• Journal of KIISE:Computer Systems and Theory
• /
• v.34 no.3
• /
• pp.101-112
• /
• 2007

Hard disks have been the most prevalent secondary storage devices and these days their usage is becoming more important in mobile computing systems due to I/O intensive applications such as multimedia applications and games. However, significant power consumption in the disk drives still limits battery lifetimes of mobile systems critically. In this paper, we show that using several smaller disks (instead of one large disk) can be an energy-efficient secondary storage solution on typical mobile platforms without a significant performance delay. Also, we propose a novel energy-efficient technique, which clusters related data into groups and migrates the correlated groups to the same disk. We compare this method with the existing data concentration scheme, and also combine them. The experiments show that our technique saves the energy consumption up to 34% when a pair of 1.8' disks is used instead of a single 2.5' disk with a negligible increase in the average response time. The results also show that our method also saves up to 14.8% of disk energy consumption and improve the average I/O response time by up to 10 times over the existing scheme.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.05a
• /
• pp.942-947
• /
• 2001

This paper provides a stability analysis of the transverse vibration of a spinning disk under the torque fluctuation from a permanent magnetic motor. An analytical model has been formulated for a flexible annular disk with its spinning velocity varying harmonically with the same frequency as the cogging torque. A perturbation method based on multiple time scales is applied to perform the stability analysis. Based on expressions for the amplitude and frequency of the parametric excitation, stability boundaries are determined in terms of a nominal spindle velocity, the least common multiple of poles and slots, the magnitude of torque fluctuation and the modal characteristics of. the disk. The stability diagrams predicted by perturbation have been verified numerically using the Floquet theory, which is in good agreement. In conclusion, the fluctuation in spinning velocity is found to affect the stability of the transverse vibration of a rotating disks. The results of this work can be applied to high precision spindle systems such as computer storage systems.

• Asian-Australasian Journal of Animal Sciences
• /
• v.17 no.12
• /
• pp.1652-1656
• /
• 2004

The aim of this study was to obtain mature ova or embryos at a single cell stage, which can be used in avian transgenesis and nuclear transfer through multiple ovulations, in vitro fertilization and culture. Chicken anterior pituitary extract (CAPE) or acetone-dried chicken anterior pituitary extract (ACAPE) was used to induce multiple ovulations in hens pretreated with pregnant mare' serum gonadotrophin (PMSG). In vitro fertilization of the multiple ovulated ova was performed by inseminating sperm onto the germinal disks in m-Ringer' solution and incubating the ova at 41$^{\circ}C$, 5% $CO_2$ for 10 h in DME-F12 medium containing 20% liquid albumen. The in vitro fertilization process was observed using an environmental scanning electron microscope. When normal laying hens (white Leghorn) were administered daily with PMSG (100 IU), egg laying ceased in most hens within 3 to 8 days. Ovulation began to occur about 7.5 h after injection of CAPE and ACAPE. The number of ovulated ova was 1.00${\pm}$0.00, 2.33${\pm}$0.52 and 2.20${\pm}$0.45, respectively, after receiving 100, 200 and 300 mg CAPE. The number of ovulated ova was 2.00${\pm}$0.00, 2.86${\pm}$0.69 and 3.00${\pm}$1.22, respectively, after receiving 10, 15 and 20 mg ACAPE. The fertilized and cultured ova were able to develop into embryos up to the 32 cell stage. The present experiments demonstrated that multiple ovulations can be induced by CAPE and ACAPE successfully, and the ova resulted from the treatment retained the capability for further fertilization and embryonic development. These data provide new information to support the establishment of an in vitro culture system for future avian transgenesis studies.

• Journal of Advanced Navigation Technology
• /
• v.13 no.4
• /
• pp.509-514
• /
• 2009

In this paper, we designed and analyzed 256GB DRAM-based SSD storage using DDR1 memory and PCI-e interface. SSD is a storage system that uses DRAM or NAND Flash as primary storage media. Since the SSD read and write data directly to memory chips, which results in storage speeds far greater than conventional magnetic storage devices, HDD. Architecture of the proposed SSD system has performance of high speed data processing duo to use multiple RAM disks as primary storage and PCI-e interface bus as communication path of RAM disks. We constructed experimental system with UNIX, Windows/Linux server, SAN Switch, and Ethernet Switch and measured IOPS and bandwidth of proposed SSD using IOmeter. In experimental results, it has been shown that IOPS, 470,000 and bandwidth,800MB/sec of the DDR-1 SSD is better than those of the HDD and Flash-based SSD.

