International Journal of Engineering
Volume:33 Issue: 10, Oct 2020

Inefficient project planning and control have been identified as the main contributor to the reduced performance of the construction industry in Iran. Meanwhile, improper use of planning and control software packages (PPCSPs) in these projects can be a key factor in this reduced performance. This study investigates different aspects of the PPCSP applications to draw the role of PPCSPs in the planning and control processes of construction projects in the country using a survey-based method. It is found that only 32.5% of the construction companies in Iran highly or very highly use PPCSPs. The low level of skill and the lack of management support are two main contributing factors to this reduced PPCSP application. The quality of the academic and vocational project management training programs and the lack of dependable PPCSP technical support are argued as possible sources of the issue. The identified PPCSP pattern in Iran is compared with the results reported for several developed and in-transition countries. This comparison reveals that Iran and in-transition countries fall deeply behind in employing PPCSPs in their construction projects compared to the developed countries.

The present study was based on a promoting statistical method known as response surface method (RSM). RSM has been applied as an efficient method to optimize many physical applications in industry for more than two decades. In the current study, the RSM was utilized as a platform to develop models as a function of some prescribed input factors to predict mechanical properties (responses) of frozen soils (i.e. peak tensile/compressive strength, elasticity modulus). Besides, RSM makes it possible to find significant factors and probable interactions as well. A widespread literature review was conducted and three case studies were chosen to evaluate the performance of the RSM in developing precise models and finally an optimum experiment. For each case study, less than half of the available data (an average of 40.8%) was employed to develop models and the remaining part was employed to evaluate the validity of derived models. A comparison between predicted and measured data showed a good agreement with a significant level of 0.05. This indicates that upon using the model a hundred times to predict an specific property for different input factors, the maximum five predictions may diverge from the measured values with ± confidence interval. In addition, some contours were plotted to give a comprehensive presentation of any probable correlations between investigated properties and input factors. Based on the developed models with an average correlation coefficients (R2) of 93.69, temperature was found to be the most significant factor affecting the mechanical properties of frozen fine soil, while the dry density was not as effective as the temperature.

Phase change material (PCM) as n-butyl stearate (n-BS) was immersed in expanded clay aggregate (ECA) by two methods, direct immersion at room temperature and immersion at elevated temperature (30oC, 40oC and 50oC). ECA after 90min of immersion with n-BS at 40oC came to standby in its weight proportion (increased by 24%). After immersion, these aggregates (40oC) were mixed in cement slurry for preventing leakage and homogenous mixture with concrete. Oozing circle a leakage test was conducted on all the ECA with and without cement slury coating (room and elevated temperatures). ECA with cement slurry coating gave a reduction in leakage of ECA-PCM by 45%. Alccofine1203 was partially replaced (10% and 20%) by cement to improve mechanical properties in lightweight aggregate concrete. Compressive, flexural, thermal conductivity, DSC analysis and leakage test on aggregate and concrete specimens were conducted on all the mixes. Compressive strength for 10% replacement gave 31.7 kN/m2 and 32.8 kN/m2 for 7th day and 28th day, respectively. Similarly, flexural strength gave 6.12 kN/m2 for 28 days. DSC analysis of pure PCM (n-BS) gave 30.42oC and 23.25 oC for its melting and freezing temperature with 134.2 J/g and 129.3J/g as enthalpy for its melting and freezing points, respectively. Thermal conductivity for mix-3 (10%PCM-ECA +10% alccofine1203) gave the lowest value of all the mixes i.e, 13% less than the reference mix. There was no leakage or any stain marks were observed on the filter paper till 10% incorporation.

