Recent advances in Bonner Sphere neutron spectrometry
International Nuclear Information System (INIS)
Johnson, T.L.; Lee, Y.; Lowry, K.A.; Gorbics, S.G.
1987-01-01
Recent innovations, and the results of recent studies at the Naval Research Laboratory (NRL), and elsewhere, have significantly increased the usefulness of the Bonner Spohere Spectrometer (BSS) for routine Health Physics applications. A summary of some of the more important of these innovations and studies is given
International Nuclear Information System (INIS)
Espinoza G, J. G.; Martinez B, M. R.; Leon P, A. A.; Hernandez P, C. F.; Castaneda M, V. H.; Solis S, L. O.; Castaneda M, R.; Ortiz R, J. M.; Vega C, H. R.; Mendez, R.; Gallego, E.; De Sousa L, M. A.
2016-10-01
For neutron spectrometry and neutron dosimetry, the Bonner spheres spectrometric system has been the most widely used system, however, the number, size and weight of the spheres composing the system, as well as the need to use a reconstruction code and the long periods of time used to carry out the measurements are some of the disadvantages of this system. For the reconstruction of the spectra, different techniques such as artificial neural networks of reverse propagation have been used. The objective of this work was to reduce the number of Bonner spheres and to use counting speeds in a reverse propagation neural network, optimized by means of the robust design methodology, to reconstruct the neutron spectra. For the design of the neural network we used the neutron spectra of the IAEA and the response matrix of the Bonner spheres with 6 LiI(Eu) detector. The performance of the network was compared; using 7 Bonner spheres against other cases where only 2 and one sphere are used. The network topologies were trained 36 times for each case keeping constant the objective error (1E(-3)), the training algorithm was trains cg and the robust design methodology to determine the best network architectures. With these, the best and worst results were compared. The results obtained using 7 spheres were similar to those with the 5-in sphere, however is still in an information analysis stage. (Author)
NSDUAZ unfolding package for neutron spectrometry and dosimetry with Bonner spheres
Energy Technology Data Exchange (ETDEWEB)
Vega C, H. R.; Martinez B, M. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Ortiz R, J. M., E-mail: fermineutron@yahoo.com [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica, Av. Ramon Lopez Velarde 801, Col. Centro, 98000 Zacatecas (Mexico)
2011-10-15
NSDUAZ (Neutron Spectrometry and Dosimetry for the Universidad Autonoma de Zacatecas) is a user friendly neutron unfolding package for Bonner sphere spectrometer with {sup 6}Lil(Eu) developed under Lab View environment. Unfolding is carried out using a recursive iterative procedure with the SPUNIT algorithm, where the starting spectrum is obtained from a library initial guess spectrum to start the iterations, the package include a statistical procedure based on the count rates relative to the count rate in the 8 inches-diameter sphere to select the initial spectrum. Neutron spectrum is unfolded in 32 energy groups ranging from 10{sup -8} up to 231.2 MeV. (Author)
Golnik, N; Králik, M
2002-01-01
A Bonner sphere spectrometer and the REM-2 recombination chamber were used for inter-comparison measurements of the neutron component of ambient dose equivalent, H sub n *(10) in reference neutron fields. The sup 2 sup 4 sup 1 Am-Be and sup 2 sup 5 sup 2 Cf neutron sources were exposed either free-in-air or placed in iron or paraffin filters. The REM-2 recombination chamber was used as a LET spectrometer. The agreement of H sub n *(10) values measured with both the methods was within experimental uncertainties of few percent. The determined neutron spectra were used for calculations of the REM-2 chamber response to H*(10).
Energy Technology Data Exchange (ETDEWEB)
Espinoza G, J. G.; Martinez B, M. R.; Leon P, A. A.; Hernandez P, C. F.; Castaneda M, V. H.; Solis S, L. O.; Castaneda M, R.; Ortiz R, J. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Av. Ramon Lopez Velarde 801, Col. Centro, 98000 Zacatecas, Zac. (Mexico); Mendez, R. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas, Laboratorio de Patrones Neutronicos, Av. Complutense 22, 28040 Madrid (Spain); Gallego, E. [Universidad Politecnica de Madrid, Departamento de Ingenieria Nuclear, C. Jose Gutierrez Abascal 2, 28006 Madrid (Spain); De Sousa L, M. A. [Centro de Desenvolvimento da Tecnologia Nuclear / CNEN, Av. Pte. Antonio Carlos 6627, Pampulha, 31270-901 Belo Horizonte, MG (Brazil)
2016-10-15
For neutron spectrometry and neutron dosimetry, the Bonner spheres spectrometric system has been the most widely used system, however, the number, size and weight of the spheres composing the system, as well as the need to use a reconstruction code and the long periods of time used to carry out the measurements are some of the disadvantages of this system. For the reconstruction of the spectra, different techniques such as artificial neural networks of reverse propagation have been used. The objective of this work was to reduce the number of Bonner spheres and to use counting speeds in a reverse propagation neural network, optimized by means of the robust design methodology, to reconstruct the neutron spectra. For the design of the neural network we used the neutron spectra of the IAEA and the response matrix of the Bonner spheres with {sup 6}LiI(Eu) detector. The performance of the network was compared; using 7 Bonner spheres against other cases where only 2 and one sphere are used. The network topologies were trained 36 times for each case keeping constant the objective error (1E(-3)), the training algorithm was trains cg and the robust design methodology to determine the best network architectures. With these, the best and worst results were compared. The results obtained using 7 spheres were similar to those with the 5-in sphere, however is still in an information analysis stage. (Author)
Neutron spectrometry with Bonner spheres for area monitoring in particle accelerators
International Nuclear Information System (INIS)
Bedogni, R.
2011-01-01
Selecting the instruments to determine the operational quantities in the neutron fields produced by particle accelerators involves a combination of aspects, which is peculiar to these environments: the energy distribution of the neutron field, the continuous or pulsed time structure of the beam, the presence of other radiations to which the neutron instruments could have significant response and the large variability in the dose rate, which can be observed when moving from areas near the beam line to free-access areas. The use of spectrometric techniques in support of traditional instruments is highly recommended to improve the accuracy of dosimetric evaluations. The multi-sphere or Bonner Sphere Spectrometer (BSS) is certainly the most used device, due to characteristics such as the wide energy range, large variety of active and passive detectors suited for different workplaces, good photon discrimination and the simple signal management. Disadvantages are the poor energy resolution, weight and need to sequentially irradiate the spheres, leading to usually long measurement sessions. Moreover, complex unfolding analyses are needed to obtain the neutron spectra. This work is an overview of the BSS for area monitoring in particle accelerators. (authors)
International Nuclear Information System (INIS)
Leon P, A. A.; Martinez B, M. R.; Hernandez P, C. F.; Espinoza G, J. G.; Castaneda M, V. H.; Solis S, L. O.; Castaneda M, R.; Ortiz R, J. M.; Vega C, H. R.; Mendez V, R.; Gallego, E.; De Sousa L, M. A.
2016-10-01
The neutron spectrometry is an experimental process for determining the energy distribution called the Spectrum. Among the methods available for neutron spectrometry, one can mention the Bonner Sphere Spectrometric System as one of the most used, consisting of a detector placed in the center of a set of polyethylene spheres whose diameters range from 2 to 18 inches, however has some disadvantages such as the long periods of time to perform the measurements, the weight and the spheres number that vary according to the system. From this, alternative methods such as artificial neural networks are proposed. For this project neural networks of reverse propagation were used with the methodology of robust design of artificial neural networks, with the aid of a computational tool that maximizes the performance, making the time used for the training s of the network is the smallest possible and thus gets the orthogonal fixes quickly to determine the best network topology. The counting rates of a spectrometric system with 7 spheres, 2 spheres and one sphere of 5 and 8 inches were used. This methodology seeks to reduce the work used as in the spectrometric system formed by a greater number of spheres, since to enter less data in the counting rates to obtain the spectra with 60 energy levels saves time and space, because at having a smaller number of spheres its portability is easier to move from one place to another, for this we performed several experiments with different errors until we reached the optimal error so that the topology of the network was appropriate and find the best design parameters. A statistical software JMP was also used to obtain the best topologies and thus to retrain obtaining its best and worst spectra, in order to determine if the reduction is possible. (Author)
Wiegel, B; Bedogni, R; Caresana, M; Esposito, A; Fehrenbacher, G; Ferrarini, M; Hohmann, E; Hranitzky, C; Kasper, A; Khurana, S; Mares, V; Reginatto, M; Rollet, S; Rühm, W; Schardt, D; Silari, M; Simmer, G; Weitzenegger, E
2009-01-01
The European Commission has funded within its 6th Framework Programme a three-year project (2005–2007) called CONRAD, COordinated Network for RAdiation Dosimetry. A major task of the CONRAD Work Package “complex mixed radiation fields at workplaces” was to organise a benchmark exercise in a workplace field at a high-energy particle accelerator where neutrons are the dominant radiation component. The CONRAD benchmark exercise took place at the Gesellschaft für Schwerionenforschung mbH (GSI) in Darmstadt, Germany in July 2006. In this paper, the results of the spectrometry using four extended -range Bonner sphere spectrometers of four different institutes are reported. Outside Cave A the neutron spectra were measured with three spectrometers at six selected positions and ambient dose equivalent values were derived for use in the intercomparison with other area monitors and dosemeters. At a common position all three spectrometers were used to allow a direct comparison of their results which acts as an int...
Energy Technology Data Exchange (ETDEWEB)
Leon P, A. A.; Martinez B, M. R.; Hernandez P, C. F.; Espinoza G, J. G.; Castaneda M, V. H.; Solis S, L. O.; Castaneda M, R.; Ortiz R, J. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Av. Ramon Lopez Velarde 801, Col. Centro, 98000 Zacatecas, Zac. (Mexico); Mendez V, R. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas, Laboratorio de Patrones Neutronicos, Av. Complutense 22, 28040 Madrid (Spain); Gallego, E. [Universidad Politecnica de Madrid, Departamento de Ingenieria Nuclear, ETSI Industriales, Jose Gutierrez Abascal 2, 28006 Madrid (Spain); De Sousa L, M. A. [Centro de Desenvolvimento da Tecnologia Nuclear / CNEN, Av. Pte. Antonio Carlos 6627, 31270-901 Pampulha, Belo Horizonte, Minas Gerais (Brazil)
2016-10-15
The neutron spectrometry is an experimental process for determining the energy distribution called the Spectrum. Among the methods available for neutron spectrometry, one can mention the Bonner Sphere Spectrometric System as one of the most used, consisting of a detector placed in the center of a set of polyethylene spheres whose diameters range from 2 to 18 inches, however has some disadvantages such as the long periods of time to perform the measurements, the weight and the spheres number that vary according to the system. From this, alternative methods such as artificial neural networks are proposed. For this project neural networks of reverse propagation were used with the methodology of robust design of artificial neural networks, with the aid of a computational tool that maximizes the performance, making the time used for the training s of the network is the smallest possible and thus gets the orthogonal fixes quickly to determine the best network topology. The counting rates of a spectrometric system with 7 spheres, 2 spheres and one sphere of 5 and 8 inches were used. This methodology seeks to reduce the work used as in the spectrometric system formed by a greater number of spheres, since to enter less data in the counting rates to obtain the spectra with 60 energy levels saves time and space, because at having a smaller number of spheres its portability is easier to move from one place to another, for this we performed several experiments with different errors until we reached the optimal error so that the topology of the network was appropriate and find the best design parameters. A statistical software JMP was also used to obtain the best topologies and thus to retrain obtaining its best and worst spectra, in order to determine if the reduction is possible. (Author)
Applications of Bonner sphere detectors in neutron field dosimetry
International Nuclear Information System (INIS)
Awschalom, M.; Sanna, R.S.
1983-09-01
The theory of neutron moderation and spectroscopy are briefly reviewed, and moderators that are useful for Bonner sphere spectrometers are discussed. The choice of the neutron detector for a Bonner sphere spectrometer is examined. Spectral deconvolution methods are briefly reviewed, including derivative, parametric, quadrature, and Monte Carlo methods. Calibration is then discussed
Energy Technology Data Exchange (ETDEWEB)
Martinez B, M.R.; Ortiz R, J.M.; Vega C, H.R. [UAZ, Av. Ramon Lopez Velarde No. 801, 98000 Zacatecas (Mexico)
2006-07-01
An Artificial Neural Network has been designed, trained and tested to unfold neutron spectra and simultaneously to calculate equivalent doses. A set of 187 neutron spectra compiled by the International Atomic Energy Agency and 13 equivalent doses were used in the artificial neural network designed, trained and tested. In order to design the neural network was used the robust design of artificial neural networks methodology, which assures that the quality of the neural networks takes into account from the design stage. Unless previous works, here, for first time a group of neural networks were designed and trained to unfold 187 neutron spectra and at the same time to calculate 13 equivalent doses, starting from the count rates coming from the Bonner spheres system by using a systematic and experimental strategy. (Author)
International Nuclear Information System (INIS)
Martinez B, M.R.; Ortiz R, J.M.; Vega C, H.R.
2006-01-01
An Artificial Neural Network has been designed, trained and tested to unfold neutron spectra and simultaneously to calculate equivalent doses. A set of 187 neutron spectra compiled by the International Atomic Energy Agency and 13 equivalent doses were used in the artificial neural network designed, trained and tested. In order to design the neural network was used the robust design of artificial neural networks methodology, which assures that the quality of the neural networks takes into account from the design stage. Unless previous works, here, for first time a group of neural networks were designed and trained to unfold 187 neutron spectra and at the same time to calculate 13 equivalent doses, starting from the count rates coming from the Bonner spheres system by using a systematic and experimental strategy. (Author)
Extraction of neutron spectral information from Bonner-Sphere data
Haney, J H; Zaidins, C S
1999-01-01
We have extended a least-squares method of extracting neutron spectral information from Bonner-Sphere data which was previously developed by Zaidins et al. (Med. Phys. 5 (1978) 42). A pulse-height analysis with background stripping is employed which provided a more accurate count rate for each sphere. Newer response curves by Mares and Schraube (Nucl. Instr. and Meth. A 366 (1994) 461) were included for the moderating spheres and the bare detector which comprise the Bonner spectrometer system. Finally, the neutron energy spectrum of interest was divided using the philosophy of fuzzy logic into three trapezoidal regimes corresponding to slow, moderate, and fast neutrons. Spectral data was taken using a PuBe source in two different environments and the analyzed data is presented for these cases as slow, moderate, and fast neutron fluences. (author)
International Nuclear Information System (INIS)
Bedogni, Roberto; Pelliccioni, Maurizio; Esposito, Adolfo
2010-01-01
Due to the increased interest of the scientific community in the applications of synchrotron light, there is an increasing demand of high-energy electron facilities, testified by the construction of several new facilities worldwide. The radiation protection around such facilities requires accurate experimental methods to determine the dose due to prompt radiation fields. Neutron fields, in particular, are the most complex to measure, because they extend in energy from thermal (10 -8 MeV) up to hundreds MeV and because the responses of dosemeters and survey meters usually have large energy dependence. The Bonner Spheres Spectrometer (BSS) is in practice the only instrument able to respond over the whole energy range of interest, and for this reason it is frequently used to derive neutron spectra and dosimetric quantities in accelerator workplaces. Nevertheless, complex unfolding algorithms are needed to derive the neutron spectra from the experimental BSS data. This paper presents a parametric model specially developed for the unfolding of the experimental data measured with BSS around high-energy electron accelerators. The work consists of the following stages: (1) Generation with the FLUKA code, of a set of neutron spectra representing the radiation environment around accelerators with different electron energies; (2) formulation of a parametric model able to describe these spectra, with particular attention to the high-energy component (>10 MeV), which may be responsible for a large part of the dose in workplaces; and (3) implementation of this model in an existing unfolding code.
Bedogni, Roberto; Pelliccioni, Maurizio; Esposito, Adolfo
2010-03-01
Due to the increased interest of the scientific community in the applications of synchrotron light, there is an increasing demand of high-energy electron facilities, testified by the construction of several new facilities worldwide. The radiation protection around such facilities requires accurate experimental methods to determine the dose due to prompt radiation fields. Neutron fields, in particular, are the most complex to measure, because they extend in energy from thermal (10 -8 MeV) up to hundreds MeV and because the responses of dosemeters and survey meters usually have large energy dependence. The Bonner Spheres Spectrometer (BSS) is in practice the only instrument able to respond over the whole energy range of interest, and for this reason it is frequently used to derive neutron spectra and dosimetric quantities in accelerator workplaces. Nevertheless, complex unfolding algorithms are needed to derive the neutron spectra from the experimental BSS data. This paper presents a parametric model specially developed for the unfolding of the experimental data measured with BSS around high-energy electron accelerators. The work consists of the following stages: (1) Generation with the FLUKA code, of a set of neutron spectra representing the radiation environment around accelerators with different electron energies; (2) formulation of a parametric model able to describe these spectra, with particular attention to the high-energy component (>10 MeV), which may be responsible for a large part of the dose in workplaces; and (3) implementation of this model in an existing unfolding code.
Photoneutron spectrum measured with Bonner Spheres in Planetary method mode
Energy Technology Data Exchange (ETDEWEB)
Benites R, J. [Centro Estatal de Cancerologia de Nayarit, Servicio de Seguridad Radiologica, Calz. de la Cruz 118 Sur, 63000 Tepic, Nayarit (Mexico); Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Apdo. Postal 336, 98000 Zacatecas (Mexico); Velazquez F, J., E-mail: jlbenitesr@prodigy.net.mx [Universidad Autonoma de Nayarit, Posgrado en Ciencias Biologico Agropecuarias, Carretera Tepic-Compostela Km 9, 63780 Jalisco-Nayarit (Mexico)
2012-10-15
We measured the spectrum of photoneutrons at 100 cm isocenter linear accelerator (Linac) Varian ix operating at 15 MV Bremsstrahlung mode. In this process was used a radiation field of 20 x 20 cm{sup 2} at a depth of 5 cm in a solid water phantom with dimensions of 30 x 30 x 15 cm{sup 3}. The measurement was performed with a system using it Bonner Spheres spectrometric method Planetary mode. As neutron detector of the spectrometer is used thermoluminescent dosimeters pairs of type 600 and 700. (Author)
Characterisation of the IPNE Bonner sphere spectrometer by comparison with the PTB system
Alevra, A V
2002-01-01
An existing set of Bonner spheres of the Institute for Physics and Nuclear Engineering in Bucharest has been modified following the PTB design for application of an sup 3 He-filled SP9 counter. By simple interpolations of the fluence responses of the PTB spheres, a preliminary fluence response matrix could be established for the IPNE Bonner sphere set. For further adjustments of the preliminary responses and for validation of the final fluence response matrix of the Romanian Bonner sphere spectrometer, calibration measurements with a reference sup 2 sup 5 sup 2 Cf neutron source and joint measurements, including the PTB Bonner sphere spectrometer, were performed in a few neutron fields differing substantially in their spectral distributions. It is estimated that the integral neutron fluences and dose-equivalent values can now be determined with the Romanian spectrometer with uncertainties of about +-4% and +-8%, respectively.
STS-36 onboard view of the 'Bonner Sphere', a neutron flux experiment
1990-01-01
STS-36 experiment called the 'Bonner Sphere', a polyethylene object containing neutron activation foils in its core, is mounted on the middeck starboard wall of Atlantis, Orbiter Vehicle (OV) 104. Different sphere sizes - this one represents the larger ones - sample different portions of high energy neutron flux. The sphere is enclosed in a fire retardant nomex bag.
Ortiz-Rodríguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.; Solís Sánches, L. O.; Miranda, R. Castañeda; Cervantes Viramontes, J. M.; Vega-Carrillo, H. R.
2013-07-01
In this work a neutron spectrum unfolding code, based on artificial intelligence technology is presented. The code called "Neutron Spectrometry and Dosimetry with Artificial Neural Networks and two Bonner spheres", (NSDann2BS), was designed in a graphical user interface under the LabVIEW programming environment. The main features of this code are to use an embedded artificial neural network architecture optimized with the "Robust design of artificial neural networks methodology" and to use two Bonner spheres as the only piece of information. In order to build the code here presented, once the net topology was optimized and properly trained, knowledge stored at synaptic weights was extracted and using a graphical framework build on the LabVIEW programming environment, the NSDann2BS code was designed. This code is friendly, intuitive and easy to use for the end user. The code is freely available upon request to authors. To demonstrate the use of the neural net embedded in the NSDann2BS code, the rate counts of 252Cf, 241AmBe and 239PuBe neutron sources measured with a Bonner spheres system.
International Nuclear Information System (INIS)
Ortiz-Rodríguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.; Solís Sánches, L. O.; Miranda, R. Castañeda; Cervantes Viramontes, J. M.; Vega-Carrillo, H. R.
2013-01-01
In this work a neutron spectrum unfolding code, based on artificial intelligence technology is presented. The code called ''Neutron Spectrometry and Dosimetry with Artificial Neural Networks and two Bonner spheres'', (NSDann2BS), was designed in a graphical user interface under the LabVIEW programming environment. The main features of this code are to use an embedded artificial neural network architecture optimized with the ''Robust design of artificial neural networks methodology'' and to use two Bonner spheres as the only piece of information. In order to build the code here presented, once the net topology was optimized and properly trained, knowledge stored at synaptic weights was extracted and using a graphical framework build on the LabVIEW programming environment, the NSDann2BS code was designed. This code is friendly, intuitive and easy to use for the end user. The code is freely available upon request to authors. To demonstrate the use of the neural net embedded in the NSDann2BS code, the rate counts of 252 Cf, 241 AmBe and 239 PuBe neutron sources measured with a Bonner spheres system
Energy Technology Data Exchange (ETDEWEB)
Ortiz-Rodriguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.; Solis Sanches, L. O.; Miranda, R. Castaneda; Cervantes Viramontes, J. M. [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica. Av. Ramon Lopez Velarde 801. Col. Centro Zacatecas, Zac (Mexico); Vega-Carrillo, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica. Av. Ramon Lopez Velarde 801. Col. Centro Zacatecas, Zac., Mexico. and Unidad Academica de Estudios Nucleares. C. Cip (Mexico)
2013-07-03
In this work a neutron spectrum unfolding code, based on artificial intelligence technology is presented. The code called ''Neutron Spectrometry and Dosimetry with Artificial Neural Networks and two Bonner spheres'', (NSDann2BS), was designed in a graphical user interface under the LabVIEW programming environment. The main features of this code are to use an embedded artificial neural network architecture optimized with the ''Robust design of artificial neural networks methodology'' and to use two Bonner spheres as the only piece of information. In order to build the code here presented, once the net topology was optimized and properly trained, knowledge stored at synaptic weights was extracted and using a graphical framework build on the LabVIEW programming environment, the NSDann2BS code was designed. This code is friendly, intuitive and easy to use for the end user. The code is freely available upon request to authors. To demonstrate the use of the neural net embedded in the NSDann2BS code, the rate counts of {sup 252}Cf, {sup 241}AmBe and {sup 239}PuBe neutron sources measured with a Bonner spheres system.
Iterative code for the reconstruction of the neutrons spectrum using the Bonner spheres
International Nuclear Information System (INIS)
Reyes H, A.; Ortiz R, J. M.; Vega C, H. R.
2012-10-01
The neutrons are the particles more difficult of detecting for their intrinsic nature. The absence of the neutrons charge makes that an interaction exists with the matter in a different way. The term radiation spectrometry can use to describe the measurement of the intensity of a radiation field with regard to the energy. The intensity distribution with relationship to the energy is commonly known as spectrum. A method to know the neutrons spectrum in the radiation fields to those that people are exposed is the use of the known system as spectrometry system of Bonner spheres, being the more used for the purposes of the radiological protection. The current interest in the electrons spectrometry has stimulated the development of several procedures to carry out the reconstruction of the spectra. During the last decades new codes have been developed such as BUNKIUT, Bums, Fruit, UMG, etc., however, these methods still present several inconveniences as the complexity in their use, the necessity of an expert user and a very near initial spectrum to the spectrum that is wanted to obtain. To solve the mentioned problems it was development the program NSDUAZ (Neutron Spectrometry and Dosimetry from Autonomous University of Zacatecas). The objective of the present work is to prove and to validate the code before mentioned making an analysis of likeness and differences and of advantages and disadvantages with relationship to the codes used at the present time. (Author)
The use of a Bonner sphere spectrometer for determining the spatial distribution of neutron fields
Varela, A; Jimenez, F; Calvillo, J
1999-01-01
The directional properties of a modified Bonner-type spectrometer, using spheres with a radial hole, are described in this report. It was found that spheres with these modifications are able to detect the spatial distribution of a neutron field. The neutrons were generated by the sup 9 Be(d,n) sup 1 sup 0 B reaction, produced by bombarding a thick Be target with 4 MeV deutrons provided by a tandem Van de Graaff accelerator.
International Nuclear Information System (INIS)
Mizukpshi, Tomoaki; Watanabe, Kenichi; Yamazaki, Atsushi; Uritan, Akira; Iguchi, Tetsuo; Ogata, Tomohiro; Muramatsu, Takashi
2016-01-01
In order to measure neutron energy spectra, the conventional Bonner Sphere Spectrometers (BSS) are widely used. In this spectrometer, several measurements with different size Bonner spheres are required. Operators should, therefore, place these spheres in several times to a measurement point where radiation dose might be relatively high. In order to reduce this effort, novel neutron energy spectrometer using an onion-like single Bonner sphere was proposed in our group. This Bonner sphere has multiple sensitive spherical shell layers in the single sphere. In this spectrometer, a band-shaped thermal neutron detection medium, which consists of a LiF-ZnS mixed powder scintillator sheet and a wavelength-shifting (WLS) fiber readout, was looped to each sphere at equal angular intervals. Amount of LiF neutron converter is reduced near polar region, where the band-shaped detectors are concentrated, in order to uniform the directional sensitivity. The LiF-ZnS mixed powder has an advantage of extremely high light yield. However, since it is opaque, scintillation photons cannot be collect uniformly. This type of detector shows no characteristic shape in the pulse height spectrum. Subsequently, it is difficult to set the pulse height discrimination level. This issue causes sensitivity fluctuation due to gain instability of photodetectors and/or electric modules. In order to solve this problem, we propose to replace the LiF-ZnS mixed powder into a flexible and Transparent RUbber SheeT type LiCaAlF6 (TRUST LiCAF) scintillator. TRUST LiCAF scintillator can show a peak shape corresponding to neutron absorption events in the pulse height spectrum. We fabricated the prototype detector with five sensitive layers using TRUST LiCAF scintillator and conducted basic experiments to evaluate the directional uniformity of the sensitivity. The fabricated detector shows excellent directional uniformity of the neutron sensitivity
Energy Technology Data Exchange (ETDEWEB)
Mizukpshi, Tomoaki; Watanabe, Kenichi; Yamazaki, Atsushi; Uritan, Akira [Nagoya University, Nagoya (Japan); Iguchi, Tetsuo; Ogata, Tomohiro; Muramatsu, Takashi [Mitsubishi Heavy Industries Ltd., Kobe(Japan)
2016-09-15
In order to measure neutron energy spectra, the conventional Bonner Sphere Spectrometers (BSS) are widely used. In this spectrometer, several measurements with different size Bonner spheres are required. Operators should, therefore, place these spheres in several times to a measurement point where radiation dose might be relatively high. In order to reduce this effort, novel neutron energy spectrometer using an onion-like single Bonner sphere was proposed in our group. This Bonner sphere has multiple sensitive spherical shell layers in the single sphere. In this spectrometer, a band-shaped thermal neutron detection medium, which consists of a LiF-ZnS mixed powder scintillator sheet and a wavelength-shifting (WLS) fiber readout, was looped to each sphere at equal angular intervals. Amount of LiF neutron converter is reduced near polar region, where the band-shaped detectors are concentrated, in order to uniform the directional sensitivity. The LiF-ZnS mixed powder has an advantage of extremely high light yield. However, since it is opaque, scintillation photons cannot be collect uniformly. This type of detector shows no characteristic shape in the pulse height spectrum. Subsequently, it is difficult to set the pulse height discrimination level. This issue causes sensitivity fluctuation due to gain instability of photodetectors and/or electric modules. In order to solve this problem, we propose to replace the LiF-ZnS mixed powder into a flexible and Transparent RUbber SheeT type LiCaAlF6 (TRUST LiCAF) scintillator. TRUST LiCAF scintillator can show a peak shape corresponding to neutron absorption events in the pulse height spectrum. We fabricated the prototype detector with five sensitive layers using TRUST LiCAF scintillator and conducted basic experiments to evaluate the directional uniformity of the sensitivity. The fabricated detector shows excellent directional uniformity of the neutron sensitivity.
AUTHOR|(INSPIRE)INSPIRE-00406842; Bay, Aurelio; Silari, Marco; Aroua, Abbas
The use of spectrometry to provide information for neutron radiation protection has become an increasingly important activity over recent years. The need for spectral data arises because neither area survey instruments nor personal dosimeters give the correct dose equivalent results at all neutron energies. It is important therefore to know the spectra of the fields in which these devices are used. One of the systems most commonly employed in neutron spectrometry and dosimetry is the Bonner Sphere Spectrometers (BSS). The extended- range BSS that was used for this work, consists of 7 spheres with an overall response to neutrons up to 2 GeV. A 3He detector is used as a thermal counter in the centre of each sphere. In the context of this thesis the BSS was calibrated in monoenergetic neutron fields at low and intermediate energies. It was also used for measurements in several high energy mixed fields. These measurements have led to the calculation of neutron yields and spectral fluences from unshielded targets....
Hu, Qingdong; Ma, Hao; Zeng, Zhi; Cheng, Jianping; Chen, Yunhua; He, Shengming; Li, Junli; Shen, Manbin; Wu, Shiyong; Yue, Qian; Yue, Jianfeng; Zhang, Hui
2017-07-01
The neutron background spectrum from thermal neutron to 20 MeV fast neutron was measured at the first experimental hall of China Jinping underground laboratory with a Bonner multi-sphere spectrometer. The measurement system was validated by a 252Cf source and inconformity was corrected. Due to micro charge discharge, the dataset was screened and background from the steel of the detectors was estimated by MC simulation. Based on genetic algorithm we obtained the energy distribution of the neutron and the total flux of neutron was (2.69±1.02) ×10-5 cm-2 s-1.
International Nuclear Information System (INIS)
Ortiz R, J.M.; Martinez B, M.R.; Arteaga A, T.; Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E.
2005-01-01
The artificial neural networks (RN) have been used successfully to solve a wide variety of problems. However to determine an appropriate set of values of the structural parameters and of learning of these, it continues being even a difficult task. Contrary to previous works, here a set of neural networks is designed to reconstruct neutron spectra starting from the counting rates coming from the detectors of the Bonner spheres system, using a systematic and experimental strategy for the robust design of multilayer neural networks of the feed forward type of inverse propagation. The robust design is formulated as a design problem of Taguchi parameters. It was selected a set of 53 neutron spectra, compiled by the International Atomic Energy Agency, the counting rates were calculated that would take place in a Bonner spheres system, the set was arranged according to the wave form of those spectra. With these data and applying the Taguchi methodology to determine the best parameters of the network topology, it was trained and it proved the same one with the spectra. (Author)
Response matrix calculation of a Bonner Sphere Spectrometer using ENDF/B-VII libraries
Energy Technology Data Exchange (ETDEWEB)
Morató, Sergio; Juste, Belén; Miró, Rafael; Verdú, Gumersindo [Instituto de Seguridad Industrial, Radiofísica y Medioambiental (ISIRYM), Universitat Politècnica de València (Spain); Guardia, Vicent, E-mail: bejusvi@iqn.upv.es [GD Energy Services, Valencia (Spain). Grupo dominguis
2017-07-01
The present work is focused on the reconstruction of a neutron spectra using a multisphere spectrometer also called Bonner Spheres System (BSS). To that, the determination of the response detector curves is necessary therefore we have obtained the response matrix of a neutron detector by Monte Carlo (MC) simulation with MCNP6 where the use of unstructured mesh geometries is introduced as a novelty. The aim of these curves was to study the theoretical response of a widespread neutron spectrometer exposed to neutron radiation. A neutron detector device has been used in this work which is formed by a multispheres spectrometer (BSS) that uses 6 high density polyethylene spheres with different diameters. The BSS consists of a set of 0.95 g/cm{sup 3} high density polyethylene spheres. The detector is composed of a lithium iodide 6LiI cylindrical scintillator crystal 4mm x 4mm size LUDLUM Model 42 coupled to a photomultiplier tube. Thermal tables are required to include polyethylene cross section in the simulation. These data are essential to get correct and accurate results in problems involving neutron thermalization. Nowadays available literature present the response matrix calculated with ENDF.B.V cross section libraries (V.Mares et al 1993) or with ENDF.B.VI (R.Vega Carrillo et al 2007). This work uses two novelties to calculate the response matrix. On the one hand the use of unstructured meshes to simulate the geometry of the detector and the Bonner Spheres and on the other hand the use of the updated ENDF.B.VII cross sections libraries. A set of simulations have been performed to obtain the detector response matrix. 29 mono energetic neutron beams between 10 KeV to 20 MeV were used as source for each moderator sphere up to a total of 174 simulations. Each mono energetic source was defined with the same diameter as the moderating sphere used in its corresponding simulation and the spheres were uniformly irradiated from the top of the photomultiplier tube. Some
International Nuclear Information System (INIS)
Wiegel, B.; Alevra, A.V.; Siebert, B.R.L.
1994-11-01
A realistic geometry model of a Bonner sphere system with a spherical 3 He-filled proportional counter and 12 polyethylene moderating spheres with diameters ranging from 7,62 cm (3'') to 45,72 cm (18'') is introduced. The MCNP Monte Carlo computer code is used to calculate the responses of this Bonner sphere system to monoenergetic neutrons in the energy range between 1 meV to 20 MeV. The relative uncertainties of the responses due to the Monte Carlo calculations are less than 1% for spheres up to 30,48 cm (12'') in diameter and less than 2% for the 15'' and 18'' spheres. Resonances in the carbon cross section are seen as significant structures in the response functions. Additional calculations were made to study the influence of the 3 He number density and the polyethylene mass density on the response as well as the angular dependence of the Bonner sphere system. The calculated responses can be adjusted to a large set of calibration measurements with only a single fit factor common to all sphere diameters and energies. (orig.) [de
Response Matrix of a Bonner Spheres Spectrometer with {sup 3} He Detector
Energy Technology Data Exchange (ETDEWEB)
Vega C, H.R.; Manzanares A, E.; Hernandez D, V.M. [Unidades Academicas de Estudios Nucleares, Ing. Electrica y Matematicas, Universidad Autonoma de Zacatecas, Apdo. Postal 336, 98000 Zacatecas (Mexico)]. e-mail: rvega@cantera.reduaz.mx
2004-07-01
Using MCNP code the response matrix of a Bonner spheres spectrometer was calculated. The spectrometer has a 3.2 cm-diameter thermal neutron detector; this is a {sup 3} He-filled proportional counter that is located at the center of a set of polyethylene spheres. The response was calculated for 0, 3, 5, 6, 8, 10, 12 and 16 inches-diameter polyethylene spheres for neutrons whose energy goes from 10-9 to 20 MeV. The response matrix was compared with a set of responses measured with several monoenergetic neutron sources, from this comparison calculated matrix is in agreement with the experimental results. Also this matrix was compared against the response matrix calculated for the PTB C spectrometer, Nevertheless that calculation was carried out using a detailed model to describe the proportional counter both matrices were in agreement, small differences are observed in the bare case because the difference in the model used during calculations. Other differences are in some spheres for 14.8 and 20 MeV neutrons probable due to the differences in the cross sections used during both calculations. (Author)
Sweezy, J; Veinot, K
2002-01-01
A new multisphere neutron spectrometer unfolding package, Bonner sphere Unfolding Made Simple (BUMS) has been developed that uses an HTML interface to simplify data input and code execution for the novice and the advanced user. This new unfolding package combines the unfolding algorithms contained in other popular unfolding codes under one easy to use interface. The interface makes use of web browsing software to provide a graphical user interface to the unfolding algorithms. BUMS integrates the SPUNIT, BON, MAXIET, and SAND-II unfolding algorithms into a single package. This package also includes a library of 14 response matrices, 58 starting spectra, and 24 dose and detector responses. BUMS has several improvements beyond the addition of unfolding algorithms. It has the ability to search for the most appropriate starting spectra. Also, plots of the unfolded neutron spectra are automatically generated. The BUMS package runs via a web server and may be accessed by any computer with access to the Internet at h...
Design, calibration and tests of an extended-range Bonner sphere spectrometer
Mitaroff, Angela; Silari, Marco
2001-01-01
Stray radiation fields outside the shielding of hadron accelerators are of complex nature. They consist of a multiplicity of radiation components (neutrons, photons, electrons, pions, muons, ...) which extend over a wide range of energies. Since the dose equivalent in these mixed fields is mainly due to neutrons, neutron dosimetry is a particularly important task. The neutron energy in these fields ranges from thermal up to several hundreds of MeV, thus making dosimetry difficult. A well known instrument for measuring neutron energy distributions from thermal energies up to about E=10 MeV is the Bonner sphere spectrometer (BSS). It consists of a set of moderating spheres of different radii made of polyethylene, with a thermal neutron counter in the centre. Each detector (sphere plus counter) has a maximum response at a certain energy value depending on its size, but the overall response of the conventional BSS drops sharply between E=10-20 MeV. This thesis focuses on the development, the calibration and tests...
Rühm, W; Pioch, C; Agosteo, S; Endo, A; Ferrarini, M; Rakhno, I; Rollet, S; Satoh, D; Vincke, H
2014-01-01
Bonner Spheres Spectrometry in its high-energy extended version is an established method to quantify neutrons at a wide energy range from several meV up to more than 1 GeV. In order to allow for quantitative measurements, the responses of the various spheres used in a Bonner Sphere Spectrometer (BSS) are usually simulated by Monte Carlo (MC) codes over the neutron energy range of interest. Because above 20 MeV experimental cross section data are scarce, intra-nuclear cascade (INC) and evaporation models are applied in these MC codes. It was suspected that this lack of data above 20 MeV may translate to differences in simulated BSS response functions depending on the MC code and nuclear models used, which in turn may add to the uncertainty involved in Bonner Sphere Spectrometry, in particular for neutron energies above 20 MeV. In order to investigate this issue in a systematic way, EURADOS (European Radiation Dosimetry Group) initiated an exercise where six groups having experience in neutron transport calcula...
Bedogni, Roberto; Esposito, Adolfo; Andreani, Carla; Senesi, Roberto; De Pascale, Maria Pia; Picozza, Piergiorgio; Pietropaolo, Antonino; Gorini, Giuseppe; Frost, Christopher D.; Ansell, Stewart
2009-12-01
One of the more actual and promising fields of applied neutron physics is the investigation of the malfunctions induced by high-energy neutrons naturally present in the atmosphere in electronic devices, called single event effects (SEE). These studies are of primary importance for the design of devices that have to fulfill high reliability requirements and those that are likely to be exposed to enhanced levels of cosmic rays background, e.g. in aerospace and avionic applications. Particle accelerators-driven neutron sources constitute valuable irradiation facilities for these purposes as they provide an opportunity for accelerated testing of the effects of these naturally occurring neutrons, provided the neutron spectrum is comparable with the atmospheric one and the neutron fields are known with high accuracy. The latter can be achieved through the use of appropriate radiation transport codes and neutron spectrometry techniques. In view of the design and construction of CHIPIR, a dedicated beam line for SEE studies at the ISIS pulsed neutron source second target station (UK) [1] ( http://ts-2.isis.rl.ac.uk/instruments/phase2/index.htm), a spectrometric characterization was performed on the VESUVIO beamline [2] (Senesi et al.,2000). The spectrometric technique was the bonner sphere spectrometer (BSS), widely used to determine neutron spectra and dose quantities around high-energy accelerators. The experimental campaign provided a complete spectrometric investigation of the VESUVIO neutron beam, allowing the integral quantities (total fluence rate, fraction of fluence in given energy intervals) to be estimated with uncertainties lower than 10%.
Müller, H; Bouassoule, T; Fernández, F; Pochat, J L; Tomas, M; Van Ryckeghem, L
2002-01-01
The experimental results on neutron energy spectra, integral fluences and equivalent dose measurements performed by means of a Bonner sphere system placed inside the containment building of the Vandellos II Nuclear Power Plant (Tarragona, Spain) are presented. The equivalent dose results obtained with this system are compared to those measured with different neutron area detectors (Berthold, Dineutron, Harwell). A realistic geometry model of the Bonner sphere system with a new cylindrical counter type 'F' (0,5NH1/1KI--Eurisys Mesures) and with a set of eight polyethylene moderating spheres is described in detail. The response function in fluence of this new device, to mono-energetic neutrons from thermal energy to 20 MeV, is calculated by the MCNP-4B code for each moderator sphere. The system has been calibrated at IPSN Cadarache facility for ISO Am-Be calibrated source and thermal neutron field, then the response functions were confirmed by measurements at PTB (Germany) for ISO recommended energies of mono-e...
Energy Technology Data Exchange (ETDEWEB)
Lemos Junior, Roberto Mendonca de
2004-07-01
This paper aims to define a procedure to use the Bonner Multisphere Spectrometer with a {sup 6}LiI(Eu) detector in order to determine of neutron spectra. It was measured {sup 238}PuBe spectra and same of reference ({sup 241}AmBe, {sup 252}Cf e {sup 252}Cf+D{sub 2}O) published in ISO 8529-1 (2001) Norm. The data were processed by a computer program (BUNKI), which presents the results in neutrons energy fluency. Each input parameter of the program was studied in order to establish their influence in the adjustment result. The environment dose equivalent rate obtained placing the detector 1 m from the {sup 241}AmBe source was 122 {+-} 4 {mu}Sv/h with 7% of uncertainty and 95% of confidence level. The procedure established in this work was tested with the {sup 238}PuBe spectrum, obtaining an environment dose equivalent rate of 286 {+-} 9 {mu}Sv/h, 8% lower than the value measured experimentally used as reference. Through this procedure will be possible to measure neutron spectra in different work places where neutrons sources are used. Knowing these spectra, it will be possible to evaluate which area monitors, are more suitable, as well as, to study better the response of individual neutron monitors, as for instance, to obtain a conversion coefficient more appropriate to the albedo dosimeter used in different work places. As the measurements need a long time to be accomplished, the work optimization is fundamental to reduce the exposing time of the Bonner spectrometer operator. For this reason, an important parameter examined in this paper was the possibility of reducing the number of spheres used during the measurement without changing the final result. Considering the radiation protection standards, this parameter has a huge importance when the measurements are performed in work places where the neutron fluency and gamma rate offer risks to the operator's health, as for instance, in nuclear centrals. Studying this parameter, it was possible to conclude that
Braga, C C
2001-01-01
A neural network structure has been used for unfolding neutron spectra measured by means of a Bonner Sphere Spectrometer set and a foil activation set using several neutron induced reactions. The present work used the SNNS (Stuttgart Neural Network Simulator) as the interface for designing, training and validation of the Multilayer Perceptron network. The back-propagation algorithm was applied. The Bonner Sphere set chosen has been calibrated at the National Physical Laboratory, United Kingdom, and uses gold activation foils as thermal neutron detectors. The neutron energy covered by the response functions goes from 0.0001 eV to 14 MeV. The foil activation set chosen has been irradiated at the IEA-R1 research reactor and measured at the Nuclear Metrology Laboratory of IPEN-CNEN/SP. Two types of neutron spectra were numerically investigated: monoenergetic and continuous The unfolded spectra were compared to a conventional method using code SAND-II as part of the neutron dosimetry system SAIPS. Good results wer...
International Nuclear Information System (INIS)
Hajek, M.; Berger, T.; Vana, N.
2002-01-01
Full text: Initiated by the recommendations of the International Commission on Radiological Protection (ICRP), the exposure of aircraft crew to cosmic radiation has been included as occupational exposure in the European Council directive 96/29/Euratom. Of the complex mixed radiation field at aviation altitudes the neutron component can contribute more than 50 % to the biologically relevant dose equivalent and is, therefore, of great importance. Applying the multi-sphere moderation technique, Bonner sphere spectrometers (BSS) are currently the only instruments providing a sufficient response over several orders of energy up to GeV. As could be demonstrated by extensive experiments in a variety of reference radiation fields, charged particles significantly contribute to the count rate of active detectors such as 6 LiI-scintillators or 3 He-proportional counters, which are commonly employed as thermal neutron detectors inside the spheres. This limitation can be overcome with a passive BSS, which uses different types of thermoluminescent dosemeters (TLDs): the thermal neutron-sensitive TLD-600 ( 6 LiF) and the thermal neutron-insensitive TLD-700 ( 7 LiF). Assuming identical responses of both types for the other radiation components, subtraction of the TLD-700 signal from the TLD-600 signal reveals a net signal from thermal neutrons. The passive BSS was calibrated in the CERN-EU High-Energy Reference Field (CERF), which provides a neutron spectrum in reasonable agreement with that occurring at aviation altitudes. Measurements onboard aircraft were performed during a series of eight north-bound flights originating from Cologne. The results are compared with calculations of the neutron spectrum by means of the well-established Monte Carlo code FLUKA. (author)
Czech Academy of Sciences Publication Activity Database
Králík, M.; Krása, Josef; Velyhan, Andriy; Scholz, M.; Ivanova-Stanik, I.M.; Bienkowska, B.; Miklaszewski, R.; Schmidt, H.; Řezáč, K.; Klír, D.; Kravárik, J.; Kubeš, P.
2010-01-01
Roč. 81, č. 11 (2010), 113503/1-113503/5 ISSN 0034-6748 R&D Projects: GA MŠk LA08024 Grant - others:FP-6 EU(XE) RITA-CT2006-26095 Institutional research plan: CEZ:AV0Z10100523 Keywords : plasma focus * fusion DD neutrons * Bonner sphere spectrometer * energy spectra of scattered neutrons * unfolded and calculated spectra Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.598, year: 2010
International Nuclear Information System (INIS)
Bedogni, R.; Esposito, A.; Chiti, M.
2008-01-01
In the framework of the 2006 experimental benchmark organized at the GSI (Darmstadt, Germany) by the EC CONRAD network, a neutron dosimetry intercomparison was performed in a workplace field around a carbon target hit by 400 MeV/u 12 C ions. The radiation protection group of the INFN-LNF participated to the intercomparison with a Bonner sphere spectrometer equipped with an active 6 LiI(Eu) scintillator and a set of passive detectors, namely MCP-6s (80mgcm -2 )/MCP-7 TLD pairs from TLD Poland. Both active and passive spectrometers, independently tested and calibrated, were used to determine the field and dosimetric quantities in the measurement point. The FRUIT unfolding code, developed at the INFN-LNF radiation protection group, was used to unfold the raw BSS data. This paper compares the results of the active or passive spectrometers, obtaining a satisfactory agreement in terms of both spectrum shape and value of the integral quantities, as the neutron fluence or the ambient dose equivalent. These results allow qualifying the BSS based on TLD pairs as a reliable passive method to be used around high energy particle accelerators even in low dose rate areas. This is particularly useful in those workplaces where the active instruments could be disturbed by the presence of pulsed fields, large photon fluence or electromagnetic noise
Energy Technology Data Exchange (ETDEWEB)
Ortiz R, J.M.; Martinez B, M.R.; Arteaga A, T.; Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E. [Universidad Autonoma de Zacatecas, A.P. 336, 98000 Zacatecas (Mexico)
2005-07-01
The artificial neural networks (RN) have been used successfully to solve a wide variety of problems. However to determine an appropriate set of values of the structural parameters and of learning of these, it continues being even a difficult task. Contrary to previous works, here a set of neural networks is designed to reconstruct neutron spectra starting from the counting rates coming from the detectors of the Bonner spheres system, using a systematic and experimental strategy for the robust design of multilayer neural networks of the feed forward type of inverse propagation. The robust design is formulated as a design problem of Taguchi parameters. It was selected a set of 53 neutron spectra, compiled by the International Atomic Energy Agency, the counting rates were calculated that would take place in a Bonner spheres system, the set was arranged according to the wave form of those spectra. With these data and applying the Taguchi methodology to determine the best parameters of the network topology, it was trained and it proved the same one with the spectra. (Author)
Agosteo, S.; Bedogni, R.; Caresana, M.; Charitonidis, N.; Chiti, M.; Esposito, A.; Ferrarini, M.; Severino, C.; Silari, M.
2012-12-01
The accurate determination of the ambient dose equivalent in the mixed neutron-photon fields encountered around high-energy particle accelerators still represents a challenging task. The main complexity arises from the extreme variability of the neutron energy, which spans over 10 orders of magnitude or more. Operational survey instruments, which response function attempts to mimic the fluence-to-ambient dose equivalent conversion coefficient up to GeV neutrons, are available on the market, but their response is not fully reliable over the entire energy range. Extended range rem counters (ERRC) do not require the exact knowledge of the energy distribution of the neutron field and the calibration can be done with a source spectrum. If the actual neutron field has an energy distribution different from the calibration spectrum, the measurement is affected by an added uncertainty related to the partial overlap of the fluence-to-ambient dose equivalent conversion curve and the response function. For this reason their operational use should always be preceded by an "in-field" calibration, i.e. a calibration made against a reference instrument exposed in the same field where the survey-meter will be employed. In practice the extended-range Bonner Sphere Spectrometer (ERBSS) is the only device which can serve as reference instrument in these fields, because of its wide energy range and the possibility to assess the neutron fluence and the ambient dose equivalent (H*(10)) values with the appropriate accuracy. Nevertheless, the experience gained by a number of experimental groups suggests that mandatory conditions for obtaining accurate results in workplaces are: (1) the use of a well-established response matrix, thus implying validation campaigns in reference monochromatic neutrons fields, (2) the expert and critical use of suitable unfolding codes, and (3) the performance test of the whole system (experimental set-up, elaboration and unfolding procedures) in a well
Energy Technology Data Exchange (ETDEWEB)
Bedogni, R. [INFN-LNF Laboratori Nazionali di Frascati, Via E. Fermi 40, 00044 Frascati (Italy); Bortot, D. [Politecnico di Milano—Dipartimento di Energia, Via Ponzio 34/3, 20133 Milano (Italy); INFN—sezione di Milano, Via Celoria 16, 20133 Milano (Italy); Buonomo, B.; Esposito, A. [INFN-LNF Laboratori Nazionali di Frascati, Via E. Fermi 40, 00044 Frascati (Italy); Gómez-Ros, J.M. [INFN-LNF Laboratori Nazionali di Frascati, Via E. Fermi 40, 00044 Frascati (Italy); CIEMAT, Av. Complutense 40, 28040 Madrid (Spain); Introini, M.V.; Lorenzoli, M.; Pola, A. [Politecnico di Milano—Dipartimento di Energia, Via Ponzio 34/3, 20133 Milano (Italy); INFN—sezione di Milano, Via Celoria 16, 20133 Milano (Italy); Sacco, D. [INFN-LNF Laboratori Nazionali di Frascati, Via E. Fermi 40, 00044 Frascati (Italy); INAIL—DPIA Via di Fontana Candida n.1, 00040 Monteporzio C. (Italy)
2014-12-11
The NESCOFI@BTF (2011–2013) international collaboration was established to develop realtime neutron spectrometers to simultaneously cover all energy components of neutron fields, from thermal up to hundreds MeV. This communication concerns a new spherical spectrometer, called SP^2, which condenses the functionality of an Extended Range Bonner Sphere Spectrometer (ERBSS) into a single moderator embedding multiple active thermal neutron detectors. The possibility of achieving the complete spectrometric information in a single exposure constitutes a great advantage compared to the ERBSS. The first experimental test of the instrument, performed with a reference 241Am–Be source in different irradiation geometries, is described. The agreement between observed and simulated response is satisfactory for all tested geometries.
Amgarou, K.; Bedogni, R.; Domingo, C.; Esposito, A.; Gentile, A.; Carinci, G.; Russo, S.
2011-10-01
The experimental characterization of the neutron fields produced as parasitic effect in medical accelerators is assuming an increased importance for either the patient protection or the facility design aspects. Medical accelerators are diverse in terms of particle type (electrons or hadrons) and energy, but the radiation fields around them have in common (provided that a given threshold energy is reached) the presence of neutrons with energy span over several orders of magnitude. Due to the large variability of neutron energy, field or dosimetry measurements in these workplaces are very complex, and in general, cannot be performed with ready-to-use commercial instruments. In spite of its poor energy resolution, the Bonner Sphere Spectrometer (BSS) is the only instrument able to simultaneously determine all spectral components in such workplaces. The energy range of this instrument is limited to Emeasurements at hadron therapy facilities, an ERBSS experiment was carried out at the Centro di AdroTerapia e Applicazioni Nucleari Avanzate (CATANA) of INFN—LNS (Laboratori Nazionali del Sud), where a proton beam routinely used for ophthalmic cancer treatments is available. The 62 MeV beam was directed towards a PMMA phantom, simulating the patient, and two neutron measurement points were established at 0° and 90° with respect to the beam-line. Here the ERBSS of UAB (Universidad Autónoma de Barcelona— Grup de Física de les Radiacions) and INFN (Istituto Nazionale di Fisica Nucleare—Laboratori Nazionali di Frascati) were exposed to characterize the "forward" and "sideward" proton-induced neutron fields. The use of two ERBSS characterized by different set of spheres, central detectors, and independently established and calibrated, is important for guaranteeing the robustness of the measured spectra and estimating their overall uncertainties.
