Mehran University Research Journal of Engineering and Technology

6

Authors: Arif Khan, Sabahat Arif, Khalid Alamgir

As the sustainable settlements have been included as a vital end product of all planning exercises, the architectural layouts should be well integrated with the sun path charts and the orientations of windows. Appropriate orientations can offer thermally indoor conditions besides physical and psychological comfort in any settlement at lesser energy demand. This investigation uses a vast number of computer simulations to visualize and make better decisions about heating and cooling requirements of a building and facades as a function of window orientation in composite climatic condition of Lahore. This study in particular evaluates the solar load in residential buildings responsive to the objective of sustainable new housing leading to thoughtful integration of architecture. The orientation of the buildings could then be essentially integrated to the current architectural and urban design practices in order to optimize the relationship between the given site ant the orientations for sustainable developments.

6

Authors: Saba Baloch, Javed Ali Baloch, Mukhtiar Ali Unar

In most digital communication systems, bandwidth limited channel along with multipath propagation causes ISI (Inter Symbol Interference) to occur. This phenomenon causes distortion of the given transmitted symbol due to other transmitted symbols. With the help of equalization ISI can be reduced. This paper presents a solution to the ISI problem by performing blind equalization using ANN (Artificial Neural Networks). The simulated network is a multilayer feedforward Perceptron ANN, which has been trained by utilizing the error back-propagation algorithm. The weights of the network are updated in accordance with training of the network. This paper presents a very effective method for blind channel equalization, being more efficient than the pre-existing algorithms. The obtained results show a visible reduction in the noise content.

8

Authors: Sabahat Arif, Arif Khan, Khalid Alamgir

Indoor thermal comfort in a building has been an important issue for the environmental sustainability. It is an accepted fact that their designs and planning consume a lot of energy in the modern architecture of 20th and 21st centuries. An appropriate orientation of a building can provide thermally comfortable indoor temperatures which otherwise can consume extra energy to condition these spaces through all the seasons. This experimental study investigates the potential effect of this solar passive design strategy on indoor temperatures and a simple model is presented for predicting indoor temperatures based upon the ambient temperatures.

8

Authors: Javed Ali Baloch, Imran Ali Jokhio, Faisal Karim Shaikh

SSN (Smart Sensor Network) systems could be used to monitor buildings with modern infrastructure, plant sites with chemical pollution, horticulture, natural habitat, wastewater management and modern transport system. To sense attributes of phenomena and make decisions on the basis of the sensed value is the primary goal of such systems. In this paper a Smart Spatially aware sensor system is presented. A smart system, which could continuously monitor the network to observe the functionality and trigger, alerts to the base station if a change in the system occurs and provide feedback periodically, on demand or even continuously depending on the nature of the application. The results of the simulation trials presented in this paper exhibit the performance of a Smart Spatially Aware Sensor Networks.

8

Authors: Tanweer Hussain, Mujeebuddin Memon, Zeeshan Ali Memon

Under the condition of elastic-plastic deformation, aero engine casings experience local stress and strain concentrations along with associated variations in load paths and stiffness. The accurate prediction of such behaviour is clearly necessary for design optimisation, potentially leading to beneficial weight savings. The present research seeks to tackle the objective of accurate characterisation of elasticplastic casing behaviour. The objective is to develop approximate techniques for predicting the elasticplastic behaviour, for both generalised load-displacement responses (i.e. for global response) and notch stress-strain responses. Accurate prediction of the stress-strain distribution at a notch is difficult and existing notch prediction techniques can only be used for small strains. This paper seeks to develop novel techniques for predicting large elastic-plastic notch strain and associated stresses, with application to aero engine casing notches. The repeated local joints at the spoke-shell casing are of particular interest as they are the most likely sites for plastic deformation and possibly crack initiation. These local joints incorporate realistic notch-type features and the load cases cover a range of loading combinations, to develop insight and understanding of the elastic-plastic behaviour. This work analyse a double edgenotched flat bar with semicircular notches and a representative case of actual aero engine casing-type structures in a more simplified form. The investigation was carried out for structures for which stress and total strain are related by a power law. The equivalent stress at a notch can be estimated, given the value of n, by a linear interpolation between the stresses for a cases n=1 and n=0. The application of the notch stress-strain prediction method is illustrated through use of examples of notch components. The predictions are compared with results obtained using finite element analyses and approximate methods proposed by Nueber and Glinka.

