Journal of Engineering The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . 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. A Modified Column Generation to Solve the Heterogeneous Fixed Fleet Open Vehicle Routing Problem Mon, 16 May 2016 06:10:49 +0000 In the heterogeneous fixed fleet open vehicle routing problem (HFFOVRP), several different types of vehicles can be used to service the customers. The types of vehicles are different in terms of capacity, fixed cost, and variable cost. In this problem, the vehicles are not required to return to the depot after completing a service and the number of vehicles of each type is fixed and limited. Since this problem belongs to NP-hard problems, in this paper a compound heuristic algorithm called SISEC which includes sweep algorithm, insert, swap, and 2-opt moves, modified elite ant system (EAS), and column generation (CG) is applied to solve the HFFOVRP. We report computational results on 22 problems and solve each problem by using our SISEC. The results which were compared to the results of exact algorithms and the classic CG confirm that the proposed algorithm produces high quality solutions within an acceptable computation time. Majid Yousefikhoshbakht, Azam Dolatnejad, Farzad Didehvar, and Farhad Rahmati Copyright © 2016 Majid Yousefikhoshbakht et al. All rights reserved. Acoustic Absorption of Natural Fiber Composites Mon, 09 May 2016 09:55:57 +0000 The current study is a bibliographic observation on prevailing tendencies in the development of acoustic absorption by natural fiber composites. Despite having less detrimental environmental effects and thorough availability, natural fibers are still unsuitable for wide implementation in industrial purposes. Some shortcomings such as the presence of moisture contents, thicker diameter, and lower antifungus quality hold up the progress of natural fiber composites in staying competitive with synthetic composites. The review indicates the importance of the pretreatment of fresh natural fiber to overcome these shortcomings. However, the pretreatment of natural fiber causes the removal of moisture contents which results in the decrease of its acoustic absorption performance. Incorporation of granular materials in treated fiber composite is expected to play a significant role as a replacement for moisture contents. This review aims to investigate the acoustic absorption behavior of natural fiber composites due to the incorporation of granular materials. It is intended that this review will provide an overview of the analytical approaches for the modeling of acoustic wave propagation through the natural fiber composites. The possible influential factors of fibers and grains were described in this study for the enhancement of low frequency acoustic absorption of the composites. Hasina Mamtaz, Mohammad Hosseini Fouladi, Mushtak Al-Atabi, and Satesh Narayana Namasivayam Copyright © 2016 Hasina Mamtaz et al. All rights reserved. Survival Analysis of Fatigue and Rutting Failures in Asphalt Pavements Sun, 08 May 2016 09:25:59 +0000 Fatigue and rutting are two primary failure mechanisms in asphalt pavements. The evaluations of fatigue and rutting performances are significantly uncertain due to large uncertainties involved with the traffic and pavement life parameters. Therefore, deterministically it is inadequate to predict when an in-service pavement would fail. Thus, the deterministic failure time which is known as design life () of pavement becomes random in nature. Reliability analysis of such time () dependent random variable is the survival analysis of the structure. This paper presents the survival analysis of fatigue and rutting failures in asphalt pavement structures. It is observed that the survival of pavements with time can be obtained using the bathtub concept that contains a constant failure rate period and an increasing failure rate period. The survival function (), probability density function (pdf), and probability distribution function (PDF) of failure time parameter are derived using bathtub analysis. It is seen that the distribution of failure time follows three parametric Weibull distributions. This paper also works out to find the most reliable life () of pavement sections corresponding to any reliability level of survivability. Pabitra Rajbongshi and Sonika Thongram Copyright © 2016 Pabitra Rajbongshi and Sonika Thongram. All rights reserved. Microcontroller Based Flexible Modulation Scheme of MLI Operation for Selective Lower Levels: A Knowledge Based Approach Wed, 04 May 2016 11:18:08 +0000 In today’s industrial world multilevel inverter (MLI) got a significant importance in medium voltage application and also a very potential topic for researchers. It is experienced