http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2013 , Hindawi Publishing Corporation . All rights reserved. Mon, 20 May 2013 13:12:25 +0000 http://www.hindawi.com/journals/je/2013/510572/ An Interactive Artificial Bee Colony (IABC) Optimization based fuzzy (IABCF) to tune optimal gains of a Robust Proportional Integral Derivative (RPID) controller is proposed for the solution of multiarea automatic generation control (AGC) simulation problem in a restructured power system. One of the important problems in the proposed method is the exact tuning of the RPID parameters for achieving the desired level of robust performance. The problem of robustly tuning of RPID based AGC design is formulated as an optimization problem according to the time domain-based objective function, which is solved by the IABC technique that has a strong ability to find the most optimistic results. The robustness and effectiveness of the proffered method are shown on a two and four areas deregulated power system with possible contracted scenarios under large load demand and area disturbances in comparison with the other methods through FD and ITAE performance indices. The evaluation results show that the proposed control strategy achieves good robust performance for worldwide experience of automatic generation control in restructured systems parameters and load changes in the presence of system nonlinearities. Javad Javidan and Ali Ghasemi Copyright © 2013 Javad Javidan and Ali Ghasemi. All rights reserved. Sun, 19 May 2013 14:20:41 +0000 http://www.hindawi.com/journals/je/2013/561651/ Quantum-dot cellular automata (QCA) is an efficient technology to create computing devices. QCA is a suitable candidate for the next generation of digital systems. Full adders are the main member of computational systems because other operations can be implemented by adders. In this paper, two QCA full adders are introduced. The first one is implemented in one layer, and the second one is implemented in three layers. Five-input majority gate is used in both of them. These full adders are better than pervious designs in terms of area, delay, and complexity. Mahdie Qanbari and Reza Sabbaghi-Nadooshan Copyright © 2013 Mahdie Qanbari and Reza Sabbaghi-Nadooshan. All rights reserved. Thu, 16 May 2013 14:18:13 +0000 http://www.hindawi.com/journals/je/2013/435628/ The wavelet transform is a well-known signal analysis method in several engineering disciplines. In image processing and pattern recognition, the wavelet transform is used in many applications for image coding as well as feature extraction purposes. It can be used to describe a given object shape by wavelet descriptors (WD). Thus, it is used to recognize objects according to their contour shape by deriving a number of WD and comparing them with the WD of stored contour patterns. For our method, we use a periodical angle function derived from an extracted object contour. In order to apply the WD, the Mexican Hat can be used as the mother wavelet. In this paper, the method of object shape recognition using wavelet descriptors is described coherently and includes details relating to the method of applying the periodical angle function and the derivation of the formulas for the Haar as well as Mexican Hat wavelet descriptors. To evaluate the results of object recognition when using wavelet descriptors taking into account the dependence on the starting point, the paper describes a sufficient method for the comparison of wavelet descriptors using the minimum distance matrix. Adnan Abou Nabout Copyright © 2013 Adnan Abou Nabout. All rights reserved. Mon, 13 May 2013 11:33:15 +0000 http://www.hindawi.com/journals/je/2013/310748/ General formulation of practically applicable fundamental approach for development of engineering applications in systems with dynamically appearing and disappearing fractal structures is proposed. The approach is illustrated on the low-temperature pyrolysis of butane/propane mixture being pumped via the liquid tin and bismuth alloy preserved at the temperature 200 ± 20°C in the U-shaped test glass. Other prospective engineering applications of the approach are proposed on the base of analysis of selected experiments described in literature. Aliaksandr Yurievich Alevanau, Olgerd Pavlovich Kuznechik, and Oleksandr Ivanovych Vyhoniailo Copyright © 2013 Aliaksandr Yurievich Alevanau et al. All rights reserved. Wed, 08 May 2013 17:25:27 +0000 http://www.hindawi.com/journals/je/2013/231847/ Radial forging is a widely used forming process for manufacturing hollow products in transport industry. As the deformation of the workpiece, during the process, is a consequence of a large number of high-speed strokes, the Johnson-Cook constitutive law (taking into account the strain rate) seems to be well adapted for representing the material behavior even if the process is performed under cold conditions. But numerous contributions concerning radial