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 6LiI(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 3He 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 3He 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)
Response Matrix of a Bonner Spheres Spectrometer with 3 He Detector
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 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)
Comparing standard Bonner spheres and high-sensitivity Bonner cylinders
Standard Bonner spheres and proposed high-sensitivity Bonner cylinders were calibrated in a neutron calibration room, using a 252Cf source. The Bonner sphere system consists of 11 polyethylene (PE) spheres of various diameters and 4 extended spheres that comprise embedded metal shells. Similar to the design of Bonner spheres, a set of Bonner cylinders was assembled using a large cylindrical 3He tube as the central probe, which was wrapped using various thicknesses of PE. A layer of lead was employed inside one of the PE cylinders to increase the detection efficiency of high-energy neutrons. The central neutron probe used in the Bonner cylinders exhibited an efficiency of ∼17.9 times higher than that of the Bonner spheres. However, compared with the Bonner spheres, the Bonner cylinders are not fully symmetric in their geometry, exhibiting angular dependence in their responses to incoming neutrons. Using a series of calculations and measurements, this study presents a systematic comparison between Bonner spheres and cylinders in terms of their response functions, detection efficiencies, angular dependences and spectrum unfolding. A high-sensitivity Bonner cylinder spectrometer was developed to facilitate neutron spectrum measurement in low-intensity environments such as the site boundaries of nuclear facilities or accelerators. The proposed spectrometer system comprises 11 cylinders of various PE thicknesses and an extended cylinder with an embedded lead shell. Compared with the standard Bonner spheres, the detection efficiency of the device increased by a factor of >10 because a large 3He tube was employed. However, the Bonner cylinders are not symmetric in their polar angle, and this causes the advantage of isotropic response to be lost. A systematic comparison was conducted between the standard Bonner spheres and the proposed Bonner cylinders, examining their response functions, calibration measurements, angular dependences and spectrum unfolding. (authors)
A realistic geometry model of a Bonner sphere system with a spherical 3He-filled proportional counter and 12 polyethylene moderating spheres with diameters ranging from 7,62 cm (3'') to 45,72 cm (18'') is introduced. The MCNP Monte Carlo computer code is used to calculate the responses of this Bonner sphere system to monoenergetic neutrons in the energy range between 1 meV to 20 MeV. The relative uncertainties of the responses due to the Monte Carlo calculations are less than 1% for spheres up to 30,48 cm (12'') in diameter and less than 2% for the 15'' and 18'' spheres. Resonances in the carbon cross section are seen as significant structures in the response functions. Additional calculations were made to study the influence of the 3He number density and the polyethylene mass density on the response as well as the angular dependence of the Bonner sphere system. The calculated responses can be adjusted to a large set of calibration measurements with only a single fit factor common to all sphere diameters and energies. (orig.)
Bonner sphere spectrometer: A CONRAD project intercomparison
The most widely used system in neutrons measurements for radiological protection is the Bonner Sphere Spectrometer (BSS). The BSS is applied to characterise neutron fields from thermal to hundreds of MeVs. The Nuclear Regulatory Authority of Argentina has developed and calibrated its own BSS system, which has been used in many Argentine facilities during the last eleven years when the regulatory activities have been carried out. Following this line of work, the present development has been done in the framework of the International Intercomparison ''Uncertainty Assessment in Computational Dosimetry: A Comparison of Approaches'', organised by the CONRAD project (Coordinated Network for Radiation Dosimetry). The aim of intercomparison was to study the response of a proposed widespread neutron spectrometer exposed to arbitrary neutron sources. With this goal in mind, the experimental system has been modelled in detail according to the provided layout. The modelled neutron spectrometer consists of 8 Bonner spheres made of high-density polyethylene (δ=0.95gc/m3). The spheres diameter range between 2' and 12' in addition to a 12' diameter leadloaded sphere. The defined active thermal neutron detector, a 6LiI(Eu) scintillation crystal, was according to provided dimensions (4 mm (diameter) by 4 mm (height)), and located at each sphere centre. Irradiation geometry has been according to measurements carried out during the experimental part of the intercomparison. The theoretical neutron response has been calculated applying the well-known MCNPX code. The complete response matrix of the system has been obtained in the energy range between thermal neutron and 17.77 MeV. The obtained system theoretical response to ISO standard 241Am-Be and 252Cf sources shows an excellent agreement with experimental results provided by EURADOS. This response can be used to calibrate the system. The obtained matrix response can be coupled to any unfolding code to complete the BSS system used in
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. PMID:25948828
Measurement with Bonner spheres spectrometer in pulsed neutron fields
Králik, M.; Turek, Karel; Vondráček, V.; Krása, Josef; Velyhan, Andriy; Scholz, M.; Ivanova-Stanik, I.M.
2010-01-01
Roč. 45, č. 10 (2010), s. 1245-1249. ISSN 1350-4487. [Neutron and Ion Dosimetry Symposium /11./. Cape Town, 12.10.2009-16.10.2009] Institutional research plan: CEZ:AV0Z10480505; CEZ:AV0Z10100523 Keywords : neutron spectrometry * bonner spheres * track detector s Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.019, year: 2010
Photoneutron spectrum measured with Bonner Spheres in Planetary method mode
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)
Real-Time Bonner Sphere Spectrometry on the HL-2A Tokamak
Jiang, Chunyu; Cao, Jing; Jiang, Xiaofei; Zhao, Yanfeng; Song, Xianying; Yin, Zejie
2016-06-01
Real-time Bonner sphere spectrometry (BSS) at the HL-2A tokamak for the neutron spectrum diagnostic is described. The spectrometer consists of eight different size Bonner spheres made of polyethylene and with a 3helium-filled detector in the center, pre-amplifiers, and parallel-processing data acquisition system (DAQ). Dynamic neutrons from plasma discharges of the HL-2A tokamak were measured and the real-time neutron spectrum was presented. supported by National Natural Science Foundation of China (No. 11375195) and the National Magnetic Confinement Fusion Science Program of China (No. 2013GB104003)
The response of a Bonner sphere spectrometer to charged hadrons
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. (authors)
Application of Neural Networks for unfolding neutron spectra measured by means of Bonner Spheres
A Neural Network structure has been used for unfolding neutron spectra measured by means of a Bonner Sphere Spectrometer set. The present work used the 'Stuttgart Neural Network Simulator' as the interface for designing, training and validation of a 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 10 MeV. Two types of neutron spectra were numerically investigated: monoenergetic and continuous. Good results were obtained, indicating that the Neural Network can be considered an interesting alternative among the neutron spectrum unfolding methodologies
Photoneutron spectrum measured with a Bonner sphere spectrometer in planetary method mode
The spectrum of photoneutrons produced by a 15 MV VARIAN iX linac working in Bremsstrahlung mode was measured a 100 cm from the IC located 5 cm-depth of a solid water phantom. The spectrum was measured with a Bonner spheres spectrometer with pairs of TLDs as thermal neutron detector. The measurements were carried out using the spectrometer in planetary method mode where a single shoot of the LINAC was required. - Highlights: • The photoneutrons spectrum of a 15 MV LINAC was measured. • A Bonner sphere spectrometer with pairs of TLDs were used. • Measurements were carried out with the BSS in Planetary method mode. • Measured spectrum is compared with calculated spectrum
Response matrix of an extended Bonner sphere system
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 11C 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
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)
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, ...
Measurement of spectrum and dose rate of natural neuron using Bonner spheres
The natural neutron spectrum indoor was measured by using Bonner spheres spectrometer in Hefei. A Bonner sphere spectrometer with maximum entropy method was used to unfold neutron spectrum. Then according to the fluence to dose coefficient, the dose rate was calculated. The software EXPACS Ver2.21 based on the analytic methods for simulating the natural neutron spectrum was adopted to verify the neutron spectrum, and the BF3 natural neutron monitors were used to confirm the effective dose rate. The verification and analysis indicated that the results from Bonner spheres spectrometer consistent with others. The ambient dose equivalent rate of neutron in Hefei was between 2.6 nSv · h-1 and 14.38 nSv · h-1. (authors)
Test of the Bonner Sphere Spectrometer Response Matrix in the 252Cf Neutron Field
Full text: Since its development in 1960, a Bonner sphere spectrometer (BSS) has been the only instrument, which enables the spectral neutron fluence to be measured in a wide range of energies from thermal up to 20 MeV. Its resolution is poor but sufficient for dosimetric specification of neutron fields at workplaces. Experimentally determined BSS count rates depends mainly on the accuracy of the response matrix characterising certain type of BSS. At presemt the BSS response matrices are calculate by neutron transport Monte Carlo codes which allow detailed description of the BSS setup. The best verification of calculated response matrix is a calibration of the BSS in fields of monoenergetic neutrons. As so as these fields are not simply achievable a simple method how to test quality of BSS response matrix in the neutron field of 252Cf source is described. Applying distance variation method we get count rates of the BSS in the 252Cf field from which contributions of scattered neutrons and influence of finite detector and source dimensions were removed. These count rates are compared with the integrals of pure 252Cf spectrum and responses for individual spheres of the BSS. Disagreement indicates for which sphere the response is not properly determined. (author)
Experimental tests of the Bonner Sphere spectrometer using filtered neutron beams
The operation of a Bonner Sphere neutron detector system has been tested using several unqiue neutron sources. Filtered neutron beams at beamport F at the University of Missouri Research Reactor (MURR) were used as a source of known quasi-monoenergetic neutrons for precise energy spectra analysis and calibration. A PuBe neutron source was used for absolute flux magnitude and spectral verification. Two computer codes, SWIFT and Least Squares Unfolding Techniques (LSUT), were used to unfold the experimental data. Several operational problems were encountered during these tests. First, many of the measurements involved neutron beam measurements in which the beams had a smaller diameter than the moderating spheres. This caused partial illumination of the spheres for which correction factors had to be developed. A partial illumination correction factor has been proposed and tested to account for this problem. Second, reactor core gamma-ray contamination in the neutron beams was of sufficient magnitude to interfere with some measurements. Gamma-ray background subtraction techniques using a multi-channel analyzer were used to alleviate this problem. After correcting for gamma-ray background and applying partial illumination correction factors, unfolded neutron spectra from the unfolding codes gave good results for most neutron sources. In particular the SWIFT results were quite good, exceeding expectations in terms of energy resolution and spectral accuracy. (orig.)
Determining the neutron spectrum of 241Am-Be and 252Cf sources using bonner sphere spectrometer
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.
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...
Bonner sphere neutron spectrometry at spent fuel casks
Rimpler, A
2002-01-01
For transport and interim storage of spent fuel elements from power reactors and vitrified highly active waste (HAW) from reprocessing, various types of casks are used. The radiation exposure of the personnel during transportation and storage of these casks is caused by mixed photon-neutron fields and, frequently, the neutron dose is predominant. In operational radiation protection, survey meters and even personal dosemeters with imperfect energy dependence of the dose-equivalent response are used, i.e. the fluence response of the devices does not match the fluence-to-dose equivalent conversion function. In order to achieve more accurate dosimetric information and to investigate the performance of dosemeters, spectrometric investigations of the neutron fields are necessary. Therefore, fluence spectra and dose rates were measured by means of a simple portable Bonner multisphere spectrometer (BSS). The paper describes briefly the experimental set-up and evaluation procedure. Measured spectra for different locat...
Neutron measurements in the Vandellos II nuclear power plant with a Bonner sphere system
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 Vandellos 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. (authors)
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 http://nukeisit.gatech.edu/bums
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...
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 were obtained, indicating that the Neural Network can be considered an interesting alternative among the neutron spectrum unfolding methodologies. (author)
NSDUAZ unfolding package for neutron spectrometry and dosimetry with Bonner spheres
NSDUAZ (Neutron Spectrometry and Dosimetry for the Universidad Autonoma de Zacatecas) is a user friendly neutron unfolding package for Bonner sphere spectrometer with 6Lil(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 10-8 up to 231.2 MeV. (Author)
NSDUAZ unfolding package for neutron spectrometry and dosimetry with Bonner spheres
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)
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
Monte Carlo calculation of the response matrix of a Bonner spheres spectrometer
The Bonner spheres spectrometer is utilized to estimate the neutron spectrum of neutrons from thermal up to several MeV neutrons. Its response is increased to few GeV neutrons by introducing large Z materials as inner shells. To use the spectrometer a matrix response and an unfolding method are required; these are crucial to assure the quality of spectrometer output. The response matrix of a Bonner sphere spectrometer was calculated by use of the MCNP code. As thermal neutron counter the spectrometer has a 0.4 θ x 0.4 cm2 6LiI(Eu) scintillator which is located at the centre of a set of polyethylene spheres. The response functions were calculated for 0, 2, 3, 5, 8, 10, and 12 inches-diameter polyethylene spheres for neutrons whose energy goes from 10-8 to 100 MeV. For energies from 10-8 to 20 MeV the MCNP4C code was utilized while for neutrons from 20 to 100 MeV calculations were carried out with MCNPX code. The response functions were compared with those reported in the literature. (author)
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
Comparison between standard unfolding and Bayesian methods in Bonner spheres neutron spectrometry
Medkour Ishak-Boushaki, G., 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); Allab, M. [Laboratoire SNIRM-Faculte de Physique, Universite des Sciences et de la Technologie Houari Boumediene, BP 32 El-Alia BabEzzouar, Algiers (Algeria)
2012-10-11
This paper compares the use of both standard unfolding and Bayesian methods to analyze data extracted from neutron spectrometric measurements with a view to deriving some integral quantities characterizing a neutron field. We consider, as an example, the determination of the total neutron fluence and dose in the vicinity of an Am-Be source from Bonner spheres measurements. It is shown that the Bayesian analysis provides a rigorous estimation of these quantities and their correlated uncertainties and overcomes difficulties encountered in the standard unfolding methods.
Comparison between standard unfolding and Bayesian methods in Bonner spheres neutron spectrometry
This paper compares the use of both standard unfolding and Bayesian methods to analyze data extracted from neutron spectrometric measurements with a view to deriving some integral quantities characterizing a neutron field. We consider, as an example, the determination of the total neutron fluence and dose in the vicinity of an Am–Be source from Bonner spheres measurements. It is shown that the Bayesian analysis provides a rigorous estimation of these quantities and their correlated uncertainties and overcomes difficulties encountered in the standard unfolding methods.
The spectra of neutrons outside the plasma focus device PF-1000 with an upper energy limit of ≅1 MJ was measured using a Bonner spheres spectrometer in which the active detector of thermal neutrons was replaced by nine thermoluminescent chips. As an a priori spectrum for the unfolding procedure, the spectrum calculated by means of the Monte Carlo method with a simplified model of the discharge chamber was selected. Differences between unfolded and calculated spectra are discussed with respect to properties of the discharge vessel and the laboratory layout.
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)
Spectral analysis of some fission neutron sources with the SOHO code from BONNER sphere data
For several tests fission neutron sources particularly 252Cf bare and D2O moderated, we present some spectral analysis results obtained with the new iterative code SOHO from BONNER spheres data. The approximative solutions are obtained upon discretization of the Fredholm Equation of the first kind whose Resolution Function is experimentally known and mathematically defined by the Log-Normal Hypothesis given in our previous reports CEA-N--2241 (1981) and CEA-R--5181 (1982). The iterative procedure solve systems of non-exact homogeneous linear equations QX = e (by optimum liquidation of the residuals esub(i) with positivity constraint and absolute convergence, leading to an appropriate physical solution with a relative error in our tests typically of the order of a fraction of one percent for the INPUT - OUTPUT Data. For the applications to Health Physics the SOHO Code has been programmed for use with a HP-41 CV calculator
NSDUAZ unfolding package for neutron spectrometry and dosimetry with Bonner spheres
NSDUAZ (Neutron Spectrometry and Dosimetry from the Universidad Autónoma de Zacatecas) is a user friendly neutron unfolding package for Bonner sphere spectrometer with 6LiI(Eu) developed under LabView® 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 spectra to start the iterations. The NSDUAZ performance was evaluated using 252Cf, 252Cf/D2O, 241AmBe neutron sources and the neutrons outside the radial beam port of a TRIGA Mark III nuclear reactor running to 10 W. - Highlights: ► This paper presents the NSDUAZ unfolding package. ► Advantages and drawbacks of NSDUAZ package are pointed out. ► NSDUAZ is evaluated with neutrons from a nuclear reactor and isotopic neutron sources.
