International Journal of Engineering
Volume:28 Issue: 10, Oct 2015

We report the synthesis of nitrogen-doped urchin-like rutile TiO2 nanostructure at room temperature without further heat treatment. The process was operated through hydrolysis of Ti(OC4H9)4 employing the direct amination of the product. The samples characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Raman spectroscopy and Brunauer- Emmett- Teller (BET) for determination of surface area. Photocatalytic activity of the product was evaluated by degradation of Methylene blue under sunlight. This analysis demonstrated that obtained titanium oxide has an urchin- like form with rutile structure and high surface area is due to formation of nanospicules on the surface. N–TiO2 exhibited excellent photocatalytic activity under sunlight due to their high surface area (148 m2 g-1) and the new absorption band in the visible region caused by nitrogen doping.

Turbulent heat transfer in Helically Corrugated tubes (HCT) was numerically investigated for pure water and SiO2 nanofluid using Computational fluid dynamics (CFD). This study was carried out for different corrugating pitches (5, 7, 8 mm) and heights (0.5, 0.75, 1.25 mm) at various Reynolds numbers ranging from 5000 to 13300. The effect of nanoparticles on heat transfer augmentation for plain tube and HCT was considered and the relative Nusselt numbers were also compared. However, the heat transfer extremely increased with increasing the volume fraction of nanoparticles in the plain tube but, the effect of helical corrugation on the heat transfer increment was much more than that of the nanoparticles enhancement in the HCT. It was concluded that the corrugated height increment and the corrugated pitch reduction increase the heat transfer process. The maximum heat transfer was obtained at Reynolds number of 13300, HTC with p=5 mm and e=1.25 mm, and SiO2 volume fraction of 1%.

Assessment of adsorption zinc (II) ions from aqueous solution using alginate-SBA-15 sorbent nanocomposite was investigated as a function of zinc concentration, solution pH, and contact time. For that purpose, the alginate-SBA-15 nanocomposite adsorbent was prepared through encapsulation method by immobilization mesoporous SBA-15 into a polymeric matrix. Identification of functional groups and surface morphology of the obtained nanocomposite was carried out by X-Ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and nitrogen porosimetry experiments. Sorption performance of the alginate-SBA-15 adsorbent during batch experiments was studied. A mathematically explanation of adsorption process using kinetics and isotherm models was also performed. Kinetic study was revealed that the pseudo second-order model has good agreement with the experimental results than the pseudo first-order model. Therefore, it indicates that the concentration of both alginate-SBA-15 and zinc metal ions are involved in the rate determining step of the sorption process. The qmax value for zinc (II) ions adsorption onto alginate-SBA-15 was found 46.3 mg g-1. According to thermodynamic analysis, physisorption and the endothermic of the sorption process nature of Zn(II) ions onto alginate-SBA-15 nanocomposite was revealed.

Nonlinear function approximation is one of the most important tasks in system analysis and identification. Several models have been presented to achieve an accurate approximation on nonlinear mathematics functions. However, the majority of the models are specific to certain problems and systems. In this paper, an evolutionary-based wavelet neural network model is proposed for structure definition and optimization of nonlinear systems. The proposed model involves structure identification and also a parameter tuning phase to be adapted for modeling of an arbitrary system. The proposed structure and the learning algorithm are validated by comparing with some other most commonly used alternatives. The simulation shows the performance and adaptability of the proposed model in approximating multivariate nonlinear mathematics functions.