forging analysis, in the literature, are based on a simple elastic-plastic formulation. As far as we know, this assumption has yet not been validated for the radial forging process. Because of the importance of the flow law in the effectiveness of the model, our purpose in this paper is to analyze the influence of the use of an elastic-viscoplastic formulation instead of an elastic-plastic one for modeling the cold radial forging process. In this paper we have selected two different laws for the simulations: the Johnson-Cook and the Ludwik ones, and we have compared the results in terms of forging force, product's thickness, strains, stresses, and CPU time. For the presented study we use an AISI 4140 steel, and we denote a fairly good agreement between the results obtained using both laws. Olivier Pantalé and Babacar Gueye Copyright © 2013 Olivier Pantalé and Babacar Gueye. All rights reserved. Thu, 02 May 2013 15:32:42 +0000 http://www.hindawi.com/journals/je/2013/687581/ A practical method is presented: how to adjust the inductance curve of a nonlinear (saturable) inductor with respect to a desired shape. For this purpose, a nonlinear model was developed based on finite element method (FEM). It is shown how a highly efficient construction with low stray fields and maximum package density can be achieved. Different prototype inductors were realized to illustrate the practical capability of photovoltaic (PV) inverters as well as active power factor correction (PFC) applications. All simulations are verified by means of experimental data drawn from electrical measurements. Alexander Stadler, Tobias Stolzke, and Christof Gulden Copyright © 2013 Alexander Stadler et al. All rights reserved. Thu, 02 May 2013 14:26:34 +0000 http://www.hindawi.com/journals/je/2013/626824/ The subject of research in this paper is multiple-valued (MV) memory cell—particularly the morphology of boundary surface of five-valued memory. By accepting the values of parasitic accumulation elements on the chip, very complicated morphology of the boundary surfaces occurs, which separates various attractors from each other. This is due to the occurrence of undesirable oscillations—a stable limit cycles, which makes it impossible to control memory. These dynamic attractors are so dominant that their regions of attraction even surround regions of attraction of static attractors—required logic levels of memory. Therefore, in the realization of the MV memory on the chip is necessary to know the values of the parasitic elements, because their presence may cause a malfunction of the memory. In this case, only calculation and displaying the boundary surface provides exact answers related to operation of the MV memory. Milan Guzan Copyright © 2013 Milan Guzan. All rights reserved. Thu, 02 May 2013 08:44:58 +0000 http://www.hindawi.com/journals/je/2013/596078/ This paper presents vibration control of a building model under earthquake loads. A magnetorheological (MR) damper is placed in the building between the first floor and ground for seismic response reduction. A new control algorithm to command the MR damper is proposed. The approach is inspired by a quasi-bang-bang controller; however, the proposed technique gives weights to control commands in a fashion that is similar to a fuzzy logic controller. Several control algorithms including decentralized bang-bang controller, Lyapunov controller, modulated homogeneous friction controller, maximum energy dissipation controller, and clipped-optimal controller are used for comparison. The new controller achieved the best reduction in maximum interstory drifts and maximum absolute accelerations over all the control algorithms presented. This reveals that the proposed controller with the MR damper is promising and may provide the best protection to the building and its contents. Aly Mousaad Aly Copyright © 2013 Aly Mousaad Aly. All rights reserved. Tue, 30 Apr 2013 16:12:56 +0000 http://www.hindawi.com/journals/je/2013/754204/ This paper examines the application of Latin Hypercube Sampling (LHS) and Antithetic Variables (AVs) to reduce the variance of estimated performance measures from microscopic traffic simulators. LHS and AV allow for a more representative coverage of input probability distributions through stratification, reducing the standard error of simulation outputs. Two methods of implementation are examined, one where stratification is applied to headways and routing decisions of individual vehicles and another where vehicle counts and entry times are more evenly sampled. The proposed methods have wider applicability in general queuing systems. LHS is found to outperform AV, and reductions of up to 71% in the standard error of estimates of traffic network performance relative to independent sampling are obtained. LHS allows for a reduction in the execution time of computationally expensive microscopic traffic simulators as fewer simulations are required to