Synthesis of hydroxy-functionalized star-branched PMMA by anionic polymerization

Living anionic polymerization has been exploited to synthesize hydroxy end-functionalized PMMA star-branched polymers. Protected hydroxy-functionalized alkyl lithium initiators have been used to initiate anionic polymerization of MMA. Subsequently the living chains with protected hydroxyl function have been used to cross-link ethylene glycol dimethacrylate (EGDMA) in order to form star-branched polymers with cross-linked EGDMA core via ‘arm-first’ method. The linear arms and the star molecules have been characterized by ¹HNMR, GPC, and light scattering. Variation in the number of arms with arm molecular weight and cross-linker loading has been studied. Star-branched PMMA-OH with as many as ~10 arms could be successfully made. Increased molecular weight of PMMA-OH led to decrease in the number of arms incorporated due to increased steric hindrance on the core. Increase in EGDMA concentration slightly increased the arm incorporation.     

Synthesis and characterization of Co and Mn doped NiO nanoparticles

Diluted magnetic semiconductors (DMS) are intensively studied for their potential spintronics applications, especially those with Curie temperature above the room temperature. Ni_1?x Mn _x O and Ni_1?x Co _x O (x=1% & 2%), nanoparticles with size around 40–50 nm, were prepared by co-precipitation method. An NiO single phase structure was confirmed by powder X-ray diffraction measurements. Also, diffraction peaks show a systematic shift towards higher angle with an increase in Mn concentration, which is associated with the lattice variation. The samples were pelleted and examined for its magnetic property using a vibrating sample magnetometer (VSM); it indicates paramagnetic-like behavior at room temperature. The increase in a.c conductivity with increasing temperature is attributed to the increase in drift mobility of the charge carriers.     

An energy‐efficient clustering and multipath routing for mobile wireless sensor network using game theory

Most of the current generation sensor nodes of mobile wireless sensor network (MWSN) are designed to have heterogeneous mobility to adapt itself in the applied environment. Energy optimization in MWSN with heterogeneous mobility is very challenging task. In this paper, a heterogeneous game theoretical clustering algorithm called mobile clustering game theory–1 (MCGT‐1) is proposed for energy optimization in a heterogeneous mobile sensor environment. Energy optimization is achieved through energy‐efficient cluster head election and multipath routing in the network. A heterogeneous clustering game is modelled with varying attributes and located an asymmetric equilibrium condition for a symmetric game with mixed strategies. The real‐time parameters, namely, predicted remaining energy, distance between a base station and nodes, distance between nodes, and mobility speed, were used to calculate the probability to elect the cluster head (CH). The efficient multipath routing is achieved through prior energy prediction strategy. It has mitigated the generation of “hot spots,” reducing its delay and improving the overall residual energy of the network. Simulation results showed that the average lifetime of MCGT‐1 has increased by 6.33 %, 13.1% and 14.2% and the PDR has improved by 4.8%,11.8%, and 17.2% than MCGT, LEACH‐ME and LEACH‐M respectively. The hot spot delay is reduced to 0.063025 seconds, improving the efficiency of the network.     

Thulium-doped barium tellurite glasses: structural,thermal, linear,and non-linear optical investigations

Journal of Materials Science: Materials in Electronics - A systematic study of structural, thermal, linear, and non-linear optical properties on...     

Intermetallic phase detection in lead-free solders using synchrotron x-ray diffraction

The high-intensity, high-resolution x-ray source at the European Synchrotron Radiation Facility (ESRF) has been used in x-ray diffraction (XRD) experiments to detect intermetallic compounds (IMCs) in lead-free solder bumps. The IMCs found in 95.5Sn3.8Ag0.7Cu solder bumps on Cu pads with electroplated-nickel immersion-gold (ENIG) surface finish are consistent with results based on traditional destructive methods. Moreover, after positive identification of the IMCs from the diffraction data, spatial distribution plots over the entire bump were obtained. These spatial distributions for selected intermetallic phases display the layer thickness and confirm the locations of the IMCs. For isothermally aged solder samples, results have shown that much thicker layers of IMCs have grown from the pad interface into the bulk of the solder. Additionally, the XRD technique has also been used in a temperature-resolved mode to observe the formation of IMCs, in situ, during the solidification of the solder joint. The results demonstrate that the XRD technique is very attractive as it allows for nondestructive investigations to be performed on expensive state-of-the-art electronic components, thereby allowing new, lead-free materials to be fully characterized.     

