• Nuclear Engineering and Technology
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• v.34 no.4
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• pp.382-395
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• 2002

An experimental study on transient critical heat flux (CHF) under flow coastdown has been performed for the water flow in a non-uniformly heated vertical annulus under low flow and a wide range of pressure conditions. The objectives of this study are to systematically investigate the effect of the flow transient on the CHF and to compare the transient CHF with steady-state CHF The transient CHF experiments have been performed for three kinds of flow transient modes based on the coastdown data of a nuclear power plant reactor coolant pump. At the same inlet subcooling, system pressure and heat flux, the effect of the initial mass flux on the critical mass flux can be negligible. However, the effect of the initial mass flux on the time-to- CHF becomes large as the heat flux decreases. The critical mass flux has the largest value for slow flow reduction rate. There is a pressure effect on the ratio of the transient CHF data to steady-state CHF data. Except under low system pressure conditions, the flow transient CHF was revealed to be conservative compared with the steady-state CHF data. Bowling CHF correlation and thermal hydraulic system code MARS show promising results for the prediction of CHF occurrence .

• The Journal of Korean Medicine
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• v.24 no.1
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• pp.9-28
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• 2003

Objects : The aim of this study was evaluate the effect of the Saengsig taken along with Behavior Modification Therapy, Methods : We examined the body compositions of 20 obese patients who were treated with Saengsig and Behavior Modification Therapy for 2 months by Inbody 2.0. Results : Changes of body composition due to Saengsig with Behavior Modification Therapy were reduction of body weight by $3.14{\pm}1.33{\;}kg$, lean body mass by $0.14{\pm}1.48{\;}kg$, fat mass by $3.00{\pm}1.53kg$ and BMI by $1.30{\pm}0.54$ Conclusion : Fat mass and body fat rate were significantly reduced after treatment with Saengsig with Behavior Modification Therapy.

• Structural Engineering and Mechanics
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• v.88 no.4
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• pp.379-387
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• 2023

Wind and earthquake loads may cause strong vibrations in large-span cable-stayed bridges, leading to the inability of the bridge to operate normally. An improved Pounding Tuned Mass Damper (PTMD) system was designed to improve the safety of the large-span cable-stayed bridge. The vibration control effect of the improved PTMD system on the large-span cablestayed bridge under the combined action of earthquake-wind-traffic was studied. Furthermore, the impact of different parameters on the vibration suppression performance of the improved PTMD system was analyzed. The numerical results indicate that the PTMD system is very effective in suppressing the displacements of the bridge caused by both the traffic-wind coupling and traffic-earthquake coupling. Moreover, the number, mass ratio, pounding stiffness, and gap values have a significant influence on the vibration suppression performance of the improved PTMD system. When the number of PTMD is increased from 3 to 9, the vibration reduction ratio of the vertical displacement is increased from 25.39% to 48.05%. As the mass ratio changes from 0.5% to 2%, the vibration reduction ratio increases significantly from 22.23% to 53.30%.

• Structural Engineering and Mechanics
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• v.81 no.4
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• pp.429-441
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• 2022

A probabilistic assessment of the seismic-excited buildings with a multiple-tuned-mass-damper (MTMD) system is carried out in the presence of uncertainties of the structural model, MTMD system, and the stochastic model of the seismic excitations. A free search optimization procedure of the individual mass, stiffness and, damping parameters of the MTMD system based on the snap-drift cuckoo search (SDCS) optimization algorithm is proposed for the optimal design of the MTMD system. Considering a 10-story structure in three cases equipped with single tuned mass damper (STMS), 5-TMD and 10-TMD, sensitivity analyses are carried out using Sobol' indices based on the Monte Carlo simulation (MCS) method. Considering different seismic performance levels, the reliability analyses are done using MCS and kriging-based MCS methods. The results show the maximum structural responses are more affected by changes in the PGA and the stiffness coefficients of the structural floors and TMDs. The results indicate the kriging-based MCS method can estimate the accurate amount of failure probability by spending less time than the MCS. The results also show the MTMD gives a significant reduction in the structural failure probability. The effect of the MTMD on the reduction of the failure probability is remarkable in the performance levels of life safety and collapse prevention. The maximum drift of floors may be reduced for the nominal structural system by increasing the TMDs, however, the complexity of the MTMD model and increasing its corresponding uncertainty sources can be caused a slight increase in the failure probability of the structure.

