Journal of Engineering The latest articles from Hindawi © 2017 , Hindawi Limited . All rights reserved. Investigation of the Effects of Submerged Arc Welding Process Parameters on the Mechanical Properties of Pressure Vessel Steel ASTM A283 Grade A Sun, 05 Feb 2017 00:00:00 +0000 The pressure vessel steel is used in boilers and pressure vessel structure applications. This research studied the effects of submerged arc welding (SAW) process parameters on the mechanical properties of this steel. The weld sample originated from ASTM A283 grade A sheet of 6.00-millimeter thickness. The welding sample was treated using SAW with the variation of three process factors. For the first factor, welding currents of 260, 270, and 280 amperes were investigated. The second factor assessed the travel speed, which was tested at both 10 and 11 millimeters/second. The third factor examined the voltage parameter, which was varied between 28 and 33 volts. Each welding condition was conducted randomly, and each condition was tested a total of three times, using full factorial design. The resulting materials were examined using tensile strength and hardness tests and were observed with optical microscopy (OM) and scanning electron microscopy (SEM). The results showed that the welding current, voltage, and travel speed significantly affected the tensile strength and hardness ( value < 0.05). The optimum SAW parameters were 270 amperes, 33 volts, and 10 millimeters/second travel speed. High density and fine pearlite were discovered and resulted in increased material tensile strength and hardness. Prachya Peasura Copyright © 2017 Prachya Peasura. All rights reserved. Experimental Study on Strain Reliability of Embroidered Passive UHF RFID Textile Tag Antennas and Interconnections Thu, 02 Feb 2017 00:00:00 +0000 We present embroidered antennas and interconnections in passive UHF RFID textile tags and test their strain reliability. Firstly, we fabricate tag antennas on two different stretchable fabric substrates by five different embroidery patterns and choose the most stretchable ones for testing. Next, the tag ICs are attached by sewing and gluing, and the tag reliability during repeated stretching cycles is evaluated through wireless measurements. Initially, the chosen tags achieve read ranges of 6–8 meters and can strain up to 140–150% of their original length. After 100 stretching cycles to 80% of their maximum strain, the read ranges of the tags with glued interconnections are similar to the initial values. In addition, also the read ranges of the tags with sewed interconnections are still more than 70%–85% of their initial values. However, some challenges with the reproducibility need to be solved next. Xiaochen Chen, Aruhan Liu, Zhigang Wei, Leena Ukkonen, and Johanna Virkki Copyright © 2017 Xiaochen Chen et al. All rights reserved. Elastoplastic Modelling of an In Situ Concrete Spalling Experiment Using the Ottosen Failure Criterion Tue, 31 Jan 2017 07:45:20 +0000 An in situ concrete spalling experiment will be carried out in the ONKALO rock characterization facility. The purpose is to establish the failure strength of a thin concrete liner on prestressed rock surface, when the stress states in both rock and concrete are increased by heating. A cylindrical hole 1.5 m in diameter and 7.2 m in depth is reinforced with a 40 mm thin concrete liner from level −3 m down. Eight 6 m long 4 kW electrical heaters are installed around the hole 1 m away. The experiment setup is described and results from predictive numerical modelling are shown. Elastoplastic modelling using the Ottosen failure criterion predicts damage initiation on week 5 and the concrete ultimate strain limit of 0.0035 is exceeded on week 10. The support pressure generated by the liner is 3.2 MPa and the tangential stress of rock is reduced by −33%. In 2D fracture mechanical simulations, the support pressure is 3 MPa and small localized damage occurs after week 3 and damage process slowly continues during week 9 of the heating period. In conclusion, external heating is a potent way of inducing damage and thin concrete liner significantly reduces the amount of damage. Lauri Kalle Tapio Uotinen and Topias Kalle Aleksi Siren Copyright © 2017 Lauri Kalle Tapio Uotinen and Topias Kalle Aleksi Siren. All rights reserved. Free Vibration of Embedded Porous Plate Using Third-Order Shear Deformation and Poroelasticity Theories Tue, 24 Jan 2017 06:40:14 +0000 This research aims at studying free vibration of rectangular plate made of porous materials in which Y-foam, G-foam, and are used and compared with each other. To obtain the Biot formulation of the constitutive equations for a porous material, linear poroelasticity theory is used. Young modulus and density of porous plate are different in transverse direction versus porosity. In order to increase the accuracy of results in