Numerical study of heat and moisture transport through concrete at elevated temperatures

This research article focuses on numerical investigation of heat and moisture transport through concrete exposed to high temperatures such as fire. The conservation equations for moisture and energy transport through concrete have been represented in terms of temperature, pore pressure and vapor content as field variables. As the resulting governing equations are coupled and non-linear, the equations were solved numerically using Galerkin’s weighted residual finite element method and an iterative solution technique. After validating the model, a detailed simulation study has been carried out to understand the role of gradients of temperature, pore pressure and vapor content on heat and moisture transport through concrete exposed to ISO 834 fire curve. Results obtained at the end of 30 minutes exposure of concrete show that the temperature gradients become very steep after 12 minutes of exposure of concrete, which in turn results in increased vapor generation and 93% of vapor generation is completed at the end of 20 minutes. Due to steep temperature gradient along the length of concrete, condensation of vapor takes place which is followed by blockage of pores giving rise to sudden peak pore pressure rise and 97% of peak pore pressure is attained at the end of 18 minutes itself. It is observed that for the initial 18 minutes, the peak pore pressure front and peak vapor content front follow the same path and after 18 minutes the peak vapor content front moves slightly ahead of the peak pore pressure front.     

Molecular modeling guided isotope separation of gadolinium with strong cation exchange resin using displacement chromatography

Molecular modeling was carried out using DFT to identify the suitable displacing agent for carrying out Gd isotope separation using displacement chromatography. EDTA was identified as the best eluting agent among EDTA, malic acid and citric acid. Displacement chromatography of Gd adsorption band in cation exchange resin was performed to observe the isotope effects in the Gd ion exchange processes involving complex forming reagent – EDTA. The heavier isotope of ¹⁶⁰Gd was found to be enriched at the front boundary of Gd adsorption band, while the lighter isotopes of ¹⁵⁵Gd and ¹⁵⁷Gd were enriched at the rear boundary.     

Fuzzy Logic-based Electrothermal Life Model for Inverter-fed Induction Motor Insulation

Pulse width modulated adjustable speed drives used in industries lead to significant advantages in terms of performance, size, and efficiency. But, the output voltage and the current waveforms become non-sinusoidal leading to an increase in voltage and thermal stresses. This results into accelerated insulation aging and premature failure of the motors. With multiple stresses, the life models for insulating materials become complex and ambiguous. This article presents the fuzzy logic application to derive an electrothermal life model to investigate the synergic effects of voltage and thermal stresses on intrinsic aging of inverter-fed induction motor insulation. Three parameters, viz. voltage stress factor, waveform slope stress factor, and spike frequency factor, are proposed to describe the insulation stresses for pulse width modulated voltages. These parameters are computed from the experimental results at different switching frequencies and are used in fuzzy logic-based life estimation algorithms. The results of the fuzzy logic life model are verified by performing the accelerated aging test with the same pulse width modulated voltages on paper insulation. An electrothermal life model is derived from the fuzzy logic results, which can be directly used for the life estimation of any general purpose low-voltage inverter-fed induction motor insulation.     

Effect of microencapsulation and spray drying on oxidative stability of flaxseed oil and its release behavior under simulated gastrointestinal conditions

Flaxseed oil is one of the richest sources of omega-3 fatty acid (α-linolenic acid, ALA). It contains high amounts of polyunsaturated fatty acids, making it extremely susceptible to oxidation. In the present study, flaxseed oil was stabilized using microencapsulation followed by spray drying and studied for its oxidative stability in terms of peroxide value (PV), thiobarbituric acid, and p-anisidine value at room temperature (35 ± 1°C) and low temperature (4–7°C) storage for 6 months. Results revealed that the developed flaxseed oil powder was stable throughout the storage period and PV remained below to the maximum permissible limit (≤5 mEq/kg oil) prescribed by the Codex Alimentarius Commission. The fatty acids profile measured by gas–liquid chromatography indicated a 14.28–15.13% decrease in ALA content in flaxseed oil as a result of microencapsulation and storage at room temperature. In vitro digestion behavior of microcapsules showed 4.39 ± 0.53 to 19.87 ± 0.47% release of flaxseed oil under simulated gastric continued, whereas under gastrointestinal conditions it was 20.00 ± 3.66 to 59.99 ± 9.29%.     

