• Geomechanics and Engineering
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• 제38권6호
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• pp.553-569
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• 2024

In recent tunneling projects, encounters with multi-layered strata have become more frequent as the desired scale of tunneling increases. Despite substantial practical experience, the design of large-diameter shield-driven tunnels often simplifies the surrounding ground as uniform, overlooking the complexities introduced by non-uniform geotechnical factors. This study comparatively analyzed the influence of design factors, particularly segment stiffness and joint parameters, on segmental lining behavior in layered ground conditions using numerical methods. A comprehensive parametric study revealed the significant impact of deformative interaction between the lining and the soft top soil layer on overall tunnel behavior. Permitting lining deformation in the soft soil layer effectively mitigated the induced internal forces but resulted in considerable tunnel lining convergence, adopting a peanut-shaped appearance. From a practical design perspective, application of a soft segment with lower stiffness near the stiff soil layer is an economically advantageous approach, alleviating internal forces within an acceptable convergence level. Notably, around the interfaces between soil layers with different stiffnesses, the induced internal forces in the lining were minimized based on joint rotational stiffness and location. This indicates the possibility of achieving an optimal design for segmental lining joints under layered ground conditions. Additionally, a preliminary design method was proposed, which sequentially optimizes parameters for joints located near soil layer interfaces. Subsequently, a specialized design based on the proposed method for complex multi-layered strata was compared with a conventional design. The results confirmed that the internal force was effectively relieved at an allowable lining deflection level.

• Archives of Plastic Surgery
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• 제50권5호
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• pp.523-528
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• 2023

The Gustilo IIIB tibiofibular fractures often result in long bone loss and extensive soft tissue defects. Reconstruction of these complex wounds is very challenging, especially when it includes long bone grafts, because the donor site is limited. We describe our experience using a set of chimeric ipsilateral vascularized fibula grafts with a thoracodorsal artery perforator free flap to reconstruct the traumatic tibia defects. A 66-year-old male suffered a severe comminuted tibia fracture and segmented fibula fracture with large soft tissue defects as a result of a traffic accident. He also had an open calcaneal fracture with soft tissue defects on the ipsilateral side. All the main vessels of the lower extremity were intact, and the cortical bone defect of the tibia was almost as large as the fractured fibula segment. We used an ipsilateral vascularized fibula graft to reconstruct the tibia and a thoracodorsal artery perforator flap to resurface the soft tissue, using the distal ends of peroneal vessels as named into sequential chimeric flaps. After 3 weeks, the calcaneal defect was reconstructed with second thoracodorsal artery perforator free flap. Reconstruction was successful and allowed rapid rehabilitation because of reduced donor site morbidity.

• Journal of Korean Neurosurgical Society
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• 제44권1호
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• pp.8-14
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• 2008

Objective : The purpose of this study was to determine the efficacy of short segment fixation following postural reduction for the re-expansion and stabilization of unstable burst fractures in patients with osteoporosis. Methods : Twenty patients underwent short segment fixation following postural reduction using a soft roll at the involved vertebra in cases of severely collapsed vertebrae of more than half their original height. All patients had unstable burst fracture with canal compromise, but their motor power was intact. The surgical procedure included postural reduction for 2 days and bone cement-augmented pedicle screw fixations at one level above, one level below and the fractured level itself. Imaging and clinical findings, including the level of the vertebra involved, vertebral height restoration, injected cement volume, local kyphosis, clinical outcome and complications were analyzed. Results : The mean follow-up period was 15 months. The mean pain score (visual analogue scale) prior to surgery was 8.1, which decreased to 2.8 at 7 days after surgery. The kyphotic angle improved significantly from $21.6{\pm}5.8^{\circ}$ before surgery to $5.2{\pm}3.7^{\circ}$ after surgery. The fraction of the height of the vertebra increased from 35% and 40% to 70% in the anterior and middle portion. There were no signs of hardware pull-out, cement leakage into the spinal canal or aggravation of kyphotic deformities. Conclusion : In the management of unstable burst fracture in patients with severe osteoporosis, short segment pedicle screw fixation with bone cement augmentation following postural reduction can be used to reduce the total levels of pedicle screw fixation and to correct kyphotic deformities.

• 폴리머
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• 제38권5호
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• pp.596-601
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• 2014

방향족 구조를 포함하고 분자량이 조절된 polyamide(PA) 올리고머를 4-aminobenzoic acid와 12-aminododecanoic acid의 축합반응으로 합성하였다. 이 올리고머를 여러 분자량의 polytetramethylene glycol(PTMG)과 축합하여 PA를 hard segment로 하고 PTMG를 soft segment로 하는 열가소성 탄성체로서 poly(ether-b-amide)(PEBA)를 제조하였다. 합성된 PEBA의 구조는 FTIR과 $^1H$ NMR로 확인하였으며 DSC와 UTM을 사용하여 hard segment의 구조변화에 따른 열적특성과 기계적 성질의 변화를 비교해 본 결과 방향족 구조를 30%까지 포함할 때 결정성의 변화 없이 PEBA들의 용융온도는 높아졌고 초기 modulus와 strength는 더 크게 나타났다.

