International Journal of Engineering
Volume:34 Issue: 5, May 2021

Ultra-High Performance Concrete (UHPC) is a cementitious composite with fine aggregates and a homogeneous matrix with high compressive strength and excellent durability against aggressive agents. It is common to use short steel fibers in the UHPC. Besides, using steel fibers considerably increases the flexural ductility, durability and energy absorption. Using glass fibers in UHPC is a novel technique which improves its mechanical properties and it has the benefit of being lighter, and cheaper than steel fibers. Furthermore, glass fibers can be used for thin concrete plates for aesthetic purposes. However, glass fibers reinforced concrete is incompatible with the hydration reaction in the alkaline environment of concrete as it can damage glass fibers, so the mechanical properties of the concrete are decreased over long periods. The mechanical properties of UHPC containing glass fibers (GF-UHPC) was investigated under three regimes of normal curing, autoclave curing, and autoclave curing plus being in hot water for 50 days (accelerated aging). Besides, the substitution of silica fume by Metakaolin in GF-UHPC was studied to understand its mechanical properties after thermal curing. The results showed that after accelerated aging, the behavior of specimens become more brittle and the modulus of rupture and toughness indices of all prismatic specimens decreased, the modulus of rupture for samples containing glass fibers was 40% lower than autoclave curing results. However, the compressive strength under accelerated aging increased at least 4% in comparison to the normal curing. Replacement of silica fume with Metakaolin slightly increased the toughness with regard to flexural strength.

This study aimed to determine the effect of various influencing parameters such as tunnel diameter (D), depth (H), width (B), length (L), number of floors, and the horizontal distance of the building from the tunnel axis (X), as well as soil properties such as internal friction angle (ϕ), Poisson ratio (υ), modulus of elasticity (E), and cohesion (C) on surface settlement using ABAQUS. According to the results, the settelment increases with increasing tunnel diameter at a constant depth, while it decreases with increasing tunnel depth. Changes in the width and length of the building also affect the settlement directly; consequently, as the width and length of the building increase due to increasing the cross-sectional area of the building and its rigidity and stiffness, the settlement of the foundation becomes more uniform and resistant to displacement, leading to a decrease in the surface settlement. Also, as the distance of the building from the tunnel axis increases, the settlement decreases and follows a constant trend after a distance equal to the tunnel diameter. Based on the results of the sensitivity analysis, the depth of the tunnel has the greatest effect on the surface settlement, which can be prevented by controlling the depth of the tunnel from the ground surface. Also, among the soil geomechanical parameters, the modulus of elasticity had the greatest effect on settlement in the present study. Finally, according to the results, the effect of tunnel, building, and soil properties on surface settlement is very important, particularly in urban environments.

Different approaches were adapted to strength the structural elements to increase the load capacity and reduce the deformation such as deflection. The easiest and light external strengthening of reinforced concrete members are Fiber Reinforced Polymer (FRP) family such as Armed, Carbon, Glass and Basalt, respectively. This paper presents the theoretical approach to check out the experimental tests of reinforced concrete beams strengthened by glass fiber reinforced polymer (GFRP) using finite elements method by ANSYS software in which all models are simulate the tested beams.  All models have the same geometry and mechanical properties but differ in GFRP layers and width. The main objectives of present work are evaluating the strength capacity, cracks propagations, deflection and tensile enhancement of reinforced concrete beams warped by GFRP strips subject to four points static load. Analysisof  results indicate that the presences of GFRP sheets enhance the capacity and ductility of reinforced concrete beams in additional to delay the post crack concrete. The delay in the formation of first crack, increase in the number of cracks and ultimate loads of the models compared with the control model. There are improvements in flexural strength based on the modulus of rupture. Also, the cracks propogation become less in case of presence of GFRP and there is improvements in tensile resistance due to flexural. Analysis results inicated that the presence of GFRP at the bottom face of reinforced concrete beam in case of two layers gave increase in ultimate load 104.3% as compared with the control model. The reduction of the deflection for same models is 10.84%. Factor of the modulus of rupture range between (0.76-1.36) that is more than with ACI code suggested as 0.6. All model results were close to the experimental tests.