achieve a fixed level of precision with reductions of up to 84% in computing time noted on the test cases considered. The benefits of LHS are amplified for more congested networks and as the required level of precision increases. Khewal Bhupendra Kesur Copyright © 2013 Khewal Bhupendra Kesur. All rights reserved. Mon, 29 Apr 2013 09:58:39 +0000 http://www.hindawi.com/journals/je/2013/214650/ In the literature, there are various algorithms available for computing the discrete fractional Fourier transform (DFRFT). In this paper, all the existing methods are reviewed, classified into four categories, and subsequently compared to find out the best alternative from the view point of minimal computational error, computational complexity, transform features, and additional features like security. Subsequently, the correlation theorem of FRFT has been utilized to remove significantly the Doppler shift caused due to motion of receiver in the DSB-SC AM signal. Finally, the role of DFRFT has been investigated in the area of steganography. Ashutosh Kumar Singh and Rajiv Saxena Copyright © 2013 Ashutosh Kumar Singh and Rajiv Saxena. All rights reserved. Sun, 28 Apr 2013 14:07:27 +0000 http://www.hindawi.com/journals/je/2013/850148/ In order to run CFD codes more efficiently on large scales, the parallel computing has to be employed. For example, in industrial scales, it usually uses tens of thousands of mesh cells to capture the details of complex geometries. How to distribute these mesh cells among the multiprocessors for obtaining a good parallel computing performance (HPC) is really a challenge. Due to dealing with the massive mesh cells, it is difficult for the CFD codes without parallel optimizations to handle this kind of large-scale computing. Some of the open source mesh partitioning software packages, such as Metis, ParMetis, Scotch, PT-Scotch, and Zoltan, are able to deal with the distribution of large number of mesh cells. Therefore they were employed as the parallel optimization tools ported into Code_Saturne, an open source CFD code, for testing if they can solve the issue of dealing with massive mesh cells for CFD codes. Through the studies, it was found that the mesh partitioning optimization software packages can help CFD codes not only deal with massive mesh cells but also have a good HPC. Zhi Shang Copyright © 2013 Zhi Shang. All rights reserved. Sun, 28 Apr 2013 11:17:43 +0000 http://www.hindawi.com/journals/je/2013/852959/ CSMA/CA-based DCF of 802.11 MAC layer employs a best-effort delivery model, in which stations compete for channel access with the same priority. In a heterogeneous network, providing different priorities to different applications for required quality of service is a challenging task, since heterogeneous conditions result in unfairness among stations and degradation in the throughput. This paper proposes a class of collision resolution schemes for 802.11 having contention window control with nonoverlapped contention slots. In the first scheme, window ranges of two consecutive stages are nonoverlapped, and it is called nonoverlapped contention slots (NOCS) scheme. In the other scheme, termed as NOCS-offset, an offset is introduced between window ranges of two stages. Selection of a random value by a station for its contention with discontinuous distribution results in reduced probability of collision. Analytical and simulation results show that the proposed scheme exhibits higher throughput and fairness with reduced delay and collision probability in homogeneous and heterogeneous networks. Performance of the proposed scheme is evaluated for mix traffic and high data rate environment with advanced back-off management techniques to meet the requirements of the present applications. Raksha Upadhyay, Prakash D. Vyavahare, and Sanjiv Tokekar Copyright © 2013 Raksha Upadhyay et al. All rights reserved. Wed, 24 Apr 2013 12:57:27 +0000 http://www.hindawi.com/journals/je/2013/216259/ Group III nitride semiconductors with direct band gaps have recently become increasingly important in optoelectronics and microelectronics applications due to their direct band gaps, which cover the whole visible spectrum and a large part of the UV range. Major developments in wide band gap III–V nitride semiconductors have recently led to the commercial production of high-temperature, high-power electronic devices, light-emitting diodes (LEDs), and laser diodes (LDs). In this study, GaN nanowires were grown on horizontal reactors by chemical vapor deposition (CVD) employing a vapor-solid mechanism. Many studies have described how to control the diameters of wires in the liquid phase catalytic process, but one-dimensional nanostructures, which are grown using a noncatalytic process, are relatively unexplored due to the challenge of producing high-quality synthetic materials of controlled size. However, vapor-solid mechanisms to make synthesized nanowires are simple to implement. We