A glimpse of the Indian space programme

This paper, based on the Presidential Address delivered at the 43rd Annual Meeting of the Indian Academy of Sciences held at Calcutta during 26–29 November 1977, is a brief survey of recent developments in the Indian space programme and of the plans for the near future.     

Modeling the oxygen diffusion of nanocomposite-based food packaging films

Polymer-layered silicate nanocomposites have been shown to improve the gas barrier properties of food packaging polymers. This study developed a computer simulation model using the commercial software, COMSOL Multiphysics to analyze changes in oxygen barrier properties in terms of relative diffusivity, as influenced by configuration and structural parameters that include volume fraction (φ), aspect ratio (α), intercalation width (W), and orientation angle (θ) of nanoparticles. The simulation was performed at different φ (1%, 3%, 5%, and 7%), α (50, 100, 500, and 1000), and W (1, 3, 5, and 7 nm). The θ value was varied from 0° to 85°. Results show that diffusivity decreases with increasing volume fraction, but beyond φ = 5% and α = 500, diffusivity remained almost constant at W values of 1 and 3 nm. Higher relative diffusivity coincided with increasing W and decreasing α value for the same volume fraction of nanoparticles. Diffusivity increased as the rotational angle increased, gradually diminishing the influence of nanoparticles. Diffusivity increased drastically as θ changed from 15° to 30° (relative increment in relative diffusivity was almost 3.5 times). Nanoparticles with exfoliation configuration exhibited better oxygen barrier properties compared to intercalation. The finite element model developed in this study provides insight into oxygen barrier properties for nanocomposite with a wide range of structural parameters. This model can be used to design and manufacture an ideal nanocomposite-based food packaging film with improved gas barrier properties for industrial applications. PRACTICAL APPLICATIONS: The model will assist in designing nanocomposite polymeric structures of desired gas barrier properties for food packaging applications. In addition, this study will be helpful in formulating a combination of nanoparticle structural parameters for designing nanocomposite membranes with selective permeability for the industrial applications including membrane separation techniques.     

An LMI Approach to Optimal Guaranteed Cost Control of Uncertain 2-D Discrete Shift-Delayed Systems via Memory State Feedback

This paper deals with the problem of optimal guaranteed cost control via memory state feedback for a class of two-dimensional (2-D) discrete shift-delayed systems in Fornasini–Marchesini (FM) second model with norm-bounded uncertainties. A new criterion for the existence of memory state feedback guaranteed cost controllers is derived, based on the linear matrix inequality (LMI) approach. Moreover, a convex optimization problem with LMI constraints is formulated to design the optimal guaranteed cost controllers which minimize the upper bound of the closed-loop cost function. Illustrative examples demonstrate the merit of the proposed method in the aspect of conservativeness over a previously reported result.     

Polarographic study of the Reduction of Cadmium(II) and Lead(II) in DL-norleucine media

In continuation of our earlier work on the electrochemical behaviour of amino acids and their metal complexes [1–3], the present investigation reports the polarographic behaviour of Cd(II) and Pb(II) in presence of DL-norleucine, formation and composition of their complexes, determination of stability constants by DE FORD and HUME'S method [4] and MIHALLOV'S mathematical approach [5] at 20° and 30°C and also thermodynamic parameters accompanying complexation reactions at 20°C.     

Preparation of conductive polyaniline solutions for electronic applications

Electrically conductive processible polyaniline films have been synthesised from the electropolymerization of aniline under non-aqueous conditions. The characterization of the polymer was carried out by spectroscopic methods.     

Synthesis of silicon carbide through the sol-gel process from different precursors

Silicon carbide (SiC) was synthesised from silicon alkoxides and various carbon sources. Tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and a mixture of TEOS and MTES were hydrolysed in the presence of phenolic resin, ethylcellulose, polyacrylonitrile (PAN) and starch to incorporate the gel into the carbon source in the silica network. The gel thus obtained was carbonized at 800°C in an argon atmosphere to obtain the mixture of silica and carbon which when heated to 1550°C in argon yielded silicon carbide. The characterization of the product by X-ray, FTIR and SEM showed it to be β SiC with different crystallite and grain sizes. The difference in the crystallite and grain sizes is attributed to the nature of the carbon source. The density of the SiC obtained by the sol—gel process was found to be lower than the values reported for SiC and this is ascribed to the porous nature of the products generally obtained by this process.     

Habitat suitability modeling of a conservation-significant fish species of the Kosi River,Uttarakhand, India

Water quality plays a vital role in the sustenance of aquatic life, including fish. Therefore, an inclusive understanding of water quality parameters can be considered an essential step in framing the conservation and management strategy of an aquatic ecosystem. This study examines the habitat suitability of a conservation-significant fish, the Tor putitora, and two associated fishes, the Labeo dyocheilus and the Garra gotyla, in relation to the water quality parameters of the Kosi River. Four crucial water quality parameters, water temperature, dissolved oxygen, electrical conductivity, and pH, were included in the QUAL2K modeling. Furthermore, hydrological processes were modeled using the soil and water assessment tool, and flow was used as an input in the QUAL2K model. The simulated water quality was correlated with fish habitat and analyzed through the analytical hierarchical process (AHP). Results suggested that the habitats of the Kosi were more suitable in the post-monsoon rather than pre-monsoon. Tor putitora, the flagship species of the Kosi, preferred the river habitats with a lower water temperature and higher dissolved oxygen for spawning. Thus, we recommend securing such habitats and managing them in collaboration with local communities for the long-term conservation of this endangered Himalayan species.