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During the last decades, many researches have been carried out on development of supplemental passive energy absorption devices especially hysteretic metallic dampers and different types of them with different capacities and potentials have been developed. The idea of buckling of thin-walled tubes and the use of this property was led to develop an accordion metallic damper (AMD) [Motamedi, Nateghi-Alahi-2007]. This damper utilizes the capability of accordion thin-walled tube for excitation of axisymmetric concertina buckling mode as a damping mechanism which in turn increases the amount of dissipated energy. In this paper filled accordion metallic damper (FAMD) is suggested and analytically and experimentally the behavior of AMD's and FAMD's under axial cyclic loading are investigated and compared. For this purpose, Firstly analytical studies based on Finite element method and nonlinear dynamic analysis was performed on FAMD's for the determination of the approximate preliminary specifications of different polymers for potential use. After specifying the preliminary material properties, 4 specimens include 2 FAMD's filled by polymeric foam and 2 AMD's were subjected to dynamic tension and compression actuator and the effect of filling AMD's by this polymeric foam on the some of important specifications of damper studied and try to use this method for improving and developing of AMD's. Based on the results obtained using the appropriate filling inside the AMD's is a suitable technique for the purpose of improvement the some of important specifications such as the number of cycles before failure, amount of dissipated energy and plastic capacity. The effect of interaction between foam and accordion thin walled tubes play an important role for this purpose especially in low capacity AMD's.

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Aims: Any surgery could be an anxiety-provoking event. A high level of preoperative anxiety may change the result of surgery. This study aimed to determine the effects of training intervention on anxiety in patients undergoing knee replacement.
Materials & Methods: This quasi-experimental study was conducted on 90 patients who were candidates for knee joint replacement surgery in teaching hospitals of Bojnord city in North khorasan Province in 2021. Patients were enrolled in three 90-minute sessions. In the first two sessions, the surgeon informed the patients about the disease, treatment approaches, surgery, and anesthesia, and in the last session, the clinical psychologist instructed them on how to control and deal with anxiety. Anxiety was assessed before, immediately after the intervention, and one day before surgery.
Findings: The mean scores of state anxiety before, immediately after the intervention, and one day before surgery were 44.38±10.76, 41.49±9.41, and 36.19±6.40, respectively. Moreover, the mean scores of trait anxiety before, immediately after the intervention, and one day before surgery were 43.87±10.81, 41.27±8.39, and 38.83±6.56, respectively, which show the effectiveness of the intervention in controlling patients' anxiety (p<0.05).
Conclusion: Informing the patients about their disease and how to deal with it and giving awareness about the effectiveness of the operation by the surgeon and the clinical psychologist is effective in controlling and reducing anxiety.

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In this paper, ratcheting behavior of stainless steel 304L cylindrical shells under cyclic combined and axial loadings are studied, experimentally. Tests were performed by a servo-hydraulic INSTRON 8802 machine and the shells were fixed normal and oblique under 20 degree and subjected to cyclic loads. In this paper, the effect of length of cylindrical shell and the effect of angle of cylindrical shell on ratcheting behavior were investigated. Based on the experimental results, it was found that bending moment plays a crucial role in waste of energy and increase in plastic deformations. Seen that due to the existence of bending moment in different cross section of oblique cylindrical shell, there are more plastic deformation and accumulation in comparison to normal cylindrical shell. Also, analyzing the loading history of cylindrical shell under combined loading, it has been seen that by keeping the mean force at constant value while increasing the force amplitude, the ratcheting displacement became higher and by the prior load with higher force amplitude retards the ratcheting behavior and plastic deformation with samller force amplitude.

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Application of carbon nanotube reinforced polymers in space industry is widely dispread due to the unique and multi-purpose properties of them Therefore, extraction of electrical and electromagnetic properties of nanocomposite materials in the frequency band of 12.4 to 18 GHz is an important issue in their development procedure. In this paper, experimental investigations on electrical and electromagnetic properties of carbon nanotube reinforced polymers are performed. The investigated properties include AC and DC electrical conductivities, permittivity, transmission and reflection coefficients, loss tangent and skin depth in Ku frequency band (12.4-18 GHz). The in situ polymerization method is selected to fabricate multi-walled carbon nanotube (MWCNT)/Vinylester nanocomposite. Ultrasonic device is used for dispersion of CNTs in resin and then Vector Network Analyzer (VNA) is employed for measurement of electrical properties of specimens. Weight fraction of MWCNT is chosen between 0.1 to 3 % in order to evaluate the influence of CNT content on investigated properties. Finally, equivalent circuit model is used to describe the observed behavior on the basis of semi-empirical study.

