• The KSFM Journal of Fluid Machinery
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• v.19 no.1
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• pp.5-10
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• 2016

As a key component of a Francis turbine facility, the runner performance plays a vital role in the performance of the turbine. It is effective and successful to design a Francis turbine runner blade with good performance by one dimensional hydraulic design method. On the basis of one dimensional hydraulic analysis, there are a lot of parameters of the internal flow passage shapes determined by experience. Among those parameters, the effect of port area of blade on the performance of a Francis turbine is investigated in this study. A given Francis turbine model was selected for investigating the port area of blade on the performance. The result shows that the effect of port area of runner blade on the outflow angle from runner passage on the performance is quite significant. A correct exit flow angle reduces the energy loss at draft tube, which has the best efficiency of the turbine model.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.3
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• pp.789-798
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• 1991

본 연구에서는 원통형 구조물의 진동해석을 위하여 통계에너지 분석방식(st- atistical energy analysis:SEA)이 사용되었다. SEA는 4개의 물리적 변수인 구조물 질량(Mi), 주파수대역에 존재하는 고유진동수(Ni), 내부손실계수(internal loss fact- or) 및 상호손실계수(coupling loss factor)를 이용하여 구조물의 진동수준과 구조물 상호간의 에너지 교환을 해석하는 방법으로서 비록 넓은 주파수 범위에 걸쳐 정확한 진동예측을 하기에는 어느정도 오차가 예상되는 단점이 있으나 진동해석이 용이하고 복잡한 계산을 필요로 하지 않기 때문에 대형구조물의 진동해석에 많이 사용되고 있 는 기법이다. 따라서 연구의 대상인 원통형 구조물의 고유진동수를 예측하기 위하여 일차적으로 반경에 의한 곡률영향을 배제시킨 평판에 대한 분석이 시도되었다. 이와 함께 주어진 주파수 대역에 걸쳐 평판및 원통형 구조물의 고유진동수의 차이를 비교하 였다.그결과로부터 원통형 구조물에 대한 고유진동수 계산식을 평판구조물의 굽힘 강성과 곡률반경으로 야기되는 표면응력에 의한 함수로 표현하였다.

• The KSFM Journal of Fluid Machinery
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• v.15 no.2
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• pp.57-62
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• 2012

The constant air volume flow fan can maintain constant flow rate to the wide range of exit pressure. Therefore, the use of this fan is increasing recently for ventilation of high building. Brushless DC motor is adopted to this fan because that has advantages of compactness and performance. But this type of motor protrude from impeller hub side to fan inlet. The Impeller inlet flow is influenced by size of this obstacle called hub. In this paper, the influence of hub shape on the fan performance characteristics are experimentally and numerically analyzed. CFX 12.0 is used to perform the fan internal flow analysis and numerical results are compared with the experiments. Depending on hub shape, internal loss is generated and the performance and efficiency are reduced. The best performance is occurred around $h/b_1$ = 0.25. The results of this study will be contribute to initial design of constant air volume flow fan development.

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.805-819
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• 2016

The numerical simulation methodologies to evaluate the structural behaviors of prestressed concrete containment vessels (PCCVs) have been substantially developed in recent decades. However, there remain several issues to be investigated more closely to narrow the gap between test results and numerical simulations. As one of those issues, the effects of no stiffness inside unbonded tendon ducts on the behavior of PCCVs are investigated in this study. Duct holes for prestressing cables' passing are provided inside the containment wall and dome in one to three directions for general PCCVs. The specific stress distribution along the periphery of the prestressing duct hole and the loss of stiffness inside the hole, especially in an unbonded tendon system, are usually neglected in the analysis of PCCVs with the assumption that the duct hole is filled with concrete. However, duct holes are not small enough to be neglected. In this study, the effects of no stiffness inside the unbonded tendon system on the behaviors of PCCVs are evaluated using both analytical and numerical approaches. From the results, the effects of no stiffness in unbonded tendons need to be considered in numerical simulations for PCCVs, especially under internal pressure loading.

