Effusion Measurements Research Articles

Thermal parameters of roofing slates from Czech Republic

Thermal performance of building materials is an important parameter from the point of view of energy consumption for heating buildings, which is obviously related to environmental protection standards. Thermal parameters of roofing slates were measured for samples from two different formations in the Czech Republic. These were rocks of lower Carboniferous Culm facies of Moravice Formation and Silesian Unit of Flysch Moravian-Silesian Carpathians. Thermal conductivity and thermal effusivity measurements were performed with use of TCi analyser. Thermal parameters were obtained in parallel and perpendicular direction to the bedding in rocks. Thermal conductivity of the Moravian slates in the direction perpendicular to the bedding ranges from 1.43 to 1.79 W m−1 K−1, while for samples from Carpathian region this parameter ranges from 1.99 to 3.15 W m−1 K−1. High values of thermal conductivity correlate to higher quartz content in the rocks. The measured thermal parameters (conductivity, effusivity, diffusivity) are strongly depending on the direction of measurement. Thermal conductivity of analysed rocks increases along with increase in temperature. The increase in thermal conductivity value is more significant in case of Moravian slates. In practice, the obtained results indicate that the traditional building material, such as roofing slates, shows better insulation properties at lower temperatures, while in conditions of strong sunlight the temperature conductivity increases. In case of roofing slates, which tend to be highly anisotropic, the essential information is the direction of thermal parameters measurement. Slates, due to their specific texture, are characterized by a very high thermal anisotropy coefficient.

Effect of post-deposition annealing on atomic layer deposited SiO2 film for silicon surface passivation

We have investigated the passivation performance of atomic layer deposited silicon dioxide (ALD-SiO2) films on crystalline silicon surface with various post-annealing temperatures. A maximum effective lifetime of 2157 μs can be achieved at the optimized annealing temperature of 650 °C on 3 Ω cm n-type silicon wafers. The improved passivation quality can be attributed to the low interface defect density and extremely high positive fixed charge density. Especially, the high positive fixed charge density of over 4 × 1012 cm-2 can be observed after annealing at high temperature. Therefore, it is inferred that the passivation mechanism for ALD-SiO2 films is based on not only chemical passivation but also field-effect passivation, which is more similar with the ALD-Al2O3 films rather than the thermally grown SiO2 films. X-ray photoelectron spectroscopy, secondary ion mass spectroscopy and thermal effusion measurement revealed the variation of elements content and distribution of silicon, oxygen, hydrogen and carbon during the post-deposition thermal treatment process, indicating that the rearrangement and release of these elements create more oxygen vacancies and result in the improvement of interface quality and positive fixed charge density of ALD-SiO2 films.

Silicon surface passivation by transparent conductive zinc oxide

Surface passivation is essential for high-efficiency crystalline silicon (c-Si) solar cells. Despite the common use of transparent conductive oxides (TCOs) in the field of solar cells, obtaining surface passivation by TCOs has thus far proven to be particularly challenging. In this work, we demonstrate outstanding passivation of c-Si surfaces by highly transparent conductive ZnO films prepared by atomic layer deposition. Effective surface recombination velocities as low as 4.8 cm/s and 11 cm/s are obtained on 3 Ω cm n- and p-type (100) c-Si, respectively. The high levels of surface passivation are achieved by a novel approach by using (i) an ultrathin SiO2 interface layer between ZnO and c-Si, (ii) a sacrificial Al2O3 capping layer on top of the ZnO film during forming gas annealing, and (iii) the extrinsic doping of the ZnO film by Al, B, or H. A combination of isotope labeling, secondary-ion mass spectrometry, and thermal effusion measurements showed that the sacrificial Al2O3 capping layer prevents the effusion of hydrogen from the crystalline ZnO and the underlying Si/SiO2 interface during annealing, which is critical in achieving surface passivation. After annealing, the Al2O3 capping layer can be removed from the ZnO film without impairing the high levels of surface passivation. The surface passivation levels increase with increased doping levels in ZnO, which can be attributed to field-effect passivation by a reduction in the surface hole concentration. The ZnO films of this work are suitable as a transparent conductor, an anti-reflection coating, and a surface passivation layer, which makes them particularly promising for simplifications in future solar cell manufacturing.

