect has been observed in materials which possess intrinsically nonlinear properties (LiNbO 3 and CdS), which have the electric susceptibility of third order different from zero, χ (3) ≠ 0, as well as in materials that become nonlinear under resonant optical excitation. In the latter case, we used poly-3,4-ethylendioxythiophene (PEDOT) in its undoped state deposited electrochemically on Au support. Raman studies corroborated with images of optical microscopy demonstrate that the production of AASRE is conditioned by the existence of a particular morphology of the sample able to ensure efficient transport of the light inside the sample through a multiple light scattering mechanism. In this context, it was found that LiNbO 3 and CdS in powder form as well as the PEDOT films layered on a rough Au substrate are suitable morphological forms. We explain AASRE as resulting from a wave-mixing mechanism of the incident laser light ω l with a Stokes-shifted Raman light ω S produced by a spontaneous Raman light scattering process, both strongly scattered inside the sample. As a CARS process, AASRE is conditioned by the achievement of phase-matching requirements, which makes the difference between the wave vectors of mixing light close to zero, Δk =/2k l - k S - k CARS /∼ 0. In condensed media, the small dispersion of the refractive index makes Δk ∼ 0 so that the formation of a favourable phase-matching geometry may be accomplished even at a crossing angle θ of travelling scattered light ω l and ω S . For tightly focused beams, the requirement of phase matching relaxes; it is no longer sensitive to the Raman shift, so that a wide intense anti-Stokes Raman spectrum is observed at an angle larger than the Stokes Raman spectrum.

Preservation and maintenance of the astronomical sites in Armenia

Science.gov (United States)

Mickaelian, A. M.

2008-01-01

Astronomy in Armenia was popular since ancient times. There are signs of astronomical observations coming from a few thousands years ago. Two ancient observatories, Karahunge and Metzamor are especially well known. Karahunge is the Armenian twin of the Stonehenge and is even older. However, there is no proper attention from the state authorities and efforts are needed for preservation of such historical-astronomical monuments. The Byurakan Astrophysical Observatory (BAO) is the modern famous Armenian observatory founded in 1946 by the outstanding scientist Victor Ambartsumian. It was one of the world astronomical centres in 1950-s to 1970-s, and at present is the largest observatory in the Middle East area. As the ancient astronomical sites, Byurakan also needs a proper attitude from the state authorities and corresponding international organizations to preserve its values and importance for the present and future astronomical activities in the region, including its rich observational archive, telescopes, and human resources. Despite all the difficulties, the Armenian astronomers keep high international level of research and display various activities organizing international meetings and schools, preparing new young generation for the future research. The Armenian Astronomical Society (ArAS) is an affiliated member of EAS. Armenia has its Virtual Observatory project (ArVO) as well. The next Joint European and National Astronomy Meeting (JENAM-2007) will be held in Yerevan, Armenia, in August 2007. There are plans to organize astronomical tours to Armenia for making observations from various sites, including the ancient observatories. The future of astronomy in Armenia strongly depends on all of this activities and the proper attention both from state authorities and society.

Basic Optics for the Astronomical Sciences

CERN Document Server

Breckinridge, James

2012-01-01

This text was written to provide students of astronomy and engineers an understanding of optical science - the study of the generation, propagation, control, and measurement of optical radiation - as it applies to telescopes and instruments for astronomical research in the areas of astrophysics, astrometry, exoplanet characterization, and planetary science. The book provides an overview of the elements of optical design and physical optics within the framework of the needs of the astronomical community.

Information seeking behavior of Greek astronomers

OpenAIRE

Brindesi, Hara; Kapidakis, Sarantos

2011-01-01

This study examines three aspects of information seeking behaviour of astronomers in Greece including a) the importance they place in keeping up- to-date with current developments b) the methods they depend on for keeping up-to-date and c) the information sources they mostly use. We adopted an intradisciplinary approach in order to investigate similarities and differences in information seeking behaviour among astronomers when examining them as groups bearing different characteristics, includ...

New astronomical references in two Catalonian late medieval documents.

Science.gov (United States)

Martínez, María José; Marco, Francisco J

2014-01-01

In 2008, after 13 years of preparation, the Generalitat of Catalunya finished the publication of the 10 volumes of the Dietaris de la Generalitat de Catalunya. The Dietaris, as well as a closely related source, the llibre de Jornades 1411/1484 de Jaume Safont, cover the period of 1411 to 1539. In this article, we examine astronomical references contained in these two sources, and place them in their historical context. Our main focus lies on astronomical phenomena that have not previously been published in the astronomical literature. In fact, relatively few astronomical records are accessible in Spanish medieval and early modern history, and our paper intends to fill this gap partially.

Astronomical Books and Charts in the Book of Bibliographie Coreenne

Directory of Open Access Journals (Sweden)

Ki-Won Lee

2008-06-01

Full Text Available We investigate astronomical materials listed in the book of Bibliographie Coreenne written by Maurice Courant. He classified ancient Korean books into nine Divisions (部 and thirty six Classes (類, and published them as three volumes (ranging from 1894 to 1896 and one supplement (in 1901. In total, 3,821 books including astronomical ones are listed together with information on physical size, possessional place, bibliographical note, and so forth. Although this book is an essential one in the field of Korea bibliography and contains many astronomical materials such as Cheon-Mun-Ryu-Cho 天文類抄, Si-Heon-Seo 時憲書, and Cheon-Sang-Yeol-Cha-Bun-Ya-Ji-Do 天象列次分野之圖, it has not been well known to the public nor to astronomical society. Of 3,821 catalogues, we found that about 50 Items (種 are related to astronomy or astrology, and verified that most of them are located in the Kyujanggak Royal Library 奎章閣. We also found an unknown astronomical chart, Hon-Cheon-Chong-Seong-Yeol-Cha-Bun-Ya-Ji-Do 渾天總星列次分野之圖. Because those astronomical materials are not well known to international astronomical community and there have been few studies on the materials in Korea, we here introduce and review them, particularly with the astronomical viewpoint.

Early results from the Infrared Astronomical Satellite

International Nuclear Information System (INIS)

Neugebauer, G.; Beichman, C.A.; Soifer, B.T.

1984-01-01

For 10 months the Infrared Astronomical Satellite (IRAS) provided astronomers with what might be termed their first view of the infrared sky on a clear, dark night. Without IRAS, atmospheric absorption and the thermal emission from both the atmosphere and Earthbound telescopes make the task of the infrared astronomer comparable to what an optical astronomer would face if required to work only on cloudy afternoons. IRAS observations are serving astronomers in the same manner as the photographic plates of the Palomar Observatory Sky Survey; just as the optical survey has been used by all astronomers for over three decades, as a source of quantitative information about the sky and as a roadmap for future observations, the results of IRAS will be studied for years to come. IRAS has demonstrated the power of infrared astronomy from space. Already, from a brief look at a miniscule fraction of the data available, we have learned much about the solar system, about nearby stars, about the Galaxy as a whole and about distant extragalactic systems. Comets are much dustier than previously thought. Solid particles, presumably the remnants of the star-formation process, orbit around Vega and other stars and may provide the raw material for planetary systems. Emission from cool interstellar material has been traced throughout the Galaxy all the way to the galactic poles. Both the clumpiness and breadth of the distribution of this material were previously unsuspected. The far-infrared sky away from the galactic plane has been found to be dominate by spiral galaxies, some of which emit more than 50% and as much as 98% of their energy in the infrared - an exciting and surprising revelation. The IRAS mission is clearly the pathfinder for future mission that, to a large extent, will be devoted to the discoveries revealed by IRAS. 8 figures

Statistics of the Navier–Stokes-alpha-beta regularization model for fluid turbulence

International Nuclear Information System (INIS)

Hinz, Denis F; Kim, Tae-Yeon; Fried, Eliot

2014-01-01

We explore one-point and two-point statistics of the Navier–Stokes-αβ regularization model at moderate Reynolds number (Re ≈ 200) in homogeneous isotropic turbulence. The results are compared to the limit cases of the Navier–Stokes-α model and the Navier–Stokes-αβ model without subgrid-scale stress, as well as with high-resolution direct numerical simulation. After reviewing spectra of different energy norms of the Navier–Stokes-αβ model, the Navier–Stokes-α model, and Navier–Stokes-αβ model without subgrid-scale stress, we present probability density functions and normalized probability density functions of the filtered and unfiltered velocity increments along with longitudinal velocity structure functions of the regularization models and direct numerical simulation results. We highlight differences in the statistical properties of the unfiltered and filtered velocity fields entering the governing equations of the Navier–Stokes-α and Navier–Stokes-αβ models and discuss the usability of both velocity fields for realistic flow predictions. The influence of the modified viscous term in the Navier–Stokes-αβ model is studied through comparison to the case where the underlying subgrid-scale stress tensor is neglected. Whereas, the filtered velocity field is found to have physically more viable probability density functions and structure functions for the approximation of direct numerical simulation results, the unfiltered velocity field is found to have flatness factors close to direct numerical simulation results. (paper)

The incompressible non-relativistic Navier-Stokes equation from gravity

International Nuclear Information System (INIS)

Bhattacharyya, Sayantani; Minwalla, Shiraz; Wadia, Spenta R.

2009-01-01

We note that the equations of relativistic hydrodynamics reduce to the incompressible Navier-Stokes equations in a particular scaling limit. In this limit boundary metric fluctuations of the underlying relativistic system turn into a forcing function identical to the action of a background electromagnetic field on the effectively charged fluid. We demonstrate that special conformal symmetries of the parent relativistic theory descend to 'accelerated boost' symmetries of the Navier-Stokes equations, uncovering a conformal symmetry structure of these equations. Applying our scaling limit to holographically induced fluid dynamics, we find gravity dual descriptions of an arbitrary solution of the forced non-relativistic incompressible Navier-Stokes equations. In the holographic context we also find a simple forced steady state shear solution to the Navier-Stokes equations, and demonstrate that this solution turns unstable at high enough Reynolds numbers, indicating a possible eventual transition to turbulence.

Wavefront sensing with all-digital Stokes measurements

CSIR Research Space (South Africa)

Dudley, Angela L

2014-09-25

Full Text Available to wavefront sensing [8] based on Stokes polarimetry which makes use of the amplitude and phase relationship between orthogonal states of polarization. With our approach a field of interest is generated by encoding an appropriate hologram on a spatial light... modulator (SLM). Since SLMs are diffraction-inefficient, we can exploit the amplitude relationship between the orthogonal polarization states allowing the execution of Stokes polarimetry of the co-linear superposition of the reference beam and the beam...

Astronomical Observatory of Belgrade from 1924 to 1955

Science.gov (United States)

Radovanac, M.

2014-12-01

History of the Astronomical Observatory in Belgrade, as the presentation is done here, become the field of interest to the author of the present monograph in early 2002. Then, together with Luka C. Popovic, during the Conference "Development of Astronomy among Serbs II" held in early April of that year, he prepared a paper entitled "Astronomska opservatorija tokom Drugog Svetskog rata" (Astronomical Observatory in the Second World War). This paper was based on the archives material concerning the Astronomical Observatory which has been professionally bearing in mind the author's position the subject of his work.

Novel Algorithms for Astronomical Plate Analyses

Czech Academy of Sciences Publication Activity Database

Hudec, René; Hudec, L.

2011-01-01

Roč. 32, 1-2 (2011), s. 121-123 ISSN 0250-6335. [Conference on Multiwavelength Variability of Blazars. Guangzhou, 22,09,2010-24,09,2010] R&D Projects: GA ČR GA205/08/1207 Grant - others:GA ČR(CZ) GA102/09/0997; MŠMT(CZ) ME09027 Institutional research plan: CEZ:AV0Z10030501 Keywords : astronomical plates * plate archives archives * astronomical algorithms Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.400, year: 2011

An Astronomer In The Classroom: Observatoire de Paris's Partnership Between Teachers and Astronomers

Science.gov (United States)

Doressoundiram, A.; Barban, C.

2006-08-01

The Observatoire de Paris is offering a partnership between teachers and astronomers. The principle is simple: any teacher wishing to undertake a pedagogical project in astronomy, in the classroom or involving the entire school, can request the help of a mentor. An astronomer from the Observatoire de Paris will then follow the teacher's project progress and offer advice and scientific support throughout the school year. The projects may take different forms: construction projects (models, instruments), lectures, posters, exhibitions, etc. The type of assistance offered is as varied as the projects: lecture(s) in class, telephone and e-mail exchanges, visits to the Observatoire; an almost made-to-measure approach that delighted the thirty or so groups that benefited such partnership in the 2005-2006 academic year. And this number is continuously growing. There was a rich variety of projects undertaken, from mounting a show and building a solar clock to visiting a high altitude observatory, or resolving the mystery of Jupiter's great red spot. The Universe and its mysteries fascinate the young (and the not so- young) and provide a multitude of scientific topics that can be exploited in class. Astronomy offers the added advantage of being a multidisciplinary field. Thus, if most projects are generally initiated by a motivated teacher, they are often taken over by teachers in other subjects: Life and Earth Sciences (SVT), history, mathematics, French, and so forth. The project may consist in an astronomy workshop or be part of the school curriculum. Whatever the case, the astronomer's task is not to replace the teacher or the textbooks, but to propose activities or experiments that are easy to implement. Representing the Solar system on a school-yard scale, for instance, is a perfect way to make youngsters realize that the Universe consists mostly of empty space. There is no shortage of topics, and the students' enthusiasm, seldom absent, is the best reward for the

Estudio comparativo de flujo de fluido a través de una placa de orificio usando las ecuaciones de Stokes y de Navier-Stokes

Directory of Open Access Journals (Sweden)

Miryam Lucía Guerra-Mazo

2016-05-01

Full Text Available Presenta los resultados de la comparación entre las ecuaciones de Stokes y de Navier-Stokes para la simulación del flujo de agua líquida, a condiciones atmosféricas, a través de una placa orificio concéntrica. A partir de los datos experimentales que fueron tomados en el banco de fluidos, se evaluaron las simulaciones de ambas ecuaciones, usando el software libre Freefem++cs, que se basa en el método de los elementos finitos; las variables evaluadas son velocidad y presión en un intervalo de tiempo. Al analizar los resultados obtenidos con las simulaciones y comparar con los datos experimentales se encontró que las ecuaciones de Navier-Stokes representan mejor el sistema que la ecuación de Stokes.

Astronomical Data and Information Visualization

Science.gov (United States)

Goodman, Alyssa A.

2010-01-01

As the size and complexity of data sets increases, the need to "see" them more clearly increases as well. In the past, many scientists saw "fancy" data and information visualization as necessary for "outreach," but not for research. In this talk, I wlll demonstrate, using specific examples, why more and more scientists--not just astronomers--are coming to rely upon the development of new visualization strategies not just to present their data, but to understand it. Principal examples will be drawn from the "Astronomical Medicine" project at Harvard's Initiative in Innovative Computing, and from the "Seamless Astronomy" effort, which is co-sponsored by the VAO (NASA/NSF) and Microsoft Research.

The South African Astronomical Observatory

International Nuclear Information System (INIS)

1989-01-01

The research work discussed in this report covers a wide range, from work on the nearest stars to studies of the distant quasars, and the astronomers who have carried out this work come from universities and observatories spread around the world as well as from South African universities and from the South African Astronomical Observatory (SAAO) staff itself. A characteristic of much of this work has been its collaborative character. SAAO studies in 1989 included: supernovae 1987A; galaxies; ground-based observations of celestial x-ray sources; the Magellanic Clouds; pulsating variables; galactic structure; binary star phenomena; the provision of photometric standards; nebulous matter; stellar astrophysics, and astrometry

The Stokes-Einstein relation at moderate Schmidt number.

Science.gov (United States)

Balboa Usabiaga, Florencio; Xie, Xiaoyi; Delgado-Buscalioni, Rafael; Donev, Aleksandar

2013-12-07

The Stokes-Einstein relation for the self-diffusion coefficient of a spherical particle suspended in an incompressible fluid is an asymptotic result in the limit of large Schmidt number, that is, when momentum diffuses much faster than the particle. When the Schmidt number is moderate, which happens in most particle methods for hydrodynamics, deviations from the Stokes-Einstein prediction are expected. We study these corrections computationally using a recently developed minimally resolved method for coupling particles to an incompressible fluctuating fluid in both two and three dimensions. We find that for moderate Schmidt numbers the diffusion coefficient is reduced relative to the Stokes-Einstein prediction by an amount inversely proportional to the Schmidt number in both two and three dimensions. We find, however, that the Einstein formula is obeyed at all Schmidt numbers, consistent with linear response theory. The mismatch arises because thermal fluctuations affect the drag coefficient for a particle due to the nonlinear nature of the fluid-particle coupling. The numerical data are in good agreement with an approximate self-consistent theory, which can be used to estimate finite-Schmidt number corrections in a variety of methods. Our results indicate that the corrections to the Stokes-Einstein formula come primarily from the fact that the particle itself diffuses together with the momentum. Our study separates effects coming from corrections to no-slip hydrodynamics from those of finite separation of time scales, allowing for a better understanding of widely observed deviations from the Stokes-Einstein prediction in particle methods such as molecular dynamics.

Optimal distribution of integration time for intensity measurements in Stokes polarimetry.

Science.gov (United States)

Li, Xiaobo; Liu, Tiegen; Huang, Bingjing; Song, Zhanjie; Hu, Haofeng

2015-10-19

We consider the typical Stokes polarimetry system, which performs four intensity measurements to estimate a Stokes vector. We show that if the total integration time of intensity measurements is fixed, the variance of the Stokes vector estimator depends on the distribution of the integration time at four intensity measurements. Therefore, by optimizing the distribution of integration time, the variance of the Stokes vector estimator can be decreased. In this paper, we obtain the closed-form solution of the optimal distribution of integration time by employing Lagrange multiplier method. According to the theoretical analysis and real-world experiment, it is shown that the total variance of the Stokes vector estimator can be significantly decreased about 40% in the case discussed in this paper. The method proposed in this paper can effectively decrease the measurement variance and thus statistically improves the measurement accuracy of the polarimetric system.

Polarization speckles and generalized Stokes vector wave: a review [invited

DEFF Research Database (Denmark)

Takeda, Mitsuo; Wang, Wei; Hanson, Steen Grüner

2010-01-01

We review some of the statistical properties of polarization-related speckle phenomena, with an introduction of a less known concept of polarization speckles and their spatial degree of polarization. As a useful means to characterize twopoint vector field correlations, we review the generalized...... Stokes parameters proposed by Korotkova and Wolf, and introduce its time-domain representation to describe the space-time evolution of the correlation between random electric vector fields at two different space-time points. This time-domain generalized Stokes vector, with components similar to those...... of the beam coherence polarization matrix proposed by Gori, is shown to obey the wave equation in exact analogy to a coherence function of scalar fields. Because of this wave nature, the time-domain generalized Stokes vector is referred to as generalized Stokes vector wave in this paper....

Compliance of the Stokes-Einstein model and breakdown of the Stokes-Einstein-Debye model for a urea-based supramolecular polymer of high viscosity.

Science.gov (United States)

Świergiel, Jolanta; Bouteiller, Laurent; Jadżyn, Jan

2014-11-14

Impedance spectroscopy was used for the study of the static and dynamic behavior of the electrical conductivity of a hydrogen-bonded supramolecular polymer of high viscosity. The experimental data are discussed in the frame of the Stokes-Einstein and Stokes-Einstein-Debye models. It was found that the translational movement of the ions is due to normal Brownian diffusion, which was revealed by a fulfillment of Ohm's law by the electric current and a strictly exponential decay of the current after removing the electric stimulus. The dependence of the dc conductivity on the viscosity of the medium fulfills the Stokes-Einstein model quite well. An extension of the model, by including in it the conductivity relaxation time, is proposed in this paper. A breakdown of the Stokes-Einstein-Debye model is revealed by the relations of the dipolar relaxation time to the viscosity and to the dc ionic conductivity. The importance of the C=O···H-N hydrogen bonds in that breakdown is discussed.

Optimal control of compressible Navier-Stokes equations

International Nuclear Information System (INIS)

Ito, K.; Ravindran, S.S.

1994-01-01

Optimal control for the viscous incompressible flows, which are governed by incompressible Navier-Stokes equations, has been the subject of extensive study in recent years, see, e.g., [AT], [GHS], [IR], and [S]. In this paper we consider the optimal control of compressible isentropic Navier-Stokes equations. We develop the weak variational formulation and discuss the existence and necessary optimality condition characterizing the optimal control. A numerical method based on the mixed-finite element method is also discussed to compute the control and numerical results are presented

Measurement of the Stokes parameters of light

International Nuclear Information System (INIS)

Berry, H.G.; Gabrielse, G.; Livingston, A.E.

1977-01-01

We describe a measuring system for determing the state of polarization of a beam of light in terms of its Stokes parameters. The technique which can be fully automated incorporates a monochromator and single photon counting detection and can thus be applied over a large wavelength range for very weak optical signals. Fourier transformation of the data by an on-line minicomputer allows immediate calculation of the Stokes parameters. We discuss special applications to light emitted from excited atomic systems with and without cylindrical symmetry

Inviscid limit of stochastic damped 2D Navier–Stokes equations

International Nuclear Information System (INIS)

Bessaih, Hakima; Ferrario, Benedetta

2014-01-01

We consider the inviscid limit of the stochastic damped 2D Navier–Stokes equations. We prove that, when the viscosity vanishes, the stationary solution of the stochastic damped Navier–Stokes equations converges to a stationary solution of the stochastic damped Euler equation and that the rate of dissipation of enstrophy converges to zero. In particular, this limit obeys an enstrophy balance. The rates are computed with respect to a limit measure of the unique invariant measure of the stochastic damped Navier–Stokes equations. (paper)

Astronomers gossip about the (cosmic) neighborhood.

Science.gov (United States)

Jayawardhana, R

1994-09-09

The Hague, Netherlands, last month welcomed 2000 astronomers from around the world for the 22nd General Assembly of the International Astronomical Union (IAU). From 15 to 27 August, they participated in symposia and discussions on topics ranging from the down-to-Earth issue of light and radio-frequency pollution to the creation of elements at the farthest reaches of time and space, in the big bang. Some of the most striking news, however, came in new findings from our galaxy and its immediate surroundings.

On the Astronomical Knowledge and Traditions of Aboriginal Australians

Science.gov (United States)

Hamacher, Duane W.

2011-12-01

Historian of science David Pingree defines science in a broad context as the process of systematically explaining perceived or imaginary phenomena. Although Westerners tend to think of science being restricted to Western culture, I argue in this thesis that astronomical scientific knowledge is found in Aboriginal traditions. Although research into the astronomical traditions of Aboriginal Australians stretches back for more than 150 years, it is relatively scant in the literature. We do know that the sun, moon, and night sky have been an important and inseparable component of the landscape to hundreds of Australian Aboriginal groups for thousands (perhaps tens-of-thousands) of years. The literature reveals that astronomical knowledge was used for time keeping, denoting seasonal change and the availability of food sources, navigation, and tidal prediction. It was also important for rituals and ceremonies, birth totems, marriage systems, cultural mnemonics, and folklore. Despite this, the field remains relatively unresearched considering the diversity of Aboriginal cultures and the length of time people have inhabited Australia (well over 40,000 years). Additionally, very little research investigating the nature and role of transient celestial phenomena has been conducted, leaving our understanding of Indigenous astronomical knowledge grossly incomplete. This thesis is an attempt to overcome this deficiency, with a specific focus on transient celestial phenomena. My research, situated in the field of cultural astronomy, draws from the sub-disciplines of archaeoastronomy, ethnoastronomy, historical astronomy, and geomythology. This approach incorporates the methodologies and theories of disciplines in the natural sciences, social sciences, and humanities. This thesis, by publication, makes use of archaeological, ethnographic, and historical records, astronomical software packages, and geographic programs to better understand the ages of astronomical traditions and the

Astronomical optics

CERN Document Server

Schroeder, Daniel J

1988-01-01

Written by a recognized expert in the field, this clearly presented, well-illustrated book provides both advanced level students and professionals with an authoritative, thorough presentation of the characteristics, including advantages and limitations, of telescopes and spectrographic instruments used by astronomers of today.Key Features* Written by a recognized expert in the field* Provides both advanced level students and professionals with an authoritative, thorough presentation of the characteristics, including advantages and limitations, of telescopes and spectrographic i

Implications of Navier-Stokes turbulence theory for plasma turbulence

International Nuclear Information System (INIS)

Montgomery, David

1977-01-01

A brief discussion of Navier-Stokes turbulence theory is given with particular reference to the two dimensional case. The MHD turbulence is introduced with possible applications of techniques developed in Navier-Stokes theory. Turbulence in Vlasov plasma is also discussed from the point of view of the ''direct interaction approximation'' (DIA). (A.K.)

Effectiveness of Amateur Astronomers as Informal Science Educators

Science.gov (United States)

Gibbs, Michael G.; Berendsen, Margaret

2007-01-01

The Astronomical Society of the Pacific (ASP) conducted a national survey of in-service teachers participating in Project ASTRO. The survey results document (1) the value that teachers place on supplemental astronomy education provided by professional and amateur astronomers, and (2) the difference that teachers perceive in the value provided by…

A note on the Stokes operator and its powers

KAUST Repository

Guermond, Jean-Luc; Salgado, Abner

2010-01-01

The so-called Stokes operator is an important tool in the analysis of the solutions of the Navier-Stokes equations and their numerical approximation. The aim of this note is to clarify certain properties of the fractional powers of this operator which are sometimes misused. © 2010 Korean Society for Computational and Applied Mathematics.

A note on the Stokes operator and its powers

KAUST Repository

Guermond, Jean-Luc

2010-04-28

The so-called Stokes operator is an important tool in the analysis of the solutions of the Navier-Stokes equations and their numerical approximation. The aim of this note is to clarify certain properties of the fractional powers of this operator which are sometimes misused. © 2010 Korean Society for Computational and Applied Mathematics.

Coronagraph for astronomical imaging and spectrophotometry

Science.gov (United States)

Vilas, Faith; Smith, Bradford A.

1987-01-01

A coronagraph designed to minimize scattered light in astronomical observations caused by the structure of the primary mirror, secondary mirror, and secondary support structure of a Cassegrainian telescope is described. Direct (1:1) and reducing (2.7:1) imaging of astronomical fields are possible. High-quality images are produced. The coronagraph can be used with either a two-dimensional charge-coupled device or photographic film camera. The addition of transmission dispersing optics converts the coronagraph into a low-resolution spectrograph. The instrument is modular and portable for transport to different observatories.

Coupling nonlinear Stokes and Darcy flow using mortar finite elements

KAUST Repository

Ervin, Vincent J.; Jenkins, Eleanor W.; Sun, Shuyu

2011-01-01

We study a system composed of a nonlinear Stokes flow in one subdomain coupled with a nonlinear porous medium flow in another subdomain. Special attention is paid to the mathematical consequence of the shear-dependent fluid viscosity for the Stokes

National Astronomical Observatory of Japan

CERN Document Server

Haubold, Hans J; UN/ESA/NASA Workshop on the International Heliophysical Year 2007 and Basic Space Science, hosted by the National Astronomical Observatory of Japan

2010-01-01

This book represents Volume II of the Proceedings of the UN/ESA/NASA Workshop on the International Heliophysical Year 2007 and Basic Space Science, hosted by the National Astronomical Observatory of Japan, Tokyo, 18 - 22 June, 2007. It covers two programme topics explored in this and past workshops of this nature: (i) non-extensive statistical mechanics as applicable to astrophysics, addressing q-distribution, fractional reaction and diffusion, and the reaction coefficient, as well as the Mittag-Leffler function and (ii) the TRIPOD concept, developed for astronomical telescope facilities. The companion publication, Volume I of the proceedings of this workshop, is a special issue in the journal Earth, Moon, and Planets, Volume 104, Numbers 1-4, April 2009.

Intrinsic coincident full-Stokes polarimeter using stacked organic photovoltaics.

Science.gov (United States)

Yang, Ruonan; Sen, Pratik; O'Connor, B T; Kudenov, M W

2017-02-20

An intrinsic coincident full-Stokes polarimeter is demonstrated by using strain-aligned polymer-based organic photovoltaics (OPVs) that can preferentially absorb certain polarized states of incident light. The photovoltaic-based polarimeter is capable of measuring four Stokes parameters by cascading four semitransparent OPVs in series along the same optical axis. This in-line polarimeter concept potentially ensures high temporal and spatial resolution with higher radiometric efficiency as compared to the existing polarimeter architecture. Two wave plates were incorporated into the system to modulate the S3 Stokes parameter so as to reduce the condition number of the measurement matrix and maximize the measured signal-to-noise ratio. Radiometric calibration was carried out to determine the measurement matrix. The polarimeter presented in this paper demonstrated an average RMS error of 0.84% for reconstructed Stokes vectors after normalized to S0. A theoretical analysis of the minimum condition number of the four-cell OPV design showed that for individually optimized OPV cells, a condition number of 2.4 is possible.

Astronomical Spectroscopy for Amateurs

CERN Document Server

Harrison, Ken M

2011-01-01

Astronomical Spectroscopy for Amateurs is a complete guide for amateur astronomers who are looking for a new challenge beyond astrophotography. The book provides a brief overview of the history and development of the spectroscope, then a short introduction to the theory of stellar spectra, including details on the necessary reference spectra required for instrument testing and spectral comparison. The various types of spectroscopes available to the amateur are then described. Later sections cover all aspects of setting up and using various types of commercially available and home-built spectroscopes, starting with basic transmission gratings and going through more complex models, all the way to the sophisticated Littrow design. The final part of the text is about practical spectroscope design and construction. This book uniquely brings together a collection of observing, analyzing, and processing hints and tips that will allow the amateur to build skills in preparing scientifically acceptable spectra data. It...

Thirteenth Joint European and National Astronomical Meeting

CERN Document Server

Iniesta, J C

2006-01-01

The book gathers the invited talks to the XIII JENAM conference, organized this time by the European Astronomical Society (EAS) and the Spanish Astronomical Society (SEA), and hosted by the Instituto de Astrofísica de Andalucía (CSIC). All branches of astrophysics are encompassed from the largest scales and cosmology to the solar system and the Sun, through the galaxies and the stars, including a section on astronomical instrumentation. Very relevant experts from all over the world speak in a single book about the most recent, exciting results from their fields in a way which is useful for both researchers in these fields and colleagues working in other disciplines. The book is accompanied by a CD-ROM including the remaining contributions of the meeting in PDF format, hence opening a wide panorama of what is going on in astrophysics nowadays.

Self-similarity in incompressible Navier-Stokes equations.

Science.gov (United States)

Ercan, Ali; Kavvas, M Levent

2015-12-01

The self-similarity conditions of the 3-dimensional (3D) incompressible Navier-Stokes equations are obtained by utilizing one-parameter Lie group of point scaling transformations. It is found that the scaling exponents of length dimensions in i = 1, 2, 3 coordinates in 3-dimensions are not arbitrary but equal for the self-similarity of 3D incompressible Navier-Stokes equations. It is also shown that the self-similarity in this particular flow process can be achieved in different time and space scales when the viscosity of the fluid is also scaled in addition to other flow variables. In other words, the self-similarity of Navier-Stokes equations is achievable under different fluid environments in the same or different gravity conditions. Self-similarity criteria due to initial and boundary conditions are also presented. Utilizing the proposed self-similarity conditions of the 3D hydrodynamic flow process, the value of a flow variable at a specified time and space can be scaled to a corresponding value in a self-similar domain at the corresponding time and space.

Elizabeth Brown (1830-1899), solar astronomer

Science.gov (United States)

Creese, M.

1998-08-01

Were it not for the fact that she was a woman, Elizabeth Brown might well be thought of as a fairly typical nineteenth-century British amateur astronomer. She has a place, although a relatively modest one, in the distinguished group of people who, with their own fortunes, carried out much of the astronomical research being done in the country at a time before extensive government support was forthcoming for the work.1 Her career in fact follows a pattern common to several of the nineteenth-century men astronomers in that her full productive period came only after she was freed from her primary responsibilities; she did not have to amass the necessary financial resources as did many of the men,2 but she had the time-consuming responsibility, not unusual for a Victorian woman, of caring for a parent through a lengthy old age. Only after her father died at the age of ninety-one, did Elizabeth, then in her early fifties, begin her sixteen years of remarkable public activity in astronomy.

Spectroscopy for amateur astronomers recording, processing, analysis and interpretation

CERN Document Server

Trypsteen , Marc F M

2017-01-01

This accessible guide presents the astrophysical concepts behind astronomical spectroscopy, covering both the theory and the practical elements of recording, processing, analysing and interpreting your spectra. It covers astronomical objects, such as stars, planets, nebulae, novae, supernovae, and events such as eclipses and comet passages. Suitable for anyone with only a little background knowledge and access to amateur-level equipment, the guide's many illustrations, sketches and figures will help you understand and practise this scientifically important and growing field of amateur astronomy, up to the level of Pro-Am collaborations. Accessible to non-academics, it benefits many groups from novices and learners in astronomy clubs, to advanced students and teachers of astrophysics. This volume is the perfect companion to the Spectral Atlas for Amateur Astronomers, which provides detailed commented spectral profiles of more than 100 astronomical objects.

The Russian-Ukrainian Observatories Network for the European Astronomical Observatory Route Project

Science.gov (United States)

Andrievsky, S. M.; Bondar, N. I.; Karetnikov, V. G.; Kazantseva, L. V.; Nefedyev, Y. A.; Pinigin, G. I.; Pozhalova, Zh. A.; Rostopchina-Shakhovskay, A. N.; Stepanov, A. V.; Tolbin, S. V.

2011-09-01

In 2004,the Center of UNESCO World Heritage has announced a new initiative "Astronomy & World Heritage" directed for search and preserving of objects,referred to astronomy,its history in a global value,historical and cultural properties. There were defined a strategy of thematic programme "Initiative" and general criteria for selecting of ancient astronomical objects and observatories. In particular, properties that are situated or have significance in relation to celestial objects or astronomical events; representations of sky and/or celestial bodies and astronomical events; observatories and instruments; properties closely connected with the history of astronomy. In 2005-2006,in accordance with the program "Initiative", information about outstanding properties connected with astronomy have been collected.In Ukraine such work was organized by astronomical expert group in Nikolaev Astronomical Observatory. In 2007, Nikolaev observatory was included to the Tentative List of UNESCO under # 5116. Later, in 2008, the network of four astronomical observatories of Ukraine in Kiev,Crimea, Nikolaev and Odessa,considering their high authenticities and integrities,was included to the Tentative List of UNESCO under # 5267 "Astronomical Observatories of Ukraine". In 2008-2009, a new project "Thematic Study" was opened as a successor of "Initiative". It includes all fields of astronomical heritage from earlier prehistory to the Space astronomy (14 themes in total). We present the Ukraine-Russian Observatories network for the "European astronomical observatory Route project". From Russia two observatories are presented: Kazan Observatory and Pulkovo Observatory in the theme "Astronomy from the Renaissance to the mid-twentieth century".The description of astronomical observatories of Ukraine is given in accordance with the project "Thematic study"; the theme "Astronomy from the Renaissance to the mid-twentieth century" - astronomical observatories in Kiev,Nikolaev and Odessa; the

Three-pulse multiplex coherent anti-Stokes/Stokes Raman scattering (CARS/CSRS) microspectroscopy using a white-light laser source

International Nuclear Information System (INIS)

Bito, Kotatsu; Okuno, Masanari; Kano, Hideaki; Leproux, Philippe; Couderc, Vincent; Hamaguchi, Hiro-o

2013-01-01

Highlights: ► We have developed a simultaneous measurement system of CARS and CSRS. ► We can obtain information on the electronic resonance effect with the measurement. ► The simultaneous measurement provides us with more reliable spectral information. - Abstract: We have developed a three-pulse non-degenerate multiplex coherent Raman microspectroscopic system using a white-light laser source. The fundamental output (1064 nm) of a Nd:YAG laser is used for the pump radiation with the white-light laser output (1100–1700 nm) for the Stokes radiation to achieve broadband multiplex excitations of vibrational coherences. The second harmonic (532 nm) of the same Nd:YAG laser is used for the probe radiation. Thanks to the large wavelength difference between the pump and probe radiations, coherent anti-Stokes Raman scattering (CARS) and coherent Stokes Raman scattering (CSRS) can be detected simultaneously. Simultaneous detection of CARS and CSRS enables us to obtain information on the electronic resonance effect that affects differently the CARS and CSRS signals. Simultaneous analysis of the CARS and CSRS signals provides us the imaginary part of χ (3) without introducing any arbitrary parameter in the maximum entropy method (MEM)

Picosecond anti-Stokes generation in a photonic-crystal fiber for interferometric CARS microscopy

DEFF Research Database (Denmark)

Keiding, Søren Rud

2006-01-01

We generate tunable picosecond anti-Stokes pulses by four-wave mixing of two picosecond pump and Stokes pulse trains in a photonic-crystal fiber. The visible, spectrally narrow anti-Stokes pulses with shifts over 150 nm are generated without generating other spectral features. As a demonstration,...

Stokes vector and its relationship to Discrete Wigner Functions of multiqubit states

Energy Technology Data Exchange (ETDEWEB)

Srinivasan, K., E-mail: sriniphysics@gmail.com; Raghavan, G.

2016-07-29

A Stokes vectors and Discrete Wigner Functions (DWF) provide two alternate ways of representing the state of multiqubit systems. A general relationship between the Stokes vector and the DWF is derived for arbitrary n-qubit states for all possible choices of quantum nets. The Stokes vector and the DWF are shown to be related through a Hadamard Matrix. Using these results, a relationship between the Stokes vector of a spin-flipped state and the DWF is derived. Finally, we also present a method to express the Minkowskian squared norm of the Stokes vector, corresponding to n-concurrence in terms of the DWF. - Highlights: • Relationship between Stokes vector (SV) and discrete Wigner function (DWF) for arbitrary multiqubit states is presented. • It is shown that SV and DWF are related to one another through Hadamard matrices. • We show that the Hadamard matrices depend on the choice of the quantum net. • Relationship between SV of the spin flipped state and the DWF is derived. • Expression to compute n-concurrence of the pure n-qubit systems purely in terms of DWF is given.

Cheyne-Stokes respiration in patients with congestive heart failure: causes and consequences.

Science.gov (United States)

Lorenzi-Filho, Geraldo; Genta, Pedro R; Figueiredo, Adelaide C; Inoue, Daniel

2005-08-01

Cheyne-Stokes respiration is a form of periodic breathing in which central apneas and hypopneas alternate with periods of hyperventilation, producing a waxing and waning pattern of tidal volume. This review focuses on the causes and consequences of Cheyne-Stokes respiration in patients with congestive heart failure, in whom the prevalence is strikingly high and ranges from 30% to 50%. Several factors have been implicated in the genesis of Cheyne-Stokes respiration, including low cardiac output and recurrent hypoxia. The key pathophysiological mechanism triggering Cheyne-Stokes respiration is hyperventilation and low arterial CO2 (PaCO2) that when below the apneic threshold triggers a central apnea. Hyperventilation is associated with pulmonary congestion, and Cheyne-Stokes respiration is more prone to occur during sleep, when the respiratory system is mainly dependent on chemical control. It is associated with recurrent dips in oxygen saturation and arousals from sleep, with oscillations in blood pressure and heart rate, sympathetic activation and increased risk of ventricular tachycardia. Cheyne-Stokes respiration is an independent marker of poor prognosis and may participate in a vicious cycle, further stressing the failing heart.

Stokes vector and its relationship to Discrete Wigner Functions of multiqubit states

International Nuclear Information System (INIS)

Srinivasan, K.; Raghavan, G.

2016-01-01

A Stokes vectors and Discrete Wigner Functions (DWF) provide two alternate ways of representing the state of multiqubit systems. A general relationship between the Stokes vector and the DWF is derived for arbitrary n-qubit states for all possible choices of quantum nets. The Stokes vector and the DWF are shown to be related through a Hadamard Matrix. Using these results, a relationship between the Stokes vector of a spin-flipped state and the DWF is derived. Finally, we also present a method to express the Minkowskian squared norm of the Stokes vector, corresponding to n-concurrence in terms of the DWF. - Highlights: • Relationship between Stokes vector (SV) and discrete Wigner function (DWF) for arbitrary multiqubit states is presented. • It is shown that SV and DWF are related to one another through Hadamard matrices. • We show that the Hadamard matrices depend on the choice of the quantum net. • Relationship between SV of the spin flipped state and the DWF is derived. • Expression to compute n-concurrence of the pure n-qubit systems purely in terms of DWF is given.

Decoding the mechanisms of Antikythera astronomical device

CERN Document Server

Lin, Jian-Liang

2016-01-01

This book presents a systematic design methodology for decoding the interior structure of the Antikythera mechanism, an astronomical device from ancient Greece. The historical background, surviving evidence and reconstructions of the mechanism are introduced, and the historical development of astronomical achievements and various astronomical instruments are investigated. Pursuing an approach based on the conceptual design of modern mechanisms and bearing in mind the standards of science and technology at the time, all feasible designs of the six lost/incomplete/unclear subsystems are synthesized as illustrated examples, and 48 feasible designs of the complete interior structure are presented. This approach provides not only a logical tool for applying modern mechanical engineering knowledge to the reconstruction of the Antikythera mechanism, but also an innovative research direction for identifying the original structures of the mechanism in the future. In short, the book offers valuable new insights for all...

Filling the Astronomical Void - A Visual Medium for a Visual Subject

Science.gov (United States)

Ryan, J.

1996-12-01

Astronomy is fundamentally a visual subject. The modern science of astronomy has at its foundation the ancient art of observing the sky visually. The visual elements of astronomy are arguably the most important. Every person in the entire world is affected by visually-observed astronomical phenomena such as the seasonal variations in daylight. However, misconceptions abound and the average person cannot recognize the simple signs in the sky that point to the direction, the hour and the season. Educators and astronomy popularizers widely lament that astronomy is not appreciated in our society. Yet, there is a remarkable dearth of popular literature for teaching the visual elements of astronomy. This is what I refer to as *the astronomical void.* Typical works use illustrations sparsely, relying most heavily on text-based descriptions of the visual astronomical phenomena. Such works leave significant inferential gaps to the inexperienced reader, who is unequipped for making astronomical observations. Thus, the astronomical void remains unfilled by much of the currently available literature. I therefore propose the introduction of a visually-oriented medium for teaching the visual elements of Astronomy. To this end, I have prepared a series of astronomy "comic strips" that are intended to fill the astronomical void. By giving the illustrations the central place, the comic strip medium permits the depiction of motion and other sequential activity, thus effectively representing astronomical phenomena. In addition to the practical advantages, the comic strip is a "user friendly" medium that is inviting and entertaining to a reader. At the present time, I am distributing a monthly comic strip entitled *Starman*, which appears in the newsletters of over 120 local astronomy organizations and on the web at http://www.cyberdrive.net/ starman. I hope to eventually publish a series of full-length books and believe that astronomical comic strips will help expand the perimeter of

Astronomers celebrate a year of new Hubble results

Science.gov (United States)

1995-02-01

"We are beginning to understand that because of these observations we are going to have to change the way we look at the Universe," said ESA's Dr Duccio Macchetto, Associate Director for Science Programs at the Space Telescope Science Institute (STScI), Baltimore, Maryland, USA. The European Space Agency plays a major role in the Hubble Space Telescope programme. The Agency provided one of the telescope's four major instruments, called the Faint Object Camera, and two sets of electricity-generating solar arrays. In addition, 15 ESA scientific and technical staff work at the STScI. In return for this contribution, European astronomers are entitled to 15 percent of the telescope's observing time, although currently they account for 20 percent of all observations. "This is a testimony to the quality of the European science community", said Dr Roger Bonnet, Director of Science at ESA. "We are only guaranteed 15 percent of the telescope's use, but consistently receive much more than that." Astronomers from universities, observatories and research institutes across Europe lead more than 60 investigations planned for the telescope's fifth observing cycle, which begins this summer. Many more Europeans contribute to teams led by other astronomers. Looking back to the very start of time European astronomer Dr Peter Jakobsen used ESA's Faint Object Camera to confirm that helium was present in the early Universe. Astronomers had long predicted that 90 percent of the newly born Universe consisted of hydrogen, with helium making up the remainder. Before the refurbished Hubble came along, it was easy to detect the hydrogen, but the primordial helium remained elusive. The ultraviolet capabilities of the telescope, combined with the improvement in spatial resolution following the repair, made it possible for Dr Jakobsen to obtain an image of a quasar close to the edge of the known Universe. A spectral analysis of this picture revealed the quasar's light, which took 13 billion years

Astronomical publications of Melbourne Observatory

Science.gov (United States)

Andropoulos, Jenny Ioanna

2014-05-01

During the second half of the 19th century and the first half of the 20th century, four well-equipped government observatories were maintained in Australia - in Melbourne, Sydney, Adelaide and Perth. These institutions conducted astronomical observations, often in the course of providing a local time service, and they also collected and collated meteorological data. As well, some of these observatories were involved at times in geodetic surveying, geomagnetic recording, gravity measurements, seismology, tide recording and physical standards, so the term "observatory" was being used in a rather broad sense! Despite the international renown that once applied to Williamstown and Melbourne Observatories, relatively little has been written by modern-day scholars about astronomical activities at these observatories. This research is intended to rectify this situation to some extent by gathering, cataloguing and analysing the published astronomical output of the two Observatories to see what contributions they made to science and society. It also compares their contributions with those of Sydney, Adelaide and Perth Observatories. Overall, Williamstown and Melbourne Observatories produced a prodigious amount of material on astronomy in scientific and technical journals, in reports and in newspapers. The other observatories more or less did likewise, so no observatory of those studied markedly outperformed the others in the long term, especially when account is taken of their relative resourcing in staff and equipment.

AESoP: Astronomical Extinction Spectrophotometer

Science.gov (United States)

Linford, Justin; McGraw, J.; Zimmer, P.; Ackermann, M.; Fitch, J.

2009-01-01

The Earth's atmosphere is a major obstruction to the precision and accuracy of ground-based photometry. The atmosphere removes light from astronomical objects both by absorption and scattering by constituent molecules, aerosols and clouds. These effects can change significantly over short time periods and over modest angles on the sky. To further understand these effects, the UNM Measurement Astrophysics Group has designed, built and recently deployed the Astronomical Extinction Spectrophotometer (AESoP), a 100mm objective grating spectrometer. By monitoring bright stars in sensibly the same direction as a larger photometric telescope is observing, AESoP will measure the wavelength-dependent extinction due to the Earth's atmosphere from 450nm to 900nm on time scales of approximately one minute. The collocated Astronomical LIDAR for Extinction (ALE) provides a high-precision monochromatic extinction measurement at 527nm. Knowing the extinction at a single wavelength allows us to pin the relative spectra generated by AESoP. These extinction spectra can then be integrated over the bandpass of the photometric telescope system to create real time corrections of observations. We present the design and construction of AESoP along with the preliminary results of our first combined observing campaign. This effort is our first step toward breaking the 1% photometry barrier. This project is funded by AFRL Grant FA9451-04-2-0355

About Navier-Stokes Equation in the Theory of Convective Heat Transfer

Science.gov (United States)

Davidzon, M. Y.

