---

Mine ventilation is one of the important functions in mining. The purpose of mine ventilation is providing enough oxygen to breath, create comfortable working conditions and dilute and remove the gases and dust from mine. Methane gas released from minerals while extraction in coal mines. To prevent the accumulation of this gas and intense explosions, the use of auxiliary ventilation beside main ventilation is essential. Auxiliary ventilation in room and pillar coal mining is used generally two methods of stopping and brattice.In this study, the equations of conservation of mass, momentum, species and energy is discrete by using computational fluid dynamics and the results have been validated with experimental work and then several scenarios have been predicted to improve mine ventilation. Results show that concentration of methane decreases 47 % using stoppings, but the concentration is still higher than the standard level. By using brattice the level of methane concentration decreased to 74.2%, but methane concentration in side walls of coal face is 3.4% that is still higher than the level of standard. Optimized case was simulated by using stoppings and brattice simultaneously and quality of air improved 88.8% and concentration of methane has been fully respected and mine safety and explosive gas concentration are desirable.

---

Heat and mass transfer in textiles are usually simulated using models that consider sorption and condensation. But in electrolyte solutions, ions existed in fluid passing the textile can cause a phenomenon called electric double layer. Charges on the textile pores will attract the ions with opposite charge which will affect the fluid flow. To investigate this effect, Poisson-Boltzmann equation is solved beside the other governing equations of the phenomenon. Net electric charge density is computed from this equation and is applied to liquid diffusion coefficient. In this research, the influence of electric double layer is shown and then the factors affecting the strength of this phenomenon have been studied. One side of the textile is thoroughly in contact with liquid and other side is in contact with air. To validate the obtained results, temperature variations in the outer side of the textile are computed and compared with the available experimental works. There is a good agreement between the results. According to the results, applying electric double layer effect in equations cause temperature difference to 20 percent in the outer surface of textile to lack of consideration this. In addition, time for textile full saturation when the electric double layer is considered, increased more than fivefold. The results show that by reducing the viscosity of fluid. The effect of electric double layer on the textile's outer surface temperature has increased. Porosity and zeta potential are other influential factors which according to calculations, increasing each effect can be accelerated electric double layer.

---

A practical method for improving the COP of an air-cooled chiller is pre-cooling the entering air of its condenser via a water mist system. This article studies a water mist system with hollow-cone spray nozzles and investigates the effects of water flow rate, water droplet diameter and the number of spray nozzles on system performance. Simulations were run by software FLUENT applying Eulerian-Lagrangian method. Solution grid independency was obtained and it was validated with experimental data. According to the results, in a constant air flow rate of 8.3 (kg/s), with increasing the water flow rate from 0.05 to 0.4 (kg/s), percent increase of COP increases from 3 to about 14, but the percentage of evaporated water decreases from 12.13 to 7.62 (however the value of evaporated water increases). Besides, decreasing the water droplets’ diameter from 200 to 50 micrometer, results in percent increase of COP from 4 to 24. Due to less water evaporation in higher flow rates, the number of spray nozzles was raised in a constant total flow rate that according to the results, increasing the number of nozzles improves the system performance. Also with other simulations it was observed that increasing the number of nozzles is more effective in higher flow rates and less drop diameters. Finally by the case study, it was demonstrated using sufficient number of nozzles, it is possible to achieve higher COPs in lower flow rates and therefore in addition to energy consumption decline, the water consumption could be lowered.

---

The management of air quality in enclosed parking lots has many challenges such as increasing pollution concentration and pollution movement between floors. In this article, the complete calculation of ventilation system in multilevel parking lots is presented and the effect of supply and exhaust vents height on pollution concentration and movement is investigated by using numerical simulation. Also a new criterion for recognition of flow pattern is presented. In the numerical simulation, the conservation equations are solved by using openFoam. For validating the numerical simulation, the results are compared with available experimental results. The comparison of results is showed good accuracy of numerical simulation. After that, the common multilevel parking lots are introduced and the effect of supply and exhaust vent heights on the amount of pollution in these parking lots are investigated. The results showed that, if the supply vents are installed on the non-dimensional heights of about 0.55 and exhaust vents are installed on the non-dimensional heights of about 0.55 to 0.7, the best ventilation flow pattern in the multilevel parking lots is obtained. Furthermore, by using the novel method of this paper, the ideal bulk flow velocity for development of piston flow in parking lot is obtained and the flow pattern is tend to piston flow by optimizing the supply and exhaust vent heights.