comparison with classical plate and first-order shear deformation theories, Reddy’s theory was utilized in this research. Besides, five coupled equations of motion have been studied using Hamilton’s principle and are solved by differential quadrature method (DQM). Detailed results of this study show the significant effect of aspect ratio, thickness ratio, boundary conditions, and porosity on dimensionless frequency and deflection of porous plate. Results of this study can contribute to the design of pneumatic conveying, handling, and control systems. Ali Ghorbanpour Arani, Zahra Khoddami Maraghi, Mehdi Khani, and Iman Alinaghian Copyright © 2017 Ali Ghorbanpour Arani et al. All rights reserved. Flexural Behavior of High-Volume Steel Fiber Cementitious Composite Externally Reinforced with Basalt FRP Sheet Mon, 26 Dec 2016 11:56:44 +0000 High-performance fiber-reinforced cementitious composites (HPFRCCs) are characterized by unique tensile strain hardening and multiple microcracking behaviors. The HPFRCC, which demonstrates remarkable properties such as strength, ductility, toughness, durability, stiffness, and thermal resistance, is a class of fiber cement composite with fine aggregates. It can withstand tensile stresses by forming distributed microcracks owing to the embedded fibers in the concrete, which improve the energy absorption capacity and apparent ductility. This high energy absorbing capacity can be enhanced further by an external stiff fiber-reinforced polymer (FRP). Basalt fabric is externally bonded as a sheet on concrete materials to enhance the durability and resistance to fire and other environmental attacks. This study investigates the flexural performance of an HPFRCC that is externally reinforced with multiple layers of basalt FRP. The HPFRCC considered in the study contains steel fibers at a volume fraction of 8%. Seungwon Kim and Cheolwoo Park Copyright © 2016 Seungwon Kim and Cheolwoo Park. All rights reserved. Fault Tolerant Operation of ISOP Multicell Dc-Dc Converter Using Active Gate Controlled SiC Protection Switch Wed, 21 Dec 2016 11:46:33 +0000 An active gate controlled semiconductor protection switch using SiC-MOSFET is proposed to achieve the fault tolerant operation of ISOP (Input Series and Output Parallel) connected multicell dc-dc converter. The SiC-MOSFET with high temperature capability simplifies the configuration of the protection circuit, and its on-resistance control by the active gate controller realizes the smooth protection without the voltage and the current surges. The first laboratory prototype of the protection switch is fabricated by using a SiC-MOSFET with a high frequency buck chopper for the active gate controller. The effectiveness of the proposed protection switch is verified, taking the impact of the volume reduction into account. Yusuke Hayashi, Yoshikatsu Matsugaki, and Tamotsu Ninomiya Copyright © 2016 Yusuke Hayashi et al. All rights reserved. Bending and Shear Experimental Tests and Numerical Analysis of Composite Slabs Made Up of Lightweight Concrete Tue, 20 Dec 2016 14:11:10 +0000 The aim of this paper is to understand the structural behaviour of composite slabs. These composite slabs are made of steel and different kinds of concrete. The methodology used in this paper combines experimental studies with advanced techniques of numerical simulations. In this paper, four types of concrete were used in order to study their different structural strengths in composite slabs. The materials used were three lightweight concretes, a normal concrete, and a cold conformed steel deck which has embossments to increase the adherence between concrete and steel. Furthermore, two lengths of slabs were studied to compare structural behaviours between short and long slabs. m-k experimental tests were carried out to obtain the flexural behaviour of the composite slabs. These tests provide dimensionless coefficients to compare different sizes of slabs. Nonlinear numerical simulations were performed by means of the finite element method (FEM). Four different multilinear isotropic hardening laws were used to simulate the four concretes. Coulomb friction contact was used to model the coefficient of friction between steel and concrete. Finally, a chemical bond was included to consider sliding resistance in the contact surface between steel and concrete. Experimental and numerical results are in good agreement; therefore, numerical models can be used to improve and optimize lightweight composite slabs. F. P. Alvarez Rabanal, J. Guerrero-Muñoz, M. Alonso-Martinez, and J. E. Martinez-Martinez Copyright © 2016 F. P. Alvarez Rabanal et al. All rights reserved. Analysis of the Single Toggle Jaw Crusher Force Transmission Characteristics Wed, 07 Dec 2016 11:12:47 +0000 This paper sets out to perform a static force analysis of the single toggle jaw crusher mechanism and to obtain