that studying and comparing results of multilevel inverter (MLI) at distinct levels are a costlier and time consuming issue for any researcher if he fabricate different inverters for each level, as designing power modules simultaneously for different level is a cumbersome task. In this paper a flexible quotient has been proposed to recognize possible conversion of available MLI to few lower level inverters by appropriately changing microcontroller programming. This is an attempt to obtain such change in levels through simulation using MATLAB Simulink on inductive load which may also be applied to induction motor. Experimental results of pulse generation using dsPIC33EP256MC202 demonstrate the feasibility of proposed scheme. Proposed flexible quotient successfully demonstrates that a five-level inverter may be operated as three and two levels also. The paper focuses on odd levels only as common mode voltage (CMV) can be reduced to zero and performance of drives is better than even level. Simulated and experimental results are given in paper. R. K. Dhatrak, R. K. Nema, and D. M. Deshpande Copyright © 2016 R. K. Dhatrak et al. All rights reserved. Prediction of Load-Carrying Capacity in Steel Shear Wall with Opening Using Artificial Neural Network Tue, 03 May 2016 08:21:54 +0000 The effects of different parameters on steel plate shear wall (SPSW) are investigated. The studied parameters are thickness of plate, location of the opening, thickness of diagonal stiffeners, and thickness of circular stiffener. Load-carrying capacity of the SPSW is studied under static load using nonlinear geometrical and material analysis in ABAQUS and the obtained simulation results are verified. An artificial neural network (ANN) is proposed to model the effects of these parameters. According to the results the circular stiffener has more effect compared with the diagonal stiffeners. However, the thickness of the plate has the most significant effect on the SPSW behavior. The results show that the best place for the opening location is the center of SPSW. Multilayer perceptron (MLP) neural network was used to predict the maximum load in SPSW with opening. The predicted maximum load values using the proposed MLP model were compared with the simulated validated data. The obtained results show that the proposed ANN model has achieved good agreement with the validated simulated data, with correlation coefficient of more than 0.9975. Therefore, the proposed model is useful, reliable, fast, and cheap tools to predict the maximum load in SPSW. E. Khalilzadeh Vahidi and M. M. Roshani Copyright © 2016 E. Khalilzadeh Vahidi and M. M. Roshani. All rights reserved. Routing in Wireless Multimedia Sensor Networks: A Survey of Existing Protocols and Open Research Issues Mon, 18 Apr 2016 11:46:51 +0000 With the advancement of wireless sensor networks (WSNs) and technology, applicability of WSNs as a system is touching new heights. The development of multimedia nodes has led to the creation of another intelligent distributed system, which can transfer real-time multimedia traffic, ubiquitously. Wireless multimedia sensor networks (WMSNs) are applicable in a wide range of areas including area monitoring and video surveillance. But due to unreliable error-prone communication medium and application specific quality of service (QoS) requirements, routing of real-time multimedia traffic in WMSNs poses a serious problem. The paper discusses various existing routing strategies in WMSNs, with their properties and limitations which lead to open research issues. Further, detailed classification and analytical comparison of discussed protocols are also presented. Vikas Bhandary, Amita Malik, and Sanjay Kumar Copyright © 2016 Vikas Bhandary et al. All rights reserved. Interaction of Magnetic Field and Nonlinear Convection in the Stagnation Point Flow over a Shrinking Sheet Mon, 18 Apr 2016 07:11:47 +0000 The steady two-dimensional boundary layer stagnation point flow due to a shrinking sheet is analyzed. The combined effects of magnetic field and nonlinear convection are taken into account. The governing equations for the flow are modeled and then simplified using the similarity transformation and boundary layer approach. The numerical solution of the reduced equations is obtained by the second-order finite difference scheme also known as Keller box method. The influence of the pertinent parameters of the problem on velocity and temperature profiles, skin friction, and sheet temperature gradient are presented through the graphs and tables and discussed. The magnetic field and nonlinear convection parameters significantly enhance the solution range. Rakesh Kumar and Shilpa Sood Copyright © 2016 Rakesh Kumar and Shilpa Sood. All