Structural,microstructural, and thermal characterizations of a chalcopyrite concentrate from the Singhbhum shear zone,India

The structural and morphological characterizations of a chalcopyrite concentrate, collected from the Indian Copper Complex, Ghatshila, India, were carried out by X-ray diffraction, scanning electron mi...     

Photon and vibration synergism on planar defects induced 2D-graphitic carbon nitride for ultrafast remediation of dyes and antibiotic ampicillin

Journal of Materials Science - Hybrid oxidation methodologies (HOMs) and active site enrichment of 2D nanocatalyst through defects induction are ubiquitously used for generating adequate reactive...     

A simulation‐based algorithm for optimal pricing policy under demand uncertainty

We propose a simulation‐based algorithm for computing the optimal pricing policy for a product under uncertain demand dynamics. We consider a parameterized stochastic differential equation (SDE) model for the uncertain demand dynamics of the product over the planning horizon. In particular, we consider a dynamic model that is an extension of the Bass model. The performance of our algorithm is compared to that of a myopic pricing policy and is shown to give better results. Two significant advantages with our algorithm are as follows: (a) it does not require information on the system model parameters if the SDE system state is known via either a simulation device or real data, and (b) as it works efficiently even for high‐dimensional parameters, it uses the efficient smoothed functional gradient estimator.     

Approximation schemes for load balanced clustering in wireless sensor networks

Clustering sensor nodes is an efficient technique to improve scalability and life time of a wireless sensor network (WSN). However, in a cluster based WSN, the leaders (cluster heads) consume more energy due to some extra load for various activities such as data collection, data aggregation, and communication of the aggregated data to the base station. Therefore, balancing the load of the cluster heads is a crucial issue for the long run operation of the WSNs. In this paper, we first present a load balanced clustering scheme for wireless sensor networks. We show that the algorithm runs in O(nlogn) time for n sensor nodes. We prove that the algorithm is optimal for the case in which the sensor nodes have equal load. We also show that it is a polynomial time 2-approximation algorithm for the general case, i.e., when the sensor nodes have variable load. We finally improve this algorithm and propose a 1.5-approximation algorithm for the general case. The experimental results show the efficiency of the proposed algorithm in terms of the load balancing of the cluster heads, execution time, and the network life.     

Preparation of water-dispersible graphene by facile surface modification of graphite oxide

Water-dispersible graphene was prepared by reacting graphite oxide and 6-amino-4-hydroxy-2-naphthalenesulfonic acid (ANS). X-ray diffraction study showed that the basal reflection (002) peak of graphite oxide was absent in the ANS-functionalized graphene (ANS-G), indicating crystal layer delamination. Ultraviolet-visible spectral data were recorded to assess the solubility of the ANS-G in water. Fourier transform infrared spectral analysis suggested the attachment of ANS molecules to the surface of graphene. Raman and x-ray photoelectron spectroscopy revealed that oxygen functionality in the graphite oxide had been removed during reduction. Atomic force microscopy found that the thickness of ANS-G in water was about 1.8 nm, much higher than that of single layer graphene. Thermal stability measurements also indicated successful removal of oxygen functionality from the graphite oxide and the attachment of thermally unstable ANS to the graphene surfaces. The electrical conductivity of ANS-G, determined by a four-point probe, was 145 S m(-1) at room temperature.     

Rubber/LDH nanocomposites by solution blending

The rubber nanocomposites containing ethylene vinyl acetate (EVA) having 60 wt % of vinyl acetate content and organomodified layered double hydroxide (DS‐LDH) as nanofiller have been prepared by solution intercalation method and characterized. The XRD and TEM analysis demonstrate the formation of completely exfoliated EVA/DS‐LDH nanocomposites for 1 wt % filler loading followed by partially exfoliated structure for 5–8 wt % of DS‐LDH content. EVA/DS‐LDH nanocomposites show improved mechanical properties such as tensile strength (TS) and elongation at break (EB) in comparison with neat EVA. The maximum value of TS (5.1 MPa) is noted for 3 wt % of DS‐LDH content with respect to TS value of pure EVA (2.6 MPa). The data from thermogravimetric analysis show the improvement in thermal stability of the nanocomposites by ≈15°C with respect to neat EVA. Limiting oxygen index measurements show that the nanocomposites act as good flame retardant materials. Swelling property analysis shows improved solvent resistance behavior of the nanocomposites (1, 3, and 5 wt % DS‐LDH content) compared with neat EVA‐60. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The effect of probe coherence and atomic coherence on the response of an open lambda-type pump–probe system

