Corrosion and Erosion-Corrosion Processes of Metal-Matrix Composites in Slurry Conditions

The corrosion and erosion-corrosion (EC) processes of four metal-matrix composites (MMCs) in a simulated cooling water environment have been assessed in this article. The MMCs consisted of two Ni-base and two Fe-base matrices alloyed with different concentrations of chromium, molybdenum, boron, silicon, and carbon; the matrices were reinforced with tungsten carbide (WC) particles. The corrosion behavior has been investigated using a combination of potentiostatic polarization and post-tests surface analysis. The EC processes were studied by in situ electrochemical techniques measuring the current density and corrosion potential response at different slurry temperatures and sand content. At static conditions it was found that as the temperature increased, there was a transition from a homogeneous corrosion of the matrix to an interfacial corrosion mechanism. The Ni-base MMCs showed a better corrosion resistance and interestingly a highly alloyed matrix did not significantly improved MMC’s corrosion resistance. In the in situ EC tests, the Fe-base MMCs showed a constant increase in the current density at all sand contents. Whereas, significant changes were not observed in the Ni-base MMCs below 0.5 g/L. Although sand content had an effect on the monitored current density (the current increased as the sand content increased) this effect was less pronounced above 3 g/L.     

Analyzing business competition by using fuzzy TOPSIS method: An example of Turkish domestic airline industry

The article uses fuzzy TOPSIS multi-methodological approach in the Turkish domestic airline industry. It starts by describing exceedingly complex nature of competition in the sector. Then, it deals with the constituent parts of the research methodology and the eclectic approach itself. The implementation of fuzzy TOPSIS method in the Turkish domestic airline industry reveals the ranking of major air carriers in light of key success variables in the sector. The article also provides an evaluation of empirical findings of fuzzy TOPSIS method from a managerial perspective.     

Integrating genetic algorithms, tabu search, and simulatedannealing for the unit commitment problem

This paper presents a new algorithm based on integrating genetic algorithms, tabu search and simulated annealing methods to solve the unit commitment problem. The core of the proposed algorithm is based on genetic algorithms. Tabu search is used to generate new population members in the reproduction phase of the genetic algorithm. A simulated annealing method is used to accelerate the convergence of the genetic algorithm by applying the simulated annealing test for all the population members. A new implementation of the genetic algorithm is introduced. The genetic algorithm solution is coded as a mix between binary and decimal representation. The fitness function is constructed from the total operating cost of the generating units without penalty terms. In the tabu search part of the proposed algorithm, a simple short-term memory procedure is used to counter the danger of entrapment at a local optimum, and the premature convergence of the genetic algorithm. A simple cooling schedule has been implemented to apply the simulated annealing test in the algorithm. Numerical results showed the superiority of the solutions obtained compared to genetic algorithms, tabu search and simulated annealing methods, and to two exact algorithms     

Cerebral mantle thickness: a measurement useful in anatomic diagnosis of fetal ventriculomegaly

The ultrasonographic diagnosis of cerebral ventriculomegaly carries grave implications, in that affected fetuses may suffer abnormal postnatal development or therapeutic abortion. It is important for pathologists to corroborate the clinical diagnosis, but because diagnostic methodologies and criteria differ so radically, this can be problematic. The clinical diagnosis is made primarily by serial ultrasound examinations of the cerebral ventricles, spaces that can be altered postmortem, particularly when the brain is autolysed or deformed artifactually. We therefore sought to learn if examination of tissue, rather than spaces, can identify accurately those fetuses diagnosed with cerebral ventriculomegaly by prenatal ultrasound. The thickness of the cerebral mantle was obtained in 100 control fetuses aged 14 to 26 postmenstrual weeks. Statistical analysis revealed significant correlation of cerebral mantle thickness with crown-rump length, foot length, and head circumference. Twenty fetuses diagnosed with ventriculomegaly showed mantle thicknesses that were less than the control mean. In a few cases, mantle thickness fell between the mean and -1 SD; in several others, thickness was diminished by -1 SD to -2 SD; in one-half of cases, mantle thickness was 2 SDs or more below the expected mean. Head circumference was within 2 SDs of the control mean in most cases, and increased beyond 2 SDs in only two cases. Head circumference is an unreliable indicator of ventriculomegaly in the midgestational fetus. By contrast, cerebral mantle thickness is a simple and useful way of corroborating ultrasonographic diagnoses at autopsy and may also prove useful in clinical settings.     