This study implemented the artificial bee colony (ABC) metaheuristic algorithm to optimize the Artificial Neural Network (ANN) values for improving the accuracy of model and evaluate the developed model. Compressive strength of RCC was investigated using mix design materials in three forms, namely volumetric weight input (cement, water, coarse aggregate, fine aggregate, and binder), value ratio (water to cement ratio, water to binder ratio, and coarse aggregate to fine aggregate ratio), as well as the percentage of mix design values of different ages. A comprehensive, proper-range dataset containing 333 mix designs was collected from various papers. The accuracy of the research models was investigated using error indices, namely correlation coefficient, root-mean-square-error (RMSE), mean absolute error (MAE), and developed hybrid models were compared. External validation and Monte Carlo simulation (MCS)-based uncertainty analysis was also used to validate the models and their results were reported. The experimental stage of the prediction of compressive strength values showed significant accuracy of the ANN-ABC model with (MAE=11.49, RMSE=0.920, RME=5.21) compared to other models in this study. Besides, the sensitivity analysis of predictor variables in this study revealed that the variables “specimen age,” “binder,” and “fine aggregate” were more effective and important in this research. Comparison of the results showed that the improved proposed model using the ABC algorithm was more capable and more accurate in reducing the error rate in providing computational relations compared to the default models examined in the prediction of the compressive strength of RCC and also tried in simplifying computational relations.

Risks are confronting the foundations of buildings and structures when exposed to earthquakes which leads to high displacements that may cause the failure of the structures. This research elaborates numerically the effect of the earthquake on the vertical and lateral displacement of footing resting on the soil. The thickness of the footing and depth of soil layer below the footing was taken as (0.5, 1.0, and 2.0 m) and (10, 20 and 40m), respectively. The stiffness ratio of soil to footing was also elaborated at 0.68, 0.8, 1.0, and 1.7. The results showed an increase in the verticle displacement of footing as the duration of the earthquake increases. The increase of soil layer thickness below the footing leads to a reduction in the vertical and lateral displacement. While an increase in the thickness of the footing leads to a decrease in the lateral displacement of the footing meanwhile no effect was noticed in the vertical displacement. It was noticed that the time lag between the maximum vertical displacement and the highest value of the earthquake loading is about 0.27 s. It was found that as the distance between the footing and the source of earthquake load increases, the effect of damping on the earthquake load increases while the lateral displacement decreases. The results revealed that an increase in the stiffness ratio leads to a decrease in the vertical displacement and a reduction in the response of the lateral displacement till reaching the value of stiffness ration of unity.

This study aims to investigate punching shear in solid and void slabs as well as simulated soil and spring models as distributed loads on the mentioned slabs. To this end, the slabs were tested using the nonlinear finite element analysis under static loading to assess their failure in terms of the final load and cracking patterns on the soil substrate and spring. For this purpose, a 3D finite element analysis was performed based on the element size, mesh, and concrete characteristic modeling. In Finite Element Software ABAQUS 6.19, the nonlinear behavior of brittle materials was defined based on the concrete damaged plasticity (CDP) model. Next, the results of the numerical analysis of the slabs were calibrated and validated based on a comparison with experimental specimens on a soil substrate. At the end, by optimizing the spring constant and obtaining the soil spring constant, the results of the numerical analysis of the slabs on the spring support were compared to the experimental results, which showed the calibrated models correctly predicted the punching cutting response of the slabs.

The seismic strengthening methods are very important in earthquake-prone countries. Steel divergent bracing with replaceable link beam tied in steel frame and embedded in a concrete frame is a new method for a concrete frame strengthening. That is low cost and easy repairable after an earthquake.In this article six concrete frame strengthening methods have been investigated, including X-bracing, reverse chevron bracing, divergent bracing with concrete link beam, divergent bracing with steel link beam connected to steel columns in the steel frame, divergent bracing with steel link beam connected to the steel frame and with steel columns between those two, divergent bracing with steel link beam connected to the steel frame. All strengthening models are attached to concrete frames by a steel frame surrounding them . These models are investigated by ETABS and PERFORM-3D softwares. In concrete frame strengthed by steel divergent bracing with steel link beam, the base shear is decreased about 20%, steel consumption decreased to 40% in 6-story, and 15% in 14- and 20-story compared to X-bracing, and the existing to allowable stress ratio decreased to 50% in 6-story, to 40% in14-story and 35% in 20-story. As the structure's height is increased, the interaction between the frame and the brace, and the lateral force in the frames increased. Nonlinear static and dynamic analysis have shown more elastic hardness, ductility, behavior coefficient, and base shear in strengthed concrete frame with divergent bracing with steel link beam connected to the steel frame model than others.