Significant effusion in the joints of the lower extremity after running an ultramarathon in extreme conditions

Introduction: The “Brocken challenge” ultramarathon takes place in the cold of February over 80 km with 1,900 m of elevation change. The purpose of this study was to evaluate the effects of an ultramarathon under extreme conditions on the lower extremities. Methods: Out of the 182 starters, 44 athletes were included into the study (n=44). We examined these athletes using a questionnaire, by measuring circumferences of their lower extremities and by standardized sonographic measurement of joint effusion of knee and ankle joints before and after the run. Results: After the run, the right leg and both feet significantly increased in circumference. Knee joints on both sides and the left ankle joint showed significantly more effusion after the run (right knee: 84%, right ankle: 43%; left knee: 80%, left ankle: 48%). Heavier and less trained athletes showed significantly more effusion in sonographic assessment of the knee and ankle. Neither swelling, nor effusion had a measurable influence on finishing time. Conclusions: Running an ultramarathon in the cold overloads the fluid draining capacity in the muscles and joints of the legs especially in heavier and less trained athletes without measurable immediate effect on performance.

The effective temperature at which fingertips sense thermal effusivity and the bias of measurements at room temperature

Thermoreceptors in the fingertips sense the temperature drop upon contact with an object and in that way its thermal effusivity.But, at which effective object temperature? That is the question that this article answers by perturbation analysis for slightly temperature dependent thermal properties.How much deviate thermal effusivity measurements at room temperature from fingertip measurements at said effective object temperature? This question is also answered by perturbation analysis.The bias may be up to 7% using nearly isothermal measurement methods and up to around 19% using fingertip-mimicking measurement methods for airy materials like wool.Rewriting the temperature model reveals a felt delay and its dependency on the thermal contact resistance between fingertip and object.

Characterization of a precast hemp concrete. Part I: Physical and thermal properties

Hemp concrete is seen as a possible solution for addressing the energy, health and comfort issues of sustainable buildings, thanks to its hygrothermal properties and environmental qualities. This paper aims to determine the physical and thermal properties of an industrial prefabricated hemp concrete block based on hemp shiv and a lime-metakaolin binder. When available, distinct measurement methods were applied and confronted on this precast material in order to evaluate the impact of the experimental procedure on the results. Concerning air permeability, the present study shows that a measurement method initially intended for regular concrete can be adapted to the specific behaviour of highly permeable material such as hemp concrete. The thermal conductivity was measured with a guarded hot plate and a hot wire. Hot wire measurements on different moist states of the material allowed the self-consistent scheme to be applied for the evaluation of the thermal conductivity as a function of the humidity. Two direct measurement methods, differential scanning calorimetry (DSC) on the components and use of a Calvet calorimeter on the hemp concrete, and one indirect method, through effusivity measurement, were adopted for evaluating the specific heat capacity of the material. The original method proposed using DSC was shown to be as accurate as direct calorimetric measurement. The direct measurement methods gave similar results while the indirect one led to a much lower value. A comprehensive analysis of the measurement values available in the literature on hemp concretes confirmed this trend.This first paper highlights the significant influence of the testing method on the determination of the thermal properties of a precast hemp concrete, especially on the heat capacity measurement. This result emphasizes the need for a large inter-laboratory experimental campaign, applied to bio-aggregate based concrete, in order to form the basis of recommendations for adequate physical and thermal characterization methods for these bio-based building materials. A second part of this study will investigate the hydric properties of the same material.

Traumatic knee injury: correlation of radiographic effusion size with the presence of internal derangement on magnetic resonance imaging.

