Study of dielectric properties of RbNO3 single crystals

Dielectric properties, dielectric constant (k), dielectric loss (tan δ) and a.c. conductivity (σ) in the solution-grown single crystals of RbNO₃ are presented from room temperature to about 200°C covering the frequency range 10² to 10⁵ Hz. A broad peak observed in tan δ-frequency data between 10³ and 10⁵Hz is thought to be due to impurity-vacancy dipoles. The sudden rise of three parameters near 160°C is attributed to the known phase transition from trigonal to CsCl structure.     

Analysis of Volatile Bread Aroma for Evaluation of Bread Freshness Using an Electronic Nose (E-Nose)

This paper presents the use of a tin-oxide sensor array and self-organized map (SOM)-based E-nose for analysis of volatile bread aroma and explores its ability to cluster bread odor data according to the freshness of bread. A low cost tin-oxide sensor array based electronic nose system has been used for the classification of state of freshness of bread. The sensor data was acquired for a period of 3 weeks, and an unsupervised self-organizing map (SOM) model was trained using this data to correlate the sensor response to classify the bread as fresh and stale. A comparative evaluation of 3 week' of bread data was carried out using the SOM. The results suggest that the system developed is able to predict the state of bread as fresh and stale up to 98% accuracy if the test bread data sets are of the same week. The classification accuracy reduces to 75-85% if test bread data sets are from different weeks. The model is also applied on three different brands of bread and similar classification results are obtained.     

Interannual variability of chlorophyll-a concentration along the southwest coast of India

The interannual variability of chlorophyll concentration along the southwest coast of India is studied using remote-sensing data from SeaWiFS. The data are analysed in conjunction with satellite-measured sea surface winds. The satellite-measured chlorophyll data for a period of 10 years from 1998 to 2007 were made use of for indexing the maximum offshore extent of chlorophyll along the coast for each month. From the empirical orthogonal functional analysis of chlorophyll data, it is observed that the dominant mode is annual. Interestingly, intraseasonal variability and the influence of climatic events like El Niño are observed in the secondary principle component of the time series. The variability of chlorophyll coincided well with variability of Ekman transport all along the coast with higher chlorophyll (>1 mg m^?3) when the Ekman transport is greater than 1000 kg/m/s. During the years 2005–2007, reduction in the meridional (along shore) component of wind resulted in reduction of Ekman transport, the phenomenon which leads to a decrease in chlorophyll. This is due to the reduction in the amount of nutrients that entrained to surface layers during upwelling of the southwest monsoon. The chlorophyll-a is minimum when Ekman transport is less than 0.5 kg/m/s on the normalized scale. For higher values of chlorophyll, the Ekman transport is higher, indicating the contribution of wind in enhancing the already upwelled chlorophyll production. The smaller value of R ² infers that there exist other forces as well involved in augmenting the surface chlorophyll. The enhanced knowledge on the offshore extent and the intraseasonal and interannual variability of chlorophyll can provide valuable inputs on fisheries and primary productivity for this region.     

Vapour-liquid equilibria. System: Acetone—hexyl alcohol

Isobaric vapour-liquid equilibrium results have been determined for the binary system acetone-hexyl alcohol at 760 mm total pressure by use of a Scatchard still. The vapour-liquid equilibrium results for this system are satisfactorily correlated by Wohl's three-suffix Margules equations.     

Liquid-vapour equilibria of binary systems of acetonitrile with chlorobenzene and n-butyl acetate

Vapour-liquid equilibrium data of the systems acetonitrile-chlorobenzene and acetonitrile-n-butyl acetate are measured at 760 mmHg pressure. Both systems are non-ideal in behaviour and show positive deviations from Raoulc's law. The two systems form symmetrical solutions and are well represented by single constant Margules equations.     

Optical properties of vanadium oxides-an analysis

In this study, the optical properties of bulk and thin films of VO₂, V₂O₃, and V₂O₅, deposited on Al₂O₃ substrates, have been analyzed from infrared to vacuum ultraviolet range (up to 12 eV). Utilizing the available data of wavelength dependent optical constants of these materials in the literature, the energy corresponding to the peaks in the imaginary part of the dielectric function (ε ₂–R spectra), have been interpreted and compared as a function of structure, polarization, and temperature. The energies corresponding to the peaks in reflectivity-energy (R–E) spectra are explained in terms of the Penn gap (E _p). E _p values for VO₂ and V₂O₅ are close to the average of energies corresponding to the peaks ( $ \bar{E} $ E ¯ ) while, their values are even closer in V₂O₃, reflecting the degree of anisotropy in the order of V₂O₃ < VO₂ < V₂O₅. The first order reversible, insulator to metal phase transition (IMT) of both bulk and thin films of the V–O systems are studied as an effect of temperature change. The effective number of electrons, n _eff, participating in the optical transitions is described from the numerical integration using the well-known sum rule. The change in n _eff with respect to the energy of incident photons is also calculated and it is found that this change is consistent with the peaks observed in the ε ₂–E spectra.     

Complex impedance analysis of Sr(NO3)2 and Sr(NO3)2:γ-Al2O3 dispersed solid electrolyte systems

Complex impedance spectroscopic studies were carried out on Sr(NO₃)₂ and Sr(NO₃)₂:-Al₂O₃ dispersed solid electrolyte systems (DSES) in the temperature range 300 to 560° C and the frequency range 100 Hz to 1 MHz. Mole percentage of the dispersoid -Al₂O₃ was varied from 17.2 to 34.2. The d.c. conductivity estimated from the Cole-Cole plots was found to increase with the mole percentage of the dispersoid. Dissipation was found to vary in a manner similar to the variation of conductivity with temperature. A.c. conductivity was found to be frequency dependent in the extrinsic region, but frequency independent in the intrinsic region. The enhanced conductivity in DSES was attributed to the formation of a space-charge layer between the host material and the dispersoid.     

Multi-rate observer design and optimal control to maximize productivity of an industry-scale fermentation process

Chemical industries focus primarily on profitable operations, resulting in growing attention and advances in the field of digital twins and optimal control algorithms. However, most industries still struggle due to a lack of physical sensors, infrequent measurements, and asynchronous sampling. Thus, in this work, we have designed a multi-rate state observer for state estimation from plant measurements and developed a model predictive controller (MPC) that maximized the profitability of an industry-scale fermentation process (fermenter volume < 378,500 L). Additionally, as the fermentation process is complex due to the use of microorganisms, which cannot be accurately captured using a first-principles model, we utilize a previously developed hybrid model in the proposed MPC formulation. The MPC uses a GAMS-MATLAB framework to determine the optimal input profiles while considering practical process constraints. It is shown using multiple datasets, that the MPC can increase productivity while also decreasing the plant operating cost.