International Journal of Engineering
Volume:33 Issue: 4, Apr 2020

In this study, Fe3O4/CMC magnetic nanoparticles were synthesized through co-precipitation method. Afterward, laccase from Trametes hirsuta was immobilized onto Carboxymethyl cellulose (CMC)-coated magnetic Fe3O4 nanoparticles by covalent bonding between carboxyl groups of carboxymethyl cellulose and amine group of laccases. Also, the resulted magnetic nanoparticles and immobilized laccase were characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and dynamic light scattering (DLS) analysis. Moreover, the vital factors in enzyme immobilization, such as contact time, amount of N-hydroxysuccinimide (NHS), and the amount of nanoparticles were optimized, which successively 48 h, 0.01 g, and 0.0125 g were achieved for 0.01g of N-ethyl-N′-(3-dimethylaminopropyl)carbodiimide (EDC). Activity recovery of 51 ± 0.8% was achieved by optimizing the immobilization process. The results also indicated that the loading of laccase onto carboxymethyl cellulose-coated Fe3O4 nanoparticles was approximately 120 (mg/g). Finally, the immobilized laccases on magnetic support could save nearly 50% of their initial activity after five consecutive cycles.

Thin perforated Steel Plate Shear (SPS) Walls are among the most common types of energy dissipating systems. The applied holes reduce the shear strength of the plate and allow to decrease the profile size of the members at the boundary of the panel when these systems are used in the typical design of structures. On the other hand, the different fracture locations of these panels are visible when considering the different perforation patterns. This paper reports on the results obtained from the experimental study under cyclic loading of the effect of different hole patterns on the seismic response of the systems and the location of the fracture. According to this, two perforated specimens by different patterns were considered. In addition, a plate without holes for a better comparison of the fracture location was chosen. The results showed that changing the pattern of the holes causes a change in the fracture location. Moreover, in perforated specimens, the amount of shear strength did not reduce suddenly after the fracture phenomenon. In the specimen which was perforated around the web plate, the pinching force was more than any other in the low cycle of the drifts. For this reason, the energy dissipation and initial stiffness were more than up to 3% drift. The experimental specimens were then simulated with a Finite Element (FE) method using the ABAQUS. Finally, a parametric FE analysis on different series of perforated panels, by changing the diameter of the holes and the plate thickness, has been carried out.

The use of supplementary cementitious materials (SCMs) in concrete manufacturing is considered as financial, technical and environmental benefit. In this regard, this paper presents the experimental and analytical study of high strength concrete (HSC) with alccofine-1203 (alccofine) and fly ash as partial replacements to cement. A total of seven mixes were prepared with different percentages of alccofine (4-14%). The prepared concrete mixes were experimentally tested for slump, compressive, flexural and split tensile strengths for 7, 28, and 56-days curing ages. Uniaxial stress-strain behavior, and water absorption and porosity were evaluated at 28-days curing age. Young’s modulus, energy absorption capacity (EAC) and integral absolute error (IAE) were assessed analytically. From the test results, it was observed that the replacement of cement with alccofine significantly improved the workability of the concrete. Among all the mixes, the mix with 10% alccofine content exhibited good behavior in all the investigated parameters. The alccofine incorporation was found to have a negative effect on the behavior of HSC beyond 10% replacement in all the investigated parameters. Based on the experimental compressive strength results, empirical relations were proposed to predict the flexural and split tensile strengths. The proposed empirical relations have the lowest IAE (3.29 and 3.32% for flexural and split tensile strength) in comparison with ACI-318, IS 456 and empirical relations proposed by earlier researchers.

Super-resolution is a process that combines information from some low-resolution images in order to produce an image with higher resolution. In most of the previous related work, the blurriness that is associated with low resolution images is assumed to be due to the integral effect of the acquisition device’s image sensor. However, in practice there are other sources of blurriness as well, including atmospheric and motion blur that may be applied to low resolution images. The research done in this paper provides a super-resolution image from some low-resolution images suffering from blurriness due to defocus. In contrast to motion blur kernels that are sparse, the defocus blur kernel is non-sparse and continuous. Because of the continuity property of defocus blurring kernel, in this paper, we bound the gradient of blurring kernel using proper regularizers to satisfy this property. Experimental results on synthetic data demonstrate the effectiveness of the proposed method to produce high resolution and de-blurred images from some blurry low-resolution images.