Topology construction and topology maintenance are significant sub-problems of topology control. Spanning tree based algorithms for topology control are basically transmission range based type construction algorithms. The construction of an effective backbone, however, is indirectly related to the placement of nodes. Also, the dependence of network reliability on the communication path undertaken by the message, subject to the place of event, remains unattended. To address this problem, we employ communication backbones (Prim’s algorithm and breadth first search (BFS)) and compute reliability based on the availability of paths for consistent message delivery from the place of event to the sink location in event driven wireless sensor networks. Our article analyses the communication reliability of a wireless sensor network in context to a topology governed by random and deterministic deployment methods. To comprehend the effect of topology on the communication reliability of a wireless network; “the within communication radii” constraint is satisfied. ANOVA is performed to validate the effect of node placement schemes on the reliability subject to varying radio ranges. It is observed that a ‘quasi’ random placement of nodes increases the communication reliability of the existing algorithms employed for analysis.

Today there are many techniques for web service compositions. Evaluation of quality parameters has great impact on evaluation of final product. Business process execution language (BPEL) is one of those techniques that several researches have been done on its evaluation. However, there are few researches on evaluation of quality of service (QoS) in eflow. This research tries to evaluate performance and reliability of eflow and BPEL through mapping them to explicit colored petri net. To achieve this goal, colored petri net was enhanced with a new block of immediate transition, called Pick split/join. Then, a transformation table was proposed to show the mapping rules from basic and structured activities in eflow and BPEL to colored petri net. Finally, theory of probability was applied on the model to measure QoS. Web servie evaluation tool (WSET), a case tool in Java programming language, was developed for further simulation.

Carbon nanotube field-effect transistors (CNFETs) are a promising candidate to replace conventional metal oxide field-effect transistors (MOSFETs) in the time to come. They have considerable characteristics such as low power consumption and high switching speed. Full adder cell is the main part of the most digital systems as it is building block of subtracter, multiplier, compressor, and other larger circuits. Therefore, it has a direct impact on the overall performance of the entire digital system. In this paper, we have presented two novel full adder cells using both capacitive threshold logic (CTL) and path transistor logic (PTL). The proposed cells have two symmetrical and identical modules to provide Sum and output carry (Cout). Intensive simulations using Synopsys HSPICE tool are run to evaluate the performance metrics of the proposed cells against some state-of-the-art full adders. Simulations are carried out in the presence of varying power supplies, temperatures, and output loads. Moreover, since process variations are a concern at the manufacturing stage of integrated circuits, we have performed Monte Carlo transient analysis to study the robustness of the proposed cells against diameter variations of carbon nanotubes (CNTs). Simulation results demonstrate that the proposed cells outperform their counterparts and exhibit reasonable results.

Image fusion is a method for obtaining a highly informative image by merging the relative information of an object obtained from two or more image sources of the same scene. The satellite cameras give a single band panchromatic (PAN) image with high spatial information and multispectral (MS) image with more spectral information. The problem exists today is either PAN or MS image is available from satellite camera. In many remote sensing applications, there is a need for enhancement of the MS image with more spatial resolution for further analysis. In this work, a new fusion technique is proposed in order to get a combined image by integrating PAN image and MS image. PAN and MS images are decomposed using non subsampled contourlet transform (NSCT). Then, the fourth order correlation coefficient (FOCC) is found between the low frequency components of both images. If FOCC is greater than an optimum threshold value, then the corresponding higher frequency components of the PAN image are injected into the respective locations of the MS image. Otherwise MS image components are retained. For calculating the optimum threshold value, n number of test fused images are formed by using n arbitrary threshold values. FOCC between the PAN image and the test fused images are plotted for various threshold values. Similarly, hamming distance of FFT based spectral histogram curves between the MS image and the above test fused images are plotted. The point of intersection of these two curves gives the optimum threshold value. The fused image is obtained using inverse NSCT. The evaluation shows that the proposed work gives better improved results than the other existing methods.

In this paper various layered planar periodic structures which provide miniaturization of planar antennas are proposed and discussed. The proposed designs are based on two concepts, reactive impedance surfaces and complementary periodic structures. In the proposed structures, complementary periodic rings and slots are patterned on the intermediate boundaries of the dielectric layers. A patch antenna is patterned on top of the first layer and the whole structure is grounded. The dielectric layers can be either similar or may have different dielectric constants and thicknesses. The dielectric constants and thicknesses of the layers can be chosen in a wide range of values. Two distinct configurations are studied simultaneously, namely, complementary circular rings and complementary square rings. The proposed designs provide a miniaturization factor in the range of 2.1-4.5 for planar antennas working in the frequency range of 2-22GHz. Parametric studies are provided to demonstrate high flexibility of the structures.

