Development of a Bonner Sphere Neutron Spectrometer from a Commercial Neutron Dosimeter
Chu, M C; Kwok, T; Leung, J K C; Lin, Y C; Liu, H; Luk, K B; Ngai, H Y; Pun, C S J; Wong, H L H
2016-01-01
Bonner Spheres have been used widely for the measurement of neutron spectra with neutron energies ranged from thermal up to at least 20 MeV. A Bonner Sphere neutron spectrometer (BSS) was developed by extending a Berthold LB 6411 neutron-dose-rate meter. The BSS consists of a $^{3}$He thermal-neutron detector with integrated electronics, a set of eight polyethylene spherical shells and two optional lead shells of various sizes. The response matrix of the BSS was calculated with GEANT4 Monte Carlo simulation. The BSS had a calibration uncertainty of $\\pm 8.6\\%$ and a detector background rate of $(1.57 \\pm 0.04) \\times 10^{-3}$ s$^{-1}$. A spectral unfolding code NSUGA was developed. The NSUGA code utilizes genetic algorithms and has been shown to perform well in the absence of a priori information.
The optimization study of Bonner sphere in the epi-thermal neutron irradiation field for BNCT.
Ueda, H; Tanaka, H; Maruhashi, A; Ono, K; Sakurai, Y
2011-12-01
The optimization study on the Bonner sphere in the epi-thermal neutron irradiation field for BNCT was done for the moderator material, moderator size, and activation foils as a neutron detector in the sphere. The saturated activity for the activation foil was obtained from the calculated response, and the effective energy range for each Bonner sphere was determined from the saturated activity. We can see that boric acid solution moderator is suitable for the spectrum measurement of a epi-thermal neutron irradiation field.
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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.
NSDUAZ unfolding package for neutron spectrometry and dosimetry with Bonner spheres
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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)
Calibration of a Bonner sphere extension (BSE) for high-energy neutron spectrometry
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Howell, R.M., E-mail: rhowell@mdanderson.or [UT M.D. Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030 (United States); Burgett, E.A. [Georgia Institute of Technology, 900 Atlantic Drive, Atlanta, GA (United States); Wiegel, B. [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany); Hertel, N.E. [Georgia Institute of Technology, 900 Atlantic Drive, Atlanta, GA (United States)
2010-12-15
In a recent work, we constructed modular multisphere system which expands upon the design of an existing, commercially available Bonner sphere system by adding concentric shells of copper, tungsten, or lead. Our modular multisphere system is referred to as the Bonner Sphere Extension (BSE). The BSE was tested in a high energy neutron beam (thermal to 800 MeV) at Los Alamos Neutron Science Center and provided improvement in the measurement of the neutron spectrum in the energy regions above 20 MeV when compared to the standard BSS (and). However, when the initial test of the system was carried out at LANSCE, the BSE had not yet been calibrated. Therefore the objective of the present study was to perform calibration measurements. These calibration measurements were carried-out using monoenergetic neutron ISO 8529-1 reference beams at the Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany. The following monoenergetic reference beams were used for these experiments: 14.8 MeV, 1.2 MeV, 565 keV, and 144 keV. Response functions for the BSE were calculated using the Monte Carlo N-Particle Code, eXtended (MCNPX). The percent difference between the measured and calculated responses was calculated for each sphere and energy. The difference between measured and calculated responses for individual spheres ranged between 7.9% and 16.7% and the arithmetic mean for all spheres was (10.9 {+-} 1.8)%. These sphere specific correction factors will be applied for all future measurements carried out with the BSE.
Calibration of a Bonner sphere extension (BSE) for high-energy neutron spectrometry.
Howell, R M; Burgett, E A; Wiegel, B; Hertel, N E
2010-12-01
In a recent work, we constructed modular multisphere system which expands upon the design of an existing, commercially available Bonner sphere system by adding concentric shells of copper, tungsten, or lead. Our modular multisphere system is referred to as the Bonner Sphere Extension (BSE). The BSE was tested in a high energy neutron beam (thermal to 800 MeV) at Los Alamos Neutron Science Center and provided improvement in the measurement of the neutron spectrum in the energy regions above 20 MeV when compared to the standard BSS (Burgett, 2008 and Howell et al., 2009).However, when the initial test of the system was carried-out at LANSCE, the BSE had not yet been calibrated. Therefore the objective of the present study was to perform calibration measurements. These calibration measurements were carried out using monoenergetic neutron ISO 8529-1 reference beams at the Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany. The following monoenergetic reference beams were used for these experiments: 14.8 MeV, 1.2 MeV, 565 keV, and 144 keV. Response functions for the BSE were calculated using the Monte Carlo N-Particle Code, eXtended (MCNPX). The percent difference between the measured and calculated responses was calculated for each sphere and energy. The difference between measured and calculated responses for individual spheres ranged between 7.9 % and 16.7 % and the arithmetic mean for all spheres was (10.9 ± 1.8) %. These sphere specific correction factors will be applied for all future measurements carried-out with the BSE.
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).
NEMUS--the PTB Neutron Multisphere Spectrometer Bonner spheres and more
Wiegel, B
2002-01-01
The original Bonner sphere spectrometer as it is used and characterized by PTB consists of 12 polyethylene spheres with diameters from 7.62 cm (3'') to 45.72 cm (18'') and a sup 3 He-filled spherical proportional counter used as a central thermal-neutron-sensitive detector and as a bare or cadmium-shielded bare detector. In this paper, a set of four new spheres made of polyethylene with copper or lead inlets is introduced. All spheres are less than 18 kg in mass and their responses to high energy neutrons increase with energy as a result of the increasing (n,xn) cross-sections of copper and lead. The fluence response matrix was calculated up to 10 GeV using an extended neutron cross-section library (LA150) and the MCNP(X) Monte Carlo code. Calibration measurements with neutron energies up to 60 MeV were used to compare the calculated response functions to measured values. For measurements outside the laboratory, a miniaturized, battery-powered electronic set-up was developed. This system with the additional, ...
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Ortiz R, J. M. [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica, Apdo. Postal 336, 98000 Zacatecas (Mexico); Martinez B, M. R.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Apdo. Postal 336, 98000 Zacatecas (Mexico); Gallego D, E.; Lorente F, A. [Universidad Politecnica de Madrid, Departamento de Ingenieria Nuclear, ETSI Industriales, C. Jose Gutierrez Abascal 2, 28006 Madrid (Spain); Mendez V, R.; Los Arcos M, J. M.; Guerrero A, J. E., E-mail: morvymm@yahoo.com.m [CIEMAT, Laboratorio de Metrologia de Radiaciones Ionizantes, Avda. Complutense 22, 28040 Madrid (Spain)
2011-02-15
Neutron spectra unfolding and dose equivalent calculation are complicated tasks in radiation protection, are highly dependent of the neutron energy, and a precise knowledge on neutron spectrometry is essential for all dosimetry-related studies as well as many nuclear physics experiments. In previous works have been reported neutron spectrometry and dosimetry results, by using the artificial neural networks (Ann) technology as alternative solution, starting from the count rates of a Bonner spheres system with a {sup 6}LiI(Eu) thermal neutrons detector, 7 polyethylene spheres and the UTA4 response matrix with 31 energy bins. In this work, an Ann was designed and optimized by using the RDAnn methodology for the Bonner spheres system used at CIEMAT Spain, which is composed of a {sup 3}He neutron detector, 12 moderator spheres and a response matrix for 72 energy bins. For the Ann design process a neutrons spectra catalogue compiled by the IAEA was used. From this compilation, the neutrons spectra were converted from lethargy to energy spectra. Then, the resulting energy fluence spectra were re-bin ned by using the MCNP code to the corresponding energy bins of the {sup 3}He response matrix before mentioned. With the response matrix and the re-bin ned spectra the counts rate of the Bonner spheres system were calculated and the resulting re-bin ned neutrons spectra and calculated counts rate were used as the Ann training data set. (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...
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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)
Ueda, H; Tanaka, H; Sakurai, Y
2015-12-01
Bonner sphere is useful to evaluate the neutron spectrum in detail. We are improving the energy resolution in epi-thermal neutron region of Bonner sphere, using boric acid water solution as a moderator. Its response function peak is narrower than that for polyethylene moderator and the improvement of the resolution is expected. The resolutions between polyethylene moderator and boric acid water solution moderator were compared by simulation calculation. Also the influence in the uncertainty of Bonner sphere configuration to spectrum estimation was simulated.
Ueda, H; Tanaka, H; Sakurai, Y
2015-10-01
Bonner sphere is useful to evaluate the neutron spectrum in detail. We are improving the energy resolution in epi-thermal neutron region of Bonner sphere, using boric acid water solution as a moderator. Its response function peak is narrower than that for polyethylene moderator and the improvement of the resolution is expected. The resolutions between polyethylene moderator and boric acid water solution moderator were compared by simulation calculation. Also the influence in the uncertainty of Bonner sphere configuration to spectrum estimation was simulated.
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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
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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.
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Reyes H, A.; Ortiz R, J. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)
2012-10-15
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)
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...
Determining the neutron spectrum of 241Am-Be and 252Cf sources using bonner sphere spectrometer
Directory of Open Access Journals (Sweden)
M.A Varshabi
2016-06-01
Full Text Available Bonner spheres system is one of the ways of measuring neutron energy distribution which is often applied in spectrometry and neutron dosimetry. This system includes a thermal neutron detector, being located in the center of several polyethylene spheres, and it is still workable due to the isotropic response of the system which in turn is derived from the spherical symmetry of moderators and the broad measurable range of the energy. In order to practically use this spectrometer, it is necessary to calibrate this system using standard neutron sources. This research aimed to determine the calibration factor of Bonner spheres spectrometry system and energy spectrum of two standard 241Am-Be and 252Cf sources in the atomic energy organization. Calibration and experimental measurement were done via the two standard sources. The response vector of each detector was derived by using MCNPX simulation code, based on the Monte Carlo method. The spectra unfolding of this system was performed through iterative method using the SPUNIT code done in software NSDUAZ6LiI and BUMS.
Mazrou, H; Nedjar, A; Seguini, T
2016-08-01
This paper describes the measurement campaign held around the neutron radiography (NR) facility of the Algerian 1MW NUR research reactor. The main objective of this work is to characterize accurately the neutron beam provided at one of the radial channels of the NUR research reactor taking benefit of the acquired CRNA Bonner spheres spectrometer (BSS). The specific objective was to improve the image quality of the NR facility. The spectrometric system in use is based on a central spherical (3)He thermal neutron proportional counter combined with high density polyethylene spheres of different diameters ranging from 3 to 12in. This counting system has good gamma ray discrimination and is able to cover an energy range from thermal to 20MeV. The measurements were performed at the sample distance of 0.6m from the beam port and at a height of 1.2m from the facility floor. During the BSS measurements, the reactor was operating at low power (100W) to avoid large dead times, pulse pileup and high level radiation exposures, in particular, during spheres handling. Thereafter, the neutron spectrum at the sample position was unfolded by means of GRAVEL and MAXED computer codes. The thermal, epithermal and fast neutron fluxes, the total neutron flux, the mean energy and the Cadmium ratio (RCd) were provided. A sensitivity analysis was performed taking into account various defaults spectra and ultimately a different response functions in the unfolding procedure. Overall, from the obtained results it reveals, unexpectedly, that the measured neutron spectrum at the sample position of the neutron radiography of the NUR reactor is being harder with a predominance of fast neutrons (>100keV) by about 60%. Finally, those results were compared to previous and more recent measurements obtained by activation foils detectors. The agreement was fairly good highlighting thereby the consistency of our findings.
Neutron measurements in the Vandellòs II nuclear power plant with a Bonner sphere system.
Fernández, F; Bakali, M; Tomás, M; Muller, H; Pochat, J L
2004-01-01
In some Spanish nuclear power plants of pressurised water reactor (PWR) type, albedo thermoluminescence dosemeters are used for personal dosimetry while survey meters, based on a thermal-neutron detector inside a cylindrical or spherical moderator, are used for dose rate assessment in routine monitoring. The response of both systems is highly dependent on the energy of the existing neutron fields. They are usually calibrated by means of ISO neutron sources with energy distributions quite different from those encountered at these installations. Spectrometric measurements with a Bonner sphere system (BSS) allow us to determine the reference dosimetric values. The UAB group, under request from the National Coordinated Research Action, was in charge of characterising the neutron fields and evaluating the response of personal dosemeters at several measurement points inside the containment building of the Catalan Nuclear Power Plant Vandellòs II. The neutron fields were characterised at five places using the UAB-BSS and a home made unfolding code called MITOM. The results obtained confirm the presence of low-energy components in the neutron field in most of the selected points. Moreover, we have found no influence of the nuclear fuel burning on the shape of the spectrum.
Atanackovic, J; Matysiak, W; Witharana, S; Dubeau, J; Waker, A J
2014-10-01
Neutron spectrometry measurements were carried out at the McMaster Accelerator Laboratory (MAL), which is equipped with a 3-MV Van de Graaff-type accelerator. Protons were accelerated onto a thick natural lithium target inducing the (7)Li(p,n)(7)Be threshold reaction. Depending on the proton energy, slightly different poly-energetic neutron fields were produced. Neutron spectra were measured at two incident proton energies: 2.15 and 2.24 MeV, which produced poly-energetic neutrons with maximum kinetic energies of 401 and 511 keV, respectively. Measurements were performed at a distance of 1.5 m from the target in the forward direction with three different instruments: Bonner sphere spectrometer, Nested Neutron Spectrometer and ROtational proton recoil SPECtrometer.
A Bonner Sphere Spectrometer for pulsed fields.
Aza, E; Dinar, N; Manessi, G P; Silari, M
2016-02-01
The use of conventional Bonner Sphere Spectrometers (BSS) in pulsed neutron fields (PNF) is limited by the fact that proportional counters, usually employed as the thermal neutron detectors, suffer from dead time losses and show severe underestimation of the neutron interaction rate, which leads to strong distortion of the calculated spectrum. In order to avoid these limitations, an innovative BSS, called BSS-LUPIN, has been developed for measuring in PNF. This paper describes the physical characteristics of the device and its working principle, together with the results of Monte Carlo simulations of its response matrix. The BSS-LUPIN has been tested in the stray neutron field at the CERN Proton Synchrotron, by comparing the spectra obtained with the new device, the conventional CERN BSS and via Monte Carlo simulations.
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)
Mazrou, H; Allab, M
2012-08-01
The present work deals with the Bonner sphere spectrometer (BSS) measurements performed, to support the authors' Monte-Carlo calculations, to estimate accurately the main characteristics of the neutron field of the (241)Am-Be-based OB26 irradiator acquired for radiation protection purposes by the Nuclear Research Centre of Algiers. The measurements were performed at a reference irradiation position selected at 150 cm from the geometrical centre of the neutron source. The spectrometric system in use is based on a central spherical (3)He thermal neutron proportional counter. The response matrix of the present spectrometer has been taken to be similar to the original Physikalisch-Technische Bundesanstalt (PTB) (Braunschweig, Germany) BSS's response matrix, with a five bins per decade energy group structure, as there is no significant difference in the BSS's physical characteristics. Thereafter, the authors' BSS measurements were used together with MCNP5 results to unfold the neutron spectrum by means of MAXED and GRAVEL computer codes from the U.M.G. 3.3 package, developed at PTB. Besides, sensitivity analysis has been performed to test the consistency of the unfolding procedure. It reveals that no significant discrepancy was observed in the total neutron fluence and total ambient dose values following the perturbation of some pertinent unfolding parameters except for the case where a 10 bins energy structure was assumed for the guess spectrum. In this latter case, a 5 % difference was observed in the ambient dose equivalent compared with the reference case. Finally, a comparative study performed between different counting systems together with MCNP5 and predictive formulas results shows that they were globally satisfactory, highlighting thereby the relevance of the unfolding procedure and the reliability of the obtained results.
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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)
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
Atanackovic, J; Matysiak, W; Hakmana Witharana, S S; Aslam, I; Dubeau, J; Waker, A J
2013-01-01
Neutron spectrometry and subsequent dosimetry measurements were undertaken at the McMaster Nuclear Reactor (MNR) and AECL Chalk River National Research Universal (NRU) Reactor. The instruments used were a Bonner sphere spectrometer (BSS), a cylindrical nested neutron spectrometer (NNS) and a commercially available rotational proton recoil spectrometer. The purposes of these measurements were to: (1) compare the results obtained by three different neutron measuring instruments and (2) quantify neutron fields of interest. The results showed vastly different neutron spectral shapes for the two different reactors. This is not surprising, considering the type of the reactors and the locations where the measurements were performed. MNR is a heavily shielded light water moderated reactor, while NRU is a heavy water moderated reactor. The measurements at MNR were taken at the base of the reactor pool, where a large amount of water and concrete shielding is present, while measurements at NRU were taken at the top of the reactor (TOR) plate, where there is only heavy water and steel between the reactor core and the measuring instrument. As a result, a large component of the thermal neutron fluence was measured at MNR, while a negligible amount of thermal neutrons was measured at NRU. The neutron ambient dose rates at NRU TOR were measured to be between 0.03 and 0.06 mSv h⁻¹, while at MNR, these values were between 0.07 and 2.8 mSv h⁻¹ inside the beam port and <0.2 mSv h⁻¹ between two operating beam ports. The conservative uncertainty of these values is 15 %. The conservative uncertainty of the measured integral neutron fluence is 5 %. It was also found that BSS over-responded slightly due to a non-calibrated response matrix.
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)
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 EFisica 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.
Bedogni, R.; Amgarou, K.; Domingo, C.; Russo, S.; Cirrone, G. A. P.; Pelliccioni, M.; Esposito, A.; Pola, A.; Introini, M. V.; Gentile, A.
2012-07-01
Neutrons constitute an important component of the radiation environment in hadron therapy accelerators. Their energy distribution may span from thermal up to hundred of MeV. The characterization of these fields in terms of dosimetric or spectrometric quantities is crucial for either the patient protection or the facility design aspects. To date, the Extended Range Bonner Sphere Spectrometer (ERBSS) is the only instrument able to simultaneously determine all spectral components in such workplaces. With the aim of providing useful data to the scientific community involved in neutron measurements at hadron therapy facilities, a measurement campaign was carried out at the Centro di AdroTerapia e Applicazioni Nucleari Avanzate (CATANA) of INFN-LNS (Laboratori Nazionali del Sud), where a 62 AMeV carbon ion is available. The 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. The ERBSSs of UAB (Universidad Autónoma de Barcelona-Grup de Física de les Radiacions) and INFN (Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali di Frascati) were used to measure the resulting neutron fields. The two ERBSSs use different detectors and sphere diameters, and have been independently calibrated. The FRUIT code was used to unfold the results.
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...
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)
The response of a Bonner Sphere spectrometer to charged hadrons
Agosteo, S; Fassò, A; Silari, M
2004-01-01
Bonner sphere spectrometers (BSSs) are employed in neutron spectrometry and dosimetry since many years. Recent developments have seen the addition to a conventional BSS of one or more detectors (moderator plus thermal neutron counter) specifically designed to improve the overall response of the spectrometer to neutrons above 10 MeV. These additional detectors employ a shell of material with a high mass number (such as lead) within the polyethylene moderator, in order to slow down high-energy neutrons via (n, xn) reactions. A BSS can be used to measure neutron spectra both outside accelerator shielding and from an unshielded target. Measurements were recently performed at CERN of the neutron yield and spectral fluence at various angles from unshielded, semithick copper, silver and lead targets, bombarded by a mixed proton/pion beam with 40 GeV per c momentum. These experiments have provided evidence that under certain circumstances, the use of lead-enriched moderators may present a problem: these detectors wer...
The Effect of the Choice or Response Matrix on Unfolded Bonner Sphere Spectra.
1984-12-31
cylindrical, 4 m high x 4 mm dia., europium- activated lithium iodide scintillation crystal as the thermal neutron detector in the centers of polyethylene... Neutroniques Avec les Spheres de Bonner Establissement d’une Matrice Log-Normale de Reference," CEA-N-2241, Commisariat d l’Energie Atomique - France (1981
The response of a bonner sphere spectrometer to charged hadrons.
Agosteo, S; Dimovasili, E; Fassò, A; Silari, M
2004-01-01
Bonner sphere spectrometers (BSSs) are employed in neutron spectrometry and dosimetry since many years. Recent developments have seen the addition to a conventional BSS of one or more detectors (moderator plus thermal neutron counter) specifically designed to improve the overall response of the spectrometer to neutrons above 10 MeV. These additional detectors employ a shell of material with a high mass number (such as lead) within the polyethylene moderator, in order to slow down high-energy neutrons via (n,xn) reactions. A BSS can be used to measure neutron spectra both outside accelerator shielding and from an unshielded target. Measurements were recently performed at CERN of the neutron yield and spectral fluence at various angles from unshielded, semi-thick copper, silver and lead targets, bombarded by a mixed proton/pion beam with 40 GeV per c momentum. These experiments have provided evidence that under certain circumstances, the use of lead-enriched moderators may present a problem: these detectors were found to have a significant response to the charged hadron component accompanying the neutrons emitted from the target. Conventional polyethylene moderators show a similar behaviour but less pronounced. These secondary hadrons interact with the moderator and generate neutrons, which are in turn detected by the counter. To investigate this effect and determine a correction factor to be applied to the unfolding procedure, a series of Monte Carlo simulations were performed with the FLUKA code. These simulations aimed at determining the response of the BSS to charged hadrons under the specific experimental situation. Following these results, a complete response matrix of the extended BSS to charged pions and protons was calculated with FLUKA. An experimental verification was carried out with a 120 GeV per c hadron beam at the CERF facility at CERN.
Response matrix of an extended Bonner sphere system
Vylet, V
2002-01-01
We have developed a system of Bonner spheres designed for use around high-energy accelerators. The upper energy limit of the system was extended using a lead radiator, which acts as an energy converter via the (n,xn) reaction. In addition, we use sup 1 sup 1 C activation as an additional component integrated into the system and the spectra unfolding process. In the first version of the system, the lead radiator was present in only one sphere with diameter of 30.48 cm. The object of the present work was to investigate the geometry of the lead radiator and its use in moderators of several different sizes. As a result, we have developed a modular design and calculated the response matrix of the new system.
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)
Muller, H.; Fernández, F.; Van Ryckeghem, L.; Alexandre, P.; Bouassoule, T.; Pochat, J.-L.; Tomas, M.
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 Vandellòs 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-energetic neutrons and with the CANEL IPSN facility which simulates realistic fields.
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...
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....
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...
Leder, Alexander; Ricochet Collaboration
2016-03-01
The Ricochet experiment seeks to measure Coherent (neutral-current) Elastic Neutrino-Nucleus Scattering (CENNS) using dark matter style detectors placed near a neutrino source, possibly the MIT research reactor (MITR), which offers a high continuous neutrino flux at high energies. Currently, Ricochet is characterizing the backgrounds at MITR. The main background is the neutrons emitted simultaneously from the core. To characterize this background, we wrapped a Bonner cylinder around a 3He thermal neutron detector, whose data was then unfolded to produce a neutron energy spectrum across several orders of magnitude. We discuss the resulting spectrum as well its implications for deploying Ricochet in the future.
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.
Gracanin, V; Guatelli, S; Prokopovich, D; Rosenfeld, A B; Berry, A
2017-01-01
The Bonner Sphere Spectrometer (BSS) system is a well-established technique for neutron dosimetry that involves detection of thermal neutrons within a range of hydrogenous moderators. BSS detectors are often used to perform neutron field surveys in order to determine the ambient dose equivalent H*(10) and estimate health risk to personnel. There is a potential limitation of existing neutron survey techniques, since some detectors do not consider the direction of the neutron field, which can result in overly conservative estimates of dose in neutron fields. This paper shows the development of a Geant4 simulation application to characterise a prototype neutron detector based on three orthogonal (3)He tubes inside a single HDPE sphere built at the Australian Nuclear Science and Technology Organisation (ANSTO). The Geant4 simulation has been validated with respect to experimental measurements performed with an Am-Be source.
Viererbl, L; Klupák, V; Lahodová, Z; Marek, M
2012-07-01
The LVR-15 research reactor's horizontal channel with its epithermal neutron beam is used mainly for boron neutron capture therapy. Neutrons from the reactor core pass through a special filter before the collimator and the beam outlet. Neutron fluence and spectrum are the basic characteristics of an epithermal neutron beam. Three methods used to measure the beam's neutron spectrum are described: the activation method, a Bonner sphere spectrometer with gold activation detectors and a Bonner sphere spectrometer with LiI(Eu) scintillation detector. Examples of results are compared and discussed.
Neutron spectrum unfolding using neural networks
Energy Technology Data Exchange (ETDEWEB)
Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E. [Universidad Autonoma de Zacatecas, A.P. 336, 98000 Zacatecas (Mexico)]. E-mail: rvega@cantera.reduaz.mx
2004-07-01
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 a large set of neutron spectra compiled by the International Atomic Energy Agency. These include spectra from iso- topic neutron sources, reference and operational neutron spectra obtained from accelerators and nuclear reactors. The spectra were transformed from lethargy to energy distribution and were re-binned to 31 energy groups using the MCNP 4C code. Re-binned spectra and UTA4 matrix were used to calculate the expected count rates in Bonner spheres spectrometer. These count rates were used as input and correspondent spectrum was used as output during neural network training. The network has 7 input nodes, 56 neurons as hidden layer and 31 neurons in the output layer. After training the network was tested with the Bonner spheres count rates produced by twelve neutron spectra. The network allows unfolding the neutron spectrum from count rates measured with Bonner spheres. Good results are obtained when testing count rates belong to neutron spectra used during training, acceptable results are obtained for count rates obtained from actual neutron fields; however the network fails when count rates belong to monoenergetic neutron sources. (Author)
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
Bedogni, R.; Buonomo, B.; Esposito, A.; Mazzitelli, G.; Foggetta, L.; Gomez Ros. J.M.; 10.1016/j.nima.2011.08.032
2011-01-01
science and studies of "single event effects". The intensity of the neutron beam obtainable with 510MeV electrons and its fluence energy distribution at a point of reference in the irradiation room were predicted by Monte Carlo simulations and experimentally determined with a Bonner Sphere Spectrometer (BSS). Due to the large photon contri...
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 dosimetry; Dosimetria de neutrons
Energy Technology Data Exchange (ETDEWEB)
Fratin, Luciano
1993-12-31
A neutron irradiation facility was designed and built in order to establish a procedure for calibrating neutron monitors and dosemeters. A 185 GBq {sup 241} Am Be source of known is used as a reference source. The irradiation facility using this source in the air provides neutron dose rates between 9 nSv s{sup -1} and 0,5 {sup {mu}}Sv s{sup -1}. A calibrated 50 nSv s{sup -1} thermal neutron field is obtained by using a specially designed paraffin block in conjunction with the {sup 241} Am Be source. A Bonner multisphere spectrometer was calibrated, using a procedure based on three methods proposed by international standards. The unfold {sup 241} Am Be neutron spectrum was determined from the Bonner spheres data and resulted in a good agreement with expected values for fluence rate, dose rate and mean energy. A dosimetric system based on the electrochemical etching of CR-39 was developed for personal dosimetry. The dosemeter badge using a (n,{alpha}) converter, the etching chamber and high frequency power supply were designed and built specially for this project. The electrochemical etching (ECE) parameters used were: a 6N KOH solution, 59 deg C, 20 kV{sub pp} cm{sup -1}, 2,0 kHz, 3 hours of ECE for thermal and intermediate neutrons and 6 hours for fast neutrons. The calibration factors for thermal, intermediate and fast neutrons were determined for this personal dosemeter. The sensitivities determined for the developed dosimetric system were (1,46{+-} 0,09) 10{sup 4} tracks cm{sup -2} mSv{sup -1} for thermal neutrons, (9{+-}3) 10{sup 2} tracks cm{sup -2} mSV{sup -1} for intermediate neutrons and (26{+-}4) tracks cm{sup -2} mSv{sup -1} for fast neutrons. The lower and upper limits of detection were respectively 0,002 mSv and 0,6 mSv for thermal neutrons, 0,04 mSv and 8 mSv for intermediate neutrons and 1 mSv and 12 mSv for fast neutrons. In view of the 1990`s ICRP recommendations, it is possible to conclude that the personal dosemeter described in this work is
SPHERES, Jülich's high-flux neutron backscattering spectrometer at FRM II.
Wuttke, Joachim; Budwig, Alfred; Drochner, Matthias; Kämmerling, Hans; Kayser, Franz-Joseph; Kleines, Harald; Ossovyi, Vladimir; Pardo, Luis Carlos; Prager, Michael; Richter, Dieter; Schneider, Gerald J; Schneider, Harald; Staringer, Simon
2012-07-01
SPHERES is a third-generation neutron backscattering spectrometer, located at the 20 MW German neutron source FRM II and operated by the Jülich Centre for Neutron Science. It offers an energy resolution (fwhm) better than 0.65 μeV, a dynamic range of ± 31 μeV, and a signal-to-noise ratio of up to 1750:1.
SPHERES, J\\"ulich's High-Flux Neutron Backscattering Spectrometer at FRM II
Wuttke, Joachim; Drochner, Matthias; Kämmerling, Hans; Kayser, Franz-Joseph; Pardo, Luis Carlos; Prager, Michael; Ossovyi, Vladimir; Schneider, Gerald J; Schneider, Harald; Staringer, Simon; Richter, Dieter
2012-01-01
SPHERES (SPectrometer with High Energy RESolution) is a third-generation neutron backscattering spectrometer, located at the 20 MW German neutron source FRM II and operated by the J\\"ulich Centre for Neutron Science. It offers an energy resolution (fwhm) better than 0.65 micro-eV, a dynamic range of +-31 micro-eV, and a signal-to-noise ratio of up to 1750:1.
SPHERES, Juelich's high-flux neutron backscattering spectrometer at FRM II
Energy Technology Data Exchange (ETDEWEB)
Wuttke, Joachim; Budwig, Alfred; Drochner, Matthias; Kaemmerling, Hans; Kayser, Franz-Joseph; Kleines, Harald; Ossovyi, Vladimir; Pardo, Luis Carlos; Prager, Michael; Richter, Dieter; Schneider, Gerald J.; Schneider, Harald; Staringer, Simon [Forschungszentrum Juelich GmbH, 52425 Juelich (Germany)
2012-07-15
SPHERES is a third-generation neutron backscattering spectrometer, located at the 20 MW German neutron source FRM II and operated by the Juelich Centre for Neutron Science. It offers an energy resolution (fwhm) better than 0.65 {mu}eV, a dynamic range of {+-} 31 {mu}eV, and a signal-to-noise ratio of up to 1750:1.
Artificial neural networks in neutron dosimetry
Energy Technology Data Exchange (ETDEWEB)
Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E.; Mercado, G.A.; Perales M, W.A.; Robles R, J.A. [Unidades Academicas de Estudios Nucleares, UAZ, A.P. 336, 98000 Zacatecas (Mexico); Gallego, E.; Lorente, A. [Depto. de Ingenieria Nuclear, Universidad Politecnica de Madrid, (Spain)
2005-07-01
An artificial neural network has been designed to obtain the neutron doses using only the Bonner spheres spectrometer's count rates. Ambient, personal and effective neutron doses were included. 187 neutron spectra were utilized to calculate the Bonner count rates and the neutron doses. The spectra were transformed from lethargy to energy distribution and were re-binned to 31 energy groups using the MCNP 4C code. Re-binned spectra, UTA4 response matrix and fluence-to-dose coefficients were used to calculate the count rates in Bonner spheres spectrometer and the doses. Count rates were used as input and the respective doses were used as output during neural network training. Training and testing was carried out in Mat lab environment. The artificial neural network performance was evaluated using the {chi}{sup 2}- test, where the original and calculated doses were compared. The use of Artificial Neural Networks in neutron dosimetry is an alternative procedure that overcomes the drawbacks associated in this ill-conditioned problem. (Author)
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)
Energy Technology Data Exchange (ETDEWEB)
Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E. [Cuerpo Academico de Radiobiologia, Estudios Nucleares, Universidad Autonoma de Zacatecas, A.P. 336, 98000 Zacatecas (Mexico)] e-mail: rvega@cantera.reduaz.mx [and others
2003-07-01
A neural network has been used to reconstruct the neutron spectra starting from the counting rates of the detectors of the Bonner sphere spectrophotometric system. A group of 56 neutron spectra was selected to calculate the counting rates that would produce in a Bonner sphere system, with these data and the spectra it was trained the neural network. To prove the performance of the net, 12 spectra were used, 6 were taken of the group used for the training, 3 were obtained of mathematical functions and those other 3 correspond to real spectra. When comparing the original spectra of those reconstructed by the net we find that our net has a poor performance when reconstructing monoenergetic spectra, this attributes it to those characteristic of the spectra used for the training of the neural network, however for the other groups of spectra the results of the net are appropriate with the prospective ones. (Author)
Wuttke, Joachim; Zamponi, Michaela
2013-11-01
The resolution of neutron backscattering spectrometers deteriorates at small scattering angles where analyzers deviate from exact backscattering. By reducing the azimuth angle range of the analyzers, the resolution can be improved with little loss of peak intensity. Measurements at the spectrometer SPHERES are in excellent agreement with simulations, which proves the dominance of geometric effects.
Energy Technology Data Exchange (ETDEWEB)
Wuttke, Joachim; Zamponi, Michaela [Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at MLZ, Lichtenbergstraße 1, 85747 Garching (Germany)
2013-11-15
The resolution of neutron backscattering spectrometers deteriorates at small scattering angles where analyzers deviate from exact backscattering. By reducing the azimuth angle range of the analyzers, the resolution can be improved with little loss of peak intensity. Measurements at the spectrometer SPHERES are in excellent agreement with simulations, which proves the dominance of geometric effects.
Wang, Pan-Feng; Ding, Ya-Dong; Wang, Qing-Bin; Ma, Zhong-Jian; Guo, Si-Ming; Li, Guan-Jia
2015-07-01
In this paper, the distribution of radiation field in the CSNS spectrometer hall at Dongguan, China, was simulated by the FLUKA program. The results show that the radiation field of the high energy proton accelerator is dominated by neutron radiation, with a broad range of neutron energies, spanning about eleven orders of magnitude. Simulation and calculation of the response functions of four Bonner spheres with a simplified model is done with FLUKA and MCNPX codes respectively, proving the feasibility of the FLUKA program for this application and the correctness of the calculation method. Using the actual model, we simulate and calculate the energy response functions of Bonner sphere detectors with polyethylene layers of different diameters, including detectors with lead layers, using the FLUKA code. Based on the simulation results, we select eleven detectors as the basic structure for an Extended Range Neutron Multisphere Spectrometer (ERNMS).
Institute of Scientific and Technical Information of China (English)
WANG Pan-Feng; DING Ya-Dong; WANG Qing-Bin; MA Zhong-Jian; GUO Si-Ming; LI Guan-Jia
2015-01-01
In this paper,the distribution of radiation field in the CSNS spectrometer hall at Dongguan,China,was simulated by the FLUKA program.The results show that the radiation field of the high energy proton accelerator is dominated by neutron radiation,with a broad range of neutron energies,spanning about eleven orders of magnitude.Simulation and calculation of the response functions of four Bonner spheres with a simplified model is done with FLUKA and MCNPX codes respectively,proving the feasibility of the FLUKA program for this application and the correctness of the calculation method.Using the actual model,we simulate and calculate the energy response functions of Bonner sphere detectors with polyethylene layers of different diameters,including detectors with lead layers,using the FLUKA code.Based on the simulation results,we select eleven detectors as the basic structure for an Extended Range Neutron Multisphere Spectrometer (ERNMS).
Measurement of the neutron spectrum by the multi-sphere method using a BF3 counter
Directory of Open Access Journals (Sweden)
Khabaz Rahim
2011-01-01
Full Text Available The multi-sphere method, a neutron detection technique, has been improved with a BF3 long cylindrical counter as a thermal detector located in the center of seven spheres with a diameter range of 3.5 to 12 inches. Energy response functions of the system have been determined by applying the MCNP4C Monte Carlo code of 10-8 MeV to 18 MeV. A new shadow cone has been designed to account for scattered neutrons. Although the newly designed shadow cone is smaller in length, its attenuation coefficient has been improved. To evaluate the system, the neutron spectrum of a 241AM-Be source has been measured.
Dumazert, Jonathan; Coulon, Romain; Carrel, Frédérick; Corre, Gwenolé; Normand, Stéphane; Méchin, Laurence; Hamel, Matthieu
2016-08-01
Neutron detection forms a critical branch of nuclear-related issues, currently driven by the search for competitive alternative technologies to neutron counters based on the helium-3 isotope. The deployment of plastic scintillators shows a high potential for efficient detectors, safer and more reliable than liquids, more easily scalable and cost-effective than inorganic. In the meantime, natural gadolinium, through its 155 and mostly 157 isotopes, presents an exceptionally high interaction probability with thermal neutrons. This paper introduces a dual system including a metal gadolinium core inserted at the center of a high-scale plastic scintillator sphere. Incident fast neutrons are thermalized by the scintillator shell and then may be captured with a significant probability by gadolinium 155 and 157 nuclei in the core. The deposition of a sufficient fraction of the capture high-energy prompt gamma signature inside the scintillator shell will then allow discrimination from background radiations by energy threshold, and therefore neutron detection. The scaling of the system with the Monte Carlo MCNPX2.7 code was carried out according to a tradeoff between the moderation of incident fast neutrons and the probability of slow neutron capture by a moderate-cost metal gadolinium core. Based on the parameters extracted from simulation, a first laboratory prototype for the assessment of the detection method principle has been synthetized. The robustness and sensitivity of the neutron detection principle are then assessed by counting measurement experiments. Experimental results confirm the potential for a stable, highly sensitive, transportable and cost-efficient neutron detector and orientate future investigation toward promising axes.
Energy Technology Data Exchange (ETDEWEB)
Dumazert, Jonathan; Coulon, Romain; Carrel, Frédérick; Corre, Gwenolé; Normand, Stéphane [CEA, LIST, Laboratoire Capteurs Architectures Electroniques, 91191 Gif-sur-Yvette (France); Méchin, Laurence [CNRS, UCBN, Groupe de Recherche en Informatique, Image, Automatique et Instrumentation de Caen, 14050 Caen (France); Hamel, Matthieu [CEA, LIST, Laboratoire Capteurs Architectures Electroniques, 91191 Gif-sur-Yvette (France)
2016-08-21
Neutron detection forms a critical branch of nuclear-related issues, currently driven by the search for competitive alternative technologies to neutron counters based on the helium-3 isotope. The deployment of plastic scintillators shows a high potential for efficient detectors, safer and more reliable than liquids, more easily scalable and cost-effective than inorganic. In the meantime, natural gadolinium, through its 155 and mostly 157 isotopes, presents an exceptionally high interaction probability with thermal neutrons. This paper introduces a dual system including a metal gadolinium core inserted at the center of a high-scale plastic scintillator sphere. Incident fast neutrons are thermalized by the scintillator shell and then may be captured with a significant probability by gadolinium 155 and 157 nuclei in the core. The deposition of a sufficient fraction of the capture high-energy prompt gamma signature inside the scintillator shell will then allow discrimination from background radiations by energy threshold, and therefore neutron detection. The scaling of the system with the Monte Carlo MCNPX2.7 code was carried out according to a tradeoff between the moderation of incident fast neutrons and the probability of slow neutron capture by a moderate-cost metal gadolinium core. Based on the parameters extracted from simulation, a first laboratory prototype for the assessment of the detection method principle has been synthetized. The robustness and sensitivity of the neutron detection principle are then assessed by counting measurement experiments. Experimental results confirm the potential for a stable, highly sensitive, transportable and cost-efficient neutron detector and orientate future investigation toward promising axes.
Yan, X; Köhler, A; Newhauser, W D
2002-01-01
Measurements of neutron dose equivalent values and neutron spectral fluences close to but outside of the therapeutic proton radiation field are presented. The neutron spectral fluences were determined at five locations with Bonner sphere measurements and established by unfolding techniques. More than 50 additional neutron dose equivalent values were measured with LiI and BF sub 3 thermal neutron detectors surrounded by a 25 cm polyethylene moderating sphere. For a large-field treatment, typical values of neutron dose equivalent per therapeutic proton absorbed dose, H/D, at 50 cm distance from isocenter, range from 1 mSv/Gy (at 0 deg.with respect to the proton beam axis) to 5 mSv/Gy (at 90 deg.). Experiments reveal that H/D varies significantly with the treatment technique, e.g., patient orientation, proton beam energy, and range-modulation. The relative uncertainty in H/D values is approximately 40% (one standard deviation).
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)
Energy Technology Data Exchange (ETDEWEB)
Sanchez G, J., E-mail: julian.sanchez@inin.gob.mx [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)
2015-09-15
The solution of the so-called Canonical problems of neutron transport theory has been given by Case, who developed a method akin to the classical eigenfunction expansion procedure, extended to admit singular eigenfunctions. The solution is given as a set consisting of a Fredholm integral equation coupled with a transcendental equation, which has to be solved for the expansion coefficients by iteration. CASE's method make extensive use of the results of the theory of functions of a complex variable and many successful approaches to solve in an approximate form the above mentioned set have been reported in the literature. We present here an entirely different approach which deals with the canonical problems in a more direct and elementary manner. As far as we know, the original idea for the latter method is due to Carlvik who devised the escape probability approximation to the solution of the neutron transport equation in its integral form. In essence, the procedure consists in assuming a sectionally constant form of the neutron density that in turn yields a set of linear algebraic equations obeyed by the assumed constant values of the density. Very well established techniques of numerical analysis for the solution of integral equations consist in independent approaches that generalize the sectionally constant approach by assuming a sectionally low degree polynomial for the unknown function. This procedure also known as the arbitrary quadratures method is especially suited to deal with cases where the kernel of the integral equation is singular. The author wishes to present the results obtained with the arbitrary quadratures method for the numerical calculation of the monoenergetic neutron density in a critical, homogeneous sphere of finite radius with isotropic scattering. The singular integral equation obeyed by the neutron density in the critical sphere is introduced, an outline of the method's main features is given, and tables and graphs of the density
Study of a gold-foil-based multisphere neutron spectrometer.
Wang, Z; Hutchinson, J D; Hertel, N E; Burgett, E; Howell, R M
2008-01-01
Multisphere neutron spectrometers with active thermal neutron detectors cannot be used in high-intensity radiation fields due to pulse pile-up and dead-time effects. Thus, a multisphere spectrometer using a passive detection system, specifically gold foils, has been investigated in this work. The responses of a gold-foil-based Bonner sphere neutron spectrometer were studied for two different gold-foil holder designs; an aluminium-polyethylene holder and a polyethylene holder. The responses of the two designs were calculated for four incident neutron beam directions, namely, parallel, perpendicular and at +/-45 degrees relative to the flat surface of the foil. It was found that the use of polyethylene holder resulted in a more isotropic response to neutrons for the four incident directions considered. The computed responses were verified by measuring the neutron spectrum of a 252Cf source with known strength.
Spectrum and H(10) of secondary neutrons around Linacs
Energy Technology Data Exchange (ETDEWEB)
Ortiz H, A.; Hernandez A, B.; 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); Rivera M, T. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, IPN, Av. Legaria 694, Col. Irrigacion, 11500 Mexico D. F. (Mexico)], e-mail: fermineutron@yahoo.com
2009-10-15
Neutron spectrum and ambient dose equivalent has been measured around two 10 MV linear accelerators. Accelerators are Siemens, one is a Mevatron model while another is the Primus. Main differences between those models are the beam collimator and the vault room. Here, Bonner sphere spectrometer with a passive thermal neutron detector has been utilized to measure the neutron spectrum inside the vault. Using an active detector the neutron spectrum was measured by the vaults door of both accelerators. With a neutron area monitor the dose equivalent was measured by the doors. Neutron strength, total fluence rate and ambient dose equivalent were compared, from this was found that shielding conditions are better in the Primus model. (Author)
Unfolding code for neutron spectrometry based on neural nets technology
Energy Technology Data Exchange (ETDEWEB)
Ortiz R, J. M.; Vega C, H. R., E-mail: morvymm@yahoo.com.mx [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica, Apdo. Postal 336, 98000 Zacatecas (Mexico)
2012-10-15
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 {sup R}obust Design of Artificial Neural Networks Methodology{sup .} 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 {sup 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)
Electro neutrons around a 12 MV Linac
Energy Technology Data Exchange (ETDEWEB)
Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Apdo. Postal 336, 98000 Zacatecas (Mexico); Perez L, L. H., E-mail: fermineutron@yahoo.com [Instituto Zacatecano del Tumor, A. C., Lago de la Encantada No. 294, Fracc. Lomas del Lago, Zacatecas (Mexico)
2012-10-15
Neutron contamination around Linacs for radiotherapy is a source of undesirable doses for the patient. The main source of these neutrons is the photonuclear reactions occurring in the Linac head and the patient body. Electrons also produce neutrons through (e, en) reactions. This reaction is known as electro disintegration and is carried out by the electron scattering that produce a virtual photon that is absorbed by the scattering nucleus producing the reaction e + A {yields} (A-1) + n + e'. In this work the electron-neutron spectrum to 100 cm from the isocenter of a 12 MV Linac has been measured using a passive Bonner spheres spectrometer in a novel procedure named Planetary mode. (Author)
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)
Energy Technology Data Exchange (ETDEWEB)
Hernandez P, C. F.; Martinez B, M. R.; Leon P, A. A.; Espinoza G, J. G.; Castaneda M, V. H.; Solis S, L. O.; Castaneda M, R.; Ortiz R, 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
Neutron dosimetry is of great importance in radiation protection as aims to provide dosimetric quantities to assess the magnitude of detrimental health effects due to exposure of neutron radiation. To quantify detriment to health is necessary to evaluate the dose received by the occupationally exposed personnel using different detection systems called dosimeters, which have very dependent responses to the energy distribution of neutrons. The neutron detection is a much more complex problem than the detection of charged particles, since it does not carry an electric charge, does not cause direct ionization and has a greater penetration power giving the possibility of interacting with matter in a different way. Because of this, various neutron detection systems have been developed, among which the Bonner spheres spectrometric system stands out due to the advantages that possesses, such as a wide range of energy, high sensitivity and easy operation. However, once obtained the counting rates, the problem lies in the neutron spectrum deconvolution, necessary for the calculation of the doses, using different mathematical methods such as Monte Carlo, maximum entropy, iterative methods among others, which present various difficulties that have motivated the development of new technologies. Nowadays, methods based on artificial intelligence technologies are being used to perform neutron dosimetry, mainly using the theory of artificial neural networks. In these new methods the need for spectrum reconstruction can be eliminated for the calculation of the doses. In this work an artificial neural network or reverse propagation was trained for the calculation of 15 equivalent doses from the counting rates of the Bonner spheres spectrometric system using a set of 7 spheres, one of 2 spheres and two of a single sphere of different sizes, testing different error values until finding the most appropriate. The optimum network topology was obtained through the robust design
Tournier, B; Medioni, R; Rich, C; Mussoni, F; Camus, L; Pichenot, G; Crovisier, P; Cutarella, D; Asselineau, B; Groetz, J E
2002-01-01
The new ICPR60 recommendations and the consideration of the ALARA principle have led the operators of nuclear facilities to evaluate with a higher care, the doses received by workers. The aim of this paper is to present a recent study concerning mixed field characterisation at a workplace located in a reprocessing laboratory. As a first step, neutron spectrum determination was achieved by two ways: simulation using MCNP code and experimental measurements with Bonner spheres and recoil proton counters. Neutron spectrum allowed the evaluation of dosimetric quantities. Measurements were then performed with different devices routinely used in radioprotection. The describe the measurement techniques, present the results obtained, and finally compare and discuss them.