Traumatic knee injury is a common clinical presentation. However, knee internal derangement often goes undiagnosed on physical exam. The authors hypothesize that patients with suprapatellar joint effusion greater than 10mm anteroposterior diameter on lateral radiograph have a high likelihood of knee internal derangement on magnetic resonance imaging. A retrospective review of knee radiographs and magnetic resonance imaging in 198 patients age 18-40years with acute knee injury was performed. Suprapatellar effusion diameter on lateral radiography was correlated to the presence of internal derangement on magnetic resonance imaging. Magnetic resonance imaging anteroposterior effusion size at four locations was correlated to radiographic suprapatellar effusion measurements. Logistic regression showed a positive correlation between radiographic effusion size and the presence of internal derangement on magnetic resonance exams (p value < 0.001). Radiographic effusion > 10mm was established as a positive test, yielding test sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 55, 96, 93, 71, and 77%, respectively. Statistical analysis showed the radiographic anteroposterior effusion diameter most closely approximated the magnetic resonance effusion diameter at the lateral patellofemoral recess. This study shows that knee radiography is a highly specific screening test for internal derangement in patients less than 40years old with acute knee injury. In this patient population, knee effusion > 10mm on lateral radiograph should prompt consideration for knee magnetic resonance examination. Adopting this approach as a clinical guideline has the potential to decrease delayed diagnosis, improve patient outcomes, and decrease cost-associated disability.

Thermal effusivity measurements of thermal insulators using the photopyroelectric technique in the front configuration

In the photopyroelectric (PPE) technique in the front configuration one surface of a pyroelectric sensor is illuminated by a modulated laser beam, whereas the other surface is in contact with the sample under study. A frequency scan of the PPE signal allows to measure the thermal effusivity of liquids. Recently, it has been applied to solid samples, by taking into account the effect of the thin grease layer used to guarantee the thermal contact between sample and sensor. In this work, we extend this method to address the challenge of measuring the effusivity of thermal insulators accurately. We have developed a complete model of the PPE signal generation, including heat losses by convection, radiation and conduction to the surrounding gas. Besides, very thin pyroelectric sensors are used since they enhance the sensitivity of the PPE signal to the sample effusivity. Moreover, the sample is placed directly in contact with the sensor, without using any coupling grease, to avoid polluting porous samples. PPE measurements on several thermal insulators (paper, cork, wood and foam) indicate that this method is well suited to retrieve the thermal effusivity of insulators precisely.

Joint thermophysical analysis of rock samples based on thermal effusivity measurements

Joint thermophysical analysis of rock samples based on thermal effusivity measurements

Thermal effusivity measurement of conventional and organic coffee oils via photopyroelectric technique

In this work, oil samples extracted from organic and conventional coffee beans were studied. A fatty acids profile analysis was done using gas chromatography and physicochemical analysis of density and acidity index to verify the oil purity. Additionally, Mid-Infrared Fourier Transform Photoacoustic Spectroscopy (FTIR-PAS) aided by Principal Component Analysis (PCA) was used to identify differences between the intensities of the absorption bands related to functional groups. Thermal effusivity values between 592±3 and 610±4Ws1/2m−2K−1 were measured using the photopyroelectric technique in a front detection configuration. The acidity index was between 1.11 and 1.27% and the density changed between 0.921 and 0.94g/mL. These variables, as well as the extraction yield between 12,6 and 14,4%, showed a similar behavior than that observed for the thermal effusivity, demonstrating that this parameter can be used as a criterion for discrimination between oil samples extracted from organic and conventional coffee beans.

Amorphous silicon passivation for 23.3% laser processed back contact solar cells

This paper presents amorphous silicon deposited at temperatures below 200 °C, leading to an excellent passivation layer for boron doped emitter and phosphorus doped back surface field areas in interdigitated back contact solar cells. A higher deposition temperature degrades the passivation of the boron emitter by an increased hydrogen effusion due to lower silicon hydrogen bond energy, proved by hydrogen effusion measurements. The high boron surface doping in crystalline silicon causes a band bending in the amorphous silicon. Under these conditions, at the interface, the intentionally undoped amorphous silicon becomes p-type conducting, with the consequence of an increased dangling bond defect density. For bulk amorphous silicon this effect is described by the defect pool model. We demonstrate, that the defect pool model is also applicable to the interface between amorphous and crystalline silicon. Our simulation shows the shift of the Fermi energy towards the valence band edge to be more pronounced for high temperature deposited amorphous silicon having a small bandgap. Application of optimized amorphous silicon as passivation layer for the boron doped emitter and phosphorus doped back surface field on the rear side of laser processed back contact solar cells, fabricated using four laser processing steps, yields an efficiency of 23.3%.