A GIS-Based Optimization Framework for Competitive Multi-Facility Location-Routing Problem

In a dynamic market setting, firms need to quickly respond to shifting demographics and economic conditions. In this paper, we investigate the problem of determining the optimum set of locations for a firm, which operates a chain of facilities under competition. We consider the objective of maximizing profit, defined as gross profit margin minus logistics costs. We propose a location-routing model where revenue is realized according to probabilistic patronization of customers and routing costs are incurred due to vehicles serving the open facilities from a central depot. We propose a hybrid heuristic optimization methodology for solving this model. The optimal locations are searched for by a Genetic Algorithm while an integrated Tabu Search algorithm is employed for solving the underlying vehicle routing problem. The solution approach is tested on a real dataset of a supermarket chain. The results show that the location decisions made by the proposed methodology lead to increased market share and profit margin, while keeping logistics costs virtually unchanged. Finally, we present a GIS-based framework that can be used to store, analyze and visualize all data as well as model solutions in geographic format.     

Electricity generation from rice husk in Indian rice mills: potential and financial viability

Rice husk generated as a by-product of rice processing is an important energy resource. The availability of this resource in India has been assessed and the technologies for exploitation of its energy potential in rice processing industry discussed. Nomographs have been developed for estimation of the husk required to meet the energy demand of parboiling, drying and milling operations. The unit cost of electricity using rice husk gasifier-based power generation systems has been calculated and its financial feasibility assessed in comparison with utility-supplied and diesel-generated electricity. With the cost and efficiency data assumed here, the unit cost of electricity produced by rice husk gasifier-dual fuel engine-generator system varies between Rs 2/kWh and Rs 7/kWh. (Note: 35 Rs approximates to $US 1.)     

Transient solutions of a software reliability model with imperfect debugging and error generation

In this paper we obtain transient solutions of a software reliability model under the assumption that the failure rate is proportional to the remaining errors in the software under imperfect debugging and error generation. The maximum number of errors in the software is assumed to be finite. We obtain the transient probabilities for the remaining errors, mean number of errors remaining, reliability of the software, expected number of failures etc. A method to estimate model parameters is given. Finally, a numerical example is presented.     

Local and regional anesthesia for functional endoscopic sinus surgery

An effective topical and regional anesthetic technique using 25% cocaine paste combined with intravenous midazolam hydrochloride was used in 554 patients undergoing functional endoscopic sinus surgery. The operative fields were excellent and all procedures were completed with little patient disturbance. Patients recovered rapidly from sedation and were usually fit for discharge on the same day. There were no anesthetic complications. The major surgical complication rate was 0.5%.     

Complexity of unification problems with associative-commutative operators

The unification problem for terms containing associative and commutative functions is of importance in theorem provers based on term rewriting and resolution methods as well as in logic programming. The complexity of determining whether two such terms are unifiable was known to be NP-hard. It is proved that the problem is NP-complete by describing a nondeterministic polynomial time algorithm for it. The case where the terms are linear and have no common variables is shown to be in P. The NP-completeness of other similar unification problems, in particular, when a function symbol is also idempotent and/or has a unit (identity), is also discussed. Finally, a table of the complexity of E-matching and E-unification problems is given.Partially supported by the National Science Foundation grant nos. DCR-8408461 and CCR-8906678. A preliminary version of this paper appeared earlier as a technical report of General Electric Corporate Research and Development, Dec. 1986.