Sci—Fri PM: Dosimetry—02: A Nested Neutron Spectrometer to Measure Neutron Spectra in Radiotherapy
Energy Technology Data Exchange (ETDEWEB)
Maglieri, R; Seuntjens, J; Kildea, J [Medical Physics Unit, McGill University, Montreal, Qc (Canada); Licea, A [Canadian Nuclear Safety Commission CNSC, Ottawa, Ontario (Canada)
2014-08-15
During high-energy radiotherapy treatments, neutrons are produced in the head of the linac through photonuclear interactions. This has been a concern for many years as photoneutrons contribute to the accepted, yet unwanted, out-of-field doses that pose an iatrogenic risk to patients and an occupational risk to personnel. Presently, in-room neutron measurements are difficult and time-consuming and have traditionally been carried out using Bonner spheres with activation foils and TLDs. In this work, a new detector, the Nested Neutron Spectrometer (NNS) is tested for use in radiotherapy bunkers. The NNS is designed for easy handling and is more practical than the traditional Bonner spheres. The NNS, operated in current mode, was used to measure the dose equivalent, average energy and energy spectrum at several positions in a radiotherapy bunker. The average energy and spectra were compared to Monte Carlo simulations while the dose equivalent was compared to bubble detector measurements. The average energies, as measured by the NNS and Monte Carlo simulations, differed by approximately 30% across the bunker. Measurements of the dose equivalent using the NNS and the bubble detectors agreed within 50% in the maze and less than 10% close to the linac head. Apart from some discrepancies at thermal energies, we also found reasonable agreement between NNS-measured and Monte Carlo-simulated spectra at a number of locations within our radiotherapy bunker. Our results demonstrate that the NNS is a suitable detector to be used in high dose-rate radiotherapy environments.
Characterization of a {sup 239}PuBe isotopic neutron source
Energy Technology Data Exchange (ETDEWEB)
Vega C, H. R.; Hernandez D, V. M. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Rivera M, T. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Calz. Legaria No. 694, Col. Irrigacion, 11500 Mexico D. F. (Mexico); Sanchez, A., E-mail: fermineutron@yahoo.com [IPN, Escuela Superior de Fisica y Matematicas, 07738 Mexico D. F. (Mexico)
2012-10-15
A Bonner sphere spectrometer was used to determine the features of a {sup 239}PuBe neutron source used to operate the ESFM-Ipn Subcritical Reactor. The spectrometer is a {sup 6}Lil(Eu) scintillator and 2, 3, 5, 8, 10 and 12 inches-diameter polyethylene spheres, that was located 100 cm from the neutron source. The count rates obtained with the spectrometer were unfolded using the NSDUAZ code and neutron spectrum, total fluence, and ambient dose equivalent were determined. A Monte Carlo calculation, using the MCNP5 code, was carried out to estimate the spectrum and integral features being less that values obtained experimentally due to the presence of {sup 241}Pu in the Pu used to fabricate the source. Using the experimental information the actual neutron yield and the mass fraction of {sup 241}Pu was estimated. (Author)
Neutron spectra at two beam ports of a TRIGA Mark III reactor loaded with HEU fuel.
Vega-Carrillo, H R; Hernández-Dávila, V M; Aguilar, F; Paredes, L; Rivera, T
2014-01-01
The neutron spectra have been measured in two beam ports, one radial and another tangential, of the TRIGA Mark III nuclear reactor from the National Institute of Nuclear Research in Mexico. Measurements were carried out with the reactor core loaded with high enriched uranium fuel. Two reactor powers, 5 and 10 W, were used during neutron spectra measurements using a Bonner sphere spectrometer with a (6)LiI(Eu) scintillator and 2, 3, 5, 8, 10 and 12 in.-diameter high-density polyethylene spheres. The neutron spectra were unfolded using the NSDUAZ unfolding code. For each spectrum total flux, mean energy and ambient dose equivalent were determined. Measured spectra show fission, epithermal and thermal neutrons, being harder in the radial beam port.
Study of the neutron field in the vicinity of an unshielded PET cyclotron.
Méndez, R; Iñiguez, M P; Martí-Climent, J M; Peñuelas, I; Vega-Carrillo, H R; Barquero, R
2005-11-01
The neutron field in the proximity of an unshielded PET cyclotron was investigated during 18F radioisotope production with an 18 MeV proton beam. Thermoluminescent detector (TLD) models TLD600 and TLD700 as well as Bonner moderating spheres were irradiated at different positions inside the vault room where the cyclotron is located to determine the thermal neutron flux, neutron spectrum and dose equivalent. Furthermore, from a combination of measurements and Monte Carlo simulations the neutron source intensity at the target was estimated. The resulting intensity is in good agreement with the IAEA recommendations. Neutron doses derived from the measured spectra were found to vary between 7 and 320 mSv per 1 microA h of proton-integrated current. Finally, gamma doses were determined from TLD700 readings and amounted to around 10% of the neutron doses.
Advantages of passive detectors for the determination of the cosmic ray induced neutron environment
Hajek, M; Schoner, W; Vana, N
2002-01-01
Due to the pronounced energy dependence of the neutron quality factor, accurate assessment of the biologically relevant dose requires knowledge of the spectral neutron fluence rate. Bonner sphere spectrometers (BSSs) are the only instruments which provide a sufficient response over practically the whole energy range of the cosmic ray induced neutron component. Measurements in a 62 MeV proton beam at Paul Scherrer Institute, Switzerland, and in the CERN-EU high-energy reference field led to the assumption that conventional active devices for the detection of thermal neutrons inside the BSS, e.g. /sup 6/LiI(Eu) scintillators, also respond to charged particles when used in high-energy mixed radiation fields. The effects of these particles cannot be suppressed by amplitude discrimination and are subsequently misinterpreted as neutron radiation. In contrast, paired TLD-600 and TLD-700 thermoluminescence dosemeters allow the determination of a net thermal neutron signal. (12 refs).
A high-resolution neutron spectra unfolding method using the Genetic Algorithm technique
Mukherjee, B
2002-01-01
The Bonner sphere spectrometers (BSS) are commonly used to determine the neutron spectra within various nuclear facilities. Sophisticated mathematical tools are used to unfold the neutron energy distribution from the output data of the BSS. This paper highlights a novel high-resolution neutron spectra-unfolding method using the Genetic Algorithm (GA) technique. The GA imitates the biological evolution process prevailing in the nature to solve complex optimisation problems. The GA method was utilised to evaluate the neutron energy distribution, average energy, fluence and equivalent dose rates at important work places of a DIDO class research reactor and a high-energy superconducting heavy ion cyclotron. The spectrometer was calibrated with a sup 2 sup 4 sup 1 Am/Be (alpha,n) neutron standard source. The results of the GA method agreed satisfactorily with the results obtained by using the well-known BUNKI neutron spectra unfolding code.
An intercomparison of neutron dosimeters and detectors for in-containment dosimetry
Energy Technology Data Exchange (ETDEWEB)
Auman, L.E.; Miller, W.H.; Graham, C.C.; Stretch, C.D.; Welty, T.J.; West, L. Jr. (Department of Nuclear Engineering, University of Missouri, Columbia (United States))
1992-02-01
To improve the methodology for assessing neutron dose at Union Electric's Callaway Nuclear Power Plant, an intercomparison of neutron detectors and dosimeters was performed. Seven different neutron detectors and dosimeters were tested in four different neutron fields utilizing facilities at the Missouri University Research Reactor and at the Southwest Radiation Calibration Center at the University of Arkansas. In general, all results agree within a factor of 2 in predicting the neutron dose equivalent. It was concluded that measurements of dose in containment should utilize the Tissue-Equivalent Proportional Counter (TEPC), the Bonner-sphere system, and the proton recoil spectrometer to accurately assess the neutron dose. These data can then be used to provide correction factors for more traditionally used dosimeters in containment, such as thermoluminescent dosimeters and survey meters.
Energy Technology Data Exchange (ETDEWEB)
Martinez B, M. R.; Ortiz R, J. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Av. Ramon Lopez Velarde No. 801, Col. Centro, Zacatecas (Mexico)], e-mail: mrosariomb@yahoo.com.mx
2009-10-15
By using the integrated accounts of spectrometric system of Bonner spheres is possible to reconstruct the neutron spectrum using various methods such as: Monte Carlo, the parameterization and iterative methods. The response matrix, counting rates and neutron spectrum are intimately related through the integral-differential of Fredholm of first type. however, the weight of Bonner spheres system, the procedure of spectra reconstruction, the need of a expert user, the high time consumption, the need to use a reconstruction code (BUNKI, SAND, among others) and the spectrum resolution, are some of problems that this system presents. The above difficulties have motivated the development of complementary procedures such as maximum entropy, genetic algorithms and artificial neural networks. In recent years, using neural network technology has become an alternative procedure in the nuclear science research area, considering a replacement for classical techniques used for years. In previous works, was used 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 noted that not exist tools for end-user that allow test and validate the designed networks. This paper presents the development of a software for neutronic spectrometry and dosimetry, based on information extracted from an artificial neural network designed in previous work, through the robust design methodology of artificial neural networks with the following characteristics: was designed in a user graphical interface easy to use, speed on the application execution, unlike other deconvolution codes, not is necessary to select and initial spectrum for spectrum reconstruction, as an additional element to this tool, besides spectrum, the calculation is performed simultaneous of 13 equivalent dose from just counting rates from a spectrometric system of Bonner spheres. (Author)
Energy Technology Data Exchange (ETDEWEB)
Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Benites R, J. L., E-mail: fermineutron@yahoo.com [Centro Estatal de Cancerologia de Nayarit, Servicio de Seguridad Radiologica, Calzada de la Cruz 118 Sur, 63000 Tepic, Nayarit (Mexico)
2014-08-15
A novel procedure to measure the neutrons spectrum originated in a lineal accelerator of medical use has been developed. The method uses a passive spectrometer of Bonner spheres. The main advantage of the method is that only requires of a single shot of the accelerator. When this is used around a lineal accelerator is necessary to operate it under the same conditions so many times like the spheres that contain the spectrometer, activity that consumes enough time. The developed procedure consists on situating all the spheres of the spectrometer at the same time and to realize the reading making a single shot. With this method the photo neutrons spectrum produced by a lineal accelerator Varian ix of 15 MV to 100 cm of the isocenter was determined, with the spectrum is determined the total flow and the ambient dose equivalent. (Author)
Energy Technology Data Exchange (ETDEWEB)
Medkour Ishak-Boushaki, Ghania, E-mail: gmedkour@yahoo.com [Laboratoire SNIRM-Faculte de Physique, Universite des Sciences et de la Technologie Houari Boumediene, BP 32 El-Alia BabEzzouar, Algiers (Algeria); Boukeffoussa, Khelifa [Laboratoire SNIRM-Faculte de Physique, Universite des Sciences et de la Technologie Houari Boumediene, BP 32 El-Alia BabEzzouar, Algiers (Algeria); Idiri, Zahir [Centre de Recherche Nucleaire d' Alger, 02 Boulevard Frantz-Fanon, BP 399, Algiers (Algeria); Allab, Malika [Laboratoire SNIRM-Faculte de Physique, Universite des Sciences et de la Technologie Houari Boumediene, BP 32 El-Alia BabEzzouar, Algiers (Algeria)
2012-03-15
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 {sup 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: Black-Right-Pointing-Pointer Low intensity neutron fields' characterization using thick threshold detectors. Black-Right-Pointing-Pointer Low activity {sup 241}Am-Be neutron source spectrum measurement. Black-Right-Pointing-Pointer Integral quantities required for radiological protection have been derived. Black-Right-Pointing-Pointer The results are in good agreement with those deduced using Bonner spheres. Black-Right-Pointing-Pointer The results are not very sensitive to the chosen deconvolution procedure.
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)
Neutron dose and energy spectra measurements at Savannah River Plant
Energy Technology Data Exchange (ETDEWEB)
Brackenbush, L.W.; Soldat, K.L.; Haggard, D.L.; Faust, L.G.; Tomeraasen, P.L.
1987-08-01
Because some workers have a high potential for significant neutron exposure, the Savannah River Plant (SRP) contracted with Pacific Northwest Laboratory (PNL) to verify the accuracy of neutron dosimetry at the plant. Energy spectrum and neutron dose measurements were made at the SRP calibrations laboratory and at several other locations. The energy spectra measurements were made using multisphere or Bonner sphere spectrometers,/sup 3/He spectrometers, and NE-213 liquid scintillator spectrometers. Neutron dose equivalent determinations were made using these instruments and others specifically designed to determine dose equivalent, such as the tissue equivalent proportional counter (TEPC). Survey instruments, such as the Eberline PNR-4, and the thermoluminescent dosimeter (TLD)-albedo and track etch dosimeters (TEDs) were also used. The TEPC, subjectively judged to provide the most accurate estimation of true dose equivalent, was used as the reference for comparison with other devices. 29 refs., 43 figs., 13 tabs.
Energy Technology Data Exchange (ETDEWEB)
Vega C, H.R. [UAZ, A.P. 336, 98000 Zacatecas (Mexico); Gallego, E.; Lorente, A. [Universidad Politecnica de Madrid, C. Jose Gutierrez Abascal 2, 28006 Madrid (Spain)] e-mail: rvega@cantera.reduaz.mx
2003-07-01
The field of neutrons produced by an isotopic source of neutrons of {sup 241} Am Be had been characterized. The characterization was carried out modeling those relevant details of the calibration room and simulating the neutron transport at different distances of the source. The calculated spectra were used to determine the equivalent environmental dose rate. A series of experiments were carried out with the Bonner sphere spectrometric system to measure the spectra in the same points where the calculations were carried out and with these spectra the rates of environmental dose were calculated. By means of a one sphere dosemeter type Berthold the rates of environmental dose were measured. To the one to compare the calculated spectra and measured its were found small differences in the group of the thermal neutrons due to the elementary composition used during the simulation. When comparing the derived rates starting from the calculated spectra with those measured it was found a maxim difference smaller to 13%. (Author)
Energy Technology Data Exchange (ETDEWEB)
Kim, Sang In; Kim, Bong Hwan; Kim, Jang Lyul; Lee, Jung Il [Health Physics Team, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2015-12-15
The calibration methods of neutron-measuring devices such as the neutron survey meter have advantages and disadvantages. To compare the calibration factors obtained by the shadow cone method and semi-empirical method, 10 neutron survey meters of five different types were used in this study. This experiment was performed at the Korea Atomic Energy Research Institute (KAERI; Daejeon, South Korea), and the calibration neutron fields were constructed using a {sup 252}Californium ({sup 252}Cf) neutron source, which was positioned in the center of the neutron irradiation room. The neutron spectra of the calibration neutron fields were measured by a europium-activated lithium iodide scintillator in combination with KAERI's Bonner sphere system. When the shadow cone method was used, 10 single moderator-based survey meters exhibited a smaller calibration factor by as much as 3.1 - 9.3% than that of the semi-empirical method. This finding indicates that neutron survey meters underestimated the scattered neutrons and attenuated neutrons (i.e., the total scatter corrections). This underestimation of the calibration factor was attributed to the fact that single moderator-based survey meters have an under-ambient dose equivalent response in the thermal or thermal-dominant neutron field. As a result, when the shadow cone method is used for a single moderator-based survey meter, an additional correction and the International Organization for Standardization standard 8529-2 for room-scattered neutrons should be considered.
Energy Technology Data Exchange (ETDEWEB)
Vega C, H. R.; Hernandez D, V. M.; Letechipia de L, C. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98060 Zacatecas (Mexico); Benites R, J. L. [Servicios de Salud de Nayarit, Centro Estatal de Cancerologia, Calzada de la Cruz 116 Sur, 63000 Tepic, Nayarit (Mexico); Salas L, M. A., E-mail: fermineutron@yahoo.com [Universidad Autonoma de Zacatecas, Unidad Academica de Agronomia, Apdo. Postal 336, 98000 Zacatecas (Mexico)
2013-10-15
An experimental procedure was developed, by means of Bonner spheres, to measure the neutrons spectrum around Linacs of medical use that only requires of a single shot of the accelerator; to this procedure we denominate Planetary or Isocentric method. One of the problems associated to the neutrons spectrum measurement in a radiotherapy room with lineal accelerator is because inside the room a mixed, intense and pulsed radiation field takes place affecting the detection systems based on active detector; this situation is solved using a passive detector. In the case of the Bonner spheres spectrometer the active detector has been substituted by activation detectors, trace detectors or thermoluminescent dosimeters. This spectrometer uses several spheres that are situated one at a time in the measurement point, this way to have the complete measurements group the accelerator should be operated, under the same conditions, so many times like spheres have the spectrometer, this activity can consume a long time and in occasions due to the work load of Linac to complicate the measurement process too. The procedure developed in this work consisted on to situate all the spectrometer spheres at the same time and to make the reading by means of a single shot, to be able to apply this procedure, is necessary that before the measurements two characteristics are evaluated: the cross-talking of the spheres and the symmetry conditions of the neutron field. This method has been applied to determine the photo-neutrons spectrum produced by a lineal accelerator of medical use Varian ix of 15 MV to 100 cm of the isocenter located to 5 cm of depth of a solid water mannequin of 30 x 30 x 15 cm. The spectrum was used to determine the total flow and the environmental dose equivalent. (Author)
Development of single-exposure, multidetector neutron spectrometers: the NESCOFI@BTF project.
Bedogni, R; Gómez-Ros, J M; Bortot, D; Pola, A; Introini, M V; Esposito, A; Gentile, A; Mazzitelli, G; Buonomo, B
2014-10-01
NESCOFI@BTF is a 3-y project (2011-13) supported by the Scientific Commission 5 of INFN (Italy). The target is the development of neutron spectrometers similar to the Bonner spheres, in terms of response energy interval and accuracy, but able to determine the neutron spectrum in only one exposure. These devices embed multiple (10 to 30) thermal neutron detectors (TNDs) within a single moderator. Two prototypes, called SPherical SPectrometer (SP(2)) and cylindrical spectrometer (CYSP), have been set up. Whilst SP(2) has spherical geometry and nearly isotropic response, the CYSP has cylindrical geometry and is intended to be used as a directional spectrometer. Suitable active TNDs will be embedded in the final version of the devices. The resulting instruments could be used as real-time neutron spectrometers in neutron-producing facilities. This communication describes the design criteria, numerical analysis, experimental issues, state-of-the-art and future developments connected with the development of these instruments.
Features of the {sup 241}AmBe-based UPM neutron facility
Energy Technology Data Exchange (ETDEWEB)
Gallego, E.; Lorente, A. [Universidad Politecnica de Madrid, Laboratorio de Ingenieria Nuclear, Jose Gutierrez Abascal No. 2, 28006 Madrid (Spain); Mendez, R. [CIEMAT, Ionizing Radiation Standard Laboratory, Av. Complutense 40, 28040 Madrid (Spain); Bedogni, R.; Esposito, A. [Laboratori Nazionali di Frascati, Istituto Nazionali di Fisica Nucleare, U.F. Fisica Sanitaria, Via E. Fermi 40, 00040 Frascati, Roma (Italy); Amgarou, K.; Domingo, C. [Universitat Autonoma de Barcelona, Grup de Fisica de les Radiacions, Campus de Bellaterra, 08193 Barcelona (Spain); Vega C, H. R., E-mail: eduardo.gallego@upm.es [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Apdo. Postal 336, 98000 Zacatecas (Mexico)
2012-10-15
A new automated bench for irradiation, using a {sup 241}AmBe neutron source, has been installed in the neutronics hall at the Universidad Politecnica de Madrid (UPM). In order to determine the neutron field features on the bench a neutron spectrometry, using the Bonner sphere spectrometer, campaign was carried out with the participation of four research teams. Each team used their own spectrometer with different unfolding codes. The UPM-UAZ spectrometer has seven spheres with a {sup 6}Lil(Eu) scintillator, for unfolding this team used the BUNKIUT code. The INFN-LNF spectrometer has 10 spheres with a {sup 6}Lil(Eu) scintillator and the Fruit code was used for unfolding. The UAB team spectrometer has 11 with a {sup 3}He proportional counter, for unfolding this team used the Fruit code. The CIEMAT team spectrometer is 12 spheres with a {sup 3}He Sp 9 counter, for unfolding this team used the UMG code. The paper shows the main results obtained in terms of neutron spectra at fixed distances from the source as well as the total neutron fluence rate and ambient dose equivalent rate H(10) determined from the spectra. The H(10) are compared with the readings of a neutron area monitor Lb 6411. (Author)
New PTB thermal neutron calibration facility: first results.
Luszik-Bhadra, M; Reginatto, M; Wershofen, H; Wiegel, B; Zimbal, A
2014-10-01
A new thermal neutron calibration facility based on a moderator assembly has been set up at PTB. It consists of 16 (241)Am-Be radionuclide sources mounted in a graphite block, 1.5 m wide, 1.5 m high and 1.8 m deep. The sources are distributed to eight different positions, at a mean distance of ∼1.25 m from the front face of the moderator. The neutron field at the reference position, 30 cm in front of the moderator device and 75 cm above the floor, has been characterised using calculations, Bonner sphere measurements and gold foil activation. First results are shown. The field is highly thermalised: 99 % in terms of fluence. It is quite homogenous within a 20 cm×20 cm area, but the absolute value of the thermal neutron fluence rate is small and yields an ambient dose equivalent rate of 3 µSv h(-1).
Multisphere neutron spectrometric system with thermoluminescence dosemeters: sensitive improvement.
Gregori, B; Papadópulos, S; Cruzate, J; Kunst, J J
2002-01-01
In this work, a neutron spectrometric system based on a set of moderating spheres with thermoluminescence detectors (TLD) is presented. The system at the Nuclear Regulatory Authority (ARN) Dosimetry Laboratory consists of 12 solid spheres made of high-density polyethylene (p = 0.95 g x cm(-3)), with diameters ranging from 2" to 12" and TLD sensitive to thermal and gamma radiation, namely TLD-600 and TLD-700, located at the centre of the spheres. The neutron response matrix for this Bonner Sphere Spectrometer (BSS) was calculated using the MCNP-IVB code and the library ENDF/B-VI in the energy range between thermal neutrons and 100 MeV. The neutron spectrum was obtained using the LOUH182 unfolding code. The improvement in sensitivity of the system is based on the election of a different heating cycle of the TLD that allows an increase in sensitivity by a factor of 2.6 compared with the standard laboratory treatment. The system response for the calibration with an Am-Be source is presented.
RDANN a new methodology to solve the neutron spectra unfolding problem
Energy Technology Data Exchange (ETDEWEB)
Ortiz R, J.M.; Martinez B, M.R.; Vega C, H.R. [UAZ, Av. Ramon Lopez Velarde No. 801, 98000 Zacatecas (Mexico)
2006-07-01
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)
Neutron spectra in two beam ports of a TRIGA Mark III reactor with HEU fuel
Energy Technology Data Exchange (ETDEWEB)
Vega C, H. R.; Hernandez D, V. M. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Paredes G, L.; Aguilar, F., E-mail: fermineutron@yahoo.com [ININ, Carretera Mexico-Toluca s/n, Ocoyoacac 52750, Estado de Mexico (Mexico)
2012-10-15
Before to change the HEU for Leu fuel of the ININ's TRIGA Mark III nuclear reactor the neutron spectra were measured in two beam ports using 5 and 10 W. Measurements were carried out in a tangential and a radial beam port using a Bonner sphere spectrometer. It was found that neutron spectra are different in the beam ports, in radial beam port the amplitude of thermal and fast neutrons are approximately the same while, in the tangential beam port thermal neutron peak is dominant. In the radial beam port the fluence-to-ambient dose equivalent factors are 131{+-}11 and 124{+-}10 p Sv-cm{sup 2} for 5 and 10 W respectively while in the tangential beam port the fluence-to-ambient dose equivalent factor is 55{+-}4 p Sv-cm{sup 2} for 10 W. (Author)
Tritium production in a sphere of /sup 6/LiD irradiated by 14-MeV neutrons
Energy Technology Data Exchange (ETDEWEB)
Hemmendinger, A.; Ragan, C.E.; Shunk, E.R.; Ellis, A.N.; Anaya, J.M.; Wallace, J.M.
1978-10-01
The specific production of tritium in samples of /sup 6/LiH and /sup 7/LiH embedded in a 600-mm-diam sphere of /sup 6/LiD irradiated by a central source of 14-MeV neutrons was determined by measuring the activity of the hydrogen evolved from the samples of each isotope at each of five different radii in the /sup 6/LiD assembly. The entire process of decomposing the LiH, transferring the evolved gas into counters, and determining the decay rate was standardized by processing LiH samples irradiated by thermal neutrons for which the /sup 6/Li(n,..cap alpha..) cross section is well known. The specific production of tritium in /sup 6/LiH and /sup 7/LiH (embedded samples) and the activation of radiochemical detector foils of /sup 45/Sc, /sup 89/Y, /sup 90/Zr, /sup 169/Tm, /sup 191/Ir /sub 373/, /sup 193/Ir /sub 627/, /sup 197/Au, /sup 235/U, and /sup 238/U placed at various positions in the /sup 6/LiD sphere were calculated and compared with the experimental data. One- and three-dimensional Monte Carlo and S/sub n/ neutron-transport calculations were performed. The most reliable (three-dimensional Monte Carlo) calculation is in reasonable agreement with both the tritium-production and the radiochemical-activation data. The existing discrepancies between calculation and experiment appear largely attributable to uncertainties in some tritium-production and radiochemical-activation cross sections. 15 references.
Evaluation of room-scattered neutrons at the JNC Tokai neutron reference field
Energy Technology Data Exchange (ETDEWEB)
Yoshida, Tadayoshi; Tsujimura, Norio [Japan Nuclear Cycle Development Inst., Tokai, Ibaraki (Japan). Tokai Works; Oyanagi, Katsumi [Japan Radiation Engineering Co., Ltd., Hitachi, Ibaraki (Japan)
2002-09-01
Neutron reference fields for calibrating neutron-measuring devices in JNC Tokai Works are produced by using radionuclide neutron sources, {sup 241}Am-Be and {sup 252}Cf sources. The reference field for calibration includes scattered neutrons from the material surrounding sources, wall, floor and ceiling of the irradiation room. It is, therefore, necessary to evaluate the scattered neutrons contribution and their energy spectra at reference points. Spectral measurements were performed with a set of Bonner multi-sphere spectrometers and the reference fields were characterized in terms of spectral composition and the fractions of room-scattered neutrons. In addition, two techniques stated in ISO 10647, the shadow-cone method and the polynomial fit method, for correcting the contributions from the room-scattered neutrons to the readings of neutron survey instruments were compared. It was found that the two methods gave an equivalent result within a deviation of 3.3% at a source-to-detector distance from 50cm to 500cm. (author)
Unfolding neutron spectra with BS-TLD system using genetic algorithms
Energy Technology Data Exchange (ETDEWEB)
Santos, Joelan A.L., E-mail: jasantos@cnen.gov.br [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear; Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil); Silva, Everton R. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Centro de Informatica; Ferreira, Tiago A.E. [Universidade Federal Rural de Pernambuco (UFRPE), Recife, PE (Brazil). Dept. de Estatistica e Informatica; Fonseca, Evaldo S. [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Vilela, Eudice C., E-mail: ecvilela@cnen.gov.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil)
2011-07-01
Due to the variability of neutron spectrum within the same environment, it is essential that the spectral distribution as function of energy to be characterized. To perform this task, the neutron spectrometer has a primary role in determining the neutron flux ({Phi}{sub E}(E)). Precise information allows radiological quantities establishment related to that spectrum but it is necessary, however, a series of steps with a spectrometric system that can cover a large interval of energy and whose answer is isotropic. The most widely used for accomplishing this task is the spectrometric Bonner spheres system. One of the biggest problems related to neutron spectrometry is the process of data analysis, known as unfolding. Most of the work undertaken to implement new techniques of this process, using data obtained with the scintillator {sup 6}LiI(I). However, characteristics related to the dead time make it not be so effective when used in high flow neutron fields. An alternative to this problem is the use of thermoluminescent detectors (TLD), but the codes used do not provide a more specific response matrix to unfolding the information obtained through these materials, which makes the development of a specific response matrix important to adequately characterize the response obtained by them. This paper proposes using a technique of artificial intelligence called genetic algorithm, which uses bio-inspired mathematical models and through the implementation of a specific matrix to unfolding data obtained from a combination of TLDs embedded in a system of Bonner spheres, such as thermal neutron detectors, to characterize the neutron spectrum as a function of energy. The results obtained with this method were in accordance with reference spectra, thus enables of this technique to unfolding neutrons spectra with BS-TLD system. (author)
Neutron spectrum and dose-equivalent in shuttle flights during solar maximum
Energy Technology Data Exchange (ETDEWEB)
Keith, J.E.; Badhwar, G.D.; Lindstrom, D.J. (National Aeronautics and Space Administration, Houston, TX (United States). Lyndon B. Johnson Space Center)
1992-01-01
This paper presents unambiguous measurements of the spectrum of neutrons found in spacecraft during spaceflight. The neutron spectrum was measured from thermal energies to about 10 MeV using a completely passive system of metal foils as neutron detectors. These foils were exposed to the neutron flux bare, covered by thermal neutron absorbers (Gd) and inside moderators (Bonner spheres). This set of detectors was flown on three U.S. Space Shuttle flights, STS-28, STS-36 and STS-31, during the solar maximum. We show that the measurements of the radioactivity of these foils lead to a differential neutron energy spectrum in all three flights that can be represented by a power law, J(E){approx equal}E{sup -0.765} neutrons cm{sup -2} day {sup -1} MeV{sup -1}. We also show that the measurements are even better represented by a linear combination of the terrestrial neutron albedo and a spectrum of neutrons locally produced in a aluminium by protons, computed by a previous author. We use both approximations to the neutron spectrum to produce a worst case and most probable case for the neutron spectra and the resulting dose-equivalents, computed using ICRP-51 neutron fluence-dose conversion tables. We compare these to the skin dose-equivalents due to charged particles during the same flights. (author).
Energy Technology Data Exchange (ETDEWEB)
Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Gallego, E.; Lorente, A.; Rubio O, I. P., E-mail: hrvegacarrillo@yahoo.com.m [Universidad Politecnica de Madrid, Departamento de Ingenieria Nuclear, C/Jose Gutierrez Abascal No. 2, 28006 Madrid (Spain)
2010-09-15
Through of measurements and calculations of a Monte Carlo series has been characterized the neutronic field of the neutronic measurements room of Nuclear Engineering Department of the Polytechnic University of Madrid. The measurements were realized with the Bonner Spheres Spectrometer that allowed establish the spectra on the new stainless steel panel and at different distances measured regarding the source. The values of the speed of environmental equivalent dose were measured with an area monitor Bert hold Lb 6411. Through of Monte Carlo methods was built a detailed model of the room with the panel and the spectra were calculated and, with these the values of the environmental equivalent dose were obtained using the conversion coefficients of the ICRP 74 and the Bert hold Lb 6411 response. The calculated values were compared with those measured and was consistency among the results. (Author)
Design of a system for neutrons dosimetry; Diseno de un sistema para dosimetria de neutrones
Energy Technology Data Exchange (ETDEWEB)
Ceron, P.; Rivera, T. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Legaria No. 694, Col. Irrigacion, 11500 Mexico D. F. (Mexico); Paredes G, L. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Azorin, J. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco 186, Col. Vicentina, 09340 Mexico D. F. (Mexico); Sanchez, A. [IPN, Escuela Superior de Fisica y Matematicas, Av. Instituto Politecnico Nacional s/n, Col. San Pedro Zacatenco, 07738 Mexico D. F. (Mexico); Vega C, H. R., E-mail: victceronr@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)
2014-08-15
At the present time diverse systems of detection of neutrons exist, as proportional counters based on BF{sub 3}, He{sub 3} and spectrometers of Bonner spheres. However, the cost and the complexity of the implementation of these systems put them far from the reach for dosimetric purposes. For these reasons a system of neutrons detection composed by a medium paraffin moderator that forms a 4π (spheres) arrangement and of several couples of thermoluminescent dosimeters TLD 600/TLD 700. The response of the system presents a minor repeatability to 5% in several assays when being irradiated with a {sup 239}PuBe source and a deviation of 13.8% in the Tl readings of four different spheres. The calibration factor of the system with regard to the neutrons source which was of 56.2 p Sv/nc also was calculated. These detectors will be used as passive monitors of photoneutrons in a radiotherapy room with lineal accelerator of high energy. (Author)
Langford, Thomas J.
The typical fast neutron detector falls into one of two categories, Bonner sphere spectrometers and liquid scintillator proton recoil detectors. These two detector types have traditionally been used to measure fast neutrons at the surface and in low background environments. The cosmogenic neutron spectrum and flux is an important parameter for a number of experimental efforts, including procurement of low background materials and the prediction of electronic device faults. Fast neutrons can also cause problems for underground low-background experiments, through material activation or signals that mimic rare events. Current detector technology is not sufficient to properly characterize these backgrounds. To this end, the University of Maryland and the National Institute of Standards and Technology designed, developed, and deployed two Fast Neutron Spectrometers (FaNS) comprised of plastic scintillator and 3He proportional counters. The detectors are based upon capture-gated spectroscopy, a technique that demands a delayed coincidence between a neutron scatter and the resulting neutron capture after thermalization. This technique provides both particle identification and knowledge that the detected neutron fully thermalized. This improves background rejection capabilities and energy resolution. Presented are the design, development, and deployment of FaNS-1 and FaNS-2. Both detectors were characterized using standard fields at NIST, including calibrated 252Cf neutron sources and two monoenergetic neutron generators. Measurements of the surface fast neutron spectrum and flux have been made with both detectors, which are compared with previous measurements by traditional detectors. Additionally, FaNS-1 was deployed at the Kimballton Underground Research Facility (KURF) in Ripplemead, VA. A measurement of the fast neutron spectrum and flux at KURF is presented as well. FaNS-2 is currently installed in a shallow underground laboratory where it is measuring the muon
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Mattingly, John K.; Pozzi, Sara A. (University of Michigan, Ann Arbor, MI); Clarke, Shaun D. (University of Michigan, Ann Arbor, MI); Dennis, Ben D. (University of Michigan, Ann Arbor, MI); Miller, Eric C. (University of Michigan, Ann Arbor, MI); Padovani, E. (Polytechnic of Milan, Italy)
2010-06-01
With increasing concern over the ability to detect and characterize special nuclear materials, the need for computer codes that can successfully predict the response of detector systems to various measurement scenarios is extremely important. These computer algorithms need to be benchmarked against a variety of experimental configurations to ensure their accuracy and understand their limitations. The Monte Carlo code MCNP-PoliMi is a modified version of the MCNP-4c code. Recently these modifications have been ported into the new MCNPX 2.6.0 code, which gives the new MCNPX-PoliMi a wider variety of options and abilities, taking advantage of the improvements made to MCNPX. To verify the ability of the MCNPX-PoliMi code to simulate the response of a neutron multiplicity detector simulated results were compared to experimental data. The experiment consisted of a 4.5-kg sphere of alpha-phase plutonium that was moderated with various thicknesses of polyethylene. The results showed that our code system can simulate the multiplicity distributions with relatively good agreement with measured data. The enhancements made to MCNP since the release of MCNP-4c have had little to no effect on the ability of the MCNP-PoliMi to resolve the discrepancies observed in the simulated neutron multiplicity distributions when compared experimental data.
Neutron spectra in two beam ports of the TRIGA Mark III reactor
Energy Technology Data Exchange (ETDEWEB)
Vega C, H. R.; Hernandez D, V. M. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98060 Zacatecas (Mexico); Aguilar, F.; Paredes, L. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Rivera M, T., E-mail: fermineutron@yahoo.com [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Legaria, Av. Legaria 694, 11500 Mexico D. F. (Mexico)
2013-10-15
The neutron spectra have been measured in two beam ports, radial and tangential, of the TRIGA Mark III nuclear reactor from the National Institute of Nuclear Research. Measurements were carried out with the core with mixed fuel (Leu 8.5/20 and Flip Heu 8.5/70). Two reactor powers, 5 and 10 W, were used during neutron spectra measurements using a Bonner sphere spectrometer with a {sup 6}Lil(Eu) scintillator and 2, 3, 5, 8, 10 and 12 inches-diameter high density polyethylene spheres. The neutron spectra were unfolded using the NSDUAZ unfolding code; from each spectrum the total neutron flux, the neutron mean energy and the neutron ambient dose equivalent dose were determined. Measured spectra show fission (E≥ 0.1 MeV), epithermal (from 0.4 eV up to 0.1 MeV) and thermal neutrons (E≤ 0.4 eV). For both reactor powers the spectra in the radial beam port have similar features which are different to the neutron spectrum characteristics in the tangential beam port. (Author)
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)
Masuda, Akihiko; Matsumoto, Tetsuro; Iwamoto, Yosuke; Hagiwara, Masayuki; Satoh, Daiki; Sato, Tatsuhiko; Iwase, Hiroshi; Yashima, Hiroshi; Nakane, Yoshihiro; Nishiyama, Jun; Shima, Tatsushi; Tamii, Atsushi; Hatanaka, Kichiji; Harano, Hideki; Nakamura, Takashi
2017-03-01
Quasi-monoenergetic high-energy neutron fields induced by 7Li(p,n) reactions are used for the response evaluation of neutron-sensitive devices. The quasi-monoenergetic high-energy field consists of high-energy monoenergetic peak neutrons and unwanted continuum neutrons down to the low-energy region. A two-angle differential method has been developed to compensate for the effect of the continuum neutrons in the response measurements. In this study, the two-angle differential method was demonstrated for Bonner sphere detectors, which are typical examples of moderator-based neutron-sensitive detectors, to investigate the method's applicability and its dependence on detector characteristics. Experiments were performed under 96-387 MeV quasi-monoenergetic high-energy neutron fields at the Research Center for Nuclear Physics (RCNP), Osaka University. The measurement results for large high-density polyethylene (HDPE) sphere detectors agreed well with Monte Carlo calculations, which verified the adequacy of the two-angle differential method. By contrast, discrepancies were observed in the results for small HDPE sphere detectors and metal-induced sphere detectors. The former indicated that detectors that are particularly sensitive to low-energy neutrons may be affected by penetrating neutrons owing to the geometrical features of the RCNP facility. The latter discrepancy could be consistently explained by a problem in the evaluated cross-section data for the metals used in the calculation. Through those discussions, the adequacy of the two-angle differential method was experimentally verified, and practical suggestions were made pertaining to this method.
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.
A neutron spectrum unfolding code based on iterative procedures
Energy Technology Data Exchange (ETDEWEB)
Ortiz R, J. M.; Vega C, H. R., E-mail: morvymm@yahoo.com.mx [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica, Apdo. Postal 336, 98000 Zacatecas (Mexico)
2012-10-15
In this work, the version 3.0 of the neutron spectrum unfolding code called Neutron Spectrometry and Dosimetry from Universidad Autonoma de Zacatecas (NSDUAZ), is presented. This code was designed in a graphical interface under the LabVIEW programming environment and it is based on the iterative SPUNIT iterative algorithm, using as entrance data, only the rate counts obtained with 7 Bonner spheres based on a {sup 6}Lil(Eu) neutron detector. The main features of the code are: it is intuitive and friendly to the user; it has a programming routine which automatically selects the initial guess spectrum by using a set of neutron spectra compiled by the International Atomic Energy Agency. Besides the neutron spectrum, this code calculates the total flux, the mean energy, H(10), h(10), 15 dosimetric quantities for radiation protection porpoises and 7 survey meter responses, in four energy grids, based on the International Atomic Energy Agency compilation. This code generates a full report in html format with all relevant information. In this work, the neutron spectrum of a {sup 241}AmBe neutron source on air, located at 150 cm from detector, is unfolded. (Author)
Neutron measurements in the stray field produced by 158 GeV c(-1) per nucleon lead ion beams.
Agosteo, S; Birattari, C; Foglio Para, A; Nava, E; Silari, M; Ulrici, L
1998-12-01
This paper discusses measurements carried out at CERN in the stray radiation field produced by 158 GeV c(-1) per nucleon 208Pb82+ ions. The purpose was to test and intercompare the response of several detectors, mainly neutron measuring devices, and to determine the neutron spectral fluence as well as the microdosimetric (absorbed dose and dose equivalent) distributions in different locations around the shielding. Both active instruments and passive dosimeters were employed, including different types of Andersson-Braun rem counters, a tissue equivalent proportional counter, a set of superheated drop detectors, a Bonner sphere system, and different types of ion chambers. Activation measurements with 12C plastic scintillators and with 32S pellets were also performed to assess the neutron yield of high energy lead ions interacting with a thin gold target. The results are compared with previous measurements and with measurements made during proton runs.
A neutron spectrum unfolding code based on generalized regression artificial neural networks.
Del Rosario Martinez-Blanco, Ma; Ornelas-Vargas, Gerardo; Castañeda-Miranda, Celina Lizeth; Solís-Sánchez, Luis Octavio; Castañeda-Miranada, Rodrigo; Vega-Carrillo, Héctor René; Celaya-Padilla, Jose M; Garza-Veloz, Idalia; Martínez-Fierro, Margarita; Ortiz-Rodríguez, José Manuel
2016-11-01
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. 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, i.e. the optimum selection of the network topology and the long training time. Compared to BPNN, it's usually much faster to train a generalized regression neural network (GRNN). That's mainly because spread constant is the only parameter used in GRNN. Another feature is that the network will converge to a global minimum, provided that the optimal values of spread has been determined and that the dataset adequately represents the problem space. In addition, GRNN are often more accurate than BPNN in the prediction. These characteristics make GRNNs to be of great interest in the neutron spectrometry domain. This work presents a computational tool based on GRNN capable to solve the neutron spectrometry problem. This computational code, automates the pre-processing, training and testing stages using a k-fold cross validation of 3 folds, 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.
