International Journal of Engineering
Volume:27 Issue: 4, Apr 2014

Nowadays, faults and failures are increasing especially in complex systems such as Network-on-Chip (NoC) based Systems-on-a-Chip (SoC) due to the increasing susceptibility and decreasing feature sizes. On the other hand, fault-tolerant routing algorithms have an evident effect on tolerating permanent faults and improving the reliability of a NoC based system. This paper presents reliability and performance evaluation of two main kinds of fault-aware routing algorithms, deterministic and adaptive, used in NoC architectures. The investigated methods have a multi-level structure for faulttolerance and therefore, each level can be separately evaluated. To demonstrate the effectiveness of these methods, we propose an analytical approach for reliability assessment based on combinatorial reliability models to show the effect of fault-aware routing algorithms on overall NoC reliability. However, for performance evaluation, we conduct extensive simulations on different applications.

In this paper a new architecture for delay locked loops is proposed. Static phase offset and reset path delay are the most important problems in phase-frequency detectors (PFD). The proposed structure decreases the jitter resulted from PFD by switching two PFDs. In this new architecture, a conventional PFD is used before locking of DLL to decrease the amount of phase difference between input and output of the DLL. Near locking, an XOR gate is used to act as a PFD which makes the DLL locks with less jitter. Also, the reset path time and glitch are decreased by using the XOR gate. The proposed architecture has been designed in TSMC 0.18um CMOS Technology. The simulation results support the theoretical design aspects.

In this paper, a numerical method for solving the constrained optimal control of time varying singular systems with quadratic performance index is presented. Presented method is based on Bernstein polynomials. Operational matrices of integration, differentiation and product are introduced and utilized to reduce the solution of optimal control problems with time-varying singular systems to the solution of algebraic equations set. The strength of the method is shown by exhibiting a numerical implementation using operational matrices that solves the determined control problem by solving an equation set. The method converges rapidly to the exact solution and gives very accurate results even by low value of. Illustrative examples are included to demonstrate the validity and efficiency of the technique and convergence of method to the exact solution especially for unstable singular systems.

Cross-docking plays an importation role in distribution networks. In the recent years, a cross-docking design network problem is addressed as a new research area in logistics management. This paper presents a new mathematical model for the location of cross-docking facilities and vehicle routing scheduling problems in the distribution networks. For this purpose, a two-phase mixed integer programming (MIP) is formulated. Then, a new heuristic-based simulated annealing (SA) is developed for solving the proposed MIP model. Finally, the presented heuristic algorithm is subsequently tested on a number of small and large-scale instances. The computational results for different sized instances illustrate that the proposed algorithm performs effectively in a reasonable time.

One of the primary concerns in any system design problem is to prepare a highly reliable system with minimum cost. One way to increase the reliability of systems is to use redundancy in different forms such as active or standby. In this paper, a new nonlinear multi- objective integer programming model with the choice of redundancy strategy and component type is developed where standby strategy is of cold type. In the proposed model, system’s reliability is maximized along with minimizing system’s cost and weight. The proposed model contributes to the literature by determining the redundancy strategies concurrently with determining redundancy levels and component types. The multi-objective model is solved using the mathematical compromise programming technique for different Lp metrics and produces different Pareto solutions.

Reliability is the most important performance issue in engineering design process but in the real world problems, there are limitations for using conventional reliability. Fuzzy logic has proved to be effective in expressing uncertainties in different fields, including engineering reliability. In this paper, for both series and parallel systems composed of three identical or different elements, the reliability has been analyzed using the fuzzy concepts and some characteristics such as the mean time to failure have been evaluated, taking in our account that all the operating units have increasable time varying failure rates with fuzzy triangular membership functions. This paper includes a numerical example to illustrate the model and validate the analytical results.

This paper investigates a single-stage and two-stage production systems where specification limits are designed for inspection. When quality characteristics fall below a lower specification limit (LSL) or above an upper specification limit (USL), a decision is made to scrap or rework the item. The purpose is to determine the optimum mean for a process based on rework or scrap costs. In contrast to previous studies, costs are not assumed to be constant. In addition, this paper provides a Markovian model for multivariate Normal process. Numerical examples are performed to illustrate the application of the proposed method.