Conventional energy sources are fast depleting due to poor conservation practises and excessive usage while the world’s energy demands are growing by minute. Additionally, the cost of producing conventional energy is rising also leading to an increase in harmful environmental pollution. Hence, there is a need to look at alternative energy sources such as sun, water and wind. Photovoltaic (PV) is a very promising option as it uses energy from naturally available sunlight distributed throughout the Earth which is not only pollution free but also abundant and recyclable in nature.Among the different DC-DC converters proposed in literature, interleaved boost converter is best suited for PV and other high power density applications.Conventional interleaved boost converters experience switching losses and switching stresses during turn-on and turn-off periods due to hard switching. In order to eliminate the power loss in the converter devices, soft switched interleaved boost converter (IBC) is proposed in this paper. Soft switching is achieved with the use of an LC resonant tank circuit. The tank circuit is responsible for zero voltage switching (ZVS) and zero current switching (ZCS), eliminating the power loss in the switches appreciably. Since photovoltaic source is used as the input to the converter, a maximum power point tracking (MPPT) algorithm is implemented to extract maximum available power from the PV panel. Furthermore, the device losses, ripple and current sharing based on input and output characteristics are recorded and examined. Simulation study of the design is carried out using MATLAB/SIMULINK software. A hardware prototype with PV module is developed to validate the simulation results.

Redundancy allocation is one of the common techniques to increase the reliability of the bridge systems. Many studies on the general redundancy allocation problems assume that the redundancy strategy for each subsystem is predetermined and fixed. In general, active redundancy has received more attention in the past. However, in real world, a particular system design contains both active and cold-standby redundancies, and the choice of the redundancy strategy becomes an additional decision variable. So, the problem is to select redundancy level for each subsystem, component and the best redundancy strategy in order to maximize the system reliability under system-level constraints. This paper presents a new mathematical model for redundancy allocation problem (RAP) for the bridge systems when the redundancy strategy can be selected for individual subsystems. The problem is classified as an NP-hard problem. In this paper, a special version of genetic algorithm (GA) is applied, which has been modified for constrained integer nonlinear problems. Finally, computational results for a typical scenario are presented.

In reliability theory, the reliability measures contend the very important and depreciative role for any system analysis. Measurement of reliability measures is not easy due to ambiguity and vagueness which exist within reliability parameters. It is also very difficult to incorporate a large amount of uncertainty in well-established methodologies and techniques. However, fuzzy logic provides an effective tool for extraction of precise conclusions based on vague and imprecise data and human perceptions. This paper suggests a rule based fuzzy logic approach for measuring reliability measures.

This study investigates the effects of micro- and nano-sized SiC powder on the rheological behavior of Al based feedstocks for powder injection molding (PIM). Different compositions of Al feedstocks with additions of micro and nano-SiC powder were prepared and their rheological properties were measured with a rotational rheometer. The effects of SiC content and shear rate were investigated and activation energies were compared amongst the feedstocks. The results showed that nano-SiC powder has a prominent effect on the viscosity and yield stress whereas micro-SiC does not have an effective role and the base micro-Al powder determines the overall rheological behavior of the feedstock. It was found that the feedstocks reveal pseudoplastic behavior at low shear rates and dilatancy at high shear rates. The critical shear rate (γcrit) was 100 s-1 for changing the rheological behavior. The activation energy of a given feedstock was found to increase with micro-SiC content while the reverse trend was observed for nano-SiC.

