جستجوی مقالات مرتبط با کلیدواژه "باد" در نشریات گروه "فیزیک"

At present, Maximum Temperature Crystal Sensors (MTCS) are of great interest in the design and optimization of engines and turbines with high efficiency. These sensors are made in very small dimensions and can measure the maximum temperature in the desired location, for example inside the turbine. It is worth mentioning that a high fluence of fast neutrons is required to produce these sensors. The MTCS method is based on the high temperature phenomenon to restore changes made in the crystal lattice caused by neutron irradiation. Calculations of the maximum fast neutron flux for the diamond sample were performed using MCNP6 with the simulation of the core of the Tehran Research Reactor (TRR). Activity calculations were done using ORIGEN2, dose rate calculations through MCNP6, and temperature calculations with ANSYS software at different points of the sample. The highest fast neutron flux was calculated, and the activity of the sample decreased significantly after 40 days, with the dose rate at a distance of one meter reaching 1.4 µSv/h. Temperature calculations showed that the maximum temperature at the lowest speed of the channel was 402 K, which would not cause any thermal problems. Additionally, using the X-Ray diffraction (XRD) method, the lattice number and unit cell volume were calculated for the sample. The results obtained suggest that the diamond sample, from the perspective of neutronics, dosimetry, thermohydraulics, and changes in crystal lattice structure, can be recommended as a crystal sensor in the Tehran Research Reactor.

Bakherz Mountain is situated in the northeast of Sangan city, at the eastern end of the Darone fault. Iron in this area has been extensively formed under the influence of granitoid masses from the upper Eocene to the lower Oligocene within the metamorphosed sedimentary unit in the form of skarn and hydrothermal deposits. Structural investigation of veins, fractures, movement mechanisms of faults, and displacement of units indicates two types of compressive tectonic regimes along N070 and N350 directions. The initial stage of mineralization occurred in the northeast-southwest direction in the Ferezeneh fault zone (N040). In the northern and middle parts of this fault, two shear-tensile zones were created, leading to the rise of iron-bearing fluids and hydrothermal iron mineralization in the northern part (Ferezeneh mine) and skarn-type iron mineralization in the middle part (Madan-Joe). Subsequently, the intersection of the Ferezeneh and Som-Ahani faults (N300) resulted in the creation of a shear-tensile zone and the ascent of iron-bearing fluids, leading to skarn-thermal iron mineralization in the Som-Ahani mine. Lastly, in the southern part of the Ferezeneh fault, uranium has been deposited in a fault zone approximately 2 km in length, within the Skarn unit. Changes in the geo-structural regime and the creation of suitable spaces in the shear-tensile zones have facilitated the flow of fluids, skarn formation, and the deposition of iron and uranium in separate phases and different directions. Structural studies will aid in the optimal extraction of mineral reserves and the identification of new resources.

Today, phytoremediation is recognized as one of the most cost-effective and environmentally friendly methods for removing pollutants from soil. This study focused on investigating the phytoremediation capabilities of Conyza canadensis (L) Cronq in removing uranium from saline soil. Soil samples were collected from the nuclear area of Isfahan, with contamination levels of 100, 300, and 500 mg/kg of uranium. The seeds were germinated in a suitable substrate and then transplanted into pots containing the contaminated soil. The plants were then cultivated in a greenhouse for one month, and the amount of uranium accumulation in various parts of the plant was determined using the ash method. Results indicated that as the concentration of uranium in the soil increased, so did the accumulation of uranium in the plant. The study revealed a direct correlation between the amount of uranium accumulation in the plant and the soil's texture and electrical conductivity (EC). The highest accumulation was found in the plant's stem, reaching 3633 mg/kg. Conyza canadensis (L) Cronq demonstrated the ability to accumulate over 1000 mg/kg of uranium in different parts of the plant, with transfer factors exceeding one. Therefore, Conyza canadensis (L) Cronq shows promise as a suitable plant for phytoremediation of saline soils.

