• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.5
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• pp.537-543
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• 2006

There have been many recent studies on the nonlinear rainfall-runoff modeling, where the use of neural networks is shown to be quite successful. Due to fundamental limitation of linear structures, employing linear models has often been considered inferior to the neural network approaches in this area. However, we believe that with an appropriate extension, the concept of linear impulse responses can be a viable tool since it enables us to understand underlying dynamics principles better. In this paper, we propose the use of multiple impulse responses for the problem of rainfall-runoff analysis. The proposed method is based on a simple and fixed strategy for switching among multiple linear impulse-response models, each of which satisfies the constraints of non-negativity and uni-modality. The computational analysis performed for a certain Korean hydrometeorologic data set showed that the proposed method can yield very meaningful results.

• Journal of the Korean GEO-environmental Society
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• v.24 no.4
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• pp.5-11
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• 2023

Impulse waves generated by landslides near water bodies can lead to fatal damage to human life and surrounding infrastructure. These impulse waves are generally called landslide-impulsed waves and occur without being limited to a specific area. Recently, localized torrential rains have frequently occurred due to the influence of abnormal weather, both the frequency and scale of landslides occurring in Korea are increasing. Therefore, in this study, the experiments were conducted according to the mass ratio of the landslide models, and among the characteristics of the generated landslide-impulse waves. And the wave amplitude was observed and analyzed. In this study, a total of 75 experiments were conducted by repeating the experiment 5 times for 15 cases with mass ratios of 5 landslide models and 3 types of slope angles. As a result of experiments with different mass ratios of landslide models, if the landslides have the same initial energy, the size of the landslide-impulse waves generated by mixing granular and block forms is higher than the size of the landslide-impulse waves generated by pure granular and block landslides. It is analyzed that the size may be larger.

• Progress in Medical Physics
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• v.17 no.3
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• pp.159-166
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• 2006

The nonlinearity of hemodynamic response in the somatosensory cortex was investigated with vibrotactile stimulation. The stimuli consisted of a train of 25 Hz, each tasting five different duration periods, 2 s, 4 s, 8 s 12 s, or 16 s with 20 sec periods of no vibration in a pseudo-random order. In order to understand the linearity on the change of stimulus duration for somatosensory cortex, two different tests- checking the linearity of system and finding the impulse response function from gamma-variate function were applied to analyze the hemodynamic response functions. They have produced nearly same results. The BOLD response in the somatosensory cortex Is nonlinear for stimuli of less than 8 seconds, but nearly linear for stimuli greater than 8 seconds. The amplitude, area, TTP, and FWHM as functions of the stimulus duration were calculated and showed a significant downward trend with Increasing stimulus duration for the amplitude and the area. It supports the ranges of nonlinearity are less than 8 seconds.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.561-565
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• 2009

The performance of supersonic impulse turbine was investigated experimentally. Experiment was performed with the compressed air instead of the high temperature burned gas because of the limitation of test facility and danger. As a result of the experiment with the compressed air, the performance in the real gas(burned gas) was predicted by the similarity method. The nozzle area of prototype turbine was calculated based on the real gas. So, it is difficult to satisfy the similarity conditions completely. Two similarity conditions were set and the design point for real gas was existed between two similarity conditions. And, the new turbine test model with calculated nozzle area based on the compressed air was tested. Therefore, similarity point of the new turbine test model was also existed between above two similarity points. It means that the design point for real gas was similar to the test point with the new turbine model.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.297-301
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• 2007

The blades of supersonic turbines with low aspect ratio are usually designed to have the same cross sectional shape in radial direction. The profile diameter definition of turbines may lead to produce unintended flow passage area variations resulting performance degradation. In this paper, the effects of profile diameter definition on the supersonic impulse turbine performance have been investigated. Computational results of three different profile diameters are compared. It has been found that flow passage area variation can be achieved according to designer's intention when blade profile is defined at rotor tip diameter. Furthermore, the turbine blade profile defined at rotor tip showed better performance than the others.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.3
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• pp.49-59
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• 2008

In this study, the design method of a 155 mm Solid Fuel Ramjet projectile is proposed and a flight performance analysis program through mathematical modelling is developed. Through flight performance analysis, ramjet performance during flight, which is comprised of thrust, specific impulse, pressure recovery ratio, location of shock waves, and magnitude of drag, was predicted. The results show that compared to Rocket Assisted Projectile(RAP), the range was increased by 90 %. Furthermore, how variations in nozzle exit area ratio and the intake area cause variations in range was observed. This research on modeling and simulation methodology will provide useful data for future development of solid fuel ramjet projectiles.

• The Journal of Korea Robotics Society
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• v.10 no.4
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• pp.200-212
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• 2015

In classical dynamics, the coefficient of restitution is one of variables to estimate the amount of impulse. In general, we have considered the coefficient of restitution as a constant value. However, coefficient of restitution (COR) is the function of contact material and colliding velocity. Furthermore, COR is also a function of contact area. Thus, without considering the variable characteristic of COR, the actual motion of an object just after impact is not the same as we expect. A general COR model is proposed in this work and its effectiveness is verified through a cart impact experiment and its result is applied to simulation of a ball impact problem. A three-degree-of-freedom manipulator is employed as a test-bed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.10
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• pp.35-40
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• 2006

In this paper, a current-mode analog variable finite-impulse-response (FIR) filter with variable tap coefficient circuits is proposed for frequency selective wireless personal area network(WPAN) system or terminals. From the circuit simulation the operation of the 7-tap FIR filter is confirmed. The 0.0625-step tap coefficient circuit is designed and fabricated with $0.8[{\mu}m]$ CMOS technology. The proposed FIR filter has a variable length of taps and variable coefficients, so it has a potential for being used to frequency selective WPAN system or frequency selective wireless communication terminals.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.604-611
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• 1998

High-speed railway trains entering and leaving tunnels generate finite amplitude pressure wave which propagate back and forth along the tunnels, reflecting at the open ends of the tunnels and at other discontinuities such as ventilation shafts and the train themselves. In present day railways, the magnitudes of the pressure waves are much too small to cause structual damage, but they are a serious potential source of aural discomport for passengers on unsealed trains. Almost always do the pressure waves propagating along the tunnels lead to a hazardous impulse noise near the exit portal of the tunnel. In order to alleviate such undesirable phenomena, some control strategies have been applied to the compression wave propagating inside the tunnel. The objective of the current work is to investigate the effect of tunnel entrance hoods on the entry compression wave at the vicinity of the tunnel entrance. Three types of entrance hoods were tested by the numerical method using the characteristics of method for a wide range of train speeds. The results show that the maximum pressure gradient of compression wave can be considerably reduced by the tunnel entrance hood. Desirable hood shape for reduction of the pressure transients and impulse noise was found to be of abrupt type hood with its cross-sectional area 2.5times the tunnel area.

• SUVANNABHUMI
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• v.10 no.2
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• pp.89-114
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• 2018

In this paper, I argue that while area studies in the United States has declined since the end of the Cold War, its area impulse of has emerged in other fields of inquiry, particularly Asian-American Studies. Accordingly, I explain how the collective reflections of Filipino-American scholars on empire, migration, diaspora, and identity point to the consolidation and viability of the transpacific as an area, which spans both the United States and the Philippines. Addressing several problems with this straddling-mainly as criticisms of Filipino-American Studies-I show how the transpacific serves as a bridge between Philippine Studies and Filipino-American Studies, and helps define the boundaries and overlaps between both fields of inquiry.