Recently, blind multi-user detection has become an important topic in code division multiple access (CDMA) systems. Direct-Sequence Spread Spectrum (DSSS) signals are well-known due to their low probability of detection, and secure communication. In this article, the problem of blind multi-user detection is studied in variable processing gain direct-sequence code division multiple access (VPG DS-CDMA). The method based on the fluctuations of autocorrelation estimators,which previously described in a single and multi-user context, is extended to an asynchronous variable processing gain (VPG) DS/CDMA systems without restrictions on the processing gains in multi-path channel condition. According to the proposed algorithm, not only the presence of the common peaks in the second-order statistic of the received signal is proved, but the relationship between these peaks and the spreading code length is also derived. The simulation results show that the proposed algorithm even in the presence a very low signal-to-noise ratio (SNR) is completely efficient in signal detection. It is remarkable that  the minimum description length (MDL) method is used to determine the number of users.

Hand posture estimation attracts researchers because of its many applications. Hand posture recognition systems simulate the hand postures by using mathematical algorithms. Convolutional neural networks have provided the best results in the hand posture recognition so far. In this paper, we propose a new method to estimate the hand skeletal posture by using deep convolutional neural networks. To simplify the proposed method and to be more functional, the depth factor is ignored. So only the simple color images of hands are used as inputs of the system. The proposed method is evaluated by using two datasets with high-diversity named Mixamo and RWTH, which include 43,986 and 1160 color images, respectively, where 74% of these images are selected as a training set and, 26% of the rest images are selected as the evaluation set. The experiments show that the proposed method provides better results in both hand posture recognition and detection of sign languages compared to state-of-the-art methods.

In this paper, an intuitive analysis of a phase noise reduction technique is done, and then a modified structure is proposed to achieve higher phase noise reduction than the original one. This method reduces the impact of noise sources on the phase noise by decreasing closed-loop gain in zero-crossings points and moving this high closed-loop gain to the non-zero-crossings points. This reduction tested on different scales and all of them showed improvement in the phase noise performance. In other words, this method reduces the phase noise by manipulating the operation region. Impulse sensitivity function (ISF) for the proposed structure shows degradation in comparison to the original structure. We have designed the proposed oscillator in 0.18 μm using CMOS TSMC standard technology. The proposed oscillator operates on 900 MHz, moreover, phase noise is -138.4 dBc/Hz at 1 MHz offset frequency while it consumes 3.11 mA from 1.8 V supply voltage. Keywords. LC cross-coupled oscillator. Phase noise reduction. ISF reduction.

This paper presents a hybrid scheme for the control of active and reactive powers using the direct vector control with stator flux orientation (SFO) of the DFIG. The hybrid scheme consists of Fuzzy logic, Reference Signal Tracking (F-RST) controllers. The proposed (F-RST) controller is compared with the classical Proportional-Integral (PI) and the Polynomial (RST) based on the pole placement theory. The various strategies are analyzed and compared in terms of tracking, robustness, and sensitivity to the speed variation. Simulations are done using MATLAB software. The simulation results prove that the proposed approach leads to good performances such as the tracking test, the rejection of disturbances and the robustness concerning the parameter variations. The hybrid controller is much more efficient compared to those of PI and RST controller, it also improves the performance of the powers and ensures some important strength despite the parameter variation of the DFIG.

This paper introduces a new hybrid hill-climbing algorithm (HHC) for solving the Economic Dispatch (ED) problem. This algorithm solves the ED problems with a systematic search structure with a global search. It improves the results obtained from an evolutionary algorithm with local search and converges to the best possible solution that grabs the accuracy of the problem. The most important goal of economic load dispatch is the optimal allocation of each generator's contribution to provide the load and reduce the costs of active units in the power system. This is generally due to presence of the nonlinear factors and limitations, such as the effect of the steam inlet valve (valve point effect (VPE)), the balance between the power generation and power demand of the system, the prohibited operating zones (POZS), power generation limits, ramp rate limits, and transmission losses. This algorithm is implemented on three 13-unit, 15-unit and 40-unit test systems with different operating conditions, and also for the same three test systems in combination with the evolutionary PSO algorithm. The simulation results show the efficiency of the proposed algorithm in solving ED problems.

