지하수 주입실험을 통한 도로노면 하부의 공동 확장 평가

박정준,유승경,홍기권 한국지반신소재학회 2019 한국지반신소재학회 논문집 Vol.18 No.3

This study described a results of groundwater injection test in cavity, in order to evaluate characteristics of cavity expansion under pavement. That is, groundwater amount proportional to the cavity volume was injected into the generated cavity step by step, and then the cavity with the changed size was monitored as the injected groundwater was drained. The test result showed that the cavity volume by groundwater injection increased, and then it converged or decreased. This means that some of the relaxation soil around the cavity collapsed, and the fine-grained soils in some soils filled the void in the surrounding soils when the cavity is expanded by groundwater injection. The volume change and expansion characteristics of the cavity according to the groundwater injection step were analyzed. The result showed that the cavity extended laterally. Therefore, it was found that the cavity expansion is caused by the repetition of the relaxation soil collapse due to the groundwater flow and the loss of the collapsed soil below the cavity. 본 연구에서는 도로노면 하부 지반에서 발생한 공동의 확장특성을 평가하기 위하여, 지하수주입 실험을 수행하였다. 즉, 공동체적에 비례한 일정량의 물을 단계별로 주입하고, 주입한 물이 배출됨에 따라 확대되는 공동을 모니터링 함으로써, 공동의체적변화를 확인하였다. 실험결과, 지하수 주입에 따른 공동의 체적은 증가하다 수렴 또는 감소하는 경향을 나타냈다. 이는지하수 주입 시, 공동이 확장되는 과정에서 주변의 이완된 지반이 일부 붕괴되거나 세립토가 주변 지반의 간극을 채우기때문인 것으로 분석되었다. 또한 지하수 주입 단계에 따른 공동의 체적변화와 확장특성을 분석한 결과, 실험대상 공동은 횡방향으로 확장되는 것을 확인할 수 있었다. 그리고 지하수 유동에 따라 이완된 공동 주변지반이 붕괴되고, 붕괴된 토사가 공동하부의 지중으로 유실되는 과정이 반복됨으로써 공동이 확장되는 것으로 평가되었다.

