• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.2
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• pp.88-97
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• 2003

Computer simulations of the recording and reading of holograms in an 8-bit phase-code multiplexing system are presented. From the computer simulation each recording time of eight holograms is obtained such that the strength of restored holograms is same. An analytic formula to predict the recording times is derived by fitting the formula to the computer simulation data. It is found that our analytic formula can predict the hologram recording time not only in 8-bit system but also in 16-bit and 32-bit systems in an error less than $\pm$8.4%. Optical experiments are also performed in a 4-bit phase code-multiplexing system. It is found that the strength of the restored holograms is more uniform compared with conventional methods.

• Transactions of the Society of Information Storage Systems
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• v.3 no.3
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• pp.139-143
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• 2007

In recent years new recording media and materials for head-disk interface (HDI) have been developed in order to increase the recording density of storage devices and decrease the cost of production. It is well known that HDI in hard disk drive (HDD) needs high durability and stability. The tribological characteristic of commercialized HDI systems is an important indicator of the HDD reliability. In this study, experimental investigation on the wear coefficient of commercialized hard disk slider pads was performed. The slider was placed on top of a hard disk and allowed to slide for a set distance. The wear of the pads was measured after the sliding tests. The result showed that the micro-bumps in commercialized HDD have extremely low wear coefficient of $10^{-11}$. The results of this work may be used for further development of the HDI technology for HDD.

• Transactions of the Society of Information Storage Systems
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• v.1 no.1
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• pp.67-72
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• 2005

This study proposes a design methodology to determine the optimum configurations of the optical flying head (OFH) for near-field recording systems. Since the OFH requires stricter static and dynamic characteristics of slider air-bearings within an optical tilt tolerance over the entire recording band, an optimum design to keep the focusing and tracking ability stable is essential. The desired flying characteristics considered in this study are to minimize the variation in flying height between the SIL and the disk from a target value, satisfying the restriction of the minimum flying height, to keep the pitch and roll angles within an optical tilt tolerance, and to ensure a higher air-bearing stiffness. Simulation results demonstrate the effectiveness of the proposed design methodology by showing that the static and dynamic flying characteristics of the optimally designed OFH are enhanced in comparison with those of the initial. The gap between the SIL and the disk can be kept at less than 100 nm even if the optical tilt tolerance of the SIL is considered.

• Transactions of the Society of Information Storage Systems
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• v.5 no.1
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• pp.41-46
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• 2009

In SIL-based NFR servo systems, the residual error and the overshoot that are occurred in the process of the modes-witching servo which consists of approach, gap-control modes, and safety mode are reduced by using PID controller. However, the design method of conventional PID controller is not sufficient for the stable air gap control system. Therefore, the optimal PID controller using LQR manner is more useful to find the designed parameters of PID controller. In this paper, we show that the performance of the optimal PID controller is better than that of the lead-lag controller.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.1
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• pp.129-140
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• 2017

In this paper, a $4{\times}32$-channel neural recording system capable of acquiring neural signals is introduced. Four 32-channel neural recording ICs, complex programmable logic devices (CPLDs), a micro controller unit (MCU) with USB interface, and a PC are used. Each neural recording IC, implemented in $0.18{\mu}m$ CMOS technology, includes 32 channels of analog front-ends (AFEs), a 32-to-1 analog multiplexer, and an analog-to-digital converter (ADC). The mid-band gain of the AFE is adjustable in four steps, and have a tunable bandwidth. The AFE has a mid-band gain of 54.5 dB to 65.7 dB and a bandwidth of 35.3 Hz to 5.8 kHz. The high-pass cutoff frequency of the AFE varies from 18.6 Hz to 154.7 Hz. The input-referred noise (IRN) of the AFE is $10.2{\mu}V_{rms}$. A high-resolution, low-power ADC with a high conversion speed achieves a signal-to-noise and distortion ratio (SNDR) of 50.63 dB and a spurious-free dynamic range (SFDR) of 63.88 dB, at a sampling-rate of 2.5 MS/s. The effectiveness of our neural recording system is validated in in-vivo recording of the primary somatosensory cortex of a rat.

• The KIPS Transactions:PartB
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• v.16B no.1
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• pp.25-34
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• 2009

DVR(Digital Video Recorder) system stores video inputs in compressed digital formats and retrieve them. DVR system has several advantages over traditional analog tape recorder system which are (1) improved real-time monitoring, recording and searching capability, and (2) other capabilities such as watermarking and remote monitoring through network. AVI format is the most popular format used for DVR systems. However, AVI format has drawbacks in recording and searching due to structural problem. Some vendors develop and use their own format, do not open the format to the public. In this paper, ESP format is proposed. ESP format solves the drawbacks of AVI format, and the advantages of AVI format apply to ESP format. Moreover, ESP format provides multistream recording/replay and event-recording. In result, ESP format enchances functionality of recording and searching in DVR system.

• Proceedings of the Korean Magnestics Society Conference
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• 2004.06a
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• pp.11-11
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• 2004

• Transactions of the Society of Information Storage Systems
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• v.6 no.1
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• pp.12-17
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• 2010

Thermally-assisted magnetic recording (TAMR) is a potentially promising approach to increase the storage density of hard disk drive (HDD). However, TAMR has some issues such as temperature effects, media problems, thermal deformation and light delivery. In this research, we focused on light delivery. One of the powerful methods to deliver the light from laser diode to recording medium is the use of an optical fiber and a specially designed prism. However, the TAMR with optical fiber may have some flyability problems induced by the mounted optical fiber and prism. Also, the TAMR suspension using an optical fiber has high vertical and pitch stiffness. Therefore, p-torque is greatly increased by the optical fiber. Also, flying height (FH) of the slider with TAMR suspension can be largely changed by p-torque. Therefore, in this paper, we focus on the pitch static attitude (PSA) tolerance and the FH by PSA of the TAMR suspension. The FH is investigated using various errors and the PSA tolerance for TAMR suspension is proposed.

• Transactions of the Society of Information Storage Systems
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• v.3 no.1
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• pp.1-4
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• 2007

A high density optical data storage device has been required for many years. In the field of the optical data storage, a near-field recording (NFR) technology is considered as a next generation one for achieving the high data density. Due to an evanescent wave effect occurred under 100nm distance which is the excessively small distance between the SIL and the disc, the most significant and difficult problem in this technology is to maintain a gap between a solid immersion lens (SIL) and a disc. Also, maintaining the gap under at least 50nm is required in the NFR gap servo system to use the evanescent wave effect efficiently. There are some institutes that have shown the novel gap servo control. In general, they use a mode switching servo method which consists of approach, hand-over and gap control mode. However there is a critical problem such as an overshoot at the tuning point from the approach mode to the hand-over mode, which may cause a collision between the SIL and the disc. In this paper, we show our NFR system and an improved gap servo system using an exponential function as the approach mode which can reduce the overshoot.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1A
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• pp.13-17
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• 2002

For elimination DC component, the optical recording systems generally exploit WRDS (word-end running digital sum) criterion. However, its performance is degraded if the lengths of the control bits and codewords are increased. Another criterion is MSW (mean-square weight) method. Whereas MSW criterion has the complexity, this hs optimal performance. In this paper, we have proposed a new dc-component suppression method (MPRDS, minimum peak RDS) of the modulation codes for high density optical recording system. This method requires less complexity than MSW's, and the performance is near to MSW's even if the lengths of the control bits and codewords are increased.