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In order to facilitate the release of floods from the dams and to prevent their damage or collapse, a structure called a spillway is used. Due to the natural and variable flow of the input to the reservoirs of the dams, there are times when the river inflow exceeds the consumption amount in the downstream agricultural lands. In these cases, excess water is discharged over the crest of the weir and flows towards the spillway, which causes high velocities. This high velocity creates low pressure areas on the spillway concrete surface, which can cause major damage to the spillway or even endanger the integrity of the dam structure. Therefore, the dam spillway must safely dissipate the kinetic energy. One of the types of weirs is the stepped spillway to facilitate the passage of the flow over the dams. One of the most obvious practical features of stepped spillways compared to other spillways is the considerable energy dissipation along the spillway. Care should be taken in designing and selecting the type of spillway to prevent potential erosion and reduce kinetic energy as the water flow passes over the spillway. One possible solution is to use a stepped spillway instead of a smooth spillway. In this study, a numeral model of a stepped spillway with different steps and slopes is used. For this purpose, ANSYS software is used for modeling free surface with application of k-ε turbulence model. In the present study, numerical simulation using the Volume of Fluid (VOF) model was used to investigate the mixing phenomenon of two phases of air and water of the free surface flow. The flow field was continued until the residuals reached 10^-7. Compared to simpler models such as Mixture, which operates solely on the basis of averaging the properties of two phases, the VOF model, is separating the phases and considering the effects of the interface. The VOF model, is capable of more accurate simulation of phenomena such as fluid mixing, turbulent flows, and heat transfer in multiphase flows. A number of hydraulic specifications which are considered in designing the stepped spillways are the pressure on the surface of the steps, velocity distribution and energy dissipation. The results from the numerical models were compared with experimental studies. They showed acceptable agreement with physical simulations. Results show that discharge and spillway slope increment reduces the amount of energy loss. In the spillway with 5 steps, for a discharge of 0.063 m³/s, the amount of energy dissipation at a slope of 26.6 degrees changes from 85 to 82% at a slope of 45 degrees, which shows a decrease of 3%. With the increase in discharge, the flow depth increases and reduces the effect of the roughness of the steps on the upper layers of the flow. Increasing the height of the steps increases the rate of energy dissipation and also increases the occurrence of negative pressures in stepped spillway. In this case, the contact surface between the main flow and the eddy currents increases. With the increase in the height of the steps, the dimensions of the rotating vortices also increase and cause a larger radius of rotation on the steps. The presence of these large rotating vortices separates the flow from the bottom of the steps and reduces the pressure on the surfaces. The number and dimensions of steps can alter the energy dissipation rate. Increase in the number of steps in a spillway with constant height, reduces the energy loss as the result of steps dimensions being shrunk

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A numerical model for two-phase debris flows is developed in this paper, on the basis of understanding of the physical characteristics of debris flows from field investigations and experiments. Employing a moving coordinate, the kinetic energy equation of gravel particles in unit volume in debris flow is developed by considering the potential energy of the particles, energy from the liquid phase, energy consumption due to inner friction-collision between the particles, energy dispersion through collisions between particles, energy for inertia force, energy consumption due to the friction with the rough bed and energy consumption at the debris front. The model is compared with measured results of two-phase debris flow experiments and the calculated velocity profiles agree well with the measured profiles. The gravel’s velocity at the debris flow head is much smaller than that of particles in the following part and the velocity profile at the front of the debris flow wave is almost linear, but the profile in the main flow shows an inverse ‘s’ shape. This is because the gravel particles in the main flow accelerate as they receive energy from the gravitational energy and flowing liquid and decelerate as they transmit the energy to the debris flow head and consume energy due to collision with the channel bed.

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    Drying is one of the most important steps in raisin processing. During this step, initial moisture content is decreased up to 15 – 17 percent (d.b) for suitable storage. Achieving optimum drying conditions can affect the processing time and improvement of raisin quality. Temperature, air velocity and pretreatment are important factors in grape drying process and its quality. In this research, effect of the following conditions on time and drying rate of Black currant grape was studied: temperature at four levels of 50,60,70, and 80 ºC, air velocity at three levels of 1, 2 and 3 m/s, and four pretreatments including hot water, %5 potassium carbonate, %0.4 olive oil, %0.5 sodium hydracids and no pretreatment. Diffusivity and activation energy of all treatments were determined. The results show that factors such as temperature, air velocity and pretreatment have significant effects on drying time and average drying rate. Pretreatment has a significant effect on drying process and decreases the time of drying up to 68 percent in some temperature levels. Also by increasing the temperature, drying time decreases up to 66.5 percent in some pretreatments. Increasing the hot air velocity decreases it about 8.3 percent.

