• Issue front cover thumbnail

      Volume 44, Issue 5

      May 2019

    • Estimation and examination of linepack pressures in long liquid pipelines


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      In the past, many researchers have carried out water-hammer pressure analysis using Joukowsky equation. However, it has been observed that the computed pressure surge is no longer applicable based on the equation. The Joukowsky equation cannot be used even within the reflection time of the long pipeline. In such cases, the actual pressure rise due to the sudden closure of a quick acting valve will be several times more than that of the sudden increase in pressure as calculated by the Joukowsky equation. The phenomenon of rising pressure at the upstream of an instantaneously closed valve with the passage of time caused by the pipe friction is commonly called as linepacking. In this paper, various parameters affecting the linepack pressure have been thoroughly investigated. As the relative roughness increases, the resulting non-dimensional linepack pressure (PLP/Po) significantly increases and the proportionality constant was equal to 1.5. The linepack pressure was determined to be decreasing with increasing valve closure time. The dominant parameter that influences the linepack pressure is found to be the Reynolds number as compared to the Mach number, and the relative roughness. Furthermore, the linepack pressure is found to be proportional to frictional head loss (hL / D), and inversely proportional to inlet pressure (Po / γcLo)). Finally, a linear regression equation was developed in terms of non-dimensional variables to estimate the linepack pressure using hand calculations without undergoing numerical modeling procedures. The proposed equation was validated for sudden valve closure pressure histories available in the literature. The proposed method is applicable to long distance water supply pipelines where the linepack pressures are significant.

    • Optimal design of the transversely vibrating Euler–Bernoulli beams segmented in the longitudinal direction


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      In this study, optimal design of the transversely vibrating Euler–Bernoulli beams segmented in the longitudinal direction is explored. Mathematical formulation of the beams in bending vibration is obtained using transfer matrix method, which is later coupled with an eigenvalue routine using the ‘‘fmincon solver’’ providedin Matlab Optimization Toolbox. Characteristic equations, namely frequency equations, for determining natural frequencies of the segmented beams for all end conditions are obtained and for each case, square of this equationis selected as a fitness function together with constraints. Due to the explicitly unavailable objective functions for the natural frequencies as a function of segment length and volume fraction of the materials, especially for the beams made of a large number of segments, initially, prescribed value is assumed for the natural frequency and then the variables minimizing objective function and satisfying the constraints are searched. Clamped–free, clamped–clamped, clamped–pinned and pinned–pinned boundary conditions are considered. Among the endconditions, maximum increment in the fundamental natural frequency is more pronounced for the case of clamped–clamped end condition and for this case, maximum increment up to 17.3274% is attained. Finally, the beam configurations maximizing fundamental natural frequencies will be presented.

    • Influence of functionalized MWCNT on microstructure and mechanical properties of cement paste


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      Today, studies on nanotechnology applications in the construction industry are looking for a solution to reduce the use of cement and consequently to reduce the emission of pollutants in the environment. In this regard, the effect of different percentages of the functionalized multi-walled carbon nanotubes with carboxylicgroups (MWCNT) on the modification of mechanical and microstructural properties of hardened cement paste was investigated. The addition ratios of Portland cement with the same weight of MWCNT-COOHs were 0, 0.025, 0.05, 0.1, and 0.2 weight percent (wt%). Moreover, the mechanical and microstructural properties ofthe hardened cement paste were investigated by the use of Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), X-powder, scanning electron microscope (SEM) and atomic force microscope (AFM) techniques. The results show that replacement of cement with 0.05 wt% of the functionalized carbon nanotube, as the optimal amount, can be considered both for improving mechanical and microstructural properties.