Measuring neutron spectra in radiotherapy using the nested neutron spectrometer
Energy Technology Data Exchange (ETDEWEB)
Maglieri, Robert, E-mail: robert.maglieri@mail.mcgill.ca; Evans, Michael; Seuntjens, Jan; Kildea, John [Medical Physics Unit, McGill University, Montreal, Quebec H4A 3J1 (Canada); Licea, Angel [Canadian Nuclear Safety Commission, Ottawa, Ontario K1P 5S9 (Canada)
2015-11-15
Purpose: Out-of-field neutron doses resulting from photonuclear interactions in the head of a linear accelerator pose an iatrogenic risk to patients and an occupational risk to personnel during radiotherapy. To quantify neutron production, in-room measurements have traditionally been carried out using Bonner sphere systems (BSS) with activation foils and TLDs. In this work, a recently developed active detector, the nested neutron spectrometer (NNS), was tested in radiotherapy bunkers. Methods: The NNS is designed for easy handling and is more practical than the traditional BSS. Operated in current-mode, the problem of pulse pileup due to high dose-rates is overcome by measuring current, similar to an ionization chamber. In a bunker housing a Varian Clinac 21EX, the performance of the NNS was evaluated in terms of reproducibility, linearity, and dose-rate effects. Using a custom maximum-likelihood expectation–maximization algorithm, measured neutron spectra at various locations inside the bunker were then compared to Monte Carlo simulations of an identical setup. In terms of dose, neutron ambient dose equivalents were calculated from the measured spectra and compared to bubble detector neutron dose equivalent measurements. Results: The NNS-measured spectra for neutrons at various locations in a treatment room were found to be consistent with expectations for both relative shape and absolute magnitude. Neutron fluence-rate decreased with distance from the source and the shape of the spectrum changed from a dominant fast neutron peak near the Linac head to a dominant thermal neutron peak in the moderating conditions of the maze. Monte Carlo data and NNS-measured spectra agreed within 30% at all locations except in the maze where the deviation was a maximum of 40%. Neutron ambient dose equivalents calculated from the authors’ measured spectra were consistent (one standard deviation) with bubble detector measurements in the treatment room. Conclusions: The NNS may
Energy Technology Data Exchange (ETDEWEB)
Benites R, J. L. [Centro Estatal de Cancerologia de Nayarit, Av. Enfermeria, Fracc. Fray Junipero Serra, 63000 Tepic, Nayarit (Mexico); Vega C, H. R.; Murillo O, R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Velazquez F, J. B., E-mail: jlbenitesr@prodigy.net.mx [Universidad Autonoma de Nayarit, Postgrado CBAP, Carretera Tepic Compostela Km. 9, Xalisco, Nayarit (Mexico)
2011-10-15
By means of an inter-comparison method, the monitor for neutrons Pug-7N was enabled like dosimeter for neutrons of two magnitudes: the environmental equivalent dose, H*(10), and the H equivalent dose. The monitor Pug-7N has a plastic detector of scintillation Pns-20 that can be used inside or outside of its polyethylene cylindrical moderator. This designed to detect the neutrons presence that is shown in ana logical form by means of a fast count. Although the instrument is useful to detect the neutrons presence its design it does not allow to estimate the dose. With the purpose of enabling it as dosimeter for neutrons, their response was compared with the response of the area monitor for neutrons Bert hold Lb 6411 and Eberline NRD model Asp-1. Under the same irradiation conditions the 3 instruments were exposed to a source of {sup 241}AmBe of 3.7E(9) Bq (100 mCi) of activity whose spectrum and dosimetric magnitudes were determined with a spectrometric system of Bonner spheres with scintillator of {sup 6}Lil(Eu) and the NSDUAZ code. Conversion factors of H*(10)/cpm and H/cpm were obtained for the two options of the monitor detector Pug-7N, with this procedure the monitor Pug-7N besides determining the presence of neutrons, it has been enabled for their use as dosimeter for neutrons. (Author)
Characterization of a Be(p,xn) neutron source for fission yields measurements
Mattera, A; Hjalmarsson, A; Lantz, M; Pomp, S; Rakopoulos, V; Solders, A; Valldor-Blücher, J; Gorelov, D; Penttilä, H; Rinta-Antila, S; Prokofiev, A V; Passoth, E; Bedogni, R; Gentile, A; Bortot, D; Esposito, A; Introini, M V; Pola, A
2013-01-01
We report on measurements performed at The Svedberg Laboratory (TSL) to characterize a proton-neutron converter for independent fission yield studies at the IGISOL-JYFLTRAP facility (Jyv\\"askyl\\"a, Finland). A 30 MeV proton beam impinged on a 5 mm water-cooled Beryllium target. Two independent experimental techniques have been used to measure the neutron spectrum: a Time of Flight (TOF) system used to estimate the high-energy contribution, and a Bonner Sphere Spectrometer able to provide precise results from thermal energies up to 20 MeV. An overlap between the energy regions covered by the two systems will permit a cross-check of the results from the different techniques. In this paper, the measurement and analysis techniques will be presented together with some preliminary results.
Energy Technology Data Exchange (ETDEWEB)
Tournier, B.; Itie, C.; Medioni, R. E-mail: roger.medioni@ipsn.fr; Rich, C.; Mussoni, F.; Camus, L.; Pichenot, G.; Crovisier, Ph.; Cutarella, D.; Asselineau, B.; Groetz, J.E
2002-01-01
The new ICPR60 recommendations and the consideration of the ALARA principle have led the operators of nuclear facilities to evaluate with a higher care, the doses received by workers. The aim of this paper is to present a recent study concerning mixed field characterisation at a workplace located in a reprocessing laboratory. As a first step, neutron spectrum determination was achieved by two ways: simulation using MCNP code and experimental measurements with Bonner spheres and recoil proton counters. Neutron spectrum allowed the evaluation of dosimetric quantities. Measurements were then performed with different devices routinely used in radioprotection. The authors describe the measurement techniques, present the results obtained, and finally compare and discuss them.
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)
Irazola, L; Terron, J; Sanchez-Doblado, F [Departamento de Fisiologia Medica y Biofisica, Universidad de Sevilla (Spain); Servicio de Radiofisica, Hospital Universitario Virgen Macarena, Sevilla (Spain); Domingo, C; Romero-Exposito, M [Departament de Fisica, Universitat Autonoma de Barcelona, Bellaterra (Spain); Garcia-Fuste, M [Health and Safety Department, ALBA Synchrotron Light Source, Cerdanyola del Valles (Spain); Sanchez-Nieto, B [Instituto de Fisica, Pontificia Universidad Catolica de Chile, Santiago (Chile); Bedogni, R [Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare (INFN) (Italy)
2015-06-15
Purpose: Previous measurements with Bonner spheres{sup 1} showed that normalized neutron spectra are equal for the majority of the existing linacs{sup 2}. This information, in addition to thermal neutron fluences obtained in the characterization procedure{sup 3}3, would allow to estimate neutron doses accidentally received by exposed workers, without the need of an extra experimental measurement. Methods: Monte Carlo (MC) simulations demonstrated that the thermal neutron fluence distribution inside the bunker is quite uniform, as a consequence of multiple scatter in the walls{sup 4}. Although inverse square law is approximately valid for the fast component, a more precise calculation could be obtained with a generic fast fluence distribution map around the linac, from MC simulations{sup 4}. Thus, measurements of thermal neutron fluences performed during the characterization procedure{sup 3}, together with a generic unitary spectra{sup 2}, would allow to estimate the total neutron fluences and H*(10) at any point{sup 5}. As an example, we compared estimations with Bonner sphere measurements{sup 1}, for two points in five facilities: 3 Siemens (15–23 MV), Elekta (15 MV) and Varian (15 MV). Results: Thermal neutron fluences obtained from characterization, are within (0.2–1.6×10{sup 6}) cm−{sup 2}•Gy{sup −1} for the five studied facilities. This implies ambient equivalent doses ranging from (0.27–2.01) mSv/Gy 50 cm far from the isocenter and (0.03–0.26) mSv/Gy at detector location with an average deviation of ±12.1% respect to Bonner measurements. Conclusion: The good results obtained demonstrate that neutron fluence and H*(10) can be estimated based on: (a) characterization procedure established for patient risk estimation in each facility, (b) generic unitary neutron spectrum and (c) generic MC map distribution of the fast component. [1] Radiat. Meas (2010) 45: 1391 – 1397; [2] Phys. Med. Biol (2012) 5 7:6167–6191; [3] Med. Phys (2015) 42
Energy Technology Data Exchange (ETDEWEB)
Fehrenbacher, G.; Iwase, H.; Radon, T.; Schardt, D.; Wiegel, B.; Schuhmacher, H.; Wittstock, J. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)
2004-03-01
Neutron spectra were measured at the GSI heavy ion accelerator using the Bonner sphere spectrometer NEMUS. The irradiation experiments were carried out at Cave A, an experimental area at the GSI heavy ion synchrotron SIS. A 400 MeV/u carbon ion beam impinging on a thick graphite target was used as neutron source. Spectral distributions were determined by unfolding the measured readings using the unfolding code MAXED for four positions outside the shielding and for four positions in the entry maze of Cave A. First results are presented for two positions from Monte Carlo simulations carried out with a newer version of FLUKA considering both the particle production in nucleus-nucleus collisions and the transportation of particles through the shielding. Measured and calculated neutron spectra are compared for these positions. (orig.)
Response of a lithium gadolinium borate scintillator in monoenergetic neutron fields.
Williams, A M; Beeley, P A; Spyrou, N M
2004-01-01
Accurate estimation of neutron dose requires knowledge of the neutron energy distribution in the working environment. Existing neutron spectrometry systems, Bonner spheres for example, are large and bulky, and require long data acquisition times. A portable system that could indicate the approximate neutron energy spectrum in a short time would be extremely useful in radiation protection. A composite scintillator, consisting of lithium gadolinium borate crystals in a plastic scintillator matrix, produced by Photogenics is being tested for this purpose. A prototype device based on this scintillator and digital pulse processing electronics has been calibrated using quasi-monoenergetic neutron fields at the low-scatter facility of the UK National Physical Laboratory (NPL). Energies selected were 144, 250, 565, 1400, 2500 and 5000 keV, with correction for scattered neutrons being made using the shadow cone technique. Measurements were also made in the NPL thermal neutron field. Pulse distributions collected with the digitiser in capture-gated mode are presented, and detection efficiency and energy resolution derived. For comparison, neutron spectra were also collected using the commercially available Microspec N-Probe from Bubble Technology Industries, which consists of an NE213 scintillator and a 3He proportional counter.
Neutron fluence rate measurements at an underground laboratory: A Bayesian approach
Reginatto, Marcel; Kasper, Angelika; Schuhmacher, Helmut; Wiegel, Burkhard; Zimbal, Andreas
2013-08-01
We describe the analysis of neutron fluence rate measurements that were carried out at the underground laboratory Felsenkeller, near Dresden, Germany, which is at a depth of 47 m. At this depth, neutrons are mainly produced by natural radioactivity via spontaneous fission and (α, n) reactions, and by reactions induced by cosmic-ray muons. The measurements were made with the NEMUS Bonner sphere spectrometer. This system consists of a set of moderating spheres of different diameters and a 3He-filled proportional counter placed at the center of each sphere. Due to time constraints, it was only possible to use three of the spheres and the "bare detector" (i.e., a 3He-filled proportional counter without a moderating sphere). In addition to the measurements carried out at Felsenkeller, we also made low-level measurements with a set of 3He-filled proportional counters in the UDO underground laboratory at the Asse salt mine, near Braunschweig, Germany, which is at a depth of 490 m. The neutron background at UDO is substantially lower than that at Felsenkeller and these data are useful for setting limits on the background of the 3He-filled proportional counters. To estimate the neutron fluence rate at Felsenkeller, we did an analysis which took into account the measurements at UDO, Felsenkeller, and calibration measurements made at our facility in PTB. The analysis was done using Bayesian parameter estimation. Since the data consisted of low-level measurements, careful attention was given to the modeling of the intrinsic background of the detector and to identifying relevant sources of uncertainty. With the approach developed here, it is possible to estimate the neutron fluence rate with a relatively small uncertainty of the order of 10%. The method should be useful for other underground laboratories.
Energy Technology Data Exchange (ETDEWEB)
Atanackovic, Jovica, E-mail: atanacjz@gmail.com [Ontario Power Generation, Whitby, ON, Canada L1N 9E3 (Canada); Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, Canada K0J 1J0 (Canada); Matysiak, Witold [University of Florida Proton Therapy Institute, Jacksonville, FL 32206 (United States); Dubeau, Jacques; Witharana, Sampath [DETEC, Gatineau, QC, Canada J8T 4J1 (Canada); Waker, Anthony [University of Ontario Institute of Technology, Oshawa, ON, Canada L1H 7K4 (Canada)
2015-02-21
The measurements of neutron energy spectra and neutron dose rates were performed using the KN Van de Graaff accelerator, located at the McMaster University Accelerator Laboratory (MAL). Protons were accelerated on the thin lithium fluoride (LiF) target and produced mono-energetic neutrons which were measured using three different spectrometers: Bonner Sphere Spectrometer (BSS), Nested Neutron Spectrometer (NNS), and Rotational Proton Recoil Spectrometer (ROSPEC). The purpose of this work is (1) measurement and quantification of low energy accelerator neutron fields in terms of neutron fluence and dose, (2) comparison of results obtained by three different instruments, (3) comparison of measurements with Monte Carlo simulations based on theoretical neutron yields from {sup 7}Li(p,n){sup 7}Be nuclear reaction, and (4) comparison of results obtained using different neutron spectral unfolding methods. The nominal thickness of the LiF target used in the experiment was 50μg/cm{sup 2}, which corresponds to the linear thickness of 0.19μm and results in approximately 6 keV energy loss for the proton energies used in the experiment (2.2, 2.3, 2.4 and 2.5 MeV). For each of the proton energies, neutron fluence per incident proton charge was measured and several dosimetric quantities of interest in radiation protection were derived. In addition, theoretical neutron yield calculations together with the results of Monte Carlo (MCNP) modeling of the neutron spectra are reported. Consistent neutron fluence spectra were obtained with three detectors and good agreement was observed between theoretically calculated and measured neutron fluences and derived dosimetric quantities for investigated proton energies at 2.3, 2.4 and 2.5 MeV. In the case of 2.2 MeV, some plausibly explainable discrepancies were observed.
Saltos, Andrea
In efforts to perform accurate dosimetry, Oakes et al. [Nucl. Intrum. Mehods. (2013)] introduced a new portable solid state neutron rem meter based on an adaptation of the Bonner sphere and the position sensitive long counter. The system utilizes high thermal efficiency neutron detectors to generate a linear combination of measurement signals that are used to estimate the incident neutron spectra. The inversion problem associated to deduce dose from the counts in individual detector elements is addressed by applying a cross-correlation method which allows estimation of dose with average errors less than 15%. In this work, an evaluation of the performance of this system was extended to take into account new correlation techniques and neutron scattering contribution. To test the effectiveness of correlations, the Distance correlation, Pearson Product-Moment correlation, and their weighted versions were performed between measured spatial detector responses obtained from nine different test spectra, and the spatial response of Library functions generated by MCNPX. Results indicate that there is no advantage of using the Distance Correlation over the Pearson Correlation, and that weighted versions of these correlations do not increase their performance in evaluating dose. Both correlations were proven to work well even at low integrated doses measured for short periods of time. To evaluate the contribution produced by room-return neutrons on the dosimeter response, MCNPX was used to simulate dosimeter responses for five isotropic neutron sources placed inside different sizes of rectangular concrete rooms. Results show that the contribution of scattered neutrons to the response of the dosimeter can be significant, so that for most cases the dose is over predicted with errors as large as 500%. A possible method to correct for the contribution of room-return neutrons is also assessed and can be used as a good initial estimate on how to approach the problem.
Holeman, G R; Price, K W; Friedman, L F; Nath, R
1977-01-01
High-energy x-ray radiotherapy machines in the supermegavoltage region generate complex neutron energy spectra which make an exact evaluation of neutron shielding difficult. Fast neutrons resulting from photonuclear reactions in the x-ray target and collimators undergo successive collisions in the surrounding materials and are moderated by varying amounts. In order to examine the neutron radiation exposures quantitatively, the neutron energy spectra have been measured inside and outside the treatment room of a Sagittaire medical linear accelerator (25-MV x rays) located at Yale-New Haven Hospital. The measurements were made using a Bonner spectrometer consisting of 2-, 3-, 5-, 8-, 10- and 12-in.-diameter polyethylene spheres with 6Li and 7Li thermoluminescent dosimeter (TLD) chips at the centers, in addition to bare and cadmium-covered chips. The individual TLD chips were calibrated for neutron and photon response. The spectrometer was calibrated using a known PuBe spectrum Spectrometer measurements were made at Yale Electron Accelerator Laboratory and results compared with a neutron time-of-flight spectrometer and an activation technique. The agreement between the results from these independent methods is found to be good, except for the measurements in the direct photon beam. Quality factors have been inferred for the neutron fields inside and outside the treatment room. Values of the inferred quality factors fall primarily between 4 and 8, depending on location.
Secondary neutron spectra from modern Varian, Siemens, and Elekta linacs with multileaf collimators.
Howell, Rebecca M; Kry, Stephen F; Burgett, Eric; Hertel, Nolan E; Followill, David S
2009-09-01
Neutrons are a by-product of high-energy x-ray radiation therapy (threshold for [gamma,n] reactions in high-Z material -7 MeV). Neutron production varies depending on photon beam energy as well as on the manufacturer of the accelerator. Neutron production from modern linear accelerators (linacs) has not been extensively compared, particularly in terms of the differences in the strategies that various manufacturers have used to implement multileaf collimators (MLCs) into their linac designs. However, such information is necessary to determine neutron dose equivalents for different linacs and to calculate vault shielding requirements. The purpose of the current study, therefore, was to measure the neutron spectra from the most up-to-date linacs from three manufacturers: Varian 21EX operating at 15, 18, and 20 MV, Siemens ONCOR operating at 15 and 18 MV, and Elekta Precise operating at 15 and 18 MV. Neutron production was measured by means of gold foil activation in Bonner spheres. Based on the measurements, the authors determined neutron spectra and calculated the average energy, total neutron fluence, ambient dose equivalent, and neutron source strength. The shapes of the neutron spectra did not change significantly between accelerators or even as a function of treatment energy. However, the neutron fluence, and therefore the ambient dose equivalent, did vary, increasing with increasing treatment energy. For a given nominal treatment energy, these values were always highest for the Varian linac. The current study thus offers medical physicists extensive information about the neutron production of MLC-equipped linacs currently in operation and provides them information vital for accurate comparison and prediction of neutron dose equivalents and calculation of vault shielding requirements.
An accurate and portable solid state neutron rem meter
Energy Technology Data Exchange (ETDEWEB)
Oakes, T.M. [Nuclear Science and Engineering Institute, University of Missouri, Columbia, MO (United States); Bellinger, S.L. [Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS (United States); Miller, W.H. [Nuclear Science and Engineering Institute, University of Missouri, Columbia, MO (United States); Missouri University Research Reactor, Columbia, MO (United States); Myers, E.R. [Department of Physics, University of Missouri, Kansas City, MO (United States); Fronk, R.G.; Cooper, B.W [Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS (United States); Sobering, T.J. [Electronics Design Laboratory, Kansas State University, KS (United States); Scott, P.R. [Department of Physics, University of Missouri, Kansas City, MO (United States); Ugorowski, P.; McGregor, D.S; Shultis, J.K. [Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS (United States); Caruso, A.N., E-mail: carusoan@umkc.edu [Department of Physics, University of Missouri, Kansas City, MO (United States)
2013-08-11
Accurately resolving the ambient neutron dose equivalent spanning the thermal to 15 MeV energy range with a single configuration and lightweight instrument is desirable. This paper presents the design of a portable, high intrinsic efficiency, and accurate neutron rem meter whose energy-dependent response is electronically adjusted to a chosen neutron dose equivalent standard. The instrument may be classified as a moderating type neutron spectrometer, based on an adaptation to the classical Bonner sphere and position sensitive long counter, which, simultaneously counts thermalized neutrons by high thermal efficiency solid state neutron detectors. The use of multiple detectors and moderator arranged along an axis of symmetry (e.g., long axis of a cylinder) with known neutron-slowing properties allows for the construction of a linear combination of responses that approximate the ambient neutron dose equivalent. Variations on the detector configuration are investigated via Monte Carlo N-Particle simulations to minimize the total instrument mass while maintaining acceptable response accuracy—a dose error less than 15% for bare {sup 252}Cf, bare AmBe, an epi-thermal and mixed monoenergetic sources is found at less than 4.5 kg moderator mass in all studied cases. A comparison of the energy dependent dose equivalent response and resultant energy dependent dose equivalent error of the present dosimeter to commercially-available portable rem meters and the prior art are presented. Finally, the present design is assessed by comparison of the simulated output resulting from applications of several known neutron sources and dose rates.
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)
Experimental characterization of HOTNES: A new thermal neutron facility with large homogeneity area
Bedogni, R.; Sperduti, A.; Pietropaolo, A.; Pillon, M.; Pola, A.; Gómez-Ros, J. M.
2017-01-01
A new thermal neutron irradiation facility, called HOTNES (HOmogeneous Thermal NEutron Source), was established in the framework of a collaboration between INFN-LNF and ENEA-Frascati. HOTNES is a polyethylene assembly, with about 70 cmx70 cm square section and 100 cm height, including a large, cylindrical cavity with diameter 30 cm and height 70 cm. The facility is supplied by a 241Am-B source located at the bottom of this cavity. The facility was designed in such a way that the iso-thermal-fluence surfaces, characterizing the irradiation volume, coincide with planes parallel to the cavity bottom. The thermal fluence rate across a given isofluence plane is as uniform as 1% on a disk with 30 cm diameter. Thermal fluence rate values from about 700 cm-2 s-1 to 1000 cm-2 s-1 can be achieved. The facility design, previously optimized by Monte Carlo simulation, was experimentally verified. The following techniques were used: gold activation foils to assess the thermal fluence rate, semiconductor-based active detector for mapping the irradiation volume, and Bonner Sphere Spectrometer to determine the complete neutron spectrum. HOTNES is expected to be attractive for the scientific community involved in neutron metrology, neutron dosimetry and neutron detector testing.
Measurement of the energy spectrum from the neutron source p lanned for IGISOL
Mattera, A; Rakopoulos, V; Lantz, M; Pomp, S; Solders, A; Al-Adili, A; Andersson, P; Hjalmarsson, A; Valldor-Blücher, B; Prokofiev, A; Passoth, E; Gentile, A; Bortot, D; Esposito, A; Introini, M V; Pola, A; Penttilä, H; Gorelov, D; Rinta-Antila, S
2014-01-01
We report on the characterisation measurements of the energ y spectra from a Be (p,xn) neutron source to be installed at the IGISOL-JYFLTRA P facility for studies of neutron-induced independent fission yields. The measurements were performed at The Svedberg Laboratory (Uppsala, Sweden), during 50 hours of beam-time in June, 2012. A 30 MeV p roton beam impinged on a mock-up of the proton-neutron converter; this was a 5 mm-thick beryllium disc inserted in an aluminium holder, with a 1-cm t hick layer of cool- ing water on the backside. The geometry of the mock-up has bee n chosen to reproduce the one that will be used as the IGISOL-JYFLTRAP so urce. During the experiment, two configurations for the neutron so urce have been used: a fast neutron field, produced using the bare target; an d a moderated field, obtained adding a 10 cm-thick Polyethylene block after the t arget assembly. The neutron fields have been measured using an Extended Range Bonner Sphere Spectrometer (ERBSS), able to simultaneously determine ...
Characterization of neutron reference fields at US Department of Energy calibration fields.
Olsher, R H; McLean, T D; Mallett, M W; Seagraves, D T; Gadd, M S; Markham, Robin L; Murphy, R O; Devine, R T
2007-01-01
The Health Physics Measurements Group at the Los Alamos National Laboratory (LANL) has initiated a study of neutron reference fields at selected US Department of Energy (DOE) calibration facilities. To date, field characterisation has been completed at five facilities. These fields are traceable to the National Institute for Standards and Technology (NIST) through either a primary calibration of the source emission rate or through the use of a secondary standard. However, neutron spectral variation is caused by factors such as room return, scatter from positioning tables and fixtures, source anisotropy and spectral degradation due to source rabbits and guide tubes. Perturbations from the ideal isotropic point source field may impact the accuracy of instrument calibrations. In particular, the thermal neutron component of the spectrum, while contributing only a small fraction of the conventionally true dose, can contribute a significant fraction of a dosemeter's response with the result that the calibration becomes facility-specific. A protocol has been developed to characterise neutron fields that relies primarily on spectral measurements with the Bubble Technology Industries (BTI) rotating neutron spectrometer (ROSPEC) and the LANL Bonner sphere spectrometer. The ROSPEC measurements were supplemented at several sites by the BTI Simple Scintillation Spectrometer probe, which is designed to extend the ROSPEC upper energy range from 5 to 15 MeV. In addition, measurements were performed with several rem meters and neutron dosemeters. Detailed simulations were performed using the LANL MCNPX Monte Carlo code to calculate the magnitude of source anisotropy and scatter factors.
Silari, Marco; Birattari, C; Foglio-Para, A; Gini, L; Mitaroff, Angela; Ulrici, L
2002-01-01
The neutron emission from 5, 10 and 20 mm thick lead and 10 and 20 mm thick copper targets bombarded by a lead ion beam with momentum of 158 GeV/c per nucleon were measured at the CERN Super Proton Synchrotron. The neutron yield and spectral fluence per incident ion on target were measured with an extended range Bonner sphere spectrometer in the angular range 30-135 degree with respect to beam direction. Monte Carlo simulations with the FLUKA code were performed to establish a guess spectrum for the unfolding of the experimental data. The results have shown that, lacking Monte Carlo radiation transport codes dealing with ions with masses larger than 1 amu, a reasonable prediction can be carried out by scaling the result of a Monte Carlo calculation for protons by the projectile mass number to the power of 0.85-0.95 for a lead target and 0.88-1.03 for a copper target.
Energy Technology Data Exchange (ETDEWEB)
Hernandez D, V. M.; Moreno M, A.; Ortiz L, M. A. [Universidad de Cordoba, 14002 Cordoba (Spain); Vega C, H. R.; Alonso M, O. E., E-mail: vic.mc68010@gmail.com [Universidad Autonoma de Zacatecas, 98000 Zacatecas, Zac. (Mexico)
2016-10-15
The increase in computing power in personal computers has been increasing, computers now have several processors in the CPU and in addition multiple CUDA cores in the graphics processing unit (GPU); both systems can be used individually or combined to perform scientific computation without resorting to processor or supercomputing arrangements. The Bonner sphere spectrometer is the most commonly used multi-element system for neutron detection purposes and its associated spectrum. Each sphere-detector combination gives a particular response that depends on the energy of the neutrons, and the total set of these responses is known like the responses matrix Rφ(E). Thus, the counting rates obtained with each sphere and the neutron spectrum is related to the Fredholm equation in its discrete version. For the reconstruction of the spectrum has a system of poorly conditioned equations with an infinite number of solutions and to find the appropriate solution, it has been proposed the use of artificial intelligence through neural networks with different platforms CPU and GPU. (Author)
Neutron monitors and muon detectors for solar modulation studies: 2. $\\phi$ time series
Ghelfi, A; Cheminet, A; Derome, L; Hubert, G; Melot, F
2016-01-01
The level of solar modulation at different times (related to the solar activity) is a central question of solar and galactic cosmic-ray physics. In the first paper of this series, we have established a correspondence between the uncertainties on ground-based detectors count rates and the parameter $\\phi$ (modulation level in the force-field approximation) reconstructed from these count rates. In this second paper, we detail a procedure to obtain a reference $\\phi$ time series from neutron monitor data. We show that we can have an unbiased and accurate $\\phi$ reconstruction ($\\Delta\\phi/\\phi\\simeq 10\\%$). We also discuss the potential of Bonner spheres spectrometers and muon detectors to provide $\\phi$ time series. Two by-products of this calculation are updated $\\phi$ values for the cosmic-ray database and a web interface to retrieve and plot $\\phi$ from the 50's to today (\\url{http://lpsc.in2p3.fr/crdb}).
Energy Technology Data Exchange (ETDEWEB)
Hajek, M. E-mail: mhajek@ati.ac.at; Berger, T.; Schoener, W.; Vana, N
2002-01-01
The European Council directive 96/29/Euratom requires dosimetric precautions if the effective dose exceeds 1 mSv/a. On an average, this value is exceeded by aircrew members. Roughly half of the radiation exposure at flight altitudes is caused by cosmic ray-induced neutrons. Active ({sup 6}LiI(Eu)-scintillator) and passive (TLDs) Bonner sphere spectrometers were used to determine the neutron energy spectra atop Mt. Sonnblick (3105 m) and Mt. Kitzsteinhorn (3029 m). Further measurements in a mixed radiation field at CERN as well as in a proton beam of 62 MeV at Paul Scherrer Institute, Switzerland, confirmed that not only neutrons but also charged particles contribute to the readings of active detectors, whereas TLD-600 and TLD-700 in pair allow the determination of the thermal neutron flux. Unfolding of the detector data obtained atop both mountains shows two relative maxima around 1 MeV and 85 MeV, which have to be considered for the assessment of the biologically relevant dose equivalent. By convoluting the spectra with appropriate conversion functions the neutron dose equivalent rate was determined to be 150{+-}15 nSv/h. The total dose equivalent rate determined by the HTR-method was 210{+-}15 nSv/h. The results are in good agreement with LET-spectrometer and Sievert counter measurements carried out simultaneously.
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)
Silari, M; Beck, P; Bedogni, R; Cale, E; Caresana, M; Domingo, C; Donadille, L; Dubourg, N; Esposito, A; Fehrenbacher, G; Fernández, F; Ferrarini, M; Fiechtner, A; Fuchs, A; García, M J; Golnik, N; Gutermuth, F; Khurana, S; Klages, Th; Latocha, M; Mares, V; Mayer, S; Radon, T; Reithmeier, H; Rollet, S; Roos, H; Rühm, W; Sandri, S; Schardt, D; Simmer, G; Spurný, F; Trompier, F; Villa-Grasa, C; Weitzenegger, E; Wiegel, B; Wielunski, M; Wissmann, F; Zechner, A; Zielczyński, M
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. The organizational framework for this project was provided by the European radiation Dosimetry Group EURADOS. Work Package 6 of CONRAD dealt with “complex mixed radiation fields at workplaces” and in this context it organised a benchmark exercise, which included both measurements and calculations, in a stray radiation field at a high-energy particle accelerator at GSI, Germany. The aim was to intercompare the response of several types of active detectors and passive dosemeters in a well-characterised workplace field. The Monte Carlo simulations of the radiation field and the experimental determination of the neutron spectra with various Bonner Sphere Spectrometers are discussed in Rollet et al. (2008) and in Wiegel et al. (2008). This paper focuses on the intercomparison of the response of the dosemeters in terms of ambient dose equivalent. Th...
Energy Technology Data Exchange (ETDEWEB)
Reyes A, A.; Ortiz R, J. M.; Reyes H, A.; Castaneda M, R.; Solis S, L. O.; Vega C, H. R., E-mail: art8291@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica, Av. Lopez Velarde No. 801, Col. Centro, 98000 Zacatecas (Mexico)
2014-08-15
In this work was used the robust design methodology of artificial neural networks to determine a good topology of net able to solve with efficiency the problems of neutrons spectrometry and dosimetry. For the design of the topology of optimized net 36 different net architectures based on an orthogonal arrangement with a configuration L{sub 9}(3{sup 4}), L{sub 4}(3{sup 2}) were trained. For the training of the neural networks, was used a computer code developed in the ambient of Mat lab programming, which automates the process and analysis of the information, reducing the time used in this activity considerably for the investigator. For the training of the propagation nets forward was utilized a neutrons spectrum compendium published by the International Atomic Energy Agency, where of the total 80% was used for the training and 20% for the test, it trained with an inverse propagation algorithm being the entrance data the count rates corresponding to the 7 spheres of the spectrometric system of Bonner spheres, as exit data, the neural network obtains the neutrons spectrum expressed in 60 energy groups and are calculated of simultaneous way 15 dosimetric quantities. (Author)
Cheminet, A; Hubert, G; Lacoste, V; Boscher, D
2014-10-01
In this paper, a Bonner Sphere Spectrometer extended to high energies (HERMEIS) was employed to measure continuously the cosmic-ray-induced neutron spectra over a long-term period (2 y) at mountain altitude and medium geomagnetic latitude (Pic du Midi de Bigorre in the French Pyrenees, +2885 m, 5.6 GV). The results showed 1-y sinusoidal oscillations in the integrated fluence rates. The amplitude of these oscillations depends on the neutron energetic domain. The fluence rate of thermal neutrons was 53 % higher in August than that in February. Those of epithermal neutrons with energies between 0.4 eV and 0.1 MeV and evaporation neutrons (from 0.1 to 20 MeV) were ∼25 % higher in the summer than those in the winter. Finally, the cascade neutron fluence rate (>20 MeV) remained quite the same (<10 % variation). To understand the effects of local and seasonal changes in the measurement environment, GEANT4 simulations were performed. The nature of rock and thickness of the snow cover during the winter period (given by meteorological data) were investigated. A reasonable agreement between experiments and calculations was found.
Hajek, M; Schoener, W; Vana, N
2002-01-01
The European Council directive 96/29/Euratom requires dosimetric precautions if the effective dose exceeds 1 mSv/a. On an average, this value is exceeded by aircrew members. Roughly half of the radiation exposure at flight altitudes is caused by cosmic ray-induced neutrons. Active ( sup 6 LiI(Eu)-scintillator) and passive (TLDs) Bonner sphere spectrometers were used to determine the neutron energy spectra atop Mt. Sonnblick (3105 m) and Mt. Kitzsteinhorn (3029 m). Further measurements in a mixed radiation field at CERN as well as in a proton beam of 62 MeV at Paul Scherrer Institute, Switzerland, confirmed that not only neutrons but also charged particles contribute to the readings of active detectors, whereas TLD-600 and TLD-700 in pair allow the determination of the thermal neutron flux. Unfolding of the detector data obtained atop both mountains shows two relative maxima around 1 MeV and 85 MeV, which have to be considered for the assessment of the biologically relevant dose equivalent. By convoluting the ...
SECONDARY NEUTRON DOSES IN A PROTON THERAPY CENTRE.
De Saint-Hubert, M; Saldarriaga Vargas, C; Van Hoey, O; Schoonjans, W; De Smet, V; Mathot, G; Stichelbaut, F; Manessi, G; Dinar, N; Aza, E; Cassell, C; Silari, M; Vanhavere, F
2016-09-01
The formation of secondary high-energy neutrons in proton therapy can be a concern for radiation protection of staff. In this joint intercomparative study (CERN, SCK•CEN and IBA/IRISIB/ULB), secondary neutron doses were assessed with different detectors in several positions in the Proton Therapy Centre, Essen (Germany). The ambient dose equivalent H(*)(10) was assessed with Berthold LB 6411, WENDI-2, tissue-equivalent proportional counter (TEPC) and Bonner spheres (BS). The personal dose equivalent Hp(10) was measured with two types of active detectors and with bubble detectors. Using spectral and basic angular information, the reference Hp(10) was estimated. Results concerning staff exposure show H(*)(10) doses between 0.5 and 1 nSv/monitoring unit in a technical room. The LB 6411 showed an underestimation of H(*)(10), while WENDI-2 and TEPC showed good agreement with the BS data. A large overestimation for Hp(10) was observed for the active personal dosemeters, while the bubble detectors showed only a slight overestimation.
Cushman, R.
2001-01-01
In this paper we show that the integral map of Rouths sphere has monodromy when the sphere becomes gyroscopically unstable This uses the nonHamiltonian monodromy of Rouths sphere has center of mass not at its geometrical center and moment of inertia tensor with two equal principal moments of inerti
Energy Technology Data Exchange (ETDEWEB)
Bedogni, R., E-mail: roberto.bedogni@lnf.infn.it [INFN – LNF, via E. Fermi n. 40, 00044 Frascati (Roma) (Italy); Gómez-Ros, J.M. [INFN – LNF, via E. Fermi n. 40, 00044 Frascati (Roma) (Italy); CIEMAT, Av. Complutense 40, 28040 Madrid (Spain); Pola, A.; Bortot, D. [Politecnico di Milano, Dipartimento di Energia, via La Masa 34, 20156 Milano (Italy); INFN – Milano, Via Celoria 16, 20133 Milano (Italy); Gentile, A. [INFN – LNF, via E. Fermi n. 40, 00044 Frascati (Roma) (Italy); Introini, M.V. [Politecnico di Milano, Dipartimento di Energia, via La Masa 34, 20156 Milano (Italy); INFN – Milano, Via Celoria 16, 20133 Milano (Italy); Buonomo, B. [INFN – LNF, via E. Fermi n. 40, 00044 Frascati (Roma) (Italy); Lorenzoli, M. [Politecnico di Milano, Dipartimento di Energia, via La Masa 34, 20156 Milano (Italy); INFN – Milano, Via Celoria 16, 20133 Milano (Italy); Mazzitelli, M. [INFN – LNF, via E. Fermi n. 40, 00044 Frascati (Roma) (Italy); Sacco, D. [INFN – LNF, via E. Fermi n. 40, 00044 Frascati (Roma) (Italy); INAIL – DPIA, Via di Fontana Candida n.1, 00040 Monteporzio Catone (Italy)
2015-05-11
A new directional neutron spectrometer called CYSP (CYlindrical SPectrometer) was developed within the NESCOFI@BTF (2011–2013) collaboration. The device, composed by seven active thermal neutron detectors located along the axis of a cylindrical moderator, was designed to simultaneously respond from the thermal domain up to hundreds of MeV neutrons. The new spectrometer condenses the performance of the Bonner Sphere Spectrometer in a single moderator; thus requiring only one exposure to determine the whole spectrum. The CYSP response matrix, determined with MCNP, has been experimentally evaluated with monochromatic reference neutron fields from 144 keV to 16.5 MeV, plus a {sup 252}Cf source, available at NPL (Teddington, UK). The results of the experiment confirmed the correctness of the response matrix within an overall uncertainty of ±2.5%. The new active spectrometer CYSP offers an innovative option for real-time monitoring of directional neutron fields as those produced in neutron beam-lines.
Gualdrini, G; Tanner, R J; Agosteo, S; Pola, A; Bedogni, R; Ferrari, P; Lacoste, V; Bordy, J-M; Chartier, J-L; de Carlan, L; Gomez Ros, J-M; Grosswendt, B; Kodeli, I; Price, R A; Rollet, S; Schultz, F; Siebert, B; Terrissol, M; Zankl, M
2008-01-01
Within the scope of CONRAD (A Coordinated Action for Radiation Dosimetry) Work Package 4 on Computational Dosimetry jointly collaborated with the other research actions on internal dosimetry, complex mixed radiation fields at workplaces and medical staff dosimetry. Besides these collaborative actions, WP4 promoted an international comparison on eight problems with their associated experimental data. A first set of three problems, the results of which are herewith summarised, dealt only with the expression of the stochastic uncertainties of the results: the analysis of the response function of a proton recoil telescope detector, the study of a Bonner sphere neutron spectrometer and the analysis of the neutron spectrum and dosimetric quantity H(p)(10) in a thermal neutron facility operated by IRSN Cadarache (the SIGMA facility). A second paper will summarise the results of the other five problems which dealt with the full uncertainty budget estimate. A third paper will present the results of a comparison on in vivo measurements of the (241)Am bone-seeker nuclide distributed in the knee. All the detailed papers will be presented in the WP4 Final Workshop Proceedings.
Energy Technology Data Exchange (ETDEWEB)
Farah, J; Bonfrate, A; Donadille, L; Dubourg, N; Lacoste, V; Martinetti, F; Sayah, R; Trompier, F; Clairand, I [IRSN - Institute for Radiological Protection and Nuclear Safety, Fontenay-aux-roses (France); Caresana, M [Politecnico di Milano, Milano (Italy); Delacroix, S; Nauraye, C [Institut Curie - Centre de Protontherapie d Orsay, Orsay (France); Herault, J [Centre Antoine Lacassagne, Nice (France); Piau, S; Vabre, I [Institut de Physique Nucleaire d Orsay, Orsay (France)
2014-06-01
Purpose: Measure stray radiation inside a passive scattering proton therapy facility, compare values to Monte Carlo (MC) simulations and identify the actual needs and challenges. Methods: Measurements and MC simulations were considered to acknowledge neutron exposure associated with 75 MeV ocular or 180 MeV intracranial passively scattered proton treatments. First, using a specifically-designed high sensitivity Bonner Sphere system, neutron spectra were measured at different positions inside the treatment rooms. Next, measurement-based mapping of neutron ambient dose equivalent was fulfilled using several TEPCs and rem-meters. Finally, photon and neutron organ doses were measured using TLDs, RPLs and PADCs set inside anthropomorphic phantoms (Rando, 1 and 5-years-old CIRS). All measurements were also simulated with MCNPX to investigate the efficiency of MC models in predicting stray neutrons considering different nuclear cross sections and models. Results: Knowledge of the neutron fluence and energy distribution inside a proton therapy room is critical for stray radiation dosimetry. However, as spectrometry unfolding is initiated using a MC guess spectrum and suffers from algorithmic limits a 20% spectrometry uncertainty is expected. H*(10) mapping with TEPCs and rem-meters showed a good agreement between the detectors. Differences within measurement uncertainty (10–15%) were observed and are inherent to the energy, fluence and directional response of each detector. For a typical ocular and intracranial treatment respectively, neutron doses outside the clinical target volume of 0.4 and 11 mGy were measured inside the Rando phantom. Photon doses were 2–10 times lower depending on organs position. High uncertainties (40%) are inherent to TLDs and PADCs measurements due to the need for neutron spectra at detector position. Finally, stray neutrons prediction with MC simulations proved to be extremely dependent on proton beam energy and the used nuclear models and
Spectrometer equipment for neutron spectra measurements in mixed neutron/photon fields
Chernov, V A; Trykov, L A
2002-01-01
The paper describes spectrometer equipment in the IPPE experimental laboratory for neutron spectra measurement in mixed (n,gamma) fields. The laboratory was founded in 1957 and it occupies a leading position in the field of nuclear facilities radiation spectrometry and benchmark experiments in Russia. Spectrometer equipment includes spectrometers based on the organic stilbene scintillator, hydrogen counter and Bonner balls. Basic fields of spectrometer application are mixed radiation neutron spectra measurement of radionuclide sources, of nuclear reactors and accelerators; study of neutron transfer through the material, including benchmark experiments and measurement of neutron spectra in the rooms of nuclear facilities.
Energy Technology Data Exchange (ETDEWEB)
Hernandez V, R.; Chacon R, A.; Hernandez D, V. M.; Mercado, G. A.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Ramirez G, J. [Instituto Nacional de Estadistica Geografia e Informatica, Direccion General de Innovacion y Tecnologia de Informacion, Av. Heroes de Nacozari Sur 2301, Fracc. Jardines del Parque, 20276 Aguascalientes (Mexico)], e-mail: ruben_zac@yahoo.com
2009-10-15
The spectrum equivalent dose and environmental equivalent dose f a {sup 239}PuBe source have been determined. The appropriate handling of a neutron source depends on the knowledge of its characteristics, such as its energy distribution, total rate of flowing and dosimetric magnitudes. In many facilities have not spectrometer that allows to determine the spectrum and then area monitors are used that give a dosimetric magnitude starting from measuring the flowing rate and the use of conversion factors, however this procedure has many limitations and it is preferable to measure the spectra and starting from this information the interest dosimetric magnitudes are calculated. In this work a Bonner sphere spectrometer has been used with a {sup 6}LiI(Eu) scintillator obtaining the count rates that produce, to a distance of 100 cm, a {sup 239}PuBe source of 1.85E(11) Bq. The spectrum was reconstructed starting from the count rates using BUNKIUT code and response matrix UTA4. With the spectrum information was calculated the source intensity, total flow, energy average, equivalent dose rate, environmental equivalent dose rate, equivalent dose coefficient and environmental equivalent dose coefficient. By means of two area monitors for neutrons, Eberline ASP-1 and LB 6411 of Berthold the equivalent dose and environmental equivalent dose were measured. The determinate values were compared with those reported in literature and it found that are coincident inside 17%. (Author)
DEFF Research Database (Denmark)
Trenz, Hans-Jörg
2015-01-01
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...... 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......, 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....
SU-F-BRE-11: Neutron Measurements Around the Varian TrueBeam Linac
Energy Technology Data Exchange (ETDEWEB)
Maglieri, R; Seuntjens, J; Kildea, J [McGill University, Montreal, QC (Canada); Liang, L; DeBlois, F [Jewish General Hospital, Montreal, QC (Canada); Evans, M [Montreal General Hospital, Montreal, QC (Canada); Licea, A [Canadian Nuclear Safety Comission, Ottawa, Ontario (Canada); Dubeau, J; Witharana, S [Detec, Gatineau, QC (Canada)
2014-06-15
Purpose: With the emergence of flattening filter free (FFF) photon beams, several authors have noted many advantages to their use. One such advantage is the decrease in neutron production by photonuclear reactions in the linac head. In the present work we investigate the reduction in neutrons from a Varian TrueBeam linac using the Nested Neutron Spectrometer (NNS, Detec). The neutron spectrum, total fluence and source strength were measured and compared for 10 MV with and without flattening filter and the effect of moderation by the room and maze was studied for the 15 MV beam. Methods: The NNS, similar to traditional Bonner sphere detectors but operated in current mode, was used to measure the neutron fluence and spectrum. The NNS was validated for use in high dose rate environments using Monte Carlo simulations and calibrated at NIST and NRC Canada. Measurements were performed at several positions within the treatment room and maze with the linac jaws closed to maximize neutron production. Results: The measurements showed a total fluence reduction between 35-40% in the room and maze when the flattening filter was removed. The neutron source strength Qn was calculated from in-room fluence measurements and was found to be 0.042 × 10{sup 2} n/Gy, 0.026 × 10{sup 2} n/Gy and 0.59 × 101{sup 2} n/Gy for the 10 MV, the 10 MV FFF and 15 MV beams, respectively. We measured ambient equivalent doses of 11 mSv/hr, 7 mSv/hr and 218 mSv/hr for the 10 MV, 10 MV FFF and 15 MV by the head. Conclusion: Our measurements revealed a decrease in total fluence, neutron source strength and equivalent dose of approximately 35-40% across the treatment room for the FFF compared to FF modes. This demonstrates, as expected, that the flattening filter is a major component of the neutron production for the TrueBeam. The authors greatly acknowledge support form the Canadian Nuclear Commission and the Natural Sciences and Engineering Research Council of Canada through the CREATE program. Co
Energy Technology Data Exchange (ETDEWEB)
Vega C, H.R. [Universidad Autonoma de Zacatecas, Cuerpo Academico de Radiobiologia, A.P. 336, 98000 Zacatecas (Mexico); Barquero, R. [Hospital Universitario Rio Hortega, Valladolid (Spain); Mendez, R.; Iniguez, M.P. [Depto. de Fisica Teorica, Atomica, Molecular y Nuclear, Universidad de Valladolid, 47011 Valladolid (Spain)
2003-07-01
By means of a series of measures and Monte Carlo calculations the dosimetric characteristics of the photoneutrons have been determined that take place in volume to a linear accelerator of radiotherapy of 18 MV, LINAC, mark Siemens Mevatron model. The measures were carried out with thermoluminescent dosemeters TLD 600 and TLD 700 that were naked exposed and confined with cover of Cd and Sn, inside a sphere of paraffin and inside spheres Bonner. (Author)
Directory of Open Access Journals (Sweden)
Vellis Vyron
2016-03-01
Full Text Available Let Ω be a planar Jordan domain and α > 0. We consider double-dome-like surfaces Σ(Ω, tα over Ω where the height of the surface over any point x ∈ Ωequals dist(x, ∂Ωα. We identify the necessary and sufficient conditions in terms of and α so that these surfaces are quasisymmetric to S2 and we show that Σ(Ω, tα is quasisymmetric to the unit sphere S2 if and only if it is linearly locally connected and Ahlfors 2-regular.