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The terminal velocity and coefficient of friction data are necessary for designing of handling and separating equipments. The terminal velocity data are also valuable in designing pneumatic conveying, fluidized bed dryer and cleaning equipments. In this paper, the terminal velocity and coefficient of static friction of saffron flower and its components (stigma, stamina, petal and stem) were determined as a function of moisture content. The experiments were conducted on saffron flower selected from fields of Kashmar. The data was statistically analyzed using factorial experiments with completely randomized design. The results showed that the terminal velocity of the saffron flower, stigma, stamina, petal and stem at moisture content of harvesting level to 40% (w.b.) were in the range of 1.03 to 5.13 m/s. With decreasing moisture content from harvesting level to 40% the terminal velocity of the flower and stem decreased significantly but the terminal velocity of the stigma, petal and stamina were not decreased significantly. The terminal velocity of the petal was the minimum value at the three moisture content levels. The coefficient of friction of saffron flower and its components on the friction surfaces were in the range of 0.52 to 1.1. The friction coefficients of all the components except the stem were the maximum values on polyethylene surface. The coefficients of friction were the minimum values on galvanized iron surface for all of the components. With decreasing moisture content from harvesting level to 40% (w.b.) the average values of coefficient of friction increased significantly for all of the components. The coefficient of friction of the stigma and flower were the maximum and minimum values, respectively at different levels of moisture content. Generally, at moisture content of harvesting it is possible to separate the flower, petal, stamina, stigma and stem from each others with changing air stream velocity. As well, it is possible to separate the petal from the others components at moisture levels of 70% and 40% (w.b.) using wind column device.  

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Knowledge of the aerodynamic properties of agricultural materials is needed in equip-ment design for operations such as pneumatic conveying in loading/unloading operations of corn silage into/from silos. While considerable information is available on seed grains, little is known about the aerodynamic behavior of corn (Zea mays L.) silage. In this re-search, the weighed mean terminal velocity of a sample representative of the entire bulk mass was determined using Wolf and Tatepo’s method. The terminal velocity of various particle types (leaf, stalk and corncob pieces) of chopped forage corn plants, which were kept in silo for six months, at different moisture contents (40-50, 50-60 and 60-70% w.b.) was also studied. The terminal velocity was determined by measuring the air velocity re-quired to suspend a particle in a vertical air stream using a wind tunnel. A 3 3 factorial treatment arrangement with 30 replications in a completely randomized design was used to study the effect of moisture content and particle type on the terminal velocity. The mass mean terminal velocities of the corn silage at 40-50, 50-60 and 60-70% moisture con-tents were 7.1, 7.3 and 7.8 m/s, respectively. The results showed that only the effect of par-ticle type on the terminal velocity of corn silage was significant. The mean values of the terminal velocity of corn leaf, stalk and cob pieces were 3.8, 6.8 and 8.8 m/s, respectively. For each particle type at a given moisture content, the terminal velocity was best de-scribed by means of the equation of velocity squared in terms of weight.

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In this paper a new approach for forming sheet metals by explosion of gas mixtures is presented. As the sheet metal shapes by the impact and pressure resulted from the explosion, it undergoes through a plastic deformation phase. Testing apparatus which is built for the first time in Iran, consists of a thick-walled cylinder (expolsion chamber), various dies for shaping, and measuring instruments. Unlike techniques used in conventional systems, in this method, the wave impact acts as the male part of the die to form and produce different engineering components. Experimental results presented show the effect of various parameters such as thickness, boundary conditions, and the material type of the work-piece, also the percentage of gas mixture on the distribution of thickness/circumferential strain in the work-piece. Furthermore, an analytical model based on the plastic work calculations for the sheet metal deformation is presented.

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The most important application of explosive welding in cylindrical geometry is cladding of cylindrical surfaces in order to increase corrosion and wear resistance and also improving the mechanical properties of bimetal product. In this study, the explosive welding of bimetal tubes made of steel and Phosphor-Bronze was investigated using two explosives (TNT and Amatol 5-95) with different explosion velocity. At first the explosive window of two metals was achieved using the theoretical-experimental relations, and then using different experiments, the key role of explosion velocity and also the position of selected parameters of explosive window in the metals weldability were determined. At the end, the successfull method of manufacturing of this bimetal tubes is presented and commented upon.