---

Unbalance mass and imperfect bearings are the main sources of vibration in rotor dynamics systems. One way to decline and control of a rotor vibration is the use of magnetic absorbers. The magnetic absorber is used to control the position of the rotor and reduce its vibration. In this study, by applying the dynamic absorber system force and creating two new natural frequencies, the magnetic absorber brings the system out of the resonance. Moreover, in order to decrease the vibration amplitude, two different types of dynamics absorbers are designed in which they are checked by the magnetic absorber in a specific range of rotational frequency. In magnetic absorber controller system, the continuous force which is applied to the main system by mass absorber is restored in sixteen levels discontinuously. It is seen that the vibration amplitude is reduced 13% in the area of natural frequency in comparison to the magnetic absorber with discontinuous force. In this paper, two different mass ratios are considered for each one of the two absorber systems. It is observed that in the case of dynamic absorbers with higher mass ratio, rotor vibration amplitude and the maximum force amplitude of the dynamic absorber system decrease. This issue can increase the accuracy of magnetic absorber system in the renewal of the dynamic absorber system force and reduce consumption electrical energy of the control system as well.

---

In this study, the effects of geometrical parameters of 6-DOF Hexa parallel robot on kinematic, and dynamic performance indices are investigated and its structure is optimized using the intelligent multi-objective Bees Algorithm. In this way, after describing the structure and specifying the geometrical parameters of the robot, inverse kinematic relations of the robot are obtained. Jacobian matrix that maps velocity from joint space to Cartesian space is developed. Mass matrix is obtained from calculating the total kinetic energy of the manipulator in terms of the actuated joints vector. Inverse of the homogen jacobian based condition number is considered as a index to evaluate the kinematic dexterity. based on mass matrix as relation between acceleration vector of the end effecter and torque vector of actuated joints, dynamic dexterity index is presented. Using the multi-objective Bees Algorithm and considering dynamic and kinematic performance indices in a pre-determined workspace as the objective functions, structure of Hexa parallel robot is optimized. In this way, the proper geometrical constraints such as limitation of universal and spherical joins, and the constraints to singularity avoidance are considered. Pareto front of the multi objective optimization of the robot is drawn. Diagrams of the kinematic and dynamic performance indices variation in the workspace and the effects of geometrical parameters variation on them are presented.

---

In this study a numerical model based on the finite element method is used to simulate the behavior of human lumber spine. Due to lack of realistic models, in the present work a lumber spine model is generated from Computational tomography (CT-Scan) images by Mimics 17 software. Also, according to the wide range of loading conditions, to achieve realistic results, optimized loads acquired from other researches are used. Human lumber spine model which is used in this study consists of five vertebrae, five discs, and all ligaments. Model is loaded under statically conditions and calculated with ANSYS-Abaqus 16 (Simulia Inc., Providence, USA) software. Obtained results are compared with other numerical simulation results and experimental measurements which are reported in other researches. Numerical modeling consists of six cases as follows: intervertebral rotation, interadiscal pressure and facet joint forces under the axial rotation and lateral bending with compressive follower force loadings. In all cases, intervertebral rotation, interadiscal pressure and facet joint forces are reported. Comparisons show that obtained results have a good agreement with experimental measurements. Therefore, results show that realistic model with optimized loadings predicted the behavior of lumber spine more accurate than other numerical models.