Self-normalized inverse photopyroelectric technique with viscous front window for thermal effusivity measurements in liquids

In this paper, the front detection (also called inverse configuration) photopyroelectric method for thermal effusivity measurement in liquids is improved by adding a viscous liquid to the front face of the pyroelectric sensor, on which the intensity modulated excitation light beam impinges, while the sample is attached to the rear side of the sensor. This viscous liquid will act as an optical transparent window. This configuration avoids problems related with the piezoelectric contribution to the photopyroelectric signal at high modulation frequencies that can be present in conventional approaches due to thermoelastic waves generated in the heated sample or by thermally induced deformations of the detector material itself. The theoretical and experimental principles behind the proposed method are presented and its usefulness is demonstrated with measurements on test samples.

Thermal effusivity measurement based on analysis of 3D heat flow by modulated spot heating using a phase lag matrix with a combination of thermal effusivity and volumetric heat capacity

The study goal was to establish a standard industrial procedure for the measurement of thermal effusivity by a thermal microscope (TM), using a periodic heating method with a thermoreflectance (TR) technique. To accomplish this goal, a working group was organized that included four research institutes. Each institute followed the same procedure: a molybdenum (Mo) film was sputtered on the surface of Pyrex, yttria-stabilized zirconia (YSZ), alumina (Al2O3), Germanium (Ge), and silicon (Si) samples, and then the phase lag of the laser intensity modulation was measured by the resultant surface temperature. A procedure was proposed to calibrate the effect of 3D heat flow, based on the analytical solution of the heat conduction equation, and thermal effusivity was measured. The derived values show good agreement with literature values. As a result, the TM calibration procedure can be recommended for practical use in measuring the thermal effusivity in a small region of the materials.

Comparing posteroanterior with lateral and anteroposterior chest radiography in the initial detection of parapneumonic effusions

BackgroundIt is unclear whether anteroposterior (AP) or posteroanterior with lateral (PA/Lat) chest radiographs are superior in the early detection of clinically relevant parapneumonic effusions (CR-PPEs). The objective of this study was to identify which technique is preferred for detection of PPEs using chest computed tomography (CCT) as a reference standard. MethodsA secondary analysis of a pneumonia database was conducted to identify patients who received a CCT within 24 hours of presentation and also received AP or PA/Lat chest radiographs within 24 hours of CCT. Sensitivity and specificity were then calculated by comparing the radiographic diagnosis of PPEs of both types of radiographs compared with CCT by using the existing attending radiologist interpretation. Clinical relevance of effusions was determined by CCT effusion measurement of >2.5 cm or presence of loculation. ResultsThere was a statistically significant difference between the sensitivity of AP (67.3%) and PA/Lat (83.9%) chest radiography for the initial detection of CR-PPE. Of 16 CR-PPEs initially missed by AP radiography, 7 either required drainage initially or developed empyema within 30 days, whereas no complicated PPE or empyema was found in those missed by PA/Lat radiography. ConclusionsPA/Lat chest radiography should be the initial imaging of choice in pneumonia patients for detection of PPEs because it appears to be statistically superior to AP chest radiography.

Using MDECR‐PECVD to study the impact of ion bombardment energy on microstructural properties of μc‐Si:H thin film grown from an SiF4/H2 chemistry

AbstractThe matrix‐distributed electron cyclotron resonance plasma‐enhanced chemical vapor deposition (MDECR‐PECVD) technique has been shown to achieve high deposition rates for hydrogenated microcrystalline silicon (μc‐Si:H) thin film. Due to the fact that plasma is sustained by a microwave discharge, by biasing the substrate holder with additional power supply, one can achieve independent control over the plasma density and the maximum ion bombardment energy (IBE). In this work, we present studies of the impact of IBE on the microstructural properties of the μc‐Si:H film deposited by MDECR‐PECVD. Insufficient ion bombardment is found to be responsible for the substantial presence of nano‐porous regions within the material, resulting in significant post‐deposition oxidation. Good agreement between transmission electron microscopy (TEM) Fresnel contrast analysis and the results of infrared absorption and hydrogen effusion measurements for the deposited films suggest that moderate IBE is of vital importance to achieve high quality μc‐Si:H. In doing so, denser films with significantly decreased nano‐porous regions and better stability are obtained, which is of great interest to optimize the process parameters for solar cell applications. (© 2016 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Evaluation of a quantitative measurement of suprapatellar effusion by ultrasonography and its association with symptoms of radiographic knee osteoarthritis: a cross-sectional observational study.

