Production of in situ aluminum-titanium diboride master alloy formed by slag-metal reaction

Al-TiB₂ master alloys have received much attention in recent years owing to their potential as efficient grain refiners for aluminum foundry alloys. In this study, the process of production of master alloys was investigated to develop a low cost method, namely, slag-metal reaction. This method can be used to fabricate Al-TiB₂ master alloy in situ from the TiO₂-H₃BO₃-Na₃AlF₆ and Al system. Since the price of the raw materials is low and the technology is simple, the processing technique appears to reduce the cost of the master alloy. Because of exothermic reactions, not much energy is needed to melt materials. In this process, Titanium diboride particles were formed in situ through the reactions of TiO₂, H₃BO₃ and Na₃AlF₆. Results showed that when the aluminum melted, the condensed TiB₂ particles that formed in situ were spherical with an average diameter of 1 μm. Furthermore, these TiB₂ particles were distributed uniformly through the master alloy.     

DESORPTION OF ETHYL ACETATE-WATER MIXTURE BY USING CROSS-LINKED POLY(VINYLALCOHOL) MEMBRANE AND COMPARISON OF RESULTS WITH PERVAPORATION

In this study using poly(vinylalcohol) (PVOH) membranes cross-linked with tartaric acid (Tac) desorption experiments were performed for selected concentrations of binary ethyl acetate (EtAc)-water mixture at temperatures of 30°, 40°, and 50°C to determine sorption of components. Sorption values measured were compared with those estimated by the Flory-Huggins approach. Additionally, desorption results were compared with pervaporation results of another study in terms of solution-diffusion theory, and the effect of thermodynamic interactions on selective transport of the binary mixture and membrane system was investigated. The results obtained show that selective transport of EtAc-water mixture was influenced by increasing temperature and water content in the feed. It is shown that preferential sorption is more effective for pervaporation selectivity than diffusion selectivity.     

Effects of mixing techniques and dentin moisture conditions on push-out bond strength of ProRoot MTA and Biodentine

Objective: To evaluate the influence of manual and mechanical mixing techniques as well as the effects of moisture on the push-out bond strength of ProRoot MTA (Dentsply Tulsa Dental, Tulsa, OK, USA) and Biodentine (Septodont, Saint Maur des Fosses, France) to radicular dentin.

Material and methods: Two hundred and forty dentin discs were assigned into three groups with respect to the moisture condition tested: (1) dry, (2) paper points, (3) wet. The discs were further divided into four subgroups according to the calcium silicate cements (CSCs) and mixing techniques used: (1) ProRoot MTA mixed manually, (2) ProRoot MTA mixed mechanically, (3) Biodentine mixed manually, and (4) Biodentine mixed mechanically. Bond strengths of the cements to root canal dentin were measured using a push-out test setup. The data were statistically analyzed using three-way ANOVA and Bonferroni post hoc test p = 0.05.

Results: The data indicated that the push-out bond strength values were significantly affected by CSCs, mixing techniques, and moisture conditions (p < 0.001). Dry conditions caused a significant decrease in bond strength values for both CSCs (p < 0.001). The mean bond strength of Biodentine was significantly higher than that of ProRoot MTA, regardless of the mixing techniques and moisture conditions (p < 0.001). Mechanical mixing favored bond strength values statistically compared to manual mixing (p < .001).

Conclusion: The mixing techniques and moisture conditions have an effect on the push-out bond strengths of ProRoot MTA and Biodentine. Dry samples and manual mixing of cements deteriorate the push-out bond strengths values.     

Defining requirements for a standard simulation environment

A simulation environment combines the many elements of simulation into one powerful tool. A standard based on a reference model would benefit users and researchers alike. We define a reference model for general-purpose discrete-event simulation environments, as well as the associated requirements for the model's functional layers, to be used as the basis for a future standard. We characterize environments by highlighting and grouping different tasks with common traits. Each group can then be related to the other groups in a logical, structured manner to create a model for a standard environment. Functionally, the standard environment would reside between the modeler (user) and the hardware platform's operating system     

Persistent left superior vena cava: Two case reports and a review from nephrologists’ perspective

Thoracic venous anomalies without congenital heart anomalies are present in minority of the population, but they are frequent enough to be encountered while placing hemodialysis catheters through the jugular or subclavian veins. Persistent left superior vena cava is the most commonly seen anomaly and it is rarely noticed before the observation of an unusual course of hemodialysis catheter or guidewire on chest X‐ray. We present two patients with previously unspotted persistent left superior vena cava and uncomplicated hemodialysis catheter insertions through the internal jugular veins with good catheter functions. Review of the relevant literature from a nephrologists’ perspective with technical aspects is provided.     

