• 한국전자파학회:학술대회논문집
• /
• 한국전자파학회 2001년도 종합학술발표회 논문집 Vol.11 No.1
• /
• pp.119-122
• /
• 2001

In this paper, an elliptic disk-loaded antenna having frequency shift characteristics with the same height of the simple monopole is studied. The proposed antenna is composed of an ellitptic disk with arbitrary ellipticity ratio. The eigenmode representations in each region of given structure are useful for the analysis of the canonical monopoly, circular disk-loaded monopole and circular dielectric-loaded top-hat monopole antennas using the artificical ground plane. The comparison between the elliptic and circular disk-leaded antenna is carried out. The effect of the shape of the loaded disk and the ellipticity ratio of the loaded disk on the input impedances, the return loss and frequency shift is also studied. We have computed the given structures using the CST MW Studio version 3.0. The typical blade antenna can be obtained by modifying and extending the proposed structure with the λ/4 balun removing the stray capacitances existing between the loaded disk and the ground plane.

• 정보저장시스템학회논문집
• /
• 제1권1호
• /
• pp.23-28
• /
• 2005

This paper investigates the effects of disk thickness and Pemto slider on PES(position error signal) for high TPI(track per inch) drives above 150kTPI at early stage of their development. In order to reduce the disk flutter which becomes a dominant contributor to the TMR, the thicker disks with both 63 and 69mi1 have been used. Also, PES of a Pemto slider with thinner thickness than Pico slider has been estimated to decrease the conversion factor of disk motion in axial direction to head off-track motion. A frequency-domain PES estimation and prediction tool has been developed via measurement of disk flutter and HSA(head stack assembly) forced vibration. It has been validated by the measured PES in drive level. Based on the model and measurement of disk flutter, PES of a drive with the thicker disk and Pemto slider is predicted and their impact is investigated.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 1999년도 제30회 추계학술대회
• /
• pp.303-309
• /
• 1999

Optimum tribological performance of the head/disk system is critical in maintaining reliable data processing in a hard disk drive. Particularly, as the flying height of the slider continues to decrease with increasing recording density, frictional interaction between the slider and the disk need to be better understood. In this work the effect of reduced ambient pressure on the tribological behavior of the head/disk interface is presented. It is found that surface damage of the components can be accelerated by reducing the ambient pressure. This method may be utilized to assess slider/disk compatibility of newly developed systems in short time.

• 정보저장시스템학회논문집
• /
• 제3권2호
• /
• pp.81-85
• /
• 2007

Reliability of a hard disk drive depends on the head disk interface (HDI) characteristics. Particularly, the disk media and the head can be damaged due to contact between the two components during operation. The contact may occur due to particles being introduced into the disk/slider interface or due to direct contact between the slider and the disk. Such contacts may be induced by external vibration or abnormal operation of the HDI. In this work the characteristics of scratches generated on the disk surface were investigated. The scratches were generated by impacting the hard disk. The type of scratches was analyzed with respect to their shape and dimensions.

• 설비공학논문집
• /
• 제3권3호
• /
• pp.206-214
• /
• 1991

Flow field in a hard disk drive has been predicted numerically. Theoretical model was constructed based on a commercially available hard disk drive with 40 Mega byte capacity. Since the gap between disk tip and shroud is not homogeneous in real hard disk drive, three kinds of gap size have been tested as computational model. The discussion has been made on the circumferential velocity, radial velocity, and pressure fields. As a result, the average shear stress on the disk surface was reduced as the gap size decreased. This means that the shroud should be designed compactly to reduce power consumption of the spindle motor.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2004년도 추계학술대회 논문집
• /
• pp.472-476
• /
• 2004

In this study, we investigate the change characteristic of friction coefficient of disk brake lining for rolling stock according to disk type, The actual brake tests were carried out under constant brake force and operating sequence by using dynamo-tester. Test results showed that instant friction coefficient was higher in the case of devided disk type rather than single body disk type, Also, averge friction coefficient was appeared similer to the above result. It is thought that ,in the case of devided disk type, friction resistance was increased due to the gap between both side of half disk.

• 한국공작기계학회논문집
• /
• 제14권4호
• /
• pp.89-95
• /
• 2005

This paper intends to identify experimentally the relationship between transverse vibration behavior of a spinning disk and high-frequency fluctuation in the driving torque. A testrig has been developed using a CD-ROM disk, a driving motor with torque-varying capability and a power transmission belt and a laser vibrometer was employed to measure the transverse vibration displacements of the disk for a certain range of the spinning speed. The results show that the spinning speed and the magnitude and frequency of the torque fluctuation affect the stability of the disk. In other word, the torque fluctuation causes the instability of the disk at several ranges of the spinning speed below the critical speed and its effects become larger as the disk spins faster or the magnitude of torque fluctuation becomes bigger. The experimental results are found to be in good agreement with analytical estimation.

• 대한산업공학회지
• /
• 제26권4호
• /
• pp.376-383
• /
• 2000

A flexible disk grinding process model has been implemented with varying disk orientation with respect to workpiece surface along with variable feed rate. Before implementing arbitrary disk orientation and translation, disk angle and feed rate variation have been implemented. The disk angle was changed with constant angular velocity only in the entrance stage. The effect of the variable feed rate was added to the geometric schematic. The feed rate was changed either from the entrance stage or from the between edges stage and process performance was evaluated. Effect of changing both angle end feed rate has been also analyzed. Disk trend showing actual disk deflection has also been visualized.

• Tribology and Lubricants
• /
• 제17권4호
• /
• pp.312-320
• /
• 2001

In magnetic hard disk drives, higher areal recording density requires reduction of head-disk spacing. To overcome the increase of stiction associated with reduction of head-disk spacing, a padder slider, which adds pads to slider's air bearing surface, can be one of the practical solution for sub 20 nm flying height, and even for near contact recording. This study investigated the tribological characteristics of a padder slider. A padder slider took off slowly but showed less friction force than a normal slider. The hot/dry CSS test and drag test indicated that pad wear of a padder slider was negligible. The tribological performance of disk is an important factor to be considered. In particular, less carbon overcoat layer of the disk will result in higher stiction and wear in slider/disk interface. In conclusion, a padder slider shows encouraging tribological performances for practical use in HDD.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제11권3호
• /
• pp.43-52
• /
• 2007

A hard disk, which can be classified as an external storage is usually capacious and economical. In spite of the attractive characteristics and efforts on the performance improvement, however, the operation of the hard disk is apparently slower than a processor and the advancement has also been slowly conducted since it is based on mechanical process. On the other hand, the advancement of the processor has been drastically performed as semiconductor technology does. So, disk I/O sub-system becomes bottleneck of computer systems' performance. For this reason, the research on disk I/O sub-system is in progress to improve computer systems' performance. In this paper, we proposed multi-level LRU scheme and then apply it to the computer systems with buffer cache and disk cache. By applying the proposed scheme to computer systems, the average access time to disk blocks can be decreased. The efficiency of the proposed algorithm was verified by simulation results.