4-, 6-, 10-MV X-선원에서 공기동이 흡수선량에 미치는 효과

김창선,양대식,김철용,최명선 대한방사선종양학회 1997 Radiation Oncology Journal Vol.15 No.4

Purpose : When an x-ray beam of small field size is irradiated to target area containing an air cavity, such as larynx, the underdosing effect is observed in the region near the interfaces of air and soft tissue. With a larynx model, air cavity embedded in tissue-equivalent material, this study is intended for examining parameters, such as beam quality, field size, and cavity size, to affect the dose distribution near the air cavity. Materials and Methods : Three x-ray beams, 4-, 6- and 10-MV, were employed to perform a measurement using a 2cm (width)×L (length in cm, one side of x-ray field used)×2cm (height) air cavity in the simulated larynx. A thin window parallel-plate chamber connected to an electrometer was used for a dosimetry system. A ratio of the dose at various distances from the cavity-tissue interface to the dose at the same points in a homogeneous phantom (observed/expected ratio, O/E), normalized buildup curves, and ratio of distal surface dose to dose at the maximum buildup depth were examined for various field sizes. Measurement for cavity size effect was performed by varying the height (Z) of the air cavity with the width kept constant for several field sizes. Results : No underdosing effect for 4-MV beam for fields larger than 5cm×5cm was found. For both 6- and 10- MV beams, the underdosing portion of the larynx at the distal surface was seen to occur for small fields, 4cm×4cm and 5cm×5cm. The underdosed tissue was increased in its volume with beam energy even for similar surface doses. The relative distal surface dose to maximum dose was changed to 0.99 from 0.95, 0.92, and 0.91 for 4-, 6-, and 10-MV, respectively, with increasing field size, 4cm×4c m to 8cm×8cm. For 6- and 10-MV beams, the dose at the surface of the cavity is measured less than the predicted by about two and three percent, respectively, but decrease was found for 4-MV beam for 5cm×5cm field. For the 4cm×L×Z (height in cm), varying depth from 0.6 to 4.8cm, cavity, O/E>1.0 was observed regardless of the cavity size for any field larger than about 8cm×8cm. Conclusion : The magnitude of underdosing depends on beam energy, field size, and cavity size for the larynx model. Based on the result of the study, caution must be used when a small field of a high quality x-ray beam is irradiated to regions including air cavities, and especially the region where the tumor extends to the surface. Low quality beam, such as, 4-MV x-ray, and larger fields can be used preferably to reduce the risk of underdosing, local failure. In the case of high quality beams such as 6- and 10-MV x-rays, however, an additional boost field is recommended to add for the compensation of the underdosing region when a typically used treatment field, 5cm×5cm, is employed. 목 적 : 공기동을 포함한 병소 부위에 X-선원을 조사할 경우 공동과 근접한 영역에서의 저흡수선량 효과는 잘 알려져 있다. 공기-연조직 사이의 불균질면의 한 예로 후두 모형 즉, 조직 등가물질과 그 사이에 삽 입 되 어 있는 공 기 동 을 만 들 었 다. 본 연구에서는 방사선의 선질 ·조사면의 크기 ·공기동의 크기에 따른 공동 가까이에서의 흡수선량의 변화를 살펴보았다. 대상 및 방법 : 4-, 6-, 10-MV X-선원을 이용하여 2cm(폭)×L(cm, 길이)×2cm(높이)인 공기동을 포함한 후두 모형의 아크릴 팬톰에 대하여 흡수선량을 측정하였다. 흡수선량의 측정장비로 평행판전리함과 전리계를 이용하였다. 제작한 후두의 기하학적 치수는 상부 연조직·공기동·하부연조직의 두께가 각각 4-, 2-, 4-cm이었다. 공기동이 없이 균일한 연조직 팬톰에 대한 공기동이 있는 경우의 흡수선량의 비(O/E) 를 공기 공동-연조직의 경계로부터 거리를 변화시키면서 측정하였다. 표준화된 증강곡선과 최대흡수선량에 대한 입사면 반대쪽 표면에서의 흡수선량의 비를 조사면의 크기를 변화시키면서 측정하였다. 공기동의 크기에 따른 효과를 알기 위하여 여러 가지조사면에 대하여 투영된 크기가 4cm(폭)×L인 공기동의 높이(Z)를 변화시켜서 측정하였다. 결 과 : 4-MV선원에서 5cm×5cm 이상의 조사면에서는 저흡수선량 효과가 없었다. 6-이나 10-MV선원에서 작은 조사야 즉, 4cm×4cm와 5cm×5cm에서는 후두에 저흡수선량 부위가 나타났으며 6cm×6cm 이상의 조사면에서는 이 효과가 관찰되지 않았다. 선원의 선질이 증가할수록 저흡수선량인 조직층이 증가하였고 이때 표면 흡수선량의 크기는 변하지 않았다. 조사면의 크기가 4cm×4cm에서 8cm×8cm로 증가할 때 최대흡수선량에 대한 입사면 반대쪽의 공기동의 표면선량은 4-, 6-, 10-MV 선원에서 각각 0.95, 0.92, 0.91에서 0.99로 증가하였다. 6-이나 10-MV선원에서 공기동 표면에서의 흡수선량은 5cm×5cm 조사면에 있어서 예상값보다 각각 2-, 3-퍼센트의 감소가 있었고 또 4-MV에서는 감소효과를 발견할 수 없었다. 4cm×L×Z 공기동에서 그 높이(Z)를 0.6에서 4.8cm까지 변화시켰을 때 조사면의 크기가 8cm×8cm에서 공동의 크기에 무관하게 O/E>1.0이 관찰되었다. 결 론 : 조사면내 공기동에 의한 저흡수선량 효과는 방사선의 선질·조사면의 크기·공기동의 크기에 의존된다. 이상의 연구 결과에서 고선질 선원이 공동을 포함한 병소 특히, 종양이 공기동의 표면까지 미치는 부위에 조사될 때 특별한 주의가 필요함을 알 수 있다. 이 경우 가능하면 조사되는 부위가 저선량이 되지않도록 저선질의 선원(예를 들면, 4-MV)을 쓰고 또 조사면을 넓혀야 한다. 6-이나 10-MV 등의 고선질의 X-선을 쓰는 경우에는 조사면의 부위에 저선량 부위가 생기 므로 한번의 추가 조사를 더 시행할 필요가 있다.