Investigation of the neutron spectrum of americium–beryllium sources by Bonner sphere spectrometry
Americium–beryllium neutron sources are certainly the most widely used in neutron dosimetry laboratories, basically due to their long half-life and their energy distribution, which covers the energy domain of interest for many applications in ambient and personal dosimetry. Nevertheless, the spectrum of this source depends on the materials and dimension of the capsule and on the amount and physical–chemical properties of the active material, thus affecting relevant quantities such as the spectrum-averaged fluence-to-dose equivalent conversion coefficient. A EURAMET (European Association of National Metrology Institutes) project (n. 1104) was initiated to experimentally investigate how the neutron spectrum changes for different source sizes and encapsulations with a view to providing improved data for a planned revision of the ISO 8529 Standard Series. The experimental campaign was carried out in the low scatter facility at NPL. Here three different Bonner sphere spectrometers, BSSs, were exposed to the neutron fields produced by three different neutron sources formats: one X3 capsule (1 Ci) and two X14 capsules (10 Ci and 15 Ci). The specific advantage of the BSS is the large sensitivity to low-energy neutrons (E<0.1 MeV) which is the component expected to be most affected by the capsule-to-capsule variations and the component which is least well known. This paper summarises the results of the campaign with emphasis on (1) estimating the low-energy component of the Am–Be neutron spectrum, according to the encapsulation type; (2) evaluating the coherence between the Bonner spheres data and the previous studies performed with high-resolution spectrometers but limited in energy to E>0.1 MeV; (3) understanding whether the ISO-recommended Am–Be spectrum needs to be amended, and for which source formats
Investigation of the neutron spectrum of americium–beryllium sources by Bonner sphere spectrometry
Bedogni, R., E-mail: roberto.bedogni@lnf.infn.it [INFN—LNF (Frascati National Laboratories), Via E. Fermi n. 40, 00044 Frascati (Italy); Domingo, C. [GRRI, Departament de Fisica, Universitat Autónoma de Barcelona, E-08193 Bellaterra (Spain); Roberts, N.; Thomas, D.J. [National Physical Laboratory, Hampton Road, TW11 0LW Teddington, Middlesex (United Kingdom); Chiti, M.; Esposito, A. [INFN—LNF (Frascati National Laboratories), Via E. Fermi n. 40, 00044 Frascati (Italy); Garcia, M.J. [GRRI, Departament de Fisica, Universitat Autónoma de Barcelona, E-08193 Bellaterra (Spain); Gentile, A [INFN—LNF (Frascati National Laboratories), Via E. Fermi n. 40, 00044 Frascati (Italy); Liu, Z.Z. [National Physical Laboratory, Hampton Road, TW11 0LW Teddington, Middlesex (United Kingdom); San-Pedro, M. de [GRRI, Departament de Fisica, Universitat Autónoma de Barcelona, E-08193 Bellaterra (Spain)
2014-11-01
Americium–beryllium neutron sources are certainly the most widely used in neutron dosimetry laboratories, basically due to their long half-life and their energy distribution, which covers the energy domain of interest for many applications in ambient and personal dosimetry. Nevertheless, the spectrum of this source depends on the materials and dimension of the capsule and on the amount and physical–chemical properties of the active material, thus affecting relevant quantities such as the spectrum-averaged fluence-to-dose equivalent conversion coefficient. A EURAMET (European Association of National Metrology Institutes) project (n. 1104) was initiated to experimentally investigate how the neutron spectrum changes for different source sizes and encapsulations with a view to providing improved data for a planned revision of the ISO 8529 Standard Series. The experimental campaign was carried out in the low scatter facility at NPL. Here three different Bonner sphere spectrometers, BSSs, were exposed to the neutron fields produced by three different neutron sources formats: one X3 capsule (1 Ci) and two X14 capsules (10 Ci and 15 Ci). The specific advantage of the BSS is the large sensitivity to low-energy neutrons (E<0.1 MeV) which is the component expected to be most affected by the capsule-to-capsule variations and the component which is least well known. This paper summarises the results of the campaign with emphasis on (1) estimating the low-energy component of the Am–Be neutron spectrum, according to the encapsulation type; (2) evaluating the coherence between the Bonner spheres data and the previous studies performed with high-resolution spectrometers but limited in energy to E>0.1 MeV; (3) understanding whether the ISO-recommended Am–Be spectrum needs to be amended, and for which source formats.
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. PMID:26508275
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. PMID:26133664
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. PMID:27203706
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. - Highlights: • Boric acid solution is useful to improve the energy resolution of Bonner sphere. • Uncertainty of the device configuration is critical for neutron spectrometry. • It is important to reduce and evaluate the uncertainty
In this work a neutron spectrum unfolding code, based on artificial intelligence technology is presented. The code called ''Neutron Spectrometry and Dosimetry with Artificial Neural Networks and two Bonner spheres'', (NSDann2BS), was designed in a graphical user interface under the LabVIEW programming environment. The main features of this code are to use an embedded artificial neural network architecture optimized with the ''Robust design of artificial neural networks methodology'' and to use two Bonner spheres as the only piece of information. In order to build the code here presented, once the net topology was optimized and properly trained, knowledge stored at synaptic weights was extracted and using a graphical framework build on the LabVIEW programming environment, the NSDann2BS code was designed. This code is friendly, intuitive and easy to use for the end user. The code is freely available upon request to authors. To demonstrate the use of the neural net embedded in the NSDann2BS code, the rate counts of 252Cf, 241AmBe and 239PuBe neutron sources measured with a Bonner spheres system
Ortiz-Rodriguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.; Solis Sanches, L. O.; Miranda, R. Castaneda; Cervantes Viramontes, J. M. [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica. Av. Ramon Lopez Velarde 801. Col. Centro Zacatecas, Zac (Mexico); Vega-Carrillo, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica. Av. Ramon Lopez Velarde 801. Col. Centro Zacatecas, Zac., Mexico. and Unidad Academica de Estudios Nucleares. C. Cip (Mexico)
2013-07-03
In this work a neutron spectrum unfolding code, based on artificial intelligence technology is presented. The code called ''Neutron Spectrometry and Dosimetry with Artificial Neural Networks and two Bonner spheres'', (NSDann2BS), was designed in a graphical user interface under the LabVIEW programming environment. The main features of this code are to use an embedded artificial neural network architecture optimized with the ''Robust design of artificial neural networks methodology'' and to use two Bonner spheres as the only piece of information. In order to build the code here presented, once the net topology was optimized and properly trained, knowledge stored at synaptic weights was extracted and using a graphical framework build on the LabVIEW programming environment, the NSDann2BS code was designed. This code is friendly, intuitive and easy to use for the end user. The code is freely available upon request to authors. To demonstrate the use of the neural net embedded in the NSDann2BS code, the rate counts of {sup 252}Cf, {sup 241}AmBe and {sup 239}PuBe neutron sources measured with a Bonner spheres system.
Iterative code for the reconstruction of the neutrons spectrum using the Bonner spheres
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)
Quantification of neutron field at the neutron therapy room of KCCH using a Bonner sphere
In order to quantify the neutron fields at the neutron therapy room of KCCH the Bonner Sphere spectrometry system (BS) was used for the measurement of neutron spectra produced from two kinds of Be targets (1.0 and 10.5 mm bombarded by protons of 35 and 45 MeV. It was found that additional neutrons produced from the beam line tube and the beam stopper, which are made of Aluminum, were included considerably as a part of neutron spectrum in the neutron field made from the thin (1.0 mm) Be target. Neutrons from the thick (10.5 mm) Be were hardened by a iron filter of 2.6 cm and collimated by the gantry, and the beam size was fitted 26 x 16 cm2) to cover the cross sectional area of a BS used in this measurement. Six kinds of neutron spectra were measured and the dosimetric quantities such as the fluence averaged energy (Eave.), the spectrum weighted dose conversion coefficient (h*) and the dose equivalent rate (H) per nano ampere were determined. These were ranged as follows, Eave. was from 4.3 to 15.1 MeV, and h* was from 326 to 447 pSv.cm2, and H was from 0.17 to 5.66 mSv.h-1.nA-1. The MXDFC31 code was used to unfold the measured data of BS and the MCNPX code (Ver. 2.4) implemented to calculate the default spectra which are necessary for unfolding as a prior information
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.
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)
A conventional Bonner Sphere (BS) set consisting of six polyethylene spheres was modified to enhance its response to a high-energy neutron by putting a lead shell inside a polyethylene moderator. The response matrix of an extended BS was calculated using the MCNPX code and calibrated using a 252Cf neutron source. In order to survey the unknown photon and neutron mixed field, a spherical tissue equivalent proportional counter (TEPC) was constructed and assembled as a portable measurement system. The extended BS and the self-constructed TEPC were employed to determine the dosimetric quantities of the neutron field produced from the thick lead target bombarded by the 2.5 GeV electron beam of Pohang Accelerator Laboratory (PAL) and the neutron calibration field of Korea Atomic Energy Research Inst. (KAERI). (authors)
This research thesis first describes the problematic of the effects of natural radiation on micro- and nano-electronic components, and the atmospheric-radiative stress of atmospheric neutrons from cosmic origin: issue of 'Single event upsets', present knowledge of the atmospheric radiative environment induced by cosmic rays. The author then presents the neutron-based detection and spectrometry by using the Bonner sphere technique: principle of moderating spheres, definition and mathematical formulation of neutron spectrometry using Bonner spheres, active sensors of thermal neutrons, response of a system to conventional Bonner spheres, extension to the range of high energies. Then, he reports the development of a Bonner sphere system extended to the high-energy range for the spectrometry of atmospheric neutrons: definition of a conventional system, Monte Carlo calculation of response functions, development of the response matrix, representation and semi-empirical verification of fluence response, uncertainty analysis, extension to high energies, and measurement tests of the spectrometer. He reports the use of a Monte Carlo simulation to characterize the spectrometer response in the high-energy range
Experimental activities are underway at INFN Legnaro National Laboratories (LNL) (Padua, Italy) and Pisa University aimed at angular-dependent neutron energy spectra measurements produced by the 9Be(p,xn) reaction, under a 5 MeV proton beam. This work has been performed in the framework of INFN TRASCO-BNCT project. Bonner Sphere Spectrometer (BSS), based on 6LiI (Eu) scintillator, was used with the shadow-cone technique. Proper unfolding codes, coupled to BSS response function calculated by Monte Carlo code, were finally used. The main results are reported here. - Highlights: • Bonner sphere spectrometer is used to determine the angular neutron energy spectrum of an accelerator-based BNCT facility. • The shadow-cone technique is a method used with Bonner sphere spectrometer to remove the neutron scattered contribution. • The response function matrix for the set of Bonner sphere spectrometer is calculated by Monte Carlo code. • Unfolding codes are used to obtain neutron spectra at different neutron emission angles (0°, 40°, 80° and 120°)
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 Eo and 90o with respect to the beam-line. Here the ERBSS of UAB (Universidad Autonoma de Barcelona-Grup de Fisica de les Radiacions) and INFN (Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali di Frascati) were exposed to characterize the 'forward' and 'sideward' proton-induced neutron fields. The use of two ERBSS characterized by different set of spheres, central detectors, and independently established and calibrated, is important for guaranteeing the robustness of the measured spectra and estimating their overall uncertainties.
The European Commission has funded within its 6th Framework Programme a three-year project (2005-2007) called CONRAD, COordinated Network for RAdiation Dosimetry. A major task of the CONRAD Work Package 'complex mixed radiation fields at workplaces' was to organise a benchmark exercise in a workplace field at a high-energy particle accelerator where neutrons are the dominant radiation component. The CONRAD benchmark exercise took place at the Gesellschaft fuer Schwerionenforschung mbH (GSI) in Darmstadt, Germany in July 2006. In this paper, the results of the spectrometry using four extended -range Bonner sphere spectrometers of four different institutes are reported. Outside Cave A the neutron spectra were measured with three spectrometers at six selected positions and ambient dose equivalent values were derived for use in the intercomparison with other area monitors and dosemeters. At a common position all three spectrometers were used to allow a direct comparison of their results which acts as an internal quality assurance. The comparison of the neutron spectra measured by the different groups shows very good agreement. A detailed analysis presents some differences between the shapes of the spectra and possible sources of these differences are discussed. However, the ability of Bonner sphere spectrometers to provide reliable integral quantities like fluence and ambient dose equivalent is well demonstrated in this exercise. The fluence and dose results derived by the three groups agree very well within the given uncertainties, not only with respect to the total energy region present in this environment but also for selected energy regions which contribute in certain strength to the total values. In addition to the positions outside Cave A one spectrometer was used to measure the neutron spectrum at one position in the entry maze of Cave A. In this case a comparison was possible to earlier measurements.
One of the more actual and promising fields of applied neutron physics is the investigation of the malfunctions induced by high-energy neutrons naturally present in the atmosphere in electronic devices, called single event effects (SEE). These studies are of primary importance for the design of devices that have to fulfill high reliability requirements and those that are likely to be exposed to enhanced levels of cosmic rays background, e.g. in aerospace and avionic applications. Particle accelerators-driven neutron sources constitute valuable irradiation facilities for these purposes as they provide an opportunity for accelerated testing of the effects of these naturally occurring neutrons, provided the neutron spectrum is comparable with the atmospheric one and the neutron fields are known with high accuracy. The latter can be achieved through the use of appropriate radiation transport codes and neutron spectrometry techniques. In view of the design and construction of CHIPIR, a dedicated beam line for SEE studies at the ISIS pulsed neutron source second target station (UK) ((http://ts-2.isis.rl.ac.uk/instruments/phase2/index.htm)), a spectrometric characterization was performed on the VESUVIO beamline (Senesi et al.,2000). The spectrometric technique was the bonner sphere spectrometer (BSS), widely used to determine neutron spectra and dose quantities around high-energy accelerators. The experimental campaign provided a complete spectrometric investigation of the VESUVIO neutron beam, allowing the integral quantities (total fluence rate, fraction of fluence in given energy intervals) to be estimated with uncertainties lower than 10%.
Wiegel, B; Bedogni, R; Caresana, M; Esposito, A; Fehrenbacher, G; Ferrarini, M; Hohmann, E; Hranitzky, C; Kasper, A; Khurana, S; Mares, V; Reginatto, M; Rollet, S; Rühm, W; Schardt, D; Silari, M; Simmer, G; Weitzenegger, E
2009-01-01
The European Commission has funded within its 6th Framework Programme a three-year project (2005–2007) called CONRAD, COordinated Network for RAdiation Dosimetry. A major task of the CONRAD Work Package “complex mixed radiation fields at workplaces” was to organise a benchmark exercise in a workplace field at a high-energy particle accelerator where neutrons are the dominant radiation component. The CONRAD benchmark exercise took place at the Gesellschaft für Schwerionenforschung mbH (GSI) in Darmstadt, Germany in July 2006. In this paper, the results of the spectrometry using four extended -range Bonner sphere spectrometers of four different institutes are reported. Outside Cave A the neutron spectra were measured with three spectrometers at six selected positions and ambient dose equivalent values were derived for use in the intercomparison with other area monitors and dosemeters. At a common position all three spectrometers were used to allow a direct comparison of their results which acts as an int...
Measurement of cosmic ray neutrons with Bonner sphere spectrometer and neutron monitor at 79{sup o}N
Pioch, C., E-mail: christian.pioch@helmholtz-muenchen.d [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health (GmbH), Institute of Radiation Protection, Ingolstaedter Landstr. 1, 85764 Neuherberg (Germany); Mares, V. [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health (GmbH), Institute of Radiation Protection, Ingolstaedter Landstr. 1, 85764 Neuherberg (Germany); Vashenyuk, E.V.; Balabin, Yu.V. [Polar Geophysical Institute, Kola Science Center, Russian Academy of Sciences, Apatity (Russian Federation); Ruehm, W. [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health (GmbH), Institute of Radiation Protection, Ingolstaedter Landstr. 1, 85764 Neuherberg (Germany)
2011-01-21
In 2007, a Bonner spheres spectrometer (BSS) was installed in Ny-Alesund, Spitsbergen, at about 79{sup o}N. The spectrometer allows continuous measurement of the spectral fluence rate distribution of secondary neutrons from cosmic radiation in absolute terms. In this way, the system complements a neutron monitor (NM) that was installed in 2005, in Barentsburg, Spitsbergen, at about 78{sup o}N. To compare the readings of both systems, the NM response functions to neutrons and protons were calculated by means of the GEANT4 code, in the energy range between 10 meV and 100 GeV, and between 40 MeV and 10 GeV, respectively, using different intra-nuclear cascade (INC) models at energies above 20 MeV. Sample spectral fluence distributions as measured by means of the BSS system for neutrons in November and December 2007 were used and folded with the calculated GEANT4 NM response. The resulting calculated NM count rates were then compared to those actually measured by the NM system and a reasonable agreement between 7% and 43% was obtained, depending on the nuclear models used in the GEANT4 calculations and the assumed {sup 10}B enrichment of the NM counters used to detect the neutrons.
