javad mokhtari

In this research, an empirical correlation is derived to determine the Nusselt number for nanofluid forced convection flow in a vertical annulus with non-uniform heat flux. The experiments investigate the heat transfer of a homogeneous combined nanofluid composed of TiO2 and Al2O3 dispersed in water. Compared to other conventional fluids, nanofluids exhibit better heat transfer performance due to higher conductivity and reducing the thermal boundary layer. Nanofluids have the potential to function in an emergency core cooling system. A 25-bar test loop with a vertical test section generating non-uniform heat flux is used for the experiment. The tests are conducted at multiple Reynolds numbers and volumetric concentrations of the nanofluid. A new correlation for nanofluid heat performance is developed based on dimensional analysis and multiple linear regression analysis. The Nusselt number derived from the developed correlation shows high accuracy, with R2 = 0.92, indicating better performance compared to existing correlations.

The agricultural sector has always played a vital role in the national economy, contributing significantly to food security, employment generation, and sustainable development. However, during the 2010s, this sector faced numerous transformations and challenges that adversely affected its productivity, sustainability, and efficiency. Statistical data indicate that, similar to the overall economy, the agricultural sector experienced a volatile growth trajectory, even recording negative growth in 2018 and 2021. The sector’s average economic growth rate over the decade was approximately 3.7%. Additionally, the capital formation rate in agriculture followed a downward trend, declining from around 6–7% at the beginning of the decade to approximately 1% by 2021. Furthermore, agriculture’s share of total capital formation remained low, averaging only 4% throughout the decade.Despite policy emphasis on self-sufficiency and national independence in agricultural production, as well as the need to support domestic farmers, data reveal a significant surge in agricultural imports. The volume of imports rose from 13,000 tons in 2011 to over 30,000 tons in 2021, marking a 2.5-fold increase. Government support for agriculture, particularly in the form of subsidies, did not follow a consistent trajectory. While annual subsidies increased from 1,700 trillion rials in 2011 to approximately 9,700 trillion rials in 2017, they sharply declined to around 1,000 trillion rials in 2020 and 2021—the lowest level in recent decades. Inflation in the agricultural sector also followed an upward trend, with producer inflation reaching approximately 64% in 2021. An analysis of the agricultural sector in the 2010s highlights key structural vulnerabilities and challenges, including low productivity and limited integration of scientific knowledge, an aging farming population, inadequate financing and investment, excessive government intervention in sectoral operations, unsustainable exploitation of natural resources, and the impact of climate change. In response, several strategic measures are proposed, including promoting agricultural and food exports, expanding arable land, achieving self-sufficiency in oilseeds, meat, and dairy production, enhancing education and training for scientific agricultural methods, integrating small farmlands, establishing agricultural training schools, focusing on rural development, and fostering industrial advancements in the agricultural sector.

The month of "Ramadan" is a remarkable instance of strong influences of culture and religion in Iranian people's behaviors and habits. Studies have reported different results in the rate of incidence, hospitalizations, time pattern and risk factors affecting stroke during fasting. This study was conducted with the aim of determining the incidence and factors related to stroke in the month before, during and after fasting in Yasuj, Iran.  This retrospective cross-sectional study was conducted on stroke patients referred to Yasuj hospitals, Iran from January 2018 to December 2020 (Shaban, Ramadan and Shawwal 1443 AH). Complete medical records of 40 stroke patients with inpatient records were used. Stroke cases were separated by month, based on age, gender and other risk factors, as well as the time of incidence of stroke. Data were analyzed using SPSS v.28 software. According to the findings of this study, 23 patients (57.5%) were male and 17 patients (42.5%) were female. The number of hospitalized patients with stroke in the months of Shaban, Ramadan and Shawwal were 12, 12 and 13 respectively. No significant correlation was observed in terms of the incidence of stroke during the month of Ramadan and other two months. In addition, there was no any significant difference between different months in terms of the studied variables (stroke history, cardiovascular diseases, hypertension, hyperlipidemia, and smoking).  This study indicated that fasting in Ramadan does not increase the incidence of stroke. Proper medical advice can significantly prevent strokes during Ramadan.

