• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.763-767
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• 2008

In a speech coding system using excitation source of voiced and unvoiced, it would be involved a distortion of speech qualify in case coexist with a voiced and an unvoiced consonants in a frame. So, We proposed TS(Transition Segment) including unvoiced consonant searching and extraction method in order to uncoexistent with a voiced and unvoiced consonants in a frame. This research present a new method of TS approximate-synthesis by using Least Mean Square and frequency band division. As a result, this method obtain a high quality approximation-synthesis waveforms within TS by using frequency information of 0.547kHz below and 2.813kHz above. The important thing is that the maximum error signal can be made with low distortion approximation-synthesis waveform within TS. This method has the capability of being applied to a new speech coding of Voiced/Silence/TS, speech analysis and speech synthesis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.8B
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• pp.699-706
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• 2003

This paper is to verify that 2-state MMPP Model conform to ATM VBR traffic characteristics by measuring and analyzing real-time VBR traffic in KT's ATM network. As a result, we validated the fact that real-time VBR traffic of ATM network cannot be apply to MMPP model and must be represented by previously general On-Off Model with characteristics as follows: arrival rate of On state (λ$_1$) is deterministic, arrival rate of Off state (λ$_2$) is zero, and two transition rate (T$_1$,T$_2$) is only random variable. As research results are to handle real traffic, these results can be used to all ATM network traffic model with traffic management function such as KT's ATM network.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.314-317
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• 2010

본 논문에서는 p-수렴 천이요소의 층별이론을 사용하여 균열을 갖는 적층판의 팻취보강 효과에 대해 알아보았다. 이 모델의 면내 변위는 각 구간별로 연속인 선형변화로 가정하였고, 두께방향으로의 면외 변위는 일정한 상수로 가정하여 적용하였다. 변위장의 정의는 적분형 르장드로 다항식을 적용하였다. 또한 에너지 방출률법과 VCCT 방법을 사용하여 응력확대계수를 산출하였다. 수치적분은 별도의 외삽법 없이 각층별의 절점에서 방생하는 적분 값을 바로 얻을 수 있는 가우스-로바토 적분법을 사용하여 계산하였으며, 수치예제를 통해 제안된 모델의 정확도와 기존의 3차원 고체요소를 사용한 것보다 동일한 정확도를 얻기 위해 휠씬 적은 요소 및 자유도가 사용됨을 알 수 있었다.

• Journal of Korea Water Resources Association
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• v.34 no.1
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• pp.57-65
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• 2001

A numerical model for analyzing transcritical flow in open channel is tested to various cases of channel shape. As the numerical models developed for transcritical flow until now mainly focused on the application to only prismatic or hypothetical channels, there are some restrictions to apply the nonprismatic channels. In this study, to verify the accuracy and stability of second-order implicit ENO scheme, the numerical model was applied to the channels which haute the varying channel bed and width. Also the numerical model was applied to unsteady flow as well as steady flow. The study shows that the numerical model provides good accuracy in the calculation of stage and velocity with no numerical oscillation, particularly in the calculation of hydraulic jump and discontinous flow Then the implicit ENO scheme demonstrated good accuracy as a high-resolution scheme and stability as an implicit scheme.

• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.194-205
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• 2022

Sandbars formed by sediment transportation and sedimentation are some of the most important habitats for specific wildlife and they provide an aesthetic landscape in streams. The purpose of this study was to understand the successional process of the colonization and development of early vegetation over time on sandbars exposed by the opening of a gate at a downstream weir. We selected the following four study sites in the Geumgang River, South Korea: three weir-upstream sites with different gate-opening times and a control site that was not affected by weir operation. Changes in the structural characteristics and spatial distribution of the riparian vegetation on the sandbars exposed after opening the gate at the weir were surveyed according to the different exposure periods of the sandbars at the study sites. The newly formed sandbars accounted for more than 33% of the area of the existing floodplain in the three weir-upstream sites of the Geumgang River after opening the gate at the weir. Nine main plant communities were distributed on the exposed sandbars. These communities were classified as annual mesophytic, perennial hydrophytic, perennial hygrophytic, subtree, and tree vegetation based on their species traits. As the duration of exposure of the sandbar increased, the area of the bare sandbar and the annual herbaceous and perennial hydrophytic communities decreased, and the areas occupied by perennial hygrophytic, subtree, and tree communities increased. Changes in vegetation on the sandbar were classified into three types of succession according to the condition of the aquatic habitat before the gate-opening and the degree of physical disturbance caused by the water flow after the gate-opening. The types of succession were: 1) succession starting from hydrophytes in the lentic aquatic zone, 2) succession starting from annual herbaceous hygrophytes in the lotic aquatic zone, and 3) willow-dominated succession in the disturbed channel side. Our results suggested that the dynamics of successional changes in vegetation should be considered during weir operation to ecologically manage the habitats and landscape of the fluvial landforms, including sandbars in streams.