Howell, Rebecca M; Burgett, E A
2014-09-01
Secondary neutrons are an unavoidable consequence of proton therapy. While the neutron dose is low compared to the primary proton dose, its presence and contribution to the patient dose is nonetheless important. The most detailed information on neutrons includes an evaluation of the neutron spectrum. However, the vast majority of the literature that has reported secondary neutron spectra in proton therapy is based on computational methods rather than measurements. This is largely due to the inherent limitations in the majority of neutron detectors, which are either not suitable for spectral measurements or have limited response at energies greater than 20 MeV. Therefore, the primary objective of the present study was to measure a secondary neutron spectrum from a proton therapy beam using a spectrometer that is sensitive to neutron energies over the entire neutron energy spectrum. The authors measured the secondary neutron spectrum from a 250-MeV passively scattered proton beam in air at a distance of 100 cm laterally from isocenter using an extended-range Bonner sphere (ERBS) measurement system. Ambient dose equivalent H*(10) was calculated using measured fluence and fluence-to-ambient dose equivalent conversion coefficients. The neutron fluence spectrum had a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate energy continuum between the thermal and evaporation peaks. The H*(10) was dominated by the neutrons in the evaporation peak because of both their high abundance and the large quality conversion coefficients in that energy interval. The H*(10) 100 cm laterally from isocenter was 1.6 mSv per proton Gy (to isocenter). Approximately 35% of the dose equivalent was from neutrons with energies ≥20 MeV. The authors measured a neutron spectrum for external neutrons generated by a 250-MeV proton beam using an ERBS measurement system that was sensitive to neutrons over the entire energy range being measured, i.e., thermal to
Neutron spectrometry and dosimetry with ANNs
Energy Technology Data Exchange (ETDEWEB)
Vega C, H. R.; Hernandez D, V. M. [Unidad Academica de Estudios Nucleares, Universidad Autonoma de Zacatecas, Cipres 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Gallego, E.; Lorente, A. [Departamento de Ingenieria Nuclear, Universidad Politecnica de Madrid, Jose Gutierrez Abascal 2, 28006 Madrid (Spain)], e-mail: fermineutron@yahoo.com
2009-10-15
Artificial neural networks technology has been applied to unfold the neutron spectra and to calculate the effective dose, the ambient equivalent dose, and the personal dose equivalent for {sup 252}Cf and {sup 241}AmBe neutron sources. A Bonner sphere spectrometry with a {sup 6}LiI(Eu) scintillator was utilized to measure the count rates of the spheres that were utilized as input in two artificial neural networks, one for spectrometry and another for dosimetry. Spectra and the ambient dose equivalent were also obtained with BUNKIUT code and the UTA4 response matrix. With both procedures spectra and ambient dose equivalent agrees in less than 10%. (author)
Neutron spectrometry using artificial neural networks
International Nuclear Information System (INIS)
Vega-Carrillo, Hector Rene; Martin Hernandez-Davila, Victor; Manzanares-Acuna, Eduardo; Mercado Sanchez, Gema A.; Pilar Iniguez de la Torre, Maria; Barquero, Raquel; Palacios, Francisco; Mendez Villafane, Roberto; Arteaga Arteaga, Tarcicio; Manuel Ortiz Rodriguez, Jose
2006-01-01
An artificial neural network has been designed to obtain neutron spectra from Bonner spheres spectrometer count rates. The neural network was trained using 129 neutron spectra. These include spectra from isotopic neutron sources; reference and operational spectra from accelerators and nuclear reactors, spectra based on mathematical functions as well as few energy groups and monoenergetic spectra. The spectra were transformed from lethargy to energy distribution and were re-binned to 31 energy groups using the MCNP 4C code. The re-binned spectra and the UTA4 response matrix were used to calculate the expected count rates in Bonner spheres spectrometer. These count rates were used as input and their respective spectra were used as output during the neural network training. After training, the network was tested with the Bonner spheres count rates produced by folding a set of neutron spectra with the response matrix. This set contains data used during network training as well as data not used. Training and testing was carried out using the Matlab ( R) program. To verify the network unfolding performance, the original and unfolded spectra were compared using the root mean square error. The use of artificial neural networks to unfold neutron spectra in neutron spectrometry is an alternative procedure that overcomes the drawbacks associated with this ill-conditioned problem
Neutron spectrometry with artificial neural networks
International Nuclear Information System (INIS)
Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E.; Rodriguez, J.M.; Mercado S, G.A.; Iniguez de la Torre Bayo, M.P.; Barquero, R.; Arteaga A, T.
2005-01-01
An artificial neural network has been designed to obtain the neutron spectra from the Bonner spheres spectrometer's count rates. The neural network was trained using 129 neutron spectra. These include isotopic neutron sources; reference and operational spectra from accelerators and nuclear reactors, spectra from mathematical functions as well as few energy groups and monoenergetic spectra. The spectra were transformed from lethargy to energy distribution and were re-bin ned to 31 energy groups using the MCNP 4C code. Re-binned spectra and UTA4 response matrix were used to calculate the expected count rates in Bonner spheres spectrometer. These count rates were used as input and the respective spectrum was used as output during neural network training. After training the network was tested with the Bonner spheres count rates produced by a set of neutron spectra. This set contains data used during network training as well as data not used. Training and testing was carried out in the Mat lab program. To verify the network unfolding performance the original and unfolded spectra were compared using the χ 2 -test and the total fluence ratios. The use of Artificial Neural Networks to unfold neutron spectra in neutron spectrometry is an alternative procedure that overcomes the drawbacks associated in this ill-conditioned problem. (Author)
Neutron spectrometry with artificial neural networks
Energy Technology Data Exchange (ETDEWEB)
Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E.; Rodriguez, J.M.; Mercado S, G.A. [Universidad Autonoma de Zacatecas, A.P. 336, 98000 Zacatecas (Mexico); Iniguez de la Torre Bayo, M.P. [Universidad de Valladolid, Valladolid (Spain); Barquero, R. [Hospital Universitario Rio Hortega, Valladolid (Spain); Arteaga A, T. [Envases de Zacatecas, S.A. de C.V., Zacatecas (Mexico)]. e-mail: rvega@cantera.reduaz.mx
2005-07-01
An artificial neural network has been designed to obtain the neutron spectra from the Bonner spheres spectrometer's count rates. The neural network was trained using 129 neutron spectra. These include isotopic neutron sources; reference and operational spectra from accelerators and nuclear reactors, spectra from mathematical functions as well as few energy groups and monoenergetic spectra. The spectra were transformed from lethargy to energy distribution and were re-bin ned to 31 energy groups using the MCNP 4C code. Re-binned spectra and UTA4 response matrix were used to calculate the expected count rates in Bonner spheres spectrometer. These count rates were used as input and the respective spectrum was used as output during neural network training. After training the network was tested with the Bonner spheres count rates produced by a set of neutron spectra. This set contains data used during network training as well as data not used. Training and testing was carried out in the Mat lab program. To verify the network unfolding performance the original and unfolded spectra were compared using the {chi}{sup 2}-test and the total fluence ratios. The use of Artificial Neural Networks to unfold neutron spectra in neutron spectrometry is an alternative procedure that overcomes the drawbacks associated in this ill-conditioned problem. (Author)
Neutron spectrometry and dosimetry using NSDAAN
International Nuclear Information System (INIS)
Martinez B, M. R.; Vega C, H. R.; Ortiz R, J. M.
2009-10-01
The reconstruction of neutron spectra from count rates of a Bonner spheres spectrometric system is performed using various methods such as Monte Carlo methods, the parameterization and iterative methods. The weight of the Bonner spheres spectrometric system, the procedure for the reconstruction of the spectra, the need of an experienced user, the high consumer of time, the need of use a reconstruction code as the BUNKI, SAND, among others, and the resolution of the spectrum are some problems that this system presents. This has motivated the development of complementary procedures such as maximum entropy, genetic algorithms and artificial neural networks. In previous work, has reported a new method called robust design methodology of artificial neural networks, to construct various network topologies capable of solving the problems of neutron spectrometry and dosimetry, however, due to the newness of this technology, be noted that there are not tools to end-user that allow test and validate the designed networks. This paper presents a software for the neutron spectrometry and dosimetry, designed from the information extracted of an artificial neural network designed by robust design methodology of artificial neural networks. This tool has the following characteristics: was designed in a user graphical interface easy to use, requires not knowledge of neural networks or neutron spectrometry by the user; execution speed of the application; unlike the deconvolution codes are not required to select an initial spectrum for the spectrum reconstruction; as an additional element to this tool, besides the spectrum, the calculation is performed simultaneous to H(10), E, H p , s (10,θ) from just counting rates from a Bonner spheres spectrometric system. (author)
Comparison of measurements with active and passive Bonner sphere spectrometers
Hajek, M; Schoner, W; Vana, N
2000-01-01
Because of its high biological efficiency, neutron radiation can be a serious source-and not only around accelerators and nuclear fusion reactors. Roughly half of the radiation exposure of aircrew members is caused by cosmic ray-induced neutrons in a wide energy range. Therefore, following the International Commission on Radiological Protection's recommendations, aircrew are treated as occupationally exposed workers by a recent directive of the European Council, which implies various safety precautions including the dosimetric surveillance. The accurate assessment of operational and limiting quantities such as ambient dose equivalent H*(10) and effective dose E requires the knowledge of the neutron energy spectrum. The CERN-CEC neutron reference field has been designed to resemble the neutron spectrum at an average subsonic aviation altitude. Therefore, it provides an excellent calibration facility for all instruments with intended applications in this field. The stray radiation field is created by a mixed be...
Energy Technology Data Exchange (ETDEWEB)
Martinez B, M. R.; Vega C, H. R. [Unidad Academica de Estudios Nucleares, Universidad Autonoma de Zacatecas, Cipres 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Ortiz R, J. M. [Departamento de Electrotecnia y Electronica, Escuela Politecnica Superior, Av. Menendez Pidal s/n, 14004 Cordoba (Spain)], e-mail: mrosariomb@yahoo.com.mx
2009-10-15
The reconstruction of neutron spectra from count rates of a Bonner spheres spectrometric system is performed using various methods such as Monte Carlo methods, the parameterization and iterative methods. The weight of the Bonner spheres spectrometric system, the procedure for the reconstruction of the spectra, the need of an experienced user, the high consumer of time, the need of use a reconstruction code as the BUNKI, SAND, among others, and the resolution of the spectrum are some problems that this system presents. This has motivated the development of complementary procedures such as maximum entropy, genetic algorithms and artificial neural networks. In previous work, has reported a new method called robust design methodology of artificial neural networks, to construct various network topologies capable of solving the problems of neutron spectrometry and dosimetry, however, due to the newness of this technology, be noted that there are not tools to end-user that allow test and validate the designed networks. This paper presents a software for the neutron spectrometry and dosimetry, designed from the information extracted of an artificial neural network designed by robust design methodology of artificial neural networks. This tool has the following characteristics: was designed in a user graphical interface easy to use, requires not knowledge of neural networks or neutron spectrometry by the user; execution speed of the application; unlike the deconvolution codes are not required to select an initial spectrum for the spectrum reconstruction; as an additional element to this tool, besides the spectrum, the calculation is performed simultaneous to H(10), E, H{sub p},{sub s}(10,{theta}) from just counting rates from a Bonner spheres spectrometric system. (author)
Neutron fluence spectrometry using disk activation
International Nuclear Information System (INIS)
Loevestam, Goeran; Hult, Mikael; Fessler, Andreas; Gasparro, Joel; Kockerols, Pierre; Okkinga, Klaas; Tagziria, Hamid; Vanhavere, Filip; Wieslander, J.S. Elisabeth
2009-01-01
A simple and robust detector for spectrometry of environmental neutrons has been developed. The technique is based on neutron activation of a series of different metal disks followed by low-level gamma-ray spectrometry of the activated disks and subsequent neutron spectrum unfolding. The technique is similar to foil activation but here the applied neutron fluence rates are much lower than usually in the case of foil activation. The detector has been tested in quasi mono-energetic neutron fields with fluence rates in the order of 1000-10000 cm -2 s -1 , where the obtained spectra showed good agreement with spectra measured using a Bonner sphere spectrometer. The detector has also been tested using an AmBe source and at a neutron fluence rate of about 40 cm -2 s -1 , again, a good agreement with the assumed spectrum was achieved
Neutron fluence spectrometry using disk activation
Energy Technology Data Exchange (ETDEWEB)
Loevestam, Goeran [EC-JRC-Institute for Reference Materials and Measurements (IRMM), Retieseweg 111, B-2440 Geel (Belgium)], E-mail: goeran.loevestam@ec.europa.eu; Hult, Mikael; Fessler, Andreas; Gasparro, Joel; Kockerols, Pierre; Okkinga, Klaas [EC-JRC-Institute for Reference Materials and Measurements (IRMM), Retieseweg 111, B-2440 Geel (Belgium); Tagziria, Hamid [EC-JRC-Institute for the Protection and the Security of the Citizen (IPSC), Via E. Fermi 1, I-21020 Ispra (Vatican City State, Holy See,) (Italy); Vanhavere, Filip [SCK-CEN, Boeretang, 2400 Mol (Belgium); Wieslander, J.S. Elisabeth [EC-JRC-Institute for Reference Materials and Measurements (IRMM), Retieseweg 111, B-2440 Geel (Belgium); Department of Physics, P.O. Box 35 (YFL), FIN-40014, University of Jyvaeskylae (Finland)
2009-01-15
A simple and robust detector for spectrometry of environmental neutrons has been developed. The technique is based on neutron activation of a series of different metal disks followed by low-level gamma-ray spectrometry of the activated disks and subsequent neutron spectrum unfolding. The technique is similar to foil activation but here the applied neutron fluence rates are much lower than usually in the case of foil activation. The detector has been tested in quasi mono-energetic neutron fields with fluence rates in the order of 1000-10000 cm{sup -2} s{sup -1}, where the obtained spectra showed good agreement with spectra measured using a Bonner sphere spectrometer. The detector has also been tested using an AmBe source and at a neutron fluence rate of about 40 cm{sup -2} s{sup -1}, again, a good agreement with the assumed spectrum was achieved.
Unfolding code for neutron spectrometry based on neural nets technology
International Nuclear Information System (INIS)
Ortiz R, J. M.; Vega C, H. R.
2012-10-01
The most delicate part of neutron spectrometry, is the unfolding process. The derivation of the spectral information is not simple because the unknown is not given directly as a result of the measurements. The drawbacks associated with traditional unfolding procedures have motivated the need of complementary approaches. Novel methods based on Artificial Neural Networks have been widely investigated. In this work, a neutron spectrum unfolding code based on neural nets technology is presented. This unfolding code called Neutron Spectrometry and Dosimetry by means of Artificial Neural Networks was designed in a graphical interface under LabVIEW programming environment. The core of the code is an embedded neural network architecture, previously optimized by the R obust Design of Artificial Neural Networks Methodology . The main features of the code are: is easy to use, friendly and intuitive to the user. This code was designed for a Bonner Sphere System based on a 6 Lil(Eu) neutron detector and a response matrix expressed in 60 energy bins taken from an International Atomic Energy Agency compilation. The main feature of the code is that as entrance data, only seven rate counts measurement with a Bonner spheres spectrometer are required for simultaneously unfold the 60 energy bins of the neutron spectrum and to calculate 15 dosimetric quantities, for radiation protection porpoises. This code generates a full report in html format with all relevant information. (Author)
Directory of Open Access Journals (Sweden)
Lin Yu-Chi
2017-01-01
Full Text Available A homemade Bonner cylinder spectrometer was used to determine the neutron spectrum from thermal energy up to several GeV at a heavily-shielded light source facility. The spectrometer, similar to the design of Bonner spheres, features high sensitivity of neutron detection because of using a long cylindrical 3He proportional counter. The spectrum measurement was performed during the facility commissioning by intentionally parking the injected electrons at the septum of the storage ring. Based on a high-fidelity FLUKA simulation, the predicted neutron spectrum at the location of measurement was adopted as the initial guess of spectrum unfolding. The unfolded result indicated an underestimation of the calculated neutron spectrum in the high-energy portion, leading to a substantial revision of the neutron dose rate at the location.
Neutron spectrometry and dosimetry in the environment and at workplaces
International Nuclear Information System (INIS)
Alevra, A.V.; Klein, H.; Knauf, K.; Wittstock, J.; Wolber, G.
1998-01-01
Results obtained in diverse environments (including workplaces) using both spectrometric and dosimetric instrumentation were compared. The following topics are included: PTB Bonner sphere spectrometers; natural cosmic ray-induced neutron background; neutron fields at the Dukovany nuclear power plant (Czech Republic); neutron fields at the isochronous cyclotron of the German Cancer Research center in Heidelberg; and accuracy of the integral results obtained with Bonner spheres. (P.A.)
Energy Technology Data Exchange (ETDEWEB)
Mendez, R.; Guerrero, J. E.; Lagares, J. I.; Sansaloni, F.; Perez, J. M.; Llop, J.; Kralik, M.
2013-07-01
The most widely used for Neutron spectrometry system is formed by the Bonner spheres with an active sensor sensitive to thermal neutrons in its Center. But, the presence of strong electromagnetic fields and the hold character around a cyclotron radiation detectors active employment make unviable so it is necessary to replace it with other liabilities. In this case it has resorted to the use of Au foils such as thermal neutron detectors, found the matrix the new spectrometer response and has been validated with a source of {sup 2}52Cf for later measurements in the interior of the bunker of a cyclotron production of radioisotopes for PET. (Author)
International Nuclear Information System (INIS)
Luszik-Bhadra, M.; Bartlett, D.; Bolognese-Milsztajn, T.; Boschung, M.; Coeck, M.; Curzio, G.; D'Errico, F.; Fiechtner, A.; Lacoste, V.; Lindborg, L.; Reginatto, M.; Schuhmacher, H.; Tanner, R.; Vanhavere, F.
2007-01-01
Within the EC project EVIDOS, 17 different mixed neutron-photon workplace fields at nuclear facilities (boiling water reactor, pressurised water reactor, research reactor, fuel processing, storage of spent fuel) were characterised using conventional Bonner sphere spectrometry and newly developed direction spectrometers. The results of the analysis, using Bayesian parameter estimation methods and different unfolding codes, some of them especially adapted to simultaneously unfold energy and direction distributions of the neutron fluence, showed that neutron spectra differed strongly at the different places, both in energy and direction distribution. The implication of the results for the determination of reference values for radiation protection quantities (ambient dose equivalent, personal dose equivalent and effective dose) and the related uncertainties are discussed. (authors)
Test and validation of the iterative code for the neutrons spectrometry and dosimetry: NSDUAZ
International Nuclear Information System (INIS)
Reyes H, A.; Ortiz R, J. M.; Reyes A, A.; Castaneda M, R.; Solis S, L. O.; Vega C, H. R.
2014-08-01
In this work was realized the test and validation of an iterative code for neutronic spectrometry known as Neutron Spectrometry and Dosimetry of the Universidad Autonoma de Zacatecas (NSDUAZ). This code was designed in a user graph interface, friendly and intuitive in the environment programming of LabVIEW using the iterative algorithm known as SPUNIT. The main characteristics of the program are: the automatic selection of the initial spectrum starting from the neutrons spectra catalog compiled by the International Atomic Energy Agency, the possibility to generate a report in HTML format that shows in graph and numeric way the neutrons flowing and calculates the ambient dose equivalent with base to this. To prove the designed code, the count rates of a spectrometer system of Bonner spheres were used with a detector of 6 LiI(Eu) with 7 polyethylene spheres with diameter of 0, 2, 3, 5, 8, 10 and 12. The count rates measured with two neutron sources: 252 Cf and 239 PuBe were used to validate the code, the obtained results were compared against those obtained using the BUNKIUT code. We find that the reconstructed spectra present an error that is inside the limit reported in the literature that oscillates around 15%. Therefore, it was concluded that the designed code presents similar results to those techniques used at the present time. (Author)
DEFF Research Database (Denmark)
Trenz, Hans-Jörg
2015-01-01
of the collective will of the people in the act of democratic self-government. The concept of the public sphere is used across the fields of media and communication research, cultural studies and the humanities, the history of ideas, legal and constitutional studies as well as democracy studies. Historically......In modern societies, the public sphere represents the intermediary realm that supports the communication of opinions, the discovery of problems that need to be dealt with collectively, the channeling of these problems through the filter of the media and political institutions, and the realization......, public spheres have undergone structural transformations that were closely connected to the emergence of different mass media. More recently, they are subject to trends of transnationalization and digitalization in politics and society....
Energy Technology Data Exchange (ETDEWEB)
Reyes H, A.; Ortiz R, J. M.; Reyes A, A.; Castaneda M, R.; Solis S, L. O.; Vega C, H. R., E-mail: alfredo_reyesh@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica, Av. Lopez Velarde 801, Col. Centro, 98000 Zacatecas (Mexico)
2014-08-15
In this work was realized the test and validation of an iterative code for neutronic spectrometry known as Neutron Spectrometry and Dosimetry of the Universidad Autonoma de Zacatecas (NSDUAZ). This code was designed in a user graph interface, friendly and intuitive in the environment programming of LabVIEW using the iterative algorithm known as SPUNIT. The main characteristics of the program are: the automatic selection of the initial spectrum starting from the neutrons spectra catalog compiled by the International Atomic Energy Agency, the possibility to generate a report in HTML format that shows in graph and numeric way the neutrons flowing and calculates the ambient dose equivalent with base to this. To prove the designed code, the count rates of a spectrometer system of Bonner spheres were used with a detector of {sup 6}LiI(Eu) with 7 polyethylene spheres with diameter of 0, 2, 3, 5, 8, 10 and 12. The count rates measured with two neutron sources: {sup 252}Cf and {sup 239}PuBe were used to validate the code, the obtained results were compared against those obtained using the BUNKIUT code. We find that the reconstructed spectra present an error that is inside the limit reported in the literature that oscillates around 15%. Therefore, it was concluded that the designed code presents similar results to those techniques used at the present time. (Author)
Energy Technology Data Exchange (ETDEWEB)
Domingo, C., E-mail: carles.domingo@uab.ca [Grup de Fisica de les Radiacions, Departament de Fisica. Edifici C, Campus UAB, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Garcia-Fuste, M.J.; Morales, E.; Amgarou, K. [Grup de Fisica de les Radiacions, Departament de Fisica. Edifici C, Campus UAB, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Terron, J.A. [Servicio de Radiofisica, Hospital Universitario Virgen Macarena. E- 41009 Sevilla. Spain (Spain); Rosello, J.; Brualla, L. [ERESA, Avda. Tres Cruces s/n. E-46014 Valencia (Spain); Nunez, L. [Servicio de Radiofisica, Hospital. Puerta de Hierro. E-28222 Majadahonda (Spain); Colmenares, R. [Serv. de Oncologia Radioterapica, Hosp. Ramon y Cajal, E-28049 Madrid (Spain); Gomez, F. [Dpto. de Particulas. Univ. de Santiago. E-15782 Santiago de Compostela. Spain (Spain); Hartmann, G.H. [DKFZ E0400 Im Neuenheimer Feld 280. D-69120 Heidelberg (Germany) (Germany); Sanchez-Doblado, F. [Servicio de Radiofisica, Hospital Universitario Virgen Macarena. E- 41009 Sevilla. Spain (Spain); Dpto. de Fisiologia Medica y Biofisica. Universidad de Sevilla. E-41009 Sevilla. Spain (Spain); Fernandez, F. [Grup de Fisica de les Radiacions, Departament de Fisica. Edifici C, Campus UAB, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Consejo de Seguridad Nuclear, Justo Dorado 11 E-28040 Madrid (Spain)
2010-12-15
A project has been set up to study the effect on a radiotherapy patient of the neutrons produced around the LINAC accelerator head by photonuclear reactions induced by photons above {approx}8 MeV. These neutrons may reach directly the patient, or they may interact with the surrounding materials until they become thermalised, scattering all over the treatment room and affecting the patient as well, contributing to peripheral dose. Spectrometry was performed with a calibrated and validated set of Bonner spheres at a point located at 50 cm from the isocenter, as well as at the place where a digital device for measuring neutrons, based on the upset of SRAM memories induced by thermal neutrons, is located inside the treatment room. Exposures have taken place in six LINAC accelerators with different energies (from 15 to 23 MV) with the aim of relating the spectrometer measurements with the readings of the digital device under various exposure and room geometry conditions. The final purpose of the project is to be able to relate, under any given treatment condition and room geometry, the readings of this digital device to patient neutron effective dose and peripheral dose in organs of interest. This would allow inferring the probability of developing second malignancies as a consequence of the treatment. Results indicate that unit neutron fluence spectra at 50 cm from the isocenter do not depend on accelerator characteristics, while spectra at the place of the digital device are strongly influenced by the treatment room geometry.
International Nuclear Information System (INIS)
Domingo, C.; Garcia-Fuste, M.J.; Morales, E.; Amgarou, K.; Terron, J.A.; Rosello, J.; Brualla, L.; Nunez, L.; Colmenares, R.; Gomez, F.; Hartmann, G.H.; Sanchez-Doblado, F.; Fernandez, F.
2010-01-01
A project has been set up to study the effect on a radiotherapy patient of the neutrons produced around the LINAC accelerator head by photonuclear reactions induced by photons above ∼8 MeV. These neutrons may reach directly the patient, or they may interact with the surrounding materials until they become thermalised, scattering all over the treatment room and affecting the patient as well, contributing to peripheral dose. Spectrometry was performed with a calibrated and validated set of Bonner spheres at a point located at 50 cm from the isocenter, as well as at the place where a digital device for measuring neutrons, based on the upset of SRAM memories induced by thermal neutrons, is located inside the treatment room. Exposures have taken place in six LINAC accelerators with different energies (from 15 to 23 MV) with the aim of relating the spectrometer measurements with the readings of the digital device under various exposure and room geometry conditions. The final purpose of the project is to be able to relate, under any given treatment condition and room geometry, the readings of this digital device to patient neutron effective dose and peripheral dose in organs of interest. This would allow inferring the probability of developing second malignancies as a consequence of the treatment. Results indicate that unit neutron fluence spectra at 50 cm from the isocenter do not depend on accelerator characteristics, while spectra at the place of the digital device are strongly influenced by the treatment room geometry.
Energy Technology Data Exchange (ETDEWEB)
Bedogni, R., E-mail: roberto.bedogni@lnf.infn.it [INFN-LNF (Frascati National Laboratories), Via E. Fermi n. 40-00044 Frascati (Italy); Gomez-Ros, J.M. [INFN-LNF (Frascati National Laboratories), Via E. Fermi n. 40-00044 Frascati (Italy); CIEMAT, Av. Complutense 40, 28040 Madrid (Spain); Esposito, A.; Gentile, A.; Chiti, M.; Palacios-Perez, L. [INFN-LNF (Frascati National Laboratories), Via E. Fermi n. 40-00044 Frascati (Italy); Angelone, M. [ENEA C.R. Frascati, C.P. 65, 00044 Frascati (Italy); Tana, L. [A.O. Universitaria Pisana-Ospedale S. Chiara, Via Bonanno Pisano, Pisa (Italy)
2012-08-21
A photon insensitive passive neutron spectrometer consisting of a single moderating polyethylene sphere with Dysprosium activation foils arranged along three perpendicular axes was designed by CIEMAT and INFN. The device is called Dy-SSS (Dy foil-based Single Sphere Spectrometer). It shows nearly isotropic response in terms of neutron fluence up to 20 MeV. The first prototype, previously calibrated with 14 MeV neutrons, has been recently tested in workplaces having different energy and directional distributions. These are a 2.5 MeV nearly mono-chromatic and mono-directional beam available at the ENEA Frascati Neutron Generator (FNG) and the photo-neutron field produced in a 15 MV Varian CLINAC DHX medical accelerator, located in the Ospedale S. Chiara (Pisa). Both neutron spectra are known through measurements with a Bonner Sphere Spectrometer. In both cases the experimental response of the Dy-SSS agrees with the reference data. Moreover, it is demonstrated that the spectrometric capability of the new device are independent from the directional distribution of the neutron field. This opens the way to a new generation of moderation-based neutron instruments, presenting all advantages of the Bonner sphere spectrometer without the disadvantage of the repeated exposures. This concept is being developed within the NESCOFI@BTF project of INFN (Commissione Scientifica Nazionale 5).
International Nuclear Information System (INIS)
Bedogni, R.; Gómez-Ros, J.M.; Esposito, A.; Gentile, A.; Chiti, M.; Palacios-Pérez, L.; Angelone, M.; Tana, L.
2012-01-01
A photon insensitive passive neutron spectrometer consisting of a single moderating polyethylene sphere with Dysprosium activation foils arranged along three perpendicular axes was designed by CIEMAT and INFN. The device is called Dy-SSS (Dy foil-based Single Sphere Spectrometer). It shows nearly isotropic response in terms of neutron fluence up to 20 MeV. The first prototype, previously calibrated with 14 MeV neutrons, has been recently tested in workplaces having different energy and directional distributions. These are a 2.5 MeV nearly mono-chromatic and mono-directional beam available at the ENEA Frascati Neutron Generator (FNG) and the photo-neutron field produced in a 15 MV Varian CLINAC DHX medical accelerator, located in the Ospedale S. Chiara (Pisa). Both neutron spectra are known through measurements with a Bonner Sphere Spectrometer. In both cases the experimental response of the Dy-SSS agrees with the reference data. Moreover, it is demonstrated that the spectrometric capability of the new device are independent from the directional distribution of the neutron field. This opens the way to a new generation of moderation-based neutron instruments, presenting all advantages of the Bonner sphere spectrometer without the disadvantage of the repeated exposures. This concept is being developed within the NESCOFI@BTF project of INFN (Commissione Scientifica Nazionale 5).
Bedogni, R.; Gómez-Ros, J. M.; Esposito, A.; Gentile, A.; Chiti, M.; Palacios-Pérez, L.; Angelone, M.; Tana, L.
2012-08-01
A photon insensitive passive neutron spectrometer consisting of a single moderating polyethylene sphere with Dysprosium activation foils arranged along three perpendicular axes was designed by CIEMAT and INFN. The device is called Dy-SSS (Dy foil-based Single Sphere Spectrometer). It shows nearly isotropic response in terms of neutron fluence up to 20 MeV. The first prototype, previously calibrated with 14 MeV neutrons, has been recently tested in workplaces having different energy and directional distributions. These are a 2.5 MeV nearly mono-chromatic and mono-directional beam available at the ENEA Frascati Neutron Generator (FNG) and the photo-neutron field produced in a 15 MV Varian CLINAC DHX medical accelerator, located in the Ospedale S. Chiara (Pisa). Both neutron spectra are known through measurements with a Bonner Sphere Spectrometer. In both cases the experimental response of the Dy-SSS agrees with the reference data. Moreover, it is demonstrated that the spectrometric capability of the new device are independent from the directional distribution of the neutron field. This opens the way to a new generation of moderation-based neutron instruments, presenting all advantages of the Bonner sphere spectrometer without the disadvantage of the repeated exposures. This concept is being developed within the NESCOFI@BTF project of INFN (Commissione Scientifica Nazionale 5).
International Nuclear Information System (INIS)
Medkour Ishak-Boushaki, Ghania; Boukeffoussa, Khelifa; Idiri, Zahir; Allab, Malika
2012-01-01
This paper discusses the use of threshold detectors of extended sizes for low intensity neutron fields' characterization. The detectors were tested by the measurement of the neutron spectrum of an 241 Am–Be source. Integral quantities characterizing the neutron field, required for radiological protection, have been derived by unfolding the measured data. A good agreement is achieved between the obtained results and those deduced using Bonner spheres. In addition, a sensitivity analysis of the results to the deconvolution procedure is given. - Highlights: ► Low intensity neutron fields' characterization using thick threshold detectors. ► Low activity 241 Am–Be neutron source spectrum measurement. ► Integral quantities required for radiological protection have been derived. ► The results are in good agreement with those deduced using Bonner spheres. ► The results are not very sensitive to the chosen deconvolution procedure.
Wiegel, B; Matzke, M; Schrewe, U J; Wittstock, J
2002-01-01
Bonner sphere measurements are presented for flights at altitudes of up to 12 km and geomagnetic latitudes between 26 deg.N and 86 deg.N and compared with results obtained by several survey meters. As an example of the natural neutron background near sea level, results from a recent longterm measurement campaign performed at the PTB site using an extended spectrometer are presented. The dependence of neutron fluence and ambient dose equivalent on the atmospheric pressure is demonstrated.
Neutron spectrometry and dosimetry by means of evolutive neural networks
International Nuclear Information System (INIS)
Ortiz R, J.M.; Martinez B, M.R.; Vega C, H.R.
2008-01-01
The artificial neural networks and the genetic algorithms are two relatively new areas of research, which have been subject to a growing interest during the last years. Both models are inspired by the nature, however, the neural networks are interested in the learning of a single individual, which is defined as fenotypic learning, while the evolutionary algorithms are interested in the adaptation of a population to a changing environment, that which is defined as genotypic learning. Recently, the use of the technology of neural networks has been applied with success in the area of the nuclear sciences, mainly in the areas of neutron spectrometry and dosimetry. The structure (network topology), as well as the learning parameters of a neural network, are factors that contribute in a significant way with the acting of the same one, however, it has been observed that the investigators in this area, carry out the selection of the network parameters through the essay and error technique, that which produces neural networks of poor performance and low generalization capacity. From the revised sources, it has been observed that the use of the evolutionary algorithms, seen as search techniques, it has allowed him to be possible to evolve and to optimize different properties of the neural networks, just as the initialization of the synaptic weights, the network architecture or the training algorithms without the human intervention. The objective of the present work is focused in analyzing the intersection of the neural networks and the evolutionary algorithms, analyzing like it is that the same ones can be used to help in the design processes and training of a neural network, this is, in the good selection of the structural parameters and of network learning, improving its generalization capacity, in such way that the same one is able to reconstruct in an efficient way neutron spectra and to calculate equivalent doses starting from the counting rates of a Bonner sphere
Neutron spectrometry for protection dosimetry at very low levels
International Nuclear Information System (INIS)
Bardell, A.G.; Thomas, D.J.
1996-01-01
Dose limits for exposure of members of the public are significantly lower than those for designated radiation workers. The new ICRP 60 recommendation for critical groups of the general public is an effective dose limit of 1 mSv per year which requires a measurement capability at levels down to about 100 nSv h - 1. Radiation protection dosimetry for neutrons at these levels is problematical, nevertheless, operators of nuclear sites are still required to demonstrate acceptably low radiation levels in areas accessible to the public. In addition to the known poor dose equivalent response of available dosemeters, there is an added problem at low levels of inadequate sensitivity. Personal dosemeters are certainly not sufficiently sensitive, and the sensitivity of area survey instruments is such that they can only be used in integral mode Even then, the statistical uncertainties are likely to be large. One further problem concerns the quantity measured. Survey instruments are designed to measure the operational quantity ambient dose equivalent, H*(10), which always tends to be an overestimate of the present limiting quantity effective dose equivalent. If in any situation exposure is near the limit, an estimate of H*(10) may not be sufficient to prove conclusively that levels are less than the statutory limit, and a direct estimate of effective dose equivalent may need to be made. The only way of estimating effective dose equivalent is via an absolute spectral measurement. From such a spectrum any relevant dosimetric quantity can be estimated via tabulated fluence to dose equivalent conversion factors. (Certain quantities also require information about the angular dependence of the field - see later text). Spectrometry at such low neutron fluence levels is difficult, however, there is one instrument available which can perform the required measurements, and this is a well characterised Bonner sphere (BS) set. (author)
Packings of deformable spheres
Mukhopadhyay, Shomeek; Peixinho, Jorge
2011-07-01
We present an experimental study of disordered packings of deformable spheres. Fluorescent hydrogel spheres immersed in water together with a tomography technique enabled the imaging of the three-dimensional arrangement. The mechanical behavior of single spheres subjected to compression is first examined. Then the properties of packings of a randomized collection of deformable spheres in a box with a moving lid are tested. The transition to a state where the packing withstands finite stresses before yielding is observed. Starting from random packed states, the power law dependence of the normal force versus packing fraction or strain at different velocities is quantified. Furthermore, a compression-decompression sequence at low velocities resulted in rearrangements of the spheres. At larger packing fractions, a saturation of the mean coordination number took place, indicating the deformation and faceting of the spheres.
Elleman, Daniel D. (Inventor); Wang, Taylor G. (Inventor)
1989-01-01
Systems are described for using multiple closely-packed spheres. In one system for passing fluid, a multiplicity of spheres lie within a container, with all of the spheres having the same outside diameter and with the spheres being closely nested in one another to create multiple interstitial passages of a known size and configuration and smooth walls. The container has an inlet and outlet for passing fluid through the interstitial passages formed between the nested spheres. The small interstitial passages can be used to filter out material, especially biological material such as cells in a fluid, where the cells can be easily destroyed if passed across sharp edges. The outer surface of the spheres can contain a material that absorbs a constitutent in the flowing fluid, such as a particular contamination gas, or can contain a catalyst to chemically react the fluid passing therethrough, the use of multiple small spheres assuring a large area of contact of these surfaces of the spheres with the fluid. In a system for storing and releasing a fluid such as hydrogen as a fuel, the spheres can include a hollow shell containing the fluid to be stored, and located within a compressable container that can be compressed to break the shells and release the stored fluid.
DEFF Research Database (Denmark)
Fiig, Christina
The paper holds a critical discussion of the Habermasian model of the public sphere and proposes a revised model of a general public......The paper holds a critical discussion of the Habermasian model of the public sphere and proposes a revised model of a general public...
Mares, Vladimir; Trinkl, Sebastian; Iwamoto, Yosuke; Masuda, Akihiko; Matsumoto, Tetsuro; Hagiwara, Masayuki; Satoh, Daiki; Yashima, Hiroshi; Shima, Tatsushi; Nakamura, Takashi
2017-09-01
This paper describes the results of neutron spectrometry and dosimetry measurements using an extended range Bonner Sphere Spectrometer (ERBSS) with 3He proportional counter performed in quasi-mono-energetic neutron fields at the ring cyclotron facility of the Research Center for Nuclear Physics (RCNP), Osaka University, Japan. Using 100 MeV and 296 MeV proton beams, neutron fields with nominal peak energies of 96 MeV and 293 MeV were generated via 7Li(p,n)7Be reactions. Neutrons produced at 0° and 25° emission angles were extracted into the 100 m long time-of-flight (TOF) tunnel, and the energy spectra were measured at a distance of 35 m from the target. To deduce the corresponding neutron spectra from thermal to the nominal maximum energy, the ERBSS data were unfolded using the MSANDB unfolding code. At high energies, the neutron spectra were also measured by means of the TOF method using NE213 organic liquid scintillators. The results are discussed in terms of ambient dose equivalent, H*(10), and compared with the readings of other instruments operated during the experiment.
Energy Technology Data Exchange (ETDEWEB)
Mendez Villafane, R.; Sansoloni florit, F.; Lagares gonzalez, J. L.; Llop Roig, J.; Guerrero Araque, J. E.; Muniz Gutierrez, J. L.; Perez Morales, J. M.
2011-07-01
To measure the neutron spectrum has been used spectrometry system based on Bonner spheres with Au flakes as thermal neutron detector at its center while the results are still pending and will be analyzing another job.
ORGANIZATION IN CONTEMPORARY PUBLIC SPHERE
Rosemarie HAINES
2013-01-01
The critical analysis of Habermas’ Public Sphere Theory and the comparative undertaking to the current day enables us to assert that in contemporary society, public sphere is no longer a political public sphere, this dimension being completed by a societal dimension, the public sphere has extended and now we can talk about partial public spheres in an ever more commercial environment. The new rebuilding and communication technologies create a new type of public character: the visible sphere –...
Electromagnetically revolving sphere viscometer
Hosoda, Maiko; Sakai, Keiji
2014-12-01
In this paper, we propose a new method of low viscosity measurement, in which the rolling of a probe sphere on the flat solid bottom of a sample cell is driven remotely and the revolution speed of the probe in a sample liquid gives the viscosity measurements. The principle of this method is based on the electromagnetically spinning technique that we developed, and the method is effective especially for viscosity measurements at levels below 100 mPa·s with an accuracy higher than 1%. The probe motion is similar to that in the well-known rolling sphere (ball) method. However, our system enables a steady and continuous measurement of viscosity, which is problematic using the conventional method. We also discuss the limits of the measurable viscosity range common to rolling-sphere-type viscometers by considering the accelerating motion of a probe sphere due to gravity, and we demonstrate the performance of our methods.
International Nuclear Information System (INIS)
Ortiz R, J. M.; Vega C, H. R.; Martinez B, M. R.; Gallego, E.
2009-10-01
The neutron dosimetry is one of the most complicated tasks of radiation protection, due to it is a complex technique and highly dependent of neutron energy. One of the first devices used to perform neutron spectrometry is the system known as spectrometric system of Bonner spheres, that continuous being one of spectrometers most commonly used. This system has disadvantages such as: the components weight, the low resolution of spectrum, long and drawn out procedure for the spectra reconstruction, which require an expert user in system management, the need of use a reconstruction code as BUNKIE, SAND, etc., which are based on an iterative reconstruction algorithm and whose greatest inconvenience is that for the spectrum reconstruction, are needed to provide to system and initial spectrum as close as possible to the desired spectrum get. Consequently, researchers have mentioned the need to developed alternative measurement techniques to improve existing monitoring systems for workers. Among these alternative techniques have been reported several reconstruction procedures based on artificial intelligence techniques such as genetic algorithms, artificial neural networks and hybrid systems of evolutionary artificial neural networks using genetic algorithms. However, the use of these techniques in the nuclear science area is not free of problems, so it has been suggested that more research is conducted in such a way as to solve these disadvantages. Because they are emerging technologies, there are no tools for the results analysis, so in this paper we present first the design of a computation tool that allow to analyze the neutron spectra and equivalent doses, obtained through the hybrid technology of neural networks and genetic algorithms. This tool provides an user graphical environment, friendly, intuitive and easy of operate. The speed of program operation is high, executing the analysis in a few seconds, so it may storage and or print the obtained information for
International Nuclear Information System (INIS)
Castaneda M, V. H.; Martinez B, M. R.; Solis S, L. O.; Castaneda M, R.; Leon P, A. A.; Hernandez P, C. F.; Espinoza G, J. G.; Ortiz R, J. M.; Vega C, H. R.; Mendez, R.; Gallego, E.; Sousa L, M. A.
2016-10-01
The Taguchi methodology has proved to be highly efficient to solve inverse problems, in which the values of some parameters of the model must be obtained from the observed data. There are intrinsic mathematical characteristics that make a problem known as inverse. Inverse problems appear in many branches of science, engineering and mathematics. To solve this type of problem, researches have used different techniques. Recently, the use of techniques based on Artificial Intelligence technology is being explored by researches. This paper presents the use of a software tool based on artificial neural networks of generalized regression in the solution of inverse problems with application in high energy physics, specifically in the solution of the problem of neutron spectrometry. To solve this problem we use a software tool developed in the Mat Lab programming environment, which employs a friendly user interface, intuitive and easy to use for the user. This computational tool solves the inverse problem involved in the reconstruction of the neutron spectrum based on measurements made with a Bonner spheres spectrometric system. Introducing this information, the neural network is able to reconstruct the neutron spectrum with high performance and generalization capability. The tool allows that the end user does not require great training or technical knowledge in development and/or use of software, so it facilitates the use of the program for the resolution of inverse problems that are in several areas of knowledge. The techniques of Artificial Intelligence present singular veracity to solve inverse problems, given the characteristics of artificial neural networks and their network topology, therefore, the tool developed has been very useful, since the results generated by the Artificial Neural Network require few time in comparison to other techniques and are correct results comparing them with the actual data of the experiment. (Author)
Kasper, M.; Beuzit, J.-L.; Feldt, M.; Dohlen, K.; Mouillet, D.; Puget, P.; Wildi, F.; Abe, L.; Baruffolo, A.; Baudoz, P.; Bazzon, A.; Boccaletti, A.; Brast, R.; Buey, T.; Chesneau, O.; Claudi, R.; Costille, A.; Delboulbé, A.; Desidera, S.; Dominik, C.; Dorn, R.; Downing, M.; Feautrier, P.; Fedrigo, E.; Fusco, T.; Girard, J.; Giro, E.; Gluck, L.; Gonte, F.; Gojak, D.; Gratton, R.; Henning, T.; Hubin, N.; Lagrange, A.-M.; Langlois, M.; Mignant, D. L.; Lizon, J.-L.; Lilley, P.; Madec, F.; Magnard, Y.; Martinez, P.; Mawet, D.; Mesa, D.; Müller-Nilsson, O.; Moulin, T.; Moutou, C.; O'Neal, J.; Pavlov, A.; Perret, D.; Petit, C.; Popovic, D.; Pragt, J.; Rabou, P.; Rochat, S.; Roelfsema, R.; Salasnich, B.; Sauvage, J.-F.; Schmid, H. M.; Schuhler, N.; Sevin, A.; Siebenmorgen, R.; Soenke, C.; Stadler, E.; Suarez, M.; Turatto, M.; Udry, S.; Vigan, A.; Zins, G.
2012-09-01
Direct imaging and spectral characterisation of exoplanets is one of the most exciting, but also one of the most challenging areas, in modern astronomy. The challenge is to overcome the very large contrast between the host star and its planet seen at very small angular separations. This article reports on the progress made in the construction of the second generation VLT instrument SPHERE, the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument. SPHERE is expected to be commissioned on the VLT in 2013.
Spectrometry and dosimetry of a neutron source
Energy Technology Data Exchange (ETDEWEB)
Vega C, H.R.; Manzanares A, E.; Hernandez D, V.M.; Ramirez G, J.; Hernandez V, R.; Chacon R, A. [Universidad Autonoma de Zacatecas, 98068 Zacatecas (Mexico)]. e-mail: fermineutron@yahoo.com
2007-07-01
Using Monte Carlo methods the spectrum, dose equivalent and ambient dose equivalent of a {sup 239}PuBe at several distances has been determined. Spectrum and both doses, at 100 cm, were determined-experimentally using a Bonner sphere spectrometer. These quantities were obtained by unfolding the spectrometer count rates using artificial neural networks. The dose equivalent, based in the ICRP 21 criteria, was measured with the area neutron dosemeter Eberline model NRI), at 100, 200 and 300 cm. All measurements were carried out in an open space to avoid the room return. With these results it was found that this source has a yield of 8.41E(6) n/s. (Author)
Spectrometry and dosimetry of a neutron source
International Nuclear Information System (INIS)
Vega C, H.R.; Manzanares A, E.; Hernandez D, V.M.; Ramirez G, J.; Hernandez V, R.; Chacon R, A.
2007-01-01
Using Monte Carlo methods the spectrum, dose equivalent and ambient dose equivalent of a 239 PuBe at several distances has been determined. Spectrum and both doses, at 100 cm, were determined-experimentally using a Bonner sphere spectrometer. These quantities were obtained by unfolding the spectrometer count rates using artificial neural networks. The dose equivalent, based in the ICRP 21 criteria, was measured with the area neutron dosemeter Eberline model NRI), at 100, 200 and 300 cm. All measurements were carried out in an open space to avoid the room return. With these results it was found that this source has a yield of 8.41E(6) n/s. (Author)
Indian Academy of Sciences (India)
Indian Acad. Sci. (Math. Sci.) Vol. 127, No. 1, February 2017, pp. 133–164. DOI 10.1007/s12044-016-0318-z. Quantum quaternion spheres. BIPUL SAURABH. Indian Statistical .... sp(2n, C) to describe the type Cn groups at the Lie algebra level, while one switches to. SP(n) at the ...... By the same reasoning, E decomposes ...
A construção do sentido simbiótico entre o Jornal Nacional e William Bonner
Directory of Open Access Journals (Sweden)
Hagen, Sean
2007-01-01
Full Text Available A simbiose na construção da imagem do Jornal Nacional e do apresentador e editor-chefe William Bonner é o centro desse artigo. Esse movimento desvela uma ação sutil na construção do mito da excelência profissional, engendrado por jornalistas da imprensa diária, de revistas e sites de informação. Através de pressupostos da análise do discurso, ressalta-se como a linguagem consegue acionar estruturas míticas na construção da notícia, abrindo espaço para a subjetivação nos processos jornalísticos. The symbiosis in the construction of two images – “Jornal Nacional” and its newscaster and editor William Bonner – is the center of this article. This movement reveals a subtle action in the construction of professional excellence myth, produced by newspapers, magazines and information sites journalists. Using discourse analyses principles, we accent how the language operates mythical structures on news production, creating space to subjectivism in journalistic processes.
Designing an extended energy range single-sphere multi-detector neutron spectrometer
International Nuclear Information System (INIS)
Gómez-Ros, J.M.; Bedogni, R.; Moraleda, M.; Esposito, A.; Pola, A.; Introini, M.V.; Mazzitelli, G.; Quintieri, L.; Buonomo, B.
2012-01-01
This communication describes the design specifications for a neutron spectrometer consisting of 31 thermal neutron detectors, namely Dysprosium activation foils, embedded in a 25 cm diameter polyethylene sphere which includes a 1 cm thick lead shell insert that degrades the energy of neutrons through (n,xn) reactions, thus allowing to extension of the energy range of the response up to hundreds of MeV neutrons. The new spectrometer, called SP 2 (SPherical SPectrometer), relies on the same detection mechanism as that of the Bonner Sphere Spectrometer, but with the advantage of determining the whole neutron spectrum in a single exposure. The Monte Carlo transport code MCNPX was used to design the spectrometer in terms of sphere diameter, number and position of the detectors, position and thickness of the lead shell, as well as to obtain the response matrix for the final configuration. This work focuses on evaluating the spectrometric capabilities of the SP 2 design by simulating the exposure of SP 2 in neutron fields representing different irradiation conditions (test spectra). The simulated SP 2 readings were then unfolded with the FRUIT unfolding code, in the absence of detailed pre-information, and the unfolded spectra were compared with the known test spectra. The results are satisfactory and allowed approving the production of a prototypal spectrometer.
ORGANIZATION IN CONTEMPORARY PUBLIC SPHERE
Directory of Open Access Journals (Sweden)
Rosemarie HAINES
2013-12-01
Full Text Available The critical analysis of Habermas’ Public Sphere Theory and the comparative undertaking to the current day enables us to assert that in contemporary society, public sphere is no longer a political public sphere, this dimension being completed by a societal dimension, the public sphere has extended and now we can talk about partial public spheres in an ever more commercial environment. The new rebuilding and communication technologies create a new type of public character: the visible sphere – non-located, non-dialogical and open. Information and communication are more and more involved in the restructuring of capitalism on an international scale and the reorganization of leadership and management systems. The reevaluation of the public sphere, public opinion, communication allows us to define public sphere according to the profound mutations from today’s democratic societies.
Guthrie, Forbes; Saidel-Keesing, Maish
2011-01-01
The only book focused on designing VMware vSphere implementations.VMware vSphere is the most widely deployed virtualization platform today. Considered the most robust and sophisticated hypervisor product, vSphere is the de facto standard for businesses, both large and small. This book is the only one of its kind to concisely explain how to execute a successful vSphere architecture, tailored to meet your company's needs. Expert authors share with you the factors that shape the design of a vSphere implementation. Learn how to make the right design decisions for your environment.Explores the late
International Nuclear Information System (INIS)
Ives, B.H.
1981-01-01
The high temperature diffusion technique for fuel filling of some future direct drive cryogenic ICF targets may be unacceptable. The following describes a technique of fitting a 1 mm diameter x 6 μm thick glass microsphere with an approx. 50 μm O.D. glass fill tube. The process of laser drilling a 50 μm diameter hole in the microsphere wall, technique for making the epoxy joint between the sphere and fill tube, as well as the assembly procedure are also discussed
Energy Technology Data Exchange (ETDEWEB)
Krogh, M.; Hansen, C.; Painter, J. [Los Alamos National Lab., NM (United States); de Verdiere, G.C. [CEA Centre d`Etudes de Limeil, 94 - Villeneuve-Saint-Georges (France)
1995-05-01
Sphere rendering is an important method for visualizing molecular dynamics data. This paper presents a parallel divide-and-conquer algorithm that is almost 90 times faster than current graphics workstations. To render extremely large data sets and large images, the algorithm uses the MIMD features of the supercomputers to divide up the data, render independent partial images, and then finally composite the multiple partial images using an optimal method. The algorithm and performance results are presented for the CM-5 and the T3D.
Energy Technology Data Exchange (ETDEWEB)
Leder, A. [MIT; Anderson, A. J. [Chicago U., KICP; Billard, J. [Lyon, IPN; Figueroa-Feliciano, E. [Northwestern U.; Formaggio, J. A. [MIT; Hasselkus, C. [Wisconsin U., Madison; Newman, E. [MIT; Palladino, K. [Wisconsin U., Madison; Phuthi, M. [MIT; Winslow, L. [MIT; Zhang, L. [MIT
2017-10-02
The Ricochet experiment seeks to measure Coherent (neutral-current) Elastic Neutrino-Nucleus Scattering using dark-matter-style detectors with sub-keV thresholds placed near a neutrino source, such as the MIT (research) Reactor (MITR), which operates at 5.5 MW generating approximately 2.2e18 neutrinos/second at the core. Currently, Ricochet is characterizing the backgrounds at MITR, the main component of which comes in the form of neutrons emitted from the core simultaneous with the neutrino signal. To characterize this background, we wrapped a Bonner cylinder around a He-3 thermal neutron detector, whose data was then unfolded to produce a neutron energy spectrum across several orders of magnitude. We discuss the resulting spectrum and its implications for deploying Ricochet in the future at the MITR site as well as the feasibility of reducing this background level via the addition of polyethylene shielding around the detector setup.
Falling-sphere radioactive viscometry
International Nuclear Information System (INIS)
Souza, R. de.
1987-01-01
In this work the falling sphere viscometric method was studies experimentally using a sphere tagged with 198 Au radiosotopo, the objective being the demosntration of the advantages of this technique in relation to the traditional method. The utilisation of the falling radioactive sphere permits the point-point monitoring of sphere position as a function of count rate. The fall tube wall and end effects were determined by this technique. Tests were performed with spheres of different diameters in four tubes. The application of this technique demosntrated the wall and end effects in sphere speed. The case of sphere fall in the steady slow regime allowed the determination of the terminal velocity, showing the increase of botton end effect as the sphere approaches the tube base. In the case the transient slow regime, the sphere was initially in a state of respose near the top surface. The data obtained show the influence of the free surface and wall on the sphere acceleration. These experimental data were applied to the Basset equation on order to verify the behaviour of the terms in this equation. (author) [pt
Guerra, Rodrigo E.; Kelleher, Colm P.; Hollingsworth, Andrew D.; Chaikin, Paul M.
2018-02-01
The best understood crystal ordering transition is that of two-dimensional freezing, which proceeds by the rapid eradication of lattice defects as the temperature is lowered below a critical threshold. But crystals that assemble on closed surfaces are required by topology to have a minimum number of lattice defects, called disclinations, that act as conserved topological charges—consider the 12 pentagons on a football or the 12 pentamers on a viral capsid. Moreover, crystals assembled on curved surfaces can spontaneously develop additional lattice defects to alleviate the stress imposed by the curvature. It is therefore unclear how crystallization can proceed on a sphere, the simplest curved surface on which it is impossible to eliminate such defects. Here we show that freezing on the surface of a sphere proceeds by the formation of a single, encompassing crystalline ‘continent’, which forces defects into 12 isolated ‘seas’ with the same icosahedral symmetry as footballs and viruses. We use this broken symmetry—aligning the vertices of an icosahedron with the defect seas and unfolding the faces onto a plane—to construct a new order parameter that reveals the underlying long-range orientational order of the lattice. The effects of geometry on crystallization could be taken into account in the design of nanometre- and micrometre-scale structures in which mobile defects are sequestered into self-ordered arrays. Our results may also be relevant in understanding the properties and occurrence of natural icosahedral structures such as viruses.
Guerra, Rodrigo E; Kelleher, Colm P; Hollingsworth, Andrew D; Chaikin, Paul M
2018-02-14
The best understood crystal ordering transition is that of two-dimensional freezing, which proceeds by the rapid eradication of lattice defects as the temperature is lowered below a critical threshold. But crystals that assemble on closed surfaces are required by topology to have a minimum number of lattice defects, called disclinations, that act as conserved topological charges-consider the 12 pentagons on a football or the 12 pentamers on a viral capsid. Moreover, crystals assembled on curved surfaces can spontaneously develop additional lattice defects to alleviate the stress imposed by the curvature. It is therefore unclear how crystallization can proceed on a sphere, the simplest curved surface on which it is impossible to eliminate such defects. Here we show that freezing on the surface of a sphere proceeds by the formation of a single, encompassing crystalline 'continent', which forces defects into 12 isolated 'seas' with the same icosahedral symmetry as footballs and viruses. We use this broken symmetry-aligning the vertices of an icosahedron with the defect seas and unfolding the faces onto a plane-to construct a new order parameter that reveals the underlying long-range orientational order of the lattice. The effects of geometry on crystallization could be taken into account in the design of nanometre- and micrometre-scale structures in which mobile defects are sequestered into self-ordered arrays. Our results may also be relevant in understanding the properties and occurrence of natural icosahedral structures such as viruses.
Hard spheres out of equilibrium
Hermes, M.
