• Title/Summary/Keyword: Closed Cavity

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Active Noise Control of a Closed Rectangular Cavity Using FXLMS Algorithms (FXLMS 알고리듬을 이용한 사각밀폐공간의 능동소음제어)

  • Ryu, Kyung-Wan;Hong, Chin-Suk;Shin, Chang-Joo;Jeong, Weui-Bong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.11
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    • pp.983-990
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    • 2011
  • This paper investigates active noise control(ANC) of a rectangular cavity using single channel filtered-x least mean square(FXLMS) algorithms to globally reduce the interior noise. To obtain the global reduction of the interior noise, multichannel active control should be incorporated in general. We, however, examined firstly the optimal location of the secondary source that produces a global reduction of the interior noise field using single channel control. We then investigated the frequency characteristics of the reduction to yield the effective frequency band of the active control system. It follows that the secondary source should be located as close to the primary source as possible in order to obtain the global reduction.

An experimental study for the filling balance of the family mold (Family 금형의 충전 밸런스를 위한 실험적 연구)

  • Cha B. S.;Rhee B. O.;Park H. P.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2005.09a
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    • pp.132-140
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    • 2005
  • It is well known that the family-mold has an advantage to reduce the cost for production and mold. However, defects are frequently occurred by over packing the smaller volume cavity during molding, especially whorl the family-mold has a volumetric difference between two cavities. In this study, we confirmed the cavity-filling imbalance by the temperature and the pressure sensors, and developed a variable-runner system for the cavity-filling balance. We carried out experiments fur balancing the cavity filling in the family-mold with the variable-runner system, and confirmed a balanced cavity-filing through analyzing the temperature and pressure change in each cavity as the cross-sectional area of the runner changed. We also examined the influence of the injection-speed to the balancing-capability of the variable-runner system in the experiment.

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An Experimental Study on the Thermal Characteristics of Hybrid Solar Receiver for Dish/Stirling System (Dish/Stirling 시스템 적용을 위한 Hybrid 태양열 흡수기의 열특성에 관한 실험 연구)

  • Kang, Myeong-Cheol;Kim, Jin-Soo;Kang, Yong-Heack;Kim, Nack-Joo;Yoo, Seong-Yeon;Kim, Jin-Heack
    • Journal of the Korean Solar Energy Society
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    • v.27 no.3
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    • pp.7-13
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    • 2007
  • A Dish type solar concentrating system consists of a parabolic concentrator and a cavity receiver. In order to achieve high temperatures from solar energy, it is essential to efficiently reflect the solar rays in the concentrator and to minimize thermal losses in the cavity receiver. Improving the economical efficiency of a solar power system required the stirling unit to be operated continuously. For continuous operation of the stilting unit, the receiver must be continuously provided with thermal energy from solar as well as additional combustion heat. It is possible for a hybrid solar receiver system equipped with an additional combustion to be operated 24 hrs/day. A hybrid solar receiver was designed and manufactured for a total thermal load of 35 kW in the operating temperature range $700^{\circ}C$ to $800^{\circ}C$. The hybrid receiver system was tested in gas-only mode by gas-fired heat to investigate thermal characteristics at inclination angle varying from 0 deg to 30 deg(cavity facing down) and the aperture to cavity diameter ratios of 0(closed cavity) and 1.0(open cavity). This paper has been conducted to measure temperature distribution in cavity surface and to analyze thermal resistances, and the evaporation and condensation heat transfer coefficient in all cases(open and closed cavity).

Experiments for the Acoustic Source Localization in 2D Cavity Flow (2차원 공동 유동에서의 소음원 위치 판별을 위한 실험적 연구)

  • Lee, Jaehyung;Park, Kyu-Chol;Choi, Jong-Soo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.12
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    • pp.1241-1248
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    • 2004
  • This paper presents an acoustic source localization technique on 2D cavity model in flow using a phased microphone array. Investigation was performed on cavity flows of open and closed types. The source distributions on 2D cavity flow were investigated in an anechoic open-jet wind tunnel. The array of microphones was placed outside the flow to measure the far field acoustic signals. The optimum sensor placement was decided by varying the relative location of the microphones to improve the spatial resolution. Pressure transducers were flush-mounted on the cavity surface to measure the near-filed pressures. It is shown that the propagated far field acoustic pressures are closely correlated to the near-field pressures and their spectral contents are affected by the cavity parameter L/D.

An Experimental Study for the Filling Balance of the Family Mold (Family 금형의 충전 균형을 위한 실험적 연구)

  • Park H. P.;Cha B. S.;Rhee B. O.
    • Transactions of Materials Processing
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    • v.15 no.1 s.82
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    • pp.47-56
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    • 2006
  • It is well known that the family-mold has an advantage to reduce the cost for production and mold. However, defects are frequently occurred by over packing the smaller volume cavity during molding, especially when the family-mold has a volumetric difference between two cavities. In this study, the cavity-filling imbalance was confirmed by the temperature and the pressure sensors, and a variable-runner system was developed for balancing the cavity-filling. Experiments of balancing the cavity filling was carried out in the family-mold with the variable-runner system, and balancing the cavity-filling was confirmed by changing the cross-sectional area of a runner in the variable-runner system with the temperature and pressure sensors. The influence of the injection speed to the balancing-capability of the variable-runner system was also examined in the experiment.