the force transmission characteristics of the mechanism. In order to obtain force transmission metrics that are characteristic of the structure of the mechanism, such influences as friction, dead weight, and inertia are considered to be extraneous and neglected. Equations are obtained by considering the balance of forces at the moving joints and appropriately relating these to the input torque and the output torque. A mechanical advantage, the corresponding transmitted torque, and the variations thereof, during the cycle of motion of the mechanism, are obtained. The mechanical advantage that characterizes the mechanism is calculated as the mean value over the active crushing stroke of the mechanism. The force transmission characteristics can be used as criteria for the comparison of different jaw crusher mechanism designs in order to select the most suitable design for a given application. The equations obtained can also be used in estimating the forces sustained by the components of the mechanism. Moses Frank Oduori, David Masinde Munyasi, and Stephen Mwenje Mutuli Copyright © 2016 Moses Frank Oduori et al. All rights reserved. Changing States of Multistage Process Chains Wed, 30 Nov 2016 10:05:33 +0000 Generally, a process describes a change of state of some kind (state transformation). This state change occurs from an initial state to a concluding state. Here, the authors take a step back and take a holistic look at generic processes and process sequences from a state perspective. The novel perspective this concept introduces is that the processes and their parameters are not the priority; they are rather included in the analysis by implication. A supervised machine learning based feature ranking method is used to identify and rank relevant state characteristics and thereby the processes’ inter- and intrarelationships. This is elaborated with simplified examples of possible applications from different domains to make the theoretical concept and results more feasible for readers from varying domains. The presented concept allows for a holistic description and analysis of complex, multistage processes sequences. This stands especially true for process chains where interrelations between processes and states, processes and processes, or states and states are not fully understood, thus where there is a lack of knowledge regarding causations, in dynamic, complex, and high-dimensional environments. Thorsten Wuest, Christopher Irgens, and Klaus-Dieter Thoben Copyright © 2016 Thorsten Wuest et al. All rights reserved. Collaborative Cloud Manufacturing: Design of Business Model Innovations Enabled by Cyberphysical Systems in Distributed Manufacturing Systems Tue, 22 Nov 2016 13:51:11 +0000 Collaborative cloud manufacturing, as a concept of distributed manufacturing, allows different opportunities for changing the logic of generating and capturing value. Cyberphysical systems and the technologies behind them are the enablers for new business models which have the potential to be disruptive. This paper introduces the topics of distributed manufacturing as well as cyberphysical systems. Furthermore, the main business model clusters of distributed manufacturing systems are described, including collaborative cloud manufacturing. The paper aims to provide support for developing business model innovations based on collaborative cloud manufacturing. Therefore, three business model architecture types of a differentiated business logic are discussed, taking into consideration the parameters which have an influence and the design of the business model and its architecture. As a result, new business models can be developed systematically and new ideas can be generated to boost the concept of collaborative cloud manufacturing within all sustainable business models. Erwin Rauch, Sven Seidenstricker, Patrick Dallasega, and Robert Hämmerl Copyright © 2016 Erwin Rauch et al. All rights reserved. In Situ Determination of the Transport Properties of Near-Surface Concrete Using AC Impedance Spectroscopy Techniques Tue, 22 Nov 2016 13:24:45 +0000 The durability of existing concrete structures has increasingly attracted widespread attention in recent years. The phenomenon of performance degradation is often associated with the intrusion of hazardous ions from outside. As the first barrier to external substances intrusion, the near-surface concrete plays an important role in durability. So the performance of in-service concrete structures often depends on the transport properties of the near-surface concrete. Accordingly, information on service conditions and life prediction can be obtained by testing these transport properties. In this paper, an in situ method for chloride ion diffusion coefficient determination is proposed based on the relationship between the alternating current impedance spectroscopy parameters and the chloride