Common-mode voltage (CMV) generated by the inverter causes motor bearing failures in multiphase drives.On the other hand, presence of undesired z-component currents in six-phase induction machine (SPIM) leads to extra current losses and have to be considered in pulse width modulation (PWM) techniques. In this paper, it is shown that the presence of z-component currents and CMV in six phase drive system are two major limiting factors in space vector selection. The calculated voltage space vectors for both symmetrical and asymmetrical SPIM drive system with three-level inverter are illustrated in the decoupled subspaces and described in terms of undesirable voltage components and CMV value. Several space vector pulse width modulation (SVPWM) techniques are investigated based on CMV and z-component currents generation. Then, a modified SVPWM technique with minimum current distortion, undesired current components and CMV with a modest torque ripple is proposed based on the simulation results.

This paper discussed the scheduling problem of outpatients in a radiology center with an emphasis on priority. To more compatibility to real-world conditions, we assume that the elapsed times in different stages to be uncertain that follow from the specific distribution function. The objective is to minimize outpatients’ total spent time in a radiology center. The problem is formulated as a flexible open shop scheduling problem and a stochastic programming model. By considering the specific distribution function for uncertain variables, deterministic mixed integer linear programming (MILP) is developed such that the proposed problem can be solved by a linear programming solver in small size. Besides an effective heuristic method is proposed for the moderate size problem. To indicate the applicability of the proposed model, it has been applied to a real radiology center. The results from the proposed optimization models indicate an increase in outpatients’ satisfaction, as well as the improving of the efficiency and productivity of the radiology center.

In this paper, a single-product, single-machine system under Markovian deterioration of machine condition and demand uncertainty is studied.  The objective is to find the optimal intervals for inspection and preventive maintenance activities in a condition-based maintenance planning with discrete monitoring framework. At first, a stochastic dynamic programming model whose state variable is the machine status is presented. In the first model, the demand is assumed to be deterministic and the objective is to minimize the sum of inspection, preventive maintenance, and lost sale costs. Then, in order to take the demand uncertainty into account, the extended model is formulated as a scenario-based two-stage stochastic programming one. In the second model, selecting the best inspection plan and finding the appropriate intervals for preventive maintenance are considered as the first and second stage decisions, respectively. Analyzing an illustrative example to study the effect of demand uncertainty in the problem shows thatthe total average cost is a non-decreasing function of machine state and demand. Moreover, if the machine state is worsened or the demand is increased, the number of inspections increase and the preventive maintenance should be executed at the same time or earlier. Finally, when the unit lost sale cost is greater than a certain amount, ignoring the demand uncertainty is not costly.

The conservation of lakes is an essential issue in sustainable development. Disruption of ecological balance, destruction of biodiversity and vegetation, desertification, and storm surges are the results of lakes drying. The purpose of this paper is to introduce an integrated bi-objective sustainable water resource management model. The first objective function deals with economically optimal allocation of water to the residential, industrial, and agricultural sectors. For compliance with the requirements of sustainable development, the second objective is to maximize the amount of water allocated to the environment. For proper utilization and reuse of water resources, the location of urban wastewater treatment plants is also considered in the problem. The model is solved with data from the most important watershed in Iran, Urmia Lake. Natural and unnatural factors have dramatically reduced the amount of water intake and balance over the past two decades. The epsilon constraint is used for solving the case study model. The results show that the model can satisfy the demand of sectors, with 70 percent of the available resources. The use of this model can meet the demands of the consumer sectors, and also, it can help revitalize Urmia Lake and the ecosystem of the river in its basin.

Geopolymer paste is an innovative construction material which shall be produced by chemical action of inorganic molecules. It is a more environmentally friendly alternative to conventional Portland cement which is abundantly available worldwide. In this study, the influence of different alkaline activators (Na and K) on the mechanical and thermal behaviors of metakaolin-based geopolymer was investigated. The aims of this study is to find out the mixes and their process parameters, which are appropriate to produce Geopolymer paste with one of the highest compressive strength, highest - lowest porosity and highest- lowest initial and final setting time. Taguchi method is used in the design of the experiments for the metakaolin-based Geopolymer. Five factors were selected as process parameters that are more likely to affect the Geopolymer characteristics. These are the amount of Si, alkali type, alkali reagents ratio, mixing time, and water content. The effect of these parameters on the setting time, density, porosity, compressive strengths at 7 and 28 days. The results of study found that the Geopolymer paste with high compressive strength of (107.2MPa) can be obtained with the formula (0.2K2O.0.8Na2O. Al2O3. 3.6SiO2.xH2O) using proper processing condition in which the alkali silicates to the alkali hydroxides molar ratio should be kept in the range of 2.26. The results revealed that the use of alkali solution of K-ions and Na-ions improves the compressive strength of the geopolymer remarkably as compared with the use of Na-ions solution along. In addition, it has been noticed that the setting time is reduced, for geopolymers with silica content of less than 3.8, when K-ions is used. Similarly, the bulk density of geopolymers is found to be reduced by adding K-ions.