New nitrile butadiene rubber (NBR) materials are being considered to use for neutron shielding especially for the positions which needs a flexible neutron shield. Such light, low-cost, and suitable material could be used for sealing of the gaps or even for shielding of low radiation environments. In the present work, experimental investigation of NBR shielding performance of neutrons and gamma rays was proposed using the beam line of the Isfahan Miniature Neutron Source Reactor . MCNPX code was used to simulate the 30 kW research reactor beam line. Six NBR sheet with 2 cm thickness were used at the outlet of the beam line respectively to measure its neutron shielding as well as gamma shielding power on thickness. The experiment situations were modeled using the computational code. The obtained results showed the flexible and cheap material could be used as a good neutron shield while it acts as a very weak shield for gamma rays too. Also there is good conformity between simulation and experimental data with maximum 37% relative discrepancy.

There are several methods to measure the reactor power. Since the power is directly related to the neutron flux in a reactor, the usual way to measure the power is to detect the neutron flux in the reactor core. The miniature neutron source reactor (MNSR) uses two fission chamber (FC) neutron detectors connected to computer and console control systems to determine the reactor power. These instruments are indicators of power, therefore the output of them has a significant role in reactor safety and needs to be calibrated. Importantly, the calibration measurements should be performed in a neutron-gamma environment very similar to the environment in which they will be used later. The aim of this study is to calibrate the fission chamber detectors in the core of the reactor by using the solid-state nuclear trace detector (SSNTD). The calibration factors of the FC detector related to the computer and control systems are equal to 1.02 and 0.88, respectively.

One method to improve heat convection is to increase the heat transfer coefficient of the working fluid. Adding metal or non-metal nanoparticles into the base fluid, known as nanofluid, is a technique to enhance the heat transfer coefficient. Research in the field of nanofluids has grown significantly in the last two decades. In this study, the effects of a homogenous combination of Al2O3 and TiO2 nanoparticles with deionized water are investigated. The thermohydraulic performance of the nanofluid inside the vertical channel is analyzed by experimental and numerical methods for turbulent and laminar flow. The turbulence model utilized in computational fluid dynamics is the k-ε model. The heating rod in the test section produces 1 kW cosine heat flux. The results show that increasing the concentration of nanoparticles significantly reduces the maximum temperature of the rod. The use of 1% homogeneous nanofluid reduces the maximum temperature by 20% at the Reynolds of 950 and 9.5% at the Reynolds of 4200 compared to pure water. Also, the heat transfer coefficient increases with the addition of nanoparticles. The difference between the results obtained by the k-ε turbulence model and the experimental method shows a difference of 10% to 13%. This research shows that the combined nanofluid with suitable thermal performance can be one of the working fluids in future thermal cycles.

Cotton textile was prepared by using cactus salts to produce shielding for electromagnetic waves. To transfer shielding properties to nanocomposites, they must be subjected to certain finishes, such as surface finishing or certain types of additives. The minerals such as copper, which absorbs radio and other electromagnetic waves, used for shielding radio frequency. In this study, cotton textile was dyed using cactus solution by exhaustion method. Scanning electron microscopy and X-ray diffraction spectroscopy and network analyzer were performed to evaluate the chemical composition and its shielding effectiveness. The results showed that the mineral salts in the cactus have been applied to the textile. Also, the degree of shielding against electromagnetic interference of the samples was measured in the range of 2 to 7 GHz and the results showed that the shielding effectiveness of textiles with the use of cactus in the frequency range of 4-5.5 GHz has increased from 34.195 to 44.912 dB. Therefore, cactus solution has been effective on the shielding effectiveness of the textile.

The accurate calculation of effective kinetics parameters is very important in the study of time-dependent behavior of neutron populations.To calculate the parameters, it is necessary to calculate the flux and adjoint flux in the phase space, which can be calculated with deterministic and probability methods. In this paper, in order to obtain the kinetic parameters of the new configuration of the Isfahan heavy water zero power reactor core in a deterministic approach, the MTR-PC package has been used and in the probabilistic approach the developed mcnp code with Iterated Fission Probability (IFP) has been used.The kinetic parameters calculated by these methods are validated by comparing the response of the point kinetics and experimental values for a reactive injection, and a good agreement was found between the results of the calculations and the experimental values.

