• Progress in Medical Physics
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• v.15 no.2
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• pp.105-111
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• 2004

The parallel plate detector with dielectric film for dosimetry was designed to measure detection characteristic of 6 MV X-ray with medical linear accelerator. PTFE film was inserted into FEP films that are made by two one-side metal coated materials for ion source. The thicknesses of PTFE dielectric film was 100 ${\mu}{\textrm}{m}$ and the thickness of FEP dielectric film was 100 ${\mu}{\textrm}{m}$, respectively. This detector was fixed by two acrylic plate for physical hardness ad geometrical consistency. The geometrical condition for measurement with parallel-plate for detector was below; SSD=100 cm and the 5 cm depth between detector and phantom surface The major parameter of detector characteristics such as zero drift current, leakage current, charge response by applied voltage, reproducibility, linearity, TMR measurement, dose rate effect were measured. The zero drift currents are 8.3 pA and leakage currents are 10 pA. The charge response of applied voltage is showing linearity in 414 voltage. The measurement deviation of reproducibility in this detector is within 1% for dose and the linearity of applied dose shows in this detector. The TMR curves in phantom between this parallel plate detector and reference detector are matched within 3% deviation from maximum dose depth to 7.5 cm depth. It is considered that this dosimetric system is satisfactory for the purpose of the constancy check of the 6 MV x-ray from medical linear accelerator.

• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.221-228
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• 2004

In recent years building floors become larger and more spacious due to the development of new design methods and high strength and light weight materials. However, such long span floor systems may provide smaller amount of damping and have a longer period so that they may be more vulnerable to the floor vertical vibration. In Korea when floors are to be checked against the floor vertical vibration, the provisions developed in foreign countries have been used. However these guidelines have been developed based on human perception, which may vary from country to country. Also, Korea have particular floor systems, such as flat plate floor system of apartment building. This study attempts to evaluate the vibration performance of the floors in typical apartment buildings. Two different floors with the area of $28 m^2$ and $32 m^2$ were investigated. The criteria provided by ATC-1(1999), AISC-11(1997), AIJ(1991) and the local criteria developed in the previous study(Han, 2003) was used to check the acceptability of the floor vertical vibration.

• Journal of the Korean Geophysical Society
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• v.3 no.3
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• pp.153-160
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• 2000

Crustal velocities around the Korea peninsula are estimated and investigated from eight IGS permanent stations in eastern Asia area. GPS data for the period of May 1995 to December 1991 were analyzed to estimate daily coordinates of each site relative to TAEJ site. The velocity vector of each site is estimated from linear regression analysis with time series of coordinates. As the result, horizontal velocity components for four stations(Tsukuba, Usuda,Taiwan and Shanghai) using thirty-two months data were estimated with the standard error less than 1 mm/year. Our GPS velocity of six sites on the interiors of the Eurasia plate are similar within 1 cm/year with small differences respectively. On the other hand, the velocities of Tsukuba and Usuda showed the great differences from the other six sites. This can be explained by the fact that these two sites are enforced by the surrounding four plates, such as the Pacific, Eurasia, North America and Philipine plate. This study showed that the distance between Korea and Japan is shortened with the rate of 3 cm per year.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1109-1110
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• 2011

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.3
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• pp.217-226
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• 2003

This study is focused on the finding out load transfer mechanism in the ground near the tunnel during tunnel excavation in the jointed sandy ground. Laboratory model tests were performed on various cases of the overburden heights above tunnel crown, location, and degree of discontinuity planes. For model tests, a movable plate was installed in the midst of the bottom of sandy ground. This plate, moving downwards, was intended to model the stress relaxation during tunnel excavation. The load transfer was measured at the fixed separated bottom plates adjacent to the movable plate. As the result, the loosening zone and the load-transfer form around the tunnelling site were affected by the overburden height and the characteristics of discontinuous planes. And large loosening zone was developed along the discontinuous planes which were close to the tunnel.

