• 한국지반신소재학회논문집
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• 제5권4호
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• pp.49-58
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• 2006

근래에 들어, 복합 라이너 시스템에서 점토차수재를 대신하여 GCL(Geosynthetic clay liner)의 사용이 급증하고 있다. 그러나, 과연 GCL의 수리학적 특성이 점토차수재와 대등하게 매립장 설계규준을 만족 시키는가의 여부는 오래동안 논란이 되어왔다. 실내시험 및 현장조사 결과 여러 가지 원인에 의해 GCL에 응력집중이나 비등방 분포 하중이 생길 때 국부적인 벤토나이트 유실로 팽윤된 GCL의 두께가 감소할 수 있음을 보여준다. 이 논문에서는 현장조사를 통하여 실내시험에서 얻어진 벤토나이트 유실을 확인하고 감소된 GCL 두께에 대한 수리학적 특성을 분석했다.

• Journal of Chest Surgery
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• 제48권1호
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• pp.82-85
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• 2015

Pyothorax-associated lymphoma is a relatively rare type of lymphoma that occurs in patients who have long histories of tuberculous pleuritis or induced pneumothorax. It is a type of non-Hodgkin's lymphoma of mainly the B-cell phenotype and is strongly associated with Epstein-Barr virus infection. A majority of these cases have been reported in Japan, although some cases have occurred in Western countries. Here, we describe a case of pyothorax-associated lymphoma in a patient with a 30-year history of chronic tuberculous empyema. The patient underwent decortication under the impression of chronic empyema with fistula. The histopathologic diagnosis was a diffuse large B-cell lymphoma associated chronic inflammation.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 추계 학술발표회논문집
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• pp.98-106
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• 2003

To construct pile-supported wharf structures that must support heavy horizontal loads, both vertical piles and batter piles are used. Batter piles are used to secure the bearing capacity against the horizontal loads. However, past case histories have shown that the heads of batter piles are vulnerable because these heads are subjected to excessive axial loads during earthquakes. Therefore, the aseismatic reinforcement method must be developed to prevent batter pile heads from breaking due to excessive seismic loads. Two different connecting methods of either inserting rubber or ball-bearing between batter pile head and upper plate were proposed to improve the aseismatic efficiency. Three large-scale pile head models(rubber type model, ball-bearing type model, and fixed type model) were manufactured and horizontal loading tests were peformed for these models. The results showed that the force-displacement relationship of the fixed type model was linear, but that of the rubber type model and the ball-bearing type model was bilinear. The increase in the horizontal displacement led to the increase in the horizontal stiffness of the rubber type models and the decrease in that of the ball-bearing type model. Compared with the values for fixed type model, the damping ratios of the rubber type model and the ball-bearing type model increased about 33~185％ and 263~269％, respectively.

• Geomechanics and Engineering
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• 제14권2호
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• pp.175-185
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• 2018

Sand Compaction Piles (SCPs) are constructed by feeding and compacting sand into soft clay ground. Sand piles have been installed with irregular cross-sectional shapes, and mixtures of both sand and clay, which violate the design requirement of circular shape according to the replacement area ratio due to various factors, including side flow pressure. Therefore, design assumptions cannot be satisfied according to the conditions of the ground and construction and the replacement area ratio. Two case histories were collected, examined, and interpreted in order to study the effect of the shape of SCPs. The effects of the distortion of SCP shape and the mixture of sand and clay were studied with the results of large direct shear tests. The design internal friction angle was secured with the irregular cross-sectional sand piles regardless of the replacement area ratio. The design internal friction angle was secured regardless of mixed condition when the mixture of sand and clay was higher than the replacement area ratio of 65%. Therefore, systematic construction management is recommended with a replacement area ratio below 65%.

• Geomechanics and Engineering
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• 제16권6호
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• pp.577-588
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• 2018

A major concern in deep excavation project in soft clay deposits is the potential for adjacent buildings to be damaged as a result of the associated excessive ground movements. In order to accurately determine the wall deflections using a numerical procedure such as the finite element method, it is critical to use the correct soil parameters such as the stiffness/strength properties. This can be carried out by performing an inverse analysis using the measured wall deflections. This paper firstly presents the results of extensive plane strain finite element analyses of braced diaphragm walls to examine the influence of various parameters such as the excavation geometry, soil properties and wall stiffness on the wall deflections. Based on these results, a multivariate adaptive regression splines (MARS) model was developed for inverse parameter identification of the soil relative stiffness ratio. A second MARS model was also developed for inverse parameter estimation of the wall system stiffness, to enable designers to determine the appropriate wall size during the preliminary design phase. Soil relative stiffness ratios and system stiffness values derived via these two different MARS models were found to compare favourably with a number of field and published records.

