• ETRI Journal
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• 제38권4호
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• pp.685-694
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• 2016

A surface micromachined piezoresistive pressure sensor with a novel internal substrate vacuum cavity was developed. The proposed internal substrate vacuum cavity is formed by selectively etching the silicon substrate under the sensing diaphragm. For the proposed cavity, a new fabrication process including a cavity side-wall formation, dry isotropic cavity etching, and cavity vacuum sealing was developed that is fully CMOS-compatible, low in cost, and reliable. The sensitivity of the fabricated pressure sensors is 2.80 mV/V/bar and 3.46 mV/V/bar for a rectangular and circular diaphragm, respectively, and the linearity is 0.39% and 0.16% for these two diaphragms. The temperature coefficient of the resistances of the polysilicon piezoresistor is 0.003% to 0.005% per degree of Celsius according to the sensor design. The temperature coefficient of the offset voltage at 1 atm is 0.0019 mV and 0.0051 mV per degree of Celsius for a rectangular and circular diaphragm, respectively. The measurement results demonstrate the feasibility of the proposed pressure sensor as a highly sensitive circuit-integrated pressure sensor.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 춘계학술대회 논문집
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• pp.119-122
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• 2009

본 연구에서는 2차원 초음속 공동유동에서 발생하는 압력진동을 제어하기 위하여 수치해석적 연구를 수행하였다. 본 계산에서는 압력진동을 제어하기 위하여 보조공동의 형상을 변화시켰으며, 유동의 마하 수를 1.50, 1.83 그리고 2.50로 변화시켰다. 그 결과, 보조공동은 압력진동을 상당히 감소시켰으며, 압력진동의 제어효과는 유동의 마하수와 보조공동의 상세형상에 크게 의존함을 알았다.

• 대한소아치과학회지
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• 제34권1호
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• pp.62-72
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• 2007

이번 실험에서는 중합수축 응력이 가장 크게 나타나는 유구치 I급 와동에서 와동벽의 위치와 중합광원의 변화에 의해 다르게 나타나는 응력의 차이를 microtensile bond strength (MTBS)를 이용하여 알아보는 것을 목적으로 하였다. 교합면 법랑질을 제거한 하악 제 2유구치 30개를 준비하여 I급 와동을 형성하였다. 제조사의 지시에 따라 상아질 접착제를 도포 후 3가지 중합광원: 할로겐 램프, 플라즈마, 발광다이오드를 이용하여 10개씩 광중합하였다. 복합레진을 한꺼번에 충전 후 각각의 중합기로 광중합하였다. 동일 치아에서 각각 치수벽과 축벽의 MTBS 측정용 시편을 제작하고 각 군을 중합광원과 와동벽 위치에 따라 할로겐 램프 - 축벽군, 할로겐 램프 - 치수벽군, 플라즈마 - 축벽군, 플라즈마 - 치수벽군, 발광다이오드 - 축벽군, 발광다이오드-치수벽군의 6개 군으로 분류하였다. 만능시험기에서 MTBS를 측정하고 파절편과 와동의 단면을 SEM을 이용하여 관찰하였다. 동일 중합광원에서 와동벽 간 비교는 T-test, 동일 와동벽에서 중합광원 간 비교는 One-way ANOVA와 Tukey's post hoc test를 이용하였고 Weibull 분포분석을 하였다. 동일 중합광원 군간 비교에서 모두 치수벽 시편의 접착강도가 축벽 시편에 비해 유의하게 높았으며 동일 와동벽 군간 비교에서 모두 중합광원에 따른 접착강도가 유의한 차이를 보이지 않았다. 축벽 시편이 치수벽 시편보다 낮은 Weibull 변수(m)를 나타내었고 SEM 관찰 결과 축벽 시편에서 보다 더 불균일한 접착이 이루어진 것을 알 수 있었다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.397-400
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• 2006

In this study, we experimentally investigate the possibility of skin-friction drag reduction by series of transverse cavities in a turbulent boundary layer flow. The effects of cavity depth (d), cavity length (l) and cavity spacing (s) on the skin friction drag are examined in the range of $Re_{\theta}\;=\;4030\;{\sim}\;7360$, $d/{\theta}_0\;=\;0.13\;{\sim}1.03$, l/d = 1 ~ 4 and s/d = 5 ~ 20. We perform experiments for twenty different cavity geometries and directly measure total drag force using in-house force measurement system. In most cases, the skin friction drag is increased. At several cases, however, small drag reduction is obtained. The variation of the skin ftiction drag is more sensitive to the cavity length than to the cavity depth or cavity spacing, and drag is reduced at $s/l\;{\geq}\;10$ and $l/{\theta}_0\;{\leq}\;0.26$ irrespective of the cavity depth. At $l/\bar{\theta}_0\;=\;0.13$ and s/l = 10, maximum 2% drag reduction is achieved. When the skin friction drag is reduced, there is little interaction between the flows inside and outside cavity, and the flow changed by the cavity is rapidly recovered at the following crest. A stable vortex is formed inside a cavity in the case of drag reduction. This vortex generates negative skin friction drag at the cavity bottom wall. Although there is form drag due to the cavity itself, total drag is reduced due to the negative skin friction drag.

