The Highly Effective Cobalt Based Metal–Organic Frameworks Catalyst for One Pot Oxidative Esterification Under Mild Conditions

Catalysis Letters - The cobalt-based metal organic frameworks (Co-MOFs) catalyst has been prepared with using terephthalic acid and 4,4′-bipyridine as organic linkers by facile solvothermal...     

Fault-tolerant embedded system design and optimization considering reliability estimation uncertainty

In this paper, we model embedded system design and optimization, considering component redundancy and uncertainty in the component reliability estimates. The systems being studied consist of software embedded in associated hardware components. Very often, component reliability values are not known exactly. Therefore, for reliability analysis studies and system optimization, it is meaningful to consider component reliability estimates as random variables with associated estimation uncertainty. In this new research, the system design process is formulated as a multiple-objective optimization problem to maximize an estimate of system reliability, and also, to minimize the variance of the reliability estimate. The two objectives are combined by penalizing the variance for prospective solutions. The two most common fault-tolerant embedded system architectures, N-Version Programming and Recovery Block, are considered as strategies to improve system reliability by providing system redundancy. Four distinct models are presented to demonstrate the proposed optimization techniques with or without redundancy. For many design problems, multiple functionally equivalent software versions have failure correlation even if they have been independently developed. The failure correlation may result from faults in the software specification, faults from a voting algorithm, and/or related faults from any two software versions. Our approach considers this correlation in formulating practical optimization models. Genetic algorithms with a dynamic penalty function are applied in solving this optimization problem, and reasonable and interesting results are obtained and discussed.     

Effects of handicraft sitting postures on lower trunk muscle fatigue

Fifteen male subjects were exposed to a primary tracking task and a variety of subsidiary tasks for a total of 15 hours. Tracking performance was assessed through the use of two error measures, amount of time off the target track, and number of times off target. Subsidiary performance tasks included: a vigilance task requiring subjects to respond to the deflection of the noodle of a small meter; two reaction time tasks requiring response to the onset of one or the other of two lights; mental multiplication, which required the solution of simple multiplication problems; and digit span, in which the subject was required to repeat as rapidly and as accurately as possible a sot of digits of either five, six or seven numbers in length. In addition, three physiological measures were obtained.

A significant decrement in trucking performance was obtained for both measures utilized. This decrement was not particularly abrupt in its occurrence but rather took place cumulatively over the entire course of the experiment. There was no clearly established performance decrement on the subsidiary tasks utilized in this investigation. A marked variability in performance over the course of the experimental session was characteristic of performance on these tasks. Performance on the vigilance task, and one of the reaction time tasks improved during the 15-hour test session.

The 17-Kotosteroid and 17-Hydroxyeortieoid values increased during the session but only in the case of the latter was the increase significant. The eosinophil count of subjects exposed to the test conditions decreased steadily throughout the experimental session. However, eosinophil measures obtained from control subjects increased during a similar time period.     

Oxidation Kinetics of Boronized Low Carbon Steel AISI 1018

The high-temperature oxidation behavior of boron coating on plain low-carbon steel AISI 1018 was studied at 500, 600, 700, 800 and 900 °C in air. The oxidation resistance of unboronized (uncoated) and boronized (boron-coated) specimens was studied isothermally in a thermogravimetric analyzer. The oxidation-rate constant represented as a parabolic rate constant (k _p ) was evaluated with the parabolic rate law. The activation energy of oxidation on unboronized and boronized steel specimens was determined by Arrhenius law. Optical microscopy, XRD and SEM were used for surface characterizations. The experimental results show that boronized coating increases the oxidation resistance of plain low carbon steel AISI 1018 about five times and prevents oxygen from penetrating into the steel substrate at temperatures below 900 °C.     

The Effect of Boronizing on Metallic Alloys for Automotive Applications

In this study the wear resistance, corrosion resistance, and oxidation resistance of boronized metallic alloys were investigated. Thermochemical treatment was performed by powder pack boronizing process at temperature 850-950 °C for 4 h. Saw-tooth morphology and smooth interface microstructures were observed with an optical microscope; microhardness was measured across the coating depth. The phases present in the boron coatings depend on the substrate material. High-temperature oxidation resistance was investigated and it was found that boron coating on ferrous alloys can resist temperatures up to 800 °C. The corrosion resistance of the boronized samples was improved and the corrosion rate was calculated for boronized and plain specimens. Wear testing was conducted by following the procedures of ASTM G99, ASTM D2526, and ASTM D4060. The obtained experimental results revealed that boronizing significantly improves the wear-resistance, corrosion-resistance, and oxidation resistance of metallic alloys. This article was presented at Materials Science & Technology 2007, Automotive and Ground Vehicles symposium held September 16-20, 2007, in Detroit, MI.     

Practical solutions for multi-objective optimization: An application to system reliability design problems

For multiple-objective optimization problems, a common solution methodology is to determine a Pareto optimal set. Unfortunately, these sets are often large and can become difficult to comprehend and consider. Two methods are presented as practical approaches to reduce the size of the Pareto optimal set for multiple-objective system reliability design problems. The first method is a pseudo-ranking scheme that helps the decision maker select solutions that reflect his/her objective function priorities. In the second approach, we used data mining clustering techniques to group the data by using the k-means algorithm to find clusters of similar solutions. This provides the decision maker with just k general solutions to choose from. With this second method, from the clustered Pareto optimal set, we attempted to find solutions which are likely to be more relevant to the decision maker. These are solutions where a small improvement in one objective would lead to a large deterioration in at least one other objective. To demonstrate how these methods work, the well-known redundancy allocation problem was solved as a multiple objective problem by using the NSGA genetic algorithm to initially find the Pareto optimal solutions, and then, the two proposed methods are applied to prune the Pareto set.     

Surface modification of ferrous alloys with boron

This paper presents the effects of boronizing on ferrous alloys such as plain-carbon steel AISI 1018, high-strength alloy steel AISI 4340, and austenitic stainless steel AISI 304. The coatings were produced by thermochemical treatment with powder mixtures at temperatures of 850°C for 4 h. The microstructure of obtained coatings was investigated, the microhardness was measured, and the corrosion resistance and oxidation resistance were tested. By metallographic analyses, the thickness of the coatings was measured. Microhardness of the boron coatings was measured using loads of 10 gf, 25 gf, and 50 gf. Corrosion tests were performed in 5% HCl, 10% HCl, and 15% HCl at room temperature. To determine the oxidation resistance of the coatings, the isothermal method was used to observe the weight change at a temperature of 600°C for 12 h. Results indicated that the presence of boronized coatings on ferrous alloys greatly improved their microhardness, oxidation resistance, and corrosion resistance.