• Imaging Science in Dentistry
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• 제49권3호
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• pp.201-208
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• 2019

Purpose: The aim of this study was to evaluate the characteristic features of oral and maxillofacial swellings that could be seen on ultrasonographic examinations. Materials and Methods: Fifty patients with oral and/or maxillofacial swellings were randomly selected, thorough case histories and clinical examinations were done, ultrasonographic examinations with Doppler imaging were performed, and the features of every group were studied. Finally, histopathological evaluations were performed to identify the final diagnosis, according to which patients were classified into 5 groups; group I: inflammatory/space infection and abscess swellings, group II: cystic swellings, group III: lymph node swellings, group IV: benign swellings, and group V: malignant neoplastic swellings. Results: A significant association (P<0.05), with a contingency coefficient of 0.88, was found between the histopathological and ultrasonographic diagnoses, with ultrasonography having a diagnostic accuracy of 89% in diagnosing maxillofacial swellings. The diagnostic accuracy of ultrasonography was 100% for lymph node and malignant swellings, followed by 98% for inflammatory and cystic swellings and 92% for benign swellings. The sensitivity of the ultrasonographic diagnosis was 100% for cystic, lymph node, and malignant swellings, followed by 91% for inflammatory swellings and 86% for benign swellings. Conclusion: Ultrasonographic features with Doppler imaging greatly aid in obtaining accurate diagnoses of oral and maxillofacial swellings. Ultrasonography is a recommended imaging tool for differentiating maxillofacial swellings and classifying them accurately.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제47권2호
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• pp.135-140
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• 2021

Since the first report of a nasal septal abscess (NSA) from a dental origin (1920), six articles have been published in the English literature to date. The most common cause of NSA is an infection of the nasal septal hematoma after trauma. This is a report of an uncommon cause of NSA with a dental origin. A PubMed search performed regardless of year and country using the terms ("nasal septal abscess") OR ("nasal septum abscess") initially yielded 229 articles. After screening, seven articles (eight patients) were selected. Addition of two related articles produced a total of nine articles (10 patients) to be included. The age of the included patients ranged from 7 to 69 years (mean, 32.82 years; standard deviation, ±23.86 years). The sex composition was as followed: males (n=7; 63.6%), females (n=4; 36.4%). Dental histories were various: periapical lesions, caries, extraction, endodontic therapy, and cystic lesions. The maxillary incisor dominated as the tooth of origin. Early diagnosis and treatment of NSAs are important to avoid not only facial deformity, but also severe complications (e.g., intracranial infection). If NSA is suspected in patients without facial trauma, the possibility of a dental origin, especially from the maxillary incisor area, should be considered.

• Geomechanics and Engineering
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• 제23권6호
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• pp.575-585
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• 2020

In this numerical study, the 2D dynamic behavior of a clayey basin and its effect on damage pattern over basin edge are investigated. To attain this goal, a fully nonlinear time domain analysis method has been applied. Then, the fragility curves of the considered two typical industrial structures for that certain point are estimated using the acceleration time histories recorded at each surface point. The results show that the use of the damage related parameters in site effect analyses, instead of amplification curves, can yield more realistic estimation of the basin dynamic response. In a distance about 150 m from outcrop at the basin edge, the differences between fragility curves increase when increasing the distance from outcrop with respect to the reference rock site. Outside this region and towards the basin center, they tend to occur in rather single curves. Furthermore, to connect the structural damage to the basin edge effect, the earthquake demand value at different points for two typical structures was evaluated. It was seen that the probability of occurrence of damage increases over 250 m from outcrop, while the effect of the basin edge was limited to 150 m in case of the basin edge evaluation by using fragility curves.

• Geomechanics and Engineering
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• 제30권1호
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• pp.1-10
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• 2022

Seismic ground response evaluation is one of the main issues in geotechnical earthquake engineering. These analyses are subsequently divided into one-, two- and three-dimensional methods, and each of which can perform in time or frequency domain. In this study, a novel approach is proposed to assess the seismic site response using two-dimensional transfer functions in frequency domain analysis. Using the proposed formulation, a program is written in MATLAB environment and then promoted utilizing the equivalent linear approach. The accuracy of the written program is evaluated by comparing the obtained results with those of actual recorded data in the Gilroy region during Loma Prieta (1989) and Coyote Lake (1979) earthquakes. In order to precise comparison, acceleration time histories, Fourier amplitude spectra and acceleration response spectra diagrams of calculated and recorded data are presented. The proposed 2D transfer function diagrams are also obtained using mentioned earthquakes which show the amount of amplification or attenuation of the input motion at different frequencies while passing through the soil layer. The results of the proposed method confirm its accuracy and efficiency to evaluate ground motion during earthquakes using two-dimensional model. Then, studies on irregular topographies are carried out, and diagrams of amplification factors are shown.

• Safety and Health at Work
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• 제14권3호
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• pp.259-266
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• 2023

Background: Recent research on occupational injuries in companies has faced difficulties in obtaining representative data, leading to studies relying on surveys or case studies. Moreover, it is difficult to find studies on how a company's industry characteristics affect occupational injuries. This study aims to address these limitations. Methods: We collected 11 years of disclosure data from 1,247 listed companies in the Korean stock market and combined it with their occupational injury histories collected by the Republic of Korea Occupational Safety and Health Agency (KOSHA) to build a dataset. We attempted to analyze a linear panel model by dividing the dataset into manufacturing, construction, and other industries. Results: The higher proportion of full-time employees and better job skills correlate with lower occupational injuries in other industries. The wage increase reduces occupational injuries in manufacturing and other industries, but the substitution effect produces the opposite outcome in construction. Also, foreign ownership and credit ratings increase effectively reduce occupational injuries mainly in the manufacturing industry. Conclusion: Our results suggest that in explaining the relationship between corporate characteristics and occupational injuries, it is necessary to consider the nature of the industry more closely, and in particular, employment and labor policies for preventing occupational injuries need to be selectively applied according to industry. In addition, to improve the limitations and increase the usability of the research results, further detailed studies are needed in the future.