Conducting polymer composites of multiwalled carbon nanotube filled doped polyaniline

A multiwalled carbon nanotube (c‐MWNT)/polyaniline (PANI) composite was synthesized by an in situ chemical oxidative polymerization process. With the carbon nanotube loading increased from 0 to 30 wt %, the conductivity also increased and became weakly temperature‐dependent. Fourier transform infrared spectroscopy studies showed that the synthesis by an in situ process led to effective site‐selective interactions between the quinoid ring of the PANI and the multiwalled nanotubes, facilitating charge‐transfer processes between the two components. The morphological analysis indicated that the c‐MWNTs were well dispersed and isolated, and the tubes became crowded proportionally to the weight percentage of c‐MWNTs used in the composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Field-oriented test methods to evaluate structural build-up at rest of flowable mortar and concrete

Thixotropy of flowable mortar and concrete is an important property that affects stability and form pressure characteristics. The increase in thixotropy can reduce lateral pressure on formwork systems. On the other hand, low thixotropy or a continuous casting is required to eliminate the formation of weak interface between lifts in multilayer casting. Thixotropy can be assessed by determining the rate of structural build-up at rest, which necessitates the use of simple and robust test methods to be quantified. Five field-oriented test methods that can be used for the determination of structural build-up at rest of mortar and concrete are proposed in this paper in an attempt to select a reliable field-oriented test. This includes the inclined plane (IP), portable vane (PV), undisturbed slump spread (USS), cone penetration (CP), and K-slump test methods. The repeatability of these test methods was determined four times using two concrete-equivalent mortars and two self-consolidating concretes (SCC) of different thixotropy levels. The IP, PV, and USS tests showed relative error (RE) values of 0.5?C37?%. The CP test was successfully used to determine structural build-up of mortar; however, it was difficult to assess the thixotropy of concrete. The K-slump test exhibited a RE, less than 12?% for SCC mixtures with low thixotropy, but up to 76?% for highly thixotropic SCC. Good correlations were established among the various structural build-up indices determined from the proposed test methods and those determined by rheometric tests using various concrete.     

Experimental and numerical study on the performance of hollow and concrete‐filled elliptical steel columns subjected to severe fire

This paper presents the results of an experimental and validated theoretical study to investigate the performance of steel columns with hollow and concrete‐filled elliptical sections subjected to hydrocarbon fire. The test programme involved 18 columns with 200 × 100 × 8‐mm, 300 × 150 × 8‐mm and 400 × 200 × 8‐mm elliptical sections representing slenderness of 50, 33 and 24, respectively. The 1800‐mm columns were subjected to the severe hydrocarbon fire curve and tested under loadings ratios of 20%, 40% and 60% of the EC3 ultimate strength. The paper presents the obtained experimental results including measured axial and lateral displacements, failure temperatures and failure time. A three‐dimensional model was built using the finite element method (FEM) and was validated using the obtained tests results. The finite element model showed an excellent agreement with tests results of failure temperatures, failure modes, and axial and lateral displacements. However, because of restrictions in the software capabilities, the mechanical–thermal behaviour of concrete including spalling was not considered in the model. The verified finite element model was used to conduct a parametric analysis involving a range of parameters of loading level and slenderness. The study has shown that the concrete‐filled sections have demonstrated an improved fire resistance when compared with the hollow sections under the low loading ratios. The FEM model has successfully predicted the unique thermal profile of elliptical section under fire, which was observed during the tests. Copyright © 2015 John Wiley & Sons, Ltd.     

Selecting the most appropriate corrective actions for energy saving in existing buildings A/C in hot arid regions

Energy consumption, especially by the A/C load, represents a major concern particularly in hot arid regions. Selecting the best energy saving option under these conditions is a function of many various variables and thus represents a multi-criteria decision making problem. This study involved building a decision-making model to specify the most important and adequate alternatives to energy conservation in cooling systems in existing buildings in hot arid regions. It examined the best corrective action(s) to be implemented based on a number of criteria that were subject to weighting by experts. The energy saving corrective action options considered were limited to Providing Sufficient Thermal Insulation, Changing Occupant’s Habits, Providing Appropriate Shading, Building Tightness (sealing air leakage), Use of Modern Controllers, and Use of Efficient Equipment. The Analytical Hierarchy Process (AHP) along with its commercial software package, EXPERT CHOICE?, were utilized in this study. The findings of the study indicated that under normal conditions, both Providing Appropriate Shading and Building Tightness represent the best choices of energy saving actions in hot arid regions and that the AHP provides a powerful analysis tool that leads to consistent judgment and reliable decision. In fact, the method demonstrated itself as a fundamental knowledge-based tool that enables quantifying and analyzing experts’ qualitative judgments that lead to sound multi-criteria decision making.     

