• 대한설비공학회지:설비저널
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• 제17권5호
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• pp.590-597
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• 1988

Characteristics of flow regime transitions in inclined upwards gas-liquid two-phase flow have been investigated based upon a statistical analysis of instantaneous pressure drop curves through an orifice. The probability density functions of the curves indicate distinct patterns depending upon two-phase flow regime, which are very similar to those of horizontal two-phase. The dimensionless intensity of fluctuations of the pressure drops sharply change as the flow transitions such as plug-slug, pseudo slug-slug and annular-slug take place. The effects of inclination angle on the flow regime transitions have been also investigated. The results show that the method to identify the flow pattern based upon the statistical analysis of instantaneous pressure drops is suitable for inclined flow as well as horizontal flow.

• 대한의용생체공학회:의공학회지
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• 제11권2호
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• pp.195-202
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• 1990

The hypothesis of asymmetric resistance to explain the phenomenon of lung hyperinflation (LHI) during hlgh frequency ventilation (HFV) was quantitatively studied. LHI was predicted by modeling the ism-volume pressure-flow (IVPF) data from 5 human subjects using the empirical Rohrer's equation. Non-steadiness during HFV was compensated by em- ploying recently proposed volume-frequency diagram. Tidal volume and ventilation frequency were 100 ml and 20 Hz, respectively. Airflow pattern was a symmetric sinusoid. The predic- tion results of mean pressure drop across the airways were averaged for those 5 subjects, and compared with zero by one-sided student's t-test. A marginally significant (P<0.1) increase in mean pressure drop was observed during HFV at low lung volumes (below FRC) , which could increase mean lung volume up to one liter When the lung volume was above FRC, no significant LHI (P >0.25) was resulted. LHI seemed to be inversely related to the lung volume. These results recommend to clinically apply HFV only at lung volumes above FRC.

• 마이크로전자및패키징학회지
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• 제22권2호
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• pp.55-59
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• 2015

Novel low-volume solder-on-pad (SoP) process is proposed for a fine pitch Cu pillar bump interconnection. A novel solder bumping material (SBM) has been developed for the $60{\mu}m$ pitch SoP using screen printing process. SBM, which is composed of ternary Sn-3.0Ag-0.5Cu (SAC305) solder powder and a polymer resin, is a paste material to perform a fine-pitch SoP in place of the electroplating process. By optimizing the volumetric ratio of the resin, deoxidizing agent, and SAC305 solder powder; the oxide layers on the solder powder and Cu pads are successfully removed during the bumping process without additional treatment or equipment. The Si chip and substrate with daisy-chain pattern are fabricated to develop the fine pitch SoP process and evaluate the fine-pitch interconnection. The fabricated Si substrate has 6724 under bump metallization (UBM) with a $45{\mu}m$ diameter and $60{\mu}m$ pitch. The Si chip with Cu pillar bump is flip chip bonded with the SoP formed substrate using an underfill material with fluxing features. Using the fluxing underfill material is advantageous since it eliminates the flux cleaning process and capillary flow process of underfill. The optimized interconnection process has been validated by the electrical characterization of the daisy-chain pattern. This work is the first report on a successful operation of a fine-pitch SoP and micro bump interconnection using a screen printing process.

• 설비공학논문집
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• 제2권4호
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• pp.303-315
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• 1990

Uniformity of velocity is quite important design points of a vertical laminar flow type clean room. In the present paper, flows in a room with a bottom pannel are numerically simulated by using a low-Reynolds number $k-{\epsilon}$ model, and a new flow model of the pannel are suggested. Resistance coefficient of the pannel and size of the exhaust channel show considerable effects on flow pattern and uniformity of flow on the bottom. Reflection coefficient also has important roles. A possibility to obtain the uniform and unidirectional flow is tested by adjusting the distribution of resistance coefficient of the pannel. Such a numerical simulation of the flow will be a good method to get optimun design parameters.

• Journal of Chest Surgery
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• 제38권2호
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• pp.101-109
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• 2005

