Complex impedance spectra of porous electrode with fractal structure

Transmission line model (TLM) is often used for the analysis of porous electrode since the current distribution in the pore can be calculated. In the present paper, the TLM is applied to the impedance analysis of complicated porous electrode with fractal structure. Activated carbon is used as electrode material for electric double layer capacitor and its pore has branch structure. Considering the fractal structure of the activated carbon, we proposed new equivalent circuit with TLM for three sizes of pores: macropore, mesopore and micropore. In this model, we defined the ratio ξ of electric double layer parts in whole inner wall of the pore because the inner wall is separated to electrolyte/electrode interface and branch base parts. Calculated electrochemical impedance of blocking electrode shows the lumped constant region in low frequency range and the distributed constant region in low frequency range. General TLM yields the straight line with slope of 45° in the distributed constant region on the Nyquist plots. In the present analysis, it was found that the slope was 22.5° at ξ = 0 in the case of double-pores (macropore and mesopore) and 11.25° at ξ = 0 in the case of triple-pores (macropore, mesopore and micropore).     

Effectiveness of a backward mixing screw element for glass fiber dispersion in a twin‐screw extruder

In the kneading of glass–fiber‐reinforced plastics by twin‐screw extrusion, the use of a backward‐mixing screw (BMS) element for melt mixing has been found to be effective in dispersing glass–fiber bundles. In this study, we use computational fluid dynamics (CFD) to investigate the mechanism for the effectiveness of BMS for glass fiber dispersion. CFD of BMS melt mixing revealed that there is high uniformity of transport in the direction of extrusion and efficient transportation occurs from low‐stress to high‐stress regions. These findings demonstrate that BMS melt mixing is highly effective at imparting stress to the overall resin passing through. In addition, there is a correlation between the incidence of nondispersion of glass–fiber bundles measured experimentally and the stress history minimum value. On the basis of the above factors, we propose a method for predicting the operating conditions in which the nondispersion of glass–fiber bundles is controlled. The operating conditions for controlling glass–fiber nondispersion can be determined for various different mixing elements and the possible production rate can be predicted. Predictions for the operating conditions were applied to BMS and a forward kneading disk element (FKD). The effectiveness of BMS for controlling glass fiber nondispersion is characterized for a broad range of operating conditions. POLYM. ENG. SCI., 54:2005–2012, 2014. © 2013 Society of Plastics Engineers     

Enzymatic synthesis of steryl esters of polyunsaturated fatty acids

Steryl esters of long-chain fatty acids have water-holding properties, and polyunsaturated fatty acids (PUFA) have various physiological functions. Because steryl ester of PUFA can be expected to have both features, we attempted to synthesize steryl esters of PUFA by enzymatic methods. Among lipases used, Pseudomonas lipase was the most effective for the synthesis of cholesteryl docosahexaenoate. When a mixture of cholesterol/docosahexaenoic acid (3:1, mol/mol), 30% water, and 3000 units/g of lipase was stirred at 40°C for 24 h, the esterification extent attained 89.5%. Under the same reaction conditions, cholesterol, cholestanol, and sitosterol were also esterified efficiently with docosahexaenoic, eicosapentaenoic, arachidonic, and γ-linolenic acids.     

Ternary and quaternary mixed electrolytes for lithium cells

This paper reports the influence of composition of mixed solvent electrolyte composition on the discharge capacity and charge–discharge cycle life of lithium metal/amorphous V2O5–P2O5 (95:5 in molar ratio) cells. The solvents used were ethylene carbonate (EC), propylene carbonate (PC), 2-methyltetrahydrofuran (2MeTHF) and THF. LiAsF6 was used as the solute. The electrolyte solutions examined here contain ternary and quaternary mixed systems. The purpose of this work is to obtain an electrolyte solution which realizes a higher rate capability and/or a longer cycle life than the previously studied EC:PC:2MeTHF (15:70:15) ternary mixed system. Of the electrolyte systems examined here, the EC:PC:2MeTHF (30:40:30 in volume) ternary mixed solvent system showed the best cell performance. In addition, a heating test was carried out on an AA- size lithium cell with EC:PC:2MeTHF (30:40:30) as a fundamental abuse test to ensure cell safety.     