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Background: Biofilm is described as an accumulation of microbial organisms connected to a living or unmoving surface mainly through self-secreted polymeric materials. With a complete understanding of biofilm behaviors and the role of rhamnolipids in its stability or dispersion, a new path could be designed in the treatment of infections like Pseudomonas aeruginosa (P. aeruginosa). The purpose of this study was to investigate the role and function of rhamnolipids in P. aeruginosa velocity and biofilm formation ability.
Materials & Methods: In this study, 68 P. aeruginosa clinical samples were isolated from February 2022 to 2023 and confirmed based on culture and molecular methods. The presence of genes associated with di-rhamnolipid (rhlC) and mono-rhamnolipid (rhlA and rhlB) biosynthesis was detected by PCR method. For velocity assay, bacterial cultures on Bushnell Haas medium were monitored for 24 and 72 hours (0.5%).
Findings: The results showed that the distribution of biofilm strength among P. aeruginosa strains was normal. The frequency of rhlC was significantly different from those of rhlA and rhlB (p= .01). In the first 24 hours, the velocity of P. aeruginosa on Bushnell Haas with glucose was 2 µm/min and decreased during 72 hours. But after 72 hours, the velocity of moderate and weak biofilm-producing strains on solid medium with glycerol was constant.
Conclusion: In this study, rhamnolipids produced from different carbon sources showed different behaviors on colony shape, velocity, and strength of bacterial biofilms.

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Aims: Dust is a natural hazard that predominantly occurs worldwide in arid and semi-arid regions. As such, it poses a significant challenge in the Khuzestan Province. This investigation seeks to understand more about the spatial distribution of dust sources based on landunits. Additionally, the study aims to estimate the threshold velocity and soil erodibility in Mahshahr, Omidiyeh, and Hendijan sources using a wind tunnel.
Materials & Methods: Due to the location of the relevant areas in flat and plain regions, the selection of samples and generally the basis of this research is on land types. Thus, in the mentioned study area, 32 points were selected. Then, by taking the average of each landunit, ten points were selected as the surface soil sample and transferred to the wind tunnel laboratory. Then, the velocity of the erosion threshold and the erodibility of the soil were measured at speeds of 15, 20, 25, and 30 (m.s-1) for a period of two (min). Findings: The results of wind erosion threshold estimation in the studied area showed that the velocity of wind erosion threshold varied from 17-6 (m.s-1), and the erosion rate ranged from 30 to 2200 (gr.m-2.min-1) at a wind velocity of 20(m.s-1). The lowest threshold velocity is located in the sedimentary plains of Jarahi-Mahshahr, located in the northwest of the center, and the highest amount of erosion was in the alluviums and Alluvial Fans of Hendijan anticline, located in the southeast of the center.
Conclusion: This study considers the primary factor of dust emission potential based on landunits and reveals the substantial of alluvium, alluvial fans, and alluvial plains as significant contributors to the erodible sediment contributing to dust emissions in the study area. Alluviums and alluvial fans deposited by ephemeral rivers in the eastern foothills of Hendijan contain fine-grained sediments and marl that are highly erodible and must be stabilized early on. Furthermore, according to the results of granulation tests conducted by the Chepil theory, the erodibility of all samples collected from the dust sources of Khuzestan Province was high, and all samples were sensitive to wind erosion. By locating dust sources based on land-units, we can implement more accurate and effective land stabilization methods against wind erosion in alluvium, alluvial fans, and alluvial plains. Furthermore, using the Chipel theory and grain size, we can classify the soil erosion susceptibility of these areas

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The estimation of velocity distribution plays a major role in the hydrodynamics of vegetated streams or rivers of extensive natural floodplains. The velocity profile in vegetated channels can be divided into three zones: uniform zone which is close to bed with uniform velocity distribution, logarithmic zone which involves the main channel with no vegetive cover and the transition zone that is affected by the upper zone flow. In order to arrive at an analytical solution to the force balance that governs the flow specific turbulence, characteristics of the flow through the vegetation are required. A new analytical model for the velocity distribution in the transition zone of vegetated (inflexible submerged vegetation) channels is hereby developed. The model is based on a force equilibrium equation and on Prandtl Mixing Length concept. Vegetation is treated as a homogeneous field of identical cylindrical stems and the flow field considered as uniform and steady. The proposed procedure is straightforward; it follows principles of fluid mechanics and shows good agreement with laboratory flume experiments. The new model can be employed for an exact estimation of discharge through naturally vegetated rivers. The model has been calibrated and verified. The results imply a desirable correlation between calculated and observed data.