ion diffusion coefficient. By a rational design, the new method can synthetically reflect the transport properties of near-surface concrete and is not affected by the presence of the reinforcing bar. In addition, the experimental results show that the method is in good agreement with “PERMIT” migration test which has been widely used. The proposed method is less time consuming and nondestructive and has good reproducibility. Lipeng Wu, Peng Dai, and Yong Li Copyright © 2016 Lipeng Wu et al. All rights reserved. Single VDTA Based Dual Mode Single Input Multioutput Biquad Filter Thu, 17 Nov 2016 13:30:22 +0000 This paper presents a dual mode, single input multioutput (SIMO) biquad filter configuration using single voltage differencing transconductance amplifier (VDTA), three capacitors, and a grounded resistor. The proposed topology can be used to synthesize low pass (LP), high pass (HP), and band pass (BP) filter functions. It can be configured as voltage mode (VM) or current mode (CM) structure with appropriate input excitation choice. The angular frequency () of the proposed structure can be controlled independently of quality factor (). Workability of the proposed biquad configuration is demonstrated through PSPICE simulations using 0.18 μm TSMC CMOS process parameters. Rajeshwari Pandey, Neeta Pandey, and Navin Singhal Copyright © 2016 Rajeshwari Pandey et al. All rights reserved. Flexural and Shear Behavior of FRP Strengthened AASHTO Type Concrete Bridge Girders Tue, 15 Nov 2016 11:30:06 +0000 Fiber-reinforced polymers (FRP) are being increasingly used for the repair and strengthening of deteriorated or unsafe concrete structures, including structurally deficient concrete highway bridges. The behavior of FRP strengthened concrete bridge girders, including failure modes, failure loads, and deflections, can be determined using an analytical finite element modeling approach, as outlined in this paper. The differences in flexural versus shear FRP strengthening and comparison with available design guidelines are also beneficial to design professionals. In this paper, a common AASHTO type prestressed concrete bridge girder with FRP wrapping was analyzed using the ANSYS FEM software and the ACI analytical approach. Both flexural and shear FRP applications, including vertical and inclined shear strengthening, were examined. Results showed that FRP wrapping can significantly benefit concrete bridge girders in terms of flexure/shear capacity increase, deflection reduction, and crack control. The FRP strength was underutilized in the section selected herein, which could be addressed through decrease of the amount of FRP and prestressing steel used, thereby increasing the section ductility. The ACI approach produced comparable results to the FEM and can be effectively and conveniently used in design. Nur Yazdani, Farzia Haque, and Istiaque Hasan Copyright © 2016 Nur Yazdani et al. All rights reserved. The Hysteresis Performance and Restoring Force Model for Corroded Reinforced Concrete Frame Columns Tue, 15 Nov 2016 09:05:45 +0000 A numerical simulation of the hysteresis performance of corroded reinforced concrete (RC) frame columns was conducted. Moreover, the results obtained were compared with experimental data. On this basis, a degenerated three-linearity (D-TRI) restoring force model was established which could reflect the hysteresis performance of corroded RC frame columns through theoretical analysis and data fitting. Results indicated that the hysteretic bearing capacity of frame columns decreased significantly due to corrosion of the rebar. In view of the characteristics of the hysteresis curve, the plumpness of the hysteresis loop for frame columns decreased and shrinkage increased with increasing rebar corrosion. All these illustrated that the seismic energy dissipation performance of frame columns reduced but their brittleness increased. As for the features of the skeleton curve, the trends for corroded and noncorroded members were basically consistent and roughly corresponded to the features of a trilinear equivalent model. Thereby, the existing Clough hysteresis rule can be used to establish the restoring force model applicable to corroded RC frame columns based on that of the noncorroded RC members. The calculated skeleton curve and hysteresis curve of corroded RC frame columns using the D-TRI model are closer to the experimental results. Guifeng Zhao, Meng Zhang, Yaoliang Li, and Dawang Li Copyright © 2016 Guifeng Zhao et al. All rights reserved. Relating Corroded Seven-Strand, Posttensioned Cable Cross-Sectional Properties to Load Capacity Thu, 27 Oct 2016 08:29:50 +0000 Multistrand anchors have seen widespread use, providing strength and stability at hydraulic Corps facilities. However, these steel tendons are subject to strength reduction as an effect of corrosion. Methods for evaluating the corroded