Investigating a Suitable Empirical Model and Performing Regional Analysis for the Suspended Sediment Load Prediction in Major Rivers of the Aegean Region,Turkey

This study investigates the appropriateness of four major empirical methods [Lane and Kalinske, Einstein, Brooks, Chang—Simons—Richardson] for predicting suspended sediment loads (SSLs) in three major rivers in the Aegean Region, Turkey. The measured data from 1975 to 2005 were used to test performance of the models. It was found that Brooks method was more appropriate, among the others, for predicting suspended sediment loads from each river. The prediction results of Brooks method were further improved by the use of genetic algorithm (GA_Brooks) optimizing a fitting parameter and showing a comparable performance to those of artificial neural networks (ANNs) and neuro-fuzzy (ANFIS) models for the same rivers. GA_Brooks, ANNs, and ANFIS models can be used for predicting loads at a regional scale. The sensitivity analysis results revealed that suspended and bed material particle diameters affect suspended sediment loads significantly.     

An intelligent supplier evaluation,selection and development system

Supplier evaluation and selection process has a critical role and significant impact on purchasing management in supply chain. It is also a complex multiple criteria decision making problem which is affected by several conflicting factors. Due to multiple criteria effects the evaluation and selection process, deciding which criteria have the most critical roles in decision making is a very important step for supplier selection, evaluation and particularly development. With this study, a hybridization of fuzzy c-means (FCM) and rough set theory (RST) techniques is proposed as a new solution for supplier selection, evaluation and development problem. First the vendors are clustered with FCM algorithm then the formed clusters are represented by their prototypes that are used for labeling the clusters. RST is used at the next step of modeling where we discover the primary features in other words the core evaluation criteria of the suppliers and extract the decision rules for characterizing the clusters. The obtained results show that the proposed method not only selects the best supplier(s), also clusters all of the vendors with respect to fuzzy similarity degrees, decides the most critical criteria for supplier evaluation and extracts the decision rules about data.     

Truncation and heme pocket mutations reduce production of functional catalase HPII in Escherichia coli

The subunit of catalase HPII from Escherichia coli is 753 residues in length and contains a core of approximately 500 residues, with high structural similarity to all other heme catalases. To this core are added extensions of approximately 80 and 180 residues at the N- and C- termini, respectively. The tetrameric structure is made up of a pair of interwoven dimers in which 90 N-terminal residues of each subunit are inserted through a loop formed by the hinge region linking the beta- barrel and alpha-helical domains of the adjacent subunit. A high concentration of proline residues is found in the vicinity of the overlap regions. To study the influence of the extended regions on folding and subunit association of HPII, a diversity of modifications have been introduced. Removal of the complete C-terminal domain or the N-terminal extension, either separately or together, effectively creating a small subunit catalase, resulted in no enzyme accumulation. Systematic truncations showed that only nine C-terminal residues (Ile745 to Ala753) could be removed without significantly affecting the accumulation of active enzyme. Removal or even conservative replacements of the side chain of Arg744 significantly reduced the accumulation of active enzyme despite this residue interacting only with the C-terminal domain. Removal of as few as 18 residues from the N- terminus also reduced accumulation of active enzyme. Changes to other residues in the protein, including residues in the heme binding pocket, also reduced the accumulation of active protein without substantially affecting the enzyme specific activity. Implications of these data for the interdependence of subunit folding and subunit-subunit interactions are discussed.      

A Comparative Study for Crisp and Fuzzy Query by a Software Tool

In this paper, through a developed software, crisp and fuzzy query were compared on a classical database. By means of this fuzzy query software tool, some fields (attribute) of a database table can be fuzzified and a supplementary database, which includes fuzzy values, is formed. Developed software tool is applied on a sample database including some fields about the students for the evaluation of scholarship application. It is concluded that, the fuzzy query method is more flexible and the results of such query are more predictive and satisfactory.This paper is an extended version of the paper which has been accepted at KES 2005 9th international conference on knowledge-based intelligent information and engineering systems.