International Journal of Engineering
Volume:27 Issue: 12, Dec 2014

Graphene oxide (GO) was synthesized by oxidation of graphite powder using a time-saving modification of Hummers’ method and its antibacterial activity was investigated. Different techniques were applied to characterize the synthesized GO. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to investigate the crystallinity, morphology, topography and thickness profile of the synthesized graphene oxide, respectively. Fourier-transform infrared spectroscopy (FT-IR) was carried out to investigate the chemical structure and purity of the synthesized sample. Optical properties were investigated by UV-Vis spectroscopy. The antibacterial activity of GO against Escherichia coli (E. coli) was evaluated by the Colony Forming Count (CFU) method. The Results confirmed that the sample had excellent antibacterial activity against Escherichia coli.

Producing crude palm oil (CPO) will have side effect on producing palm oil mill effluent (POME). Besides of high COD /BOD contents, POME still contains high amount of nutrients (nitrogen, phosphor and mineral). Traditional treatment of palm oil mill effluent using facultative anaerobic method not fully eliminated COD and BOD into allowable limit. The objective of this research was to utilize phytoremediation technology to reduce COD, and nutrients of POME at various retention times and activated sludge concentration. The residence time was varied at 1-5 days and activated sludge at 35-60%. The result showed that water lettuce as aquatic plant in the first remediation process could reduce COD content up to 39.1% -59.66%, absorb nitrogen content up to 17.73% -30.78%, and absorb the phosphorus content up to 6.14% -18.46%. At the second remediation, the remediated POME was fed to Spirulina and the nutrients were consumed by 90%.

In this study, operation of compressor station has been investigated by exergy approach. Exergy analysis is a thermodynamic method which shows the irreversibility of a system quantitatively. Gas compressors are used to compensate the pressure drop along the gas pipeline significantly. The compression process causes temperature rise of gas; in this regard gas cooler is applied to reduce the temperature. The compressors are run at variable speed; fuel consumed in combustion chamber is changed accordingly. The estimation of operating parameters needed the performance curve of compressor and that of turbine which are unique for each turbo-compressor. The case study is focused on transmission of sour gas through IGAT5 pipeline, located in south of Iran. The effect of H2S and CO2 is considered in using a real gas model. The results show that exergetic efficiency of each turbo-compressor severely is depended on operating condition of compressor and required compression ratio of station. The maximum irreversibility is signified by turbine, hence any attempts to improve turbine performance affects the total efficiency of station.

Sloshing due to ground motion develops large pressure on the walls of water retaining tanks. This paper evaluates the efficacy of padded walls on the reduction of sloshing effects in rectangular water storage tanks subjected to ground motion. An analytical solution based on velocity potential function is provided to obtain the response of rigid and padded wall tanks in terms of the wave elevation, maximum pressure on the tank wall and FFT spectrum of pressure on the water surface. In the proposed method, the boundary condition on the tank wall is kinetic representing pressure distribution on the tank walls against the usual methods with kinematic boundary condition only. The fluid is assumed to be inviscid, incompressible, and irrotational. Tanks with and without padded walls are evaluated under different types of ground motions classified as near source and far-field records. The results show noteworthy effect of the padded wall on reduction of above-mentioned sloshing responses.

In this paper a two-phase supply modulator suitable for envelope tracking power amplifier is presented. The designed supply modulator has the linear assisted switching architecture. Two-phase architecture is used in order to reduce the output switching ripples. The proposed architecture uses hysteretic control instead of pulse width modulation (PWM) which significantly reduces the circuit complexity. Moreover, fewer number of external R and C elements are used which leads to simpler architecture in comparison with reported two-phase PWM supply modulators. The proposed envelope modulator is evaluated with 0.18 µm CMOS technology. The results show that the designed two-phase modulator improves the output switching noise ripples and consequently enhances the overall linearity of the modulator compared to the single-phase case. The overall efficiency of the two-phase envelope modulator is 72.5% with 80 MHz switching frequency for a one-tone 5 MHz envelope signals at 27.4 dBm output power. The RMS output voltage ripples is less than 7.2 mV in a wide range of input signal amplitude while a SFDR of 50.4dB is achieved.