• Journal of Sensor Science and Technology
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• v.10 no.1
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• pp.42-51
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• 2001

In this study, the effects of embedded optical fibers on the static properties under tensile load and dynamic properties under fatigue load of composite laminates were investigated by experimental tests and finite element analysis. Based on the results, it can be concluded that the embedded optical fiber sensors do not have significant effects on the structural integrity of the smart composite structures except when the sensors are embedded perpendicular to the adjacent reinforcing fibers under fatigue loading. An intensity-based optical fiber sensor was embedded in the crossply composite laminates to monitor the fatigue damage by detecting the stiffness changes of the laminates. The result of this experiment has shown that the intensity-based optical fiber sensor has large potential to monitor the fatigue damage of composite structures by detecting the stiffness changes of the structures with simple and inexpensive instruments and without complex post-processing of measured signals. In addition, the optical fiber sensor showed good resistance to fatigue loading and wide sensing ranges of stiffness.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.3117-3122
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• 2011

Skull A-P projections are the bi-product where the ESD (Entrance Surface Dose) for digital radiography is much higher than that conventional screen-film radiography. Therefore, the aim of this study was to reduce radiation doses to patients by using an added filter. This research focuses on the identification of the reduction of exposure to radiation based on the thickness of an added filter when applying the 'Skull A-P Projection' by using the 'Skull Phantom'. Also, an experiment was conducted to evaluate the qualitative decline of images through filtration. The measurement of one's exposed dose to radiation was executed by locating the 'Skull Phantom' on the position of the 'Skull AP,' while changing 16 kinds of added filters from 0.1 mmAl to 0.5 mmCu + 2.0 mmAl in terms of incident and penetrating doses. For the qualitative evaluation of images, a total number of 17 images have been acquired in the 'Skull Phantom' under the same conditions as those for the measurement of one's exposed dose. The acquired images have been evaluated by a radiological specialist. As a result, the images with a diagnostic value have been obtained by using such added filters as the compound filter of 0.2 mmCu +1.0 mmAl. The exposed dose absorbed on the 'Skull Phantom' is about 0.6 mGy. The value is only 12% of 5 mGy, the ESD value acquired on the 'Skull P-A Projection', which is recommended by the International Atomic Energy Agency (IAEA). As a result, depending on the parts of inspection, it is possible to reduce the patient's exposed dosage of radiation considerably by using an appropriate added filter.

• Journal of Korea Foresty Energy
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• v.21 no.1
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• pp.1-6
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• 2002

The following conclusions were obtained with measuring the surface temperature change of woodceramics which were made of MDF to identify usability of using them as a sub-material for heating system when installing Ondol heating floor. For this purpose, woodceramics were burned at the temperature of $650^{\circ}C$ and $800^{\circ}C$ 1. Surface temperature of woodceramics increased with the increase of density of woodceramics, but no significant difference was detected at the surface temperature when burning temperature was changed. 2. Surface temperature change under given temperature increased as time passed and it showed more increase in temperature at the burning temperature of 80$0^{\circ}C$. 3. Surface temperature change with the change in floor temperature increased u hen floor temperature increased and heating mechanism was fast with increase of measuring temperature.

• Journal of the Korean Orthopaedic Association
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• v.52 no.1
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• pp.59-64
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• 2017

Purpose: To analyze the result of a repeat discectomy for ipsilateral recurrent lumbar disc herniation and to investigate the potential factors that influenced the outcomes for this surgery. Materials and Methods: Fifty-nine patients, who underwent reoperation after lumbar discectomy with a minimum follow-up period of 2 years, were reviewed. The surgical outcome was assessed using the visual analogue scale (VAS) and Macnab classification, and the recovery rate was calculated in accordance with VAS. A statistical analysis was carried out by SPSS to evaluate the possible factors that may have influenced the outcomes of the reoperation. Results: The rate of reoperation after lumbar disc surgery due to the recurrent disc herniation was 6.0% (59/983 cases). The average recovery rate of VAS from the 1st operation was approximately 77%, and from the 2nd operation was 71%. According to the Macnab criteria, the results were "excellent" or "good" in 96% of cases. Statistical analysis revealed that there was no difference of the average recovery rate (p<0.05). There is no additional instability after repeat discectomy. Factors, such as smoking, precipitating traumatic events, and diabetes mellitus did not have much influence on the average recovery rate after repeat discectomy for ipsilateral recurrent lumbar disc herniation. Conclusion: The outcomes of repeat discectomy were satisfactory. Moreover, factors, smoking, trauma history and diabetic mellitus, only had a minor impact on the outcomes of a repeat discectomy.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.2
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• pp.8-17
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• 2008

This paper proposes a robust license plate extraction method from images taken under unconstrained environments. Utilization of the color and the edge information in complementary fashion makes the proposed method deal with not only various lighting conditions, hilt blocking artifacts frequently observed in compressed images. Computational complexity is significantly reduced by applying Hough transform to estimate the skew angle, and subsequent do-skewing procedure only to the candidate regions. The true plate region is determined from the candidates under examination using clues including the aspect ratio, the number of zero crossings from vertical scan lines, and the number of connected components. The performance of the proposed method is evaluated using compressed images collected under various realistic circumstances. The experimental results show 94.9% of correct license plate extraction rate.