Improved deterministic calculational methods for irregularly shaped shields
Dorning, J.J.
1992-12-01
A new discrete nodal transport method has been developed for general two-dimensional curvilinear geometry by using a boundary-fitted coordinate transformation from the general 'physical' coordinates to square 'computational' coordinates. The metrics which appear in the transformed transport equation are expanded using a simple polynomial function, and the angular divergence term is treated in the same way it is treated in S[sub N] methods for curved geometries. Because the metrics of the transformation depend upon the computational coordinates, the technical details of the formal development of the nodal method differ from those of ordinary nodal methods for rectangular geometry. However, the computational process in the transformed rectangular coordinate system is very similar to that used in conventional discrete nodal transport methods. A discrete S[sub N] method also has been developed to solve the boundary-fitted coordinate transformed transport equation. Simple test problems for non-simple geometries were solved using the zeroth-order nodal method, the first-order nodal method, and the S[sub N] method for the same physical and computational grids. The results for the test problems studied showed that, for most performance criteria, the computational efficiency of the zeroth-order nodal method was the highest of the three methods.
Lee, C.; Yang, W. S.
2013-07-01
An improved resonance self-shielding method has been developed to accurately estimate the effective multigroup cross sections for heterogeneous fast reactor assembly and core calculations. In the method, the heterogeneity effect is considered by the use of isotopic escape cross sections while the resonance interference effect is accounted for through the narrow resonance approximation or slowing-down calculations for specific compositions. The isotopic escape cross sections are calculated by solving fixed-source transport equations with the method of characteristics for the whole problem domain. This method requires no pre-calculated resonance integral tables or parameters that are typically necessary in the subgroup method. Preliminary results for multi pin-cell fast reactor problems show that the escape cross sections estimated from the explicit-geometry fixed source calculations produce more accurate eigenvalue and self-shielded effective cross sections than those from conventional one-dimensional geometry models. (authors)
Comparison of hybrid methods for global variance reduction in shielding calculations
Peplow, D. E.
2013-07-01
For Monte Carlo shielding problems that calculate a mesh tally over the entire problem, the statistical uncertainties computed for each voxel can vary widely. This can lead to unacceptably long run times in order to reduce the uncertainties in all areas of the problem to a reasonably low level. Hybrid methods - using estimates from deterministic calculations to create importance maps for variance reduction in Monte Carlo calculations - have been successfully used to optimize the calculation of specific tallies. For the global problem, several methods have been proposed to create importance maps that distribute Monte Carlo particles in such a way as to achieve a more uniform distribution of relative uncertainty across the problem. The goal is to compute a mesh tally with nearly the same relative uncertainties in the low flux/dose areas as in the high flux/dose areas. Methods based on only forward deterministic estimates and methods using both forward and adjoint deterministic methods have been implemented in the SCALE/MAVRIC package and have been compared against each other by computing global mesh tallies on several representative shielding problems. Methods using both forward and adjoint estimates provide better performance for computing more uniform relative uncertainties across a global mesh tally. (authors)
Application of the first collision source method to CSNS target station shielding calculation
NASA Astrophysics Data System (ADS)
Zheng, Ying; Zhang, Bin; Chen, Meng-Teng; Zhang, Liang; Cao, Bo; Chen, Yi-Xue; Yin, Wen; Liang, Tian-Jiao
2016-04-01
Ray effects are an inherent problem of the discrete ordinates method. RAY3D, a functional module of ARES, which is a discrete ordinates code system, employs a semi-analytic first collision source method to mitigate ray effects. This method decomposes the flux into uncollided and collided components, and then calculates them with an analytical method and discrete ordinates method respectively. In this article, RAY3D is validated by the Kobayashi benchmarks and applied to the neutron beamline shielding problem of China Spallation Neutron Source (CSNS) target station. The numerical results of the Kobayashi benchmarks indicate that the solutions of DONTRAN3D with RAY3D agree well with the Monte Carlo solutions. The dose rate at the end of the neutron beamline is less than 10.83 μSv/h in the CSNS target station neutron beamline shutter model. RAY3D can effectively mitigate the ray effects and obtain relatively reasonable results. Supported by Major National S&T Specific Program of Large Advanced Pressurized Water Reactor Nuclear Power Plant (2011ZX06004-007), National Natural Science Foundation of China (11505059, 11575061), and the Fundamental Research Funds for the Central Universities (13QN34).
NASA Technical Reports Server (NTRS)
Capo, M. A.; Disney, R. K.; Jordan, T. A.; Soltesz, R. G.; Woodsum, H. C.
1969-01-01
Eight computer programs make up a nine volume synthesis containing two design methods for nuclear rocket radiation shields. The first design method is appropriate for parametric and preliminary studies, while the second accomplishes the verification of a final nuclear rocket reactor design.
Holmes, Sean T; Alkan, Fahri; Iuliucci, Robbie J; Mueller, Karl T; Dybowski, Cecil
2016-07-01
(29) Si and (31) P magnetic-shielding tensors in covalent network solids have been evaluated using periodic and cluster-based calculations. The cluster-based computational methodology employs pseudoatoms to reduce the net charge (resulting from missing co-ordination on the terminal atoms) through valence modification of terminal atoms using bond-valence theory (VMTA/BV). The magnetic-shielding tensors computed with the VMTA/BV method are compared to magnetic-shielding tensors determined with the periodic GIPAW approach. The cluster-based all-electron calculations agree with experiment better than the GIPAW calculations, particularly for predicting absolute magnetic shielding and for predicting chemical shifts. The performance of the DFT functionals CA-PZ, PW91, PBE, rPBE, PBEsol, WC, and PBE0 are assessed for the prediction of (29) Si and (31) P magnetic-shielding constants. Calculations using the hybrid functional PBE0, in combination with the VMTA/BV approach, result in excellent agreement with experiment. © 2016 Wiley Periodicals, Inc. PMID:27117609
Calculation of shielding parameters
NASA Astrophysics Data System (ADS)
Montoya, Zeferino Jorge
Within the nuclear reaction exists three types of energy producing reactions: (1) radioactive disintegration; (2) fission; and (3) fusion. Besides the radiation produced in these reactions there are radioactive emissions of a different type, and in some of these cases they are of great penetration power and scope. The radiation produces great damage when interacted with materials, in particular the most dangerous are neutrons and gamma photons. For this reason it is necessary to protect people who work in places which operate with radioactive sources from the radiation, in addition to reducing the radiation doses to the most reasonably possible, considering the circumstances of the installations. The three determining factors in the proposition of reducing exposure to radiation are: (1) to maintain control over the reduced exposure in the time of the permanence in the irradiated areas; (2) to increase the distance between the source and the operating personnel as much as possible; and (3) to place an armor-plate between the source and the receptor. The work described in this paper has its objective a calculation of the parameters of an armor-plate in radioactive sources, with the goal of estimating the doses of radiation in protecting people and other biological systems from exposure to radiation produced during the nuclear reactions. The parameters to be principally considered are: (1) characteristics of the source; (2) geometry of the source at the point of exposure; and (3) material and thickness of the armor-plate.
Cho, S; Shin, E H; Kim, J; Ahn, S H; Chung, K; Kim, D-H; Han, Y; Choi, D H
2015-06-15
Purpose: To evaluate the shielding wall design to protect patients, staff and member of the general public for secondary neutron using a simply analytic solution, multi-Monte Carlo code MCNPX, ANISN and FLUKA. Methods: An analytical and multi-Monte Carlo method were calculated for proton facility (Sumitomo Heavy Industry Ltd.) at Samsung Medical Center in Korea. The NCRP-144 analytical evaluation methods, which produced conservative estimates on the dose equivalent values for the shielding, were used for analytical evaluations. Then, the radiation transport was simulated with the multi-Monte Carlo code. The neutron dose at evaluation point is got by the value using the production of the simulation value and the neutron dose coefficient introduced in ICRP-74. Results: The evaluation points of accelerator control room and control room entrance are mainly influenced by the point of the proton beam loss. So the neutron dose equivalent of accelerator control room for evaluation point is 0.651, 1.530, 0.912, 0.943 mSv/yr and the entrance of cyclotron room is 0.465, 0.790, 0.522, 0.453 mSv/yr with calculation by the method of NCRP-144 formalism, ANISN, FLUKA and MCNP, respectively. The most of Result of MCNPX and FLUKA using the complicated geometry showed smaller values than Result of ANISN. Conclusion: The neutron shielding for a proton therapy facility has been evaluated by the analytic model and multi-Monte Carlo methods. We confirmed that the setting of shielding was located in well accessible area to people when the proton facility is operated.
A comparison of calculated NMR shielding probes.
Martin, Ned H; Loveless, David M; Wade, Dustin C
2004-12-01
In a strong magnetic field, covalently bonded hydrogen nuclei located over the plane of an anisotropic pi bond-containing functional group experience magnetic shielding (or deshielding) that results from the combined effect of the magnetic anisotropy of the functional group and other nearby covalent bonds plus other intramolecular shielding effects. These effects can now be calculated with reasonable accuracy using ab initio methods. We have investigated several computational probes of the magnetic shielding surface near anisotropic functional groups and compared the results to previous reports of experimental observations in example structures. GIAO-HF in Gaussian 03 was employed to calculate isotropic shielding values and to predict the net NMR shielding increment for several computational probes: methane, diatomic hydrogen, a hydrogen atom, a helium atom, or a ghost atom, each held in various positions over simple test molecules (ethene, ethyne, benzene and HCN) that contain the functional groups studied. Also, the effect of performing single point calculations versus constrained geometry-optimized calculations was examined. In addition, the effect of the angle of the orientation of the probe molecule (in the case of CH(4) and H(2)) relative to the pi bond in the test molecule was studied. Finally, the atomic charges in the molecular probes (CH(4) and H(2)) were computed to investigate the nature of the interaction of the probe with the test molecule. The optimal, most economical computational results were obtained using single point calculations of a diatomic hydrogen probe oriented perpendicular to the surface (or axis) of the test molecule. PMID:15530824
Dorning, J.J.
1992-12-01
A new discrete nodal transport method has been developed for general two-dimensional curvilinear geometry by using a boundary-fitted coordinate transformation from the general `physical` coordinates to square `computational` coordinates. The metrics which appear in the transformed transport equation are expanded using a simple polynomial function, and the angular divergence term is treated in the same way it is treated in S{sub N} methods for curved geometries. Because the metrics of the transformation depend upon the computational coordinates, the technical details of the formal development of the nodal method differ from those of ordinary nodal methods for rectangular geometry. However, the computational process in the transformed rectangular coordinate system is very similar to that used in conventional discrete nodal transport methods. A discrete S{sub N} method also has been developed to solve the boundary-fitted coordinate transformed transport equation. Simple test problems for non-simple geometries were solved using the zeroth-order nodal method, the first-order nodal method, and the S{sub N} method for the same physical and computational grids. The results for the test problems studied showed that, for most performance criteria, the computational efficiency of the zeroth-order nodal method was the highest of the three methods.
Benchmark calculations of the shielding constants in the water dimer
NASA Astrophysics Data System (ADS)
Pecul, Magdalena; Lewandowski, Józef; Sadlej, Joanna
2001-01-01
The NMR shielding constants in (H 2O) 2 have been calculated using GIAO-SCF, MP2, MP4 and CCSD methods and for a range of basis sets. According to the obtained results the 6-311++G ** or aug-cc-pVDZ basis sets are recommended for SCF calculations, and the aug-cc-pVXZ series is suggested for correlated calculations of the interaction-induced changes in the shielding constants. The counterpoise correction improves the results towards the basis set limit and is essential in the case of 17O shielding. Correlation effects are substantial for the changes in 17O shielding, less so for 1H shielding. They are overestimated by the MP2 method.
Komasa, J.; Cencek, W.; Rychlewski, J. )
1992-09-01
Values of the magnetic shielding constant in the ground state of the hydrogen molecule are calculated using explicitly correlated Gaussian functions. The total shielding at equilibrium amounts to 26.73 ppm.
Subsurface Shielding Source Term Specification Calculation
S.Su
2001-04-12
The purpose of this calculation is to establish appropriate and defensible waste-package radiation source terms for use in repository subsurface shielding design. This calculation supports the shielding design for the waste emplacement and retrieval system, and subsurface facility system. The objective is to identify the limiting waste package and specify its associated source terms including source strengths and energy spectra. Consistent with the Technical Work Plan for Subsurface Design Section FY 01 Work Activities (CRWMS M&O 2001, p. 15), the scope of work includes the following: (1) Review source terms generated by the Waste Package Department (WPD) for various waste forms and waste package types, and compile them for shielding-specific applications. (2) Determine acceptable waste package specific source terms for use in subsurface shielding design, using a reasonable and defensible methodology that is not unduly conservative. This calculation is associated with the engineering and design activity for the waste emplacement and retrieval system, and subsurface facility system. The technical work plan for this calculation is provided in CRWMS M&O 2001. Development and performance of this calculation conforms to the procedure, AP-3.12Q, Calculations.
Diagnostic X-Ray Shielding Calculation.
1986-05-27
Version 00 XSHLD will calculate the primary and/or secondary leakage/scatter barrier requirements for diagnostic radiographic and/or fluorescent x-ray units operating at 50, 70, 100, 125, and 150 kVp. Requirements are given for Pb shielding and for gypsum, plate glass, brick, concrete, and concrete block.
RZ calculations for self shielded multigroup cross sections
Li, M.; Sanchez, R.; Zmijarevic, I.; Stankovski, Z.
2006-07-01
A collision probability method has been implemented for RZ geometries. The method accounts for white albedo, specular and translation boundary condition on the top and bottom surfaces of the geometry and for a white albedo condition on the outer radial surface. We have applied the RZ CP method to the calculation of multigroup self shielded cross sections for Gadolinia absorbers in BWRs. (authors)
Shielding design at Fermilab: Calculations and measurements
Cossairt, J.D.
1986-11-01
The development of the Fermilab accelerator complex during the past two decades from its concept as the ''200 BeV accelerator'' to that of the present tevatron, designed to operate at energies as high as 1 TeV, has required a coincidental refinement and development in methods of shielding design. In this paper I describe these methods as used by the radiation protection staff of Fermilab. This description will review experimental measurements which substantiate these techniques in realistic situations. Along the way, observations will be stated which likely are applicable to other protron accelerators in the multi-hundred GeV energy region, including larger ones yet to be constructed.
A converse approach to the calculation of NMR shielding tensors
Thonhauser, Timo; Ceresoli, Davide; Mostofi, Arash A.; Marzari, Nicola N.; Resta, Raffaele; Vanderbilt, David
2009-09-08
We introduce an alternative approach to the first-principles calculation of NMR shielding tensors. These are obtained from the derivative of the orbital magnetization with respect to the application of a microscopic, localized magnetic dipole. The approach is simple, general, and can be applied to either isolated or periodic systems. Calculated results for simple hydrocarbons, crystalline diamond, and liquid water show very good agreement with established methods and experimental results.
Thermal neutron shield and method of manufacture
Metzger, Bert Clayton; Brindza, Paul Daniel
2014-03-04
A thermal neutron shield comprising boron shielding panels with a high percentage of the element Boron. The panel is least 46% Boron by weight which maximizes the effectiveness of the shielding against thermal neutrons. The accompanying method discloses the manufacture of boron shielding panels which includes enriching the pre-cursor mixture with varying grit sizes of Boron Carbide.
Pivotably mounted reactor shroud shield and shielding method
Hankinson, M.F.
1987-03-31
A method is described for shielding persons working around a nuclear reactor having a reactor head an a shroud extending upward from the reactor head, comprising: (a) mounting a plurality of swingout arms around the shroud, each swingout arm being pivotable about a respective axis that is substantially vertical and that is fixed with respect to the shroud; (b) positioning a shielding member adjacent a swingout arm with a hoist; (c) pivoting the swingout arm horizontally away from the shroud and toward the hoist; (d) transferring the shielding member from the hoist to the swingout arm so that the swingout arm supports the shielding member; (e) pivoting the swingout arm horizontally back toward the shroud; and (f) repeating steps (b) through (c) until the shroud is substantially surrounded by shielding members.
Calculations of nuclear electric shielding in molecules
NASA Astrophysics Data System (ADS)
Lazzeretti, P.; Zanasi, R.
1980-05-01
The electric shielding tensor at nuclei in the molecules H 2O, NH 3, CH 4 and CO has been evaluated via coupled Hartree-Fock perturbation theory. The average trace of the shielding tensor is linearly dependent on atomic electronegativities in the isoelectronic series H 2O, NH 3, CH 4.
Brachytherapy structural shielding calculations using Monte Carlo generated, monoenergetic data
Zourari, K.; Peppa, V.; Papagiannis, P.; Ballester, Facundo; Siebert, Frank-André
2014-04-15
Purpose: To provide a method for calculating the transmission of any broad photon beam with a known energy spectrum in the range of 20–1090 keV, through concrete and lead, based on the superposition of corresponding monoenergetic data obtained from Monte Carlo simulation. Methods: MCNP5 was used to calculate broad photon beam transmission data through varying thickness of lead and concrete, for monoenergetic point sources of energy in the range pertinent to brachytherapy (20–1090 keV, in 10 keV intervals). The three parameter empirical model introduced byArcher et al. [“Diagnostic x-ray shielding design based on an empirical model of photon attenuation,” Health Phys. 44, 507–517 (1983)] was used to describe the transmission curve for each of the 216 energy-material combinations. These three parameters, and hence the transmission curve, for any polyenergetic spectrum can then be obtained by superposition along the lines of Kharrati et al. [“Monte Carlo simulation of x-ray buildup factors of lead and its applications in shielding of diagnostic x-ray facilities,” Med. Phys. 34, 1398–1404 (2007)]. A simple program, incorporating a graphical user interface, was developed to facilitate the superposition of monoenergetic data, the graphical and tabular display of broad photon beam transmission curves, and the calculation of material thickness required for a given transmission from these curves. Results: Polyenergetic broad photon beam transmission curves of this work, calculated from the superposition of monoenergetic data, are compared to corresponding results in the literature. A good agreement is observed with results in the literature obtained from Monte Carlo simulations for the photon spectra emitted from bare point sources of various radionuclides. Differences are observed with corresponding results in the literature for x-ray spectra at various tube potentials, mainly due to the different broad beam conditions or x-ray spectra assumed. Conclusions
Current status of methods for shielding analysis
Engle, W.W.
1980-01-01
Current methods used in shielding analysis and recent improvements in those methods are discussed. The status of methods development is discussed based on needs cited at the 1977 International Conference on Reactor Shielding. Additional areas where methods development is needed are discussed.
Kharrati, Hedi
2005-05-01
In this study, a new approach has been introduced for derivation of the effective dose from air kerma to calculate shielding requirements in mammography facilities. This new approach has been used to compute the conversion coefficients relating air kerma to the effective dose for the mammography reference beam series of the Netherlands Metrology Institute Van Swinden Laboratorium, National Institute of Standards and Technology, and International Atomic Energy Agency laboratories. The results show that, in all cases, the effective dose in mammography energy range is less than 25% of the incident air kerma for the primary and the scatter radiations and does not exceed 75% for the leakage radiation.
Thermal neutron shield and method of manufacture
Brindza, Paul Daniel; Metzger, Bert Clayton
2013-05-28
A thermal neutron shield comprising concrete with a high percentage of the element Boron. The concrete is least 54% Boron by weight which maximizes the effectiveness of the shielding against thermal neutrons. The accompanying method discloses the manufacture of Boron loaded concrete which includes enriching the concrete mixture with varying grit sizes of Boron Carbide.
Shielding Calculations for NSLS-II Beamlines.
Job,P.K.; Casey, W.R.
2008-04-13
Brookhaven National Laboratory is in the process of designing a new Electron Synchrotron for scientific research using synchrotron radiation. This facility, called the 'National Synchrotron Light Source II' (NSLS-II), will provide x-ray radiation of ultra-high brightness and exceptional spatial and energy resolution. It will also provide advanced insertion devices, optics, detectors, and robotics, and a suite of scientific instruments designed to maximize the scientific output of the facility. The project scope includes the design, construction, installation, and commissioning of the following accelerators: a 200 MeV linac, a booster accelerator operating from 200 MeV to 3.0 GeV, the storage ring which stores 500 mA current of electrons at an energy of 3.0 GeV and 56 beamlines for experiments. It is planned to operate the facility primarily in a top-off mode, thereby maintaining the maximum variation in stored beam current to < 1%. Because of the very demanding requirements for beam emittance and synchrotron radiation brilliance, the beam life-time is expected to be quite low, on the order of 2 hours. Each of the 56 beamlines will be unique in terms of the source properties and configuration. The shielding designs for five representative beamlines are discussed in this paper.
X-Ray Shield Calculation System.
1984-10-04
Version: 00 NCRP49 will calculate the primary and/or secondary leakage/scatter barrier requirements (in mm of lead) for diagnostic radio-graphic and/or fluoroscopic x-ray units operating at 50, 70, 100, 125 or 150 kV.
D0 Solenoid Upgrade Project: Chimney LN2 Radiation Shield Attachment Area Calculation
Rucinski, R.; /Fermilab
1993-05-26
A short calculation was done to check the attachment method of the radiation shield to it's LN2 cooling tubes. The case considered was only for the obround chimney section. The proposed attachment method was to use 1/8-inch plug welds spaced every 5-inch along the length of the shield. The calculations were done conservatively for 6-inch spacing between plug welds. The criteria used was that the LN2 shield warmest temperature be less than 2 K above the temperature of the LN2 fluid. Using a very conservative heat transfer model. the calculations predict that the warmest temperature on the radiation shield will be < 1.4 K warmer than the LN2 fluid temperature.
Shield weight optimization using Monte Carlo transport calculations
NASA Technical Reports Server (NTRS)
Jordan, T. M.; Wohl, M. L.
1972-01-01
Outlines are given of the theory used in FASTER-3 Monte Carlo computer program for the transport of neutrons and gamma rays in complex geometries. The code has the additional capability of calculating the minimum weight layered unit shield configuration which will meet a specified dose rate constraint. It includes the treatment of geometric regions bounded by quadratic and quardric surfaces with multiple radiation sources which have a specified space, angle, and energy dependence. The program calculates, using importance sampling, the resulting number and energy fluxes at specified point, surface, and volume detectors. Results are presented for sample problems involving primary neutron and both primary and secondary photon transport in a spherical reactor shield configuration. These results include the optimization of the shield configuration.
Nasrabadi, M N; Mohammadi, A; Jalali, M
2009-01-01
In this paper bulk sample prompt gamma neutron activation analysis (BSPGNAA) was applied to aqueous sample analysis using a relative method. For elemental analysis of an unknown bulk sample, gamma self-shielding coefficient was required. Gamma self-shielding coefficient of unknown samples was estimated by an experimental method and also by MCNP code calculation. The proposed methodology can be used for the determination of the elemental concentration of unknown aqueous samples by BSPGNAA where knowledge of the gamma self-shielding within the sample volume is required. PMID:19328700
Reliability Methods for Shield Design Process
NASA Technical Reports Server (NTRS)
Tripathi, R. K.; Wilson, J. W.
2002-01-01
Providing protection against the hazards of space radiation is a major challenge to the exploration and development of space. The great cost of added radiation shielding is a potential limiting factor in deep space operations. In this enabling technology, we have developed methods for optimized shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of space missions. The total shield mass over all pieces of equipment and habitats is optimized subject to career dose and dose rate constraints. An important component of this technology is the estimation of two most commonly identified uncertainties in radiation shield design, the shielding properties of materials used and the understanding of the biological response of the astronaut to the radiation leaking through the materials into the living space. The largest uncertainty, of course, is in the biological response to especially high charge and energy (HZE) ions of the galactic cosmic rays. These uncertainties are blended with the optimization design procedure to formulate reliability-based methods for shield design processes. The details of the methods will be discussed.
Spacesuit Radiation Shield Design Methods
NASA Technical Reports Server (NTRS)
Wilson, John W.; Anderson, Brooke M.; Cucinotta, Francis A.; Ware, J.; Zeitlin, Cary J.
2006-01-01
Meeting radiation protection requirements during EVA is predominantly an operational issue with some potential considerations for temporary shelter. The issue of spacesuit shielding is mainly guided by the potential of accidental exposure when operational and temporary shelter considerations fail to maintain exposures within operational limits. In this case, very high exposure levels are possible which could result in observable health effects and even be life threatening. Under these assumptions, potential spacesuit radiation exposures have been studied using known historical solar particle events to gain insight on the usefulness of modification of spacesuit design in which the control of skin exposure is a critical design issue and reduction of blood forming organ exposure is desirable. Transition to a new spacesuit design including soft upper-torso and reconfigured life support hardware gives an opportunity to optimize the next generation spacesuit for reduced potential health effects during an accidental exposure.
Shielding calculations for a production target for secondary beams
Rehm, K.E.; Back, B.B.; Jiang, C.L.
1995-08-01
In order to estimate the amount of shielding required for a radioactive beam facility dose rate were performed. The calculations for production targets with different geometries were performed. The calculations were performed with the MSU shielding code assuming a 500-p{mu}A 200-MeV deuteron beam stopped in a thick Al target. The target and the ion-optical elements for beam extraction are located in a 2 m{sup 3} large volume at the center of the production cell. These dose rate calculations show that with a combination of Fe and concrete it is possible to reduce the dose rate expected at the surface of a 7-m-wide cube housing the production target to less than 2 mrem/hr.
NASA Astrophysics Data System (ADS)
Kudo, K.; Maeda, H.; Kawakubo, T.; Ootani, Y.; Funaki, M.; Fukui, H.
2006-06-01
The normalized elimination of the small component (NESC) theory, recently proposed by Filatov and Cremer [J. Chem. Phys. 122, 064104 (2005)], is extended to include magnetic interactions and applied to the calculation of the nuclear magnetic shielding in HX (X =F,Cl,Br,I) systems. The NESC calculations are performed at the levels of the zeroth-order regular approximation (ZORA) and the second-order regular approximation (SORA). The calculations show that the NESC-ZORA results are very close to the NESC-SORA results, except for the shielding of the I nucleus. Both the NESC-ZORA and NESC-SORA calculations yield very similar results to the previously reported values obtained using the relativistic infinite-order two-component coupled Hartree-Fock method. The difference between NESC-ZORA and NESC-SORA results is significant for the shieldings of iodine.
Exact calculation of demagnetization field in micromagnetic simulation of shielded read heads
Wang, Lei; Giusti, James H.; Fernandez-de-Castro, Juan
2001-06-01
In micromagnetic simulation of shielded GMR heads, the self-demagnetizing field is usually calculated under the assumption that the two shields extend to infinity beyond the air bearing surface. Under this assumption, the demagnetization tensor for rectangular cells in free space and the method of images are used to calculate the self-demagnetizing field in the sensor. An unanswered question for this approach is how accurate it is. In this work, the Fourier series method is used to calculate the self-demagnetizing field of the sensor in the shielded environment exactly. Simulation results from this rigorous approach and the common approach are compared for both simple spin valve and synthetic antiferromagnet (SAF) biased spin valve heads. It is shown that the error of the common approach is very small for a SAF spin valve head and can be as large as 10% for a simple spin valve head. {copyright} 2001 American Institute of Physics.
Development of a New Shielding Model for JB-Line Dose Rate Calculations
Buckner, M.R.
2001-08-09
This report describes the shielding model development for the JB-Line Upgrade project. The product of this effort is a simple-to-use but accurate method of estimating the personnel dose expected for various operating conditions on the line. The current techniques for shielding calculations use transport codes such as ANISN which, while accurate for geometries which can be accurately approximated as one dimensional slabs, cylinders or spheres, fall short in calculating configurations in which two-or three-dimensional effects (e.g., streaming) play a role in the dose received by workers.
NASA Technical Reports Server (NTRS)
Thomsen, III, Donald Laurence (Inventor); Cano, Roberto J. (Inventor); Jensen, Brian J. (Inventor); Hales, Stephen J. (Inventor); Alexa, Joel A. (Inventor)
2014-01-01
Methods of building Z-graded radiation shielding and covers. In one aspect, the method includes: providing a substrate surface having about medium Z-grade; plasma spraying a first metal having higher Z-grade than the substrate surface; and infusing a polymer layer to form a laminate. In another aspect, the method includes electro/electroless plating a first metal having higher Z-grade than the substrate surface. In other aspects, the methods include improving an existing electronics enclosure to build a Z-graded radiation shield by applying a temperature controller to at least part of the enclosure and affixing at least one layer of a first metal having higher Z-grade from the enclosure.
Calculation of an optimized design of magnetic shields with integrated demagnetization coils
NASA Astrophysics Data System (ADS)
Sun, Z.; Schnabel, A.; Burghoff, M.; Li, L.
2016-07-01
Magnetic shielding made from permalloy is frequently used to provide a time-stable magnetic field environment. A low magnetic field and low field gradients inside the shield can be obtained by using demagnetization coils through the walls, encircling edges of the shield. We first introduce and test the computational models to calculate magnetic properties of large size shields with thin shielding walls. We then vary the size, location and shape of the openings for the demagnetization coils at the corners of a cubic shield. It turns out that the effect on the shielding factor and the expected influence on the residual magnetic field homogeneity in the vicinity of the center of the shield is negligible. Thus, a low-cost version for the openings can be chosen and their size could be enlarged to allow for additional cables and easier handling. A construction of a shield with beveled edges and open corners turned out to substantially improve the shielding factor.
Monserrat, Bartomeu Needs, Richard J.; Pickard, Chris J.
2014-10-07
We study the effects of atomic vibrations on the solid-state chemical shielding tensor using first principles density functional theory calculations. At the harmonic level, we use a Monte Carlo method and a perturbative expansion. The Monte Carlo method is accurate but computationally expensive, while the perturbative method is computationally more efficient, but approximate. We find excellent agreement between the two methods for both the isotropic shift and the shielding anisotropy. The effects of zero-point quantum mechanical nuclear motion are important up to relatively high temperatures: at 500 K they still represent about half of the overall vibrational contribution. We also investigate the effects of anharmonic vibrations, finding that their contribution to the zero-point correction to the chemical shielding tensor is small. We exemplify these ideas using magnesium oxide and the molecular crystals L-alanine and β-aspartyl-L-alanine. We therefore propose as the method of choice to incorporate the effects of temperature in solid state chemical shielding tensor calculations using the perturbative expansion within the harmonic approximation. This approach is accurate and requires a computational effort that is about an order of magnitude smaller than that of dynamical or Monte Carlo approaches, so these effects might be routinely accounted for.
Validation of calculated self-shielding factors for Rh foils
NASA Astrophysics Data System (ADS)
Jaćimović, R.; Trkov, A.; Žerovnik, G.; Snoj, L.; Schillebeeckx, P.
2010-10-01
Rhodium foils of about 5 mm diameter were obtained from IRMM. One foil had thickness of 0.006 mm and three were 0.112 mm thick. They were irradiated in the pneumatic transfer system and in the carousel facility of the TRIGA reactor at the Jožef Stefan Institute. The foils were irradiated bare and enclosed in small cadmium boxes (about 2 g weight) of 1 mm thickness to minimise the perturbation of the local neutron flux. They were co-irradiated with 5 mm diameter and 0.2 mm thick Al-Au (0.1%) alloy monitor foils. The resonance self-shielding corrections for the 0.006 and 0.112 mm thick samples were calculated by the Monte Carlo simulation and amount to about 10% and 60%, respectively. The consistency of measurements confirmed the validity of self-shielding factors. Trial estimates of Q0 and k0 factors for the 555.8 keV gamma line of 104Rh were made and amount to 6.65±0.18 and (6.61±0.12)×10 -2, respectively.
MCNPX Cosmic Ray Shielding Calculations with the NORMAN Phantom Model
NASA Technical Reports Server (NTRS)
James, Michael R.; Durkee, Joe W.; McKinney, Gregg; Singleterry Robert
2008-01-01
The United States is planning manned lunar and interplanetary missions in the coming years. Shielding from cosmic rays is a critical aspect of manned spaceflight. These ventures will present exposure issues involving the interplanetary Galactic Cosmic Ray (GCR) environment. GCRs are comprised primarily of protons (approx.84.5%) and alpha-particles (approx.14.7%), while the remainder is comprised of massive, highly energetic nuclei. The National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) has commissioned a joint study with Los Alamos National Laboratory (LANL) to investigate the interaction of the GCR environment with humans using high-fidelity, state-of-the-art computer simulations. The simulations involve shielding and dose calculations in order to assess radiation effects in various organs. The simulations are being conducted using high-resolution voxel-phantom models and the MCNPX[1] Monte Carlo radiation-transport code. Recent advances in MCNPX physics packages now enable simulated transport over 2200 types of ions of widely varying energies in large, intricate geometries. We report here initial results obtained using a GCR spectrum and a NORMAN[3] phantom.
Superconducting magnetic shielding apparatus and method
Clem, John R.; Clem, John R.
1983-01-01
Disclosed is a method and apparatus for providing magnetic shielding around a working volume. The apparatus includes a hollow elongated superconducting shell or cylinder having an elongated low magnetic pinning central portion, and two high magnetic pinning end regions. Transition portions of varying magnetic pinning properties are interposed between the central and end portions. The apparatus further includes a solenoid substantially coextensive with and overlying the superconducting cylinder, so as to be magnetically coupled therewith. The method includes the steps passing a longitudinally directed current through the superconducting cylinder so as to depin magnetic reservoirs trapped in the cylinder. Next, a circumferentially directed current is passed through the cylinder, while a longitudinally directed current is maintained. Depinned magnetic reservoirs are moved to the end portions of the cylinder, where they are trapped.
Superconducting magnetic shielding apparatus and method
Clem, J.R.; Clem, J.R.
1983-10-11
Disclosed are a method and apparatus for providing magnetic shielding around a working volume. The apparatus includes a hollow elongated superconducting shell or cylinder having an elongated low magnetic pinning central portion, and two high magnetic pinning end regions. Transition portions of varying magnetic pinning properties are interposed between the central and end portions. The apparatus further includes a solenoid substantially coextensive with and overlying the superconducting cylinder, so as to be magnetically coupled therewith. The method includes the steps passing a longitudinally directed current through the superconducting cylinder so as to depin magnetic reservoirs trapped in the cylinder. Next, a circumferentially directed current is passed through the cylinder, while a longitudinally directed current is maintained. Depinned magnetic reservoirs are moved to the end portions of the cylinder, where they are trapped. 5 figs.
Superconducting magnetic shielding apparatus and method
Clem, J.R.
1982-07-09
Disclosed is a method and apparatus for providing magnetic shielding around a working volume. The apparatus includes a hollow elongated superconducting shell or cylinder having an elongated low magnetic pinning central portion, and two high magnetic pinning end regions. Transition portions of varying magnetic pinning properties are interposed between the central and end portions. The apparatus further includes a solenoid substantially coextensive with and overlying the superconducting cylinder, so as to be magnetically coupled therewith. The method includes the steps passing a longitudinally directed current through the superconducting cylinder so as to depin magnetic reservoirs trapped in the cylinder. Next, a circumferentially directed current is passed through the cylinder, while a longitudinally directed current is maintained. Depinned magnetic reservoirs are moved to the end portions of the cylinder, where they are trapped.
Standardized Radiation Shield Design Methods: 2005 HZETRN
NASA Technical Reports Server (NTRS)
Wilson, John W.; Tripathi, Ram K.; Badavi, Francis F.; Cucinotta, Francis A.
2006-01-01
Research committed by the Langley Research Center through 1995 resulting in the HZETRN code provides the current basis for shield design methods according to NASA STD-3000 (2005). With this new prominence, the database, basic numerical procedures, and algorithms are being re-examined with new methods of verification and validation being implemented to capture a well defined algorithm for engineering design processes to be used in this early development phase of the Bush initiative. This process provides the methodology to transform the 1995 HZETRN research code into the 2005 HZETRN engineering code to be available for these early design processes. In this paper, we will review the basic derivations including new corrections to the codes to insure improved numerical stability and provide benchmarks for code verification.
Neutron source in the MCNPX shielding calculating for electron accelerator driven facility
Zhong, Z.; Gohar, Y.
2012-07-01
Argonne National Laboratory (ANL) of USA and Kharkov Inst. of Physics and Technology (KIPT) of Ukraine have been collaborating on the design development of an experimental neutron source facility. It is an accelerator driven system (ADS) utilizing a subcritical assembly driven by electron accelerator. The facility will be utilized for performing basic and applied nuclear researches, producing medical isotopes, and training young nuclear specialists. Monte Carlo code MCNPX has been utilized as a design tool due to its capability to transport electrons, photons, and neutrons at high energies. However the facility shielding calculations with MCNPX need enormous computational resources and the small neutron yield per electron makes sampling difficulty for the Monte Carlo calculations. A method, based on generating and utilizing neutron source file, was proposed and tested. This method reduces significantly the required computer resources and improves the statistics of the calculated neutron dose outside the shield boundary. However the statistical errors introduced by generating the neutron source were not directly represented in the results, questioning the validity of this methodology, because an insufficiently sampled neutron source can cause error on the calculated neutron dose. This paper presents a procedure for the validation of the generated neutron source file. The impact of neutron source statistic on the neutron dose is examined by calculating the neutron dose as a function of the number of electron particles used for generating the neutron source files. When the value of the calculated neutron dose converges, it means the neutron source has scored sufficient records and statistic does not have apparent impact on the calculated neutron dose. In this way, the validity of neutron source and the shield analyses could be verified. (authors)
Methods and Procedures for Shielding Analyses for the SNS
Gallmeier, Franz X.; Iverson, Erik B.; Remec, Igor; Lu, Wei; Popova, Irina
2014-01-01
In order to provide radiologically safe Spallation Neutron Source operation, shielding analyses are performed according to Oak Ridge National Laboratory internal regulations and to comply with the Code of Federal Regulations. An overview of on-going shielding work for the accelerator facility and neutrons beam lines, methods, used for the analyses, and associated procedures and regulations is presented. Methods used to perform shielding analyses are described as well.
NMR Shielding in Metals Using the Augmented Plane Wave Method
2015-01-01
We present calculations of solid state NMR magnetic shielding in metals, which includes both the orbital and the complete spin response of the system in a consistent way. The latter contains an induced spin-polarization of the core states and needs an all-electron self-consistent treatment. In particular, for transition metals, the spin hyperfine field originates not only from the polarization of the valence s-electrons, but the induced magnetic moment of the d-electrons polarizes the core s-states in opposite direction. The method is based on DFT and the augmented plane wave approach as implemented in the WIEN2k code. A comparison between calculated and measured NMR shifts indicates that first-principle calculations can obtain converged results and are more reliable than initially concluded based on previous publications. Nevertheless large k-meshes (up to 2 000 000 k-points in the full Brillouin-zone) and some Fermi-broadening are necessary. Our results show that, in general, both spin and orbital components of the NMR shielding must be evaluated in order to reproduce experimental shifts, because the orbital part cancels the shift of the usually highly ionic reference compound only for simple sp-elements but not for transition metals. This development paves the way for routine NMR calculations of metallic systems. PMID:26322148
George, G. L.; Olsher, R. H.; Seagraves, D. T.
2002-01-01
MCNP-4C1 was used to perform the shielding design for the new Central Health Physics Calibration Facility (CHPCF) at Los Alamos National Laboratory (LANL). The problem of shielding the facility was subdivided into three separate components: (1) Transmission; (2) Skyshine; and (3) Maze Streaming/ Transmission. When possible, actual measurements were taken to verify calculation results. The comparison of calculation versus measurement results shows excellent agreement for neutron calculations. For photon comparisons, calculations resulted in conservative estimates of the Effective Dose Equivalent (EDE) compared to measured results. This disagreement in the photon measurements versus calculations is most likely due to several conservative assumptions regarding shield density and composition. For example, reinforcing steel bars (Rebar) in the concrete shield walls were not included in the shield model.
Santoro, R.T.; Alsmiller, R.G. Jr.; Barnes, J.M.; Chapman, G.T.
1980-08-01
Integral experiments that measure the transport of approx. 14 MeV D-T neutrons through laminated slabs of proposed fusion reactor shield materials have been carried out. Measured and calculated neutron and gamma ray energy spectra are compared as a function of the thickness and composition of stainless steel type 304, borated polyethylene, and Hevimet (a tungsten alloy), and as a function of detector position behind these materials. The measured data were obtained using a NE-213 liquid scintillator using pulse-shape discrimination methods to resolve neutron and gamma ray pulse height data and spectral unfolding methods to convert these data to energy spectra. The calculated data were obtained using two-dimensional discrete ordinates radiation transport methods in a complex calculational network that takes into account the energy-angle dependence of the D-T neutrons and the nonphysical anomalies of the S/sub n/ method.
Shielded beam delivery apparatus and method
Hershcovitch, Ady; Montano, Rory Dominick
2006-07-11
An apparatus includes a plasma generator aligned with a beam generator for producing a plasma to shield an energized beam. An electrode is coaxially aligned with the plasma generator and followed in turn by a vortex generator coaxially aligned with the electrode. A target is spaced from the vortex generator inside a fluid environment. The electrode is electrically biased relative to the electrically grounded target for driving the plasma toward the target inside a vortex shield.
Yan Xiangsheng; Poon, Emily; Reniers, Brigitte; Vuong, Te; Verhaegen, Frank
2008-11-15
Colorectal cancer patients are treated at our hospital with {sup 192}Ir high dose rate (HDR) brachytherapy using an applicator that allows the introduction of a lead or tungsten shielding rod to reduce the dose to healthy tissue. The clinical dose planning calculations are, however, currently performed without taking the shielding into account. To study the dose distributions in shielded cases, three techniques were employed. The first technique was to adapt a shielding algorithm which is part of the Nucletron PLATO HDR treatment planning system. The isodose pattern exhibited unexpected features but was found to be a reasonable approximation. The second technique employed a ray tracing algorithm that assigns a constant dose ratio with/without shielding behind the shielding along a radial line originating from the source. The dose calculation results were similar to the results from the first technique but with improved accuracy. The third and most accurate technique used a dose-matrix-superposition algorithm, based on Monte Carlo calculations. The results from the latter technique showed quantitatively that the dose to healthy tissue is reduced significantly in the presence of shielding. However, it was also found that the dose to the tumor may be affected by the presence of shielding; for about a quarter of the patients treated the volume covered by the 100% isodose lines was reduced by more than 5%, leading to potential tumor cold spots. Use of any of the three shielding algorithms results in improved dose estimates to healthy tissue and the tumor.
An update on the circuit approach to calculate shielding effectiveness
NASA Astrophysics Data System (ADS)
Bridges, Jack E.
1988-08-01
The shielding effectiveness of an enclosure at low frequencies can be computed using a circuit approach. Not only does this technique include the effects of the properties of the shield material, but it also includes the details of the geometry of the enclosure. This approach allows a nonempirical consideration of mesh enclosures and the effects of resistive seams in enclosure walls. By working with the circuit analog, penetration by transient fields can be computed. Essentially the enclosure is viewed as an antenna. In the case of magnetic shielding effectiveness, the enclosure is viewed as a short-circuited loop antenna. In the case of electric-field penetration, the enclosure is viewed as a fat electric dipole. Using this characterization and exact solutions where available, the current distribution on the outside of the enclosure is determined. Based on the current distribution, the penetrating fields are computed. The equations are developed in such a way as to preserve a lumped circuit analog for the low-frequency region. The basic circuit equations for magnetic-field penetration are rederived from a rigorous solution. Rules to estimate the rise time, fall time, and peak magnitudes of transient penetrating fields are developed. The electric shielding effectiveness is developed in a similar manner.
Ab initio calculation of Ti NMR shieldings for titanium oxides and halides
NASA Astrophysics Data System (ADS)
Tossell, J. A.
Titanium NMR shielding constants have been calculated using ab initio coupled Hartree-Fock perturbation theory and polarized double-zeta basis sets for TiF 4, TiF 62-, TiCI 4, Ti(OH) 4, Ti(OH 2) 64+, Ti(OH) 4O, and Ti(OH) 3O -. In all cases the calculations were performed at Hartree-Fuck energy-optimized geometries. For Ti(OH) 4 a S4-symmetry geometry with nonlinear ∠ TiOH was employed. Relative shieldings are in reasonable agreement with experiment for TiF 62-, TiCI 4, and Ti(OR) 4, where R = H or alkyl. Ti(OH 2) 64+ is predicted to be more highly shielded than Ti(OH) 4 by about 340 ppm. The five-coordinate complex Ti(OH) 4O, whose calculated structure matches well that measured by extended X-ray absorption fine structure in K 2O · TiO 2 · SiO 2 glass, is actually deshielded compared to Ti(OH) 4 by about 40 ppm. X-ray absorption-near-edge spectral energies have also been calculated for TiF 4, TiCI 4, Ti(OH) 4, and Ti(OH) 4O using an equivalent ionic core virtual-orbital method and the observed reduction in term energy for the five-coordinate species compared to Ti(OH) 4 has been reproduced. Replacement of the H atoms in Ti(OH) 4 by point charges has only a slight effect upon σTi, suggesting a possible means of incorporating second-neighbor effects in NMR calculations for condensed phases.
MORSE Monte Carlo shielding calculations for the zirconium hydride reference reactor
NASA Technical Reports Server (NTRS)
Burgart, C. E.
1972-01-01
Verification of DOT-SPACETRAN transport calculations of a lithium hydride and tungsten shield for a SNAP reactor was performed using the MORSE (Monte Carlo) code. Transport of both neutrons and gamma rays was considered. Importance sampling was utilized in the MORSE calculations. Several quantities internal to the shield, as well as dose at several points outside of the configuration, were in satisfactory agreement with the DOT calculations of the same.
Shielding analysis methods available in the scale computational system
Parks, C.V.; Tang, J.S.; Hermann, O.W.; Bucholz, J.A.; Emmett, M.B.
1986-01-01
Computational tools have been included in the SCALE system to allow shielding analysis to be performed using both discrete-ordinates and Monte Carlo techniques. One-dimensional discrete ordinates analyses are performed with the XSDRNPM-S module, and point dose rates outside the shield are calculated with the XSDOSE module. Multidimensional analyses are performed with the MORSE-SGC/S Monte Carlo module. This paper will review the above modules and the four Shielding Analysis Sequences (SAS) developed for the SCALE system. 7 refs., 8 figs.
Neutron streaming through shield ducts using a discrete ordinates/Monte Carlo method
Urban, W.T.; Baker, R.S.
1993-08-18
A common problem in shield design is determining the neutron flux that streams through ducts in shields and also that penetrates the shield after having traveled partway down the duct. Obviously the determination of the neutrons that stream down the duct can be computed in a straightforward manner using Monte Carlo techniques. On the other hand those neutrons that must penetrate a significant portion of the shield are more easily handled using discrete ordinates methods. A hybrid discrete ordinates/Monte Carlo cods, TWODANT/MC, which is an extension of the existing discrete ordinates code TWODANT, has been developed at Los Alamos to allow the efficient, accurate treatment of both streaming and deep penetration problems in a single calculation. In this paper we provide examples of the application of TWODANT/MC to typical geometries that are encountered in shield design and compare the results with those obtained using the Los Alamos Monte Carlo code MCNP{sup 3}.
Radiation predictions and shielding calculations for RITS-6
Maenchen, John Eric; O'Malley, John; Kensek, Ronald Patrick; Fan, Wesley C.; Bollinger, Lance
2005-06-01
The mission of Radiographic Integrated Test Stand-6 (RITS-6) facility is to provide the underlying science and technology for pulsed-power-driven flash radiographic X-ray sources for the National Nuclear Security Administration (NNSA). Flash X-ray radiography is a penetrating diagnostic to discern the internal structure in dynamic experiments. Short (~50 nanosecond (ns) duration) bursts of very high intensity Xrays from mm-scale source sizes are required at a variety of voltages to address this mission. RITS-6 was designed and is used to both develop the accelerator technology needed for these experiments and serves as the principal test stand to develop the high intensity electron beam diodes that generate the required X-ray sources. RITS is currently in operation with three induction cavities (RITS-3) with a maximum voltage output of 5.5 MV and is classified as a low hazard non-nuclear facility in accordance with CPR 400.1.1, Chapter 13, Hazards Identification/Analysis and Risk Management. The facility will be expanded from three to six cavities (RITS-6) effectively doubling the operating voltage. The increase in the operating voltage to above 10 MV has resulted in RITS-6 being classified as an accelerator facility. RITS-6 will come under DOE Order 420.2B, Safety of Accelerator Facilities. The hazards of RITS are detailed in the "Safety Assessment Document for the Radiographic Integrated Test Stand Facility." The principal non-industrial hazard is prompt x-ray radiation. As the operating voltage is increased, both the penetration power and the total amount (dose) of x-rays are increased, thereby increasing the risk to local personnel. Fixed site shielding (predominantly concrete walls and a steel/lead skyshine shield) is used to attenuate these x-rays and mitigate this risk. This SAND Report details the anticipated x-ray doses, the shielding design, and the anticipated x-ray doses external to this shielding structure both in areas where administrative access
Calculations of cosmic-ray helium transport in shielding materials
NASA Technical Reports Server (NTRS)
Cucinotta, Francis A.
1993-01-01
The transport of galactic cosmic-ray helium nuclei and their secondaries through bulk shielding is considered using the straight-ahead approximation to the Boltzmann equation. A data base for nuclear interaction cross sections and secondary particle energy spectra for high-energy light-ion breakup is presented. The importance of the light ions H-2, H-3, and He-3 for cosmic-ray risk estimation is discussed, and the estimates of the fractional contribution to the neutron flux from helium interactions compared with other particle interactions are presented using a 1977 solar minimum cosmic-ray spectrum.
Schreckenbach, Georg
2002-12-16
In this and a previous article (J. Phys. Chem. A 2000, 104, 8244), the range of application for relativistic density functional theory (DFT) is extended to the calculation of nuclear magnetic resonance (NMR) shieldings and chemical shifts in diamagnetic actinide compounds. Two relativistic DFT methods are used, ZORA ("zeroth-order regular approximation") and the quasirelativistic (QR) method. In the given second paper, NMR shieldings and chemical shifts are calculated and discussed for a wide range of compounds. The molecules studied comprise uranyl complexes, [UO(2)L(n)](+/-)(q); UF(6); inorganic UF(6) derivatives, UF(6-n)Cl(n), n = 0-6; and organometallic UF(6) derivatives, UF(6-n)(OCH(3))(n), n = 0-5. Uranyl complexes include [UO(2)F(4)](2-), [UO(2)Cl(4)](2-), [UO(2)(OH)(4)](2-), [UO(2)(CO(3))(3)](4-), and [UO(2)(H(2)O)(5)](2+). For the ligand NMR, moderate (e.g., (19)F NMR chemical shifts in UF(6-n)Cl(n)) to excellent agreement [e.g., (19)F chemical shift tensor in UF(6) or (1)H NMR in UF(6-n)(OCH(3))(n)] has been found between theory and experiment. The methods have been used to calculate the experimentally unknown (235)U NMR chemical shifts. A large chemical shift range of at least 21,000 ppm has been predicted for the (235)U nucleus. ZORA spin-orbit appears to be the most accurate method for predicting actinide metal chemical shifts. Trends in the (235)U NMR chemical shifts of UF(6-n)L(n) molecules are analyzed and explained in terms of the calculated electronic structure. It is argued that the energy separation and interaction between occupied and virtual orbitals with f-character are the determining factors. PMID:12470051
NASA-Lewis experiences with multigroup cross sections and shielding calculations
NASA Technical Reports Server (NTRS)
Lahti, G. P.
1972-01-01
The nuclear reactor shield analysis procedures employed at NASA-Lewis are described. Emphasis is placed on the generation, use, and testing of multigroup cross section data. Although coupled neutron and gamma ray cross section sets are useful in two dimensional Sn transport calculations, much insight has been gained from examination of uncoupled calculations. These have led to experimental and analytic studies of areas deemed to be of first order importance to reactor shield calculations. A discussion is given of problems encountered in using multigroup cross sections in the resolved resonance energy range. The addition to ENDF files of calculated and/or measured neutron-energy-dependent capture gamma ray spectra for shielding calculations is questioned for the resonance region. Anomalies inherent in two dimensional Sn transport calculations which may overwhelm any cross section discrepancies are illustrated.
Analysis methods for Kevlar shield response to rotor fragments
NASA Technical Reports Server (NTRS)
Gerstle, J. H.
1977-01-01
Several empirical and analytical approaches to rotor burst shield sizing are compared and principal differences in metal and fabric dynamic behavior are discussed. The application of transient structural response computer programs to predict Kevlar containment limits is described. For preliminary shield sizing, present analytical methods are useful if insufficient test data for empirical modeling are available. To provide other information useful for engineering design, analytical methods require further developments in material characterization, failure criteria, loads definition, and post-impact fragment trajectory prediction.
Evaluation of approximate methods for the prediction of noise shielding by airframe components
NASA Technical Reports Server (NTRS)
Ahtye, W. F.; Mcculley, G.
1980-01-01
An evaluation of some approximate methods for the prediction of shielding of monochromatic sound and broadband noise by aircraft components is reported. Anechoic-chamber measurements of the shielding of a point source by various simple geometric shapes were made and the measured values compared with those calculated by the superposition of asymptotic closed-form solutions for the shielding by a semi-infinite plane barrier. The shields used in the measurements consisted of rectangular plates, a circular cylinder, and a rectangular plate attached to the cylinder to simulate a wing-body combination. The normalized frequency, defined as a product of the acoustic wave number and either the plate width or cylinder diameter, ranged from 4.6 to 114. Microphone traverses in front of the rectangular plates and cylinders generally showed a series of diffraction bands that matched those predicted by the approximate methods, except for differences in the magnitudes of the attenuation minima which can be attributed to experimental inaccuracies. The shielding of wing-body combinations was predicted by modifications of the approximations used for rectangular and cylindrical shielding. Although the approximations failed to predict diffraction patterns in certain regions, they did predict the average level of wing-body shielding with an average deviation of less than 3 dB.
Mohammadi, A; Hassanzadeh, M; Gharib, M
2016-02-01
In this study, shielding calculation and criticality safety analysis were carried out for general material testing reactor (MTR) research reactors interim storage and relevant transportation cask. During these processes, three major terms were considered: source term, shielding, and criticality calculations. The Monte Carlo transport code MCNP5 was used for shielding calculation and criticality safety analysis and ORIGEN2.1 code for source term calculation. According to the results obtained, a cylindrical cask with body, top, and bottom thicknesses of 18, 13, and 13 cm, respectively, was accepted as the dual-purpose cask. Furthermore, it is shown that the total dose rates are below the normal transport criteria that meet the standards specified. PMID:26720262
T. Downar
2009-03-31
The overall objective of the work here has been to eliminate the approximations used in current resonance treatments by developing continuous energy multi-dimensional transport calculations for problem dependent self-shielding calculations. The work here builds on the existing resonance treatment capabilities in the ORNL SCALE code system.