2017-10-01

A system of differential equations (Navier-Stokes, continuity, heat conductivity) is used to solve convective heat transfer problems. While solving Navier-Stokes equation, it is usually assumed that tangent stress is proportional to the velocity gradient. This assumption is valid with a small velocity gradient, for example, near an axis of the channel, but velocity gradient can be very large near the channel wall. Our paper shows that if we accept power law instead of linear law for tangential stress, then the velocity profile for creeping, laminar, and turbulent flow in the channel can be calculated without using Navier-Stokes equation. Also, in this case Navier-Stokes equation itself changes: the coefficient of dynamic viscosity changes its value from normal (in case of the creeping flow) to tending to infinity (in case of the well-developed turbulent flow).

Astronomical optics and elasticity theory

CERN Document Server

Lemaitre, Gerard Rene

2008-01-01

Astronomical Optics and Elasticity Theory provides a very thorough and comprehensive account of what is known in this field. After an extensive introduction to optics and elasticity, the book discusses variable curvature and multimode deformable mirrors, as well as, in depth, active optics, its theory and applications. Further, optical design utilizing the Schmidt concept and various types of Schmidt correctors, as well as the elasticity theory of thin plates and shells are elaborated upon. Several active optics methods are developed for obtaining aberration corrected diffraction gratings. Further, a weakly conical shell theory of elasticity is elaborated for the aspherization of grazing incidence telescope mirrors. The very didactic and fairly easy-to-read presentation of the topic will enable PhD students and young researchers to actively participate in challenging astronomical optics and instrumentation projects.

Preserving and Archiving Astronomical Photographic Plates

Science.gov (United States)

Castelaz, M. W.; Cline, J. D.

2005-05-01

Astronomical objects change with time. New observations complement past observations recorded on photographic plates. Analyses of changes provide essential routes to information about an object's formation, constitution and evolution. Preserving a century of photographic plate observations is thus of paramount importance. Plate collections are presently widely dispersed; plates may be stored in poor conditions, and are effectively inaccessible to both researchers and historians. We describe a planned project at Pisgah Astronomical Research Institute to preserve the collections of astronomical plates in the United States by gathering them into a single storage location. Collections will be sorted, cleaned, and cataloged on-line so as to provide access to researchers. Full scientific and historic use of the material then requires the observations themselves to be accessible digitally. The project's goal will be the availability of these data as a unique, fully-maintained scientific and educational resource. The new archive will support trans-disciplinary research such as the chemistry of the Earth's atmosphere, library information science, trends in local weather patterns, and impacts of urbanization on telescope use, while the hand-written observatory logs will be a valuable resource for science historians and biographers.

Astronomers Without Borders: A Global Astronomy Community

Science.gov (United States)

Simmons, M.

2011-10-01

Astronomers Without Borders (AWB) brings together astronomy enthusiasts of all types - amateur astronomers, educators, professionals and "armchair" astronomers for a variety of online and physicalworld programs. The AWB web site provides social networking and a base for online programs that engage people worldwide in astronomy activities that transcend geopolitical and cultural borders. There is universal interest in astronomy, which has been present in all cultures throughout recorded history. Astronomy is also among the most accessible of sciences with the natural laboratory of the sky being available to people worldwide. There are few other interests for which people widely separated geographically can engage in activities involving the same objects. AWB builds on those advantages to bring people together. AWB also provides a platform where projects can reach a global audience. AWB also provides unique opportunities for multidisciplinary collaboration in EPO programs. Several programs including The World at Night, Global Astronomy Month and others will be described along with lessons learned.

ASURV: Astronomical SURVival Statistics

Science.gov (United States)

Feigelson, E. D.; Nelson, P. I.; Isobe, T.; LaValley, M.

2014-06-01

ASURV (Astronomical SURVival Statistics) provides astronomy survival analysis for right- and left-censored data including the maximum-likelihood Kaplan-Meier estimator and several univariate two-sample tests, bivariate correlation measures, and linear regressions. ASURV is written in FORTRAN 77, and is stand-alone and does not call any specialized libraries.

The South African astronomical observatory

International Nuclear Information System (INIS)

Feast, M.

1985-01-01

A few examples of the activities of the South African Astronomical Observatory are discussed. This includes the studying of stellar evolution, dust around stars, the determination of distances to galaxies and collaboration with space experiments

Incompressible limit of compressible Navier-Stokes equations

International Nuclear Information System (INIS)

Bessaih, H.

1994-01-01

In this paper we study the system which describes the motion of compressible viscous fluid in a bounded domain Ω of R 3 . When we introduce a parameter λ, that is the inverse of the Mach number, we prove, under small initial data and external force (for barotropic flows), that the solution of Navier-Stokes equations is the incompressible limit of the solution of compressible Navier-Stokes equations, as the Mach number becomes small. For this, we show the existence of a solution verifying estimates independent of λ. Compactness argument allow us to pass to the limit on λ in the nonlinear terms. (author). 17 refs

The National Astronomical Observatory of Japan and Post-war Japanese Optical Astronomy

Science.gov (United States)

Tajima, Toshiyuki

This paper depicts some aspects of the formative process of the Japanese optical and infrared astronomical community in the post-war period, featuring the transition of the National Astronomical Observatory of Japan(NAOJ). We take up three cases of telescope construction, examining their background and their contribution to the Japanese astronomical community. Through these cases, the characteristics of traditions and cultures of optical and infrared astronomy in Japan are considered. Although the Tokyo Astronomical Observatory (TAO) of the University of Tokyo, the predecessor of NAOJ, was originally founded as an agency for practical astronomical observation such as time and almanac service, it has become an international centre for all types of astrophysical research. Research and development of telescopes and observational instruments have become an important part of the astronomers' practice. Now, however, a number of Japanese universities are planning to have their own large to middle-sized telescopes, and a new style of astronomical research is emerging involving astrophysical studies utilising data acquired from the Virtual Observatory, so there is a distinct possibility that the status of the NAOJ will change even further in the future.

A Brief History of Manchester Astronomical Society

Science.gov (United States)

Kilburn, K. J.

Manchester Astronomical Society celebrated its centenary in September 2003. But that centenary was of a hundred years as the MAS: the history of the society goes back much further, and can be traced directly to that great era of.public awareness of astronomy and amateur interest in Victorian England in the last half of the nineteenth century. Allan Chapman has discussed this period in detail, so the present paper concentrates on the MAS's particular influence on Manchester astronomers and recent work on the history of the society.

Cavitation Modeling in Euler and Navier-Stokes Codes

Science.gov (United States)

Deshpande, Manish; Feng, Jinzhang; Merkle, Charles L.

1993-01-01

Many previous researchers have modeled sheet cavitation by means of a constant pressure solution in the cavity region coupled with a velocity potential formulation for the outer flow. The present paper discusses the issues involved in extending these cavitation models to Euler or Navier-Stokes codes. The approach taken is to start from a velocity potential model to ensure our results are compatible with those of previous researchers and available experimental data, and then to implement this model in both Euler and Navier-Stokes codes. The model is then augmented in the Navier-Stokes code by the inclusion of the energy equation which allows the effect of subcooling in the vicinity of the cavity interface to be modeled to take into account the experimentally observed reduction in cavity pressures that occurs in cryogenic fluids such as liquid hydrogen. Although our goal is to assess the practicality of implementing these cavitation models in existing three-dimensional, turbomachinery codes, the emphasis in the present paper will center on two-dimensional computations, most specifically isolated airfoils and cascades. Comparisons between velocity potential, Euler and Navier-Stokes implementations indicate they all produce consistent predictions. Comparisons with experimental results also indicate that the predictions are qualitatively correct and give a reasonable first estimate of sheet cavitation effects in both cryogenic and non-cryogenic fluids. The impact on CPU time and the code modifications required suggests that these models are appropriate for incorporation in current generation turbomachinery codes.

Two-Level Iteration Penalty Methods for the Navier-Stokes Equations with Friction Boundary Conditions

Directory of Open Access Journals (Sweden)

Yuan Li

2013-01-01

Full Text Available This paper presents two-level iteration penalty finite element methods to approximate the solution of the Navier-Stokes equations with friction boundary conditions. The basic idea is to solve the Navier-Stokes type variational inequality problem on a coarse mesh with mesh size H in combining with solving a Stokes, Oseen, or linearized Navier-Stokes type variational inequality problem for Stokes, Oseen, or Newton iteration on a fine mesh with mesh size h. The error estimate obtained in this paper shows that if H, h, and ε can be chosen appropriately, then these two-level iteration penalty methods are of the same convergence orders as the usual one-level iteration penalty method.

Astronomical databases of Nikolaev Observatory

Science.gov (United States)

Protsyuk, Y.; Mazhaev, A.

2008-07-01

Several astronomical databases were created at Nikolaev Observatory during the last years. The databases are built by using MySQL search engine and PHP scripts. They are available on NAO web-site http://www.mao.nikolaev.ua.

Cheyne-Stokes respiration in patients with congestive heart failure: causes and consequences

OpenAIRE

Lorenzi-Filho,Geraldo; Genta,Pedro R; Figueiredo,Adelaide C.; Inoue,Daniel

2005-01-01

Cheyne-Stokes respiration is a form of periodic breathing in which central apneas and hypopneas alternate with periods of hyperventilation, producing a waxing and waning pattern of tidal volume. This review focuses on the causes and consequences of Cheyne-Stokes respiration in patients with congestive heart failure, in whom the prevalence is strikingly high and ranges from 30% to 50%. Several factors have been implicated in the genesis of Cheyne-Stokes respiration, including low cardiac outpu...

Quasineutral limit for the quantum Navier-Stokes-Poisson equation

OpenAIRE

Li, Min; Pu, Xueke; Wang, Shu

2015-01-01

In this paper, we study the quasineutral limit and asymptotic behaviors for the quantum Navier-Stokes-Possion equation. We apply a formal expansion according to Debye length and derive the neutral incompressible Navier-Stokes equation. To establish this limit mathematically rigorously, we derive uniform (in Debye length) estimates for the remainders, for well-prepared initial data. It is demonstrated that the quantum effect do play important roles in the estimates and the norm introduced depe...

Astronomical dating in the 19th century

Science.gov (United States)

Hilgen, Frederik J.

2010-01-01

Today astronomical tuning is widely accepted as numerical dating method after having revolutionised the age calibration of the geological archive and time scale over the last decades. However, its origin is not well known and tracing its roots is important especially from a science historic perspective. Astronomical tuning developed in consequence of the astronomical theory of the ice ages and was repeatedly used in the second half of the 19th century before the invention of radio-isotopic dating. Building upon earlier ideas of Joseph Adhémar, James Croll started to formulate his astronomical theory of the ice ages in 1864 according to which precession controlled ice ages occur alternatingly on both hemispheres at times of maximum eccentricity of the Earth's orbit. The publication of these ideas compelled Charles Lyell to revise his Principles of Geology and add Croll's theory, thus providing an alternative to his own geographical cause of the ice ages. Both Croll and Lyell initially tuned the last glacial epoch to the prominent eccentricity maximum 850,000 yr ago. This age was used as starting point by Lyell to calculate an age of 240 million years for the beginning of the Cambrium. But Croll soon revised the tuning to a much younger less prominent eccentricity maximum between 240,000 and 80,000 yr ago. In addition he tuned older glacial deposits of late Miocene and Eocene ages to eccentricity maxima around 800,000 and 2,800,000 yr ago. Archibald and James Geikie were the first to recognize interglacials during the last glacial epoch, as predicted by Croll's theory, and attempted to tune them to precession. Soon after Frank Taylor linked a series of 15 end-moraines left behind by the retreating ice sheet to precession to arrive at a possible age of 300,000 yr for the maximum glaciation. In a classic paper, Axel Blytt (1876) explained the scattered distribution of plant groups in Norway to precession induced alternating rainy and dry periods as recorded by the

Impact of the inherent separation of scales in the Navier-Stokes- alphabeta equations.

Science.gov (United States)

Kim, Tae-Yeon; Cassiani, Massimo; Albertson, John D; Dolbow, John E; Fried, Eliot; Gurtin, Morton E

2009-04-01

We study the effect of the length scales alpha and beta in the Navier-Stokes- alphabeta equations on the energy spectrum and the alignment between the vorticity and the eigenvectors of the stretching tensor in three-dimensional homogeneous and isotropic turbulent flows in a periodic cubic domain, including the limiting cases of the Navier-Stokes- alpha and Navier-Stokes equations. A significant increase in the accuracy of the energy spectrum at large wave numbers arises for betaNavier-Stokes- alphabeta equations also improve as beta decreases away from alpha . However, optimal choices for alpha and beta depend not only on the problem of interest but also on the grid resolution.

TPCs in high-energy astronomical polarimetry

International Nuclear Information System (INIS)

Black, J K

2007-01-01

High-energy astrophysics has yet to exploit the unique and important information that polarimetry could provide, largely due to the limited sensitivity of previously available polarimeters. In recent years, numerous efforts have been initiated to develop instruments with the sensitivity required for astronomical polarimetry over the 100 eV to 10 GeV band. Time projection chambers (TPCs), with their high-resolution event imaging capability, are an integral part of some of these efforts. After a brief overview of current astronomical polarimeter development efforts, the role of TPCs will be described in more detail. These include TPCs as photoelectric X-ray polarimeters and TPCs as components of polarizationsensitive Compton and pair-production telescopes

Division B Commission 6: Astronomical Telegrams

Science.gov (United States)

Yamaoka, H.; Green, D. W. E.; Samus, N. N.; Aksnes, K.; Gilmore, A. C.; Nakano, S.; Sphar, T.; Tichá, J.; Williams, G. V.

2016-04-01

IAU Commission 6 ``Astronomical Telegrams'' had a single business meeting during Honolulu General Assembly of the IAU. It took place on Tuesday, 11 August 2015. The meeting was attended by Hitoshi Yamaoka (President), Daniel Green (Director of the Central Bureau for Astronomical Telegrams, CBAT, via Skype), Steven Chesley (JPL), Paul Chodas (JPL), Alan Gilmore (Canterbury University), Shinjiro Kouzuma (Chukyo University), Paolo Mazzali (Co-Chair of the Supernova Working Group), Elena Pian (Scuola Normale Superiore di Pisa), Marion Schmitz (chair IAU Working Group Designations + NED), David Tholen (University of Hawaii), Jana Ticha (Klet Observatory), Milos Tichy (Klet Observatory), Giovanni Valsecchi (INAF\\slash Italy), Gareth Williams (Minor Planet Center). Apologies: Nikolai Samus (General Catalogue of Variable Stars, GCVS).

Hydrothermal modification of host rock geochemistry within Mo-Cu porphyry deposits in the Galway Granite, western Ireland

Science.gov (United States)

Tolometti, Gavin; McCarthy, Will

2016-04-01

Hydrothermal alteration of host rock is a process inherent to the formation of porphyry deposits and the required geochemical modification of these rocks is regularly used to indicate proximity to an economic target. The study involves examining the changes in major, minor and trace elements to understand how the quartz vein structures have influenced the chemistry within the Murvey Granite that forms part of the 380-425Ma Galway Granite Complex in western Ireland. Molybdenite mineralisation within the Galway Granite Complex occurred in close association with protracted magmatism at 423Ma, 410Ma, 407Ma, 397Ma and 383Ma and this continues to be of interest to active exploration. The aim of the project is to characterize hydrothermal alteration associated with Mo-Cu mineralisation and identify geochemical indicators that can guide future exploration work. The Murvey Granite intrudes metagabbros and gneiss that form part of the Connemara Metamorphic complex. The intrusion is composed of albite-rich pink granite, garnetiferous granite and phenocrytic orthoclase granite. Minor doleritic dykes post-date the Murvey Granite, found commonly along its margins. Field mapping shows that the granite is truncated to the east by a regional NW-SE fault and that several small subparallel structures host Mo-Cu bearing quartz veins. Petrographic observations show heavily sericitized feldspars and plagioclase and biotite which have undergone kaolinization and chloritisation. Chalcopyrite minerals are fine grained, heavily fractured found crystallized along the margins of the feldspars and 2mm pyrite crystals. Molybdenite are also seen along the margins of the feldspars, crystallized whilst the Murvey Granite cooled. Field and petrographic observations indicate that mineralisation is structurally controlled by NW-SE faults from the selected mineralization zones and conjugate NE-SW cross cutting the Murvey Granite. Both fault orientations exhibit quartz and disseminated molybdenite

The Green Monster: Stokes's 1944 Modern Clinical Syphilology.

Science.gov (United States)

Jackson, Robert

2010-01-01

There is much information on the life and accomplishments of John Hinchman Stokes (1885-1961), the dermatologist and syphilologist. There is little detailed information on his 1944 classic text on syphilis, Modern Clinical Syphilology. To review and critique this book. A careful review of the book, his life, and the accomplishments that were undertaken in relation to the age in which he lived. The book is indeed a goldmine of information of all aspects of syphilis from pre-World War I (1905) until the late (1944) World War II era. The factors that make it a classic are as follows: (1) the disease had a specific cause; (2) Stokes's 25-year obsession with the disease; (3) there was no effective simple cure for most of the time he was studying it; (4) Stokes was an obsessive, intelligent, well-trained physician; (5) he lived in a well-developed, reasonably stable country; and (6) he was able to see how the disease could be adequately treated with penicillin and compare these events with those in the prepenicillin era.

p-Euler equations and p-Navier-Stokes equations

Science.gov (United States)

Li, Lei; Liu, Jian-Guo

2018-04-01

We propose in this work new systems of equations which we call p-Euler equations and p-Navier-Stokes equations. p-Euler equations are derived as the Euler-Lagrange equations for the action represented by the Benamou-Brenier characterization of Wasserstein-p distances, with incompressibility constraint. p-Euler equations have similar structures with the usual Euler equations but the 'momentum' is the signed (p - 1)-th power of the velocity. In the 2D case, the p-Euler equations have streamfunction-vorticity formulation, where the vorticity is given by the p-Laplacian of the streamfunction. By adding diffusion presented by γ-Laplacian of the velocity, we obtain what we call p-Navier-Stokes equations. If γ = p, the a priori energy estimates for the velocity and momentum have dual symmetries. Using these energy estimates and a time-shift estimate, we show the global existence of weak solutions for the p-Navier-Stokes equations in Rd for γ = p and p ≥ d ≥ 2 through a compactness criterion.

Discrete adjoint of fractional step Navier-Stokes solver in generalized coordinates

Science.gov (United States)

Wang, Mengze; Mons, Vincent; Zaki, Tamer

2017-11-01

Optimization and control in transitional and turbulent flows require evaluation of gradients of the flow state with respect to the problem parameters. Using adjoint approaches, these high-dimensional gradients can be evaluated with a similar computational cost as the forward Navier-Stokes simulations. The adjoint algorithm can be obtained by discretizing the continuous adjoint Navier-Stokes equations or by deriving the adjoint to the discretized Navier-Stokes equations directly. The latter algorithm is necessary when the forward-adjoint relations must be satisfied to machine precision. In this work, our forward model is the fractional step solution to the Navier-Stokes equations in generalized coordinates, proposed by Rosenfeld, Kwak & Vinokur. We derive the corresponding discrete adjoint equations. We also demonstrate the accuracy of the combined forward-adjoint model, and its application to unsteady wall-bounded flows. This work has been partially funded by the Office of Naval Research (Grant N00014-16-1-2542).

Astrobiology: An astronomer's perspective

International Nuclear Information System (INIS)

Bergin, Edwin A.

2014-01-01

In this review we explore aspects of the field of astrobiology from an astronomical viewpoint. We therefore focus on the origin of life in the context of planetary formation, with additional emphasis on tracing the most abundant volatile elements, C, H, O, and N that are used by life on Earth. We first explore the history of life on our planet and outline the current state of our knowledge regarding the delivery of the C, H, O, N elements to the Earth. We then discuss how astronomers track the gaseous and solid molecular carriers of these volatiles throughout the process of star and planet formation. It is now clear that the early stages of star formation fosters the creation of water and simple organic molecules with enrichments of heavy isotopes. These molecules are found as ice coatings on the solid materials that represent microscopic beginnings of terrestrial worlds. Based on the meteoritic and cometary record, the process of planet formation, and the local environment, lead to additional increases in organic complexity. The astronomical connections towards this stage are only now being directly made. Although the exact details are uncertain, it is likely that the birth process of star and planets likely leads to terrestrial worlds being born with abundant water and organics on the surface

Astronomical Virtual Observatories Through International Collaboration

Directory of Open Access Journals (Sweden)

Masatoshi Ohishi

2010-03-01

Full Text Available Astronomical Virtual Observatories (VOs are emerging research environment for astronomy, and 16 countries and a region have funded to develop their VOs based on international standard protocols for interoperability. The 16 funded VO projects have established the International Virtual Observatory Alliance (http://www.ivoa.net/ to develop the standard interoperable interfaces such as registry (meta data, data access, query languages, output format (VOTable, data model, application interface, and so on. The IVOA members have constructed each VO environment through the IVOA interfaces. National Astronomical Observatory of Japan (NAOJ started its VO project (Japanese Virtual Observatory - JVO in 2002, and developed its VO system. We have succeeded to interoperate the latest JVO system with other VOs in the USA and Europe since December 2004. Observed data by the Subaru telescope, satellite data taken by the JAXA/ISAS, etc. are connected to the JVO system. Successful interoperation of the JVO system with other VOs means that astronomers in the world will be able to utilize top-level data obtained by these telescopes from anywhere in the world at anytime. System design of the JVO system, experiences during our development including problems of current standard protocols defined in the IVOA, and proposals to resolve these problems in the near future are described.

Astrobiology: An astronomer's perspective

Energy Technology Data Exchange (ETDEWEB)

Bergin, Edwin A. [University of Michigan, Department of Astronomy, 500 Church Street, Ann Arbor, MI 48109 (United States)

2014-12-08

In this review we explore aspects of the field of astrobiology from an astronomical viewpoint. We therefore focus on the origin of life in the context of planetary formation, with additional emphasis on tracing the most abundant volatile elements, C, H, O, and N that are used by life on Earth. We first explore the history of life on our planet and outline the current state of our knowledge regarding the delivery of the C, H, O, N elements to the Earth. We then discuss how astronomers track the gaseous and solid molecular carriers of these volatiles throughout the process of star and planet formation. It is now clear that the early stages of star formation fosters the creation of water and simple organic molecules with enrichments of heavy isotopes. These molecules are found as ice coatings on the solid materials that represent microscopic beginnings of terrestrial worlds. Based on the meteoritic and cometary record, the process of planet formation, and the local environment, lead to additional increases in organic complexity. The astronomical connections towards this stage are only now being directly made. Although the exact details are uncertain, it is likely that the birth process of star and planets likely leads to terrestrial worlds being born with abundant water and organics on the surface.

Oscillatory Stokes Flow Past a Slip Cylinder

Science.gov (United States)

Palaniappan, D.

2013-11-01

Two-dimensional transient slow viscous flow past a circular cylinder with Navier slip boundary conditions is considered in the limit of low-Reynolds number. The oscillatory Stokes flow problem around a cylinder is solved using the stream function method leading to an analytic solution in terms of modified Bessel functions of the second kind. The corresponding steady-state behavior yields the familiar paradoxical result first detected by Stokes. It is noted that the two key parameters, viz., the frequency λ, and the slip coefficient ξ have a significant impact on the flow field in the vicinity of the cylinder contour. In the limit of very low frequency, the flow is dominated by a term containing a well-known biharmonic function found by Stokes that has a singular behavior at infinity. Local streamlines for small times show interesting flow patterns. Attached eddies due to flow separation - observed in the no-slip case - either get detached or pushed away from the cylinder surface as ξ is varied. Computed asymptotic results predict that the flow exhibits inviscid behavior far away from the cylinder in the frequency range 0 < λ << 1 . Although the frequency of oscillations is finite, our exact solutions reveal fairly rapid transitions in the flow domain. Research Enhancement grant, TAMUCC.

Different Categories of Astronomical Heritage: Issues and Challenges

Science.gov (United States)

Ruggles, Clive

2012-09-01

Since 2008 the AWHWG has, on behalf of the IAU, been working with UNESCO and its advisory bodies to help identify, safeguard and promote cultural properties relating to astronomy and, where possible, to try to facilitate the eventual nomination of key astronomical heritage sites onto the World Heritage List. Unfortunately, the World Heritage Convention only covers fixed sites (i.e., the tangible immovable heritage of astronomy), and a key question for the UNESCO-IAU Astronomy and World Heritage Initiative (AWHI) is the extent to which the tangible moveable and intangible heritage of astronomy (e.g. moveable instruments; ideas and theories) influence the assessment of the tangible immovable heritage. Clearly, in an ideal world we should be concerned not only with tangible immovable heritage but, to quote the AWHWG's own Terms of Reference, ``to help ensure that cultural properties and artefacts significant in the development of astronomy, together with the intangible heritage of astronomy, are duly studied, protected and maintained, both for the greater benefit of humankind and to the potential benefit of future historical research''. With this in mind, the IAU/INAF symposium on ``Astronomy and its Instruments before and after Galileo'' held in Venice in Sep-Oct 2009 recommended that urgent steps should be taken 1. to sensitise astronomers and the general public, and particularly observatory directors and others with direct influence and control over astronomical resources, to the importance of identifying, protecting and preserving the various material products of astronomical research and discovery that already have, or have significant potential to acquire, universal value; (N.B. National or regional interests and concerns have no relevance in the assessment of ``universal value'', which, by definition, extends beyond cultural boundaries and, by reasonable expectation, down the generations into the future. 2. to identify modes of interconnectivity between

Lessons from the masters current concepts in astronomical image processing

CERN Document Server

2013-01-01

There are currently thousands of amateur astronomers around the world engaged in astrophotography at increasingly sophisticated levels. Their ranks far outnumber professional astronomers doing the same and their contributions both technically and artistically are the dominant drivers of progress in the field today. This book is a unique collaboration of individuals, all world-renowned in their particular area, and covers in detail each of the major sub-disciplines of astrophotography. This approach offers the reader the greatest opportunity to learn the most current information and the latest techniques directly from the foremost innovators in the field today.   The book as a whole covers all types of astronomical image processing, including processing of eclipses and solar phenomena, extracting detail from deep-sky, planetary, and widefield images, and offers solutions to some of the most challenging and vexing problems in astronomical image processing. Recognized chapter authors include deep sky experts su...

High Precision Stokes Polarimetry for Scattering Light using Wide Dynamic Range Intensity Detector

Directory of Open Access Journals (Sweden)

Shibata Shuhei

2015-01-01

Full Text Available This paper proposes a Stokes polarimetry for scattering light from a sample surface. To achieve a high accuracy measurement two approaches of an intensity detector and analysis algorism of a Stokes parameter were proposed. The dynamic range of this detector can achieve up to 1010 by combination of change of neutral-density (ND filters having different density and photon counting units. Stokes parameters can be measured by dual rotating of a retarder and an analyzer. The algorism of dual rotating polarimeter can be calibrated small linear diattenuation and linear retardance error of the retarder. This system can measured Stokes parameters from −20° to 70° of its scattering angle. It is possible to measure Stokes parameters of scattering of dust and scratch of optical device with high precision. This paper shows accuracy of this system, checking the polarization change of scattering angle and influence of beam size.

Efficient SDM-MIMO Stokes-space equalization

DEFF Research Database (Denmark)

Caballero, F. J.Vaquero; Zanaty, A.; Pittala, F.

2016-01-01

We propose a novel frequency-domain 6x6 MIMO Stokes-space equalizer and compare its performance to a 6x6 MIMO LMS architecture. This method is suited to overcome DSP complexity and laser linewidth issues in SDM transmission systems....

Application of thin-layer Navier-Stokes equations near maximum lift

Science.gov (United States)

Anderson, W. K.; Thomas, J. L.; Rumsey, C. L.

1984-01-01

The flowfield about a NACA 0012 airfoil at a Mach number of 0.3 and Reynolds number of 1 million is computed through an angle of attack range, up to 18 deg, corresponding to conditions up to and beyond the maximum lift coefficient. Results obtained using the compressible thin-layer Navier-Stokes equations are presented as well as results from the compressible Euler equations with and without a viscous coupling procedure. The applicability of each code is assessed and many thin-layer Navier-Stokes benchmark solutions are obtained which can be used for comparison with other codes intended for use at high angles of attack. Reasonable agreement of the Navier-Stokes code with experiment and the viscous-inviscid interaction code is obtained at moderate angles of attack. An unsteady solution is obtained with the thin-layer Navier-Stokes code at the highest angle of attack considered. The maximum lift coefficient is overpredicted, however, in comparison to experimental data, which is attributed to the presence of a laminar separation bubble near the leading edge not modeled in the computations. Two comparisons with experimental data are also presented at a higher Mach number.

Cutaneous porphyrins exhibit anti-stokes fluorescence that is detectable in sebum (Conference Presentation)

Science.gov (United States)

Tian, Giselle; Zeng, Haishan; Zhao, Jianhua; Wu, Zhenguo; Al Jasser, Mohammed; Lui, Harvey; Mclean, David I.

2016-02-01

Porphyrins produced by Propionibacterium acnes represent the principal fluorophore associated with acne, and appear as orange-red luminescence under the Wood's lamp. Assessment of acne based on Wood's lamp (UV) or visible light illumination is limited by photon penetration depth and has limited sensitivity for earlier stage lesions. Inducing fluorescence with near infrared (NIR) excitation may provide an alternative way to assess porphyrin-related skin disorders. We discovered that under 785 nm CW laser excitation PpIX powder exhibits fluorescence emission in the shorter wavelength range of 600-715 nm with an intensity that is linearly dependent on the excitation power. We attribute this shorter wavelength emission to anti-Stokes fluorescence. Similar anti-Stokes fluorescence was also detected focally in all skin-derived samples containing porphyrins. Regular (Stokes) fluorescence was present under UV and visible light excitation on ex vivo nasal skin and sebum from uninflamed acne, but not on nose surface smears or sebum from inflamed acne. Co-registered CW laser-excited anti-Stokes fluorescence and fs laser-excited multi-photon fluorescence images of PpIX powder showed similar features. In the skin samples because of the anti-Stokes effect, the NIR-induced fluorescence was presumably specific for porphyrins since there appeared to be no anti-Stokes emission signals from other typical skin fluorophores such as lipids, keratins and collagen. Anti-Stokes fluorescence under NIR CW excitation is more sensitive and specific for porphyrin detection than UV- or visible light-excited regular fluorescence and fs laser-excited multi-photon fluorescence. This approach also has higher image contrast compared to NIR fs laser-based multi-photon fluorescence imaging. The anti-Stokes fluorescence of porphyrins within sebum could potentially be applied to detecting and targeting acne lesions for treatment via fluorescence image guidance.

Topology Optimization of Large Scale Stokes Flow Problems

DEFF Research Database (Denmark)

Aage, Niels; Poulsen, Thomas Harpsøe; Gersborg-Hansen, Allan

2008-01-01

This note considers topology optimization of large scale 2D and 3D Stokes flow problems using parallel computations. We solve problems with up to 1.125.000 elements in 2D and 128.000 elements in 3D on a shared memory computer consisting of Sun UltraSparc IV CPUs.......This note considers topology optimization of large scale 2D and 3D Stokes flow problems using parallel computations. We solve problems with up to 1.125.000 elements in 2D and 128.000 elements in 3D on a shared memory computer consisting of Sun UltraSparc IV CPUs....

Stokes polarimetry probe for skin lesion evaluation: preliminary results

Science.gov (United States)

Louie, Daniel C.; Tchvialeva, Lioudmilla; Kalia, Sunil; Lui, Harvey; Lee, Tim K.

2018-02-01

This paper reports on the design of a prototype in-vivo Stokes polarimetry probe for skin lesion evaluation, and preliminary results from skin phantom and clinical trials of this device. The probe releases a single millisecond-long pulse from a laser diode with either linear or circular polarization. It then captures the resulting backscattered far-field polarization speckle and calculates the Stokes parameters. This probe was designed with three novel innovations in mind. First, the Stokes vector is captured quickly, using low-cost components without the use of moving parts. Second, a compact collimated laser diode was used as the light source. Third, the device and detector geometry were designed to produce and capture a uniform speckle field. In the first clinical trial of this device, measurements were taken from a variety of skin lesions, both cancerous and benign. The Stokes vector was measured and used to calculate the degree of polarization (DOP), the azimuth angle, and the ellipticity angle of the polarization ellipse for two input light polarizations. Among other findings, the DOP for circular polarized input light was consistently lower than the DOP for linear polarized input light. These findings indicate the potential for a fast and low-cost in-vivo skin cancer screening tool, and encourages the continuing development of this probe's techniques.

Super resolution for astronomical observations

Science.gov (United States)

Li, Zhan; Peng, Qingyu; Bhanu, Bir; Zhang, Qingfeng; He, Haifeng

2018-05-01

In order to obtain detailed information from multiple telescope observations a general blind super-resolution (SR) reconstruction approach for astronomical images is proposed in this paper. A pixel-reliability-based SR reconstruction algorithm is described and implemented, where the developed process incorporates flat field correction, automatic star searching and centering, iterative star matching, and sub-pixel image registration. Images captured by the 1-m telescope at Yunnan Observatory are used to test the proposed technique. The results of these experiments indicate that, following SR reconstruction, faint stars are more distinct, bright stars have sharper profiles, and the backgrounds have higher details; thus these results benefit from the high-precision star centering and image registration provided by the developed method. Application of the proposed approach not only provides more opportunities for new discoveries from astronomical image sequences, but will also contribute to enhancing the capabilities of most spatial or ground-based telescopes.

Astronomía Mocoví

Science.gov (United States)

López, A.; Giménez Benitez, S.; Fernández, L.

El presente trabajo, es una revisión crítica de la astronomía en la cultura Mocoví, aportando a lo realizado previamente por Lehmann Nistche (Lehmann Nistche, 1924 y 1927) el resultado de nuestro trabajo de campo. Un mayor conocimiento de las cosmovisiones de las etnias de esta área es fundamental para una mejor comprensión de la dispersión de las ideas cosmológicas entre los pueblos aborígenes americanos, dada la importancia del corredor chaqueño como conexión entre las altas culturas andinas, la mesopotamia y la región pampeana (Susnik, 1972). Para ello se realiza una comparación con otras cosmovisiones del área americana. Nuestro aporte se enmarca dentro de las actuales líneas de trabajo mundialmente en desarrollo en Astronomía en la Cultura.

Pattern recognition of obstructive sleep apnoea and Cheyne–Stokes respiration

International Nuclear Information System (INIS)

Weinreich, Gerhard; Teschler, Helmut; Armitstead, Jeff

2008-01-01

The aim of this study was to assess the validity of an artificial neural network based on flow-related spectral entropy as a diagnostic test for obstructive sleep apnoea and Cheyne–Stokes respiration. A data set of 37 subjects was used for spectral analysis of the airflow by performing a fast Fourier transform. The examined intervals were divided into epochs of 3 min. Spectral entropy S was applied as a measure for the spread of the related power spectrum. The spectrum was divided into several frequency areas with various subsets of spectral entropy. We studied 11 subjects with obstructive apnoeas (n = 267 epochs), 10 subjects with obstructive hypopnoeas (n = 80 epochs), 11 subjects with Cheyne–Stokes respiration (n = 253 epochs) and 5 subjects with normal breathing in non-REM sleep (n = 174 epochs). Based on spectral entropy an artificial neural network was built, and we obtained a sensitivity of 90.2% and a specificity of 90.9% for distinguishing between obstructive apnoeas and Cheyne–Stokes respiration, and a sensitivity of 91.3% and a specificity of 94.6% for discriminating between obstructive hypopnoeas and normal breathing in non-REM sleep. This resulted in an accuracy of 91.5% for identifying flow patterns of obstructive sleep apnoea, Cheyne–Stokes respiration and normal breathing in non-REM sleep. It is concluded that the use of an artificial neural network relying on spectral analysis of the airflow could be a useful method as a diagnostic test for obstructive sleep apnoea and Cheyne–Stokes respiration

Reproductive solutions for the g-Navier-Stokes and g-Kelvin-Voight equations

Directory of Open Access Journals (Sweden)

Luis Friz

2016-01-01

Full Text Available This article presents the existence of reproductive solutions of g-Navier-Stokes and g-Kelvin-Voight equations. In this way, for weak solutions, we reach basically the same result as for classic Navier-Stokes equations.

High-order Stokes and anti-Stokes Raman generation in monoisotopic CVD {sup 12}C-diamond

Energy Technology Data Exchange (ETDEWEB)

Kaminskii, Alexander A. [Institute of Crystallography, Russian Academy of Sciences, Moscow (Russian Federation); Lux, Oliver; Rhee, Hanjo; Eichler, Hans J. [Institute of Optics and Atomic Physics, Technische Universitaet Berlin (Germany); Ralchenko, Victor G.; Bolshakov, Andrey P. [General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Shirakawa, Akira; Yoneda, Hitoki [Institute for Laser Science, University of Electro-Communications, Tokyo (Japan)

2016-06-15

We determined, for the first time, the room temperature phonon energy related to the F{sub 2g} vibration mode (ω{sub SRS(12C)} ∝ 1333.2 cm{sup -1}) in a mono-crystalline single-isotope CVD {sup 12}C-diamond crystal by means of stimulated Raman scattering (SRS) spectroscopy. Picosecond one-micron excitation using a Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12}-laser generates a nearly two-octave spanning SRS frequency comb (∝12000 cm{sup -1}) consisting of higher-order Stokes and anti-Stokes components. The spacing of the spectral lines was found to differ by Δω{sub SRS} ∝ 0.9 cm{sup -1} from the comb spacing (ω{sub SRS(natC)} ∝ 1332.3 cm{sup -1}) when pumping a conventional CVD diamond crystal with a natural composition of the two stable carbon isotopes {sup 12}C (98.93%) and {sup 13}C (1.07%). (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Stokes-vector and Mueller-matrix polarimetry [Invited].

Science.gov (United States)

Azzam, R M A

2016-07-01

This paper reviews the current status of instruments for measuring the full 4×1 Stokes vector S, which describes the state of polarization (SOP) of totally or partially polarized light, and the 4×4 Mueller matrix M, which determines how the SOP is transformed as light interacts with a material sample or an optical element or system. The principle of operation of each instrument is briefly explained by using the Stokes-Mueller calculus. The development of fast, automated, imaging, and spectroscopic instruments over the last 50 years has greatly expanded the range of applications of optical polarimetry and ellipsometry in almost every branch of science and technology. Current challenges and future directions of this important branch of optics are also discussed.

Stokes phenomena in discrete Painlevé I.

Science.gov (United States)

Joshi, N; Lustri, C J

2015-05-08

In this study, we consider the asymptotic behaviour of the first discrete Painlevé equation in the limit as the independent variable becomes large. Using an asymptotic series expansion, we identify two types of solutions which are pole-free within some sector of the complex plane containing the positive real axis. Using exponential asymptotic techniques, we determine Stokes phenomena effects present within these solutions, and hence the regions in which the asymptotic series expression is valid. From a careful analysis of the switching behaviour across Stokes lines, we find that the first type of solution is uniquely defined, while the second type contains two free parameters, and that the region of validity may be extended for appropriate choice of these parameters.

Quantification of Stokes Drift as a Mechanism for Surface Oil Advection in the DWH Oil Spill

Science.gov (United States)

Clark, M.

2013-12-01

Stokes drift has previously been qualitatively shown to be a factor in ocean surface particle transport, but has never been comprehensively quantified. In addition, most operational ocean particle advection models used during the Deepwater Horizon oil spill do not explicitly account for Stokes drift, instead using a simple parameterization based on wind drift (or ignoring it completely). This research works to quantify Stokes drift via direct calculation, with a focus on shallow water, where Stokes drift is more likely to have a relatively large impact compared to other transport processes such as ocean currents. For this study, WaveWatch III modeled waves in the Gulf of Mexico are used, from which Stokes drift is calculated using the peak wave period and significant wave height outputs. Trajectories are also calculated to examine the role Stokes drift plays in bringing surface particles (and specifically surface oil slicks) onshore. The impact of Stokes drift is compared to transport by currents and traditional estimates of wind drift.

Velocity profiles of acoustic streaming in resulting stokes layer by acoustic standing wave in a duct; Kannai kichi shindo ni okeru stokes sonai onkyoryu ryusoku bunpu no kaiseki

Energy Technology Data Exchange (ETDEWEB)

Arakawa, M; Kawahashi, M [Saitama University, Saitama (Japan). Faculty of Engineering

1995-07-25

Acoustic streaming is generated by Reynolds stress in the sense of mean acoustic momentum flux in a sound field. In the case of an acoustic standing wave produced by an air column oscillation in a closed duct, the friction and the Reynolds stress in the resulting Stokes layer are the essentials of acoustic streaming generation in the vicinity of the duct wall. The thickness of the Stokes layer decreases with the oscillatory Reynolds number. The plane wave propagation in the duct is assumed for the case of high Reynolds number except for the thin Stokes layer adjacent to the duct wall. The velocity profiles of the streaming are estimated theoretically from the steady component of the second-order term of a perturbation expansion in which the first-order approximation is a sinusoidal oscillation of the air column with plane waves. The present paper describes theoretical analysis of the velocity profiles of the acoustic streaming in the Stokes layer by means of the matched asymptotic expansion method. The results obtained show the existence of reverse streaming in a very thin layer adjacent to the wall and the effects of thermal boundary conditions at the wall on the velocity profiles of acoustic streaming in the Stokes layer. 9 refs., 8 figs.

Top astronomers head to the city. Experts to talk on exciting quasar discoveries.

CERN Multimedia

Grant, S

2002-01-01

The UK National Astronomy Meeting - NAM 2002 - is at Bristol University this week. The meeting is one of the most important regular gatherings of astronomers in the UK. Sponsored by the Royal Astronomical Society and PPARC, it should attract about 300 astronomers from the UK and beyond.

AWOB: A Collaborative Workbench for Astronomers

Science.gov (United States)

Kim, J. W.; Lemson, G.; Bulatovic, N.; Makarenko, V.; Vogler, A.; Voges, W.; Yao, Y.; Kiefl, R.; Koychev, S.

2015-09-01

We present the Astronomers Workbench (AWOB1), a web-based collaboration and publication platform for a scientific project of any size, developed in collaboration between the Max-Planck institutes of Astrophysics (MPA) and Extra-terrestrial Physics (MPE) and the Max-Planck Digital Library (MPDL). AWOB facilitates the collaboration between geographically distributed astronomers working on a common project throughout its whole scientific life cycle. AWOB does so by making it very easy for scientists to set up and manage a collaborative workspace for individual projects, where data can be uploaded and shared. It supports inviting project collaborators, provides wikis, automated mailing lists, calendars and event notification and has a built in chat facility. It allows the definition and tracking of tasks within projects and supports easy creation of e-publications for the dissemination of data and images and other resources that cannot be added to submitted papers. AWOB extends the project concept to larger scale consortia, within which it is possible to manage working groups and sub-projects. The existing AWOB instance has so far been limited to Max-Planck members and their collaborators, but will be opened to the whole astronomical community. AWOB is an open-source project and its source code is available upon request. We intend to extend AWOB's functionality also to other disciplines, and would greatly appreciate contributions from the community.

Skype Me! Astronomers, Students, and Cutting-Edge Research

Science.gov (United States)

Hickox, Ryan C.; Gauthier, Adrienne J.

2014-06-01

A primary goal of many university science courses is to promote understanding of the process of contemporary scientific inquiry. One powerful way to achieve this is for students to explore current research and then interact directly with the leading scientist, the feasibility of which has recently increased dramatically due to free online video communication tools. We report on a program implemented at Dartmouth College in which students connect with a guest astronomer through Skype (video chat). The Skype session is wrapped in a larger activity where students explore current research articles, interact with the astronomer, and then reflect on the experience. The in-class Skype discussions require a small time commitment from scientists (20-30 minutes, with little or no need for preparation) while providing students direct access to researchers at the cutting edge of modern astronomy. We outline the procedures used to implement these discussions, and present qualitative assessments of student's understanding of the process of research, as well as feedback from the guest astronomers.

Breakthrough! 100 astronomical images that changed the world

CERN Document Server

Gendler, Robert

2015-01-01

This unique volume by two renowned astrophotographers unveils the science and history behind 100 of the most significant astronomical images of all time. The authors have carefully selected their list of images from across time and technology to bring to the reader the most relevant photographic images spanning all eras of modern astronomical history.    Based on scientific evidence today we have a basic notion of how Earth and the universe came to be. The road to this knowledge was paved with 175 years of astronomical images acquired by the coupling of two revolutionary technologies – the camera and telescope. With ingenuity and determination humankind would quickly embrace these technologies to tell the story of the cosmos and unravel its mysteries.   This book presents in pictures and words a photographic chronology of our aspiration to understand the universe. From the first fledgling attempts to photograph the Moon, planets, and stars to the marvels of orbiting observatories that record the cosmos a...

An analytical solution of the Navier-Stokes equation for internal flows

International Nuclear Information System (INIS)

Lyberg, Mats D; Tryggeson, Henrik

2007-01-01

This paper derives a solution to the Navier-Stokes equation by considering vorticity generated at system boundaries. The result is an explicit expression for the velocity. The Navier-Stokes equation is reformulated as a divergence and integrated, giving a tensor equation that splits into a symmetric and a skew-symmetric part. One equation gives an algebraic system of quadratic equations involving velocity components. A system of nonlinear partial differential equations is reduced to algebra. The velocity is then explicitly calculated and shown to depend on boundary conditions only. This removes the need to solve the Navier-Stokes equation by a 3D numerical computation, replacing it by computation of 2D surface integrals over the boundary. (fast track communication)

The PACA Project: When Amateur Astronomers Become Citizen Scientists

Science.gov (United States)

Yanamandra-Fisher, P. A.

2014-12-01

The Pro-Am Collaborative Astronomy (PACA) project evolved from the observational campaign of C/2012 S1 or C/ISON in 2013. Following the success of the professional-amateur astronomer collaboration in scientific research via social media, it is now implemented in other comet observing campaigns. While PACA identifies a consistent collaborative approach to pro-am collaborations, given the volume of data generated for each campaign, new ways of rapid data analysis, mining access and storage are needed. Several interesting results emerged from the synergistic inclusion of both social media and amateur astronomers: (1) the establishment of a network of astronomers and related professionals, that can be galvanized into action on short notice to support observing campaigns; (2) assist in various science investigations pertinent to the campaign; (3) provide an alert-sounding mechanism should the need arise; (4) immediate outreach and dissemination of results via our media/blogger members; (5) provide a forum for discussions between the imagers and modelers to help strategize the observing campaign for maximum benefit. In 2014, two new comet observing campaigns involving pro-am collaborations have been initiated: (1) C/2013 A1 (C/SidingSpring) and (2) 67P/Churyumov-Gerasimenko (CG), target for ESA/Rosetta mission. The evolving need for individual customized observing campaigns has been incorporated into the evolution of PACA portal that currently is focused on comets: from supporting observing campaigns of current comets, legacy data, historical comets; interconnected with social media and a set of shareable documents addressing observational strategies; consistent standards for data; data access, use, and storage, to align with the needs of professional observers. The integration of science, observations by professional and amateur astronomers, and various social media provides a dynamic and evolving collaborative partnership between professional and amateur astronomers

A website for astronomical news in Spanish

Science.gov (United States)

Ortiz-Gil, A.

