Effect of Mn substitution on the oxidation/adsorption abilities of iron(III) oxyhydroxides

In this study, divalent manganese ions [Mn(II)] were substituted a part of divalent iron ions [Fe(II)] present in Fe oxyhydroxides to prepare novel composites (Mn@Feox). The composites were prepared by (1) simultaneous hydrolysis of Fe(II) and Mn(II), and (2) rapid oxidation with H₂O₂. The resulting Mn@Feox prepared with different molar ratios of Fe and Mn was characterized and evaluated for their abilities to adsorb arsenic species [As(III) and As(V)] in aqueous solution. X-ray diffraction and field emission transmission electron microscope analyses revealed Mn@Feox has a δ-(Fe_1?x, Mn_x)OOH-like structure with their mineralogical properties resembling those of feroxyhyte (δ-FeOOH). The increase in Mn substitution in Mn@Feox enhanced the oxidative ability to oxidize As(III) to As(V), but it decreased the adsorption capacity for both arsenic species. The optimal Mn/Fe molar ratio that could endow oxidation and magnetic capabilities to the composite without significantly compromising As adsorption capability was determined to be 0.1 (0.1Mn@Feox). The adsorption of As(III) on 0.1Mn@Feox was weakly influenced by pH change while As(V) adsorption showed high dependence on pH, achieving nearly complete removal at pH?<?5.7 but gradual decrease at pH?>?5.7. The adsorption kinetics and isotherms of As(III) and As(V) showed good conformity to pseudo-second-order kinetics model and Freundlich model, respectively.     

A gain-clamped SOA with distributed Bragg reflectors fabricated under both ends of active waveguide with different lengths

We demonstrate a gain-clamped semiconductor optical amplifier (GC-SOA) which has gratings under both end regions of an active waveguide. Two gratings of the new GC-SOA are fabricated in different lengths. Their lasing modes and gain characteristics are measured and analyzed with different combinations of grating lengths. It shows different gain and noise characteristics according to the measurement direction in asymmetric grating combinations.     

Trellis-coded multiple-pulse-position modulation for wireless infrared communications

We present new trellis codes based on multiple-pulse-position modulation (MPPM) for wireless infrared communication. We assume that the receiver uses maximum-likelihood sequence detection to mitigate the effects of channel dispersion, which we model using a first-order lowpass filter. Compared to trellis codes based on PPM, the new codes are less sensitive to multipath dispersion and offer better power efficiency when the desired bit rate is large, compared with the channel bandwidth. For example, when the bit rate equals the bandwidth, trellis-coded (17 2)-MPPM requires 1.4 dB less optical power than trellis-coded 16-PPM having the same constraint length.     

A RAKE Receiver With an ICI/ISI Equalizer for a CCK Modem

In this paper, we first derive the theoretical performance of a complementary code keying (CCK) code on an additive white Gaussian noise (AWGN) channel and over a multipath channel. To derive the error performance, we use the weight and cross-correlation distributions of the CCK code for optimal and suboptimal decoding, respectively, based on union bound. In addition, we propose a RAKE receiver for a CCK modem, which is suitable for a multipath environment with a large delay spread. The RAKE receiver principle is acceptable for modest multipath because it can coherently combine multipath components to provide signal-to-noise ratio (SNR) enhancement. However, as the delay spread is larger and the data rate of systems goes higher, intersymbol interference (ISI) generated due to multipath environments are increased. To handle the increasing ISI, the CCK modem needs an equalization technique to remove the ISI, together with RAKE processing. Thus, our proposed system is based on a channel matched filter (CMF) with a decision feedback equalizer (DFE). The CMF is applied for RAKE processing, whereas the DFE structure is used for ISI cancellation. In our system, ISI is calculated and removed by using a decoded CCK codeword.     

Incorporation of carbon nanotube into direct-patternable ZnO thin film formed by photochemical solution deposition

Direct-patterning of ZnO hybrid films containing MWNT was realized without using photoresist and dry etching. Photosensitive 2-nitrobenzaldehyde was introduced into the solution precursors as a stabilizer and contributed to form a cross-linked network structure during photochemical reaction. According to the incorporation of multi-walled nanotube (MWNT) into ZnO films, the transmittance of ZnO hybrid film containing MWNT did not change but the sheet resistance was improved due to the enhancement of charge mobility due to π-bonding nature of MWNT. These results suggested a possibility that a micro-patterned system can be fabricated relatively easily and without high-cost processes, for example, by conventional etching procedure.     

Machine learning based approach for multimedia surveillance during fire emergencies

Multimedia Tools and Applications - Video based surveillance of manmade disasters such as fire has become very hot topic in research and it is playing an important role in the development of smart...     

Oxidation characteristics of airborne carbon nanoparticles by NO(2)

The oxidation characteristics of airborne carbon nanoparticles were investigated at various temperatures and NO(2) concentrations. Airborne carbon nanoparticles were generated by spark-discharging method using nitrogen as a carrier gas. Monodisperse carbon particles classified using a differential mobility analyzer were introduced into a tube furnace with NO(2) for oxidation reaction. The size distributions of oxidized carbon aerosol particles were measured using a scanning mobility particle spectrometer system which consisted of a differential mobility analyzer and a condensation particle counter. The result was that as NO(2) concentrations and reaction temperatures increased, the surface oxidation rate of carbon aerosol particles increased. For NO(2) gas, the activation energy of the oxidation reaction was approximately 76.3 kJ/mol. The activation energy of the oxidation reaction for the mixture of NO(2) and O(2) gases was 65.9 kJ/mol, which is smaller than that for only NO(2) gas.     

Infrared spectroscopic study of SiOx film formation and decomposition of vinyl silane derivative by heat treatment. I. On KBr and gold surface

The free-radical copolymerization of vinyltrimethoxysilane (VTS) with vinylimidazole (VI) was carried out in benzene at 68°C. Thermooxidative degradation and the SiO_x film-formation mechanism of poly(VI-co-VTS) both on gold and KBr were studied with Fourier transform infrared (FTIR) spectroscopy. Reflection-absorption (R-A) spectra on gold were compared with transmission spectra on KBr. In the initial stage of heat treatment, the Si—O—Si bond formation was caused mainly by the residual water in the copolymer film. As heating time increased, however, both the water resulting from the thermal decomposition of the copolymer and the water vapor in air began to participate in the hydrolysis of the Si—O—CH₃ group followed by the condensation reaction. The structure of the SiO_x film became closer to the structure of SiO₂ with increasing heating temperature. In addition, the differences between the transmission spectra and R-A spectra were observed at the peaks related to Si—O—Si stretching due to the optical effect. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:775–784, 1998     

Electrohydrodynamic drop-on-demand patterning in pulsed cone-jet mode at various frequencies

The patterning of a series of drops was investigated by the electrohydrodynamic printing method in the drop-on-demand fashion. A positive pulse voltage was applied to the capillary nozzle periodically to eject a pulsed liquid jet. The ejected jet was directed to the moving substrate, to which DC bias voltage was applied. High-speed imaging revealed that a Taylor cone was established at the nozzle tip during the ejection of the liquid jet, and that the jet directly struck the substrate to form a drop without the jet break-up. The frequency of drop generation can be controlled precisely, because the frequency of the pulsed voltage was almost same as the pulsating frequency of the liquid in pulsed cone-jet mode. The deposited patterns showed a series of uniformly sized drops with a regular spacing. At the pulse voltage frequency of 25 Hz, the diameter of the drops was approximately 95 μm. Using this drop-on-demand method, it is feasible to produce a variety of patterns of dots and continuous/discontinuous lines.