A 3D micromagnetic model is established to analyze the dynamics of single-pole-type (SPT) heads, in which a main pole and a soft underlayer (SUL) are included. It is found that, in an SPT head whose write pole thickness L_m and pole width W are 40 nm each, the throat height should be no greater than the pole tip width to avoid high remnant field at the static state. The influences of the head's parameters and the damping constant on switching time of SPT head are analyzed respectively. The crystalline anisotropy field of SUL is also proved to have great effect on the switching characteristics: a high anisotropy field along the cross-track direction could stabilize the magnetic moments in SUL and greatly shorten the switching time.

Pole-tip-driven structure, which is composed of a coil wounded at the main pole tip, is favorable for obtaining a sharp and strong head field as a single-pole-type head. Three kinds of pole-tip-driven-type heads with different yoke and coil structures are investigated in terms of magnetomotive force dependence of head field and effect of coil recession. Field calculation by finite-element method (FEM) showed that the three heads exhibited the same field sensitivity in spite of the difference in distribution of coil exciting field and magnetization of the main pole. In a lower range of magnetomotive force the heads showed different dependence of field sensitivity on the coil recession. However, there was not much difference in degradation of sensitivity in a region near the saturation of field. Thus, the importance of reducing coil recession was confirmed as reported earlier.

Mn_1-xZn_xFe₂O₄ thin films with various Zn contents, 300 nm in thickness, were synthesized on glass substrates directly by electroless plating in aqueous solution at 90 without a heat treatment. With XRD, SEM, VSM, the crystallographic structure, morphology of the films and the macroscopic magnetic properties were characterized. The Mn-Zn ferrite films have a single phase spinel structure and well-crystallized columnar grains grow perpendicularly to the substrate. The change of the coercivity is not consistent with that of the bulk materials. As the Zn content in the films increases, the value of H_c decreases firstly, and then increases. At x=0.5, the minimum value of H_c is 3.7 kA/m and the value of M_s is 419.6 kA/m. The hyperfine magnetic fields, cation occupations and the distribution of the magnetic moments in film plane were studied by the conversion electron Mossbauer spectroscopy (CEMS).

Fe thin films were deposited directly and via Ag underlayer on glass and MgO(100) substrates by MBE. Polycrystal Fe films grew on the glass substrate while single crystal films grew on the MgO(100) substrate. Fe film growth followed the Volmer-Weber mode for both cases. The Fe film structure was influenced by the surface roughness of Ag underlayer at the early stage of film growth. The relationships between the Fe thin film morphology and the magnetic properties are discussed.

The FePt films were fabricated by using RF sputtering for magnetic recording media. The efforts have been done to reduce the grain size, to decrease the ordering temperature, and to control the crystalline orientation. It was found that the proper amount of alumina led to decrease the grain size and weak the interparticle exchange coupling. 15% N₂ partial pressure can reduce the transform temperature from fcc to fct phase. In order to control the texture in the FePt films, two kinds of methods were used. On the one hand, the addition of W in Cr underlayer and the usage of Mo and Pt as intermediate layer caused the texture of FePt films changed from (200) to (001). On the other hand, the (Pt/Fe)_n multilayers were fabricated to produce the FePt (001) orientation.

Effect of dispersions of medium parameters and structure on the recording performance was systematically investigated. Moderately increased M-H loop slope is effective for obtaining higher thermal stability, smaller saturation fields, and higher resolution. It was found that the most influential factor is the dispersion in anisotropy field, H_k. Small H_k dispersion reduced the noise when exchange coupled media were used. Reduced grain size and a stacked structure of the media were expected to give a restricted gain in the signal to noise ratio.

The long-term bit error rate (BER) performance of partial response maximum likelihood (PRML) system using an adaptive equalizer in a perpendicular magnetic recording (PMR) channel with thermal decay is studied. A thermal decay model based on the experimental data giving the amplitude change of reproducing waveforms with the elapsed time for CoPtCr-SiO₂ PMR medium is obtained. The BER performance of PR1ML channel for the 16/17(0,6/6) run-length-limited (RLL) code is evaluated by computer simulation using the model. The relationship between the ratio R_J of the jitter-like media noise power to the total noise power at the reading point and the required SNR to achieve a BER of 10^-4 is also obtained and the performance is compared with that of the conventional equalization. The results show that the significant improvement in SNR by utilizing the adaptive equalization is recognized over all R_J compared with the conventional equalization.

There are two methods of writing servo signals with high speed in a perpendicular magnetic recording medium by magnetic duplication: bit printing (BP) and edge printing (EP). In this study, the influence of spacing between master and slave media on duplication characteristics in both BP and EP has been investigated by the three-dimensional finite-element method. The results show that the duplication characteristic in each method is deteriorated with a large spacing. Also, the influence of a small spacing is stronger in BP than in EP.

Shift margins in down and cross track directions and skew angle were investigated using micromagnetic simulation with a shielded planar head for patterned media with an areal density of 1 Tbit/in². The shift margins were quantitatively estimated using parameters of the head field and the magnetic properties of media. It is essential to use a head with a higher field gradient and a medium with a small field width between saturation and nucleation fields, to obtain a larger down track shift margin, and a head with a narrower cross track field distribution to obtain a larger cross track shift margin and skew angle margin.

