International Journal of Engineering
Volume:29 Issue: 5, May 2016

Fluid-structure interaction (FSI) occurs when the dynamic water hammer forces cause vibrations in the pipe wall. FSI in pipe systems due to Poisson and junction coupling has been the center of attention in recent years. It causes fluctuations in pressure heads and vibrations in the pipe wall. The governing equations of this phenomenon include a system of first order hyperbolic partial differential equations (PDEs) in terms of hydraulic and structural quantities. In the present paper, a two-step variant of the Lax-Friedrichs (LxF) method, and a method based on the Nessyahu-Tadmor (NT) are used to simulate FSI in a reservoir-pipe-valve system. The computational results are compared with those of the Method of Characteristics (MOC), Godunov's scheme and also the exact solution of linear hyperbolic fourequation system to verify the proposed numerical solution. The results reveal that the proposed LxF and NT schemes can predict discontinuity in fluid pressure with an acceptable order of accuracy. The independency of time and space steps allows for setting different spatial grid sizes with a unique time step, thus increasing the accuracy with respect to the conventional MOC. In these schemes, no Riemann problems were solved and hence field-by-field decompositions were avoided which led to reduced run times compared with Godunov scheme.

The granite stone is the most widely used in the construction and granite slurry is generated through cutting and polishing of the stone. Granite slurry is waste material consisting of very fine powder and creats disposal and environmental problems in worldwide today. Disposal of granite waste leads to health hazards like respiratory and allergy problems to the people around. It also causes the pollution of air and water. Concrete is the most widely used construction material and innovation in ingredient material (cement and coarse aggregate) is urgently needed. The replacement of natural resources in the production of cement is an important issue in the present construction scenario. Also, the cement industry is one of the principal producers of carbon dioxides. Utilization of granite slurry waste in concrete can solve many problems related to waste generation, reduction in the consumption of natural resources and CO2 emission. Systematic experimental study has been carried out using granite slurry waste in place of cement at various replacement levels. This study has been carried out for w/c 0.5 and 0.4. Specimens have been cast to perform compressive strength test and flexural strength test. It has been shown that inclusion of granite slurry modifies the compressive strength and maximum strength has been obtained depending upon replacement level and w/c ratio. Flexural strength is also influenced by the addition of granite slurry waste in a similar way. These replacement studies demonstrate that the granite slurry concrete will be economically cheaper and more sustainable.

Because of difficulty in inspection and retrofit of foundation in comparison with other elements, the common design philosophy is to avoid any nonlinear deformation in the foundation. This paper shows that by employing controlled foundation nonlinearity, in predetermined sections with arrangements for inspection and retrofit, it is possible to reduce seismic demand on superstructure. Localizing nonlinear deformation to pre-specified zones in the foundation, it is possible to avoid wide spread nonlinear deformation across various members in the superstructure in the case of strong ground motions. To evaluate the efficiency of the proposed model, the response of steel braced frames is examined on rigid foundation, rocking elastic foundation and finally on rocking foundation with controlled nonlinear deformation. Results show that while rocking could be used to protect the superstructure elements from possible overloading during large earthquakes for low-rise structures; it has no remarkable effect on the response of high-rise structures. However, the proposed model with nonlinearity in the foundation could be used in both cases (low-rise and high-rise structures) to effectively control the response of structure.

Sampling rate conversion (SRC) is one of important issues in modern sampling theory. It can be realized by up-sampling, filtering, and down-sampling operations, which need large complexity. Although some efficient algorithms have been presented to do the sampling rate conversion, they all need to compute the N-point original signal to obtain the up-sampling or the down-sampling signal in the time domain. Most of the published papers about the sampling rate conversion require the signal to be band limited in the Fourier transform domain, and there are few paper published related to the SRC in the linear canonical transform (LCT) domain. This paper investigates how to perform the SRC in the discrete linear canonical transform (DLCT) domain for integer and fractional rate conversion. The simulations are performed to verify the correctness of the proposed results.

Single-source binary hybrid multilevel inverters with cascaded transformers have a bulky transformer connected to their main H-bridge cells in each phase. This bulky transformer has been eliminated in this work without any effect on operation and modulation strategies. The proposed topology has significant advantages from view point of dimensions and number of transformers, design of transformers, modeling and application aspects. Modulation strategy of the proposed inverter is the conventional binary hybrid modulation. Simulation and experimental results demonstrate suitable performance of the proposed topology.

This paper proposes a new sub-threshold low power 9T static random-access memory (SRAM) cell compatible with bit interleaving structure in which the effective sizing adjustment of access transistors in write mode is provided by isolating writing and reading paths. In the proposed cell, we consider a weak inverter to make better write mode operation. Moreover applying boosted word line feature decreases write mode failure. An access buffer seperates storage node from read access transistor to improve cell stability and prevent data-related leakage in read operation. Applying virtual ground also reduces the leakage. Furthermore, we design the cell control unit. The simulation results at VDD=0.5V exhibit the effectiveness of our proposed cell compared with other counterparts which are suitable for bit interleaving structure. Comparison results on the proposed cell and 6T cell show our cell improved 70% in write power consumption and 90.45% in read power consumption.

