• 한국농공학회논문집
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• 제57권1호
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• pp.11-23
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• 2015

In this study the laboratory test for hydraulic conductivity and the seepage analysis with finite element method on measurement section of sea dike embankment were performed for the purpose of estimating the relative density of embankment from the measured pore water pressures, and both results of the test and the analysis were coupled with the method of estimating seepage blocking state with the hydraulic head loss rate in sea dike embankment. The relationship of void ratio vs hydraulic head loss rate was obtained by setting hydraulic conductivity as common ordinate on the relationships between the void ratio and the hydraulic conductivity and between the hydraulic conductivity and the hydraulic head loss rate. The void ratio on the segment between measuring points was calculated from the coupled relationship of the void ratio vs the hydraulic conductivity. The allowable upper and lower limits of hydraulic head loss rate and those of void ratio on the safety were generated from the coupled relationship between the laboratory compaction test and the sedimentation test. Current hydraulic head loss rate and void ratio were evaluated in the allowable range between upper and lower limits.

• Smart Structures and Systems
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• 제9권2호
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• pp.165-188
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• 2012

In the first part of the paper, the optimal design parameters for tuned liquid column dampers (TLCD) in harmonic pitching motion were investigated. The configurations in design tables include uniform and non-uniform TLCDs with cross-sectional ratios of 0.3, 0.6, 1, 2 and 3 for the design in different situations. A closed-form solution of the structural response was used for performing numerical optimization. The results from optimization indicate that the optimal structural response always occurs when the two resonant peaks along the frequency axis are equal. The optimal frequency tuning ratio, optimal head loss coefficient, the corresponding response and other useful quantities are constructed in design tables as a guideline for practitioners. As the value of the head loss coefficient is only available through experiments, in the second part of the paper, the prediction of head loss coefficients in the form of a design chart are proposed based on a series of large scale tests in pitching base motions, aiming to ease the predicament of lacking the information of head loss for those who wishes to make designs without going through experimentation. A large extent of TLCDs with cross-sectional ratios of 0.3, 0.6, 1, 2 and 3 and orifice blocking ratios ranging from 0%, 20%, 40%, 60% to 80% were inspected by means of a closed-form solution under harmonic base motion for identification. For the convenience of practical use, the corresponding empirical formulas for predicting head loss coefficients of TLCDs in relation to the cross-sectional ratio and the orifice blocking ratio were also proposed. For supplemental information to horizontal base motion, the relation of head loss values versus blocking ratios and the corresponding empirical formulas were also presented in the end.

• 상하수도학회지
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• 제22권6호
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• pp.619-625
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• 2008

Urban sewer systems are designed to operate in open-channel flow regime and energy loss at square manholes is usually not significant. However, the energy loss at surcharged manholes is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the head loss associated with manholes, especially in surcharged flow. Hydraulic experimental apparatus which can change the manhole inner profile(CASE I, II, III, and IV) and the invert types(CASE A, B, C) were installed for this study. The experimental discharge was $16{\ell}/sec$. As the ratio of b/D(manhole width/inflow pipe diameter) increases, head loss coefficient increases due to strong horizontal swirl motion. The head loss coefficients for CASE I, II, III, and IV were 0.46, 0.38, 0.28 and 0.37, respectively. Side covers increase considerably drainage capacity at surcharged square manhole when the ratio of d/D(side cover diameter/inflow pipe diameter) was 1.0. The head loss coefficients for CASE A, B, and C were 0.45, 0.37, and 0.30, respectively. Accordingly, U-invert is the most effective for energy loss reduction at surcharged square manhole. This head loss coefficients could be available to evaluate the urban sewer system with surcharged flow.

• 대한토목학회논문집
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• 제37권6호
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• pp.989-999
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• 2017

본 연구에서는 분기수로에서 발생되는 에너지손실을 계산하기 위한 손실계수의 경험식을 산정하기 위해 수리모형실험을 수행했다. 수리모형은 유입수로와 90도의 각도를 갖는 두 유출수로로 구성되어 있으며, 유입수로과 유출수로에서 압력수두와 속도수두를 측정하여 분기수로에서 발생되는 에너지손실을 분석했다. 각 측선에서 동수경사선의 변화를 비교한 결과, 수로의 분기점에서 동수경사선이 급격히 하강하여 에너지손실이 분기점에서 발생되었으며, 유량비의 증가에 따라 속도수두의 감소폭이 증가했다. 유량비와 Froude수가 증가함에 따라 유출량이 더 큰 수로에서 수두손실량이 지수적으로 증가하는 결과를 보였으며, 손실계수 또한 증가했다. 반면에, 유출량이 작은 수로에서는 유량비와 Froude수의 증가에 따라 손실계수가 감소하는 결과가 나타났다. 손실계수 계산결과를 이용하여 두 유출수로에서 손실계수 경험식을 제안하였으며, 경험식의 계산오차가 각각 3.91%, 5.19%로 나타났다. 그리고 두 경험식을 이용하여 계산한 총 손실계수를 실험결과와 비교하여 3.62%의 오차가 발생했다.

