Rendering the transient hot wire experimental method to dual-phase applications

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.The Transient Hot Wire method is well established as the most accurate, reliable and robust technique for evaluating the thermal conductivity of fluids and solids. Unfortunately its direct application to dual-phase systems such as solid suspensions in fluids or porous media cannot be supported by the very principles and methodology underlying this method. The derivation of possible ways of rendering the transient hot wire method to dual-phase applications including the development of validity criteria for such applications is proposed and discussed.cs201

Chaotic and periodic natural convection for moderate and high Prandtl numbers in a porous layer subject to vibrations

The analysis of natural convection for moderate and high Prandtl numbers in a fluid-saturated porous layer heated from below and subject to vibrations is presented with a twofold objective. First, it aims at investigating the significance of including a time derivative term in Darcy’s equation when wave phenomena are being considered. Second, it is dedicated to reporting results related to the route to chaos formoderate and high Prandtl number convection. The results present conclusive evidence indicating that the time derivative term in Darcy’s equation cannot be neglected when wave phenomena are being considered even when the coefficient to this term is extremely small. The results also show occasional chaotic “bursts” at specific values (or small range of values) of the scaled Rayleigh number, R, exceeding some threshold. This behavior is quite distinct from the case without forced vibrations, when the chaotic solution occupies a wide range of R values, interrupted only by periodic “bursts.” Periodic and chaotic solution alternate as the value of the scaled Rayleigh number varies.University of Pretoriahttp://link.springer.com/journal/11242hb201

Experimental study of vibration effects on heat transfer during solidification of paraffin in a spherical shell

Two effects that have been observed when metals and metal alloys are vibrated during solidification are a decrease in dendritic spacing, which directly affects density, and faster cooling rates and associated solidification times. Because these two effects happen simultaneously during solidification, it is challenging to determine the one effect independently from the other. Most previous studies were on metals and metal alloys. In these studies, the one effect, i.e., the decrease in dendritic spacing, might influence the other, i.e., the faster cooling rates, and vice versa. The direct link between vibration and heat transfer has not yet been studied independently. The purpose of this study was to experimentally investigate the effect of vibration only on heat transfer and thus solidification rate. Experiments were conducted on paraffin wax, because it had a clearly defined macroscopic crystal structure consisting of mostly large straight-chain hydrocarbons. The advantage of the large straight-chain hydrocarbons was that the dendritic spacing was not affected by the cooling rate. Experiments were done with paraffin wax inside hollow plastic spheres of 40mm diameter with 1mm wall thickness. The paraffin wax was initially in a liquid state at a uniform temperature of 608C and then submerged into a thermal bath at a uniform constant temperature of 158C, which was approximately 208C below the mean solidification temperature of the wax. Experiments were conducted in approximately 300 samples, with and without vibration at frequencies varying from 10–300 Hz. The first set of experiments was conducted to determine the solidification times. In the second set of experiments, the mass of wax solidified was determined at discrete time steps, with and without vibration. The results showed that paraffin wax had vibration independent of solid density contrary to other materials, e.g., metals and metal alloys. Enhancement of heat transfer resulted in quicker solidification times and possible control over the heat transfer rate. The increase in heat transfer leading to faster solidifcation times was observed to first occur as frequency increased and then to decrease.The University of Pretoria and Prof. J. P. Meyer.http://www.tandfonline.com/loi/ueht202017-05-31hb2016Mechanical and Aeronautical Engineerin

Vibration effects on heat transfer during solidification of paraffin

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.Previous work looked at the solidification process of PCM (phase change material) paraffin wax. Experimental results were compared with numerical work done in CFD package FLUENT. In the current study, the effects of vibration on heat transfer during the solidification process of PCM in a sphere shell are investigated. Enhancement of heat transfer results in quicker solidification times and desirable mechanical properties of the solid. The amount of PCM used was kept constant during each experiment by using a digital scale to check the weight, and thermocouple to check consistent temperature. A small amount of air was present in the sphere so that the sphere was not filled completely. Commercially available paraffin wax, RT35, was used in the experiments. Experimentations were done on a sphere of 40 mm diameter, wall temperature 20°C below mean solidification temperature, and consistent initial temperature. A vibration frequency was varied from 10-300 Hz was applied to the set-up and results compared with that of no vibration. Samples were taken at different times during the solidification process and compared with respect to solid material presentdc201

Selecting, refining and identifying priority Cochrane Reviews in health communication and participation in partnership with consumers and other stakeholders

