• Geosystem Engineering
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• v.21 no.6
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• pp.344-351
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• 2018

It is reported that the flooding rate in low permeability sandstones is low and the oil recovery is hard to increase after water breakthrough. Understanding characteristics of waterflood is hence important for the recovery improvement. In this work, flooding tests on low permeability sandstones were conducted. The corresponding flooding characteristics were investigated by means of CT scanning and Nuclear Magnetic Resonance. Effects of irreducible water and different rates were also discussed in detail. Experimental results reveal a piston-like displacement at a low rate in low permeability samples. The saturation profile is steep and almost vertical to the forward direction. The results at a low rate confirm that once water broke through, increasing the flooding rate or flooding time can hardly reduce the remaining oil inside the sample. It is probably due to the high pore-throat ratio proven by rate-controlled mercury. Results also confirm that the presence of initial water enhanced sweep efficiency substantially. On one hand, because water had previously occupied the small pores, the subsequent oil can only invade relatively large pores and became more movable. On the other hand, stable collars can not form due to the steep front, which may suppress the snap-off.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.6
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• pp.258-269
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• 1999

It is important to evaluate fatigue damage of in-service material in respect to assure safety and remaining fatigue life in structure and mechanical components under cyclic load . Fatigue damage is represented by mathematical modelling with crack growth rate da/dN and cycle ration N/Nf and is detected by X-ray diffraction and ultrasonic wave method etc. But this is estimated generally by single parameter but influenced by many test conditions The characteristics of it indicates fatigue damage has complex fracture mechanism. Therefore, in this study we propose that back-propagation neural networks on the basis of ration of X-ray half-value breath B/Bo, fractal dimension Df and fracture mechanical parameters can construct artificial intelligent networks estimating crack growth rate da/dN and cycle ratio N/Nf without regard to stress amplitude Δ $\sigma$.

• Journal of Intelligence and Information Systems
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• v.3 no.1
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• pp.47-68
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• 1997

This paper discusses a method of modified Elman network(1990) for nonlinear predictions and its a, pp.ication to forecasting daily exchange rate returns. The method consists of two stages that take advantages of both time domain filter and modified feedback networks. The first stage straightforwardly employs the filtering technique to remove extreme noise. In the second stage neural networks are designed to take the feedback from both hidden-layer units and the deviation of outputs from target values during learning. This combined feedback can be exploited to transfer unconsidered information on errors into the network system and, consequently, would improve predictions. The method a, pp.ars to dominate linear ARMA models and standard dynamic neural networks in one-step-ahead forecasting exchange rate returns.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.1
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• pp.8-12
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• 2019

Combined Cycle Unit(CC) generates the primary power from the Gas Turbine(GT) and supplies the remaining heat of the GT to the Steam Turbine(ST) to generate the secondary power from the ST. It plays a major role in terms of energy efficiency and Load Frequency Control(LFC). Incremental Heat Rate(IHR) curves of economic dispatch(ED) of CC is applied differently by GT/ST combination. But It is practically difficult because of performance test by all combinations. This paper suggests a reasonable method for estimating IHR curves for partial combinations(1:1~(N-1):1) using IHR curves when operating with GT alone(1:0) and with all(N:1) combinations of CC.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.35-36
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• 2022

In order to supplement the flame-retardant performance of oil stain, which can prevent wooden buildings from contamination, (NH4)2HPO4, a phosphorus flame-retardant, was added to oil stain and applied for each type of plywood, and an experiment was conducted. The addition rate was set to 0-60%, but white powder appeared on the surface of plywood from 40% and thus it was impossible to experiment, so the maximum addition rate was selected as 30%. As a result of the experiment, acacia plywood had the best performance. As the rate of addition of the flame retardant increased, the remaining time and carbonization length of all plywood decreased, but the carbonization length of the MDF plywood was not met with the standards.

