Communications in Theoretical Physics (02536102)37(4)pp. 457-460
The level densities of even-odd and even-even isotopes 161,162Dy, 166Er and 171,172Yb were calculated using microscopic theory of interacting fermions and compared with experiments. It is found that the data can be well reproduced with level density formalism for nuclei with static deformation. The nuclear temperature as well as the entropy of nuclear system as a function of excitation energy has been extracted from the BCS theory. It is shown that the entropy exhibits an S-formed shape as a function of excitation energy. This is interpreted as a phase transition. Procedure of treating the even-odd and even-even nuclear systems has been presented and discussed.
Journal of Nuclear Science and Technology (18811248)39pp. 826-827
The level densities of 162Dy, 166Er and 172Yb are calculated using the microscopic theory of interacting fermions and is compared with experiment. It is concluded that the data can be reproduced with level density formalism for nuclei with static deformation. © 2014 Atomic Energy Society of Japan. All Rights Reserved.
Journal of Radioanalytical and Nuclear Chemistry (15882780)270(2)pp. 319-324
A reconnaissance study has been made on the distribution of 238U, 232Th, 40K, 137Cs and geochemical features in soil and sediment samples at various locations in the coast of Persian Gulf. Activity concentration levels due to radionuclides were measured in 50 samples of soils and sediments collected from the coast of Hormozgan. From the measured spectra, activity concentrations were determined for 40K (range from 140 to 1172 Bq·kg-1), 137Cs (from 0 to 15 Bq·kg-1), 238U (from 29 to 385 Bq·kg-1) and 2321Th (from 9 to 156 Bq·kg-1) with the lowest limit of detection (LLD) of 68, 3.2, 4.3 and 4.3 Bq·kg-1, respectively. The dose rate from ambient air at the soil ranges was between 23 to 177 nGy·h-1 with an average of 60±7.86 nGy·h-1. © 2006 Akadémiai Kiadó.
Iranian Journal of Science and Technology, Transaction A: Science (10286276)30(3)pp. 259-269
A reconnaissance study has been made on the distribution of 238U, 232Th, 40K, 137Cs and geochemical features in soil and sediment samples at various locations on the coast of Bushehr in the Persian Gulf. In this study a gamma-ray spectrometer based on a High Purity Germanium detector and a PC based MCA and X-ray fluorescence (XRF) method were used. Estimation of the measured radionuclide content have been made for the absorbed dose rate of gamma radiation. The Activity concentration (A), the equivalent radium (Req), and the external hazard index (Hex) which resulted from the natural radionuclides in soil and sediment are also calculated. The base-line data of radionuclides and heavy metals in view of the commissioning of nuclear and non-nuclear industries for the coast of Bushehr, which does not yet exist, was obtained. Activity concentration levels due to radionuclides were measured in 50 soil and sediment samples collected from this region. The measurement was performed with respect to their gamma radioactivity for a counting time of 24 hour intervals. From the accumulated spectra, activity concentration were determined for 40K (range from 108 to 520 Bq Kg-1), 137Cs (from 6 to 40 Bq Kg-1), 238U (from 12 to 75 Bq Kg1) and 232Th (from 8 to 33 Bq Kg-1) with the lowest limit detection (LLD) of, respectively, 68, 3.2, 4.3 and 4.3 Bq Kg-1. The dose rate from ambient air at the soil ranges was between 14 to 44 nGy h-1 with an average of 30.56 ± 7.86 nGy h -1. © Shiraz University.
