Harmonic measurements, analysis, and power factor correction in amodern steel manufacturing facility

Maximizing electric power transfer directly affects the productivity of an electric arc furnace operation. Arc furnaces and rolling mill loads operate at power factors that result in penalty charges and lower bus voltages. In addition, the nonlinear characteristics of the furnace arcs and rolling mill drives generate significant harmonic currents that flow through the plant and utility power system. These harmonic currents cause system voltage distortion and power loss in the system, and can interact with power factor correction capacitor banks leading to equipment failures. This paper presents the analytical technique used to correct power factor in a modern steel manufacturing facility. The study included field measurements, harmonic analysis, and filter design work to reduce the amount of harmonic distortion in the plant. The modeling of arc furnaces and rolling mills for a harmonic analysis study is also discussed. The solutions recommended in this paper to increase power factor and reduce harmonics can be applied to other steel manufacturing facilities to improve power quality and therefore plant productivity     

Novel impact modification in a TPO system

An innovative TPO, based upon a complex fluid, is described, which shows an unusual balance of physical properties. The effects of complex fluid composition are addressed in a statistically designed experiment. Physical performance, rheological effects, thermal analysis, and morphological characterization are reported. J. VINYL ADDIT. TECHNOL., 12:183–191, 2006. © 2006 Society of Plastics Engineers     

Effects of substitution of Thr63 by alanine on the structure and function of Lactobacillus casei dihydrofolate reductase

A mutant of Lactobacillus casei dihydrofolate reductase hasbeen constructed in which Thr63, a residue which interacts withthe 2'-phosphate group of the bound coenzyme, is replaced byalanine. This substitution does not affect k_cat, but producesan 800-fold increase in the K_m for NADPH, which reflects dissociationof NADPH from the enzyme-NADPH-tetrahydrofolate complex, anda 625-fold increase (corresponding to 3.8 kcal/mol) in the dissociationconstant for the enzyme-NADPH complex. The difference in magnitudeof these effects indicates a small effect of the substitutionon the negative cooperativity between NADPH and tetrahydrofolate.Stopped-flow studies of the kinetics of NADPH binding show thatthe weaker binding arises predominantly from a decrease in theassociation rate constant. NMR spectroscopy was used to comparethe structures of the mutant and wild-type enzymes in solution,in their complexes with methotrexate and with methotrexate andNADPH. This showed that only minimal structural changes resultfrom the mutation; a total of 47 residues were monitored fromtheir resolved ¹H resonances, and of these nine in the binarycomplex and six in the ternary differed in chemical shift betweenmutant and wild-type enzyme. These affected residues are confinedto the immediate vicinity of residue 63. There is a substantialdifference in the ³¹P chemical shift of the 2'-phosphate ofthe bound coenzyme, reflecting the loss of the interaction withthe side chain of Thr63. The only changes in nuclear Overhausereffects (NOEs) observed were decreases in the intensity of NOEsbetween protons of the adenine ring of the bound coenzyme andthe nearby residues Leu62 and Ile102, showing that the substitutionof Thr63 does cause a change in the position or orientationof the adenine ring in its binding site.     