Fire accidents are inevitable and it is one of the significant hazards, which causes loss of life and valuables. The present investigation focused to study the influence of fibers on shear strength of concrete exposed to elevated temperature as per ISO 834. The fibers used in the study were Basalt, Carbon, Glass, Polypropylene and Poly vinyl alcohol. M20, M30, M40 and M50 grades of concrete were used for the investigation. The results revealed that the shear strength is declined with increase in temperature. The shear strength is enhanced by the addition of fiber in the reinforced concrete beams exposed to elevated temperature. Carbon fiber reinforced concrete specimens exhibited better residual shear strength than the other specimens. Addition of carbon fiber and basalt fiber in concrete reduced the micro cracks in the specimens exposed to elevated temperature. Addition of polypropylene fiber and poly vinyl alcohol fiber reduced the spalling but the crack propagation was not prevented in the specimens exposed to high temperatures.

Flip buckets are a common configuration for side channel spillways. Similar to other spillways, the flip bucket or ski jump has its disadvantages, among which the scour hole downstream due to the flip bucket jet is the most important. The structure safety and stability may be influenced by the scour holes generated at the downstream side of bucket type energy dissipators. This study has employed an experimental model in order to examine the sediment scour created at the end of flip bucket energy dissipators at various flow rates and tail water depths. A total of 45 experiments were performed under different conditions. The experimental invistigation was conducted at the hydraulic laboratory of Shahid Chamran University in Iran. The main objective of this research was to identify the maximum depth of sediment scour ( ) and the maximum distance of sediment scour hole ( ) from the structures. The results showed that the maximum depth of scour and its distance from the structure increased by increasing discharge. The results of experimental models show that, at the downstream depths ( ) of 0.2 and 0.3 m, the stack was formed by the scouring at the upstream side of the hole, and at a depth of 0.1 m, this stack was transferred to the area after the scour hole. This could be explained by the fact that at downstream depths of 0.2 and 0.3 m, the rolling flow moved from the bottom upwards in the opposite direction of the water flow and sequestrated the sediments upstream. According to Equation Mean Absolute Relative Error(MARE) proposed relation based on laboratory studies has MARE of about 34.2%.

Adhesive joints represent a viable alternative to traditional joining methods. The analysis of frequencies and modal shapes is fundamental to predict the vibrational behaviour of a structural component subjected to dynamic stress. There are numerous studies in the literature to determine the trend of stresses in the bonded region. It has been proved that the introduction of a slot in the inner adherend allows to reduce the stress concentration at the edges of the adhesive region. In this paper, the influence of imperfections in the central adherend is investigated by FEM analysis. The FE software ANSYS©19 is used for the modal analysis of the double lap adhesive joints and the first five modes are considered. The results show the influence of Young’s modulus and density ratio on the natural frequencies, varying with the material. Moreover, the introduction of the imperfection is found to influence the vibrational behavior as the frequency increases. It is also observed that the mass reduction due to the introduction of the crack does not change the shape and modal frequency for the most significant modes, while it causes more important changes for the last vibrational mode. Therefore the introduction of the crack does not significantly change the dynamic behaviour of the joint and allows to realize a more even distribution of stresses, reducing the stress peaks values.

Metaheuristic optimization algorithms are a relatively new class of optimization algorithms that are widely used for difficult optimization problems in which classic methods cannot be applied and are considered as known and very broad methods for crucial optimization problems. In this study, a new metaheuristic optimization algorithm is presented, the main idea of which is inspired by models in kinematics. This algorithm obtains better results compared to other optimization algorithms in this field and is able to explore new paths in its search for desirable points. Hence, after introducing the projectiles optimization (PRO) algorithm, in the first experiment, it is evaluated by the determined test functions of the IEEE congress on evolutionary computation (CEC) and compared with the known and powerful algorithms of this field. In the second try out, the performance of the PRO algorithm is measured in two practical applications, one for the training of the multi-layer perceptron (MLP) neural networks and the other for pattern recognition by Gaussian mixture modeling (GMM). The results of these comparisons are presented in various tables and figures. Based on the presented results, the accuracy and performance of the PRO algorithm are much higher than other existing methods.

