• Restorative Dentistry and Endodontics
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• 제25권3호
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• pp.435-445
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• 2000

The purpose of this study was to compare the leakage of four different obturation techniques in conjunction with immediate apical barrier of ${\beta}$-tricalcium phosphate(TCP) in teeth with open apex. Eighty single-rooted human premolar teeth were prepared and sectioned horizontally, so maximum diameter in apex was 4mm. Apical defects that were similar to open apex, were created with #1/2 round bur and SF104R bur. The apical foramen were opened to a size 80 file extended 3mm beyond the apex. The teeth were placed into the oasis block soaked saline to simulate periapical tissue often associated with pulpless teeth and received apical barriers consisting of TCP followed by obturation using lateral condensation technique, vertical condensation technique, continuous wave technique and thermoplasticized gutta-percha injection technique. Two unobturated teeth served as positive and negative controls. Teeth were immersed in resorcinol-formaldehyde resin for S days at $4^{\circ}C$, and the resin was allowed to polymerize completely for 4 days at room temperature. Teeth were then sectioned horizontally at 1.5mm(level 1), 2.5mm(level 2) and 3.5mm(level 3) from the apex, and examined under a stereomicroscope at ${\times}40$ magnification. The photographs were taken at ${\times}40$ magnification of the filling in each level and scanned. The leakage length in tooth/resin interface was measured at each of the three levels. Each ratio of leakage was obtained by calculating the ratio of the leakage length of canal wall infiltrated with resin to the total length of the canal and was analyzed statistically(One-way ANOVA and Scheffe test). The result were as follows : 1. At the level 1, there was the least leakage in the thermoplasticized gutta-percha injection technique group(group 4), but there was statistically significant(p<0.05). 2. At the level 2, there was the least leakage in the thermoplasticized gutta-percha injection technique group(group 4), and the most leakage in the continuous wave technique group(group 3). There was statistically significant difference between the thermoplasticized gutta-percha injection technique group and the continuous wave technique group(p<0.05). 3. At the level 3, there was the least leakage in the thermoplasticized gutta-percha injection technique group(group 4), but there were no statistically significant differences between other groups(p>0.05). These results suggest that thermoplasticized gutta-percha injection technique which had 1mm apical gutta-percha matrix after the formation of TCP apical barrier, can demonstrate favorable apical sealing.

• Journal of Magnetics
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• 제19권2호
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• pp.185-191
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• 2014

In this study we evaluated that flow rate changes affect the (time of flight) TOF image and contrast-enhanced (CE) in a three-dimensional TOF angiography. We used a 3.0T MR System, a nonpulsatile flow rate model. Saline was used as a fluid injected at a flow rate of 11.4 cm/sec by auto injector. The fluid signal strength, phantom body signal strength and background signal strength were measured at 1, 5, 10, 15, 20 and 25-th cross-section in the experienced images and then they were used to determine signal-to-noise ratio and contrast-to-noise ratio. The inlet, middle and outlet length were measured using coronal images obtained through the maximum intensity projection method. As a result, the length of inner cavity was 2.66 mm with no difference among the inlet, middle and outlet length. We also could know that the magnification rate is 49-55.6% in inlet part, 49-59% in middle part and 49-59% in outlet part, and so the image is generally larger than in the actual measurement. Signal-to-noise ratio and contrast-to-noise ratio were negatively correlated with the fluid velocity and so we could see that signal-to-noise ratio and contrast-to-noise ratio are reduced by faster fluid velocity. Signal-to-noise ratio was 42.2-52.5 in 5-25th section and contrast-to-noise ratio was from 34.0-46.1 also not different, but there was a difference in the 1st section. The smallest 3D TOF MRA measure was $2.51{\pm}0.12mm$ with a flow velocity of 40 cm/s. Consequently, 3D TOF MRA tests show that the faster fluid velocity decreases the signal-to-noise ratio and contrast-to-noise ratio, and basically it can be determined that 3D TOF MRA and 3D CE MRA are displayed larger than in the actual measurement.