The use of metal matrix composites can provide a combination of desirable properties of metals as well as the special physical properties of neutron absorber reinforcing particles such as boron carbide, which alone may be brittle. Therefore, in the present study on neutron attenuation power of composite shielding, several Al-B4C composite samples with weight fractions of 5, 10 and 20% B4C have been used. In order to investigate the neutron absorption properties of the studied samples, the MCNP Monte Carlo code and the neutron source of the dry channel of the MNSR reactor with a flux of 2.13E+5 n.cm-2.s-1 have been used  ,which provided in nominal reactor power of 30 kW. The results show that the neutron flux in the presence of 5, 10 and 20% boron carbide samples is predicted to be 1.32E+05 n.cm-2.s-1,1.12E+05 n.cm-2.s-1 and 1.07E+05 n.cm-2.s-1, respectively. With this increase in the percentage of reinforcement phase, neutron flux is reduced down to 50%.

In the last decades, metal oxide nanoparticles (NPs) have been used as inexpensive efficient heterogeneous catalysts in different chemical reactions, due to their favorable properties such as high available surface area, small loading of catalyst, convenient catalyst recycling, and degradation of environmental pollutants. An efficient synthesis of xanthenones and [1]benzopyrano[d]pyrimidinediones are achieved by cyclocondensation reaction of 3,4-methylenedioxyphenol, aromatic aldehydes, and active methylene compound including dimedone or 1,3-dimethylbarbituric acid using CdO NPs as a robust catalyst under ultrasonic irradiation in water at room temperature. The described catalyst was prepared successfully by a simple precipitation method and characterized by the Fourier transformed infrared absorption (FT-IR) spectroscopy, X-Ray diffraction (XRD) analytical technique, and scanning electron microscopy (SEM). All synthesized compounds were well characterized by IR, 1H and 13C NMR spectroscopy, and also by elemental analyses. The remarkable advantages of this protocol are high yields of products, short reaction times, use of simple and readily available starting materials, experimental simplicity, and applying the sonochemical method as an efficient method and innocuous tool for the synthesis of heterocycles.

In this study, the neutron and gamma doses in the dry channel and in the internal irradiation site of the Miniature Neutron Source research reactor (MNSR) has been calculated and measured. The MNSR reactor is a light water reactor with a maximum power of 30 kW and equipped with various irradiation facilities, including five irradiated sites, five irradiation sites and a dry channel. The internal irradiation sites have the closest gap to the core of the reactor, with the highest flux and doses available in these locations. Dose calculations have been performed using simulation of the reactor by MCNP computational code and dose measurement using TLD600 and TLD700 thermo-luminescence dosimeters. The experiments have been carried out at both the shutdown and operational status of reactor. In order to validate the computational code, the neutron flux in the internal irradiation site and at the end of the dry channel has been measured by foil activation method and validated by the calculation results. The results of the calculation and measurement of the neutron and gamma doses were in good agreement. The determination of neutron and gamma doses at these sites makes possible such experiments and researches that need to receive a precise amount of neutron and gamma doses.

Neutron radiography is an unique, advanced and useful non-destructive test method in various industries and researches. Nuclear reactors are powerful and stable neutron sources for the neutron radiography system. In this research, the MNSR research reactor has been used as a neutron source for a neutron radiography system, and its neutron beam parameters have been evaluated. Also, using the direct conversion method and the gadolinium converter, the neutron image was obtained in its neutron beam and the image quality of the neutron was evaluated using the standard image quality standard ASTM-E545. The results of the measurements show that the neutron flux of the system in the maximum reactor power is equal to 3×105 n.cm-2.s-1 and the collimation ratio is 100. Image quality evaluation also showed that the obtained image has a V quality category based on the ASTM-E545 standard.