2008-06-01

Noticias del Cosmos is a collection of web pages within the Astronomical Observatory of the University of Valencia's website where we publish short daily summaries of astronomical press releases. Most, if not all of, the releases are originally written in English, and often Spanish readers may find them difficult to understand because not many people are familiar with the scientific language employed in these releases. Noticias del Cosmos has two principal aims. First, we want to communicate the latest astronomical news on a daily basis to a wide Spanish-speaking public who would otherwise not be able to read them because of the language barrier. Second, daily news can be used as a tool to introduce the astronomical topics of the school curriculum in a more immediate and relevant way. Most of the students at school have not yet reached a good enough level in their knowledge of English to fully understand a press release, and Noticias del Cosmos offers them and their teachers this news in their mother tongue. During the regular programme of school visits at the Observatory we use the news as a means of showing that there is still a lot to be discovered. So far the visits to the website have been growing steadily. Between June 2003 and June 2007 we had more than 30,000 visits (excluding 2006). More than 50% of the visits come from Spain, followed by visitors from South and Central America. The feedback we have received from teachers so far has been very positive, showing the usefulness of news items in the classroom when teaching astronomy.

Stoked nondynamos: sustaining field in magnetically non-closed systems

International Nuclear Information System (INIS)

Byington, B M; Brummell, N H; Stone, J M; Gough, D O

2014-01-01

Much effort has gone into identifying and classifying systems that might be capable of dynamo action, i.e. capable of generating and sustaining magnetic field indefinitely against dissipative effects in a conducting fluid. However, it is difficult, if not almost technically impossible, to derive a method of determining in both an absolutely conclusive and a pragmatic manner whether a system is a dynamo or not in the nonlinear regime. This problem has generally been examined only for closed systems, despite the fact that most realistic situations of interest are not strictly closed. Here we examine the even more complex problem of whether a known nondynamo closed system can be distinguished pragmatically from a true dynamo when a small input of magnetic field to the system is allowed. We call such systems ‘stoked nondynamos’ owing to the ‘stoking’ or augmentation of the magnetic field in the system. It may seem obvious that magnetic energy can be sustained in such systems since there is an external source, but crucial questions remain regarding what level is maintained and whether such nondynamo systems can be distinguished from a true dynamo. In this paper, we perform 3D nonlinear numerical simulations with time-dependent ABC forcing possessing known dynamo properties. We find that magnetic field can indeed be maintained at a significant stationary level when stoking a system that is a nondynamo when not stoked. The maintained state results generally from an eventual rough balance of the rates of input and decay of magnetic field. We find that the relevance of this state is dictated by a parameter κ representing the correlation of the resultant field with the stoking forcing function. The interesting regime is where κ is small but non-zero, as this represents a middle ground between a state where the stoking has no effect on the pre-existing nondynamo properties and a state where the effect of stoking is easily detectable. We find that in this regime, (a

South African Astronomical Observatory

International Nuclear Information System (INIS)

1987-01-01

Work at the South African Astronomical Observatory (SAAO) in recent years, by both staff and visitors, has made major contributions to the fields of astrophysics and astronomy. During 1986 the SAAO has been involved in studies of the following: galaxies; celestial x-ray sources; magellanic clouds; pulsating variables; galactic structure; binary star phenomena; nebulae and interstellar matter; stellar astrophysics; open clusters; globular clusters, and solar systems

On astronomical drawing [1846

Science.gov (United States)

Smyth, Charles Piazzi

Reprinted from the Memoirs of the Royal Astronomical Society 15, 1846, pp. 71-82. With annotations and illustrations added by Klaus Hentschel. The activities of the Astronomer Royal for Scotland, Charles Piazzi Smyth (1819-1900), include the triangulation of South African districts, landscape painting, day-to-day or tourist sketching, the engraving and lithographing of prominent architectural sites, the documentary photography of the Egyptian pyramids or the Tenerife Dragon tree, and `instant photographs' of the clouds above his retirement home in Clova, Ripon. His colorful records of the aurora polaris, and solar and terrestrial spectra all profited from his trained eye and his subtle mastery of the pen and the brush. As his paper on astronomical drawing, which we chose to reproduce in this volume, amply demonstrates, he was conversant in most of the print technology repertoire that the 19th century had to offer, and carefully selected the one most appropriate to each sujet. For instance, he chose mezzotint for the plates illustrating Maclear's observations of Halley's comet in 1835/36, so as to achieve a ``rich profundity of shadows, the deep obscurity of which is admirably adapted to reproduce those fine effects of chiaroscuro frequently found in works where the quantity of dark greatly predominates.'' The same expertise with which he tried to emulate Rembrandt's chiaroscuro effects he applied to assessing William and John Herschel's illustrations of nebulae, which appeared in print between 1811 and 1834. William Herschel's positive engraving, made partly by stippling and partly by a coarse mezzotint, receives sharp admonishment because of the visible ruled crossed lines in the background and the fact that ``the objects, which are also generally too light, [have] a much better definition than they really possess.'' On the other hand, John Herschel's illustration of nebulae and star clusters, given in negative, ``in which the lights are the darkest part of the

Influence of the dispersive and dissipative scales alpha and beta on the energy spectrum of the Navier-Stokes alphabeta equations.

Science.gov (United States)

Chen, Xuemei; Fried, Eliot

2008-10-01

Lundgren's vortex model for the intermittent fine structure of high-Reynolds-number turbulence is applied to the Navier-Stokes alphabeta equations and specialized to the Navier-Stokes alpha equations. The Navier-Stokes alphabeta equations involve dispersive and dissipative length scales alpha and beta, respectively. Setting beta equal to alpha reduces the Navier-Stokes alphabeta equations to the Navier-Stokes alpha equations. For the Navier-Stokes alpha equations, the energy spectrum is found to obey Kolmogorov's -5/3 law in a range of wave numbers identical to that determined by Lundgren for the Navier-Stokes equations. For the Navier-Stokes alphabeta equations, Kolmogorov's -5/3 law is also recovered. However, granted that beta Navier-Stokes alphabeta equations may have the potential to resolve features smaller than those obtainable using the Navier-Stokes alpha equations.

Stokes phenomena in discrete Painlevé II.

Science.gov (United States)

Joshi, N; Lustri, C J; Luu, S

2017-02-01

We consider the asymptotic behaviour of the second discrete Painlevé equation in the limit as the independent variable becomes large. Using asymptotic power series, we find solutions that are asymptotically pole-free within some region of the complex plane. These asymptotic solutions exhibit Stokes phenomena, which is typically invisible to classical power series methods. We subsequently apply exponential asymptotic techniques to investigate such phenomena, and obtain mathematical descriptions of the rapid switching behaviour associated with Stokes curves. Through this analysis, we determine the regions of the complex plane in which the asymptotic behaviour is described by a power series expression, and find that the behaviour of these asymptotic solutions shares a number of features with the tronquée and tri-tronquée solutions of the second continuous Painlevé equation.

Broadband multiplex coherent anti-Stokes Raman scattering microscopy employing photonic-crystal fibers

DEFF Research Database (Denmark)

Andresen, Esben Ravn; Paulsen, Henrik Nørgaard; Birkedal, Victoria

2006-01-01

We demonstrate spectral multiplex coherent anti-Stokes Raman scattering (CARS) spectroscopy and microscopy based on a single Ti:sapphire oscillator and a nonlinear photonic-crystal fiber (PCF). The Stokes pulse is generated by spectral conversion of the laser pulse in a PCF. The pump pulse is eit...

Astronomers find distant planet like Jupiter

CERN Multimedia

2003-01-01

Astronomers searching for planetary systems like our solar system have found a planet similar to Jupiter orbiting a nearby star similar to our Sun, about 90 light-years from Earth, according to researchers (1/2 page).

Incompressible limit of the degenerate quantum compressible Navier-Stokes equations with general initial data

Science.gov (United States)

Kwon, Young-Sam; Li, Fucai

2018-03-01

In this paper we study the incompressible limit of the degenerate quantum compressible Navier-Stokes equations in a periodic domain T3 and the whole space R3 with general initial data. In the periodic case, by applying the refined relative entropy method and carrying out the detailed analysis on the oscillations of velocity, we prove rigorously that the gradient part of the weak solutions (velocity) of the degenerate quantum compressible Navier-Stokes equations converge to the strong solution of the incompressible Navier-Stokes equations. Our results improve considerably the ones obtained by Yang, Ju and Yang [25] where only the well-prepared initial data case is considered. While for the whole space case, thanks to the Strichartz's estimates of linear wave equations, we can obtain the convergence of the weak solutions of the degenerate quantum compressible Navier-Stokes equations to the strong solution of the incompressible Navier-Stokes/Euler equations with a linear damping term. Moreover, the convergence rates are also given.

The Top Ten Astronomical 'breakthroughs' of the 20th century

Directory of Open Access Journals (Sweden)

Hughes, D. W.

2007-10-01

Full Text Available Astronomy was revolutionized in the 20th century. The electron was discovered in 1897 and this transformed spectroscopy and introduced plasma and magnetohydrodynamic physics and astro-chemistry. Einstein’s E = mc2, solved the problem of stellar energy generation and spawned the study of elemental nuclear synthesis. Large telescopes led to a boom in astronomical spectroscopic and photometric data collection, leading to such cornerstones as the Hertzprung-Russell diagram and the mass-luminosity relationship, and to the realization that the Universe contained a multitude of galaxies and was expanding. Radio astronomy was introduced and the advent of the space age saw the astronomical wavelength range expand into the ultraviolet, X-ray and gamma-ray regions, as well as the infrared and millimetre. We also startedwandering around roaming the Solar System instead of merely glimpsing its members from the bottom of our warm, turbulent atmosphere. Astronomical “breakthroughs” abounded. We have asked astronomers to select their “top ten” and these are listed and discussed in this paper.

Dante, astrología y astronomía

OpenAIRE

Gangui, Alejandro

2017-01-01

En este artículo, los versos de Dante Alighieri nos llevan a reflexionar acerca de los diferentes métodos -cada vez más divergentes- con los que la ciencia y las creencias se aproximan a la realidad. Fil: Gangui, Alejandro. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Físi...

TMT in the Astronomical Landscape of the 2020s

Science.gov (United States)

Dickinson, Mark; Inami, Hanae

2014-07-01

Thirty Meter Telescope Observatory and NOAO will host the second TMT Science Forum at Loews Ventana Canyon Resort in Tucson, Arizona. The TMT Science Forum is an an annual gathering of astronomers, educators, and observatory staff, who meet to explore TMT science, instrumentation, observatory operations, archiving and data processing, astronomy education, and science, technology, engineering, and math (STEM) issues. It is an opportunity for astronomers from the international TMT partners and from the US-at-large community to learn about the observatory status, discuss and plan cutting-edge science, establish collaborations, and to help shape the future of TMT. One important theme for this year's Forum will be the synergy between TMT and other facilities in the post-2020 astronomical landscape. There will be plenary sessions, an instrumentation workshop, topical science sessions and meetings of the TMT International Science Development Teams (ISDTs).

Stokes profile analysis and vector magnetic fields. III. Extended temperature minima of sunspot umbrae as inferred from Stokes profiles of Mg I 4571 A

International Nuclear Information System (INIS)

Lites, B.W.; Skumanich, A.; Rees, D.E.; Murphy, G.A.; Carlsson, M.; Sydney Univ., Australia; Oslo Universitetet, Norway)

1987-01-01

Observed Stokes profiles of Mg I 4571 A are analyzed as a diagnostic of the magnetic field and thermal structure at the temperature minimum of sunspot umbrae. Multilevel non-LTE transfer calculations of the Mg I-II-III excitation and ionization balance in model umbral atmospheres show: (1) Mg I to be far less ionized in sunspot umbrae than in the quiet sun, leading to greatly enhanced opacity in 4571 A, and (2) LTE excitation of 4571 A. Existing umbral models predict emission cores of the Stokes I profile due to the chromospheric temperature rise. This feature is not present in observed umbral profiles. Moreover, such an emission reversal causes similar anomalous features in the Stokes Q, U, V profiles, which are also not observed. Umbral atmospheres with extended temperature minima are suggested. Implications for chromospheric heating mechanisms and the utility of this line for solar vector magnetic field measurements are discussed. 35 references

CUDA GPU based full-Stokes finite difference modelling of glaciers

Science.gov (United States)

Brædstrup, C. F.; Egholm, D. L.

2012-04-01

Many have stressed the limitations of using the shallow shelf and shallow ice approximations when modelling ice streams or surging glaciers. Using a full-stokes approach requires either large amounts of computer power or time and is therefore seldom an option for most glaciologists. Recent advances in graphics card (GPU) technology for high performance computing have proven extremely efficient in accelerating many large scale scientific computations. The general purpose GPU (GPGPU) technology is cheap, has a low power consumption and fits into a normal desktop computer. It could therefore provide a powerful tool for many glaciologists. Our full-stokes ice sheet model implements a Red-Black Gauss-Seidel iterative linear solver to solve the full stokes equations. This technique has proven very effective when applied to the stokes equation in geodynamics problems, and should therefore also preform well in glaciological flow probems. The Gauss-Seidel iterator is known to be robust but several other linear solvers have a much faster convergence. To aid convergence, the solver uses a multigrid approach where values are interpolated and extrapolated between different grid resolutions to minimize the short wavelength errors efficiently. This reduces the iteration count by several orders of magnitude. The run-time is further reduced by using the GPGPU technology where each card has up to 448 cores. Researchers utilizing the GPGPU technique in other areas have reported between 2 - 11 times speedup compared to multicore CPU implementations on similar problems. The goal of these initial investigations into the possible usage of GPGPU technology in glacial modelling is to apply the enhanced resolution of a full-stokes solver to ice streams and surging glaciers. This is a area of growing interest because ice streams are the main drainage conjugates for large ice sheets. It is therefore crucial to understand this streaming behavior and it's impact up-ice.

Astronomical random numbers for quantum foundations experiments

Science.gov (United States)

Leung, Calvin; Brown, Amy; Nguyen, Hien; Friedman, Andrew S.; Kaiser, David I.; Gallicchio, Jason

2018-04-01

Photons from distant astronomical sources can be used as a classical source of randomness to improve fundamental tests of quantum nonlocality, wave-particle duality, and local realism through Bell's inequality and delayed-choice quantum eraser tests inspired by Wheeler's cosmic-scale Mach-Zehnder interferometer gedanken experiment. Such sources of random numbers may also be useful for information-theoretic applications such as key distribution for quantum cryptography. Building on the design of an astronomical random number generator developed for the recent cosmic Bell experiment [Handsteiner et al. Phys. Rev. Lett. 118, 060401 (2017), 10.1103/PhysRevLett.118.060401], in this paper we report on the design and characterization of a device that, with 20-nanosecond latency, outputs a bit based on whether the wavelength of an incoming photon is greater than or less than ≈700 nm. Using the one-meter telescope at the Jet Propulsion Laboratory Table Mountain Observatory, we generated random bits from astronomical photons in both color channels from 50 stars of varying color and magnitude, and from 12 quasars with redshifts up to z =3.9 . With stars, we achieved bit rates of ˜1 ×106Hz/m 2 , limited by saturation of our single-photon detectors, and with quasars of magnitudes between 12.9 and 16, we achieved rates between ˜102 and 2 ×103Hz /m2 . For bright quasars, the resulting bitstreams exhibit sufficiently low amounts of statistical predictability as quantified by the mutual information. In addition, a sufficiently high fraction of bits generated are of true astronomical origin in order to address both the locality and freedom-of-choice loopholes when used to set the measurement settings in a test of the Bell-CHSH inequality.

Astronomy Legacy Project - Pisgah Astronomical Research Institute

Science.gov (United States)

Barker, Thurburn; Castelaz, Michael W.; Rottler, Lee; Cline, J. Donald

2016-01-01

Pisgah Astronomical Research Institute (PARI) is a not-for-profit public foundation in North Carolina dedicated to providing hands-on educational and research opportunities for a broad cross-section of users in science, technology, engineering and math (STEM) disciplines. In November 2007 a Workshop on a National Plan for Preserving Astronomical Photographic Data (2009ASPC,410,33O, Osborn, W. & Robbins, L) was held at PARI. The result was the establishment of the Astronomical Photographic Data Archive (APDA) at PARI. In late 2013 PARI began ALP (Astronomy Legacy Project). ALP's purpose is to digitize an extensive set of twentieth century photographic astronomical data housed in APDA. Because of the wide range of types of plates, plate dimensions and emulsions found among the 40+ collections, plate digitization will require a versatile set of scanners and digitizing instruments. Internet crowdfunding was used to assist in the purchase of additional digitization equipment that were described at AstroPlate2014 Plate Preservation Workshop (www.astroplate.cz) held in Prague, CZ, March, 2014. Equipment purchased included an Epson Expression 11000XL scanner and two Nikon D800E cameras. These digital instruments will compliment a STScI GAMMA scanner now located in APDA. GAMMA will be adapted to use an electroluminescence light source and a digital camera with a telecentric lens to achieve high-speed high-resolution scanning. The 1μm precision XY stage of GAMMA will allow very precise positioning of the plate stage. Multiple overlapping CCD images of small sections of each plate, tiles, will be combined using a photo-mosaic process similar to one used in Harvard's DASCH project. Implementation of a software pipeline for the creation of a SQL database containing plate images and metadata will be based upon APPLAUSE as described by Tuvikene at AstroPlate2014 (www.astroplate.cz/programs/).

Astronomers Win Protection for Key Part of Radio Spectrum

Science.gov (United States)

2000-06-01

Astronomers using the millimeter-wave region of the radio spectrum have won crucial protection for their science. Dedicated allocations for radio astronomy have been given final approval by the 2,500 delegates to the World Radiocommunication Conference (WRC-00), which recently concluded a month of deliberations in Istanbul, Turkey. Radio services can transmit in these parts of the spectrum as long as they don't hinder astronomers' attempts to catch faint signals from the cosmos. The new allocations represent the culmination of more than three years of cooperative planning by radio astronomers in many countries. Millimeter waves -- high-frequency radio waves -- have come of age as an astronomical tool in the last ten years. They are one of the last technological frontiers for astronomers. WRC-00 has protected for science all the frequencies between 71 and 275 Gigahertz (GHz) that radio astronomers currently use, adding more than 90 GHz of spectrum to the 44 GHz already set aside in this frequency range. As a result, radio astronomy is now allocated most of the frequencies between 71 and 275 GHz that can get through the Earth's atmosphere. "We have formal access to all three atmospheric 'windows', apart from their very edges," said Dr. Tom Gergely of the National Science Foundation, one of the U.S. delegates to WRC-00. The WRC also changed most of the frequencies allocated to satellite downlinks within the 71-275 GHz range to frequencies not used for science. Since no satellites yet operate at these high frequencies, no equipment needs to be altered. "Commercial technologies are just starting to develop above 50 GHz," said Dr. Klaus Ruf, Chairman of the Inter-Union Commission for the Allocation of Frequencies. "The WRC's actions mean that, when they are, radio astronomers should be able to share this part of the spectrum with most terrestrial services." The World Radiocommunication Conference is held every two or three years. Here member countries of the

Maraghe Observatory and an Effort towards Retrieval of Architectural Design of Astronomical Units

Directory of Open Access Journals (Sweden)

Javad Shekari Niri

2015-03-01

Full Text Available Maraghe observatory was built by such engineers as Moayiededdin Orozi etc. under supervision of Khaje Nasireddin Tousi in 7th century AH. The most significant feature associated with Maraghe observatory is the fact that architecture is employed to achieve astronomical purposes in this site. The reason for preferring observatory by astronomers was the fact that these units are superior to wooden and metal instruments with respect to accuracy, no size limitations, etc. Architectural design and function of astronomical units of Maraghe observatory site after discovery of its foundation in the course of explorations before Islamic Revolution remained unclear until recent years. After conducting required studies and investigations, the author managed to find significant cues and after some precise comparisons, he succeeded to recover the main design and function of some astronomical units of this international center. Based on these findings these astronomical structures can reliably be rebuilt. This research showed that every circular or polygonal building cannot be considered as an observatory. For example form and function of cemetery structures are completely different with astronomical ones. Following this research also valuable results were obtained in relation to stone architectural structures present on Maraghe observatory hill. In addition, claims about invention of astronomical units of Maraghe observatory by non-Iranian scientists are rejected and rights of Iranian scientists are rationally defended in this regard.

On Critical Spaces for the Navier-Stokes Equations

Science.gov (United States)

Prüss, Jan; Wilke, Mathias

2017-10-01

The abstract theory of critical spaces developed in Prüss and Wilke (J Evol Equ, 2017. doi: 10.1007/s00028-017-0382-6), Prüss et al. (Critical spaces for quasilinear parabolic evolution equations and applications, 2017) is applied to the Navier-Stokes equations in bounded domains with Navier boundary conditions as well as no-slip conditions. Our approach unifies, simplifies and extends existing work in the L_p -L_q setting, considerably. As an essential step, it is shown that the strong and weak Stokes operators with Navier conditions admit an H^∞-calculus with H^∞-angle 0, and the real and complex interpolation spaces of these operators are identified.

Assessment of tissue polarimetric properties using Stokes polarimetric imaging with circularly polarized illumination.

Science.gov (United States)

Qi, Ji; He, Honghui; Lin, Jianyu; Dong, Yang; Chen, Dongsheng; Ma, Hui; Elson, Daniel S

2018-04-01

Tissue-depolarization and linear-retardance are the main polarization characteristics of interest for bulk tissue characterization, and are normally interpreted from Mueller polarimetry. Stokes polarimetry can be conducted using simpler instrumentation and in a shorter time. Here, we use Stokes polarimetric imaging with circularly polarized illumination to assess the circular-depolarization and linear-retardance properties of tissue. Results obtained were compared with Mueller polarimetry in transmission and reflection geometry, respectively. It is found that circular-depolarization obtained from these 2 methods is very similar in both geometries, and that linear-retardance is highly quantitatively similar for transmission geometry and qualitatively similar for reflection geometry. The majority of tissue circular-depolarization and linear-retardance image information (represented by local image contrast features) obtained from Mueller polarimetry is well preserved from Stokes polarimetry in both geometries. These findings can be referred to for further understanding tissue Stokes polarimetric data, and for further application of Stokes polarimetry under the circumstances where short acquisition time or low optical system complexity is a priority, such as polarimetric endoscopy and microscopy. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

GalileoMobile: Astronomical activities in schools

Science.gov (United States)

Dasi Espuig, Maria; Vasquez, Mayte; Kobel, Philippe

GalileoMobile is an itinerant science education initiative run on a voluntary basis by an international team of astronomers, educators, and science communicators. Our team's main goal is to make astronomy accessible to schools and communities around the globe that have little or no access to outreach actions. We do this by performing teacher workshops, activities with students, and donating educational material. Since the creation of GalileoMobile in 2008, we have travelled to Chile, Bolivia, Peru, India, and Uganda, and worked with 56 schools in total. Our activities are centred on the GalileoMobile Handbook of Activities that comprises around 20 astronomical activities which we adapted from many different sources, and translated into 4 languages. The experience we gained in Chile, Bolivia, Peru, India, and Uganda taught us that (1) bringing experts from other countries was very stimulating for children as they are naturally curious about other cultures and encourages a collaboration beyond borders; (2) high-school students who were already interested in science were always very eager to interact with real astronomers doing research to ask for career advice; (3) inquiry-based methods are important to make the learning process more effective and we have therefore, re-adapted the activities in our Handbook according to these; (4) local teachers and university students involved in our activities have the potential to carry out follow-up activities, and examples are those from Uganda and India.

Astronomical Spectroscopy A Short History

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education; Volume 3; Issue 5. Astronomical Spectroscopy A Short History. J C Bhattacharyya. General Article Volume 3 Issue 5 May 1998 pp 24-29. Fulltext. Click here to view fulltext PDF. Permanent link: https://www.ias.ac.in/article/fulltext/reso/003/05/0024-0029 ...

[Selected enhancement of different order stokes lines of SRS by using fluorescence of mixed dye solution].

Science.gov (United States)

Zuo, Hao-yi; Gao, Jie; Yang, Jing-guo

2007-03-01

A new method to enhance the intensity of the different orders of Stokes lines of SRS by using mixed dye fluorescence is reported. The Stokes lines from the second-order to the fifth-order of CCl4 were enhanced by the fluorescence of mixed R6G and RB solutions in different proportions of 20:2, 20:13 and 20:40 (R6g:Rb), respectively. It is considered that the Stokes lines from the second-order to the fifth-order are near the fluorescence peaks of the three mixed solutions, and far from the absorption peaks of R6g and Rb, so the enhancement effect dominates the absorption effect; as a result, these stokes lines are enhanced. On the contrary, the first-order stokes line is near the absorption peak of RB and far from the fluorescence peaks of the mixed solutions, which leads to the weakening of this stokes line. It is also reported that the first-order, the second-order and the third-order Stokes lines of benzene were enhanced by the fluorescence of mixed solutions of R6g and DCM with of different proportions. The potential application of this method is forecasted.

Astronomical Photometry Past, Present, and Future

CERN Document Server

Milone, Eugene F

2011-01-01

This book brings together experts in the field of astronomical photometry to discuss how their subfields provide the precision and accuracy in astronomical energy flux measurements that are needed to permit tests of astrophysical theories. Differential photometers and photometry, improvements in infrared precision, the improvements in precision and accuracy of CCD photometry, the absolute calibration of flux, the development of the Johnson UBVRI photometric system and other passband systems to measure and precisely classify specific types of stars and astrophysical quantities, and the current capabilities of spectrophotometry and polarimetry to provide precise and accurate data, are all discussed in this volume. The discussion of `differential’ or `two-star’ photometers ranges from early experiments in visual photometry through the Harvard and Princeton polarizing photometers to the pioneering work of Walraven and differential photometers designed to minimize effects of atmospheric extinction and to count...

Isaac Newton and the astronomical refraction.

Science.gov (United States)

Lehn, Waldemar H

2008-12-01

In a short interval toward the end of 1694, Isaac Newton developed two mathematical models for the theory of the astronomical refraction and calculated two refraction tables, but did not publish his theory. Much effort has been expended, starting with Biot in 1836, in the attempt to identify the methods and equations that Newton used. In contrast to previous work, a closed form solution is identified for the refraction integral that reproduces the table for his first model (in which density decays linearly with elevation). The parameters of his second model, which includes the exponential variation of pressure in an isothermal atmosphere, have also been identified by reproducing his results. The implication is clear that in each case Newton had derived exactly the correct equations for the astronomical refraction; furthermore, he was the first to do so.

The data analysis facilities that astronomers want

International Nuclear Information System (INIS)

Disney, M.

1985-01-01

This paper discusses the need and importance of data analysis facilities and what astronomers ideally want. A brief survey is presented of what is available now and some of the main deficiencies and problems with today's systems are discussed. The main sources of astronomical data are presented incuding: optical photographic, optical TV/CCD, VLA, optical spectros, imaging x-ray satellite, and satellite planetary camera. Landmark discoveries are listed in a table, some of which include: our galaxy as an island, distance to stars, H-R diagram (stellar structure), size of our galaxy, and missing mass in clusters. The main problems at present are discussed including lack of coordinated effort and central planning, differences in hardware, and measuring performance

On singularity formation of a 3D model for incompressible Navier–Stokes equations

OpenAIRE

Hou, Thomas Y.; Shi, Zuoqiang; Wang, Shu

2012-01-01

We investigate the singularity formation of a 3D model that was recently proposed by Hou and Lei (2009) in [15] for axisymmetric 3D incompressible Navier–Stokes equations with swirl. The main difference between the 3D model of Hou and Lei and the reformulated 3D Navier–Stokes equations is that the convection term is neglected in the 3D model. This model shares many properties of the 3D incompressible Navier–Stokes equations. One of the main results of this paper is that we prove rigorously th...

Cheyne-Stokes respiration in patients with congestive heart failure: causes and consequences A respiração de Cheyne-Stokes em pacientes com insuficiência cardíaca congestiva: causas e conseqüências

Directory of Open Access Journals (Sweden)

Geraldo Lorenzi-Filho

2005-08-01

Full Text Available Cheyne-Stokes respiration is a form of periodic breathing in which central apneas and hypopneas alternate with periods of hyperventilation, producing a waxing and waning pattern of tidal volume. This review focuses on the causes and consequences of Cheyne-Stokes respiration in patients with congestive heart failure, in whom the prevalence is strikingly high and ranges from 30% to 50%. Several factors have been implicated in the genesis of Cheyne-Stokes respiration, including low cardiac output and recurrent hypoxia. The key pathophysiological mechanism triggering Cheyne-Stokes respiration is hyperventilation and low arterial CO2 (PaCO2 that when below the apneic threshold triggers a central apnea. Hyperventilation is associated with pulmonary congestion, and Cheyne-Stokes respiration is more prone to occur during sleep, when the respiratory system is mainly dependent on chemical control. It is associated with recurrent dips in oxygen saturation and arousals from sleep, with oscillations in blood pressure and heart rate, sympathetic activation and increased risk of ventricular tachycardia. Cheyne-Stokes respiration is an independent marker of poor prognosis and may participate in a vicious cycle, further stressing the failing heart.A respiração de Cheyne-Stokes é uma forma de respiração periódica na qual apnéias e hipopnéias se alternam com períodos de hiperpnéias que apresentam um padrão crescendo e decrescendo de volume corrente. Esta revisão enfoca as causa e conseqüências da respiração de Cheyne- Stokes em pacientes com insuficiência cardíaca congestiva na qual a prevalência é extremamente alta e varia entre 30 a 50%. Vários fatores foram implicados na gênese da respiração de Cheyne-Stokes, incluindo baixo debito cardíaco e hipoxia recorrente. Hiperventilacão e baixos níveis de CO2 arterial (PaCO2, que quando abaixo do limiar de apnéia desencadeiam apnéia central são os mecanismos fisiopatológicos chave na g

On convergence of trajectory attractors of the 3D Navier-Stokes-α model as α approaches 0

International Nuclear Information System (INIS)

Vishik, M I; Chepyzhov, V V; Titi, E S

2007-01-01

We study the relations between the long-time dynamics of the Navier-Stokes-α model and the exact 3D Navier-Stokes system. We prove that bounded sets of solutions of the Navier-Stokes-α model converge to the trajectory attractor A 0 of the 3D Navier-Stokes system as the time approaches infinity and α approaches zero. In particular, we show that the trajectory attractor A α of the Navier-Stokes-α model converges to the trajectory attractor A 0 of the 3D Navier-Stokes system as α→0+. We also construct the minimal limit A min (subset or equal A 0 ) of the trajectory attractor A α as α→0+ and prove that the set A min is connected and strictly invariant. Bibliography: 35 titles.

Grigor Narekatsi's astronomical insights

Science.gov (United States)

Poghosyan, Samvel

2015-07-01

What stand out in the solid system of Gr. Narekatsi's naturalistic views are his astronomical insights on the material nature of light, its high speed and the Sun being composed of "material air". Especially surprising and fascinating are his views on stars and their clusters. What astronomers, including great Armenian academician V. Ambartsumian (scattering of stellar associations), would understand and prove with much difficulty thousand years later, Narekatsi predicted in the 10th century: "Stars appear and disappear untimely", "You who gather and scatter the speechless constellations, like a flock of sheep". Gr. Narekatsti's reformative views were manifested in all the spheres of the 10th century social life; he is a reformer of church life, great language constructor, innovator in literature and music, freethinker in philosophy and science. His ideology is the reflection of the 10th century Armenian Renaissance. During the 9th-10th centuries, great masses of Armenians, forced to migrate to the Balkans, took with them and spread reformative ideas. The forefather of the western science, which originated in the period of Reformation, is considered to be the great philosopher Nicholas of Cusa. The study of Gr. Narekatsti's logic and naturalistic views enables us to claim that Gr. Narekatsti is the great grandfather of European science.

Solutions to three-dimensional Navier-Stokes equations for incompressible fluids

Directory of Open Access Journals (Sweden)

Jorma Jormakka

2010-07-01

Full Text Available This article gives explicit solutions to the space-periodic Navier-Stokes problem with non-periodic pressure. These type of solutions are not unique and by using such solutions one can construct a periodic, smooth, divergence-free initial vector field allowing a space-periodic and time-bounded external force such that there exists a smooth solution to the 3-dimensional Navier-Stokes equations for incompressible fluid with those initial conditions, but the solution cannot be continued to the whole space.

Amateur astronomers in support of observing campaigns

Science.gov (United States)

Yanamandra-Fisher, P.

2014-07-01

The Pro-Am Collaborative Astronomy (PACA) project evolved from the observational campaign of C/2012 S1 or C/ISON. The success of the paradigm shift in scientific research is now implemented in other comet observing campaigns. While PACA identifies a consistent collaborative approach to pro-am collaborations, given the volume of data generated for each campaign, new ways of rapid data analysis, mining access, and storage are needed. Several interesting results emerged from the synergistic inclusion of both social media and amateur astronomers: - the establishment of a network of astronomers and related professionals that can be galvanized into action on short notice to support observing campaigns; - assist in various science investigations pertinent to the campaign; - provide an alert-sounding mechanism should the need arise; - immediate outreach and dissemination of results via our media/blogger members; - provide a forum for discussions between the imagers and modelers to help strategize the observing campaign for maximum benefit. In 2014, two new comet observing campaigns involving pro-am collaborations have been identified: (1) C/2013 A1 (C/Siding Spring) and (2) 67P/Churyumov-Gerasimenko (CG). The evolving need for individual customized observing campaigns has been incorporated into the evolution of PACA (Pro-Am Collaborative Astronomy) portal that currently is focused on comets: from supporting observing campaigns for current comets, legacy data, historical comets; interconnected with social media and a set of shareable documents addressing observational strategies; consistent standards for data; data access, use, and storage, to align with the needs of professional observers. The integration of science, observations by professional and amateur astronomers, and various social media provides a dynamic and evolving collaborative partnership between professional and amateur astronomers. The recent observation of comet 67P, at a magnitude of 21.2, from Siding

Astronomers no longer in the dark

CERN Multimedia

MacMillan, L

2002-01-01

In a significant breakthrough, British and US astronomers have begun to pin down the most elusive material in the universe. They have made a map of dark matter - the heavy, invisible stuff that gives the galaxies their shape (1 page).

LGBT Workplace Issues for Astronomers

Science.gov (United States)

Kay, Laura E.; Danner, R.; Sellgren, K.; Dixon, V.; GLBTQastro

2011-01-01

Federal Equal Employment Opportunity laws and regulations do not provide protection from discrimination on the basis of sexual orientation or gender identity or gender expression. Sexual minority astronomers (including lesbian, gay, bisexual and transgender people; LGBT) can face additional challenges at school and work. Studies show that LGBT students on many campuses report experiences of harassment. Cities, counties, and states may or may not have statutes to protect against such discrimination. There is wide variation in how states and insurance plans handle legal and medical issues for transgender people. Federal law does not acknowledge same-sex partners, including those legally married in the U.S. or in other countries. Immigration rules in the U.S. (and many other, but not all) countries do not recognize same-sex partners for visas, employment, etc. State `defense of marriage act' laws have been used to remove existing domestic partner benefits at some institutions, or benefits can disappear with a change in governor. LGBT astronomers who change schools, institutions, or countries during their career may experience significant differences in their legal, medical, and marital status.

What Lies Behind NSF Astronomer Demographics? Subjectivities of Women, Minorities and Foreign-born Astronomers within Meshworks of Big Science Astronomy

Science.gov (United States)

Guillen, Reynal; Gu, D.; Holbrook, J.; Murillo, L. F.; Traweek, S.

2011-01-01

Our current research focuses on the trajectory of scientists working with large-scale databases in astronomy, following them as they strategically build their careers, digital infrastructures, and make their epistemological commitments. We look specifically at how gender, ethnicity, nationality intersect in the process of subject formation in astronomy, as well as in the process of enrolling partners for the construction of instruments, design and implementation of large-scale databases. Work once figured as merely technical support, such assembling data catalogs, or as graphic design, generating pleasing images for public support, has been repositioned at the core of the field. Some have argued that such databases enable a new kind of scientific inquiry based on data exploration, such as the "fourth paradigm" or "data-driven" science. Our preliminary findings based on oral history interviews and ethnography provide insights into meshworks of women, African-American, "Hispanic," Asian-American and foreign-born astronomers. Our preliminary data suggest African-American men are more successful in sustaining astronomy careers than Chicano and Asian-American men. A distinctive theme in our data is the glocal character of meshworks available to and created by foreign-born women astronomers working at US facilities. Other data show that the proportion of Asian to Asian American and foreign-born Latina/o to Chicana/o astronomers is approximately equal. Futhermore, Asians and Latinas/os are represented in significantly greater numbers than Asian Americans and Chicanas/os. Among professional astronomers in the US, each ethnic minority group is numbered on the order of tens, not hundreds. Project support is provided by the NSF EAGER program to University of California, Los Angeles under award 0956589.

Convergence acceleration of Navier-Stokes equation using adaptive wavelet method

International Nuclear Information System (INIS)

Kang, Hyung Min; Ghafoor, Imran; Lee, Do Hyung

2010-01-01

An efficient adaptive wavelet method is proposed for the enhancement of computational efficiency of the Navier-Stokes equations. The method is based on sparse point representation (SPR), which uses the wavelet decomposition and thresholding to obtain a sparsely distributed dataset. The threshold mechanism is modified in order to maintain the spatial accuracy of a conventional Navier-Stokes solver by adapting the threshold value to the order of spatial truncation error. The computational grid can be dynamically adapted to a transient solution to reflect local changes in the solution. The flux evaluation is then carried out only at the points of the adapted dataset, which reduces the computational effort and memory requirements. A stabilization technique is also implemented to avoid the additional numerical errors introduced by the threshold procedure. The numerical results of the adaptive wavelet method are compared with a conventional solver to validate the enhancement in computational efficiency of Navier-Stokes equations without the degeneration of the numerical accuracy of a conventional solver

Preserving Astronomy's Photographic Legacy: Current State and the Future of North American Astronomical Plates

Science.gov (United States)

Osborn, W.; Robbins, L.

2009-08-01

This book contains articles on preserving astronomy's valuable heritage of photographic observations, most of which are on glass plates. It is intended to serve as a reference for institutions charged with preserving and managing plate archives and astronomers interested in using archival photographic plates in their research. The first portion of the book focuses on previous activities and recommendations related to plate archiving. These include actions taken by the International Astronomical Union, activities in Europe and a detailed account of a workshop on preserving astronomical photographic data held in 2007 at the Pisgah Astronomical Research Institute, North Carolina. The workshop discussions covered a wide range of issues that must be considered in any effort to archive plates and culminated in a set of recommendations on preserving, cataloging and making publicly available these irreplaceable data. The second part of the book reports on some recent efforts to implement the recommendations. These include essays on the recently established Astronomical Photographic Data Archive, projects to make photographic collections available electronically, evaluations of commercial scanners for digitization of astronomical plates and the case for the continuing value of these data along with a report on the census of astronomical plate collections in North America carried out in 2008. The census cataloged the locations, numbers, and types of astronomical plates in the US and Canada. Comprehensive appendices identify all the significant collections in North America and detail the current contents, state and status of their holdings.

Recent Advances for LGBT Astronomers in the United States

Science.gov (United States)

Dixon, William V.; Rigby, Jane; Oppenheimer, Rebecca

2015-08-01

The legal environment for lesbian, gay, bisexual, and transgender (LGBT) astronomers in the United States has changed dramatically in recent years. In 2013, the Supreme Court ruled that Section 3 of the Defense of Marriage Act (DOMA), which had barred the federal government from recognizing same-sex marriages, was unconstitutional. This decision particularly affects astronomers, since astronomers in the U.S. are more likely than the general population to be foreign nationals, to have a foreign-born spouse, or to work for the federal government. In 2014, the Attorney General directed the Department of Justice to take the position in litigation that the protection of Title VII of the Civil Rights Act of 1964 extends to claims of discrimination based on an individual’s gender identity, including transgender status. Title VII makes it unlawful for employers to discriminate in the employment of an individual “because of such individual’s... sex,” among other protected characteristics. As of March 2015, more than 70% of the population lives in states that recognize same-sex marriage, and the Supreme Court is expected to rule on the constitutionality of the remaining same-sex marriage bans during the current term. In this poster, we discuss these advances and their implications for the personal and professional lives of LGBT astronomers across the United States.

How did the Supreme Court ruling on DOMA affect astronomers?

Science.gov (United States)

Rigby, Jane R.; The AAS Working Group on LGBTIQ Equality

2014-01-01

In June 2013, the United States Supreme Court ruled that Section 3 of the Defense of Marriage Act (DOMA) was unconstitutional. Section 3 had barred the federal government from recognizing same-sex marriages. The decision in United States v. Windsor, made headlines around the world, and particularly affected astronomers, since astronomers in the US are more likely than the general population to be foreign nationals, to have a foreign-born spouse, or to work for the federal government. In this poster, we highlight some of the real-world ways that the Windsor case has affected US astronomers and our profession. Bi-national couples can now apply for green cards granting permanent residency. Scientists who work for the federal government, including NASA and the NSF, can now obtain health insurance for a same-sex spouse. From taxes to death benefits, health insurance to daycare, immigration to ethics laws, the end of S3 of DOMA has had profoundly improved the lives of US scientists who are lesbian, gay, bisexual, or transgender (LGBT). Here we, highlight several real-world examples of how DOMA's demise has improved the lives and careers of US astronomer.

Approximate controllability of the Navier-Stokes system in unbounded domains

International Nuclear Information System (INIS)

Shorygin, P O

2003-01-01

The question of the approximate controllability for the 2- and the 3-dimensional Navier-Stokes system defined in the exterior of a bounded domain ω or in the entire space is studied. It is shown that one can find boundary controls or locally distributed controls (having support in a prescribed bounded domain) defined on the right-hand side of the system such that in prescribed time the solution of the Navier-Stokes system becomes arbitrarily close to an arbitrary prescribed divergence-free vector field

Statistical methods for astronomical data analysis

CERN Document Server

Chattopadhyay, Asis Kumar

2014-01-01

This book introduces “Astrostatistics” as a subject in its own right with rewarding examples, including work by the authors with galaxy and Gamma Ray Burst data to engage the reader. This includes a comprehensive blending of Astrophysics and Statistics. The first chapter’s coverage of preliminary concepts and terminologies for astronomical phenomenon will appeal to both Statistics and Astrophysics readers as helpful context. Statistics concepts covered in the book provide a methodological framework. A unique feature is the inclusion of different possible sources of astronomical data, as well as software packages for converting the raw data into appropriate forms for data analysis. Readers can then use the appropriate statistical packages for their particular data analysis needs. The ideas of statistical inference discussed in the book help readers determine how to apply statistical tests. The authors cover different applications of statistical techniques already developed or specifically introduced for ...

ARNICA, the Arcetri near-infrared camera: Astronomical performance assessment.

Science.gov (United States)

Hunt, L. K.; Lisi, F.; Testi, L.; Baffa, C.; Borelli, S.; Maiolino, R.; Moriondo, G.; Stanga, R. M.

1996-01-01

The Arcetri near-infrared camera ARNICA was built as a users' instrument for the Infrared Telescope at Gornergrat (TIRGO), and is based on a 256x256 NICMOS 3 detector. In this paper, we discuss ARNICA's optical and astronomical performance at the TIRGO and at the William Herschel Telescope on La Palma. Optical performance is evaluated in terms of plate scale, distortion, point spread function, and ghosting. Astronomical performance is characterized by camera efficiency, sensitivity, and spatial uniformity of the photometry.

Applying artificial intelligence to astronomical databases - a surveyof applicable technology.

Science.gov (United States)

Rosenthal, D. A.

This paper surveys several emerging technologies which are relevant to astronomical database issues such as interface technology, internal database representation, and intelligent data reduction aids. Among the technologies discussed are natural language understanding, frame and object representations, planning, pattern analysis, machine learning and the nascent study of simulated neural nets. These techniques will become increasingly important for astronomical research, and in particular, for applications with large databases.

EDUCATIONAL ASTRONOMICAL OBSERVATIONS ON REMOTE ACCESS TELESCOPES

Directory of Open Access Journals (Sweden)

Ivan P. Kriachko

2016-01-01

Full Text Available The purpose of this article is to show the way of overcoming one of the major problems of astronomy teaching methods in upper secondary school – organization of educational astronomical observations. Nowadays it became possible to perform such observations on remote access telescopes. By using up-to-date informational and communicational technologies, having an opportunity to work with robotic telescopes allows us to organize a unique cognitive and research oriented activities for students while conducting their specialized astronomical studies. Below here is given a brief description of the most significant robotic telescopes and the way of the usage of open remote access telescopic network which was created by professors and scientists of Harvard-Smithsonian Center for Astrophysics, USA.

How do astronomers share data? Reliability and persistence of datasets linked in AAS publications and a qualitative study of data practices among US astronomers.

Science.gov (United States)

Pepe, Alberto; Goodman, Alyssa; Muench, August; Crosas, Merce; Erdmann, Christopher

2014-01-01

We analyze data sharing practices of astronomers over the past fifteen years. An analysis of URL links embedded in papers published by the American Astronomical Society reveals that the total number of links included in the literature rose dramatically from 1997 until 2005, when it leveled off at around 1500 per year. The analysis also shows that the availability of linked material decays with time: in 2011, 44% of links published a decade earlier, in 2001, were broken. A rough analysis of link types reveals that links to data hosted on astronomers' personal websites become unreachable much faster than links to datasets on curated institutional sites. To gauge astronomers' current data sharing practices and preferences further, we performed in-depth interviews with 12 scientists and online surveys with 173 scientists, all at a large astrophysical research institute in the United States: the Harvard-Smithsonian Center for Astrophysics, in Cambridge, MA. Both the in-depth interviews and the online survey indicate that, in principle, there is no philosophical objection to data-sharing among astronomers at this institution. Key reasons that more data are not presently shared more efficiently in astronomy include: the difficulty of sharing large data sets; over reliance on non-robust, non-reproducible mechanisms for sharing data (e.g. emailing it); unfamiliarity with options that make data-sharing easier (faster) and/or more robust; and, lastly, a sense that other researchers would not want the data to be shared. We conclude with a short discussion of a new effort to implement an easy-to-use, robust, system for data sharing in astronomy, at theastrodata.org, and we analyze the uptake of that system to-date.

