مجله پژوهش فیزیک ایران
سال بیست و دوم شماره 3 (پاییز 1401)

This experimental study aims to investigate the effect of the closed cycle of air circulation on the thermal performance of the solar air collector with attached fins in the site of Laghouat in Algeria, under climatic conditions. Our experimental procedure includes two types of cycles: open cycle and closed cycle. For each cycle, we have considered two tilt angle: 0 and 30 degree. Moreover, the solar collector is oriented in a southerly direction with a definite angle of inclination. The flow rate used in experiment is equal to 0.0129402 m3/s. Then, by comparing the experimental and theoretical results, we observe that the maximum temperature difference between the outlet and inlet air for the open cycle (27 °C, at 14h30) is higher than that of the close cycle (17 °C, at 14h00). The maximum efficiencies obtained for the open cycle for the both configurations were η (30 degrees) = 25.29 % and η (0 degree) = 35.71 % at 4 pm. These values are higher than those of the maximum efficiencies of the closed cycle with η (30 degrees) = 7.86 % at 4 pm and η (0  degree) = 13.31% at 12h00, respectively

Three equal-depth traps reported in NaCl have been attributed to different defect configurations. In this trio system, the basic trap configuration proposed is the bi-vacancy, the analogy being drawn through observations in KCl crystal. Two other defect configurations that emerged are the derivatives of bi-vacancy with the next nearest neighbor I-V pair and the VF center which represents a hole linked to a cation vacancy.

According to the estimates of many authors, in 10-15 years, the world market for nanotechnology products will amount to about 1 trillion $. The share of nanomaterials, in this case, is very large (about 340 billion). Therefore, research on nanomaterials properties becomes one of the most important tasks of the science of nanostructured materials. In this regard, it will be essential to expand research on the influence of size and thermal stability; as two common problems for almost all types of nanomaterials. This review article will discuss the most popular topics on nanomaterials, nanostructures, their history, characteristics and classification as well as status of their scientific articles published in recent years. This study focuses on a range of topics related to the development, research and manufacturing applications of nanomaterials and nanotechnology. There are many problems and challenges that scientists are investigating on them. For example: what are the main differences between the properties of interfaces of nanomaterials (including hybrid ones) from the characteristics of ordinary bulk states? How widely can the self-assembly technique of nanoscale devices elements be developed, considering possible installation errors?

Nanopowders/Nanostructures have attracted the attention of engineers and scientists for their tunable properties and extended applications. One of the extended application of nanopowders is nanofluids. Nanofluids are assumed as the most preferred next generation coolants and their stability is essential for their successful implementation. Iron oxide nanoparticles were prepared by the sol-gel method using Ferrous sulphate as precursors. The prepared nanoparticles were characterized by XRD and photo luminescence. Iron oxide nanofluids (0.1 & 0.3 vol%) with ethylene glycol as base fluid were prepared by a two-step method. The nanofluids were tested for dynamic stability (at 1, 3, 6, 12 and 24-hour intervals). The variation in zeta potential with time is analyzed to predict their stability transformations. We observe that 0.3 vol% nanofluid exhibits better dynamic stability characteristics than the less stable 0.1 vol% nanofluid

Copper antimony sulphide (CuSbS2) is a semiconductor with narrow band gap and a potential absorber material for applications in various optoelectronic devices like infrared detectors and solar cells. In this paper, CuSbS2 thin films were deposited by spray pyrolysis technique on glass substrates at a temperature of 3000 ℃, using cupric chloride, antimony chloride, and thiourea as precursors. The samples were prepared by varying the antimony concentration (0.1M, 0.15M, and 0.2M) at a pressure of 3.5 bar and a solution flow rate of 2 ml/min for 5 minutes, while the precursor solutions of Cu:S molar ratio (0.1:0.2) was maintained. Elemental, morphological, optical, and structural characterization of these films was done from data obtained from energy dispersive X-ray fluorescence (EDXRF), UV-VIS spectrophotometer, scanning electron microscope (SEM) and X-Ray diffraction (XRD) respectively. The prepared thin films were polycrystalline with a preferential peak at (111).  Electrical properties of the thin films were obtained by simulating the UV-VIS spectra in SCOUT software using the Drude and Kim oscillator model. Deposited films have a band gap range of 1.84 – 1.98 eV, conductivity range of 199.59 – 204.67 Ω-1cm-1, and carrier concentration range of 1.12×1019 - 1.27×1019  cm-3.