BackgroundQuantitative measurement of knee joint effusion by ultrasonography has not been well established; however, a categorical measurement (e.g., a ≥4-mm-deep suprapatellar pouch) is recommended. Therefore, the current study aimed to elucidate the association between symptoms of knee osteoarthritis (OA) and the quantitative measurement of suprapatellar effusion by ultrasonography.MethodsOne hundred twenty-seven volunteers participated (31 men and 96 women; mean age: 68.3 ± 9.8 years; body mass index: 23.2 ± 3.0 kg/m2). The Kellgren-Lawrence grades (KLGs) of both knees were assessed; all subjects had definitive osteoarthritic change (KLG ≥2) in both knee joints. Joint effusion was evaluated using an ultrasound probe, which was placed longitudinally on the suprapatellar pouch, and we determined the area (mm2) of the echo-free space. Then we summed the effusion area of both knees. All subjects answered the knee injury and osteoarthritis outcome scale (KOOS) questionnaire. Multiple linear regression analysis was conducted to elucidate the association between the summed value of the knee effusion area and the KOOS subscales, which were adjusted by age, sex, body mass index, and KLG.ResultsOf 254 knees, 180 were KLG 2, 57 were KLG 3, and 17 were KLG 4. The multiple regression models showed that the quantitative knee effusion area significantly correlated with the following KOOS subscales: pain (B = −0.057; β = −0.253; P = 0.002), symptom (B = −0.053; β = −0.251; P = 0.002), sport and recreation (B = −0.069; β = −0.205; P = 0.007), and quality of life (B = −0.083; β = −0.276; P = 0.001).ConclusionIn this cross-sectional study, the quantitative measurement of suprapatellar effusion by ultrasonography was associated with symptoms of radiographic knee OA.

Low temperature deposition of a-SiC:H thin films applying a dual plasma source process

The utilization of silicon carbide (SiC) thin films is of great interest whenever a high robustness is requested for MEMS/NEMS-based devices, which are operated in harsh environments beyond the applicability of standard silicon technology. Hydrogenated amorphous SiC (a-SiC:H) is especially attractive for these scenarios, as it can be deposited at temperatures lower than 400°C while still being beneficial for enhanced device performance. Furthermore, the thin film properties can be tailored to a great extent during synthesis or via post-deposition annealing. This study reports on the deposition of a-SiC:H thin films at a substrate temperature of 250°C applying a dual plasma process by superimposing a radio frequency (RF) plasma which excites the substrate table to an inductively-coupled RF plasma. This auxiliary plasma source has a huge impact on the resulting thin film properties due to the interaction of various opposing processes during film growth. To understand these processes, the layer composition was determined using time-of-flight elastic recoil detection analyses, Fourier transform infrared spectroscopy and by mass effusion measurements up to 1000°C, thus revealing changes in chemical composition, but also the power dependent incorporation of gaseous species from the plasma. This, for example, allows modification of the residual stress ranging from nearly stress free to highly compressively stressed layers of more than −2GPa, Young's modulus values ranging from about 168GPa down to 48GPa, but also greatly affects the surface topography which can be adjusted to a very low root mean squared roughness of less than 0.1nm.

The diagnostic utility and tendency of the soluble receptor for advanced glycation end products (sRAGE) in exudative pleural effusion.