Visual vehicle tracking is an important topic in intelligent transportation systems. Intersections are challenging locations for visual systems to track vehicles which are simultaneously moving in different directions. In addition, normal traffic flow may change at intersections due to accidents. Congestion, occlusion and undetermined motion flows are the nominated challenging issues of vehicle tracking at intersections. In this paper, a method for tracking multiple vehicles is proposed considering the vehicle motion directions to overcome undetermined motion flows. For this purpose, a multilayer model is presented, which assigns each motion flows to distinct layers. Moreover, we introduce different neighborhoods for various layers considering the regular motion flows in a layer. Hence, vehicles entering from the same side of intersection with the same motion direction are assigned to the same layer. Then the tracking is performed on different layers separately. In special cases such as vehicles crossing each other, misdetections or occlusion, the proposed tracking method can predict the vehicles tracks by using the stored tracking history and considering neighborhoods in that layer. Experimental results show consistency between proposed tracking method results and ground truth, also outperformance of other tracking methods in tracking vehicles crossing the intersection.

In this paper, the design of an inverter control structure based on the Proportional Resonant (PR) controller is dealt with in detail for attaining smooth transitions between the operating modes of a grid- connected  microgrid system. The control strategy applied for the inverter is cascaded three-loop control viz., the grid current, voltage across the load, and the inverter output current loops. The inverter control is mainly focused to retain the voltage magnitude within the prescribed set limits and to have a good quality of the voltage across the load under all the modes of operation. A proportional resonant controller is designed by considering the transients and stability criteria into account under varying modes of operation. The design procedure of the Proportional resonant controller is given in detail. The three-phase grid-connected microgrid system considered under study is simulated in MATLAB/Simulink environment to operate under islanding condition as well as grid-connected condition and also changing modes from islanding to grid connected and vice versa. The simulation results are presented under various modes of operation to validate the controller design for a smooth transition between the modes of operation.

In this paper, Vienna rectifier has been inspected as one of the prominent topologies among three-level switched-mode rectifiers. A fast processing discontinuous modulation strategy has been proposed with the aim of improving the rectifier’s performance. The proposed method not only takes advantage of special properties available in three-phase three-level rectifiers, but also reduces the control design complexity and the switching loss. Moreover, neutral point voltage balancing is inherently realized. To achieve these goals, the rectifier is decoupled into two 2-level boost converters in every defined region, leading to simple modulation algorithm and fast processing control strategy. The validity of the proposed technique has been verified via simulation and experimental results conducted on a laboratory prototype.

This paper proposes a new approach for discrimination between short circuit fault, magnetic saturation phenomenon and supply voltage unbalance in permanent magnet synchronous motor. This proposed approach is based on tracking the simultaneous position in the polar coordinates of the amplitude and phase angle of the voltage and current indicator FFT signals of the harmonics characterizing the three phenomena. The voltage indicator set using three supply voltages to check the status of the power source. In the same way, the current indicator defined using three line currents to discriminate between the short circuit fault and the magnetic saturation phenomenon. To highlight the effectiveness and the capability of this approach, a series of simulations are performed on signals obtained from a permanent magnet synchronous motor mathematical model. This model is based on a 2D-extension of the modified winding function approach.

