Showing papers by "Indian Institute of Technology Kharagpur published in 1994"

Stochastic assembly line balancing using simulated annealing

Abstract: The problem of balancing assembly lines with stochastic task processing times is addressed. The size of the problems that can be solved by optimal methods is limited and hence many heuristics have been developed, which give sub-optimal solutions. An approach for solving the problem using the simulated annealing technique is presented here. The proposed approach tries to reach the global optimum by not getting trapped at the different local optimum points. Another feature of this method is the non-dependence of the final solution on the initial solution. Solutions for line balancing problems obtained using the above method compare favourably with the results of other greedy heuristics.

Artificial neural network-based nonlinearity estimation of pressure sensors

Abstract: A new approach to pressure sensor modeling based on a simple functional link artificial neural network (FLANN) is proposed. The response of the sensor is expressed in terms of its input by a power series. In the direct modeling, using a FLANN trained by a simple neural algorithm, the unknown coefficients of the power series are estimated accurately. The FLANN-based inverse model of the sensor can estimate the applied pressure accurately. The maximum error between the measured and estimated values is found to be only /spl plusmn/2%. The existing techniques utilize ROM or nonlinear schemes for linearization of the sensor response. However, the proposed inverse model approach automatically compensates the effect of the associated nonlinearity to estimate the applied pressure. Frequent modification of the ROM or nonlinear coding data is required for correct readout during changing environmental conditions. Under such conditions, in the proposed technique, for correct readout, the FLANN is to be retrained and a new set of coefficients is entered into the plug-in module. Thus this modeling technique provides greater flexibility and accuracy in a changing environment. >

Optimization of tannase biosynthesis by a newly isolated Rhizopus oryzae

Abstract: A strain isolated locally and identified as Rhizopus oryzae (RO, IIT KGP) was found to synthesise an extracellular enzyme, tanin acyl hydrolase, showing its degradability of tannic acid to gallic acid. For maximizing the enzyme secretion in the fermented broth, the influencing parameters were optimized in shake flask culture. Experiments showed that modified Czapek dox medium with 2% tannic acid, 1% glucose, 0.05% sodium nitrate incubated for 4 days with 2 days old inoculum was the optimum for the synthesis of tannase by Rhizopus oryzae (RO, IIT KGP). Maximum enzyme activity was found to be 6.12 U/ml.

Improvement in the oxidation behavior of austenitic stainless steels by superficially applied, cerium oxide coatings

Abstract: The influence of superficially applied CeO2 coatings on the isothermal-oxidation behavior, preceded by nonisothermal heating, as well as cyclic-oxidation behavior of three grades of austenitic stainless steel (AISI-316, −321, and −304), in dry air is reported. The superficial coating had a thickness of 2.1 μm. The linear heating rate employed was 6 K min−1 up to a maximum temperature of 1423 K, and the isothermal holding temperature was 1273 K. The results clearly depict that CeO2 coatings not only reduced the rates of scale growth for all three varieties of steel but also imparted improved scale adhesion to the respective alloy substrates, as evident from the fact that the coated steels could withstand a number of thermal cycles without scale rupture. In the bare condition, 321-grade steel exhibited the best performance. However, in the presence of the coating, the improved performances of 316 and 321 grades were almost identical, whereas the 304 variety showed improvement only in the first cycle of exposure. The kinetics results have been substantiated by postoxidation analyses of the alloy/scale combinations by SEM, EDS, EPMA, and XRD techniques to reveal the role of rare-earthoxide coatings on the observed behavior.

