• 한국해양공학회지
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• 제19권2호
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• pp.19-28
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• 2005

The present paper outlines the numerical investigation of the incident wave interactions with fully submerged and floating dual double hull pontoon/vertical porous membrane breakwaters. Two dimensional five fluid-domains hydro-elastic formulation was carried out in the context of linear wave body interaction theory to study the wave interaction with the double hull of pontoon-membranes. The submerged circular pontoon is consisted of double hulls, which is filled with water in the void space between the outer structure and inner solid buoyant structure. Hydrodynamic characteristics of the proposed system with dual floating double-hull-pontoons filled with water have been studied numerically for the various incident waves. This study is a beginning stage research for the dual double hull porous pontoons/vertical porous membranes breakwaters which is ideally designed in order to suppress significantly the transmitted and reflected waves simultaneously.

• Geomechanics and Engineering
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• 제21권2호
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• pp.123-132
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• 2020

Due to the various restrictions and problems related to the construction of new roads in urban areas, underground road construction has been receiving a great deal of attention in the field of tunnel engineering. In this study, a double-deck road tunnel with a diverging section was analyzed for the evaluation of its stability. Both numerical analysis and scale model tests were performed, the results were used to develop a stability evaluation method for double-deck tunnels with diverging sections constructed in rocks by NATM. From regression analyses conducted on the results of the numerical analysis, an equation and a chart were derived, these tools allow us to obtain the strength/stress ratio (SSR) for double-deck road tunnels with a diverging tunnel in various diverging conditions quickly and accurately. These tools have great potential to help engineers evaluate the stability of double-deck tunnels in the preliminary design stage.

• 대한소아치과학회지
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• 제34권3호
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• pp.447-453
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• 2007

본 연구는 유치열에서 치아기형 발생빈도와 영구치열에 미치는 영향을 조사하여 치아기형의 조기진단의 필요성을 평가하기 위한 것이다. 2000년도에서 2005년까지 전남대학교병원에 내원한 환자 중 파노라마 방사선 사진을 촬영한 2세에서 7세 사이의 어린이를 조사하여 유치열에서 이중치와 선천적 결손치의 유병율을 조사하고 그러한 유치열의 이상과 영구치열과의 상호관계를 조사하였다. 134명의 남아와 120명의 여아로 총 254명의 파노라마 필름을 조사하였으며 이중 8명(5명의 남아, 3명의 여아)에서 유치열에서의 결손치가 발견되었고 4명(2명의 남아, 2명의 여아)에서 유치열에서의 이중치가 발견되었다. 유치열에서 이중치의 유병율은 1.6%였으며 선천적 결손치의 유병율은 3.1%였다. 피검자 중1명은 하악의 이중치와 상악의 결손치를 가지고 있었다. 유치열의 이상이 나타난 11명 중 7명에서 계승 영구치의 결손이 발견되었다. 본 연구에서 유치열의 치아기형이 나타난 경우 계승 영구치에서 치아결손이 빈발할 수 있다는 것을 보여주었다.

• 전자공학회논문지SC
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• 제37권3호
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• pp.44-54
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• 2000

본 논문에서는 표준 메모리 공정에 구현 가능한 주파수 적응성을 갖는 부지연 회로의 설계기법에 대해 제안한다. 제안하는 설계기법은 기본적으로 아날로그 SMD (synchronous mirror delay) 형태의 부지연 회로로서 입력클록의 주기와 구현하고자 하는 부의 지연 시간의 차이에 해당하는 시간을 아날로그 회로의 개념으로 측정하고 다음 번 주기에서 반복한다. 출력클록의 발생과 관련되는 부수적인 지연을 측정단의 앞 단인 지연모델 단에서 상쇄하는 기존의 SMB 기법과는 달리, 반복단에서 상쇄하는 새로운 기법을 통하여 넓은 부지연 범위를 구현하여 특히 고속동작에서의 부지연 특성을 원할하게 한다. 또한 넓은 범위의 주파수 동작범위를 구현하기 위해 해당하는 주파수 범위에서 아날로그 회로가 최적의 동작 조건을 갖추도록 하기 위한 새로운 주파수 감지기 및 최적조건 설정기법을 제안한다. 제안된 회로의 응용으로서 초고속 DRAM인 DDR SDRAM에 적용하는 예를 보였으며, 0.6㎛ n-well double-poly double-metal CMOS 공정을 사용하여 모의실험 함으로써 그 유용성을 입증한다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1999년도 동계 학술대회 논문집
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• pp.428-435
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• 1999

• 한국전산유체공학회지
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• 제20권4호
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• pp.1-6
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• 2015

Centrifugal pumps consume considerable amount of energy in various industrial applications. Therefore, improvement of the efficiency of these machines has become a major challenge. Cavitation is a phenomenon which decreases the pump efficiency and even causes structural demage. Hence, the goal of this paper is to investigate the cavitation problem in the single-stage and double-stage centrifugal pumps. The Volume of Fraction (VOF) method has been used for the numerical simulations together with Rayliegh-Plesset model for the gas-liquid two-phase flow inside the pump. In order to capture the turbulent phenomena, the standard k-${\varepsilon}$ turbulence model has been adopted, and the simulations have been done as unsteady cases. In addition, the motion of the rotating parts has been simulated using Multi Reference Frame(MRF) method. The results are presented and compared in terms of hydraulic head and NPSH for both the single-stage and double-stage pumps. The H-Q curves show the effects of cavitation on decreasing the pumps performances.

