• The Journal of Engineering Geology
• /
• v.18 no.4
• /
• pp.433-437
• /
• 2008

It's essential to build an earth retaining structure at the beginning and end point of a tunnel constructed in a colluvium area. A large scale of colluvial soil may cause a problem to the stability of the excavation ground. An excavation in colluvium has different behavior characteristics from those in a sandy soil due to unstable elements and needs counter measures for it. There are few systematic research efforts on the behavior characteristics of an earth retaining structure installed in colluvial soil. Thus this study set out to collect measuring data from an excavation site at the tunnel pit mouth in colluvium and set quantitative criteria for the safety of an earth retaining structure. After comparing and analyzing the theoretical and empirical earth pressure from the measuring data, the lateral earth pressure distribution acted on the earth retaining wall was suggested.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2011.05a
• /
• pp.428-428
• /
• 2011

댐은 우리사회에 다양한 이익을 제공하는 반면 과거의 댐 붕괴 사례에 비추어 볼 때 붕괴로 인한 피해 규모는 막대하다. 세계 각국에서는 기존 댐들에 대한 잠재적 붕괴에 대비하기 위해 비상대처계획(Emergency Action Plan, EAP)과 같은 대책을 수립하여 붕괴로 인한 피해를 최소화하기 위한 노력을 기울이고 있다. 댐붕괴 모델링은 크게 댐 결괴부에 대한 예측과정과 댐 붕괴로 인한 하류부 홍수추적 과정으로 분류할 수 있다. 결괴부 예측과정은 댐붕괴로 인한 저수지 유출량에 가장 큰 영향을 미치는 부분이며 하류부 영향지역의 평가에도 매우 중요한 요소이다. 댐붕괴 예측모형은 결괴부에 대한 예측에 따라 매개변수 기반 모형과 물리기반 모형으로 분류된다. 매개변수 기반모형은 결괴형성과정을 단순 시간에 의한 함수로 고려하고 있으며 결괴부를 통한 흐름은 위어흐름으로 가정하고 있다. 이 모형은 현재 댐 붕괴 실무에서 가장 널리 이용되고 있으며 대표적인 모형은 FLDWAV/ DAMBRK 모형, HEC-RAS 모형 등이 있다. 물리기반 모형은 댐 붕괴진행 과정의 상세한 이해를 위해 시작되었으며 결괴부 흐름상황, 제체 침식, 제체가 불안정해지는 과정을 수리실험과 수리학, 토질역학, 구조역학 등의 이론을 통합하여 예측하는 기법으로 댐붕괴 과정을 좀 더 현실적으로 예측할 수 있으며 기존 붕괴된 댐들에 대한 붕괴 원인 및 진행과정을 규명할 수 있는 장점을 가진다. 최근 개발된 물리기반 댐 붕괴 모형은 HR-BREACH 모형, WINDAM 모형, FIREBIRD 모형 등이 있으며 지속적으로 연구되고 있다. 본 연구에서는 현재 진행 중에 있는 물리기반 댐 붕괴 모형들을 검토하고 현재 USDA, ARS에서 개발 중에 있는 WINDAM 모형을 이용하여 물리기반 모형의 수행에 요구되는 입력변수, 수행과정, 결과물에 대한 검토를 통해 댐 붕괴 관련 연구의 발전 방향을 모색하고 국내에서 물리기반 댐 붕괴 모형을 적용하기 위해 요구되는 사항과 한계점을 파악하여 댐 붕괴 실무로의 적용 방안을 마련하는 데 그 목적이 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2012.05a
• /
• pp.100-103
• /
• 2012

The blending method that is an addition of small quantity of fuel was used to increase the performance of green propellant thruster. 90 wt.% hydrogen peroxide as a green propellant was selected, and ethanol was used as a blended fuel. The o/f ratio was chosen as 50 which has higher theoretical performance than 98 wt.% hydrogen peroxide. The chamber temperature of blended hydrogen peroxide was higher than adiabatic chamber temperature of hydrogen peroxide. Therefore, performance can be improved by ethanol blending. Several catalyst and its support were compared to find appropriate catalyst for decomposition and combustion of ethanol blended hydrogen peroxide. As a experimental results, Pt was suitable, but $MnO_2$ had a chamber instability when it was reused. The ${\alpha}-Al_2O_3$ which is high heat-resistant support showed very unstable performance in both Pt and $MnO_2$ catalyst since it has low decomposition performance.

