Outer-loop control of target SIR for fast transmit power control inturbo-coded W-CDMA mobile radio

A technique for obtaining outer-loop control of the target SIR for closed-loop fast transmit power control (TPC) is presented for turbo-coded wideband DS-CDMA (W-CDMA) mobile radio systems. The frame error rate (FER) of an intermediate decoding output in the turbo-decoder. i.e. before the final iteration stage is reached, is measured to control the target SIR. The bit error rate (BER) after the final decoding iteration can be maintained accurately at the prescribed BER value, e.g. BER=10^-6, without losing the tracking ability in the presence of slowly changing propagation channel conditions. Computer simulation results supporting this ability are reported     

Dependence of morphological changes of polymer particles on hydrophobic/hydrophilic additives

Fairly uniform microspheres of poly(styrene‐co‐methyl methacrylate) were prepared by employing a microporous glass membrane [Shirasu porous glass (SPG)]. The single‐step SPG emulsification, the emulsion composed mainly of monomers, hydrophobic additives, and an oil‐soluble initiator, suspended in the aqueous phase containing a stabilizer and inhibitor, was then transferred to a reactor, and subsequent suspension polymerization followed. The droplets obtained were polymerized at 75°C under a nitrogen atmosphere for 24 h. The uniform poly(styrene‐co‐methyl methacrylate) microspheres with diameters ranging from 7 to 14 μm and a narrow particle‐size distribution with a coefficient of variation close to 10% were prepared by using SPG membrane with a pore size of 1.42 μm. The effects of the crosslinking agent and hydrophobic additives on the particle size, particle‐size distribution, and morphologies were investigated. It was found that the particle size decreased with a narrower size distribution when the additives were changed from long‐chain alkanes to long‐chain alcohols and long‐chain esters, respectively. Various microspheres with different morphologies were obtained, depending on the composition of the oil phase. The spherical poly(styrene‐co‐methyl methacrylate) particles without phase separation were obtained when using an adequate amount of the crosslinking agent and methyl palmitate as an additive. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1013–1028, 2000     

Partially hydrolyzed polyacrylamide–poly(N-vinylpyrrolidone) copolymers as superabsorbents synthesized by gamma irradiation

Partially hydrolyzed polyacrylamide-co-poly(n-vinyl pyrrolidone) used as a superabsorbent was prepared from acrylamide monomers exposed to γ-rays to become polyacrylamide that was subsequently partially hydrolyzed and was then copolymerized with n-vinylpyrrolidone to obtain a terpolymeric superabsorbent with a water retention value of 1100 times its dried weight. The total dose and dose rate along with the appropriate degree of hydrolysis were investigated for percentage conversion in each polymerization and the extent of water absorption. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:191–203, 1998     

LMI-based controller synthesis: A unified formulation and solution

This paper proposes a unified approach to linear controller synthesis that employs various LMI conditions to represent control specifications. We define a comprehensive class of LMIs and consider a general synthesis problem described by any LMI of the class. We show a procedure that reduces the synthesis problem, which is a BMI problem, to solving a certain LMI. The derived LMI condition is equivalent to the original BMI condition and also gives a convex parametrization of all the controllers that solve the synthesis problem. The class contains many of widely-known LMIs (for H_∞ norm, H₂ norm, etc.), and hence the solution of this paper unifies design methods that have been proposed depending on each LMI. Further, the class also provides LMIs for multi-objective performance measures, which enable a new formulation of controller design through convex optimization. © 1998 John Wiley & Sons, Ltd.     

Improved high temperature performance of La0.8Sr0.2MnO3 cathode by addition of CeO2

Ceria is proposed as an additive for La_0.8Sr_0.2MnO₃ (LSM) cathodes in order to increase both their thermal stability and electrochemical properties after co-sintering with an yttria-stabilized zirconia (YSZ) electrolyte at 1350 °C. Results show that LSM without CeO₂ addition is unstable at 1350 °C, whereas the thermal stability of LSM is drastically improved after addition of CeO₂. In addition, results show a correlation between CeO₂ addition and the maximum power density obtained in 300 μm thick electrolyte-supported single cells in which the anode and modified cathode have been co-sintered at 1350 °C. Single cells with cathodes not containing CeO₂ produce only 7 mW cm⁻² at 800 °C, whereas the power density increases to 117 mW cm⁻² for a CeO₂ addition of 12 mol%. Preliminary results suggest that CeO₂ could increase the power density by at least two mechanisms: (1) incorporation of cerium into the LSM crystal structure, and (2) by modification or reduction of La₂Zr₂O₇ formation at high temperature. This approach permits the highest LSM-YSZ co-sintering temperature so far reported, providing power densities of hundreds of mW cm⁻² without the need for a buffer layer between the LSM cathode and YSZ electrolyte. Therefore, this method simplifies the co-sintering of SOFC cells at high temperature and improves their electrochemical performance.     

