The combined effects of ZDDP, surface texture and hardness on the running-in of ferrous metals

The effects of surface characteristics including roughness, lay direction and hardness of rubbing pairs on the antiwear performance of secondary short chain ZDDPs under a boundary lubrication condition are studied experimentally. The antiwear performance of the ZDDPs is evaluated by the duration of running-in periods recorded in wear tests of specially prepared specimens. A running-in period is defined as the time interval from the beginning of a wear test to the time at which the contact resistance between the rubbing pair approaches infinity. The shorter running-in period yields the better antiwear performance. The wear tests were conducted with a reciprocating sliding contact made by flat-on-flat specimens which were made from grey cast iron, quenched medium carbon steel and bearing steel. Two lay directions of the surface texture, namely, parallel and perpendicular to the sliding direction were ground, which made four possible combinations in a rubbing action. The CLA roughness of the specimens ranged from 0.35 μm to 0.04 μm. It is found that to obtain a shorter running-in period and to enhance the antiwear performance of ZDDPs, the following rules should be obeyed. If the hardness numbers of the two rubbing members are near the same, the combination of their lay directions should be both in parallel but perpendicular to the sliding direction and, the roughness values should be smaller than 0.09 μm. If the hardness number of one member is much greater than that of the other, the soft member should be the smaller one and the surface of the hard member should be as smooth as possible. Under any circumstance, the smaller members should be chamfered.     

Whitening prefiltered TLS linear predictor for frequency estimation

A new total least squares (TLS) technique for linear prediction based on a whitening procedure is presented. This technique can solve the problems due to the bias inherent in the prefiltered TLS solution so as to give a good performance over a wide range of SNRs, thereby outperforming common TLS solutions     

Pilot Symbol Assisted Hybrid Detection for OFDM‐Based Spatial Multiplexing Systems

In this paper, we provide a new detection scheme for a pilot symbol assisted interference nulling and cancellation operation to reduce unexpected effects owing to parallel transmission in orthogonal frequency division multiplexing (OFDM)‐based spatial multiplexing systems. We have shown that the investigated OFDM vertical Bell laboratories layered space time (VBLAST) detection based on hybrid processing performs better than ordinary OFDM‐VBLAST detections based on serial processing and parallel processing, respectively.     

Refinement method for structure from stereo motion

A new method for overcoming bas-relief ambiguity, using a calibrated stereo image sequence, is presented. The proposed method uses a direct method for motion estimation as the initial guess, and refines both stereo and motion displacement with sub-pixel accuracy. Experimental results show that the proposed algorithm improves the estimation accuracy under such ambiguity     

FDTD modeling of transient microwave signals in dispersive and lossy bi-isotropic media

In this paper, we present a novel finite-difference time-domain model of transient wave propagation in general dispersive bi-isotropic media with losses. The special properties of these materials may lead to new applications in microwave and millimeter-wave technology. While their frequency-domain properties have been well described in the literature, their time-domain behavior has only been modeled thus far for special sub-classes and monochromatic time dependence. We have validated our method by first computing time-harmonic wave propagation through a bi-isotropic medium and comparing it with analytical results. Agreement is typically better than 1%. We have then computed transient field propagation in a general lossy dispersive bi-isotropic medium.     

A generalized weighted linear predictor frequency estimation approach for a complex sinusoid

Based on linear prediction and weighted least squares, three simple iterative algorithms for frequency estimation of a complex sinusoid in additive white noise are devised. The proposed approach, which utilizes the first-order as well as higher order linear prediction terms simultaneously but does not require phase unwrapping, can be considered as a generalized version of the weighted linear predictor frequency estimator. In particular, convergence as well as mean and variance analysis of the most computationally efficient frequency estimator, namely, GWLP 2, are provided. Computer simulations are included to contrast the performance of the proposed algorithms with several conventional computationally attractive frequency estimators and Crame/spl acute/r-Rao lower bound for different frequencies, observation lengths, and signal-to-noise ratios.     

Intercomparison of calibration systems for AC shunts up to audio frequencies

An intercomparison of calibration systems for AC shunts up to audio frequencies (10 kHz) between the National Research Council of Canada, Japan Electric Meters Inspection Corporation, and the National Institute of Standards and Technology, is presented. The comparison was implemented with a transfer standard of 10 A, 0.1 /spl Omega/ calculable AC/DC shunt, designed by Japan Electric Meters Inspection Corporation. The results indicate that there are no significant differences in the overall accuracy of calibration systems for AC shunts at frequencies up to 10 kHz in each laboratory.     

Impact of Solvent Additive on Carrier Transport in Polymer:Fullerene Bulk Heterojunction Photovoltaic Cells

The effects of a solvent additive, 1,8‐diiodooctane (DIO), on both hole and electron transport are investigated in a state‐of‐the‐art bulk‐heterojunction (BHJ) system, namely PTB7:PC₇₁BM. For a polymer:fullerene weight ratio of 1:1.5, the electron mobility in the blend film increases by two orders of magnitude with the DIO concentration while almost no change is found in the hole mobility. For lower DIO concentrations, the electron mobility is suppressed because of large, but poorly connected PC₇₁BM domains. For higher concentrations of DIO, the electron mobility is improved progressively and the hole mobility becomes the limiting factor. Between 1 and 5 vol%, the electron and hole mobilities are balanced. Using the Gaussian disorder model (GDM), we found that the DIO concentration modifies fundamentally the average hopping distances of the electrons. In addition, there exist alternative donor–acceptor ratios to achieve optimized PTB7:PC₇₁BM based solar cells. It is demonstrated that the fullerene content of the BHJ film can be significantly reduced from 1:1.5 to 1:1 while the optimized performance can still be preserved.