Showing papers by "Indian Institute of Technology Kharagpur published in 1988"

Miscible blends from rigid poly(vinyl chloride) and epoxidized natural rubber

Abstract: Mechanical properties and fracture of melt-blended poly(vinyl chloride) (PVC) and epoxidized natural rubber (ENR) having 50 mol % epoxidation level are studied at different compositions. The effect of blend ratio on tensile strength, tear strength, elongation at break, tension set after failure, and hardness are determined. The stress-strain behaviour of low ENR blends exhibits yielding and necking, whereas that of high ENR blends exhibits soft elastomeric deformation. At higher compositions of ENR, plots of tensile strength, tear strength, and hardness against blend composition are concave in nature; and plots of the elongation at break deviate markedly from the additive value with a pronounced maximum occurring at the 70wt% composition of ENR. The scanning electron microscopic examination of fracture surfaces of blends does not show any features of phase separation of ENR or PVC. The tensile fracture surface of rigid PVC exhibits partially fused particle structures of PVC and that of blends exhibits features of shearing and horizontal discontinuous striations. The torn surface of rigid PVC shows evidence of intrinsic crazing and that of blends shows features of shear fibrils, vertically changed discontinuous striations, steps, and unstable and stable tear fronts.

Rheological and drag reduction characteristics of xanthan gum solutions

Abstract: The rheological and turbulent drag reducing characteristics of commercial and purified xanthan gum solutions of concentrations 50–500 ppm have been studied with and without addition of 100 ppm NaCl. The purification by soxlet extraction of xanthan gum using 95% ethanol is effective in removing low-molecular-weight impurities from xanthan. The increased content of higher molecular-weight xanthan in purified xanthan is evident from rheological and drag reduction behavior. The addition of 100 ppm salt to dilute solutions introduces semi-flexibility in xanthan gum solution without occurrence of self-association. The change in molecular behavior in the presence of salt is evident from rheological normal-stress and turbulent drag reduction behaviors.

Effect of green manuring and mineral fertilizer on growth and yield of crops in rice-based cropping on acid lateritic soil

Abstract: Green manuring in situ with sunnhemp (Crotalaria juncea) and dhaincha (Sesbania aculeata) significantly improved growth and yield of transplanted rice. Giving the green manure crops 15 kg N/ha or 15 kg N and 30 kg P2O5/ha further increased yield. Interaction between green manuring and N fertilizer revealed that a considerable quantity of fertilizer N (45–60 kg N/ha) applied to rice could be replaced by incorporation of green manure crops to which a small amount of fertilizer had been applied. Residual fertility in terms of organic carbon and available N, P and K increased under green manuring, whereas N fertilizer made no impact on fertility build up. Grain yield of wheat and gram increased when grown after rice in plots which had grown green manure.

Fuzzy goal programming in multi-criteria decision systems: A case study in agricultural planning

Abstract: This paper proposes a general Fuzzy Goal Programming (FGP) methodology involving pre-emptive priorities and fuzzy goals which can be applied to tackle Multi-Criteria Decision Systems (MCDS) with imprecise parameters. Specifically, it emphasizes certain assumptions about the psychology of the decision system (DS) where the dynamic involvement of the decision-maker (DM) is highlighted. The methodology, which is mostly DM oriented, is applied to a case study of a tube-well command area planning. The results demonstrate that (i) the DM normally satisfices rather than optimizes and (ii) the output of a DS is his best acceptable course of action.

Dielectric properties of LaPO4 ceramics

Abstract: Dielectric constant (K) and loss (tanδ), and hence conductivity (σ), have been measured for LaPO4 ceramics prepared by a molten urea process in the frequency region 102 to 107 Hz and in the temperature range −193 to 280° C. At room temperature (≈ 30°C),K decreases with frequency up to 105 Hz, beyond which it attains a constant value; tanδ behaves in a similar way. The values ofK and tanδ at 30°C and 106 Hz for this material are 14 and 2.7 × 10−3, respectively. As a function of temperature,K exhibits two stages of increase: (i) a slow stage up to −30° C and (ii) a fast one beyond −30° C which is considerably frequency dependent,K having larger values at lower frequencies. Similar behaviour is exhibited by tanδ. Plots ofσ against 1/T for LaPO4 exhibit the usual extrinsic and intrinsic regions; the activation energy for conduction in the intrinsic region is calculated to be 0.61 eV. It seems possible to understand the results through space charge polarization effects due to lattice defects in LaPO4.