Acoustic Source Localization in 2D Cavity Flow using a Phased Microphone Array (마이크로폰 어레이를 이용한 2차원 공동 유동에 대한 소음원 규명)

  • 이재형;최종수;박규철
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.701-708
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    • 2003
  • This paper presents an acoustic source localization technique on 2D cavity model in flow using a phased microphone way. Investigation was performed on cavity flows of open and closed types. The source distributions on 2D cavity flow were investigated in anechoic open-jet wind tunnel. The array of microphones was placed outside the flow to measure the far field acoustic signals. The optimum sensor placement was decided by varying the relative location of the microphones to improve the spatial resolution. Pressure transducers were flush-mounted on the cavity surface to measure the near-filed pressures. It is shown that the propagated far field acoustic pressures are closely correlated to the near-field pressures. It is also shown that their spectral contents are affected by the cavity parameter L/D.

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A Study of Heat Transfer Phenomena due to a Formed Gas Bubble under Heat-Conduction Domain in A Closed Square Cavity (TLC 를 이용한 사각공동내의 열전도 영역에 기포의 형성으로 인한 열전달 현상 구명)

  • Eom, Young-Kyoon;You, Jae-Bong
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.85-89
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    • 2003
  • In a closed square cavity filled with a liquid, a cooled the upper horizontal wall and a heated the lower horizontal wall, the flow isn't generated under the ground-based condition when Rayleigh number is lower than 1700. In such case the flow phenomena near an air bubble under a cooled horizontal wall were investigated. The temperature and the flow fields were studied by using the Thermo-sensitive Liquid-Crystal and the image processing. The qualitative analysis for the temperature and the flow fields were carried out by applying the image processing technique to the original data. Injecting bubble at the center point of upper cooled wall, the symmetry shape of two vortexes near an air bubble was observed. The bubble size increased, the size of velocity and the magnitude of velocity increased. In spite of elapsed time, a pair of two vortexes was the unique and steady-state flow in a square cavity and wasn't induce to the other flow in the surround region.

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The Thermocapillary Effect on Pure Conduction Mechanism in a Closed Square Cavity (수평 사각밀폐공간내의 전도열전달 기구에서 열모세관효과)

  • Yu, Jae-Bong;An, Do-Won;Yoo, Joo-Sik;Eom, Yong-Kyoon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.11 s.242
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    • pp.1209-1219
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    • 2005
  • In a closed square cavity filled with a liquid, a cooling horizontal upper wall and a heating lower wall, the flow isn't generated under the ground-based condition when Rayleigh number is lower than 1700. In this mechanism, Ra=1534, Temperature and velocity fields near an air-bubble in silicon-oil under a cooled upper wall were investigated. Temperature and velocity fields is visualized using the thermo-sensitive liquid-crystal and light sheet visualization technique. The quantitative analysis fer the temperature and the flow fields were carried out by applying the image processing technique to the original data. The symmetry shape of two vortexes near an air bubble was observed. As the bubble size increased, the size of vortex and the magnitude of velocity increased. In spite of elapsed time, a pair of vortexes was the unique and steady-state flow in a square cavity and wasn't induced to the other flow in the surround region.

Fabrication of closed hollow obturator for hard palate defect patient undergone maxillectomy (상악절제술로 인한 경구개 결손 환자에서의 closed hollow obturator 제작 증례)

  • Jang, Woo-Hyung;Lim, Hyun-Pil;Yun, Kwi-Dug;Park, Chan;Yang, Hong-So
    • The Journal of Korean Academy of Prosthodontics
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    • v.58 no.1
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    • pp.30-34
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    • 2020
  • Maxillectomy is performed to remove the tumor in the palate, maxillary sinus, buccal mucosa or nasal cavity. The resection range depends on the size and the extent of the tumor and it affects speech production or cause nasal regurgitation during feeding. Obturator can occlude an opening such as an oro-nasal fistula and protect the defect area. Successful reconstrucion of the patient's oral cavity who have gone over the maxillectomy is a difficult task. The condition and number of teeth, the remaining support area, and the extent of the defect area have a great influence on manufacturing the obturator. If these factors are disadvantageous, the prognosis of the prosthesis is uncertain. The final obturator must have a sufficient retention in the patient's oral cavity and must not irritate the surrounding tissue and support area where the resection was performed.In this case, a 55 year old female went through the maxillectomy and the only 3 teeth remained. And the retention of the maxillary prosthesis seems to be poor. So that, we fabricated the closed hollow obturator which has reduced weight compared to the conventional obturator. Consequently the closed hollow obturator can give better sealing and the adaptation.

Extracuterine Pregnancy in a Bitch (개의 자궁외 임신 증례)

  • 김휘율;한규보;김현수;김종성;임희란
    • Journal of Veterinary Clinics
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    • v.17 no.1
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    • pp.275-278
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    • 2000
  • A 3-year-old yorkshire terrier was examined because of the green-like vaginal discharge. Abdominal ultrasonographs revealed dead fetuses in the abdominal cavity. Surgical exploration revealed fetuses located in the region of the uterine wall, the omentum, the ileum, and the upper right side of the liver respectively. Fetal structures were removed and an ovariohysterectomy was performed. The abdominal cavity was flushed with warm saline and then the incision closed. These fetuses were at different stages of development. It was suggested that the development of the fetuses apparently continued in extrauterine pregnancy until the blood supply became inadquate for further growth.

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