Amgarou, K. [Grup de Recerca en Radiacions Ionitzants, Departament de Fisica, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Bedogni, R., E-mail: roberto.bedogni@lnf.infn.it [INFN-Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, Via E. Fermi n. 40, 00044 Frascati (Italy); Domingo, C. [Grup de Recerca en Radiacions Ionitzants, Departament de Fisica, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Esposito, A.; Gentile, A.; Carinci, G. [INFN-Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, Via E. Fermi n. 40, 00044 Frascati (Italy); Russo, S. [INFN-Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, via S. Sofia 44, 95123 Catania (Italy)
2011-10-21
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 E<20 MeV if only polyethylene spheres are used, but can be extended to hundreds of MeV by including metal-loaded spheres (extended range BSS, indicated with ERBSS). With the aim of providing useful data to the scientific community involved in neutron measurements at hadron therapy facilities, an ERBSS experiment was carried out at the Centro di AdroTerapia e Applicazioni Nucleari Avanzate (CATANA) of INFN-LNS (Laboratori Nazionali del Sud), where a proton beam routinely used for ophthalmic cancer treatments is available. The 62 MeV beam was directed towards a PMMA phantom, simulating the patient, and two neutron measurement points were established at 0{sup o} and 90{sup o} with respect to the beam-line. Here the ERBSS of UAB (Universidad Autonoma de Barcelona-Grup de Fisica de les Radiacions) and INFN (Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali di Frascati) were exposed to characterize the 'forward' and 'sideward' proton-induced neutron fields. The use of two ERBSS characterized by different set of spheres, central detectors, and
The AECL Bonner Sphere Spectrometer (BSS) was taken to National Physical Laboratory (NPL) for calibration in mono-energetic neutron fields and bare 252Cf neutron fields. The mono-energetic radiations were performed using ISO-8529 prescribed neutron energies: 0.071, 0.144, 0.565, 1.2, 5 and 17 MeV. A central SP9 proportional counter was also evaluated at the NPL thermal neutron calibration facility in order to assess an effective pressure of 3He inside the counter, i.e. number density of 3He atoms. Based on these measurements and methods outlined by Thomas and Soochak, a new BSS response matrix was generated. The response matrix is then verified by unfolding spectra corresponding to various neutron fields. Those are NPL bare 252Cf source, National Institute of Standards and Technology bare and heavy water moderated 252Cf source and 241AmBe calibration source located at National Research Council. A good agreement was observed with expected neutron fluence rates, as well as derived dosimetric quantities, such as International Commission on Radiological Protection-74 ambient dose equivalent. The AECL BSS response matrix was created based on methods proposed by Wiegel et al., Thomas and Thomas and Soochak. The response matrix was further corrected for the mono-energetic neutron measurements taken and NPL. In order to experimentally verify the response matrix, four neutron measurements were taken at three laboratories: NPL, NIST and NRC. Good agreement with expected values both for integrated neutron fluence and derived dosimetric quantities was observed in all four cases. (authors)
Neutron monitoring using moderating sphere detectors
Three moderating sphere-detector systems are examined as a neutron area monitoring instruments. The thermal neutron detectors used are the (bare-Cd covered) Li6 (Eu) crystal scintillating detector, the U235-mica track detector and the partially Cd-covered R.M. film. The response of the 12 s sphere-detector systems to Pu-Be neutrons are found to be 0.22 counts/neutrons for the Li6I-system. 8x10-4 tracks per neutron for the track-detector system and 10 mR equivalent γ-ray exposure per 2x10-neutrons per cm- for the Cd-covered R.M. film system
Hu, Z M; Xie, X F; Chen, Z J; Peng, X Y; Du, T F; Cui, Z Q; Ge, L J; Li, T; Yuan, X; Zhang, X; Hu, L Q; Zhong, G Q; Lin, S Y; Wan, B N; Gorini, G; Li, X Q; Zhang, G H; Chen, J X; Fan, T S
2014-11-01
To assess the neutron energy spectra and the neutron dose for different positions around the Experimental Advanced Superconducting Tokamak (EAST) device, a Bonner Sphere Spectrometer (BSS) was developed at Peking University, with totally nine polyethylene spheres and a SP9 (3)He counter. The response functions of the BSS were calculated by the Monte Carlo codes MCNP and GEANT4 with dedicated models, and good agreement was found between these two codes. A feasibility study was carried out with a simulated neutron energy spectrum around EAST, and the simulated "experimental" result of each sphere was obtained by calculating the response with MCNP, which used the simulated neutron energy spectrum as the input spectrum. With the deconvolution of the "experimental" measurement, the neutron energy spectrum was retrieved and compared with the preset one. Good consistence was found which offers confidence for the application of the BSS system for dose and spectrum measurements around a fusion device. PMID:25430324
Purpose: Secondary neutrons are an unavoidable consequence of proton therapy. While the neutron dose is low compared to the primary proton dose, its presence and contribution to the patient dose is nonetheless important. The most detailed information on neutrons includes an evaluation of the neutron spectrum. However, the vast majority of the literature that has reported secondary neutron spectra in proton therapy is based on computational methods rather than measurements. This is largely due to the inherent limitations in the majority of neutron detectors, which are either not suitable for spectral measurements or have limited response at energies greater than 20 MeV. Therefore, the primary objective of the present study was to measure a secondary neutron spectrum from a proton therapy beam using a spectrometer that is sensitive to neutron energies over the entire neutron energy spectrum. Methods: The authors measured the secondary neutron spectrum from a 250-MeV passively scattered proton beam in air at a distance of 100 cm laterally from isocenter using an extended-range Bonner sphere (ERBS) measurement system. Ambient dose equivalent H*(10) was calculated using measured fluence and fluence-to-ambient dose equivalent conversion coefficients. Results: The neutron fluence spectrum had a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate energy continuum between the thermal and evaporation peaks. The H*(10) was dominated by the neutrons in the evaporation peak because of both their high abundance and the large quality conversion coefficients in that energy interval. The H*(10) 100 cm laterally from isocenter was 1.6 mSv per proton Gy (to isocenter). Approximately 35% of the dose equivalent was from neutrons with energies ≥20 MeV. Conclusions: The authors measured a neutron spectrum for external neutrons generated by a 250-MeV proton beam using an ERBS measurement system that was sensitive to neutrons over the entire
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
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
Guerrero Araque, J. E.; Mendez Villafane, R.
2013-07-01
This work intends to heavily describe simulation steps used in code MCNPX for calculation for Neutron response of a BSS with passive or active detector. Has it been calculated with MCNPX the matrix response of a system of Bonner spheres, with passive or active detector, which described in detail the steps to be followed by the code are part of the solution. (Author)
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)
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)
Rühm, W; Pioch, C; Agosteo, S; Endo, A; Ferrarini, M; Rakhno, I; Rollet, S; Satoh, D; Vincke, H
2014-01-01
Bonner Spheres Spectrometry in its high-energy extended version is an established method to quantify neutrons at a wide energy range from several meV up to more than 1 GeV. In order to allow for quantitative measurements, the responses of the various spheres used in a Bonner Sphere Spectrometer (BSS) are usually simulated by Monte Carlo (MC) codes over the neutron energy range of interest. Because above 20 MeV experimental cross section data are scarce, intra-nuclear cascade (INC) and evaporation models are applied in these MC codes. It was suspected that this lack of data above 20 MeV may translate to differences in simulated BSS response functions depending on the MC code and nuclear models used, which in turn may add to the uncertainty involved in Bonner Sphere Spectrometry, in particular for neutron energies above 20 MeV. In order to investigate this issue in a systematic way, EURADOS (European Radiation Dosimetry Group) initiated an exercise where six groups having experience in neutron transport calcula...
Bedogni, Roberto; Pelliccioni, Maurizio; Esposito, Adolfo
2010-03-01
Due to the increased interest of the scientific community in the applications of synchrotron light, there is an increasing demand of high-energy electron facilities, testified by the construction of several new facilities worldwide. The radiation protection around such facilities requires accurate experimental methods to determine the dose due to prompt radiation fields. Neutron fields, in particular, are the most complex to measure, because they extend in energy from thermal (10 -8 MeV) up to hundreds MeV and because the responses of dosemeters and survey meters usually have large energy dependence. The Bonner Spheres Spectrometer (BSS) is in practice the only instrument able to respond over the whole energy range of interest, and for this reason it is frequently used to derive neutron spectra and dosimetric quantities in accelerator workplaces. Nevertheless, complex unfolding algorithms are needed to derive the neutron spectra from the experimental BSS data. This paper presents a parametric model specially developed for the unfolding of the experimental data measured with BSS around high-energy electron accelerators. The work consists of the following stages: (1) Generation with the FLUKA code, of a set of neutron spectra representing the radiation environment around accelerators with different electron energies; (2) formulation of a parametric model able to describe these spectra, with particular attention to the high-energy component (>10 MeV), which may be responsible for a large part of the dose in workplaces; and (3) implementation of this model in an existing unfolding code.
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 -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. (authors)
High-resolution neutron energy spectra, covering the entire energy range of interest, for two standard radionuclide neutron sources (241Am-B and 241Am-F) have been derived from Bonner sphere measurements by using high-resolution a priori data in the unfolding process. In each case, two a priori spectra were used, one from a two-stage calculation and also one from a combination of the calculated spectrum with a high-resolution measured spectrum. The unfolded spectra are compared with those published elsewhere and show significant differences from the ISO- and IAEA-recommended spectra for 241Am-B and 241Am-F, respectively. Values for the fluence-average energy and fluence-to-dose-equivalent conversion coefficients are presented for the new spectra, and the implications of the new spectra for the emission rates of the sources when measured by the manganese bath technique are also determined. A combination of calculations and measurements has been performed to determine the spectral fluence from two reference neutron sources over the entire energy range of interest. For the Am-B source, this approach has supported the spectra of Marsh et al. and Zimbal and reduced confidence in the ISO 8529 spectrum. However, in terms of derived quantities, there is a good agreement between all the available spectra. In contrast, the new Am-F spectrum presented here is significantly different from those already published. The fluence to dose conversion coefficients derived from the new spectrum are 9 % lower than the currently accepted values, and the emission rates of Am-F sources measured by the manganese bath technique may need to be increased by up to 0.5 %. (authors)
Mazrou, Hakim [Centre de Recherche Nucleaire d' Alger (CRNA), 02 Boulevard Frantz Fanon, B.P. 399, 16000 Alger (Algeria)], E-mail: mazrou_h@comena-dz.org; Sidahmed, Tassadit; Idiri, Zahir; Lounis-Mokrani, Zohra; Bedek, Said [Centre de Recherche Nucleaire d' Alger (CRNA), 02 Boulevard Frantz Fanon, B.P. 399, 16000 Alger (Algeria); Allab, Malika [Faculte de Physique, Universite des Sciences et de la Technologie Houari-Boumediene (USTHB), Alger (Algeria)
2008-02-15
In the present work, measurements have been performed using an available multisphere neutron spectrometer based on a calibrated {sup 6}LiI scintillation detector (10mmox2mm) exposed to an {sup 241}Am-Be neutron source. Sensitive analysis has been performed to assess influence of angle and source-detector distances dependence on the detector responses. Our experimental responses were compared with the published experimental and calculated data for two {sup 241}Am-Be (ISO, PTB) neutron spectra with (4mmox4mm) {sup 6}LiI detector. A discrepancy by a factor of about two was achieved and it is chiefly due to the difference shown in active surface of both detectors.
Low complexity Breadth First Search Sphere Detector for MIMO Systems
Shirly Edward.A
2015-12-01
Full Text Available Multiple Input Multiple Output (MIMO technology is the key to meet the demands for data rate and link reliability of modern wireless communication system, such as 3GPP-LTE.The full potential of such a system can be achieved only by high performance detection algorithms, which exhibit prohibitive computational complexity. Therefore, in this paper, a low complexity and highly parallel Breadth First search Sphere Detector (BFSD is proposed for MIMO detection, which takes forward only the symbol set with minimum partial Euclidean distances (PEDs of the expanded node in the tree search process. We had designed a BFSD scheme for 16QAM modulation with 2 x 2 and 4 x4 antenna configurations and implemented on a state-of-the-art Xilinx Virtex 5 FPGA device. The results indicate that with less computational complexity compared with the literature the detector can achieve a throughput of up to 98Mbps which makes it suitable for 3GPP-LTE uplink transmission.
On the sensitivity of a hollow sphere as a multi-modal resonant gravitational wave detector
Dubath, F [KITP, Kohn Hall, UCSB CA 93106 (United States); Extermann, J [GAP-Biophotonics, Universite de Geneve, 20 rue de l' Ecole de Medecine, CH-1211 Geneva 4 (Switzerland); Gottardi, L [SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht (Netherlands)
2007-05-07
We present a numerical analysis to simulate the response of a spherical resonant gravitational wave detector and to compute its sensitivity. Under the assumption of optimal filtering, we work out the sensitivity curve for a sphere first taking into account only a single transducer, and then using a coherent analysis of the whole set of transducers. We use our model for computing the sensitivity and therefore compare different designs of spherical detectors. In particular, we present the case of 1 m radius bulk and hollow spheres equipped with transducers in a TIGA configuration, and we explore the sensitivity of a hollow sphere as a multi-modal detector.
The Indiana silicon sphere (ISiS) 4 π detector
A 4 π detector array for the study of multifragment emission processes in light-ion-induced reactions is described. The detector array is based on ion-implanted passivated silicon detector technology, combined with gas-ionization and CsI(T1) scintillator devices to measure light-charged particles up to 100 MeV/A and all heavier fragments with discrete Z identification up to Z ≤ 14. The design criteria include good granularity (162 elements), very low energy thresholds (0.1-0.2 MeV/A), excellent energy resolution and stability, broad dynamic range and ease of calibration
Application-Specific Instruction Set Processor Implementation of List Sphere Detector
Salmela Perttu
2007-01-01
Full Text Available Multiple-input multiple-output (MIMO technology enables higher transmission capacity without additional frequency spectrum and is becoming a part of many wireless system standards. Sphere detection has been introduced in MIMO systems to achieve maximum likelihood (ML or near-ML estimation with reduced complexity. This paper reviews related work on sphere detector implementations and presents an application-specific instruction set processor (ASIP implementation of K-best list sphere detector (LSD using transport triggered architecture (TTA. The implementation is based on using memory and heap data structure for symbol vector sorting. The design space is explored by presenting several variations of the implementation and comparing them with each other in terms of their latencies and hardware complexities. An early proposal for a parallelized architecture with a decoding throughput of approximately 5.3 Mbps is presented
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 241Am–Be source. Integral quantities characterizing the neutron field, required for radiological protection, have been derived by unfolding the measured data. A good agreement is achieved between the obtained results and those deduced using Bonner spheres. In addition, a sensitivity analysis of the results to the deconvolution procedure is given. - Highlights: ► Low intensity neutron fields' characterization using thick threshold detectors. ► Low activity 241Am–Be neutron source spectrum measurement. ► Integral quantities required for radiological protection have been derived. ► The results are in good agreement with those deduced using Bonner spheres. ► The results are not very sensitive to the chosen deconvolution procedure.
In this work experimental studies are aimed at studying the effect of the detector type, moderator shape, moderator size, beam size as well as gamma ray effect on the response of the moderating detectors for neutron dosimetry. The detectors used are the scintillation, the 3He counter, FFTD and the TLD. Experimental investigation showed that the 10 in, Bonner sphere system and the DNA-1 scintillation system as well as the FFTD and TLD 10 in. sphere systems are recommended for neutron dosimetric measurements. The effect of beam size is found to be dependent on the moderator size and shape. (Auth.)
Study of reproducibility of measurements with the spectrometer of Bonner multispheres
Azevedo, G.A.; Pereira, W.W.; Patrao, K.C.S.; Fonseca, E.S., E-mail: geisadeazevedo@gmail.com, E-mail: walsan@ird.gov.br, E-mail: karla@ird.gov.br, E-mail: evaldo@ird.gov.br [Instituto de Radionprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)
2013-07-01
This work aims to study the metrological behavior of the Bonner Multisphere Spectrometer (BMS) of the LN / LNMRI / IRD - Laboratorio Metrologia de Neutrons / Laboratorio Nacional de Metrologia e Radiacao Ionizante / Instituto de Radioprotecao e Dosimetria, for measurements in repeatability and reproducibility conditions. Initially, a simulation was done by applying the Monte Carlo method, using the MCNP code and respecting the ISO 8529-1 (2001), using the sources of Californium ({sup 252} Cf), Americium-Beryllium ({sup 241} AmBe) and californium in heavy water (Cf + D{sub 2}O), all located at a distance of 100 cm from the neutron detector ({sup 6}Li (Eu) - crystal scintillator). In this program, the counting of neutrons that are captured by the detector was made. The source is located in the center of a sphere of radius 300 cm. Analyzes the impact of these neutrons in a point of the sphere wall, which in this case acted as a neutron detector and from there, it is estimated the number of neutrons that collide in the whole sphere. The purpose is to obtain the neutron count for different energy bands in a solid field of neutrons, since they have a spectrum ranging from a low to a high energy that can also vary within a particular environment. Wishes to obtain new fields with different sources and moderators materials to be used as new reference fields. Measurements are being conducted for these fields, with the aim of analyzing the variability conditions of the measurement (repeatability and reproducibility) in LEN - Laboratorio de Espectrometria de Neutrons of the LN/LMNRI/IRD. Thus, the spectrometer will be used to improve both the knowledge of the spectrum as the standard of neutrons of the lab, proving that a spectrometry is essential for correct measurement.
2002-01-01
The Bonner Ball Neutron Detector measures neutron radiation. Neutrons are uncharged atomic particles that have the ability to penetrate living tissues, harming human beings in space. The Bonner Ball Neutron Detector is one of three radiation experiments during Expedition Two. The others are the Phantom Torso and Dosimetric Mapping.
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...
