Shalangwa D. A. and Waba A. S.

The objective of this research is to design a model of modern variable reluctance tachogenerator (electromagnetic sensor) for measuring angular velocity of a rotating shaft using frequency to digital conversion techniques. The method used in the design is an adaptation of standard tachogenerator design although the design utilized reasonable number of slots (60) in a disc, NE 572 as a special comparator and bubble resolver. These improved the sensitivity, speed and eliminate ±1 error that is inherent in most digital systems, respectively. The model was tested with a DC motor; and was able to measured angular velocity ranging from 100-1000rpm with their corresponding frequencies 16Hz-160Hz. The model is capable of measuring angular velocity of other devices if the speed of revolution is not more than 10,000 rpm.

Dynamic modeling and control of a two wheeled robotic vehicle with a virtual payload

K. M. Goher, M. O. Tokhi and N. H. Siddique

One of the challenging issues to consider in balancing a two-wheeled robotic machine (TWRM) is when the load carried by the machine is changing position along the vehicle intermediate body (IB). An issue of interest in this case is the resulting impact on the system behaviour due to changing position of the load. Further complications arise with changing the size of the load.  This work presents investigations into controlling a TWRM with a payload positioned at different locations along its IB. Two types of control techniques are developed and implemented on the system, the traditional proportional-derivative (PD) control and fuzzy logic (FL) control. PD and PD-fuzzy logic control techniques are developed to balance the vehicle with a payload incorporating two different scenarios. Firstly, the payload is positioned at different locations along its IB.  Secondly, it is considered to perform a continuous sliding motion along the IB. The balancing of the robot has to be achieved during the motion of the vehicle and the payload along the IB.  An external disturbance force is applied to the rod which constitutes the IB in order to test the robustness of the developed controllers. Investigations are carried out on the effect of changing the level and duration of the disturbance force, and changing the speed of the payload on the system during the balancing mode. Simulation results of both control algorithms are analyzed on a comparative basis. 

Finite difference analysis of curved deep beams on Winkler foundation

Adel A. Al-Azzawi and Ali S. Shaker

This research deals with the linear elastic behavior of curved deep beams resting on elastic foundations with both compressional and frictional resistances. Timoshenko’s deep beam theory is extended to include the effect of curvature and the externally distributed moments under static conditions. As an application to the distributed moment generations, the problems of deep beams resting on elastic foundations with both compressional and frictional restraints have been investigated in detail. The finite difference method was used to represent curved deep beams and the results were compared with other methods to check the accuracy of the developed analysis. Several important parameters are incorporated in the analysis, namely, the vertical subgrade reaction, horizontal subgrade reaction, beam width, and also the effect of beam thickness to radius ratio on the deflections, bending moments, and shear forces. The computer program (CDBFDA) (Curved Deep Beam Finite Difference Analysis Program) coded in Fortran-77 for the analysis of curved deep beams on elastic foundations was formed. The results from this method are compared with other methods exact and numerical and check the accuracy of the solutions. Good agreements are found, the average percentages of difference for deflections and moments are 5.3% and 7.3%, respectively, which indicate the efficiency of the adopted method for analysis.

Studies on the production of caustic soda using solar powered diaphragm cells

Babatope A. Olufemi, Williams O. Ozowe and Ololade O. Komolafe

An experimental study was performed using an array of solar panels to power asbestos and non-asbestos diaphragm type electrolytic cells whose anodes consisted of carbon rods and cathodes made up of stainless steel plate for the electrolysis of a 25% w/w sodium chloride solution, with the aim of producing caustic soda. The asbestos and non-asbestos diaphragms served to hinder the formation of unwanted substances as well as permit reasonable production of the desired products. Quantitative analysis showed that the quantity and concentration of caustic soda produced varied with the current and voltage obtained from the solar panels which were dependent upon the intensity of the sun on any particular day and the length of time the panels were exposed to sunlight. The asbestos and non-asbestos diaphragm cells exhibited various characteristic performances, which is a reflection of their design, fabrication, composition and operation parameters. The non-asbestos diaphragm cell showed similar trend with the conventional asbestos diaphragm cell performances indicating higher yield of caustic soda per d.c. Watt. The research served as an encouraging inquisitive foundation into the possibility of producing caustic soda directly from solar powered electrolytic diaphragm cells in comparison with present conventional modes of electrochemical production.

