Mehran University Research Journal of Engineering and Technology

6

Authors: Muhammad Ramzan, Murtaza Ali, Fiaz Hussain

Conformal vector fields are treated as generalization of homothetic vector fields while disformal vector fields are defined through disformal transformations which are generalization of conformal transformations, therefore it is important to study conformal and disformal vector fields. In this paper, conformal and disformal structure of 3D (Three Dimensional) circularly symmetric static metric is discussed in the framework of f(R) theory of gravity. The purpose of this paper is twofold. Firstly, we have found some dust matter solutions of EFEs (Einstein Field Equations) by considering 3D circularly symmetric static metric in the f(R) theory of gravity. Secondly, we have found CKVFs (Conformal Killing Vector Fields) and DKVFs (Disformal Killing Vector Fields) of the obtained solutions by means of some algebraic and direct integration techniques. A metric version of f(R) theory of gravity is used to explore the solutions and dust matter as a source of energy momentum tensor. This study reveals that no proper DVFs exists. Here, DVFs for the solutions under consideration are either HVFs (Homothetic Vector Fields) or KVFs (Killing Vector Fields) in the f(R) theory of gravity. In this study, two cases have been discussed. In the first case, both CKVFs and DKVFs become HVFs with dimension three. In the second case, there exists two subcases. In the first subcase, DKVFs become HVFs with dimension seven. In the second subcase, CKVFs and DKVFs become KVFs having dimension four.

8

Authors: Asghar Ali Chandio, Mehwish Leghari, Mukhtiar Ahmed Memon, Mehjabeen Leghari, Akhtar Hussain Jalbani

Conventional solar cells are not economical and are recently too expensive to the manufacturers for extensive-scale electricity generation. Cost and efficiency is most vital factor in the accomplishment of any solar technology. In order to improve the conversion efficiency, the major research in thirdgeneration photovoltaic (PV) cells is directed toward retaining more sunlight using nanotechnology. Advancement in nanotechnology solar cell via quantum dots (QDs) could reduce the cost of PV cell and additionally enhance cell conversion efficiency. Silicon quantum dots (Si-QDs) are semiconductor nano crystals of nanometers dimension whose electron-holes are confined in all three spatial dimensions. Quantum dots have discrete electronic states. Quantum dots have capacity to change band gap with the adjustment in size of quantum dot. As the quantum dots size fluctuates over a wide range that demonstrates the variety of band gap so it will assimilate or discharge light. In this paper, the generic mathematical models of PV cell are adopted and then I-V and P-V characteristic curves are obtained from selected parameters using MATLAB software. The essential parameters are taken from datasheets. I-V and P-V characteristics curves are obtained for selected model. Silicon quantum dots have the tunable band gap that is added to conventional PV cell and obtain the I-V and P-V curves. After simulation, efficiency and power of Conventional PV cell to quantum dots based PV cell is compared. The property of quantum dots is used in extending the band gap of solar cells and increasing the maximum proportion of incident sunlight absorbed, hence improving efficiency.

8

Authors: Hummaira Kanwal, Muhammad Shahzad Aslam, Tayyaba Latif Mughal, Muhammad Asim, Reena Majid Memon

FRC (Fibre Reinforced Concrete) is fibrous material which increases its structural integrity, resists to explosive spalling in case of environmental affects, improves mix cohesion, improves ductility, reduces of steel reinforcement requirements and reduces the voids due to good stiffness. It contains short discrete fibres that are uniformly distributed. Mostly, natural fibers are the waste material which may have negative impact on environment. Synthetic fibres include steel fibres and glass fibres but natural fibres are coconut fibres and human hair fibres which tends to vary the properties to concrete. In addition, the character of FRC changes with varying concrete, fibre material, geometries, distribution, orientation and densities. Hair fibre concrete gives a practical, cost-effective and convenient method to avoid cracks and deficiencies regarding strength and proper mixing ratio which occurs at a longer period. Fibres have been used to reduce plastic shrinkage and drying shrinkage in concrete. In some structural elements, fibrous concrete can be used to reduce the cost of structure. Different fibres are used to improve the tensile strength of concrete. Human hair are strong in tension. Hair fibres can be utilized as a strengthening material. Hair fibre is a non-decay able matter and available at a cheap rate. Experiments have been performed on fibrous concrete cylinders containing various percentages of human hair which is 0, 0.5, 1 and 1.5% by the weight of cement. A total of seventy-two cylinders have been prepared with FRC having different %ages of hair content. Workability, compressive strength and split tensile strength have been checked at three curing ages i.e. 7, 14 and 28 days. This research will open a new wicket in the horizon of reuse of waste material efficiently in construction industry. This innovation in construction industry will save our natural resources and use fibre in productive and an effective approach.