Fins are protrusions on a heat transfer surface to augment heat transfer rate from it. The increase in area exposed to convection in case of finned surfaces results in increased heat transfer rate. In this study heat transfer characteristics of a pin fin with perforation is numerically analyzed. A pin fin is fabricated and experiments are done under forced convection conditions. The experimental results are used for validating the numerical model. The numerical analysis of perforated pin fin with varying parameters such as diameter of perforation, location of perforation and number of perforations is done. The perforated pin fin is found to enhance heat transfer rate compared to ordinary pin fin with a lesser material requirement.

One of the main vibration problems of aerospace vehicles with liquid fuel propulsion system is fuel sloshing. This phenomenon is a low frequency vibrational challenge which can affect the motion of the vehicle and degrade the stability of the main control system. In this regards, the motion of the liquid will be very critical when the frequency of the sloshing is very close to the frequencies of the main dynamic system. In addition, dominant frequencies of the sloshing are varied due to the flight time in the aerospace vehicles. In this paper, an aerospace launch vehicle with fuel sloshing is considered as a multi body dynamic system and in order to reduce the undesired effects of the fuel vibration, a new subband adaptive filter based on the lyapunov theorem and the discrete fourier transform (DFT) is designed. In this way, the new control system is implemented on the attitude control of the vehicle and the simulation of the nonlinear model is carried out. Numerical results of the simulation show that the effects of the fuel sloshing on the vehicle are effectively omitted by means of the new subband adaptive controller.

To reduce the damages of aeolian vibration of conductors to the power transmission networks, the most common method is installation of Stock-bridge dampers. Estimation of the damper’s dissipated energy is an important factor in determining the number and location of installation of these types of vibration absorbers. This estimation is strongly dependent upon the assumed mode shape of the conductor vibration. The results of current study show that the available methods do not provide an accurate answer for energy dissipation of a conductor with more than one damper. This paper provides a comprehensive method for calculating the mode shapes and dissipated energy in which the effects of travelling wave, amplitude and phase variations, boundary conditions as well as the influence of the number, position, and impedance of the dampers on the mode shape are taken into account. Moreover, the frequency bands of high-amplitude vibration potential can be identified without the need to extract the vibration amplitude.

The purpose of this paper is to evaluate the effect of different methods for improving the temperature gradient of a specified gasoline engine piston. With a robust finite element (FE) based software, 3D thermal analyses have been carried out for the piston model. Unlike previous studies, the effects of both fully and locally ceramic layers on the crown top surface were considered. It was found that a fully ceramic layer provides just 10-15% more thermal protection. The effects of thermal dam and lubricating oil temperature on crown and skirt surfaces were then separately investigated. Using these methods, the maximum surface temperature of the piston was greatly improved and the temperature distribution of piston skirt was effectively controlled.

In this paper, it is tried to find an approximate single layer equivalent for multi-layer graphene sheets based on third order non-local elasticity theory. The plates are embedded in two parameter Winkler-Pasternak elastic foundation, and also the thermal effects are considered. A uniform transverse load is imposed on the plates. Applying the non-local theory of Eringen based on third order shear deformation theory and considering the van der Waals interaction between the layers, the governing equations are derived for a multi-layer graphene sheet. The governing equations for single layer graphene sheet are obtained by eliminating the van der Waals interaction. In this study, two different methods are applied to solve the governing equations. First, the results are obtained applying the differential quadrature method (DQM), which is a numerical method, and then a new semi-analytical polynomial method (SAPM) is presented. The results from DQM and SAPM are compared and it is concluded that the SAPM results are satisfactorily accurate in comparison with DQM. Since analyzing a multi-layer graphene sheet needs a time-consuming computational process, it is investigated to find an appropriate thickness for a single layer sheet to equalize the maximum deflections of multi-layer and single layer sheets. It is concluded that by considering a constant value of the van der Waal interaction between the layers, the maximum deflections of multi and single layer sheets are equal in a specific thickness of the single layer sheet.