Input voltage of Magneto Rheological (MR) dampers is the only controllable parameter as a semi-active control device. Therefore, voltage selection has an important role in control procedure via MR dampers. In many of semi-active control algorithms, a mathematical modelling method is required for determining the MR damper voltage at each time instant. As a result, applying different mathematical modelling methods can lead to different voltages for the MR damper, which subsequently results in different control performance. In the present research, the effects of mathematical modelling method of an MR damper hysteretic behaviour on its control performance were investigated. The most exact and common Maxwell nonlinear slider and modified Bouc-Wen hysteretic models were employed through a nonlinear comparative numerical study. A building structure was utilized for numerical investigations. A ten-story office building steel structure is excited by seven acceleration time histories. Nonlinear instantaneous optimal control and linear quadratic regulator controllers were utilized as two active-based semi-active algorithms. Results of nonlinear investigations showed an obvious difference between the Maxwell nonlinear slider and the modified Bouc-Wen models from the control performance viewpoint. Outputs show a very slight better performance for the MNS model in reducing the nonlinear responses.

This study presents the effect of super absorbent polymer (SAP) as internal curing agent on workability, durability and compressive strength of self-consolidating concrete (SCC). In order to estimate the internal curing efficiency of SAP in different curing conditions and curing ages, compressive strength and electrical resistivity tests have been performed. Homogenous and denser microstructure was formed by gradual release of water from SAP into pores created by SAP. Further pozzolanic reaction of fly ash has enhanced the strength and durability properties. High desorption rate of water from SAP in air curing condition resulted in an increased electrical resistivity and compressive strength. Compressive strength of internal cured SCC mixtures increased to 15-25% at 7 days and 10-19% at 28 days. Electrical resistivity values were increased 11-30% in water curing condition and 16-53% in air curing condition. The costs for 0.35w/b and 0.40 w/b at optimum internal cured SCC mixtures compared to control SCC mixtures were reduced to 9.39 and 9.70%, respectively.

Strengthening of the existing reinforced concrete (RC) column is nessesary to enhance their axial load-carrying capacity or ductility. This paper presents the results of an experimental study relating to the performance of reinforced concrete columns strengthened with different techniques such as the steel angle, steel straps, and ferro-cement under pure axial load. A total of six square short reinforced concrete columns were constructed. The cross-section and height of tested columns are 150×150 mm and 1.2 m, respectively. Two specimens were set as the control columns (without strengthening). The other four reinforced concrete columns were strengthened with different techniques. Two columns are strengthened with four steel angles at each corner of the column confined with prestressed steel straps. Another two columns are also strengthened with four steel angles confined with prestressed steel straps and ferro-cement. The experimental results are reported in terms of the load-deformation curves as well as the failure modes. A significant enhancement of the maximum axial load-carrying capacity and the ductility is observed for the strengthened reinforced concrete columns. Finally, the discussion of the use of different strengthening techniques is also carried out in this paper.

Numerous studies have been conducted on self-centering seismic lateral force resisting systems, the consequences of which have resulted in removing many ambiguities regarding the use of such systems in retrofitting the existing frames. The present study evaluated the new approach of improvement of multi-stage performance using such systems. Due to the significant costs of running the whole retrofit project in one stage, as well as some issues such as the impossibility of stopping the use of all floors in some of the existing buildings, multi-stage improvement can be considered as a good suggestion. In this regard, a part of the floors are retrofitted in the first stage and the next stage of improvement are then implemented by spending less budget and time. Accordingly, the execution of the first stage leads to an enhancement in the frame performance to an appropriate extent. In addition, the measuremets taken in the stage are a part of final retrofit project. In the present study, PUF and PEF coefficients were introduced and utilized to select the most appropriate pattern for applying post-tensioned connections in different floors. After analyzing frames, a model was proposed for the multi-stage improvement of each frame by selecting the appropriate pattern using post-tensioned connections in the floors. In the first stage of the suggested plan, for 3-, 6-, and 10-story frames the performance improvements were 15.3, 11.4, and 8.5%, respectively.

