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In the  Bacillusamyloliquefaciens α-amylase (BAA), the loop (residues from 177-185; region І) is the constructive part of the cage responsible for attachment to calcium. It has two more amino acid residues than the α-amylase from Bacillus licheniformis (BLA). Arg176 in this region makes an ionic interaction with Glu126 from region ІІ (residues 118-131) but this interaction is lost in BLA due to substitution of R176Q and E126V. It is the common feature of α-amylases that calcium ion is required for their thermal stability. The present work quantitatively estimates the effect of ionic interaction on the overall stability of the enzyme. To clarify the functional and structural significance of corresponding salt bridge, first an automated homology model of the mutant enzyme (∆E126) was built by the Swiss-Model Protein Modeling Server.  Bacillus amyloliquefaciens α-amylase (3BH4.pdb) was used as the template and examined by GETAREA and WHAT IF programs, then Glu126 was deleted (∆E126) by site-directed mutagenesis and the thermostability was examined for the wild-type and mutant enzymes. Modeling results showed that deletion of salt bridge affected on the hydrophobic and hydrophilic residues orientation of two discussed regions (Ι, ΙΙ). The mutant enzyme also exhibited lower thermostability relative to the wild-type enzyme. Thus, it may be suggested that salt bridge could affect on accessible surface area of the discussed regions, decrease water diffusion,  prevent diffusion of cations and improve the thermostability of the whole protein.

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Abstract The moment connections sustained by many steel buildings were damaged during the recent earthquakes due to brittle fractures in the special moment resistant frames. Previous studies showed that although the top beam flange resisted due to the interaction of concrete slab, many damages are created because of weld cracking between the bottom beam flange and the column flange. Different methods of retrofit and rehabilitation could be used to prevent weld cracking and brittle fracture of the joints. The reduction of the bottom flanges of steel beams near the beam-column joints in the special moment resistant frames is currently an acceptable alteration of a connection because the top flange is located in the concrete slab and removing of concrete slab has financial and technical problems. RBS connection is one of the different kinds of Post-Northridge connections in which by cutting some parts of the flange near the end of the beam (where the possibility of making plastic hinges is high), the plastic hinge moves by the side of the column into the area within the beam. By using this method, the connection is altered from the special moment frame into a more ductile connection that has more ability to endure in plastic rotation, and generally ductility increases. The ductility of the panel zone is one of the parameters, which undoubtedly affects the manner of the yield of beams with RBS connection. Our findings in this work showed that new method causes the beam plastic rotation to increase by 30%. In addition, the applied force at the panel zone (according to the capacity of panel zone) is decreased. When compared to the frames without cuts, these reductions result in a 52% decrease in the plastic rotation of the panel zone, we also investigated the amount of dissipated energy by beams in the conditions before and after retrofitting. ANSYS software was used to study and analyze the non-linear behavior in the area of connections.

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Contact interfaces are known as the main source of energy dissipation in the structural joints. Therefore it is important in structural dynamic analysis to use predictive joint models which are capable to simulate the structural response and energy dissipation with an acceptable accuracy. In this paper an analytical model is proposed for energy dissipation evaluation due to micro slip mechanism in a beam structure with frictional-free boundary condition. The bending response governing equations are derived under harmonic external excitation and are solved in order to detect transition from stick to slip at the contact interface. The resultant hysteresis loops are obtained and parametric study is done for a numerical case study.

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This paper presents the closed-form calibration procedure of a 5-Dof Mitsubishi robot. In this method only the joint angle information is required. But due to the limitation of the robot degrees of freedom it is not possible to attach the end-effector of the robot directly to the ground; however, we can use a bar with two ball end joints for this purpose. By doing this, the robot can move freely in space. The most limiting factor of the closed-loop calibration of robot is that we cannot measure the non-moving joints, and we have to use other joint to estimate the motion of these joints. A novel approach to estimate the non-moving degrees of freedom are presented in the paper that can be extended to other robots. Experimental results validate the proposed method and the deviation of the joint parameters compared with the nominal values of the robot parameters delivered in the catalogue is very limited and are in an acceptable ranges.

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 to enhance the closed loop performance in presence of disturbance, uncertainties and delay a double loop mixture of MPC and robust controller is proposed. This double loop controller ensures smooth tracking for a 3-axis gyro-stabilized platform which has delay intrinsically. This control idea is suggested to eliminate high frequency disturbances and minimize steady state error with minimum power consumption in simulation and experiment. Proposed controller based on the combination of ℋ₂ and ℋ_∞ controllers in the inner control loop shows the robustness of the proposed methodology. In the outer loop to have a good tracking performance, an integrated MPC is used to handle delay in system dynamics. Also, the main idea for dealing with uncertainties is using integral and derivative of platform attitude. In the proposed platform, the ℋ_∞ controller is compared with ℋ_∞/ℋ₂ controller in KNTU laboratory in theory and experiment. Results of experimental set up shows the same reaction of two controllers against disturbance and uncertainties in delayed system.

