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Usman, Ali,Ahmad Cheema, Taqi,Woo Park, Cheol SAGE Publications 2015 Proceedings of the Institution of Mechanical Engin Vol.229 No.12
<P>The interface between piston ring and cylinder liner is lubricated with an oil film to improve wear resistance and operating life of the engine. The high combustion pressure, variable loadings, manufacturing errors, and thermal distortions in the engine cylinder deform the cylinder liner, thus making a significant effect on the lubricant performance. To investigate the effects of cylinder liner deformation on the piston ring lubrication, a 2D model of elastohydrodynamic lubrication under fully flooded conditions was considered. Various elliptically deformed profiles of the cylinder liner were tested to evaluate conformability, lubricating film thickness, friction, power loss, and lubrication flow rate for a complete four-stroke engine cycle. Comparative analysis of the simulation results was conducted to evaluate the dependency of engine performance on deformed bore shape. Results showed that the lubricating film thickness and engine performance parameters strongly depend on the cylinder liner shape and the degree of distortion.</P>
Usman, A.R.A.,Almaroai, Yaser.A.,Ahmad, M.,Vithanage, M.,Ok, Y.S. Elsevier Scientific Pub. Co 2013 Journal of hazardous materials Vol.262 No.-
Chelating agents added to contaminated soils may increase solubility and phytoextraction efficiency of soil metals. However, they can create negative effects on soil biological quality. A 90-day incubation experiment was conducted to evaluate mixed effects of chelating agents and poultry manure on changes in available Cd, Pb and As, CO<SUB>2</SUB>-C efflux, microbial biomass C, dissolved organic C (DOC), and N mineralization in metal-polluted agricultural soil. Application of poultry manure resulted in a considerable increase in soil pH, DOC, CO<SUB>2</SUB>-C efflux, net N mineralization, net N nitrification, and microbial biomass C compared to those in unmanured soil. Availability of arsenic increased twice in manure amended soil due to changes in pH and DOC. However, adding poultry manure did not affect the concentrations of available Pb and Cd compared to those in control soil. Chelating agents increased CO<SUB>2</SUB>-C efflux, DOC, and metal availability but decreased microbial biomass C and net N mineralization. Maximum decrease in microbial biomass C, net N mineralization, and net N nitrification, was observed in EDTA applied soil possibly due to high metal availability to soil microorganisms. Overall results revealed that the application of synthetic chelators in combination with poultry manure enhances available As and demonstrates better environment for soil biota.
SYSTEM OF MIXED VARIATIONAL INEQUALITIES IN REFLEXIVE BANACH SPACES
Ahmad, Rais,Usman, Farhat The Korean Society for Computational and Applied M 2009 Journal of applied mathematics & informatics Vol.27 No.3
In this paper, we introduce and study a system of mixed variational inequalities in Banach spaces. By using J-proximal mapping and its Lipschitz continuity for a nonconvex, lower semicontinuous, subdifferentiable, proper functional, an iterative algorithm for computing the approximate solutions of system of mixed variational inequalities is suggested and analyzed. The convergence criteria of the iterative sequences generated by iterative algorithm is also discussed.