Journal of Radioanalytical and Nuclear Chemistry (15882780)268(3)pp. 539-544
A nonlinear function was applied in combination with the method of mixing activity calibration for fitting the experimental peak efficiency of HPGe spectrometers in the 50-2614 keV energy range. The preparation of Marinelli beaker standards of mixed gamma- and RG-Set at secular equilibrium with its daughter radionucliedes was studied. Self-absorption was measured for the activity calculation of the gamma-ray lines for daughters of 238U series, 232Th series, as well as 137Cs and 40K in soil samples. Self-absorption in the sample depends on a number of factors including sample composition, density, sample size and gamma-ray energy. Seven Marinelli beaker standards were prepared in different degrees of compaction with bulk density (ρ) of 1.000 to 1.600 g·cm-3. The detection efficiency versus density was obtained and the equation of self-absorption correction factors was calculated for soil samples. © 2006 Akadémiai Kiadó.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms (0168583X)263(2)pp. 473-476
In this work thermal neutron self-shielding in aqueous bulk samples containing neutron absorbing materials is studied using bulk sample prompt gamma neutron activation analysis (BSPGNAA) with the MCNP code. The code was used to perform three dimensional simulations of a neutron source, neutron detector and sample of various material compositions. The MCNP model was validated against experimental measurements of the neutron flux performed using a BF3 detector. Simulations were performed to predict thermal neutron self-shielding in aqueous bulk samples containing neutron absorbing solutes. In practice, the MCNP calculations are combined with experimental measurements of the relative thermal neutron flux over the sample's surface, with respect to a reference water sample, to derive the thermal neutron self-shielding within the sample. The proposed methodology can be used for the determination of the elemental concentration of unknown aqueous samples by BSPGNAA where knowledge of the average thermal neutron flux within the sample volume is required. © 2007 Elsevier B.V. All rights reserved.
Annals of Nuclear Energy (03064549)35(12)pp. 2313-2320
This paper describes the application of a multilayer cellular neural network (CNN) to model and solve the time dependent one-speed neutron transport equation in slab geometry. We use a neutron angular flux in terms of the Chebyshev polynomials (TN) of the first kind and then we attempt to implement the equations in an equivalent electrical circuit. We apply this equivalent circuit to analyze the TN moments equation in a uniform finite slab using Marshak type vacuum boundary condition. The validity of the CNN results is evaluated with numerical solution of the steady state TN moments equations by MATLAB. Steady state, as well as transient simulations, shows a very good comparison between the two methods. We used our CNN model to simulate space-time response of total flux and its moments for various c (where c is the mean number of secondary neutrons per collision). The complete algorithm could be implemented using very large-scale integrated circuit (VLSI) circuitry. The efficiency of the calculation method makes it useful for neutron transport calculations. © 2008 Elsevier Ltd. All rights reserved.
Design and synthesis of a nonlinear supersonic missile longitudinal dynamics control for angle-of-attack output tracking are presented. In addition a sliding mode observ er is designed to estimate the angle-of-attack which is difficult to measure in practice. The employed method is simple to implement in practical applications and enables the sliding mode control design to exhibit the desired dynamic properties during the entire output-tracking process independent of perturbations. Results of simulations are presented to demonstrate the performance, robustness, and stability of the considered autopilot.
Marine Pollution Bulletin (0025326X)58(5)pp. 658-662
The determination of activity concentrations of the radioactive elements 238U, 232Th, 40K and 137Cs was performed on grab samples taken from a polluted environment. The samples were sliced into strata from 5 cm depth, dried and ground to sieved through a 170 mesh size prior to the analysis. Activity concentration was quantified using gamma spectroscopy. The results showed that the concentrations of activity in the sediment samples are 177 ± 12.4, 117 ± 11.5, 1085 ± 101.6 and 131 ± 4.8 Bq kg-1 for 238U, 232Th, 40K and 137Cs, respectively. In general, the distribution of activity concentrations along the southern coast of the Caspian Sea area exceeded international limits. The hazard index of the samples was 0.19-0.88, with an average of 0.49. The mean values of radium equivalent activity and dose rate are 176 Bq kg-1 and 63 nGy h-1, respectively. © 2009 Elsevier Ltd. All rights reserved.
Applied Radiation and Isotopes (09698043)67(7-8)pp. 1208-1212
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. © 2009 Elsevier Ltd. All rights reserved.
Turkish Journal Of Physics (13036122)33(3)pp. 149-154
We derive the partition function of the one-body and two-body systems of classical noncommutative harmonic oscillator in two dimensions. Then, we employ the path integral approach to the quantum noncommutative harmonic oscillator and derive the partition function of the both systems at finite temperature. © Tub̈itak.