2010-01-01
In this thesis, experiments and simulations are combined to investigate the nonequilibrium behaviour of hard spheres. In the first chapters we use Molecular Dynamics simulations to investigate the dynamic glass transition of polydisperse hard spheres. We show that this dynamic transition is
Energy Technology Data Exchange (ETDEWEB)
Ortiz R, J.M.; Martinez B, M.R.; Vega C, H.R. [UAZ, Av. Ramon Lopez Velarde Num. 801, 98000 Zacatecas (Mexico)
2008-07-01
The artificial neural networks and the genetic algorithms are two relatively new areas of research, which have been subject to a growing interest during the last years. Both models are inspired by the nature, however, the neural networks are interested in the learning of a single individual, which is defined as fenotypic learning, while the evolutionary algorithms are interested in the adaptation of a population to a changing environment, that which is defined as genotypic learning. Recently, the use of the technology of neural networks has been applied with success in the area of the nuclear sciences, mainly in the areas of neutron spectrometry and dosimetry. The structure (network topology), as well as the learning parameters of a neural network, are factors that contribute in a significant way with the acting of the same one, however, it has been observed that the investigators in this area, carry out the selection of the network parameters through the essay and error technique, that which produces neural networks of poor performance and low generalization capacity. From the revised sources, it has been observed that the use of the evolutionary algorithms, seen as search techniques, it has allowed him to be possible to evolve and to optimize different properties of the neural networks, just as the initialization of the synaptic weights, the network architecture or the training algorithms without the human intervention. The objective of the present work is focused in analyzing the intersection of the neural networks and the evolutionary algorithms, analyzing like it is that the same ones can be used to help in the design processes and training of a neural network, this is, in the good selection of the structural parameters and of network learning, improving its generalization capacity, in such way that the same one is able to reconstruct in an efficient way neutron spectra and to calculate equivalent doses starting from the counting rates of a Bonner sphere
International Nuclear Information System (INIS)
Koshiishi, H.; Matsumoto, H.; Chishiki, A.; Goka, T.; Omodaka, T.
2007-01-01
The Bonner Ball Neutron Detector (BBND) experiment was conducted onboard the US Laboratory Module of the International Space Station (ISS) as part of the Human Research Facility project of NASA in order to evaluate the neutron radiation environment in the energy range from thermal up to 15 MeV inside the ISS. The BBND experiment was carried out over an eight-month period from 23 March through 14 November 2001, corresponding to the maximum period of solar-activity variation. The neutron differential-energy spectra are compared with the model neutron spectrum predicted for the inside of the ISS, and are found to be in good agreement for E>10keV. In contrast, the ISS model spectrum has lower flux for E<10keV, which is likely due to the difference in the shielding environment. The neutron dose equivalent rates are 69 and 88μSv/day for the two locations inside the US Laboratory Module, representing a 30% increase due to the difference in the localized shielding environment inside the same pressurized module. The influence of the ISS altitude variation is estimated for the neutron dose equivalent rate to increase by a factor of 2 over the ISS altitude variation of 300-500 km. The increase in the cumulative neutron dose equivalent due to the most significant solar event during the BBND experiment is 0.15 mSv, which contributes less than 1% to the annual neutron dose equivalent estimated from the BBND experiment
Morse functions with sphere fibers
Saeki, Osamu
2006-01-01
A smooth closed manifold is said to be an almost sphere if it admits a Morse function with exactly two critical points. In this paper, we characterize those smooth closed manifolds which admit Morse functions such that each regular fiber is a finite disjoint union of almost spheres. We will see that such manifolds coincide with those which admit Morse functions with at most three critical values. As an application, we give a new proof of the characterization theorem of those closed manifolds ...
Chesneau, O.; Schmid, H.-M.; Carbillet, M.; Chiavassa, A.; Abe, L.; Mouillet, D.
2013-05-01
SPHERE, the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument for the VLT is optimized towards reaching the highest contrast in a limited field of view and at short distances from the central star, thanks to an extreme AO system. SPHERE is very well suited to study the close environment of Betelgeuse, and has a strong potential for detecting the ejection activity around this key red supergiant.
Porous Ceramic Spheres From Cation Exchange Beads
Dynys, Fred
2005-01-01
This document is a slide presentation that examines the use of a simple templating process to produce hollow ceramic spheres with a pore size of 1 to 10 microns. Using ion exchange process it was determined that the method produces porous ceramic spheres with a unique structure: (i.e., inner sphere surrounded by an outer sphere.)
Energy Technology Data Exchange (ETDEWEB)
Ortiz R, J. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica, Av. Ramon Lopez Velarde No. 801, Col. Centro, Zacatecas (Mexico); Martinez B, M. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Av. Ramon Lopez Velarde No. 801, Col. Centro, Zacatecas (Mexico); Gallego, E. [Universidad Politecnica de Madrid, Departamento de Ingenieria Nuclear, Jose Gutierrez Abascal No. 2, E-28006 Madrid (Spain)], e-mail: morvymmyahoo@com.mx
2009-10-15
The neutron dosimetry is one of the most complicated tasks of radiation protection, due to it is a complex technique and highly dependent of neutron energy. One of the first devices used to perform neutron spectrometry is the system known as spectrometric system of Bonner spheres, that continuous being one of spectrometers most commonly used. This system has disadvantages such as: the components weight, the low resolution of spectrum, long and drawn out procedure for the spectra reconstruction, which require an expert user in system management, the need of use a reconstruction code as BUNKIE, SAND, etc., which are based on an iterative reconstruction algorithm and whose greatest inconvenience is that for the spectrum reconstruction, are needed to provide to system and initial spectrum as close as possible to the desired spectrum get. Consequently, researchers have mentioned the need to developed alternative measurement techniques to improve existing monitoring systems for workers. Among these alternative techniques have been reported several reconstruction procedures based on artificial intelligence techniques such as genetic algorithms, artificial neural networks and hybrid systems of evolutionary artificial neural networks using genetic algorithms. However, the use of these techniques in the nuclear science area is not free of problems, so it has been suggested that more research is conducted in such a way as to solve these disadvantages. Because they are emerging technologies, there are no tools for the results analysis, so in this paper we present first the design of a computation tool that allow to analyze the neutron spectra and equivalent doses, obtained through the hybrid technology of neural networks and genetic algorithms. This tool provides an user graphical environment, friendly, intuitive and easy of operate. The speed of program operation is high, executing the analysis in a few seconds, so it may storage and or print the obtained information for
Energy Technology Data Exchange (ETDEWEB)
Castaneda M, V. H.; Martinez B, M. R.; Solis S, L. O.; Castaneda M, R.; Leon P, A. A.; Hernandez P, C. F.; Espinoza G, J. G.; Ortiz R, J. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, 98000 Zacatecas, Zac. (Mexico); Mendez, R. [CIEMAT, Departamento de Metrologia de Radiaciones Ionizantes, Laboratorio de Patrones Neutronicos, Av. Complutense 22, 28040 Madrid (Spain); Gallego, E. [Universidad Politecnica de Madrid, Departamento de Ingenieria Nuclear, C. Jose Gutierrez Abascal 2, 28006 Madrid (Spain); Sousa L, M. A. [Comision Nacional de Energia Nuclear, Centro de Investigacion de Tecnologia Nuclear, Av. Pte. Antonio Carlos 6627, Pampulha, 31270-901 Belo Horizonte, Minas Gerais (Brazil)
2016-10-15
The Taguchi methodology has proved to be highly efficient to solve inverse problems, in which the values of some parameters of the model must be obtained from the observed data. There are intrinsic mathematical characteristics that make a problem known as inverse. Inverse problems appear in many branches of science, engineering and mathematics. To solve this type of problem, researches have used different techniques. Recently, the use of techniques based on Artificial Intelligence technology is being explored by researches. This paper presents the use of a software tool based on artificial neural networks of generalized regression in the solution of inverse problems with application in high energy physics, specifically in the solution of the problem of neutron spectrometry. To solve this problem we use a software tool developed in the Mat Lab programming environment, which employs a friendly user interface, intuitive and easy to use for the user. This computational tool solves the inverse problem involved in the reconstruction of the neutron spectrum based on measurements made with a Bonner spheres spectrometric system. Introducing this information, the neural network is able to reconstruct the neutron spectrum with high performance and generalization capability. The tool allows that the end user does not require great training or technical knowledge in development and/or use of software, so it facilitates the use of the program for the resolution of inverse problems that are in several areas of knowledge. The techniques of Artificial Intelligence present singular veracity to solve inverse problems, given the characteristics of artificial neural networks and their network topology, therefore, the tool developed has been very useful, since the results generated by the Artificial Neural Network require few time in comparison to other techniques and are correct results comparing them with the actual data of the experiment. (Author)
Public Sphere as Digital Assemblage
DEFF Research Database (Denmark)
Salovaara-Moring, Inka
the 1990s onwards digitalization brought concepts of network and complexity into the theoretical discourse. This relational turn changed the social ontology of the public sphere into a dynamic and complex system, erasing the division between the fields of reality (the world), representation (discourse...... theories. Drawing from Deleuze & Guattari (1987), Bennett (2010), and Latour (2004) in order to imagine post-human assemblages of public sphere, this paper argues for a relational ontology that emphasizes the complex interactions of political assemblages. Empirically, it draws from the author’s studies......Normative theories of public sphere have struggled with the topic of materiality. The historical narrative of the ‘public sphere’ situated the phenomenon in specific spaces, where practices (public deliberation) and language (discourse) constructed political agencies, and further publics. From...
Sphere of Nursing Advocacy Model.
Hanks, Robert G
2005-01-01
The Sphere of Nursing Advocacy (SNA) model explains and depicts nursing advocacy on behalf of a client. The SNA model views the client as continually protected from the external environment by a semipermeable sphere of nursing advocacy that allows clients to self advocate if the client is emotionally and physically able or to be advocated for by the nurse if the patient is unable to advocate for him- or herself. The SNA model can be used to guide research or it can provide the basis for instruction on the subject of nursing advocacy.
Troubleshooting vSphere storage
Preston, Mike
2013-01-01
This is a step-by-step example-oriented tutorial aimed at showing the reader how to troubleshoot a variety of vSphere storage problems, and providing the reader with solutions that can be completed with minimal effort and time in order to limit damage to work.If you are a vSphere administrator, this is the book for you. This book will provide you with 'need to know' information about the various storage transports that ESXi utilizes, the tools and techniques we can use to identify problems, and the fundamental knowledge and steps to take to troubleshoot storage-related issues. Prior knowledge
Spheres of Justice within Schools
DEFF Research Database (Denmark)
Sabbagh, Clara; Resh, Nura; Mor, Michal
2006-01-01
This article argues that there are distinct spheres of justice within education and examines a range of justice norms and distribution rules that characterize the daily life of schools and classrooms. Moving from the macro to micro level, we identify the following five areas: the right to education......, and on the practices used in the actual allocation of these goods. In line with normative ‘spheres of justice’ arguments in social theory, we conclude that the ideals of social justice within schools vary strongly according to the particular resource to be distributed. Moreover, these ideals often do not correspond...
Phase diagram of Hertzian spheres
Pàmies, J.C.; Cacciuto, A.; Frenkel, D.
2009-01-01
We report the phase diagram of interpenetrating Hertzian spheres. The Hertz potential is purely repulsive, bounded at zero separation, and decreases monotonically as a power law with exponent 5/2, vanishing at the overlapping threshold. This simple functional describes the elastic interaction of
Performance and Politics in the Public Sphere
Wiegmink, Pia
2011-01-01
Pia Wiegmink’s timely examination of the transforming transnational spaces of protest in a globalizing and technologically mediated public sphere in “Performance and Politics in the Public Sphere” offers a well-researched review of contemporary theory surrounding ideas of the political (Chantal Mouffe), the public sphere (Jürgen Habermas), the transnational public sphere (Nancy Fraser), and the reterritorialized transnational public sphere (Markus Schroer) as the basis for her analysis of how...
Capillary holdup between vertical spheres
Directory of Open Access Journals (Sweden)
S. Zeinali Heris
2009-12-01
Full Text Available The maximum volume of liquid bridge left between two vertically mounted spherical particles has been theoretically determined and experimentally measured. As the gravitational effect has not been neglected in the theoretical model, the liquid interface profile is nonsymmetrical around the X-axis. Symmetry in the interface profile only occurs when either the particle size ratio or the gravitational force becomes zero. In this paper, some equations are derived as a function of the spheres' sizes, gap width, liquid density, surface tension and body force (gravity/centrifugal to estimate the maximum amount of liquid that can be held between the two solid spheres. Then a comparison is made between the result based on these equations and several experimental results.
Mie scattering of magnetic spheres.
Tarento, R-J; Bennemann, K-H; Joyes, P; Van de Walle, J
2004-02-01
The Mie scattering intensity of a magnetic sphere has been derived by extending the classical Mie scattering approach to a media where the dielectric constant is no more a real number but a tensor with a gyrotropic form. Using a perturbation method the propagation equations of the electromagnetic field are derived. For an incident plane wave the magnetization effect could be detectable. The Mie scattering intensity is analyzed for special incident wave configurations, in particular, for the case where the magnetic field of the incident plane wave is polarized along the magnetization direction. This magnetization effect is most important for the finger pattern of the backscattering intensity. Magnetic Mie scattering is still significant for a magnetic sphere of radius larger than 10 nm.
FRUIT: An operational tool for multisphere neutron spectrometry in workplaces
Bedogni, Roberto; Domingo, Carles; Esposito, Adolfo; Fernández, Francisco
2007-10-01
FRUIT (Frascati Unfolding Interactive Tool) is an unfolding code for Bonner sphere spectrometers (BSS) developed, under the Labview environment, at the INFN-Frascati National Laboratory. It models a generic neutron spectrum as the superposition of up to four components (thermal, epithermal, fast and high energy), fully defined by up to seven positive parameters. Different physical models are available to unfold the sphere counts, covering the majority of the neutron spectra encountered in workplaces. The iterative algorithm uses Monte Carlo methods to vary the parameters and derive the final spectrum as limit of a succession of spectra fulfilling the established convergence criteria. Uncertainties on the final results are evaluated taking into consideration the different sources of uncertainty affecting the input data. Relevant features of FRUIT are (1) a high level of interactivity, allowing the user to follow the convergence process, (2) the possibility to modify the convergence tolerances during the run, allowing a rapid achievement of meaningful solutions and (3) the reduced dependence of the results from the initial hypothesis. This provides a useful instrument for spectrometric measurements in workplaces, where detailed a priori information is usually unavailable. This paper describes the characteristics of the code and presents the results of performance tests over a significant variety of reference and workplace neutron spectra ranging from thermal up to hundreds MeV neutrons.
FRUIT: An operational tool for multisphere neutron spectrometry in workplaces
International Nuclear Information System (INIS)
Bedogni, Roberto; Domingo, Carles; Esposito, Adolfo; Fernandez, Francisco
2007-01-01
FRUIT (Frascati Unfolding Interactive Tool) is an unfolding code for Bonner sphere spectrometers (BSS) developed, under the Labview environment, at the INFN-Frascati National Laboratory. It models a generic neutron spectrum as the superposition of up to four components (thermal, epithermal, fast and high energy), fully defined by up to seven positive parameters. Different physical models are available to unfold the sphere counts, covering the majority of the neutron spectra encountered in workplaces. The iterative algorithm uses Monte Carlo methods to vary the parameters and derive the final spectrum as limit of a succession of spectra fulfilling the established convergence criteria. Uncertainties on the final results are evaluated taking into consideration the different sources of uncertainty affecting the input data. Relevant features of FRUIT are (1) a high level of interactivity, allowing the user to follow the convergence process, (2) the possibility to modify the convergence tolerances during the run, allowing a rapid achievement of meaningful solutions and (3) the reduced dependence of the results from the initial hypothesis. This provides a useful instrument for spectrometric measurements in workplaces, where detailed a priori information is usually unavailable. This paper describes the characteristics of the code and presents the results of performance tests over a significant variety of reference and workplace neutron spectra ranging from thermal up to hundreds MeV neutrons
Lowe, Scott
2011-01-01
A new and updated edition of bestselling Mastering VMware vSphere 4 Written by leading VMware expert, this book covers all the features and capabilities of VMware vSphere. You'll learn how to install, configure, operate, manage, and secure the latest release.Covers all the new features and capabilities of the much-anticipated new release of VMware vSphereDiscusses the planning, installation, operation, and management for the latest releaseReviews migration to the latest vSphere softwareOffers hands-on instruction and clear explanations with real-world examples Mastering VMware vSphere is the
Indian Academy of Sciences (India)
Academy News. IAS Logo. Theory Of Evolution. Posted on 23 January 2018. Joint Statement by the Three Science Academies of India on the teaching of the theory of evolution more... ACADEMY PUBLIC LECTURE: How Things Break – The Mechanics of Dynamic Fracture. Posted on 16th February 2018. SPEAKER: Prof.
Generating perfect fluid spheres in general relativity
International Nuclear Information System (INIS)
Boonserm, Petarpa; Visser, Matt; Weinfurtner, Silke
2005-01-01
Ever since Karl Schwarzschild's 1916 discovery of the spacetime geometry describing the interior of a particular idealized general relativistic star--a static spherically symmetric blob of fluid with position-independent density--the general relativity community has continued to devote considerable time and energy to understanding the general-relativistic static perfect fluid sphere. Over the last 90 years a tangle of specific perfect fluid spheres has been discovered, with most of these specific examples seemingly independent from each other. To bring some order to this collection, in this article we develop several new transformation theorems that map perfect fluid spheres into perfect fluid spheres. These transformation theorems sometimes lead to unexpected connections between previously known perfect fluid spheres, sometimes lead to new previously unknown perfect fluid spheres, and in general can be used to develop a systematic way of classifying the set of all perfect fluid spheres
Spheres of Justice within Schools
DEFF Research Database (Denmark)
Sabbagh, Clara; Resh, Nura; Mor, Michal
2006-01-01
, the allocation of (or selection into) learning places, teaching–learning practices, teachers’ treatment of students, and student evaluations of grade distribution. We discuss the literature on the beliefs by students and teachers about the just distribution of educational goods in these five domains......This article argues that there are distinct spheres of justice within education and examines a range of justice norms and distribution rules that characterize the daily life of schools and classrooms. Moving from the macro to micro level, we identify the following five areas: the right to education...
Guthrie, Forbes
2013-01-01
Achieve the performance, scalability, and ROI your business needs What can you do at the start of a virtualization deployment to make things run more smoothly? If you plan, deploy, maintain, and optimize vSphere solutions in your company, this unique book provides keen insight and solutions. From hardware selection, network layout, and security considerations to storage and hypervisors, this book explains the design decisions you'll face and how to make the right choices. Written by two virtualization experts and packed with real-world strategies and examples, VMware v
Porous Ceramic Spheres from Ion Exchange Resin
Dynys, Fred
2005-01-01
A commercial cation ion exchange resin, cross-linked polystyrene, has been successfully used as a template to fabricate 20 to 50 micron porous ceramic spheres. Ion exchange resins have dual template capabilities. Pore architecture of the ceramic spheres can be altered by changing the template pattern. Templating can be achieved by utilizing the internal porous structure or the external surface of the resin beads. Synthesis methods and chemical/physical characteristics of the ceramic spheres will be reported.
Method for producing small hollow spheres
International Nuclear Information System (INIS)
Hendricks, C.D.
1979-01-01
A method is described for producing small hollow spheres of glass, metal or plastic, wherein the sphere material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature (T >approx. 600 0 C). As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming a hollow sphere of controllable thickness. The thus produced hollow spheres (20 to 10 3 μm) have a variety of application, and are particularly useful in the fabrication of targets for laser implosion such as neutron sources, laser fusion physics studies, and laser initiated fusion power plants
Electric dipoles on the Bloch sphere
Vutha, Amar C.
2014-01-01
The time evolution of a two-level quantum mechanical system can be geometrically described using the Bloch sphere. By mapping the Bloch sphere evolution onto the dynamics of oscillating electric dipoles, we provide a physically intuitive link between classical electromagnetism and the electric dipole transitions of atomic & molecular physics.
African Journals Online (AJOL)
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2011-03-09
Mar 9, 2011 ... Discourse, as seen in Habermas's definition of the public sphere, is an essential aspect of the participation of .... Ambadiang: Public Sphere, Linguistic Sphericules and Discourse Communities in Africa argumentation and may ..... (c) 'Je ne connais que le nom des condiments pour faire mon marché'. (ibid).
Bridging conflicting innovation spheres of tourism innovation
DEFF Research Database (Denmark)
Fuglsang, Lars; Sørensen, Flemming; Nordli, Anne Jørgensen
2016-01-01
that in tourist destinations actors belong to conflicting innovation spheres but can be brought together in innovation processes when a diplomat enable compromises and when innovation spheres change from personalized to more generalized forms of activity during interaction. The findings are relevant not only...
Point defects in hard-sphere crystals
Pronk, S.; Frenkel, D.
2001-01-01
We report numerical calculations of the concentration of interstitials in hard-sphere crystals. We find that in a three-dimensional fcc hard-sphere crystal at the melting point, the concentration of interstitials is 2.7(4) × 10-8. This is some 3 orders of magnitude lower than the concentration of
NEW ECONOMY: APPROACHES, FEATURES, SOCIAL SPHERE DEVELOPMENT
Babicheva E.E.
2015-01-01
The article presents main features of the New economy. Special consideration was given to social sphere development and social institutions restructuring in the context of the New economy. A number of social problems arisen out of this processes had been covered. In the issue author concluded that social sphere development occurred under the conditions of the New economy is fundamental process
Theorising Public and Private Spheres
Directory of Open Access Journals (Sweden)
Sima Remina
2016-12-01
Full Text Available The 19th century saw an expression of women’s ardent desire for freedom, emancipation and assertion in the public space. Women hardly managed to assert themselves at all in the public sphere, as any deviation from their traditional role was seen as unnatural. The human soul knows no gender distinctions, so we can say that women face the same desire for fulfillment as men do. Today, women are more and more encouraged to develop their skills by undertaking activities within the public space that are different from those that form part of traditional domestic chores. The woman of the 19th century felt the need to be useful to society, to make her contribution visible in a variety of domains. A woman does not have to become masculine to get power. If she is successful in any important job, this does not mean that she thinks like a man, but that she thinks like a woman. Women have broken through the walls that cut them off from public life, activity and ambition. There are no hindrances that can prevent women from taking their place in society.
Dense, layered, inclined flows of spheres
Jenkins, James T.; Larcher, Michele
2017-12-01
We consider dense, inclined flows of spheres in which the particles translate in layers, whose existence may be promoted by the presence of a rigid base and/or sidewalls. We imagine that in such flows a sphere of a layer is forced up the back of a sphere of the layer below, lifting a column of spheres above it, and then falls down the front of the lower sphere, until it bumps against the preceding sphere of the lower layer. We calculate the forces and rate of momentum transfer associated with this process of rub, lift, fall, and bump and determine a relation between the ratio of shear stress to normal stress and the rate of strain that may be integrated to obtain the velocity profile. The fall of a sphere and that of the column above it results in a linear increase in the magnitude of the velocity fluctuations with distance from the base of the flow. We compare the predictions of the model with measured profiles of velocity and granular temperature in several different dense, inclined flows.
Unsteady flow over a decelerating rotating sphere
Turkyilmazoglu, M.
2018-03-01
Unsteady flow analysis induced by a decelerating rotating sphere is the main concern of this paper. A revolving sphere in a still fluid is supposed to slow down at an angular velocity rate that is inversely proportional to time. The governing partial differential equations of motion are scaled in accordance with the literature, reducing to the well-documented von Kármán equations in the special circumstance near the pole. Both numerical and perturbation approaches are pursued to identify the velocity fields, shear stresses, and suction velocity far above the sphere. It is detected that an induced flow surrounding the sphere acts accordingly to adapt to the motion of the sphere up to some critical unsteadiness parameters at certain latitudes. Afterward, the decay rate of rotation ceases such that the flow at the remaining azimuths starts revolving freely. At a critical unsteadiness parameter corresponding to s = -0.681, the decelerating sphere rotates freely and requires no more torque. At a value of s exactly matching the rotating disk flow at the pole identified in the literature, the entire flow field around the sphere starts revolving faster than the disk itself. Increasing values of -s almost diminish the radial outflow. This results in jet flows in both the latitudinal and meridional directions, concentrated near the wall region. The presented mean flow results will be useful for analyzing the instability features of the flow, whether of a convective or absolute nature.
Energy Technology Data Exchange (ETDEWEB)
Cavalcante, D.B.S., E-mail: cavalcante@ird.gov.b [Universidade Federal do Rio de Janeiro (IF/UFRJ), RJ (Brazil). Inst. de Fisica; Fonseca, E.S. da, E-mail: evaldo@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Lemos Junior, R.M. [Coordenacao dos Programas de Pos-Graduacao de Engenharia (COPPE/UFRJ), RJ (Brazil); Batista, D.V.S. [Instituto Nacional do Cancer (INCa), Rio de Janeiro, RJ (Brazil)
2009-07-01
The generated neutron field varies considerably and depends on the beam energy, on the shielding of the accelerator, on the filters for beam homogeneity, and also on the mobile collimators and geometry of irradiation. The estimation of the component relative to the photoneutrons has practical interest for evaluation of the radiological risks for the workers and for the patient as well. Due to the high frequency magnetic field, and to the photon abundance resulting of the escape and scattering at treatment room, those measurements present some difficulties. Measurements of the neutron fields can be made with a Bonner spectrometer. Those system was calibrated with referred neutron standard sources and used for make measurements on a spot of the room where a Variant 2300C/D Linac is installed. The unfolding process used the BUNKI computer code for determination of the neutron spectra at the measurement spot
Finding a source inside a sphere
International Nuclear Information System (INIS)
Tsitsas, N L; Martin, P A
2012-01-01
A sphere excited by an interior point source or a point dipole gives a simplified yet realistic model for studying a variety of applications in medical imaging. We suppose that there is an exterior field (transmission problem) and that the total field on the sphere is known. We give analytical inversion algorithms for determining the interior physical characteristics of the sphere as well as the location, strength and orientation of the source/dipole. We start with static problems (Laplace’s equation) and then proceed to acoustic problems (Helmholtz equation). (paper)
Evolutionary neural networks: a new alternative for neutron spectrometry
International Nuclear Information System (INIS)
Ortiz R, J. M.; Martinez B, M. R.; Vega C, H. R.; Galleo, E.
2009-10-01
A device used to perform neutron spectroscopy is the system known as a system of Bonner spheres spectrometer, this system has some disadvantages, one of these is the need for reconstruction using a code that is based on an iterative reconstruction algorithm, whose greater inconvenience is the need for a initial spectrum, as close as possible to the spectrum that is desired to avoid this inconvenience has been reported several procedures in reconstruction, combined with various types of experimental methods, based on artificial intelligence technology how genetic algorithms, artificial neural networks and hybrid systems evolved artificial neural networks using genetic algorithms. This paper analyzes the intersection of neural networks and evolutionary algorithms applied in the neutron spectroscopy and dosimetry. Due to this is an emerging technology, there are not tools for doing analysis of the obtained results, by what this paper presents a computing tool to analyze the neutron spectra and the equivalent doses obtained through the hybrid technology of neural networks and genetic algorithms. The toolmaker offers a user graphical environment, friendly and easy to operate. (author)
Einstein metrics on tangent bundles of spheres
Energy Technology Data Exchange (ETDEWEB)
Dancer, Andrew S [Jesus College, Oxford University, Oxford OX1 3DW (United Kingdom); Strachan, Ian A B [Department of Mathematics, University of Hull, Hull HU6 7RX (United Kingdom)
2002-09-21
We give an elementary treatment of the existence of complete Kaehler-Einstein metrics with nonpositive Einstein constant and underlying manifold diffeomorphic to the tangent bundle of the (n+1)-sphere.
Elastic spheres can walk on water
Belden, Jesse; Hurd, Randy C.; Jandron, Michael A.; Bower, Allan F.; Truscott, Tadd T.
2016-02-01
Incited by public fascination and engineering application, water-skipping of rigid stones and spheres has received considerable study. While these objects can be coaxed to ricochet, elastic spheres demonstrate superior water-skipping ability, but little is known about the effect of large material compliance on water impact physics. Here we show that upon water impact, very compliant spheres naturally assume a disk-like geometry and dynamic orientation that are favourable for water-skipping. Experiments and numerical modelling reveal that the initial spherical shape evolves as elastic waves propagate through the material. We find that the skipping dynamics are governed by the wave propagation speed and by the ratio of material shear modulus to hydrodynamic pressure. With these insights, we explain why softer spheres skip more easily than stiffer ones. Our results advance understanding of fluid-elastic body interaction during water impact, which could benefit inflatable craft modelling and, more playfully, design of elastic aquatic toys.
Acoustic levitation of a large solid sphere
Energy Technology Data Exchange (ETDEWEB)
Andrade, Marco A. B., E-mail: marcobrizzotti@gmail.com [Institute of Physics, University of São Paulo, São Paulo 05508-090 (Brazil); Bernassau, Anne L. [School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Adamowski, Julio C. [Department of Mechatronics and Mechanical Systems Engineering, Escola Politécnica, University of São Paulo, São Paulo 05508-030 (Brazil)
2016-07-25
We demonstrate that acoustic levitation can levitate spherical objects much larger than the acoustic wavelength in air. The acoustic levitation of an expanded polystyrene sphere of 50 mm in diameter, corresponding to 3.6 times the wavelength, is achieved by using three 25 kHz ultrasonic transducers arranged in a tripod fashion. In this configuration, a standing wave is created between the transducers and the sphere. The axial acoustic radiation force generated by each transducer on the sphere was modeled numerically as a function of the distance between the sphere and the transducer. The theoretical acoustic radiation force was verified experimentally in a setup consisting of an electronic scale and an ultrasonic transducer mounted on a motorized linear stage. The comparison between the numerical and experimental acoustic radiation forces presents a good agreement.
Spheres of Exemption, Figures of Exclusion
DEFF Research Database (Denmark)
, the history of ideas, social science, political science and literature studies, Spheres of Exemption, Figures of Exclusion offers thirteen investigations into the co-constitutive relationship between subjectivity and political and legal order, combining theoretical reflection with empirical and historical...
Hydrodynamic interaction between bacteria and passive sphere
Zhang, Bokai; Ding, Yang; Xu, Xinliang
2017-11-01
Understanding hydrodynamic interaction between bacteria and passive sphere is important for identifying rheological properties of bacterial and colloidal suspension. Over the past few years, scientists mainly focused on bacterial influences on tracer particle diffusion or hydrodynamic capture of a bacteria around stationary boundary. Here, we use superposition of singularities and regularized method to study changes in bacterial swimming velocity and passive sphere diffusion, simultaneously. On this basis, we present a simple two-bead model that gives a unified interpretation of passive sphere diffusion and bacterial swimming. The model attributes both variation of passive sphere diffusion and changes of speed of bacteria to an effective mobility. Using the effective mobility of bacterial head and tail as an input function, the calculations are consistent with simulation results at a broad range of tracer diameters, incident angles and bacterial shapes.
Gender, Diversity and the European Public Sphere
DEFF Research Database (Denmark)
Pristed Nielsen, Helene
2009-01-01
This paper argues that feminist criticism of Habermasian theory leads to new ways of approaching empirical analyses of public sphere deliberation, and gives some concrete indications of which methodological consequences such a critique may lead to....
vSphere high performance cookbook
Sarkar, Prasenjit
2013-01-01
vSphere High Performance Cookbook is written in a practical, helpful style with numerous recipes focusing on answering and providing solutions to common, and not-so common, performance issues and problems.The book is primarily written for technical professionals with system administration skills and some VMware experience who wish to learn about advanced optimization and the configuration features and functions for vSphere 5.1.
Geometrical Dynamics in a Transitioning Superconducting Sphere
Directory of Open Access Journals (Sweden)
Claycomb J. R.
2006-10-01
Full Text Available Recent theoretical works have concentrated on calculating the Casimir effect in curved spacetime. In this paper we outline the forward problem of metrical variation due to the Casimir effect for spherical geometries. We consider a scalar quantum field inside a hollow superconducting sphere. Metric equations are developed describing the evolution of the scalar curvature after the sphere transitions to the normal state.
Ethnography and the public sphere: summarizing questions
Cunha, Manuela Ivone; Lima, Antónia
2013-01-01
In line with the conference Ethnografeast III. Ethnography and the Public Sphere, from which it stems, this issue aims at equating uses and products of ethnography as they relate with each other within the context of the public sphere. Keeping the conference’s commitment to interdisciplinarity, pluralism in genres and theoretical suasions, it focuses on the way political and civic uses of ethnography enter into the conceptual elaboration of its products, and, conversely, on how the design and...
Point Defects in Hard Sphere Crystals
Pronk, Sander; Frenkel, Daan
2001-01-01
We report numerical calculations of the concentration of interstitials in hard-sphere crystals. We find that, in a three-dimensional fcc hard-sphere crystal at the melting point, the concentration of interstitials is 2 * 10^-8. This is some three orders of magnitude lower than the concentration of vacancies. A simple, analytical estimate yields a value that is in fair agreement with the numerical results.
vSphere virtual machine management
Fitzhugh, Rebecca
2014-01-01
This book follows a step-by-step tutorial approach with some real-world scenarios that vSphere businesses will be required to overcome every day. This book also discusses creating and configuring virtual machines and also covers monitoring virtual machine performance and resource allocation options. This book is for VMware administrators who want to build their knowledge of virtual machine administration and configuration. It's assumed that you have some experience with virtualization administration and vSphere.
Inverse Magnus effect on a rotating sphere
Kim, Jooha; Park, Hyungmin; Choi, Haecheon; Yoo, Jung Yul
2011-11-01
In this study, we investigate the flow characteristics of rotating spheres in the subcritical Reynolds number (Re) regime by measuring the drag and lift forces on the sphere and the two-dimensional velocity in the wake. The experiment is conducted in a wind tunnel at Re = 0 . 6 ×105 - 2 . 6 ×105 and the spin ratio (ratio of surface velocity to the free-stream velocity) of 0 (no spin) - 0.5. The drag coefficient on a stationary sphere remains nearly constant at around 0.52. However, the magnitude of lift coefficient is nearly zero at Re Magnus effect, depending on the magnitudes of the Reynolds number and spin ratio. The velocity field measured from a particle image velocimetry (PIV) indicates that non-zero lift coefficient on a stationary sphere at Re > 2 . 0 ×105 results from the asymmetry of separation line, whereas the inverse Magnus effect for the rotating sphere results from the differences in the boundary-layer growth and separation along the upper and lower sphere surfaces. Supported by the WCU, Converging Research Center and Priority Research Centers Program, NRF, MEST, Korea.
DEFF Research Database (Denmark)
Nyvang Hartmeyer, Gitte; Jensen, Anne Kvistholm; Böcher, Sidsel
2010-01-01
Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is currently being introduced for the rapid and accurate identification of bacteria. We describe 2 MALDI-TOF MS identification cases - 1 directly on spinal fluid and 1 on grown bacteria. Rapidly obtained...
Use of X-Ray Fluorescence Spectrometry to Determine Trace ...
African Journals Online (AJOL)
This paper deals with application of X-ray fluorescence spectrometry for the detection of trace elements in graphic. An X-ray spectrometer was constructed and used to carry out measurements on graphite spheres impregnated with different chemical elements. The intensities of the lines of these trace elements, as function of ...
The Separate Spheres Model of Gendered Inequality.
Directory of Open Access Journals (Sweden)
Andrea L Miller
Full Text Available Research on role congruity theory and descriptive and prescriptive stereotypes has established that when men and women violate gender stereotypes by crossing spheres, with women pursuing career success and men contributing to domestic labor, they face backlash and economic penalties. Less is known, however, about the types of individuals who are most likely to engage in these forms of discrimination and the types of situations in which this is most likely to occur. We propose that psychological research will benefit from supplementing existing research approaches with an individual differences model of support for separate spheres for men and women. This model allows psychologists to examine individual differences in support for separate spheres as they interact with situational and contextual forces. The separate spheres ideology (SSI has existed as a cultural idea for many years but has not been operationalized or modeled in social psychology. The Separate Spheres Model presents the SSI as a new psychological construct characterized by individual differences and a motivated system-justifying function, operationalizes the ideology with a new scale measure, and models the ideology as a predictor of some important gendered outcomes in society. As a first step toward developing the Separate Spheres Model, we develop a new measure of individuals' endorsement of the SSI and demonstrate its reliability, convergent validity, and incremental predictive validity. We provide support for the novel hypotheses that the SSI predicts attitudes regarding workplace flexibility accommodations, income distribution within families between male and female partners, distribution of labor between work and family spheres, and discriminatory workplace behaviors. Finally, we provide experimental support for the hypothesis that the SSI is a motivated, system-justifying ideology.
The Separate Spheres Model of Gendered Inequality
Miller, Andrea L.; Borgida, Eugene
2016-01-01
Research on role congruity theory and descriptive and prescriptive stereotypes has established that when men and women violate gender stereotypes by crossing spheres, with women pursuing career success and men contributing to domestic labor, they face backlash and economic penalties. Less is known, however, about the types of individuals who are most likely to engage in these forms of discrimination and the types of situations in which this is most likely to occur. We propose that psychological research will benefit from supplementing existing research approaches with an individual differences model of support for separate spheres for men and women. This model allows psychologists to examine individual differences in support for separate spheres as they interact with situational and contextual forces. The separate spheres ideology (SSI) has existed as a cultural idea for many years but has not been operationalized or modeled in social psychology. The Separate Spheres Model presents the SSI as a new psychological construct characterized by individual differences and a motivated system-justifying function, operationalizes the ideology with a new scale measure, and models the ideology as a predictor of some important gendered outcomes in society. As a first step toward developing the Separate Spheres Model, we develop a new measure of individuals’ endorsement of the SSI and demonstrate its reliability, convergent validity, and incremental predictive validity. We provide support for the novel hypotheses that the SSI predicts attitudes regarding workplace flexibility accommodations, income distribution within families between male and female partners, distribution of labor between work and family spheres, and discriminatory workplace behaviors. Finally, we provide experimental support for the hypothesis that the SSI is a motivated, system-justifying ideology. PMID:26800454
The Separate Spheres Model of Gendered Inequality.
Miller, Andrea L; Borgida, Eugene
2016-01-01
Research on role congruity theory and descriptive and prescriptive stereotypes has established that when men and women violate gender stereotypes by crossing spheres, with women pursuing career success and men contributing to domestic labor, they face backlash and economic penalties. Less is known, however, about the types of individuals who are most likely to engage in these forms of discrimination and the types of situations in which this is most likely to occur. We propose that psychological research will benefit from supplementing existing research approaches with an individual differences model of support for separate spheres for men and women. This model allows psychologists to examine individual differences in support for separate spheres as they interact with situational and contextual forces. The separate spheres ideology (SSI) has existed as a cultural idea for many years but has not been operationalized or modeled in social psychology. The Separate Spheres Model presents the SSI as a new psychological construct characterized by individual differences and a motivated system-justifying function, operationalizes the ideology with a new scale measure, and models the ideology as a predictor of some important gendered outcomes in society. As a first step toward developing the Separate Spheres Model, we develop a new measure of individuals' endorsement of the SSI and demonstrate its reliability, convergent validity, and incremental predictive validity. We provide support for the novel hypotheses that the SSI predicts attitudes regarding workplace flexibility accommodations, income distribution within families between male and female partners, distribution of labor between work and family spheres, and discriminatory workplace behaviors. Finally, we provide experimental support for the hypothesis that the SSI is a motivated, system-justifying ideology.
Thermodynamic properties of non-conformal soft-sphere fluids with effective hard-sphere diameters.
Rodríguez-López, Tonalli; del Río, Fernando
2012-01-28
In this work we study a set of soft-sphere systems characterised by a well-defined variation of their softness. These systems represent an extension of the repulsive Lennard-Jones potential widely used in statistical mechanics of fluids. This type of soft spheres is of interest because they represent quite accurately the effective intermolecular repulsion in fluid substances and also because they exhibit interesting properties. The thermodynamics of the soft-sphere fluids is obtained via an effective hard-sphere diameter approach that leads to a compact and accurate equation of state. The virial coefficients of soft spheres are shown to follow quite simple relationships that are incorporated into the equation of state. The approach followed exhibits the rescaling of the density that produces a unique equation for all systems and temperatures. The scaling is carried through to the level of the structure of the fluids.
Scattering by two spheres: Theory and experiment
DEFF Research Database (Denmark)
Bjørnø, Irina; Jensen, Leif Bjørnø
1998-01-01
of suspended sediments. The scattering properties of single regular-shaped particles have been studied in depth by several authors in the past. However, single particle scattering cannot explain all features of scattering by suspended sediment. When the concentration of particles exceeds a certain limit......, multiple particle scattering becomes important. As a first step in the investigation of mutual interactions between several particles, the acoustical scattering by two spheres has been studied theoretically and experimentally and the results are reported in this paper. The study has mainly been focused...... on three issues: (1) to develop a simplified theory for scattering by two elastical spheres; (2) to measure the scattering by two spheres in a water tank, and (3) to compare the theoretical/numerical results with the measured data. A number of factors influencing multiple scattering, including...
Silo outflow of soft frictionless spheres
Ashour, Ahmed; Trittel, Torsten; Börzsönyi, Tamás; Stannarius, Ralf
2017-12-01
Outflow of granular materials from silos is a remarkably complex physical phenomenon that has been extensively studied with simple objects like monodisperse hard disks in two dimensions (2D) and hard spheres in 2D and 3D. For those materials, empirical equations were found that describe the discharge characteristics. Softness adds qualitatively new features to the dynamics and to the character of the flow. We report a study of the outflow of soft, practically frictionless hydrogel spheres from a quasi-2D bin. Prominent features are intermittent clogs, peculiar flow fields in the container, and a pronounced dependence of the flow rate and clogging statistics on the container fill height. The latter is a consequence of the ineffectiveness of Janssen's law: the pressure at the bottom of a bin containing hydrogel spheres grows linearly with the fill height.
Fuzzy spheres from inequivalent coherent states quantizations
International Nuclear Information System (INIS)
Gazeau, Jean Pierre; Huguet, Eric; Lachieze-Rey, Marc; Renaud, Jacques
2007-01-01
The existence of a family of coherent states (CS) solving the identity in a Hilbert space allows, under certain conditions, to quantize functions defined on the measure space of CS parameters. The application of this procedure to the 2-sphere provides a family of inequivalent CS quantizations based on the spin spherical harmonics (the CS quantization from usual spherical harmonics appears to give a trivial issue for the Cartesian coordinates). We compare these CS quantizations to the usual (Madore) construction of the fuzzy sphere. Due to these differences, our procedure yields new types of fuzzy spheres. Moreover, the general applicability of CS quantization suggests similar constructions of fuzzy versions of a large variety of sets
Glass transition in soft-sphere dispersions
International Nuclear Information System (INIS)
RamIrez-Gonzalez, P E; Medina-Noyola, M
2009-01-01
The concept of dynamic equivalence among mono-disperse soft-sphere fluids is employed in the framework of the self-consistent generalized Langevin equation (SCGLE) theory of colloid dynamics to calculate the ideal glass transition phase diagram of model soft-sphere colloidal dispersions in the softness-concentration state space. The slow dynamics predicted by this theory near the glass transition is compared with available experimental data for the decay of the intermediate scattering function of colloidal dispersions of soft-microgel particles. Increasing deviations from this simple scheme occur for increasingly softer potentials, and this is studied here using the Rogers-Young static structure factor of the soft-sphere systems as the input of the SCGLE theory, without assuming a priori the validity of the equivalence principle above.
The Positive Freedom of the Public Sphere
DEFF Research Database (Denmark)
Hansen, Ejvind
2015-01-01
calls for new reflections on the possible relationship between media, public sphere and democracy. This paper argues that we should change the questions that are raised when we try to assess the public sphere. It is argued that the traditional (Enlightenment) focus upon negative liberties and the truth......-value of utterances is not adequate. Negative freedom and truth are certainly important in the public sphere, because they are necessary conditions for taking a qualified stance towards the challenges that we face. It is, however, important also to reflect on what negative liberties are used for—which kinds of truths...... are articulated in public discussions. To answer this question it is argued that it is important to distinguish between affirmative truths and liberating truths (based on courage), the latter being what is required in democratic dialogues....
Depletion zones and crystallography on pinched spheres
Chen, Jingyuan; Xing, Xiangjun; Yao, Zhenwei
2018-03-01
Understanding the interplay between ordered structures and substrate curvature is an interesting problem with versatile applications, including functionalization of charged supramolecular surfaces and modern microfluidic technologies. In this work, we investigate the two-dimensional packing structures of charged particles confined on a pinched sphere. By continuously pinching the sphere, we observe cleavage of elongated scars into pleats, proliferation of disclinations, and subsequently, emergence of a depletion zone at the negatively curved waist that is completely void of particles. We systematically study the geometrics and energetics of the depletion zone, and reveal its physical origin as a finite size effect, due to the interplay between Coulomb repulsion and concave geometry of the pinched sphere. These results further our understanding of crystallography on curved surfaces, and have implications in design and manipulation of charged, deformable interfaces in various applications.
Energy Technology Data Exchange (ETDEWEB)
Vega C, H. R.; Ortiz R, J. M.; Hernandez D, V. M; Martinez B, M. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Gallego, E.; Lorente, A. [Universidad Politecnica de Madrid, Departamento de Ingenieria Nuclear, C/Jose Gutierrez Abascal No. 2, 28006 Madrid (Spain); Barquero, R., E-mail: fermineutron@yahoo.co [Hospital del Rio Hortega, C/Dulzaina No. 2, 47012 Valladolid (Spain)
2010-09-15
The artificial neural networks technology has been applied to reconstruct the neutrons spectra of two isotopic sources: {sup 252}Cf, and {sup 241}Am-Be. Also, this technology has been applied to obtain the effective dose, E, and the personal dose equivalents, Hp(10) and environmental, H *(10). To obtain the spectra and the doses only were used the count rates produced in a Bonner Spheres spectrometer with a scintillator of {sup 6}LiI(Eu) of 0.4 {phi} x 0.4 cm{sup 2}. The equivalent environmental dose and the spectra of the sources were also obtained by means of the reconstruction code BUNKIUT. When comparing the results obtained by means of both procedures it was found that they are consistent. (Author)
Does Negative Type Characterize the Round Sphere?
DEFF Research Database (Denmark)
Kokkendorff, Simon Lyngby
2007-01-01
We discuss the measure theoretic metric invariants extent, mean distance and symmetry ratio and their relation to the concept of negative type of a metric space. A conjecture stating that a compact Riemannian manifold with symmetry ratio 1 must be a round sphere, was put forward in a previous paper....... We resolve this conjecture in the class of Riemannian symmetric spaces by showing, that a Riemannian manifold with symmetry ratio 1 must be of negative type and that the only compact Riemannian symmetric spaces of negative type are the round spheres....
Bolander, Brian
2014-01-01
An easy-to-follow guide full of hands-on examples of real-world design best practices. Each topic is explained and placed in context, and for the more inquisitive, there are more details on the concepts used.If you wish to learn about vSphere best practices and how to apply them when designing virtual, high performance, reliable datacenters that support business critical applications to work more efficiently and to prepare for official certifications, this is the book for you. Readers should possess a good working knowledge of vSphere as well as servers, storage, and networking.
Garcia, J G; Ghaly, E S
2001-03-01
The objective of this research was to use the natural polymer Carrageenan to obtain controlled release spheres loaded with glipizide using the cross-linking technique. The effect of polymer level and drug load were investigated. The drug was dispersed in Carrageenan solution and the dispersion was dropped by a device containing 3 disposable syringes into cross-linking solution containing 3% calcium chloride. After 15 minutes residence time, the spheres were collected by decantation and dried in hot air oven at 38 degrees C +/- 2 degrees C for 24 hours. The dried spheres were successfully compacted into tablets using rotary Manesty B-3B machine equipped with 12/32 inches round flat face punches, target tablet weight was 400 mg +/- 5%. As the polymer level was increased in the sphere formulation, the drug release rate was increased. However, as the drug level was increased in the sphere formulation, the release rate was decreased. This trend was also true for tablets compacted from spheres. The scanning electron microscope photographs supported the dissolution data. More cracks and rough surface were observed in tablets compacted from spheres containing high polymer level and low drug level.
Wall effects on a rotating sphere
Liu, Qianlong; Prosperetti, Andrea
2010-01-01
The flow induced by a spherical particle spinning in the presence of no-slip planar boundaries is studied by numerical means. In addition to the reference case of an infinite fluid, the situations considered include a sphere rotating near one or two infinite plane walls parallel or perpendicular to
Log Gaussian Cox processes on the sphere
DEFF Research Database (Denmark)
Pacheco, Francisco Andrés Cuevas; Møller, Jesper
We define and study the existence of log Gaussian Cox processes (LGCPs) for the description of inhomogeneous and aggregated/clustered point patterns on the d-dimensional sphere, with d = 2 of primary interest. Useful theoretical properties of LGCPs are studied and applied for the description of sky...
Steel Spheres and Skydiver--Terminal Velocity
Costa Leme, J.; Moura, C.; Costa, Cintia
2009-01-01
This paper describes the use of open source video analysis software in the study of the relationship between the velocity of falling objects and time. We discuss an experiment in which a steel sphere falls in a container filled with two immiscible liquids. The motion is similar to that of a skydiver falling through air.
Physics of the granite sphere fountain
Snoeijer, Jacobus Hendrikus; van der Weele, J.P.
2014-01-01
A striking example of levitation is encountered in the “kugel fountain” where a granite sphere, sometimes weighing over a ton, is kept aloft by a thin film of flowing water. In this paper, we explain the working principle behind this levitation. We show that the fountain can be viewed as a giant
Performance and Politics in the Public Sphere
Directory of Open Access Journals (Sweden)
Pia Wiegmink
2011-12-01
Full Text Available Pia Wiegmink’s timely examination of the transforming transnational spaces of protest in a globalizing and technologically mediated public sphere in “Performance and Politics in the Public Sphere” offers a well-researched review of contemporary theory surrounding ideas of the political (Chantal Mouffe, the public sphere (Jürgen Habermas, the transnational public sphere (Nancy Fraser, and the reterritorialized transnational public sphere (Markus Schroer as the basis for her analysis of how the performance of political action in public—virtual or physical—is transformed by the capacity of the local to be played on a global stage, thus turning the citizen-actor into a cosmopolitan, transnational force. Tracing examples from the Seattle protests against the World Trade Organization meetings in 1999 by the Global Justice Movement to the work of the Electronic Disturbance Theater, from the civil rights movement to the subject matter of her larger study, “The Church of Life After Shopping,” “Billionaires for Bush,” and “The Yes Men,” Wiegmink provides an important analysis of the “alternative aesthetics” of the counterpublics’ formation, dissent, and action in and against hegemony. This selection is taken from her monograph, Protest EnACTed: Activist Performance in the Contemporary United States, a strong, cultural studies–focused contribution to transnational American Studies.
Performance and Politics in the Public Sphere
Directory of Open Access Journals (Sweden)
Pia Wiegmink
2011-12-01
Full Text Available Pia Wiegmink’s timely examination of the transforming transnational spaces of protest in a globalizing and technologically mediated public sphere in “Performance and Politics in the Public Sphere” offers a well-researched review of contemporary theory surrounding ideas of the political (Chantal Mouffe, the public sphere (Jürgen Habermas, the transnational public sphere (Nancy Fraser, and the reterritorialized transnational public sphere (Markus Schroer as the basis for her analysis of how the performance of political action in public—virtual or physical—is transformed by the capacity of the local to be played on a global stage, thus turning the citizen-actor into a cosmopolitan, transnational force. Tracing examples from the Seattle protests against the World Trade Organization meetings in 1999 by the Global Justice Movement to the work of the Electronic Disturbance Theater, from the civil rights movement to the subject matter of her larger study, “The Church of Life After Shopping,” “Billionaires for Bush,” and “The Yes Men,” Wiegmink provides an important analysis of the “alternative aesthetics” of the counterpublics’ formation, dissent, and action in and against hegemony. This selection is taken from her monograph, Protest EnACTed: Activist Performance in the Contemporary United States, a strong, cultural studies–focused contribution to transnational American Studies.
On the torus cobordant cohomology spheres
Indian Academy of Sciences (India)
Is it true that for any smooth action of on a homotopy sphere with exactly two fixed points, the tangent -modules at these two points are isomorphic?" A result due to Atiyah and Bott proves that the answer is `yes' for Z Z p and it is also known ...
New interior solution describing relativistic fluid sphere
Indian Academy of Sciences (India)
General relativity; exact solution; embedding class I; anisotropy; compact star. Abstract. Anewexact solution of embedding class I is presented for a relativistic anisotropicmassive fluid sphere. The new exact solution satisfies Karmarkar condition, is well-behaved in all respects, and therefore is suitable for the modelling of ...
Art, politics and the public sphere
Gielen, Pascal
2014-01-01
Contemporary art, with its foundation in the modern age, can merely exist by the grace of a political democracy; a democracy that in turn only exists by the grace of there being a public domain. Also, political democracy makes it possible for art to play a part in the public sphere and at the same
Models of diffusive noise on the sphere
International Nuclear Information System (INIS)
Spina, M E; Saraceno, M
2004-01-01
We analyse Haake et al method for coarse graining quantum maps on the sphere from the point of view of realizable physical quantum operations achieved with completely positive superoperators. We conclude that sharp truncations in the style of Haake do not fall into this class. (letter to the editor)
New interior solution describing relativistic fluid sphere
Indian Academy of Sciences (India)
Anewexact solution of embedding class I is presented for a relativistic anisotropicmassive fluid sphere. The new exact solution satisfies Karmarkar condition, is well-behaved in all respects, and therefore is suitable for the modelling of superdense stars. Consequently, using this solution, we have studied in detail two ...
Stacked spheres and lower bound theorem
Indian Academy of Sciences (India)
BASUDEB DATTA
2011-11-20
Nov 20, 2011 ... Preliminaries. Lower bound theorem. On going work. Definitions. An n-simplex is a convex hull of n + 1 affinely independent points. (called vertices) in some Euclidean space R. N . Stacked spheres and lower bound theorem. Basudeb Datta. Indian Institute of Science. 2 / 27 ...
Institutional change and spheres of authority
DEFF Research Database (Denmark)
Aagaard, Peter
institutioner. Denne tilgang bidrager til at udvikle global governance begrebet "spheres of authority" Det forklarer hvordan transnational lederskab kan bevares, selv om magten spredes i en globaliseret verden. Gennem en illustrativ case om microcredit, viser artiklen hvordan en tilgang baseret på institutional...
Pious Entertainment: Hizbullah's Islamic Cultural Sphere
Alagha, J.E.; Nieuwkerk, K. van
2011-01-01
Alagha’s chapter on Hezbollah’s Islamic cultural sphere is sure to generate some of the most interesting discussion. Lebanon and Hezbollah in particular are among the hottest topics in the studies of contemporary Islam, but few people actually have the appropriate levels of both access to and
The Dirac operator on the Fuzzy sphere
International Nuclear Information System (INIS)
Grosse, H.
1994-01-01
We introduce the Fuzzy analog of spinor bundles over the sphere on which the non-commutative analog of the Dirac operator acts. We construct the complete set of eigenstates including zero modes. In the commutative limit we recover known results. (authors)
Spheres: from Ground Development to ISS Operations
Katterhagen, A.
2016-01-01
SPHERES (Synchronized Position Hold Engage and Reorient Experimental Satellites) is an internal International Space Station (ISS) Facility that supports multiple investigations for the development of multi-spacecraft and robotic control algorithms. The SPHERES National Lab Facility aboard ISS is managed and operated by NASA Ames Research Center (ARC) at Moffett Field California. The SPHERES Facility on ISS consists of three self-contained eight-inch diameter free-floating satellites which perform the various flight algorithms and serve as a platform to support the integration of experimental hardware. SPHERES has served to mature the adaptability of control algorithms of future formation flight missions in microgravity (6 DOF (Degrees of Freedom) / long duration microgravity), demonstrate key close-proximity formation flight and rendezvous and docking maneuvers, understand fault diagnosis and recovery, improve the field of human telerobotic operation and control, and lessons learned on ISS have significant impact on ground robotics, mapping, localization, and sensing in three-dimensions - among several other areas of study.
