NOPR Collection:

An analytical study of vibration neutralizers

Fri, 01 Oct 1999 00:00:00 GMT

Title: An analytical study of vibration neutralizers Authors: Khalil, Gazi Md.; Islam, Md. Shahidul Abstract: A machine or structure on which a steady alternating force of constant frequency is acting may take up obnoxious vibrations, especially when it is close to resonance. One method of reducing the vibration under such conditions is to use a vibration damper or neutralizer. This paper presents a detailed mathematical analysis of the principle of vibration neutralizers. The results are presented in terms of non-dimensional parameters for explaining the salient features of vibration neutralizers. It is shown that the vibration damper exercises its effect in neutralizing vibrations when its own natural frequency matches with that of the exciting force. Furthermore, the motion of the vibration neutralizer depends on the mass ratio (neutralizer mass/main mass). The higher the mass ratio the lower is its motion. Hence, an appropriate mass ratio should be chosen for keeping the motion of the neutralizer within reasonable limits. Page(s): 256-262

Reducing generation times for large optical orthogonal codes

Fri, 01 Oct 1999 00:00:00 GMT

Title: Reducing generation times for large optical orthogonal codes Authors: Kar, S; Mehta, R; Shah, L Abstract: A (n,w,λ)-optical orthogonal code(OOC) is a family of (0,1) sequences of length n and constant Hamming weight w that have both out-of phase auto-correlation and cross-correlation not exceeding λ. We discuss the optimal codes for λ=2. Some of the new generated codes for large number of users are presented. The algorithm to develop those codes and some generalizations are also given. Some very large size codes generated by using projective geometry are tabulated and methods for fast generation of the codes are also discussed. Page(s): 289-291

Studies on exhaust emissions in semi-adiabatic compression ignition engine with alternate fuels

Fri, 01 Oct 1999 00:00:00 GMT

Title: Studies on exhaust emissions in semi-adiabatic compression ignition engine with alternate fuels Authors: Reddy, Ch Venkata Ramana; Krishna, M V S Murali; Prasad, C M Vara Abstract: Alcohols (ethanol and methanol) and a few non-edible vegetable oils are showing a great potential for replacing conventional diesel fuels quite effectively. The low heat rejection semi-adiabatic compression ignition (C.I.) engines are gaining prominence for adopting these alternate fuels. The major pollutants of the exhaust emissions of C.I. engines are oxides of nitrogen (NO_x) and black smoke. When alcohols are used as alternate fuels, the pollutants have to be checked specifically for aldehydes which are carcinogenic in nature. The pollution levels of black smoke, NO_x and aldehydes emitted through exhaust of engine are reported here on both conventional and insulated versions of C. I. engines with different proportions of ethanol-diesel and methanol-diesel mixtures. The non-edible vegetable oils crude, and esterified jatropha and pongamia oils are used for total replacement of diesel fuel on both configurations of the engine. The NO_x and smoke levels have been found to be lower with both ethanol and methanol induction with both conventional and insulated versions of the engine in comparison to pure diesel operation. Also, production of aldehydes in the form of formaldehyde has been found to increase with both ethanol and methanol operations. However, the insulated version of the engine with ethanol operation helps in reducing formaldehyde emissions of the engine. With the non-edible vegetable oils, generation of smoke is drastically increased in comparison to pure diesel operation. However, with preheating of vegetable oil and increased injection pressure, the smoke levels get reduced and NO_x levels increase marginally. Page(s): 249-255

Rheological studies on mineral wool fibre reinforced PP/HDPE blend

Fri, 01 Oct 1999 00:00:00 GMT

Title: Rheological studies on mineral wool fibre reinforced PP/HDPE blend Authors: Chand, Navin; Vashishtha, S R Abstract: Mineral wool (MW) fibre reinforced polypropylene (PP)/high density polyethylene (PP/HDPE) blends have been developed by varying mineral wool fibre loading ranging from 5 to 15 wt%. Rheological data on reinforced blends are obtained by using a capillary rheometer at 220°C in shear rate ranging from I to 10³ s^-1. It has been found that incorporation of mineral wool fibre in to PP/HDPE blends increases the melt viscosity and reduces the recoverable shear strain (S_R). Also, the shear rigidity (G) increases with the increase of mineral wool fibre loading. Page(s): 292-296