• Journal of IKEEE
• /
• v.25 no.3
• /
• pp.467-472
• /
• 2021

Stable operation of semiconductor devices is needed even at high temperatures. Among the structures of semiconductor devices, the area that can cause unstable electrical responses at high temperatures is the contact layer between the metal and the semiconductor. In this study, the effect of annealing conditions included in the process of forming a contact layer of nickel silicide(NiSix) on a p-type SiC layer on the specific contact resistance of the contact layer and the total resistance between the metal and the semiconductor was investigated. To this end, a series of electrodes for TLM (transfer length method) measurements were patterned on the 4 inch p-type SiC layer under conditions of changing annealing temperature of 1700 and 1800 ℃ and annealing time of 30 and 60 minutes. As a result, it was confirmed that the annealing conditions affect the resistance of the contact layer and the electrical stability of the device.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.2
• /
• pp.714-720
• /
• 2021

The ITL (information theoretic learning) based on the kernel density estimation method that has successfully been applied to machine learning and signal processing applications has a drawback of severe sensitiveness in choosing proper kernel sizes. For the maximization of correntropy criterion (MCC) as one of the ITL-type criteria, several methods of adapting the remaining kernel size ( ) after removing the term have been studied. In this paper, it is shown that the main cause of sensitivity in choosing the kernel size derives from the term and that the adaptive adjustment of in the remaining terms leads to approach the absolute value of error, which prevents the weight adjustment from continuing. Thus, it is proposed that choosing an appropriate constant as the kernel size for the remaining terms is more effective. In addition, the experiment results when compared to the conventional algorithm show that the proposed method enhances learning performance by about 2dB of steady state MSE with the same convergence rate. In an experiment for channel models, the proposed method enhances performance by 4 dB so that the proposed method is more suitable for more complex or inferior conditions.

• Maritime Security
• /
• v.1 no.1
• /
• pp.119-148
• /
• 2020

The purpose of this study is to examine the perceptions of neighboring countries on the gray zone and to explore Korea's maritime strategy. The concept of gray zones appears in various ways from country to country. In international relations, the gray zone is a comprehensive space between war and peace. The gray zone in the ocean is an unstable space in which competition between the US and China is represented and proxy wars are possible, and the gray zone needs strategic management. This study summarizes the concept of gray zones in the maritime security field, examines the gray zone strategies of neighboring countries, and suggests Korea's gray zone strategies. In particular, the recognition of the gray zone itself is the core of the problem, and it is necessary to strengthen information sharing to clarify the problem about the gray zone and accurately recognize the gray zone situation. The CMG(Complex Maritime Geostrategy) framework attempted in this study is expected to be helpful in understanding the nature of various gray zone issues around Korea and preparing for a geostrategy based on the analysis.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.3
• /
• pp.627-632
• /
• 2021

ITL (information-theoretic learning) has been applied successfully to adaptive signal processing and machine learning applications, but there are difficulties in deciding the kernel size, which has a great impact on the system performance. The correntropy algorithm, one of the ITL methods, has superior properties of impulsive-noise robustness and channel-distortion compensation. On the other hand, it is also sensitive to the kernel sizes that can lead to system instability. In this paper, considering the sensitivity of the kernel size cubed in the denominator of the cost function slope, a new adaptive kernel estimation method using the rate of change in error power in respect to the kernel size variation is proposed for the correntropy algorithm. In a distortion-compensation experiment for impulsive-noise and multipath-distorted channel, the performance of the proposed kernel-adjusted correntropy algorithm was examined. The proposed method shows a two times faster convergence speed than the conventional algorithm with a fixed kernel size. In addition, the proposed algorithm converged appropriately for kernel sizes ranging from 2.0 to 6.0. Hence, the proposed method has a wide acceptable margin of initial kernel sizes.