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In this paper, the effect of the crack on the vibration behavior of a thick-walled cracked pipe conveying fluid is investigated. The presence of a crack on the pipe introduces considerable local flexibility at the crack location. This flexibility is modeled by the fracture mechanics approach. The accuracy of the model is validated through the experimental data reported in the literature. Then, by using the mentioned model, the vibration analysis of the cracked pipe conveying fluid has been accomplished. Moreover, in order to solve the equation governing the vibration of the cracked pipe conveying fluid, a new analytical technique based on the power series method is proposed. Then, by applying the boundary conditions and the compatibility conditions at the crack location, the frequency equation is obtained. The results are presented by appropriate curves showing the variation of the natural frequency of the cracked pipe conveying fluid in terms of the crack depth and the fluid flow velocity. Also, the results show that for a cracked pipe with a given depth and location for the crack, by increasing the fluid flow velocity, the natural frequencies of the pipe decrease. Also, as the fluid velocity approaches to a certain value, the fundamental natural frequency approaches zero and instability occurs.

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The vertical wind tunnel, which has been designed for sky-diving operations, consists of an octagonal to square diffuser. The diffuser configuration indicates that the wall angles in the diffuser are not symmetrical: the smaller and larger angles being 3.43 and 10.66 degrees, respectively. Estimation of pressure drop and study of flow separation in the diffuser is of great importance for the design of the vertical wind tunnel. In this research work, a 7.8 % model of the original diffuser has been constructed, and airflow, in both blower and suction modes, has been studied in the diffuser using electronic pressure gauges. Pressure drop in the test diffuser has been measured and compared with pressure drop in a circular to square diffuser, which is installed in the vicinity of the test diffuser. To estimate the pressure drop in the test diffuser, the larger diffuser angle from the above, namely 10.66 degrees should be used in the semi-empirical equations, and use of the equivalent diffuser angle is not recommended. In addition, study of the pressure recovery coefficient showed no significant flow separation in the tested diffuser.

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In this paper, analytical solutions of low velocity transverse impact of a nanoparticle on a nanobeam are presented by using the nonlocal theory to bring out the effect of the nonlocal behavior on dynamic deflection. Impact of a mass on simply supported and clamped nanobeams are investigated by using nonlocal Euler–Bernoulli beam theory. In order to obtain an analytical result for this problem, an approximate method has been developed wherein the applied impulse is replaced by a suitable boundary condition. A number of numerical examples with analytical solutions for both nonlocal and classic beam have been presented and discussed. The dynamic deflection predicted by the classical theory is always smaller than those predicted by the nonlocal theory due to the nonlocal effects. The inclusion of the nonlocal effect increases the magnitudes of dynamic deflection and decreases frequencies. Furthermore, the mass and the velocity of the nanoparticle (striker) have significant effects on the dynamic behavior of nanobeam.

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In order to provide the data needed for the design of saffron processing equipment, physical properties of its flower were investigated. These properties included dimensions, mass, true and bulk densities, porosity, static and dynamic coefficients of friction, and terminal velocity as a function of moisture content. The average range of these properties for the three different parts of saffron flower was about 0.03 to 0.16 gcm-3 for bulk density, 0.55 to 1.56 gcm-3 for true density, and 85.2 to 95.5% for porosity. Also, the coefficients of friction were measured for three flower parts by using three surface materials including plywood, iron, and galvanized steel sheets. The minimum and the maximum values of static coefficients of friction were found on galvanized steel sheet. They were 0.8 and 2.14 for anther and stigma, respectively. The dynamic coefficient of friction ranged from 0.45 for anther on iron to 1.14 for petal on galvanized steel sheet. The variation range of terminal velocity for three different parts of the flower was recorded between 0.9 and 2.38 ms-1. The results of friction coefficients and terminal velocity measurements suggest that, based on these properties, design of a separator for saffron flower parts is feasible.