cable strength do not exist to accurately estimate the time until tendon cables would have to be replaced (at great expense). The following five research tasks are used to address this deficiency: laboratory accelerated corrosion; pull-tests on pristine and laboratory corroded cables; optical scanning; data collection correlated with cross-sectional properties of cables; and development of a method to relate this data to the field. The pull-tests provide measured capacities for seven-strand, posttensioned (PT) cables. An optical scan of the corroded cables provides cross-sectional properties of individual wires within the pulled cables. Trendlines are established for the related peak cable capacities and cross-sectional properties in an effort to determine their correlations. Trendlines for minimum wire area and second-moment short axis diameter are found with low error, making them good predictors of loaded cable capacity. This pull-test dataset has been related back to cable failure in the field, assuming a linear rate of corrosion loss for the cross-sectional properties and required PT capacity. Richard Haskins, Barry White, Robert Ebeling, and James Evans Copyright © 2016 Richard Haskins et al. All rights reserved. Determination of the Transport Properties of Structural Concrete Using AC Impedance Spectroscopy Techniques Wed, 26 Oct 2016 10:05:30 +0000 All over the world, particularly in severe environmental conditions, there are reinforced concrete structures that develop nonnegligible phenomena of durability problems. Most of the durability problems are related to hazardous substances invasion. Both engineering practice and scientific studies have revealed that the transport property of near-surface concrete is a main factor in the durability of concrete structures. Among many transport parameters, the chloride ion diffusion coefficient is the most important one, which provides important information on material design and service life prediction. In this paper, AC impedance spectroscopy technology was employed in the measurement of chloride ion diffusion coefficient. The relationship between mesostructure parameters and chloride ion diffusion coefficient was deduced by introducing a reasonable equivalent circuit model. Taking into account the conductivity difference caused by various cementitious material systems, the diffusion coefficient can be corrected, and a diffusion coefficient determination method based on AC impedance spectroscopy technique was established. For the convenience of application, a relationship between the newly proposed method and a widely recognized standard method was obtained. The proposed method can be applied to laboratory testing and establishes the theoretical basis for field tests. Lipeng Wu, Peng Dai, and Yong Li Copyright © 2016 Lipeng Wu et al. All rights reserved. Study on the AFM Force Curve Common Errors and Their Effects on the Calculated Nanomechanical Properties of Materials Sun, 23 Oct 2016 09:35:49 +0000 The atomic force microscope (AFM) force curve has been widely used for determining the mechanical properties of materials due to its high resolution, whereby very low (piconewton) forces and distances as small as nanometers can be measured. However, sometimes the resultant force curve obtained from AFM is slightly different from those obtained from a more typical nanoindentation force curve due to the AFM piezo’s hysteresis. In this study the nanomechanical properties of either a sulfonated polyether ether ketone (SPEEK) treated layer or bare polyether ether ketone (PEEK) were evaluated via AFM nanoindentation and a nanomechanical test system to probe the possible error of the calculated nanomechanical properties due to the AFM piezo’s hysteresis. The results showed that AFM piezo’s hysteresis caused the error in the calculated nanomechanical properties of the materials. D. Almasi, R. Sharifi, M. R. Abdul Kadir, G. Krishnamurithy, and T. Kamarul Copyright © 2016 D. Almasi et al. All rights reserved. Rolling Bearing Fault Diagnosis Based on ELCD Permutation Entropy and RVM Wed, 07 Sep 2016 09:08:58 +0000 Aiming at the nonstationary characteristic of a gear fault vibration signal, a recognition method based on permutation entropy of ensemble local characteristic-scale decomposition (ELCD) and relevance vector machine (RVM) is proposed. First, the vibration signal was decomposed by ELCD; then a series of intrinsic scale components (ISCs) were obtained. Second, according to the kurtosis of ISCs, principal ISCs were selected and then the permutation entropy of principal ISCs was calculated and they were combined into a feature vector. Finally, the feature vectors were input in RVM classifier to train and test and identify the type of rolling bearing faults. Experimental results show that this method can effectively diagnose four kinds of working condition, and