• 터널과지하공간
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• 제16권4호
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• pp.313-325
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• 2006

본 연구에서는 이방성 암반의 방향성 및 측압조건이 터널 변형거동에 미치는 영향을 조사하기 위하여 서로 다른 15가지 이방성 터널 모형에 대해 축소모형실험을 실시하였다. 이를 위해 모래 석고 물의 중량비를 달리한 모형재료에 대한 물성 실험을 통하여 모형재료의 특성을 연구하였다. 대부분의 이방성 터널 모형은 응력이 집중되는 곳에서 전단파괴 현상을 보였으며 절리면을 따라 미끄러짐이 발생하여 절리면의 경사 방향이 터널 변형거동에 큰 영향을 미친 것으로 나타났다. 절리 경사가 $30^{\circ}$보다 작은 모형에서는 반팽창현상이 두드러지게 나타났으며 절리경사가 $50^{\circ}$인 모형은 측압조건에 관계없이 수직 및 수평 내공변위가 가장 작게 나타나 실험된 모형중에서 가장 안정적인 모형으로 판단된다. 또한 모형터널의 파괴 및 변형양상은 측압계수 조건에 따라 매우 상이하게 나타났다.

• 한국통신학회논문지
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• 제27권1B호
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• pp.114-124
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• 2002

본 논문에서는 실내 전파환경에서의 페이딩을 분석하기 위하여 영상법 기반의 3차원 광선추적법에 패치산란모델을 첨가한 모델을 제시하였다. 영상법 기반의 광선추적법은 정확한 경로를 얻을 수 있다는 장점 때문에, 안테나의 빔패턴 및 편파, 그리고 전파의 진행에 따른 편파를 고려함으로써 페이딩 특성 분석이 가능하다. 또한 실내 구조물을 모델링하기 위한 패치산란모델은 패치형태의 직사각형 평면에 대한 RCS (Radar Cross Section)를 이용하여 입사에 대한 산란현상을 정의한 것으로써, 책상이나 테이블 같은 평면적인 실내 구조물에 대한 산란현상을 각각의 구조물에 대한 영상 안테나를 발생시키는 복잡한 과정 없이 간단하게 해석하기 위한 것이다. 제안된 모델은 신호강도 뿐만 아니라 채널의 페이딩 특성을 예측할 수 있기 때문에 안테나 종류별 편파 다이버시티 기법의 성능을 분석하는데 이용될 수 있다.

• Geomechanics and Engineering
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• 제12권4호
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• pp.611-626
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• 2017

The research reported herein is concerned with the model testing of piles socketed in soft rock which was simulated by cement, plaster, sand, water and concrete hardening accelerator. Model tests on a single pile socketed in simulated soft rock under axial cyclic loading were conducted and the bearing capacity and accumulated deformation characteristics under different static, and cyclic loads were studied by using a device which combined oneself-designed test apparatus with a dynamic triaxial system. The accumulated deformation of the pile head, and the axial force, were measured by LVDT and strain gauges, respectively. Test results show that the static load ratio (SLR), cyclic load ratio (CLR), and the number of cycles affect the accumulated deformation, cyclic secant modulus of pile head, and ultimate bearing capacity. The accumulated deformation increases with increasing numbers of cycles, however, its rate of growth decreases and is asymptotic to zero. The cyclic secant modulus of pile head increases and then decreases with the growth in the number of cycles, and finally remains stable after 50 cycles. The ultimate bearing capacity of the pile is increased by about 30% because of the cyclic loading thereon, and the axial force is changed due to the applied cyclic shear stress. According to the test results, the development of accumulated settlement is analysed. Finally, an empirical formula for accumulated settlement, considering the effects of the number of cycles, the static load ratio, the cyclic load ratio and the uniaxial compressive strength, is proposed which can be used for feasibility studies or preliminary design of pile foundations on soft rock subjected to cyclic loading.

• 한국치위생학회지
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• 제20권1호
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• pp.11-18
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• 2020

Objectives: We analyzed the correlation between physique and size of the dental arch of college students with normal occlusion. Methods: Ninety-nine college students filled out the prepared questionnaire. The length and width of the dental arch of the students was measured using a plaster model after taking an impression. The data were analyzed using the t-test and correlational analysis. Results: The maxilla arch length was 3.70 mm longer and the inter-molar width of the maxilla was 3.06 mm longer in men (both p<0.01) than in women. Additionally, the mandible was 3.66 mm longer in men as compared to those in the women (p<0.01). As height increased, there was increase in the body weight (α=0.683, p<0.01), maxilla arch length (α=0.373, p<0.01), molar width of the maxilla (α=0.214, p<0.05), and the mandible (α=0.280, p<0.01). The greater the weight increase, the greater the maxillary arch length increase (α=0.392, p<0.01), and the greater the molar width of the maxilla (α=0.336, p<0.01) and mandible (α=0.502, p<0.01) increase. Conclusions: As physical size (both height and weight) increased, the maxillary length and molar width also increased. Based on the results of this study, the cause of malocclusion, form and size of the dental arch, and stable occlusion can be used as basic data.

