Reductive alkylation of illinois No. 6 coal. 1H and 13C n.m.r. spectra of the 13C-enriched alkylation products

The reductive alkylation of Illinois No. 6 coal has been carried out using potassium and naphthalene in tetrahydrofuran and methyl-¹³C and butyl-1 -¹³C iodides to alkylate the resultant polyanion. The soluble products of the reductive alkylation reaction were isolated by extraction and chromatography. Proton and carbon n.m.r. spectra were recorded. The intense resonance signal at δ3.95 which appears in the proton n.m.r. spectra of Illinois No. 6 coal butylated with unenriched butyl iodide is split into a doublet by the ¹³C nuclei. Similar results were obtained for the methylation products. The chemical shift and coupling interaction establish that aryl ethers are a very important constituent of the alkylated coal. The carbon n.m.r. spectra of the coal alkylated with ¹³C-enriched alkyl iodides are intense. The resonances of the C-alkylation products appear in a single broad band with a maximum intensity in spectral regions compatible with the formation of the reductive alkylation products of certain polynuclear aromatic hydrocarbons or the base-catalysed alkylation of certain benzylic carbon atoms. The resonances of the N -alkylation products appear in two distinct bands. These resonances are tentatively assigned to amines produced as a result of reductive alkylation of heterocyclic compounds. The resonances of the 0-alkylation products appear in three distinct bands which can be assigned to alkyl aryl ethers, alkyl aryl ethers with substituents at the adjacent positions, and to alkyl carboxylates. The ratio of ethers to carboxylates in the soluble alkylation products was determined to be 7.8 for butylation and 8.0 for methylation. The Chromatographic fractions contain different amounts of C-, N-, and 0-alkylation products. This finding suggests that the coal structure is not highly uniform.     

Solid state magnetic resonance spectra of Illinois No. 6 coal and some reductive alkylation products

Illinois No. 6 coal and its reductive methylation and butylation products have been studied by magnetic resonance techniques. Conventional CP-MAS¹³Cn.m.r. spectroscopy indicates that 62% of the carbon atoms in the coal are aromatic and that about 6% of the carbon atoms are carbonyl. Esters are more abundant than carboxylic acids. The resonances of methoxy groups and other novel etheric carbon atoms are apparent in the high field region. Dipolar dephasing experiments suggest that methyl carbon atoms constitute no more than 16% of the carbon, methylene and methine carbon atoms about 14% and quaternary aliphatic carbon atoms about 2%. The dipolar dephasing experiments in conjunction with previous work also permit estimates of the hydrogen atom distribution. The THF-insoluble products obtained in the reductive alkylation reactions with¹³C-enriched alkylating agents contain paramagnetic and ferromagnetic substances that adversely influence the solid state n.m.r. spectra. However, good ¹³C n.m.r. spectra were obtained after these substances were extracted with aqueous hydrochloric acid. The O:C alkylation ratios are 1.2 and 1.0 for methylation and butylation, respectively. Dipolar dephasing experiments establish that the decay constants of functional groups in the whole coal and of C- and O-methyl-¹³C and C- and O-butyl-1 -¹³C nuclei in the labelled coal molecules are very similar to those of reference compounds. These findings suggest that the decay constants measured for the ¹³C nuclei in coals and coal-derived solids provide reliable information about their degree of substitution.     

Reductive alkylation of Illinois No. 6 coal in liquid ammonia

The reductive alkylation of Illinois No. 6 coal was investigated using alkali metals and alkyl halides in liquid ammonia. Potassium is the most effective reducing agent and butyl iodide is the most effective alkylating agent for the preparation of coal alkylate that is soluble in tetrahydrofuran. The overall yield of soluble product is often improved through the reaction of the tetrahydrofuran-insoluble portion of the initial reaction products with an alkylating agent in the presence of tetrabutylammonium hydroxide. The infrared spectra of these materials suggest that the phase transfer agent catalyses the esterification of residual carboxylic acid functions. The intermolecular interactions between such acid groups and acceptor groups markedly restrict the solubility of the coal alkylate. The gel permeation chromatograms of the soluble reaction products are essentially featureless with only modest maxima at short and long elution volumes. The proton and carbon nuclear magnetic resonance spectra of the reductive methylation products, prepared using methyl-¹³C iodide, suggest that carbon alkylation exceeds oxygen alkylation and that the alkylation of phenolic groups is the dominant O-alkylation reaction. The spectra also suggest that fewer ethers are cleaved in the reaction in liquid ammonia than under the conditions of the Sternberg reaction.     