Amidinate Ligands in Zinc coordination sphere
Indian Academy of Sciences (India)
Home; Journals; Journal of Chemical Sciences; Volume 128; Issue 6. Amidinate Ligands in Zinc coordination sphere: Synthesis and structural diversity. SRINIVAS ANGA INDRANI BANERJEE TARUN K PANDA. Regular Article Volume 128 Issue 6 June 2016 pp ... Keywords. Zinc; carbodiimides; amidinate; alkyl migration.
Micro sphere with nanoporosity by electrospinning
International Nuclear Information System (INIS)
He Jihuan; Liu Yong; Xu Lan; Yu Jianyong
2007-01-01
Nanoporous structures are potentially of great technological interest for the development of electronic, catalytic and hydrogen-storage systems, invisibility device (e.g. stealth plane) and others. Here we describe a general strategy for the synthesis of micro sphere with nanoporosity by electrospinning, the porous sizes having uniform but tunable diameters can be controlled by voltage applied in the electrospinning process
Production of Liquid Metal Spheres by Molding
Directory of Open Access Journals (Sweden)
Mohammed G. Mohammed
2014-10-01
Full Text Available This paper demonstrates a molding technique for producing spheres composed of eutectic gallium-indium (EGaIn with diameters ranging from hundreds of microns to a couple millimeters. The technique starts by spreading EGaIn across an elastomeric sheet featuring cylindrical reservoirs defined by replica molding. The metal flows into these features during spreading. The spontaneous formation of a thin oxide layer on the liquid metal keeps the metal flush inside these reservoirs. Subsequent exposure to acid removes the oxide and causes the metal to bead up into a sphere with a size dictated by the volume of the reservoirs. This technique allows for the production and patterning of droplets with a wide range of volumes, from tens of nanoliters up to a few microliters. EGaIn spheres can be embedded or encased subsequently in polymer matrices using this technique. These spheres may be useful as solder bumps, electrodes, thermal contacts or components in microfluidic devices (valves, switches, pumps. The ease of parallel-processing and the ability to control the location of the droplets during their formation distinguishes this technique.
Ligand sphere conversions in terminal carbide complexes
DEFF Research Database (Denmark)
Morsing, Thorbjørn Juul; Reinholdt, Anders; Sauer, Stephan P. A.
2016-01-01
Metathesis is introduced as a preparative route to terminal carbide complexes. The chloride ligands of the terminal carbide complex [RuC(Cl)2(PCy3)2] (RuC) can be exchanged, paving the way for a systematic variation of the ligand sphere. A series of substituted complexes, including the first exam...
Piezoelectric hollow sphere transducers: The 'BBs'
Alkoy, Sedat
This thesis describes the design, fabrication, modeling and device characteristics of ultrasound transducers developed from millimeter size piezoelectric ceramic hollow spheres. Green ceramic hollow spheres were produced using a coaxial nozzle slurry process and a sacrificial core coating process in the size range of 1-6 mm in diameter and 12-200 μm in wall thickness. Ceramic powders with the morphotropic phase boundary compositions of lead zirconate titanate solid solution known as PZT-4 and PZT-5A, and a modified lead titanate composition were used in these two processes. After sintering, the desired shapes were obtained by drilling, grinding, or polishing. Sphere surfaces were then coated with an electrode material in desired shapes and area of coverage. Two main poling configurations were studied: a radial poling configuration with inside and outside electrodes, and a tangential poling with top and bottom outside electrodes with several different electrode patterns. Dielectric, piezoelectric and ferroelectric properties of these transducers were measured. Vibration modes were determined using the ATILA™ finite element analysis (FEA) code, and associated resonance frequencies were measured and compared to the calculated values. The effect of sphere dimensions, materials and electrode configurations were analyzed using FEA. It was determined from the finite elements analysis of the structure that wall thickness variations do not have a pronounced affect on the vibrations of the structure at lower frequencies (from kHz to low MHz). Focused transducers were prepared for biomedical ultrasound imaging from dish-shape shell sections of the hollow spheres. Pulse-echo characteristics such as, insertion loss, waveform and bandwidth were measured. These transducers were also modeled using the FEA. Transducer operation frequencies of up to 50 MHz were achieved with f-numbers down to 1. Omnidirectional miniature hydrophones were prepared from radially poled hollow
Full sphere hydrodynamic and dynamo benchmarks
Marti, P.
2014-01-26
Convection in planetary cores can generate fluid flow and magnetic fields, and a number of sophisticated codes exist to simulate the dynamic behaviour of such systems. We report on the first community activity to compare numerical results of computer codes designed to calculate fluid flow within a whole sphere. The flows are incompressible and rapidly rotating and the forcing of the flow is either due to thermal convection or due to moving boundaries. All problems defined have solutions that alloweasy comparison, since they are either steady, slowly drifting or perfectly periodic. The first two benchmarks are defined based on uniform internal heating within the sphere under the Boussinesq approximation with boundary conditions that are uniform in temperature and stress-free for the flow. Benchmark 1 is purely hydrodynamic, and has a drifting solution. Benchmark 2 is a magnetohydrodynamic benchmark that can generate oscillatory, purely periodic, flows and magnetic fields. In contrast, Benchmark 3 is a hydrodynamic rotating bubble benchmark using no slip boundary conditions that has a stationary solution. Results from a variety of types of code are reported, including codes that are fully spectral (based on spherical harmonic expansions in angular coordinates and polynomial expansions in radius), mixed spectral and finite difference, finite volume, finite element and also a mixed Fourier-finite element code. There is good agreement between codes. It is found that in Benchmarks 1 and 2, the approximation of a whole sphere problem by a domain that is a spherical shell (a sphere possessing an inner core) does not represent an adequate approximation to the system, since the results differ from whole sphere results. © The Authors 2014. Published by Oxford University Press on behalf of The Royal Astronomical Society.
Benavides, Jose
2017-01-01
SPHERES/Astrobee Working Group (SAWG) Quarterly meeting. Membership includes MIT, FIT, AFS, DARPA, CASIS, SJSU, and NASA (HQ, KSC, JSC, MSFC, and ARC)Face-to-Face, twice a year Purpose: Information sharing across the SPHERES community Program office shares National Lab Facility availability Status of resources (batteries, CO2 tanks, etc.), Overall Calendar (scheduled Test Sessions, up mass return), and Updates on new PD, Investigations, and ISS infrastructure. Provide the SPHERES community (PD, investigators, etc.) with up-to-date information to determine opportunities to use the NL Facility Discuss proposed changes updates to SPHERES Nat Lab which may be required to support a specific activity or research. Discuss specific support requests made to the ISS Office.
Revitalization of the Public Sphere: A Comparison between Habermasian and the New Public Sphere
Directory of Open Access Journals (Sweden)
Muhammad Zubair Khan
2014-06-01
Full Text Available “Public sphere” is an important component of modern polity. Civil society brings the state in touch with the needs of the citizens through the medium of public sphere. However, Habermas argues that “public sphere” experienced refeudalization owing to various factors i.e. propaganda, cultural industry, market and state intervention. The “public” was condemned to be mere spectator again. This article argues that modern technologies enabled new public sphere (NPS can help restore public status as participant in the democratic process. By employing interpretivist approach the article compares the Habermasian ideal of public sphere with NPS and constructs a matrix, depicting the various related aspects between the two models for highlighting the revival of the public sphere.
VMware vSphere PowerCLI Reference Automating vSphere Administration
Dekens, Luc; Sizemore, Glenn; van Lieshout, Arnim; Medd, Jonathan
2011-01-01
Your One-Stop Reference for VMware vSphere Automation If you manage vSphere in a Windows environment, automating routine tasks can save you time and increase efficiency. VMware vSphere PowerCLI is a set of pre-built commands based on Windows PowerShell that is designed to help you automate vSphere processes involving virtual machines, datacenters, storage, networks, and more. This detailed guide-using a practical, task-based approach and real-world examples-shows you how to get the most out of PowerCLI's handy cmdlets. Learn how to: Automate vCenter Server and ESX/ESX(i) Server deployment and
Innovation embedded in entrepreneurs' networks in private and public spheres
DEFF Research Database (Denmark)
Schøtt, Thomas; Cheraghi, Maryam; Rezaei, Shahamak
2014-01-01
Global studies have found tendencies: traditional culture promotes entrepreneurs' networking in the private sphere, impeding innovation, whereas secular-rational culture facilitates networking in the public sphere, benefiting innovation. This embeddedness is here scrutinised in contrasting...
Cavity formation by the impact of Leidenfrost spheres
Marston, Jeremy
2012-05-01
We report observations of cavity formation and subsequent collapse when a heated sphere impacts onto a liquid pool. When the sphere temperature is much greater than the boiling point of the liquid, we observe an inverted Leidenfrost effect where the sphere is encompassed by a vapour layer that prevents physical contact with the liquid. This creates the ultimate non-wetting scenario during sphere penetration through a free surface, producing very smooth cavity walls. In some cases during initial entry, however, the liquid contacts the sphere at the equator, leading to the formation of a dual cavity structure. For cold sphere impacts, where a contact line is observed, we reveal details of the contact line pinning, which initially forms a sawtooth pattern. We also observe surface waves on the cavity interface for cold spheres. We compare our experimental results to previous studies of cavity dynamics and, in particular, the influence of hydrophobicity on the entry of the sphere. © 2012 Cambridge University Press.
Innovation embedded in entrepreneurs’ networks in private and public spheres
DEFF Research Database (Denmark)
Schøtt, Thomas; Cheraghi, Maryam; Rezaei, Shahamak
2014-01-01
societies, China and Denmark. Global Entrepreneurship Monitor has surveyed entrepreneurs in China, Denmark and elsewhere. Analyses reconfirm the global tendencies and show that, China in contrast to Denmark, public sphere networking is sparser, but private sphere networking is denser. Innovation......Global studies have found tendencies: traditional culture promotes entrepreneurs' networking in the private sphere, impeding innovation, whereas secular-rational culture facilitates networking in the public sphere, benefiting innovation. This embeddedness is here scrutinised in contrasting...
21 CFR 886.3320 - Eye sphere implant.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Eye sphere implant. 886.3320 Section 886.3320 Food... DEVICES OPHTHALMIC DEVICES Prosthetic Devices § 886.3320 Eye sphere implant. (a) Identification. An eye sphere implant is a device intended to be implanted in the eyeball to occupy space following the removal...
Social movements and the Transnational Transformation of Public Spheres
DEFF Research Database (Denmark)
Bourne, Angela
2017-01-01
This article presents a theoretical framework for the empirical study of social movements as agents and arenas in the transnational transformation of public spheres. It draws on the existing literature on transnationalisation of public spheres, which predominantly focuses on the broadcast media a...... of public spheres and illustrate their applicability for the study of social movements using contemporary examples of movement practices and discourses....
International Nuclear Information System (INIS)
Sanchez, Rene G.; Loaiza, David J.; Kimpland, Robert H.; Hayes, David K.; Cappiello, Charlene C.; Myers, William L.; Jaegers, Peter J.; Clement, Steven D.; Butterfield, Kenneth B.
2003-01-01
A critical mass experiment using a 6-kg 237 Np sphere has been performed. The purpose of the experiment is to get a better estimate of the critical mass of 237 Np. To attain criticality, the 237 Np sphere was surrounded with 93 wt% 235 U shells. A 1/M as a function of uranium mass was performed. An MCNP neutron transport code was used to model the experiment. The MCNP code yielded a k eff of 0.99089 ± 0.0003 compared with a k eff 1.0026 for the experiment. Based on these results, it is estimated that the critical mass of 237 Np ranges from kilogram weights in the high fifties to low sixties. (author)
Fibonacci numerical integration on a sphere
International Nuclear Information System (INIS)
Hannay, J H; Nye, J F
2004-01-01
For elementary numerical integration on a sphere, there is a distinct advantage in using an oblique array of integration sampling points based on a chosen pair of successive Fibonacci numbers. The pattern has a familiar appearance of intersecting spirals, avoiding the local anisotropy of a conventional latitude-longitude array. Besides the oblique Fibonacci array, the prescription we give is also based on a non-uniform scaling used for one-dimensional numerical integration, and indeed achieves the same order of accuracy as for one dimension: error ∼N -6 for N points. This benefit of Fibonacci is not shared by domains of integration with boundaries (e.g., a square, for which it was originally proposed); with non-uniform scaling the error goes as N -3 , with or without Fibonacci. For experimental measurements over a sphere our prescription is realized by a non-uniform Fibonacci array of weighted sampling points
Coated sphere scattering by geometric optics approximation.
Mengran, Zhai; Qieni, Lü; Hongxia, Zhang; Yinxin, Zhang
2014-10-01
A new geometric optics model has been developed for the calculation of light scattering by a coated sphere, and the analytic expression for scattering is presented according to whether rays hit the core or not. The ray of various geometric optics approximation (GOA) terms is parameterized by the number of reflections in the coating/core interface, the coating/medium interface, and the number of chords in the core, with the degeneracy path and repeated path terms considered for the rays striking the core, which simplifies the calculation. For the ray missing the core, the various GOA terms are dealt with by a homogeneous sphere. The scattering intensity of coated particles are calculated and then compared with those of Debye series and Aden-Kerker theory. The consistency of the results proves the validity of the method proposed in this work.
Packing circles and spheres on surfaces
Schiftner, Alexander
2009-12-01
Inspired by freeform designs in architecture which involve circles and spheres, we introduce a new kind of triangle mesh whose faces\\' incircles form a packing. As it turns out, such meshes have a rich geometry and allow us to cover surfaces with circle patterns, sphere packings, approximate circle packings, hexagonal meshes which carry a torsion-free support structure, hybrid tri-hex meshes, and others. We show how triangle meshes can be optimized so as to have the incircle packing property. We explain their relation to conformal geometry and implications on solvability of optimization. The examples we give confirm that this kind of meshes is a rich source of geometric structures relevant to architectural geometry.
Packing circles and spheres on surfaces
Schiftner, Alexander
2009-01-01
Inspired by freeform designs in architecture which involve circles and spheres, we introduce a new kind of triangle mesh whose faces\\' incircles form a packing. As it turns out, such meshes have a rich geometry and allow us to cover surfaces with circle patterns, sphere packings, approximate circle packings, hexagonal meshes which carry a torsion-free support structure, hybrid tri-hex meshes, and others. We show how triangle meshes can be optimized so as to have the incircle packing property. We explain their relation to conformal geometry and implications on solvability of optimization. The examples we give confirm that this kind of meshes is a rich source of geometric structures relevant to architectural geometry. © 2009 ACM.
DEFF Research Database (Denmark)
Brimberg, Jack; Juel, Henrik; Schöbel, Anita
2003-01-01
We consider the problem of locating a spherical circle with respect to existing facilities on a sphere, such that the sum of weighted distances between the circle and the facilities is minimized, or such that the maximum weighted distance is minimized. The problem properties are analyzed, and we...... give solution procedures. When the circle to be located is restricted to be a great circle, some simplifications are possible....
The sea - landfill or sphere of life
International Nuclear Information System (INIS)
Haury, H.J.; Koller, U.; Assmann, G.
1990-01-01
The Environmental Information Agency held its third seminar for journalists, entitled 'The sea - landfill or sphere of life' in Hamburg on July 18, 1989. Some 40 journalists - radio journalists and journalists from the staff of dailies and the technical press - took the opportunity to listen for a day to short lectures on selected subjects and submit their questions concerning sea pollution to scientists of diverse disciplines. (orig.) [de
On the revolution of heavenly spheres
Copernicus, Nicolaus
1995-01-01
The Ptolemaic system of the universe, with the earth at the center, had held sway since antiquity as authoritative in philosophy, science, and church teaching. Following his observations of the heavenly bodies, Nicolaus Copernicus (1473-1543) abandoned the geocentric system for a heliocentric model, with the sun at the center. His remarkable work, On the Revolutions of Heavenly Spheres, stands as one of the greatest intellectual revolutions of all time, and profoundly influenced, among others, Galileo and Sir Isaac Newton.
On the torus cobordant cohomology spheres
Indian Academy of Sciences (India)
Abstract. Let G be a compact Lie group. In 1960, P A Smith asked the following question: “Is it true that for any smooth action of G on a homotopy sphere with exactly two fixed points, the tangent G-modules at these two points are isomorphic?” A result due to Atiyah and Bott proves that the answer is 'yes' for Zp and it is also ...
Surface modes of two spheres embedded into a third medium
International Nuclear Information System (INIS)
Nkoma, J.S.
1990-07-01
Surface modes of two spheres embedded into a third medium are studied. We obtain a result which relates the dependence of frequency on the distance between the two spheres. The derived expression reproduces previous results in the limit where the separation between the spheres is very large. Two surface mode branches are shown to exist for each order n. We apply the theory to three cases of practical interest: first, two similar metallic spheres in vacuum; secondly, two similar metallic spheres embedded into a different metal; thirdly, two spherical voids embedded into a metal. (author). 19 refs, 6 figs
Agglomeration techniques for the production of spheres for packed beds
International Nuclear Information System (INIS)
Sullivan, J.D.
1988-03-01
One attractive fusion-breeder-blanket design features a lithium bearing ceramic in the form of spheres packed into a random array. The spheres have diameters of 3 mm and 0.3 mm. This report surveys techniques used to produce ceramic spheres on an industrial scale. The methods examined include tumbling and mixing granulation, extrusion, briquetting and pelletizing. It is concluded that the required quantities of 0.3 mm diameter spheres can be produced by the tumbling agglomeration of a feed powder. The 3 mm diameter spheres will be made using a process of extrusion, chopping and rolling
Hopf Maps, Lowest Landau Level, and Fuzzy Spheres
Directory of Open Access Journals (Sweden)
Kazuki Hasebe
2010-09-01
Full Text Available This paper is a review of monopoles, lowest Landau level, fuzzy spheres, and their mutual relations. The Hopf maps of division algebras provide a prototype relation between monopoles and fuzzy spheres. Generalization of complex numbers to Clifford algebra is exactly analogous to generalization of fuzzy two-spheres to higher dimensional fuzzy spheres. Higher dimensional fuzzy spheres have an interesting hierarchical structure made of ''compounds'' of lower dimensional spheres. We give a physical interpretation for such particular structure of fuzzy spheres by utilizing Landau models in generic even dimensions. With Grassmann algebra, we also introduce a graded version of the Hopf map, and discuss its relation to fuzzy supersphere in context of supersymmetric Landau model.
Evolution of nickel sulfide hollow spheres through topotactic transformation
Wei, Chengzhen; Lu, Qingyi; Sun, Jing; Gao, Feng
2013-11-01
In this study, a topotactic transformation route was proposed to synthesize single-crystalline β-NiS hollow spheres with uniform phase and morphology evolving from polycrystalline α-NiS hollow spheres. Uniform polycrystalline α-NiS hollow spheres were firstly prepared with thiourea and glutathione as sulfur sources under hydrothermal conditions through the Kirkendall effect. By increasing the reaction temperature the polycrystalline α-NiS hollow spheres were transformed to uniform β-NiS hollow spheres. The β-NiS crystals obtained through the topotactic transformation route not only have unchanged morphology of hollow spheres but are also single-crystalline in nature. The as-prepared NiS hollow spheres display a good ability to remove the organic pollutant Congo red from water, which makes them have application potential in water treatment.In this study, a topotactic transformation route was proposed to synthesize single-crystalline β-NiS hollow spheres with uniform phase and morphology evolving from polycrystalline α-NiS hollow spheres. Uniform polycrystalline α-NiS hollow spheres were firstly prepared with thiourea and glutathione as sulfur sources under hydrothermal conditions through the Kirkendall effect. By increasing the reaction temperature the polycrystalline α-NiS hollow spheres were transformed to uniform β-NiS hollow spheres. The β-NiS crystals obtained through the topotactic transformation route not only have unchanged morphology of hollow spheres but are also single-crystalline in nature. The as-prepared NiS hollow spheres display a good ability to remove the organic pollutant Congo red from water, which makes them have application potential in water treatment. Electronic supplementary information (ESI) available: XRD patterns; SEM images and TEM images. See DOI: 10.1039/c3nr03371f
Hsieh, Paul A.; Barber, Michael E.; Contor, Bryce A.; Hossain, Md. Akram; Johnson, Gary S.; Jones, Joseph L.; Wylie, Allan H.
2007-01-01
This report presents a computer model of ground-water flow in the Spokane Valley-Rathdrum Prairie (SVRP) aquifer in Spokane County, Washington, and Bonner and Kootenai Counties, Idaho. The aquifer is the sole source of drinking water for more than 500,000 residents in the area. In response to the concerns about the impacts of increased ground-water withdrawals resulting from recent and projected urban growth, a comprehensive study was initiated by the Idaho Department of Water Resources, the Washington Department of Ecology, and the U.S. Geological Survey to improve the understanding of ground-water flow in the aquifer and of the interaction between ground water and surface water. The ground-water flow model presented in this report is one component of this comprehensive study. The primary purpose of the model is to serve as a tool for analyzing aquifer inflows and outflows, simulating the effects of future changes in ground-water withdrawals from the aquifer, and evaluating aquifer management strategies. The scale of the model and the level of detail are intended for analysis of aquifer-wide water-supply issues. The SVRP aquifer model was developed by the Modeling Team formed within the comprehensive study. The Modeling Team consisted of staff and personnel working under contract with the Idaho Department of Water Resources, personnel working under contract with the Washington Department of Ecology, and staff of the U.S. Geological Survey. To arrive at a final model that has the endorsement of all team members, decisions on modeling approach, methodology, assumptions, and interpretations were reached by consensus. The ground-water flow model MODFLOW-2000 was used to simulate ground-water flow in the SVPR aquifer. The finite-difference model grid consists of 172 rows, 256 columns, and 3 layers. Ground-water flow was simulated from September 1990 through September 2005 using 181 stress periods of 1 month each. The areal extent of the model encompasses an area of
DEFF Research Database (Denmark)
Brimberg, Jack; Juel, Henrik; Schöbel, Anita
2007-01-01
We consider the problem of locating a spherical circle with respect to existing facilities on a sphere, such that the sum of distances between the circle and the facilities is minimized or such that the maximum distance is minimized. The problem properties are analyzed, and we give solution...... procedures. When the circle to be located is restricted to be a great circle, some simplifications are possible. The models may be used in preliminary studies on the location of large linear facilities on the earth's surface, such as superhighways, pipelines, and transmission lines, or in totally different...
Determinantal point process models on the sphere
DEFF Research Database (Denmark)
Møller, Jesper; Nielsen, Morten; Porcu, Emilio
We consider determinantal point processes on the d-dimensional unit sphere Sd . These are finite point processes exhibiting repulsiveness and with moment properties determined by a certain determinant whose entries are specified by a so-called kernel which we assume is a complex covariance function...... and eigenfunctions in a spectral representation for the kernel, and we figure out how repulsive isotropic DPPs can be. Moreover, we discuss the shortcomings of adapting existing models for isotropic covariance functions and consider strategies for developing new models, including a useful spectral approach....
Sphere impact and penetration into wet sand
Marston, J. O.
2012-08-07
We present experimental results for the penetration of a solid sphere when released onto wet sand. We show, by measuring the final penetration depth, that the cohesion induced by the water can result in either a deeper or shallower penetration for a given release height compared to dry granular material. Thus the presence of water can either lubricate or stiffen the granular material. By assuming the shear rate is proportional to the impact velocity and using the depth-averaged stopping force in calculating the shear stress, we derive effective viscosities for the wet granular materials.
The Finite Deformation Dynamic Sphere Test Problem
Energy Technology Data Exchange (ETDEWEB)
Versino, Daniele [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Brock, Jerry Steven [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-09-02
In this manuscript we describe test cases for the dynamic sphere problem in presence of finite deformations. The spherical shell in exam is made of a homogeneous, isotropic or transverse isotropic material and elastic and elastic-plastic material behaviors are considered. Twenty cases, (a) to (t), are thus defined combining material types and boundary conditions. The inner surface radius, the outer surface radius and the material's density are kept constant for all the considered test cases and their values are r_{i} = 10mm, r_{o} = 20mm and p = 1000Kg/m^{3} respectively.
Fermions, Skyrmions and the 3-sphere
International Nuclear Information System (INIS)
Goatham, Stephen W; Krusch, Steffen
2010-01-01
This paper investigates a background charge one Skyrme field chirally coupled to light fermions on the 3-sphere. The Dirac equation for the system commutes with a generalized angular momentum or grand spin. It can be solved explicitly for a Skyrme configuration given by the hedgehog form. The energy spectrum and degeneracies are derived for all values of the grand spin. Solutions for non-zero grand spin are each characterized by a set of four polynomials. The paper also discusses the energy of the Dirac sea using zeta-function regularization.
On the simplified path integral on spheres
Energy Technology Data Exchange (ETDEWEB)
Bastianelli, Fiorenzo [Universita di Bologna, Dipartimento di Fisica ed Astronomia, Bologna (Italy); INFN, Sezione di Bologna, Bologna (Italy); Albert-Einstein-Institut, Max-Planck-Institut fuer Gravitationsphysik, Golm (Germany); Corradini, Olindo [Universita degli Studi di Modena e Reggio Emilia, Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Modena (Italy); INFN, Sezione di Bologna, Bologna (Italy); Albert-Einstein-Institut, Max-Planck-Institut fuer Gravitationsphysik, Golm (Germany)
2017-11-15
We have recently studied a simplified version of the path integral for a particle on a sphere, and more generally on maximally symmetric spaces, and proved that Riemann normal coordinates allow the use of a quadratic kinetic term in the particle action. The emerging linear sigma model contains a scalar effective potential that reproduces the effects of the curvature. We present here further details of the construction, and extend its perturbative evaluation to orders high enough to read off the type-A trace anomalies of a conformal scalar in dimensions d = 14 and d = 16. (orig.)
Predictability limit for collapsing isothermal spheres
International Nuclear Information System (INIS)
Buff, J.; Gerola, H.; Stellingwerf, R.F.
1979-01-01
Using numerical hydrodynamic techniques, we have analyzed he radial instabilities of the nonhomologous collapse of isothermal spheres. The linear stability analysis shows that modes with shorter and shorter lengths become unstable as the collapse proceeds, as expected from a simple application of the Jeans criterion. The nonlinear analysis shows that the large-scale structure of the cloud is affected by initial perturbations in less than the free-fall time. We take these results to imply that, given the practical impossibility of knowing the initial spectrum of perturbations, no theoretical calculation can predict the complete evolution of a collapsing cloud
Test Results of PBMR Fuel Spheres
International Nuclear Information System (INIS)
Koshcheev, Konstantin; Diakov, Alexander; Beltyukov, Igor; Barybin, Andrey; Chernetsov, Mikhail
2014-01-01
Results of pre-irradiation testing of fuel spheres (FS) and coated particles (CP) manufactured by PBMR SOC (Republic of South Africa) are described. The stable high quality level of major characteristics (dimensions, CP coating structure, uranium-235 contamination of the FS matrix graphite and the outer PyC layer of the CP coating) are shown. Results of a methodical irradiation test of two FS in helium and neon medium at temperatures of 800 to 1300 °C with simultaneous determination of release-to-birth ratios for major gaseous fission products (GFP) are described. (author)
Diagnosis of a Poorly Performing Liquid Hydrogen Bulk Storage Sphere
Krenn, Angela G.
2011-01-01
There are two 850,000 gallon Liquid Hydrogen (LH2) storage spheres used to support the Space Shuttle Program; one residing at Launch Pad A and the other at Launch Pad B. The LH2 Sphere at Pad B has had a high boiloff rate since being brought into service in the 1960's. The daily commodity loss was estimated to be approximately double that of the Pad A sphere, and well above the minimum required by the sphere's specification. Additionally, after being re-painted in the late 1990's a "cold spot" appeared on the outer sphere which resulted in a poor paint bond, and mold formation. Thermography was used to characterize the area, and the boiloff rate was continually evaluated. All evidence suggested that the high boiloff rate was caused by an excessive heat leak into the inner sphere due to an insulation void in the annulus. Pad B was recently taken out of Space Shuttle program service which provided a unique opportunity to diagnose the sphere's poor performance. The sphere was drained and inerted, and then opened from the annular relief device on the top where a series of boroscoping operations were accomplished. Boroscoping revealed a large Perlite insulation void in the region of the sphere where the cold spot was apparent. Perlite was then trucked in and off-loaded into the annular void region until the annulus was full. The sphere has not yet been brought back into service.
Röntgen spheres around active stars
Locci, Daniele; Cecchi-Pestellini, Cesare; Micela, Giuseppina; Ciaravella, Angela; Aresu, Giambattista
2018-01-01
X-rays are an important ingredient of the radiation environment of a variety of stars of different spectral types and age. We have modelled the X-ray transfer and energy deposition into a gas with solar composition, through an accurate description of the electron cascade following the history of the primary photoelectron energy deposition. We test and validate this description studying the possible formation of regions in which X-rays are the major ionization channel. Such regions, called Röntgen spheres may have considerable importance in the chemical and physical evolution of the gas embedding the emitting star. Around massive stars the concept of Röntgen sphere appears to be of limited use, as the formation of extended volumes with relevant levels of ionization is efficient just in a narrow range of gas volume densities. In clouds embedding low-mass pre-main-sequence stars significant volumes of gas are affected by ionization levels exceeding largely the cosmic-ray background ionization. In clusters arising in regions of vigorous star formation X-rays create an ionization network pervading densely the interstellar medium, and providing a natural feedback mechanism, which may affect planet and star formation processes.
Clifford coherent state transforms on spheres
Dang, Pei; Mourão, José; Nunes, João P.; Qian, Tao
2018-01-01
We introduce a one-parameter family of transforms, U(m)t,t > 0, from the Hilbert space of Clifford algebra valued square integrable functions on the m-dimensional sphere, L2(Sm , dσm) ⊗Cm+1, to the Hilbert spaces, ML2(R m + 1 ∖ { 0 } , dμt) , of solutions of the Euclidean Dirac equation on R m + 1 ∖ { 0 } which are square integrable with respect to appropriate measures, dμt. We prove that these transforms are unitary isomorphisms of the Hilbert spaces and are extensions of the Segal-Bargman coherent state transform, U(1) :L2(S1 , dσ1) ⟶ HL2(C ∖ { 0 } , dμ) , to higher dimensional spheres in the context of Clifford analysis. In Clifford analysis it is natural to replace the analytic continuation from Sm to SCm as in (Hall, 1994; Stenzel, 1999; Hall and Mitchell, 2002) by the Cauchy-Kowalewski extension from Sm to R m + 1 ∖ { 0 } . One then obtains a unitary isomorphism from an L2-Hilbert space to a Hilbert space of solutions of the Dirac equation, that is to a Hilbert space of monogenic functions.
Global warming in the public sphere.
Corfee-Morlot, Jan; Maslin, Mark; Burgess, Jacquelin
2007-11-15
Although the science of global warming has been in place for several decades if not more, only in the last decade and a half has the issue moved clearly into the public sphere as a public policy issue and a political priority. To understand how and why this has occurred, it is essential to consider the history of the scientific theory of the greenhouse effect, the evidence that supports it and the mechanisms through which science interacts with lay publics and other elite actors, such as politicians, policymakers and business decision makers. This article reviews why and how climate change has moved from the bottom to the top of the international political agenda. It traces the scientific discovery of global warming, political and institutional developments to manage it as well as other socially mediated pathways for understanding and promoting global warming as an issue in the public sphere. The article also places this historical overview of global warming as a public issue into a conceptual framework for understanding relationships between society and nature with emphasis on the co-construction of knowledge.
Chaotic Fluid Mixing in Crystalline Sphere Arrays
Turuban, Regis; Lester, Daniel; Meheust, Yves; Le Borgne, Tanguy
2017-11-01
We study the Lagrangian dynamics of steady 3D Stokes flow over simple cubic (SC) and body-centered cubic (BCC) lattices of close-packed spheres, and uncover the mechanisms governing chaotic mixing. Due to the cusp-shaped sphere contacts, the topology of the skin friction field is fundamentally different to that of continuous (non-granular) media (e.g. open pore networks), with significant implications for fluid mixing. Weak symmetry breaking of the flow orientation with respect to the lattice symmetries imparts a transition from regular to strong chaotic mixing in the BCC lattice, whereas the SC lattice only exhibits weak mixing. Whilst the SC and BCC lattices share the same symmetry point group, these differences are explained in terms of their space groups, and we find that a glide symmetry of the BCC lattice generates chaotic mixing. These insights are used to develop accurate predictions of the Lyapunov exponent distribution over the parameter space of mean flow orientation, and point to a general theory of mixing and dispersion based upon the inherent symmetries of arbitrary crystalline structures. The authors acknowledge the support of ERC project ReactiveFronts (648377).
Chaotic Fluid Mixing in Crystalline Sphere Arrays
Turuban, R.; Lester, D. R.; Le Borgne, T.; Méheust, Y.
2017-12-01
We study the Lagrangian dynamics of steady 3D Stokes flow over simple cubic (SC) and body-centered cubic (BCC) lattices of close-packed spheres, and uncover the mechanisms governing chaotic mixing. Due to the cusp-shaped sphere contacts, the topology of the skin friction field is fundamentally different to that of continuous (non-granular) media (e.g. open pore networks), with significant implications for fluid mixing. Weak symmetry breaking of the flow orientation with respect to the lattice symmetries imparts a transition from regular to strong chaotic mixing in the BCC lattice, whereas the SC lattice only exhibits weak mixing. Whilst the SC and BCC lattices share the same symmetry point group, these differences are explained in terms of their space groups, and we find that a glide symmetry of the BCC lattice generates chaotic mixing. These insight are used to develop accurate predictions of the Lyapunov exponent distribution over the parameter space of mean flow orientation, and point to a general theory of mixing and dispersion based upon the inherent symmetries of arbitrary crystalline structures.
Measurement of dynamic and static radiation force on a sphere.
Chen, Shigao; Silva, Glauber T; Kinnick, Randall R; Greenleaf, James F; Fatemi, Mostafa
2005-05-01
Dynamic radiation force from ultrasound has found increasing applications in elasticity imaging methods such as vibro-acoustography. Radiation force that has both static and dynamic components can be produced by interfering two ultrasound beams of slightly different frequencies. This paper presents a method to measure both static and dynamic components of the radiation force on a sphere suspended by thin threads in water. Due to ultrasound radiation force, the sphere deflects to an equilibrant position and vibrates around it. The static radiation force is estimated from the deflection of the sphere. The dynamic radiation force is estimated from the calculated radiation impedance of the sphere and its vibration speed measured by a laser vibrometer. Experimental results on spheres of different size, vibrated at various frequencies, confirm the theoretical prediction that the dynamic and static radiation force on a sphere have approximately equal magnitudes [G. T. Silva, Phys. Rev. E 71, 056617 (2005)].
A novel synthesis of micrometer silica hollow sphere
International Nuclear Information System (INIS)
Pan Wen; Ye Junwei; Ning Guiling; Lin Yuan; Wang Jing
2009-01-01
Silica microcapsules (hollow spheres) were synthesized successfully by a novel CTAB-stabilized water/oil emulsion system mediated hydrothermal method. The addition of urea to a solution of aqueous phase was an essential step of the simple synthetic procedure of silica hollow spheres, which leads to the formation of silica hollow spheres with smooth shell during hydrothermal process. The intact hollow spheres were obtained by washing the as-synthesized solid products with distilled water to remove the organic components. A large amount of silanol groups were retained in the hollow spheres by this facile route without calcination. The morphologies and optical properties of the product were characterized by transmission electron microscopy, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. Furthermore, on the basis of a series of SEM observations, phenomenological elucidation of a mechanism for the growth of the silica hollow spheres has been presented
Sun, Bin; Wang, Ming; Lou, Zhichao; Huang, Mingjun; Xu, Chenglong; Li, Xiaohong; Chen, Li-Jun; Yu, Yihua; Davis, Grant L; Xu, Bingqian; Yang, Hai-Bo; Li, Xiaopeng
2015-02-04
Directed by increasing the density of coordination sites (DOCS) to increase the stability of assemblies, discrete 2D ring-in-rings and 3D sphere-in-sphere were designed and self-assembled by one tetratopic pyridyl-based ligand with 180° diplatinum(II) acceptors and naked Pd(II), respectively. The high DOCS resulted by multitopic ligand provided more geometric constraints to form discrete structures with high stability. Compared to reported supramolecular hexagons and polyhedra by ditotpic ligands, the self-assembly of such giant architectures using multitopic ligands with all rigid backbone emphasized the structural integrity with precise preorganization of entire architecture, and required elaborate synthetic operations for ligand preparation. In-depth structural characterization was conducted to support desired structures, including multinuclear NMR ((1)H, (31)P, and (13)C) analysis, 2D NMR spectroscopy (COSY and NOESY), diffusion-ordered NMR spectroscopy (DOSY), multidimensional mass spectrometry, TEM and AFM. Furthermore, a quantitative definition of DOCS was proposed to compare 2D and 3D structures and correlate the DOCS and stability of assemblies in a quantitative manner. Finally, ring-in-rings in DMSO or DMF could undergo hierarchical self-assembly into the ordered nanostructures and generated translucent supramolecular metallogels.
Elastic two-sphere swimmer in Stokes flow
Nasouri, Babak; Khot, Aditi; Elfring, Gwynn J.
2017-04-01
Swimming at low Reynolds number in Newtonian fluids is only possible through nonreciprocal body deformations due to the kinematic reversibility of the Stokes equations. We consider here a model swimmer consisting of two linked spheres, wherein one sphere is rigid and the other an incompressible neo-Hookean solid. The two spheres are connected by a rod that changes its length periodically. We show that the deformations of the body are nonreciprocal despite the reversible actuation and hence the elastic two-sphere swimmer propels forward. Our results indicate that even weak elastic deformations of a body can affect locomotion and may be exploited in designing artificial microswimmers.
On $k$-stellated and $k$-stacked spheres
Bagchi, Bhaskar; Datta, Basudeb
2012-01-01
We introduce the class $\\Sigma_k(d)$ of $k$-stellated (combinatorial) spheres of dimension $d$ ($0 \\leq k \\leq d + 1$) and compare and contrast it with the class ${\\cal S}_k(d)$ ($0 \\leq k \\leq d$) of $k$-stacked homology $d$-spheres. We have $\\Sigma_1(d) = {\\cal S}_1(d)$, and $\\Sigma_k(d) \\subseteq {\\cal S}_k(d)$ for $d \\geq 2k - 1$. However, for each $k \\geq 2$ there are $k$-stacked spheres which are not $k$-stellated. The existence of $k$-stellated spheres which are not $k$-stacked remains...
Steady state temperature profile in a sphere heated by microwaves
Barmatz, M.; Jackson, H. W.
1992-01-01
A new theory has been developed to calculate the microwave absorption and resultant temperature profile within a sphere positioned in a single mode rectangular cavity. This theory is an extension of a total absorption model based on Mie scattering results. Temperature profiles have been computed for alumina spheres at the center of a rectangular cavity excited in the TM354 mode. Parametric studies reveal significant structure in those profiles under special conditions that are associated with electromagnetic resonances inside the spheres. Anomalous behavior similar to thermal runaway occurs at moderate temperatures when there is enhanced absorption associated with resonant conditions in the sphere.
Process development and fabrication for sphere-pac fuel rods
International Nuclear Information System (INIS)
Welty, R.K.; Campbell, M.H.
1981-06-01
Uranium fuel rods containing sphere-pac fuel have been fabricated for in-reactor tests and demonstrations. A process for the development, qualification, and fabrication of acceptable sphere-pac fuel rods is described. Special equipment to control fuel contamination with moisture or air and the equipment layout needed for rod fabrication is described and tests for assuring the uniformity of the fuel column are discussed. Fuel retainers required for sphere-pac fuel column stability and instrumentation to measure fuel column smear density are described. Results of sphere-pac fuel rod fabrication campaigns are reviewed and recommended improvements for high throughput production are noted
Human postprandial gastric emptying of 1-3-millimeter spheres
International Nuclear Information System (INIS)
Meyer, J.H.; Elashoff, J.; Porter-Fink, V.; Dressman, J.; Amidon, G.L.
1988-01-01
Microspheres of pancreatin should empty from the stomachs of patients with pancreatic insufficiency as fast as food. The present study was undertaken in 26 healthy subjects to identify the size of spheres that would empty from the stomach with food and to determine whether different meals alter this size. Spheres of predefined sizes were labeled with /sup 113m/In or /sup 99m/Tc. Using a gamma-camera, we studied the concurrent gastric emptying of spheres labeled with /sup 113m/In and of chicken liver labeled with /sup 99m/Tc in 100-g, 154-kcal or 420-g, 919-kcal meals, or the concurrent emptying of 1-mm vs. larger spheres. One-millimeter spheres emptied consistently (p less than 0.01, paired t-test) faster than 2.4- or 3.2-mm spheres when ingested together with either the 420- or 100-g meals. Thus, in the 1-3-mm range of diameters, sphere size was a more important determinant of sphere emptying than meal size. Statistical analyses indicated that spheres 1.4 +/- 0.3 mm in diameter with a density of 1 empty at the same rate as /sup 99m/Tc-liver. Our data indicate some commercially marketed microspheres of pancreatin will empty too slowly to be effective in digestion of food
International Nuclear Information System (INIS)
Patrinoiu, Greta; Calderón-Moreno, Jose Maria; Culita, Daniela C.; Birjega, Ruxandra; Ene, Ramona; Carp, Oana
2013-01-01
A green template route for the synthesis of mesoscale solid ZnO spheres was ascertained. The protocol involves a double coating of the carbonaceous spheres with successive layers of zinc-containing species by alternating a non-ultrasound and ultrasound-assisted deposition, followed by calcination treatments. The composites were characterized by FTIR spectroscopy, thermal analysis, scanning electron microscopy while the obtained ZnO spheres by X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, N 2 adsorption–desorption isotherms and photoluminescence investigations. A growth mechanism of the solid spheres is advanced based on these results. While the spheres' diameters and the mean size values of ZnO are independent on deposition order, the surface area and the external porosity are fairly dependent. The photoluminescence measurements showed interesting emission features, with emission bands in the violet to orange region. The spheres present high photocatalytical activity towards the degradation of phenol under UV irradiation, the main reaction being its mineralization. - Graphical abstract: A novel and eco-friendly methodology for the synthesis of mesoscale solid ZnO spheres was developed. The protocol involves a double coating of the starch-derived carbonaceous spheres with successive layers of zinc-containing species by alternating a non-ultrasound and ultrasound-assisted deposition, followed by calcination treatments. - Highlights: • ZnO solid spheres are obtained via a template route using carbonaceous spheres. • Two-step coatings of interchangeable order are used as deposition procedure. • The coating procedure influences the porosity and surface area. • ZnO spheres exhibited interesting visible photoluminescence properties. • Solid spheres showed photocatalytical activity in degradation of phenol
Barton, Gary J.; McDonald, Richard R.; Nelson, Jonathan M.; Dinehart, Randal L.
2005-01-01
In 1994, the Kootenai River white sturgeon (Acipenser transmontanus) was listed as an Endangered Species as a direct result of two related observations. First, biologists observed that the white sturgeon population in the Kootenai River was declining. Second, they observed a decline in recruitment of juvenile sturgeon beginning in the 1950s with an almost total absence of recruitment since 1974, following the closure of Libby Dam in 1972. This second observation was attributed to changes in spawning and (or) rearing habitat resulting from alterations in the physical habitat, including flow regime, sediment-transport regime, and bed morphology of the river. The Kootenai River White Sturgeon Recovery Team was established to find and implement ways to improve spawning and rearing habitat used by white sturgeon. They identified the need to develop and apply a multidimensional flow model to certain reaches of the river to quantify physical habitat in a spatially distributed manner. The U.S. Geological Survey has addressed these needs by developing, calibrating, and validating a multidimensional flow model used to simulate streamflow and sediment mobility in the white sturgeon critical-habitat reach of the Kootenai River. This report describes the model and limitations, presents the results of a few simple simulations, and demonstrates how the model can be used to link physical characteristics of streamflow to biological or other habitat data. This study was conducted in cooperation with the Kootenai Tribe of Idaho along a 23-kilometer reach of the Kootenai River, including the white sturgeon spawning reach near Bonners Ferry, Idaho that is about 108 to 131 kilometers below Libby Dam. U.S. Geological Survey's MultiDimensional Surface-Water Modeling System was used to construct a flow model for the critical-habitat reach of the Kootenai River white sturgeon, between river kilometers 228.4 and 245.9. Given streamflow, bed roughness, and downstream water-surface elevation
Gold finger formation studied by high-resolution mass spectrometry and in silico methods
Laskay, Ü.A.; Garino, C.; Tsybin, Y.O.; Salassa, L.; Casini, A.
2015-01-01
High-resolution mass spectrometry and quantum mechanics/molecular mechanics studies were employed for characterizing the formation of two gold finger (GF) domains from the reaction of zinc fingers (ZF) with gold complexes. The influence of both the gold oxidation state and the ZF coordination sphere
Modelling Priorities of Financial Provision of the Social Sphere
Directory of Open Access Journals (Sweden)
Mamonova Hanna V.
2014-01-01
Full Text Available The article studies the modern state of the social sphere and conducts modelling of priorities of financial provision of the social sphere at the state level. Social sphere should be considered as the basis of development of the national economy. The goal of this article is the study of the modern state and modelling priorities of financial provision of the social sphere at the state level. The subject of the study is modelling priority directions of financial provision of components of the social sphere. Taking into account fast changes in the social sphere of the country and regular increase of social standards, the article identifies a necessity of changing priorities of the social policy, first of all, problems of financing the social sphere and formation of priority directions on improvement of this system. The article shows that the main problems of financial provision of the social sphere are: insufficient volumes of budget funds for financing the social sphere, financing practically all items of social expenditures in a smaller volume than it is required for the existing social support of the population and absence of mechanisms of ensuring quality of social services. The article offers to use the hierarchy analysis method for identifying immediate and priority directions of financing components of the social sphere. On the basis of the built directed communication graph the article presents a binary matrix of dependence of components of the social sphere and builds a hierarchy model of these components. As a result it is seen that the highest level of hierarchy is taken by science, then healthcare and social sphere are at the same level, then education, sports and at the lowest level are culture and art. The obtained results could be used when improving financing of the social sphere. In order to ensure efficiency of functioning of the social sphere it is necessary to improve the system of financing of its components on the basis of use
Creeping Viscous Flow around a Heat-Generating Solid Sphere
DEFF Research Database (Denmark)
Krenk, Steen
1981-01-01
The velocity field for creeping viscous flow around a solid sphere due to a spherically symmetric thermal field is determined and a simple thermal generalization of Stokes' formula is obtained. The velocity field due to an instantaneous heat source at the center of the sphere is obtained in close...... form and an application to the storage of heat-generating nuclear waste is discussed....
Sphere sovereignty in late-modern society and social theory
van Putten, R.J.
2016-01-01
This paper analyses to which extent the concept of sphere sovereignty, as developed by Kuyper and Dooyeweerd, is relevant for the understanding of late modern society. The central topic therefore is sphere sovereignty as view on social order. Firstly, I argue the urgency of studying the
Radioactive spheres without inactive wall for lesion simulation in PET
International Nuclear Information System (INIS)
Bazanez-Borgert, M.; Bundschuh, R.A.; Herz, M.; Martinez, M.J.; Schwaiger, M.; Ziegler, S.I.
2008-01-01
With the growing importance of PET and PET/CT in diagnosis, staging, therapy monitoring and radiotherapy planning, appropriate tools to simulate lesions in phantoms are important. Normally hollow spheres, made of plastic or glass, which can be filled with radioactive solutions, are used. As these spheres have an inactive wall they do not reflect the real situation in the patient and lead to quantification errors in the presence of background activity. We propose spheres made of radioactive wax, which are easy to produce, give a high flexibility to the user and a more accurate quantification. These wax spheres were evaluated for their applicability in PET phantoms and it was found that the activity is not diffusing into the surrounding water in relevant quantities, that they show a sufficient homogeneity, and that their attenuation properties are equivalent to water for photons of PET energies. Recovery coefficients for the wax spheres were measured and compared with those obtained for fillable plastic spheres for diameters of 28, 16, 10, and 6 mm in the presence of background activity. Recovery coefficients of the wax spheres were found to be up to 21% higher than for the fillable spheres. (orig.)
Thermodynamics and vibrational modes of hard sphere colloidal systems
Zargar, R.
2014-01-01
The central question that we address in this thesis is the thermodynamics of colloidal glasses. The thermodynamics of colloidal hard sphere glasses are directly related to the entropy of the system, since the phase behavior of hard sphere systems is dictated only by entropic contributions, and also
Covariant differential calculus on quantum spheres of odd dimension
International Nuclear Information System (INIS)
Welk, M.
1998-01-01
Covariant differential calculus on the quantum spheres S q 2N-1 is studied. Two classification results for covariant first order differential calculi are proved. As an important step towards a description of the noncommutative geometry of the quantum spheres, a framework of covariant differential calculus is established, including first and higher order calculi and a symmetry concept. (author)
The sintering behavior of close-packed spheres
DEFF Research Database (Denmark)
Bjørk, Rasmus; Tikare, V.; Frandsen, Henrik Lund
2012-01-01
The sintering behavior of close-packed spheres is investigated using a numerical model. The investigated systems are the body-centered cubic (bcc), face-centered cubic (fcc) and hexagonal close-packed spheres (hcp). The sintering behavior is found to be ideal, with no grain growth until full dens...
Women, Power and Performance in the Yoruba Public Sphere
African Journals Online (AJOL)
chifaou.amzat
2010-04-14
Apr 14, 2010 ... Songs of the King's Wives: Women, Power and Performance in the Yoruba Public Sphere. Bode Omojola*. Abstract. Indigenous festivals, which rely significantly on music and dance, of- ten constitute the village public sphere and the social arena within which the structures of power are performed and ...
Convexity of spheres in a manifold without conjugate points
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
Abstract. For a non-compact, complete and simply connected manifold M without conjugate points, we prove that if the determinant of the second fundamental form of the geodesic spheres in M is a radial function, then the geodesic spheres are convex. We also show that if M is two or three dimensional and without ...
G B, Abhilash
2015-01-01
This is an excellent handbook for system administrators, support professionals, or for anyone intending to give themselves a headstart in learning how to install, configure, and manage a vSphere environment. It is also a good task-oriented reference guide for consultants or infrastructure architects who design and deploy vSphere environments.
Rigid sphere transport through a colloidal gas–liquid interface
de Folter, J.W.J.; de Villeneuve, V.W.A.; Aarts, D.G.A.L.; Lekkerkerker, H.N.W.
2010-01-01
In this paper we report on the gravity-driven transport of rigid spheres of various sizes through the fluid–fluid interface of a demixed colloid–polymer mixture. Three consecutive stages can be distinguished: (i) the sphere approaches the interface by sedimenting through the polymer-rich phase, (ii)
Axioms of spheres in lightlike geometry of submanifolds
Indian Academy of Sciences (India)
Introduction. The notion of axioms of planes for Riemannian manifolds was originally introduced by. Cartan [2]. In [8], Leung and Nomizu generalized the notion of axioms of planes to the axioms of spheres on Riemannian manifolds. In [7], Kumar et al. studied the axioms of spheres and planes for indefinite Riemannian ...
Orbital Motion of Electrically Charged Spheres in Microgravity
Banerjee, Shubho; Andring, Kevin; Campbell, Desmond; Janeski, John; Keedy, Daniel; Quinn, Sean; Hoffmeister, Brent
2008-01-01
The similar mathematical forms of Coulomb's law and Newton's law of gravitation suggest that two uniformly charged spheres should be able to orbit each other just as two uniform spheres of mass are known to do. In this paper we describe an experiment that we performed to demonstrate such an orbit. This is the first published account of a…
Segregation in inclined flows of binary mixtures of spheres
Directory of Open Access Journals (Sweden)
Larcher Michele
2017-01-01
Full Text Available We outline the equations that govern the evolution of segregation of a binary mixture of spheres in flows down inclines. These equations result from the mass and momentum balances of a kinetic theory for dense flows of inelastic spheres that interact through collisions. The theory employed for segregation is appropriate for particles with relatively small differences in size and mass. The flow of the mixture is assumed to reach a fully developed state much more rapidly than does the concentrations of the two species. We illustrate the predictions of the theory for a mixture of spheres of the same diameter but different masses and for spheres of different diameters but nearly the same mass. We show the evolution of the profiles of the concentration fractions of the two types of spheres and the profiles in the final, steady state. The latter compare favourably with those obtained in discrete-element numerical simulations.
Fe2O3 hollow sphere nanocomposites for supercapacitor applications
Zhao, Yu; Wen, Yang; Xu, Bing; Lu, Lu; Ren, Reiming
2018-02-01
Nanomaterials have attracted increasing interest in electrochemical energy storage and conversion. Hollow sphere Fe2O3 nanocomposites were successfully prepared through facile low temperature water-bath method with carbon sphere as hard template. The morphology and microstructure of samples were characterized by X-ray diffraction (XRD) and Scanning electron microscope (SEM), respectively. Through hydrolysis mechanism, using ferric chloride direct hydrolysis, iron hydroxide coated on the surface of carbon sphere, after high temperature calcination can form the hollow spherical iron oxide materials. Electrochemical performances of the hollow sphere Fe2O3 nanocomposites electrodes were investigated by cyclic voltammery (CV) and galvanostatic charge/discharge. The Pure hollow sphere Fe2O3 nanocomposites achieves a specific capacitance of 125 F g-1 at the current density of 85 mA g-1. The results indicate that the uniform dispersion of hollow ball structure can effectively reduce the particle reunion in the process of charging and discharging.
Recovering functions defined on the unit sphere by integration on a special family of sub-spheres
Salman, Yehonatan
2017-06-01
The aim of this article is to derive a reconstruction formula for the recovery of C1 functions, defined on the unit sphere S^{n - 1}, given their integrals on a special family of n - 2 dimensional sub-spheres. For a fixed point \\overline{a} strictly inside S^{n - 1}, each sub-sphere in this special family is obtained by intersection of S^{n - 1} with a hyperplane passing through \\overline{a}. The case \\overline{a} = 0 results in an inversion formula for the special case of integration on great spheres (i.e., Funk transform). The limiting case where p\\in S^{n - 1} and \\overline{a}→ p results in an inversion formula for the special case of integration on spheres passing through a common point in S^{n - 1}.
Experimental study on combustion of a methane hydrate sphere
Yoshioka, Tomoki; Yamamoto, Yuji; Yokomori, Takeshi; Ohmura, Ryo; Ueda, Toshihisa
2015-10-01
The combustion behavior of a methane hydrate sphere under normal gravity is experimentally investigated. The initial diameter of the sphere is 20 mm. Variation in temperature at the center of the sphere ( T c) is measured with a K-type thermocouple at ignition temperatures ( T c,i) from 193 to 253 K at 20 K intervals. Variation in the near-surface temperature of the sphere ( T s) is measured at ignition temperatures ( T s,i) from 233 to 263 K at 10 K intervals. Two combustion phases are observed. When the hydrate is ignited, a stable flame envelope is formed around the sphere (phase 1). In phase 1, the surface of the sphere is dry. After a few seconds, water formed by dissociation of the methane hydrate appears on the surface and methane bubbles are formed by methane ejected from inside the sphere (phase 2), thus destabilizing the flame and causing local extinction. Methane bubbles move down along the surface and merge into a large methane bubble at the bottom of the sphere. This bubble bursts, releasing methane to form a temporary flame, and the water drops from the hydrate sphere. Water on the surface is cooled by the hydrate inside, and an ice shell confines the methane gas that dissociated inside the sphere. Because the dissociation occurs continuously inside the hydrate, the inner pressure gradually increases and at some instant, the ice cracks and methane gas is ejected from the cracks, which results in a micro-explosion with a flame. In phase 1, the surface temperature is below the freezing point of water, and so the surface remains dry and a stable flame envelope is formed; in phase 2, the surface temperature is above the freezing point, and so water appears on the surface. When the temperature at the center of the sphere is lower (193, 213, or 233 K), some methane hydrate remains even after flame extinction because heat transfer from the flame decreases in phase 2 as a result of local extinction. The diameter of the sphere decreases during combustion in
Stress relaxation in viscous soft spheres.