How Do Astronomers Share Data? Reliability and Persistence of Datasets Linked in AAS Publications and a Qualitative Study of Data Practices among US Astronomers

Science.gov (United States)

Pepe, Alberto; Goodman, Alyssa; Muench, August; Crosas, Merce; Erdmann, Christopher

2014-08-01

We analyze data sharing practices of astronomers over the past fifteen years. An analysis of URL links embedded in papers published by the American Astronomical Society reveals that the total number of links included in the literature rose dramatically from 1997 until 2005, when it leveled off at around 1500 per year. The analysis also shows that the availability of linked material decays with time: in 2011, 44% of links published a decade earlier, in 2001, were broken. A rough analysis of link types reveals that links to data hosted on astronomers' personal websites become unreachable much faster than links to datasets on curated institutional sites. To gauge astronomers' current data sharing practices and preferences further, we performed in-depth interviews with 12 scientists and online surveys with 173 scientists, all at a large astrophysical research institute in the United States: the Harvard-Smithsonian Center for Astrophysics, in Cambridge, MA. Both the in-depth interviews and the online survey indicate that, in principle, there is no philosophical objection to data-sharing among astronomers at this institution. Key reasons that more data are not presently shared more efficiently in astronomy include: the difficulty of sharing large data sets; over reliance on non-robust, non-reproducible mechanisms for sharing data (e.g. emailing it); unfamiliarity with options that make data-sharing easier (faster) and/or more robust; and, lastly, a sense that other researchers would not want the data to be shared. We conclude with a short discussion of a new effort to implement an easy-to-use, robust, system for data sharing in astronomy, at theastrodata.org, and we analyze the uptake of that system to-date.

How do astronomers share data? Reliability and persistence of datasets linked in AAS publications and a qualitative study of data practices among US astronomers.

Directory of Open Access Journals (Sweden)

Alberto Pepe

Full Text Available We analyze data sharing practices of astronomers over the past fifteen years. An analysis of URL links embedded in papers published by the American Astronomical Society reveals that the total number of links included in the literature rose dramatically from 1997 until 2005, when it leveled off at around 1500 per year. The analysis also shows that the availability of linked material decays with time: in 2011, 44% of links published a decade earlier, in 2001, were broken. A rough analysis of link types reveals that links to data hosted on astronomers' personal websites become unreachable much faster than links to datasets on curated institutional sites. To gauge astronomers' current data sharing practices and preferences further, we performed in-depth interviews with 12 scientists and online surveys with 173 scientists, all at a large astrophysical research institute in the United States: the Harvard-Smithsonian Center for Astrophysics, in Cambridge, MA. Both the in-depth interviews and the online survey indicate that, in principle, there is no philosophical objection to data-sharing among astronomers at this institution. Key reasons that more data are not presently shared more efficiently in astronomy include: the difficulty of sharing large data sets; over reliance on non-robust, non-reproducible mechanisms for sharing data (e.g. emailing it; unfamiliarity with options that make data-sharing easier (faster and/or more robust; and, lastly, a sense that other researchers would not want the data to be shared. We conclude with a short discussion of a new effort to implement an easy-to-use, robust, system for data sharing in astronomy, at theastrodata.org, and we analyze the uptake of that system to-date.

Leading curriculum change: Reflections on how Abakhwezeli stoked ...

African Journals Online (AJOL)

Delport, Aletta (Prof) (Summerstrand Campus South)

2016-11-24

Nov 24, 2016 ... School for Initial Teacher Education, Faculty of Education, Nelson Mandela Metropolitan University ... 'Abakhwezeli', in stoking the fires of curriculum change in the Nelson Mandela ...... NY: Continuum International Publishing.

Moment realizability and the validity of the Navier - Stokes equations for rarefied gas dynamics

International Nuclear Information System (INIS)

Levermore, C.D.; Morokoff, W.J.; Nadiga, B.T.

1998-01-01

We present criteria for monitoring the validity of the Navier - Stokes approximation during the simulation of a rarefied gas. Our approach is based on an underlying kinetic formulation through which one can construct nondimensional non-negative definite matrices from moments of the molecular distribution. We then identify one such 3x3 matrix that can be evaluated intrinsically in the Navier - Stokes approximation. Our criteria are based on deviations of the eigenvalues of this matrix from their equilibrium value of unity. Not being tied to a particular benchmark problem, the resulting criteria are portable and may be applied to any Navier - Stokes simulation. We study its utility here by comparing stationary planar shock profiles computed using the Navier - Stokes equations with those computed using Monte Carlo simulations. copyright 1998 American Institute of Physics

Localization of small obstacles in Stokes flow

International Nuclear Information System (INIS)

Caubet, Fabien; Dambrine, Marc

2012-01-01

We want to detect small obstacles immersed in a fluid flowing in a larger bounded domain Ω in the three-dimensional case. We assume that the fluid motion is governed by the steady-state Stokes equations. We make a measurement on a part of the exterior boundary ∂Ω and then take a Kohn–Vogelius approach to locate these obstacles. We use here the notion of the topological derivative in order to determine the number of objects and their rough locations. Thus we first establish an asymptotic expansion of the solution of the Stokes equations in Ω when we add small obstacles inside. Then, we use it to find a topological asymptotic expansion of the considered Kohn–Vogelius functional which gives us the formula of its topological gradient. Finally, we make some numerical simulations exploring the efficiency and the limits of this method. (paper)

Spectral atlas for amateur astronomers a guide to the spectra of astronomical objects and terrestrial light sources

CERN Document Server

Walker, Richard

2017-01-01

Featuring detailed commented spectral profiles of more than one hundred astronomical objects, in colour, this spectral guide documents most of the important and spectroscopically observable objects accessible using typical amateur equipment. It allows you to read and interpret the recorded spectra of the main stellar classes, as well as most of the steps from protostars through to the final stages of stellar evolution as planetary nebulae, white dwarfs or the different types of supernovae. It also presents integrated spectra of stellar clusters, galaxies and quasars, and the reference spectra of some terrestrial light sources, for calibration purposes. Whether used as the principal reference for comparing with your recorded spectra or for inspiring independent observing projects, this atlas provides a breathtaking view into our Universe's past. The atlas is accompanied and supplemented by Spectroscopy for Amateur Astronomers, which explains in detail the methods for recording, processing, analysing and interp...

Stokes image reconstruction for two-color microgrid polarization imaging systems.

Science.gov (United States)

Lemaster, Daniel A

2011-07-18

The Air Force Research Laboratory has developed a new microgrid polarization imaging system capable of simultaneously reconstructing linear Stokes parameter images in two colors on a single focal plane array. In this paper, an effective method for extracting Stokes images is presented for this type of camera system. It is also shown that correlations between the color bands can be exploited to significantly increase overall spatial resolution. Test data is used to show the advantages of this approach over bilinear interpolation. The bounds (in terms of available reconstruction bandwidth) on image resolution are also provided.

Analysis of regularized Navier-Stokes equations, 2

Science.gov (United States)

Ou, Yuh-Roung; Sritharan, S. S.

1989-01-01

A practically important regularization of the Navier-Stokes equations was analyzed. As a continuation of the previous work, the structure of the attractors characterizing the solutins was studied. Local as well as global invariant manifolds were found. Regularity properties of these manifolds are analyzed.

A new astronomical dating of Odysseus return to Ithaca.

Science.gov (United States)

Papamarinopoulos, St. P.; Preka-Papadema, P.; Antonopoulos, P.; Mitropetrou, H.; Tsironi, A.; Mitropetros, P.

The annular solar eclipse, of 30 October 1207 B.C. (Julian Day-JD 1280869), calculated by NASA together with the analysis of the weather's and the environment's description (long nights, plants, animals and peoples' habits) and the astronomical data (guiding constellations and Venus in the east horizon) mentioned by Homer in the epic, constitute an autumn return of Odysseus to Ithaca five days before the above characterized day. The latter offers a precise astronomical dating of the event and dates the legendary Trojan War's end as well.

AAS Publishing News: Astronomical Software Citation Workshop

Science.gov (United States)

Kohler, Susanna

2015-07-01

Do you write code for your research? Use astronomical software? Do you wish there were a better way of citing, sharing, archiving, or discovering software for astronomy research? You're not alone! In April 2015, AAS's publishing team joined other leaders in the astronomical software community in a meeting funded by the Sloan Foundation, with the purpose of discussing these issues and potential solutions. In attendance were representatives from academic astronomy, publishing, libraries, for-profit software sharing platforms, telescope facilities, and grantmaking institutions. The goal of the group was to establish “protocols, policies, and platforms for astronomical software citation, sharing, and archiving,” in the hopes of encouraging a set of normalized standards across the field. The AAS is now collaborating with leaders at GitHub to write grant proposals for a project to develop strategies for software discoverability and citation, in astronomy and beyond. If this topic interests you, you can find more details in this document released by the group after the meeting: http://astronomy-software-index.github.io/2015-workshop/ The group hopes to move this project forward with input and support from the broader community. Please share the above document, discuss it on social media using the hashtag #astroware (so that your conversations can be found!), or send private comments to julie.steffen@aas.org.

Longwave Imaging for Astronomical Applications, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — We propose to develop a compact portable longwave camera for astronomical applications. In Phase 1, we successfully developed the eye of the camera, i.e. the focal...

Astronomical calibration of the geological timescale: closing the middle Eocene gap

Science.gov (United States)

Westerhold, T.; Röhl, U.; Frederichs, T.; Bohaty, S. M.; Zachos, J. C.

2015-09-01

To explore cause and consequences of past climate change, very accurate age models such as those provided by the astronomical timescale (ATS) are needed. Beyond 40 million years the accuracy of the ATS critically depends on the correctness of orbital models and radioisotopic dating techniques. Discrepancies in the age dating of sedimentary successions and the lack of suitable records spanning the middle Eocene have prevented development of a continuous astronomically calibrated geological timescale for the entire Cenozoic Era. We now solve this problem by constructing an independent astrochronological stratigraphy based on Earth's stable 405 kyr eccentricity cycle between 41 and 48 million years ago (Ma) with new data from deep-sea sedimentary sequences in the South Atlantic Ocean. This new link completes the Paleogene astronomical timescale and confirms the intercalibration of radioisotopic and astronomical dating methods back through the Paleocene-Eocene Thermal Maximum (PETM, 55.930 Ma) and the Cretaceous-Paleogene boundary (66.022 Ma). Coupling of the Paleogene 405 kyr cyclostratigraphic frameworks across the middle Eocene further paves the way for extending the ATS into the Mesozoic.

The Impact of the Qur'anic Conception of Astronomical Phenomena on Islamic Civilization

Science.gov (United States)

Ahmad, I. A.

Discussions of astronomical phenomena in religious texts usually center around either their literal astronomical content or their symbolic significance. We shall instead consider the use of frequent references to astronomical phenomena in the Qur'an as exhortations to a worldview that ushered in the modern era. The Qur'anic conception of astronomical phenomena had a critical impact on Islamic civilization and the civilizations that followed because it introduced and mandated the adoption of certain attitudes. Among these were a greater respect for empirical data than was common in the preceding Greek civilization and an insistence that the Universe is ruled by a single set of laws. Both of these were rooted in the Islamic concept of tawhîd, the unity of God.

International Astronomical Union Sympoisum No.50

CERN Document Server

Westerlund, B

1973-01-01

Dr J. Landi Dessy, Director of the Astronomical Observatory, Cordoba, Argentina, invited the International Astronomical Union to hold a Symposium in Cordoba in connection with the celebration of the Centennial of the Cordoba Observatory; the date of foundation is October 24, 1871. He proposed that the Symposium should deal with Spectral Classification and Multicolour Photometry as seven years had elapsed since the Symposium No. 24 in Saltsj6baden, and much development had occurred in the field. The invitation and the proposal were accepted by the IAU, and the Symposium was held in Villa Carlos Paz, near Cordoba, between October 18 and October 24, 1971. It was attended by about 50 scientists representing Argentina, Canada, Chile, Den­ mark, France, Germany, Italy, Mexico, Sweden, Switzerland, U.K., U.S.A., Vatican City State and Venezuela. The Symposium was divided into four sessions: 1. Classification of slit spectra, 2. Classification of objective-prism spectra, 3. Photometric classification, 4. Catalogues ...

Large Astronomical Surveys, Catalogs and Databases

Directory of Open Access Journals (Sweden)

Mickaelian A. M.

2012-09-01

Full Text Available We review the status of all-sky and large astronomical surveys and their catalogued data over the whole range of electromagnetic spectrum, from gamma-ray to radio, such as ROSAT in X-ray, GALEX in UV, SDSS and several POSS1/2 based catalogs (APM, MAPS, USNO, GSC in optical, 2MASS and WISE in NIR, IRAS and AKARI in MIR/FIR, NVSS and FIRST in radio range and others. Present astronomical archives contain billions of objects, Galactic as well as extragalactic, and the vast amount of data in them permit new studies and discoveries. Cross-correlations result in revealing new objects and new samples. Very often, dozens of thousands of sources hide a few very interesting ones that are needed to be discovered by comparison of various physical characteristics. Most of the modern databases currently provide VO access to the stored information. This permits not only open access but also fast analysis and managing of these data.

Recruitment and Retention of LGBTIQ Astronomers

Science.gov (United States)

Dixon, William Van Dyke

2012-01-01

While lesbian, gay, bisexual, transgender, intersex, or questioning (LGBTIQ) astronomers face many of the same workplace challenges as women and racial/ethnic minorities, from implicit bias to overt discrimination, other challenges are unique to this group. An obvious example is the absence at many institutions of health insurance and other benefits for the same-sex domestic partners of their employees. More subtle is the psychological toll paid by LGBTIQ astronomers who remain "in the closet," self-censoring every statement about their personal lives. Paradoxically, the culture of the physical sciences, in which sexuality, gender identity, and gender expression are considered irrelevant, can discourage their discussion, further isolating LGBTIQ researchers. Addressing these challenges is not just a matter of fairness; it is an essential tool in the recruitment and retention of the brightest researchers and in assuring their productivity. We will discuss these issues and what individuals and departments can to make their institutions more welcoming to their LGBTIQ colleagues.

Instrument Remote Control via the Astronomical Instrument Markup Language

Science.gov (United States)

Sall, Ken; Ames, Troy; Warsaw, Craig; Koons, Lisa; Shafer, Richard

1998-01-01

The Instrument Remote Control (IRC) project ongoing at NASA's Goddard Space Flight Center's (GSFC) Information Systems Center (ISC) supports NASA's mission by defining an adaptive intranet-based framework that provides robust interactive and distributed control and monitoring of remote instruments. An astronomical IRC architecture that combines the platform-independent processing capabilities of Java with the power of Extensible Markup Language (XML) to express hierarchical data in an equally platform-independent, as well as human readable manner, has been developed. This architecture is implemented using a variety of XML support tools and Application Programming Interfaces (API) written in Java. IRC will enable trusted astronomers from around the world to easily access infrared instruments (e.g., telescopes, cameras, and spectrometers) located in remote, inhospitable environments, such as the South Pole, a high Chilean mountaintop, or an airborne observatory aboard a Boeing 747. Using IRC's frameworks, an astronomer or other scientist can easily define the type of onboard instrument, control the instrument remotely, and return monitoring data all through the intranet. The Astronomical Instrument Markup Language (AIML) is the first implementation of the more general Instrument Markup Language (IML). The key aspects of our approach to instrument description and control applies to many domains, from medical instruments to machine assembly lines. The concepts behind AIML apply equally well to the description and control of instruments in general. IRC enables us to apply our techniques to several instruments, preferably from different observatories.

High energy astrophysics in radio-astronomical form

International Nuclear Information System (INIS)

Laan, H. van der

1980-01-01

The application of high energy astrophysics in observational astronomy, and in particular in radioastronomy, is considered. The current situation of extragalactic HEA, as brought to light by radio-astronomical techniques, is sketched. (C.F.)

Navier-Stokes-Fourier Equations A Rational Asymptotic Modelling Point of View

CERN Document Server

Zeytounian, Radyadour Kh

2012-01-01

This research monograph deals with a modeling theory of the system of Navier-Stokes-Fourier equations for a Newtonian fluid governing a compressible viscous and heat conducting flows. The main objective is threefold. First , to 'deconstruct' this Navier-Stokes-Fourier system in order to unify the puzzle of the various partial simplified approximate models used in Newtonian Classical Fluid Dynamics and this, first facet, have obviously a challenging approach and a very important pedagogic impact on the university education. The second facet of the main objective is to outline a rational consistent asymptotic/mathematical theory of the of  fluid flows modeling on the basis of a typical Navier-Stokes-Fourier  initial and boundary value problem. The third facet is devoted to an illustration of our rational asymptotic/mathematical modeling theory for various technological and geophysical stiff  problems from: aerodynamics, thermal and thermocapillary convections and also meteofluid dynamics.

A stable penalty method for the compressible Navier-Stokes equations: I. Open boundary conditions

DEFF Research Database (Denmark)

Hesthaven, Jan; Gottlieb, D.

1996-01-01

The purpose of this paper is to present asymptotically stable open boundary conditions for the numerical approximation of the compressible Navier-Stokes equations in three spatial dimensions. The treatment uses the conservation form of the Navier-Stokes equations and utilizes linearization...

Astroinformatics, data mining and the future of astronomical research

Energy Technology Data Exchange (ETDEWEB)

Brescia, Massimo, E-mail: longo@na.infn.it [INAF, Astronomical Obs. of Capodimonte, Via Moiariello 16, I-80131 Napoli (Italy); Longo, Giuseppe [Department of Physics, University Federico II, Via Cintia 6, 80126 Napoli (Italy); Department of Astronomy, Caltech, Pasadena (United States)

2013-08-21

Astronomy, as many other scientific disciplines, is facing a true data deluge which is bound to change both the praxis and the methodology of every day research work. The emerging field of astroinformatics, while on the one end appears crucial to face the technological challenges, on the other is opening new exciting perspectives for new astronomical discoveries through the implementation of advanced data mining procedures. The complexity of astronomical data and the variety of scientific problems, however, call for innovative algorithms and methods as well as for an extreme usage of ICT technologies.

Astroinformatics, data mining and the future of astronomical research

International Nuclear Information System (INIS)

Brescia, Massimo; Longo, Giuseppe

2013-01-01

Astronomy, as many other scientific disciplines, is facing a true data deluge which is bound to change both the praxis and the methodology of every day research work. The emerging field of astroinformatics, while on the one end appears crucial to face the technological challenges, on the other is opening new exciting perspectives for new astronomical discoveries through the implementation of advanced data mining procedures. The complexity of astronomical data and the variety of scientific problems, however, call for innovative algorithms and methods as well as for an extreme usage of ICT technologies

Study of Tip-loss Using an Inverse 3D Navier-Stokes Method

DEFF Research Database (Denmark)

Mikkelsen, Robert; Sørensen, Jens Nørkær; Shen, Wen Zhong

2003-01-01

the 3D Navier-Stokes equations combined with the actuator line technique where blade loading is applied using an inverse method. The numerical simulations shows that the method captures the tip-correction when comparing with the theories of Prandtl and Goldstein, however, the accuracy of the obtained...... results reveal that further refinements still is needed. Keywords: Tip-loss; Actuator line; 3D Navier-Stokes methods....

New discoveries on astronomical orientation of Inca site in Ollantaytambo, Peru

Directory of Open Access Journals (Sweden)

Karolína Hanzalová

2015-12-01

Full Text Available This paper deals with astronomical orientation of Incas objects in Ollantaytambo, which is located about 35 km southeast from Machu Picchu, about 40 km northwest from Cusco, and lies in the Urubamba valley. Everybody writing about Ollantaytambo, shoud read Protzen. (1  He devoted his monograph to description and interpretation of that locality. Book of Salazar and Salazar (2 deals, among others, with the orientation of objects in Ollantaytambo with respect to the cardinal direction. Zawaski and Malville (3 documented astronomical context of major monuments of nine sites in Peru, including Ollantaytambo. We tested astronomical orientation in these places and confirm or disprove hypothesis about purpose of Incas objects. For assessment orientation of objects we used our measurements and also satellite images on Google Earth and digital elevation model from ASTER. The satellite images were used to estimate the astronomical-solar-solstice orientation, together with terrestrial images from Salazar and Salazar (2. The digital elevation model is useful in the mountains, where we need the actual horizon for a calculation of sunset and sunrise on specific days (solstices, which were for Incas people very important. We tested which astronomical phenomenon is connected with objects in Ollantaytambo. First, we focused on Temple of the Sun, also known the Wall of six monoliths.  We tested winter solstice sunrise and the rides of the Pleiades for the epochs 2000, 1500 and 1000 A.D. According with our results the Temple isn´t connected neither with winter solstice sunrise nor with the Pleiades. Then we tested also winter solstice sunset. We tried to use the line from an observation point near ruins of the Temple of Sun, to west-north, in direction to sunset. The astronomical azimuth from this point was about 5° less then we need. From this results we found, that is possible to find another observation point. By Salazar and Salazar (2 we found observation

"Word of Discovery": A Planetary Example from Volume I of the Astronomical Journal

Science.gov (United States)

Hockey, T.

1998-09-01

In 1850, William Lassell (1799-1880) discovered a series of bright white spots, in the south temperate latitudes of Jupiter, unlike any that that been seen before. Lassell's note on these STZ features is a useful example of how astronomical discoveries of the day were communicated among astronomers. Word of Lassell's Spots spread quickly by nineteenth-century standards. This was due, in part, to the recent appearance of journals devoted exclusively to astronomy. The transition from letters as a means of conveying scientific information to journals is reflected in the propagation of Lassell's announcement: a report of Lassell's description of the white spots to the Royal Astronomical Society appeared in the Monthly Notices of the Royal Astronomical Society along with a woodblock print of one of his drawings. This report reappeared shortly thereafter in German translation. It was part of a letter to the editor of the Astronomische Nachrichten, Heinrich Schumacher (1780-1850), from an English correspondent of his, the Reverend Richard Sheepshanks (1974-1855). (Sheepshanks was himself editor of the Monthly Notices of the Royal Astronomical Society.) It then made its way across the Atlantic as a letter from Schumacher to Benjamin Gould (1824-1896), who published it in the first volume of his upstart Astronomical Journal. There it appears in English, again, as Schumacher quoting Sheepshanks quoting Lassell! The observations by Lassell and William Dawes (1799-1868) of this phenomenon also were the first major planetary discovery made using a silvered-glass reflecting telescope. Lassell's Spots have remained in the "astronomical news" of the last 150 years: Most recently, they appeared worldwide in images showing the Comet Shoemaker-Levy 9 impact sites.

On the fluid-dynamical approximation to the Boltzmann equation at the level of the Navier-Stokes equation

International Nuclear Information System (INIS)

Kawashima, S.; Matsumara, A.; Nishida, T.

1979-01-01

The compressible and heat-conductive Navier-Stokes equation obtained as the second approximation of the formal Chapman-Enskog expansion is investigated on its relations to the original nonlinear Boltzmann equation and also to the incompressible Navier-Stokes equation. The solutions of the Boltzmann equation and the incompressible Navier-Stokes equation for small initial data are proved to be asymptotically equivalent (mod decay rate tsup(-5/4)) as t → + infinitely to that of the compressible Navier-Stokes equation for the corresponding initial data. (orig.) 891 HJ/orig. 892 MKO

Stokes and anti-Stokes photoluminescence towards five different In-x(Al0.17Ga0.83)(1-x)As/Al0.17Ga0.83As quantum wells

DEFF Research Database (Denmark)

Machida, S.; Tadakuma, T.; Satake, A.

2005-01-01

Stokes and anti-Stokes photoluminescence (AS-PL) has been investigated in a step-graded Inx(Al0.17Ga0.83)1–xAs/Al0.17Ga0.83As quantum-well (QW) heterostructure consisting of five QWs with different x values. Stokes PL spectra of this sample show a significant difference in PL intensity between...... the wells under indirect excitation conditions due to the existence of competitive resonant and nonresonant capture processes, while they exhibit a rather uniform PL intensity distribution under direct excitation. When the excitation wavelength is tuned to 810 nm for AS-PL detection, it is transparent...... is basically determined by the competitive capture of photoexcited carriers through the thick barriers, generated far from the five wells due to the nonlinear excitation processes in GaAs. ©2005 American Institute of Physics...

Augmented Lagrangian methods to solve Navier-Stokes equations for a Bingham fluid flow

International Nuclear Information System (INIS)

Boscardin, Laetitia

1999-01-01

The objective of this research thesis is to develop one or more methods for the numerical resolution of equations of movement obtained for a Bingham fluid. The resolution of Navier-Stokes equations is processed by splitting elliptic and hyperbolic operators (Galerkin transport). In this purpose, the author first studied the Stokes problem, and then addressed issues of stability and consistency of the global scheme. The variational formulation of the Stokes problem can be expressed under the form of a minimisation problem under the constraint of non linear and non differentiable functions. Then, the author proposes a discretization of the Stokes problem based on a hybrid finite element method. Then he extends the demonstrations of stability and consistency of the Galerkin-transport scheme which have been established for a Newtonian fluid, to the case of a Bingham fluid. A relaxation algorithm and a Newton-GMRES algorithm are developed to solve the problem, and their convergence is studied. To ensure this convergence, some constraints must be verified. In order to do so, a specific speed element has been developed [fr

Astronomical theory of climate change

Energy Technology Data Exchange (ETDEWEB)

Berger, A.; Loutre, M.F. [Universite Catholique de Louvain (UCL), Louvain-la-Neuve (Belgium). Inst. d' Astronomie et de Geophysique G. Lemaitre

2004-12-01

The astronomical theory of paleo-climates aims to explain the climatic variations occurring with quasi-periodicities lying between tens and hundreds of thousands of years. The origin of these quasi-cycles lies in the astronomically driven changes in the latitudinal and seasonal distributions of the energy that the Earth receives from the Sun. These changes are then amplified by the feedback mechanisms which characterize the natural behaviour of the climate system like those involving the albedo-, the water vapor-, and the vegetation- temperature relationships. Climate models of different complexities are used to explain the chain of processes which finally link the long-term variations of three astronomical parameters to the long-term climatic variations at time scale of tens to hundreds of thousands of years. In particular, sensitivity analysis to the astronomically driven insolation changes and to the CO{sub 2} atmospheric concentrations have been performed with the 2-dimension climate model of Louvain-la-Neuve. It could be shown that this model simulates more or less correctly the entrance into glaciation around 2.75 million year (Myr) BP (before present), the late Pliocene-early Pleistocene 41-kyr (thousand years) cycle, the emergence of the 100-kyr cycle around 850 kyr BP and the glacial-interglacial cycles of the last 600 kyr. During the Late Pliocene (in an ice-free - warm world) ice sheets can only develop during times of sufficiently low summer insolation. This occurs during large eccentricity times when climatic precession and obliquity combine to obtain such low values, leading to the 41-kyr period between 3 and 1 million years BP. On the contrary in a glacial world, ice sheets persist most of the time except when insolation is very high in polar latitudes, requiring large eccentricity again, but leading this time to interglacial and finally to the 100-kyr period of the last 1 Myr. Using CO{sub 2} scenarios, it has been shown that stage 11 and stage 1

The Growth of Interest in Astronomical X-Ray Polarimetry

Directory of Open Access Journals (Sweden)

Frédéric Marin

2018-03-01

Full Text Available Astronomical X-ray polarimetry was first explored in the end of the 1960s by pioneering rocket instruments. The craze arising from the first discoveries of stellar and supernova remnant X-ray polarization led to the addition of X-ray polarimeters to early satellites. Unfortunately, the inadequacy of the diffraction and scattering technologies required to measure polarization with respect to the constraints driven by X-ray mirrors and detectors, coupled with long integration times, slowed down the field for almost 40 years. Thanks to the development of new, highly sensitive, compact X-ray polarimeters in the beginning of the 2000s, observing astronomical X-ray polarization has become feasible, and scientists are now ready to explore our high-energy sky thanks to modern X-ray polarimeters. In the forthcoming years, several X-ray missions (rockets, balloons, and satellites will create new observational opportunities. Interest in astronomical X-ray polarimetry field has thus been renewed, and this paper presents for the first time a quantitative assessment, all based on scientific literature, of the growth of this interest.

Uzawa smoother in multigrid for the coupleD porous medium and stokes flow system

NARCIS (Netherlands)

P. Luo (Peiyao); C. Rodrigo (Carmen); F.J. Gaspar Lorenz (Franscisco); C.W. Oosterlee (Kees)

2017-01-01

textabstractThe multigrid solution of coupled porous media and Stokes flow problems is considered. The Darcy equation as the saturated porous medium model is coupled to the Stokes equations by means of appropriate interface conditions. We focus on an efficient multigrid solution technique for the

Hydrodynamic potentials for the micropolar Navier-Stokes problem

International Nuclear Information System (INIS)

Martynenko, M.D.; Dimian, M.

1995-01-01

An integral representation of linear and angular velocities and pressure for the description of linear stationary flows of micropolar viscous liquid media is obtained, and on its basis hydrodynamic potentials for the micropolar Navier-Stokes problem are introduced

Second-degree Stokes coefficients from multi-satellite SLR

Czech Academy of Sciences Publication Activity Database

Blossfeld, M.; Mueller, H.; Gerstl, M.; Štefka, Vojtěch; Bouman, J.; Goettl, F.; Horwath, M.

2015-01-01

Roč. 89, č. 9 (2015), s. 857-871 ISSN 0949-7714 Institutional support: RVO:67985815 Keywords : multi-satellite SLR * stokes coefficients * equatorial excitation functions Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.486, year: 2015

Origin of the Size-Dependent Stokes Shift in CsPbBr3 Perovskite Nanocrystals.

Science.gov (United States)

Brennan, Michael C; Herr, John E; Nguyen-Beck, Triet S; Zinna, Jessica; Draguta, Sergiu; Rouvimov, Sergei; Parkhill, John; Kuno, Masaru

2017-09-06

The origin of the size-dependent Stokes shift in CsPbBr 3 nanocrystals (NCs) is explained for the first time. Stokes shifts range from 82 to 20 meV for NCs with effective edge lengths varying from ∼4 to 13 nm. We show that the Stokes shift is intrinsic to the NC electronic structure and does not arise from extrinsic effects such as residual ensemble size distributions, impurities, or solvent-related effects. The origin of the Stokes shift is elucidated via first-principles calculations. Corresponding theoretical modeling of the CsPbBr 3 NC density of states and band structure reveals the existence of an intrinsic confined hole state 260 to 70 meV above the valence band edge state for NCs with edge lengths from ∼2 to 5 nm. A size-dependent Stokes shift is therefore predicted and is in quantitative agreement with the experimental data. Comparison between bulk and NC calculations shows that the confined hole state is exclusive to NCs. At a broader level, the distinction between absorbing and emitting states in CsPbBr 3 is likely a general feature of other halide perovskite NCs and can be tuned via NC size to enhance applications involving these materials.

The re-definition of the astronomical unit of length:reasons and consequences

Science.gov (United States)

Capitaine, Nicole; Klioner, Sergei; McCarthy, Dennis

2012-08-01

The astronomical unit (au) is a unit of length approximating the Sun - Earth distance that is used mainly to express the scale of the solar system. Its current definition is based on the value of the Gaussian gravitational constant, k. This conveniently provided accurate relative distances (expressed in astronomical units) when absolute distances could not be estimated with high accuracy. The huge improvement achieved in solar system ephemerides during the last decade provides an opportunity to re - consider the definition and status of the au. This issue was discussed recently by Klioner (2008), Capitaine & Guinot (2009) and Capitaine et al. (2011), as well as within the IAU Working Group on "Numerical Standards for Fundamental astronomy". This resulted in a proposed IAU Resolution recommending that the astronomical unit be re - defined as a fixed number of Système International d ’ Unités (SI) metres through a defining constant. For continuity that constant should be the value of the current best estimate in metres as adopted by IAU 2009 Resolution B2 (i.e. 149 597 870 700 m). After reviewing the properties of the IAU 1976 astronomical unit and its status in the IAU 2009 System of Astronomical Constants, we explain the main reasons for a change; we present and discuss the proposed new definition as well as the advantages over the historical definition. One important consequence is that the heliocentric gravitational constant, GM(Sun), would cease to have a fixed value in astronomical units and will have to be determined experimentally. This would be compliant with modern dynamics of the solar system as it would allow

Automatic astronomical coordinate determination using digital zenith cameras

Directory of Open Access Journals (Sweden)

S Farzaneh

2009-12-01

Full Text Available Celestial positioning has been used for navigation purposes for many years. Stars as the extra-terrestrial benchmarks provide unique opportunity in absolute point positioning. However, astronomical field data acquisition and data processing of the collected data is very time-consuming. The advent of the Global Positioning System (GPS nearly made the celestial positioning system obsolete. The new satellite-based positioning system has been very popular since it is very efficient and convenient for many daily life applications. Nevertheless, the celestial positioning method is never replaced by satellite-based positioning in absolute point positioning sense. The invention of electro-optical devices at the beginning of the 21st century was really a rebirth in geodetic astronomy. Today, the digital cameras with relatively high geometric and radiometric accuracy has opened a new insight in satellite attitude determination and the study of the Earth's surface geometry and physics of its interior, i.e., computation of astronomical coordinates and the vertical deflection components. This method or the so-called astrogeodetic vision-based method help us to determine astronomical coordinates with an accuracy better than 0.1 arc second. The theoretical background, an innovative transformation approach and the preliminary numerical results are addressed in this paper.

The Amateur Astronomer's Introduction to the Celestial Sphere

Science.gov (United States)

Millar, William

2005-12-01

This introduction to the night sky is for amateur astronomers who desire a deeper understanding of the principles and observations of naked-eye astronomy. It covers topics such as terrestrial and astronomical coordinate systems, stars and constellations, the relative motions of the sky, sun, moon and earth leading to an understanding of the seasons, phases of the moon, and eclipses. Topics are discussed and compared for observers located in both the northern and southern hemispheres. Written in a conversational style, only addition and subtraction are needed to understand the basic principles and a more advanced mathematical treatment is available in the appendices. Each chapter contains a set of review questions and simple exercises to reinforce the reader's understanding of the material. The last chapter is a set of self-contained observation projects to get readers started with making observations about the concepts they have learned. William Charles Millar, currently Professor of Astronomy at Grand Rapids Community College in Michigan, has been teaching the subject for almost twenty years and is very involved with local amateur astronomy groups. Millar also belongs to The Planetary Society and the Astronomical Society of the Pacific and has traveled to Europe and South America to observe solar eclipses. Millar holds a Masters degree in Physics from Western Michigan University.

Climate and carbon-cycle response to astronomical forcing over the last 35 Ma.

Science.gov (United States)

De Vleeschouwer, D.; Palike, H.; Vahlenkamp, M.; Crucifix, M.

2017-12-01

On a million-year time scale, the characteristics of insolation forcing caused by cyclical variations in the astronomical parameters of the Earth remain stable. Nevertheless, Earth's climate responded very differently to this forcing during different parts of the Cenozoic. The recently-published ∂18Obenthic megasplice (De Vleeschouwer et al., 2017) allowed for a clear visualization of these changes in global climate response to astronomical forcing. However, many open questions remain regarding how carbon-cycle dynamics influence Earth's climate sensitivity to astronomical climate forcing. To provide insight into the interaction between the carbon cycle and astronomical insolation forcing, we built a benthic carbon isotope (∂13Cbenthic) megasplice for the last 35 Ma, employing the same technique used to build the ∂18Obenthic megasplice. The ∂13Cbenthic megasplice exhibits a strong imprint of the 405 and 100-kyr eccentricity cycles throughout the last 35 Ma. This is intriguing, as the oxygen isotope megasplice looses its eccentricity imprint after the mid-Miocene climatic transition (MMCT; see Fig. 1 in De Vleeschouwer et al., 2017). In other words, the carbon cycle responded completely differently to astronomical forcing, compared to global climate during the late Miocene. We visualize this difference in response by the application of a Gaussian process, which renders the dependence of one variable (here ∂18Obenthic or ∂13Cbenthic) in a multidimensional space (here precession, obliquity and eccentricity). Together, the ∂13Cbenthic and ∂18Obenthic megasplices thus provide a unique tool for paleoclimatology, allowing for the quantification and visualization of the changing paleoclimate and carbon-cycle response to astronomical forcing throughout geologic time. References De Vleeschouwer, D., Vahlenkamp, M., Crucifix, M., Pälike, H., 2017. Alternating Southern and Northern Hemisphere climate response to astronomical forcing during the past 35 m

Astronomical sketching a step-by-step introduction

CERN Document Server

Handy, Richard; Perez, Jeremy; Rix, Erika; Robbins, Sol

2007-01-01

This book presents the amateur with fine examples of astronomical sketches and step-by-step tutorials in each medium, from pencil to computer graphics programs. This unique book can teach almost anyone to create beautiful sketches of celestial objects.

Powerful Radio Burst Indicates New Astronomical Phenomenon

Science.gov (United States)

2007-09-01

Astronomers studying archival data from an Australian radio telescope have discovered a powerful, short-lived burst of radio waves that they say indicates an entirely new type of astronomical phenomenon. Region of Strong Radio Burst Visible-light (negative greyscale) and radio (contours) image of Small Magellanic Cloud and area where burst originated. CREDIT: Lorimer et al., NRAO/AUI/NSF Click on image for high-resolution file ( 114 KB) "This burst appears to have originated from the distant Universe and may have been produced by an exotic event such as the collision of two neutron stars or the death throes of an evaporating black hole," said Duncan Lorimer, Assistant Professor of Physics at West Virginia University (WVU) and the National Radio Astronomy Observatory (NRAO). The research team led by Lorimer consists of Matthew Bailes of Swinburne University in Australia, Maura McLaughlin of WVU and NRAO, David Narkevic of WVU, and Fronefield Crawford of Franklin and Marshall College in Lancaster, Pennsylvania. The astronomers announced their findings in the September 27 issue of the online journal Science Express. The startling discovery came as WVU undergraduate student David Narkevic re-analyzed data from observations of the Small Magellanic Cloud made by the 210-foot Parkes radio telescope in Australia. The data came from a survey of the Magellanic Clouds that included 480 hours of observations. "This survey had sought to discover new pulsars, and the data already had been searched for the type of pulsating signals they produce," Lorimer said. "We re-examined the data, looking for bursts that, unlike the usual ones from pulsars, are not periodic," he added. The survey had covered the Magellanic Clouds, a pair of small galaxies in orbit around our own Milky Way Galaxy. Some 200,000 light-years from Earth, the Magellanic Clouds are prominent features in the Southern sky. Ironically, the new discovery is not part of these galaxies, but rather is much more distant

Investigation of vortex breakdown on a delta wing using Euler and Navier-Stokes equations

Science.gov (United States)

Agrawal, S.; Barnett, R. M.; Robinson, B. A.

1991-01-01

A numerical investigation of leading edge vortex breakdown in a delta wing at high angles of attack is presented. The analysis was restricted to low speed flows on a flat plate wing with sharp leading edges. Both Euler and Navier-Stokes equations were used and the results were compared with experimental data. Predictions of vortex breakdown progression with angle of attack with both Euler and Navier-Stokes equations are shown to be consistent with the experimental data. However, the Navier-Stokes predictions show significant improvements in breakdown location at angles of attack where the vortex breakdown approaches the wing apex. The predicted trajectories of the primary vortex are in very good agreement with the test data, the laminar solutions providing the overall best comparison. The Euler shows a small displacement of the primary vortex, relative to experiment, due to the lack of secondary vortices. The turbulent Navier-Stokes, in general, fall between the Euler and laminar solutions.

Using multivariate analyses and GIS to identify pollutants and their spatial patterns in urban soils in Galway, Ireland

International Nuclear Information System (INIS)

Zhang Chaosheng

2006-01-01

Galway is a small but rapidly growing tourism city in western Ireland. To evaluate its environmental quality, a total of 166 surface soil samples (0-10 cm depth) were collected from parks and grasslands at the density of 1 sample per 0.25 km 2 at the end of 2004. All samples were analysed using ICP-AES for the near-total concentrations of 26 chemical elements. Multivariate statistics and GIS techniques were applied to classify the elements and to identify elements influenced by human activities. Cluster analysis (Canada) and principal component analysis (PCA) classified the elements into two groups: the first group predominantly derived from natural sources, the second being influenced by human activities. GIS mapping is a powerful tool in identifying the possible sources of pollutants. Relatively high concentrations of Cu, Pb and Zn were found in the city centre, old residential areas, and along major traffic routes, showing significant effects of traffic pollution. The element As is enriched in soils of the old built-up areas, which can be attributed to coal and peat combustion for home heating. Such significant spatial patterns of pollutants displayed by urban soils may imply potential health threat to residents of the contaminated areas of the city. - Multivariate statistics and GIS are useful tools to identify pollutants in urban soils

The Hunt for Pristine Cretaceous Astronomical Rhythms at Demerara Rise (Cenomanian-Coniacian)

Science.gov (United States)

Ma, C.; Meyers, S. R.

2014-12-01

Rhythmic Upper Cretaceous strata from Demerara Rise (ODP leg 207) preserve a strong astronomical signature, and this attribute has facilitated the development of continuous astrochronologies to refine the geologic time scale and calibrate Late Cretaceous biogeochemical events. While the mere identification of astronomical rhythms is a crucial first step in many deep-time paleoceanographic investigations, accurate evaluation of often subtle amplitude and frequency modulations are required to: (1) robustly constrain the linkage between climate and sedimentation, and (2) evaluate the plausibility of different theoretical astrodynamical models. The availability of a wide range of geophysical, lithologic and geochemical data from multiple sites drilled at Demerara Rise - when coupled with recent innovations in the statistical analysis of cyclostratigraphic data - provides an opportunity to hunt for the most pristine record of Cretaceous astronomical rhythms at a tropical Atlantic location. To do so, a statistical metric is developed to evaluate the "internal" consistency of hypothesized astronomical rhythms observed in each data set, particularly with regard to the expected astronomical amplitude modulations. In this presentation, we focus on how the new analysis yields refinements to the existing astrochronologies, provides constraints on the linkages between climate and sedimentation (including the deposition of organic carbon-rich sediments at Demerara Rise), and allows a quantitative evaluation of the continuity of deposition across sites at multiple temporal scales.

Discretizations in isogeometric analysis of Navier-Stokes flow

DEFF Research Database (Denmark)

Nielsen, Peter Nørtoft; Gersborg, Allan Roulund; Gravesen, Jens

2011-01-01

This paper deals with isogeometric analysis of 2-dimensional, steady state, incompressible Navier-Stokes flow subjected to Dirichlet boundary conditions. We present a detailed description of the numerical method used to solve the boundary value problem. Numerical inf-sup stability tests...

Sigma-convergence of stationary Navier-Stokes type equations

Directory of Open Access Journals (Sweden)

Gabriel Nguetseng

2009-06-01

Full Text Available In the framework of homogenization theory, the Sigma-convergence method is carried out on stationary Navier-Stokes type equations on a fixed domain. Our main tools are the two-scale convergence concept and the so-called homogenization algebras.

Topology optimization considering design-dependent Stokes flow loads

NARCIS (Netherlands)

Picelli, R.; Vicente, W.M.; Pavanello, R.; van Keulen, A.; Li, Qing; Steven, Grant P.; Zhang, Zhongpu

2015-01-01

This article presents an evolutionary topology optimization method for mean compliance minimization of structures under design-dependent viscous fluid flow loads. The structural domain is governed by the elasticity equation and the fluid by the incompressible Stokes flow equations. When the

Development Of A Navier-Stokes Computer Code

Science.gov (United States)

Yoon, Seokkwan; Kwak, Dochan

1993-01-01

Report discusses aspects of development of CENS3D computer code, solving three-dimensional Navier-Stokes equations of compressible, viscous, unsteady flow. Implements implicit finite-difference or finite-volume numerical-integration scheme, called "lower-upper symmetric-Gauss-Seidel" (LU-SGS), offering potential for very low computer time per iteration and for fast convergence.

The Classical Version of Stokes' Theorem Revisited

Science.gov (United States)

Markvorsen, Steen

2008-01-01

Using only fairly simple and elementary considerations--essentially from first year undergraduate mathematics--we show how the classical Stokes' theorem for any given surface and vector field in R[superscript 3] follows from an application of Gauss' divergence theorem to a suitable modification of the vector field in a tubular shell around the…

Astronomical fire: Richard Carrington and the solar flare of 1859.

Science.gov (United States)

Clark, Stuart

2007-09-01

An explosion on the Sun in 1859, serendipitously witnessed by amateur astronomer Richard Carrington, plunged telegraphic communications into chaos and bathed two thirds of the Earth's skies in aurorae. Explaining what happened to the Sun and how it could affect Earth, 93 million miles away, helped change the direction of astronomy. From being concerned principally with charting the stars to aid navigation, astronomers became increasingly concerned with what the celestial objects were, how they behaved and how they might affect life on Earth.

Discrete Exterior Calculus Discretization of Incompressible Navier-Stokes Equations

KAUST Repository

Mohamed, Mamdouh S.; Hirani, Anil N.; Samtaney, Ravi

2017-01-01

A conservative discretization of incompressible Navier-Stokes equations over surface simplicial meshes is developed using discrete exterior calculus (DEC). Numerical experiments for flows over surfaces reveal a second order accuracy

Time evolution of the eddy viscosity in two-dimensional navier-stokes flow

Science.gov (United States)

Chaves; Gama

2000-02-01

The time evolution of the eddy viscosity associated with an unforced two-dimensional incompressible Navier-Stokes flow is analyzed by direct numerical simulation. The initial condition is such that the eddy viscosity is isotropic and negative. It is shown by concrete examples that the Navier-Stokes dynamics stabilizes negative eddy viscosity effects. In other words, this dynamics moves monotonically the initial negative eddy viscosity to positive values before relaxation due to viscous term occurs.

Astronomical relativistic reference systems with multipolar expansion: the global one

International Nuclear Information System (INIS)

Xie Yi

2014-01-01

With the rapid development of techniques for astronomical observations, the precision of measurements has been significantly increasing. Theories describing astronomical relativistic reference systems, which are the foundation for processing and interpreting these data now and in the future, may require extensions to satisfy the needs of these trends. Besides building a framework compatible with alternative theories of gravity and the pursuit of higher order post-Newtonian approximation, it will also be necessary to make the first order post-Newtonian multipole moments of celestial bodies be explicitly expressed in the astronomical relativistic reference systems. This will bring some convenience into modeling the observations and experiments and make it easier to distinguish different contributions in measurements. As a first step, the global solar system reference system is expressed as a multipolar expansion and the post-Newtonian mass and spin moments are shown explicitly in the metric which describes the coordinates of the system. The full expression of the global metric is given. (research papers)

All-sky brightness monitoring of light pollution with astronomical methods.