In this paper, the short-term creep behavior of the Inconel-713C superalloy after different pre-treatments including the ageing and forging processes has been studied at 850 °C. The ageing heat treatment was heating at 930 °C for 16 hours without solutioning process. The optical microscopy (OM) and the scanning electron microscopy (SEM) techniques were applied for microstructural evaluations. The results showed that although the ageing treatment increased the γ’ phase content, the age-hardened material had a lower creep lifetime (about 40%) with respect to the as-cast alloy. This was related to the decrease in the amount of M23C6-type secondary carbides precipitation. When the Inconel-713C superalloy specimen was forged at 1200 °C, the third stage of the creep curve (strain versus time) increased drastically and shortened the creep lifetime. The small grain size of the forged specimen was responsible for such inverse creep behavior. In addition, fractographs of this specimen indicated intragranular cracks on the ruptured surface. When the forged sample was age-hardened directly without the solutioning treatment, the creep lifetime increased about 4 times as compared to the forged specimen. Inconel-713C Superalloy Short-term Creep Age-hardening Forging Microstructure

Pure and doped magnesium oxide nanoparticles were successfully synthesized employing a sol-gel process. The synthesized nanoparticles were characterized by thermal differential analysis, X-ray powder diffraction, transmission electron microscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, and vibrating sample magnetometer. X-ray diffraction patterns confirmed the crystallization of MgO structure and correspondingly ratified that the transition metal atoms were incorporated into the MgO host lattice. The crystallite size decreases as the concentration of dopants were augmented. TEM images showed that the particles of pristine magnesium oxide were embedded in the sheet matrix of the graphene-like layer with a size of 22.06 nm. The EDS spectra revealed the presence of carbon in pure MgO nanoparticles, while nickel and chromium were distributed in the host lattice. Based on VSM measurements, room temperature ferromagnetism in pristine MgO-NPs could be ascribed to the presence of either Mg vacancy or carbon atoms. Furthermore, paramagnetic ordering had been observed upon doping. Overall, the prepared MgO-NPs may be found as a potential application in spintronics devices.

The aim of this study, is to use finite element simulation to achieve the optimal geometry of a broaching tool that creates the lowest tensile stress at the machined surface of the Ti6Al4V alloy. It plays a major role in reducing production costs and improves the surface integrity of the machined parts. The type and amount of residual stress determined by the thermal and mechanical loads transmitted to the workpiece. In this research, the two-dimensional simulation of the broaching process is done by finite element DEFORM-2D® software for the two end teeth of the tool that perform the cutting operation. In simulating the first tooth, Response Surface Method is used to select the desired controllable parameters of the process such as cutting speed, rake angle, clearance angle, rise per tooth and depth of cut. In order to establish low thermal and high mechanical load in workpiece, multi-objective genetic algorithm employed after perform simulation in the first tooth. In simulating the second tooth, Response Surface Method used to select desired controllable parameters of the process such as rake angle, clearance angle and radius of cutting edge. For the second tooth, a multi-objective genetic algorithm has been used. Ultimately, the geometry of the broaching tool utility has been designed to store the lowest tensile residual stresses in the machined surface for Ti6Al4V alloy.

The rotating machinery is a common class of machinery in the industry. The root cause of faults in the rotating machinery is often faulty rolling element bearings. This paper presents a novel technique using artificial neural network learning for automated diagnosis of localized faults in rolling element bearings. The inputs of this technique are a number of features (harmmean and median), which are extracted from the vibration signals of the test data. Effectiveness and novelty of this proposed method are illustrated by using the experimentally obtained the bearing vibration data based on laboratory application. In this research, based on the fast kurtogram method in the time-frequency domain, a technique for the first time is presented using other types of statistical features instead of the kurtosis. For this study, the problem of four classes for bearing fault detection is studied using various statistical features. This study is conducted in four stages. At first, the stability of each feature for each fault mode is investigated, then resistance to load change as well as failure growth is studied. At the end, the resolution and fault detection for each feature using the comparison with a determined pattern and the coherence rate is calculated. From the above results, the best feature that is both resistant and repeatable to different variations, as well as the suitable accuracy of detection and resolution, is selected and with comparing to the kurtosis feature, it is found that this feature is not in a good condition in compared with other statistical features such as harmmean and median. The results show that the accuracy of the proposed approach is 100% by using the proposed neural network, even though it uses only two features.

