• Journal of the Korean Wood Science and Technology
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• 제46권5호
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• pp.437-448
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• 2018

본 연구는 태백산맥을 기준으로 영동(고성군), 영서(홍천군), 영남(봉화군) 세 지역 간 소나무의 재질차이의 유무를 알기위해 물리적 특성을 조사하였다. 기건함수율 및 생재함수율(인위적)의 산지 간 차이를 보이지 않았다. 비중은 심재부와 변재부에서 봉화군 소나무가 두 산지보다 높았으며, 고성군과 홍천군 소나무 사이에는 심재부에서는 고성군 소나무가 높고 변재부에서는 홍천군 소나무가 고성군 소나무 보다 높게 나타났다. 심재부의 비중이 높게 나타난 고성군 소나무가 강도적으로 홍천군 소나무보다 클 것으로 판단된다. 수축율은 방사방향의 경우 산지 간 차이가 없고, 접선방향의 경우는 가도관장이 긴 봉화군 소나무가 높게 나타났다. 흡습율은 산지 간 차이가 거의 없는 것으로 나타났다. 이 결과로 소나무를 효율적으로 사용할 수 있고, 육종적으로 좋은 재질의 품종생산에도 도움이 될 것으로 생각한다.

• Journal of Chest Surgery
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• 제51권3호
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• pp.180-186
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• 2018

Background: Endovascular aortic repair (EVAR) is widely performed to treat infrarenal abdominal aortic aneurysms (AAAs), and related techniques and devices continue to be developed. Although continuous attempts have been made to perform EVAR in patients with unfavorable aortic anatomy, the outcomes are still controversial. This study examined the short-term outcomes of EVAR for the treatment of infrarenal AAAs in patients with a 'hostile' neck and unfavorable iliac anatomy. Methods: Thirty-eight patients who underwent EVAR from January 2012 to December 2017 were enrolled in this study. A hostile neck was defined based on neck length, angulation, the presence of an associated thrombus, or a conical shape. Unfavorable iliac anatomy was considered to be present in patients with a short common iliac artery (<15 mm) or the presence of aneurysmal changes. Results: No perioperative mortality was recorded. No significant differences were found depending on the presence of a hostile neck, but aneurysmal sac shrinkage was significantly less common in the group with unfavorable iliac anatomy (p=0.04). A multivariate analysis performed to analyze the risk factors for aneurysmal progression revealed only unfavorable iliac anatomy to be a risk factor (p=0.02). Conclusion: Patients with unfavorable aortic anatomy showed relatively satisfactory short-term outcomes after EVAR. No difference in the surgical outcomes was observed in patients with a hostile neck. However, unfavorable iliac anatomy was found to inhibit the shrinkage of the aneurysmal sac.

• 공업화학
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• 제18권5호
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• pp.407-414
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• 2007

Moldflow사의 CAE 해석 프로그램인 MPI (Moldflow Plastics Insight)를 이용하여 PP(polypropylene)에 talc 20%가 들어간 수지를 사용한 자동차 공기 청정기 상부 덮개의 최적 공정을 찾았다. 핀 게이트가 하나인 기존 시스템을 CASE-1, 두 개로 새로운 공정을 CASE-2로 디자인하여 두 공정에 대한 유동 발란스 등을 비교하였다. CASE-2는 충진 시간이 더 짧아 생산성과 공정성의 향상이, 유동성과 부피수축율이 하부 덮개와 유사하게 나타나 조립성과 조립 후의 변형 및 물성발현이 향상되었다. 또한 전단속도와 전단응력의 해석결과, CASE-1의 문제점은 잔류 응력에 의한 것보다는 상 하부 덮개의 크기 차이에 의한 것으로 판단되며, 결국 수지의 배향 문제는 게이트 구조를 최적화 함으로써 파손 문제를 해결할 수 있을 것이라 예상된다.

• 환경생물
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• 제20권4호
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• pp.386-390
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• 2002

소나무 구과의 열개현상을 비교형태학적 형질을 통해 관찰하였다. 어린 구과에서는 조직의 분화가 완전하게 일어나지 않았지만 각 기관으로 분화되는 과정임을 알 수 있었다. 성숙한 구과와 동일 크기의 녹색 구과에서 유관속다발과 보강조직의 수축률은 각각 1.0∼l.5%와 14.0∼l6.0%였다 실편의 종단부는 유조직과 보강세포로만 구성되어 있었고, 중앙부는 종단부와 기부 두께가 비슷하였다. 기부는 실편과 실편 받침이 있어 더욱 두꺼웠으며, 유관속다발보다 보강조직이 2배 이상 두껍게 나타났다. 결론적으로 구과가 완전 성숙하여 건조됨에 따라, 종단부는 보강조직으로만 구성되어있어 조직내 수축만 일어나고 중앙부는 두 조직간 두께가 비슷해 밖으로 휘지 않는다. 그러나 실편내 기부에서 배축면에 위치한 보강조직이 두껍고, 유관속다발보다 보강조직에서 수축률이 훨씬 크므로 실편의 기부가 밖으로 펴지게 되어 구과는 열개된다.