Science.gov (United States)

Rabaza, O; Galadí-Enríquez, D; Estrella, A Espín; Dols, F Aznar

2010-06-01

This paper describes a mobile prototype and a protocol to measure light pollution based on astronomical methods. The prototype takes three all-sky images using BVR filters of the Johnson-Cousins astronomical photometric system. The stars are then identified in the images of the Hipparcos and General Catalogue of Photometric Data II astronomical catalogues, and are used as calibration sources. This method permits the measurement of night-sky brightness and facilitates an estimate of which fraction is due to the light up-scattered in the atmosphere by a wide variety of man-made sources. This is achieved by our software, which compares the sky background flux to that of many stars of known brightness. The reduced weight and dimensions of the prototype allow the user to make measurements from virtually any location. This prototype is capable of measuring the sky distribution of light pollution, and also provides an accurate estimate of the background flux at each photometric band. (c) 2010 Elsevier Ltd. All rights reserved.

Stokes phenomena and monodromy deformation problem for nonlinear Schrodinger equation

International Nuclear Information System (INIS)

Chowdury, A.R.; Naskar, M.

1986-01-01

Following Flaschka and Newell, the inverse problem for Painleve IV is formulated with the help of similarity variables. The Painleve IV arises as the eliminant of the two second-order ordinary differential equations originating from the nonlinear Schrodinger equation. Asymptotic expansions are obtained near the singularities at zero and infinity of the complex eigenvalue plane. The corresponding analysis then displays the Stokes phenomena. The monodromy matrices connecting the solution Y /sub j/ in the sector S /sub j/ to that in S /sub j+1/ are fixed in structure by the imposition of certain conditions. It is then shown that a deformation keeping the monodromy data fixed leads to the nonlinear Schrodinger equation. While Flaschka and Newell did not make any absolute determination of the Stokes parameters, the present approach yields the values of the Stokes parameters in an explicit way, which in turn can determine the matrix connecting the solutions near zero and infinity. Finally, it is shown that the integral equation originating from the analyticity and asymptotic nature of the problem leads to the similarity solution previously determined by Boiti and Pampinelli

Astronomical Signatures of Dark Matter

Directory of Open Access Journals (Sweden)

Paul Gorenstein

2014-01-01

Full Text Available Several independent astronomical observations in different wavelength bands reveal the existence of much larger quantities of matter than what we would deduce from assuming a solar mass to light ratio. They are very high velocities of individual galaxies within clusters of galaxies, higher than expected rotation rates of stars in the outer regions of galaxies, 21 cm line studies indicative of increasing mass to light ratios with radius in the halos of spiral galaxies, hot gaseous X-ray emitting halos around many elliptical galaxies, and clusters of galaxies requiring a much larger component of unseen mass for the hot gas to be bound. The level of gravitational attraction needed for the spatial distribution of galaxies to evolve from the small perturbations implied by the very slightly anisotropic cosmic microwave background radiation to its current web-like configuration requires much more mass than is observed across the entire electromagnetic spectrum. Distorted shapes of galaxies and other features created by gravitational lensing in the images of many astronomical objects require an amount of dark matter consistent with other estimates. The unambiguous detection of dark matter and more recently evidence for dark energy has positioned astronomy at the frontier of fundamental physics as it was in the 17th century.

The League of Astronomers: Outreach

Science.gov (United States)

Paat, Anthony; Brandel, A.; Schmitz, D.; Sharma, R.; Thomas, N. H.; Trujillo, J.; Laws, C. S.; Astronomers, League of

2014-01-01

The University of Washington League of Astronomers (LOA) is an organization comprised of University of Washington (UW) undergraduate students. Our main goal is to share our interest in astronomy with the UW community and with the general public. The LOA hosts star parties on the UW campus and collaborates with the Seattle Astronomical Society (SAS) on larger Seattle-area star parties. At the star parties, we strive to teach our local community about what they can view in our night sky. LOA members share knowledge of how to locate constellations and use a star wheel. The relationship the LOA has with members of SAS increases both the number of events and people we are able to reach. Since the cloudy skies of the Northwest prevent winter star parties, we therefore focus our outreach on the UW Mobile Planetarium, an inflatable dome system utilizing Microsoft’s WorldWide Telescope (WWT) software. The mobile planetarium brings astronomy into the classrooms of schools unable to travel to the UW on-campus planetarium. Members of the LOA volunteer their time towards this project and we make up the majority of the Mobile Planetarium volunteers. Our outreach efforts allow us to connect with the community and enhance our own knowledge of astronomy.

Astronomers in the Chemist's War

Science.gov (United States)

Trimble, Virginia L.

2012-01-01

World War II, with radar, rockets, and "atomic" bombs was the physicists' war. And many of us know, or think we know, what our more senior colleagues did during it, with Hubble and Hoffleit at Aberdeen; M. Schwarzschild on active duty in Italy; Bondi, Gold, and Hoyle hunkered down in Dunsfeld, Surrey, talking about radar, and perhaps steady state; Greenstein and Henyey designing all-sky cameras; and many astronomers teaching navigation. World War I was The Chemists' War, featuring poison gases, the need to produce liquid fuels from coal on one side of the English Channel and to replace previously-imported dyesstuffs on the other. The talke will focus on what astronomers did and had done to them between 1914 and 1919, from Freundlich (taken prisoner on an eclipse expedition days after the outbreak of hostilities) to Edwin Hubble, returning from France without ever having quite reached the front lines. Other events bore richer fruit (Hale and the National Research Council), but very few of the stories are happy ones. Most of us have neither first nor second hand memories of The Chemists' War, but I had the pleasure of dining with a former Freundlich student a couple of weeks ago.

A Liouville Problem for the Stationary Fractional Navier-Stokes-Poisson System

Science.gov (United States)

Wang, Y.; Xiao, J.

2017-06-01

This paper deals with a Liouville problem for the stationary fractional Navier-Stokes-Poisson system whose special case k=0 covers the compressible and incompressible time-independent fractional Navier-Stokes systems in R^{N≥2} . An essential difficulty raises from the fractional Laplacian, which is a non-local operator and thus makes the local analysis unsuitable. To overcome the difficulty, we utilize a recently-introduced extension-method in Wang and Xiao (Commun Contemp Math 18(6):1650019, 2016) which develops Caffarelli-Silvestre's technique in Caffarelli and Silvestre (Commun Partial Diff Equ 32:1245-1260, 2007).

Symmetry breaking and uniqueness for the incompressible Navier-Stokes equations

International Nuclear Information System (INIS)

Dascaliuc, Radu; Thomann, Enrique; Waymire, Edward C.; Michalowski, Nicholas

2015-01-01

The present article establishes connections between the structure of the deterministic Navier-Stokes equations and the structure of (similarity) equations that govern self-similar solutions as expected values of certain naturally associated stochastic cascades. A principle result is that explosion criteria for the stochastic cascades involved in the probabilistic representations of solutions to the respective equations coincide. While the uniqueness problem itself remains unresolved, these connections provide interesting problems and possible methods for investigating symmetry breaking and the uniqueness problem for Navier-Stokes equations. In particular, new branching Markov chains, including a dilogarithmic branching random walk on the multiplicative group (0, ∞), naturally arise as a result of this investigation

Symmetry breaking and uniqueness for the incompressible Navier-Stokes equations.

Science.gov (United States)

Dascaliuc, Radu; Michalowski, Nicholas; Thomann, Enrique; Waymire, Edward C

2015-07-01

The present article establishes connections between the structure of the deterministic Navier-Stokes equations and the structure of (similarity) equations that govern self-similar solutions as expected values of certain naturally associated stochastic cascades. A principle result is that explosion criteria for the stochastic cascades involved in the probabilistic representations of solutions to the respective equations coincide. While the uniqueness problem itself remains unresolved, these connections provide interesting problems and possible methods for investigating symmetry breaking and the uniqueness problem for Navier-Stokes equations. In particular, new branching Markov chains, including a dilogarithmic branching random walk on the multiplicative group (0, ∞), naturally arise as a result of this investigation.

Astronomical Instrumentation Systems Quality Management Planning: AISQMP (Abstract)

Science.gov (United States)

Goldbaum, J.

2017-12-01

(Abstract only) The capability of small aperture astronomical instrumentation systems (AIS) to make meaningful scientific contributions has never been better. The purpose of AIS quality management planning (AISQMP) is to ensure the quality of these contributions such that they are both valid and reliable. The first step involved with AISQMP is to specify objective quality measures not just for the AIS final product, but also for the instrumentation used in its production. The next step is to set up a process to track these measures and control for any unwanted variation. The final step is continual effort applied to reducing variation and obtaining measured values near optimal theoretical performance. This paper provides an overview of AISQMP while focusing on objective quality measures applied to astronomical imaging systems.

Homogenization of the evolutionary Navier-Stokes system

Czech Academy of Sciences Publication Activity Database

Feireisl, Eduard; Namlyeyeva, Yuliya; Nečasová, Šárka

2016-01-01

Roč. 149, č. 1 (2016), s. 251-274 ISSN 0025-2611 R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : Navier-Stokes system Subject RIV: BA - General Mathematics Impact factor: 0.607, year: 2016 http://link.springer.com/article/10.1007%2Fs00229-015-0778-y

Eulerian derivations of non-inertial Navier-Stokes equations

CSIR Research Space (South Africa)

Combrinck, MA

2014-09-01

Full Text Available The paper presents an Eulerian derivation of the non-inertial Navier-Stokes equations as an alternative to the Lagrangian fluid parcel approach. This work expands on the work of Kageyama and Hyodo [1] who derived the incompressible momentum equation...

A stable penalty method for the compressible Navier-Stokes equations: II: One-dimensional domain decomposition schemes

DEFF Research Database (Denmark)

Hesthaven, Jan

1997-01-01

This paper presents asymptotically stable schemes for patching of nonoverlapping subdomains when approximating the compressible Navier-Stokes equations given on conservation form. The scheme is a natural extension of a previously proposed scheme for enforcing open boundary conditions and as a res......This paper presents asymptotically stable schemes for patching of nonoverlapping subdomains when approximating the compressible Navier-Stokes equations given on conservation form. The scheme is a natural extension of a previously proposed scheme for enforcing open boundary conditions...... and as a result the patching of subdomains is local in space. The scheme is studied in detail for Burgers's equation and developed for the compressible Navier-Stokes equations in general curvilinear coordinates. The versatility of the proposed scheme for the compressible Navier-Stokes equations is illustrated...

Partial Averaged Navier-Stokes approach for cavitating flow

International Nuclear Information System (INIS)

Zhang, L; Zhang, Y N

2015-01-01

Partial Averaged Navier Stokes (PANS) is a numerical approach developed for studying practical engineering problems (e.g. cavitating flow inside hydroturbines) with a resonance cost and accuracy. One of the advantages of PANS is that it is suitable for any filter width, leading a bridging method from traditional Reynolds Averaged Navier-Stokes (RANS) to direct numerical simulations by choosing appropriate parameters. Comparing with RANS, the PANS model will inherit many physical nature from parent RANS but further resolve more scales of motion in great details, leading to PANS superior to RANS. As an important step for PANS approach, one need to identify appropriate physical filter-width control parameters e.g. ratios of unresolved-to-total kinetic energy and dissipation. In present paper, recent studies of cavitating flow based on PANS approach are introduced with a focus on the influences of filter-width control parameters on the simulation results

Global regularity for a family of 3D models of the axi-symmetric Navier–Stokes equations

Science.gov (United States)

Hou, Thomas Y.; Liu, Pengfei; Wang, Fei

2018-05-01

We consider a family of three-dimensional models for the axi-symmetric incompressible Navier–Stokes equations. The models are derived by changing the strength of the convection terms in the axisymmetric Navier–Stokes equations written using a set of transformed variables. We prove the global regularity of the family of models in the case that the strength of convection is slightly stronger than that of the original Navier–Stokes equations, which demonstrates the potential stabilizing effect of convection.

Astronomical chemistry.

Science.gov (United States)

Klemperer, William

2011-01-01

The discovery of polar polyatomic molecules in higher-density regions of the interstellar medium by means of their rotational emission detected by radioastronomy has changed our conception of the universe from essentially atomic to highly molecular. We discuss models for molecule formation, emphasizing the general lack of thermodynamic equilibrium. Detailed chemical kinetics is needed to understand molecule formation as well as destruction. Ion molecule reactions appear to be an important class for the generally low temperatures of the interstellar medium. The need for the intrinsically high-quality factor of rotational transitions to definitively pin down molecular emitters has been well established by radioastronomy. The observation of abundant molecular ions both positive and, as recently observed, negative provides benchmarks for chemical kinetic schemes. Of considerable importance in guiding our understanding of astronomical chemistry is the fact that the larger molecules (with more than five atoms) are all organic.

"She is an astronomer" in Spain; the International Year of Astronomy 2009 and beyond

Science.gov (United States)

Márquez, I.

2011-11-01

The work of the Spanish node for the IYA2009 Cornerstoneproject, "She is an Astronomer" is presented. Our team developedseveral projects with the common goal of promoting gender equality andwomen participation in professional and amateur astronomy, andsupporting the training of young women researchers andtechnologists. The main ones were: 1)Calendar "Women astronomerswho made history". We highlighted exceptional women, fromdifferent epochs and countries, whose contributions to theadvancement of science deserve to transcend anonymity and occupy aplace in history.2) "Women in the stars" was a series of 8 TV programsdevoted to the contribution of Spanish women astronomers, made incollaboration with the UNED.3) "Women in Spanish Astronomy: analysis of a peculiar situation: A universe to discover", was the first sociological study of this type, including quantitative and qualitative (individual and group interviews) analyses. 4) The exhibit "She Astronomer", was aimed at teaching astronomy from a new perspective: the relevant contributions by women astronomers from different times and places.The main aims of the "Commission for Women and Astronomy",recently created within the Spanish Astronomical Society (SEA), are alsodescribed.

The caracol tower at chichen itza: an ancient astronomical observatory?

Science.gov (United States)

Aveni, A F; Gibbs, S L; Hartung, H

1975-06-06

Although our investigations reveal a number of significant astronomical events coinciding with many of the measured alignments presented in Table 1, not every alignment appears to have an astronomical match which we can recognize. It may be that only some of the sighting possibilities we have discussed were actually functional. Moreover, our search of significant astronomical events to match the alignments has included only those which seem of obvious functional importance to us: sun, moon, and planetary extremes and the setting positions of the brightest stars. We have emphasized those celestial bodies which are documented in the literature as having been of importance. Perhaps hitherto unrecognized constellations were sighted in the windows, perhaps fainter stars, the heliacal rising and setting times of which could have served to mark important dates in the calendar. While we propose no grand cosmic scheme for the astronomical design of the Caracol it can be inferred that the building, apart from being a monument related to Quetzalcoatl, was erected primarily for the purpose of embodying in its architecture certain significant astronomical event alignments, in the same sense that a modern astronomical ephemeris exhibits information of importance to us in the keeping of the current calendar. There are examples in the Mesoamerican historical literature of deliberate attempts to align buildings with astronomical directions of importance. For example, Maudslay (33) quotes Father Motolinia, who tells us that in Tenochtitlan the festival called Tlacaxipeualistli "took place when the sun stood in the middle of Huicholobos, which was at the equinox, and because it was a little out of the straight, Montezuma wished to pull it down and set it right." According to Maudslay, worshipers were probably facing east to watch the sun rise between the two oratories on the Great Temple of Tenochtitlan at the time of the equinox. The directions of the faces of the Lower and Upper

Astronomical Research Institute Photometric Results

Science.gov (United States)

Linder, Tyler R.; Sampson, Ryan; Holmes, Robert

2013-01-01

The Astronomical Research Institute (ARI) conducts astrometric and photometric studies of asteroids with a concentration on near-Earth objects (NEOs). A 0.76-m autoscope was used for photometric studies of seven asteroids of which two were main-belt targets and five were NEOs, including one potentially hazardous asteroid (PHA). These objects are: 3122 Florence, 3960 Chaliubieju, 5143 Heracles, (6455) 1992 HE, (36284) 2000 DM8, (62128) 2000 SO1, and 2010 LF86.

Tunable KTA Stokes laser based on stimulated polariton scattering and its intracavity frequency doubling.

Science.gov (United States)

Zang, Jie; Cong, Zhenhua; Chen, Xiaohan; Zhang, Xingyu; Qin, Zengguang; Liu, Zhaojun; Lu, Jianren; Wu, Dong; Fu, Qiang; Jiang, Shiqi; Zhang, Shaojun

2016-04-04

This paper presents the tunable Stokes laser characteristics of KTiOAsO4 (KTA) crystal based on stimulated polariton scattering (SPS). When the pumping laser wavelength is 1064.2 nm, the KTA Stokes wave can be discontinuously tuned from 1077.9 to 1088.4 nm with four gaps from 1079.0 to 1080.1 nm, from 1080.8 to 1082.8 nm, from 1083.6 to 1085.5 nm, and from 1085.8 to 1086.8 nm. When a frequency doubling crystal LiB3O5 (LBO) is inserted into the Stokes laser cavity, the frequency-doubled wave can be discontinuously tuned from 539.0 to 539.5 nm, from 540.1 to 540.4 nm, from 541.3 to 541.8 nm, from 542.7 to 542.9 nm and from 543.4 to 544.2 nm. With a pumping pulse energy of 130.0 mJ and an output coupler reflectivity of about 30%, the obtained maximum Stokes laser pulse energy at 1078.6 nm is 33.9 mJ and the obtained maximum frequency-doubled laser pulse energy at 543.8 nm is 15.7 mJ. By using the most probably coupled transverse optical modes obtained from the literature, the polariton refractive indexes, and the simplified polariton Sellmeier equations, the polariton dispersion curve is obtained. The formation of the Stokes frequency gaps is explained.

``Orion, I Don't Love You'': The Astronomical Legacy of Carl Sandburg

Science.gov (United States)

Ricca, B.

2013-04-01

Can poetry provide an accurate means of representing the scientific universe? This paper looks at the astronomical poetry of Carl Sandburg and how the poet employs a scientific framework to deepen his work. Sandburg's method is then compared to a class project of middle school students who use his poetry (and their own) to learn and understand astronomical facts.

Regularity of the 3D Navier-Stokes equations with viewpoint of 2D flow

Science.gov (United States)

Bae, Hyeong-Ohk

2018-04-01

The regularity of 2D Navier-Stokes flow is well known. In this article we study the relationship of 3D and 2D flow, and the regularity of the 3D Naiver-Stokes equations with viewpoint of 2D equations. We consider the problem in the Cartesian and in the cylindrical coordinates.

The Production Rate and Employment of Ph.D. Astronomers

Science.gov (United States)

Metcalfe, Travis S.

2008-02-01

In an effort to encourage self-regulation of the astronomy job market, I examine the supply of, and demand for, astronomers over time. On the supply side, I document the production rate of Ph.D. astronomers from 1970 to 2006 using the UMI Dissertation Abstracts database, along with data from other independent sources. I compare the long-term trends in Ph.D. production with federal astronomy research funding over the same time period, and I demonstrate that additional funding is correlated with higher subsequent Ph.D. production. On the demand side, I monitor the changing patterns of employment using statistics about the number and types of jobs advertised in the AAS Job Register from 1984 to 2006. Finally, I assess the sustainability of the job market by normalizing this demand by the annual Ph.D. production. The most recent data suggest that there are now annual advertisements for about one postdoctoral job, half a faculty job, and half a research/support position for every new domestic Ph.D. recipient in astronomy and astrophysics. The average new astronomer might expect to hold up to 3 jobs before finding a steady position.

Parametric Raman crystalline anti-Stokes laser at 503 nm with collinear beam interaction at tangential phase matching

Science.gov (United States)

Smetanin, S. N.; Jelínek, M.; Kubeček, V.

2017-07-01

Stimulated-Raman-scattering in crystals can be used for the single-pass frequency-conversion to the Stokes-shifted wavelengths. The anti-Stokes shift can also be achieved but the phase-matching condition has to be fulfilled because of the parametric four-wave mixing process. To widen the angular-tolerance of four-wave mixing and to obtain high-conversion-efficiency into the anti-Stokes, we developed a new scheme of the parametric Raman anti-Stokes laser at 503 nm with phase-matched collinear beam interaction of orthogonally-polarized Raman components in calcite oriented at the phase-matched angle under 532 nm 20 ps laser excitation. The excitation laser beam was split into two orthogonally-polarized components entering the calcite at the certain incidence angles to fulfill the nearly collinear phase-matching and also to compensate walk-off of extraordinary waves for collinear beam interaction. The phase matching of parametric Raman interaction is tangential and insensitive to the angular mismatch if the Poynting vectors of the biharmonic pump and parametrically generated (anti-Stokes) waves are collinear. For the first time it allows to achieve experimentally the highest conversion efficiency into the anti-Stokes wave (503 nm) up to 30% from the probe wave and up to 3.5% from both pump and probe waves in the single-pass picosecond parametric calcite Raman laser. The highest anti-Stokes pulse energy was 1.4 μJ.

Polishers around the globe: an overview on the market of large astronomical mirrors

Science.gov (United States)

Döhring, Thorsten

2014-07-01

Astronomical mirrors are key elements in modern optical telescopes, their dimensions are usually large and their specifications are demanding. Only a limited number of skilled companies respectively institutions around the world are able to master the challenge to polish an individual astronomical mirror, especially in dimensions above one meter. This paper presents an overview on the corresponding market including a listing of polishers around the globe. Therefore valuable information is provided to the astronomical community: Polishers may use the information as a global competitor database, astronomers and project managers may get more transparency on potential suppliers, and suppliers of polishing equipment may learn about unknown potential customers in other parts of the world. An evaluation of the historical market demand on large monolithic astronomical mirrors is presented. It concluded that this is still a niche market with a typical mean rate of 1-2 mirrors per year. Polishing of such mirrors is an enabling technology with impact on the development of technical know-how, public relation, visibility and reputation of the supplier. Within a corresponding technical discussion different polishing technologies are described. In addition it is demonstrated that strategic aspects and political considerations are influencing the selection of the optical finisher.

Symmetric approximations of the Navier-Stokes equations

International Nuclear Information System (INIS)

Kobel'kov, G M

2002-01-01

A new method for the symmetric approximation of the non-stationary Navier-Stokes equations by a Cauchy-Kovalevskaya-type system is proposed. Properties of the modified problem are studied. In particular, the convergence as ε→0 of the solutions of the modified problem to the solutions of the original problem on an infinite interval is established

On analytical solution of the Navier-Stokes equations

International Nuclear Information System (INIS)

Scheffel, J.

2001-04-01

An analytical method for solving the dissipative, nonlinear and non-stationary Navier-Stokes equations is presented. Velocity and pressure is expanded in power series of cartesian coordinates and time. The method is applied to 2-D incompressible gravitational flow in a bounded, rectangular domain

Inertial algorithms for the stationary Navier-Stokes equations

NARCIS (Netherlands)

Hou, Yanren; Mattheij, R.M.M.

2003-01-01

Several kind of new numerical schemes for the stationary Navier-Stokes equations based on the virtue of Inertial Manifold and Approximate Inertial Manifold, which we call them inertial algorithms in this paper, together with their error estimations are presented. All these algorithms are constructed

Two-dimensional Navier-Stokes turbulence in bounded domains

NARCIS (Netherlands)

Clercx, H.J.H.; van Heijst, G.J.F.

In this review we will discuss recent experimental and numerical results of quasi-two-dimensional decaying and forced Navier–Stokes turbulence in bounded domains. We will give a concise overview of developments in two-dimensional turbulence research, with emphasis on the progress made during the

Two-dimensional Navier-Stokes turbulence in bounded domains

NARCIS (Netherlands)

Clercx, H.J.H.; Heijst, van G.J.F.

2009-01-01

In this review we will discuss recent experimental and numerical results of quasi-two-dimensional decaying and forced Navier–Stokes turbulence in bounded domains. We will give a concise overview of developments in two-dimensional turbulence research, with emphasis on the progress made during the

Science Initiatives of the US Virtual Astronomical Observatory

Science.gov (United States)

Hanisch, R. J.

2012-09-01

The United States Virtual Astronomical Observatory program is the operational facility successor to the National Virtual Observatory development project. The primary goal of the US VAO is to build on the standards, protocols, and associated infrastructure developed by NVO and the International Virtual Observatory Alliance partners and to bring to fruition a suite of applications and web-based tools that greatly enhance the research productivity of professional astronomers. To this end, and guided by the advice of our Science Council (Fabbiano et al. 2011), we have focused on five science initiatives in the first two years of VAO operations: 1) scalable cross-comparisons between astronomical source catalogs, 2) dynamic spectral energy distribution construction, visualization, and model fitting, 3) integration and periodogram analysis of time series data from the Harvard Time Series Center and NASA Star and Exoplanet Database, 4) integration of VO data discovery and access tools into the IRAF data analysis environment, and 5) a web-based portal to VO data discovery, access, and display tools. We are also developing tools for data linking and semantic discovery, and have a plan for providing data mining and advanced statistical analysis resources for VAO users. Initial versions of these applications and web-based services are being released over the course of the summer and fall of 2011, with further updates and enhancements planned for throughout 2012 and beyond.

Science Initiatives of the US Virtual Astronomical Observatory

Directory of Open Access Journals (Sweden)

Hanisch Robert J.

2012-09-01

Full Text Available The United States Virtual Astronomical Observatory program is the operational facility successor to the National Virtual Observatory development project. The primary goal of the US VAO is to build on the standards, protocols, and associated infrastructure developed by NVO and the International Virtual Observatory Alliance partners and to bring to fruition a suite of applications and web-based tools that greatly enhance the research productivity of professional astronomers. To this end, and guided by the advice of our Science Council (advisory committee, we are focusing on five science initiatives in the first two years of VAO operations: (1 scalable cross-comparisons between astronomical source catalogs, (2 dynamic spectral energy distribution construction, visualization, and model fitting, (3 integration and periodogram analysis of time series data from the Harvard Time Series Center and NASA Star and Exoplanet Database, (4 integration of VO data discovery and access tools into the IR AF data analysis environment, and (5 a web-based portal to VO data discovery, access, and display tools. We are also developing tools for data linking and semantic discovery, and have a plan for providing data mining and advanced statistical analysis resources for VAO users. Initial versions of these applications and web-based services are being released over the course of the summer and fall of 2011, with further updates and enhancements planned for throughout 2012 and beyond.

A Stokes drift approximation based on the Phillips spectrum

Science.gov (United States)

Breivik, Øyvind; Bidlot, Jean-Raymond; Janssen, Peter A. E. M.

2016-04-01

A new approximation to the Stokes drift velocity profile based on the exact solution for the Phillips spectrum is explored. The profile is compared with the monochromatic profile and the recently proposed exponential integral profile. ERA-Interim spectra and spectra from a wave buoy in the central North Sea are used to investigate the behavior of the profile. It is found that the new profile has a much stronger gradient near the surface and lower normalized deviation from the profile computed from the spectra. Based on estimates from two open-ocean locations, an average value has been estimated for a key parameter of the profile. Given this parameter, the profile can be computed from the same two parameters as the monochromatic profile, namely the transport and the surface Stokes drift velocity.

Trading Nets for Guns: The Impact of Illegal Fishing on Piracy in Somalia

Science.gov (United States)

2010-09-01

and World Order, Draft, Royal Irish Academy, National University of Ireland , Galway (Galway: Centr for Ocean Policy Studies, 2009), 26–27...Kismayo.75 Thus, piracy was transformed by warlord entrepreneurship , in its organization, targets, tactics, and potential profitability beginning in...World Order, Draft, Royal Irish Academy, National University of Ireland , Galway (Galway: Centr for Ocean Policy Studies, 2009), 26–27. Percy, Sara

Navier-Stokes Computations of Sabot Discard Using Chimera Scheme

National Research Council Canada - National Science Library

Ferry, E

1997-01-01

.... Numerical flow field computations have been made for various orientations and locations of sabots using an unsteady, zonal Navier-Stokes code and the Chimera composite grid discretization technique at M = 4.0 and alpha = 0...

Eighth Scientific Meeting of the Spanish Astronomical Society

CERN Document Server

Diego, Jose M; González-Serrano, J. Ignacio; Gorgas, Javier; Highlights of Spanish Astrophysics V

2010-01-01

This volume collects the invited contributions and plenary sessions presented at the Eighth Scientific Meeting of the Spanish Astronomical Society (Sociedad Española de Astronomía, SEA) held on July 7-11, 2008 in Santander. These contributions cover all fields of astronomy and astrophysics, i.e., the Sun and solar system, the galaxy and its components, galaxies and cosmology, observatories and instrumentation, as well as astronomy teaching and dissemination. Further plenary sessions were devoted to selected hot topics, including the exploration of the solar system, gravitational lensing, exoplanets, X-ray binaries, solar magnetism, gravitational waves, the ALHAMBRA collaboration, and the OSIRIS instrument on the new 10-m GTC. Abstracts of the contributions presented at the parallels sessions and posters are also included in the book. Complete versions of those papers are available online.

Emerging technology for astronomical optics metrology

Science.gov (United States)

Trumper, Isaac; Jannuzi, Buell T.; Kim, Dae Wook

2018-05-01

Next generation astronomical optics will enable science discoveries across all fields and impact the way we perceive the Universe in which we live. To build these systems, optical metrology tools have been developed that push the boundary of what is possible. We present a summary of a few key metrology technologies that we believe are critical for the coming generation of optical surfaces.

Astronomical and Atmospheric Observations in the Anglo-Saxon Chronicle and in Bede

Science.gov (United States)

Härke, H.

2012-01-01

Textual sources of the early Middle Ages (fifth to tenth centuries AD) contain more astronomical observations than is popularly assumed. The Anglo-Saxon Chronicle lists some 40 observations of astronomical and atmospheric events for the just over 600 years it covers. But the contexts in which these are set show that eclipses, comets, meteor showers and aurorae were seen as portents of evil events, not as objects of early scientific curiosity. The case of Bede in the early eighth century shows that this was true, to an extent, even for the educated ecclesiastical elite. BedeÕs eclipse records also appear to show that astronomical events could be used to explain unusual phenomena such as the postulated volcanic Ôdust-veilÕ event of AD 536.

Revealing silent vibration modes of nanomaterials by detecting anti-Stokes hyper-Raman scattering with femtosecond laser pulses.

Science.gov (United States)

Zeng, Jianhua; Chen, Lei; Dai, Qiaofeng; Lan, Sheng; Tie, Shaolong

2016-01-21

We proposed a scheme in which normal Raman scattering is coupled with hyper-Raman scattering for generating a strong anti-Stokes hyper-Raman scattering in nanomaterials by using femtosecond laser pulses. The proposal was experimentally demonstrated by using a single-layer MoS2 on a SiO2/Si substrate, a 17 nm-thick MoS2 on an Au/SiO2 substrate and a 9 nm-thick MoS2 on a SiO2-SnO2/Ag/SiO2 substrate which were confirmed to be highly efficient for second harmonic generation. A strong anti-Stokes hyper-Raman scattering was also observed in other nanomaterials possessing large second-order susceptibilities, such as silicon quantum dots self-assembled into "coffee" rings and tubular Cu-doped ZnO nanorods. In all the cases, many Raman inactive vibration modes were clearly revealed in the anti-Stokes hyper-Raman scattering. Apart from the strong anti-Stokes hyper-Raman scattering, Stokes hyper-Raman scattering with small Raman shifts was detected during the ablation process of thick MoS2 layers. It was also observed by slightly defocusing the excitation light. The detection of anti-Stokes hyper-Raman scattering may serve as a new technique for studying the Raman inactive vibration modes in nanomaterials.

Polarization ellipse and Stokes parameters in geometric algebra.

Science.gov (United States)

Santos, Adler G; Sugon, Quirino M; McNamara, Daniel J

2012-01-01

In this paper, we use geometric algebra to describe the polarization ellipse and Stokes parameters. We show that a solution to Maxwell's equation is a product of a complex basis vector in Jackson and a linear combination of plane wave functions. We convert both the amplitudes and the wave function arguments from complex scalars to complex vectors. This conversion allows us to separate the electric field vector and the imaginary magnetic field vector, because exponentials of imaginary scalars convert vectors to imaginary vectors and vice versa, while exponentials of imaginary vectors only rotate the vector or imaginary vector they are multiplied to. We convert this expression for polarized light into two other representations: the Cartesian representation and the rotated ellipse representation. We compute the conversion relations among the representation parameters and their corresponding Stokes parameters. And finally, we propose a set of geometric relations between the electric and magnetic fields that satisfy an equation similar to the Poincaré sphere equation.

Navier-Stokes dynamics on a differential one-form

Science.gov (United States)

Story, Troy L.

2006-11-01

After transforming the Navier-Stokes dynamic equation into a characteristic differential one-form on an odd-dimensional differentiable manifold, exterior calculus is used to construct a pair of differential equations and tangent vector(vortex vector) characteristic of Hamiltonian geometry. A solution to the Navier-Stokes dynamic equation is then obtained by solving this pair of equations for the position x^k and the conjugate to the position bk as functions of time. The solution bk is shown to be divergence-free by contracting the differential 3-form corresponding to the divergence of the gradient of the velocity with a triple of tangent vectors, implying constraints on two of the tangent vectors for the system. Analysis of the solution bk shows it is bounded since it remains finite as | x^k | ->,, and is physically reasonable since the square of the gradient of the principal function is bounded. By contracting the characteristic differential one-form with the vortex vector, the Lagrangian is obtained.

KNOW-BLADE task-4 report: Navier-Stokes aeroelasticity

DEFF Research Database (Denmark)

Politis, E.S.; Nikolaou, I.G.; Chaviaropoulos, P.K.

2004-01-01

wind turbine blade have been combined with 2D and 3D unsteady Navier-Stokes solvers. The relative disadvantage of the quasi-3D approach (where the elastic solver is coupled with a 2D Navier-Stokes solver) isits inability to model induced flow. The lack of a validation test case did not allow...... the computations for the full blade, 2D computations for the so-called “typical section” have been carried out. The 2D aeroelastic tools resulted in similar aerodynamic damping values. Qualitative agreement was better for the lead-lagmode. The presence of roughness tapes has a small, rather negligible impact...... on aeroelastic stability as depicted by the results of both aeroelastic tools. On the other hand, in conformity to the inability of the adopted computational model to successfullypredict the corresponding test cases under work package 2 of the project, the aeroelastic tools are not capable to predict the correct...

Benzothiadiazole oligoene fatty acids: fluorescent dyes with large Stokes shifts

Directory of Open Access Journals (Sweden)

Lukas J. Patalag

2016-12-01

Full Text Available Herein, we report on the synthesis and characterization of novel fluorescent fatty acids with large Stokes shifts. Three examples consisting of the same number of carbon atoms and thus of similar chain length are presented differing in their degree of unsaturation. As major fluorogenic contributor at the terminus benzo[c][1,2,5]thiadiazole was used. Respective syntheses based on Wittig reactions followed by iodine-mediated isomerization are presented. The absorption properties are modulated by the number of conjugated C=C double bonds of the oligoene chain ranging from one to three. Large Stokes shifts of about 4900–5700 cm−1 and fluorescence quantum yields of up to 0.44 were observed.

Numerical Investigations on Several Stabilized Finite Element Methods for the Stokes Eigenvalue Problem

Directory of Open Access Journals (Sweden)

Pengzhan Huang

2011-01-01

Full Text Available Several stabilized finite element methods for the Stokes eigenvalue problem based on the lowest equal-order finite element pair are numerically investigated. They are penalty, regular, multiscale enrichment, and local Gauss integration method. Comparisons between them are carried out, which show that the local Gauss integration method has good stability, efficiency, and accuracy properties, and it is a favorite method among these methods for the Stokes eigenvalue problem.

A nonperturbative approximation for the moderate Reynolds number Navier-Stokes equations.

Science.gov (United States)

Roper, Marcus; Brenner, Michael P

2009-03-03

The nonlinearity of the Navier-Stokes equations makes predicting the flow of fluid around rapidly moving small bodies highly resistant to all approaches save careful experiments or brute force computation. Here, we show how a linearization of the Navier-Stokes equations captures the drag-determining features of the flow and allows simplified or analytical computation of the drag on bodies up to Reynolds number of order 100. We illustrate the utility of this linearization in 2 practical problems that normally can only be tackled with sophisticated numerical methods: understanding flow separation in the flow around a bluff body and finding drag-minimizing shapes.

Multilevel solvers of first-order system least-squares for Stokes equations

Energy Technology Data Exchange (ETDEWEB)

Lai, Chen-Yao G. [National Chung Cheng Univ., Chia-Yi (Taiwan, Province of China)

1996-12-31

Recently, The use of first-order system least squares principle for the approximate solution of Stokes problems has been extensively studied by Cai, Manteuffel, and McCormick. In this paper, we study multilevel solvers of first-order system least-squares method for the generalized Stokes equations based on the velocity-vorticity-pressure formulation in three dimensions. The least-squares functionals is defined to be the sum of the L{sup 2}-norms of the residuals, which is weighted appropriately by the Reynolds number. We develop convergence analysis for additive and multiplicative multilevel methods applied to the resulting discrete equations.

Database retrieval systems for nuclear and astronomical data

International Nuclear Information System (INIS)

Suda, Takuma; Korennov, Sergei; Otuka, Naohiko; Yamada, Shimako; Katsuta, Yutaka; Ohnishi, Akira; Kato, Kiyoshi; Fujimoto, Masayuki Y.

2006-01-01

Data retrieval and plot systems of nuclear and astronomical data are constructed on a common platform. Web-based systems will soon be opened to the users of both fields of nuclear physics and astronomy. (author)

Coupling nonlinear Stokes and Darcy flow using mortar finite elements

KAUST Repository

Ervin, Vincent J.

2011-11-01

We study a system composed of a nonlinear Stokes flow in one subdomain coupled with a nonlinear porous medium flow in another subdomain. Special attention is paid to the mathematical consequence of the shear-dependent fluid viscosity for the Stokes flow and the velocity-dependent effective viscosity for the Darcy flow. Motivated by the physical setting, we consider the case where only flow rates are specified on the inflow and outflow boundaries in both subdomains. We recast the coupled Stokes-Darcy system as a reduced matching problem on the interface using a mortar space approach. We prove a number of properties of the nonlinear interface operator associated with the reduced problem, which directly yield the existence, uniqueness and regularity of a variational solution to the system. We further propose and analyze a numerical algorithm based on mortar finite elements for the interface problem and conforming finite elements for the subdomain problems. Optimal a priori error estimates are established for the interface and subdomain problems, and a number of compatibility conditions for the finite element spaces used are discussed. Numerical simulations are presented to illustrate the algorithm and to compare two treatments of the defective boundary conditions. © 2010 Published by Elsevier B.V. on behalf of IMACS.

Spatial Fourier modes controlling Navier-Stokes flow

International Nuclear Information System (INIS)

Treve, Y.M.

1982-01-01

As shown by Foias and Prodi in the limit of infinite times the solutions of the two-dimensional Navier-Stokes equations depend only on a finite number of modes, a number for which rigorous estimates can be obtained. A survey of these results is given together with further developments, notably in connection with the numerical approximation to the exact solutions. (Auth.)

Astronomy Against Terrorism: an Educational Astronomical Observatory Project in Peru

Science.gov (United States)

Ishitsuka, M.; Montes, H.; Kuroda, T.; Morimoto, M.; Ishitsuka, J.

2003-05-01

The Cosmos Coronagraphic Observatory was completely destroyed by terrorists in 1988. In 1995, in coordination with the Minister of Education of Peru, a project to construct a new Educational Astronomical Observatory has been executed. The main purpose of the observatory is to promote an interest in basic space sciences in young students from school to university levels, through basic astronomical studies and observations. The planned observatory will be able to lodge 25 visitors; furthermore an auditorium, a library and a computer room will be constructed to improve the interest of people in astronomy. Two 15-cm refractor telescopes, equipped with a CCD camera and a photometer, will be available for observations. Also a 6-m dome will house a 60-cm class reflector telescope, which will be donated soon, thanks to a fund collected and organized by the Nishi-Harima Astronomical Observatory in Japan. In addition a new modern planetarium donated by the Government of Japan will be installed in Lima, the capital of Peru. These installations will be widely open to serve the requirements of people interested in science.

Sports Stars: Analyzing the Performance of Astronomers at Visualization-based Discovery

Science.gov (United States)

Fluke, C. J.; Parrington, L.; Hegarty, S.; MacMahon, C.; Morgan, S.; Hassan, A. H.; Kilborn, V. A.

2017-05-01

In this data-rich era of astronomy, there is a growing reliance on automated techniques to discover new knowledge. The role of the astronomer may change from being a discoverer to being a confirmer. But what do astronomers actually look at when they distinguish between “sources” and “noise?” What are the differences between novice and expert astronomers when it comes to visual-based discovery? Can we identify elite talent or coach astronomers to maximize their potential for discovery? By looking to the field of sports performance analysis, we consider an established, domain-wide approach, where the expertise of the viewer (i.e., a member of the coaching team) plays a crucial role in identifying and determining the subtle features of gameplay that provide a winning advantage. As an initial case study, we investigate whether the SportsCode performance analysis software can be used to understand and document how an experienced Hi astronomer makes discoveries in spectral data cubes. We find that the process of timeline-based coding can be applied to spectral cube data by mapping spectral channels to frames within a movie. SportsCode provides a range of easy to use methods for annotation, including feature-based codes and labels, text annotations associated with codes, and image-based drawing. The outputs, including instance movies that are uniquely associated with coded events, provide the basis for a training program or team-based analysis that could be used in unison with discipline specific analysis software. In this coordinated approach to visualization and analysis, SportsCode can act as a visual notebook, recording the insight and decisions in partnership with established analysis methods. Alternatively, in situ annotation and coding of features would be a valuable addition to existing and future visualization and analysis packages.

Unstructured Navier-Stokes Analysis of Full TCA Configuration

Science.gov (United States)

Frink, Neal T.; Pirzadeh, Shahyar Z.

1999-01-01

This paper presents an Unstructured Navier-Stokes Analysis of Full TCA (Technology Concept Airplane) Configuration. The topics include: 1) Motivation; 2) Milestone and approach; 3) Overview of the unstructured-grid system; 4) Results on full TCA W/B/N/D/E configuration; 5) Concluding remarks; and 6) Future directions.

Some strange numerical solutions of the non-stationary Navier-Stokes equations in pipes

Energy Technology Data Exchange (ETDEWEB)

Rummler, B.

2001-07-01

A general class of boundary-pressure-driven flows of incompressible Newtonian fluids in three-dimensional pipes with known steady laminar realizations is investigated. Considering the laminar velocity as a 3D-vector-function of the cross-section-circle arguments, we fix the scale for the velocity by the L{sub 2}-norm of the laminar velocity. The usual new variables are introduced to get dimension-free Navier-Stokes equations. The characteristic physical and geometrical quantities are subsumed in the energetic Reynolds number Re and a parameter {psi}, which involves the energetic ratio and the directions of the boundary-driven part and the pressure-driven part of the laminar flow. The solution of non-stationary dimension-free Navier-Stokes equations is sought in the form u=u{sub L}+u, where u{sub L} is the scaled laminar velocity and periodical conditions in center-line-direction are prescribed for u. An autonomous system (S) of ordinary differential equations for the time-dependent coefficients of the spatial Stokes eigenfunction is got by application of the Galerkin-method to the dimension-free Navier-Stokes equations for u. The finite-dimensional approximations u{sub N({lambda}}{sub )} of u are defined in the usual way. (orig.)

Focus on astronomical predictable events

DEFF Research Database (Denmark)

Jacobsen, Aase Roland

2006-01-01

At the Steno Museum Planetarium we have for many occasions used a countdown clock to get focus om astronomical events. A countdown clock can provide actuality to predictable events, for example The Venus Transit, Opportunity landing on Mars and The Solar Eclipse. The movement of the clock attracs...... the public and makes a point of interest in a small exhibit area. A countdown clock can be simple, but it is possible to expand the concept to an eye-catching part of a museum....

The South African Astronomical Observatory

International Nuclear Information System (INIS)

1988-01-01

The geographical position, climate and equipment at the South African Astronomical Observatory (SAAO), together with the enthusiasm and efforts of SAAO scientific and technical staff and of visiting scientists, have enabled the Observatory to make a major contribution to the fields of astrophysics and cosmology. During 1987 the SAAO has been involved in studies of the following: supernovae; galaxies, including Seyfert galaxies; celestial x-ray sources; magellanic clouds; pulsating variables; galatic structure; binary star phenomena; nebulae; interstellar matter and stellar astrophysics

The War's Positive Impact on the Canadian Astronomical Community

Science.gov (United States)

Broughton, Peter

2015-01-01

At the beginning of WWI, the Canadian astronomical community was tiny and astrophysical research was just beginning. By the end of the war, the country had established the forerunner of its National Research Council and had the world's largest fully operational telescope, thanks to the late entry of the USA into the conflict. By 1918, Canada was on the verge of making significant contributions to science.In spite of the immense loss of life in this pointless war, I am aware of only one casualty affecting Canadian professional astronomers, and that was the indirect death of James Chant, son of University of Toronto's only professor of astronomy. Other Canadian astronomers, including Tom Parker, Bert Topham, and Harry Plaskett were on active service; each of their stories is unique.Among those engaged in scientific work during the war were two Canadians temporarily in England: John McLennan whose helium research for dirigibles led him to establish a cryogenic lab in Toronto where the green line in the spectrum of the aurora was identified in 1925, and Allie Douglas who worked as a statistician in the War Office. Later work with Eddington led her to become his biographer and to her distinction as the first person in Canada to earn a PhD in astronomy (in 1926).

Letters from Augustin Hallerstein, an eighteenth century Jesuit astronomer in Beijing

Science.gov (United States)

Juznic, Stanislav

2008-11-01

Augustin Hallerstein (1703-1774) was the last astronomer sent to Beijing by the Society of Jesus. He left Europe for China in his mid-thirties, and continued to send letters back home until he died thirty-five years later. These letters and reports contained important information on Chinese astronomy, and were read in the courts of Europe; many were also published. Hallerstein was one of the most important European astronomers in Beijing, his European publications surpassing those of his predecessors.

Inversions of High-Cadence SOLIS-VSM Stokes Observations

NARCIS (Netherlands)

Fischer, C.E.; Keller, C.U.; Snik, F.

2008-01-01

We have processed full-Stokes observations made with the SOLIS-VSM using Fe I 630.15 and Fe I 630.25 nm. The data have high spectral and temporal resolution, moderate spatial resolution, and large polarimetric sensitivity and accuracy. We use the code LILIA, an LTE inversion code written by

C++, objected-oriented programming, and astronomical data models

Science.gov (United States)

Farris, A.

1992-01-01

Contemporary astronomy is characterized by increasingly complex instruments and observational techniques, higher data collection rates, and large data archives, placing severe stress on software analysis systems. The object-oriented paradigm represents a significant new approach to software design and implementation that holds great promise for dealing with this increased complexity. The basic concepts of this approach will be characterized in contrast to more traditional procedure-oriented approaches. The fundamental features of objected-oriented programming will be discussed from a C++ programming language perspective, using examples familiar to astronomers. This discussion will focus on objects, classes and their relevance to the data type system; the principle of information hiding; and the use of inheritance to implement generalization/specialization relationships. Drawing on the object-oriented approach, features of a new database model to support astronomical data analysis will be presented.

