Parameter estimation method for flash thermal diffusivity with two different heat transfer coefficients

Determining thermal diffusivity using flash diffusivity tests at high temperatures is investigated using parameter estimation. One aspect is development of a method for determining two different heat transfer coefficients, one at the heated face and one at the opposite face. Both simulated exact and experimental data are used to illustrate the procedure. Although the heat transfer coefficients are different, assuming identical coefficients in the estimation process does not significantly affect the thermal diffusivity estimates. Insight into estimation of thermal diffusivity and other parameters is obtained from a study of the sensitivity coefficients. Although the thermal diffusivity is the primary parameter of interest, a measured signal proportional to the temperature rise also depends on the heat transfer coefficients and energy input, which are called nuisance parameters (if not of interest). As the temperatures increase above 1500 C, heat losses become very large and greatly influence the temperature response. By using insights from the study of the sensitivity coefficients for each of these parameters, the thermal diffusivity can be estimated despite the large heat losses

Thermal diffusivity mapping of 4D carbon-carbon composites

High resolution, 2-D thermal diffusivity maps of carbon-carbon composites were obtained by a state-of-the-art infrared thermal imaging system. Unlike the traditional single-point IR detector used for thermal diffusivity measurements, the IR camera is capable of capturing images in its 256 x 256 pixel Focal Plane Array detector in a snap-shot mode. The camera takes up to 200 images at a rate of 120 frames/second. The temperature resolution of the Ir camera is 0.015 C and the spatial resolution is 20 {micro}m. Thermal diffusivity was calculated for each pixel. Four-direction carbon-carbon composites were used for the thermal diffusivity mapping study. The fiber bundles along the heat flow direction were found to have 25% higher diffusivity values than the surrounding matrix. The diffusivity map also showed detailed local variations in diffusivity which were impossible to measure using a single-point detector. Accurate diffusivity maps are very important to the design of composite materials

Thermal conductivity of zirconia thermal barrier coatings

Thermal barrier coatings (TBC's) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBC's is of primary importance. Physical vapor description (PVD) and plasma spraying (PS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The PS coatings were applied with either standard power or hollow sphere particles. The hollow sphere particles yielded a lower density and lower thermal conductivity coating. The thermal conductivity of both fully and partially stabilized zirconia, before and after thermal aging, will be compared. The thermal conductivity of the coatings permanently increase upon being exposed to high temperatures. These increases are attributed to microstructural changes within the coatings. Sintering of the as fabricated plasma sprayed lamellar structure is observed by scanning electron microscopy of coatings isothermally heat treated at temperatures greater than 1100 C. During this sintering process the planar porosity between lamella is converted to a series of small spherical pores. The change in pore morphology is the primary reason for the observed increase in thermal conductivity. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the PVD coatings are less susceptible to thermal aging effects, preliminary results suggest that they have a higher thermal conductivity than PS coatings, both before and after thermal aging. The increases in thermal conductivity due to thermal aging for partially stabilized plasma sprayed zirconia have been found to be less than for fully stabilized plasma sprayed zirconia coatings. The high temperature thermal diffusivity data indicates that if these coatings reach a temperature above 1100 C during operation, they will begin to lose their effectiveness as a thermal barrier

Multiple station thermal diffusivity instrument

A multiple furnace laser flash thermal diffusivity system has been developed. The system is equipped with a movable Nd:Glass laser unit, two IR detectors and furnaces for precise measurements of thermal diffusivity over the temperature range from {minus}150{degree}C to 2500{degree}C. All furnaces can operate in vacuum and inert gas; the environmental effects furnace also supports oxidizing and reducing environments. To increase testing speed the graphite and aluminum furnaces are both equipped with six-sample carousels. Thermal diffusivity measurements of three standard reference materials show excellent results over the entire temperature range

Two strategies for partner notification and partner HIV self-testing reveal no evident predictors of male partner HIV testing in antenatal settings: A secondary analysis