Hyperbranched polymers from divinylbenzene and 1,3-diisopropenylbenzene through anionic self-condensing vinyl polymerization

Hyperbranched polymers were synthesized using anionic self-condensing vinyl polymerization (ASCVP) by forming ‘inimer’ (initiator within a monomer) in situ from divinylbenzene (DVB) and 1,3-diisopropenylbenzene (DIPB) using anionic initiators in THF at −40 °C. The reaction of equimolar amounts of DVB and nBuLi results in the formation of hyperbranched poly(divinylbenzene) through self-condensing vinyl polymerization (SCVP). The hyperbranched polymers were invariably contaminated with small amount of gel (<15%). No gelation was observed when using DIBP with anionic initiators. The presence of monomer-polymer equilibrium in the SCVP of DIPB restricts the growth of hyperbranched poly(DIPB). The inimer synthesized from DIPB at 35 °C undergoes intermolecular self-condensation to different extent depending on the nature of anionic initiator at −40 °C. The molecular weight of the hyperbranched polymers was higher when DPHLi was used as initiator. A small amount of styrene ([styrene]/[Li⁺]=1) was used to promote the chain growth by inducing cross-over reaction with styrene, and subsequent reaction of styryl anion with isopropenyl groups of inimer/hyperbranched oligomer. The hyperbranched polymers were soluble in organic solvents and exhibited broad molecular weight distribution (2<M_w/M_n<17).     

Magnetic and magnetoresistance of BiFe0.5Cr0.5O3 thin film over Pt(111) substrate at various thicknesses by sol‐gel method

The effect of thickness on distorted double perovskite structured BiFe_0.5Cr_0.5O₃ (BFCO) thin films have been investigated for the first time using soft chemical method over Pt(111)/Ti/SiO₂/Si substrate. The X‐ray diffraction (XRD) shows the presence of both BFO and BCO phases and confirms the formation of double perovskite‐structured BFCO. The morphology of the films changes with the increase in layers signifying the thickness dependence. The magnetization (M) versus magnetizing field (H) curve was well consistent with magnetoresistance (M‐R) results and exhibits anisotropic magnetoresistance. Thickness‐dependent dielectric behaviors of BFCO thin films were deeply understood from space charge, intrinsic and extrinsic mechanisms. The BiFe_0.5Cr_0.5O₃ crystal systems with 60 nm thin layer showed an improved magnetism and magnetoresistance properties and are applicable to future magnetic application in the field of spintronics as a promising device.     

Synthesis of some new divalent metal salts of mono(hydroxyethyl)phthalate

Summary Divalent metal salts of mono(hydroxyethyl)phthalate (HEP) were considered to be of interest as difunctional ionic monomers and are useful for the preparation of condensation polymers. Recently, Matsuda¹ reported the preparation of Ca, Mg and Zn salts of mono-(hydroxyethyl)phthalate and their polymers^2–7. He prepared these salts by the reaction of HEP with the respective divalent metal oxides. But so far there was no report on the preparation of Pb²⁺ and Mn²⁺ salts of HEP. Since metal dicarboxylates can be obtained by the reaction of organic dibasic acids and metal acetates⁸, Pb²⁺ and Mn²⁺ acetates can similarly react with HEP to give their respective salts at the optimum temperature. We report here the synthesis and characterisation of Pb²⁺ and Mn²⁺ salts of mono(hydroxyethyl)-phthalate (HEP).     

Monte Carlo study of solder paste microstructure and ultra-fine-pitch stencil printing

In this paper, we apply a Monte Carlo simulation technique to study the microstructure of solder pastes and investigate the influence of solder particle-size distribution on the ultra-fine-pitch stencil printing. First, the microstructures of bulk solder pastes with different particle-size distributions were generated using a random-packing model. Then a statistic model was applied to simulate the packing of solder paste inside the apertures. The numbers of solder particles and solid volume fraction embodied in the apertures were counted. Five particle-size distributions and two aperture shapes (circular and square) were investigated. Simulation results showed that the mean solid volume fraction of the solder particles inside the apertures is lower than that in the bulk solder paste. For the same aperture size and shape, as the particle size increases the mean solid volume fraction decreases and the standard deviation increases. This implies that to obtain consistent paste deposits in ultra-fine-pitch printing, the particle size must be proportionally reduced with the aperture size. The reasonable size ratio of the aperture to the solder particle was found to be around five. Excessive reduction in particle size could not improve the printing quality further, in contrast, it may lead to poor printability due to the increase in the paste viscosity and poor solder joints due to the generation of solder balls in the reflow soldering process.     

利用高分辨率卫星影像分析工业城市的土地利用

The spatial differentiation of land use changes of Tuticorin is studied using high resolution LISS Ⅲ satellite imagery and Maximum Likelihood algorithms. The classification accuracy of 95.2% was obtained. In this study, the land use of Tuticorin is classified as settlement, salt pan, agricultural land, wasteland, water bodies and shrubs. The settlement area is increased to 4.6 km2 during the year 2001 and 2006. The settlement area change is mainly driven by growth of industries and migration of people from peripheral villages. Shrub is increased to 3.63 km2 in the six year period. Water logging due to growth of shrubs in Tuticorin leads to several environmental and health hazard. This study warrants proper urban planning for Tuticorin for sustainable use of resource and environment.