Showing papers by "Indian Institute of Technology Kharagpur published in 1969"

Large deflections of heated circular plates

Abstract: Large deflections of heated circular plates with or without a concentric circular hole and with different boundary conditions and temperature distributions are analyzed in the light ofBerger's analysis. The subject is treated in a simple and unified manner. Numerical results are shown in graphical form.

Dielectric Properties of Single Crystals of MnO and of Mixed Crystals of MnO/CoO and MnO/NiO

Abstract: Dielectric constant (K′), loss (K″), and conductivity (σ) of single crystals of MnO and solid solutions of MnO/CoO and MnO/NiO have been measured as a function of frequency in the range 102 to 107 Hz and at temperatures between 30 and 450 °C. The value for K′ of MnO at 30 °C is 18.1 and practically frequency-independent. In the solid solutions of MnO/CoO and MnO/NiO (50:50 composition) K′ decreases with frequency to a frequency-independent value of 16.4 and 14.4, respectively. The K″-values of the solid solutions are much larger at lower frequencies (compared to MnO). The larger values of K′ and K″ for the solid solutions at low frequencies are due to the space charge polarization. In all crystals, the dielectric constant increases with temperature but decreases with frequency. The dependence of the high-temperature dielectric constant on frequency is attributed to the creation and destruction of dipoles at such temperatures. log ΔK′ vs. 1/T plots (where ΔK′ is the difference between dielectric constant values at any temperature T and room temperature) are straight lines for these compounds giving activation energy values of 0.57, 0.41, and 0.35 eV for MnO, MnO/CoO, and MnO/NiO, respectively. The plots of log σ vs. 1/T also give straight lines for all the crystals studied, and one obtains activation energies of 0.6, 0.52, and 0.52 eV, respectively, for the above mentioned compounds. The proximity of these activation energy values for the two processes suggest that the same charge carriers are responsible for changes in K′ and K″. The lower activation energy for the solid solutions is attributed to lattice distortion. In solid solutions, the room temperature conductivity exhibits a maximum — and the activation energy for conduction a minimum — near the composition Mn0.9X0.1O (where X stands for Co or Ni) which is explained as being due to scattering of charge carriers at larger concentrations than 10% for X. Die komplexe Dielektrizitatskonstante (K′ und K″) und die Leitfahigkeit (σ) wurden an MnO-Einkristallen und an MnO/CoO- und MnO/NiO-Mischkristallen als Funktion der Frequenz in Bereich von 102 bis 107 Hz bei Temperaturen von 30 bis 450 °C gemessen. Der Wert fur K′ betragt fur MnO bei 30 °C 18,1 und ist praktisch frequenzunabhangig. In den Mischkristallen MnO/CoO und MnC/NiO (Zusammensetzung 50:50) nimmt K′ mit der Frequenz auf einen frequenzunabhangigen Wert von 16,4 bzw. 14,4 ab. Im Vergleich zu MnO sind die K″-Werte der Mischkristalle bei niedrigen Temperaturen viel groser. Die groseren Werte von K′ und K″ fur die Mischkristalle bei niedrigen Frequenzen werden durch eine Raumladungspolarisation hervorgerufen. In allen Kristallen steigt die Dielektrizitatskonstante mit der Temperatur an, fallt jedoch mit der Frequenz ab. Die Abhangigkeit der Dielektrizitatskonstante von der Frequenz wird der Erzeugung und Vernichtung von Dipolen bei solchen Temperaturen zugeschrieben. log ΔK′ uber 1/T-Kurven (wobei ΔK′ die Differenz der Dielektrizitatskonstanten bei der Temperatur T und Zimmertemperatur ist) sind fur diese Verbindungen Geraden und ergeben Aktivierungsenergien von 0,57, 0,41 und 0,35 eV fur MnO, MnO/CoO bzw. MnO/NiO. Die Kurven von log σ uber 1/T ergeben ebenfalls Geraden fur alle untersuchten Kristalle, und man erhalt Aktivierungsenergien von 0,6, 0,52 bzw. 0,52 eV fur die oben erwahnten Verbindungen. Die Ubereinstimmung dieser Aktivierungsenergien fur die beiden Prozesse weist darauf hin, das dieselben Ladungstrager fur die Anderungen von K′ und K″ verantwortlich sind. Die niedrigere Aktivierungsenergie fur die Mischkristalle wird Gitterstorungen zugeschrieben. Bei den Mischkristallen zeigt die Leitfahigkeit bei Zimmertemperatur ein Maximum — die Aktivierungsenergie fur die Leitfahigkeit ein Minimum — in der Nahe der Zusammensetzung Mn0.9X0.1O (wobei X fur Co oder Ni steht), was durch Streuung der Ladungstrager bei hoheren Konzentrationen als 10% fur X erklart wird.

