The Effect of Iron Content on Microstructure and Mechanical Properties of A356 Cast Alloy

In the present study, microstructure and mechanical properties of A356 alloy including various amounts (0.2 to 1.2 wt pct) of iron were investigated. The alloys were produced by conventional gravity sand casting method. In order to determine the effect of iron addition to A356, optical and scanning electron microscopes (SEM/EDS) were used for microstructural examinations, and X-ray diffraction (XRD) analysis was carried out for phase characterization. Tensile tests were also conducted in order to determine effect of the Fe content on mechanical properties. It was found that as the Fe content of A356 was increased, the secondary dendrite arm spacing (SDAS) was decreased and the morphology of Al-Si eutectic became finer. From XRD examinations, different iron-based intermetallic compounds (β-Al₅FeSi and α-Al₈Fe₂Si) formations were observed. It was also observed that as iron content increased, α-Al₈Fe₂Si intermetallic was transformed into β-Al₅FeSi intermetallic. The tensile test results revealed that tensile strength and elongation values were reduced by increasing Fe content. It was also determined that β-Al₅FeSi intermetallics were more negatively effective on tensile strength than α-Al₈Fe₂Si intermetallics.     

Comparison of antioxidant activities of bovine whey proteins before and after simulated gastrointestinal digestion

Oxidative stress caused by free radicals has been implicated in several human disorders. Dietary antioxidants can help the body to counteract those reactive species and reduce oxidative stress. Antioxidant activity is one of the multiple health-promoting attributes assigned to bovine whey products. The present study investigated whether this activity was retained during upper gut transit using a static simulated in vitro gastrointestinal digestion (SGID) model. The capacity to scavenge free radicals and reduce ferric ion of whey protein isolate (WPI), individual whey proteins, and hydrolysates pre- and post-SGID were measured and compared using various antioxidant assays. In addition, the free AA released from individual protein fractions in physiological gut conditions were characterized. Our results indicated that the antioxidant activity of WPI after exposure to the harsh conditions of the upper gut significantly increased compared with intact WPI. From an antioxidant bioactivity viewpoint, this exposure negates the need for prior hydrolysis of WPI. The whey protein α-lactalbumin showed the highest antioxidant properties post-SGID (oxygen radical absorbance capacity = 1,825.94 ± 50.21 μmol of Trolox equivalents/g of powder) of the 4 major whey proteins tested with the release of the highest amount of the antioxidant AA tryptophan, 6.955 μmol of tryptophan/g of protein. Therefore, α-lactalbumin should be the preferred whey protein in food formulations to boost antioxidant defenses.     

On the independence requirement in Dempster-Shafer theory for combining classifiers providing statistical evidence

In classifier combination, the relative values of beliefs assigned to different hypotheses are more important than accurate estimation of the combined belief function representing the joint observation space. Because of this, the independence requirement in Dempster’s rule should be examined from classifier combination point of view. In this study, it is investigated whether there is a set of dependent classifiers which provides a better combined accuracy than independent classifiers when Dempster’s rule of combination is used. The analysis carried out for three different representations of statistical evidence has shown that the combination of dependent classifiers using Dempster’s rule may provide much better combined accuracies compared to independent classifiers.     

Comprehensive stability design of planar steel members and framing systems via inelastic buckling analysis

This paper presents a comprehensive approach for the design of planar structural steel members and framing systems using a direct computational buckling analysis configured with appropriate column, beam and beam-column inelastic stiffness reduction factors. The stiffness reduction factors are derived from the ANSI/AISC 360-16 Specification column, beam and beam-column strength provisions. The resulting procedure provides a rigorous check of all member in-plane and out-of-plane design resistances accounting for continuity effects across braced points as well as lateral and/or rotational restraint from other framing. The method allows for the consideration of any type and configuration of stability bracing. With this approach, no member effective length (K) or moment gradient and/or load height (C _b ) factors are required. The buckling analysis rigorously captures the stability behavior commonly approximated by these factors. A pre-buckling analysis is conducted using the AISC Direct Analysis Method (the DM) to account for second-order effects on the in-plane internal forces. The buckling analysis is combined with cross-section strength checks based on the AISC Specification resistance equations to fully capture all the member strength limit states. This approach provides a particularly powerful mechanism for the design of frames utilizing general stepped and/or tapered I-section members.     

