Optical Constants Retrieval from a Thin Film at Elevated Temperatures Using Emittance

Refractive index and extinction coefficient (optical constants) are essential in photonic design and thermal radiation utilization. These constants vary with the material phase, temperature, wavelength, and subject dimension. Precisely retrieving these constants of a thin film is thus challenging at elevated temperatures. To tackle this challenge, a methodology for retrieval using emittance at different emission angle θ has been developed here. The method contains four steps and takes advantages of an emissometry. The method is firstly validated using simulation and then demonstrates its feasibility by retrieving optical constants of a phase change germanium-antimony-tellurium (Ge2Sb2Te5, GST) film. Emittance from samples at 100°C, 200°C, 300°C, and 400°C is measured at θ = 0°, 15°, and 30°. The spectral range of retrieval covers from 4 μm to 18 μm where thermal radiation dominates. The investigated film phase considers amorphous, face-centered cubic (FCC), and hexagonal close packed (HCP). The retrieved constants exhibit temperature and substrate independence, but they show up significant phase reliance.

Thermal and Dielectric Properties of Cyanate Ester Cured Main Chain Rigid-Rod Epoxy Resin

Thermal and dielectric properties of rigid-rod bifunctional epoxy resin 4,4-bis(2,3-epoxypropoxy) biphenyl epoxy (BP) and commercial epoxy resin diglycidyl ether of bisphenol A (DGEBA) were studied using differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), dynamic mechanical analyzer (DMA), thermal mechanical analyzer (TMA) and dielectric analyzer (DEA). These two epoxies were cured with cyanate ester hardener 2,2’-bis(4-cyanatophenyl) propane (AroCy B10). The BP/B10 system consisting of a rigid-rod structure exhibited better thermal properties than the DGEBA/B10 system with a flexible structure. Anisotropic BP/B10 (2:1) had the highest 5% weight loss temperature, the highest amount of residue and a smaller thermal expansion coefficient than the commercial DGEBA/B10 system. The BP/B10 system, which cured at the LC phase temperature, had higher Tg than the commercial DGEBA/B10 system, as found from dynamic mechanical analysis. The BP/B10 system also demonstrated better dielectric properties than the commercial DGEBA/B10 system when enough curing agent was provided.

Polymer-Stabilized Blue Phase and Its Application to a 1.5 µm Band Wavelength Selective Filter

The use of polymer-stabilized blue phase (PSBP) including a tolane-type liquid crystal was investigated to develop a voltage-controlled wavelength selective filter for wavelength-division-multiplexing optical fiber network. It was found that the tolane-type liquid crystal introduction can increase both a blue-phase temperature range and a Kerr coefficient. A Fabry–Perot etalon filled with PSBP functioned as a wavelength selective filter, as expected. The tuning wavelength range was 62 nm although peak transmission was not as high as expected. Numerical analysis suggested that light absorption in transparent electrodes may cause the issue. Minor change to the etalon structure will result in improved performance.

Thermal Properties of Fullerene С56

The behavior of С56 fullerene when heated in a nitrogen atmosphere at a pressure of 105 Pa was studied using computer thermodynamic modeling. The modeling consisted in a complete thermodynamic analysis of the system using the TERRA software package, which is one of the most developed and efficient ones that implements such thermodynamic calculations. Experiment temperature ranges are from 273 to 3373 К. Based on the calculated data, a graph of the carbon balance in the С56-N2 system was constructed, the ongoing physicochemical processes were described, divided into four classes: sublimation, dissociation in the gas phase, chemical reactions occurring in the gas phase, dissociation and chemical reaction in the gas phase. Temperature intervals of reactions are identified. The equilibrium constants of the reactions are calculated and described, as well as the coefficients of these constants are found using the least squares method. The temperature interval of thermal stability of the condensed C56 fullerene and C56 vapors is defined. This work is one of the series of works on the properties of nanoparticles, in the future it is planned to study the thermal properties of higher fullerenes. The data obtained can be used to determine the explosive and fire hazardous properties of fullerenes as a dispersed solid.

Preliminary Study of the Superlubricity Behavior of Polyimide-Induced Liquid Crystal Alignment

We have studied the friction behavior based on liquid crystal (LC) alignment of a unique tribological system composed of a nematic LC and polyimide (PI). The LC was used as a lubricant and a tribological factor with molecular alignment ability. PI was used as both a rubbing pair part and a LC alignment agent. The LCs used as lubricants included the single LC 5CB and the mixed LCs 5CB–2UTPP3 and 3PEP5–3UTPP4. The PI used as the friction pair was 6FDA-ODA PI, and its counterpart was GCr15 steel. For this system, it was found that under the premise that the nematic phase temperature range of the selected LC meets the operating temperature of the friction test at a suitable ambient temperature, the operating speed and load are controlled to maintain a stable lubricating film thickness between the friction pairs during operation of the system. Moreover, by avoiding excessive or insufficient friction heat generated by the running speed being too high or too low to change the phase state of the LC, with the anchoring energy between the PI and the LC, the LC molecules will align in the rubbing direction, that is, they will arrange parallel to each other along the grooves, which can contribute to achieve superlubricity behavior.

Quantitative definition of fever needs a change

Background The age-old definition of fever was derived using cross-sectional population surveying utilizing old techniques without considering symptomatology. However, the diagnosis of fever must be made only in the presence of associated symptoms that can distinguish it from the mere asymptomatic physiologic rise of temperature. Association of the temperature values with the symptoms to define the cut-off for fever is need of the hour. Methods A longitudinal study on the healthy population of Northen-India were followed-up over 1-year. Participants were advised for self-monitoring of oral temperature with a standard digital thermometer in either left or right sublingual pocket and record it in the thermometry diary. The study was considered complete if the participant had all the three phases of the study (i.e. non-febrile, febrile, and post-febrile phases) or completed the duration of the study. Results Per protocol analysis done for febrile participants (n=144, temperature recordings= 23851). The mean febrile phase temperature was 100.25 ± 1.440F. A temperature of 99.10F had maximum diagnostic accuracy for feeling feverish (98.2%), along with one (98.3%) or two (99%) associated symptoms. Summer and spring months showed higher temperatures (100.38 ± 1.44 v/s 99.80 ± 1.49, P<0.001), whereas no significant temperature difference could be noted amongst the gender. Conclusions A revised cut-off for the temperature to decide fever is hereby proposed: 99.10F along with one or two associated symptoms. This is going to redefine fever in the modern era completely.

Effect of Wall Heat Transfer on the Fluidization Process

The fluidized bed and the fluidization process and characteristics were studied in this paper numerically using Computational Fluid Dynamics (CFD) Ansys Fluent 15.0. Constant temperature was applied to both sides of the two-dimensional fluidized bed geometry. The superficial velocity of the working fluid ranged amid (0.08 – 0.5 m/s) and the initial height of the solid particles changed amid (0.05, 0.1, 0.2 m). Aluminum particles and water was used as working materials within the fluidized bed. The model used for the investigations was validated using Ngoh and Lim research results. The results showed that the fluidization head increases as the water inlet superficial velocity increases. As well as when the water inlet superficial velocity increases, the average solid phase temperature increases.