• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.126-133
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• 2006

This paper deals with technological and design skills for all pneumatical, hydraulical, mechanical and electrical parts related to control valve. Especially, a variety of dynamic characteristics, which are not easily extracted from field tests using control valves, are studied by system-simulation code, AMESim. The simulated results are also compared and examined with actual testing results in terms of physical dynamic characteristics. In addition, this paper contains the simulated system characteristics including dynamic characteristics in component level of valve itself. Based on the results, it is applied to control system of propellant feeding system in liquid-propellant engine of satellite launcher.

• The Journal of Industrial Distribution & Business
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• v.9 no.5
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• pp.37-46
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• 2018

Purpose - This paper explores the determinants of bank lending to firms during and after the global financial crisis using firm- and bank-level data to answer the questions what caused the contraction of lending to firms despite the loosening monetary policy during this crisis period. Research design, data, and methodology - We investigate the effects of the monetary policy that followed the global financial crisis on firms borrowing. We use a dynamic panel model to address how firms lending respond to monetary policy. The data are obtained from CRETOP and we consider the manufacturing sector for the analysis to control for unobserved heterogeneity such as industry-specific shocks. Results - The findings from the empirical analysis suggest that both bank- and firm-level characteristics are significant determinants of bank lending. Especially, we find that corporate risk, measured by default risk, is one of the key factors that led to a decline in lending during the crisis. Conclusions - This paper shows that companies borrow more from liquid banks, and high bank capital can also contribute to an increase in a firm's borrowing from banks. Especially, the results confirm that the default rate measured at the firm level has increased during and after the global financial crisis, which implies that default risk interplays with other firm and bank-level characteristics.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.765-772
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• 2002

Many researchers have studied several vibration control devices such as TMD, TLD, and VED to reduce the acceleration level for tall buildings. Advantages of TLD (tuned liquid damper) include easy installation, low cost, and less maintenance. However, the dynamic characteristics of TLD must be verified by experiment and analysis due to the difficulties in evaluating the characteristics of water sloshing. In this study, free vibration and dynamic excitation experiments of structure with TLD were conducted to verify vibration control force of the proposed TLD for high-rise building. The parameters were mass ratio of water to structure, number of damping nets, and aspect ratio. From the test results, the responses of structure with water tank were observed to be smaller than those of structure alone. Furthermore, better damping effect could be achieved with larger mass ratio, more damping nets, and larger aspect ratio. However, in the case of water tank with no damping net, little damping effect was obtained.

• Journal of The Korean Association For Science Education
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• v.17 no.3
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• pp.313-321
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• 1997

The purpose of this study was to investigate the instructional effect of a four-stage problem solving approach visually emphasizing the molecular level of matter upon students' conceptions and problem solving ability. On the basis of the research results regarding molecular representation in learning chemistry, problem-solving instruction, and the effect of visual materials, the instructional strategy was developed while considering Korean educational situations. The treatment and control groups (2 classes) were selected from a girls' high school in Seoul and taught about stoichiometry, gas, liquid, solid, and solution for 13 weeks. For the treatment group, 52 charts were supplied in order to emphasize the molecular level of matter and/or 4 stage problem solving strategy-understanding, planning, solving, and reviewing. For the control group, traditional instruction was used. Before the instructions, the Group Assessment of Logical Thinking and the Spatial Ability Test were administered, and their scores were used as covariate and blocking variable, respectively. After the instructions, students' conceptions and problem solving ability were measured by the Chemistry Conceptions Test (CCT) and the Chemistry Problem Solving Ability Test (CPSAT), respectively. The results indicated that the CCT scores of the treatment group were significantly higher than those of the control group. The students in the treatment group also exhibited less misconceptions than those in the control group. However, there was not significant difference for the CPSAT scores. No interaction with students' spatial ability was found for both students' conceptions and problem solving ability. Educational implications are discussed.