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Heat transfer of Alumina/water nanofluids in a uniform-temperature porous pipe has been investigated in a wide range of Reynolds number, i.e. 700<Re<5000. Investigation of force convective heat transfer of nanofluids in a porous pipe with uniform wall temperature has not been considered completely in the literature. In this experimental study, Alumina nanofluids with different volume fractions have been completely employed. By measuring the nanofluid temperatures, the Nusslet numbers have been reported as a function of the Reynolds number. Also, the pressure drop of nanofluids inside the porous pipe has been measured. The accuracy of the experimental results has been also validated by the presented theoretical formulas in the literature. The result shows a considerable increase in the Nusslet number by using nanofluids instead of water. Convective heat transfer of a porous pipe has been also studied as a novel method to increase the heat transfer rate. The related results show a significant increase in the heat transfer in the presence of porous medium. Both heat transfer and pressure drop of nanofluids in the porous pipe have been also reported and discussed.

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A novel geometrically nonlinear high order sandwich panel theory considering finite strains of sandwich components is presented in this paper. The equations are derived based on high order sandwich panel theory in which the Green strain and the second Piola-Kirchhoff stress tensor are used. The model uses Timoshenko beam theory assumptions for behavior of the composite face sheets. The core is modeled as a two dimensional linear elastic continuum that possessing shear and vertical normal and also in-plane rigidities. Nonlinear equations for a simply supported sandwich beam are derived using Ritz method in conjunction with minimum potential energy principle. After obtaining nonlinear results based on this enhanced model, simplification was applied to derive the linear model in which kinematic relations for face sheets and core reduced based on small displacement theory assumptions. A parametric study is done to illustrate the effect of geometrical parameters on difference between results of linear and nonlinear models. Also, to verify the analytical predictions some three point bending tests were carried out on sandwich beams with glass/epoxy face sheets and Nomex cores. In all cases good agreement is achieved between the nonlinear analytical predictions and experimental results.

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Woody debris accumulates in front of bridge piers, reduces the flow area, deviates the flow and increases the velocity around the bridge piers. Debris accumulation in front of bridge piers increases the downward flow, and shear stress around the bridge pier, therefore, the scour hole depth increases and bed degradation accelerates. Most of previous researchers focused on the scour depth around the bridge piers, and less researchers have investigated the effect of debris accumulation on the scour depth. To the best of our knowledge, the effect of debris accumulation on the scour depth has not been reported in previously published literature, as explored in this work. The purpose of this study is to experimentally investigate the effect of accumulation of woody debris in front of a square pier with a parabolic nose on the scour depth. The experiments were performed in clear water condition, with and without debris accumulation and with 20, 30 and 40 l/s discharges and for different debris dimensions. The experiments were performed in a sixty centimeter width channel at the hydraulic laboratory of Shahrekord University. Previous field studies showed that most debris accumulates in front of bridge piers in rectangular shapes, therefore three different rectangular shapes debris are designed and are placed in front of bridge piers during the experiments. Since, performed experiments at twelve hours showed the maximum equilibrium scour depth occurs at the first seven hours, therefore, all experiments are done in 420 minutes. The results showed that when woody debris is placed over, at, and below the water surface respectively, the ratio of scour depth to the scour depth of control sample is 2.2, 2.36 and 1.44, respectively. Moreover, when the percentage of blockage (ratio of the occupied flow area by debris to the flow cross section) is 30% and when debris is located below the water surface, the maximum scour depth will occur (2.36 with respect to the control sample). Also, the comparison between a square pier with parabolic nose and a sharp nose piers at the same hydraulic condition, show when there are no debris, the scour depth around the square pier with a parabolic nose is less than the scour around a sharp nose square pier (1.5 times). For the case in which debris are placed in front of bridge pier, the scour depth, width, and length around a square pier with a parabolic nose are significantly decreased with respect to a sharp nose square pier (2.3 times). Also, using dimensional analysis an equation is presented for predicting the maximum scour depth around a square pier with a parabolic nose in presence of woody debris accumulation. The results show that there is good agreement between predicted and observed scour depth.

