• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.3
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• pp.299-307
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• 2007

In this study, a new concept for simulating a physical damage of tunnel shotcrete lining due to a long-term chemical deterioration has been proposed. It is known that the damage takes place mainly by internal cracks, reduction of stiffness and strength, which results mainly from volume expansion of the lining and corrosion of cement materials, respectively. This damage mechanism of shotcrete lining appears similar in most kinds of chemical reactions in tunnels. Therefore, the mechanical deterioration mechanism induced by a series of chemical reactions was generalized in this study and mathematically formulated in the framework of thermodynamics. The numerical model was implemented to a 3D finite element code, which can be used to simulate behaviour of tunnel structures undergoing external loads as well as chemical deterioration in time. A number of illustrative examples were given to show a feasibility of the model in tunnel designs.

• Journal of the Korean Society of Radiology
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• v.81 no.6
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• pp.1348-1363
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• 2020

The newly revised 2018 Organ Injury Scale (OIS) has a similar format to the previous American Association for Surgery and Trauma (AAST) Emergency General Surgery Grading System, dividing the criteria for grading solid organ damage into three groups; imaging, operation, and pathology. The most significant alteration in the OIS system 2018 revision is the incorporation of multidetector CT (MDCT) findings of vascular injury including pseudoaneurysm and arteriovenous fistula. Similar to the previous OIS, the highest of the three criteria is assigned the final grade. In addition, if multiple grade I or II injuries are present, one grade is advanced for multiple injuries up to grade III. This pictorial essay demonstrates the MDCT findings of solid organ injury grades based on the 2018 OIS system.

• The Journal of Engineering Geology
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• v.20 no.1
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• pp.89-100
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• 2010

Although various methods for determination of damage threshold in rock have been suggested, clear damage thresholds were determined by some methods, but different thresholds were measured by other methods. We determined the damage thresholds in Hangdeung granite using all the methods suggested, and investigated the best methods, applicability and errors of each method. The crack initiation threshold and the crack damage threshold which are important in investigation of characteristics of crack development and failure were verified by field strength ratio method and long-term constant load test. The crack closure stress and the crack initiation stress were 57.5 MPa and 77.6 MPa, and the most exact values were yielded by crack volumetric strain. The secondary crack initiation stress was 90.6 MPa and AE event count and AE event count rate were the effective methods. The volumetric stiffness, AE event count and AE event count rate were the most effective methods for determination of crack coalescence threshold and crack coalescence stress was 110.3 MPa. The crack damage stress was 127.5 MPa and was measured correctly by volumetric stiffness and AE event count rate. The ratio between crack initiation stress and uniaxial compressive strength was 0.47 which was very similar with the FSR value of 0.46. The ratio between crack damage stress and uniaxial compressive strength was almost the same as the ratio between long-term strength and uniaxial compressive strength, indicating that the crack initiation stress and the crack damage stress measured were correct.

• Journal of the Korean Geosynthetics Society
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• v.4 no.4
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• pp.23-37
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• 2005

The factors affecting the long-term design strength of geogrid can be classified into factors on creep deformation, installation damage, temperature, chemical degradation and biological degradation. Especially, creep deformation and installation damage are considered as main factors to determine the long-term design strength of geogrid. Current practice in the design of a reinforced soil structures is to calculate the long-term design strength of a geosynthetic reinforcement damaged during installation by multiplying the two partial safety factors, $RF_{ID}$ and $RF_{CR}$. This method assumes that there is no evaluation of synergy effect between installation damage and creep deformation of geogrids. This paper describes the results of a series of experimental study, which are carried out to assess the combined effect of the installation damage and the creep deformation for the long-term design strength of geogrid reinforcements. A series of field tests was carried out to assess installation damage of various geogrids with respect to different fill materials, and then creep tests are conducted to evaluate the creep deformation of both undamaged and damaged geogrids. The results indicated that the tensile strength reduction factors, RF, considering the combined effect between the installation damage and the creep deformation is less than that calculated by the current design method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.189-196
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• 2005

The effects of the impulse and the magnitude of the impulsive loads to the responses of the structure are analyzed with the safety criteria established with the peak load and impulse ratio. It is shown for the loadings with short duration that the impulse is dominant factor for the damage of the structures due to the inertial effect. On the other hand the magnitude of the load is dominant factor for the load with long duration due to the duration time long enough for the loads to overcome the inertia force. It is also shown that the peak particle velocity and the peak particle acceleration of the foundation have the same influences as the impulse and the magnitude of the loads do to the structures.

• Journal of the Korean Geosynthetics Society
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• v.3 no.4
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• pp.29-40
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• 2004

The factors affecting the long-term design strength of geogrids can be classified into factors on creep deformation, installation damage, temperature, chemical degradation, biological degradation. Especially, creep deformation and installation damage are considered as main factors to determine the long-term design strength of geogrids. This paper describes the results of a series of experimental investigation, which were conducted to assess the installation damage according to different fill materials and creep characteristic of various geogrids. The results of this study show that the installation damage and creep deformation of geogrids significantly depends on a row material and a manufacturing process of geogrids.