Evaluation of Road Cavity Detection using Road Deflection as a Complementary Method

Jun-Seong Choi,Jin-Sung Yoon 한국도로학회 2018 한국도로학회 학술대회 발표논문 초록집 Vol.2018 No.05

This is the abstract section. One paragraph only Road cavities recently in urban are causing collapse of road surface layer due to loss of support bearing capacity. Detecting road cavities with ground penetrating radar(GPR) test, then excavation and backfill are performed in the anticipated cavity area. However sometimes detecting errors are occurred because of the complexity of the GPR test result analysis or interval space between larger gravels. So before unnecessary excavation, verification for detect the cavities results should be needed. The purpose of this study suggest deflection method by the light weight deflectometer(LWD) as a verification way of GPR test results and as a tracking investigation method continuously at the sites having small size cavity. LWD devices has more advantages than larger NDT because FWD has difficulties in a traffic control and entrance of narrow-back road. In this study, LWD tests were conducted on the pavement sections with and without road cavity detected by GPR tests and after excavating the area, the cavity sizes were measured. LWD test results can be applied to verify a subsurface cavity by comparing maximum deflection and deflection ratio between cavity area and non cavity area at the loading center. The higher deflection and lower modulus was measured at cavity sections. Based on the results of the comparative analysis, It is found that deflection method has a possibility of complementary for detecting road cavity. Also cavity size prediction equation was attempted to propose through deflection ratio using a database. Compared with another validation data, the proposed prediction equation is more suitable for detecting cavity existence than size estimation because the average error rate is larger. As a results of the analysis with depth ratio as a factor, it is necessary to improve the cavity size prediction through the normalization using the parameter of road properties.

Air Cavity Effects on the Absorbed Dose for 4-, 6- and 10-MV X-ray Beams : Larynx Model

김창선,양대식,김철용,최명선,Kim Chang-Seon,Yang Dae-Sik,Kim Chul-Yong,Choi Myung-Sun The Korean Society for Radiation Oncology 1997 Radiation Oncology Journal Vol.15 No.4

