International Journal of Engineering
Volume:32 Issue: 2, Feb 2019

In this study, the potential of four different culture selection methods under short-term enrichment time (STE) to accumulate PHA-producing bacteria in mixed activated sludge was compared and the most efficient culture selection method was introduced. This means, PHA-producing microbial community was firstly enriched in a sequencing batch bioreactor (SBR) with four different selection methods including an anaerobic-aerobic process (SBR1), a fully aerobic batch process (SBR2), an uncoupled carbon and nitrogen feeding regime (SBR3) and aerobic/anoxic process (SBR4). In the next step, cellular PHA content was maximized in a fed-batch accumulator. From the obtained results, PHA could be accumulated up to 13.2, 10.8, 22.36, and 6 % (mg-PHA/mg-TSS) in SBR1, SBR2, SBR3, and SBR4, respectively. Uncoupled carbon and nitrogen feeding regime (SBR3) showed the best PHA accumulating ability when acetate was used as feed. Also, the SBR3 was fed by soft-drink industrial wastewater to evaluate the capability of the selected strategy for treating real wastewater, which 13.75% of mg-PHA/mg-TSS was achieved.

In this study, nanoporous hydroxyapatite was synthesized and functionalized via tetraethylenepentamine in order to obtain a novel adsorbent for efficient removal of Acid Blue 25 dye from aqueous solution. Functionalized hydroxyapatite was characterized by Fourier transform infrared spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and N2 adsorption-desorption. Batch adsorption studies were performed to investigate the effect of various parameters such as pH, initial dye concentration, adsorbent dosage, contact time and temperature. The results illustrated that dye removal percentage was reduced with incrementing pH of the solution and dye concentration. Maximum removal of Acid Blue 25 in the solution having an initial dye concentration of 40 mg/L using 10 mg of adsorbent at 25 °C was 88%. Experimental kinetic data obeyed the pseudo second order model was appointed in 180 min. The Freundlich isotherm model also represented a suitable fit with adsorption data. The thermodynamic study was indicated that the adsorption process was spontaneous and exothermic. Results confirmed that FHAp adsorbent possesses the potential to be used as a suitable candidate for Acid Blue 25 Dye removal from aqueous solutions.

Solubility prediction of high molecular weight molecules in high-pressure solvents is an interesting field of research. Sometimes the solubility data are not available for several components due to lacking of valid equipments. Therefore, an accurate prediction technique can help the researchers. According to the literature, the simple Equations of State (EoSs) such as Soave-Redlich-Kwong (SRK), Peng-Robinson (PR) and the others require some data such as intermolecular energy parameters, critical properties, acentric factors, and molar refractions. Since these data are not available for a lot of high molecular weight molecules, there are some limitations in applying them. Furthermore, the calculations are more complicated when the high molecular weight molecule is a polar one due to the interference of polar factors in the calculations process. The polar factors for this kind of molecules are not available or cannot easily be calculated. One of these polar biomolecules is β-carotene. In this research, the solubility of β-carotene in high-pressure carbon dioxide was calculated by a two-parameter EoS and compared with the experimental data although it had already been successfully used for binary systems,. The results showed that the two-parameter Mohsen-Nia-Modarress-Mansoori (MMM) EoS was an accurate model for the solubility prediction in supercritical and near critical conditions for the multicomponent systems. The binary coefficients of β-carotene and carbon dioxide in various pressures and temperatures were obtained by the genetic algorithm from the literature.

In the present study, textural and structural characterizations of chitosan bead for immobilization of alpha amylase were studied in detail by N2 adsorption–desorption, Microspore Analysis (MP), Barrett–Joyner–Halenda (BJH) plots and Field Emission Scanning Electron Microscope (FESEM) observations. Pore structure observation revealed chemical activation of chitosan bead by glutaraldehyde can change both the isotherm type of adsorption and pores shape. In consistence with textural analysis, the high value of pore volume distribution with range of mesopores region indicated the porosity of activated chitosan bead was uniformly increased. Intra-particle diffusion model indicated that 97.6% of amylase was adsorbed inside the mesopores of activated chitosan bead owing to increase in kid (rate constant) and reduce of boundary layer effect on diffusion process. In addition, the stability experiments (pH, storage and thermal stability), enzyme leakage, Ca2+ and salt concentration effects were evaluated for immobilized amylase and compared with its free form. Ca2+ concentration of 1 mM shows an excellent impact on relative activity of amylase in its free and immobilized form. NaCl experiments indicated that 84% of amylase was covalently immobilized on activated chitosan beads. Further, the Michaelis–Menten kinetic coefficients, Km (~0.4mg/ml) and, Vmax(~227 U/mg Enzyme), point out strong affinity and high activity of immobilized enzyme