the effect is better than local characteristic-scale decomposition (LCD) method. Jiang Xingmeng, Wu Li, Pan Liwu, Ge Mingtao, and Hu Daidi Copyright © 2016 Jiang Xingmeng et al. All rights reserved. Investigating Surface Effects on Thermomechanical Behavior of Embedded Circular Curved Nanosize Beams Tue, 30 Aug 2016 15:40:05 +0000 To investigate the surface effects on thermomechanical vibration and buckling of embedded circular curved nanosize beams, nonlocal elasticity model is used in combination with surface properties including surface elasticity, surface tension, and surface density for modeling the nanoscale effect. The governing equations are determined via the energy method. Analytically Navier method is utilized to solve the governing equations for simply supported nanobeam at both ends. Solving these equations enables us to estimate the natural frequency and critical buckling load for circular curved nanobeam including Winkler and Pasternak elastic foundations and under the effect of a uniform temperature change. The results determined are verified by comparing the results with available ones in literature. The effects of various parameters such as nonlocal parameter, surface properties, Winkler and Pasternak elastic foundations, temperature, and opening angle of circular curved nanobeam on the natural frequency and critical buckling load are successfully studied. The results reveal that the natural frequency and critical buckling load of circular curved nanobeam are significantly influenced by these effects. Farzad Ebrahimi and Mohsen Daman Copyright © 2016 Farzad Ebrahimi and Mohsen Daman. All rights reserved. The Mechanical Properties of the Concrete Using Metakaolin Additive and Polymer Admixture Thu, 18 Aug 2016 06:06:48 +0000 Environmentally friendly and high performance concrete is very import for the applications in sewage and water treatment industry. Using mineral additives such as fly ash and silica fume has been proven to be an effective approach to improve concrete properties. This paper reports a study of the effect of using both polymer and metakaolin additives together on the mechanical and durability properties of concrete. Different proportions of the combination using two different polymers, metakaolin, and recycled fiber reinforcement have been studied. The effects of water-to-cement ratio and the curing methods have also been compared. At last an optimized mixture and curing method has been suggested. Adel Al Menhosh, Yan Wang, and Yu Wang Copyright © 2016 Adel Al Menhosh et al. All rights reserved. An Improved Micromechanical Framework for Saturated Concrete Repaired by the Electrochemical Deposition Method considering the Imperfect Bonding Tue, 16 Aug 2016 12:20:58 +0000 The interfaces between the deposition products and concrete are not always well bonded when the electrochemical deposition method (EDM) is adopted to repair the deteriorated concrete. To theoretically illustrate the deposition healing process by micromechanics for saturated concrete considering the imperfect interfaces, an improved micromechanical framework with interfacial transition zone (ITZ) is proposed based on our recent studies. In this extension, the imperfect bonding is characterized by the ITZ, whose effects are calculated by modifying the generalized self-consistent model. Meanwhile, new multilevel homogenization schemes are employed to predict the effective properties of repaired concrete considering the ITZ effects. Moreover, modification procedures are presented to reach the properties of repaired concrete with ITZs in the dry state. To demonstrate the feasibility of the proposed micromechanical model, predictions obtained via the proposed micromechanical model are compared with those of the existing models and the experimental data, including results from extreme states during the EDM healing process. Finally, the influences of ITZ and deposition product on the healing effectiveness of EDM are discussed based on the proposed micromechanical model. Qing Chen, Zhengwu Jiang, Hehua Zhu, J. Woody Ju, Zhiguo Yan, and Yaqiong Wang Copyright © 2016 Qing Chen et al. All rights reserved. Financial and Performance Analyses of Microcontroller Based Solar-Powered Autorickshaw for a Developing Country Tue, 26 Jul 2016 10:03:18 +0000 This paper presents a case study to examine the economic viability and performance analysis of a microcontroller based solar powered battery operated autorickshaw (m-SBAR), for the developing countries, which is compared with different types of rickshaws such as pedal rickshaw (PR), battery operated autorickshaw (BAR), and solar-powered battery operated autorickshaw (SBAR), available in Bangladesh. The BAR consists of a rickshaw structure, a battery bank, a battery charge controller, a DC motor driver, and a DC motor whereas the proposed m-SBAR contains additional components