Khadijeh, R.E.S.,
Elias, S.B.,
Wood, A.K.,
Abdi, M.R. Journal of Rare Earths (10020721)27(6)pp. 1066-1071
In the east coast Peninsular Malaysia region, sediments are transported by several rivers from the east Malaysia into the South China Sea estuary. In the vicinity of the five river estuaries core sediments were collected in order to investigate rare earth elements (REEs) profile. Core sediments were divided into strata of between 2 to 4 cm intervals and prepared for analyzing by ICP-AES. REE concentrations of 54.3 μg/gr at 24-26 cm in EC4 increased to 114.1 μg/gr at 20-22 cm in EC5. The measured concentration of LREEs and Fe normalized enrichment factors indicated that sediments were not enriched with light rare earth elements derived from effluents of anthropogenic activities. Results of the total concentration were used to establish baseline data in environmental pollution assessment and to develop the correlations between the Ce/Ce* and Eu/Eu* anomalies and the distribution patterns of some light rare earth elements (LREEs) and the heavy rare earth elements (HREEs). The chondrite-normalized ratios of REEs showed LREEs enrichment and flat HREE depletion. © 2009 The Chinese Society of Rare Earths.
Powder Technology (1873328X)189(1)pp. 52-56
The zeolite NaA was synthesized from natural clinoptilolite as Si source and aluminum sulfate or sodium aluminate as Al source. The use of aluminum sulfate for the synthesis of zeolite A has not been reported in the literature. This study presents as the first time a synthesis approach in which the low cost and available source is used to prepare zeolite NaA. These nano particles of zeolite were prepared at different conditions in autoclave and a mixer was designed specifically for this purpose. The synthesized zeolites were characterized by instrumental analysis methods, such as X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM), transmission electron microscope (TEM) and wet chemical analysis by atomic absorption spectroscopy (AAS). Cation exchange capacity (CEC) and loss on ignition (LOI) have been also measured on the prepared samples. The influences of different parameters such as reaction time, temperature, initial gel concentration, mechanical stirring and drying conditions on the improvement of the final products were experienced and the procedure for the efficient synthesis of zeolite NaA was optimized with available quality control tests. Solubility of clinoptilolite as the Si source in alkaline solutions was also investigated. © 2008 Elsevier B.V. All rights reserved.
Brazilian Journal Of Physics (01039733)40(2)pp. 125-130
In this work, a 2.5kJ plasma focus device (named as SBUPF1) has been constructed on the basis of a simple configuration. The most important characteristics of this configuration is relative simplicity and using less components in its structure compared with common configurations. SBUPF1 has been tested between 18-25kV and wide range of pressure for various gases including Argon, Neon and Deuterium. The system shows consistent and reproducible plasma focusing action as well as fusion neutron production (when deuterium is used as working gas).
Nuclear Physics A (03759474)834(1-4)
Determination of accurate nuclear level densities is of crucial importance for a variety of pure and applied nuclear physics. The density of accessible levels is calculated for 166Er nucleus using the microscopic theory of interacting fermions and is compared with experimental data. It is shown that the data can be reproduced by a level density formalism developed for nuclei with static deformation. Our results are in a good agreement with the experimental data obtained by the Oslo group. © 2010 Elsevier B.V. All rights reserved.
Rezaee k.h., K.,
Saion, E.,
Wood, A.K.,
Abdi, M.R. Journal of Radioanalytical and Nuclear Chemistry (15882780)283(3)pp. 823-829
Results obtained from the analysis of sediments surface samples taken from rivers mouth and polluted marine environment were analyzed for REE contents to determine the concentrations of La, Ce, Sm, Eu, Tb, Dy, Lu and Yb using instrumental neutron activation analysis. Thirty surface samples were collected from ten sites in the coastal marine sediments of the South China Sea along 957 km stretch of the east coast of Peninsular Malaysia. The samples prepared in the powdered form before irradiating them in a neutron flux of ∼4 × 1012 n cm-2 s-1 at 750 kW power using the TRIGA Mark II research reactor at Malaysian Institute for Nuclear Technology (MINT). Results of the total concentration are used to establish baseline data in environmental pollution assessment and to develop the correlations between the Ce/Ce*anomalies and the distribution patterns of some the light rare earth elements (LREEs) and the heavy rare earth elements (HREEs). The Chondrite-normalized REE pattern from each site examined and used to explain the sedimentation patterns by anthropogenic activities and by natural processes such as shoreline erosion, weathering deposits. Shale-normalized (NASC) patterns suggest enrichment of LREEs relative to the HREEs with a positive Ce/Ce*anomaly. Validation of the used method was done using a Soil-7 SRM. © 2009 Akadémiai Kiadó, Budapest, Hungary.