Boschan, Julia; Vasudevan, Siddarth A; Boukany, Pouyan E; Somfai, Ellák; Tighe, Brian P
2017-10-04
We report the results of molecular dynamics simulations of stress relaxation tests in athermal viscous soft sphere packings close to their unjamming transition. By systematically and simultaneously varying both the amplitude of the applied strain step and the pressure of the initial condition, we access both linear and nonlinear response regimes and control the distance to jamming. Stress relaxation in viscoelastic solids is characterized by a relaxation time τ* that separates short time scales, where viscous loss is substantial, from long time scales, where elastic storage dominates and the response is essentially quasistatic. We identify two distinct plateaus in the strain dependence of the relaxation time, one each in the linear and nonlinear regimes. The height of both plateaus scales as an inverse power law with the distance to jamming. By probing the time evolution of particle velocities during relaxation, we further identify a correlation between mechanical relaxation in the bulk and the degree of non-affinity in the particle velocities on the micro scale.
Second-order impartiality and public sphere
Directory of Open Access Journals (Sweden)
Sládeček Michal
2016-01-01
Full Text Available In the first part of the text the distinction between first- and second-order impartiality, along with Brian Barry’s thorough elaboration of their characteristics and the differences between them, is examined. While the former impartiality is related to non-favoring fellow-persons in everyday occasions, the latter is manifested in the institutional structure of society and its political and public morality. In the second part of the article, the concept of public impartiality is introduced through analysis of two examples. In the first example, a Caledonian Club with its exclusive membership is considered as a form of association which is partial, but nevertheless morally acceptable. In the second example, the so-called Heinz dilemma has been reconsidered and the author points to some flaws in Barry’s interpretation, arguing that Heinz’s right of giving advantage to his wife’s life over property rights can be recognized through mitigating circum-stances, and this partiality can be appreciated in the public sphere. Thus, public impartiality imposes limits to the restrictiveness and rigidity of political impartiality implied in second-order morality. [Projekat Ministarstva nauke Republike Srbije, br. 179049
Bubble entrapment during sphere impact onto quiescent liquid surfaces
Marston, Jeremy
2011-06-20
We report observations of air bubble entrapment when a solid sphere impacts a quiescent liquid surface. Using high-speed imaging, we show that a small amount of air is entrapped at the bottom tip of the impacting sphere. This phenomenon is examined across a broad range of impact Reynolds numbers, 0.2 a Re = (DU0/Il) a 1.2\\' 105. Initially, a thin air pocket is formed due to the lubrication pressure in the air layer between the sphere and the liquid surface. As the liquid surface deforms, the liquid contacts the sphere at a finite radius, producing a thin sheet of air which usually contracts to a nearly hemispherical bubble at the bottom tip of the sphere depending on the impact parameters and liquid properties. When a bubble is formed, the final bubble size increases slightly with the sphere diameter, decreases with impact speed but appears independent of liquid viscosity. In contrast, for the largest viscosities tested herein, the entrapped air remains in the form of a sheet, which subsequently deforms upon close approach to the base of the tank. The initial contact diameter is found to conform to scalings based on the gas Reynolds number whilst the initial thickness of the air pocket or adimplea scales with a Stokes\\' number incorporating the influence of the air viscosity, sphere diameter and impact speed and liquid density. © 2011 Cambridge University Press.
Forming MOFs into spheres by use of molecular gastronomy methods.
Spjelkavik, Aud I; Aarti; Divekar, Swapnil; Didriksen, Terje; Blom, Richard
2014-07-14
A novel method utilizing hydrocolloids to prepare nicely shaped spheres of metal-organic frameworks (MOFs) has been developed. Microcrystalline CPO-27-Ni particles are dispersed in either alginate or chitosan solutions, which are added dropwise to solutions containing, respectively, either divalent group 2 cations or base that act as gelling agents. Well-shaped spheres are immediately formed, which can be dried into spheres containing mainly MOF (>95 wt %). The spheronizing procedures have been optimized with respect to maximum specific surface area, shape, and particle density of the final sphere. At optimal conditions, well-shaped 2.5-3.5 mm diameter CPO-27-Ni spheres with weight-specific surface areas <10 % lower than the nonformulated CPO-27-Ni precursor, and having sphere densities in the range 0.8 to 0.9 g cm(-3) and particle crushing strengths above 20 N, can be obtained. The spheres are well suited for use in fixed-bed catalytic or adsorption processes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Review of reaction spheres for spacecraft attitude control
Zhu, Linyu; Guo, Jian; Gill, Eberhard
2017-05-01
With respect to spacecraft attitude control, reaction spheres are promising alternatives to conventional momentum exchange devices for the benefits brought by their 4π rotation. Many design concepts of reaction spheres have been proposed in the past decades, however, developments of the driving unit and the bearing, as well as their combination remain great challenges. To facilitate research and push developments in this field, this paper provides a comprehensive review of reaction spheres. To some extent, an in-depth survey of multi-DOF (degree of freedom) spherical motors and possible bearings is provided, along with their advantages and weaknesses addressed. Some multi-DOF actuators for different applications, such as robotic joints, are investigated since they share many similar challenges and techniques with reaction spheres. The experimental performances of realized reaction spheres are listed and compared. Limits of current designs are identified and their causes are analyzed and discussed. Compared with existing summaries on multi-DOF actuators and some surveys done for specific reaction spheres' design, this paper provides the first thorough review on reaction spheres, considering approaches to excite and support the free 4π rotation.
Public sphere as assemblage: the cultural politics of roadside memorialization.
Campbell, Elaine
2013-09-01
This paper investigates contemporary academic accounts of the public sphere. In particular, it takes stock of post-Habermasian public sphere scholarship, and acknowledges a lively and variegated debate concerning the multiple ways in which individuals engage in contemporary political affairs. A critical eye is cast over a range of key insights which have come to establish the parameters of what 'counts' as a/the public sphere, who can be involved, and where and how communicative networks are established. This opens up the conceptual space for re-imagining a/the public sphere as an assemblage. Making use of recent developments in Deleuzian-inspired assemblage theory - most especially drawn from DeLanda's (2006) 'new philosophy of society' - the paper sets out an alternative perspective on the notion of the public sphere, and regards it as a space of connectivity brought into being through a contingent and heterogeneous assemblage of discursive, visual and performative practices. This is mapped out with reference to the cultural politics of roadside memorialization. However, a/the public sphere as an assemblage is not simply a 'social construction' brought into being through a logic of connectivity, but is an emergent and ephemeral space which reflexively nurtures and assembles the cultural politics (and political cultures) of which it is an integral part. The discussion concludes, then, with a consideration of the contribution of assemblage theory to public sphere studies. (Also see Campbell 2009a). © London School of Economics and Political Science 2013.
Radar Imaging of Spheres in 3D using MUSIC
Energy Technology Data Exchange (ETDEWEB)
Chambers, D H; Berryman, J G
2003-01-21
We have shown that multiple spheres can be imaged by linear and planar EM arrays using only one component of polarization. The imaging approach involves calculating the SVD of the scattering response matrix, selecting a subset of singular values that represents noise, and evaluating the MUSIC functional. The noise threshold applied to the spectrum of singular values for optimal performance is typically around 1%. The resulting signal subspace includes more than one singular value per sphere. The presence of reflections from the ground improves height localization, even for a linear array parallel to the ground. However, the interference between direct and reflected energy modulates the field, creating periodic nulls that can obscure targets in typical images. These nulls are largely eliminated by normalizing the MUSIC functional with the broadside beam pattern of the array. The resulting images show excellent localization for 1 and 2 spheres. The performance for the 3 sphere configurations are complicated by shadowing effects and the greater range of the 3rd sphere in case 2. Two of the three spheres are easily located by MUSIC but the third is difficult to distinguish from other local maxima of the complex imaging functional. Improvement is seen when the linear array is replace with a planar array, which increases the effective aperture height. Further analysis of the singular values and their relationship to modes of scattering from the spheres, as well as better ways to exploit polarization, should improve performance. Work along these lines is currently being pursued by the authors.
Making three-dimensional Monson's sphere using virtual dental models.
Nam, Shin-Eun; Park, Young-Seok; Lee, WooCheol; Ahn, Sug-Joon; Lee, Seung-Pyo
2013-04-01
The Monson's sphere and curve of Wilson can be used as reference for prosthetic reconstructions or orthodontic treatments. This study aimed to generate and measure the three-dimensional (3-D) Monson's sphere and curve of Wilson using virtual dental models and custom software. Mandibular dental casts from 79 young adults of Korean descent were scanned and rendered as virtual dental models using a 3-D digitizing scanner. 26 landmarks were digitized on the virtual dental models using a custom made software program. The Monson's sphere was estimated by fitting a sphere to the cusp tips using a least-squares method. Two curves of Wilson were generated by finding the intersecting circle between the Monson's sphere and two vertical planes orthogonal to a virtual occlusal plane. Non-parametric Mann-Whitney and Kruskal-Wallis tests were performed to test for difference between sex and in cusp number within tooth position. The mean radius of Monson's sphere was 110.89 ± 25.75 mm. There were significant differences between males and females in all measurements taken (pocclusal curvature (p>0.05). This study describes a best-fit algorithm for generating 3-D Monson's sphere using occlusal curves quantified from virtual dental models. The radius of Monson's sphere in Korean subjects was greater than the original four-inch value suggested by Monson. The Monson's sphere and curve of Wilson can be used as a reference for prosthetic reconstruction and orthodontic treatment. The data found in this study may be applied to improve dental treatment results. Copyright © 2013 Elsevier Ltd. All rights reserved.
Formation of Public Spheres and Islamist Movements in Malay Muslim Society of Malaysia
Shiozaki, Yuki
2007-01-01
Muslim society originally had spheres for discussion based on Islamic logic, which are similar to a "public sphere." Such spheres were organized by ulama (Islamic clerics) and tariqa (Islamic order of mystics). Buildings established through waqf (religious endowment) including mosques and religious schools also provided such spheres for discussion. On the premise of the existence of plural public spheres rather than the single civil sphere advocated by Habermas, the contemporary Islamist move...
Gender and Diversity in the European Public Spheres
DEFF Research Database (Denmark)
Siim, Birte
The increasing institutionalization of rights in EU has inspired a debate about the gap between the EU polity and citizens' abilities to influence multilevel governance and politics. The objective of the paper is to discuss diversity in the European public spheres from a gender perspective...... state and to link feminist proposals for gender justice with frames for a multilayered trans-national citizenship. The paper aims to contribute to debates about theoretical approaches and models to study gender and diversity in the public sphere in general and in particular The European Public Sphere...
POSTGRADUATE EDUCATION FUNCTIONING PATTERNS OF TOURISM SPHERE SPECIALISTS IN SWITZERLAND
Directory of Open Access Journals (Sweden)
Наталія Закордонець
2014-04-01
Full Text Available Functioning patterns of postgraduate education of tourism sphere specialists in Switzerland have been established. The competences of tourism sphere specialist, the formation of which programs of postgraduate education are focused on have been considered. The benefits of educational qualification of Masters in Business Administration with a major specialization in tourism have been outlined. The characteristics of the core curriculum of the Doctor of Management of leading universities in the field of tourism education have been determined. The performance criteria of postgraduate education system functioning of tourism sphere specialists in Switzerland have been revealed.
Lowe, Scott; Guthrie, Forbes; Liebowitz, Matt; Atwell, Josh
2013-01-01
The 2013 edition of the bestselling vSphere book on the market Virtualization remains the hottest trend in the IT world, and VMware vSphere is the industry's most widely deployed virtualization solution. The demand for IT professionals skilled in virtualization and cloud-related technologies is great and expected to keep growing. This comprehensive Sybex guide covers all the features and capabilities of VMware vSphere, showing administrators step by step how to install, configure, operate, manage, and secure it. This perfect blend of hands-on instruction, conceptual explanation, and practic
High pressure gas spheres for neutron and photon experiments
Rupp, G.; Petrich, D.; Käppeler, F.; Kaltenbaek, J.; Leugers, B.; Reifarth, R.
2009-09-01
High pressure gas spheres have been designed and successfully used in several nuclear physics experiments on noble gases. The pros and cons of this solution are the simple design and the high reliability versus the fact that the density is limited to 40-60% of liquid or solid gas samples. Originally produced for neutron capture studies at keV energies, the comparably small mass of the gas spheres were an important advantage, which turned out to be of relevance for other applications as well. The construction, performance, and operation of the spheres are described and examples for their use are presented.
Twistor Interpretation of Harmonic Spheres and Yang–Mills Fields
Directory of Open Access Journals (Sweden)
Armen Sergeev
2015-03-01
Full Text Available We consider the twistor descriptions of harmonic maps of the Riemann sphere into Kähler manifolds and Yang–Mills fields on four-dimensional Euclidean space. The motivation to study twistor interpretations of these objects comes from the harmonic spheres conjecture stating the existence of the bijective correspondence between based harmonic spheres in the loop space \\(\\Omega G\\ of a compact Lie group \\(G\\ and the moduli space of Yang–Mills \\(G\\-fields on \\(\\mathbb R^4\\.
Energy Technology Data Exchange (ETDEWEB)
Ortiz R, J. M. [Departamento de Electrotecnia y Electronica, Escuela Politecnica Superior, Av. Menendez Pidal s/n, 14004 Cordoba (Spain); Martinez B, M. R.; Vega C, H. R. [Unidad Academica de Estudios Nucleares, Universidad Autonoma de Zacatecas, Cipres 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Galleo, E. [Departamento de Ingenieria Nuclear, Universidad Politecnica de Madrid, Jose Gutierrez Abascal 2, 28006 Madrid (Spain)], e-mail: morvymm@yahoo.com.mx
2009-10-15
A device used to perform neutron spectroscopy is the system known as a system of Bonner spheres spectrometer, this system has some disadvantages, one of these is the need for reconstruction using a code that is based on an iterative reconstruction algorithm, whose greater inconvenience is the need for a initial spectrum, as close as possible to the spectrum that is desired to avoid this inconvenience has been reported several procedures in reconstruction, combined with various types of experimental methods, based on artificial intelligence technology how genetic algorithms, artificial neural networks and hybrid systems evolved artificial neural networks using genetic algorithms. This paper analyzes the intersection of neural networks and evolutionary algorithms applied in the neutron spectroscopy and dosimetry. Due to this is an emerging technology, there are not tools for doing analysis of the obtained results, by what this paper presents a computing tool to analyze the neutron spectra and the equivalent doses obtained through the hybrid technology of neural networks and genetic algorithms. The toolmaker offers a user graphical environment, friendly and easy to operate. (author)
Ensuring Economic Security in Lending Sphere
Directory of Open Access Journals (Sweden)
Ivan Vadimovich Kochikin
2016-06-01
Full Text Available Relevance of the topic is determined by the need for sustainable development of the country’s banking system, capable of ensuring the process of raising funds to producers and the public for their projects. One of the implementation of this objective is to discourage unfair behavior in financial markets. Trust is a key factor in the development of financial markets, therefore it is necessary to suppress the appearance of unfair practices and participants – black creditors, falsification of financial statements, trading on insider information and market manipulation. It requires a whole range of activities, and above all ensuring the inevitability and proportionality of punishment for unscrupulous players, the introduction of requirements for the business reputation of the management of financial institutions.The article is devoted to structuring legal violations in the lending sphere. The analysis of indicators of credit organizations in Russia was conducted to fulfill this aim. This analysis revealed the causes of sustainable growth of overdue accounts payable – job cuts in enterprises, violations in the financial sector, various errors in the credit granting / raising. The authors carry out the systematization and classification of offenses in the area of lending, provide examples, as well as factual material illustrating the violations in the lending process having the characteristics of a fraud. The article substantiates the obligations of employees of the credit institution, in the result of which risks of granting credit to fraudsters can be reduced. The methods of fraud prevention should include the identified methods of protection against fraud in the area under consideration – exchange of information by banks associated with the criminal intentions of customers; technology development and technical support, training, and personnel responsibilities.
TIDALLY DRIVEN DYNAMOS IN A ROTATING SPHERE
International Nuclear Information System (INIS)
Cébron, D.; Hollerbach, R.
2014-01-01
Large-scale planetary or stellar magnetic fields generated by a dynamo effect are mostly attributed to flows forced by buoyancy forces in electrically conducting fluid layers. However, these large-scale fields may also be controlled by tides, as previously suggested for the star τ-boo, Mars, or the early Moon. By simulating a small local patch of a rotating fluid, Barker and Lithwick have recently shown that tides can drive small-scale dynamos by exciting a hydrodynamic instability, the so-called elliptical (or tidal) instability. By performing global magnetohydrodynamic simulations of a rotating spherical fluid body, we investigate if this instability can also drive the observed large-scale magnetic fields. We are thus interested in the dynamo threshold and the generated magnetic field in order to test if such a mechanism is relevant for planets and stars. Rather than solving the problem in a geometry deformed by tides, we consider a spherical fluid body and add a body force to mimic the tidal deformation in the bulk of the fluid. This allows us to use an efficient spectral code to solve the magnetohydrodynamic problem. We first compare the hydrodynamic results with theoretical asymptotic results and numerical results obtained in a truly deformed ellipsoid, which confirms the presence of elliptical instability. We then perform magnetohydrodynamic simulations and investigate the dynamo capability of the flow. Kinematic and self-consistent dynamos are finally simulated, showing that the elliptical instability is capable of generating a dipole-dominated large-scale magnetic field in global simulations of a fluid rotating sphere
On the motion of linked spheres in a Stokes flow
Box, F.; Han, E.; Tipton, C. R.; Mullin, T.
2017-04-01
The results of an experimental investigation into the motion of linked spheres at low Reynolds number are presented. Small permanent magnets were embedded in the spheres and torques were generated by application of an external magnetic field. Pairs of neutrally buoyant spheres, connected by either glass rods or thin elastic struts, move in a reciprocal orbit when driven by an oscillatory field. An array of three spheres linked by elastic struts buckles in a periodic, non-reciprocal manner. The induced magneto-elastic buckling propels the elemental swimmer and we find that the geometrical asymmetry of the device, introduced by the struts of different lengths, determines the swimming direction. We propose that this novel method of creating movement remotely is suitable for miniaturization.
Equivariant harmonic maps into the sphere via isoparametric maps
International Nuclear Information System (INIS)
Xin, Y.L.
1992-08-01
By using concrete isoparametric maps we obtain some new equivariant harmonic maps between spheres and solve equivariant boundary value problems for harmonic maps from unit open ball B m+1 into S n . (author). 22 refs
Friction and drag forces on spheres propagating down inclined planes
Tee, Yi Hui; Longmire, Ellen
2017-11-01
When a submerged sphere propagates along an inclined wall at terminal velocity, it experiences gravity, drag, lift, and friction forces. In the related equations of motion, the drag, lift and friction coefficients are unknown. Experiments are conducted to determine the friction and drag coefficients of the sphere over a range of Reynolds numbers. Through high speed imaging, translational and rotational velocities of spheres propagating along a glass plate are determined in liquids with several viscosities. The onset of sliding motion is identified by computing the dimensionless rotation rate of the sphere. Using drag and lift coefficients for Re friction coefficients are calculated for several materials. The friction coefficients are then employed to estimate the drag coefficient for 350 frictional force over this Re range. Supported by NSF (CBET-1510154).
[The power of religion in the public sphere] / Alar Kilp
Kilp, Alar, 1969-
2012-01-01
Arvustus: Buthler, Judith, Habermas, Jürgen, Taylor, Charles, West, Cornel. The power of religion in the public sphere. (Eduardo Mendieta, Jonathan VanAntwerpen (eds.) Afterword by Craig Calhoun.) New York ; Chichester : Columbia University Press, 2011
Method for producing dustless graphite spheres from waste graphite fines
Pappano, Peter J [Oak Ridge, TN; Rogers, Michael R [Clinton, TN
2012-05-08
A method for producing graphite spheres from graphite fines by charging a quantity of spherical media into a rotatable cylindrical overcoater, charging a quantity of graphite fines into the overcoater thereby forming a first mixture of spherical media and graphite fines, rotating the overcoater at a speed such that the first mixture climbs the wall of the overcoater before rolling back down to the bottom thereby forming a second mixture of spherical media, graphite fines, and graphite spheres, removing the second mixture from the overcoater, sieving the second mixture to separate graphite spheres, charging the first mixture back into the overcoater, charging an additional quantity of graphite fines into the overcoater, adjusting processing parameters like overcoater dimensions, graphite fines charge, overcoater rotation speed, overcoater angle of rotation, and overcoater time of rotation, before repeating the steps until graphite fines are converted to graphite spheres.
(Dis)guises: Spheres of Government, Functional Areas and Authority
African Journals Online (AJOL)
regional planning and development', 'urban and rural development', 'provincial planning' and 'municipal planning' are divided among the three spheres of government. Yet the boundaries between these items listed in Schedules 4 and 5 of ...
A Reaction Sphere for High Performance Attitude Control, Phase I
National Aeronautics and Space Administration — Our innovative reaction sphere (Doty pending patent application serial number 61/164,868) has the potential to provide much higher performance than a conventional...
Method and apparatus for producing small hollow spheres
International Nuclear Information System (INIS)
Hendricks, C.D.
1979-01-01
A method and apparatus are described for producing small hollow spheres of glass, metal or plastic, wherein the sphere material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature (T greater than or equal to 600 0 C). As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming a hollow sphere of controllable thickness. The thus produced hollow spheres (20 to 10 3 μm) have a variety of application, and are particularly useful in the fabrication of targets for laser implosion such as neutron sources, laser fusion physics studies, and laser initiated fusion power plants
SPHERES: From Ground Development to Operations on ISS
Katterhagen, A.
2015-01-01
SPHERES (Synchronized Position Hold Engage and Reorient Experimental Satellites) is an internal International Space Station (ISS) Facility that supports multiple investigations for the development of multi-spacecraft and robotic control algorithms. The SPHERES Facility on ISS is managed and operated by the SPHERES National Lab Facility at NASA Ames Research Center (ARC) at Moffett Field California. The SPHERES Facility on ISS consists of three self-contained eight-inch diameter free-floating satellites which perform the various flight algorithms and serve as a platform to support the integration of experimental hardware. To help make science a reality on the ISS, the SPHERES ARC team supports a Guest Scientist Program (GSP). This program allows anyone with new science the possibility to interface with the SPHERES team and hardware. In addition to highlighting the available SPHERES hardware on ISS and on the ground, this presentation will also highlight ground support, facilities, and resources available to guest researchers. Investigations on the ISS evolve through four main phases: Strategic, Tactical, Operations, and Post Operations. The Strategic Phase encompasses early planning beginning with initial contact by the Principle Investigator (PI) and the SPHERES program who may work with the PI to assess what assistance the PI may need. Once the basic parameters are understood, the investigation moves to the Tactical Phase which involves more detailed planning, development, and testing. Depending on the nature of the investigation, the tactical phase may be split into the Lab Tactical Phase or the ISS Tactical Phase due to the difference in requirements for the two destinations. The Operations Phase is when the actual science is performed; this can be either in the lab, or on the ISS. The Post Operations Phase encompasses data analysis and distribution, and generation of summary status and reports. The SPHERES Operations and Engineering teams at ARC is composed of
Relaxation of Thick-Walled Cylinders and Spheres
DEFF Research Database (Denmark)
Saabye Ottosen, N.
1982-01-01
Using the nonlinear creep law proposed by Soderberg, (1936) closed-form solutions are derived for the relaxation of incompressible thick-walled spheres and cylinders in plane strain. These solutions involve series expressions which, however, converge very quickly. By simply ignoring these series...... expressions, extremely simple approximate solutions are obtained. Despite their simplicity these approximations possess an accuracy that is superior to approximations currently in use. Finally, several physical aspects related to the relaxation of cylinders and spheres are discussed...
Integral measurements using the 'sphere method'. The case of carbon
International Nuclear Information System (INIS)
Haouat, G.; Lachkar, J.; Patin, Y.; Cocu, F.; Sigaud, J.; Cotten, D.
1977-01-01
The time-of-flight spectrum of direct and scattered neutrons with a 10cm diameter carbon sphere. (The direct neutron energy is 14.81MeV, the basic time-of-flight being 6m). The time-of-flight spectrum of the neutrons from T(d,n) 4 He is given in the same experimental conditions (without the carbon sphere) [fr
Silica hollow spheres with nano-macroholes like diatomaceous earth.
Fujiwara, Masahiro; Shiokawa, Kumi; Sakakura, Ikuko; Nakahara, Yoshiko
2006-12-01
Artificial synthesis of hollow cell walls of diatoms is an ultimate target of nanomaterial science. The addition of some water-soluble polymers such as sodium polymethacrylate to a solution of water/oil/water emulsion system, which is an essential step of the simple synthetic procedure of silica hollow spheres (microcapsules), led to the formation of silica hollow spheres with nano-macroholes (>100 nm) in their shell walls, the morphologies of which are analogous to those of diatom earth.
A note on automorphisms of the sphere complex
Indian Academy of Sciences (India)
Introduction. In [1], Aramayona and Souto have shown that the group Aut(S(M)) of simplicial auto- morphisms of the sphere complex S(M) associated to the manifold M = ♯nS2 × S1 is isomorphic to the group Out(Fn) of outer automorphisms of the free group Fn of rank n ≥ 3. The idea of the proof is as follows: the sphere ...
Methods of neutron spectrometry
International Nuclear Information System (INIS)
Doerschel, B.
1981-01-01
The different methods of neutron spectrometry are based on the direct measurement of neutron velocity or on the use of suitable energy-dependent interaction processes. In the latter case the measuring effect of a detector is connected with the searched neutron spectrum by an integral equation. The solution needs suitable unfolding procedures. The most important methods of neutron spectrometry are the time-of-flight method, the crystal spectrometry, the neutron spectrometry by use of elastic collisions with hydrogen nuclei, and neutron spectrometry with the aid of nuclear reactions, especially of the neutron-induced activation. The advantages and disadvantages of these methods are contrasted considering the resolution, the measurable energy range, the sensitivity, and the experimental and computational efforts. (author)
Electric potential on solid spheres in a plasma
De, B. R.
1974-01-01
Derivation of the general expression for the potential on a solid sphere immersed in a plasma, showing the dependence of the potential on the radius (a) of the sphere and the radius (s) of the plasma sheath that develops around the sphere. In the limit where the radius a is much larger than the sheath thickness s-a, the well-known result for the potential on an infinite wall in contact with a plasma is recovered from this expression. At the other extreme, where s is much larger than a, the result derived by Spitzer (1941) for the potential on spherical grains in the interstellar plasma is obtained. Since the surface of the sphere forms a sink for the charged particles, there is a net drift of the plasma towards the surface. The effect of this drift on the potential is examined. Finally, for very small metallic spheres, an effect leading to a revision of the potential is discussed. This effect consists in a lowering of the potential barrier for the electrons due to the image force. The various effects limiting the potential on spheres are discussed.
Squeeze flow of a Carreau fluid during sphere impact
Uddin, J.
2012-07-19
We present results from a combined numerical and experimental investigation into the squeeze flow induced when a solid sphere impacts onto a thin, ultra-viscous film of non-Newtonian fluid. We examine both the sphere motion through the liquid as well as the fluid flow field in the region directly beneath the sphere during approach to a solid plate. In the experiments we use silicone oil as the model fluid, which is well-described by the Carreau model. We use high-speed imaging and particle tracking to achieve flow visualisation within the film itself and derive the corresponding velocity fields. We show that the radial velocity either diverges as the gap between the sphere and the wall diminishes (Z tip → 0) or that it reaches a maximum value and then decays rapidly to zero as the sphere comes to rest at a non-zero distance (Z tip = Z min ) away from the wall. The horizontal shear rate is calculated and is responsible for significant viscosity reduction during the approach of the sphere. Our model of this flow, based on lubrication theory, is solved numerically and compared to experimental trials. We show that our model is able to correctly describe the physical features of the flow observed in the experiments.
Solvation Sphere of I- and Br- in Water
Energy Technology Data Exchange (ETDEWEB)
2011-06-22
The solvation sphere of halides in water has been investigated using a combination of extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) analysis techniques. The results have indicated that I- and Br- both have an asymmetric, 8 water molecule primary solvation spheres. These spheres are identical, with the Br{sup -} sphere about .3 {angstrom} smaller than the I{sup -} sphere. This study utilized near-edge analysis to supplement EXAFS analysis which suffers from signal dampening/broadening due to thermal noise. This paper has reported on the solvation first sphere of I{sup -} and Br{sup -} in water. Using EXAFS and XANES analysis, strong models which describe the geometric configuration of water molecules coordinated to a central anion have been developed. The combination of these techniques has provided us with a more substantiated argument than relying solely on one or the other. An important finding of this study is that the size of the anion plays a smaller role than previously assumed in determining the number of coordinating water molecules Further experimental and theoretical investigation is required to understand why the size of the anion plays a minor role in determining the number of water molecules bound.
Sound Scattering and Its Reduction by a Janus Sphere Type
Directory of Open Access Journals (Sweden)
Deliya Kim
2014-01-01
Full Text Available Sound scattering by a Janus sphere type is considered. The sphere has two surface zones: a soft surface of zero acoustic impedance and a hard surface of infinite acoustic impedance. The zones are arranged such that axisymmetry of the sound field is preserved. The equivalent source method is used to compute the sound field. It is shown that, by varying the sizes of the soft and hard zones on the sphere, a significant reduction can be achieved in the scattered acoustic power and upstream directivity when the sphere is near a free surface and its soft zone faces the incoming wave and vice versa for a hard ground. In both cases the size of the sphere’s hard zone is much larger than that of its soft zone. The boundary location between the two zones coincides with the location of a zero pressure line of the incoming standing sound wave, thus masking the sphere within the sound field reflected by the free surface or the hard ground. The reduction in the scattered acoustic power diminishes when the sphere is placed in free space. Variations of the scattered acoustic power and directivity with the sound frequency are also given and discussed.
Scattering characteristics of relativistically moving concentrically layered spheres
Garner, Timothy J.; Lakhtakia, Akhlesh; Breakall, James K.; Bohren, Craig F.
2018-02-01
The energy extinction cross section of a concentrically layered sphere varies with velocity as the Doppler shift moves the spectral content of the incident signal in the sphere's co-moving inertial reference frame toward or away from resonances of the sphere. Computations for hollow gold nanospheres show that the energy extinction cross section is high when the Doppler shift moves the incident signal's spectral content in the co-moving frame near the wavelength of the sphere's localized surface plasmon resonance. The energy extinction cross section of a three-layer sphere consisting of an olivine-silicate core surrounded by a porous and a magnetite layer, which is used to explain extinction caused by interstellar dust, also depends strongly on velocity. For this sphere, computations show that the energy extinction cross section is high when the Doppler shift moves the spectral content of the incident signal near either of olivine-silicate's two localized surface phonon resonances at 9.7 μm and 18 μm.
Global Calibration of Multiple Cameras Based on Sphere Targets
Directory of Open Access Journals (Sweden)
Junhua Sun
2016-01-01
Full Text Available Global calibration methods for multi-camera system are critical to the accuracy of vision measurement. Proposed in this paper is such a method based on several groups of sphere targets and a precision auxiliary camera. Each camera to be calibrated observes a group of spheres (at least three, while the auxiliary camera observes all the spheres. The global calibration can be achieved after each camera reconstructs the sphere centers in its field of view. In the process of reconstructing a sphere center, a parameter equation is used to describe the sphere projection model. Theoretical analysis and computer simulation are carried out to analyze the factors that affect the calibration accuracy. Simulation results show that the parameter equation can largely improve the reconstruction accuracy. In the experiments, a two-camera system calibrated by our method is used to measure a distance about 578 mm, and the root mean squared error is within 0.14 mm. Furthermore, the experiments indicate that the method has simple operation and good flexibility, especially for the onsite multiple cameras without common field of view.
Conception of a New Recoil Proton Telescope for Real-Time Neutron Spectrometry in Proton-Therapy
Combe, Rodolphe; Arbor, Nicolas; el Bitar, Ziad; Higueret, Stéphane; Husson, Daniel
2018-01-01
Neutrons are the main type of secondary particles emitted in proton-therapy. Because of the risk of secondary cancer and other late occurring effects, the neutron dose should be included in the out-of-field dose calculations. A neutron spectrometer has to be used to take into account the energy dependence of the neutron radiological weighting factor. Due to its high dependence on various parameters of the irradiation (beam, accelerator, patient), the neutron spectrum should be measured independently for each treatment. The current reference method for the measurement of the neutron energy, the Bonner Sphere System, consists of several homogeneous polyethylene spheres with increasing diameters equipped with a proportional counter. It provides a highresolution reconstruction of the neutron spectrum but requires a time-consuming work of signal deconvolution. New neutron spectrometers are being developed, but the main experimental limitation remains the high neutron flux in proton therapy treatment rooms. A new model of a real-time neutron spectrometer, based on a Recoil Proton Telescope technology, has been developed at the IPHC. It enables a real-time high-rate reconstruction of the neutron spectrum from the measurement of the recoil proton trajectory and energy. A new fast-readout microelectronic integrated sensor, called FastPixN, has been developed for this specific purpose. A first prototype, able to detect neutrons between 5 and 20 MeV, has already been validated for metrology with the AMANDE facility at Cadarache. The geometry of the new Recoil Proton Telescope has been optimized via extensive Geant4 Monte Carlo simulations. Uncertainty sources have been carefully studied in order to improve simultaneously efficiency and energy resolution, and solutions have been found to suppress the various expected backgrounds. We are currently upgrading the prototype for secondary neutron detection in proton therapy applications.
Vescovi, Dalila; Berzi, Diego; Richard, Patrick; Brodu, Nicolas
2014-01-01
International audience; We use existing 3D Discrete Element simulations of simple shear flows of spheres to evaluate the radial distribution function at contact that enables kinetic theory to correctly predict the pressure and the shear stress, for different values of the collisional coefficient of restitution. Then, we perform 3D Discrete Element simulations of plane flows of frictionless, inelastic spheres, sheared between walls made bumpy by gluing particles in a regular array, at fixed av...
Collective modes in simple melts: Transition from soft spheres to the hard sphere limit.
Khrapak, Sergey; Klumov, Boris; Couëdel, Lénaïc
2017-08-11
We study collective modes in a classical system of particles with repulsive inverse-power-law (IPL) interactions in the fluid phase, near the fluid-solid coexistence (IPL melts). The IPL exponent is varied from n = 10 to n = 100 to mimic the transition from moderately soft to hard-sphere-like interactions. We compare the longitudinal dispersion relations obtained using molecular dynamic (MD) simulations with those calculated using the quasi-crystalline approximation (QCA) and find that this simple theoretical approach becomes grossly inaccurate for [Formula: see text]. Similarly, conventional expressions for high-frequency (instantaneous) elastic moduli, predicting their divergence as n increases, are meaningless in this regime. Relations of the longitudinal and transverse elastic velocities of the QCA model to the adiabatic sound velocity, measured in MD simulations, are discussed for the regime where QCA is applicable. Two potentially useful freezing indicators for classical particle systems with steep repulsive interactions are discussed.
International Nuclear Information System (INIS)
Sanz-Medel, A.
1997-01-01
The elemental inorganic analysis seems to be dominated today by techniques based on atomic spectrometry. After an evaluation of advantages and limitations of using mass analysers (ion detectors) versus conventional photomultipliers (photon detector) a brief review of the more popular techniques of the emerging Atomic Mass spectrometry is carried out. Their huge potential for inorganic trace analysis is such that in the future we could well witness how this end of the century and millennium marked the fall of the photons empire in Analytical Atomic Spectrometry. (Author)
Tin-wall hollow ceramic spheres from slurries. Final report
Energy Technology Data Exchange (ETDEWEB)
Chapman, A.T.; Cochran, J.K.
1992-12-31
The overall objective of this effort was to develop a process for economically fabricating thin-wall hollow ceramic spheres from conventional ceramic powders using dispersions. This process resulted in successful production of monosized spheres in the mm size range which were point contact bonded into foams. Thin-wall hollow ceramic spheres of small (one to five millimeter) diameter have novel applications as high-temperature insulation and light structural materials when bonded into monolithic foams. During Phase 1 of this program the objective as to develop a process for fabricating thin-wall hollow spheres from powder slurries using the coaxial nozzle fabrication method. Based on the success during Phase 1, Phase 2 was revised to emphasize the assessment of the potential structural and insulation applications for the spheres and modeling of the sphere formation process was initiated. As more understanding developed, it was clear that to achieve successful structural application, the spheres had to be bonded into monolithic foams and the effort was further expanded to include both bonding into structures and finite element mechanical modeling which became the basis of Phase 3. Successful bonding techniques and mechanical modeling resulted but thermal conductivities were higher than desired for insulating activities. In addition, considerable interest had been express by industry for the technology. Thus the final Phase 4 concentrated on methods to reduce thermal conductivity by a variety of techniques and technology transfer through individualized visits. This program resulted in three Ph.D. theses and 10 M.S. theses and they are listed in the appropriate technical sections.
Molecular Imaging Mass Spectrometry
Directory of Open Access Journals (Sweden)
Kovac, S.
2009-05-01
Full Text Available Molecular imaging mass spectrometry (IMS is a recently developed method for direct determination of spatial distribution of biopolymers, preferably proteins on cell surface and tissues. Imaging mass spectrometry data are mainly based on Matrix-Assisted Laser Desorption/Ionization- Time of Flight (MALDI TOF. The MALDI TOF based imaging mass spectrometry was applied for determination of changes in kidney tissue of sensitive mice after poisoning with aristolochic acid I. The second application presented here were changes in the gastric tissue in mice after infection with Helicobacter pylori, as a model of gastric cancer in humans caused by this pathogen microorganism. Molecular imaging mass spectrometry can be applied in medicine, mostly for identification of candidate biomarkers for malignant and non-malignant diseases. Furthermore, imaging MS has almost unlimited capacity in agriculture, food technology and biotechnology, e. g. for monitoring, process development and quality control of manufactured tissue of animal, plant and microbial origin.
Software for nuclear spectrometry
International Nuclear Information System (INIS)
1998-10-01
The Advisory Group Meeting (AGM) on Software for Nuclear Spectrometry was dedicated to review the present status of software for nuclear spectrometry and to advise on future activities in this field. Because similar AGM and consultant's meetings had been held in the past; together with an attempt to get more streamlined, this AGM was devoted to the specific field of software for gamma ray spectrometry. Nevertheless, many of the issues discussed and the recommendations made are of general concern for any software on nuclear spectrometry. The report is organized by sections. The 'Summary' gives conclusions and recommendations adopted at the AGM. These conclusions and recommendations resulted from the discussions held during and after presentations of the scientific and technical papers. These papers are reported here in their integral form in the following Sections
Genetic algorithms used to optimize an artificial neural network design used in neutron spectrometry
International Nuclear Information System (INIS)
Arteaga A, T.; Ortiz R, J. M.; Vega C, H. R.
2016-10-01
Artificial neural networks (Ann) are widely used; it which consist of an input layer, one or more hidden layers and an output layer; these layers contain neurons and each has connections called weights, where the knowledge are allowed and let to Ann solve problems proposed. These Ann is used to reconstruction of the energy spectrum of neutrons from count rates and develop Bonner sphere neutron dosimetry. Currently, we have developed Ann with high performance and generalization ability. Determine your optimal architecture is usually a difficult task, an exhaustive search of all possible combinations of parameters is rarely possible further training of the neural network with random initial weights can cause two major drawbacks: it can stuck in local minima or converge very slowly. In this project it will be used Genetic Algorithms (Ga); which are based on the principle or analogy of evolution through natural selection and has shown to be very effective in optimizing complex search functions and large spaces or to find a near optimal overall efficiency. The aim is to decrease the architecture in number of hidden neurons and therefore the total number of connections is reducing. The benefits obtained by optimizing the network are that the number of connections would be considerably smaller and thus the computational complexity, hardware integration, resources will be lower such that will allow to be even more viable implemented. To use the Ga three problems must be solve: 1) coding the problem into chromosomes. 2) Construct a fitness function. 3) Proper selection of genetic operators; crossover, selection, mutation. As a result, the scientific knowledge obtained can to be applied to similar problems having a reference parameters used and their impact on the optimization would to be generated. It concluded that the input layer and output are subject to the problem; the Ga propose the optimal number of neurons in the hidden layer without losing the quality of the
Formation of Innovative Infrastructure of the Industrial Sphere
Directory of Open Access Journals (Sweden)
M. Ya. Veselovsky
2017-01-01
Full Text Available Purpose: in article problems of formation of innovative infrastructure of the industrial sphere in the Russian Federation are investigated, her merits and demerits are considered. In the context of foreign experience the analysis of statistics of development of innovative infrastructure on the basis of which is carried out the main shortcomings constraining efficiency of her work are allocated. Among them lack of cooperation between the organizations of infrastructure, a gap between scientific sector and business community, lack of effective communications between participants of innovative process, information opacity, extremely insufficient financing, and also low demand for innovations from the industrial enterprises, lack of motivation at business to carry out financing of innovative projects. Authors offer mechanisms of formation and management of innovative infrastructure. The purpose of article is increase in efficiency of innovative infrastructure of the industrial sphere. Article tasks: to analyse a condition of innovative infrastructure of the industrial sphere in Russia; to study foreign experience of formation of innovative infrastructure; to reveal shortcomings of functioning of innovative infrastructure; to offer mechanisms of formation and management of innovative infrastructure of the industrial sphere. Methods: hen carrying out a research data of Rosstat, legislative and normative legal acts, state programs of development of innovative activities and the industrial sphere, fundamental and application-oriented works of authoritative scientists in the field of innovative development were the main sources of basic data. The research is based on theoretical methods of scientific knowledge, in particular use of methods of synthesis and deduction, and also methods of empirical knowledge for which allowed to open a range of a set of problems which hinder with innovative development of the industrial sphere. Results: the analysis of the
Glass transition of dense fluids of hard and compressible spheres
Berthier, Ludovic; Witten, Thomas A.
2009-08-01
We use computer simulations to study the glass transition of dense fluids made of polydisperse repulsive spheres. For hard particles, we vary the volume fraction, φ , and use compressible particles to explore finite temperatures, T>0 . In the hard sphere limit, our dynamic data show evidence of an avoided mode-coupling singularity near φMCT≈0.592 ; they are consistent with a divergence of equilibrium relaxation times occurring at φ0≈0.635 , but they leave open the existence of a finite temperature singularity for compressible spheres at volume fraction φ>φ0 . Using direct measurements and a scaling procedure, we estimate the equilibrium equation of state for the hard sphere metastable fluid up to φ0 , where pressure remains finite, suggesting that φ0 corresponds to an ideal glass transition. We use nonequilibrium protocols to explore glassy states above φ0 and establish the existence of multiple equations of state for the unequilibrated glass of hard spheres, all diverging at different densities in the range φɛ[0.642,0.664] . Glassiness thus results in the existence of a continuum of densities where jamming transitions can occur.
Crown sealing and buckling instability during water entry of spheres
Marston, J. O.
2016-04-05
We present new observations from an experimental investigation of the classical problem of the crown splash and sealing phenomena observed during the impact of spheres onto quiescent liquid pools. In the experiments, a 6 m tall vacuum chamber was used to provide the required ambient conditions from atmospheric pressure down to of an atmosphere, whilst high-speed videography was exploited to focus primarily on the above-surface crown formation and ensuing dynamics, paying particular attention to the moments just prior to the surface seal. In doing so, we have observed a buckling-type azimuthal instability of the crown. This instability is characterised by vertical striations along the crown, between which thin films form that are more susceptible to the air flow and thus are drawn into the closing cavity, where they atomize to form a fine spray within the cavity. To elucidate to the primary mechanisms and forces at play, we varied the sphere diameter, liquid properties and ambient pressure. Furthermore, a comparison between the entry of room-temperature spheres, where the contact line pins around the equator, and Leidenfrost spheres (i.e. an immersed superheated sphere encompassed by a vapour layer), where there is no contact line, indicates that the buckling instability appears in all crown sealing events, but is intensified by the presence of a pinned contact line. © 2016 Cambridge University Press.
Corrected Four-Sphere Head Model for EEG Signals
Directory of Open Access Journals (Sweden)
Solveig Næss
2017-10-01
Full Text Available The EEG signal is generated by electrical brain cell activity, often described in terms of current dipoles. By applying EEG forward models we can compute the contribution from such dipoles to the electrical potential recorded by EEG electrodes. Forward models are key both for generating understanding and intuition about the neural origin of EEG signals as well as inverse modeling, i.e., the estimation of the underlying dipole sources from recorded EEG signals. Different models of varying complexity and biological detail are used in the field. One such analytical model is the four-sphere model which assumes a four-layered spherical head where the layers represent brain tissue, cerebrospinal fluid (CSF, skull, and scalp, respectively. While conceptually clear, the mathematical expression for the electric potentials in the four-sphere model is cumbersome, and we observed that the formulas presented in the literature contain errors. Here, we derive and present the correct analytical formulas with a detailed derivation. A useful application of the analytical four-sphere model is that it can serve as ground truth to test the accuracy of numerical schemes such as the Finite Element Method (FEM. We performed FEM simulations of the four-sphere head model and showed that they were consistent with the corrected analytical formulas. For future reference we provide scripts for computing EEG potentials with the four-sphere model, both by means of the correct analytical formulas and numerical FEM simulations.
Hydrothermal Syntheses of Colloidal Carbon Spheres from Cyclodextrins
Energy Technology Data Exchange (ETDEWEB)
Shin, Yongsoon; Wang, Li Q.; Bae, In-Tae; Arey, Bruce W.; Exarhos, Gregory J.
2008-09-18
Colloidal carbon spheres have been prepared from aqueous alpha-, beta-, and gamma-cyclodextrin (CD) solutions in closed systems under hydrothermal conditions at 160 oC. Both liquid and solid-state 13C NMR spectra taken for samples at different reaction times have been used to monitor the dehydration and carbonization pathways. CD slowly hydrolyzes to glucose and forms 5-hydroxymethyl furfural (HMF) followed by carbonization into colloidal carbon spheres. The isolated carbon spheres are 70-150 nm in diameter, exhibit a core-shell structure, and are comprised of a condensed core (C=C) peppered with resident chemical functionalities including carboxylate and hydroxyl groups. Evidence from 13C solid-state NMR and FT-IR spectra reveal that the evolving carbon spheres show a gradual increase in the amount of aromatic carbon as a function of reaction time and that the carbon spheres generated from gamma-CD contain significantly higher aromatic carbon than those derived from alpha- and beta-CD.
ORSPHERE: CRITICAL, BARE, HEU(93.2)-METAL SPHERE
Energy Technology Data Exchange (ETDEWEB)
Margaret A. Marshall
2013-09-01
In the early 1970’s Dr. John T. Mihalczo (team leader), J.J. Lynn, and J.R. Taylor performed experiments at the Oak Ridge Critical Experiments Facility (ORCEF) with highly enriched uranium (HEU) metal (called Oak Ridge Alloy or ORALLOY) in an attempt to recreate GODIVA I results with greater accuracy than those performed at Los Alamos National Laboratory in the 1950’s (HEU-MET-FAST-001). The purpose of the Oak Ridge ORALLOY Sphere (ORSphere) experiments was to estimate the unreflected and unmoderated critical mass of an idealized sphere of uranium metal corrected to a density, purity, and enrichment such that it could be compared with the GODIVA I experiments. “The very accurate description of this sphere, as assembled, establishes it as an ideal benchmark for calculational methods and cross-section data files.” (Reference 1) While performing the ORSphere experiments care was taken to accurately document component dimensions (±0. 0001 in. for non-spherical parts), masses (±0.01 g), and material data The experiment was also set up to minimize the amount of structural material in the sphere proximity. A three part sphere was initially assembled with an average radius of 3.4665 in. and was then machined down to an average radius of 3.4420 in. (3.4425 in. nominal). These two spherical configurations were evaluated and judged to be acceptable benchmark experiments; however, the two experiments are highly correlated.
Experimental performance evaluation of sintered Gd spheres packed beds
DEFF Research Database (Denmark)
Tura, A.; Nielsen, Klaus K.; Van Nong, Ngo
2016-01-01
Research in magnetic refrigeration heavily relies on the use of packed spheres in regenerators, however little investigation to verify that such non-monolithic arrangements guarantee a sufficiently constrained structure has yet been performed. This work presents a preliminary comparison of the pe......Research in magnetic refrigeration heavily relies on the use of packed spheres in regenerators, however little investigation to verify that such non-monolithic arrangements guarantee a sufficiently constrained structure has yet been performed. This work presents a preliminary comparison...... of the performance of AMRs consisting of Gd spheres with diameters ranging from 450-550 microns partially sintered by Spark Plasma Sintering (SPS) to similar spheres, sorted in the same size range and from the same batch, but merely packed. Pressure drop is compared at uniform temperature and at a range of heat...... rejection temperatures and temperature spans. Performance is compared in terms of temperature span at a range of heat rejection temperatures (295-308 K) and 0 and 10 W cooling loads. Results show a moderate increase of pressure drop with the sintered spheres, while temperature spans were consistently 2...
Eiceman, GA
2005-01-01
Key Developments for Faster, More Precise Detection Capabilities Driven by the demand for the rapid and advanced detection of explosives, chemical and biological warfare agents, and narcotics, ion mobility spectrometry (IMS) undergone significant refinements in technology, computational capabilities, and understanding of the principles of gas phase ion chemistry and mobility. Beginning with a thorough discussion of the fundamental theories and physics of ion mobility, Ion Mobility Spectrometry, Second Edition describes the recent advances in instrumentation and newly
Review of diagnostic methods for TFTR D{endash}T radiation shielding and neutronics studies
Energy Technology Data Exchange (ETDEWEB)
Kugel, H.W.; Ascione, G.; Gilbert, J. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Azziz, N.; Goldhagen, P.; Reginatto, M.; Shebell, P. [U.S. Department of Energy Environmental Measurements Laboratory, New York, New York 10014-4811 (United States); Kumar, A. [School of Engineering and Applied Science, University of California at Los Angeles, Los Angeles, California 90095 (United States)
1997-01-01
The methods and instrument systems used for TFTR D{endash}T radiation shielding and neutronics studies involving signal strengths ranging over 10 orders of magnitude are reviewed. Neutron and gamma dose-equivalent, fluence, spectral, and materials activation measurements have been performed at various locations from the TFTR vessel to the nearest property lines. The detection systems include {sup 3}He, BF{sub 3}, and {sup 235}U proportional counters in moderated spheres, Bonner sphere arrays, advanced thermoluminescent detectors, argon ionization chambers, intrinsic Ge gamma detectors, and activation foil spectrometry methods. {copyright} {ital 1997 American Institute of Physics.}
Review of diagnostic methods for TFTR D-T radiation shielding and neutronics studies
Energy Technology Data Exchange (ETDEWEB)
Kugel, H.W.; Ascione, G.; Gilbert, J. [Princeton Univ., NJ (US). Princeton Plasma Physics Lab.; Azziz, N.; Goldhagen, P.; Reginatto, M.; Shebell, P. [Dept. of Energy, New York, NY (US). Environmental Measurements Lab.; Kumar, A. [Univ. of California, Los Angeles, CA (US). School of Engineering and Applied Science
1996-10-01
The methods and instrument systems used for TFTR D-T radiation shielding and neutronics studies involving signal strengths ranging over 10 orders of magnitude are reviewed. Neutron and gamma dose-equivalent, fluence, spectral, and materials activation measurements have been performed at various locations from the TFTR vessel to the nearest property lines. The detection systems include {sup 3}He, BF{sub 3}, and {sup 235}U proportional counters in moderated spheres, Bonner sphere arrays, advanced thermoluminescent detectors, argon ionization chambers, intrinsic Ge gamma detectors, and activation foil spectrometry methods.
Impact of a Hydrophobic Sphere onto a Bath
Harris, Daniel M.; Edmonds, John; Galeano-Rios, Carlos A.; Milewski, Paul A.
2017-11-01
Small hydrophobic particles impacting a water surface can rebound completely from the interface (Lee & Kim, Langmuir, 2008). In the present work, we focus on the bouncing dynamics of millimetric hydrophobic spheres impacting the surface of a quiescent water bath. Particular attention is given to the dependence of the normal coefficient of restitution and contact time on the impact velocity and the radius and density of the sphere. Our experimental observations are compared to the predictions of a fluid model derived from linearized Navier-Stokes under the assumption of a high Reynolds number regime (Galeano-Rios et al., JFM, in press). In the model, the motions of the sphere and the fluid interface are found by imposing the natural geometric and kinematic compatibility conditions. Future directions will be discussed. C.A.G.-R. and P.A.M. gratefully acknowledge support through the EPSRC project EP/N018176/1.
Fast breeder reactor primary pump discharge sphere support device
International Nuclear Information System (INIS)
Terny, P.; Blaix, J.C.
1987-01-01
In their lower part, the fast breeder reactor primary pump are connected to a sphere-shaped discharge capacity from which the diagrid feedpipes emerge. This discharge capacity is rigidly set on the strongback by means of a device that bears the forces resulting from the bottom effect. This last being generated by the pressure of the sodium discharged from primary pump. When the reactor operating conditions undergo some rapid changes combined to temperature changes, the structures differential expansions result in high stresses in the sphere support as well as in the feedpipes. This paper aims at describing a sphere support which is provided with flexibility under horizontal forces and a higher stiffness under vertical forces for a better adaptation to the various loading conditions. (orig.)
Burning molten metallic spheres: One class of ball lightning?
Stephan, Karl D.; Massey, Nathan
2008-08-01
Abrahamson and Dinniss [2000. Ball lightning caused by oxidation of nanoparticle networks from normal lightning strikes on soil. Nature 403, 519-521] proposed a theory of ball lighting in which silicon nanoparticles undergo slow oxidation and emit light. Paiva et al. [2007. Production of ball-lightning-like luminous balls by electrical discharges in silicon. Physical Review Letters 98, 048501] reported that an electric arc to silicon produced long-lasting luminous white spheres showing many characteristics of ball lightning. We show experimentally that these consist of burning molten silicon spheres with diameters in the 0.1-1 mm range. The evidence of our experiments leads us to propose that a subset of ball lightning events may consist of macro-scale molten spheres of burning metallic materials likely to be ejected from a conventional lightning strike to earth.
Electrodepositing of Au on hollow PS micro-spheres
International Nuclear Information System (INIS)
Sun Jingyuan; Zhang Yunwang; Du Kai; Wan Xiaobo; Xiao Jiang; Zhang Wei; Zhang Lin; Chen Jing
2010-01-01
Using the self-regulating new micro-sphere electrodepositing device, the techniques of electrodepositing gold on hollow PS micro-spheres were established. The experiment was carried out under the following conditions: voltage was about 0.7 ∼ 0.8 V, current density was 2.0 mA · cm -2 , the temperature was 45 degree C, cathode rotating rate was 250 r · min -1 , flow rate of the solution was 7 mL · min -1 · cm -2 . Hollow gold-plated micro-spheres were prepared with well spherical symmetry, uniform thickness and surface smoothness under 500 nm. The speed of the gold depositing was 6 μm · h -1 . (authors)
Topologically Directed Assemblies of Semiconducting Sphere-Rod Conjugates.
