• 대한치과보철학회지
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• 제33권2호
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• pp.177-197
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• 1995

The endodontically treated tooth is generally restored with post & core, owing to the brittleness and the loss of large amount of tooth structure. Although there have been lots of studies about the endodontically treated teeth, the three-dimensional quantitative studies about the strees distribution of them are in rare cases. In this study, it was assumed that the coronal portion of the upper incisou had severely damaged. After the root canal therapy it was post cored, and restored with PFM crown, for this experiment nine types of model were constructed : 1); long, 2); medium, 3); short gold post for the roots supported with a narmal alveolar bone, 4); long, 5); medium, 6); short gold post for the roots supported with an alveolar bone resorbed to its 1/3 of root length, 7); long, 8); medium, 9); short base metal post for the roots supported with an alveolar bone resorbed to its 1/3 of root length. Force was applied from two directions. One was functional maximum bite force(300N) applied to the spot just lingual to the incisal edge with the angle of 45 degrees to the long axis of the tooth, and the other one was horizontal force(300N) applied to the labial surface. The results analyzed with three-dimensional finite element method were as follows : 1. Stress was concentrated on the middle portion of the labial side dentin of the root and the lingual portion of the apical dentin of the root. Stress in the post showed maximum value at 2 mm above the post apex. 2. In case of the long post and base metal post, strees was concentrated on the apex of the root and the post. 3. In case of the longer post, the displacement on the post-cement interface was lessened. The gold post was more displaceable than the base metal post. 4. In case of the alveolar bone resorption, stress concentrated on the root and the post and displacement on the post-cement interface were increased.

• 한국지반공학회논문집
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• 제27권6호
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• pp.39-48
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• 2011

본 논문에서는 모형실험과 수치해석을 수행하여 유한한 두께의 모래지반 위에 놓인 얕은 띠기초의 지지력 평가방법을 제안하였다. 모형실험은 현장에서 채취한 모래시료를 사용하여 모래지반의 상대밀도와 대상 기초폭(B) 에 대한 모래층 두께(H)의 비(H/B)를 변화시키면서 1g와 20g 중력수준의 원심모형실험을 실시하였다. 실험결과, H/B가 감소함에 따라 지지력은 증가하고 침하는 감소하는 경향을 보였으며, 상대밀도 증가에 따라 지지력이 증가하는 경향도 나타났다. 강성지반 위 두께가 얇은 모래층의 지지력 평가방법을 제안하기 위하여 실험 결과 얻은 지지력 계수를 H/B의 영향을 고려한 Mandel & Salencon(1972)의 수정지지력계수와 비교 분석하였다. H/B에 따른 지지력계수비 관계를 제안하여 보수적인 설계에 적용할 수 있도록 하였다. 기초 제원, 사질토 상대밀도, H/B를 변화시킨 수치해석을 실시한 결과, 제시된 관계식과 유사한 경향성을 확인하였다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제31권3호
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• pp.248-254
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• 2005

The purpose of this study was to investigate the distribution of stress within the regenerated bone surrounding the implant using three dimensional finite element stress analysis method. Using ANSYS software revision 6.0 (IronCAD LLC, USA), a program was written to generate a model simulating a cylindrical block section of the mandible 20 mm in height and 10 mm in diameter. The $5.0{\times}11.5-mm$ screw implant (3i, USA) was used for this study, and was assumed to be 100% osseointegrated. And it was restored with gold crown with resin filling at the central fossa area. The implant was surrounded by the regenerated type IV bone, with 4 mm in width and 7 mm apical to the platform of implant in length. And the regenerated bone was surrounded by type I, type II, and type III bone, respectively. The present study used a fine grid model incorporating elements between 250,820 and 352,494 and nodal points between 47,978 and 67,471. A load of 200N was applied at the 3 points on occlusal surfaces of the restoration, the central fossa, outside point of the central fossa with resin filling into screw hole, and the functional cusp, at a 0 degree angle to the vertical axis of the implant, respectively. The results were as follows: 1. The stress distribution in the regenerated bone-implant interface was highly dependent on both the density of the native bone surrounding the regenerated bone and the loading point. 2. A load of 200N at the buccal cusp produced 5-fold increase in the stress concentration at the neck of the implant and apex of regenerated bone irrespective of surrounding bone density compared to a load of 200N at the central fossa. 3. It was found that stress was more homogeneously distributed along the side of implant when the implant was surrounded by both regenerated bone and native type III bone. In summary, these data indicate that concentration of stress on the implant-regenerated bone interface depends on both the native bone quality surrounding the regenerated bone adjacent to implant and the load direction applied on the prosthesis.