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Nowadays, buildings are built without required separation distance as many engineers do not consider the building pounding effects. If adjacent buildings are not separated properly from each other, pounding can occur upon earthquake occurrence, and severe damages to the buildings can be observed even if they are well designed and constructed. Engineers should realize that building pounding is a serious hazard and it has to be considered during design and construction of buildings. There are many residential building complexes, service office, agencies, schools and hospital in cities around the world which are located next to each other as the cost of land is high. In this term, hospitals with emergency facilities and emergency centers have to be protected against the damages due to the significance of such structures prior and after earthquake. Many researchers have studied building pounding to calculate the dissipated energy and the impact force between two buildings during earthquake. For this challenge, they need to have a link element, which describes impact by using spring and dashpot. Several mathematical equations were suggested to calculate two mentioned parameters. In this paper, based on mathematic relation, a new relation of damping term of impact formula is simulated to measure impact force and energy dissipation. The results of this formula are compared with another suggested formula. As it was mentioned, different materials used in building constructions cause various dynamic behaviors during earthquake. Concrete structures are typically more rigid than steel structures in similar conditions. Consequently, lateral displacements of concrete buildings may also be less than lateral displacements of similar steel structures as stiffness of concrete buildings causes decrease in natural periods during earthquake. Naturally, large lateral nonlinear displacements under time history lateral loading in concrete structures may not be observed. Buildings can collide with adjacent buildings in left and right directions. For concrete buildings, however, the impact of pounding may be more significant than those on steel structures in most situations. Many researchers have suggested new relations in terms of impact to increase the dissipated energy. Based on mathematic relation, they showed that energy dissipation depends significantly on stiffness, impact velocity and coefficient of restitution. For this challenge, by using a suggested link element, a new formula is presented to calculate the impact force and energy dissipation. To optimize the results of dissipated energy, a new relation between CR and impact velocity is suggested. As it seems that it is a need to have a reference curve to select impact velocity based on coefficient of restitution, several impact velocity and CR were evaluated. Using this curve, all of results can be optimized. Finally, a new equation of motion is assumed to select the best impact velocity and coefficient of restitution.

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Nowadays, buildings are built without required separation distance as many engineers do not consider building pounding effects. If adjacent buildings are not separated properly from each other, pounding can occur upon earthquake occurrence, and severe damages to the buildings can be observed even if they are well designed and constructed. Engineers should realize that building pounding is a serious hazard and it has to be considered during design and construction of buildings. There are many residential building complexes, service office, agencies, schools and hospital in cities around the world which are located next to each other as the cost of land is high. In this term, hospitals with emergency facilities and emergency centers have to be protected against the damages due to the significance of such structures prior and after earthquake. Many researchers have studied building pounding to calculate the dissipated energy and the impact force between two buildings during earthquake. For this challenge, they need to have a link element, which describes impact by using spring and dashpot. Several mathematical equations were suggested to calculate two mentioned parameters. In this paper, based on mathematic relation, a new relation of damping term of impact formula is simulated to measure impact force and energy dissipation. The results of this formula are compared with another suggested formula. As it was mentioned, different materials used in building constructions cause various dynamic behaviors during earthquake. Concrete structures are typically more rigid than steel structures in similar conditions. Consequently, lateral displacements of concrete buildings may also be less than lateral displacements of similar steel structures as stiffness of concrete buildings causes decrease in natural periods during earthquake. Naturally, large lateral nonlinear displacements under time history lateral loading in concrete structures may not be observed. Buildings can collide with adjacent buildings in left and right directions. For concrete buildings, however, the impact of pounding may be more significant than those on steel structures in most situations Many researchers have suggested new relations in terms of impact to increase the dissipated energy. Based on mathematic relation, they showed that energy dissipation depends significantly on stiffness, impact velocity and coefficient of restitution. For this challenge, by using a suggested link element, a new formula is presented to calculate the impact force and energy dissipation. To optimize the results of dissipated energy, a new relation between CR and impact velocity is suggested. As it seems that it is a need to have a reference curve to select impact velocity based on coefficient of restitution, several impact velocity and CR were evaluated. Using this curve, all of results can be optimized. Finally, a new equation of motion is assumed to select the best impact velocity and coefficient of restitution.

