Influence of medium on the nanostructure and properties of poly(4‐aminodiphenylamine)‐silver nanocomposites

Poly(4‐aminodiphenylamine)‐silver nanocomposites were synthesized by an easy one‐step aqueous chemical oxidative polymerization of 4‐aminodiphenylamine (4ADPA) using silver nitrate (AgNO₃) as the oxidant. Two different structure directing surfactants, p‐toluene sulfonic acid (p‐TSA) and cetyl trimethyl ammonium bromide/hydrochloric acid (CTAB/HCl), were independently used for the nanocomposite (NC) preparation. The NCs prepared in p‐TSA and CTAB/HCl medium were designated as P4ADPA/AgNC_(p?TSA) and P4ADPA/AgNC_(CTAB/HCl), respectively. We investigated the morphological variations in the NCs based on the medium. P4ADPA/AgNC_(p?TSA) and P4ADPA/AgNC_(CTAB/HCl) were characterized by field emission scanning electron microscopy, X‐ray diffraction analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis and UV‐visible spectroscopy. Copyright © 2011 Society of Chemical Industry     

Quality evaluation of Korean soy sauce fermented in Korean earthenware (Onggi) with different glazes

The aim of this study was to investigate the effect of porosity‐controlled earthenware as fermentation vessels for Korean soy sauce. Porosity of fermentation vessels was controlled by glazing the surfaces of Korean earthenware. Three kinds of onggis– the outside glazed, inside and outside glazed, and unglazed onggi – were made and used to investigate the effect of glazing on the fermentation of soy sauce. During fermentation of soy sauce in porosity‐controlled earthenwares at 30 °C for 4 months, physical, chemical, microbiological and sensory quality attributes were monitored. Compared to other vessels, soy sauce fermented in onggi with both inside and outside surfaces glazed showed less water loss (10.7%), salt content (17.6%) and pH (pH4.4) after the fourth month. It also produced higher total acidity (1.43%), protease activity (810 μg mL^?1 min^?1) and microbiological changes that included total aerobic bacteria [4.3 log(cfu mL^?1)], lactic acid bacteria [3.8 log(cfu mL^?1)] and yeast [4.2 log(cfu mL^?1)]. The contents of total nucleotide (200–255 mg per 100 g sample) and free amino acids (4634–4848 mg per 100 g sample) in soy sauce were not consistent with glazing, which may be more affected by other factors, such as water loss, than the porosity of vessels. However, the percentage of glutamic acid among total free amino acids was 23.6% in onggi with both surfaces glazed, which was a little higher than the 21.9% in the outside glazed and 21.5% in the unglazed. These positive physicochemical and microbiological changes during fermentation in onggi with both sides glazed also resulted in higher sensory quality.     

Partial feedback schemes for MIMO–OFDMA systems using random beamforming: analysis and optimization

In this paper, partial feedback schemes for a multiple input multiple output orthogonal frequency division multiple access system using a random beamforming are analyzed and optimized. For partial feedback schemes, the partial channel quality indicator feedback schemes and the partial channel quality rank indicator feedback schemes are considered. For these schemes, we first derive the effective downlink spectral efficiencies by considering the required uplink resource for feedback together over block fading channels. Then, by using the analysis, the amount of feedback overhead per user is optimized to maximize the effective downlink spectral efficiency according to the system and channel parameters. From the analysis and numerical examples, we show that the partial channel quality rank indicator feedback scheme provides better performance than the partial channel quality indicator feedback scheme unless the channel rapidly varies owing to its feedback efficiency, and the proposed adaptive control of the feedback overhead can improve the performance of practical systems, such as the 3rd generation partnership project (3GPP) long term evolution, in practical scenarios. Copyright © 2012 John Wiley & Sons, Ltd.     

A 4.2% efficient flexible dye-sensitized TiO2 solar cells using stainless steel substrate

An efficient flexible dye-sensitized solar cells (DSSCs) using stainless steel supporting substrate for fabricating nanocrystalline TiO₂ film electrodes were developed, intending to improve the photoelectrochemical properties of plastic substrate-based DSSCs. The most important advantage of a stainless steel-based TiO₂ film electrode over a plastic-based electrode lies in its high-temperature sinterability. Optimal photovoltaic properties were obtained with a cell where the TiO₂ film was coated on both ITO- and SiO_x-sputtered stainless steel (denoted as TiO₂/ITO/SiO_x/StSt). The photocurrent of the flexible cells with a TiO₂/ITO/SiO_x/StSt electrode increased significantly, leading to a much higher overall solar conversion efficiency η of 4.2% at 100 mW/cm², based on short-circuit photocurrent density, open-circuit voltage and fill factor of 11.2 mA/cm², 0.61 and 0.61 V, respectively, than those reported for cells with plastic substrates.     

Novel Bumping Material for Solder‐on‐Pad Technology

A novel bumping material, which is composed of a resin and Sn3Ag0.5Cu (SAC305) solder power, has been developed for the maskless solder‐on‐pad technology of the fine‐pitch flip‐chip bonding. The functions of the resin are carrying solder powder and deoxidizing the oxide layer on the solder power for the bumping on the pad on the substrate. At the same time, it was designed to have minimal chemical reactions within the resin so that the cleaning process after the bumping on the pad can be achieved. With this material, the solder bump array was successfully formed with pitch of 150 µm in one direction.     

Scanning electron microscope image enhancement using spread spectrum through dither signal imposition

Noise is a primary issue in obtaining an image in a scanning microscope. This noise needs to be minimized in order to have a clear image of the sample in case of a nanosize level measurement. In this work, we propose a method to improve the image quality by applying dither signal injection to the scanning signal. This method involves minimizing the noise that occurs in scan control circuits, which results in a blurry or distorted image. The collected secondary electrons are first multiplied through a photomultiplier tube and are then converted into digital form using an analog/digital (A/D) converter. We propose a solution for the noise from the scan control circuit that appears on the image by adopting the spread spectrum method.     

Digitally tunable physicochemical coding of material composition and topography in continuous microfibres

Heterotypic functional materials with compositional and topographical properties that vary spatiotemporally on the micro- or nanoscale are common in nature. However, fabricating such complex materials in the laboratory remains challenging. Here we describe a method to continuously create microfibres with tunable morphological, structural and chemical features using a microfluidic system consisting of a digital, programmable flow control that mimics the silk-spinning process of spiders. With this method we fabricated hydrogel microfibres coded with varying chemical composition and topography along the fibre, including gas micro-bubbles as well as nanoporous spindle-knots and joints that enabled directional water collection. We also explored the potential use of the coded microfibres for tissue engineering applications by creating multifunctional microfibres with a spatially controlled co-culture of encapsulated cells.