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Fire can not only lead to many human and financial losses, but also can cause structures to collapse and destroy them. For this reason, it is necessary and inevitable to protect buildings against fire and conduct more research in the field of better understanding the effects of combining different materials with each other and obtaining materials with greater resistance to fire. Concrete and concrete structures are always used by construction engineers due to their resistance, availability and resilience against fire. Ordinary concrete loses its strength at high temperatures, and the use of unreinforced concrete is not very useful due to its brittleness and weakness in tensile strength. In concrete, the tensile strength is lower than its compressive strength, and for this reason, researchers are trying to increase the resistance to fire and heating by improving the tensile strength of concrete. Reinforcing concrete with rebar is always a solution to increase the tensile strength in concrete parts, one of the most important weaknesses of using rebar in concrete is that the reinforcements form a small part of the concrete cross-section and actually cause the concrete to be inhomogeneous. In this research, double-bent steel fibers have been used to overcome the mentioned weakness and reinforce the concrete. It should be noted that concrete containing steel fibers has favorable compressive and tensile strength due to the high tensile strength of steel fibers. In order to achieve this goal and achieve fiber concrete that has good fire resistance, we defined seven different mixing plans with different percentages of steel fibers and lubricants. Concrete samples were produced using double-bent steel fibers in amounts of 0.5, 1, and 1.2 percent by volume of concrete and superlubricant in 0.5, 1, and 1.3 percent by weight of cement, and then in Cubic molds with dimensions of 10x10x10 cm and cylindrical ones were sampled as standard, and after setting the cement, the 28-day-old concrete samples, after heating and placing inside the electric heater with different temperatures, were divided into two The method of gradual cooling with ambient air and fog spraying (water spraying) is similar to what firefighters do when extinguishing a fire, after measuring the amount of weight loss of the heated samples, the weight loss values ​​were presented in the form of a diagram, then the samples were subjected to tests Compressive strength, tensile strength (Brazilian test) and ultrasonic wave speed (ultrasonic test) were placed, and the results and data of each of them for each mixing design were presented in the form of a diagram after examination and classification, so that the effect of high heat on Concrete containing steel fibers and super-lubricant should be determined. The results clearly showed the improvement of the tensile strength in three volume percentages of fibers by 14.6, 16.8 and 64.5%, respectively, compared to concrete without fibers, and also the compressive strength of concrete after bearing the heat of 250 degrees Celsius and cooling to the fogging method had 44.5, 31.6, and 9.3 percent, respectively, and in the gradual air cooling method, the compressive strength was 43.3, 44.9, and 50 percent, respectively.


 

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Variable rate spray applications using proportional control systems can greatly reduce pesticide use and off-target contamination of environment in orchards. Variable rate spraying of the canopy allows growers to apply pesticides only to the target, only use the correct quantity according to canopy size, season and growth stage and to apply plant protection products in an economic and environmentally sound manner. A major challenge is the reduction of agrochemicals used as Plant Protection Products (PPP) while achieving suitable deposition on the canopy. Spraying efficiency can be improved by reducing the spray losses associated with deposition on the ground and off-target drift. Adjustment of application rate proportional to the size and shape of tree crops has shown high potential for reducing agrochemicals in automatically controlled sprayers. In recent years target detection methods have been developed by using advanced techniques such as vision and laser scanning systems or simpler ultrasound, infrared and spectral systems. These systems have made it possible to develop geometric maps of trees allowing site-specific management of orchards. Variable rate spraying can thus be utilized as a methodology for applying the required amount of PPPs to the canopy while preventing over dosage as well as drift. Utilization of sensors to monitor canopy, distances and location ensures better use of expensive inputs, resulting in a sustainable approach to an important practice. This paper discusses various methodologies available for determination of canopy structural parameters and introduces some applicable commercial systems while pointing out their similarities and differences.  

