International Journal of Engineering
Volume:33 Issue: 6, Jun 2020

In this research, graphene oxide (GO) was functionalized by tannic acid to produce GO-TA and fabricate a novel functionalized graphene oxide/ polyacrylonitrile (PAN) nanofibrous as an adsorbent in order to remove two hazardous heavy metals from aqueous solutions. The results showed that the composite adsorbent can properly adsorb Pb2+ and Cd2+ metal cations, due to having the numerous potential active sites. The optimum conditions for 97.37% of Pb2+ and 94.28% of Cd2+ ions removal were meanly obtained at pH of 6.3, nanoparticles weight percentage of 4.26 wt.%, metal ions concentration of 35.74 ppm and contact time of 70.5 min. The maximum adsorption capacities for lead and cadmium ions.were found at 344.83 and 312.5 mg/g, respectively.

Use of biosurfactant as a green stabilizer for the biological synthesis of gold nanoparticles (AuNPs) is now emerging as a nontoxic and environmentally acceptable "green chemistry" procedure. Stability of AuNPs at different pHs is very important because our body has different pHs. This paper addresses this issue. In this work, first P. aeruginosa PTCC 13401 was used to produce rhamnolipid biosurfactant. The highest rhamnolipid production occurred at 120 h, achieving a value of 3.1 g/L. The thin layer chromatography (TLC) indicated that the crude product is a mixture of mono-rhamnolipid and di-rhamnolipid with retardation factor (Rf) value of about 0.35 and 0.78, respectively. Moreover, rhamnolipid solutions with different pHs were added to HAuCl4 solution and incubated for 24 h at 37 oC and 150 rpm. The formation of spherical AuNPs was monitored using a UV–vis spectrophotometer and verified by TEM. Our results showed that the formation of AuNPs occurred just for pH values between 7.0 -8.0. Measurement of the surface tension of the solution at different pH values was performed to find out the reason for this observation. Our results showed that the surface tension was also stable only between pH 7.0-8.0. This was inferred from precipitation of rhamnolipid at higher and lower pH values. The results of this work may help pharmacists to have a good prediction of behavior of rhamnolipid biosurfactants as a green stabilizer for biomedical applications including tissue engineering and drug delivery.

In this study, nanoscale zero-valent copper (nZVC) as catalyst activated persulfate (PS) was used for the degradation of p-chlorophenol (p-CP) under ultrasonic (US) irradiation in aqueous solution. The effect of different operational parameters such as solution pH (3.5-10.5), PS concentration (1-7.5 mm/L), nZVC dosage (5-35 mg/L) and initial p-CP concentration (10-100 mg/L) were evaluated at different contact time. Results indicated that US/PS/nZVC system achieve higher efficiency in p-CP degradation than US/PS, US/nZVC and PS/nZVC systems. The optimal p-CP removal efficiency (98%) was achieved within 40 min with 5 mm/L PS and 30mg/L nanocatalyst at 25 mg/L initial p-CP concentration. It was also observed that the p-CP degradation rate depends on initial p-CP concentrations. To clarify the mineralization of p-CP, TOC and COD were analyzed at optimum conditions. COD and TOC removal rate obtained from the US/PS/nZVC system with contact time of 60 min were 61and 75%, respectively. Through the use of methanol (MA) and tert-butyl alcohol (TBA) as radical scavengers,  was identified as the main radical species that are generated during processes. The removal process of p-CP could be described by the pseudo-first-order kinetics. The apparent degradation rate constant (k) was 0.076 min-1 in US/PS/nZVC system at optimal conditions.

Electric potential measurement technique (tomography) was introduced as a nondestructive method to evaluate concrete properties and durability. In this study, numerical meshless method was developed to solve a differential equation which simulates electric potential distribution for concrete with inclusion in two dimensions. Therefore, concrete samples with iron block inclusion in different locations were cast. Then, via a pair of electrodes attached to the samples, DC current was injected into concrete and electric potential was measured through 14 electrodes placed in the perimeter of the samples. In total, 35 different pair electrode configurations were planned for current injection. Bayesian theorem was employed to perform probabilistic tomography as well as to calculate the optimal shape coefficient in the numerical meshless method. Results of this study indicated that shape coefficient in multiquadratic radial-based function (MQ-RBF) model does significantly depend on boundary conditions. Furthermore, when the main current line is long, distribution of random variables c and e fits well with normal distribution, which is in agreement with the study assumption. Also, results reveal that probabilistic tomography is more precise than deterministic tomography even without using prior functions. Experimental results showed that MQ-RBF model has good performance in electrical tomography. This is due to uncertainty of concrete physical properties in real conditions which can be resolved by meshless method using optimization of shape coefficient.