Applicability of a Bonner Shere technique for pulsed neutron in 120 GeV proton facility
Sanami, T.; Hagiwara, M.; Iwase, H.; /KEK, Tsukuba; Iwamoto, Y.; Sakamoto, Y.; Nakashima, H.; /JAEA, Ibaraki; Arakawa, H.; Shigyo, N.; /Kyushu U.; Leveling, A.F.; Boehnlein, D.J.; Vaziri, K.; /Fermilab
2008-02-01
The data on neutron spectra and intensity behind shielding are important for radiation safety design of high-energy accelerators since neutrons are capable of penetrating thick shielding and activating materials. Corresponding particle transport codes--that involve physics models of neutron and other particle production, transportation, and interaction--have been developed and used world-wide [1-8]. The results of these codes have been ensured through plenty of comparisons with experimental results taken in simple geometries. For neutron generation and transport, several related experiments have been performed to measure neutron spectra, attenuation length and reaction rates behind shielding walls of various thicknesses and materials in energy range up to several hundred of MeV [9-11]. The data have been used to benchmark--and modify if needed--the simulation modes and parameters in the codes, as well as the reference data for radiation safety design. To obtain such kind of data above several hundred of MeV, Japan-Fermi National Accelerator Laboratory (FNAL) collaboration for shielding experiments has been started in 2007, based on suggestion from the specialist meeting of shielding, Shielding Aspects of Target, Irradiation Facilities (SATIF), because of very limited data available in high-energy region (see, for example, [12]). As a part of this shielding experiment, a set of Bonner sphere (BS) was tested at the antiproton production target facility (pbar target station) at FNAL to obtain neutron spectra induced by a 120-GeV proton beam in concrete and iron shielding. Generally, utilization of an active detector around high-energy accelerators requires an improvement on its readout to overcome burst of secondary radiation since the accelerator delivers an intense beam to a target in a short period after relatively long acceleration period. In this paper, we employ BS for a spectrum measurement of neutrons that penetrate the shielding wall of the pbar target
Results on the primary CR spectrum and composition reconstructed with the SPHERE-2 detector
Antonov, R A; Bonvech, E A; Chernov, D V; Dzhatdoev, T A; Finger, Mir; Finger, Mix; Galkin, V I; Kabanova, N V; Petkun, A S; Podgrudkov, D A; Roganova, T M; Shaulov, S B; Sysoeva, T I
2012-01-01
First preliminary results of the balloon-borne experiment SPHERE-2 on the all-nuclei primary cosmic rays (PCR) spectrum and primary composition are presented. The primary spectrum in the energy range $10^{16}$--$5\\cdot10^{17}$ eV was reconstructed using characteristics of Vavilov-Cherenkov radiation of extensive air showers (EAS), reflected from a snow surface. Several sources of systematic uncertainties of the spectrum were analysed. A method for separation of the primary nuclei' groups based on the lateral distribution function' (LDF) steepness parameter is presented. Preliminary estimate of the mean light nuclei' fraction $f_{30-150}$ at energies $3\\cdot10^{16}$--$1.5\\cdot10^{17}$ eV was performed and yielded $f_{30-150}$= (21$\\pm$11)%.
Efficient Sphere Detector Algorithm for Massive MIMO using GPU Hardware Accelerator
Arfaoui, Mohamed-Amine
2016-06-01
To further enhance the capacity of next generation wireless communication systems, massive MIMO has recently appeared as a necessary enabling technology to achieve high performance signal processing for large-scale multiple antennas. However, massive MIMO systems inevitably generate signal processing overheads, which translate into ever-increasing rate of complexity, and therefore, such system may not maintain the inherent real-time requirement of wireless systems. We redesign the non-linear sphere decoder method to increase the performance of the system, cast most memory-bound computations into compute-bound operations to reduce the overall complexity, and maintain the real-time processing thanks to the GPU computational power. We show a comprehensive complexity and performance analysis on an unprecedented MIMO system scale, which can ease the design phase toward simulating future massive MIMO wireless systems.
The Indiana silicon sphere 4π charged-particle detector array
A low threshold charged particle detector array for the study of fragmentation processes in light-ion-induced reactions has been constructed and successfully implemented at the IUCF and Saturne II accelerators. The array consists of 162-triple-element detector telescopes mounted in a spherical geometry and covering 74% of 4π in solid angle. Telescope elements are composed of (1) an axial-field gas ionization chamber operated with C3F8 gas; (2) a 0.5 mm thick passivated silicon detector, and (3) a 2.8 cm thick CsI(Tl) scintillation crystal with photodiode readout. Discrete element identification is obtained for ejectiles up to Z similar 16 over the dynamic range 0.7≤E/A≤95 MeV/nucleon. Isotopes are also distinguished for H, He, Li and Be ejectiles with 8< or ∼E/A< or ∼95 MeV. Custom-designed electronics are employed for bias supplies and linear signal processing. Data are acquired via a CAMAC/VME/Ethernet system. (orig.)
The Indiana silicon sphere 4 π charged-particle detector array
Kwiatkowski, K.; Bracken, D. S.; Morley, K. B.; Brzychczyk, J.; Foxford, E. Renshaw; Komisarcik, K.; Viola, V. E.; Yoder, N. R.; Dorsett, J.; Poehlman, J.; Madden, N.; Ottarson, J.
1995-02-01
A low threshold charged particle detector array for the study of fragmentation processes in light-ion-induced reactions has been constructed and successfully implemented at the IUCF and Saturne II accelerators. The array consists of 162-triple-element detector telescopes mounted in a spherical geometry and covering 74% of 4π in solid angle. Telescope elements are composed of (1) an axial-field gas ionization chamber operated with C3F8 gas; (2) a 0.5 mm thick passivated silicon detector, and (3) a 2.8 cm thick CsI(TI) scintillation crystal with photodiode readout. Discrete element identification is obtained for ejectiles up to Z ~ 16 over the dynamic range 0.7 <= E/A <= 95 MeV/nucleon. Isotopes are also distinguished for H, He, Li and Be ejectiles with 8 <~ E/A <~ 95 MeV. Custom-designed electronics are employed for bias supplies and linear signal processing. Data are acquired via a CAMAC/VME/Ethernet system.
The Indiana silicon sphere 4{pi} charged-particle detector array
Kwiatkowski, K. [Indiana Univ., Bloomington, IN (United States). Dept. of Chem. and Phys. and IUCF; Bracken, D.S. [Indiana Univ., Bloomington, IN (United States). Dept. of Chem. and Phys. and IUCF; Morley, K.B. [Indiana Univ., Bloomington, IN (United States). Dept. of Chem. and Phys. and IUCF; Brzychczyk, J. [Indiana Univ., Bloomington, IN (United States). Dept. of Chem. and Phys. and IUCF; Renshaw Foxford, E. [Indiana Univ., Bloomington, IN (United States). Dept. of Chem. and Phys. and IUCF; Komisarcik, K. [Indiana Univ., Bloomington, IN (United States). Dept. of Chem. and Phys. and IUCF; Viola, V.E. [Indiana Univ., Bloomington, IN (United States). Dept. of Chem. and Phys. and IUCF; Yoder, N.R. [Indiana Univ., Bloomington, IN (United States). Dept. of Chem. and Phys. and IUCF; Dorsett, J. [Department of Chemistry Technical Services, Indiana University, Bloomington, IN 47405 (United States); Poehlman, J. [Department of Chemistry Technical Services, Indiana University, Bloomington, IN 47405 (United States); Madden, N. [Consultant, Livermore, CA (United States); Ottarson, J. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States)
1995-06-15
A low threshold charged particle detector array for the study of fragmentation processes in light-ion-induced reactions has been constructed and successfully implemented at the IUCF and Saturne II accelerators. The array consists of 162-triple-element detector telescopes mounted in a spherical geometry and covering 74% of 4{pi} in solid angle. Telescope elements are composed of (1) an axial-field gas ionization chamber operated with C{sub 3}F{sub 8} gas; (2) a 0.5 mm thick passivated silicon detector, and (3) a 2.8 cm thick CsI(Tl) scintillation crystal with photodiode readout. Discrete element identification is obtained for ejectiles up to Z similar 16 over the dynamic range 0.7{<=}E/A{<=}95 MeV/nucleon. Isotopes are also distinguished for H, He, Li and Be ejectiles with 8< or {approx}E/A< or {approx}95 MeV. Custom-designed electronics are employed for bias supplies and linear signal processing. Data are acquired via a CAMAC/VME/Ethernet system. (orig.).
The neutron response functions for a Bonner Sphere Spectrometer (BSS) with 3He proportional counter were calculated employing the MCNP and LAHET Monte Carlo codes for the neutron energy range from 10 MeV to 1 GeV. The MCNP calculations were extended up to 100 MeV using the neutron cross-sections from the transport data libraries LA-100 of LANL. The effect of the different physics models implemented in the LAHET code on the response of the Bonner spectrometer are documented and the possible reasons are discussed. The MCNP and LAHET results are also compared with calculations using the Monte Carlo high energy transport code HADRON. Verification experiments were conducted at the CERN high energy calibration facility which gave some insight to the question how appropriate the physical models are which are used for the calculation of the BSS responses. (author)
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.
Fiber optic inclination detector system having a weighted sphere with reference points
Cwalinski, Jeffrey P.
1995-01-01
A fiber optic inclination detector system for determining the angular displacement of an object from a reference surface includes a simple mechanical transducer which requires a minimum number of parts and no electrical components. The system employs a single light beam which is split into two light beams and provided to the transducer. Each light beam is amplitude modulated upon reflecting off the transducer to detect inclination. The power values associated with each of the reflected light beams are converted by a pair of photodetectors into voltage signals, and a microprocessor manipulates the voltage signals to provide a measure of the angular displacement between the object and the reference surface.
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.
Thomas N Bonner (1923-2003), medical historian.
Bickel, Marcel H
2016-05-01
Thomas Bonner made a long academic career, teaching medical history and higher education at several American universities and presiding over three of these. He engaged in politics for 2 years. As a historian of medicine, he published important books on topics including Midwestern medicine, medical education in the United States and in European countries, the entry of women into medicine in the 19th century and on the educator Abraham Flexner. His works were based on exhaustive research, penetrating analysis, language skills and the ability to explain complex information in understandable terms. Bonner lived a passionate life of commitment and devotion to various worthwhile causes. PMID:24986396
Construction of the Calibration Neutron Fields and Spectrum Weighted Response of Several Detectors
The types and the forms of radioactive source term are getting a variety due to expansion of the radiation industry such as medical radiation treatments and research. of materials. For neutron sources, it is necessary to account for the neutron energy distribution to evaluate exactly the dose equivalent, because the energy range of the neutron from thermal neutrons (0.025 eV) to a few GeV. The neutron dose equivalent depends heavily on the energy of the neutrons. The neutron field spectra from a DT neutron generator at Korea Atomic Energy research Institute (KAERI) and the proton accelerators at Korea Institute of Radiological and Medical Science (KIRAMS) were measured by using the Bonner sphere measurement system (BS system) and several neutron detectors. The spectrum weighted response was obtained by using the response function of the neutron detectors as given in the IAEA Technical Report Series 403 (TRS)
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}).
Neutron detector development and measurements around particle accelerators
Various neutron detectors for spectrometry, environmental dosimetry and personal dosimetry have been developed by our group. For high energy neutron spectrometry, spallation detectors of C and Bi, large plastic and NE-213 scintillators, self TOF detector were used for neutron production and shielding experiments at several high energy accelerator facilities, ISIS of Rutherford Appleton Laboratory, UK, Two-mile Linac of Stanford Linear Accelerator Center, U.S.A., HIMAC of National Institute of Radiological Sciences, Japan, and RCNP of Osaka University, Japan. The response functions of these detectors were obtained by measurements and calculations. Thick target neutron yields produced from high-energy particles from protons to Xe ions have been summarized, together with shielding benchmark experiments through concrete and iron at these facilities. Neutron measurements over wide energy range including cosmic neutron field were done with Phoswich detector and Bonner sphere spectrometer. For environmental neutron dosimetry, two types of dose equivalent dosimeters, so-called rem counters, high-sensitive type and light-weight type, have been developed and for personal dosimetry, silicon semiconductor dosimeter has been developed for use in nuclear facilities. These dosimeters have good quality to give ambient and personal dose equivalents for neutrons in the mixed radiation fields. The outline of these works will be reviewed in this invited talk. (author)
DH-A-1 dosimeter and 6LiJ(Eu) detector, located in the center of polyethylene spheres with various diameters, were calibrated by means of neutrons with the energy of about 30 keV. The data on the detectors responses enable one to determine the shape of responses as a function of neutron energy more definitely at the energy range from some keV to some tens of keV. For DN-A-1 dosimeter response at neutrons and at neutrons in the energy range of about 30 keV the agreement is better than the uncertainties of measurements (about 20%)
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......, 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....... 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...
Scintillation forward spectrometer of the SPHERE setup
The construction of the forward spectrometer for the 4π SPHERE setup to study multiple production of particles in nucleus-nucleus interactions is described. The measured parameters of the spectrometer detectors are presented. 7 refs.; 14 figs.; 1 tab
A new method of researching fermion tunneling from the Vaidya-Bonner de Sitter black hole
Lin Kai; Yang Shu-Zheng
2009-01-01
Using the general tortoise coordinate transformation, we research the fermion tunneling of the Vaidya-Bonner de Sitter black hole via a semi-classical method and finally obtain the right surface gravity, Hawking temperature and tunneling rate near the event horizon and cosmical horizon.
A new method of researching fermion tunneling from the Vaidya–Bonner de Sitter black hole
Using the general tortoise coordinate transformation, we research the fermion tunneling of the Vaidya–Bonner de Sitter black hole via a semi-classical method and finally obtain the right surface gravity, Hawking temperature and tunneling rate near the event horizon and cosmical horizon
Neutron equivalent dose-rate measuring according to the single-sphere albedo method
This report reproduces the results of calibration radiation using the single-sphere albedo measuring method. It was done for the purpose of optimising the arrangement of detectors on the surface of the sphere and reduce the diameter of the moderator sphere from hitherto 30 cm whilst in addition determining the energy- and direction-dependency of a neutron equivalent dose-rate meter with He-3 detectors. Optimisation of the detector arrangement on the sphere's surface resulted in a corresponding boron-plastic capsulation with detector depths inside or outside the moderator di=-6 mm, and da=5 mm with albedo neutron detectors and thermal neutron detectors, respectively. (orig./DG)
A photon insensitive passive neutron spectrometer consisting of a single moderating polyethylene sphere with Dysprosium activation foils arranged along three perpendicular axes was designed by CIEMAT and INFN. The device is called Dy-SSS (Dy foil-based Single Sphere Spectrometer). It shows nearly isotropic response in terms of neutron fluence up to 20 MeV. The first prototype, previously calibrated with 14 MeV neutrons, has been recently tested in workplaces having different energy and directional distributions. These are a 2.5 MeV nearly mono-chromatic and mono-directional beam available at the ENEA Frascati Neutron Generator (FNG) and the photo-neutron field produced in a 15 MV Varian CLINAC DHX medical accelerator, located in the Ospedale S. Chiara (Pisa). Both neutron spectra are known through measurements with a Bonner Sphere Spectrometer. In both cases the experimental response of the Dy-SSS agrees with the reference data. Moreover, it is demonstrated that the spectrometric capability of the new device are independent from the directional distribution of the neutron field. This opens the way to a new generation of moderation-based neutron instruments, presenting all advantages of the Bonner sphere spectrometer without the disadvantage of the repeated exposures. This concept is being developed within the NESCOFI@BTF project of INFN (Commissione Scientifica Nazionale 5).
Bedogni, R.; Gómez-Ros, J. M.; Esposito, A.; Gentile, A.; Chiti, M.; Palacios-Pérez, L.; Angelone, M.; Tana, L.
2012-08-01
A photon insensitive passive neutron spectrometer consisting of a single moderating polyethylene sphere with Dysprosium activation foils arranged along three perpendicular axes was designed by CIEMAT and INFN. The device is called Dy-SSS (Dy foil-based Single Sphere Spectrometer). It shows nearly isotropic response in terms of neutron fluence up to 20 MeV. The first prototype, previously calibrated with 14 MeV neutrons, has been recently tested in workplaces having different energy and directional distributions. These are a 2.5 MeV nearly mono-chromatic and mono-directional beam available at the ENEA Frascati Neutron Generator (FNG) and the photo-neutron field produced in a 15 MV Varian CLINAC DHX medical accelerator, located in the Ospedale S. Chiara (Pisa). Both neutron spectra are known through measurements with a Bonner Sphere Spectrometer. In both cases the experimental response of the Dy-SSS agrees with the reference data. Moreover, it is demonstrated that the spectrometric capability of the new device are independent from the directional distribution of the neutron field. This opens the way to a new generation of moderation-based neutron instruments, presenting all advantages of the Bonner sphere spectrometer without the disadvantage of the repeated exposures. This concept is being developed within the NESCOFI@BTF project of INFN (Commissione Scientifica Nazionale 5).