8

Authors: Anis Fatima, Syed Amir Iqbal

Non-traditional machining processes are popular for generating complex features on the work piece. With advances in material engineering, new ways of cutting technologies has been emerged. However, EDM (Electric Discharge Machining) has gained recognition for producing extraordinary surface finished, intricate part geometries with accuracy and its ability to cut through difficult to machined materials. However, like every product cycle, manufacturing processes also require energy to convert raw materials into finished product. In manufacturing operations, energy input gives carbon footprints which have an effect on our environment. It is observed that reducing energy consumption is becoming the main concern of manufacturers because of enforcing environmental laws and due to the economics of the processing. It is argued that world’s 70% of energy consumption is consumed by manufacturing sector. The aim of the work was to identify direct energy demands in wire cut EDM. The variability in energy demand was explored by operating wire cut EDM at no-load and loaded conditions.Stainless steel S304 was used as a work piece. Experiments were performed on three different wire-cut EDM.Molybdenum wire, brass wire andcopper wire were used as an electrode wire and distilled water was used as a working fluid. During the experiment, electrical current was measured and the variation of power requirement was evaluated. Power required by different features of EDM was compared with the existing energy models and factors were identified that consume most of the electrical energy. Further, a comparison is made between traditional and non-traditional machining processes. This contribution will help to assess energy efficiency of EDM technology and identify priority areas for improvements. This work is also significant for machine tool designers for optimum utilization of energy,reduced environmental impact and reduced production cost of their machine tool.

10

Authors: Muhammad Adil Khan; Asjad Javed; Mahboob Ali Chowdhry

The most important property of concrete is its compressive strength, which is carried out after 28-days of proper curing of concrete. This test is affected by other factors like the condition of curing, water to cement ratio, method of transportation, handling of the concrete, extent of vibrations and quality of the ingredients of mix proportion. This research study is an attempt to develop a simple mathematical model, by using linear regression analysis to estimate the 28-day fc’ (Compressive Strength) of concrete from the test results carried out at early age. This simple linear equation develops a relationship of 28.5 hours. These results show that most of the predicted values of compressive strength, calculated via equations, lie within permissible range difference for compressive strength achieved by experimental method, which is clear indication of credibility of the equations obtained for compressive strength at different age of concrete. The results show that compressive strength of concrete increases with the increase in content of FA (Fly Ash) upto 30% replacement, and the compressive strength of the concrete starts decreasing beyond 30% FA substitution. This argument is totally in line with all the literature carried out for this research.

10

Authors: Shahid Hussain Abro, Syed Aqeel Ahmed Shah, Abdul Aziz Solaiman Alaboodi, Talha Shoaib

The aim of nuclear power plant ageing management and assessment is to maintain an adequate safety level throughout the life time of the plant and helps in determining the useful operation. Various factors involved in the insulation of polymeric cables such as continuous heat, radiation and atmosphere result in the alteration of chemical and physical properties as well as lowers the service life of material. PVC (Poly Vinyl Chloride) is the most commonly used insulation material in NPP (Nuclear Power Plant). Purpose of this work is to predict the service life of PVC insulation cable for which extrapolation ageing has been performed. Ageing mechanism proceeds in laboratory scale rig to provide temperature and radiation sources. The variation in temperature is regulated and monitored through thermocouple. At higher temperature, semi crystalline free radical may escape out resulting in the degradation of polymer. Different tests have been carried out like shore hardness testing, tensile testing, Differential Scanning Calorimeter and Thermo gravimetric Analysis before and after ageing to analyze the Ageing effect. The impact of ageing days upon yield strength of single stress ageing has been carried out in this research work and it is found that aging has significant effect on service life of cables used in power plants.

12

Authors: Nguyen Tuan Anh

Flammability of polymer composite appears to be one of the greatest threats and hence limits its advanced applications. Polymer composite materials can be designed to obtain wide ranges of properties in comparison with traditional materials. However, almost common polymers include the intrinsic flammability, restricting their applications in spite of their flexibility and performance efficiency. In this study, a material based on epoxy Epikote 240 resin 90 phr and epoxidized linseed oil 10 phr was prepared. In order to improve the material's flame retardancy ability but maintain its mechanical strength, the mixture of flame retardants including 9 phr antimony trioxide and 11 phr chlorinated paraffins along with amin compounds as a curing agent were added into the material. In addition, E-glass woven fabric (E 600g/m2 ) was used to improve mechanical strength of the material. As a result, the material was considered as the flame- retardant material with LOI index to be 30.3%.

