• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.166-171
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• 2004

The Rate-of-Loading(ROL) effect of motor operated gate valves causes a decrease in the thrust delivered at a specific torque by the actuator under dynamic flow ${\Delta}$P conditions as compared to the no-flow, static conditions. This effect needs to be studied for the quantitative evaluation of motor operated gate valve operability. This study is performed to verify the validity for the application of ROL in the evaluation of operability of motor operated gate valves for the opening stroke. The ROL is assessed on the basis of in-situ test data for the opening and closing strokes. The results show that the distribution of the ROL for the operling sake has a tendency to the negative value when DP is higher than 150psid.

• Geotechnical Engineering
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• v.13 no.1
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• pp.147-158
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• 1997

In this study, it is examined that partial drain has an effect of bearing capacities and deformations on intermediate soils. To compare the numerical and experimental results, this study uses CRISP90 which is composed of Modify Cam-Clay Model for calculation and Geotechnical Centrifuge in model test. As the results of analysis, we can classify relative loading rate into three ranges which are drain, undrain and partial drain. Besides it is proved that partial drain range is about 103.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.6
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• pp.637-644
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• 2021

Dynamic response of structures can be evaluated experimentally by conducting cyclic loading tests. It has been known that steel materials are rate-dependent and the lateral response of a structure is significantly affected by the presence of axial force. However, the rate-dependency of steel column structures subjected to both axial and lateral loads has not been sufficiently studied yet due to the difficulty of controlling the axial force in a real-time manner during test. This study introduces an advanced way to apply the axial load in real-time to a column specimen using the adaptive time series (ATS) compensator and the flexible loading beam (FLB), where the H-shape steel columns made of SS275 are used for monotonic and cyclic loading tests with various loading rates with axial loads. The lateral strength and post-yield response of the steel columns are compared for each of monotonic and cyclic loading tests. The estimating equation of yield stress of various strain rate has proposed and finite element analysis were performed for comparison.

• Earthquakes and Structures
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• v.8 no.3
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• pp.665-679
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• 2015

The strain rate of reinforced concrete (RC) structures stimulated by earthquake action has been generally recognized as in the range from $10^{-4}/s$ to $10^{-1}/s$. Because both concrete and steel reinforcement are rate-sensitive materials, the RC beam-column joints are bound to behave differently under different strain rates. This paper describes an investigation of seismic behavior of RC beam-column joints which are subjected to large cyclic displacements on the beam ends with three loading velocities, i.e., 0.4 mm/s, 4 mm/s and 40 mm/s respectively. The levels of strain rate on the joint core region are correspondingly estimated to be $10^{-5}/s$, $10^{-4}/s$, and $10^{-2}/s$. It is aimed to better understand the effect of strain rates on seismic behavior of beam-column joints, such as the carrying capacity and failure modes as well as the energy dissipation. From the experiments, it is observed that with the increase of loading velocity or strain rate, damage in the joint core region decreases but damage in the plastic hinge regions of adjacent beams increases. The energy absorbed in the hysteresis loops under higher loading velocity is larger than that under quasi-static loading. It is also found that the yielding load of the joint is almost independent of the loading velocity, and there is a marginal increase of the ultimate carrying capacity when the loading velocity is increased for the ranges studied in this work. However, under higher loading velocity the residual carrying capacity after peak load drops more rapidly. Additionally, the axial compression ratio has little effect on the shear carrying capacity of the beam-column joints, but with the increase of loading velocity, the crack width of concrete in the joint zone becomes narrower. The shear carrying capacity of the joint at higher loading velocity is higher than that calculated with the quasi-static method proposed by the design code. When the dynamic strengths of materials, i.e., concrete and reinforcement, are directly substituted into the design model of current code, it tends to be insufficiently safe.

• Journal of Pharmaceutical Investigation
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• v.24 no.3
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• pp.33-39
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• 1994

We have studied the effect of loading amount and particle size on the rate of release of 5-fluorouracil (5-FU) from ethylene-vinyl acetate (EVA) matrix. Release rate increased as the loading amount and particle size increase. We also studied the effect of additives (lactose and algin) on the rate of release of 5-FU. Both algin and lactose promoted the rate of release. The ability to increase the rate is in the order of algin>lactose>5-FU. Scanning electron microscope study clearly shows that large cavities and cracks are created. The results imply that, by the proper combinations of the amount of the additive, $EVA_c$ and drug, the rate of drug release can be modulated over a wide range of values.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2905-2918
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• 2023

The valve assembly used in nuclear power plants is important safety-related equipment. In the new standard, the physical attributes are measured using a valve diagnosis test, which is used in the expansion to other non-tested valves using a quantitative test-basis methodology. With a motor-operated actuator, the state of stem's lubrication is related to physical attributes such as the stem factor and the friction coefficient. This study analyzed the numerical transient of fluid and solid lubrication with a squeeze film effect due to the loading rate on the stem and the stem nut using the experimental data. The differential equation that governs the motion mechanism of the stem and stem nut is established and analyzed. The flow rate, the fluid and the solid contact forces are calculated with the friction coefficient. Finally, we found that a change in the friction coefficient results from a change of the shear force in the solid contact mode during the interchange process between the solid contact mode and the fluid contact mode. The qualitative understanding of the squeeze film effect is expanded quantitatively for forces, thread surface distance, velocity, and acceleration, with consideration of the metal solid contact and fluid contact.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.776-780
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• 2007