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Research Subject: Optical sensors based on porous coordination polymers or metal-organic frameworks (MOF) with luminescent properties with high sensitivity and selectivity are considered as important identification tools in chemical and environmental research. Today, pesticides/herbicides are widely used in order to protect the widely used food resources of human society against pests and to preserve the richness of arable land against weeds and unnecessary things in industries. Agriculture is considered. A large or chronic amount of these compounds can cause high levels of toxicity in humans, animals and plants and endanger the lives of organisms. Therefore, the identification of this group of compounds is of great importance.
Research Approach: In this study, metal-organic framework UiO-66-NH₂ fluorescence nanosensor (1) was synthesized to identify the herbicide Trifluralin (TFA) by ultrasonic method. The properties of nanosensor 1 were identified by X-ray powder diffraction analysis, infrared Fourier transform, thermal analysis, photoluminescence spectra, ultraviolet-visible spectrophotometry, and scanning electron microscopy. The blue emission of compound 1 caused by n-π* electron transfers of 2-aminoterephthalic acid ligand was investigated to identify TFA. The experimental results show that the blue fluorescence emission of nanosensor 1 is turned off in the presence of TFA molecule and the gradual increase in its concentration.
Main Results: Nanosensor 1 is associated with fast, stable, selectable response and high sensitivity in determining TFA. Considering the good linear correlation of the fluorescence response of nanosensor 1 to TFA concentration in the range of 10 to 100 µM and the lowest detection limit (LOD) equal to 2.32 µM, it indicates the reliability and practicality of the synthetic nanosensor in identifying TFA herbicide.

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Research subject: Using microwave and ultrasonic waves is a novel method in the petroleum industry that has been investigated for various purposes. Due to polar elements such as oxygen, nitrogen, and sulfur, oil molecules are affected by the electric field of microwave waves and create dipole moments that generate hotspots, increasing the temperature of the oil and breaking down heavy compounds such as asphaltene. Ultrasonic waves eliminate intermolecular forces by creating tiny bubbles and bursting them. It also leads to the breakdown of heavy molecules such as asphaltene.
Research approach: In this study, crude oil was exposed to microwave and ultrasonic radiation, and changes in its properties were investigated. The effects of changing parameters such as power and time on crude oil properties were also examined. Changes in the specific gravity and API can indicate the extent of the breakdown of heavy molecules such as asphaltene and improvement in crude oil quality.
Main results: Using microwave and ultrasonic waves can reduce the viscosity of crude oil by 12.4% and 6% and increase the API by 2.8 and 1.2 degrees, respectively. Asphaltene reduction due to microwave and ultrasonic waves is 9.3% and 4.3%, respectively, indicating the breakdown of these compounds and the conversion to smaller compounds soluble in oil, resulting in improved crude oil quality. The EDS results show an increase in the weight percentage of carbon and the reduction of elements such as oxygen and sulfur, which confirms this issue. Examining crude oil structure under microwave and ultrasonic radiation showed that microwave waves, in addition to affecting straight-chain hydrocarbons, also reduced aromatic compounds. However, ultrasonic waves had a more significant effect on straight-chain hydrocarbon structure.

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The aim of present study is to investigate the kinematics of tool-workpiece’s relative movement in conventional and ultrasonic-vibration assisted turning (UAT). The kinematic analysis of UAT shows that the movement of cutting tool edge relative to the workpiece resulted from the cutting speed, feed speed and tool’s vibration affects the lateral machined surface of workepiece and leaves a repeating pattern of crushed and toothed regions on it. This results in an increase in the surface hardness of the lateral machined surface in comparison with conventional turning (CT). A model of the tool-workpiece’s relative movement has first been developed in the present study. This model predicts a surface hardening effect for the lateral surface in UAT in comparison with CT. Several experiments were subsequently carried out employing a surface micro-hardness testing machine and an optical microscope to verify the predicted results.

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The spring-back of a work-piece during machining operation causes dimensional error of the work-piece. In the present study, the spring-back of work-piece in ultrasonic-vibration assisted turning and conventional turning has been modeled. It is illustrated that the reaction of the work-piece in high frequency vibration cutting is similar to a static behavior, whereas the spring-back in this process is theoretically and experimentally smaller than the conventional cutting leading to smaller error. A method has also been proposed to obtain the errors caused by rigid assumption of the spindle assembly used for correction of the results.