Continuous anti-Stokes Raman laser operation

International Nuclear Information System (INIS)

Feitisch, A.; Muller, T.; Welling, H.; Wellegehausen, B.

1988-01-01

The anti-Stokes Raman laser (ASRL) process has proved to be a method that works well for frequency upconversion and for the generation of powerful tunable narrowband (pulsed) laser radiation in the UV and VUV spectral range. This conversion process allows large-frequency shifts in single step, high output energies, and high efficiencies. A basic requirement is population inversion on a two-photon transition, where, in general, the upper level of the transition should be metastable. Up to now the ASRL technique has only been demonstrated for the pulsed regime, where the necessary population inversion was generated by photodissociation or inner shell photoionization. These inversion techniques, however, cannot be transferred to cw operation of an ASRL, and, therefore, other inversion techniques have to be developed. Here a novel approach for the creation of the necessary population inversion is proposed, that uses well-known cw gas lasers as the active material for the conversion process. The basic idea is to use either existing two-photon population inversions in a cw laser material or to generate the necessary population inversion by applying a suitable population transfer process to the material. A natural two-photon inversion situation in a laser material is evident whenever a cascade laser can be operated. Cascade laser-based anti-Stokes schemes are possible in a He-Ne laser discharge, and investigations of these schemes are discussed

Remote observatories for amateur astronomers using high-powered telescopes from home

CERN Document Server

Hubbell, Gerald R; Billard, Linda M

2015-01-01

Amateur astronomers who want to enhance their capabilities to contribute to science need look no farther than this guide to using remote observatories.  The contributors cover how to build your own remote observatory as well as the existing infrastructure of commercial networks of remote observatories that are available to the amateur. They provide specific advice on which programs to use based on your project objectives and offer practical project suggestions. Remotely controlled observatories have many advantages—the most obvious that the observer does not have to be physically present to carry out observations. Such an observatory can also be used more fully because its time can be scheduled and usefully shared among several astronomers working on different observing projects. More and more professional-level observatories are open to use by amateurs in this way via the Internet, and more advanced amateur astronomers can even build their own remote observatories for sharing among members of a society ...

Communicating the Science of Global Warming — the Role of Astronomers

Science.gov (United States)

Bennett, Jeffrey

2018-06-01

Global Warming is one of the most important and issues of our times, yet it is widely misunderstood among the general public (and politicians!). The American Astronomical Society has already joined many other scientific organizations in advocating for action on global warming (by supporting the AGU statement on global warming), but we as astronomers can do much more. The high public profile of astronomy gives us a unique platform — and credibility as scientists — for doing our part to educate the public about the underlying science of global warming. And while astronomers are not climate scientists, we use the same basic physics, and many aspects of global warming science come directly from astronomy, including the ways in which we measure the heat-absorbing potential of carbon dioxide and the hard evidence of greenhouse warming provided by studies of Venus. In this session, I will briefly introduce a few methods for communicating about global warming that I believe you will find effective in your own education efforts.

A Compact Numerical Implementation for Solving Stokes Equations Using Matrix-vector Operations

KAUST Repository

Zhang, Tao; Salama, Amgad; Sun, Shuyu; Zhong, Hua

2015-01-01

In this work, a numerical scheme is implemented to solve Stokes equations based on cell-centered finite difference over staggered grid. In this scheme, all the difference operations have been vectorized thereby eliminating loops. This is particularly important when using programming languages that require interpretations, e.g., MATLAB and Python. Using this scheme, the execution time becomes significantly smaller compared with non-vectorized operations and also become comparable with those languages that require no repeated interpretations like FORTRAN, C, etc. This technique has also been applied to Navier-Stokes equations under laminar flow conditions.

A Compact Numerical Implementation for Solving Stokes Equations Using Matrix-vector Operations

KAUST Repository

Zhang, Tao

2015-06-01

In this work, a numerical scheme is implemented to solve Stokes equations based on cell-centered finite difference over staggered grid. In this scheme, all the difference operations have been vectorized thereby eliminating loops. This is particularly important when using programming languages that require interpretations, e.g., MATLAB and Python. Using this scheme, the execution time becomes significantly smaller compared with non-vectorized operations and also become comparable with those languages that require no repeated interpretations like FORTRAN, C, etc. This technique has also been applied to Navier-Stokes equations under laminar flow conditions.

Navier-Stokes Calculations of Helicopter Fuselage Flowfield and Loads

DEFF Research Database (Denmark)

M, Costes; Filippone, Antonino; N, Kroll

1999-01-01

This paper describes the theoretically basedactivities conducted during the first year of theBrite/Euram Helifuse Porgramme. These activitiesmainly consisted of the numerical prediction ofhelicopter fuselage flowfields with existing Navier-Stokes solvers on a number of pre-selectedcases, taken out...

Simulations of transition and turbulence on the Navier-Stokes computer

International Nuclear Information System (INIS)

Krist, S.E.; Zang, T.A.

1987-01-01

The Navier-Stokes Computer (NSC) consists of multiple local memory parallel processors interconnected in a hypercube network. Efficient implementation of algorithms on the NSC thus requires the effective utilization of both the coarse and fine grain paralelism inherent in the architectural design. The basic approach to implementing an algorithm on the NSC is presented herein. The particular finite-difference algorithm considered was developed for performing transition and turbulence simulations by direct solution of the time-dependent incompressible Navier-Stokes equations. The suitability of this algorithm for performing simulations of the isotropic turbulence problem is verified from computations performed on a Cray 2. Projected timing results for the algorithm on the NSC itself are presented for both the isotropic turbulence and laminar turbulent transition problems. 7 references

Incompressible Navier-Stokes inverse design method based on adaptive unstructured meshes

International Nuclear Information System (INIS)

Rahmati, M.T.; Charlesworth, D.; Zangeneh, M.

2005-01-01

An inverse method for blade design based on Navier-Stokes equations on adaptive unstructured meshes has been developed. In the method, unlike the method based on inviscid equations, the effect of viscosity is directly taken into account. In the method, the pressure (or pressure loading) is prescribed. The design method then computes the blade shape that would accomplish the target prescribed pressure distribution. The method is implemented using a cell-centered finite volume method, which solves the incompressible Navier-Stokes equations on unstructured meshes. An adaptive unstructured mesh method based on grid subdivision and local adaptive mesh method is utilized for increasing the accuracy. (author)

A nonperturbative approximation for the moderate Reynolds number Navier–Stokes equations

Science.gov (United States)

Roper, Marcus; Brenner, Michael P.

2009-01-01

The nonlinearity of the Navier–Stokes equations makes predicting the flow of fluid around rapidly moving small bodies highly resistant to all approaches save careful experiments or brute force computation. Here, we show how a linearization of the Navier–Stokes equations captures the drag-determining features of the flow and allows simplified or analytical computation of the drag on bodies up to Reynolds number of order 100. We illustrate the utility of this linearization in 2 practical problems that normally can only be tackled with sophisticated numerical methods: understanding flow separation in the flow around a bluff body and finding drag-minimizing shapes. PMID:19211800

Astronomical Instruments in India

Science.gov (United States)

Sarma, Sreeramula Rajeswara

The earliest astronomical instruments used in India were the gnomon and the water clock. In the early seventh century, Brahmagupta described ten types of instruments, which were adopted by all subsequent writers with minor modifications. Contact with Islamic astronomy in the second millennium AD led to a radical change. Sanskrit texts began to lay emphasis on the importance of observational instruments. Exclusive texts on instruments were composed. Islamic instruments like the astrolabe were adopted and some new types of instruments were developed. Production and use of these traditional instruments continued, along with the cultivation of traditional astronomy, up to the end of the nineteenth century.

Block iterative restoration of astronomical images with the massively parallel processor

International Nuclear Information System (INIS)

Heap, S.R.; Lindler, D.J.

1987-01-01

A method is described for algebraic image restoration capable of treating astronomical images. For a typical 500 x 500 image, direct algebraic restoration would require the solution of a 250,000 x 250,000 linear system. The block iterative approach is used to reduce the problem to solving 4900 121 x 121 linear systems. The algorithm was implemented on the Goddard Massively Parallel Processor, which can solve a 121 x 121 system in approximately 0.06 seconds. Examples are shown of the results for various astronomical images

New knowledge in determining the astronomical orientation of Incas object in Ollantaytambo, Peru

Science.gov (United States)

Hanzalová, K.; Klokočník, J.; Kostelecký, J.

2014-06-01

This paper deals about astronomical orientation of Incas objects in Ollantaytambo, which is located about 35 km southeast from Machu Picchu, about 40 km northwest from Cusco, and lies in the Urubamba valley. Everybody writing about Ollantaytambo, shoud read Protzen (1993). He devoted his monograph to description and interpretation of that locality. Book of Salazar and Salazar (2005) deals, among others, with the orientation of objects in Ollantaytambo with respect to the cardinal direction. Zawaski and Malville (2007) documented astronomical context of major monuments of nine sites in Peru, including Ollantaytambo. We tested astronomical orientation in these places and confirm or disprove hypothesis about purpose of Incas objects. For assessment orientation of objects we used our measurements and also satellite images on Google Earth and digital elevation model from ASTER. The satellite images used to approximate estimation of astronomical orientation. The digital elevation model is useful in the mountains, where we need the really horizon for a calculation of sunset and sunrise on specific days (solstices), which were for Incas people very important. By Incas is very famous that they worshiped the Sun. According to him they determined when to plant and when to harvest the crop. In this paper we focused on Temple of the Sun, also known the Wall of six monoliths. We tested which astronomical phenomenon is connected with this Temple. First, we tested winter solstice sunrise and the rides of the Pleiades for the epochs 2000, 1500 and 1000 A.D. According with our results the Temple isn't connected neither with winter solstice sunrise nor with the Pleiades. Then we tested also winter solstice sunset. We tried to use the line from an observation point near ruins of the Temple of Sun, to west-north, in direction to sunset. The astronomical azimuth from this point was about 5° less then we need. From this results we found, that is possible to find another observation

New knowledge in determining the astronomical orientation of Incas object in Ollantaytambo, Peru

Directory of Open Access Journals (Sweden)

K. Hanzalová

2014-06-01

Full Text Available This paper deals about astronomical orientation of Incas objects in Ollantaytambo, which is located about 35 km southeast from Machu Picchu, about 40 km northwest from Cusco, and lies in the Urubamba valley. Everybody writing about Ollantaytambo, shoud read Protzen (1993. He devoted his monograph to description and interpretation of that locality. Book of Salazar and Salazar (2005 deals, among others, with the orientation of objects in Ollantaytambo with respect to the cardinal direction. Zawaski and Malville (2007 documented astronomical context of major monuments of nine sites in Peru, including Ollantaytambo. We tested astronomical orientation in these places and confirm or disprove hypothesis about purpose of Incas objects. For assessment orientation of objects we used our measurements and also satellite images on Google Earth and digital elevation model from ASTER. The satellite images used to approximate estimation of astronomical orientation. The digital elevation model is useful in the mountains, where we need the really horizon for a calculation of sunset and sunrise on specific days (solstices, which were for Incas people very important. By Incas is very famous that they worshiped the Sun. According to him they determined when to plant and when to harvest the crop. In this paper we focused on Temple of the Sun, also known the Wall of six monoliths. We tested which astronomical phenomenon is connected with this Temple. First, we tested winter solstice sunrise and the rides of the Pleiades for the epochs 2000, 1500 and 1000 A.D. According with our results the Temple isn't connected neither with winter solstice sunrise nor with the Pleiades. Then we tested also winter solstice sunset. We tried to use the line from an observation point near ruins of the Temple of Sun, to west-north, in direction to sunset. The astronomical azimuth from this point was about 5° less then we need. From this results we found, that is possible to find another

Drifting solutions with elliptic symmetry for the compressible Navier-Stokes equations with density-dependent viscosity

International Nuclear Information System (INIS)

An, Hongli; Yuen, Manwai

2014-01-01

In this paper, we investigate the analytical solutions of the compressible Navier-Stokes equations with dependent-density viscosity. By using the characteristic method, we successfully obtain a class of drifting solutions with elliptic symmetry for the Navier-Stokes model wherein the velocity components are governed by a generalized Emden dynamical system. In particular, when the viscosity variables are taken the same as Yuen [M. W. Yuen, “Analytical solutions to the Navier-Stokes equations,” J. Math. Phys. 49, 113102 (2008)], our solutions constitute a generalization of that obtained by Yuen. Interestingly, numerical simulations show that the analytical solutions can be used to explain the drifting phenomena of the propagation wave like Tsunamis in oceans

Quantitative assessment of spinal cord injury using circularly polarized coherent anti-Stokes Raman scattering microscopy

Science.gov (United States)

Bae, Kideog; Zheng, Wei; Huang, Zhiwei

2017-08-01

We report the quantitative assessment of spinal cord injury using the circularly polarized coherent anti-Stokes Raman scattering (CP-CARS) technique together with Stokes parameters in the Poincaré sphere. The pump and Stokes excitation beams are circularly polarized to suppress both the linear polarization-dependent artifacts and the nonresonant background of tissue CARS imaging, enabling quantitative CP-CARS image analysis. This study shows that CP-CARS imaging uncovers significantly increased phase retardance of injured spinal cord tissue as compared to normal tissue, suggesting that CP-CARS is an appealing label-free imaging tool for determining the degree of tissue phase retardance, which could serve as a unique diagnostic parameter associated with nervous tissue injury.

AstroFrauenNetzwerk Survey Results - Career situation of female astronomers in Germany

Science.gov (United States)

Fohlmeister, J.; Helling, Ch.

2012-04-01

We survey the job situation of women in astronomy in Germany and of German women abroad and review indicators for their career development. Our sample includes women astronomers from all academic levels from doctoral students to professors, as well as female astronomers who have left the field. We find that networking and human support are among the most important factors for success. Experience shows that students should carefully choose their supervisor and collect practical knowledge abroad. We reflect the private situation of female German astronomers and find that prejudices are abundant, and are perceived as discriminating. We identify reasons why women are more likely than men to quit astronomy after they obtain their PhD degree. We give recommendations to young students on what to pay attention to in order to be on the successful path in astronomy.

The Selection and Protection of Optical Astronomical Observing Sites in China

Science.gov (United States)

Wenjing, Jin; Bai, Jinming; Yao, Yongqiang

2015-03-01

Before 1950 there are two observatories, Shanghai and Purple Mountain Astronomical Observatories (SHAO and PMO), and two observing stations, Qingdao and Kunming stations in China. With the requirements of astronomical research, two observatories, Beijing and Shaanxi Astronomical Observatories (BAO and SXAO) and two artificial satellite stations, Urumqi and Changchun, were established about 1960. Based on the current management, now there are 4 observatories, SHAO, PMO, NAOC(National Astronomical Observatories), which was grouped from BAO, YNAO and 2 others, as well as XAO (Xinjiang Astronomical Observatory). The optical 1-2 m class telescopes are being operated at former four observatories. SXAO is changed as National Time Service Center. Because of city expansion as well as the traveling and economic developments, these observatories are suffered severe light pollution. For example, Zo Ce is located at the suburb of Shanghai city. A 40 cm double astrograph was installed in 1900 and a 1.56 m optical reflector have been operated since November 1987. In 1994 the seeing is better than 1 and the night sky brightness in V is about 19 mag/arcsec 2, stars fainter than 20 mag with CCD are visibles. In 2007 a large playground was built in Zô Cè area. The light pollution is severe gradually. The night sky brightness has been increased to 15.8 mag/arcsec 2. The other observatories have similar situation. New site surveys and found new stations to solve the problem. Except the solar and radio stations of each Astronomical Observatory, now there are 3 optical observing sites at PMO (Hong-He, Xu-Yi and Yaoan), 2 at SHAO (Zô Cè and Tian Huang Ping) and 2 at YNAO (Kunming and Gao-Mei-Gu) as well as 1 optical observing site at BAO (Xing-Long). The best observing site is Gao-Mei-Gu, which is selected as the optical observing site of YNAO and where atmospheric turbulence distribution is 0.11 near ground with heights from 6.5m to 2.7m during night. Sky brightness in B and V band

BOOK REVIEW: The Wandering Astronomer

Science.gov (United States)

Swinbank, Elizabeth

2000-09-01

Fans of Patrick Moore will like this book. I enjoyed it more than I expected, having anticipated a collection of personal anecdotes of the type favoured by certain tedious after-dinner speakers. Some of the 41 short items it contains do tend towards that category, but there are also some nuggets which might enliven your physics teaching. For example, did you know that, in a murder trial in 1787, the defendant's belief that the Sun was inhabited was cited as evidence of his insanity? This was despite his views being shared by many astronomers of the day including William Herschel. Or that Clyde Tombaugh had a cat called Pluto after the planet he discovered, which was itself named by an eleven-year-old girl? Another gem concerns a brief flurry, in the early 1990s, over a suspected planet orbiting a pulsar; variations in the arrival time of its radio pulses indicated the presence of an orbiting body. These shifts were later found to arise from an error in a computer program that corrected for the Earth's motion. The programmer had assumed a circular orbit for the Earth whereas it is actually elliptical. The book is clearly intended for amateur astronomers and followers of Patrick Moore's TV programmes. There is plenty of astronomy, with an emphasis on the solar system, but very little astrophysics. The author's metricophobia means that quantities are given in imperial units throughout, with metric equivalents added in brackets (by an editor, I suspect) which can get irritating, particularly as powers-of-ten notation is avoided. It is quite a novelty to see the temperature for hydrogen fusion quoted as 18 000 000 °F (10 000 000 °C). By way of contrast, astronomical terms are used freely - ecliptic, first-magnitude star, and so on. Such terms are defined in a glossary at the end, but attention is not drawn to this and I only stumbled across it by chance. Patrick Moore obviously knows his public, and this book will serve them well. For physics teachers and students

A Virtual Astronomical Research Machine in No Time (VARMiNT)

Science.gov (United States)

Beaver, John

2012-05-01

We present early results of using virtual machine software to help make astronomical research computing accessible to a wider range of individuals. Our Virtual Astronomical Research Machine in No Time (VARMiNT) is an Ubuntu Linux virtual machine with free, open-source software already installed and configured (and in many cases documented). The purpose of VARMiNT is to provide a ready-to-go astronomical research computing environment that can be freely shared between researchers, or between amateur and professional, teacher and student, etc., and to circumvent the often-difficult task of configuring a suitable computing environment from scratch. Thus we hope that VARMiNT will make it easier for individuals to engage in research computing even if they have no ready access to the facilities of a research institution. We describe our current version of VARMiNT and some of the ways it is being used at the University of Wisconsin - Fox Valley, a two-year teaching campus of the University of Wisconsin System, as a means to enhance student independent study research projects and to facilitate collaborations with researchers at other locations. We also outline some future plans and prospects.

Harvey Butcher: a passion for astronomical instrumentation

Science.gov (United States)

Bhathal, Ragbir

2014-11-01

This paper covers some aspects of the scientific life of Harvey Butcher who was the Director of the Research School for Astronomy and Astrophysics at the Australian National University in Canberra from September 2007 to January 2013. He has made significant contributions to research on the evolution of galaxies, nucleosynthesis, and on the design and implementation of advanced astronomical instrumentation including LOFAR (Low Frequency Array Radio telescope). He is well known for his discovery of the Butcher-Oemler effect. Before coming to Australia he was the Director of the Netherlands Foundation for Research in Astronomy from September 1991 to January 2007. In 2005 he was awarded a Knighthood in the Order of the Netherlands Lion for contributions to interdisciplinary science, innovation and public outreach.This paper is based on an interview conducted by the author with Harvey Butcher for the National Project on Significant Australian Astronomers sponsored by the National Library of Australia. Except otherwise stated, all quotations used in this paper are from the Butcher interview which has been deposited in the Oral History Archives of the National Library.

Test facility for astronomical x-ray optics

DEFF Research Database (Denmark)

Christensen, Finn Erland; Lewis, Robert A.; Bordas, J.

1990-01-01

Grazing incidence x-ray optics for x-ray astronomical applications are used outside the earth's atmosphere. These devices require a large collection aperture and the imaging of an x-ray source that is essentially placed at infinity. The ideal testing system for these optical elements has to appro......Grazing incidence x-ray optics for x-ray astronomical applications are used outside the earth's atmosphere. These devices require a large collection aperture and the imaging of an x-ray source that is essentially placed at infinity. The ideal testing system for these optical elements has...... to approximate that encountered under working conditions; however, the testing of these optical elements is notoriously difficult with conventional x-ray generators. Synchrotron radiation (SR) sources are sufficiently brilliant to produce a nearly perfect parallel beam over a large area while still retaining...... a flux considerably higher than that available from conventional x-ray generators. A facility designed for the testing of x-ray optics, particularly in connection with x-ray telescopes, is described. It is proposed that this facility will be accommodated at the Synchrotron Radiation Source...

Sketching the moon an astronomical artist's guide

CERN Document Server

Handy, Richard; McCague, Thomas; Rix, Erika; Russell, Sally

2012-01-01

Soon after you begin studying the sky through your small telescope or binoculars, you will probably be encouraged by others to make sketches of what you see. Sketching is a time-honored tradition in amateur astronomy and dates back to the earliest times, when telescopes were invented. Even though we have lots of new imaging technologies nowadays, including astrophotography, most observers still use sketching to keep a record of what they see, make them better observers, and in hopes of perhaps contributing something to the body of scientific knowledge about the Moon. Some even sketch because it satisfies their artistic side. The Moon presents some unique challenges to the astronomer-artist, the Moon being so fond of tricks of the light. Sketching the Moon: An Astronomical Artist’s Guide, by five of the best lunar observer-artists working today, will guide you along your way and help you to achieve really high-quality sketches. All the major types of lunar features are covered, with a variety of sketching te...

SAADA: Astronomical Databases Made Easier

Science.gov (United States)

Michel, L.; Nguyen, H. N.; Motch, C.

2005-12-01

Many astronomers wish to share datasets with their community but have not enough manpower to develop databases having the functionalities required for high-level scientific applications. The SAADA project aims at automatizing the creation and deployment process of such databases. A generic but scientifically relevant data model has been designed which allows one to build databases by providing only a limited number of product mapping rules. Databases created by SAADA rely on a relational database supporting JDBC and covered by a Java layer including a lot of generated code. Such databases can simultaneously host spectra, images, source lists and plots. Data are grouped in user defined collections whose content can be seen as one unique set per data type even if their formats differ. Datasets can be correlated one with each other using qualified links. These links help, for example, to handle the nature of a cross-identification (e.g., a distance or a likelihood) or to describe their scientific content (e.g., by associating a spectrum to a catalog entry). The SAADA query engine is based on a language well suited to the data model which can handle constraints on linked data, in addition to classical astronomical queries. These constraints can be applied on the linked objects (number, class and attributes) and/or on the link qualifier values. Databases created by SAADA are accessed through a rich WEB interface or a Java API. We are currently developing an inter-operability module implanting VO protocols.

Procesos para una Astronomía que le aporte a Colombia

OpenAIRE

Duque Escobar, Gonzalo

2011-01-01

Se ha validado el Plan Nacional de Desarrollo Tecnológico en Astronomía 2011-2030, para el Plan Estratégico 2009-2012 de la Comisión Colombiana del Espacio CCE, por el Grupo de Astronáutica, Astronomía y Medicina Aeroespacial. Esperamos que el grupo de astrónomos convocado, responsable de la investigación centrado en procesos científicos existentes y no en distractores, pueda señalar las acciones pertinentes e identificar los recursos necesarios, para hacer viable un desarrollo científico y t...

Explaining formation of Astronomical Jets using Dynamic Universe Model

Science.gov (United States)

Naga Parameswara Gupta, Satyavarapu

2016-07-01

Astronomical jets are observed from the centres of many Galaxies including our own Milkyway. The formation of such jet is explained using SITA simulations of Dynamic Universe Model. For this purpose the path traced by a test neutron is calculated and depicted using a set up of one densemass of the mass equivalent to mass of Galaxy center, 90 stars with similar masses of stars near Galaxy center, mass equivalents of 23 Globular Cluster groups, 16 Milkyway parts, Andromeda and Triangulum Galaxies at appropriate distances. Five different kinds of theoretical simulations gave positive results The path travelled by this test neutron was found to be an astronomical jet emerging from Galaxy center. This is another result from Dynamic Universe Model. It solves new problems like a. Variable Mass Rocket Trajectory Problem b. Explaining Very long baseline interferometry (VLBI) observations c. Astronomical jets observed from Milkyway Center d. Prediction of Blue shifted Galaxies e. Explaining Pioneer Anomaly f. Prediction of New Horizons satellite trajectory etc. Dynamic Universe Model never reduces to General relativity on any condition. It uses a different type of mathematics based on Newtonian physics. This mathematics used here is simple and straightforward. As there are no differential equations present in Dynamic Universe Model, the set of equations give single solution in x y z Cartesian coordinates for every point mass for every time step

Parabolized Navier-Stokes solutions of separation and trailing-edge flows

Science.gov (United States)

Brown, J. L.

1983-01-01

A robust, iterative solution procedure is presented for the parabolized Navier-Stokes or higher order boundary layer equations as applied to subsonic viscous-inviscid interaction flows. The robustness of the present procedure is due, in part, to an improved algorithmic formulation. The present formulation is based on a reinterpretation of stability requirements for this class of algorithms and requires only second order accurate backward or central differences for all streamwise derivatives. Upstream influence is provided for through the algorithmic formulation and iterative sweeps in x. The primary contribution to robustness, however, is the boundary condition treatment, which imposes global constraints to control the convergence path. Discussed are successful calculations of subsonic, strong viscous-inviscid interactions, including separation. These results are consistent with Navier-Stokes solutions and triple deck theory.

A mimetic finite difference method for the Stokes problem with elected edge bubbles

Energy Technology Data Exchange (ETDEWEB)

Lipnikov, K [Los Alamos National Laboratory; Berirao, L [DIPARTMENTO DI MATERMATICA

2009-01-01

A new mimetic finite difference method for the Stokes problem is proposed and analyzed. The unstable P{sub 1}-P{sub 0} discretization is stabilized by adding a small number of bubble functions to selected mesh edges. A simple strategy for selecting such edges is proposed and verified with numerical experiments. The discretizations schemes for Stokes and Navier-Stokes equations must satisfy the celebrated inf-sup (or the LBB) stability condition. The stability condition implies a balance between discrete spaces for velocity and pressure. In finite elements, this balance is frequently achieved by adding bubble functions to the velocity space. The goal of this article is to show that the stabilizing edge bubble functions can be added only to a small set of mesh edges. This results in a smaller algebraic system and potentially in a faster calculations. We employ the mimetic finite difference (MFD) discretization technique that works for general polyhedral meshes and can accomodate non-uniform distribution of stabilizing bubbles.

La astronomía: ciencia olvidada en la escuela, ¿cómo recuperarla?

OpenAIRE

Aranzazu Zea, Daniel Alejandro

2013-01-01

Resumen: Esta propuesta tiene la intención de diseñar una cartilla para la enseñanza de la astronomía en la básica primaria, principalmente en el Colegio Santo Domingo de Guzmán, ubicado en el sector de Zamora, Bello. Se inicia la propuesta debido a que en el Colegio la astronomía no es un tema de mucha importancia en la enseñanza y es muy poca la transversalización con las diferentes áreas de la institución. La astronomía es vista como algo aparte de todas las asignaturas, sin saber la gran ...

The Navier-Stokes Equations Theory and Numerical Methods

CERN Document Server

Masuda, Kyûya; Rautmann, Reimund; Solonnikov, Vsevolod

1990-01-01

These proceedings contain original (refereed) research articles by specialists from many countries, on a wide variety of aspects of Navier-Stokes equations. Additionally, 2 survey articles intended for a general readership are included: one surveys the present state of the subject via open problems, and the other deals with the interplay between theory and numerical analysis.

The planar Dirichlet problem for the Stokes equations

Czech Academy of Sciences Publication Activity Database

Medková, Dagmar; Varnhorn, W.

2011-01-01

Roč. 34, č. 9 (2011), s. 1097-1109 ISSN 0170-4214 R&D Projects: GA AV ČR IAA100190804 Institutional research plan: CEZ:AV0Z10190503 Keywords : Stokes system * single- layer potential * double - layer potential Subject RIV: BA - General Mathematics Impact factor: 0.743, year: 2011 http://onlinelibrary.wiley.com/doi/10.1002/mma.1425/full

Radio Recombination Lines Their Physics and Astronomical Applications

CERN Document Server

Gordon, MA

2008-01-01

Includes the history of RRL detections, the astrophysics underlying their intensities and line shapes including topics like departures from LTE and Stark broadening, the maximum possible size of an atom, and descriptions of the astronomical topics for which RRLs have proved to be effective tools.

Radio astronomical interferometry and x-ray's computerized tomography

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, L F [Universidad Nacional Autonoma de Mexico, Mexico City. Inst. de Astronomia

1982-01-01

Radio astronomical interferometry and computerized tomography are techniques of great importance for astronomy and medicine, respectively. In this paper we emphasize that both techniques are based on the same mathematical principles, and present them as an example of interaction between basic and applied science.

Metal-Containing Molecules Beyond the Solar System: a Laboratory and Radio Astronomical Perspective

Science.gov (United States)

Ziurys, L. M.

2010-06-01

Although the history of interstellar molecules began around 1970, with the millimeter-wave detection of CO in the Orion Nebula, metal-containing species have been somewhat elusive for astronomical searches. Only in the past two decades have metal-bearing molecules been identified in space, starting with metal halides (NaCl, KCl, AlCl, and AlF), and then metal cyanide and isocyanide species (MgNC, MgCN, NaCN, and AlNC). Moreover, the metal-containing molecules seemed to be present in a single astronomical object: the envelope of a dying, carbon-rich star, IRC+10216. However, with improvements both in laboratory spectroscopy and telescope sensitivity, it is becoming clear that the relevance of metal-containing species in astrophysics is increasing. Metal oxide and hydroxide species, such as AlO and AlOH, have recently been identified in interstellar space. Metal-containing molecules are now being found in other astronomical sources, such as the oxygen-rich shell surrounding VY Canis Majoris, a supergiant star. These new astronomical discoveries will be presented, as well as the laboratory measurements that made them possible. New directions in rotational spectroscopy of metal-bearing molecules will also be discussed.

Improving the Determination of Eastern Elongations of Planetary Satellites in the Astronomical Almanac

Science.gov (United States)

Rura, Christopher; Stollberg, Mark

2018-01-01

The Astronomical Almanac is an annual publication of the US Naval Observatory (USNO) and contains a wide variety of astronomical data used by astronomers worldwide as a general reference or for planning observations. Included in this almanac are the times of greatest eastern and northern elongations of the natural satellites of the planets, accurate to 0.1 hour UT. The production code currently used to determine elongation times generates X and Y coordinates for each satellite (16 total) in 5 second intervals. This consequentially caused very large data files, and resulted in the program devoted to determining the elongation times to be computationally intensive. To make this program more efficient, we wrote a Python program to fit a cubic spline to data generated with a 6-minute time step. This resulted in elongation times that were found to agree with those determined from the 5 second data currently used in a large number of cases and was tested for 16 satellites between 2017 and 2019. The accuracy of this program is being tested for the years past 2019 and, if no problems are found, the code will be considered for production of this section of The Astronomical Almanac.

Pipe Flow and Wall Turbulence Using a Modified Navier-Stokes Equation

International Nuclear Information System (INIS)

Jirkovsky, L.; Muriel, A.

2012-01-01

We use a derived incompressible modified Navier-Stokes equation to model pipe flow and wall turbulence. We reproduce the observed flattened paraboloid velocity profiles of turbulence that cannot be obtained directly using standard incompressible Navier-Stokes equation. The solutions found are in harmony with multi-valued velocity fields as a definition of turbulence. Repeating the procedure for the flow of turbulent fluid between two parallel flat plates we find similar flattened velocity profiles. We extend the analysis to the turbulent flow along a single wall and compare the results with experimental data and the established controversial von Karman logarithmic law of the wall. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Global solubility of the three-dimensional Navier-Stokes equations with uniformly large initial vorticity

International Nuclear Information System (INIS)

Makhalov, A S; Nikolaenko, V P

2003-01-01

This paper is a survey of results concerning the three-dimensional Navier-Stokes and Euler equations with initial data characterized by uniformly large vorticity. The existence of regular solutions of the three-dimensional Navier-Stokes equations on an unbounded time interval is proved for large initial data both in R 3 and in bounded cylindrical domains. Moreover, the existence of smooth solutions on large finite time intervals is established for the three-dimensional Euler equations. These results are obtained without additional assumptions on the behaviour of solutions for t>0. Any smooth solution is not close to any two-dimensional manifold. Our approach is based on the computation of singular limits of rapidly oscillating operators, non-linear averaging, and a consideration of the mutual absorption of non-linear oscillations of the vorticity field. The use of resonance conditions, methods from the theory of small divisors, and non-linear averaging of almost periodic functions leads to the limit resonant Navier-Stokes equations. Global solubility of these equations is proved without any conditions on the three-dimensional initial data. The global regularity of weak solutions of three-dimensional Navier-Stokes equations with uniformly large vorticity at t=0 is proved by using the regularity of weak solutions and the strong convergence

Astronomers Gain Clues About Fundamental Physics

Science.gov (United States)

2005-12-01

An international team of astronomers has looked at something very big -- a distant galaxy -- to study the behavior of things very small -- atoms and molecules -- to gain vital clues about the fundamental nature of our entire Universe. The team used the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) to test whether the laws of nature have changed over vast spans of cosmic time. The Green Bank Telescope The Robert C. Byrd Green Bank Telescope CREDIT: NRAO/AUI/NSF (Click on image for GBT gallery) "The fundamental constants of physics are expected to remain fixed across space and time; that's why they're called constants! Now, however, new theoretical models for the basic structure of matter indicate that they may change. We're testing these predictions." said Nissim Kanekar, an astronomer at the National Radio Astronomy Observatory (NRAO), in Socorro, New Mexico. So far, the scientists' measurements show no change in the constants. "We've put the most stringent limits yet on some changes in these constants, but that's not the end of the story," said Christopher Carilli, another NRAO astronomer. "This is the exciting frontier where astronomy meets particle physics," Carilli explained. The research can help answer fundamental questions about whether the basic components of matter are tiny particles or tiny vibrating strings, how many dimensions the Universe has, and the nature of "dark energy." The astronomers were looking for changes in two quantities: the ratio of the masses of the electron and the proton, and a number physicists call the fine structure constant, a combination of the electron charge, the speed of light and the Planck constant. These values, considered fundamental physical constants, once were "taken as time independent, with values given once and forever" said German particle physicist Christof Wetterich. However, Wetterich explained, "the viewpoint of modern particle theory has changed in recent years," with ideas such as

Astronomical tunings of the Oligocene-Miocene transition from Pacific Ocean Site U1334 and implications for the carbon cycle

NARCIS (Netherlands)

Beddow, Helen M.; Liebrand, Diederik; Wilson, Douglas S.; Hilgen, Frits J.; Sluijs, Appy; Wade, Bridget S.; Lourens, Lucas J.

2018-01-01

Astronomical tuning of sediment sequences requires both unambiguous cycle pattern recognition in climate proxy records and astronomical solutions, as well as independent information about the phase relationship between these two. Here we present two different astronomically tuned age models for the

On Coupled System of Navier-Stokes Equations and Temperature

African Journals Online (AJOL)

Dr. Anthony Peter

ABSTRACT. This paper deals with the coupled system of Navier-Stokes equations and temperature (Thermohydraulics) in a strip in the class of spatially non-decaying (infinite-energy) solutions belonging to the properly chosen uniformly local Sobolev spaces. The global well-posedness and dissipativity of the Navier- ...

Support for the Astronomically Calibrated 40Ar/39Ar Age of Fish Canyon Sanidine

DEFF Research Database (Denmark)

Rivera, Tiffany; Storey, Michael; Zeeden, Christian

2011-01-01

al. (2008) determined an astronomically calibrated 40Ar/39Ar age of 28.201 0.046 Ma (2), relative to the indirect astronomically tuned Moroccan Melilla Basin Messâdit section. Here, we provide independent verification for the Kuiper, et al. (2008) FCs age using sanidines extracted from the A1 tephra...

Alexander the Great's Tomb at Siwa: The Astronomical Orientation

Science.gov (United States)

Papathanassiou, M.; Souvaltzis, Em.; Souvaltzi, L.; Moussas, X.

A preliminary report on the possible astronomical orientation of the Tomb of Alexander the Great, recently found and excavated by the greek archaeologist Liana Souvaltzi. The tomb is a greek building of doric style. Its enormous dimensions make it the largest amongst the found macedonian tombs (much bigger than the tomb of Philip II, Alexander's father). The tomb faces generally south---west and its orientation could be related either to the constellation of Centaurus or to the star Canopus. The walls of the two long sides of the building have strickingly different widhts. Moreover each wall has three doors (opposite in pairs) of slightly different sizes. We examine the possibility the openings of the doors and their assymetries to be designed and constructed according to some astronomical (solar or stellar) orientations.

Generation of sub-100-fs Stokes pulses upon SRS in a barium nitrate crystal

International Nuclear Information System (INIS)

Konyashchenko, Aleksandr V; Losev, Leonid L; Tenyakov, S Yu

2010-01-01

72-fs pulses are generated at the first Stokes component frequency upon stimulated Raman scattering in a barium nitrate crystal for the radiation of the Ti 3+ :Al 2 O 3 laser with the pulse duration of 50 fs. The energy efficiency of conversion is 20%. The barium nitrate crystal was optically pumped by two consecutive orthogonally polarised chirped pulses with the following time compression of the Stokes radiation pulse. (nonlinear optical phenomena)

Viewing and imaging the solar system a guide for amateur astronomers

CERN Document Server

Clark, Jane

2015-01-01

Viewing and Imaging the Solar System: A Guide for Amateur Astronomers is for those who want to develop their ability to observe and image Solar System objects, including the planets and moons, the Sun, and comets and asteroids. They might be beginners, or they may have already owned and used an astronomical telescope for a year or more. Newcomers are almost always wowed by sights such as the rings of Saturn and the moons of Jupiter, but have little idea how to find these objects for themselves (with the obvious exceptions of the Sun and Moon). They also need guidance about what equipment to use, besides a telescope. This book is written by an expert on the Solar System, who has had a lot of experience with outreach programs, which teach others how to make the most of relatively simple and low-cost equipment. That does not mean that this book is not for serious amateurs. On the contrary, it is designed to show amateur astronomers, in a relatively light-hearted—and math-free way—how to become serious.

Boussinesq approximation of the Cahn-Hilliard-Navier-Stokes equations.

Science.gov (United States)

Vorobev, Anatoliy

2010-11-01

We use the Cahn-Hilliard approach to model the slow dissolution dynamics of binary mixtures. An important peculiarity of the Cahn-Hilliard-Navier-Stokes equations is the necessity to use the full continuity equation even for a binary mixture of two incompressible liquids due to dependence of mixture density on concentration. The quasicompressibility of the governing equations brings a short time-scale (quasiacoustic) process that may not affect the slow dynamics but may significantly complicate the numerical treatment. Using the multiple-scale method we separate the physical processes occurring on different time scales and, ultimately, derive the equations with the filtered-out quasiacoustics. The derived equations represent the Boussinesq approximation of the Cahn-Hilliard-Navier-Stokes equations. This approximation can be further employed as a universal theoretical model for an analysis of slow thermodynamic and hydrodynamic evolution of the multiphase systems with strongly evolving and diffusing interfacial boundaries, i.e., for the processes involving dissolution/nucleation, evaporation/condensation, solidification/melting, polymerization, etc.

MULTI-LINE STOKES INVERSION FOR PROMINENCE MAGNETIC-FIELD DIAGNOSTICS

International Nuclear Information System (INIS)

Casini, R.; Lopez Ariste, A.; Paletou, F.; Leger, L.

2009-01-01

We present test results on the simultaneous inversion of the Stokes profiles of the He I lines at 587.6 nm (D 3 ) and 1083.0 nm in prominences (90 deg. scattering). We created data sets of synthetic Stokes profiles for the case of quiescent prominences (B -3 of the peak intensity for the polarimetric sensitivity of the simulated observations. In this work, we focus on the error analysis for the inference of the magnetic field vector, under the usual assumption that the prominence can be assimilated to a slab of finite optical thickness with uniform magnetic and thermodynamic properties. We find that the simultaneous inversion of the two lines significantly reduces the errors on the inference of the magnetic field vector, with respect to the case of single-line inversion. These results provide a solid justification for current and future instrumental efforts with multi-line capabilities for the observations of solar prominences and filaments.

An efficient iterative method for the generalized Stokes problem

Energy Technology Data Exchange (ETDEWEB)

Sameh, A. [Univ. of Minnesota, Twin Cities, MN (United States); Sarin, V. [Univ. of Illinois, Urbana, IL (United States)

1996-12-31

This paper presents an efficient iterative scheme for the generalized Stokes problem, which arises frequently in the simulation of time-dependent Navier-Stokes equations for incompressible fluid flow. The general form of the linear system is where A = {alpha}M + vT is an n x n symmetric positive definite matrix, in which M is the mass matrix, T is the discrete Laplace operator, {alpha} and {nu} are positive constants proportional to the inverses of the time-step {Delta}t and the Reynolds number Re respectively, and B is the discrete gradient operator of size n x k (k < n). Even though the matrix A is symmetric and positive definite, the system is indefinite due to the incompressibility constraint (B{sup T}u = 0). This causes difficulties both for iterative methods and commonly used preconditioners. Moreover, depending on the ratio {alpha}/{nu}, A behaves like the mass matrix M at one extreme and the Laplace operator T at the other, thus complicating the issue of preconditioning.

A Mythological, Philosophical and Astronomical approach of our solar system

Science.gov (United States)

Drivas, Sotirios; Kastanidou, Sofia

2016-04-01

Teaching Geography in the first Class of Gymnasium - secondary education we will focus in Solar System: Astronomical approach: Students will look and find the astronomical data of the planets, they will make comparisons between the sizes of their radius, they will find the distance from the Sun, they will search the relative motion, they will calculate the gravity on each planet, etc. Mythological approach: We will search the names and meanings of the planets based on Greek mythological origin. Philosophical approach: Regarding the philosophical approach of the "solar system" we will look and find: • Why planets are called so? • How did planets get their names? • What are the periods of Greek astronomy? • What were the astronomical instruments of ancient Greeks and who did built them? • What were the Greek philosophers and astronomers? When did they live and what did they discover? • Which method did Eratosthenes of Cyrene apply about 206B.C. to serve a real measurement of the earth's radius? • What was the relationship between science and religion in ancient Greece? Literature approach: At the end of the program students will write their opinion in subject "Having a friend from another planet" based on the book of Antoine de Saint - Exupéry "The little prince". Law approach: A jurist working in Secondary Education will visits our school and engages students in the Space Law. Artistic approach: Students will create their own posters of our planetary system. The best posters will be posted on the school bulletin board to display their work. Visit: Students and teachers will visit the Observatory of Larissa where they will see how observatory works and talk with scientists about their job. They will look through telescopes and observe the sun.

Navier-Stokes-like equations for traffic flow.

Science.gov (United States)

Velasco, R M; Marques, W

2005-10-01

The macroscopic traffic flow equations derived from the reduced Paveri-Fontana equation are closed starting with the maximization of the informational entropy. The homogeneous steady state taken as a reference is obtained for a specific model of the desired velocity and a kind of Chapman-Enskog method is developed to calculate the traffic pressure at the Navier-Stokes level. Numerical solution of the macroscopic traffic equations is obtained and its characteristics are analyzed.

Astronomical Polarimetry with the RIT Polarization Imaging Camera

Science.gov (United States)

Vorobiev, Dmitry V.; Ninkov, Zoran; Brock, Neal

2018-06-01

In the last decade, imaging polarimeters based on micropolarizer arrays have been developed for use in terrestrial remote sensing and metrology applications. Micropolarizer-based sensors are dramatically smaller and more mechanically robust than other polarimeters with similar spectral response and snapshot capability. To determine the suitability of these new polarimeters for astronomical applications, we developed the RIT Polarization Imaging Camera to investigate the performance of these devices, with a special attention to the low signal-to-noise regime. We characterized the device performance in the lab, by determining the relative throughput, efficiency, and orientation of every pixel, as a function of wavelength. Using the resulting pixel response model, we developed demodulation procedures for aperture photometry and imaging polarimetry observing modes. We found that, using the current calibration, RITPIC is capable of detecting polarization signals as small as ∼0.3%. The relative ease of data collection, calibration, and analysis provided by these sensors suggest than they may become an important tool for a number of astronomical targets.

156th Symposium of the International Astronomical Union

CERN Document Server

Kołaczek, Barbara

1993-01-01

In this review talk, I would like to report on the proper motion analysis, which has been recently carried out together with M. Soma and M. Yoshizawa: There has been a persistent demand in astronomy for accurate stellar positions and proper motions, which are represented by an inertial reference system constructed on the basis of a set of consistent astronomical constants. In the reference system the precessional constant plays a primary role. In a series of papers Fricke (1967a,b, 1977a,b) has deter­ mined the luni-solar precessional correction to Newcomb's value and the fictitious motion of the equinox, which have been adopted in the "IAU (1976) System of Astronomical Con­ stants". Based on the precessional correction and the equinoctial motion thus established, the fundamental reference system, the FK5 system (Fricke et al. 1988) for positions and proper motions, has been constructed. However, for several years geodetic VLBI (McCarthy & Luzum 1991) and LLR (Williams et at. 1991) observations have bee...

Celestial delights the best astronomical events through 2020

CERN Document Server

Reddy, Francis

2012-01-01

Celestial Delights is the essential 'TV Guide' for the sky. Through extensive graphics integrated with an eight-year-long calendar of sky events, it provides a look at "don't miss" sky events, mostly for naked-eye and binocular observing. It is organized by ease of observation – lunar phases and the brighter planets come first, with solar eclipses, the aurora, and comets coming later. This third edition also includes a hefty dose of sky lore, astronomical history, and clear overviews of current science. It provides a handy reference to upcoming naked-eye events, with information broken out in clear and simple diagrams and tables that are cross-referenced against a detailed almanac for each year covered. This book puts a variety of information all in one place, presents it in a friendly way that does not require prior in-depth astronomical knowledge, and provides the context and historical background for understanding events that astronomy software or web sites lack.

Visualization of Multi-mission Astronomical Data with ESASky

Science.gov (United States)

Baines, Deborah; Giordano, Fabrizio; Racero, Elena; Salgado, Jesús; López Martí, Belén; Merín, Bruno; Sarmiento, María-Henar; Gutiérrez, Raúl; Ortiz de Landaluce, Iñaki; León, Ignacio; de Teodoro, Pilar; González, Juan; Nieto, Sara; Segovia, Juan Carlos; Pollock, Andy; Rosa, Michael; Arviset, Christophe; Lennon, Daniel; O'Mullane, William; de Marchi, Guido

2017-02-01

ESASky is a science-driven discovery portal to explore the multi-wavelength sky and visualize and access multiple astronomical archive holdings. The tool is a web application that requires no prior knowledge of any of the missions involved and gives users world-wide simplified access to the highest-level science data products from multiple astronomical space-based astronomy missions plus a number of ESA source catalogs. The first public release of ESASky features interfaces for the visualization of the sky in multiple wavelengths, the visualization of query results summaries, and the visualization of observations and catalog sources for single and multiple targets. This paper describes these features within ESASky, developed to address use cases from the scientific community. The decisions regarding the visualization of large amounts of data and the technologies used were made to maximize the responsiveness of the application and to keep the tool as useful and intuitive as possible.