Determination of chemical cross‐links in rubbers

Abstract: The cross-link density of dicumyl peroxide (DCP) vulcanizates of NR and SBR has been determined by the equilibrium swelling method. From a plot of elastically effective cross-links corrected for chain ends against the moles of DCP decomposed, the efficiency of crosslinking has been found. The values of g in the FLORY equation have been calculated at varying densities of cross-links, and it has been found that both the FLORY equation as well as other equations relating chemical cross-links to physical ones can be satisfactorily empolyed for the calculation of chemical cross-links from the physical cross-links determined by swelling measurement.

Combined free and forced convection effects on the magnetohydrodynamic flow through a channel

Abstract: Die freie Konvektion einer elektrisch leitenden Flussigkeit in einer horizontalen Kanalstromung in Anwesenheit eines homogenen vertikalen Magnetfeldes wird analysiert. Fur die Erwarmung der oberen Wand ergibt sich eine Neigung der Stromung zur Instabilitat. Der starke Einfluss des Magnetfeldes auf die Stromung wird diskutiert.

Hall Effect, Magnetic Resistivity, and Magnetic Susceptibility of Nickel and Nickel-Copper Alloys

Abstract: Hall-effect, electrical-resistivity, and magnetic-susceptibility measurements have been made on polycrystalline specimens of nickel-copper alloys. The temperature range covered is 100 to 700\ifmmode^\circ\else\textdegree\fi{}K. The spontaneous Hall coefficient ${R}_{p}$ in the paramagnetic region has been separated out by simultaneous measurement of the Hall resistivity per unit field and the atomic susceptibility. The magnetic resistivity of the same specimen has also been determined. It has been shown that, for pure nickel, intrinsic spin-orbit interaction provides the right order of magnitude of the spontaneous Hall coefficient ${R}_{p}$. A linear relationship between ${R}_{\mathrm{pi}}$, the impurity part of the paramagnetic Hall coefficient, and ${\ensuremath{\rho}}_{\mathrm{mi}}$, the impurity part of the magnetic resistivity, with a constant of proportionality 4.5 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}5}$ ${\mathrm{G}}^{\ensuremath{-}1}$, has been observed in alloys.

Studies on Dicumylperoxide Vulcanization of Natural Rubber in Presence of Sulfur and Accelerators

Abstract: The effect of sulfur, MBT, zinc oxide and stearic acid, either singly or in mixtures, on the DCP vulcanization of NR has been studied. In all cases DCP decomposes by a first order law, but...

Suspension of solids by bubble agitation

Abstract: Using fundamental aspects of the fluid mechanics of a single particle, a relation for the velocity of liquid necessary to suspend solid particles in a shallow depth column is derived. This liquid velocity is developed by the movement of the gas bubbles inside the column with the potential energy dissipated by the bubble during its ascent taken as the gain in the kinetic energy of the liquid. This energy brings about sufficient liquid motion to suspend the particles. The corresponding superficial gas velocity to suspend all the particles present in the column is theoretically estimated and compared to experimental values of superficial gas velocities obtained for various solids concentrations. A set pattern of deviation is observed, and empirical correlations are suggested for predicting the superficial gas velocity to suspend a given amount of solid particles in liquid.