The aim of this study was to improve the characteristics of natural collapsible soils using the geogrid-encased stone column technique. For this purpose, 20 large-scale specimens of stone columns were prepared using rigid metal cylinders with a diameter of 308 mm and a height of 97 to 154 mm according to the unit cell theory. The aspect ratio was 10% to 25%. For the occurrence of bulging failure, the height of the stone columns was considered six times the diameter. The stone columns were encased with geogrids of varying stiffness from 80 to 200 kN/m. The soil around the stone column inside the unit cell was compacted to similar site conditions. Loading was applied similar to the test, which determines the soil collapsibility potential while the specimens were being inundated from the bottom of the metal cylinder by a water feeding system. During loading, the vertical displacements of the stone columns were measured at two locations on the loading plate. The results showed that the columns settlement due to inundation diminished by increasing the stiffness of the encased stone columns and aspect ratio. The optimum aspect ratio was approximately 15%. Encasement of the stone columns increased the lateral pressure in the collapsible soil and prevented the collapse of the stone column. The settlement values of stone columns were compared with a settlement prediction model and showed a good agreement. The data obtained in this study can be used as a practical method to improve natural collapsible soils during inundation.

Cracked concrete arch dam’s behavior due to moderate earthquake magnitude and water pressure variation was investigated. Plain concrete was used to cast the dam’s models with 45 Mpa design strength. A shake table has been planned, manufactured, and built to create a dynamic testing facility. The experimental work was included testing of four scaled-down concrete arch dams’ models, which is divided into two groups, each group contains two different degrees of curvature models. An artificial crack was made at the center of the dam’s body. The extended finite element method (XFEM) is outlined in order to address the numerical predicate for the propagation of a crack. The results showed that a good behavior of all arch dams under moderate earthquake intensity. The arch dam with a higher degree of curvature was recorded 17.8% and 16.2% low displacement at Z and X-direction respectively, stress evaluation and crack propagation in comparison with the arch dam owns the lowest degree of curvature. Hence, increasing the degree of curvature led to raising the stability of the dam, earthquake resistance, less displacement, and less growth of tensile cracks.

The growth of tall buildings in the United Arab Emirates (UAE) has paved the way for a surge in interest in the country's seismic vulnerability investigation. The case study building comprises of shear walls and RC columns as its lateral force-resisting system. It is a newly constructed G+17 storey building and is about 78 meters high. The non-linear dynamic seismic analysis which is the time history modal analysis, also known as Fast Non-linear analysis was performed on the study building with about 45 earthquakes in 3 sets of hazard levels (2%, 5%, and 10% Probability of Exceedance [PE]) to generate the inter-story drift values. Based on the Performance-based approach given by FEMA 356, the Fragility curves are developed by creating the Probabilistic Seismic Design Modal. The resultant fragility curves are given in terms of 3 probabilities i.e., (1) Immediate Occupancy, (2) Life Safety, and (3) Collapse Prevention. The whole study depends on the idea that comparative sort of structures will have a similar likelihood of a given harm state for a given seismic force

This paper aims to illuminate the influence of hydrodynamic pressure generated in a water storage tank on the behavior of saturated sand that its support. Experimental tests were performed on two cylindrical water tank models using a fabricated shaking table which consists of a flexible laminar shear box. The first model is a water storage tank partially full of water, and the second one is a tank model with an equivalent load of water pressure to simulate the water storage tank without hydrodynamic pressure. Three earthquake histories (Kobe, El-Centro, and Ali Al Gharbi) were implemented on models to study a varied range of acceleration. It was found that the settlement and lateral displacement directions in the water storage tank were significantly increased compared to the equivalent load resulted in the second model in all cases of the acceleration histories. Also, it was monitored the pore water pressure during the testing period, and it was noticed that the excess pore pressures were affected by the hydrodynamic pressure and increased compared to the results recorded at the condition of no hydrodynamic pressure.

Despite the fact that many governments try to set rules that guarantee having resistant buildings, there are many vulnerable structures in the world. Hence, establishing earthquake relief centers is an important issue in order to control the effect of an earthquake. Iran is a country in middle east which is severely vulnerable against earthquake. Yazd is a central city in Iran. Since there is no such a study for Yazd city, this city is considered in this study.  The parcels' layer of the GIS map of Yazd city has been used as the input of the problem. Since the location allocation of relief centers is a problem with huge complexity and cannot be solved in polynomial time, Whale Optimization Algorithm (WOA) has been used to solve the problem. The Whale Optimization Algorithm or The WOA is a particle based heuristic algorithm which is suitable for solving hard problems. The main contributions of the research are modifying WOA function for the problem and designing a new method for creating whales. In order to reduce the time of reaching to the reasonable solution an innovative whale generating method has been  designed.  The results show that average distance of each parcel from its relief center is 1541 meters and the standard deviation of 114