The TRADE experiment: shielding calculations for the building hosting the subcritical system.
Burn, K W; Carta, M; Casalini, L; Kadi, Y; Monti, S; Nava, E; Palomba, M; Petrovich, C; Picardi, L; Rubbia, C; Troiani, F
2005-01-01
The TRADE project (TRiga Accelerator Driven Experiment), to be performed at the existing TRIGA reactor at ENEA Casaccia, has been proposed as a validation of the accelerator-driven system (ADS) concept. TRADE will be the first experiment in which the three main components of an ADS--the accelerator, spallation target and sub-critical blanket--are coupled at a power level sufficient to encounter reactivity feedback effects. As such, TRADE represents the necessary intermediate step in the development of hybrid transmutation systems, its expected outcomes being considered crucial--in terms of proof of stability of operation, dynamic behaviour and licensing issues--for the subsequent realisation of an ADS Transmutation Demonstrator. An essential role in the feasibility study of the experiment is played by radioprotection calculations. Such a system exhibits new characteristics with respect to a traditional reactor, owing to the presence of the proton accelerator. As beam losses always occur under normal operating conditions of an accelerator, shielding studies need to be performed not only around the reactor but also along the beam line from the accelerator to the spallation target. This paper illustrates a preliminary evaluation, using Monte Carlo methods, of the additional shielding to be located around the reactor structures, the beam transport line and the existing reactor building to allow access into the reactor hall and to restrict the doses outside to their legal limits. PMID:16381710
1990-11-20
Version 00 REX2-87 is a computer code developed for the calculation of self-shielded multigroup average cross sections, and self-shielding factors for total, elastic, fission and capture processes from an ENDF/B formatted nuclear data file in which the tabulated cross sections follow linear interpolation throughout.
Dosimetric evaluation of photon dose calculation under jaw and MLC shielding
Fogliata, A.; Clivio, A.; Vanetti, E.; Nicolini, G.; Belosi, M. F.; Cozzi, L.
2013-10-15
Purpose: The accuracy of photon dose calculation algorithms in out-of-field regions is often neglected, despite its importance for organs at risk and peripheral dose evaluation. The present work has assessed this for the anisotropic analytical algorithm (AAA) and the Acuros-XB algorithms implemented in the Eclipse treatment planning system. Specifically, the regions shielded by the jaw, or the MLC, or both MLC and jaw for flattened and unflattened beams have been studied.Methods: The accuracy in out-of-field dose under different conditions was studied for two different algorithms. Measured depth doses out of the field, for different field sizes and various distances from the beam edge were compared with the corresponding AAA and Acuros-XB calculations in water. Four volumetric modulated arc therapy plans (in the RapidArc form) were optimized in a water equivalent phantom, PTW Octavius, to obtain a region always shielded by the MLC (or MLC and jaw) during the delivery. Doses to different points located in the shielded region and in a target-like structure were measured with an ion chamber, and results were compared with the AAA and Acuros-XB calculations. Photon beams of 6 and 10 MV, flattened and unflattened were used for the tests.Results: Good agreement between calculated and measured depth doses was found using both algorithms for all points measured at depth greater than 3 cm. The mean dose differences (±1SD) were −8%± 16%, −3%± 15%, −16%± 18%, and −9%± 16% for measurements vs AAA calculations and −10%± 14%, −5%± 12%, −19%± 17%, and −13%± 14% for Acuros-XB, for 6X, 6 flattening-filter free (FFF), 10X, and 10FFF beams, respectively. The same figures for dose differences relative to the open beam central axis dose were: −0.1%± 0.3%, 0.0%± 0.4%, −0.3%± 0.3%, and −0.1%± 0.3% for AAA and −0.2%± 0.4%, −0.1%± 0.4%, −0.5%± 0.5%, and −0.3%± 0.4% for Acuros-XB. Buildup dose was overestimated with AAA, while Acuros-XB gave
[Calculation of radiation loads in a space station compartment with a secondary shielding].
Kartashov, D A; Tolochek, R V; Shurshakov, V A; Yarmanova, E N
2013-01-01
Doses from space ionizing radiation were estimated using a model of ISS cosmonaut's quarters (CQ) outfitted with secondary shielding ("Protective shutter" (PS) as part of experiment MATRYOSHKA-R). Protective shutter is a "blanket" of water-containing material with mass thickness of - 6 g/cm2 covering the CQ exterior wall. Calculation was performed specifically for locations of experimental dosimetry assemblies. Agreement of calculations and experimental data reaching accuracy - 15% proves model applicability to estimating protective effectiveness of secondary shielding in the present-day and future space vehicles. This shielding may reduce radiation loading onto crewmembers as an equivalent dose by more than 40% within a broad range of orbit altitudes equally during the solar minimum and maximum. PMID:24660246
Biological shielding assessment and dose rate calculation for a neutron inspection portal
NASA Astrophysics Data System (ADS)
Donzella, A.; Bonomi, G.; Giroletti, E.; Zenoni, A.
2012-04-01
With reference to the prototype of neutron inspection portal built and successfully tested in the Rijeka seaport (Croatia) within the EURITRACK (EURopean Illicit Trafficking Countermeasures Kit) project, an assessment of the biological shielding in different set-up configurations of a future portal has been calculated with MCNP Monte Carlo code in the frame of the Eritr@C (European Riposte against Illicit TR@ffiCking) project. In the configurations analyzed the compliance with the dose limits for workers and the population stated by the European legislation is provided by appropriate shielding of the neutron sources and by the delimitation of a controlled area.
NASA Technical Reports Server (NTRS)
Lahti, G. P.; Mueller, R. A.
1973-01-01
Measurements of MeV neutron were made at the surface of a lithium hydride and depleted uranium shielded reactor. Four shield configurations were considered: these were assembled progressively with cylindrical shells of 5-centimeter-thick depleted uranium, 13-centimeter-thick lithium hydride, 5-centimeter-thick depleted uranium, 13-centimeter-thick lithium hydride, 5-centimeter-thick depleted uranium, and 3-centimeter-thick depleted uranium. Measurements were made with a NE-218 scintillation spectrometer; proton pulse height distributions were differentiated to obtain neutron spectra. Calculations were made using the two-dimensional discrete ordinates code DOT and ENDF/B (version 3) cross sections. Good agreement between measured and calculated spectral shape was observed. Absolute measured and calculated fluxes were within 50 percent of one another; observed discrepancies in absolute flux may be due to cross section errors.
Calculation of the 13C NMR shieldings of the C0 2 complexes of aluminosilicates
NASA Astrophysics Data System (ADS)
Tossell, J. A.
1995-04-01
13C NMR shieldings have been calculated using the random-phase-approximation, localized-orbital local-origins version of ab initio coupled Hartree-Fuck perturbation theory for CO 2 and and for several complexes formed by the reaction of CO 2 with molecular models for aluminosilicate glasses, H 3TOT'H3 3-n, T,T' = Si,Al. Two isomeric forms of the CO 2-aluminosilicate complexes have been considered: (1) "CO 2-like" complexes, in which the CO 2 group is bound through carbon to a bridging oxygen and (2) "CO 3-like" complexes, in which two oxygens of a central CO 3 group form bridging bonds to the two TH 3 groups. The CO 2-like isomer of CO 2-H 3SiOSiH 3 is quite weakly bonded and its 13C isotropic NMR shielding is almost identical to that in free CO 2. As Si is progressively replaced by Al in the - H terminated aluminosilicate model, the CO 2-like isomers show increasing distortion from the free CO 2 geometry and their 13C NMR shieldings decrease uniformly. The calculated 13C shielding value for H 3AlO(CO 2)AlH 3-2 is only about 6 ppm larger than that calculated for point charge stabilized CO 3-2. However, for a geometry of H 3SiO(CO 2) AlH 3-1, in which the bridging oxygen to C bond length has been artificially increased to that found in the - OH terminated cluster (OH) 3SiO(CO 2)Al(OH) 3-1, the calculated 13C shielding is almost identical to that for free CO 2. The CO 3-like isomers of the CO 2-aluminosili-cate complexes show carbonate like geometries and 13C NMR shieldings about 4-9 ppm larger than those of carbonate for all T,T' pairs. For the Si,Si tetrahedral atom pair the CO 2-like isomer is more stable energetically, while for the Si,Al and Al,Al cases the CO 3-like isomer is more stable. Addition of Na + ions to the CO 3-2 or H 3AlO(CO 2)AlH 3-2 complexes reduces the 13C NMR shieldings by about 10 ppm. Complexation with either Na + or CO 2 also reduces the 29Si NMR shieldings of the aluminosilicate models, while the changes in 27Al shielding with Na + or CO 2
Modeling of spacecraft proton shielding by the discrete ordinates method
Drumm, C.R. )
1992-01-01
Radiation in space can be damaging to personnel and electronics in space missions. Solar flare and trapped protons are a significant component of the near-earth radiation environment. It is important to assess the effectiveness of materials (typically aluminum) for shielding protons for manned and unmanned space flights. The discrete ordinates method is a convenient and efficient method for modeling proton transport. With the adjoint capability, a set of proton environments for many different orbit trajectories can be modeled extremely efficiently. Modeling a slab geometry and a spherical shell geometry shield should provide bounds on the dose that a component inside of a satellite would be expected to receive. Neutron and other secondary particle production are neglected in this model.
NASA Astrophysics Data System (ADS)
Sharaf, J. M.; Saleh, H.
2015-05-01
The shielding properties of three different construction styles, and building materials, commonly used in Jordan, were evaluated using parameters such as attenuation coefficients, equivalent atomic number, penetration depth and energy buildup factor. Geometric progression (GP) method was used to calculate gamma-ray energy buildup factors of limestone, concrete, bricks, cement plaster and air for the energy range 0.05-3 MeV, and penetration depths up to 40 mfp. It has been observed that among the examined building materials, limestone offers highest value for equivalent atomic number and linear attenuation coefficient and the lowest values for penetration depth and energy buildup factor. The obtained buildup factors were used as basic data to establish the total equivalent energy buildup factors for three different multilayer construction styles using an iterative method. The three styles were then compared in terms of fractional transmission of photons at different incident photon energies. It is concluded that, in case of any nuclear accident, large multistory buildings with five layers exterior walls, style A, could effectively attenuate radiation more than small dwellings of any construction style.
Hartman, Joshua D.; Neubauer, Thomas J.; Caulkins, Bethany G.; Mueller, Leonard J.; Beran, Gregory J. O.
2015-01-01
Ab initio chemical shielding calculations greatly facilitate the interpretation of nuclear magnetic resonance (NMR) chemical shifts in biological systems, but the large sizes of these systems requires approximations in the chemical models used to represent them. Achieving good convergence in the predicted chemical shieldings is necessary before one can unravel how other complex structural and dynamical factors affect the NMR measurements. Here, we investigate how to balance trade-offs between using a better basis set or a larger cluster model for predicting the chemical shieldings of the substrates in two representative examples of protein-substrate systems involving different domains in tryptophan synthase: the N-(4′-trifluoromethoxybenzoyl)-2-aminoethyl phosphate (F9) ligand which binds in the α active site, and the 2-aminophenol (2AP) quinonoid intermediate formed in the β active site. We first demonstrate that a chemically intuitive three-layer, locally dense basis model that uses a large basis on the substrate, a medium triple-zeta basis to describe its hydrogen-bonding partners and/or surrounding van derWaals cavity, and a crude basis set for more distant atoms provides chemical shieldings in good agreement with much more expensive large basis calculations. Second, long-range quantum mechanical interactions are important, and one can accurately estimate them as a small-basis correction to larger-basis calculations on a smaller cluster. The combination of these approaches enables one to perform density functional theory NMR chemical shift calculations in protein systems that are well-converged with respect to both basis set and cluster size. PMID:25993979
NASA Astrophysics Data System (ADS)
Lazzeretti, P.; Malagoli, M.; Turci, L.; Zanasi, R.
1993-10-01
Theoretical methods based on the random-phase approximation have been applied to evaluate near Hartree-Fock dynamic electric polarizability and shielding tensors of carbon and hydrogen nuclei in the benzene molecule. Cauchy moments of the various properties have been determined. The results obtained in different gauges (dipole length, velocity, and acceleration) are reported.
Modeling resonance interference by 0-D slowing-down solution with embedded self-shielding method
Liu, Y.; Martin, W.; Kim, K. S.; Williams, M.
2013-07-01
The resonance integral table based methods employing conventional multigroup structure for the resonance self-shielding calculation have a common difficulty on treating the resonance interference. The problem arises due to the lack of sufficient energy dependence of the resonance cross sections when the calculation is performed in the multigroup structure. To address this, a resonance interference factor model has been proposed to account for the interference effect by comparing the interfered and non-interfered effective cross sections obtained from 0-D homogeneous slowing-down solutions by continuous-energy cross sections. A rigorous homogeneous slowing-down solver is developed with two important features for reducing the calculation time and memory requirement for practical applications. The embedded self-shielding method (ESSM) is chosen as the multigroup resonance self-shielding solver as an integral component of the interference method. The interference method is implemented in the DeCART transport code. Verification results show that the code system provides more accurate effective cross sections and multiplication factors than the conventional interference method for UO{sub 2} and MOX fuel cases. The additional computing time and memory for the interference correction is acceptable for the test problems including a depletion case with 87 isotopes in the fuel region. (authors)
NASA Astrophysics Data System (ADS)
Žagar, Tomaž; Božič, Matjaž; Ravnik, Matjaž
2004-12-01
In this paper, a process of long-lived activity determination in research reactor concrete shielding is presented. The described process is a combination of experiment and calculations. Samples of original heavy reactor concrete containing mineral barite were irradiated inside the reactor shielding to measure its long-lived induced radioactivity. The most active long-lived (γ emitting) radioactive nuclides in the concrete were found to be 133Ba, 60Co and 152Eu. Neutron flux, activation rates and concrete activity were calculated for actual shield geometry for different irradiation and cooling times using TORT and ORIGEN codes. Experimental results of flux and activity measurements showed good agreement with the results of calculations. Volume of activated concrete waste after reactor decommissioning was estimated for particular case of Jožef Stefan Institute TRIGA reactor. It was observed that the clearance levels of some important long-lived isotopes typical for barite concrete (e.g. 133Ba, 41Ca) are not included in the IAEA and EU basic safety standards.
van Wüllen, Christoph
2012-03-21
State-of-the art effective core potentials (ECPs) that replace electrons of inner atomic cores involve non-local potentials. If such an effective core potential is added to the Hamiltonian of a system in a magnetic field, the resulting Hamiltonian is not gauge invariant. This means, magnetic properties such as magnetisabilities and magnetic shieldings (or magnetic susceptibilities and nuclear magnetic resonance chemical shifts) calculated with different gauge origins are different even for exact solutions of the Schrödinger equation. It is possible to restore gauge invariance of the Hamiltonian by adding magnetic field dependent terms arising from the effective core potential. Numerical calculations on atomic and diatomic model systems (potassium mono-cation and potassium dimer) clearly demonstrate that the standard effective core potential Hamiltonian violates gauge invariance, and this affects the calculation of magnetisabilities more strongly than the calculation of magnetic shieldings. The modified magnetic field dependent effective core potential Hamiltonian is gauge invariant, and therefore it is the correct starting point for distributed gauge origin methods. The formalism for gauge including atomic orbitals (GIAO) and individual gauge for localized orbitals methods is worked out. ECP GIAO results for the potassium dimer are presented. The new method performs much better than a previous ECP GIAO implementation that did not account for the non-locality of the potential. For magnetic shieldings, deviations are clearly seen, but they amount to few ppm only. For magnetisabilities, our new ECP GIAO implementation is a major improvement, as demonstrated by the comparison of all-electron and ECP results. PMID:22443751
Park, J; Lee, J; Kim, H; Kim, I; Ye, S
2015-06-15
Purpose: To evaluate the effect of a tungsten eye-shield on the dose distribution of a patient. Methods: A 3D scanner was used to extract the dimension and shape of a tungsten eye-shield in the STL format. Scanned data was transferred into a 3D printer. A dummy eye shield was then produced using bio-resin (3D systems, VisiJet M3 Proplast). For a patient with mucinous carcinoma, the planning CT was obtained with the dummy eye-shield placed on the patient’s right eye. Field shaping of 6 MeV was performed using a patient-specific cerrobend block on the 15 x 15 cm{sup 2} applicator. The gantry angle was 330° to cover the planning target volume near by the lens. EGS4/BEAMnrc was commissioned from our measurement data from a Varian 21EX. For the CT-based dose calculation using EGS4/DOSXYZnrc, the CT images were converted to a phantom file through the ctcreate program. The phantom file had the same resolution as the planning CT images. By assigning the CT numbers of the dummy eye-shield region to 17000, the real dose distributions below the tungsten eye-shield were calculated in EGS4/DOSXYZnrc. In the TPS, the CT number of the dummy eye-shield region was assigned to the maximum allowable CT number (3000). Results: As compared to the maximum dose, the MC dose on the right lens or below the eye shield area was less than 2%, while the corresponding RTP calculated dose was an unrealistic value of approximately 50%. Conclusion: Utilizing a 3D scanner and a 3D printer, a dummy eye-shield for electron treatment can be easily produced. The artifact-free CT images were successfully incorporated into the CT-based Monte Carlo simulations. The developed method was useful in predicting the realistic dose distributions around the lens blocked with the tungsten shield.
Development and verification of design methods for ducts in a space nuclear shield
NASA Technical Reports Server (NTRS)
Cerbone, R. J.; Selph, W. E.; Read, P. A.
1972-01-01
A practical method for computing the effectiveness of a space nuclear shield perforated by small tubing and cavities is reported. Performed calculations use solutions for a two dimensional transport code and evaluate perturbations of that solution using last flight estimates and other kernel integration techniques. In general, perturbations are viewed as a change in source strength of scattered radiation and a change in attenuation properties of the region.
A Visualization Code System for Gamma and Neutron Shielding Calculations, Version 2.0
2008-08-01
EASYQAD, Version 2.0, is a standalone Windows XP or Windows 7 code system which facilitates gamma and neutron shielding calculations with user friendly graphical interfaces. It is used to analyze radiation shielding problems and includes: - 8 kinds of geometry types - Various flexible source options - Common material library - Various detector types The update contents of EASYQAD Version 2.0 are below: - Addition of starting option with P-code files - Addition of multi-sourcemore » calculation function - Expansion of source geometries - Addition of warning message - Modifications of EASYQAD program errors a. Coordination application problem in source division b. Source position error c. Rotation problem of source geometry d. Program running error in using more than six gamma energy distribution e. EASYQAD display problem of the right elliptic cylinder, ellipsoid and truncated right cone geometries Through intuitive windows and their interactions inside EASYQAD, the user can specify the dimensions of 3D-shapes, their material compositions, their densities, the type of radioactive sources, the locations of the sources, the type and positions of detectors. With the ease of using these sequences, shielding problems will become simpler and more clearly understandable to the analyzer. Furthermore, the error checking system can prevent users from making mistakes by automatically debugging the user inputs and giving modal dialog windows. The included AECL implementation of QAD-CGGP-A, Version 95.2 (C00645MNYCP00), is run from the user interface.« less
Identification of an unknown material in a radiation shield using the schwinger inverse method.
Favorite, J. A.; Bledsoe, K. C.
2004-01-01
The Schwinger method for solving inverse gamma-ray transport problems was proposed in a previous paper. The method is iterative and requires a set of uncoupled forward and adjoint transport calculations in each iteration. In this paper, the Schwinger inverse method is applied to the problem of identifying an unknown material in a radiation shield by calculating its total macroscopic photon cross sections. The gamma source is known and the total (angle-independent) gamma leakage is measured. In numerical one-dimensional spherical and slab test problems, the Schwinger inverse method successfully calculated the photon cross sections of an unknown material. Material identification was successfully achieved by comparing the calculated cross sections with those in a precomputed material cross section library, although there was some ambiguity when realistic measurements were used. The Schwinger inverse method compared very favorably with the standard single energy transmission technique (SET).
Court, J.D.; Pitcher, E.J.; Ferguson, P.D.; Russell, G.J.; Patton, B.W.
1998-07-01
The authors have performed calculations using the LAHET Code System (LCS) to obtain an estimation of the amount of earth berm shielding that will be required for the 1700-MeV proton accelerator proposed for the Accelerator Production of Tritium (APT) Project. A source scenario of 10 nA/m beam loss along the beam line was used to calculate the dose values above a 6-m earth berm from high-energy neutrons, low-energy neutrons, and photons. LAHET, a Monte Carlo based particle transport code, was used to transport a 1700-MeV protons from the beam along a divergence path of 1{degree} from the original beam direction and impacting representative beampipe material along a 300-m beamline. LAHET was then used to track all high-energy neutron production until the neutrons either escape the berm shield, or scatter down in energy to 20 MeV, where their parameters were then written to a source file for MCNP. Photon production data was also written to a source file used by MCNP. MCNP transported all neutrons and photons from the LAHET source file until they (1) were absorbed, scattered down to an energy cutoff, or (2) escaped from the system. Doses were calculated from surface flux tallies obtained from LAHET and MCNP. These doses were then compared to earlier Moyer model calculations.
Early test facilities and analytic methods for radiation shielding: Proceedings
Ingersoll, D.T. ); Ingersoll, J.K. )
1992-11-01
This report represents a compilation of eight papers presented at the 1992 American Nuclear Society/European Nuclear Society International Meeting. The meeting is of special significance since it commemorates the fiftieth anniversary of the first controlled nuclear chain reaction. The papers contained in this report were presented in a special session organized by the Radiation Protection and Shielding Division in keeping with the historical theme of the meeting. The paper titles are good indicators of their content and are: (1) The origin of radiation shielding research: The Oak Ridge experience, (2) Shielding research at the hanford site, (3) Aircraft shielding experiments at General Dynamics Fort Worth, 1950-1962, (4) Where have the neutrons gone , a history of the tower shielding facility, (5) History and evolution of buildup factors, (6) Early shielding research at Bettis atomic power laboratory, (7) UK reactor shielding: then and now, (8) A very personal view of the development of radiation shielding theory.
X-ray spectroscopy applied to radiation shielding calculation in mammography
Kuenzel, Roseli; Levenhagen, Ronaldo Savarino; Herdade, Silvio Bruni; Terini, Ricardo Andrade; Costa, Paulo Roberto
2008-08-15
The protective shielding design of a mammography facility requires the knowledge of the scattered radiation by the patient and image receptor components. The shape and intensity of secondary x-ray beams depend on the kVp applied to the x-ray tube, target/filter combination, primary x-ray field size, and scattering angle. Currently, shielding calculations for mammography facilities are performed based on scatter fraction data for Mo/Mo target/filter, even though modern mammography equipment is designed with different anode/filter combinations. In this work we present scatter fraction data evaluated based on the x-ray spectra produced by a Mo/Mo, Mo/Rh and W/Rh target/filter, for 25, 30 and 35 kV tube voltages and scattering angles between 30 and 165 deg. Three mammography phantoms were irradiated and the scattered radiation was measured with a CdZnTe detector. The primary x-ray spectra were computed with a semiempirical model based on the air kerma and HVL measured with an ionization chamber. The results point out that the scatter fraction values are higher for W/Rh than for Mo/Mo and Mo/Rh, although the primary and scattered air kerma are lower for W/Rh than for Mo/Mo and Mo/Rh target/filter combinations. The scatter fractions computed in this work were applied in a shielding design calculation in order to evaluate shielding requirements for each of these target/filter combinations. Besides, shielding requirements have been evaluated converting the scattered air kerma from mGy/week to mSv/week adopting initially a conversion coefficient from air kerma to effective dose as 1 Sv/Gy and then a mean conversion coefficient specific for the x-ray beam considered. Results show that the thickest barrier should be provided for Mo/Mo target/filter combination. They also point out that the use of the conversion coefficient from air kerma to effective dose as 1 Sv/Gy is conservatively high in the mammography energy range and overestimate the barrier thickness.
Methods for Melting Temperature Calculation
NASA Astrophysics Data System (ADS)
Hong, Qi-Jun
Melting temperature calculation has important applications in the theoretical study of phase diagrams and computational materials screenings. In this thesis, we present two new methods, i.e., the improved Widom's particle insertion method and the small-cell coexistence method, which we developed in order to capture melting temperatures both accurately and quickly. We propose a scheme that drastically improves the efficiency of Widom's particle insertion method by efficiently sampling cavities while calculating the integrals providing the chemical potentials of a physical system. This idea enables us to calculate chemical potentials of liquids directly from first-principles without the help of any reference system, which is necessary in the commonly used thermodynamic integration method. As an example, we apply our scheme, combined with the density functional formalism, to the calculation of the chemical potential of liquid copper. The calculated chemical potential is further used to locate the melting temperature. The calculated results closely agree with experiments. We propose the small-cell coexistence method based on the statistical analysis of small-size coexistence MD simulations. It eliminates the risk of a metastable superheated solid in the fast-heating method, while also significantly reducing the computer cost relative to the traditional large-scale coexistence method. Using empirical potentials, we validate the method and systematically study the finite-size effect on the calculated melting points. The method converges to the exact result in the limit of a large system size. An accuracy within 100 K in melting temperature is usually achieved when the simulation contains more than 100 atoms. DFT examples of Tantalum, high-pressure Sodium, and ionic material NaCl are shown to demonstrate the accuracy and flexibility of the method in its practical applications. The method serves as a promising approach for large-scale automated material screening in which
Kartashov, D A; Shurshakov, V A
2015-01-01
The paper presents the results of calculating doses from space ionizing radiation for a modeled orbital station cabin outfitted with an additional shield aimed to reduce radiation loads on cosmonaut. The shield is a layer with the mass thickness of -6 g/cm2 (mean density = 0.62 g/cm3) that covers the outer cabin wall and consists of wet tissues and towels used by cosmonauts for hygienic purposes. A tissue-equivalent anthropomorphic phantom imitates human body. Doses were calculated for the standard orbit of the International space station (ISS) with consideration of the longitudinal and transverse phantom orientation relative to the wall with or without the additional shield. Calculation of dose distribution in the human body improves prediction of radiation loads. The additional shield reduces radiation exposure of human critical organs by -20% depending on their depth and body spatial orientation in the ISS compartment. PMID:26554132
CRYPTOSPORIDIUM LOG INACTIVATION CALCULATION METHODS
Appendix O of the Surface Water Treatment Rule (SWTR) Guidance Manual introduces the CeffT10 (i.e., reaction zone outlet C value and T10 time) method for calculating ozone CT value and Giardia and virus log inactivation. The LT2ESWTR Pre-proposal Draft Regulatory Language for St...
Geant4 calculations for space radiation shielding material Al2O3
NASA Astrophysics Data System (ADS)
Capali, Veli; Acar Yesil, Tolga; Kaya, Gokhan; Kaplan, Abdullah; Yavuz, Mustafa; Tilki, Tahir
2015-07-01
Aluminium Oxide, Al2O3 is the most widely used material in the engineering applications. It is significant aluminium metal, because of its hardness and as a refractory material owing to its high melting point. This material has several engineering applications in diverse fields such as, ballistic armour systems, wear components, electrical and electronic substrates, automotive parts, components for electric industry and aero-engine. As well, it is used as a dosimeter for radiation protection and therapy applications for its optically stimulated luminescence properties. In this study, stopping powers and penetrating distances have been calculated for the alpha, proton, electron and gamma particles in space radiation shielding material Al2O3 for incident energies 1 keV - 1 GeV using GEANT4 calculation code.
Couture, A.
2013-06-07
Nuclear facilities sometimes use hand-held plastic scintillator detectors to detect attempts to divert special nuclear material in situations where portal monitors are impractical. MCNP calculations have been performed to determine the neutron and gamma radiation field arising from a Category I quantity of weapons-grade plutonium in various shielding configurations. The shields considered were composed of combinations of lead and high-density polyethylene such that the mass of the plutonium plus shield was 22.7 kilograms. Monte-Carlo techniques were also used to determine the detector response to each of the shielding configurations. The detector response calculations were verified using field measurements of high-, medium-, and low- energy gamma-ray sources as well as a Cf-252 neutron source.
Graphene shield enhanced photocathodes and methods for making the same
Moody, Nathan Andrew
2014-09-02
Disclosed are graphene shield enhanced photocathodes, such as high QE photocathodes. In certain embodiments, a monolayer graphene shield membrane ruggedizes a high quantum efficiency photoemission electron source by protecting a photosensitive film of the photocathode, extending operational lifetime and simplifying its integration in practical electron sources. In certain embodiments of the disclosed graphene shield enhanced photocathodes, the graphene serves as a transparent shield that does not inhibit photon or electron transmission but isolates the photosensitive film of the photocathode from reactive gas species, preventing contamination and yielding longer lifetime.
NASA Astrophysics Data System (ADS)
Pescarini, M.; Sinitsa, V.; Orsi, R.; Frisoni, M.
2013-03-01
This paper presents a synthesis of the ENEA-Bologna Nuclear Data Group programme dedicated to generate and validate group-wise cross section libraries for shielding and radiation damage deterministic calculations in nuclear fission reactors, following the data processing methodology recommended in the ANSI/ANS-6.1.2-1999 (R2009) American Standard. The VITJEFF311.BOLIB and VITENDF70.BOLIB finegroup coupled n-γ (199 n + 42 γ - VITAMIN-B6 structure) multi-purpose cross section libraries, based on the Bondarenko method for neutron resonance self-shielding and respectively on JEFF-3.1.1 and ENDF/B-VII.0 evaluated nuclear data, were produced in AMPX format using the NJOY-99.259 and the ENEA-Bologna 2007 Revision of the SCAMPI nuclear data processing systems. Two derived broad-group coupled n-γ (47 n + 20 γ - BUGLE-96 structure) working cross section libraries in FIDO-ANISN format for LWR shielding and pressure vessel dosimetry calculations, named BUGJEFF311.BOLIB and BUGENDF70.BOLIB, were generated by the revised version of SCAMPI, through problem-dependent cross section collapsing and self-shielding from the cited fine-group libraries. The validation results on the criticality safety benchmark experiments for the fine-group libraries and the preliminary validation results for the broad-group working libraries on the PCA-Replica and VENUS-3 engineering neutron shielding benchmark experiments are reported in synthesis.
The Linac Coherent Light Source at SLAC. Radiological Considerations and Shielding calculations
Mao, X.S.; Fasso, A.; Nakao, N.; Rokni, S.H.; Vincke, H.; /SLAC
2005-12-02
The Linac Coherent Light Source (LCLS) at SLAC will be the world's first X-ray free electron laser when it becomes operational in 2009. Pulses of X-ray laser light from LCLS will be many orders of magnitude brighter and several orders of magnitude shorter than what can be produced by other X-ray sources available in the world. These characteristics will enable frontier new science in many areas. This paper describes the LCLS beam parameters and its lay-out. Results of the Monte Carlo calculations for the shielding design of the electron dump line, radiation damage to undulator, the residual radiation and the soil activation around the electron dump are presented.
Calculations of neutron shielding data for 10-100 MeV proton accelerators.
Chen, C C; Sheu, R J; Jian, S H
2005-01-01
The characteristics of neutron sources and their attenuation in concrete were investigated in detail for protons with energies ranging from 10 to 100 MeV striking on target materials of C, N, Al, Fe, Cu and W. A two-step approach was adopted: thick-target double-differential neutron yields were first calculated from the (p, xn) cross sections recommended in the ICRU Report 63; further, transport simulations of those neutrons in concrete were performed by using the FLUKA Monte Carlo code. The purpose of this study is to provide reasonably accurate parameters for shielding design for 10-100 MeV proton accelerators. Source terms and the corresponding attenuation lengths in concrete for several target materials are given as a function of proton energies and neutron emission angles. PMID:16604637
Calculated volumes of individual shield volcanoes at the young end of the Hawaiian Ridge
Robinson, J.E.; Eakins, B.W.
2006-01-01
High-resolution multibeam bathymetry and a digital elevation model of the Hawaiian Islands are used to calculate the volumes of individual shield volcanoes and island complexes (Niihau, Kauai, Oahu, the Maui Nui complex, and Hawaii), taking into account subsidence of the Pacific plate under the load of the Hawaiian Ridge. Our calculated volume for the Island of Hawaii and its submarine extent (213 ?? 103 km3) is nearly twice the previous estimate (113 ?? 103 km3), due primarily to crustal subsidence that had not been accounted for in the earlier work. The volcanoes that make up the Island of Hawaii (Mahukona, Kohala, Mauna Kea, Hualalai, Mauna Loa, Kilauea and Loihi) are generally considered to have been formed within the past million years, and our revised volume for the island indicates that magma supply rates are greater than previously estimated, 0.21 km3/yr as opposed to ???0.1 km3/yr. This result also shows that compared with rates calculated for the Hawaiian Islands (0-6 Ma, 0.095 km3/yr), the Hawaiian Ridge (0-45 Ma, 0.017 km3/yr), and the Emperor Seamounts (45-80 Ma, 0.010 km3/yr), magma supply rates have increased dramatically to build the Island of Hawaii.
Parks, C.V.; Broadhead, B.L.; Hermann, O.W.; Tang, J.S.; Cramer, S.N.; Gauthey, J.C.; Kirk, B.L.; Roussin, R.W.
1988-07-01
This report provides a preliminary assessment of the computational tools and existing methods used to obtain radiation dose rates from shielded spent nuclear fuel and high-level radioactive waste (HLW). Particular emphasis is placed on analysis tools and techniques applicable to facilities/equipment designed for the transport or storage of spent nuclear fuel or HLW. Applications to cask transport, storage, and facility handling are considered. The report reviews the analytic techniques for generating appropriate radiation sources, evaluating the radiation transport through the shield, and calculating the dose at a desired point or surface exterior to the shield. Discrete ordinates, Monte Carlo, and point kernel methods for evaluating radiation transport are reviewed, along with existing codes and data that utilize these methods. A literature survey was employed to select a cadre of codes and data libraries to be reviewed. The selection process was based on specific criteria presented in the report. Separate summaries were written for several codes (or family of codes) that provided information on the method of solution, limitations and advantages, availability, data access, ease of use, and known accuracy. For each data library, the summary covers the source of the data, applicability of these data, and known verification efforts. Finally, the report discusses the overall status of spent fuel shielding analysis techniques and attempts to illustrate areas where inaccuracy and/or uncertainty exist. The report notes the advantages and limitations of several analysis procedures and illustrates the importance of using adequate cross-section data sets. Additional work is recommended to enable final selection/validation of analysis tools that will best meet the US Department of Energy's requirements for use in developing a viable HLW management system. 188 refs., 16 figs., 27 tabs.
Overview of active methods for shielding spacecraft from energetic space radiation
NASA Technical Reports Server (NTRS)
Townsend, L. W.; Wilson, J. W. (Principal Investigator)
2001-01-01
During the 1960's and into the early 1970's, investigations were conducted related to the feasibility of using active radiation shielding methods, such as afforded by electromagnetic fields, as alternatives to passive, bulk material shielding to attenuate space radiations. These active concepts fall into four categories: (1) electrostatic fields; (2) plasma shields; (3) confined magnetic fields; and (4) unconfined magnetic fields. In nearly all of these investigations, consideration was given only to shielding against protons or electrons, or both. During the 1980's and 1990's there were additional studies related to proton shielding and some new studies regarding the efficacy of using active methods to shield from the high energy heavy ion (HZE particle) component of the galactic cosmic ray spectrum. In this overview, each concept category is reviewed and its applicability and limitations for the various types of space radiations are described. Recommendations for future research on this topic are made.
Overview of active methods for shielding spacecraft from energetic space radiation.
Townsend, L W
2001-01-01
During the 1960's and into the early 1970's, investigations were conducted related to the feasibility of using active radiation shielding methods, such as afforded by electromagnetic fields, as alternatives to passive, bulk material shielding to attenuate space radiations. These active concepts fall into four categories: (1) electrostatic fields; (2) plasma shields; (3) confined magnetic fields; and (4) unconfined magnetic fields. In nearly all of these investigations, consideration was given only to shielding against protons or electrons, or both. During the 1980's and 1990's there were additional studies related to proton shielding and some new studies regarding the efficacy of using active methods to shield from the high energy heavy ion (HZE particle) component of the galactic cosmic ray spectrum. In this overview, each concept category is reviewed and its applicability and limitations for the various types of space radiations are described. Recommendations for future research on this topic are made. PMID:11770543
A method for estimating muon production and penetration through a shield
NASA Astrophysics Data System (ADS)
Sullivan, A. H.
1985-09-01
An approximate expression is derived that describes muon production by high-energy protons and the subsequent attenuation of the muons in a shield. It is shown that the muon flux at x ahead of an interaction by a proton of energy ɛ GeV and where pions have a path length of Δ m in which to decay, will be given by: φ=8.5×10 -2{ɛΔ}/{x 2}e-( {αt}/{ɛ}) μ/ m2, where t is the shield thickness in m and α is an effective muon energy loss rate which has a value of 22 GeV/m for iron and 7.8 GeV/m for concrete. It is further shown that the effective muon attenuation mean-free path is equivalent to {1}/{16} of the range of a muon with the energy of the interacting proton. The width of the muon beam that passes through the shield is also considered and it is shown that the beam profile approximates a Gaussian distribution with a diameter at half-maximum intensity of: d= {4.6x}/{ɛαt}m. Calculated muon fluxes are shown to correspond reasonably with those obtained by more sophisticated computer methods for proton energies up to at least 30 GeV and over the entire range of shield thicknesses of interest for radiation safety. Results of measurements of muon levels behind beam dumps under various conditions are presented and are shown to be in reasonable agreement with predictions based on the above model.
NASA Astrophysics Data System (ADS)
Leniak, Arkadiusz; Jaźwiński, Jarosław
2015-03-01
Benchmark calculations of 15N NMR shielding constants for a set of model complexes of rhodium(II) tetraformate with nine organic ligands using the Density Functional Theory (DFT) methods have been carried out. The calculations were performed by means of several methods: the non-relativistic, relativistic scalar ZORA, and spin-orbit ZORA approaches at the CGA-PBE/QZ4P theory level, and the GIAO NMR method using the B3PW91 functional with the 6-311++G(2d,p) basis set for C, H, N, O atoms and the Stuttgart basis set for the Rh atom. The geometry of compounds was optimised either by the same basis set as for the NMR calculations or applying the B3LYP functional with the 6-31G(2d) basis set for C, H, N, O atoms and LANL2DZ for the Rh atom. Computed 15N NMR shielding constants σ were compatible with experimental 15N chemical shifts δ of complexes exhibiting similar structure and fulfil the linear equation δ = aσ + b. The a and b parameters for all data sets have been estimated by means of linear regression analysis. In contrast to the correlation method giving "scaled" chemical shifts, the conversion of shielding constants to chemical shifts with respect to the reference shielding of CH3NO2 provided very inaccurate "raw" δ values. The application of the former to the calculation of complexation shifts Δδ (Δδ = δcompl - δlig) reproduced experimental values qualitatively or semi-quantitatively. The non-relativistic B3PW91/[6-311++G(2d,p), Stuttgart] theory level reproduced the NMR parameters as good as the more expensive relativistic CGA-PBE//QZ4P ZORA approaches.
NASA Astrophysics Data System (ADS)
Infantino, Angelo; Marengo, Mario; Baschetti, Serafina; Cicoria, Gianfranco; Longo Vaschetto, Vittorio; Lucconi, Giulia; Massucci, Piera; Vichi, Sara; Zagni, Federico; Mostacci, Domiziano
2015-11-01
Biomedical cyclotrons for production of Positron Emission Tomography (PET) radionuclides and radiotherapy with hadrons or ions are widely diffused and established in hospitals as well as in industrial facilities and research sites. Guidelines for site planning and installation, as well as for radiation protection assessment, are given in a number of international documents; however, these well-established guides typically offer analytic methods of calculation of both shielding and materials activation, in approximate or idealized geometry set up. The availability of Monte Carlo codes with accurate and up-to-date libraries for transport and interactions of neutrons and charged particles at energies below 250 MeV, together with the continuously increasing power of nowadays computers, makes systematic use of simulations with realistic geometries possible, yielding equipment and site specific evaluation of the source terms, shielding requirements and all quantities relevant to radiation protection. In this work, the well-known Monte Carlo code FLUKA was used to simulate two representative models of cyclotron for PET radionuclides production, including their targetry; and one type of proton therapy cyclotron including the energy selection system. Simulations yield estimates of various quantities of radiological interest, including the effective dose distribution around the equipment, the effective number of neutron produced per incident proton and the activation of target materials, the structure of the cyclotron, the energy degrader, the vault walls and the soil. The model was validated against experimental measurements and comparison with well-established reference data. Neutron ambient dose equivalent H*(10) was measured around a GE PETtrace cyclotron: an average ratio between experimental measurement and simulations of 0.99±0.07 was found. Saturation yield of 18F, produced by the well-known 18O(p,n)18F reaction, was calculated and compared with the IAEA recommended
NASA Astrophysics Data System (ADS)
Munoz-Cobos, J. G.
1981-08-01
A FORTRAN 4 code was developed to calculate cross section probability tables, Bondarenko self-shielding factors, and average self-indication ratios for non-fissile isotopes, below the inelastic threshold, on the basis of prescriptions for the unresolved resonance region. Monte-Carlo methods are utilized to generate ladders of resonance parameters in he unresolved resonance region, from average resonance parameters and their appropriate distribution functions. The neutron cross sections are calculated by the single level Breit-Wigner formalism, with s, p and d-wave contributions. The cross section probability tables are constructed by sampling the Doppler-broadened cross sections. The various self-shielded factors are computed numerically as Lebesgue integrals over the cross section probability tables. The program was validated through extensive comparisons with several deterministic codes.
Monte Carlo Modeling of Computed Tomography Ceiling Scatter for Shielding Calculations.
Edwards, Stephen; Schick, Daniel
2016-04-01
Radiation protection for clinical staff and members of the public is of paramount importance, particularly in occupied areas adjacent to computed tomography scanner suites. Increased patient workloads and the adoption of multi-slice scanning systems may make unshielded secondary scatter from ceiling surfaces a significant contributor to dose. The present paper expands upon an existing analytical model for calculating ceiling scatter accounting for variable room geometries and provides calibration data for a range of clinical beam qualities. The practical effect of gantry, false ceiling, and wall attenuation in limiting ceiling scatter is also explored and incorporated into the model. Monte Carlo simulations were used to calibrate the model for scatter from both concrete and lead surfaces. Gantry attenuation experimental data showed an effective blocking of scatter directed toward the ceiling at angles up to 20-30° from the vertical for the scanners examined. The contribution of ceiling scatter from computed tomography operation to the effective dose of individuals in areas surrounding the scanner suite could be significant and therefore should be considered in shielding design according to the proposed analytical model. PMID:26910026
Truflandier, L; Paris, M; Payen, C; Boucher, F
2006-11-01
We present the first density functional theory based calculations of NMR shielding parameters for a transition metal nucleus using periodic boundary conditions. These calculations employ the gauge-including projected augmented-wave pseudopotential approach. The quality of this method is discussed by comparing experimental and calculated chemical shift tensor eigenvalues for the quadrupolar 51V nucleus in the diamagnetic solid-state compound AlVO4. Furthermore, the combination of shielding tensor with fast and accurate projector augmented-wave electric field gradient tensor calculations allows us to determine the relative orientation of these two tensors. PMID:17064085
NASA Astrophysics Data System (ADS)
Arcisauskaite, Vaida; Melo, Juan I.; Hemmingsen, Lars; Sauer, Stephan P. A.
2011-07-01
We investigate the importance of relativistic effects on NMR shielding constants and chemical shifts of linear HgL2 (L = Cl, Br, I, CH3) compounds using three different relativistic methods: the fully relativistic four-component approach and the two-component approximations, linear response elimination of small component (LR-ESC) and zeroth-order regular approximation (ZORA). LR-ESC reproduces successfully the four-component results for the C shielding constant in Hg(CH3)2 within 6 ppm, but fails to reproduce the Hg shielding constants and chemical shifts. The latter is mainly due to an underestimation of the change in spin-orbit contribution. Even though ZORA underestimates the absolute Hg NMR shielding constants by ˜2100 ppm, the differences between Hg chemical shift values obtained using ZORA and the four-component approach without spin-density contribution to the exchange-correlation (XC) kernel are less than 60 ppm for all compounds using three different functionals, BP86, B3LYP, and PBE0. However, larger deviations (up to 366 ppm) occur for Hg chemical shifts in HgBr2 and HgI2 when ZORA results are compared with four-component calculations with non-collinear spin-density contribution to the XC kernel. For the ZORA calculations it is necessary to use large basis sets (QZ4P) and the TZ2P basis set may give errors of ˜500 ppm for the Hg chemical shifts, despite deceivingly good agreement with experimental data. A Gaussian nucleus model for the Coulomb potential reduces the Hg shielding constants by ˜100-500 ppm and the Hg chemical shifts by 1-143 ppm compared to the point nucleus model depending on the atomic number Z of the coordinating atom and the level of theory. The effect on the shielding constants of the lighter nuclei (C, Cl, Br, I) is, however, negligible.
Arcisauskaite, Vaida; Melo, Juan I; Hemmingsen, Lars; Sauer, Stephan P A
2011-07-28
We investigate the importance of relativistic effects on NMR shielding constants and chemical shifts of linear HgL(2) (L = Cl, Br, I, CH(3)) compounds using three different relativistic methods: the fully relativistic four-component approach and the two-component approximations, linear response elimination of small component (LR-ESC) and zeroth-order regular approximation (ZORA). LR-ESC reproduces successfully the four-component results for the C shielding constant in Hg(CH(3))(2) within 6 ppm, but fails to reproduce the Hg shielding constants and chemical shifts. The latter is mainly due to an underestimation of the change in spin-orbit contribution. Even though ZORA underestimates the absolute Hg NMR shielding constants by ∼2100 ppm, the differences between Hg chemical shift values obtained using ZORA and the four-component approach without spin-density contribution to the exchange-correlation (XC) kernel are less than 60 ppm for all compounds using three different functionals, BP86, B3LYP, and PBE0. However, larger deviations (up to 366 ppm) occur for Hg chemical shifts in HgBr(2) and HgI(2) when ZORA results are compared with four-component calculations with non-collinear spin-density contribution to the XC kernel. For the ZORA calculations it is necessary to use large basis sets (QZ4P) and the TZ2P basis set may give errors of ∼500 ppm for the Hg chemical shifts, despite deceivingly good agreement with experimental data. A Gaussian nucleus model for the Coulomb potential reduces the Hg shielding constants by ∼100-500 ppm and the Hg chemical shifts by 1-143 ppm compared to the point nucleus model depending on the atomic number Z of the coordinating atom and the level of theory. The effect on the shielding constants of the lighter nuclei (C, Cl, Br, I) is, however, negligible. PMID:21806118
NASA Technical Reports Server (NTRS)
Bannister, Tommy; Karr, Gerald R.
1987-01-01
Progress on the modeling of the flow field around a wake shield using a recently obtained code based on the Monte Carlo method is discussed. The direct simulation Monte Carlo method is a method for solving the Boltzman Equation using an approximation to the collision integral term. The collision integrand is evaluated for randomly selected values of its arguments and the summation will approach the integral for large enough samples. The collision effects may be modeled for either hard sphere or various power law potentials. The convective side of the Boltzman equation is approximated over a time step using a simple trajectory calculation of molecules as they travel through the domain of interest.
Calculation of self-shielding factor for neutron activation experiments using GEANT4 and MCNP
NASA Astrophysics Data System (ADS)
Romero-Barrientos, Jaime; Molina, F.; Aguilera, Pablo; Arellano, H. F.
2016-07-01
The neutron self-shielding factor G as a function of the neutron energy was obtained for 14 pure metallic samples in 1000 isolethargic energy bins from 1.10-5eV to 2.107eV using Monte Carlo simulations in GEANT4 and MCNP6. The comparison of these two Monte Carlo codes shows small differences in the final self-shielding factor mostly due to the different cross section databases that each program uses.
Kartashov, D A; Shurshakov, V A
2012-01-01
The article presents a new procedure of calculating the shielding functions for irregular objects formed from a set of nonintersecting (adjacent) triangles covering completely the surface of each object. Calculated and experimentally derived distributions of space ionizing radiation doses in the spherical tissue-equivalent phantom (experiment MATRYOSHKA-R) inside the International space station were in good agreement in the mass of phantom depths with allowance for measurement error (-10%). The procedure can be applied in modeling radiation loads on cosmonauts, calculating effectiveness of secondary protection in spacecraft, and design review of radiation protection for future space exploration missions. PMID:23457971
Early Test Facilities and Analytic Methods for Radiation Shielding
Ingersoll, D.T.
1992-01-01
This report represents a compilation of eight papers presented at the 1992 American Nuclear Society/European Nuclear Society International Meeting held in Chicago, Illinois on November 15 20,1992. The meeting is of special significance since it commemorates the 50th anniversary of the first controlled nuclear chain reaction, which occurred, not coincidentally, in Chicago. The papers contained in this report were presented in a special session organized by the Radiation Protection and Shielding Division in keeping with the historical theme of the meeting.
Method for calculating alloy energetics
NASA Technical Reports Server (NTRS)
Bozzolo, Guillermo; Ferrante, John; Smith, John R.
1992-01-01
A semiempirical method for the computation of alloy energies is introduced. It is based on the equivalent-crystal theory of defect-formation energies in elemental solids. The method is both simple and accurate. Heats of formation as a function of composition are computed for some binary alloys of Cu, Ni, Al, Ag, Pd, Pt, and Au using the heats of solution in the dilute limit as experimental input. The separation of heats into strain and chemical components helps in understanding the energetics. In addition, lattice-parameter contractions seen in solid solutions of Ag and Au are accurately predicted. Good agreement with experiment is obtained in all cases.
Method for fabricating fan-fold shielded electrical leads
Rohatgi, Rajeev R.; Cowan, Thomas E.
1994-01-01
Fan-folded electrical leads made from copper cladded Kapton, for example, with the copper cladding on one side serving as a ground plane and the copper cladding on the other side being etched to form the leads. The Kapton is fan folded with the leads located at the bottom of the fan-folds. Electrical connections are made by partially opening the folds of the fan and soldering, for example, the connections directly to the ground plane and/or the lead. The fan folded arrangement produces a number of advantages, such as electrically shielding the leads from the environment, is totally non-magnetic, and has a very low thermal conductivity, while being easy to fabricate.
Method of shielding a liquid-metal-cooled reactor
Sayre, Robert K.
1978-01-01
The primary heat transport system of a nuclear reactor -- particularly for a liquid-metal-cooled fast-breeder reactor -- is shielded and protected from leakage by establishing and maintaining a bed of a powdered oxide closely and completely surrounding all components thereof by passing a gas upwardly therethrough at such a rate as to slightly expand the bed to the extent that the components of the system are able to expand without damage and yet the particles of the bed remain close enough so that the bed acts as a guard vessel for the system. Preferably the gas contains 1 to 10% oxygen and the gas is passed upwardly through the bed at such a rate that the lower portion of the bed is a fixed bed while the upper portion is a fluidized bed, the line of demarcation therebetween being high enough that the fixed bed portion of the bed serves as guard vessel for the system.
2001-10-01
Version 01 GUI2QAD is an aid in preparation of input for the included QAD-CGPIC program, which is based on CCC-493/QAD-CGGP and PICTURE. QAD-CGPIC is a Fortran code for fast neutron and gamma-ray shielding calculations through various shield configurations defined by combinatorial geometry specifications. Provision is available to interactively input the geometry and view the same in three dimensions with arbitrary rotations along x,y,z axis. The salient features of the present package include: a) Handles offmore » centered multiple identical sources b) Axis of cylindrical sources can be parallel to any of the axes. c) Provides plots of buildup factors (ANSI-1990) and material cross sections d) Estimates dose rate for point source-slab shield situations e) Interactive input of CG geometry with 3D view and rotation f) Fission product decay power computation and plots for source term calculations. g) Provision to read and graphical 1y display picture input file.« less
NASA Astrophysics Data System (ADS)
Buck, Henk
In an effort to overcome a significant difference between high-level ab initio calculations and X-ray data of DNA duplexes, Fonseca Guerra et al. 9-11 studied a number of model systems for A-T and G-C basepairs at various levels of nonlocal Density Functional Theory. There was an excellent agreement with the gas-phase experimental bond enthalpies for the A-T and G-C basepairs. On the other hand the hydrogen bond lengths between the bases differ from the X-ray results. After introduction of a molecular environment as local water and Na+ ions, the agreement between theory and experiment was excellent. However, careful analysis shows that this picture is far from correct. In fact, the model was constructed as a backbone-modified DNA duplex in which the nonbonding oxygens of the phosphate linkages are completely shielded by proton addition. Experimental results with respect to backbone-modified DNAs clearly show that changes in the backbone focused on phosphate shielding result in DNA duplexes with a variety in conformational behavior. In addition to an analysis of the aforementioned contradiction, we also give molecular mechanics calculations which show that the A-T and G-C bond enthalpies are of the same order as the corresponding results of Fonseca Guerra et al. under the condition of complete anionic shielding of the nonbonded oxygens in the phosphate linkages.
NASA Technical Reports Server (NTRS)
Brendley, K.; Chato, J. C.
1982-01-01
The parameters of the efflux from a helium dewar in space were numerically calculated. The flow was modeled as a one dimensional compressible ideal gas with variable properties. The primary boundary conditions are flow with friction and flow with heat transfer and friction. Two PASCAL programs were developed to calculate the efflux parameters: EFFLUZD and EFFLUXM. EFFLUXD calculates the minimum mass flow for the given shield temperatures and shield heat inputs. It then calculates the pipe lengths, diameter, and fluid parameters which satisfy all boundary conditions. Since the diameter returned by EFFLUXD is only rarely of nominal size, EFFLUXM calculates the mass flow and shield heat exchange for given pipe lengths, diameter, and shield temperatures.