The most important causes of bridge failure are local scour. In this study, laboratory experiments were conducted to investigate the effectiveness of slot as a protection device in reduction of depth of scour at cylindrical piers under clear water flow conditions. The development time of scour depth at the circular pier with and without a slot as a protection device was conducted. The experiments focused on the effect of using different lengths of slot, calculating efficiency and deriving a suitable equation. It was observed that the scour depth decreases as the size of slot length increases; and also the maximum reduction in scour depth equals to 49%. The technique of dimensional analysis was used, and based on laboratory results an empirical formula was derived by using IBM SPSS statistics v24 software. The coefficient of determination (R²) was determined to be (0.961), There was a good agreement between the predicated and observed data.

Masonry infill has been widely used as building material due to its cost effectiveness and availability. The failure of these masonry infill walls during the past earthquakes have underscored the importance of ensuring the safety of the infill walls when it is subjected to lateral loads. In-plane and out of plane failures have been observed in many reinforced concrete framed building with masonry infill. To prevent the failure of the infill walls researchers have worked on various confinement techniques like, textile reinforced mortar, ferro cement, and diagonal bracings using fiberglass reinforced panels (FRP) etc. In this paper chicken mesh were used as a confinement technique and the experimental investigation is presented for enhancing the in-plane properties of masonry infill walls like diagonal tension and shear thereby improving the in-plane strength of masonry infill wall. For studying the lateral load capacity of the infill wall two specimens are cast namely, i) infill wall without mesh (B2), ii) infill wall with mesh (B3). Single bay, single floor 1:3 scaled down reinforced cement concrete (RCC) frames designed as per codal provisions are cast with scaled down bricks for construction of infill walls and because of incorporation of skin reinforcement for infill walls the ductility, energy dissipation, ultimate loads are improved considerably and reduced the displacements.

Oil spills from tanker or oil well have detrimental effects on environment and economy. One of the most economical and efficient methods for oil spill clean-up is mechanical extraction by sorbents which are not only the safest methods but also the least expensive of spill control. The potential use of agricultural by-products such as corn silk for adsorbent of crude oil from water systems was published in our previous work. In the current research, the percentage of acetylation and hydrophobicity of the treated corn silk were measured. The reflux time for the acetylation process was one of the primary parameters that enhanced the acetylation process. The characteristics of the enhanced corn silk was determined at different reflux times by FT-IR spectroscopy. The experimental data followed the pseudo second order kinetic model. The study suggested the Freundlich model show good correlation coefficients for the adsorption of crude oil on acetylated corn silk.

In this paper, an almost new control approach called terminal synergetic control which works based on user defined manifold is applied to a nonlinear helicopter model. Stability analysis is convestigated using Lyapunov stability theory. Synergetic controller is applied to this nonlinear fifth-order helicopter model to control height and angle. Simulation results showed that it has faster and smoother response in tracking reference inputs in comparison to sliding mode control, intelligent autopilot controller and feedback linearization method.

Due to the increasing need to distributed energy resources in power systems, their problems should be studied. One of the main problem of distributed energy resources is unplanned islanding. The unplanned islanding has some dangers to the power systems and the repairman which are works with the incorrect devices. In this paper, a passive local method is proposed. The proposed method is based on wavelet transform and a new classifier named as wavenet. The wavelet transform is used to extract features from the current waveform of current at the point of common coupling (PCC) point. PCC is assumed as the connection point of distributed generation to the distribution system. The proposed method is implemented on a 15 bus grid in MATLAB/SIMULINK software. The results show the high accuracy of islanding detection of the proposed method. In this paper, one wind turbine is assumed as a distributed resource.

The dark channel prior (DCP) technique is an effective method to enhance hazy images. Dark channel is an image with the same size as the hazy image which represents the haze severity in different places of the image. The DCP method suffers from two problems: it is incapable for removing haze from smooth regions, causing blocking effects on these areas; it cannot properly reduce a haze with a non-monotonic behavior. In this paper, an adaptive image dehazing method is proposed based on the DCP method to solve the problem of this method. In this method, to overcome the dark channel deficiency of the blocking effects, the dark channel is initially extracted. The hazy image is subsequently segmented into smooth and non-smooth regions. Regarding the smooth regions, the pixel values in the dark channel are reduced by dividing them with a rather great number. To solve the second problem, depending upon the haze severity, the haze removing technique is applied repeatedly until all the regions of the image are enhanced. Finally, the Gamma correction approach is used for contrast enhancement of the smooth regions. The performed subjective and objective comparison attest the superiority of the proposed method to the DCP one in removing the haze.

