NOPR Collection:

Effect of uniaxial cyclic compression on the mechanical behavior of rocks

2016-07-20T06:00:49Z

Title: Effect of uniaxial cyclic compression on the mechanical behavior of rocks Authors: Singh, T N; Ray, S K; Singh, D P Abstract: This paper mainly deals the mechanical behavior of Chunar sandstone under cyclic loading. Compressive strength decreases as the number of cycles increases from 90.62% at 100 cycles to 65.50% at 600 cycles. Results indicate that rocks are significantly weakened by cyclic loading. Page(s): 118-120

Non-linear instability of capillary-gravity waves in the presence of an air stream

2016-07-20T05:59:32Z

Title: Non-linear instability of capillary-gravity waves in the presence of an air stream Authors: Chhabra, R K; Khosla, H K Abstract: Using multiple time scale method, the weakly non-linear waves on the interface between a liquid layer and a subsonic gas flowing parallel to the undisturbed interface are investigated The evolution of the complex amplitude of a quasi-monochromatic progressive wave is shown to be governed by a nonlinear Schrodinger equation (NLSE). The wave train of constant amplitude is unstable against modulation. On the other hand, the amplitude of the standing wave near the cut-off is governed by a NLSE in which the roles of time and space variables are interchanged This equation makes it possible to determine the non-linear cut-off wave number. Page(s): 111-117

Study of the reliability and accuracy of thermistors for temperature measurements using transportable mercury triple point cells

2016-07-20T05:58:37Z

Title: Study of the reliability and accuracy of thermistors for temperature measurements using transportable mercury triple point cells Authors: El-Sayed, NI; Megahed, F M; Ammar, M M Abstract: The triple point of high purity mercury filled in small sealed cells of borosilicate glass has been determined by using calibrated thermistors. The aim of the work is to check the accuracy of temperature measurement by using thermistors below zero degrees Celsius. Two small sealed cells were used. The first was filled with mercury purified at the thermometery laboratory of the National Institute for Standard (NIS) by chemical treatment followed by triple distillation (NIS sample). The second cell was filled with mercury of purity 99.9999% obtained from the National Institute for Standards and Technology (NIST), USA (NIST sample).The values obtained for the triple point of mercury are: -38.833±6.4 x 10^{-3 o}C and -38.834±6.4 x 10^{-3 o}C for the NIS and NIST samples, respectively. These two values are in good agreement with each other and reproduce well the value adopted by the International Temperature Scale of 1990 (ITS-90) for the triple point of mercury, which is -38.8344.C. The results obtained indicate that the method of purification used in the present work is suitable to obtain mercury of purity better than 99.999%. It indicates also that thermistors can be used for precise temperature measurement below zero degrees Celsius. Page(s): 107-110

Phosphorylated CNSL prepolymer as a foundry sand core binder

2016-07-20T05:57:33Z

Title: Phosphorylated CNSL prepolymer as a foundry sand core binder Authors: Biswas, P K; Balagopal, N.; Pillai, C K S Abstract: The performance of phosphorylated cashew-nut shell liquid prepolymer (PCNSL) as a core binder in foundry applications is studied. Moulding properties such as strength and permeability and casting characteristics such as surface quality of castings, core-metal reactions, core collapsibility and anti-damping behaviour are analyzed. PCNSL gave superior performance in all these factors when compared to other system of binders such as sodium silicate. Studies based on IR spectra and SEM on the nature of bonding between sand and PCNSL indicate involvement mostly of physical and mechanical interactions rather than chemical bonding. The formation (during casting) of higher content of char (due to the presence of phosphate group in the resin) with open porous structure as revealed by SEM is thought to give better collapsibility to the system. Page(s): 99-106