---

The robotic sensor deployment task to achieve maximum converge is one of the main phases in feasibility studies and development of communication infrastructures and environment monitoring systems. In this article, a new approach is proposed to treat the maximum coverage in 3D vector spaces. For this purpose, a new geometric strategy is first presented to compute the area covered by an individual sensor. To maximize the coverage of the robotic network, the fractal search algorithm was employed. This population-based evolutionary algorithm has been proposed based on the growth of the random fractal and demonstrates a robust performance in tackling constrained and unconstrained optimization problems. Then, based on several scenarios and by considering spatial constraints, the efficiency of the fractal search optimizer was compared with other methods in terms of robustness, running time, quality of the coverage results, convergence rate, as well as the statistical test of Wilcoxon. The comprehensive assessment and analysis of the results certify better performance of the proposed approach to maximize the coverage in 3D vector spaces. The proposed approach can obtain the optimal deployment and coverage of the robots by the best convergence rate and computational and statistical precision.

---

Stenosis in coronary artery and the other cardiac diseases such as Atherosclerosis is major cause of death in the world. Numerical simulation of blood flow can help medical evaluation to curve arteries have been stenosis. The purpose of this paper is to find the effect of arteries stenosis on the hemodynamic parameters by simulation of blood flow in LAD branch of coronary artery. The computational domain has been determined from CT images of human heart. In this study, blood is assumed to be homogeneous, Newtonian and the blood flow assumed to be pulsatile. In order to more realistic modeling of flow and pressure, Seven–element lumped model has been used in coronary artery outlet, in order words the 0D and 3D models are coupled together. The results indicate that the calculated flow wave is the minimum in systolic phase and maximum in diastolic phase in coronary artery, in contrast with Aorta. On the other hand, by increasing the stenosis percent from 30 to 60 percent, no significant drop of flow has been observed in the state of rest, and it has been validated with experimental results. The results indicate that with increasing stenosis, time average wall shear stress in the stenosis region increases, while it decreases before and after the stenosis, also the investigation of oscillating shear index indicates that in the state of 60% of stenosis and in the main downstream branch, it has the maximum value, that is indicative of the presence of turbulent flow in this region.

---

Due to detrimental effects of synthetic antioxidants, application of natural antioxidants which mainly are extracted from botanical sources, in addition to stabilizing food products will reduce undesirable effects of free radicals and synthetic antioxidants. In this research effect of drying methods and solvent type were evaluated on chemical composition and antioxidant activity of sacred fig. at first fruits were dried in oven (40 and 60 °C) and microwave (400 and 700 W) and two solvents of methanol and ethanol were used for extraction. Total phenol and flavonoid content were measured with folin ciocalteu and aluminum chloride methods respectively. Antioxidant activity were measured using DPPH and ABTS methods. Results showed that the lowest IC₅₀ value was for 60 °C oven and methanol solvent (150.11 ppm for DPPH and 222.9 ppm for ABTS) and the highest value was observed in 400 W microwave and ethanol solvent (455.145 ppm in DPPH and 500.1 ppm for ABTS). The highest total phenol and flavonoid content was seen in extract of 60 °C and methanolic solvent (1032 mg GAE/g extract and 63.31 mg QE/g extract).
 

---

With recent developments in sprinkler technology, water mist system is becoming more and more useful in fire suppressions. The computational method is an efficient way to investigating effect of Nozzle parameter of water mists and optimize them. In this research, a open source fire dynamic simulator (FDS) is used to numerically investigating the different nozzle parameter on the fire suppression and extinguishment mechanism.The range of droplet size was determined based on the NFPA 750 standard. Extinguishing mechanisms in water mist systems and their effect on extingushing time and nozzle parameter such as droplet size, water flow rate and spray cone angle were investigated. The simulation concluded that droplet sizes I hollow cone angle smaller than 121 μm and larger than 600 μm were appropriate for fire extingushment. With a full cone angle nozzle and 1/5 flowrate compared with hollow cone nozzle, fire extingush time reduce from 26 second to 7.4 second. Spray cone angle in fine droplets does not much affect the duration of fire extinguishing, however, for large droplets, the desired result can be achieved by reducing the spary cone angle. So with recognition of nozze parameter and its effects on fire extingushing time could rich the optimum design.
Keywords
m design.

