Chul-woo Lee

Method and apparatus for encoding envelopes of harmonic signals and method and apparatus for decoding envelopes of harmonic signals

Provided are a methods and apparatuses for encoding/decoding an audio signal to efficiently encode/decode a harmonic envelope. The method of encoding an audio signal includes performing harmonic analysis with respect to an input signal to determine harmonic parameters with respect to harmonic signals; correlating the amplitudes of the harmonic signals to signals in a time domain instead of signals in a frequency domain; applying a time-frequency transformation operation to the amplitudes in the time domain to generate time-frequency transformed values in the frequency domain; and encoding the time-frequency transformed values. When expressing a harmonic envelope, the amplitudes of the harmonic signals are regarded as signals in the time domain so as to perform a time-frequency transformation and only a part from among the transformed values is selected to be encoded. Therefore, sound quality is not affected and coding efficiency greatly improves.

Investigation of flow disturbance by disk-shroud configuration of Servo Track Writer

The flow of air in a simplified model of a Off-line Servo Track Writer system has been investigated numerically. The study focused on the space between disks with a fixed shroud. The disk-shroud configuration is especially important in the Servo Track Writer because the flow disturbance by the rotating disks can seriously disrupt accurate electromagnetic data transfer on servo patterning. To improve the reliability and performance of a current Servo Track Writer system while providing a basis for the improved design of future device, it is necessary to advance the understanding the flow pattern by several shrouded disks configuration. The investigation of the flow disturbance by disk shrouded configuration gives advantages and disadvantages for the shroud design.

Optimal arm configuration to reduce arm bending resonance-induced off-track in a hard disk drive

In order to reduce the off-track due to the arm bending mode, whose effect is considerable in a high capacity drive, an arm configuration with maximum arm bending stiffness should be considered. The objective of this work is to find the optimal arm configuration that maximizes the arm bending stiffness subject to the constraint imposed on the moment of inertia of the arm. Herein, the problem of finding the optimal arm configuration maximizing the arm bending stiffness is formulated as a topology optimization for eigenvalue maximization problem. By applying this method, an arm configuration having two balance holes instead of a single balance hole was obtained. Finally, the efficacy of the optimized arm is verified by measuring the position error signal (PES) of actual sample drives; when the optimized arm was used, the PES was reduced by 25%.

Optimal magnet shape design for wideband magnetic bias torque in a hard disk drive

In order to prevent the swing arm parked on the ramp from rotating due to a rotary shock, a wideband magnetic bias torque is generated on a retract pin. This paper presents the optimal magnet shape to generate a wideband magnetic bias torque. To find the optimal magnet shape, the standard shape optimization is employed. The physics behind why the optimized shape of the magnet yielded better performance is briefly explained using numerical simulation. To verify the effectiveness of the optimized magnet, the actual experiment was conducted. Experimental result shows that the optimized magnet shape generates a wideband magnetic bias torque while maintaining the maximum magnetic bias torque compared to a nominal magnet shape.

Ramp Load/Unload Velocity Control of VCM Using BEMF in HDD

Since most of small form-factor drives have a load/unload mechanism and the flying height of the head is getting lower as the capacity of disk drives increases, the load/unload velocity becomes one of the important factors to ensure the reliability of the load/unload mechanism. To control the load/unload velocity accurately, velocity sensing is essential. In this paper, we introduce a very practical method that acquires the load/unload velocity from the back electromotive force (BEMF) of a voice coil motor (VCM) and propose a calibration method for measuring the BEMF from a given circuit. Moreover, the effect of calibration error and temperature variation on the measurement of BEMF is shown by simulation. Then, this present method is applied to the load/unload velocity controller and is verified from the experimental result.

Parallelization of a relaxation method to run on the Intel Paragon

We present a fast parallelized under-relaxation iterative algorithm applicable in solving a large scale Laplace equation that is incorporated into injection molding analysis. The rate of speed gain versus number of processors is studied using three models with different data sizes. Experimental results of running on 32 Intel Paragon processors show reductions up to 98% of original computation time obtained by using a SGI Challenge. Moreover, due to a better memory utilization, the observed speed gain is greater than the proportional increase in the number of processors used.