• 대한치과기공학회지
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• 제42권1호
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• pp.27-33
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• 2020

Purpose: This study is to compare and analyze the precision of glass fiber resin dentures. Methods: A lower edentulous model was prepared. Ten study models were produced using Type IV stone. Ten wax lower resin dentures containing artificial teeth were prepared. The lower wax denture was buried with plaster and deflasking was performed to remove the wax. Five conventional lower resin dentures and five glass fiber lower resin dentures were produced. The scanning spray was coated on the impression surface and then scanned. Independent sample t-test were performed using statistical software. Results: In the color different map, which is a qualitative evaluation, the green area of the precision of the conventional lower resin denture occupied the whole. The glass fiber conventional resin dentures had many negative and positive area. In quantitative evaluation, the RMS of conventional lower resin was 89.83 ㎛ and that of fiberglass resin was 224.92 ㎛. The two groups showed statistically significant differences (p<0.05). Conclusion: Conventional lower resin dentures were superior in precision, and glass fiber resin dentures would have to improve the process.

• 한국공간구조학회논문집
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• 제7권2호
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• pp.115-124
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• 2007

막 구조물을 설계하기 위해서는 우선 초기장력 도입으로 인한 구조물의 형상을 정확히 알아야 한다. 이를 위해서 모형을 통한 모델링이나 컴퓨터를 이용한 형상해석이 요구되며, 초기장력의 도입으로 형성되는 막 구조물의 곡면은 일반적으로 등장력 곡면이다. 이와 같은 특성을 가진 막 구조물은 모형만을 대상으로 형상을 구할 때에는 정량적으로 형상의 정보를 얻기가 힘들고, 형상해석만을 수행한 경우는 예기치 않은 문제가 발생하기도 한다. 또 설계자의 의도에 따른 형상은 실질적으로 등장력 곡면에 부합되지 않는 경우가 많고, 심지어 실현 불가능한 발생한다. 따라서 설계프로세스에 따른 구조물의 형상에 부합되면서 실현가능한 형상으로의 초기형상 결정과정은 막 구조물의 설계에 있어서 무엇보다 중요한 과정이다. 본 연구에서는 건축 설계프로세스에 따른 모델링과 수치적 형상해석과의 결과에 대한 차이를 살펴보고 피드벡 과정을 통하여 막 구조물의 초기형상을 결정하는 프로세스에 대해서 연구한다.

• Archives of Plastic Surgery
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• 제34권1호
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• pp.18-23
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• 2007

Purpose: Anthropometry can be divided into two methods, direct anthropometry and indirect anthropometry. The most ideal and accurate method is a direct anthropometry. However, it is difficult to measure in the case of children because of poor cooperation, and it lacks re-productivity. Cast model has advantages of three dimensional featuring, inexpensive and easy fabrication. This study is conducted to find out an accuracy of indirect anthropometry on cast model by comparing it with direct anthropometry. Methods: Total 48 cleft lip nasal deformity patients (unilateral, 40; bilateral, 8) were included in this study. Cast models were made before surgery under general anesthesia with alginate impression material and model plaster. Eleven linear measurements among 7 landmarks were taken as direct anthropometry before surgery with Castroviejo spreading caliper. At the same time, indirect anthropometry on cast model was done at the same linear distances as well. Results: Of the total 11 linear measurements, both ala lengths, both columella lengths, nose width, projective distance between facial insertion points of the ala, projective distance between the alar base points, right nostril floor width, and columella width were statistically correlated between indirect anthropometry on cast model and direct anthropometry. However, the nasal tip protrusion and the left nostril floor width were not statistically correlated. Conclusion: Accuracy of indirect anthropometry on cast model can be influenced by cast model fabrication techniques and correct identification of landmarks. Nasal tip protrusion could be reduced by compression of the nasal tip in the process of cast model fabrication and nostril floor width can be varied by muscle relaxation of anesthetics and incorrect identification of subalare in cleft lip nasal deformity. If sufficient care is taken to make cast model and to define landmarks exactly, indirect anthropometry on cast model can be a reliable method as direct anthropometry.