The hierarchical hub covering facility location problems are applied to distribution systems, transportation, waste disposal, treatment services, emergency services and remote communication. The problems attempt to determine the location of service providers'' facilities at different levels and specify their linking directions in order to reduce costs and to establish an appropriate condition in distribution network. By utilizing these problems, the present paper attempts to allocate «capacitated» option to each provider service and consequently establish and choose the best possible condition, so that demands centers are rationally and effectively guided by service providers'' centers and their request never remains without response. To do this, the model «the capacitated single allocation hierarchical hub median location problem» is developed, created and provided. In addition, considering of the increasing demand, modulating choices are addressed in order to fulfill the future needs and to impose uncertainty in decision making in the results. To validate the model, we used IAD data, which the results confirm its consistency.

This paper develops a robust optimization approach for a dynamic cellular manufacturing system (DCMS) integrated with production planning under uncertainty of parts processing time. To deal with this uncertainty, a robust optimization as a tractable approach is adopted. The model includes cell formation, inter-cell layout and production planning concepts under a dynamic environment. The aim of the model is to minimize inter and intra-cell material handling, inventory holding, back order and reconfiguration costs. To verify the behavior of the presented model and the performance of the developed approach, a numerical example solved in finding an optimal solution.

In this paper, the authors have focused on the stochastic analysis of an internet data center (IDC), which consists of a database main server connected to a redundant server. Observing the different possibilities of functioning of the system, analysis has been done to evaluate the various reliability characteristics of the system. The system can completely fail due to failure of redundant server before repair of database server, router failure and switch failure. The system can also fail completely due to a cooling failure or some natural calamity like earthquake, fire; etc. All the failure rates are assumed constant while the repairs follow two types of distributions namely general and Gumbel Hougaard family copula.

This article discusses detailed study on crystallization، optical properties of Li-Al-Si-La glass containing nanocrystalline LaF3. and their optical energy gaps. The Urbach energy of glass samples was evaluated. By using (2% mole) Tb the green–blue range emission occurred، while by accumulation 1% mole Gd beside Tb، the indigo emission intensity (418 to 441 nm) increased.

Al2O3-ZrO2composite has unique properties such as high toughness, high wear resistant and relative low thermal expansion. In this study, nanocomposite of Al2O3-ZrO2 was produced by Mechanical activated Self propagating High-temperature Synthesis (MASHS) using laser beam for ignition. Al and ZrO2 powders were mixed in the mole ratio of 1:1 and milled for 1, 3 and 6 hours. The mixtures were pressed and were exposed by continuous wave (CW) CO2 laser for combustion reaction to start. In order to characterize the products, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Energy-Dispersive X-ray spectroscopy (EDX) were implemented. The XRD results show that samples have α-Alumina and also cubic and monoclinic phases Zirconium oxides together. The dendrite structures were formed during the process.

Nitriding treatments of low alloyed steels can be performed only at relatively low temperatures in order to avoid a decrease in corrosion resistance due to nitride layers formation. These conditions promote the formation of compound layer and diffusion zone, which shows high hardness and good corrosion resistance. In the present paper, the influence of the gas mixture N2-H2 in plasma nitriding process on the microstructural and mechanical characteristics of 32CDV13 steel samples was evaluated. This nuance is used in manufacturing mechanical partsthat are greatly solicited in fatigue as the transmission gearings on the helicopters’ rotors and the rolling used in aeronautics. Plasma nitriding treatments were performed at temperatures in the range 773K for 4h. The modified surface layer of the nitrided samples consists mainly of the γ’ and ε phases, according to metallographic technique analysis, it seems to be essentially a modification of the austenite matrix. High hardness values are observed in the modified layer with a steep decrease to matrix values.

