Cooling effect of MWCNT-containing composite coatings on cotton fabrics

Multiwalled carbon nanotubes (MWCNTs) were dispersed in an aqueous solution of epichlohydrin based resin with the aid of a surfactant. The MWCNT-resin solutions were applied onto cotton fabrics to form a thin coating with different MWCNT contents (0, 11.1, 20.0, 33.3, and 50%). The thermal conductivity of the fabrics was measured based on the Newton’s law of cooling. The coating containing 50% MWCNTs showed 151% increase in the thermal conductivity. Infrared thermography was used to characterize the heating/cooling behavior of the fabrics. On contact with a 50°C hot surface, coated fabric that had 50% MWCNTs in the coating layer showed a 3.9°C lower equilibrium surface temperature than the untreated fabric. The cooling rate increased with increasing the MWCNT content within the coating layer. Such an effective cooling performance was attributed to the increased thermal conductivity and surface emissivity of the MWCNT-containing coating layer. The coating showed little influence on water contact angle of the coated fabrics, but slightly decreased the air permeability.

The effect of prescribed fluid consumption on physiology and work behavior of wildfire fighters

The purpose of this study was to examine 1) wildfire fighters' ability to consume the prescribed fluid volume (1200 mL h-1), 2) the effect of fluid intake on plasma sodium and hydration, and 3) the effect of fluid intake on firefighters' heart rate, core temperature and activity during emergency suppression shifts. Methods: Thirty-four firefighters were divided into ad libitum (AD, n = 17) and prescribed (PR, n = 17) drinking groups. Results: PR drinkers did not meet the prescribed fluid target, yet consumed over double the volume of AD drinkers. No differences between groups in plasma sodium or hydration were noted. PR drinking resulted in lower core temperature between 2 and 6 h. This did not coincide with reduced cardiovascular strain, greater work activity or larger distances covered when compared to AD drinkers. Conclusion: Extra fluid consumption (above AD) did not improve firefighter activity or physiological function (though PR firefighters core temperature was lower earlier in their shift). Firefighter can self-regulate their fluid consumption behavior and work rate to leave the fireground euhydrated.

The significant effect of the phase composition on the oxygen reduction reaction activity of a layered oxide cathode

Layered oxides of Sr4Fe4Co2O13 (SFC2) which contains alternating perovskite oxide octahedral and polyhedral oxide double layers are attractive for their mixed ionic and electronic conducting and oxygen reduction reaction properties. In this work, we used the EDTA–citrate synthesis technique to prepare SFC2 and vary the calcination temperature between 900 and 1100 _C to obtain SFC2, containing different phase content of perovskite (denoted as SFC-P) and (Fe,Co) layered oxide phases (SFC-L). Rietveld refinements show that the SFC-P phase content increased from _39 wt% to _50 wt% and _61 wt% as the calcination temperature increased from 900 _C (SFC2-900) to 1000 _C (SFC2-1000) and 1050 _C (SFC2-1050). At 1100 _C (SFC2-1100), SFC-P became the dominant phase. The oxygen transport properties (e.g. oxygen chemical diffusion coefficient and oxygen permeability), electrical conductivity and oxygen reduction reaction activity is enhanced in the order of SFC2-1000, SFC2-1100 and SFC2-1050. The trend established here therefore negates the hypothesis that the perovskite phase content correlates with the oxygen transport property enhancement. The results suggest instead that there is an optimum composition value (e.g. 61 wt% of SFC-L for SFC2-1050 in this work) on which synergistic effects take place between the SFC-P and SFC-L phase.

Effect of multiple cations in the feed solution on the performance of forward osmosis

In this study, different combinations of feed stream such as 0.2, 0.3 and 0.4 M of CaCl2 were, respectively, added with 1.0, 0.9 and 0.8 M of NaCl while maintaining the draw solution concentration at either 2.0 M of NaCl or CaCl2 in order to compare likely changes to the flux generated when the feed stream contained NaCl only. The results obtained showed that more constituents in feed stream generated lesser flux. Increase in CaCl2 concentration in feed stream resulted in more severe dilutive internal concentration polarisation (DICP) and hence, reduction in the performance ratio. The temperature and distribution of aggregated particle size also played a significant role in the overall performance of forward osmosis process. Further analysis showed that there is a relationship between the normalised driving force and flux behaviour which is governed by the effect of DICP. Additionally, the reflection coefficient was not unity as less than 2% traces of salt was found to permeate alongside with water towards the draw solution side. © 2014 © 2014 Balaban Desalination Publications. All rights reserved.