• Journal of KIISE:Databases
• /
• v.32 no.2
• /
• pp.142-150
• /
• 2005

A shared disks (SD) cluster couples multiple computing nodes, and every node shares a common database at the disk level. A great deal of research indicates that the SD cluster is suitable to high performance transaction processing, but the aggregation of SD cluster with real-time processing has not been investigated at all. A real-time transaction has not only ACID properties of traditional transactions but also time constraints. By adopting cluster technology, the real-time services will be highly available and can exploit inter-node parallelism. In this paper, we first develop an experiment model of an SD-based real-time database system (SD-RTDBS). Then we investigate the feasibility of real-time transaction processing in the SD cluster using the experiment model. We also evaluate the cross effect of real-time transaction processing algorithms and SD cluster algorithms under a wide variety of database workloads.

• Journal of Internet of Things and Convergence
• /
• v.10 no.2
• /
• pp.109-114
• /
• 2024

Enterprise storage systems that require high data reliability are applying RAID (Redundant Array of Independent Disks) systems to recover from data loss and failure. In particular, RAID 5 ensures space efficiency and reliability by distributing parity across multiple storage devices. However, when storage devices have different capacities, RAID is built based on the smallest capacity storage device, resulting in wasted storage space. Therefore, research is needed to solve this resource management problem. In this paper, we propose a method for RAID grouping of each independent NAND flash memory block in a RAID consisting of SSD (Solid State Disk) with external SSDs as well as internal SSDs. This method is divided into a policy for delivering block information inside SSDs to the RAID system and a policy for RAID grouping of physical addresses delivered from the RAID system. This method allows us to maintain a RAID that does not waste resources when SSDs of different capacities are grouped into RAID5. Finally, we demonstrate the effectiveness of the proposed method through experiments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1998.04a
• /
• pp.211-217
• /
• 1998

A disk rotor dynamic analysis program called by DR. DAP is developed for disk drive spindle systems to analyze dynamic characteristics in operation and to estimate the effects of excitation sources. It is applicable to design for stabilization and to select parts of disk drive spindle systems. The disk drive spindle system in this program is modeled as a flexible shaft with multiple flexible disks, which is supported by bearings and driven by electric motor, and its complicated coupled vibration characteristics are analyzed by using a substructure synthesis technique with the assumed-modes method. All the coupled modes of interest can be well predicted by the example of a three disk hard disk drive with the three tuning parameters. It is also shown that, with the introduction of the excitation sources associated with the defects of ball bearing systems, the magnetic unbalance of spindle motor, the program can well predict the stability of the system, i.e., the possibility of resonance.

• The Bulletin of The Korean Astronomical Society
• /
• v.39 no.2
• /
• pp.86.1-86.1
• /
• 2014

Two substellar companion candidates with planetary mass, around a T-Tauri star in the ${\rho}$ Ophiuchi star-forming region, are discovered by results of Subaru Telescope's near-infrared imaging. Candidates are separated by 1400au and 500au. If these candidates were real companions, they are the widest-orbit and the lowest mass planetary-mass companions(PMCs) candidates. This discovery may suggest that PMCs form via extreme case of cloud core fragmentation for multiple stars. And also stellar disk are imaged by HiCIAO, hight contrast instrument for exoplanets and disks, with Subaru Telescope. This could be the first case, which imaged both of planetary mass companions and disk around same star. Even two companions candidates are not bounded around the star, they still could be one of the lowest mass objects. In this presentation, I will discuss about observations and confirmations of these objects, and the latest results about their properties.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1997.10a
• /
• pp.43-49
• /
• 1997

A rotating rigid disk, attached on a flexible shaft or supported by a torsional spring, experiences precessional whirling due to gyroscopic moment loading. It is well known in rotor dynamics area that, as the rotational speed increases, the precessional mode of the rotating rigid disk starts splitting into two: forward and backward precessional modes. On the other hand, it is also well known in disk vibration area that a rotating flexible disk also shows another kind of mode splitting phenomenon due to the rotation, resulting in forward and backward traveling waves. When rotating multiple flexible disks are coupled in vibration with the supporting Flexible shaft, the associated mode splitting should be compatible with the two seemingly different vibration analysis methods. This paper investigates the possibility of fusing the precessional and traveling wave mode splittings so that the bending coupled disk vibrations in HDD spindle systems can be better understood.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2011.11a
• /
• pp.123-125
• /
• 2011

A SATA hard disk has been widely used in recent years and NCQ is one of its crucial features. Despite the development from IDE to SATA disk, there is still much room for improvement for a SATA disk. In addition, until now a hard disk is a black box to us and it is very hard to make research at the level of a disk controller. To enhance the performance of NCQ, we try to do I/O clustering over the requests, which combines multiple sequential requests into a single large one. To evaluate the effect of an I/O clustering mechanism, we created a simple but practical SATA hard disk simulator. Experimental results show that the proposed approach is effective in enhancing the I/O performance of a SATA disk.