• 대한치과보철학회지
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• 제39권3호
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• pp.250-259
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• 2001

Since the late 1930s, acrylic resins have been the materials of choice for the fabrication of complete denture bases. It has excellent esthetic properties, adequate strength, low water sorption, and low solubility. But acrylic resin has disadvantage of processing shrinkage that reduces denture retention and accuracy of denture occlusion. Metals also have been used in denture base material. Metals used in denture bases display excellent strength and dimensional stability. The major disadvantages associated with metal denture bases include increased cost, difficulty in fabrication, compromised esthetic qualities, and inability to re-base. The purpose of this study is to compare the artificial tooth movements of complete dentures with resin bases and metal bases after curing, deflasking, polishing immersion in water for 1 week and 4 weeks. Twenty-four maxillary complete resin denture bases with artificial teeth were fabricated. Twelve of them were resin based and other twelve of them were metal based. Fine crosses were marked on the incisal edges of right central incisors and distobuccal cusps of be second molars. Measurements were done for the changes of distances of reference points at the time of wax denture, after deflasking after decasting after polishing after immersion in water for 1 week and 4 weeks Meaurements were done to the accuracy of 0.001mm with a measuring microscope. The results were as follows : 1. Metal base showed significantly less tooth movement than resin base after curing and decasting (p<0.01). 2. Metal base showed significantly less tooth movement than resin base after polishing (p<0.01). 3. After immersion in water for 1 week and 4 weeks, metal base showed less movement than resin base. Difference was significant for anterior-posterior distances (p<0.01), but not significant for molar-to-molar distance (p>0.01). 4. 1 week and 4 weeks of immersion failed to compensate the initial processing shrinkage of metal and resin bases (p>0.01).

• 한국세라믹학회지
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• 제36권1호
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• pp.61-68
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• 1999

층상구조를 이루는 재료의 소결시 형성되는 다양한 결함 및 잔류응력을 고찰하기 위해 TZP-SUS계 및 ZT/SUS계다층재료와 porcelain/alumina 및 porcelain/Y-TZP 이층재료를 소결법으로 제조하였다. 상압소결로 제조한 다층재료에서는 층간의 소결수축율 차이에 의해 warping, splitting, 균열 등의 소결결함이 관찰되었으며, 중간층수 및 두께의 조절과 출발물질의 제어를 통해 이러한 소결결함이 완화됨을 알 수 있었다. Tape casting법으로 제조한 다층재료에서는 소결시 가한 압력에 의해 소결결함, 특히 warping이 제어됨을 확인할 수 있었다. 이층재료에서 형성되는 잔류응력은 vickers 압입법으로 관찰하였다. Porcelain/alumina에서는 porcelain 측의 계면에 작은 인장응력이, porcelain/Y-TZP에서는 압축응력이 형성됨을 확인할 수 있었으며, 이러한 잔류응력은 이층재료의 강도에도 영향을 미침을 알수 있었다. 결국 다층재료의 소결결함 및 잔류응력은 재료설계와 출발물질 상수에 영향을 받는다는 것을 알 수 있었다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제50권4호
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• pp.197-205
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• 2024

Objectives: To evaluate the effectiveness of decompression and various parameters that may affect volume change in cystic lesions. Patients and Methods: This retrospective study included patients who visited the Department of Oral and Maxillofacial Surgery at Ewha Womans University Medical Center between 2012 and 2022 for decompression of cystic lesions of the jaw. To measure volume changes, pre- and post-decompression cone-beam computed tomography was performed and reconstructed in three dimensions using Mimics 25.0 software (Materialise NV). A comparative analysis was performed based on sex, age, initial cyst volume, location, degree of cortical layer expansion, and pathologic diagnosis using the Mann-Whitney U and Kruskal-Wallis tests. Results: In all 20 cases, the duration of decompression was 7.84±3.35 months, and all patients successfully completed the decompression period without any complications. Significant differences were observed in the reduction rate and shrinkage speed based on the degree of cortical layer expansion. However, only the shrinkage speed (not the reduction rate) showed a significant difference with respect to the initial cyst volume. Significant differences were not observed based on sex, age, location, or pathologic diagnosis. Conclusion: Although the present study involved a small number of cases, the effectiveness of decompression was confirmed. In particular, 3D analysis overcame the shortcomings of previous studies of decompression and allowed earlier resection. Further studies with more patients are required to provide a rationale for these results and identify factors that influence decompression.

• Journal of Mechanical Science and Technology
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• 제14권1호
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• pp.19-29
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• 2000

A viscoelastic finite element analysis is presented to investigate residual stresses occurred in a laminated cylindrical shell during cure. An incremental viscoelastic constitutive equation that can describe stress relaxation during the cure is derived as a recursive formula which can be used conveniently for a numerical analysis. The finite element analysis program is developed on the basis of a 3-D degenerated shell element and the first order shear deformation theory, and is verified by comparing with an one dimensional exact solution. Viscoelastic effect on the residual stresses in the laminated shell during the cure is investigated by performing both the viscoelastic and linear elastic analyses considering thermal deformation and chemical shrinkage simultaneously. The results show that there is big difference between viscoelastic stresses and linear elastic stresses. The effect of cooling rates and cooling paths on the residual stresses is also examined.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 봄 학술발표회논문집
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• pp.141-149
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• 2000

This study performs the elastic and viscoelastic analysis of composite continuous beams with flexible shear connectors. Due to creep and shrinkage of the concrete part, the stress redistribution between the concrete slab and steel beam, and the evolution of the redundant restraint reaction occur with time. Using the equation of equilibrium, internal and external compatibility condition, and constitutive relationships, mathematical formulations are formulated. The solution is obtained by means of numerical step-by-step techniques and the finite difference method. Numerical parametric studies are performed to evaluate the stress redistribution, and the evolution of the redundant restraint reaction. The parameters include the stiffness and spacing of shear connectors, the age of concrete at loading, and the relative humidity.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 추계 학술논문 발표대회
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• pp.134-135
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• 2015

This study analysed compressive strength and the expansion characteristic to utilize a high volume mineral admixture mortar for a aerated mortar and a plastering mortar. In this experiment, the result shows that the compressive strength gain was satisfactory in case that WR was replaced within 5%. Also, the difference between WR1 and WR was insignificant. It shows that the drying shringkage properties at large was showed being satisfactory generally compared with Plain when WR was replaced, but the effect was not significant.