In this paper, the problem of control a single-stage boost inverter is studied. The goal is to achieve a system with robustness against variations in parameters, fast response, high-quality AC voltage, and smooth DC current. To this end, a new type of dynamic sliding mode control is proposed to apply to various scenarios such as parameter uncertainties and DC input voltages. In comparison with the conventional double-loop controllers, the proposed sliding mode controller utilizes only a single loop in its design, while having attractive features such as robustness against parametric uncertainties. In addition, a methodology is proposed for the decoupling of double-frequency power ripples based on proportional-resonant (PR) control to remove the low-frequency current ripples without using additional power components. Compared to conventional controllers, the proposed controller provides several features such as fast and chattering-free response, robustness against uncertainty in the parameters, smooth control, proper steady-state error, decoupled power and good total harmonic distortion (THD) over the output voltage and input currents, and simple implementation. In a fair comparison with classical sliding mode control, simulation results demonstrate more satisfactory performance and effectiveness of the proposed control method.

End-of-life products have a severe impact on the ecological system. Potential production policies and distribution strategies for the newly manufactured product have attracted significant attention to sustainable development. Sustainability in supply chain management has much importance to achieve eco-friendly goals. In this study, we have developed sustainable objectives in the supply chain optimization framework with different constraints. The trade-off between economic, environmental and social effects objectives have identified by ensuring the optimal allocation of different products among various levels.  In this regard, a new sustainability multi-objective mixed-integer linear programming mathematical model in the medicine supply chain network is developed. Although the proposed model is an NP-hard problem, we develop a novel hybrid Particle Swarm Optimization and Genetic Algorithm to achieve Pareto solutions. Then, to adjust the important parameters of the algorithms and chose the optimum levels of the significant factors for more efficiency is employed the Taguchi method. The results show that the economic and environmental effects tend to be decreased and the social impacts tend to be increased in the medicine supply chain network which can exhibit the best sustainability performance. The various outcomes of numerical experiments indicate that the proposed solution algorithm is more reliable than other algorithms. The solution methods are complemented with several sensitivity analyses on the input parameters of the model.

There is a high interest in optimization of transportation and logistics networks due to its high impact on the economic performance of supply chain networks. This paper presents a bilevel mixed-integer programming model as well as a solution method to manage distribution process in a logistic network, where two decision makers, called distributor and interdictor, make efforts to achieve their contradictory targets. This problem, known as arc interdiction location-routing problem (AI-LRP), is in fact a new, extended version of the classical LRP. The distributor strives to deliver goods to customers with minimal risk and cost, while the interdictor, by contrast, endeavors to disrupt products flow through a few critical arcs. AI-LRP has wide applications in reality, including distribution of particular goods like money, precious metals, hazardous materials, and prisoners that may need security measures. The interplay between two decision makers is formulated as a bilevel model. To solve the model, a novel genetic algorithm (NGA) is devised in which the density ordered heuristic of the knapsack problem is applied to generate an initial population of solutions. Computational results illustrate that NGA outperforms a commercial solver in terms of computational time and quality of solutions.

Undoubtedly, metals are the basis of the sustainable development of all human societies. In the last century, the role of copper, as the third most widely used metal, after steel and aluminum, has been crucial. Copper is a recyclable metal. It has many applications such as industrial electricity, plumping, wiring, electronic equipment, transportation, and infrastructure. Today, with the growth of the industry in societies, the demand for copper has increased. This motivated us to study its supply chain network design firstly. To the best of our knowledge, there is no research reported about copper supply chain network design. This paper aims to maximize the profit of the copper closed-loop supply chain. We formulate this network design problem as a Mixed Integer Programming model. The model is considered as single-objective and multi-product. The exact solution of the model is found by using GAMS software. Sensitivity analysis results provide useful results that managers can use them in decisions.

Todays, Information and Communications Technology (ICT), as one of the most effective factors of the advancement in all the aspects such as governance, security and risk, economics and technology, which is among the industries rapidly growing and developing. This paper examines the specific criteria and standards of ICT area for improving the quality of the services of the Telecommunications Backbone Network of Iran (TBNI). The research was done through the two methods of data collection, library and the field study. European Foundation for Quality Management Excellence Model (EFQM) was selected as the base model and with full attention to the specific requirements of ICT industry and due to adapt this model from the viewpoints of the security and risk, governance and economic, a novel integrated excellence model of TBNI was developed and customized. To achieve the highest level of reliability and  internal coherence of each criterion, based on expert opinion polls, sub-criteria was categorized and analyzed in several stages using the factor analysis approach. The causal relationships and the influence of the criteria of this model on each other were investigated and the weights of each criterion and sub-criteria, using the structural analysis and shannon entropy methods, were determined. The self-evaluation of TBNI was systematically carried out and major opportunities for the improvement had been identified. Results showed that the establishment of this model had led to an improvement in a quality of services provided by this network and the products of all organizations that use any services of TBNI.

