• The Journal of the Acoustical Society of Korea
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• v.14 no.1
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• pp.31-39
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• 1995

In this paper, we have constructed phoneme discriminant filters [PDF] according to the linear discriminant function. These discriminant filters do not follow the heuristic rules by the experts but the mathematical methods in iterative learning. Proposed system. is based on the piecewise linear classifier and error correction learning method. The segmentation of speech and the classification of phoneme are carried out simutaneously by the PDF. Because each of them operates independently, some speech intervals may have multiple outputs. Therefore, we introduce the unified coefficients by the output unification process. But sometimes the output has a region which shows no response, or insensitive. So we propose time windows and median filters to remove such problems. We have trained this system with the 549 monosyllables uttered 3 times by 3 male speakers. After we detect the endpoint of speech signal using threshold value and zero crossing rate, the vowels and consonants are separated by the PDF, and then selected phoneme passes through the following PDF. Finally this system unifies the outputs for competitive region or insensitive area using time window and median filter.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.2
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• pp.35-42
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• 2020

Recently the reusable launch vehicle is being a major trend in the worldwide space market, because a few commercial companies, especially SpaceX, are trying to cut down the launch price through developing and succeeding the reusable launch vehicles. However, there is still a big controversy about whether in view point of the launch cost which is more favorable between expendable and reusable. Therefore, a study and close examination is required for the launch cost in the early development phase of the reusable launch vehicle. In this study the sensitivity analysis is performed with respect to the major cost parameters which have great effects on the launch cost and price. The standard vehicle of this sensitivity analysis is the expendable vehicle having a payload 20 tons. The cost estimation relationships used in this calculation are referred from the commonly proven cost models such as TRANSCOST. The major cost parameters chosen in this study are as follows: development cost, production cost, refurbishment cost, and maximum reusable number.

• The Journal of Korean Association of Computer Education
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• v.9 no.6
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• pp.41-51
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• 2006

Educators have recognized the usefulness of the e-BBS(electronic-Bulletin Board System) as an asynchronous communication medium for collaborative learning. However, theoretical outcomes to understand the structural analysis of thc e-BBS are not adequate enough. As a consequence, we are left with inadequate supportive tools to understand complex communication phenomena and to assist teachers to guide students to educational purposes. This can cause teachers to have a laissez-faire approach using BBS as a communication medium for education due to the lack of understanding the structural and overall situation. To address this issue, this paper presents a theoretical foundation to help understand the structure of discussion activities via the e-BBS and then presents a computational model, based on the structural analysis, for the behavioral analysis of participants. The formal representation of bi-directional discussion activities is realized by devising two graphs - the reply graph and the connection graph. Various measurements and statistics for the analysis are presented in the paper. To clarify the analysis, we classify the results produced through the analysis of discussion activities and participants' behaviors.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1731-1737
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• 2007

This paper considers subway routing problem. Given a schedule of train to be routed by a railway stock, the routing problem determines a sequence of trains while satisfying turnaround time and maintenance restrictions. Generally, the solution of routing problem is generated from set partition formulation solved by column generation method, a typical integer programming approach for train-set. However, we find the characteristics of metropolitan subway which has a simple rail network, a few end stations and 13 departure-arrival patterns. We reflect a turn-around constraint due to spatial limitations has no existence in conventional railroad. Our objective is to minimize the number of daily train-sets. In this paper, we develop two basic techniques that solve the subway routing problem in a reasonable time. In first stage, we formulate the routing problem as a Min-cost-flow problem. Then, in the second stage, we attempt to normalize the distance covered to each routes and reduce the travel distance using our heuristic approach. Applied to the current daily timetable, we could find the subway routings, which is an approximately 14% improvement on the number of train-sets reducing 15% of maximum traveling distance and 8% of the standard deviation.

• Journal of the Korea Society for Simulation
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• v.21 no.2
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• pp.11-17
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• 2012

The past combats depended often on a number of firepower and manpower. However, integrated decision support viewpoint from communications, surveillance, reconnaissance, intelligence and so forth in combats witnessed in the Gulf, the Middle East, and Afghanistan have changed the trends of combat. That is, the force multipliers which many support systems enhance the combat potential of the fighting forces significantly become big issues to win or not in that combat. According to changing recent combat trend, Lanchester's combat model is being challenged to develop keeping pace with the new trend. We approach this paper as mathematical modeling about how the effect of terrain affects in the combat. Terrain information is invisible, but it is necessary to consider for analysis of warfare. Additionally, tangible or intangible elements affecting to attrition coefficients are continuely reflected to the combat model from decision-makers, then it will be a model closer to the reality and very suggestive to the actual world.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.6
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• pp.819-826
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• 2005

To guarantee the disinfection ability in clearwell, a value of CT is considered where C[mg/l] is disinfectant residual at the exit of clearwell and T[min] means $T_{10}$, the contact time when 10% of tracer is out of clearwell after introducing the tracer at the inlet. To meet a CT value required, increasing the C value is not recommended because high C value can increase potential of producing disinfection by product like THMs. Increasing the hydraulic efficiency surrogated by $T_{10}$ is thus an option widely recommended. Right now, it is widely adopted estimating $T_{10}$ considering LW ratio only due to the suggestions of previous researches. The authors think however there are other factors to consider including shape, flow rate, configuration of inlet and outlet, and the existence of intra basin. This study is initiated to closely look at the effects of two factor on hydraulic efficiency. The factors are shape and inlet flow velocity, i.e., inflow. For that, computational fluid dynamics (CFD) model is developed and pilot test is also carried out. The results show that at a L/W ratio, disinfection ability is overestimated with larger length in shape and higher inlet flow velocity. This suggests that in determining $T_{10}$, the shapes of clearwell and inlet flow velocity should also be considered as well as L/W ratio.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.145-149
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• 2011