Space Radiation Detector with Spherical Geometry
Wrbanek, John D. (Inventor); Fralick, Gustave C. (Inventor); Wrbanek, Susan Y. (Inventor)
2012-01-01
A particle detector is provided, the particle detector including a spherical Cherenkov detector, and at least one pair of detector stacks. In an embodiment of the invention, the Cherenkov detector includes a sphere of ultraviolet transparent material, coated by an ultraviolet reflecting material that has at least one open port. The Cherenkov detector further includes at least one photodetector configured to detect ultraviolet light emitted from a particle within the sphere. In an embodiment of the invention, each detector stack includes one or more detectors configured to detect a particle traversing the sphere.
Hawking radiation of the Vaidya-Bonner-de Sitter black hole
Chen Deyou; Yang Shuzheng [Institute of Theoretical Physics, China West Normal University, Nanchong, Sichuan 637002 (China)
2007-08-15
Considering the unfixed background space-time and the self-gravitational interaction, we view the Hawking radiation of the Vaidya-Bonner- de Sitter black hole by the Hamilton-Jacobi method and the radial geodesic method. The result shows the tunneling rate is related not only to the change of Bekenstein-Hawking entropy but also to the integral of the black hole mass and charge, which does not satisfy the unitary theory and is not in accordance with the known result.
Hollow sphere, a flexible multimode Gravitational Wave antenna
Lobo, J. Alberto
2001-01-01
Hollow spheres have the same theoretical capabilities as the usual solid ones, since they share identical symmetries. The hollow sphere is however more flexible, as thickness is an additional parameter one can vary to approach given specifications. I will briefly discuss the more relevant properties of the hollow sphere as a GW detector (frequencies, cross sections), and suggest some scenarios where it can generate significant astrophysical information.
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.).
杨波
2007-01-01
采用新的Tortoise坐标变换,将Vaidya-Bonner-de Sitter黑洞中的Klein-Gordon方程,在黑洞视界面附近化成典型的波动方程,得到在视界面附近Hawking辐射温度,导出了Hawking热辐射谱.
邓娟; 蒋青权; 冯中文; 李国平
2012-01-01
采用一种新的广义乌龟坐标变换对Vaidya-Bonner-de Sitter黑洞的熵进行研究,同时对其在旧乌龟坐标变换下的情况也做了对比分析.其结果表明两种情况下熵的形式相近,但是,新的广义乌龟坐标的结果对Vaidya-Bonner-de Sitter黑洞的熵做了相应的修正,新的乌龟坐标变换显得更加合理.%The principal focus of this paper is to study the entropy of Vaidya-Bonner-de Sitter black hole under a new general tortoise coordinate transformation, and then, to make the contrast and analysis of it with the old tortoise coordinates. It is found that the entropies obtained from both the new and old tortoise coordinate transformations are close to each other. The new general tortoise coordinate transformation makes the corresponding modification for the entropy of Vaidya-Bonner-de Sitter black hole and appears to be more reasonable.
孙鸣超
2005-01-01
在Tortoise坐标系中,利用brick-wall模型研究了电磁场对Vaidya-Bonner-de Sitter黑洞熵的量子修正. 当黑洞事件视界不随超前时间变化时,结果与Reissner-Nordstrm-de Sitter黑洞的量子熵完全相同.
Thermoluminescent detectors for neutron dosimetry at high altitudes
At high altitudes in the earth's atmosphere cosmic-ray induced neutrons become the dominant contributors to the biologically relevant dose equivalent. Depending on the geomagnetic latitude and the solar activity cycle, neutron dose onboard aircraft amounts, for example, to roughly 50 to 70 % of the overall dose equivalent. Neutron detection in complexly mixed radiation environments by means of active, i.e. power-consuming, detectors is commonly aggravated by the fact that a variety of charged particles present in the field cannot be discriminated and therefore biases the measurement. Passive thermoluminescent dosemeters (TLDs) are proposed as a convenient alternative. They are easy-to-handle in practical use, contain no flammable gases and emit no electromagnetic radiation that could interfere with sensitive electronics. The simultaneous application of specific detector types is known in neutron dosimetry as the pair method. Neutron-sensitive TLD-600 (6LiF) is combined with TLD-700 (7LiF) which is almost insensitive to neutrons. The sensitivity for all other radiations is identical for both types, so that a simple subtraction of the measured detector signals leads to the thermal neutron dose. As the neutron cross sections of 6Li and 7Li differ significantly only below 200 keV, the pair method in its conventional form assesses the dose only from neutrons in this energy region. The method can be extended for utilization at high altitudes, such as onboard aircraft, if the calibration of the TLDs is performed in a reference field which simulates in close proximity the atmospheric neutron environment. For our purposes we used the CERN-EU High-Energy Reference Field (CERF) for which the relative contribution of neutrons with energies below 200 keV to the entire fluence is practically the same as for the cosmic-ray induced neutron spectrum. Measurements with Bonner sphere spectrometers at the CERF facility and onboard aircraft and subsequent comparison with a FLUKA Monte
Chaney, A.; Lu, Lei; Stern, A.
2015-09-01
We show that fuzzy spheres are solutions of Lorentzian Ishibashi-Kawai-Kitazawa-Tsuchiya-type matrix models. The solutions serve as toy models of closed noncommutative cosmologies where big bang/crunch singularities appear only after taking the commutative limit. The commutative limit of these solutions corresponds to a sphere embedded in Minkowski space. This "sphere" has several novel features. The induced metric does not agree with the standard metric on the sphere, and, moreover, it does not have a fixed signature. The curvature computed from the induced metric is not constant, has singularities at fixed latitudes (not corresponding to the poles) and is negative. Perturbations are made about the solutions, and are shown to yield a scalar field theory on the sphere in the commutative limit. The scalar field can become tachyonic for a range of the parameters of the theory.
Song, F.; Toksoz, M. N.
2012-12-01
Over the last decade, hydraulic fracturing has become one important key enabling technique in the development of unconventional oil and gas reservoirs. Microseismic monitoring has proved to be an effective diagnostic tool to image complex fracturing and to understand fracture growth. The initial uptake of this geophysical technology has been focused on fast and accurate microearthquake locations. In addition to locations, microearthquake source mechanisms, represented by the complete moment tensors, reveal important information on geomechanical understanding of hydrofrac growth and have profound implications on fracturing design. The retrieval of complete moment tensors has been hindered by several factors including limited geophone azimuthal coverage, relatively poor data quality (due to small event magnitudes and high borehole noise) and velocity model uncertainty. In this paper, the complete microseismic moment tensors have been inverted using full waveforms. We use the waveforms to obtain an accurate velocity structure. The unconstrained inversion using two-well data and constrained inversion with one-well data have been conducted on Barnett shale and Bonner sand, respectively. Different fracture growth patterns are seen in these two datasets. The source mechanisms show mixed failure modes in the complex fracture network from the Barnett shale. In the Bonner sands, a planar fracture grows mostly by shear failure at tip characterized by a double couple mechanism. The results may be explained by different reservoir conditions, including the geomechanical properties of the formations. Correctly inverted microearthquake source mechanisms help better understand both the hydraulic fracturing and the underlying reservoir, and aid the development of sophisticated horizontal well completions.
The expedition carried out in March, 2008 to Lake Baikal became an important stage in the development of the SPHERE experiment. During the expedition the SPHERE-2 installation was hoisted, for the first time, on a tethered balloon, APA, to a height of 700 m over the lake surface covered with ice and snow. A series of test measurements were made. Preliminary results of the data processing are presented. The next plan of the SPHERE experiment is to begin a set of statistics for constructing the CR spectrum in the energy range 1016-1018 eV.
孙鸣超
2003-01-01
在Tortoise坐标系中,利用Brick-Wall模型研究中微子场和标量场对Vaidya-Bonner-de Sitter黑洞熵的量子修正.当黑洞事件视界不随超前时间变化时,结果与Reissner-Nordstrom-de Sitter黑洞的量子熵完全相同.
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.
Klotsa, Daphne; Hill, Richard J A; Bowley, Roger M; Swift, Michael R
2015-01-01
We describe experiments and simulations demonstrating the propulsion of a neutrally-buoyant swimmer that consists of a pair of spheres attached by a spring, placed in a vibrating fluid. The vibration of the fluid induces relative motion of the spheres which, for sufficiently large amplitudes, can lead to motion of the center of mass of the two spheres. We find that the swimming speed obtained from both experiment and simulation agree and collapse onto a single curve if plotted as a function of the streaming Reynolds number, suggesting that the propulsion is related to streaming flows. There appears to be a critical onset value of the streaming Reynolds number for swimming to occur. The mechanism for swimming is traced to a jet of fluid generated by the relative motion of the spheres.
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.
Scattering by a nihility sphere
Lakhtakia, A
2006-01-01
On interrogation by a plane wave, the back-scattering efficiency of a nihility sphere is identically zero, and its extinction and forward-scattering efficiencies are higher than those of a perfectly conducting sphere.
ORGANIZATION IN CONTEMPORARY PUBLIC SPHERE
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.
Electrical characteristics of sphere-plane type spark counters
The authors describe here the mechanical construction and operating characteristics of spark detectors using a small (0.30 mm) diameter sphere as anode, set opposite to a plane cathode and working by the ''corona'' effect, in air at atmospheric pressure. Counting characteristics are very similar to those of Rosenblum-type anode wire detectors. However, the sphere counter has a certain superiority over the Rosenblum counter inherent in its geometry : (a) there sidual current (background) is low and the release of ozone and nitrous oxides during the spark is not of great significance; (b) its self-capacity being very small, the detector gives a faster response; (c) unlike in the case of wire counters, efficiency is independent of particle incidence direction; (d) its sensitive volume, that of a solid of revolution around the axis of symmetry of the detector, amounts to a few cubic millimetres and, being very clearly defined, permits realization of accurate telescopic devices. (author)
Algebraic properties of Bier spheres
Inga Heudtlass
2012-05-01
Full Text Available We give a classification of flag Bier spheres, as well as descriptions of the first and second Betti numbers of general Bier spheres. Additionally, we compute the Betti numbers for a specific class of Bier spheres, constructed from skeletons of a full simplex.
Entanglement entropy for odd spheres
Dowker, J S
2010-01-01
It is shown, non--rigorously, that the effective action on a Z_q factored odd spheres (lune) has a vanishing derivative at q=1. This leaves the effective action on the ordinary odd d-sphere as (minus) the value of the entanglement entropy associated with a (d-2)-sphere. Some numbers are given.
Peternell, Martin; Sendra, Juana
2011-01-01
The conchoid of a surface $F$ with respect to given fixed point $O$ is roughly speaking the surface obtained by increasing the radius function with respect to $O$ by a constant. This paper studies {\\it conchoid surfaces of spheres} and shows that these surfaces admit rational parameterizations. Explicit parameterizations of these surfaces are constructed using the relations to pencils of quadrics in $\\R^3$ and $\\R^4$. Moreover we point to remarkable geometric properties of these surfaces and their construction.
Godsil, C. D.; Zaks, J.
2012-01-01
Let $G$ be the graph with the points of the unit sphere in $\\mathbb{R}^3$ as its vertices, by defining two unit vectors to be adjacent if they are orthogonal as vectors. We present a proof, based on work of Hales and Straus chromatic number of this graph is four. We also prove that the subgraph of G induced by the unit vectors with rational coordinates is 3-colourable.
Berenstein, David; Lashof-Regas, Robin
2015-01-01
We construct various exact analytical solutions of the $SO(3)$ BMN matrix model that correspond to rotating fuzzy spheres and rotating fuzzy tori.These are also solutions of Yang Mills theory compactified on a sphere times time and they are also translationally invariant solutions of the $\\mathcal{N} = 1^*$ field theory with a non-trivial charge density. The solutions we construct have a $\\mathbb{Z}_N$ symmetry, where $N$ is the rank of the matrices. After an appropriate ansatz, we reduce the problem to solving a set of polynomial equations in $2N$ real variables. These equations have a discrete set of solutions for each value of the angular momentum. We study the phase structure of the solutions for various values of $N$. Also the continuum limit where $N\\to \\infty$, where the problem reduces to finding periodic solutions of a set of coupled differential equations. We also study the topology change transition from the sphere to the torus.
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
Falling-sphere radioactive viscometry
In this work the falling sphere viscometric method was studies experimentally using a sphere tagged with 198Au radiosotopo, the objective being the demosntration of the advantages of this technique in relation to the traditional method. The utilisation of the falling radioactive sphere permits the point-point monitoring of sphere position as a function of count rate. The fall tube wall and end effects were determined by this technique. Tests were performed with spheres of different diameters in four tubes. The application of this technique demosntrated the wall and end effects in sphere speed. The case of sphere fall in the steady slow regime allowed the determination of the terminal velocity, showing the increase of botton end effect as the sphere approaches the tube base. In the case the transient slow regime, the sphere was initially in a state of respose near the top surface. The data obtained show the influence of the free surface and wall on the sphere acceleration. These experimental data were applied to the Basset equation on order to verify the behaviour of the terms in this equation. (author)
Plaquettes, Spheres, and Entanglement
Grimmett, Geoffrey R
2010-01-01
The high-density plaquette percolation model in d dimensions contains a surface that is homeomorphic to the (d-1)-sphere and encloses the origin. This is proved by a path-counting argument in a dual model. When d=3, this permits an improved lower bound on the critical point p_e of entanglement percolation, namely p_e >= \\mu^-2 where \\mu is the connective constant for self-avoiding walks on Z^3. Furthermore, when the edge density p is below this bound, the radius of the entanglement cluster containing the origin has an exponentially decaying tail.
Generalized Sphere Packing Bound
Fazeli, Arman; Vardy, Alexander; Yaakobi, Eitan
2014-01-01
Kulkarni and Kiyavash recently introduced a new method to establish upper bounds on the size of deletion-correcting codes. This method is based upon tools from hypergraph theory. The deletion channel is represented by a hypergraph whose edges are the deletion balls (or spheres), so that a deletion-correcting code becomes a matching in this hypergraph. Consequently, a bound on the size of such a code can be obtained from bounds on the matching number of a hypergraph. Classical results in hyper...
Dowker, J S
2012-01-01
I give some scalar field theory calculations on a d-dimensional lune of arbitrary angle, evaluating, numerically, the effective action which is expressed as a simple quadrature, for conformal coupling. Using this, the entanglement and Renyi entropies are computed. Massive fields are also considered and a renormalisation to make the (one-loop) effective action vanish for infinite mass is suggested and used, not entirely successfully. However a universal coefficient is derived from the large mass expansion. For the round sphere, I show how to convert the quadrature form of the conformal Laplacian determinant into the more usual sum of Riemann zeta functions (and log2).
Particle tracks fitted on the Riemann sphere
Strandlie, A; Frühwirth, R; Lillekjendlie, B
2000-01-01
We present a novel method of fitting trajectories of charged particles in high-energy physics particle detectors. The method fits a circular arc to two-dimensional measurements by mapping the measurements onto the Riemann sphere and fitting a plane to the transformed coordinates of the measurements. In this way, the non- linear task of circle fitting, which in general requires the application of some iterative procedure, is turned into a linear problem which can be solved in a fast, direct and non-iterative manner. We illustrate the usefulness of our approach by stating results from two simulation experiments of tracks from the ATLAS Inner Detector Transition Radiation Tracker (TRT). The first experiment shows that with a significantly lower execution time, the accuracy of the estimated track parameters is virtually as good as the accuracy obtained by applying an optimal, non-linear least- squares procedure. The second experiment focuses on track parameter estimation in the presence of ambiguous measurements....
Regular Totally Separable Sphere Packings
Reid, Samuel
2015-01-01
The topic of totally separable sphere packings is surveyed with a focus on regular constructions, uniform tilings, and contact number problems. An enumeration of all regular totally separable sphere packings in $\\mathbb{R}^2$, $\\mathbb{R}^3$, and $\\mathbb{R}^4$ which are based on convex uniform tessellations, honeycombs, and tetracombs, respectively, is presented, as well as a construction of a family of regular totally separable sphere packings in $\\mathbb{R}^d$ that is not based on a convex...
Properties of lithium orthosilicate spheres
Lithium ceramic spheres have been proposed as a tritium breeding material for a fusion reactor blanket. Spheres fabricated by Schott, Mainz show a glass-like structure in light and scanning electron microscopy. A crystalline structure, however, was detected by X-ray diffraction. Part of the spheres were annealed at 10000C for 2 h to heal microcracks and to relieve internal stress. After annealing a grain structure was found by microscopy with grains of 10-30 μm grain size. When stored in air the spheres took up moisture. After some days the water content yielded 2-3 mol%. A thermo-mechanical test was conducted with the spheres by cycling between 60 and 6000C in a stainless steel capsule which simulated the pressure load during thermal cycling of the fusion reactor blanket. Examination of the spheres after 10 cycles showed that 11% of as-fabricated spheres were broken. The amount of broken spheres which had been annealed was only 2%. It is assumed that healing of microcracks and relieve of internal stress improves the behavior of the spheres. (orig.)
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.
Sphere Recognition: Heuristics and Examples
Joswig, Michael; Lutz, Frank H.; Tsuruga, Mimi
2014-01-01
Heuristic techniques for recognizing PL spheres using the topological software polymake are presented. These methods have been successful very often despite sphere recognition being known to be hard (for dimensions $d \\ge 3$) or even undecidable (for $d \\ge 5$). A deeper look into the simplicial complexes for which the heuristics failed uncovered a trove of examples having interesting topological and combinatorial properties.