Near‐Infrared Intraoperative Chemiluminescence Imaging

Intraoperative imaging technologies recently entered the operating room, and their implementation is revolutionizing how physicians plan, monitor, and perform surgical interventions. In this work, we present a novel surgical imaging reporter system: intraoperative chemiluminescence imaging (ICI). To this end, we have leveraged the ability of a chemiluminescent metal complex to generate near‐infrared light upon exposure to an aqueous solution of Ce⁴⁺ in the presence of reducing tissue or blood components. An optical camera spatially resolves the resulting photon flux. We describe the construction and application of a prototype imaging setup, which achieves a detection limit as low as 6.9 pmol cm^?2 of the transition‐metal‐based ICI agent. As a proof of concept, we use ICI for the in vivo detection of our transition metal tracer following both systemic and subdermal injections. The very high signal‐to‐noise ratios make ICI an interesting candidate for the development of new intraoperative imaging technologies.     

Fully-coupled simulations of thermally-induced cracking in pegmatite due to microwave irradiation

Fully-coupled thermo-mechanical simulations are implemented in COMSOL Multiphysics to investigate micro-scale stress-strain variability in pegmatite specimens subjected to thermal loading using microwaves. Thermally-induced compressive and tensile stresses increase as the microwave irradiation duration increases. The dielectric constant, coefficient of expansion, and type and size of mineralogical boundary have significant impacts on the responses of the rock to microwave irradiation. The maximum principal stress of the chlorite is the smallest, indicating that the chlorite experiences the most damage under microwave irradiation, followed by the quartz. The maximum principal stress values of plagioclase and orthoclase are larger, indicating that they are likely to incur the least damage. Where quartz or chlorite is dominant, the resulting von Mises stresses are consistently higher after 120 s of microwave irradiation. The rate of generation of von Mises stresses increases most rapidly along the interface between quartz and plagioclase, and the interface between quartz and orthoclase, followed by the interface between quartz and chlorite, and finally the interface between plagioclase and orthoclase. The presented modeling approach provides a practical method to investigate stress-strain relationships within mineralogical boundaries inside a rock thin section.     

Heavy metal accumulation in vegetables irrigated with water from different sources

The present study was carried out to assess levels of different heavy metals like iron, manganese, copper and zinc, in vegetables irrigated with water from different sources. The results indicated a substantial build-up of heavy metals in vegetables irrigated with wastewater. The range of various metals in wastewater-irrigated plants was 116–378, 12–69, 5.2–16.8 and 22–46 mg/kg for iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn), respectively. The highest mean levels of Fe and Mn were detected in mint and spinach, whereas the levels of Cu and Zn were highest in carrot. The present study highlights that both adults and children consuming vegetables grown in wastewater-irrigated soils ingest significant amount of these metals. However, the values of these metals were below the recommended maximum tolerable levels proposed by the [Joint FAO/WHO Expert Committee on Food Additives (1999). Summary and conclusions. In 53rd Meeting, Rome, June 1–10, 1999]. However, the regular monitoring of levels of these metals from effluents and sewage, in vegetables and in other food materials is essential to prevent excessive build-up of these metals in the food chain.     

Direct quantification of topological protection in symmetry-protected photonic edge states at telecom wavelengths

Topological on-chip photonics based on tailored photonic crystals(PhCs)that emulate quantum valley-Hall effeas has recently gained widespread interest owing to its promise of robust unidirectional transport of classical and quantum information.We present a direct quantitative evaluation of topological photonic edge eigenstates and their transport properties in the telecom wavelength range using phase-resolved near-field optical microscopy.Experimentally visualizing the detailed sub-wavelength structure of these modes propagating along the interface between two topologically non-trivial mirror-symmetric lattices allows us to map their dispersion relation and differentiate between the contributions of several higher-order Bloch harmonics.Selective probing of forward-and backward-propagating modes as defined by their phase velocities enables direct quantification of topological robustness.Studying near-field propagation in controlled defects allows us to extract upper limits of topological protection in on-chip photonic systems in comparison with conventional PhC waveguides.We find that protected edge states are two orders of magnitude more robust than modes of conventional PhC waveguides.This direct experimental quantification of topological robustness comprises a crucial step toward the application of topologically protected guiding in integrated photonics,allowing for unprecedented error-free photonic quantum networks。     

PHOTOCHEMICAL AND CHEMICAL TRANSFORMATION OF Calotropis procera LATEX TOWARDS OBTAINING VALUE ADDED CHEMICALS AND FUELS

ABSTRACT

Photothermal degradation of the latex obtained from Calotropis procera showed enhanced extraction in heptane up to 50%. Treatment of the latex with different concentrations of NaOH resulted in the reduction in heptane extraction of the latex. Treatment of latex with aqueous HC1 coagulated it and thus resulted in an increase in extraction yield. The ¹HNMR, ^l3CNMR and FTTR spectral analyses of treated latex showed an increase in the olefinic and carbonyl groups in the latex. Thus, this showed that photothermal treatments rendered the latex more amenable to hydrocracking for obtaining value added chemicals and fuels from the latex.