• 콘크리트학회지
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• 제11권1호
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• pp.231-242
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• 1999

면외 바닥하중과 토압과 수압에 의한 면내 압축력을 받는, 깊은 지하구조에 사용되는 플랫플레이트 슬래브에 대한 수치해석연구를 실시하였다. 비선형 유한요서해석을 위하여 재료와 기하학적 비선형효과를 고려한 수치해석프로그램을 개발하였으며, 이 수치해석방법은 4 변이 단순지지된 플레이트에 대한 실험결과와 비교에 의하여 검증되었다. 해석모델로서 국내 콘크리트계산규준의 직접설계법에 의하여 설계된 플랫플레이트 슬래브가 사용되었다. 하중조합과 하중순서에 대한 연구를 통하여 플랫플레이트 슬래브의 강도를 지배하는 하중조건을 연구하였으며, 이 지배하중을 받는 슬래브에 대한 변수연구를 통하여 철근비, 형상비, 콘크리트강도, 세장비에 따를 슬래브의 강도변화를 연구하였다. 이 연구결과를 바탕으로 바닥하중증대법을 제시하였다.

• 대한세포병리학회지
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• 제6권2호
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• pp.204-208
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• 1995

The cytologic findings of endodermal sinus tumor of the ovary are reported. The cytologic preperations were obtained from ascitic specimens. The findings on Papanicolaou-stained smears included a clean background and poorly preserved atypical cells loosely arranged in irregular or papillary groups. At high magnification, the cells had ill-defined and microvacuolated cytoplasms, with an increased nuclear-cytoplasmic ratio and prominent nucleoli. Hyaline globules characteristic of the alpha-fetoprotein (AFP)-synthesizing cells of endodermal sinus tumor were observed within the cells with periodic-acid-Schiff(PAS) stain. The presence of PAS-positive hyaline globules can be regarded, therefore, as a diagnostic clue to endodermal sinus tumor in an appropriate clinical setting and in the presence of AFP production. The cytologic findings in a cell block is important, in addition to smears, to obtain more diagnostic clues. A preliminary cytomorphologic diagnosis of this highly malignant tumor is valuable as a guide in planning further immunocytochemical and serologic studies.

• Imaging Science in Dentistry
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• 제34권3호
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• pp.159-164
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• 2004

Purpose: To compare alveolar bony height of pantomograph with bony height of thin slice, multiplanar reformatted (MPR) Computed Tomograph. Materials and Methods : Panoramic radiograms of 12 young adult patients had been taken by one radologic technitian and the measurements were corrected by magnification ratio (1.20). The slice thickness of Multi-detector Computed Tomography (CT) was at least 1mm for the accuracy. The raw CT datas were imported into the V-works 4.0 (CyberMed Corp., Seoul, Korea) and transformed to MPR images. Pantomographic measurements of alveolar bone were compared to CT values by average mean bony height measurements for the accuracy. Inter-, and Intra-observer variability was evaluated. Results : There was no significant differences between height measurement of pantomography and that of CT (P>0.05). There were no significant differences in either inter-or intra-observer measurements (P>0.05). Conclusion : Pantomography showed relatively high accuracy and precision in measuring alveolar bony height.

• 한국컴퓨터정보학회논문지
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• 제18권2호
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• pp.49-57
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• 2013

본 논문에서는 확대 영상의 화질을 개선하기 위하여 인접픽셀 값 정보를 이용하여 영상의 단순 볼록 곡면과 단순 오목 곡면을 추정하는 기법과 영상이 단순 볼록 곡면과 단순 오목 곡면의 특성을 반영하여 확대 영상을 구성하는 기법을 제안하였다. 제안된 기법을 사용하여 확대 영상을 구성하면 기존의 기법들을 사용하여 확대한 영상보다 실제 영상에 더욱 충실하게 된다. 제안된 기법을 적용하여 확대한 영상의 화질향상 정도를 측정하기 위하여 PSNR(Peak Signal to Noise Ratio)을 사용하였다. 제안된 기법을 적용하여 확대한 영상들의 PSNR 값들은 기존의 기법들을 적용하여 확대한 영상들의 PSNR 값보다 큰 것을 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.461-464
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• 2004