rights reserved. Slip Effect on MHD Chemically Reacting Convictive Boundary Layer Flow with Heat Absorption Mon, 11 Apr 2016 12:59:09 +0000 The aim of this paper is to investigate steady magneto micropolar fluid past a stretched semi-infinite vertical and permeable surface taking into account heat absorption, hall and ion-slip effect, first-order chemical reaction, and radiation effects. The system of coupled nonlinear equations is solved numerically and the effects of various parameters on the velocity, the microrotation, the temperature, and the concentration field are calculated. The following discovery was made: an increase in the hall parameter strongly enhances the fluid velocity, an increase in the heat absorption parameter increases the temperature, and an increase in the slip parameter decreases the velocity. Additionally, the local skin friction, Nusselt number, and Sherwood number are also analyzed for various parameters and presented in table form. Mekonnen Shifferaw Ayano and Negussie Tadege Demeke Copyright © 2016 Mekonnen Shifferaw Ayano and Negussie Tadege Demeke. All rights reserved. Sorption Profile of Phosphorus Ions onto ZnO Nanorods Synthesized via Sonic Technique Mon, 11 Apr 2016 09:16:43 +0000 High surface area zinc oxide material in nanorod morphological structure was synthesized using an ultrasonic technique in the presence of polyvinyl pyrrolidone as stabilizing agent. The crystallite, morphology, and surface area of the prepared white powder material were identified using XRD, SEM, and BET techniques, respectively. X-ray analysis confirms the high purity of synthesized ZnO. The evaluated specific surface area of prepared ZnO was 16.7 m2/g; this value guarantees high efficiency for water purification. The feasibility of synthesized ZnO nanorods for phosphorus sorption from aqueous solution was established using batch technique. Nano-zinc oxide exhibits high efficiency for phosphorus removal; the equilibrium state was recorded within 90 minutes. The most effective hydrogen ion concentration of the polluted solution was recorded at pH = 1 for phosphorus decontamination. The equilibrium of phosphorus sorption onto ZnO nanorods was well explained using both Langmuir and Temkin isotherm models. The calculated maximum monolayer sorption capacity was 89 mg/g according to Langmuir isotherm at 27°C. In order to explain the phosphorus sorption mechanism onto the prepared ZnO nanorods, three simplified kinetic models of pseudo-first order, pseudo-second order, and intraparticle diffusion rate models were tested. Kinetics was well fitted by pseudo-second order kinetic model with a contribution of intraparticle diffusion. M. F. Elkady, H. Shokry Hassan, and Eslam Salama Copyright © 2016 M. F. Elkady et al. All rights reserved. Machine Learning Based Statistical Prediction Model for Improving Performance of Live Virtual Machine Migration Sun, 10 Apr 2016 06:30:49 +0000 Service can be delivered anywhere and anytime in cloud computing using virtualization. The main issue to handle virtualized resources is to balance ongoing workloads. The migration of virtual machines has two major techniques: (i) reducing dirty pages using CPU scheduling and (ii) compressing memory pages. The available techniques for live migration are not able to predict dirty pages in advance. In the proposed framework, time series based prediction techniques are developed using historical analysis of past data. The time series is generated with transferring of memory pages iteratively. Here, two different regression based models of time series are proposed. The first model is developed using statistical probability based regression model and it is based on ARIMA (autoregressive integrated moving average) model. The second one is developed using statistical learning based regression model and it uses SVR (support vector regression) model. These models are tested on real data set of Xen to compute downtime, total number of pages transferred, and total migration time. The ARIMA model is able to predict dirty pages with 91.74% accuracy and the SVR model is able to predict dirty pages with 94.61% accuracy that is higher than ARIMA. Minal Patel, Sanjay Chaudhary, and Sanjay Garg Copyright © 2016 Minal Patel et al. All rights reserved. Application of Unit Commitment with Market Pool in a Peaking Power Generation Firm in the Philippines for a Cost Reduction Case Study Thu, 07 Apr 2016 11:50:41 +0000 This paper attempts to provide an optimum loading schedule of power generating units with the least cost by solving a unit commitment (UC) problem and to present good estimates of cost differences when UC problem is not applied. UC is a fundamental optimization problem of power generation systems which determines