Viscoelastic properties of a 60 mol% para-hydroxybenzoic acid/40 mol% poly(ethylene terephthalate) liquid crystalline copolyester. I: Effect of temperature history

In this paper, the rheology of a 60 mol% para-hydroxybenzoic acid (PHB)/40 mol% poly(ethylene terephthalate) (PET) copolyester (herein referred to as PHB60/PET40) produced by Unitika Co., Japan, was investigated using viscoelastic property temperature sweeps. In addition to the large-scale hysteresis (super-cooling) of viscoelastic properties that has also been seen with other PHB-based materials, in which it is possible for several PHB linkages to occur side by side along the polymer backbone (most notably the PHB60/PET40 polymer produced by Tennessee Eastman), smaller-scale viscoelastic transitions, one present in heating, and believed to be associated with the partial isotropization of liquid crystalline material, and the other apparent on cooling, occurring at a lower temperature than the first and thought to be associated with the opposite process, were observed. When overall mol% PHB composition along individual chains is considered, the well-defined appearance of the additional smaller-scale rheological transitions seen here is believed to be due to a unimodal composition distribution, rather than a bimodal distribution of which there is increasing evidence in the Tennessee Eastman materials. This difference is believed to be caused by differences in the preparation technique used for the Unitika version of the polymer.     

Active Control of Laminar Boundary Layer Using Various Wall Motions

In this study, three types of surface motion of wall motion actuators were proposed and used to control the Tollmien-Schlichting (T-S) wave in the laminar boundary layer of a plate. These three types of motion are standing transverse wave (with out-of-plane displacement), traveling transverse wave (with out-of-plane displacement) and standing longitudinal wave (with in-plane displacement). The length of a wall motion actuator was set to 1, 2 or 3 cycles of waveform. Numerical simulation was performed on the generation of T-S wave and its suppression with the three types of surface motion of the wall motion actuator and the dependence of control effect on the amplitude and the phase of the surface motion, and the number of waveform was investigated.     

Differences in characteristics of dye-sensitized solar cells containing acetonitrile and ionic liquid-based electrolytes studied using a novel model

A performance simulation model of dye-sensitized solar cells including a “bulk” electrolyte layer separated from a TiO₂ layer has been presented. The calculation results with this novel model agree well with experimental results, which indicates the importance of considering the bulk electrolyte layer in theoretical models. The model allows us to specify the diffusion coefficients of ionic species in nano-pores of the TiO₂ layer and in the bulk electrolyte layer separately, and the importance of ionic diffusions in each layer is discussed. We further clarify the difference between ionic liquid-type cells and acetonitrile type cells, and discuss the important issues for increasing the efficiencies in cells containing ionic liquid-based electrolytes.     

Layered ultrathin proton conductive film based on polymer nanosheet assembly

As described in this paper, a layered ultrathin proton conductive film was prepared using a poly(N-dodecylacrylamide-co-2-acrylamido-2-methylpropanesulfonic acid) (p(DDA/AMPS)) polymer nanosheet. The surface pressure-area isotherm revealed that p(DDA/AMPS) formed a stable monolayer at the air-water interface. The polymer monolayer was transferred onto a solid substrate using the Langmuir-Blodgett technique. X-ray diffraction measurements of a 30-layer film of p(DDA/AMPS) showed clear Kiessig fringes and one Bragg peak, which indicate that the multilayer film took a uniform layered structure. The monolayer thickness was determined as 1.85 nm from the Bragg peak. The proton conductivity of p(DDA/AMPS) polymer nanosheet through the layer plane direction was studied with changing temperature and relative humidity. The proton conductivity of the multilayer film was on the order of 1 × 10?? S/cm at 100% RH with 20 °C and increased to 1 × 10?2 S/cm at 70 °C. The proton conductivity of the multilayer film showed a more than 10 times higher value than that of the spin-coated film because of the formation of a uniform and consecutive hydrophilic nanochannel through the hydrophilic region in the multilayer film.     

Polymer film produced by a marine bacterium

Biojelly is a sort of polymer that is formed on a cellulose acetate membrane immersed in seawater. Interestingly, Biojelly inhibits attachment of marine organisms such as algae and barnacles. We could successfully isolate several marine microorganisms from Biojelly-attached microorganisms. One of these isolates, strain SHY1-1, produced water-insoluble polymeric materials in natural seawater supplemented with yeast extracts and glucose. This strain was assigned to be Alteromonas sp. by the method of the 165 rRNA gene sequencing and phylogenetic analysis. Biojelly and the polymer film produced by Alteromonas sp. SHY1-1 were qualitatively characterized by Fourier transformed infrared (FT-IR) spectroscopy and thin-layer chromatography (TLC). The result indicated that naturally occurring Biojelly and the polymeric materials obtained in this work both were a sort of mucopolysaccharide consisting of amino sugars. In addition, the attachment assay with larvae indicated that both polymer films had similar anti-fouling activity against barnacle (Balanus amphitrite).     