Mutation breeding has proven to be efficient for developing new cultivars adapted to normal and stress conditions, including salinity. Mutant populations developed through gamma irradiation of Tarom Mahalli, Hassani, and Anbarboo local rice varieties were evaluated and screened for agronomic traits for 10 years in saline paddy fields of Mazandaran. These traits included plant height, early maturity, yield, yield components, and relative tolerance to salinity stress. The salinity levels of both soil and irrigation water varied between 4-11 and 2-9 dS/m, respectively, in different years and locations. The tolerance indices of the mutants were either 3 or 5, with 13 mutants showing lower stress sensitivity indices than their respective parents. Most mutants reached 50% flowering in fewer days than their parents, with selected mutants (2310, 2212, and 133) flowering between 80 and 90 days after sowing. The average plant height of selected mutants (M5-M7) in the saline paddy fields of Mazandaran ranged between 110-130 cm. All selected mutants produced a higher number of panicles per hill compared to Tarom Mahalli. The average yield of rice mutants varied between 3000 and 4500 kg/ha in different locations and years, with mutants 2212 and 2310 showing the highest yields in Bahnamir and Fereydoonkenar. These mutants exhibited at least a 35% increase in yield compared to Tarom Mahalli. The amylose percentage of the mutants ranged between 18-23%. Based on these results, mutants 2212, 2310, and 133 were selected for cultivation in paddy fields with saline or brackish water.

In this paper, quantum phase transitions and nuclear structure were investigated based on quantum entanglement. One of the measures for entanglement between two bodies is the von Neumann entropy, which is considered a suitable criterion for examining entanglement. The entanglement entropy of s-d bosons within the framework of the Interacting Boson Model (IBM) is investigated using the consistent-Q formalism and semiclassical approximation. This research presents a method for deriving the entanglement entropy in the dynamical symmetry limits of the IBM, including transition regions between different shapes. By utilizing the entanglement effect, the quantum phase transition was described, and the entanglement behavior of s and d bosons was investigated in various regions of the Castan triangle. A method for determining entropy in the IBM model using the semiclassical approximation was presented. The results showed that entanglement entropy values are sensitive to phase changes and can be a powerful tool for detecting quantum phase transitions in nuclei.

In this paper, aluminum 5052 (AA 5052), one of the candidate alloys for nuclear fuel cladding, has been selected for study regarding its corrosion behavior in an electrolyte containing NaCl and Na2SO4. Potentiodynamic polarization and electrochemical impedance methods were used to investigate the corrosion of AA 5052. The morphology and characterization of corrosion products were carried out using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Fourier-Transform Infrared Spectroscopy (FTIR) methods. In the Na2SO4 electrolyte, the corrosion resistance of the sample improved over time, with the corrosion current decreasing from 10-5.4 mA/cm2 after 1 hour to 10-6 mA/cm2 after 11 days. AA 5052 showed a wider passivation potential range (ΔEpass) and less passivation current (ipass) after 11 days. In the NaCl electrolyte, pitting corrosion, elimination of the passivation zone, and an increase in the number and size of pits were observed with increased time. These results confirm that the time has an influence on the passivation behavior of AA 5052, primarily dependent on the chemical composition of the electrolyte (presence or absence of chlorine and sulfate anions). Additionally, the application of tensile stress showed a destructive effect on the passive layer, as the passivation behavior of AA 5052 was eliminated.

Exploring and mapping radioactive environments presents potentially challenging and risky tasks. To ensure safety, the use of robots can help mitigate these risks. However, deploying a single robot may not be enough to effectively cover the entire area. Therefore, the technique of using multiple robots or a robot swarm can play a significant role in reducing time and improving the exploration and mapping process. Additionally, multi-robot systems have high reliability, and if a number of robots fail due to reasons such as radiation exposure, the remaining robots can continue the mission. This article focuses on the use of several autonomous robots simultaneously for radiation mapping and the discovery of radioactive sources. The study has examined various approaches, including the effect of the number and absorbed dose of robots. The results indicate that increasing the number of robots can enhance the speed of exploration, but the rate of increase is lower than the rate of the robot number due to the crowding of robots. To achieve optimal exploration, it is necessary to utilize more advanced models, such as movement patterns inspired by nature. This paper presents valuable insights into the coordination of collective robots for searching in radioactive environments, which could open up opportunities for the application of swarm intelligence in nuclear scenarios.