배경: 심정지와 같은 위급상황에서 관상동맥의 혈류를 유지하는 것은 심장근육의 보존과 회복 및 환자의 생명을 보존하는 데 중요하다. 최근 들어 Extra-Corporeal Life Support System (ECLS)의 기계식 순환장치의 사용으로 심정지 환자의 생명을 보존하고자 하는 노력이 시도되고 있다 본 연구는 체외순환 모델에서 박동성 혈류와 비박동성 혈류가 관상동맥의 혈류량 및 심근에 미치는 영향에 대해 알아보고자 하였다. 대상 및 방법: 실험은 $25\~35Kg$의 돼지 14마리를 각각 7마리씩 두 군으로 나누어 진행하였다. 제 1군은 비박동성 혈류 펌프인 원심펌프를 사용하였고 제2군은 이중 박동형 펌프를 사용하였다. 체외순환은 우심방에서 상행대동맥으로 심폐바이패스를 하고, 9V의 전기 충격으로 심실세동을 만들었다. 체외순환은 2시간 동안 유지하였으며, 펌프량은 두 군 모두 2 L/min로 유지하였다. 초음파를 이용한 관상동맥 혈류 측정장치를 이용하여 좌전하행지의 관상동맥 관류량을 펌프 시작 전(기초치)과 시작 후 20분마다 측정하였다. 또한 관상 정맥동의 혈액을 펌프 시작 전(기초치)과 시작 후 1시간, 2시간에 채취하여 두 군간의 심근효소의 차이와 대사물질의 차이를 비교하였다. 각 관찰지표의 군간 비교는 STATISTICA 통계프로그램(Version 6.0)의 Mann-Whitney U test를 이용하였고 통계적 유의수준은 p값이 0.05 이하인 경우로 하였다. 결과: 관상동맥의 저항지수는 제 2군에서 낮게 나타났으며, 펌프 구동 후 40분, 80분, 100분, 120분에서 통계적으로 의미 있게 나타났다 (p<0.05). 관상동맥의 평균 혈류 속도는 제 2군에서 펌프 구동 후 20분부터 의미 있게 높게 유지되었다(p<0.05). 관상동맥의 혈류량도 제2군에서 높게 유지되었으며, 펌프 구동 후 40분, 60분, 100분, 120분에서 통계적으로 의미 있는 차이를 보였다(p<0.05). 그러나, 관상정맥동의 혈액학적 검사에서는 두 군간에 차이가 없었다. 결론: 박동성 혈류는 비박동성 혈류보다 좌전하행지 관상동맥의 저항지수를 낮추고, 관상동맥의 관류속도를 빠르게 하여, 관상동맥으로의 혈류량을 높게 유지하였다.

• 한국산학기술학회논문지
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• 제22권4호
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• pp.601-610
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• 2021

해안구조물 설치 전, 후의 금강하구역 해수유동 양상을 CASE별로 비교하기 위해서 수심적분된 그리고 조간대 처리기법이 적용된 해수유동 수치모형인 FLOW2DH를 사용하였다. 실험조건은 해안구조물 설치 전(CASE1), 해안구조물 설치 후(CASE2), 배수갑문운영 추가(CASE1Q, CASE2Q) 및 현재 상태(CASE3)로 구성된다. CASE1의 경우, 자연형 하구의 안정화된 해수유동 양상을 보여주고 있고, CASE2의 경우, 설치된 해안구조물들로 인하여 금강하구역의 유속 및 유향에 변화가 발생하였다. 특히, CASE2의 개야수로 구간(P5~P9)은 CASE1과 대비하여 유속이 10~30% 크게 계산되었다. 금강하굿둑과 가장 가까운 군산 내항(P4)의 경우는, CASE1Q와 CASE2Q의 낙조 시 2.7시간의 배수갑문의 방류로 인하여 낙조 유속이 다른 CASE들과 비교하여 약 250~300% 빨라졌다. 이는 퇴적물이동에 영향을 줄 것이고, 나아가 해저지형변화를 야기할 것으로 예측된다. 현재 상태인 CASE3의 경우, 금강하구와 주변 해안역의 유속과 유향을 검토한 결과 안정화 단계로 접어들고 있는 것으로 판단된다.

• The Korean Journal of Pain
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• 제25권1호
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• pp.22-27
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• 2012

Background: The common causes of lower back pain with or without leg pain includes disk disease and spinal stenosis. A definitive diagnosis is usually made by means of magnetic resonance imaging (MRI), but treatment is often difficult because the MRI findings are not consistent with the symptoms of the patient in many cases. The objective of this study was to observe the correlation between the patterns of epidurography performed in patients having lower back pain with or without leg pain and the position or severity of the pain as subjectively described by the patients. Methods: The subjects of this study were 69 outpatients with lower back pain with or without leg pain who visited our clinic and complained of predominant pain on one side. We performed caudal epidural block using an image intensifier. A mixture of the therapeutic drug and the contrast agent (10 ml) was injected to observe the contrast flow pattern. The patients who complained of predominant pain on one side were divided into the left side group and the right side group. A judgment of inconsistency was made if the contrast agent flowed to the side of the pain, while a judgment of consistency was made if the contrast agent flowed to the opposite side of the pain. The degree of the drug distribution was evaluated by counting the number of cells to which the contrast agent's flowed for evaluating the correlation between the contrasted cell and the severity of pain (one group ${\leq}$ VAS 7, the other group ${\geq}$ VAS 8) the degree of the contrast agent's contrast was evaluated by dividing and counting an image into 15 cells (the left, right, and middle sections at each level of L4, L5, S1, S2, and S3). Results: Thirty out of the 69 patients who had laterality in pain, that is, those who complained of predominant pain on one side, showed that the laterality of the pain and the contrast agent flow was consistent, while 39 patients showed that the laterality was inconsistent (P: 0.137). The evaluation of the correlation between the pain and the contrast agent flow showed that the mean number of contrasted cells was $9.0{\pm}2.2$ for the 46 patients in the group with a VAS of 7 or lower and $6.5{\pm}2.0$ for the 23 patients in the group with a VAS of 8 or higher, indicating that the former group showed a significantly greater number of contrasted cells (P < 0.001). Conclusions: This study, conducted with patients having lower back pain with or without leg pain, showed that the contrast flow pattern of caudal epidurography had a significant correlation with the severity of the pain but not with the laterality of the pain.