New lipophilic catechin derivatives by oxa-Pictet-Spengler reaction

Synthesis of lipophilic catechin derivatives was carried out to improve their solubility in lipidic substances that must be protected against oxidation. For this purpose, an oxa-Pictet-Spengler coupling reaction, which is not only conservative for antioxidative activity, but also simple, mild and inexpensive, was applied. This method permitted grafting of alkyl chains, from various methyl ketones, between the C and B rings of catechin. The derivatives were isolated, on the one hand, by silica gel column chromatography and, on the other, by simple aqueous washing of the crude product. Both treatments produced almost the same purity; products of the second one had best antioxidative activities given by inhibition of the induced oxidation of methyl linoleate and by reactivity with the free radical 2,2-diphenyl-picrylhydrazyl. All derivatives acquired a lipophilic character as proven by measurement of the partition coefficient between octanol and water.     

Disassembly line balancing using linear physical programming

Disassembly is the separation of a product into its constituent parts in a systematic way. It has gained importance recently due to its vital importance in product recovery. Cost-effective implementation of disassembly operation has a direct impact on the profitability of product recovery activities (recycling, remanufacturing etc.). Although it is possible to carry out disassembly operations in a disassembly station or in a disassembly cell, the highest productivity is achieved in a disassembly line. The output of a disassembly line can be maximised only if the line is balanced. A linear physical programming-based disassembly line balancing method is proposed in this study. This method was used to balance a mixed-model disassembly line and the effectiveness of the method was illustrated by analysing the results.     

Radionuclides and heavy metals concentrations in Turkish market tea

Tea is one of the most popular beverages in the world. The Eastern Black Sea Region of Turkey is one of the main tea producers in Turkey and the fifth in the world. Thus, the chemical components in tea have received great interest because they are related to health. Since this region was contaminated by the Chernobyl accident in 1986, a comprehensive study was planned and carried out to determine the radioactivity level in the tea growing region. The activity concentrations of ²³²Th, ²³⁸U, ⁴⁰K and ¹³⁷Cs were measured in 29 black tea and one green tea samples from local Turkish markets using gamma spectrometry with an HpGe detector. The average activity concentration of ²³²Th, ²²⁶Ra, ⁴⁰K and ¹³⁷Cs were found 3.2 ± 0.6 Bq/kg, 6.4 ± 0.7 Bq/kg, 445.6 ± 17.8 Bq/kg and 42.0 ± 1.4 Bq/kg in tea samples, respectively.In addition, the concentration of five heavy metals including Fe, Mn, Zn, Cu and Pb were determined by inductively coupled plasma spectroscopy (ICP/OES) on tea samples. Among the investigated metals, Mn was the highest levels. The levels of manganese were in the range of 1850.75–292.65 μg/g (mean: 1286.35 ± 0.58 μg/g). Levels of Pb in the tea samples analyzed were below the detection limits. The concentrations of all elements for daily intake are below safety levels for human consumptions.     

Trapezoidal fuzzy multi-number and its application to multi-criteria decision-making problems

In this paper, the concept of trapezoidal fuzzy multi-number (TFM-number) is proposed and some desired operational laws with properties are introduced. In the TFM-number, the occurrences are more than one with the possibility of the same or the different membership functions and the TFM-number is an extension of both fuzzy number set and fuzzy set, allowing the repeated occurrences of any element. Also, aim of this paper is to investigate a multiple criteria decision-making (MCDM) method under TFM-number environment. To construct this method, we first introduce some operational laws on TFM-number based on t-norm and s-norm. Then, TFM-number arithmetic and geometric operators are proposed. Finally, we develop an MCDM method and apply to an MCDM problem to verify the introduced decision-making methods.