like solar panel and microcontroller based DC motor driver. The complete design considered the local radiation data and load profile of the proposed m-SBAR. The Levelized Cost of Energy (LCOE) analysis, Net Present Worth, payback periods, and Benefit-to-Cost Ratio methods have been used to evaluate the financial feasibility and sensitivity analysis of m-SBAR, grid-powered BAR, and PR. The numerical analysis reveals that LCOE and Benefit-to-Cost Ratio of the proposed m-SBAR are lower compared to the grid-powered BAR. It has also been found that microcontroller based DC motor control circuit reduces battery discharge rate, improves battery life, and controls motor speed efficiency. Abu Raihan Mohammad Siddique and M. Shamim Kaiser Copyright © 2016 Abu Raihan Mohammad Siddique and M. Shamim Kaiser. All rights reserved. Experimental Evaluation on the Influence of RCD Snubbers in a 3-Level Thyristor Based MLCR CSC Thu, 14 Jul 2016 12:07:11 +0000 Multilevel current reinjection (MLCR) concept provides self-commutation capability to thyristors, enabling thyristor based current source converters (CSC) to operate under negative firing angle. It also lowers the input current harmonic distortion. This is achieved by using an auxiliary reinjection bridge. Extensive experimental results are presented in this paper to analyse the performance of the 3-level MLCR CSC for different snubber components across the reinjection bridge. The trade-off in the choice of the snubber circuit is illustrated, with its influence on the AC side line current and DC side output voltage of the 3-level MLCR CSC. Bhaba P. Das, Neville R. Watson, and Yonghe Liu Copyright © 2016 Bhaba P. Das et al. All rights reserved. Mutation Testing Approach to Negative Testing Wed, 13 Jul 2016 09:46:46 +0000 Negative testing deals with an important problem of assessing a system ability to handle unexpected situations. Such situations, if unhandled, may lead to system failures that in some cases can have catastrophic consequences. This paper presents a mutation testing-based approach for generation of test cases supporting negative testing. Application of this approach can provide, in a systematic and human-unbiased way, test cases effectively testing wide range of unexpected situations. Thus, it can contribute to improvement of a tested system. The paper formally defines mutation operators used to control the generation process, describes a generic framework for the generation and execution of the test cases, and explains how to interpret results. Joanna Strug Copyright © 2016 Joanna Strug. All rights reserved. Similarity Solution for High Weissenberg Number Flow of Upper-Convected Maxwell Fluid on a Linearly Stretching Sheet Sun, 12 Jun 2016 07:34:07 +0000 High Weissenberg boundary layer flow of viscoelastic fluids on a stretching surface has been studied. The flow is considered to be steady, low inertial, and two-dimensional. Upon proper scaling and by means of an exact similarity transformation, the nonlinear momentum and constitutive equations of each layer transform into the respective system of highly nonlinear and coupled ordinary differential equations. Numerical solutions to the resulting boundary value problem are obtained using an efficient shooting technique in conjunction with a variable stepping method for different values of pressure gradients. It is observed that, unlike the Newtonian flows, in order to maintain a potential flow, normal stresses must inevitably develop. The velocity field and stresses distributions over plate are presented for difference values of pressure gradient and Weissenberg numbers. Meysam Mohamadali and Nariman Ashrafi Copyright © 2016 Meysam Mohamadali and Nariman Ashrafi. All rights reserved. Partial Control of a Continuous Bioreactor: Application to an Anaerobic System for Heavy Metal Removal Thu, 09 Jun 2016 10:42:29 +0000 This work presents a control strategy for a continuous bioreactor for heavy metal removal. For this aim, regulation of the sulfate concentration, which is considered the measured and controlled state variable, allowed diminishing the cadmium concentration in the bioreactor, where the corresponding controller was designed via nonlinear bounded function. Furthermore, a nonlinear controllability analysis was done, which proved the closed-loop instability of the inner or uncontrolled dynamics of the bioreactor. A mathematical model, experimentally corroborated for cadmium removal, was employed as a benchmark for the proposed controller. Numerical experiments clearly illustrated the successful implementation of this methodology; therefore, cadmium removal amounted to more than 99%, when the initial cadmium concentration was up to 170 mg/L in continuous operating mode. M. I. Neria-González, P. A. López-Pérez, and R. Aguilar-López Copyright © 2016 M. I. Neria-González et al. All rights reserved. Development