    • Increasing the effectiveness of handwritten Manipuri Meetei-Mayek character recognition using multiple-HOG-feature descriptors


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      Detection and reading of the text from natural images is a difficult computer vision task, which is essential in a variety of emerging applications. Document character recognition is one such problem, which has been widely studied and documented by many machine learning and computer vision researchers, which is practically used for solving applications like recognizing handwritten digits. In this paper, a new approach for efficiently extracting cognition out of a total of 56 different classes of Handwritten Manipuri Meetei-Mayek (HMMM) (an Indian language) is described. Although character recognition algorithms have been researchedand developed for other Indian scripts, no research work has been reported so far for recognizing all the characters of the Manipuri Meetei-Mayek (MMM). The work begins with a thorough analysis of the recognition task using a single hidden layer type Multilayer Perceptron Feedforward Artificial Neural Network with Histogramof Oriented Gradient (HOG) feature descriptors. After reviewing the level of accuracy and time it takes to train the network, the limitations are experimentally removed using multiple-sized cell grids using HOG descriptors. HOG, being a gradient-based descriptor, is very efficient in data discrimination and very stable with illumination variation. For efficient classification of the HOG features of the MMM, a linear multiclass support vector machine (SVM) classifier has been proposed for classifying the different offline characters because of itssimplicity and speed. The classification based on linear multiclass SVM yielded a very high overall accuracy of 96.928%

    • Multi-objective solid transportation problem under stochastic environment


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      In real life, three-dimensional (solid) transportation problem is an uncertain multi-objective decision- making (MODM) problem. In particular, it involves searching for the best transportation set-up that meets the decision maker’s preferences by considering the conflicting objectives/criteria such as transportation cost,transportation time, environmental and social issues. To tackle such complex situations, this paper proposes a general formulation of the multi-objective solid transportation problem (STP) with some random parameters. The paper makes the following contributions: (i) proposes a solution methodology based on chance-constraint programming technique to solve an STP with the uncertainty characterized by gamma distribution, (ii) proposes the initial feasibility conditions for the problem and (iii) extends fuzzy programming approach for solving themulti-objective stochastic problems. A numerical example is presented to illustrate the model and methodology.

    • Single- and double-beam reflectarrays for Ka band communication


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      The Ka band has found applications in satellite, and radar communications. It is also expected that this band will be utilized for 5G applications. This paper presents single- and double-beam microstrip reflectarrays with single layer and compact size for Ka band communications at 28 GHz. Three different unit cells are investigated in this paper. Single- and double-beam reflectarrays are investigated. The reflectarrays are designed at 28 GHz with a physical size of 10λ χ 10λ. A pyramidal horn antenna is used for the feeding purpose. Thefocal-length-to-diameter (F/D) ratio is equal to one. Two different scenarios for single-beam reflectarrays are presented: one with a broadside direction and the other with a 10° tilt angle. The simulation results show that for the broadside single-beam scenario, it is possible to achieve a gain up to 28.5 dB, and a 1-dB gain-bandwidth up to 30.7%. On the other hand, the presented reflectarray for the single-beam design at 10° tilt angle gives a gain of about 26.4 dB, a side lobe level (SLL) of about -15.6 dB, and a 19.3% gain-bandwidth. For the double-beam reflectarray, four different designs at different angles of 5°, 10°, 15°, and 20° have been simulated and compared. Moreover, the simulation results on the double-beam reflectarray show that the double-beam design at 10° is better from the gain and SLL perspectives. Two prototypes for broadside single-beam reflectarrays have been fabricated and measured. The measurement results show a good match with the simulation results. Gain flatnessis guaranteed for both the simulated and measured results over the band of interest.

    • Analysis of heat and fluid flow around two co-rotating side-by-side cylinders


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      Analysis of the heat and fluid flow around two co-rotating side-by-side cylinders is the subject of this numerical study which is done at constant Reynolds and Prandtl numbers of 200 and 7.0, respectively. Both cylinders rotate in the counterclockwise direction with an identical rotating speed (RS) in the range from 0 to 4. On the other hand, several gap spaces between the rotating cylinders such as G/D = 1.5, 2.0, and 3.0 are considered in the present study. The obtained results are validated against the available data in the open literature. Many different results have been reported in this investigation. It is observed that co-rotating thecylinders deforms the wake region downstream of both cylinders which the vortex strength of the lower cylinder against the rotation is stronger than that of the upper cylinder. On the other hand, co-rotating the cylinders develops a negative lift force on both cylinders. Finally, it was concluded that rotating the side-by-side cylindersreduces the heat transfer rate between the fluid flow and cylinders in general. At whole RS and G/D values, the heat transfer rate of the upper cylinder is realized to be less than that of the lower cylinder.