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Water-storage capacity of reservoir reduces mainly due to sediment laden. Turbidity current has an important role on sediment transfer in reservoir. It is necessary to study sediment interaction and flow in order to predict mechanism of turbidity current. In this paper effects of changes in entrance hydraulic condition of turbidity current on head velocity, layer-average thickness, layer-average velocity, body velocity and turbulent structure have investigated experimentally. The front velocity of the head of turbidity current was determined by video recording and body velocity and turbulence parameters measured by Vecterino. When the initial Froude number decreases the maximum velocity increases in body and head. Positive shear Reynolds stress near bed indicates that major contributor in this region is sweep or ejection while major contributor near interface is inward interaction or outward interaction. Entrainment is dominated at interface. The investigation shows that head velocity depends on inlet Froude number and inlet Reynolds number. Variation of head velocity along channel is exponential. The maximum reduction of head velocity takes place at  whereas variation of head velocity at  is negligible. Driving forces at  are inertial force and gravity force. Driving force decreases after hydraulic jump and only gravity force remains as driving force. Therefore head velocity is constant at . Head velocity increases when inlet Reynolds number increases. Body velocity increases when inlet Froude number decreases, as gravity force increases when inlet Froude number decreases. Effects of inlet Froude as number on body velocity is negligible at the end of channel. Negative value of body velocity at the interface of turbidity current and ambient fluid indicates entrainment phenomenon at this region. When inlet Froude number decreases, vertical component of velocity increases too,then maximum velocity approaches to the bed. Elevation of maximum velocity increases along the channel due to sedimentation of particles and decreases of vertical component of velocity. Body velocity decreases along the channel due to decrease of inertial force. Vertical Reynolds stress decreases when inlet Froude number decreases. Because of increase in particle turbulence dissipates and therefore vertical Reynolds stress decreases. Oscillation of vertical Reynolds stress is due to turbulence at this region. The maximum of vertical Reynolds stress tacks place near bed and interface of turbidity current and ambient fluid and minimum of vertical Reynolds stress tacks place near maximum velocity elevation. Shear Reynolds stress have two maximum values. One is near the bed and the other one is near the interface of turbidity current and ambient fluid. Maximum Reynolds shear stress is positive near bed and negative near interface. Minimum of Reynolds shear stress take place near maximum velocity elevation.

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In a vertical wind tunnel, in order to prevent persons or an experimental model from falling, a protective screen should be installed at the end of the nozzle section. Since the air has the maximum velocity at this section, the pressure drop due to the protective screen will be significantly high. On the other hand, as the protective screen is alternatively exposed to dynamic forces due to free fall of the floating persons or the model, the screen wires will experience fatigue. To prevent this, multi strand cables should be used in the manufacturing of these protective screens. In this research work, using the momentum difference method, drag coefficient for the multi strand cables and circular rods has been measured and compared. For this purpose, a hot wire anemometer (HWA) with a one-dimensional probe has been used. Results show that at Reynolds number in proximity of 2 × 103, the drag coefficient for the multi strand cable exceeds that of a circular rod by 16% and that this amount decreases with further increase in Reynolds number. The trend is such that for Reynolds number of 104, the drag coefficients of the multi strand cable and circular rod are almost equal.

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In this article, analytical solutions of low velocity transverse impact on a nanobeam are presented using the nonlocal theory to bring out the effect of the nonlocal behavior on dynamic deflections. Impact of a projectile (mass) on simply supported and clamped nanobeams are investigated using nonlocal Timoshenko beam theory. In order to obtain an analytical result for this problem, an approximate method has been developed wherein the applied impulse is replaced by a suitable boundary condition and initial momentum of projectile and nanobeam. A number of numerical examples with analytical solutions for nonlocal nanobeam and classical beam (steel and aluminum) have been presented and discussed. When the value of the striker mass is increased, the frequencies are decreased and the maximum dynamic deflection at the center of the beam is increased for both of the simply supported and the clamped-clamped nanobeams. The inclusion of the nonlocal effect increases the magnitudes of dynamic deflections and decreases frequencies. Furthermore, the mass and the velocity of the nanoparticle (striker) have significant effects on the dynamic behavior of nanobeam.

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An advance cooling method for buildings is use of radiant cooling system, which is not only economically feasible but also enhances thermal comfort for occupants. In this numerical study the flow and temperature fields in a room equipped with radiant cooling panel, either on the ceiling or on the wall, are studied. Outside summer design temperatures of Tehran and Semnan have been considered and to model the presence of an occupant a cube is placed in the center of the room with its external walls having constant heat flux. The results show that the vertical and horizontal temperature distributions become uniform and the maximum absolute air speed is around 0.2 m/s. The share of radiation heat transfer to the ceiling or the wall cooling panel is at least 58% or 65%, respectively, which increases due to presence of a human model. The net radiation decreases by increasing the panel temperature, but increases by increasing the outside temperature. The wall cooling uses less energy and regarding temperature and velocity distribution provides a better comfort condition