• 한국수자원학회논문집
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• 제50권12호
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• pp.877-887
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• 2017

도시유역의 중 하류부에 주로 설치되는 4방향 합류맨홀에서 과부하 흐름에 의한 에너지 손실은 도심지 침수피해를 가중시키는 주요 원인이다. 과부하 4방향 합류맨홀에는 유입관의 유입조건에 따라 흐름 양상이 크게 변화되며, 중간맨홀 뿐만 아니라 3방향(T형) 합류맨홀의 흐름조건을 구성한다. 그러므로 유입관의 유입유량 변화에 따른 과부하 4방향 합류맨홀의 에너지 손실 변화 분석 및 손실계수 산정이 필요하다. 본 연구에서는 하수도시설기준을 준용하여 맨홀직경 및 관경을 1/5로 축소 한 수리실험 장치를 제작하였다. 과부하 사각형 4방향 합류맨홀에서 유입관의 유입유량비 변화에 따른 손실계수를 산정하기 위하여 유입관(주 유입관 및 양측면 유입관)의 유입유량비를 10% 간격으로 변화시켜 다양한 유량조건(40 case)을 선정하였다. 실험 결과 중간맨홀에서 0.40의 가장 낮은 손실계수가, $90^{\circ}$ 접합맨홀에서 1.58의 가장 높은 손실계수가 산정되었다. 또한 합류맨홀(T형, 4방향)의 경우 측면 유입유량이 한쪽으로 편향될수록 보다 큰 손실계수를 나타냈다. 유입관의 유입유량 조건 변화에 따른 손실계수를 산정하여 손실계수 범위도를 작도하였으며, 과부하 사각형 4방향 합류맨홀에서 모든 흐름조건을 고려할 수 있는 손실계수 산정식을 제시하였다. 제시된 산정식은 유입관의 유입유량이 변화하는 배수시스템의 설계 및 검증에 적용이 가능할 것으로 판단된다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1493-1495
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• 1997

Cropping of head and tail ends of rod in wire Rolling Process is required to aviod roll damage, and prevent cobbles. In order to reduce the crop loss, the new crop control system for rotary shear of Wire rolling Process has been developed. Performance shows the developed system cut precisely within setting length. As a result, it is expected to increase the yield ratio of products about 0.2 percent and stabilize the operantional condition.

• Journal of Audiology & Otology
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• 제25권1호
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• pp.27-35
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• 2021

Background and Objectives: This study aimed to evaluate the clinical features and the clinical factors associated with prognosis of sudden sensorineural hearing loss (SSNHL) in diabetic patients. Subjects and Methods: Forty-nine diabetic with unilateral SSNHL were retrospectively included. All patients received systemic high dose steroid therapy within one month after onset and had more than one month of follow-up audiogram. The basic characteristics of the patients, initial and follow-up audiograms, laboratory data, and methods of steroid treatment were collected. Results: Compared to reference values in healthy subjects, 79%, 55%, and 45% of the patients had higher values of mean neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), and lymphocyte-monocyte ratio (LMR), respectively. Older patients had significantly less degree of hearing loss, but they also had significantly worse hearing thresholds in the unaffected ear. After steroid treatment, less than half patients (47%) showed hearing recovery. Simultaneous intratympanic dexamethasone (ITD) injections with systemic steroid did not confer an additional hearing gain or an earlier recovery rate in diabetic patients with SSNHL. In the multivariate analysis, initial hearing thresholds of affected ear and timing of steroid treatment were significantly associated with hearing prognosis in diabetic patients with SSNHL. Conclusions: Diabetic patients with SSNHL tended to have increased NLR, LMR, and PLR, which are reported to be associated with microvascular angiopathy. Simultaneous ITD injections to improve hearing recovery in diabetic patients with SSNHL seems unnecessary.