Dose estimation and shielding calculation for X-ray hazard at high intensity laser facilities
NASA Astrophysics Data System (ADS)
Qiu, Rui; Zhang, Hui; Yang, Bo; James, C. Liu; Sayed, H. Rokni; Michael, B. Woods; Li, Jun-Li
2014-12-01
An ionizing radiation hazard produced from the interaction between high intensity lasers and solid targets has been observed. Laser-plasma interactions create “hot” electrons, which generate bremsstrahlung X-rays when they interact with ions in the target. However, up to now only limited studies have been conducted on this laser-induced radiological protection issue. In this paper, the physical process and characteristics of the interaction between high intensity lasers and solid targets are analyzed. The parameters of the radiation sources are discussed, including the energy conversion efficiency from laser to hot electrons, hot electron energy spectrum and electron temperature, and the bremsstrahlung X-ray energy spectrum produced by hot electrons. Based on this information, the X-ray dose generated with high-Z targets for laser intensities between 1014 and 1020 W/cm2 is estimated. The shielding effects of common shielding items such as the glass view port, aluminum chamber wall and concrete wall are also studied using the FLUKA Monte Carlo code. This study provides a reference for the dose estimation and the shielding design of high intensity laser facilities.
Nakanishi, Noriyoshi; Shikata, Takashi; Fujita, Shin; Kosako, Toshiso
1995-10-01
Shielding characteristics of iron, lead, ordinary concrete, heavy concrete, graphite, marble, water, and paraffin were calculated for monoenergetic source neutrons with energies < 400 MeV. The depth dependence of neutron and secondary photon transmitted dose equivalents at the exit surfaces of shields of varying thickness is exhibited for some monoenergetic source neutrons and for each material. Their shielding characteristics are compared and discussed in terms of the degradation process of neutron energy and the change of neutron spectrum in typical shielding materials. Calculations were carried out by using the one-dimensional discrete ordinates code ANISN-JR and the cross-section library DLC-87/HILO. Systematic knowledge concerning the shielding of neutrons with energies < 400 MeV was successfully obtained.
An improved method for correction of air temperature measured using different radiation shields
NASA Astrophysics Data System (ADS)
Cheng, Xinghong; Su, Debin; Li, Deping; Chen, Lu; Xu, Wenjing; Yang, Meilin; Li, Yongcheng; Yue, Zhizhong; Wang, Zijing
2014-11-01
The variation of air temperature measurement errors using two different radiation shields (DTR502B Vaisala, Finland, and HYTFZ01, Huayun Tongda Satcom, China) was studied. Datasets were collected in the field at the Daxing weather station in Beijing from June 2011 to May 2012. Most air temperature values obtained with these two commonly used radiation shields were lower than the reference records obtained with the new Fiber Reinforced Polymers (FRP) Stevenson screen. In most cases, the air temperature errors when using the two devices were smaller on overcast and rainy days than on sunny days; and smaller when using the imported rather than the Chinese shield. The measured errors changed sharply at sunrise and sunset, and reached maxima at noon. Their diurnal variation characteristics were, naturally, related to changes in solar radiation. The relationships between the record errors, global radiation, and wind speed were nonlinear. An improved correction method was proposed based on the approach described by Nakamura and Mahrt (2005) (NM05), in which the impact of the solar zenith angle (SZA) on the temperature error is considered and extreme errors due to changes in SZA can be corrected effectively. Measurement errors were reduced significantly after correction by either method for both shields. The error reduction rate using the improved correction method for the Chinese and imported shields were 3.3% and 40.4% higher than those using the NM05 method, respectively.
Assessment of seismic margin calculation methods
Kennedy, R.P.; Murray, R.C.; Ravindra, M.K.; Reed, J.W.; Stevenson, J.D.
1989-03-01
Seismic margin review of nuclear power plants requires that the High Confidence of Low Probability of Failure (HCLPF) capacity be calculated for certain components. The candidate methods for calculating the HCLPF capacity as recommended by the Expert Panel on Quantification of Seismic Margins are the Conservative Deterministic Failure Margin (CDFM) method and the Fragility Analysis (FA) method. The present study evaluated these two methods using some representative components in order to provide further guidance in conducting seismic margin reviews. It is concluded that either of the two methods could be used for calculating HCLPF capacities. 21 refs., 9 figs., 6 tabs.
NASA Astrophysics Data System (ADS)
Farshid, Tabbakh; Azim, Ahmadinyar
2008-11-01
In this paper we study the analytical and statistical results of estimating the gamma dose rate at pool access floor in TRR when the core shield accidentally decreases to some non-permitted levels. Due to the risk of experimental techniques, we use the analytical and statistical methods. In normal conditions (no risk), the discrepancies between experiment and two methods are justified and it is found that for such problems we have to normalize these methods to experimental results as follows: the analytical method by factor 0.13 and MCNP by 1.7.
Jabbari, Keyvan; Roayaei, Mahnaz; Saberi, Hosein
2012-07-01
For superficial lesions, the electrons may be used for radiation therapy. The high energy photons and electrons are produced by a Linear accelerator (Linac). Many of electron fields need the shielding of normal or critical organs. The electron shields are usually lead slabs with few millimeter thicknesses which should be placed near the skin, less than 1 cm away from skin. In the inspection of patients setting in a clinic by a physicist, it was noted that in some cases the technician places the shields far away from skin in the way that the shadow of the field still matches the shielded area. This is due to a conceptual mistake in which one assumes that electrons travel in a straight line and matching the shadow of lead slab is enough for the shielding. This project is about Monte Carlo simulation of this case and dosimetry in which the excess dose to the tissue under the shield is calculated. In this study, BEAMnrc and DOSXYZnrc are used for simulation of the Linac and the electron shields. The water phantom as well as the Linac head (NEPTON Linac) is simulated in the electron mode. The simulation is performed in three various cases in which the lead shield is placed in distances of 1, 20, 40 cm from the surface of the phantom. In all cases, the edge of the shield is matched with the light field, so the shields get smaller as they move from the surface because of the divergence of the light field. The simulations were done in two energies, 6 and 13 MeV. The experiments also were done with EDR2 film dosimetry and the simulation results were validated using the experimental results. In all cases, the dose under the shield was normalized to the dose in the center. The dose of the normal organ under the shield was 2, 38, 43% with respect to the center for shield distances of 1, 20, 40 cm, respectively. So there is a considerable increasing of the dose due to the distanced shielding. In this work exact amount of the dose from this mistake (distanced shielding) is
Jabbari, Keyvan; Roayaei, Mahnaz; Saberi, Hosein
2012-01-01
For superficial lesions, the electrons may be used for radiation therapy. The high energy photons and electrons are produced by a Linear accelerator (Linac). Many of electron fields need the shielding of normal or critical organs. The electron shields are usually lead slabs with few millimeter thicknesses which should be placed near the skin, less than 1 cm away from skin. In the inspection of patients setting in a clinic by a physicist, it was noted that in some cases the technician places the shields far away from skin in the way that the shadow of the field still matches the shielded area. This is due to a conceptual mistake in which one assumes that electrons travel in a straight line and matching the shadow of lead slab is enough for the shielding. This project is about Monte Carlo simulation of this case and dosimetry in which the excess dose to the tissue under the shield is calculated. In this study, BEAMnrc and DOSXYZnrc are used for simulation of the Linac and the electron shields. The water phantom as well as the Linac head (NEPTON Linac) is simulated in the electron mode. The simulation is performed in three various cases in which the lead shield is placed in distances of 1, 20, 40 cm from the surface of the phantom. In all cases, the edge of the shield is matched with the light field, so the shields get smaller as they move from the surface because of the divergence of the light field. The simulations were done in two energies, 6 and 13 MeV. The experiments also were done with EDR2 film dosimetry and the simulation results were validated using the experimental results. In all cases, the dose under the shield was normalized to the dose in the center. The dose of the normal organ under the shield was 2, 38, 43% with respect to the center for shield distances of 1, 20, 40 cm, respectively. So there is a considerable increasing of the dose due to the distanced shielding. In this work exact amount of the dose from this mistake (distanced shielding) is
A new method of normal mode calculation
NASA Astrophysics Data System (ADS)
Kobayashi, N.
2004-12-01
Numerical method of calculating normal modes of the Earth is classical problem in seismology and many methods have been developed, e.g. MINEOS, OBANI (Woodhouse 1989) and DISPER80 (Saito 1989). These methods are based on direct numerical integration of the governing differential equations (Runge-Kutta method). The methods are efficient for search for (real) eigenvalues of non dissipative cases but have some trouble to seek complex eigenvalues of dissipative or leaky oscillations. On the other hand, in solar seismology, the Henyey type relaxation method is used to calculate acoustic and gravity modes of the sun and stars (e.g. Unno et al. 1989). The latter method is generally more stable for eigenvalue problems of a self-gravitating gaseous body where the density and pressure vary exponentially near its surface. The efficiency of the method is, however, depends on initial guess of eigenvalues and eigenfunctions. Here we propose a new method to overcome the deficiency of the above methods. This method is formulated with the aid of the concept of the Henyey type relaxation method but does not needs initial guess of eigenfuctions and solves the problem more directly like the Runge-Hutta method. Some mumerical tests show good convergence of complex eigenvalues in our method. So the proposed method is effective to calculate solid modes, acoustic and gravity modes and ocean modes interfered with the other parts of the earth and planets.
Johnson, William C.; Shokair, Isaac R.
2011-12-01
Conventional full spectrum gamma spectroscopic analysis has the objective of quantitative identification of all the radionuclides present in a measurement. For low-energy resolution detectors such as NaI, when photopeaks alone are not sufficient for complete isotopic identification, such analysis requires template spectra for all the radionuclides present in the measurement. When many radionuclides are present it is difficult to make the correct identification and this process often requires many attempts to obtain a statistically valid solution by highly skilled spectroscopists. A previous report investigated using the targeted principal component analysis method (TPCA) for detection of embedded sources for RPM applications. This method uses spatial/temporal information from multiple spectral measurements to test the hypothesis of the presence of a target spectrum of interest in these measurements without the need to identify all the other radionuclides present. The previous analysis showed that the TPCA method has significant potential for automated detection of target radionuclides of interest, but did not include the effects of shielding. This report complements the previous analysis by including the effects of spectral distortion due to shielding effects for the same problem of detection of embedded sources. Two examples, one with one target radionuclide and the other with two, show that the TPCA method can successfully detect shielded targets in the presence of many other radionuclides. The shielding parameters are determined as part of the optimization process using interpolation of library spectra that are defined on a 2D grid of atomic numbers and areal densities.
NASA Astrophysics Data System (ADS)
Srinivasan, P.; Priya, S.; Patel, Tarun; Gopalakrishnan, R. K.; Sharma, D. N.
2015-01-01
DD/DT fusion neutron generators are used as sources of 2.5 MeV/14.1 MeV neutrons in experimental laboratories for various applications. Detailed knowledge of the radiation dose rates around the neutron generators are essential for ensuring radiological protection of the personnel involved with the operation. This work describes the experimental and Monte Carlo studies carried out in the Purnima Neutron Generator facility of the Bhabha Atomic Research Center (BARC), Mumbai. Verification and validation of the shielding adequacy was carried out by measuring the neutron and gamma dose-rates at various locations inside and outside the neutron generator hall during different operational conditions both for 2.5-MeV and 14.1-MeV neutrons and comparing with theoretical simulations. The calculated and experimental dose rates were found to agree with a maximum deviation of 20% at certain locations. This study has served in benchmarking the Monte Carlo simulation methods adopted for shield design of such facilities. This has also helped in augmenting the existing shield thickness to reduce the neutron and associated gamma dose rates for radiological protection of personnel during operation of the generators at higher source neutron yields up to 1 × 1010 n/s.
NASA Astrophysics Data System (ADS)
Maeda, H.; Ootani, Y.; Fukui, H.
2007-05-01
A previous relativistic shielding calculation theory based on the regular approximation to the normalized elimination of the small component approach is improved by the inclusion of the magnetic interaction term contained in the metric operator. In order to consider effects of the metric perturbation, the self-consistent perturbation theory is used for the case of perturbation-dependent overlap integrals. The calculation results show that the second-order regular approximation results obtained for the isotropic shielding constants of halogen nuclei are well improved by the inclusion of the metric perturbation to reproduce the fully relativistic four-component Dirac-Hartree-Fock results. However, it is shown that the metric perturbation hardly or does not affect the anisotropy of the halogen shielding tensors and the proton magnetic shieldings.
Drag calculations of wings using Euler methods
NASA Technical Reports Server (NTRS)
Van Dam, C. P.; Chang, I. C.; Vijgen, P. M. H. W.; Nikfetrat, Koorosh
1991-01-01
Several techniques for the calculation of drag using Euler-equation formulations are discussed and compared. Surface-pressure integration (a nearfield technique) as well as two different farfield calculation techniques are described and applied to three-dimensional flow-field solutions for an aspect-ratio-7 wing with attached flow. The present calculations are limited to steady, low-Mach-number flows around three-dimensional configurations in the absence of active systems such as surface blowing/suction and propulsion. Although the main focus of the paper is the calculation of aerodynamic drag, the calculation of aerodynamic lift is also briefly discussed. Three Euler methods are used to obtain the flowfield solutions. The farfield technique based on the evaluation of a wake-integral appears to provide the most consistent and accurate drag predictions.
NASA Astrophysics Data System (ADS)
Marius Mudd, Simon; Harel, Marie-Alice; Hurst, Martin D.; Grieve, Stuart W. D.; Marrero, Shasta M.
2016-08-01
We report a new program for calculating catchment-averaged denudation rates from cosmogenic nuclide concentrations. The method (Catchment-Averaged denudatIon Rates from cosmogenic Nuclides: CAIRN) bundles previously reported production scaling and topographic shielding algorithms. In addition, it calculates production and shielding on a pixel-by-pixel basis. We explore the effect of sampling frequency across both azimuth (Δθ) and altitude (Δϕ) angles for topographic shielding and show that in high relief terrain a relatively high sampling frequency is required, with a good balance achieved between accuracy and computational expense at Δθ = 8° and Δϕ = 5°. CAIRN includes both internal and external uncertainty analysis, and is packaged in freely available software in order to facilitate easily reproducible denudation rate estimates. CAIRN calculates denudation rates but also automates catchment averaging of shielding and production, and thus can be used to provide reproducible input parameters for the CRONUS family of online calculators.
Calculation methods for compressible turbulent boundary layers
NASA Technical Reports Server (NTRS)
Bushnell, D. M.; Cary, A. M., Jr.; Harris, J. E.
1976-01-01
Calculation procedures for non-reacting compressible two- and three-dimensional turbulent boundary layers were reviewed. Integral, transformation and correlation methods, as well as finite difference solutions of the complete boundary layer equations summarized. Alternative numerical solution procedures were examined, and both mean field and mean turbulence field closure models were considered. Physics and related calculation problems peculiar to compressible turbulent boundary layers are described. A catalog of available solution procedures of the finite difference, finite element, and method of weighted residuals genre is included. Influence of compressibility, low Reynolds number, wall blowing, and pressure gradient upon mean field closure constants are reported.
Fractional tiers in fast multipole method calculations
NASA Astrophysics Data System (ADS)
White, Christopher A.; Head-Gordon, Martin
1996-08-01
One defining characteristic of the fast multipole calculation is the number of tiers (depth of tree) used to group the particles. For three dimensions, the standard boxing scheme restricts the number of lowest level boxes to be a power of eight. We present a method which through a simple scaling of the particle coordinates allows an arbitrary number of lowest level boxes. Consequently, one can better balance the near-field and far-field work by minimizing the variation in the number of particles per lowest level box from its optimal value. Test calculations show systems where this method gives a speedup approaching two times.
NASA Technical Reports Server (NTRS)
Townsend, Lawrence W.; Wilson, John W.
1986-01-01
An energy-dependent, perturbation expansion solution for heavy ion transport in one dimension is used to perform depth-dose calculations for 670/MeV nucleon Ne-20 beams incident upon a thick water target. Comparisons of predictions obtained by using typical energy-independent approximations and those obtained with fully energy-dependent input parameters are made. It is found that the calculated doses are underestimated when the energy-independent input approximations are used. The major source of error, however, is the lack of charge and mass conservation in the Silberberg-Tsao fragmentation parameters.
Pressure Profile Calculation with Mesh Ewald Methods.
Sega, Marcello; Fábián, Balázs; Jedlovszky, Pál
2016-09-13
The importance of calculating pressure profiles across liquid interfaces is increasingly gaining recognition, and efficient methods for the calculation of long-range contributions are fundamental in addressing systems with a large number of charges. Here, we show how to compute the local pressure contribution for mesh-based Ewald methods, retaining the typical N log N scaling as a function of the lattice nodes N. This is a considerable improvement on existing methods, which include approximating the electrostatic contribution using a large cutoff and the, much slower, Ewald calculation. As an application, we calculate the contribution to the pressure profile across the water/vapor interface, coming from different molecular layers, both including and removing the effect of thermal capillary waves. We compare the total pressure profile with the one obtained using the cutoff approximation for the calculation of the stresses, showing that the stress distributions obtained using the Harasima and Irving-Kirkwood path are quite similar and shifted with respect to each other at most 0.05 nm. PMID:27508458
Simplified methods for calculating photodissociation rates
NASA Technical Reports Server (NTRS)
Shimazaki, T.; Ogawa, T.; Farrell, B. C.
1977-01-01
Simplified methods for calculating the transmission of solar UV radiation and the dissociation coefficients of various molecules are compared. A significant difference sometimes appears in calculations of the individual band, but the total transmission and the total dissociation coefficients integrated over the entire SR (solar radiation) band region agree well between the methods. The ambiguities in the solar flux data affect the calculated dissociation coefficients more strongly than does the method. A simpler method is developed for the purpose of reducing the computation time and computer memory size necessary for storing coefficients of the equations. The new method can reduce the computation time by a factor of more than 3 and the memory size by a factor of more than 50 compared with the Hudson-Mahle method, and yet the result agrees within 10 percent (in most cases much less) with the original Hudson-Mahle results, except for H2O and CO2. A revised method is necessary for these two molecules, whose absorption cross sections change very rapidly over the SR band spectral range.
NASA Astrophysics Data System (ADS)
Harris, Chad T.; Haw, Dustin W.; Handler, William B.; Chronik, Blaine A.
2013-09-01
Eddy currents are generated in MR by the use of rapidly switched electromagnets, resulting in time varying and spatially varying magnetic fields that must be either minimized or corrected. This problem is further complicated when non-cylindrical insert magnets are used for specialized applications. Interruption of the coupling between an insert coil and the MR system is typically accomplished using active magnetic shielding. A new method of actively shielding insert gradient and shim coils of any surface geometry by use of the boundary element method for coil design with a minimum energy constraint is presented. This method was applied to shield x- and z-gradient coils for two separate cases: a traditional cylindrical primary gradient with cylindrical shield and, to demonstrate its versatility in surface geometry, the same cylindrical primary gradients with a rectangular box-shaped shield. For the cylindrical case this method produced shields that agreed with analytic solutions. For the second case, the rectangular box-shaped shields demonstrated very good shielding characteristics despite having a different geometry than the primary coils.
A New Iterative Method to Calculate [pi
ERIC Educational Resources Information Center
Dion, Peter; Ho, Anthony
2012-01-01
For at least 2000 years people have been trying to calculate the value of [pi], the ratio of the circumference to the diameter of a circle. People know that [pi] is an irrational number; its decimal representation goes on forever. Early methods were geometric, involving the use of inscribed and circumscribed polygons of a circle. However, real…
Efficient pseudospectral methods for density functional calculations
Murphy, R. B.; Cao, Y.; Beachy, M. D.; Ringnalda, M. N.; Friesner, R. A.
2000-06-15
Novel improvements of the pseudospectral method for assembling the Coulomb operator are discussed. These improvements consist of a fast atom centered multipole method and a variation of the Head-Gordan J-engine analytic integral evaluation. The details of the methodology are discussed and performance evaluations presented for larger molecules within the context of DFT energy and gradient calculations. (c) 2000 American Institute of Physics.
Neutron and photon shielding benchmark calculations by MCNP on the LR-0 experimental facility.
Hordósy, G
2005-01-01
In the framework of the REDOS project, the space-energy distribution of the neutron and photon flux has been calculated over the pressure vessel simulator thickness of the LR-0 experimental reactor, Rez, Czech Republic. The results calculated by the Monte Carlo code MCNP4C are compared with the measurements performed in the Nuclear Research Institute, Rez. The spectra have been measured at the barrel, in front of, inside and behind the pressure vessel in different configurations. The neutron measurements were performed in the energy range 0.1-10 MeV. This work has been done in the frame of the 5th Frame Work Programme of the European Community 1998-2002. PMID:16604591
The calculation of neutron capture gamma-ray yields for space shielding applications
NASA Technical Reports Server (NTRS)
Yost, K. J.
1972-01-01
The application of nuclear models to the calculation of neutron capture and inelastic scattering gamma yields is discussed. The gamma ray cascade model describes the cascade process in terms of parameters which either: (1) embody statistical assumptions regarding electric and magnetic multipole transition strengths, level densities, and spin and parity distributions or (2) are fixed by experiment such as measured energies, spin and parity values, and transition probabilities for low lying states.
NASA Astrophysics Data System (ADS)
Teale, Andrew M.; Lutnæs, Ola B.; Helgaker, Trygve; Tozer, David J.; Gauss, Jürgen
2013-01-01
Accurate sets of benchmark nuclear-magnetic-resonance shielding constants and spin-rotation constants are calculated using coupled-cluster singles-doubles (CCSD) theory and coupled-cluster singles-doubles-perturbative-triples [CCSD(T)] theory, in a variety of basis sets consisting of (rotational) London atomic orbitals. The accuracy of the calculated coupled-cluster constants is established by a careful comparison with experimental data, taking into account zero-point vibrational corrections. Coupled-cluster basis-set convergence is analyzed and extrapolation techniques are employed to estimate basis-set-limit quantities, thereby establishing an accurate benchmark data set. Together with the set provided for rotational g-tensors and magnetizabilities in our previous work [O. B. Lutnæs, A. M. Teale, T. Helgaker, D. J. Tozer, K. Ruud, and J. Gauss, J. Chem. Phys. 131, 144104 (2009)], 10.1063/1.3242081, it provides a substantial source of consistently calculated high-accuracy data on second-order magnetic response properties. The utility of this benchmark data set is demonstrated by examining a wide variety of Kohn-Sham exchange-correlation functionals for the calculation of these properties. None of the existing approximate functionals provide an accuracy competitive with that provided by CCSD or CCSD(T) theory. The need for a careful consideration of vibrational effects is clearly illustrated. Finally, the pure coupled-cluster results are compared with the results of Kohn-Sham calculations constrained to give the same electronic density. Routes to future improvements are discussed in light of this comparison.
A new method to calculate normal modes
NASA Astrophysics Data System (ADS)
Kobayashi, Naoki
2007-01-01
We developed a new method to calculate normal modes of the Earth and planets. It can treat anelasticity directly as imaginary parts of elastic constants and leaky modes due to the open boundary condition set at the upper atmosphere. The eigenvalue problem is described in complex numbers. It is formulated based on a similar treatment of the global matrix governing the system of oscillations to that in the Henyey-type relaxation method used in solar seismology. In our method, the complex eigenvalue problem of a large system is reduced to an eigenvalue problem of a quite small size matrix. The eigenvalue of the small problem is a correction of an assumed complex eigenfrequency and components of the eigenvector are values of eigenfunctions at the outer boundary. Starting from an arbitrary complex frequency around the eigenfrequency of a target mode, we can arrive there within, at most, a dozen of steps of iterative calculations. We compared the results of our method with those calculated by DISPER80, and found good agreement between them. The rate of convergence of the method depends on the linearity of the correction around the eigenfrequency. A numerical example shows good behaviour of them. Even for a model with an atmosphere in which the fundamental spheroidal mode 0S29 and the fundamental acoustic mode 0P29 nearly degenerate, we can easily reach the eigenfrequency of 0S29 and distinguish it from that of 0P29 without any confusion. And we found that the eigenfrequency of 0P29 calculated for a realistic atmospheric model which varies annually, most approaches the solid mode in August. The behaviour of 0P29 can be interpreted with the aid of an acoustic potential which characterizes vertical propagation of sound waves. In addition to the efficiency in the convergence to the eigenfrequencies, numerical tests show strong numerical stability of the method. It stems from the stability in the relaxation method because of the similarity in algebraic structure. For those
Linear Transformation Method for Multinuclide Decay Calculation
Ding Yuan
2010-12-29
A linear transformation method for generic multinuclide decay calculations is presented together with its properties and implications. The method takes advantage of the linear form of the decay solution N(t) = F(t)N{sub 0}, where N(t) is a column vector that represents the numbers of atoms of the radioactive nuclides in the decay chain, N{sub 0} is the initial value vector of N(t), and F(t) is a lower triangular matrix whose time-dependent elements are independent of the initial values of the system.
Rokni, S.H.; Khater, H.; Liu, J.C.; Mao, S.; Vincke, H.; /SLAC
2006-01-03
The FLUKA Monte Carlo particle generation and transport code was used to calculate shielding requirements for the 3 GeV, 500 mA SPEAR3 storage ring at the Stanford Synchrotron Radiation Laboratory. The photon and neutron dose equivalent source term data were simulated for a 3 GeV electron beam interacting with two typical target/shielding geometries in the ring. The targets simulated are a rectangular block of 0.7 cm thick copper and a 5 cm thick iron block, both tilted at 1{sup o} relative to the beam direction. Attenuation profiles for neutrons and photons in concrete and lead as a function of angle at different shield thicknesses were calculated. The first, second and equilibrium attenuation lengths of photons and neutrons in the shield materials are derived from the attenuation profiles. The source term data and the attenuation lengths were then used to evaluate the shielding requirements for the ratchet walls of all front-ends of the SPEAR3 storage ring.
The design of reactive shielded magnet clutches
NASA Technical Reports Server (NTRS)
Gertsov, S. M.
1978-01-01
The design of reactive shielded magnet clutches is considered along with their schematics, design formulas and characteristics of clutches in general. The design method suggested makes it possible to reduce calculation errors to 10%.
Sherrod, D.R.; Murai, T.; Tagami, Takahiro
2007-01-01
Thirty-seven new K-Ar ages from West Maui volcano, Hawai'i, are used to define the waning stages of shield growth and a brief episode of postshield volcanism. All but two samples from shield-stage strata have reversed polarity magnetization, so conceivably the exposed shield is not much older than the Olduvai Normal-Polarity subchron, or about 1.8 Ma. The oldest ages obtained are in the range 1.9-2.1 Ma but have large analytical error. Shield volcanism ended about 1.35 Ma, and postshield volcanism followed soon thereafter, persisting until about 1.2 Ma. Exposed shield-stage strata were emplaced at a rate of about 0.001 km3 per year, a rate smaller than historic Hawaiian magmatic rates by a factor of 100. Stratigraphic accumulation rates are similar to those measured previously at Wai'anae volcano (O'ahu) or the upper part of the Mauna Kea shield sequence (Hilo drill core, Hawai'i). These rates diminish sharply during the final 0.3-0.5 m.y. of the shield stage. Hawaiian shield volcanoes begin waning well before their last 0.5 m.y. of life, then end quickly, geologically speaking, if West Maui is representative. ?? Springer-Verlag 2006.
Optimation of cooled shields in insulations
NASA Technical Reports Server (NTRS)
Chato, J. C.; Khodadadi, J. M.; Seyed-Yagoobi, J.
1984-01-01
A method to optimize the location, temperature, and heat dissipation rate of each cooled shield inside an insulation layer was developed. The method is based on the minimization of the entropy production rate which is proportional to the heat leak across the insulation. It is shown that the maximum number of shields to be used in most practical applications is three. However, cooled shields are useful only at low values of the overall, cold wall to hot wall absolute temperature ratio. The performance of the insulation system is relatively insensitive to deviations from the optimum values of the temperature and location of the cooling shields. Design curves for rapid estimates of the locations and temperatures of cooling shields in various types of insulations, and an equation for calculating the cooling loads for the shields are presented.
Monte Carlo methods to calculate impact probabilities
NASA Astrophysics Data System (ADS)
Rickman, H.; Wiśniowski, T.; Wajer, P.; Gabryszewski, R.; Valsecchi, G. B.
2014-09-01
Context. Unraveling the events that took place in the solar system during the period known as the late heavy bombardment requires the interpretation of the cratered surfaces of the Moon and terrestrial planets. This, in turn, requires good estimates of the statistical impact probabilities for different source populations of projectiles, a subject that has received relatively little attention, since the works of Öpik (1951, Proc. R. Irish Acad. Sect. A, 54, 165) and Wetherill (1967, J. Geophys. Res., 72, 2429). Aims: We aim to work around the limitations of the Öpik and Wetherill formulae, which are caused by singularities due to zero denominators under special circumstances. Using modern computers, it is possible to make good estimates of impact probabilities by means of Monte Carlo simulations, and in this work, we explore the available options. Methods: We describe three basic methods to derive the average impact probability for a projectile with a given semi-major axis, eccentricity, and inclination with respect to a target planet on an elliptic orbit. One is a numerical averaging of the Wetherill formula; the next is a Monte Carlo super-sizing method using the target's Hill sphere. The third uses extensive minimum orbit intersection distance (MOID) calculations for a Monte Carlo sampling of potentially impacting orbits, along with calculations of the relevant interval for the timing of the encounter allowing collision. Numerical experiments are carried out for an intercomparison of the methods and to scrutinize their behavior near the singularities (zero relative inclination and equal perihelion distances). Results: We find an excellent agreement between all methods in the general case, while there appear large differences in the immediate vicinity of the singularities. With respect to the MOID method, which is the only one that does not involve simplifying assumptions and approximations, the Wetherill averaging impact probability departs by diverging toward
Singularity embedding method in potential flow calculations
NASA Technical Reports Server (NTRS)
Jou, W. H.; Huynh, H.
1982-01-01
The so-called H-type mesh is used in a finite-element (or finite-volume) calculation of the potential flow past an airfoil. Due to coordinate singularity at the leading edge, a special singular trial function is used for the elements neighboring the leading edge. The results using the special singular elements are compared to those using the regular elements. It is found that the unreasonable pressure distribution obtained by the latter is removed by the embedding of the singular element. Suggestions to extend the present method to transonic cases are given.
Health state evaluation of shield tunnel SHM using fuzzy cluster method
NASA Astrophysics Data System (ADS)
Zhou, Fa; Zhang, Wei; Sun, Ke; Shi, Bin
2015-04-01
Shield tunnel SHM is in the path of rapid development currently while massive monitoring data processing and quantitative health grading remain a real challenge, since multiple sensors belonging to different types are employed in SHM system. This paper addressed the fuzzy cluster method based on fuzzy equivalence relationship for the health evaluation of shield tunnel SHM. The method was optimized by exporting the FSV map to automatically generate the threshold value. A new holistic health score(HHS) was proposed and its effectiveness was validated by conducting a pilot test. A case study on Nanjing Yangtze River Tunnel was presented to apply this method. Three types of indicators, namely soil pressure, pore pressure and steel strain, were used to develop the evaluation set U. The clustering results were verified by analyzing the engineering geological conditions; the applicability and validity of the proposed method was also demonstrated. Besides, the advantage of multi-factor evaluation over single-factor model was discussed by using the proposed HHS. This investigation indicated the fuzzy cluster method and HHS is capable of characterizing the fuzziness of tunnel health, and it is beneficial to clarify the tunnel health evaluation uncertainties.
Development of deterministic transport methods for low energy neutrons for shielding in space
NASA Technical Reports Server (NTRS)
Ganapol, Barry
1993-01-01
Transport of low energy neutrons associated with the galactic cosmic ray cascade is analyzed in this dissertation. A benchmark quality analytical algorithm is demonstrated for use with BRYNTRN, a computer program written by the High Energy Physics Division of NASA Langley Research Center, which is used to design and analyze shielding against the radiation created by the cascade. BRYNTRN uses numerical methods to solve the integral transport equations for baryons with the straight-ahead approximation, and numerical and empirical methods to generate the interaction probabilities. The straight-ahead approximation is adequate for charged particles, but not for neutrons. As NASA Langley improves BRYNTRN to include low energy neutrons, a benchmark quality solution is needed for comparison. The neutron transport algorithm demonstrated in this dissertation uses the closed-form Green's function solution to the galactic cosmic ray cascade transport equations to generate a source of neutrons. A basis function expansion for finite heterogeneous and semi-infinite homogeneous slabs with multiple energy groups and isotropic scattering is used to generate neutron fluxes resulting from the cascade. This method, called the FN method, is used to solve the neutral particle linear Boltzmann transport equation. As a demonstration of the algorithm coded in the programs MGSLAB and MGSEMI, neutron and ion fluxes are shown for a beam of fluorine ions at 1000 MeV per nucleon incident on semi-infinite and finite aluminum slabs. Also, to demonstrate that the shielding effectiveness against the radiation from the galactic cosmic ray cascade is not directly proportional to shield thickness, a graph of transmitted total neutron scalar flux versus slab thickness is shown. A simple model based on the nuclear liquid drop assumption is used to generate cross sections for the galactic cosmic ray cascade. The ENDF/B V database is used to generate the total and scattering cross sections for neutrons in
EMPLACEMENT DRIFT SHIELDING CALCULATION
A. Nielsen
1999-10-13
The purpose of this analysis is to determine the structural response of a TRIGA Department of Energy (DOE) spent nuclear fuel (SNF) codisposal canister placed in a 5-Defense High Level Waste (DHLW) waste package (WP) and subjected to a tipover design basis event (DBE) dynamic load; the results will be reported in terms of displacements and stress magnitudes. This activity is associated with the WP design.
NASA Astrophysics Data System (ADS)
Kost, A.; Jacobs, R. T.; Hahn, A.
2007-08-01
The shielding of strong electromagnetic fields at power frequency, performed by ferromagnetic plates, is often successfully modelled by the effective reluctivity. This method delivers good results for the RMSvalue of the shielded field. The following paper shows that a small variation of the magnetization curve (e.g.by taking another material charge) can strongly influence the shielded field. The field calculation is performed by the Finite Element Method (FEM), where for the interior plate region a)finite elements and b)non-linear Impedance Boundary Conditions (IBC) are used which circumvents the need to discretize the shielding plate.
Growth of ZnSe single crystal by CVT method with self-moving convection shield
NASA Astrophysics Data System (ADS)
Fujiwara, S.; Namikawa, Y.; Hirota, Y.; Irikura, M.; Matsumoto, K.; Kotani, T.
1999-01-01
The self-moving convection shield was used in the growth of ZnSe single crystal by chemical vapor transport method using iodine as a transport agent. The reduction of the convection enables the growth of a 1-in diameter ZnSe single crystal. The incorporation efficiency of iodine on (1 1 1)B facet was proved to be larger than that on (1 0 0) facet. Impurity-hardening effect of incorporated iodine in the grown ZnSe crystal is also suggested.
Somasundaram, E.; Palmer, T. S.
2013-07-01
In this paper, the work that has been done to implement variance reduction techniques in a three dimensional, multi group Monte Carlo code - Tortilla, that works within the frame work of the commercial deterministic code - Attila, is presented. This project is aimed to develop an integrated Hybrid code that seamlessly takes advantage of the deterministic and Monte Carlo methods for deep shielding radiation detection problems. Tortilla takes advantage of Attila's features for generating the geometric mesh, cross section library and source definitions. Tortilla can also read importance functions (like adjoint scalar flux) generated from deterministic calculations performed in Attila and use them to employ variance reduction schemes in the Monte Carlo simulation. The variance reduction techniques that are implemented in Tortilla are based on the CADIS (Consistent Adjoint Driven Importance Sampling) method and the LIFT (Local Importance Function Transform) method. These methods make use of the results from an adjoint deterministic calculation to bias the particle transport using techniques like source biasing, survival biasing, transport biasing and weight windows. The results obtained so far and the challenges faced in implementing the variance reduction techniques are reported here. (authors)
Performance analysis of superconducting generator electromagnetic shielding
NASA Astrophysics Data System (ADS)
Xia, D.; Xia, Z.
2015-12-01
In this paper, the shielding performance of electromagnetic shielding systems is analyzed using the finite element method. Considering the non-iron-core rotor structure of superconducting generators, it is proposed that the stator alternating magnetic field generated under different operating conditions could decompose into oscillating and rotating magnetic field, so that complex issues could be greatly simplified. A 1200KW superconducting generator was analyzed. The distribution of the oscillating magnetic field and the rotating magnetic field in rotor area, which are generated by stator winding currents, and the distribution of the eddy currents in electromagnetic shielding tube, which are induced by these stator winding magnetic fields, are calculated without electromagnetic shielding system and with three different structures of electromagnetic shielding system respectively. On the basis of the results of FEM, the shielding factor of the electromagnetic shielding systems is calculated and the shielding effect of the three different structures on the oscillating magnetic field and the rotating magnetic field is compared. The method and the results in this paper can provide reference for optimal design and loss calculation of superconducting generators.
Calculation of NMR chemical shifts. 7. Gauge-invariant INDO method
NASA Astrophysics Data System (ADS)
Fukui, H.; Miura, K.; Hirai, A.
A gauge-invariant INDO method based on the coupled Hartree-Fuck perturbation theory is presented and applied to the calculation of 1H and 13C chemical shifts of hydrocarbons including ring compounds. Invariance of the diamagnetic and paramagnetic shieldings with respect to displacement of the coordinate origin is discussed. Comparison between calculated and experimental results exhibits fairly good agreement, provided that the INDO parameters of Ellis et al. (J. Am. Chem. Soc.94, 4069 (1972)) are used with the inclusion of all multicenter one-electron integrals.
NASA Technical Reports Server (NTRS)
Lahti, G. P.
1972-01-01
A two- or three-constraint, two-dimensional radiation shield weight optimization procedure and a computer program, DOPEX, is described. The DOPEX code uses the steepest descent method to alter a set of initial (input) thicknesses for a shield configuration to achieve a minimum weight while simultaneously satisfying dose constaints. The code assumes an exponential dose-shield thickness relation with parameters specified by the user. The code also assumes that dose rates in each principal direction are dependent only on thicknesses in that direction. Code input instructions, FORTRAN 4 listing, and a sample problem are given. Typical computer time required to optimize a seven-layer shield is about 0.1 minute on an IBM 7094-2.
NASA Astrophysics Data System (ADS)
Yoshizawa, Terutaka; Hada, Masahiko
2013-08-01
We propose a novel Foldy-Wouthuysen transformation including a vector potential A, which can be used to introduce restricted magnetic balance in the Douglas-Kroll-Hess (DKH) method. We also demonstrate that the DKH method can be used in combination with the gauge-including atomic orbital method. For the numerical examination, we calculate the NMR shielding constants and anisotropies of noble gas atoms (Ne, Ar, Kr, Xe), halogens (F, Cl, Br, I), and chalcogens (O, S, Se, Te) in molecules without using extremely large basis sets.
Shielding measurements for 230-Mev protons
Siebers, J.V.; DeLuca, P.M. Jr.; Pearson, D.W. . Dept. of Medical Physics); Coutrakon, G. . Medical Center)
1993-09-01
Energetic neutrons, produced as protons interact with matter, dominate the radiation shielding environment for proton accelerators. Because of the scarcity of data describing the shielding required to protect personnel from these neutrons, absorbed dose and dose-equivalent values are measured as a function of depth in a thick concrete shield at neutron emission angles of 0, 22, 45, and 90 deg for 230-MeV protons incident upon stopping-length aluminum, iron, and lead targets. Neutron attenuation lengths vary sharply with angle but are independent of the target material. Comparing results with prior shielding calculations, the High-Energy Transport Code overestimates neutron production and attenuation lengths in the forward direction. Analytical methods compare favorably in the forward direction but overestimate the production and attenuation lengths at large angles. The results presented are useful for determining the shielding requirements for proton radiotherapy facilities and as a benchmark for future calculations.
Multigrid Methods in Electronic Structure Calculations
NASA Astrophysics Data System (ADS)
Briggs, Emil
1996-03-01
Multigrid techniques have become the method of choice for a broad range of computational problems. Their use in electronic structure calculations introduces a new set of issues when compared to traditional plane wave approaches. We have developed a set of techniques that address these issues and permit multigrid algorithms to be applied to the electronic structure problem in an efficient manner. In our approach the Kohn-Sham equations are discretized on a real-space mesh using a compact representation of the Hamiltonian. The resulting equations are solved directly on the mesh using multigrid iterations. This produces rapid convergence rates even for ill-conditioned systems with large length and/or energy scales. The method has been applied to both periodic and non-periodic systems containing over 400 atoms and the results are in very good agreement with both theory and experiment. Example applications include a vacancy in diamond, an isolated C60 molecule, and a 64-atom cell of GaN with the Ga d-electrons in valence which required a 250 Ry cutoff. A particular strength of a real-space multigrid approach is its ready adaptability to massively parallel computer architectures. The compact representation of the Hamiltonian is especially well suited to such machines. Tests on the Cray-T3D have shown nearly linear scaling of the execution time up to the maximum number of processors (512). The MPP implementation has been used for studies of a large Amyloid Beta Peptide (C_146O_45N_42H_210) found in the brains of Alzheimers disease patients. Further applications of the multigrid method will also be described. (in collaboration D. J. Sullivan and J. Bernholc)
Open Rotor Tone Shielding Methods for System Noise Assessments Using Multiple Databases
NASA Technical Reports Server (NTRS)
Bahr, Christopher J.; Thomas, Russell H.; Lopes, Leonard V.; Burley, Casey L.; Van Zante, Dale E.
2014-01-01
Advanced aircraft designs such as the hybrid wing body, in conjunction with open rotor engines, may allow for significant improvements in the environmental impact of aviation. System noise assessments allow for the prediction of the aircraft noise of such designs while they are still in the conceptual phase. Due to significant requirements of computational methods, these predictions still rely on experimental data to account for the interaction of the open rotor tones with the hybrid wing body airframe. Recently, multiple aircraft system noise assessments have been conducted for hybrid wing body designs with open rotor engines. These assessments utilized measured benchmark data from a Propulsion Airframe Aeroacoustic interaction effects test. The measured data demonstrated airframe shielding of open rotor tonal and broadband noise with legacy F7/A7 open rotor blades. Two methods are proposed for improving the use of these data on general open rotor designs in a system noise assessment. The first, direct difference, is a simple octave band subtraction which does not account for tone distribution within the rotor acoustic signal. The second, tone matching, is a higher-fidelity process incorporating additional physical aspects of the problem, where isolated rotor tones are matched by their directivity to determine tone-by-tone shielding. A case study is conducted with the two methods to assess how well each reproduces the measured data and identify the merits of each. Both methods perform similarly for system level results and successfully approach the experimental data for the case study. The tone matching method provides additional tools for assessing the quality of the match to the data set. Additionally, a potential path to improve the tone matching method is provided.
M. Gross
2006-12-08
The overall objective of the work scope covered by this technical work plan (TWP) is to develop new damage abstractions for the seismic scenario class in total system performance assessment (TSPA). The new abstractions will be based on a new set of waste package and drip shield damage calculations in response to vibratory ground motion and fault displacement. The new damage calculations, which are collectively referred to as damage models in this TWP, are required to represent recent changes in waste form packaging and in the regulatory time frame. The new damage models also respond to comments from the Independent Validation Review Team (IVRT) postvalidation review of the draft TSPA model regarding performance of the drip shield and to an Additional Information Need (AIN) from the U.S. Nuclear Regulatory Commission (NRC).
Free-slit shielding of stress waves by the photoelasticity method
Freishist, N.A.; Dmitrienko, O.L.
1986-05-01
This paper is devoted to the study of an experimental model investigation of the distribution of dynamic stresses beyond a free shielding slit as a longitudinal wave from a blast source strikes the shield. The studies were conducted by the method of photoelasticity on a dynamic polarization apparatus in the stress-study laboratory at the Moscow V.V. Kuibyshev Civil Engineering Institute. The problem was solved in the plane elastic statement on models in the form of plates made of an optically sensitive epoxy-resin-base material. The pulse effect was created by the detonation of a cylindrical lead azide microcharge. The dynamic stressed state at internal points of the model was evaluated from the magnitudes and distribution of maximum tangential stresses, and on the free perimeter of the model from the magnitudes and distribution of the normal stress parallel to the perimeter. The experimental studies indicated that a zone in which the stress amplitude is reduced as compared with the nominal stresses exists beyond the slit in all cases examined. The investigations made it possible to evaluate these relationships within the range of parameters under consideration.
Polynominal Interpolation Methods for Viscous Flow Calculations
NASA Technical Reports Server (NTRS)
Rubin, S. G.; Khosla, P. K.
1976-01-01
Higher-order collocation procedures resulting in tridiagonal matrix systems are derived from polynomial spline interpolation and by Hermitian (Taylor series) finite-difference discretization. The similarities and special features of these different developments are discussed. The governing systems apply for both uniform and variable meshes. Hybrid schemes resulting from two different polynomial approximations for the first and second derivatives lead to a nonuniform mesh extension of the so-called compact or Pad? difference technique (Hermite 4). A variety of fourth-order methods are described and the Hermitian approach is extended to sixth-order (Hermite 6). The appropriate spline boundary conditions are derived for all procedures. For central finite differences, this leads to a two-point, second-order accurate generalization of the commonly used three-point end-difference formula. Solutions with several spline and Hermite procedures are presented for the boundary layer equations, with and without mass transfer, and for the incompressible viscous flow in a driven cavity. Divergence and nondivergence equations are considered for the cavity. Among the fourth-order techniques, it is shown that spline 4 has the smallest truncation error. The spline 4 procedure generally requires one-quarter the number of mesh points in a given coordinate direction as a central finite-difference calculation of equal accuracy. The Hermite 6 procedure leads to remarkably accurate boundary layer solutions.
Marshall, A.C.
1997-10-01
Three relatively simple mathematical models have been developed to estimate minimum reactor and radiation shield masses for liquid-metal-cooled reactors (LMRs), in-core thermionic fuel element (TFE) reactors, and out-of-core thermionic reactors (OTRs). The approach was based on much of the methodology developed for the Reactor/Shield Mass (RSMASS) model. Like the original RSMASS models, the new RSMASS-derivative (RSMASS-D) models use a combination of simple equations derived from reactor physics and other fundamental considerations, along with tabulations of data from more detailed neutron and gamma transport theory computations. All three models vary basic design parameters within a range specified by the user to achieve a parameter choice that yields a minimum mass for the power level and operational time of interest. The impact of critical mass, fuel damage, and thermal limitations are accounted for to determine the required fuel mass. The effect of thermionic limitations are also taken into account for the thermionic reactor models. All major reactor component masses are estimated, as well as instrumentation and control (I&C), boom, and safety system masses. A new shield model was developed and incorporated into all three reactor concept models. The new shield model is more accurate and simpler to use than the approach used in the original RSMASS model. The estimated reactor and shield masses agree with the mass predictions from separate detailed calculations within 15 percent for all three models.
Shielding from the Cosmic Radiation for Interplanetary Missions: Active and Passive Methods
NASA Astrophysics Data System (ADS)
Spillantini, P.; Topical Team Of ESA On Radiation Shielding
Shielding is arguably the main countermeasure for the exposure to cosmic radiation during interplanetary exploratory missions. However, shielding of cosmic rays, both of galactic or solar origin, is highly problematic, because of the high-energy of the charged particles involved and the nuclear fragmentation occurring in shielding materials. Although computer codes can predict the shield performance in space, there is a lack of biological and physical measurements to benchmark the codes. An attractive alternative to passive, bulk material shielding is the use of magnetic fields to deflect the charged particles from the spacecraft target. A shielding system based on superconducting magnetic lenses could effectively shield a spacecraft from solar particle events, at least for the portion of energetic particles roughly collinear with the direction of the solar magnetic field. To address these issues, the European Space Agency (ESA) established a Topical Team in 2003 including several European experts in the field of space radiation shielding and superconducting magnets. The Topical Team identified a number of open research questions to be addressed, including development and testing of novel shielding materials, studies on the angular distributions of energetic solar particles, and cooling systems for magnetic lenses in space. A detailed report to ESA will be published within the Fall of the 2004. A summary of the Topical Team conclusions and recommendations will be discussed in this paper. (Work supported by ESA Opportunities for Research in Life Sciences grant # ESA-RA-LS-01-PREP/TT-007).
Overview of multifluid-flow-calculation methods
Stewart, H.B.
1981-01-01
Two categories of numerical methods which may be useful in multiphase flow research are discussed. The first category includes methods which are specifically intended for accurate computation of discontinuities, such as the method of characteristics, particle-in-cell method, flux-corrected transport, and random choice methods. Methods in this category could be applied to research on rocket exhaust plumes and interior ballistics. The second category includes methods for smooth, subsonic flows, such as fractional step methods, semi-implicit method, and methods which treat convection implicitly. The subsonic flow methods could be of interest for ice flows. (LCL)
NASA Technical Reports Server (NTRS)
Ballarini, F.; Biaggi, M.; De Biaggi, L.; Ferrari, A.; Ottolenghi, A.; Panzarasa, A.; Paretzke, H. G.; Pelliccioni, M.; Sala, P.; Scannicchio, D.; Zankl, M.; Townsend, L. W. (Principal Investigator)
2004-01-01
Distributions of absorbed dose and DNA clustered damage yields in various organs and tissues following the October 1989 solar particle event (SPE) were calculated by coupling the FLUKA Monte Carlo transport code with two anthropomorphic phantoms (a mathematical model and a voxel model), with the main aim of quantifying the role of the shielding features in modulating organ doses. The phantoms, which were assumed to be in deep space, were inserted into a shielding box of variable thickness and material and were irradiated with the proton spectra of the October 1989 event. Average numbers of DNA lesions per cell in different organs were calculated by adopting a technique already tested in previous works, consisting of integrating into "condensed-history" Monte Carlo transport codes--such as FLUKA--yields of radiobiological damage, either calculated with "event-by-event" track structure simulations, or taken from experimental works available in the literature. More specifically, the yields of "Complex Lesions" (or "CL", defined and calculated as a clustered DNA damage in a previous work) per unit dose and DNA mass (CL Gy-1 Da-1) due to the various beam components, including those derived from nuclear interactions with the shielding and the human body, were integrated in FLUKA. This provided spatial distributions of CL/cell yields in different organs, as well as distributions of absorbed doses. The contributions of primary protons and secondary hadrons were calculated separately, and the simulations were repeated for values of Al shielding thickness ranging between 1 and 20 g/cm2. Slight differences were found between the two phantom types. Skin and eye lenses were found to receive larger doses with respect to internal organs; however, shielding was more effective for skin and lenses. Secondary particles arising from nuclear interactions were found to have a minor role, although their relative contribution was found to be larger for the Complex Lesions than for the
Optimal shield mass distribution for space radiation protection
NASA Technical Reports Server (NTRS)
Billings, M. P.
1972-01-01
Computational methods have been developed and successfully used for determining the optimum distribution of space radiation shielding on geometrically complex space vehicles. These methods have been incorporated in computer program SWORD for dose evaluation in complex geometry, and iteratively calculating the optimum distribution for (minimum) shield mass satisfying multiple acute and protected dose constraints associated with each of several body organs.
Resonance self-shielding methodology in MPACT
Liu, Y.; Collins, B.; Kochunas, B.; Martin, W.; Kim, K. S.; Williams, M.
2013-07-01
The resonance self-shielding methods of the neutron transport code Michigan Parallel Characteristics based Transport (MPACT) are described in this paper. Two resonance-integral table based methods are utilized to resolve the resonance self-shielding effect. The subgroup method is a mature approach used in MPACT as the basic functionality for the resonance calculation. Another new iterative method, named the embedded self-shielding method is also implemented in MPACT. Comparisons of the two methods as well as their numerical verifications are presented. The results show that MPACT is capable of modeling the resonance self-shielding in a variety of PWR benchmarking cases, including difficult fuel lattice cases with poison, control rods or mixed gadolinia fuel rods. (authors)
NASA Astrophysics Data System (ADS)
Mueller, J. M.; Ahmed, M. W.; Kafkarkou, A.; Kendellen, D. P.; Sikora, M. H.; Spraker, M. C.; Weller, H. R.; Zimmerman, W. R.
2015-03-01
A novel method to identify Special Nuclear Material was recently developed (Mueller et al., 2014) [1]. This method relies upon using a linearly polarized γ-ray beam to induce photofission of a sample and then comparing the prompt fission neutron yields in and out of the plane of beam polarization. The present paper will describe experimental tests of this new technique and assess its sensitivity in the presence of shielding. The capability of this technique to measure the enrichment of uranium was tested by using combinations of thin 235U and 238U foils of known enrichments. The sensitivity of this assay to shielding by lead, steel, and polyethylene was experimentally measured and simulated using GEANT4. These tests show that the measured asymmetry can indeed be used to determine the enrichment of materials composed of an admixture of 235U and 238U, and this asymmetry is relatively insensitive to moderate amounts of shielding.
Deconstructing Calculation Methods, Part 3: Multiplication
ERIC Educational Resources Information Center
Thompson, Ian
2008-01-01
In this third of a series of four articles, the author deconstructs the primary national strategy's approach to written multiplication. The approach to multiplication, as set out on pages 12 to 15 of the primary national strategy's "Guidance paper" "Calculation" (DfES, 2007), is divided into six stages: (1) mental multiplication using…
Valmianski, Emanuil I.; Petzoldt, Ronald W.; Alexander, Neil B.
2003-05-15
The heat flux from both gas convection and chamber radiation on a direct drive target must be limited to avoid target damage from excessive D-T temperature increase. One of the possibilities of protecting the target is a wake shield flying in front of the target. A shield will also reduce drag force on the target, thereby facilitating target tracking and position prediction. A Direct Simulation Monte Carlo (DSMC) code was used to calculate convection heat loads as boundary conditions input into ANSYS thermal calculations. These were used for studying the quality of target protection depending on various shapes of shields, target-shield distance, and protective properties of the shield moving relative to the target. The results show that the shield can reduce the convective heat flux by a factor of 2 to 5 depending on pressure, temperature, and velocity. The protective effect of a shield moving relative to the target is greater than the protective properties of a fixed shield. However, the protective effect of a shield moving under the drag force is not sufficient for bringing the heat load on the target down to the necessary limit. Some other ways of diminishing heat flux using a protective shield are discussed.
Pace, J.V.
2002-02-14
Achieving agreement between measured and calculated neutron activation data resulting from Hiroshima and Nagasaki A-bomb detonations has been a major problem since the early 1980's. This has been particularly true for the materials that are activated by thermal and epithermal neutrons. Since thermal and epithermal neutrons are not transported very far from the weapon, the local shielding environment around the measurement location can be very important. A set of calculations incorporating an average density local-environment material (mush) has been made to demonstrate that the local environment plays an important role in the calculation-measurement agreement process. The optimum solution would be to include the local environment in all thermal neutron response calculations.