Effect of zwitterions on electrochemical properties of oligoether-based electrolytes

Solid polymer electrolytes show great potential in electrochemical devices. Poly(ethylene oxide) (PEO) has been studied as a matrix for solid polymer electrolytes because it has relatively high ionic conductivity. In order to investigate the effect of zwitterions on the electrochemical properties of poly(ethylene glycol) dimethyl ether (G5)/lithium bis(fluorosulfonyl) amide (LiFSA) electrolytes, a liquid zwitterion (ImZ2) was added to the G5-based electrolytes. In this study, G5, which is a small oligomer, was used as a model compound for PEO matrices. The thermal properties, ionic conductivity, and electrochemical stability of the electrolytes with ImZ2 were evaluated. The thermal stabilities of all the G5-based electrolytes with ImZ2 were above 150 °C, and the ionic conductivity values were in the range of 0.8–3.0 mS cm−1 at room temperature. When the electrolytes contained less than 5.5 wt% ImZ2, the ionic conductivity values were almost the same as that of the electrolyte without ImZ2. The electrochemical properties were improved with the incorporation of ImZ2. The anodic limit of the electrolyte with 5.5 wt% ImZ2 was 5.3 V vs. Li/Li+, which was over 1 V higher than that of G5/LiFSA.

Evolution of the electrochemical capacitance of transition metal oxynitrides with time: the effect of ageing and passivation

A number of transition metal nitrides and oxynitrides, which are actively investigated today as electrode materials in a wide range of energy conversion and storage devices, possess an oxide layer on the surface. Upon exposure to ambient air, properties of this layer progressively change in the process known as "ageing". Since a number of electrochemical processes involve the surface or sub-surface layers of the active electrode compounds only, ageing could have a significant effect on the overall performance of energy conversion and storage devices. In this work, the influence of the ageing of tungsten and molybdenum oxynitrides on their electrochemical properties in supercapacitors is explored for the first time. Samples are synthesised by the temperature-programmed reduction in NH3 and are treated with different gases prior to exposure to air in order to evaluate the role of passivation in the ageing process. After the synthesis, products are subjected to controlled ageing and are characterised by low temperature nitrogen adsorption, X-ray photoelectron spectroscopy and transmission electron microscopy. Capacitive properties of the compounds are evaluated by performing cyclic voltammetry and galvanostatic charge and discharge measurements in the 1 M H2SO4 electrolyte. © 2014 the Partner Organisations.

The effect of high yttrium solute concentration on the twinning behaviour of magnesium alloys

The deformation behaviour of two single phase binary alloys, Mg-5Y and Mg-10Y, have been examined. In compression, two twin types were observed, the common {101¯2} twin as well as the less common {112¯1} extension twin. It is shown that the {112¯1} twin is much less sensitive to solute concentration than the {101¯2} twin, and it is suggested that the simple atomic shuffle of the {112¯1} twin reduces the solute strengthening imparted by Y additions. The common {101¯2} twin showed significant hardening as a result of alloying with Y. An analysis of solute behaviour has indicated that of the four chemical parameters investigated, i.e. atomic size, shear modulus, electronegativity and solute distribution, it appears to be the larger atomic radius of Y compared to Mg that increases the stress required to activate the {101¯2} twin. It is suggested that the large atomic radius inhibits the atomic shuffling process which accompanies the twinning shear in this twin type.

The effect of environmental conditions on performance in timed cycling events

Air temperature, pressure and humidity are environmental factors that affect air density and therefore the relationship between a cyclist’s power output and their velocity. These environmental factors are changeable and are routinely quite different at elite cycling competitions conducted around the world, which means that they have a variable effect on performance in timed events. The present work describes a method of calculating the effect of these environmental factors on timed cycling events and illustrates the magnitude and significance of these effects in a case study. Formulas are provided to allow the calculation of the effect of environmental conditions on performance in a time trial cycling event. The effect of environmental factors on time trial performance can be in the order of 1.5%, which is significant given that the margins between ranked performances is often less than this. Environmental factors may enhance or hinder performance depending upon the conditions and the comparison conditions. To permit the fair comparison of performances conducted in different environmental conditions, it is recommended that performance times are corrected to the time that would be achieved in standard environmental conditions, such as 20 oC, 760 mmHg (1013.25 hPa) and 50% RH.