• Parasites, Hosts and Diseases
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• 제22권2호
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• pp.229-237
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• 1984

마우스를 실험동물로 하여 스파르가눔(sparganum)을 경구감염시킨 후 충체의 이행과정 및 충체분포를 관찰함으로써 스파르가눔의 병원성을 이해하고 실험적 스파르가눔토에 대한 기초자료를 마련하고자 이 연구를 실시 하였다. 스파르가눔은 강원도 횡성군에서 포획한 유혈목이(Matrix tigrina lateralis)의 피하조직 및 내장에서 회득한 것을 사용하였고 ICR계 마우스 21∼259정도의 수컷 28마리에 대하여 각각 5마리의 스파르가눔 두절(scolex) 및 경부(neck)를 경구감염시킨 후 10분후부터 14일까지 도살하고 전신부검을 실시하여 충체 이행 과정 및 분포를 관찰한 바 결과는 다음과 같다. 1. 스파르가눔은 감염 10분후 이미 마우스 십이지사의 장벽을 관통하고 있는 것이 관찰되었고 30분 이내에 관통을 끝낸 다음 복륙내에 주로 분포하였다. 특히 장벽을 관통할 때에는 계관에서 복륙쪽으로 직접 뚫고 나오는 것이 관찰되었다. 2. 감염 1시간부터 1일까지는 대부분의 충체가 복륙내에서 발견되었고 1일에 근육이나 피하조직으로 이행한 것도 관찰되었다. 3. 충체가 대부분 피하조직으로 이행한 것은 감염 7일이내인 것으로 나타났는데 감염 14일까지 관찰한 바 피하 또는 근금조직에서 고수된 28마리의 충체는 마우스 경부(neck) 주위조직에 13마리, 체간부(trunk)에 12마리, 두부(head)에 3마리가 분포하였고 이들중 하악골하부 및 견갑하부의 피하조직에서 가장 많은 충체가 발견되었다. 이들 피하조직 또는 장관벽의 조직반응은 거의 관찰되지 않았다. 4. 마우스에 감염된 스파르가눔은 처음에 평균 4mm이던 것이 7일후 평균 12mm, 14일후 평균 35mm로 성장하였다. 이상의 결과로 미루어볼 때 마우스에 경구감염된 스파르가눔은 10∼30분후에 위 또는 십이지사벽을 관통하여 복륙으로 나온 후 롱격막 또는 복막을 뚫고 7R이내에 주로 경부 및 그 주위조직으로 이행하는 것으로 생각되었다.

• Advances in aircraft and spacecraft science
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• 제9권2호
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• pp.131-148
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• 2022

The paper presents the surface-modified NACA 2412 airfoil performance with variable cavity characteristics such as size, shape and orientation, by numerically investigated with the pre-validation study. The study attempts to improve the airfoil aerodynamic performance at 30 m/s with a variable angle of attack (AOA) ranging from 0° to 20° under Reynolds number (R_e) 4.4×10⁵. Through passive surface control techniques, a boundary layer control strategy has been enhanced to improve flow performance. An intense background survey has been carried out over the modifier orientation, shape, and numbers to differentiate the sub-critical and post-critical flow regimes. The wall-bounded flows along with its governing equations are investigated using Reynolds Average Navier Strokes (RANS) solver coupled with one-equational transport Spalart Allmaras model. It was observed that the aerodynamic efficiency of cavity airfoil had been improved by enhancing maximum lift to drag ratio ((l/d) max) with delayed flow separation by keeping the flow attached beyond 0.25C even at a higher angle of attack. Detailed investigation on the cavity distribution pattern reveals that cavity depth and width are essential in degrading the early flow separation characteristics. In this study, overall general performance comparison, all the cavity airfoil models have delayed stalling compared to the original airfoil.