10

Authors: Junaid Ali Abbasi , Sarwar Ali Abbasi , Mukhtar Hussain Sahir

This research paper focuses on the process of machining complex and varying contour aerofoil parts used in aerospace industry like wings, blades of turbine and diffusers, etc. The main theme is to enhance productivity and on the other hand achieving accurate machining results for complex profile parts. The research consists of three main parts viz. Accurate and optimized tool path generation of complex profile, understanding and conversion of a 5-axes machine kinematics into mathematical relationships and developing a post processor which converts cutter location file into machine readable file, and finally a time and accuracy study has been made and compared with techniques used previously for machining of such components. Tool path is generated on CAM software from where CL (Cutter Location) file is generated, then by use of mathematical calculations post processor is developed and used for the conversion of that CL file into machine readable file. Time and accuracy analysis has been made in the end on an impeller blade machining. Tool paths generated in CAM software requires to be very closely analyzed in order to ensure collision free tool paths as movement in all 5-axes increases the chances of collision of head to work piece or with the table. For the study of 5-axes machine kinematics and calculations, a general 5-axes machine having 3 linear axes and two axes in rotary/tilting table has been used. By applying mathematical relationships using rotational matrix theorem and dot product of two vector quantities, equations were derived for rotary and tilting axes and then written in programming language (Visual C++) for line to line conversion of CL file into machine readable file. For the generation of CL file three different tool paths were generated. First process was the roughing of the area between every two adjacent blades then the next step was to finish the surface of the blades and the leading/trailing edge and the last process was to finish the hub surface of the impeller. The cutting parameters like feed, speed, axial depth of cut, radial depth of cut are dependent on the spindle power of the machine and the type of the material of part to be machined and that of the cutter itself. The selection of the size of the cutting tool used for the machining of each process is also dependant on the minimum area between two adjacent surfaces of the blades of impeller and maximum curvature of the blade from shroud surface to hub surface in order to avoid collision of the cutting tool with the blade surfaces. In the end, how the new approach has benefited is analyzed. The need for research on new approach was very demanding as to manufacture complex profile parts mostly used in aerospace industry with traditional machining approaches causes unpredictable delays due to manual calculations, inaccurate machining results like poor surface finish, tool breakage, etc, as well as requirement of various jigs/fixtures and skilled workers for accomplishing the task all the time. Now by adopting the approach as explored in this research gives a lot of advantages over traditional manufacturing approach. Some important features compared are presented in the tabular form.

12

Authors: Attaullah Shah, Saeed Ahmad

Experimental research on the shear capacity of HSRC (High Strength Reinforced Concrete) beams is relatively very limited as compared to the NSRC (Normal Strength Reinforced Concrete) beams. Most of the Building Codes determine the shear strength of HSRC with the help of empirical equations based on experimental work of NSRC beams and hence these equations are generally regarded as un-conservative for HSRC beams particularly at low level of longitudinal reinforcement. In this paper, 42 beams have been tested in two sets, such that in 21 beams no transverse reinforcement has been used, whereas in the remaining 21 beams, minimum transverse reinforcement has been used as per ACI-318 (American Concrete Institute) provisions. Two values of compressive strength 52 and 61 MPa, three values of longitudinal steel ratio and seven values of shear span to depth ratio have been have been used. The beams were tested under concentrated load at the mid span. The results are compared with the equations proposed by different international building codes like ACI, AASHTO LRFD, EC (Euro Code), Canadian Code and Japanese Code for shear strength of HSRC beams.From comparison, it has been observed that some codes are less conservative for shear design of HSRC beams and further research is required to rationalize these equations.