• Journal of Korean Neurosurgical Society
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• 제62권5호
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• pp.594-602
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• 2019

Objective : Although surgical intervention, such as percutaneous vertebroplasty (PVP), is the standard treatment for osteoporotic vertebral compression fractures (OVCFs), its effectiveness and safety are unclear. Therefore, this study compared the safety and efficacy of conservative treatment with that of PVP for acute OVCFs. Methods : Patients with single-level OVCFs who were treated conservatively with a transdermal fentanyl patch (TFP) or with PVP between March 2013 and December 2017 and followed-up for more than 1 year were retrospectively evaluated. Patients with pathologic fractures, fractures of more than two columns, or a history of PVP were excluded. Clinical outcomes (visual analog scale [VAS] scores) and radiographic factors were evaluated, including changes in the compression rate of the corresponding vertebral body at onset and after 12 months, sagittal Cobb angle at onset and after 6 and 12 months, and the incidence of adjacent compression fractures. Results : Of the 131 patients evaluated, 75 were treated conservatively using TFPs and 56 underwent PVP. We divided the patients into TFP and PVP groups. Their baseline characteristics (including sex, level of fracture, and bone mineral density T-scores) were similar, but the TFP group was significantly younger. The overall VAS score for pain showed a greater decrease during the first month (1 week after PVP) in the PVP group but remained similar in the two groups thereafter. The compression rate after 12 months increased in the TFP group but decreased in the PVP group. Five patients in the PVP group, but none in the TFP group, experienced adjacent compression fractures within 12 months. Conclusion : We compared clinical and radiological outcomes between the TFP and PVP groups. The immediate pain reduction effect was superior in the PVP group, but the final clinical outcome was similar. Although the PVP group had a better-preserved compression rate than the TFP group for 1 year, the development of adjacent fractures was significantly higher. Although TFPs seemed to be beneficial in reducing the failure rate of conservative treatment, the possibility of side effects (22.6%, 17 out of 75 patients, in this study) should be carefully monitored.

• 무역학회지
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• 제41권2호
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• pp.231-250
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• 2016

본 연구는 선하증권이 발행된 국제무역거래에서 화물이 서류보다 일찍 도착하여 원본 선하증권 없이 화물을 인도 받기 위해 국제적으로 통용되고 있는 상관행인 수입화물선취보증서를 기존 연구와 다른 관점에서 고찰하고자 한다. 혼합결제방식 하에서 발행된 수입화물선취보증서의 보증책임 범위를 판례를 통해 분석하고 국제적인 상관행으로 자리잡고 있는 수입화물선취보증서의 원활한 활용을 위한 다음 두 개의 대안을 제언한다. 첫째, 혼합결제방식을 이용한 경우, 수출업자는 상업송장을 발행함에 있어 결제방식의 결제대금을 각각 분리해서 발급해야 수입화물선취보증서의 보증책임 한도에 대한 명확한 의사표시가 이루어질 수 있을 것이다. 둘째, 수입화물선취보증서의 발행은행은 보증서 발행의 보증책임 범위를 명확히 하기 위해 기존 양식에 책임한도를 제한한다는 취지의 문구를 추가한 새로운 수입화물선취보증서 양식의 구축이 필요하다.

• 한국재료학회지
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• 제23권3호
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• pp.155-160
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• 2013

ZnO thin films co-doped with Mg and Ga (MxGyZzO, x + y + z = 1, x = 0.05, y = 0.02 and z = 0.93) were prepared on glass substrates by RF magnetron sputtering with different sputtering powers ranging from 100W to 200W at a substrate temperature of $350^{\circ}C$. The effects of the sputtering power on the structural, morphological, electrical, and optical properties of MGZO thin films were investigated. The X-ray diffraction patterns showed that all the MGZO thin films were grown as a hexagonal wurtzite phase with the preferred orientation on the c-axis without secondary phases such as MgO, $Ga_2O_3$, or $ZnGa_2O_4$. The intensity of the diffraction peak from the (0002) plane of the MGZO thin films was enhanced as the sputtering power increased. The (0002) peak positions of the MGZO thin films was shifted toward, a high diffraction angle as the sputtering power increased. Cross-sectional field emission scanning electron microscopy images of the MGZO thin films showed that all of these films had a columnar structure and their thickness increased with an increase in the sputtering power. MGZO thin film deposited at the sputtering power of 200W showed the best electrical characteristics in terms of the carrier concentration ($4.71{\times}10^{20}cm^{-3}$), charge carrier mobility ($10.2cm^2V^{-1}s^{-1}$) and a minimum resistivity ($1.3{\times}10^{-3}{\Omega}cm$). A UV-visible spectroscopy assessment showed that the MGZO thin films had high transmittance of more than 80 % in the visible region and that the absorption edges of MGZO thin films were very sharp and shifted toward the higher wavelength side, from 270 nm to 340 nm, with an increase in the sputtering power. The band-gap energy of MGZO thin films was widened from 3.74 eV to 3.92 eV with the change in the sputtering power.

