International Journal of Engineering
Volume:20 Issue: 1, Apr 2007

The effect of a Nd: YAG laser (1064 nm) has been studied on Ti6Al4V alloy in terms of optical and physical parameters for biomedical applications. The superior surface microhardness hardness (i.e. 377 VHN) is attributed to grain refinement associated with laser melting and rapid solidification. The electrochemical property, mainly pitting corrosion resistance, has been carried out in Hanks salt balanced physiological solution using standard potentiodynamic polarization testing. At the optimium laser treating fluence (140 Jcm-2), the EDX spectroscopy showed a decrease of about 30% in the vanadium and the contact angle measurements also indicated an improved surface wettability seen in the characteristics with a contact angle of 35°. Finally, Cell spreading on the implanted specimens was analyzed by SEM and their condition in a specific area was studied for 10 cells for three separate regions on the same specimen using Image J Program software. The in vivo tests provided some useful clinical and pathological information regarding tissue response to the implants with different surface topography.

With the advent of high strength geogrids, the interest of civil engineers in using geosynthetics as reinforcement material in pavement construction has increased. An experimental study is carried out at IIT Delhi to understand the effect of geogrid in unpaved roads. Behavior of composite material, which comprises of Yamuna sand as subgrade and Water Bound Macadam (WBM) as base course is studied with and without geogrid reinforcement under drained conditions. A geogrid is used as reinforcing material. Drained triaxial tests were performed at three different confining pressures of 50, 100 and 200 kPa on both unreinforced composite and reinforced composite materials of specimen size 100mm diameter and 200mm height. Hierarchical single surface (HISS) model developed by Desai and co-workers is used to model the unreinforced and reinforced composite material. A computer program PARA6 is used to calculate the various parameters and to back predict the stress-strain-volume change behavior of unreinforced and reinforced composite materials. The predicted results match closely with the observed results.

Reduced web section beams in shear-yielding moment-resistant steel frames are used for energy dissipating of earthquakes. The finite element analysis indicates that failure mode of these beams are governed by the combination of shear force and flexural moment. Therefore the analysis of frames with reduced web section beams needs consideration of shear-flexural interaction in those sections. In the present paper, modeling and analysis of reduced web section beams are investigated by using a special element which is called VM link element. The elastic and inelastic shear and flexural deformations and tangential stiffnesses in this link element are considered by using the multi-surfaces plasticity concept with dissimilar yield surfaces. The developed VM link element is examined for some reduced web section beams and it is shown that the results have a good agreement with the finite element results.

Approximate dynamic analysis of structures is achieved by fast wavelet transform (FWT). The loads are considered as time history earthquake loads. To reduce the computational work, FWT is used by which the number of points in the earthquake record are reduced. For this purpose, the theory of wavelets together with filter banks are used. The low and high pass filters are used for the decomposition of earthquake records in the high and low frequency of the records. The low frequency content is the most important part; therefore this part of the record is used for dynamic analysis. A number of structures are analysed and the results are compared with exact dynamic analysis and the Fast Fourier method (FFT).

In this research, using the results of 6 tests, the effect of Carbon Fiber Reinforced Polymer (CFRP) sheets on the behavior of reinforced concrete coupling beams of shear walls is studied. First, in the experimental part of the study, four coupling beams with different reinforcements were manufactured and tested. Then, after the failure of the specimens, two of them were rehabilitated and strengthened with CFRP sheets, and retested. Four specimens were constrained longitudinally in order to evaluate the effect of the slab diaphragm on the coupling beam behavior. In each test, the applied load and the displacement of the coupling beam were measured. Test results show that the CFRP sheets can increase the shear strength of the conventional reinforced coupling beams. The Canadian Institute ISIS equations are in agreement with the test results of the strengthened beams. The assumption of a major diagonal crack instead of 45 degrees inclined cracks due to shear forces results in a better prediction of the strength of coupling beams. Based on the results of this study, the effect of longitudinal constraint may not be remarkable for the strength of coupling beams with conventional reinforcements. The rehabilitated and strengthened coupling beams with CFRP sheets can achieve appropriate strengths even larger than those of original beams. However, their stiffness decreases.