About local fractional three-dimensional compressible Navier-Stokes equations in Cantor-type cylindrical co-ordinate system

Directory of Open Access Journals (Sweden)

Gao Guo-Ping

2016-01-01

Full Text Available In this article, we investigate the local fractional 3-D compressible Navier-Stokes equation via local fractional derivative. We use the Cantor-type cylindrical co-ordinate method to transfer 3-D compressible Navier-Stokes equation from the Cantorian co-ordinate system to the Cantor-type cylindrical co-ordinate system.

Effective temperatures and the breakdown of the Stokes-Einstein relation for particle suspensions.

Science.gov (United States)

Mendoza, Carlos I; Santamaría-Holek, I; Pérez-Madrid, A

2015-09-14

The short- and long-time breakdown of the classical Stokes-Einstein relation for colloidal suspensions at arbitrary volume fractions is explained here by examining the role that confinement and attractive interactions play in the intra- and inter-cage dynamics executed by the colloidal particles. We show that the measured short-time diffusion coefficient is larger than the one predicted by the classical Stokes-Einstein relation due to a non-equilibrated energy transfer between kinetic and configuration degrees of freedom. This transfer can be incorporated in an effective kinetic temperature that is higher than the temperature of the heat bath. We propose a Generalized Stokes-Einstein relation (GSER) in which the effective temperature replaces the temperature of the heat bath. This relation then allows to obtain the diffusion coefficient once the viscosity and the effective temperature are known. On the other hand, the temporary cluster formation induced by confinement and attractive interactions of hydrodynamic nature makes the long-time diffusion coefficient to be smaller than the corresponding one obtained from the classical Stokes-Einstein relation. Then, the use of the GSER allows to obtain an effective temperature that is smaller than the temperature of the heat bath. Additionally, we provide a simple expression based on a differential effective medium theory that allows to calculate the diffusion coefficient at short and long times. Comparison of our results with experiments and simulations for suspensions of hard and porous spheres shows an excellent agreement in all cases.

Tribute to an Astronomer: The Work of Max Ernst on Wilhelm Tempel

Science.gov (United States)

Nazé, Yaël

2016-05-01

In 1964-1974, the German artist Max Ernst created, with the help of two friends, a series of works (books, movie, and paintings) related to the astronomer Wilhelm Tempel. Mixing actual texts by Tempel and artistic features, this series pays homage to the astronomer by recalling his life and discoveries. Moreover, the core of the project, the book Maximiliana or the Illegal Practice of Astronomy, actually depicts the way science works, making this work of art a most original tribute to a scientist.

Using Modern Technologies to Capture and Share Indigenous Astronomical Knowledge

Science.gov (United States)

Nakata, Martin; Hamacher, Duane W.; Warren, John; Byrne, Alex; Pagnucco, Maurice; Harley, Ross; Venugopal, Srikumar; Thorpe, Kirsten; Neville, Richard; Bolt, Reuben

2014-06-01

Indigenous Knowledge is important for Indigenous communities across the globe and for the advancement of our general scientific knowledge. In particular, Indigenous astronomical knowledge integrates many aspects of Indigenous Knowledge, including seasonal calendars, navigation, food economics, law, ceremony, and social structure. Capturing, managing, and disseminating this knowledge in the digital environment poses a number of challenges, which we aim to address using a collaborative project emerging between experts in the higher education, library, archive and industry sectors. Using Microsoft's WorldWide Telescope and Rich Interactive Narratives technologies, we propose to develop software, media design, and archival management solutions to allow Indigenous communities to share their astronomical knowledge with the world on their terms and in a culturally sensitive manner.

Mixed isogeometric finite cell methods for the stokes problem

NARCIS (Netherlands)

Hoang, T.; Verhoosel, C.V.; Auricchio, F.; van Brummelen, E.H.; Reali, A.

2017-01-01

We study the application of the Isogeometric Finite Cell Method (IGA-FCM) to mixed formulations in the context of the Stokes problem. We investigate the performance of the IGA-FCM when utilizing some isogeometric mixed finite elements, namely: Taylor-Hood, Sub-grid, Raviart-Thomas, and Nédélec

Stirring by blinking rotlets in a bounded Stokes flow

NARCIS (Netherlands)

Woude, van der D.; Clercx, H.J.H.; Heijst, van G.J.F.; Meleshko, V.V.

2004-01-01

A blinking rotlet model is used for the analysis of stirring in a Stokes flow in a rectangular domain. After the two-dimensional biharmonic equation is solved analytically, the associated velocity field of a pair of blinking rotlets positioned symmetrically on the y -axis, is used studying the

Finite elements volumes methods: applications to the Navier-Stokes equations and convergence results

International Nuclear Information System (INIS)

Emonot, P.

1992-01-01

In the first chapter are described the equations modeling incompressible fluid flow and a quick presentation of finite volumes method. The second chapter is an introduction to the finite elements volumes method. The box model is described and a method adapted to Navier-Stokes problems is proposed. The third chapter shows a fault analysis of the finite elements volumes method for the Laplacian problem and some examples in one, two, three dimensional calculations. The fourth chapter is an extension of the error analysis of the method for the Navier-Stokes problem

Available Tools and Challenges Classifying Cutting-Edge and Historical Astronomical Documents

Science.gov (United States)

Lagerstrom, Jill

2015-08-01

The STScI Library assists the Science Policies Division in evaluating and choosing scientific keywords and categories for proposals for the Hubble Space Telescope mission and the upcoming James Webb Space Telescope mission. In addition we are often faced with the question “what is the shape of the astronomical literature?” However, subject classification in astronomy in recent times has not been cultivated. This talk will address the available tools and challenges of classifying cutting-edge as well as historical astronomical documents. In at the process, we will give an overview of current and upcoming practices of subject classification in astronomy.

AstroWeb -- Internet Resources for Astronomers

Science.gov (United States)

Jackson, R. E.; Adorf, H.-M.; Egret, D.; Heck, A.; Koekemoer, A.; Murtagh, F.; Wells, D. C.

AstroWeb is a World Wide Web (WWW) interface to a collection of Internet accessible resources aimed at the astronomical community. The collection currently contains more than 1000 WWW, Gopher, Wide Area Information System (WAIS), Telnet, and Anonymous FTP resources, and it is still growing. AstroWeb provides the additional value-added services: categorization of each resource; descriptive paragraphs for some resources; searchable index of all resource information; 3 times daily search for ``dead'' or ``unreliable'' resources.

Astronomical Image Compression Techniques Based on ACC and KLT Coder

Directory of Open Access Journals (Sweden)

J. Schindler

2011-01-01

Full Text Available This paper deals with a compression of image data in applications in astronomy. Astronomical images have typical specific properties — high grayscale bit depth, size, noise occurrence and special processing algorithms. They belong to the class of scientific images. Their processing and compression is quite different from the classical approach of multimedia image processing. The database of images from BOOTES (Burst Observer and Optical Transient Exploring System has been chosen as a source of the testing signal. BOOTES is a Czech-Spanish robotic telescope for observing AGN (active galactic nuclei and the optical transient of GRB (gamma ray bursts searching. This paper discusses an approach based on an analysis of statistical properties of image data. A comparison of two irrelevancy reduction methods is presented from a scientific (astrometric and photometric point of view. The first method is based on a statistical approach, using the Karhunen-Loeve transform (KLT with uniform quantization in the spectral domain. The second technique is derived from wavelet decomposition with adaptive selection of used prediction coefficients. Finally, the comparison of three redundancy reduction methods is discussed. Multimedia format JPEG2000 and HCOMPRESS, designed especially for astronomical images, are compared with the new Astronomical Context Coder (ACC coder based on adaptive median regression.

Extracting meaning from astronomical telegrams

Science.gov (United States)

Graham, Matthew; Conwill, L.; Djorgovski, S. G.; Mahabal, A.; Donalek, C.; Drake, A.

2011-01-01

The rapidly emerging field of time domain astronomy is one of the most exciting and vibrant new research frontiers, ranging in scientific scope from studies of the Solar System to extreme relativistic astrophysics and cosmology. It is being enabled by a new generation of large synoptic digital sky surveys - LSST, PanStarrs, CRTS - that cover large areas of sky repeatedly, looking for transient objects and phenomena. One of the biggest challenges facing these is the automated classification of transient events, a process that needs machine-processible astronomical knowledge. Semantic technologies enable the formal representation of concepts and relations within a particular domain. ATELs (http://www.astronomerstelegram.org) are a commonly-used means for reporting and commenting upon new astronomical observations of transient sources (supernovae, stellar outbursts, blazar flares, etc). However, they are loose and unstructured and employ scientific natural language for description: this makes automated processing of them - a necessity within the next decade with petascale data rates - a challenge. Nevertheless they represent a potentially rich corpus of information that could lead to new and valuable insights into transient phenomena. This project lies in the cutting-edge field of astrosemantics, a branch of astroinformatics, which applies semantic technologies to astronomy. The ATELs have been used to develop an appropriate concept scheme - a representation of the information they contain - for transient astronomy using aspects of natural language processing. We demonstrate that it is possible to infer the subject of an ATEL from the vocabulary used and to identify previously unassociated reports.

Multigrid and defect correction for the steady Navier-Stokes equations

NARCIS (Netherlands)

Koren, B.

1990-01-01

Theoretical and experimental convergence results are presented for nonlinear multigrid and iterative defect correction applied to finite volume discretizations of the full, steady, 2D, compressible Navier-Stokes equations. Iterative defect correction is introduced for circumventing the difficulty in

MPFA algorithm for solving stokes-brinkman equations on quadrilateral grids

KAUST Repository

Iliev, Oleg; Kirsch, Ralf; Lakdawala, Zahra; Printsypar, Galina

2014-01-01

This work is concerned with the development of a robust and accurate numerical method for solving the Stokes-Brinkman system of equations, which describes a free fluid flow coupled with a flow in porous media. Quadrilateral boundary fitted grid

Shape Optimization for Navier-Stokes Equations with Algebraic Turbulence Model: Existence Analysis

International Nuclear Information System (INIS)

Bulicek, Miroslav; Haslinger, Jaroslav; Malek, Josef; Stebel, Jan

2009-01-01

We study a shape optimization problem for the paper machine headbox which distributes a mixture of water and wood fibers in the paper making process. The aim is to find a shape which a priori ensures the given velocity profile on the outlet part. The mathematical formulation leads to an optimal control problem in which the control variable is the shape of the domain representing the header, the state problem is represented by a generalized stationary Navier-Stokes system with nontrivial mixed boundary conditions. In this paper we prove the existence of solutions both to the generalized Navier-Stokes system and to the shape optimization problem

Transition from fractional to classical Stokes-Einstein behaviour in simple fluids.

Science.gov (United States)

Coglitore, Diego; Edwardson, Stuart P; Macko, Peter; Patterson, Eann A; Whelan, Maurice

2017-12-01

An optical technique for tracking single particles has been used to evaluate the particle diameter at which diffusion transitions from molecular behaviour described by the fractional Stokes-Einstein relationship to particle behaviour described by the classical Stokes-Einstein relationship. The results confirm a prior prediction from molecular dynamic simulations that there is a particle size at which transition occurs and show it is inversely dependent on concentration and viscosity but independent of particle density. For concentrations in the range 5 × 10 -3 to 5 × 10 -6  mg ml -1 and viscosities from 0.8 to 150 mPa s, the transition was found to occur in the diameter range 150-300 nm.

Strasbourg Astronomical Data Center (CDS

Directory of Open Access Journals (Sweden)

F Genova

2013-01-01

Full Text Available The Centre de Donnees astronomiques de Strasbourg (CDS, created in 1972, has been a pioneer in the dissemination of digital scientific data. Ensuring sustainability for several decades has been a major issue because science and technology evolve continuously and the data flow increases endlessly. The paper briefly describes CDS activities, major services, and its R&D strategy to take advantage of new technologies. The next frontiers for CDS are the new Web 2.0/3.0 paradigm and, at a more general level, global interoperability of astronomical on-line resources in the Virtual Observatory framework.

Proceedings of the VI Serbian-Bulgarian Astronomical Conference, May 7 - 11 2008, Belgrade, Serbia

Science.gov (United States)

Dimitrijević, M. S.; Tsvetkov, M.; Popović, L. C.; Golev, V.

2009-07-01

The Sixth Serbian-Bulgarian Astronomical Conference was organized by Belgrade Astronomical Observatory, and held in Belgrade, in the building of Mathematical Faculty in Jagiceva Street, from 75th to 11th May 2008. Co-organizers were Mathematical Faculty, Astronomical Society "Rudjer Boskovic", Institute of Astronomy of the Bulgarian Academy of Sciences (BAS), Space Research Institute of BAS and Department of Astronomy of the University of Sofia. Co-chairmen of the Scientific Organizing Committee were Milan Dimitrijevic and Milcho Tsvetkov and Co-vice chairmen Luka C. Popovic and Valeri Golev. Chair of the Local Organizing Committee was Andjelka Kovacevic. The conference [was] attended by 58 participants. From Serbia were 36, from Belgrade Astronomical Observatory, Mathematical Faculty, Faculty of Sciences from Nis, Institute of Physics from Zemum, High School for pedagogues of occupational studies from Aleksinac, Faculty of Sciences from Kragujevac, Mathematical Institute of Serbian Academy of Sciences and Arts, Astronomical Society "Rudjer Boskovic" and Astronomical Society "Magellanic Cloud." From Bulgaria were present 17 colleagues: Svetlana Boeva, Ana Borisova, Momchil Dechev, Peter Duchlev, Lostadinka Koleva, Georgi Petrov, Vasil Popov, Konstatin Stavrev, Katya Ysvetkova and Milcho Tsvetkov from Institute of Astronomy of BAS, Rumen Bogdanovski and Krasmimira Ianova from Space Research Institute of BAS, Georgi R. Ivanov, Georgi Petrov and Grigor Nikolov from Department of Astronomy, Sofia University "St Kliment Ohridski,", Yavor Chapanov from Central Laboratory for Geodesy of BAS and Petya Pavlova from Technical University of Sofia, Branch Plovdiv. Besides participants from Serbia and Bulgaria the Conference [was] attended [by] Vlado Milicevic from Canada, Jan Vondrak from Czech Republic, Aytap Sezer from Turkey and Tetyana Sergeeva and Alexandr Sergeev from Ukraine. On the Conference were presented 13 invited lectures, 22 short talks and 35 posters, in total

Astronomical Alignments in a Neolithic Chinese Site?

Science.gov (United States)

Nelson, S.; Stencel, R. E.

1997-12-01

In the Manchurian province of Liaoning, near 41N19' and 119E30', exist ruins of a middle Neolithic society (2500 to 4000 BC) known as the Hongshan culture. This location, called Niuheliang, is comprised of 16 locations with monumental structures scattered over 80 square kilometers of hills. Most are stone burial structures that contain jade artifacts implying wealth and power. One structure is unique in being unusually shaped and containing oversized effigies of goddess figures. This structure also has a commanding view of the surrounding landscape. The presence of decorated pottery, jade and worked copper suggests the Hongshan people were sophisticated artisans and engaged in long-distance trading. During 1997, we've conducted a course at Denver as part of our Core Curriculum program for upper division students, that has examined the astronomical and cultural aspects of the Niuheliang site, to attempt to determine whether these contemporaries of the builders of Stonehenge may have included astronomical alignments into their constructions. The preliminary result of our studies suggests that certain monuments have potential for lunar standstill observation from the "goddess temple". For updates on these results, please see our website: www.du.edu/ rstencel/core2103.html.

Integrating the IA2 Astronomical Archive in the VO: The VO-Dance Engine

Science.gov (United States)

Molinaro, M.; Laurino, O.; Smareglia, R.

2012-09-01

Virtual Observatory (VO) protocols and standards are getting mature and the astronomical community asks for astrophysical data to be easily reachable. This means data centers have to intensify their efforts to provide the data they manage not only through proprietary portals and services but also through interoperable resources developed on the basis of the IVOA (International Virtual Observatory Alliance) recommendations. Here we present the work and ideas developed at the IA2 (Italian Astronomical Archive) data center hosted by the INAF-OATs (Italian Institute for Astrophysics - Trieste Astronomical Observatory) to reach this goal. The core point is the development of an application that from existing DB and archive structures can translate their content to VO compliant resources: VO-Dance (written in Java). This application, in turn, relies on a database (potentially DBMS independent) to store the translation layer information of each resource and auxiliary content (UCDs, field names, authorizations, policies, etc.). The last token is an administrative interface (currently developed using the Django python framework) to allow the data center administrators to set up and maintain resources. This deployment, platform independent, with database and administrative interface highly customizable, means the package, when stable and easily distributable, can be also used by single astronomers or groups to set up their own resources from their public datasets.

Implicit methods for the Navier-Stokes equations

Science.gov (United States)

Yoon, S.; Kwak, D.

1990-01-01

Numerical solutions of the Navier-Stokes equations using explicit schemes can be obtained at the expense of efficiency. Conventional implicit methods which often achieve fast convergence rates suffer high cost per iteration. A new implicit scheme based on lower-upper factorization and symmetric Gauss-Seidel relaxation offers very low cost per iteration as well as fast convergence. High efficiency is achieved by accomplishing the complete vectorizability of the algorithm on oblique planes of sweep in three dimensions.

The Absence of Stokes Drift in Waves

OpenAIRE

Chafin, Clifford

2015-01-01

Stokes drift has been as central to the history of wave theory as it has been distressingly absent from experiment. Neither wave tanks nor experiments in open bodies detect this without nearly canceling "eulerian flows." Acoustic waves have an analogous problem that is particularly problematic in the vorticity production at the edges of beams. Here we demonstrate that the explanation for this arises from subtle end-of-packet and wavetrain gradient effects such as microbreaking events and wave...

Modeling Vortex Generators in a Navier-Stokes Code

Science.gov (United States)

Dudek, Julianne C.

2011-01-01

A source-term model that simulates the effects of vortex generators was implemented into the Wind-US Navier-Stokes code. The source term added to the Navier-Stokes equations simulates the lift force that would result from a vane-type vortex generator in the flowfield. The implementation is user-friendly, requiring the user to specify only three quantities for each desired vortex generator: the range of grid points over which the force is to be applied and the planform area and angle of incidence of the physical vane. The model behavior was evaluated for subsonic flow in a rectangular duct with a single vane vortex generator, subsonic flow in an S-duct with 22 corotating vortex generators, and supersonic flow in a rectangular duct with a counter-rotating vortex-generator pair. The model was also used to successfully simulate microramps in supersonic flow by treating each microramp as a pair of vanes with opposite angles of incidence. The validation results indicate that the source-term vortex-generator model provides a useful tool for screening vortex-generator configurations and gives comparable results to solutions computed using gridded vanes.

The Material Culture of Nineteenth-Century Astrometry, its Circulation and Heritage at the Astronomical Observatory of Lisbon

Science.gov (United States)

Raposo, Pedro

The Astronomical Observatory of Lisbon was founded in 1857 in the sequence of a controversy on stellar parallax measurements involving astronomers from the Observatory of Paris and the Observatory of Pulkovo. The development of this discussion led the contenders to recognize Lisbon as a suitable place to carry out this kind of measurements and to foster the field of stellar astronomy. Some local actors strived to keep up with this wave of international interest and establish a first-rank astronomical institution in the Portuguese capital. In order to fulfil this goal, correspondence was intensively exchanged with leading foreign astronomers and instrument makers. Besides, a Portuguese Navy officer bound to become the first director of the new institution was commissioned to visit several observatories and instrument workshops abroad, and to spend a few years in Pulkovo as a trainee astronomer. Although founded with generous financial support from the Portuguese crown and lavishly equipped and constructed, the Observatory of Lisbon was later affected by limiting budgets and a shortage of qualified personnel. Nevertheless, local efforts to improve instruments as well as observation and calculation techniques enabled its astronomers to yield important contributions to positional astronomy, especially towards the end of the nineteenth century and the beginnings of the twentieth century. The original instruments and spaces of the Observatory of Lisbon, strongly modelled on those of Pulkovo, are very well preserved, constituting an outstanding extant example of a mid-nineteenth century advanced observatory. The history they embody testifies the connectedness of the astronomical heritage worldwide.

Training Young Astronomers in EPO: An Update on the AAS Astronomy Ambassadors Program

Science.gov (United States)

Fraknoi, A.; Fienberg, R. T.; Gurton, S.; Schmitt, A. H.; Schatz, D.; Prather, E. E.

2014-07-01

The American Astronomical Society, with organizations active in EPO, has launched professional-development workshops and a community of practice to help improve early-career astronomers' ability to communicate effectively. Called “Astronomy Ambassadors,” the program provides mentoring and training for participants, from advanced undergraduates to beginning faculty. By learning to implement effective EPO strategies, Ambassadors become better teachers, meeting presenters, and representatives of our science to the public and government. Because young astronomers are a more diverse group than those who now do most outreach, they help the astronomy community present a more multicultural and gender-balanced face to the public, enabling underserved groups to see themselves as scientists. Ambassadors are given a library of outreach activities and materials, including many developed by cooperating organizations such as the ASP, plus some that have been created by Andrew Fraknoi specifically for this program.

Stokes vector based interpolation method to improve the efficiency of bio-inspired polarization-difference imaging in turbid media

Science.gov (United States)

Guan, Jinge; Ren, Wei; Cheng, Yaoyu

2018-04-01

We demonstrate an efficient polarization-difference imaging system in turbid conditions by using the Stokes vector of light. The interaction of scattered light with the polarizer is analyzed by the Stokes-Mueller formalism. An interpolation method is proposed to replace the mechanical rotation of the polarization axis of the analyzer theoretically, and its performance is verified by the experiment at different turbidity levels. We show that compared with direct imaging, the Stokes vector based imaging method can effectively reduce the effect of light scattering and enhance the image contrast.

Astronomers Get New Tools for Gravitational-Wave Detection

Science.gov (United States)

2010-01-01

Teamwork between gamma-ray and radio astronomers has produced a breakthrough in finding natural cosmic tools needed to make the first direct detections of the long-elusive gravitational waves predicted by Albert Einstein nearly a century ago. An orbiting gamma-ray telescope has pointed radio astronomers to specific locations in the sky where they can discover new millisecond pulsars. Millisecond pulsars, rapidly-spinning superdense neutron stars, can serve as extremely precise and stable natural clocks. Astronomers hope to detect gravitational waves by measuring tiny changes in the pulsars' rotation caused by the passage of the gravitational waves. To do this, they need a multitude of millisecond pulsars dispersed widely throughout the sky. However, nearly three decades after the discovery of the first millisecond pulsar, only about 150 of them had been found, some 90 of those clumped tightly in globular star clusters and thus unusable for detecting gravitational waves. The problem was that millisecond pulsars could only be discovered through arduous, computing-intensive searches of small portions of sky. "We've probably found far less than one percent of the millisecond pulsars in the Milky Way Galaxy," said Scott Ransom of the National Radio Astronomy Observatory (NRAO). The breakthrough came when an instrument aboard NASA's Fermi Gamma-Ray Space Telescope began surveying the sky in 2008. This instrument located hundreds of gamma-ray-emitting objects throughout our Galaxy, and astronomers suspected many of these could be millisecond pulsars. Paul Ray of the Naval Research Laboratory initiated an international collaboration to use radio telescopes to confirm the identity of these objects as millisecond pulsars. "The data from Fermi were like a buried-treasure map," Ransom said. "Using our radio telescopes to study the objects located by Fermi, we found 17 millisecond pulsars in three months. Large-scale searches had taken 10-15 years to find that many," Ransom

A strongly conservative finite element method for the coupling of Stokes and Darcy flow

KAUST Repository

Kanschat, G.

2010-08-01

We consider a model of coupled free and porous media flow governed by Stokes and Darcy equations with the Beavers-Joseph-Saffman interface condition. This model is discretized using divergence-conforming finite elements for the velocities in the whole domain. Discontinuous Galerkin techniques and mixed methods are used in the Stokes and Darcy subdomains, respectively. This discretization is strongly conservative in Hdiv(Ω) and we show convergence. Numerical results validate our findings and indicate optimal convergence orders. © 2010 Elsevier Inc.

The Superconvergence Phenomenon and Proof of the MAC Scheme for the Stokes Equations on Non-uniform Rectangular Meshes

KAUST Repository

Li, Jichun; Sun, Shuyu

2014-01-01

For decades, the widely used finite difference method on staggered grids, also known as the marker and cell (MAC) method, has been one of the simplest and most effective numerical schemes for solving the Stokes equations and Navier–Stokes equations

Astronomical virtual observatory and the place and role of Bulgarian one

Science.gov (United States)

Petrov, Georgi; Dechev, Momchil; Slavcheva-Mihova, Luba; Duchlev, Peter; Mihov, Bojko; Kochev, Valentin; Bachev, Rumen

2009-07-01

Virtual observatory could be defined as a collection of integrated astronomical data archives and software tools that utilize computer networks to create an environment in which research can be conducted. Several countries have initiated national virtual observatory programs that combine existing databases from ground-based and orbiting observatories, scientific facility especially equipped to detect and record naturally occurring scientific phenomena. As a result, data from all the world's major observatories will be available to all users and to the public. This is significant not only because of the immense volume of astronomical data but also because the data on stars and galaxies has been compiled from observations in a variety of wavelengths-optical, radio, infrared, gamma ray, X-ray and more. In a virtual observatory environment, all of this data is integrated so that it can be synthesized and used in a given study. During the autumn of the 2001 (26.09.2001) six organizations from Europe put the establishment of the Astronomical Virtual Observatory (AVO)-ESO, ESA, Astrogrid, CDS, CNRS, Jodrell Bank (Dolensky et al., 2003). Its aims have been outlined as follows: - To provide comparative analysis of large sets of multiwavelength data; - To reuse data collected by a single source; - To provide uniform access to data; - To make data available to less-advantaged communities; - To be an educational tool. The Virtual observatory includes: - Tools that make it easy to locate and retrieve data from catalogues, archives, and databases worldwide; - Tools for data analysis, simulation, and visualization; - Tools to compare observations with results obtained from models, simulations and theory; - Interoperability: services that can be used regardless of the clients computing platform, operating system and software capabilities; - Access to data in near real-time, archived data and historical data; - Additional information - documentation, user-guides, reports

Astronomical Research with the MicroObservatory Net

Science.gov (United States)

Brecher, K.; Sadler, P.; Gould, R.; Leiker, S.; Antonucci, P.; Deutsch, F.

1997-05-01

We have developed a fully integrated automated astronomical telescope system which combines the imaging power of a cooled CCD, with a self-contained and weatherized 15 cm reflecting optical telescope and mount. The MicroObservatory Net consists of five of these telescopes. They are currently being deployed around the world at widely distributed longitudes. Remote access to the MicroObservatories over the Internet has now been implemented. Software for computer control, pointing, focusing, filter selection as well as pattern recognition have all been developed as part of the project. The telescopes can be controlled in real time or in delay mode, from a Macintosh, PC or other computer using Web-based software. The Internet address of the telescopes is http://cfa- www.harvard.edu/cfa/sed/MicroObservatory/MicroObservatory.html. In the real-time mode, individuals have access to all of the telescope control functions without the need for an `on-site' operator. Users can sign up for a specific period of ti me. In the batch mode, users can submit requests for delayed telescope observations. After a MicroObservatory completes a job, the user is automatically notified by e-mail that the image is available for viewing and downloading from the Web site. The telescopes were designed for classroom instruction, as well as for use by students and amateur astronomers for original scientific research projects. We are currently examining a variety of technical and educational questions about the use of the telescopes including: (1) What are the best approaches to scheduling real-time versus batch mode observations? (2) What criteria should be used for allocating telescope time? (3) With deployment of more than one telescope, is it advantageous for each telescope to be used for just one type of observation, i.e., some for photometric use, others for imaging? And (4) What are the most valuable applications of the MicroObservatories in astronomical research? Support for the Micro

Shape optimization for Stokes problem with threshold slip

Czech Academy of Sciences Publication Activity Database

Haslinger, J.; Stebel, Jan; Taoufik, S.

2014-01-01

Roč. 59, č. 6 (2014), s. 631-652 ISSN 0862-7940 R&D Projects: GA ČR GA201/09/0917; GA ČR(CZ) GAP201/12/0671 Institutional support: RVO:67985840 Keywords : Stokes problem * friction boundary condition * shape optimization Subject RIV: BA - General Mathematics Impact factor: 0.400, year: 2014 http://link.springer.com/article/10.1007%2Fs10492-014-0077-z

Parallel computation of Euler and Navier-Stokes flows

International Nuclear Information System (INIS)

Swisshelm, J.M.; Johnson, G.M.; Kumar, S.P.

1986-01-01

A multigrid technique useful for accelerating the convergence of Euler and Navier-Stokes flow computations has been restructured to improve its performance on both SIMD and MIMD computers. The new algorithm allows both the construction of longer coarse-grid vectors and the multitasking of entire grids. Computational results are presented for the CDC Cyber 205, Cray X-MP, and Denelcor HEP I. 15 references

The Astronomical Instrument, So-Gahui Invented During King Sejong Period

Science.gov (United States)

Lee, Yong-Sam Lee; Kim, Sang-Hyuk

2002-09-01

So-ganui, namely small simplified armillary sphere, was invented as an astronomical instrument by Lee Cheon, Jeong Cho, Jung In-Ji under 16 years' rule of King Sejong. We collect records and observed data on So-ganui. It is designed to measure position of celestial sphere and to determine time. It also can be transformed equatorial to horizontal, and horizontal to equatorial coordinate. It can measure the right ascension, declination, altitude and azimuth. It is composed of Sayu-hwan (Four displacements), Jeokdo-hwan (Equatorial dial), Baekgak-hwan (Ring with one hundred-interval quarters), Gyuhyeong (Sighting aliadade), Yongju (Dragon-pillar) and Bu (Stand). So-ganui was used conveniently portable surveying as well as astronomical instrument and possible to determine time during day and night.

FIRST ZEEMAN DOPPLER IMAGING OF A COOL STAR USING ALL FOUR STOKES PARAMETERS

International Nuclear Information System (INIS)

Rosén, L.; Kochukhov, O.; Wade, G. A.

2015-01-01

Magnetic fields are ubiquitous in active cool stars, but they are in general complex and weak. Current Zeeman Doppler imaging (ZDI) studies of cool star magnetic fields chiefly employ circular polarization observations because linear polarization is difficult to detect and requires a more sophisticated radiative transfer modeling to interpret. But it has been shown in previous theoretical studies, and in the observational analyses of magnetic Ap stars, that including linear polarization in the magnetic inversion process makes it possible to correctly recover many otherwise lost or misinterpreted magnetic features. We have obtained phase-resolved observations in all four Stokes parameters of the RS CVn star II Peg at two separate epochs. Here we present temperature and magnetic field maps reconstructed for this star using all four Stokes parameters. This is the very first such ZDI study of a cool active star. Our magnetic inversions reveal a highly structured magnetic field topology for both epochs. The strength of some surface features is doubled or even quadrupled when linear polarization is taken into account. The total magnetic energy of the reconstructed field map also becomes about 2.1–3.5 times higher. The overall complexity is also increased as the field energy is shifted toward higher harmonic modes when four Stokes parameters are used. As a consequence, the potential field extrapolation of the four Stokes parameter ZDI results indicates that magnetic field becomes weaker at a distance of several stellar radii due to a decrease of the large-scale field component

Stereoscopy in Astronomical Visualizations to Support Learning at Informal Education Settings

Science.gov (United States)

Price, Aaron; Lee, Hee-Sun

2015-08-01

Stereoscopy has been used in science education for 100 years. Recent innovations in low cost technology as well as trends in the entertainment industry have made stereoscopy popular among educators and audiences alike. However, experimental studies addressing whether stereoscopy actually impacts science learning are limited. Over the last decade, we have conducted a series of quasi-experimental and experimental studies on how children and adult visitors in science museums and planetariums learned about the structure and function of highly spatial scientific objects such as galaxies, supernova, etc. We present a synthesis of the results from these studies and implications for stereoscopic visualization development. The overall finding is that the impact of stereoscopy on perceptions of scientific objects is limited when presented as static imagery. However, when presented as full motion films, a significantly positive impact was detected. To conclude, we present a set of stereoscopic design principles that can help design astronomical stereoscopic films that support deep and effective learning. Our studies cover astronomical content such as the engineering of and imagery from the Mars rovers, artistic stereoscopic imagery of nebulae and a high-resolution stereoscopic film about how astronomers measure and model the structure of our galaxy.

Validity of the Stokes-Einstein relation in liquids: simple rules from the excess entropy.

Science.gov (United States)

Pasturel, A; Jakse, N

2016-12-07

It is becoming common practice to consider that the Stokes-Einstein relation D/T~ η -1 usually works for liquids above their melting temperatures although there is also experimental evidence for its failure. Here we investigate numerically this commonly-invoked assumption for simple liquid metals as well as for their liquid alloys. Using ab initio molecular dynamics simulations we show how entropy scaling relationships developed by Rosenfeld can be used to predict the conditions for the validity of the Stokes-Einstein relation in the liquid phase. Specifically, we demonstrate the Stokes-Einstein relation may break down in the liquid phase of some liquid alloys mainly due to the presence of local structural ordering as evidenced in their partial two-body excess entropies. Our findings shed new light on the understanding of transport properties of liquid materials and will trigger more experimental and theoretical studies since excess entropy and its two-body approximation are readily obtainable from standard experiments and simulations.

Leslie Peltier, Amateur Astronomer and Observer Extraordinaire

Science.gov (United States)

Corbin, B. G.

2003-12-01

Leslie Copus Peltier, (Jan. 2, 1900-May 10, 1980) was called "the world's greatest non-professional astronomer" by none other than Harlow Shapley, and also referred to as the "the world's greatest living amateur astronomer". He began observing variable stars on March 1, 1918 with an observation of R. Leonis and at the time of his death had made a total of 132,123 observations of variable stars. These were reported to the AAVSO on a consecutive monthly basis stretching from 1918 to his death in 1980. As of October 2003, he was still on AAVSO's list of the top 25 observers in its history. Born on a farm near Delphos, Ohio, his parents were well read and their home was filled with books on different subjects, including nature guides. As a young man he studied the flora and fauna of the area and in 1915 began his study of the heavens with Vega being the first star he identified. After the purchase of a 2-inch spyglass, his observations of variable stars began to be noticed by professional astronomers and the AAVSO loaned him a 4-inch Mogey refractor; shortly thereafter Henry Norris Russell of Princeton loaned him via the AAVSO a 6-inch refractor, a comet seeker of short focus. He discovered 12 comets, 10 of which carry his name, and 6 novae or recurring novae. His design of the "Merry-Go-Round Observatory" was a novel approach with the whole observatory revolving around the observer while seated in his observing chair. Miami University (Ohio) later donated to him their 12-inch Clark refractor with its dome. His first book, Starlight Nights: The Adventures of a Star-Gazer, appeared in 1965. This autobiography, an ode to the joys of observing both the night sky and nature, was written in beautifully descriptive language that helped lead countless readers into astronomy. Departing from astronomy, in 1977 he published The Place on Jennings Creek. Written in the style of the 19th century naturalist, the book was devoted to his family's home, Brookhaven, and its natural

Modeling shock waves in an ideal gas: Going beyond the Navier-Stokes level

International Nuclear Information System (INIS)

Holian, B.L.; Patterson, C.W.; Mareschal, M.; Salomons, E.

1993-01-01

We model a shock wave in an ideal gas by solving a modified version of the compressible Navier-Stokes equations of hydrodynamics, where, following an earlier conjecture by Holian [Phys. Rev. A 37, 2562 (1988)], we use the temperature in the direction of shock propagation T xx , rather than the average temperature T=(T xx +T yy +T zz )/3, in the evaluation of the linear transport coefficients. The results are found to agree much better with the molecular-dynamics simulations of Salomons and Mareschal [Phys. Rev. Lett. 69, 269 (1992)] than standard Navier-Stokes theory

Mingantu, 18th-Century Mongol Astronomer and Radioheliograph Namesake

Science.gov (United States)

Pasachoff, Jay M.

2013-01-01

The 18th-century Mongol astronomer Mingantu (1692-1765) has been honored with a city named after him and a nearby solar telescope array. During the IAU/Beijing, my wife and I went to the new Chinese solar radioheliograph, the Mingantu Observing Station, in Inner Mongolia, ~400 km northwest of Beijing, a project of the National Astronomical Observatories, Chinese Academy of Sciences. It currently contains 40 dishes each 4.5 m across, with a correlator from Beijing. Within a year, 60 2-m dishes will be added. We passed by the 12-century ruins of Xanadu (about 20 km north of Zhangbei) about halfway. The radioheliograph is in a plane about 1 km across, forming a three-armed spiral for interferometric solar mapping, something colleagues and I had carried out with the Jansky Very Large Array, taking advantage of the lunar occultation before annularity at the 20 May 2012 solar eclipse. In the central square of Mingantu city, a statue ~10-m high of the Mongol astronomer Mingantu appears. Its base bears a plaque ~1-m high of IAU Minor Planet Circular MPC 45750 announcing the naming in 2002 of asteroid 28242 Mingantu, discovered at a Chinese observatory in 1999. Mingantu carried out orbital calculations, mapping, mathematical work on infinite series, and other scientific research. He is honored by a modern museum behind the statue. The museum's first 40% describes Mingantu and his work, and is followed by some artifacts of the region from thousands of years ago. The final, large room contains a two-meter-square scale model of the radioheliograph, flat-screen televisions running Solar Dynamics Observatory and other contemporary visualizations, orreries and other objects, and large transparencies of NASA and other astronomical imagery. See my post at http://www.skyandtelescope.com/community/skyblog/newsblog/ specfically Astro-Sightseeing_in_Inner_Mongolia-167712965.html. We thank Yihua Yan for arranging the visit and Wang Wei (both NAOC) for accompanying us. My solar research

This Month in Astronomical History: Providing Context for the Advancement of Astronomy

Science.gov (United States)

Wilson, Teresa

2018-01-01

This Month in Astronomical History is a short (~500 word) illustrated column hosted on the AAS website (https://had.aas.org/resources/astro-history). Its mission is to highlight people and events that have shaped the development of astronomy to convey a historical context to current researchers, to provide a resource for education and public outreach programs seeking to incorporate a historical perspective, and to share the excitement of astronomy with the public. Knowing how the astronomical journey has proceeded thus far allows current professionals to map where to go next and how to get there. The column charts the first part of this journey by celebrating anniversaries of births, discoveries, and deaths, and the technological advances that made discoveries possible. A new “Further Reading” section encourages readers to pursue subjects in greater depth and strengthens the articles as classroom resources.In the months preceding the 21 August 2017 solar eclipse, the column featured astronomical bodies that come between Earth and the Sun: 2004 Venus transit, the 1878 solar eclipse, and the search for the hypothetical planet Vulcan. Venusian transits were an early but technically challenging way to measure the astronomical unit, now easily done with radar-ranging. Like this year’s event, eclipse chasing and citizen science were part of the 1878 experience. Newton’s Laws seemed to require a planet inside Mercury’s orbit, but General Relativity explained the behavior of Mercury without it. Studying each of these transiting bodies has expanded our knowledge and understanding of the universe differently. Transiting extrasolar planets remain to be explored in a future column. In September, an article on the discovery of Neptune followed the discussion of the non-existent Vulcan quite naturally and expanded on the brief mention of this event in relation to the discovery of Pluto. Suggestions for additional topics are always welcome.The Dudley Observatory

Smooth solutions of the Navier-Stokes equations

International Nuclear Information System (INIS)

Pokhozhaev, S I

2014-01-01

We consider smooth solutions of the Cauchy problem for the Navier-Stokes equations on the scale of smooth functions which are periodic with respect to x∈R 3 . We obtain existence theorems for global (with respect to t>0) and local solutions of the Cauchy problem. The statements of these depend on the smoothness and the norm of the initial vector function. Upper bounds for the behaviour of solutions in both classes, which depend on t, are also obtained. Bibliography: 10 titles

Novel Algorithms for Astronomical Plate Analyses Rene Hudec1,2 ...

Indian Academy of Sciences (India)

2Czech Technical University in Prague, Faculty of Electrical Engineering, Technicka 2,. Prague 6 ... Abstract. Powerful computers and dedicated software allow effective data mining and scientific analyses in astronomical plate archives. We.

SIP: A Web-Based Astronomical Image Processing Program

Science.gov (United States)

Simonetti, J. H.

1999-12-01

I have written an astronomical image processing and analysis program designed to run over the internet in a Java-compatible web browser. The program, Sky Image Processor (SIP), is accessible at the SIP webpage (http://www.phys.vt.edu/SIP). Since nothing is installed on the user's machine, there is no need to download upgrades; the latest version of the program is always instantly available. Furthermore, the Java programming language is designed to work on any computer platform (any machine and operating system). The program could be used with students in web-based instruction or in a computer laboratory setting; it may also be of use in some research or outreach applications. While SIP is similar to other image processing programs, it is unique in some important respects. For example, SIP can load images from the user's machine or from the Web. An instructor can put images on a web server for students to load and analyze on their own personal computer. Or, the instructor can inform the students of images to load from any other web server. Furthermore, since SIP was written with students in mind, the philosophy is to present the user with the most basic tools necessary to process and analyze astronomical images. Images can be combined (by addition, subtraction, multiplication, or division), multiplied by a constant, smoothed, cropped, flipped, rotated, and so on. Statistics can be gathered for pixels within a box drawn by the user. Basic tools are available for gathering data from an image which can be used for performing simple differential photometry, or astrometry. Therefore, students can learn how astronomical image processing works. Since SIP is not part of a commercial CCD camera package, the program is written to handle the most common denominator image file, the FITS format.

Unveiling galaxies the role of images in astronomical discovery

CERN Document Server

Roy, Jean-René

2017-01-01

Galaxies are known as the building blocks of the universe, but arriving at this understanding has been a thousand-year odyssey. This journey is told through the lens of the evolving use of images as investigative tools. Initial chapters explore how early insights developed in line with new methods of scientific imaging, particularly photography. The volume then explores the impact of optical, radio and x-ray imaging techniques. The final part of the story discusses the importance of atlases of galaxies; how astronomers organised images in ways that educated, promoted ideas and pushed for new knowledge. Images that created confusion as well as advanced knowledge are included to demonstrate the challenges faced by astronomers and the long road to understanding galaxies. By examining developments in imaging, this text places the study of galaxies in its broader historical context, contributing to both astronomy and the history of science.

Radio and Optical Telescopes for School Students and Professional Astronomers

Science.gov (United States)

Hosmer, Laura; Langston, G.; Heatherly, S.; Towner, A. P.; Ford, J.; Simon, R. S.; White, S.; O'Neil, K. L.; Haipslip, J.; Reichart, D.

2013-01-01

The NRAO 20m telescope is now on-line as a part of UNC's Skynet worldwide telescope network. The NRAO is completing integration of radio astronomy tools with the Skynet web interface. We present the web interface and astronomy projects that allow students and astronomers from all over the country to become Radio Astronomers. The 20 meter radio telescope at NRAO in Green Bank, WV is dedicated to public education and also is part of an experiment in public funding for astronomy. The telescope has a fantastic new web-based interface, with priority queuing, accommodating priority for paying customers and enabling free use of otherwise unused time. This revival included many software and hardware improvements including automatic calibration and improved time integration resulting in improved data processing, and a new ultra high resolution spectrometer. This new spectrometer is optimized for very narrow spectral lines, which will allow astronomers to study complex molecules and very cold regions of space in remarkable detail. In accordance with focusing on broader impacts, many public outreach and high school education activities have been completed with many confirmed future activities. The 20 meter is now a fully automated, powerful tool capable of professional grade results available to anyone in the world. Drop by our poster and try out real-time telescope control!

Managing distributed software development in the Virtual Astronomical Observatory

Science.gov (United States)

Evans, Janet D.; Plante, Raymond L.; Boneventura, Nina; Busko, Ivo; Cresitello-Dittmar, Mark; D'Abrusco, Raffaele; Doe, Stephen; Ebert, Rick; Laurino, Omar; Pevunova, Olga; Refsdal, Brian; Thomas, Brian

2012-09-01

The U.S. Virtual Astronomical Observatory (VAO) is a product-driven organization that provides new scientific research capabilities to the astronomical community. Software development for the VAO follows a lightweight framework that guides development of science applications and infrastructure. Challenges to be overcome include distributed development teams, part-time efforts, and highly constrained schedules. We describe the process we followed to conquer these challenges while developing Iris, the VAO application for analysis of 1-D astronomical spectral energy distributions (SEDs). Iris was successfully built and released in less than a year with a team distributed across four institutions. The project followed existing International Virtual Observatory Alliance inter-operability standards for spectral data and contributed a SED library as a by-product of the project. We emphasize lessons learned that will be folded into future development efforts. In our experience, a well-defined process that provides guidelines to ensure the project is cohesive and stays on track is key to success. Internal product deliveries with a planned test and feedback loop are critical. Release candidates are measured against use cases established early in the process, and provide the opportunity to assess priorities and make course corrections during development. Also key is the participation of a stakeholder such as a lead scientist who manages the technical questions, advises on priorities, and is actively involved as a lead tester. Finally, frequent scheduled communications (for example a bi-weekly tele-conference) assure issues are resolved quickly and the team is working toward a common vision.

Spectral/hp least-squares finite element formulation for the Navier-Stokes equations

International Nuclear Information System (INIS)

Pontaza, J.P.; Reddy, J.N.

2003-01-01

We consider the application of least-squares finite element models combined with spectral/hp methods for the numerical solution of viscous flow problems. The paper presents the formulation, validation, and application of a spectral/hp algorithm to the numerical solution of the Navier-Stokes equations governing two- and three-dimensional stationary incompressible and low-speed compressible flows. The Navier-Stokes equations are expressed as an equivalent set of first-order equations by introducing vorticity or velocity gradients as additional independent variables and the least-squares method is used to develop the finite element model. High-order element expansions are used to construct the discrete model. The discrete model thus obtained is linearized by Newton's method, resulting in a linear system of equations with a symmetric positive definite coefficient matrix that is solved in a fully coupled manner by a preconditioned conjugate gradient method. Spectral convergence of the L 2 least-squares functional and L 2 error norms is verified using smooth solutions to the two-dimensional stationary Poisson and incompressible Navier-Stokes equations. Numerical results for flow over a backward-facing step, steady flow past a circular cylinder, three-dimensional lid-driven cavity flow, and compressible buoyant flow inside a square enclosure are presented to demonstrate the predictive capability and robustness of the proposed formulation

A SURVEY OF ASTRONOMICAL RESEARCH: A BASELINE FOR ASTRONOMICAL DEVELOPMENT

International Nuclear Information System (INIS)

Ribeiro, V. A. R. M.; Russo, P.; Cárdenas-Avendaño, A.