obtained results from GaN nanostructures that were a preferential c-axis orientation from the substrate. The morphology and crystallinity of the GaN nanowires were characterized by field-emission scanning electron microscopy and X-ray diffraction. The chemical compositions of GaN with Mn were analyzed by energy dispersive X-ray spectroscopy. Optical properties were investigated using photo luminescence and cathode-luminescence measurements. Sang-Wook Ui, In-Seok Choi, and Sung-Churl Choi Copyright © 2013 Sang-Wook Ui et al. All rights reserved. Mon, 22 Apr 2013 15:03:24 +0000 http://www.hindawi.com/journals/je/2013/580805/ This paper presents the results obtained and the deductions made from an analytical modeling involving friction stir welding of Al 6061-T6. A new database was developed to simulate the contact temperature between the tool and the workpiece. A second-order equation is proposed for simulating the temperature in the contact boundary and the thermal history during the plunge phase. The effect of the preheating temperature on the process time was investigated with the proposed model. The results show that an increase of the preheating time leads to a decrease in the process time up to the plunge and the preheating stage. Results of modeling the thermal history showed acceptable agreement with corresponding experimental data from the literature. Masoud Jabbari Copyright © 2013 Masoud Jabbari. All rights reserved. Sun, 21 Apr 2013 15:07:31 +0000 http://www.hindawi.com/journals/je/2013/685969/ A short-cut method for batch distillation columns working at constant reflux was applied to solve a problem of four components that needed to be separated and purified to a mole fraction of 0.97 or better. Distillation columns with 10, 20, 30, 40, and 50 theoretical stages were used; reflux ratio was varied between 2 and 20. Three quality indexes were used and compared: Luyben’s capacity factor, total annual cost, and annual profit. The best combinations of theoretical stages and reflux ratio were obtained for each method. It was found that the best combinations always required reflux ratios close to the minimum. Overall, annual profit was the best quality index, while the best combination was a distillation column with 30 stages, and reflux ratio’s of 2.0 for separation of benzene (i), 5.0 for the separation of toluene (ii), and 20 for the separation of ethylbenzene (iii) and purification of o-xylene (iv). Asteria Narvaez-Garcia, Jose del Carmen Zavala-Loria, Luis Enrique Vilchis-Bravo, and Jose Antonio Rocha-Uribe Copyright © 2013 Asteria Narvaez-Garcia et al. All rights reserved. Wed, 17 Apr 2013 16:26:37 +0000 http://www.hindawi.com/journals/je/2013/526072/ The concepts of resistance and inductance are strewn with misunderstanding and errors that result from inaccurate terminology, mistakes in their definitions, and from the fact that they are quantities that characterize elements of ideal electrical circuits as well as real solid conductors. This is shown unfavourably not only in the respective field of the theory of electrical engineering, but also in the calculation of resistance and inductance. In this paper, a brief theoretical analysis of the state of the art is given, and its results are applied in the calculation of the current density, resistance, and inductance of two coaxial solid tubular conductors. Oldřich Coufal Copyright © 2013 Oldřich Coufal. All rights reserved. Wed, 17 Apr 2013 10:34:24 +0000 http://www.hindawi.com/journals/je/2013/645745/ The objective of this article is to present various aspects of Fiber-Wireless (Fi-Wi) networks, which is a technology of current interest of the researchers. Fiber-wireless technology, known in short as “Fi-Wi,” is a combination of optical-fiber-based network and wireless network. Fi-Wi has recently come forward as one of the emerging future network technologies yet the term is often mixed up with wireless-fidelity (Wi-Fi) technology. In fact, Wi-Fi network could be included in a Fi-Wi architecture. Due to the unfamiliarity with the term, “Fi-Wi” and similar sounding commonly known “Wi-Fi,” many students, even academics and practitioners sometimes may not be able to differentiate between these. In the recent years, a good number of works on various issues of Fi-Wi have come out, but an overall survey with the latest advancements in the area is yet to be found. Hence, in this work, we analyze various issues and challenges of implementing Fi-Wi networks in practical scenarios to allow researchers to find future directions of research and general readers to understand the issues better. Harry Tin Win and Al-Sakib Khan Pathan Copyright © 2013 Harry Tin Win and Al-Sakib Khan Pathan. All rights reserved. Mon, 15 Apr 2013 19:20:15 +0000 http://www.hindawi.com/journals/je/2013/512971/ We study analytically and numerically in which way the width of ring aperture containing a phase jump affects the size and intensity of