    • Logistics competitiveness of OECD countries using an improved TODIM method


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      The Organization for Economic Co-operation and Development (OECD) provides a forum where governments can work together to increase the global welfare and to seek solutions to common problems through economic growth, where logistics plays an important role and contributes to financial stability. Evaluationof the logistics competitiveness of countries is a technical decision-making issue involving a variety of criteria. Most importantly, these criteria usually conflict with each other and they often act and react upon one another. As in logistics competitiveness as well as in many decision-making problems, the relationships among criteria are interdependent. Moreover, different dimensions and criteria weights also affect the evaluation results. By considering these situations, in order to handle these criteria interactions, Mahalanobis distance (MD) basedTODIM (an acronym in Portuguese for Interactive and Multicriteria Decision Making) method has been developed and it has been applied to evaluate the logistics competitiveness of the OECD countries. Evaluation of the correlation between criteria develops the consideration outcomes (regarding sorting) to a certain degree with the traditional TODIM method.

    • Simultaneous estimation of parameter uncertainties and disturbance trajectory for robotic manipulator


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      In this work, a systematic approach is proposed to estimate the disturbance trajectory using a new generalized Lyapunov matrix valued function of the joint angle variables and the robot’s physical parameters using the maximum likelihood estimate (MLE). It is also proved that the estimated disturbance error remainsbounded over the infinite time interval. Here, the manipulator is excited with a periodic torque and by the position and velocity data collected at discrete time points construct an ML estimator of the parameters at time t + dt. This process is carried over hand in hand in a recursive manner, thus resulting in a novel unifieddisturbance rejection and parameter estimation in a general frame work. These parameter estimates are then analyzed for mean and covariance and compared with the Cramer Rao Lower Bound (CRLB) for the parametric statistical model. Using the Lyapunov method, convergence of the ‘‘disturbance estimation error’’ to zero is established. We assume that a Lyapunov matrix dependent on the link angle and form the energy corresponding to this matrix as a quadratic function of the disturbance estimate error. Using the dynamics of the disturbanceobserver, the rate of change of the Lyapunov energy is evaluated as a quadratic form in the disturbance error. This quadratic form is negative definite for the angular velocity in a certain range and for a certain structured form of the Lyapunov energy matrix. The most general form of the Lyapunov matrix is obtained that guarantees negative rate of increase of the energy and a better bound on the disturbance estimation error convergence rate to zero. This is possible only because we have used the most general form of the Lyapunov energy matrix.

    • A novel approach for text summarization using optimal combination of sentence scoring methods


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      In this paper, a novel multi-document summarization scheme based on metaheuristic optimization is introduced that generates a summary by extracting salient and relevant sentences from a collection of documents. The proposed work generates optimal combinations of sentence scoring methods and theirrespective optimal weights to extract the sentences with the help of a metaheuristic approach known as teaching–learning-based optimization. In addition, the proposed scheme is compared to two summarization methods that use different metaheuristic approaches. The experimental results show the efficacy of the proposed summarization scheme.