The purpose of this study was to introduce a proposed method to retrofit RC beams. For this purpose self-compacting concrete containing aluminium oxide nanoparticles (ANPs) and silica fume (SF) was used in RC jackets. The laboratory experiment and numerical simulation were used to investigate the behavior of the beams. The experimental variables were included the amount of ANPs used in the jackets (0 and 2.5% by weight of cement) and the surface interaction between beam and jacket (75% and 100% of the side and bottom surfaces of the beam). Five RC beams with a length of 1.4 m and the same dimensions were made and subjected to four-point loading. After completing the laboratory steps, RC beams were simulated according to laboratory conditions using the finite element method and ABAQUS software. After verifying the used method, parametric analysis was performed and parameters such as beam span length (1.5, 3, 4.5 m), concrete jacket thickness (4, 8, and 12 cm), and the diameter of the bars used in the jacket (8, 10 and 12 mm) were examined. The results showed that the use of RC jackets containing ANPs, depending on the jacket thickness, the diameter of the bars used in the jacket, and the length of the beam span increased the beams flexural strength by 155 to 447%. It was observed that the crushing of concrete without nanoparticles compared to concrete contain nanoparticles is more severe because nanoparticles affected the concrete matrix and reduced its crushing in RC jackets.

Electrical motor are the ubiquitous workhorses of the industry, working over wide range of conditions and applications. Modern motors, designed to exact ratings using new materials and improved manufacturing techniques, are now much smaller but have higher loadings. They are being operated much closer to the point of overload than ever before. To ensure a satisfactory lifespan for the motor, temperature rise must be limited to the safe values. This paper proposes an analytical approach to estimate core losses of induction motor supplied by either harmonic content or voltage unbalance source. A model based on the thermal lumped parameters is introduced and used to predict the insulation lifespan of induction motors. Lumped parameters network of the motor is developed based on dimensions of the motor, thermal resistances, thermal capacitances, and loss sources. Then, the model is used to estimate the temperature in different parts of the machine and its insulation lifespan. Finally, the predicted results are verified by experiments.

Most of the man-made objects are having some straight lines with colors. A very high-speed object recognition method using color straight line patterns is carried out using a novel self-learning device (RKD - Rasiq Krishnakumar Device). Instead of that Artificial Neural Networks (ANN), RKD based networks are used for different steps in this pattern classification. The color and straight-line features are extracted by using high-speed color segmentation and fast efficient straight-line segment extraction methods using the RKD based systems. The training and the testing algorithms of the pattern classification are using RKD-based processing. The fast color features extraction method uses an array of RKD-based devices and the fast efficient straight-line segment extraction method employs an array of processing elements and a main control unit. Some fusion devices are used for a straight line with colors features. The area of interest and the area of line segments of a particular object are other features for improving the accuracy of object classification.

A novel gain boosted folded cascode Op-Amp using simple single stage auxiliary amplifiers is presented. The proposed auxiliary amplifiers are designed in a way that have proper input and output DC common mode voltage without using common mode feedback network. The inputs of the auxiliary amplifiers are insulated by the coupling capacitors and floating-gate MOS transistors. Thus, the DC input voltage level limit has been removed. Diode connected transistors are also used in the output of the auxiliary amplifiers, which keep the output voltage level at the desired. A simple single stage auxiliary amplifier imposes fewer poles and zeroes on the main amplifier compared to more complicated amplifiers where consumes also less power consumption. Simulation results in a 0.18μm CMOS technology show a DC gain enhancement of about 20dB while output swing, slew rate, settling time, phase margin and gain-bandwidth retain almost as the same as previous folded cascode design.

The aim of this paper is to present a model predictive voltage control (MPVC) strategy for stabilizing the amplitude and frequency of the output voltages in a Brushless Cascade Doubly-Fed Induction Generator (BCDFIG) under load changing and variable speed of generator shaft in stand-alone mode. BCDFIGs are a particular model of BDFIGs that consist of two induction machines called the control machine and the power machine, so that their rotors are electrically and mechanically coupled together. In this paper, unlike previous studies, which the BCDFIG rotor was integrated, the generator rotor is analyzed as a complex of two rotors of two separate induction machines. Also, the output voltages of generator are predicted and regulated in different operating conditions by using model predictive voltage control. In order to stabilize the amplitude and frequency of BCDFIG output voltages, the appropriate voltage vector is determined to apply to the stator of control machine. This generation system is simulated and simulation results prove the accuracy of proposed method. Experimental results on prototype BCDFIG are provided to validate the proposed methods. Finally, the effectiveness of the proposed controller brings better power capture optimization under variable speed wind turbine.