The morphological and microstructural changes during mechanical milling of Al powder mixed with 2.5, 5 and 10 wt.% Al2O3 particles were studied. The milling was performed in a planetary ball mill for various times up to 20h. The produced composite powders were investigated using X-ray diffraction pattern (XRD) to elucidate the role of particle size, secondary phase content and milling time on grain size and lattice strain of Al matrix. The aluminum crystallite size estimated with broadening of XRD peaks by Williamson–Hall formula. The morphological changes were studied by SEM technique. The results show that the addition of hard Al2O3 particles accelerates the milling process, leading to faster work hardening rate and fracture of the aluminum matrix. Furthermore, Al becomes smaller crystallite size during ball milling of Al powder in the presence of Al2O3 particles. The results revealed that the grain size of milled powders was about 45nm with a noticeable presence of agglomerates. Uniform distribution of nano-sized Al2O3 particles in the Al matrix could be achieved with increasing milling time.

This paper aims to investigate the pull-in phenomenon of functionally graded (FG) capacitive nanocantilevers subjected to an electrostatic force and thermal moment due to an applied voltage and thermal shock considering the intermolecular force within the framework of nonlocal elasticity theory to account for the small scale effect. The FG nano-beam is made of mixture of metal and ceramic which the material properties vary continuously through the thickness according to an exponential distribution law (E-FGM). The nonlocal elastic behavior is described by the differential constitutive model of Eringen which enables the present model to become effective in the analysis and design of nano-sensors. The nano-beam is modeled assuming the Euler–Bernoulli beam theory and the equations are derived using the equilibrium of an element. A Galerkin-based step by step linearization method has been used to solve the governing static deflection equation. The present solution is validated with existing results reported in previous studies. The effects of temperature change, Van der Waals (VdW) or Casimir force and small scale factor on the five types of FG nano-beams are discussed in detail. The results indicate that VdW/Casimir force and thermal moment reduce the pull-in voltage; however, on the contrary, small scale effect causes to slightly increase the amount of pull-in voltage.

Reciprocating diaphragm micro-pumps are the most common type among indirectly driven micropumps. This paper addresses the hydroelastic vibration of a circular elastic diaphragm interacting with the incompressible and inviscid liquid inside the cylindrical chamber with a central discharge opening. Taking into account axisymmetric vibration of the diaphragm, the fluid pressure exerted upon the plate is formulated using linear Bernoulli’s equation. The kinematic and compatibility conditions are incorporated into the elastic vibration of the circular plate to derive the governing eigen matrix equation. Numerical results are presented for different materials for diaphragm (silicon and glass) and pumped liquid (water and methanol). Normal frequencies of the coupled system, wet mode shapes of diaphragm and fluid oscillation modes are presented in numerical simulations. It is seen that the hydroelastic interaction lowers the natural frequencies considerably. However, the wet mode shapes for diaphragm vibration are very similar to the dry mode shapes. Finally, the effects of chamber height and operating fluid density on the normal frequencies are illustrated for the lowest four modes.

Continuous counter-current extraction of rhenium from roasting dust leach liquor was carried out using a mixer-settler extractor. Tributylphosphate was used as the extractant diluted in kerosene. The effects of the flow rates and extraction stages were investigated. The extraction efficiency was affected by the flow rates of the aqueous and organic phases, and its mechanism was qualitatively discussed on the basis of the stoichiometric relations of the extraction. Rhenium extraction mass balance and simulation in the mixer-settler was also studied. A high rhenium extraction percentage (95.43%) in the phase ratio 1:1 was achieved using a counter-current four-stage extraction process. The continuous counter-current extraction technique was used in this research work showed to be effective for rhenium extraction from the leach solutions of the dust of the molybdenite roasting furnaces.

This paper analyzed the characteristics of managed pressure drilling (MPD) technology and impact of wellhead back pressure on the wellbore annulus pressure profile, and found that the application of this technology provides situation for improvement in the current casing program design. Meanwhile, the equivalent density of drilling fluid in wellbore annulus needs to consider the impact of back pressure. On this basis, casing program design for top-down design approach and multi-pressure system formation in MPD are established. Comparing and analyzing the results of casing program design in MPD and conventional drilling, it can be concluded that for the top-down design method, each layer of casing can reach to a deeper depth. It can also reduce the casing level for the multi pressure system formation using wellhead back pressure to make the wellbore annulus pressure profiles bend. Thus, it can cleverly pass through the complex formation which needs multi-layer intermediate casings in conventional drilling. In this condition, the well structure can be simplified.