• Title, Summary, Keyword: Cavity

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The study of the consuming time and difficulties depending on the cavity types (와동 형태에 따른 소요 시간 및 난이도에 관한 연구)

  • Roh, Byoung-Duck
    • The Journal of the Korean dental association
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    • v.36 no.2
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    • pp.144-150
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    • 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.

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Experimental/Computational Study on the Supersonic Cavity Flow with a Sub-Cavity to Reduce the Pressure Oscillation (압력진동을 저감하기 위한 sub-cavity를 가진 초음속 공동유동에 대한 실험 및 수치해석적 연구)

  • Lim, Chae-Min;Lee, Young-Ki;Kim, Heuy-Dong
    • Proceedings of the KSME Conference
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    • pp.3009-3014
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    • 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.

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Mode Matching Technique in a Cylindrical Cavity with Center Wire

  • Han, Dae Hyun
    • Journal of Multimedia Information System
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    • v.5 no.2
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    • pp.143-146
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    • 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.

Design and Strength Evaluation of an Anodically Bonded Pressurized Cavity Array for Wafer-Level MEMS Packaging (기판단위 밀봉 패키징을 위한 내압 동공열의 설계 및 강도 평가)

  • Gang, Tae-Gu;Jo, Yeong-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.1
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    • pp.11-15
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    • 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.

Experimental study of boundary layer at the entrance of a cavity (공동 입구의 경계층에 관한 실험적 연구)

  • Jung Yong-Wun;Park Seung-O;Lee Duck-Joo
    • Proceedings of the KSME Conference
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    • pp.775-778
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    • 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.

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Aeroacoustic Investigation of a Cavity with and without Doors by Delayed Detached Eddy Simulation

  • Liu, Yu;Tong, Mingbo
    • International Journal of Aeronautical and Space Sciences
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    • v.16 no.1
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    • pp.19-27
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    • 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.

The Pressure and Degree of Filling Balance between Cavity to Cavity in Multi-Cavity Injection Mold (다수 캐비티 금형에서 캐비티 간의 압력과 균형충전도)

  • Noh, Byeong-Su;Park, Tae-Won;Jeong, Yeong-Deug
    • Journal of the Korea Society of Die & Mold Engineering
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    • v.2 no.6
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    • pp.33-37
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    • 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).

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A Passive Control of Cavity-Induced Pressure Oscillations Using Sub-Cavity System (보조공동계를 이용한 공동 유기 압력진동의 피동제어)

  • Kang, M.S.;Kwon, J.K.;Lee, J.S.;Kim, H.D.;Setoguchi, T.
    • 한국전산유체공학회:학술대회논문집
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    • pp.452-455
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    • 2008
  • A new passive control technique of cavity-induced pressure oscillations has been investigated numerically for a supersonic two-dimensional flow over open rectangular cavities at Mach number 1.83 just upstream of a cavity, in which a sub-cavity system is installed on the backward-facing step of the main cavity. A third-order TVD (Total Variation Diminishing) finite difference scheme with MUSCL is used to discretize the spatial derivatives in the unsteady compressible Navier-Stokes equations. The results obtained show that the present sub-cavity system is very effective in reducing cavity-induced pressure oscillations. The results also showed that the resultant amount of attenuation of cavity-induced pressure oscillations was dependent on the length and thickness of the flat plate, and also on the depth of the sub-cavity used as an oscillation suppressor.

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Experimental/ Computational Study on the Passive Control of Supersonic Cavity Flow using a Sub-Cavity (Sub-cavity를 이용한 초음속 cavity 유동의 피동제어에 대한 실험 및 수치해석적 연구)

  • Lim, Chae-Min;Lee, Young-Ki;Kim, Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.295-298
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    • 2007
  • The effectiveness of passive control techniques for reducing the pressure oscillation generated in a supersonic cavity flow was investigated numerically and experimentally, respectively. The control device includes a sub-cavity installed in the upstream 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.

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The Study on Cavity Flow in Supersonic flow field (초음속 유동장에 놓인 공동 유동에 대한 연구)

  • Yoon Y. H.;Hong S. K.;Kwon K. B.
    • 한국전산유체공학회:학술대회논문집
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    • pp.139-143
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    • 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.

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