• 한국소음진동공학회논문집
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• 제27권1호
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• pp.94-99
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• 2017

Breaking the rigid connection between the two faces of the wall can significantly improve the sound transmission loss of the wall. This is usually achieved by resiliently mounting the gypsum board on one of the two faces of the wall using resilient channel. Resilient channel with less stiffness than that of air cavity could move the resonance frequency of the light-weight wall. So we can get higher sound transmission loss at low frequencies for light-weight wall using resilient channel. It's sound transmission loss is 17 dB higher than that of single stud wall, and 5 dB higher than that of double stud wall.

• Journal of Chest Surgery
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• 제9권2호
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• pp.175-186
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• 1976

The cellular change of the pulmonary tuberculous lesions may be divided into two groups,exudative and proliferative form by their course and fate. In the most cases, the patients usually have very much complex type of cellular changes. Therefore, the shadows of the chest films in pulmonary tuberculosis are also much variable in nature. And Daniel said that knowledge of the pathology of tuberculosis and an appreciation of the method of progression and healing are essential to proper interpretation of the films. Author, having reviewed 33 cases of resected tuberculous lung obtained in N.M.T.H. for one year from Oct. '75 to Sep. '76 by surgical managements, classified the Pathological findings such as: 1) caseation only, 2) tuberculoma, 3) atelectatic lung 4) cavitary lesion and 5) atelectasis with cavity, and examined the relationship between the roentgenological characteristics of the chest films and the pathological process of tuberculous lesions of the resected lungs, The result were obtained as follows. (1) Tuberculoma was commonly appeared in $S_2$ segment in right and $S_6$ segment in left. (2) Atelectasis and destroyed lung were more commonly appeared in left lung than right, and their containing rate of cavity was 82%. (3) Cavities were mostly appeared in $S_1$ and $S_2$ segments of both lung and the appearance-rate of cavity on $S_6$ segment was higher in left than right. And among the cavitary lesions of the resected lung, cavity was not seen in the preoperative chest films in 22%. (4) The configuration, thickness and sharpness of the walls of cavities, which revealed the cavitary shadows in the preoperative chest films, were mostly depended on the degree of increased collagenous fiber of the wall, existence of perifocalitis, and more or less of the caseous masses on the inner surface of the cavity wall.

• Archives of Plastic Surgery
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• 제38권3호
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• pp.323-325
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• 2011

Purpose: Breast implant ruptures and displacement are problematic complications after augmentation mammoplasty. The authors report a patient whose cohesive silicone gel implant ruptured and migrated into the pleural cavity after augmentation mammoplasty. Methods: A 23-year-old female had received augmentation mammoplasty at a local clinic a week before visiting our hospital. When the patient's doctor performed a breast massage on the sixth postoperative day, the left breast became flattened. The doctor suspected a breast implant rupture and performed revision surgery. The implant, however, was not found in the submuscular pocket and no definite chest wall defect was found in the operative field. The doctor suspected implant migration into the pleural cavity, and after inserting a new breast implant, the doctor referred the patient to our hospital for further evaluation. The patient's vital signs were stable and she showed no specific symptoms except mild, intermittent pain in the left chest. A CT scan revealed the ruptured implant in the left pleural cavity and passive atelectasis. Results: The intrapleurally migrated ruptured implant was removed by video-assisted thoracic surgery (VATS). There were no adhesions but there was mild inflammation of the pleura. No definite laceration of the pleura was found. The patient was discharged on the first day after the operation without any complications. Conclusion: Surgeons should be aware that breast implants can rupture anytime and the injury to the chest wall, which may displace the breast implant into the pleural cavity, can happen during submuscular pocket dissection and implant insertion.

• 한국전산유체공학회지
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• 제4권1호
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• pp.8-18
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• 1999

In devising a numerical approximation for the convective spatial transport of a fluid mechanical quantity, it is noted that the convective motion of a scalar quantity occurs in one-way, or from upstream to downstream. This consideration leads to a new scheme termed a pure upwind difference scheme (PUDS) in which an estimated value for a fluid mechanical quantity at a control surface is not influenced from downstream values. The formal accuracy of the proposed scheme is third order accurate. Two typical benchmark problems of a wall-driven fluid flow in a square cavity and a buoyancy-driven natural convection in a tall cavity are computed to evaluate performance of the proposed method. for comparison, the widely used simple upwind scheme, power-law scheme, and QUICK methods are also considered. Computation results are encouraging: the proposed PUDS sensitized to the convection direction produces the least numerical diffusion among tested convection schemes, and, notable improvements in representing recirculation of fluid stream and spatial change of a scalar. Although the formal accuracy of PUDS and QUICK are the same, the accuracy difference of approximately a single order is observed from the revealed results.