• Investigative Magnetic Resonance Imaging
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• 제18권4호
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• pp.314-322
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• 2014

배경: 심장의 이완기능 이상은 비대성심근증 환자에서 흔히 발견되는 문제이다. 본 연구는 비대성심근증 환자의 심장 이완기능을 평가하는 데 있어, 승모판과 폐정맥의 유속을 이용한 MRI의 역할을 알아보고자 하였다. 방법과 결과: 승모판과 폐정맥의 유속을 이용한 위상차 MRI와 심초음파검사가 59명 (남:여 = 44:15, 평균 연령 = 51세)의 비대성심근증 환자에서 시행되었다. 49명의 환자가 심초음파검사에서 다양한 정도의 심장 이완기능 이상을 보였다; grade 1 (20명), grade 2 (27명), and grade 3 (2명). MRI로 계산한 승모판 유속인자들 (E, A, E/A ratios)은 심초음파검사로 구한 동일 인자들과 양의 상관관계를 보였다 (Pearson's r values = 0.47, 0.60, 0.75 for E, A, E/A, respectively, all P < 0.001). MRI로 폐정맥 유속정보를 이용하는 경우, pseudo-normalized pattern (8명)이 정상 충만 양상(filling pattern) (17명)과 구분될 수 있었고, 이들을 이용하여 이완기능 정도를 평가를 하는 경우, 심장 MRI가 심초음파검사와 중등도의 일치도를 보였다 (kappa value = 0.45, P < 0.001). 결론: 비대성심근증 환자에서 위상차 MRI를 이용한 심장 이완기능 평가는 임상적으로 적용 가능한 방법이며, 폐정맥 유속 분석을 추가하는 경우, 정상과 pseudo-normal을 구분하는데 유용하다.

• 정보학연구
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• 제1권2호
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• pp.181-193
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• 1998

주가지수선물거래에 있어 외국인의 투자제한이 완전히 철폐된 상태이고, 특히 이들 거래가 우리나라 기관투자자 뿐만 아니라 일반개인에게까지 정보의 주도자로써 미치는 영향이 클 수밖에 없다. 그래서 이들 외국인이 우리나라 선물시장에서 과연 어떠한 거래를 하고 있는 지에 대하여 비거주외국인은행, 비거주외국인증권회사, 비거주외국인계약형투신, 비거주외국인기타법인, 거주외국인증권회사로 구체화시켜 분석하였다. 이 논문은 외국인의 하루중 투자가 어떠한 패턴을 그리고 있으며 특히 이들 외국인간의 정보유입에 따른 시간대별 유의적인 차이를 보이고 있는지에 대하여 실증분석하였다.

• 한국대기환경학회지
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• 제23권1호
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• pp.14-28
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• 2007

This study presented the selection of ozone ($O_3$) potential factors and designed and assessed its potential prediction model using multiple-linear regression equations in Ulsan area during the springtime from April to June, $2000{\sim}2004$. $O_3$ potential factors were selected by analyzing the relationship between meterological parameters and surface $O_3$ concentrations. In addition, cluster analysis (e.g., average linkage and K-means clustering techniques) was performed to identify three major synoptic patterns (e.g., $P1{\sim}P3$) for an $O_3$ potential prediction model. P1 is characterized by a presence of a low-pressure system over northeastern Korea, the Ulsan was influenced by the northwesterly synoptic flow leading to a retarded sea breeze development. P2 is characterized by a weakening high-pressure system over Korea, and P3 is clearly associated with a migratory anticyclone. The stepwise linear regression was performed to develop models for prediction of the highest 1-h $O_3$ occurring in the Ulsan. The results of the models were rather satisfactory, and the high $O_3$ simulation accuracy for $P1{\sim}P3$ synoptic patterns was found to be 79, 85, and 95%, respectively ($2000{\sim}2004$). The $O_3$ potential prediction model for $P1{\sim}P3$ using the predicted meteorological data in 2005 showed good high $O_3$ prediction performance with 78, 75, and 70%, respectively. Therefore the regression models can be a useful tool for forecasting of local $O_3$ concentration.