Application of CNT nanofluids in a turbulent flow heat exchanger

Nanofluids have received much attention since its discovery owing to its enhanced thermal conductivity and heat transfer characteristics which makes them a promising coolant in heat transfer application. In this study, the enhancement in heat transfer of carbon nanotube (CNT) nanofluids under turbulent flow conditions is investigated experimentally. The CNT concentration was varied from 0.051 to 0.085 wt%, respectively. The nanofluid suspension was stabilised by gum arabic through a process of homogenisation and water bath sonication at 25 °C. The flow rate of cold fluid (water) is varied from 1.7 to 3 L/min, while flow rate of the hot fluid is varied between 2 and 3.5 L/min. Thermal conductivity, density, and viscosity of the nanofluids are also measured as a function of temperature and CNT concentration. The experimental results were validated with theoretical correlations for turbulent flow available in the literature. Results showed an enhancement in heat transfer between 9% and 67% as a function of temperature and CNT concentration.     

Similarity measures in formal concept analysis

Formal concept analysis (FCA) has been applied successively in diverse fields such as data mining, conceptual modeling, social networks, software engineering, and the semantic web. One shortcoming of FCA, however, is the large number of concepts that typically arise in dense datasets hindering typical tasks such as rule generation and visualization. To overcome this shortcoming, it is important to develop formalisms and methods to segment, categorize and cluster formal concepts. The first step in achieving these aims is to define suitable similarity and dissimilarity measures of formal concepts. In this paper we propose three similarity measures based on existent set-based measures in addition to developing the completely novel zeros-induced measure. Moreover, we formally prove that all the measures proposed are indeed similarity measures and investigate the computational complexity of computing them. Finally, an extensive empirical evaluation on real-world data is presented in which the utility and character of each similarity measure is tested and evaluated.     

Study of the effect of using different levels of tahinah (sesame butter) on the protein digestibility‐corrected amino acid score (PDCAAS) of chickpea dip

This study was conducted to investigate the effect of using different proportions of tahinah (0–25%) on the protein digestibility‐corrected amino acid score (PDCAAS) of chickpea dip and to evaluate this parameter when chickpea dip is consumed with wheat bread. Protein quality was evaluated using the methods of amino acid score and true protein digestibility in weanling Sprague–Dawley rats. The levels of tahinah that provided the best true protein digestibility and protein digestibility‐corrected amino acid score were 20 and 25%. Values of true protein digestibility were significantly higher (P ≤ 0.05) than for the other types of chickpea dip (0.87 and 0.88 respectively). The consumption of wheat bread with chickpea dip led to a marked improvement in the true protein digestibility of the protein mixture (0.90); however, the protein digestibility‐corrected amino acid score did not change in the same manner owing to the relatively low amino acid score. It can be concluded that the addition of tahinah to chickpea led to an increase in the protein digestibility‐corrected amino acid score of chickpea dip (based on laboratory rat requirements for essential amino acids) and that the consumption of chickpea dip with bread led to an improvement in the protein digestibility of chickpea dip but not in the protein digestibility‐corrected amino acid score. © 2002 Society of Chemical Industry     

Enterotoxigenicity and drug sensitivity of Aeromonas hydrophila isolated from well water in Sweden: a case study

A large number of Aeromonas spp. have been found in drinking water from a drilled well in Sweden. Isolates identified as A. hydrophila were tested for production of enterotoxin, hemolysin, enzymes and for resistant patterns to different antibiotics. The enterotoxin-producing A. hydrophila could be responsible for the long-term diarrhoeal case of a 1 1/2 year old child who consumed the contaminated water.