The Sphere Anemometer - A Fast Alternative to Cup Anemometry
Heißelmann, Hendrik; Hölling, Michael; Peinke, Joachim
The main problem of cup anemometry is the different response time for increasing and decreasing wind velocities due to its moment of inertia. This results in an overestimation of wind speed under turbulent wind conditions, the so-called over-speeding. Additionally, routine calibrations are necessary due to the wear of bearings. Motivated by these problems the sphere anemometer, a new simple and robust sensor for wind velocity measurements without moving parts, was developed at the University of Oldenburg. In contrast to other known thrust-based sensors, the sphere anemometer uses the light pointer principle to detect the deflection of a bending tube caused by the drag force acting on a sphere mounted at its top. This technique allows the simultaneous determination of wind speed and direction via a two-dimensional position sensitive detector.
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".
Public Sphere as Digital Assemblage
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......), and subjectivity (agency). This changed the public sphere into an assemblage consisting of both human and non-human actors interactingin a highly dynamic, networked environment. This paper proposes a framework for considering this new materiality in the field of the public sphere: the assemblage and complexity...
Simple manipulator for rotating spheres
We describe a simple device for rapidly rotating a small sphere to any orientation for inspection of the surface. The ball is held between two small, flat surfaces and rolls as the surfaces are moved differentially parallel to one another
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.
Economics and the Public Sphere
Reinert, Erik S.
2012-01-01
This paper identifies four different periods (1848, 1890s - partly also 1930s - and neoliberalism today) where the same tendencies recur: a Rise of Academic Monoculture (of esoteric knowledge), Refeudalization (tendencies towards a plutocracy), Crisis and Renewal. These sequences and their recurrence define the changing relationship between economics and the public sphere, and it is only through activities in the public sphere that any renewal will take place.
Isentropic Spheres in General Relativity
Humi, Mayer; Roumas, John
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 she...
McEwen, J D; Lasenby, A N
2006-01-01
We derive optimal filters on the sphere in the context of detecting compact objects embedded in a stochastic background process. The matched filter and the scale adaptive filter are derived on the sphere in the most general setting, allowing for directional template profiles and filters. The performance and relative merits of the two optimal filters are discussed. The application of optimal filter theory on the sphere to the detection of compact objects is demonstrated on simulated mock data. A naive detection strategy is adopted, with an initial aim of illustrating the application of the new optimal filters derived on the sphere. Nevertheless, this simple object detection strategy is demonstrated to perform well, even a low signal-to-noise ratio. Code written to compute optimal filters on the sphere (S2FIL), to perform fast directional filtering on the sphere (FastCSWT) and to construct the simulated mock data (COMB) are all made publicly available. (Accompanying code will be made publicly available on publi...
Tom Bonner Prize: Gamma-ray energy tracking array GRETINA and its early science results
Lee, I.-Yang
2016-03-01
Gamma-ray detector with good energy resolution has been one of the essential instruments for the study of nuclear structure. To push these studies toward the exotic nuclei near the particle stability line, we need detectors with higher peak efficiency and good peak-to-total ratio. In addition, radioactive ion beams needed for such studies are often produced by the projectile fragmentation method. They have high velocities, and detectors must provide adequate position resolution for accurate Doppler correction. To fulfill these requirements, the new concept of gamma ray energy tracking array was developed. GRETINA, with 1 π solid angle coverage, is the first implementation of this concept. It uses electrically segmented Ge crystals in a close packed geometry, fast digital electronics, and signal decomposition to determine the position and energy of the individual interaction points. Then the path of a gamma ray can be tracked using the angle-energy relation of the scattering process. GRETINA was completed at LBNL and started physics operation in 2012. It has been used at NSCL at MSU and ATLAS at ANL for a large number of experiments addressing diverse topics from nuclear structure to nuclear astrophysics. In this talk I will describe the concept of gamma-ray energy tracking and the technology developed for GRETINA. A few representative experiments showing the breadth of the science and the power of the instrument will be discussed. Finally the plan toward the full 4 π array GRETA will be presented.
Non-equilibrium Casimir forces: Spheres and sphere-plate
Krüger, Matthias; Bimonte, Giuseppe; Kardar, Mehran
2011-01-01
We discuss non-equilibrium extensions of the Casimir force (due to electromagnetic fluctuations), where the objects as well as the environment are held at different temperatures. While the formalism we develop is quite general, we focus on a sphere in front of a plate, as well as two spheres, when the radius is small compared to separation and thermal wavelengths. In this limit the forces can be expressed analytically in terms of the lowest order multipoles, and corroborated with results obtained by diluting parallel plates of vanishing thickness. Non-equilibrium forces are generally stronger than their equilibrium counterpart, and may oscillate with separation (at a scale set by material resonances). For both geometries we obtain stable points of zero net force, while two spheres may have equal forces in magnitude and direction resulting in a self-propelling state.
A technique for improving the calibration of large-area sphere sources
Walker, James H.; Cromer, Chris L.; Mclean, James T.
1991-01-01
A new technique for improving the accuracy of radiance calibrations for large-area integrating-sphere sources has been investigated. Such sources are used to calibrate numerous aircraft and spacecraft remote sensing instruments. Recent measurements performed at NIST and NASA Goddard Space Flight Center have demonstrated that the uncertainty of sphere-source radiance measurements can be improved from the present 5 to 10 percent level to a 1 to 2 percent level. Silicon detectors with bandpass filters mounted in front of them and calibrated for absolute spectral responsivity can be used to confirm and to monitor the absolute radiance of a sphere source.
Measurement of Neutron Transmission Through Iron Spheres
We have measured the transmission of neutrons through iron spheres with several different neutron sources. The D(d,n) reaction and the 15N(n,p) reaction were found to be the best candidates for nearly monoenergetic sources at energies below 11 MeV. We have used a quasi monoenergetic source with 3.0-, 5.0-, and 7.0-MeV deuterons incident on a deuteron gas cell and 5.1-MeV protons incident on a 15N gas cell. The Ohio University Beam Swinger Facility was used in these measurements. This allowed a single fixed detector in a well-shielded time-of-flight (TOF) tunnel to be used for measurements at all angles. This allows a great reduction in the background from room scattered neutrons. The detector, either NE-213 or lithium glass, was calibrated relative to the neutron spectrum from the B(d,n) or the Al(d,n) source reaction. These spectra have been measured relative to the primary neutron standard, 235U(n, f). The transmitted neutrons have been measured for all source reactions at several angles. The data will be reported as the number of neutrons versus time-of-flight since multiple scattering does not allow the energy to be determined accurately by time-of-flight. We have also measured the source reaction at several angles to enhance the modeling of the source spectrum
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.
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
Neutron dose equivalent rate meter on the basis of the single sphere Albedo technique
In area monitoring there is a need for a more accurate neutron reference dose rate meter, especially for the purpose of albedo dosemeter calibrations in neutron stray radiation fields of interest. The so-called Single Sphere Albedo Counter makes use of three active 3He proportional counters as thermal neutron detectors positioned in the centre and on the surface (albedo dosemeter configurations) of a polyethylene sphere. The linear combination of the detector readings allows for the indication of different quantities like H*(10),D,φ, and reduces the energy dependence significantly. The paper describes the dosimetric properties of a prototype instrument and its application in routine monitoring. (author)
Laflamme-Sanders, Alexandra; Zhu, Mu
2008-11-01
LAGO is an efficient kernel algorithm designed specifically for the rare target detection problem. However, unlike other kernel algorithms, LAGO cannot be easily used with many domain-specific kernels. We solve this problem by first providing a unified framework for LAGO and clarifying its basic principle, and then applying that principle on the unit sphere instead of in the Euclidean space. PMID:18775643
Boulatov, D. V.
1993-01-01
We give the formula for a simple Wilson loop on a sphere which is valid for an arbitrary QCD$_2$ saddle-point $\\rho(x)$: \\mbox{$W(A_1,A_2)=\\oint \\frac{dx}{2\\pi i} \\exp(\\int dy \\frac{\\rho(y)}{y-x}+A_2x)$}. The strong-coupling-phase solution is investigated.
Schleimer, Saul
2004-01-01
We prove that the three-sphere recognition problem lies in the complexity class NP. Our work relies on Thompson's original proof that the problem is decidable [Math. Res. Let., 1994], Casson's version of her algorithm, and recent results of Agol, Hass, and Thurston [ArXiv, 2002].
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
Simulation and calibration of the response function of multi-sphere neutron spectrometer
In order to realize the on-line real-time measurement of neutron spectrum of ITER fusion, this paper presents a multi-sphere spectrometer system which consists of eight thermal neutron detectors, namely SP9 3He proportional counter, embedded in eight different diameter polyethylene spheres. The response function of eight polyethylene spheres of multi-sphere neutron spectrometer was calculated after the simulation of the neutron transport processes in multi-sphere spectrometer by adopting software Geant4. The peak of the response function is in the low energy region for smaller diameter polyethylene sphere. As the polyethylene sphere diameter increased, the peak of the response function moves to the high energy region. The experimental calibration adopts 241Am-Be neutron source. The relative error between normalized data of experiment 4π solid angle counts and normalized data of simulated detection efficiency of 4 in to 8 in polyethylene sphere is from 1.152% to 12.222%. The experimental results verify the response function of the simulation. All these results provide a theoretical and experimental basis for solving the on-line real-time neutron spectrum of ITER fusion. (authors)
Anon.
2009-11-15
In the ''Bonner Bogen'' construction project, the focus was on resources-saving technology and maximum user comfort, resulting in an integrated planning and implementation process. According to the investor, BonnVisio, the technical infrastructure and energy center of the building - based on groundwater geothermal energy with aquifer storage - is unique in Germany and Europe in terms of size, mode of operation, and efficiency. (orig.)
Eddy currents in a conducting sphere
Bergman, John; Hestenes, David
1986-01-01
This report analyzes the eddy current induced in a solid conducting sphere by a sinusoidal current in a circular loop. Analytical expressions for the eddy currents are derived as a power series in the vectorial displacement of the center of the sphere from the axis of the loop. These are used for first order calculations of the power dissipated in the sphere and the force and torque exerted on the sphere by the electromagnetic field of the loop.
Minimality of Symplectic Fiber Sums along Spheres
Dorfmeister, Josef G
2010-01-01
In this note we complete the discussion of minimality of symplectic fiber sums. We find, that for fiber sums along spheres the minimality of the sum is determined by the cases discussed by M. Usher and one additional case: If the sum is the result of the rational blow-down of a symplectic -4-sphere in X, then it is non-minimal if X contains a certain configuration of exceptional spheres in relation to this -4-sphere.
Coating a Sphere With Evaporated Metal
Strayer, D. M.; Jackson, H. W.; Gatewood, J. R.
1986-01-01
In vacuum coating apparatus, metal evaporated onto sphere from small source located some distance away. Sphere held in path of metal vapor while rotated about axis that rocks back and forth. One tilting motion particularly easy to produce is sinusoidal rocking with frequency much lower than rotational frequency. Apparatus developed for coating single-crystal sapphire spheres with niobium.
Experimental verification of the JRR-4 BNCT facility. Pt. 1
The report is structured as follows: (1) Introduction (JAERI facility; Modes, parameters); (2) Experimental methods (Activation foils: activity measurements, spectrum adjustment; Bonner spheres spectrometer; Al-P glass TLD; Semiconductor detector; Si diode for fast neutron kerma determination); (3) Experimental set-up (Free beam measurements: neutron spectrum measurement, photon dose and fast neutron kerma measurement, beam profile measurement, BSS measurement; Phantom measurements: neutron dose depth measurement, photon dose and fast neutron kerma depth profiles, on-line thermal neutron measurement in water phantom, on-line thermal neutron measurement in cylindrical water phantom); 4. Si-Li detector dead time and effectiveness; and (5) The Bonner sphere spectrometer responses. (P.A.)
Spheres of Justice within Schools
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......, the allocation of (or selection into) learning places, teaching–learning practices, teachers’ treatment of students, and student evaluations of grade distribution. We discuss the literature on the beliefs by students and teachers about the just distribution of educational goods in these five domains......, and on the practices used in the actual allocation of these goods. In line with normative ‘spheres of justice’ arguments in social theory, we conclude that the ideals of social justice within schools vary strongly according to the particular resource to be distributed. Moreover, these ideals often do...
Sknepnek, Rastko; Henkes, Silke
2015-02-01
We show that coupling to curvature nontrivially affects collective motion in active systems, leading to motion patterns not observed in flat space. Using numerical simulations, we study a model of self-propelled particles with polar alignment and soft repulsion confined to move on the surface of a sphere. We observe a variety of motion patterns with the main hallmarks being polar vortex and circulating band states arising due to the incompatibility between spherical topology and uniform motion—a consequence of the "hairy ball" theorem. We provide a detailed analysis of density, velocity, pressure, and stress profiles in the circulating band state. In addition, we present analytical results for a simplified model of collective motion on the sphere showing that frustration due to curvature leads to stable elastic distortions storing energy in the band.
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
2016-02-23
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. PMID:26843132
The status and recent progress of silicon detectors for high energy physics is reviewed. Emphasis is put on detectors with high spatial resolution and the use of silicon detectors in calorimeters. (orig.)
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
Fusion breeder sphere - PAC blanket design
There is a considerable world-wide effort directed toward the production of materials for fusion reactors. Many ceramic fabrication groups are working on making lithium ceramics in a variety of forms, to be incorporated into the tritium breeding blanket which will surround the fusion reactor. Current blanket designs include ceramic in either monolithic or packed sphere bed (sphere-pac) forms. The major thrust at AECL is the production of lithium aluminate spheres to be incorporated in a sphere-pac bed. Contemporary studies on breeder blanket design offer little insight into the requirements on the sizes of the spheres. This study examined the parameters which determine the properties of pressure drop and coolant requirements. It was determined that an optimised sphere-pac bed would be composed of two diameters of spheres: 75 weight % at 3 mm and 25 weight % at 0.3 mm
Generating perfect fluid spheres in general relativity
Ever since Karl Schwarzschild's 1916 discovery of the spacetime geometry describing the interior of a particular idealized general relativistic star--a static spherically symmetric blob of fluid with position-independent density--the general relativity community has continued to devote considerable time and energy to understanding the general-relativistic static perfect fluid sphere. Over the last 90 years a tangle of specific perfect fluid spheres has been discovered, with most of these specific examples seemingly independent from each other. To bring some order to this collection, in this article we develop several new transformation theorems that map perfect fluid spheres into perfect fluid spheres. These transformation theorems sometimes lead to unexpected connections between previously known perfect fluid spheres, sometimes lead to new previously unknown perfect fluid spheres, and in general can be used to develop a systematic way of classifying the set of all perfect fluid spheres
On Sphere Detection and Minimum-Phase Prefiltered Reduced-State Sequence Estimation
Hansen, Morten; Christensen, Lars P.B.; Winther, Ole
2007-01-01
reducedstate sequence estimation, providing a unifying framework for the two detection methods. It is illustrated how minimum-phase prefiltering or the Linear Minimum Mean-Square Error Decision Feedback Equalization (LMMSE-DFE) forward filter is capable of reducing the complexity of sphere detectors...
A novel ionization detector for use in X-ray tomography is described in detail. To achieve the ultimate resolution, the use of small detectors is necessary and, for ionization detectors, this implies using xenon gas at high pressure. Conventional small detectors can suffer from ''bowing'' but the present design overcomes their problems. (U.K.)
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
Duan, Zhipeng; He, Boshu; Duan, Yuanyuan
2015-07-01
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.
Second-sphere complexes in analytical chemistry
Literary data on the application in the modern analytical chemistry of outer-sphere complexes, forming from coordination-saturated inner-sphere complexes and ligands, cation particles or organic solvent molecules in the second sphere are summarised. It is shown, that the outer-sphere complexes peculiarities, involving in their relatively low stability and activation energy for the processes in the second sphere, together with their variety allows one to effectively use these complexes for separation, extraction and, especially, determination of inorganic and organic substances. Outer-sphere complexes are used to determine some transition metals, lanthanides, berillium, boron and some other elements. The improvement of sensitivity, selectivity and expressiveness of analytical determination, achieved here, is discussed
Sphere-Pac Evaluation for Transmutation
Icenhour, A.S.
2005-05-19
The U.S. Department of Energy Advanced Fuel Cycle Initiative (AFCI) is sponsoring a project at Oak Ridge National Laboratory with the objective of conducting the research and development necessary to evaluate the use of sphere-pac transmutation fuel. Sphere-pac fuels were studied extensively in the 1960s and 1970s. More recently, this fuel form is being studied internationally as a potential plutonium-burning fuel. For transmutation fuel, sphere-pac fuels have potential advantages over traditional pellet-type fuels. This report provides a review of development efforts related to the preparation of sphere-pac fuels and their irradiation tests. Based on the results of these tests, comparisons with pellet-type fuels are summarized, the advantages and disadvantages of using sphere-pac fuels are highlighted, and sphere-pac options for the AFCI are recommended. The Oak Ridge National Laboratory development activities are also outlined.
