• 한국자동차공학회논문집
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• 제10권2호
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• pp.1-8
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• 2002

The flow and combustion patterns have been investigated inside the gasoline engine cylinder with the swirl or tumble flow, whereas the air flow characteristics, which are generated in the part of intake system before entering into the intake manifold, have not been known completely. It is necessary to analyze the flow field in the intake system consisting of air rater, throttle valve and intake manifold. The throttle valve, used to control the intake air flow rate, is important because it makes various mass flow rate and flow patterns. Three-dimen-sional How characteristics such as velocities, turbulent intensities and Reynolds shear stresses are measured by the hot wire anemometer at the exit of the throttle valve with the variation in the valve opening angle($15^{\circ}$, $45^{\circ}$, $75^{\circ}$ and $90^{\circ}$) and the Reynolds numbers (45000, 70000 and 140000). There are a lot of changes in flow characteristics at $75^{\circ}$ due to the large recirculation flow comparing with those of the other cases, and the streamwise velocity is especially enforced strongly below the valve shaft. The other component velocities are relatively large near the centerline parallel to the valve shaft. The effects of the Reynolds number on the flow field are not severe.

• 대한기계학회논문집
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• 제16권8호
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• pp.1575-1582
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• 1992

본 연구에서는 정상운전 중인 4사이클 6실린더 터보과급 디젤기관에 갑자기 큰 부하가 작용하였을 경우, 기관 및 과급기 관성 모멘트의 변화가 기관과 과급기의 실제 회전속도, 압축기 압력비, 실린더내 공기유량, 연소효율, 배기온도 등의 과도 응 답성능에 미치는 영향을 시뮬레이션해석과 실험을 통하여 규명하였다.

• 한국항공우주학회지
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• 제47권1호
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• pp.17-25
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• 2019

항공기의 Intake는 공간적 제약 또는 생존성 확보의 이유로 S형태의 곡률을 갖는 덕트를 가진다. 그러나 덕트의 곡률은 2차유동과 유동박리의 발생을 야기하며 불균일한 압력분포 생성의 원인이 된다. 본 연구에서는 RAE M 2129 S-Duct의 형상에 보조 Duct를 적용하여 경계층 흡입을 수행하였다. 경계층 흡입의 위치와 각도를 설계변수로 설정하였으며, 흡입면에서 동일 유량을 흡입하는 조건을 부여하였다. S-Duct의 전산해석 타당성을 검증하기 위하여 Port Side와 Starboard Side의 무차원 압력 분포를 ARA 실험값, 전산해석 값과 각각 비교하여 확인하였다. 본 연구에서는 유동 왜곡을 판단하는 공기역학적 성능인자로 유동 왜곡 계수를 사용 하였으며, 경계층 흡입에 의한 유동박리, 와류, 유량 분포 및 압력 분포를 비교 분석 하였다. 그 결과 경계층 흡입 적용 이전과 비교하여 최대 26.14%의 유동 왜곡 계수 저감 효과를 확인하였다.

• 대한환경공학회지
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• 제37권5호
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• pp.262-268
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• 2015

본 연구는 on-line micro extraction by packed sorbent (on-line MEPS)와 시료다량주입장치인 programmed temperature vaporizer (PTV) injector를 결합한 가스크로마토그래피 질량분석 시스템을 이용하여 유기인계 농약인 methyldemetone-S, diazinon, fenitrothion, parathion, phentoate, O-ethyl O-(4-nitrophenyl) phenylphosphonothioate (EPN)과 카바이트계인 carbaryl에 대한 동시 수질분석법을 확립하였다. MEPS 내 sorbent는 polystyrene divinylbenzene (PDVB) 재질을 이용하였다. 시료전처리시 추출용매 종류, pH, 추출용매량 및 시료주입왕복횟수가 분석에 미치는 영향과 정도보증(QA/QC), 그리고 환경시료에 대한 각 물질의 회수율을 평가하였다. 추출용매는 acetone과 dichloromethane을 80 : 20 (v/v)으로 혼합하여 사용하였고, 내부표준물질과 황산을 첨가한 시료 1 mL를 대상으로 추출용매량 $30{\mu}L$, 시료주입왕복횟수를 7회로 추출하여 분석조건을 최적화하였다. pH가 낮을수록 Diazinon의 분석감응도는 감소한 반면 carbaryl의 분석감응도는 증가하였다. 정도보증결과 항목별 방법검출한계 및 정량한계는 각각 $0.02{\sim}0.18{\mu}g/L$, $0.08{\sim}0.59{\mu}g/L$로 낮았으며, 농도범위 $0.5{\sim}5.0{\mu}g/L$ 수준에서 정밀도와 정확도 범위는 각각 1.5~11.5%, 83.3~129.8%로 나타났다. 환경시료 중 carbaryl을 제외한 모든 항목의 회수율은 75.7~129.3%로 적합하였다. Carbaryl에 대한 회수율은 수돗물, 지하수, 하천수 분석에서 적합한 범위를 나타냈으나, 하수처리방류수에서는 200% 이상으로 만족하지 못하였다.

