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A novel amphoteric polyacrylamide (PDAA) was prepared by inverse emulsion polymerization. The influence of its cationic degree and molecular weight on retention property was discussed. Then, the chemical structure and micromorphology of the obtained PDAA were characterized by Fourier infrared spectrum (FTIR), NMR hydrogen spectrum (1H NMR), gel permeation chromatography (GPC), and scanning electron microscope (SEM). Finally, the synergistic retention effects of polydimethyldiallylammonium chloride (PDADMAC), cationic starch (CS), cationic guar gum (CHPG), cationic chitosan (CTS), and polyamine (PA) on the novel PDAA were investigated. The results showed that the optimum cationic degree and molecular weight of PDAA were 25% and 4 million, respectively. The chemical structure of PDAA was confirmed by FTIR, 1H NMR, and GPC. SEM showed that the particle size of PDAA was between 150 and 600 nm, and the particles were very stable because no broken particles were found. In addition, most of the five cationic polymers have good synergistic retention effect on PDAA, and the order of synergistic effect was PDAA/PDADMAC > PDAA/CTS > PDAA/CS > PDAA/CHPG > PDAA/PA.

Nowadays, the oxidation activity at the low-temperature regime for Co3O4 catalysts needs to be improved to meet the stringent regulation of multi-pollutant diesel exhaust. Herein, nanoflower-like Co3O4 diesel oxide catalysts (DOCs) were fabricated with the addition of a low-content Pt to trigger better catalytic activities for oxidizing multi-pollutants (CO, C3H6, and NO) emissions by taking advantage of the strong-metal supporting interaction. Compared to the conventional DOCs based on Pt/Al2O3, the as-synthesized Pt/Co3O4 catalysts not only exhibited better multi-pollutants oxidation activities at the low temperature but also obtained better resistance toward NO inhibition. Moreover, Pt/Co3O4 catalysts showed exceptional hydrothermal durability throughout long-term tests in the presence of water vapor. According to the XPS and H2-TPR results, Pt promoted low-temperature catalytic activity by increasing the active surface oxygen species and reducibility due to the robust synergistic interaction between metallic Pt and supporting Co3O4. Meanwhile, TGA curves confirmed the Pt atoms that facilitated the desorption of surface-active oxygen and hydroxyl radicals in a low-temperature regime. Furthermore, instead of probing the intermediates during CO and C3H6 oxidation for Pt/Co3O4 catalysts, which included carbonates, formate, and acetate species, in situ DRIFTs experiments also revealed C3H6 oxidation mainly took place over metallic Pt sites. [ABSTRACT FROM AUTHOR]

We have designed a readback-signal generator to provide noise-corrupted signals to a read channel simulator. It is implemented in a Xilinx Virtex-E field-programmable gate array (FPGA) device. The generator simulates in hardware the noise processes and distortions observed in hard drives. It uses embedded nonuniform random number generators to simulate the random characteristics of various disturbances in the read/write process. The signal generator can simulate readback pulses, intersymbol interference, transition noise, electronics noise, head and media nonlinearity, intertrack interference, and write timing error according to the characteristics specified by the user. A sample implementation operates at a 70-MHz clock speed. The design can easily be scaled for different error rates. The generator can be reconfigured in real time to give the user flexibility and increase the capacity of the FPGA device. The readback-signal generator can be integrated into an FPGA read channel simulator or serve as a test bench for data-recovery circuits. Index Terms--Field programmable gate array (FPGA), Gaussian pseudorandom number generator, magnetic recording, read channel, read channel modeling, reconfigurable computing, transition noise.

Although deep learning algorithms have been widely used, their performance depends heavily on a good set of hyperparameters. This article presents an efficient Hyperband and trust-region-based mode-pursuing sampling hybrid method for hyperparameter optimization. First, Hyperband is modified and used to select the optimum quickly from a large number of random sampling points to construct a trust region. Secondly, mode-pursuing sampling is performed in the trust region to generate more points systematically around the minimum, and the location or size of the trust region is dynamically adjusted to accelerate its convergence. Thirdly, the process of selection and sampling is repeated until a termination criterion is met. Numerical examples are presented to verify the effectiveness of the hybrid method, the results of which are compared with those of five well-known algorithms. Comparison results show that better optimal solutions are obtained through the hybrid method, with a higher efficiency. [ABSTRACT FROM AUTHOR]

Soft sendust keeper layer has been sputtered on top of longitudinal thin film media which has an [M.sub.r]t value of 0.49 memu/[cm.sup.2]. Measurements of time-decay in both keepered and non-keepered longitudinal thin film media have been performed on a spin-stand tester. Experimental results showed that time-decay is larger in tested media which has lower [M.sub.r]t values compared to those that have a larger [M.sub.r]t of 1.26 memu/[cm.sup.2]. A 50[Angstrom] thick sendust keepered media has about half the decay rate compared to its non-keepered counterpart ([M.sub.r]t = 0.49 memu/[cm.sup.2]) at a recording density of 6000 fr/mm. Also, it was found that time-decay in 100[Angstrom] and 150[Angstrom] thick keepered media is less than that in a 50[Angstrom] keeper media. Index Terms - keepered media, superparamagnetism, thermal decay, time-decay

The time decay of remanent magnetization, remanent coercivity, and readback signal of ultra-thin longitudinal Co[Cr.sub.12][Ta.sub.2]/Cr thin film media have been studied experimentally with a VSM and a recording spin-stand tester using a MR read head. The time decay rate of the remanent magnetization or magnetic viscosity S increases significantly with decreasing magnetic layer thickness, especially for a [M.sub.r]t of less than 0.5 memu/[cm.sup.2] and it is found to be strongly related to the strength of the magnetic interactions between grains. For such thin media (CoCrTa=6 nm) with a [M.sub.r]t] = 0.36 memu/[cm.sup.2], the readback signal amplitude decreases at a high decay rate of about 5% per decade of time (sec) which is found to be essentially independent of the linear recording density from 2000 to 6000 fc/mm. To obtain Co[Cr.sub.12][Ta.sub.2]/Cr media with a time decay rate of less than 10 % in 5 years, the value of the ratio of the anisotropy energy barrier to the thermal energy (Kv/kT) should be greater than 80 which corresponds to a CoCrTa thickness of greater than about 10 nm.

Sendust and CoZrNb were sputtered on longitudinal Co[Cr.sub.12][Ta.sub.2] thin film media as alternative keeper materials to NiFe. Experiments were performed to study the dependence of recording performance on the thickness of the keeper and Cr break layer, head bias current, and recording density. It was found that a thinner (50 [Angstrom]) CoZrNb keepered media can achieve the same amplitude improvement as obtained by a 150 [Angstrom] thick sendust keeper. Spin-stand time decay measurements show that Sendust keepered media has a significantly lower decay rate (1.1% per decade) than its unkeepered counterpart (2.8% per decade). A magnetic force microscope (MFM) was used to observe the flux from transitions under a 50 [Angstrom] and 250 [Angstrom] keeper layers when a external magnetic field of 60 Oe is applied.