This study is an attempt to produce surface nanocrystalline composite of Fe-Co-TiO2 at various current densities in the range of 20 to 50 mA/cm2 via pulse electrodeposition method. The prepared composites were characterized by field emission scanning microscope (FESEM), electron dispersive spectrum (EDS), Vickers microhardness, vibrating sample magnetometer (VSM), and x- ray diffraction techniques (XRD). The results showed that the formation of cauliflower morphology was preferred at lower current densities. Moreover, the higher current densities enhanced the Fe content and at the same time diminished the Co and TiO2 contents of prepared surface composites. XRD patterns and Rietveld analysis confirmed the formation of combinations of BCC (as dominant) and FCC phases. Higher current density enhanced the saturation magnetization and decreased lower coercivity due to the higher Fe content and the reduction of TiO2 nanoparticles in coatings. In addition, the lowest coercivity and highest saturation magnetization were gained at 50 mA/cm2, while, the maximum microhardness obtained at 30 mA/cm2.

Demand for increasing strength to weight ratio, elimination of electromagnetic waves, and vibration damping has led to the wide application of magnesium-base alloys such as AZ91 in various industries like aerospace, military, vehicle, and shipbuilding. However, because of the unstable secondary particles and casting defects located on the rough grain boundaries and in the dendritic regions, due to sliding of the grain boundary, the creep resistance and tensile strength of Mg alloys at high temperatures reduce. To improve the high-temperature properties, rapid deformation processes such as friction stir processing can be employed. In this study, the influence of multi-pass friction stir processing on microhardness, tensile, and creep behavior of AZ91 at several temperatures from 25 to 210 °C has been studied. Optical microscopy and scanning electron micrograph were used to study the microstructure of the cast and processed samples and Clemex commercial software was used for grain size measurement. The experimental results indicated that at room temperature, the microhardness, tensile, and creep strength of the processed samples as compared to the unprocessed ones increased by 23, 29 and 38%, respectively. In addition, after multi-pass friction stir processing, the tensile and creep strength of the samples at 210 °C  increased by 31 and 47%, respectively. Also, the average grain size of the multi-passed friction stir processed AZ91 alloy decreased by 88%. The maximum ultimate tensile strength of 276 MPa was obtained at the tool rotational speed of 1200 r/min, the traverse speed of 60 mm/min, and the tool tilt angle of 3°. The empirical results indicated that this rapid deformation process can be useful in enhancing the mechanical properties of AZ91 alloy at high temperatures.

This research presents a compact and computationally-efficient two-equation compressible-liquid model. The model is specifically developed for the numerical computation of hydraulic surges in pipes under high fluid pressure where cavitation is absent. The proposed model aims to simplify the three-equation model of Neuhaus et al. for two-phase cavitational hammers. Compressible effects in liquid during the transients are considered by including a suitable equation of state into the model. A tunable function of the relative local pressure fluctuation called 'Variable Friction Coefficient' (VFC) for the flow transients is also incorporated into the model. For the accurate modeling of wave propagation, the split-coefficient matrix (SCM) method for characteristic-direction based splitting of eigenvalues is used in the study. The results show that the proposed two-equation model can reproduce the results from the three-equation model at a substantially reduced computational cost. The integration of the variable friction coefficient into the two-equation compressible-liquid model further improved the solver capability.  The results computed using this aggregate solver are superior to the original three-equation model and the two-equation model without VFC. The results also suggest that the variable friction coefficient imparts adaptive damping capability to the solver model. This feature of the model is visible in the improved accuracy in the modeling of decaying pressure waves. The aggregate solver model, i.e., `the variable friction coefficient integrated two-equation compressible-liquid model,' offers a greatly simplified mathematical model and an inexpensive computational solver for the simulation of hydraulic surges in non -cavitating flow transients.

