• Solar Energy
• /
• v.19 no.2
• /
• pp.29-36
• /
• 1999

Heat transfer characteristics of a low temperature latent heat storage system during the heat storage stage was examined for the circular finned tubes using fatty acid which shows the big density difference during melting as phase change materials. The heat storage vessel has the dimension of 530 mm height, 74 mm inside diameter and inner heat transfer tube is 480 mm in height and 13.5 mm outside diameter. Hot water was employed as the heat transfer fluid. During the heat storage stage, it was found that both conduction and natural convection were the major heat transfer mechanism. It was also found that the effect of natural convection on the heat transfer was more significant for the unfinned tube system than that for the finned tube system. The experimentally determined overall heat transfer coefficients were in the range of $50{\sim}250W/m^2K$ and the correlation for natural convection heat transfer as a function of Nusselt and Rayleigh number was proposed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11a
• /
• pp.360.1-360
• /
• 2002

Current information storage devices, such as HDD, CD/DVD-ROM/RW, probe-based memory and cabon nano tubes, are compared with biological information storage mechanisms in DNA and brain memory. Various biological components in living cells are analyzed based on "irreducible complexity" of intelligent design concept. Linear and arel density of information stored in the biological and mechanical storages are compared for the applications and developments of new storage devices.

• 한국전산유체공학회:학술대회논문집
• /
• 2002.10a
• /
• pp.127-132
• /
• 2002

Numerical and experimental works have been made in order to figure out the physical mechanism of thermal storage system for the determination of optimal design and to enhance the thermal efficiency of the system. To this end a computer program is developed and evaluated successfully against experimental data measured with a bench scale facility. Considering the thermal efficiency of storage is critically impaired by the mixing effect, the minimum flow mixing situation is calculated by the assumption of uniform plug-type flow as a reference condition. Further a parametric systematic calculations have been made for a hypothetical full-scale storage system with Fr, storage dimension, diffuser type and loading hour, etc.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.472_473
• /
• 2009

It is fascinated research theme to store electric energy as much as possible and to utilize it at the point of proper time. Especially, the demand for energy storage devices has been increased based on the interest for distributed generation and smartgrid. As the results for a number of researches on it, various types of energy storage devices have been developed. Each devices have its own dynamic characteristics, power capacity, and storage capacity followed by storage mechanism. In this paper, the comparison research for various energy storage devices has been performed based on power capacity, storage capacity, discharging time, lifetime, efficiency, and cost. Application researches of SFES(superconducting flywheel energy storage), characterized as 300kW-100kWh, have been performed also.

• Journal of the Korean Society for Precision Engineering
• /
• v.32 no.3
• /
• pp.243-251
• /
• 2015

In order to develop an automatic system for welding thin steel plates with curvature such as the corrugated membranes of an LNG storage tank, a rotating mechanism should be firstly designed for the torch to easily follow the weld seam with a constant distance and angle. In this study, a torch rotating mechanism consisting of three circular links, two square-type links and a torch link was proposed for automation of the welding process. A weld-seam tracking system with two axis slides and the proposed rotating mechanism was successfully simulated with a dynamic simulation software. A prototype tracking system was manufactured and a tracking test with the system was then carried out. The test results with tracking system showed that the rotating mechanism could be implemented and it was feasible to be used in automatic tracking of weld seam with curvature.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.26-26
• /
• 2003

Lithium storage electrodes for rechargeable batteries require mixed electronic-ionic conduction at the particle scale in order to deliver desired energy density and power density characteristics at the device level. Recently, lithium transition metal phosphates of olivine and Nasicon structure type have become of great interest as storage cathodes for rechargeable lithium batteries due to their high energy density, low raw materials cost, environmental friendliness, and safety. However, the transport properties of this family of compounds, and especially the electronic conductivity, have not generally been adequate for practical applications. Recent work in the model olivine LiFePO$_4$, showed that control of cation stoichiometry and aliovalent doping results in electronic conductivity exceeding 10$^{-2}$ S/cm, in contrast to ~10$^{-9}$ S/cm for high purity undoped LiFePO$_4$. The increase in conductivity combined with particle size refinement upon doping allows current rates of >6 A/g to be utilized while retaining a majority of the ion storage capacity. These properties are of much practical interest for high power applications such as hybrid electric vehicles. The defect mechanism controlling electronic conductivity, and understanding of the microscopic mechanism of lithiation and delithiation obtained from combined electrochemical and microanalytical techniques, will be discussed