the optimum schedule of generating units which minimizes generation costs. However, for small power generation firms which are situated in developing countries, UC-based problems are poorly understood if not implemented and the scheduling of generating units is based on some methodologies which may provide results that are not optimal. Thus, a case study in a small power generation firm in central Philippines is carried out to elucidate these objectives. The case requires a solution of the mixed-integer nonlinear programming (MINLP) problem. Results show that the proposed UC-based problem yields optimal costs and the cost disparity from the current scheduling scheme is approximately at 27% which may be considered as potential cost savings. This shows that UC-based problem provides a reliable platform in achieving minimal generation costs. These results are significant to decision-makers particularly in small power generation firms and to engineering practitioners in the Philippines and in some developing countries as these provide an overview of the disparity of cost figures of not implementing UC. Luke Rey Santillan, Kenn Brylle Senen, Robert Wamilda Jr., Lanndon Ocampo, Rafael Seva Jr., Reuella J. Bacalso, and Alaine Liggayu Copyright © 2016 Luke Rey Santillan et al. All rights reserved. Early and Late Strength Characterization of Portland Cement Containing Calcined Low-Grade Kaolin Clay Mon, 04 Apr 2016 16:55:52 +0000 Heat treated low-grade kaolin clays are now considered as a suitable pozzolanic material to metakaolins. However their suitability as a good pozzolanic material depends on the geochemistry and structure of the clay which is usually influenced by the geographical environment. This study investigated a low-grade kaolin clay from Nyamebekyere in the Ashanti Region of Ghana. The influence of the calcined material on the early and late strength development of Portland cement was analyzed. The early 3- and 7-day strength as well as the late 28-day strength of Portland cement replaced with 20% by weight of the calcined material yielded the optimum strength values. Further analysis using Solid State Magic Angle Spinning Nuclear Magnetic Resonance (Ss MAS NMR) probed into the Aluminium (Al) environment to detect the presence and nature of Al hydrates using the optimum mixture proportion. The Ss MAS NMR results showed that the strength enhancement of the optimum mixture was due to the growth of stable monosulphate compounds at the octahedral environment resulting from metastable aluminate phases at the tetrahedral environment. For greater reliability on concrete strength performance, the study recommends the use of 20% calcined clay of Nyamebekyere clay as Portland cement replacement. Mark Bediako, S. K. Y. Gawu, A. A. Adjaottor, and John Solomon Ankrah Copyright © 2016 Mark Bediako et al. All rights reserved. Possibilities for Advanced Encoding Techniques at Signal Transmission in the Optical Transmission Medium Thu, 31 Mar 2016 11:42:24 +0000 This paper presents a possible simulation of negative effects in the optical transmission medium and an analysis for the utilization of different signal processing techniques at the optical signal transmission. An attention is focused on the high data rate signal transmission in the optical fiber influenced by linear and nonlinear environmental effects presented by the prepared simulation model. The analysis includes possible utilization of OOK, BPSK, DBPSK, BFSK, QPSK, DQPSK, 8PSK, and 16QAM modulation techniques together with RS, BCH, and LDPC encoding techniques for the signal transmission in the optical fiber. Moreover, the prepared simulation model is compared with real optical transmission systems. In the final part, a comparison of the selected modulation techniques with different encoding techniques and their implementation in real transmission systems is shown. Filip Čertík and Rastislav Róka Copyright © 2016 Filip Čertík and Rastislav Róka. All rights reserved. A Higher-Order Thermomechanical Vibration Analysis of Temperature-Dependent FGM Beams with Porosities Tue, 29 Mar 2016 12:43:25 +0000 In the present paper, thermomechanical vibration characteristics of functionally graded (FG) Reddy beams made of porous material subjected to various thermal loadings are investigated by utilizing a Navier solution method for the first time. Four types of thermal loadings, namely, uniform, linear, nonlinear, and sinusoidal temperature rises, through the thickness direction are considered. Thermomechanical material properties of FG beam are assumed to be temperature-dependent and supposed to vary through thickness direction of the constituents according to power-law distribution (P-FGM) which is modified to approximate the porous