Diffuse reflectance spectra of printed cotton/nylon blend fabrics coated with inorganic compounds are investigated in near infrared (NIR) and short-wave infrared (SWIR) in order to tune the diffuse reflectance behavior of them with the ones in woodland and desert backgrounds. Cotton/nylon blend fabrics printed with four-color digital pattern were used as the substrate and different concentrations of zirconium and cerium dioxide (ZrO2 and CeO2) with and without citric acid as cross-linker were loaded on these fabrics using pad-dry-cure method. Coated fabrics were measured by diffuse reflectance spectroscopy (DRS), field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). Adding 1% (w/v) of nanoparticles to fabric could approach the reflection spectrum of fabrics to reflection pattern of forest and desert areas by reducing the reflection trend. Also, adding 6% (w/v) citric acid combined with 1% (w/v) cerium dioxide and magnesium oxide to the fabric could reduce the total reflection at all wavelengths. However, the reduction of reflection intensity of magnesium oxide was higher at all wavelengths. Electron microscopy images also showed that fabrics coated with cerium dioxide had a better dispersion on the surface of fabric and a mean particle size about 50 to 70 nanometers. In contrast, magnesium oxide nanoparticles, when bonded with citric acid, exhibit better adsorption on the fabric but are more likely to accumulate.

In this study, surface modification of silk fabrics was done through adsorbing multi-walled carbon nanotubes (MWCNTs) on the silk fabric surface. For this purpose, a simple method of immersing silk in the solution MWCNTs dispersion was used. In order to increase adsorption of activated MWCNTs on the silk fabric surface, citric acid was used as a crosslinking agent in the presence of sodium Hypophosphite as a catalyst. Results of potentiometric measurements showed that electrical conductivity of CNT modified silk fabric increases with the concentration of CNTs in the solution. Washing fastness of the CNT modified samples were assessed by a spectrophotometer just before and after washing out. Brightness was increased for all samples after washing. Scanning electron microscope (SEM) images was used to investigate morphology of fabric surfaces. SEM images represent that, in the same density, accumulation of single-wall carbon nanotubes was more in samples that obtained in presence of citric acid.

Steady state natural convection is numerically investigated in an enclosure using variable thermal conductivity, viscosity and thermal expansion coefficient of Al2O3–water nanofluid. This study has been conducted for a wide range of Rayleigh numbers (103≤ Ra ≤ 106), concentrations of nanoparticles (0% ≤ Φ ≤ 7%), enclosure aspect ratios (0.5 ≤ AR ≤ 2) and temperature differences between the cold and the hot walls (1≤ ∆T≤ 30). The main idea in this study is about the effect of temperature on natural convection pattern of nanofluid by changing nanoparticles concentration. Also, changing thermal expansion coefficient with temperature is considerd in this study which will have significant effects on natural convection and has not been considerd before. In low Rayleigh numbers (Ra= 103) and for cavities with AR≥1, the pattern shown in the average Nusselt number versus volume fraction of nanoparticles diagram deteriorates by increasing ∆T. However, for other cases, increasing ∆T has a positive effect on Nu-Φ diagram. The actual Nuselt number curve depicts that dispersing nanoparticles in base fluid deteriorate natural convection heat transfer which is in a good agreement with experimental works.

Encapsulated pharmaceuticals are presently the object of comprehensive investigations in many research centers due to their increased therapeutic efficiency, bioavailability, and high dissolution rate. There are different procedures for encapsulation and choice of procedure influences the size of particles for intended applications. In this study, Nanocapsules of Poly-Lactic-co-Glycolic Acid (PLGA) containing Bovine Serum Albumin (BSA) at ratios of 0.25/0.25, 0.4/0.1 and 0.45/0.05 were fabricated by electrospraying method. Also, the effect of some parameters in electrospraying was evaluated, including PLGA concentration, voltage and flow rate on the morphology and size of particles.  BSA loaded PLGA Nanocapsules were successfully prepared by using electrospraying technique. The formation of capsules was confirmed by TEM. SEM results of the samples showed that decreasing the flow rate and increasing voltage decreased the average size of nanocapsules and led to producing the capsules with a size in the range of 85-260 nm. The presence of the drug in nanocapsules was confirmed by DSC results. Drug release test showed that about 90% of BSA had been released during 24 h. PLGA nanocapsules containing therapeutic proteins were produced by the electrospraying technique under different operation parameters and physical properties.