The effect of two oxygenates on diesel engine emissions

Abstract:

Improvement of fuel properties is essential for the suppression of diesel pollutant emissions along with the optimization of combustion-related design factors and exhaust after-treatment equipment. Studies conducted in the past have shown that a significant reduction of pollutants using oxygenates as alcohols, ethers, glycol ethers, methylals and carbonates. The present paper experimentally investigates the influence of oxygenated diesel fuels on the emissions with the use of two different synthetic oxygenated compounds namely Diphenyl ether (DPE) and Diet helene glycol dim ethyl ether (DIGLYME). Several diesel fuel blends, which contain 10% and 15% by volume of DPE and DIGLYME, were prepared and the effect of these blends on emission characteristics were studied on a twin cylinder direct injection diesel engine. The blends were tested under the different load conditions and the results shows, there is significant reduction of engine emissions of hydrocarbon  and carbon mono oxide emissions  while the coefficient of light absorption of smoke opacimeter decreases by about 50% for DPE10, DIGLYME10 blend and it was reduced by about 60%for DPE15 and DIGLYME15 blend .

Peristaltic pumping of a Jeffrey fluid in a porous tube

S. V. H. N. Krishna Kumari P., M. V. Ramana Murthy, Y. V. K. Ravi Kumar and S. Sreenadh

Abstract:

Peristaltic pumping of a Jeffrey fluid in a porous tube is studied under long wavelength and low Reynolds number assumptions. Solutions are obtained by using Beavers - Joseph and Saffman boundary conditions. The effect of various parameters on the pumping characteristics is studied and discussed through graphs. Comparison of various wave forms (namely sinusoidal, triangular and trapezoidal) on the flow is discussed.

Selective modal space control approach for smart composite cylindrical shell structure

G. Vijaya Kumar, K. Mohana Rao, J. Suresh Kumar and S. Raja

This paper presents selective modal space control approach (SMSC) to address the vibration suppression of critical elastic modes of composite cylindrical shell, using collocated/non collocated sensor/actuator. A four node, electro-mechanically coupled field consistent facet shell finite element is used to model the shell vibration. Subsequently, a linear quadratic regulator (LQR) is designed in modal domain to conduct the vibration control simulation studies. The results of active vibration control (AVC) of a laminated composite cylindrical shell, equipped with piezoelectric composite actuators i.e., Macro Fiber Composite (MFC) and PZT sensors are presented. The effectiveness of MFC in controlling shell vibration is evaluated. An effort has been made to addresses the question of whether performance is affected by the collocation/non-collocation of the sensors and actuator.

Fibre reinforced concrete using domestic waste plastics as fibres

R. Kandasamy and R. Murugesan

Abstract:

Fibre Reinforced Concrete (FRC) is a composite material consisting of cement based matrix with an ordered or random distribution of fibre which can be Steel, Nylon, Polythene etc. The addition of steel fibre increases the properties of concrete, viz., flexural strength, impact strength and shrinkage properties to name a few. A number of papers have already been published on the use of steel fibres in concrete and a considerable amount of research has been directed towards studying the various properties of concrete as well as reinforced concrete due to the addition of steel fibres. Hence, an attempt has been made in the present investigations to study the influence of addition of polythene fibers (domestic waste plastics) at a dosage of 0.5% by weight of cement. The properties studied include compressive strength and flexural strength. The studies were conducted on a M20 mix and tests have been carried out as per recommended procedures of relevant codes. The results are compared and conclusions are made.

Impact of a concrete room on the performance of cellular telephone communications for low bit rate applications

M. S. H. Al-Salameh and Y. S. A. Al-Mashhadani

Abstract:

In this paper, a new propagation model, in macro-cellular wireless communication systems, is derived. The model characterizes the base station to mobile radio channel when the propagated signal is being obstructed by lossy concrete room in which the mobile phone moves. The analysis is performed by using ray-tracing techniques combined with uniform theory of diffraction (UTD), in addition to using a UTD modified heuristic diffraction coefficient for non-perfectly conducting wedges. The maximum considered ray reflections are three, single and double diffractions are also considered in this study. Therefore, all expected significant ray contributions in multipath channel are included. These rays include direct, reflected, refracted and diffracted paths, or any combination of the mentioned paths. The mathematical propagation model is derived, after which the model is implemented by different computer programs written in Matlab. For low bit rate applications (narrowband systems), the attenuation and fading of the propagated signal are the main causes of signal degradation. Therefore, the signal strength, as a function of mobile location inside the room, was computed for base station with an antenna array. The depolarization effect on propagated signal as well as the cumulative distribution function (CDF) and probability density function (PDF), that are useful for statistical prediction models, are studied. Details of the present model that may facilitate implementation are given. Comparison with measurements revealed acceptable agreement. The results of this research work should be useful in radio link design of macro-cellular land mobile communication systems.