Effect of heat on firefighters' work performance and physiology

Wildland firefighters often perform their duties under both hot and mild ambient temperatures. However, the direct impact of different ambient temperatures on firefighters' work performance has not been quantified. This study compared firefighters' work performance and physiology during simulated wildland firefighting work in hot (HOT; 32°C, 43% RH) and temperate (CON; 19°C, 56% RH) conditions. Firefighters (n=38), matched and allocated to either the CON (n=18) or HOT (n=20) condition, performed simulated self-paced wildland fire suppression tasks (e.g., hose rolling/dragging, raking) in firefighting clothing for six hours, separated by dedicated rest breaks. Task repetitions were counted (and converted to distance or area). Core temperature (Tc), skin temperature (Tsk), and heart rate were recorded continuously throughout the protocol. Urine output was measured before and during the protocol, and urine specific gravity (USG) analysed, to estimate hydration. Ad libitum fluid intake was also recorded. There were no differences in overall work output between conditions for any physical task. Heart rate was higher in the HOT (55±2% HRmax) compared to the CON condition (51±2% HRmax) for the rest periods between bouts, and for the static hose hold task (69±3% HRmax versus 65±3% HRmax). Tc and Tsk were 0.3±0.1°C and 3.1±0.2°C higher in the HOT compared to the CON trial. Both pre- and within- shift fluid intake were increased two-fold in the heat, and participants in the heat recorded lower USG results than their CON counterparts. There was no difference between the CON and HOT conditions in terms of their work performance, and firefighters in both experimental groups increased their work output over the course of the simulated shift. Though significantly hotter, participants in the heat also managed to avoid excessive cardiovascular and thermal strain, likely aided by the frequent rest breaks in the protocol, and through doubling their fluid intake. Therefore, it can be concluded that wildland firefighters are able to safely and efficiently perform their duties under hot conditions, at least over six hours.

Effect of strain ageing on the mechanical properties of partially damaged structural mild steel

ABSTRACT
This paper addresses the strain ageing effects on the mechanical properties of the partially damaged structural mild steel. Since repairing partly damaged structures may not occur immediately, the strain ageing effect can significantly influence the structural behaviour. The changes due to this effect have not so far been considered in the civil engineering design guidelines. In order to investigate strain ageing effects, two-stage experimental tests are carried out on the mild-steel specimens. In the first stage, partial damage is made using quasi-static loading. During the second stage, the strength and ductility of the specimens are examined after 2 and 7 days ‘ageing’ at room temperature and the results are compared with the corresponding no-age samples. The microstructure of the specimens is examined using scanning electron microscopy (SEM). To illustrate the effect of strain ageing on the global behaviour of steel structures, a numerical example is provided in which strain ageing impacts on loading capacity and deflection of a steel beam. Finally, the stress–strain relation of partially damaged mild-steel material incorporating strain ageing effects is expressed by calibrating the parameters of Ramberg–Osgood model.

The effect of fibrous structural difference on thermal insulation properties of biological composites: silkworm cocoons

As a biological fibrous structure, silkworm cocoon provides multiple protective functionalities to safeguard the silk moth pupa’s metabolic activity. The mechanism of this protection could be adopted in clothing manufacture to provide more comfortable apparel. In this study, the thermal insulation properties of both domestic Bombyx mori (B. mori) and wild Antheraea pernyi (A. pernyi) cocoons were investigated under both warm and cold environmental conditions. Computational fluid dynamics models have been developed to simulate the heat transfer process through both types of cocoon wall structures. The simulation results show that the wild A. pernyi cocoon reduces the intensity of convection and heat flux between the environment and the cocoon interior and has higher wind resistance than its domestic counterpart. Compared with A. pernyi cocoon, the B. mori cocoon facilitates easy air transfer and decreases the temperature lag when the surrounding conditions are changed. The new knowledge has significant implications for developing biomimetic thermal functional materials.