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In certain applications, it is improtant to measure the mechanical properties of steel with high accuracy. These properties are usually measured by destructive methods. However, the small changes made during heat treatment processes are not usually detectable by destructive methods. Ultrasonic non destructive testing is an alternative method that can be used for measuring the mechanical properties of steels. In this paper, the ultrasonic method has been used for measurement of meachanical properties of AISI D6 steel samples processed by various heat treatment processes. Each sample has a differnet micro stucture and hardness due to its specific heat treatment. To find the meachanical properties, the velocity of longitudinal and shear ultrasonic waves were measured for each sample. Comparison of the results obtained from ultrasonic measurements with those available in reference tables shows that the ultrasonic non destructive method can measure the elastic properties of AISI D6 samples with high accuracy.

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Abstract- Low frequencies vibration is known as a method for stress relieving of metals. This paper shows that the high frequency vibration (ultrasonic) is also a promising method for stress relieving. In this paper the effect of parameters including stress relieving time, vibration amplitude, grain size and pre-load on samples are investigated. In order to evaluate the residual stress before and after ultrasonic relieving process Almen test was used. The samples were made according to Almen standard and after heat treatment, were shot peened so that, the compressive and tensional residual stress induced into the samples, then the stress relieved by means of ultrasonic vibration. Results show that the residual stress has decreased about 46 percent for coarse grain samples and 27 percent for fine grain samples. Also it was found that the most effective factor on the stress relieving rate is the grain size and the pre-load has the least effect.

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In this study, the structural health of a thick steel beam, made of ST-52, is inspected by ultrasonic guided wave propagation method using piezoelectric wafer active sensors that is one of the most important techniques of on-line structural health monitoring. The key parameters of the diagnostic waveform such as excitation frequency and cycle number are determined in relation to beam dimensions as well as pulse-echo configuration of PZT active sensors attached to the beam. Finite element simulations were conducted to characterize wave propagation in the beam, and the signals of wave propagation were experimentally measured. For signal processing and feature extraction, continuous wavelet transform and scaled average wavelet power technique are used. Using the extracted features, probable existing damage in the structure is detected, localized, and intensified. The acquired results are representing a higher precision of the implemented method for damage identification and characterization with respect to a previous study.

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One directional and elliptical vibration cutting of IN738 at ultrasonic frequency has been investigated both experimentally and by FEM in the present study. The influence of each process on the cutting force was studied. The FEM modeling was carried out by using MSC-MARC. The results were compared with the experimental findings of the conventional cutting. The ultrasonic vibration was applied to a rigid cutting tool along the cutting velocity in one directional vibration cutting. In elliptical vibration cutting the vibration was applied both along the cutting velocity and in the chip flow direction. The experiments were carried out on an ultra precision CNC lathe with single crystal diamond tools. The same effects were confirmed in the machining practice and by FEM. It was quite feasible when machining IN738 to obtain the advantages of elliptical vibration cutting already reported for some other materials such as copper, aluminum, tungsten and super alloys.

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Abstract- This research develops a Lamb wave technique to determine the dispersion curves of a two layered bonded component: an aluminum sheet attached to a composite layer by means of a cohesive. A commercial finite element code (ABAQUS Explicit) is used to determine the dispersion curves of the Aluminum-cohesive-composite multilayer component. The finite element model includes three plain strain layers that the middle one is cohesive. Then a lamb wave is propagated in the model and some output signals are received. The dispersion curves are obtained by using 2D Fourier transformation of finite element model output signals. In addition, to produce various modes, experiments are carried out on a composite-aluminum assembly using two 2 MHz variable angle transducers. Comparison of modes obtained from finite element method and experiments shows that group velocities are almost identical. Hence, good agreement between finite element method results and experimental results indicates that finite element is reasonably accurate for determination of dispersion curves.

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In tube hydroforming process, due to friction condition, uniform wall thickness, as well as sharp corners may not be achieved. Use of ultrasonic vibration can improve the contact conditions at the tube-die interface. The current work studies the effect of applying ultrasonic vibration on wall thickness and corner filling of hydroformed tubes. Firstly, a numerical model based on geometric relationships and stress-strain state has been established by which wall thickness and corner radius of hydroformed tubes can be obtained. In this model, the ultrasonic vibrations affect the nonlinear friction conditions at the tube-die interface. By comparing the FEM models of tubes in two cases of with vibration and without vibration, it is possible to investigate the effects of vibration on wall thickness and corner filling. The results indicate superimposing ultrasonic vibrations to the process will increase corner filling ratio of the tube significantly, and more uniform tube wall thickness will be achieved.