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 the performance of two neutron spectrum unfolding codes based on iterative procedures and artificial neural networks is evaluated. The first one code based on traditional iterative procedures and called Neutron spectrometry and dosimetry from the Universidad Autonoma de Zacatecas (NSDUAZ) use the SPUNIT iterative algorithm and was designed to unfold neutron spectrum and calculate 15 dosimetric quantities and 7 IAEA survey meters. The main feature of this code is the automated selection of the initial guess spectrum trough a compendium of neutron spectrum compiled by the IAEA. The second one code known as Neutron spectrometry and dosimetry with artificial neural networks (NDSann) is a code designed using neural nets technology. The artificial intelligence approach of neural net does not solve mathematical equations. By using the knowledge stored at synaptic weights on a neural net properly trained, the code is capable to unfold neutron spectrum and to simultaneously calculate 15 dosimetric quantities, needing as entrance data, only the rate counts measured with a Bonner spheres system. Similarities of both NSDUAZ and NSDann codes are: they follow the same easy and intuitive user's philosophy and were designed in a graphical interface under the LabVIEW programming environment. Both codes unfold the neutron spectrum expressed in 60 energy bins, calculate 15 dosimetric quantities and generate a full report in HTML format. Differences of these codes are: NSDUAZ code was designed using classical iterative approaches and needs an initial guess spectrum in order to initiate the iterative procedure. In NSDUAZ, a programming routine was designed to calculate 7 IAEA instrument survey meters using the fluence-dose conversion coefficients. NSDann code use artificial neural networks for solving the ill-conditioned equation system of neutron spectrometry problem through synaptic weights of a properly trained neural network. Contrary to iterative procedures, in
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
First quantum correction to entropy of Vaidya-Bonner black holes due to arbitrary spin fields
Institute of Scientific and Technical Information of China (English)
高长军; 沈有根
2002-01-01
Using the improved brick-wall model, we have calculated the first quantum correction to the entropy of non-staticblack holes, Vaidya-Bonner black holes, due to the gravitational, electro-magnetic and neutrino fields. The result showsthat both bosonic entropy and fermionic entropy are exactly proportional to the area of the event horizon. Thus, theentropy-area law still holds in such a non-static case.
Matsumoto, H; Goka, T; Koga, K; Iwai, S; Uehara, T; Sato, O; Takagi, S
2001-06-01
We have developed a real-time, Bonner Ball-type (neutron energy range is from thermal to 15 MeV) neutron spectral measurement system (Bonner Ball Neutron Detector (BBND)) for use on board the International Space Station (ISS). From measurements taken inside STS-89 (S/MM-8), we successfully distinguished neutrons from protons and other particles in a mixed radiation field; a task hitherto considered difficult. Although the experimental period was short, only 3.5 days (January 24-27, 1998), we were able to obtain energy spectral data and the Earth's neutron dose-equivalent map for the ISS orbital conditions (altitude 400 km, orbit inclination angle 51.6 degrees). A method for calculating the neutron energy spectrum and compensating for the particle interaction with the sensors is also described in detail.
Energy Technology Data Exchange (ETDEWEB)
Reupke, W.A.; Davidson, J.N.; Muir, D.W.
1982-12-01
The authors present algorithms, describe a computer program, and gives a computational procedure for the statistical consistency analysis of neutron cross-section data, S /SUB N/ calculations, and measured tritium production in 14-MeV neutron-driven integral assemblies. Algorithms presented include a reduced matrix manipulation technique suitable for manygroup, 14-MeV neutron transport calculations. The computer program incorporates these algorithms and is expanded and improved to facilitate analysis of such integral experiments. Details of the computational procedure are given for a natural lithium deuteride experiment performed at the Los Alamos National Laboratory. Results are explained in terms of calculated cross-section sensitivities and uncertainty estimates. They include a downward adjustment of the /sup 7/Li(n,xt) 14-MeV cross section from 328 + or - 22 to 284 + or - 24 mb, which is supported by the trend of recent differential and integral measurements. It is concluded that with appropriate refinements, the techniques of consistency analysis can be usefully applied to the analysis of 14-MeV neutron-driven tritium production integral experiments.
Energy Technology Data Exchange (ETDEWEB)
Arteaga A, T.; Ortiz R, J.M.; Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E.; Mercado S, G.A. [Unidades Academicas de Estudios Nucleares, Ingenieria Electrica y Matematicas, Universidad de Zacatecas, A.P. 336, 98000 Zacatecas (Mexico)]. e-mail: tarcicio70@yahoo.co.uk
2006-07-01
People that live in high places respect to the sea level, in latitudes far from the equator or that they travel by plane, they are exposed to atmospheres of high radiation generated by the cosmic rays. Another atmosphere with radiation is the medical equipment, particle accelerators and nuclear reactors. The evaluation of the biological risk for neutron radiation requires an appropriate and sure dosimetry. A commonly used system is the Bonner Sphere Spectrometer (EEB) with the purpose of reconstructing the spectrum that is important because the equivalent dose for neutrons depends strongly on its energy. The count rates obtained in each sphere are treated, in most of the cases, for iterative methods, Monte Carlo or Maximum Entropy. Each one of them has difficulties that it motivates to the development of complementary procedures. Recently it has been used Artificial Neural Networks, ANN) and not yet conclusive results have been obtained. In this work it was designed an ANN to obtain the neutron energy spectrum neutrons starting from the counting rate of count of an EEB. The ANN was trained with 129 reference spectra obtained of the IAEA (1990, 2001), 24 were built as defined energy, including isotopic sources of neutrons of reference and operational, of accelerators, reactors, mathematical functions, and of defined energy with several peaks. The spectrum was transformed from lethargy units to energy and were reaccommodated in 31 energies using the Monte Carlo code 4C. The reaccommodated spectra and the response matrix UTA4 were used to calculate the prospective count rates in the EEB. These rates were used as entrance and its respective spectrum was used as output during the net training. The net design is Retropropagation type with 5 layers of 7, 140, 140, 140 and 31 neurons, transfer function logsig, tansig, logsig, logsig, logsig respectively. Training algorithm, traingdx. After the training, the net was proven with a group of training spectra and others that
Bonner Prize Talk: Parity Violation in Compound-Nuclear Resonances
Bowman, J. David
2002-04-01
I will describe a series of experiments that observed large parity-violating asymmetries in the scattering of polarized neutrons from a number of nuclei. I will review statistical models of compound-nuclear resonances and the statistical interpretation of observables. I will present the results of the experiments and the analysis of the measured asymmetries to extract the strength function of the nuclear weak interaction. In A=232 10 of 10 measured asymmetries had a common sign, in contradiction to the predictions of statistical models. I will describe the interpretation of this phenomenon in terms of doorway states. I will summarize the status of theoretical efforts to obtain constraints on the couplings of the hadronic weak interaction from measured weak strength functions.
Development of active environmental and personal neutron dosemeters.
Nakamura, T; Nunomiya, T; Sasaki, M
2004-01-01
For neutron dosimetry in the radiation environment surrounding nuclear facilities, two types of environmental neutron dosemeters, the high-sensitivity rem counter and the high-sensitivity multi-moderator, the so-called Bonner ball, have been developed and the former is commercially available from Fuji Electric Co. By using these detectors, the cosmic ray neutrons at sea level have been sequentially measured for about 3 y to investigate the time variation of neutron spectrum and ambient dose equivalent influenced by cosmic and terrestrial effects. Our Bonner ball has also been selected as the neutron detector in the International Space Station and has already been used to measure neutrons in the US experimental module. The real time wide-range personal neutron dosemeter which uses two silicon semiconductor detectors has been developed for personal dosimetry and is commercially available from Fuji Electric Co. This dosemeter has good characteristics, fitted to the fluence-to-dose conversion factor in the energy range from thermal energies to several tens of mega-electron-volts and is now widely used in various nuclear facilities.
Neutron scattering. Experiment manuals
Energy Technology Data Exchange (ETDEWEB)
Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)
2010-07-01
The following topics are dealt with: The thermal triple axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, neutron polarization analysis with tht time-of-flight spectrometer DNS, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering with the KWS-1 and KWS-2 diffractometers, the very-small-angle neutron scattering diffractrometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)
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
Hawking radiation of charged Dirac particles in Vaidya-Bonner space-time
Institute of Scientific and Technical Information of China (English)
朱建阳; 张建华; 赵峥
1995-01-01
The dynamical properties of charged Dirac spinor particles in the Vaidya-Bonner space-time are investigated. The asymptotic solution to the radial part of the charged Dirac equation near the event horizon of the black hole is obtained. The Hawking temperature and the event horizon of the charged evaporating black hole, as well as the spectrum of the Hawking radiation of the Dirac particles, are exactly shown. Thereby, a new approach to the back-reaction of radiation from the non-stationary black holes is established.
Neutron scattering. Experiment manuals
Energy Technology Data Exchange (ETDEWEB)
Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)
2014-07-01
The following topics are dealt with: The thermal triple-axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot-single-crystal diffractometer HEiDi, the three-axis spectrometer PANDA, the backscattering spectrometer SPHERES, the DNS neutron-polarization analysis, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering at KWS-1 and KWS-2, a very-small-angle neutron scattering diffractometer with focusing mirror, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)
Energy Technology Data Exchange (ETDEWEB)
Arteaga A, T.; Ortiz R, J. M.; Vega C, H. R., E-mail: tarcicio70@yahoo.co.uk [Universidad Autonoma de Zacatecas, Av. Lopez Velarde 117, 98600 Zacatecas, Zac. (Mexico)
2016-10-15
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
Energy Technology Data Exchange (ETDEWEB)
Mandev, P.
1984-01-01
The hydrocarbon sphere is understood to be the area in which hydrocarbon compounds are available. It is believed that the lower boundary on the hydrocarbon sphere is most probably located at a depth where the predominant temperatures aid in the destruction of hydrocarbons (300 to 400 degrees centigrade). The upper limit on the hydrocarbon sphere obviously occurs at the earth's surface, where hydrocarbons oxidize to H20 and CO2. Within these ranges, the occurrence of the hydrocarbon sphere may vary from the first few hundred meters to 15 kilometers or more. The hydrocarbon sphere is divided into the external (mantle) sphere in which the primary gas, oil and solid hydrocarbon fields are located, and the internal (metamorphic) sphere containing primarily noncommercial accumulations of hydrocarbon gases and solid carbon containing compounds (anthraxilite, shungite, graphite, etc.) based on the nature and scale of hydrocarbon compound concentrations (natural gas, oil, maltha, asphalt, asphaltite, etc.).
Investigating hard sphere interactions through spin echo scattering angle measurement
Washington, Adam
Spin Echo Scattering Angle Measurement (SESAME) allows neutron scattering instruments to perform real space measurements on large micron scale samples by encoding the scattering angle into the neutron's spin state via Larmor precession. I have built a SESAME instrument at the Low Energy Neutron Source. I have also assisted in the construction of a modular SESAME instrument on the ASTERIX beamline at Los Alamos National lab. The ability to tune these instruments has been proved mathematically and optimized and automated experimentally. Practical limits of the SESAME technique with respect to polarization analyzers, neutron spectra, Larmor elements, and data analysis were investigated. The SESAME technique was used to examine the interaction of hard spheres under depletion. Poly(methyl methacrylate) spheres suspended in decalin had previously been studied as a hard sphere solution. The interparticle correlations between the spheres were found to match the Percus-Yevick closure, as had been previously seen in dynamical light scattering experiments. To expand beyond pure hard spheres, 900kDa polystyrene was added to the solution in concentrations of less than 1% by mass. The steric effects of the polystyrene were expected to produce a short-range, attractive, "sticky" potential. Experiment showed, however, that the "sticky" potential was not a stable state and that the spheres would eventually form long range aggregates.
Jammed lattice sphere packings
Kallus, Yoav; Marcotte, Étienne; Torquato, Salvatore
2013-01-01
We generate and study an ensemble of isostatic jammed hard-sphere lattices. These lattices are obtained by compression of a periodic system with an adaptive unit cell containing a single sphere until the point of mechanical stability. We present detailed numerical data about the densities, pair correlations, force distributions, and structure factors of such lattices. We show that this model retains many of the crucial structural features of the classical hard-sphere model and propose it as a...
DISE: directed sphere exclusion.
Gobbi, Alberto; Lee, Man-Ling
2003-01-01
The Sphere Exclusion algorithm is a well-known algorithm used to select diverse subsets from chemical-compound libraries or collections. It can be applied with any given distance measure between two structures. It is popular because of the intuitive geometrical interpretation of the method and its good performance on large data sets. This paper describes Directed Sphere Exclusion (DISE), a modification of the Sphere Exclusion algorithm, which retains all positive properties of the Sphere Exclusion algorithm but generates a more even distribution of the selected compounds in the chemical space. In addition, the computational requirement is significantly reduced, thus it can be applied to very large data sets.
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)
Self-diffusion in liquid gallium and hard sphere model
Directory of Open Access Journals (Sweden)
Blagoveshchenskii Nikolay
2015-01-01
Full Text Available Incoherent and coherent components of quasielastic neutron scattering have been studied in the temperature range of T = 313 K – 793 K aiming to explore the applicability limits of the hard-sphere approach for the microscopic dynamics of liquid gallium, which is usually considered as a non-hard-sphere system. It was found that the non-hard-sphere effects come into play at the distances shorter than the average interatomic distance. The longer range diffusive dynamics of liquid Ga is dominated by the repulsive forces between the atoms.
Benavides, Jose
2014-01-01
SPHERES is a facility of the ISS National Laboratory with three IVA nano-satellites designed and delivered by MIT to research estimation, control, and autonomy algorithms. Since Fall 2010, The SPHERES system is now operationally supported and managed by NASA Ames Research Center (ARC). A SPHERES Program Office was established and is located at NASA Ames Research Center. The SPHERES Program Office coordinates all SPHERES related research and STEM activities on-board the International Space Station (ISS), as well as, current and future payload development. By working aboard ISS under crew supervision, it provides a risk tolerant Test-bed Environment for Distributed Satellite Free-flying Control Algorithms. If anything goes wrong, reset and try again! NASA has made the capability available to other U.S. government agencies, schools, commercial companies and students to expand the pool of ideas for how to test and use these bowling ball-sized droids. For many of the researchers, SPHERES offers the only opportunity to do affordable on-orbit characterization of their technology in the microgravity environment. Future utilization of SPHERES as a facility will grow its capabilities as a platform for science, technology development, and education.
Bathymetric surveys of the Kootenai River near Bonners Ferry, Idaho, water year 2011
Fosness, Ryan L.
2013-01-01
In 2009, the Kootenai Tribe of Idaho released and implemented the Kootenai River Habitat Restoration Master Plan. This plan aimed to restore, enhance, and maintain the Kootenai River habitat and landscape to support and sustain habitat conditions for aquatic species and animal populations. In support of these restoration efforts, the U.S. Geological Survey, in cooperation with the Kootenai Tribe of Idaho, conducted high-resolution multibeam echosounder bathymetric surveys in May, June, and July 2011, as a baseline bathymetric monitoring survey on the Kootenai River near Bonners Ferry, Idaho. Three channel patterns or reaches exist in the study area—braided, meander, and a transitional zone connecting the braided and meander reaches. Bathymetric data were collected at three study areas in 2011 to provide: (1) surveys in unmapped portions of the meander reach; (2) monitoring of the presence and extent of sand along planned lines within a section of the meander reach; and (3) monitoring aggradation and degradation of the channel bed at specific cross sections within the braided reach and transitional zone. The bathymetric data will be used to update and verify flow models, calibrate and verify sediment transport modeling efforts, and aid in the biological assessment in support of the Kootenai River Habitat Restoration Master Plan. The data and planned lines for each study reach were produced in ASCII XYZ format supported by most geospatial software.
Jammed lattice sphere packings.
Kallus, Yoav; Marcotte, Étienne; Torquato, Salvatore
2013-12-01
We generate and study an ensemble of isostatic jammed hard-sphere lattices. These lattices are obtained by compression of a periodic system with an adaptive unit cell containing a single sphere until the point of mechanical stability. We present detailed numerical data about the densities, pair correlations, force distributions, and structure factors of such lattices. We show that this model retains many of the crucial structural features of the classical hard-sphere model and propose it as a model for the jamming and glass transitions that enables exploration of much higher dimensions than are usually accessible.
Energy Technology Data Exchange (ETDEWEB)
Cullen, Dermott E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2017-01-30
Here I attempt to explain what physically happens when we pulse an object with neutrons, specifically what we expect the time dependent behavior of the neutron population to look like. Emphasis is on the time dependent emission of both prompt and delayed neutrons. I also describe how the TART Monte Carlo transport code models this situation; see the appendix for a complete description of the model used by TART. I will also show that, as we expect, MCNP and MERCURY, produce similar results using the same delayed neutron model (again, see the appendix).
Minguzzi, E.
2016-11-01
We investigate spacetimes whose light cones could be anisotropic. We prove the equivalence of the structures: (a) Lorentz-Finsler manifold for which the mean Cartan torsion vanishes, (b) Lorentz-Finsler manifold for which the indicatrix (observer space) at each point is a convex hyperbolic affine sphere centered on the zero section, and (c) pair given by a spacetime volume and a sharp convex cone distribution. The equivalence suggests to describe (affine sphere) spacetimes with this structure, so that no algebraic-metrical concept enters the definition. As a result, this work shows how the metric features of spacetime emerge from elementary concepts such as measure and order. Non-relativistic spacetimes are obtained replacing proper spheres with improper spheres, so the distinction does not call for group theoretical elements. In physical terms, in affine sphere spacetimes the light cone distribution and the spacetime measure determine the motion of massive and massless particles (hence the dispersion relation). Furthermore, it is shown that, more generally, for Lorentz-Finsler theories non-differentiable at the cone, the lightlike geodesics and the transport of the particle momentum over them are well defined, though the curve parametrization could be undefined. Causality theory is also well behaved. Several results for affine sphere spacetimes are presented. Some results in Finsler geometry, for instance in the characterization of Randers spaces, are also included.
Transport properties of the Fermi hard-sphere system
Mecca, Angela; Benhar, Omar; Polls, Artur
2015-01-01
The transport properties of neutron star matter play an important role in a variety of astrophysical processes. We report the results of a calculation of the shear viscosity and thermal conductivity coefficients of the hard-sphere fermion system of degeneracy $\
Criticality of a {sup 237}Np Sphere
Energy Technology Data Exchange (ETDEWEB)
Sanchez, Rene G.; Hayes, David K.; Cappiello, Charlene C.; Myers, William L.; Jaegers, Peter J.; Clement, Steven D.
2003-07-22
A critical mass experiment using a 6-kg {sup 237}Np sphere has been performed. The purpose of the experiment is to get a better estimate of the critical mass of {sup 237}Np. To attain criticality, the {sup 237}Np sphere was surrounded with 93 wt % {sup 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{sub eff} of 0.99089 {+-} 0.0003 compared with a k{sub eff} 1.0026 for the experiment. Based on these results, it is estimated that the critical mass of {sup 237}Np ranges from kilogram weights in the high fifties to low sixties.
2003-03-01
9, 1962. (21) The 31 corresponding flux at the surface of the source was 1.06x105 ≤ 1.2x103 n/cm2-sec. ORIGEN , a Monte Carlo based program...4.7x103 n/cm2-sec, which is within the known error of the values determined by ORIGEN . The ORIGEN values and those obtained with the Bonner Sphere...Price, Jonathan B. Market Manager, Saint-Gobain, Newberry OH. Personal Correspondence. 3 January 2003. 24) Heath, R. L. Gamma-Ray Spectrum
Place, A.; Lacey, L.; Mitchell, T.
2013-01-01
The AlphaSphere is an electronic musical instrument featuring a series of tactile, pressure sensitive touch pads arranged in a spherical form. It is designed to offer a new playing style, while allowing for the expressive real-time modulation of sound available in electronic-based music. It is also designed to be programmable, enabling the flexibility to map a series of different notational arrangements to the pad-based interface.\\ud \\ud The AlphaSphere functions as an HID, MIDI and OSC devic...
Eckstein, Michał; Wulkenhaar, Raimar
2016-01-01
We construct a family of constant curvature metrics on the Moyal plane and compute the Gauss-Bonnet term for each of them. They arise from the conformal rescaling of the metric in the orthonormal frame approach. We find a particular solution, which corresponds to the Fubini-Study metric and which equips the Moyal algebra with the geometry of a noncommutative sphere.
Eckstein, Michał; Sitarz, Andrzej; Wulkenhaar, Raimar
2016-11-01
We construct a family of constant curvature metrics on the Moyal plane and compute the Gauss-Bonnet term for each of them. They arise from the conformal rescaling of the metric in the orthonormal frame approach. We find a particular solution, which corresponds to the Fubini-Study metric and which equips the Moyal algebra with the geometry of a noncommutative sphere.
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.
Absolute multilateration between spheres
Muelaner, Jody; Wadsworth, William; Azini, Maria; Mullineux, Glen; Hughes, Ben; Reichold, Armin
2017-04-01
Environmental effects typically limit the accuracy of large scale coordinate measurements in applications such as aircraft production and particle accelerator alignment. This paper presents an initial design for a novel measurement technique with analysis and simulation showing that that it could overcome the environmental limitations to provide a step change in large scale coordinate measurement accuracy. Referred to as absolute multilateration between spheres (AMS), it involves using absolute distance interferometry to directly measure the distances between pairs of plain steel spheres. A large portion of each sphere remains accessible as a reference datum, while the laser path can be shielded from environmental disturbances. As a single scale bar this can provide accurate scale information to be used for instrument verification or network measurement scaling. Since spheres can be simultaneously measured from multiple directions, it also allows highly accurate multilateration-based coordinate measurements to act as a large scale datum structure for localized measurements, or to be integrated within assembly tooling, coordinate measurement machines or robotic machinery. Analysis and simulation show that AMS can be self-aligned to achieve a theoretical combined standard uncertainty for the independent uncertainties of an individual 1 m scale bar of approximately 0.49 µm. It is also shown that combined with a 1 µm m‑1 standard uncertainty in the central reference system this could result in coordinate standard uncertainty magnitudes of 42 µm over a slender 1 m by 20 m network. This would be a sufficient step change in accuracy to enable next generation aerospace structures with natural laminar flow and part-to-part interchangeability.
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
Transport properties of the Fermi hard-sphere system
Energy Technology Data Exchange (ETDEWEB)
Mecca, Angela; Lovato, Alessandro; Benhar, Omar; Polls, Artur
2016-03-01
The transport properties of neutron star matter play an important role in many astrophysical processes. We report the results of a calculation of the shear viscosity and thermal conductivity coefficients of the hard-sphere fermion system of degeneracy ν = 2, that can be regarded as a model of pure neutron matter. Our approach is based on the effective interaction obtained from the formalism of correlated basis functions and the cluster expansion technique. The resulting transport coefficients show a strong sensitivity to the quasiparticle effective mass, reflecting the effect of second-order contributions to the self-energy that are not taken into account in nuclear matter studies available in the literature.
A SINGLE-EXPOSURE, MULTIDETECTOR NEUTRON SPECTROMETER FOR WORKPLACE MONITORING.
Bedogni, R; Bortot, D; Buonomo, B; Esposito, A; Gómez-Ros, J M; Introini, M V; Mazzitelli, G; Moraleda, M; Pola, A; Romero, A M
2016-09-01
This communication describes a recently developed single-exposure neutron spectrometer, based on multiple active thermal neutron detectors located within a moderating sphere, which have been developed jointly by CIEMAT (Spain), INFN (Italy) and Politecnico di Milano (Italy) in the framework of Italian and Spanish collaboration projects. The fabricated prototypes permit to achieve spectrometric resolution with nearly isotropic response for neutron with energies from thermal to 100-200 MeV, thus being able to characterise the complete neutron spectrum in only one exposure by unfolding the measured responses of the detectors. This makes it especially advantageous for characterising neutron fields and workplace monitoring purposes in neutron-producing facilities.
Panoramic stereo sphere vision
Feng, Weijia; Zhang, Baofeng; Röning, Juha; Zong, Xiaoning; Yi, Tian
2013-01-01
Conventional stereo vision systems have a small field of view (FOV) which limits their usefulness for certain applications. While panorama vision is able to "see" in all directions of the observation space, scene depth information is missed because of the mapping from 3D reference coordinates to 2D panoramic image. In this paper, we present an innovative vision system which builds by a special combined fish-eye lenses module, and is capable of producing 3D coordinate information from the whole global observation space and acquiring no blind area 360°×360° panoramic image simultaneously just using single vision equipment with one time static shooting. It is called Panoramic Stereo Sphere Vision (PSSV). We proposed the geometric model, mathematic model and parameters calibration method in this paper. Specifically, video surveillance, robotic autonomous navigation, virtual reality, driving assistance, multiple maneuvering target tracking, automatic mapping of environments and attitude estimation are some of the applications which will benefit from PSSV.
Evaluation of Delayed Critical ORNL Unreflected HEU Metal Sphere (ORSphere)
Marshall, M. A.; Bess, J. D.
2014-04-01
In 1971 and 1972 experimenters at the Oak Ridge Critical Experiment Facility performed critical experiments using an unreflected metal sphere of highly enriched uranium (HEU). The sphere used for the criticality experiments, originally used for neutron leakage spectrum measurements by General Atomic Company, consisted of three main parts and were assembled with a vertical assembly machine. Two configurations were tested. The first was nearly spherical with a nominal radius of 3.467 inches and had a reactivity of 68.1 ± 2.0 cents. The sphere parts were then re-machined as a sphere with a nominal radius of 3.4425 inches. This assembly had a reactivity of -23 cents. The method, dimensions, and uncertainty of the critical experiment were extensively recorded and documented. The original purpose of the experiments was for comparison to GODIVA I experiments. The ORNL unreflected HEU Metal Spheres have been evaluated for inclusion in the International Handbook of Evaluated Criticality Safety Benchmark Experiments (scheduled for inclusion in the September 2013 edition).
Haphazard Packing of Unequal Spheres
Institute of Scientific and Technical Information of China (English)
叶大年; 张金民
1991-01-01
Haphazard packing of equal and unequal spheres can be performed for the spheres of molecular sieve material with a density of 1.80.The packing of such spheres in air is equivalent to that of nat-ural grains in water.Packing concentrations of equal spheres have been obtained for different pac-king intensities.Unequal spheres can be regarded as equal ones in a wide range of diameter ratios,so far as the packing concentration is concerned.A threshold of diameter ratio exists at 0.70,be-low which the packing concentration is expected to increase.The variation curves of concentration vs.diameter ratio were established in the experiment.The result will help us to understand the process of sedimentation and the concentration of voids in sedimentary rocks.
Tom W. Bonner Prize in Nuclear Physics Lecture: The limits of nuclear landscape
Nazarewicz, Witold
2012-03-01
Understanding nuclei is a quantum many-body problem of incredible richness and diversity and studies of nuclei address some of the great challenges that are common throughout modern science. Nuclear structure research strives to build a unified and comprehensive microscopic framework in which bulk nuclear properties, nuclear excitations, and nuclear reactions can all be described. A new and exciting focus in this endeavor lies in the description of exotic and short-lived nuclei at the limits of proton-to-neutron asymmetry, mass, and angular momentum. In this talk, advances in the nuclear density functional theory will be reviewed in the context of the main scientific questions, experimental developments, and the advent of extreme-scale computing platforms.
Isentropic Spheres in General Relativity
Humi, Mayer
2016-01-01
Astrophysical gas clouds undergo thermodynamically irreversible processes and emit heat to their surroundings. Due the emission of this heat one can envision an idealized situation in which gas entropy remains (almost) constant. With this motivation in mind we derive in this paper interior solutions to the Einstein equations of General Relativity for spheres which consist of isentropic gas. In particular we investigate solutions in which the mass distribution inside the sphere has several shells. Such spheres might be considered an early stage for the formation of a "solar system".
Data compression on the sphere
McEwen, J D; Eyers, D M; 10.1051/0004-6361/201015728
2011-01-01
Large data-sets defined on the sphere arise in many fields. In particular, recent and forthcoming observations of the anisotropies of the cosmic microwave background (CMB) made on the celestial sphere contain approximately three and fifty mega-pixels respectively. The compression of such data is therefore becoming increasingly important. We develop algorithms to compress data defined on the sphere. A Haar wavelet transform on the sphere is used as an energy compression stage to reduce the entropy of the data, followed by Huffman and run-length encoding stages. Lossless and lossy compression algorithms are developed. We evaluate compression performance on simulated CMB data, Earth topography data and environmental illumination maps used in computer graphics. The CMB data can be compressed to approximately 40% of its original size for essentially no loss to the cosmological information content of the data, and to approximately 20% if a small cosmological information loss is tolerated. For the topographic and il...
Dyson Spheres around White Dwarfs
Semiz, İbrahim
2015-01-01
A Dyson Sphere is a hypothetical structure that an advanced civilization might build around a star to intercept all of the star's light for its energy needs. One usually thinks of it as a spherical shell about one astronomical unit (AU) in radius, and surrounding a more or less Sun-like star; and might be detectable as an infrared point source. We point out that Dyson Spheres could also be built around white dwarfs. This type would avoid the need for artificial gravity technology, in contrast to the AU-scale Dyson Spheres. In fact, we show that parameters can be found to build Dyson Spheres suitable --temperature- and gravity-wise-- for human habitation. This type would be much harder to detect.
Manuel, Oliver K.
2011-01-01
Earth is connected gravitationally, magnetically and electrically to its heat source - a neutron star that is obscured from view by waste products in the photosphere. Neutron repulsion is like the hot filament in an incandescent light bulb. Excited neutrons are emitted from the solar core and decay into hydrogen that glows in the photosphere like a frosted light bulb. Neutron repulsion was recognized in nuclear rest mass data in 2000 as the overlooked source of energy, the keystone of an arch...
Tom W. Bonner Prize in Nuclear Physics Talk: Symmetries and Simple Patterns in Nuclei
Casten, Richard
2011-04-01
Nuclei are complex many-body objects that display remarkably simple patterns and regularities, both for a given nucleus and across regions of nuclei. The juxtaposition of these two facets of nuclear structure is reflected in two general, and complementary, approaches to their description - a microscopic (femtoscopic, of course) perspective in terms of the motions of the individual nucleons and their interactions, and a macroscopic view of the nucleus as a whole, in terms of its shapes, symmetries, and collective behavior. The first part of this talk will discuss the simple patterns nuclei exhibit and interpret them in terms of symmetries, such as those of the Interacting Boson Approximation (IBA) model, elementary collective modes, changes in shell structure, and quantum phase transitions in the equilibrium structure. It is also possible to approach structural evolution in nuclei with an extremely simple, more microscopic, perspective focusing on the competition of the most important residual interactions, pairing and the valence proton-neutron (p - n) interaction. While this is not a substitute for a comprehensive theoretical treatment, which remains a challenge and goal of nuclear theory, such an analysis leads to simple approaches, such as the NpNn scheme and the P-factor, that correlate large amounts of nuclear data, can guide estimates of unknown nuclei, and which are highly sensitive indicators of changes in shell structure and of nuclei that exhibit behavior deviating from normal tends. Finally, empirical means of extracting information on the critical valence p - n interaction will be discussed and the systematic behavior of these interaction strengths will be linked to shell structure on the one hand, and the onset and development of collectivity on the other. Work supported by the US DOE under Grant No. DE-FG02-91ER-40609.
Unveiling small sphere's scattering behavior
Tzarouchis, Dimitrios C; Sihvola, Ari
2016-01-01
A classical way for exploring the scattering behavior of a small sphere is to approximate Mie coefficients with a Taylor series expansion. This ansatz delivered a plethora of insightful results, mostly for small spheres supporting electric localized plasmonic resonances. However, many scattering aspects are still uncharted, especially for the case of magnetic resonances. Here, an alternative system ansatz is proposed based on the Pad\\'e approximants for the Mie coefficients. The extracted results reveal new aspects, such as the existence of a self-regulating radiative damping mechanism for the first magnetic resonance. Hence, a systematic way of exploring the scattering behavior is introduced, sharpening our understanding about sphere's scattering behavior and its emergent functionalities.
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...
Matrix dynamics of fuzzy spheres
Jatkar, D P; Wadia, S R; Yogendran, K P; Jatkar, Dileep P.; Mandal, Gautam; Wadia, Spenta R.
2002-01-01
We study the dynamics of fuzzy two-spheres in a matrix model which represents string theory in the presence of RR flux. We analyze the stability of known static solutions of such a theory which contain commuting matrices and SU(2) representations. We find that irreducible as well as reducible representations are stable. Since the latter are of higher energy, this stability poses a puzzle. We resolve this puzzle by noting that reducible representations have marginal directions corresponding to non-spherical deformations. We obtain new static solutions by turning on these marginal deformations. These solutions now have instability or tachyonic directions. We discuss condensation of these tachyons which correspond to classical trajectories interpolating from multiple, small fuzzy spheres to a single, large sphere. We briefly discuss spatially independent configurations of a D3/D5 system described by the same matrix model which now possesses a supergravity dual.
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
Phase diagram of elastic spheres.
Athanasopoulou, L; Ziherl, P
2017-02-15
Experiments show that polymeric nanoparticles often self-assemble into several non-close-packed lattices in addition to the face-centered cubic lattice. Here, we explore theoretically the possibility that the observed phase sequences may be associated with the softness of the particles, which are modeled as elastic spheres interacting upon contact. The spheres are described by two finite-deformation theories of elasticity, the modified Saint-Venant-Kirchhoff model and the neo-Hookean model. We determine the range of indentations where the repulsion between the spheres is pairwise additive and agrees with the Hertz theory. By computing the elastic energies of nine trial crystal lattices at densities far beyond the Hertzian range, we construct the phase diagram and find the face- and body-centered cubic lattices as well as the A15 lattice and the simple hexagonal lattice, with the last two being stable at large densities where the spheres are completely faceted. These results are qualitatively consistent with observations, suggesting that deformability may indeed be viewed as a generic property that determines the phase behavior in nanocolloidal suspensions.
Approximation on the complex sphere
Alsaud, Huda; Kushpel, Alexander; Levesley, Jeremy
2012-01-01
We develop new elements of harmonic analysis on the complex sphere on the basis of which Bernstein's, Jackson's and Kolmogorov's inequalities are established. We apply these results to get order sharp estimates of $m$-term approximations. The results obtained is a synthesis of new results on classical orthogonal polynomials, harmonic analysis on manifolds and geometric properties of Euclidean spaces.
Tsekov, R
2014-01-01
The finite size effect of electron and nucleus is accounted for in the model of atom. Due to their hard sphere repulsion the energy of the 1s orbital decreases and the corrections amount up to 8 % in Uranium. Several models for boundary conditions on the atomic nucleus surface are discussed as well.
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...
Kinetic theory of hard spheres
Beijeren, H. van; Ernst, M.H.
1979-01-01
Kinetic equations for the hard-sphere system are derived by diagrammatic techniques. A linear equation is obtained for the one-particle-one particle equilibrium time correlation function and a nonlinear equation for the one-particle distribution function in nonequilibrium. Both equations are nonloca
Ignatovich, V K
2005-01-01
A new, algebraic, method is applied to calculation of neutron albedo from substance to check the claim that use of ultradispersive fuel and moderator of an active core can help to gain in size and mass of the reactor. In a model of isotropic distribution of incident and reflected neutrons it is shown that coherent scattering on separate grains in the case of thermal neutrons increases transport cross section negligibly, however it decreases albedo from a wall of finite thickness because of decrease of substance density. A visible increase of albedo takes place only for neutrons with wave length of the order of the size of a single grain.
Mueller, J. M.; Mattingly, J.
2016-07-01
There is a significant and well-known anisotropy between the prompt neutrons emitted from a single fission event; these neutrons are most likely to be observed at angles near 0° or 180° relative to each other. However, the propagation of this anisotropy through different generations of a fission chain reaction has not been previously studied. We have measured this anisotropy in neutron-neutron coincidences from a subcritical highly-multiplying assembly of plutonium metal. The assembly was a 4.5 kg α-phase plutonium metal sphere composed of 94% 239Pu and 6% 240Pu by mass. Data were collected using two EJ-309 liquid scintillators and two EJ-299 plastic scintillators. The angular distribution of neutron-neutron coincidences was measured at 90° and 180° and found to be largely isotropic. Simulations were performed using MCNPX-PoliMi of similar plutonium metal spheres of varying sizes and a correlation between the neutron multiplication of the assembly and the anisotropy of neutron-neutron coincidences was observed. In principle, this correlation could be used to assess the neutron multiplication of an unknown assembly.
Berenbrock, Charles; Bennett, James P.
2005-01-01
Characterization of sediment transport of the Kootenai River in the white sturgeon spawning reach is needed by the Kootenai River White Sturgeon Recovery Team to predict sediment-transport conditions that improve spawning conditions for the white sturgeon (Acipenser transmontanus) in the Kootenai River near Bonners Ferry, Idaho. The decreasing population and spawning failure of the white sturgeon has led to much concern. Few wild juvenile sturgeon are found in the river today. The Kootenai River begins in British Columbia, Canada, and flows through Montana, Idaho, and back into British Columbia. A 15-mile reach of the Kootenai River in Idaho was studied, including the white sturgeon spawning reach that has been designated as a critical habitat near Bonners Ferry, Idaho, and a 1-mile long side channel around the western side of Shorty Island. A one-dimensional sediment-transport model of the study reach was developed, calibrated, and used to simulate the response of the hydraulic and sediment system to varying discharges and water-surface elevations. The model comprises 79 cross sections, most of which came from a previous river survey conducted in 2002-03. Bed-sediment samples collected in 2002 and additional samples collected for this study in 2004 were used in the model. The model was calibrated to discharge and water-surface elevations at two U.S. Geological Survey gaging stations. The model also was calibrated to suspended-sediment discharge at several sites in the study reach. The calibrated model was used to simulate six different management alternatives to assess erosion and deposition under varying hydraulic conditions at the end of 21 days of simulation. Alternative 1 was simulated with a discharge of 6,000 cubic feet per second (ft3/s), alternative 2 with 20,000 ft3/s, alternative 3 with 40,000 ft3/s, and alternatives 4 through 6 with 60,000 ft3/s and represents low to high discharges in the river since the construction of Libby Dam. Sediment deposition
Spin-Echo Small Angle Neutron Scattering analysis of liposomes and bacteria
Van Heijkamp, L.F., et al.
2010-01-01
Two types of liposomes, commonly used in drug delivery studies, and E. coli bacteria, all prepared in H2O, were resuspended in D2O and measured with Small Angle Spin-Echo Neutron Scattering (SESANS). Modeling was performed using correlation functions for solid spheres and hollow spheres. The signal
Orsphere: Physics Measurments For Bare, HEU(93.2)-Metal Sphere
Energy Technology Data Exchange (ETDEWEB)
Marshall, Margaret A. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Bess, John D. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Briggs, J. Blair [Idaho National Lab. (INL), Idaho Falls, ID (United States); White, Christine E. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Dyrda, James P. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Tancock, Nigel P. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mihalczo, John [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2015-03-01
In the early 1970s 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 1950s (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 inches), masses (±0.01 g), and material data. The experiment was also set up to minimize the amount of structural material in the sphere proximity. Two, correlated spheres were evaluated and judged to be acceptable as criticality benchmark experiments. This evaluation is given in HEU-MET-FAST-100. The second, smaller sphere was used for additional reactor physics measurements. Worth measurements (Reference 1, 2, 3 and 4), the delayed neutron fraction (Reference 3, 4 and 5) and surface material worth coefficient (Reference 1 and 2) are all measured and judged to be acceptable as benchmark data. The prompt neutron decay (Reference 6), relative fission density (Reference 7) and relative neutron importance (Reference 7) were measured, but are not evaluated. Information for the evaluation was compiled from References 1 through 7, the experimental logbooks 8 and 9 ; additional drawings and notes provided by the experimenter; and communication with the lead experimenter, John T. Mihalczo.
ORSPHERE: PHYSICS MEASUREMENTS FOR BARE, HEU(93.2)-METAL SPHERE
Energy Technology Data Exchange (ETDEWEB)
Margaret A. Marshall
2014-03-01
In the early 1970s 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 1950s (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 inches), masses (±0.01 g), and material data. The experiment was also set up to minimize the amount of structural material in the sphere proximity. Two, correlated spheres were evaluated and judged to be acceptable as criticality benchmark experiments. This evaluation is given in HEU-MET-FAST-100. The second, smaller sphere was used for additional reactor physics measurements. Worth measurements (Reference 1, 2, 3 and 4), the delayed neutron fraction (Reference 3, 4 and 5) and surface material worth coefficient (Reference 1 and 2) are all measured and judged to be acceptable as benchmark data. The prompt neutron decay (Reference 6), relative fission density (Reference 7) and relative neutron importance (Reference 7) were measured, but are not evaluated. Information for the evaluation was compiled from References 1 through 7, the experimental logbooks 8 and 9 ; additional drawings and notes provided by the experimenter; and communication with the lead experimenter, John T. Mihalczo.
Koga, K.; Muraki, Y.; Shibata, S.; Yamamoto, T.; Matsumoto, H.; Okudaira, O.; Kawano, H.; Yumoto, K.
2013-12-01
To support future space activities, it is crucial to acquire space environmental data related to the space-radiation degradation of space parts and materials, and spacecraft anomalies. Such data are useful for spacecraft design and manned space activity. SEDA-AP was mounted on 'Kibo' of the ISS (International Space Station) to measure the space environment at a 400-kilometer altitude. Neutrons are very harmful radiation, with electrical neutrality that makes them strongly permeable. SEDA-AP measures the energy of neutrons from thermal to 100 MeV in real time using a Bonner Ball Detector (BBND) and a Scintillation Fiber Detector (FIB). BBND detects neutrons using He-3 counters, which have high sensitivity to thermal neutrons. Neutron energy is derived using the relative response function of polyethylene moderators of 6 different thicknesses. FIB measures the tracks of recoil protons caused by neutrons within a cubic arrayed sensor of 512 scintillation fibers. The charged particles are excluded using an anti-scintillator which surrounds the cube sensor, and the neutron energy is obtained from the track length of a recoil proton. There are three sources of neutrons in space; 1. Albedo Neutrons Produced by reactions of galactic cosmic rays or radiation belt particles with the atmosphere 2. Local Neutrons Produced by the reactions of galactic cosmic rays or radiation belt particles with spacecraft 3. Solar Neutrons Produced by accelerated particles in solar flares An accurate energy spectrum of the solar neutrons includes important information on high-energy particle generation mechanism in a solar flare, because neutrons are unaffected by interplanetary magnetic fields. These data will become useful to forecast solar energetic particles in future. Some candidate events involving solar neutrons were found as a result of analyzing data of the solar flare of M>2 since September 2009. Moreover, it is important to measure albedo neutrons, since protons generated by neutron
De Gennes Narrowing and Hard-Sphere Approach.
Sobolev, Oleg
2016-09-22
The energy width Δω of the quasielastic coherent dynamic structure factor S(Q, ω) for a simple liquid exhibits the oscillating dependence on wavenumber Q with the sharp minimum at Qmax corresponding to the maximum of the structure factor S(Q). The only known expression for Δω(Q) was derived for a dense hard-sphere (HS) fluid (Cohen et al., Phys. Rev. Lett. 1987, 59, 2872). Though this expression has been frequently used for the analysis of the experimental data obtained for liquid metals, until now, it has never been tested against a true HS fluid. A test performed by means of HS molecular dynamic simulations reveals a considerable discrepancy between the simulations results and the examined model. The main output of the analysis is the finding that the ΔωHS(Q) behavior is defined in terms of the average cage size, ⟨Lc⟩, rather than of the HS diameter, σHS. The simulated ΔωHS(Q) has been compared with the results for the soft-spherical potential. The microscopic dynamics of the soft-sphere fluid shows significant difference in comparison to the HS system. Nevertheless, the diffusive mobility of soft spheres can be characterized within the HS approximation using an effective diameter, σeff, and this parameter can be found from Δω(Q) at Q ≈ Qmax. A similar result has been obtained for the neutron scattering data measured for liquid Rb.
Mattner, Trent; Chong, Min; Joubert, Peter
2000-11-01
Vortical flow past a sphere in a constant diameter pipe was studied experimentally in a guide vane apparatus similar to those used in fundamental experimental studies of vortex breakdown. The initial effect of swirl was to shorten the downstream separation bubble. For a small range of the swirl intensity, an almost stagnant upstream separation bubble formed. As the swirl intensity was increased, the bubble became unstable and an unsteady spiral formed. At high swirl intensity there was a mean recirculation region which penetrated far upstream while the flow on the downstream hemisphere was attached. Measurements of the velocity field were obtained using laser Doppler velocimetry. Analysis of these results suggests that the onset of upstream separation is associated with the formation of a negative azimuthal vorticity component which slows the axial flow near the axis of symmetry. This is consistent with inviscid distortion of the vortex filaments in the diverging flow approaching the sphere.
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.