Gallium-68 (68Ga) is a radionuclide widely used for diagnostic purposes in Nuclear Medicine. With the availability of 68Ge/68Ga generators, the radiopharmaceutical industry is currently focused on developing this generator. The development and application of 68Ge/68Ga generators remain a hot topic in nuclear medicine. In recent years, Pars Isotope Company in Iran has produced 68Ge/68Ga generators (Pars-GalluGen generator) that are eluted with 5 ml of 0.6 M hydrochloric acid. Additionally, Pars Isotope has developed the second generation of Pars-GalluGen generators. This new generator is based on a SnO2-TiO2 resin matrix and is eluted with 3 ml 0.1 M hydrochloric acid. This research aimed to determine the main characteristics of the second generation of Pars-GalluGen generators and evaluate their quality control. The results obtained indicate that this generator meets all specifications of the European Pharmacopoeia for use and has better performance characteristics, including higher chemical, radiochemical, and radionuclide purity, as well as a higher elution yield compared to the first generation.

In this research using the MCNPX code, calculations were done for nuclear designing of portable two-chamber gamma irradiator facility for irradiation of grains and legumes according to international standards. Calculations were made in two parts of dose uniformity ratio and mass flow rate of the irradiated product, as well as gamma-ray shielding using 100 kCi Cobalt-60 line sources, model GIK-A6m of Mayak Co., Russia. The dose uniformity ratios of internal and external irradiation chambers were found to be about 1.77 and 2.18, respectively. Also, the mass flow rate of an irradiated typical grain with bulk density of 800 kg m-3 was calculated to be about 3.2 ton h-1. A typical grain will receive a dose between 300-656 Gy, which is less than the maximum recommended limit of absorbed dose for grains and legumes (1 kGy) in purpose of shelf-life extension and insect disinfestation by the IAEA. According to ANSI/HPS N43.7, the leakage dose rate at a distance of 5 cm far from the surface of the irradiator in the irradiate mode and for restricted areas, was calculated to be less than 200 µSv/h (maximum permissible radiation level). The results showed that the lead shield of irradiator facility with maximum thickness of 29 cm, easily blocks the emitted gamma rays and working with such a facility would not pose any radiation risk to the employees. Finally, the energy efficiency of the facility was estimated to be about 25% with an increase of about 10.5% due to the addition of external chamber.

Nuclear level density is a critical parameter in nuclear physics as it represents the number of energy levels per unit of energy (MeV) in a nucleus. This study calculates the level density and level density parameter for heavy and super heavy isotopes  and based on the back-shifted Fermi gas method. The level density parameter is determined through a semi-classical approach using the nuclear Woods-Saxon potential. This research investigates the influence of pairing energy, and temperature-dependent shell effects on level density and thermodynamic quantities such as entropy, nuclear temperature, and nuclear-specific heat. Furthermore, the research explores the effects of nuclear spin, parity, rotational, and vibrational motion on these quantities. A graphical representation is used to illustrate the variations in nuclear level density, entropy, temperature, and specific heat as a function of nuclear excitation energy, highlighting the influence of nuclear spin, parity, and rotational and vibrational motions on them. The results show that considering these effects leads to changes in the parameters studied without altering the overall trends. Additionally, a specific heat diagram demonstrates the effects of vibrational and rotational motions, spin and parity effects, shell effects, and temperature-dependent pairing energy on excitation energy, revealing the breaking of the first nucleon pair at energies of E=2.948 MeV and E=3.04 MeV for isotopes and , respectively.

67Cu is a suitable radioisotope for targeted radionuclide therapy, nuclear medicine imaging, and dosimetry calculations during treatment. In this study, the most suitable reaction for the production of 67Cu radioisotope in cyclotron accelerators is investigated. At first, the excitation functions of the reactions of 68Zn(p,2p)67Cu, 70Zn(p,α)67Cu, 70Zn(d,x)67Cu and 64Ni(α,p)67Cu was simulated in the energy range of 0 to 100 MeV using TALYS-1/96 and EMPIRE-3-2-2 Monte Carlo codes. The target thickness and the mass stopping power of these reactions were calculated using the SRIM-2013 code. The theoretical yield of these reactions was calculated from the data of excitation functions and mass stopping power and was compared with the experimental results. The maximum yield of 67Cu production in the reactions of 68Zn(p,2p)67Cu, 70Zn(p,α)67Cu, 70Zn(d,x)67Cu and 64Ni(α,p)67Cu without the presence of 64Cu contamination at energies of 100, 35, 40 and 30 MeV respectively was obtained and according to the results of EMPIRE and TALYS codes were equal to 0/442, 1/248, 9/842, 7/77, 21/131, 11/542, 1/638 and 1/621 MBq/µAh respectively. Based on the obtained results and their comparison with the experimental results, the 70Zn(d,x)67Cu reaction at energy of 40 MeV is the best reaction to produce 67Cu without the presence of 64Cu contamination.