Antibiotic susceptibility profile of group B streptococcus acquired vertically

OBJECTIVE: To determine the contemporary antibiotic susceptibility profile of vertically acquired group B streptococcal isolates. METHODS: Susceptibility to ampicillin, penicillin G, erythromycin, clindamycin, cefazolin, and gentamicin was assessed by two methods, minimal inhibitory concentration and disc diffusion. RESULTS: The susceptibility profiles of 119 colonizing and eight invasive strains of group B streptococcus isolated from January 1996 to September 1997 at two hospitals in Birmingham, Alabama-University of Alabama at Birmingham and Cooper Green-were studied. Minimal inhibitory concentration determinations indicated that all colonizing strains were susceptible or moderately susceptible to ampicillin and penicillin G. Resistance was noted by at least one strain to each of the other antibiotics; all were resistant to gentamicin, whereas 27 (21%) were resistant to erythromycin, five (4%) to clindamycin, and one (1%) to cefazolin. All of the eight invasive strains were susceptible or moderately susceptible to ampicillin, penicillin G, clindamycin, and cefazolin; one (13%) was resistant to erythromycin, and all were resistant to gentamicin. Disc diffusion results generally were concordant with minimal inhibitory concentration results, although by disc diffusion fewer isolates were classified as susceptible, and more as moderately susceptible, to ampicillin and penicillin G than by minimal inhibitory concentration. CONCLUSION: Universal susceptibility of group B streptococcus to members of the penicillin family supports the continued use of penicillin G or ampicillin for early onset neonatal group B streptococcal disease prevention. For patients allergic to beta-lactam agents, clindamycin (4% resistance) may be a better alternative than erythromycin (21% resistance).     

The growth of high purity GaAs by molecular beam epitaxy in diffusion pumped system

Diffusion pumped MBE systems are likely to be technologically important in the development of production semiconductor growth equipment. It is demonstrated, for the first time, that high quality GaAs can be produced in such systems. Both electrical and optical results are presented to illustrate these findings.     

Evaluation of functions on microcomputers: square root

This paper treats the evaluation of one of the elementary functions on short wordlength computers. The setting is a binary fixed point short wordlength (8–16 bits) machine where the intent is to suggest improvements in ROM- or microcode-based software which include the square root function as part of a more general mathematical software library or for special computation in real-time applications. This paper focuses on the evaluation of square roots and features a careful treatment of Newton's method with linear initialization. Comparisons with other popular algorithms are made based on storage requirements, speed, and accuracy, with some indication of the effect that special hardware features have on the performance of these routines.     

A generalized theory of fracture mechanics

A fracture-mechanics theory is developed which gives fracture criteria for solids in general, without limitations as to their linearity, elastic behaviour or infinitesimal strain. Besides the “standard” results of the theory which reduce to familiar forms like the Griffith equation for linear, elastic solids, several new results emerge from the theory. These include a relationship between the surface work and the true surface energy of the solid, an explanation of certain departures from standard fracture mechanics obtained with inelastic materials, and a prediction and explanation of the phenomenon of notch brittleness. Further applications of the theory, such as adhesive failure and fatigue, will be explored in a subsequent paper.     

Liquid phase epitaxial growth of InAs1-xSbx on GaSb

Reported here, for the first time, is the lattice matched growth of InAs_1-xSb_x on GaSb. The thermodynamic incompatibility of the system, i.e., the strong tendency for the In-As-Sb liquid to dissolve the GaSb substrate, was solved via a novel liquid phase epitaxial growth technique. Liquid compositions for lattice matching conditions have been determined in the 400-600°C range. Epitaxial growth has been examined for (100), (111)B and (111)A orientations. Dislocation etch pit densities for lattice matched, and near lattice matched conditions are shown to be less than 10⁴-cm⁻² and 10⁵-cm⁻⁴, respectively. The composition of the epitaxial layers are determined by the Gandolfi X-ray diffraction technique and compositional homogeneity has been confirmed by SEM X-ray analysis. Some material related device properties which demonstrate the reproducibility of the growth technique are presented.     

Asymmetric phase-transfer catalysis utilizing chiral quaternary ammonium salts: asymmetric alkylation of glycine imines

O-Alkyl N-anthracenylmethyl derivatives of Cinchona alkaloids can function as enantioselective phase-transfer catalysts. By employing these catalysts in the asymmetric alkylation of glycine imines, one can generate a range of alpha-amino acid derivatives with high levels of enantiomeric excess. It is also possible to generate the catalysts in situ from commercially available chiral amines, which offers the opportunity to evaluate libraries of related structures. This latter approach has been successfully applied to a series of biphenyl quaternary ammonium salts resulting in the development of a new highly selective catalyst and opening up the potential of further expanding the range of alpha-amino acid derivatives that can be prepared.