Dye-sensitized nanocrystalline TiO2 solar cells based on novel coumarin dyes

We have developed dye-sensitized nanocrystalline TiO₂ solar cells (DSSCs) based on novel coumarin-dye photosensitizers. The absorption spectra of these novel dyes are red-shifted remarkably in the visible region relative to the spectrum of C343, a conventional coumarin dye. Introduction of a methine unit (–CH=CH–) connecting the cyano (–CN) and carboxyl (–COOH) groups into the coumarin framework expanded the π-conjugation in the dye and thus resulted in a wide absorption in the visible region. These novel dyes performed as efficient photosensitizers for DSSCs. A DSSC based on 2-cyano-5-(1,1,6,6-tetramethyl-10-oxo-2,3,5,6-tetrahydro-1H,4H,10H-11-oxa-3a-aza-benzo[de]anthracen-9-yl)-penta-2,4-dienoic acid (NKX-2311), produced a 6.0% solar energy-to-electricity conversion efficiency (η), the highest performance among DSSCs based on organic-dye photosensitizers, under AM 1.5 irradiation (100 mW cm^–2) with a short-circuit current density (J_sc) of 14.0 mA cm^–2, an open-circuit voltage (V_oc) of 0.60 V, and a fill factor of 0.71. Our results suggests that the structure of NKX-2311 whose carboxyl group is directly connected to the –CH=CH– unit, is advantageous for effective electron injection from the dye into the conduction band of TiO₂. In addition, the cyano group, owing to its strong electron-withdrawing ability, might play an important role in electron injection in addition to a red shift in the absorption region. On a long-term stability test under continuous irradiation with white light (80 mW cm^–2), stable performance was attained with a solar cell based on the NKX-2311 dye with a turnover number of 2.6×10⁷ per one molecule.     

Structural and Physicochemical Properties of Endosperm Starches Possessing Different Alleles at the Amylose-extender and Waxy Locus in Maize (Zea mays L.)

The structure and some physicochemical properties of endosperm starches from seven amylose-extender (ae) and two waxy (wx) alleles of maize (Zea mays L.) were studied. Starches prepared from mature kernels of six ae mutants, Oh43 inbred line ae (standard ae), ae-RWB-2 and ae-RWB-3, and W23 × L317 hybrid line ae-PP, ae-Bol 561 and ae-emll, were uniquely ae type, as was concluded from B type X-ray diffractograms; high gelatinization temperatures determined by differential scanning calorimetry (DSC); with poor starch-granule digestibility to amylase; high amylose (37—45 %) and high intermediate fraction (13—18 %) contents; and low ratios (1.0—1.2) of long α-1,4-chains to short α-1,4-chains of amylopectin determined by gel permeation chromatography (GPC) of isoamylase-debranched starches. The results also indicated that different ae alleles had different effects on the amylose content of endosperm starches. Mature kernels of Oh43 ae-RWB-1 mutant showed tarnished and translucent phenotype characteristics of the ae genotype but contained endosperm starch with 21—22 % of amylose which was lower than that of the Oh43 normal counterpart. Both wx-B and wx-C (standard wx) genes have similar effect on structure and physicochemical properties of waxy starches of A632, B37, C105, Oh43, and W64A inbred lines.     

Incorporating reserve supplying demand response in customer's decision making model for simultaneous energy and reserve markets

In this letter, the customer profit‐maximization‐model is expanded to incorporate the probabilistic profit of reserve supply. This extended model will change the customer behavior and therefore will affect the system performance. The analysis of the extended model is carried out to show how this model, considering energy and reserve market parameters, affects the customer decision. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.