Recent scientific concerns to achieve sustainability in construction have suggested the implementation of using recycled aggregate in concrete; because it has the potential to reduce the demand for extraction of natural raw materials and decrease the volume of wastes landfilled. In this respect, this study aims to investigate the suitability of using ceramic tile (CT) and ceramic sanitary (CS) wastes as coarse aggregate in production of high-strength concrete (HSC). Different concrete mixes were produced by partial replacement of 10, 20 and 30% of natural coarse aggregate with recycled aggregates. Besides investigating the characteristics of recycled aggregate, slump, compressive strength, initial and final absorption and chloride ion penetration depth of HSC specimens were evaluated and compared with that of plain HSC. Results showed that using recycled ceramic aggregates increased the superplasticizer dosage to maintain the target slump. Although by incorporation of high percentage of CT or CS aggregate, compressive strength of HSCs was reduced compared with reference HSC, it is possible to produce HSC with 28-days compressive strength higher than 60.7 MPa. Moreover, the absorption and chloride ion penetration depth of recycled aggregate incorporated HSC were higher than those of estimated for plain concrete. Generally, waste ceramic aggregate at optimum replacement ratio can be used in the sustainable development of HSC.

Considering economic reasons and attempting to reduce the carbon footprint of concrete structures, there is an increasing tendency toward the use of high strength reinforcement in seismically active regions. ACI 318-19, Iranian steel rebars standard INSO 3132 and next edition of Iranian national building allow the use of high strength rebars in elements of ductile force-resisting systems. Therefore it is important to verify that if S520 rebars are capable of providing adequate, a) strain capacity, b) out of plane buckling deformation capacity, which are the two common sources of failures observed in recent earthquakes in boundary elements of lightly reinforced shear walls. An experimental program is designed to compare strain capacity of boundary elements reinforced with S400 and S520 rebars, which include monotonic and cyclic loading considering probable loading on lightly reinforced boundary elements. Considering test results for specimens under monotonic and cyclic loading it is shown that, a) gauge length suggested by INSO for rebar test could be misleading in the evaluation of rebar axial strain capacity, b) S520 rebars have limited ductility compared to S400, but considering strain demand, this limited strain capacity is adequate to avoid rebar fracture, c) local strain (crack width) has a better correlation with out of plane buckling compared to average strain as suggested by some researchers, d) it seems that out of plane buckling for S520 rebars occurs at smaller deformation, which means there is the need for larger minimum dimension for sections reinforced with S520 compared to S400.

The objective of this research is to improve the 3-D imaging system using near-infrared light emission in breast tissue to achieve a more accurate diagnosis of the tumor. Experimental results in this research on this imaging system indicate that a more accurate diagnosis of abnormal areas depends on the location of the sources and detectors. Therefore, an improved location model has been proposed to determine a more suitable placement of sources and detectors. In this article, no human breast cancer samples were examined due to inaccessibility to a 3-D imaging system using near-infrared lights. Since such experiments should be conducted several times to obtain more accurate reconstructed images, the proposed method was evaluated using the optical images reconstruction toolbox of NIRFAST 7.2 in the MATLAB programming environment. The results were then compared with the results of similar articles. The obtained results showed that the proposed placement of sources and detectors can detect abnormal areas with a much lower error rate. Furthermore, the proposed placement of sources and detectors achieved a good result in simultaneously diagnosing two abnormal areas.

One of the specifications of wireless sensor networks is the limited power sources for their nodes. Therefore, assessment of energy consumption in these networks is very important, andusing  traditional simulators to evaluate the energy consumption of network nodes has become common practice. Simulators often have problems such as fluctuating output values in different implementations of the same scenario, lack of a visual structure to understand the system, and lack of theoretical background for the gained results. In contrast, analytical modeling methods such as Petri nets do not have the aforementioned problems. Also, they have the necessary tools to model and evaluate the performance of investigated system.The Sensor-MAC (S-MAC) protocol in these networks, which operates in MAC layer, is a competition-based protocol designed to reduce power consumption. This paper presents an analytical model based on a Generalized Stochastic Petri Net (GSPN) to evaluate the power consumption of nodes in an S-MAC-based wireless sensor network. The presented Petri model was implemented in PIPE software, and by applying mathematical calculations from the model, we were able to derive the equations for calculating its energy consumption. The validity of the proposed model is measured by implementing similar scenarios in the Castalia simulator. The experiments were conducted in terms of the number of nodes, duty cycle rate, upper layer data flow, and packet size. The results of the presented model are extracted in a much shorter time than the simulator with the same gained values.

In this paper a new optimization function for increasing the flux weakening range and output torque value of segmented interior permanent magnet synchronous motor (SIPMSM) is presented. In proposed objective function normalized characteristic current and saliency ratio are considered as two optimization variables during optimization process. The focus of this paper is rotor structure design such as PM segmentation technique and new flux barrier design. Increasing the constant power speed range (CPSR) of SIPMSM is done by minimization of characteristic current. This minimization leads to decreasing the output torque therefore in this paper using maximization of saliency ratio, this problem during optimization process will overcomed. For calculation resource reduction a detailed design of PM segmented and flux barriers configuration in rotor structure is carried out by simplified magnetic equivalent circuit of SIPMSM. The output results of proposed magnetic equivalent circuit which is contained PM flux linkage and dq inductances, are verified by Finite Element Method. Simulation results demonstrate that the CPSR of optimized SIPMSM has been doubled and its  output torque has been increased related to the typical design.