    • Miniaturized composite band pass filter using folded transmission lines for wideband radar


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      A composite design of Band Pass Filter (BPF) is developed with 3-dB fractional bandwidth (FBW) of more than 140%. This BPF is suitable for the development of wideband radar, communication and EW system in 1 to 6 GHz. Composite BPF design utilizes stepped impedance Low Pass Filter (LPF) along with thequarter wavelength (λg/4) short circuited stub. λg/4 short circuited stubs incorporated High Pass Filter (HPF) response which transforms overall design into BPF. Four cases of filter have been discussed. In case-I, the proposed BPF is developed with a size of 32.6 mm X 7.0 mm. Further in case-II, design has been realized with improved roll-off at the lower edge of the bandwidth (i.e., 1GHz). In case-III, developed design is 75% lengthwise miniaturized that of case-I. Further in case-IV, about 55% length-wise miniaturization is done. Case-III andIV have their response similar to that of the case-I with miniaturized design. All designs are simulated, optimized and fabricated over RT-Duroid 5880 substrate. For case-I, III and IV fabrication has been done on 20 mil thick substrate, whereas for case-II 31 mil thick substrate is used. Comparisons between all the cases havebeen presented in tables and S-parameter plots.

    • Analysis of a novel disc-type hybrid stepper motor with field circuit model


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      This paper presents modelling and analysis of a novel disc-type hybrid stepper motor (DTHSM) and brings out its relative merits over the cylindrical version. The machine is characterized by winding free rotorand stator-placed field coils/permanent magnets, creating homopolar field. DTHSM has the advantage of providing independent space for the field and armature, while other stator field machines have to share the same core space for both the field and armature. This increases field strength both by permanent magnet as well as field coils to achieve increased torque and speed ranges. The machine parameters are obtained using a field circuit model and its performance is predicted using analytical equations. A 50-W, 200 steps DTHSM prototype is fabricated and tested. Aggregation of simulation and experimental results validates the effectiveness of theproposed configuration.

    • Experimental studies on structure of airblast spray in crossflow


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      The present investigation is focused on experimental studies on the structure of airblast spray in crossflow. Atomizer is at a higher pressure than ambient and the airblast gas is expected to exhibit features generally found in under-expanded gas jets. High-speed images are captured using shadowgraphy technique.Certain wave-like structures observed in the near-nozzle region are attributed to shock–vortex interactions, generally observed in under-expanded gas jets. Proper Orthogonal Decomposition (POD) analysis has been carried out using these images. POD mode shapes clearly show signatures of shock–vortex oscillations and frequencies close to the screeching frequency observed in under-expanded jets. The POD modes are compared for different conditions and the significance of dynamic structures and their temporal behavior is discussed. Finally, a regime map is also proposed to characterize spray behavior in crossflow.

    • Application of image enhancement and mixture of Gaussian approach in combustion research


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      Chemiluminescence is one of the most commonly used optical diagnostic techniques in combustion research where a line-of-sight projected information is generated from spatial fields. The exactness and uniqueness of reconstruction along with ease of implementation gives Abel inversion an edge over the otherexisting single-view reconstruction techniques for efficient estimation of spatial field from line-of-sight projections. Though there exist many such algorithms, the primary focus of these has been to ensure tractable inversion through a systematic regularization by imposing a smoothness constraint on discrete data points. Butthese techniques do not have the provision to process the input image prior to deconvolution in order to prevent accumulation of noise infiltrated during data acquisition. Another major limitation of these algorithms is to adoptthe changes in characteristics of the input data points while maintaining optimal storage and time complexity. To address these issues, we have proposed a new image processing technique using standard Abel inversion for the application in combustion research. It provides a suitable model to ensure regularized inversion by imposing a smoothness constraint on acquired raw data. The new algorithm has been implemented to yield the physically significant chemiluminescence emission from hydroxyl radicals in flames from line-of-sight integrated images.The effectiveness of this algorithm is highlighted using exemplary OH chemiluminescence images captured from a standard swirl stabilized research burner.