---

The flow induced vibration in transonic turbomachines is an important and challenging issue in this field. Blades aeroelastic behavior, in addition to the aeroelastic instability, can leads to blades failure, flow instability and reduce efficiency of the system. Aerodynamic behavior of the system should be investigated prior to aeroelastic study. The purpose of this article is an investigation of aeroelastic instability and behavior of a selected turbomachine. For this purpose, transonic flow in Nasa 37 rotor is simulated and verified using CFX software. Then, rotor blade aeroelastic stability is investigated in three operating points; design, near stall and stall using blade forced vibration in the specified inter blade phase angle (IBPA). In order to reduce grid points and consequently, computational time, phase-lagged boundary condition and fourier transformation method is used. Also, in this research, the algorithm of simultaneous structure-fluid grid generation and the solution algorithm of force vibration structure-fluid interaction of turbomachines is codified and introduced in detail. Employment of fourier transformation method in CFX software for aeroelastic simulation is another innovation of this article. The value of the critical inter blade phase angle which is independent from rotor operational conditions, is obtained in the present research. Aeroelastic simulations show aeroelastic instability of Nasa 37 rotor in the stall condition. In this condition, flow entropy is increased rapidly relative to the design and near stall condition. The blade pressure side has more important role in stall aeroelastic instability and needs further attention in re-design phase.

---

In this study, micromorphological properties of some samples collected from pedons polluted with petroleum refinery wastes and some adjacent unpolluted pedons were studied. After description of the studied pedons, disturbed and undisturbed samples were collected for physicochemical and micromorphological analyses. The results showed that the physicochemical properties (i.e. structure, bulk density, pH, EC and organic matter) of the soils polluted with petroleum wastes were strongly changed. Prolonged exposure of soils to the petroleum wastes resulted in the formation of specific and distinctive micromorphological features. Strongly developed granular microstructure and infillings of solid petroleum wastes alone or mixed with soil aggregates were some of the most important pedofeatures which were observed in deeper horizons. The existence of excrement belonging to different soil micro and macro fauna, coatings, hypocoatings, quasicoatings, and zones depleted from petroleum dissolvable materials at different depths were the other features throughout the pedons. The type of developed pedofeatures was correlated with the state of petroleum wastes and their fluidity in penetration, deposition, or dissolving and removal of soil compounds. This study demonstrated that micromorphology can be used as a powerful technique in characterization of petroleum polluted soils.

---

in recent years, Variety of analytical methods have been used to calculate the output piezoelectric energy, but it is new something the use of finite element method and compared using analysis software with numerical methods. And also check the types of circuit connection of piezoelectric layers So in this article particular form of numerical analysis method is called separation of variables method compared with the finite element method, To take advantage of these methods is to be determined. The model is a Bimorph beam with two piezoelectric layers and a central elastic layer. This Bimorph beam starts vibrating at various frequencies as a result of base excitation. First, frequency behavior of the Bimorph beam is simulated using the separation of variables method. In this method, the equations of motion in parallel and series connection of piezoelectric layers are obtained as separate parameters. The coupled mechanical and electrical equations are derived using the solution of equations obtained from the separation of variables method. Finally, the output voltage, current and power are obtained in terms of frequency.
Then, the Bimorph beam is modeled based on finite element method using ABAQUS software. after the illustrating Output voltage, current and power diagrams is illustrated for a certain range of frequencies and the results of the finite element method and the steady state method are compared to validate the model.

---

Detecting and Preventing wheels slipping is at the core of all researches related to railway vehicle dynamics. In this paper, three fast non-elliptic contact models are evaluated and compared to each other in terms of contact patch, pressure and traction distributions as well as the creep forces. Among them Johnson and Kalker method was really useful to the similar problems while the common assumption is elastic half-space that many errors could be made especially in gauge-corner contact. Based on the conclusions drawn from this evaluation, two new methods is proposed which results in more accurate contact patch and pressure distribution estimation while maintaining the same computational efficiency. The Beam and Bristle model are proposed for tire engineering in automotive industries but they can predict slip in wheel-rail contact too. New methods are typically used for tire engineering. Tire engineering usually is dealing with higher values of slippage than there is rail engineering. So that they can be applied into the saturation zone. At last a FEM analysis will be done for evaluating the methods proposed. Also in the special case there is similar experimental projects done by other scientists. It should be noted that good agreement between FEM analysis results, tire engineering models, experimental results has been found for several contact applications including S1002 wheel profile over UIC60 rail profile for four different initial braking speed 30, 60, 100, 140 km/h have been compared with experimental results.

