Hybrid Approach to Optimal Packing Using Genetic Algorithm and Coulomb Potential Algorithm

It is difficult and computationally time-consuming to find the best possible solutions for blank packing problems, because they include a lot of underlying combinational conditions. This paper presents two approaches for packing two-dimensional irregular-shaped polygonal elements—a real-encoded genetic algorithm and a hybrid algorithm using a real-encoded genetic algorithm and a local optimization algorithm. The local optimization algorithm presented is a novel one utilizing the Coulomb potential technique.

In the hybrid approach, the real-encoded genetic algorithm generates the order of the polygons while the coulomb potential algorithm determines the embodiment layout under the fixed combinations so as to minimize the scrap. The hybrid genetic algorithm is found to give better results for problems of larger size although it takes more computational time.     

Pulsed laser deposition of metal films and nanoparticles in vacuum using subnanosecond laser pulses

A study of silver, chromium, stainless-steel, and indium thin films prepared by subnanosecond laser deposition in vacuum is reported. We compare the laser ablation in vacuum at the weak- and tight-focusing conditions of a Ti:sapphire laser beam and analyze the nanoparticles synthesized in the latter case using absorption spectroscopy, x-ray fluorescence, atomic force microscopy, and scanning electron microscopy. Our results show that the nanoparticle formation can be accomplished using long laser pulses under tight-focusing conditions.     

Comparative study of porphyrin derivatives in monolayers at the air-water interface and in Langmuir-Blodgett films

The orientation and aggregation of various porphyrin derivatives at the air-water interface and in Langmuir-Blodgett films were investigated. Monolayer properties of these molecules, where long alkyl chain(s) were covalently bound through different functionality of varying hydrophilicity were studied by measuring surface pressure area isotherms. Such derivatives, where ether functionality (functionalities) was (were) used for linking long alkyl chain(s), did not form uniform monolayer; instead they were found to form multilayer clusters or aggregates on the water surface. On the other hand, porphyrin derivative functionalized at the four peripheral phenyl rings with eight hexadecyl ether chains formed stable spherical vesicles when deposited on mica. Tetra N-alkyl pyridinium porphyrins with long alkyl chain were found to form various phases on the water surface. Evidence of transition from horizontal orientation to vertical orientation of porphyrin rings of porphyrin molecules having C₁₄ chains was observed. This type of transition was lost with the porphyrin molecule with a relatively smaller chain (C₈).     

Effect of pH on the extra cellular synthesis of gold and silver nanoparticles by Saccharomyces cerevisae

In the present study, the synthesis of gold and silver nanoparticles was investigated using the culture supernatant broth of the yeast Saccharomyces cerevisae. Gold nanoparticles were formed within 24 hours of gold ion coming in contact with the culture supernatant broth. In case of silver the reduction process took 48 hours. The synthesized nanoparticles were investigated by UV-Visible spectroscopy. Distinct surface plasmon peaks were observed at 540 nm and 415 nm for gold and silver nanoparticles respectively. Bio-TEM micrographs of the synthesized nanoparticles indicated that the particles were well dispersed and near spherical in shape. The size range of the gold and silver nanoparticles was around 20-100 nm and 5-20 nm respectively. XRD patterns showed the presence of three distinct peaks corresponding to gold and silver nanoparticles respectively. A pH range of 4 to 6 and 8 to 10 favored optimum synthesis of gold and silver nanoparticles respectively. The process of reduction being extra cellular could be used in future for downstream processing in an eco friendly manner.     

Synthesis of S-doped graphene by liquid precursor

Doping is a common and effective approach to tailor semiconductor properties. Here, we demonstrate the growth of large-area sulfur (S)-doped graphene sheets on copper substrate via the chemical vapor deposition technique by using liquid organics (hexane in the presence of S) as the precursor. We found that S could be doped into graphene's lattice and mainly formed linear nanodomains, which was proved by elemental analysis, high resolution transmission microscopy and Raman spectra. Measurements on S-doped graphene field-effect transistors (G-FETs) revealed that S-doped graphene exhibited lower conductivity and distinctive p-type semiconductor properties compared with those of pristine graphene. Our approach has produced a new member in the family of graphene based materials and is promising for producing graphene based devices for multiple applications.     

Grinding-induced rapid,convenient and solvent free approach for the one pot synthesis of α-aminophosphonates using aluminium pillared interlayered clay catalyst

An easy to prepare aluminium pillared interlayered clay (PILC) has been developed as a stable, recyclable and heterogeneous catalyst to promote the one-pot three component synthesis of α-aminophosphonates under solvent-free conditions using grindstone chemistry. Utilization of mild reaction conditions, clean conversion and greater selectivity under grinding conditions along with effortless separation, and purification of reaction products make this process extra attractive.     

37—THE PROPERTIES OF JUTE FIBRES AT DIFFERENT STAGES OF PLANT GROWTH

An investigation is described in which cell-wall thickness, linear density, and filament tenacity were studied for jute fibres of both the C. capsularis and C. olitorius species at different stages of growth of the jute plant. It is shown that the cell-wall thickness goes on increasing for 120 days and then levels off, whereas the linear density goes on increasing for only about 60 days and then falls and levels off after 80 days. The fact that, despite the increase in cell-wall thickness, the linear density does not increase afier 70–80 days indicates that filaments become split at some stage prior to ihe determination of linear density. Breaking strength at first increases rapidly and then levels off after 80 days and falls after 120 days. Variation in breaking strengih is consistent with the variation in multicellular character, cementing material, and fine structure of the fibre with the growth of the plant.     

Neutron Reflectometry: A Tool to Investigate Diffusion Processes in Solids on the Nanometer Scale

The investigation of self‐diffusion for the characterization of kinetic process in solids is one of the most fundamental tasks in materials science. We present the method of neutron reflectometry (NR), which allows the detection of extremely short diffusion lengths in the order of 1 nm and below at corresponding low self‐diffusivities between 10^?25 and 10^?20 m² s^?1. Such a combination of values cannot be achieved by conventional methods of diffusivity determination, like the radiotracer method, secondary ion mass spectrometry, quasielastic neutron scattering, or nuclear magnetic resonance. Using our method, the extensive characterization of materials which are in a non‐equilibrium state, like amorphous or nanocrystalline solids becomes possible. Due to the small experimentally accessible diffusion length microstructural changes (grain growth and crystallization) taking place simultaneously during the actual diffusion experiment can be avoided. For diffusion experiments with NR isotope multilayers are necessary, which are chemical homogeneous but isotope modulated films. We illustrate the basic aspects and potential of this technique using model systems of different classes of materials: single crystalline germanium, amorphous silicon nitride, and nanocrystalline iron.