A biofilm reactor packed with porous media was investigated for nitrogen removal of synthetic wastewater. The effect of different loading rates on the nitrification was sustained to be steady state with stable efficiency of 50~60% in the range of $0.0083{\sim}0.017gNH_4-N/gMLVSS{\cdot}day$ of F/MN ratio and $1{\sim}2kgNH_4-N/m^3{\cdot}day$ of media volumetric loading rate. However, nitrification efficiency was rapidly decreased to 25~30% as F/MN ratio and media volumetric loading rate were increased to the range of $0.025{\sim}0.034gNH_4-N/gMLVSS{\cdot}day$ and $3{\sim}4kgNH_4-N/m^3{\cdot}day$, respectively. Also the consumption rate of alkalinity was higher under 8 hours of HRT than unter 6 hours of HRT. Accordingly the influent loading rate variation by detention time with influent flow influenced more on the nitrification efficiency than the influent loading rate variation by the influent concentration did. The temperature effect on the nitrification showed 25% higher in summer than in winter as the results reported by other researchers who reported that the nitrification efficiency in biofilm showed 20% increase from 55% to 75% when the temperature was raised from $20^{\circ}C$ to $25^{\circ}C$. Denitrification with sulfur-media showed 90% removal efficiency under steady-state with no effect from the increase of influent concentration and empty bed contact time (EBCT) change such as EBCT was decreased from 8.4 hr to 4.3 hr and $NO_3-N$ loading rate was changed within the range of $0.1{\sim}0.4kgNO^3-N/m^3{\cdot}day$. Accordingly Denitrification with sulfur-media is feasible for post denitrification at the concentration less than $80mgNO^3-N/L$.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.711-716
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• 2008

A circular tube undergoes bucking behavior when it is subjected to axial loading. An upper bound analysis can be an attractive approach to predict the buckling load and energy absorption efficiently. The upper bound analysis obtains the load or energy absorption by means of assumption of the kinematically admissible velocity fields. In order to obtain an accurate solution, kinematically admissible velocity fields should be defined by considering many factors such as geometrical parameters, dynamic effect, etc. In this study, experiments and finite element analyses are carried out for circular tubes with various dimensions and loading conditions. As a result, the kinematically admissible velocity field is newly proposed in order to consider various dimensions and the strain rate effect of material. The upper bound analysis with the suggested velocity field accurately estimates the mean load and energy absorption obtained from results of experiment and finite element analysis.

• Journal of Korean Society on Water Environment
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• v.21 no.6
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• pp.687-694
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• 2005

Lab-scale experiments have been carried out to investigate the effect of F/R ratio of ASBR (Anaerobic Sequencing Batch Reactor) process on the removal of the organic matters in ammonia stripped swine wastewater. Three ASBR inoculated with sludge mixed with granular sludge of UASB (Upflow Anaerobic Sludge Blanket) and anaerobic digested sludge of municipal wastewater treatment plant were operated. Ammonia stripped swine wastewater was used as influent. Prior to conducting the experiments with varied conditions, the effect of increasing organic loading rate from 2.34 to $5.79gTCOD_{Cr}/L$-day at a fixed F/R ratio of 0.1 on the organic removal efficiency has been studied during start-up period. As the result of the experiment, under the condition of varied organic loadings, less than $4.14gTCOD_{Cr}/L$-day, the removed efficiency $TCOD_{Cr}$ of the ASBR process is 83% resulted from the mean value of effluent $TCOD_{Cr}$, 9,125 mg/L during the start-up period. Then ASBRs were operated with F/R ratio of 0.024, 0.303 and 0.91 respectively. Organic loading rate was increased from 4.56 to $15.43gTCOD_{Cr}/L$-day to investigate the effects of F/R ratio and organic loading rate on the organic removal efficiency. As the result of the experiment, less than $6.23gTCOD_{Cr}/L$/L-day, F/R ratio haven't an effect on the organic removal efficiency and the mean removal efficiency of TSS, $TCOD_{Cr}$ and $SCOD_{Cr}$ was about 80%, 86% and 78% at the all of F/R ratio. But as organic loading rate was increased from 8.54 to $12.04gTCOD_{Cr}/L$-day at the F/R ratio of 0.024, the removal efficiency of $SCOD_{Cr}$ decreased from 71% to 63%. The range of decreased removal efficiency of $SCOD_{Cr}$ at the F/R ratio of 0.024 was much more higher than at the F/R ratio of 0.303, 0.91. Thus, as organic loading rate was increased, ASBRs were operated with high F/R ratio to obtain high removal efficiency.

• Structural Engineering and Mechanics
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• v.37 no.2
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• pp.215-231
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• 2011

As a brittle and heterogeneous material, concrete behaves differently under different stress conditions and its bulk strength is loading rate dependent. To a large extent, the varying behavioural properties of concrete can be explained by the mechanical failure processes at a mesoscopic level. The development of a computational mesoscale model in a general finite element environment, as presented in the preceding companion paper (Part 1), makes it possible to investigate into the underlying mechanisms governing the bulk-scale behaviour of concrete under a variety of loading conditions and to characterise the variation in quantitative terms. In this paper, we first present a series of parametric studies on the behaviour of concrete material under quasi-static compression and tension conditions. The loading-face friction effect, the possible influences of the non-homogeneity within the mortar and ITZ phases, and the effect of randomness of coarse aggregates are examined. The mesoscale model is then applied to analyze the dynamic behaviour of concrete under high rate loading conditions. The potential contribution of the mesoscopic heterogeneity towards the generally recognized rate enhancement of the material compressive strength is discussed.