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When two bodies slide on each other the asperities are engaged and friction is created. By superposing ultrasonic vibrations to one of the bodies, the friction force is reduced .This phenomenon is widely used in metal forming and metal cutting. In this research, experimental study of the effect of ultrasonic vibrations has been on sliding friction force in longitudinal direction. For this purpose, set-up was designed and fabricated. The main components of the set-up, including generators, transducers, first engaged body and second engaged body. The Set-up was installed on the machine lathe for investigation of the effect of ultrasonic vibrations on sliding friction force in longitudinal direction. The experiments were performed for eight different performance conditions. Next, the effect of each parameter ultrasonic wave velocity, roughness and material of contact surfaces were studied on the reduction of the friction force due to addition of ultrasonic vibrations. The result show that range of reduction friction force due to addition of ultrasonic vibrations in longitudinal direction is between 40 to 100% for the different performance conditions also friction force significantly reduced by increasing ultrasonic wave velocity so that friction force can be brought to zero by significant increase in ultrasonic wave velocity. The results also show that friction force has a more reduction for the surface has a less roughness. Aluminum-aluminum surfaces can be more reduction friction force from aluminum – steel surfaces.

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Hydraulic jump is a rapid and sudden transition from a high-velocity supercritical flow to a subcritical flow in an open channel flow. Stilling basins are used to control the hydraulic jump at the downstream of chutes, sluice gates,… End Sills, baffle blocks and negative steps are often used to control hydraulic jumps in stilling basins. The present study focuses on the formation of hydraulic jump in the new type of stilling basins with stepped sills. Extensive experiments were conducted in a rectangular flume 0.6 m wide, 12.0 m long and 1.0 m deep, with various discharges from 30 to 120 l/s. Water was pumped from an underground sump into a head tank and the discharge was measured with a ultrasonic flowmeter. At the downstream end of the head tank there was a sluice gate into the flume. The edge of the sluice gate has a streamlined lip in the shape of a half-cylinder of diameter 20 cm to minimize flow contraction and provide a uniform supercritical flow. A point gauge with an accuracy of 0.1 mm was used to measure water depths. In order to visualize the flow field, the dye-injection method and a high speed camera were employed. A tailgate located at the downstream end of the flume was used to control the tailwater depth. The effects of stepped end sills on hydraulic jumps were investigated experimentally. Firstly, dimentionless parameters affecting the hydraulic jump on stepped sill introduced using Buckingham π theorem. The effect of important parameters such as approach Froude number (Fr1), relative tailwater depth (〖y_t/y〗_2^*) and the end sill geometry (shape and relative height of sill (s/y1)) on hydraulic jump were investigated. The hydraulic jumps over stepped end sills were classified into A-jump, B-jump, minimum B-jump, C-jump and minimum C-jump. By changing the type of flow from A-jump to minimum C-jump, the jump is going to sweepout from basin. A-jump is entirely formed in the basin and at the upstream of sill. In the case of minimum C-jump, most of the surface roller of jump formed at the downstream of sill. The flow types are presented in the form of 6 different diagrams as functions of the relative step height s/y1. By increasing the tailwater depth, sill height, the probability of occurance of hydraulic jump in the stilling basin increased. It was found that the sill with 2 steps have better performance in stabilizing the jump in the stilling basin as compare to sill with 3 steps. By increasing the approach Froude number, the jump began to sweep away from basin. By knowing the initial condition like upstream velocity and upstream froude number, tailwater depth, sill height and its number of steps the toe distance from sill can be found out with desirable accuracy.

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Study air infiltration into the building in several ways such as energy, air quality, thermal comfort and pollution entering in the building is very important. In this context, many studies have been conducted in different countries. In our country due to the use of steel doors and windows, do independent research on the gap size and air infiltration is necessary .In this study, by practical view and in order to localize results, based on a field study, the actual dimensions of the gaps around conventional doors and windows in Iran is measured. The results of these measurements are used to simulate gaps, then with experimental study, air infiltration rate of this gaps is calculated at different pressures. In present study, after investigating the effect of different aspects of gaps on air infiltration rate, two common equations, power law and quadratic equation, in order to fitting data were compared. Results show that power law equation can adapt better to the experimental data. Coefficients of the power law equation to estimate the air infiltration rate through the gaps was presented. By analysis of the results, due to the proximity factor of the pressure difference to the number 0.5 in most of the results, it was concluded that the Bernoulli equation can be used to predict the air infiltration rate through the gaps. This equation is better compliance with laws and physical principles. Discharge coefficient of the Bernoulli equation for gaps with different dimensions are calculated.