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This paper presents a gain scheduled autopilot for pitch channel of a flying vehicle. The selected method is based on polynomial fuzzy systems. The method does not involve linearization about operating point. First the polynomial fuzzy model of pitch channel of the flight body is derived. Next, using polynomial fuzzy system methodology the controller is design such that the outputs of the nonlinear plant drive to follow those of a stable reference model. Because of avoiding actuator saturation, some constraints derived that guarantees the amplitude of control signals be less than a specific threshold. It is considered that the controller has a known structure like three-loop autopilot. In other words the three-loop fuzzy polynomial autopilot is design to satisfy stability and performance of the closed loop system over a wide range of parameter variation. Stability and performance conditions derived in terms of sum of square will solve numerically via SOSTOOLS.
 
 

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Working memory as a cognitive system is considered as one of the sources of individual differences in second language learning by many researchers. In order to examine the relationship between the capacity of two components of working memory (as one of the sources of individual differences in learning) and learning English vocabulary and grammar (as basic components in learning a second language), and also to explore the effect of instructional method as an effective variable along with working memory capacity, a convenience sampling method research was conducted. Subjects of this study were 74 female language learners selected from children between 9-12years old. These learners were at the beginner level in terms of English language proficiency. In order to determine the phonological loop capacity, non-word repetition test and digit recall test were used and, counting recall test and backward digit recall test were employed to determine central executive capacity. Based on the scores of these tests, language learners were divided into two homogeneous groups. The first group received inductive instruction and the second group underwent deductive instruction. Linear regression and two sample independent t-test were used for data analysis. The results indicated that both the phonological loop capacity and the central executive capacity had a significant effect on English vocabulary and grammar learning. Moreover, deductive teaching method significantly leads to better results in terms of grammar learning compared to the inductive teaching method.
 

1.  Introduction

Second language teachers observe significant differences between language learners regarding learning speed and final achievement in classrooms. Many factors can lead to such individual differences in learning a second language. Working memory as one of these sources of individual differences has been the focus of attention by many researchers over the past three decades. Learning a second language depends on a set of cognitive processes and systems, and working memory is one of these cognitive systems. Accordingly, this study attempts to find the effect of working memory on second language learning in children and under various instructional methods as a subject that has remained almost untouched, especially in Iran. Baddeley’s model of working memory was adopted as the theoretical framework of this study.
Research questions:
Q1- Do the capacity of the phonological loop and the capacity of central executive as two components of working memory have a significant effect on learning English vocabulary and grammar in 9-12-year-old children?
Q2- Does the deductive instructional method compared to the inductive method have any more significant effect on learning English vocabulary and grammar in 9-12-year-old children with almost the same level of working memory capacity?

2. Literature review
Working memory is a term that has grown out of memory studies and refers to the active processing system that manipulates information, explains our ability to remember information, and often occurs despite distracting information that we have to ignore (Alloway & Alloway, 2010). According to Baddeley (2015) to explore the role of working memory in learning a second language, which is a relatively new research field, it is necessary to conduct more extensive researches in different languages, different age groups, and different environmental and educational conditions. The greater the number of studies, the more accurate the results and findings will be. A number of studies have confirmed that the phonological loop capacity plays an important role in vocabulary learning. Martin and Ellis (2012), Kormos and Sáfár (2008), French (2006) and O'Brien et al. (2006) are examples of these researches. Moreover some studies indicate that working memory plays an important role in the production and processing of second language such as Trude &Tokowicz (2011), Gass and Lee (2011), Finardi and Weissheimer (2009), Leeser (2007), French (2006) and Sunderman and Kroll (2006).