• Journal of Chest Surgery
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• 제9권2호
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• pp.139-142
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• 1976

A 33 year old male patient was admitted with 20 years history of recurrent hemoptysis. On clinical examination, mild left chest discomfortness and foul odored sputum with occasional rusty hemoptysis were principal complaints noted. Chest X-ray film revealed moderately advanced active tuberculosis lesion on both upper lung fields, and hen-egg sized mass surrounded with linear crescent of air shadow in a cavity on his left upper lung field. On left thoracotomy, dense pleural adhesions on left apicoposterior segmental surface with multiple lymphnode enlargements were noted, and the soft encapsulated mass of $5{\times}5{\times}8cm$ was localized in the apicoposterior segment of the left upper lobe. Apicoposterior segment with anterior segment of the left upper lobe was resected. Cavity was opened to find a rusty grayish colored, fragile mass, which was confirmed as "fungus ball" of aspergillosis by histological section slide with Gomori staining. The authors report one case of pulmonary aspergilloma superinfected with previous long standing pulmonary tbc.

• Structural Engineering and Mechanics
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• 제51권1호
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• pp.89-110
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• 2014

In this study, two beam-column elements based on the Elasto-Fiber element theory for reinforced concrete (RC) element have been developed and compared with each other. The first element is based on Elasto Fiber Approach (EFA) was initially developed for steel structures and this theory was applied for RC element in there and the second element is called as Fiber & Bernoulli-Euler element approach (FBEA). In this element, Cubic Hermitian polynomials are used for obtaining stiffness matrix. The beams or columns element in both approaches are divided into a sub-element called the segment for obtaining element stiffness matrix. The internal freedoms of this segment are dynamically condensed to the external freedoms at the ends of the element by using a dynamic substructure technique. Thus, nonlinear dynamic analysis of high RC building can be obtained within short times. In addition to, external loads of the segment are assumed to be distributed along to element. Therefore, damages can be taken account of along to element and redistributions of the loading for solutions. Bossak-${\alpha}$ integration with predicted-corrected method is used for the nonlinear seismic analysis of RC frames. For numerical application, seismic damage analyses for a 4-story frame and an 8-story RC frame with soft-story are obtained to comparisons of RC element according to both approaches. Damages evaluation and propagation in the frame elements are studied and response quantities from obtained both approaches are investigated in the detail.

• 대한구순구개열학회지
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• 제15권2호
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• pp.89-96
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• 2012

Le Fort 1 osteotomy or maxillary advancement with distraction osteogenesis (DO) is main treatment strategy for cleft palate patients with maxillary hypoplasia. Maxillary DO allows greater maxillary advancement within physiological limit than Le Fort 1 osteotomy. Moreover, it is better for velopharyngeal function. However, there is a greater tendency for an increase in nasal sound when maxilla is advanced excessively. Therefore, the advancement of anterior maxillary segment using DO has been utilized. It offers advantages such as an increase in the length of the palate, a prevention of the change in palatopharyngeal depth, and a preservation of the velopharyngeal function. Moreover, it will obliterate the necessity of bone graft, and it prevents the occurrence of oronasal or oroantral fistula. Finally, it stimulates the regeneration of the soft and hard tissue of alveolus, and subsequently makes possible to place implant.

• 한국정밀공학회지
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• 제20권10호
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• pp.226-232
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• 2003

Difficulties in the finite element modeling of human spine are evaded by using a stiffness matrix element whose properties can be characterized from experimentally measured stiffness of functional spinal units. Relative easiness is in that inter-vertebral discs, ligaments, and soft tissues connecting vertebrae do not need to be modeled as they are. The remarkable coupling effect between distinct degrees of freedom induced by the geometric complexity can be accommodated without much effort. An idealized block model with simple geometry for vertebra is employed to assess the feasibility of this method. Analyses are performed in both levels of motion segment and spinal column, and the result is compared with that from detail model. As far as the global behavior of spine is concerned, the simplification is found not to aggravate inaccuracy only if sufficient experimental data is provided and interpreted properly.

• 한국컴퓨터그래픽스학회논문지
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• 제7권1호
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• pp.1-9
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• 2001

소프트 물체 가시화 방법의 개선을 위해, 크기가 적응 분할되는 셀들로 공간을 분할 하는 방법과 자료 구조를 제안한다. 소프트 물체의 가시화를 위해서는 필드 함수 값을 공간상의 모든 점들에서 구할 수 있어야 한다. 본 논문에서는 주어진 한 점에 영향을 미치는 소프트 물체들을 인터벌 트리 (interval tree)라는 자료구조를 검색함으로써 계산할 수 있다. 인터벌트리는 물체들의 제한 용적 (bounding volume)에 기반하며, 점이나 선분들과 같은 단순한 뼈대 (skeleton)로부터 생성된 소프트 물체를 나타내고 있다. 각 구성 컴포넌트 (componet)의 제한 용적은 국지 필드 함수의 반경, 한계 값 (threshold value), 이웃한 컴포넌트들과의 관계 등으로부터 계산된다. 제안된 방법은 소프트 물체의 모델링이나 렌더링 등의 많은 응용에 사용될 수 있으며, 특히 대화형 모델링 과정에 유용하다.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 가을 학술발표회 논문집
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• pp.261-262
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• 2003

Shape memory polyurethane (PU) with soft and hard segments has been extensively researched since its discovery by Mitsubishi in 1988 [1]. Hard segments can be formed via hydrogen bonding and crystallization, function as physical crosslinks below melting point (Tm). The reversible phase transformation of the soft segment is responsible for the shape memory effect. (omitted)