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Side weir is one of the most important structures in flood treatment projects that are designed provided the main channel bed is rigid. However, in the most practical channels, the main channel bed is movable and the changes in bed can produce wavelike patterns known as bed forms and another additional effect of side weir on bed forms is that it causes an aggradation of sediment particles in front of itself. These two products of using side weir in movable beds cause an additional bed resistance in comparison with the state that there isn’t any weir on sidewall of main channel and so the flow level with using side weir will rise subsequently and this means more diversion ratio. Thus, In order to study the effect of side weir hydraulic and geometric properties through Froude Numbers, diversion discharge ratios and flow depths on bed forms and its effect on design conditions, the present research work is carried out. A set of 9 experiments were conducted in a flume with dimensions of 0.85 m width, 0.40 m height and 10 m length on a mobile bed having median sediment particle size of 0.23 mm running with side weirs of crest lengths of 20, 40 and 60 cm . In addition a set of 3 experiments without using a weir were considered as bench mark experiments for comparison purposes. After running a determined flow in flume regarding with the bed profiles should reach a balance it was stopped after 1-3 hours. The bed topography at the end of each experimental run was recorded using automatic bed profiler in a length of 220 cm of main channel. This topography was recorded in a net of points that were distributed in a distance of 5 cm in length and 3 cm in width. The dimensions of bed forms were then determined using the well-known crest-through method. The results indicated that the effect of flow depth, discharge, and diversion ratio on bed form dimensions are significant and increasing these parameters cause an increasing influence on bed form dimensions. In this study 4 equations are suggested that both of them are for bench mark experiments and two others are for main experiment. The coefficients of these relations were determined by Solver Add In program in Excel with using 80 percent of data that were selected in chance and then they were verified with using remaining 20 percent of data. Verification of relations also illustrated that for both length and width of bed form in main experiments the maximum error of related equations is 50 percent and maximum error of relations for bench mark experiments is 30 percent. Analyzing these relations revealed an important influence of applying side weirs on lateral variation of bed form dimensions in the main channel so that it is indicated that bed form length and height near side weir will increase up to 70 and 2 percent of channel width, respectively, in comparison with the experiments that side weir is not used.

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Vacuum tube solar water heaters are one of the most common types of solar water heaters, and they have been used widely in recent years. Evacuated tube solar collectors compared to flat plate collectors have higher absorption coefficient and lower heat loss. Many factors are effective on thermal efficiency of evacuated solar water heaters and many studies have been done to increase their efficiency. In this study, thermal performance of a modified model has been investigated experimentally. Two laboratory samples, one of them with the modified structure and the other like commercial samples have been made and their performance has been studied under equal solar radiation and ambient temperature. The results have shown that this structure modification has a positive effect on collector performance. This change has made the temperature distribution in the pipe and tank more uniform, and has increased the efficiency to 11 percent. Absorbing thermal energy in the modified model was more than typical model about 25 percent in duration one hour. Also, effects of solar radiation on the average temperature of water in the storage tank have been investigated in both cases. In this study, an experimental method is used to calculate the radiation received to vacuum tubes.

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Although many researchers investigated the effect of geometrical imperfection on the buckling load of unstiffened shells, the stiffened shells were not studied yet. In this paper, the effects of geometrical imperfection the buckling load of unstiffened and stiffened composite shell with and without cutout are investigated. For this goal, several specimens are manufactured and tested. The mechanical properties of fibers and resin matrix and volume fraction of fibers in the shell and the stiffeners are determined based on the standard tests. Finally, the mechanical properties of each component are calculated by micromechanical relations. These properties are used for finite element modeling by ABAQUS package. Linear eigen value analysis and nonlinear RIKS method -which can consider the geometrical imperfection- are used. FE results are validated in comparison with experimental tests. Using FE model, the effects of imperfection amplitude on the buckling behavior of unstiffened and stiffened shell with and without cutout are studied. The results show that geometrical imperfections have more effect on the buckling load of unstiffened shells in comparison with stiffened ones. Nevertheless, ignoring these imperfections and using eigen value analysis overestimate the buckling load. This fact is more evidence for shells without an opening. In perforated shells, the cutout itself represents an imperfection that is much more significant than geometric imperfections.

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In the present study, free surface vortex dynamic was experimentally investigated in a horizontal intake. Air entrainment rate into the intake due to the air-core vortices was also discussed. The results presented are the relationship between the vortex type and the intake hydraulic parameters, general pattern of surface displacement of the vortex core and its relation with the vortex type, the required time duration to fully development of the vortex core, and finally evaluation of the vortex induced air entrainment rate. In this research by defining intake number as intake Froude number over the intake relative submergence, a relationship was established between the vortex type and the intake number. Moreover, it was shown that while the intake number increases, surface instability of the vortex core decreases, in which, for the intake numbers greater than one, surface movement of the vortex core is limited to an area of the twice of the intake diameter. Then, another relationship was also established between the time requirement of the vortex air-core formation and the intake number, and it was shown that there will be an exponentially decrease in the mentioned time scale, while the intake number increases. In this context, a relationship was suggested and compared with one of previous works. In the last section, the dependency between air entrainment rate due to the air-core vortices and the intake number was considered, and another relationship was also suggested and compared with previous works.