Entanglement Entropy of Two Spheres
Shiba, Noburo
2012-01-01
We study the entanglement entropy S_{AB} of a massless free scalar field on two spheres A and B whose radii are R_1 and R_2, respectively, and the distance between them is r. The state of the massless free scalar field is the vacuum state. We obtain the result that the mutual information S_{A;B}:=S_A+S_B-S_{AB} is independent of the ultraviolet cutoff and proportional to the product of the areas of the two spheres when r>>R_1,R_2, where S_A and S_B are the entanglement entropy on the inside region of A and B, respectively. We discuss possible connections of this result with the physics of black holes.
Entanglement entropy of two spheres
Shiba, Noburo
2012-07-01
We study the entanglement entropy S AB of a massless free scalar field on two spheres A and B whose radii are R 1 and R 2, respectively, and the distance between the centers of them is r. The state of the massless free scalar field is the vacuum state. We obtain the result that the mutual information {S_{{A;B}}} equiv {S_A} + {S_B} - {S_{{AB}}} is independent of the ultraviolet cutoff and proportional to the product of the areas of the two spheres when r ≫ R 1 ,R 2,where S A and S B aretheentanglemententropyontheinsideregionof A and B, respectively. We discuss possible connections of this result with the physics of black holes.
Sphere-to-rod transition of triblock copolymer micelles at room temperature
Indian Academy of Sciences (India)
R Ganguly; V K Aswal; P A Hassan; I K Gopalakrishnan; J V Yakhmi
2004-08-01
A room temperature sphere-to-rod transition of the polyethylene oxide-polypropylene oxide-polyethylene oxide-based triblock copolymer, (PEO)20 (PPO)70 (PEO)20 micelles have been observed in aqueous medium under the influence of ethanol and sodium chloride. Addition of 5-10% ethanol induces a high temperature sphere-to-rod transition of the micelles, which is brought to room temperature upon addition of NaCl. The inference about the change in the shape of the micelles has been drawn from small-angle neutron scattering (SANS) and viscosity studies.
Principal Fibrations from Noncommutative Spheres
Landi, Giovanni; Suijlekom, Walter Van
2005-11-01
We construct noncommutative principal fibrations Sθ7→Sθ4 which are deformations of the classical SU(2) Hopf fibration over the four sphere. We realize the noncommutative vector bundles associated to the irreducible representations of SU(2) as modules of coequivariant maps and construct corresponding projections. The index of Dirac operators with coefficients in the associated bundles is computed with the Connes-Moscovici local index formula. "The algebra inclusion is an example of a not-trivial quantum principal bundle."
Gerlach, Henryk
2010-01-01
What is the longest rope on the unit sphere? Intuition tells us that the answer to this packing problem depends on the rope's thickness. For a countably infinite number of prescribed thickness values we construct and classify all solution curves. The simplest ones are similar to the seamlines of a tennis ball, others exhibit a striking resemblance to Turing patterns in chemistry, or to ordered phases of long elastic rods stuffed into spherical shells.
Hard sphere packings within cylinders.
Fu, Lin; Steinhardt, William; Zhao, Hao; Socolar, Joshua E S; Charbonneau, Patrick
2016-03-07
Arrangements of identical hard spheres confined to a cylinder with hard walls have been used to model experimental systems, such as fullerenes in nanotubes and colloidal wire assembly. Finding the densest configurations, called close packings, of hard spheres of diameter σ in a cylinder of diameter D is a purely geometric problem that grows increasingly complex as D/σ increases, and little is thus known about the regime for D > 2.873σ. In this work, we extend the identification of close packings up to D = 4.00σ by adapting Torquato-Jiao's adaptive-shrinking-cell formulation and sequential-linear-programming (SLP) technique. We identify 17 new structures, almost all of them chiral. Beyond D ≈ 2.85σ, most of the structures consist of an outer shell and an inner core that compete for being close packed. In some cases, the shell adopts its own maximum density configuration, and the stacking of core spheres within it is quasiperiodic. In other cases, an interplay between the two components is observed, which may result in simple periodic structures. In yet other cases, the very distinction between the core and shell vanishes, resulting in more exotic packing geometries, including some that are three-dimensional extensions of structures obtained from packing hard disks in a circle.
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
SURFACES OF HARD-SPHERE SYSTEMS
Directory of Open Access Journals (Sweden)
Dietrich Stoyan
2014-07-01
Full Text Available In various situations surfaces appear that are formed by systems of hard spheres. Examples are porous layers as surfaces of sand heaps and biofilms or fracture surfaces of concrete. The present paper considers models where a statistically homogeneous system of hard spheres with random radii is intersected by a plane and the surface is formed by the spheres with centers close to this plane. Formulae are derived for various characteristics of such surfaces: for the porosity profile, i.e. the local porosity in dependence on the distance from the section plane and for the geometry of the sphere caps that look above the section plane.It turns out that these characteristics only depend on the first-order characteristics of the sphere system, its sphere density and the sphere radius distribution.Comparison with empirically studied biofilms shows that the model is realistic.
Uranium target for electron accelerator based neutron source for BNCT
Tonchev, A. P.; Harmon, F.; Collens, T. J.; Kennedy, K.; Sabourov, A.; Harker, Y. D.; Nigg, D. W.; Jones, J. L.
2001-07-01
Calculations of the epithermal-neutron yield of photoneutrons from a uranium-beryllium converter using a 27 MeV electron linear accelerator have been investigated. In this concept, relativistic electron beams from a 30 MeV LINAC impinge upon a small uranium sphere surrounded by a cylindrical tank of circulating heavy water (D2O) nested in a beryllium cube. The photo-fission neutron spectrum from the uranium sphere is thermalized in deuterium and beryllium, filtered and moderated in special material (AlF3/Al/LiF), and directed to the patient. The results of these calculations demonstrate that photoneutron devices could offer a promising alternative to nuclear reactors for the production of epithermal neutrons for Neutron Capture Therapy. The predicted parameter for the epithermal flux is more than 108n.cm-2.mA-1.
Evaluation of response matrix of a multisphere neutron spectrometer with water moderator
Indian Academy of Sciences (India)
Rahim Khabaz; Hashem Miri Hakimabad
2011-10-01
Neutron energy responses of water sphere spectrometers (WSS) to 30 MeV have been calculated by means of Monte Carlo calculations, using the computer code MCNP4C with ENDF/B-VI.0 neutron cross-section. The calculations have been performed for 3He detector (typical SP9) placed inside 2, 3, 5, 8, 12 and 18-inch diameter moderating spheres composed of water in aluminum shell. These simulations included a detailed description of the geometry of the system. The newly calculated responses have been compared to polyethylene sphere responses.
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
Entanglement entropy of round spheres
Energy Technology Data Exchange (ETDEWEB)
Solodukhin, Sergey N., E-mail: Sergey.Solodukhin@lmpt.univ-tours.f [Laboratoire de Mathematiques et Physique Theorique, Universite Francois-Rabelais Tours Federation Denis Poisson - CNRS, Parc de Grandmont, 37200 Tours (France)
2010-10-18
We propose that the logarithmic term in the entanglement entropy computed in a conformal field theory for a (d-2)-dimensional round sphere in Minkowski spacetime is identical to the logarithmic term in the entanglement entropy of extreme black hole. The near horizon geometry of the latter is H{sub 2}xS{sub d-2}. For a scalar field this proposal is checked by direct calculation. We comment on relation of this and earlier calculations to the 'brick wall' model of 't Hooft. The case of generic 4d conformal field theory is discussed.
Non-Spherical Models of Neutron Stars
Zubairi, O; Romero, A; Mellinger, R; Weber, F; Orsaria, M; Contrera, G
2015-01-01
Non-rotating neutron stars are generally treated in theoretical studies as perfect spheres. Such a treatment, however, may not be correct if strong magnetic fields are present (such as for magnetars) and/or the pressure of the matter in the cores of neutron stars is non-isotropic (e.g., color superconducting). In this paper, we investigate the structure of non-spherical neutron stars in the framework of general relativity. Using a parameterized metric to model non-spherical mass distributions, we first derive a stellar structure equation for deformed neutron stars. Numerical investigations of this model equation show that the gravitational masses of deformed neutron stars depend rather strongly on the degree and type (oblate or prolate) of stellar deformation. In particular, we find that the mass of a neutron star increases with increasing oblateness but decreases with increasing prolateness. If this feature carries over to a full two-dimensional treatment of deformed neutron stars, this opens up the possibil...
Small-angle scattering from precipitates: Analysis by use of a polydisperse hard-sphere model
DEFF Research Database (Denmark)
Pedersen, J.S.
1993-01-01
A general polydisperse hard-sphere model for analyzing small-angle-scattering data from spherical precipitates in alloys is presented. In the model the size distribution is chosen as a Weibull density distribution and the hard-sphere interaction radius is taken as being proportional to the radius...... very good fits to the experimental data and the results are in agreement with a Li content of 25% in the precipitates. The concentration of Li in the matrix is also in good agreement with the phase diagram of Al-Li found in the literature. Results from the application of a monodisperse hard-sphere...... of the precipitates. The Weibull distribution is monomodal, and depending on the parameters describing the distribution, it can skew to either side. Small-angle x-ray- and neutron-scattering data, taken from the literature, from spherical delta' precipitates in Al-Li alloys have been analyzed with the model. It gives...
Floating behavior of hydrophobic glass spheres.
Liu, Xinjie; Wang, Xiaolong; Liang, Yongmin; Zhou, Feng
2009-08-15
When a hydrophobic solid sphere is floating on water or salt solutions with different concentrations, it is at equilibrium under the impact of gravity, buoyancy force, and curvature force, the component of surface tension in the vertical direction. We have changed the diameters of the spheres and the concentrations of the two selected salts, NaCl and NaNO(3), to study the floating behaviors of these spheres and the contributions of surface tension and buoyancy force to their floatation. Generally speaking, the surface tension plays a more important role than the buoyancy force when the gravity is small, but the buoyancy force plays an identical or a more important role when the spheres are big enough. The wettability of the spheres significantly influences the height below the contact perimeter especially in salt solutions. The theoretical calculation meniscus slope angles at the sphere three-phase contact line are in agreement with experimental results.
Sphere Drag and Heat Transfer.
Duan, Zhipeng; He, Boshu; Duan, Yuanyuan
2015-07-20
Modelling fluid flows past a body is a general problem in science and engineering. Historical sphere drag and heat transfer data are critically examined. The appropriate drag coefficient is proposed to replace the inertia type definition proposed by Newton. It is found that the appropriate drag coefficient is a desirable dimensionless parameter to describe fluid flow physical behavior so that fluid flow problems can be solved in the simple and intuitive manner. The appropriate drag coefficient is presented graphically, and appears more general and reasonable to reflect the fluid flow physical behavior than the traditional century old drag coefficient diagram. Here we present drag and heat transfer experimental results which indicate that there exists a relationship in nature between the sphere drag and heat transfer. The role played by the heat flux has similar nature as the drag. The appropriate drag coefficient can be related to the Nusselt number. This finding opens new possibilities in predicting heat transfer characteristics by drag data. As heat transfer for flow over a body is inherently complex, the proposed simple means may provide an insight into the mechanism of heat transfer for flow past a body.
Energy spectrum measurement and dose rate estimation of natural neutrons in Tibet region
Institute of Scientific and Technical Information of China (English)
吴建华; 徐勇军; 刘森林; 汪传高
2015-01-01
In this work, natural neutron spectra at nine sites in Tibet region were measured using a multi-sphere neutron spectrometer. The altitude-dependence of the spectra total fluence rate and ambient dose equivalent rate were analyzed. From the normalized natural neutron spectra at different altitudes, the spectrum fractions for neutrons of greater than 0.1 MeV do not differ obviously, while those of the thermal neutrons differ greatly from each other. The total fluence rate, effective dose rate and the ambient dose equivalent rate varied with the altitude according to an exponential law.
The Chiral Dipolar Hard Sphere Model.
Mazars, Martial
2009-01-01
Abstract A simple molecular model of chiral molecules is presented in this paper : the chiral dipolar hard sphere model. The discriminatory interaction between enantiomers is represented by electrostatic (or magnetic) dipoles-dipoles interactions : short ranged steric repulsion are represented by hard sphere potential and, in each molecule, two point dipoles are located inside the sphere. The model is described in detail and some of its elementary properties are given ; in particul...
Manuel, Oliver K
2011-01-01
Earth is connected gravitationally, magnetically and electrically to its heat source - a neutron star that is obscured from view by waste products in the photosphere. Neutron repulsion is like the hot filament in an incandescent light bulb. Excited neutrons are emitted from the solar core and decay into hydrogen that glows in the photosphere like a frosted light bulb. Neutron repulsion was recognized in nuclear rest mass data in 2000 as the overlooked source of energy, the keystone of an arch that locked together these puzzling space-age observations: 1.) Excess 136Xe accompanied primordial helium in the stellar debris that formed the solar system (Fig. 1); 2.) The Sun formed on the supernova core (Fig. 2); 3.) Waste products from the core pass through an iron-rich mantle, selectively carrying lighter elements and lighter isotopes of each element into the photosphere (Figs. 3-4); and 4.) Neutron repulsion powers the Sun and sustains life (Figs. 5-7). Together these findings offer a framework for understanding...
Absolute Stability Limit for Relativistic Charged Spheres
Giuliani, Alessandro
2007-01-01
We find an exact solution for the stability limit of relativistic charged spheres for the case of constant gravitational mass density and constant charge density. We argue that this provides an absolute stability limit for any relativistic charged sphere in which the gravitational mass density decreases with radius and the charge density increases with radius. We then provide a cruder absolute stability limit that applies to any charged sphere with a spherically symmetric mass and charge distribution. We give numerical results for all cases. In addition, we discuss the example of a neutral sphere surrounded by a thin, charged shell.
Small-world networks on a sphere
Corso, Gilberto; Torres Cruz, Claudia P.
2017-01-01
The Small-World Network on a Sphere SWNS is a non-crossing network that has no hubs and presents the small-world property diam log N with diam being the maximal distance between any two vertices and N being the number of vertices. The SWNS is constructed using a partition of the sphere and the parallels are regular sections of the sphere with constant latitude. The number of cells on the parallels, however, increases exponentially from the pole to the equator of the sphere. We analytically compute the distribution of connectivity, the clustering coefficient and the SWNS distances. The resilience of the model against selective attacks is also discussed.
Takada, Masashi; Mihara, Erika; Sasaki, Michiya; Nakamura, Takashi; Honma, Toshihiko; Kono, Koji; Fujitaka, Kazunobu
2004-01-01
Biological data is necessary for estimation of protection from neutrons, but there is a lack of data on biological effects of neutrons for radiation protection. Radiological study on fast neutrons has been done at the National Institute of Radiological Sciences. An intense neutron source has been produced by 25 MeV deuterons on a thick beryllium target. The neutron energy spectrum, which is essential for neutron energy deposition calculation, was measured from thermal to maximum energy range by using an organic liquid scintillator and multi-sphere moderated 3He proportional counters. The spectrum of the gamma rays accompanying the neutron beam was measured simultaneously with the neutron spectrum using the organic liquid scintillator. The transmission by the shield of the spurious neutrons originating from the target was measured to be less than 1% by using the organic liquid scintillator placed behind the collimator. The measured neutron energy spectrum is useful in dose calculations for radiobiology studies.
Energy Technology Data Exchange (ETDEWEB)
Heger, G. [Rheinisch-Westfaelische Technische Hochschule Aachen, Inst. fuer Kristallographie, Aachen (Germany)
1996-12-31
X-ray diffraction using conventional laboratory equipment and/or synchrotron installations is the most important method for structure analyses. The purpose of this paper is to discuss special cases, for which, in addition to this indispensable part, neutrons are required to solve structural problems. Even though the huge intensity of modern synchrotron sources allows in principle the study of magnetic X-ray scattering the investigation of magnetic structures is still one of the most important applications of neutron diffraction. (author) 15 figs., 1 tab., 10 refs.
Phononic crystals of poroelastic spheres
Alevizaki, A.; Sainidou, R.; Rembert, P.; Morvan, B.; Stefanou, N.
2016-11-01
An extension of the layer-multiple-scattering method to phononic crystals of poroelastic spheres immersed in a fluid medium is developed. The applicability of the method is demonstrated on specific examples of close-packed fcc crystals of submerged water-saturated meso- and macroporous silica microspheres. It is shown that, by varying the pore size and/or the porosity, the transmission, reflection, and absorption spectra of finite slabs of these crystals are significantly altered. Strong absorption, driven by the slow waves in the poroelastic material and enhanced by multiple scattering, leads to negligible transmittance over an extended frequency range, which might be useful for practical applications in broadband acoustic shielding. The results are analyzed by reference to relevant phononic dispersion diagrams in the viscous and inertial coupling limits, and a consistent interpretation of the underlying physics is provided.
Status of the SPHERE experiment
Antonov, R A; Bonvech, E A; Chernov, D V; Dzhatdoev, T A; Finger, Mir; Finger, M; Galkin, V I; Kabanova, N N; Petkun, A S; Podgrudkov, D A; Roganova, T M; Shaulov, S B; Sysoeva, T I
2012-01-01
Here is presented the current state of the SPHERE-2 balloon-borne experiment. The detector is elevated up to 1 km above the snow surface and registers the reflected Vavilov-Cherenkov radiation from extensive air showers. This method has good sensitivity to the mass-composition of the primary cosmic rays due to its high resolution near the shower axis. The detector consists of a 1500 mm spherical mirror with a 109 PMT cluster in its focus. The electronics record a signal pulse profile in each PMT. In the last 2 years the detector was upgraded: time resolution of pulse registration was enhanced up to 12.5 ns, channel sensitivity was increased by a factor of 3, a new LED-based relative PMT calibration method was introduced, and new hardware and etc. was installed.
The Hubble Sphere Hydrogen Survey
Peterson, J B; Pen, U L; Peterson, Jeffrey B.; Bandura, Kevin; Pen, Ue Li
2006-01-01
An all sky redshift survey, using hydrogen 21 cm emission to locate galaxies, can be used to track the wavelength of baryon acoustic oscillations imprints from z ~ 1.5 to z = 0. This will allow precise determination of the evolution of dark energy. A telescope made of fixed parabolic cylindrical reflectors offers substantial benefit for such a redshift survey. Fixed cylinders can be built for low cost, and long cylinders also allow low cost fast fourier transform techniques to be used to define thousands of simultaneous beams. A survey made with fixed reflectors naturally covers all of the sky available from it's site with good uniformity, minimizing sample variance in the measurement of the acoustic peak wavelength. Such a survey will produce about a billion redshifts, nearly a thousand times the number available today. The survey will provide a three dimensional mapping of a substantial fraction of the Hubble Sphere.
Point Scattered Function (PScF) for fast neutron radiography
Energy Technology Data Exchange (ETDEWEB)
Hassan, Mohamed H. [Nuclear and Radiation Engineering Department, Alexandria University, Alexandria 21544 (Egypt)], E-mail: mhmheg@yahoo.com
2009-08-01
Fast neutron radiography opened up a new range of possibilities to image extremely dense objects. The removal of the scattering effect is one of the most challenging problems in neutron imaging. Neutron scattering in fast neutron radiography did not receive much attention compared with X-ray and thermal neutron radiography. The purpose of this work is to investigate the behavior of the Point Scattered Function (PScF) as applied in fast neutron radiography. The PScF was calculated using MCNP as a spatial distribution of scattered neutrons over the detector surface for one emitting source element. Armament and explosives materials, namely, Rifle steel, brass, aluminum and trinitrotoluene (TNT) were simulated. Effect of various sample thickness and sample-to-detector distance were considered. Simulated sample geometries included a slab with varying thickness, a sphere with varying radii, and a cylinder with varying base radii. Different neutron sources, namely, Cf-252, DT as well as DD neutron sources were considered. Neutron beams with zero degree divergence angle; and beams with varying angles related to the normal to the source plane were simulated. Curve fitting of the obtained PScF, in the form of Gaussian function, were given to be used in future work using image restoration codes. Analytical representation of the height as well as the Full Width at Half Maximum (FWHM) of the obtained Gaussian functions eliminates the need to calculate the PScF for sample parameters that were not investigated in this study.
Scattering by two spheres: Theory and experiment
DEFF Research Database (Denmark)
Bjørnø, Irina; Jensen, Leif Bjørnø
1998-01-01
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...
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.
The Positive Freedom of the Public Sphere
DEFF Research Database (Denmark)
Hansen, Ejvind
2015-01-01
The relationship between democracy and the media since the appearance of Habermas' major texts in the 1960s has been articulated through theories of the public sphere. The structure of the public sphere is significantly influenced by the communicative media, and the emergence of the internet thus...
Reversible thermal gelation in soft spheres
DEFF Research Database (Denmark)
Kapnistos, M.; Vlassopoulos, D.; Fytas, G.
2000-01-01
Upon heating, concentrated solutions of star polymers and block copolymer micelles in a good solvent, representing soft spheres, undergo a reversible gelation. This phenomenon is attributed to the formation of clusters causing a partial dynamic arrest of the swollen interpenetrating spheres at hi...
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...... is negatively affected by private sphere networking and positively affected by public sphere networking, but innovation is less promoted by public sphere networking in China than in Denmark....
Instability of Extremal Relativistic Charged Spheres
Anninos, P; Anninos, Peter; Rothman, Tony
2002-01-01
With the question, ``Can relativistic charged spheres form extremal black holes?" in mind, we investigate the properties of such spheres from a classical point of view. The investigation is carried out numerically by integrating the Oppenheimer-Volkov equation for relativistic charged fluid spheres and finding interior Reissner-Nordstr\\"om solutions for these objects. We consider both constant density and adiabatic equations of state, as well as several possible charge distributions, and examine stability by both a normal mode and an energy analysis. In all cases, the stability limit for these spheres lies between the extremal ($Q = M$) limit and the black hole limit ($R = R_+$). That is, we find that charged spheres undergo gravitational collapse before they reach $Q = M$, suggesting that extremal Reissner-Nordtr\\"om black holes produced by collapse are ruled out. A general proof of this statement would support a strong form of the cosmic censorship hypothesis, excluding not only stable naked singularities, ...
Crump, James C., III; Richards, Wade J.; Shields, Kevin C.
1995-07-01
The McClellan Nuclear Radiation Center's (MNRC) staff in conjunction with a Cooperative Research and Development Agreement (CRDA) with the U.C. Santa Barbara facility has developed a system that can be used for aircraft inspection of jet engine blades. The problem was to develop an inspection system that can detect very low concentrations of hydrogen (i.e., greater than 100 ppm) in metal matricies. Specifically in Titanium alloy jet engine blades. Entrapment and precipitation of hydrogen in metals is an undesirable phenomenon which occurs in many alloys of steel and titanium. In general, metals suffer a loss of mechanical properties after long exposures to hydrogen, especially at high temperatures and pressures, thereby becoming embrittled. Neutron radiography has been used as a nondestructive testing technique for many years. Neutrons, because of their unique interactions with materials, are especially useful in the detection of hydrogen. They have an extremely high interaction cross section for low atomic number nuclei (i.e., hydrogen). Thus hydrogen in a metal matrix can be visualized using neutrons. Traditional radiography is sensitive to the total attenuation integrated over the path of radiation through the material. Increased sensitivity and quantitative cross section resolution can be obtained using three-dimensional volumetric imaging techniques such as tomography. The solution used to solve the problem was to develop a neutron tomography system. The neutron source is the McClellan Nuclear Radiation Center's 1 MW TRIGA reactor. This paper describes the hardware used in the system as well as some of the preliminary results.
Energy Technology Data Exchange (ETDEWEB)
Mueller, J.M., E-mail: jonathan_mueller@ncsu.edu; Mattingly, J.
2016-07-21
There is a significant and well-known anisotropy between the prompt neutrons emitted from a single fission event; these neutrons are most likely to be observed at angles near 0° or 180° relative to each other. However, the propagation of this anisotropy through different generations of a fission chain reaction has not been previously studied. We have measured this anisotropy in neutron–neutron coincidences from a subcritical highly-multiplying assembly of plutonium metal. The assembly was a 4.5 kg α-phase plutonium metal sphere composed of 94% {sup 239}Pu and 6% {sup 240}Pu by mass. Data were collected using two EJ-309 liquid scintillators and two EJ-299 plastic scintillators. The angular distribution of neutron–neutron coincidences was measured at 90° and 180° and found to be largely isotropic. Simulations were performed using MCNPX-PoliMi of similar plutonium metal spheres of varying sizes and a correlation between the neutron multiplication of the assembly and the anisotropy of neutron–neutron coincidences was observed. In principle, this correlation could be used to assess the neutron multiplication of an unknown assembly.
3D Space Radiation Transport in a Shielded ICRU Tissue Sphere
Wilson, John W.; Slaba, Tony C.; Badavi, Francis F.; Reddell, Brandon D.; Bahadori, Amir A.
2014-01-01
A computationally efficient 3DHZETRN code capable of simulating High Charge (Z) and Energy (HZE) and light ions (including neutrons) under space-like boundary conditions with enhanced neutron and light ion propagation was recently developed for a simple homogeneous shield object. Monte Carlo benchmarks were used to verify the methodology in slab and spherical geometry, and the 3D corrections were shown to provide significant improvement over the straight-ahead approximation in some cases. In the present report, the new algorithms with well-defined convergence criteria are extended to inhomogeneous media within a shielded tissue slab and a shielded tissue sphere and tested against Monte Carlo simulation to verify the solution methods. The 3D corrections are again found to more accurately describe the neutron and light ion fluence spectra as compared to the straight-ahead approximation. These computationally efficient methods provide a basis for software capable of space shield analysis and optimization.
Hitting spheres on hyperbolic spaces
Cammarota, Valentina
2011-01-01
For a hyperbolic Brownian motion on the Poincar\\'e half-plane $\\mathbb{H}^2$, starting from a point of hyperbolic coordinates $z=(\\eta, \\alpha)$ inside a hyperbolic disc $U$ of radius $\\bar{\\eta}$, we obtain the probability of hitting the boundary $\\partial U$ at the point $(\\bar \\eta,\\bar \\alpha)$. For $\\bar{\\eta} \\to \\infty$ we derive the asymptotic Cauchy hitting distribution on $\\partial \\mathbb{H}^2$ and for small values of $\\eta$ and $\\bar \\eta$ we obtain the classical Euclidean Poisson kernel. The exit probabilities $\\mathbb{P}_z\\{T_{\\eta_1}
Lines, Circles, Planes and Spheres
Purdy, George B
2009-01-01
Let $S$ be a set of $n$ points in $\\mathbb{R}^3$, no three collinear and not all coplanar. If at most $n-k$ are coplanar and $n$ is sufficiently large, the total number of planes determined is at least $1 + k \\binom{n-k}{2}-\\binom{k}{2}(\\frac{n-k}{2})$. For similar conditions and sufficiently large $n$, (inspired by the work of P. D. T. A. Elliott in \\cite{Ell67}) we also show that the number of spheres determined by $n$ points is at least $1+\\binom{n-1}{3}-t_3^{orchard}(n-1)$, and this bound is best possible under its hypothesis. (By $t_3^{orchard}(n)$, we are denoting the maximum number of three-point lines attainable by a configuration of $n$ points, no four collinear, in the plane, i.e., the classic Orchard Problem.) New lower bounds are also given for both lines and circles.
2001-01-01
StenniSphere, the John C. Stennis Space Center's visitor center in Hancock County, Miss., features a 14,000-square-foot museum and outdoor exhibits about Stennis Space Center. Designed to entertain while educating, StenniSphere includes informative displays and exhibits from NASA, the Naval Meteorology and Oceanography Command, and other resident agencies. Recently named Mississippi's Travel Attraction of the Year, StenniSphere hosted a quarter of a million visitors in its first year and is a major school field trip destination.
Performance Evaluation of List Sphere Detector
Institute of Scientific and Technical Information of China (English)
HE Xiang; LUO Han-wen; YI Yang
2005-01-01
A list sphere detector can use a smaller list than commonly believed by employing an appropriate soft output approximation method. Its effect on the "quality" of detector's soft output value is evaluated by measuringmutual information under ergodic channel. The result shows a length 40 list is adequate for a 4 × 4 16QAM MIMO system without system-level iteration. For the ergodic channel, the gain of a sphere detector over the linear MMSE detector is dependent on channel coding rate, which answers an important question when sphere detector should be used in system level design. All these theoretical results are then verified by Monte Carlo simulation.
Spallation Neutron Source (SNS)
Federal Laboratory Consortium — The SNS at Oak Ridge National Laboratory is a next-generation spallation neutron source for neutron scattering that is currently the most powerful neutron source in...
Computer simulation of rod-sphere mixtures
Antypov, D
2003-01-01
Results are presented from a series of simulations undertaken to investigate the effect of adding small spherical particles to a fluid of rods which would otherwise represent a liquid crystalline (LC) substance. Firstly, a bulk mixture of Hard Gaussian Overlap particles with an aspect ratio of 3:1 and hard spheres with diameters equal to the breadth of the rods is simulated at various sphere concentrations. Both mixing-demixing and isotropic-nematic transition are studied using Monte Carlo techniques. Secondly, the effect of adding Lennard-Jones particles to an LC system modelled using the well established Gay-Berne potential is investigated. These rod-sphere mixtures are simulated using both the original set of interaction parameters and a modified version of the rod-sphere potential proposed in this work. The subject of interest is the internal structure of the binary mixture and its dependence on density, temperature, concentration and various parameters characterising the intermolecular interactions. Both...
ANALYSIS OF MECHANISMS FINANCING OF CULTURAL SPHERE
Directory of Open Access Journals (Sweden)
Costandachi Gheorghe
2008-01-01
Full Text Available In this work is made analysis concern basically state structures of culture and arts activities, is describes the problems are met during the reforming process the financial mechanisms in cultural sphere. Author disclosed the ways evolve private and estate financing cultural sphere, also is disclosed why is need estate financial support. The work contains something detailed measures actions to improve financial and mechanisms financing of cultural sphere. Analyzing questions of modernization of budgetary financing of branch the author have formulated effectiveness of use of budgetary funds at all levels in cultural structures and proposed the ways of finishing of market reforms in cinematography. In the final of work is presented scheme system of financing, formation and distribution of financial resources in cinematography and is making conclusions and is offered wais of the solutions created present situation in this sphere in Moldova.
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...
Scalar Casimir effect between two concentric spheres
Ozcan, Mustafa
2012-01-01
The Casimir effect giving rise to an attractive force between the closely spaced two concentric spheres that confine the massless scalar field is calculated by using a direct mode summation with contour integration in the complex plane of eigenfrequencies. We devoleped a new approach appropriate for the calculation of the Casimir energy for spherical boundary conditions. The Casimir energy for a massless scalar field between the closely spaced two concentric spheres coincides with the Casimir energy of the parallel plates for a massless scalar field in the limit when the dimensionless parameter {\\eta}, ({\\eta}=((a-b)/(\\surd(ab))) where a (b) is inner (outer) radius of sphere), goes to zero. The efficiency of new approach is demonstrated by calculation of the Casimir energy for a massless scalar field between the closely spaced two concentric half spheres. PACS number(s): 03.70.+k, 12.20.DS, 11.10.Gh
Directional spin wavelets on the sphere
McEwen, Jason D; Büttner, Martin; Peiris, Hiranya V; Wiaux, Yves
2015-01-01
We construct a directional spin wavelet framework on the sphere by generalising the scalar scale-discretised wavelet transform to signals of arbitrary spin. The resulting framework is the only wavelet framework defined natively on the sphere that is able to probe the directional intensity of spin signals. Furthermore, directional spin scale-discretised wavelets support the exact synthesis of a signal on the sphere from its wavelet coefficients and satisfy excellent localisation and uncorrelation properties. Consequently, directional spin scale-discretised wavelets are likely to be of use in a wide range of applications and in particular for the analysis of the polarisation of the cosmic microwave background (CMB). We develop new algorithms to compute (scalar and spin) forward and inverse wavelet transforms exactly and efficiently for very large data-sets containing tens of millions of samples on the sphere. By leveraging a novel sampling theorem on the rotation group developed in a companion article, only hal...
Acoustic levitation of a large solid sphere
Andrade, Marco A. B.; Bernassau, Anne L.; Adamowski, Julio C.
2016-07-01
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.
Method to determine the strength of a neutron source
Energy Technology Data Exchange (ETDEWEB)
Vega C, H.R.; Manzanares A, E.; Hernandez D, V.M.; Chacon R, A.; Mercado, G.A. [UAZ, A.P. 336, 98000 Zacatecas (Mexico); Gallego, E.; Lorente, A. [Depto. Ingenieria Nuclear, Universidad Politecnica de Madrid, (Spain)
2006-07-01
The use of a gamma-ray spectrometer with a 3 {phi} x 3 NaI(Tl) detector, with a moderator sphere has been studied in the aim to measure the neutron fluence rate and to determine the source strength. Moderators with a large amount of hydrogen are able to slowdown and thermalize neutrons; once thermalized there is a probability that thermal neutron to be captured by hydrogen producing 2.22 MeV prompt gamma-ray. The pulse-height spectrum collected in a multicharmel analyzer shows a photopeak around 2.22 MeV whose net area is proportional to total neutron fluence rate and to the neutron source strength. The characteristics of this system were determined by a Monte Carlo study using the MCNP 4C code, where a detailed model of the Nal(Tl) was utilized. As moderators 3, 5, and 10 inches-diameter spheres where utilized and the response was calculated for monoenergetic and isotopic neutrons sources. (Author)
Energy Technology Data Exchange (ETDEWEB)
Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)
2010-07-01
The following topics are dealt with: Neutron sources, neutron properties and elastic scattering, correlation functions measured by scattering experiments, symmetry of crystals, applications of neutron scattering, polarized-neutron scattering and polarization analysis, structural analysis, magnetic and lattice excitation studied by inelastic neutron scattering, macromolecules and self-assembly, dynamics of macromolecules, correlated electrons in complex transition-metal oxides, surfaces, interfaces, and thin films investigated by neutron reflectometry, nanomagnetism. (HSI)
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.
Effective Depletion Potential of Colloidal Spheres
Institute of Scientific and Technical Information of China (English)
LI Wei-Hua; MA Hong-Ru
2004-01-01
@@ A new semianalytical method, which is a combination of the density functional theory with Rosenfeld density functional and the Ornstein-Zernike equation, is proposed for the calculation of the effective depletion potentials between a pair of big spheres immersed in a small hard sphere fluid. The calculated results are almost identical to the integral equation method with the Percus-Yevick approximation, and are also in agreement well with the Monte Carlo simulation results.
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.......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....
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 * 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.
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.
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.
Federal Laboratory Consortium — The Neutron Therapy Facility provides a moderate intensity, broad energy spectrum neutron beam that can be used for short term irradiations for radiobiology (cells)...
Critical Dimensions of Water-tamped Slabs and Spheres of Active Material
Greuling, E.; Argo, H.: Chew, G.; Frankel, M. E.; Konopinski, E.J.; Marvin, C.; Teller, E.
1946-08-06
The magnitude and distribution of the fission rate per unit area produced by three energy groups of moderated neutrons reflected from a water tamper into one side of an infinite slab of active material is calculated approximately in section II. This rate is directly proportional to the current density of fast neutrons from the active material incident on the water tamper. The critical slab thickness is obtained in section III by solving an inhomogeneous transport integral equation for the fast-neutron current density into the tamper. Extensive use is made of the formulae derived in "The Mathematical Development of the End-Point Method" by Frankel and Goldberg. In section IV slight alterations in the theory outlined in sections II and III were made so that one could approximately compute the critical radius of a water-tamper sphere of active material. The derived formulae were applied to calculate the critical dimensions of water-tamped slabs and spheres of solid UF{sub 6} leaving various (25) isotope enrichment fractions. Decl. Dec. 16, 1955.
Neutron transmission measurements on hydrogen filled microspheres
Energy Technology Data Exchange (ETDEWEB)
Dyrnjaja, Eva, E-mail: dyrnjaja@ati.ac.at [Vienna University of Technology, Institute of Atomic and Subatomic Physics, Stadionallee 2, Vienna (Austria); Hummel, Stefan, E-mail: hummel@fotec.at [FOTEC GmbH, Viktor Kaplan-Straße 2, 2700 Wiener Neustadt (Austria); Keding, Marcus, E-mail: keding@fotec.at [FOTEC GmbH, Viktor Kaplan-Straße 2, 2700 Wiener Neustadt (Austria); Smolle, Marie-Theres, E-mail: marie-theres.smolle@tuwien.ac.at [Vienna University of Technology, Institute of Atomic and Subatomic Physics, Stadionallee 2, Vienna (Austria); Gerger, Joachim, E-mail: gerger@fotec.at [FOTEC GmbH, Viktor Kaplan-Straße 2, 2700 Wiener Neustadt (Austria); Zawisky, Michael, E-mail: zawisky@ati.ac.at [Vienna University of Technology, Institute of Atomic and Subatomic Physics, Stadionallee 2, Vienna (Austria)
2014-01-01
Hollow microspheres are promising candidates for future hydrogen storage technologies. Although the physical process for hydrogen diffusion through glass is well understood, measurements of static quantities (e.q. hydrogen pressure inside the spheres) as well as dynamic properties (e.g. diffusion rate of hydrogen through glass) are still difficult to handle due to the small size of the spheres (d≈15μm). For diffusion rate measurements, the long-term stability of the experiment is also mandatory due to the relatively slow diffusion rate. In this work, we present an accurate and long-term stable measurement technique for static and dynamic properties, using neutron radiography. Furthermore, possible applications for hydrogen filled microspheres within the scope of radiation issues are discussed.
Terminal energy distribution of blast waves from bursting spheres
Adamczyk, A. A.; Strehlow, R. A.
1977-01-01
The calculation results for the total energy delivered to the surroundings by the burst of an idealized massless sphere containing an ideal gas are presented. The logic development of various formulas for sphere energy is also presented. For all types of sphere bursts the fraction of the total initial energy available in the sphere that is delivered to the surroundings is shown to lie between that delivered for the constant pressure addition of energy to a source region and that delivered by isentropic expansion of the sphere. The relative value of E sub/Q increases at fixed sphere pressure/surrounding pressure as sphere temperature increases because the velocity of sound increases.
Collinear swimmer propelling a cargo sphere at low Reynolds number
Felderhof, B U
2014-01-01
The swimming velocity and rate of dissipation of a linear chain consisting of two or three little spheres and a big sphere is studied on the basis of low Reynolds number hydrodynamics. The big sphere is treated as a passive cargo, driven by the tail of little spheres via hydrodynamic and direct elastic interaction. The fundamental solution of Stokes' equations in the presence of a sphere with no-slip boundary condition, as derived by Oseen, is used to model the hydrodynamic interactions between the big sphere and the little spheres.
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.
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.
Energy Technology Data Exchange (ETDEWEB)
Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)
2010-07-01
The following topics are dealt with: Neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)
Water exit dynamics of buoyant spheres
Truscott, Tadd T.; Epps, Brenden P.; Munns, Randy H.
2016-11-01
Buoyant spheres released below the free surface can rise well above the surface in a phenomenon known as pop-up. Contrary to intuition, increasing the release depth sometimes results in a lower pop-up height. We present the pop-up height of rising buoyant spheres over a range of release depths (1-12.5 diameters) and Reynolds numbers (4 ×104 to 6 ×105 ). While the dynamics of rising buoyant spheres and bubbles has been thoroughly investigated for Reynolds numbers below 104, pop-up in these larger-Reynolds-number regimes has not been studied. Yet the underwater motions of the sphere for the Reynolds numbers we study are the key to understanding the pop-up height. Two major regimes are apparent: vertical and oscillatory. The vertical regime exhibits a nearly vertical underwater trajectory and results in the largest pop-up heights. The oscillatory regime exhibits an underwater trajectory with periodic lateral motions and results in lower pop-up heights; this periodic lateral motion is modulated by unsteady vortex shedding in the wake of the sphere. Despite these complex fluid structure interactions, the experiments presented herein yield extremely repeatable results.
Robotics Programming Competition Spheres, Russian Part
Sadovski, Andrei; Kukushkina, Natalia; Biryukova, Natalia
2016-07-01
Spheres" such name was done to Russian part of the Zero Robotics project which is a student competition devoted to programming of SPHERES (SPHERES - Synchronized Position Hold Engage and Reorient Experimental Satellites are the experimental robotics devices which are capable of rotation and translation in all directions, http://ssl.mit.edu/spheres/), which perform different operations on the board of International Space Station. Competition takes place online on http://zerorobotics.mit.edu. The main goal is to develop a program for SPHERES to solve an annual challenge. The end of the tournament is the real competition in microgravity on the board of ISS with a live broadcast. The Russian part of the tournament has only two years history but the problems, organization and specific are useful for the other educational projects especially for the international ones. We introduce the history of the competition, its scientific and educational goals in Russia and describe the participation of Russian teams in 2014 and 2015 tournaments. Also we discuss the organizational problems.
Neutron Capture Nucleosynthesis
Kiss, Miklos
2016-01-01
Heavy elements (beyond iron) are formed in neutron capture nucleosynthesis processes. We have proposed a simple unified model to investigate the neutron capture nucleosynthesis in arbitrary neutron density environment. We have also investigated what neutron density is required to reproduce the measured abundance of nuclei assuming equilibrium processes. We found both of these that the medium neutron density has a particularly important role at neutron capture nucleosynthesis. About these results most of the nuclei can formed at medium neutron capture density environment e.g. in some kind of AGB stars. Besides these observations our model is capable to use educational purpose.
DEFF Research Database (Denmark)
Klösgen-Buchkremer, Beate Maria
2014-01-01
Neutron (and X-ray) reflectometry constitute complementary interfacially sensitive techniques that open access to studying the structure within thin films of both soft and hard condensed matter. Film thickness starts oxide surfaces on bulk substrates, proceeding to (pauci-)molecular layers and up...... of new material. Understanding self-assembly of 2D-3D nanostructures at surfaces and the related interfaces in layered films is a precondition for the development of tailored tools with distributed functions, like new clothes (self-cleaning surfaces combined with mechanical resistance, low permeability...... of polar molecules like water and high permeability for gases), films to be applied as specific sensors or for packaging, surface coverage for implants with incorporated antibiotics, thin magnetic material with designed domain distributions, … . The structures of interest range from a few Ǻngstrøm up...
Magnetised Neutron Stars An Overview
Goyal, A
2003-01-01
In the presence of strong magnetic field reported to have been observed on the surface of some neutron stars and on what are called Magnetars, a host of physical phenomenon from the birth of a neutron star to free streaming neutrino cooling phase will be modified. In this review I will discuss the effect of magnetic field on the equation of state of high density nuclear matter by including the anomalous magnetic moment of the nucleons into consideration. I would then go over to discuss the neutrino interaction processes in strong as well as in weak magnetic fields. The neutrino processes are important in studying the propagation of neutrinos and in studying the energy loss, Their study is a prerequisite for the understanding of actual dynamics of supernova explosion and on the stabilization of radial pulsation modes through the effect on bulk viscosity. The anisotropy introduced in the neutrino emission and through the modification of the shape of the neutrino sphere may explain the observed pulsar kicks.
Solar Proton Transport within an ICRU Sphere Surrounded by a Complex Shield: Combinatorial Geometry
Wilson, John W.; Slaba, Tony C.; Badavi, Francis F.; Reddell, Brandon D.; Bahadori, Amir A.
2015-01-01
The 3DHZETRN code, with improved neutron and light ion (Z (is) less than 2) transport procedures, was recently developed and compared to Monte Carlo (MC) simulations using simplified spherical geometries. It was shown that 3DHZETRN agrees with the MC codes to the extent they agree with each other. In the present report, the 3DHZETRN code is extended to enable analysis in general combinatorial geometry. A more complex shielding structure with internal parts surrounding a tissue sphere is considered and compared against MC simulations. It is shown that even in the more complex geometry, 3DHZETRN agrees well with the MC codes and maintains a high degree of computational efficiency.
Classical and quantum dynamics of the sphere
Lasukov, Vladimir; Moldovanova, Evgeniia; Abdrashitova, Maria; Malik, Hitendra; Gorbacheva, Ekaterina
2016-07-01
In Minkowski space, there has been developed the mathematic quantum model of the real particle located on the sphere evolving owing to the negative pressure inside the sphere. The developed model is analogous to the geometrodynamic model of the Lemaitre-Friedmann primordial atom in superspace-time, whose spatial coordinate is the scale factor functioning as a radial coordinate. There is a formulation of quantum geometrodynamics in which the spatial coordinate is an offset of the scale factor and wave function at the same time. With the help of the Dirac procedure for extracting the root from the Hamiltonian operator we have constructed a Dirac quantum dynamics of the sphere with fractional spin.
Oyarzun, B.A.; Van Westen, T.; Vlugt, T.J.H.
2013-01-01
he liquid crystal phase behavior of linear and partially flexible hard-sphere chain fluids and the solubility of hard spheres in hard-sphere chain fluids are studied by constant pressure Monte Carlo simulations. An extensive study on the phase behavior of linear fluids with a length of 7, 8, 9, 10,
Visual distortions near a neutron star and black hole
Nemiroff, R J
1993-01-01
The visual distortion effects visible to an observer traveling around and descending to the surface of an extremely compact star are described. Specifically, trips to a "normal" neutron star, a black hole, and an ultracompact neutron star with extremely high surface gravity, are described. Concepts such as multiple imaging, red- and blue-shifting, conservation of surface brightness, the photon sphere, and the existence of multiple Einstein rings are discussed in terms of what the viewer would see. Computer generated, general relativistically accurate illustrations highlighting the distortion effects are presented and discussed. A short movie (VHS) depicting many of these effects is available to those interested free of charge.
Weapons Neutron Research Facility (WNR)
Federal Laboratory Consortium — The Weapons Neutron Research Facility (WNR) provides neutron and proton beams for basic, applied, and defense-related research. Neutron beams with energies ranging...
