Applied Mechanics and Materials Vols. 110-116

Abstract: Tribological study on a 12.7 mm diameter steel ball bearing specimen has been carried out in a four-ball machine. The synthesis of 3-(N-n-octadecylammonium) quinazolin-4-ones was described. The 3-(N-n-octadecylammonium) quinazolin-4-ones has been found to be quite effective as a potential ashless additive without phosphorus and sulphur in liquid paraffin according to the experimental results. Employing scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), the film formed when the the additive interreacted with the metal was investigated.

Abstract: This paper presents the simultaneous optimization of multiple quality characteristics (Material removal rate and Average surface roughness) using Taguchi method for electrical discharge diamond cut-off grinding (EDDCG) during machining of cemented carbides material. The experiments are carried out on a self-developed electrical discharge diamond grinding setup in cut-off mode, In the present work four input parameters ( current, pulse on-time, duty factor and wheel RPM ) were selected in which each parameter was at three levels. The total degree of freedom (dof) has been calculated without considering the effects of interaction among the different control factors. Based on design of experiments (DOE), a standard L9 orthogonal array (OA) was taken for experimentation. The result shows the considerable improvement of 13.999dB in multiple S/N ratio as compared to initial condition. Also, the comparison of results from single and multi-objective optimization has been presented.

Abstract: Use of common parts for different products (commonality) is important methods for managing product variety and preserving competitiveness in the age of mass customization and supply chain competition. In literature, the advantages of inclusion of common components in a product family are well established. Unfortunately, most of the works have been conducted via simulation or conceptual thinking. The mathematical models in the premises are not adequate for production, planning and control in multistage production. This paper focuses on the advancement of venerable manufacturing resources planning models by incorporating the part commonality concept in a multiproduct, multi-period and multistage manufacturing system under a deterministic situation. The models are validated with established MRPII models. The material requirement schedule for the basic MRP II and proposed models are compared. It is really a good matching shown between the two schedules. The later bearing additional information of the location where to be available the parts in a time frame. The effects of commonality on cost, capacity and requirement schedule are discussed based on the outcomes of the mathematical models executed with the available live data.

Abstract: Energy conservation and its efficient use are nowadays a major issue. The evident reduction in oil reserves combined with the increase in its price, as well as the need for ‘cleaner’ fuels, have led in the past years to an increasing interest and research in the field of alternative fuels for spark ignition engines propulsion. Also, there are interesting to increase the technical focus on conventional cycles for making them more optimum in terms of performance. In this study, a comparative performance analysis and optimisation have been performed for irreversible Otto cycle with ethanol, methanol and gasoline fuels. The results show that the maximum power output, the working range of the cycle, the optimal power output corresponding to maximum thermal efficiency, the optimal thermal efficiency corresponding to maximum power output increase, the compression ratio at the maximum power output and the compression ratio at the maximum thermal efficiency when ethanol-engine operation is changed to gasoline-engine operation. The results obtained in this work can help us to understand how the power output and thermal efficiency are influenced by ethanol and gasoline fuels in an Otto engine.

Abstract: Today, the world community is looking for fuel efficient and environmentally viable alternatives for many of the traditional energy conversion approaches. This development has further worked to increase the technical focus on conventional cycles for making them more optimum in terms of performance. Hence, the objective of this paper is to study the effect of ethanol-air equivalence ratio on the power output and the indicated thermal efficiency of an air standard Otto cycle. Optimization of the cycle has been performed for power output as well as for thermal efficiency with respect to compression ratio. The results show that the maximum power output, the optimal compression ratio corresponding to maximum power output point, the optimal compression ratio corresponding to maximum thermal efficiency point and the working range of the cycle first increase and then decrease as the equivalence ratio increases. The result obtained herein provides a guide to the performance evaluation and improvement for practical Otto engines.

Abstract: Dielectric properties of proton conducting polymer electrolyte system, containing polyethylene oxide (PEO) as host polymer and ammonium hexfluorophosphate (NH₄PF₆) as complexing salt plasticized with EC and EC:PC, are investigated. The free standing films of thickness ~ 200 - 300µm are synthesized by solution casting technique. The electrical conductivity studies show that plasticization of the polymer electrolyte results into an enhancement in its conductivity by about two orders of magnitude. The maximum room temperature bulk conductivity is obtained to be ~ 10^-5 S/cm for the plasticized polymer electrolyte. To understand the ion transport mechanism, different frequency dependent parameters are measured like dielectric permittivity, loss tangent and AC conductivity. The ionic transference number of the prepared systems is found to be close to unity which shows ion dominant charge transport in the electrolyte system. The conductivity of the polymer electrolyte has been found to be very sensitive to the relative humidity, which makes it a good candidate for its application for humidity sensor.

Abstract: This paper considered two organisms competing for a nutrient in the chemostat in the presence of an inhibitor, where the yields and growth rates are general increasing function of the nutrient concentration. The inhibitor is produced by one organisms and is lethal to the other organism. By the theory of qualitative analysis for ordinary equations, first, conditions of the existence and local stability of the rest points are obtain; then the global asymptotical stability, the existence of limit cycles and Hopf bifurcation are discussed.

Abstract: The polarization-voltage (P-V) and leakage currents density (J-V) characteristics were investigated on the ferroelectric PZT films deposited on Pt/Al2O3/SiO2/Si substrate with a vapor-deposited gold top electrode. The P-V hysteresis loops and the J-V characteristics were measured after performing a rapid thermal annealing (RTA) process. A ferroelectric test system (Precision LC Radiant Technology) was used to measure their electrical properties with a 90-nm PZT thickness and an area of 7.85 x10-5 cm2. The measurements were taken by connecting a Pt bottom electrode to the drive of the precision LC and the Au top electrode to the drive of the precision LC. The P-V hysteresis and J-V characteristics of PZT samples showed the asymmetry for both measurements. The asymmetric hysteresis loops and leakage current behavior were shifted in the positive direction when the drive was applied to the Pt electrode, while being negatively shifted in the converse case. The asymmetric behavior of the polarized state in the hysteresis loops due to the electrode configuration resulted from different work function between the Pt and Au electrodes, further influencing the leakage current behavior.

Abstract: The Galton´s board is a periodic lattice with fixed nails at its nodes, spherical grains travel through them due to gravity. This system is commonly used to show the central limit theorem when a big quantity of grains fall down from the upper edge. We show the convenience of this system to present the main concepts of Markovian-stochastic motion of only one particle.

Abstract: In the age of technology, with smaller and smaller electronic components being used in a growing number of applications, one pertinent application of mathematics and physics is the study of superconductivity. Superconductive materials are capable of conducting electricity without any resistance and were first discovered by Kamerlingh Onnes in 1911 in a compound He at 4.2 K in what was to prove to be one of the most significant scientific breakthroughs of the 20th Century. Superconductivity and Magnetism are mutually exclusive to each other but the coexistence of both the phenomena leads to very interesting research of superconductivity at room temperature. In this paper, we have studied the effect of ferromagnetic and antiferromagnetic interactions on the superconducting transition temperature.