Lin, Zhiwei; Yang, Xing; Xu, Hui; Sakurai, Tsuneaki; Matsuda, Wakana; Seki, Shu; Zhou, Yangbin; Sun, Jian; Wu, Kuan-Yi; Yan, Xiao-Yun; Zhang, Ruimeng; Huang, Mingjun; Mao, Jialin; Wesdemiotis, Chrys; Aida, Takuzo; Zhang, Wei; Cheng, Stephen Z D
2017-12-27
Spontaneous organizations of designed elements with explicit shape and symmetry are essential for developing useful structures and materials. We report the topologically directed assemblies of four categories (a total of 24) of sphere-rod conjugates, composed of a sphere-like fullerene (C 60 ) derivative and a rod-like oligofluorene(s) (OF), both of which are promising organic semiconductor materials. Although the packing of either spheres or rods has been well-studied, conjugates having both shapes substantially enrich resultant assembled structures. Mandated by their shapes and topologies, directed assemblies of these conjugates result not only in diverse unconventional semiconducting supramolecular lattices with controlled domain sizes but also in tunable charge transport properties of the resulting structures. These results demonstrate the importance of persistent molecular topology on hierarchically assembled structures and their final properties.
SPHERES: a platform for formation-flight research
Saenz-Otero, Alvar; Miller, David W.
2005-08-01
New space missions, such as the Terrestrial Planet Finder (TPF) and Darwin programs, call for the use of spacecraft which maintain precise formation to achieve the effective aperture of a much larger spacecraft. Achieving this requires the development of several new space technologies. The SPHERES program was specifically designed to develop a wide range of algorithms in support of formation flight systems. Specifically, SPHERES allows the incremental development of metrology, control, autonomy, artificial intelligence, and communications algorithms. To achieve this, SPHERES exhibits a wide array of features to 1) facilitate the iterative research process, 2) support experiments, 3) support multiple scientists, and 4) enable reconfiguration and modularity. The effectiveness of these aspects of the facility have been demonstrated by several programs including development of system identification routines, coarse formation flight control algorithms, and demonstration of tethered systems.
Spontaneous orbiting of two spheres levitated in a vibrated liquid.
Pacheco-Martinez, H A; Liao, L; Hill, R J A; Swift, Michael R; Bowley, R M
2013-04-12
In the absence of gravity, particles can form a suspension in a liquid irrespective of the difference in density between the solid and the liquid. If such a suspension is subjected to vibration, there is relative motion between the particles and the fluid which can lead to self-organization and pattern formation. Here, we describe experiments carried out to investigate the behavior of two identical spheres suspended magnetically in a fluid, mimicking weightless conditions. Under vibration, the spheres mutually attract and, for sufficiently large vibration amplitudes, the spheres are observed to spontaneously orbit each other. The collapse of the experimental data onto a single curve indicates that the instability occurs at a critical value of the streaming Reynolds number. Simulations reproduce the observed behavior qualitatively and quantitatively, and are used to identify the features of the flow that are responsible for this instability.
Directory of Open Access Journals (Sweden)
Teruhiko Kawano
2015-09-01
Full Text Available We reconsider the relation of superconformal indices of superconformal field theories of class S with five-dimensional N=2 supersymmetric Yang–Mills theory compactified on the product space of a round three-sphere and a Riemann surface. We formulate the five-dimensional theory in supersymmetric backgrounds preserving N=2 and N=1 supersymmetries and discuss a subtle point in the previous paper concerned with the partial twisting on the Riemann surface. We further compute the partition function by localization of the five-dimensional theory on a squashed three-sphere in N=2 and N=1 supersymmetric backgrounds and on an ellipsoid three-sphere in an N=1 supersymmetric background.
Hyperuniformity of self-assembled soft colloidal spheres
Bretz, Coline
2015-03-01
Hyperuniformity characterizes a state of matter for which density fluctuations vanish on large scales. Hyperuniform materials are of technological importance as they exhibit interesting photonic properties. We have shown that such materials can be obtained by assembling spheres into a disordered jammed 2D- packing. To this end, we use a binary mixture of large and small Poly(NIPAM) particles confined between two cover slips. These soft spheres have been chosen for their temperature-sensitive properties. We can locally increase or decrease the volume fraction occupied by the spheres by finely tuning the temperature. By applying various temperature patterns, we are studying the spatial arrangements of the microgels and characterizing their hyperuniform properties through reconstruction and detection algorithms. CNRS-Rhodia-UPenn UMI 3254, Bristol, PA 19007-3624, USA
VMware vSphere 5 Administration Instant Reference
Kusek, Christopher; Daniel, Andy
2011-01-01
Compact and portable reference guide for quick answers to VMware vSphere If you're looking to migrate to the newest version of VMware vSphere, this concise guide will get you up to speed and down to business in no time. If you're new to VMware vSphere, this book is for you too! The compact size of this quick reference makes it easy for you to have by your side—whether you're in the field, server room, or at your desk. Helpful elements for finding information such as thumb tabs, tables of contents with page numbers at the beginning of each chapter, and special headers puts what you need a
Steady flow in a rotating sphere with strong precession
Kida, Shigeo
2018-04-01
The steady flow in a rotating sphere is investigated by asymptotic analysis in the limit of strong precession. The whole spherical body is divided into three regions in terms of the flow characteristics: the critical band, which is the close vicinity surrounding the great circle perpendicular to the precession axis, the boundary layer, which is attached to the whole sphere surface and the inviscid region that occupies the majority of the sphere. The analytic expressions, in the leading order of the asymptotic expansion, of the velocity field are obtained in the former two, whereas partial differential equations for the velocity field are derived in the latter, which are solved numerically. This steady flow structure is confirmed by the corresponding direct numerical simulation.
Symmetry in Sphere-Based Assembly Configuration Spaces
Directory of Open Access Journals (Sweden)
Meera Sitharam
2016-01-01
Full Text Available Many remarkably robust, rapid and spontaneous self-assembly phenomena occurring in nature can be modeled geometrically, starting from a collection of rigid bunches of spheres. This paper highlights the role of symmetry in sphere-based assembly processes. Since spheres within bunches could be identical and bunches could be identical, as well, the underlying symmetry groups could be of large order that grows with the number of participating spheres and bunches. Thus, understanding symmetries and associated isomorphism classes of microstates that correspond to various types of macrostates can significantly increase efficiency and accuracy, i.e., reduce the notorious complexity of computing entropy and free energy, as well as paths and kinetics, in high dimensional configuration spaces. In addition, a precise understanding of symmetries is crucial for giving provable guarantees of algorithmic accuracy and efficiency, as well as accuracy vs. efficiency trade-offs in such computations. In particular, this may aid in predicting crucial assembly-driving interactions. This is a primarily expository paper that develops a novel, original framework for dealing with symmetries in configuration spaces of assembling spheres, with the following goals. (1 We give new, formal definitions of various concepts relevant to the sphere-based assembly setting that occur in previous work and, in turn, formal definitions of their relevant symmetry groups leading to the main theorem concerning their symmetries. These previously-developed concepts include, for example: (i assembly configuration spaces; (ii stratification of assembly configuration space into configurational regions defined by active constraint graphs; (iii paths through the configurational regions; and (iv coarse assembly pathways. (2 We then demonstrate the new symmetry concepts to compute the sizes and numbers of orbits in two example settings appearing in previous work. (3 Finally, we give formal
Complex cobordism and stable homotopy groups of spheres
Ravenel, Douglas C
2003-01-01
Since the publication of its first edition, this book has served as one of the few available on the classical Adams spectral sequence, and is the best account on the Adams-Novikov spectral sequence. This new edition has been updated in many places, especially the final chapter, which has been completely rewritten with an eye toward future research in the field. It remains the definitive reference on the stable homotopy groups of spheres. The first three chapters introduce the homotopy groups of spheres and take the reader from the classical results in the field though the computational aspects
Temperature-dependent and optimized thermal emission by spheres
Nguyen, K. L.; Merchiers, O.; Chapuis, P.-O.
2018-03-01
We investigate the temperature and size dependencies of thermal emission by homogeneous spheres as a function of their dielectric properties. Different power laws obtained in this work show that the emitted power can depart strongly from the usual fourth power of temperature given by Planck's law and from the square or the cube of the radius. We also show how to optimize the thermal emission by selecting permittivities leading to resonances, which allow for the so-called super-Planckian regime. These results will be useful as spheres, i.e. the simplest finite objects, are often considered as building blocks of more complex objects.
Thermal and mechanical stresses in a functionally graded thick sphere
International Nuclear Information System (INIS)
Eslami, M.R.; Babaei, M.H.; Poultangari, R.
2005-01-01
In this paper, a general solution for the one-dimensional steady-state thermal and mechanical stresses in a hollow thick sphere made of functionally graded material is presented. The temperature distribution is assumed to be a function of radius, with general thermal and mechanical boundary conditions on the inside and outside surfaces of the sphere. The material properties, except Poisson's ratio, are assumed to vary along the radius r according to a power law function. The analytical solution of the heat conduction equation and the Navier equation lead to the temperature profile, radial displacement, radial stress, and hoop stress as a function of radial direction
Animating Impacting Spheres with the Elastic Leidenfrost Effect
Waitukaitis, Scott; Souslov, Anton; van Hecke, Martin
2016-11-01
Liquid droplets impacting on hot surfaces above the Leidenfrost temperature can squeeze out the vapor layer and enter the contact boiling regime. What happens to soft but vaporizable solids, such as hydrogel spheres, under such conditions? I will show how this combination leads to sustained bouncing dynamics. The key physics is the coupling between the sphere's elastic deformations and vaporization. Beyond being a new facet of the Leidenfrost effect, this phenomenon promises to be useful in fields such as fluid dynamics, microfluidics, and active matter. NWO Veni and Vici Programs.
Quantum black holes: the event horizon as a fuzzy sphere
International Nuclear Information System (INIS)
Dolan, Brian P.
2005-01-01
Modeling the event horizon of a black hole by a fuzzy sphere leads us to modify some suggestions in the literature concerning black hole mass spectra. We derive a formula for the mass spectrum of quantum black holes in terms of four integers which define the area, angular momentum, electric and magnetic charge of the black hole. Although the event horizon becomes a commutative sphere in the classical limit a vestige of the quantum theory still persists in that the event horizon stereographically projects onto the non-commutative plane. We also suggest how the classical bounds on extremal black holes might be modified in the quantum theory. (author)
Diversity and the European Public Sphere. The Case of Denmark
DEFF Research Database (Denmark)
Pristed Nielsen, Helene; Siim, Birte; Agustin, Lise Rolandsen
2010-01-01
This report contains empirical findings from the Danish case within the Eurosphere project. It is based on 55 interviews with Danish opinion makers on the topics of diversity, EU polity and the European public sphere The empirical research programme of EUROSPHERE aims to explore whether it is pos......This report contains empirical findings from the Danish case within the Eurosphere project. It is based on 55 interviews with Danish opinion makers on the topics of diversity, EU polity and the European public sphere The empirical research programme of EUROSPHERE aims to explore whether......, and is primarily based on expert interviews with 55 opinion makers within Denmark....
Photonic Bandgaps in Mie Scattering by Concentrically Stratified Spheres
Smith, David D.; Fuller, Kirk A.; Curreri, Peter A.
2002-01-01
The Mie formulation for homogeneous spheres is generalized to handle core/shell systems and multiple concentric layers in a manner that exploits an analogy with stratified planar systems, thereby allowing concentric multi-layered structures to be treated as photonic bandgap materials. Representative results from a Mie code employing this analogy demonstrate that photonic bands are present for periodic concentric spheres, though not readily apparent in extinction spectra. Rather, the periodicity simply alters the scattering profile, enhancing the ratio of backscattering to forward scattering inside the bandgap, whereas modification of the interference structure is evident in extinction spectra in accordance with the optical theorem
Smith-Purcell radiation from a chain of spheres
International Nuclear Information System (INIS)
Lekomtsev, K V; Strikhanov, M N; Tishchenko, A A
2010-01-01
Smith-Purcell and diffraction radiation were investigated. These types of radiation appear when a charged particle moves close to a conducting target. Spectral and angular distribution of diffraction radiation from the non-periodic chain of spheres is obtained analytically; local field effects are discussed. Analytical expression for the distribution of Smith-Purcell radiation from the periodic chain of spheres is obtained as well. For the first time it has been shown, that Smith-Purcell radiation for such a system is distributed over the cone. The results are investigated for the particles of different sizes, dielectric and metal, and for both ultrarelativistic and nonrelativistic cases.
Pulsed sphere measurements for weapons and fusion reactor design
International Nuclear Information System (INIS)
Anon.
1978-01-01
Pulsed sphere measurements provide a way of validating the Monte Carlo transport codes and the input cross sections used in the design of thermonuclear weapons and fusion reactors. In these measurements pulsed 14-MeV neutrons are generated at the center of spheres of materials to be investigated, and the emitted neutron spectrum is measured by time-of-flight techniques. The measurements described in this article cannot reproduce the complex conditions found in weapons and fusion reactors. However, agreement between measurement and calculations for a simple geometry and one material (or simple composites) is a necessary prerequisite to reliable fusion reactor calculations
Political Intersectionality and Democratic Politics in the European Public Sphere
DEFF Research Database (Denmark)
Siim, Birte
2015-01-01
Public Sphere (EPS). It is inspired by results and reflections from the European Gender Project (EGP) , where intersectionality was used as an approach for analysing negotiations between gender and ethno-national diversity in selected European countries and in relation to the European Public Sphere...... intersections of gender and ethnic diversity in political life at the national and transnational levels across Europe. In this context, political intersectionality refers to the framing of gender and ethnic diversity by major political actors as well as by activities of women’s and anti-racist organisations...
On the sedimentation velocity of spheres in a polymeric liquid
DEFF Research Database (Denmark)
Rasmussen, Henrik Koblitz; Hassager, Ole
1996-01-01
A Lagrangian finite element method is used to simulate the transient sedimentation of spheres in polymeric liquids. The liquid is described by an integral constitutive equation of the Rivlin-Sawyers type. The simulations show a marked increase in the drag, which is apparently related to the elong......A Lagrangian finite element method is used to simulate the transient sedimentation of spheres in polymeric liquids. The liquid is described by an integral constitutive equation of the Rivlin-Sawyers type. The simulations show a marked increase in the drag, which is apparently related...
GB, Abhilash
2013-01-01
A fast-paced, task-oriented Cookbook covering recipes on the installation and configuration of vSphere 5.1 components. The recipes are accompanied with relevant screenshots with an intention to provide a visual guidance as well. The book concentrates more on the actual task rather than the theory around it, making it easier to understand what is really needed to achieve the task.This book is a guide for anyone who wants to learn how to install and configure VMware vSphere components. This is an excellent handbook for support professionals or for anyone intending to give themselves a head start
Gazzillo, Domenico
2011-03-28
For fluids of molecules with short-ranged hard-sphere-Yukawa (HSY) interactions, it is proven that the Noro-Frenkel "extended law of corresponding states" cannot be applied down to the vanishing attraction range, since the exact HSY second virial coefficient diverges in such a limit. It is also shown that, besides Baxter's original approach, a fully correct alternative definition of "adhesive hard spheres" can be obtained by taking the vanishing-range-limit (sticky limit) not of a Yukawa tail, as is commonly done, but of a slightly different potential with a logarithmic-Yukawa attraction.
Radio making waves in the italian diaspora: Public sphere ...
African Journals Online (AJOL)
The deterritorialised publics of diaspora are conceptually quite different from the homogenous nationally bound public originally conceived to participate in Habermas' public sphere. However, with globalisation and parallel advances in media technologies the qualities of diasporic communication increasingly come to ...
Determination of corrosion potential of coated hollow spheres
International Nuclear Information System (INIS)
Fedorkova, Andrea; Orinakova, Renata; Orinak, Andrej; Dudrova, Eva; Kupkova, Miriam; Kalavsky, Frantisek
2008-01-01
Copper hollow spheres were created on porous iron particles by electro-less deposition. The consequent Ni plating was applied to improve the mechanical properties of copper hollow micro-particles. Corrosion properties of coated hollow spheres were investigated using potentiodynamic polarisation method in 1 mol dm -3 NaCl solution. Surface morphology and composition were studied by scanning electron microscopy (SEM), light microscopy (LM) and energy-dispersive X-ray spectroscopy (EDX). Original iron particles, uncoated copper spheres and iron particles coated with nickel were studied as the reference materials. The effect of particle composition, particularly Ni content on the corrosion potential value was investigated. The results indicated that an increase in the amount of Ni coating layer deteriorated corrosion resistivity of coated copper spheres. Amount of Ni coating layer depended on conditions of Ni electrolysis, mainly on electrolysis time and current intensity. Corrosion behaviour of sintered particles was also explored by potentiodynamic polarisation experiments for the sake of comparison. Formation of iron rich micro-volumes on the particle surface during sintering caused the corrosion potential shift towards more negative values. A detailed study of the morphological changes between non-sintered and sintered micro-particles provided explanation of differences in corrosion potential (E corr )
Characterization of silane coated hollow sphere alumina-reinforced
Indian Academy of Sciences (India)
Silane coated hollow sphere alumina ceramic particles were moulded with ultra high molecular weight polyethylene (UHMWPE) to form a series of composites with alumina weight percent in the range from 15 to 50. The composites were prepared in a cylindrical mould using powder-processing technique. The composites ...
Superconducting Sphere in an External Magnetic Field Revisited
Sazonov, Sergey N.
2013-01-01
The purpose of this article is to give the intelligible procedure for undergraduate students to grasp proof of the fact that the magnetic field outside the hollow superconducting sphere (superconducting shell) coincides with the field of a point magnetic dipole both when an uniform external magnetic field is applied as when a ferromagnetic sphere…
Passive control of a sphere by complex-shaped appendages
Bagheri, Shervin; Lacis, Ugis; Olivieri, Stefano; Mazzino, Andrea
2015-11-01
Appendages of various shapes and sizes (e.g. plumes, barbs, tails, feathers, hairs, fins) play an important role in dispersion and locomotion. In our previous work (Lacis, U. et al. Passive appendages generate drift through symmetry breaking. Nat. Commun. 5:5310, doi: 10.1038/ncomms6310, 2014), we showed that a free-falling cylinder with a splitter plate turns and drifts due to a symmetry-breaking instability (called inverted-pendulum instability or IPL). In other words, in a separated flow, the straight position of a short splitter plate is unstable and as a consequence a side force and a torque are induced on the cylinder. In this work, we seek the three-dimensional (3D) appendage shape (on a sphere at Re =200) that induces the largest drift of the sphere. We find that highly non-trivial shapes of appendages on a sphere increase the side force significantly compared to trivial shapes (such as an elliptic sheet). We also find that appendages may be designed to generate drift in either direction, that is, a free-falling sphere can drift either in the direction in which appendage is tilted or in the opposite direction depending on the particular geometry of the appendage. We discuss the physical mechanisms behind these optimal appendage shapes in the context of the IPL instability.
Holomorphic two-spheres in complex Grassmann manifold
Indian Academy of Sciences (India)
Home; Journals; Proceedings – Mathematical Sciences; Volume 118; Issue 3. Holomorphic Two-Spheres in Complex Grassmann Manifold (2, 4). Xiaowei Xu ... Author Affiliations. Xiaowei Xu1 Xiaoxiang Jiao1. School of Mathematical Sciences, Graduate University of Chinese Academy of Sciences, Beijing 100049, China ...
Two-body quantum mechanical problem on spheres
Shchepetilov, Alexey V.
2005-01-01
The quantum mechanical two-body problem with a central interaction on the sphere ${\\bf S}^{n}$ is considered. Using recent results in representation theory an ordinary differential equation for some energy levels is found. For several interactive potentials these energy levels are calculated in explicit form.
Amidinate Ligands in Zinc coordination sphere: Synthesis and ...
Indian Academy of Sciences (India)
... Refresher Courses · Symposia · Live Streaming. Home; Journals; Journal of Chemical Sciences; Volume 128; Issue 6. Amidinate Ligands in Zinc coordination sphere: Synthesis and structural diversity. SRINIVAS ANGA INDRANI BANERJEE TARUN K PANDA. Regular Article Volume 128 Issue 6 June 2016 pp 867-873 ...
Geometrical frustration: A study of four-dimensional hard spheres
van Meel, J.A.; Frenkel, D.; Charbonneau, P.
2009-01-01
The smallest maximum-kissing-number Voronoi polyhedron of three-dimensional (3D) Euclidean spheres is the icosahedron, and the tetrahedron is the smallest volume that can show up in Delaunay tessellation. No periodic lattice is consistent with either, and hence these dense packings are geometrically
Error analysis of the track fit on the Riemann sphere
Strandlie, A
2002-01-01
We present in this paper a derivation of the covariance matrix of the estimated track parameters given by the Riemann sphere track fitting method. Results of a simulation experiment from the ATLAS Transition Radiation Tracker show that the covariance matrix presented herein very well reflects the actual spread of the track parameters. (6 refs).
Characterization of silane coated hollow sphere alumina-reinforced ...
Indian Academy of Sciences (India)
Silane coated hollow sphere alumina ceramic particles were moulded with ultra high molecular weight polyethylene (UHMWPE) to form a series of composites with alumina weight percent in the range from 15 to 50. The composites were prepared in a cylindrical mould using powder-processing technique. The composites ...
Violence against Brazilian Women in Public and Mediatic Spheres
Souza-Leal, Bruno; de-Carvalho, Carlos-Alberto; Antunes, Elton
2018-01-01
This paper explores the capacity of the media to incorporate controversies in circulation in the public sphere. For that, it is based on the analysis of a set of 607 news stories about violence against women in context of gender relations and proximity, collected in nine Brazilian media during the years of 2013 and 2014. Recognized as one of the…
Do European elections create a European public sphere?
Boomgaarden, H.G.; de Vreese, C.H.; van der Brug, W.; de Vreese, C.H.
2016-01-01
This chapter answers the question whether the news coverage of European Parliament (EP) elections across time has helped create a European public sphere. The focus is on the salience of European Union affairs in the mass media during EP election campaigns and on the Europeanness of such coverage,
Rigidity theorem for Willmore surfaces in a sphere
Indian Academy of Sciences (India)
(Math. Sci.) Vol. 126, No. 2, May 2016, pp. 253–260. c Indian Academy of Sciences. Rigidity theorem for Willmore surfaces in a sphere. HONGWEI XU1 and DENGYUN YANG2,∗. 1Center of Mathematical Sciences, Zhejiang University, Hangzhou 310027,. People's Republic of China. 2College of Mathematics and ...
The Polyakov relation for the sphere and higher genus surfaces
International Nuclear Information System (INIS)
Menotti, Pietro
2016-01-01
The Polyakov relation, which in the sphere topology gives the changes of the Liouville action under the variation of the position of the sources, is also related in the case of higher genus to the dependence of the action on the moduli of the surface. We write and prove such a relation for genus 1 and for all hyperelliptic surfaces. (paper)
User Modeling and Personalization in the Microblogging Sphere
Gao, Q.
2013-01-01
Microblogging has become a popular mechanism for people to publish, share, and propagate information on the Web. The massive amount of digital traces that people have left in the microblogging sphere, creates new possibilities and poses challenges for user modeling and personalization. How can
The unsteady motion of a sphere in a viscoelastic fluid
DEFF Research Database (Denmark)
Becker, L.E.; McKinley, G. H.; Rasmussen, Henrik K.
1994-01-01
The motion of a sphere accelerating from rest along the center line of a cylindrical tube filled with a polyisobutylene (PIB) Boger fluid is examined both experimentally, using a digital imaging system, and numerically via a Lagrangian finite element method for single and multimode Oldroyd models...
Simple liquids’ quasiuniversality and the hard-sphere paradigm
DEFF Research Database (Denmark)
Dyre, Jeppe C.
2016-01-01
This topical review discusses the quasiuniversality of simple liquids' structure and dynamics and two possible justifications of it. The traditional one is based on the van der Waals picture of liquids in which the hard-sphere system reflects the basic physics. An alternative explanation argues t...
Simple liquids' quasiuniversality and the hard-sphere paradigm
DEFF Research Database (Denmark)
Dyre, Jeppe C.
This presentation reflects on the well-known quasiuniversality of simple liquids’ structure and dynamics [1, 2, 3, 4, 5]. We discuss two possible justifications of it [6, 7]. The traditional one is based on the van der Waals picture of liquids in which the hard-sphere system reflects the basic ph...
Mesoscale organization of CuO nanoslices: Formation of sphere
Indian Academy of Sciences (India)
WINTEC
Mesoscale organization of CuO nanoslices. 195. Figure 4. Illustration of formation mechanism of the sphere. 3. Results and discussion. The structure and chemical composition of CuO sample synthesized in this work was confirmed by XRD method. As reported in figure 1, typical XRD pattern for the sam- ple is displayed.
Simulating colloids with Baxter's adhesive hard sphere model
Miller, M.A.; Frenkel, D.
2004-01-01
The structure of the Baxter adhesive hard sphere fluid is examined using computer simulation. The radial distribution function (which exhibits unusual discontinuities due to the particle adhesion) and static structure factor are calculated with high accuracy over a range of conditions and compared
Everyday political talk in the internet-based public sphere
Graham, Todd; Coleman, Stephen; Freelon, Deen
Ever since the advent of the Internet, political communication scholars have debated its potential to facilitate and support public deliberation as a means of revitalizing and extending the public sphere. Much of the debate has focused on the medium’s potential in offering communicative spaces that
Three-sphere swimmer in a nonlinear viscoelastic medium
Curtis, Mark P.
2013-04-10
A simple model for a swimmer consisting of three colinearly linked spheres attached by rods and oscillating out of phase to break reciprocal motion is analyzed. With a prescribed forcing of the rods acting on the three spheres, the swimming dynamics are determined analytically in both a Newtonian Stokes fluid and a zero Reynolds number, nonlinear, Oldroyd-B viscoelastic fluid with Deborah numbers of order one (or less), highlighting the effects of viscoelasticity on the net displacement of swimmer. For instance, the model predicts that the three-sphere swimmer with a sinusoidal, but nonreciprocal, forcing cycle within an Oldroyd-B representation of a polymeric Boger fluid moves a greater distance with enhanced efficiency in comparison with its motility in a Newtonian fluid of the same viscosity. Furthermore, the nonlinear contributions to the viscoelastic constitutive relation, while dynamically nontrivial, are predicted a posteriori to have no effect on swimmer motility at leading order, given a prescribed forcing between spheres. © 2013 American Physical Society.
Phase diagram of the adhesive hard sphere fluid
Miller, M.A.; Frenkel, D.
2004-01-01
The phase behavior of the Baxter adhesive hard sphere fluid has been determined using specialized Monte Carlo simulations. We give a detailed account of the techniques used and present data for the fluid–fluid coexistence curve as well as parametrized fits for the supercritical equation of state and
Magnetohydraulic flow through a packed bed of electrically conducting spheres
International Nuclear Information System (INIS)
Sanders, T.L.
1985-01-01
The flow of an electrically conducting fluid through a packed bed of electrically conducting spheres in the presence of a strong magnetic field constitutes a very complex flow situation due to the constant turning of the fluid in and out of magnetic field lines. The interaction of the orthogonal components of the velocity and magnetic field will induce electric fields that are orthogonal to both and the electric fields in turn can cause currents that interact with the magnetic field to generate forces against the direction of flow. The strengths of these generated forces depend primarily upon the closure paths taken by the induced currents which, in turn, depend upon the relative ratio of the electrical resistance of the solid spheres to that of the fluid. Both experimental and analytical analyses of the slow flow of a eutectic mixture of sodium and potassium (NaK) through packed cylinders containing stainless steel spheres in the presence of a strong transverse magnetic field were completed. A theory of magnetohydraulic flow is developed by analogy with the development of hydraulic radius theories of flow through porous media. An exact regional analysis is successfully applied to an infinite bed of electrically conducting spheres with a conducting or non-conducting constraining wall on one side. The equations derived are solved for many different combinations of flowrate, magnetic field strength, porosity, and electrical resistance ratio
Scattering of linearly polarized Bessel beams by dielectric spheres
Shoorian, Hamed
2017-09-01
The scattering of a Linearly Polarized Bessel Beam (LPBB) by an isotropic and homogenous dielectric sphere is investigated. Using analytical relation between the cylindrical and the spherical vector wave functions, all the closed- form analytical expressions, in terms of spherical wave-functions expansions, are derived for the scattered field. It is shown that in the case of conical angle of incident Bessel beam is equal to zero, the Linearly Polarized Bessel Beam becomes a plane wave and its scattering coefficients become the same as the expansion coefficients of plane wave in Mie theory. The transverse Cartesian and spherical components of the electric field, scattered by a sphere are shown in the z-plane for different cases, moreover the intensity of the incident Bessel beam and the effects of its conical angle on the scattered field and the field inside the sphere are investigated. To quantitatively study the scattering phenomenon and the variations of the fields inside and outside of the sphere, the scattering and absorption efficiencies are obtained for the scattering of the linearly-polarized Bessel beam, and are compared with those of the plane wave scattering.
Consolidation of metallic hollow spheres by electric sintering
Mironov, V.; Tatarinov, A.; Lapkovsky, V.
2017-07-01
This paper considers peculiarities of the technology of production of structures from metallic hollow spheres (MHS) using magnetic fields and electric sintering. In these studies, the raw material was MHS obtained by burning of polystyrene balls coated by carbon steel. MHS had an outer diameter of 3-5 mm and a steel wall thickness of 70-120 microns. Pulsed current generators were used for electric sintering of MHS to obtain different spatial structures. Since MHS have small strength, the compressive pressure during sintering should be minimal. To improve the adhesion strength and reduce the required energy for sintering, hollow spheres were coated with copper by ion-plasma sputtering in vacuum. The coating thickness was 10-15 microns. The ferromagnetic properties of MHS allowed using of magnet fields for orientation of the spheres in the structures, as well as using of perforated tapes acting as orienting magnetic cores. Ultrasonic testing of MHS structures has been tried using through propagation of ultrasound in low kilohertz frequency range. Sensitivity of the propagation parameters to water filling of inter-spheres space and sintering temperature was demonstrated.
Axioms of spheres in lightlike geometry of submanifolds
Indian Academy of Sciences (India)
In [7], Kumar et al. studied the axioms of spheres and planes for indefinite Riemannian manifolds having lightlike submanifolds. Yano and Mogi [10] generalized the concept of axioms of planes for Riemannian mani- folds to the axioms of holomorphic planes for Kaehler manifolds. The same conclusion prevails for a Kaehler ...
Exact anisotropic sphere with polytropic equation of state
Indian Academy of Sciences (India)
self-gravitating, static, isotropic fluid spheres when pressure explicitly depends on matter density, which invariably leads to non-integrable equations [32]. However, our treatment of anisotropic fluids with polytropic equation of state gets some flexibility in solving the. Einstein field equations with uncharged matter in static ...
Amidinate Ligands in Zinc coordination sphere: Synthesis and ...
Indian Academy of Sciences (India)
Amidinate Ligands in Zinc coordination sphere: Synthesis and structural diversity. SRINIVAS ANGA, INDRANI BANERJEE and TARUN K PANDA. ∗. Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi 502 285,. Sangareddy, Telangana, India e-mail: tpanda@iith.ac.in. MS received 25 February 2016; ...
Absorption of continuum radiation in a resonant expanding gaseous sphere
International Nuclear Information System (INIS)
Shaparev, N Y
2014-01-01
The paper deals with absorption of external continuum radiation in a self-similarly expanding gaseous sphere. Frequency probability and integral probability of radiation absorption in the resonance frequency range are determined depending on the expansion velocity gradient and thickness of the optical medium. It is shown that expansion results in a reduced optical thickness of the medium and enhanced integral absorption. (paper)
Hard sphere colloidal dispersions: Mechanical relaxation pertaining to thermodynamic forces
Mellema, J.; de Kruif, C.G.; Blom, C.; Vrij, A.
1987-01-01
The complex viscosity of sterically stabilized (hard) silica spheres in cyclohexane has been measured between 80 Hz and 170 kHz with torsion pendulums and a nickel tube resonator. The observed relaxation behaviour can be attributed to the interplay of hydrodynamic and thermodynamic forces. The
The Perception of Community Radio as Public Sphere and its ...
African Journals Online (AJOL)
Levi Manda
engage in public issue debates in a rational-critical fashion, then guide state actions. Thus, the public sphere ... local sports; not crime in general but crime in the community” (p. 33). The democratic decision-making ... production of content to distribution and consumption of programming, each of which accounts for its social ...
Interrogating Public Sphere and Popular Culture as Theoretical ...
African Journals Online (AJOL)
Because of its theoretical roots in Western liberal thinking, scholars in African studies such as Comaroffs, Mamdani and Ekeh have vigorously debated the extent to which the concept of civil society is useful in explaining and interrogating developments in Africa. However, the concept of the public sphere has been subjected ...
Ion Mobility Spectrometry (IMS) and Mass Spectrometry
Energy Technology Data Exchange (ETDEWEB)
Shvartsburg, Alexandre A.
2010-04-20
In a media of finite viscosity, the Coulomb force of external electric field moves ions with some terminal speed. This dynamics is controlled by “mobility” - a property of the interaction potential between ions and media molecules. This fact has been used to separate and characterize gas-phase ions in various modes of ion mobility spectrometry (IMS) developed since 1970. Commercial IMS devices were introduced in 1980-s for field detection of volatile traces such as explosives and chemical warfare agents. Coupling to soft-ionization sources, mass spectrometry (MS), and chromatographic methods in 1990-s had allowed IMS to handle complex samples, enabling new applications in biological and environmental analyses, nanoscience, and other areas. Since 2003, the introduction of commercial systems by major instrument vendors started bringing the IMS/MS capability to broad user community. The other major development of last decade has been the differential IMS or “field asymmetric waveform IMS” (FAIMS) that employs asymmetric time-dependent electric field to sort ions not by mobility itself, but by the difference between its values in strong and weak electric fields. Coupling of FAIMS to conventional IMS and stacking of conventional IMS stages have enabled two-dimensional separations that dramatically expand the power of ion mobility methods.
Chemical flowsheet conditions for preparing urania spheres by internal gelation
International Nuclear Information System (INIS)
Haas, P.A.; Begovich, J.M.; Ryon, A.D.; Vavruska, J.S.
1979-01-01
Small, ceramic urania spheres can be prepared for use as nuclear fuel by internal chemical gelation of uranyl nitrate solution droplets. Decomposition of hexamethylenetetramine (HMTA) dissolved in the uranyl nitrate solution releases ammonia to precipitate hydrated UO 3 . Previously established flowsheet conditions have been improved and modified at ORNL and have been applied to prepare dense UO 2 spheres with average diameters of 1200, 300, and 30 μm. Acid-deficient uranyl nitrate (ADUN) solutions up to 3.4 M in uranium with NO 3 - /U mole ratios of 1.5 to 1.7 are prepared by dissolution of U 3 O 8 or UO 3 . Continuous mixing of metered, cooled ADUN containing urea and HMTA solutions provides a smooth, regulated flow of the temperature-sensitive feed solution. The gelation times for solution drops in organic liquids at 45 to 95 0 C depend on both the chemical reaction rates and the rates of heat transfer. The gel properties vary with temperature and other gelation variables. Gelation conditions were determined which allow easy washing, drying, firing, and sintering to produce dense UO 2 spheres of all three sizes. The 1200- and 300-μm UO 2 spheres were pepared by gelation in trichloroethylene at 50 to 65 0 C; 2-ethyl-l-hexanol was used as the gelation medium to prepare 30-μm UO 2 spheres. Washing and drying requirements were determined. The gel dried to 225 0 C contains about 95% UO 3 ; the remaining components are H 2 O, NH 3 - , which are volatilized during firing to UO 2
International Nuclear Information System (INIS)
Zhu, Qingjun; Song, Fengquan; Ren, Jie; Chen, Xueyong; Zhou, Bin
2014-01-01
To further expand the application of an artificial neural network in the field of neutron spectrometry, the criteria for choosing between an artificial neural network and the maximum entropy method for the purpose of unfolding neutron spectra was presented. The counts of the Bonner spheres for IAEA neutron spectra were used as a database, and the artificial neural network and the maximum entropy method were used to unfold neutron spectra; the mean squares of the spectra were defined as the differences between the desired and unfolded spectra. After the information entropy of each spectrum was calculated using information entropy theory, the relationship between the mean squares of the spectra and the information entropy was acquired. Useful information from the information entropy guided the selection of unfolding methods. Due to the importance of the information entropy, the method for predicting the information entropy using the Bonner spheres' counts was established. The criteria based on the information entropy theory can be used to choose between the artificial neural network and the maximum entropy method unfolding methods. The application of an artificial neural network to unfold neutron spectra was expanded. - Highlights: • Two neutron spectra unfolding methods, ANN and MEM, were compared. • The spectrum's entropy offers useful information for selecting unfolding methods. • For the spectrum with low entropy, the ANN was generally better than MEM. • The spectrum's entropy was predicted based on the Bonner spheres' counts
Pan, Jia Hong; Bai, Yuqing; Wang, Qing
2015-04-21
Despite the significant progress in developing various synthetic strategies for metal oxide hollow spheres (h-MO), the so-far explored materials are mostly chemically inert metal oxides. Very few attempts have been made for amphoteric metal oxides such as Al2O3 and ZnO due to the difficulties in the control of the dissolution and recrystallization process. Herein, a facile self-template route to the synthesis of amphoteric h-MO with tunable size and shell thickness is developed by targeted etching via an acid-base reaction. With the protection of polyvinylpyrrolidone (PVP) on the surface, the interior of metal oxide solid colloidal spheres (c-MOs) that possess radially divergent structures could be selectively etched with acid/alkali as an etchant, forming h-MO of Al2O3 and ZnO. Our results also show that a wide variety of metal oxide colloidal spheres can be potential self-templates for targeted etching, which paves the way for developing a generalized strategy for the synthesis of various metal oxide hollow spheres.
Inner-Sphere versus Outer-Sphere Coordination of BF4– in a NHC-Gold(I) Complex
Veenboer, Richard M. P.
2017-07-20
The role of counterions in chemistry mediated by gold complexes stretches much further than merely providing charge balance to cationic gold species. Interplay between their basicities and coordination strengths influences interactions with both the gold center and substrates in catalysis. Actual monogold(I) active species are generally believed to be monocoordinated species, formed from the abstraction or the decoordination of a second ligand from precursor complexes, but only a small amount of experimental evidence exists to underpin the existence of these transient species. The formation of a bench-stable neutral IPrCl-gold(I) tetrafluoroborate complex is reported herein. Experimental studies by X-ray diffraction analysis and NMR spectroscopy and theoretical studies by DFT calculations were conducted to determine the composition, structure, and behavior of this complex. The absence of an auxiliary ligand resulted in inner-sphere coordination of the counterion in the solid state. In solution, an equilibrium between two conformations was found with the counterion occupying inner-sphere and outer-sphere positions, respectively. Stoichiometric and catalytic reactivity studies with the tetrafluoroborate complex have been conducted. These confirmed the lability of the inner-sphere coordinating counterion that gives the IPrCl-gold(I) fragment behavior similar to that of related systems.
Fourier Transform Mass Spectrometry.
Gross, Michael L.; Rempel, Don L.
1984-01-01
Discusses the nature of Fourier transform mass spectrometry and its unique combination of high mass resolution, high upper mass limit, and multichannel advantage. Examines its operation, capabilities and limitations, applications (ion storage, ion manipulation, ion chemistry), and future applications and developments. (JN)
Miniaturization and Mass Spectrometry
le Gac, S.; le Gac, Severine; van den Berg, Albert; van den Berg, A.; Unknown, [Unknown
2009-01-01
With this book we want to illustrate how two quickly growing fields of instrumentation and technology, both applied to life sciences, mass spectrometry and microfluidics (or microfabrication) naturally came to meet at the end of the last century and how this marriage impacts on several types of
DEFF Research Database (Denmark)
Osinalde, Nerea; Aloria, Kerman; Omaetxebarria, Miren J.
2017-01-01
biological processes in the cell and it is one the most characterized PTM up to date. During the last decade, the development of phosphoprotein/phosphopeptide enrichment strategies and mass spectrometry (MS) technology has revolutionized the field of phosphoproteomics discovering thousands of new site...
Dual Smarandache Curves of a Timelike Curve lying on Unit dual Lorentzian Sphere
Kahraman, Tanju; Hüseyin Ugurlu, Hasan
2016-01-01
In this paper, we give Darboux approximation for dual Smarandache curves of time like curve on unit dual Lorentzian sphere. Firstly, we define the four types of dual Smarandache curves of a timelike curve lying on dual Lorentzian sphere.
Casimir interaction between spheres in (D+1)-dimensional Minkowski spacetime
Energy Technology Data Exchange (ETDEWEB)
Teo, L.P. [Department of Applied Mathematics, Faculty of Engineering, University of Nottingham Malaysia Campus, Jalan Broga, 43500, Semenyih, Selangor Darul Ehsan (Malaysia)
2014-05-06
We consider the Casimir interaction between two spheres in (D+1)-dimensional Minkowski spacetime due to the vacuum fluctuations of scalar fields. We consider combinations of Dirichlet and Neumann boundary conditions. The TGTG formula of the Casimir interaction energy is derived. The computations of the T matrices of the two spheres are straightforward. To compute the two G matrices, known as translation matrices, which relate the hyper-spherical waves in two spherical coordinate frames differ by a translation, we generalize the operator approach employed in R.C. Wittman, Spherical Wave Operators and the Translation Formulas, IEEE Trans. Antennas Propag. 36 (1988) 1078. . The result is expressed in terms of an integral over Gegenbauer polynomials. In contrast to the D=3 case, we do not re-express the integral in terms of 3j-symbols and hyper-spherical waves, which in principle, can be done but does not simplify the formula. Using our expression for the Casimir interaction energy, we derive the large separation and small separation asymptotic expansions of the Casimir interaction energy. In the large separation regime, we find that the Casimir interaction energy is of order L{sup −2D+3}, L{sup −2D+1} and L{sup −2D−1} respectively for Dirichlet-Dirichlet, Dirichlet-Neumann and Neumann-Neumann boundary conditions, where L is the center-to-center distance of the two spheres. In the small separation regime, we confirm that the leading term of the Casimir interaction agrees with the proximity force approximation, which is of order d{sup −((D+1)/2)}, where d is the distance between the two spheres. Another main result of this work is the analytic computations of the next-to-leading order term in the small separation asymptotic expansion. This term is computed using careful order analysis as well as perturbation method. In the case the radius of one of the sphere goes to infinity, we find that the results agree with the one we derive for sphere-plate configuration
Finite Element in Angle Unit Sphere Meshing for Charged Particle Transport.
Energy Technology Data Exchange (ETDEWEB)
Ortega, Mario Ivan [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Drumm, Clifton R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2017-10-01
Finite element in angle formulations of the charged particle transport equation require the discretization of the unit sphere. In Sceptre, a three-dimensional surface mesh of a sphere is transformed into a two-dimensional mesh. Projection of a sphere onto a two-dimensional surface is well studied with map makers spending the last few centuries attempting to create maps that preserve proportion and area. Using these techniques, various meshing schemes for the unit sphere were investigated.
Motion of a sphere in an oscillatory boundary layer: an optical ...
Indian Academy of Sciences (India)
Shankar Ghosh
2006-11-12
Nov 12, 2006 ... Introduction. WATER. Strong distortion of motion of the sphere at high frequencies. GLYCEROL. Motion of the sphere is sinusoidal and monochromatic. Shankar Ghosh. Motion of a sphere in an oscillatory boundary layer: an optical tweezer based study ...
Electric field of not completely symmetric systems earthed sphere-uniformly charged dielectric plan
International Nuclear Information System (INIS)
Vila, F.
1994-07-01
In this paper we study theoretically the electric field in the not completely symmetric system, earthed metallic sphere-uniformly charged dielectric plan, for sphere surface points situated in the plan that contains sphere's center and vertical symmetry axe of dielectric plan. (author). 11 refs, 1 fig
From “Threads” to Threats: Religion, the Public Sphere, and Why ...
African Journals Online (AJOL)
The first part of this article is a theoretical exploration of the use and understanding of the term religion; the notion of the public sphere according to Jürgen Habermas; the media as public sphere; and finally, religion in the media as public sphere. By way of using, but also contesting, Habermas's and other theories of media ...
Random close packing of hard spheres and disks
International Nuclear Information System (INIS)
Berryman, J.G.
1983-01-01
A simple definition of random close packing of hard spheres is presented, and the consequences of this definition are explored. According to this definition, random close packing occurs at the minimum packing fraction eta for which the median nearest-neighbor radius equals the diameter of the spheres. Using the radial distribution function at more dilute concentrations to estimate median nearest-neighbor radii, lower bounds on the critical packing fraction eta/sub RCP/ are obtained and the value of eta/sub RCP/ is estimated by extrapolation. Random close packing is predicted to occur for eta/sub RCP/ = 0.64 +- 0.02 in three dimensions and eta/sub RCP/ = 0.82 +- 0.02 in two dimensions. Both of these predictions are shown to be consistent with the available experimental data
Signal Analysis by Generalized Hilbert Transforms on the Unit Sphere
International Nuclear Information System (INIS)
Wietzke, Lennart; Fleischmann, Oliver; Sommer, Gerald
2008-01-01
In 1D signal processing local energy and phase can be determined by the analytic signal. Local energy, phase and orientation of 2D signals can be analyzed by the monogenic signal for all i(ntrinsic)1D signals in an rotational invariant way by the generalized Hilbert transform. In order to analyze both i1D and i2D signals in one framework the main idea of this contribution is to lift up 2D signals to the higher dimensional conformal space in which the original signal can be analyzed with more degrees of freedom by the generalized Hilbert transform on the unit sphere. An appropriate embedding of 2D signals on the unit sphere results in an extended feature space spanned by local energy, phase, orientation/direction and curvature. In contrast to classical differential geometry, local curvature can now be determined by the generalized Hilbert transform in monogenic scale space without any derivatives.
Optimum radars and filters for the passive sphere system
Luers, J. K.; Soltes, A.
1971-01-01
Studies have been conducted to determine the influence of the tracking radar and data reduction technique on the accuracy of the meteorological measurements made in the 30 to 100 kilometer altitude region by the ROBIN passive falling sphere. A survey of accuracy requirements was made of agencies interested in data from this region of the atmosphere. In light of these requirements, various types of radars were evaluated to determine the tracking system most applicable to the ROBIN, and methods were developed to compute the errors in wind and density that arise from noise errors in the radar supplied data. The effects of launch conditions on the measurements were also examined. Conclusions and recommendations have been made concerning the optimum tracking and data reduction techniques for the ROBIN falling sphere system.
CFD simulation of dimpled sphere and its wind tunnel verification
Directory of Open Access Journals (Sweden)
Spálenský Vojtěch
2017-01-01
Full Text Available Paper deals with problems of CFD simulating airflow over a dimpled spherical surface and its verification by the wind tunnel measurement. The low-cost simulation approach was applied to be run on a common PC using the commercial software ANSYS CFX. The wind tunnel testing has been performed in the laboratory of aerodynamics at the Department of Air Force and Aircraft Technology of the University of Defence. Measured results of the drag coefficient versus the Reynolds number for smooth and dimpled spheres were compared and discussed. Presented simulation corresponds adequately to the experimental results. It can be stated that the CFD simulation is suitable for simulating the flow over the dimpled surfaces similar to sphere.
Charged-soft-sphere potentials for trivalent metal halides
International Nuclear Information System (INIS)
Erbolukbas, A.; Akdeniz, Z.; Tosi, M.P.
1991-09-01
Octahedral-type coordination by halogens in the liquid state has been reported for a number of trivalent metal ions from diffraction and Raman scattering experiments on their molten trihalides and from Raman scattering spectroscopy of liquid mixtures of trihalides with alkali halides. We analyze the available data on bond lengths and Raman frequencies by treating an isolated (MX 6 ) 3- species within a model which adopts charged-soft-sphere interionic potentials supplemented by an account of ionic polarization. The trivalent metal ions that we consider are M = La, Ce, Pr, Nd, Sm, Gd, Dy and Y for X = Cl and M = Al for X = F. The main result of the analysis is the prediction of trends in the soft-sphere repulsive parameters for the trivalent metal ions, leading to estimates of all the vibrational frequencies and the binding energy of such octahedral species. (author). 26 refs, 1 fig., 4 tabs
Breeder fuel pellet fabrication from gel-sphere conversion
International Nuclear Information System (INIS)
McLemore, D.R.; Bennett, D.W.; Hart, P.E.; Norman, R.E.
1980-01-01
The development of automated nuclear fuel fabrication methods is the goal of the United States breeder reactor program and will form the technological basis for the future breeder reactor fuel supply. A major factor in achieving this goal is the development of remotely operated fuel fabrication equipment. The program schedule is to demonstrate the feasibility of automated pellet fuel fabrication and remote maintenance techniques by the mid-1980's. Development of major ceramic unit operations and the required computer control system is currently in the engineering testing stage. This report describes the planned program activities for evaluating the gel-sphere conversion process and demonstrating the fabrication of breeder fuel pellets from these gel-derived spheres
Analytic study of a rolling sphere on a rough surface
Directory of Open Access Journals (Sweden)
Olivia A. Florea
2016-11-01
Full Text Available In this paper it is realized an analytic study of the rolling’s sphere on a rough horizontal plane under the action of its own gravity. The necessities of integration of the system of dynamical equations of motion lead us to find a reference system where the motion equations should be transformed into simpler expressions and which, in the presence of some significant hypothesis to permit the application of some original methods of analytical integration. In technical applications, the bodies may have a free rolling motion or a motion constrained by geometrical relations in assemblies of parts and machine parts. This study involves a lot of investigations in the field of tribology and of applied dynamics accompanied by experiments. Multiple recordings of several trajectories of the sphere, as well as their treatment of images, also followed by statistical processing experimental data allowed highlighting a very good agreement between the theoretical findings and experimental results.
Hard sphere dynamics for normal and granular fluids.
Dufty, James W; Baskaran, Aparna
2005-06-01
A fluid of N smooth, hard spheres is considered as a model for normal (elastic collision) and granular (inelastic collision) fluids. The potential energy is discontinuous for hard spheres so that the pairwise forces are singular and the usual forms of Newtonian and Hamiltonian mechanics do not apply. Nevertheless, particle trajectories in the N particle phase space are well defined and the generators for these trajectories can be identified. The first part of this presentation is a review of the generators for the dynamics of observables and probability densities. The new results presented in the second part refer to applications of these generators to the Liouville dynamics for granular fluids. A set of eigenvalues and eigenfunctions of the generator for this Liouville dynamics system is identified in a special stationary representation. This provides a class of exact solutions to the Liouville equation that are closely related to hydrodynamics for granular fluids.
Radioembolization for hepatocellular carcinoma using TheraSphere®.
Ali, Safiyya Mohamed
2011-01-01
Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver. Radioembolization with yttrium-90 (Y90) microspheres is a new concept in radiation therapy for HCC. This review focuses on the indications, efficacy, side effects, and future direction of Y90 therapy, using TheraSphere® , in HCC patients. Comprehensive literature reviews have described the clinical and scientific evidence of Y90 therapy. The Radioembolization Brachytherapy Oncology Consortium has concluded that there is sufficient evidence to support the safe and effective use of this locoregional therapy in HCC patients, including those with portal vein thrombosis. There are currently no randomized clinical trials done on TheraSphere® and none of the studies so far have shown a survival benefit. Thus, although it represents a very promising therapy with excellent initial results, it cannot be fully recommended yet, till well-designed, large, randomized clinical studies are conducted showing survival benefits.
Creating learning opportunities for students with Science on a Sphere
Bates, Kara
2014-01-01
In many classrooms, teachers are looking for ways to increase student engagement. Disengaged students are not reaching their full potential and experience relatively high levels of anxiety and frustration, which negatively impacts learning. Providing multiple hands-on and problem-solving learning opportunities can increase student engagement. The new curriculum developed for use on the Science on a Sphere provides educators with a resource to create problem-solving learning opportunities in t...
Elastodynamic cloaking and field enhancement for soft spheres
Diatta, Andre; Guenneau, Sebastien
2016-11-01
We propose a spherical cloak described by a non-singular asymmetric elasticity tensor {C} depending upon a small parameter η, that defines the softness of a region one would like to conceal from elastodynamic waves. By varying η, we generate a class of soft spheres dressed by elastodynamic cloaks, which are shown to considerably reduce the scattering of the soft spheres. Importantly, such cloaks also provide some wave protection except for a countable set of frequencies, for which some large elastic field enhancement can be observed within the soft spheres. Through an investigation of trapped modes in elasticity, we supply a good approximation of such Mie-type resonances by some transcendental equation. Our results, unlike previous studies that focused merely on the invisibility aspects, shed light on potential pitfalls of elastodynamic cloaks for earthquake protection designed via geometric transforms: a seismic cloak needs to be designed in such a way that its inner resonances differ from eigenfrequencies of the building one wishes to protect. In order to circumvent this downfall of field enhancement inside the cloaked area, we introduce a novel generation of cloaks, named here, mixed cloaks. Such mixed cloaks consist of a shell that detours incoming waves, hence creating an invisibility region, and of a perfectly matched layer (PML, located at the inner boundary of the cloaks) that absorbs residual wave energy in such a way that aforementioned resonances in the soft sphere are strongly attenuated. The designs of mixed cloaks with a non-singular elasticity tensor combined with an inner PML and non-vanishing density bring seismic cloaks one step closer to a practical implementation. Note in passing that the concept of mixed cloaks also applies in the case of singular cloaks and can be translated in other wave areas for a similar purpose (i.e. to smear down inner resonances within the invisibility region).
Role of moving planes and moving spheres following Dupin cyclides
Jia, Xiaohong
2014-03-01
We provide explicit representations of three moving planes that form a μ-basis for a standard Dupin cyclide. We also show how to compute μ-bases for Dupin cyclides in general position and orientation from their implicit equations. In addition, we describe the role of moving planes and moving spheres in bridging between the implicit and rational parametric representations of these cyclides. © 2014 Elsevier B.V.
Upgrading the Investment Capacity of the Scientific Sphere in Ukraine
Directory of Open Access Journals (Sweden)
Burdonos Ludmila
2016-11-01
Full Text Available The article analyzes the effective system of distribution of public funds for investing into the sphere of science. Alternative factors of promoting cooperation with foreign subjects of scientific activity are determined. It is established that an important factor, determining the activity of research and development in the country, is the system of redistribution of financial risks from investing into research and development.
The public sphere, women and the casamance peace process
Directory of Open Access Journals (Sweden)
Irene N. Osemeka
2011-06-01
Full Text Available Las mujeres en la Casamance tradicionalmente se limita a la esfera privada como madres, esposas y los agricultores, mientras que algunos sacerdotes son mujeres. La naturaleza prolongada del conflicto de Casamance ha tenido efectos devastadores sobre la población civil, incluidas las mujeres. Pero también ha ofrecido oportunidades para que las mujeres contribuyan al proceso de paz lo que les empuja a la esfera pública, que de otro modo, es el dominio de los hombres. El documento se centra en los esfuerzos de reconciliación en la región de Casamance que muestra la relación entre la esfera pública, las mujeres y la resolución de conflictos. Asimismo, ofrecer soluciones que pueden conducir a un proceso más integrador, teniendo en cuenta el enfoque de exclusión de los esfuerzos de paz de Casamance, que ha contribuido significativamente a la imposibilidad de lograr una solución duradera al conflicto.Palabras claves: espacio público. Proceso de Paz.___________________________Abstract:Women in the Casamance are traditionally confined to the private sphere as mothers, wives and farmers while a few are female priests. The protracted nature of the Casamance conflict has had devastating effects on the civilian population including women. But it has also provided opportunities for women to contribute to the peace process thereby thrusting them into the public sphere, which otherwise, is the domain of men. The paper focuses on the reconciliatory efforts in the Casamance showing the link between the public sphere, women and the resolution of conflicts. It will also proffer solutions that can lead to a more inclusive process, taking into consideration the exclusionary approach of the Casamance peace efforts which has contributed significantly to the failure to achieve durable solution to the conflict.Keywords: Public Sphere. Peace Process.