of a Medical Care Terminal for Efficient Monitoring of Bedridden Subjects Thu, 09 Jun 2016 06:45:33 +0000 This work is developed in the context of Ambient Assisted Living (AAL) and has as main objective the development of a mechatronic system that allows the care of bedridden patients with ongoing medical care handled by a single person. The developed Medical Care Terminal (MCT) improves autonomy in home care, safety, comfort, and hygiene of bedridden patients. The MCT has six biomedical sensors and four environmental sensors. Data acquisition and processing is performed using Arduino and LabVIEW platforms, respectively. The proposed solution has, as main feature, its adaptability to the patient needs. One of the MCT functionalities is the remote access to the patient data through the web. The caregiver may request help from a specialist who sends back information in real time to perform first aid assistance. This device has a flexible configuration allowing a fast and cheap reconfiguration according the specific needs of the patient. The proposed mechatronic system intends to meet the needs of bedridden patients improving their quality of life, health, safety, and comfort, while enabling the remote monitoring of the patients. Filipe Pereira, Vítor Carvalho, Filomena Soares, José Machado, Karolina Bezerra, Rui Silva, and Demétrio Matos Copyright © 2016 Filipe Pereira et al. All rights reserved. Performance Evaluation of Antlion Optimizer Based Regulator in Automatic Generation Control of Interconnected Power System Mon, 06 Jun 2016 12:05:10 +0000 This paper presents an application of the recently introduced Antlion Optimizer (ALO) to find the parameters of primary governor loop of thermal generators for successful Automatic Generation Control (AGC) of two-area interconnected power system. Two standard objective functions, Integral Square Error (ISE) and Integral Time Absolute Error (ITAE), have been employed to carry out this parameter estimation process. The problem is transformed in optimization problem to obtain integral gains, speed regulation, and frequency sensitivity coefficient for both areas. The comparison of the regulator performance obtained from ALO is carried out with Genetic Algorithm (GA), Particle Swarm Optimization (PSO), and Gravitational Search Algorithm (GSA) based regulators. Different types of perturbations and load changes are incorporated to establish the efficacy of the obtained design. It is observed that ALO outperforms all three optimization methods for this real problem. The optimization performance of ALO is compared with other algorithms on the basis of standard deviations in the values of parameters and objective functions. Esha Gupta and Akash Saxena Copyright © 2016 Esha Gupta and Akash Saxena. All rights reserved. Constitutive Equations of Yield Stress Sensitivity to Strain Rate of Metals: A Comparative Study Thu, 02 Jun 2016 08:22:25 +0000 Several constitutive equations have proposed to model the strain rate sensitivity of metals to strain rate. This paper presents a comparative of six equations reported in the open literature. All equations are used to fit the yield stress of three copper materials and one steel material at two different temperatures. A specific cost function and an optimization problem are defined. The authors recommend the use of the Cowper-Symonds equation or a modified-Eyring equation as both of them fit well the experimental data while using only three material constants. A modified flow stress Johnson-Cook equation is then proposed for metallic materials. Ammar A. Al Salahi and Ramzi Othman Copyright © 2016 Ammar A. Al Salahi and Ramzi Othman. All rights reserved. Stagnation Point Flow of Nanofluid over a Moving Plate with Convective Boundary Condition and Magnetohydrodynamics Wed, 25 May 2016 11:21:35 +0000 A theoretical investigation is carried out to examine the effects of volume fraction of nanoparticles, suction/injection, and convective heat and mass transfer parameters on MHD stagnation point flow of water-based nanofluids (Cu and Ag). The governing partial differential equations for the fluid flow, temperature, and concentration are reduced to a system of nonlinear ordinary differential equations. The derived similarity equations and corresponding boundary conditions are solved numerically using Runge-Kutta Fehlberg fourth-fifth order method. To exhibit the effect of the controlling parameters on the dimensionless velocity, temperature, nanoparticle volume fraction, skin friction factor, and local Nusselt and local Sherwood numbers, numerical results are presented in graphical and tabular forms. It is found that the friction factor and heat and mass transfer rates increase with magnetic field and suction/injection parameters. Fazle Mabood, Nopparat Pochai, and Stanford Shateyi Copyright © 2016 Fazle Mabood et al. All rights reserved.