Computational methods for probability of instability calculations
NASA Technical Reports Server (NTRS)
Wu, Y.-T.; Burnside, O. H.
1990-01-01
This paper summarizes the development of the methods and a computer program to compute the probability of instability of a dynamic system than can be represented by a system of second-order ordinary linear differential equations. Two instability criteria based upon the roots of the characteristics equation or Routh-Hurwitz test functions are investigated. Computational methods based on system reliability analysis methods and importance sampling concepts are proposed to perform efficient probabilistic analysis. Numerical examples are provided to demonstrate the methods.
METHODS FOR CALCULATING AN LC50
A variety of graphical and computational methods can be used to derive a median lethal concentration (LC50) from concentration-mortality data produced by an acute mortality test. In the selection of a method, practical considerations should receive as much attention as the usual ...
Evaluation of a method to shield a welding electron beam from magnetic interference
NASA Technical Reports Server (NTRS)
Wall, W. A.
1976-01-01
It is known that electron beams are easily deflected by magnetic and electrostatic fields. Therefore, to prevent weld defects, stray electromagnetic fields are avoided in electron beam welding chambers if at all possible. The successful results of tests conducted at MSFC to evaluate a simple magnetic shield made from steel tubing are reported. Tests indicate that this shield was up to 85 percent effective in reducing magnetic effects on the electron beam of a welding machine. In addition, residual magnetic fields within the shield were so nearly uniform that the net effect on the beam alignment was negligible. It is concluded that the shield, with the addition of a tungsten liner, could be used in production welding.
Examinations of electron temperature calculation methods in Thomson scattering diagnostics
Oh, Seungtae; Lee, Jong Ha; Wi, Hanmin
2012-10-15
Electron temperature from Thomson scattering diagnostic is derived through indirect calculation based on theoretical model. {chi}-square test is commonly used in the calculation, and the reliability of the calculation method highly depends on the noise level of input signals. In the simulations, noise effects of the {chi}-square test are examined and scale factor test is proposed as an alternative method.
An Integrated Calculation Method to Predict Arc Behavior
NASA Astrophysics Data System (ADS)
Li, Xingwen; Chen, Degui
The precision of magnetic field calculation is crucial to predict the arc behavior using magnetohydrodynamic (MHD) model. A integrated calculation method is proposed to couple the calculation of magnetic field and fluid dynamics based on the commercial software ANSYS and FLUENT, which especially benefits to take into account the existence of the ferromagnetic parts. An example concerning air arc is presented using the method.
Vortex particle methods in aeroacoustic calculations
NASA Astrophysics Data System (ADS)
Huberson, Serge; Rivoalen, Elie; Voutsinas, Spyros
2008-11-01
The connection between vortex particle methods and aeroacoustics is considered within the framework of Lighthill's acoustic analogy which allows to decouple the flow from noise propagation. For the flow, techniques such as tree-algorithms and the particle-mesh method are brought together with the aim to achieve the best possible performance in view of analyzing complex problems. The flow results are then input to the acoustic wave equation which is solved in integral form. It will involve monopole, dipole and quadrupole terms which can be successively integrated. The significance of such an approach is first demonstrated in two problems, both related to vortex-solid interactions. The first is a generic one and considers the interaction of a vortex filament interacting with a sphere while the second considers helicopter noise as an example of a complex engineering set-up.
Enhanced Method for Cavity Impedance Calculations
Frank Marhauser, Robert Rimmer, Kai Tian, Haipeng Wang
2009-05-01
With the proposal of medium to high average current accelerator facilities the demand for cavities with extremely low Higher Order Mode (HOM) impedances is increasing. Modern numerical tools are still under development to more thoroughly predict impedances that need to take into account complex absorbing boundaries and lossy materials. With the usually large problem size it is preferable to utilize massive parallel computing when applicable and available. Apart from such computational issues, we have developed methods using available computer resources to enhance the information that can be extracted from a cavities? wakefield computed in time domain. In particular this is helpful for a careful assessment of the extracted RF power and the mitigation of potential beam break-up or emittance diluting effects, a figure of merit for the cavity performance. The method is described as well as an example of its implementation.
Calculating Pi Using the Monte Carlo Method
NASA Astrophysics Data System (ADS)
Williamson, Timothy
2013-11-01
During the summer of 2012, I had the opportunity to participate in a research experience for teachers at the center for sustainable energy at Notre Dame University (RET @ cSEND) working with Professor John LoSecco on the problem of using antineutrino detection to accurately determine the fuel makeup and operating power of nuclear reactors. During full power operation, a reactor may produce 1021 antineutrinos per second with approximately 100 per day being detected. While becoming familiar with the design and operation of the detectors, and how total antineutrino flux could be obtained from such a small sample, I read about a simulation program called Monte Carlo. Further investigation led me to the Monte Carlo method page of Wikipedia2 where I saw an example of approximating pi using this simulation. Other examples where this method was applied were typically done with computer simulations2 or purely mathematical.3 It is my belief that this method may be easily related to the students by performing the simple activity of sprinkling rice on an arc drawn in a square. The activity that follows was inspired by those simulations and was used by my AP Physics class last year with very good results.
The application of the phase space time evolution method to electron shielding
NASA Technical Reports Server (NTRS)
Cordaro, M. C.; Zucker, M. S.
1972-01-01
A computer technique for treating the motion of charged and neutral particles and called the phase space time evolution method was developed. This technique employs the computer's bookkeeping capacity to keep track of the time development of a phase space distribution of particles. This method was applied to a study of the penetration of electrons. A 1 MeV beam of electrons normally incident on a semi-infinite slab of aluminum was used. Results of the calculation were compared with Monte Carlo calculations and experimental results. Time-dependent PSTE electron penetration results for the same problem are presented.
Patient-specific dose calculation methods for high-dose-rate iridium-192 brachytherapy
NASA Astrophysics Data System (ADS)
Poon, Emily S.
In high-dose-rate 192Ir brachytherapy, the radiation dose received by the patient is calculated according to the AAPM Task Group 43 (TG-43) formalism. This table-based dose superposition method uses dosimetry parameters derived with the radioactive 192Ir source centered in a water phantom. It neglects the dose perturbations caused by inhomogeneities, such as the patient anatomy, applicators, shielding, and radiographic contrast solution. In this work, we evaluated the dosimetric characteristics of a shielded rectal applicator with an endocavitary balloon injected with contrast solution. The dose distributions around this applicator were calculated by the GEANT4 Monte Carlo (MC) code and measured by ionization chamber and GAFCHROMIC EBT film. A patient-specific dose calculation study was then carried out for 40 rectal treatment plans. The PTRAN_CT MC code was used to calculate the dose based on computed tomography (CT) images. This study involved the development of BrachyGUI, an integrated treatment planning tool that can process DICOM-RT data and create PTRAN_CT input initialization files. BrachyGUI also comes with dose calculation and evaluation capabilities. We proposed a novel scatter correction method to account for the reduction in backscatter radiation near tissue-air interfaces. The first step requires calculating the doses contributed by primary and scattered photons separately, assuming a full scatter environment. The scatter dose in the patient is subsequently adjusted using a factor derived by MC calculations, which depends on the distances between the point of interest, the 192Ir source, and the body contour. The method was validated for multicatheter breast brachytherapy, in which the target and skin doses for 18 patient plans agreed with PTRAN_CT calculations better than 1%. Finally, we developed a CT-based analytical dose calculation method. It corrects for the photon attenuation and scatter based upon the radiological paths determined by ray tracing
The TAB method for numerical calculation of spray droplet breakup
NASA Astrophysics Data System (ADS)
Orourke, P. J.; Amsden, A. A.
A short history is given of the major milestones in the development of the stochastic particle method for calculating liquid fuel sprays. The most recent advance has been the discovery of the importance of drop breakup in engine sprays. A new method, called TAB, for calculating drop breakup is presented. Some theoretical properties of the method are derived; its numerical implementation in the computer program KIVA is described; and comparisons are presented between TAB-method calculations and experiments and calculations using another breakup model.
Heat Shielding: A Novel Method of Colonial Thermoregulation in Honey Bees
NASA Astrophysics Data System (ADS)
Starks, Philip T.; Gilley, David C.
Honey bees, Apis mellifera, maintain constant colony temperatures throughout the year. Honey bees fan their wings to cool the colony, and often spread fluid in conjunction with this behavior to induce evaporative cooling. We present an additional, previously undescribed mechanism used by the honey bee to maintain constant colony temperature in response to localized temperature increases. Worker bees shield the comb from external heat sources by positioning themselves on hot interior regions of the hive's walls. Although honey comb and brood comb were both shielded, the temperature-sensitive brood received a greater number of heat shielders and was thus better protected from overheating. Heat shielding appears to be a context-dependent adaptive behavior performed by worker bees who would previously have been considered "unemployed."
NASA Technical Reports Server (NTRS)
Fieno, D.
1972-01-01
Perturbation theory for fixed sources was applied to radiation shielding problems to determine changes in neutron and gamma ray doses due to changes in various shield layers. For a given source and detector position, the perturbation method enables dose derivatives due to all layer changes to be determined from one forward and one inhomogeneous adjoint calculation. The direct approach requires two forward calculations for the derivative due to a single layer change. Hence, the perturbation method for a obtaining dose derivatives permits an appreciable savings in computation for a multilayered shield. A comparison was made of the fractional change in the dose per unit change in shield layer thickness as calculated by perturbation theory and by successive direct calculations; excellent agreement was obtained between the two methods.
NASA Technical Reports Server (NTRS)
Fieno, D.
1972-01-01
The perturbation theory for fixed sources was applied to radiation shielding problems to determine changes in neutron and gamma ray doses due to changes in various shield layers. For a given source and detector position the perturbation method enables dose derivatives due to all layer changes to be determined from one forward and one inhomogeneous adjoint calculation. The direct approach requires two forward calculations for the derivative due to a single layer change. Hence, the perturbation method for obtaining dose derivatives permits an appreciable savings in computation for a multilayered shield. For an illustrative problem, a comparison was made of the fractional change in the dose per unit change in the thickness of each shield layer as calculated by perturbation theory and by successive direct calculations; excellent agreement was obtained between the two methods.
Some methods for calculation of perturbations in nuclear reactors
Abramov, B. D.
2015-12-15
Some methods for calculation of local perturbations of neutron fields and reactivity effects accompanying them are considered. Existence, uniqueness, properties and methods for finding solutions to the considered problems are discussed.
Kuehl, Kerry S; Elliot, Diane L; MacKinnon, David P; O'Rourke, Holly P; DeFrancesco, Carol; Miočević, Milica; Valente, Matthew; Sleigh, Adriana; Garg, Bharti; McGinnis, Wendy; Kuehl, Hannah
2016-05-01
The SHIELD (Safety & Health Improvement: Enhancing Law Enforcement Departments) Study is a worksite wellness team-based intervention among police and sheriff departments assessing the program's effectiveness to reduce occupational risks and unhealthy lifestyle behaviors. The SHIELD program focused on improving diet, physical activity, body weight and sleep, and reducing the effects of unhealthy stress and behaviors, such as tobacco and substance abuse. The SHIELD team-based health promotion program was found to be feasible and effective at 6 months in improving diet, sleep, stress, and overall quality of life of law enforcement department personnel. Both intervention and control groups were followed for 24 months, and we report those durability findings, along with qualitative group interview results that provide insight into the changes of the long-term outcomes. Long-term effects were observed for consumption of fruits and vegetables, and there was some evidence for effects on tobacco and alcohol use. Assessment of dietary habits, physical activity behaviors, weight loss maintenance, and substance use is rare more than 1 year following an intervention, and in general, initial positive changes do not persist in prior research. The SHIELD program was feasible, effective, and durable for improving dietary changes. PMID:27158956
Method of characteristics - Based sensitivity calculations for international PWR benchmark
Suslov, I. R.; Tormyshev, I. V.; Komlev, O. G.
2013-07-01
Method to calculate sensitivity of fractional-linear neutron flux functionals to transport equation coefficients is proposed. Implementation of the method on the basis of MOC code MCCG3D is developed. Sensitivity calculations for fission intensity for international PWR benchmark are performed. (authors)
A method for calculating the productivity of cable communications networks
NASA Astrophysics Data System (ADS)
Shulikin, S. N.; Shulikina, M. S.; Maryin, S. S.; Vinogradova, D. V.; Zavgorodnyaya, M. E.
2016-04-01
A probabilistic-mathematical instrument was used to develop a method for calculating the productivity of a cable line. The effect of deviation of factors from data of recording devices was determined when identifying random stream characteristics. The developed method was used to perform predictive calculation of the productivity of the modern cable communication line.
Calculation methods for compressible turbulent boundary layers, 1976
NASA Technical Reports Server (NTRS)
Bushnell, D. M.; Cary, A. M., Jr.; Harris, J. E.
1977-01-01
Equations and closure methods for compressible turbulent boundary layers are discussed. Flow phenomena peculiar to calculation of these boundary layers were considered, along with calculations of three dimensional compressible turbulent boundary layers. Procedures for ascertaining nonsimilar two and three dimensional compressible turbulent boundary layers were appended, including finite difference, finite element, and mass-weighted residual methods.
Calculation of transonic flows using an extended integral equation method
NASA Technical Reports Server (NTRS)
Nixon, D.
1976-01-01
An extended integral equation method for transonic flows is developed. In the extended integral equation method velocities in the flow field are calculated in addition to values on the aerofoil surface, in contrast with the less accurate 'standard' integral equation method in which only surface velocities are calculated. The results obtained for aerofoils in subcritical flow and in supercritical flow when shock waves are present compare satisfactorily with the results of recent finite difference methods.
Iterative acceleration methods for Monte Carlo and deterministic criticality calculations
Urbatsch, T.J.
1995-11-01
If you have ever given up on a nuclear criticality calculation and terminated it because it took so long to converge, you might find this thesis of interest. The author develops three methods for improving the fission source convergence in nuclear criticality calculations for physical systems with high dominance ratios for which convergence is slow. The Fission Matrix Acceleration Method and the Fission Diffusion Synthetic Acceleration (FDSA) Method are acceleration methods that speed fission source convergence for both Monte Carlo and deterministic methods. The third method is a hybrid Monte Carlo method that also converges for difficult problems where the unaccelerated Monte Carlo method fails. The author tested the feasibility of all three methods in a test bed consisting of idealized problems. He has successfully accelerated fission source convergence in both deterministic and Monte Carlo criticality calculations. By filtering statistical noise, he has incorporated deterministic attributes into the Monte Carlo calculations in order to speed their source convergence. He has used both the fission matrix and a diffusion approximation to perform unbiased accelerations. The Fission Matrix Acceleration method has been implemented in the production code MCNP and successfully applied to a real problem. When the unaccelerated calculations are unable to converge to the correct solution, they cannot be accelerated in an unbiased fashion. A Hybrid Monte Carlo method weds Monte Carlo and a modified diffusion calculation to overcome these deficiencies. The Hybrid method additionally possesses reduced statistical errors.
Mainardi, E.; Premuda, F.; Lee, E.
2002-07-01
For heavy-ion beam driven inertial fusion ''liquid-protected'' reactor designs such as HYLIFE-II, a mixture of molten salts made of F{sup 10}, Li{sup -6}, Li{sup 7} and Be{sup 9} (called flibe) allows small chambers and final-focus magnets closer to the target with superconducting coils suffering higher radiation damage, though they can stand only a certain amount of energy deposited before quenching. This work has been primarily focusing on verifying that total energy deposited by fusion neutrons and induced gamma rays remain under such limit values and the final purpose is the optimization of the shielding of the magnetic lens system from the points of view of the geometrical configuration and of the physical nature of the materials adopted. The system is analyzed in terms of six geometrical models going from simplified up to much more realistic representations of a system of 192 beam lines, each focused by six magnets. A 3-D transport calculation of the radiation penetrating through ducts, that takes into account the complexity of the system, requires Monte Carlo methods. The quantities analyzed, using the two codes MCNP and TART include: neutron mean free path and total path length dependence on energy, energy deposited by neutrons and gamma photons, values of the total fluence integrated in the whole energy range, and the neutron spectrum in different zones of the system. The technical nature of the design problem and the methodology followed were presented in a previous paper by summarizing briefly the results for the deposited energy distribution on the six focal magnets. Now a much more extensive comparison of the performances of the two codes for different configurations of the system is discussed, separating the n and {gamma} contributions, in the light of the physical interpretation of the results in terms of first flight and of scattered neutron fluxes, of primary {gamma} and of secondary {gamma} generated by inelastically scattered or radiatively
ToA Coordinate Calculation Method Using a PID Algorithm
NASA Astrophysics Data System (ADS)
Hwang, Jae Ho; Kim, Jae Moung
This paper introduces a coordinate calculation method for a real-time locating system. A ToA algorithm is used to obtain the target node coordinates, but a conventional DC method, which incurs heavy calculation time, is not suitable for embedded systems. This paper proposes the use of a P-control in the PID control algorithm to resolve real-time locating system issues. Performance measures of the accumulated operator number and position error are evaluated. It is shown that the PID method has less calculation and more robust performance than the DC method.
Point-Kernel Shielding Code System.
1982-02-17
Version 00 QAD-BSA is a three-dimensional, point-kernel shielding code system based upon the CCC-48/QAD series. It is designed to calculate photon dose rates and heating rates using exponential attenuation and infinite medium buildup factors. Calculational provisions include estimates of fast neutron penetration using data computed by the moments method. Included geometry routines can describe complicated source and shield geometries. An internal library contains data for many frequently used structural and shielding materials, enabling the codemore » to solve most problems with only source strengths and problem geometry required as input. This code system adapts especially well to problems requiring multiple sources and sources with asymmetrical geometry. In addition to being edited separately, the total interaction rates from many sources may be edited at each detector point. Calculated photon interaction rates agree closely with those obtained using QAD-P5A.« less
A method of calculating the ultimate strength of continuous beams
NASA Technical Reports Server (NTRS)
Newlin, J A; Trayer, George W
1931-01-01
The purpose of this study was to investigate the strength of continuous beams after the elastic limit has been passed. As a result, a method of calculation, which is applicable to maximum load conditions, has been developed. The method is simpler than the methods now in use and it applies properly to conditions where the present methods fail to apply.
A Multigroup Method for the Calculation of Neutron Fluence with a Source Term
NASA Technical Reports Server (NTRS)
Heinbockel, J. H.; Clowdsley, M. S.
1998-01-01
Current research on the Grant involves the development of a multigroup method for the calculation of low energy evaporation neutron fluences associated with the Boltzmann equation. This research will enable one to predict radiation exposure under a variety of circumstances. Knowledge of radiation exposure in a free-space environment is a necessity for space travel, high altitude space planes and satellite design. This is because certain radiation environments can cause damage to biological and electronic systems involving both short term and long term effects. By having apriori knowledge of the environment one can use prediction techniques to estimate radiation damage to such systems. Appropriate shielding can be designed to protect both humans and electronic systems that are exposed to a known radiation environment. This is the goal of the current research efforts involving the multi-group method and the Green's function approach.
NASA Technical Reports Server (NTRS)
Christiansen, Eric L. (Inventor); Crews, Jeanne L. (Inventor)
2005-01-01
Flexible multi-shock shield system and method are disclosed for defending against hypervelocity particles. The flexible multi-shock shield system and method may include a number of flexible bumpers or shield layers spaced apart by one or more resilient support layers, all of which may be encapsulated in a protective cover. Fasteners associated with the protective cover allow the flexible multi-shock shield to be secured to the surface of a structure to be protected.
Self-shielding flex-circuit drift tube, drift tube assembly and method of making
Jones, David Alexander
2016-04-26
The present disclosure is directed to an ion mobility drift tube fabricated using flex-circuit technology in which every other drift electrode is on a different layer of the flex-circuit and each drift electrode partially overlaps the adjacent electrodes on the other layer. This results in a self-shielding effect where the drift electrodes themselves shield the interior of the drift tube from unwanted electro-magnetic noise. In addition, this drift tube can be manufactured with an integral flex-heater for temperature control. This design will significantly improve the noise immunity, size, weight, and power requirements of hand-held ion mobility systems such as those used for explosive detection.
Neutron streaming analysis for shield design of FMIT Facility
Carter, L.L.
1980-12-01
Applications of the Monte Carlo method have been summarized relevant to neutron streaming problems of interest in the shield design for the FMIT Facility. An improved angular biasing method has been implemented to further optimize the calculation of streaming and this method has been applied to calculate streaming within a double bend pipe.
Elongation method for electronic structure calculations of random DNA sequences.
Orimoto, Yuuichi; Liu, Kai; Aoki, Yuriko
2015-10-30
We applied ab initio order-N elongation (ELG) method to calculate electronic structures of various deoxyribonucleic acid (DNA) models. We aim to test potential application of the method for building a database of DNA electronic structures. The ELG method mimics polymerization reactions on a computer and meets the requirements for linear scaling computational efficiency and high accuracy, even for huge systems. As a benchmark test, we applied the method for calculations of various types of random sequenced A- and B-type DNA models with and without counterions. In each case, the ELG method maintained high accuracy with small errors in energy on the order of 10(-8) hartree/atom compared with conventional calculations. We demonstrate that the ELG method can provide valuable information such as stabilization energies and local densities of states for each DNA sequence. In addition, we discuss the "restarting" feature of the ELG method for constructing a database that exhaustively covers DNA species. PMID:26337429
Magnetic shielding for a spaceborne adiabatic demagnetization refrigerator (ADR)
NASA Technical Reports Server (NTRS)
Warner, Brent A.; Shirron, Peter J.; Castles, Stephen H.; Serlemitsos, Aristides T.
1991-01-01
The Goddard Space Flight Center has studied magnetic shielding for an adiabatic demagnetization refrigerator. Four types of shielding were studied: active coils, passive ferromagnetic shells, passive superconducting coils, and passive superconducting shells. The passive superconducting shells failed by allowing flux penetration. The other three methods were successful, singly or together. Experimental studies of passive ferromagnetic shielding are compared with calculations made using the Poisson Group of programs, distributed by the Los Alamos Accelerator Code Group of the Los Alamos National Laboratory. Agreement between calculation and experiment is good. The ferromagnetic material is a silicon iron alloy.
Yang, W.; Wu, H.; Cao, L.
2012-07-01
More and more MOX fuels are used in all over the world in the past several decades. Compared with UO{sub 2} fuel, it contains some new features. For example, the neutron spectrum is harder and more resonance interference effects within the resonance energy range are introduced because of more resonant nuclides contained in the MOX fuel. In this paper, the wavelets scaling function expansion method is applied to study the resonance behavior of plutonium isotopes within MOX fuel. Wavelets scaling function expansion continuous-energy self-shielding method is developed recently. It has been validated and verified by comparison to Monte Carlo calculations. In this method, the continuous-energy cross-sections are utilized within resonance energy, which means that it's capable to solve problems with serious resonance interference effects without iteration calculations. Therefore, this method adapts to treat the MOX fuel resonance calculation problem natively. Furthermore, plutonium isotopes have fierce oscillations of total cross-section within thermal energy range, especially for {sup 240}Pu and {sup 242}Pu. To take thermal resonance effect of plutonium isotopes into consideration the wavelet scaling function expansion continuous-energy resonance calculation code WAVERESON is enhanced by applying the free gas scattering kernel to obtain the continuous-energy scattering source within thermal energy range (2.1 eV to 4.0 eV) contrasting against the resonance energy range in which the elastic scattering kernel is utilized. Finally, all of the calculation results of WAVERESON are compared with MCNP calculation. (authors)
A Recursive Method for Calculating Certain Partition Functions.
ERIC Educational Resources Information Center
Woodrum, Luther; And Others
1978-01-01
Describes a simple recursive method for calculating the partition function and average energy of a system consisting of N electrons and L energy levels. Also, presents an efficient APL computer program to utilize the recursion relation. (Author/GA)
Comparison of finite-difference and analytic microwave calculation methods
Friedlander, F.I.; Jackson, H.W.; Barmatz, M.; Wagner, P.
1996-12-31
Normal modes and power absorption distributions in microwave cavities containing lossy dielectric samples were calculated for problems of interest in materials processing. The calculations were performed both using a commercially available finite-difference electromagnetic solver and by numerical evaluation of exact analytic expressions. Results obtained by the two methods applied to identical physical situations were compared. The studies validate the accuracy of the finite-difference electromagnetic solver. Relative advantages of the analytic and finite-difference methods are discussed.
Comparison of Fourier transform methods for calculating MTF
NASA Astrophysics Data System (ADS)
LaVeigne, Joseph D.; Burks, Stephen D.; Nehring, Brian
2008-04-01
Fourier transform methods common in infrared spectroscopy were applied to the problem of calculating the modulation transfer function (MTF) from a system's measured line spread function (LSF). Algorithms, including apodization and phase correction, are discussed in their application to remove unwanted noise from the higher frequency portion of the MTF curve. In general, these methods were found to significantly improve the calculated MTF. Apodization reduces the proportion of noise by discarding areas of the LSF where there is no appreciable signal. Phase correction significantly reduces the rectification of noise that occurs when the MTF is calculated by taking the power spectrum of the complex optical transfer function (OTF).
Turbomachinery flow calculation on unstructured grids using finite element method
NASA Astrophysics Data System (ADS)
Koschel, W.; Vornberger, A.
An explicit finite-element scheme based on a two-step Taylor-Galerkin algorithm allows the solution of the Euler and Navier-Stokes equations on unstructured grids. Mesh generation methods for unstructured grids are described which lead to efficient flow calculations. Turbulent flow is calculated by using an algebraic turbulence model. To test the numerical accuracy, a laminar and turbulent flow over a flat plate and the supersonic flow in a corner has been calculated. For validation the method is applied to the simulation of the inviscid flow through a transonic turbine cascade and the viscous flow through a subsonic turbine cascade.
Universal calculation formula and calibration method in Fourier transform profilometry
Wen Yongfu; Li Sikun; Cheng Haobo; Su Xianyu; Zhang Qican
2010-12-01
We propose a universal calculation formula of Fourier transform profilometry and give a strict theoretical analysis about the phase-height mapping relation. As the request on the experimental setup of the universal calculation formula is unconfined, the projector and the camera can be located arbitrarily to get better fringe information, which makes the operation flexible. The phase-height calibration method under the universal condition is proposed, which can avoid measuring the system parameters directly. It makes the system easy to manipulate and improves the measurement velocity. A computer simulation and experiment are conducted to verify its validity. The calculation formula and calibration method have been applied to measure an object of 22.00 mm maximal height. The relative error of the measurement result is only 0.59%. The experimental results prove that the three-dimensional shape of tested objects can be reconstructed exactly by using the calculation formula and calibration method, and the system has better universality.
NASA Astrophysics Data System (ADS)
Yu, Xiaozheng; Shen, Zhigang
2009-09-01
Ni-coated cenosphere particles were successfully fabricated by an ultrasonic-assisted magnetron sputtering equipment. Their surface morphology and microstructure were analyzed using field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). FE-SEM results indicate that the Ni films coated by magnetron sputtering are uniform and compact. Ni film uniformity was related with the sputtering power and a large uniform film could be achieved at lower sputtering power. XRD results imply that the Ni film coated on cenospheres was a face-centered cubic (fcc) structure and the crystallization of film sample increases with increasing the sputtering power. The electromagnetic interference (EMI) shielding effectiveness (SE) of Ni-coated cenosphere particles were measured to be 4-27 dB over a frequency range 80-100 GHz, higher than those of uncoated cenosphere particles. The higher sputtering power and Ni film thickness are the higher EMI SE of the specimens. Ni-coated cenosphere particles are most promising alternative candidates for millimeter wave EMI shielding due to their lightweight, low cost, ease of processing, high floating time, good dispersion and tunable conductivities as compared with typical electromagnetic wave countermeasure materials.
Experimental verification of a recursive method to calculate evapotranspiration
Technology Transfer Automated Retrieval System (TEKTRAN)
Recently, a recursive combination method (RCM) to calculate potential and crop evapotranspiration (ET) was given by Lascano and Van Bavel (Agron. J. 2007, 99:585–590). The RCM differs from the Penman-Monteith (PM) method, the main difference being that the assumptions made regarding the temperature ...
A Simple Method for Calculating Clebsch-Gordan Coefficients
ERIC Educational Resources Information Center
Klink, W. H.; Wickramasekara, S.
2010-01-01
This paper presents a simple method for calculating Clebsch-Gordan coefficients for the tensor product of two unitary irreducible representations (UIRs) of the rotation group. The method also works for multiplicity-free irreducible representations appearing in the tensor product of any number of UIRs of the rotation group. The generalization to…
New methods for neutron response calculations with MCNP
Hendricks, J.S.
1997-05-01
MCNP4B was released for international distribution in February, 1997. The author summarized the new MCNP4B features since the release of MCNP4A over three years earlier and compare some results. Then he describes new methods being developed for future code releases. The focus is methods and applications of ex-core neutron response calculations.
Pressure algorithm for elliptic flow calculations with the PDF method
NASA Technical Reports Server (NTRS)
Anand, M. S.; Pope, S. B.; Mongia, H. C.
1991-01-01
An algorithm to determine the mean pressure field for elliptic flow calculations with the probability density function (PDF) method is developed and applied. The PDF method is a most promising approach for the computation of turbulent reacting flows. Previous computations of elliptic flows with the method were in conjunction with conventional finite volume based calculations that provided the mean pressure field. The algorithm developed and described here permits the mean pressure field to be determined within the PDF calculations. The PDF method incorporating the pressure algorithm is applied to the flow past a backward-facing step. The results are in good agreement with data for the reattachment length, mean velocities, and turbulence quantities including triple correlations.
Calculation of Solar Radiation by Using Regression Methods
NASA Astrophysics Data System (ADS)
Kızıltan, Ö.; Şahin, M.
2016-04-01
In this study, solar radiation was estimated at 53 location over Turkey with varying climatic conditions using the Linear, Ridge, Lasso, Smoother, Partial least, KNN and Gaussian process regression methods. The data of 2002 and 2003 years were used to obtain regression coefficients of relevant methods. The coefficients were obtained based on the input parameters. Input parameters were month, altitude, latitude, longitude and landsurface temperature (LST).The values for LST were obtained from the data of the National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (NOAA-AVHRR) satellite. Solar radiation was calculated using obtained coefficients in regression methods for 2004 year. The results were compared statistically. The most successful method was Gaussian process regression method. The most unsuccessful method was lasso regression method. While means bias error (MBE) value of Gaussian process regression method was 0,274 MJ/m2, root mean square error (RMSE) value of method was calculated as 2,260 MJ/m2. The correlation coefficient of related method was calculated as 0,941. Statistical results are consistent with the literature. Used the Gaussian process regression method is recommended for other studies.
Refinement of thermal imager minimum resolvable temperature difference calculating method
NASA Astrophysics Data System (ADS)
Kolobrodov, V. G.; Mykytenko, V. I.
2015-11-01
Calculating methods, which accurately predict minimum resolvable temperature difference (MRTD), are of significant interest for many years. The article deals with improvement the accuracy of determining the thermal imaging system MRTD by elaboration the visual perception model. We suggest MRTD calculating algorithm, which is based on a reliable approximation of the human visual system modulation transfer function (MTF) proposed by N. Nill. There was obtained a new expression for the bandwidth evaluation, which is independent of angular size of the Foucault bar target.
Method and models for R-curve instability calculations
NASA Technical Reports Server (NTRS)
Orange, Thomas W.
1990-01-01
This paper presents a simple method for performing elastic R-curve instability calculations. For a single material-structure combination, the calculations can be done on some pocket calculators. On microcomputers and larger, it permits the development of a comprehensive program having libraries of driving force equations for different configurations and R-curve model equations for different materials. The paper also presents several model equations for fitting to experimental R-curve data, both linear elastic and elastoplastic. The models are fit to data from the literature to demonstrate their viability.
Method and models for R-curve instability calculations
NASA Technical Reports Server (NTRS)
Orange, Thomas W.
1988-01-01
This paper presents a simple method for performing elastic R-curve instability calculations. For a single material-structure combination, the calculations can be done on some pocket calculators. On microcomputers and larger, it permits the development of a comprehensive program having libraries of driving force equations for different configurations and R-curve model equations for different materials. The paper also presents several model equations for fitting to experimental R-curve data, both linear elastic and elastoplastic. The models are fit to data from the literature to demonstrate their viability.
Armstrong, Jerawan C.; Favorite, Jeffrey A.
2012-06-20
The Levenberg-Marquardt (or simply Marquardt) and differential evolution (DE) optimization methods were recently applied to solve inverse transport problems. The Marquardt method is fast but convergence of the method is dependent on the initial guess. While it has been shown to work extremely well at finding an optimum independent of the initial guess, the DE method does not provide a global optimal solution in some problems. In this paper, we apply the Mesh Adaptive Direct Search (MADS) algorithm to solve the inverse problem of material interface location identification in one-dimensional spherical radiation source/shield systems, and we compare the results obtained by MADS to those obtained by Levenberg-Marquardt and DE.
Shape integral method for magnetospheric shapes. [boundary layer calculations
NASA Technical Reports Server (NTRS)
Michel, F. C.
1979-01-01
A method is developed for calculating the shape of any magnetopause to arbitrarily high precision. The method uses an integral equation which is evaluated for a trial shape. The resulting values of the integral equation as a function of auxiliary variables indicate how close one is to the desired solution. A variational method can then be used to improve the trial shape. Some potential applications are briefly mentioned.
The heterogeneous anti-radiation shield for spacecraft*
NASA Astrophysics Data System (ADS)
Telegin, S. V.; Draganyuk, O. N.
2016-04-01
The paper deals with modeling of elemental composition and properties of heterogeneous layers in multilayered shields to protect spacecraft onboard equipment from radiation emitted by the natural Earth’s radiation belt. This radiation causes malfunctioning of semiconductor elements in electronic equipment and may result in a failure of the spacecraft as a whole. We consider four different shield designs and compare them to the most conventional radiation-protective material for spacecraft - aluminum. Out of light and heavy chemical elements we chose the materials with high reaction cross sections and low density. The mass attenuation coefficient of boron- containing compounds is 20% higher than that of aluminum. Heterogeneous shields consist of three layers: a glass cloth, borated material, and nickel. With a protective shield containing heavy metal the output bremsstrahlung can be reduced. The amount of gamma rays that succeed to penetrate the shield is 4 times less compared to aluminum. The shields under study have the thicknesses of 5.95 and 6.2 mm. A comparative analysis of homogeneous and multilayered protective coatings of the same chemical composition has been performed. A heterogeneous protective shield has been found to be advantageous in weight and shielding properties over its homogeneous counterparts and aluminum. The dose characteristics and transmittance were calculated by the Monte Carlo method. The results of our study lead us to conclude that a three-layer boron carbide shield provides the most effective protection from radiation. This shield ensures twice as low absorbed dose and 4 times less the number of penetrated gamma-ray photons compared to its aluminum analogue. Moreover, a heterogeneous shield will have a weight 10% lighter than aluminum, with the same attenuation coefficient of the electron flux. Such heterogeneous shields can be used to protect spacecraft launched to geostationary orbit. Furthermore, a protective boron-containing and
A method for trap factor calculation and its effect
Xinguo, Z. )
1992-01-01
The accumulations and distributions of oil and gas in fault-block oil field are greatly controlled by various faults. Such oil field is characterized by complicated structure, multiple reservoirs, complex contact between oil and water, and big oil abundance difference among the reservoirs. The properties bring many troubles to the exploration and development of such oil and gas fields. There is no uniform statistical calculation standard that is special for multitudinous fault block traps. Common trap factor calculation methods are suitable for anticlinal trap, but they are not applicable to complicated fault block traps. In this paper, a new factor calculation method for fault traps in which there are quite thick reservoir and overlying formation is presented on the basis of fault trap property and interrelations among the factors which influence trap characteristics. Quite accurate closing areas of oil traps have been obtained by using the method in Dongpu seg.
Calculation of infrared system operating distance by spectral bisection method
NASA Astrophysics Data System (ADS)
Zhao, Yu; Wu, Ping; Sun, Wenfang
2014-03-01
During the transmission of infrared radiation, the atmospheric transmittance could be a complex parameter due to the absorbing and scattering of atmosphere, as well as the influences from the environment and transmission distance. With the help of a spectral bisection method, a new assessing formula and solution is raised by calculating the operating distance of infrared system. In the small segments, MODTRAN can be used to figure out the percentage of penetration, which is called by advanced program, so as to get the infrared radiation in those segments. The calculated data of the segments were summed up and used to calculate the operating distance of the infrared system. Compared with the conventional calculation methods that the transmittance was used as a constant or a average, The calculation precise of the operating distance is highly increased by this method the results of all small segments by comparing with the traditional methods. The whole computing process becomes more clear and effective by taking the influences from visibility of atmosphere, altitude, targets zenith angle and spatial frequency into consideration, and by building an instant monitoring system of the operating distance. The final computing result and real effecting distance are based on the general simulation for penetration rate and the tendency of operating distance in all conditions.
New methods for calculating short-wave radio paths
NASA Astrophysics Data System (ADS)
Popov, A. V.; Tsedilina, E. E.; Cherkashin, Iu. N.
Recent research on the calculation of short-wave paths at IZMIRAN (the Soviet Institute for the Study of Terrestrial Magnetism, the Ionosphere, and the Propagation of Radio Waves) is reviewed. Particular attention is given to: (1) the development of approximate analytical methods for ray-tracing calculations and for determining the geometrical-optics characteristics of a radio signal in a horizontally irregular ionosphere; (2) investigations of the long-range and short-wave propagation of decametric waves; and (3) the development of a parabolic-equation method for considering diffraction and scattering in a medium with regular and random irregularities.
A simplified spherical harmonic method for coupled electron-photon transport calculations
Josef, J.A.
1997-12-01
In this thesis the author has developed a simplified spherical harmonic method (SP{sub N} method) and associated efficient solution techniques for 2-D multigroup electron-photon transport calculations. The SP{sub N} method has never before been applied to charged-particle transport. He has performed a first time Fourier analysis of the source iteration scheme and the P{sub 1} diffusion synthetic acceleration (DSA) scheme applied to the 2-D SP{sub N} equations. The theoretical analyses indicate that the source iteration and P{sub 1} DSA schemes are as effective for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. In addition, he has applied an angular multigrid acceleration scheme, and computationally demonstrated that it performs as well as for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. It has previously been shown for 1-D S{sub N} calculations that this scheme is much more effective than the DSA scheme when scattering is highly forward-peaked. The author has investigated the applicability of the SP{sub N} approximation to two different physical classes of problems: satellite electronics shielding from geomagnetically trapped electrons, and electron beam problems.
Composite electron propagator methods for calculating ionization energies
NASA Astrophysics Data System (ADS)
Díaz-Tinoco, Manuel; Dolgounitcheva, O.; Zakrzewski, V. G.; Ortiz, J. V.
2016-06-01
Accurate ionization energies of molecules may be determined efficiently with composite electron-propagator (CEP) techniques. These methods estimate the results of a calculation with an advanced correlation method and a large basis set by performing a series of more tractable calculations in which large basis sets are used with simpler approximations and small basis sets are paired with more demanding correlation techniques. The performance of several CEP methods, in which diagonal, second-order electron propagator results with large basis sets are combined with higher-order results obtained with smaller basis sets, has been tested for the ionization energies of closed-shell molecules from the G2 set. Useful compromises of accuracy and computational efficiency employ complete-basis-set extrapolation for second-order results and small basis sets in third-order, partial third-order, renormalized partial-third order, or outer valence Green's function calculations. Analysis of results for vertical as well as adiabatic ionization energies leads to specific recommendations on the best use of regular and composite methods. Results for 22 organic molecules of interest in the design of photovoltaic devices, benzo[a]pyrene, Mg-octaethylporphyrin, and C60 illustrate the capabilities of CEP methods for calculations on large molecules.
Composite electron propagator methods for calculating ionization energies.
Díaz-Tinoco, Manuel; Dolgounitcheva, O; Zakrzewski, V G; Ortiz, J V
2016-06-14
Accurate ionization energies of molecules may be determined efficiently with composite electron-propagator (CEP) techniques. These methods estimate the results of a calculation with an advanced correlation method and a large basis set by performing a series of more tractable calculations in which large basis sets are used with simpler approximations and small basis sets are paired with more demanding correlation techniques. The performance of several CEP methods, in which diagonal, second-order electron propagator results with large basis sets are combined with higher-order results obtained with smaller basis sets, has been tested for the ionization energies of closed-shell molecules from the G2 set. Useful compromises of accuracy and computational efficiency employ complete-basis-set extrapolation for second-order results and small basis sets in third-order, partial third-order, renormalized partial-third order, or outer valence Green's function calculations. Analysis of results for vertical as well as adiabatic ionization energies leads to specific recommendations on the best use of regular and composite methods. Results for 22 organic molecules of interest in the design of photovoltaic devices, benzo[a]pyrene, Mg-octaethylporphyrin, and C60 illustrate the capabilities of CEP methods for calculations on large molecules. PMID:27305999
Snyder, Keith W.
2002-01-01
A modular system for containing projectiles has a sheet of material including at least a polycarbonate layer held by a metal frame having a straight frame member corresponding to each straight edge of the sheet. Each frame member has a U-shaped shield channel covering and holding a straight edge of the sheet and an adjacent U-shaped clamp channel rigidly held against the shield channel. A flexible gasket separates each sheet edge from its respective shield channel; and each frame member is fastened to each adjacent frame member only by clamps extending between adjacent clamp channels.
Numerical Method for the Astronomical Almanac and Orbit Calculations
NASA Astrophysics Data System (ADS)
Kim, Kap-Sung
1993-12-01
We have calculated the astronomical almanac 1994 and simulated the trajectory of a satellite orbit considering all perturbative forces with various initial conditions. In this work, Gauss Jackson multistep integration method has been used to calculate our basic equation of motion with high numerical accuracy. It has been found that our results agree well with the Astronomical Almanac Data distributed by JPL of NASA and the orbit simulations have been carried out with fast speed, stability and excellent round-off error accumulation, comparing with other numerical methods. In order to be carried out our works on almanac and orbit calculations easily by anyone who uses a personal computer, we have made a computer program on graphical user interface to provide various menus for detail works selected by a mouse.
A method for calculating externally blown flap noise
NASA Technical Reports Server (NTRS)
Fink, M. R.
1978-01-01
Several basic noise components were described. These components are: (1) compact lift dipoles associated with the wing and flaps; (2) trailing edge noise associated with the last trailing edge; and (3) quadrupole noise associated with the undeflected exhaust jet and the free jet located downstream of the trailing edge. These noise components were combined to allow prediction of directivity and spectra for under the wing (UTW) slotted flaps with conventional or mixer nozzles, UTW slotless flaps, upper surface blowing (USB) slotless flaps, and engine in front of the wing slotted flaps. A digital computer program listing was given for this calculation method. Directivities and spectra calculated by this method were compared with free field data for UTW and USB configurations. The UTRC method best predicted the details of the measured noise emission, but the ANOP method best estimated the noise levels directly below these configurations.
An Annotated Bibliography of the Chisanbop Method of Finger Calculation.
ERIC Educational Resources Information Center
Dougherty, Mary K.
The term Chisanbop is the trademark for the finger calculation method originally developed by a Korean, Sung Jin Pai. It was refined and simplified by his son, Hang Young Pai, who introduced the technique to the United States in 1976. This annotated bibliography has been organized in five categories. Readings in the first category, Historical…
Further Stable methods for the calculation of partition functions
Wilson, B G; Gilleron, F; Pain, J
2007-06-27
The extension to recursion over holes of the Gilleron and Pain method for calculating partition functions of a canonical ensemble of non-interacting bound electrons is presented as well as a generalization for the efficient computation of collisional line broadening.
Emergy Algebra: Improving Matrix Methods for Calculating Tranformities
Transformity is one of the core concepts in Energy Systems Theory and it is fundamental to the calculation of emergy. Accurate evaluation of transformities and other emergy per unit values is essential for the broad acceptance, application and further development of emergy method...
Calculating Resonance Positions and Widths Using the Siegert Approximation Method
ERIC Educational Resources Information Center
Rapedius, Kevin
2011-01-01
Here, we present complex resonance states (or Siegert states) that describe the tunnelling decay of a trapped quantum particle from an intuitive point of view that naturally leads to the easily applicable Siegert approximation method. This can be used for analytical and numerical calculations of complex resonances of both the linear and nonlinear…
30 CFR 282.41 - Method of royalty calculation.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Method of royalty calculation. 282.41 Section 282.41 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE OPERATIONS IN THE OUTER CONTINENTAL SHELF FOR MINERALS OTHER THAN OIL, GAS, AND SULPHUR Payments § 282.41...
LEGO-Method--New Strategy for Chemistry Calculation
ERIC Educational Resources Information Center
Molnar, Jozsef; Molnar-Hamvas, Livia
2011-01-01
The presented strategy of chemistry calculation is based on mole-concept, but it uses only one fundamental relationship of the amounts of substance as a basic panel. The name of LEGO-method comes from the famous toy of LEGO[R] because solving equations by grouping formulas is similar to that. The relations of mole and the molar amounts, as small…
NASA Technical Reports Server (NTRS)
Fieno, D.
1972-01-01
Perturbation theory formulas were derived and applied to determine changes in neutron and gamma-ray doses due to changes in various radiation shield layers for fixed sources. For a given source and detector position, the perturbation method enables dose derivatives with respect to density, or equivalently thickness, for every layer to be determined from one forward and one inhomogeneous adjoint calculation. A direct determination without the perturbation approach would require two forward calculations to evaluate the dose derivative due to a change in a single layer. Hence, the perturbation method for obtaining dose derivatives requires fewer computations for design studies of multilayer shields. For an illustrative problem, a comparison was made of the fractional change in the dose per unit change in the thickness of each shield layer in a two-layer spherical configuration as calculated by perturbation theory and by successive direct calculations; excellent agreement was obtained between the two methods.
NASA Astrophysics Data System (ADS)
Li, R.; Bohn, C. L.; Bisognano, J. J.
1997-05-01
There have been several studies([1] J. S. Nodvick and D. S. Saxon, Phys. Rev.) 96, 180 (1954); [2] S. A. Kheifets and B. Zotter, CERN SL-95-92 (AP), 1995; [3] B. Murphy, S. Krinsky, and R. L. Gluckstern, Phys. Rev. E 35, 2584 (1996). on the shielding effect of the coherent synchrotron radiation (CSR) emitted by a Gaussian bunch on a circular orbit in the center plane between two parallel plates. A functional dependence of the beam and machine parameters was given in [2] using the asymptotic analysis in the frequency domain. It indicates the shielded CSR mainly arises from harmonics n_th < n < n_c, where the threshold harmonic is n_th = √2/3(π ρ /h)^3/2, and harmonic cutoff is nc = ρ/σ (ρ: bend radius, h: spacing between plates, σ_s: bunch rms length). In this paper, we extend the frequency domain analysis to the parameter regime n_th > n_c, and the result is compared with the steady state CSR power obtained using the image charge method.
Iron shielded MRI optimization
NASA Astrophysics Data System (ADS)
Borghi, C. A.; Fabbri, M.
1998-09-01
The design of the main current systems of an actively shielded and of an iron shielded MRI device for nuclear resonance imaging, is considered. The model for the analysis of the magnetic induction produced by the current system, is based on the combination of a Boundary Element technique and of the integration of two Fredholm integral equations of the first and the second kind. The equivalent current magnetization model is used for the calculation of the magnetization produced by the iron shield. High field uniformity in a spherical region inside the device, and a low stray field in the neighborhood of the device are required. In order to meet the design requirements a multi-objective global minimization problem is solved. The minimization method is based on the combination of the filled function technique and the (1+1) evolution strategy algorithm. The multi-objective problem is treated by means of a penalty method. The actively shielded MRI system results to utilize larger amount of conductor and produce higher magnetic energy than the iron shield device. On veut étudier le projet du système des courants principaux d'un MRI à écran en fer et d'un MRI à écran actif. Le modèle d'analyse du champ magnétique produit par le système de courants est basé sur la combinaison d'une technique Boundary Element et de l'intégration de deux équations intégrales de Fredholm de première et de seconde sorte. On utilise pour calculer la magnétisation produite par l'écran en fer le modèle à cou rants de magné ti sa tion équivalents. On exige une élévation uniforme du champ dans une région sphérique au cœur de l'appareil et un bas champ magnétique dispersé à proximité de l'appareil. Dans le but de répondre aux impératifs du projet, on va résoudre un problème multiobjectif de minimisation globale. On utilise une technique de minimisation obtenue par la combinaison des méthodes “Filled Function” et “(1+1) Evolution Strategy”. Le probl
Magnetic Shield for Adiabatic Demagnetization Refrigerators (ADR)
NASA Technical Reports Server (NTRS)
Chui, Talso C.; Haddad, Nicolas E.
2013-01-01
A new method was developed for creating a less expensive shield for ADRs using 1018 carbon steel. This shield has been designed to have similar performance to the expensive vanadium permendur shields, but the cost is 30 to 50% less. Also, these shields can be stocked in a variety of sizes, eliminating the need for special forgings, which also greatly reduces cost.
Wigner, E.P.; Ohlinger, L.E.; Young, G.J.; Weinberg, A.M.
1959-02-17
Radiation shield construction is described for a nuclear reactor. The shield is comprised of a plurality of steel plates arranged in parallel spaced relationship within a peripheral shell. Reactor coolant inlet tubes extend at right angles through the plates and baffles are arranged between the plates at right angles thereto and extend between the tubes to create a series of zigzag channels between the plates for the circulation of coolant fluid through the shield. The shield may be divided into two main sections; an inner section adjacent the reactor container and an outer section spaced therefrom. Coolant through the first section may be circulated at a faster rate than coolant circulated through the outer section since the area closest to the reactor container is at a higher temperature and is more radioactive. The two sections may have separate cooling systems to prevent the coolant in the outer section from mixing with the more contaminated coolant in the inner section.
Improved numerical method for subchannel cross-flow calculations
Kaya, S.; Anghaie, S.
1986-01-01
COBRA-OSU is a fast running computer code for coupled kinetic and thermal-hydraulic analysis of nuclear reactor core subchannels, currently under development at Oregon State University. This code is a modified version of COBRA-IV with two major improved features. First, COBRA-OSU uses the Gaussian elimination method instead of Gauss-Seidel iteration for subchannel cross-flow calculation. Second, COBRA-OSU has an additional model for regionwise point reactor kinetics which includes all major feedback reactivity effects on calculation of the axial power profile during the course of a transient. This paper summarizes the improved numerical features of the COBRA-OSU code.
Real-space method for highly parallelizable electronic transport calculations
NASA Astrophysics Data System (ADS)
Feldman, Baruch; Seideman, Tamar; Hod, Oded; Kronik, Leeor
2014-07-01
We present a real-space method for first-principles nanoscale electronic transport calculations. We use the nonequilibrium Green's function method with density functional theory and implement absorbing boundary conditions (ABCs, also known as complex absorbing potentials, or CAPs) to represent the effects of the semi-infinite leads. In real space, the Kohn-Sham Hamiltonian matrix is highly sparse. As a result, the transport problem parallelizes naturally and can scale favorably with system size, enabling the computation of conductance in relatively large molecular junction models. Our use of ABCs circumvents the demanding task of explicitly calculating the leads' self-energies from surface Green's functions, and is expected to be more accurate than the use of the jellium approximation. In addition, we take advantage of the sparsity in real space to solve efficiently for the Green's function over the entire energy range relevant to low-bias transport. We illustrate the advantages of our method with calculations on several challenging test systems and find good agreement with reference calculation results.
Accelerating molecular property calculations with nonorthonormal Krylov space methods.
Furche, Filipp; Krull, Brandon T; Nguyen, Brian D; Kwon, Jake
2016-05-01
We formulate Krylov space methods for large eigenvalue problems and linear equation systems that take advantage of decreasing residual norms to reduce the cost of matrix-vector multiplication. The residuals are used as subspace basis without prior orthonormalization, which leads to generalized eigenvalue problems or linear equation systems on the Krylov space. These nonorthonormal Krylov space (nKs) algorithms are favorable for large matrices with irregular sparsity patterns whose elements are computed on the fly, because fewer operations are necessary as the residual norm decreases as compared to the conventional method, while errors in the desired eigenpairs and solution vectors remain small. We consider real symmetric and symplectic eigenvalue problems as well as linear equation systems and Sylvester equations as they appear in configuration interaction and response theory. The nKs method can be implemented in existing electronic structure codes with minor modifications and yields speed-ups of 1.2-1.8 in typical time-dependent Hartree-Fock and density functional applications without accuracy loss. The algorithm can compute entire linear subspaces simultaneously which benefits electronic spectra and force constant calculations requiring many eigenpairs or solution vectors. The nKs approach is related to difference density methods in electronic ground state calculations and particularly efficient for integral direct computations of exchange-type contractions. By combination with resolution-of-the-identity methods for Coulomb contractions, three- to fivefold speed-ups of hybrid time-dependent density functional excited state and response calculations are achieved. PMID:27155623
Accelerating molecular property calculations with nonorthonormal Krylov space methods
NASA Astrophysics Data System (ADS)
Furche, Filipp; Krull, Brandon T.; Nguyen, Brian D.; Kwon, Jake
2016-05-01
We formulate Krylov space methods for large eigenvalue problems and linear equation systems that take advantage of decreasing residual norms to reduce the cost of matrix-vector multiplication. The residuals are used as subspace basis without prior orthonormalization, which leads to generalized eigenvalue problems or linear equation systems on the Krylov space. These nonorthonormal Krylov space (nKs) algorithms are favorable for large matrices with irregular sparsity patterns whose elements are computed on the fly, because fewer operations are necessary as the residual norm decreases as compared to the conventional method, while errors in the desired eigenpairs and solution vectors remain small. We consider real symmetric and symplectic eigenvalue problems as well as linear equation systems and Sylvester equations as they appear in configuration interaction and response theory. The nKs method can be implemented in existing electronic structure codes with minor modifications and yields speed-ups of 1.2-1.8 in typical time-dependent Hartree-Fock and density functional applications without accuracy loss. The algorithm can compute entire linear subspaces simultaneously which benefits electronic spectra and force constant calculations requiring many eigenpairs or solution vectors. The nKs approach is related to difference density methods in electronic ground state calculations and particularly efficient for integral direct computations of exchange-type contractions. By combination with resolution-of-the-identity methods for Coulomb contractions, three- to fivefold speed-ups of hybrid time-dependent density functional excited state and response calculations are achieved.