This paper, proposes an Intelligent Loop Based Artificial Neural Network (ILANN) based detection technique for the detection of cyber intrusion in a smart grid against False Data Injection Attack (FDIA). This method compares the deviation of a system with the equipment load profile present on the system node(s) and any deviation from predefined values generates an alarm. Every 2 milliseconds (ms) the data obtained by the measurement is passed through the attack detection system, in case if the deviation is continuously for 5 measurement cycles i.e. for 10 ms and it does not match with the load combination the operator will get the first alert alarm. In case the deviation is not fixed after 8 measurement cycles then the system alerts the control centre. FDI attack is used by attackers to affect the healthy operation of the smart grid. Using FDI the hackers can permanently damage many power system equipment’s which may lead to higher fixing costs. The result and analysis of the proposed cyber detection approach help operator and control centre to identify cyber intrusion in the smart grid scenario. The method is used to detect a cyberattack on IEEE-9 Bus test system using MATLAB software.

In recent years, many industries in developed countries have integrated the important process of reverse logistics into their supply chain for different reasons, including growing environmental concerns. Given fish as perishable food, re-employing unused products and waste in each step of the chain constitute a major concern for the decision-makers. The present study is conducted to maximize responsiveness to customer demand and minimize the cost of the fish closed-loop supply chain (CLSC) by proposing a novel mathematical model. To solve this model, the epsilon-constraint method and Lp-metric were employed. Then, the solution methods were compared with each other based on the performance metrics and a statistical hypothesis. The superior method is ultimately determined using the TOPSIS method. The model application is tested on a case study of the trout CLSC in the north of Iran by performing a sensitivity analysis of demand. This analysis showed the promising results of using the proposed solution method and model.

In this research, an improved model of Parkinsonian tremor is presented by using a mathematical and computational approach. In Parkinson’s disease (PD), an abnormal signal is produced by basal ganglia (BG). This signal goes to the thalamus, then enters cortex and after interaction with peripheral system goes to muscle and finally appears as tremor. In the presented model, all of the mentioned process are simulated. Also, the skeletal muscle model as well as the central nervous system (basal ganglia, thalamus, cortex and supplementary motor area) and peripheral nervous system (spinal reflex) mechanisms are considered. In addition, two methods for tremor suppression are applied in this paper, 1) deep brain stimulation (DBS) which affects dopamine level in BG and 2) a mechanical method which is based on a negative feedback. The accuracy and efficiency of the presented simulation are demonstrated by comparison of the obtained results with those obtained by clinical tests.

This paper proposes a novel control strategy of an islanded microgrid based on virtual flux droop (VFD) control. In the conventional VFD method, the direct flux control (DFC) technique is used to generate the switching signals using the hysteresis regulators and a switching look-up table. Therefore, the voltage and the current ripples are inevitable. Moreover, as a single switching vector is applied in each control period and none of the switching vectors can produce the desired voltage, the desired dynamic performance is not achieved. Here, a novel direct flux fuzzy control (DFFC) technique is proposed to choose the best switching vector based on fuzzy logic. Furthermore, only a fraction of the control period is allocated to the appropriate active switching vector which is selected by the DFFC technique whereas the rest of the time is allocated to a null vector. The duty cycle of the selected active switching vector is optimized using a simple and robust mechanism. In order to evaluate the performance of the proposed method, an islanded microgrid and the proposed control strategy is simulated in Matlab/Simulink software. The results prove that the dynamic performance response is improved and the demanded load power is proportionately shared between the sources, while the voltage and current ripples are significantly reduced

At present, the reduction of circuit design power is a prime research topic. The reversible computation satisfies the criteria of the power consumption reduction compared to the traditional logic design. Thereby, reversible computation is gaining much attention in recent decades. Two reversible design approaches of binary-coded-decimal (BCD) to densely-packed-decimal (DPD) converter (encoder) and two design approaches of DPD to BCD converter (decoder) are proposed in this paper. The designs are carried out through the appropriate selection of the gates and further proper organization of such gates with parallel implementation. The proposed design approaches offer a low quantum cost implementation compared to state-of-the-art design. The cost results analysis of reversible DPD encoder shows appreciable reduction by at least ~23%, and that of decoder by at least ~62% compared to the state-of-art design found in the literature. Furthermore, the structures are decomposed into the primitive-quantum-gates and compressed in compact form for delay calculation