• Earthquakes and Structures
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• v.6 no.1
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• pp.111-125
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• 2014

Multiple level performance of seismically isolated elevated storage tank isolated with multi-phase friction pendulum bearing is investigated under totally 60 records developed for multiple level seismic hazard analysis (SLE, DBE and MCE). Mathematical formulations involving complex time history analysis have been proposed for analysis of typical storage tank by multi-phase friction pendulum bearing. Multi-phase friction pendulum bearing represent a new generation of adaptive friction isolation system to control super-structure demand in different hazard levels. This isolator incorporates four concave surfaces and three independent pendulum mechanisms. Pendulum stages can be set to address specific response criteria for moderate, severe and very severe events. The advantages of a Triple Pendulum Bearing for seismic isolation of elevated storage tanks are explored. To study seismic performance of isolated elevated storage tank with multi-phase friction pendulum, analytical simulations were performed with different friction coefficients, pendulum radii and slider displacement capacities.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.6
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• pp.650-656
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• 2023

In order to efficiently control boil-off rate of a liquefied hydrogen tank, the important thing is to maintain an appropriate vacuum level. however, compared to small and medium-sized storage tank, it is very difficult to create and maintain vacuum in large-capacity storage tanks. In this study, we aim to determine the target level of future large-capacity storage tank technology development and secure basic data on performance test methods by analyzing the corelation between evaporation gas and thermal conductivity of liquefied hydrogen storage tanks.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.4
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• pp.47-55
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• 2009

The purpose of this study is to verify the transfer function of input acceleration and output control force by linearizing a velocity-dependent damping term of Liquid Column Vibration Absorber (LCVA). Analytical and experimental research is conducted to identify natural frequency, damping ratio and participated mass ratio of LCVA with various section ratios of vertical and horizontal areas. Findings obtained experimentally by the shaking table test are compared with analytical findings using optimization technique with constraints. The results indicate that the level of liquid and section ratio of LCVA affect the characteristics of damping ratio and mass ratio. Damping and mass ratio increase as the section of vertical column of LCVA decreases, due to turbulence in the elbow of LCVA.

• Journal of the Korean Chemical Society
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• v.68 no.4
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• pp.191-198
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• 2024

Endocrine disrupting chemicals (EDCs) are compounds that come from outside the body and disrupt hormone action within the body's endocrine system. Examples include parabens, benzophenones, bisphenols, and phthalates, which are currently used in a wide range of applications. However, continuous exposure to them can have negative effects on glycemic control, reproduction, metabolism, nervous system development, pregnancy, childbirth, and growth. In this study, human samples (urine) were pretreated using liquid-liquid-extraction to determine the exposure level of EDCs and then analyzed effectively and rapidly by UPLC-MS/MS. In this way, the analytical conditions were established and the reliability of the simultaneous analysis method was evaluated through method validation. The results showed that the accuracy ranged from 75.28 to 122.36% and the precision ranged from 2.16 to 22.74%. The analytical method established in this study can be used as a methodology for future studies to evaluate and monitor the exposure of EDCs in human samples.

• Journal of Nutrition and Health
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• v.29 no.9
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• pp.981-990
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• 1996

To define the risk facots of subclinical vitamin D deficiency in postmenopausal women, circulating serum 25-hydroxyvitamin D levels, known to be the indicator of vitamin D status, were measured and risk faxtors affecting it were investigated in 27 women with low 25-hydoxyvitamin d level(ie, the study group : serum 25-hydroxyvitamin D<10ng/ml) by comparing to 55 age-matched control(the control group) were analyzed. The serum level of 25-hydorxyvitamin D was analyzed by HPLC(High Pressure Liquid Chor-matography) and analyzed biochemical parameter. The following information was obtained by interviews : sociodemographic charateristics, the intake of food containing vitamin D, proxy measure of sunlight exposure(time spent outdoors), and reprocuctive histpry of the subjects. The study group had significantly lower levels of serum calcium, increased levels of iPTH and alkaline phosphatase, Among the dietary determents, energy, protein, fat, calcium, phophorus, and vitamin D intakes were lower in the study group than the normal group. The time spent outdoors in a day was not significantly different between the two groups. However, during the day, a specific time of time spent out doors between 12:00 and 14:00 was significantly lower in the study group. Logistic analysis revealed that vitamin D and calcium intake were more important affecting factors than the time spent outdoors in post menopausal women.

• Journal of IKEEE
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• v.7 no.1 s.12
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• pp.107-118
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• 2003

In this paper, dynamic control model is formulated by considering the geometrical structure of the deaerator storage tank in nuclear power plant and input-output flow rate at steady state, and we describe fault detection and diagnosis (FDD) scheme based on the adaptive estimator. The performance and effectiveness of the proposed FDD scheme are evaluated by applying real operating data obtained from the YOUNGKWANG 3 & 4 FSAR.