In this paper, a novel and simple control strategy, based on state feedback method is suggested to control the power injection system (PIS). The considered PIS is composed of, a DC voltage source, a voltage source inverter (VSI) and a L-C-L filter. The DC source includes the battery source with boosted voltage. The battery can be charged with photovoltaic cells. Since, the grid voltage acts as a disturbance, so, the state space model is modified to reject the disturbance. In the proposed method, for the power injection requirement, the minimum input DC voltage, is calculated. Moreover, to avoid measurement problems such as noise and cost, an observer is also designed. The major problem of the single-phase PISs is the injection of somewhat DC current together with AC current. We show that the proposed controller not only implements nearly perfect tracking, but also eliminates the injected DC current to the grid. In addition, a Proportional-Resonant (PR) is also designed and applied to PIS. Simulation results show that the proposed method has significant advantages versus PR such as simple realization and application, low overshoot, no DC offset at the output current and fast response. The simulations are performed on average and accurate models. The accurate model encompasses practical conditions.

In this paper, a new model for resonance frequency of clamped circular corrugated diaphragm has been presented. First, an analytical analyzes has been carried out to derive mathematic expressions for mechanical sensitivity of diaphragm with residual stress. Next by using Rayleigh''s method we present mathematical model to calculate the resonance frequency of corrugated diaphragm and investigate the effect of residual stress, Young modulus and corrugation numbers on resonance frequency of diaphragm. In this work, MATLAB software for analytical analyzes and Intellisuite MEMS tool for finite element simulation have been used. The analytical and simulated results have been compared together and there is good agreement between them.

Document images produced by scanner or digital camera, usually suffer from geometric and photometric distortions. Both of them deteriorate the performance of OCR systems. In this paper, we present a novel method to compensate for undesirable geometric distortions aiming to improve OCR results. Our methodology is based on finding text lines by dynamic local connectivity map and then applying a low cost transformation to project curved area to 2-D rectangular area. We evaluate the performance of the proposed methods in combination with three participating methods on the public DFKI-I dataset (CBDAR 2007 dewarping contest), which contains camera-captured document images. Experimental results indicate the effectiveness and superiority of the proposed method.

In this paper, we study an outsourced supply chain consisting of one buyer and two suppliers in which the buyer outsources manufacturing of a physical product to two competing suppliers. The suppliers compete for the buyers'' demands share, and the buyer allocates the demands to the competing suppliers based on three-dimensional allocation functions. We consider two certain types of allocation function which depend on price, service level and product quality level. They include the exponential allocation function and the Cobb-Douglas allocation function. A three-stage game-theoretic framework is presented to derive the equilibrium values. Since the problem lacks a closed-form solution, numerical studies are conducted over a wide range of some key parameters.

The purpose of this paper is using the concepts of value engineering (VE) in evaluating the improvement caused by preventive maintenance (PM) systems in construction project. A real case is used to show how we can implement the proposed method. VE is the systematic application of recognized techniques by multi-disciplined teams that identifies the function of a product or service, establishes a worth for that function, generates alternatives through the use of creative thinking, and provides the needed functions and reliably at the lowest overall cost. In evaluation phase of PM system, system''s expenses and satisfaction rate of submitted service quality by PM system of workshop (by questioners) has been investigated. Then, in identification and survey phase principle of operation in PM system were identified. (by fast charts) consequently, ideas and suggestion for improvement was submitted by attending the VE workshops and brain storming meeting. Accepted suggestions were implemented by priority. After implementation of VE phase, the system again were evaluated in regard of expenses deduction and keeping or increasing the quality of services’ giving in. Performing value engineering caused saving in incurred cost and development the quality of PM system related to the civil projects.

Determining and selecting an appropriate location to construct a hotel is one of the most challenging concerns which hotel industry investors are facing with. In this study we attempt to find a suitable response to this research/application need by a mathematical model using the queueing theory and the fuzzy logic. Therefore hotel, the reception system and travelers accommodations are formulated by appropriate queueing models. Considering the fact that the arrival rate for hotel and the amount of time spent in hotel is uncertain thus a profit function is defined using the fuzzy logic and the fuzzy queueing models. Using the values of this function, candidate locations for constructing a hotel are compared and the one with maximum profit for the investors is selected. Due to using fuzzy parameters in the profit function, the amounts of profit obtained for different locations are in the form of fuzzy numbers, thus we use fuzzy ranking techniques to prioritize the candidate locations for constructing the hotel.

Vertical cooperative (co-op) advertising is typically a cost sharing mechanism and coordinated effort by the channel’s members in order to increase demand and overall profits. In this marketing strategy, the manufacturer shares a fraction of the retailer’s advertising investment. This paper studies the advertising and pricing decisions in a retailer-manufacturer supply chain in which the market demand is simultaneously affected by retail price and members’ advertising efforts. We establish three non-cooperative game-theoretic models and one cooperative model. A particular non-cooperative game can be played based on the channel type which can be retailer-dominant, manufacturer-dominant, or the same-power. We investigate feasibility of the cooperative game with the aim of channel coordination, and, utilize bargaining model in order to discuss how the both member should split the extra profit obtained by moving to cooperation case.