Many control schemes have been proposed for induction motor and permanent magnet synchronous motor control, which are almost highly complex and non-linear. Also, a simple and efficient method for unified control of the electric moto are rarely investigated. In this paper, a novel control method based on rotor flux orientation is proposed. The novelties of proposed method are elimination of q-axis current loop (one controller is omitted) and utilization of a new dynamic current rate limiter. Also, unlike the conventional methods, the proposed control method could be applied on both induction motor and permanent magnet synchronous motor with only minor modifications. In addition to mentioned advantages, the torque ripple and current harmonic is reduced, too. Theoretical survey and simulation results clearly show the capability of proposed method for high and low speed applications in steady and transient states.

This paper introduces a robust task-space control scheme for a robotic system with an adaptive observer. The proposed approach does not require the availability of the system states and an adaptive observer is developed to estimate the state variables. These estimated states are then used in the control scheme. First, the dynamic model of a robot is derived. Next, an observer-based robust control scheme is designed to compensate the uncertainties occurring in the control system. Moreover, upper bound of the lumped uncertainty is essential in the design of the robust controller. However, the upper bound of the lumped uncertainty is difficult to obtain in practical applications. Therefore, an adaptive law is derived to adapt the value of the lumped uncertainty, and an adaptive observer-based robust task-space controller is obtained. In this paper, we proved that the proposed adaptive observer-based controller can guarantee that the task-space tracking error and also the observation error converge to zero. To demonstrate the effectiveness of the proposed method, simulation results are illustrated in this paper.

This paper describes a new design for direct sliding mode method with a high switching frequency using the PD-PI type sliding surface applied to a negative output Luo converter worked in continuous current mode for applications required constant power source such as aerospace applications, medical equipment and etc. Because of the output power and line changes, the converter model is also nonlinear and time varying. In addition, losses dissipation and voltage drops caused a deviation between the theoretical and actual output voltage of this converter. For improvement of the converter performance along with the current and voltage regulations, a nonlinear controller is required. This suggested controller is proper to inherently variable structure of the converter and can cope with nonlinearities associated with its model. The goal is to ensure a satisfactory response for the converter. The practical results showed that the proposed strategy helps to eliminate the voltage error along with continuous current operation of the converter in very light loads and high switching frequency in different operating points.

This paper proposes a novel axial flux switching permanent magnet generator for small wind turbine applications. Surface mounted axial flux switching permanent magnet (SMAFSPM) machine is a new type of these machines that is introduced in this paper. One of the most important challenges in optimal designing of this kind of machines, is ease of construction and maintenance. One of the main features of this machine is putting the magnets on the surface, which makes the construction of the machine easier. The overlapped three-phase winding improves the quality of voltages and power of the machine.To reach the optimum dimensions of machine, centeral composite design (CCD) and response surface methodology (RSM) combined with 3D finite element methods have been used.

Nowadays, one of the major goals of the distribution environment is to reduce lead times and inventories. Cross-docking is a logistics technique which removes the storage and picking up the functions of a warehouse. The term cross-docking refers to moving products directly from incoming to outgoing trailers with little or no storage in between. According to the recent related papers, the truck scheduling problem is one of the objectives for cross-docking systems which is divide into smaller parts. The first stage is about the assignment of the trucks to the dock doors while the second stage aims to sequence all inbound and outbound trucks, in an effective way. Therefore, for dealing with the truck scheduling problem in a cross-docking system, this paper develops five heuristics. The obtained results are compared with those from the previous works. We use many test problems in the literature that were created in different sizes to study the performance of the novel heuristics. In small and medium dimensions the minimum value which found is related to one of the methods CDH3 (Cross Dock Heuristic) which has been proposed in this paper beside in all scales the method CDH4 is the best among others. The numerical results show that the developed heuristics are able to find quick good solutions with fast convergence.