• 한국토양비료학회지
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• 제7권3호
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• pp.127-135
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• 1974

The samples were taken from the following localities previously classified as "Akiochi" area: Yangpyung, Puchun, and Pyungtaik, all of Kyonggi-do province. Five soil profiles were described in the field, and taken to the laboratory for physical and chemical analysis and mineralogical analysis by X-ray diffraction. The predominant clay minerals consist mainly of illite, vermiculite, chlorites and intergrade with vermiculite, and kaolinite. Illite or mica was found present in all samples and in all horizons. This was identified by the 9.83 to $10{\AA}$ (0.01) and $3.32{\AA}$ (003) basal reflections, Interhorizontal variations in mineral content and crystallinity are illustrated in their respective Xray diffractogram. Comparing the peak intensity, of the $14{\AA}$, $10{\AA}$ and $7{\AA}$ indicated the degree of weathering from the surface to the lower horizons. In general, the weathering of illite on the surface produced less pronounced $10{\AA}$ and $14{\AA}$ peak as compared to the lower horizons. The same may be said with kaolinite. On K-saturation, the $14{\AA}$ peak broadening on the low angle side was observed. This is interpreted to be due to chlorization. Heat treament from $100^{\circ}C$, $200^{\circ}C$, $400^{\circ}C$, $600^{\circ}C$, and $800^{\circ}C$. caused significant changes in the different diffractograms. Heating caused collasped of the $14{\AA}$ to $10{\AA}$ and the appearance of scattered peaks between $10-14{\AA}$. This is interpreted to the presence of vermiculite chlorite intergradient. The complete collapse of the $14{\AA}$ at $800^{\circ}C$ to $10{\AA}$ with increased intensity was attributed to the preservce of vermiculite. The principal difference among the clay minerals in each horizon is the concomitant increase and decrease in intensity with depth of the $14{\AA}$, $10{\AA}$ and $7{\AA}$ diffraction spacings. Apparently the weathering of illite ($10{\AA}$) is resulting in the formation of vermiculite ($14{\AA}$) and the interstratified material being an intermediate stage and the beginning of the formation of vermiculite. Some broadening- in the 17 to $18{\AA}$ was observed in Puchun-1 Pyungtaik-1 and Pyungtaik-2 specially so in the lower horizon in the Ca or Mg-saturated sample. Heated treatment tend to shift this peak to $14{\AA}$ indicating the presence of regular layering of the interstratified complex. The high amount of extractable aluminum and iron coupled with low exchange capacity indicate that iron and aluminum plays an important role in the weathering of these soils and is responsible to the low exchange capacity, high acidity and high phosphate absorptive capacity. The results presented substantiated the weathering sequence of Jackson in that mica ${\rightarrow}$ vermiculite ${\rightarrow}$ chloritezed vermiculite ${\rightarrow}$ kaolinite.

• 자원환경지질
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• 제19권3호
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• pp.225-230
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• 1986

Various interpretations on the boundary between the $Okch{\check{o}}n$ system and the Great Limestone series of the $Chos{\check{o}}n$ system, and on the geologic structure and stratigraphy of the $Okch{\check{o}}n$ system have been yielded by the previous studies, and they are still in hot debate. The present work has mainly studied on the boundary between the $Okch{\check{o}}n$ and $Chos{\check{o}}n$ systems in the south of $Jech{\check{o}}n$, and the geology in its vicinity to clarify the previous misinterpretations if any on the geologic structure and in trun stratigraphy of the area concerned. The boundary between the $Okch{\check{o}}n$ system and the Great Limestone series of the $Chos{\check{o}}n$ system has been thought to be (1) gradational relation which means two systems are the same formation, (2) unconformable relation in which the $Okch{\check{o}}n$ system overlies the $Chos{\check{o}}n$ system, (3) unconformable relation in which the $Chos{\check{o}}n$ system overlies the Okchon system indicating that the age of the $Okch{\check{o}}n$ system is Precambrian, and (4) fault contact in which the $Okch{\check{o}}n$ system of Precambrian age comes in contact with the $Chos{\check{o}}n$ system of Cambro-Ordovician age. The present study clearly found that the relationship between the two systems is a fault zone contact. Shear zone of a width of 300 to 400m is developed, and andesitic volcanics and basic dikes are intruded along the fault zone. This fault contact is exactly the north extension of the Bonghwajae fault, which was denominated long time ago by two of the present authors. The eastern side of the fault has been uplifted so that the $S{\check{o}}changri$ formation of the $Okch{\check{o}}n$ system cropped out in the zone of the Great Limestone series. All the previous workers thought that the $S{\check{o}}changri$ formation rests on the Great Limestone series, but the present study found an overthrust having a strike of $N8^{\circ}E$ and dip of $30^{\circ}NW$ between them, and the $S{\check{o}}changri$ formation has thrusted over the Great Limestone series at the central part of the study area. In the southern and northern parts of this uplifted $S{\check{o}}changri$ formation, the Great Limestone series rests unconformably on it. In the eastern part of the study area where the Mt. Dangdu is located and the previous workers thought that the $S{\check{o}}changri$ formation rests on the Great Limestone series, Precambrian basement rock whose age is older than 1720+50 m.y. crops out in the northern part of the east-west trending high angle fault, and the Great Limestone series rests unconformably on the basement.