In a global economy, an efficient supply chain as a main core competency empowers enterprises to provide products or services at the right time in the right quantity, at a low cost. This paper is to plan a single product, multi-echelon, multi-period closed loop supply chain for high-tech products (which have continuous price decrease). Ultimately, considering components rated to procurement, production, distribution, recycling and disposal, the final decisions are made. To solve the mixed integer linear programming (MILP) model for closed loop supply chain (CLSC) network plan of the paper, four heuristics-based methods including genetic algorithm (GA), particle swarm optimization (PSO), differential evolution (DE), and artificial bee colony (ABC) are proposed. Finally, the computational results of these four methods are compared with the solutions obtained by GAMS optimization software. The solution revealed that the ABC methodology performs comparatively better in terms of both quality of solutions and computational time.

Functionally graded materials (FGM) in the form of layered structure consisting of yttria stabilized zirconia (8 mol% Y2O3) and nickel were fabricated by spark plasma sintering procedure. The relative density, linear shrinkage and Vickers hardness of each layer of graded materials were measured. The microstructure and the composition of these components were studied. The results obtained show that functionally graded materials produced by spark plasma sintering exhibited consequently fully dense specimens. Also, the results demonstrate that the composition and microstructure of YSZ/Ni FGM have the expected gradient distribution. There are no macroscopic distinct interfaces in YSZ/Ni FGM due to the gradient change in components. This good continuity of microstructure can eliminate the disadvantage of traditional macroscopic interface in YSZ/Ni joint, and reflect the design idea of FGM. Vicker’s hardness of YSZ/Ni is lower than that of pure zirconia (YSZ) and increases by increasing the relative density of the layer of YSZ/Ni.

Periodic deformation of a tire during its rolling motion causes energy dissipating and heat generation due to hysteretic nature of the rubber. The increase in tire temperature may have disastrous effects on safe service life and safety of vehicles. In this study a numerical simulation based on finite element method is used for evaluating the effect of various working conditions on temperature field of a rolling tire. Compared with related published studies, the obtained results show a very good consistency and validity.

The xerogel samples were prepared by hydrolysis and condensation of tetraethyl orthosilicate (TEOS) by the sol-gel method. In this investigation, a new molar ratio of H2O/TEOS was determined to be 11.7. Also, the necessary amounts of tri-hydrated copper nitrate and penta-hydrated copper sulfate were added to the solution in such a manner that the concentration of the copper oxide in final solution reach to 10-12 wt %. After ambient drying, the xerogel samples were heated at 400, 600, and 800˚C at a slow heating rate (50°C/h). The structural properties were characterized by Transmission Electron Microscopy (TEM), Brunauer, Emmett and Teller theory for specific surface area determination (BET) and Thermal Program Reduction (TPR) methods at different temperatures. Finally, characterization of nano-composites was studied for NH3 selective catalytic reduction (NH3-SCR) of NO in gas phase. The results were presented the systematic reactivity study of NO reduction by NH3 on dispersed copper oxide nano-composites over silica supports, in order to determine the ability of these materials to convert into harmless species at different temperatures.

Shrinking the engine has been a great interest for many years. Providing more amount of heat transfer may supply possibilities for size reduction in engine parts specifically the engine water jacket that is of concentration for the present study. Boiling phenomenon, by providing more amounts of heat transfer in comparison with single-phase, provides conditions for size reduction. In this paper an experimental correlation has been introduced in order to model boiling effect in a gasoline engine. In this work effects of boiling have been considered through calculation of the coolant convection coefficient. The introduced correlation and the method have been used to simulate thermal behaviour of the coolant within water jacket of a gasoline engine. Data show that the proposed model has good accuracy and it can be employed in designing procedure. Finally the onset of boiling phenomenon as well as heat transfer coefficient has been obtained through the present simulation.

In thin-layered reservoirs, drilling engineers face tough challenges—planning their drilling programs to follow the most productive reservoir layers while avoiding nearby water, gas or high-pressure zones. The rewards for a successful drilling strategy are clear—increased oil production and reduced water cut. In an oil field in the Persian Gulf, for example, oil production was increased four- to six fold and water cut was reduced by one-third using the latest formation modeling and geosteering techniques. Until recently, drilling thin layers was extremely difficult. Traditional geometrical drilling trajectories were unable to match the subtle variations in layer dip and depth, so many wells left the target zone and encountered watered-out layers. This paper has implemented modern geosteering methods to give drillers much greater control and help change the way operators develop thin-layered oil reservoirs, enabling them to increase hydrocarbon recovery and reduce water cut.