• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.224-234
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• 2019

Waterproof layers are installed in civil engineering structures and bridge construction is commonly finished by applying a layer of regular or asphalt concrete above the waterproof layer. However, asphalt materials are susceptible to melting at high temperature due to its superior temperature sensitivity, and this causes the waterproofing material to melt due to the high temperature of the asphalt concrete, thereby increasing the defect occurrence rate due to the thickness reduction. In this study, tensile strength and elongation of hard and soft type of MMA(Methyl Methacrylate) applied to bridges were compared in accordance to standard performance criteria based on different mixture ratios. Results of comparative testing showed that hard MMA resin can display a satisfactory tensile strength, and soft MMA resin displays satisfactory elongation properties, but as the two resin types are separately used, neither types are able to satisfy the standard requirements outlined in KS F 4932. When the amount of the powder exceeds 56.25% of the total amount, voids are generated on the surface after curing and self leveling was impossible and a heterogeneous surface is formed. Furthermore, when the hard resin: soft resin: powder mixture ratio was set to 15g: 85g: 150g. the tensile strength was $1.5N/mm^2$ and the elongation percentage was 133% which satisfy the tensile performance of KS F 4932.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.2
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• pp.143-151
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• 2013

NAND flash-based SSDs (Solid State Drive) have advantages of fast input/output performance and low power consumption so that they could be widely used as storages on tablet, desktop PC, smart-phone, and server. But, SSD has the disadvantage of wear-leveling due to increase of the number of writes. In order to improve the lifespan of the SSD, a variety of data deduplication techniques have been introduced. General fixed-size splitting method allocates fixed size of chunk without considering locality of data so that it may execute unnecessary chunking and hash key generation, and variable-size splitting method occurs excessive operation since it compares data byte-by-byte for deduplication. This paper proposes adaptive chunking method based on application locality and file name locality of written data in SSD-based server storage. The proposed method split data into 4KB or 64KB chunks adaptively according to application locality and file name locality of duplicated data so that it can reduce the overhead of chunking and hash key generation and prevent duplicated data writing. The experimental results show that the proposed method can enhance write performance, reduce power consumption and operation time compared to existing variable-size splitting method and fixed size splitting method using 4KB.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.105-113
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• 2013

RAID systems have been widely used by connecting several disks in parallel structure. to resolve the delay and bottleneck of data I/O. Recently, SSD based RAID systems are emerging since SSDs have better I/O performance than HDD. However, endurance and power consumption problems due to frequent write operation in SSD based RAID system should be resolved. In this paper, we propose a de-duplication method of parity disk in SSD based RAID system with expensive update cost. The proposed method segments chunk of parity data into small pieces and removes duplicate data, therefore, it can reduce wear-leveling and power consumption by decreasing write operation for duplicated parity data. Experimental results show that bit update rate of the proposed method is 16% in total disk, 31% in parity disk less than that of existing method in RAID-6 system using EVENODD erasure code, and the power consumption of the proposed method is 30% less than that of existing method. Besides the proposed method is 12% in total disk, 32% in parity disk less than that of existing method in RAID-5 system, and the power consumption of the proposed method is 36% less than that of existing method.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.472-479
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• 2000

A persimmon harvesting vehicle that can be operated in hilly orchards as well as a manipulator that can be used to harvest persimmons located in remote positions in the trees were designed and developed. The vehicle could be operated with keeping balanced position in an inclined field and its working platform could be moved up and down easy to approach fruits in a remote region with the aids of a hydraulic and a electrical and electronics systems. The weight of the vehicle was 927 kg and the center of gravity was located at 427 mm to the inner side from the center of a right driving caterpillar, 607 mm to a rear axle from the center of a front axle, and 562 mm to upward from ground. The automatic level control sensor for leveling the working platform was activated within 14.5 ∼ 16.5 degrees of slope variation. The total length of the manipulator was 1.39 m and weight is 975 g. It was powered by a 12 V geared motor to detach persimmon fruits with a rotational force. The gripper was made of plastic and rubber to increase a frictional force. In a performance evaluation test, static tipping angle, dynamic tipping angle toward front side when the vehicle was moving downward, climbing angle, driving speed of the vehicle were measured or calculated. In persimmon harvesting tests 24.9% of yield was increased by hand picking with the aid of the vehicle and additional 7% of yield were increased when the manipulator was used. Therefore, 99010 of total possible yield was achievable when both of the vehicle and the manipulator were used for the manual persimmon harvesting. Increase in 22.5% of total yield was achieved with the manipulator only.

• Journal of Korean Library and Information Science Society
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• v.52 no.4
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• pp.79-102
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• 2021

This research is based on open data from the National Library Statistics System and Seoul Survey 2020 from Seoul to analyze the Seoul citizens' usage of public libraries. For such purposes, this research compared and diagnosed the condition of public libraries services at 25 districts of Seoul, focusing on objective indicators of library management and general usage records to understand the correlations between the two. Objective indicators such as budgets, human labor, the number of books, and total ground area were compared with usage records of different classes of Seoul citizens, organized by the citizens' place of living, educational background, and monthly household income. As a result of the research, the correlation between the objective indicators and public usage records of different classes was confirmed. Seoul citizens' usage of public libraries and reading tendency were identified. In addition to, a balanced development of the public libraries in Seoul was proposed to overcome regional disparities and leveling the service level by investigating usage behavior and reading tendency of the public libraries in Seoul.

• Journal of the Korean Geotechnical Society
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• v.38 no.12
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• pp.67-78
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• 2022

In this study, the measurement results of the coastal deep soft ground buried in the upper part of the dredged clay were analyzed and compared with the current specification standards. Based on the results, a suitable proposal was suggested for the selection, installation, data arrangement, and analysis of each instrument used in the deep soft ground improvement construction. The pore water pressure meter has a range of 1.5 times or more of the expected measurement range, considering the field conditions of the soft ground. The groundwater level meter installed in the horizontal drainage layer checks the change in the groundwater level during the embanking as well as the performance of the catchment well and the horizontal drainage layer. Therefore, it is important to manage so that the groundwater level exists inside the horizontal drainage layer during embanking. It is enough to install the inclinometer in the gravel layer below the soft ground or weathered rock with an N value of 40 or more for the deep soft ground. It seems desirable to install a screw type for differential settlement meter. However, the screw type should not settle due to its own weight. Considering that it is a dredged landfill where subsidence occurs significantly, it is sufficient to manage the tolerance of leveling at about 10 mm (L is the one-way distance (km)).