Effect of B4C, TiB2 and ZrSiO4 ceramic particles on mechanical properties of aluminium matrix composites: Experimental investigation and predictive modelling

This paper focuses on the influence of processing temperature and inclusion of micron-sized B4C, TiB2 and ZrSiO4 on the mechanical performance of aluminium matrix composites fabricated through stir casting. The ceramic/aluminium composite could withstand greater external loads, due to interfacial ceramic/aluminium bonding effect on the movement of grain and twin boundaries. Based on experimental results, the tensile strength and hardness of ceramic reinforced composite are significantly increased. The maximum improvement is achieved through adding ZrSiO4 and TiB2, which has led to 52% and 125% increase in tensile strength and hardness, respectively. To predict the effect of incorporating ceramic reinforcements on the mechanical properties of composites, experimental data of mechanical tests are used to create 3 models named Levenberg-Marquardt Algorithm (LMA) neural networks. The results show that the LMA- neural networks models have a high level of accuracy in the prediction of mechanical properties for ceramic reinforced-aluminium matrix composites.

Self-cleaning wool: effect of noble metals and silica on visible-light-induced functionalities of nano TiO2 colloid

© 2014 The Textile Institute. This study intends to enhance the functionality of titanium dioxide (TiO2) nanoparticles applied to wool fabrics under visible light. Herein, TiO2, TiO2/SiO2, TiO2/Metal, and TiO2/Metal/SiO2 nanocomposite sols were synthesized and applied to wool fabrics through a low-temperature sol–gel method. The impacts of three types of noble metals, namely gold (Au), platinum (Pt), and silver (Ag), on the photoefficiency of TiO2 and TiO2/SiO2 under visible light were studied. Different molar ratios of Metal toTiO2 (0.01, 0.1, 0.5, and 1%) were employed in synthesizing the sols. Photocatalytic efficiency of fabrics was analyzed through monitoring the removal of red wine stain and degradation of methylene blue under simulated sunlight and visible light, respectively. Also, the antimicrobial activity against Escherichia coli (E. coli) bacterium and the mechanical properties of fabrics were investigated. Through applying binary and ternary nanocomposite sols to fabrics, an enhanced visible-light-induced self-cleaning property was imparted to wool fabrics. It was concluded that the presence of silica and optimized amount of noble metals had a synergistic impact on boosting the photocatalytic and antimicrobial activities of coated samples. The fabrics were further characterized using attenuated total reflectance, energy-dispersive X-ray spectrometry, and scanning electron microscopy images.

Effect of δ-ferrite co-existence on hot deformation and recrystallization of austenite

This work evaluates the effect of co-existence of a large volume fraction of δ-ferrite on the hot deformation and dynamic recrystallization (DRX) of austenite using comparative hot torsion tests on AISI 304 austenitic and 2205 duplex stainless steels. The comparison was performed under similar deformation conditions (i.e. temperature and strain rate) and also under similar Zener-Hollomon, Z, values. The torsion data were combined with electron backscatter diffraction (EBSD) analysis to study the microstructure development. The results imply a considerable difference between DRX mechanisms, austenite grain sizes and also DRX kinetics of two steels. Whereas austenitic stainless steel shows the start of DRX at very low strains and then development of that microstructure based on the necklace structure, the DRX phenomena in the austenite phase of duplex structure does not proceed to a very high fraction. Also, the DRX kinetics in the austenitic steel are much higher than the austenite phase of the duplex steel. The results suggest that at a similar deformation condition the DRX grain size of austenitic steel is almost three times larger than the DRX grains of austenite phase in duplex steel. Similarly, the ratio of DRX grain size in the austenitic to the duplex structure at the same Z values is about 1.5.

Effect of single and double austenitization treatments on the microstructure and hardness of AISI D2 tool steel

This investigation is concerned with the study of effect of Double Austenitization (DA) and Single Austenitization (SA) heat treatment processes on microstructure and mechanical property of AISI D2type cold worked tool steel. To maximize hardness, tool steels are used in a quenched and tempered condition. This involves heating the material to the austenitizing temperature (~850-1100. °C), quenching at an appropriate rate to form martensite, and tempering to reduce the retained austenite content and induce toughness. The merits of DA treatment isto promote dissolution of carbides at the same time proscribe grain coarsening significantly was attempted in D2 tool steel. The study has found that DA treatment has induced high hardness with insignificant growth in grains. The increase in hardness is attributed to increase in carbon content in matrix due to dissolution of carbides; whereas finer grains due to role of inclusions.