Rezaee k.h., K.,
Saion, E.,
Yap c.k., ,
Abdi, M.R.,
Riyahi bakhtiari a., International Journal Of Environmental Research (17356865)4(4)pp. 877-886
Forty seven sediment cores recovered from the South China Sea coasts along the east coast of Peninsular Malaysia were analysed for As, Cd, Cr, Cu, Hg, Ni, Pb and Zn using instrumental neutron activation analysis. The results indicate a homogeneous distribution except for As and Pb in all stations. Assessment of heavy metal pollution in marine sediments requires knowledge of pre-anthropogenic metal concentrations to act as a reference against which measured values can be compared. Primitive values for the cored sediments were determined from shale average metal. Various methods for calculating metal enrichment and contamination factors are reviewed in detail and a modified and more robust version of the procedure for calculating the degree of contamination is proposed. The revised procedure allows the incorporation of a flexible range of pollutants, including various organic species, and the degree of contamination is expressed as an average ratio rather than an absolute summation number. Comparative data for normalized enrichment factors and the modified degree of contamination show that the South China Sea sediments are in uncontaminated to moderately contaminated level of heavy metal contamination. Compared to obtained values the Kelantan and Pahang big rivers mouth show higher enrichment averaged across other sites.
Radiation Protection Dosimetry (17423406)147(1-2)pp. 296-299
Cardiac disease is one of the most important causes of death in the world. Coronary artery stenosis is a very common cardiac disease. Intravascular brachytherapy (IVBT) is one of the radiotherapy methods which have been used recently in coronary artery radiation therapy for the treatment of restenosis. 90Sr/ 90Y, a beta-emitting source, is a proper option for cardiovascular brachytherapy. In this research, a Monte Carlo simulation was done to calculate dosimetry parameters and effective equivalent doses to the heart and its surrounding tissues during IVBT. The results of this study were compared with the published experimental data and other simulations performed by different programs but with the same source of radiation. A very good agreement was found between results of this work and the published data. An assessment of the risk for cardiac and other sensitive soft tissues surrounding the treated vessel during 90Sr/ 90Y IVBT was also performed in the study. © The Author 2011. Published by Oxford University Press. All rights reserved.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (01689002)659(1)pp. 378-382
Nuclear-based explosive detection methods can detect explosives by identifying their elemental components, especially nitrogen. Thermal neutron capture reactions have been used for detecting prompt gamma 10.8 MeV following radioactive neutron capture by 14N nuclei. We aimed to study the feasibility of using field-portable prompt gamma neutron activation analysis (PGNAA) along with improved nuclear equipment to detect and identify explosives, illicit substances or landmines. A 252Cf radio-isotopic source was embedded in a cylinder made of high-density polyethylene (HDPE) and the cylinder was then placed in another cylindrical container filled with water. Measurements were performed on high nitrogen content compounds such as melamine (C3H6N6). Melamine powder in a HDPE bottle was placed underneath the vessel containing water and the neutron source. Gamma rays were detected using two NaI(Tl) crystals. The results were simulated with MCNP4c code calculations. The theoretical calculations and experimental measurements were in good agreement indicating that this method can be used for detection of explosives and illicit drugs. © 2011 Elsevier B.V. All rights reserved.
