Natural convection of nano-fluids

Fluids with nano size solid particles suspended in them have been given the name nano-fluid which in recent studies have shown tremendous promise as heat transfer fluids. However, before suggesting such fluids for applications a thorough knowledge of physical mechanism of heat transfer in such fluids is wanted. The present study deals with one such aspect of natural convection of nano fluids inside horizontal cylinder heated from one end and cooled from the other. An apparently paradoxical behaviour of heat transfer deterioration was observed in the experimental study. Nature of this deterioration and its dependence on parameters such as particle concentration, material of the particles and geometry of the containing cavity have been investigated. The fluid shows characters distinct from that of common slurries.     

AN EXPERIMENTAL INVESTIGATION OF POOL BOILING ON NARROW HORIZONTAL TUBES

Pool boiling characteristics on horizontal tubes with diameter lying between wires and industrial tubes have been investigated experimentally. Boiling experiments are carried out at near atmospheric pressures with water and R-123 as boiling liquids. The experimental results show quite a different boiling behavior compared to larger tubes or plates. The commonly used correlations are found to be ineffective over this range of diameters. A developing sliding bubble mechanism can be attributed to such behavior which shows a strong diameter effect. The heat transfer is found to increase with diameter which is contrary to that on industrial size tubes. Useful boiling data are presented in this range of diameters in which experimental data are scarce. The need for more investigations is stressed in view of emerging applications in this area.     

Eiweisstoffe

Ohne Zusammenfassung     

Mechanical and thermal properties of polylactide/talc microcomposites: before and after accelerated weathering

The purpose of the first part of this study was to investigate effects of micron‐sized talc content on the properties of polylactide (PLA). PLA/talc microcomposites were compounded by melt‐mixing method via twin‐screw extruder, while specimens for testing and analyses were shaped by injection molding. It was observed that, because of the effective stiffening, strengthening, toughening mechanisms of talc, and also their nucleation agent effects for higher crystallinity, many mechanical and thermal properties were improved. In the second part of the study, effects of accelerated weathering on the behavior of PLA microcomposites with 5 wt% talc were investigated by applying ultra violet irradiation and humidity steps according to Cycle‐C of International Organization for Standardization 4892‐3 standards for durations of 100, 200, and 300 hr. Various analyses revealed that, because of the degradation mechanisms of photolysis and hydrolysis during each weathering periods, molecular weight of PLA reduced drastically, that is, mechanical properties almost vanished. Copyright © 2015 John Wiley & Sons, Ltd.     

Robust multiclass kernel-based classifiers

In this research, a robust optimization approach applied to multiclass support vector machines (SVMs) is investigated. Two new kernel based-methods are developed to address data with input uncertainty where each data point is inside a sphere of uncertainty. The models are called robust SVM and robust feasibility approach model (Robust-FA) respectively. The two models are compared in terms of robustness and generalization error. The models are compared to robust Minimax Probability Machine (MPM) in terms of generalization behavior for several data sets. It is shown that the Robust-SVM performs better than robust MPM.     

Potential of using uric acid fluorescence in eye fluid for freshness assessment on Red Sea bream (Pagrus major)

Abstract

Fluorescence characteristics of uric acid in Red Sea bream (Pagrus major) eye fluid was explored as a potential rapid and simple assessment for fish freshness. To investigate this, eye fluid samples were collected during storage at 22?±?2?°C for standard uric acid measurements by high-performance liquid chromatography at 12?h intervals up until 36?h storage. Simultaneously, uric acid fluorescence spectroscopy measurements by fluorophotometer at 3?h intervals up until 36?h storage were made. High-performance liquid chromatography results showed the concentration of uric acid increased with storage time in the Red Sea bream eye fluid; changes similar to those observed in Japanese dace eye fluid, only differing in concentration and rate of accumulation. The fluorescence signals of uric acid in Red Sea bream eye fluid increased with storage time, which the high-performance liquid chromatography results confirmed. To further explore this, uric acid fluorescence signals were plotted against a standard fish freshness indicator “K value”, which is calculated from the concentration of adenosine triphosphate and its breakdown products using paper electrophoresis method. A good exponential relationship between these two parameters (determination coefficient of 0.94). A high linear correlation between the predicted K value from the uric acid fluorescence signals and the measured K value (determination coefficient of 0.94 and root mean square error of prediction of 6.37%) indicate uric acid fluorescence characteristics in fish eye fluid has a high potential to be employed as a new, fast and simple method to assess fish freshness.     

Synthesis, characterization, and electrical, electrochemical and gas sensing properties of a novel ball-type four t-butylcalix[4]arene bridged binuclear zinc(II) phthalocyanine

1,3 dimethoxy-4-t-butylcalix[4]arene has been used to synthesize a novel ball-type dimeric zinc(II) phthalocyanine, [Zn2Pc2(tbca)4] that exhibits mixed-valence behaviour and non-Arrhenius type dependence of conductivity.     

Determination of heavy metal concentrations in plants exposed to different degrees of pollution using ICP-AES

Plant samples (Plantago lanceolata – narrow leaf plantain and Cichorium endiviae – endive) were collected in the surroundings of heavy metal emission sources and in other less contaminated areas. After digestion in a closed microwave system using HNO₃, the concentrations of Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn were determined using ICP-AES. Detection limits for all the elements of interest are given. Differences in heavy metal uptake rate between both plant species were observed. The uptake is more intensive for endive than for narrow leaf plantain. High concentrations of some heavy metals were determined in the unwashed plant samples as a result of exposure to aerosols. Tukeys statistical test was used to confirm the discrepancy of Cr concentration in plant samples from various areas. Washing the leaves with water was found to remove a large amount of water-soluble aerosols.