We studied the behavior of the earthquake network using the HEALPix spherical pixelization and square cells methods. In the first method, the geographical region is divided into isolatitude rhombic-spherical cells of the same areas using the HEALPix method. In the second method, we divided the geographical region into isolatitude equal areas of the square cells. To construct a network, if an earthquake happens in a cell, that cell will become a node, and two nodes will be connected with an edge for two successive events. The earthquake network is built from Iran’s seismic data from 1900 June 12 to 2015 December 12. We determined the Hurst exponent (H = 0.6) due to the rescaled range (R/S) analysis. This value reveals a long temporal correlation in earthquake time-series; therefore, the earthquake system is suggested to be self-organized. We showed that among the five major seismotectonic provinces of Iran (Alborz-Azarbayejan, Kope Dagh, Central-East Iran, Zagros, and Makran), the earthquake network hubs are located in the Zagros region, which is a seismically very active region. According to this result, the Zagros earthquakes affect the surrounding earthquakes. The probability distribution function’s power-law behavior with a network built in the pixelization rhombic-spherical cells shows scale free behavior’s properties than a network constructed based on the square cells. The mean clustering coefficient’s power-law nature with networks built using two methods shows that the earthquake network is scale-free and non-random. We concluded that the rhombic-spherical cell pixelization is a more reliable method for building the large geographical region’s earthquake network.

The electrical properties of zirconium thin films has been studied by Langmuir probe technique. The electron energy, electronic density, and ionic density of the samples were measured at low pressure with a varying power (60  to 160 W). Our results show that the energy of electrons decreases with increasing power, while the densities of electrons and ions have increased. Scanning electron microscope (SEM) images were used to determine the thickness as well as surface morphology of zirconium thin films, where the thickness was increased with the increasing of the power of the plasma DC generator. The energy dispersive X-ray spectroscopy (EDX) analysis method was employed to reveal information about the composition of the films. Plasma characterization and the quality of prepared films (roughness and thickness) allows us using these films in several potential applications.

Proton therapy with accelerator systems has been used in the last 30 years to destroy tumors by producing highly energetic ion beams. Although different systems have been introduced and designed to accelerate ions, the superconductive cyclotron accelerator is one of the most efficient treatment equipment compared to other systems. In this research, the design study of Iranian Medical Proton Superconducting Cyclotron (IMSIC-250) was considered. The IMSIC-250 system is a fixed frequency cyclotron with four spiral sector magnets designed to accelerate protons in the form of H2+ particles up to 250 MeV/amu. In the current study, the design process of the superconducting magnet and coil structure was reported. The 3D model of the spiral pole magnet alongside the superconducting coil was modeled. The main characteristics of the cyclotron magnet and coil structure were also studied. It was demonstrated that the designed magnet is capable of producing the desired isochronous magnetic field in order to accelerate protons up to 250 MeV. The stability of the acceleration process was achieved by a nonnegative value of flutter over the acceleration of particles. For coil structure, the current density over coil turns and the applied force was modeled. The flutter concept was also used to investigate the stability of the acceleration process. It was discovered that flutter has a nonnegative value when compared to particle acceleration. Finally, the stability of a magnetic coil against applied magnetics (Lorentz) force was investigated and it was demonstrated that the applied magnetic field on the coil would not have a destructive influence on the superconducting structure of the coil.

Long-term exposure to radon increases the risk of developing lung cancer. There is a considerable public concern about radon exhalation from building materials and its contribution to indoor radon levels. To address this concern, radon exhalation rates were determined for 24 different samples of building material commonly used in Al - Diwaniyah, Iraq dwellings, using solid-state nuclear track detectors (CR-39). The highest contribution is found in Granite from Italy, 169.04  ±  11.38 (Bq/m3), 386.184 (mBq/m2h), and 4.26 (mSv/y) for radon concentration, surface radon exhalation rate, and the annual effective dose, respectively. On the other hand, the lowest contribution is found in Gypsum from Najaf - Iraq with radon concentration (Bq/m3), radon exhalation rate (mBq/m2h), and the annual effective dose (mSv/y) of about 11.40  ±  0.11, 22.716, and 0.284. The obtained average values of these three quantities are 104.276  ±  7,50, 108.21, and 1.45, respectively. The average annual effective dose of radon concentrations is acceptable, compared with the standard limit value presented in ICRP.