3. Methodology
This research is a quasi-experimental classroom research. Convenience sampling was used in recruiting the subjects of this study. The study was carried out at Lesan English language institute in Gorgan, Iran. The age of the participants ranged from 9  to 12. The participants consisted of 74  language learners who were beginners in terms of English language proficiency level and had almost no knowledge of English writing, speech, vocabulary, and grammar. Initially, the students took 4  subtests of "working Memory Test Battery for Children". To determine the phonological loop capacity, two tests of non-word repetition and digit recall were used, and to determine the central executive capacity, two tests of counting recall and backward digit recall were taken. Learners were divided into two homogeneous groups according to their working memory test results. 36 of these language learners were taught inductively (-rule-explanation, +production-practice, self/pair-correction) and 38  were taught deductively (+rule-explanation, +production-practice, teacher-correction). Both groups completed 21 instructional sessions. During the instructional sessions, both groups took four classroom written tests and four oral tests, and the average scores of the subjects in vocabulary and grammar were considered as a criterion for their learning. The relationship between the phonological loop and the central executive capacity and the scores of English grammar and vocabulary as a learning criterion were examined to determine whether there is a significant correlation between them or not. First, the reliability of collected data and data distribution normality were checked and confirmed. Then the effect of the phonological loop and the central executive capacity was first examined separately and then in combination with the learning of English vocabulary and grammar.

4. Results
The results revealed that both independent variables, namely the phonological loop and the central executive capacity (both separately and in combination) have a positive and significant effect on the dependent variables, English vocabulary, and grammar learning, in children. The capacity of the phonological loop has a greater impact on learning English vocabulary, and the central executive capacity has a greater impact on learning English grammar. Considering the second hypothesis, the results of this study indicated that there is no significant difference in learners’ performance regarding vocabulary learning in inductive and deductive instructional groups, but the learners of the deductive group performed significantly better in grammar learning than the inductive group. This may be due to the fact that attention is one of the functions of the central executive component and by reducing the pressure on working memory, or in other words, by reducing the need for simultaneous attention to form and meaning, better results can be achieved in learning grammar (specially for learners with poor working memory).
 

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In this paper, a real time simulator of the engine-generator for a series hybrid electric bus is designed which can be used for hardware in the loop testing of the hybrid bus control unit. As an important step for designing a hardware in the loop simulator, messages that the engine and generator receive from the vehicle control unit are identified. Design of the simulator is based on these received messages and dynamic behavior of the components. Since the engine and generator receive speed or torque commands from the vehicle control unit, two PID controllers are designed to bring the engine or generator to the desired speed. By applying appropriate inputs, different modes of operation of the diesel-generator is simulated including the soft start process and steady state operation. For a simulator, the ability to interface with a real hardware requires a real time simulation. To do so, the design process is implemented in LabVIEW environment and results show that the designed simulator gives responses close to real test results and it is suitable for developing the hybrid vehicle control unit.

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Due to the complexity in the control system of hybrid vehicles, the electronic control units should go through extensive testing before getting installed in a prototype vehicle. In the first stages of the development process, Hardware-in-the-Loop (HiL) simulation can not be performed because the hardware components of the vehicle are not yet available. In this case, Model-in-the-loop (MiL) simulation is used which couples the designed control software with an environment simulation with no need for a special hardware. In this paper, the MiL simulation is introduced for verification of the vehicle control software in a series hybrid electric bus. To do so, considering the dynamic behavior of various components of the vehicle, a simulator of the hybrid bus is designed by going through with the input/outputs of the vehicle control software. Using the designed test bench, the user can act as a real driver and experience different driving regimes and analyze the control software commands. In the designed simulator, all subsystems are simulated separately in LabVIEW environment and real-time simulation is achieved with an acceptable error. Therefore, it can be used in a HiL test bench for testing each of the vehicle components. The designed simulation model has been validated using real test results. Using that, results show that all control functions in the vehicle control software can be tested and verified with no cost and in the shortest possible time.

