• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.6
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• pp.115-120
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• 2008

There are many typesof accelerometer sensor. There was mainly used high-g accelerometer to obtain data for vehicle in crash test. Accelerometer was mounted on test vehicle with mounting blocks. Test result can be influenced by condition of mounting i.e. bonding material and type of block. These influences can be evaluated to variation of sensitivity in calibration test. In this paper, Calibration test were carried out for 3 types of bonding material i.e. stud, beewax and double side tape. Other factor was taken into consideration by 3-types for mounting block. All test was conducted by sinusoidal signal vibrator up to 4500Hz. In order to investigate influence for sensitivity from different input voltage in the calibrator, the same test was repeated. Test results were compared with standard accelerometer data. Relative sensitivities and phases were showed small difference in sensitivity for bonding materials with one block, but significant one for another block and different input voltage below 1000Hz.

• Journal of Information Technology Applications and Management
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• v.11 no.2
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• pp.29-43
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• 2004

As the development of an information technique, gradually, mobile device is going to be miniaturized and operates at high speed. By such the requirements, the devices using a flash memory as a storage media are increasing. The flash memory consumes low power, is a small size, and has a fast access time like the main memory. But the flash memory must erase for recording and the erase cycle is limited. JFFS is a representative filesystem which reflects the characteristics of the flash memory. JFFS to be consisted of LSF structure, writes new data to the flash memory in sequential, which is not related to a file size. Mounting a filesystem or an error recovery is achieved through the sequential approach. Therefore, the mounting delay time is happened according to the file system size. This paper proposes a MJFFS to use a multi-checkpoint information to manage a mass flash file system efficiently. A MJFFS, which improves JFFS, divides a flash memory into the block for suitable to the block device, and stores file information of a checkpoint structure at fixed interval. Therefore mounting and error recovery processing reduce efficiently a number of filesystem access by collecting a smaller checkpoint information than capacity of actual files. A MJFFS will be suitable to a mobile device owing to accomplish fast mounting and error recovery using advantage of log foundation filesystem and overcoming defect of JFFS.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.2
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• pp.120-128
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• 2011

This paper presents an efficient method to analyze noise and vibration of marine diesel engines mounted on flexible hull structure. The analysis model should in general include the hull structure, leading to lots of computational efforts. To minimize the computational efforts, in this paper, the transfer synthesis utilizing the receptance at the mounting points is proposed. The procedure is then verified by comparing the results with those from the full model calculation. The effects of flexible hull structure on the acoustic power from engine block are finally investigated. It is found that the effect of the hull is significant when the receptance of hull structure is similar to or greater than that of mount or engine block.

• Journal of the Semiconductor & Display Technology
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• v.8 no.2
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• pp.31-35
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• 2009

In the silicon wafer polishing process, the mounting stage of silicon wafer on the ceramic carrier block has been using the polishing template which utilizes the porous surface instead of traditional wax mounting method. Here in this article, the experimental study is carried out in order to study the wafer demounting by water jet and the effects of operating conditions such as the water jet flowrate and the number of water jet nozzles on the wafer demounting time. It is found that the measured wafer demounting time is inversely proportional to the water flowrate per nozzle, regardless of number of nozzles used; implying that the stagnation pressure by the water jet impingement is the dominant key factor. Additionally, by using the transparent disk instead of wafer, the air bubble formation and growth is observed under the disk, making the passage of water flow, and subsequently demounting the wafer from the porous pad.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.3
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• pp.41-50
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• 2009

The flash memory has many advantages such as low power consumption, strong shock resistance, fast I/O and non-volatility. And it is increasingly used in the mobile storage device. Many researchers are studying the YAFFS, NAND flash file system, which is widely used in the embedded device. However, the existing YAFFS has two problems. First, it takes long time to mount the YAFFS file system because it scans whole spare areas in all pages. Second, the cleaning policy of the YAFFS does not consider the wear-leveling so that it cannot guarantee the duration of data completely. In order to solve these problems, this paper proposes a new content-based YAFFS that consists of a mounting time reduction technique and a content-cleaning policy by using content-based block management. The proposed method only scans partial spare areas of some special pages and provides the block swapping which enables the wear-leveling of data blocks. We performed experiments to compare the performance of the proposed method with those of the JFFS2 system and YAFFS system. Experimental results show that the proposed method reduces the average mounting time by 82.2% comparing with JFFS2 and 42.9% comparing with YAFFS. Besides, it increases the life time of the flash memory by 35% comparing with the existing YAFFS whereas no overheat is added.