• Journal of the Korean Arthroscopy Society
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• v.15 no.2
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• pp.140-145
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• 2011

후방십자인대 손상의 이상적 치료는 아직까지도 확립되지 않았다. 과거 몇 십 년간 후방십자인대에 대한 지식과 슬관절 안정성에 대한 후방십자인대의 생역학에 대한 지식이 증가하였다. 특히 이중 다발에 대한 지식이 증가하고 이러한 모든 노력들은 후방십자인대의 해부학적인 특징을 최대한 복원하기 위해 이루어졌다. 재건술의 수술 방법은 특정 손상 양상에 따라 그에 맞게 이루어지는데 만성 손상의 경우나 remnant가 거의 존재하지 않는 경우에는 이중 다발을 재건하는 것이 만족스러운 결과를 보인다. 아직까지 이중 다발 후방십자인대 재건술의 결과에 대해서는 논란이 많은 것은 사실이나 장기 추시가 가능해지면 이중 다발 후방십자인대 재건술이 해부학적으로나 생역학적으로 더욱 정상에 가깝기 때문에 더 나은 장기적 결과를 보여줄 것으로 예상된다.

• The Korean Journal of Financial Studies
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• v.11 no.1
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• pp.1-36
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• 2005

한 시계열의 원래 관찰치가 본래 가지고 있는 정보를 하나도 잃지 않고 또한 손상시키지 않고 그대로 보존되며 계산이 용이하고, 뿐만 아니라 가능도함수나 비모수 추정함수를 계산함에 있어 수치적 불안정 잠재성이 존재하지 않도록 변환된 시계열을 얻을 수 있으면, 다시 말해 각종 통계량의 계산에 용이하게 적용 가능하되 원래 시계열이 보유하고 있는 모든 성질들은 추호도 손상시킴이 없이 이 시계열을 변환시킬 수 있는 변환방법이 존재한다면, 모수의 추정치와 검정통계량을 정확히 얻을 수 있을 것이다. 이와 같은 변환방법이 웨이브렛 변환이다. 이 변환은 푸리에 분석의 결점을 극복하되 후리에 변환이 적용되는 분야에는 거의 모두 적용 가능한 변환방법이다. 이 논문에서는 시계열의 웨이브렛 변환을 소개하고 이 변환이 재무시계열의 모형화에 한몫을 단단히 할 수 있다는 점을 밝히고자 한다. 그리고 웨이브렛 변환을 성공적으로 적용할 수 있는 주가과정을 하나의 예로 제시하여 웨이브렛 변환의 구체적 적용방법을 탐구하고자 한다. 웨이브렛의 주가 시계열의 적용방법의 한 예로 주가의 장기기억과정을 분석한다. 한국과 외국의 일별 주가지수의 수익률 시계열들이 장기기억과정을 따르는 시계열임이 발견되었다. 여러 형태의 웨이브들을 사용하여 검정하였는데 이 모두가 한결같이 주가지수가 장기기억성과정임을 지지하고 있다.

• Advances in pediatric surgery
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• v.5 no.1
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• pp.15-25
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• 1999

Injured spleens have been successfully managed without operation in a number of children; however, splenectomy or splenic-conserving surgery may not be avoided because of exsanguinating hemorrhage. This study was performed to evaluate the efficacy of splenic arterial embolization (SAE) to control hemorrhage from injured spleens in children. We compared the outcomes of two groups of children with splenic injury. The first group (G1) consisted of eighteen children who were managed with conventional selective nonoperative treatment between 1993 and 1994. The second group (G2) consisted of 23 children prospectively studied from 1996 to 1997 after SAE was added in the management protocol of splenic injury. The criteria for SAE were grade III or IV injury, extravasation of contrast material revealed by CT, or unstable vital signs without evidence of associated injuries. Laparotomy was performed in 6 patients of G1 (33.3 %), 2 of whom had associated injuries. Five underwent splenectomy and the overall salvage rate in G1 was 72.2 % (13/18). In G2, eight patients (34.8 %) had SAE, which stopped bleeding successfully in all patients. Two of G2 (8.7 %) had laparotomy because of associated injuries. Only one patient underwent splenectomy and the salvage rate was 95.6 % (22/23). No patients required transfusion after SAE. In conclusion, the SAE effectively controlled hemorrhage from injured spleens. More spleens were salvaged with a reduced laparotomy rate after application of SAE in splenic injury.

• KEPCO Journal on Electric Power and Energy
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• v.7 no.1
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• pp.69-72
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• 2021

한전에서 운영중인 요르단 알카트라나발전소에서 발전기 고정자권선 전계완화 절연물의 손상되었다. Overlap 부위의 정비를 수행한 결과를 분석하였고, 손상원인을 규명하여 불시정지로 인한 손실을 최소화하기 위한 단기대책과 장기적인 대책을 제시하였다.