Path integral representations on the complex sphere
Energy Technology Data Exchange (ETDEWEB)
Grosche, C. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik
2007-08-15
In this paper we discuss the path integral representations for the coordinate systems on the complex sphere S{sub 3C}. The Schroedinger equation, respectively the path integral, separates in exactly 21 orthogonal coordinate systems. We enumerate these coordinate systems and we are able to present the path integral representations explicitly in the majority of the cases. In each solution the expansion into the wave-functions is stated. Also, the kernel and the corresponding Green function can be stated in closed form in terms of the invariant distance on the sphere, respectively on the hyperboloid. (orig.)
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.
Willmore energy estimates in conformal Berger spheres
Energy Technology Data Exchange (ETDEWEB)
Barros, Manuel, E-mail: mbarros@ugr.es [Departamento de Geometria y Topologia, Facultad de Ciencias Universidad de Granada, 1807 Granada (Spain); Ferrandez, Angel, E-mail: aferr@um.es [Departamento de Matematicas, Universidad de Murcia Campus de Espinardo, 30100 Murcia (Spain)
2011-07-15
Highlights: > The Willmore energy is computed in a wide class of surfaces. > Isoperimetric inequalities for the Willmore energy of Hopf tori are obtained. > The best possible lower bound is achieved on isoareal Hopf tori. - Abstract: We obtain isoperimetric inequalities for the Willmore energy of Hopf tori in a wide class of conformal structures on the three sphere. This class includes, on the one hand, the family of conformal Berger spheres and, on the other hand, a one parameter family of Lorentzian conformal structures. This allows us to give the best possible lower bound of Willmore energies concerning isoareal Hopf tori.
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....
Packing Effect of Excluded Volume on Hard-Sphere Colloids
Institute of Scientific and Technical Information of China (English)
肖长明; 金国钧; 马余强
2001-01-01
We apply the principle of maximum entropy to consider the excluded volume effect on the phase separation of binary mixtures consisting of hard spheres with two different diameters. We show that a critical volume fraction of hard spheres exists locating the packing of large spheres. In particular, through numerical calculation, we have found that the critical volume fraction becomes lower when the ratio α = σ1/σ2 of large-to-small sphere diameters increases, but becomes higher when the ratio of the large sphere volume fraction to the total volume fraction of large and small spheres increases.
The effect of PTSA on preparation of mesophase carbon spheres.
Directory of Open Access Journals (Sweden)
Youliang Cheng
2009-05-01
Full Text Available Mesophase spheres have been synthesized by heat-treating a medium coal tar pitch at 420 ºC for 2 hours in the presence of P-toluene sulphonic acid (PTSA. The effect of PTSA on synthesis of mesophase spheres had been studied. It was found that PTSA promotes the formation of mesophase spheres in coal tar pitch through acceleratingpolymerization of aromatic hydrocarbons. PTSA content between 3 and 5 wt % gave similar size spheres, beyond which as the PTSA content increases, the size of spheres increases. 5 wt % PTSA gives uniform spheres with small size, good spherical shape and smooth surface.
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.
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.
First results of the SPHERE experiment
Directory of Open Access Journals (Sweden)
Shaulov Sergey
2013-06-01
Full Text Available First results of the balloon-borne experiment SPHERE are presented. The primary spectrum in the energy range 1016 – 5 · 1017 eV is compared with data of other experiments. The primary energies were reconstructed using characteristics of the Vavilov-Cherenkov radiation from extensive air showers, reflected from a snow surface.
1/4-pinched contact sphere theorem
DEFF Research Database (Denmark)
Ge, Jian; Huang, Yang
2016-01-01
Given a closed contact 3-manifold with a compatible Riemannian metric, we show that if the sectional curvature is 1/4-pinched, then the contact structure is universally tight. This result improves the Contact Sphere Theorem in [EKM12], where a 4/9-pinching constant was imposed. Some tightness res...
SPHERE ZIMPOL: Overview and performance simulation
Thalmann, C.; Schmid, H.M.; Boccaletti, A.; Mouillet, D.; Dohlen, K.; Roelfsema, R.; Carbillet, M.; Gisler, D.; Beuzit, J.-L.; Feldt, M.; Gratton, R.; Joos, F.; Keller, C.U.; Kragt, J.; Pragt, J.H.; Puget, P.; Rigal, F.; Snik, F.; Waters, R.; Wildi, F.
2008-01-01
The ESO planet finder instrument SPHERE will search for the polarimetric signature of the reflected light from extrasolar planets, using a VLT telescope, an extreme AO system (SAXO), a stellar coronagraph, and an imaging polarimeter (ZIMPOL). We present the design concept of the ZIMPOL instrument, a
Casimir stress on lossy magnetodielectric spheres
Raabe, C; Welsch, D G; Raabe, Christian; Knoell, Ludwig; Welsch, Dirk-Gunnar
2003-01-01
An expression for the Casimir stress on arbitrary dispersive and lossy linear magnetodielectric matter at finite temperature, including left-handed material, is derived and applied to spherical systems. To cast the relevant part of the scattering Green tensor for a general magnetodielectric sphere in a convenient form, classical Mie scattering is reformulated.
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...
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.
The Public Sphere, Globalization and Technological Development
Tina Sikka
2006-01-01
Tina Sikka examines the emergence and transformation of Habermas's theory of the public sphere, looking at how this concept informs the debates around communication technologies in development. Development (2006) 49, 87–93. doi:10.1057/palgrave.development.1100277
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.
Transnational public spheres : A spatial perspective
Forough, Mohammadbagher
2015-01-01
Whereas more and more transnational challenges (such as global financial crises, climate change, terrorism, migration, and so forth) are affecting people’s lives, democratic systems and their public spheres (i.e. spaces in which citizens can express their collective concerns) are national. To give a
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.
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 functi...
The Nationalisation of the Domestic Sphere
Storm, H.J.
2016-01-01
Banal forms of nationalism permeate our everyday life. However, it is not very clear when all kinds of banal objects and practices became nationalised. In this article, I focus on the domestic sphere by analysing how around 1900 a small group of activists began to propagate the nationalisation of do
Pious Entertainment: Hizbullah's Islamic Cultural Sphere
Alagha, J.E.
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 unders
Metal-Matrix/Hollow-Ceramic-Sphere Composites
Baker, Dean M.
2011-01-01
A family of metal/ceramic composite materials has been developed that are relatively inexpensive, lightweight alternatives to structural materials that are typified by beryllium, aluminum, and graphite/epoxy composites. These metal/ceramic composites were originally intended to replace beryllium (which is toxic and expensive) as a structural material for lightweight mirrors for aerospace applications. These materials also have potential utility in automotive and many other terrestrial applications in which there are requirements for lightweight materials that have high strengths and other tailorable properties as described below. The ceramic component of a material in this family consists of hollow ceramic spheres that have been formulated to be lightweight (0.5 g/cm3) and have high crush strength [40.80 ksi (.276.552 MPa)]. The hollow spheres are coated with a metal to enhance a specific performance . such as shielding against radiation (cosmic rays or x rays) or against electromagnetic interference at radio and lower frequencies, or a material to reduce the coefficient of thermal expansion (CTE) of the final composite material, and/or materials to mitigate any mismatch between the spheres and the matrix metal. Because of the high crush strength of the spheres, the initial composite workpiece can be forged or extruded into a high-strength part. The total time taken in processing from the raw ingredients to a finished part is typically 10 to 14 days depending on machining required.
Experimentation on recurrent sphere collision with Audacity
Muradoglu, Murat; Ng, Enoch Ming Wei; Ng, Tuck Wah
2014-11-01
Under the theme of collisions that occur repeatedly, we conducted easy and inexpensive experiments of rebounding spheres and Newton’s cradle with two spheres to determine the coefficients of restitution using the sound record feature in modern laptops and a free and open source software called Audacity. In the rebounding sphere experiment, the coefficients of restitution of the golf and ping pong balls used were found to be 0.727 ± 0.025 and 0.816 ± 0.041 respectively. With the Netwon’s cradle experiment, the coefficient of restitution of two steel sphere balls was found to be 0.987 ± 0.003. The contrasts in the results obtained from both experiments permit the operational principles of a pendulum to be emphasized, and engagements to be made to consider the transfer of kinetic energy in the form of vibrational energy of the bodies’ constituents. Using a one-dimensional two-mass model with spring and damper linkages to account for harmonic motions that occur during impact, we found it possible to perform a simple analysis to account for this, and how it can be linked to high energy transfer modes such as the phenomenon of resonance and impedance matching.
Hollow silica spheres: synthesis and mechanical properties.
Zhang, Lijuan; D'Acunzi, Maria; Kappl, Michael; Auernhammer, Günter K; Vollmer, Doris; van Kats, Carlos M; van Blaaderen, Alfons
2009-03-03
Core-shell polystyrene-silica spheres with diameters of 800 nm and 1.9 microm were synthesized by soap-free emulsion and dispersion polymerization of the polystyrene core, respectively. The polystyrene spheres were used as templates for the synthesis of silica shells of tunable thickness employing the Stöber method [Graf et al. Langmuir 2003, 19, 6693]. The polystyrene template was removed by thermal decomposition at 500 degrees C, resulting in smooth silica shells of well-defined thickness (15-70 nm). The elastic response of these hollow spheres was probed by atomic force microscopy (AFM). A point load was applied to the particle surface through a sharp AFM tip, and successively increased until the shell broke. In agreement with the predictions of shell theory, for small deformations the deformation increased linearly with applied force. The Young's modulus (18 +/- 6 GPa) was about 4 times smaller than that of fused silica [Adachi and Sakka J. Mater. Sci. 1990, 25, 4732] but identical to that of bulk silica spheres (800 nm) synthesized by the Stöber method, indicating that it yields silica of lower density. The minimum force needed to irreversibly deform (buckle) the shell increased quadratically with shell thickness.
Energy Technology Data Exchange (ETDEWEB)
Ortiz R, J. M. [Escuela Politecnica Superior, Departamento de Electrotecnia y Electronica, Avda. Menendez Pidal s/n, Cordoba (Spain); Martinez B, M. R.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Gallego D, E.; Lorente F, A. [Universidad Politecnica de Madrid, Departamento de Ingenieria Nuclear, ETSI Industriales, C. Jose Gutierrez Abascal 2, 28006 Madrid (Spain); Mendez V, R.; Los Arcos M, J. M.; Guerrero A, J. E., E-mail: morvymm@yahoo.com.m [CIEMAT, Laboratorio de Metrologia de Radiaciones Ionizantes, Avda. Complutense 22, 28040 Madrid (Spain)
2011-02-15
With the Bonner spheres spectrometer neutron spectrum is obtained through an unfolding procedure. Monte Carlo methods, Regularization, Parametrization, Least-squares, and Maximum Entropy are some of the techniques utilized for unfolding. In the last decade methods based on Artificial Intelligence Technology have been used. Approaches based on Genetic Algorithms and Artificial Neural Networks (Ann) have been developed in order to overcome the drawbacks of previous techniques. Nevertheless the advantages of Ann still it has some drawbacks mainly in the design process of the network, vg the optimum selection of the architectural and learning Ann parameters. In recent years the use of hybrid technologies, combining Ann and genetic algorithms, has been utilized to. In this work, several Ann topologies were trained and tested using Ann and Genetically Evolved Artificial Neural Networks in the aim to unfold neutron spectra using the count rates of a Bonner sphere spectrometer. Here, a comparative study of both procedures has been carried out. (Author)
Superheated drop neutron spectrometer
Das, M; Roy, B; Roy, S C; Das, Mala
2000-01-01
Superheated drops are known to detect neutrons through the nucleation caused by the recoil nuclei produced by the interactions of neutrons with the atoms constituting the superheated liquid molecule. A novel method of finding the neutron energy from the temperature dependence response of SDD has been developed. From the equivalence between the dependence of threshold energy for nucleation on temperature of SDD and the dependence of dE/dx of the recoil ions with the energy of the neutron, a new method of finding the neutron energy spectrum of a polychromatic as well as monochromatic neutron source has been developed.
Wang, Ching L.
1983-09-13
Apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon.
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.
Radiation of non-relativistic particle on a conducting sphere and a string of spheres
Shul'ga, N F; Larikova, E A
2016-01-01
The radiation arising under uniform motion of non-relativistic charged particle by (or through) perfectly conducting sphere is considered. The rigorous results are obtained using the method of images known from electrostatics.
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
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.
Revitalization of the Public Sphere: A Comparison between Habermasian and the New Public Sphere
2014-01-01
“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 ...
Energy Technology Data Exchange (ETDEWEB)
Bacon, G.E. [Univ. of Sheffield (United Kingdom)
1994-12-31
The familiar extremes of crystalline material are single-crystals and random powders. In between these two extremes are polycrystalline aggregates, not randomly arranged but possessing some preferred orientation and this is the form taken by constructional materials, be they steel girders or the bones of a human or animal skeleton. The details of the preferred orientation determine the ability of the material to withstand stress in any direction. In the case of bone the crucial factor is the orientation of the c-axes of the mineral content - the crystals of the hexagonal hydroxyapatite - and this can readily be determined by neutron diffraction. In particular it can be measured over the volume of a piece of bone, utilizing distances ranging from 1mm to 10mm. The major practical problem is to avoid the intense incoherent scattering from the hydrogen in the accompanying collagen; this can best be achieved by heat-treatment and it is demonstrated that this does not affect the underlying apatite. These studies of bone give leading anatomical information on the life and activities of humans and animals - including, for example, the life history of the human femur, the locomotion of sheep, the fracture of the legs of racehorses and the life-styles of Neolithic tribes. We conclude that the material is placed economically in the bone to withstand the expected stresses of life and the environment. The experimental results are presented in terms of the magnitude of the 0002 apatite reflection. It so happens that for a random powder the 0002, 1121 reflections, which are neighboring lines in the powder pattern, are approximately equal in intensity. The latter reflection, being of manifold multiplicity, is scarcely affected by preferred orientation so that the numerical value of the 0002/1121 ratio serves quite accurately as a quantitative measure of the degree of orientation of the c-axes in any chosen direction for a sample of bone.
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.
Ultrasonic beam-plotting with very small spheres.
Round, W H; Swan, H
1991-12-01
A method of pulse-echo ultrasonic beam plotting is described. It differs from traditional pulse-echo beam plotting in that the ultrasonic pulses are scattered off a totally isolated sphere rather than a sphere suspended on a wire. The method also allows extremely small spheres to be used thus providing greater resolution. It is demonstrated that pulse-echo beam plotting using spheres of different size produces different iso-echo amplitude curves.
On Vassiliev invariants of braid groups of the sphere
Kaabi, N
2012-01-01
We construct a universal Vassiliev invariant for braid groups of the sphere and the mapping class groups of the sphere with $n$ punctures. The case of a sphere is different from the classical braid groups or braids of oriented surfaces of genus strictly greater than zero, since Vassiliev invariants in a group without 2-torsion do not distinguish elements of braid group of a sphere.
Imaging with Scattered Neutrons
Ballhausen, H.; Abele, H.; Gaehler, R.; Trapp, M.; Van Overberghe, A.
2006-01-01
We describe a novel experimental technique for neutron imaging with scattered neutrons. These scattered neutrons are of interest for condensed matter physics, because they permit to reveal the local distribution of incoherent and coherent scattering within a sample. In contrast to standard attenuation based imaging, scattered neutron imaging distinguishes between the scattering cross section and the total attenuation cross section including absorption. First successful low-noise millimeter-re...
Self-lensing of a Singular Isothermal Sphere
Wang, Yun
1999-01-01
Many astrophysical systems can be approximated as isothermal spheres. In an isothermal sphere, the ``foreground'' objects can act as lenses on ``background'' objects in the same distribution. We study gravitational lensing by a singular isothermal sphere analytically. Our results may have interesting applications.
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...
Prototype Neutron Energy Spectrometer
Energy Technology Data Exchange (ETDEWEB)
Stephen Mitchell, Sanjoy Mukhopadhyay, Richard Maurer, Ronald Wolff
2010-06-16
The project goals are: (1) Use three to five pressurized helium tubes with varying polyethylene moderators to build a neutron energy spectrometer that is most sensitive to the incident neutron energy of interest. Neutron energies that are of particular interest are those from the fission neutrons (typically around 1-2 MeV); (2) Neutron Source Identification - Use the neutron energy 'selectivity' property as a tool to discriminate against other competing processes by which neutrons are generated (viz. Cosmic ray induced neutron production [ship effect], [a, n] reactions); (3) Determine the efficiency as a function of neutron energy (response function) of each of the detectors, and thereby obtain the composite neutron energy spectrum from the detector count rates; and (4) Far-field data characterization and effectively discerning shielded fission source. Summary of the presentation is: (1) A light weight simple form factor compact neutron energy spectrometer ready to be used in maritime missions has been built; (2) Under laboratory conditions, individual Single Neutron Source Identification is possible within 30 minutes. (3) Sources belonging to the same type of origin viz., (a, n), fission, cosmic cluster in the same place in the 2-D plot shown; and (4) Isotopes belonging to the same source origin like Cm-Be, Am-Be (a, n) or Pu-239, U-235 (fission) do have some overlap in the 2-D plot.
Advanced neutron absorber materials
Branagan, Daniel J.; Smolik, Galen R.
2000-01-01
A neutron absorbing material and method utilizing rare earth elements such as gadolinium, europium and samarium to form metallic glasses and/or noble base nano/microcrystalline materials, the neutron absorbing material having a combination of superior neutron capture cross sections coupled with enhanced resistance to corrosion, oxidation and leaching.
Khabaz, Rahim; Rene Vega-Carrillo, Hector
2013-08-01
In this study, the neutron emission rate from neutron sources using prompt gamma rays in hydrogen was determined, and several improvements were applied. Using Monte Carlo calculations, the best positions for the source, moderator and detector relative to each other were selected. For (241)Am-Be and (252)Cf sources, the sizes for polyethylene spheres with the highest efficiency were 12- and 10-inch, respectively. In addition, a new shielding cone was designed to account for scattered neutrons and gamma rays. The newly designed shielding cone, which is 45 cm in length, provided suitable attenuation for the source radiation.
THE SPECTRUM OF COMPACT HYPERSURFACE IN SPHERE
Institute of Scientific and Technical Information of China (English)
Xu Senlin; Deng Qintao; Chen Dongmei
2004-01-01
Let M be a compact minimal hypersurface of sphere Sn+1(1). Let (M) be H (r)-torus of sphere Sn+ 1 (1).Assume they have the same constant mean curvature H, the result in [1] is that ifSpec0(M, g) =Spec0((M), g),then for 3≤ n ≤ 6, r2≤n-1/n or n ≥ 6, r2 ≥ n-1, then M is isometric to (M). We improved the result and prove that: if Spec0(M,g) =Spec0((M),g), then M is isometric to (M). Generally, if Specp(M,g) =Specp((M),g), here p is fixed and satisfies that n(n - 1) ≠ 6p(n - p), then M is isometric to (M).
Event Driven Langevin simulations of Hard Spheres
Scala, Antonio
2011-01-01
The blossoming of interest in colloids and nano-particles has given renewed impulse to the study of hard-body systems. In particular, hard spheres have become a real test system for theories and experiments. It is therefore necessary to study the complex dynamics of such systems in presence of a solvent; disregarding hydrodynamic interactions, the simplest model is the Langevin equation. Unfortunately, standard algorithms for the numerical integration of the Langevin equation require that interactions are slowly varying during an integration timestep. This in not the case for hard-body systems, where there is no clearcut between the correlation time of the noise and the timescale of the interactions. Starting first from a splitting of the Fokker-Plank operator associated with the Langevin dynamics, and then from an approximation of the two-body Green's function, we introduce and test two new algorithms for the simulation of the Langevin dynamics of hard-spheres.
Electromagnetic Scattering by Spheres of Topological Insulators
Ge, Lixin; Zi, Jian
2015-01-01
The electromagnetic scattering properties of topological insulator (TI) spheres are systematically studied in this paper. Unconventional backward scattering caused by the topological magneto-electric (TME) effect of TIs are found in both Rayleigh and Mie scattering regimes. This enhanced backward scattering can be achieved by introducing an impedance-matched background which can suppress the bulk scattering. For the cross-polarized scattering coefficients, interesting antiresonances are found in the Mie scattering regime, wherein the cross-polarized electromagnetic fields induced by the TME effect are trapped inside TI spheres. In the Rayleigh limit, the quantized TME effect of TIs can be determined by measuring the electric-field components of scattered waves in the far field.
Theory of tectonics in the sphere
Ribeiro, A; Taborda, R; Ribeiro, Antonio; Matias, Luis; Taborda, Rui
2005-01-01
Soft or Deformable Plate Tectonics in the sphere must follow geometric rules inferred from the orthographic projection. An analytic equivalent of this geometry can be derived by the application of Potential Field Methods in the case of Atlantic type oceans. Laplace equation must be obeyed by the velocity field between the ridge and the passive margin if we neglect the very slight compressibility of ocean lithosphere. A strain wave propagates in the sphere analogous to the behaviour of a free harmonic oscillator. Combining zonal harmonics of order one and sectorial harmonics of degree one we obtain a tesseral harmonic equivalent to the orthographic solution. This potential field approach is valid for homogeneous deformation regime in oceanic lithosphere. Above a compression threshold of 5 to 10% buckling and simultaneous faulting occurs. In Pacific type oceans a dynamic approach, similar to a forced oscillation, must be applied because there are sinks in subduction zones.
Entanglement entropy for the n-sphere
Casini, H
2010-01-01
We calculate the entanglement entropy for a sphere and a massless scalar field in any dimensions. The reduced density matrix is expressed in terms of the infinitesimal generator of conformal transformations keeping the sphere fixed. The problem is mapped to the one of a thermal gas in a hyperbolic space and solved by the heat kernel approach. The coefficient of the logarithmic term in the entropy for 2 and 4 spacetime dimensions are in accordance with previous numerical and analytical results. In particular, the four dimensional result, together with the one reported by Solodukhin, gives support to the Ryu-Takayanagi holographic anzats. We also find there is no logarithmic contribution to the entropy for odd space time dimensions.
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.
Second-Generation Curvelets on the Sphere
Chan, Jennifer Y H; Kitching, Thomas D; McEwen, Jason D
2015-01-01
Curvelets are efficient to represent highly anisotropic signal content, such as local linear and curvilinear structure. First-generation curvelets on the sphere, however, suffered from blocking artefacts. We present a new second- generation curvelet transform, where scale-discretised curvelets are constructed directly on the sphere. Scale-discretised curvelets exhibit a parabolic scaling relation, are well-localised in both spatial and harmonic domains, support the exact analysis and synthesis of both scalar and spin signals, and are free of blocking artefacts. We present fast algorithms to compute the exact curvelet transform, reducing computational complexity from $\\mathcal{O}(L^5)$ to $\\mathcal{O}(L^3\\log_{2}{L})$ for signals band-limited at $L$. The implementation of these algorithms is made publicly available. Finally, we present an illustrative application demonstrating the effectiveness of curvelets for representing directional curve-like features in natural spherical images.
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.
Black carbon measurements using an integrating sphere
Hitzenberger, R.; Dusek, U.; Berner, A.
1996-08-01
An integrating sphere was used to determine the black carbon (BC) content of aerosol filter samples dissolved in chloroform (method originally described by Heintzenberg [1982]). The specific absorption coefficient Ba (equal to absorption per mass) of the samples was also measured using the sphere as an integrating detector for transmitted light. Comparing the Ba of ambient samples taken in Vienna, Austria, to the BC concentrations measured on the dissolved filters, a value of approximately 6 m2/g was found to be a reasonable value for the Ba of the black carbon found at the site. The size dependence of Ba of a nebulized suspension of soot was measured using a rotating impactor, and a reasonable agreement between measured and calculated values was found.
Nineteenth Century Public And Private Spheres
Directory of Open Access Journals (Sweden)
SIMA REMINA
2014-12-01
Full Text Available The aim of this paper is to illustrate the public and private spheres. The former represents the area in which each of us carries out their daily activities, while the latter is mirrored by the home. Kate Chopin and Charlotte Perkins Gilman are two salient nineteenth-century writers who shape the everyday life of the historical period they lived in, within their literary works that shed light on the areas under discussion.
Supersymmetric theories on squashed five-sphere
Imamura, Yosuke
2012-01-01
We construct supersymmetric theories on the SU(3)xU(1) symmetric squashed five-sphere with 2, 4, 6, and 12 supercharges. We first determine the Killing equation by dimensional reduction from 6d, and use Noether procedure to construct actions. The supersymmetric Yang-Mills action is straightforwardly obtained from the supersymmetric Chern-Simons action by using a supersymmetry preserving constant vector multiplet.
Lp CONVERGENCE OF CESARO MEANS ON SPHERE
Institute of Scientific and Technical Information of China (English)
Dai Feng; Zhang Xirong
2000-01-01
Let Rnbe n-dimensional Euclidean space with n≤3. Denote by Ωn the unit sphere in Rn. For f ∈ L(Ωn) ve denote by σNo (f) its Cesaro means of order δ for spherical harmonic expansions. The special value λ＝ 2λ n-2 of δ is knowm as the critical one. For 0<δ≤λ, we set P0=2 λ/δ＋λ
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....
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.
Stable Stationary Harmonic Maps to Spheres
Institute of Scientific and Technical Information of China (English)
Fang Hua LIN; Chang You WANG
2006-01-01
For k ≥ 3, we establish new estimate on Hausdorff dimensions of the singular set of stable-stationary harmonic maps to the sphere Sk. We show that the singular set of stable-stationary harmonic maps from B5 to S3 is the union of finitely many isolated singular points and finitely many Holder continuous curves. We also discuss the minimization problem among continuous maps from Bn to S2.
Poincar\\'e Sphere and Decoherence Problems
Kim, Y S
2012-01-01
Henri Poincar\\'e formulated the mathematics of the Lorentz transformations, known as the Poincar\\'e group. He also formulated the Poincar\\'e sphere for polarization optics. It is shown that these two mathematical instruments can be combined into one mathematical device which can address the internal space-time symmetries of elementary particles, decoherence problems in polarization optics, entropy problems, and Feynman's rest of the universe.
Soft-sphere model for liquid metals
Energy Technology Data Exchange (ETDEWEB)
Young, D.A.
1977-11-08
A semi-empirical soft-sphere model of fluids is modified for application to the thermodynamic properties of liquid metals. Enthalpy, volume, and sound speed are computed as functions of temperature for 13 metals and compared with experimental data. Critical points and coexistence curves are also computed and compared with experimental data, where these have been measured. Strengths and weaknesses of the model are discussed.
Energy Technology Data Exchange (ETDEWEB)
Kidambi, R.; Newton, P.K. [Southern California Univ., Los Angeles (United States). Dept. of Aerospace Engineering, Center for Applied Mathematical Sciences
1999-12-01
The self-similar collapse of three vortices moving on the surface of a sphere of radius R is analysed and compared with known results of critical literature. Formulas for the collapsing trajectories are derived and compared with the planar formulas. The Hamiltonian system is derived governing the vortex motion. In this projected plane, the solutions are not self-similar. In the last section, the collapse process is studied using tri-linear coordinates, which reduces the system to a planar one.
A property of the bidimensional sphere
Cavachi, Marius
2011-01-01
It is natural to ask for a reasonable constant k having the property that any open set of area greater than k on a bidimensional sphere of area 1 always contains the vertices of a regular tetrahedron. We shall prove that it is sufficient to take k=3/4. In fact we shall prove a more general result. The interested reader will not have any problem in establishing that 3/4 is the best constant with this property.
The Internet And The Public Sphere
Kürşat, Fide; Özad, Bahire Efe
2005-01-01
Habermas (1989) proposes a ‘public sphere’, a setting where people talk freely on the public issues. In his early works, Habermas was rather pessimistic about the provision of the public sphere; however, soon after the introduction of the Internet as an ultimately decentralized medium, in his later work, Habermas (1996) seems more optimistic about the Internet as the provider of the ‘public sphere’. The Internet which is particularly popular among the young people, not only pro...
Effects of confinement on a rotating sphere
Liu, Qianlong; Prosperetti, Andrea
2009-11-01
The hydrodynamic force and couple acting on a rotating sphere in a quiescent fluid are modified by nearby boundaries with possible consequences on spin-up and spin-down times of particles uspended in a fluid, their wall deposition, entraiment and others. Up to now, the vast majority of papers dealing with these problems have considered the low-Reynolds-number regime. This paper focuses on the effect of inertia on the hydrodynamic interaction of a spinning sphere with nearby boundaries. Rotation axes parallel and perpendicular to a plane boundary as well as other situations are studied. Several steady and transient numerical results are presented and interptreted in terms of physical scaling arguments. The Navier-Stokes equations for an incompressible, constant-property Newtonian fluid are solved by the finite-difference PHYSALIS method. Among the noteworthy features of this method are the fact that the no-slip condition at the particle surface is satisfied exactly and that the force and torque on the sphere are obtained directly as a by-product of the computation. This feature avoids the need to integrate the stress over the particle surface, which with other methods is a step prone to numerical inaccuracies. A locally refined mesh surrounding the particle is used to enhance the resolution of boundary layers maintaining a manageable overall computational cost.
Willmore Spheres in Compact Riemannian Manifolds
Mondino, Andrea
2012-01-01
The paper is devoted to the variational analysis of the Willmore, and other L^2 curvature functionals, among immersions of 2-dimensional surfaces into a compact riemannian m-manifold (M^m,h) with m>2. The goal of the paper is twofold, on one hand, we give the right setting for doing the calculus of variations (including min max methods) of such functionals for immersions into manifolds and, on the other hand, we prove existence results for possibly branched Willmore spheres under various constraints (prescribed homotopy class, prescribed area) or under curvature assumptions for M^m. To this aim, using the integrability by compensation, we develop first the regularity theory for the critical points of such functionals. We then prove a rigidity theorem concerning the relation between CMC and Willmore spheres. Then we prove that, for every non null 2-homotopy class, there exists a representative given by a Lipschitz map from the 2-sphere into M^m realizing a connected family of conformal smooth (possibly branche...
Grazing Incidence Neutron Optics
Gubarev, Mikhail V. (Inventor); Ramsey, Brian D. (Inventor); Engelhaupt, Darell E. (Inventor)
2013-01-01
Neutron optics based on the two-reflection geometries are capable of controlling beams of long wavelength neutrons with low angular divergence. The preferred mirror fabrication technique is a replication process with electroform nickel replication process being preferable. In the preliminary demonstration test an electroform nickel optics gave the neutron current density gain at the focal spot of the mirror at least 8 for neutron wavelengths in the range from 6 to 20.ANG.. The replication techniques can be also be used to fabricate neutron beam controlling guides.
Mascarenhas, Nicholas; Marleau, Peter; Brennan, James S.; Krenz, Kevin D.
2010-06-22
An instrument that will directly image the fast fission neutrons from a special nuclear material source has been described. This instrument can improve the signal to background compared to non imaging neutron detection techniques by a factor given by ratio of the angular resolution window to 4.pi.. In addition to being a neutron imager, this instrument will also be an excellent neutron spectrometer, and will be able to differentiate between different types of neutron sources (e.g. fission, alpha-n, cosmic ray, and D-D or D-T fusion). Moreover, the instrument is able to pinpoint the source location.
Ultra-small angle neutron scattering on structured materials
Hainbuchner, M
2000-01-01
neutrons has reached a level that makes it a complementary method to conventional small angle scattering at each neutron source supplying enough neutron flux. prove high order interference effects. Measuring this kind of samples the performance of an USANS instrument can simply be determined. This allows the comparison of different instruments. For the calibration of the instrument and testing of the data treatment routines suspensions of latex spheres of various diameters were examined. In order to demonstrate that the evaluation of samples showing strong multiple scattering can produce meaningful results, measurements on sintered alumina using various sample thickness were carried out. The investigation of the scattering behavior of sedimentary source rocks revealed that only selected samples show a fractal scattering behavior and, therefore, a fractal inner structure. Time resolved measurements on hardening cement paste demonstrate that time dependent information on the changes of the structural parameter ...
Light Curves for Rapidly-Rotating Neutron Stars
Cadeau, C; Leahy, D; Campbell, S S; Cadeau, Coire; Morsink, Sharon M.; Leahy, Denis; Campbell, Sheldon S.
2006-01-01
We present raytracing computations for light emitted from the surface of a rapidly-rotating neutron star in order to construct light curves for X-ray pulsars and bursters. These calculations are for realistic models of rapidly-rotating neutron stars which take into account both the correct exterior metric and the oblate shape of the star. We find that the most important effect arising from rotation comes from the oblate shape of the rotating star. We find that approximating a rotating neutron star as a sphere introduces serious errors in fitted values of the star's radius and mass if the rotation rate is very large. However, in most cases acceptable fits to the ratio M/R can be obtained with the spherical approximation.
Advances in neutron tomography
Indian Academy of Sciences (India)
W Treimer
2008-11-01
In the last decade neutron radiography (NR) and tomography (NCT) have experienced a number of improvements, due to the well-known properties of neutrons interacting with matter, i.e. the low attenuation by many materials, the strong attenuation by hydrogenous constituent in samples, the wavelength-dependent attenuation in the neighbourhood of Bragg edges and due to better 2D neutron detectors. So NR and NCT were improved by sophisticated techniques that are based on the attenuation of neutrons or on phase changes of the associated neutron waves if they pass through structured materials. Up to now the interaction of the neutron spin with magnetic fields in samples has not been applied to imaging techniques despite the fact that it was proposed many years ago. About ten years ago neutron depolarization as imaging signal for neutron radiography or tomography was demonstrated and in principle it works. Now one can present much improved test experiments using polarized neutrons for radiographic imaging. For this purpose the CONRAD instrument of the HMI was equipped with polarizing and analysing benders very similar to conventional scattering experiments using polarized neutrons. Magnetic fields in different coils and in samples (superconductors) at low temperatures could be visualized. In this lecture a summary about standard signals (attenuation) and the more `sophisticated' imaging signals as refraction, small angle scattering and polarized neutrons will be given.
Fermi, Enrico; Zinn, Walter H.
The argument of the present Patent is a radiation shield suitable for protection of personnel from both gamma rays and neutrons. Such a shield from dangerous radiations is achieved to the best by the combined action of a neutron slowing material (a moderator) and a neutron absorbing material. Hydrogen is particularly effective for this shield since it is a good absorber of slow neutrons and a good moderator of fast neutrons. The neutrons slowed down by hydrogen may, then, be absorbed by other materials such as boron, cadmium, gadolinium, samarium or steel. Steel is particularly convenient for the purpose, given its effectiveness in absorbing also the gamma rays from the reactor (both primary gamma rays and secondary ones produced by the moderation of neutrons). In particular, in the present Patent a shield is described, made of alternate layers of steel and Masonite (an hydrolized ligno-cellulose material). The object of the present Patent is not discussed in any other published paper.
Confined disordered strictly jammed binary sphere packings
Chen, D.; Torquato, S.
2015-12-01
Disordered jammed packings under confinement have received considerably less attention than their bulk counterparts and yet arise in a variety of practical situations. In this work, we study binary sphere packings that are confined between two parallel hard planes and generalize the Torquato-Jiao (TJ) sequential linear programming algorithm [Phys. Rev. E 82, 061302 (2010), 10.1103/PhysRevE.82.061302] to obtain putative maximally random jammed (MRJ) packings that are exactly isostatic with high fidelity over a large range of plane separation distances H , small to large sphere radius ratio α , and small sphere relative concentration x . We find that packing characteristics can be substantially different from their bulk analogs, which is due to what we term "confinement frustration." Rattlers in confined packings are generally more prevalent than those in their bulk counterparts. We observe that packing fraction, rattler fraction, and degree of disorder of MRJ packings generally increase with H , though exceptions exist. Discontinuities in the packing characteristics as H varies in the vicinity of certain values of H are due to associated discontinuous transitions between different jammed states. When the plane separation distance is on the order of two large-sphere diameters or less, the packings exhibit salient two-dimensional features; when the plane separation distance exceeds about 30 large-sphere diameters, the packings approach three-dimensional bulk packings. As the size contrast increases (as α decreases), the rattler fraction dramatically increases due to what we call "size-disparity" frustration. We find that at intermediate α and when x is about 0.5 (50-50 mixture), the disorder of packings is maximized, as measured by an order metric ψ that is based on the number density fluctuations in the direction perpendicular to the hard walls. We also apply the local volume-fraction variance στ2(R ) to characterize confined packings and find that these
Neutron dose measurements with the GSI ball at high-energy accelerators.
Fehrenbacher, G; Gutermuth, F; Kozlova, E; Radon, T; Schuetz, R
2007-01-01
A moderator-type neutron monitor containing pairs of TLD 600/700 elements (Harshaw) modified with the addition of a lead layer (GSI ball) for the measurement of the ambient dose equivalent from neutrons at medium- and high-energy accelerators, is introduced in this work. Measurements were performed with the Gesellschaft für Schwerionenforschung (GSI) ball as well as with conventional polyethylene (PE) spheres at the high-energy accelerator SPS at European Organization for Nuclear Research [CERN (CERF)] and in Cave A of the heavy-ion synchrotron SIS at GSI. The measured dose values are compared with dose values derived from calculated neutron spectra folded with dose conversion coefficients. The estimated reading of the spheres calculated by means of the response functions and the neutron spectra is also included in the comparison. The analysis of the measurements shows that the PE/Pb sphere gives an improved estimate on the ambient dose equivalent of the neutron radiation transmitted through shielding of medium- and high-energy accelerators.
Preparation and antibacterial activities of hollow silica-Ag spheres.
Lin, Lin; Zhang, Haifang; Cui, Haiying; Xu, Mingqiang; Cao, Shunsheng; Zheng, Guanghong; Dong, Mingdong
2013-01-01
Hollow silica spheres with round mesoporous shells were synthesized by core-shell template method, using monodispersed cationic polystyrene particles as core, and TEOS (tetraethoxysilane) as the silica source to form shell. After calcination at 550°C, uniform spheres with a thin shell of silica and hollow interior structures. Transmission electron microscopy results showed that the size of the spheres is about 700 nm in diameter with narrow distribution. In addition, the spheres have a high surface area of 183 m(2)/g. The spheres were subsequently used as silver-loading substrates and the silver loaded spheres were tested in antimicrobial study against gram negative bacteria Eschrichia coli in vitro. The hollow silica-Ag spheres proved significantly higher antibacterial efficacy against E. coli as compared to that of the common silica-Ag particles.
A neutron scattering study of triblock copolymer micelles
Energy Technology Data Exchange (ETDEWEB)
Gerstenberg, M.C.
1997-11-01
The thesis describes the neutron scattering experiments performed on poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) triblock copolymer micelles in aqueous solution. The studies concern the non-ionic triblock copolymer P85 which consists of two outer segments of 25 monomers of ethylene oxide attached to a central part of 40 monomers of propylene oxide. The amphiphilic character of P85 leads to formation of various structures in aqueous solution such as spherical micelles, rod-like structures, and a BCC liquid-crystal mesophase of spherical micelles. The present investigations are centered around the micellar structures. In the first part of this thesis a model for the micelle is developed for which an analytical scattering form factor can be calculated. The micelle is modeled as a solid sphere with tethered Gaussian chains. Good agreement was found between small-angle neutron scattering experiments and the form factor of the spherical P85 micelles. Above 60 deg. C some discrepancies were found between the model and the data which is possibly due to an elongation of the micelles. The second part focuses on the surface-induced ordering of the various micellar aggregates in the P85 concentration-temperature phase diagram. In the spherical micellar phase, neutron reflection measurements indicated a micellar ordering at the hydrophilic surface of quartz. Extensive modeling was performed based on a hard sphere description of the micellar interaction. By convolution of the distribution of hard spheres at a hard wall, obtained from Monte Carlo simulations, and the projected scattering length density of the micelle, a numerical expression was obtained which made it possible to fit the data. The hard-sphere-hard-wall model gave an excellent agreement in the bulk micellar phase. However, for higher concentrations (25 wt % P85) close to the transition from the micellar liquid into a micellar cubic phase, a discrepancy was found between the model and the
Liquid bridge force between two unequal-sized spheres or a sphere and a plane
Institute of Scientific and Technical Information of China (English)
You chuan Chen; Yong zhi Zhao; Hong li Gao; Jin yang Zheng
2011-01-01
Liquid bridge force acting between wet particles is an important property in particle characterization.This paper deals with liquid bridge force between either two unequal-sized spherical particles or a sphere and a flat plate under conditions where gravitational effect arising from bridge distortion is negligible.In order to calculate the force of the liquid bridge efficiently and accurately,expressions of liquid configuration and liquid bridge force were derived by building a mechanical model,which assumes the liquid bridge to be circular in shape between either two unequal-sized spheres or a sphere and a plane.To assess the accuracy of the numerical results of the calculated liquid bridge forces,they were compared to the published experimental data.
Wang, Xiaocong; Tang, Saide; Liu, Jing; He, Ziqiong; An, Lijuan; Zhang, Chenxi; Hao, Jingmei; Feng, Wei
2009-05-01
Core-shell multifunctional composite spheres consisting of Fe3O4-polyaniline (PANi) shell and polystyrene (PS) core were fabricated using core-shell-structured sulfonated PS spheres (with uniform diameter of 250 nm) as templates. PANi was doped in situ by sulfonic acid resulting the composite spheres are well conductive. Dissolved with solvent, PS cores were removed from the core-shell composite spheres and hollow Fe3O4-PANi spheres were obtained. Removing the PANi and PS components by calcinations produced hollow Fe3O4 spheres. The cavity size of the hollow spheres was uniformly approximate to 190 nm and the shell thickness was 30 nm. The cavity size and the shell thickness can be synchronously controlled by varying the sulfonation time of the PS templates. The shell thickness in size range was of 20-86 nm when the sulfonation time was changed from 1 to 4 h. These resulting spheres could be arranged in order by self-assembly of the templates. Both the Fe3O4-PANi/PS composite spheres and the hollow Fe3O4 spheres exhibit a super-paramagnetic behavior. Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray powder scattering were used to characterize these as-prepared spheres.
Electromagnetic-scattering by bi-sphere groups and coherent-beam scattering by homogeneous spheres
Institute of Scientific and Technical Information of China (English)
Linsheng LIU; Hengyu KE; Zhensen WU; Lu BAI
2008-01-01
By using Mie's theory, the boundary condi-tions, and some advanced mathematical knowledge, the scattering problem of a plane-wave by bi-sphere groups and of cores-traversed coherent Gauss-beams by one sphere was addressed. In each, the coefficients of the scattering-field expressions were deduced. Finally, the result was predigested and transfigured so that the available form for programming was achieved. On deducing, the former adopted the undetermined coeffi-cient method and the latter used the plane geometry method. Moreover, the complexity of the calculation was decreased here.
Dosimetry at an interim storage for spent nuclear fuel.
Králík, M; Kulich, V; Studeny, J; Pokorny, P
2007-01-01
The Czech nuclear power plant Dukovany started its operation in 1985. All fuel spent from 1985 up to the end of 2005 is stored at a dry interim storage, which was designed for 60 CASTOR-440/84 casks. Each of these casks can accommodate 84 fuel assemblies from VVER 440 reactors. Neutron-photon mixed fields around the casks were characterized in terms of ambient dose equivalent measured by standard area dosemeters. Except this, neutron spectra were measured by means of a Bonner sphere spectrometer, and the measured spectra were used to derive the corresponding ambient dose equivalent due to neutrons.
Status of spallation neutron source
Energy Technology Data Exchange (ETDEWEB)
Oyama, Yukio [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
1997-03-01
Existing and planned facilities using proton accelerator driven spallation neutron source are reviewed. These include new project of neutron science proposed from Japan Atomic Energy Research Institute. The present status of facility requirement and accelerator technology leads us to new era of neutron science such as neutron scattering research and nuclear transmutation study using very intense neutron source. (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.
Zinc coordination spheres in protein structures.
Laitaoja, Mikko; Valjakka, Jarkko; Jänis, Janne
2013-10-07
Zinc metalloproteins are one of the most abundant and structurally diverse proteins in nature. In these proteins, the Zn(II) ion possesses a multifunctional role as it stabilizes the fold of small zinc fingers, catalyzes essential reactions in enzymes of all six classes, or assists in the formation of biological oligomers. Previously, a number of database surveys have been conducted on zinc proteins to gain broader insights into their rich coordination chemistry. However, many of these surveys suffer from severe flaws and misinterpretations or are otherwise limited. To provide a more comprehensive, up-to-date picture on zinc coordination environments in proteins, zinc containing protein structures deposited in the Protein Data Bank (PDB) were analyzed in detail. A statistical analysis in terms of zinc coordinating amino acids, metal-to-ligand bond lengths, coordination number, and structural classification was performed, revealing coordination spheres from classical tetrahedral cysteine/histidine binding sites to more complex binuclear sites with carboxylated lysine residues. According to the results, coordination spheres of hundreds of crystal structures in the PDB could be misinterpreted due to symmetry-related molecules or missing electron densities for ligands. The analysis also revealed increasing average metal-to-ligand bond length as a function of crystallographic resolution, which should be taken into account when interrogating metal ion binding sites. Moreover, one-third of the zinc ions present in crystal structures are artifacts, merely aiding crystal formation and packing with no biological significance. Our analysis provides solid evidence that a minimal stable zinc coordination sphere is made up by four ligands and adopts a tetrahedral coordination geometry.
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.
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.
Sphere impact and penetration into wet sand
Marston, J. O.; Vakarelski, I. U.; Thoroddsen, S. T.
2012-08-01
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.
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...
A pattern formation problem on the sphere
Directory of Open Access Journals (Sweden)
Clara E. Garza-Hume
2007-02-01
Full Text Available We consider a semi-linear elliptic equation on the sphere $mathbf{S}^n subset mathbb{R}^{n+1}$ with $n$ odd and subcritical nonlinearity. We show that given any positive integer $k$, if the exponent $p$ of the nonlinear term is sufficiently close to the critical Sobolev exponent $p^*$, then there exists a positive solution with $k$ peaks. Moreover, the minimum energy solutions with $k$ peaks are such that the centers of these concentrations converge as $po p^*$ to the solution of an underlying geometrical problem, namely, arranging $k$ points on $mathbf{S}^n$ so they are as far away from each other as possible.