The soluble receptor for advanced glycation end products (sRAGE) may have an inflammatory or homeostatic function in lung tissue. The aim of this study was to assess the usefulness of sRAGE as a diagnostic marker for exudative pleural effusions, which are common manifestations of a variety of diseases. Patients with an undiagnosed pleural effusion were prospectively enrolled between January 2013 and January 2015. Samples of blood and pleural fluid were centrifuged and the supernatant stored at -70 °C. The levels of sRAGE in serum and pleural fluid were determined using a commercially available enzyme-linked immunosorbent assay (ELISA) kit. In total 47 patients, 21 patients were diagnosed with a tuberculous effusion, and the groups diagnosed with parapneumonic or malignant effusions comprised 13 patients each. The serum sRAGE levels for tuberculosis were significantly elevated [median, 1,291 pg/mL; interquartile range (IQR), 948-1,711 pg/mL] when compared with those for both pneumonia (median, 794 pg/mL; IQR, 700-1,255 pg/mL) and lung cancer (median, 886 pg/mL; IQR, 722-1,285 pg/mL) (P=0.029). The pleural sRAGE levels for pneumonia (median, 1,763 pg/mL; IQR, 1,262-4,431 pg/mL) were lower than those for both tuberculosis (median, 5,081 pg/mL; IQR, 3,300-6,004 pg/mL) and lung cancer (median, 4,936 pg/mL; IQR, 3,282-7,018 pg/mL) (P=0.009) The receiver operating characteristic (ROC) curve analysis selected 896 pg/mL as the best cutoff value in the sRAGE serum level for tuberculosis [sensitivity, 86%; specificity 58%; area under the curve (AUC) =0.727, P=0.008]. For the pleural effusion sRAGE level, the ROC curve analysis selected 2,231 pg/mL as the best cutoff value for pneumonia (sensitivity, 91%; specificity, 62%, AUC =0.792, P=0.002). Among patients with exudative effusion, pleural and serum sRAGE measurements may be useful supportive diagnostic tools in the evaluation of ambiguous pleural effusion. Furthermore, the behavior of sRAGE in the serum and pleural fluid of various pulmonary diseases suggests that sRAGE may be linked to the chronic process of lung damage and inflammation rather than acute bacterial infection.

Surface passivation of heavily boron or phosphorus doped crystalline silicon utilizing amorphous silicon

Excellent surface passivation of heavily boron or phosphorus doped crystalline silicon is presented utilizing undoped hydrogenated amorphous silicon (a-Si:H). For passivating boron doped crystalline silicon surfaces, amorphous silicon needs to be deposited at low temperatures 150 °C≤Tdep≤200 °C, leading to a high bandgap. In contrast, low bandgap amorphous silicon causes an inferior surface passivation of highly boron doped crystalline silicon. Boron doping in crystalline silicon leads to a shift of the Fermi energy towards the valence band maximum in the undoped a-Si:H. A simulation, implementing dangling bond defects according to the defect pool model, shows this shift in the undoped a-Si:H passivation to be more pronounced if the a-Si:H has a lower bandgap. Hence, the inferior passivation of boron doped surfaces with low bandgap amorphous silicon stems from a lower silicon-hydrogen bond energy due to this shift of the Fermi energy. Hydrogen effusion and ellipsometry measurements support our interpretation.

High temperature annealing effects on the chemical and mechanical properties of inductively-coupled plasma-enhanced chemical vapor deposited a-SiC:H thin films

This paper reports the impact of thermal annealing up to temperatures of 1200°C on the chemical and mechanical properties of hydrogenated amorphous silicon carbide (a-SiC:H) thin films. These layers were deposited using an inductively-coupled plasma-enhanced chemical vapor deposition process with methane, silane and argon as precursor gases. The results of mass effusion measurements up to 1000°C are presented and the temperature-dependent effusion characteristics are compared to changes in the Fourier-transform infrared spectra. Furthermore, a simple method is presented that enables us to detect the onset of nanocrystallization in the a-SiC:H films caused by the high temperature annealing. The changes in chemical and crystallographic properties are discussed and related to the mechanical thin film properties, such as a substantial increase in Young's modulus from 176 up to 267GPa, in hardness from 24 up to 34.5GPa, as well as in residual film stress from −683 up to +3800MPa. Additionally, the decrease in layer thickness to about 70% of the initial value and the increase in refractive index from 2.33 to 2.78 are explained.