14

Authors: Muhammad Asif Chaudhry, Habib-Ur-Rehman

Globally there are about 25,500 storage reservoirs with total storage volume of about 6,464 Bcm. The maximum number of reservoirs are in North America, i.e. 7205 with the total storage volume of about 1,844 Bcm, whereas minimum number of reservoirs are in Central Asia, i.e. 44, with the total storage volume of about 148 Bcm. Over the globe, average annual reservoir storage loss due to sedimentation varies from 0.1-2.3%, however, average annual world storage loss is about 1.0%. In order to combat the storage loss, the techniques used globally are: watershed management, dredging of deposited sediments, sediment routing/sluicing, sediment bypassing, density current venting and sediment flushing through reservoir, separately and also in combination. Each approach has its own limitations, depending on the site conditions. Sediment flushing technique is used by two ways i.e. Drawdown flushing and Emptying and Flushing. In Emptying and Flushing, the reservoir is emptied before the flood season, resulting in the creation of river-like flow conditions in the reservoir. The flow velocities in the reservoir are increased to such an extent that deposited sediments are remobilized and transported through the low level outlets provided slightly above the original riverbed level with sufficient flow capacity. Flushing is not a new technique and has been experienced for the last 6 decades on several reservoirs of the world. The results of the study reveal that there are about 50 reservoirs which are flushed, out of which flushing data is available for about 22 reservoirs only. However 6 reservoirs have been found with successful application of flushing operation and all other are flushed with low flushing efficiency. Flushing has been successfully implemented at Baira-India, Gebidem-Switzerland, Gmund-Austria, Hengshan-China, Palagnedraswitzerland, Santo-Domingo-Venezuela Reservoirs, while the unsuccessfully flushed reservoirs are: Chinese reservoirs, Gaunting, Heisonglin, sanmenxia, Shuicaozi, Naodehai, Nanqin, Guernsey-USA, Ichari-India, ouchi-Kurgan and Zemo-Afchar of former USSR, sufid-Rud-Iran, Warsak-Pakistan, Jensanpei-Taiwan, Khashm El Gibra-Sudan, Mangahao-Newzealand, and Cachi of Costa Rica.

14

Authors: Kamran Ansari, Ashfaque Ahmed Memon, Naeem Aziz Memon

A numerical analysis of the ridges on the bed of wide, open channels and their effects on the distribution of secondary currents and wall shear is undertaken using CFD (Computational Fluid Dynamics). The presence of the lines of boil, consisting of low speed streaks, periodically in the transverse direction, is reported in the literature due to the presence of the ridges. In the present work, simulations are run on channel sections with varying the number of ridges on the bed and the size of these ridges. The effect of these variations on the flow structures and shear stress distribution in wide open channels is reported. The results offer an interesting insight into the 3D (Three-Dimensional flow structures involved and the link between flow structures and bed morpho-dynamics in prismatic channels.

20

Authors: Zeeshan Ali Memon, Saleh Jumani, Javed Larik

Automotive vehicle following systems are essential for the design of automated highway system. The problem associated with the automatic vehicle following system is the string stability of the platoon of vehicles, i.e. the problem of uniform velocity and spacing errors propagation. Different control algorithm for the longitudinal control of a platoon are discussed based on different spacing policies, communication link among the vehicles of a platoon, and the performance of a platoon have been analysed in the presence of disturbance (noise) and parametric uncertainties. This paper presented the PID (Proportional Integral Derivative) feedback control algorithm for the longitudinal control of a platoon in the presence of noise signal and investigates the performance of platoon under the influence of sudden acceleration and braking in severe conditions. This model has been applied on 6 vehicles moving in a platoon. The platoon has been analysed to retain the uniform velocity and safe spacing among the vehicles. The limitations of PID control algorithm have been discussed and the alternate methods have been suggested. Model simulations, in comparison with the literature, are also presented.