Investigation of potential profile in electrolyte membrane of PEFC by using microprobe technique

Potential profile in PEFC electrolyte membrane has been investigated by using microprobe technique in order to help understand membrane degradation mechanism. In particular, potential distribution in the membrane under several operation conditions has been measured by using microprobes inserted in the membrane. A theoretical model has been developed to predict the potential distribution under different cell current density with cells of different rib/channel width. The model showed good agreement with experimental result.     

Potential of a direct contact adsorption heat pump system for generating steam from waste water

An adsorption heat pump with a direct contact system for steam generation has been developed and the feasibility of the proposed system was confirmed both theoretically and experimentally. The basic cycle for the system has been proposed to use zeolite–water working pairs in the p‐T‐x equilibrium curve. To generate steam above 150°C from low‐energy level water at 80°C, a direct contact adsorption heat pump prototype was constructed. The experimental results show that steam could be generated by the direct contact system and the relationship between the amount of water adsorbed and the change in temperature with time is discussed. This study is expected to serve as a foundation for developing continuous adsorption heat pump systems for steam generation. Copyright © 2011 John Wiley & Sons, Ltd.     

Mesoscale-structure control at anode/electrolyte interface in solid oxide fuel cell

To enhance the power density of a solid oxide fuel cell, a mesoscale-structure control of an electrode/electrolyte interface was proposed; here, the mesoscale means a size range of 10-100 μm, which is larger than the microscale of the electrode particles but smaller than the macroscale of the cell geometries. Therefore, the mesoscale structure does not only change the local thickness of the electrolyte and electrode but also enlarge the electrode/electrolyte interface area, and thus influence the cell performance. First, to find effective conditions for the mesoscale-structure control, a preliminary theoretical analysis in a conventional flat cell was performed focusing on the ratio of the ion-conducting resistance to the reaction resistance. In the light of this basic knowledge, as a second step, the effects of the mesoscale structure on an anode side of an electrolyte-supported cell were studied numerically and experimentally. A 2D numerical simulation based on an equivalent electrical circuit model and the dusty-gas model was carried out. As a result, the mesoscale-grooved structure was found to be effective for enhancement of the power generation, if the groove scale is sufficiently larger than that of the active reaction region of the electrode. Qualitatively similar results were obtained from the experiments using a segmented electrode with both flat and mesoscale-grooved surface in a button-type cell.     

Ag<Subscript>2</Subscript>O<Subscript>3</Subscript> clathrate is a novel and effective antimicrobial agent

Silver compounds and silver ions are used extensively in medical devices because of their wide-spectrum antimicrobial activity. In particular, nanoparticles of silver and silver (I) oxide show great promise for widespread usage in medical polymers and nanodrugs. Here, we demonstrate that a crystalline powder and a saturated aqueous solution of silver (III) oxide clathrate show much stronger antimicrobial activities and oxidative activities than silver (I) oxide.     

Development of a biochip with serially connected pneumatic balloons for cell-stretching culture

The stretch stimulus is one of the most important mechanical stimuli sensed by cells. In the present study, a simple microdevice was developed to study the effects of the application of different strain magnitudes to cells. The pressure drop effect in a microchannel was utilized to generate a wide range of strain magnitudes in a single device. The microdevice consisted of 2 layers of polydimethylsiloxane (PDMS), and no alignment process was needed to fabricate it. Eight serially connected balloon structures were included in the device. Cells cultured on the surface of the balloons were stretched by inflating the balloons pneumatically. Finite element analysis (FEA) revealed that 8 different balloons in a single device could generate strains of 14.3-7.7% when air pressure was applied at 50 kPa to the air inlet. Cell culture experiments confirmed the useful application of a wide range of strain magnitudes to cells cultured on balloons inflated to different degrees. The new microdevice utilizing the pressure drop effect is a convenient instrument for the study of cellular mechanotransduction.     

In situ modification of lipid-loaded MCM-41 channels with bovine serum albumin at a planar lipid bilayer for biosensing

An in situ method for modifying a receptor site on mesoporous silica MCM-41 channels in planar lipid bilayers is described, in which bovine serum albumin (BSA) is covalently linked to the MCM-41 channels via head groups of lipids loaded in the nanopores. Prior to receptor modification, lipid-loaded MCM-41 channels were incorporated with lipid bilayers formed at an aperture of a Teflon film. The in situ coupling of BSA to lipid-loaded MCM-41 channels at the lipid bilayer interface was achieved by the sulfhydryl coupling method. The lipid bilayers containing BSA-modified MCM-41 exhibited channel-like currents, which were augmented in a concentration-dependent manner by the addition of anti-BSA at fM level. The in situ modification of lipid-loaded MCM-41 channels with BSA by the amine coupling technique was also investigated. The potential of the present approach for the development of channel-type biosensors is discussed in terms of modifying bilayer interfaces with bioreceptors.     