Using Computational Fluid Dynamics (CFD) technique, the dispersion contours and the exposure rate of Flexographic printing workers to VOCs in a printing department is evaluated. Firstly, VOCs distribution is determined in the printing room due to the existing ventilation system. Through next steps, 4 scenarios for lowering VOCs concentration and its exposure rate to workers are analyzed. Concentration distributions of ethylene glycol (MEG) as a representative of VOCs are determined for 4 scenarios. The results show that, regarding the existing ventilation, the concentration of MEG at the breathing height is 1×10-5 mg/m3 and it is higher than the standard permissible level. Finally, the findings of this study lead to lowered VOCs concentrations to 13.87×10-9 mg/m3 via changing the ventilation system for the Flexography Printing Room.

One of the major components of tissue engineering is the scaffold. The main role of the scaffold is to provide a suitable environment that defines the shape of the tissue. In fact, scaffold can support cell adhesion and proliferation. In tissue engineering, three-dimensional (3D) nanofibrous structures are preferred owing to their structural similarity to human body tissues. 3D porous scaffolds serve not only as structural molds for tissue production but also provide signaling cues to cells and facilitate oxygen and therapeutic agent delivery. The fabrication of 3D scaffolds cannot be achieved using conventional processes, so cultured cells could only develop into flat shapes. Therefore, to improve the thickness of scaffolds, several approaches have been suggested to fabricate 3D porous scaffolds. This article summarizes chemical methods of producing 3D porous scaffolds including particulate leaching, phase separation and gas foaming. This review will cover the production methods of 3D scaffolds using electrospinning by focusing on solution electrospinning. Furthermore, the role of various factors like charge density and humidity in electrospun scaffolds is discussed.

The aim of this study is preparation and evaluation of regenerated cellulose nanofibers treated with cyclodextrin molecules in order to release gradually of particles from the surface of textile. In this study, cellulosic nanofibers were prepared by electrospinning of cellulose acetate solution in the mixed solvents of acetone and dimethyl sulfoxide and then prepared cellulose acetate nanofibers were deacetylated. Acetate nanofibers were deacetylated and evaluated with both Potassium hydroxide and Sodium hydroxide. In order to graft β-Cyclodextrins molecules to regenerated cellulose nanofibers, the method of crosslinking by polycarboxilic acids was used. Physical and chemical properties of prepared nanofibers were investigated by SEM, FTIR and DSC. In order to evaluation the performance of prepared nanofibers, Gentamicin antibiotic molecules were loaded into cyclodextrins’ cavities and the rate of delivery was measured by UV-visible spectrophotometer. According to obtained results, it is obvious that presence of cyclodextrins on the surface of nanofibers has a great impact on controlled release of guest molecules from the surface of textile.

Nanofiber scaffolds possess high surface-to-volume ratios and adjustable porosity which promotes cellular activities such as attachment and infiltration, therefore providing some key characteristics of the native extracellular matrix. Compared to other production methods of nanofibers, electrospinning is a versatile and simple procedure. Due to recent developments and improvements, electrospinning is becoming a popular technique in the fabrication of three-dimensional (3D) scaffolds. In general, 3D scaffolds can provide a better link between single cells and organs than conventional 2D scaffolds. To date, several approaches have been proposed to fabricate 3D fiber structures by electrospinning. This article summarizes the production of 3D scaffolds using electrospinning techniques by physical methods including combining rapid prototyping and direct-write with electrospinning, post-processing after electrospinning (laser process, physical punching method), liquid-assisted collection, template-assisted collection, porogen-added electrospinning, co-axial electrospinning, and needleless electrospinning. Furthermore, the role of various factors like voltage and humidity in electrospun scaffolds is discussed.

Capsules formulations are widely used to improve the bioavailability of drugs. Electrospraying was used as a novel method to produced drug nanocapsules. In the present study PLGA (Poly-lactic Co-glycolic acid) nanocapsules containing therapeutic proteins were prepared. The nanocapsules of PLGA/BSA at different ratios were obtained.The effects of system operation parameters and formulation of spraying solution were tested.Morphology and diameter of nanocapsules were studied using Scanning electron microscope (SEM). The size of nanocapsules was reduced by increasing the voltage and decreasing the flow rate and led to producing the capsules in range of 85-260 nm Thermal analysis(DSC) results indicated that the endothermic peak was broader and shifted to lower temperature implying the presence of drug. More than 90% of drug of nanocapsules was detected in phosphate buffer (pH=7.4) and 37°C temperature using UV-Vis spectrophotometry.