Synthesis and characterization of hydrocarbon sphere
With glucose as starting material, hydrocarbon sphere which was rich in oxygen containing functional groups was synthesized by hydrothermal carbonization process, and characterized by SEM and FTIR techniques. The results show that the size and dispersion of carbon spheres depend on many factors, including the concentration of glucose, the reaction temperature and the adulterated organic monomer. The obtained hydrocarbon spheres contain rich functional groups which can greatly improve the hydrophilicity and chemical reactivity. (authors)
Counter public spheres and global modernity
Fenton, Natalie; Downey, John
2015-01-01
This article explores the concept of counter public spheres and their relationship to the dominant public sphere. We argue that counter public spheres are increasingly relevant due to particular social and political configurations that mark out a distinct stage of modernity. We suggest that this stage is characterised in particular by the intensification of globalisation, the rise of neo-liberalism and a decline of trust and social democracy resulting in instability in the dominant public sph...
Counter public spheres and global modernity:
Downey, John; Fenton, Natalie
2003-01-01
This article explores the concept of counter public spheres and their relationship to the dominant public sphere. We argue that counter public spheres are increasingly relevant due to particular social and political configurations that mark out a distinct stage of modernity. We suggest that this stage is characterised in particular by the intensification of globalisation, the rise of neo-liberalism and a decline of trust and social democracy resulting in instability in the dominant public sph...
The fuzzy sphere *-product and spin networks
We analyze the expansion of the fuzzy sphere noncommutative product in powers of the noncommutativity parameter. To analyze this expansion we develop a graphical technique that uses spin networks. This technique is potentially interesting in its own right as introducing spin networks of Penrose into noncommutative geometry. Our analysis leads to a clarification of the link between the fuzzy sphere noncommutative product and the usual deformation quantization of the sphere in terms of the *-product
Method for producing small hollow spheres
A method is described for producing small hollow spheres of glass, metal or plastic, wherein the sphere material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature (T >approx. 6000C). As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming a hollow sphere of controllable thickness. The thus produced hollow spheres (20 to 103μm) have a variety of application, and are particularly useful in the fabrication of targets for laser implosion such as neutron sources, laser fusion physics studies, and laser initiated fusion power plants
Hollow Spheres in Composite Materials and Metallic Hollow Sphere Composites (MHSC)
Baumeister, Erika; Molitor, Martin
The newly developed metallic hollow spheres are used in combination with a polymeric matrix for producing metallic hollow-sphere-composites (MSHC), which have been developed for mechanical engineering applications in the “InnoZellMet” project.
The periodically oscillating plasma sphere
A new method of operating an inertial electrostatic confinement (IEC) device is proposed, and its performance is evaluated. The scheme involved an oscillating thermal cloud of ions immersed in a bath of electrons that form a harmonic oscillator potential. The scheme is called the periodically oscillating plasma sphere, and it appears to solve many of the problems that may limit other IEC systems to low gain. A set of self-similar solutions to the ion fluid equations is presented, and plasma performance is evaluated. Results indicate that performance enhancement of gridded IEC systems such as the Los Alamos intense neutron source device is possible as well as high-performance operation for low-loss systems such as the Penning trap experiment. Finally, a conceptual idea for a massively modular Penning trap reactor is also presented
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
Habitable sphere and fine structure constant
Kozlovskii, Miroslaw P; Kozlowski, Miroslaw; Marciak-Kozlowska, Janina
2005-01-01
Future space missions, TPF and Darwin will focus on searches of signatures of life on extrasolar planets. In this paper we look for model independ definition of the habitable zone. It will be shown that the radius of the habitable sphere depends only on the constants of the Nature. Key words: Habitable sphere, fine structure constant.
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.
Electric dipoles on the Bloch sphere
Vutha, Amar C.
2015-03-01
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 and molecular physics.
Reversible thermal gelation in soft spheres
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 high...... temperatures. A phase diagram analogous to that of sterically stabilized colloids is proposed....
Marketing approach to management of service sphere
Остафійчук, Ярослав Васильович
2015-01-01
Approaches to management service sphere at different hierarchical levels with the use of marketing methodology have been considered. Functions of regional marketing in service sphere and its structure, possibilities of integration into marketing of components from other administrative conceptshave been analyzed.
Cheng, Hongbo
2013-01-01
The Casimir energies for plate-sphere system and sphere-sphere system under PFA in the presence of one extra compactified universal dimension are analyzed. We find that the Casimir energy between a plate and a sphere in the case of sphere-based PFA is divergent. The Casimir energy of plate-sphere system in the case of plate-based PFA is finite and keeps negative. The extra-dimension corrections to the Casimir energy will be more manifest if the sphere is larger or farther away from the plate. It is shown that the negative Casimir energy for two spheres is also associated with the sizes of spheres and extra space. The larger spheres and the longer distance between them make the influence from the additional dimension stronger.
Cheng, Hongbo
2015-08-01
The Casimir energies for plate-sphere system and sphere-sphere systems under PFA in the presence of one extra compactified universal dimension are analyzed. We find that the Casimir energy between a plate and a sphere in the case of sphere-based PFA is divergent. The Casimir energy of plate-sphere system in the case of plate-based PFA is finite and keeps negative. The extra-dimension corrections to the Casimir energy will be more manifest if the sphere is larger or farther away from the plate. It is shown that the negative Casimir energy for two spheres is also associated with the sizes of spheres and extra space. The larger spheres and the longer distance between them make the influence from the additional dimension stronger.
Superelastic carbon spheres under high pressure
Li, Meifen; Guo, Junjie; Xu, Bingshe
2013-03-01
We report a superelastic deformation behavior of carbon spheres by the in situ Raman spectroscopy in a high-pressure diamond anvil cell. The carbon spheres produced by arc discharging in toluene have a mean diameter of 200 nm and an onion-like multilayer graphitic structure. We find that the elastic coefficients, during both the compression and decompression processes, remain a constant up to 10 GPa, indicating a superior high-pressure structural stability. Such superelastic behavior is related to the isotropic and concentric configuration of carbon spheres and provides additional insight into improving the microscopic mechanical properties of small-scale particles.
Two-sphere low Reynold's propeller
Najafi, Ali; Zargar, Rojman
2010-01-01
A three-dimensional model of a low-Reynold's swimmer is introduced and analyzed in this paper. This model consists of two large and small spheres connected by two perpendicular thin rods. The geometry of this system is motivated by the microorganisms that use a single tail to swim, the large sphere represents the head of microorganism and the small sphere resembles its tail. Each rod changes its length and orientation in a non-reciprocal manner that effectively propel the system. Translationa...
Modern Monte Carlo transport simulations of the Lawrence Livermore National Laboratory pulsed-sphere time of flight experiments have recently been performed. In these experiments, 14 MeV neutrons, generated via the 3H(d, n)4He reaction, interact with a sphere of material that surrounds the neutron generating target. The time of arrival of the uncollided and collided neutrons are recorded in a detector system placed up to 10 meters from the center of the sphere. A collection of experiments with varying sphere materials, mean-free-paths and detector systems have been modeled using the Mercury Monte Carlo transport code. This effort serves to validate new features of the Mercury code, including general sources, tallies and point-detector / biased-collisions variance reduction methods, as well as assess the quality of evaluated nuclear data sets. In general, the level of agreement between the calculations and experiment is very good. However, for certain pulsed spheres, discrepancies are observed between the simulations using different nuclear data sets. (author)
An accuracy test of the Monte Carlo ball-point detector estimator
The Monte Carlo ball-point detector estimator is an alternative technique to remove the standard point-detector estimator singularity. Collisions in the neighborhood of the detector have their contributions made towards the cross sectional area of a sphere centered at the detector position. The theoretical foundation is based on the incremental-sphere concept of the flux and the technique presents new approaches to the calculation of the contributions from collisions inside and outside the sphere. The results indicate that for the demonstration problem, the new formalism is more accurate than the averaged flux calculation inside the sphere volume. This new technique can be easily included in standard Monte Carlo radiation transport codes. (author)
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.
Entanglement entropy across a deformed sphere
Mezei, Márk
2014-01-01
I study the entanglement entropy (EE) across a deformed sphere in conformal field theories (CFTs). I show that the sphere (locally) minimizes the universal term in EE among all shapes. In arXiv:1407.7249 it was derived that the sphere is a local extremum, by showing that the contribution linear in the deformation parameter is absent. In this paper I demonstrate that the quadratic contribution is positive and is controlled by the coefficient of the stress tensor two point function, $C_T$. Such a minimization result contextualizes the fruitful relation between the EE of a sphere and the number of degrees of freedom in field theory. I work with CFTs with gravitational duals, where all higher curvature couplings are turned on. These couplings parametrize conformal structures in stress tensor $n$-point functions, hence I show the result for infinitely many CFT examples.
Exceptional cosmetic surgeries on homology spheres
Ravelomanana, Huygens C.
2016-01-01
We investigate the cosmetic surgery conjecture for hyperbolic knots in integer homology spheres, focusing on exceptional surgeries. We give some restrictions on the slopes of exceptional truly cosmetic surgeries according to the type of surgery.
Gender, Diversity and the European Public Sphere
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....
Elastic spheres can walk on water
Belden, Jesse; Hurd, Randy C.; Jandron, Michael A.; Bower, Allan F.; Truscott, Tadd T.
2016-02-01
Incited by public fascination and engineering application, water-skipping of rigid stones and spheres has received considerable study. While these objects can be coaxed to ricochet, elastic spheres demonstrate superior water-skipping ability, but little is known about the effect of large material compliance on water impact physics. Here we show that upon water impact, very compliant spheres naturally assume a disk-like geometry and dynamic orientation that are favourable for water-skipping. Experiments and numerical modelling reveal that the initial spherical shape evolves as elastic waves propagate through the material. We find that the skipping dynamics are governed by the wave propagation speed and by the ratio of material shear modulus to hydrodynamic pressure. With these insights, we explain why softer spheres skip more easily than stiffer ones. Our results advance understanding of fluid-elastic body interaction during water impact, which could benefit inflatable craft modelling and, more playfully, design of elastic aquatic toys.
ANALYSIS OF MECHANISMS FINANCING OF CULTURAL SPHERE
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.
A sphere moving down the surface of a static sphere and a simple phase diagram
Jayanth, V; Biswas, Anindya Kumar
2008-01-01
A small sphere placed on the top of a big static frictionless sphere, slips until it leaves the surface at an angle $\\theta_{l}=\\cos^{-1}{2/3}$. On the other extreme, if the surface of the big sphere has coefficient of static friction, $\\mu_s\\to\\infty$, the small sphere starts rolling and continues to do so until it leaves the surface at an angle $\\theta_{l} =\\cos^{-1}{10/17}$. In the case where, $0\\leq\\mu_s<\\infty$, we get a simple phase diagram. The three phases are pure rolling, rolling with slipping and detached state. One phase line separates pure rolling from rolling with slipping. This diagram is obtained when stopping angles for pure rolling are plotted against static friction coefficients $\\mu_s$. Study in this article is restricted to the case when the mobile sphere starts at the top of the static sphere with infinitesimal kinetic energy.
Please comply: the water entry of soft spheres
Belden, Jesse; Hurd, Randy; Fanning, Tate; Jandron, Michael; Rekos, John; Bower, Allan; Truscott, Tadd
2015-11-01
The typical phenomena associated with sphere water impact are significantly altered when the sphere material is highly compliant rather than rigid. We describe the water impact physics of homogenous and hollow elastic spheres. The homogeneous spheres undergo large oscillatory deformations throughout entry that carve nested disturbances into the normally smooth air cavity, altering cavity shape and pinch off. Using an analytical model, we relate the maximum sphere deformation to the material properties and impact velocity. This characteristic deformation is used to reconcile the differences between cavities formed by compliant and rigid spheres. In addition to the nested disturbances seen with the homogeneous spheres, we observe azimuthal irregularities on the cavity during water entry of hollow elastic spheres. Based on experiments and finite-element modeling, we suggest that these disturbances are initiated by vibration mode shapes excited in the hollow spheres upon impact. For all sphere types, we compare the forces throughout water entry to the rigid sphere case.
Hollow sphere ceramic particles for abradable coatings
A hollow sphere ceramic flame spray powder is disclosed. The desired constituents are first formed into agglomerated particles in a spray drier. Then the agglomerated particles are introduced into a plasma flame which is adjusted so that the particles collected are substantially hollow. The hollow sphere ceramic particles are suitable for flame spraying a porous and abradable coating. The hollow particles may be selected from the group consisting of zirconium oxide and magnesium zirconate
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.
Liouville Quantum Gravity on the Riemann Sphere
David, François; Kupiainen, Antti; Rhodes, Rémi; Vargas, Vincent
2016-03-01
In this paper, we rigorously construct Liouville Quantum Field Theory on the Riemann sphere introduced in the 1981 seminal work by Polyakov. We establish some of its fundamental properties like conformal covariance under PSL{_2({C})}-action, Seiberg bounds, KPZ scaling laws, KPZ formula and the Weyl anomaly formula. We also make precise conjectures about the relationship of the theory to scaling limits of random planar maps conformally embedded onto the sphere.
Surface polaritons on left-handed spheres
Ancey, Stéphane; Décanini, Yves; Folacci, Antoine; Gabrielli, Paul
2007-01-01
We consider the interaction of an electromagnetic field with a left-handed sphere, i.e., with a sphere fabricated from a left-handed material, in the framework of complex angular momentum techniques. We emphasize more particularly, from a semiclassical point of view, the resonant aspects of the problem linked to the existence of surface polaritons. We prove that the long-lived resonant modes can be classified into distinct families, each family being generated by one surface polariton propaga...
Geometrical Dynamics in a Transitioning Superconducting Sphere
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.
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.
Volume bounds of conic 2-spheres
Fang, Hao; Lai, Mijia
2016-01-01
We obtain sharp volume bound for a conic 2-sphere in terms of its Gaussian curvature bound. We also give the geometric models realizing the extremal volume. In particular, when the curvature is bounded in absolute value by $1$, we compute the minimal volume of a conic sphere in the sense of Gromov. In order to apply the level set analysis and iso-perimetric inequality as in our previous works, we develop some new analytical tools to treat regions with vanishing curvature.
Anisotropic fluid spheres in general relativity
A procedure is developed to find static solutions for anisotropic fluid spheres from known static solutions for perfect fluid spheres. The method is used to obtain four exact analytical solutions of Einstein's equations for spherically symmetric self-gravitating distribution of anisotropic matter. The solutions are matched to the Schwarzschild exterior metric. The physical features of one of the solutions are briefly discussed. Many previously known perfect fluid solutions are derived as particular cases. (author)
A novel sampling theorem on the sphere
McEwen, J D
2011-01-01
We develop a novel sampling theorem on the sphere and corresponding fast algorithms by associating the sphere with the torus through a periodic extension. The fundamental property of any sampling theorem is the number of samples required to represent a band-limited signal. To represent exactly a signal on the sphere band-limited at L, all sampling theorems on the sphere require O(L^2) samples. However, our sampling theorem requires less than half the number of samples of other equiangular sampling theorems on the sphere and an asymptotically identical, but smaller, number of samples than the Gauss-Legendre sampling theorem. The complexity of our algorithms scale as O(L^3), however, the continual use of fast Fourier transforms reduces the constant prefactor associated with the asymptotic scaling considerably, resulting in algorithms that are fast. Furthermore, we do not require any precomputation and our algorithms apply to both scalar and spin functions on the sphere without any change in computational comple...
Viererbl, L.; Lahodová, Z.; Klupák, V.; Sus, F.; Kučera, Jan; Kůs, P.; Marek, M.
2011-01-01
Roč. 632, č. 1 (2011), s. 109-111. ISSN 0168-9002 Institutional research plan: CEZ:AV0Z10480505 Keywords : Transmutation detector * Activation method * Neutron detector * Neutron fluence Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.207, year: 2011
Fischer, Hans Gerhard
1996-01-01
Detector physics and operational aspects of gaseous detectors will be discussed. Topics such as ionization processes, gas amplification and its limitations, pulse formation and decoupling, related electronics constraints, operational stability and ageing phenomena will be touched with the aim at some quantitative understanding.
Harrington-Lueker, Donna
1992-01-01
Schools that count on metal detectors to stem the flow of weapons into the schools create a false sense of security. Recommendations include investing in personnel rather than hardware, cultivating the confidence of law-abiding students, and enforcing discipline. Metal detectors can be quite effective at afterschool events. (MLF)
Innovation embedded in entrepreneurs’ networks in private and public spheres
Schøtt, Thomas; Cheraghi, Maryam; Rezaei, Shahamak; Vang, Jan
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...... societies, China and Denmark. Global Entrepreneurship Monitor has surveyed entrepreneurs in China, Denmark and elsewhere. Analyses reconfirm the global tendencies and show that, China in contrast to Denmark, public sphere networking is sparser, but private sphere networking is denser. Innovation 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....
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.
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.
The Separate Spheres Model of Gendered Inequality.
