http://nopr.niscair.res.in/handle/123456789/3301 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/7303 Title: Two different methods for improving the properties of IC-221M alloy <br/> <br/>Authors: Kamali, Ali Reza; Hadi, Morteza; Nazarian-Samani, Masoud <br/> <br/>Abstract: The formation of the Ni-Ni₅Zr eutectic structure is the most important reason for the impoverished mechanical properties of the Ni₃Al-based alloy containing Zr. On the other hand, this low melting point phase has a positive effect on castability of the alloy. Two different methods are used in this study for the development of a Ni₅Zr-free structure. In the first method, arc remelting process, using Mo₃Al₈, ZrAl₃and NiAl master alloys, followed by a proper heat treatment led to the production of a modified Ni₃Al-based alloy. In the second method, a powder metallurgy process is used to replace the casting method, thereby, lifting the need for Zr addition. A Ni₃Al-based alloy containing Mo, Cr, and B is produced via mechanical alloying followed by hot pressing densification. The alloys thus produced are studied for their improved yield strengths. <br/> <br/>Page(s): 449-455 Sat, 28 Nov 2009 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/7302 Title: Free vibration of layered annular circular plate of variable thickness using spline function approximation <br/> <br/>Authors: Viswanathan, K K; Sheen, Dongwoo <br/> <br/>Abstract: Free vibration of layered annular circular plate of variable thickness, made up of isotropic or specially orthotropic materials, is studied using spline function approximation by applying the point collocation method. Three different thickness variations are considered, namely, linear, exponential and sinusoidal, along the radial directions. The equations of motion are derived by extending Love’s first approximation theory. A system of coupled differential equations, in terms of longitudinal, circumferential and transverse displacement functions is obtained by assuming the solution in a separable form. These functions are approximated by using Bickley-type splines of suitable orders. A generalized eigenvalue problem is obtained by applying a point collocation technique with suitable boundary conditions, from which the values of a frequency parameter and the corresponding mode shapes of vibration, for specific values of various parameters, are obtained. <br/> <br/>Page(s): 433-448 Sat, 28 Nov 2009 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/7301 Title: A new method to predict activation energies of nitroparaffins <br/> <br/>Authors: Keshavarz, M H <br/> <br/>Abstract: A novel relationship has been derived to predict the activation energies (<i style="">E</i>_a) of low-temperature non-autocatalyzed thermolysis of nitroparaffins through suitable combination of elemental composition. The new correlation of <i style="">E</i>_a is based on the experimental data using the isothermal monomethric method, which is useful method to examine the kinetics of thermolysis of energetic materials in vacuum. The new method uses the optimized number of carbon, hydrogen and oxygen divided by molecular weight of nitroparaffins to obtain a reliable correlation. The new correlation is a general relationship because it can be applied for various nitroparafifins as compared to previous method which uses oxygen balance for some specific groups of mentioned compounds. <i style="">R</i>-squared value or the coefficient of determination of the new correlation is 0.954. <br/> <br/>Page(s): 429-432 Sat, 28 Nov 2009 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/7300 Title: Thermolysis of pyridinium perchlorate salts <br/> <br/>Authors: Srivastava, Pratibha; Kapoor, I P S; Singh, G <br/> <br/>Abstract: Three perchlorate salts of pyridine have been prepared and characterized by gravimetric and elemental analyses. Thermogravimetry (TG) and differential thermal analysis (DTA) have been carried out in static air, to examine the thermal decomposition process of these salts. Isothermal TG of these salts have been done to evaluate the kinetics of thermal decomposition in the temperature range 290-410^oC using both model fitting and isoconversional methods. Isoconversional method has been found to be superior over conventional model fitting method and is able to describe the decomposition process of these salts. Moreover, Explosion delay (<i style="">D</i>_E) measurements have been carried out to investigate the response of the salts under the condition of rapid heating. <br/> <br/>Page(s): 423-428 Sat, 28 Nov 2009 22:58:59 GMT