    • Real-time implementation of SMC–PID for Magnetic Levitation System


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      Magnetic levitation is significant in almost all arenas of engineering. This principle is used to levitate objects such as a bullet train, flywheel, etc. This paper presents an experimental set-up of Magnetic Levitation System (MLS) in which a ball is levitated to a desired position and is sustained at a desired level for a stipulated time. The ball position is measured using an optoelectronic sensor and a controller is used to determine the time span of the ball at desired heights. To achieve this, a Sliding Mode Controller (SMC) is designed in such a way so as to regulate the current, which in turn controls the position through an electromagnet.Real-time observations of such ball positions have been recorded and compared to those of conventional PID (Proportional Integral Derivative) and robust SMC. Disturbance rejection, servo operation and set point tracking have also been tested and verified for the same. The outcome of such results processed throughMATLAB proves that SMC’s performance is predominant over other controllers.

    • Univariate equation-based SHE-PWM for multilevel inverter


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      This article presents a selective harmonic elimination-pulse-width modulation (SHE-PWM) method for cascaded H-bridge multilevel inverters. The concept of volt–second area balancing is applied to estimate the voltage ratings of the dc sources, which provides different voltage ratings of each dc source. The control ofoutput voltage is achieved by varying switching notch created at the centre of each level. This method calculates switching angles in real time easily owing to the usage of univariate equations. A comparison study shows that the proposed method eliminates more harmonics compared with the conventional SHE-PWM methods. Simulation and experimental studies are conducted to validate the performance of the proposed SHE-PWM method.

    • Conceptual modeling of temperature effects on capillary pressure in dead-end pores


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      The effect of temperature on the liquid–gas interface and consequently on the capillary pressure in unsaturated dead-end pores is conceptually modeled in this paper. Trapping of non-wetting fluid (e.g., air) in the dead-end pores impacts the capillary pressure–saturation relationship and affects the continuous flow of wetting fluids. In the dead-end pore, which is assumed to be a simple vertical cylindrical capillary tube with one end closed and the other end open to the liquid body, the dependence of solid–liquid and solid–air interfacial tensions on temperature and its subsequent effects on the contact angles are deduced. A non-linear ordinary differential equation, using the Young–Laplace equation, in terms of a contact-angle-sensitive temperature function is derived and numerically solved using the fourth order Runge–Kutta method. This temperature function is used to obtain the capillary pressure–temperature relationship for a solid–liquid–air capillary system. Two example problems, first a glass–water–air capillary system and second a polytetrafluoroethylene–n-hexadecane– air capillary system, are solved here. A linear decrease in capillary pressure with temperature isobserved, suggesting that entrapped air affects capillary pressure in dead-end pores. A similar linear decrease in capillary pressure, consistent with experimental observations, is observed for open-end pores.

    • Flow due to an infinite flat plate suddenly set into motion in a viscoelastic fluid: first Stokes problem

      S DHOLEY

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      The problem of flow and heat transfer due to an infinite flat surface suddenly set into motion in an unbounded mass of viscoelastic fluid is investigated under the consideration of time-dependent temperature distribution along the plate surface. A new type of similarity solution is devised that converts the governing partial differential equations into a set of non-linear ordinary differential equations with four physical parameters, viz., viscoelastic parameter β, unsteadiness parameter b, Eckert number E and Prandtl number Pr. These equations are then solved numerically by finite-difference method after using the perturbation technique owing to the inherent unavailability of the necessary boundary conditions for solving this type of flow problem. The influences of these parameters on this flow dynamics are graphically analysed. The present analysis disclosesthat both the velocity and temperature at a given location decrease with the increase of the elasticity in the fluid as well as the unsteadiness of the flow field. The analysis reveals that the elastic property of the fluids causes theback-flow inside the boundary layer after a certain value of the unsteadiness parameter depending upon the presence of elasticity in the fluids. Another important result of this study that comes from the heat transfer analysis is that the elasticity of the fluids reduces the severity of the unwanted effect of the viscous heating.