• 구강회복응용과학지
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• 제34권2호
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• pp.104-115
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• 2018

목적: 본 연구는 현재 시판되고 있는 구강스캐너를 사용하여 구강스캐너 정확도 평가를 위해 국제표준이 제안하고 있는 모형의 스캔이미지 획득이 가능한 지 분석하고, 이를 통해 표준모델이 가지고 있는 문제점을 파악하는 데 있다. 연구 재료 및 방법: ISO12836과 ANSI/ADA no.132에서 규정하는 국제표준을 참고하여 3D 프린터기를 이용하여 모델을 제작하였으며, 모델스캐너와 두 가지 구강스캐너를 이용하여 스캔을 하였다. 스캔이미지 획득 정도를 3등급으로 분류하여 스캐너의 성능을 비교하였으며, 모델 표면의 상태에 따른 이미지 획득 능력도 비교하였다. 결과: 모델 스캐너가 모든 모델에서 가장 우수한 이미지를 얻을 수 있었으며 TRIOS3는 둥근 형태의 구조물, CS3500은 각진 형태의 구조물에 대한 이미지 재현이 좋은 결과를 보였다. 표준 모델의 표면상태에 따른 스캔이미지 재현에서는 초경석고 모델이 스캐너 종류와 관계없이 가장 우수하였다. 3D 프린팅 모델의 경우, 표면에 파우더 처리를 한 모델에서 가장 우수한 스캔이미지를 얻을 수 있었다. 결론: ISO12836과 ANSI/ADA 132의 표준모델의 경우, 구강스캐너의 field of view (FOV)를 벗어나는 구조물을 스캔할 때 서로 다른 면인 것을 구분하는 기준점이 존재하지 않게 되면 연속적인 스캔 및 정합과정에서 정확한 이미지를 나타내지 못한다는 것을 알 수 있었다. 그러므로 단순한 패턴의 반복과 대칭구조를 가지지 않는 새로운 표준모델이 필요하다고 여겨진다.

• The Journal of Advanced Prosthodontics
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• 제10권4호
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• pp.279-285
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• 2018

PURPOSE. The aim of this clinical study was to assess the accuracy of the implants placed using a universal digital surgical guide. MATERIALS AND METHODS. Among 17 patients, 28 posterior implants were included in this study. The digital image of the soft tissue acquired from cast scan and hard tissue from CBCT have been superimposed and planned the location, length, diameter of the implant fixture. Then digital surgical guides were created using 3D printer. Each of angle deviations, coronal, apical, depth deviations of planned and actually placed implants were calculated using CBCT scans and casts. To compare implant positioning errors by CBCT scans and plaster casts, data were analyzed with independent samples t-test. RESULTS. The results of the implant positioning errors calculated by CBCT and casts were as follows. The means for CBCT analyses were: angle deviation: $4.74{\pm}2.06^{\circ}$, coronal deviation: $1.37{\pm}0.80mm$, and apical deviation: $1.77{\pm}0.86mm$. The means for cast analyses were: angle deviation: $2.43{\pm}1.13^{\circ}$, coronal deviation: $0.82{\pm}0.44mm$, apical deviation: $1.19{\pm}0.46mm$, and depth deviation: $0.03{\pm}0.65mm$. There were statistically significant differences between the deviations of CBCT scans and cast. CONCLUSION. The model analysis showed lower deviation value comparing the CBCT analysis. The angle and length deviation value of the universal digital guide stent were accepted clinically.

• 대한치과기공학회지
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• 제40권4호
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• pp.201-207
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• 2018

Purpose: The purpose of this study is to evaluate the fitness of lower jaw compete denture with glass fiber. Methods: Lower jaw edentulous model was selected as the master model. Ten study models were produced using Type IV stone(n=10). Lower jaw trial dentures were produced by the wax denture base and artificial teeth. Conventional complete denture (CD) group was fabricated by excluding glass fiber reinforcement (n=5). Glass fiber complete denture (GD) group was fabricated with glass fiber reinforcement (n=5). The lower jaw trial complete denture was invested using a plaster. PMMA resin was injected and curing was performed. The CD and GD groups measured the fit using silicone replica technology. The measured data was verified by t-test. Results: The anterior area of the CD group showed the smallest value. There was a statistically significant difference in the anterior area of the CD group and the GD group (p<0.05), but there was no statistically significant difference in the posterior area (p>0.05). Conclusion : Complete denture with glass fiber showed low fitness and further study is needed to apply it clinically.