Temperature variation intensively affects parameters of the friction force, particularly the average bristle deflections. In our earlier research work, a temperature dependent friction compensation scheme was developed for serial rigid robot manipulators which was comprised of a temperature dependent viscous friction compensation scheme and a temperature dependent disturbance rejection scheme. In this paper, a new criterion for the uniformly ultimate boundedness of the temperature dependent average bristle deflections is proposed in such a way that the temperature dependent average bristle deflections preserve the property of uniformly ultimately boundedness in a larger region. This is an improvement to our earlier research work. As the result of this improvement, it is shown that the proposed method in our earlier work, is applicable to larger temperature dependent disturbance terms. These two improvements are the main contributions of this paper that augment our earlier research work. The idea is supported by a new theorem.

Control systems with digital communication between sensors, controllers and actuators are called Networked Control Systems (NCSs). In general, NCSs encounter with some problems such as packet dropouts and network induced delays. When plant uncertainty is added to the aforementioned problems, the design of the robust controller that is able to guarantee the stability becomes more complex. In this paper, a method based on Robust Model Predictive Control (RMPC) is proposed to overcome model uncertainty together with unknown delay caused in NCSs. The previous RMPC methods, called Normal RMPC, was proposed to compensate delay or model uncertainty, individually. Hereby, we propose a method, named Improved RMPC, to compensate the effects of delay and model uncertainty on NCSs, simultaneously. The proposed method is based on uncertainty polytope and LMIs (Linear Matrix Inequlities). Also, an experimental evaluation of time-delays in MODBUS networked control systems is proposed. The simulation results show the ability of the proposed method. For comparison, the Normal RMPC is applied as well. The results show that the Normal RMPC has an acceptable performance for time delay compensation, but its performance gets destroyed or even get unstable when the model uncertainty is also considered.

Bimetallic parts are used in many industries for weight and cost reduction of workpieces, working under high loads and wear. One of the application for this type of composite material is in automotive industry. In this work, the tool wear and cutting forces in the face milling of bimetallic parts made of aluminum and cast iron were investigated. A356 and GG25 alloys that are common materials for bimetallic engine cylinder block were selected as material for aluminum and cast iron samples, respectively.  Machining length was  3.6 meters in the experiments and the tool wear was calculated on the flank face of tool using image processing method (KNN approach). Results indicated that with the machining parameters selected here, the wear of aluminum sample is not significant but the wear for cast iron and bimetallic materials was considered. It was also discovered that the wear and machining force for bimetallic parts are much higher than samples with cast iron material and the analogy was observed between cutting force and tool wear quantities. From this, it can be concluded that instead of time consuming wear tests, the tool wear trend in face milling of bimetallic parts can be predicted from cutting force measurements. It is also conculded that KNN image processing method is very accurate for calculating the tool wear.

Gaynarje spring is one of the hottest springs in the world and is located around Meshginshahr in northwest of Iran. Because of the water at temperature of 82 ºC, it is not appropriate to use this mineral water for swimming and bathing. In this study, in addition to lowering the water temperature to the appropriate swimming temperature (29 ºC), the hot water is used for power and natural gas production in a combined cycle based on Organic Rankine Cycle (ORC) and LNG cold. The proposed configuration has been studied thermodynamically and optimized for important performance parameters. For this purpose, mass, energy and exergy equations were developed for components and the whole system. Also, performance parameters were calculated. For achieving the best results, several working fluids are examined for the ORC. According to the obtained results R245fa as an ORC working fluid has the best performance from the thermodynamic viewpoint. Also, for optimum condition of the cogeneration cycle, net output power, natural gas production, thermal and exergy efficiencies were calculated to be 524.9 kW, 1.352 kg/s, 24.11 and 48.99%, respectively. The parametric study is also indicated that the performance parameters have optimum values with respect to the evaporator temperature.

In this paper, the thermal characteristics of single and double flow plane solar heaters with radiating working gas were analyzed and compared by numerical analysis for the first time. The laminar mixed convection gas flow in the heaters was numerically simulated by the CFD method using the finite volume technique. The set of governing equations included the conservation of mass, momentum and energy for the convective gas flows and the conduction equation for solid parts. Besides, the radiative transfer equation was solved by the discrete ordinate method for radiant intensity computation. From numerical results, the thermal efficiency of single flow heater found very sensitive to gas optical thickness, such that gas radiation always has positive influence on the performance of system. The efficiency increase about 50% was computed for optical thicknesses more than 2 in the test cases.  However, for double flow gas heater with less sensitivity to gas radiation and reciprocating trend for thermal efficiency with optical thickness, 15% increase in thermal efficiency was seen at the optimum optical thickness. Comparison between the present numerical results and those reported in literature, showed good consistency.