    • Dual-layer security of image steganography based on IDEA and LSBG algorithm in the cloud environment


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      The architecture development of cloud computing technology is growing tremendously in recent times, which leads to improvement of scalability, accessibility and cost reduction measures in the IT sectors of all enterprises. In this service, the data storage without reviewing security policies and procedures is a challenging task and probabilities of extracting secret information by an unauthorized intervention are more. However, to prevent the breaches of security in the cloud service, the steganography art plays an essential role inthe data communication medium to improve the security measures, and it is an indispensable technique for hiding the secret information into a cover object. This paper describes the implementation of new steganography method with International Data Encryption Standard Algorithm (IDEA) and Least Significant Bit Grouping (LSBG) algorithm for embedding the secret information into an original image and extracting the same. The result shows the improvement of data embedding capacity and reduces the issues related to data security byeffective utilization of this new approach, which reveals the remarkable achievement of the combinational execution of steganography and cryptography technique. The IDEA and LSBG have some vital qualities such asdata confidentiality, integrity verification, capacity and robustness, which are crucial factors to achieve successful implementation of steganography process in data security system. The effectiveness and properties of the stego image can be evaluated by some specific measures like mean squared error, root mean squared error, peak signal to noise ratio and structural similarity index matrix to analyse the image quality. The results show that the proposed technique outperforms the existing methodologies and resolves the data security problem in datatransmission and storage system of cloud computing services.

    • Discovering structural similarities among rāgas in Indian Art Music: a computational approach


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      Indian Art Music has a huge variety of rāgas. The similarity across rāgas has traditionally been approached from various musicological viewpoints. This work aims at discovering structural similarities among renditions of rāgas using a data-driven approach. Starting from melodic contours, we obtain the descriptive note-level transcription of each rendition. Repetitive note patterns of variable and fixed lengths are derived using stochastic models. We propose a latent variable approach for raga distinction based on statistics of these patterns. The posterior probability of the latent variable is shown to capture similarities across raga renditions. We show that it is possible to visualize the similarities in a low-dimensional embedded space. Experiments show that it is possible to compare and contrast relations and distances between ragas in the embedded space with the musicological knowledge of the same for both Hindustani and Carnatic music forms. The proposed approach also shows robustness to duration of rendition.

    • Optimization and analysis of exergy, economic, and environmental of a combined cycle power plant


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      In this study, a combined cycle power plant with a nominal capacity of 500 MW, including two gas turbine units and one steam turbine unit, is considered by a mathematical model. This study is carried out to optimize three objective functions of exergy efficiency, CO₂ emission and produced power costs. This multiobjective optimization has been carried out by using the Non-Dominated Sorting Genetic Algorithm (NSGA-II). The results indicate that the efficiency of the combined cycle power plant depends on the design parameters including gas turbine input temperature, compressor pressure ratio, and pinch point temperature. Furthermore, any change occurring in these settings may lead to noticeable changes in objective functions, so that the efficiency of this power plant is increased after optimization by up to 8.12 %, and its heat rate is correspondinglyreduced from 7233 (kJ/kWh) to 7023 (kJ/kWh). Similarly, exergy destruction in the total system shows a reduction by 7.23%.

    • Comparative analysis of trip generation models according to household characteristics for developed, developing and non-developed provinces in Turkey


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      Trip generation is the first step of transportation planning and trip distribution, stochastic separation, and assignment of traffic are done at the end of the finding of the values. In the scope of this study, the three provinces were selected from developed, developing, and non-developed provinces in Turkey and the field of thestudy was determined. In the determined provinces, trip generation models were generated according to the household characteristics by making household transportation surveys in the determined provinces. The aim of this study is to determine the trip generation of provinces of different categories according to the household characteristics related to the size and development situation of the provinces and to determine the factors affecting trip generation in these provinces. Besides, it is decided which one of the multiple linear, poisson, andnegative binomial regression models is more appropriate for trip generation and Artificial Neural Networks model is compared with the most significant regression model. At the end of the analyses, Artificial Neural Network models have shown better performance among three different data sets. As a result, Artificial NeuralNetworks was proposed as an alternative method in the trip generation of the provinces.