Modified heterojunction based on zinc oxide thin film for hydrogen gas-sensor application

Abstract: Device-quality ZnO thin film is deposited by using an indigenously developed modified CVD method and a Pd/ZnO/p-Si heterojuncion is fabricated. A study of the current-voltage characteristics of the heterojunction in pure air and in air with different concentrations (2000−20 000 ppm) of hydrogen reveals that the device can be used as a room-temperature hydrogen sensor down to a level of hydrogen below its explosion mixture with air. The saturation sensitivity and time response of the device with respect to the different hydrogen concentrations in air has been studied. The device operating at 1 V forward bias shows a maximum saturation sensitivity in different hydrogen concentrations. At 20 000 ppm. H2 in air, the sensitivity is found to be 5×102, while the time response is 162 s. The increase of surface conductivity of ZnO at the Pd/ZnO interface due to the adsorption and chemical interaction of hydrogen is found to play a key role in sensing. This mechanism of hydrogen sensing is verified by a double-metal-gate heterojunction.

Design of CAECC - cellular automata based error correcting code

Abstract: A new scheme for designing error detecting and error correcting codes around cellular automata (CA) is reported. A simple and efficient scheme for generating SEC-DED codes is presented which can also be extended for generating codes with higher distances. A CA-based hardware scheme for very fast decoding (and correcting) of the codewords is also reported. >

Miscibility and interaction studies on some aqueous polymer blend solutions by ultrasonic and rheological techniques

Abstract: The aqueous solutions of poly(ethylene oxide)–polyacrylic acid, poly(vinyl pyrrolidone)–poly(vinyl alcohol), and poly(ethylene oxide)–poly(vinyl alcohol) blends have been studied by ultrasonic, rheological, and viscometric techniques. Extensive investigation over a wide range of concentrations, temperatures, compositions, pH, and shear rates indicate the degree of miscibility, extent of interaction between the polymers, and stoichiometry of the polymer complexes formed by the strong interaction between the polymers in solutions. These investigations indicate the miscibility of poly(ethylene oxide)–polyacrylic acid and poly(ethylene oxide)–poly(vinyl pyrrolidone) blends and the immiscibility of poly(ethylene oxide)–poly(vinyl alcohol) blends in conformity with other reported investigations. © 1994 John Wiley & Sons, Inc.

Production of some extracellular enzymes by a lignin peroxidase-producing brown rot fungus, Polyporus ostreiformis, and its comparative abilities for lignin degradation and dye decolorization.

Abstract: Polyporus ostreiformis produced Mn peroxidase, acid protease, alpha-amylase, and lignin peroxidase, with maximum activities of 40, 8,300, and 4,200 U liter-1 and 50 nkat liter-1, respectively, in nitrogen-limited liquid media. The fungus removed only 18.6% lignin from rice straw in 3 weeks but effected 99% decolorization of Congo red dye in 9 days.

A class of two-dimensional cellular automata and their applications in random pattern testing

Abstract: A basic framework to characterize the behavior of two-dimensional (2-D) cellular automata (CA) has been proposed. The performance of the regular structure of the 2-D CA has been evaluated for pseudo-random pattern generation. The potential increase in the local neighborhood structure for 2-D CA has led to better randomness of the generated patterns as compared to LFSR and 1-D CA. The quality of the random patterns generated with 2-D CA based built-in-self-test (BIST) structure has been evaluated by comparing the fault coverage on several benchmark circuits. Also a method of synthesizing 2-D CAs to generate patterns of specified length has been reported. The patterns generated can serve as a very good source of random two-dimensional sequences and also variable length parallel pattern generation having virtually nil correlation among the bit patterns.

Phosphorus containing polymers. III. Polyimidophosphonates

Abstract: Synthesis of dihydroxybisimide monomers and their subsequent polycondensation with dichlorophenylphosphine oxide by use of a phase-transfer catalyst are reported. The monomers were characterized by melting point, elemental analysis, and IR spectroscopy. The polyimidophosphonates were characterized by viscosity measurement, molecular weight determination, elemental analysis, IR, ESCA, 1H-NMR, 31P-NMR, and X-ray diffraction. Thermal stability and glass transition temperature (Tg) of the polymers were evaluated by TGA, DTA, and TMA. These polymers are self-extinguishing and readily soluble in highly polar solvents like DMF, DMSO, DMAC, NMP, HMPA, etc. © 1994 John Wiley & Sons, Inc.