Studing metal complexes of organic molecules has attracted great attention to explore the mechanisms of charge transfer through organometallic single molecules. In this work, we investigate the optoelectronic properties of diphenyl - bipyridine coordination chloride transition metal complex. By varying the transition metal in the group of Co, Cu, Fe, Mg, Ru and Zn atoms, we demonstrate the ability to manipulate the optical and electronic properties of the system. Density function theory (DFT) calculations with B3LYP functional are used to determine electronic properties of the metallo-molecules, including ionization potential, electronic affinity, energy gap, electronegativity, hardness, softness, and dipole moment. To understand the optical performance of the systems, we consider their absorption spectra in the ultraviolet and infrared regions, in the framework of time-dependent DFT. We argue that the six metallic atoms have the ability to tune the optoelectronic properties of the complex molecules.

Similar to the role of carriers in classical communications as a medium for transmitting messages, entangled states can also be considered a medium that plays the role of the information carrier. In this way, we can define protocols with entangled carriers for quantum communications which can also be used for quantum secret-sharing. The outspread of quantum secret-sharing for many users is the substructure of a quantum internet, so it is essential to study such protocols in terms of their practical implementations. Since protocols are performed in noisy environments without interruption, it is necessary to investigate the performance of protocols under continuous noise. This paper studies the stability of these protocols against dephasing and depolarizing noise. It shows that despite the constant effect of noise, the carrier remains in two types of spaces with the entangled basis, which forms complete spaces for the carrier’s qubits. These spaces are compatible with the protocol performance; therefore, the protocol is stable under the noise effect.

Back-bending phenomenon which occurs at high spin states of some heavy mass nuclei has been studied, for the first time, by using the ratio of electromagnetic reduced transition probabilities B(M1) / B(E2) within the Projected Shell Model (PSM). In this model, all angular momenta are projected on the symmetry axis of the deformed nucleus, which makes shell model calculations much easier. The electric quadrupole transition probability  B(E2) and the magnetic dipole transition probability B(M1) are sensitive to the nuclear shape deformation and nuclear charge distribution, respectively. As a result, any change in the nuclear rotation speed can change the transition probability ratios at high spins. Our ratio findings at high state spins in even - even 152-164Dy isotopes confirm the previous back-bendings seen in these isotopes, in good agreement wth the experimental data. Increasing spectroscopic quadrupole moments with spin is another high spin phenomenon in heavy mass nuclei studied in this paper. While intrinsic quadrupole moments are constant for each Dy isotope, this study shows that spectroscopic (observed) quadrupole moments are increasing with spin.

Experimental results have shown that dadding boron to tumor tissue during proton therapy increases the mortality of cancer cells. This work has investigated how to form a spread-out Bragg peak in the proton therapy of a liver-located tumor by simulating the MIRD phantom and designing a range modulator. The simulations were carried out using a GEANT4 Monte Carlo toolkit. Also, the absorbed dose of the different organs near the liver was determined via simulations. To study the effect of boron on liver proton therapy, a tumor impregnated with different percentages of boron was simulated and the effect of energy released in the tumor as a result of alpha particles, protons and their combinations was investigated. The absorbed dose in the tumor at different proton energies and with varying percentages of boron was investigated. It was found that the absorbed dose in the tumor increases by adding boron, however; it decreases by increasing the energy from a certain limit (~80 MeV) of more than 60% boron.

In the last few years, the tendency to utilization of bottled water has significantly expanded. Therefore, its radioactivity level must be strictly evaluated. This work aims to measure the activity concentrations of gross beta and alpha in bottled drinking water to evaluate its quality and annual effective dose as well as the lifetime risk. The radioactivity of 30 bottled mineral water samples from several brands was analyzed with Wallac Quantulus 1220 LSC. The measurement results showed that the gross beta and alpha activity concentrations in bottled mineral water samples ranged from 29 to 49 mBqL-1 with an average of 38.7 mBqL-1 and 48 to 76 mBqL-1 with an average of 60.8 mBqL-1 respectively. Furthermore, Annual effective doses ranged from 30.11 to 48.3 µSv y-1 with an average value of 38.54 µSv y-1, which is below the 0.1 mSv y−1 as reference dose limit. The variation of lifetime risk is from 1.70 × 10-4 to 2.60 × 10-4 with an average of 2.14 × 10-4. According to  this study’s results, radiologically, these bottled mineral waters can be considered safe drinking water in Iran.