In this paper, the influence of the locating additive or placing porous-medium film on the heat transfer of a micro-channel by injecting fluid from its lower wall is investigated. The boundary condition slip-walls for the lower and higher walls of the micro-channel and orderly, as insulation and constant temperature is considered, respectively results show that the heat transfer increased with increasing Darcy number and the porous-medium film thickness. The consequences disclosed that the place of the porous-film has a substantial effect on heat transfer. The percentage changes observed for cases such the porous layer in the middle of the micro-channel, near the two upper and lower walls, near the upper wall, near the upper wall and in the form of a rib, along the length of the micro-channel with L /3 and L/5 is -14%, 2.25%, 5.46%, 55.53%, 70.5% and 86.27% for nusselt number compared to the porous layer-less state.

Porous materials especially closed-cell metallic foams play important roles among novel materials because of their good characteristics e.g. high strength to weight ratio and crashworthiness. On the other hand, mechanical behavior determination and detailed characterization are essential in efficient manipulation and material tailoring. In the present research especial hybrid experimental-numerical approach is used for aluminum foam behavior determination as to the main goal, i.e. continuous deformation field measurement using digital image correlation (DIC) and finite element analysis (FEA) on porous specimen’s surface.  To overcome the 3D modelling problem of closed-cell foams structure, we present the method based on CT-scan and digital optic microscope imaging combination. In the experimental part of the study, aluminum foams and proper specimens are manufactured, and then high-resolution digital imaging and illumination setup are employed. Finally, the deformation field is obtained using DIC. On the other hand, measurement verification and DIC parameters optimization processes are conducted using ABAQUS 2019 with comprehensive mesh independency study and response surface methodology (RSM) respectively as major research achievement. Finally, correlation equations based on high regression models are obtained. Using detailed geometrical micro-model and optimal DIC parameters yields to good numerical-experimental accordance. The novel approach of combined CT and digital microscope imaging instead of industrial micro-CT lowered imaging costs while yielded to accurate numerical results.

Gear systems are one of the most functional power transmission systems in the industry. Crack is one of the common defects in gears which is caused by excessive loading, sudden impact and shortcomings in the gears construction. Initially, the crack will not result in structure collapse, but its growth can lead to irreparable damage. Therefore, detecting the crack and determining its location and depth are very important in this respect. In this paper, two encoders are used to obtain the spur gear pair transmission error speed. Moreover, the short-time averaging method (STAM) has been proposed thereby detecting the crack location and some statistical indicators have been used to estimate the crack depth in the spur gear tooth. For this purpose, a dynamical model in which mesh stiffness varying with time has been deployed to achieve the transmission error speed of the gear system. Additionally, a gear test rig including a single-stage gearbox, two encoders, and also an electronic board has been used. Encoders were installed on input and output shafts and the angular position of each shaft in time was saved in the computer using the electronic board. In addition, the transmission error speed was obtained by analyzing the received signals. Then, short-time averaging method was used to identify the crack location. Ultimately, some indicators such as ABS-max, FM0, Energy Ratio (ER) and Residual Signal Average were applied to the simulated results and experimental signals to fine the crack depth ratio. According to  the results of this study, it seems safe to conclude that the STAM is a useful method in cracked tooth detection and the indicators have acceptable accuracy to find the crack depth ratio.

