• 대한치과의사협회지
• /
• 제36권2호통권345호
• /
• pp.144-150
• /
• 1998

The dental insurance had been enforced in Korea past 20 years. The major part of the insurance was filling, and the filling was divided into two parts-the cavity preparation and cavity filling, The Cavity filling was estimated into 6 levels according to the cavity types. But the tooth cavity preparations was not evaluated by the cavity types but merely only one-the one visit filling or cavity preparation. Korean dentists tend to turn away from the amalgam to the non-insurance treatments. The purpose of this study was to relate the cavity preparations and cavity fillings to the cavity types. So I measured the real time and surveyed the relative difficulties of cavity preparations from the 31 dentists according to the cavity types, who had been trained in conservative dentistry. The conclusion of this study was below. 1. The estimations of tooth cavity preparation was divided same as the cavity filling. 2. There must be reasonable considerations about the times and difficulties in cavity preparation. 3. There was differences between the premolars and molars, upper jaw and lower one. 4. Two or more cavities in one tooth must be evaluated according to the number of cavities, not in one cavity.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2003년도 추계 학술대회논문집
• /
• pp.139-143
• /
• 2003

In this study the numerical analyses on cavity flow in supersonic flow field are conducted. According to the length-to-depth ratio of cavity, the shear layer is changed, consequently influencing on vortex structure inside the cavity. Especially in case the fluid flow outside cavity impinges inside the cavity, the oscillation of the cavity flow is identified. Another result is that though the cavity flow shows the unsteadiness, characteristics of cavity flow can be represented by pressure coefficients converged.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.3009-3014
• /
• 2007

The effectiveness of passive control techniques for alleviating the pressure oscillation generated in a supersonic cavity flow was investigated numerically and experimentally, respectively. The control device includes a sub-cavity installed near the leading edge of a rectangular cavity. Time-dependent supersonic cavity flow characteristics with turbulent features were examined by using the three-dimensional, mass-averaged Navier-Stokes computation based on a finite volume scheme and large eddy simulation. The results show that the pressure oscillation near the trailing edge dominates overall time-dependent cavity pressure variations. Such an oscillation can be attenuated more significantly in the presence of the sub-cavity compared with the cavity without sub-cavity, and a larger sub-cavity leads to better control performance.

• Journal of Multimedia Information System
• /
• 제5권2호
• /
• pp.143-146
• /
• 2018

The eigen value problem of a coaxial cavity and a modified pill box cavity is investigated using the mode matching technique. The coaxial cavity has a cylindrical cavity with beam ports and center conductor. The pill box cavity is the same as a coaxial cavity without center conductor. The electric field and magnetic field are formulated in propagation region and resonance region. The boundary and orthogonal conditions are applied to the electric and magnetic fields. We derived the eigen value equation by the proposed procedure in a coaxial cavity and a modified pill box cavity. The electromagnetic field of the real structure is disturbed by the coaxial wire. The effect of the coaxial wire in pill box cavity with beam ports increase the dominant resonant frequency. The coaxial line method of the coupling impedance is not adequate for a cylindrical cavity. The results of the mode matching technique and simulation agree well. The results confirm the proposed formulation is valid.

• 대한기계학회논문집A
• /
• 제25권1호
• /
• pp.11-15
• /
• 2001

We present the design and strength evaluation of an anodically bonded pressurized cavity array, based on the energy release rate measured from the anodically bonded plates of two dissimilar materials. From a theoretical analysis, a simple fracture mechanics model of the pressurized cavity array has been developed. The energy release rate (ERR) of the bonded cavity with an infinite bonding length has been derived in terms of cavity pressure, cavity size, bonding length, plate size and material properties. The ERR with a finite bonding length has been evaluated from the finite element analysis performed for varying cavity and plate sizes. It is found that, for an inter-cavity bonding length greater than the half of the cavity length, the bonding strength of cavity array approaches to that of the infinite plate. For a shorter bonding length, however, the bonding strength of the cavity array is monotonically decreased with the ratio of the bonding length to the cavity length. The critical ERR of 6.21J/㎡ has been measured from anodically bonded silicon-glass plates. A set of critical pressure curves has been generated for varying cavity array sizes, and a design method of the pressurized cavity array has been developed for the failure-free wafer-level packaging of MEMS devices.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2002년도 학술대회지
• /
• pp.775-778
• /
• 2002

In order to analyse the mechanism of a flow tone around a cavity, the correlations between the flow in the cavity and the boundary layer flow in front of the cavity are studied experimentally in this paper. The instability In the boundary layer forms the vortex at the front edge of the cavity and the flow tone is occurred by the vortex breakdown at the rear edge of the cavity Therefore, the boundary layer measurement is important in the cavity flow control. We measure the velocity of the boundary layer at the entrance of the cavity using hot-wire anemometry and the flow tone around the cavity by microphone. The boundary layer characteristic is changed by the various angle of the flap on the front edge of the cavity, while it is less influenced by the ratio of length and depth of the cavity.