Transparent conductive oxide‐less back contact dye‐sensitized solar cells using cobalt electrolyte

Transparent conductive oxide‐less (TCO‐less) dye‐sensitized solar cells (DSSCs) have been fabricated and characterized using nanoporous TiO₂‐coated stainless steel metal mesh as flexible photoanode and cobalt bipyridyl complex (Co(bpy))‐based one electron redox shuttle electrolyte. Attempts have been made towards enhancing the efficiency of TCO‐less DSSCs to match with their TCO‐based DSSC counterparts. It has been found that surface protection of metal mesh is highly required for enhancing the efficiency of TCO‐less DSSCs specially using cobalt electrolytes as confirmed by dark current–voltage characteristics. Photocurrent action spectra clearly reveal that TCO‐based DSSCs using (Co(bpy)) electrolyte exhibits photon harvesting (incident photon to current conversion efficiency (IPCE) 52%) in the 370–450 nm wavelength region as compared to photon harvesting at peak absorption of the dye (IPCE 56% at 550 nm), which is almost the same (IPCE 47%) in the 400–610 nm wavelength region for TCO‐less DSSCs. Under similar experimental conditions, replacing indoline dye D‐205 to porphyrin‐based dye YD2‐o‐C8 led to the enhancement in the photoconversion efficiency from 3.33% to 4.84% under simulated solar irradiation. Copyright © 2014 John Wiley & Sons, Ltd.     

Studies on Langmuir-Blodgett multilayer formation from preformed poly(N-alkylacrylamides)

The spreading behaviour of preformed poly(N-alkylacrylamides) having hexyl (PHA), octyl (POA), decyl (PDA), dodecyl (PDDA), tetradecyl (PTDA), hexadecyl (PHDA), and octadecyl (PODA) substituents on a water surface, and the properties of the Langmuir-Blodgett (LB) films deposited from these polymer monolayers were investigated. The surface pressure (F)-area (A) isotherms of the polymer monolayers were changed by the chain length of the substituents and the subphase temperature. The optimum conditions for the formation of a stable condensed monolayer from the polymer series of similar molecular weight (c. 4 × 10³) were found when the alkyl substituent was the dodecyl group (i.e. PDDA) and the subphase temperature was 19°C. The condensed monolayers of PDA, PDDA, and PTDA could be transferred successively on to solid supports such as quartz slides, giving the Y-type uniform polymer LB films. The successive uniform depositions of PDDA monolayer up to 320 layers were confirmed by a relationship between the absorbance at around 200 nm due to carbonyl group and the number of layers deposited. The thickness of PDDA monolayer in the LB film was 1.72nm which agrees with the length of the dodecylamide substituent. F-A isotherms, FTIR, and X-ray diffraction measurements support that the polymer main chains are laid horizontally on the water surface and the alkyl substituents are oriented perpendicular to the chain in the condensed monolayer (see Scheme 1).     

A 600-MHz single-chip multiprocessor with 4.8-GB/s internal shared pipelined bus and 512-kB internal memory

A 600-MHz single-chip multiprocessor, which includes two M32R 32-bit CPU cores , a 512-kB shared SRAM and an internal shared pipelined bus, was fabricated using a 0.15-/spl mu/m CMOS process for embedded systems. This multiprocessor is based on symmetric multiprocessing (SMP), and supports modified-exclusive-shared-invalid (MESI) cache coherency protocol. The multiprocessor inherits the advantages of previously reported single-chip multiprocessors, while its multiprocessor architecture is optimized for use as an embedded processor. The internal shared pipelined bus has a low latency and large bandwidth (4.8 GB/s). These features enhance the performance of the multiprocessor. In addition, the multiprocessor employs various low-power techniques. The multiprocessor dissipates 800 mW in a 1.5-V 600-MHz multiprocessor mode. Standby power dissipation is less than 1.5 mW at 1.5 V. Hence, the multiprocessor achieves higher performance and lower power consumption. This paper presents a single-chip multiprocessor architecture optimized for use as an embedded processor and its various low-power techniques.