• The Journal of Pediatrics of Korean Medicine
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• v.21 no.3
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• pp.177-188
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• 2007

Objectives The purpose of this study is to investigate the effects of simultaneous treatment with supplementary therapy and treatment interval for improving symptoms and satisfaction rate by treating child rhinitis or paranasal sinusitis patients. Methods 41 rhinitis or paranasal sinusitis patients who visited the clinic between April 2004 and April 2006 were involved for this study. The patients were classified into Group A(2 sessions per week, simultaneous supplementary therapy), Group B(1 session in 2 weeks, simultaneous supplementary therapy) and Group C(1 session in 2 weeks, no supplementary therapy). After the experiment, the improvement rates of symptoms and satisfaction rate were surveyed by the questionnaires. Supplementary therapies used in Group A and B were aroma spray, Saengbit-patch, cutaneous acupuncture, nebulizer and Chuna manipulation. Results From 41 of the rhinitis or paranasal sinusitis patients, the Group A(simultaneous treatment group, 2 sessions of intensive care per week with supplementary therapy) showed the remaining symptoms score of $12.1{\pm}10.0$ in average. This score was the lowest comparing with the average of $25.7{\pm}12.9$ in Group B(1 session in 2 weeks, simultaneous treatment group with supplementary therapy) and the average of $21.0{\pm}20.1$ in Group C(1 session in 2 weeks, no supplementary therapy). Nose symptoms and sleep scores were significantly lower in Group A(p<0.01). The satisfaction score was the highest in Group B that had the most remaining symptoms and it had no significant relationship with the symptom improvement. Additional analysis showed that among many factors such as treatment interval, treatment method, cost, accessibility of the clinic, family history and satisfaction with the doctor; the satisfaction with their doctor was the most closely related to the satisfaction rate of the patients. Conclusions In this study with 41 of rhinitis or paranasal sinusitis patients, the 2 sessions of intensive care group showed the best results in improving symptoms. Supplementary treatments were also used simultaneously; aroma spray, cutaneous acupuncture, Saengbit-patch, Chuna manipulation and nebulizer. The questionnaires showed that the satisfaction rate of the patients(care taker) was not related to the symptom improvement. Additional analysis of the factors that influence the satisfaction rate showed that it was more closely related to the satisfaction with their doctors.

• Journal of Korean Institute of Industrial Engineers
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• v.15 no.2
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• pp.65-75
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• 1989

A general software reliability model is developed, which includes the Jelinski-Moranda model, the Goel-Okumoto model, the Shanthikumar model and the Ross model as special cases. In each of above models estimators of the software failure rate and the number of remaining errors are presented and compared in terms of the expected absolute error loss and the expected squared error loss by a Monte Carlo simulation.

• Communications for Statistical Applications and Methods
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• v.16 no.4
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• pp.639-645
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• 2009

Fractional Brwonian motion(fBm) has properties of behaving tails and exhibiting long memory while remaining Gaussian. In particular, it is well known that interest rates show some long memories and non-Markovian. We present no aribitrage condition for HJM model under the multi-factor fBm reflecting the long range dependence in the interest rate model.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.688-693
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• 2000

Recently great efforts and investment have been made in order to evaluate concrete durability by steel corrosion. But most of study is relatively or qualitatively estimated, therefore it has a great limitation in evaluating a remaining service life of concrete. In this research, steel corrosion rate was measured quantitatively by polarization resistance method and multi-regressed considering chloride, carbonation, coverage depth, relative humidity, W/C, and the use of deicing salts. And a half cell potential method was used at th same time for the purpose of comparing with polarization resistance method.

• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.2351-2354
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• 2003

A new transform coder for arbitrarily shaped image segments is proposed. In the encoder, a block-based DCT is applied to the resulting image block after shifting pixels within the image segment to block border and padding the mean value of the pixels to empty region. For reducing the transmission bit rate, the transform coefficients located in padded region are truncated and only the remaining transform coefficients are transmitted to the decoder. In the decoder, the transform coefficients truncated in the encoder are recovered using received transform coefficients and a block-based inverse DCT is performed.