The gradient of the finite element variational indicator with respect to nodal and applications in fracture mechanics and mesh optimization

We derive a closed-form expression for the change in the variational indicator of a finite element mesh with respect to perturbations in nodal point co-ordinates. The expression is evaluated very effectively from standard finite element data obtained in one solution, and may be easily programmed as part of a general finite element code. We present the derivation for two- and three-dimensional isoparametric elements used in linear and nonlincar elasticity. The expression has practical applications in the computation of stress intensity factors in fracture mechanics and in the determination of the ‘optimal’ mesh with a given element-node connectivity. We demonstrate both applications by accurately determining the stress intensity factor of a Mode I crack using a finite element mesh which was improved using mesh optimization.     

Oxidation of oleuropein studied by EPR and spectrophotometry

The autoxidation at alkaline pH and enzymatic oxidation by mushroom tyrosinase of oleuropein, the dominant biophenol present in the fruits and leaves of Olea europea, was followed by both electron paramagnetic resonance (EPR) and absorption spectroscopy. For comparison, the same oxidation processes were applied to 4‐methylcatechol, a simple polyphenol present in olive mill wastewaters. EPR spectra of stable o‐semiquinone radicals produced during autoxidation at pH 12 and short‐lived o‐semiquinone free radicals produced during autoxidation at pH 9.0 or tyrosinase action and stabilized by chelation with a diamagnetic metal ion (Mg²⁺) were recorded for both polyphenols, and the corresponding hyperfine splitting constants were determined. The UV‐Vis spectral characteristics of the oxidation of polyphenols were highly dependent on the type of polyphenol, oxidant type and the pH of the reaction. The kinetic behavior of tyrosinase in the presence of oleuropein and 4‐methylcatechol was followed by recording spectral changes at 400 nm (absorption maximum) over time. The tysosinase activity with oleuropein showed a pronounced pH optimum at pH 6.5 and a minor one around pH 8. From the data analysis of the initial rate at pH 6.5, the kinetic parameters K_m = 0.34 ± 0.03 mM and V_max = 0.029 ± 0.002 ΔA₄₀₀ min^–1 were determined for oleuropein.     

Support vector regression for determining the minimum zone sphericity

Several methods have been investigated to determine the deviation of manufactured spherical parts from ideal geometry. One of the most popular is the least squares technique, which is still widely employed in coordinate measuring machines used by industries. The least squares algorithm is optimal under the assumption that the data set is very large and has the inherent disadvantage of overestimating the minimum tolerance zone, resulting sometimes in the rejection of good parts. In addition, it requires that the data be distributed normally. The support vector regression approach alleviates the necessity for these assumptions. While most fitting algorithms in practice today require that the sampled data accurately represent the surface being inspected, support vector regression provides a generalization over the surface. We describe how the concepts of support vector regression can be applied to the determination of tolerance zones of nonlinear surfaces; to demonstrate the unique potential of support vector machine algorithms in the area of coordinate metrology. In specific, we address part quality inspection of spherical geometries.     

Parallel-access memory management using fast-fits

The two most common approaches to managing shared-access memory-free lists and buddy systems-have significant drawbacks. Free list algorithms have poor memory access characteristics, and buddy systems utilize their space inefficiently. In this paper, we present an alternative approach to parallel-access memory management based on the fast-fits algorithm. A fast-fits memory manager stores free blocks in a tree structure, providing fast access and efficient space use. Since the fast-fits algorithm accesses fewer blocks than a free list algorithm, it reduces the amount of cache invalidation overhead due to the memory manager. Our performance experiments show that the parallel-access fast-fits memory manager allows significantly greater access rates than a serial-access fast-fits memory manager does. We note that shared-memory multiprocessor systems need efficient dynamic storage allocators, both for system purposes and to support parallel programs.     

Active memory chips: A brief survey and case study

Conventional random access memories are capable only of writing data into and reading data from the storage location corresponding to a given address. The availability of VLSI circuits containing hundreds of thousands of switching devices, however, has recently made practical the implementation of active memory chips capable of performing a range of complex operations on their stored data. Such designs are characterized by the extensive intermingling of processing and memory resources within a single chip to achieve the rapid and cost-effective parallel execution of operations relevant to such tasks as image processing, computer graphics, artificial intelligence, and database management.This paper presents a brief survey of a number of active memory chips that have been implemented or proposed, along with a more detailed examination of a particular active memory circuit, the NON-VON 3 primary processing subsystem chip.This research was supported in part by the Defense Advanced Research Projects Agency, under contract N00039-84-C-0165, in part by the New York Center for Advanced Technology in Computers and Information Systems at Columbia University, and in part by an IBM Faculty Development Award.     