This paper presents a new design of a conformal microstrip antenna operating in a dual-band for several applications including Wireless Local Area Networks (WLAN), Wi-Fi networks, and Wireless Body Area Networks (WBAN). The proposed design was achieved using the stacked patch technique on a conformal microstrip antenna. One of the patches is square-shaped and the other is triangular-shaped constructed on a cylindrical surface with a 50 mm radius using a substrate with a permittivity of 2.98. The proposed design can be called a stacked square-shaped triangular cylindrical microstrip antenna. The operating resonant frequencies have been set at 623 and 795 GHz. For the standard antenna, the bandwidths of dual-band are equal to 0.65 % and 0.92 %. By adding an air gap between the ground plane and substrate, bandwidths are enhanced to 6.15 % and 3.07 %, and then increasing the substrates' thickness leads to more improvement of the percentage of bandwidth to 40.2 % and 24.12 %. The Finite-Difference in Time Domain (FDTD) method is used to design and analyze the proposed antenna.

It turns out that the ground states of some systems are symmetry-broken states in which some property is not symmetrically distributed. In the case of strongly correlated electron systems that were studied by the DFT+U method, researchers have shown that the total energy of the system is a multi-minima function of electron-configuration parameters and one has to single out the ground state out of the couples of minimum-energy states. However, the methods already introduced to determine these local minimum states, were not able to predict all such states, which may include the "true" ground state. In this work, we introduce a new simple and straight-forward method of SMC to find the GS as well as the meta-stable states of the 1k-order anti-ferromagnetic configuration for UO2. Using this method, it is shown that the ground state of the UO2 system is a spin-symmetry broken state of the electron spin magnetizations of oxygen atoms. Depending on the way we apply the SMC method, we obtain different numbers of meta-stable states, but the same ground states. The energetic properties, geometric properties, the electronic density distributions, and the electronic polarization density distributions of the ground state and the meta-stable states are shown to be different from each other. These properties also are shown to be sensitive to the magnitude of the initial opposite magnetizations of up-spin U-atoms (U1) and down-spin U-atoms (U2) in the 1k-order anti-ferromagnetic configuration, but the number of meta-stable states as well as the ground-state properties are insensitive to this magnitude. Using the PBEsol-GGA approximation for the exchange-correlation, we obtain the ground-state properties in excellent agreement with experiments.

The present paper reports on the effect of substrate temperature on the physical properties of zinc oxide (ZnO) thin films deposited using spray-pyrolysis technique. The films exhibit a polycrystalline nature with a preferred orientation along [002]. Furthermore, the average crystallites size increases with increasing the substrate temperature. The scanning electron microscopy results showed that the films were evenly distributed and homogeneous. The average optical transmittance varies in the range of 62 to 90% depending on the substrate temperature. On the other hand, with increasing the substrate temperature, the absorption coefficient decreases and the optical band gap varies in the range of 3.25 - 3.28 eV. The electrical conductivity of films varies between 18 and 58 mS.cm-1.

This paper presents the fabrication process and operation of a bio-sensor based on tapered optical fiber by using optical spectrum shift in the presence of PBS buffer and dissolved streptavidin. The taper-fiber sensors are 18 and 24 μm in diameter and are fabricated by use of an oxy-butane torch. The optical spectrum is obtained using a broadband light source and an optical spectrum analyzer (OSA) in a 40 nm wavelength range. The existence of streptavidin on the tapered fiber surface is confirmed. The experiments on PBS buffer have shown that, the output spectrum demonstrates a red-shift by adding the streptavidin. The maximum sensitivity obtained is 29000 nm/RIU.

The quantum theory of a damped harmonic oscillator has been continuously studied since 1939. For quantization, an oscillation oscillator usually uses a reservoir that includes a number of finite and discrete oscillators. However, a set of discrete oscillators is unable to study the quantum theory of an Ohmic damping (damping proportional to velocity). In this research, a continuous set of harmonic oscillators has been used to investigate Ohmic damping. Using a continuum reservoir instead of a discrete reservoir will enrich the results of the dynamic system. The results of this research can be used to study nano-mechanical systems and opto-mechanical systems.

In this paper we examine asymptotically anti–de Sitter rotating black string solutions of four-dimensional Einsteinian cubic gravity in the presence of nonlinear Born-Infeld electrodynamics. By assuming that the solutions are completely regular at the horizon and studying the asymptotic and near-horizon behavior of the solutions, we compute independently the Hawking temperature, the Wald entropy, the mass, the angular momentum, the charge and the electrostatic potential, and show that the first law of thermodynamics for rotating black strings with non-linear Born-Infeld source holds exactly in Einsteinian cubic gravity. We also show that when the nonlinear parameter goes to infinity, the solutions tend to those obtained from Maxwell’s electrodynamics