Ultra-short laser pulse interaction with nickel films

E. Annan and H. V. Snelling

Abstract:

Laser induced forward transfer method involves three sequence of events (i) laser pulse heats up the front surface of the film until it melts (ii) the melt front propagates through the film until it reaches the back surface and finally (iii) at or close to melt-through the metal vapour pressure at the front propels the molten film to the substrate. Many authors have shown potentials of this method in direct writing and photo-mask repair. In this paper, we present laser induced forward technique applied to nickel films of thicknesses 98nm, 200nm and 322nm by using Ti: Sapphire femtosecond laser. Direct ablation of nickel films resulted in threshold energy values 0.03µJ, 0.56µJ and 2.49µJ for film thickness 98nm, 200nm and 322nm respectively. Backside ablation threshold energies were found to be 0.37µJ, 3.05µJ, and 4.55 µJ for 98nm, 200nm, and 322nm film thicknesses respectively. The feasibility of the transfer process is also demonstrated on nickel film on silicon wafer. Elevated features observed on films during ablation are explained.

Experimental study on D I diesel engine performance and emission characteristics (NO_x) with COME- diesel blends

P. Venkateswara Rao and M. Lokanadha Rao

Abstract:

The biodiesel from edible oils is non-toxic, biodegradable and renewable alternate fuel that can be used as a substitute for diesel in diesel engines. The objective of present work is to study performance and emission characteristics of single cylinder, direct injection diesel engine with coconut oil methyl ester (COME) and blends with diesel in varying proportions. Experiments were conducted when the engine fuelled with pure diesel and the blends of diesel- COME by volume for full load range. The exhaust conditions were measured using exhaust gas analyzer similarly AVL smoke meter for measuring smoke density. Results were compared graphically in performance of the engine for specific fuel consumption, brake thermal efficiency, exhaust temperatures and in exhaust emissions for concentrations of NO_x and smoke density.

Voltage sag influence on fatigue life of the drivetrain of fixed speed wind turbines

Badrinath Veluri, David Santos Martin and Henrik Myhre Jensen

Abstract:

Occurrence of voltage sags due to electrical grid faults and other network disturbances generate transients of the generator electromagnetic torque which result in significant high stresses and noticeable vibrations for the wind turbine mechanical system and may also have a detrimental effect on the fatigue life of important drivetrain components. The high penetration of wind energy in the electrical grids demands new requirements for the operation of wind energy conversion systems. Although fixed speed wind turbine technology is nowadays replaced by variable speed wind turbines. In some countries (Spain and Germany) with high wind energy penetration it is mandatory or under bonus to retrofit these fixed speed wind turbines and provide ride through capability. An electro-mechanical model is built to simulate the grid disturbances that easily excite the asynchronous generators poorly damped by the stator flux oscillations which cause high transients of the generator electromagnetic torque. This paper focuses in estimating the resulting significant stresses transients due to the electromagnetic torque transients, which transmits to the wind turbine mechanical system that may have a detrimental effect on the fatigue life of drivetrain components. The capability to simulate these phenomena is a novel aspect in the present effort.

Approximate method to singularity behaviour of nonlinear problems in fluid dynamics

M. S. Alam and R. A. Rouf

Abstract:

The singularity behaviour of nonlinear problems in fluid dynamics is numerically investigated. The behaviour of the first painleve transcendent is introduced as a model problem. Then the laminar unsteady flow of a viscous fluid away from a plane stagnation point is studied as second model problem. We have applied approximate method to these problems with the aid of algebraic programming language MAPLE. Analysis based on approximate method suggests that the convergence of the series of shear stress is limited by a pair of singularities. The location and nature of the singularities in the complex plane are presented. The shear stress in real plane is also depicted graphically.

Effects of different pretreatments on drying characteristics of banana slices

Abano E. E. and Sam-Amoah L. K.

Abstract:

The effects of different pretreatments and temperature on the drying characteristics of ripe Gros Michel banana slices were investigated. 5 and 7 mm thick slices of bananas were pretreated with four different pretreatments such as ascorbic acid, lemon juice, salt solution, honey dip and a control for 10 minutes, each replicated three times. Pretreated banana slices were dried in a cabinet oven dryer using a completely randomized design at 60 and 70°C and their drying characteristics such as rate of drying, moisture diffusivity, re-hydration ratio, and coefficient of re-hydration were studied. The moisture content of the fresh ripe bananas for both the untreated and treated samples was found to be in the range of 75-77% (w b) which reduced to 16.8 to 27% after oven drying for various thicknesses and temperatures of air drying for 16 hours. The moisture diffusivity during oven drying varied from 7.89E^-5 to 14.94E^-5 m/s², and increased with drying air temperature. The 5 mm thick slices at a drying air temperature of 70 dried better than the others and resulted in about 13% savings in time. The minimum re-hydration ratio of 1.215 was obtained for 7 mm thick slices treated with ascorbic acid and the maximum re-hydration ratio of 1.716 was obtained for lemon juice samples. This means that the lemon juice treated dried bananas will reconstitute more moisture when exposed to air.