This paper proposes state and fault estimations for uncertain time-varying nonlinear stochastic systems with unknown inputs. we suppose, the information about the fault and unknown inputs is not perfectly known. For this purpose, in this manuscript, we developed a robust three-stage central difference Kalman filter (RThSCDKF). We used RThSCDKF for model-based fault detection and identification (FDI) in nonlinear hover mode of helicopter unmanned aerial vehicle (HUAV) in the presence of external disturbance. In this system, actuator faults are affected by each other. The proposed method estimates and decouples actuator faults in the presence of external disturbances. This model can detect stuck and floating faults that are important to detect. At the end, this method is compared with the three-stage extended Kalman filter (ThSEKF). Simulation results show the effectiveness of the proposed robust method for detection and isolation of various actuator faults and also this shows more accuracy with respect to ThSEKF.

The surface layer machined after electrical discharge machining (EDM) is different from it after traditional methods, and studying the surface layer structure machined by this method will contribute significantly to the selection of finishing methods. In this study, the surface layer of SKD61 steel after EDM using copper (Cu) electrode was analyzed. Technological parameters including discharge current (Ie), pulse on time (Ton), pulse off time (Tof), and voltage (Ue) were used in the study. The minimum recast layer thickness (RLT) was determined using the Taguchi method. The results showed that Ie, Ton, and Tof were significant influences on RLT, and Ue was insignificant. Minimum, value of RLT = 3.72 µm at process parameters Ie = 1 A, Ton = 50 µs, Tof = 12 µs, and Ue = 30 V. The machined surface layer after EDM is inconsistent with the workability of the product, and it should be removed from the machined surface.

In this paper, the loading path was optimized in hot metal gas forming (HMGF) process for making AA6063 cylindrical stepped tubes. For this purpose, the response surface method (RSM) and finite element method (FEM) were applied using Design-Expert and ABAQUS softwares, respectively. The parameters of internal pressure, pressure rate, axial feeding, and punch speed were examined based on the central-composite design in the three levels. The maximum die filling and the minimum tube thinning percentages were selected as the objective functions. The analysis of variance showed that the axial feeding, internal pressure, and their interaction were the most significant parameter in the die filling and tube thinning. The optimum loading path at the temperature of 550 oC was obtained at pressure of about 7 bars, pressure rate of 0.01 bar/s, axial feeding of 7 mm from each side and punch speed of 0.02 mm/s. Experimental tests were performed for the specified process parameters. The numerical results were validated by experimental testing.

The development of special grease makes it possible for angular contact ball bearings to operate at high speed and temperature, so, it become necessary to investigate thermal-fluid characteristics inside high-speed angular contact ball bearing lubricated with grease. In this paper, a simulation model for angular contact ball bearing was established with CFD software Fluent, the heat-fluid-solid coupling method was used to analyze the distribution and flow of grease, heat transfer, and temperature field inside the bearing chamber. The results show that, grease distribution inside bearing chamber was very inhomogeneous, most of grease was distributed on the both sides of the rolling elements along outer raceway and its flow velocity was very low, only a little grease was adhered on the surface of roll-ing elements, cage, and inner ring, its flow velocity was high; grease distribution inside bearing chamber becomes more inhomoge-neous with the increase of bearing speed; in bearing heat transfer conduction was dom-inant and grease plays a key role, convec-tion of air and grease was insignificant; affected by heat transfer condition the temperature rise of bearing components was obviously different, rolling elements have the highest temperature, the tempera-ture of inner ring was slightly lower than that of rolling elements, temperature of outer ring was the lowest. Bearing tempera-ture experiment was conducted on self-made test rig and verified the validity and accuracy of numerical simulation. The results of this study will provide some reference for lubrication design and thermal analysis of high speed angular contact ball bearing lubricated with grease.