---

In this paper heat transfer through argon gas between two stationary walls of a nano sized channel, is investigated by the use of molecular dynamic method. Comparison between two and three-dimensional solutions shows that for accurate modeling of wall force filed on heat transfer, the accuracy of two-dimensional molecular dynamic solution is inadequate. Two-dimensional solution predicts the value for density and temperature less than the value of three-dimensional solution near each wall. Considering the effect of domain size on accuracy of thermal solution shows that domain size should be extended at least for one mean free path in periodic direction to have domain independent results. Distribution of fluid properties in the width of the channel shows that independent of implemented temperature difference, presence of the wall force field changes the temperature and density profile in one nanometer from each wall drastically. In addition to variation in density due to the wall force filed, temperature difference between the walls cause additional variation in density profile near walls. Increasing the temperature difference between the walls to value more than 20 degree, make a notable density variation to more than 5 percent in comparison with gas density distribution in isothermal walls case. Variation in density near walls due to temperature differences leads to mismatch between the non-dimensional temperature profiles and calculated thermal conductivity coefficient of the gas for various temperature differences.

---

One of the focused problem in airway flow simulation is pulmonary airways modeling. There are two kind of Lung models, one is created anatomically based on bronchial data and second is realistic model which is created based on CT scan images. Unfortunately cause of modeling process or simplification cause of restriction of CPU and time, the result model is different from a really pulmonary airways. Anatomically model are many simplification and realistic model from CT scan have major limitation in CT image resolution and smoothing stage of make out the 3D model. Anyway the lung has many rough and the first thing that is vital on this way is cartilage rings as macro scale roughness. So the presented work, compared the airflow in both simple and modified Horsfield model by cartilage rings in term of time averaged wall shear stress which are important in engineering of Cell-Fluid Interactions (CFI). This is shown that cartilage rings affected the trachea and second generation of brunches so this is not reasonable to neglect the cartilage rings.

---

In recent years, increased pollution and traffic in urban has caused the development of underground transport. One conventional approach for urban tunnel ventilation is construction mid-tunnel shafts. These shafts are usually located in high-density urban areas and emissions from them can be harmful for the residents of adjacent buildings. The geometry of these shafts is determined so far based on taste and only for the purpose of compliance standards criteria for tunnel indoor air. In this paper, pollutant dispersion from different and conventional geometries of mid-tunnel shafts with the assumption of a taller downstream building was investigated for the first time. The results can help to reach a better design of these shafts and surrounding buildings to have healthier air for residents of buildings. For this purpose, simulations were done by OpenFOAM. Reynolds-Averaged Navier-Stokes equations method and standard k-ε model were used in simulations. The results showed for the same exhaust velocity, the effect of rectangular and square configuration on front wall depends on dimension of the side which is perpendicular to wind direction. For the exhaust velocity less than 6 m/s, the downstream building prevents pollutants to reach higher altitude and the amount of pollutants will be increased around 100 percent and for exhaust velocity of more than 6m/s, increasing velocity will cause to less changes in pollutant concentration at lower level. In addition, the results showed that exhaust velocity has more effect than geometry configuration on pollutant dispersion and this influence will be decreased by increasing the velocity.