Use of low-cost gelling agents and support matrices for industrial scale plant tissue culture

Abstract: The efficacies of sago (from Metroxylon sagu Rottb.) and isubgol (from Plantago ovata Forsk.) as gelling agents and those of filter paper, nylon cloth, polystyrene foam and glass wool cloth as support matrices have been tested for the propagation of plantlets of chrysanthemum (Dendranthema grandiflora Tzvelev). The performances of these low-cost gelling agents and matrices were found satisfactory and could compare well with that of agar. Glass wool cloth was, however, found to be the best matrix. Comparative cost estimations of the matrices and gelling agents have been presented and their merits and/or demerits have been discussed. For a given quantity of a medium, sago and isubgol cost about 1/18th and 1/10th respectively, compared to agar (e.g. Sigma, purified agar, No. A. 7921). The corresponding costs of the matrices are also less than that of agar. The results showed the potential of the substitutes for economic commercial application, replacing the costliest, though not indispensable, gelling agent agar.

Peristaltic transport of a particle-fluid suspension in a cylindrical tube

Abstract: Peristaltic pumping induced by a sinusoidal travelling wave of moderate amplitude is analysed in the axisymmetrical case for a viscous incompressible and Newtonian fluid mixed with rigid spherical particles which are of identical size. A perturbation method has been employed to find the solution of the problem, choosing the amplitude ratio (i.e., wave amplitude/tube radius) as a parameter. The analysis has been carried out by duly accounting for the nonlinear convective acceleration terms, and the nonslip condition for the fluid part on the wavy wall. The governing equations are developed up to the second order of the amplitude ratio. The zeroth order terms yield the Poiseuille flow and the first order terms give the Orr-Sommerfeld equation. In the absence of the pressure gradient and the wall motion, the mean flows (for the fluid and the solid particles) and the mean pressure gradient (averaged over time) are all found to be proportional to the square of the amplitude ratio. Numerical results are obtained for this simple case by approximating complicated groups of the products of Bessel functions by polynomials. It is observed that a reversal of flow occurs when the pressure gradient exceeds the critical value; this is favoured by the presence of the solid particles. The reversal of flow may take place near the boundaries also.

Chemical crosslink densit and network structure of natural rubber vulcanizates modified with phosphorylated cardnol prepolymer

Abstract: The chemical crosslink density (CLD) and network structure of natural rubber (NR) vulcanizates, modified with phosphorylated cardanol prepolymer (PCP), have been studied by equilibrium swelling and other chemical methods. The PCP-modified NR vulcanizates showed lower CLD, as compared to the unmodified NR samples, the decrease being lesser for the semiefficient vulcanization (SEV) system, as compared to the conventional (CV) and efficient (EV) vulcanization system. The superior tensile characteristics of the PCP-modified vulcanizates of the SEV system is presumed to be partly due to the presence of an entangled network structure between the aliphatic segment of PCP and the isoprene chains, as evident from X-ray diffraction studies. The critical role of Zn++ions in the crosslinking reactions, especially at higher concentrations of PCP, was evident from the increase in CLD at higher concentrations of ZnO. The reduction in the IR absorption intensity, in the presence of ZnO, indicated the probable complex formation of Zn++ions with the phosphate groups of PCP. © 1994 John Wiley & Sons, Inc.

On-line search based pulsating torque compensation of a fault mode single phase variable frequency induction motor drive

Abstract: Improved reliability and fault tolerant operation of inverter-fed variable frequency AC drives are very important for critical industrial applications, The paper describes variable frequency variable voltage operation of a three-phase induction motor drive in single phase mode for inverter fault conditions, such as open base drive and device short circuit. The detailed mathematical analysis of the machine in single phase mode indicates that odd harmonic voltages of appropriate magnitude and phase can be injected at the machine terminal to neutralize the large low frequency pulsating torques so it permits smooth drive operation. The magnitude and phase angle of the desired harmonic voltages have been derived theoretically. However, to eliminate the parameter variation effect and operating point dependencies, a general purpose search algorithm has been proposed in the paper which fabricates the desired harmonic voltages on real time basis. The search algorithm was initially exercised manually on a simulated drive system to prove its validity, and then tested extensively on a volts/Hz controlled 3 hp drive system in the laboratory. The on-line search algorithm along with estimation and control related to the project was implemented with C language on a TMS320C30 digital signal processor board. The extensive laboratory investigation shows that the proposed search algorithm performs well and successfully eliminates low frequency pulsating torques not only in steady state condition but also during slow acceleration and deceleration of the drive. >