14

Authors: Suheb Ali Rajper, Imran Nazir Unar, Azizullah Channa, Zulfiqar Ali Bhatti

Pakistan has proven huge coal reserves but still unable to harvest the energy due to unavailability of ingenious technology. Coal gasification is robust, efficient and environmental friendly technology but it is highly sensitive to the coal characteristics. Scant literature is available on the development of the coal gasification technology which suits the characteristics of indigenous coal reserves. This papers presents the simulation of entrained flow gasifier for using indigenous coal through process modeling software namely Aspen Plus® to evaluate various system flow steps within an entrained flow gasifier. General techniques have also been discussed for creating the equilibrium-bases simulations of gasification systems. Peng-Robinson equation was used to correlate the volume of species with respect to state variables (temperature and pressure). The effects of composition of different indigenous coals like Thar, Lakhra and Sonda were investigated through simulations along with O/C (Oxygen-to-Carbon) ratio. Parametric study revealed that the O/C ratio along with other related system parameters have great influence on the performance. Sulfur could be available in different forms in coal like pyrite, sulfate or organic sulfur so appropriate form of sulfur in feedstocks should be corrected for better accuracy of model results. The highest percentages of CO i.e. 44.2, 37.8, and 46.6% were obtained from Thar coal (air dried form), Lakhra coal and Sonda coal respectively at the 0.3 O/C ratio. The decrease in LHV and HHV (Lower and Higher Heating Values) of syngas was observed on increase of O/C ratio for all coal types. The composition of as received Thar coal gave maximum LHV (1.5x104 KJ/Kg) and HHV (1.78x104 KJ/Kg) at the 0.3 O/C ratio. The future work could be extended by simulating biomass composition in the developed model of gasifier in transient simulations.

16

Authors: Sunny Katyara, Ashfaque Ahmed Hashmani, Bhawani Shankar Chowdhary

SVPWM (Space Vector Pulse Width Modulation) technique is type of traditional PWM method that efficiently utilizes its dc link voltage and generates high voltage pulses with low harmonic content and high modulation index. VSI (Voltage Source Inverter) with SVPWM generates adjustable voltage and frequency signals for VSDs (Variable Speed Drives). This research work presents the simplified SVPWM technique for controlling the speed and torque of induction motor. The performance of developed SVPWM technique is analyzed in terms of its switching losses and harmonic content and compared with SPWM (Sinusoidal Pulse Width Modulation). Mathematical modeling for induction motor control through two-level VSI with SVPWM and SPWM is presented. The voltage and current TDHs (Total Harmonic Distortions) of the drive with SVPWM technique are 73.23 and 63.3% respectively as compared to 101.99 and 77.89% with SPWM technique. Similarly, the switching losses with SVPWM technique are 178.79 mW and that of with SPWM are 269.45 mW. Simulink modeling and laboratory setup are developed to testify the efficacy of SVPWM and SPWM techniques. The modulation factor of SVPWM technique is 0.907 which is higher as compared to SPWM technique with 0.785 modulation factor.

16

Authors: Sohail Akram, Shafi Uddin, Syed Husain Imran Jaffery, Mian Aamer Jalil, Syed Waqar Haider Kazmi

Non-traditional machining processes are popular for generating complex features on the work piece. With advances in material engineering, new ways of cutting technologies has been emerged. However, EDM (Electric Discharge Machining) has gained recognition for producing extraordinary surface finished, intricate part geometries with accuracy and its ability to cut through difficult to machined materials. However, like every product cycle, manufacturing processes also require energy to convert raw materials into finished product. In manufacturing operations, energy input gives carbon footprints which have an effect on our environment. It is observed that reducing energy consumption is becoming the main concern of manufacturers because of enforcing environmental laws and due to the economics of the processing. It is argued that world’s 70% of energy consumption is consumed by manufacturing sector. The aim of the work was to identify direct energy demands in wire cut EDM. The variability in energy demand was explored by operating wire cut EDM at no-load and loaded conditions.Stainless steel S304 was used as a work piece. Experiments were performed on three different wire-cut EDM.Molybdenum wire, brass wire andcopper wire were used as an electrode wire and distilled water was used as a working fluid. During the experiment, electrical current was measured and the variation of power requirement was evaluated. Power required by different features of EDM was compared with the existing energy models and factors were identified that consume most of the electrical energy. Further, a comparison is made between traditional and non-traditional machining processes. This contribution will help to assess energy efficiency of EDM technology and identify priority areas for improvements. This work is also significant for machine tool designers for optimum utilization of energy,reduced environmental impact and reduced production cost of their machine tool.