    • Heat transfer correlation for a triangular protruded surface with a cross-flow jet


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      In this paper, the fluid flow and heat transfer characteristics of a small rectangular channel fitted with triangular protrusions have been studied in a three-dimensional computational domain. A hybrid cooling strategy employing forced convection air stream with jet impingement on the protruded surface has been numerically studied by solving the conservation equations for mass, momentum, energy as well as turbulent kinetic energy and its dissipation rate in the frame work of finite volume method. The duct and nozzle Reynolds numbers and Prandtl number are varied in the range of 17; 827 ≤ ReDh;duct ≤ 53; 480, 5; 135 ≤ ReDh;nz ≤ 12; 044 and 0:7 ≤ Pr ≤ 12, respectively. The effects of the duct Reynolds number, nozzle Reynolds number and Prandtl number on heat transfer rate have been quantified. Extensive numerical computation has also been executed to collect the data for Nusselt number by varying each of the independent parameters. A non-linear regression analysis based on Lvenberg–Marquardt (L–M) method has been used to fit a correlation for Nusselt number utilizing the data captured from CFD analysis.

    • A parametric study on the dynamics of two-span roll-to-roll microcontact printing system


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      The recent trend towards micro-patterning of thin film webs brought stricter manufacturing tolerances than traditionally admissible vibration levels. Therefore, one has to consider roll-to-roll (R2R) systems with their system dynamics model encompassing all systems’ components, namely, the axially moving web(s),the rotating rolls and other accessories. In this study, the dynamic characteristics of an axially moving web in a two-span R2R system are investigated. Influence of geometrical parameters on the R2R dynamics and the parametric resonances of the moving web is presented. The time variations of web axial speed and web-transmitted tension are rigorously obtained by solving the web tension–roller angular speed equation, which is obtained from the conservation of mass law. The effects of system parameters such as length of the web, inertia of idler roll and radius of the rewinding/unwinding roll on the angular speed and web-transmitted tension have been discussed. The axially moving web was modelled as a string, which was mathematically represented by a second-order hyperbolic partial differential equation. The effect of the frequency of the disturbance at the roll onthe web dynamics is also discussed. The transverse vibration response at selected points on the web shows higher frequency fluctuations corresponding to lower transport axial speed. It is noted that instability in the transverse response will occur when the first and second frequencies of the oscillation converge.

    • Design and architecture of new 11:2 decimal compressors


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      Design and architectures of new 11:2 decimal compressors have been reported in this paper. Two design methodologies viz. delay and area optimized compressors have been introduced and implemented through tree structure of decimal number system. The architectures have been realized through vertical carry save addition algorithm, wherein to build up such addition of unconventional (4221 and 5211) binary coded decimal technique has been incorporated. Configurations of such compressors have been prototyped and transistor level implementation have been carried out to evaluate performance parameters like speed (propagationdelay), power dissipation, area and area delay product. The architecture has been validated by Cadence virtuoso platform using 90 nm, 65 nm and 45 nm CMOS technology which provides useful statistics to determine the compressor’s performance parameters. The propagation delay of the delay optimized compressor equals to ~0.094 ns while the propagation delay of the area optimized compressor is ~0.124 ns using 90 nm CMOS technology at 1 V supply voltage. The reported architectures are ~24% and ~41% faster from its counterpart.

    • Effect of bonding pressure on microstructure and mechanical properties of aluminium/copper diffusion-bonded joint