• Journal of Korea Multimedia Society
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• v.11 no.5
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• pp.651-660
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• 2008

Flash memory is widely used in embedded systems because of its benefits such as non-volatile, shock resistant, and low power consumption. However, NAND flash memory suffers from out-place-update, limited erase cycles, and page based read/write operations. To solve these problems, YAFFS and RFFS, the flash memory file systems, are proposed. However YAFFS takes long time to mount the file system, because all the files are scattered all around flash memory. Thus YAFFS needs to fully scan the flash memory. To provide fast mounting, RFFS has been proposed. It stores all the block information, the addresses of block information and meta data to use them at mounting time. However additional operations for the meta data management are decreasing the performance of the system. This paper presents a new NAND flash file system called ERFFS (Efficient and Reliable Flash File System) which provides fast mounting and recovery with minimum mata data management. Based on the experimental results, ERFFS reduces the flash mount/recovery time and the file system overhead.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.72-77
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• 2011

In this study, the natural frequencies and mode shape of an external mounting pod were verified using the modal analysis and modal testing technique for a pod mounted on an aircraft. The procedure associated with the FEM building of an external mounted pod to predict the dynamic behavior of aircraft structures is described. The simplified FEM reflecting the results of the modal testing of a pod is built through the optimization, applied to the structural dynamic model of an Aircraft, used to verified the stability of vibration and flutter of an aircraft.

• IEMEK Journal of Embedded Systems and Applications
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• v.13 no.5
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• pp.235-243
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• 2018

NAND flash memory has been widely used for embedded systems as storage device and the flash memory file systems such as JFFS2, YAFFS/YAFFS2 have been adopted by these embedded systems. The flash memory file systems provide the high performance and overcome the limitations of flash memory. However, these file systems don't solve the slow mount time problem when a sudden power failure happens. In this paper, we proposed a flash memory management method for enhancing the recovery performance. The proposed method manages the flash memory block type and stores the block type information at recovery image block. When file operations are occurred, our method stores the file information at the metadata block before and after the file operation. When mounting the flash memory, our method only scans the recovery image blocks and metadata blocks. The proposed method reduces the mount time by seeking the metadata block locations fast by using the recovery image blocks. We implemented the proposed method and evaluation results show that our method reduces the mount time 13 ~ 46 % compared with YAFFS2.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.6
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• pp.495-501
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• 2012

In this study, the natural frequencies and mode shape of an external mounting pod were verified using the modal analysis and modal testing technique for a pod mounted on an aircraft. The procedure associated with the FE model building of an external mounted pod to predict the dynamic behavior of aircraft structures is described. The simplified FE model reflecting the results of the modal testing of a pod is built through the optimization and will be applied to the structural dynamic model of an aircraft which is used to verified the stability of vibration and flutter of an aircraft.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.640-647
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• 2018

Many harbor structures have been constructed, and some structures are now under construction in Korea, which is a peninsular state and a logistics hub in Northeast Asia. Expansions and extensions of existing harbors are also being planned to meet increasing natural disaster threats. Wave-dissipation concrete blocks are recycled or discarded based on the personal experience of engineers only, and there are no safety checks or criteria. To check the safety of used blocks, material evaluations were done by visual inspection of blocks on the ground and under water and from 20 non-destructive measurements of the rebound hardness test and 3 concrete core samples. Wave-dissipation blocks are sometimes fully or partially damaged in the process of transferring and mounting them or during construction. Therefore, a safety check is essential for recycling blocks with an evaluation of materials while considering the construction phases. To do this, a block was modeled with a 3D finite element method using ADINA, and impact analyses were done according to the transfer, mounting, and construction phases. From the results of the impact analyses and material evaluation, the safety checks and reasonable evaluation of used blocks were examined, and detailed construction methods are proposed. The methods are expected to maximize the reuse of used wave-dissipation blocks from an economical point of view.