the focal spot generated with a radially polarized beam. It is shown that by means of destructive interference of beams coming from the different-phase rings it becomes possible to overcome the scalar diffraction limit corresponding to the first zero of the zero-order Bessel function. The minimal focal spot size (FWHM ) is found to be attained when the annular aperture width amounts to 20% of the full-aperture radius. In this case, the side-lobe intensity is not larger than 30% of the central peak. A wider annular aperture with the phase jump introduced is also shown to form a focal spot not exceeding the diffraction limit for a narrow annular aperture, simultaneously providing a nearly six times higher intensity. In this case, the side lobes amount to 35% of the central peak. Svetlana N. Khonina and Andrei V. Ustinov Copyright © 2013 Svetlana N. Khonina and Andrei V. Ustinov. All rights reserved. Mon, 15 Apr 2013 17:10:19 +0000 http://www.hindawi.com/journals/je/2013/928078/ A dual-band microstrip patch antenna is designed and analyzed using metamaterial artificial substrate. Metamaterial based substrate is designed using Square Split Ring Resonator (SSRR) and Wire Strip. The antenna is tuned to work at two resonating frequencies in the frequency range from 1 GHz to 4 GHz depending on the geometric specifications of SSRR, strip line, radiating patch, and feed location point. Proposed antenna provides good return loss behavior at both resonating frequencies. The obtained VSWR at both resonating frequencies is very much near to 1. Proposed antenna covers applications in mobile communication and Wi-MAX. Proposed patch antenna is compared with the conventional patch antenna, which shows the significant miniaturization as compared to conventional patch antenna. Indrasen Singh, Vijay Shanker Tripathi, and Sudarshan Tiwari Copyright © 2013 Indrasen Singh et al. All rights reserved. Mon, 15 Apr 2013 15:03:51 +0000 http://www.hindawi.com/journals/je/2013/375628/ This paper considers four types of the most prominent risks in the supply chain. Their subcriteria and relations between them and within the network are also considered. In a supply chain, risks are mostly created by fluctuations. The aim of this study is to adopt a strategy for eliminating or reducing risks in a supply chain network. Having various solutions helps the supply chain to be resilient. Therefore, five alternatives are considered, namely, total quality management (TQM), leanness, alignment, adaptability, and agility. This paper develops a new network of supply chain risks by considering the interactions between risks. Perhaps, the network elements have interacted with some or all of the factors (clusters) or subfactors. We constitute supply chain risks in the analytic network process (ANP), which attracted less attention in the previous studies. Most of the studies about making a decision in supply chains have been applied in analytic hierarchy process (AHP) network. The present study considers the ANP as a well-known multicriteria decision making (MCDM) technique to choose the best alternative, because of the interdependency and feedbacks of different levels of the network. Finally, the ANP selects TQM as the best alternative among the considered ones. L. Hosseini, R. Tavakkoli-Moghaddam, B. Vahdani, S. M. Mousavi, and R. Kia Copyright © 2013 L. Hosseini et al. All rights reserved. Sun, 14 Apr 2013 13:34:12 +0000 http://www.hindawi.com/journals/je/2013/937614/ The future electricity network must be flexible, accessible, reliable, and economic according to the worldwide smartgrid initiative. This is also echoed by the Sustainable Energy Authority of Ireland (SEAI) and European Electricity Grid Initiative (EEGI). In order to facilitate these objectives and to reduce green house gas (GHG) emission, research on various configurations of microgrid (μG) system is gaining importance, particularly with high penetration of renewable energy sources. Depending on the resource availability, geographical locations, load demand, and existing electrical transmission and distribution system, μG can be either connected to the grid or can work in an autonomous mode. Storage can also be a part of the μG architecture. This paper presents a critical literature review of various μG architectures. The benefits of grid-connected or isolated μG with storage have also been identified. Lubna Mariam, Malabika Basu, and Michael F. Conlon Copyright © 2013 Lubna Mariam et al. All rights reserved. Tue, 09 Apr 2013 11:44:39 +0000 http://www.hindawi.com/journals/je/2013/197295/ This paper introduces a traffic load and interference based bandwidth allocation (TLIBA) scheme for wireless mesh network (WMN) that improves the delay and throughput performance by proper utilization of assigned bandwidth. The bandwidth is allocated based jointly on traffic load and interference. Then a suitable path is selected based upon the least routing metric (RM) value. Simulation results are presented to demonstrate the effectiveness of the proposed approach which indicates higher bandwidth utilization and throughput as compared with existing fair end-to-end bandwidth allocation (FEBA). Sanjeev Jain, Vijay Shanker Tripathi, and Sudarshan Tiwari Copyright © 2013 Sanjeev Jain et al. All rights reserved. Tue, 09 Apr 2013 10:48:51 +0000 http://www.hindawi.com/journals/je/2013/795237/ A numerical modeling of a 2D Navier-Stokes equation by a particular vertex centered control volume framework on an unstructured grid is presented in this paper. Triangular elements are applied with an effective high performance fully coupled algorithm, to simulate incompressible laminar flow over a circular cylinder. The cell face velocities in the discretization of the continuity and momentum equations are calculated by a combined linear and momentum interpolation scheme, respectively, and their performances are compared. Flow analyses have been conducted based on various Reynolds numbers up to 200 for the steady and unsteady flows using structured and unstructured grids. The robustness and accuracy of the scheme in the unstructured mesh are proved using the benchmark problems of incompressible laminar flow over a circular cylinder at low and medium Reynolds numbers. Results have been compared with the structured grid results, both cases with equal cell numbers and same strategy for the mesh refinement. Current results display good agreement with the experimental values. Overall, it is shown that, using the suggested method for the current problem, unstructured grids are highly competitive with the structured grids. Mahdi Yousefifard, Parviz Ghadimi, and Rahim Zamanian Copyright © 2013 Mahdi Yousefifard et al. All rights reserved. Tue, 09 Apr 2013 10:19:20 +0000 http://www.hindawi.com/journals/je/2013/845051/ Approximately 40% of global CO2 emissions are emitted from electricity generation through the combustion of fossil fuels to generate heat needed to power steam turbines. Burning these fuels results in the production of carbon dioxide (CO2)—the primary heat-trapping, “greenhouse gas” responsible for global warming. Applying smart electric grid technologies can potentially reduce CO2 emissions. Electric grid comprises three major sectors: generation, transmission and distribution grid, and consumption. Smart generation includes the use of renewable energy sources (wind, solar, or hydropower). Smart transmission and distribution relies on optimizing the existing assets of overhead transmission lines, underground cables, transformers, and substations such that minimum generating capacities are required in the future. Smart consumption will depend on the use of more efficient equipment like energy-saving lighting lamps, enabling smart homes and hybrid plug-in electric vehicles technologies. A special interest is given to the Egyptian case study. Main opportunities for Egypt include generating electricity from wind and solar energy sources and its geographical location that makes it a perfect center for interconnecting electrical systems from the Nile basin, North Africa, Gulf, and Europe. Challenges include shortage of investments, absence of political will, aging of transmission and distribution infrastructure, and lack of consumer awareness for power utilization. Lamiaa Abdallah and Tarek El-Shennawy Copyright © 2013 Lamiaa Abdallah and Tarek El-Shennawy. All rights reserved. Tue, 09 Apr 2013 08:26:46 +0000 http://www.hindawi.com/journals/je/2013/326496/ The objective of this research is to propose a new reduced-order modeling method. This approach is based on fluid eigenmodes and body vortices without using static correction. The vortex lattice method (VLM) is used to analyze unsteady flows over two-dimensional airfoil and three-dimensional wing. Eigenanalysis and reduced-order modeling are performed using a conventional method with static correction and an unconventional one without the static correction. Numerical examples are proposed to demonstrate the performance of the present method. The results show that the new method can be considered an alternative way to perform the reduced-order models of unsteady flow. Suwin Sleesongsom and Sujin Bureerat Copyright © 2013 Suwin Sleesongsom and Sujin Bureerat. All rights reserved. Thu, 04 Apr 2013 17:18:01 +0000 http://www.hindawi.com/journals/je/2013/972019/ The effect of the glazed layer and firing conditions (temperature and duration) on the thermal shocks behavior of tableware porcelains has been studied. Two types of glazed layers and three firing conditions, used industrially in the commercial porcelains manufacture, are used in this investigation. Repeated thermal shock tests showed that the glazed layer with higher alumina/silica ratio is more resistant to thermal shocks and that the slow firing cycle, even at a relatively low temperature, is very beneficial for the thermal shock resistance