Vendor managed inventory (VMI) is an integrated approach for buyer–vendor coordination, according to which the vendor (supplier or manufacturer) decides on the appropriate buyer’s (retailer’s) inventory levels. The time value of money has not traditionally been considered in evaluating VMI supply chain’s total inventory cost in any studies up to now. Therefore, in the present study a new model for two-echelon single-manufacturer multi-retailer supply chain under non-consignment VMI program by considering time value of money is proposed. In order to take the time value of money into consideration, the present value of each inventory cost is evaluated in a single period and generalized to infinity horizon and then is transformed to the equivalent annual cost. This model also explicitly includes contractual agreements between the manufacturer and each retailer. Under this type of contracts, an upper bound on each retailer’s inventory level is placed such that the manufacturer is penalized for items exceeding this bound. At the end, a sensitivity analysis is conducted to study effects of key parameters on the optimal solution and validate the proposed model.

This paper presents a new robust two-stage Data Envelopment Analysis (DEA) for efficiency evaluation of the electricity power production and distribution companies. DEA has been widely used for benchmarking the electricity companies. Traditional studies in DEA consider systems as a whole when measuring the efficiency, ignoring the operation of individual processes within a system. To tackle this issue, many works, aptly labeled Network DEA (NDEA), have been done to decompose the decision making units (DMU) overall efficiency. The two-stage DEA model is a special variation which evaluates the efficiency of the DMUs having a two-stage internal structure. In two-stage DEA model initial inputs are used to make intermediate outputs and in the next Sub-process, intermediate outputs are transformed to the final output. Conventional two stage data envelopment analysis (DEA) models require the exact data of inputs or outputs. However, in many real world applications this simple assumption does not hold. Robust optimization technique has been introduced for entering perturbation in the mathematical programming problem such as two-stage DEA. This paper adopts this concept with the existing two-stage DEA model. The implementation of the proposed method of this paper is applied for ranking different electricity power production and distribution companies in Iran.

This paper investigates the network location problem for single-server facilities that are subjected to congestion. On each network edge, customers are uniformly distributed, and their requests for service are assumed to be generated according to a Poisson process. A number of facilities are to be selected from a number of candidate sites, and a single server is located at each facility with exponentially distributed service times. Using queueing analysis, we develop a mixed integer mathematical model to minimize the total travel and the average waiting times for customers. For evaluation of the validity of the proposed model, a numerical example is solved and analyzed using GAMS software. In addition, since the proposed problem is NP-hard, two metaheuristic algorithms including a genetic algorithm and a simulated annealing algorithm are developed and applied for large-size problems.

Ag-TiO2 nanocomposite with the optimum concentration of 1wt% was produced by a sol-gel process using Rhodamine B for the catalytic activity. The initial samples were prepared by heat treatment at various temperatures (266, 338, 390, 485, 600 and 700°C) with a holding time of 2 h. DTA and XRD of these samples led to choosing the temperature of 530°C as the heat treatment temperature. Then some samples were heat treated at this temperature for various times (0.5, 1, 2, 4, and 6 h). The samples heat treated for 2 h at 266 and 338°C exhibited better degradation efficiency. The 530°C-1 hr sample exhibited the best degradation performance even in comparison with the commercial nano TiO2 purchased from Degussa. To the best of our knowledge, we report (for the first time) the formation of Ag2Ti4O9 phase at ambient temperature. This silver titanate phase gives rise to a better degradation efficiency compared to anatase. Characterization of Ag-TiO2 samples was done by DTA, XRD, PL and SEM.

The effect of weld heat input on the formation of intermetallic compound (IMCs) layer during arc welding–brazing of aluminium and steel dissimilar alloys was investigated through both finite element method (FEM) numerical simulations and experimental measurements. The results of FEM analysis as well as welding experiments indicated that increasing weld heat input increases the thickness of IMCs layer. The thickness of IMCs layers, as calculated from FEM simulations, was approximately equal to that measured from microstructural images in the range of 2-6 μm. The tensile strength of arc welding– brazing joints was dependent on the thickness of IMCs layer and spreading of molten weld metal on the surfaces of steel sheet. The highest mechanical strength of 120 MPa was obtained in the optimized heat input of 420 J/mm. The presence of the Si element in the Al-5Si filler metal led to IMCs layer with the composition of Fe(Al,Si)3 phase in side of the steel and Al7.2Fe1.6Si phase in side of the weld seam.