The modeling of corneal tissue cutting is essential in developing haptic training simulators and robot-assisted surgeries. A finite element model was developed for the ovine corneal cutting process and validated with an experimental setup for the first time. The experimental setup measured force in pre-cutting, cutting, and relaxation phases. The mechanical behavior of corneal incision was modeled by the finite element method. A test setup was built to conduct experiments on 32 fresh and well-preserved ovine cornea. Force was recorded with the sampling rate of 200 Hz. The tests were performed for intraocular pressures from 15 mm-Hg to 18 mm-Hg, and keratome velocities of 1 mm/s and 2 mm/s. The finite element model characterized the nonlinear behavior of the ovine corneal tissue. In the pre-cutting phase, force increased until the instrument tip penetrated. A 12.3% (2 mm/s) and 19.1% (1 mm/s) reduction in force indicated the onset of the cutting phase after which force remained constant. At the relaxation phase, force returned to zero. The cutting force values varied by pressure between 0.183N and 0.287 N for 1 mm/s and between 0.211 N and 0.281 N for 2 mm/s of keratome velocity, respectively. The finite element simulations show that the maximum force errors predicted by the model is 0.042 N for 2 mm/s of keratome velocity. The root mean square of force error between the finite element simulations and the experiments is 0.025 N.

Friction stir spot welding of dissimilar aluminum and copper sheets was investigated in details using Taguchi approach in this study. Analysis of variance was conducted to identify the effective parameters and their contributions on the mechanical performance. The findings revealed that the outputs followed normal distribution. The results indicated that the rotational speed with the contribution of 87.7% was the most effective parameter on the maximum tensile force tolerated by the welded samples. Dwell time and penetration depth were in second and third ranks from effectiveness viewpoint with the contributions of 8.8 and 2.9%, respectively. The results revealed that the maximum tensile force was significantly improved with the rotational speed. The maximum tensile force was enhanced by almost 228% by increasing the rotational speed from 550 rpm to 1500 rpm. Increasing the dwell time from 10 to 20 s led to improve the maximum tensile force by 31%.The sequence of the parameters was as rotational speed, dwell time and penetration depth from standpoint of influence on the maximum force according to the results of signal to noise ratio analysis. The signal to noise ratio analysis showed that the rotational speed of 1500 rpm, the penetration depth of 2.85 mm, and the dwell time of 20 s were the optimum conditions.

As a typical buffer energy absorbing structure, thin-walled tube filled with foam aluminum has good mechanical properties and energy absorption characteristics. Therefore, the axial compression performance of square tube and foam aluminum filled square tube was experimentally studied by quasi-static mechanical loading method. On the basis of the existing experimental research and theoretical analysis, the strain rate is introduced into the dynamic compression theory, and the mathematical model of the average crushing load of foam aluminum filled square tube under the axial quasi-static and impact loads is obtained. By comparing the theoretical results with the simulation results, the relative error of quasi-static and impact state is 2.8% and 8% respectively. This paper not only proves that foam aluminum filling can significantly improve the bearing capacity and energy absorption performance of square tube structure in the axial compression process, but also provides a more specific theoretical basis for the axial compression energy absorption design of square tube filled with foam aluminum.

The present study is to carry out a numerical sloshing using smoothed particle hydrodynamics (SPH) in the prismatic tank. Sloshing is a violent flow caused by the resonance of fluid in the tank by external oscillation. The prismatic tank was used to resemble a membrane LNG type carrier. The sloshing experiment was carried out using three pressure sensors, a camera high resolution, and four degrees of freedom forced oscillation machine. In this study, a filling ratio of 25% was used to reproduce sloshing in a low filling ratio. Only roll motion is used in the numerical simulation. Roll motion is directly imposing from the experiment displacement, and a comparison of hydrostatic and dynamic pressure was made to validate the SPH result. The time duration of the sloshing is the same as the experiment. Single-phase and multiphase SPH are conducted to reproduce sloshing in the prismatic tank. Sloshing was done both for the 2D and 3D domain. It shows that SPH has a good agreement with analytical and experimental results. The dynamic pressure is similar to an experiment through a spurious pressure oscillation exist. The dynamics pressure results show fairly for short time simulation and slightly decrease after that. The free surface deformation tendency is similar to experiment.