• Korean Journal of Child Studies
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• v.35 no.5
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• pp.113-134
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• 2014

This study sought to develop a 'Meaning of Parenting Scale for Mothers(MPS-M)' in order to measure how Korean mothers perceive the meaning of parenting. To this end, in Study I, a preliminary scale was designed, based firstly on socio-cultural and evolutionary psychological perspectives and secondly on the responses from 118 mothers concerning meaning of parenting. This was followed up by the collection of 887 mothers' responses to the preliminary scale, which then underwent exploratory factor analysis for scale revision. In Study 2, confirmatory factor analysis was conducted on a collection of responses from 548 mothers using the revised scale. Concurrent validity was tested using a parenting stress scale, and reliability was then checked by conducting calculations for internal consistency. As a result, the MPS-M was finally developed, consisting of 25 items under six factors: 'Internal Maturity', 'Restoration of Naturality', 'Familial Union', 'Physical Burden', 'Affective Disorientation', and 'Comprehensive Loss'. Accordingly, the meaning of parenting was statistically confirmed as a hierarchical two-sided concept possessing six factors under positive and negative meaning categories.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.4
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• pp.76-86
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• 1998

Structural intensity of plates experiencing bending vibration is analytically evaluated using the modal analysis based on assumed mode method. To evaluate the convergence of structural intensity according to the number of superposition modes, the power obtained by structural intensity integration over the closed curve containing the excitation source is compared with the power injected into plates. The erect of power reduction due to the material internal loss is evaluated using the intensity around a localized damping point, In addition, the dominant component among internal forces in the power transfer by the bending vibration of plates and the change of power flow due to stiffener are also investigated.

• Nuclear Engineering and Technology
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• v.56 no.7
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• pp.2859-2874
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• 2024

This paper presents the finite element deformation and failure simulation of a typical Korean high-power reactor vessel under a severe accident characterized by large break loss of coolant (LBLOCA) with in-vessel retention of molten corium through external reactor vessel cooling (IVR-ERVC) conditions. Temperature distributions calculated using Modular Accident Analysis Program Version 5 (MAAP5) as thermal boundary conditions were used, and ABAQUS thermal and structural analyses were performed. After full ablation, the temperature of the inner surface in the thinnest section remained high (920 ℃), but the stress remained relatively low (less than 6 MPa). At the outer surface, the stress was as high as 250 MPa; however, the resulting plastic strain was small owing to the low temperature of 200 ℃. Variations in stress, inelastic strain, and temperature with time in the thinnest section suggest that the plastic and creep strains are saturated owing to stress relaxation, resulting in low cumulative damage. Thus, the lower head of the vessel can maintain its structural integrity under LBLOCA with IVR-ERVC conditions. The sensitivity analysis of internal pressure indicates the occurrence of failure in the thinnest section at an internal pressure >9.6 MPa via local necking followed by failure due to high stresses.

• Journal of Biomedical Engineering Research
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• v.32 no.1
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• pp.7-14
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• 2011

This study suggested an optimized algorithm for detecting the loss of balance(LOB) in the seated position. And the sensitivity analysis was performed in order to identify the role of each design variable in the algorithm. The LOB algorithm consisted of data processing of measured signals, an internal model of the central nervous system and a control error anomaly(CEA) detector. This study optimized design variables of a CEA detector to obtain improved values of the success rate(SR) of detecting the LOB and the margin time(MT) provided for preventing the falling. Nine healthy adult volunteers were involved in the experiments. All the subjects were asked to balance their body in a predescribed seated posture with the rear legs of a four-legged wooden chair. The ground reaction force from the right leg was measured from the force plate while the accelerations of the chair and the head were measured from a couple of piezoelectric accelerometers. The measured data were processed to predict the LOB using a detection algorithm. Variables S2, h2 and hd are related to the detector: S2 represents a data selecting window, h2 a time shift and hd an operating period of the LOB detection algorithm. S2 was varied from 0.1 to 10 sec with an increment of 0.1 sec, and both h2 and hd were varied from 0.01 to 1.0 sec with an increment of 0.01 sec. It was found that the SR and MT were increased by up to 9.7% and 0.497 sec comparing with the previously published case when the values of S2, h2 and hd were set to 4.5, 0.3 and 0.2 sec, respectively. Also the results of sensitivity analysis showed that S2 and h2 had considerable influence on the SR while these variables were not so sensitive to the MT.