The function of precipitation intensity-duration-frequency is needed for the planning and design of water resource projects. Short duration precipitation data are hardly available. However the total hourly-recorded available precipitation data for different parts of NWFP from different departments have been collected and analyzed for the present study. The data from WAPDA is found to be more authentic. Making use of the data, functions of intensity-duration-frequency for precipitation are developed for the Bannu region, representing the lower hilly and plane areas in NWFP. The IDF curves are plotted for 2, 5, 10, 25, 50 and 100-year return periods. The theoretical intensities of precipitation calculated by the developed functions are in close agreement with those recorded at the stations through automatic gages. Only 7 % variation is observed for most of the time. The values of the constants k, b and exponents n, m in the IDF function are calculated from the observed precipitation data. The correctness of the developed function is ascertained through its comparison with existing equations for depth duration developed for the world’s largest rainfall events. The function developed is found to produce more realistic results for regions in NWFP. The developed function may be used in the same region in a radius of about 100 km. For design practices regarding the prediction of precipitation in the future, instead of consulting 26 years of data available for the same region on hourly basis.

The quality of an architectural design of a software system has a great influence on achieving non-functional requirements of a system. A regular software development project is often influenced by non-functional factors such as the customers'' expectations about the performance and reliability of the software as well as the reduction of underlying risks. The evaluation of non-functional parameters of a software system at the early stages of design and its development process are often considered as major factors in dealing with these issues. Because these evaluations can help us to choose the most proper model which is the securest and the most reliable.In this paper, a method is presented to obtain performance parameters from Generalized Stochastic Petri Net (GSPN) to be able to analyze the stochastic behavior of the system. The embedded Continuous Time Markov Chain (CTMC) is derived from the GSPN and the Markov chain theory is used to obtain the performance parameters.

The Brushless DC (BLDC) motor is a simple robust machine which has found application over a wide power and speed of ranges in different shapes and geometry. This paper briefly reviews the fundamentals behind the motor and also the different types of BLDC motors with different geometries and then presents a new configuration for BLDC motor/generator, which does not use a permanent magnet in the rotor. The proposed novel motor/generator consists of two magnetically dependent stator and rotor sets (layers), where each stator set includes nine salient poles with windings wrapped around them while, the rotor comprises of six salient poles. The magnetic field passes through a guide to the rotor then the stator and finally completes its path via the motor housing. This is a three phase motor/generator and every stator and rotor pole arcs are about 30º. A new power electronic converter is also presented. This topology provides bidirectional control of the current for each motor phase independently. This control scheme permits the motor to operate with any number of phases at any time. In this converter, four power switches in the form of a bridge connection for each motor phase has been utilized therefore, the motor can operate by switching different sequences for the current direction in each motor phase windings and also offers the choice of having any number of phases to be on at any time. A proto-type motor/generator and the drive circuit have been built and tested in the laboratory and the numerical and experimental results are presented. Due to the ruggedness of the proposed motor/generator in comparison with the conventional and brushless dc motors used for automobile applications, this unit looks very promising for use as an integrated motor generator for hybrid vehicle

Mathematical modeling based on a probabilistic approach for making decisions for organ transplantation can be successfully employed in cases when the choice of decisions can affect the results produced. In this study, the minimum probability of success required for organ transplantion in case of multi-donors is determined. The governing equations are constructed in terms of probabilities and some other factors like quality adjusted life-years (QALYs) of recipients, donors, expected knowledge gain, medical benefit and expected fame of surgeon. The analytical results are obtained by solving equations and illustrated numerically.

This work presents a set of three simple and explicit equations as a function of temperature, pressure, and mass fraction for calculation of the entropy of the ammonia-water mixture in saturated and super heated conditions. They are intended for use in the optimization and second law efficiency of absorption processes. The equations are constructed by the least square method for curve fitting using the valid available data in the literature. The presented equations are valid for the calculation entropy of the saturated liquid and vapor mixture within -40 ≤ T ≤ 140ºC, and the super heated vapor mixture within 0.1 ≤ P ≤ 10 MPa and Tsat(P) ≤ T ≤ 350ºC, and the entire composition range. The obtained results are compared with available data in graphical and statistical forms, and comparisons reveal that the deviations are ±0.05 kJ/kg.K in the saturated liquid mixture, within −0.04 to +0.06 kJ/kg.K in the saturated vapor mixture, and within −0.08 to +0.02 kJ/kg.K in the super heated region.