Dissimilar welded joints of AISI 430 and AISI 316L stainless steel were produced by the GMAW process using two different shielding gas mixtures composed of 97Ar-3N2 and 80Ar-19He-1O2. The microstructure of the heat-affected zone was characterized by optical and scanning electron microscopy, and Vickers microhardness measurements were carried out along the cross-section of the specimens. The dissimilar welded joints were submitted to immersion corrosion test in a 10%v/v hydrochloric acid solution for 24 and 72 hours. Afterward, yields strength, tensile strength, and elongation percentage were measured using tensile tests according to ASTM E8 standard. Non-immersed welded joints were used for comparison purposes. An analysis of variance was developed to evaluate the influence of immersion time and shielding gas mixture on yielding strength and tensile strength. The microstructure characterization showed that the heat-affected zone on AISI 430 side was the widest, and it was observed a significant presence of acicular ferrite, martensite, and coarsened ferritic grains. In contrast, on the heat-affected zone on AISI 316L side was not observed coarsening nor refinement of austenite grains. The AISI 430 heat-affected zone showed the maximum hardness values and higher susceptibility to corrosion damage. Tensile tests results evidenced that immersion corrosion tests did not change significantly ultimate strength in comparison to non-immersed specimens while yielding strength and elongation percentage were drastically decreased due to immersion time. According to the p-value, the immersion time is the most influencing factor on yielding strength and tensile strength of the dissimilar welded joints.

Calorific value, as a key component for fuel quality assessment, directly affects the thermal power plants' efficiency. While high-quality coal is consumed as metallurgical coal, low-rank coals are used by coal-fired power plants. The high moisture content of the thermal coals significantly influences their heating values. In this study, the drying performances of the fixed bed and air dense medium fluidized bed (ADMFB) dryers were investigated under the superficial air velocity of 15-18 cm/s, inlet air temperature of 55-75 ºC, and up to 80 minutes of operation. Low air consumption is an intrinsic characteristic for ADMFB, while a low-temperature range for drying air was selected to address the coal-fired power plants' waste heat. It was found that an increase in air velocity and temperature favored the drying efficiency of both systems (i.e., 18 cm/s and 75 ºC), with the temperature being more effective than the air velocity. The ADMFB dryer removed comparatively more moisture than the fixed bed for the shorter drying durations. For example, for 10% moisture reduction at 75 °C, the ADMFB dryer needed 5 minutes less time than the fixed bed. The fitting quality and goodness of serval well-known thin-layer models for describing fluidized bed and ADMFB coal drying kinetics were assessed by several models and statistical evaluators, respectively. It was found that the Middilli & Kucuk model best describes the fixed bed coal drying (i.e., R2=0.999, RSE=0.001, RMSE=0.008), while the Page model much properly simulates the ADMFB coal drying (i.e., R2=0.998, RSE=0.002, RMSE=0.009).

Kudryavy volcano is the world's only deposit of rare elements in the form of pure rhenium mineralization. The development of the field is hampered by numerous factors: high temperatures of geothermal fields, strong winds, fumarolic activity, where the use of a drilling and blasting method to destroy rocks in a crater can lead to the closure of all fumarole channels, which will lead to the accumulation of enormous energy and further eruption. The article describes the existing electrical methods for the rock destruction, it was found that the current-voltage characteristic of volcanogenic breccia with an increase in the distance between the electrodes more than 50 cm turns into a C-shaped dependence, reducing the current strength from 0.85 A to 0.2 A, forming a full breakdown channel. In this case, the minimum breakdown strength of the electric field is 0.3±0.1 kV/cm, with an increase in this indicator to 3.7 kV/cm, the efficiency of channeling increases to 2%. Around the breakdown channel, a new substance is formed with new conductive properties, different from volcanic breccia, which prevents the formation of the channel along the old trajectory.

Suitable pattern design of drilling and blasting is very important in open pit mines. Using of explosive energy for rock fragmentation with minimum cost of production is one of the blasting purposes in open pit mines. The most important parameters of blasting are including diameter of hole, specific charge, burden thickness and suitable dimensions of rock fragmentation. In this paper, specific charge is calculated based on quality of rock mass and then based on definition of specific charge, maximum and minimum thickness of burden in open pit mines is calculated. In this paper, a new models of burden estimation based on quadratic equations is presented. Therefore, based on this new equations, other parameters of blasting are corrected. Also, the validation results of the new equations in this article show the new burden thicknesses have slightly differences with the experimental results. The maximum error of calculated burden is equal 3% based on obtained data. Therefore, the output results of these new equations can be reliable and accurate for calculations of the burden thickness.