• 대한청각학회지
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• 제25권1호
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• pp.27-35
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• 2021

Background and Objectives: This study aimed to evaluate the clinical features and the clinical factors associated with prognosis of sudden sensorineural hearing loss (SSNHL) in diabetic patients. Subjects and Methods: Forty-nine diabetic with unilateral SSNHL were retrospectively included. All patients received systemic high dose steroid therapy within one month after onset and had more than one month of follow-up audiogram. The basic characteristics of the patients, initial and follow-up audiograms, laboratory data, and methods of steroid treatment were collected. Results: Compared to reference values in healthy subjects, 79%, 55%, and 45% of the patients had higher values of mean neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), and lymphocyte-monocyte ratio (LMR), respectively. Older patients had significantly less degree of hearing loss, but they also had significantly worse hearing thresholds in the unaffected ear. After steroid treatment, less than half patients (47%) showed hearing recovery. Simultaneous intratympanic dexamethasone (ITD) injections with systemic steroid did not confer an additional hearing gain or an earlier recovery rate in diabetic patients with SSNHL. In the multivariate analysis, initial hearing thresholds of affected ear and timing of steroid treatment were significantly associated with hearing prognosis in diabetic patients with SSNHL. Conclusions: Diabetic patients with SSNHL tended to have increased NLR, LMR, and PLR, which are reported to be associated with microvascular angiopathy. Simultaneous ITD injections to improve hearing recovery in diabetic patients with SSNHL seems unnecessary.

• 한국방재학회 논문집
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• 제11권3호
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• pp.143-150
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• 2011

도시 우수 배수 시스템에서 우수 관거는 개수로 흐름 상태로 가정하여 설계되었기 때문에 맨홀에서의 에너지 손실은 일반적으로 중요하게 고려되지 않았다. 그러나 과부하흐름에서 에너지 손실은 관거의 배수능력을 저하시켜 도심지역의 침수피해를 가중시키는 요인이 된다. 그러므로 과부하 사각형 맨홀 내에서의 수두 손실을 분석할 필요가 있다. 본 연구에서는 FLUENT 6.3 모형을 이용하여 과부하 사각형 합류맨홀에서의 흐름특성을 모의하고 맨홀 내 손실수두의 변화를 계산하여 손실계수를 산정하였다. 또한 실험결과와 수치모의 결과를 비교 및 분석하여 사각형 맨홀에서의 손실계수 산정에 FLUENT 6.3모형의 적용성을 확인하였다. 맨홀 폭(B)과 연결관경(d)의 비(B/d)에 따른 손실계수를 산정하였다. B/d가 증가할수록 사각형 합류 맨홀에서의 손실계수는 증가하였다. 중간 단차 맨홀에서 단차 변화에 따른 손실계수의 변화를 산정하였다. 단차가 5 cm이상 증가하면 맨홀 내 수심과 손실계수가 점진적으로 증가하였으므로 중간 맨홀에서의 적정 단차는 5 cm로 판단된다. 따라서 우수 관거 시스템의 여러 형태의 사각형 맨홀에서의 흐름의 변화 및 손실계수를 예측할 때, Fluent 6.3 모형은 사용 가능하리라 판단된다.

• 한국수자원학회논문집
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• 제49권12호
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• pp.1015-1025
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• 2016

일반적으로 도심지 배수시설로 설치되는 맨홀은 중간맨홀, $90^{\circ}$ 접합맨홀, 3방향 합류맨홀 및 4방향 합류맨홀 등 다양한 접합 형태를 가지고 있다. 특히 도시유역의 중․하류부에 주로 설치되는 4방향 합류맨홀에서의 과부하흐름은 에너지 손실을 발생시켜 도심지의 침수피해를 가중시키는 주요 원인이다. 그러므로 과부하 4방향 합류맨홀에서의 흐름특성 분석 및 손실계수의 산정이 필요하다. 본 연구에서는 현황조사 결과를 고려하여 수리실험 장치를 제작하였으며, 맨홀 및 관경은 하수도 시설기준을 준용하여 1/5로 축소 제작하였다. 선정된 실험조건인 맨홀 형상 조건(사각형, 원형), 유출유량($Q_{out}$)에 대한 측면유입유량($Q_{lat}$)의 비($Q_{lat}/Q_{out}$) 및 실험 유량(2.0, 3.0, 4.0, $4.8{\ell}/sec$)을 변화시키면서 실험을 실시하였다. 실험결과 측면유량비가 증가할수록 손실계수는 증가하였으며, 사각형 맨홀보다 원형 맨홀에서의 손실계수가 다소 낮게 산정되었다. 그러나 유출유량 변화에 따른 손실계수의 변화는 미미하였다. 측면유량비에 따른 과부하 4방향 합류맨홀의 손실계수는 0.4~0.8로 산정되었다. 또한, 측면유량비 변화를 고려한 4방향 합류맨홀에서의 손실계수 산정식을 제시하였다.