• The Journal of the Convergence on Culture Technology
• /
• v.9 no.5
• /
• pp.167-173
• /
• 2023

The purpose of this study was to analyze the accuracy of artificial respiration and chest compressions using CPR mannequins for university students. First, in the number of chest compressions, subjects A, F, H, I, and J showed similar numbers from 60 to 63, respectively, which were much lower than the standard. Subjects B, D, E, and G showed 90 to 91 times, maintaining the normal range. However, C was rather high with 119 times. Second, the depth of chest compression was 58.60mm, and most of them were deeply compressed. Subject C was close to normal at 51mm, and subjects A to J were significantly higher at 55mm to 62mm. The reason seems to be the result of an unstable psychological state with no experience of chest compressions and a lack of self-confidence. Third, in terms of accuracy, subject E showed the lowest accuracy at 12%, and A~J showed 33%~80%. Experiment subject B showed 95% accuracy, which seems to be the result of D accurately recognizing the chest compression point through theoretical training during military service.

• KDI Journal of Economic Policy
• /
• v.12 no.3
• /
• pp.125-151
• /
• 1990

This paper reviews the economic liberalization experiences of the Southern Cone countries and draws some lessons from their experiences. The Southern Cone countries-Chile, Argentina and Uruguay-followed the different sequences in liberalization. Chile implemented the fiscal reform and the following comprehensive trade reform in the beginning of liberalization, but capital controls were maintained until 1979. Argentina and Uruguay placed more emphasis on the financial reform with the goods market reformed afterwards, but the fiscal sector was never reformed in Argentina. Since the serious inflation plagued the Southern Cone countries, they combined the economic liberalization scheme with the economic stabilization programmes which are based on the monetarist model. Although economic situations in the Southern Cone countries are quite different from those of Korea, we can learn many lessons from their experiences. First, the monetary and fiscal policies should consist of strict financial discipline to bring in the stable domestic inflation. Without the domestic stabilization, the financial liberalization could disturb the domestic economy as the capital inflows in particular generate a real exchange rate appreciation. Second, the monetary approach which is based on the full purchasing power parity and perfect capital mobility make stabilization as simple as a matter of the appropriate exchange rate policy and the proper rate of domestic credit creation. The unsuccessful experiences with monetarist stabilization in the Southern Cone countries suggest that the monetarist model cannot make real exchange rate and real interest rate stable with the trade and financial reform. Third, both the theory and practice have not yet provided a precise solution on the optimal sequencing and speed of the goods and financial market. Nonetheless, it seems desirable to keep the real exchange rate and the real interest rate stable by gradually opening up the current account and then the capital account.

• The Journal of Engineering Geology
• /
• v.20 no.3
• /
• pp.243-255
• /
• 2010

The slope design of an open-pit mine must consider economical efficiency and stability. Thus, the overall slope angle is the principal factor because of limited support or reinforcement options available in such a setting. In this study, slope displacement, as monitored by a GPS system, was analyzed for a coal mine at Pasir, Indonesia. Predictions of failure time by inverse velocity analysis showed good agreement with field observations. Therefore, the failure time of an unstable slope can be roughly estimated prior to failure. A GIS model that combines fuzzy theory and the analytical hierarchy process (AHP) was developed to assess slope instability in open-pit coal mines. This model simultaneously considers seven factors that influence the instability of open-pit slopes (i.e., overall slope gradient, slope height, surface flows, excavation plan, tension cracks, faults, and water body). Application of the proposed method to an open-pit coal mine revealed an enhanced prediction accuracy of failure time and failure site compared with existing methods.