This research investigates and optimizes the parameters of solvent extraction processes using thorium leach solutions from Chahghaz ore with D2EHPA. The effective parameters in the solvent extraction process were evaluated through experimental design to maximize thorium extraction and minimize iron extraction. Under optimum conditions—pH 0.6, extraction time of 2 minutes, 16% solvent concentration, and an organic-to-aqueous phase ratio of 1:2—thorium and iron recoveries were 99.47% and 9.60%, respectively. For the optimization of the stripping process, 89.75% thorium and 0.6% iron were recovered in 3.34 minutes with an organic-to-aqueous phase ratio of 2:1 and a sulfuric acid concentration of 3.9M.

In this research, the gamma ray protective properties of iron-doped nano-hydroxides were evaluated by calculating effective quantities such as the half-value layer (HVL), mean free path (MFP), mass attenuation coefficient (𝜇m) and linear attenuation coefficient (LAC) in the range of 0.015 to 15 MeV using the Geant4 Monte Carlo simulation tool. To investigate the quantitative difference between the mass attenuation coefficient of nano-materials and normal materials, the simulation results were compared with data extracted from the NIST-XCOM database, which can only calculate the mass attenuation coefficient of normal materials. In this comparison, it was observed that the data extracted from the database and the results of the Geant4 simulation tool differed as the concentration of iron contamination increased. The percentage of deviation (RD) between the data extracted from the database and the results of the Geant4 simulation tool increased from 0.1 to 3.2%. This deviation was attributed the increase in the concentration of nano-iron contamination in the composition. Therefore, the nano-hydroxide composition with the highest percentage of iron contamination (Fe-HAp-48) had the most favorable protective composition in terms of density compared to other selected protective materials. This composition, which is lightweight and antibacterial, provides effective protection against gamma rays in the specified energy range.

This research evaluates the hydrodynamic behavior of a packed-agitated column, which includes agitated and irregularly packed sections, for extracting thorium ions from an aqueous solution. The effects of various operating parameters on the column's hydrodynamic conditions were investigated. Results indicate that increasing operating parameters such as agitation speed, dispersed phase velocity, and continuous phase velocity enhances thorium extraction efficiency. The maximum extraction efficiency achieved was 97.54% at an agitation speed of 220 rpm, with dispersed and continuous phase velocities of 0.66 mm/s. Increasing the agitation speed results in smaller droplet sizes and a narrower droplet size distribution. Additionally, an increase in continuous phase velocity, while keeping other parameters constant, creates resistance to the movement of dispersed phase droplets, leading to a decrease in slip velocity.

Liquid wastes containing fission fragments are valuable sources of useful radioisotopes that can be extracted using suitable radiochemical methods. This article addresses the challenge of unavailable waste by simulating a solution equivalent to the liquid waste from a 99Mo production facility using the MCNPX code and preparing it with laboratory-available salts. Various radiotracers of elements were subsequently produced via the neutron activation method and added to the equivalent solution. Investigations focused on tracing cerium in the process, utilizing the 145.4 keV gamma radiation from 141Ce produced during activation. The irradiation mechanism and spectroscopy were simulated using the MCNPX code, and the results were compared with experimental measurements.

In this research, among the types of adsorbents known in nature, Kaolin was used as an adsorbent material due to its unique characteristics and special capabilities in the absorption stages. Atmospheric pressure was irradiated and after testing by a gas analyzer, we saw an improvement in the absorption performance of CO and CO2 gases in this type of adsorbent material. The effect of the output power and flow of argon gas and the duration of plasma irradiation on the properties of Kaolin was also investigated. XRD and FTIR analyses were used as characterization methods to determine the purity of Kaolin before and after irradiation, and a gas analyzer was used to analyze the obtained results. The findings of this research provide a new way to control and reduce air pollutants in cities where air pollution is one of the biological problems. In addition, the achievements of this research can lead to the expansion and effective progress in reducing the costs related to the control of pollutants and also bring reassurance in terms of biocompatibility.