목적 : 공기동을 포함한 병소 부위에 X-선원을 조사할 경우 공동과 근접한 영역에서의 저흡수선량 효과는 잘 알려져 있다. 공기-연조직 사이의 불균질면의 한 예로 후두 모형 즉, 조직 둥가물질과 그 사이에 삽입되어 있는 공기동을 만들었다. 본 연구에서는 방사선의 선질 조사면의 크기 공기동의 크기에 따른 공동 가까이에서의 흡수선량의 변화를 살펴보았다. 대상 및 방법 : 4-, 6-, 10-MV X-선원을 이용하여 2cm(폭)$\times$L(cm, 길이)$\times$2cm(높이)인 공기동을 포함한 후두 모형의 아크릴 팬톰에 대하여 흡수선량을 측정하였다. 흡수선량의 측정장비로 평행판전리함과 전리계를 이용하였다. 제작한 후두의 기하학적 치수는 상부 연조직$\cdot$공기동$\cdot$하부 연조직의 두께가 각각 4-, 2-, 4-cm이었다. 공기동이 없이 균일한 연조직 팬톰에 대한 공기동이 있는 경우의 흡수선량의 비(O/E)를 공기 공동-연조직의 경계로부터 거리를 변화시키면서 측정하였다. 표준화된 중강곡선과 최대흡수선량에 대한 입사면 반대쪽 표면에서의 흡수선량의 비를 초사면의 크기를 변화시키면서 측정하였다. 공기동의 크기에 따른 효과를 알기 위하여 여러 가지 조사면에 대하여 투영된 크기가 4cm(폭)$\times$L인 공기동의 높이(Z)를 변화시켜서 측정하였다. 결과 : 4-MV선원에서 $5cm\times5cm$ 이상의 조사면에서는 저흡수선량 효과가 없었다. 6-이나 10-MV선원에서 작은 조사야 즉, $4cm\times4cm$와 $5cm\times5cm$에서는 후두에 저흡수선량 부위가 나타났으며 $6cm\times6cm$ 이상의 조사면에서는 이 효과가 관찰되지 않았다. 선원의 선질이 증가할수록 저흘수선량인 조직층이 증가하였고 이때 표면 흡수선량의 크기는 변하지 않았다. 조사면의 크기가 $4cm\times4cm$에서 $8cm\times8cm$로 증가할 때 최대흡수선량에 대한 입사면 반대쪽의 공기동의 표면 선량은 4-, 6-, 10-MV 선원에서 각각 0.95, 0.92, 0.91에서 0.99로 증가하였다. 6-이나 10-MV 선원에서 공기동 표면에서의 흡수선량은 $5cm\times5cm$ 조사면에 있어서 예상값보다 각각 2-, 3-퍼센트의 감소가 있었고 또 4-MV에서는 감소효과를 발견할 수 없었다. $4cm\timesL\timesZ$ 공기동에서 그높이(Z)를 0.6에서 4.8cm까지 변화시켰을 때 조사면의 크기가 $8cm\times8cm$에서 공동의 크기에 무관하게 O/E>1.0이 관찰되었다. 결론 : 조사면내 공기동에 의한 저흘수선량 효과는 방사선의 선질$\cdot$조사면의 크기$\cdot$공기동의 크기에 의존된다. 이상의 연구 결과에서 고선질 선원이 공동을 포함한 병소 특히, 종양이 공기동의 표면까지 미치는 부위에 조사될 째 특별한 주의가 필요함을 알 수 있다. 이 경운 가능하면 조사되는 부위가 저전량이 되지않도록 저선질의 선원(예를 들면, 4-MV)을 쓰고 또 조사면을 넓혀야한다. 6-이나 10-MV 등의 고선질의 X-선을 쓰는 경우에는 조사면의 부위에 저선랸 부위가 생기므로 한번의 추가 조사를 더 시행할 필요가 있다. Purpose : When an x-ray beam of small field size is irradiated to target area containing an air cavity, such as larynx, the underdosing effect is observed in the region near the interfaces of air and soft tissue. With a larynx model, air cavity embedded in tissue-equivalent material, this study is intonded for examining Parameters, such as beam quality, field size, and cavity size, to affect the dose distribution near the air cavity. Materials and Methods : Three x-rar beams, 4-, 6- and 10-MV, were employed to Perform a measurement using a 2cm $(width){\times}L$ (length in cm, one side of x-ray field used 2cm (height) air cavity in the simulated larynx. A thin window parallel-plate chamber connected to an electrometer was used for a dosimetry system. A ratio of the dose at various distances from the cavity-tissue interface to the dose at the same points in a homogeneous Phantom (ebservedlexpected ratio, O/E) normalized buildup curves, and ratio of distal surface dose to dose at the maximum buildup depth were examined for various field sizes. Measurement for cavity size effect was performed by varying the height (Z) of the air cavity with the width kept constant for several field sizes. Results : No underdosing effect for 4-MV beam for fields larger than $5cm\times5cm$ was found For both 6- and 10-MV beams, the underdosing portion of the larynx at the distal surface was seen to occur for small fields, $4cm\times4cm\;and\;5cm\times5cm$. The underdosed tissue was increased in its volume with beam energy even for similar surface doses. The relative distal surface dose to maximum dose was changed to 0.99 from 0.95, 0.92, and 0.91 for 4-, 6-, and 10-MV, respectively, with increasing field size, $4cm\times4cm\;to\;8cm\times8cm$, For 6- and 10-MV beams, the dose at the surface of the cavity is measured less than the predicted by about two and three percent. respectively. but decrease was found for 4-MV beam for $5cm\times5cm$ field. For the $4cm\timesL\timesZ$ (height in cm). varying depth from 0.0 to 4.8cm, cavity, O/E> 1.0 was observed regardless of the cavity size for any field larger than about $8cm\times8cm$. Conclusion : The magnitude of underdosing depends on beam energy, field size. and cavity size for the larynx model. Based on the result of the study. caution must be used when a small field of a high quality x-ray beam is irradiated to regions including air cavities. and especially the region where the tumor extends to the surface. Low quality beam. such as. 4-MV x-ray, and larger fields can be used preferably to reduce the risk of underdosing, local failure. In the case of high quality beams such as 6- and 10-MV x-rays, however. an additional boost field is recommended to add for the compensation of the underdosing region when a typically used treatment field. $8cm\times8cm$, is employed.

