Vinyl acetate monomer—a pilot plant study

The kinetics of the reaction of acetic acid and acetylene over zinc acetate-activated carbon catalyst was investigated over a wide range of process variables in a pilot reactor. Although various catalytic reaction mechanisms were postulated, the rate of reaction was most satisfactorily correlated by a mechanism of surface reaction between charged adsorbed acetic acid and acetylene, which assumes that the rate controlling step was the irreversible charged adsorption of acetylene and acetic acid.     

Impact of QOS requirements on video coding for ATM networks

The broadband integrated services digital networks (B-ISDN) based on asynchronous transfer mode (ATM) technology can support a wide range of applications such as voice, video, still images, and data. Compression techniques increase the effective bandwidth utilization, but the bursty and asynchronous nature of the traffic can still lead to congestion in the network, and degradation of image quality and quality of service (QOS). Some of the features to provide better coding schemes for ATM networks are layered coding, resynchronization, buffering, interleaved schemes, constrained bit rate due to buffers, encapsulation with the RTP or AAL1 for clock recovery, lapped transforms, motion compensation, and optimal bit allocation for coders based on wavelet transforms. We review various techniques forimage and video coding such as transforms, motion compensation, vector quantization, and subband coding. We outline the impact of the cell loss ratio (CLR), delay and cell delay variation (CDV) on video coding: blocking effects, loss of frame synchronization, motion vectors, and vector quantization codewords. The open problems include tuning coding parameters to the available QOS provided by the network.     

Integrating statistical and nonstatistical audit evidence using belief functions: A case of variable sampling

The main purpose of this article is to show how one can integrate statistical and nonstatistical items of evidence in the belief function framework. First, we use the properties of consonant belief functions to define the belief that the true mean of a variable lies in a given interval when a statistical test is performed for the variable. Second, we use the above definition to determine the sample size for a statistical test when a desired level of belief is needed from the sample. Third, we determine the level of belief that the true mean lies in a given interval when a statistical test yields certain values for the sample mean and the standard deviation of the mean for the variable. Finally, we use the auditing situation to illustrate the process of integrating statistical and nonstatistical items evidence. © 1994 John Wiley & Sons, Inc.     

Use of AgInTe2 for optoelectronic switching at higher frequencies

A possible application of AgInTe₂ for optoelectronic switching is reported. Alternating and direct current (a.c. and d.c.) response of the material has been studied over a wide frequency range (5 Hz to 1 MHz) through measurements of conductance, capacitance and photocurrent at different temperature and illumination levels. The switching/recovery time has been analysed in terms of time constant and found to be of the order of microseconds for this material. Higher frequencies of operation (>40 kHz) are preferable because, at such frequencies, becomes almost independent of illumination level and temperature. Furthermore, the switching speed can be conveniently controlled with d.c. bias applied across the sample. Elliott's CBH model has been satisfactorily used to explain the switching behaviour for AgInTe₂.     

Influence of variables in nickel-manganese-zinc alloy plating from a sulphate bath

An Ni-Mn-Zn alloy has been satisfactorily electrodeposited from a sulphate bath containing nickel sulphate (20–23 g dm⁻³), manganese sulphate (76–88 g dm⁻³), zinc sulphate (18–24 g dm⁻³), ammonium sulphate (30 g dm⁻³), thiourea (18g dm⁻³) and ascorbic acid (0.8 g dm⁻³) under various plating conditions, namely, current density 1.0–3.0 A dm⁻²; temperature 30–45° C; pH 2.7–4.2 and duration of electrolysis 15–30 min. Semibright, blackish-grey, thin films were generally deposited with the proportion of nickel and manganese in the deposits increasing with increasing current density, temperature and duration of electrolysis. However, the amount of zinc increased as the pH of the solution was raised. The cathode efficiency for alloy deposition increased linearly as the temperature or the pH of the solution was decreased, whereas at any particular pH and temperature it continuously rose with increasing current density or the time of deposition. The cathode polarization shifted to more negative values on increasing the current density and to less negative values at higher pH values and temperatures which consequently lowered the throwing power under the latter conditions.     

Quantification of crustal geotherms along with their error bounds for seismically active regions of India: A Matlab toolbox

Determination of the thermo-mechanical structure of the crust for seismically active regions using available geophysical and geological data is of great importance. The most important feature of the intraplate earthquakes in the Indian region are that the seismicity occurs within the entire crust. In Latur region of India an earthquake occurred in the upper crust. In such situations, quantifying the uncertainties in seismogenic depths becomes very important. The stochastic heat conduction equation has been solved for different sets of boundary conditions, an exponentially decreasing radiogenic heat generation and randomness in thermal conductivity. Closed form analytical expressions for mean and variance in the temperature depth distribution have been used and an automatic formulation has been developed in Matlab for computing and plotting the thermal structure. The Matlab toolbox presented allows us to display the controlling thermal parameters on the screen directly, and plot the subsurface thermal structure along with its error bounds. The software can be used to quantify the thermal structure for any given region and is applied here to the Latur earthquake region of India.     

Studies on Tamarind Kernel Polysaccharide Part III. Structure of a Dextrin

Tamarind kernel polysaccharide (TKP), isolated by fractionation of tamarind kernel powder, was heated at 153°C for 5 h in presence of 0.074% hydrochloric acid. The resulting product was fractionated to yield a homogeneous dextrin which on hydrolysis produced D -xylose, D -galactose and D -glucose in the molar ratio of 2:1:10. Methylation of the dextrin followed by hydrolysis yielded 2,3,4-tri-O-methyl-D -xylose (2 moles); 2,3,4,6-tetra-O-methyl-D -glucose (1 mole); 2,3,4,6-tetra-O-methyl-D -galactose (1 mole); 2,3,4-tri-O-methyl-D -glucose (1 mole); 2,3,6-tri-O-methyl-D -glucose (4 moles); 2,3-di-O-methyl-D -glucose (4 moles); and 2-O-methyl-D -glucose (trace amounts). Upon oxidation of the dextrin with sodium metaperiodate, 1.4 moles of the oxidant was consumed with concomitant liberation of 0.38 mole of formic acid. Reduction of the oxopolysaccharide with sodium borohydride followed by acid hydrolysis of the polyol produced erythritol, glycerol and ethylene glycol in the molar ratio of 8:3:2. The above results suggest that the main reaction during dextrinization of TKP is that of hydrolysis. The side branches of the polymer are hydrolyzed to a greater extent than its backbone. Transglycosidation, which is the predominant reaction in starch dextrinization, takes place only to a small extent.     

On the dyadic Green's functions for Beltrami fields

A simple derivation of the Green's functions for Beltrami fields is presented for use with time-harmonic electromagnetism in homogeneous biisotropic media.