• International Journal of Aeronautical and Space Sciences
• /
• 제16권1호
• /
• pp.19-27
• /
• 2015

In the present study, an effort was made to numerically investigate rectangular cavity aeroacoustics with and without doors. The simulation was performed on an open cavity with an aspect ratio of 5:1:1 at Mach 0.85 using the delayed detached eddy simulation (DDES) approach based on the Spalart-Allmaras model. Two cavity configurations, a clean cavity and a cavity with doors, were modeled. The results obtained from the clean cavity were compared with the experimental sound pressure levels (SPL) and the root mean square for the pressures applied. Furthermore, comparisons of frequencies were made using a modified semi-empirical Rossiter formula. The simulation using DDES precisely predicted the pressure fluctuation and the results matched the experiment quite well. The SPLs at the rear of the cavity were much higher than those in the front due to the instability of the shear layer impinging on the rear wall. Comparisons of DDES for the clean cavity and the doors-on cavity revealed that the SPLs inside the cavity as well as the magnitude of tones are amplified by the side doors. The main focus of this investigation was to obtain a better understanding of the open cavity acoustic resonance phenomenon and investigate the effects of cavity doors on the SPL.

• Design & Manufacturing
• /
• 제2권6호
• /
• pp.33-37
• /
• 2008

Almost all injection molds have multi-cavity, which are designed with geometrically balanced runner system in order to made filling balance between cavity to cavity during injection molding. However, filling imbalance has been existed in the geometrically balanced runner system. In this study, we made an experiment and investigated that are filling balanced according to material. Also, in case of filling imbalance was occurred, we conducted experiments in order to find out difference of cavity pressure with cavity pressure sensor. When filling imbalance was occurred between cavity to cavity, we investigated the filling imbalance and pressure differences by computer-aided engineering(CAE).

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
• /
• pp.310-313
• /
• 2006

본 연구에서는 sub-cavity를 적용한 경우 얻어지는 압력진동의 제어효과를 수치계산 방법을 사용하여 조사하였으며, 삼각돌기와 블로잉제트를 사용하여 얻어진 결과들과 비교하여 그 효율성을 검토하였다. 사각형의 공동을 지나는 유동장은 3차원 비정상 압축성 Wavier-Stokes 방정식에 완전 내제적 유한체적법 및 다단계 Runge-Kutta 방법을 적용하여 수치모사하였으며, 공동유동의 난류상태량들을 적절히 예측하기 위하여 large eddy simulation(LES)을 수행하였다. 본 연구의 결과로부터, 공동후단 부근에서 발생하는 압력진동이 전체 공동유동의 비정상 거동을 지배하며, sub-cavity를 사용하여 압력진동의 폭을 감소시킬 수 있음을 알았다.

• 한국재난정보학회 논문집
• /
• 제18권2호
• /
• pp.261-268
• /
• 2022

연구목적: 지표투과레이더 탐사에 의해 발견된 공동의 경우, 정확히 예측된 공동의 체적에 상응하도록 주입재를 충분히 채우고 강도를 발휘하게 함으로써 안정성을 확보하여 지반함몰을 예방하여야 한다. 연구방법: 지표투과레이더 탐사에 의한 공동파형 분석 방법과 공동형상 촬영장비를 이용한 방법을 바탕으로, 공동의 규모와 형상이 불규칙한 실제 공동을 실측하여 긴급복구시 주입재의 공동채움량을 산정하였다. 연구결과: 지표투과레이더 탐사에 의한 방법과 공동형상화 장비를 활용한 공동 규모 산정을 통하여 공동규모 및 토피에 따른 주입재 채움량과의 상관관계를 분석하여 예상 채움량을 제시하였다. 결론: 공동형상화 장비에 의해 실측된 공동체적은 지표투과레이더 탐사에 의한 공동 체적의 20% ~ 40% 범위로 나타났다. 또한, GPR탐사에 의해 예측된 공동규모 대비 주입재 채움량은 약 60% ~ 140% 범위였으며, 공동 형상화 장비에 의한 공동규모 대비 주입재 채움량은 약 260% ~ 320%로 확인되었다.