• Membrane and Water Treatment
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• 제10권2호
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• pp.113-120
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• 2019

To investigate surface properties and interception performances of the new modified PVDF membrane coated with Graphene Oxide (GO) and nano-$TiO_2$ (for short the modified membrane) via the interface polymerization method combined with the pumping suction filtration way, filtration experiments of the modified membrane on Humic Acid (HA) were conducted. Results showed that the contact angle (characterizing the hydrophilicity) of the modified membrane decreased from $80.6{\pm}1.8^{\circ}$ to $38.6{\pm}1.2^{\circ}$. The F element of PVDF membrane surface decreased from 60.91% to 17.79% after covered with GO and $TiO_2$. O/C element mass ratio has a fivefold increase, the percentage of O element on the modified membrane surface increased from 3.83 wt% to 20.87%. The modified membrane surface was packed with hydrophilic polar groups (like -COOH, -OH, C-O, C=O, N-H) and a functional hydrophilic GO-polyamide-$TiO_2$ composite configuration. This configuration provided a rigid network structure for the firm attachment of GO and $TiO_2$ on the surface of the membrane and for a higher flux as well. The total flux attenuation rate of the modified membrane decreased to 35.6% while 51.2% for the original one. The irreversible attenuation rate has dropped 71%. The static interception amount of HA on the modified membrane was $158.6mg/m^2$, a half of that of the original one ($295.0mg/m^2$). The flux recovery rate was increased by 50%. The interception rate of the modified membrane on HA increased by 12% approximately and its filtration cycle was 2-3 times of that of the original membrane.

• 한국수산과학회지
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• 제42권1호
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• pp.15-19
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• 2009

A simple and sensitive method for erythromycin quantification by liquid chromatography electrospray mass spectrometry (LC-MS/MS) in fishery products was developed. Samples were extracted by liquid-liquid extraction using 70% acetonitrile. Lipids were removed by acetonitrile saturated hexane. LC separation was performed on a Shiseido UG C-18 column ($150\;mm{\times}2.0\;mm$ internal diameter.) with a gradient system of 0.2% acetic acid-acetonitrile containing 0.2% acetic acid as a mobile phase at flow rate of 0.2 mL/min. The mass spectrometer was operated in selected reaction monitoring with positive electro-spray interface. Transitions were monitored a m/z $734{\to}577$ and $734{\to}158$, with m/z $734{\to}577$ chosen for quantification. Recovery of erythromycin from fish and shrimp fortified at the 10 ng/mL, 50 ng/mL and 100 ng/mL were 91.6-109.4%, 84.4-111.2% and 98.8-109.6% with high precision, respectively. Limits of quantification and limits of detection of erythromycin in both fish and shrimp were 10.0 ng/mL and 1.0 ng/mL, respectively. This analysis method for erythromycin has been proposed for registration in the Korean Official Methods of Food Analysis and has been utilized for fishery products analysis by the Korea Food and Drug Adminstration and the National Fisheries Products Quality Inspection Service.

• Neurospine
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• 제15권4호
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• pp.362-367
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• 2018

Objective: To assess the efficacy of cervical open-door laminoplasty by hydroxyapatite implant insertion between the lamina and the lateral mass without suturing. Methods: All patients who underwent cervical open-door laminoplasty with C2/C7 undermining and insertion of hydroxyapatite implants from C3 to C6 were retrospectively evaluated for surgical time and neurological outcomes according to the Japanese Orthopaedic Association (JOA) score. To assess the alignment of the cervical spine and postoperative cervical pain, the C2-7 angle and a visual analogue scale score were used, respectively. Results: The population consisted of 102 women and 222 men ranging in age from 32 to 90 years. The average surgical time was 86 minutes. Fourteen of 1,296 hydroxyapatite implants were kept in place with sutures due to a weak restoration force of the hinge during surgery. No hydroxyapatite implant dislocation was detected on cervical computed tomography at 1 year after surgery. The average JOA score was $10.2{\pm}2.5$ before surgery and $14.6{\pm}2.8$ at 1 year after surgery. The average recovery rate was 61.8%. The average C2-7 angle at the neutral position was $7.1^{\circ}{\pm}6.2^{\circ}$ before surgery and $6.5^{\circ}{\pm}6.3^{\circ}$ at 1 year after surgery. Conclusion: This method enabled us to achieve minimal exposure of the lateral mass, prevention of lateral mass injury and dural injury, and a shorter surgical time while maintaining acceptable surgical outcomes. The idea that firm suture fixation is needed to prevent spacer deviation during cervical open-door laminoplasty may need to be revisited.