[General calculation method of diffraction efficiency of concave blazed gratings].
Li, Ting; Huang, Yuan-Shen; Xu, Bang-Lian; Li, Bai-Cheng; Zhang, Da-Wei; Tao, Chun-Xian; Ling, Jin-Zhong; Zhuang, Song-Lin
2013-07-01
In order to make diffraction energy of concave gratings more concentrated in the desired order, the present paper puts forward that the concave blazed grating with variable groove angles could be fabricated on the concave substrates by mechanical ruling method, and the theoretical method of simultaneously calculating the diffraction efficiency in the main section and non-main section is deduced by using Fresnel-Kirchhoff's diffraction formula, which makes up the shortage of the diffraction efficiency calculated only in the main section. Finally, the diffraction efficiency curves varied with wavelength is simulated by Matlab software, and the variation laws of the diffraction efficiency are compared for different production methods and application parameters, which provides a valuable reference for the design and production of the concave gratings. PMID:24059218
A simplified spherical harmonic method for coupled electron-photon transport calculations
Josef, J.A.
1996-12-01
In this thesis we have developed a simplified spherical harmonic method (SP{sub N} method) and associated efficient solution techniques for 2-D multigroup electron-photon transport calculations. The SP{sub N} method has never before been applied to charged-particle transport. We have performed a first time Fourier analysis of the source iteration scheme and the P{sub 1} diffusion synthetic acceleration (DSA) scheme applied to the 2-D SP{sub N} equations. Our theoretical analyses indicate that the source iteration and P{sub 1} DSA schemes are as effective for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. Previous analyses have indicated that the P{sub 1} DSA scheme is unstable (with sufficiently forward-peaked scattering and sufficiently small absorption) for the 2-D S{sub N} equations, yet is very effective for the 1-D S{sub N} equations. In addition, we have applied an angular multigrid acceleration scheme, and computationally demonstrated that it performs as well for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. It has previously been shown for 1-D S{sub N} calculations that this scheme is much more effective than the DSA scheme when scattering is highly forward-peaked. We have investigated the applicability of the SP{sub N} approximation to two different physical classes of problems: satellite electronics shielding from geomagnetically trapped electrons, and electron beam problems. In the space shielding study, the SP{sub N} method produced solutions that are accurate within 10% of the benchmark Monte Carlo solutions, and often orders of magnitude faster than Monte Carlo. We have successfully modeled quasi-void problems and have obtained excellent agreement with Monte Carlo. We have observed that the SP{sub N} method appears to be too diffusive an approximation for beam problems. This result, however, is in agreement with theoretical expectations.
A Graphical Method for Calculating Reflection Errors in Radiation Thermometry
NASA Astrophysics Data System (ADS)
White, D. R.; Saunders, P.
2008-02-01
This article presents a graphical method to calculate reflection corrections for radiation thermometry. The method is based on the observation that the measured radiance of a target is a linear combination of radiances dependent on the emissivity of the target. The method is most easily implemented as a nomogram, enabling thermometer users to estimate reflection corrections immediately when measurements are taken. The nomogram also provides a visual means of explaining the impact of reflection errors on measurements and for explaining the impact of measurement uncertainties on temperature measurements corrected for reflections.
NASA Astrophysics Data System (ADS)
Hamaya, S.; Maeda, H.; Funaki, M.; Fukui, H.
2008-12-01
The relativistic calculation of nuclear magnetic shielding tensors in hydrogen halides is performed using the second-order regular approximation to the normalized elimination of the small component (SORA-NESC) method with the inclusion of the perturbation terms from the metric operator. This computational scheme is denoted as SORA-Met. The SORA-Met calculation yields anisotropies, Δσ =σ∥-σ⊥, for the halogen nuclei in hydrogen halides that are too small. In the NESC theory, the small component of the spinor is combined to the large component via the operator σ⃗ṡπ⃗U/2c, in which π⃗=p⃗+A⃗, U is a nonunitary transformation operator, and c ≅137.036 a.u. is the velocity of light. The operator U depends on the vector potential A⃗ (i.e., the magnetic perturbations in the system) with the leading order c-2 and the magnetic perturbation terms of U contribute to the Hamiltonian and metric operators of the system in the leading order c-4. It is shown that the small Δσ for halogen nuclei found in our previous studies is related to the neglect of the U(0,1) perturbation operator of U, which is independent of the external magnetic field and of the first order with respect to the nuclear magnetic dipole moment. Introduction of gauge-including atomic orbitals and a finite-size nuclear model is also discussed.
PX and PXT: New Methods for Calculating Shoreline Change Rates
NASA Astrophysics Data System (ADS)
Genz, A. S.; Frazer, L. N.; Fletcher, C. H.; Romine, B. M.; Barbee, M. M.; Lim, S.; Dyer, M.
2007-12-01
It is imperative that coastal erosion studies produce valid erosion rates and erosion hazard predictions to aid in the development of public policy and protect coastal resources. Currently, the Single-Transect method is the most common shoreline change model, which calculates a rate at each shore-normal transect without regard to influences of data from adjacent transects along a beach. Improving on Single-Transect, the University of Hawaii Coastal Geology Group has developed the PX (Polynomial in distance X) and PXT (Polynomial in distance X and Time) shoreline change rate calculation methods, which model all the shoreline positions within a beach simultaneously using polynomial techniques. PX is a special case of PXT that models shoreline change rates spatially along a beach. PXT not only models the shoreline change spatially, but it lets the rate change with time (acceleration). This is an important advance, as beaches may not erode or accrete at a constant (linear) rate. A linear sum of basis functions characterizes the shoreline change rate for both PX and PXT. These methods are an improvement on previous methods as they produce more meaningful, i.e., statistically significant rates and erosion hazard predictions. To date, PX and PXT improve the significance in the rate by 25% on Maui. We use an information criterion (gMDL) to (1) identify the number of coefficients of the basis functions that are needed to describe shoreline change in PX and PXT, and (2) compare different methods to determine which method best describes shoreline change. We present an overview of the PX and PXT methods and results from a shoreline change study of the beaches of southeast Oahu, Hawaii, utilizing these rate calculation methods.
NASA Technical Reports Server (NTRS)
Benton, E. V.; Frank, A. L.; Benton, E. R.; Marenny, A. M.; Nymmik, R. A.; Suslov, A. A.
1995-01-01
Fluxes of cosmic ray particles with different LET values were measured on board the COSMOS-2044 biosatellite under various thicknesses of shielding by stacks of CR-39 and nitrocellulose plastic nuclear track detectors (mounted outside the satellite). The component composition of the particles detected under shieldings of 0.1-2.5 g cm(exp -2) is verified by comparing experimental data with the results of model simulations of the fluxes of galactic cosmic ray particles and of radiation belt protons.
NASA Technical Reports Server (NTRS)
Marenny, A. M.; Nymmik, R. A.; Suslov, A. A.; Benton, E. V.; Frank, A. L.; Benton, E. R.
1992-01-01
Fluxes of cosmic ray particles with different LET values were measured on board the Cosmos-2044 biosatellite under various thicknesses of shielding by stacks of CR-39 and nitrocellulose plastic nuclear track detectors (mounted outside the satellite). The component composition of the particles detected under shieldings of 0.1-2.5 g cm-2 is verified by comparing experimental data with the results of model simulations of the fluxes of galactic cosmic ray particles and of radiation belt protons.
Magsat investigation. [Canadian shield
NASA Technical Reports Server (NTRS)
Hall, D. H. (Principal Investigator)
1980-01-01
A computer program was prepared for modeling segments of the Earth's crust allowing for heterogeneity in magnetization in calculating the Earth's field at Magsat heights. This permits investigation of a large number of possible models in assessing the magnetic signatures of subprovinces of the Canadian shield. The fit between the model field and observed fields is optimized in a semi-automatic procedure.
Tumor dosimetry in radioimmunotherapy: Methods of calculation for beta particles
Leichner, P.K. ); Kwok, C.S. )
1993-03-01
Calculational methods of beta-particle dosimetry in radioimmunotherapy (RIT) are reviewed for clinical and experimental studies and computer modeling of tumors. In clinical studies, absorbed-dose estimates are usually based on the [ital in]-[ital vivo] quantitation of the activity in tumors from gamma camera images. Because of the limited spatial resolution of gamma cameras, clinical dosimetry is necessarily limited to the macroscopic level (macrodosimetry) and the MIRD formalism for absorbed-dose calculations is appropriate. In experimental RIT, tumor dimensions are often comparable to or smaller than the beta-particle range of commonly used radionuclides (for example, [sup 131]I, [sup 67]Cu, [sup 186]Re, [sup 188]Re, [sup 90]Y) and deviations from the equilibrium dose must be taken into account in absorbed-dose calculations. Additionally, if small tumors are growing rapidly at the time of RIT, the effects of tumor growth will need to be included in absorbed-dose estimates. In computer modeling of absorbed-dose distributions, analytical, numerical, and Monte Carlo methods have been used to investigate the consequences of uniform and nonuniform activity distributions and the effects of inhomogeneous media. Measurements and calculations of the local absorbed dose at the multicellular level have shown that variations in this dose are large. Knowledge of the absorbed dose is essential for any form of radiotherapy. Therefore, it is important that clinical, experimental, and theoretical investigations continue to provide information on tumor dosimetry that is necessary for a better understanding of the radiobiological effects of RIT.
Radiation shielding effectiveness of newly developed superconductors
NASA Astrophysics Data System (ADS)
Singh, Vishwanath P.; Medhat, M. E.; Badiger, N. M.; Saliqur Rahman, Abu Zayed Mohammad
2015-01-01
Gamma ray shielding effectiveness of superconductors with a high mass density has been investigated. We calculated the mass attenuation coefficients, the mean free path (mfp) and the exposure buildup factor (EBF). The gamma ray EBF was computed using the Geometric Progression (G-P) fitting method at energies 0.015-15 MeV, and for penetration depths up to 40 mfp. The fast-neutron shielding effectiveness has been characterized by the effective neutron removal cross-section of the superconductors. It is shown that CaPtSi3, CaIrSi3, and Bi2Sr2Ca1Cu2O8.2 are superior shielding materials for gamma rays and Tl0.6Rb0.4Fe1.67Se2 for fast neutrons. The present work should be useful in various applications of superconductors in fusion engineering and design.
Implicit calculations of transonic flows using monotone methods
NASA Astrophysics Data System (ADS)
Goorjian, P. M.; van Buskirk, R.
1981-01-01
Implicit approximate-factorization algorithms have been developed that use monotone methods for the calculation of steady and unsteady transonic flows governed by the small-disturbance-potential equation. These algorithms use the new Engquist-Osher switch in the type-dependent differencing in place of the standard Murman-Cole switch. The resulting algorithms are more stable; hence, calculations can be done more efficiently. For steady flows, the convergence rate is about 35% faster, and for unsteady flows the allowable time step is about 10 times larger. These improvements are achieved with no increase in computer storage and with only minor modifications in codes that use the Murman-Cole switch. Also an implicit algorithm has been developed for the steady full-potential equation in one-dimension, which uses monotone methods.
Application de la methode des sous-groupes au calcul Monte-Carlo multigroupe
NASA Astrophysics Data System (ADS)
Martin, Nicolas
This thesis is dedicated to the development of a Monte Carlo neutron transport solver based on the subgroup (or multiband) method. In this formalism, cross sections for resonant isotopes are represented in the form of probability tables on the whole energy spectrum. This study is intended in order to test and validate this approach in lattice physics and criticality-safety applications. The probability table method seems promising since it introduces an alternative computational way between the legacy continuous-energy representation and the multigroup method. In the first case, the amount of data invoked in continuous-energy Monte Carlo calculations can be very important and tend to slow down the overall computational time. In addition, this model preserves the quality of the physical laws present in the ENDF format. Due to its cheap computational cost, the multigroup Monte Carlo way is usually at the basis of production codes in criticality-safety studies. However, the use of a multigroup representation of the cross sections implies a preliminary calculation to take into account self-shielding effects for resonant isotopes. This is generally performed by deterministic lattice codes relying on the collision probability method. Using cross-section probability tables on the whole energy range permits to directly take into account self-shielding effects and can be employed in both lattice physics and criticality-safety calculations. Several aspects have been thoroughly studied: (1) The consistent computation of probability tables with a energy grid comprising only 295 or 361 groups. The CALENDF moment approach conducted to probability tables suitable for a Monte Carlo code. (2) The combination of the probability table sampling for the energy variable with the delta-tracking rejection technique for the space variable, and its impact on the overall efficiency of the proposed Monte Carlo algorithm. (3) The derivation of a model for taking into account anisotropic
Calculations of pair production by Monte Carlo methods
Bottcher, C.; Strayer, M.R.
1991-01-01
We describe some of the technical design issues associated with the production of particle-antiparticle pairs in very large accelerators. To answer these questions requires extensive calculation of Feynman diagrams, in effect multi-dimensional integrals, which we evaluate by Monte Carlo methods on a variety of supercomputers. We present some portable algorithms for generating random numbers on vector and parallel architecture machines. 12 refs., 14 figs.
Feasibility of a wavelet expansion method to treat energy in cell calculations
Van Rooijen, W. F. G.
2012-07-01
This paper discusses the application of the Discrete Wavelet Transform (DWT) for the functional expansion of the energy variable in a cell calculation. The motivation of the work is the desire to obtain a self-shielding methodology in which the treatment of the energy variable in a given material region can be automatically adapted to the complexity of the cross section in that region. Unfortunately, the work presented in this paper shows that it is generally not possible to obtain the desired adaptivity. The most fundamental reason is that in a multi-region system, the energy dependence of the flux in a given material region is a function of the energy dependent cross sections and sources in all material regions through which the neutrons have crossed before entering into the present material. The complexity of the energy dependence of the cross section in a material region is thus not necessarily linked to the energy dependence of the flux in that region. If one sacrifices the objective of adaptivity, then an accurate method can be obtained using the DWT as a functional expansion. However, the resulting system of equations is more complicated than the direct solution of a hyper-fine group calculation. The conclusion is thus that the DWT approach is not very practical. (authors)
The Multi-Step CADIS method for shutdown dose rate calculations and uncertainty propagation
Ibrahim, Ahmad M.; Peplow, Douglas E.; Grove, Robert E.; Peterson, Joshua L.; Johnson, Seth R.
2015-12-01
Shutdown dose rate (SDDR) analysis requires (a) a neutron transport calculation to estimate neutron flux fields, (b) an activation calculation to compute radionuclide inventories and associated photon sources, and (c) a photon transport calculation to estimate final SDDR. In some applications, accurate full-scale Monte Carlo (MC) SDDR simulations are needed for very large systems with massive amounts of shielding materials. However, these simulations are impractical because calculation of space- and energy-dependent neutron fluxes throughout the structural materials is needed to estimate distribution of radioisotopes causing the SDDR. Biasing the neutron MC calculation using an importance function is not simple becausemore » it is difficult to explicitly express the response function, which depends on subsequent computational steps. Furthermore, the typical SDDR calculations do not consider how uncertainties in MC neutron calculation impact SDDR uncertainty, even though MC neutron calculation uncertainties usually dominate SDDR uncertainty.« less
The Multi-Step CADIS method for shutdown dose rate calculations and uncertainty propagation
Ibrahim, Ahmad M.; Peplow, Douglas E.; Grove, Robert E.; Peterson, Joshua L.; Johnson, Seth R.
2015-12-01
Shutdown dose rate (SDDR) analysis requires (a) a neutron transport calculation to estimate neutron flux fields, (b) an activation calculation to compute radionuclide inventories and associated photon sources, and (c) a photon transport calculation to estimate final SDDR. In some applications, accurate full-scale Monte Carlo (MC) SDDR simulations are needed for very large systems with massive amounts of shielding materials. However, these simulations are impractical because calculation of space- and energy-dependent neutron fluxes throughout the structural materials is needed to estimate distribution of radioisotopes causing the SDDR. Biasing the neutron MC calculation using an importance function is not simple because it is difficult to explicitly express the response function, which depends on subsequent computational steps. Furthermore, the typical SDDR calculations do not consider how uncertainties in MC neutron calculation impact SDDR uncertainty, even though MC neutron calculation uncertainties usually dominate SDDR uncertainty.
Probabilistic methods for the calculation of laminate properties
Mcmanus, H.L. )
1993-06-01
A method for calculating the properties of advanced composite laminates, including their variations due to known variations in the properties of the individual plies and the laminate geometry, is presented. The method is useful for understanding scatter in the measured properties of composite laminates. This scatter is particularly important in the design of ultra-low coefficient of thermal expansion (CTE) laminates. Such laminates are designed with a theoretically zero CTE, but in practice have a distribution of nonzero CTEs. Information useful for designing ultra-low expansion laminates is discussed. A practical limit on how close to zero the CTE of a laminate can be assumed to be is found. 10 refs.
Methods for calculating conjugate problems of heat transfer
NASA Astrophysics Data System (ADS)
Kalinin, E. K.; Dreitser, G. A.; Kostiuk, V. V.; Berlin, I. I.
Methods are examined for calculating various conjugate problems of heat transfer in channels and closed vessels in cases of single-phase and two-phase flow in steady and unsteady conditions. The single-phase-flow studies involve the investigation of gaseous and liquid heat-carriers in pipes, annular and plane channels, and pipe bundles in cases of cooling and heating. General relationships are presented for heat transfer in cases of film, transition, and nucleate boiling, as well as for boiling crises. Attention is given to methods for analyzing the filling and cooling of conduits and tanks by cryogenic liquids; and ways to intensify heat transfer in these conditions are examined.
Unfolding method for first-principles LCAO electronic structure calculations
NASA Astrophysics Data System (ADS)
Lee, Chi-Cheng; Yamada-Takamura, Yukiko; Ozaki, Taisuke
2013-08-01
Unfolding the band structure of a supercell to a normal cell enables us to investigate how symmetry breakers such as surfaces and impurities perturb the band structure of the normal cell. We generalize the unfolding method, originally developed based on Wannier functions, to the linear combination of atomic orbitals (LCAO) method, and present a general formula to calculate the unfolded spectral weight. The LCAO basis set is ideal for the unfolding method because the basis functions allocated to each atomic species are invariant regardless of the existence of surface and impurity. The unfolded spectral weight is well defined by the property of the LCAO basis functions. In exchange for the property, the non-orthogonality of the LCAO basis functions has to be taken into account. We show how the non-orthogonality can be properly incorporated in the general formula. As an illustration of the method, we calculate the dispersive quantized spectral weight of a ZrB2 slab and show strong spectral broadening in the out-of-plane direction, demonstrating the usefulness of the unfolding method.
Unfolding method for first-principles LCAO electronic structure calculations.
Lee, Chi-Cheng; Yamada-Takamura, Yukiko; Ozaki, Taisuke
2013-08-28
Unfolding the band structure of a supercell to a normal cell enables us to investigate how symmetry breakers such as surfaces and impurities perturb the band structure of the normal cell. We generalize the unfolding method, originally developed based on Wannier functions, to the linear combination of atomic orbitals (LCAO) method, and present a general formula to calculate the unfolded spectral weight. The LCAO basis set is ideal for the unfolding method because the basis functions allocated to each atomic species are invariant regardless of the existence of surface and impurity. The unfolded spectral weight is well defined by the property of the LCAO basis functions. In exchange for the property, the non-orthogonality of the LCAO basis functions has to be taken into account. We show how the non-orthogonality can be properly incorporated in the general formula. As an illustration of the method, we calculate the dispersive quantized spectral weight of a ZrB2 slab and show strong spectral broadening in the out-of-plane direction, demonstrating the usefulness of the unfolding method. PMID:23912816
Comparison of dose calculation methods for brachytherapy of intraocular tumors
Rivard, Mark J.; Chiu-Tsao, Sou-Tung; Finger, Paul T.; Meigooni, Ali S.; Melhus, Christopher S.; Mourtada, Firas; Napolitano, Mary E.; Rogers, D. W. O.; Thomson, Rowan M.; Nath, Ravinder
2011-01-15
Purpose: To investigate dosimetric differences among several clinical treatment planning systems (TPS) and Monte Carlo (MC) codes for brachytherapy of intraocular tumors using {sup 125}I or {sup 103}Pd plaques, and to evaluate the impact on the prescription dose of the adoption of MC codes and certain versions of a TPS (Plaque Simulator with optional modules). Methods: Three clinical brachytherapy TPS capable of intraocular brachytherapy treatment planning and two MC codes were compared. The TPS investigated were Pinnacle v8.0dp1, BrachyVision v8.1, and Plaque Simulator v5.3.9, all of which use the AAPM TG-43 formalism in water. The Plaque Simulator software can also handle some correction factors from MC simulations. The MC codes used are MCNP5 v1.40 and BrachyDose/EGSnrc. Using these TPS and MC codes, three types of calculations were performed: homogeneous medium with point sources (for the TPS only, using the 1D TG-43 dose calculation formalism); homogeneous medium with line sources (TPS with 2D TG-43 dose calculation formalism and MC codes); and plaque heterogeneity-corrected line sources (Plaque Simulator with modified 2D TG-43 dose calculation formalism and MC codes). Comparisons were made of doses calculated at points-of-interest on the plaque central-axis and at off-axis points of clinical interest within a standardized model of the right eye. Results: For the homogeneous water medium case, agreement was within {approx}2% for the point- and line-source models when comparing between TPS and between TPS and MC codes, respectively. For the heterogeneous medium case, dose differences (as calculated using the MC codes and Plaque Simulator) differ by up to 37% on the central-axis in comparison to the homogeneous water calculations. A prescription dose of 85 Gy at 5 mm depth based on calculations in a homogeneous medium delivers 76 Gy and 67 Gy for specific {sup 125}I and {sup 103}Pd sources, respectively, when accounting for COMS-plaque heterogeneities. For off
Comparison of dose calculation methods for brachytherapy of intraocular tumors
Rivard, Mark J.; Chiu-Tsao, Sou-Tung; Finger, Paul T.; Meigooni, Ali S.; Melhus, Christopher S.; Mourtada, Firas; Napolitano, Mary E.; Rogers, D. W. O.; Thomson, Rowan M.; Nath, Ravinder
2011-01-01
Purpose: To investigate dosimetric differences among several clinical treatment planning systems (TPS) and Monte Carlo (MC) codes for brachytherapy of intraocular tumors using 125I or 103Pd plaques, and to evaluate the impact on the prescription dose of the adoption of MC codes and certain versions of a TPS (Plaque Simulator with optional modules). Methods: Three clinical brachytherapy TPS capable of intraocular brachytherapy treatment planning and two MC codes were compared. The TPS investigated were Pinnacle v8.0dp1, BrachyVision v8.1, and Plaque Simulator v5.3.9, all of which use the AAPM TG-43 formalism in water. The Plaque Simulator software can also handle some correction factors from MC simulations. The MC codes used are MCNP5 v1.40 and BrachyDose∕EGSnrc. Using these TPS and MC codes, three types of calculations were performed: homogeneous medium with point sources (for the TPS only, using the 1D TG-43 dose calculation formalism); homogeneous medium with line sources (TPS with 2D TG-43 dose calculation formalism and MC codes); and plaque heterogeneity-corrected line sources (Plaque Simulator with modified 2D TG-43 dose calculation formalism and MC codes). Comparisons were made of doses calculated at points-of-interest on the plaque central-axis and at off-axis points of clinical interest within a standardized model of the right eye. Results: For the homogeneous water medium case, agreement was within ∼2% for the point- and line-source models when comparing between TPS and between TPS and MC codes, respectively. For the heterogeneous medium case, dose differences (as calculated using the MC codes and Plaque Simulator) differ by up to 37% on the central-axis in comparison to the homogeneous water calculations. A prescription dose of 85 Gy at 5 mm depth based on calculations in a homogeneous medium delivers 76 Gy and 67 Gy for specific 125I and 103Pd sources, respectively, when accounting for COMS-plaque heterogeneities. For off-axis points
Accelerating molecular property calculations with nonorthonormal Krylov space methods
Furche, Filipp; Krull, Brandon T.; Nguyen, Brian D.; Kwon, Jake
2016-05-03
Here, we formulate Krylov space methods for large eigenvalue problems and linear equation systems that take advantage of decreasing residual norms to reduce the cost of matrix-vector multiplication. The residuals are used as subspace basis without prior orthonormalization, which leads to generalized eigenvalue problems or linear equation systems on the Krylov space. These nonorthonormal Krylov space (nKs) algorithms are favorable for large matrices with irregular sparsity patterns whose elements are computed on the fly, because fewer operations are necessary as the residual norm decreases as compared to the conventional method, while errors in the desired eigenpairs and solution vectors remainmore » small. We consider real symmetric and symplectic eigenvalue problems as well as linear equation systems and Sylvester equations as they appear in configuration interaction and response theory. The nKs method can be implemented in existing electronic structure codes with minor modifications and yields speed-ups of 1.2-1.8 in typical time-dependent Hartree-Fock and density functional applications without accuracy loss. The algorithm can compute entire linear subspaces simultaneously which benefits electronic spectra and force constant calculations requiring many eigenpairs or solution vectors. The nKs approach is related to difference density methods in electronic ground state calculations and particularly efficient for integral direct computations of exchange-type contractions. By combination with resolution-of-the-identity methods for Coulomb contractions, three- to fivefold speed-ups of hybrid time-dependent density functional excited state and response calculations are achieved.« less
Solar Opacity Calculations Using the Super-transition-array Method
NASA Astrophysics Data System (ADS)
Krief, M.; Feigel, A.; Gazit, D.
2016-04-01
A new opacity model has been developed based on the Super-Transition-Array (STA) method for the calculation of monochromatic opacities of plasmas in local thermodynamic equilibrium. The atomic code, named STAR (STA-Revised), is described and used to calculate spectral opacities for a solar model implementing the recent AGSS09 composition. Calculations are carried out throughout the solar radiative zone. The relative contributions of different chemical elements and atomic processes to the total Rosseland mean opacity are analyzed in detail. Monochromatic opacities and charge-state distributions are compared with the widely used Opacity Project (OP) code, for several elements near the radiation–convection interface. STAR Rosseland opacities for the solar mixture show a very good agreement with OP and the OPAL opacity code throughout the radiation zone. Finally, an explicit STA calculation was performed of the full AGSS09 photospheric mixture, including all heavy metals. It was shown that, due to their extremely low abundance, and despite being very good photon absorbers, the heavy elements do not affect the Rosseland opacity.
Measurement of the transient shielding effectiveness of shielding cabinets
NASA Astrophysics Data System (ADS)
Herlemann, H.; Koch, M.
2008-05-01
Recently, new definitions of shielding effectiveness (SE) for high-frequency and transient electromagnetic fields were introduced by Klinkenbusch (2005). Analytical results were shown for closed as well as for non closed cylindrical shields. In the present work, the shielding performance of different shielding cabinets is investigated by means of numerical simulations and measurements inside a fully anechoic chamber and a GTEM-cell. For the GTEM-cell-measurements, a downscaled model of the shielding cabinet is used. For the simulations, the numerical tools CONCEPT II and COMSOL MULTIPHYSICS were available. The numerical results agree well with the measurements. They can be used to interpret the behaviour of the shielding effectiveness of enclosures as function of frequency. From the measurement of the electric and magnetic fields with and without the enclosure in place, the electric and magnetic shielding effectiveness as well as the transient shielding effectiveness of the enclosure are calculated. The transient SE of four different shielding cabinets is determined and discussed.
The new performance calculation method of fouled axial flow compressor.
Yang, Huadong; Xu, Hong
2014-01-01
Fouling is the most important performance degradation factor, so it is necessary to accurately predict the effect of fouling on engine performance. In the previous research, it is very difficult to accurately model the fouled axial flow compressor. This paper develops a new performance calculation method of fouled multistage axial flow compressor based on experiment result and operating data. For multistage compressor, the whole compressor is decomposed into two sections. The first section includes the first 50% stages which reflect the fouling level, and the second section includes the last 50% stages which are viewed as the clean stage because of less deposits. In this model, the performance of the first section is obtained by combining scaling law method and linear progression model with traditional stage stacking method; simultaneously ambient conditions and engine configurations are considered. On the other hand, the performance of the second section is calculated by averaged infinitesimal stage method which is based on Reynolds' law of similarity. Finally, the model is successfully applied to predict the 8-stage axial flow compressor and 16-stage LM2500-30 compressor. The change of thermodynamic parameters such as pressure ratio, efficiency with the operating time, and stage number is analyzed in detail. PMID:25197717
The New Performance Calculation Method of Fouled Axial Flow Compressor
Xu, Hong
2014-01-01
Fouling is the most important performance degradation factor, so it is necessary to accurately predict the effect of fouling on engine performance. In the previous research, it is very difficult to accurately model the fouled axial flow compressor. This paper develops a new performance calculation method of fouled multistage axial flow compressor based on experiment result and operating data. For multistage compressor, the whole compressor is decomposed into two sections. The first section includes the first 50% stages which reflect the fouling level, and the second section includes the last 50% stages which are viewed as the clean stage because of less deposits. In this model, the performance of the first section is obtained by combining scaling law method and linear progression model with traditional stage stacking method; simultaneously ambient conditions and engine configurations are considered. On the other hand, the performance of the second section is calculated by averaged infinitesimal stage method which is based on Reynolds' law of similarity. Finally, the model is successfully applied to predict the 8-stage axial flow compressor and 16-stage LM2500-30 compressor. The change of thermodynamic parameters such as pressure ratio, efficiency with the operating time, and stage number is analyzed in detail. PMID:25197717
Correlated Uncertainties in Radiation Shielding Effectiveness
NASA Technical Reports Server (NTRS)
Werneth, Charles M.; Maung, Khin Maung; Blattnig, Steve R.; Clowdsley, Martha S.; Townsend, Lawrence W.
2013-01-01
The space radiation environment is composed of energetic particles which can deliver harmful doses of radiation that may lead to acute radiation sickness, cancer, and even death for insufficiently shielded crew members. Spacecraft shielding must provide structural integrity and minimize the risk associated with radiation exposure. The risk of radiation exposure induced death (REID) is a measure of the risk of dying from cancer induced by radiation exposure. Uncertainties in the risk projection model, quality factor, and spectral fluence are folded into the calculation of the REID by sampling from probability distribution functions. Consequently, determining optimal shielding materials that reduce the REID in a statistically significant manner has been found to be difficult. In this work, the difference of the REID distributions for different materials is used to study the effect of composition on shielding effectiveness. It is shown that the use of correlated uncertainties allows for the determination of statistically significant differences between materials despite the large uncertainties in the quality factor. This is in contrast to previous methods where uncertainties have been generally treated as uncorrelated. It is concluded that the use of correlated quality factor uncertainties greatly reduces the uncertainty in the assessment of shielding effectiveness for the mitigation of radiation exposure.
Analysis of the new GCFR upper and lower plenum flow-through shields
Cramer, S.N.; Reed, D.A.; Emmett, M.B.; Rouse, C.A.
1980-09-14
Analysis of the proposed GCFR upper and lower plenum flow-through shields has been performed using both discrete ordinate (DOT) and Monte Carlo (MORSE) methods. Several shields having one change of direction in the coolant path (chevron) and two changes of direction (herringbone) were investigated. The shields were modeled as unit cells with periodic boundary conditions. From plenum fluence calculations and design constraints at the reactor vessel liner, it was determined that all the shield configurations analyzed should be adequate for the necessary radiation attenuation.
Perturbation method to calculate the density of states
NASA Astrophysics Data System (ADS)
Persson, Rasmus A. X.
2012-12-01
Monte Carlo switching moves (“perturbations”) are defined between two or more classical Hamiltonians sharing a common ground-state energy. The ratio of the density of states (DOS) of one system to that of another is related to the ensemble averages of the microcanonical acceptance probabilities of switching between these Hamiltonians, analogously to the case of Bennett's acceptance ratio method for the canonical ensemble [C. H. Bennett, J. Comput. Phys.JCTPAH0021-999110.1016/0021-9991(76)90078-4 22, 245 (1976)]. Thus, if the DOS of one of the systems is known, one obtains those of the others and, hence, the partition functions. As a simple test case, the vapor pressure of an anharmonic Einstein crystal is computed, using the harmonic Einstein crystal as the reference system in one dimension; an auxiliary calculation is also performed in three dimensions. As a further example of the algorithm, the energy dependence of the ratio of the DOS of the square-well and hard-sphere tetradecamers is determined, from which the temperature dependence of the constant-volume heat capacity of the square-well system is calculated and compared with canonical Metropolis Monte Carlo estimates. For these cases and reference systems, the perturbation calculations exhibit a higher degree of convergence per Monte Carlo cycle than Wang-Landau (WL) sampling, although for the one-dimensional oscillator the WL sampling is ultimately more efficient for long runs. Last, we calculate the vapor pressure of liquid gold using an empirical Sutton-Chen many-body potential and the ideal gas as the reference state. Although this proves the general applicability of the method, by its inherent perturbation approach the algorithm is suitable for those particular cases where the properties of a related system are well known.
Optimization of the National Ignition Facility primary shield design
Annese, C.E.; Watkins, E.F.; Greenspan, E.; Miller, W.F.; Latkowski, J.; Lee, J.D.; Soran, P.; Tobin, M.L.
1993-10-01
Minimum cost design concepts of the primary shield for the National Ignition laser fusion experimental Facility (NIF) are searched with the help of the optimization code SWAN. The computational method developed for this search involves incorporating the time dependence of the delayed photon field within effective delayed photon production cross sections. This method enables one to address the time-dependent problem using relatively simple, time-independent transport calculations, thus significantly simplifying the design process. A novel approach was used for the identification of the optimal combination of constituents that will minimize the shield cost; it involves the generation, with SWAN, of effectiveness functions for replacing materials on an equal cost basis. The minimum cost shield design concept was found to consist of a mixture of polyethylene and low cost, low activation materials such as SiC, with boron added near the shield boundaries.
Large Scale Electronic Structure Calculations using Quantum Chemistry Methods
NASA Astrophysics Data System (ADS)
Scuseria, Gustavo E.
1998-03-01
This talk will address our recent efforts in developing fast, linear scaling electronic structure methods for large scale applications. Of special importance is our fast multipole method( M. C. Strain, G. E. Scuseria, and M. J. Frisch, Science 271), 51 (1996). (FMM) for achieving linear scaling for the quantum Coulomb problem (GvFMM), the traditional bottleneck in quantum chemistry calculations based on Gaussian orbitals. Fast quadratures(R. E. Stratmann, G. E. Scuseria, and M. J. Frisch, Chem. Phys. Lett. 257), 213 (1996). combined with methods that avoid the Hamiltonian diagonalization( J. M. Millam and G. E. Scuseria, J. Chem. Phys. 106), 5569 (1997) have resulted in density functional theory (DFT) programs that can be applied to systems containing many hundreds of atoms and ---depending on computational resources or level of theory-- to many thousands of atoms.( A. D. Daniels, J. M. Millam and G. E. Scuseria, J. Chem. Phys. 107), 425 (1997). Three solutions for the diagonalization bottleneck will be analyzed and compared: a conjugate gradient density matrix search (CGDMS), a Hamiltonian polynomial expansion of the density matrix, and a pseudo-diagonalization method. Besides DFT, our near-field exchange method( J. C. Burant, G. E. Scuseria, and M. J. Frisch, J. Chem. Phys. 105), 8969 (1996). for linear scaling Hartree-Fock calculations will be discussed. Based on these improved capabilities, we have also developed programs to obtain vibrational frequencies (via analytic energy second derivatives) and excitation energies (through time-dependent DFT) of large molecules like porphyn or C_70. Our GvFMM has been extended to periodic systems( K. N. Kudin and G. E. Scuseria, Chem. Phys. Lett., in press.) and progress towards a Gaussian-based DFT and HF program for polymers and solids will be reported. Last, we will discuss our progress on a Laplace-transformed \\cal O(N^2) second-order pertubation theory (MP2) method.
Ripley, Edward B.
2009-11-24
A thermocouple shield for use in radio frequency fields. In some embodiments the shield includes an electrically conductive tube that houses a standard thermocouple having a thermocouple junction. The electrically conductive tube protects the thermocouple from damage by an RF (including microwave) field and mitigates erroneous temperature readings due to the microwave or RF field. The thermocouple may be surrounded by a ceramic sheath to further protect the thermocouple. The ceramic sheath is generally formed from a material that is transparent to the wavelength of the microwave or RF energy. The microwave transparency property precludes heating of the ceramic sheath due to microwave coupling, which could affect the accuracy of temperature measurements. The ceramic sheath material is typically an electrically insulating material. The electrically insulative properties of the ceramic sheath help avert electrical arcing, which could damage the thermocouple junction. The electrically conductive tube is generally disposed around the thermocouple junction and disposed around at least a portion of the ceramic sheath. The concepts of the thermocouple shield may be incorporated into an integrated shielded thermocouple assembly.
Efficient hybrid-symbolic methods for quantum mechanical calculations
NASA Astrophysics Data System (ADS)
Scott, T. C.; Zhang, Wenxing
2015-06-01
We present hybrid symbolic-numerical tools to generate optimized numerical code for rapid prototyping and fast numerical computation starting from a computer algebra system (CAS) and tailored to any given quantum mechanical problem. Although a major focus concerns the quantum chemistry methods of H. Nakatsuji which has yielded successful and very accurate eigensolutions for small atoms and molecules, the tools are general and may be applied to any basis set calculation with a variational principle applied to its linear and non-linear parameters.
Supersampling method for efficient grid-based electronic structure calculations
NASA Astrophysics Data System (ADS)
Ryu, Seongok; Choi, Sunghwan; Hong, Kwangwoo; Kim, Woo Youn
2016-03-01
The egg-box effect, the spurious variation of energy and force due to the discretization of continuous space, is an inherent vexing problem in grid-based electronic structure calculations. Its effective suppression allowing for large grid spacing is thus crucial for accurate and efficient computations. We here report that the supersampling method drastically alleviates it by eliminating the rapidly varying part of a target function along both radial and angular directions. In particular, the use of the sinc filtering function performs best because as an ideal low pass filter it clearly cuts out the high frequency region beyond allowed by a given grid spacing.
Empirically corrected HEAT method for calculating atomization energies
Brand, Holmann V
2008-01-01
We describe how to increase the accuracy ofthe most recent variants ofthe HEAT method for calculating atomization energies of molecules by means ofextremely simple empirical corrections that depend on stoichiometry and the number ofunpaired electrons in the molecule. Our corrections reduce the deviation from experiment for all the HEAT variants. In particular, our corrections reduce the average absolute deviation and the root-mean-square deviation ofthe 456-QP variant to 0.18 and 0.23 kJoule/mol (i.e., 0.04 and 0.05 kcallmol), respectively.
Supersampling method for efficient grid-based electronic structure calculations.
Ryu, Seongok; Choi, Sunghwan; Hong, Kwangwoo; Kim, Woo Youn
2016-03-01
The egg-box effect, the spurious variation of energy and force due to the discretization of continuous space, is an inherent vexing problem in grid-based electronic structure calculations. Its effective suppression allowing for large grid spacing is thus crucial for accurate and efficient computations. We here report that the supersampling method drastically alleviates it by eliminating the rapidly varying part of a target function along both radial and angular directions. In particular, the use of the sinc filtering function performs best because as an ideal low pass filter it clearly cuts out the high frequency region beyond allowed by a given grid spacing. PMID:26957151
An approximate method for calculating aircraft downwash on parachute trajectories
Strickland, J.H.
1989-01-01
An approximate method for calculating velocities induced by aircraft on parachute trajectories is presented herein. A simple system of quadrilateral vortex panels is used to model the aircraft wing and its wake. The purpose of this work is to provide a simple analytical tool which can be used to approximate the effect of aircraft-induced velocities on parachute performance. Performance issues such as turnover and wake recontact may be strongly influenced by velocities induced by the wake of the delivering aircraft, especially if the aircraft is maneuvering at the time of parachute deployment. 7 refs., 9 figs.
Newton like: Minimal residual methods applied to transonic flow calculations
NASA Technical Reports Server (NTRS)
Wong, Y. S.
1984-01-01
A computational technique for the solution of the full potential equation is presented. The method consists of outer and inner iterations. The outer iterate is based on a Newton like algorithm, and a preconditioned Minimal Residual method is used to seek an approximate solution of the system of linear equations arising at each inner iterate. The present iterative scheme is formulated so that the uncertainties and difficulties associated with many iterative techniques, namely the requirements of acceleration parameters and the treatment of additional boundary conditions for the intermediate variables, are eliminated. Numerical experiments based on the new method for transonic potential flows around the NACA 0012 airfoil at different Mach numbers and different angles of attack are presented, and these results are compared with those obtained by the Approximate Factorization technique. Extention to three dimensional flow calculations and application in finite element methods for fluid dynamics problems by the present method are also discussed. The Inexact Newton like method produces a smoother reduction in the residual norm, and the number of supersonic points and circulations are rapidly established as the number of iterations is increased.
NASA Astrophysics Data System (ADS)
Zhang, B.; Xu, C. L.; Wang, S. M.
2016-07-01
The infrared temperature measurement technique has been applied in various fields, such as thermal efficiency analysis, environmental monitoring, industrial facility inspections, and remote temperature sensing. In the problem of infrared measurement of the metal surface temperature of superheater surfaces, the outer wall of the metal pipe is covered by radiative participating flue gas. This means that the traditional infrared measurement technique will lead to intolerable measurement errors due to the absorption and scattering of the flue gas. In this paper, an infrared measurement method for a metal surface in flue gas is investigated theoretically and experimentally. The spectral emissivity of the metal surface, and the spectral absorption and scattering coefficients of the radiative participating flue gas are retrieved simultaneously using an inverse method called quantum particle swarm optimization. Meanwhile, the detected radiation energy simulated using a forward simulation method (named the source multi-flux method) is set as the input of the retrieval. Then, the temperature of the metal surface detected by an infrared CCD camera is modified using the source multi-flux method in combination with these retrieved physical properties. Finally, an infrared measurement system for metal surface temperature is built to assess the proposed method. Experimental results show that the modified temperature is closer to the true value than that of the direct measured temperature.
Simulation of FEL pulse length calculation with THz streaking method.
Gorgisyan, I; Ischebeck, R; Prat, E; Reiche, S; Rivkin, L; Juranić, P
2016-05-01
Having accurate and comprehensive photon diagnostics for the X-ray pulses delivered by free-electron laser (FEL) facilities is of utmost importance. Along with various parameters of the photon beam (such as photon energy, beam intensity, etc.), the pulse length measurements are particularly useful both for the machine operators to measure the beam parameters and monitor the stability of the machine performance, and for the users carrying out pump-probe experiments at such facilities to better understand their measurement results. One of the most promising pulse length measurement techniques used for photon diagnostics is the THz streak camera which is capable of simultaneously measuring the lengths of the photon pulses and their arrival times with respect to the pump laser. This work presents simulations of a THz streak camera performance. The simulation procedure utilizes FEL pulses with two different photon energies in hard and soft X-ray regions, respectively. It recreates the energy spectra of the photoelectrons produced by the photon pulses and streaks them by a single-cycle THz pulse. Following the pulse-retrieval procedure of the THz streak camera, the lengths were calculated from the streaked spectra. To validate the pulse length calculation procedure, the precision and the accuracy of the method were estimated for streaking configuration corresponding to previously performed experiments. The obtained results show that for the discussed setup the method is capable of measuring FEL pulses with about a femtosecond accuracy and precision. PMID:27140142
Simulation of FEL pulse length calculation with THz streaking method
Gorgisyan, I.; Ischebeck, R.; Prat, E.; Reiche, S.; Rivkin, L.; Juranić, P.
2016-01-01
Having accurate and comprehensive photon diagnostics for the X-ray pulses delivered by free-electron laser (FEL) facilities is of utmost importance. Along with various parameters of the photon beam (such as photon energy, beam intensity, etc.), the pulse length measurements are particularly useful both for the machine operators to measure the beam parameters and monitor the stability of the machine performance, and for the users carrying out pump–probe experiments at such facilities to better understand their measurement results. One of the most promising pulse length measurement techniques used for photon diagnostics is the THz streak camera which is capable of simultaneously measuring the lengths of the photon pulses and their arrival times with respect to the pump laser. This work presents simulations of a THz streak camera performance. The simulation procedure utilizes FEL pulses with two different photon energies in hard and soft X-ray regions, respectively. It recreates the energy spectra of the photoelectrons produced by the photon pulses and streaks them by a single-cycle THz pulse. Following the pulse-retrieval procedure of the THz streak camera, the lengths were calculated from the streaked spectra. To validate the pulse length calculation procedure, the precision and the accuracy of the method were estimated for streaking configuration corresponding to previously performed experiments. The obtained results show that for the discussed setup the method is capable of measuring FEL pulses with about a femtosecond accuracy and precision. PMID:27140142
Molecular Photoionization Calculations Using the Complex Basis Function Method.
NASA Astrophysics Data System (ADS)
Yu, Chin-Hui
The complex basis function method (CBF) using both real and complex basis functions has been applied to the calculation of photoionization cross sections. The CBF method requires less computational resources than rigorous full-scattering methods and is effective for the evaluation of shape-resonance features. Neither the number of electrons in the system nor the molecular geometry is restricted. Moreover, the cross section obtained by the CBF method satisfies a variational principle and provides a practical diagnostic tool for the calculation of cross sections. The photoionization cross sections of H _sp{2}{+}, H _2, N_2, CO _2, and SF_6 have been computed using the CBF method. The computed partial cross sections for linear molecules agreed fairly well with other theoretical and experimental values. Particularly encouraging is the nearly perfect agreement of the CBF results with the results by rigorous full-scattering methods in the regions of sharp resonance features such as the K-shell ionization of N_2 and the 4sigma_{rm g} --> ksigma_ {rm u} transition of CO _2. The effect of averaging over all vibrational modes on the ionization cross sections for the 4 sigma_{rm g} orbital in CO_2 has also been studied for the first time. The resonance peak in the totally vibrationally averaged cross sections was reduced by 20%, but still represents a feature which has not yet been detected experimentally. The photoionization of SF_6 valence shells, 1t_{1rm g} , 5t_{1rm u}, 1t_{2rm u}, 3e _{rm g}, 1t_ {2rm g}, 4t_{1 rm u}, and 5a_{1 rm g}, has also been studied for the continuum symmetries a_{1rm g }, t_{1rm u} , e_{rm g}, and t_{2rm g}. The CBF results of SF_6 are numerically stable and essentially approach the static-exchange limit. These static-exchange partial cross sections, however, do not compare well with the experimental measurements. The discrepancy may be attributed to the physical approximations made in the theoretical model and to the quality of the ground -state
Lunar Surface Reactor Shielding Study
NASA Technical Reports Server (NTRS)
King, Shawn; Lipinksi, Ronald; McAlpine, William
2006-01-01
Nuclear reactor system could provide power to support a long term human exploration to the moon. Such a system would require shielding to protect astronauts from its emitted radiations. Shielding studies have been performed for a Gas Cooled Reactor (GCR) system because it is considered to be the most suitable nuclear reactor system available for lunar exploration, based on its tolerance of oxidizing lunar regolith and its good conversion efficiency (Wright, 2003). The goals of the shielding studies were to provide optimal material shielding configuration that reduces the dose (rem) to the required level in order to protect astronauts, and to estimate the mass of regolith that would provide an equivalent protective effect if it were used as the shielding material. All calculations were performed using MCNPX code, a Monte Carlo transport code.
Shielding and activity estimator for template-based nuclide identification methods
Nelson, Karl Einar
2013-04-09
According to one embodiment, a method for estimating an activity of one or more radio-nuclides includes receiving one or more templates, the one or more templates corresponding to one or more radio-nuclides which contribute to a probable solution, receiving one or more weighting factors, each weighting factor representing a contribution of one radio-nuclide to the probable solution, computing an effective areal density for each of the one more radio-nuclides, computing an effective atomic number (Z) for each of the one more radio-nuclides, computing an effective metric for each of the one or more radio-nuclides, and computing an estimated activity for each of the one or more radio-nuclides. In other embodiments, computer program products, systems, and other methods are presented for estimating an activity of one or more radio-nuclides.
New method for calculation of nuclear cluster structure of nuclei
Ibishi, A.I.
2005-05-06
In the calculations of the many-nucleon bound states, using the realistic nucleon-nucleon potential, and a three- and four-nucleon potential, the Exact Many-Body Nuclear Cluster Model (EMBNCM) was found to give accurate results, that converege much more rapidly, than those obtained by the Faddeev equation calculations. With the use of realistic nucleon-nucleon potentials, and many-nucleon potentials, containing strong tensor, Majorana, and repulsive core components, the many-body cluster structure of 16O, 27Al, 44Ti, and 48Ti is discussed. In 27Al(p,x)Na reactions we assume that two different nuclear cluster structures of 27Al, gives us two different isotopes of Na: 22Na and 24Na. But the most important result is the existence of two different permutations symmetries of 27Al. Using new method for calculation of nuclear cluster structure of 27Al, we have found two different nuclear cluster structures of 27Al: 24Na+3He and 25Na+d. The internal nuclear cluster wave functions of different nuclear cluster models (nuclear cluster isomers) of the same isotope are not equivalent, if we take into account Many-Body Nuclear Forces, such as 3BF and 4BF. The core clusters of 16O, 27Al, 44Ti, and 48Ti nuclei have a trigonal-pyramide Td, D2d, and C3v symmetry, while exterior clusters in 16O and 27Al[(24Na +3 He)model] nuclei have a trigonal symmetry C2v, and D3h. We have developed a new system of Jacobi coordinates for our EMBNCM model with the symmetry above. The new computer code for determination of direct nuclear cluster reactions has been written in Mathematica 5 programming language. We have found a high level of dependence of the nuclear cluster wave functions from the center of mass and cluster effects.
Parameterizations for shielding electron accelerators based on Monte Carlo studies
P. Degtyarenko; G. Stapleton
1996-10-01
Numerous recipes for designing lateral slab neutron shielding for electron accelerators are available and each generally produces rather similar results for shield thicknesses of about 2 m of concrete and for electron beams with energy in the 1 to 10 GeV region. For thinner or much thicker shielding the results tend to diverge and the standard recipes require modification. Likewise for geometries other than lateral to the beam direction further corrections are required so that calculated results are less reliable and hence additional and costly conservatism is needed. With the adoption of Monte Carlo (MC) methods of transporting particles a much more powerful way of calculating radiation dose rates outside shielding becomes available. This method is not constrained by geometry, although deep penetration problems need special statistical treatment, and is an excellent approach to solving any radiation transport problem providing the method has been properly checked against measurements and is free from the well known errors common to such computer methods. This present paper utilizes the results of MC calculations based on a nuclear fragmentation model named DINREG using the MC transport code GEANT and models them with the normal two parameter shielding expressions. Because the parameters can change with electron beam energy, angle to the electron beam direction and target material, the parameters are expressed as functions of some of these variables to provide a universal equations for shielding electron beams which can used rather simply for deep penetration problems in simple geometry without the time consuming computations needed in the original MC programs. A particular problem with using simple parameterizations based on the uncollided flux is that approximations based on spherical geometry might not apply to the more common cylindrical cases used for accelerator shielding. This source of error has been discussed at length by Stevenson and others. To study
NASA Technical Reports Server (NTRS)
Creel, T. R., Jr.; Beckwith, I. E. (Inventor)
1982-01-01
An improved test section for a supersonic or hypersonic wind tunnel is disclosed wherein the model tested is shielded from the noise normally radiated by the turbulent tunnel wall boundary layer. A vacuum plenum surrounds spaced rod elements making up the test chamber to extract some of the boundary layer as formed along the rod elements during a test to thereby delay the tendency of the rod boundary layers to become turbulent. Novel rod construction involves bending each rod slightly prior to machining the bent area to provide a flat segment on each rod for connection with the flat entrance fairing. Rods and fairing are secured to provide a test chamber incline on the order of 1 deg outward from the noise shield centerline to produce up to 65% reduction of the root mean square (rms) pressure over previously employed wind tunnel test sections at equivalent Reynolds numbers.
Reliability-Based Electronics Shielding Design Tools
NASA Technical Reports Server (NTRS)
Wilson, J. W.; O'Neill, P. J.; Zang, T. A.; Pandolf, J. E.; Tripathi, R. K.; Koontz, Steven L.; Boeder, P.; Reddell, B.; Pankop, C.
2007-01-01
Shielding design on large human-rated systems allows minimization of radiation impact on electronic systems. Shielding design tools require adequate methods for evaluation of design layouts, guiding qualification testing, and adequate follow-up on final design evaluation.
A simple dose calculation method for total body photon irradiation
Curran, W.J. Jr.; Galvin, J.M.; D'Angio, G.J.
1989-07-01
A simple technique for calculation of the prescribed dose for total body irradiation (TBI) is presented. The technique uses a standard calibration procedure and applies standard correction methods to account for variations in the field size, depth, and treatment distance. Since the scattering volume (the entire body) is smaller than the X ray field for this treatment, the change in output with field size is handled separately from changes due to scatter within the phantom. The latter is shown to be a function of the phantom size (corresponding to the frontal area of the trunk of the body for patient irradiation) rather than the size of the field opening. Dosimetric tests of this technique have been conducted and the errors determined. For these tests, three different phantom sizes were used to represent the upper body sizes of a 2-year old child, an 8-year old, and an adult, and three linear accelerator energies (6, 10, and 15 MV) were included. Calculations were performed using the technique and compared to measurements for the same phantom sizes. Differences of less than 1.3 were found.
Radiation Shielding Materials and Containers Incorporating Same
Mirsky, Steven M.; Krill, Stephen J.; and Murray, Alexander P.
2005-11-01
An improved radiation shielding material and storage systems for radioactive materials incorporating the same. The PYRolytic Uranium Compound (''PYRUC'') shielding material is preferably formed by heat and/or pressure treatment of a precursor material comprising microspheres of a uranium compound, such as uranium dioxide or uranium carbide, and a suitable binder. The PYRUC shielding material provides improved radiation shielding, thermal characteristic, cost and ease of use in comparison with other shielding materials. The shielding material can be used to form containment systems, container vessels, shielding structures, and containment storage areas, all of which can be used to house radioactive waste. The preferred shielding system is in the form of a container for storage, transportation, and disposal of radioactive waste. In addition, improved methods for preparing uranium dioxide and uranium carbide microspheres for use in the radiation shielding materials are also provided.