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In this study, a galloping-based energy harvesting system is designed using a nonlinear energy harvesting sink (NES). In doing so, electromechanical equations of motion for the energy harvesting system are derived and the theoretical results are validated with experimental results. Then, three steps are presented to make system work efficiently. In the first step, several cross-section geometries for the bluff body are investigated and the results are verified by the Harmonic Balance Method. These results indicate that isosceles triangular section can harvest more energy than the other ones. In the second step, effect of changing the electrical load resistance on electromechanical behavior of the system is investigated and it is demonstrated that the maximum energy is harvested for load resistance values of more than 1 MΩ. In the third step, influence of changing the tip mass on the system is studied and it is shown that increasing the tip mass leads to increase the output voltage while the bluff body amplitudes remain constant. Consequently, the system is designed to work with the maximum possible tip mass which is about 35.3 gr. Finally, this system with a bluff body of isosceles triangular section can generate 700 mV using the load resistance value of 10 MΩ in the wind speed of 2.5 m/s. This system with the total mass of less than 500 gr and low-amplitude oscillations is designed to work properly in low wind speeds and presents an efficient application for low-power energy harvesting systems.

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In this study, application of a dynamic vibration absorber system consists of two symmetric cantilever beams with tip mass and piezoelectric layer, in order to suppress undesired vibrations and harvest electrical energy, is studied. The main vibratory system is a simply supported beam, which is excited by a DC motor with rotating unbalance mass. To derive the governing electromechanical equations, the Euler-Bernoulli beam theory and the energy method are used. Then the governing electromechanical equations are experimentally validated and accommodation between theoretical and experimental results is shown using several frequency response plots. Using the non-dimensional governing equations, effect of changing the system parameters such as the tip mass, load resistance and length of the cantilever beam is studied. Then, considering ability of system to effectively suppress undesired vibrations and increase the harvested electrical energy, the proper range for selecting the non-dimensional tip mass and non-dimensional load resistance is presented. Finally, using the so-called perfection rate parameter, the best parameters, to have a good vibration suppressor and energy harvester, are obtained. Results shown that both of energy and vibration considerations can be satisfied using the system.

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In this paper, the effect of nozzle divergent section geometry on fluid flow and heat transfer within the convergent-divergent nozzle numerically and experimentally is investigated. Axisymmetric supersonic flow simulation for the converging-diverging nozzle is conducted. The flow field is a steady turbulent two-dimensional flow. The working fluid is a combustion product and is considered as a compressible ideal gas. The flow field is simulated using the commercial code FLUENT. The equations are discretized implicitly with the second order of accuracy. In this study, two convergent-divergent nozzles have been analyzed that the divergent part of one is a cone-shaped and the other is bell-shaped. The calculated parameters in the simulation have been compared with the experimental results. Based on the simulation results and the values obtained in the experimental test, the error is less than 4% that is acceptable and appropriate. According to the results, flow simulation accuracy is appropriate.
 

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Wave conditions have a significant effect on the hydrodynamic behavior of OWC. As the interactions of the WEC and the incident waves are important, therefore, due to the importance of coefficients in evaluating the performance of the OWC, in this paper, the experimental evaluation of dimensionless hydrodynamic coefficients of a MC-OWC is applied. To define the experimental tests, considering the installation location of the converter on the break water, the conditions of the Caspian Sea implemented. Calibration and uncertainty analysis have performed, experimental tests have been carried out in the wave tank of the BNUT. According to the results, assuming a dimensionless water depth, with increasing dimensionless frequency of the wave, the dimensionless coefficient of transmitted wave, the dimensionless coefficient of reflected wave, dimensionless coefficient of discharge and the dimensionless coefficient of pressure increase. The results showed that due to the change of dimensionless wave number from 1.9 to 3.3, discharge coefficients, reflected wave, pressure and transmitted wave are 1.6 times, 2.2 times, 2.8 times, respectively, are 3.5 times, the dimensionless coefficient of the transmitted wave is highly sensitive to the wave conditions; the dimensional coefficient of discharge will have less changes compared to other coefficients. On the other hand, the results showed that the OWC in this study has an efficiency of 41.8% in the best case. This efficiency occurs at the dimensionless natural frequency of 0.88 and the dimensionless water intake depth of 0.032; under these conditions, the amplitude of water fluctuations inside the OWC reaches 9.6 cm.