material properties with even and uneven distributions of porosities phases. The governing differential equations of motion are derived based on higher order shear deformation beam theory. Hamilton’s principle is applied to obtain the governing differential equations of motion which are solved by employing an analytical technique called the Navier type solution method. Influences of several important parameters such as power-law exponents, porosity distributions, porosity volume fractions, thermal effects, and slenderness ratios on natural frequencies of the temperature-dependent FG beams with porosities are investigated and discussed in detail. It is concluded that these effects play significant role in the thermodynamic behavior of porous FG beams. Farzad Ebrahimi and Ali Jafari Copyright © 2016 Farzad Ebrahimi and Ali Jafari. All rights reserved. Case Study: LCA Methodology Applied to Materials Management in a Brazilian Residential Construction Site Mon, 28 Mar 2016 10:29:13 +0000 The construction industry is increasingly concerned with improving the social, economic, and environmental indicators of sustainability. More than ever, the growing demand for construction materials reflects increased consumption of raw materials and energy, particularly during the phases of extraction, processing, and transportation of materials. This work aims to help decision-makers and to promote life cycle thinking in the construction industry. For this purpose, the life cycle assessment (LCA) methodology was chosen to analyze the environmental impacts of building materials used in the construction of a residence project in São Gonçalo, Rio de Janeiro, Brazil. The LCA methodology, based on ISO 14040 and ISO 14044 guidelines, is applied with available databases and the SimaPro program. As a result, this work shows that there is a substantial waste of nonrenewable energy, increasing global warming and harm to human health in this type of construction. This study also points out that, for this type of Brazilian construction, ceramic materials account for a high percentage of the mass of a total building and are thus responsible for the majority of environmental impacts. João de Lassio, Josué França, Kárida Espirito Santo, and Assed Haddad Copyright © 2016 João de Lassio et al. All rights reserved. Modeling of the Strain Rate Dependency of Polycarbonate’s Yield Stress: Evaluation of Four Constitutive Equations Mon, 14 Mar 2016 08:19:20 +0000 The main focus of this paper is in evaluating four constitutive relations which model the strain rate dependency of polymers yield stress. Namely, the two-term power-law, the Ree-Eyring, the cooperative, and the newly modified-Eyring equations are used to fit tensile and compression yield stresses of polycarbonate, which are obtained from the literature. The four equations give good agreement with the experimental data. Despite using only three material constants, the modified-Eyring equation, which considers a strain rate-dependent activation volume, gives slightly worse fit than the three other equations. The two-term power-law and the cooperative equation predict a progressive increase in the strain rate sensitivity of the yield stress. Oppositely, the Ree-Eyring and the modified-Eyring equations show a clear transition between the low and high strain rate ranges. Namely, they predict a linear dependency of the yield stress in terms of the strain rate at the low strain rate range. Crossing a threshold strain rate, the yield stress sensitivity sharply increases as the strain rate increases. Hence, two different behaviors were observed though the four equations fit well the experimental data. More experimental data, mainly at the intermediate strain rate range, are needed to conclude which, of the two behaviors, is more appropriate for polymers. Abdullah A. Al-Juaid and Ramzi Othman Copyright © 2016 Abdullah A. Al-Juaid and Ramzi Othman. All rights reserved. Sediment and Cavitation Erosion Studies through Dam Tunnels Sun, 13 Mar 2016 14:33:23 +0000 This paper presents results of sediment and cavitation erosion through Tunnel 2 and Tunnel 3 of Tarbela Dam in Pakistan. Main bend and main branch of Tunnel 2 and outlet 1 and outlet 3 of Tunnel 3 are concluded to be critical for cavitation and sediment erosion. Studies are also performed for increased sediments flow rate, concluding 5 kg/sec as the critical value for sudden increase in erosion rate density. Erosion rate is concluded to be the function of sediment flow rate and head condition. Particulate mass presently observed is reasonably low, hence presently not affecting the velocity and the flow field. Muhammad Abid, Jamal Saeed, and Hafiz Abdul Wajid Copyright © 2016 Muhammad Abid et al. All rights reserved.