• The Journal of the Acoustical Society of Korea
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• v.10 no.2
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• pp.13-22
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• 1991

The presence of an unbalanced mass is originated the common source of vibration in machines with rotating rotor. In this study, the unbalanced rigid rotor mounted on an overhang shaft is balanced using the static balancing procedure, and the compensation mass is estimated by the phase angle method and four run method. Also, the reduction of vibration level before and after balancing is examined. In the experimental results, it is shown that the vibration due to the unbalanced mass is decreased by eliminating the effect of the unbalance. Above all, the four run method is proved more effective on the ability of vibration reduction, in small unbalanced mass, the phase angle method.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.487-490
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• 2005

This study was performed to investigate the effect of ternary blended cement concrete mixed with slag cement and fly ash on the compressive strength, the resistance to chloride ion penetration and reduction of hydration heat. Each performance of ternary blended cement concrete compared with binary blended cement concrete and ordinary portland cement concrete. As a result, it was concluded that ternary blended cement concrete is suitable to mass concrete under marine environment.

• Membrane and Water Treatment
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• v.4 no.4
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• pp.251-263
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• 2013

The internal reflux effect on dialysis through the retentate phase of a countercurrently cross-flow rectangular module is investigated. Theoretical analysis of mass transfer in cross-flow devices with or without recycling is analogous to heat transfer in cross-flow heat exchangers. In contrast to a device without reflux, considerable mass transfer is achievable if cross-flow dialyzers are operated with reflux, which provides an increase in fluid velocity, resulting in a reduction in mass-transfer resistance. It is concluded that reflux can enhance mass transfer, especially for large flow rate and feed-concentration operated under high reflux ratio.

• Korean Journal of Community Nutrition
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• v.20 no.4
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• pp.281-290
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• 2015

Objectives: Obesity is known to influence physical and mental health as well as the general quality of life. The aim of this study was to evaluate the effect of obesity related quality of life on selecting a goal for weight management in overweight and obese female patients. Methods: A total of 140 overweight or obese (Body mass index $23kg/m^2$) female outpatients aged ${\geq}20$ and ${\leq}60$ years from one clinic participated in this study. Patients' desired weight (goal weight, ideal weight, satisfactory weight, acceptable weight and disappointed weight) and obesity related quality of life measures were evaluated. Univariate and multivariate analysis were performed to evaluate the effect of obesity related quality of life on goal weight reduction (%) and goal body mass index (BMI). Results: Mean BMI of overweight group, mild obesity group and severe obesity group were $62.0{\pm}4.8kg$, $68.5{\pm}5.5kg$ and $83.5{\pm}9.6kg$, respectively. Mean weight loss expectations of the three groups were $16.4{\pm}4.7%$, $19.5{\pm}5.3%$ and $30.2{\pm}6.8%$, respectively and goal weight was significantly different among the three groups. Severe obesity group had a lower total quality of life score including physical, work-related, daily living domains than overweight or mild obesity groups. In univariate and multivariate regression analysis, psychosocial domain of quality of life had an effect on goal weight reduction (%) and goal BMI. Conclusions: The results of this study demonstrated that the obese patients with poorer quality of life and psychosocial health tended to choose higher goal weight reduction and lower goal BMI.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.6
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• pp.165-169
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• 2007

The purpose of this study is to investigate the effect of rotating unbalance mass on vibration characteristics of the front axle. The power-train systemof the vehicle is composed of several rotating parts. These component parts should be properly balanced by the balancing machine, however,sometimes these have the unbalance mass which causes the critical vibration in the vehicle. Therefore, this study suggests the vibration improvement method based on reducing the unbalance mass through changing the assembly type between the companion flange and the constant velocity joints. In addition, the way to increase the inertia moment of the companion flange was proposed.

• Journal of Korean Association for Spatial Structures
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• v.20 no.3
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• pp.107-116
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• 2020

In this paper, the displacement response to seismic loads was analyzed after installing TMD in spatial structures and high-rise buildings. In the case of a spatial structures, since it exhibits complex dynamic behavior under the influence of various vibration modes, it is not possible to effectively control the seismic response by installing only one TMD, unlike ordinary structures. Therefore, after installing eight TMDs in the structure, the correlation between displacement response and mass ratio was examined while changing the mass. The TMD must be designed to have the same frequency as the structure frequency so that the maximum response reduction effect can be exhibited. It can be confirmed that the most important variable is to select the optimal TMD mass in order to install the TMD on the structure and secure excellent control performance against the earthquake load. As a result of analyzing the TMD mass ratio, in the case of high-rise buildings, a mass ratio of 0.4% to 0.6% is preferable. In spatial structures, it is desirable to select a mass ratio of 0.1% to 0.2%. Because this study is based on the theoretical study based on numerical analysis, in order to design a TMD for a real structure, it is necessary to select within a range that does not affect the safety of the structure.