BackgroundTo meet global targets for the elimination of mother-to-child HIV transmission, tailored approaches to HIV testing strategies need prioritizing. Herein, we sought to identify individual-level factors associated with male partner HIV testing.MethodsWe conducted a secondary analysis of data from two parallel randomized trials of pregnant women living with HIV and those HIV-negative in Lusaka, Zambia. Across both trials, control groups received partner notification services only, while intervention groups received partner notification services plus HIV self-test kits for their partners. Associations between baseline factors and male partner testing were estimated using a probability difference. The outcome of interest was uptake of male partner HIV testing of any kind within 30 days of randomization.ResultsThe parent study enrolled 326 participants. Among the 151 women in the control groups, no clear associations were noted between maternal or male partner characteristics and reported uptake of male partner HIV testing. There were positive trends favouring partner testing among women who completed primary school education, had larger households (>2 members), and whose partners were circumcised. Likewise, no clear predictors of male partner testing were identified among the 149 women in the intervention groups. However, negative trends favouring no testing were noted among older, multiparous women from larger households.ConclusionNo consistent predictors for male partner HIV testing across two compared strategies were observed. Our findings suggest that differentiated strategies for male partner HIV testing may not be necessary. Instead, consideration should be given to universal approaches when bringing such services to scale

Heat transfer between a nano-tip and a surface

We study quasi-ballistic heat transfer through air between a hot nanometer-scale tip and a sample. The hot tip/surface configuration is widely used to perform nonintrusive confined heating. Using a Monte-Carlo simulation, we find that the thermal conductance reaches 0.8 MW.m-2K-1 on the surface under the tip and show the shape of the heat flux density distribution (nanometer-scale thermal spot). These results show that a surface can be efficiently heated locally without contact. The temporal resolution of the heat transfer is a few tens of picoseconds.Comment: 4 page

No straight lines – young women’s perceptions of their mental health and wellbeing during and after pregnancy: a systematic review and meta-ethnography

Background: Young mothers face mental health challenges during and after pregnancy including increased rates of depression compared to older mothers. While the prevention of teenage pregnancy in countries such as the United States and the United Kingdom has been a focus for policy and research in recent decades, the need to understand young women’s own experiences has been highlighted. The aim of this meta-ethnography was to examine young women’s perceptions of their mental health and wellbeing during and after pregnancy to provide new understandings of those experiences. Methods: A systematic review and meta-ethnographic synthesis of qualitative research was conducted. Seven databases were systematically searched and forward and backward searching conducted. Papers were included if they were from Organisation for Economic Co-operation and Development countries and explored mental health and wellbeing experiences of young mothers (age under 20 in pregnancy; under 25 at time of research) as a primary research question – or where evidence about mental health and wellbeing from participants was foregrounded. Nineteen papers were identified and the Critical Appraisal Skills Programme checklist for qualitative research used to appraise the evidence. Following the seven-step process of meta-ethnography, key constructs were examined within each study and then translated into one another. Results: Seven translated themes were identified forming a new line of argument wherein mental health and wellbeing was analysed as relating to individual bodily experiences; tied into past and present relationships; underpinned by economic insecurity and entangled with feelings of societal surveillance. There were ‘no straight lines’ in young women’s experiences, which were more complex than dominant narratives around overcoming adversity suggest. Conclusions: The synthesis concludes that health and social care professionals need to reflect on the operation of power and stigma in young women’s lives and its impact on wellbeing. It adds to understanding of young women’s mental health and wellbeing during and after pregnancy as located in physical and structural factors rather than individual capacities alone

Incidence and classification of pediatric diffuse parenchymal lung diseases in Germany

<p>Abstract</p> <p>Background</p> <p>Diffuse parenchymal lung diseases (DPLD) in children represent a rare and heterogeneous group of chronic pulmonary disorders. Despite substantial advances in genetics and pathomechanisms, these often lethal diseases are still under-diagnosed. This is due to the fact that (i) the incidence is low, and (ii) clinical presentation, (iii) disease classification and (iv) specific treatment options are largely unknown.</p> <p>Methods</p> <p>Here we systematically assessed the incidence, the presentation, the diagnostic yield and treatments of pediatric DPLD in Germany, using the Surveillance Unit for Rare Paediatric Disorders (ESPED).</p> <p>Results</p> <p>The incidence of DPLD was 1.32 new cases per 1 million of children per year. The majority of these children were diagnosed within the first year of life. Overall survival was 87%. Using centralized data entry and stratification tools, the patients were categorized into an advanced classification system based on diagnostic algorithms, including clinical presentations, genetics and/or histology. Combining molecular and clinical information, this survey provides an etiological overview and specific diagnostic recommendations for children with DPLD.</p> <p>Conclusions</p> <p>Standardized surveys and systematic classifications are valuable tools for the clinical handling of children with DPLD and aim to improve the disease understanding and the prognosis of these rare detrimental lung diseases.</p

Resolving the genetic heterogeneity of prelingual hearing loss within one family: Performance comparison and application of two targeted next generation sequencing approaches.

published_or_final_versio