• Journal of Hydrogen and New Energy
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• v.29 no.4
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• pp.307-316
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• 2018

In this study, the failure mode and effect analysis (FMEA) of hydrogen production process by using the Thermococcus onnurineus NA1 was conducted and advanced methodology to compensate the weakness of previous FMEA methodology was applied. To bring out more quantitative and precise FMEA result for bio-hydrogen production process, fuzzy logic and potential loss cost estimated from ASPEN Capital Cost Estimator (ACCE) was introduced. Consequently, risk for releasing the flammable gases via internal leakage of steam tube which to control the operating temperature of main reactor was caution status in FMEA result without applying the fuzzification and ACCE. Moreover, probability of the steam tube plugging caused by solid property like medium was still caution status. As to apply the fuzzy logic and potential loss cost estimated from ACCE, a couple of caution status was unexpectedly upgraded to high dangerous status since the potential loss cost of steam tube for main reactor and decrease in product gases are higher than expected.

• Korean Journal of Veterinary Research
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• v.34 no.1
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• pp.195-212
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• 1994

For the purpose to increase productivities of livestock the present investigations were undertaken in order to clarify the clinical and suclinical status of Korean native cattle, dairy cattle(holstein) and Korean native goat. Blood, feces and urine samples were collected from 247 Korean native cattle(222 adult and 25 calf), 224 dairy cattle(211 adult and 13 calf) and 142 Korean native goat rearing at Chonbuk area and analyzed for clinical, serum chemical, hematological and urinary findings. In addition, we were examined the infection rate of theileriosis, internal parasite and ring worm. The mean value for each component was calculated by statistical analysis using Excel computer program. From these investigations the following results were obtained. The mean values for RBC, PCV and etc in 433 adult cow(Korean native cattle and dairy cattle) were similar with other reports. But the mean values for MCHC of all species were lower than normal. Adult Korean native cattle and adult dairy cattle which showed hematologically normal levels were only 9.01% and 9.48%, respectively. Abnormally high values for PCV, RBC and Hb were recorded in 7.66% of adult Korean native cattle, 20% of korean native calf, 15.38% of dairy calf and 13.36% of Korean native goat. Adult Korean native cattle and adult dairy cattle which showed hematologically anemia were 4.95% and 19.43% respectively, but Korean native calf and dairy calf showed normal. Adult Korean native cattle, adult dairy cattle, Korean native calf and dairy calf which showed normal serum protein level 84.0%, 90.8%, 50% and 44.4%, respectively. In present investigations, 50% of Korean native calf and 55.6% of dairy calf were decreased serum protein values under range. These abnormally decreased serum protein values mean the shortage of antibody, and these have a possibility to occurs to pneumonia and diarrhea. From these results, the economical loss caused by pneumonia was calculated as 124,038,833 won in the KNC and 742,703,430 won in the dairy calf rearing in Chonbuk area. Calculated economical loss caused by enteritis was 56,658,690 won in Korean native cattle, 476,775,799 won in dairy calf, and the total loss amount of 533,434,488 won in Chonbuk area. Abnormally high values$(21.7{\pm}4.0mg/dl)$ for serum calcium were recorded 49.6% in dairy cattle. The mean values for serum total cholesterol were $170.8{\pm}99.8mg/dl$ in Korean native cattle, $196.0{\pm}40.6mg/dl$ in Korean native calf, $202.9{\pm}86.0mg/dl$ in adult dairy cattle and $289.4{\pm}97.5mg/dl$ in dairy calf. The infection rate of internal parsite were as follows; adult Korean native cattle: 21.2%, Korean native calf: 8.0%, adult dairy cattle: 67.8% and Korean native goat: 81.5%. The estimated economical loss caused by internal parasites infection were 1,120,855,837 won in Korean native calf, 4,994,959,405 won in adult Korean native cattle, 3,334,751,066 won in adult holstein, and the total loss amount to 9,450,566,308 won. The infection rate of theileriosis were 1.4% in Korean native cattle and 6.6% in dairy cattle. The presumed economical loss by T. sergenti infection were 154,408,482 won in Korean native cattle and 171,577,237 won in dairy cattle rearing at Chonbuk area. The infection rate of ringworm were 0.5% in Korean native cattle, 0.9% adult dairy cattle and 7.7% in dairy calf. The presumed economical loss by dermatomycophyte were 12,061,532 won in Korean native cattle, 16,895,403 won in dairy cattle, and the total estimated loss amount to 28,955,935 won a year in Chonbuk area.