Andrea L Miller
Full Text Available Research on role congruity theory and descriptive and prescriptive stereotypes has established that when men and women violate gender stereotypes by crossing spheres, with women pursuing career success and men contributing to domestic labor, they face backlash and economic penalties. Less is known, however, about the types of individuals who are most likely to engage in these forms of discrimination and the types of situations in which this is most likely to occur. We propose that psychological research will benefit from supplementing existing research approaches with an individual differences model of support for separate spheres for men and women. This model allows psychologists to examine individual differences in support for separate spheres as they interact with situational and contextual forces. The separate spheres ideology (SSI has existed as a cultural idea for many years but has not been operationalized or modeled in social psychology. The Separate Spheres Model presents the SSI as a new psychological construct characterized by individual differences and a motivated system-justifying function, operationalizes the ideology with a new scale measure, and models the ideology as a predictor of some important gendered outcomes in society. As a first step toward developing the Separate Spheres Model, we develop a new measure of individuals' endorsement of the SSI and demonstrate its reliability, convergent validity, and incremental predictive validity. We provide support for the novel hypotheses that the SSI predicts attitudes regarding workplace flexibility accommodations, income distribution within families between male and female partners, distribution of labor between work and family spheres, and discriminatory workplace behaviors. Finally, we provide experimental support for the hypothesis that the SSI is a motivated, system-justifying ideology.
The Separate Spheres Model of Gendered Inequality.
Miller, Andrea L; Borgida, Eugene
2016-01-01
Research on role congruity theory and descriptive and prescriptive stereotypes has established that when men and women violate gender stereotypes by crossing spheres, with women pursuing career success and men contributing to domestic labor, they face backlash and economic penalties. Less is known, however, about the types of individuals who are most likely to engage in these forms of discrimination and the types of situations in which this is most likely to occur. We propose that psychological research will benefit from supplementing existing research approaches with an individual differences model of support for separate spheres for men and women. This model allows psychologists to examine individual differences in support for separate spheres as they interact with situational and contextual forces. The separate spheres ideology (SSI) has existed as a cultural idea for many years but has not been operationalized or modeled in social psychology. The Separate Spheres Model presents the SSI as a new psychological construct characterized by individual differences and a motivated system-justifying function, operationalizes the ideology with a new scale measure, and models the ideology as a predictor of some important gendered outcomes in society. As a first step toward developing the Separate Spheres Model, we develop a new measure of individuals' endorsement of the SSI and demonstrate its reliability, convergent validity, and incremental predictive validity. We provide support for the novel hypotheses that the SSI predicts attitudes regarding workplace flexibility accommodations, income distribution within families between male and female partners, distribution of labor between work and family spheres, and discriminatory workplace behaviors. Finally, we provide experimental support for the hypothesis that the SSI is a motivated, system-justifying ideology. PMID:26800454
Neutron energy spectrum from 7 to 180 MeV and photon energy spectrum from 4 to 50 MeV were measured onboard an aircraft using a newly developed phoswich-type neutron detector at 10.8 km altitude (atmospheric depth of 249 g/cm2) and geographical latitude of 39degN (a vertical cut-off rigidity of 10.2 GV) near Japan on February 13, 2008 (at a heliocentric potential of 312 MV). Our results were compared with other measurements obtained using 3He-loaded or extended-energy multi moderator neutron spectrometers (Bonner balls) at aviation altitudes, an organic liquid scintillator on the ground, and a double-scatter neutron telescope at the top of the atmosphere and with calculations using the LUIN2000, EXPACS and RMC codes. Our measured results give a large, sharp peak around a neutron energy of 70 MeV, although Bonner balls present a broad peak around 100 MeV due to low energy resolution. Our neutron fluxes agree well with the others. The measured photon energy spectrum is between the LUIN2000- and EXPACS-calculated spectra and agrees with measured vertical photon spectra at the top of the atmosphere. This onboard study provides the first experimental neutron energy spectrum in the high-energy region (over 10 MeV) with a high energy resolution. (author)
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.
The thermal conductivity of beds of spheres
McElroy, D.L.; Weaver, F.J.; Shapiro, M.; Longest, A.W.; Yarbrough, D.W.
1987-01-01
The thermal conductivities (k) of beds of solid and hollow microspheres were measured using two radial heat flow techniques. One technique provided k-data at 300 K for beds with the void spaces between particles filled with argon, nitrogen, or helium from 5 kPa to 30 MPa. The other technique provided k-data with air at atmospheric pressure from 300 to 1000 K. The 300 K technique was used to study bed systems with high k-values that can be varied by changing the gas type and gas pressure. Such systems can be used to control the operating temperature of an irradiation capsule. The systems studied included beds of 500 ..mu..m dia solid Al/sub 2/O/sub 3/, the same Al/sub 2/O/sub 3/ spheres mixed with spheres of silica--alumina or with SiC shards, carbon spheres, and nickel spheres. Both techniques were used to determine the k-value of beds of hollow spheres with solid shells of Al/sub 2/O/sub 3/, Al/sub 2/O/sub 3//center dot/7 w/o Cr/sub 2/O/sub 3/, and partially stabilized ZrO/sub 2/. The hollow microspheres had diameters from 2100 to 3500 ..mu..m and wall thicknesses from 80 to 160 ..mu..m. 12 refs., 7 figs., 4 tabs.
Koppenaal, David W.; Barinaga, Charles J.; Denton, M Bonner B.; Sperline, Roger P.; Hieftje, Gary M.; Schilling, G. D.; Andrade, Francisco J.; Barnes IV., James H.
2005-11-01
Good eyesight is often taken for granted, a situation that everyone appreciates once vision begins to fade with age. New eyeglasses or contact lenses are traditional ways to improve vision, but recent new technology, i.e. LASIK laser eye surgery, provides a new and exciting means for marked vision restoration and improvement. In mass spectrometry, detectors are the 'eyes' of the MS instrument. These 'eyes' have also been taken for granted. New detectors and new technologies are likewise needed to correct, improve, and extend ion detection and hence, our 'chemical vision'. The purpose of this report is to review and assess current MS detector technology and to provide a glimpse towards future detector technologies. It is hoped that the report will also serve to motivate interest, prompt ideas, and inspire new visions for ion detection research.
The laboratory type of an active single sphere albedo dosemeter system using three 3He proportional counters in a polyethylene sphere for the measurement of neutron dose equivalent rates and the field calibration of personnel neutron dosemeters was optimized with respect to the detector-moderator combination by means of calibration exposures. One detector is located in the centre of the sphere to measure the neutron dose equivalent rate and the other two detectors near the moderator surface, in order to simulate the response of the albedo neutron detector and the thermal neutron detector. The response of the detectors to neutrons in the range between thermal and 14 MeV neutrons was investigated for various moderator-absorber combinations. Comparison was made between the system response and the response of the passive detector system. After completion the active system could be used for comprehensive neutron field measurements in radiation protection. By means of a microprocessor the linear combination of the three detector readings gives energy independent readings of the neutron dose equivalent rate, the absorbed dose rate and the neutron flux density at particle accelerators and nuclear facilities. (orig./HP)
Java meshing tool for sphere arrangements
A tool for meshing sphere arrangements was programmed in order to perform finite element calculations. Sphere arrangements are investigated in frame of the feasibility study of the sphere-pac nuclear fuel. One major concern of this study is the thermal conductivity of the arrangement. Further concerns are the mechanical behavior and sintering of the fuel. The thermal conductivity of the fuel was addressed with the computer code SPACON based on a unit cell approach and a radial heat flow experiment. However, a further approach using the finite element method is desirable, in order to better understanding the thermal flow through the package and to cross check with SPACON data and with experimental data. Also the mechanical behavior of the fuel could be addressed using the finite element technique. (author)
Two-sphere low Reynold's propeller
Najafi, Ali
2010-01-01
A three-dimensional model of a low-Reynold's swimmer is introduced and analyzed in this paper. This model consists of two large and small spheres connected by two perpendicular thin rods. The geometry of this system is motivated by the microorganisms that use a single tail to swim, the large sphere represents the head of microorganism and the small sphere resembles its tail. Each rod changes its length and orientation in a non-reciprocal manner that effectively propel the system. Translational and rotational velocities of the swimmer are studied for different values of parameters. Our findings show that by changing the parameters we can adjust both the velocity and the direction of motion of the swimmer.
Scalar Solitons on the Fuzzy Sphere
Austing, P; Thorlacius, L; Austing, Peter; Jonsson, Thordur; Thorlacius, Larus
2002-01-01
We study scalar solitons on the fuzzy sphere at arbitrary radius and noncommutativity. We prove that no solitons exist if the radius is below a certain value. Solitons do exist for radii above a critical value which depends on the noncommutativity parameter. We construct a family of soliton solutions which are stable and which converge to solitons on the Moyal plane in an appropriate limit. These solutions are rotationally symmetric about an axis and have no allowed deformations. Solitons that describe multiple lumps on the fuzzy sphere can also be constructed but they are not stable.
Path integral representations on the complex sphere
In this paper we discuss the path integral representations for the coordinate systems on the complex sphere S3C. 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.
Scattering by two spheres: Theory and experiment
Bjørnø, Irina; Jensen, Leif Bjørnø
1998-01-01
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 the......Extensive studies of scattering of acoustical signals by targets of different regular shapes have formed a useful background for attempts to develop procedures for remote monitoring of suspended materials in marine environments as, for instance, measurements of characteristic parameters of...
Bridging conflicting innovation spheres of tourism innovation
Fuglsang, Lars; Sørensen, Flemming; Nordli, Anne Jørgensen
2016-01-01
competition which may inhibit networked and open innovation. Tourist destinations are examples of such localized systems. In this paper we present two extreme cases of tourist destinations in which collaborative innovation processes were established in spite of fierce disagreements between actors. We argue...... that in tourist destinations actors belong to conflicting innovation spheres but can be brought together in innovation processes when a diplomat enable compromises and when innovation spheres change from personalized to more generalized forms of activity during interaction. The findings are relevant...
Predicted performance of neutron spectrometers using scintillating fibers
A variety of needs exists for knowing the energy spectral content of a neutron flux. Among these needs are arms-control and national-security applications, which arise because different neutron sources produce different neutron energy spectra. This work is primarily directed at these applications. The concept described herein is a spectrometer in the same sense as a Bonner sphere. The instrument response reflects a statistical average of the energy spectrum. The Bonner sphere is an early rendition of this class. In this, a neutron detector is placed at the center of a moderating (and absorbing) sphere (of varying thickness and composition). Spectral unfolding is required, and the resolution and efficiency are, typically, poor, although the potential bandwidth is very large. A recent variation on the Bonner-sphere approach uses 3He gas proportional counters with resistive wires to locate the position of the event (Toyokawa et al 1996). The spectrometer concept investigated here has the potential for better resolution and much improved neutron efficiency compared to Bonner spheres and similar devices. These improvements are possible because of the development of neutron-sensitive, scintillating-glass fibers. These fibers can be precisely located in space, which allows a corresponding precision in energy resolution. Also, they can be fabricated into arrays that intercept a large fraction of incident thermal neutrons, providing the improvement in neutron economy
J. Seguinot and T. Ypsilantis have recently described the theory and history of Ring Imaging Cherenkov (RICH) detectors. In this paper, I will expand on these excellent review papers, by covering the various photon detector designs in greater detail, and by including discussion of mistakes made, and detector problems encountered, along the way. Photon detectors are among the most difficult devices used in physics experiments, because they must achieve high efficiency for photon transport and for the detection of single photo-electrons. For gaseous devices, this requires the correct choice of gas gain in order to prevent breakdown and wire aging, together with the use of low noise electronics having the maximum possible amplification. In addition, the detector must be constructed of materials which resist corrosion due to photosensitive materials such as, the detector enclosure must be tightly sealed in order to prevent oxygen leaks, etc. The most critical step is the selection of the photocathode material. Typically, a choice must be made between a solid (CsI) or gaseous photocathode (TMAE, TEA). A conservative approach favors a gaseous photocathode, since it is continuously being replaced by flushing, and permits the photon detectors to be easily serviced (the air sensitive photocathode can be removed at any time). In addition, it can be argued that we now know how to handle TMAE, which, as is generally accepted, is the best photocathode material available as far as quantum efficiency is concerned. However, it is a very fragile molecule, and therefore its use may result in relatively fast wire aging. A possible alternative is TEA, which, in the early days, was rejected because it requires expensive CaF2 windows, which could be contaminated easily in the region of 8.3 eV and thus lose their UV transmission
Va`vra, J.
1995-10-01
J. Seguinot and T. Ypsilantis have recently described the theory and history of Ring Imaging Cherenkov (RICH) detectors. In this paper, I will expand on these excellent review papers, by covering the various photon detector designs in greater detail, and by including discussion of mistakes made, and detector problems encountered, along the way. Photon detectors are among the most difficult devices used in physics experiments, because they must achieve high efficiency for photon transport and for the detection of single photo-electrons. For gaseous devices, this requires the correct choice of gas gain in order to prevent breakdown and wire aging, together with the use of low noise electronics having the maximum possible amplification. In addition, the detector must be constructed of materials which resist corrosion due to photosensitive materials such as, the detector enclosure must be tightly sealed in order to prevent oxygen leaks, etc. The most critical step is the selection of the photocathode material. Typically, a choice must be made between a solid (CsI) or gaseous photocathode (TMAE, TEA). A conservative approach favors a gaseous photocathode, since it is continuously being replaced by flushing, and permits the photon detectors to be easily serviced (the air sensitive photocathode can be removed at any time). In addition, it can be argued that we now know how to handle TMAE, which, as is generally accepted, is the best photocathode material available as far as quantum efficiency is concerned. However, it is a very fragile molecule, and therefore its use may result in relatively fast wire aging. A possible alternative is TEA, which, in the early days, was rejected because it requires expensive CaF{sub 2} windows, which could be contaminated easily in the region of 8.3 eV and thus lose their UV transmission.
Radiation field mapping using a mechanical-electronic detector
Czayka, M.; Fisch, M.
2010-04-01
A method of radiation field mapping of a scanned electron beam using a Faraday-type detector and an electromechanical linear translator is presented. Utilizing this arrangement, fluence and fluence rate measurements can be made at different locations within the radiation field. The Faraday-type detector used in these experiments differs from most as it consists of a hollow stainless steel sphere. Results are presented in two- and three-dimensional views of the radiation field.
Packing Effect of Excluded Volume on Hard-Sphere Colloids
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.
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
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
Einstein Metrics on Rational Homology Spheres
Boyer, Charles P.; Galicki, Krzysztof
2003-01-01
We prove the existence of Sasakian-Einstein metrics on infinitely many rational homology spheres in all odd dimensions greater than 3. In dimension 5 we obain somewhat sharper results. There are examples where the number of effective parameters in the Einstein metric grows exponentially with dimension.
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.
String Field Theory and the Fuzzy Sphere
Ita, Harald; Oz, Yaron
2001-01-01
We use boundary string field theory to study open string tachyon condensation on a three-sphere closed string background. We consider the closed string background described by $SU(2)_k$ WZW model in the limit of large $k$. We compute the exact tachyon potential and analyse the decay modes.
Performance and Politics in the Public Sphere
Pia Wiegmink
2011-12-01
Full Text Available Pia Wiegmink’s timely examination of the transforming transnational spaces of protest in a globalizing and technologically mediated public sphere in “Performance and Politics in the Public Sphere” offers a well-researched review of contemporary theory surrounding ideas of the political (Chantal Mouffe, the public sphere (Jürgen Habermas, the transnational public sphere (Nancy Fraser, and the reterritorialized transnational public sphere (Markus Schroer as the basis for her analysis of how the performance of political action in public—virtual or physical—is transformed by the capacity of the local to be played on a global stage, thus turning the citizen-actor into a cosmopolitan, transnational force. Tracing examples from the Seattle protests against the World Trade Organization meetings in 1999 by the Global Justice Movement to the work of the Electronic Disturbance Theater, from the civil rights movement to the subject matter of her larger study, “The Church of Life After Shopping,” “Billionaires for Bush,” and “The Yes Men,” Wiegmink provides an important analysis of the “alternative aesthetics” of the counterpublics’ formation, dissent, and action in and against hegemony. This selection is taken from her monograph, Protest EnACTed: Activist Performance in the Contemporary United States, a strong, cultural studies–focused contribution to transnational American Studies.
On configuration spaces of hard spheres
Baryshnikov, Yuliy; Kahle, Matthew
2011-01-01
We study configuration spaces of hard spheres in a bounded region. We develop a general Morse-theoretic framework, and show that mechanically balanced configurations play the role of critical points. As an application, we find the precise threshold radius for a configuration space to be homotopy equivalent to the configuration space of points.
Performance and Politics in the Public Sphere
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.
Production of Liquid Metal Spheres by Molding
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.
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...... contexts such as search-and-rescue missions and medical or biological studies....
Second virial coefficients of dipolar hard spheres
Philipse, A.P.; Kuipers, B.W.M.
2010-01-01
An asymptotic formula is reported for the second virial coefficient B2 of a dipolar hard-sphere (DHS) fluid, in zero external field, for strongly coupled dipolar interactions. This simple formula, together with the one for the weak-coupling B2, provides an accurate prediction of the second virial co
Ligand sphere conversions in terminal carbide complexes
Morsing, Thorbjørn Juul; Reinholdt, Anders; Sauer, Stephan P. A.; Bendix, Jesper
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...