원형 Cavity를 이용한 펄스형 Nb:YAG 레이저의 출력특성 및 병렬메쉬 회로의 최적화

홍정환,송금영,양동민,김휘영,김희제 부산대학교 생산기술연구소 2001 生産技術硏究所論文集 Vol.60 No.-

본 연구에서는 기존의 타원형 cavity가 아닌 원형 cavity를 설계 및 제작하여 그 동작특성에 관하여 연구하였다. 그 결과 타원형 cavity 보다 다소 적은 레이저 출력 효율 2.1%를 얻었다. 원형 cavity는 타원형 cavity 보다 컴팩트하며 제작하기가 용이하고, 제작 단가가 저렴하다는 장점이 있다. 입력에너지, 입력전압 및 펄스 폭을 동일하게 했을 경우 주회로 병렬 메쉬회로수를 최적화하고자 한다. PFN 회로를 1단에서 8단까지 PSPICE로 모의시험한 전류파형과 실제 실험한 전류파형이 거의 일치하였다. 그 결과 500㎲이상의 펄스 폭에서 6단 메쉬가 최적의 병렬 메쉬라는 결론을 얻었다. In this study, we have deigned and manufactured not only a present elliptic cavity but also a circular cavity, and experimented the operational characteristics. As a result, we obtained the maximum efficiency of 2.1% that was not less than that of an elliptic cavity. A circular cavity is much more compact and is easier to be manufactured than an elliptic cavity. And it can be made at a low cost. When the input energy, input voltage, and pulse width were in the same condition, we tried to decide the optimization of the mesh number of a parallel-mesh circuit which was connected with main power supply. The PSPICE simulation waveform of PFP(Pulse Forming network) circuit ranging from 1-mesh to 8-mesh nearly corresponded with the real current waveform obtained through a practical experiment. From these experimental results, we obtained the result that 6-mesh was the optimal parallel-mesh circuit in case that the pulse width was more than 500㎲.