Polymerization of N‐vinylearbazole with vanadium compounds. Part I. Polymerization with vanadium pentoxide and metal vanadates

Abstract: Bulk polymerization of N-Vinylcarbazole (NVC) has been carried out using vanadium pentoxide as the contact catalyst. The rate of polymerizatlon has been found to depend upon catalyst to monomer ratio. A cationic mechanism has been suggested and the role of V2O5 surface in the polymerization has been tentatively analyzed. The π-acid characteristies of V5⊕ ion is believed to be involved in initiating the polymerization. The effect of a number of additives on the polymerization rate has been studied, which endorses the cationic mechanism. The catalytic efficiency of a number of metal vanadates for the polymerization of NVC has also been studied. A fairly good correlation between the activity and electronegativity of the metallic moiety has been established. In Gegenwart von Vanadiumpentoxid als heterogenern Katalysator Wurde N-Vinylcarbazol (NVC) in Substanz polymerisiert. Die Polymerisationsgeschwindigkeit hangt vom Verhaltnis des Katalysators zum Monomeren ab. Es wurde ein kationischer Reaktionsmechanismus vorgeschlagen, und es wurde versucht, die Rolle der V2O5-Oberflache bei der Polymerisation aufzuklaren. Es wird vermutet, das die π-Saureeigenschaft des V5⊕-Ions bei der Initiierung der Polymerisation miteinbezogen werden mus. Die Wirkung einer Anzahl von Zusatzen auf die Polymerisationsgeschwindigkeit wurde untersucht; das Ergebnis bekraftigt die Annahme eines kationischen Verlaufs. Es wurde auch die katalytische Wirksamkeit einer Anzahl von Metallvanadaten bei der Polymerisation von NVC untersucht. Es ergab sich eine hinreichend gute Bezichung zwischen der katalytischen Wirksamkeit und dem elektronegativen Charakter des metallischen Bestandteils.

Synchronizing characteristics of a step motor

Abstract: Based on the analogy between the equation of motion of a step motor and that of a simple pendulum with viscous damping, the paper develops the necessary criteria for synchronization when the motor is subjected to a series of steps. The problem is first analyzed ignoring the discrete nature of the input leading to approximate determination of the critical stepping rates. This is followed by a more accurate analysis. The results of these analyses are presented in nondimensional form and can be used for the design of the motor.

The application of differential thermal analysis technique to the study of single, binary and ternary oxide catalyst systems

Abstract: The authors have reviewed the salient features of the thermal behavior of the following systems: Excellent correlations have been obtained in most of the systems between the thermal characteristics of the solids, as revealed by DTA, and their specific surface areas and catalytic activity.

Vertical electric dipole over an inhomogeneous and anisotropic earth

Abstract: The propagation of electromagnetic waves in a two-layer anisotropic earth from an oscillating vertical electric dipole placed over it has been studied. Formal expression for the vector potential in the top layer has been determined for the general case when both the layers are electrically anisotropic. The conductivity and the permittivity tensors of the layers are assumed to have simple diagonal forms. Three special cases of practical interest have been considered in detail, for which the results are given in terms of tabulated functions. It has been shown that at the surface of the earth, only the electric field components are influenced by the anisotropy.

Kinetics of Accelerated Vulcanization—III N-Cyclohexyl-Benzothiazole-2-Sulfenamide Accelerated Sulfur Vulcanization of Rubbers

Abstract: Sulfenamide type of accelerators are well known for their outstanding processing safety combined with ultra-strong accelerating activity resulting in superior quality vulcanizates. Sulfenamides derived from different amines afford varying degrees of scorch delay and accelerating activity. Since there is no unanimity on the chemistry involved in this type of accelerated vulcanization, a preliminary study has been carried out to gain some insight into the mechanistic scheme. The present paper contains reports on the effects of varying concentrations of N-cyclohexyl-benzothiazole-2-sulfenamide (CBS) on the rate of free sulfur decrease and cross-link formation as well as zinc sulfide formation—whenever it occurs—both in the absence and presence of zinc oxide and of zinc oxide and stearic acid. The influence of temperature has also been investigated.