This study investigates uranium recovery from a chloride medium using a bulk liquid membrane containing the crown ether DB18C6. The effects of pH and chloride concentration in the donor phase, diluent type and carrier concentration in the liquid membrane phase, and the type and concentration of the acceptor phase, along with transport kinetics, were examined. Results indicated that increasing the crown ether concentration in the liquid membrane phase initially enhanced ion transfer. However, beyond a certain point, further increases in crown ether concentration reduced ion transfer due to increased viscosity. While diluents alone could not transfer ions, the type of diluent influenced the transfer process. Optimal uranyl ion transfer was achieved with a donor phase containing 2 M potassium chloride at pH 4. The type and concentration of the mineral acid in the acceptor phase significantly affected the transfer efficiency, with 0.1 M hydrochloric acid facilitating the maximum transfer of uranyl ions. The study of transfer kinetics revealed that the rate-controlling step is the release of uranyl ions from the liquid membrane into the acceptor phase. Under optimal conditions, selective transfer of uranyl ions was achieved in the presence of molybdenum, niobium, titanium, vanadium, and tungsten. The uranium transfer rate from the donor to the receiving phase exceeded 91%.

Rapidly oscillating Ap stars are a special type of variable stars that are not in hydrostatic equilibrium. Their pulsation period is very short compared to other stars of this group and is less than one hour. These stars have spectral type A and lines related to rare-earth elements are increasingly observed in their spectrum, so they are known as Ap stars. In this research, the equation of motion of the rapidly oscillating Ap star was solved using the perturbation method in the presence of a smooth and uniform rotation and it was determined that under the effect of rotation in the stellar system, the modes are coupled among themselves. Each mode with a specific l is separated into 2l+1 modes due to rotation, and each of these modes under disturbance does not correspond to a specific value of m, but each mode under perturbation consists of a linear combination of m=2l+1modes.

Before sailing, submarines with ferromagnetic hulls are demagnetized to avoid damage and detection by sea mines and airborne systems. The increase in the residual magnetization of the submarine body after demagnetization due to the rising and falling can reduce the effect of demagnetization. This study aimed to investigate how internal hydrostatic pressure affects the magnetic signatures of a demagnetized submarine model. Magnetic sensors were placed at specific points under the body, and the changes in magnetic signatures were recorded when pressure was applied from 0 to 60 bar. The results show that by increasing the pressure up to 60 bar before demagnetization, the magnetic field components originating from the sample's internal stresses showed a linear increase. After depressurization, there was an exponential decrease followed by a subsequent increase in permanent magnetization of about 6%. However, after demagnetization, as the pressure increased up to 60 bar, the magnetic field generated by internal stresses in the sample increased by about 27%, but upon decreasing pressure, this magnetic field did not decrease but remained unchanged. This phenomenon negatively impacted the performance of the deperming process. Also, for further investigation, the increasing trend of magnetic signatures was evaluated at pressures of 30, 45, and 60 bar.

The experimental investigation of supercontinuum generation in deionized water using an amplified Ti:sapphire femtosecond laser pulses is presented. During the propagation of femtosecond pulses in deionized water, self-focusing leads to filamentation and subsequent supercontinuum generation. The effects of varying the focal point distance from the cell and altering the incident femtosecond laser pulse energy on the supercontinuum spectra were studied. Near critical power, ring and cone emissions contribute significantly to the continuum. The central white light part covers the output signal at very high laser powers. A supercontinuum emission with a bandwidth of 600 nm was achieved using a laser pulse energy of 1.19 mJ. The spectrum broadening, due to Kerr self-focusing and plasma defocusing, was analyzed for 37 femtosecond laser pulses with average powers ranging from 420 to 3800 times the critical power. Increasing the input pulse energy to 460 µJ, corresponding to 2900 times the critical power, resulted in an asymmetric broadening of the spectrum, with the blue edge shifting to 400 nm. Further increases in energy showed no additional shift due to intensity clamping.