비정상 초음속 유동장에서의 cavity 유동 연구

송병호,김재수 朝鮮大學校 機械技術硏究所 2001 機械技術硏究 Vol.4 No.2

Open cavity 주위의 비정상 초음속 난류 유동을 Noavier-Stokes 방정식을 이용하여 수치해석해보았다. Cavity 내부에서 발생하는 자체진동 현상을 κ-ε난류모델을 적용한 2차원, 비정상, 압축성 full Navier-Stokes 방정식을 이용하여 계산하였다. 본 계산에서는 길이 대 깊이 비(L/D)가 3인 open cavity에 대해 계산하였다. 결과는 자유류 마하수는 1.5이고, Re=4.5×10^5일 때의 cavity의 앞전과 뒷전의 압력 변화와 cavity 전체 영역에 대한 유동의 현상을 비교하였다. 또한, 유량의 증감에 의한 open cavity 유동의 주기성을 확인할 수 있었다. A Navier-Stokes simulation of unsteady spersonic turbulent flow over open cavity is conducted. The self-sustained oscillatory motion within the cavity is obtained by numerically solving the unsteady, compressible, two-dimensional, full Naiver-Stokes equations. The length to depth ratios(L/D) of the two calculated cavity models are 3. For the open cavity of the freestream Mach number is 1.5 and Reynolds No is 4.5×10^5, the results are compared with the front and rear pressure distribution as cavity flow and flow appearance as full cavity region. the results are confirmed periodical for flow addition and reduction.

공동(air cavity)의 존재 시 실험적 선량분포와 치료계획상의 선량분포 비교

김연래(Yon-Lae Kim),서태석(Tae-Suk Suh),고신관(Shin-Gwan Ko),이정우(Jeong-Woo Lee) 대한방사선과학회(구 대한방사선기술학회) 2010 방사선기술과학 Vol.33 No.3

고 에너지 광자선 치료 시 공동의 존재로 인한 실험적 선량분포와 치료계획상의 선량분포의 변화를 비교, 평가 하고자 하였으며, 선형가속기의 6 MV 광자선을 이용해서 폴리스틸렌 팬텀, 자체 제작한 아크릴 팬텀으로 공동을 만들고 표면에서 공동까지의 거리는 3 cm로 하고 선원-측정기간 거리는 100 cm로 고정하였고 공동의 크기는 가로 × 세로 × 높이로 정하였다. 공동의 넓이, 높이, 존재 유무, 그리고 조사면과 공동의 크기 비율에 따른 깊이에 대한 선량변화를 평판형전리함과 미소전류계를 이용하여 측정하였다. 치료계획상의 선량분포는 불균질 보정을 하고 치료계획을 하여 비교하였다. 그 결과 공동의 넓이가 커짐에 따라 선량은 점차 감소하였다. 공동의 존재 시에, 공동후면 이후 깊이선량은 공동의 비존재시보다 크게 나타났다. 공동의 크기를 5×5×3 cm 3 로 고정했을 때 조사면이 4×4 cm 2 , 5×5cm, 6×6 cm일 경우에 rebuild-up이 일어났다. 그러나 조사면이 10×10 cm에서는 선량감소만이 나타났다. 또한 조사면을 5×5 cm 2로 고정했을 때, 공동의 넓이가 4×4 cm , 5×5 cm 2 일 경우에는 rebuild-up현상 이 일어났지만, 2×2 cm 2 , 3×3 cm 2 일 경우에는 일어나지 않았다. 모든 경우에서 치료계획상의 선량분포에서 rebuild-up 현상이 나타나지 않았다. 따라서 공동이 위치한 곳에 종양이 존재할 때는 치료계획상의 선량분포에 차이가 있으므로 주의를 할 필요가 있다. This study is compared that the dose distribution by experimentation and radiation therapy planning (RTP) when the air cavity region was treated high energy photon.The dose measurements were performed with a 6 MV photon beam of linear accelerator. The poly-styrene and self made acyl phantom were similar to tissue density of the human body. A parallel plate chamber was connected to an electrometer. The measurement setup was SCD (Source Chamber Distance) 100 cm and the distance of surface from air cavity was 3 cm. Absorbed dose of interface were measured by area and height. The percent depth dose were measured presence and absence of air cavity, depth ac-cording to a ratio of field size and air cavity size. The dose distribution on planning was expressed to do the inhomogeneity correction. As the area of air cavity was increased, the absorbed dose were gradually reduced. It was slightly in-creased, when the height of air cavity was changed from 0 cm to 0.5 cm. After the point, dose was decreased. In case of presence of air cavity, dose after distal air cavity interface was more great than ab-sence of air cavity. The rebuild up by field size and area of air cavity occurred for field size, 4×4 cm 2 , 5×5 cm and 6×6 cm, with fixed on area of air cavity, 5×5 cm. But it didn't occur at 10×10 cmfield size. On the contrary, the field size was fixed on 5×5 cm 2 , rebuild up occurred in area of air cavity, 4×4 cm 2 , 5×5 cm 2 . but, it did not occur for air cavity, 2×2 cm 2 , 3×3 cm 2 . All of the radiation therapy planning were not occurred rebuild up. It was required to pay attention to treat tumor in air cavity because the dose distribution of planning was different from the dose distribution of patient.