2013-01-01

Measuring scientific development is a difficult task. Different metrics have been put forward to evaluate scientific development; in this paper we explore a metric that uses the number of peer-reviewed, and when available non-peer-reviewed, research articles as an indicator of development in the field of astronomy. We analyzed the available publication record, using the Smithsonian Astrophysical Observatory/NASA Astrophysics Database System, by country affiliation in the time span between 1950 and 2011 for countries with a gross national income of less than 14,365 USD in 2010. This represents 149 countries. We propose that this metric identifies countries in ''astronomical development'' with a culture of research publishing. We also propose that for a country to develop in astronomy, it should invest in outside expert visits, send its staff abroad to study, and establish a culture of scientific publishing. Furthermore, we propose that this paper may be used as a baseline to measure the success of major international projects, such as the International Year of Astronomy 2009

astroplan: Observation Planning for Astronomers

Science.gov (United States)

Morris, Brett

2016-03-01

Astroplan is an observation planning package for astronomers. It is an astropy-affiliated package which began as a Google Summer of Code project. Astroplan facilitates convenient calculation of common observational quantities, like target altitudes and azimuths, airmasses, and rise/set times. Astroplan also computes when targets are observable given various extensible observing constraints, for example: within a range of airmasses or altitudes, or at a given separation from the Moon. Astroplan is taught in the undergraduate programming for astronomy class, and enables observational Pre- MAP projects at the University of Washington. In the near future, we plan to implement scheduling capabilities in astroplan on top of the constraints framework.

Visualizing Astronomical Data with Blender

Science.gov (United States)

Kent, Brian R.

2014-01-01

We present methods for using the 3D graphics program Blender in the visualization of astronomical data. The software's forte for animating 3D data lends itself well to use in astronomy. The Blender graphical user interface and Python scripting capabilities can be utilized in the generation of models for data cubes, catalogs, simulations, and surface maps. We review methods for data import, 2D and 3D voxel texture applications, animations, camera movement, and composite renders. Rendering times can be improved by using graphic processing units (GPUs). A number of examples are shown using the software features most applicable to various kinds of data paradigms in astronomy.

Capability of State-of-the-Art Navier-Stokes Solvers for the Prediction of Helicopter Fuselage Aerodynamics

DEFF Research Database (Denmark)

N., Kroll; P., Renzoni; M., Amato

1998-01-01

The purpose of this paper is to describe the influence of different Navier-Stokes solvers and grids on the prediction of the global coefficients for a simplified geometry of a helicopter fuselage.......The purpose of this paper is to describe the influence of different Navier-Stokes solvers and grids on the prediction of the global coefficients for a simplified geometry of a helicopter fuselage....

On the equivalence of spherical splines with least-squares collocation and Stokes's formula for regional geoid computation

Science.gov (United States)

Ophaug, Vegard; Gerlach, Christian

2017-11-01

This work is an investigation of three methods for regional geoid computation: Stokes's formula, least-squares collocation (LSC), and spherical radial base functions (RBFs) using the spline kernel (SK). It is a first attempt to compare the three methods theoretically and numerically in a unified framework. While Stokes integration and LSC may be regarded as classic methods for regional geoid computation, RBFs may still be regarded as a modern approach. All methods are theoretically equal when applied globally, and we therefore expect them to give comparable results in regional applications. However, it has been shown by de Min (Bull Géod 69:223-232, 1995. doi: 10.1007/BF00806734) that the equivalence of Stokes's formula and LSC does not hold in regional applications without modifying the cross-covariance function. In order to make all methods comparable in regional applications, the corresponding modification has been introduced also in the SK. Ultimately, we present numerical examples comparing Stokes's formula, LSC, and SKs in a closed-loop environment using synthetic noise-free data, to verify their equivalence. All agree on the millimeter level.

An Equal-Order DG Method for the Incompressible Navier-Stokes Equations

KAUST Repository

Cockburn, Bernardo; Kanschat, Guido; Schö tzau, Dominik

2008-01-01

We introduce and analyze a discontinuous Galerkin method for the incompressible Navier-Stokes equations that is based on finite element spaces of the same polynomial order for the approximation of the velocity and the pressure. Stability

The Educational Activities of the Astronomical Society of the Pacific.

Science.gov (United States)

Fraknoi, Andrew

1981-01-01

Describes educational activities of the Astronomical Society of the Pacific including learning packets on various astronomy concepts, Morrison lectures, newspaper columns, teacher workshops, cosponsoring astronomy oriented lectures, and providing speakers for various groups. (DS)

Five-dimensional truncation of the plane incompressible navier-stokes equations

Energy Technology Data Exchange (ETDEWEB)

Boldrighini, C [Camerino Univ. (Italy). Istituto di Matematica; Franceschini, V [Modena Univ. (Italy). Istituto Matematico

1979-01-01

A five-modes truncation of the Navier-Stokes equations for a two dimensional incompressible fluid on a torus is considered. A computer analysis shows that for a certain range of the Reynolds number the system exhibits a stochastic behaviour, approached through an involved sequence of bifurcations.

Assessing the Polarization of a Quantum Field from Stokes Fluctuations

DEFF Research Database (Denmark)

Klimov, A. B.; Björk, G.; Söderholm, J.

2010-01-01

We propose an operational degree of polarization in terms of the variance of the Stokes vector minimized over all the directions of the Poincaré sphere. We examine the properties of this second-order definition and carry out its experimental determination. Quantum states with the same standard...

Coherent anti-Stokes Raman scattering microscopy with a photonic crystal fiber based light source

DEFF Research Database (Denmark)

Paulsen, H.N.; Hilligsøe, Karen Marie; Thøgersen, J.

2003-01-01

A coherent anti-Stokes Raman scattering microscope based on a Ti:sapphire femtosecond oscillator and a photonic crystal fiber is demonstrated. The nonlinear response of the fiber is used to generate the additional wavelength needed in the Raman process. The applicability of the setup is demonstra......A coherent anti-Stokes Raman scattering microscope based on a Ti:sapphire femtosecond oscillator and a photonic crystal fiber is demonstrated. The nonlinear response of the fiber is used to generate the additional wavelength needed in the Raman process. The applicability of the setup...

Strategies for personnel sustainable lifecycle at astronomical observatories and local industry development

Science.gov (United States)

Bendek, Eduardo A.; Leatherbee, Michael; Smith, Heather; Strappa, Valentina; Zinnecker, Hans; Perez, Mario

2014-08-01

Specialized manpower required to efficiently operate world-class observatories requires large investments in time and resources to train personnel in very specific areas of engineering. Isolation and distances to mayor cities pose a challenge to retain motivated and qualified personnel on the mountain. This paper presents strategies that we believe may be effective for retaining this specific know-how in the astronomy field; while at the same time develop a local support industry for observatory operations and astronomical instrumentation development. For this study we choose Chile as a research setting because it will host more than 60% of the world's ground based astronomical infrastructure by the end of the decade, and because the country has an underdeveloped industry for astronomy services. We identify the astronomical infrastructure that exists in the country as well as the major research groups and industrial players. We further identify the needs of observatories that could be outsourced to the local economy. As a result, we suggest spin-off opportunities that can be started by former observatory employees and therefore retaining the knowhow of experienced people that decide to leave on-site jobs. We also identify tools to facilitate this process such as the creation of a centralized repository of local capabilities and observatory needs, as well as exchange programs within astronomical instrumentation groups. We believe that these strategies will contribute to a positive work environment at the observatories, reduce the operation and development costs, and develop a new industry for the host country.

Partnerships between Professional and Amateur Astronomers: A Shift in Research Paradigm

Science.gov (United States)

Yanamandra-Fisher, Padma A.; Orton, G. S.; Casquinha, P.; Coffelt, A.; Delcroix, M.; Go, C.; Hueso, R.; Jaeschke, W.; Kardasis, M.; Kraaikamp, E.; Morales, E.; Peach, D.; Rogers, J.; Wesley, A.; Willems, F.; Wilson, T.

2012-10-01

"Citizen Astronomy" can be thought of as the paradigm shift transforming the nature of observational astronomy. The night sky, with all its delights and mysteries, enthralls professional and amateur astronomers, and students who will form the next generation of scientists and engineers. These students are matriculating in an era of reduced funding for core competencies such as science, technology, mathematics and engineering (STEM) sciences and an ongoing general decline in these sciences. How then do we re-generate their interest and engage students while we perform cutting-edge planetary science in a fiscally constrained environment? One promising solution is to promote the emerging partnerships between professional and dedicated proficient amateur astronomers, that rely on creating a niche for long timeline of multispectral remote sensing. In the past decade, it is the collective observations and their analyses by the ever-increasing global network of amateur astronomers that has discovered interesting phenomena and provided the reference backdrop for observations by professional ground-based professional astronomers and spacecraft missions. We shall focus on our collaboration or "Citizen Astronomy: Jupiter and Saturn" for the past five years and illustrate the strong synergy between the two groups that has produced new scientific results. With the active inclusion and use of emerging social media (Facebook, Twitter, etc.), the near daily communication and updates (via email, Skype, Facebook) between the two groups is becoming a powerful tool for ground-based remote sensing. However, what is sorely lacking in this paradigm is the inclusion of teachers and students and, therefore, its inclusion in the secondary and tertiary classrooms. We will provide various scenarios to address this issue, and emphasize the various aspects of STEM learning/teaching that is necessary for students and teachers - all that can be performed at low cost; and showcase some of our

Stokes Space-Based Optical Modulation Format Recognition for Digital Coherent Receivers

DEFF Research Database (Denmark)

Borkowski, Robert; Zibar, Darko; Caballero Jambrina, Antonio

2013-01-01

We present a technique for modulation format recognition for heterogeneous reconfigurable optical networks. The method is based on Stokes space signal representation and uses a variational Bayesian expectation maximization machine learning algorithm. Differentiation between diverse common coheren...

The NASA Astrophysics Data System Free Access to the Astronomical Literature On-Line and through Email

CERN Document Server

Eichhorn, G; Grant, C S; Kurtz, M J; Murray, S S

2001-01-01

The Astrophysics Data System (ADS) provides access to the astronomical literature through the World Wide Web. It is a NASA funded project and access to all the ADS services is free to everybody world-wide.The ADS Abstract Service allows the searching of four databases with abstracts in Astronomy, Instrumentation, Physics/Geophysics, and the LANL Preprints with a total of over 2.2 million references. The system also provides access to reference and citation information, links to on-line data, electronic journal articles, and other on-line information. The ADS Article Service contains the articles for most of the astronomical literature back to volume 1. It contains the scanned pages of all the major journals (Astrophysical Journal, Astronomical Journal, Astronomy & Astrophysics, Monthly Notices of the Royal Astronomical Society, and Solar Physics), as well as most smaller journals back to volume 1. The ADS can be accessed through any web browser without signup or login. Alternatively an email interface is ...

The classical version of Stokes' Theorem revisited

DEFF Research Database (Denmark)

Markvorsen, Steen

2008-01-01

Using only fairly simple and elementary considerations - essentially from first year undergraduate mathematics - we show how the classical Stokes' theorem for any given surface and vector field in $\\mathbb{R}^{3}$ follows from an application of Gauss' divergence theorem to a suitable modification...... exercise, which simply relates the concepts of divergence and curl on the local differential level. The rest of the paper uses only integration in $1$, $2$, and $3$ variables together with a 'fattening' technique for surfaces and the inverse function theorem....

Professional- Amateur Astronomer Partnerships in Scientific Research: The Re-emergence of Jupiter's 5-Micron Hot Spots

Science.gov (United States)

Yanamandra-Fisher, P. A.

2012-12-01

The night sky, with all its delights and mysteries, enthrall professional and amateur astronomers alike. The discrete data sets acquired by professional astronomers via their approved observing programs at various national facilities are supplemented by the nearly daily observations of the same celestial object by amateur astronomers around the world. The emerging partnerships between professional and dedicated amateur astronomers rely on creating a niche for long timeline of multispectral remote sensing. "Citizen Astronomy" can be thought of as the paradigm shift transforming the nature of observational astronomy. In the past decade, it is the collective observations and their analyses by the ever-increasing global network of amateur astronomers that has discovered interesting phenomena and provided the reference backdrop for observations by ground-based professional astronomers and spacecraft missions. We shall present results from our collaborations to observe the recent global upheaval on Jupiter for the past five years and illustrate the strong synergy between the two groups. Global upheavals on Jupiter involve changes in the albedo of entire axisymmetric regions, lasting several years, with the last two occurring in 1989 and 2006. Against this backdrop of planetary-scale changes, discrete features such as the Great Red Spot (GRS), and other vortices exhibit changes on shorter spatial- and time-scales. One set of features we are currently tracking is the variability of the discrete equatorial 5-μm hot spots, semi-evenly spaced in longitude and confined to a narrow latitude band centered at 6.5°N (southern edge of the North Equatorial Belt, NEB), abundant in Voyager images (1980-1981). Tantalizingly similar patterns were observed in the visible (bright plumes and blue-gray regions), where reflectivity in the red is anti-correlated with 5-μm thermal radiance. During the recent NEB fade (2011 - early 2012), however, these otherwise ubiquitous features were

World's fastest and most sensitive astronomical camera

Science.gov (United States)

2009-06-01

The next generation of instruments for ground-based telescopes took a leap forward with the development of a new ultra-fast camera that can take 1500 finely exposed images per second even when observing extremely faint objects. The first 240x240 pixel images with the world's fastest high precision faint light camera were obtained through a collaborative effort between ESO and three French laboratories from the French Centre National de la Recherche Scientifique/Institut National des Sciences de l'Univers (CNRS/INSU). Cameras such as this are key components of the next generation of adaptive optics instruments of Europe's ground-based astronomy flagship facility, the ESO Very Large Telescope (VLT). ESO PR Photo 22a/09 The CCD220 detector ESO PR Photo 22b/09 The OCam camera ESO PR Video 22a/09 OCam images "The performance of this breakthrough camera is without an equivalent anywhere in the world. The camera will enable great leaps forward in many areas of the study of the Universe," says Norbert Hubin, head of the Adaptive Optics department at ESO. OCam will be part of the second-generation VLT instrument SPHERE. To be installed in 2011, SPHERE will take images of giant exoplanets orbiting nearby stars. A fast camera such as this is needed as an essential component for the modern adaptive optics instruments used on the largest ground-based telescopes. Telescopes on the ground suffer from the blurring effect induced by atmospheric turbulence. This turbulence causes the stars to twinkle in a way that delights poets, but frustrates astronomers, since it blurs the finest details of the images. Adaptive optics techniques overcome this major drawback, so that ground-based telescopes can produce images that are as sharp as if taken from space. Adaptive optics is based on real-time corrections computed from images obtained by a special camera working at very high speeds. Nowadays, this means many hundreds of times each second. The new generation instruments require these

Astronomical technology - the past and the future. Karl Schwarzschild Award Lecture 2015

Science.gov (United States)

Appenzeller, I.

2016-07-01

The past fifty years have been an epoch of impressive progress in the field of astronomical technology. Practically all the technical tools, which we use today, have been developed during that time span. While the first half of this period has been dominated by advances in the detector technologies, during the past two decades innovative telescope concepts have been developed for practically all wavelength ranges where astronomical observations are possible. Further important advances can be expected in the next few decades. Based on the experience of the past, some of the main sources of technological progress can be identified.

From research institution to astronomical museum: a history of the Stockholm Observatory

Science.gov (United States)

Yaskell, Steven Haywood

2008-07-01

The Royal Swedish Academy of Sciences (RSAS) (or Kungliga Vetenskapsakademien [KvA] in Swedish) founded 1739, opened its first permanent building, an astronomical and meteorological observatory, on 20 September 1753. This was situated at Brunkebergsåsen (formerly Observatorie Lunden, or Observatory Hill), on a high terrace in a northern quarter of Stockholm. This historic building is still sometimes called Gamla Observatoriet (the Old Observatory) and now is formally the Observatory Museum. This paper reviews the history of the Observatory from its function as a scientific astronomical institution to its relatively-recent relegation to museum status.

Astronomers Anonymous Getting Help with the Puzzles and Pitfalls of Practical Astronomy

CERN Document Server

Ringwood, Steve

2010-01-01

In this entertaining parody of letters to a typical “lonely hearts” columnist, real-life expert and long-time astronomy columnist Steve Ringwood presents a sweeping overview of common questions and problems practical and amateur astronomers face, compiled from Ringwood's own experiences in the world of astronomy. His screamingly funny comments will keep you laughing out loud throughout, so be careful of reading this book in public! Written especially for troubled astronomers, but also accessible to anyone with an interest in space or astronomy, readers will easily recognize the difficulties they face and enjoy the humor being directed at them and their science.

Navier–Stokes flow in converging–diverging distensible tubes

Directory of Open Access Journals (Sweden)

Taha Sochi

2015-09-01

Full Text Available We use a method based on the lubrication approximation in conjunction with a residual-based mass-continuity iterative solution scheme to compute the flow rate and pressure field in distensible converging–diverging tubes for Navier–Stokes fluids. We employ an analytical formula derived from a one-dimensional version of the Navier–Stokes equations to describe the underlying flow model that provides the residual function. This formula correlates the flow rate to the boundary pressures in straight cylindrical elastic tubes with constant-radius. We validate our findings by the convergence toward a final solution with fine discretization as well as by comparison to the Poiseuille-type flow in its convergence toward analytic solutions found earlier in rigid converging–diverging tubes. We also tested the method on limiting special cases of cylindrical elastic tubes with constant-radius where the numerical solutions converged to the expected analytical solutions. The distensible model has also been endorsed by its convergence toward the rigid Poiseuille-type model with increasing the tube wall stiffness. Lubrication-based one-dimensional finite element method was also used for verification. In this investigation five converging–diverging geometries are used for demonstration, validation and as prototypes for modeling converging–diverging geometries in general.

Nikolay N. Donitch - the astronomer

Science.gov (United States)

Gaina, Alex B.; Volyanskaya, M. Yu.

1999-08-01

The article is devoted to milestones of life and scientific activity of the eminent astronomer Nikolay Nikolaevich Donitch (Nicolae N. Donici) (1874-1956), a graduate from the Odessa (Novorossiski) university. He was a wellknown expert in the field of reseacrh of objects of Solar system. A person highly cultured, which built the first in Bessarabia (actually a part of the Republic of Moldova) observatory. He was borne in Kishinev (Chisinau) in a nobles family of notable Moldavian landersmen. N.D. graduated from the Richelieu lyceym in Odessa and afterwards, in 1897, graduated from the Odessa (Novorossiysky) University. A.K. Kononovich (1850-1910)headed the chair of astronomy and the Observatory at that time - a foremost authority in the field of astrophysics and stellar astronomy. Many of his disciples became eminent scientists of their time. N. Donitch was among them. N.D. worked till 1918 at Pulkovo Observatory and became a master in the field of studying of such phenomena as solar and lunar eclipses. To observe the Sun N.D., could afford to design and manufacture a spectroheliograph, the first in Russia, with the assistance of a famous Odessa mechanic J.A. Timchenko. This instrument enabled him to obtain topquality photos of the Sun's surface and prominences. It was mounted together with coelostat in the private observatory of N.D. , built in the village Staryie Doubossary in 1908. Besides the heliograoph, the observatory was equiped with a five inch refractor-equatorial with numerous instruments for various observations. Of the other instruments should be mentioned : "a comet triplet" - an instrument consisting of guiding refractor, a photographic camera and a spectrograph with an objective prism. N.D. was lucky enough to observe rare astronomical phenomena. He observed the transit of Mercury through the disk of the Sun on November 14, 1907 and showed the athmosphere absence around this planet, observed the Halley's comet in 1910, the bright Pons-Winneke comet

Stokes phenomena and quantum integrability in non-critical string/M theory

International Nuclear Information System (INIS)

Chan, Chuan-Tsung; Irie, Hirotaka; Yeh, Chi-Hsien

2012-01-01

We study Stokes phenomena of the k×k isomonodromy systems with an arbitrary Poincaré index r, especially which correspond to the fractional-superstring (or parafermionic-string) multi-critical points (p-hat,q-hat)=(1,r-1) in the k-cut two-matrix models. Investigation of this system is important for the purpose of figuring out the non-critical version of M theory which was proposed to be the strong-coupling dual of fractional superstring theory as a two-matrix model with an infinite number of cuts. Surprisingly the multi-cut boundary-condition recursion equations have a universal form among the various multi-cut critical points, and this enables us to show explicit solutions of Stokes multipliers in quite wide classes of (k,r). Although these critical points almost break the intrinsic Z k symmetry of the multi-cut two-matrix models, this feature makes manifest a connection between the multi-cut boundary-condition recursion equations and the structures of quantum integrable systems. In particular, it is uncovered that the Stokes multipliers satisfy multiple Hirota equations (i.e. multiple T-systems). Therefore our result provides a large extension of the ODE/IM correspondence to the general isomonodromy ODE systems endowed with the multi-cut boundary conditions. We also comment about a possibility that N=2 QFT of Cecotti-Vafa would be “topological series” in non-critical M theory equipped with a single quantum integrability.

The High Road to Astronomical Photometric Precision : Differential Photometry

NARCIS (Netherlands)

Milone, E. F.; Pel, Jan Willem

2011-01-01

Differential photometry offers the most precise method for measuring the brightness of astronomical objects. We attempt to demonstrate why this should be the case, and then describe how well it has been done through a review of the application of differential techniques from the earliest visual

Penn State astronomical image processing system

International Nuclear Information System (INIS)

Truax, R.J.; Nousek, J.A.; Feigelson, E.D.; Lonsdale, C.J.

1987-01-01

The needs of modern astronomy for image processing set demanding standards in simultaneously requiring fast computation speed, high-quality graphic display, large data storage, and interactive response. An innovative image processing system was designed, integrated, and used; it is based on a supermicro architecture which is tailored specifically for astronomy, which provides a highly cost-effective alternative to the traditional minicomputer installation. The paper describes the design rationale, equipment selection, and software developed to allow other astronomers with similar needs to benefit from the present experience. 9 references

Far-infrared spectrophotometer for astronomical observations

Science.gov (United States)

Moseley, H.; Silverberg, R. F.

1981-01-01

A liquid-helium-cooled far infrared spectrophotometer was built and used to make low resolution observations of the continua of several kinds of astronomical objects using the Kuiper Airborne Observatory. This instrument fills a gap in both sensitivity to continuum sources and spectral resolution between the broadband photometers with lambda/Delta lambda approximately 1 and spectrometers with lambda/Delta lambda greater than 50. While designed primarily to study planetary nebulae, the instrument permits study of the shape of the continua of many weak sources which cannot easily be observed with high resolution systems.

Le Verrier magnificent and detestable astronomer

CERN Document Server

Lequeux, James

2013-01-01

Le Verrier was a superb scientist. His discovery of Neptune in 1846 made him the most famous astronomer of his time. He produced a complete theory of the motions of the planets which served as a basis for planetary ephemeris for a full century. Doing this, he discovered an anomaly in the motion of Mercury which later became the first proof of General Relativity. He also founded European meteorology. However his arrogance and bad temper created many enemies, and he was even fired from his position of Director of the Paris Observatory.

The astronomical revolution Copernicus, Kepler, Borelli

CERN Document Server

Koyre, Alexandre

2013-01-01

Originally published in English in 1973. This volume traces the development of the revolution which so drastically altered man's view of the universe in the sixteenth and seventeenth centuries. The ""astronomical revolution"" was accomplished in three stages, each linked with the work of one man. With Copernicus, the sun became the centre of the universe. With Kepler, celestial dynamics replaced the kinematics of circles and spheres used by Copernicus. With Borelli the unification of celestial and terrestrial physics was completed by abandonment of the circle in favour the straight line to inf

Intrinsic coincident full-Stokes polarimeter using stacked organic photovoltaics and architectural comparison of polarimeter techniques

Science.gov (United States)

Yang, Ruonan; Sen, Pratik; O'Connor, B. T.; Kudenov, M. W.

2017-08-01

An intrinsic coincident full-Stokes polarimeter is demonstrated by using stain-aligned polymer-based organic photovoltaics (OPVs) which can preferentially absorb certain polarized states of incident light. The photovoltaic-based polarimeter is capable of measuring four stokes parameters by cascading four semitransparent OPVs in series along the same optical axis. Two wave plates were incorporated into the system to modulate the S3 stokes parameter so as to reduce the condition number of the measurement matrix. The model for the full-Stokes polarimeter was established and validated, demonstrating an average RMS error of 0.84%. The optimization, based on minimizing the condition number of the 4-cell OPV design, showed that a condition number of 2.4 is possible. Performance of this in-line polarimeter concept was compared to other polarimeter architectures, including Division of Time (DoT), Division of Amplitude (DoAm), Division of Focal Plane (DoFP), and Division of Aperture (DoA) from signal-to-noise ratio (SNR) perspective. This in-line polarimeter concept has the potential to enable both high temporal (as compared with a DoT polarimeter) and high spatial resolution (as compared with DoFP and DoA polarimeters). We conclude that the intrinsic design has the same √2 SNR advantage as the DoAm polarimeter, but with greater compactness.

Experimental studies of the influence of fuel properties and operational conditions on stoking when combusting fuels in a fixed-bed reactor

Energy Technology Data Exchange (ETDEWEB)

Arias, Fabiana; Kolb, T.; Seifert, H.; Gehrmann, Hans-Joachim [Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany). Inst. for Technical Chemistry (ITC)

2013-09-01

Besides from knowledge about pollutant emission, knowledge of the combustion behavior of fuels plays a major role in the operation and optimization of combustion plants for waste and biomass. If the fuel is exchanged partly or completely in existing or newly designed grate-type combustion plants, adaptation of technical parameters is usually based on purely empirical studies. In the KLEAA fixed-bed reactor of KIT, Institute for Technical Chemistry (ITC), quantitative data on the combustion behavior can be determined from experimental investigations on the laboratory scale. Based on the characteristics obtained, the combustion behavior on a continuous grate can be estimated, This estimation is based on the assumption that no back mixing of the fuel occurs on the grate. Depending on the type of grate, however, stoking and back mixing play an important role. To improve the quality of the characteristics determined in KLEAA and enhance their transferability to the continuous process, it is necessary to determine the influence of fuel properties and operation conditions on stoking. Work is aimed at further developing the characteristics model taking into account a stoking factor describing the combustion behavior of a non-stoked fixed bed compared to a stoked fixed bed. The main task is to make a systematic study of the major parameters influencing stoking (e.g. stroke length, stroke frequency, geometry of the stoking unit, and fuel properties) in a fixed-bed reactor. The results shall be presented in the form of a semi-empirical equation. It is recommended to first study a model fuel, whose fuel properties are defined exactly and can be adjusted variably. Then, a stoking factor shall be derived from the studies. Possibly, a dimension analysis may be helpful. Finally, the results obtained are to be verified for residue-derived fuel. (orig.)

The Astronomical Pulse of Global Extinction Events

Directory of Open Access Journals (Sweden)

David F.V. Lewis

2006-01-01

Full Text Available The linkage between astronomical cycles and the periodicity of mass extinctions is reviewed and discussed. In particular, the apparent 26 million year cycle of global extinctions may be related to the motion of the solar system around the galaxy, especially perpendicular to the galactic plane. The potential relevance of Milankovitch cycles is also explored in the light of current evidence for the possible causes of extinction events over a geological timescale.

Astrophysics is easy! an introduction for the amateur astronomer

CERN Document Server

Inglis, Mike

2007-01-01

With some justification, many amateur astronomers believe astrophysics is a very difficult subject, requiring at least degree-level mathematics to understand it properly. This isn’t necessarily the case. Mike Inglis' quantitative approach to the subject explains all aspects of astrophysics in simple terms and cuts through the incomprehensible mathematics with which this fascinating subject is all too often associated. Astrophysics is Easy! begins by looking at the H-R diagram and other basic tools of astrophysics, then ranges across the universe, from a first look at the interstellar medium and nebulae, through the birth, evolution and death of stars, to the physics of galaxies and clusters of galaxies. A unique feature of this book is the way that Dr. Inglis lists example objects for practical observation at every stage, so that practical astronomers can go and look at the object or objects under discussion – using only easily-available commercial amateur equipment.

Large Deviations for Stochastic Tamed 3D Navier-Stokes Equations

International Nuclear Information System (INIS)

Roeckner, Michael; Zhang, Tusheng; Zhang Xicheng

2010-01-01

In this paper, using weak convergence method, we prove a large deviation principle of Freidlin-Wentzell type for the stochastic tamed 3D Navier-Stokes equations driven by multiplicative noise, which was investigated in (Roeckner and Zhang in Probab. Theory Relat. Fields 145(1-2), 211-267, 2009).

Getting in Shape : Swimming with Stokes and Surfing with Brinkman

NARCIS (Netherlands)

Bet, B.P.

2018-01-01

In this dissertation, we investigate the effect of shape on the motion of microscopic particles that perform a swimming motion or ‘surf’, driven by an external flow, through microscopic channels. These motions take place in a fluid, and fluid motion is in general described by the Navier-Stokes

Pseudo-stokes vector from complex signal representation of a speckle pattern and its applications to micro-displacement measurement

DEFF Research Database (Denmark)

Wang, W.; Ishijima, R.; Matsuda, A.

2010-01-01

As an improvement of the intensity correlation used widely in conventional electronic speckle photography, we propose a new technique for displacement measurement based on correlating Stokes-like parameters derivatives for transformed speckle patterns. The method is based on a Riesz transform of ...... are presented that demonstrate the validity and advantage of the proposed pseudo-Stokes vector correlation technique over conventional intensity correlation technique....... of the intensity speckle pattern, which converts the original real-valued signal into a complex signal. In closest analogy to the polarisation of a vector wave, the Stokes-like vector constructed from the spatial derivative of the generated complex signal has been applied for correlation. Experimental results...

Fine structure of the stimulated Raman spectrum in compressed hydrogen. The relaxation-oscillation mode of backscattered Stokes emission

International Nuclear Information System (INIS)

Bespalov, V.G.; Efimov, Yu.N.; Staselko, D.I.

1992-01-01

This paper studies the emission spectra of backscattered stimulated Raman scattering (SRS) in compressed hydrogen in the relaxation-oscillation mode and the compression SRS mode for the minimum width of the spontaneous scattering spectrum (in the region of the Dicke dip). It is shown that the generation of a train of Stokes-emission subpulses results in the appearance of fine structure in the backscattered SRS spectrum. The influence of the temporal structure of reflected Stokes pulses on this spectrum and on the appearance of fine structure in it is analyzed. The conditions for generating spectrally limited (without phase modulation), extremely coherent Stokes pulses are explained. 18 refs., 3 figs

Astronomers Detect Powerful Bursting Radio Source Discovery Points to New Class of Astronomical Objects

Science.gov (United States)

2005-03-01

Astronomers at Sweet Briar College and the Naval Research Laboratory (NRL) have detected a powerful new bursting radio source whose unique properties suggest the discovery of a new class of astronomical objects. The researchers have monitored the center of the Milky Way Galaxy for several years and reveal their findings in the March 3, 2005 edition of the journal, “Nature”. This radio image of the central region of the Milky Way Galaxy holds a new radio source, GCRT J1745-3009. The arrow points to an expanding ring of debris expelled by a supernova. CREDIT: N.E. Kassim et al., Naval Research Laboratory, NRAO/AUI/NSF Principal investigator, Dr. Scott Hyman, professor of physics at Sweet Briar College, said the discovery came after analyzing some additional observations from 2002 provided by researchers at Northwestern University. “"We hit the jackpot!” Hyman said referring to the observations. “An image of the Galactic center, made by collecting radio waves of about 1-meter in wavelength, revealed multiple bursts from the source during a seven-hour period from Sept. 30 to Oct. 1, 2002 — five bursts in fact, and repeating at remarkably constant intervals.” Hyman, four Sweet Briar students, and his NRL collaborators, Drs. Namir Kassim and Joseph Lazio, happened upon transient emission from two radio sources while studying the Galactic center in 1998. This prompted the team to propose an ongoing monitoring program using the National Science Foundation’s Very Large Array (VLA) radio telescope in New Mexico. The National Radio Astronomy Observatory, which operates the VLA, approved the program. The data collected, laid the groundwork for the detection of the new radio source. “Amazingly, even though the sky is known to be full of transient objects emitting at X- and gamma-ray wavelengths,” NRL astronomer Dr. Joseph Lazio pointed out, “very little has been done to look for radio bursts, which are often easier for astronomical objects to produce

Existence and uniqueness of global solutions for the modified anisotropic 3D Navier−Stokes equations

KAUST Repository

Bessaih, Hakima

2016-01-27

We study a modified three-dimensional incompressible anisotropic Navier−Stokes equations. The modification consists in the addition of a power term to the nonlinear convective one. This modification appears naturally in porous media when a fluid obeys the Darcy−Forchheimer law instead of the classical Darcy law. We prove global in time existence and uniqueness of solutions without assuming the smallness condition on the initial data. This improves the result obtained for the classical 3D incompressible anisotropic Navier−Stokes equations.

Entropy Stable Staggered Grid Spectral Collocation for the Burgers' and Compressible Navier-Stokes Equations

Science.gov (United States)

Carpenter, Mark H.; Parsani, Matteo; Fisher, Travis C.; Nielsen, Eric J.

2015-01-01

Staggered grid, entropy stable discontinuous spectral collocation operators of any order are developed for Burgers' and the compressible Navier-Stokes equations on unstructured hexahedral elements. This generalization of previous entropy stable spectral collocation work [1, 2], extends the applicable set of points from tensor product, Legendre-Gauss-Lobatto (LGL) to a combination of tensor product Legendre-Gauss (LG) and LGL points. The new semi-discrete operators discretely conserve mass, momentum, energy and satisfy a mathematical entropy inequality for both Burgers' and the compressible Navier-Stokes equations in three spatial dimensions. They are valid for smooth as well as discontinuous flows. The staggered LG and conventional LGL point formulations are compared on several challenging test problems. The staggered LG operators are significantly more accurate, although more costly to implement. The LG and LGL operators exhibit similar robustness, as is demonstrated using test problems known to be problematic for operators that lack a nonlinearly stability proof for the compressible Navier-Stokes equations (e.g., discontinuous Galerkin, spectral difference, or flux reconstruction operators).

Stability result for Navier-Stokes equations with entropy transport

Czech Academy of Sciences Publication Activity Database

Michálek, Martin

2015-01-01

Roč. 17, č. 2 (2015), s. 279-285 ISSN 1422-6928 R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : compressible Navier-Stokes system * entropy transport * effective viscous flux Subject RIV: BA - General Mathematics Impact factor: 1.023, year: 2015 http://link.springer.com/article/10.1007%2Fs00021-015-0205-x

On three-dimensional incompressible Navier-Stokes fluid on cantor sets in spherical Cantor type co-ordinate system

Directory of Open Access Journals (Sweden)

Meng Zhi-Jun

2016-01-01

Full Text Available This paper addresses the systems of the incompressible Navier-Stokes equations on Cantor sets without the external force involving the fractal heat-conduction problem vial local fractional derivative. The spherical Cantor type co-ordinate method is used to transfer the incompressible Navier-Stokes equation from the Cantorian co-ordinate system into the spherical Cantor type co-ordinate system.

Astronomical Data in Undergraduate courses

Science.gov (United States)

Clarkson, William I.; Swift, Carrie; Hughes, Kelli; Burke, Christopher J. F.; Burgess, Colin C.; Elrod, Aunna V.; Howard, Brittany; Stahl, Lucas; Matzke, David; Bord, Donald J.

2016-06-01

We present status and plans for our ongoing efforts to develop data analysis and problem-solving skills through Undergraduate Astronomy instruction. While our initiatives were developed with UM-Dearborn’s student body primarily in mind, they should be applicable for a wide range of institution and of student demographics. We focus here on two strands of our effort.Firstly, students in our Introductory Astronomy (ASTR 130) general-education course now perform several “Data Investigations”, in which they interrogate the Hubble Legacy Archive to illustrate important course concepts. This was motivated in part by the realization that typical public data archives now include tools to interrogate the observations that are sufficiently accessible that introductory astronomy students can use them to perform real science, albeit mostly at a descriptive level. We are continuing to refine these investigations, and, most importantly, to critically assess their effectiveness in terms of the student learning outcomes we wish to achieve. This work is supported by grant HST-EO-13758, provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.Secondly, at the advanced-undergraduate level, students taking courses in our Astronomy minor are encouraged to gain early experience in techniques of astronomical observation and analysis that are used by professionals. We present two example projects from the Fall 2015 iteration of our upper-division course ASTR330 (The Cosmic Distance Ladder), one involving Solar System measurements, the second producing calibrated aperture photometry. For both projects students conducted, analysed, and interpreted observations using our 0.4m campus telescope, and used many of the same analysis tools as professional astronomers. This work is supported partly from a Research Initiation and Seed grant from the

Breakdown of the Stokes-Einstein Relation for the Rotational Diffusivity of Polymer Grafted Nanoparticles in Polymer Melts.

Science.gov (United States)

Maldonado-Camargo, Lorena; Rinaldi, Carlos

2016-11-09

We report observations of breakdown of the Stokes-Einstein relation for the rotational diffusivity of polymer-grafted spherical nanoparticles in polymer melts. The rotational diffusivity of magnetic nanoparticles coated with poly(ethylene glycol) dispersed in poly(ethylene glycol) melts was determined through dynamic magnetic susceptibility measurements of the collective rotation of the magnetic nanoparticles due to imposed time-varying magnetic torques. These measurements clearly demonstrate the existence of a critical molecular weight for the melt polymer, below which the Stokes-Einstein relation accurately describes the rotational diffusivity of the polymer-grafted nanoparticles and above which the Stokes-Einstein relation ceases to apply. This critical molecular weight was found to correspond to a chain contour length that approximates the hydrodynamic diameter of the nanoparticles.

Resolving collisions in Stokes suspensions with an efficient and stable potential-free constrained optimization algorithm

Science.gov (United States)

Yan, Wen; Corona, Eduardo; Veerapaneni, Shravan; Shelley, Michael

2017-11-01

A common challenge in simulating dense suspension of rigid particles in Stokes flow is the numerical instability that arises due to particle collisions. To overcome this problem, often a strong repulsive potential between particles is prescribed. This in turn leads to numerical stiffness and dramatic reduction in stable time-step sizes. In this work, we eliminate such stiffness by introducing contact constraints explicitly and solving the hydrodynamic equations in tandem with a linear complementarity problem with inequality constraints. The Newton's third law of the collision force is explicitly guaranteed to allow consistent calculation of collision stresses. Efficient parallelization for shared-memory and distributed-memory architectures is also implemented. This method can be coupled to any Stokes hydrodynamics solver for particles with various shapes and allows us to simulate 104 107 spheres on a laptop, depending on the cost of the Stokes hydrodynamics solver. We demonstrate its performance on a range of applications from active matter to multi-physics problems.

Newton-like methods for Navier-Stokes solution

Science.gov (United States)

Qin, N.; Xu, X.; Richards, B. E.

1992-12-01

The paper reports on Newton-like methods called SFDN-alpha-GMRES and SQN-alpha-GMRES methods that have been devised and proven as powerful schemes for large nonlinear problems typical of viscous compressible Navier-Stokes solutions. They can be applied using a partially converged solution from a conventional explicit or approximate implicit method. Developments have included the efficient parallelization of the schemes on a distributed memory parallel computer. The methods are illustrated using a RISC workstation and a transputer parallel system respectively to solve a hypersonic vortical flow.

PPARC: Grid technology helps astronomers keep pace with the Universe

CERN Multimedia

2003-01-01

"Intelligent Agent" computer programs are roaming the Internet and watching the skies. These programs, using Grid computing technology, will help astronomers detect some of the most dramatic events in the universe, such as massive supernova explosions (1 page).

ASTROPOP: ASTROnomical Polarimetry and Photometry pipeline

Science.gov (United States)

Campagnolo, Julio C. N.

2018-05-01

AstroPoP reduces almost any CCD photometry and image polarimetry data. For photometry reduction, the code performs source finding, aperture and PSF photometry, astrometry calibration using different automated and non-automated methods and automated source identification and magnitude calibration based on online and local catalogs. For polarimetry, the code resolves linear and circular Stokes parameters produced by image beam splitter or polarizer polarimeters. In addition to the modular functions, ready-to-use pipelines based in configuration files and header keys are also provided with the code. AstroPOP was initially developed to reduce the IAGPOL polarimeter data installed at Observatório Pico dos Dias (Brazil).

Laboratory measurements and astronomical search for the HSO radical.

Science.gov (United States)

Cazzoli, Gabriele; Lattanzi, Valerio; Kirsch, Till; Gauss, Jürgen; Tercero, Belén; Cernicharo, José; Puzzarini, Cristina

2016-07-01

Despite the fact that many sulfur-bearing molecules, ranging from simple diatomic species up to astronomical complex molecules, have been detected in the interstellar medium, the sulfur chemistry in space is largely unknown and a depletion in the abundance of S-containing species has been observed in the cold, dense interstellar medium (ISM). The chemical form of the missing sulfur has yet to be identified. For these reasons, in view of the fact that there is a large abundance of triatomic species harbouring sulfur, oxygen, and hydrogen, we decided to investigate the HSO radical in the laboratory to try its astronomical detection. High-resolution measurements of the rotational spectrum of the HSO radical were carried out within a frequency range well up into the THz region. Subsequently, a rigorous search for HSO in the two most studied high-mass star-forming regions, Orion KL and Sagittarius (Sgr) B2, and in the cold dark cloud Barnard 1 (B1-b) was performed. The frequency coverage and the spectral resolution of our measurements allowed us to improve and extend the existing dataset of spectroscopic parameters, thus enabling accurate frequency predictions up to the THz range. These were used to derive the synthetic spectrum of HSO, by means of the MADEX code, according to the physical parameters of the astronomical source under consideration. For all sources investigated, the lack of HSO lines above the confusion limit of the data is evident. The derived upper limit to the abundance of HSO clearly indicates that this molecule does not achieve significant abundances in either the gas phase or in the ice mantles of dust grains.

Research on the optimal dynamical systems of three-dimensional Navier-Stokes equations based on weighted residual

Science.gov (United States)

Peng, NaiFu; Guan, Hui; Wu, ChuiJie

2016-04-01

In this paper, the theory of constructing optimal dynamical systems based on weighted residual presented by Wu & Sha is applied to three-dimensional Navier-Stokes equations, and the optimal dynamical system modeling equations are derived. Then the multiscale global optimization method based on coarse graining analysis is presented, by which a set of approximate global optimal bases is directly obtained from Navier-Stokes equations and the construction of optimal dynamical systems is realized. The optimal bases show good properties, such as showing the physical properties of complex flows and the turbulent vortex structures, being intrinsic to real physical problem and dynamical systems, and having scaling symmetry in mathematics, etc.. In conclusion, using fewer terms of optimal bases will approach the exact solutions of Navier-Stokes equations, and the dynamical systems based on them show the most optimal behavior.

The Moon in Close-up A Next Generation Astronomer's Guide

CERN Document Server

Wilkinson, John

2010-01-01

Information collected by recent space probes sent to explore the Moon by the USA, the European Space Agency, Japan, China and India has changed our knowledge and understanding of the Moon, particularly its geology, since the Apollo missions. This book presents those findings in a way that will be welcomed by amateur astronomers, students, educators and anyone interested in the Moon. Enhanced by many colour photos, it combines newly acquired scientific understanding with detailed descriptions and labelled photographic maps of the lunar surface. Guided by observation methods explained in the book and 17 Study Areas presented and carefully explained in the last chapter, amateur astronomers can observe these features from Earth using telescopes and binoculars. Readers who consult the photographic maps will gain a better understanding about the Moon’s topography and geology. The book is rounded out by a helpful glossary.

Generalized extended Navier-Stokes theory

DEFF Research Database (Denmark)

Hansen, J. S.; Daivis, Peter J.; Dyre, Jeppe C.

2013-01-01

in molecular fluids. To discuss these phenomena in detail, molecular dynamics simulations of molecular chlorine are performed for three different state points. In general, the theory captures the behavior for small wavevector and frequencies as expected. For example, in the hydrodynamic regime......The extended Navier-Stokes theory accounts for the coupling between the translational and rotational molecular degrees of freedom. In this paper, we generalize this theory to non-zero frequencies and wavevectors, which enables a new study of spatio-temporal correlation phenomena present...... and for molecular fluids with small moment of inertia like chlorine, the theory predicts that the longitudinal and transverse intrinsic angular velocity correlation functions are almost identical, which is also seen in the molecular dynamics simulations. However, the theory fails at large wavevector and frequencies...

Towards a robust and consistent middle Eocene astronomical timescale

Science.gov (United States)

Boulila, Slah; Vahlenkamp, Maximilian; De Vleeschouwer, David; Laskar, Jacques; Yamamoto, Yuhji; Pälike, Heiko; Kirtland Turner, Sandra; Sexton, Philip F.; Westerhold, Thomas; Röhl, Ursula

2018-03-01

Until now, the middle Eocene has remained a poorly constrained interval of efforts to produce an astrochronological timescale for the entire Cenozoic. This has given rise to a so-called "Eocene astronomical timescale gap" (Vandenberghe et al., 2012). A high-resolution astrochronological calibration for this interval has proven to be difficult to realize, mainly because carbonate-rich deep-marine sequences of this age are scarce. In this paper, we present records from middle Eocene carbonate-rich sequences from the North Atlantic Southeast Newfoundland Ridge (IODP Exp. 342, Sites U1408 and U1410), of which the cyclical sedimentary patterns allow for an orbital calibration of the geologic timescale between ∼38 and ∼48 Ma. These carbonate-rich cyclic sediments at Sites U1408 and U1410 were deposited as drift deposits and exhibit prominent lithological alternations (couplets) between greenish nannofossil-rich clay and white nannofossil ooze. The principal lithological couplet is driven by the obliquity of Earth's axial tilt, and the intensity of their expression is modulated by a cyclicity of about 173 kyr. This cyclicity corresponds to the interference of secular frequencies s3 and s6 (related to the precession of nodes of the Earth and Saturn, respectively). This 173-kyr obliquity amplitude modulation cycle is exceptionally well recorded in the XRF (X-ray fluorescence)-derived Ca/Fe ratio. In this work, we first demonstrate the stability of the (s3-s6) cycles using the latest astronomical solutions. Results show that this orbital component is stable back to at least 50 Ma, and can thus serve as a powerful geochronometer in the mid-Eocene portion of the Cenozoic timescale. We then exploit this potential by calibrating the geochronology of the recovered middle Eocene timescale between magnetic polarity Chrons C18n.1n and C21n. Comparison with previous timescales shows similarities, but also notable differences in durations of certain magnetic polarity chrons. We