Combined Natural and Forced Convection Hydromagnetic Flow in Vertical Channels

Abstract: The combined natural and forced convection fully developed flow and heat transfer of an electrically conducting fluid with and without temperature dependent heat sources in a vertical channel has been studied under the influence of transverse applied magnetic field and external circuit. The two plane walls of the channel are having the same temperature gradient along their lengths but both are art different temperatures. The system of non-linear integro-differential equations have been solved by an iteration method and the shearing stress and Nusselt number at the walls have been calculated. It has been found that the temperature dependent heat sources impose oscillatory behaviour on the temperature profiles and the heat transfer between the wall and the adjacent fluid changes its direction for different ranges of values of the heat source per unit volume. The magnetic field reduces the velocity but increases the temperature and the presence of linear variation of the wall temperature helps in cooling the walls. In der vorliegenden Arbeit werden die in einem vertikalen Kanal verlaufende vollentwickelte laminare Konvektionsstromung einer elektrisch leitenden Flussigkeit, die der Wirkung eines magnetischen Querfeldes und eines auseren Stromkreises unterworfen ist, und die sich dabei vollziehende Warmeubertragung untersucht, wobei noch Warmequellen vorhanden sein konnen. Die beiden ebenen Wande des Kanals haben verschiedene Temperaturen aber in Langsrischtung denselben Temperaturgradienten. Das den Vorgang beherrschende System von Integrodifferentialgleichungen wird iterativ gelost, und es werden die Schubspannung und die Nusselt-Zahl-an den Wanden berechnet. Es zeigt sich, das die Warmequellung temperaturabhangig ist und an den Temperaturprojilen ein oszillatorisches Verhalten bewirkt und das der Warmeubergang zwischen Wand und angrenzender Flussigkeit in Abhangigkeit von den Werten der Warmequellergiebigkeit seine Richtung andert. Das Magnetfeld reduziert die Geschwindigkeit, last aber die Temperatur anwachsen, und durch eine lineare Anderung der Wandtemperatur last sich eine Kuhlung der Wande erreichen.

Studien über Lactame

Abstract: Aus der starken Aktivierung des Methinwasserstoffs in den Halogenacetaminomalonaten und -phenylacetaten 4 durch eine N-[4-Nitro-phenyl]-Gruppe bei der Cyclisierung zu den β-Lactamen 5 sowie der Lage der CO-Bande der Amidgruppe in 5 und der Ringbestandigkeit wird auf Coplanaritat des N-Nitrophenylrings mit den drei Valenzen des Stickstoffs in den Amiden 4 und Lactamen 5 geschlossen. In den N-[2-Chlor-4-nitro-phenyl]-und N-[2-Nitrophenyl]-halogenacetaminoestern 4h und i ist der Arylring aus der Ebene des sp2-Stickstoffs herausgedreht, begleitet von einer deutlichen Abnahme der Methinwasserstoff-Aktivierung.

Cohesive energy density of cis‐polybutadiene

Abstract: The cohesive energy density of cis-polybutadiene has been estimated from viscosity and swelling measurements. The method was extended to turbidiometric titrations with a nonsolvent and the results were found to be very consistent. The average value of the solubility parameter (under-root of cohesive energy density) was observed to lie between 8.5 to 8.6 (cal/ml)1/2. The FLORY-HUGGINS solvent-polymer interaction parameter, determined from HUMMEL'S method, was found to be 0.3889. Die Kohasionsenergiedichten von cis-Polybutadien wurden aus Dichte- und Quellungsmessungen abgeschazt. Das Verfahren wurde durch Trubungstitrationen mit einem Fallungsmittel erweitert. Die Ergebnisse der beiden Methoden zeigten gute ubereinstimmung. Der Mittelwert des Loslichkeitsparameters (Wurzel aus der Kohasionsenergiedichte) lag zwischen 8,5 und 8,6 (cal/ml)1/2. Der FLORY-HUGGINS-Losungsmittel-Polymer-Wechselwirkungsparameter, der nach der Methode von HUMMEL bestimmt wurde, ergab sich zu 0,3889.

Effects of Moisture and Nitrogen on Growth, Yield and Mineral Content of Rice

Abstract: Limited moisture supply caused reduction in leaf area, number of effective tillers, ratio of sound to unsound grains and the nitrogen, phosphorus, iron and manganese content of rice. Crop yield was adversely affected in the absence of standing water. Two levels of nitrogen (40 and 60 kg.N/ha.) caused no significant difference in yield in 1965, but in 1966, when 30 and 60 kg. N/ha. were used, the latter gave better yields.

Hydromagnetic Noncyclic Squeeze Films in Journal Bearing with Radial Magnetic Field

Abstract: A theoretical study is made of noncyclic squeeze films in full and half journal bearings of infinite length between two insulating surfaces in the presence of radial magnetic field. It is shown that the time of approach increases with the large Hartmann number. Further it is seen that the increase in the time of approach is much for large values of the Hartmann number whereas the increase in the time of approach is very small for small Hartmann numbers.