와동 형태와 충전 방법에 따른 Class V 복합 레진 수복치의 유한요소법적 응력 분석

손윤희,조병훈,엄정문,Son, Yoon-Hee,Cho, Byeong-Hoon,Um, Chung-Moon 대한치과보존학회 2000 Restorative Dentistry & Endodontics Vol.25 No.1

Most of cervical abrasion and erosion lesions show gingival margin where the cavosurface angle is on cementum or dentin. Composite resin restoration of cervical lesion shrink toward enamel margin due to polymerization contraction. This shrinkage has clinical problem such as microleakage and secondary caries. Several methods to diminish contraction stress of composite resin restoration, such as modifying cavity form and building up restorations in several increments have been attempted. The purpose of this study was to compare polymerization contraction stress of composite resin in Class V cavity subjected to cavity forms and placement methods. In this study, finite element model of 5 types of Class V cavity was developed on computer tomogram of maxillary central incisor. The types are : 1) Box cavity 2) Box cavity with incisal bevel 3) V shape cavity 4) V shape cavity with incisal bevel 5) Saucer shape cavity. The placement methods are 1) Incisal first oblique incremental curing 2) Bulk curing. An FEM based program for light activated polymerization is not available. For simulation of curing dynamics, time dependent transient thermal conduction analysis was conducted on each cavity and each placement method. For simulation of polymerization shrinkage, thermal stress analysis was performed with each cavity and each placement method. The time-temperature dependent volume shrinkage rate, elastic modulus, and Poisson's ratio were determined in thermal conduction data. The results were as follows : 1. With all five Class V cavifies, the highest Von Mises stress at the composite-tooth interface occurred at gingival margin. 2. With box cavity, V shape cavity and saucer cavity, Von Mises stress at gingival margin of V shape cavity was lower than the others. And that of box cavity was lower than that of saucer cavity. 3. Preparing bevel at incisal cavosurface margin decreased the rate of stress development in early polymerization stage. 4. Preparing bevel at incisal cavosurface margin of V shape cavity increased the Von Mises stress at gingival margin, but decreased at incisal margin. 5. At incisal margin, stress development by bulk curing method was rapid at early stage. Stress development by first increment of incremental curing method was also rapid but lower than that by bulk curing method, however after second increment curing final stress was the same for two placement methods. 6. At gingival margin, stress development by incremental curing method was suddenly rapid at early stage of second increment curing, but final stress was the same for two placement methods.