• 설비공학논문집
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• 제11권3호
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• pp.422-430
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• 1999

This paper concerns the study of a two-stage absorption heat pump cycle to utilize treated sewage. This two-stage cycle consists of coupling double-effect with parallel or series flow type and single effect cycle so that the first stage absorber and condenser produces hot water to evaporate refrigerant in the evaporator of the second stage. The effects of operating variables such as absorber temperature on the coefficient of performance have been studied for two-stage absorption heat pump cycle. The working fluid is lithium bromide and water solution. The efficiency of the two-stage absorption heat pump cycle has been studied and simulation results show that higher coefficient of performance could be obtained for the first stage with parallel flow type. The optimum ratio of solution distribution can be shown by considering the COP, the crystallization of solution and the generator temperature.

• 한국전자파학회논문지
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• 제17권8호
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• pp.719-724
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• 2006

본 논문에서는 Half-LO 주파수를 이용하는 새로운 방식의 double-conversion down mixer를 2.3 GHz 대역에서 설계하였다. 제안된 mixer에서는 Half-LO 주파수를 2개의 HEMT에 인가하여 두 HEMT에서의 변환 방식을 gate type과 resistive type으로 다르게 함으로서 IF 주파수를 얻게 된다. 기존의 sub-harmonic mixers와 같이 Half-LO 주파수를 사용하지만 제안된 mixer는 Half-LO의 second harmonic 성분을 이용하지 않고 Half-LO의 기본 주파수를 이용하여 주파수 변환을 하고 두 번째 HEMT에서 Resistive mixer type으로 IF 신호를 얻기 때문에 기존의 능동 mixer보다 향상된 선형성을 얻을 수 있다. 2.3 GHz 대역에서 설계 제작된 mixer는 Half-LO 전력 10 dBm을 이용하여 5dB의 변환 손실과 16.25dBm의 IIP3 특성을 얻을 수 있었다.

• Clinics in Orthopedic Surgery
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• 제10권4호
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• pp.413-419
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• 2018

Background: We aimed to examine the factors that influence synovialization of the grafted tendon after double-bundle anterior cruciate ligament (ACL) reconstruction based on second-look arthroscopic findings. Methods: Out of 205 knees that were treated between August 2008 and May 2016 with double-bundle ACL reconstruction using bio-absorbable cross-pins and Endobuttons for femoral tunnel fixation, we enrolled 65 knees (64 patients) that underwent second-look arthroscopy with hardware removal at 1 year postoperatively. Measured clinical outcomes included the Lysholm score and Tegner activity score that were evaluated preoperatively and during the final follow-up. We analyzed the relationship between synovial coverage and patient age, length of the preserved remnant tissue on the tibial side, type of bundle (anteromedial or posterolateral), type of graft (autograft or allograft), and time from injury to surgery. Results: The area of synovial coverage showed a significant statistical correlation with patient age and the length of the preserved remnant tissue on the tibial side. The average synovial coverage was significantly better for the anteromedial bundle than for the posterolateral bundle, better for the autograft than for the allograft reconstruction, and better when treated in the acute stage than in the chronic stage. However, synovialization of grafted tendon did not correlate to clinical outcomes. Conclusions: While we were able to identify several factors influencing synovialization of the grafted tendon after double-bundle ACL reconstruction, including patient age, length of preserved remnant tissue of the torn ACL, type of bundle, type of graft, and time from injury to surgery, we found no evidence that increased synovialization improves clinical outcomes at 1 year postoperatively.

• Journal of Korean Neurosurgical Society
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• 제62권1호
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• pp.123-129
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• 2019

Objective : Ventriculoperitoneal (VP) shunt surgery is a common and effective treatment for hydrocephalus and cerebrospinal fluid disorders. Infection remains a major cause of morbidity and mortality after a VP shunt. There is evidence that a deep skin flora microbiome may have a role to play in post-operative infections. In this technical note, we present a skin preparation technique that addresses the issue of the skin flora beyond the initial incision. Methods : The patient is initially prepped, as standard, with. a single layer of 2% CHG+70% isopropyl alcohol. The novel stage is the 'double incision' whereby an initial superficial incision receives a further application of povidone-iodine prior to completing the full depth incision. Results : Of the 84 shunts inserted using the double-incision method (September 2015 to September 2016), only one developed a shunt infection. Conclusion : The double incision approach to skin preparation is a unique operative stage in VP shunt surgery that may have a role to play in reducing acute shunt infection.