Nonlinear sequential laminates reproducing hollow sphere assemblages
Idiart, Martín I.
2007-07-01
A special class of nonlinear porous materials with isotropic 'sequentially laminated' microstructures is found to reproduce exactly the hydrostatic behavior of 'hollow sphere assemblages'. It is then argued that this result supports the conjecture that Gurson's approximate criterion for plastic porous materials, and its viscoplastic extension of Leblond et al. (1994), may actually yield rigorous upper bounds for the hydrostatic flow stress of porous materials containing an isotropic, but otherwise arbitrary, distribution of porosity. To cite this article: M.I. Idiart, C. R. Mecanique 335 (2007).
NATURAL FREQUENCIES OF SUBMERGED PIEZOCERAMIC HOLLOW SPHERES
Institute of Scientific and Technical Information of China (English)
Cai Jinbiao; Chen Weiqiu; Ye Guiru; Ding Haojiang
2000-01-01
An exact 3D analysis of free vibration of a piezoceramic hollow sphere submerged in a compressible fluid is presented in this paper.A separation method is adopted to simplify the basic equations for spherically isotropic piezoelasticity.It is shown that there are two independent classes of vibration.The first one is independent of the fluid medium as well as the electric field,while the second is associated with both the fluid parameter and the piezoelectric effect.Exact frequency equations are derived and numerical results are obtained.
Neutron sources and applications
Energy Technology Data Exchange (ETDEWEB)
Price, D.L. [ed.] [Argonne National Lab., IL (United States); Rush, J.J. [ed.] [National Inst. of Standards and Technology, Gaithersburg, MD (United States)
1994-01-01
Review of Neutron Sources and Applications was held at Oak Brook, Illinois, during September 8--10, 1992. This review involved some 70 national and international experts in different areas of neutron research, sources, and applications. Separate working groups were asked to (1) review the current status of advanced research reactors and spallation sources; and (2) provide an update on scientific, technological, and medical applications, including neutron scattering research in a number of disciplines, isotope production, materials irradiation, and other important uses of neutron sources such as materials analysis and fundamental neutron physics. This report summarizes the findings and conclusions of the different working groups involved in the review, and contains some of the best current expertise on neutron sources and applications.
Prototype Stilbene Neutron Collar
Energy Technology Data Exchange (ETDEWEB)
Prasad, M. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Shumaker, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Snyderman, N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Verbeke, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wong, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2016-10-26
A neutron collar using stilbene organic scintillator cells for fast neutron counting is described for the assay of fresh low enriched uranium (LEU) fuel assemblies. The prototype stilbene collar has a form factor similar to standard He-3 based collars and uses an AmLi interrogation neutron source. This report describes the simulation of list mode neutron correlation data on various fuel assemblies including some with neutron absorbers (burnable Gd poisons). Calibration curves (doubles vs ^{235}U linear mass density) are presented for both thermal and fast (with Cd lining) modes of operation. It is shown that the stilbene collar meets or exceeds the current capabilities of He-3 based neutron collars. A self-consistent assay methodology, uniquely suited to the stilbene collar, using triples is described which complements traditional assay based on doubles calibration curves.
Energy Technology Data Exchange (ETDEWEB)
Terry, James Russell [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-05-05
Emission of neutrons in a given event is modeled by the DioramaEmitterNeutron object, a subclass of the abstract DioramaEmitterModule object. The GenerateEmission method of this object is the entry point for generation of a neutron population for a given event. Shown in table 1, this method requires a number of parameters to be defined in the event definition.
Multidensity integral-equation theory for short diblock hard-sphere-sticky-hard-sphere chains.
Wu, Ning; Chiew, Y C
2010-04-01
The multidensity Ornstein-Zernike integral equation theory is applied to study a simple model of hard sphere/sticky hard sphere diblock chains. The multidensity integral equation formalism has been successfully used to model the equilibrium structure and thermodynamic properties of homonuclear chains and shorter dimer fluids; to our knowledge it has not been applied to model diblock chains. In this work, a diblock chain fluids is represented by an m-component equal molar mixture of hard spheres with species 1,2,...,mh and sticky hard spheres with species mh+1,mh+2,...,m. Each spherical particle has two attractive sites A and B except species 1 and m, which have only one site per particle. In the limit of complete association, this mixture yields a system of monodisperse diblock chains. A general solution of this model is obtained in the Percus-Yevick, Polymer Percus-Yevick and ideal chain approximations. Both structural and thermodynamic properties of this model are investigated. From this study, a microphase separation is predicted for relatively short diblock symmetric and asymmetric chains. This microphase separation is enhanced at lower temperature and higher density. When chain length increases, the phase transition changes from a microphase level to a macrophase level. The size of microdomain structure is found to be dependent on total chain length, relative ratio of block lengths, temperature, and density.
Neutron-emission measurements at a white neutron source
Energy Technology Data Exchange (ETDEWEB)
Haight, Robert C [Los Alamos National Laboratory
2010-01-01
Data on the spectrum of neutrons emittcd from neutron-induced reactions are important in basic nuclear physics and in applications. Our program studies neutron emission from inelastic scattering as well as fission neutron spectra. A ''white'' neutron source (continuous in energy) allows measurements over a wide range of neutron energies all in one experiment. We use the tast neutron source at the Los Alamos Neutron Science Center for incident neutron energies from 0.5 MeV to 200 MeV These experiments are based on double time-of-flight techniques to determine the energies of the incident and emitted neutrons. For the fission neutron measurements, parallel-plate ionization or avalanche detectors identify fission in actinide samples and give the required fast timing pulse. For inelastic scattering, gamma-ray detectors provide the timing and energy spectroscopy. A large neutron-detector array detects the emitted neutrons. Time-of-flight techniques are used to measure the energies of both the incident and emitted neutrons. Design considerations for the array include neutron-gamma discrimination, neutron energy resolution, angular coverage, segmentation, detector efficiency calibration and data acquisition. We have made preliminary measurements of the fission neutron spectra from {sup 235}U, {sup 238}U, {sup 237}Np and {sup 239}Pu. Neutron emission spectra from inelastic scattering on iron and nickel have also been investigated. The results obtained will be compared with evaluated data.
Percolation of disordered jammed sphere packings
Ziff, Robert M.; Torquato, Salvatore
2017-02-01
We determine the site and bond percolation thresholds for a system of disordered jammed sphere packings in the maximally random jammed state, generated by the Torquato–Jiao algorithm. For the site threshold, which gives the fraction of conducting versus non-conducting spheres necessary for percolation, we find {{p}\\text{c}}=0.3116(3) , consistent with the 1979 value of Powell 0.310(5) and identical within errors to the threshold for the simple-cubic lattice, 0.311 608, which shares the same average coordination number of 6. In terms of the volume fraction ϕ, the threshold corresponds to a critical value {φ\\text{c}}=0.199 . For the bond threshold, which apparently was not measured before, we find {{p}\\text{c}}=0.2424(3) . To find these thresholds, we considered two shape-dependent universal ratios involving the size of the largest cluster, fluctuations in that size, and the second moment of the size distribution; we confirmed the ratios’ universality by also studying the simple-cubic lattice with a similar cubic boundary. The results are applicable to many problems including conductivity in random mixtures, glass formation, and drug loading in pharmaceutical tablets.
Characterizing HR3549B using SPHERE
Mesa, D; D'Orazi, V; Ginski, C; Desidera, S; Bonnefoy, M; Gratton, R; Langlois, M; Marzari, F; Messina, S; Antichi, J; Biller, B; Bonavita, M; Cascone, E; Chauvin, G; Claudi, R U; Curtis, I; Fantinel, D; Feldt, M; Garufi, A; Galicher, R; Henning, Th; Incorvaia, S; Lagrange, A M; Millward, M; Perrot, C; Salasnich, B; Scuderi, S; Sissa, E; Wahhaj, Z; Zurlo, A
2016-01-01
Aims. In this work, we characterize the low mass companion of the A0 field star HR3549. Methods. We observed HR3549AB in imaging mode with the the NIR branch (IFS and IRDIS) of SPHERE@VLT, with IFS in YJ mode and IRDIS in the H band. We also acquired a medium resolution spectrum with the IRDIS long slit spectroscopy mode. The data were reduced using the dedicated SPHERE GTO pipeline, purposely designed for this instrument. We employed algorithms such as PCA and TLOCI to reduce the speckle noise. Results. The companion was clearly visible both with IRDIS and IFS.We obtained photometry in four different bands as well as the astrometric position for the companion. Based on our astrometry, we confirm that it is a bound object and put constraints on its orbit. Although several uncertainties are still present, we estimate an age of ~100-150 Myr for this system, yielding a most probable mass for the companion of 40-50MJup and T_eff ~300-2400 K. Comparing with template spectra points to a spectral type between M9 and...
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.
Resonance for loop homology of spheres
Hingston, Nancy
2011-01-01
A Riemannian or Finsler metric on a compact manifold M gives rise to a length function on the free loop space \\Lambda M, whose critical points are the closed geodesics in the given metric. If X is a homology class on \\Lambda M, the minimax critical level cr(X) is a critical value. Let M be a sphere of dimension >2, and fix a metric g and a coefficient field G. We prove that the limit as deg(X) goes to infinity of cr(X)/deg(X) exists. We call this limit the "global mean frequency" of M. As a consequence we derive resonance statements for closed geodesics on spheres; in particular either all homology on \\Lambda M of sufficiently high degreee lies hanging on closed geodesics whose mean frequency (average index / length) equals the global mean frequency, or there is a sequence of infinitely many closed geodesics whose mean frequencies converge to the global mean frequency. The proof uses the Chas-Sullivan product and results of Goresky-Hingston [GH].
Approximating and learning by Lipschitz kernel on the sphere
Institute of Scientific and Technical Information of China (English)
CAO Fei-long; WANG Chang-miao
2014-01-01
This paper investigates some approximation properties and learning rates of Lips-chitz kernel on the sphere. A perfect convergence rate on the shifts of Lipschitz kernel on the sphere, which is faster than O(n-1/2), is obtained, where n is the number of parameters needed in the approximation. By means of the approximation, a learning rate of regularized least square algorithm with the Lipschitz kernel on the sphere is also deduced.
Lightcone dualities for curves in the lightcone unit 3-sphere
2013-01-01
In this paper, we consider the curves in the unit 3-sphere in the lightcone. The unit 3-sphere can be canonically embedded in the lightcone and de Sitter 4-space in Lorentz-Minkowski 5-space. We investigate these curves in the framework of the theory of Legendrian dualities between pseudo-spheres in Lorentz-Minkowski 5-space. (C) 2013 AIP Publishing LLC.
GRADIENT INDEX SPHERES BY THE SEQUENTIAL ACCRETION OF GLASS POWDERS
Energy Technology Data Exchange (ETDEWEB)
MARIANO VELEZ
2008-06-15
The Department of Energy is seeking a method for fabricating mm-scale spheres having a refractive index that varies smoothly and continuously from the center to its surface [1]. The fabrication procedure must allow the creation of a range of index profiles. The spheres are to be optically transparent and have a refractive index differential greater than 0.2. The sphere materials can be either organic or inorganic and the fabrication technique must be capable of scaling to low cost production. Mo-Sci Corporation proposed to develop optical quality gradient refractive index (GRIN) glass spheres of millimeter scale (1 to 2 mm diameter) by the sequential accretion and consolidation of glass powders. Other techniques were also tested to make GRIN spheres as the powder-accretion method produced non-concentric layers and poor optical quality glass spheres. Potential ways to make the GRIN spheres were (1) by "coating" glass spheres (1 to 2 mm diameter) with molten glass in a two step process; and (2) by coating glass spheres with polymer layers.
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...
Oil capture from a water surface by a falling sphere
Smolka, Linda; McLaughlin, Clare; Witelski, Thomas
2015-11-01
When a spherical particle is dropped from rest into an oil lens that floats on top of a water surface, a portion of the oil adheres to the sphere. Once the sphere comes to rest at the subsurface, the oil forms a pendant drop that remains attached in equilibrium to the sphere effectively removing oil from the water surface. Best fit solutions of the Laplace equation to experimental profiles are used to investigate the parameter dependence of the radius of curvature and the filling and contact angles at the three-phase contact line of the pendant drop for spheres with different wetting properties, densities and radii. The volume of oil captured by a sphere increases with a sphere's mass and diameter. However, lighter and smaller spheres capture more oil relative to their own volume than do heavier and larger spheres (scaling with the sphere mass ~M - 0 . 544) and are thus more efficient at removing oil from a water surface. The authors wish to acknowledge the support of the National Science Foundation Grant Nos. DMS-0707755 and DMS-0968252.
Bifundamental Fuzzy 2-Sphere and Fuzzy Killing Spinors
Directory of Open Access Journals (Sweden)
Horatiu Nastase
2010-07-01
Full Text Available We review our construction of a bifundamental version of the fuzzy 2-sphere and its relation to fuzzy Killing spinors, first obtained in the context of the ABJM membrane model. This is shown to be completely equivalent to the usual (adjoint fuzzy sphere. We discuss the mathematical details of the bifundamental fuzzy sphere and its field theory expansion in a model-independent way. We also examine how this new formulation affects the twisting of the fields, when comparing the field theory on the fuzzy sphere background with the compactification of the 'deconstructed' (higher dimensional field theory.
IBM WebSphere Application Server 80 Administration Guide
Robinson, Steve
2011-01-01
IBM WebSphere Application Server 8.0 Administration Guide is a highly practical, example-driven tutorial. You will be introduced to WebSphere Application Server 8.0, and guided through configuration, deployment, and tuning for optimum performance. If you are an administrator who wants to get up and running with IBM WebSphere Application Server 8.0, then this book is not to be missed. Experience with WebSphere and Java would be an advantage, but is not essential.
Extensive nuclear sphere generation in the human Alzheimer's brain.
Kolbe, Katharina; Bukhari, Hassan; Loosse, Christina; Leonhardt, Gregor; Glotzbach, Annika; Pawlas, Magdalena; Hess, Katharina; Theiss, Carsten; Müller, Thorsten
2016-12-01
Nuclear spheres are protein aggregates consisting of FE65, TIP60, BLM, and other yet unknown proteins. Generation of these structures in the cellular nucleus is putatively modulated by the amyloid precursor protein (APP), either by its cleavage or its phosphorylation. Nuclear spheres were preferentially studied in cell culture models and their existence in the human brain had not been known. Existence of nuclear spheres in the human brain was studied using immunohistochemistry. Cell culture experiments were used to study regulative mechanisms of nuclear sphere generation. The comparison of human frontal cortex brain samples from Alzheimer's disease (AD) patients to age-matched controls revealed a dramatically and highly significant enrichment of nuclear spheres in the AD brain. Costaining demonstrated that neurons are distinctly affected by nuclear spheres, but astrocytes never are. Nuclear spheres were predominantly found in neurons that were negative for threonine 668 residue in APP phosphorylation. Cell culture experiments revealed that JNK3-mediated APP phosphorylation reduces the amount of sphere-positive cells. The study suggests that nuclear spheres are a new APP-derived central hallmark of AD, which might be of crucial relevance for the molecular mechanisms in neurodegeneration.
Polymeric microspheres for radionuclide synovectomy containing neutron-activated holmium-166.
Mumper, R J; Mills, B J; Ryo, U Y; Jay, M
1992-03-01
Poly-L-lactic acid (PLA) microspheres containing neutron-activated 166Ho were investigated as potential agents for radionuclide synovectomy. Stable 165Ho, complexed to acetylacetone (AcAc), was incorporated into PLA spheres by the solvent evaporation technique. Spheres prepared with the optimal mean particle size of 7.2 microns (range 2-13 microns) containing 25.4% 165Ho-AcAc (9.1% 165Ho) were irradiated in a high neutron flux to produce 31.1-36.0 mCi 166Ho. In vitro human plasma studies showed that the irradiated spheres retained 99.0 +/- 0.01% of the 166Ho at 314 hr. In-vivo retention studies were conducted by administering irradiated PLA spheres with 257-591 microCi 166Ho into the joint space of normal rabbits (n = 6). Biodistribution analysis and gamma camera analysis showed 166Ho retention in the joint space after 120 hr of 97.7% +/- 0.8% and 98.2% +/- 2.4%, respectively, with no uptake by the lymph nodes. The ease with which the PLA spheres can be made in the optimal size range for later irradiation and their ability to retain the 166Ho make them attractive agents for radionuclide synovectomy.
Mitarai, Namiko; Nakanishi, Hiizu
2002-01-01
Dynamical behavior of steady granular flow is investigated numerically in the inelastic hard sphere limit of the soft sphere model. We find distinctively different limiting behaviors for the two flow regimes, i.e., the collisional flow and the frictional flow. In the collisional flow, the hard sphere limit is straightforward; the number of collisions per particle per unit time converges to a finite value and the total contact time fraction with other particles goes to zero. For the frictional...
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
Neutron resonance spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Gunsing, F
2005-06-15
The present document has been written in order to obtain the diploma 'Habilitation a Diriger des Recherches'. Since this diploma is indispensable to supervise thesis students, I had the intention to write a document that can be useful for someone starting in the field of neutron resonance spectroscopy. Although the here described topics are already described elsewhere, and often in more detail, it seemed useful to have most of the relevant information in a single document. A general introduction places the topic of neutron-nucleus interaction in a nuclear physics context. The large variations of several orders of magnitude in neutron-induced reaction cross sections are explained in terms of nuclear level excitations. The random character of the resonances make nuclear model calculation predictions impossible. Then several fields in physics where neutron-induced reactions are important and to which I have contributed in some way or another, are mentioned in a first synthetic chapter. They concern topics like parity nonconservation in certain neutron resonances, stellar nucleosynthesis by neutron capture, and data for nuclear energy applications. The latter item is especially important for the transmutation of nuclear waste and for alternative fuel cycles. Nuclear data libraries are also briefly mentioned. A second chapter details the R-matrix theory. This formalism is the foundation of the description of the neutron-nucleus interaction and is present in all fields of neutron resonance spectroscopy. (author)
Development of Neutron Spectrometer
Energy Technology Data Exchange (ETDEWEB)
Lee, Chang Hee; Lee, J. S.; Seong, B. S. (and others)
2007-06-15
Neutron spectrometers which are used in the basic researches such as physics, chemistry and materials science and applied in the industry were developed at the horizontal beam port of HANARO reactor. In addition, the development of core components for neutron scattering and the upgrade of existing facilities are also performed. The vertical neutron reflectometer was fabricated and installed at ST3 beam port. The performance test of the reflectometer was completed and the reflectometer was opened to users. The several core parts and options were added in the polarized neutron spectrometer. The horizontal neutron reflectometer from Brookhaven National Laboratory was moved to HANARO and installed, and the performance of the reflectometer was examined. The HIPD was developed and the performance test was completed. The base shielding for TAS was fabricated. The soller collimator, Cu mosaic monochromator, Si BPC monochromator and position sensitive detector were developed and applied in the neutron spectrometer as part of core component development activities. In addition, the sputtering machine for mirror device are fabricated and the neutron mirror is made using the sputtering machine. The FCD was upgraded and the performance of the FCD are improved over the factor of 10. The integration and upgrade of the neutron detection system were also performed.
Energy Technology Data Exchange (ETDEWEB)
Yanch, Jacquelyn C. (Cambridge, MA); Shefer, Ruth E. (Newton, MA); Klinkowstein, Robert E. (Winchester, MA)
1999-01-01
In one embodiment there is provided an application of the .sup.10 B(n,.alpha.).sup.7 Li nuclear reaction or other neutron capture reactions for the treatment of rheumatoid arthritis. This application, called Boron Neutron Capture Synovectomy (BNCS), requires substantially altered demands on neutron beam design than for instance treatment of deep seated tumors. Considerations for neutron beam design for the treatment of arthritic joints via BNCS are provided for, and comparisons with the design requirements for Boron Neutron Capture Therapy (BNCT) of tumors are made. In addition, exemplary moderator/reflector assemblies are provided which produce intense, high-quality neutron beams based on (p,n) accelerator-based reactions. In another embodiment there is provided the use of deuteron-based charged particle reactions to be used as sources for epithermal or thermal neutron beams for neutron capture therapies. Many d,n reactions (e.g. using deuterium, tritium or beryllium targets) are very prolific at relatively low deuteron energies.
Energy Technology Data Exchange (ETDEWEB)
Yanch, J.C.; Shefer, R.E.; Klinkowstein, R.E.
1999-11-02
In one embodiment there is provided an application of the {sup 10}B(n,{alpha}){sup 7}Li nuclear reaction or other neutron capture reactions for the treatment of rheumatoid arthritis. This application, called Boron Neutron Capture Synovectomy (BNCS), requires substantially altered demands on neutron beam design than for instance treatment of deep seated tumors. Considerations for neutron beam design for the treatment of arthritic joints via BNCS are provided for, and comparisons with the design requirements for Boron Neutron Capture Therapy (BNCT) of tumors are made. In addition, exemplary moderator/reflector assemblies are provided which produce intense, high-quality neutron beams based on (p,n) accelerator-based reactions. In another embodiment there is provided the use of deuteron-based charged particle reactions to be used as sources for epithermal or thermal neutron beams for neutron capture therapies. Many d,n reactions (e.g. using deuterium, tritium or beryllium targets) are very prolific at relatively low deuteron energies.
DEFF Research Database (Denmark)
Holm, Torkil; Crossland, Ingolf
1996-01-01
Deuterium and 13C kinetic isotope effects (KIEs) have been determined for the conversion of methyl iodide into methyl radical via inner sphere ET (electron transfer) and via outer sphere ET. The alfa-deuterium KIE was found to be very high for in......Deuterium and 13C kinetic isotope effects (KIEs) have been determined for the conversion of methyl iodide into methyl radical via inner sphere ET (electron transfer) and via outer sphere ET. The alfa-deuterium KIE was found to be very high for in...
Pocked surface neutron detector
Energy Technology Data Exchange (ETDEWEB)
McGregor, Douglas (Whitmore Lake, MI); Klann, Raymond (Bolingbrook, IL)
2003-04-08
The detection efficiency, or sensitivity, of a neutron detector material such as of Si, SiC, amorphous Si, GaAs, or diamond is substantially increased by forming one or more cavities, or holes, in its surface. A neutron reactive material such as of elemental, or any compound of, .sup.10 B, .sup.6 Li, .sup.6 LiF, U, or Gd is deposited on the surface of the detector material so as to be disposed within the cavities therein. The portions of the neutron reactive material extending into the detector material substantially increase the probability of an energetic neutron reaction product in the form of a charged particle being directed into and detected by the neutron detector material.
THERMAL NEUTRON BACKSCATTER IMAGING.
Energy Technology Data Exchange (ETDEWEB)
VANIER,P.; FORMAN,L.; HUNTER,S.; HARRIS,E.; SMITH,G.
2004-10-16
Objects of various shapes, with some appreciable hydrogen content, were exposed to fast neutrons from a pulsed D-T generator, resulting in a partially-moderated spectrum of backscattered neutrons. The thermal component of the backscatter was used to form images of the objects by means of a coded aperture thermal neutron imaging system. Timing signals from the neutron generator were used to gate the detection system so as to record only events consistent with thermal neutrons traveling the distance between the target and the detector. It was shown that this time-of-flight method provided a significant improvement in image contrast compared to counting all events detected by the position-sensitive {sup 3}He proportional chamber used in the imager. The technique may have application in the detection and shape-determination of land mines, particularly non-metallic types.
Becker, Werner
2009-01-01
Neutron stars are the most compact astronomical objects in the universe which are accessible by direct observation. Studying neutron stars means studying physics in regimes unattainable in any terrestrial laboratory. Understanding their observed complex phenomena requires a wide range of scientific disciplines, including the nuclear and condensed matter physics of very dense matter in neutron star interiors, plasma physics and quantum electrodynamics of magnetospheres, and the relativistic magneto-hydrodynamics of electron-positron pulsar winds interacting with some ambient medium. Not to mention the test bed neutron stars provide for general relativity theories, and their importance as potential sources of gravitational waves. It is this variety of disciplines which, among others, makes neutron star research so fascinating, not only for those who have been working in the field for many years but also for students and young scientists. The aim of this book is to serve as a reference work which not only review...
Quantum Baker map on the sphere
Pakonski, P; Zyczkowski, K; Pakonski, Prot; Ostruszka, Andrzej; Zyczkowski, Karol
1998-01-01
We construct analogue of the baker map on the sphere. We analyze its classical and quantum versions. The classical map is characterized by dynamical entropy equal to ln(2) and has a similar set of periodic orbits as the map on the torus. The quantum map is represented by a real, orthogonal matrix of an even dimension. Semiclassical dynamics and time evolution may be studied with the help of the SU(2) coherent states and the generalized Husimi distribution. In contrast to the standard baker map on the torus, the map analyzed in this paper does not exhibit the time reversal symmetry. Semiclassical ensemble of quantum maps, obtained by averaging over a range of matrix sizes, displays statistical properties characteristic of circular unitary ensemble.
On the Torus Cobordant Cohomology Spheres
Indian Academy of Sciences (India)
Ali Özkurt; Doğan Dönmez
2009-02-01
Let be a compact Lie group. In 1960, P A Smith asked the following question: ``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 $\\mathbb{Z}_p$ and it is also known to be the same for connected Lie groups. In this work, we prove that two linear torus actions on $S^n$ which are -cobordant (cobordism in which inclusion of each boundary component induces isomorphisms in $\\mathbb{Z}$-cohomology) must be linearly equivalent. As a corollary, for connected case, we prove a variant of Smith’s question.
SINGLE CRYSTAL NEUTRON DIFFRACTION.
Energy Technology Data Exchange (ETDEWEB)
KOETZLE,T.F.
2001-03-13
Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.
Optical polarizing neutron devices designed for pulsed neutron sources
Energy Technology Data Exchange (ETDEWEB)
Takeda, M.; Kurahashi, K.; Endoh, Y. [Tohoku Univ, Sendai (Japan); Itoh, S. [National Lab. for High Energy Physics, Tsukuba (Japan)
1997-09-01
We have designed two polarizing neutron devices for pulsed cold neutrons. The devices have been tested at the pulsed neutron source at the Booster Synchrotron Utilization Facility of the National Laboratory for High Energy Physics. These two devices proved to have a practical use for experiments to investigate condensed matter physics using pulsed cold polarized neutrons.
Institute of Scientific and Technical Information of China (English)
MA Fang-wei; SUN Li-ping; ZHAO Hui; LI Qiang; HUO Li-hua; XIA Tian; GAO Shan
2013-01-01
The nitrogen and oxygen co-doped hollow carbon spheres(HCSs) were prepared via a simple pyrolysis of solid melamine-formaldhyde resin spheres.The carbonization temperature has an important influence on the specific surface area,pore-size distribution and heteroatom contents of HCSs.The synergistic effects of those physical and chemical properties on supercapacitor performance were systematically investigated.Among the HCSs obtained at different temperatures,HCSs-800(co-doped HCSs at 800 ℃) exhibits the best reversible specific capacitance in 2 mol/L H2SO4 electrolyte and meanwhile maintains a high-class capacitance retention capability.The nitrogen heteroatoms were confirmed to play a crucial role in improving capacitance in an acid medium.This kind of nitrogen doped HCSs is a potential candidate for an efficient electrode material for supercapacitors.
Bedogni, R; Sacco, D; Gómez-Ros, J M; Lorenzoli, M; Gentile, A; Buonomo, B; Pola, A; Introini, M V; Bortot, D; Domingo, C
2016-01-01
A new thermal neutron irradiation facility based on an (241)Am-Be source embedded in a polyethylene moderator has been designed, and is called ETHERNES (Extended THERmal NEutron Source). The facility shows a large irradiation cavity (45 cm × 45 cm square section, 63 cm in height), which is separated from the source by means of a polyethylene sphere acting as shadowing object. Taking advantage of multiple scattering of neutrons with the walls of this cavity, the moderation process is especially effective and allows obtaining useful thermal fluence rates from 550 to 800 cm(-2) s(-1) with a source having nominal emission rate 5.7×10(6) s(-1). Irradiation planes parallel to the cavity bottom have been identified. The fluence rate across a given plane is as uniform as 3% (or better) in a disk with 30 cm (or higher) diameter. In practice, the value of thermal fluence rate simply depends on the height from the cavity bottom. The thermal neutron spectral fraction ranges from 77% up to 89%, depending on the irradiation plane. The angular distribution of thermal neutrons is roughly isotropic, with a slight prevalence of directions from bottom to top of the cavity. The mentioned characteristics are expected to be attractive for the scientific community involved in neutron metrology, neutron dosimetry and neutron detector testing.
Weighted Approximation for Jackson-Matsuoka Polynomials on the Sphere
Directory of Open Access Journals (Sweden)
Guo Feng
2012-01-01
Full Text Available We consider the best approximation by Jackson-Matsuoka polynomials in the weighted Lp space on the unit sphere of Rd. Using the relation between K-functionals and modulus of smoothness on the sphere, we obtain the direct and inverse estimate of approximation by these polynomials for the h-spherical harmonics.
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.
Squeeze flow between a sphere and a textured wall
Energy Technology Data Exchange (ETDEWEB)
Chastel, T.; Mongruel, A., E-mail: anne.mongruel@upmc.fr [Physique et Mécanique des Milieux Hétérogènes, UMR 7636 CNRS–ESPCI, Université Pierre et Marie Curie–Université Paris-Diderot, 10 rue Vauquelin, 75231 Paris Cedex 05 (France)
2016-02-15
The motion of a millimetric sphere, translating in a viscous fluid towards a wettable textured wall, is investigated experimentally. The textures consist of square arrays of cylindrical or square micro-pillars, the height, width, and spacing of which are varied, keeping the periodicity small compared to the sphere radius. An interferometric device is used to measure the sphere vertical displacement, for distances between the sphere and the base of the pillars smaller than 0.1 sphere radius, and with a resolution of 200 nm. At a given distance from the top of the pillars, the sphere velocity is found to be significantly larger than the corresponding velocity for a smooth solid wall. A squeeze flow model of two adjacent fluid layers is developed in the lubrication approximation, one fluid layer having an effective viscosity that reflects the viscous dissipation through the array of pillars. The pressure field in the gap between the sphere and the textured surface is then used to obtain the drag force on the sphere and hence its velocity. Adjustment of the model to the velocity measurements yields the effective viscosity for a given texture. Finally, a correlation between the effective viscosity and the geometry of the pillar array is proposed.
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…
Homological properties of Podle′s quantum spheres
Institute of Scientific and Technical Information of China (English)
LIU LiYu; SHEN YunYi; WU QuanShui
2014-01-01
The standard Podle′s quantum sphere is Artin-Schelter regular as showed by Kra¨hmer（2012）.The non-standard Podle′s quantum spheres are proved to be Auslander-regular,Cohen-Macaulay and Artin-Schelter regular in this paper.
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...
Axioms of spheres in lightlike geometry of submanifolds
Indian Academy of Sciences (India)
RACHNA RANI; RAKESH KUMAR; R K NAGAICH
2016-10-01
We prove that if an indefinite Kaehler manifold $\\bar{M}$ with lightlike submanifolds satisfies the axioms of holomorphic 2$r$-spheres, axioms of holomorphic 2$r$-planes, axioms of transversal $r$-spheres and axioms of transversal $r$-planes, then it is an indefinite complex space form.
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....
A REMARK ON THE QUASI-HARMONIC SPHERES
Institute of Scientific and Technical Information of China (English)
XuDeliang; ZhouChunqin
2002-01-01
Several theorems on the finiteness of energy for quasi-harmonic spheres are proved,some counter-examples which state that the energy of quasi-harmonic sphere may be infinite are given. The results support some conditions of a question posed by Lin Fanghua and Wang Changyou.
Dual-Purpose Millikan Experiment with Polystyrene Spheres
Wall, C. N.; Christensen, F. E.
1975-01-01
This procedure, using polystyrene spheres of specified diameter, renders the Millikan oil drop experiment more accurate than the conventional procedure of the polystyrene spheres, eliminates size estimation error, and removes the guesswork involved in assigning proper index integers to the observed charges. (MLH)
Direct measurement of thermodynamic properties of colloidal hard spheres
Dullens, R.P.A.; Kegel, W.K.; Aarts, D.G.A.L.
2008-01-01
Recently, we have shown how to measure thermodynamic properties of colloidal hard sphere suspensions by microscopy [Dullens et al. (2006) PNAS 103, 529]. Here, we give full experimental details on how to acquire three dimensional snapshots of a colloidal hard sphere suspension over a wide range of d
Savvidis, I.; Giomataris, I.; Bougamont, E.; Irastorza, I.; Aune, S.; Chapelier, M.; Charvin, P. H.; Colas, P.; Derre, J.; Ferrer, E.; Gerbier, G.; Gros, M.; Mangier, P.; Navick, X. F.; Salin, P.; Vergados, J. D.; Zampalo, M.
2010-01-01
A large volume (1m3) spherical proportional counter has been developed at CEA/Saclay, for low flux neutron measurements. The high voltage is applied to a small sphere 15mm in diameter, located in the center of the counter and the wall of the counter is grounded. Neutrons can be measured successfully, with high sensitivity, using 3He gas in the detector. The proton and tritium energy deposition in the drift gaseous volume, from the reaction 3He(n,p)3H, can provide the neutron spectra from thermal neutrons up to several MeV. The detector has been installed in the underground laboratory in Modane (LSM) to measure the neutron background. The sphere has been has been filled with gas mixture of Ar + 2% CH4 +3gr He-3, at 275 mbar. The thermal neutron peak is well separated from the cosmic ray and gamma background, permitting of neutron flux calculation. Other potential applications requiring large volume of about 10 m in radius are described in detail in reference
Impact of supersymmetry on the nonperturbative dynamics of fuzzy spheres
Anagnostopoulos, K N; Nagao, K; Nishimura, J; Anagnostopoulos, Konstantinos N.; Azuma, Takehiro; Nagao, Keiichi; Nishimura, Jun
2005-01-01
We study a 4d supersymmetric matrix model with a cubic term, which incorporates fuzzy spheres as classical solutions, using Monte Carlo simulations and perturbative calculations. The fuzzy sphere in the supersymmetric model turns out to be always stable if the large-N limit is taken in such a way that various correlation functions scale. This is in striking contrast to analogous bosonic models, where the fuzzy sphere decays into the pure Yang-Mills vacuum due to quantum effects when the coefficient of the cubic term becomes smaller than a critical value. We also find that the power-law tail of the eigenvalue distribution, which exists in the supersymmetric model without the cubic term, disappears in the presence of the fuzzy sphere in the large-N limit. Coincident fuzzy spheres turn out to be unstable, which implies that the dynamically generated gauge group is U(1).
On-Chip Fabrication of Glass Sphere Laser
Directory of Open Access Journals (Sweden)
Kishi Tetsuo
2015-01-01
Full Text Available Fabrication and application of glass spherical micro-cavity for lasing are reported. Surface-tension molding (StM and localized-laser heating (LLH techniques have been developed to fabricate glass super sphere, which is partially truncated spherical shape, and true spheres, respectively. Whispering gallery mode (WGM resonances or laser oscillations from the spherical glasses were demonstrated. Super-spherical glasses possessed WGM resonances on its equatorial plane. The equatorial plane with high roundness (>0.99 serves a high quality factor to lead laser oscillation. LLH technique enables us to fabricate true spheres on a transparent substrate. Tellurite glass spheres prepared by the LLH technique showed laser oscillation with few-mW-order thresholds by direct pumping. StM and LLH technique are very suitable for both preparation and utilization of glass spheres for optical micro-cavity.
SPHERE: a scalable multicast framework in overlay networks
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
This paper presents Sphere, a scalable multicast framework in overlay network. Sphere is a highly efficient, self-organizing and robust multicast protocol overlayed on the Internet. The main contributions of this paper are twofold. First, Sphere organizes the control topology of overlay network in two directions: horizontal and vertical. The horizontal meshes are used to locate and organize hosts in tracks, and the vertical meshes are used to manage the data paths between tracks. Second, Sphere balances stress and stretch of the overlay network by assigning hosts into different tracks and clusters. This structure distributes stress on the multicast trees uniformly, and meantime makes path stretch as small as possible.Simulations results show that Sphere can support multicast with large group size and has good performance on organizing meshes and building data delivery trees.
Encapsulation of urease enzyme in xanthan-alginate spheres.
Elçin, Y M
1995-10-01
Urease-containing xanthan-alginate spheres were prepared by a two-step process which involved the Ca2+ coupling of the polysaccharides, followed by gentle glutaraldehyde cross-linking with amine groups of gelatin present in the initial mixture. This second step caused a slight decrease in the enzymatic activity but increased the stability. The water content and size distribution of the spheres were examined together with the sphere morphology. The effect of polymer ratio and enzyme loading on urease activity was investigated. An increase in xanthan content was found to affect the water uptake of the spheres. Temperature and pH stability of encapsulated urease was found to be higher than the free form. The xanthan-alginate spheres showed 75% of maximum urease activity even after 20 repeated uses under optimal conditions.
Imaging spheres with general incident wavefronts using a dipole decomposition
Izen, Steven H.; Ovryn, Ben
1998-06-01
Although scattering for spheres with plane wave illumination was solved precisely by Mie in 1909, often it is of interest to image spheres with non-planar illumination. An extension of Mie theory which incorporates non-planar illumination requires knowledge of the coefficients for a spherical harmonic expansion of the incident wavefront about the center of the sphere. These coefficients have been determined for a few special cases, such as Gaussian beams, which have a relatively simple model. Using a vectorized Huygen's principle, a general vector wavefront can be represented as a superposition of dipole sources. We have computed the spherical wave function expansion coefficients of an arbitrarily placed dipole and hence the scattering from a sphere illuminated by a general wavefront can be computed. As a special case, Mie's solution of plane wave scattering was recovered. POtential applications include scattering with partially coherent illumination. Experimental results from the scattering from polystyrene spheres using Koehler illumination show agreement with numerical tests.
Priority Guidelines Of The Service Sphere Development In Uzbekistan
Directory of Open Access Journals (Sweden)
Bakhtiyor Safarov
2011-04-01
Full Text Available The present research article is devoted to study the priorities of service sphere development in Uzbekistan. The comparative analysis of service sphere development during 1996-2009 were presented, survey of disperse territories, analysis and generalization methods used to identify trends in services sphere. Disperse markets were grouped into markets with high, medium and low development level. Retail trade is identified one of the most important components of service sphere in Uzbekistan. Retail turnover figures were predicted until 2013 used retrospective data for forecasting. Linear trend - trends of increase or decrease of index, visual analysis of time series dynamics(graphic presentation were used to solve the studied problem. Main priorities and targets in service sphere in Uzbekistan and it’s role in economy were determined.
Holomorphic Two-Spheres in Complex Grassmann Manifold (2, 4)
Indian Academy of Sciences (India)
Xiaowei Xu; Xiaoxiang Jiao
2008-08-01
In this paper, we use the harmonic sequence to study the linearly full holomorphic two-spheres in complex Grassmann manifold (2,4). We show that if the Gaussian curvature (with respect to the induced metric) of a non-degenerate holomorphic two-sphere satisfies ≤ 2 (or ≥ 2), then must be equal to 2. Simultaneously, we show that one class of the holomorphic two-spheres with constant curvature 2 is totally geodesic. Concerning the degenerate holomorphic two-spheres, if its Gaussian curvature ≤ 1 (or ≥ 1), then =1. Moreover, we prove that all holomorphic two-spheres with constant curvature 1 in (2,4) must be (4)-equivalent.
Energy Technology Data Exchange (ETDEWEB)
Herzkamp, Matthias; Engels, Ralf; Kemmerling, Guenter [ZEA-2, Forschungszentrum Juelich (Germany); Brueckel, Thomas [JCNS, Forschungszentrum Juelich (Germany); Stahl, Achim [III. Physikalisches Institut B, RWTH Aachen (Germany); Waasen, Stefan van [ZEA-2, Forschungszentrum Juelich (Germany); Faculty of Engineering, University of Duisburg-Essen (Germany)
2015-07-01
In neutron scattering experiments it is important to have position sensitive large scale detectors for thermal neutrons. A detector based on a neutron scintillator with wave length shifting fibers is a new kind of such a detector. We present the simulation of the detector based on the microscopic structure of the scintillation material of the mentioned detector. It consists of a converter and a scintillation powder bound in a matrix. The converter in our case is lithium fluoride with enriched lithium 6, to convert thermal neutrons into high energetic alpha and triton particles. The scintillation material is silver doped zinc sulfide. We show that pulse height spectra obtained by these scintillators can be be explained by the simple model of randomly distributed spheres of zinc sulfide and lithium fluoride. With this model, it is possible to optimise the mass ratio of zinc sulfide to lithium fluoride with respect to detection efficiency and/or energy deposition in zinc sulfide.
Energy Technology Data Exchange (ETDEWEB)
Barocchi, F. [Florence Univ. (Italy). Ist. di Fisica
1996-12-31
Together with X-rays, thermal neutrons are the ideal probe to study the microscopic structure of condensed matter, however the precision attainable usually with neutrons for the measurement of atomic position correlation functions in liquids is, at least, one order of magnitude better than for X-rays. In order to measure properly the microscopic dynamics a wide range of momentum transfer with corresponding energy transfer must be available in the range of liquid state excitations. This again is only attainable, with good resolution, with neutrons. (author) 7 figs., 3 refs.
Imae, Toyoko; Furusaka, Michihiro; Torikai, Naoya
2011-01-01
Neutron and synchrotron facilities, which are beyond the scale of the laboratory, and supported on a national level in countries throughout the world. These tools for probing micro- and nano-structure research and on fast dynamics research of atomic location in materials have been key in the development of new polymer-based materials. Different from several existing professional books on neutron science, this book focuses on theory, instrumentation, an applications. The book is divided into five parts: Part 1 describes the underlying theory of neutron scattering. Part 2 desc
Dynamic simulation of sphere motion in a vertical tube
Yu, Zhaosheng; Phan-Thien, Nhan; Tanner, Roger I.
2004-11-01
In this paper, the sedimentation of a sphere and its radial migration in a Poiseuille flow in a vertical tube filled with a Newtonian fluid are simulated with a finite-difference-based distributed Lagrange multiplier (DLM) method. The flow features, the settling velocities, the trajectories and the angular velocities of the spheres sedimenting in a tube at different Reynolds numbers are presented. The results show that at relatively low Reynolds numbers, the sphere approaches the tube axis monotonically, whereas in a high-Reynolds-number regime where shedding of vortices takes place, the sphere takes up a spiral trajectory that is closer to the tube wall than the tube axis. The rotation motion and the lateral motion of the sphere are highly correlated through the Magnus effect, which is verified to be an important (but not the only) driving force for the lateral migration of the sphere at relatively high Reynolds numbers. The standard vortex structures in the wake of a sphere, for Reynolds number higher than 400, are composed of a loop mainly located in a plane perpendicular to the streamwise direction and two streamwise vortex pairs. When moving downstream, the legs of the hairpin vortex retract and at the same time a streamwise vortex pair with rotation opposite to that of the legs forms between the loops. For Reynolds number around 400, the wake structures shed during the impact of the sphere on the wall typically form into streamwise vortex structures or else into hairpin vortices when the sphere spirals down. The radial, angular and axial velocities of both neutrally buoyant and non-neutrally buoyant spheres in a circular Poiseuille flow are reported. The results are in remarkably good agreement with the available experimental data. It is shown that suppresion of the sphere rotation produces significant large additional lift forces pointing towards the tube axis on the spheres in the neutrally buoyant and more-dense-downflow cases, whereas it has a negligible
Macromolecular Dynamics in Red Blood Cells Investigated Using Neutron Spectroscopy
Stadler, Andreas Maximilian; Demmel, Franz; Artmann, Gerhard; 10.1098/rsif.2010.0306
2011-01-01
We present neutron scattering measurements on the dynamics of hemoglobin (Hb) in human red blood cells in vivo. Global and internal Hb dynamics were measured in the ps to ns time- and {\\AA} length-scale using quasielastic neutron backscattering spectroscopy. We observed the cross-over from global Hb short-time to long-time self-diffusion. Both short- and long-time diffusion coefficients agree quantitatively with predicted values from hydrodynamic theory of non-charged hard-sphere suspensions when a bound water fraction of around 0.23g H2O/ g Hb is taken into account. The higher amount of water in the cells facilitates internal protein fluctuations in the ps time-scale when compared to fully hydrated Hb powder. Slower internal dynamics of Hb in red blood cells in the ns time-range were found to be rather similar to results obtained with fully hydrated protein powders, solutions and E. coli cells.
Gelation and state diagram for a model nanoparticle system with adhesive hard sphere interactions
Wagner, Norman; Aaron, Eberle
2012-02-01
We provide the first comprehensive state diagram of thermoreversible gelation in a model nanoparticle system from dilute concentrations to the attractive driven glass. We show the temperature dependence of the interparticle potential is related to a surface molecular phase transition of the brush layer using neutron reflectivity (NR) and small-angle neutron scattering (SANS) [1]. We establish the temperature dependence of the interparticle potential using SANS, dynamic light scattering (DLS), and rheology. The potential parameters extracted from SANS suggest that, for this system, gelation is an extension of the Mode Coupling Theory (MCT) attractive driven glass line (ADG) to lower volume fractions and follows the percolation transition. Below the critical concentration, gelation proceeds without competition for phase separation [2]. These results are used to develop a complete state diagram for the sticky hard sphere reference system. [4pt] [1] A.P.R. Eberle, N.J. Wagner, B. Akgun, S.K. Satija, Langmuir 26 3003 (2010).[0pt] [2] A.P.R. Eberle, N.J. Wagner, R. Castaneda-Priego, Phys. Rev. Let. 105704 (2011).