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This paper briefly reviews Fiber Reinforced Elastomeric Isolators (FREIs) as a relatively new type of elastomeric bearings. In comparison with conventional Steel Reinforced Elastomeric Isolators (SREIs) that are reinforced with steel plates, FREIs utilize fiber fabric layers as the reinforcement material. The fiber reinforcement is employed to prevent the lateral bulging of elastomer layers when the bearing is subjected to vertical compression. Fiber reinforced isolators are categorized in two groups, namely, “bonded-“ and “unbonded-“ FREIs, depending on the boundary conditions at top and bottom surfaces of the bearing. The main objective of this paper is to simulate the lateral load-displacement hysteresis loops of unbonded-FREIs. In an unbonded-FREI, no bonding is provided between the bearing and its top and bottom contact supports. As such, shear forces are transferred via friction at the contact surfaces. When an unbonded-FREI is deformed laterally, portion of its contact surfaces roll off the contact supports, and the bearing exhibits a specific deformation called “rollover deformation”. As a result of rollover deformation, the effective lateral stiffness of the bearing is decreased significantly. This in turn improves the seismic isolation efficiency due to the increased base isolated period of bearing. The ultimate lateral displacement in an unbonded-FREI may achieve when the originally vertical faces of the bearing contact top and bottom supports. Lateral load-displacement response in an unbonded-FREI is characterized with a gradual softening (due to rollover deformation) that is followed by a stiffening behavior at the ultimate stage of lateral bearing displacement. Under a cyclic excitation, the response characteristics of the bearing during the first load-cycle are different than the subsequent cycles of the same load amplitude. This phenomenon that is specific to elastomeric materials is known as Mullins’ effect. In this paper an extended Bouc-Wen model is developed to simulate the lateral load-displacement hysteresis loops of unbonded-FREIs. The model captures the gradual softening and ultimate stiffening behavior in the load-displacement curve of the bearing, and addresses the Mullins’ effect in the simulation of hysteresis loops. The proposed model comprises two simultaneous coupled equations which employ six constant coefficients altogether. To determine these coefficients, the model is fitted to experimentally-evaluated load-displacement hysteresis loops of prototype bearings. The experimental loops are obtained from cyclic shear tests that are conducted on the bearing while it is subjected to constant vertical compression. In order to account for Mullins’ effect, an individual set of coefficients corresponding to unscragged loops (the first cycle of each displacement amplitude) are evaluated. The second set of coefficients is attributed to scragged response (subsequent cycles of each displacement amplitude) of the bearing. To simulate the load-displacement hysteresis loops, the proposed model switches between the first and the second set of coefficients depending on the unscragged or scragged state of the elastomer, respectively. A constraint is imposed on the model to assure its continuity when the model coefficients are alternated. Comparison between analytical and experimental results (shake-table test data) indicates that the proposed model is accurate in dynamic response simulation of the unbonded-FREIs studied in this paper.

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This work presents a fully integrated 8-12 GHz fractional-N frequency synthesizer (FNPLL) for using in communication satellites. The FNPLL implemented in a 90-nm standard CMOS technology. The simulation results demonstrate that the Voltage Controlled Oscillator (VCO) has a phase noise of -106 dBc/Hz at 1-MHz offset for a 10 GHz Local Oscillator (LO) signal, and the higher fractional spur is -55 dBc in a 10-GHz LO signal. The proposed FNPLL consumes 5.029-6.579 mW from 1.2-V power supply and has a phase noise of -70 dBc/Hz, -88 dBc/Hz and -116 dBc/Hz at 10-KHz, 100-KHz and 1-MHz offsets, respectively.
 

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The far-field acoustic signature of this transient impinging jet is experimentally investigated in this study. Feedback loop mechanism which is an acoustic resonance mode generated by the reflection of jet shear layer noise from the impinging plate and affecting jet mixing shear layer, is also investigated. The stagnation temperature of jet is increased by means of a reflected type shock tube up to 950 (K). A convergent-divergent nozzle generates jet with Mach number of 1.4. The far-field mixing layer noise of this quasi-steady free jet is compared by the results of steady state generated ones. The acoustic signal of this transient jet is investigated when impinges to a normal plate. It is seen that every specific phenomenon has its most powerful acoustic signature at a distinct angle relative to the impingement point. The time-frequency investigations by the means of wavelet transform and related scalograms reveal that the sound wave generated by feedback loop mechanism is tonal and continuous in time compared to the acoustic signals of the jet shear layer that are seen as the intermittent acoustic events in the far-field acoustic scalograms.

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In this paper, a novel closed loop guidance method is provided for sub-orbital systems. The proposed method can be used in the first phase of a flying vehicle system that flies in atmosphere. In this method, sub-optimal integrated solution of control and guidance in closed-loop is developed. This Sub-optimal guidance technique has been named Model Predictive Static Programming (MPSP) that based on nonlinear optimal control theory and derived from combined philosophies of Model Predictive Control and Approximate Dynamic Programming solves a class of finite horizon optimal control problems with terminal constraints. Also because sensitivity matrices that are necessary for obtaining this solution can be computed recursively, this technique is computationally efficient and is appropriate for online implementation. In this paper, the system’s dynamic equations are modeled in the presence of aerodynamic forces and moment and the dynamic servo-mechanism effect is also assumed in the equations. Furthermore, by simultaneously considering the guidance and control loops, an integrated solution of the guidance and control system is proposed by three-degree of freedom spherical earth simulation model. Result show that proposed closed-loop guidance is able to remove modeling errors by flight data update and guide flying vehicle to the desired point.

