جستجوی مقالات مرتبط با کلیدواژه « Radiation » در نشریات گروه « فیزیک »

The purpose of this study was to investigate the effects of human age and gender on the estimation of the death risk due to cancer in head and neck CT scans. The participants were selected from a representative statistical population of different ages and genders who underwent head and neck CT scans. To determine the radiation dose of the patients, Impact-dose calculation software was installed on the computer of the studied device. Using the report of the Biologic Effects of Ionizing Radiation (BEIR) Committee, the risk of death due to cancer has been estimated according to the amount of radiation exposure and dose conversion coefficient, according to the patient's age and gender. The relation between human age and gender in estimating cancer death risk was examined using the obtained data and the SPSS statistical analysis program. A significant relationship was found between the estimation of the radiation-related death risk and gender and age in the studies. In other words, the death risk associated with head and neck CT scans is higher among women than men, at 32 and 27 per million, respectively. Moreover, human age plays a significant role in the estimation of the death risk caused by radiation. So, the younger the patient, the greater the risk of death due to radiation.

Cargo inspection systems aim to detect illegal goods such as weapons, explosives and narcotics, by imaging the object being inspected such as cargo containers, vehicles, trains, trucks or boats. These systems have been common for the last decade and their use has expanded rapidly. This work examines the necessary radiation standards and how to assess the compliance of inspection systems made in Iran with the standard set by the competent authorities. So, the dose ranges of three Cargo inspection systems made in Iran and one foreign system is compared with the authorized dose range, which results show the fulfillment of international requirements by Iran made inspection systems. It was found that the dose rate of the driver in each inspection operation is less than other sources such as natural exposure. Therefore, the authorized times for drivers to use these systems is determined by annual exposure limit of people.

Knowledge of distribution and emission pattern of natural and artificial radioactive elements and their radiation level in the environment is very important to assess its effects on human health and living organisms. In this study, the specific activity of natural and artificial radioactive elements for 30 soil and sediment samples collected from upstream and the outlet of Qarasu River to Gorgan Bay as well as sediments in the eastern part of Gorgan Bay were measured using High-Purity Germanium detector and their distribution map with using SURFER and GIS software was drawn. Specific activity of 226Ra, 232Th, 40K and 137Cs was obtained from 8.80 to 31.92, from 11.16 to 43.19, from 183.77 to 562.88 and from 0.83 to 12.72 in Bq/kg respectively.  Upstream of the Qarasu River, the average concentration of 226Ra, 232Th, 40K and 137Cs in the soil samples beside the Qarasu River was higher than the sediments of the river, which indicates the washing of sediments and the transport of radioactive elements by water flow and transfer of these elements to lower areas. In Qarasu estuary and Gorgan Bay, 232Th and 40K distribution patterns are almost similar and the highest concentrations of 226Ra, 232Th and 40K elements are related to Qarasu estuary sediments. The concentration of 137Cs in the mouth of Qarasu River has the lowest value and increases with its distance from the mouth to the middle parts of Gorgan Bay, which indicates a high mobility and a tendency to sediment in calmer places for 137Cs. The measured values for radiological parameters and risk indices due to nuclear radiation in this study are within the allowable range and the amount of available nuclear radiation does not threaten the health of the inhabitants of the region‎‎‎.‎

This research is dedicated to studying the alpha-spectroscopy of U and Th isotopes of the Saghand ore Anomaly 2 and the surface part Anomaly 1. At first, for complete dissolution of the ores, the concentrated hydrofluoric acid (23M), the concentrated hydrochloric and the concentrated nitric acids were used. Then the radioactive elements U and Th were separated by ion exchange chromatography using Dowex АВ-17-8 anion exchanger. During the next stage U and Th sources were prepared by molecular plating and the radioactive sources were analyzed using the alpha–spectroscopy. In both ores the 234U/238U activity ratios showed that the secular equilibrium is maintained in the series of 238U decay. Referring to scientific arguments and designing different hypotheses, the resistance of the uranium minerals of the ores against natural leaching was investigated and finally  during two experiments for every ore, by applying the radiation the weight percents of uranium were calculated: in the Anomaly 2, 0/1149 wt % and in the surface part Anomaly 1, 0/0930  wt %.

In this study, to calculate the radioactivity of radioisotopes such as 11C, 15O, 18F and 123,124I in a focus plasma device for the production of medical radioisotopes, the particles of neutrons and protons with cubic targets of Nitrogen, Xenon, Carbon and a solid natural Boron is used. Particles energy are at the input of the program from 1MeV to 10MeV. Also, the total yield coefficient is considered. In this paper, with the help of MCNPX 2.7 code, the amount of flux and deposited energy of neutron and proton particles is calculated for the production of medical radioisotopes in the focal plasma system. According to the obtained results in this study, it is shown that due to the different absorption and resonance cross sections for the considered targets with the energy of the neutrons and the protons are not a linear increase in the flux of particles. But after an energy of approximately 10 MeV, this slope is almost constant due to the constant cross section. Also, the results of this study show that with increasing energy of protons in these targets, the deposited energy of protons increases linearly, but its maximum value for the nitrogen target and its lowest value for the Xenon target due to different interactions cross-section.

The Space Environment consists of various radiations sources which emit different types of particle. Due to their high energy and high speed, these space particles can affect materials which they impact, in different ways. One of the most important damages which affect electronic instruments is Total Ionizing Dose (TID).In this article, modeling of these effects is performed by GEANT4 toolkit and Monte Carlo method. This toolkit performs simulations by using C programming language. Total Ionizing Dose effects are simulated for an operational satellite. Regards to considered conditions, failure or success probability in worst case has been analyzed. Based on ECSS, results satisfy standard and mission requirements.

The development of a graphite ionization chamber in Iran is reported for first time, using graphite coatings collecting electrodes and guard rings. Its sensitive volume is about 200cm³, with a shape of a ring which is different from its older equivalents and a 7cm central hole that allows the passage of the direct radiation beam without attenuation. This kind of ionization chamber has already been designed with aluminum electrodes in IPEN (institute de pesquisas energetic as e nucleares, Brazil), however in the present model, the whole of the inside part of the ionization chamber is coated with graphite instead of aluminum. By changing the electrode material from aluminum to a graphite coating, an improvement in action of ionization chamber response in pre-operational tests such as stability, saturation curve, repeatability, polarity effect, linearity response and calibration is expected, which is in accordance with the international recommendations.

The quantitative evaluation of uranium content in the Khoshomi boreholes has been mainly carried out based on logging and XRF laboratory data. In order to determine the correlation between aforesaid data, composition and chemical analysis has been accomplished at 115 zones by considering 3.05 meter intervals that is equal to the length of each drilling rod. In this relation, 55 parts with the core recovery coefficient more than 90% were selected and the correlation between their uranium and thorium contents were studied to determine the amount of radiation resulted from thorium. In the next stage, the regression equation was obtained using two methods, i.e. correlation between the total count and the uranium content, and the thorium depleted radiation and the uranium content. Using the first method, the average estimation error is approximately zero. But, as the estimated error variance is relatively high, complementary information is required for a favorable mining design.