Radiation shielding materials and containers incorporating same
Mirsky, Steven M.; Krill, Stephen J.; Murray, Alexander P.
2005-11-01
An improved radiation shielding material and storage systems for radioactive materials incorporating the same. The PYRolytic Uranium Compound ("PYRUC") shielding material is preferably formed by heat and/or pressure treatment of a precursor material comprising microspheres of a uranium compound, such as uranium dioxide or uranium carbide, and a suitable binder. The PYRUC shielding material provides improved radiation shielding, thermal characteristic, cost and ease of use in comparison with other shielding materials. The shielding material can be used to form containment systems, container vessels, shielding structures, and containment storage areas, all of which can be used to house radioactive waste. The preferred shielding system is in the form of a container for storage, transportation, and disposal of radioactive waste. In addition, improved methods for preparing uranium dioxide and uranium carbide microspheres for use in the radiation shielding materials are also provided.
The finite element method for calculating the marine structural design
NASA Astrophysics Data System (ADS)
Ion, A.; Ticu, I.
2015-11-01
The aim of this paper is to optimally design and dimension marine structures in order for them to fulfil both functional and safety requirements. A master level of structural mechanics is vital in order to check tests and analysis and to develop new structures. This study can improve the calculation and estimation of the effects of hydrodynamics and of other loads; movements, strains and internal forces in fixed and floating platforms and ships. The finite element method (FEM) ensures basic understanding of the finite element model as applied on static cases including beam and plate elements, experience with static analysis of marine structures like platforms and ships, along with the basic understanding of dynamic response of systems with one degree of freedom and simple continuous beams, and also how analysis models can be established for real structures by the use of generalized coordinates and superposition.
Calculating the spectrum of anisotropic waveguides using a spectral method.
Zharnikov, T V; Syresin, D E; Hsu, C-J
2013-09-01
The computation of the spectrum of a waveguide with arbitrary anisotropy with spatial dependence is a challenging task due to the coupling between axial and azimuthal harmonics. This problem is tackled in cylindrical coordinates by extending a spectral method for the general case. By considering the matrix representation of the operator on the right-hand side of the governing equations, the latter are exactly reformulated as an infinite set of integro-differential equations. Essential part of this study is taking into account the coupling of different harmonics, which becomes evident from the kernels of these equations. Provided a waveguide is translationally invariant in the axial direction, the coupling of axial harmonics vanishes. A practical approximation and truncation procedure yields a generalized eigenvalue problem, which can be solved numerically to obtain the entire spectrum of the operator and to construct the dispersion curves for the eigenmodes. The spectral method is tested against the results from the measurements of dispersion curves for the monopole, dipole, and quadrupole normal modes of scaled boreholes in tilted transverse isotropy anisotropic rock sample. Besides, the comparison of dispersion curves calculated by the spectral method and those computed from the synthetic data is discussed. PMID:23967909
Improving stochastic estimates with inference methods: calculating matrix diagonals.
Selig, Marco; Oppermann, Niels; Ensslin, Torsten A
2012-02-01
Estimating the diagonal entries of a matrix, that is not directly accessible but only available as a linear operator in the form of a computer routine, is a common necessity in many computational applications, especially in image reconstruction and statistical inference. Here, methods of statistical inference are used to improve the accuracy or the computational costs of matrix probing methods to estimate matrix diagonals. In particular, the generalized Wiener filter methodology, as developed within information field theory, is shown to significantly improve estimates based on only a few sampling probes, in cases in which some form of continuity of the solution can be assumed. The strength, length scale, and precise functional form of the exploited autocorrelation function of the matrix diagonal is determined from the probes themselves. The developed algorithm is successfully applied to mock and real world problems. These performance tests show that, in situations where a matrix diagonal has to be calculated from only a small number of computationally expensive probes, a speedup by a factor of 2 to 10 is possible with the proposed method. PMID:22463179
New method for calculating a mathematical expression for streamflow recession
Rutledge, Albert T.
1991-01-01
An empirical method has been devised to calculate the master recession curve, which is a mathematical expression for streamflow recession during times of negligible direct runoff. The method is based on the assumption that the storage-delay factor, which is the time per log cycle of streamflow recession, varies linearly with the logarithm of streamflow. The resulting master recession curve can be nonlinear. The method can be executed by a computer program that reads a data file of daily mean streamflow, then allows the user to select several near-linear segments of streamflow recession. The storage-delay factor for each segment is one of the coefficients of the equation that results from linear least-squares regression. Using results for each recession segment, a mathematical expression of the storage-delay factor as a function of the log of streamflow is determined by linear least-squares regression. The master recession curve, which is a second-order polynomial expression for time as a function of log of streamflow, is then derived using the coefficients of this function.
Status of reactor-shielding research in the US
Maienshein, F.C.
1980-01-01
While reactor programs change, shielding analysis methods are improved slowly. Version-V of ENDF/B provides improved data and Version-VI will be cost effective in advanced fission reactors are to be developed in the US. Benchmarks for data and methods validation are collected and distributed in the US in two series, one primarily for FBR-related experiments and one for LWR calculational methods. For LWR design, cavity streaming is now handled adequately, if with varying degrees of elegance. Investigations of improved detector response for LWRs rely upon transport methods. The great potential importance of pressure-vessel damage is dreflected in widespread studies to aid in the prediction of neutron fluences in vessels. For LMFBRS, the FFTF should give attenuation results on an operating reactor. For larger power reactors, the advantages of alternate shield materials appear compelling. A few other shielding studies appear to require experimental confirmation if LMFBRs are to be economically competitive. A coherent shielding program for the GCFR is nearing completion. For the fusion-reactor program, methods verification is under way, practical calculations are well advanced for test devices such as the TFTR and FMIT, and consideration is now given to shielding problems of large reactors, as in the ETF study.
New Materials for EMI Shielding
NASA Technical Reports Server (NTRS)
Gaier, James R.
1999-01-01
Graphite fibers intercalated with bromine or similar mixed halogen compounds have substantially lower resistivity than their pristine counterparts, and thus should exhibit higher shielding effectiveness against electromagnetic interference. The mechanical and thermal properties are nearly unaffected, and the shielding of high energy x-rays and gamma rays is substantially increased. Characterization of the resistivity of the composite materials is subtle, but it is clear that the composite resistivity is substantially lowered. Shielding effectiveness calculations utilizing a simple rule of mixtures model yields results that are consistent with available data on these materials.
Three-dimensional boundary layer calculation by a characteristic method
NASA Technical Reports Server (NTRS)
Houdeville, R.
1992-01-01
A numerical method for solving the three-dimensional boundary layer equations for bodies of arbitrary shape is presented. In laminar flows, the application domain extends from incompressible to hypersonic flows with the assumption of chemical equilibrium. For turbulent boundary layers, the application domain is limited by the validity of the mixing length model used. In order to respect the hyperbolic nature of the equations reduced to first order partial derivative terms, the momentum equations are discretized along the local streamlines using of the osculator tangent plane at each node of the body fitted coordinate system. With this original approach, it is possible to overcome the use of the generalized coordinates, and therefore, it is not necessary to impose an extra hypothesis about the regularity of the mesh in which the boundary conditions are given. By doing so, it is possible to limit, and sometimes to suppress, the pre-treatment of the data coming from an inviscid calculation. Although the proposed scheme is only semi-implicit, the method remains numerically very efficient.
Validation of a numerical method for unsteady flow calculations
Giles, M.; Haimes, R. . Dept. of Aeronautics and Astronautics)
1993-01-01
This paper describes and validates a numerical method for the calculation of unsteady inviscid and viscous flows. A companion paper compares experimental measurements of unsteady heat transfer on a transonic rotor with the corresponding computational results. The mathematical model is the Reynolds-averaged unsteady Navier-Stokes equations for a compressible ideal gas. Quasi-three-dimensionality is included through the use of a variable streamtube thickness. The numerical algorithm is unusual in two respects: (a) For reasons of efficiency and flexibility, it uses a hybrid Navier-Stokes/Euler method, and (b) to allow for the computation of stator/rotor combinations with arbitrary pitch ratio, a novel space-time coordinate transformation is used. Several test cases are presented to validate the performance of the computer program, UNSFLO. These include: (a) unsteady, inviscid flat plate cascade flows (b) steady and unsteady, viscous flat plate cascade flows, (c) steady turbine heat transfer and loss prediction. In the first two sets of cases comparisons are made with theory, and in the third the comparison is with experimental data.
The nuclear magnetic shielding as a function of internuclear separation
NASA Astrophysics Data System (ADS)
Jameson, Cynthia J.; de Dios, Angel C.
1993-02-01
Ab initio calculations of nuclear magnetic shielding surfaces for 23Na in the NaH molecule, 39Ar in ArNe, 21Ne in NeHe, and 39Ar in Ar...NaH are carried out over a wide range of internuclear separations, using a local origin method (LORG) which damps out the long-range errors due to incomplete basis sets. The R dependence of the intermolecular shielding in the attractive region of the potential in these systems and in Ar...Ar and Ar...Na+ are consistent with the long-range limiting forms associated with the shielding hyperpolarizability in conjunction with a mean square electric field approximation. The Cl and F shieldings over the range of nuclear displacements spanning the classical turning points of the ground vibrational states of ClF and F2 are found to be remarkably superposable upon scaling by the factors
Fowe, Emmanuel Penka; Belser, Peter; Daul, Claude; Chermette, Henry
2005-04-21
In the present work, the ZORA spin-orbit Hamiltonian, in conjunction with the gauge including orbital (GIAO) method based on DFT theory has been used to calculate 195Pt chemical shift of 195PtClxBr(6-x)(2-) complexes. Excellent agreement with experiments has been obtained for calculations bearing on optimized geometries and all electrons triple zeta + polarization (TZP) STO basis sets: the relative error with respect to experiment amounts to <1.5%. It is found that the Pt chemical shift is dominated by the paramagnetic and the spin orbit contribution, whereas the diamagnetic term remains negligible. The influence of the quality of the basis sets has been studied and found to be small, provided a basis set like TZP is used. Several calculations have been performed in order to establish the sensitivity of the chemical shift to a variation in the bond lengths. A strong dependence has been found, with an increase of the chemical shift amounting to 150 ppm pm(-1) for a distance decrease. Large sensitivity to the solvation, leading to changes in the structure, is then expected. Different tests using conductor-like screening models have been performed in order to establish the sensitivity of the chemical shift to solvation. It has been observed that the changes in the geometry are more important than charge transfers. Finally, the sensitivity of the system to the exchange-correlation functional is found rather weak, at least among the GGA functionals. PMID:19787932
GCFR shielding design and supporting experimental programs
Perkins, R.G.; Hamilton, C.J.; Bartine, D.
1980-05-01
The shielding for the conceptual design of the gas-cooled fast breeder reactor (GCFR) is described, and the component exposure design criteria which determine the shield design are presented. The experimental programs for validating the GCFR shielding design methods and data (which have been in existence since 1976) are also discussed.
SSC environmental radiation shielding
Jackson, J.D.
1987-07-01
The environmental radiation shielding requirements of the SSC have been evaluated using currently available computational tools that incorporate the well known processes of energy loss and degradation of high energy particles into Monte Carlo computer codes. These tools permit determination of isodose contours in the matter surrounding a source point and therefore the specification of minimum thicknesses or extents of shielding in order to assure annual dose equivalents less than some specified design amount. For the general public the annual dose equivalent specified in the design is 10 millirem, small compared to the dose from naturally occurring radiation. The types of radiation fall into two classes for the purposes of shielding determinations-hadrons and muons. The sources of radiation at the SSC of concern for the surrounding environment are the interaction regions, the specially designed beam dumps into which the beams are dumped from time to time, and beam clean-up regions where stops remove the beam halo in order to reduce experimental backgrounds. A final, unlikely source of radiation considered is the accidental loss of the full beam at some point around the ring. Conservative choices of a luminosity of 10{sup 34} cm{sup {minus}2}s{sup {minus}1} and a beam current three times design have been made in calculating the required shielding and boundaries of the facility. In addition to determination of minimum distances for the annual dose equivalents, the question of possible radioactivity produced in nearby wells or in municipal water supplies is addressed. The designed shielding distances and beam dumps are such that the induced radioactivity in ground water is safely smaller than the levels permitted by EPA and international agencies.
NASA Astrophysics Data System (ADS)
Ding, W. Q.; Yue, Z. Q.; Tham, L. G.; Zhu, H. H.; Lee, C. F.; Hashimoto, T.
2004-01-01
This paper proposes a two-dimensional finite element model for the analysis of shield tunnels by taking into account the construction process which is divided into four stages. The soil is assumed to behave as an elasto-plastic medium whereas the shield is simulated by beam-joint discontinuous model in which curved beam elements and joint elements are used to model the segments and joints, respectively. As grout is usually injected to fill the gap between the lining and the soil, the property parameters of the grout are chosen in such a way that they can reflect the state of the grout at each stage. Furthermore, the contact condition between the soil and lining will change with the construction stage, and therefore, different stress-releasing coefficients are used to account for the changes. To assess the accuracy that can be attained by the method in solving practical problems, the shield tunnelling in the No. 7 Subway Line Project in Osaka, Japan, is used as a case history for our study. The numerical results are compared with those measured in the field. The results presented in the paper show that the proposed numerical procedure can be used to effectively estimate the deformation, stresses and moments experienced by the surrounding soils and the concrete lining segments. The analysis and method presented in this paper can be considered to be useful for other subway construction projects involving shield tunnelling in soft soils. Copyright
Welding shield for coupling heaters
Menotti, James Louis
2010-03-09
Systems for coupling end portions of two elongated heater portions and methods of using such systems to treat a subsurface formation are described herein. A system may include a holding system configured to hold end portions of the two elongated heater portions so that the end portions are abutted together or located near each other; a shield for enclosing the end portions, and one or more inert gas inlets configured to provide at least one inert gas to flush the system with inert gas during welding of the end portions. The shield may be configured to inhibit oxidation during welding that joins the end portions together. The shield may include a hinged door that, when closed, is configured to at least partially isolate the interior of the shield from the atmosphere. The hinged door, when open, is configured to allow access to the interior of the shield.
Stone, M. E.
2012-11-07
The purpose of this document is to describe the current state of the art for determination of hydrogen generation rates of radioactive slurries and solutions to provide a basis for design, fabrication, testing, and implementation of a measurement method for Hydrogen Generation Rate (HGR) during qualification of waste feeds for the Hanford Waste Treatment and Immobilization Plant (WTP). The HGR measurement will be performed on samples of the Low Activity Waste (LAW) and High Level Waste (HLW) staged waste feeds for the WTP as well as on samples from selected unit operations testing during the qualification program. SRNL has performed a review of techniques utilized to measure HGR of high level radioactive waste slurries, evaluated the Hanford 222-S Laboratory method for measurement of hydrogen, and reviewed the hydrogen generation rate models for Hanford waste.Based on the literature review, method evaluation, and SRNL experience with measuring hydrogen generation rate, SRNL recommends that a continuous flow system with online gas analysis be used as the HGR measurement method during waste qualification.
Lunar Surface Reactor Shielding Study
Kang, Shawn; McAlpine, William; Lipinski, Ronald
2006-01-20
A nuclear reactor system could provide power to support long term human exploration of the moon. Such a system would require shielding to protect astronauts from its emitted radiations. Shielding studies have been performed for a Gas Cooled Reactor system because it is considered to be the most suitable nuclear reactor system available for lunar exploration, based on its tolerance of oxidizing lunar regolith and its good conversion efficiency. The goals of the shielding studies were to determine a material shielding configuration that reduces the dose (rem) to the required level in order to protect astronauts, and to estimate the mass of regolith that would provide an equivalent protective effect if it were used as the shielding material. All calculations were performed using MCNPX, a Monte Carlo transport code. Lithium hydride must be kept between 600 K and 700 K to prevent excessive swelling from large amounts of gamma or neutron irradiation. The issue is that radiation damage causes separation of the lithium and the hydrogen, resulting in lithium metal and hydrogen gas. The proposed design uses a layer of B4C to reduce the combined neutron and gamma dose to below 0.5Grads before the LiH is introduced. Below 0.5Grads the swelling in LiH is small (less than about 1%) for all temperatures. This approach causes the shield to be heavier than if the B4C were replaced by LiH, but it makes the shield much more robust and reliable.
Status of reactor shielding research in the United States
Bartine, D.E.
1983-01-01
Shielding research in the United States continues to place emphasis on: (1) the development and refinement of shielding design calculational methods and nuclear data; and (2) the performance of confirmation experiments, both to evaluate specific design concepts and to verify specific calculational techniques and input data. The successful prediction of the radiation levels observed within the now-operating Fast Flux Test Facility (FFTF) has demonstrated the validity of this two-pronged approach, which has since been applied to US fast breeder reactor programs and is now being used to determine radiation levels and possible further shielding needs at operating light water reactors, especially under accident conditions. A similar approach is being applied to the back end of the fission fuel cycle to verify that radiation doses at fuel element storage and transportation facilities and within fuel reprocessing plants are kept at acceptable levels without undue economic penalties.
NASA Astrophysics Data System (ADS)
Kaneko, H.; Hada, M.; Nakajima, T.; Nakatsuji, H.
1996-10-01
The 119Sn NMR chemical shifts of SnX 4(X=H, Cl, Br and I) and SnBr 4- nI n ( n = 1, 2, 3) are calculated by the ab initio UHF method including the spin-orbit (SO) interaction combined with the finite perturbation method. The calculated Sn chemical shifts are in good agreement with experiment when the SO interaction is included. As the halogen ligand becomes heavier, the SO effect increases and the chemical shift moves to a higher field. The normal halogen dependence by the substitution from Cl to I in tin tetrahalides is reproduced only when the SO interaction is included. The origin of the SO effect is ascribed to the Fermi contact term.
Comparison of Methods for Calculating Radiative Heat Transfer
Schock, Alfred; Abbate, M J
2012-01-19
Various approximations for calculating radioactive heat transfer between parallel surfaces are evaluated. This is done by applying the approximations based on total emissivities to a special case of known spectral emissivities, for which exact heat transfer calculations are possible. Comparison of results indicates that the best approximation is obtained by basing the emissivity of the receiving surface primarily on the temperature of the emitter. A specific model is shown to give excellent agreement over a very wide range of values.
McDonald, Douglas B.; Buchholz, Carol E.
1994-01-01
A shield for restricting molten corium from flowing into a water sump disposed in a floor of a containment vessel includes upper and lower walls which extend vertically upwardly and downwardly from the floor for laterally bounding the sump. The upper wall includes a plurality of laterally spaced apart flow channels extending horizontally therethrough, with each channel having a bottom disposed coextensively with the floor for channeling water therefrom into the sump. Each channel has a height and a length predeterminedly selected for allowing heat from the molten corium to dissipate through the upper and lower walls as it flows therethrough for solidifying the molten corium therein to prevent accumulation thereof in the sump.
Radiation shielding for neutron guides
NASA Astrophysics Data System (ADS)
Ersez, T.; Braoudakis, G.; Osborn, J. C.
2006-11-01
Models of the neutron guide shielding for the out of bunker guides on the thermal and cold neutron beam lines of the OPAL Reactor (ANSTO) were constructed using the Monte Carlo code MCNP 4B. The neutrons that were not reflected inside the guides but were absorbed by the supermirror (SM) layers were noted to be a significant source of gammas. Gammas also arise from neutrons absorbed by the B, Si, Na and K contained in the glass. The proposed shielding design has produced compact shielding assemblies. These arrangements are consistent with safety requirements, floor load limits, and cost constraints. To verify the design a prototype was assembled consisting of 120 mm thick Pb(96%)Sb(4%) walls resting on a concrete block. There was good agreement between experimental measurements and calculated dose rates for bulk shield regions.
Advanced Multifunctional MMOD Shield: Radiation Shielding Assessment
NASA Technical Reports Server (NTRS)
Rojdev, Kristina; Christiansen, Eric
2013-01-01
Deep space missions must contend with a harsh radiation environment Impacts to crew and electronics. Need to invest in multifunctionality for spacecraft optimization. MMOD shield. Goals: Increase radiation mitigation potential. Retain overall MMOD shielding performance.
NASA Technical Reports Server (NTRS)
Hamilton, H. H., II
1982-01-01
An approximate method for calculating heating rates at general three dimensional stagnation points is presented. The application of the method for making stagnation point heating calculations during atmospheric entry is described. Comparisons with results from boundary layer calculations indicate that the method should provide an accurate method for engineering type design and analysis applications.
Methods for calculating SEU rates for bipolar and NMOS circuits
NASA Astrophysics Data System (ADS)
McNulty, P. J.; Abdel-Kader, W. G.; Bisgrove, J. M.
1985-12-01
Computer codes developed at Clarkson for simulating charge generation by proton-induced nuclear reactions in well-defined silicon microstructures can be used to calculate SEU rates for specific devices when the critical charge and the dimensions of all SEU sensitive junctions on the device are known, provided one can estimate the contribution from externally-generated charge which enters the sensitive junction by drift and diffusion. Calculations for two important bipolar devices, the AMD 2901B bit slice and the Fairchild 93L422 RAM, for which the dimensions of the sensitive volumes were estimated from available heavy-ion test data, have been found to be in agreement with experimental data. Circuit data for the Intel 2164A, an alpha sensitive dRAM, was provided by the manufacturer. Calculations based on crude assumptions regarding which nuclear recoils and which alphas trigger upsets in the 2164A were found to agree with experimental data.
Eigenvalue methods for unimolecular rate calculations with several products.
Pritchard, Huw O
2007-10-25
When the calculation of a unimolecular reaction rate constant is cast in the form of a master equation eigenvalue problem, the magnitude of that rate is often smaller than the rounding error of the trace of the corresponding reaction matrix. Here, a previously published procedure (Pritchard, H. O. J. Phys. Chem. A 2004, 108, 5249-5252) for solving this problem is extended to the case of more than one reaction product. An Appendix notes the occurrence of avoided crossings between eigenvalues of the master equation in reversible, in mixed reversible-irreversible, and in multiwell unimolecular reaction calculations. PMID:17914776
Improving the calculation of magnetic coupling constants in MRPT methods.
Spivak, Mariano; Angeli, Celestino; Calzado, Carmen J; de Graaf, Coen
2014-09-01
The magnetic coupling in transition metal compounds with more than one unpaired electron per magnetic center has been studied with multiconfigurational perturbation theory. The usual shortcomings of these methodologies (severe underestimation of the magnetic coupling) have been overcome by describing the Slater determinants with a set of molecular orbitals that maximally resemble the natural orbitals of a high-level multiconfigurational reference configuration interaction calculation. These orbitals have significant delocalization tails onto the bridging ligands and largely increase the coupling strengths in the perturbative calculation. PMID:24992654
Shielding Ddsign and analyses of KIPT neutron source facility.
Zhong, Z.; Gohar, Y.
2011-01-01
Argonne National Laboratory (ANL) of USA and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have been collaborating on the conceptual design development of a neutron source facility. An electron accelerator drives a sub-critical facility (ADS) is used for generating the neutron source. The facility will be utilized for performing basic and applied nuclear researches, producing medical isotopes, and training young nuclear specialists. Monte Carlo code MCNPX has been utilized as the major design tool for the design, due to its capability to transport electrons, photons, and neutrons at high energies. However the ADS shielding calculations with MCNPX need enormous computational resources and the small neutron yield per electron makes sampling difficulty for the Monte Carlo calculations. The high energy electrons (E > 100 MeV) generate very high energy neutrons and these neutrons dominant the total radiation dose outside the shield. The radiation dose caused by high energy neutrons is {approx}3-4 orders of magnitude higher than that of the photons. However, the high energy neutron fraction within the total generated neutrons is very small, which increases the sampling difficulty and the required computational time. To solve these difficulties, the user subroutines of MCNPX are utilized to generate a neutron source file, which record the generated neutrons from the photonuclear reactions caused by electrons. This neutron source file is utilized many times in the following MCNPX calculations for weight windows (importance function) generation and radiation dose calculations. In addition, the neutron source file can be sampled multiple times to improve the statistics of the calculated results. In this way the expensive electron transport calculations can be performed once with good statistics for the different ADS shielding problems. This paper presents the method of generating and utilizing the neutron source file by MCNPX for the ADS shielding calculation
Radiation environment and shielding for a high luminosity collider detector
Diwan, M.V.; Fisyak, Y.; Mokhov, N.V.
1995-12-01
Detectors now under design for use in the proposed high energy high luminosity colliders must deal with unprecedented radiation levels. We have performed a comprehensive study for the GEM detector at the SSC to determine the best way to shield critical detector components from excessive radiation, with special attention paid to the low energy neutrons and photons. We have used several detailed Monte-Carlo simulations to calculate the particle fluxes in the detector. We describe these methods and demonstrate that two orders of magnitude reduction in the neutron and photon fluxes can be obtained with appropriate shielding of critical forward regions such as the low beta quadrupoles and the forward calorimeter.
Zwan, Benjamin J. O’Connor, Daryl J.; King, Brian W.; Greer, Peter B.
2014-08-15
Purpose: To develop a frame-by-frame correction for the energy response of amorphous silicon electronic portal imaging devices (a-Si EPIDs) to radiation that has transmitted through the multileaf collimator (MLC) and to integrate this correction into the backscatter shielded EPID (BSS-EPID) dose-to-water conversion model. Methods: Individual EPID frames were acquired using a Varian frame grabber and iTools acquisition software then processed using in-house software developed inMATLAB. For each EPID image frame, the region below the MLC leaves was identified and all pixels in this region were multiplied by a factor of 1.3 to correct for the under-response of the imager to MLC transmitted radiation. The corrected frames were then summed to form a corrected integrated EPID image. This correction was implemented as an initial step in the BSS-EPID dose-to-water conversion model which was then used to compute dose planes in a water phantom for 35 IMRT fields. The calculated dose planes, with and without the proposed MLC transmission correction, were compared to measurements in solid water using a two-dimensional diode array. Results: It was observed that the integration of the MLC transmission correction into the BSS-EPID dose model improved agreement between modeled and measured dose planes. In particular, the MLC correction produced higher pass rates for almost all Head and Neck fields tested, yielding an average pass rate of 99.8% for 2%/2 mm criteria. A two-sample independentt-test and fisher F-test were used to show that the MLC transmission correction resulted in a statistically significant reduction in the mean and the standard deviation of the gamma values, respectively, to give a more accurate and consistent dose-to-water conversion. Conclusions: The frame-by-frame MLC transmission response correction was shown to improve the accuracy and reduce the variability of the BSS-EPID dose-to-water conversion model. The correction may be applied as a preprocessing step
The proton nuclear magnetic shielding tensors in biphenyl: experiment and theory.
Schönborn, Frank; Schmitt, Heike; Zimmermann, Herbert; Haeberlen, Ulrich; Corminboeuf, Clémence; Grossmann, Gisbert; Heine, Thomas
2005-07-01
Line-narrowing multiple pulse techniques are applied to a spherical sample crystal of biphenyl. The 10 different proton shielding tensors in this compound are determined. The accuracy level for the tensor components is 0.3 ppm. The assignment of the measured tensors to the corresponding proton sites is given careful attention. Intermolecular shielding contributions are calculated by the induced magnetic point dipole model with empirical atom and bond susceptibilities (distant neighbours) and by a new quantum chemical method (near neighbours). Subtracting the intermolecular contributions from the (correctly assigned) measured shielding tensors leads to isolated-molecule shielding tensors for which there are symmetry relations. Compliance to these relations is the criterion for the correct assignment. The success of this program indicates that intermolecular proton shielding contributions can be calculated to better than 0.5 ppm. The isolated-molecule shielding tensors obtained from experiment and calculated intermolecular contributions are compared with isolated-molecule quantum chemical results. Expressed in the icosahedral tensor representation, the rms differences of the respective tensor components are below 0.5 ppm for all proton sites in biphenyl. In the isolated molecule, the least shielded direction of all protons is the perpendicular to the molecular plane. For the para proton, the intermediate principal direction is along the C-H bond. It is argued that these relations also hold for the protons in the isolated benzene molecule. PMID:15949748
Platts, James A; Gkionis, Konstantinos
2009-11-28
Ab initio and density functional theory (DFT) calculations of nuclear magnetic resonance shielding tensors in benzene-methane and two isomers of the benzene dimer are reported, with the aim of probing the changes in shielding induced by the formation of supramolecular complexes from isolated molecules. It is shown that the changes in shielding (and hence of chemical shift) for hydrogen nuclei are broadly in line with expectations from "shielding cones" based on aromatic ring current, but that changes for carbon nuclei are rather more subtle. More detailed analysis indicates that the change in isotropic shielding results from much larger changes in individual components of the shielding tensor and in diamagnetic/paramagnetic shielding contributions. Benchmark data were obtained using Møller-Plesset 2nd order perturbation theory with a medium-sized basis set, but it is shown that Hartree-Fock and most density functional theory methods reproduce all essential changes in shielding, and do so in a reasonably basis set independent fashion. The chosen method is then applied to a DNA-intercalator complex. PMID:19890517
Kerns, J.A.; Stone, R.R.; Fabyan, J.
1985-02-12
A magnetically-conductive filler material bridges the gap between a multi-part magnetic shield structure which substantially encloses a predetermined volume so as to minimize the ingress or egress of magnetic fields with respect to that volume. The filler material includes a heavy concentration of single-magnetic-domain-sized particles of a magnetically conductive material (e.g. soft iron, carbon steel or the like) dispersed throughout a carrier material which is generally a non-magnetic material that is at least sometimes in a plastic or liquid state. The maximum cross-sectional particle dimension is substantially less than the nominal dimension of the gap to be filled. An epoxy base material (i.e. without any hardening additive) low volatility vacuum greases or the like may be used for the carrier material. The structure is preferably exposed to the expected ambient field while the carrier is in a plastic or liquid state so as to facilitate alignment of the single-magnetic-domain-sized particles with the expected magnetic field lines.
Kerns, J.A.; Stone, R.R.; Fabyan, J.
1987-10-06
A magnetically-conductive filler material bridges the gap between a multi-part magnetic shield structure which substantially encloses a predetermined volume so as to minimize the ingress or egress of magnetic fields with respect to that volume. The filler material includes a heavy concentration of single-magnetic-domain-sized particles of a magnetically conductive material (e.g. soft iron, carbon steel or the like) dispersed throughout a carrier material which is generally a non-magnetic material that is at least sometimes in a plastic or liquid state. The maximum cross-sectional particle dimension is substantially less than the nominal dimension of the gap to be filled. An epoxy base material (i.e. without any hardening additive) low volatility vacuum greases or the like may be used for the carrier material. The structure is preferably exposed to the expected ambient magnetic field while the carrier is in a plastic or liquid state so as to facilitate alignment of the single-magnetic-domain-sized particles with the expected magnetic field lines. 3 figs.
Kerns, John A.; Stone, Roger R.; Fabyan, Joseph
1987-01-01
A magnetically-conductive filler material bridges the gap between a multi-part magnetic shield structure which substantially encloses a predetermined volume so as to minimize the ingress or egress of magnetic fields with respect to that volume. The filler material includes a heavy concentration of single-magnetic-domain-sized particles of a magnetically conductive material (e.g. soft iron, carbon steel or the like) dispersed throughout a carrier material which is generally a non-magnetic material that is at least sometimes in a plastic or liquid state. The maximum cross-sectional particle dimension is substantially less than the nominal dimension of the gap to be filled. An epoxy base material (i.e. without any hardening additive) low volatility vacuum greases or the like may be used for the carrier material. The structure is preferably exposed to the expected ambient magnetic field while the carrier is in a plastic or liquid state so as to facilitate alignment of the single-magnetic-domain-sized particles with the expected magnetic field lines.
Calculations of NMR chemical shifts with APW-based methods
NASA Astrophysics Data System (ADS)
Laskowski, Robert; Blaha, Peter
2012-01-01
We present a full potential, all electron augmented plane wave (APW) implementation of first-principles calculations of NMR chemical shifts. In order to obtain the induced current we follow a perturbation approach [Pickard and Mauri, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.63.245101 63, 245101 (2001)] and extended the common APW + local orbital (LO) basis by several LOs at higher energies. The calculated all-electron current is represented in traditional APW manner as Fourier series in the interstitial region and with a spherical harmonics representation inside the nonoverlapping atomic spheres. The current is integrated using a “pseudocharge” technique. The implementation is validated by comparison of the computed chemical shifts with some “exact” results for spherical atoms and for a set of solids and molecules with available published data.
Experiences with leak rate calculations methods for LBB application
Grebner, H.; Kastner, W.; Hoefler, A.; Maussner, G.
1997-04-01
In this paper, three leak rate computer programs for the application of leak before break analysis are described and compared. The programs are compared to each other and to results of an HDR Reactor experiment and two real crack cases. The programs analyzed are PIPELEAK, FLORA, and PICEP. Generally, the different leak rate models are in agreement. To obtain reasonable agreement between measured and calculated leak rates, it was necessary to also use data from detailed crack investigations.
Intercalated graphite fiber composites as EMI shields in aerospace structures
NASA Technical Reports Server (NTRS)
Gaier, James R.
1990-01-01
The requirements for electromagnetic interference (EMI) shielding in aerospace structures are complicated over that of ground structures by their weight limitations. As a result, the best EMI shielding materials must blend low density, high strength, and high elastic modulus with high shielding ability. In addition, fabrication considerations including penetrations and joints play a major role. The EMI shielding properties are calculated for shields formed from pristine and intercalated graphite fiber/epoxy composites and compared to preliminary experimental results and to shields made from aluminum. Calculations indicate that EMI shields could be fabricated from intercalated graphite composites which would have less than 12 percent of the mass of conventional aluminum shields, based on mechanical properties and shielding properties alone.
Intercalated graphite fiber composites as EMI shields in aerospace structures
NASA Technical Reports Server (NTRS)
Gaier, James R.
1992-01-01
The requirements for electromagnetic interference (EMI) shielding in aerospace structures are more complicated than those for ground structures because of their weight limitations. As a result, the best EMI shielding materials must combine low density, high strength, and high elastic modulus with high shielding ability. EMI shielding characteristics were calculated for shields formed from pristine and intercalated graphite fiber/epoxy composites and compare to preliminary experimental results for these materials and to the characteristics of shields made from aluminum. Calculations indicate that effective EMI shields could be fabricated from intercalated graphite composites which would have less than 12 percent of the mass of conventional aluminum shields, based on mechanical properties and shielding characteristics alone.
78 FR 64030 - Monitoring Criteria and Methods To Calculate Occupational Radiation Doses
Federal Register 2010, 2011, 2012, 2013, 2014
2013-10-25
... monitoring and calculating occupational radiation doses. On December 4, 2007 (72 FR 68043), the NRC revised... COMMISSION Monitoring Criteria and Methods To Calculate Occupational Radiation Doses AGENCY: Nuclear... Criteria and Methods to Calculate Occupational Radiation Doses.'' This guide describes methods that the...
Advanced Multifunctional MMOD Shield: Radiation Shielding Assessment
NASA Technical Reports Server (NTRS)
Rojdev, Kristina; Christiansen, Eric
2011-01-01
As NASA is looking to explore further into deep space, multifunctional materials are a necessity for decreasing complexity and mass. One area where multifunctional materials could be extremely beneficial is in the micrometeoroid orbital debris (MMOD) shield. A typical MMOD shield on the International Space Station (ISS) is a stuffed whipple shield consisting of multiple layers. One of those layers is the thermal blanket, or multi-layer insulation (MLI). By increasing the MMOD effectiveness of MLI blankets, while still preserving their thermal capabilities, could allow for a less massive MMOD shield. Thus, a study was conducted to evaluate concept MLI blankets for MMOD shields. In conjunction, these MLI blankets and the subsequent MMOD shields were also evaluated for their radiation shielding effectiveness towards protecting crew. These concepts were evaluated against the ISS MLI blankets and the ISS MMOD shield, which acted as the baseline. These radiation shielding assessments were performed using the high charge and energy transport software (HZETRN). This software is based on a one-dimensional formula of the Boltzmann transport equation with a straight-ahead approximation. Each configuration was evaluated against the following environments to provide a diverse view of radiation shielding effectiveness in most space environments within the heliosphere: August 1972 solar particle event, October 1989 solar particle event, 1982 galactic cosmic ray environment (during solar maximum), 1987 galactic cosmic ray environment (during solar minimum), and a low earth orbit environment in 1970 that corresponded to an altitude of 400 km and inclination of 51.6 . Both the absorbed dose and the dose equivalent were analyzed, but the focus of the discussion was on the dose equivalent since the data is most concerned with radiation shielding of the crew. The following paper outlines the evaluations performed and discusses the results and conclusions of this evaluation for
Survey of methods for calculating sensitivity of general eigenproblems
NASA Technical Reports Server (NTRS)
Murthy, Durbha V.; Haftka, Raphael T.
1987-01-01
A survey of methods for sensitivity analysis of the algebraic eigenvalue problem for non-Hermitian matrices is presented. In addition, a modification of one method based on a better normalizing condition is proposed. Methods are classified as Direct or Adjoint and are evaluated for efficiency. Operation counts are presented in terms of matrix size, number of design variables and number of eigenvalues and eigenvectors of interest. The effect of the sparsity of the matrix and its derivatives is also considered, and typical solution times are given. General guidelines are established for the selection of the most efficient method.
A database method for binary atomic scattering angle calculation
NASA Astrophysics Data System (ADS)
Yuan, B.; Yu, P. C.; Tang, S. M.
1993-11-01
Calculation of the classical binary atomic scattering angle is a critical factor in computer simulations of ion beam interactions with matter. Different approaches intended for more accurate results with sufficient speed have been reported in the literature. This paper presents an approach using database evaluation. This approach has been tested and found to be extremely fast (18 times faster than the Biersack-Haggmark's Magic-Formula for scattering [Nucl. Instr. and Meth. 174 (1980) 257]), and its accuracy is better than 0.5%. This database takes only 216 kB of computer memory.
Dietary analysis with programmable calculator: a simplified method.
Dorea, J G; Horner, M R; Johnson, N E
1981-02-01
The use and applications of programmable calculator in dietary analysis are presented. Results which approximate those of large computers can be obtained with considerably less time, money, and data manipulation. Program flexibility allows operators to determine the number of foods and nutrients to be analyzed. Input, data checking, and results of total nutrient consumption are achieved within minutes. The dietary analysis described in this article is well suited for small hospitals and clinics, for teaching purposes and dietary surveys and for use by non-nutritionists who have a one-time or regular need to incorporate dietary information into their work. PMID:7217573
Space reactor shielding fabrication
NASA Technical Reports Server (NTRS)
Welch, F. H.
1972-01-01
The fabrication of space reactor neutron shielding by a melting and casting process utilizing lithium hydride is described. The first neutron shield fabricated is a large pancake shape 86 inches in diameter, containing about 1700 pounds of lithium hydride. This shield, fabricated by the unique melting and casting process, is the largest lithium hydride shield ever built.
Calculating PI Using Historical Methods and Your Personal Computer.
ERIC Educational Resources Information Center
Mandell, Alan
1989-01-01
Provides a software program for determining PI to the 15th place after the decimal. Explores the history of determining the value of PI from Archimedes to present computer methods. Investigates Wallis's, Liebniz's, and Buffon's methods. Written for Tandy GW-BASIC (IBM compatible) with 384K. Suggestions for Apple II's are given. (MVL)
O(N) methods in electronic structure calculations
NASA Astrophysics Data System (ADS)
Bowler, D. R.; Miyazaki, T.
2012-03-01
Linear-scaling methods, or O(N) methods, have computational and memory requirements which scale linearly with the number of atoms in the system, N, in contrast to standard approaches which scale with the cube of the number of atoms. These methods, which rely on the short-ranged nature of electronic structure, will allow accurate, ab initio simulations of systems of unprecedented size. The theory behind the locality of electronic structure is described and related to physical properties of systems to be modelled, along with a survey of recent developments in real-space methods which are important for efficient use of high-performance computers. The linear-scaling methods proposed to date can be divided into seven different areas, and the applicability, efficiency and advantages of the methods proposed in these areas are then discussed. The applications of linear-scaling methods, as well as the implementations available as computer programs, are considered. Finally, the prospects for and the challenges facing linear-scaling methods are discussed.
An artificial energy method for calculating flows with shocks
NASA Technical Reports Server (NTRS)
Rose, M. E.
1980-01-01
The artificial-viscosity method, first proposed by von Neumann and Richtmyer, introduces an artificial viscous pressure term in regions of compression such that an increase in entropy occurs in shock transition zones. The paper describes how dissipative flows can be induced by reducing the total energy available for adiabatic processes in shock zones. A class of inviscid fluid flows, called semiflows, is described in which the flows exhibit thermodynamic differences. Induced dissipative flows modify the pressure in regions of compression in a manner analogous to the artificial-viscosity method and for a gas, the effect is equivalent to suitably modifying the gas constant in the equation of state. By employing MacCormack's method and the usual non-adiabatic equations, numerical solutions of a Riemann problem are compared with the modified artificial energy method, showing that the dissipation effect predicted by the analytical formulation is reflected in the numerical method as well.
'Nose method' of calculating critical cooling rates for glass formation
NASA Technical Reports Server (NTRS)
Weinberg, Michael C.; Uhlmann, Donald R.; Zanotto, Edgar D.
1989-01-01
The use of the so-called 'nose method' for computing critical cooling rates for glass formation is examined and compared with other methods, presenting data for the glass-forming systems SiO2, GeO2, and P2O5. It is shown that, for homogeneous crystallization, the nose-method will give an overestimate of Rc, a conclusion which was drawn after assessing the enfluence of a range of values for the parameters which control crystal growth and nucleation. The paper also proposes an alternative simple procedure (termed the 'cutoff method') for computing critical cooling rates from T-T-T diagrams, which was shown in the SiO2 and GeO2 systems to be superior to the nose method.
The ORNL-SNAP shielding program
NASA Technical Reports Server (NTRS)
Mynatt, F. R.; Clifford, C. E.; Muckenthaler, F. J.; Gritzner, M. L.
1972-01-01
The effort in the ORNL-SNAP shielding program is directed toward the development and verification of computer codes using numerical solutions to the transport equation for the design of optimized radiation shields for SNAP power systems. A brief discussion is given for the major areas of the SNAP shielding program, which are cross-section development, transport code development, and integral experiments. Detailed results are presented for the integral experiments utilizing the TSF-SNAP reactor. Calculated results are compared with experiments for neutron and gamma-ray spectra from the bare reactor and as transmitted through slab shields.
Godunov Method for Calculating Multicomponent Heterogeneous Medium Flows
NASA Astrophysics Data System (ADS)
Surov, V. S.
2014-03-01
The modified Godunov method intended for integrating the nondivergent systems that describe a multivelocity heterogeneous mixture flow is presented. The linearized Riemann solver has been used in solving the Riemann problems.
EMI Shields made from intercalated graphite composites
NASA Technical Reports Server (NTRS)
Gaier, James R.; Terry, Jennifer
1995-01-01
Electromagnetic interference (EMI) shielding typically makes up about twenty percent of the mass of a spacecraft power system. Graphite fiber/polymer composites have significantly lower densities and higher strengths than aluminum, the present material of choice for EMI shields, but they lack the electrical conductivity that enables acceptable shielding effectiveness. Bromine intercalated pitch-based graphite/epoxy composites have conductivities fifty times higher than conventional structural graphite fibers. Calculations are presented which indicate that EMI shields made from such composites can have sufficient shielding at less than 20% of the mass of conventional aluminum shields. EMI shields provide many functions other than EMI shielding including physical protection, thermal management, and shielding from ionizing radiation. Intercalated graphite composites perform well in these areas also. Mechanically, they have much higher specific strength and modulus than aluminum. They also have shorter half thicknesses for x-rays and gamma radiation than aluminum. Thermally, they distribute infra-red radiation by absorbing and re-radiating it rather than concentrating it by reflection as aluminum does. The prospects for intercalated graphite fiber/polymer composites for EMI shielding are encouraging.
Advanced Multifunctional MMOD Shield: Radiation Shielding Assessment
NASA Technical Reports Server (NTRS)
Rojdev, Kristina; Christiansen, Eric
2013-01-01
As NASA is looking to explore further into deep space, multifunctional materials are a necessity for decreasing complexity and mass. One area where multifunctional materials could be extremely beneficial is in the micrometeoroid orbital debris (MMOD) shield. A typical MMOD shield on the International Space Station (ISS) is a stuffed whipple shield consisting of multiple layers. One of those layers is the thermal blanket, or multi-layer insulation (MLI). Increasing the MMOD effectiveness of MLI blankets, while still preserving their thermal capabilities, could allow for a less massive MMOD shield. Thus, a study was conducted to evaluate a concept MLI blanket for an MMOD shield. In conjunction, this MLI blanket and the subsequent MMOD shield was also evaluated for its radiation shielding effectiveness towards protecting crew. The overall MMOD shielding system using the concept MLI blanket proved to only have a marginal increase in the radiation mitigating properties. Therefore, subsequent analysis was performed on various conceptual MMOD shields to determine the combination of materials that may prove superior for radiation mitigating purposes. The following paper outlines the evaluations performed and discusses the results and conclusions of this evaluation for radiation shielding effectiveness.
NASA Astrophysics Data System (ADS)
Vasilopoulou, T.; Stamatelatos, I. E.; Batistoni, P.; Conroy, S.; Obryk, B.; Popovichev, S.; Syme, D. B.
2015-11-01
Experiments and Monte Carlo simulations were performed at the Joint European Torus (JET) in order to validate the computational tools and methods applied for neutron streaming calculations through penetrations in the JET Hall biological shielding. In the present work the sensitivity of the simulations on the hydrogen and boron content in concrete shielding was investigated. MCNP code was used to simulate neutron streaming along the JET Hall personnel entrance labyrinth for deuterium-deuterium and deuterium-tritium plasma sources for different concrete wall compositions. Neutron fluence and ambient dose equivalent along the labyrinth were calculated. Simulation results for the "as built" JET concrete composition were compared against measurements performed using thermoluminescence detectors. This study contributes to the optimization of the radiation shielding of JET and, furthermore, provides information from JET experience that may assist in optimizing and validating the radiation shielding design methodology used in its successor fusion devices ITER and DEMO.
Potential theoretic methods for far field sound radiation calculations
NASA Technical Reports Server (NTRS)
Hariharan, S. I.; Stenger, Edward J.; Scott, J. R.
1995-01-01
In the area of computational acoustics, procedures which accurately predict the far-field sound radiation are much sought after. A systematic development of such procedures are found in a sequence of papers by Atassi. The method presented here is an alternate approach to predicting far field sound based on simple layer potential theoretic methods. The main advantages of this method are: it requires only a simple free space Green's function, it can accommodate arbitrary shapes of Kirchoff surfaces, and is readily extendable to three-dimensional problems. Moreover, the procedure presented here, though tested for unsteady lifting airfoil problems, can easily be adapted to other areas of interest, such as jet noise radiation problems. Results are presented for lifting airfoil problems and comparisons are made with the results reported by Atassi. Direct comparisons are also made for the flat plate case.
Comparison of methods for numerical calculation of continuum damping
Bowden, G. W.; Hole, M. J.; Dennis, G. R.; Könies, A.; Gorelenkov, N. N.
2014-05-15
Continuum resonance damping is an important factor in determining the stability of certain global modes in fusion plasmas. A number of analytic and numerical approaches have been developed to compute this damping, particularly, in the case of the toroidicity-induced shear Alfvén eigenmode. This paper compares results obtained using an analytical perturbative approach with those found using resistive and complex contour numerical approaches. It is found that the perturbative method does not provide accurate agreement with reliable numerical methods for the range of parameters examined. This discrepancy exists even in the limit where damping approaches zero. When the perturbative technique is implemented using a standard finite element method, the damping estimate fails to converge with radial grid resolution. The finite elements used cannot accurately represent the eigenmode in the region of the continuum resonance, regardless of the number of radial grid points used.
Radiation Shielding Properties of Some Marbles in Turkey
Guenoglu, K.; Akkurt, I.
2011-12-26
Especially after development of technology, radiation started to be used in a large fields such as medicine, industry and energy. Using radiation in those fields bring hazardous effect of radiation into humancell. Thus radiation protection becomes important in physics. Although there are three ways for radiation protection, shielding of the radiation is the most commonly used method. Natural Stones such as marble is used as construction material especially in critical building and thus its radiation shielding capability should be determined.In this study, gamma ray shielding properties of some different types of marble mined in Turkey, have been measured using a NaI(Tl) scintillator detector. The measured results were also compared with the theoretical calculations XCOM.
A probabilistic method of calculating circulation-induced trends
NASA Astrophysics Data System (ADS)
Brox Nilsen, Irene; Stagge, James Howard; Merete Tallaksen, Lena
2015-04-01
The water cycle in Europe has changed substantially over the past three decades. Increasing runoff is observed during winter and at northern latitudes in particular. Spring and summer months, as well as southern latitudes, are facing drier conditions. To understand what is driving large-scale changes in runoff, we look into changes in precipitation and temperature and link these to changes in atmospheric circulation. Previous studies have used the method of trend ratios (Cahynová and Huth, 2009) to attribute precipitation and temperature trends to changes in the frequency of circulation types. A trend ratio is the ratio of hypothetical trend, i.e., the trend that would result due to changes in circulation type frequency only, to the observed trend. However, the method of trend ratios has two drawbacks. First, if the observed trend is small, division by a very low value results in a meaningless trend ratio and thus requires a cut-off value to keep the trend ratio within meaningful boundaries. Second, the method does not allow a comparison of the observed trend to the spread of possible outcomes, because the method of hypothetical trends is based on a deterministic model. We propose a new, more robust method for detecting the importance of circulation-induced changes in explaining the observed trends, which has the benefit of being a non-parametric statistical test that assesses the entire range of hypothetical trends. Instead of creating a hypothetical series by replacing the observation on a given day with the long-term climatic mean of a certain month and circulation type (as in the existing trend ratio method), the new approach replaces the observation on a given day with a random sample from the distribution of the variable for the given month and circulation type. The method introduces the possibility to assign a rejection rate, thus allowing statistical significance to be assessed. We apply the method on time series of precipitation and temperature from the
Subtleties in Energy Calculations in the Image Method
ERIC Educational Resources Information Center
Taddei, M. M.; Mendes, T. N. C.; Farina, C.
2009-01-01
In this pedagogical work, we point out a subtle mistake that can be made by undergraduate or graduate students in the computation of the electrostatic energy of a system containing charges and perfect conductors if they naively use the image method. Specifically, we show that naive expressions for the electrostatic energy for these systems…
Exploratory Environmental Tests of Several Heat Shields
NASA Technical Reports Server (NTRS)
Goodman, George P.; Betts, John, Jr.
1961-01-01
Exploratory tests have been conducted with several conceptual radiative heat shields of composite construction. Measured transient temperature distributions were obtained for a graphite heat shield without insulation and with three types of insulating materials, and for a metal multipost heat shield, at surface temperatures of approximately 2,000 F and 1,450 F, respectively, by use of a radiant-heat facility. The graphite configurations suffered loss of surface material under repeated irradiation. Temperature distribution calculated for the metal heat shield by a numerical procedure was in good agreement with measured data. Environmental survival tests of the graphite heat shield without insulation, an insulated multipost heat shield, and a stainless-steel-tile heat shield were made at temperatures of 2,000 F and dynamic pressures of approximately 6,000 lb/sq ft, provided by an ethylene-heated jet operating at a Mach number of 2.0 and sea-level conditions. The graphite heat shield survived the simulated aerodynamic heating and pressure loading. A problem area exists in the design and materials for heat-resistant fasteners between the graphite shield and the base structure. The insulated multipost heat shield was found to be superior to the stainless-steel-tile heat shield in retarding heat flow. Over-lapped face-plate joints and surface smoothness of the insulated multi- post heat shield were not adversely affected by the test environment. The graphite heat shield without insulation survived tests made in the acoustic environment of a large air jet. This acoustic environment is random in frequency and has an overall noise level of 160 decibels.
Residual stresses calculation in autofrettage using variable material properties method
Jahed, H.; Dubey, R.N.
1996-12-01
Autofrettaged cylinders are used for variety of applications in chemical and nuclear industries where large internal pressures have to be withstood. Autofrettage is in the process by which beneficial residual stresses are introduced into thick-walled tubes by initially subjected the tube to high internal pressure which causes inelastic deformation. Here, the variable material properties method is employed to obtain elastic-plastic analysis of an autofrettaged tube. This method develops inelastic solution from the elastic solution by treating the material properties as field variables. The distribution of these parameters are obtained in an iterative manner as a part of the solution. An energy based scheme is used to update these variables. The residual stress field of autofrettaged tubes based on the actual material curve and isotropic and kinematic hardening models are obtained. The results are shown to be in good agreement with the published experimental and finite element results.
Computational methods. [Calculation of dynamic loading to offshore platforms
Maeda, H. . Inst. of Industrial Science)
1993-02-01
With regard to the computational methods for hydrodynamic forces, first identification of marine hydrodynamics in offshore technology is discussed. Then general computational methods, the state of the arts and uncertainty on flow problems in offshore technology in which developed, developing and undeveloped problems are categorized and future works follow. Marine hydrodynamics consists of water surface and underwater fluid dynamics. Marine hydrodynamics covers, not only hydro, but also aerodynamics such as wind load or current-wave-wind interaction, hydrodynamics such as cavitation, underwater noise, multi-phase flow such as two-phase flow in pipes or air bubble in water or surface and internal waves, and magneto-hydrodynamics such as propulsion due to super conductivity. Among them, two key words are focused on as the identification of marine hydrodynamics in offshore technology; they are free surface and vortex shedding.
Shielding of manned space vehicles against protons and alpha particles
NASA Technical Reports Server (NTRS)
Alsmiller, R. G., Jr.; Santoro, R. T.; Barish, J.; Claiborne, H. C.
1972-01-01
The available information on the shielding of manned space vehicles against protons and alpha particles is summarized. The emphasis is placed on shielding against Van Allen belt protons and against solar-flare protons and alpha particles, but information on shielding against galactic cosmic rays is also presented. The approximation methods for use by nonexperts in the space shielding field are those that are standard in the space shielding literature.
Method for calculating longitudinal microstrip antennas in planar phased arrays
NASA Astrophysics Data System (ADS)
Indenbom, M. V.