Solvothermal synthesis of cobalt ferrite hollow spheres with chitosan.
Briceño, Sarah; Suarez, Jorge; Gonzalez, Gema
2017-09-01
Cobalt ferrite hollow spheres with chitosan (CoFe 2 O 4 /CS) were synthesized by two different approaches using the solvothermal method. The first approach involves in-situ incorporation of FeCl 3 :6H 2 O and CoNO 3 :6H 2 O in the solvothermal reaction (M1) and in second approach already prepared CoFe 2 O 4 nanoparticles (NPs) using the thermal decomposition method was placed in the solvothermal reaction to form the hollow spheres (M2). Structural identification of the samples were characterized by Fourier transform infrared spectra (FTIR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analyses (DSC-TGA) and energy dispersive X-ray spectroscopy (EDX). The magnetic properties were evaluated using a vibrating sample magnetometer (VSM). The presence of chitosan on the hollow sphere was confirmed by FTIR. The XRD analyses proved that the synthesized samples were cobalt ferrite with spinel structure. The structure of the surface and the average particle size of the spheres were observed by SEM and TEM showing the nano scale of the CoFe 2 O 4 component. Structural characterization demonstrating that chitosan does not affect the crystallinity, chemical composition, and magnetic properties of the CoFe 2 O 4 /CS. This work demonstrates that the CoFe 2 O 4 /CS prepared using the as synthesized CoFe 2 O 4 NPs have better structural and magnetic properties. Copyright © 2017 Elsevier B.V. All rights reserved.
Spectrophotometer-Integrating-Sphere System for Computing Solar Absorptance
Witte, William G., Jr.; Slemp, Wayne S.; Perry, John E., Jr.
1991-01-01
A commercially available ultraviolet, visible, near-infrared spectrophotometer was modified to utilize an 8-inch-diameter modified Edwards-type integrated sphere. Software was written so that the reflectance spectra could be used to obtain solar absorptance values of 1-inch-diameter specimens. A descriptions of the system, spectral reflectance, and software for calculation of solar absorptance from reflectance data are presented.
Regularity of optimal transport maps on multiple products of spheres
Figalli, Alessio; Kim, Young-Heon; McCann, Robert J.
2010-01-01
This article addresses regularity of optimal transport maps for cost="squared distance" on Riemannian manifolds that are products of arbitrarily many round spheres with arbitrary sizes and dimensions. Such manifolds are known to be non-negatively cross-curved [KM2]. Under boundedness and non-vanishing assumptions on the transfered source and target densities we show that optimal maps stay away from the cut-locus (where the cost exhibits singularity), and obtain injectivity and continuity of o...
Solar sphere viewed through the Skylab solar physics experiment
1973-01-01
The solar sphere viewed through the Skylab solar physics experiment (S082) Extreme Ultraviolet Spectroheliographis seen in this photographic reproduction taken from a color television transmission made by a TV camera aboard the Skylab space station in Earth orbit. The solar chromosphere and lower corona are much hotter than the surface of the Sun characterized by the white light emissions. This image was recorded during the huge solar prominence which occurred on August 21, 1973.
Satellite Relative Motion Control for MIT’s SPHERES Program
2012-03-01
verv iew 128 Desire(! Position...fi1CortrllAI[1Jrittrnto be lmplemerteCI on SPHERES Oli:puts F igu re B .2: E rror D eterm in ation O verv iew 129 Desired Translational States (Global Frame...lltl G) I • I Desired Pointing Vector Mag1 1 Eigenaxis of Rotation F igu re B .9: S p eed & P ath C on troller O verv iew 137 3-0
The Strategic Partnership between Russia and China in Educational Sphere
Directory of Open Access Journals (Sweden)
Lyu Tseya
2013-01-01
Full Text Available The paper is devoted to the scientific and educational cooperation of Russia and China. Over the last two decades it has developed dramatically due to the constant support of the countries’ leaders and resultedin a large number of agreements in scientific, technical, educational and cultural spheres. The partnership involves the joint research programs, training programs, scientific and educational activities, mutual support of academic mobility of teachers and students, international conferences, workshops, contests of innovative projects and students’ festivals. The research methodology combines general scientific methods of logicalcognition, analysis and synthesis, and statistic methods of selection, combination, comparison and generalization. The paper demonstrates the dynamics of Chinese students graduated in Russia from 1950 to 2013 and Russian students graduated in China in the last thirteen years, as well as therelated prognoses for 2020.The partnership between Russia and China in educational sphere has a strategic importance for economic stability and steady development of both countries in the nearest and distant future, given the globalization processes, complicated international situation, etc. However, there still remains a considerable potential for the reciprocal friendly cooperation in educational and cultural spheres. The author emphasizes a need for further exploration and development of the intellectual exchange mechanisms and effectiveness of the process.
Anisotropic fluid spheres of embedding class one using Karmarkar condition
Energy Technology Data Exchange (ETDEWEB)
Maurya, S.K. [University of Nizwa, Department of Mathematical and Physical Sciences, College of Arts and Science, Nizwa (Oman); Maharaj, S.D. [School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Astrophysics and Cosmology Research Unit, Private Bag X54001, Durban (South Africa)
2017-05-15
We obtain a new anisotropic solution for spherically symmetric spacetimes by analyzing the Karmarkar embedding condition. For this purpose we construct a suitable form of one of the gravitational potentials to obtain a closed form solution. This form of the remaining gravitational potential allows us to solve the embedding equation and integrate the field equations. The resulting new anisotropic solution is well behaved, which can be utilized to construct realistic static fluid spheres. Also we estimated the masses and radii of fluid spheres for LMC X-4, EXO 1785-248, PSR J1903+327 and 4U 1820-30 by using observational data set values. The masses and radii obtained show that our anisotropic solution can represent fluid spheres to a very good degree of accuracy. The physical validity of the solution depends on the parameter values of a, b and c. The solution is well behaved for the wide range of parameters values 0.00393 ≤ a ≤ 0.0055, 0.0002 ≤ b ≤ 0.0025 and 0.0107 ≤ c ≤ 0.0155. The range of corresponding physical parameters for the different compact stars are 0.3266 ≤ v{sub r0} ≤ 0.3708, 0.1583 ≤ v{sub t0} ≤ 0.2558, 0.3256 ≤ z{sub s} ≤ 0.4450 and 4.3587 ≤ Γ{sub 0} ≤ 5.6462. (orig.)
Inelastic accretion of inertial particles by a towed sphere
Vallée, Robin; Henry, Christophe; Hachem, Elie; Bec, Jérémie
2018-02-01
The problem of accretion of small particles by a sphere embedded in a mean flow is studied in the case where the particles undergo inelastic collisions with the solid object. The collision efficiency, which gives the flux of particles experiencing at least one bounce on the sphere, is found to depend upon the sphere Reynolds number only through the value of the critical Stokes number below which no collision occurs. In the absence of molecular diffusion, it is demonstrated that multiple bounces do not provide enough energy dissipation for the particles to stick to the surface within a finite time. This excludes the possibility of any kind of inelastic collapse, so that determining an accretion efficiency requires modeling more precisely particle-surface microphysical interactions. A straightforward choice is to assume that the particles stick when their kinetic energy at impact is below a threshold. In this view, numerical simulations are performed to describe the statistics of impact velocities at various values of the Reynolds number. Successive bounces are shown to enhance accretion. These results are put together to provide a general qualitative picture on how the accretion efficiency depends upon the nondimensional parameters of the problem.
Composite micro-sphere optical resonators for electric field measurement
Stubblefield, J.; Womack, D.; Ioppolo, T.; Ayaz, U.; Otugen, M. V.
2012-02-01
Polymer-based, multi-layered dielectric microspheres are investigated for high-resolution electric field sensing. The external electric field induces changes in the morphology of the spheres, leading to shifts in the whispering gallery modes (WGMs). Light from a distributed feedback (DFB) laser is sidecoupled into the microspheres using a tapered section of a single mode optical fiber to interrogate the optical modes. The base material of these multi-layered spheres is polydimethylsiloxane (PDMS). Three microsphere geometries are investigated: (1) cores comprised of a 60:1 volumetric ratio of PDMS-to-curing agent mixture that are mixed with varying amounts of barium titanate (BaTiO3) nano particles, (2) cores comprised of 60:1 PDMS that are coated with a thin layer of 60:1 PDMS that is mixed with varying amounts of barium titanate and (3) a composite Carbon Black-BaTiO3 prototype. The outermost layer for all sphere geometries is a thin coat of 60:1 PDMS which serves as the shell waveguide. Light from the tapered laser is coupled into this outermost shell that provides high optical quality factor WGM (Q ~ 106). The microspheres are poled for several hours at electric fields of ~ 1 MV/m to increase their sensitivity to electric field. Preliminary results show that electric fields of the order of 100 V/m can be detected using these composite micro-resonators.
The sphere-in-contact model of carbon materials.
Zeinalipour-Yazdi, Constantinos D; Pullman, David P; Catlow, C Richard A
2016-01-01
A sphere-in-contact model is presented that is used to build physical models of carbon materials such as graphite, graphene, carbon nanotubes and fullerene. Unlike other molecular models, these models have correct scale and proportions because the carbon atoms are represented by their atomic radius, in contrast to the more commonly used space-fill models, where carbon atoms are represented by their van der Waals radii. Based on a survey taken among 65 undergraduate chemistry students and 28 PhD/postdoctoral students with a background in molecular modeling, we found misconceptions arising from incorrect visualization of the size and location of the electron density located in carbon materials. Based on analysis of the survey and on a conceptual basis we show that the sphere-in-contact model provides an improved molecular representation of the electron density of carbon materials compared to other molecular models commonly used in science textbooks (i.e., wire-frame, ball-and-stick, space-fill). We therefore suggest that its use in chemistry textbooks along with the ball-and-stick model would significantly enhance the visualization of molecular structures according to their electron density. Graphical Abstract A sphere-in-contact model of C60-fullerene.
Platonic polyhedra tune the 3-sphere: harmonic analysis on simplices
International Nuclear Information System (INIS)
Kramer, Peter
2009-01-01
A spherical topological manifold of dimension n- 1 forms a prototile on its cover, the (n- 1)-sphere. The tiling is generated by the fixpoint-free action of the group of deck transformations. By a general theorem, this group is isomorphic to the first homotopy group. A basis for the harmonic analysis on the (n- 1)-sphere is given by the spherical harmonics that transform according to irreducible representations of the orthogonal group. Multiplicity and selection rules appear in the form of reduction of group representations. The deck transformations form a subgroup and so the representations of the orthogonal group can be reduced to those of this subgroup. Upon reducing to the identity representation of the subgroup, the reduced subset of spherical harmonics becomes periodic on the tiling and tunes the harmonic analysis on the (n-1)-sphere to the manifold. A particular class of spherical 3-manifolds arises from the Platonic polyhedra. The harmonic analysis on the Poincare dodecahedral 3-manifold was analyzed along these lines. For comparison we construct here the harmonic analysis on simplicial spherical manifolds of dimension n=1, 2, 3. Harmonic analysis can be applied to the cosmic microwave background observed in astrophysics. Selection rules found in this analysis can detect the multiple connectivity of spherical 3-manifolds on the space part of cosmic space-time.
AGEISM IN THE SPHERE OF HEALTH SUPPORT OF SENIOR CITIZENS
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Lola Vladimirovna Kolpina
2013-10-01
Full Text Available The paper based on the results of the focus group which includes a medical and social workers; the ageism’s problems of the elderly people in the spheres of medical care, social protection and security are discussed. It is proved that the display of ageism is more typical for the medical sphere; practice of ageism has moral, organizational and socio-economic aspects, in the sphere of social protect and ensuring the greatest risks of ageism are associated with high psychological stress on social workers, which is conditioned with the complexity of communication with the elderly people.Purpose. Sociological diagnostics displays ageism elderly people in health and social work in the Belgorod region.Methodology. To achieve this goal, in May 2013 we carried out a focus group composed of doctors, nurses and employees of social service agencies and security in the amount of 16 people.Results. Theoretical and empirical models of ageismPractical implications. Institutions of medical and social services, and educational institutions that train specialists of relevant specialties.DOI: http://dx.doi.org/10.12731/2218-7405-2013-7-24
Transnational Chinese Sphere in Singapore: Dynamics, Transformations and Characteristics
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Hong Liu
2012-01-01
Full Text Available Based upon an empirical analysis of Singaporean Chinese’s intriguing and changing linkages with China over the past half century, this paper suggests that multi-layered interactions between the Chinese diaspora and the homeland have led to the formulation of an emerging transnational Chinese social sphere, which has three main characteristics: First, it is a space for communication by ethnic Chinese abroad with their hometown/ homeland through steady and extensive flows of people, ideas, goods and capital that transcend the nation-state borders, although states also play an important role in shaping the nature and characteristics of these flows. Second, this transnational social sphere constitutes a dynamic interface between economy, politics and culture, which has contributed to creating a collective diasporic identity as well as social and business networks. Third, the key institutional mechanism of the transnational social sphere is various types of Chinese organizations – ranging from hometown associations to professional organizations – which serve as integral components of Chinese social and business networks.
Desorption in Mass Spectrometry.
Usmanov, Dilshadbek Tursunbayevich; Ninomiya, Satoshi; Chen, Lee Chuin; Saha, Subhrakanti; Mandal, Mridul Kanti; Sakai, Yuji; Takaishi, Rio; Habib, Ahsan; Hiraoka, Kenzo; Yoshimura, Kentaro; Takeda, Sen; Wada, Hiroshi; Nonami, Hiroshi
2017-01-01
In mass spectrometry, analytes must be released in the gas phase. There are two representative methods for the gasification of the condensed samples, i.e. , ablation and desorption. While ablation is based on the explosion induced by the energy accumulated in the condensed matrix, desorption is a single molecular process taking place on the surface. In this paper, desorption methods for mass spectrometry developed in our laboratory: flash heating/rapid cooling, Leidenfrost phenomenon-assisted thermal desorption (LPTD), solid/solid friction, liquid/solid friction, electrospray droplet impact (EDI) ionization/desorption, and probe electrospray ionization (PESI), will be described. All the methods are concerned with the surface and interface phenomena. The concept of how to desorb less-volatility compounds from the surface will be discussed.
Rutherford Backscattering Spectrometry
International Nuclear Information System (INIS)
Gyulai, J.
1981-02-01
The bases of Rutherford ion backscattering and its combination with channeling effect technique are reviewed. This combined method is recently referred to as Backscattering Spectrometry. The measurement of chemical compositions, the detection of crystal defects etc are dealt with. Comparison with other surface analysis methods is also given. The review was delivered as a lecture during the ''International School for Surface Physics'' (Varna, Bulgaria, Sep 18 - Oct 20, 1980). (author)
Mass spectrometry in oceanography
International Nuclear Information System (INIS)
Aggarwal, Suresh K.
2000-01-01
Mass spectrometry plays an important role in oceanography for various applications. Different types of inorganic as well as organic mass spectrometric techniques are being exploited world-wide to understand the different aspects of marine science, for palaeogeography, palaeoclimatology and palaeoecology, for isotopic composition and concentrations of different elements as well as for speciation studies. The present paper reviews some of the applications of atomic mass spectrometric techniques in the area of oceanography
Smart SPHERES: A Telerobotic Free-Flyer for Intravehicular Activities in Space
Fong, Terrence; Micire, Mark J.; Morse, Ted; Park, Eric; Provencher, Chris; To, Vinh; Wheeler, D. W.; Mittman, David; Torres, R. Jay; Smith, Ernest
2013-01-01
Smart SPHERES is a prototype free-flying space robot based on the SPHERES platform. Smart SPHERES can be remotely operated by astronauts inside a spacecraft, or by mission controllers on the ground. We developed Smart SPHERES to perform a variety of intravehicular activities (IVA), such as operations inside the International Space Station (ISS). These IVA tasks include environmental monitoring surveys (radiation, sound levels, etc.), inventory, and mobile camera work. In this paper, we first discuss the motivation for free-flying space robots. We then describe the development of the Smart SPHERES prototype, including avionics, software, and data communications. Finally, we present results of initial flight tests on-board the ISS.
Model of the absorbed dose on a small sphere into a gamma irradiation field
International Nuclear Information System (INIS)
Mangussi, J.
2009-01-01
Several models of the absorbed dose calculated as the energy deposited by the secondary electrons on a small volume sphere are presented. The calculations use the Compton scattering of a uniform photon beam in water, the photon attenuation and the electron stopping power are included. The sphere total absorbed dose is due to the stopping of the electrons generated in three regions: into the sphere volume, ahead and behind the sphere volume. Calculations are performed for spheres of different radius and placed at various depth of the vacuum - water interface. (author)
Initial Examination of Low Velocity Sphere Impact of Glass Ceramics
Energy Technology Data Exchange (ETDEWEB)
Morrissey, Timothy G [ORNL; Fox, Ethan E [ORNL; Wereszczak, Andrew A [ORNL; Ferber, Mattison K [ORNL
2012-06-01
This report summarizes US Army TARDEC sponsored work at Oak Ridge National Laboratory (ORNL) involving low velocity (< 30 m/s or < 65 mph) sphere impact testing of two materials from the lithium aluminosilicate family reinforced with different amounts of ceramic particulate, i.e., glass-ceramic materials, SCHOTT Resistan{trademark}-G1 and SCHOTT Resistan{trademark}-L. Both materials are provided by SCHOTT Glass (Duryea, PA). This work is a follow-up to similar sphere impact studies completed by the authors on PPG's Starphire{reg_sign} soda-lime silicate glass and SCHOTT BOROFLOAT{reg_sign} borosilicate glass. A gas gun or a sphere-drop test setup was used to produce controlled velocity delivery of silicon nitride (Si{sub 3}N{sub 4}) spheres against the glass ceramic tile targets. Minimum impact velocities to initiate fracture in the glass-ceramics were measured and interpreted in context to the kinetic energy of impact and the elastic property mismatch between sphere and target material. Quasistatic spherical indentation was also performed on both glass ceramics and their contact damage responses were compared to those of soda-lime silicate and borosilicate glasses. Lastly, variability of contact damage response was assessed by performing spherical indentation testing across the area of an entire glass ceramic tile. The primary observations from this low velocity (< 30 m/s or < 65 mph) testing were: (1) Resistan{trademark}-L glass ceramic required the highest velocity of sphere impact for damage to initiate. Starphire{reg_sign} soda-lime silicate glass was second best, then Resistan{trademark}-G1 glass ceramic, and then BOROFLOAT{reg_sign} borosilicate glass. (2) Glass-ceramic Resistan{trademark}-L also required the largest force to initiate ring crack from quasi-static indentation. That ranking was followed, in descending order, by Starphire{reg_sign} soda-lime silicate glass, Resistan{trademark}-G1 glass ceramic, and BOROFLOAT{reg_sign} borosilicate glass
Mass spectrometry with accelerators.
Litherland, A E; Zhao, X-L; Kieser, W E
2011-01-01
As one in a series of articles on Canadian contributions to mass spectrometry, this review begins with an outline of the history of accelerator mass spectrometry (AMS), noting roles played by researchers at three Canadian AMS laboratories. After a description of the unique features of AMS, three examples, (14)C, (10)Be, and (129)I are given to illustrate the methods. The capabilities of mass spectrometry have been extended by the addition of atomic isobar selection, molecular isobar attenuation, further ion acceleration, followed by ion detection and ion identification at essentially zero dark current or ion flux. This has been accomplished by exploiting the techniques and accelerators of atomic and nuclear physics. In 1939, the first principles of AMS were established using a cyclotron. In 1977 the selection of isobars in the ion source was established when it was shown that the (14)N(-) ion was very unstable, or extremely difficult to create, making a tandem electrostatic accelerator highly suitable for assisting the mass spectrometric measurement of the rare long-lived radioactive isotope (14)C in the environment. This observation, together with the large attenuation of the molecular isobars (13)CH(-) and (12)CH 2(-) during tandem acceleration and the observed very low background contamination from the ion source, was found to facilitate the mass spectrometry of (14)C to at least a level of (14)C/C ~ 6 × 10(-16), the equivalent of a radiocarbon age of 60,000 years. Tandem Accelerator Mass Spectrometry, or AMS, has now made possible the accurate radiocarbon dating of milligram-sized carbon samples by ion counting as well as dating and tracing with many other long-lived radioactive isotopes such as (10)Be, (26)Al, (36)Cl, and (129)I. The difficulty of obtaining large anion currents with low electron affinities and the difficulties of isobar separation, especially for the heavier mass ions, has prompted the use of molecular anions and the search for alternative
Vescovi, D.; Berzi, D.; Richard, P.; Brodu, N.
2014-05-01
We use existing 3D Discrete Element simulations of simple shear flows of spheres to evaluate the radial distribution function at contact that enables kinetic theory to correctly predict the pressure and the shear stress, for different values of the collisional coefficient of restitution. Then, we perform 3D Discrete Element simulations of plane flows of frictionless, inelastic spheres, sheared between walls made bumpy by gluing particles in a regular array, at fixed average volume fraction and distance between the walls. The results of the numerical simulations are used to derive boundary conditions appropriated in the cases of large and small bumpiness. Those boundary conditions are, then, employed to numerically integrate the differential equations of Extended Kinetic Theory, where the breaking of the molecular chaos assumption at volume fraction larger than 0.49 is taken into account in the expression of the dissipation rate. We show that the Extended Kinetic Theory is in very good agreement with the numerical simulations, even for coefficients of restitution as low as 0.50. When the bumpiness is increased, we observe that some of the flowing particles are stuck in the gaps between the wall spheres. As a consequence, the walls are more dissipative than expected, and the flows resemble simple shear flows, i.e., flows of rather constant volume fraction and granular temperature.
International Nuclear Information System (INIS)
Vescovi, D.; Berzi, D.; Richard, P.; Brodu, N.
2014-01-01
We use existing 3D Discrete Element simulations of simple shear flows of spheres to evaluate the radial distribution function at contact that enables kinetic theory to correctly predict the pressure and the shear stress, for different values of the collisional coefficient of restitution. Then, we perform 3D Discrete Element simulations of plane flows of frictionless, inelastic spheres, sheared between walls made bumpy by gluing particles in a regular array, at fixed average volume fraction and distance between the walls. The results of the numerical simulations are used to derive boundary conditions appropriated in the cases of large and small bumpiness. Those boundary conditions are, then, employed to numerically integrate the differential equations of Extended Kinetic Theory, where the breaking of the molecular chaos assumption at volume fraction larger than 0.49 is taken into account in the expression of the dissipation rate. We show that the Extended Kinetic Theory is in very good agreement with the numerical simulations, even for coefficients of restitution as low as 0.50. When the bumpiness is increased, we observe that some of the flowing particles are stuck in the gaps between the wall spheres. As a consequence, the walls are more dissipative than expected, and the flows resemble simple shear flows, i.e., flows of rather constant volume fraction and granular temperature
Triassico: A Sphere Positioning System for Surface Studies with IBA Techniques
Fontana, Cristiano L.; Doyle, Barney L.
We propose here a novel device, called the Triassico, to microscopically study the entire surface of millimeter-sized spheres. The sphere dimensions can be as small as 1 mm, and the upper limit defined only by the power and by the mechanical characteristics of the motors used. Three motorized driving rods are arranged so an equilateral triangle is formed by the rod's axes, on such a triangle the sphere sits. Movement is achieved by rotating the rods with precise relative speeds and by exploiting the friction between the sphere and the rods surfaces. The sphere can be held in place by gravity or by an opposing trio of rods. By rotating the rods with specific relative angular velocities, a net torque can be exerted on the sphere which then rotates. No repositioning of the sphere or of the motors is needed to cover the full surface with the investigating tools. An algorithm was developed to position the sphere at any arbitrary polar and azimuthal angle. The algorithm minimizes the number of rotations needed by the rods, in order to efficiently select a particular position on the sphere surface. A prototype Triassico was developed for the National Ignition Facility, of the Lawrence Livermore National Laboratory (Livermore, California, USA), as a sphere manipulation apparatus for ion microbeam analysis at Sandia National Laboratories (Albuquerque, NM, USA) of Xe-doped DT inertial confinement fusion fuel spheres. Other applications span from samples orientation, ball bearing manufacturing, or jewelry.
The onset of cavitation during the collision of a sphere with a wetted surface
Mansoor, Mohammad M.
2014-01-01
We investigate the onset of cavitation during the collision of a sphere with a solid surface covered with a layer of Newtonian liquid. The conventional theory dictates cavitation to initiate during depressurization, i.e. when the sphere rebounds from the solid surface. Using synchronized dual-view high-speed imaging, we provide conclusive experimental evidence that confirms this scenario- namely-that cavitation occurs only after the sphere makes initial contact with the solid surface. Similar to previous experimental observations for spheres released above the liquid surface, bubbles are formed on the sphere surface during entry into the liquid layer. These were found to squeeze radially outwards with the liquid flow as the sphere approached the solid surface, producing an annular bubble structure unrelated to cavitation. In contrast, spheres released below the liquid surface did not exhibit these patterns. © Springer-Verlag Berlin Heidelberg 2014.
Study on 14C content in post-irradiation graphite spheres of HTR-10
International Nuclear Information System (INIS)
Wang Shouang; Pi Yue; Xie Feng; Li Hong; Cao Jianzhu
2014-01-01
Since the production mechanism of the 14 C in spherical fuel elements was similar to that of fuel-free graphite spheres, in order to obtain the amount of 14 C in fuel elements and graphite spheres of HTR-10, the production mechanism of the 14 C in graphite spheres was studied. The production sources of the 14 C in graphite spheres and fuel elements were summarized, the amount of 14 C in the post-irradiation graphite spheres was calculated, the decomposition techniques of graphite spheres were compared, and experimental methods for decomposing the graphite spheres and preparing the 14 C sample were proposed. The results can lay the foundation for further experimental research and provide theoretical calculations for comparison. (authors)
Wake structures of two side by side spheres in a tripped boundary layer flow
Directory of Open Access Journals (Sweden)
Canli Eyüb
2014-03-01
Full Text Available Two independent spheres were placed in a side by side arrangement and flow structure in the wake region of the spheres was investigated with a Particle Image Velocimetry (PIV system when the spheres were in a boundary layer over a flat plate as a special case. Reynolds number was 5000 based on the sphere diameter which was 42.5 mm. Boundary layer was tripped 8mm away from the leading edge of the flat plate with a 5 mm trip wire. The thickness of the hydrodynamically developed boundary layer was determined as 63mm which was larger than the sphere diameter of D=42.5mm. Wake region of the spheres was examined from point of flow physics for the different sphere locations in the ranges of 0≤G/D ≤1.5 and 0≤S/D ≤1.5 where G and S were the distance between the spheres and the distance between the bottom point of the spheres and the flat plate surface, respectively. Depending on the different sphere locations, instantaneous and time averaged vorticity data, scalar values of time-averaged velocity components and their root mean square (rms values and time averaged vorticity data are presented in the study for the evaluation of wake region of the spheres. It is demonstrated that the gap between the two spheres and the interaction between the gap and the boundary layer greatly affects flow pattern, especially when spheres are located near to the flat plate surface, i.e. S/D=0.1 for 0≤G/D ≤1.5. Different distances between the spheres resulted in various flow patterns as the spheres were approached to the flat plate. The distance S/D=0.1 for all gap values has the strongest effect on the wake structures. Beyond G/D=1.0, the sphere wakes tend to be similar to single sphere case. The instantaneous vorticity fields of the side by side arrangements comprised wavy structures in higher level comparing to an individual sphere case. The gap flow intensifies the occurrence of small scale eddies in the wake region. The submersion rate of the spheres
A neutron spectrum unfolding computer code based on artificial neural networks
International Nuclear Information System (INIS)
Ortiz-Rodríguez, J.M.; Reyes Alfaro, A.; Reyes Haro, A.; Cervantes Viramontes, J.M.; Vega-Carrillo, H.R.
2014-01-01
The Bonner Spheres Spectrometer consists of a thermal neutron sensor placed at the center of a number of moderating polyethylene spheres of different diameters. From the measured readings, information can be derived about the spectrum of the neutron field where measurements were made. Disadvantages of the Bonner system are the weight associated with each sphere and the need to sequentially irradiate the spheres, requiring long exposure periods. Provided a well-established response matrix and adequate irradiation conditions, the most delicate part of neutron spectrometry, is the unfolding process. The derivation of the spectral information is not simple because the unknown is not given directly as a result of the measurements. The drawbacks associated with traditional unfolding procedures have motivated the need of complementary approaches. Novel methods based on Artificial Intelligence, mainly Artificial Neural Networks, have been widely investigated. In this work, a neutron spectrum unfolding code based on neural nets technology is presented. This code is called Neutron Spectrometry and Dosimetry with Artificial Neural networks unfolding code that was designed in a graphical interface. The core of the code is an embedded neural network architecture previously optimized using the robust design of artificial neural networks methodology. The main features of the code are: easy to use, friendly and intuitive to the user. This code was designed for a Bonner Sphere System based on a 6 LiI(Eu) neutron detector and a response matrix expressed in 60 energy bins taken from an International Atomic Energy Agency compilation. The main feature of the code is that as entrance data, for unfolding the neutron spectrum, only seven rate counts measured with seven Bonner spheres are required; simultaneously the code calculates 15 dosimetric quantities as well as the total flux for radiation protection purposes. This code generates a full report with all information of the unfolding
High-resolution plasma spectrometry
International Nuclear Information System (INIS)
Edelson, M.C.
1987-01-01
In this chapter, the authors consider the topic of high-resolution plasma spectrometry (HRPS). Several different experimental approaches to HRPS are reviewed, and the benefits derived from increased spectral resolution are discussed. Results from the scientific literature are presented, but no attempt is made to provide an encyclopedic review. The discussion is limited to plasma emission spectrometry and, in particular, to inductively coupled plasma-atomic emission spectrometry (ICP-AES)
Low Velocity Sphere Impact of a Borosilicate Glass
Energy Technology Data Exchange (ETDEWEB)
Morrissey, Timothy G [ORNL; Ferber, Mattison K [ORNL; Wereszczak, Andrew A [ORNL; Fox, Ethan E [ORNL
2012-05-01
This report summarizes US Army TARDEC sponsored work at Oak Ridge National Laboratory (ORNL) involving low velocity (< 30 m/s or < 65 mph) ball impact testing of Borofloat borosilicate glass, and is a follow-up to a similar study completed by the authors on Starphire soda-lime silicate glass last year. The response of the borosilicate glass to impact testing at different angles was also studied. The Borofloat glass was supplied by the US Army Research Laboratory and its tin-side was impacted or indented. The intent was to better understand low velocity impact response in the Borofloat. Seven sphere materials were used whose densities bracket that of rock: borosilicate glass, soda-lime silicate glass, silicon nitride, aluminum oxide, zirconium oxide, carbon steel, and a chrome steel. A gas gun or a ball-drop test setup was used to produce controlled velocity delivery of the spheres against the glass tile targets. Minimum impact velocities to initiate fracture in the Borofloat were measured and interpreted in context to the kinetic energy of impact and the elastic property mismatch between the seven sphere-Borofloat-target combinations. The primary observations from this low velocity (< 30 m/s or < 65 mph) testing were: (1) BS glass responded similarly to soda-lime silicate glass when spherically indented but quite differently under sphere impact conditions; (2) Frictional effects contributed to fracture initiation in BS glass when it spherically indented. This effect was also observed with soda-lime silicate glass; (3) The force necessary to initiate fracture in BS glass under spherical impact decreases with increasing elastic modulus of the sphere material. This trend is opposite to what was observed with soda-lime silicate glass. Friction cannot explain this trend and the authors do not have a legitimate explanation for it yet; (4) The force necessary to initiate contact-induced fracture is higher under dynamic conditions than under quasi-static conditions. That
Formal Variability of Terms in the Sphere of Network Technologies
Directory of Open Access Journals (Sweden)
Roman Viktorovich Deniko
2015-09-01
Full Text Available The article addresses the problem of formal variability of terms in the sphere of network terminology in the Russian language. The research is based on data from the Internet communication in the sphere of network technologies. Such formal variability types as graphical, phonemic, word building and complex (graphic and phonetic, morphologic and accentual are discussed in this article. The authors reveal the reasons for graphic variability of foreign origin terms making up the international terminological fund. These reasons cover such aspects as the use of graphics of source language and recipient language; the presence or absence of hyphenation, etc. It is determined that the phonemic variants of terms appear as a result of oral or written borrowings. The existence of such variants is also connected with the stage of their adaptation in the Russian language after borrowing. In this case the variants are related with soft or hard pronunciation of consonants. There are also some cases of phonemic variability on the graphic level. The complex variability is regarded as a part of active processes taking place in the modern Russian language, and these processes involve both native and foreign origin terms. The particular attention is paid to the word-building variants – word-building affixes the variability of which is peculiar of network technologies. The results of the research show that the variability of professional units belonging to the network technologies sublanguage is caused by the active process of borrowing of specialpurpose vocabulary into the Russian language. The process is due to the intensification of intercultural communication in the professional spheres.
Phylogeography by diffusion on a sphere: whole world phylogeography
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Remco Bouckaert
2016-09-01
Full Text Available Background Techniques for reconstructing geographical history along a phylogeny can answer many questions of interest about the geographical origins of species. Bayesian models based on the assumption that taxa move through a diffusion process have found many applications. However, these methods rely on diffusion processes on a plane, and do not take the spherical nature of our planet in account. Performing an analysis that covers the whole world thus does not take in account the distortions caused by projections like the Mercator projection. Results In this paper, we introduce a Bayesian phylogeographical method based on diffusion on a sphere. When the area where taxa are sampled from is small, a sphere can be approximated by a plane and the model results in the same inferences as with models using diffusion on a plane. For taxa sampled from the whole world, we obtain substantial differences. We present an efficient algorithm for performing inference in a Markov Chain Monte Carlo (MCMC algorithm, and show applications to small and large samples areas. We compare results between planar and spherical diffusion in a simulation study and apply the method by inferring the origin of Hepatitis B based on sequences sampled from Eurasia and Africa. Conclusions We describe a framework for performing phylogeographical inference, which is suitable when the distortion introduced by map projections is large, but works well on a smaller scale as well. The framework allows sampling tips from regions, which is useful when the exact sample location is unknown, and placing prior information on locations of clades in the tree. The method is implemented in the GEO_SPHERE package in BEAST 2, which is open source licensed under LGPL and allows joint tree and geography inference under a wide range of models.
Lazy orbits: An optimization problem on the sphere
Vincze, Csaba
2018-01-01
Non-transitive subgroups of the orthogonal group play an important role in the non-Euclidean geometry. If G is a closed subgroup in the orthogonal group such that the orbit of a single Euclidean unit vector does not cover the (Euclidean) unit sphere centered at the origin then there always exists a non-Euclidean Minkowski functional such that the elements of G preserve the Minkowskian length of vectors. In other words the Minkowski geometry is an alternative of the Euclidean geometry for the subgroup G. It is rich of isometries if G is "close enough" to the orthogonal group or at least to one of its transitive subgroups. The measure of non-transitivity is related to the Hausdorff distances of the orbits under the elements of G to the Euclidean sphere. Its maximum/minimum belongs to the so-called lazy/busy orbits, i.e. they are the solutions of an optimization problem on the Euclidean sphere. The extremal distances allow us to characterize the reducible/irreducible subgroups. We also formulate an upper and a lower bound for the ratio of the extremal distances. As another application of the analytic tools we introduce the rank of a closed non-transitive group G. We shall see that if G is of maximal rank then it is finite or reducible. Since the reducible and the finite subgroups form two natural prototypes of non-transitive subgroups, the rank seems to be a fundamental notion in their characterization. Closed, non-transitive groups of rank n - 1 will be also characterized. Using the general results we classify all their possible types in lower dimensional cases n = 2 , 3 and 4. Finally we present some applications of the results to the holonomy group of a metric linear connection on a connected Riemannian manifold.
Equilibrium and nonequilibrium dynamics of soft sphere fluids.
Ding, Yajun; Mittal, Jeetain
2015-07-14
We use computer simulations to test the freezing-point scaling relationship between equilibrium transport coefficients (self-diffusivity, viscosity) and thermodynamic parameters for soft sphere fluids. The fluid particles interact via the inverse-power potential (IPP), and the particle softness is changed by modifying the exponent of the distance-dependent potential term. In the case of IPP fluids, density and temperature are not independent variables and can be combined to obtain a coupling parameter to define the thermodynamic state of the system. We find that the rescaled coupling parameter, based on its value at the freezing point, can approximately collapse the diffusivity and viscosity data for IPP fluids over a wide range of particle softness. Even though the collapse is far from perfect, the freezing-point scaling relationship provides a convenient and effective way to compare the structure and dynamics of fluid systems with different particle softness. We further show that an alternate scaling relationship based on two-body excess entropy can provide an almost perfect collapse of the diffusivity and viscosity data below the freezing transition. Next, we perform nonequilibrium molecular dynamics simulations to calculate the shear-dependent viscosity and to identify the distinct role of particle softness in underlying structural changes associated with rheological properties. Qualitatively, we find a similar shear-thinning behavior for IPP fluids with different particle softness, though softer particles exhibit stronger shear-thinning tendency. By investigating the distance and angle-dependent pair correlation functions in these systems, we find different structural features in the case of IPP fluids with hard-sphere like and softer particle interactions. Interestingly, shear-thinning in hard-sphere like fluids is accompanied by enhanced translational order, whereas softer fluids exhibit loss of order with shear. Our results provide a systematic evaluation
Sample Preprocessing For Atomic Spectrometry
International Nuclear Information System (INIS)
Kim, Sun Tae
2004-08-01
This book gives descriptions of atomic spectrometry, which deals with atomic absorption spectrometry such as Maxwell-Boltzmann equation and Beer-Lambert law, atomic absorption spectrometry for solvent extraction, HGAAS, ETASS, and CVAAS and inductively coupled plasma emission spectrometer, such as basic principle, generative principle of plasma and device and equipment, and interferences, and inductively coupled plasma mass spectrometry like device, pros and cons of ICP/MS, sample analysis, reagent, water, acid, flux, materials of experiments, sample and sampling and disassembling of sample and pollution and loss in open system and closed system.
Mass spectrometry in clinical chemistry
International Nuclear Information System (INIS)
Pettersen, J.E.
1977-01-01
A brief description is given of the functional elements of a mass spectrometer and of some currently employed mass spectrometric techniques, such as combined gas chromatography-mass spectrometry, mass chromatography, and selected ion monitoring. Various areas of application of mass spectrometry in clinical chemistry are discussed, such as inborn errors of metabolism and other metabolic disorders, intoxications, quantitative determinations of drugs, hormones, gases, and trace elements, and the use of isotope dilution mass spectrometry as a definitive method for the establishment of true values for concentrations of various compounds in reference sera. It is concluded that mass spectrometry is of great value in clinical chemistry. (Auth.)
Extinction in finite perfect crystals: Case of a sphere
International Nuclear Information System (INIS)
Al Haddad, M.; Becker, P.
1990-01-01
The extinction factor in finite perfect crystals is calculated from pure dynamical theory. In particular, a detailed solution is proposed for a sphere, in which case the extinction factor depends on the Bragg angle θ and the parameter (R/Λ), where R is the radius of the crystal and Λ the extinction length. An approximate solution based on the Laue geometry is proposed and corrections to take care of the complex boundary conditions are presented. An expression easily usable in refinement programs is proposed that fits the exact value to better than 1%. (orig.)
Dynamical study of a polydisperse hard-sphere system
Nogawa, Tomoaki
2010-08-10
We study the interplay between the fluid-crystal transition and the glass transition of elastic sphere system with polydispersity using nonequilibrium molecular dynamics simulations. It is found that the end point of the crystal-fluid transition line, which corresponds to the critical polydispersity above which the crystal state is unstable, is on the glass transition line. This means that crystal and fluid states at the melting point becomes less distinguishable as polydispersity increases and finally they become identical state, i.e., marginal glass state, at critical polydispersity. © 2010 The American Physical Society.
WebSphere Application Server Step by Step
Cline, Owen; Van Sickel, Peter
2012-01-01
WebSphere Application Server (WAS) is complex and multifaceted middleware used by huge enterprises as well as small businesses. In this book, the authors do an excellent job of covering the many aspects of the software. While other books merely cover installation and configuration, this book goes beyond that to cover the critical verification and management process to ensure a successful installation and implementation. It also addresses all of the different packages-from Express to Network-so that no matter what size your company is, you will be able to successfully implement WAS V6. To de
Theory of amorphous packings of binary mixtures of hard spheres.
Biazzo, Indaco; Caltagirone, Francesco; Parisi, Giorgio; Zamponi, Francesco
2009-05-15
We extend our theory of amorphous packings of hard spheres to binary mixtures and more generally to multicomponent systems. The theory is based on the assumption that amorphous packings produced by typical experimental or numerical protocols can be identified with the infinite pressure limit of long-lived metastable glassy states. We test this assumption against numerical and experimental data and show that the theory correctly reproduces the variation with mixture composition of structural observables, such as the total packing fraction and the partial coordination numbers.
Charging changes contact composition in binary sphere packings.
Schella, André; Weis, Simon; Schröter, Matthias
2017-06-01
Equal volume mixtures of small and large polytetrafluorethylene spheres are shaken in an atmosphere of controlled humidity which allows one to also control their tribocharging. We find that the contact numbers are charge dependent: As the charge density of the beads increases, the number of same-type contacts decreases and the number of opposite-type contacts increases. This change is not caused by a global segregation of the sample. Hence, tribocharging can be a way to tune the local composition of a granular material.
Magnetic and Optical Properties of Submicron-Size Hollow Spheres
Directory of Open Access Journals (Sweden)
Hirofumi Yoshikawa
2010-02-01
Full Text Available Magnetic hollow spheres with a controlled diameter and shell thickness have emerged as an important class of magnetic nanomaterials. The confined hollow geometry and pronouncedly curved surfaces induce unique physical properties different from those of flat thin films and solid counterparts. In this paper, we focus on recent progress on submicron-size spherical hollow magnets (e.g., cobalt- and iron-based materials, and discuss the effects of the hollow shape and the submicron size on magnetic and optical properties.
Templated Sphere Phase Liquid Crystals for Tunable Random Lasing
Directory of Open Access Journals (Sweden)
Ziping Chen
2017-11-01
Full Text Available A sphere phase liquid crystal (SPLC composed of three-dimensional twist structures with disclinations among them exists between isotropic phase and blue phase in a very narrow temperature range, about several degrees centigrade. A low concentration polymer template is applied to improve the thermal stability of SPLCs and broadens the temperature range to more than 448 K. By template processing, a wavelength tunable random lasing is demonstrated with dye doped SPLC. With different polymer concentrations, the reconstructed SPLC random lasing may achieve more than 40 nm wavelength continuous shifting by electric field modulation.
Lie theory and control systems defined on spheres
Brockett, R. W.
1972-01-01
It is shown that in constructing a theory for the most elementary class of control problems defined on spheres, some results from the Lie theory play a natural role. To understand controllability, optimal control, and certain properties of stochastic equations, Lie theoretic ideas are needed. The framework considered here is the most natural departure from the usual linear system/vector space problems which have dominated control systems literature. For this reason results are compared with those previously available for the finite dimensional vector space case.
Experimental study and DEM simulation of granular flow through a new sphere discharge valve
International Nuclear Information System (INIS)
Zhang He; Li Tianjin; Huang Zhiyong; Gao Zhi; Qi Weiwei; Bo Hanliang
2015-01-01
Experiments and DEM simulation have been conducted to investigate the granular flow through a new type of sphere discharge valve. The new sphere discharge valve was based on the principle of angle of repose. The glass sphere was used in the granular discharge experiments. Experimental results showed that the relation between the averaging sphere discharge mass flow rate and the stroke of the sphere discharge valve were consisted of three zones, i.e. the idle stroke zone, linearly zone and orifice restriction zone. The Beverloo's law was suitable for the granular flow through multi-orifices in the orifice restriction zone. The variation of averaging sphere discharge mass flow rate with the stroke of the sphere discharge valve was described by Beverloo's law with the modification based on the stroke of the sphere discharge valve. DEM simulation results showed that the drained angle of repose during granular flow in the sphere storage vessel remained 23 degrees with different stroke of the sphere discharge valve. (authors)
Comparison of Flow Characteristics of Different Sphere Geometries Under the Free Surface Effect
Directory of Open Access Journals (Sweden)
Sahin B.
2013-04-01
Full Text Available Comparison of the experimental results of turbulent flow structures between a smooth sphere and a sphere with a vent hole, roughened, and o-ring is presented in the presence of a free-surface. Dye visualization and particle image velocimetry (PIV techniques were performed to examine effects of passive control methods on the sphere wake for Reynolds number Re = 5000 based on the sphere diameter with a 42.5mm in an open water channel. Instantaneous and time-averaged flow patterns in the wake region of the sphere were examined from point of flow physics for the different sphere locations in the range of 0≤h/D≤2.0 where h was the space between the top point of the sphere and the free surface. The ratio of ventilation hole to sphere diameter was 0.15, o-ring was located at 55° with a 2 mm from front stagnation point of the sphere and roughened surface was formed by means of totally 410 circular holes with a 3 mm diameter and around 2 mm depth in an equilateral triangle arrangement. The flow characteristics of instantaneous velocity vectors, vorticity contours, time-averaged streamline patterns, Reynolds stress correlations and streamwise and cross-stream velocity fluctuations for both the smooth and passively controlled sphere were interpreted.
Passive control of flow structure interaction between a sphere and free-surface
Directory of Open Access Journals (Sweden)
Akilli Huseyin
2012-04-01
Full Text Available Flow characteristics for both a smooth and a vented sphere such as velocity vectors, patterns of streamlines, vorticity contours, stream-wise fluctuations, cross-stream velocity fluctuations and Reynolds stress correlations between a sphere and free-surface for various submerged ratio at Re =5,000 are studied by using dye visualization and the particle image velocimetry technique. Passive control of flow structure interaction between sphere and free surface was examined by using a modified geometry which has a 15% sphere diameter hole passing through the sphere equator. Both of the spheres were separately placed beneath the free surface with different positions from touching to the free surface to two sphere diameters below the free surface. It is demonstrated that reattachment point of the separated flow to the free surface varies for both of the sphere cases as the sphere position alters vertically through the water flow while the flow structure for the vented sphere occurs considerably symmetrical due to forming of a pair of counter-rotating ring vortices.
Alpha spectrometry and secondary ion mass spectrometry of thorium
International Nuclear Information System (INIS)
Strisovska, Jana; Kuruc, Jozef; Galanda, Dusan; Matel, Lubomir; Velic, Dusan; Aranyosiova, Monika
2009-01-01
A sample of thorium content on steel discs was prepared by electrodeposition with a view to determining the natural thorium isotope. Thorium was determined by alpha spectrometry and by secondary ion mass spectrometry and the results of the two methods were compared
Nanoscience, nanotechnology and spectrometry
Energy Technology Data Exchange (ETDEWEB)
Adams, Freddy C. [Department of Chemistry, University of Antwerp, B-2610 Wilrijk (Belgium); Barbante, Carlo, E-mail: barbante@unive.it [Institute for the Dynamics of Environmental Processes — CNR, Venice (Italy); Department of Environmental Sciences, Informatics and Statistics, Ca' Foscari University, Venice (Italy)
2013-08-01
Nanoscience has outgrown its infancy, and nanotechnology has found important applications in our daily life — with many more to come. Although the central concepts of the nano world, namely the changes of particular physical properties on the length scale of individual atoms and molecules, have been known and developed for quite some time already, experimental advances since the 1980s and recognition of the potential of nanomaterials led to a genuine breakthrough of the inherently multidisciplinary nanoscience field. Analytical nanoscience and nanotechnology and especially the use of micro and nano electro mechanical systems, of the quantum dots and of mass spectrometry, currently provide one of the most promising avenues for developments in analytical science, derived from their two main fields of action, namely (a) the analysis of nano-structured materials and (b) their use as new tools for analysis. An overview is given of recent developments and trends in the field, highlighting the importance and point out future directions, while also touching drawbacks, such as emerging concerns about health and environmental issues. - Highlights: • We review the analysis of nano-structured materials. • Nano-structured materials can be used as new tools for analysis. • Use of nano electro mechanical systems, of quantum dots and of mass spectrometry • Nanotechnologies are among the most promising tools in analytical science.
Nanoscience, nanotechnology and spectrometry
International Nuclear Information System (INIS)
Adams, Freddy C.; Barbante, Carlo
2013-01-01
Nanoscience has outgrown its infancy, and nanotechnology has found important applications in our daily life — with many more to come. Although the central concepts of the nano world, namely the changes of particular physical properties on the length scale of individual atoms and molecules, have been known and developed for quite some time already, experimental advances since the 1980s and recognition of the potential of nanomaterials led to a genuine breakthrough of the inherently multidisciplinary nanoscience field. Analytical nanoscience and nanotechnology and especially the use of micro and nano electro mechanical systems, of the quantum dots and of mass spectrometry, currently provide one of the most promising avenues for developments in analytical science, derived from their two main fields of action, namely (a) the analysis of nano-structured materials and (b) their use as new tools for analysis. An overview is given of recent developments and trends in the field, highlighting the importance and point out future directions, while also touching drawbacks, such as emerging concerns about health and environmental issues. - Highlights: • We review the analysis of nano-structured materials. • Nano-structured materials can be used as new tools for analysis. • Use of nano electro mechanical systems, of quantum dots and of mass spectrometry • Nanotechnologies are among the most promising tools in analytical science
Axial acoustic radiation force on a sphere in Gaussian field
Energy Technology Data Exchange (ETDEWEB)
Wu, Rongrong; Liu, Xiaozhou, E-mail: xzliu@nju.edu.cn; Gong, Xiufen [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)
2015-10-28
Based on the finite series method, the acoustical radiation force resulting from a Gaussian beam incident on a spherical object is investigated analytically. When the position of the particles deviating from the center of the beam, the Gaussian beam is expanded as a spherical function at the center of the particles and the expanded coefficients of the Gaussian beam is calculated. The analytical expression of the acoustic radiation force on spherical particles deviating from the Gaussian beam center is deduced. The acoustic radiation force affected by the acoustic frequency and the offset distance from the Gaussian beam center is investigated. Results have been presented for Gaussian beams with different wavelengths and it has been shown that the interaction of a Gaussian beam with a sphere can result in attractive axial force under specific operational conditions. Results indicate the capability of manipulating and separating spherical spheres based on their mechanical and acoustical properties, the results provided here may provide a theoretical basis for development of single-beam acoustical tweezers.
Artificial black opal fabricated from nanoporous carbon spheres.
Yamada, Yuri; Ishii, Masahiko; Nakamura, Tadashi; Yano, Kazuhisa
2010-06-15
A nanocasting method via chemical vapor deposition of acetonitrile was successfully employed to fabricate porous carbon colloidal crystal using colloidal crystal from monodispersed mesoporous silica spheres (MMSS) as a sacrificial scaffold. The mesostructure as well as periodic arrays within (111) plane of MMSS were replicated for the carbon colloidal crystal (black opal) with the length scale in the centimeter range. Brilliant iridescent colors were clearly observed for the first time on the black carbon colloidal crystal fabricated from porous carbon spheres, and they changed dramatically in accordance with the observation angle, like natural black opals. Reflection spectra measurements based on 2D surface diffraction and Bragg diffraction in the mirror mode were conducted for the fabricated carbon periodic arrays. The periodicity in the (111) plane as well as in the direction perpendicular to the (111) plane of the colloidal crystal was evaluated by comparing the results obtained from these two measurements. It was found that the periodicity in the direction perpendicular to the (111) surface is not high for the obtained black carbon opal. On the other hand, the relationship between the incident angles and the peak wavelengths of the reflection spectra, collected in the condition where the incident light and the reflected light pass through in the same direction, is governed by an approximation based on 2D surface diffraction. The results imply that the origin of the iridescent colors on the fabricated black carbon opal is derived from the periodicity not in the direction perpendicular to the (111) plane but within the (111) plane.
Emotional Sphere in Elderly People: Age and Regional Differences
Directory of Open Access Journals (Sweden)
Shagidaeva A.B.
2014-08-01
Full Text Available We present a study of the negative aspects of the emotional sphere in elderly man: depression and loneliness. Empirical research was carried out in Moscow and Grozny involving elderly people living in families and in geriatric centers (201 subjects, as well as with middle-aged people (132 subjects. We used the following methods: Zung differential diagnosis of depressive states inventory in adaptation by T.I. Balachova and D. Russell and M. Ferguson Loneliness scale (UKL in adaptation by N.E. Vodopyanova. It is shown that at the present stage of development of society, middle-aged people already have quite high level of depression and pronounced sense of loneliness. We confirmed the hypothesis that the preservation of the negative aspects of the emotional sphere in elderly people is less dependent on the conditions of life at the micro level (family or gerontology center and more dependent from the living conditions at the macro level (socio-economic situation in the region. In Grozny, a city of more complex socio-economic situation, negative emotional states are more pronounced than in Moscow.
The Cognitive Modeling of Development of Tourism Sphere
Directory of Open Access Journals (Sweden)
Los Vita O.
2017-10-01
Full Text Available The article explores the inter-sectoral interaction in the tourism sphere, which is based on the application of cognitive modeling. The authors consider the interaction of powers (political environment, tourism (tourism business, business (socio-economic environment and ecology (ecological environment. The ecology is identified as the exceptional decisive factor in creating an enabling environment for the development of the market for tourism services. A static analysis of the cognitive model was carried out, which revealed 624 contours, of which 473 were stabilizing and 151 were destabilizing. Based on results of the systemic characterizations of the cognitive model, it was found that the interaction between the two sectors, tourism (tourist business and business (socio-economic environment needs special attention. A dynamic analysis of the built cognitive model was carried out using the method of impulse processes that helped to generate alternative scenarios for the development of tourism services. As a result, it has been found that increased investment in restaurant and hotel activities facilitates the increase in the level of development of market for tourism services for one period earlier than the increase in financing tourism sphere from the budget.
Ligand-mediated adhesive mechanics of two static, deformed spheres.
Sircar, Sarthok; Nguyen, Giang; Kotousov, Andrei; Roberts, Anthony J
2016-10-01
A self-consistent model is developed to investigate attachment/detachment kinetics of two static, deformable microspheres with irregular surface and coated with flexible binding ligands. The model highlights how the microscale binding kinetics of these ligands as well as the attractive/repulsive potential of the charged surface affects the macroscale static deformed configuration of the spheres. It is shown that in the limit of smooth, neutrally charged surface (i.e., the dimensionless inverse Debye length, [Formula: see text]), interacting via elastic binders (i.e., the dimensionless stiffness coefficient, [Formula: see text]) the adhesion mechanics approaches the regime of application of the JKR theory, and in this particular limit, the contact radius, R c , scales with the particle radius, R, according to the scaling law, [Formula: see text]. We show that static, deformed, highly charged, ligand-coated surface of micro-spheres exhibit strong adhesion. Normal stress distribution within the contact area adjusts with the binder stiffness coefficient, from a maximum at the center to a maximum at the periphery of the region. Although reported in some in vitro experiments involving particle adhesion, until now a physical interpretation for this variation of the stress distribution for deformable, charged, ligand-coated microspheres is missing. Surface roughness results in a diminished adhesion with a distinct reduction in the pull-off force, larger separation gap, weaker normal stress and limited area of adhesion. These results are in agreement with the published experimental findings.