Flow through blood vessels under the action of a periodic acceleration field:A mathematical analysis

Abstract: The paper is devoted to an analytical study of flow through blood vessels subjected to a periodic acceleration field. The analysis consists of two parts. In the first case, the wall is treated as a non-linear orthotropic elastic cylindrical membrane and the blood as a Newtonian viscous fluid, while in the second case the experimentally observed material damping properties of the wall tissues and the viscoelasticity of blood have been incorporated in the analysis. In each of these two cases, analytical expressions for the displacement and shear stresses developed in the wall as well as the velocity distribution, fluid acceleration and volume flow rate of blood are derived. The influence of material damping of the wall tissues as well as the viscoelastic properties of blood on the flow and deformation characteristic of a blood vessel has been estimated by using the values of the different material constants (involved in the analysis) determined experimentally for the human abdominal aorta. Numerical results presented in the paper correspond to observed parameters of the circulatory system of living animals.

Threshold Fracture of Elastomers

Abstract: Fracture of an elastomer starts from small flaws where the local stress exceeds a critical limit for tearing. A criterion for the onset of tearing can be conveniently described in terms of a characteristic energy or a tearing energy which defines the fracture property and is independent of the form of the test piece.

A two-dimensional analytical model of threshold voltages of short-channel MOSFETs with Gaussian-doped channels

Abstract: A two-dimensional analytical model for the threshold voltage of a short-channel MOSFET with a Gaussian-doped channel has been developed. The Gaussian profile has been simulated by a novel integrable function. This makes possible a purely analytical solution of the two-dimensional Poissons equation in the channel region of the MOSFET. >

Polymers from renewable resources. XII: Structure property relation in polyamideimides from Rosin

Abstract: Polyamideimides were synthesized from rosin maleic anhydride adduct either by reacting the acid chloride of the latter with different diamines or by self-polycondensation of rosin imido amino acid in the presence of thionyl chloride The rosin imido amino acids were prepared by condensing rosin-maleic anhydride adduct with diamines The presence of lithium chloride was found to have pronounced effect on yield and molecular weight of the polymers The polyamideimides were characterized by infrared, elemental analysis, and viscosity measurements The polymers were either amorphous or poorly crystalline in nature and soluble only in highly polar solvents The thermal stability of the polymers has been studied Some generalizations about structure-property relation in polyamideimides were made

Vibratory Conveying by Non-Sinusoidal Excitation

Abstract: A vibratory conveyor is essentially an inclined plane which is subjected to an acceleration cycle, conventionally sinusoidal. It is used to transport components or material. Usually rapid upward motion is desired. This paper presents the results of an investigation on the performance of a vibratory conveyor excited by two in-phase non-sinusoidal displacement cycles composed of the first two harmonics along the trough and perpendicular to it. Mean conveying velocity is found to be considerably larger than that of conventional vibratory conveyers if the proper amplitudes of the second harmonics are chosen.

Effect of combinations of organic materials and nitrogen fertilizer on growth, yield and nitrogen uptake of rice

Abstract: In a 2-year study, the growth and yield of lowland rice increased significantly with the combined use of organic materials and N fertilizer in an acid-lateritic soil. Application of farmyard manure (FYM) or water hyacinth compost (WHC) at 10 t/ha along with paddy straw (PS) at 2·5 t/ha increased grain yield by 28%, similar to the increase given by 30 kg N/ha as fertilizer. The combination of FYM and WHC with or without PS produced yields equivalent to those using 50–60 kg/ha N as fertilizer urea. Uptake of N increased but the recovery of applied N decreased both with the application of organic materials and with increasing N. Organic materials considerably improved the fertility status of the soil, as measured by % C and available N, after crop harvest, whereas N fertilizer made no impact on fertility build-up.

