Enhanced surface morphologies of screen-printed carbon nanotube films by heat treatment and their field-emission properties

A heating process for obtaining free-standing carbon nanotube emitters is presented with the aim of improving field-emission properties from the screen-printed multiwalled carbon nanotube (MWCNT) films. Using an atmosphere with an optimum combination of nitrogen and air for heat treatment of CNT films, the CNT emitters can be made to protrude from the surface. This allows for a high emission current and the formation of very uniform emission sites without special surface treatment. The morphological change of the CNT film by this technique has eliminated additional processing steps, such as surface treatment which may result in secondary contamination and damage to the film. Despite its simplicity the process provides a high reproducibility in emission current density which makes the films suitable for practical applications.     

Sintering Behavior of Cadmium-Doped Pb(Ni1/3Nb2/3)O3–PbZrO3–PbTiO3 Ceramics

Substituting Cd²⁺ ions into the A and B sites in a Pb(Ni_1/3Nb_2/3)O₃PbZrO₃PbTiO₃ (PNNPZPT) ternary perovskite material made it possible to determine the effects of the Cd²⁺ ion substitution site on sintering behavior. The substitution site of the Cd²⁺ ion was identified by using X-ray photoelectron spectroscopy spectra. Although Cd²⁺ ions were substituted into the A and B sites in PNNPZPT, the Cd²⁺ ions preferred the A site over the B site. When Cd²⁺ ions replaced Pb²⁺ ions, a weight gain was observed during sintering. On the other hand, replacing Ni2 ions with Cd²⁺ ions promoted weight loss. Those weight changes indicated that Cd²⁺ ions change the bonding strength between the B-site cations and the oxygen of the octahedron in a perovskite structure. Density was influenced by the Cd²⁺ ion substitution site, and the A-site-doped compositions had higher densities than the B-site-doped compositions.     

Single‐shot High Dynamic Range Imaging Using Coded Electronic Shutter

Typical high dynamic range (HDR) imaging approaches based on multiple images have difficulties in handling moving objects and camera shakes, suffering from the ghosting effect and the loss of sharpness in the output HDR image. While there exist a variety of solutions for resolving such limitations, most of the existing algorithms are susceptible to complex motions, saturation, and occlusions. In this paper, we propose an HDR imaging approach using the coded electronic shutter which can capture a scene with row‐wise varying exposures in a single image. Our approach enables a direct extension of the dynamic range of the captured image without using multiple images, by photometrically calibrating rows with different exposures. Due to the concurrent capture of multiple exposures, misalignments of moving objects are naturally avoided with significant reduction in the ghosting effect. To handle the issues with under‐/over‐exposure, noise, and blurs, we present a coherent HDR imaging process where the problems are resolved one by one at each step. Experimental results with real photographs, captured using a coded electronic shutter, demonstrate that our method produces a high quality HDR images without the ghosting and blur artifacts.     

Process development for the removal of copper from wastewater using ferric/limestone treatment

The removal of copper from wastewater by ferric/limestone coagulation followed by screen filtration was carried out at a laboratory scale. The optimum coagulant (FeCl₃) dose and working pH were 50 mg// of Fe(m) and pH 7.5, respectively, through jar tests. For the efficient removal of copper from wastewater, we developed a novel process including the co-precipitation of copper with FeCl₃, alkalization in a limestone aeration bed, and separation of precipitates in a sedimentation tank coupled with internal stainless steel screen filter. The performance results showed that removal of copper from the solution was over 99.5%. The pH was effectively maintained over 7.5 in limestone bed during the whole process. Ferric hydroxide/copper aggregates were removed over 99% by stainless steel screen filter of 1,450 mesh. Periodic air backwashing alleviated fouling of the filter surface.     