Syntheses of sulfonated star-hyperbranched polyimides and their proton exchange membrane properties

We synthesized novel sulfonated star-hyperbranched polyimides composed of a hydrophobic hyperbranched polymer for polymer stability and a hydrophilic sulfonated polyimide as the proton-transport site in the core-shell structure. The proton conductivities of the star-hyperbranched polyimide membranes were measured as functions of the relative humidity and temperature using electrochemical impedance spectroscopy. Although the water uptake and IEC value for the sulfonated star-hyperbranched polyimide membranes were almost constant, the proton conductivity of the membrane strongly depended on the molecular weight of the hydrophilic sulfonated polyimide as the shell. Especially, the conductivity of the high molecular weight star-hyperbranched polyimide membranes was significantly superior to that determined in Nafion^® at all temperatures and was 0.51 S cm⁻¹ at 80 °C and 98% RH, which may suggest that a good proton-transport pathway in the core-shell structure is formed. Consequently, this material proved to be promising as a proton exchange membrane and may have potential applications for use in fuel cells.     

On-line and off-line wheel/rail contact algorithm in the analysis of multibody railroad vehicle systems

An on-line and off-line hybrid contact algorithm for modeling wheel/rail contact problems is developed based on the elastic contact formulation. In the hybrid algorithm developed in this investigation, the off-line tabular search is used for predicting the location of tread contact points, while the on-line iterative search is used for predicting flange contact points. By so doing, a computationally efficient procedure is achieved while keeping accurate predictions of contact points for severe contact scenarios such as sharp curve and turnout negotiations. The use of the proposed hybrid algorithm can eliminate the time-consuming on-line iterative search for the second points of contact. Since the location of the second point of contact is pre-computed by the contact geometry analysis, the occurrence of two-point contact can be predicted by using the look-up table at the one-point contact configuration. A flange climb simulation demonstrates that the proposed hybrid contact search algorithm can be effectively used for modeling wheel/rail contacts in the analysis of general multibody railroad vehicle systems. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Hiroyuki Sugiyama received his Ph.D. from the University of Illinois at Chicago in 2005. Dr. Sugiyama is currently an Assistant Professor at Tokyo University of Science, Tokyo, Japan. His research interests include the development of computer formulations for contact problems in vehicle systems and the large deformation problems of constrained multibody systems. Kohei Araki received his BS degree in Mechanical Engineering from Osaka City University in 2006. Mr. Araki is currently a Master’s student at Osaka City University, Osaka, Japan. His research interest is in the modeling of wheel/contact problems in railroad vehicle dynamics. Yoshihiro Suda received his Doctoral degree from the University of Tokyo in 1987. Dr. Suda is currently a Professor at the University of Tokyo, Tokyo, Japan. His research interests are in the dynamics of railroad vehicles and automobiles, in-telligent transportation systems (ITS) and personal mobility vehicles. He is currently serving as an Associate Editor of the IMechE Journal of Multi-Body Dynamics.     

PARAMETERS INFLUENCING TONER CHARGING CHARACTERISTICS IN ELECTROPHOTOGRAPHIC PRINTING

ABSTRACT

The charge-to-mass ratio, q/m, of a two-component developer is the important factor in an electrophotographic system, since the toner charge controls the developed tone mass and the print quality. This article investigates the charging properties of differently shaped toners (spherical and irregular), and carrier particles that differ in their composition and surface oxide layer thickness by adjusting the applied current. The parameters for toner charging involving the mixing force, the toner concentration, the shape of the toner, the carrier type, and the current of the carrier surface are studied. The print quality is evaluated by focusing on the solid density, 60 and 40% halftone densities, background density, and edge sharpness of the characters. An explanation of the force between the toner and carrier particles is proposed.     

Thermoplastic elastomers based on epoxidized natural rubber and high‐density polyethylene blends: Effect of blend compatibilizers on the mechanical and morphological properties

Epoxidized natural rubber (ENR) with a level of epoxide groups of 20 mol % was prepared via the performic epoxidation method. It was then used to blend with high‐density polyethylene (HDPE) at various blend ratios. Three types of blend compatibilizers were prepared. These included a graft copolymer of HDPE and maleic anhydride (MA; i.e., HDPE‐g‐MA) and two types of phenolic modified HDPEs using phenolic resins SP‐1045 and HRJ‐10518 (i.e., PhSP‐PE and PhHRJ‐PE), respectively. We found that the blend with compatibilizer exhibited superior tensile strength, hardness, and set properties to that of the blend without compatibilizer. The ENR and HDPE interaction via the link of compatibilizer molecules was the polar functional groups of the compatibilizer with the oxirane groups in the ENR molecules. Also, another end of the compatibilizer molecules (i.e., HDPE segments) was compatibilizing with the HDPE molecules in the blend components. The blend with compatibilizer also showed smaller phase morphology than the blend without compatibilizer. Among the three types of the blend compatibilizer, HDPE‐g‐MA provided the blend with the greatest strength and hardness properties but the lowest set properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008