In the present study, an attempt has been made to use Computational Fluid Dynamics (CFD) in the assessment of hazardous gas dispersion over obstacles. For this aim, the accidental dispersion of hazardous gas from the hole and the effect of different parameters such as changes in inlet wind velocity, the direction of the pollutant cloud and its movement, mass fraction of gas dispersion, and the pressure distribution were numerically analyzed. The flow was assumed as three-dimensional, unsteady, turbulent, and compressible. Different turbulent models were used in modeling the gas release and the most accurate one was suggested. The numerical simulation demonstrated that the gas mass fraction increased significantly due to the sudden dispersion of the gas. The amount of gas concentration gradually decreased after the formation of pollutant clouds by moving in the horizontal direction. Moreover, gas mass fraction had decreased by increasing the height. Comparing the results revealed that the pollutant cloud did not cover the surrounding area in the wind velocity of 1 m/s. Therefore, the pollutant clouds generated in this case could not impose a threat. In higher wind velocities (3 m/s and 5 m/s), the pollutant cloud approximately covered the surrounding areas, which caused a severe threat. The maximum overpressure at the hole is 5.7 Pa for a wind velocity of 5 m/s, while the maximum negative pressure was about -7.1 Pa. The influencing radius was obtained about 9.3 m. The overpressure did not cause obvious damage to buildings but led to a slight hurt to humans.

During the ultrasound imaging process, the ultrasound contrast agents (UCAs) are beating near the blood vessel wall. Therefore, the purpose of the present simulation study is to investigate the effect of the presence of an elastic wall on the radial and frequency acoustic response of a UCA microbubble oscillating in a nonlinear regime. For this reason, the numerical simulation of the dynamic behavior of a coated microbubble was performed using coding in MATLAB and a Rayleigh-Plesset equation modified by Doinikov. To study the nonlinear bubble oscillations, its compression-only behavior and the sub-harmonic nonlinear component are taken from a nonlinear shell model presented by Marmottant et al. Initially, coated bubble oscillations in two linear and nonlinear regimes were investigated for two types of shell models, and it was observed that presence of the elastic wall affects the bubble's compression-only behavior. Finally, due to the importance of the subharmonic component in the nonlinear oscillation of the coated bubble, the threshold of the appearance of subharmonic components for a coated bubble near an elastic wall was investigated using the Fast Fourier Transform (FFT) and compared with the oscillation in the infinite fluid.

In order to improve the heat transfer performance of an exhaust gas recirculation (EGR) cooler, different structural characteristics are numerically and experimentally studied. In numerical analyses, the presented pitted tube model and inner fin model, are compared under two typical working conditions, heat transfer efficiency solutions of inner fin model were 3~5% higher than that of pitted tube model. The inner fin model also gives smaller gas side pressure drop, which is only 17% of the pitted tube model. Then, the structural optimization of the inner fin model by analysing the various amplitude A was investigated. It is shown that increasing A results in increment of heat transfer efficiency and gas side pressure drop, the temperature requirement is satisfied and pressure drop is minimized when A=0.9 mm. The optimized numerical heat transfer efficiency solutions were 86.4% and 84%, and experimental results were 88.5% and 86.3% corresponding to working conditions, respectively. A good agreement was obtained. The optimized inner fin structure can be used efficiently to improve the heat transfer performance for an EGR cooler, the study method has been proven to be feasible by the simulations and experiments.

Hydrochloric acid treatment is the most common oil production stimulation treatment to date. Yet, most of operations fail to deliver the targeted results. For a more competent design of acid treatment of carbonate reservoirs, flow studies on core samples are conducted preliminary to determine the most effective acid composition and the technology of its injection into formation. The authors believe that, at present, processing of flow research results is incorrect, as not all parameters are taken into account when making recommendations. This study examined the influence of geological and technological parameters on effectiveness of hydrochloric acid treatment. In the course of studies using the flow unit and X-ray tomography, a number of factors have been identified that affect the outcome of the treatment. The volume of acid composition required to create a highly conductive channel in a core sample is a parameter using which it is possible to conduct a comparative analysis of effectiveness of the acid compositions under test and the methods of their injection. Therefore, exactly this parameter is used as a core in this paper, based on which the authors have derived an integrated indicator that provides for the most reliable evaluation of the flow study results. Using this indicator, it is possible to provide more competent recommendations as to the choice of acid compositions and the technology of oilfield hydrochloric acid treatments, which will provide the greatest effect of the planned operations to enhance oil recovery.