The reaction garnet+clinopyroxene+quartz =2 orthopyroxene+anorthite: A potential geobarometer for granulites

Abstract: A mineralogic geobarometer based on the reaction garnet+clinopyroxene+quartz=2 orthopyroxene+anorthite is proposed. The geobarometric formulations for the Fe- and Mg- end member equilibria are $$\begin{gathered} P_{({\text{Fe}})} {\text{ }}({\text{bars}}){\text{ = 32}}{\text{.097 }}T{\text{ }} - {\text{ 26385 }} - {\text{ 22}}{\text{.79 (}}T - 848 - T1{\text{n(}}T/848{\text{))}} \hfill \\ {\text{ }} - (3.655 + 0.0138T){\text{ }}\left( {\frac{{{\text{(}}T - 848{\text{)}}^{\text{2}} }}{T}} \right) \hfill \\ {\text{ }} - {\text{(3}}{\text{.123) }}T1{\text{n }}\frac{{(a_{a{\text{n}}}^{{\text{Plag}}} )(a_{{\text{fs}}}^{{\text{P}}\ddot u{\text{x}}} )^2 }}{{(a_{{\text{alm}}}^{{\text{Gt}}} )(a_{{\text{hed}}}^{{\text{Opx}}} )}} \hfill \\ P_{({\text{Mg}})} {\text{ (bars) = 9}}{\text{.270 }}T + 4006 - 0.9305{\text{ }}(T - 848 - T1{\text{n (}}T/848{\text{)}}) \hfill \\ {\text{ }} - (1.1963{\text{ }} - {\text{ }}6.0128{\text{ x 10}}^{ - {\text{3}}} T)\left( {\frac{{(T - 848)^2 }}{T}} \right) \hfill \\ {\text{ }} - 3.489{\text{ }}T1{\text{n }}\frac{{(a_{an}^{{\text{Plag}}} ){\text{ }}(a_{{\text{ens}}}^{{\text{Opx}}} )}}{{{\text{(}}a_{{\text{pyr}}}^{{\text{Gt}}} {\text{) (}}a_{{\text{diop}}}^{{\text{Cpx}}} {\text{)}}}}. \hfill \\ \end{gathered}$$ The end member thermodynamic data have been taken from the data base of Helgeson et al. (1978) and Saxena and Erikson (1983). The activities of pyroxene components and anorthite in plagioclase have been modelled after Wood and Banno (1973) and Newton (1983) respectively. The activities of pyrope and almandine are calculated from the binary interaction parameters for garnet solid solutions proposed by Saxena and Erikson (1983).

Growth and Yield of Peanut as Influenced by Degree and Duration of Shading

Abstract: Peanuts (Arachis hypogaea L.) which are commonly grown in intercropping systems often suffer from shading caused by the associated crop. Through this study an attempt has been made to estimate the effect of different levels of shade at different growth stages on crop yield. Field experiments were laid out during monsoon and winter seasons of 1985 and 1986 by creating artificial shading up to 25 and 50 per cent of the day/natural light at flowering-pegging, pod filling and maturity stages of a Spanish bunch type peanut. Dry matter production has shown linear response to light intensity and due to 50 per cent shading it was reduced by 55 per cent. Vegetative growth rate during pod filling stage was very poor as a result of increase in shading at this stage. In shaded plants the nodulation was less and some reduction in chlorophyll content was also observed. However, oil content in kernel was not affected by shading. Shading caused significant reduction in pod number and kernel weight and thus there was decrease in pod yield. Flowering to pegging and pod filling stages seemed to be sensitive to shading while increase in shading at maturity stage did not cause any reduction in yield. It could be possible to obtain about 90 per cent pod yield by avoiding shading during flowering to pegging stage (45 DAS).

Analysis of coupled cylindrical striplines filled with multilayered dielectrics

Abstract: A method of analysis for coupled cylindrical striplines filled with multilayered dielectrics is presented that uses a variational technique in the space domain Coupled-mode analysis is presented for the case of a pair of coupled circular arc strips arbitrarily located between cylindrical ground planes filled with multilayered dielectrics An even and odd-mode approach is used for the analysis of shielded cylindrically curved edge-coupled pairs of broadside parallel strips (broadside, edge-coupled cylindrical striplines) The effect of environmental changes on an otherwise planar structure is also studied by extending the present analysis to cylindrically warped coupled striplines >