Rezaee ebrahim saraee, K.,
Abdi, M.R.,
Naghavi, K.,
Saion, E.,
Shafaei, M.A.,
Soltani, N. Environmental Monitoring And Assessment (01676369)183(1-4)pp. 545-554
The concentrations of arsenic, cadmium, chromium, copper, mercury, nickel, lead and zinc in surface sediments collected from the east coast of peninsular Malaysia, along the South China Sea, were measured by two methods instrumental neutron activation analysis and inductively coupled plasma mass spectroscopy. The obtained results were use to determine the areal distribution of the metals of in the east coast of peninsular Malaysia and potential sources of these metals to this environment. The geochemical data propose that most of the metals found in the east coast of peninsular Malaysia constitute a redistribution of territorial materials within the ecosystem. Then, the metal concentrations can be considered to be present at natural background levels in surface sediments. © 2011 Springer Science+Business Media B.V.
Rezaee k.h., K.,
Abdi, M.R.,
Saion, E.,
Naghavi, K.,
Shafaei, M.A. Journal of Radioanalytical and Nuclear Chemistry (15882780)287(3)pp. 733-740
In order to complete having data base of elemental assessment of the east coast of Peninsular Malaysia marine sediments along the South China Sea coasts, trace elements are analyzed and their distribution in marine sediments is undertaken. The present study is done parallel with pervious study on elemental assessment of heavy metals, rare earth elements and actinides in the marine sediments of the east coast of Peninsular Malaysia. Thirty surface sediment samples were collected in this area, including regions of Kelantan, Terengganu, Pahang, Rompin and Johor Baharu. Multielemental analysis was carried out by instrumental neutron activation analysis and inductively coupled plasma atomic emission spectroscopy. In both cases methodology validation was performed by certified reference material analyses. For the surface elemental distributions the enrichment factor values, average I geo and mC d values indicate that the trace elements of the surface sediments are uncontaminated in all sampling stations that are consistent with previous studies results of heavy metals, rare earth elements and actinides. © 2011 Akadémiai Kiadó, Budapest, Hungary.
Applied Radiation and Isotopes (09698043)69(2)pp. 521-526
The concept of a virtual point detector (VPD) has been developed and validated in the past for Ge(Li) and HPGe detectors. In the present research, a new semi-empirical equation involving photon energy and source-virtual point detector distance for the efficiency of point sources by HPGe detectors is introduced , which is based on the VPD model. The calculated efficiencies for both coaxial and off-axis geometries by this equation are in good agreement with experimental data. The estimated uncertainties are less than 4%. © 2010.
Progress in Nuclear Energy (01491970)53(6)pp. 651-663
U-Tube Steam Generator (UTSG) is one of the most important facilities in a pressurized-water nuclear reactor. Poor control of the Steam Generator (SG) water level in the secondary circuit of a nuclear power plant can lead to frequent reactor shutdowns or damage of turbine blades. The control problem is challenging, especially at low power levels due to shrink and swell phenomena and flow measurement errors. In addition, the dynamics of steam generator vary as the power level changes. Therefore, designing a suitable controller for all power levels is a necessary step to enhance the plant availability factor. The purpose of this paper is to design, analyze and evaluate a water level controller for U-tube steam generators using dynamic sliding mode control. The employed method is easy to implement in practical applications and moreover, the dynamic sliding mode control exhibits the desired dynamic properties during the entire output-tracking process independent of perturbations. Gain scheduling is used to obtain a global water level controller. Simulation results are presented to demonstrate the performance, robustness, and stability of the proposed controller. Computer simulations show that the proposed controller improves the transient response of steam generator water level and demonstrates its superiority to existing controllers. © 2011 Elsevier Ltd. All rights reserved.
World Applied Sciences Journal (discontinued) (18184952)15(4)pp. 532-536
Paramagnetic inelastic neutron scattering measurements have been carried out to investigate the crystal of anomalous rare earth of cerium. The physics of rare earth such as cerium has become very attractive because hybridization of the f electrons with electrons in the conduction band gives rise to a variety of interesting phenomena. In particular, magnetic form factor can use to help in the understanding of the wave functions of localized electrons and inelastic neutron scattering experiments measure energy scales of magnetic fluctuations and characteristic temperatures. At high temperature, the magnetic scattering can be described by two coherent broad peaks. At low temperatures, one narrow inelastic peak indicates dynamic magnetic correlation and paramagnetic effective moment in cerium ions. These results allow us to establish that in Ce+3 ions, at low T, inelastic scattering is contribution of the Kondo effect. © IDOSI Publications, 2011.