In this paper, we reviewed researches about the titanium nitride (TiN) and titanium carbide (TiC) single and multilayer coatings. These coatings were deposited by the plasma assisted chemical vapor deposition (PACVD) technique. Plasma-based technologies are used for the processing of thin films and coatings for different applications such as automobile and aerospace parts, computer disc drives, food industry and surgical/medical instruments. We describe the state of the performance of different coating systems and thin film architectures in PACVD suitable for industrial-scale or laboratory applications. Mechanical properties of coatings such as wear resistance, hardness and the scratch resistance, structural characteristics, physical and chemical properties like coatings adhesion into different substrates, wetting behavior and corrosion resistance were studied. Thus, this paper represents a source of information for those who want to familiarize with the status of knowledge in the area of materials science of functional coatings, in particular TiN/TiC coatings that was deposited by a new Plasma-based technologies.

In this article, small scale effects on free vibration analysis of non-uniform nanobeams is discussed. Small scale effects are modelled after Eringen’s nonlocal elasticity theory while the non-uniformity is presented by exponentially varying width among the beams length with constant thickness. Analytical solution is achieved for free vibration with different boundary conditions. It is shown that section variation accompanying small scale effects has a noticeable effect on natural frequencies of nonuniform beams at nano scale. First, five natural frequencies of single-layered graphene nanoribbons (GNRs) with various boundary conditions are obtained for different nonlocal and nonuniform parameters which shows a great sensitivity to non-uniformity in different shape modes.

The following article investigates nonlinear symmetric buckling of moderately thick circular Nano plates with an orthotropic property under uniform radial compressive in-plane mechanical load. Taking into account Eringen nonlocal elasticity theory, principle of virtual work, first order shear deformation plate theory (FSDT) and nonlinear Von-Karman strains, the governing equations are obtained based on displacements. The differential quadrature method (DQM) as a numerical procedure is applied for solving the equations. In this analysis, for solving the stability equations, adjacent equilibrium methodis employed. In nonlinear buckling analyses and for obtaining the buckling load, generally the available nonlinear terms of the stability equation are neglected. However, in this study, for getting the most accurate data, nonlinear terms are considered and the non-dimensional buckling load is compared with the condition of considering or neglecting that of terms and the effect of that of terms are also studied. The accuracy of the present results is validated by comparing the solutions with available studies. The effects of nonlocal parameter, thickness, radiusand elastic foundation are investigated on non-dimensional buckling loads. The results of analyses based on local and non-local theories are compared. From the results, it can be seen that the effect of nonlocal parameter on simply support condition is less than clamped condition. It can be observed that with increasing the radius of the plate, the difference between local and non-local analyses,increases.

The alternating current electroosmotic flow of a non-Newtonian power-law fluid is studied in a circular microchannel. A numerical method is employed to solve the non-linear Poisson-Boltzmann and the momentum equations. The main parameters which affect the flow field are the flow behavior index, the dimensionless zeta potential and the dimensionless frequency. At very low dimensionless frequencies (slow oscillatory motion, small channel size, or large effective viscosity), the plug-like velocity profiles similar to steady-state electroosmotic flow are observed at nearly all times. At very high dimensionless frequencies, the flow is shown to be restricted to a thin region near the channel wall, while the bulk fluid remains essentially stationary. Velocity distributions of pseudoplastics and dilatants may be widened at low values of the dimensionless frequency depending on the dimensionless zeta potential; at high dimensionless frequencies, however, both fluids represent enhanced velocity magnitudes with the dimensionless zeta potential. In the case of high shear rate and/or suddenly-started flows, pseudoplastics tend to produce higher velocities than dilatants. These two kinds of fluids may produce same velocity profiles relying on the value of the dimensionless zeta potential as well as the ratio of their flow behavior indexes.

Nowadays, piezoelectric materials have wide applications in various industries. Therefore, investigation of these materials and their applications has a special importance. In this paper first, the natural frequencies of a traveling-wave piezoelectric motor are achieved, using finite elements simulations. Then, applying an alternative electrical voltage to the piezoelectric ring, a traveling wave is generated in the stator, and the stability, damping effects, and characteristics of the traveling wave are studied. Additionally, the output torque and rotational speed of the motor are obtained and validated by experimental values. Finally, the stator diameter is increased and its effects on the output torque and rotational speed are inspected. The results reveal that the output torque and maximum rotational speed of the enlarged motor respectively increases and decreases.

In this paper, the effect of the cell-temperature on the performance of photovoltaic (PV) module is evaluated. The evaluation is based on a mathematical module (single diode equivalent circuit) and practically based on solar module tester (SMT). Solara®130W PV crystalline silicon module was used in this simulation. The SMT is able to supply a constant irradiance level (1000W/m2) or any other desired value during the test (100 -1200W/m2). The evaluation results showed that the output power of PV reduces by about 0.48W as the temperature of the module surface increases by one degree Celsius.