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Recently, robotic systems are widely used in surgery, due to their characteristics such as having high precision, being tireless and making no mistakes. They are especially suitable for operation on hard tissue, as the bone is stationary and does not change shape and therefore preoperative planning of the system is much more straightforward. Nevertheless, proposed robotic systems for surgery on skull bone are still in the research stage. In this study, by considering the requirements of craniotomy surgery, a Remote Center of Motion spherical mechanism is used in design and prototyping of a surgical system. The kinematic equations and Jacobian of the mechanism are calculated analytically and later verified through software simulation. Detailed design and force analysis helped selection and use of appropriate AC servo motors for actuation. An aluminum prototype is fabricated out of CNC machined parts. Performance of different connection methods between PC and the robot were tested and a combination of them is proposed for higher reliability and speed. Finally, a software library is generated in LabVIEW environment to simplify the connection with servo motors and utilization and control of the robotic system.

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In this paper, ferrofluid flow in a closed cooling loop without any mechanical pump has been simulated. The flow of the ferrofluid in the closed loop is resulted from applying a non-uniform magnetic field and the thermo-magnetic effect of the ferrofluids. The ferrofluid consist water and different volume fractions of iron oxide nanoparticles with nanoparticle diameter of 13nm. The two phase mixture model and the control volume technique have been used in the present study. The applied non-uniform magnetic field is resulted from an electromagnetic solenoid and the steady and also the transient modeling of the flow in the cooling loop from start point (stagnant ferrofluid in loop) have been carried out. The obtained results show that by applying magnetic field and also by taking advantage of temperature dependent property of the magnetic susceptibility, a flow of ferrofluid is created in the loop and by increasing the heat input (heater power) in the loop, the flow rate in the loop is increased. Moreover, the results show that by having a cold source (for rejection of produced heat) with higher constant temperature, the flow rate in the loop increases. Furthermore, the flow rate in the cooling loop is increased as the volume fraction of the nanoparticles in the base fluid increases. The mentioned cooling loop can be used in the electronic cooling systems.

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A natural circulation loop receives heat from a high-temperature source and rejects it to a low-temperature source without using a mechanical pump. Single phase natural circulation loop has been applied in many industrial systems for cooling. The heat transport capability of natural circulation loops (NCLs) is directly proportional to the flow rate that it can generate. To establish the heat transport capability of a natural circulation loop, it is essential to know the flow rate. Friction force and gravitational force are balanced with each other along the loop at steady state. In this paper, firstly the governing equations have been written for a natural circulation loop. Then the governing equations have been rewritten in the dimensionless form. Then, effects of heater length, cooler length, tube diameter, loop height, loops inclination angle, the distance of heater from the right side or left side, the distance of cooler from right or left sides and power of the heater on the loop mass flow rate and loop temperature distribution have been investigated. The results show that increasing of loop height, loop diameter and power of heater increase the mass flow rate. Also, increasing or decreasing of heater length, has no effect on the mass flow rate, whereas increasing of loop inclination angle decreases the mass flow rate. In this study, the friction coefficient is considered as continues for all regimes. In addition, the position of the heater and cooler has been unsymmetrically investigated.

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In recent years, due to the reverse logistics and particularly integration with direct Logistics is considered important in reducing supply chain costs. In this paper, a closed supply chain with multi-objective, multi-product and multi-period is designed. The objective functions consists of minimizing transportation costs between centers and processing cost within centers and centers construction and also the minimization of carbon dioxide is published within centers and carbon dioxide is published of transportation between centers. For this purpose, a mixed integer programming model is used and the problem is NP Hard. This model is superior to previous models,Considering multi-product and multi-period in relevant two objectives and also the relevant model constraints Production carbon dioxide between centers and within centers consideration. In order to integrate the supply chain's two goals the same phase and by multi-objective planning became an object. In order to validate the model and the influence of objective functions Weights several problem is designed and is solved with CPLEX 12.3 and in the end, the results are analyzed.

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Today's world is more competitive than ever, and industry increasingly looks to supply chain management as a competitive weapon. the objective of this research is to suggest an integrated approach for Closed Loop Supply Chain network including two phases. In the first phase, a framework for supplier selection criteria in RL is proposed. Beside a fuzzy method is utilized to evaluate suppliers based on quantitative and qualitative criteria. The output of this stage is the weight of each supplier according to each part.in the second phase, we propose a Multi Objctive mixd-integer linear programming model to determine weight of suppliers and amount of item for purching from them(strategic decisions), as well as weight of remanufacturing subcontractor and dedicate product to them (tactical decisions), and find out the optimal number of part and products in CLSC network(operational decisions). The objective functions maximize profit of selling, minimize factory cost as well as cost of unsatisfied demand and rest of them maximize weight of suppliers and allocate return product between recoverable centers in factory and remanufacturing subcontractors. the mathematical programming model is validated through numerical analysis.

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