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.12 no.3
• /
• pp.1002-1015
• /
• 2018

The advent of Internet of Things (IoT) and the evident inadequacy of Cloud networks concerning management of numerous end nodes have brought about a shift of paradigm giving birth to Fog computing. Fog computing is an extension of Cloud computing that extends Cloud resources at the edge of the network, closer to the user. Cloud computing has become one of the essential needs of people over the Internet but with the emerging concept of IoT, traditional Clouds seem inadequate. IoT entails extremely low latency and for that, the Cloud servers that are distant and unknown to the user appear to be unsuitable. With the help of Fog computing, the Fog devices installed would be closer to the user that will provide an immediate storage for the frequently needed data. This paper discusses data migration between different storage types especially between Cloud devices and then presents a mechanism to migrate data between Cloud and Fog Layer. We call this mechanism Adaptive Deadline-Aware Scheme (ADAS) for Data migration between Cloud and Fog. We will demonstrate that we can access and process latency sensitive "hot" data through the proposed ADAS more efficiently than with a traditional Cloud setup.

• Applied Microscopy
• /
• v.30 no.1
• /
• pp.21-44
• /
• 2000

This study was carried out to investigate sperm storage, and the fate of spermatozoa in the female reproductive tract during hibernation in Korean greater horseshoe bat, Rhinolophus ferrumequinum korai. (1) Numerous sperm occurring in uterine lumen and glands were engulfed, and disappeared by the polymorphouclear leucocytes during the hibernation. (2) The stored sperm present in caudal isthmus of oviduct only, the heads of sperm toward the oviductal epithelial cells. Therefore, the projected sperm during the mating season are only alive in the caudal isthmus of oviduct in the long hibernation. The present result suggests that the caudal isthmus of oviduct may play an important role as the principal storage site in capacitation of sperm. (3) In March, the sperm do not occur in the caudal isthmus of oviduct. It suggests that the stored sperm in the caudal isthmus of oviduct should migrate to the ampulla of the site of fertilization to meet ovum in the period of ovulation. The results of this experiment consider that prolonged sperm storage, fate of sperm and sperm migration in the long hibernation have a kind of mechanism for the fertilization.

• International journal of advanced smart convergence
• /
• v.9 no.3
• /
• pp.253-259
• /
• 2020

Most of today's large-scale cloud systems and enterprise data centers are distributing resources to improve scalability and resource utilization. NVMe-over-Fabric protocol allows submitting NVMe commands to a remote NVMe SSD through RDMA (Remote Direct Memory Access) network. It is attracting attention recently because it is possible to construct a disaggregation storage system with low latency through the protocol. However, the current I/O stack of NVMe-over-Fabric has an inefficient structure for maintaining compatibility with the traditional I/O stack. Therefore, in this paper, we propose a new mechanism to reduce I/O latency and CPU overhead by modifying I/O path of NVMe-over-Fabric to pass through legacy block layer. According to the performance evaluation results, the proposed mechanism is able to reduce the I/O latency and CPU overhead by up to 22% and 24% compared to the existing NVMe-over-Fabrics protocol, respectively.

• Transactions of the Society of Information Storage Systems
• /
• v.6 no.2
• /
• pp.74-78
• /
• 2010

In this paper, 2-axis driving mechanism, which uses voice coil motor (VCM), is proposed to measure the friction force. The proposed VCM actuator consists of two parts; structural part and magnetic circuit part. Structural part is simplified to perform the friction experiments. Magnetic circuit part is composed of two parts. The experiments are accomplished by changing the mass of moving part. Through the experiments, optimal dimension is selected. Finally, the experimental results are verified and the optimal case is applied to the 2-axis driving mechanism, optical image stabilization actuator.