Angular response performance study of a new Harshaw neutron albedo TLD
Energy Technology Data Exchange (ETDEWEB)
Liu, J.C.; Sims, C.S. (Oak Ridge National Lab., TN (USA)); West, L.; Welty, T. (Arkansas Univ., Fayetteville, AK (USA). Southwest Radiation Calibration Center)
1990-01-01
The angular response of a new Harshaw albedo neutron TLD was studied with two sources: a bare {sup 252}Cf source and a {sup 252}Cf source moderated by a 15 cm D{sub 2}O sphere covered with a cadmium shell. The effect of photon angular dependence on the neutron response of the albedo TLD was examined with {sup 137}Cs and X rays. The angular response performance of the albedo TLD was also evaluated in terms of the directional dose equivalent quantity. The results of these studies are presented and discussed. (author).
Tsuruta, Sachiko
2016-07-01
We start with a brief introduction to the historical background in the early pioneering days when the first neutron star thermal evolution calculations predicted the presence of neutron stars hot enough to be observable. We then report on the first detection of neutron star temperatures by ROSAT X-ray satellite, which vindicated the earlier prediction of hot neutron stars. We proceed to present subsequent developments, both in theory and observation, up to today. We then discuss the current status and the future prospect, which will offer useful insight to the understanding of basic properties of ultra-high density matter beyond the nuclear density, such as the possible presence of such exotic particles as pion condensates.
Decoherence Free Neutron Interferometry
Pushin, Dmitry A; Cory, David G
2016-01-01
Perfect single-crystal neutron interferometers are adversely sensitive to environmental disturbances, particularly mechanical vibrations. The sensitivity to vibrations results from the slow velocity of thermal neutrons and the long measurement time that are encountered in a typical experiment. Consequently, to achieve a good interference solutions for reducing vibration other than those normally used in optical experiments must be explored. Here we introduce a geometry for a neutron interferometer that is less sensitive to low-frequency vibrations. This design may be compared with both dynamical decoupling methods and decoherence-free subspaces that are described in quantum information processing. By removing the need for bulky vibration isolation setups, this design will make it easier to adopt neutron interferometry to a wide range of applications and increase its sensitivity.
Neutron signal transfer analysis
Pleinert, H; Lehmann, E
1999-01-01
A new method called neutron signal transfer analysis has been developed for quantitative determination of hydrogenous distributions from neutron radiographic measurements. The technique is based on a model which describes the detector signal obtained in the measurement as a result of the action of three different mechanisms expressed by signal transfer functions. The explicit forms of the signal transfer functions are determined by Monte Carlo computer simulations and contain only the distribution as a variable. Therefore an unknown distribution can be determined from the detector signal by recursive iteration. This technique provides a simple and efficient tool for analysis of this type while also taking into account complex effects due to the energy dependency of neutron interaction and single and multiple scattering. Therefore this method provides an efficient tool for precise quantitative analysis using neutron radiography, as for example quantitative determination of moisture distributions in porous buil...
Energy Technology Data Exchange (ETDEWEB)
Lewis, W.B
1966-07-01
The presentation discusses both the economic and research contexts that would be served by producing neutrons in gram quantities at high intensities by electrical means without uranium-235. The revenue from producing radioisotopes is attractive. The array of techniques introduced by the multipurpose 65 megawatt Intense Neutron Generator project includes liquid metal cooling, superconducting magnets for beam bending and focussing, super-conductors for low-loss high-power radiofrequency systems, efficient devices for producing radiofrequency power, plasma physics developments for producing and accelerating hydrogen, ions at high intensity that are still far out from established practice, a multimegawatt high voltage D.C. generating machine that could have several applications. The research fields served relate principally to materials science through neutron-phonon and other quantum interactions as well as through neutron diffraction. Nuclear physics is served through {mu}-, {pi}- and K-meson production. Isotope production enters many fields of applied research. (author)
Neutron Stars Recent Developments
Heiselberg, H
1999-01-01
Recent developments in neutron star theory and observation are discussed. Based on modern nucleon-nucleon potentials more reliable equations of state for dense nuclear matter have been constructed. Furthermore, phase transitions such as pion, kaon and hyperon condensation, superfluidity and quark matter can occur in cores of neutron stars. Specifically, the nuclear to quark matter phase transition and its mixed phases with intriguing structures is treated. Rotating neutron stars with and without phase transitions are discussed and compared to observed masses, radii and glitches. The observations of possible heavy $\\sim 2M_\\odot$ neutron stars in X-ray binaries and QPO's require relatively stiff equation of states and restrict strong phase transitions to occur at very high nuclear densities only.
Directed synthesis of stable large polyoxomolybdate spheres.
Roy, Soumyajit; Bossers, Lydia C A M; Meeldijk, Hans J D; Kuipers, Bonny W M; Kegel, Willem K
2008-02-05
Polyoxometalates or POMs, a class of inorganic transition metal-oxide based clusters, have gained significant interest owing to their catalytic, magnetic, and material science applications. All such applications require high surface area POM based materials. However, chemically synthesized POMs are still at most in the range of a few nanometers, with their size and morphology being difficult to control. Hence, there is an immediate need to develop design principles that allow easy control of POM morphology and size on mesoscopic (50-500 nm) length scales. Here, we report a design strategy to meet this need. Our method reported here avoids a complex chemical labyrinth by using a prefabricated cationic 1,2-dioleol-3-trimethylammonium-propane (DOTAP) vesicle as a scaffold/structure directing agent and gluing simple anionic heptamolybdates by electrostatic interaction and hydrogen bonds to form large POM spheres. By this method, complexity in the resulting structure can be deliberately induced either via the scaffold or via the oxometalate. The high degree of control in the matter of the size and morphology of the resulting POM superstructures renders this method attractive from a synthetic standpoint.
Seethaler, Dominik
2008-01-01
The most promising approaches for efficient detection in multiple-input multiple-output (MIMO) wireless systems are based on sphere-decoding (SD). The conventional (and optimum) norm that is used to conduct the tree traversal step in SD is the l-two norm. It was, however, recently shown that using the l-infinity norm instead significantly reduces the VLSI implementation complexity of SD at only a marginal performance loss. These savings are due to a reduction in the length of the critical path and the silicon area of the circuit, but also, as observed previously through simulation results, a consequence of a reduction in the computational (algorithmic) complexity. The aim of this paper is an analytical performance and computational complexity analysis of l-infinity norm SD. For i.i.d. Rayleigh fading MIMO channels, we show that l-infinity norm SD achieves full diversity order with an asymptotic SNR gap, compared to l-two norm SD, that increases at most linearly in the number of receive antennas. Moreover, we ...
Collective excitations in soft-sphere fluids.
Bryk, Taras; Gorelli, Federico; Ruocco, Giancarlo; Santoro, Mario; Scopigno, Tullio
2014-10-01
Despite that the thermodynamic distinction between a liquid and the corresponding gas ceases to exist at the critical point, it has been recently shown that reminiscence of gaslike and liquidlike behavior can be identified in the supercritical fluid region, encoded in the behavior of hypersonic waves dispersion. By using a combination of molecular dynamics simulations and calculations within the approach of generalized collective modes, we provide an accurate determination of the dispersion of longitudinal and transverse collective excitations in soft-sphere fluids. Specifically, we address the decreasing rigidity upon density reduction along an isothermal line, showing that the positive sound dispersion, an excess of sound velocity over the hydrodynamic limit typical for dense liquids, displays a nonmonotonic density dependence strictly correlated to that of thermal diffusivity and kinematic viscosity. This allows rationalizing recent observation parting the supercritical state based on the Widom line, i.e., the extension of the coexistence line. Remarkably, we show here that the extremals of transport properties such as thermal diffusivity and kinematic viscosity provide a robust definition for the boundary between liquidlike and gaslike regions, even in those systems without a liquid-gas binodal line. Finally, we discuss these findings in comparison with recent results for Lennard-Jones model fluid and with the notion of the "rigid-nonrigid" fluid separation lines.
Quantum Hall effect on odd spheres
Coşkun, Ü. H.; Kürkçüoǧlu, S.; Toga, G. C.
2017-03-01
We solve the Landau problem for charged particles on odd dimensional spheres S2 k -1 in the background of constant SO (2 k -1 ) gauge fields carrying the irreducible representation (I/2 ,I/2 ,…,I/2 ). We determine the spectrum of the Hamiltonian, the degeneracy of the Landau levels and give the eigenstates in terms of the Wigner D -functions, and for odd values of I , the explicit local form of the wave functions in the lowest Landau level (LLL). The spectrum of the Dirac operator on S2 k -1 in the same gauge field background together with its degeneracies is also determined, and in particular, its number of zero modes is found. We show how the essential differential geometric structure of the Landau problem on the equatorial S2 k -2 is captured by constructing the relevant projective modules. For the Landau problem on S5, we demonstrate an exact correspondence between the union of Hilbert spaces of LLLs, with I ranging from 0 to Imax=2 K or Imax=2 K +1 to the Hilbert spaces of the fuzzy CP 3 or that of winding number ±1 line bundles over CP 3 at level K , respectively.
Integrated marketing communications in educational sphere
2013-01-01
The article investigates the paradigm of Integrated Marketing Communication and their main features. The author explains concept of Integrated Marketing Communication on the practical example in educational sphere. В статье рассказывается о понятии и основных чертах интегрированных маркетинговых коммуникаций. Автор поясняет положения концепции интегрированных маркетинговых коммуниакций на конкретном примере в образовательной сфере....
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.
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.
Synthesis and Characterization of Oil-Chitosan Composite Spheres
Directory of Open Access Journals (Sweden)
Wei-Ting Wang
2013-05-01
Full Text Available Oil-chitosan composite spheres were synthesized by encapsulation of sunflower seed oil in chitosan droplets, dropping into NaOH solution and in situ solidification. Hydrophilic materials (i.e., iron oxide nanoparticles and lipophilic materials (i.e., rhodamine B or epirubicin could be encapsulated simultaneously in the spheres in a one step process. The diameters of the prepared spheres were 2.48 ± 0.11 mm (pure chitosan spheres, 2.31 ± 0.08 mm (oil-chitosan composites, 1.49 ± 0.15 mm (iron-oxide embedded oil-chitosan composites, and 1.69 ± 0.1 mm (epirubicin and iron oxide encapsulated oil-chitosan composites, respectively. Due to their superparamagnetic properties, the iron-oxide embedded oil-chitosan composites could be guided by a magnet. A lipophilic drug (epirubicin could be loaded in the spheres with encapsulation rate measured to be 72.25%. The lipophilic fluorescent dye rhodamine B was also loadable in the spheres with red fluorescence being observed under a fluorescence microscope. We have developed a novel approach to an in situ process for fabricating oil-chitosan composite spheres with dual encapsulation properties, which are potential multifunctional drug carriers.
Synthesis and characterization of oil-chitosan composite spheres.
Huang, Keng-Shiang; Wang, Chih-Yu; Yang, Chih-Hui; Grumezescu, Alexandru Mihai; Lin, Yung-Sheng; Kung, Chao-Pin; Lin, I-Yin; Chang, Yi-Ching; Weng, Wei-Jie; Wang, Wei-Ting
2013-05-16
Oil-chitosan composite spheres were synthesized by encapsulation of sunflower seed oil in chitosan droplets, dropping into NaOH solution and in situ solidification. Hydrophilic materials (i.e., iron oxide nanoparticles) and lipophilic materials (i.e., rhodamine B or epirubicin) could be encapsulated simultaneously in the spheres in a one step process. The diameters of the prepared spheres were 2.48 ± 0.11 mm (pure chitosan spheres), 2.31 ± 0.08 mm (oil-chitosan composites), 1.49 ± 0.15 mm (iron-oxide embedded oil-chitosan composites), and 1.69 ± 0.1 mm (epirubicin and iron oxide encapsulated oil-chitosan composites), respectively. Due to their superparamagnetic properties, the iron-oxide embedded oil-chitosan composites could be guided by a magnet. A lipophilic drug (epirubicin) could be loaded in the spheres with encapsulation rate measured to be 72.25%. The lipophilic fluorescent dye rhodamine B was also loadable in the spheres with red fluorescence being observed under a fluorescence microscope. We have developed a novel approach to an in situ process for fabricating oil-chitosan composite spheres with dual encapsulation properties, which are potential multifunctional drug carriers.
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).
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.
Introduction to neutron scattering
Energy Technology Data Exchange (ETDEWEB)
Fischer, W.E. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)
1996-11-01
We give here an introduction to the theoretical principles of neutron scattering. The relationship between scattering- and correlation-functions is particularly emphasized. Within the framework of linear response theory (justified by the weakness of the basic interaction) the relation between fluctuation and dissipation is discussed. This general framework explains the particular power of neutron scattering as an experimental method. (author) 4 figs., 4 refs.
Pulsed spallation Neutron Sources
Energy Technology Data Exchange (ETDEWEB)
Carpenter, J.M. [Argonne National Lab., IL (United States)
1994-12-31
This paper reviews the early history of pulsed spallation neutron source development at Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provides a few examples of applications in fundamental condensed matter physics, materials science and technology.
Neutron Nucleic Acid Crystallography.
Chatake, Toshiyuki
2016-01-01
The hydration shells surrounding nucleic acids and hydrogen-bonding networks involving water molecules and nucleic acids are essential interactions for the structural stability and function of nucleic acids. Water molecules in the hydration shells influence various conformations of DNA and RNA by specific hydrogen-bonding networks, which often contribute to the chemical reactivity and molecular recognition of nucleic acids. However, X-ray crystallography could not provide a complete description of structural information with respect to hydrogen bonds. Indeed, X-ray crystallography is a powerful tool for determining the locations of water molecules, i.e., the location of the oxygen atom of H2O; however, it is very difficult to determine the orientation of the water molecules, i.e., the orientation of the two hydrogen atoms of H2O, because X-ray scattering from the hydrogen atom is very small.Neutron crystallography is a specialized tool for determining the positions of hydrogen atoms. Neutrons are not diffracted by electrons, but are diffracted by atomic nuclei; accordingly, neutron scattering lengths of hydrogen and its isotopes are comparable to those of non-hydrogen atoms. Therefore, neutron crystallography can determine both of the locations and orientations of water molecules. This chapter describes the current status of neutron nucleic acid crystallographic research as well as the basic principles of neutron diffraction experiments performed on nucleic acid crystals: materials, crystallization, diffraction experiments, and structure determination.
Energy Technology Data Exchange (ETDEWEB)
Bingham, Philip R [ORNL; Santos-Villalobos, Hector J [ORNL
2011-01-01
Coded aperture techniques have been applied to neutron radiography to address limitations in neutron flux and resolution of neutron detectors in a system labeled coded source imaging (CSI). By coding the neutron source, a magnified imaging system is designed with small spot size aperture holes (10 and 100 m) for improved resolution beyond the detector limits and with many holes in the aperture (50% open) to account for flux losses due to the small pinhole size. An introduction to neutron radiography and coded aperture imaging is presented. A system design is developed for a CSI system with a development of equations for limitations on the system based on the coded image requirements and the neutron source characteristics of size and divergence. Simulation has been applied to the design using McStas to provide qualitative measures of performance with simulations of pinhole array objects followed by a quantitative measure through simulation of a tilted edge and calculation of the modulation transfer function (MTF) from the line spread function. MTF results for both 100um and 10um aperture hole diameters show resolutions matching the hole diameters.
Bingham, Philip; Santos-Villalobos, Hector; Tobin, Ken
2011-03-01
Coded aperture techniques have been applied to neutron radiography to address limitations in neutron flux and resolution of neutron detectors in a system labeled coded source imaging (CSI). By coding the neutron source, a magnified imaging system is designed with small spot size aperture holes (10 and 100μm) for improved resolution beyond the detector limits and with many holes in the aperture (50% open) to account for flux losses due to the small pinhole size. An introduction to neutron radiography and coded aperture imaging is presented. A system design is developed for a CSI system with a development of equations for limitations on the system based on the coded image requirements and the neutron source characteristics of size and divergence. Simulation has been applied to the design using McStas to provide qualitative measures of performance with simulations of pinhole array objects followed by a quantitative measure through simulation of a tilted edge and calculation of the modulation transfer function (MTF) from the line spread function. MTF results for both 100μm and 10μm aperture hole diameters show resolutions matching the hole diameters.
Neutron scattering in Australia
Energy Technology Data Exchange (ETDEWEB)
Knott, R.B. [Australian Nuclear Science and Technology Organisation, Menai (Australia)
1994-12-31
Neutron scattering techniques have been part of the Australian scientific research community for the past three decades. The High Flux Australian Reactor (HIFAR) is a multi-use facility of modest performance that provides the only neutron source in the country suitable for neutron scattering. The limitations of HIFAR have been recognized and recently a Government initiated inquiry sought to evaluate the future needs of a neutron source. In essence, the inquiry suggested that a delay of several years would enable a number of key issues to be resolved, and therefore a more appropriate decision made. In the meantime, use of the present source is being optimized, and where necessary research is being undertaken at major overseas neutron facilities either on a formal or informal basis. Australia has, at present, a formal agreement with the Rutherford Appleton Laboratory (UK) for access to the spallation source ISIS. Various aspects of neutron scattering have been implemented on HIFAR, including investigations of the structure of biological relevant molecules. One aspect of these investigations will be presented. Preliminary results from a study of the interaction of the immunosuppressant drug, cyclosporin-A, with reconstituted membranes suggest that the hydrophobic drug interdigitated with lipid chains.
Generation of Spheres from Dental Epithelial Stem Cells
Natsiou, Despoina; Granchi, Zoraide; Mitsiadis, Thimios A.; Jimenez-Rojo, Lucia
2017-01-01
The in vitro three-dimensional sphere model has already been established as an important tool in fundamental sciences. This model facilitates the study of a variety of biological processes including stem cell/niche functions and tissue responses to injury and drugs. Here we describe the complete protocol for the in vitro formation of spheres originated from the epithelium of rodent incisors. In addition, we show that in these spheres cell proliferation is maintained, as well as the expression of several key molecules characterizing stem cells such as Sox2 and p63. These epithelial dentospheres could be used as an in vitro model system for stem cell research purposes. PMID:28154538
Oscillation effects upon film boiling from a sphere.
Schmidt, W. E.; Witte, L. C.
1972-01-01
Heat transfer rates from a silver-plated copper sphere, 0.75 in. in diameter, were studied by high speed photography during oscillations of the sphere in saturated liquid nitrogen and Freon-11. The oscillation frequencies ranged from zero to 13 Hz, and the amplitude-to-diameter ratio varied from zero to 2.67. The sphere was supported by a thin-walled stainless steel tube and carried a thermocouple attached near the lower stagnation point. A Fastax WF-3 16mm movie camera was used at about 2000 frames/sec. The differences in the vapor removal process at lower and higher oscillation frequencies are discussed.
Spherical interferometry for the characterization of precision spheres
Nicolaus, R. A.; Bartl, G.
2016-09-01
Interferometry with spherical wavefronts is usually used for characterizing precise optics. A special spherical interferometer was set up to measure the volume of high precision spheres used for the new definition of the SI unit kilogram, for which a fundamental constant, such as Planck’s constant h or Avogadro’s constant N A, was to be determined. Furthermore with this type of interferometer and with a special evaluating algorithm, absolute form deviations of spheres can be determined. With this knowledge, a sphere can be processed further to reach unrivaled small sphericity deviations.
From Ewald sphere to Ewald shell in nonlinear optics
Huang, Huang; Huang, Cheng-Ping; Zhang, Chao; Hong, Xu-Hao; Zhang, Xue-Jin; Qin, Yi-Qiang; Zhu, Yong-Yuan
2016-07-01
Ewald sphere is a simple vector scheme to depict the X-ray Bragg diffraction in a crystal. A similar method, known as the nonlinear Ewald sphere, was employed to illustrate optical frequency conversion processes. We extend the nonlinear Ewald sphere to the Ewald shell construction. With the Ewald shell, a variety of quasi-phase-matching (QPM) effects, such as the collective envelope effect associated with multiple QPM resonances, the enhanced second- harmonic generation due to multiple reciprocal vectors etc., are suggested theoretically and verified experimentally. By rotating the nonlinear photonic crystal sample, the dynamic evolution of these QPM effects has also been observed, which agreed well with the Ewald shell model.
Simulations of a supersymmetry inspired model on a fuzzy sphere
Energy Technology Data Exchange (ETDEWEB)
Volkholz, J. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Bietenholz, W. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2007-11-15
We present a numerical study of a two dimensional model of the Wess-Zumino type. We formulate this model on a sphere, where the fields are expanded in spherical harmonics. The sphere becomes fuzzy by a truncation in the angular momenta. This leads to a finite set of degrees of freedom without explicitly breaking the space symmetries. The corresponding field theory is expressed in terms of a matrix model, which can be simulated. We present first numerical results for the phase structure of a variant of this model on a fuzzy sphere. The prospect to restore exact supersymmetry in certain limits is under investigation. (orig.)
Stochastic hard-sphere dynamics for hydrodynamics of nonideal fluids.
Donev, Aleksandar; Alder, Berni J; Garcia, Alejandro L
2008-08-15
A novel stochastic fluid model is proposed with a nonideal structure factor consistent with compressibility, and adjustable transport coefficients. This stochastic hard-sphere dynamics (SHSD) algorithm is a modification of the direct simulation Monte Carlo algorithm and has several computational advantages over event-driven hard-sphere molecular dynamics. Surprisingly, SHSD results in an equation of state and a pair correlation function identical to that of a deterministic Hamiltonian system of penetrable spheres interacting with linear core pair potentials. The fluctuating hydrodynamic behavior of the SHSD fluid is verified for the Brownian motion of a nanoparticle suspended in a compressible solvent.
VMware vSphere 4 Administration Instant Reference
Lowe, Scott; Johnson, Matthew K
2009-01-01
The only quick reference guide to the number one virtualization product!. Get all your solutions about VMware's newest virtualization infrastructure software on the spot with this handy reference guide. Designed for quick access with special headings, thumb tabs, easy-to-read lists, and more, this book is the perfect companion to any comprehensive VMware guide, such as Mastering VMware vSphere 4 .: Covers the market-leading virtualization product, VMware's new vSphere 4; Offers a quick-access reference for your day-to-day administration of vSphere 4; Includes thumb tabs, secondary and tertiary
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
Energy Technology Data Exchange (ETDEWEB)
ZALIZNYAK,I.A.; LEE,S.H.
2004-07-30
Much of our understanding of the atomic-scale magnetic structure and the dynamical properties of solids and liquids was gained from neutron-scattering studies. Elastic and inelastic neutron spectroscopy provided physicists with an unprecedented, detailed access to spin structures, magnetic-excitation spectra, soft-modes and critical dynamics at magnetic-phase transitions, which is unrivaled by other experimental techniques. Because the neutron has no electric charge, it is an ideal weakly interacting and highly penetrating probe of matter's inner structure and dynamics. Unlike techniques using photon electric fields or charged particles (e.g., electrons, muons) that significantly modify the local electronic environment, neutron spectroscopy allows determination of a material's intrinsic, unperturbed physical properties. The method is not sensitive to extraneous charges, electric fields, and the imperfection of surface layers. Because the neutron is a highly penetrating and non-destructive probe, neutron spectroscopy can probe the microscopic properties of bulk materials (not just their surface layers) and study samples embedded in complex environments, such as cryostats, magnets, and pressure cells, which are essential for understanding the physical origins of magnetic phenomena. Neutron scattering is arguably the most powerful and versatile experimental tool for studying the microscopic properties of the magnetic materials. The magnitude of the cross-section of the neutron magnetic scattering is similar to the cross-section of nuclear scattering by short-range nuclear forces, and is large enough to provide measurable scattering by the ordered magnetic structures and electron spin fluctuations. In the half-a-century or so that has passed since neutron beams with sufficient intensity for scattering applications became available with the advent of the nuclear reactors, they have became indispensable tools for studying a variety of important areas of modern
Fundamental neutron physics at LANSCE
Energy Technology Data Exchange (ETDEWEB)
Greene, G.
1995-10-01
Modern neutron sources and science share a common origin in mid-20th-century scientific investigations concerned with the study of the fundamental interactions between elementary particles. Since the time of that common origin, neutron science and the study of elementary particles have evolved into quite disparate disciplines. The neutron became recognized as a powerful tool for studying condensed matter with modern neutron sources being primarily used (and justified) as tools for neutron scattering and materials science research. The study of elementary particles has, of course, led to the development of rather different tools and is now dominated by activities performed at extremely high energies. Notwithstanding this trend, the study of fundamental interactions using neutrons has continued and remains a vigorous activity at many contemporary neutron sources. This research, like neutron scattering research, has benefited enormously by the development of modern high-flux neutron facilities. Future sources, particularly high-power spallation sources, offer exciting possibilities for continuing this research.
Transuranics Transmutation Using Neutrons Spectrum from Spallation Reactions
Directory of Open Access Journals (Sweden)
Maurício Gilberti
2015-01-01
Full Text Available The aim is to analyse the neutron spectrum influence in a hybrid system ADS-fission inducing transuranics (TRUs transmutation. A simple model consisting of an Accelerator-Driven Subcritical (ADS system containing spallation target, moderator or coolant, and spheres of actinides, “fuel,” at different locations in the system was modelled. The simulation was performed using the MCNPX 2.6.0 particles transport code evaluating capture (n,γ and fission (n,f reactions, as well as the burnup of actinides. The goal is to examine the behaviour and influences of the hard neutron spectrum from spallation reactions in the transmutation, without the contribution or interference of multiplier subcritical medium, and compare the results with those obtained from the neutron fission spectrum. The results show that the transmutation efficiency is independent of the spallation target material used, and the neutrons spectrum from spallation does not contribute to increased rates of actinides transmutation even in the vicinity of the target.
Radiography with polarised neutrons
Energy Technology Data Exchange (ETDEWEB)
Schulz, Michael L.
2010-08-20
In this thesis I present a new technique for the spatially resolved investigation of the magnetic properties of bulk samples. Standard one dimensional neutron depolarisation analysis is combined with neutron radiography to a method we call Neutron Depolarisation Imaging (NDI). The experimental setup which was installed at the neutron radiography beam line ANTARES at FRM II consists of a double crystal monochromator, neutron polariser, spin flipper, polarisation analyser and a position sensitive CCD detector. A comprehensive discussion of the requirements for these components is given and the limitations of the method are shown. The maximum spatial resolution which can be achieved with a neutron radiography setup is determined by the collimation of the neutron beam and the distance between sample and detector. Different types of polarisers have been tested and their advantages and disadvantages are discussed. A double crystal monochromator and a new type of polariser employing polarising neutron supermirrors based on the principle of an optical periscope were developed and tested during this work. Furthermore, NDI measurements on various samples of the weakly ferromagnetic materials Pd{sub 1-x}Ni{sub x} and Ni{sub 3}Al are presented. Neutron depolarisation radiography and tomography measurements were conducted with a spatial resolution as high as 0.3 mm on Pd{sub 1-x}Ni{sub x} and Ni{sub 3}Al samples. The feasibility of NDI experiments under hydrostatic pressures up to 10 kbar was shown on a sample of Ni{sub 3}Al using a modified Cu:Be clamp cell. A decrease of the ordering temperature by 2 K under hydrostatic pressure was determined from the NDI measurements and shows the potential of the method for further high pressure experiments. Additionally a method was developed which in principle allows to obtain the intrinsic dependence of the ordering temperature T{sub C} on the ordered moment Ms from NDI measurements on inhomogeneous samples containing regions with
Calibration of indium response functions in an Au-In-BSE system up to 800 MeV.
Wang, Zhonglu; Howell, Rebecca M; Burgett, Eric A; Kry, Stephen F; Hertel, Nolan E; Salehpour, Mohammad
2010-06-01
Calibration of the response functions of a gold (Au)-indium (In) dual foil Bonner sphere extended (BSE) system was described. The response of the In and Au foil of the system was calculated using MCNPX code with different activation cross-sectional libraries: (ACTL and ENDF VI for gold and ACTL and 532DOS2 for In). To verify and correct the calculated response functions the Bonner sphere set (BSS) was irradiated using (252)Cf and (241)AmBe sources of known neutron strengths for neutrons ranging from thermal to 20 MeV, and was irradiated at the 800-MeV neutron beam of the Los Alamos Neutron Science Center. The neutron spectrum of the 800 MeV beam was determined using time-of-flight (TOF) technique. We observed that the uncertainty of activation cross section in the resonance region can result in great uncertainty in the MCNPX-calculated response functions of activation foil-based BSS. The MCNPX-calculated response functions must be corrected using neutron sources of known spectrum and strength.
TIDALLY DRIVEN DYNAMOS IN A ROTATING SPHERE
Energy Technology Data Exchange (ETDEWEB)
Cébron, D.; Hollerbach, R., E-mail: david.cebron@ujf-grenoble.fr, E-mail: r.hollerbach@leeds.ac.uk [Institut für Geophysik, Sonneggstrasse 5, ETH Zürich, Zürich CH-8092 (Switzerland)
2014-07-01
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.
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.
Reducing neutron multiplicity counting bias for plutonium warhead authentication
Energy Technology Data Exchange (ETDEWEB)
Goettsche, Malte
2015-06-05
Confidence in future nuclear arms control agreements could be enhanced by direct verification of warheads. It would include warhead authentication. This is the assessment based on measurements whether a declaration that a specific item is a nuclear warhead is true. An information barrier can be used to protect sensitive information during measurements. It could for example show whether attributes such as a fissile mass exceeding a threshold are met without indicating detailed measurement results. Neutron multiplicity measurements would be able to assess a plutonium fissile mass attribute if it were possible to show that their bias is low. Plutonium measurements have been conducted with the He-3 based Passive Scrap Multiplicity Counter. The measurement data has been used as a reference to test the capacity of the Monte Carlo code MCNPX-PoliMi to simulate neutron multiplicity measurements. The simulation results with their uncertainties are in agreement with the experimental results. It is essential to use cross-sections which include neutron scattering with the detector's polyethylene molecular structure. Further MCNPX-PoliMi simulations have been conducted in order to study bias that occurs when measuring samples with large plutonium masses such as warheads. Simulation results of solid and hollow metal spheres up to 6000 g show that the masses are underpredicted by as much as 20%. The main source of this bias has been identified in the false assumption that the neutron multiplication does not depend on the position where a spontaneous fission event occurred. The multiplication refers to the total number of neutrons leaking a sample after a primary spontaneous fission event, taking induced fission into consideration. The correction of the analysis has been derived and implemented in a MATLAB code. It depends on four geometry-dependent correction coefficients. When the sample configuration is fully known, these can be exactly determined and remove this type of
Neutron-Induced Failures in Semiconductor Devices
Energy Technology Data Exchange (ETDEWEB)
Wender, Stephen Arthur [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-04-06
This slide presentation explores single event effect, environmental neutron flux, system response, the Los Alamos Neutron Science Center (LANSCE) neutron testing facility, examples of SEE measurements, and recent interest in thermal neutrons.
[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
An elastic two-sphere swimmer in Stokes flow
Nasouri, Babak; Elfring, Gwynn J
2016-01-01
Swimming at low Reynolds number in Newtonian fluids is only possible through non-reciprocal 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 which changes its length periodically. We show that the deformations of the body are non-reciprocal 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 qualitatively alter swimming dynamics and should not be neglected in analyzing swimming in Stokes flows.
An elastic two-sphere swimmer in Stokes flow
Nasouri, Babak; Elfring, Gwynn
2016-11-01
Swimming at low Reynolds number in Newtonian fluids is only possible through non-reciprocal 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 which changes its length periodically. We show that the deformations of the body are non-reciprocal 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 qualitatively alter swimming dynamics and should not be neglected in analyzing swimming in Stokes flows.
Synthesis of Nanometer-sized Mesoporous Oxide Spheres
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A few hundreds nanometer-sized mesoporous silica and alumina spheres were synthesized in organic solvents. The impacts of ammonia, N,N-dimethylformamide (DMF) and stirring speed were also investigated.
A Breakthrough in Sphere Packing: The Search for Magic Functions
Laat, D. de; Vallentin, F.
2016-01-01
This paper by David de Laat and Frank Vallentin is an exposition about the two recent breakthrough results in the theory of sphere packings. It includes an interview with Henry Cohn, Abhinav Kumar, Stephen D. Miller and Maryna Viazovska.
Numerical simulation of negative Magnus force on a rotating sphere
Muto, Masaya; Tsubokura, Makoto; Oshima, Nobuyuki
2010-11-01
Flow characteristics and fluid force on a sphere rotating along with axis perpendicular to mean air flow were investigated using Large Eddy Simulation at two different Reynolds numbers of 10,000 and 200,000. As a result of simulation, opposite flow characteristics around the sphere and displacement of the separation point were visualized depending on the Reynolds number even though the sphere rotates at the same rotation speed according to the Reynolds number. When Reynolds number is 10,000, flow characteristics agree with the flow field explained in the Magnus effect. However sphere rotates at the same rotation speed while increasing Reynolds number to 200,000, separation point moves in opposite direction and wake appears in the different direction. The reason of the negative Magnus force was discussed in terms of the boundary layer transition on the surface.
Dynamic equivalences in the hard-sphere dynamic universality class.
López-Flores, Leticia; Ruíz-Estrada, Honorina; Chávez-Páez, Martín; Medina-Noyola, Magdaleno
2013-10-01
We perform systematic simulation experiments on model systems with soft-sphere repulsive interactions to test the predicted dynamic equivalence between soft-sphere liquids with similar static structure. For this we compare the simulated dynamics (mean squared displacement, intermediate scattering function, α-relaxation time, etc.) of different soft-sphere systems, between them and with the hard-sphere liquid. We then show that the referred dynamic equivalence does not depend on the (Newtonian or Brownian) nature of the microscopic laws of motion of the constituent particles, and hence, applies independently to colloidal and to atomic simple liquids. Finally, we verify another more recently proposed dynamic equivalence, this time between the long-time dynamics of an atomic liquid and its corresponding Brownian fluid (i.e., the Brownian system with the same interaction potential).
The Blaschke conjecture and great circle fibrations of spheres
2001-01-01
We construct an explicit diffeomorphism taking any fibration of a sphere by great circles into the Hopf fibration, using elementary geometry--indeed the diffeomorphism is a local (differential) invariant, algebraic in derivatives.
Method for producing dustless graphite spheres from waste graphite fines
Pappano, Peter J; Rogers, Michael R
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.
A Reaction Sphere for High Performance Attitude Control Project
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...
ANOMIE DEVELOPMENT IN RELIGIOUS SPHERE OF POSTSOVIET SOCIETY
Directory of Open Access Journals (Sweden)
Pletnev Alexander Vladislavovich
2013-04-01
Full Text Available In the current article the author analyzes influence of amendments in the religious sphere of postsoviet society for the increase of anomie in it. He indicates main factors that influence the anomie and charactarize specific features of religious sphere of modern Russian society. They are religious variety, caused by missionery activity and restore of traditional confessions (Orthodox, Islam, Judiasm, Buddism, Lutheranism, and also actualization of the religious identity matter, the phenomen of “out of confession herecy” and religious conflicts. According to the researcher opinion, amendments in the spiritual sphere influence the studied phenomen as well as trasnformation of political and economic system, caused by transfer from communism to democracy and from planning to market economy. The possible ways of anomie decrease via religious sphere of the society such as increase of Orthodox church belivers, adaptation of its tradition and practics, new religious cult inctitualization are indicated in this article as well.
Experimental evidence of zero forward scattering by magnetic spheres.
Mehta, R V; Patel, Rajesh; Desai, Rucha; Upadhyay, R V; Parekh, Kinnari
2006-03-31
Magnetically induced diffraction patterns by micron sized magnetic spheres dispersed in a ferrofluid disappear at a certain critical magnetic field. This critical field is found to depend on the concentration of the ferrofluid and on the volume of the magnetic spheres. We attribute this effect to the zero forward scattering by magnetic spheres as predicted by Kerker, Wang, and Giles [J. Opt. Soc. Am. 73, 765 (1983)]. We suggest that such a dispersion can be used to study the optical analogues of localization of electrons in condensed matter, the Hall effect, and the anisotropic diffusion, etc. The combination of the micron sized magnetic spheres and the ferrofluid will also be useful to design magnetically tunable photonic devices.
Forces encountered by a sphere during impact into sand
Joubaud, Sylvain; Homan, Tess; Gasteuil, Y.; Lohse, Detlef; van der Meer, Devaraj
2014-12-01
We describe direct measurements of the acceleration of an object impacting on a loosely packed granular bed under various pressures, using an instrumented sphere. The sphere acts as a noninvasive probe that measures and continuously transmits the acceleration as it penetrates into the sand, using a radio signal. The time-resolved acceleration of the sphere reveals the detailed dynamics during the impact that cannot be resolved from the position information alone. Because of the unobstructed penetration, we see a downward acceleration of the sphere at the moment the air cavity collapses. The compressibility of the sand bed is observed through the oscillatory behavior of the acceleration curve for various ambient pressures; it shows the influence of interstitial air on the compaction of the sand as a function of time.
Phonon contribution to the entropy of hard-sphere crystals.
Elser, Veit
2014-05-01
Comparing the entropies of hard spheres in the limit of close packing, for different stacking sequences of the hexagonal layers, has been a challenge because the differences are so small. Here we present a method based on a "sticky-sphere" model by which the system interpolates between hard spheres in one limit and a harmonic crystal in the other. For the fcc and hcp stackings we have calculated the entropy difference in the harmonic (sticky) limit, as well as the differences in the free energy change upon removing the stickiness in the model. The former, or phonon entropy, accounts for most of the entropy difference. Our value for the net entropy difference, Δs = 0.001164(8)k(B) per sphere, is in excellent agreement with the best previous estimate by Mau and Huse [Phys. Rev. E 59, 4396 (1999)].
On isometric extension problem between two unit spheres
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
In this paper we introduce the isometric extension problem of isometric mappings between two unit spheres. Some important results of the related problems are outlined and the recent progress is mentioned.
On isometric extension problem between two unit spheres
Institute of Scientific and Technical Information of China (English)
Ding GuangGui
2009-01-01
In this paper we introduce the isometric extension problem of isometric mappings between two unit spheres.Some important results of the related problems are outlined and the recent progress is mentioned.
Diffusive Wave Spectroscopy of a random close packing of spheres
Crassous, J.
2007-06-01
We are interested in the propagation of light in a random packing of dielectric spheres within the geometrical optics approximation. Numerical simulations are performed using a ray tracing algorithm. The effective refractive indexes and the transport mean free path are computed for different refractive indexes of spheres and intersticial media. The variations of the optical path length under small deformations of the spheres assembly are also computed and compared to the results of Diffusive Wave Spectroscopy experiments. Finally, we propose a measure of the transport mean free path and a Diffusive Wave Spectroscopy experiment on a packing of glass spheres. The results of those experiments agree with the predictions of this ray tracing approach.
The Volume of a Sphere: A Chinese Derivation.
Swetz, Frank J.
1995-01-01
Examines how ancient Chinese mathematicians attempted to correct an error concerning the volume of a sphere in the Nine Chapters on the Mathematical Art, a compendium of the mathematics known and used in China in ancient times. (MKR)
Wind speed and direction measurements using the sphere anemometer
Heisselmann, Hendrik; Hoelling, Michael; Peinke, Joachim
2009-11-01
In times of growing energy demand, the importance of wind energy is rapidly increasing and so is the need for accurate wind speed and direction measurements. The widely spread cup anemometers show significant over-speeding under turbulent wind conditions as inherent in atmospherical flows while being solely capable of detecting the wind speed. Therefore, we propose the newly developed sphere anemometer as a simple an robust sensor for direction and velocity measurements. The sphere anemometer exploits the velocity-dependent deflection of a tube, which is the order of μm and can be detected by means of a light pointer as used in atomic force microscopes. In comparative measurements under laboratory conditions the sphere anemometer showed a significantly higher temporal resolution then cup anemometers while it does not exhibit any over-speeding. Additionally, results of atmospherical wind measurements with the sphere anemometer and state-of-the-art cup anemometry are presented.
Neutron drip transition in accreting and nonaccreting neutron star crusts
Chamel, N; Zdunik, J L; Haensel, P
2015-01-01
The neutron-drip transition in the dense matter constituting the interior of neutron stars generally refers to the appearance of unbound neutrons as the matter density reaches some threshold density $\\rho_\\textrm{drip}$. This transition has been mainly studied under the cold catalyzed matter hypothesis. However, this assumption is unrealistic for accreting neutron stars. After examining the physical processes that are thought to be allowed in both accreting and nonaccreting neutron stars, suitable conditions for the onset of neutron drip are derived and general analytical expressions for the neutron drip density and pressure are obtained. Moreover, we show that the neutron-drip transition occurs at lower density and pressure than those predicted within the mean-nucleus approximation. This transition is studied numerically for various initial composition of the ashes from X-ray bursts and superbursts using microscopic nuclear mass models.
Satellite Relative Motion Control for MIT’s SPHERES Program
2012-03-01
firing combinations of its twelve cold gas thrusters [2]. These thrusters either fire at a specific value or they do not fire at all. This on-off...Satellite Relative Motion Control for MIT’s SPHERES Program THESIS Samuel P. Barbaro, Second Lieutenant, USAF AFIT/ GA /ENY/12-M02 DEPARTMENT OF THE...United States. AFIT/ GA /ENY/12-M02 Satellite Relative Motion Control for MIT’s SPHERES Program THESIS Presented to the Faculty Department of
Sphere Lower Bound for Rotated Lattice Constellations in Fading Channels
Fabregas, Albert Guillen i
2007-01-01
We study the error probability performance of rotated lattice constellations in frequency-flat Nakagami-$m$ block-fading channels. In particular, we use the sphere lower bound on the underlying infinite lattice as a performance benchmark. We show that the sphere lower bound has full diversity. We observe that optimally rotated lattices with largest known minimum product distance perform very close to the lower bound, while the ensemble of random rotations is shown to lack diversity and perform far from it.
Magnetic relaxation in chain-of-spheres ferromagnetic particles
Yang, J S
2002-01-01
The thermal activation of elongated ferromagnetic particles is analyzed using a chain-of-spheres model. The spheres within the chain are assumed to be coupled magnetically with dipolar interaction. The effect of uniaxial magnetocrystalline anisotropy along the chain is also taken into account. It was shown that the behavior of thermal switching critically depends on the relative strength of shape anisotropy and magnetocrystalline anisotropy, field orientation, sweep field rate and temperature.
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.
Low Velocity Sphere Impact of a Soda Lime Silicate Glass
Energy Technology Data Exchange (ETDEWEB)
Wereszczak, Andrew A [ORNL; Fox, Ethan E [ORNL; Morrissey, Timothy G [ORNL; Vuono, Daniel J [ORNL
2011-10-01
This report summarizes TARDEC-sponsored work at Oak Ridge National Laboratory (ORNL) during the FY11 involving low velocity (< 30 m/s or < 65 mph) ball impact testing of Starphire soda lime silicate glass. The intent was to better understand low velocity impact response in the Starphire for sphere densities that bracketed that of rock. Five sphere materials were used: borosilicate glass, soda-lime silicate glass, steel, silicon nitride, and alumina. A gas gun was fabricated to produce controlled velocity delivery of the spheres against Starphire tile targets. Minimum impact velocities to initiate fracture in the Starphire were measured and interpreted in context to the kinetic energy of impact and the elastic property mismatch between the any of the five sphere-Starphire-target combinations. The primary observations from this low velocity (< 30 m/s or < 65 mph) testing were: (1) Frictional effects contribute to fracture initiation. (2) Spheres with a lower elastic modulus require less force to initiate fracture in the Starphire than spheres with a higher elastic modulus. (3) Contact-induced fracture did not initiate in the Starphire SLS for impact kinetic energies < 150 mJ. Fracture sometimes initiated or kinetic energies between {approx} 150-1100 mJ; however, it tended to occur when lower elastic modulus spheres were impacting it. Contact-induced fracture would always occur for impact energies > 1100 mJ. (4) The force necessary to initiate contact-induced fracture is higher under dynamic or impact conditions than it is under quasi-static indentation conditions. (5) Among the five used sphere materials, silicon nitride was the closest match to 'rock' in terms of both density and (probably) elastic modulus.
Preparation of Nanocrystalline MoS2 Hollow Spheres
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
Nanocrystalline MoS2 with hollow spherical morphology has been prepared by the hydrothermal method. The products are characterized by means of X-ray powder diffraction, transmission electron microscopy and high-resolution transmission electron microscopy. The experimental results give the evidence that the sample is consists of hollow spheres 400～600 nm in diameter, and there is much whisker on the surface of MoS2 hollow sphere.
Existence of conformal metrics on spheres with prescribed Paneitz curvature
Ben-Ayed, M
2003-01-01
In this paper we study the problem of prescribing a fourth order conformal invariant (the Paneitz curvature) on the n-spheres, with n >= 5. Using tools from the theory of critical points at infinity, we provide some topological conditions on the level sets of a given function defined on the sphere, under which we prove the existence of conformal metric with prescribed Paneitz curvature.
Semiclassical and quantum Liouville theory on the sphere
Menotti, Pietro; Vajente, Gabriele
2004-01-01
We solve the Riemann-Hilbert problem on the sphere topology for three singularities of finite strength and a fourth one infinitesimal, by determining perturbatively the Poincare' accessory parameters. In this way we compute the semiclassical four point vertex function with three finite charges and a fourth infinitesimal. Some of the results are extended to the case of n finite charges and m infinitesimal. With the same technique we compute the exact Green function on the sphere with three fin...