• 한국재료학회지
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• 제9권10호
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• pp.962-969
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• 1999

Ag-Cu-Ti 삽입금속을 이용하여 제조된 AlN/Cu와 AlN/W 활성금속브레이징 접합체의 잔류응력을 유한요소법으로 탄성 및 탄소성 해석을 행하여 그 결과를 접합강도 측정 결과와 파단 거동 관찰 결과와 비교, 분석하였다. 최대 잔류 주응력의 크기는 AlN/W 접합체보다 모재간 열팽창계수 차이가 큰 AlN/Cu 접합체에서 더 크게 나타났으며, 접합계면에 인접한 AlN 세라믹스 자유표면에 인장 성분의 응력집중이 확인되었다. 모재와 삽입금속의 탄소성 변형을 모두 고려할 경우, AlN/Cu 접합체의 경우 연질의 삽입금속에 의해 최대 잔류 주응력이 감소하여 소성변형에 의한 응력완화 효과가 있음을 확인하였으나, 100$\mu\textrm{m}$ 이상으로 삽입금속 두께를 증가시키더라도 잔류 주응력의 크기는 더 이상 크게 감소하지 않았다. 측정된 최대 접합강도는 AlN/Cu와 AlN/W 접합체에서 각각 52 MPa와 108 MPa이었으며, 파단 형태는 AlN/Cu 접합체는 AlN 자유표면으로부터 AlN 내부로 큰 각도를 이루면 진행되는 돔형의 파단이, AlN/W 접합체에서는 접합계면의 삽입금속층을 따라 AlN 측에서 파단이 일어나는 형태를 보였다.

• 한국운동역학회지
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• 제31권4호
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• pp.308-313
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• 2021

Objective: The purpose of this study was to investigate the effect of different kettlebell mass (30%, 40%, and 50% of the body mass) on kinematics and kinetic variables of kettlebell swing. Method: Total of 16 healthy male who had at least 1 year of kettlebell training experience were participated in this study (age: 31.69 ± 3.46 yrd., height: 173.38 ± 4.84 cm, body mass: 74.53 ± 6.45 kg). In this study, a 13-segments whole-body model (upper trunk, lower trunk, pelvis, both side of forearm, upperarm, thigh, and shank) was used and 26 reflective markers were attached to the body to identify the segments during the movement. A 3-dimensional motion analysis with 8 infrared cameras and 4 channeled EMG was performed to find the effect of kettlebell mass on its swing. To verify the kettlebell mass effect, a one-way ANOVA with a repeated measure was used and the statistical significance level was set at 𝛼=.05. Results: Firstly, in all lower extremity joints and thoracic vertebrae, a statistically significant change in angle was shown according to an increase in kettlebell mass during kettlebell swing (p<.05). Secondly, in both the up-swing and down-swing phases, the knee joint and ankle joint ROM showed a statistically significant increase as the kettlebell mass increased (p<.05) but no statistically significant difference was found in the hip joint and thoracic spine (p>.05). Lastly, the hamstrings muscle activity was statistically significantly increased as the kettlebell mass increased during up-swing phases (p<.05). Also, as the kettlebell mass increased in P4 of the down swing phase, the gluteus maximus showed a statistically significantly increased muscle activation, whereas the rectus femoris showed a statistically significantly decreased muscle activation (p <.05). Conclusion: As a result of this study, hip extension decreased and knee extension increased at 40% and 50% of body mass, and the spine also failed to maintain neutrality and increased flexion. Also, when kettlebell swings are performed with 50% of body mass, synergistic muscle dominance appears over 30% and 40% of body mass, which is judged to have a risk of potential injury. Therefore, it is thought that for beginners who start kettlebell exercise, swing practice should be performed with 30% of body mass. In addition, even in the case of experienced seniors, as the weight increases, the potential injury risk may increase, so it is thought that caution should be exercised when performing swings with 40% and 50% of body mass. In conclusion, it is thought that increasing the weight after sufficiently training with 30% of the weight of all subjects performing kettlebell swing is a way to maximize the exercise effect as well as prevent injury.