In this paper, the elastic epoxy added elastomer having viscoelasticity to existing epoxy was measured thermal, structural properties through TGA(Thermogravimetric Analysis) and FESEM(Field Emission Scanning Electron Microscope). Specimens were made of dumbbell forms by the ratio of 5[phr], 10[phr], 15[phr], and 20[phr] by regulation with elastomer contents. The measurement temperature dimensions of TGA were $0[^{\circ}C]\;to\;800[^{\circ}C]$, and rising temperature was $5[^{\circ}C/min]$. And we observed structure through FESEM at the magnification of 1000times with the voltage of 15[kV] after breaking by quenching specimens. As thermal analysis results, we could know that thermal and structural properties was improved quantity according to decrease of elastomer contents. In general, thermal, structural properties of 15[phr] was excellent among the specimens.

• 한국광학회지
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• 제1권1호
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• pp.12-15
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• 1990

홀로그래피 간섭법과 스펙클 사진법을 결합한 홀로스펙클 간섭법을 이용하여 3차원 변형을 측정하였다. 이 방법은 이중노출된 하나의 사진건판으로부터 종변위와 횡변위를 모두 알아낼 수 있어 3차원 변형측정에 매우 유용하게 사용되고 있다. 본 연구에서는 물체의 일부분에 밀집되어 일어나는 변형을 측정하기 위하여 image holography에 기초를 둔 광학시스템을 구성하였다. 시스템의 배율을 적절히 증가시키고 기준파의 세기를 감소시킴으로써 보통의 홀로그램에 비해 스펙클의 효과를 증대시켰다. 이로써 가시도가 높은 Young의 무늬 뿐만 아니라 확대되고 명확한 홀로 그래피 간섭무늬를 얻을 수 있어 indentor에 의한 3차원 접촉변형을 측정하였다.

• Structural Engineering and Mechanics
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• 제40권4호
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• pp.453-469
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• 2011

A one-story, wooden-frame, intermediate-bay model with Dou-Gon designed according to the Building Standards of the Song Dynasty (A.D.960-1279), was tested on a unidirectional shaking table. The main objectives of this experimental study were to investigate the seismic performance of Chinese historic wooden structure under various base input intensities. El Centro wave (N-S), Taft wave and Lanzhou wave were selected as input excitations. 27 seismic geophones were instrumented to measure the real-time displacement, velocity and acceleration respectively. Dynamic characteristics, failure mode and hysteretic energy dissipation performance of the model are analyzed. Test results indicate that the nature period and damping ratio of the model increase with the increasing magnitude of earthquake excitation. The nature period of the model is within 0.5~0.6 s, the damping ratio is 3~4%. The maximum acceleration dynamic magnification factor is less than 1 and decreases as the input seismic power increases. The frictional slippage of Dou-Gon layers (corbel brackets) between beams and plates dissipates a certain amount of seismic energy, and so does the slippage between posts and plinths. The mortise-tenon joint of the timber frame dissipates most of the seismic energy. Therefore, it plays a significant part in shock absorption and isolation.

• Wind and Structures
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• 제25권1호
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• pp.1-24
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• 2017

This paper presents a 1:25 multi-freedom aero-elastic model for a high lighting pole at the Zhoushan stadium. To validate the similarity characteristics of the model, a free vibration test was performed before the formal test. Beat phenomenon was found and eliminated by synthesis of vibration in the X and Y directions, and the damping ratio of the model was identified by the free decay method. The dynamic characteristics of the model were examined and compared with the real structure; the similarity results were favorable. From the test results, the major along-wind dynamic response was the first vibration component. The along-wind wind vibration coefficient was calculated by the China code and Eurocode. When the peak factor equaled 3.5, the coefficient calculated by the China code was close to the experimental result while Eurocode had a slight overestimation of the coefficient. The wind vibration coefficient during typhoon flow was analyzed, and a magnification factor was suggested in typhoon-prone areas. By analyzing the power spectrum of the dynamic cross-wind base shear force, it was found that a second-order vortex-excited resonance existed. The cross-wind response in the test was smaller than Eurocode estimation. The aerodynamic damping ratio was calculated by random decrement technique and the results showed that aerodynamic damping ratios were mostly positive at the design wind speed, which means that the wind-induced galloping phenomenon is predicted not to occur at design wind speeds.