Monophasic silica glasses with large neodymia concentration

Abstract: The use of one ideal candidate for high-powered lasers, neodymia-silica glass, is unfortunately limited by phase separation into undesirable Nd-rich crystalline droplets within an Nd-deficient matrix. Plasma CVD and sol-gel process using NdCl3 or Nd(NO3)3 as dopant both failed to produce single-phase Nd2O3SiO2 glass when neodymia exceeded 5 wt%. Using Nd(COOCH3)3 and acetic acid hydrolysed tetraethyl orthosilicate, the present authors produced monolithic glasses 10 (wt%) Nd2O3 · 90 SiO2 with no observable phase separation. Nd chloride doped gels, where the neodymium concentration increased from the interior to the surface, were much poorer in chemical homogeneity than Nd acetate doped gels of equivalent composition. Free salts of neodymium are responsible for causing the concentration gradient.

An experimental investigation of cross-flow turbine efficiency

Abstract: An experimental investigation was conducted to study the effect of some geometric parameters on the efficiency of the cross-flow turbine. Turbine models were constructed with three different numbers of blades, three different angles of water entry to the runner, and three different inner-to-outer diameter ratios. Nozzles were also constructed for the experiments to match the three different angles of water entry to the runner. A total of 27 runners were tested with the three nozzles. The results of the experiments clearly indicated that efficiency increased with increase in the number of blades. Moreover, it was determined that an increase in the angle of attack beyond 24 deg does not improve the maximum turbine efficiency. In addition, as a result of these experiments, it was determine that for a 24 deg angle of attack 0.68 was the most efficient inner-to-outer diameter ratio, whereas for higher angles of attack the maximum efficiency decreases with an increase in the diameter ratio from 0.60 to 0.75.

A reexamination of the degradation of polyvinylchloride by thermal analysis

Abstract: Degradation of polyvinylchloride has been reexamined in the light of its DT-DSC-TG analytical behavior up to a temperature of 1000°C in an inert atmosphere. Four distinct stages of degradation have been identified. The first stage is almost eventless with no change in weight for untreated PVC samples. The second stage is almost exclusively dehydrochlorination. The third stage appears to be a structural reorganization involving such processes as cis-trans isomerization, aromatization, and crosslinking. The fourth stage appears to be a structural degradation and is associated with the evolution of hydrocarbons. The role of liberated hydrogen chloride has been better appreciated in catalyzing the above secondary reactions on the polyene residue obtained on partial or total dehydrochlorination. The effect of the particle dimension and chemical and physical pretreatments of the samples, such as low temperature dehydrochlorination by an alkali and vacuum heat treatment, respectively, on the degradation pattern has been studied. © 1994 John Wiley & Sons, Inc.

A new chemical route for the preparation of fine ferrite powders

Abstract: Precursors to MFe2O4 [spinels ferrites; where M = Ni(II), Co(II) and Zn(II)] have been prepared by the evaporation of polyvinyl alcohol added mixed metal nitratesolution, in presence and absence of urea. Theprecursor materials have low ignition temperature and are spontaneously combustible at low temperatures (250°C to 400°C). The heat liberated through the process is sufficient for the crystallization of the desired ferrite phase. The urea added process resulted in finer, superparamagnetic particles (12–17 nm) compared to the process without urea (particle size 25–30 nm). The ultrafine ferrite powders obtained have been characterized by X-ray powder diffraction (XRD), thermal gravimetry (TG), differential scanning calorimetry (DSC), infrared spectroscopy (IR), transmission electron microscopy (TEM) and room temperature magnetic measurement studies.