Stability of barotropic vortex strip on a rotating sphere.
Sohn, Sung-Ik; Sakajo, Takashi; Kim, Sun-Chul
2018-02-01
We study the stability of a barotropic vortex strip on a rotating sphere, as a simple model of jet streams. The flow is approximated by a piecewise-continuous vorticity distribution by zonal bands of uniform vorticity. The linear stability analysis shows that the vortex strip becomes stable as the strip widens or the rotation speed increases. When the vorticity constants in the upper and the lower regions of the vortex strip have the same positive value, the inner flow region of the vortex strip becomes the most unstable. However, when the upper and the lower vorticity constants in the polar regions have different signs, a complex pattern of instability is found, depending on the wavenumber of perturbations, and interestingly, a boundary far away from the vortex strip can be unstable. We also compute the nonlinear evolution of the vortex strip on the rotating sphere and compare with the linear stability analysis. When the width of the vortex strip is small, we observe a good agreement in the growth rate of perturbation at an early time, and the eigenvector corresponding to the unstable eigenvalue coincides with the most unstable part of the flow. We demonstrate that a large structure of rolling-up vortex cores appears in the vortex strip after a long-time evolution. Furthermore, the geophysical relevance of the model to jet streams of Jupiter, Saturn and Earth is examined.
Pair Interaction of Catalytical Sphere Dimers in Chemically Active Media
Directory of Open Access Journals (Sweden)
Jing-Min Shi
2018-01-01
Full Text Available We study the pair dynamics of two self-propelled sphere dimers in the chemically active medium in which a cubic autocatalytic chemical reaction takes place. Concentration gradient around the dimer, created by reactions occurring on the catalytic sphere surface and responsible for the self-propulsion, is greatly influenced by the chemical activities of the environment. Consequently, the pair dynamics of two dimers mediated by the concentration field are affected. In the particle-based mesoscopic simulation, we combine molecular dynamics (MD for potential interactions and reactive multiparticle collision dynamics (RMPC for solvent flow and bulk reactions. Our results indicate three different configurations between a pair of dimers after the collision, i.e., two possible scenarios of bound dimer pairs and one unbound dimer pair. A phase diagram is sketched as a function of the rate coefficients of the environment reactions. Since the pair interactions are the basic elements of larger scale systems, we believe the results may shed light on the understanding of the collective dynamics.
Two-Loop Scattering Amplitudes from the Riemann Sphere
Geyer, Yvonne; Monteiro, Ricardo; Tourkine, Piotr
2016-01-01
The scattering equations give striking formulae for massless scattering amplitudes at tree level and, as shown recently, at one loop. The progress at loop level was based on ambitwistor string theory, which naturally yields the scattering equations. We proposed that, for ambitwistor strings, the standard loop expansion in terms of the genus of the worldsheet is equivalent to an expansion in terms of nodes of a Riemann sphere, with the nodes carrying the loop momenta. In this paper, we show how to obtain two-loop scattering equations with the correct factorization properties. We adapt genus-two integrands from the ambitwistor string to the nodal Riemann sphere and show that these yield correct answers, by matching standard results for the four-point two-loop amplitudes of maximal supergravity and super-Yang-Mills theory. In the Yang-Mills case, this requires the loop analogue of the Parke-Taylor factor carrying the colour dependence, which includes non-planar contributions.
Crystallization and dynamical arrest of attractive hard spheres.
Babu, Sujin; Gimel, Jean-Christophe; Nicolai, Taco
2009-02-14
Crystallization of hard spheres interacting with a square well potential was investigated by numerical simulations using so-called Brownian cluster dynamics. The phase diagram was determined over a broad range of volume fractions. The crystallization rate was studied as a function of the interaction strength expressed in terms of the second virial coefficient. For volume fractions below about 0.3 the rate was found to increase abruptly with increasing attraction at the binodal of the metastable liquid-liquid phase separation. The rate increased until a maximum was reached after which it decreased with a power law dependence on the second virial coefficient. Above a critical percolation concentration, a transient system spanning network of connected particles was formed. Crystals were formed initially as part of the network, but eventually crystallization led to the breakup of the network. The lifetime of the transient gels increased very rapidly over a small range of interaction energies. Weak attraction destabilized the so-called repulsive crystals formed in pure hard sphere systems and shifted the coexistence line to higher volume fractions. Stronger attraction led to the formation of a denser, so-called attractive, crystalline phase. Nucleation of attractive crystals in the repulsive crystalline phase was observed close to the transition.
Diverse assembly behavior in colloidal Platonic polyhedral sphere clusters
Marson, Ryan; Teich, Erin; Dshemuchadse, Julia; Glotzer, Sharon; Larson, Ronald
We simulate the self-assembly of colloidal ``polyhedral sphere clusters (PSCs)'', which consist of equal-sized spheres placed at the vertices of a polyhedron such that they just touch along each edge. These colloidal building blocks have recently been experimentally fabricated; here we predict crystal structures that would appear in the phase diagram of resulting particle assemblies. We use Brownian dynamics (BD) simulations of rigid body clusters performed in the open-source GPU-based HOOMD-Blue particle simulation package to show the assembly behavior of the 5 Platonic PSCs. The simulations contain as many as 4096 individual polyhedra, across over 30 different densities per cluster geometry, with some ordered phases possessing unit cells with 20 or more particles. We observe the formation of not only traditional cubic structures such as BCC and FCC, but also more complex phases having structure symmetries with Pearson symbols - hP7, cP20, cI2, mP6, and hR3. The observations reported here will serve as a guide for future colloidal assembly experiments using an expanded library of PSCs, consisting of other regular and irregular polyhedra, allowing researchers to target specific arrangements of ``halo'' and ``core'' particles for technologically relevant applications including photonics and structural color.
Supercooled liquid dynamics for the charged hard-sphere model
International Nuclear Information System (INIS)
Lai, S.K.; Chang, S.Y.
1994-08-01
We study the dynamics of supercooled liquid and the liquid-glass transition by applying the mode coupling theory to the charged hard-sphere model. By exploiting the two independent parameters inherent in the charged hard-sphere system we examine structurally the subtle and competitive role played by the short-range hard-core correlation and the long-range Coulomb tail. It is found in this work that the long-range Coulombic charge factor effect is generally a less effective contribution to structure when the plasma parameter is less than 500 and becomes dominant when it is greater thereof. To extend our understanding of the supercooled liquid and the liquid-glass transition, an attempt is made to calculate and to give physical relevance to the mode-coupling parameters which are frequently used as mere fitting parameters in analysis of experiments on supercooled liquid systems. This latter information enables us to discuss the possible application of the model to a realistic system. (author). 22 refs, 4 figs
One-loop amplitudes on the Riemann sphere
Geyer, Yvonne; Monteiro, Ricardo; Tourkine, Piotr
2016-01-01
The scattering equations provide a powerful framework for the study of scattering amplitudes in a variety of theories. Their derivation from ambitwistor string theory led to proposals for formulae at one loop on a torus for 10 dimensional supergravity, and we recently showed how these can be reduced to the Riemann sphere and checked in simple cases. We also proposed analogous formulae for other theories including maximal super-Yang-Mills theory and supergravity in other dimensions at one loop. We give further details of these results and extend them in two directions. Firstly, we propose new formulae for the one-loop integrands of Yang-Mills theory and gravity in the absence of supersymmetry. These follow from the identification of the states running in the loop as expressed in the ambitwistor-string correlator. Secondly, we give a systematic proof of the non-supersymmetric formulae using the worldsheet factorisation properties of the nodal Riemann sphere underlying the scattering equations at one loop. Our f...
Stability of barotropic vortex strip on a rotating sphere
Sohn, Sung-Ik; Sakajo, Takashi; Kim, Sun-Chul
2018-02-01
We study the stability of a barotropic vortex strip on a rotating sphere, as a simple model of jet streams. The flow is approximated by a piecewise-continuous vorticity distribution by zonal bands of uniform vorticity. The linear stability analysis shows that the vortex strip becomes stable as the strip widens or the rotation speed increases. When the vorticity constants in the upper and the lower regions of the vortex strip have the same positive value, the inner flow region of the vortex strip becomes the most unstable. However, when the upper and the lower vorticity constants in the polar regions have different signs, a complex pattern of instability is found, depending on the wavenumber of perturbations, and interestingly, a boundary far away from the vortex strip can be unstable. We also compute the nonlinear evolution of the vortex strip on the rotating sphere and compare with the linear stability analysis. When the width of the vortex strip is small, we observe a good agreement in the growth rate of perturbation at an early time, and the eigenvector corresponding to the unstable eigenvalue coincides with the most unstable part of the flow. We demonstrate that a large structure of rolling-up vortex cores appears in the vortex strip after a long-time evolution. Furthermore, the geophysical relevance of the model to jet streams of Jupiter, Saturn and Earth is examined.
Energy dissipation in head-on collisions of spheres
International Nuclear Information System (INIS)
Krijt, S; Tielens, A G G M; Güttler, C; Heißelmann, D; Dominik, C
2013-01-01
Collisions between spheres are a common ingredient in a variety of scientific problems, and the coefficient of restitution (COR) is a key parameter to describe their outcome. We present a new collision model that treats adhesion and viscoelasticity self-consistently, while energy losses arising from plastic deformation are assumed to be additive. Results show that viscoelasticity can significantly increase the energy that is dissipated in a collision, enhancing the sticking velocity. Furthermore, collisions well above the sticking velocity remain dissipative. We systemically compare the model to a large and unbiased set of published laboratory experiments to show its general applicability. The model is well capable of reproducing the important relation between impact velocity and COR as measured in the experiments, covering a wide range of materials, particle sizes, and collision velocities. Furthermore, the fitting parameters from those curves provide physical parameters such as the surface energy, yield strength, and characteristic viscous relaxation time. Our results show that all three aspects—adhesion, viscoelastic dissipation and plastic deformation—are required for a proper description of the kinetic energy losses in sphere collisions. (paper)
Evaluation framework for K-best sphere decoders
Shen, Chungan
2010-08-01
While Maximum-Likelihood (ML) is the optimum decoding scheme for most communication scenarios, practical implementation difficulties limit its use, especially for Multiple Input Multiple Output (MIMO) systems with a large number of transmit or receive antennas. Tree-searching type decoder structures such as Sphere decoder and K-best decoder present an interesting trade-off between complexity and performance. Many algorithmic developments and VLSI implementations have been reported in literature with widely varying performance to area and power metrics. In this semi-tutorial paper we present a holistic view of different Sphere decoding techniques and K-best decoding techniques, identifying the key algorithmic and implementation trade-offs. We establish a consistent benchmark framework to investigate and compare the delay cost, power cost, and power-delay-product cost incurred by each method. Finally, using the framework, we propose and analyze a novel architecture and compare that to other published approaches. Our goal is to explicitly elucidate the overall advantages and disadvantages of each proposed algorithms in one coherent framework. © 2010 World Scientific Publishing Company.
Protection of qubit-coherence on a Bloch sphere
Zong, Xiao-Lan; Chu, Wen-Jing; Yang, Ming; Yang, Qing; Cao, Zhuo-Liang
2017-07-01
Single qubit pure state is a fundamental resource in quantum information and quantum computation. Therefore, it is of great importance to protect the coherence of single qubits against decoherence. In this letter, we demonstrate that decoherence caused by spontaneous emission can be effectively suppressed by adding a universal static external field. In order to have an intuitive view to the protection effects and its physical mechanisms, we study the coherence evolution of a single qubit on a Bloch sphere. We can clearly see that different external resonant drivings can rotate the Bloch vector around different axes, and the steady-state solution of the master equation (under protection) are visualized on the Bloch sphere. Furthermore, the frequency detuning between the qubit system and the driving is taken into account, and the results show that our protection scheme still works fine in the detuned cases and the smaller the detuning is, the better the protection effect is. In addition, this protocol can protect the coherence of single qubit states with a wide range of driving parameters, and help people to design simple coherence protection schemes for qubit states. The simplicity and the abundance of the current scheme may warrant its experimental realization.
Negative chemical ionization mass spectrometry
International Nuclear Information System (INIS)
Smit, A.L.C.
1979-01-01
This thesis describes some aspects of Negative Chemical Ionization (NCI) mass spectrometry. The reasons for the growing interest in NCI are: (i) to extend the basic knowledge of negative ions and their reactions in the gas phase; (ii) to investigate whether or not this knowledge of negative ions can be used successfully to elucidate the structure of molecules by mass spectrometry. (Auth.)
Laboratory of acceleration mass spectrometry
International Nuclear Information System (INIS)
Hybler, P.; Chrapan, J.
2002-01-01
In this paper authors describe the principle of the method of acceleration mass spectrometry and the construction plans of this instrument at the Faculty of ecology and environmental sciences in Banska Stiavnica. Using of this instrument for radiocarbon dating is discussed. A review of laboratories with acceleration mass spectrometry is presented
Preface Miniaturization and Mass Spectrometry
Unknown, [Unknown; le Gac, Severine; le Gac, S.; van den Berg, Albert; van den Berg, A.
2009-01-01
Miniaturization and Mass Spectrometry illustrates this trend and focuses on one particular analysis technique, mass spectrometry whose popularity has "dramatically" increased in the last two decades with the explosion of the field of biological analysis and the development of two "soft" ionization
Directory of Open Access Journals (Sweden)
Haibo Yao
2013-01-01
Full Text Available A simple and widely applicable methodology was presented to synthesize monodisperse micrometer hollow titania spheres (HTS based on the templating method. It was performed by using the preformed poly(styrene-acrylic acid (PSA as template spheres which was mixed with tetrabutyltitanate (TBOT in an ethanol solvent under steam treatment. The HTS which were obtained by the calcination of PSA/TiO2 composite core-shell spheres had a narrow particle size distribution and commendable surface topography characterized by SEM. The calcined HTS at 500°C displayed crystalline reflection peaks that were characteristic to the anatase phase by XRD. Moreover, some key influencing factors including TBOT concentration and reaction time were analyzed. As expected, the diameter of HTS could be readily controlled by altering the size of PSA template spheres. In addition, the approach was also applied to fabricate hollow zirconia spheres and other inorganic spheres.
A General Synthesis Strategy for Hierarchical Porous Metal Oxide Hollow Spheres
Directory of Open Access Journals (Sweden)
Huadong Fu
2015-01-01
Full Text Available The hierarchical porous TiO2 hollow spheres were successfully prepared by using the hydrothermally synthesized colloidal carbon spheres as templates and tetrabutyl titanate as inorganic precursors. The diameter and wall thickness of hollow TiO2 spheres were determined by the hard templates and concentration of tetrabutyl titanate. The particle size, dispersity, homogeneity, and surface state of the carbon spheres can be easily controlled by adjusting the hydrothermal conditions and adding certain amount of the surfactants. The prepared hollow spheres possessed the perfect spherical shape, monodispersity, and hierarchically pore structures, and the further experiment verified that the present approach can be used to prepare other metal oxide hollow spheres, which could be used as catalysis, fuel cells, lithium-air battery, gas sensor, and so on.
Cavitation and radicals drive the sonochemical synthesis of functional polymer spheres
Energy Technology Data Exchange (ETDEWEB)
Narayanan, Badri, E-mail: bnarayanan@anl.gov; Deshmukh, Sanket A.; Sankaranarayanan, Subramanian K. R. S., E-mail: ssankaranarayanan@anl.gov [Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Shrestha, Lok Kumar; Ariga, Katsuhiko [World Premier International Center for Materials Nanoarchitechtonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 (Japan); Pol, Vilas G. [School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)
2016-07-25
Sonochemical synthesis can lead to a dramatic increase in the kinetics of formation of polymer spheres (templates for carbon spheres) compared to the modified Stöber silica method applied to produce analogous polymer spheres. Reactive molecular dynamics simulations of the sonochemical process indicate a significantly enhanced rate of polymer sphere formation starting from resorcinol and formaldehyde precursors. The associated chemical reaction kinetics enhancement due to sonication is postulated to arise from the localized lowering of atomic densities, localized heating, and generation of radicals due to cavitation collapse in aqueous systems. This dramatic increase in reaction rates translates into enhanced nucleation and growth of the polymer spheres. The results are of broad significance to understanding mechanisms of sonication induced synthesis as well as technologies utilizing polymers spheres.
Type-I superconductivity in carbon-coated Sn nano-spheres
Shani, L.; Kumar, V. B.; Gedanken, A.; Shapiro, I.; Shapiro, B. Ya.; Shaulov, A.; Yeshurun, Y.
2018-03-01
Tin spheres of diameter ∼120 nm and ∼1400 nm coated with sub-nanometer carbon layers were fabricated, using a sonochemical technique. Samples of both spheres reveal a type-I superconducting behavior characterized by super-critical fields and an intermediate state manifested by a gradual increase of the magnetization to zero. However, the small and large tin spheres exhibit a similar critical field, Hc, contrary to the expected increase in Hc in spheres with size smaller than the coherence length (∼230 nm). Analysis of the data shows that a relative high degree of carbon doping in the small tin spheres, eliminates the expected size-effect on Hc. Simulations, based on the time dependent Ginzburg-Landau equations, imply that the intermediate state in both measured samples consists of only one superconducting domain surrounded by a normal domain, whereas a rich multi-domain structure is predicted for larger Sn spheres.
A reliable parameter to standardize the scoring of stem cell spheres.
Directory of Open Access Journals (Sweden)
Xiaochen Zhou
Full Text Available Sphere formation assay is widely used in selection and enrichment of normal stem cells or cancer stem cells (CSCs, also known as tumor initiating cells (TICs, based on their ability to grow in serum-free suspension culture for clonal proliferation. However, there is no standardized parameter to accurately score the spheres, which should be reflected by both the number and size of the spheres. Here we define a novel parameter, designated as Standardized Sphere Score (SSS, which is expressed by the total volume of selected spheres divided by the number of cells initially plated. SSS was validated in quantification of both tumor spheres from cancer cell lines and embryonic bodies (EB from mouse embryonic stem cells with high sensitivity and reproducibility.
Preparation of SnO 2 /Carbon Composite Hollow Spheres and Their Lithium Storage Properties
Lou, Xiong Wen
2008-10-28
In this work, we present a novel concept of structural design for preparing functional composite hollow spheres and derived double-shelled hollow spheres. The approach involves two main steps: preparation of porous hollow spheres of one component and deposition of the other component onto both the interior and exterior surfaces of the shell as well as in the pores. We demonstrate the concept by preparing SnO2/carbon composite hollow spheres and evaluate them as potential anode materials for lithium-ion batteries. These SnO2/carbon hollow spheres are able to deliver a reversible Li storage capacity of 473 mA h g-1 after 50 cycles. Unusual double-shelled carbon hollow spheres are obtained by selective removal of the sandwiched porous SnO2 shells. © 2008 American Chemical Society.
International Mass Spectrometry Society (IMSS).
Cooks, R G; Gelpi, E; Nibbering, N M
2001-02-01
This paper gives a brief description of the recently formalized International Mass Spectrometry Society (IMSS). It is presented here in order to increase awareness of the opportunities for collaboration in mass spectrometry in an international context. It also describes the recent 15th International Mass Spectrometry Conference, held August/September 2000, in Barcelona. Each of the authors is associated with the IMSS. The 15th Conference, which covers all of mass spectrometry on a triennial basis, was chaired by Professor Emilio Gelpi of the Instituto de Investigaciones Biomedicas, Barcelona. The outgoing and founding President of the IMSS is Professor Graham Cooks, Purdue University, and the incoming President is Professor Nico Nibbering, University of Amsterdam. Similar material has been provided to the Editors of other journals that cover mass spectrometry.
Facile Synthesis and High Photocatalytic Degradation Performance of ZnO-SnO2 Hollow Spheres
Jin, Changqing; Ge, Chenghai; Jian, Zengyun; Wei, Yongxing
2016-01-01
ZnO-SnO2 hollow spheres were successfully synthesized through a hydrothermal method-combined carbon sphere template. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). The average diameter of hollow spheres is about 150?nm. The photocatalytic activity of the as-prepared samples was investigated by photodegrading Rhodamine B. The results indicated that the ph...
Ji, Guipeng; Yang, Zhenzhen; Zhao, Yanfei; Zhang, Hongye; Yu, Bo; Xu, Jilei; Xu, Huanjun; Liu, Zhimin
2015-04-30
Zinc porphyrin (TP-Zn)-based conjugated microporous polymer (Zn-CMP) spheres were obtained via Sonagashira-Hagihara cross coupling reactions between 5,10,15,20-tetrakis(4-ethynylphenyl)porphyrin-Zn(II) and brominated monomers directed by bidentate bipyridine (BP)-type ligands for the first time, and the sphere diameters could be adjusted from 320 to 740 nm. The coordination between BP and TP-Zn was proved to be the key to forming spheres.
International Nuclear Information System (INIS)
Kumar, Rajiv; Sharma, Shagun; Singh, Pradeep; Kharab, Rajesh
2016-01-01
The energy-independent touching spheres schemes commonly used for the determination of the safe minimum value of the impact parameter for Coulomb excitation experiments are modified through the inclusion of an energy-dependent term. The touching spheres+3fm scheme after modification emerges out to be the best one while touching spheres+4fm scheme is found to be better in its unmodified form. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Beatty, R.L. Norman, R.E.; Notz, K.J. (comps.)
1979-11-01
Recent interest in proliferation-resistant fuel cycles for light-water reactors has focused attention on spiked plutonium and /sup 233/U-Th fuels, requiring remote refabrication. The gel-sphere-pac process for fabricating metal-clad fuel elements has drawn special attention because it involves fewer steps. Gel-sphere-pac fabrication technology involves two major areas: the preparation of fuel spheres of high density and loading these spheres into rods in an efficiently packed geometry. Gel sphere preparation involves three major steps: preparation of a sol or of a special solution (broth), gelation of droplets of sol or broth to give semirigid spheres of controlled size, and drying and sintering these spheres to a high density. Gelation may be accomplished by water extraction (suitable only for sols) or ammonia gelation (suitable for both sols and broths but used almost exclusively with broths). Ammonia gelation can be accomplished either externally, via ammonia gas and ammonium hydroxide, or internally via an added ammonia generator such as hexamethylenetetramine. Sphere-pac fuel rod fabrication involves controlled blending and metering of three sizes of spheres into the rod and packing by low- to medium-energy vibration to achieve about 88% smear density; these sizes have diametral ratios of about 40:10:1 and are blended in size fraction amounts of about 60% coarse, 18% medium, and 22% fine. Irradiation test results indicate that sphere-pac fuel performs at least as well as pellet fuel, and may in fact offer an advantage in significantly reducing mechanical and chemical interaction between the fuel and cladding. The normal feed for gel sphere preparation, heavy metal nitrate solution, is the usual product of fuel reprocessing, so that fabrication of gel spheres performs all the functions performed by both conversion and pellet fabrication in the case of pellet technology.
SPHERE DAQ and off-line systems: implementation based on the qdpb system
International Nuclear Information System (INIS)
Isupov, A.Yu.
2003-01-01
Design of the on-line data acquisition (DAQ) system for the SPHERE setup (LHE, JINR) is described. SPHERE DAQ is based on the qdpb (Data Processing with Branchpoints) system and configurable experimental data and CAMAC hardware representations. Implementation of the DAQ and off-line program code, depending on the SPHERE setup's hardware layout and experimental data contents, is explained as well as software modules specific for such implementation
Array of the two arc monopoles on a sphere with surface impedance
Dakhov, Viktor M.; Berdnik, Sergey L.; Blinova, Natalya K.; Penkin, Yu. M.
2017-01-01
The antenna array of two arc monopoles which are located parallel to the surface of a perfectly conducting or impedance sphere is considered. The influences of the phase of excitation of a monopole, the distance to the sphere surface, and sphere radius and its surface impedance on the directivity of the radiator are considered. It is shown that the radiation pattern of the antenna for antiphase excitation is highly directional and has a single maximum in the plane of arrangement of the emitters.
Guan, Mingyun; Tao, Feifei; Sun, Jianhua; Xu, Zheng
2008-08-05
We have developed a template-free hydrothermal method of constructing rare earth phosphate hollow spheres using H(6)P(4)O(13) as the PO(4) (3-) source. The mechanism of hollow spheres formation was proposed on the basis of Ostwald ripening. The resulting hollow spheres, especially with the aid of doping of other lanthanide cations, exhibit emission spanning the whole UV-visible wavelength range.
An internet-mediated political public sphere in China and South Korea
Chase, Thomas
2017-01-01
This thesis investigates the growing volume of online political commentary being produced by Internet users in Mainland China and South Korea, analysing the qualities and characteristics of these discourses through adaptation of the argument provided by German sociologist Jürgen Habermas about the workings of the public sphere. In evaluating the gap between the idealised qualities of the public sphere and real-life communication, the study uses the concept of the public sphere as a heuristic...
Accelerator-based ultrasensitive mass spectrometry
International Nuclear Information System (INIS)
Gove, H.E.
1985-01-01
This chapter describes a new mass spectrometry technique involving charged particle accelerators normally used for basic research in nuclear science. Topics considered include the limitations of conventional mass spectrometry, the limitations of the direct measurement of radioactive decay, mass spectrometry using a tandem electrostatic accelerator, mass spectrometry using a cyclotron, how accelerator mass spectrometry circumvents the limitations of conventional mass spectrometry, measurements of stable isotopes, nuclear physics and astrophysics applications, modifications to existing accelerators, descriptions of dedicated systems, and future applications
A neutron spectrum unfolding code based on generalized regression artificial neural networks
Energy Technology Data Exchange (ETDEWEB)
Ortiz R, J. M.; Martinez B, M. R.; Castaneda M, R.; Solis S, L. O. [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica, Av. Ramon Lopez Velarde 801, Col. Centro, 98000 Zacatecas, Zac. (Mexico); Vega C, H. R., E-mail: morvymm@yahoo.com.mx [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico)
2015-10-15
The most delicate part of neutron spectrometry, is the unfolding process. Then derivation of the spectral information is not simple because the unknown is not given directly as result of the measurements. Novel methods based on Artificial Neural Networks have been widely investigated. In prior works, back propagation neural networks (BPNN) have been used to solve the neutron spectrometry problem, however, some drawbacks still exist using this kind of neural nets, as the optimum selection of the network topology and the long training time. Compared to BPNN, is usually much faster to train a generalized regression neural network (GRNN). That is mainly because spread constant is the only parameter used in GRNN. Another feature is that the network will converge to a global minimum. In addition, often are more accurate than BPNN in prediction. These characteristics make GRNN be of great interest in the neutron spectrometry domain. In this work is presented a computational tool based on GRNN, capable to solve the neutron spectrometry problem. This computational code, automates the pre-processing, training and testing stages, the statistical analysis and the post-processing of the information, using 7 Bonner spheres rate counts as only entrance data. The code was designed for a Bonner Spheres System based on a {sup 6}LiI(Eu) neutron detector and a response matrix expressed in 60 energy bins taken from an International Atomic Energy Agency compilation. (Author)
A neutron spectrum unfolding code based on generalized regression artificial neural networks
International Nuclear Information System (INIS)
Ortiz R, J. M.; Martinez B, M. R.; Castaneda M, R.; Solis S, L. O.; Vega C, H. R.
2015-10-01
The most delicate part of neutron spectrometry, is the unfolding process. Then derivation of the spectral information is not simple because the unknown is not given directly as result of the measurements. Novel methods based on Artificial Neural Networks have been widely investigated. In prior works, back propagation neural networks (BPNN) have been used to solve the neutron spectrometry problem, however, some drawbacks still exist using this kind of neural nets, as the optimum selection of the network topology and the long training time. Compared to BPNN, is usually much faster to train a generalized regression neural network (GRNN). That is mainly because spread constant is the only parameter used in GRNN. Another feature is that the network will converge to a global minimum. In addition, often are more accurate than BPNN in prediction. These characteristics make GRNN be of great interest in the neutron spectrometry domain. In this work is presented a computational tool based on GRNN, capable to solve the neutron spectrometry problem. This computational code, automates the pre-processing, training and testing stages, the statistical analysis and the post-processing of the information, using 7 Bonner spheres rate counts as only entrance data. The code was designed for a Bonner Spheres System based on a 6 LiI(Eu) neutron detector and a response matrix expressed in 60 energy bins taken from an International Atomic Energy Agency compilation. (Author)
Energy Technology Data Exchange (ETDEWEB)
RINTOUL,MARK DANIEL
2000-01-25
The void percolation threshold is calculated for a distribution of overlapping spheres with equal radii, and for a binary sized distribution of overlapping spheres, where half of the spheres have radii twice as large as the other half. Using systems much larger than previous work, the authors determine a much more precise value for the percolation thresholds and correlation length exponent. The values for the percolation thresholds are shown to be significantly different, in contrast with previous, less precise works that speculated that the threshold might be universal with respect to sphere size distribution.
A novel approach for fabricating NiO hollow spheres for gas sensors
Kuang, Chengwei; Zeng, Wen; Ye, Hong; Li, Yanqiong
2018-03-01
Hollow spheres are usually fabricated by hard template methods or soft template methods with soft surfactants, which is quiet tedious and time-consuming. In this paper, NiO hollow spheres with fluffy surface were successfully synthesized by a facile hydrothermal method and subsequent calcination, where bubbles acted as the template. NiO hollow spheres exhibited excellent gas sensing performances, which results from its hollow structure and high specific surface area. In addition, a possible evolution mechanism of NiO hollow spheres was proposed based on experimental results.
Controllable Fabrication and Optical Properties of Uniform Gadolinium Oxysulfate Hollow Spheres
Chen, Fashen; Chen, Gen; Liu, Tao; Zhang, Ning; Liu, Xiaohe; Luo, Hongmei; Li, Junhui; Chen, Limiao; Ma, Renzhi; Qiu, Guanzhou
2015-01-01
Uniform gadolinium oxysulfate (Gd2O2SO4) hollow spheres were successfully fabricated by calcination of corresponding Gd-organic precursor obtained via a facile hydrothermal process. The Gd2O2SO4 hollow spheres have a mean diameter of approximately 550?nm and shell thickness in the range of 30?70?nm. The sizes and morphologies of as-prepared Gd2O2SO4 hollow spheres could be deliberately controlled by adjusting the experimental parameters. Eu-doped Gd2O2SO4 hollow spheres have also been prepare...
Liebowitz, Matt; Spies, Rynardt
2014-01-01
Covering the latest VMware vSphere software, an essential book aimed at solving vSphere performance problems before they happen VMware vSphere is the industry's most widely deployed virtualization solution. However, if you improperly deploy vSphere, performance problems occur. Aimed at VMware administrators and engineers and written by a team of VMware experts, this resource provides guidance on common CPU, memory, storage, and network-related problems. Plus, step-by-step instructions walk you through techniques for solving problems and shed light on possible causes behind the problems. Divu
The electromagnetic radiation from simple sources in the presence of a homogeneous dielectric sphere
Mason, V. B.
1973-01-01
In this research, the effect of a homogeneous dielectric sphere on the electromagnetic radiation from simple sources is treated as a boundary value problem, and the solution is obtained by the technique of dyadic Green's functions. Exact representations of the electric fields in the various regions due to a source located inside, outside, or on the surface of a dielectric sphere are formulated. Particular attention is given to the effect of sphere size, source location, dielectric constant, and dielectric loss on the radiation patterns and directivity of small spheres (less than 5 wavelengths in diameter) using the Huygens' source excitation. The computed results are found to closely agree with those measured for waveguide-excited plexiglas spheres. Radiation patterns for an extended Huygens' source and for curved electric dipoles located on the sphere's surface are also presented. The resonance phenomenon associated with the dielectric sphere is studied in terms of the modal representation of the radiated fields. It is found that when the sphere is excited at certain frequencies, much of the energy is radiated into the sidelobes. The addition of a moderate amount of dielectric loss, however, quickly attenuates this resonance effect. A computer program which may be used to calculate the directivity and radiation pattern of a Huygens' source located inside or on the surface of a lossy dielectric sphere is listed.
Random sequential addition of hard spheres in high Euclidean dimensions
Torquato, S.; Uche, O. U.; Stillinger, F. H.
2006-12-01
Sphere packings in high dimensions have been the subject of recent theoretical interest. Employing numerical and theoretical methods, we investigate the structural characteristics of random sequential addition (RSA) of congruent spheres in d -dimensional Euclidean space Rd in the infinite-time or saturation limit for the first six space dimensions (1≤d≤6) . Specifically, we determine the saturation density, pair correlation function, cumulative coordination number and the structure factor in each of these dimensions. We find that for 2≤d≤6 , the saturation density ϕs scales with dimension as ϕs=c1/2d+c2d/2d , where c1=0.202048 and c2=0.973872 . We also show analytically that the same density scaling is expected to persist in the high-dimensional limit, albeit with different coefficients. A byproduct of this high-dimensional analysis is a relatively sharp lower bound on the saturation density for any d given by ϕs≥(d+2)(1-S0)/2d+1 , where S0ɛ[0,1] is the structure factor at k=0 (i.e., infinite-wavelength number variance) in the high-dimensional limit. We demonstrate that a Palàsti-type conjecture (the saturation density in Rd is equal to that of the one-dimensional problem raised to the d th power) cannot be true for RSA hyperspheres. We show that the structure factor S(k) must be analytic at k=0 and that RSA packings for 1≤d≤6 are nearly “hyperuniform.” Consistent with the recent “decorrelation principle,” we find that pair correlations markedly diminish as the space dimension increases up to six. We also obtain kissing (contact) number statistics for saturated RSA configurations on the surface of a d -dimensional sphere for dimensions 2≤d≤5 and compare to the maximal kissing numbers in these dimensions. We determine the structure factor exactly for the related “ghost” RSA packing in Rd and demonstrate that its distance from “hyperuniformity” increases as the space dimension increases, approaching a constant asymptotic value
Spectrometry techniques for radioactivity measurements
International Nuclear Information System (INIS)
Anilkumar, S.
2016-01-01
The energy of the radiation emission following the nuclear decay is unique and the characteristic of the radio nuclide which undergoes decay. Thus measurement of the energy of the radiation offers a method of identifying the radio nuclides. The prime requirement of the energy measurement is a suitable detector which shows response proportional to the energy of the radiation rather than the presence of the radiation. The response from such detectors are suitably processed and distributed with respect to the signal strength which is proportional to incident energy. This distribution is normally referred as energy spectrum and is recorded in the multichannel analyser. The measurement of energy and intensity of radiation from the spectrum is called radiation spectrometry. Thus the radiation spectrometry allows the identification and quantification of radioactive isotopes in variety of matrices. The radiation spectrometry has now become a popular radioanalytical technique in wide area of nuclear fuel cycle programs. The popular spectrometry techniques commonly used for the radioactivity measurement and analysis are Alpha spectrometry, Gamma ray spectrometry and Beta spectrometry
The Detailed Evolution of Carbon Spheres by Hydrothermal Method
Directory of Open Access Journals (Sweden)
Trevor Mwenya
2016-01-01
Full Text Available Carbon spheres (CSs can be synthesized easily by hydrothermal method using various solutions and a lot of mechanisms have been employed to explain their formation. In our work, some special phenomena such as the uniform size and surface corruption have been found as the reaction time increased. However, less attention has been focused on the detailed evolution phenomena of CSs. In order to understand these special phenomena well, classical nucleation theory was employed to study the reaction dynamics of CSs during the evolution processes. This work not only deeply reveals the evolution mechanism of CSs, but also opens a possible way for the control of size and morphologies of CSs through hydrothermal methods.
Packing Different Cuboids with Rotations and Spheres into a Cuboid
Directory of Open Access Journals (Sweden)
Y. G. Stoyan
2014-01-01
Full Text Available The paper considers a packing optimization problem of different spheres and cuboids into a cuboid of the minimal height. Translations and continuous rotations of cuboids are allowed. In the paper, we offer a way of construction of special functions (Φ-functions describing how rotations can be dealt with. These functions permit us to construct the mathematical model of the problem as a classical mathematical programming problem. Basic characteristics of the mathematical model are investigated. When solving the problem, the characteristics allow us to apply a number of original and state-of-the-art efficient methods of local and global optimization. Numerical examples of packing from 20 to 300 geometric objects are given.
Density Fluctuations of Hard-Sphere Fluids in Narrow Confinement
Directory of Open Access Journals (Sweden)
Kim Nygård
2016-02-01
Full Text Available Spatial confinement induces microscopic ordering of fluids, which in turn alters many of their dynamic and thermodynamic properties. However, the isothermal compressibility has hitherto been largely overlooked in the literature, despite its obvious connection to the underlying microscopic structure and density fluctuations in confined geometries. Here, we address this issue by probing density profiles and structure factors of hard-sphere fluids in various narrow slits, using x-ray scattering from colloid-filled nanofluidic containers and integral-equation-based statistical mechanics at the level of pair distributions for inhomogeneous fluids. Most importantly, we demonstrate that density fluctuations and isothermal compressibilities in confined fluids can be obtained experimentally from the long-wavelength limit of the structure factor, providing a formally exact and experimentally accessible connection between microscopic structure and macroscopic, thermodynamic properties. Our approach will thus, for example, allow direct experimental verification of theoretically predicted enhanced density fluctuations in liquids near solvophobic interfaces.
Fuzzy Logic Control of a Ball on Sphere System
Directory of Open Access Journals (Sweden)
Seyed Alireza Moezi
2014-01-01
Full Text Available The scope of this paper is to present a fuzzy logic control of a class of multi-input multioutput (MIMO nonlinear systems called “system of ball on a sphere,” such an inherently nonlinear, unstable, and underactuated system, considered truly to be two independent ball and wheel systems around its equilibrium point. In this work, Sugeno method is investigated as a fuzzy controller method, so it works in a good state with optimization and adaptive techniques, which makes it very attractive in control problems, particularly for such nonlinear dynamic systems. The system’s dynamic is described and the equations are illustrated. The outputs are shown in different figures so as to be compared. Finally, these simulation results show the exactness of the controller’s performance.
Echoes of the Glass Transition in Athermal Soft Spheres.
Morse, Peter K; Corwin, Eric I
2017-09-15
Recent theoretical advances have led to the creation of a unified phase diagram for the thermal glass and athermal jamming transitions. This diagram makes clear that, while related, the mode-coupling-or dynamic-glass transition is distinct from the jamming transition, occurring at a finite temperature and significantly lower density than the jamming transition. Nonetheless, we demonstrate a prejamming transition in athermal frictionless spheres which occurs at the same density as the mode-coupling transition and is marked by percolating clusters of locally rigid particles. At this density in both the thermal and athermal systems, individual motions of an extensive number of particles become constrained, such that only collective motion is possible. This transition, which is well below jamming, exactly matches the definition of collective behavior at the dynamical transition of glasses. Thus, we reveal that the genesis of rigidity in both thermal and athermal systems is governed by the same underlying topological transition in their shared configuration space.
Perturbative dynamics of fuzzy spheres at large N
International Nuclear Information System (INIS)
Azuma, Takehiro; Nagao, Keiichi; Nishimura, Jun
2005-01-01
We clarify some peculiar aspects of the perturbative expansion around a classical fuzzy-sphere solution in matrix models with a cubic term. While the effective action in the large-N limit is saturated at the one-loop level, we find that the 'one-loop dominance' does not hold for generic observables due to one-particle reducible diagrams. However, we may exploit the one-loop dominance for the effective action and obtain various observables to all orders from one-loop calculation by simply shifting the center of expansion to the 'quantum solution', which extremizes the effective action. We confirm the validity of this method by comparison with the direct two-loop calculation and with Monte Carlo results in the 3d Yang-Mills-Chern-Simons matrix model. From the all order result we find that the perturbative expansion has a finite radius of convergence
Environment protection and other political spheres of the European Community
International Nuclear Information System (INIS)
Rengeling, H.W.
1993-01-01
It has long been known that environment protection is largely a cross-sectional task. The provision of Article 130 r Section 2 Clause 2 of the EEC Treaty that states that environment protection forms an integral part of all the other polticial spheres of the Community is not only a plank in the platform of the Community but also a juridical innovation. Time will tell what concrete legal claims can be derived from this provision, particularly on the part of the European Court of Justice. The lectures relate amongst others to the following topics: Environment protection and competition politics, environment protection and energy poltics, environment protection and development aid politics. Eight of the lectures were abstracted individually. (orig./HSCH) [de
Why the Left Ventricle Is Not a Sphere
Directory of Open Access Journals (Sweden)
Felix A. Blyakhman
2004-01-01
Full Text Available In this study, we have tried to understand why the left ventricle (LV is not a homogeneous sphere. An experimental model of a spherical ventricle was developed. The chamber was configured as a mathematical model, and the wall properties were represented by isolated cardiac muscles. The stroke work of the spherical LV when modelling different types of inhomogeneity in the wall structure was investigated. It was found that the emergence of even slight inhomogeneity in a spherical ventricle inevitably results in a diminution of pump function. It was concluded that at a given level of the myocardial contractility, a homogeneous spherical LV would not have any functional reserve, ie no ability to maintain pump function in case of additional load. Functional reserve can be achieved only with a certain degree of inhomogeneity. Thus, inhomogeneity in the normal left ventricular wall structure constitutes a strategic functional reserve that is absent in a homogeneous spherical ventricle.
Sphere-cone-polynomial special window with good aberration characteristic
International Nuclear Information System (INIS)
Wang Chao; Zhang Xin; Qu He-Meng; Wang Ling-Jie; Wang Yu
2013-01-01
Optical windows with external surfaces shaped to satisfy operational environment needs are known as special windows. A novel special window, a sphere-cone-polynomial (SCP) window, is proposed. The formulas of this window shape are given. An SCP MgF 2 window with a fineness ratio of 1.33 is designed as an example. The field-of-regard (FOR) angle is ±75°. From the window system simulation results obtained with the calculated fluid dynamics (CFD) and optical design software, we find that compared to the conventional window forms, the SCP shape can not only introduce relatively less drag in the airflow, but also have the minimal effect on imaging. So the SCP window optical system can achieve a high image quality across a super wide FOR without adding extra aberration correctors. The tolerance analysis results show that the optical performance can be maintained with a reasonable fabricating tolerance to manufacturing errors
Physics of Hard Spheres Experiment: Significant and Quantitative Findings Made
Doherty, Michael P.
2000-01-01
Direct examination of atomic interactions is difficult. One powerful approach to visualizing atomic interactions is to study near-index-matched colloidal dispersions of microscopic plastic spheres, which can be probed by visible light. Such spheres interact through hydrodynamic and Brownian forces, but they feel no direct force before an infinite repulsion at contact. Through the microgravity flight of the Physics of Hard Spheres Experiment (PHaSE), researchers have sought a more complete understanding of the entropically driven disorder-order transition in hard-sphere colloidal dispersions. The experiment was conceived by Professors Paul M. Chaikin and William B. Russel of Princeton University. Microgravity was required because, on Earth, index-matched colloidal dispersions often cannot be density matched, resulting in significant settling over the crystallization period. This settling makes them a poor model of the equilibrium atomic system, where the effect of gravity is truly negligible. For this purpose, a customized light-scattering instrument was designed, built, and flown by the NASA Glenn Research Center at Lewis Field on the space shuttle (shuttle missions STS 83 and STS 94). This instrument performed both static and dynamic light scattering, with sample oscillation for determining rheological properties. Scattered light from a 532- nm laser was recorded either by a 10-bit charge-coupled discharge (CCD) camera from a concentric screen covering angles of 0 to 60 or by sensitive avalanche photodiode detectors, which convert the photons into binary data from which two correlators compute autocorrelation functions. The sample cell was driven by a direct-current servomotor to allow sinusoidal oscillation for the measurement of rheological properties. Significant microgravity research findings include the observation of beautiful dendritic crystals, the crystallization of a "glassy phase" sample in microgravity that did not crystallize for over 1 year in 1g
Religious Diversity in the Public Sphere: The Canadian Case
Directory of Open Access Journals (Sweden)
Lori G. Beaman
2017-11-01
Full Text Available This paper analyzes the contours of religious and nonreligious diversity in the Canadian public sphere. The ever-changing (nonreligious landscape offers an opportunity to consider the flow of ideas from this new diversity to responses and choices at the individual, group, and state levels to inclusion and exclusion. The paper first begins with a descriptive approach to religious diversity, identifying the normatively-charged nature inherent to measures of religion. It then turns to the notion of choices, considering the somewhat uniquely Canadian contributions of multiculturalism, reasonable accommodation, and the recent complication of nonreligion as a category of religious identity. The paper then considers three case studies which reveal the tensions embedded in the new diversity and responses to it in Canada, including (1 the Saint-Sacrement Hospital crucifix incident; (2 Zunera Ishaq’s challenge to the citizenship ceremony niqab ban; and (3 school controversies in Ontario’s Peel Region.
Construction of the Voronoi mesh on a sphere
International Nuclear Information System (INIS)
Augenbaum, J.M.; Peskin, C.S.
1985-01-01
A new construction of the Voronoi mesh on the sphere is presented. The main feature is that the algorithm adds points one at a time until the final Voronoi mesh is built up. By adding one point to an existing Voronoi mesh of K points, only local changes are needed to construct a Voronoi mesh of K+1 points. This construction is particularly well suited to time-dependent problems since using information from the Voronoi mesh at the previous time step allows us to reduce the construction to O(N) operations when the two configurations are close, while the algorithm does not break down when they are far apart. Numerical experiments are presented to substantiate the O(N) operation count for a ''typical'' case
Energy Technology Data Exchange (ETDEWEB)
Santos, A.R.L.; Silva, F.S.; Martins, M.M.; Pereira, W.W., E-mail: aleiras@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ/LNMRI/LN), Rio de Janeiro, RJ (Brazil). Lab. de Neutrons; Freitas, B.M. [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear; Tavares, D.Y.S. [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)
2014-07-01
This work intends to assess materials for moderation of neutrons, trying to reduce the rate of H{sub p}(10) and H⁎p(10), reducing the effective dose of Occupationally Exposed Workers (OEW) who handle this source daily. The neutron spectra moderated by different materials was performed with a neutron source of {sup 241}Am-Be in an electronic positioning system, using a neutron spectrometry with Bonner Sphere at 50 cm from the center of source. The materials used for moderation were paraffin, silicone and Polyvinyl Chloride (PVC) resin ball. (author)
RDANN a new methodology to solve the neutron spectra unfolding problem
International Nuclear Information System (INIS)
Ortiz R, J.M.; Martinez B, M.R.; Vega C, H.R.
2006-01-01
The optimization processes known as Taguchi method and DOE methodology are applied to the design, training and testing of Artificial Neural Networks in the neutron spectrometry field, which offer potential benefits in the evaluation of the behavior of the net as well as the ability to examine the interaction of the weights and neurons inside the same one. In this work, the Robust Design of Artificial Neural Networks methodology is used to solve the neutron spectra unfolding problem, designing, training and testing an ANN using a set of 187 neutron spectra compiled by the International Atomic Energy Agency, to obtain the better neutron spectra unfolded from the Bonner spheres spectrometer's count rates. (Author)
Computing variational bounds for flow through random aggregates of Spheres
International Nuclear Information System (INIS)
Berryman, J.G.
1983-01-01
Known formulas for variational bounds on Darcy's constant for slow flow through porous media depend on two-point and three-poiint spatial correlation functions. Certain bounds due to Prager and Doi depending only a two-point correlation functions have been calculated for the first time for random aggregates of spheres with packing fractions (eta) up to eta = 0.64. Three radial distribution functions for hard spheres were tested for eta up to 0.49: (1) the uniform distribution or ''well-stirred approximation,'' (2) the Percus Yevick approximation, and (3) the semi-empirical distribution of Verlet and Weis. The empirical radial distribution functions of Benett andd Finney were used for packing fractions near the random-close-packing limit (eta/sub RCP/dapprox.0.64). An accurate multidimensional Monte Carlo integration method (VEGAS) developed by Lepage was used to compute the required two-point correlation functions. The results show that Doi's bounds are preferred for eta>0.10 while Prager's bounds are preferred for eta>0.10. The ''upper bounds'' computed using the well-stirred approximation actually become negative (which is physically impossible) as eta increases, indicating the very limited value of this approximation. The other two choices of radial distribution function give reasonable results for eta up to 0.49. However, these bounds do not decrease with eta as fast as expected for large eta. It is concluded that variational bounds dependent on three-point correlation functions are required to obtain more accurate bounds on Darcy's constant for large eta
Benchmark validation by means of pulsed sphere experiment at OKTAVIAN
Energy Technology Data Exchange (ETDEWEB)
Ichihara, Chihiro [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.; Hayashi, S.A.; Kimura, Itsuro; Yamamoto, Junji; Takahashi, Akito
1997-03-01
The new version of Japanese nuclear data library JENDL-3.2 has recently been released. JENDL Fusion File which adopted DDX representations for secondary neutrons was also improved with the new evaluation method. On the other hand, FENDL nuclear data project to compile nuclear data library for fusion related research has been conducted partly under auspices of International Atomic Energy Agency (IAEA). The first version FENDL-1 consists of JENDL-3.1, ENDF/B-VI, BROND-2 and EFF-1 and has been released in 1995. The work for the second version FENDL-2 is now ongoing. The Bench mark validation of the nuclear data libraries have been performed to help selecting the candidate for the FENDL-2. The benchmark experiment have been conducted at OKTAVIAN of Osaka university. The sample spheres were constructed by filling the spherical shells with sample. The leakage neutron spectra from sphere piles were measured with a time-of-flight method. The measured spectra were compared with the theoretical calculation using MCNP 4A and the processed libraries from JENDL-3.1, JENDL-3.2, JENDL Fusion File, and FENDL-1. JENDL Fusion File and JENDL-3.2 gave almost the same prediction for the experiment. And both prediction are almost satisfying for Li, Cr, Mn, Cu, Zr, Nb and Mo, whereas for Al, LiF, CF2, Si, Ti, Co and W there is some discrepancy. However, they gave better prediction than the calculations using the library from FENDL-1, except for W. (author)
Inhomogeneous quasistationary state of dense fluids of inelastic hard spheres.
Fouxon, Itzhak
2014-05-01
We study closed dense collections of freely cooling hard spheres that collide inelastically with constant coefficient of normal restitution. We find inhomogeneous states (ISs) where the density profile is spatially nonuniform but constant in time. The states are exact solutions of nonlinear partial differential equations that describe the coupled distributions of density and temperature valid when inelastic losses of energy per collision are small. The derivation is performed without modeling the equations' coefficients that are unknown in the dense limit (such as the equation of state) using only their scaling form specific for hard spheres. Thus the IS is the exact state of this dense many-body system. It captures a fundamental property of inelastic collections of particles: the possibility of preserving nonuniform temperature via the interplay of inelastic cooling and heat conduction that generalizes previous results. We perform numerical simulations to demonstrate that arbitrary initial state evolves to the IS in the limit of long times where the container has the geometry of the channel. The evolution is like a gas-liquid transition. The liquid condenses in a vanishing part of the total volume but takes most of the mass of the system. However, the gaseous phase, which mass grows only logarithmically with the system size, is relevant because its fast particles carry most of the energy of the system. Remarkably, the system self-organizes to dissipate no energy: The inelastic decay of energy is a power law [1+t/t(c)](-2), where t(c) diverges in the thermodynamic limit. This is reinforced by observing that for supercritical systems the IS coincide in most of the space with the steady states of granular systems heated at one of the walls. We discuss the relation of our results to the recently proposed finite-time singularity in other container's geometries.
Sphere-forming cell subpopulations with cancer stem cell properties in human hepatoma cell lines
Directory of Open Access Journals (Sweden)
Chen Lei
2011-06-01
Full Text Available Abstract Background Cancer stem cells (CSCs are regarded as the cause of tumor formation and recurrence. The isolation and identification of CSCs could help to develop novel therapeutic strategies specifically targeting CSCs. Methods Human hepatoma cell lines were plated in stem cell conditioned culture system allowed for sphere forming. To evaluate the stemness characteristics of spheres, the self-renewal, proliferation, chemoresistance, tumorigenicity of the PLC/PRF/5 sphere-forming cells, and the expression levels of stem cell related proteins in the PLC/PRF/5 sphere-forming cells were assessed, comparing with the parental cells. The stem cell RT-PCR array was performed to further explore the biological properties of liver CSCs. Results The PLC/PRF/5, MHCC97H and HepG2 cells could form clonal nonadherent 3-D spheres and be serially passaged. The PLC/PRF/5 sphere-forming cells possessed a key criteria that define CSCs: persistent self-renewal, extensive proliferation, drug resistance, overexpression of liver CSCs related proteins (Oct3/4, OV6, EpCAM, CD133 and CD44. Even 500 sphere-forming cells were able to form tumors in NOD/SCID mice, and the tumor initiating capability was not decreased when spheres were passaged. Besides, downstream proteins DTX1 and Ep300 of the CSL (CBF1 in humans, Suppressor of hairless in Drosophila and LAG1 in C. elegans -independent Notch signaling pathway were highly expressed in the spheres, and a gamma-secretase inhibitor MRK003 could significantly inhibit the sphere formation ability. Conclusions Nonadherent tumor spheres from hepatoma cell lines cultured in stem cell conditioned medium possess liver CSC properties, and the CSL-independent Notch signaling pathway may play a role in liver CSCs.
Accelerator mass spectrometry.
Hellborg, Ragnar; Skog, Göran
2008-01-01
In this overview the technique of accelerator mass spectrometry (AMS) and its use are described. AMS is a highly sensitive method of counting atoms. It is used to detect very low concentrations of natural isotopic abundances (typically in the range between 10(-12) and 10(-16)) of both radionuclides and stable nuclides. The main advantages of AMS compared to conventional radiometric methods are the use of smaller samples (mg and even sub-mg size) and shorter measuring times (less than 1 hr). The equipment used for AMS is almost exclusively based on the electrostatic tandem accelerator, although some of the newest systems are based on a slightly different principle. Dedicated accelerators as well as older "nuclear physics machines" can be found in the 80 or so AMS laboratories in existence today. The most widely used isotope studied with AMS is 14C. Besides radiocarbon dating this isotope is used in climate studies, biomedicine applications and many other fields. More than 100,000 14C samples are measured per year. Other isotopes studied include 10Be, 26Al, 36Cl, 41Ca, 59Ni, 129I, U, and Pu. Although these measurements are important, the number of samples of these other isotopes measured each year is estimated to be less than 10% of the number of 14C samples. Copyright 2008 Wiley Periodicals, Inc.
Li, Zhihua; Zhu, Lin; Liu, Qian; Du, Yu; Wang, Feng
2013-10-01
Multifunctional SiO2 · Re2O3 (Re = Y, Eu, La, Sm, Tb, Pr) hollow spheres (HSs) have been fabricated using an acidic Re3+ ion solution. Under ultraviolet radiation, functional HSs emit different colors of light according to the different rare-earth ions embedded into the shell of SiO2 hollow spheres. The as-prepared hollow capsules were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, Brunauer-Emmett-Teller method, scanning electron microscopy, and energy-dispersive spectrometry. Drug loading and release experiments have been carried out using SiO2 · Eu2O3 HSs that acted as drug carriers. The results demonstrate that the multifunctional HSs exhibit a high storage capacity and the ability of retaining drug stability and activity, which indicates that the as-synthesized fluorescent hollow capsules are a potential candidate as drug delivery materials.