• 자원환경지질
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• 제53권2호
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• pp.147-157
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• 2020

남극 빙상의 질량 변화는 지구온난화와 관련된 기후 변화와 해수면 상승의 가장 중요한 지표 중 하나이다. 본 연구에서는 위성 중력 자료와 광역 기후 수치 모델을 사용하여, 남극 빙상 질량에 대한 시공간 변화의 특성을 분석하였다. 중력 자료의 분석을 통해 연구 기간(2002.08-2016.08) 동안 지속적으로 남극 빙상의 심각한 질량 손실이 서남극을 중심으로 발생하였음을 확인하였고, 상대적으로 미약한 질량 증가가 동남극에 존재함을 확인하였다. 또한 이들 질량 변동이 해안 지역에 집중되어 있음을 함께 확인하였다. 광역 기후 수치 모델을 사용하여 이러한 질량 변동의 시간적, 공간적 패턴을 유사하게 재현할 수 있었으나, 관측 값에 비해 그 변화 폭이 매우 작았다. 이러한 문제는 빙하의 기저 유출량에 대한 조정을 통해 상당 부분 해결이 되었다. 이 과정에서 재현된 빙상의 질량 변화는 2009년 이전 관측 값의 추세를 97%정도 설명할 수 있었다. 이러한 결과는 빙하 흐름의 역학적 변동이 빙상의 가장 자리를 따라 크게 변하였고, 이러한 변화가 지난 10여 년 동안 남극 빙상의 질량 변화에 크게 영향을 주었다는 것을 의미한다.

• 한국환경보건학회지
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• 제36권1호
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• pp.44-51
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• 2010

This study aimed to develop analytical method for 8-isoprostanes as biomarkers for oxidative stress with LC/MS/MS technique and to apply the method for human urine samples. Analyzed compounds for urinary oxidative stress markers were 7 stereo-isomers of prostaglandins and the internal standard (iso-$PGF_{2{\alpha}}-d_4$) was used to adjust the recovery rate. The method for determining urinary iso-$PGF_{2{\alpha}}$ consisted of solid phase extraction and LC/MS/MS detection. Separation of isomers of prostaglandins completed by porous graphitic carbon column and buffer solution. Detection limits for urinary markers of oxidative stress, iso-$PGF_{2{\alpha}}$ with LC/MS/MS were 0.01 ng/ml by S/N ratio 3 and 0.028 ng/ml by calculated as to FDA method. The recovery (92.8~101.9%) and precision (8.8~20.7%) of analysis were feasible for detecting iso-$PGF_{2{\alpha}}$ in real human urine samples. We detected 4 isomers of prostaglandins in human urine samples. Mean (standard deviation) of urinary iso-$PGF_{2{\alpha}}$ concentration were 0.231 (0.117) ng/mg creatinine for smoking group and 0.154 (0.082) ng/mg creatinine for non-smoking group.

• Archives of Reconstructive Microsurgery
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• 제10권2호
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• pp.93-98
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• 2001

Purpose : This describes our experience with a tenocutaneous free flap from the dorsum of the foot or radial forearm to reconstruct the dorsal skin and extensor tendons of the hand. Material and Methods : Between february 1987 and July 1998, we treated 9 patients with composite tissue loss on the dorsal hand caused by crushing injury. Nine men had an average age of 26.4 years(range, $19{\sim}47$). We treated 5 patients with the free dorsalis pedis flap including the extensor tendons and the superficial peroneal nerve and 4 patients with reverse forearm flap including the brachioradialis tendon and/or superficial radial nerve. Flap size was average 4.4(3,2cm. Evaluation of the results was based on the survived flap rate, the recovery rates for range of motion of the metacarpophalageal joints in the operated fingers. two-point discrimination. Results : All flaps were well vascularized and survived completely. Recovery rates for range of motion of the metacarpophalageal joints in operated fingers range from $78%{\sim}99%$(average, 90%). Two-point discrimination of the transferred flaps in 5 patients average $20{\pm}3.5mm$. Conclusion : The advantages of this procedure are mass action reconstruction with tendon, one-stage operation, faster healing with less adhesion formation, and early mobilization.