Post-manufacturing, 17-times acceptable raw bit error rate enhancement, dynamic codeword transition ECC scheme for highly reliable solid-state drives, SSDs

A dynamic codeword transition ECC scheme is proposed for highly reliable solid-state drives, SSDs. By monitoring the error number or the write/erase cycles, the ECC codeword dynamically increases from 512 Byte (+parity) to 1 KByte, 2 KByte, 4 KByte…32 KByte. The proposed ECC with a larger codeword decreases the failure rate after ECC. As a result, the acceptable raw bit error rate, BER, before ECC is enhanced. Assuming a NAND Flash memory which requires 8-bit correction in 512 Byte codeword ECC, a 17-times higher acceptable raw BER than the conventional fixed 512 Byte codeword ECC is realized for the mobile phone application without an interleaving. For the MP3 player, digital-still camera and high-speed memory card applications with a dual channel interleaving, 15-times higher acceptable raw BER is achieved. Finally, for the SSD application with 8 channel interleaving, 13-times higher acceptable raw BER is realized. Because the ratio of the user data to the parity bits is the same in each ECC codeword, no additional memory area is required. Note that the reliability of SSD is improved after the manufacturing without cost penalty. Compared with the conventional ECC with the fixed large 32 KByte codeword, the proposed scheme achieves a lower power consumption by introducing the “best-effort” type operation. In the proposed scheme, during the most of the lifetime of SSD, a weak ECC with a shorter codeword such as 512 Byte (+parity), 1 KByte and 2 KByte is used and 98% lower power consumption is realized. At the life-end of SSD, a strong ECC with a 32 KByte codeword is used and the highly reliable operation is achieved. The random read performance is also discussed. The random read performance is estimated by the latency. The latency is below 1.5 ms for ECC codeword up to 32 KByte. This latency is below the average latency of 15,000 rpm HDD, 2 ms.     

Thermoelectric properties of Ti1+xS2 prepared by CS2 sulfurization

Titanium disulfide (TiS₂) powder was prepared by sulfurizing TiO₂ powder with CS₂ gas at 1073 K for 4 h. Because CS₂ gas is a powerful sulfurizing agent for TiO₂, CS₂ sulfurization can be performed at a low temperature. The TiS₂ powder thus prepared was first mixed with sulfur powder in a mass ratio of 1:0.04 and pressure sintered at 973 K for 1 h under a uniaxial pressure of 50 MPa in vacuum. The addition of a small amount of sulfur powder to the TiS₂ powder prevents sulfur deficiency in the sintered compact, resulting in the formation of a near-stoichiometric Ti_1.008S₂ composition. X-ray diffraction patterns show that the crystalline ab-axis is preferentially oriented perpendicular to the pressing direction. The Seebeck coefficient, electrical resistivity and thermal conductivity of the oriented TiS₂ sintered compacts with near-stoichiometric and sulfur-poor (titanium-rich) compositions were measured in the temperature range 300–723 K. The thermoelectric figure of merit ZT was enhanced by prevention of sulfur deficiency and formation of the oriented texture. The highest ZT of 0.34 was observed at 663 K in Ti_1.008S₂ for the direction perpendicular to the pressing axis.     

Thermodynamic studies on the helix-sense inversion of polyaspartates in the solid state

The Clapeyron analysis has been performed on polyaspartate samples (–[NH–CH(CH₂C(O)OX)C(O)]_n–) carrying side chains such as X = benzyl (1PLA), phenethyl (2PLA), phenylpropyl (3PLA), and phenoxyethyl (PPOLA). In all cases examined, the unwinding and rewinding process of the helical backbone is consistent with the zippering mechanism previously elucidated for the concentrated LC solution. Variation of the PVT properties such as the volume and enthalpy changes at the transition was carefully examined. In the bulk solid state, contribution from the thermodynamic quantities associated with the redistribution of molecules in the configurational space (molecular packing) becomes substantial. It has been concluded that the characteristic features of the ?-α|?-ω transition of 1PLA (140 °C) are inconsistent with the Clapeyron concept, suggesting that the phase transition may involve a non-equilibrium step. The r-α|?-ω transitions of the other polymers were found to conform to the Clapeyron relation. The screw-sense inversion seems to be reversible only when the crystalline structure (hexagonal) remains unaltered before and after the transition. The purpose of this work is to elucidate the key factor responsible for the reversibility of the solid-sate transition, thus providing a basis to understand the role of flanking side chains.