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The advantages of ultrasonic flow meters is measurement without pressure drop. In this article an ultrasonic flow meter based on transit time measurement by Heterodyne technique is designed and fabricated. The principles of the flow meter, selection procedure of transmitter and receiver transducers and the excitation frequency of those are presented. A closed loop pipeline has been designed in order to test the flow meter. The results present that the flow measurement in range of 22 up to 37 Liter per second contain errors in range of -2.7 up to +4.2 present of actual flow.

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In this study the interaction of material and ultrasonic vibration of workpiece at different pulse on times (Ti) and discharge currents (I) in the electrical discharge machining (EDM) has been studied. The materials of machined samples were AISI H13 tool steel and FW4 weld steel. The results show that ultrasonic vibration of workpiece, independent of workpiece material increase material removal rate (MRR) and reduce tool wear ratio (TWR) and surface roughness. Also the results indicate that the effect of ultrasonic vibration on the material removal rate increase of FW4weld steel is higher than AISI H13 tool steel, and the reduction of tool wear ratio of FW4 weld steel is more than AISI H13 tool steel.

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Ultrasonic technology has been applied in many industrial processes such as ultrasonic machining, welding, cutting, sewing, homogenizing, etc. In an ultrasonic system, acoustic horn transmits the vibration energy of ultrasonic transducer to the application area and amplifies the oscillation amplitude. Depending on the application and industrial operating conditions, different horns with different geometries and magnifications are required to be designed. In the present study exponential horns with rectangular cross-section for application in ultrasonic assisted grinding process are designed and analyzed. An analytical approach is applied to model this type of horns. For evaluating the analytical model, some acoustic horns are designed using analytical method and then analyzed by the finite-element method (FEM) in ANSYS. Then, their design parameters such as resonance frequency and amplification factor are compared and verified. A very good agreement is obtained between the results of analytical modeling and those of FEM simulation. Furthermore, geometrical modification was introduced as a solution to coincide the vibration related parameters of the horn to the desired design values. Moreover, a horn-workpiece assembly for applying in ultrasonic assisted grinding was simulated.

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Virgin olive oil due to having unsaturated fatty acids is exposed to various types of corruptions such as enzymatic reactions and lipid oxidation. One way to prevent oxidation of oils and fats is addition of antioxidants. Rosemary due to phenolic compounds and other antioxidant compounds have antioxidant as well. In this study, the extraction phenolic compounds of rosemary leaves in virgin olive oil with was performed using by ultrasonic technique. In this method, rosemary leaves with three levels (5, 7 and 10%) and three ultrasonic times (10, 15 and 20 minutes) were added to the olive oil. Phenolic compounds present in the extracts, was measured. The results showed that in the ultrasonic method the sample of virgin olive oil with 10% rosemary and 10 minute extraction time has the highest total polyphenols (457.59 ppm). In this case study the effect of this extract in retarding oxidation of virgin olive oil during the 4-month by determining the peroxide value, thiobarbituric acid, oxidative stability, at the end of each month were reviewed. After four months keeping, the ultrasonic's peroxide number, the thiobarbituric acid (20.75meq O₂/kg oil, 1.32 molonaldehyde/kg oil, respectively) significantly decreased. The results of antioxidant activity of the extracts using rancimat method showed that during the period of induction at 110 °C  in the ultrasonic's sample (29.10 hours) with respect to control's sample (6.28 hours) are increased. The acidity value of the ultrasonic's sample (2.05 FFA %) and thermal's sample (1.84 FFA %) are less than the control's (3.18 FFA %). Measurement results showed that the amount of chlorophyll pigments within ultrasonic's sample (1.4mg/kg) had the highest value and with respect to control's sample (0.63mg/kg) had high value. Also in the sensory evaluation, the ultrasonic's sample has top rated in terms of taste, odor, bitter and won general acceptance. Therefore, the phenolic compounds in the olive oil containing rosemary and extracted by ultrasonic method, be able to retard the oxidation process well. Thus, rosemary can be recommended as a source of natural antioxidants for increase virgin olive oil oxidative stability.