Regenerated silk fibers were fabricated through dry/wet spinning process, N-methyl morpholine- N-oxide (NMMO) solvent and methanol coagulant. Several concentrations of polyhexamethylene biguanide (0.5, 0.75 and 1% (v/v)) and silver nanoparticles (5, 15, 55, 95 and 135 ppm) were used separately and mixed as the antibacterial agent for producing antibacterial fibers from dipping process and also antibacterial property against the gram-positive bacterium: Staphylococcus aurous was investigated. The results showed that; high concentrations of silver nanoparticles in the fibers had more inhibitory effect, but these high concentrations were caused to change the color of goods. Also in the case of polyhexamethylene biguanide; the inhibitory effect of fibers were improved with increasing the concentrations of them. Compositions of these two antimicrobial agent determined that maximum inhibitory effect in this situation can be achieved in smaller amounts of that. As concentrations of 55 ppm AgNPs and 0.75% (v/v) of PHMB were demonstrated the maximum inhibitory effect with the least amount of discoloration in fibers.

Sutures with the help of needles are usually used to hold together the injured tissues until full recovery. Because there are many sutures for different tissues therefore, there may be reactions toward absorption or rejections processes using the wrong type of suture leading to unintentional injuries such as wound rupture. Surgery yarns generally are sterile single-filament or multi-filaments. The selection of methods and techniques of sutures depend on several factors such as the purpose, wound configuration, healing time, its depth, type of suture texture and the specific condition of each patient (including the age, weight, general health status and extent of infection). One of the latest approaches to make sure of a suture material behavior is to use it as a drug release matrix in order to prevent bacterial growth.

Camouflage، in visual and near infrared region (NIR)، is one of the important topics developed for military purposes. In order to impart camouflage in NIR region، the reflectance profile of the object and its surrounding should be matched. So، the reflectance profile of a selected dye in NIR region is of great importance. If the fabrics are dyed with various pigments and then examined for their power of imparting camouflage in NIR region there would be much waste of human effort and cost to use a reflectance spectrophotometer. To challenge these problems، a new method is developed and reported in this study. For this purpose، a UV-Vis absorbance spectrophotometer is employed and the transmittance profiles of the selected dyes are compared with a known NIR camouflage imparting dye. The novel dye has been studied and evaluated for its potentials as camouflage substance. Since C. I. Vat Blue 13 is one of the camouflage dyes and because structural properties of the dye such as the transmittance curve or the reflectance curve are influenced by its structure، it was concluded that C. I. Vat Blue 6 dye can be used as a camouflage dye in NIR region by similarity of its transmittance curve with that of C. I. Vat Blue 13.

Chromic behavior and electrical conductivity of poly (3-methylthiophene) nanoparticles - coated polyester fabric was investigated by chemical polymerization method. The electrochromic behavior of poly (3-methylthiophene) coated polyester fabrics were measured by digital voltmeter on the samples surface and the reflectance spectra were recorded. The effects of reaction time، temperature، and oxidant concentration on conductivity and other properties of the coated fabric were studied. Scanning electron microscopy confirmed that the surface of fabric has entirely been coated with poly (3-methylthiophene) particles at range of nanometer. Further characterizations were investigated using Fourier transform infrared spectroscopy to provide evidence of forming nanoparticles onto the fabric، UV-Vis absorption spectroscopy، electrical surface resistivity and pressure dependence visible reflectance spectrophotometer measurements. It can be found that the oxidant polymerization has been done physically without any structural changes. Results showed that the increasing of reaction time and temperature (less than 40°C) and oxidant to monomer molar ratio up to 3:1 led to a decrease in the electrical resistance of polymer-coated fabric. Also، the strength of samples was decreased during the polymerization (raw polyester fabric''s strength، 23. 36 kgf; coated polyester fabric''s strength، 19. 42 kgf). The blue shift in the reflectance spectra under high pressure represented the piezochromism in poly (3-methylthiophene) nanoparticlescoated polyester fabric.