---

This study presented the results of an experimental study on the dense flow discharging from convergent and inclined plane surface jet in stagnant and deep ambient resources. Development of industrial and commercial activities throughout the world leads to pollution of water resources. For example, The salt water obtaining from desalination process whose density exceeds the one of the ambient water is discharged into the sea by the desalination plants through discharging structures. Therefore, it is essential to study related processes to suitable transfer of effluent into the ambient. With respect to the importance of this matter, extensive studies have been conducted in recent years as physical and numerical modeling on examining and understanding of flow behavior discharging through submerged and surface jets. This study discusses the plunge and impact location under the effect of different variables. The study tests were carried out in a 3.2×0.6×0.9 m3 flume. The Jet fluid obtained from salt dissolution in water was prepared in three concentrations of 5, 15, and 45 g/lit. To show fluid’s moving path, the obtained solution was colored by using a substance with no effect on density changing. The flow rate of the jet fluid in values of 0.042, 0.08 and 0.105 lit/sec was adjusted by using an electromagnetic flow meter with the accuracy of 0.01 lit/sec. The injection of the jet fluid was carried out by using rectangular channels in four convergence angle of 12.5, 25, 45 and 90 degrees and the constant width of 0.06m. Width of the outlet section in all the channels were considered 0.035 m. Discharge channels injected the jet fluid tangent to the surface of the ambient water. Thus, the channels were installed and adjusted on a base at slopes of zero, 0.04 and 0.08 and certain convergence angle. The water depth in the flume was adjusted at a constant value of 0.7m in all experiments. The ambient fluid was settled before injection of the jet fluid. During this time interval, the temperature of the jet fluid and the ambient fluid were measured by a thermometer and their densities were measured by a hydrometer. For each experiment, the moving path of the jet fluid in the receiving ambient was recorded by using a Sony digital camcorder (DSC-WX220) with the frequency of 50 FPS. This camera recorded the images of flow’s section that was placed in front of the flume’s wall and perpendicular to the central vertical plane of the jet flow. The data was obtained by using of images routing process. Based on the results, the 8-percent slope has the longest length of plunge and impact locations. The 8-percent slope provides high initial momentum. Therefore, the flow has further advance in this condition. Slopes of 0 and 4 percent are very close to each other. Although the value of initial momentum exceeds zero in the 4-percent slope, the length of plunge and impact locations in the 4-percent slope are lower than zero slope. The initial momentum is divided into X and Z directions in 4 percent slope, but all initial momentum is in X direction in zero slope. While the longitudinal slope of the discharge channel is fixed, the length of plunge and impact locations reduce with the jet fluid concentration increasing. Density difference and buoyancy force increase with the concentration increasing. Flow becomes denser and it loses its contact with the surface more quickly. Besides that, the length of plunge and impact locations increases with the convergence angle decreasing. The initial momentum and the discharge velocity of jet flow increase with the convergence angle of discharge channel decreasing. Increasing the initial momentum leads to further advance of jet flow. As the ambient has a fixed depth, was seen the location of the plunge point in the range of 1.2 and the location of the impact point depending on the ambient depth. Finally, the ratio of the length of plunge to impact locations for data was within the range of 0.1-0.8.

---

In order to simulate the heat transfer process from wall to fluid in nanochannel numerically, extensive range of spring constants with regard to wall material is used. In this paper, the effect of variation in wall spring constant on the heat transfer and distribution of the macroscopic properties of fluid has investigated. In this regard, heat transfer in argon gas between two stationary walls of a 5.4 nm nanochannel with Knudsen number 10 has simulated using the molecular dynamic method. Comparison between the results shows that by reducing the wall spring constant, the amplitude of wall atoms vibration increased so it makes the gas atoms to become closer to the wall surface that results in an increase in the heat flux and thermal conductivity coefficient of the gas. Evaluating the result reveals that while the spring constant reduces from k_s=1100εσ^(-2) to k_s=100εσ^(-2), the thermal conductivity coefficient of the gas changes from 0.11 mW⁄(m-K) to 0.27 mW⁄(m-K). Furthermore, the reduced distance between the gas atoms and wall surface results in a decrease in the temperature jump on the wall so it increases the gas density near the cold wall while it decreases near warm wall. Comparison between temperature, density and pressure profiles in the nanochannel height shows that regardless to the amount of spring constant variation, the maximum of these properties has occurred at σ⁄2 from the walls.