• Journal of Korean Society on Water Environment
• /
• v.26 no.3
• /
• pp.491-496
• /
• 2010

This study aimed to obtain equilibrium concentration on adsorption removal of phosphorus by activated carbon, to express the adsorption characteristics following Freundlich isotherm and also, based on the value obtained, to investigate the relationship between physical properties of activated carbon and dynamics of phosphorus removal by obtaining rate constant and effective pore diffusivity. The results summarized from this study are as follows. Phosphorus adsorption equilibrium reaching time of powdered activated carbon was reduced as the dosage of activated carbon increases, while granular activated carbon despite increased dosage did not have influence on adsorption equilibrium reaching times of phosphorus as well, taking more than 10 hours. It was also noted that powdered activated carbon showed better adsorption ability than granular activated carbon. The value of constant (f) of Freundlich isotherm of powered activated carbon on phosphorus was 4.26 which is bigger than those of granular activated carbon. The adsorption rate constant on phosphorus of powered activated carbon with low effective diameter and iodine number was highest as $8.888hr^{-1}$ and the effective pore diffusivity ($D_e$) was lowest as $2.45{\times}10^{-5}cm^2/hr$, and the value of phosphorus adsorption rate constant of granular activated carbon was $0.174{\sim}0.372hr^{-1}$, It was revealed that, with the same amount of dosage, the adsorptive power of activated carbon with lower effective diameter was better and its rate constant was also high.

• Journal of Institute of Control, Robotics and Systems
• /
• v.2 no.2
• /
• pp.108-114
• /
• 1996

We present proofs of the stability and convergence of Self-organizing feature map (SOFM) neural network with time-invarient learning rate and binary reinforcement function. One of the major problems in Self-organizing feature map neural network concerns with learning rate-"Kalman Filter" gain in stochsatic control field which is monotone decreasing function and converges to 0 for satisfying minimum variance property. In this paper, we show that the stability and convergence of Self-organizing feature map neural network with time-invariant learning rate. The analysis of the proposed algorithm shows that the stability and convergence is guranteed with exponentially stable and weak convergence properties as well.s as well.

• KDI Journal of Economic Policy
• /
• v.37 no.4
• /
• pp.1-20
• /
• 2015

We examine the validity of popular exchange rate models such as the purchasing power parity (PPP) hypothesis and the monetary model for Korean won/US dollar exchange rate. Various specification tests demonstrate that Korean data are more favorable for both models based on time-varying cointegration coefficients as compared to those based on constant cointegration coefficients. When the abilities to predict future exchange rates between those models based on time-varying cointegration coefficients are compared, an in-sample analysis shows that the time-varying PPP (monetary model) has better predictive power over horizons shorter (longer) than one year. Results from an out-of-sample analysis indicate that the time-varying PPP outperforms models based on constant cointegration coefficients when predicting future exchange rate changes in the long run.

• Journal of Educational Research in Mathematics
• /
• v.27 no.3
• /
• pp.599-614
• /
• 2017

The purpose of this study is to compare and analyze middle school students' understanding of constant rate of change, in terms of observing, representing and interpreting dynamic functions in various ways using the SimCalc MathWorlds. For this purpose, parts of a class conducted for six students in the first grade of middle school were analyzed. The results suggested two implications for a class that used this program (SimCalc MathWorlds): First, we confirmed that the relationships between the two quantities that students notice in the same situation can be different. Second, the program helped students to develop a more comprehensive understanding of the meaning of the constant rate of change. The study also revealed the need to use technology in teaching and learning about functions, particularly to represent and interpret a given situation that involves the constant rate of change in various ways. Further, the results can contribute to developing contents and methods to teach functions using technology in consideration of students' different levels of understanding.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.10
• /
• pp.2391-2397
• /
• 1993

The distribution of fatigue crack growth rate is influenced by the measuring interval and methods of calculation of crack growth rate. The purpose of this paper is to suggest a method for the evaluation of crack growth rate distribution without the influence. The constant ${\Delta}P$ test and the constant .DELTA.K test are executed by using the CT specimen. The measuring interval of (${\Delta}a$/W=0.0067~0.014) crack length is not affected by methods of the calculation of the fatigue crack growth rate is suggested.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.4
• /
• pp.362-367
• /
• 2008