우리나라의 강우특성은 여름철인 6월~9월에 집중되며 대부분이 일시에 집중적으로 발생하여 하천을 통하여 호소 및 바다로 유입된다. 이러한 강우특성으로 여름철에 집중되는 강우로 인한 하천의 유량을 댐과 같은 수공시설물을 통해 저류시킴으로써 하류지역의 홍수피해를 예방하고 이용할 수 있는 물을 안정적으로 확보할 수 있도록 하고 있으나 대형 인공호의 유역에서는 인구 증가와 상업 및 공업화에 따른 토지이용이 변화함에 따라 오염물질의 유입이 증가하고 있는 추세이다. 댐이나 호소는 지표면에 고여 있는 수체를 말하며 물이 천천히 흐르거나 흐름이 전혀 없는 경우도 있다. 댐이나 호소에서는 장기간 수류의 지체현상이 발생하므로 발생하는 수체 및 수질의 문제가 하천과는 다르다고 할 수 있다(서동일 등, 2009). 호소의 물은 정체되어 있기 때문에 흐르는 물에 비해 자정능력이 부족하고 바닥에 퇴적된 유기물이 분해되어 수질에 나쁜 영향을 미치기 때문에 수질관리에 여러 가지 어려움이 따른다(박석순, 2009). 따라서 흐름방향 보다 수심방향으로의 특성이 강하게 작용하는 댐이나 호소에서는 3차원 수리 수질 모형의 적용이 타당하며 본 연구에서는 이를 위하여 EFDC를 적용하였다. 섬진강 유역의 경우 전체유역의 65.8%가 임야로 이루어진 산림유역으로 비교적 적은 양의 유역오염물질이 발생하지만 산불이나 벌채와 같은 산림의 손실은 홍수기 때 유역오염물질의 발생 및 유출을 증가시켜 주변수체의 수질을 악화시킬 우려가 있다. 이에 본 연구에서는 운암호 수질측정망 상류 유역면적인 $526.23km^2$에 대하여 토지변화 시나리오를 임야의 25%, 50%, 75%가 손실되어 나대지화 되었다고 가정하고, EFDC 모형을 이용하여 산림지역의 소실에 따른 토지피복 변화가 섬진강 댐 운암호의 수질에 미치는 영향 정도를 파악하였다.

• Journal of Korea Water Resources Association
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• v.37 no.11
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• pp.915-927
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• 2004

The purpose of this paper is to estimate the instream flow of the South Han River Basin to ensure an adequate supply of suitable quality of water for preservation and enhancement of aquatic ecosystems. Proposed methods is Physical Habitant Simulation System of Instream Flow Incremental Methodology. Accurate estimation on a water depth and a velocity distribution was acquired by applying a two dimensional hydrodynamic model for a simulation of a hydraulic parameter necessary for the habitat evaluation to be used in a physical habitat simulation system. The Habitat Suitability Criteria with the application of univariate curve on zacco platypus as a representative fish was able to be established by conducting a field investigation. The establishment of a hydrological materialistic balance between upper and lower streams was confirmed by conducting a simulation simultaneously together with a mainstream section, which was excluded from the considered sections for the inhabitation evaluation of fish.

• Journal of Korea Water Resources Association
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• v.49 no.1
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• pp.51-60
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• 2016

The purpose of this study is to examine the control function of discharged flow due to the shape and plane arrangement of permeable submerged breakwater. For the discussion on it in detail, 3-dimensional numerical model based on PBM (Porous Body Model), which is able to simulate directly interaction of Fluid Permeable structure Seabed has been used to simulate water discharge in a NWT (Numerical Water Tank). To verify the applicability, LES-WASS-3D is analyzed comparing to the experimental result about propagation characteristics of dam-break wave through a permeable structure. Using the results obtained from numerical simulation, the effects of the shape and plane arrangement of submerged breakwater on reducing velocity and flow induction have been discussed related to the mean flow distribution and vertical distributions of horizontal velocities around ones.

• Journal of IKEEE
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• v.24 no.3
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• pp.691-698
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• 2020

The installation cost or the magnitude of the fault current varies depending on the grid connection method of the offshore wind farm. Therefore, there is a need for an efficient power grid connection method considering the capacity and location of the complex. In particular, most power cables in offshore wind farms use 3-core considering cost and efficiency. In the event of a failure such as a short circuit, the entire cable must be replaced, which can lead to significant losses in terms of cost, considering repair costs and turbine downtime. Therefore, in this paper, a radial, ring, and molding method is introduced into a 100 MW wind farm to be installed at Jeju offshore, and a three-phase short circuit failure is performed using a PSCAD/EMTDC program to perform computer analysis. I would like to propose a suitable power grid connection method.