• Journal of Korea Water Resources Association
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• v.46 no.12
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• pp.1209-1220
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• 2013

Roughness coefficients calibrated by flow modeling using the 1-dimensional numerical model were analyzed for the downstream section of Naesung Stream in this study. Also, the bedform configuration at the Hyangseok Station was predicted for measured and simulated hydraulic conditions of flows and total flow roughness was estimated with the coefficient of grain roughness. The Manning's n coefficients calibrated by numerical modeling and estimated by considering of grain and bedform roughness were compared and examined. As a result, the Manning's n by numerical modeling was greater than the coefficient range estimated by grain and bedform roughness at the low flow regime due to the other factors such as vegetation, sinuosity, and sand bar. However, the Manning's n by numerical modeling was included in the coefficient range by grain and bedform roughness at the transition and high flow regime over $500m^3/s$ of flow discharge.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.632-638
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• 2019

This paper presents the conceptual design and reaction force analysis of a bogie structure for an inter-modal automated transportation system, including road and rail transportation. The proposed system was based on a train with rotation-aligning bogie mechanism that can save significant time and cost. One of the critical issues in conceptual design is the lateral forces applied to the rail caused by the characteristic shapes and structure of the rails and bogie. In particular, the lateral forces are significant in the transition section between the driving and platform sections. This paper provides design guidance for the transition section through reaction force analysis. Based on the analysis result, it was confirmed that the proposed concept can be a valid design candidate of a practical system, and the radius of the rail and the distance between rails are major factors for reaction force generation.

• Korean Journal of Environment and Ecology
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• v.27 no.6
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• pp.733-744
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• 2013

This study was launched in order to collect basic data such as emergent species, a succession trend based on the actual vegetation at the ridge from Haneoryoung to Daetjae, thereby designating 46 quadrats($10m{\times}10m:100m^2$). As a result of classification by TWINSPAN, the plant community was categorized into eight different communities, such as Pinus densiflora-Quercus mongolica-Fraxinus rhynchophylla, P. densiflora-Q. mongolica, Ulmus davidiana var. japonica, Q. mongolica-Deciduous Broad-leaved, Q. mongolica, Q. mongolica-Betula davurica, Q. mongolica-F. sieboldiana, and Larix kaempferi. An analyzation of each communities indicated that P. densiflora dominant community will change into a Q. mongolica dominant community if there are no outside artificial disturbances. U. davidiana var. japonica community maintains its present condition, because it doesn't appear to be a competitive species. In the case of Q. mongolica dominant community, if nothing comes in a competitive species against Q. monglica, it is possible to succeed to a muture stand. These communities with competitive species such as F. rhynchophylla, B. davurica that do not emerge at a canopy layer will gradually progress to the Deciduous Broad-leaved community. With regard to the species diversity index per unit ($400m^2$), succession processing communities (P. densiflora: 1.0477~1.1283) tend to be higher than succession-processed communities (Q. mongolica dominant: 0.6446~0.9424).

• Journal of Korea Water Resources Association
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• v.34 no.1
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• pp.45-55
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• 2001

Transcritical flow is a term intended to denote the existence of both supercritical and subcritical flows within a computational domain. The major problems that need to be addressed while modeling transcritical flows include handling the differing features of signal propagation in subcritical and supercritical flow regions and maintaining conservation. The present study proposes the implicit ENO method as a high-resolution scheme for transcritical flow. This implicit ENO scheme is based on the ENO method, a new class of uniformly high-order-accurate essentially non-oscillatory implicit scheme, which has the advantage of unconditional stability. The implicit ENO scheme has not been used for the transcritical flow in open channel until now. As a result of application to the hypothetical dam-break flow, the implicit ENO scheme was ploved to produce accurate results with good robustness even though in the case of verb strong shock wave.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2
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• pp.85-89
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• 1996

In this paper, transition constrained Hidden Markov Model(HMM) in which the transition between states occur only within prescribed time slot is proposed and the performance is evaluated in the noisy environment. The transition constrained HMM can explicitly limit the state durations and accurately de scribe the temporal structure of speech signal simply and efficiently. The transition constrained HMM is not only superior to the conventional HMM but also require much less computation time. In order to evaluate the performance of the transition constrained HMM, speaker independent isolated word recognition experiments were conducted using semi-continuous HMM with the noisy speech for 20, 10, 0 dB SNR. Experiment results show that the proposed method is robust to the environmental noise. The 81.08% and 75.36% word recognition rates for conventional HMM was increased by 7.31% and 10.35%, respectively, by using transition constrained HMM when two kinds of noises are added with 10dB SNR.