of the porcelain matrix. Three-point bending tests showed that the crazing phenomenon, which affects the glazed layers as well as the porcelain matrix, does not affect significantly the mechanical resistance of these materials. Habib Sahlaoui, Kamel Makhlouf, and Habib Sidhom Copyright © 2013 Habib Sahlaoui et al. All rights reserved. Thu, 04 Apr 2013 10:29:49 +0000 http://www.hindawi.com/journals/je/2013/970487/ Scheduling is often a difficult task specially in complex systems. Few tools are targeted at both modeling and scheduling of the systems. In controller synthesis, a scheduler is seen as a controller to manage shared resources and timing requirements of a system. This paper proposes a time Petri net-based approach for controller synthesis and finding a scheduler using stopwatch. The solution suggested here is particularly interesting for preemptive scheduling purposes. This paper deals with time Petri nets with controllable and uncontrollable transitions and assumes that a controllable transition can be suspended and retrieved when necessary. In fact, the paper supposes that every controllable transition can be associated with stopwatch. With this hypothesis, the objective is to model a system by time Petri nets and calculate subintervals where the system violates the given property. Then, the controller associates the corresponding controllable transitions with stopwatch to suspend them in their bad subintervals. The interesting advantage of this solution is that this approach synthesizes an ordinary time Petri net model before adding stopwatch. Therefore, complicated computations and overapproximations required during controller synthesis of time Petri nets associated with stopwatch are avoided. Parisa Heidari and Hanifa Boucheneb Copyright © 2013 Parisa Heidari and Hanifa Boucheneb. All rights reserved. Sun, 31 Mar 2013 15:21:23 +0000 http://www.hindawi.com/journals/je/2013/982354/ Cuckoo optimization algorithm (COA) is one of the latest evolutionary algorithms. Finding the best optimal point, rapid convergence, and simplicity in determining algorithm parameters are some merits of COA. In this paper, COA is applied to tuning optimal fuzzy parameters for Sugeno-type fuzzy logic controllers (S-FLCs) which are used for liquid level control. A programmable logic controller (PLC) is used with fuzzy controller. For this purpose, a liquid level control set and PLC have been assembled together. MATLAB/Simulink program has been used to achieve the optimal parameters of the membership functions. The results show clearly that the optimized FLC using COA has better performance compared to manually adjustments of the system parameters for different datasets. Saeed Balochian and Eshagh Ebrahimi Copyright © 2013 Saeed Balochian and Eshagh Ebrahimi. All rights reserved. Sun, 31 Mar 2013 12:52:56 +0000 http://www.hindawi.com/journals/je/2013/192176/ With advancement in the field of structural engineering, hunt for smarter materials has channelised the research towards the application of composite material. It is the high specific weight and specific stiffness of this material that have drawn the interest of different industrial sectors. Civil engineers also picked up composites to use it as a roofing material. Laminated composite shells, which can cover large column-free area and reduces dead weight of structure, show vulnerability under sudden impact due to their low transverse shear resistances. This study utilises finite element tool to investigate the dynamic response of a multilayered laminated composite hypar shells for fully clamped boundary condition. This class of shells is unique in a sense that the curvature has only the radius of cross curvature and these shells do not admit easy closed form solution particularly when the boundary conditions are complicated. Contact behavior of impactor and impacted mass has been modeled by modified Hertzian contact law and time-dependent equations are solved using Newmark’s time integration technique. Basic aim is to analyse the shell for symmetrically placed multilayered angle and cross ply lamination under different impact velocities. Sanjoy Das Neogi, Amit Karmakar, and Dipankar Chakravorty Copyright © 2013 Sanjoy Das Neogi et al. All rights reserved. Sun, 31 Mar 2013 12:21:07 +0000 http://www.hindawi.com/journals/je/2013/936495/ We propose and analyze a noncoherent receiver with PN code tracking for direct sequence code division multiple access (DS-CDMA) communication systems. We employ the delay-lock loop (DLL) architectures for the tracking stage. The choice of DLL parameters is studied with special focus on DS-CDMA communication systems and orthogonality conditions. We described the modeling and simulation of the NCO using hardware description language VHDL. Details of the VHDL implementation are shown. Aicha Alami Hassani, Mohcine Zouak, and Mostafa Mrabti Copyright © 2013 Aicha Alami Hassani et al. All rights reserved.