Present study focuses on the micro-structural and mechanical behavior effect of friction time for similar (AISI 316-AISI 316 and AISI 304-AISI 304) and dissimilar (AISI 304-AISI 316) joint during continuous drive friction welding. The welding carried out with different friction time: 6.5, 8.5 and 10 s while kept all other conditions constant. The effect of that time on the strength, structural and behavior of welded metals was investigated by Energy Dispersive Spectroscopy (EDAX), Scanning Electron Microscope (SEM), micro-hardness and tensile test. The obtained results illustrated that the friction time extended was responsible on some harmful mechanical and micro-structural properties of the welded joint. Therefore, increasing in friction time is led to reduce of Ultimate Tensile Strength (UTS), reduce of ductility, increasing in level of micro-hardness and larger HPDZ, that was clearly observed in similar joint (AISI 316-AISI 316 and AISI 304-AISI 304).

Shoulder geometry of tool plays an important role in friction-stir welding because it controls thermal interactions and heat generation. This work is proposed and developed a coupled rigid-viscoplastic numerical modeling based on computational fluid dynamics and finite element calculations aiming to understand these interactions. Model solves mass conservation, momentum, and energy equations in three dimensions, using appropriate boundary conditions, considering mass flow as a non-Newtonian, incompressible, viscoplastic material. Boundary conditions of heat transfer and material flow were determined using a sticking/sliding contact condition at tool / workpiece interface. Thermal history, as well as shear stress and rotational speed fields, forces and torque values for three shoulder geometry conditions were calculated. Numerical results of thermal history, torque and forces during welding showed good correlation with experimentally measured data.

The system design of window air conditioner does not evolve in one day. Due to the continous efforts are taken by the refrigeration and air conditionging professionals, successful and economic models of window air conditioners are currently used. This paper states about the development of window air conditioner with phase change material and water as refrigerants. Developed air conditioner was tested for its thermal performance achievement. Outcomes specify that thermal comfort acheivement was in satisfactory levels. Predicted mean vote and percentage of people dissatisfied values were calculated and the results were in the range of neutral to a slight cooling, according to Americal Society of Heating and Refrigeration and Air conditioning standard 55.

Energy balance method is an effective and simple method which is used in the amplitude calculation of Aeolian vibration in transmission lines with Stockbridge damper. However, the accuracy of the results obtained by this method, heavily depends on the assumed mode shapes of the conductor vibration. In this study, by considering an appropriate model for the conductor vibration, a comprehensive methodology is presented to calculate the steady-state vibration amplitude of a conductor with arbitrary number of dampers. In this proposed method, the effects of traveling waves, variations of amplitude and phase, boundary conditions (finite length of the conductor), as well as the effect of number, location and impedance of the dampers are taken into account. Natural frequencies, damping rates and complex mode shapes are also obtained from forming and solving the nonlinear eigenvalue problem. Using this method, the effects of the damper placement on the vibration amplitude and bending strain are examined to achieve an optimum damper location. The comparison of the obtained values shows that considering the above parameters has a significant effect on the accuracy of the results.

In directional drilling, the most important thing that leads to pulling out the drill string is end of mud motor working life. Considering the working conditions of down hole mud motors; increasing the mechanical properties of their stator’s elastomer is crucial. Some attempts were done to increase the motor performance through geometrical changes but lack of material improvement is significant in previous studies. In this study, NBR/nanoclay composite samples were prepared through melt intercalation in an internal mixer and tested with regard to the temperature and drilling mud of down hole. Hardness, tear, fatigue and tensile test results of neat NBR elastomer and nanocomposite of NBR and different loading of nanoclay showed that the mechanical strength of new composites are considerably increased. With the help of strain energy method it was revealed that the life of NBR/nanoclay composite compared to neat NBR was enhanced. Therefore, increasing the working life and performance of the motor is achievable by using this nanocomposite. In the drilling industry, there is a direct relation between time and cost; therefore, increasing the working life of the motor leads to a considerable cost reduction in this expensive industry.

One of the most important issues in all stages of mining study is capital cost estimation. Determination of capital expenditure is a challenging issue for mine designers. In recent decade, quite a few number of studies have focused on proposing estimation models to predict mining capital cost. However, these efforts have not achieved to a predictor model with reliable range of error. Both of overestimation and underestimation of capital expenditure are causing huge problems. The former leads to estimating the value of projects less than the real value, and the latter causes to fail or postpone the project. In this paper, in order to achieve a reliable cost model, the technical and economic data of 15 open pit porphyry copper mines have been collected. The proposed cost model is developed based on stepwise multi variate regression . The R square of the presented model was 97.53% and indicated a proper fit on the data set. In addition, the mean absolute error with respect to the average capital cost of data set used in the modelling procedure was obtained ±8%. The results showed that this model is capable of estimating open pit porphyry copper mine capital expenditure in an acceptable range of error.