The characteristics of longitudinal microstrip antennas in a planar phased array are examined on the basis of the application of the finite element method to an integral equation for the 'charge' on the microstrip line. Microstrip dipoles, and Yagi and log-periodic antennas are examples of such radiators. The analysis takes into account the complex configuration of the conductors, both current components, and the presence of dielectric substrates and a protective coating.
Compressible flow calculations employing the Galerkin/least-squares method
NASA Technical Reports Server (NTRS)
Shakib, F.; Hughes, T. J. R.; Johan, Zdenek
1989-01-01
A multielement group, domain decomposition algorithm is presented for solving linear nonsymmetric systems arising in the finite-element analysis of compressible flows employing the Galerkin/least-squares method. The iterative strategy employed is based on the generalized minimum residual (GMRES) procedure originally proposed by Saad and Shultz. Two levels of preconditioning are investigated. Applications to problems of high-speed compressible flow illustrate the effectiveness of the scheme.
Free-energy calculation methods for collective phenomena in membranes
NASA Astrophysics Data System (ADS)
Smirnova, Yuliya G.; Fuhrmans, Marc; Barragan Vidal, Israel A.; Müller, Marcus
2015-09-01
Collective phenomena in membranes are those which involve the co-operative reorganization of many molecules. Examples of these are membrane fusion, pore formation, bending, adhesion or fission. The time and length scales, on which these processes occur, pose a challenge for atomistic simulations. Therefore, in order to solve the length scale problem it is popular to introduce a coarse-grained representation. To facilitate sampling of the relevant states additional computational techniques, which encourage the system to explore the free-energy landscape far from equilibrium and visit transition states, are needed. These computational techniques provide insights about the free-energy changes involved in collective transformations of membranes, yielding information about the rate limiting states, the transformation mechanism and the influence of architectural, compositional and interaction parameters. A common approach is to identify an order parameter (or reaction coordinate), which characterizes the pathway of membrane reorganization. However, no general strategy exists to define such an order parameter that can properly describe cooperative reorganizations in membranes. Recently developed methods can overcome this problem of the order-parameter choice and allow us to study collective phenomena in membranes. We will discuss such methods as thermodynamic integration, umbrella sampling, and the string method and results provided by their applications to particle-based simulations, particularly focusing on membrane fusion and pore formation.
Radiation shielding for lunar bases using lunar concrete
NASA Astrophysics Data System (ADS)
Huston, S. L.; Oishi, K.; Saito, T.
1992-08-01
The radiation shielding requirements for an advanced lunar base concept which uses concrete made from lunar resources are evaluated. Some of the features of this lunar base concept are discussed. The results of radiation transport calculations are presented to determine the radiation dose as a function of shielding depth. The shielding effectiveness of concrete is compared with that of aluminum, lunar regolith, and water. It is shown that lunar concrete is a fairly effective radiation shield, and that the concrete lunar base concept can provide a significant amount of intrinsic shielding without requiring additional parasitic shielding.
An improved filtered spherical harmonic method for transport calculations
Ahrens, C.; Merton, S.
2013-07-01
Motivated by the work of R. G. McClarren, C. D. Hauck, and R. B. Lowrie on a filtered spherical harmonic method, we present a new filter for such numerical approximations to the multi-dimensional transport equation. In several test problems, we demonstrate that the new filter produces results with significantly less Gibbs phenomena than the filter used by McClarren, Hauck and Lowrie. This reduction in Gibbs phenomena translates into propagation speeds that more closely match the correct propagation speed and solutions that have fewer regions where the scalar flux is negative. (authors)
A combined representation method for use in band structure calculations. 1: Method
NASA Technical Reports Server (NTRS)
Friedli, C.; Ashcroft, N. W.
1975-01-01
A representation was described whose basis levels combine the important physical aspects of a finite set of plane waves with those of a set of Bloch tight-binding levels. The chosen combination has a particularly simple dependence on the wave vector within the Brillouin Zone, and its use in reducing the standard one-electron band structure problem to the usual secular equation has the advantage that the lattice sums involved in the calculation of the matrix elements are actually independent of the wave vector. For systems with complicated crystal structures, for which the Korringa-Kohn-Rostoker (KKR), Augmented-Plane Wave (APW) and Orthogonalized-Plane Wave (OPW) methods are difficult to apply, the present method leads to results with satisfactory accuracy and convergence.
Heat-shield design for glovebox applications.
Frigo, A. A.
1998-07-10
Heat shields can often be used in place of insulation materials as an effective means of insulating glovebox furnace vessels. If used properly, shields can accomplish two important objectives: thermal insulation of the vessel to maintain a desired process temperature and protection of the glovebox, equipment, and user. A heat-shield assembly can be described as an arrangement of thin, properly-spaced, metal sheets that reduce radiation heat transfer. The main problem encountered in the design of a heat shield assembly is choosing the number of shields. In determining the heat transfer characteristics of a heat-shield assembly, a number of factors must be taken into consideration. The glovebox or outside environment, material properties, geometry, and operating temperature all have varying effects on the expected results. A simple method, for planar-horizontal and cylindrical-vertical shields, allowing the approximation of the outermost shield temperature, the practical number of shields, and the net heat-transfer rate will be presented. Methods used in the fabrication of heat-shield assemblies will also be discussed.
An approximate method for residual stress calculation infunctionally graded materials
Becker, T.L.
1999-06-02
Thermal residual stresses in functionally graded materials(FGMs) arise primarily from nonlinear spatial variations in the thermalexpansion coefficient, but can be significantly adjusted by variations inmodulus. Thermoelastic analysis of FGMs is complicated by such modulusgradients. A class of problems for which thermal stress solutions formaterials with constant modulus can be used as a basis for approximationsfor FGMs is discussed. The size of the error in this approximation due togradients in elastic modulus is investigated. Analytical and finiteelement solutions for the thermal stresses in various FGM geometries arecompared to results from this approximate method. In a geometry ofpractical interest, a right cylinder graded along the z-axis, the errorfor a Ni-Al2O3 FGM was found to be within 15 percent for all gradientsconsidered. The form of the approximation makes it easier to identifydesirable types of spatial nonlinearity in expansion coefficient andvariations in modulus: this would allow the manipulation of the locationof compressive stresses.
DABCO mono-betaine hydrate studied by X-ray diffraction, DFT calculations and spectroscopic methods
NASA Astrophysics Data System (ADS)
Barczyński, P.; Dega-Szafran, Z.; Katrusiak, A.; Perdoch, W.; Szafran, M.
2009-09-01
A new DABCO mono-betaine (1-carboxymethyl-1,4-diazabicyclo[2.2.2]octane inner salt) has been synthesized. It crystallizes as monohydrate in orthorhombic space group Pmn2 1. The DABCO mono-betaine and water molecules are located on a mirror plane. The water molecules link DABCO mono-betaine into linear chains through the H-O-H⋯OOC and H-O-H⋯N hydrogen bonds of 2.709(2) and 2.875(2) Å. The structure of the title compound optimized at B3LYP/6-31G(d,p) level of theory is consistent with X-ray diffraction. The absorption bands in the FTIR spectrum have been assigned. The calculated magnetic isotropic shielding tensors confirm the assignments of the 13C NMR resonance signals.
NASA Technical Reports Server (NTRS)
Simonich, J. C.; Amiet, R. K.; Schlinker, R. H.
1986-01-01
An experimental and theoretical study was conducted to develop a validated first principle analysis for predicting the jet noise reduction achieved by shielding one jet exhaust flow with a second, closely spaced, identical jet flow. A generalized fuel jet noise analytical model was formulated in which the acoustic radiation from a source jet propagates through the velocity and temperature discontinuity of the adjacent shielding jet. Input variables to the prediction procedure include jet Mach number, spacing, temperature, diameter, and source frequency. Refraction, diffraction, and reflection effects, which control the dual jet directivity pattern, are incorporated in the theory. The analysis calculates the difference in sound pressure level between the dual jet configuration and the radiation field based on superimposing two independent jet noise directivity patterns. Jet shielding was found experimentally to reduce noise levels in the common plane of the dual jet system relative to the noise generated by two independent jets.
NASA Technical Reports Server (NTRS)
Christiansen, Eric L.
2003-01-01
This report provides innovative, low-weight shielding solutions for spacecraft and the ballistic limit equations that define the shield's performance in the meteoroid/debris environment. Analyses and hypervelocity impact testing results are described that have been used in developing the shields and equations. Spacecraft shielding design and operational practices described in this report are used to provide effective spacecraft protection from meteoroid and debris impacts. Specific shield applications for the International Space Station (ISS), Space Shuttle Orbiter and the CONTOUR (Comet Nucleus Tour) space probe are provided. Whipple, Multi-Shock and Stuffed Whipple shield applications are described.
Preconditioned Conjugate Gradient methods for low speed flow calculations
NASA Technical Reports Server (NTRS)
Ajmani, Kumud; Ng, Wing-Fai; Liou, Meng-Sing
1993-01-01
An investigation is conducted into the viability of using a generalized Conjugate Gradient-like method as an iterative solver to obtain steady-state solutions of very low-speed fluid flow problems. Low-speed flow at Mach 0.1 over a backward-facing step is chosen as a representative test problem. The unsteady form of the two dimensional, compressible Navier-Stokes equations are integrated in time using discrete time-steps. The Navier-Stokes equations are cast in an implicit, upwind finite-volume, flux split formulation. The new iterative solver is used to solve a linear system of equations at each step of the time-integration. Preconditioning techniques are used with the new solver to enhance the stability and the convergence rate of the solver and are found to be critical to the overall success of the solver. A study of various preconditioners reveals that a preconditioner based on the lower-upper (L-U)-successive symmetric over-relaxation iterative scheme is more efficient than a preconditioner based on incomplete L-U factorizations of the iteration matrix. The performance of the new preconditioned solver is compared with a conventional line Gauss-Seidel relaxation (LGSR) solver. Overall speed-up factors of 28 (in terms of global time-steps required to converge to a steady-state solution) and 20 (in terms of total CPU time on one processor of a CRAY-YMP) are found in favor of the new preconditioned solver, when compared with the LGSR solver.
Solution of Cubic Equations by Iteration Methods on a Pocket Calculator
ERIC Educational Resources Information Center
Bamdad, Farzad
2004-01-01
A method to provide students a vision of how they can write iteration programs on an inexpensive programmable pocket calculator, without requiring a PC or a graphing calculator is developed. Two iteration methods are used, successive-approximations and bisection methods.
Testicular shielding in penile brachytherapy
Bindal, Arpita; Tambe, Chandrashekhar M.; Ghadi, Yogesh; Murthy, Vedang; Shrivastava, Shyam Kishore
2015-01-01
Purpose Penile cancer, although rare, is one of the common genitourinary cancers in India affecting mostly aged uncircumcised males. For patients presenting with small superficial lesions < 3 cm restricted to glans, surgery, radical external radiation or brachytherapy may be offered, the latter being preferred as it allows organ and function preservation. In patients receiving brachytherapy, testicular morbidity is not commonly addressed. With an aim to minimize and document the doses to testis after adequate shielding during radical interstitial brachytherapy for penile cancers, we undertook this study in 2 patients undergoing brachytherapy and forms the basis of this report. Material and methods Two patients with early stage penile cancer limited to the glans were treated with radical high-dose-rate (HDR) brachytherapy using interstitial implant. A total of 7-8 tubes were implanted in two planes, parallel to the penile shaft. A total dose of 44-48 Gy (55-60 Gy EQD2 doses with α/β = 10) was delivered in 11-12 fractions of 4 Gy each delivered twice daily. Lead sheets adding to 11 mm (4-5 half value layer) were interposed between the penile shaft and scrotum. The testicular dose was measured using thermoluminescent dosimeters. For each patient, dosimetry was done for 3 fractions and mean calculated. Results The cumulative testicular dose to left and right testis was 31.68 cGy and 42.79 cGy for patient A, and 21.96 cGy and 23.28 cGy for patient B. For the same patients, the mean cumulative dose measured at the posterior aspect of penile shaft was 722.15 cGy and 807.72 cGy, amounting to 16.4% and 16.8% of the prescribed dose. Hence, the application of lead shield 11 mm thick reduced testicular dose from 722-808 cGy to 21.96-42.57 cGy, an “absolute reduction” of 95.99 ± 1.5%. Conclusions With the use of a simple lead shield as described, we were able to effectively reduce testicular dose from “spermicidal” range to “oligospermic” range with possible
Perfetti, Christopher M; Rearden, Bradley T
2014-01-01
This work introduces a new approach for calculating sensitivity coefficients for generalized neutronic responses to nuclear data uncertainties using continuous-energy Monte Carlo methods. The approach presented in this paper, known as the GEAR-MC method, allows for the calculation of generalized sensitivity coefficients for multiple responses in a single Monte Carlo calculation with no nuclear data perturbations or knowledge of nuclear covariance data. The theory behind the GEAR-MC method is presented here, and proof of principle is demonstrated by using the GEAR-MC method to calculate sensitivity coefficients for responses in several 3D, continuous-energy Monte Carlo applications.
Spacecraft ceramic protective shield
NASA Technical Reports Server (NTRS)
Larriva, Rene F. (Inventor); Nelson, Anne (M.); Czechanski, James G. (Inventor); Poff, Ray E. (Inventor)
1995-01-01
A low areal density protective shield apparatus, and method for making same, for protecting spacecraft structures from impact with hypervelocity objects, including a bumper member comprising a bumper ceramic layer, a bumper shock attenuator layer, and a bumper confining layer. The bumper ceramic layer can be SiC or B.sub.4 C; the bumper shock attenuator layer can be zirconia felt; and the bumper confining layer can be aluminum. A base armor member can be spaced from the bumper member and a ceramic fiber-based curtain can be positioned between the bumper and base armor members.
NASA Astrophysics Data System (ADS)
de Paiva, Eduardo
2016-04-01
Every year millions of people contract cancer in the world, and according to prediction of the World Health Organization by the year 2030 there will be about 27 million new cases. Because of these figures and the resulting social and economic implications of this disease, radiotherapy, which is one form of treatment that uses ionizing radiation, has a great importance. In the classroom the teacher can introduce the subject of the use of ionizing radiation in medicine and the basic physical principles to calculate the thickness of the walls of the rooms that house ionizing radiation sources.
Testing the bioelectric shield.
Blackmore, Susan J; Rose, Nicholas
2002-01-01
A pendant was claimed to provide numerous health benefits, including reduced stress, increased strength, and protection from electromagnetic radiation from computers and mobile phones. Three experiments tested the effectiveness of this pendant's effect as a bioelectric shield. In the first experiment, 12 subjects who work with computers wore shields (6 real, 6 sham) for several weeks and were regularly tested for hand strength and mood changes. Both types of shield increased calmness, but the real shields did not have any greater effect. In 2 further studies (in each N=40) hand strength was measured at baseline, with mobile phone, and with mobile phone and bioelectric or sham shield. The shields did not differ in their effects. Both studies showed a significant correlation between the change in strength with and without the shield and subjects'scores on a questionnaire concerning their belief in and use of alternative therapies. The shields appear to produce a measurable placebo effect but are otherwise ineffective. PMID:12233804
Perfetti, Christopher M; Martin, William R; Rearden, Bradley T; Williams, Mark L
2012-01-01
Three methods for calculating continuous-energy eigenvalue sensitivity coefficients were developed and implemented into the SHIFT Monte Carlo code within the Scale code package. The methods were used for several simple test problems and were evaluated in terms of speed, accuracy, efficiency, and memory requirements. A promising new method for calculating eigenvalue sensitivity coefficients, known as the CLUTCH method, was developed and produced accurate sensitivity coefficients with figures of merit that were several orders of magnitude larger than those from existing methods.
Fermi, E.; Zinn, W.H.
1957-09-24
The reactor radiation shield material is comprised of alternate layers of iron-containing material and compressed cellulosic material, such as masonite. The shielding material may be prefabricated in the form of blocks, which can be stacked together in ary desired fashion to form an effective shield.
Gamma heating in reflector heat shield of gas core reactor
NASA Technical Reports Server (NTRS)
Lofthouse, J. H.; Kunze, J. F.; Young, T. E.; Young, R. C.
1972-01-01
Heating rate measurements made in a mock-up of a BeO heat shield for a gas core nuclear rocket engine yields results nominally a factor of two greater than calculated by two different methods. The disparity is thought to be caused by errors in neutron capture cross sections and gamma spectra from the low cross-section elements, D, O, and Be.
NASA Astrophysics Data System (ADS)
Ebru Ermis, Elif; Celiktas, Cuneyt
2015-07-01
Calculations of gamma-ray mass attenuation coefficients of various detector materials (crystals) were carried out by means of FLUKA Monte Carlo (MC) method at different gamma-ray energies. NaI, PVT, GSO, GaAs and CdWO4 detector materials were chosen in the calculations. Calculated coefficients were also compared with the National Institute of Standards and Technology (NIST) values. Obtained results through this method were highly in accordance with those of the NIST values. It was concluded from the study that FLUKA MC method can be an alternative way to calculate the gamma-ray mass attenuation coefficients of the detector materials.
NASA Technical Reports Server (NTRS)
Quinn, Robert D.; Gong, Leslie
2000-01-01
This report describes a method that can calculate transient aerodynamic heating and transient surface temperatures at supersonic and hypersonic speeds. This method can rapidly calculate temperature and heating rate time-histories for complete flight trajectories. Semi-empirical theories are used to calculate laminar and turbulent heat transfer coefficients and a procedure for estimating boundary-layer transition is included. Results from this method are compared with flight data from the X-15 research vehicle, YF-12 airplane, and the Space Shuttle Orbiter. These comparisons show that the calculated values are in good agreement with the measured flight data.
Fast calculation with point-based method to make CGHs of the polygon model
NASA Astrophysics Data System (ADS)
Ogihara, Yuki; Ichikawa, Tsubasa; Sakamoto, Yuji
2014-02-01
Holography is one of the three-dimensional technology. Light waves from an object are recorded and reconstructed by using a hologram. Computer generated holograms (CGHs), which are made by simulating light propagation using a computer, are able to represent virtual object. However, an enormous amount of computation time is required to make CGHs. There are two primary methods of calculating CGHs: the polygon-based method and the point-based method. In the polygon-based method with Fourier transforms, CGHs are calculated using a fast Fourier transform (FFT). The calculation of complex objects composed of multiple polygons requires as many FFTs, so unfortunately the calculation time become enormous. In contrast, in the point-based method, it is easy to express complex objects, an enormous calculation time is still required. Graphics processing units (GPUs) have been used to speed up the calculations of point-based method. Because a GPU is specialized for parallel computation and CGH calculation can be calculated independently for each pixel. However, expressing a planar object by the point-based method requires a signi cant increase in the density of points and consequently in the number of point light sources. In this paper, we propose a fast calculation algorithm to express planar objects by the point-based method with a GPU. The proposed method accelerate calculation by obtaining the distance between a pixel and the point light source from the adjacent point light source by a difference method. Under certain speci ed conditions, the difference between adjacent object points becomes constant, so the distance is obtained by only an additions. Experimental results showed that the proposed method is more effective than the polygon-based method with FFT when the number of polygons composing an objects are high.
Hubbell rectangular source integral calculation using a fast Chebyshev wavelets method.
Manai, K; Belkadhi, K
2016-07-01
An integration method based on Chebyshev wavelets is presented and used to calculate the Hubbell rectangular source integral. A study of the convergence and the accuracy of the method was carried out by comparing it to previous studies. PMID:27152913
An Effective Method to Accurately Calculate the Phase Space Factors for β - β - Decay
Neacsu, Andrei; Horoi, Mihai
2016-01-01
Accurate calculations of the electron phase space factors are necessary for reliable predictions of double-beta decay rates and for the analysis of the associated electron angular and energy distributions. We present an effective method to calculate these phase space factors that takes into account the distorted Coulomb field of the daughter nucleus, yet it allows one to easily calculate the phase space factors with good accuracy relative to the most exact methods available in the recent literature.
Study on the Calculation of Magnetic Force Based on the Equivalent Magnetic Charge Method
NASA Astrophysics Data System (ADS)
Li, Jiangang; Tan, Qingchang; Zhang, Yongqi; Zhang, Kuo
Magnetic drivers have been used widely in the pharmaceutical, chemical, petroleum, food and other industries with its perfect sealing without contact. Common method of calculating of the magnetic force are the Maxwell equations, empirical formulas, and he equivalent magnetic charge method as well. The Maxwell equations method is the most complicated and the empirical formulas method is the simplest with low accuracy. The equivalent magnetic charge method is simpler than the Maxwell equations method and more accurate than the empirical formulas method. In this paper, the magnetic force of the magnetic driver of reciprocate in line is calculated with the equivalent magnetic charge method and was compared with the experiment.
20 CFR 1001.150 - Method of calculating State basic grant awards.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false Method of calculating State basic grant... Grant Funds to State Agencies § 1001.150 Method of calculating State basic grant awards. (a) In... the Current Population Survey (CPS) and the unemployment data will be obtained from the Local...
Rotating shielded crane system
Commander, John C.
1988-01-01
A rotating, radiation shielded crane system for use in a high radiation test cell, comprises a radiation shielding wall, a cylindrical ceiling made of radiation shielding material and a rotatable crane disposed above the ceiling. The ceiling rests on an annular ledge intergrally attached to the inner surface of the shielding wall. Removable plugs in the ceiling provide access for the crane from the top of the ceiling into the test cell. A seal is provided at the interface between the inner surface of the shielding wall and the ceiling.
NASA Technical Reports Server (NTRS)
Power, J. L. (Inventor)
1976-01-01
An ion thruster beam shield is provided that comprises a cylindrical housing that extends downstream from the ion thruster and a plurality of annular vanes which are spaced along the length of the housing, and extend inwardly from the interior wall of the housing. The shield intercepts and stops all charge exchange and beam ions, neutral propellant, and sputter products formed due to the interaction of beam and shield emanating from the ion thruster outside of a fixed conical angle from the thruster axis. Further, the shield prevents the sputter products formed during the operation of the engine from escaping the interior volume of the shield.
Excited calculations of large scale multiwalled nanotubes using real-space pseudopotential methods
NASA Astrophysics Data System (ADS)
Lena, Charles; Chelikowsky, James; Deslippe, Jack; Saad, Yousef; Yang, Chao; Louie, Steven G.
2015-03-01
One method for calculating excited states is the GW method. The GW method has many computational requirements. One of the bottlenecks is the calculation of numerous empty states. Within density functional theory, we use a real-space pseudopotential method (PARSEC) to calculate these empty states for multiwalled nanotubes. We illustrate the use of these empty states for calculating excited states using the GW method (BerkeleyGW). We demonstrate why using real-space density functional theory is advantageous for calculating empty states. Support provided by the SciDAC program, Department of Energy, Office of Science, Advanced Scientific Computing Research and Basic Energy Sciences. Grant Numbers DE-SC0008877 (Austin) and DE-FG02-12ER4 (Berkeley)
Efficient calculation method for realistic deep 3D scene hologram using orthographic projection
NASA Astrophysics Data System (ADS)
Igarashi, Shunsuke; Nakamura, Tomoya; Matsushima, Kyoji; Yamaguchi, Masahiro
2016-03-01
We propose a fast calculation method to synthesize a computer-generated hologram (CGH) of realistic deep three-dimensional (3D) scene. In our previous study, we have proposed a calculation method of CGH for reproducing such scene called ray-sampling-plane (RSP) method, in which light-ray information of a scene is converted to wavefront, and the wavefront is numerically propagated based on diffraction theory. In this paper, we introduce orthographic projection to the RSP method for accelerating calculation time. By numerical experiments, we verified the accelerated calculation with the ratio of 28-times compared to the conventional RSP method. The calculated CGH was fabricated by the printing system using laser lithography and demonstrated deep 3D image reconstruction in 52mm×52mm with realistic appearance effect such as gloss and translucent effect.
NASA Astrophysics Data System (ADS)
Zhang, X. N.; Li, H. P.; Murphy, A. B.; Xia, W. D.
2015-06-01
Two main methods have been used to calculate the transport properties of two-temperature (2-T) plasmas in local chemical equilibrium: the method of Devoto (method B), in which coupling between electrons and heavy species is neglected, and the method of Rat et al (method C), in which coupling is included at the cost of a considerable increase in complexity. A new method (method A) has recently been developed, based on the modified Chapman-Enskog solution of the species Boltzmann equations. This method retains coupling between electrons and heavy species by including the electron-heavy-species collision term in the heavy-species Boltzmann equation. In this paper, the properties of 2-T argon plasmas calculated using the three methods are compared. The viscosity, electrical conductivity and translational thermal conductivity obtained using all three methods are very similar. method B does not allow a complete set of species diffusion coefficient to be obtained. It is shown that such a set can be calculated using method A without any significant loss of accuracy. Finally, it is important to note that, by using the physical fact that the mass of heavy particles is much larger than that of electrons (i.e. me << mh), the complexity of calculations using method A is not increased compared with method B; that is to say, the calculation procedure is much simpler than with method C.
Roan, M.-L.; Chen, Y.-H.; Huang, C.-Y.
2008-08-28
In this study, a variety of concentrations of chelating agents were added to obtain the anchoring effect and chelating effect in the electroless plating bath. The mechanism of the Cu{sub x(x=1,2)}S growth and the electromagnetic interference shielding effectiveness (EMI SE) of the composite were studied. It was found that the vinyl acetate residued in PAN substrate would be purged due to the swelling effect by chelating agents solution. And then, the anchoring effect occurred due to the hydrogen bonding between the pits of PAN substrate and the chelating agent. Consequently, the copper sulfide layer deposited by the electroless plating reaction with EDTA and TEA. The swelling degree (S{sub d}) was proposed and evaluated from the FT-IR spectra. The relationship between swelling degree of the PAN films and EDTA (C) is expressed as: S{sub d} = 0.13+0.90xe and (-15.15C). And TEA series is expressed as: S{sub d} = 0.07+1.00xe and (-15.15C). On the other hand, the FESEM micrograph showed that the average thickness of copper sulfide increased from 76 nm to 383 nm when the concentration of EDTA increased from 0.00M to 0.20M. Consequently, the EMI SE of the composites increased from 10{approx}12 dB to 25{approx}27 dB. The GIA-XRD analyze indicated that the deposited layer consisted of CuS and Cu{sub 2}S.
Burger, Marga R; Kramer, J; Chermette, H; Koch, Klaus R
2010-12-01
A comparison between experimental and calculated gas-phase as well as the conductor-like screening model DFT (195)Pt chemical shifts of a series of octahedral [PtX(6-n)Y(n)](2-) complexes for X = Cl, Br, F, I was carried out to assess the accuracy of computed NMR shielding and to gain insight into the dominant σ(dia), σ(para) and σ(SO) shielding contributions. The discrepancies between the experimental and the DFT-calculated (195)Pt chemical shifts vary for these complexes as a function of the coordinated halide ions, the largest being obtained for the fluorido-chlorido and fluorido-bromido complexes, while negligible discrepancies are found for the [PtCl(6-n)Br(n)](2-) series; the discrepancies are somewhat larger where a significant deviation from the ideal octahedral symmetry such as for the geometric cis/trans or fac/mer isomers of [PtF(6-n)Cl(n)](2-) and [PtF(6-n)Br(n)](2-) may be expected. The discrepancies generally increase in the order [PtCl(6-n)Br(n)](2-) < [PtBr(6-n)I(n)](2-) < [PtCl(6-n)I(n)](2-) < [PtF(6-n)Br(n)](2-) ≈ [PtF(6-n)Cl(n)](2-), and show a striking correlation with the increase in electronegativity difference Δχ between the two halide ligands (X(-) and Y(-)) bound to Pt(IV) for these anions: 0.09 < 0.52 < 0.63 < 1.36 ≈ 1.27, respectively. The computed (195)Pt sensitivity to Pt-X bond displacement, ∂(δ(195)Pt)/∂(ΔPt-X), of these complexes is very large and depends on the halide ion, decreasing from 24 800, 18 300, 15 700 to 12 000 ppm/Å for [PtF(6)](2-), [PtCl(6)](2-), [PtBr(6)](2-) and [PtI(6)](2-), respectively. PMID:21104761
Alam, Todd M.; Henry, Marc
1999-08-05
Organically modified alkoxy silanes play an important role in tailoring different properties of silica produced by the sol-gel method. Changes in the size and functionality of the organic group allows control of both physical and chemical properties of the resulting gel, with the kinetics of the polymerization process playing an important role in the design of new siloxane materials. High resolution {sup 29}Si NMR has proven to be valuable tool for monitoring the polymerization reaction, and has been used to investigate a variety of organically modified alkoxy silane systems.
NASA Astrophysics Data System (ADS)
Perez-Gussinye, M.; Lowry, A. R.; Watts, A. B.; Velicogna, I.
2003-12-01
The effective elastic thickness, Te, represents the response to long-term loading of the lithosphere; it is thus a useful measure of its strength. However, the use of different methods and assumptions to calculate Te yield different results, leading to controversial interpretations of the relationship of Te to rheology. We investigate the ability of the Bouguer coherence and free air admittance to recover Te assuming that surface and subsurface loads exist. We use synthetic data to show that the estimated Te using both functions is similar; the recovery with admittance is somewhat poorer due to leakage problems. When the underlying Te is constant, the bias and variance of the resulting Te increases with decreasing analysis window size and increasing underlying Te value. When Te varies spatially, Te estimation using sliding, overlapping windows retrieves a structure that approximates the true spatial variability, but window sizes must be chosen carefully. In light of these results, we analyse Te in Fennoscandia using both techniques and obtain similar estimates. Te is 20-40 km in the Caledonides, 40- 60 km in the Swedish Svecofennides, 40-60 km in the Kola peninsula and 70-100 km in southern Karelia and Svecofennian central Finland. These estimates are not biased by unrecovered post-glacial rebound and also potential noise introduced by long-term erosion and sedimentation does not appear to affect Te. An independent estimate of Te using rheological modelling, confirms that Te in central Finland should be high. Because Te exceeds crustal thickness ( ˜ 60 km), the mantle must contribute significant strength to the total. Te is also larger than the seismogenic thickness, thus indicating that they represent different physical behaviours. In general, Te in Fennoscandia increases with tectonic age, seismic lid thickness and decreasing heat flow. Te is low where seismicity is frequent and high where it is reduced. In Proterozoic and Archean lithosphere, the relationship
Facility target insert shielding assessment
Mocko, Michal
2015-10-06
Main objective of this report is to assess the basic shielding requirements for the vertical target insert and retrieval port. We used the baseline design for the vertical target insert in our calculations. The insert sits in the 12”-diameter cylindrical shaft extending from the service alley in the top floor of the facility all the way down to the target location. The target retrieval mechanism is a long rod with the target assembly attached and running the entire length of the vertical shaft. The insert also houses the helium cooling supply and return lines each with 2” diameter. In the present study we focused on calculating the neutron and photon dose rate fields on top of the target insert/retrieval mechanism in the service alley. Additionally, we studied a few prototypical configurations of the shielding layers in the vertical insert as well as on the top.
Radiation shielding for diagnostic radiology.
Martin, Colin J
2015-07-01
Scattered radiation makes up the majority of the stray radiation field around an X-ray unit. The scatter is linked to the amount of radiation incident on the patient. It can be estimated from quantities used to assess patient dose such as the kerma-area product, and factors have been established linking this to levels of scattered radiation for radiography and fluoroscopy. In radiography shielding against primary radiation is also needed, but in other modalities this is negligible, as the beam is intercepted by the image receptor. In the same way scatter from CT can be quantified in terms of dose-length product, but because of higher radiation levels, exposure to tertiary scatter from ceilings needs to be considered. Transmission requirements are determined from comparisons between calculated radiation levels and agreed dose criteria, taking into account the occupancy of adjacent areas. Thicknesses of shielding material required can then be calculated from simple equations. PMID:25813477
The Three-Point Sinuosity Method for Calculating the Fractal Dimension of Machined Surface Profile
NASA Astrophysics Data System (ADS)
Zhou, Yuankai; Li, Yan; Zhu, Hua; Zuo, Xue; Yang, Jianhua
2015-04-01
The three-point sinuosity (TPS) method is proposed to calculate the fractal dimension of surface profile accurately. In this method, a new measure, TPS is defined to present the structural complexity of fractal curves, and has been proved to follow the power law. Thus, the fractal dimension can be calculated through the slope of the fitted line in the log-log plot. The Weierstrass-Mandelbrot (W-M) fractal curves, as well as the real surface profiles obtained by grinding, sand blasting and turning, are used to validate the effectiveness of the proposed method. The calculation values are compared to those obtained from root-mean-square (RMS) method, box-counting (BC) method and variation method. The results show that the TPS method has the widest scaling region, the least fit error and the highest accuracy among the methods examined, which demonstrates that the fractal characteristics of the fractal curves can be well revealed by the proposed method.
Simple energy-calculation method for solar industrial-process-heat steam systems
NASA Astrophysics Data System (ADS)
Gee, R. C.
1983-01-01
Designing a solar industrial process heat (IPH) system, sizing its components and predicting its annual energy delivery requires a method for calculating solar system performance. A calculation method that is accurate, easy to use, accounts for the impact of all important system parameters, and does not require use of a computer is described. Only simple graphs and a hand calculator are required to predict annual collector field performance and annual system losses. The energy calculation method is applicable to a variety of solar system configurations. The calculation method applied only to parabolic trough steam generation systems that do not employ thermal storage is described. Both flash tank and unfired boiler steam systems are covered.
Simple energy-calculation method for solar industrial-process-heat steam systems
Gee, R.
1983-01-01
Designing a solar industrial-process heat (IPH) system, sizing its components and predicting its annual energy delivery requires a method for calculating solar system performance. A calculation method that is accurate, easy to use, accounts for the impact of all important system parameters, and does not require use of a computer is described. Only simple graphs and a hand calculator are required to predict annual collector field performance and annual system losses. The energy-calculation method is applicable to a variety of solar-system configurations. The calculation method applied only to parabolic-trough steam-generation systems that do not employ thermal storage is described. Both flash tank and unfired-boiler steam systems are covered.
NASA Technical Reports Server (NTRS)
Maskew, B.
1976-01-01
A discrete singularity method has been developed for calculating the potential flow around two-dimensional airfoils. The objective was to calculate velocities at any arbitrary point in the flow field, including points that approach the airfoil surface. That objective was achieved and is demonstrated here on a Joukowski airfoil. The method used combined vortices and sources ''submerged'' a small distance below the airfoil surface and incorporated a near-field subvortex technique developed earlier. When a velocity calculation point approached the airfoil surface, the number of discrete singularities effectively increased (but only locally) to keep the point just outside the error region of the submerged singularity discretization. The method could be extended to three dimensions, and should improve nonlinear methods, which calculate interference effects between multiple wings, and which include the effects of force-free trailing vortex sheets. The capability demonstrated here would extend the scope of such calculations to allow the close approach of wings and vortex sheets (or vortices).
MicroShield/ISOCS gamma modeling comparison.
Sansone, Kenneth R
2013-08-01
Quantitative radiological analysis attempts to determine the quantity of activity or concentration of specific radionuclide(s) in a sample. Based upon the certified standards that are used to calibrate gamma spectral detectors, geometric similarities between sample shape and the calibration standards determine if the analysis results developed are qualitative or quantitative. A sample analyzed that does not mimic a calibrated sample geometry must be reported as a non-standard geometry and thus the results are considered qualitative and not quantitative. MicroShieldR or ISOCSR calibration software can be used to model non-standard geometric sample shapes in an effort to obtain a quantitative analytical result. MicroShieldR and Canberra's ISOCSR software contain several geometry templates that can provide accurate quantitative modeling for a variety of sample configurations. Included in the software are computational algorithms that are used to develop and calculate energy efficiency values for the modeled sample geometry which can then be used with conventional analysis methodology to calculate the result. The response of the analytical method and the sensitivity of the mechanical and electronic equipment to the radionuclide of interest must be calibrated, or standardized, using a calibrated radiological source that contains a known and certified amount of activity.
Recent experiences with shielding a PET/CT facility.
Erdman, Mike; King, Steve; Miller, Ken
2004-08-01
Since the photon energy of positron emitting radionuclides is significantly higher than the maximum kVp of diagnostic x rays, designing a shielding plan for a PET/CT imaging facility requires careful consideration of future workloads and potential occupancy of surrounding spaces. The shielding calculations can be done by hand or with the aid of available software. In calculating the shielding, specific considerations arise. Some of these are presented as a checklist of things to consider when preparing to calculate the shielding required for a PET/CT facility. PMID:15220722
Criteria for establishing shielding of multi-detector computed tomography (MDCT) rooms.
Verdun, F R; Aroua, A; Baechler, S; Schmidt, S; Trueb, P R; Bochud, F O
2010-01-01
The aim of this work is to compare two methods used for determining the proper shielding of computed tomography (CT) rooms while considering recent technological advances in CT scanners. The approaches of the German Institute for Standardisation and the US National Council on Radiation Protection and Measurements were compared and a series of radiation measurements were performed in several CT rooms at the Lausanne University Hospital. The following three-step procedure is proposed for assuring sufficient shielding of rooms hosting new CT units with spiral mode acquisition and various X-ray beam collimation widths: (1) calculate the ambient equivalent dose for a representative average weekly dose length product at the position where shielding is required; (2) from the maximum permissible weekly dose at the location of interest, calculate the transmission factor F that must be taken to ensure proper shielding and (3) convert the transmission factor into a thickness of lead shielding. A similar approach could be adopted to use when designing shielding for fluoroscopy rooms, where the basic quantity would be the dose area product instead of the load of current (milliampere-minute). PMID:20215444
Nucleonic analysis of a preliminary design for the ETF neutral-beam-injector duct shielding
Urban, W.T.; Seed, T.J.; Dudziak, D.J.
1980-01-01
A nucleonic analysis of the Engineering Test Facility Neutral-Beam-Injector duct shielding has been made using a hybrid Monte Carlo/discrete-ordinates method. This method used Monte Carlo to determine internal and external boundary surface sources for a subsequent discrete-ordinates calculation of the neutron and gamma-ray transport through the shield. The analysis also included determination of the energy and angular distribution of neutrons and gamma rays entering the duct from the torus plasma chamber. Confidence in the hybrid method and the results obtained were provided through a comparison with three-dimensional Monte Carlo results.
NASA Technical Reports Server (NTRS)
Cour-Palais, Burton G. (Inventor); Crews, Jeanne Lee (Inventor)
1991-01-01
A hypervelocity impact shield and method for protecting a wall structure, such as a spacecraft wall, from impact with particles of debris having densities of about 2.7 g/cu cm and impact velocities up to 16 km/s are disclosed. The shield comprises a stack of ultra thin sheets of impactor disrupting material supported and arranged by support means in spaced relationship to one another and mounted to cover the wall in a position for intercepting the particles. The sheets are of a number and spacing such that the impacting particle and the resulting particulates of the impacting particle and sheet material are successively impact-shocked to a thermal state of total melt and/or vaporization to a degree as precludes perforation of the wall. The ratio of individual sheet thickness to the theoretical diameter of particles of debris which may be of spherical form is in the range of 0.03 to 0.05. The spacing between adjacent sheets is such that the debris cloud plume of liquid and vapor resulting from an impacting particle penetrating a sheet does not puncture the next adjacent sheet prior to the arrival thereat of fragment particulates of sheet material and the debris particle produced by a previous impact.
Diagnostics of ballistic resistance of constructional shields and experimental verification
NASA Astrophysics Data System (ADS)
Zatorski, Z.
2006-08-01
New diagnostic methodology of ballistic resistance of multi layered shields has been developed. The energy density absorbed through shield has been introduced, { }in general form as absorbed energy density VBL[R]2 according to Recht's and Ipson's method, and VBL[Z]2 according to author's method. The absorption of kinetic energy of bullet mp \\cdot V_p2 / 2 and momentum I transfered to dynamometer of ballistic pendelum has been used to assignation of absorbed energy density VBL[Z]2 . The effectiveness used method to assignation of absorbed energy density VBL2 has been calculated by effectiveness coefficientβ s of absorbed energy density VBL2 as well as by mass coefficients α_s^2.
Afonin, Andrei V; Pavlov, Dmitry V; Albanov, Alexander I; Levanova, Ekaterina P; Levkovskaya, Galina G
2011-11-01
In the (1)H and (13)C NMR spectra of selenophene-2-carbaldehyde azine, the (1)H-5, (13)C-3 and (13)C-5 signals of the selenophene ring are shifted to higher frequencies, whereas those of the (1)H-1, (13)C-1, (13)C-2 and (13)C-4 are shifted to lower frequencies on going from the EE to ZZ isomer or from the E moiety to the Z moiety of EZ isomer. The (15)N chemical shift is significantly larger in the EE isomer relative to the ZZ isomer and in the E moiety relative to the Z moiety of EZ isomer. A very pronounced difference (60-65 mg/g) between the (77)Se resonance positions is revealed in the studied azine isomers, the (77)Se peak being shifted to higher frequencies in the ZZ isomer and in the Z moiety of EZ isomer. The trends in the changes of the measured chemical shifts are reasonably reproduced by the GIAO calculations at the MP2 level of the (1)H, (13)C, (15)N and (77)Se shielding constants in the energy-favorable conformation with the syn orientation of both selenophene rings relative to the C = N groups. The NBO analysis suggests that such an arrangement of the selenophene rings may take place because of a higher energy of some intramolecular interactions. PMID:22002712
NASA Astrophysics Data System (ADS)
Kjær, Hanna; Sauer, Stephan P. A.; Kongsted, Jacob
2011-01-01
We present a benchmark study of a combined multipole shielding polarizability/reaction field (MSP/RF) approach to the calculation of both specific and bulk solvation effects on nuclear magnetic shielding constants of solvated molecules. The MSP/RF scheme is defined by an expansion of the shielding constants of the solvated molecule in terms of electric field and field gradient property derivatives derived from single molecule ab initio calculations. The solvent electric field and electric field gradient are calculated based on data derived from molecular dynamics simulations, thereby accounting for solute-solvent dynamical effects. The MSP/RF method is benchmarked against polarizable quantum mechanics/molecular mechanics (QM/MM) calculations. The best agreement between the MSP/RF and QM/MM approaches is found by truncating the electric field expansion in the MSP/RF approach at the linear electric field level which is due to the cancelation of errors. In addition, we investigate the sensitivity of the results due to the choice of one-electron basis set in the ab initio calculations of the property derivatives and find that these derivatives are affected by the basis set in a way similar to the shielding constants themselves.
NASA Technical Reports Server (NTRS)
Campbell, John P; Mckinney, Marion O
1952-01-01
A summary of methods for making dynamic lateral stability and response calculations and for estimating the aerodynamic stability derivatives required for use in these calculations is presented. The processes of performing calculations of the time histories of lateral motions, of the period and damping of these motions, and of the lateral stability boundaries are presented as a series of simple straightforward steps. Existing methods for estimating the stability derivatives are summarized and, in some cases, simple new empirical formulas are presented. Detailed estimation methods are presented for low-subsonic-speed conditions but only a brief discussion and a list of references are given for transonic and supersonic speed conditions.
Four Methods for Calculating Blood-loss after Total Knee Arthroplasty
Gao, Fu-Qiang; Li, Zi-Jian; Zhang, Ke; Sun, Wei; Zhang, Hong
2015-01-01
Background: Currently, various calculation methods for evaluating blood-loss in patients with total knee arthroplasty (TKA) are applied in clinical practice. However, different methods may yield different results. The purpose of this study was to determine the most reliable method for calculating blood-loss after primary TKA. Methods: We compared blood-loss in 245 patients who underwent primary unilateral TKA from February 2010 to August 2011. We calculated blood-loss using four methods: Gross equation, hemoglobin (Hb) balance, the Orthopedic Surgery Transfusion Hemoglobin European Overview (OSTHEO) formula, and Hb-dilution. We determined Pearson's correlation coefficients for the four methods. Results: There were large differences in the calculated blood-loss obtained by the four methods. In descending order of combined correlation coefficient based on calculated blood-loss, the methods were Hb-balance, OSTHEO formula, Hb-dilution, and Gross equation. Conclusions: The Hb-balance method may be the most reliable method of estimating blood-loss after TKA. PMID:26521781
A Simple and Convenient Method of Multiple Linear Regression to Calculate Iodine Molecular Constants
ERIC Educational Resources Information Center
Cooper, Paul D.
2010-01-01
A new procedure using a student-friendly least-squares multiple linear-regression technique utilizing a function within Microsoft Excel is described that enables students to calculate molecular constants from the vibronic spectrum of iodine. This method is advantageous pedagogically as it calculates molecular constants for ground and excited…
NASA Astrophysics Data System (ADS)
Prel, P.
1991-12-01
A three dimensional method for calculating the concentration coefficients of water droplets, its general principles, as well as the details of the calculating computer programs that were used, are described. The applications are presented for locating probes on the Airbus 340 and ATR 72 airplanes, mainly showing the effect of the drop diameter on the measured concentration.
7 CFR 51.308 - Methods of sampling and calculation of percentages.
Code of Federal Regulations, 2010 CFR
2010-01-01
..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Apples Methods of Sampling and Calculation... where the minimum diameter of the smallest apple does not vary more than 1/2 inch from the minimum diameter of the largest apple, percentages shall be calculated on the basis of count. (b) In all...
7 CFR 51.308 - Methods of sampling and calculation of percentages.
Code of Federal Regulations, 2012 CFR
2012-01-01
..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Apples Methods of Sampling and Calculation... where the minimum diameter of the smallest apple does not vary more than 1/2 inch from the minimum diameter of the largest apple, percentages shall be calculated on the basis of count. (b) In all...
7 CFR 51.308 - Methods of sampling and calculation of percentages.
Code of Federal Regulations, 2011 CFR
2011-01-01
..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Apples Methods of Sampling and Calculation... where the minimum diameter of the smallest apple does not vary more than 1/2 inch from the minimum diameter of the largest apple, percentages shall be calculated on the basis of count. (b) In all...
Cable shield connecting device
Silva, Frank A.
1979-01-01
A cable shield connecting device for installation on a high voltage cable of the type having a metallic shield, the device including a relatively conformable, looped metal bar for placement around a bared portion of the metallic shield to extend circumferentially around a major portion of the circumference of the metallic shield while being spaced radially therefrom, a plurality of relatively flexible metallic fingers affixed to the bar, projecting from the bar in an axial direction and spaced circumferentially along the bar, each finger being attached to the metallic shield at a portion located remote from the bar to make electrical contact with the metallic shield, and a connecting conductor integral with the bar.
Perfetti, C.; Martin, W.; Rearden, B.; Williams, M.
2012-07-01
Three methods for calculating continuous-energy eigenvalue sensitivity coefficients were developed and implemented into the Shift Monte Carlo code within the SCALE code package. The methods were used for two small-scale test problems and were evaluated in terms of speed, accuracy, efficiency, and memory requirements. A promising new method for calculating eigenvalue sensitivity coefficients, known as the CLUTCH method, was developed and produced accurate sensitivity coefficients with figures of merit that were several orders of magnitude larger than those from existing methods. (authors)
Integral method for the calculation of three-dimensional, laminar and turbulent boundary layers
NASA Technical Reports Server (NTRS)
Stock, H. W.
1978-01-01
The method for turbulent flows is a further development of an existing method; profile families with two parameters and a lag entrainment method replace the simple entrainment method and power profiles with one parameter. The method for laminar flows is a new development. Moment of momentum equations were used for the solution of the problem, the profile families were derived from similar solutions of boundary layer equations. Laminar and turbulent flows at the wings were calculated. The influence of wing tapering on the boundary layer development was shown. The turbulent boundary layer for a revolution ellipsoid is calculated for 0 deg and 10 deg incidence angles.
Wigner, E.P.; Young, G.J.
1958-09-23
ABS>A radiation shield that is suitable for the protection of personnel from both gamma rays and nentrons is described. The shield is comprised of a hollow wall and an aggregate consisting of iron and water in approximately equal amounts by volume substantially filling the wall. A means is provided to circulate the water through the wall to cool the shield when in use.
Radiation shielding for 250 MeV protons
Awschalom, M.
1987-04-01
This paper is targetted at personnel who have the responsibility of designing the radiation shielding against neutron fluences created when protons interact with matter. Shielding of walls and roofs are discussed, as well as neutron dose leakage through labyrinths. Experimental data on neutron flux attenuation are considered, as well as some calculations using the intranuclear cascade calculations and parameterizations.
Modified Anderson Method for Accelerating 3D-RISM Calculations Using Graphics Processing Unit.
Maruyama, Yutaka; Hirata, Fumio
2012-09-11
A fast algorithm is proposed to solve the three-dimensional reference interaction site model (3D-RISM) theory on a graphics processing unit (GPU). 3D-RISM theory is a powerful tool for investigating biomolecular processes in solution; however, such calculations are often both memory-intensive and time-consuming. We sought to accelerate these calculations using GPUs, but to work around the problem of limited memory size in GPUs, we modified the less memory-intensive "Anderson method" to give faster convergence to 3D-RISM calculations. Using this method on a Tesla C2070 GPU, we reduced the total computational time by a factor of 8, 1.4 times by the modified Andersen method and 5.7 times by GPU, compared to calculations on an Intel Xeon machine (eight cores, 3.33 GHz) with the conventional method. PMID:26605714
METHOD FOR CALCULATING ELECTRIC AND MAGNETIC FIELDS IN TEM CELLS AT ELF (JOURNAL VERSION)
A method is presented whereby the electric and magnetic field distributions within rectangular strip transmission lines (TEM cells) can be calculated. Quasi-static approximations are employed, thereby restricting the validity of the results to operational frequencies well below t...
A vortex panel method for calculating aircraft downwash on parachute trajectories
Fullerton, T.L.; Strickland, J.H.; Sundberg, W.D.
1991-01-01
This paper presents a discussion of a methodology of the paneled-wing method for calculating aircraft-induced wake velocities. This discussion will include a description of how an aircraft and its wake are represented by finite length vortex filaments, how the strength and location of these filaments are determined based upon aircraft characteristics and trajectory data, and how the induced velocity values are determined once the location and strength of the vortex filaments are known. Examples will be presented showing comparisons between induced velocity values calculated using both the paneled-wing method and Strickland's lifting line method. Comparison is also made between calculated results from the paneled-wing method and wind tunnel data collected in the wake of a scale model aircraft. Additional examples will show the effect of including aircraft downwash calculations in a trajectory analysis for a parachute-retarded store delivered via aircraft. 3 refs., 12 figs.
A FINITE-DIFFERENCE, DISCRETE-WAVENUMBER METHOD FOR CALCULATING RADAR TRACES
A hybrid of the finite-difference method and the discrete-wavenumber method is developed to calculate radar traces. The method is based on a three-dimensional model defined in the Cartesian coordinate system; the electromagnetic properties of the model are symmetric with respect ...
Evapotranspiration: Measured with a lysimeter vs. calculated with a recursive method
Technology Transfer Automated Retrieval System (TEKTRAN)
Recently, a recursive combination method (RCM) to calculate potential and crop evapotranspiration (ET) was given by Lascano and Van Bavel (Agron. J. 2007, 99:585-590) that differs from the Penman-Monteith (PM) method. The main difference between the two methods is that the assumptions made regarding...
A biharmonic relaxation method for calculating thermal stress in cooled irregular cylinders
NASA Technical Reports Server (NTRS)
Holms, Arthur G
1952-01-01
A numerical method was developed for calculating thermal stresses in irregular cylinders cooled by one or more internal passages. The use of relaxation methods and elementary methods of finite differences was found to give approximations to the correct values when compared with previously known solutions for concentric circular cylinders possessing symmetrical and asymmetrical temperature distributions.
A FINITE-DIFFERENCE, DISCRETE-WAVENUMBER METHOD FOR CALCULATING RADAR TRACES
A hybrid of the finite-difference method and the discrete-wavenumber method is developed to calculate radar traces. The method is based on a three-dimensional model defined in the Cartesian coordinate system; the electromag-netic properties of the model are symmetric with respect...
Using matrix summation method for three dimensional dose calculation in brachytherapy
Zibandeh-Gorji, Mahmoud; Mowlavi, Ali Asghar; Mohammadi, Saeed
2012-01-01
Aim The purpose of this study is to calculate radiation dose around a brachytherapy source in a water phantom for different seed locations or rotation the sources by the matrix summation method. Background Monte Carlo based codes like MCNP are widely used for performing radiation transport calculations and dose evaluation in brachytherapy. But for complicated situations, like using more than one source, moving or rotating the source, the routine Monte Carlo method for dose calculation needs a long time running. Materials and methods The MCNPX code has been used to calculate radiation dose around a 192Ir brachytherapy source and saved in a 3D matrix. Then, we used this matrix to evaluate the absorbed dose in any point due to some sources or a source which shifted or rotated in some places by the matrix summation method. Results Three dimensional (3D) dose results and isodose curves were presented for 192Ir source in a water cube phantom shifted for 10 steps and rotated for 45 and 90° based on the matrix summation method. Also, we applied this method for some arrays of sources. Conclusion The matrix summation method can be used for 3D dose calculations for any brachytherapy source which has moved or rotated. This simple method is very fast compared to routine Monte Carlo based methods. In addition, it can be applied for dose optimization study. PMID:24377009
NASA Technical Reports Server (NTRS)
Schwinghamer, R. J.
1975-01-01
The loss of the micrometeoroid shield from the Orbital Workshop section of Skylab I, about 63 seconds after lift-off, proved to be the harbinger of a prodigious effort to quickly develop a workable substitute for the carefully tailored passive portion of the thermal-control system. The paper describes the intensive ten-day around-the-clock effort in which numerous potential thermal-shield materials were assessed, and during which period ten specific shield designs were developed and carried through various stages of development and test. Thermal-shield materials data are discussed, including optical, strength, fatigue, outgassing, tackiness, ultraviolet radiation, and material 'memory' properties.
RADIATION SHIELDING COMPOSITION
Dunegan, H.L.
1963-01-29
A light weight radiation shielding composition is described whose mechanical and radiological properties can be varied within wide limits. The composition of this shielding material consists of four basic ingredients: powder of either Pb or W, a plastic resin, a resin plasticizer, and a polymerization catalyst to promote an interaction of the plasticizer with the plastic resin. Air may be mixed into the above ingredients in order to control the density of the final composition. For equivalent gamma attenuation, the shielding composition weighs one-third to one-half as much as conventional Pb shielding. (AEC)
Development of fiber shields for engine containment. [mathematical models
NASA Technical Reports Server (NTRS)
Bristow, R. J.; Davidson, C. D.