As the most important working area of gear, teeth play the role of transmitting load and power. Tooth line and tooth profile are the two main characteristics of the tooth surface, which affect the shape of the tooth surface, tooth meshing characteristics and contact characteristics. Taking the elliptical cylinder gear pair in the reversing device of a new type of drum pumping unit as the research object, the dynamic meshing process of the gear is simulated by LS-PREPOST software based on loaded tooth contact analysis (LTCA) technology. The distribution law of the effective plastic strain, effective stress and tooth surface pressure in the direction of the tooth line and tooth profile as well as the tooth meshing force under different speed conditions are obtained. The results show that the effective plastic strain, effective stress and tooth surface pressure will decrease with the transition of the center position of the elliptical contact area on the tooth surface to both sides. The distribution of stress and strain in the direction of tooth line will change with the location of the teeth, and the rotational speed has a certain influence on the meshing force of the teeth. The results of this research can provide a theoretical basis for the subsequent analysis of the dynamic meshing characteristics and modification of non-circular gear.

In this paper, the energy absorption features of tri-layer explosive-welded deep-drawn cups subjected to quasi-static axial compressive loading are investigated numerically and experimentally. To produce the cups, tri-layer blanks composed of aluminum and stainless steel alloys were fabricated by an explosive-welding process and formed by a deep drawing setup. The quasi-static tests were carried out at a rate of 2 mm/min. Based on the structure of the tri-layer cups and to calculate the energy absorption features of these structures, a numerical model was established and validated by experimental findings. Moreover, based on a surrogate model and using non-domain sorting genetic algorithm II, multi-objective optimizations were performed on specific energy absorption and initial peak load. The results indicated that the total absorbed energy and mean crush force of the pure stainless steel tri-layer cup were about 5.8 and 5.7 times the values of those for the pure aluminum specimen, respectively.

In view of the uneven artificial sowing, low sowing, as well as the fact that the existing seeders cannot meet the sowing requirements of Pteris vittata, this paper designed an automatic plug seeder by using the method of spraying and sowing after mixing spores and water. In order to obtain the optimum working parameters of the seeder, response surface method (RSM) was employed to design the experiments and evaluate the results with the purpose of optimizing parameters for improving spraying uniformity. The parameters such as the distance between the nozzle and plug and the nozzle angle and transmission speed were selected, and then the regression equation of spraying uniformity was established. The results showed that the influence of various factors on spraying uniformity coefficient from high to low were nozzle angle, distance between the nozzle and plug and transmission speed. Through the experimental analysis, it can be concluded that when the distance between the nozzle and plug was 11.63 cm, the nozzle angle and the transmission speed were 79.23° and 0.21 m/s, respectively; the seeding uniformity coefficient was the largest, 83.43%. The verification test results indicated that the optimized result was reliable. This study can provide reference for the development of micro seed seeder.

The article discusses researches performed in the Well Drilling Department of the St. Petersburg Mining University. The directions of development of the department are shown. Special attention in this article is paid to research in the field of developing drilling fluids for drilling wells in various mining and geological conditions. It is shown that the gas-liquid mixtures studied by the department will be effective for under balanced drilling under conditions of abnormally low reservoir pressures when using a binary mixture of sodium lauryl sulfate 0.5% + linear sodium alkyl benzene sulfate 0.5% as a surfactant and polyacrylamide FP complex 107 (0.05%) as a forming and stabilizing additive  +  carboxymethyl starch BUR-2 (1%). Studies in the field of development of inhibitory fluids have shown that an increase in the concentration of polar compounds in the drilling fluid compared to their concentration in the rock Cp> Cn by 0.25 mol/L makes it possible to increase the stability of the rocks around the wellbore compared to the initial conditions. Studies of lubricating additives showed that introducing 1.5–2.0% of FRW additive reduces the friction coefficient of the metal– metal pair in a clay solution by 70–75% and in an aqueous solution up to 65%. The findings suggest that drilling fluids developed at the Well Drilling Department of the St. Petersburg Mining University have a high potential for their application in oil and gas fields in order to improve the efficiency of drilling and completion of wells. It is also noted that the scientific and technical potential of the department allows for input control of reagents in drilling fluids, as well as the development and research of various compositions not only for drilling and completion of wells, but also for development and repair, which are applicable in real field conditions.10.5829/ije.2020.33.04a.22