We have Manufactured the low-k dielectric interlayer fabricated by plasma enhanced chemical vapor deposition (PECVD), The thin film of SiOCH is studied correlation between components and Dielectric constant. The precursor was evaporated and introduced with the flow rates from 16 sccm to 25 sccm by 1sccm step in the constant flow rate of 60 sccm $O_2$ in process chamber. The chemical characteristics of SiOCH were analyzed by measuring FT/IR absorption lines and obtained each dielectric constant measuring C-V. Then compare respectively. ILD of BTMSM/$O_2$ could have low dielectric constant about $k\sim2$, and react sensitively. Also dielectric constant could be decreased by the effects of decreasing $CH_3$ and growing Si-O-Si(C) after annealing process.

• Journal of the Korean Geosynthetics Society
• /
• v.13 no.4
• /
• pp.33-43
• /
• 2014

Recently, the case to construct the structure on the soft clayey ground has increased and in order to the reduction of the cost of construction and maintenance on the social infrastructure facilities we have been trying to improve the soft clayey ground using the existing methods such as the pre-loading method and the vertical drain method. Like this, when various ground improvement methods are applied on the soft clayey ground, a long-term consolidation settlement will be key issue due to low permeability coefficient of cohesive soil. According to existing research results that relate to the consolidation settlement, the loading periods for existing the standard consolidation test (Oedometer test) to obtain the consolidation parameters are needed for minimum ten days or more. Therefore, in this study, the standard consolidation test (24 hours step-loading) and constant strain rate consolidation test changed by strain rate was performed using the remolded marine clay on Gwangyang bay composed of a soft clayey ground of the south-west coast. From the laboratory test results, the characteristics of compression, strain-effective stress relations by constant strain rate and the variation characteristic of the pore water pressure by different of loading speed and the relation between consolidation parameters and constant strain rate are compared and analyzed.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.17 no.4
• /
• pp.1-7
• /
• 2008

Fine grained superplastic Zn-22%Al alloy was extruded using a laser machined micro-die to produce a micro-gear shaft. Extrusion process was conducted under a constant pressure at constant temperatures ranging from 503 to 563K. Laser machining was capable to machine a micro-die with close tolerances and adequate surface quality. The extrusion rate increased with extrusion load under constant extrusion temperature. The rate reached a steady state and became constant after a certain period. There was a small instantaneous stroke on application of the load and then a very brief primary stage which preceded steady-state flow. The micro-extrusion process was proven to produce a micro-gear shaft successfully using a fine grained superplastic Zn-22%Al alloy.

• Journal of the Korean Society for Precision Engineering
• /
• v.9 no.2
• /
• pp.116-121
• /
• 1992

The optimal extrusion process for the rate sensitive materials have been developed in this study. The preliminary designs of the die shapes have been carried out to maintain constant strain rate during extrusion and the upper bound approach has been applied to define the process variables (the die entrance velocity and the die length) including the rheology during deformation. The result for the axisymmetric extrusion process has been verified with rigid-viscoplastic finite element analysis. It has been confirmed that the optimal die has wider band of constant strain rate than the conical one does.

• Journal of Pharmaceutical Investigation
• /
• v.14 no.1
• /
• pp.11-18
• /
• 1984

This paper was attempted to study on the effect of metoclopramide or propantheline on the absorption rate and bioavailability and pharmacokinetic parameter of fluorouracil in rats and rabbits. The result are as follows; Metoclopramide increased the absorption rate of fluorouracil but propantheline decreased in situ experiment with rat small intestine. Metoclopramide increased the blood level and relative bioavailability and absorption rate constant of fluorouracil in rabbits. Prolonged the peak blood level (tmax) and decreased the absorption rate constant (Ka) but did not affect the blood level and relative bioavailability of fluorouracil in rabbits. As a matter of fact, it is considerd that the coadministration of metoclopramide or propantheline is more desirable than the single administration of fluorouracil for available dosage regimen.