The response of a coherently prepared four-level λ-type system, interacting with two electromagnetic fields in a Doppler-free pump–probe configuration is analytically formulated. Under density matrix formalism the probe coherence (field-dependent phase) and atomic coherence (field-independent phase) are introduced through the off-diagonal matrix elements. The coherent effects on probe response is investigated for probe coherence, as well as for the driving contribution (coherence) of the pump field. We show how probe coherence can modify the Rabi splitting and two-photon absorption, through shifting and broadening of spectral lines for on- and off-resonance pumping, respectively. In addition, we report on the enhancement of absorptionless dispersion (i.e. refractive index for on and around probe resonance) and two-photon absorption, via coherent control of the driving contribution of the pump field.     

All‐Organic,Temporally Pure White Afterglow in Amorphous Films Using Complementary Blue and Greenish‐Yellow Ultralong Room Temperature Phosphors

Organic molecules exhibiting afterglow emission (lifetime longer than 0.1 s) under ambient conditions have sparked tremendous attention in recent years as a sustainable energy source with potential applications in displays, lighting, and bioimaging. However, white afterglow organic materials with color purity during the entire period of delayed emission, after the cessation of excitation source, are yet to be achieved due to the different excited state lifetimes of its primary or complementary components. Herein, a remarkable, ambient “temporally pure white afterglow,” which lasts for over 7 s, by coorganizing complementary blue and greenish‐yellow organic room temperature phosphors with similar ultralong lifetimes and efficiency, in an amorphous polymer film is demonstrated. One of the most efficient blue afterglow room temperature phosphors is also reported, with an ultralong lifetime up to 2.26 s and maximum quantum efficiency of 36.8%, from purely organic triazatruxenes en route to the realization of this white afterglow. Further, broad and complementary absorption features of the coorganized phosphors in the visible region facilitates an excitation‐dependent dynamic color‐tuning of the afterglow from sky‐blue to greenish‐yellow.     

Enhanced properties of lignin-based biodegradable polymer composites using injection moulding process

Composites from polybutylene succinate (PBS) and lignin-based natural material were fabricated using a melt mixing process. The effects of lignin material and polymeric methylene diphenyl diisocyanate (PMDI) compatibilizer on the properties of composites were investigated. Incorporation of 65% lignin material into PBS was achieved with an improvement in the tensile and flexural properties of composites. Incorporation of 1% PMDI in 50% lignin filled composites enhanced the tensile, flexural and impact strength simultaneously. Heat deflection temperature (HDT) of the virgin plastic also increased with lignin and PMDI incorporation. Improved interfacial adhesion was observed from SEM micrographs of the compatibilized composites.     

Synthesis of full interpenetrating network membranes of poly(acrylic acid-co-acrylamide) in the matrix of polyvinyl alcohol for dehydration of ethylene glycol by pervaporation

Polyvinyl alcohol (PVOH) has been chemically modified by crosslink copolymerization of acrylic acid (AA) and acrylamide (AM) in aqueous solution of PVOH and finally crosslinking the copolymer with methylene bis acrylamide (MBA) and PVOH with glutaraldehyde to produce a full interpenetrating network (FIPN) membrane. Accordingly, three such fully crosslinked IPNs i.e. FIPN25, FIPN50 and FIPN75 have been synthesized with different mass ratio of PVOH:copolymer i.e. 1:0.25 (FIPN25), 1:0.50 (FIPN50) and 1:0.75 (FIPN75). These full IPN membranes were used for pervaporative dehydration of ethylene glycol (EG). All of these IPN membranes were characterized with various conventional methods like FTIR, mechanical properties, DTA and SEM. The performances of the membranes were evaluated in terms of sorption and pervaporative dehydration of EG. The IPN membranes were found to show preferential sorption and diffusion for water. Flux and water selectivity of these membranes were found to increase with increasing amount of copolymer in PVOH matrix. However, among the three membranes, FIPN75 were found to show the highest flux but lower selectivity for water while FIPN50 membrane showed optimum performance in terms of both flux and selectivity. Diffusion coefficient and plasticization interaction of water and EG through all the IPN membranes were determined using modified solution-diffusion model.