Journal of Physics: Conference Series (17426588)295(1)
In this study, the single-particle level densities are calculated by using the isospin dependent nuclear level density (NLD) formula. The calculations are performed using the experimental data for 28Al achieved from 27 Al(n, γ)28Al resonances. Considering the symmetry energy and parity corrections, the NLDs at the excitation energy, E=20MeV are calculated and the maximum possible isospin in the range from ground state up to this excitation energy is estimated. The first correction led to reduced level densities and the later resulted in decreased densities for some of the levels while increased densities for the others. It is observed that the maximum level density occurs for T=1 and at low energies for which the experimental data are available there is a good agreement between calculated and experimental data.
Nuclear Engineering and Design (00295493)241(5)pp. 1459-1462
The MCNP4c code, based on the probabilistic approach, was used to simulate 3D configuration of the core of the heavy water zero power reactor (HWZPR). In present work, first, all of the constituents of the core such as fuel pellets, fuel element, moderator (D2O) and annular graphite reflector were modeled using MCNP4c code. Then calculations of axial and radial neutron fluxes were performed in three energy groups such as thermal (0-0.625 eV), epithermal (0.625-550 eV), and fast (0.550-20 MeV). The cadmium ratio was calculated as well and the neutron flux parameters such as extrapolated height (H e), extrapolated radius (Re) and physical center of the core (z0) were computed using cadmium ratio. Comparison of the neutron flux parameters with the experimental data showed that the MCNP4c model of the HWZPR was validated. © 2011 Elsevier B.V. All rights reserved.
A novel method is presented to extract the important parameters of semiconductor detectors using artificial neural networks (ANN). We have designed a feed-forward (FF) Multi-layer Perceptron (MLP) ANN, with supervised training based on Levenberg-Marquardt (LM) back propagation algorithm (BP). In this method the sampling points of the transient current are the inputs of the network and the outputs are some important parameters of the detector, which are selected by sensitivity analysis. The training set is obtained by uniform sampling of the parameter space within the range of typical experimental data. These data are collected from drift-diffusion model for the transient current of laser illuminated hydrogenated amorphous silicon p+-i-n+ diode in reversed bias. At final step the trained ANN is used to extract the parameters of a real detector by using the transient current technique (TCT) measurements. It is observed that the simulated transient current with the extracted parameters by ANN exhibit an excellent agreement with experimental results. The new developments in semiconductor technology and the necessity of having a more accurate estimation of the parameters of advanced semiconductor devices to predict their behavior and also the capabilities of ANN in this field, is explained in section 1. In section 2 a brief review of ANN and its historical applications in designing and extracting the fabrication parameters of semiconductors devices is presented. The new advances in fabrication of amorphous devices, the theoretical bases and advantages of TCT and the signal induction are discussed in section 3. The complexity of hydrogenated amorphous silicon detectors, the trapping model, the simulation steps and also the required equations is the subject of section 4. In section 5 by using the Finite Element Method (FEM), the two dimensional simulation of the transient current of simple p+-i-n+ diode is performed and a method for reduction the execution time is presented. The strategy for extracting the transient current of the detector from the preamplifier output by using the Laplace transform is introduced in section 6. In section 7 the transient current of the detector is used to extract the electric field profile, the electron mobility, and the ionized dangling bonds and electrons collection time. In this section, the effect of lifetime of electrons and holes on the behavior of such detectors is also estimated. In section 8 the ANN structure and modeling scheme and some practical notes for optimizing the performance of ANN structure is presented. The final results and the performance of ANN in validation and testing steps and its excellent ability in extracting the parameters of a real amorphous silicon detector is also discussed in this section. © 2011 by Nova Science Publishers, Inc. All rights reserved.