1977-01-01
Tests were conducted in translational launchers and spin pits to generate empirical data used in the design of a Kevlar shield for containing engine burst debris. Methods are given for modeling the relationship of fragment characteristics to shielding requirements. The change in relative importance of shield mounting provisions as fragment energy is increased is discussed.
Analytical method for calculation of navigational data for the position of a satellite
NASA Technical Reports Server (NTRS)
Lala, P.
1975-01-01
A method is described for calculating the position of a satellite at the instants when measurements are made on board. The initial conditions used were the mean orbital elements of the satellite and their time derivatives in one orbit. The results of the calculation are compared with those obtained by numerical integration, and it is found that results are identical at the beginning of an orbit, but change as the orbit progresses. The advantages and disadvantages of the analytical method are presented.
An efficient method for calculating RMS von Mises stress in a random vibration environment
Segalman, D.J.; Fulcher, C.W.G.; Reese, G.M.; Field, R.V. Jr.
1998-02-01
An efficient method is presented for calculation of RMS von Mises stresses from stress component transfer functions and the Fourier representation of random input forces. An efficient implementation of the method calculates the RMS stresses directly from the linear stress and displacement modes. The key relation presented is one suggested in past literature, but does not appear to have been previously exploited in this manner.
An efficient method for calculating RMS von Mises stress in a random vibration environment
Segalman, D.J.; Fulcher, C.W.G.; Reese, G.M.; Field, R.V. Jr.
1997-12-01
An efficient method is presented for calculation of RMS von Mises stresses from stress component transfer functions and the Fourier representation of random input forces. An efficient implementation of the method calculates the RMS stresses directly from the linear stress and displacement modes. The key relation presented is one suggested in past literature, but does not appear to have been previously exploited in this manner.
A new method for modeling rough membrane surface and calculation of interfacial interactions.
Zhao, Leihong; Zhang, Meijia; He, Yiming; Chen, Jianrong; Hong, Huachang; Liao, Bao-Qiang; Lin, Hongjun
2016-01-01
Membrane fouling control necessitates the establishment of an effective method to assess interfacial interactions between foulants and rough surface membrane. This study proposed a new method which includes a rigorous mathematical equation for modeling membrane surface morphology, and combination of surface element integration (SEI) method and the composite Simpson's approach for assessment of interfacial interactions. The new method provides a complete solution to quantitatively calculate interfacial interactions between foulants and rough surface membrane. Application of this method in a membrane bioreactor (MBR) showed that, high calculation accuracy could be achieved by setting high segment number, and moreover, the strength of three energy components and energy barrier was remarkably impaired by the existence of roughness on the membrane surface, indicating that membrane surface morphology exerted profound effects on membrane fouling in the MBR. Good agreement between calculation prediction and fouling phenomena was found, suggesting the feasibility of this method. PMID:26519696
NASA Astrophysics Data System (ADS)
Shimobaba, Tomoyoshi; Nagahama, Yuki; Kakue, Takashi; Takada, Naoki; Okada, Naohisa; Endo, Yutaka; Hirayama, Ryuji; Hiyama, Daisuke; Ito, Tomoyoshi
2014-02-01
A calculation reduction method for color digital holography (DH) and computer-generated holograms (CGHs) using color space conversion is reported. Color DH and color CGHs are generally calculated on RGB space. We calculate color DH and CGHs in other color spaces for accelerating the calculation (e.g., YCbCr color space). In YCbCr color space, a RGB image or RGB hologram is converted to the luminance component (Y), blue-difference chroma (Cb), and red-difference chroma (Cr) components. In terms of the human eye, although the negligible difference of the luminance component is well recognized, the difference of the other components is not. In this method, the luminance component is normal sampled and the chroma components are down-sampled. The down-sampling allows us to accelerate the calculation of the color DH and CGHs. We compute diffraction calculations from the components, and then we convert the diffracted results in YCbCr color space to RGB color space. The proposed method, which is possible to accelerate the calculations up to a factor of 3 in theory, accelerates the calculation over two times faster than the ones in RGB color space.
Theory to boil-off gas cooled shields for cryogenic storage vessels
NASA Astrophysics Data System (ADS)
Hofmann, A.
2004-03-01
An intermediate refrigeration with boil-off gas cooled shields using the boil-off gas stream is an alternative method to the conventional intermediate refrigeration with a cryogenic liquid. By using an analytical calculation method relations are derived, which enable complete predictions about the effectiveness of an intermediate refrigeration with boil-off gas cooled shields as a function of the number of shields for the different stored cryogenic liquids. For this theoretical derivation however, the restrictive assumption must be made that the thermal conductivity of the used insulation material has a constant value between the considered temperature boundaries. For purposes of a more exact calculation a numerical method is therefore suggested, which takes into consideration that the thermal conductivity is temperature-dependent. For a liquid hydrogen storage vessel with a perlite-vacuum insulation e.g., the effectiveness of one shield and its equilibrium temperature are given as a function of the position of the shield in the insulation space.
Evaluation of gamma radiation shielding for nuclear waste shipping casks
Liu, Y.Y.; Carlson, R.D.; Primeau, S.J.; Wangler, M.E.
1998-05-01
A method has been developed for evaluating gamma radiation shielding of shipping casks that are used to transport nuclear waste with ill-defined radionuclide contents. The method is based on calculations that establish individual limits for a comprehensive list of radionuclides in the waste, assuming that each radionuclide is uniformly distributed in a volumetric source in the cask. For multiple radionuclide mixtures, a linear fraction rule is used to restrict the total amount of radionuclides such that the sum of the fractions does not exceed 1. As long as the radionuclide limits and the linear fraction rule are followed, it can be shown that the regulatory dose rate requirements for a cask will be satisfied under normal conditions of transport and in a hypothetical accident during which the shielding thickness of the cask has been reduced by 40%.
McCormack, W.D.; Ramsdell, J.V.; Napier, B.A.
1984-05-01
This document serves as a guide to Hanford contractors for obtaining or performing Hanford-related environmental dose calculations. Because environmental dose estimation techniques are state-of-the-art and are continually evolving, the data and standard methods presented herein will require periodic revision. This document is scheduled to be updated annually, but actual changes to the program will be made more frequently if required. For this reason, PNL's Occupational and Environmental Protection Department should be contacted before any Hanford-related environmental dose calculation is performed. This revision of the Hanford Dose Overview Program Report primarily reflects changes made to the data and models used in calculating atmospheric dispersion of airborne effluents at Hanford. The modified data and models are described in detail. In addition, discussions of dose calculation methods and the review of calculation results have been expanded to provide more explicit guidance to the Hanford contractors. 19 references, 30 tables.
Flanigan, Vincent J.; Zablocki, Charles J.
1984-01-01
Feasibility studies of two electromagnetic methods were made in selected areas of the Jabal Hibshi (1:250,000) quadrangle, 26F, in the Kingdom of Saudi Arabia in March of 1983. The methods tested were the natural source-field telluricelectric and audio-magnetotelluric methods developed and extensively used in recent years by the U.S. Geological Survey in some of its domestic programs related to geothermal and mineral resource assessment. Results from limited studies in the Meshaheed district, the Jabal as Silsilah ring complex, and across a portion of the Raha fault zone clearly demonstrate the appropriateness of these sub-regional scale, reconnaissance-type studies to mineral resource assessment. The favorable results obtained are largely attributed to distinctive and large contrasts in the electrical resistivity of the major rock types encountered. It appears that the predominant controlling factor governing the rock resistivities is the amount of contained clay minerals. Accordingly, unaltered (specifically, non-argillic) igneous and metamorphic rocks have very high resistivities; metasedimentary rocks of the Murdama group that contain several percent clay minerals have intermediate values of resistivity; and highly altered rocks, containing abundant clay minerals, have very low values of resistivity. Water-filled fracture porosity may be a secondary, but important, factor in some settings. However, influences from variations in interstitial or intercrystalline, water-filled porosity are probably small because these types of porosity are generally low. It is reasonable to expect similar results in other areas within the Arabian Shield.
Predictions for Radiation Shielding Materials
NASA Technical Reports Server (NTRS)
Kiefer, Richard L.
2002-01-01
Radiation from galactic cosmic rays (GCR) and solar particle events (SPE) is a serious hazard to humans and electronic instruments during space travel, particularly on prolonged missions outside the Earth s magnetic fields. Galactic cosmic radiation (GCR) is composed of approx. 98% nucleons and approx. 2% electrons and positrons. Although cosmic ray heavy ions are 1-2% of the fluence, these energetic heavy nuclei (HZE) contribute 50% of the long-term dose. These unusually high specific ionizations pose a significant health hazard acting as carcinogens and also causing microelectronics damage inside spacecraft and high-flying aircraft. These HZE ions are of concern for radiation protection and radiation shielding technology, because gross rearrangements and mutations and deletions in DNA are expected. Calculations have shown that HZE particles have a strong preference for interaction with light nuclei. The best shield for this radiation would be liquid hydrogen, which is totally impractical. For this reason, hydrogen-containing polymers make the most effective practical shields. Shielding is required during missions in Earth orbit and possibly for frequent flying at high altitude because of the broad GCR spectrum and during a passage into deep space and LunarMars habitation because of the protracted exposure encountered on a long space mission. An additional hazard comes from solar particle events (SPEs) which are mostly energetic protons that can produce heavy ion secondaries as well as neutrons in materials. These events occur at unpredictable times and can deliver a potentially lethal dose within several hours to an unshielded human. Radiation protection for humans requires safety in short-term missions and maintaining career exposure limits within acceptable levels on future long-term exploration missions. The selection of shield materials can alter the protection of humans by an order of magnitude. If improperly selected, shielding materials can actually
Structural system reliability calculation using a probabilistic fault tree analysis method
NASA Technical Reports Server (NTRS)
Torng, T. Y.; Wu, Y.-T.; Millwater, H. R.
1992-01-01
The development of a new probabilistic fault tree analysis (PFTA) method for calculating structural system reliability is summarized. The proposed PFTA procedure includes: developing a fault tree to represent the complex structural system, constructing an approximation function for each bottom event, determining a dominant sampling sequence for all bottom events, and calculating the system reliability using an adaptive importance sampling method. PFTA is suitable for complicated structural problems that require computer-intensive computer calculations. A computer program has been developed to implement the PFTA.
Method for the calculation of spacecraft umbra and penumbra shadow terminator points
NASA Technical Reports Server (NTRS)
Ortizlongo, Carlos R.; Rickman, Steven L.
1995-01-01
A method for calculating orbital shadow terminator points is presented. The current method employs the use of an iterative process which is used for an accurate determination of shadow points. This calculation methodology is required since orbital perturbation effects can introduce large errors when a spacecraft orbits a planet in a high altitude and/or highly elliptical orbit. To compensate for the required iteration methodology, all reference frame change definitions and calculations are performed with quaternions. Quaternion algebra significantly reduces the computational time required for the accurate determination of shadow terminator points.
Yamaguchi, Nobuyoshi; Nakao, Masato; Murakami, Masahide; Miyazawa, Kenji
2008-07-08
For seismic design, ductility-related force modification factors are named R factor in Uniform Building Code of U.S, q factor in Euro Code 8 and Ds (inverse of R) factor in Japanese Building Code. These ductility-related force modification factors for each type of shear elements are appeared in those codes. Some constructions use various types of shear walls that have different ductility, especially for their retrofit or re-strengthening. In these cases, engineers puzzle the decision of force modification factors of the constructions. Solving this problem, new method to calculate lateral strengths of stories for simple shear wall systems is proposed and named 'Stiffness--Potential Energy Addition Method' in this paper. This method uses two design lateral strengths for each type of shear walls in damage limit state and safety limit state. Two lateral strengths of stories in both limit states are calculated from these two design lateral strengths for each type of shear walls in both limit states. Calculated strengths have the same quality as values obtained by strength addition method using many steps of load-deformation data of shear walls. The new method to calculate ductility factors is also proposed in this paper. This method is based on the new method to calculate lateral strengths of stories. This method can solve the problem to obtain ductility factors of stories with shear walls of different ductility.
Shielding Effectiveness of a Collinear Unequal Paired-Narrow-Slot Array in Conducting Screens
NASA Astrophysics Data System (ADS)
Kim, Ki-Chai
This letter presents a method that offers the simple calculation of the electric shielding effectiveness of a collinear unequal narrow slot array in a planar conducting screen. An integral equation for an aperture electric field on the unequal narrow slot array is used instead of coupled integral equations for a multiple slot and solved by applying Galerkin's method of moments. Numerical results illustrate the shielding effectiveness and aperture electric field distributions of the collinear unequal two-narrow slot array by using single integral equation.
Radiation Shielding for Nuclear Thermal Propulsion
NASA Technical Reports Server (NTRS)
Caffrey, Jarvis A.
2016-01-01
Design and analysis of radiation shielding for nuclear thermal propulsion has continued at Marshall Space Flight Center. A set of optimization tools are in development, and strategies for shielding optimization will be discussed. Considerations for the concurrent design of internal and external shielding are likely required for a mass optimal shield design. The task of reducing radiation dose to crew from a nuclear engine is considered to be less challenging than the task of thermal mitigation for cryogenic propellant, especially considering the likely implementation of additional crew shielding for protection from solar particles and cosmic rays. Further consideration is thus made for the thermal effects of radiation absorption in cryogenic propellant. Materials challenges and possible methods of manufacturing are also discussed.
Repository Waste Package Transporter Shielding Weight Optimization
C.E. Sanders; Shiaw-Der Su
2005-02-02
The Yucca Mountain repository requires the use of a waste package (WP) transporter to transport a WP from a process facility on the surface to the subsurface for underground emplacement. The transporter is a part of the waste emplacement transport systems, which includes a primary locomotive at the front end and a secondary locomotive at the rear end. The overall system with a WP on board weights over 350 metric tons (MT). With the shielding mass constituting approximately one-third of the total system weight, shielding optimization for minimal weight will benefit the overall transport system with reduced axle requirements and improved maneuverability. With a high contact dose rate on the WP external surface and minimal personnel shielding afforded by the WP, the transporter provides radiation shielding to workers during waste emplacement and retrieval operations. This paper presents the design approach and optimization method used in achieving a shielding configuration with minimal weight.
A New Method for the Calculation of Diffusion Coefficients with Monte Carlo
NASA Astrophysics Data System (ADS)
Dorval, Eric
2014-06-01
This paper presents a new Monte Carlo-based method for the calculation of diffusion coefficients. One distinctive feature of this method is that it does not resort to the computation of transport cross sections directly, although their functional form is retained. Instead, a special type of tally derived from a deterministic estimate of Fick's Law is used for tallying the total cross section, which is then combined with a set of other standard Monte Carlo tallies. Some properties of this method are presented by means of numerical examples for a multi-group 1-D implementation. Calculated diffusion coefficients are in general good agreement with values obtained by other methods.
NASA Astrophysics Data System (ADS)
Wu, G. Q.; Huang, R. Q.
1994-06-01
This paper introduces a new calculation method of non-LTE stellar atmospheres. This method is based on the combination of the advantages of the complete linearization method by Auer and Mihalas (1969) and the separated-iteration technique. First, the equation of radiative transfer and constraints are linearized respectively, then the linearized equation of the radiative transfer and the linearized constraints are solved, separately. It overcomes the disadvantages of requiring the simultaneous solution of the corresponding equations by the complete linearization. The applicability of this method by calculating a small sample of H-He atmospheres and H line formations is demonstrated.
NASA Astrophysics Data System (ADS)
Spirou, S. V.; Tsialios, P.; Loudos, G.
2015-09-01
In Magnetic Nanoparticle Hyperthermia (MNH) an externally applied electromagnetic field transfers energy to the magnetic nanoparticles in the body, which in turn convert this energy into heat, thus locally heating the tissue they are located in. This external electromagnetic field is sufficiently strong so as to cause interference and affect sensitive electronic equipment. Standard shielding of magnetic fields involves Faraday cages or coating with high-permeability shielding alloys; however, these techniques cannot be used with optically sensitive devices, such as those employed in Optical Coherence Tomography or radionuclide imaging. In this work we present a method to achieve magnetic shielding using an array of coils. The magnetic field generated by a single coil was calculated using the COMSOL physics simulation toolkit. Software was written in C/C++ to import the single-coil data, and then calculate the positions, number of turns and currents in the shielding coils in order to minimize the magnetic field strength at the desired location. Simulations and calculations have shown that just two shielding coils can reduce the magnetic field by 2-3 orders of magnitude.
Puncher, M; Birchall, A; Bull, R K
2012-08-01
Estimating uncertainties on doses from bioassay data is of interest in epidemiology studies that estimate cancer risk from occupational exposures to radionuclides. Bayesian methods provide a logical framework to calculate these uncertainties. However, occupational exposures often consist of many intakes, and this can make the Bayesian calculation computationally intractable. This paper describes a novel strategy for increasing the computational speed of the calculation by simplifying the intake pattern to a single composite intake, termed as complex intake regime (CIR). In order to assess whether this approximation is accurate and fast enough for practical purposes, the method is implemented by the Weighted Likelihood Monte Carlo Sampling (WeLMoS) method and evaluated by comparing its performance with a Markov Chain Monte Carlo (MCMC) method. The MCMC method gives the full solution (all intakes are independent), but is very computationally intensive to apply routinely. Posterior distributions of model parameter values, intakes and doses are calculated for a representative sample of plutonium workers from the United Kingdom Atomic Energy cohort using the WeLMoS method with the CIR and the MCMC method. The distributions are in good agreement: posterior means and Q(0.025) and Q(0.975) quantiles are typically within 20 %. Furthermore, the WeLMoS method using the CIR converges quickly: a typical case history takes around 10-20 min on a fast workstation, whereas the MCMC method took around 12-72 hr. The advantages and disadvantages of the method are discussed. PMID:22355169
Calculation Method for Flight Limit Load of V-band Clamp Separation Shock
NASA Astrophysics Data System (ADS)
Iwasa, Takashi; Shi, Qinzhong
A simplified calculation method for estimating a flight limit load of the V-band clamp separation shock was established. With this method, the flight limit load is estimated through addition of an appropriate envelope margin to the results acquired with the simplified analysis method proposed in our previous paper. The envelope margin used in the method was calculated based on the reviews on the differences observed between the results of a pyroshock test and the analysis. Using the derived envelope margin, a calculating formula of the flight limit load, which envelopes the actual pyroshock responses with a certain probability, was developed. Based on the formula, flight limit loads for several actual satellites were estimated and compared to the test results. The comparative results showed that the estimated flight limit loads appropriately envelope the test results, which confirmed the effectiveness of the proposed method.
TORT/MCNP coupling method for the calculation of neutron flux around a core of BWR.
Kurosawa, Masahiko
2005-01-01
For the analysis of BWR neutronics performance, accurate data are required for neutron flux distribution over the In-Reactor Pressure Vessel equipments taking into account the detailed geometrical arrangement. The TORT code can calculate neutron flux around a core of BWR in a three-dimensional geometry model, but has difficulties in fine geometrical modelling and lacks huge computer resource. On the other hand, the MCNP code enables the calculation of the neutron flux with a detailed geometry model, but requires very long sampling time to give enough number of particles. Therefore, a TORT/MCNP coupling method has been developed to eliminate the two problems mentioned above in each code. In this method, the TORT code calculates angular flux distribution on the core surface and the MCNP code calculates neutron spectrum at the points of interest using the flux distribution. The coupling method will be used as the DOT-DOMINO-MORSE code system. This TORT/MCNP coupling method was applied to calculate the neutron flux at points where induced radioactivity data were measured for 54Mn and 60Co and the radioactivity calculations based on the neutron flux obtained from the above method were compared with the measured data. PMID:16604689
Comment on 'Discrepancies in the resonance-fluorescence spectrum calculated with two methods'
Ficek, Zbigniew
2009-05-15
There are two alternative methods used in the literature to calculate the incoherent part of the spectrum of light scattered by an atomic system. In the first, one calculates the spectrum of the total light scattered by the system and obtains the incoherent part by subtracting the coherent part. In the second method, one introduces the fluctuation operators and obtains the incoherent part of the spectrum by taking the Fourier transform of the two-time correlation function of the fluctuation operators. These two methods have been recognized for years as completely equivalent for evaluating the incoherent part of the spectrum. In a recent paper, Xu et al. [Phys. Rev. A 78, 013407 (2008)] showed that there are discrepancies between the incoherent parts of the stationary spectrum of a three-level {lambda}-type system calculated with these two methods. The predicted discrepancies can be severe that over a wide range of the Rabi frequencies and atomic decay rates, the spectrum calculated with the variance method can have negative values. In this Comment, we show that there are no discrepancies between these two methods. We show the equivalence of these two methods that leads to the same incoherent spectra which are positive for all frequencies independent of values of the parameters involved. We also identify the source of the discrepancy, that is, in an incorrect treatment of the incoherent part of the spectrum calculated with the two-time correlation function of the fluctuation operators.
NASA Astrophysics Data System (ADS)
Ajiki, Hiroshi
2013-05-01
A new method for calculating exciton wavefunctions in the presence of a long-range electron--hole (e--h) exchange interaction (EXI) is presented. The e--h EXI arises, for example, for cross-polarized excitons in a single-walled carbon nanotube (SWNT). Cross-polarized excitons have previously been calculated as an eigenvalue problem of a Bethe--Salpeter equation (BSE) within the Tamm--Dancoff-type approximation (TDA). The resulting wavefunctions provide quite different absorption spectra in comparison with those calculated in the self-consistent-field method [S. Uryu and T. Ando, J. Phys.: Conf. Ser. 302 (2011) 012004]. Although the self-consistent-field method is more reliable, exciton wavefunctions cannot be obtained from this method. A general method is derived here to obtain exciton wavefunctions that take the e--h EXI into account within the TDA, and the method is applied to the cross-polarized excitons of a SWNT. The absorption spectra calculated from the resulting exciton wavefunctions agree well with the spectra calculated from the self-consistent-field method within a rotating-wave approximation.
NASA Technical Reports Server (NTRS)
Yew, Calinda; Stephens, Matt
2015-01-01
The JWST IEC conformal shields are mounted onto a composite frame structure that must undergo qualification testing to satisfy mission assurance requirements. The composite frame segments are bonded together at the joints using epoxy, EA 9394. The development of a test method to verify the integrity of the bonded structure at its operating environment introduces challenges in terms of requirements definition and the attainment of success criteria. Even though protoflight thermal requirements were not achieved, the first attempt in exposing the structure to cryogenic operating conditions in a thermal vacuum environment resulted in approximately 1 bonded joints failure during mechanical pull tests performed at 1.25 times the flight loads. Failure analysis concluded that the failure mode was due to adhesive cracks that formed and propagated along stress concentrated fillets as a result of poor bond squeeze-out control during fabrication. Bond repairs were made and the structures successfully re-tested with an improved LN2 immersion test method to achieve protoflight thermal requirements.
Borst, L.B.
1961-07-11
A special hydrogenous concrete shielding for reactors is described. In addition to Portland cement and water, the concrete essentially comprises 30 to 60% by weight barytes aggregate for enhanced attenuation of fast neutrons. The biological shields of AEC's Oak Ridge Graphite Reactor and Materials Testing Reactor are particular embodiments.
Ohlinger, R.D.; Humphrey, H.W.
1985-08-26
A gamma ray detector shield comprised of a rigid, lead, cylindrical-shaped vessel having upper and lower portions with an pneumatically driven, sliding top assembly. Disposed inside the lead shield is a gamma ray scintillation crystal detector. Access to the gamma detector is through the sliding top assembly.
a New Method for Calculating the Fractal Dimension of Surface Topography
NASA Astrophysics Data System (ADS)
Zuo, Xue; Zhu, Hua; Zhou, Yuankai; Li, Yan
2015-06-01
A new method termed as three-dimensional root-mean-square (3D-RMS) method, is proposed to calculate the fractal dimension (FD) of machined surfaces. The measure of this method is the root-mean-square value of surface data, and the scale is the side length of square in the projection plane. In order to evaluate the calculation accuracy of the proposed method, the isotropic surfaces with deterministic FD are generated based on the fractional Brownian function and Weierstrass-Mandelbrot (WM) fractal function, and two kinds of anisotropic surfaces are generated by stretching or rotating a WM fractal curve. Their FDs are estimated by the proposed method, as well as differential boxing-counting (DBC) method, triangular prism surface area (TPSA) method and variation method (VM). The results show that the 3D-RMS method performs better than the other methods with a lower relative error for both isotropic and anisotropic surfaces, especially for the surfaces with dimensions higher than 2.5, since the relative error between the estimated value and its theoretical value decreases with theoretical FD. Finally, the electrodeposited surface, end-turning surface and grinding surface are chosen as examples to illustrate the application of 3D-RMS method on the real machined surfaces. This method gives a new way to accurately calculate the FD from the surface topographic data.
NASA Astrophysics Data System (ADS)
Zimmermann, Anke; Kuhn, Sandra; Richter, Marten
2016-01-01
Often, the calculation of Coulomb coupling elements for quantum dynamical treatments, e.g., in cluster or correlation expansion schemes, requires the evaluation of a six dimensional spatial integral. Therefore, it represents a significant limiting factor in quantum mechanical calculations. If the size or the complexity of the investigated system increases, many coupling elements need to be determined. The resulting computational constraints require an efficient method for a fast numerical calculation of the Coulomb coupling. We present a computational method to reduce the numerical complexity by decreasing the number of spatial integrals for arbitrary geometries. We use a Green's function formulation of the Coulomb coupling and introduce a generalized scalar potential as solution of a generalized Poisson equation with a generalized charge density as the inhomogeneity. That enables a fast calculation of Coulomb coupling elements and, additionally, a straightforward inclusion of boundary conditions and arbitrarily spatially dependent dielectrics through the Coulomb Green's function. Particularly, if many coupling elements are included, the presented method, which is not restricted to specific symmetries of the model, presents a promising approach for increasing the efficiency of numerical calculations of the Coulomb interaction. To demonstrate the wide range of applications, we calculate internanostructure couplings, such as the Förster coupling, and illustrate the inclusion of symmetry considerations in the method for the Coulomb coupling between bound quantum dot states and unbound continuum states.
The effective atomic numbers of some biomolecules calculated by two methods: A comparative study
Manohara, S. R.; Hanagodimath, S. M.; Gerward, L.
2009-01-15
The effective atomic numbers Z{sub eff} of some fatty acids and amino acids have been calculated by two numerical methods, a direct method and an interpolation method, in the energy range of 1 keV-20 MeV. The notion of Z{sub eff} is given a new meaning by using a modern database of photon interaction cross sections (WinXCom). The results of the two methods are compared and discussed. It is shown that for all biomolecules the direct method gives larger values of Z{sub eff} than the interpolation method, in particular at low energies (1-100 keV) At medium energies (0.1-5 MeV), Z{sub eff} for both methods is about constant and equal to the mean atomic number of the material. Wherever possible, the calculated values of Z{sub eff} are compared with experimental data.
NASA Astrophysics Data System (ADS)
Punegov, V. I.; Sivkov, D. V.
2015-03-01
Two independent approaches to calculate the angular distribution of X-ray diffusion scattering from a crystalline medium with spheroidal quantum dots (QDs) have been proposed. The first method is based on the analytical solution involving the multipole expansion of elastic strain fields beyond QDs. The second approach is based on calculations of atomic displacements near QDs by the Green's function method. An analysis of the diffuse scattering intensity distribution in the reciprocal space within these two approaches shows that both methods yield similar results for the chosen models of QD spatial distribution.
Punegov, V. I. Sivkov, D. V.
2015-03-15
Two independent approaches to calculate the angular distribution of X-ray diffusion scattering from a crystalline medium with spheroidal quantum dots (QDs) have been proposed. The first method is based on the analytical solution involving the multipole expansion of elastic strain fields beyond QDs. The second approach is based on calculations of atomic displacements near QDs by the Green’s function method. An analysis of the diffuse scattering intensity distribution in the reciprocal space within these two approaches shows that both methods yield similar results for the chosen models of QD spatial distribution.
A simple method of calculating lower-bound limit loads for axisymmetric thin shells
Boyle, J.T.; Hamilton, R.; Shi, J.; Mackenzie, D.
1997-05-01
In this paper, a simple method for calculating lower-bound limit loads for shells is presented, based on Ilyushin`s and Ivanov`s generalized yield criterion, respectively, and using the elastic compensation procedure. Several examples, including torispherical and conical ends, radial nozzles, and a skirted vessel, are examined using this method. The results are compared with previously published results.
A Method for Calculating Fermi Energy and Carrier Concentrations in Semiconducts
ERIC Educational Resources Information Center
Gaylord, T. K.; Linxwiler, J. N., Jr.
1976-01-01
An efficient numerical method for calculating the Fermi energy, the free electron and free hole concentrations, and the ionized impurity conductors in a semiconductor material is described. The method allows freedom with respect to type of material, temperature, and amount and type of donor and acceptor impurities. (Author/CP)
Z method calculations to determine the melting curve of silica at high pressures
NASA Astrophysics Data System (ADS)
González-Cataldo, F.; Davis, S.; Gutiérrez, G.
2016-05-01
The Z method is a novel technique that allows to calculate the melting temperature of materials at different pressures from the microcanonical ensemble. In this work, we apply this method to study the melting behavior of silica at high pressures, determining melting temperatures and dynamical properties.
A simple method to calculate P50 from a single blood sample.
Doyle, D J
1997-01-01
Hill's equation relating oxygen tension, saturation and P50 is used as the basis for a simple method to calculate P50 from a single blood sample. The effects of errors of measurement in oxygen tension and saturation are considered using the technique of sensitivity analysis. The method is illustrated using data published by Severinghaus. PMID:9336736
Invariant-theoretic method for calculating Clebsch-Gordan coefficients for space groups
Aizenberg, A.Ya.; Gufan, Yu.M.
1995-03-01
A new invariant-theoretic method to directly calculate Clebsch-Gordan coefficients for space and point groups representations is proposed. The method is exemplified with the space groups O{sub h}{sup 5} and D{sub 6h}{sup 1}. 34 refs.
The Theory of Propellers II : Method for Calculating the Axial Interference Velocity
NASA Technical Reports Server (NTRS)
Theodorsen, Theodore
1944-01-01
A technical method is given for calculating the axial interference velocity of a propeller. The method involves the use of certain weight functions p, q, and f. Numerical values for the weight functions are given for two-blade, three-blade, and six-blade propellers.
7 CFR 51.308 - Methods of sampling and calculation of percentages.
Code of Federal Regulations, 2014 CFR
2014-01-01
... Grades of Apples Methods of Sampling and Calculation of Percentages § 51.308 Methods of sampling and... weigh ten pounds or less, or in any container where the minimum diameter of the smallest apple does not vary more than 1/2 inch from the minimum diameter of the largest apple, percentages shall be...
7 CFR 51.308 - Methods of sampling and calculation of percentages.
Code of Federal Regulations, 2013 CFR
2013-01-01
... Grades of Apples Methods of Sampling and Calculation of Percentages § 51.308 Methods of sampling and... weigh ten pounds or less, or in any container where the minimum diameter of the smallest apple does not vary more than 1/2 inch from the minimum diameter of the largest apple, percentages shall be...
A Method of Calculating Motion Error in a Linear Motion Bearing Stage
Khim, Gyungho; Park, Chun Hong; Oh, Jeong Seok
2015-01-01
We report a method of calculating the motion error of a linear motion bearing stage. The transfer function method, which exploits reaction forces of individual bearings, is effective for estimating motion errors; however, it requires the rail-form errors. This is not suitable for a linear motion bearing stage because obtaining the rail-form errors is not straightforward. In the method described here, we use the straightness errors of a bearing block to calculate the reaction forces on the bearing block. The reaction forces were compared with those of the transfer function method. Parallelism errors between two rails were considered, and the motion errors of the linear motion bearing stage were measured and compared with the results of the calculations, revealing good agreement. PMID:25705715
NASA Astrophysics Data System (ADS)
Patashova, T.
2009-04-01
Calculation of mineral resources and their proper assessment is relevant, since the stock of resources determines the economic independence of the state. I would like present the work wherein discusses gravel and sand deposits of different genetic type (kames, eskers, marginal glaciofluvial ridges, sandurs, glaciofluvial deltas and redrifted glaciofluvial aeolian formations). Their geological structure and formation conditions have been assessed; quality characteristics of mineral resources have been analysed; calculation of resources has been performed by applying most popular resources calculating methods used in Lithuania up to now, such as those of geological blocks, profiles and isolines, as well as the up-to-date GRID method created on the basis of triangle method in GIS environment. Comparison of resources assessed by different methods has revealed their advantages and disadvantages, their availability subject to deposits‘genetic types.
[Calculation of spectral shifts of the mutants of bacteriorhodopsin by QM/MM methods].
Orekhov, F S; Shaĭtan, A K; Shaĭtan, K V
2012-01-01
In the present work spectral shifts of adsorption maxima for the number of mutants of bacteriorhodopsin have been calculated using QM/MM hybrid methodology. Along with this calculation an analysis of possible mechanisms of spectral modulation has been performed. Also we have carried out a comparative analysis of modern quantum chemical methods in respect of the level of optical spectra predictability they allow. We have shown that modern hybrid quantum chemical methods reach an acceptable level of preciseness when applied in the calculation of spectral shifts even if the absolute values of adsorption maxima predicted by these methods are underestimated. The number of rules has been found linking the value of spectral shift with the structural rearrangement in the apoprotein. The methods we were using as well as those rules we have found out both may be useful for development of nanoelectronical devices based on mutant species of bacteriorhodopsin (memory elements, optical triggers etc.). PMID:22594277
Calculation method of load distribution on pipe threaded connections under tension load
NASA Astrophysics Data System (ADS)
Chen, Shoujun; Gao, Lianxin; An, Qi
2011-06-01
This paper presents a new calculation method that can calculate the load distribution on pipe threaded connections under tension load. On the basis of elastic mechanics, the new method was developed by analyzing each thread tooth, and a new deformation and covariant equation by making a mechanics analysis on each thread tooth was obtained. Compared with the traditional method proposed by the previous references, the new deformation and covariant equation could be used to describe the relation between the previous and the next thread tooth. By applying the new method on the sample of P-110S pipe threaded connection, the obtained results show that the load on thread tooth mainly concentrates on the four or five threads engaged and the middle teeth were not utilized well to bear the loads. The model offers a new way to calculate the loads carried on the thread teeth under tension load.
A finite element method for shear stresses calculation in composite blade models
NASA Astrophysics Data System (ADS)
Paluch, B.
1991-09-01
A finite-element method is developed for accurately calculating shear stresses in helicopter blade models, induced by torsion and shearing forces. The method can also be used to compute the equivalent torsional stiffness of the section, their transverse shear coefficient, and the position of their center of torsion. A grid generator method which is a part of the calculation program is also described and used to discretize the sections quickly and to condition the grid data reliably. The finite-element method was validated on a few sections composed of isotropic materials and was then applied to a blade model sections made of composite materials. Good agreement was obtained between the calculated and experimental data.
Electronic Structure Calculation of Permanent Magnets using the KKR Green's Function Method
NASA Astrophysics Data System (ADS)
Doi, Shotaro; Akai, Hisazumi
2014-03-01
Electronic structure and magnetic properties of permanent magnetic materials, especially Nd2Fe14B, are investigated theoretically using the KKR Green's function method. Important physical quantities in magnetism, such as magnetic moment, Curie temperature, and anisotropy constant, which are obtained from electronics structure calculations in both cases of atomic-sphere-approximation and full-potential treatment, are compared with past band structure calculations and experiments. The site preference of heavy rare-earth impurities are also evaluated through the calculation of formation energy with the use of coherent potential approximations. Further, the development of electronic structure calculation code using the screened KKR for large super-cells, which is aimed at studying the electronic structure of realistic microstructures (e.g. grain boundary phase), is introduced with some test calculations.
NASA Astrophysics Data System (ADS)
Rodný, Marek; Nolz, Reinhard; Novák, Viliam; Hlaváčiková, Hana; Loiskandl, Willibald; Himmelbauer, Margarita
2016-04-01
The aim of this study was to present and validate an alternative evapotranspiration calculation procedure that includes specific expression for the aerodynamic resistance. Calculated daily potential evapotranspiration totals were compared to the results of FAO56 procedure application and to the results of measurements taken with a precision weighing lysimeter permanently grown with irrigated, short grass. For the examination period from March 17 through October 31, 2011, it was found that daily potential evapotranspiration estimates obtained by both calculation procedures fitted well to the lysimeter measurements. Potential evapotranspiration daily totals calculated with the use of the proposed aerodynamic resistance calculation procedure gave better results for days with higher evapotranspiration, compared to the FAO56 method. The most important is that the approach based on the proposed alternative aerodynamic resistance could be effectively used even for a wide variety of crops, because it is not limited to any particular crop.
NASA Astrophysics Data System (ADS)
Ding, E. J.
2015-06-01
The time-independent lattice Boltzmann algorithm (TILBA) is developed to calculate the hydrodynamic interactions between two particles in a Stokes flow. The TILBA is distinguished from the traditional lattice Boltzmann method in that a background matrix (BGM) is generated prior to the calculation. The BGM, once prepared, can be reused for calculations for different scenarios, and the computational cost for each such calculation will be significantly reduced. The advantage of the TILBA is that it is easy to code and can be applied to any particle shape without complicated implementation, and the computational cost is independent of the shape of the particle. The TILBA is validated and shown to be accurate by comparing calculation results obtained from the TILBA to analytical or numerical solutions for certain problems.
Mitrikas, V G
2015-01-01
Monitoring of the radiation loading on cosmonauts requires calculation of absorbed dose dynamics with regard to the stay of cosmonauts in specific compartments of the space vehicle that differ in shielding properties and lack means of radiation measurement. The paper discusses different aspects of calculation modeling of radiation effects on human body organs and tissues and reviews the effective dose estimates for cosmonauts working in one or another compartment over the previous period of the International space station operation. It was demonstrated that doses measured by a real or personal dosimeters can be used to calculate effective dose values. Correct estimation of accumulated effective dose can be ensured by consideration for time course of the space radiation quality factor. PMID:26292419
[The model of radiation shielding of the service module of the International space station].
Kolomenskiĭ, A V; Kuznetsov, V G; Laĭko, Iu A; Bengin, V V; Shurshakov, V A
2001-01-01
Compared and contrasted were models of radiation shielding of habitable compartments of the basal Mir module that had been used to calculate crew absorbed doses from space radiation. Developed was a model of the ISS Service module radiation shielding. It was stated that there is a good agreement between experimental shielding function and the one calculated from this model. PMID:11915750
Moore, Stan G; Crozier, Paul S
2014-06-21
Several extensions and improvements have been made to the multilevel summation method (MSM) of computing long-range electrostatic interactions. These include pressure calculation, an improved error estimator, faster direct part calculation, extension to non-orthogonal (triclinic) systems, and parallelization using the domain decomposition method. MSM also allows fully non-periodic long-range electrostatics calculations which are not possible using traditional Ewald-based methods. In spite of these significant improvements to the MSM algorithm, the particle-particle particle-mesh (PPPM) method was still found to be faster for the periodic systems we tested on a single processor. However, the fast Fourier transforms (FFTs) that PPPM relies on represent a major scaling bottleneck for the method when running on many cores (because the many-to-many communication pattern of the FFT becomes expensive) and MSM scales better than PPPM when using a large core count for two test problems on Sandia's Redsky machine. This FFT bottleneck can be reduced by running PPPM on only a subset of the total processors. MSM is most competitive for relatively low accuracy calculations. On Sandia's Chama machine, however, PPPM is found to scale better than MSM for all core counts that we tested. These results suggest that PPPM is usually more efficient than MSM for typical problems running on current high performance computers. However, further improvements to MSM algorithm could increase its competitiveness for calculation of long-range electrostatic interactions. PMID:24952528
Analytic flux formulas and tables of shielding functions
Wallace, O.J.
1981-06-01
Hand calculations of radiation flux and dose rates are often useful in evaluating radiation shielding and in determining the scope of a problem. The flux formulas appropriate to such calculations are almost always based on the point kernel and allow for at most the consideration of laminar slab shields. These formulas often require access to tables of values of integral functions for effective use. Flux formulas and function tables appropriate to calculations involving homogeneous source regions with the shapes of lines, disks, slabs, truncated cones, cylinders, and spheres are presented. Slab shields may be included in most of these calculations, and the effect of a cylindrical shield surrounding a cylindrical source may be estimated. Detector points may be located axially, laterally, or interior to a cylindrical source. Line sources may be tilted with respect to a slab shield. All function tables are given for a wide range of arguments.
RSMASS: A simple model for estimating reactor/shield masses
NASA Technical Reports Server (NTRS)
Marshall, Albert C.
1987-01-01
A comparison was completed of the reactor/shield masses obtained from detailed calculations by the proposers of space power reactors. This comparison included a variety of liquid metal cooled, gas cooled and thermionic reactors. An initial goal for agreement between RSMASS (reactor/shield mass model) calculated masses and the masses obtained from detailed calculations was chosen to be a factor of 2. The preliminary comparison demonstrated that the reactor/shield masses estimated by RSMASS agree with the masses obtained from detailed calculations within 50 percent. It can be concluded that RSMASS can provide good estimates of reactor/shield masses for a broad variety of reactor concepts proposed for MMW space power applications. RSMASS is being used to compare the masses of various reactor types and is providing some insights into the mass advantages and disadvantages for the various concepts as a function of operating conditions and reactor or shield parameters. Some mass estimates obtained with RSMASS are presented.
NASA Astrophysics Data System (ADS)
Meng, Qing-Xin; Pan, He-Ping; Luo, Miao
2015-12-01
We conducted a study on the numerical calculation and response analysis of a transient electromagnetic field generated by a ground source in geological media. One solution method, the traditional discrete image method, involves complex operation, and its digital filtering algorithm requires a large number of calculations. To solve these problems, we proposed an improved discrete image method, where the following are realized: the real number of the electromagnetic field solution based on the Gaver-Stehfest algorithm for approximate inversion, the exponential approximation of the objective kernel function using the Prony method, the transient electromagnetic field according to discrete image theory, and closed-form solution of the approximate coefficients. To verify the method, we tentatively calculated the transient electromagnetic field in a homogeneous model and compared it with the results obtained from the Hankel transform digital filtering method. The results show that the method has considerable accuracy and good applicability. We then used this method to calculate the transient electromagnetic field generated by a ground magnetic dipole source in a typical geoelectric model and analyzed the horizontal component response of the induced magnetic field obtained from the "ground excitation-stratum measurement" method. We reached the conclusion that the horizontal component response of a transient field is related to the geoelectric structure, observation time, spatial location, and others. The horizontal component response of the induced magnetic field reflects the eddy current field distribution and its vertical gradient variation. During the detection of abnormal objects, positions with a zero or comparatively large offset were selected for the drillhole measurements or a comparatively long observation delay was adopted to reduce the influence of the ambient field on the survey results. The discrete image method and forward calculation results in this paper
Dose calculation and in-phantom measurement in BNCT using response matrix method.
Rahmani, Faezeh; Shahriari, Majid
2011-12-01
In-phantom measurement of physical dose distribution is very important for Boron Neutron Capture Therapy (BNCT) planning validation. If any changes take place in therapeutic neutron beam due to the beam shaping assembly (BSA) change, the dose will be changed so another group of simulations should be carried out for dose calculation. To avoid this time consuming procedure and speed up the dose calculation to help patients not wait for a long time, response matrix method was used. This procedure was performed for neutron beam of the optimized BSA as a reference beam. These calculations were carried out using the MCNPX, Monte Carlo code. The calculated beam parameters were measured for a SNYDER head phantom placed 10 cm away from beam the exit of the BSA. The head phantom can be assumed as a linear system and neutron beam and dose distribution can be assumed as an input and a response of this system (head phantom), respectively. Neutron spectrum energy was digitized into 27 groups. Dose response of each group was calculated. Summation of these dose responses is equal to a total dose of the whole neutron/gamma spectrum. Response matrix is the double dimension matrix (energy/dose) in which each parameter represents a depth-dose resulted from specific energy. If the spectrum is changed, response of each energy group may be differed. By considering response matrix and energy vector, dose response can be calculated. This method was tested for some BSA, and calculations show statistical errors less than 10%. PMID:21450471
Methods for calculating phase angle from measured whole body bioimpedance modulus
NASA Astrophysics Data System (ADS)
Nordbotten, Bernt J.; Martinsen, Ørjan G.; Grimnes, Sverre
2010-04-01
Assuming the Cole equation we have developed a method to calculate the Cole parameters (R0, R∞, α, τZ) and the phase angle from four frequency measurements of impedance modulus values. The values obtained compare well with impedance measurements obtained using the Solatron 1294/1260 as obtained when making whole body measurements on five persons. We have also performed calculations using an algorithm based on the Kramers-Kronig approach. The results which are presented show that it is possible to obtain complete body impedance data combining relatively simple measurements with advanced calculation using a laptop. This extends the potential of portable equipment, since the measurements will require less instrumentation.
Stabilizing canonical-ensemble calculations in the auxiliary-field Monte Carlo method
NASA Astrophysics Data System (ADS)
Gilbreth, C. N.; Alhassid, Y.
2015-03-01
Quantum Monte Carlo methods are powerful techniques for studying strongly interacting Fermi systems. However, implementing these methods on computers with finite-precision arithmetic requires careful attention to numerical stability. In the auxiliary-field Monte Carlo (AFMC) method, low-temperature or large-model-space calculations require numerically stabilized matrix multiplication. When adapting methods used in the grand-canonical ensemble to the canonical ensemble of fixed particle number, the numerical stabilization increases the number of required floating-point operations for computing observables by a factor of the size of the single-particle model space, and thus can greatly limit the systems that can be studied. We describe an improved method for stabilizing canonical-ensemble calculations in AFMC that exhibits better scaling, and present numerical tests that demonstrate the accuracy and improved performance of the method.
A new method of calculating electrical conductivity with applications to natural waters
NASA Astrophysics Data System (ADS)
McCleskey, R. Blaine; Nordstrom, D. Kirk; Ryan, Joseph N.; Ball, James W.
2012-01-01
A new method is presented for calculating the electrical conductivity of natural waters that is accurate over a large range of effective ionic strength (0.0004-0.7 mol kg-1), temperature (0-95 °C), pH (1-10), and conductivity (30-70,000 μS cm-1). The method incorporates a reliable set of equations to calculate the ionic molal conductivities of cations and anions (H+, Li+, Na+, K+, Cs+, NH4+, Mg2+, Ca2+, Sr2+, Ba2+, F-, Cl-, Br-, SO42-, HCO3-, CO32-, NO3-, and OH-), environmentally important trace metals (Al3+, Cu2+, Fe2+, Fe3+, Mn2+, and Zn2+), and ion pairs (HSO4-, NaSO4-, NaCO3-, and KSO4-). These equations are based on new electrical conductivity measurements for electrolytes found in a wide range of natural waters. In addition, the method is coupled to a geochemical speciation model that is used to calculate the speciated concentrations required for accurate conductivity calculations. The method was thoroughly tested by calculating the conductivities of 1593 natural water samples and the mean difference between the calculated and measured conductivities was -0.7 ± 5%. Many of the samples tested were selected to determine the limits of the method and include acid mine waters, geothermal waters, seawater, dilute mountain waters, and river water impacted by municipal waste water. Transport numbers were calculated and H+, Na+, Ca2+, Mg2+, NH4+, K+, Cl-, SO42-, HCO3-, CO32-, F-, Al3+, Fe2+, NO3-, and HSO4-substantially contributed (>10%) to the conductivity of at least one of the samples. Conductivity imbalance in conjunction with charge imbalance can be used to identify whether a cation or an anion measurement is likely in error, thereby providing an additional quality assurance/quality control constraint on water analyses.
A new method of calculating electrical conductivity with applications to natural waters
McCleskey, R. Blaine; Nordstrom, D. Kirk; Ryan, Joseph N.; Ball, James W.
2012-01-01
A new method is presented for calculating the electrical conductivity of natural waters that is accurate over a large range of effective ionic strength (0.0004–0.7 mol kg-1), temperature (0–95 °C), pH (1–10), and conductivity (30–70,000 μS cm-1). The method incorporates a reliable set of equations to calculate the ionic molal conductivities of cations and anions (H+, Li+, Na+, K+, Cs+, NH4+, Mg2+, Ca2+, Sr2+, Ba2+, F-, Cl-, Br-, SO42-, HCO3-, CO32-, NO3-, and OH-), environmentally important trace metals (Al3+, Cu2+, Fe2+, Fe3+, Mn2+, and Zn2+), and ion pairs (HSO4-, NaSO4-, NaCO3-, and KSO4-). These equations are based on new electrical conductivity measurements for electrolytes found in a wide range of natural waters. In addition, the method is coupled to a geochemical speciation model that is used to calculate the speciated concentrations required for accurate conductivity calculations. The method was thoroughly tested by calculating the conductivities of 1593 natural water samples and the mean difference between the calculated and measured conductivities was -0.7 ± 5%. Many of the samples tested were selected to determine the limits of the method and include acid mine waters, geothermal waters, seawater, dilute mountain waters, and river water impacted by municipal waste water. Transport numbers were calculated and H+, Na+, Ca2+, Mg2+, NH4+, K+, Cl-, SO42-, HCO3-, CO32-, F-, Al3+, Fe2+, NO3-, and HSO4- substantially contributed (>10%) to the conductivity of at least one of the samples. Conductivity imbalance in conjunction with charge imbalance can be used to identify whether a cation or an anion measurement is likely in error, thereby providing an additional quality assurance/quality control constraint on water analyses.
NASA Technical Reports Server (NTRS)
Campbell, John P; Mckinney, Marion O
1951-01-01
A summary of methods for making dynamic lateral stability and response calculations and for estimating the aerodynamic stability derivatives required for use in these calculations is presented. The processes of performing calculations of the time histories of lateral motions, of the period and damping of these motions, and of the lateral stability boundaries are presented as a series of simple straightforward steps. Existing methods for estimating the stability derivatives are summarized and, in some cases, simple new empirical formulas are presented. Reference is also made to reports presenting experimental data that should be useful in making estimates of the derivatives. Detailed estimating methods are presented for low-subsonic-speed conditions but only a brief discussion and a list of references are given for transonic- and supersonic-speed conditions.
[The calculation of the intraocular lens power based on raytracing methods: a systematic review].
Steiner, Deborah; Hoffmann, Peter; Goldblum, David
2013-04-01
A problem in cataract surgery consists in the preoperative identification of the appropriate intraocular lens (IOL) power. Different calculation approaches have been developed for this purpose; raytracing methods represent one of the most exact but also mathematically more challenging methods. This article gives a systematic overview of the different raytracing calculations available and described in the literature and compares their results. It has been shown that raytracing includes physical measurements and IOL manufacturing data but no approximations. The prediction error is close to zero and an essential advantage is the applicability to different conditions without the need of modifications. Compared to the classical formulae the raytracing methods are more precise overall, but due to the various data and property situations they are hardly comparable yet. The raytracing calculations represent a good alternative to the 3rd generation formulae. They minimize refractive errors, are wider applicable and provide better results overall, particularly in eyes with preconditions. PMID:23629771
Takeda, T.; Shimazu, Y.; Hibi, K.; Fujimura, K.
2012-07-01
Under the R and D project to improve the modeling accuracy for the design of fast breeder reactors the authors are developing a neutronics calculation method for designing a large commercial type sodium- cooled fast reactor. The calculation method is established by taking into account the special features of the reactor such as the use of annular fuel pellet, inner duct tube in large fuel assemblies, large core. The Verification and Validation, and Uncertainty Qualification (V and V and UQ) of the calculation method is being performed by using measured data from the prototype FBR Monju. The results of this project will be used in the design and analysis of the commercial type demonstration FBR, known as the Japanese Sodium fast Reactor (JSFR). (authors)
A fast high-order method to calculate wakefields in an electron beam
NASA Astrophysics Data System (ADS)
Qiang, Ji; Mitchell, Chad; Ryne, Robert D.
2012-08-01
In this paper, we report on a high-order fast method to numerically calculate wakefields in an electron beam given a wake function model. This method is based on a Newton-Cotes quadrature rule for integral approximation and an FFT method for discrete summation that results in an O(N log(N)) computational cost, where N is the number of grid points. Using the Simpson quadrature rule with an accuracy of O(h4), where h is the grid size, we present numerical calculation of the wakefields from a resonator wake function model and from a one-dimensional coherent synchrotron radiation (CSR) wake model. Besides the fast speed and high numerical accuracy, the calculation using the direct line density instead of the first derivative of the line density avoids numerical filtering of the electron density function for computing the CSR wakefield.
Calculation of exact vibration modes for plane grillages by the dynamic stiffness method
NASA Technical Reports Server (NTRS)
Hallauer, W. L., Jr.; Liu, R. Y. L.
1982-01-01
A dynamic stiffness method is developed for the calculation of the exact modal parameters for plane grillages which consist of straight and uniform beams with coincident elastic and inertial axes. Elementary bending-torsion beam theory is utilized, and bending translation is restricted to one direction. The exact bending-torsion dynamic stiffness matrix is obtained for a straight and uniform beam element with coincident elastic and inertial axes. The element stiffness matrices are assembled using the standard procedure of the static stiffness method to form the dynamic stiffness matrix of the complete grillage. The exact natural frequencies, mode shapes, and generalized masses of the grillage are then calculated by solving a nonlinear eigenvalue problem based on the dynamic stiffness matrix. The exact modal solutions for an example grillage are calculated and compared with the approximate solutions obtained by using the finite element method.
An Efficient Method to Calculate the Aggregated Isotopic Distribution and Exact Center-Masses
NASA Astrophysics Data System (ADS)
Claesen, Jürgen; Dittwald, Piotr; Burzykowski, Tomasz; Valkenborg, Dirk
2012-04-01
In this article, we present a computation- and memory-efficient method to calculate the probabilities of occurrence and exact center-masses of the aggregated isotopic distribution of a molecule. The method uses fundamental mathematical properties of polynomials given by the Newton-Girard theorem and Viete's formulae. The calculation is based on the atomic composition of the molecule and the natural abundances of the elemental isotopes in normal terrestrial matter. To evaluate the performance of the proposed method, which we named BRAIN, we compare it with the results obtained from five existing software packages ( IsoPro, Mercury, Emass, NeutronCluster, and IsoDalton) for 10 biomolecules. Additionally, we compare the computed mass centers with the results obtained by calculating, and subsequently aggregating, the fine isotopic distribution for two of the exemplary biomolecules. The algorithm will be made available as a Bioconductor package in R, and is also available upon request.