Enhanced electrochemical performance and thermal stability of La2O3-coated LiCoO2

An enhanced electrochemical performance LiCoO₂ cathode was synthesized by coating with various wt.% of La₂O₃ to the LiCoO₂ particle surfaces by a polymeric method, followed by calcination at 923 K for 4 h in air. The surface-coated materials were characterized by XRD, TGA, SEM, TEM, BET and XPS/ESCA techniques. XRD patterns of La₂O₃-coated LiCoO₂ revealed that the coating did not affect the crystal structure, α-NaFeO₂, of the cathode material compared to pristine LiCoO₂. TEM images showed a compact coating layer on the surface of the core material that had an average thickness of about ∼15 nm. XPS data illustrated that the presence of two different environmental O 1s ions corresponds to the surface-coated La₂O₃ and core material. The electrochemical performance of the coated materials by galvanostatic cycling studies suggest that 2.0 wt.% coated La₂O₃ on LiCoO₂ improved cycle stability (284 cycles) by a factor of ∼7 times over the pristine LiCoO₂ cathode material and also demonstrated excellent cell cycle stability when charged at high voltages (4.4, 4.5 and 4.6 V). Impedance spectroscopy demonstrated that the enhanced performance of the coated materials is attributed to slower impedance growth during the charge-discharge processes. The DSC curve revealed that the exothermic peak corresponding to the release of oxygen at ∼464 K was significantly smaller for the La₂O₃-coated cathode material and recognized its high thermal stability.     

Synthesis and characterization of poly(1,8-diethynylnaphthalene)

Summary The cyclopolymerization of 1,8-diethynylnaphthalene(DEN) and its copolymerization with diethyl dipropargylmalonate(DEDPM) were carried out by various transition metal catalysts. MoCl₅-based catalyst was found to be very effective and gave almost a quantitative polymer yield. The resulting dark-brown homopolymer(PDEN) was partially soluble in chloroform, tetrahydrofuran, and dimethyl sulfoxide, whereas copolymer (1:1) with number avaerage molecular weight of 2.1x10⁴ by GPC showed good solubility in those solvents. The structure of the polymers was analysed by IR, NMR, and UV-VIS spectroscopies. From the spectral and solubility data, it is proposed that cyclized products with the conjugated system are formed. Room temperature conductivities of the I₂-doped homo and copolymer were found to be about 7.5x10^-3 and 5.1x10^-3 S/cm, respectively.     

Adsorption and desorption characteristics of 2-methyl-4-chlorophenoxyacetic acid onto activated carbon

Adsorption and desorption characteristics of the 2-methyl-4-chlorophenoxyacetic acid (MCPA) from aqueous solution onto the activated carbon (GAC, F-400) were studied. Adsorption equilibrium capacities of the MCPA increased with decreasing pH and temperature of the solution. Adsorption equilibrium of the MCPA could be represented by the Sips equation. The internal diffusion coefficients were determined by comparing the experimental concentration decay curves with those predicted from surface diffusion model and pore diffusion model. The adsorption model based on the linear driving force approximation (LDFA) was used for simulating the adsorption behavior of the MCPA in a fixed bed. Over ninety five percent desorption of the MCPA could be obtained using distilled water.     

Transport of oxygen and carbon dioxide through polycarbonate membrane

Sorption equilibria and permeation rates for oxygen and carbon dioxide in polycarbonate membrane were measured at different temperature between 30 and 60°C and at pressures up to 2.5 MPa. The pressure dependence of mean permeability coefficient to oxygen obeyed the conventional dual-mode mobility model, whereas that to carbon dioxide followed a modified dual-mode mobility model with concentration-dependent diffusivities, as that of polystyrene to the same gas did.     

Virtual target tracking of mobile robot and its application to formation control

A virtual target tracking approach is proposed for kinematic control of mobile robot. In the controller, linear and angular velocity inputs are generated by using the local data of robot position and orientation along with the estimated velocity of target object. Applying the proposed approach to a cooperative robot group with arbitrary number of multiple mobile robots, it is possible to create various robot formations for cooperative navigation and tracking of moving object. The developed controller is shown to be stable and convergent through theoretical proof and a series of experiments.