Conjugated dienes and trienes from methyl oleate and methyl linoleate

Methyl oleate and methyl linoleate were converted to conjugated dienes and trienes, respectively, by selecting and modifying the conventional procedures usually applied to the generation and characterization of fatty hydroperoxides. Conditions have been studied in the laboratory for: (a) the optimum production of hydroperoxides with a minimum of by-products, (b) the effective separation and concentration of the resulting hydroperoxide, (c) the economic reduction of the hydroperoxide mixture, (d) simple dehydration of the reduced product, and, (e) recovery of the resulting polyene-rich material. If the processing sequence is halted after the reduction step, the resulting product,is a mixture of allylic hydroxy monoene or diene methyl esters. Our investigations have been extended to include studies on the methyl esters of commercial oleic acid and the mixture of methyl esters resulting from alcoholysis of lard oil. Products containing 20–25% conjugated diene and lesser proportions of conjugated triene were obtained. Presented at the AOCS Meeting, Houston, April 1965. E. Utiliz, Res. Dev. Div., ARS, USDA.     

Duration of slip-resistant shoe usage and the rate of slipping in limited-service restaurants: results from a prospective and crossover study

Several studies have indicated that slip-resistant shoes may have a positive effect on reducing the risk of slips and falls, a leading cause of injury at work. Few studies, however, have examined how duration of shoe usage affects their slip-resistance properties. This study examined the association between the duration of slip-resistant shoes usage and the self-reported rate of slipping in limited-service restaurant workers. A total of 475 workers from 36 limited-service restaurants in the USA were recruited to participate in a 12-week prospective study of workplace slipping. Of the 475 participants, 83 reported changing to a new pair of shoes at least once during the 12-week follow-up. The results show that slip-resistant shoes worn for less than six months were moderately more effective than those worn for more than six months. Changing to a new pair of shoes among those wearing slip-resistant shoes at baseline was associated with a 55% reduction in the rate of slipping (RR = 0.45, 95% CI = 0.23–0.89). Further research is needed to develop criteria for the replacement of slip-resistant shoes.

Practitioner Summary: The duration of usage impacts the slip-resistance properties of slip-resistant shoes. Slip-resistant shoes worn for less than six months were moderately more effective in reducing slips than slip-resistant shoes worn for more than six months. Shoe use policies should not only encourage or require their use but also include guidance on replacing slip-resistant shoes at regular intervals.     

Kinetic Study of the Steam Reforming of Isobutane Using a Pt–CeO2–Gd2O3 Catalyst

Steam reforming of isobutane on a 0.5% Pt–Ce_0.8Gd_0.2O_1.9 catalyst was carried out from 300 to 700 °C under integral conditions with a gas hourly space velocity (GHSV) of 12,000 h⁻¹. The major products were H₂, CO₂, CO and CH₄. The other products produced were ethane, ethylene, propane and propylene with a total molar composition of less than 1.5%. A complete conversion of isobutane was achieved at 700 °C, Kinetic data was obtained by changing the partial pressure of the reactants and the temperature under differential conditions with a GHSV of 55,400 h⁻¹. This was done after observing stable isobutane steam reforming for 160 h and under conditions where the mass transfer limitations were insignificant. An empirical Langmuir–Hinshelwood type model that best fit the kinetic data available was developed.     

Production of hydrogen for fuel cells by reformation of biomass-derived ethanol

The reformation of biomass-derived ethanol to a hydrogen-rich gas stream suitable for feeding fuel cells is investigated as an efficient and environmentally friendly process for the production of electricity for mobile and stationary applications. Steam reforming of ethanol is investigated over Ni catalysts supported on La₂O₃, Al₂O₃, YSZ and MgO. The influence of several parameters on the catalytic activity and selectivity is examined including reaction temperature, water-to-ethanol ratio and space velocity. Results reveal that the Ni/La₂O₃ catalyst exhibits high activity and selectivity toward hydrogen production and, most important, long term stability for steam reforming of ethanol. The enhanced stability of this catalyst may be due to scavenging of coke deposition on the Ni surface by lanthanum oxycarbonate species which exist on top of the Ni particles under reaction conditions.