Abstract : Background: Priority-setting partnerships between researchers and stakeholders (meaning consumers, health professionals and health decision-makers) may improve research relevance and value. The Cochrane Consumers and Communication Group (CCCG) publishes systematic reviews in 'health communication and participation', which includes concepts such as shared decision-making, patient-centred care and health literacy. We aimed to select and refine priority topics for systematic reviews in health communication and participation, and use these to identify five priority CCCG Cochrane Reviews. Methods: Twenty-eight participants (14 consumers, 14 health professionals/decision-makers) attended a 1-day workshop in Australia. Using large-group activities and voting, participants discussed, revised and then selected 12 priority topics from a list of 21 previously identified topics. In mixed small groups, participants refined these topics, exploring underlying problems, who they affect and potential solutions. Thematic analysis identified cross-cutting themes, in addition to key populations and potential interventions for future Cochrane Reviews. We mapped these against CCCG's existing review portfolio to identify five priority reviews. Results: Priority topics included poor understanding and implementation of patient-centred care by health services, the fact that health information can be a low priority for health professionals, communication and coordination breakdowns in health services, and inadequate consumer involvement in health service design. The four themes underpinning the topics were culture and organisational structures, health professional attitudes and assumptions, inconsistent experiences of care, and lack of shared understanding in the sector. Key populations for future reviews were described in terms of social health characteristics (e.g. people from indigenous or culturally and linguistically diverse backgrounds, elderly people, and people experiencing socioeconomic disadvantage) more than individual health characteristics. Potential interventions included health professional education, interventions to change health service/health professional culture and attitudes, and health service policies and standards. The resulting five priority Cochrane Reviews identified were improving end-of-life care communication, patient/family involvement in patient safety, improving future doctors' communication skills, consumer engagement strategies, and promoting patient-centred care. Conclusions: Stakeholders identified priority topics for systematic reviews associated with structural and cultural challenges underlying health communication and participation, and were concerned that issues of equity be addressed. Priority-setting with stakeholders presents opportunities and challenges for review producers

Additional degrees of parallelism within the Adomian decomposition method

4th International Conference on Computational Engineering (ICCE 2017), 28-29 September 2017, DarmstadtThis is the author accepted manuscript. The final version is available from Springer via the DOI in this record.The trend of future massively parallel computer architectures challenges the exploration of additional degrees of parallelism also in the time dimension when solving continuum mechanical partial differential equations. The Adomian decomposition method (ADM) is investigated to this respects in the present work. This is accomplished by comparison with the Runge-Kutta (RK) time integration and put in the context of the viscous Burgers equation. Our studies show that both methods have similar restrictions regarding their maximal time step size. Increasing the order of the schemes leads to larger errors for the ADM compared to RK. However, we also discuss a parallelization within the ADM, reducing its runtime complexity from O(n^2) to O(n). This indicates the possibility to make it a viable competitor to RK, as fewer function evaluations have to be done in serial, if a high order method is desired. Additionally, creating ADM schemes of high-order is less complex as it is with RK.The work of Andreas Schmitt is supported by the ’Excellence Initiative’ of the German Federal and State Governments and the Graduate School of Computational Engineering at Technische Universit¨at Darmstadt

Particulate matter Air Pollution induces hypermethylation of the p16 promoter Via a mitochondrial ROS-JNK-DNMT1 pathway

Exposure of human populations to chronically elevated levels of ambient particulate matter air pollution < 2.5 μm in diameter (PM2.5) has been associated with an increase in lung cancer incidence. Over 70% of lung cancer cell lines exhibit promoter methylation of the tumor suppressor p16, an epigenetic modification that reduces its expression. We exposed mice to concentrated ambient PM2.5 via inhalation, 8 hours daily for 3 weeks and exposed primary murine alveolar epithelial cells to daily doses of fine urban PM (5 µg/cm2). In both mice and alveolar epithelial cells, PM exposure increased ROS production, expression of the DNA methyltransferase 1 (DNMT1), and methylation of the p16 promoter. In alveolar epithelial cells, increased transcription of DNMT1 and methylation of the p16 promoter were inhibited by a mitochondrially targeted antioxidant and a JNK inhibitor. These findings provide a potential mechanism by which PM exposure increases the risk of lung cancer

A new heat propagation velocity prevails over Brownian particle velocities in determining the thermal conductivities of nanofluids

An alternative insight is presented concerning heat propagation velocity scales in predicting the effective thermal conductivities of nanofluids. The widely applied Brownian particle velocities in published literature are often found too slow to describe the relatively higher nanofluid conductivities. In contrast, the present model proposes a faster heat transfer velocity at the same order as the speed of sound, rooted in a modified kinetic principle. In addition, this model accounts for both nanoparticle heat dissipation as well as coagulation effects. This novel model of effective thermal conductivities of nanofluids agrees well with an extended range of experimental data