FWD 역산 기법을 활용한 동공구간 아스팔트 포장 지지력 평가 연구

박희문,최연우 한국도로학회 2019 한국도로학회논문집 Vol.21 No.4

PURPOSES: The objective of this study is to evaluate the structural capacity of asphalt pavement in subsurface cavity sections using falling weight deflectometer (FWD) backcalculation method. METHODS: It is necessary to analyze the reduction of structural capacity in asphalt pavements due to the occurrence of subsurface cavities. The FWD testing was conducted on the cavity and intact asphalt pavement in the city of Seoul. The GAPAVE, backcalculation program for FWD deflections, was utilized to determine the layer moduli in asphalt pavements. The remaining life of asphalt pavements in cavity sections were predicted using the pavement performance model for fatigue cracking. The backcalculated layer moduli between cavity and intact sections were compared to determine the reduction of structural capacity due to subsurface cavity. The relationship between the reduction of layer modulus and cavity depth/length was analyzed to estimate the effect of cavity characteristics on the structural capacity degradation. RESULTS: According to the FWD backcalculation results, the modulus of asphalt layer, subbase, and subgrade in cavity sections are generally lower than those in intact sections. In the case of asphalt layers, the backcalculated modulus in cavity section was reduced by 50% compared to intact section. A study for the prediction of remaining life of cavity section shows that the occurrence of subsurface cavity induces the decrease of the pavement life significantly. It is found that there is no close relationship between the backcalculated modulus and cavity length. However, the reduction of asphalt layer modulus is highly correlated with the cavity depth and was found to increase with the decrease of cavity depth. CONCLUSIONS : This reduction of structural capacity due to the occurrence of cavities underneath asphalt pavements was determined using FWD backcalculation analysis. In the future, this approach will be utilized to establish the criteria of road collapse risk and predict the remaining life of cavity sections under numerous varied conditions.

CAD/CAM 세라믹 인레이로 수복한 치아의 응력분포에 관한 유한요소법적 연구

송보경,엄정문 대한치과보존학회 2001 Restorative Dentistry & Endodontics Vol.26 No.6

When restoring a tooth, the dentist tries to choose the ideal material for existing situation. One criterion that is considered is its suitability for restoring coronal strength. As more tooth structure is removed, the cusps are weakened and susceptible to fracture. Further, this increased deformation may cause the formation of intermittent gaps at the margin between the hard tissue and the restoration, facilitating marginal leakage. The improvements in ceramic materials now make it possible for alternatives to amalgams, composites, and cast metal to be offered for posterior teeth. Of the materials used, ceramics most closely approximates the properties of enamel. The introduction of computer-aided design/computer-aided manufacture(CAD/CAM) systems to restorative dentistry represents a major technological breakthrough. It is possible to design and fabricate ceramic restorations at a single appointment. Additionally, CAD/CAM systems eliminate certain errors and inaccuracies that are inherent to the indirect method and provide an esthetic restoration. The aim of this investigation was to study the loading characteristics of CAD/CAM ceramic inlay and to compare the stress distribution and displacement associated with different designs of cavity(the isthmus width and cavity depth) . A human maxillary left first premolar was prepared with standard mesio-occlusal cavity preparation, as recommended by the manufacturer. Ceramic Inlay was fabricated with CEREC 2 CAD/CIM equipment and cemented into the prepared cavity. Three dimensional model was made by the serial photographic method. The cavity width was varied 1/3, 1/2 and 1/3 of intercuspal distance between buccal and lingual cusp tip. The cavity depth was varied 1.5mm and 2.3mm. So six models were constructed to simulate six conditions. A point load of 500N was applied vertically onto the first node of the lingual slope from the buccal cusp tip. The stress distribution and displacement were solved using ANSYS finite element program(Swanson Analysis System) . The results were as follows ; 1.The displacement occurred buccal, distal and cervical direction from the buccal cusp. In case of the deep cavity, the displacement decreased and with the increase of the cavity width, it increased. 2.In ceramic inlay, the stress decreased in the deep cavity and it increased with the increase of the cavity width. The stress in composite resin cement was less than in ceramic inlay, therefore the stress propagation was blocked by composite resin cement. 3.As the width of cavity increased, the stress spread and increased at the buccal cavosurface margin, so the possibility of crack increased. In case of the deep cavity, the stress decreased at the distal margin of cavity. 4.With the increase of cavity width and depth, the stress on the facio-pulpal line angle increased. In case of narrow cavity width, stress increased on the facio-gingival line angle. Therefore the possibility of crack increased. 5.In case of the shallow cavity, the direction of crack was cervico-lingual on the facio-pulpal line angle. In case of the deep cavity, the direction of crack was cervico-buccal on the facio-pulpal line angle and move vertically with the increase of the cavity width. Key words : Finite element stress analysis, CAD/CAM ceramic inlay, Cavity width, Cavity depth, Stress, Displacement