Ruthenium tetroxide catalysed oxidation of Illinois No. 6 coal: The formation of volatile monocarboxylic acids

Ruthenium tetroxide selectively oxidizes activated aromatic compounds under mild conditions and has been used for the catalytic oxidation of several different coals. The quantities of the volatile monocarboxylic acids with 2–6 carbon atoms have been determined by an isotope dilution technique. The amount of ethanoic acid ranges from 1 to 3mol/100C and the quantities of propanoic acid, and butanoic acid exceed 0.1 mol/100C. Methylpropanoic, pentanoic, 2-methylbutanoic, 3-methylbutanoicand hexanoic acid are formed in lesser amounts. The outcome of the experiment depends upon whether or not the coal has been extracted prior to oxidation. The results for Illinois No. 6 coal expressed in moles of ethanoic acid produced/l00C illustrate this feature: raw whole coal, 1.9; coal extracted by the method of Hayatsu and co-workers, 1.0. Dehydrogenation with benzoquinone prior to oxidation increases the yield of ethanoic acid to $\text{sol1.5mol}\text{100C.}$ The amounts of ethanoic acid obtained from the other extracted coals are 1.0 for Texas lignite, 1.2 for Rawhide subbituminous, 3.4 for Pittsburgh No. 8, 3.3 for a higher ranking bituminous coal (PSOC 726) and 0.7 for an anthracite (PSOC872). The results obtained in this study are compared with related information concerning the distribution of alkyl groups within coal by other methods.     

Recent advances in molecular weight determination

The aging and lifetimes of polymeric materials depend on the reaction of these materials to the particular stresses which are applied. In many cases the molecular weight of the polymer is changed and this affords a way to follow aging phenomena. In the simplest case a homopolymer is subjected to a stress which increases or decreases its molecular weight without any chemical changes. As the situation becomes more complicated, changes in chemical composition occur and different sized molecular species are generated. These new species may be of extremely low molecular weight or they may be in the form of crosslinked gel. This paper reviews methods which are available for the determination of molecular weight and molecular weight distribution of polymeric materials. Recently developed or modified techniques are treated in more detail. Techniques which may be used to characterize the oligomer region or analyze for the presence of crosslinked gel are included.     

Figure of merit for the quality of ZrO2 coatings on stainless steel and nickel-based alloy surfaces

A figure of merit (FOM) has been developed to define the quality of ceramic (e.g., ZrO₂) coatings on metal and alloy [Type 304SS and Alloy 600] surfaces. Zirconia (ZrO₂) coatings were developed as a means of protecting the metal/alloy surfaces from stress corrosion cracking (SCC) in boiling water reactor (BWR) primary heat transport circuits, by inhibiting the cathodic reaction (reduction of oxygen and hydrogen peroxide) on the surface external to the crack. The distribution of pores in the coating plays an important role in corrosion prevention, such that the lower the porosity of the coating, the better the protection afforded to the system against SCC. Since the reactors operate at high temperature (e.g., at 288 °C under full power conditions), the temperature dependence of the FOM was investigated. The figure of merit (FOM) was developed by measuring impedance data over a wide range of frequency (10 mHz-5 kHz) at temperatures of 25, 100, 200, and 288 °C in hydrogenated, buffered solutions, with the hydrogen electrode reaction (HER) being used as a “fast” redox couple. An “equivalent circuit” analog was first developed from the bare surface impedance data and this analog was then employed in a second step to model the pore bottom in defining the pore distribution on the coated surface. A lognormal distribution (LND) of the pores was assumed and the parameters of the LND were determined using a constrained optimization technique to fit the model to the experimental data for the coated surface at different temperatures. The results suggest that, as temperature increases, the coating becomes more porous, making the substrate more susceptible to corrosion cracking. At 288 °C, 87% of the SS and 85% of the Ni-alloy surfaces become porous with the pore radius varying from 0.0001 cm to 0.01 cm.     