In order to realize a higher density version of the conventional optical disk, shorter wavelength laser and narrower track pitch have been put to practical use. However, using narrow track pitch can cause the increase of the crosstalk from the adjacent tracks. Moreover, the use of narrow pitch and short wavelength can also give rise to the increase of deterioration of the detected signal characteristics due to the microscopic roughness of disk surface. In this paper, in order to estimate the effect of surface roughness theoretically, we try to analyze the light-beam scattering and detected signal characteristics of a blue laser optical disk model with random rough surfaces by the Finite Difference Time Domain (FDTD) method.

In this paper, we presented a computer simulation analysis of high-density hologram recording, which is a promising mass optical memory technique. A simulation method for off-axis speckle-shift multiplexed recording by three-dimensional computer simulation analysis was presented, as well the signal evaluation of recording and reproduction. By this simulation method, the characteristic features of recording and reproduction are studied from the viewpoints of signal-to-noise-ratio and the reproduced image's quality, and a high-density speckle-shift multiplexed recording condition is proposed.

The neural network equalization for polytopic multiplexing holography is studied to reduce interpixel interference. The bit error rate performance of the bilinear or bicubic interpolator followed by a neural network as an equalizer is obtained by computer simulation. The results show that the neural network equalizer provides an SNR improvement of about 1.0 dB over conventional equalization.

We propose a new label recognition system for photonic label switching using self-routing of labels. Binary-coded labels in on-off keying format are considered. The system consists of an all-optical demultiplexer (DeMUX) and an address recognition unit (ARU) consisting of tree-structured switches. The system uses self-routing propagation of an indication bit controlled with address bits. The indication bit is placed in advance of the address bits in the label. In DeMUX, all-optical switches in a configuration of Mach-Zehnder interferometer with semiconductor optical amplifiers (SOA-MZI) are controlled by the indication bit pulse to separate each of the label bits. The indication bit pulse is routed to the destination output port corresponding to the code of the address in ARU. It is shown that all the binary number codes can be recognized with this system. The operation principle is verified by numerical simulation using coupled-mode theory and a rate equation. Moreover, the switching crosstalk is also evaluated.

This paper reports a novel design in Photonic Crystal Fibers (PCFs) with nearly zero ultra-flattened dispersion characteristics. We describe the chromatic dispersion controllability taking non-uniform air hole structures into consideration. Through optimizing non-uniform air hole structures, the ultra-flattened zero dispersion PCFs can be efficiently designed. We show numerically that the proposed non-uniform air cladding structures successfully archive flat dispersion characteristics as well as extremely low confinement losses. As an example, the proposed PCF with flattened dispersion of 0.27 ps/(nmkm) from 1.5 µm to 1.8 µm wavelength with confinement losses of less than 10^-11 dB/m. Finally, we point out that full controllability of the chromatic dispersion and confinement losses, along with the fabrication technique, are the main advantages of the proposed PCF structure.

This paper reports the development of a lead-free brush material for a high-load starter. These brushes are used in much more extreme conditions -- at the PV-value (the product of brush contact pressure and sliding velocity) approximately three times that of other starter brushes, and double the electrical current density. The major technical requirement of this development was to decrease the electrical wear in brushes caused by commutation sparking. We developed a brush material that reduces electrical wear by adding zinc phosphate. Because zinc phosphate can improve the lubricity at high-temperature and the contact stability of brushes, the developed brush reduces commutation sparks. The life of the developed brush is about 1.5 times longer than that of conventional brushes containing lead.

In this paper, we describe the effect of p-regions on the I-V kink in GaAs FETs. A kink-free p-pocket-type self-aligned gate GaAs MESFET (PP-MESFET), which does not include p-regions under the channel, has been analyzed and compared with a conventional buried-p-type self-aligned gate GaAs MESFET (BP-MESFET) using two-dimensional device simulation. The relation between the I-V kink and the layout of p-regions has been demonstrated by numerical simulation for the first time. For both the BP-MESFET and PP-MESFET, impact ionization produces holes in high-field regions. The holes accumulate under the channel, widen the channel, and cause an abrupt increase in drain current in turn in the BP-MESFET. On the other hand, in the PP-MESFET, holes generated in the high-field region are transported to the source region easily over the lower barrier owing to the absence of p-regions under the channel. Holes do not accumulate under the channel, leading to kink-free I-V characteristics of the PP-MESFET. P-regions should be located so as not to cause the accumulation of holes in GaAs FETs where p-regions are required for high-frequency performance.

This study investigates a new transmission method of light from a point source in a multimode graded-index fiber. The position of the point source is arranged along with a mode pattern to precisely determine the location of an output point image. Propagation performance is observed in an experiment and estimated by simulation.

In this paper, a compact ultra-wideband bandpass filter (UWB-BPF) using pseudo-interdigital stepped-impedance resonators (PIDT-SIRs) is designed and implemented on a commercial printed circuit board (PCB) of RT/Duroid 5880 substrate. The first two resonant modes of the SIR are coupled together and they are applied to create a wide passband. The proposed filter at center frequency f₀ of 7.1 GHz has very good measured characteristics including the bandwidth of 3.68-10.46 GHz (3-dB fractional bandwidth of 95%), low insertion loss of -0.50.4 dB, sharp rejection due to two transmission zeros in the passband edge created by the inter-stage coupling. Experimental results of the fabricated filter show a good agreement with the predicted results.