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      Pressure pulsation is notable for improving diffusion bonding process by breaking oxide layer present at the faying metal surfaces while an increased bonding pressure is envisaged to produce more compressive deformation (squeezing effect) on the reaction layer. This work aims at improving inter-atomic intersperse and mechanical properties of Al/Cu joint via the control of the bonding-compressive pressure. The bonding temperature (600 ° C) and time (60 min) were kept constant while the bonding pressure was varied between 5 and 12.5 MPa. The metallurgical and mechanical properties of the joint were studied. The results revealed that an oxide-free bond interface was produced in a pressure range of 5–12.5 MPa. The rise in the bonding pressure (5–12.5 MPa) increases the bond strength (78.39–108.47 MPa) and the diffusion depth(11.32–20.87 μm) between the Al/Cu interfaces. Five (5) distinctive regions having CuAl2.4, Al1.3Cu3.1Sn,Al2.5Cu1.5Sn, CuAl1.8 and AlCu2.3Sn1.4 phases were formed within the reaction layer due to the varying level of interspersing/inter-atomic diffusion. Maximum hardness increases with bonding pressure level towards the Cu side from 57 to 111 HV due to the precipitation of Al2.5Cu1.5Sn and AlCu2.3Sn1.4 phases.

    • Determination of the wear performance of diamond saw blades using inductively coupled plasma


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      Saw blades are one of the most used cutting tools. They compose the expensive parts of a cutting machine. Therefore, saw-blade wear is an important parameter governing the economy of the cutting process. Significant savings could be made when it is controlled effectively. In this study, a new methodology isemployed for the determination of the saw-blade wear in the cutting of two types of marble. Wear of segments is determined by high-precision inductively coupled plasma method. Two types of marbles were used to investigate the wear performance of diamond-impregnated segments of circular saw-blade matrix. Taguchi mixed design L16 (4³ 2¹) is used as an experimental design and the results are evaluated statistically with Minitab. The results reveal that the specific wear rate (SWR) of Beige marble increases with the increase of the peripheral speed, traverse speed, depth of cut and down-cut mode operation. Additionally, it is demonstrated that the traverse speed and peripheral speed are the dominant cutting parameters affecting the SWR. It is also seen thatsimilar trends are observed for Onyx marble (excluding peripheral speed). Finally, it is concluded that the proposed models can be effectively used for the estimation of the SWR.

    • Influence of refinery processing methods on ageing of bitumen


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      This investigation reports the influence of processing condition (air rectification and component blending) on ageing and stress relaxation behaviour in bitumen. FTIR spectra were recorded on two samples of bitumen at unaged, short-term aged and long-term aged conditions. Indices such as aliphaticity, aromaticity,carbonyl and sulphoxide calculated from the FTIR spectra were used in the analysis. It was seen that the ageing compounds in the air-rectified bitumen were higher at the end of the production process compared with theblended bitumen while the rate of oxidation compounds formed during short-term and long-term ageing was higher in the blended bitumen. In addition, a stress relaxation test was performed at 25°C in the unaged, shorttermand long-term ageing conditions. Since the formation of ageing compounds leads to change in ‘stiffness’ and hence a change in the stress relaxation behaviour of the material, it is seen that the stress relaxation results are in line with the material behaviour as seen from the FTIR tests.

    • Mechanical and tribological properties of Al7475-SiCp composites by stir casting method and wear rate modeling using RSM

      K SEKAR

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      The microstructure, mechanical and wear properties of the Al 7475-SiCp composites and to investigate the effects of SiC micro-particles reinforcement with alloy have been studied. Al 7475-SiCp composites have been developed by a stir casting method. The SiCp size in the range of 15–40 lm with weight.% of 0, 5, 10 and 15 were injected in molten Aluminum 7475 alloy in argon gas environment and stirrer using a mechanical method at 450 rpm to ensure uniform distribution of SiC particles. The mechanical properties such as hardness and compressive strength of the composites were found to be gradually improved with the addition of 5–15% SiCp reinforcement. The ultimate tensile and impact strength increased with 10% of SiCp reinforcement. For modeling the wear rate, the experiments were conducted in Pin-on Disc tribometer at room condition. A three-level central composite design with response surface methodology was used to reduce the experimental conditions and to predict the abrasive response of wear rate through the development of mathematical models. The model developed is efficiently predicted the rate of wear at 95% confidence level and the entire model validate with analysis of variance.

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