Estimation of Defects Based on Defect Decay Model: ED^{3}M

An accurate prediction of the number of defects in a software product during system testing contributes not only to the management of the system testing process but also to the estimation of the product's required maintenance. Here, a new approach called ED³M is presented that computes an estimate of the total number of defects in an ongoing testing process. ED³M is based on estimation theory. Unlike many existing approaches the technique presented here does not depend on historical data from previous projects or any assumptions about the requirements and/or testers' productivity. It is a completely automated approach that relies only on the data collected during an ongoing testing process. This is a key advantage of the ED³M approach, as it makes it widely applicable in different testing environments. Here, the ED³M approach has been evaluated using five data sets from large industrial projects and two data sets from the literature. In addition, a performance analysis has been conducted using simulated data sets to explore its behavior using different models for the input data. The results are very promising; they indicate the ED³M approach provides accurate estimates with as fast or better convergence time in comparison to well-known alternative techniques, while only using defect data as the input.     

Free-form object reconstruction from silhouettes, occluding edges and texture edges: a unified and robust operator based on duality

In this paper, the duality in differential form is developed between a 3D primal surface and its dual manifold formed by the surface's tangent planes, i.e., each tangent plane of the primal surface is represented as a four-dimensional vector which constitutes a point on the dual manifold. The iterated dual theorem shows that each tangent plane of the dual manifold corresponds to a point on the original 3D surface, i.e., the dual of the dual goes back to the primal. This theorem can be directly used to reconstruct 3D surface from image edges by estimating the dual manifold from these edges. In this paper we further develop the work in our original conference papers resulting in the robust differential dual operator. We argue that the operator makes good use of the information available in the image data, by using both points of intensity discontinuity and their edge directions; we provide a simple physical interpretation of what the abstract algorithm is actually estimating and why it makes sense in terms of estimation accuracy; our algorithm operates on all edges in the images, including silhouette edges, self occlusion edges, and texture edges, without distinguishing their types (thus resulting in improved accuracy and handling locally concave surface estimation if texture edges are present); the algorithm automatically handles various degeneracies; and the algorithm incorporates new methodologies for implementing the required operations such as appropriately relating edges in pairs of images, evaluating and using the algorithm's sensitivity to noise to determine the accuracy of an estimated 3D point. Experiments with both synthetic and real images demonstrate that the operator is accurate, robust to degeneracies and noise, and general for reconstructing free-form objects from occluding edges and texture edges detected in calibrated images or video sequences.     

The effect of flaming on computer-mediated negotiations

There is an increasing use of computer media for negotiations. However, the use of computer-mediated channels increases the hostile expressions of emotion, termed flaming. Although researchers agree that flaming has important effects on negotiation, predictions concerning these effects are inconsistent, suggesting a need for further investigation. We address this need by extending current flaming and negotiation research in two ways. First, we identify two different types of flaming: that which is motivated by perceptions concerning the negotiating opponent (e.g., he/she is unfair) and that which is motivated by perceptions concerning the negotiating context (e.g., the communication channel is too slow). Second, we differentiate between the effects of flaming on the concession behaviors of the flame sender and the flame recipient, and the effects of these behaviors on negotiated agreement. Via a laboratory study, we demonstrate that flames directed at the negotiation opponent slightly decrease the likelihood of reaching an agreement, and when an agreement is reached, it result in outcomes significantly favoring the flame recipient rather than the flame sender. In contrast, flames directed at the negotiation context significantly increase the likelihood of agreement, although outcomes still favor the flame recipient over the flame sender. These results suggest that flame senders are generally worse off than flame recipients, which provides an important basis for the strategic use of flaming in negotiations.     

Intuitive robust stability metric for PID control of self-regulating processes

Published methods establish how plant-model mismatch in the process gain and dead time impacts closed-loop stability. However, these methods assume no plant-model mismatch in the process time constant. The work presented here proposes the robust stability factor metric, RSF, to examine the effect of plant-model mismatch in the process gain, dead time, and time constant. The RSF is presented in two forms: an equation form and a visual form displayed on robustness plots derived from the Bode and Nyquist stability criteria. This understanding of robust stability is reinforced through visual examples of how closed-loop performance changes with various levels of plant-model mismatch. One example shows how plant-model mismatch in the time constant can impact closed-loop stability as much as plant-model mismatch in the gain and/or dead time. Theoretical discussion shows that the impact is greater for small dead time to time constant ratios. As the closed-loop time constant used in Internal Model Control (IMC) tuning decreases, the impact becomes significant for a larger range of dead time to time constant ratios. To complete the presentation, the RSF is used to compare the robust stability of IMC-PI tuning to other PI, PID, and PID with Filter tuning correlations.