Ahmad, Zubair,Din, Nasir Ud,Memon, Aisha,Tariq, Mohammad Usman,Idrees, Romana,Hasan, Sheema Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.3
Background: Central neurocytomas are rare neuronal neoplasms with a favorable prognosis. They are typically located in the lateral ventricles of the brain and mostly histologically correspond to WHO grade II with a Mib 1 labelling index of <2%. Similar tumors located in the cerebral hemispheres and spinal cord, for example, are called "extraventricular neurocytomas". A few tumors histologically show atypia, mitoses, vascular proliferation and/or necrosis and a Mib 1 index >2 % and are designated as "atypical neurocytomas. Aim: The aim of our study was to describe the common as well as unusual morphologic features and the role of various immunohistochemical stains in the diagnosis of these rare tumors. Materials and Methods: We retrieved and reviewed 35 cases diagnosed between 2001 and 2015. Results: Sixty percent of patients were males, and the mean age was 26 years. 31 cases (88.6%) were intraventricular and 4(11.4%) were extraventricular. Histologically, 6 cases (17.1%) were compatible with "atypical neurocytomas". All cases showed the classic morphology comprising nests and sheets of uniform, round cells with uniform round to oval nuclei with finely speckled chromatin and perinuclear cytoplasmic clearing (halos). All cases also showed delicate, fibrillary, neuropil-like matrices. Other common histologic features included capillary-sized blood vessels in a branching pattern in 57.1%, foci of calcification in 34.3% and perivascular pseudorosettes in 20%. Rare findings included Homer-Wright or true rosettes in 8.6% and ganglioid cells in 2.9%. Synaptophysin was the most consistent and valuable marker, being positive in almost all cases. GFAP positivity in tumor cells was seen in 25.7% of cases. Follow up was available in 13 patients. Of these 9 had histologically typical and 4 had atypical tumors. Only 1 (with an atypical neurocytoma) died, probably due to complications of surgery within one month, while 12 (including 3 with atypical neurocytomas) remained alive. Recurrence developed in 1 of these 12 patients (histologically consistent with typical morphology) almost 9 years after surgery. Only 4 patients, including 2 with atypical tumors, received postoperative radiotherapy, all with surgery in 2010 or later. Overall, prognosis was excellent with prolonged, recurrence free survival and most patients, even without receiving radiation therapy, were alive and well for many years, even a decade or more after surgery, without developing any recurrence, indicating the benign nature of these neoplasms.
Mahtab Ahmad,Adel R.A. Usman,이상수,Sung-Chul Kim,Jin-Ho Joo,양재의,옥용식 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.1
Rapid industrialization in Korea has led to the discharge of heavy metals to water, posing a threat to the environment. The use of natural materials as low cost sorbents for the removal of heavy metals from aqueous solutions has recently received increasing attention. The present study was conducted to evaluate the effectiveness of eggshell and coral wastes for the removal of Pb2+, Cd2+ and Cu2+ from aqueous solutions. Batch equilibrium experiments were conducted using heavy metal solutions with waste eggshell and coral powders. Langmuir and Freundlich adsorption models were used for the mathematical description of sorption equilibrium. The maximum amounts of metals (Cu2+, Pb2+ and Cd2+) adsorbed were found to be 32.3, 22.9 and 4.47 mmol kg1 for eggshell and 6.77, 5.52 and 1.03 mmol kg1 for coral wastes,respectively. At low initial concentrations the adsorption of heavy metals onto both sorbents can be described as H-type (except for the Cd adsorption onto coral), indicating high-affinity isotherms and strong adsorbate–adsorptive interactions such as inner sphere complexes. However, the metal adsorption was described by L-type isotherm at high initial concentrations. Based on the distribution coefficient (Kd) values and the percentage of metal removed, the selectivity sequence in eggshells and coral wastes was found to be Pb2+ > Cu2+ > Cd2+. The Kd values and the percentage of metals removed were higher in eggshells than coral with its higher capacity to adsorb heavy metals. Based on the results of the present study, eggshell and coral wastes can be used for the removal of heavy metals from aqueous solutions.
System of mixed variational inequalities in reflexive Banach spaces
Rais Ahmad,Farhat Usman 한국전산응용수학회 2009 Journal of applied mathematics & informatics Vol.27 No.3
In this paper, we introduce and study a system of mixed vari- ational inequalities in Banach spaces. By using J-proximal mapping and its Lipschitz continuity for a nonconvex, lower semicontinuous, subdifferen- tiable, proper functional, an iterative algorithm for computing the approx- imate solutions of system of mixed variational inequalities is suggested and analyzed. The convergence criteria of the iterative sequences generated by iterative algorithm is also discussed. In this paper, we introduce and study a system of mixed vari- ational inequalities in Banach spaces. By using J-proximal mapping and its Lipschitz continuity for a nonconvex, lower semicontinuous, subdifferen- tiable, proper functional, an iterative algorithm for computing the approx- imate solutions of system of mixed variational inequalities is suggested and analyzed. The convergence criteria of the iterative sequences generated by iterative algorithm is also discussed.