• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.297-307
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• 2010

Recently, maintenance engineering and technology for civil and building structures have begun to draw big attention and actually the number of structures that need to be evaluate on structural safety due to deterioration and performance degradation of structures are rapidly increasing. When stiffness is decreased because of deterioration of structures and member cracks, dynamic characteristics of structures would be changed. And it is important that the damaged areas and extent of the damage are correctly evaluated by analyzing dynamic characteristics from the actual behavior of a structure. In general, typical measurement instruments used for structure monitoring are dynamic instruments. Existing dynamic instruments are not easy to obtain reliable data when the cable connecting measurement sensors and device is long, and have uneconomical for 1 to 1 connection process between each sensor and instrument. Therefore, a method without attaching sensors to measure vibration at a long range is required. The representative applicable non-contact methods to measure the vibration of structures are laser doppler effect, a method using GPS, and image processing technique. The method using laser doppler effect shows relatively high accuracy but uneconomical while the method using GPS requires expensive equipment, and has its signal's own error and limited speed of sampling rate. But the method using image signal is simple and economical, and is proper to get vibration of inaccessible structures and dynamic characteristics. Image signals of camera instead of sensors had been recently used by many researchers. But the existing method, which records a point of a target attached on a structure and then measures vibration using image processing technique, could have relatively the limited objects of measurement. Therefore, this study conducted shaking table test and field load test to verify the validity of the method that can measure multi-point displacement responses of structures using image processing technique.

• Progress in Medical Physics
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• v.26 no.3
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• pp.160-167
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• 2015

Radiation exposure from medical diagnostic imaging procedures to patients is one of the most significant interests in diagnostic x-ray system. A miniature x-ray intraoral tube was developed for the first time in the world which can be inserted into the mouth for imaging. Dose evaluation should be carried out in order to utilize such an imaging device for clinical use. In this study, dose evaluation of the new x-ray unit was performed by 1) using a custom made in vivo Pig phantom, 2) determining exposure condition for the clinical use, and 3) measuring patient dose of the new system. On the basis of DRLs (Diagnostic Reference Level) recommended by KDFA (Korea Food & Drug Administration), the ESD (Entrance Skin Dose) and DAP (Dose Area Product) measurements for the new x-ray imaging device were designed and measured. The maximum voltage and current of the x-ray tubes used in this study were 55 kVp, and 300 mA. The active area of the detector was $72{\times}72mm$ with pixel size of $48{\mu}m$. To obtain the operating condition of the new system, pig jaw phantom images showing major tooth-associated tissues, such as clown, pulp cavity were acquired at 1 frame/sec. Changing the beam currents 20 to $80{\mu}A$, x-ray images of 50 frames were obtained for one beam current with optimum x-ray exposure setting. Pig jaw phantom images were acquired from two commercial x-ray imaging units and compared to the new x-ray device: CS 2100, Carestream Dental LLC and EXARO, HIOSSEN, Inc. Their exposure conditions were 60 kV, 7 mA, and 60 kV, 2 mA, respectively. Comparing the new x-ray device and conventional x-ray imaging units, images of the new x-ray device around teeth and their neighboring tissues turn out to be better in spite of its small x-ray field size. ESD of the new x-ray device was measured 1.369 mGy on the beam condition for the best image quality, 0.051 mAs, which is much less than DRLs recommended by IAEA (International Atomic Energy Agency) and KDFA, both. Its dose distribution in the x-ray field size was observed to be uniform with standard deviation of 5~10 %. DAP of the new x-ray device was $82.4mGy*cm^2$ less than DRL established by KDFA even though its x-ray field size was small. This study shows that the new x-ray imaging device offers better in image quality and lower radiation dose compared to the conventional intraoral units. In additions, methods and know-how for studies in x-ray features could be accumulated from this work.

• Korean Journal of Heritage: History & Science
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• v.51 no.2
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• pp.170-203
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• 2018

From the period of Japanese colonialism up to the present, the researchers of archaeology and ancient history in Korea and Japan have paid much attention to the Honam area. Recently the ruins and relics of Wae lineage are often discovered at archaeological excavation sites in this region. In particular, at least 17 keyhole-shaped mounds were confirmed. The fact that three mounds were built on one site was newly revealed. Haniwa, a representative earthenware object of the Kofun period in Japan, was discovered as well. Therefore, the study of a historical meaning of archaeological materials about Wae lineage in the Honam area thus far must be reexamined. The ruins and relics of Wae lineage in the Honam area have been studied by selecting only specific cases. I identified all the ruins and relics of Wae lineage in the Honam area and analyzed the process of their change in this paper. I reviewed the relationship between Wae and Mahan, and the purpose of their negotiation based on archaeological characteristics, changing processes, and historical records on a quarterly basis. The ruins and relics of Wae lineage have increased and widely spread since the early period of the 5th century in the Honam area. This tendency continued until the late period of the 6th century. Weapons of Wae lineage were introduced and tombs in the style of Wae were built from the late 4th century to the early period of the 5th century (TG232~TK216 period). Sueki was introduced from the middle to late period of the 5th century (TK208~TK23 period). Keyhole-shaped mounds and tombs in the style of Wae were built from the late period of the 5th century to the early period of the 6th century (TK47~MT15 period). Japanese weapons were introduced from the middle to late period of the 6th century (TK10~TK209 period). In other words, the archaeological appearance is different in each quarterly period. There was an intensive diplomatic relationship between Baekje and Wae in the TG232~TK216 period. The military might be included in a mission of Wae. The materials of Wae lineage of this period are likely to be related to this. Sueki spread to the inland part of the Honam area in the TK208~TK23 period. This Sueki tends to be excavated on advantageous sites for the accumulation and distribution of supplies. The main characters of the keyhole-shaped mounds are presumed to be a group of traders which were under the control of a certain influence in the north of Kyushu. The keyhole-shaped mounds were abruptly built at some distance from mounds of the leaders in the Honam area. Additionally, there was no special influence base to which the characters of the keyhole-shaped mounds belonged in the surroundings. However, it might have been impossible for the group of traders to build the keyhole-shaped mounds without the support from the residents at all because there was a big difference in the building technology of the keyhole-shaped mounds between Japan and the Honam area. The time of building some keyhole-shaped mounds is the same or almost the same with that of the mounds built for the regional leaders. This proves a close relationship with the residents as well. What do the archaeological materials of Wae lineage which have been used and buried mean over 200 years in the Honam area? Geumgwan Gaya, which had exported iron resources to Japan, perished in the early period of the 5th century. Instead of Gaya, the Honam area might have played an important role to supply the necessary resources to Japan. We assume that the Japanese (Wae) actively worked to acquire various resources focusing on the underground resources in the Honam area.