• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.429-439
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• 2009

When Catastrophic extreme flood occurs due to dam break, the response time for flood warning is much shorter than for natural floods. Numerical models can be powerful tools to predict behaviors in flood wave propagation and to provide the information about the flooded area, wave front arrival time and water depth and so on. But flood wave propagation due to dam break can be a process of difficult mathematical characterization since the flood wave includes discontinuous flow and dry bed propagation. Nevertheless, a lot of numerical models using finite volume method have been recently developed to simulate flood inundation due to dam break. As Finite volume methods are based on the integral form of the conservation equations, finite volume model can easily capture discontinuous flows and shock wave. In this study the numerical model using Riemann approximate solvers and finite volume method applied to the conservative form for two-dimensional shallow water equation was developed. The MUSCL scheme with surface gradient method for reconstruction of conservation variables in continuity and momentum equations is used in the predictor-corrector procedure and the scheme is second order accurate both in space and time. The developed finite volume model is applied to 2D partial dam break flows and dam break flows with triangular bump and validated by comparing numerical solution with laboratory measurements data and other researcher's data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6B
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• pp.382-389
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• 2007

In this paper we report the development of mobility test bed, the realization of basic protocol that supports L3 mobility and the measurement of performance parameters that can affect handover performance. Previously proposed mobility management system, BBM (Break Before Make) method such as MIPV6 and Fast MIPV6, uses one interface in wireless network. In this method, to connect to new AP, it first disconnects existing AP and tries to connect to new AP. This can cause packet loss for the traffic vulnerable to delay such as VoIP. To provide seamless handover between different wireless networks, we propose MBB (Make Before Break) handover method having two network interfaces. Comparative study of previous method and proposed method on mobility and handover was conducted under simulated real environment on the test bed. Almost no packet loss was found with newly proposed method. In conclusion, it is shown that mobility protocol with proposed handover method can be applied to the application services sensitive to delay and packet loss.

• Korean Journal of Cognitive Science
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• v.19 no.1
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• pp.89-105
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• 2008

In this paper, we suggest a rule-based system for the prediction of natural prosodic phrase breaks from Korean texts. For the implementation of the rule-based system, (1) sentence constituents are sub-categorized according to their syntactic functions, (2) syntactic phrases are recognized using the dependency relations among sub-categorized constituents, (3) rules for predicting prosodic phrase breaks are created. In addition, (4) the length of syntactic phrases and sentences, the position of syntactic phrases in a sentence, sense information of contextual words have been considered as to determine the variable prosodic phrase breaks. Based on these rules and features, we obtained the accuracy over 90% in predicting the position of major break and no break which have high correlation with the syntactic structure of the sentence. As for the overall accuracy in predicting the whole prosodic phrase breaks, the suggested system shows Break_Correct of 87.18% and Juncture Correct of 89.27% which is higher than that of other models.

• Fisheries and Aquatic Sciences
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• v.1 no.1
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• pp.48-62
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• 1998

Seasonal volume transport on the Texas-Louisiana continental shelf is investigated in terms of objectively fitted transport streamfunction fields based on the current meter data of the Texas­Louisiana Shelf Circulation and Transport Processes Study. Adopted here for the objective mapping is a method employing a two-dimensional truncated Fourier representation of the streamfunction over a domain, with the amplitudes determined by least square fit of the observation. The fitting was done with depth-averaged flow rather than depth-integrated flow to reduce the root-mean-square error. The fitting process filters out $11\%$ of the kinetic energy in the monthly mean transport fields. The shelf-wide pattern of streamfunction fields is similar to that of near-surface velocity fields over the region. The nearshore transport, about 0.1 to 0.3 Sv $(1 Sv= 10^6\;m^3/sec)$, is well correlated with the seasonal signal of along-shelf wind stress. The spring transport is weak compared to other seasons in the inner shelf region. The transport along the shelf break is large and variable. In the southwestern shelf break, transport amounts up to 4.7 Sv, which is associated with the activities of the encroaching of energetic anticyclonic eddies originated in Loop Current of the eastern Gulf of Mexico. The first empirical orthogonal function (EOF) of streamfunction variability contains $67.3\%$ of the variance and shows a simple, shelf-wide, along-shelf pattern of transport. The amplitude evolution of the first EOF is highly correlated (correlation coefficient: 0.88) with the evolution of the along-shelf wind stress. This provides strong evidence that the large portion of seasonal variation of the shelf transport is wind-forced. The second EOF contains $23.7\%$ of the variance and shows eddy activities at the southwestern shelf break. The correlation coefficient between the amplitudes of the second EOF and wind stress is 0.42. We assume that this mode is coupled a periodic inner shelf process with a non-periodic eddy process on the shelf break. The third EOF (accounting for $7.2\% of the variance) shows several cell structures near the shelf break associated with the variability of the Loop Current Eddies. The amplitude time series of the third EOF show little correlation with the along-shelf wind.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.623-627
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• 2015

To compile a flood hazard map it is essential to identify the potential risk areas. A scenario-based numerical modeling approach is commonly used to build a flood hazard map in the case of a levee-break. The model parameters that capture peak discharge, including breach formation and progress, are important in the modeling method. In this study an earth-levee-break model is constructed under the assumption that the failure mechanism and hydraulic processes are identical for all levee-break river activities. Estimation of the hydrograph at the outlet as a function of time is highlighted. The constructed hydrograph can then serve as an upper boundary condition in running the flood routing model downstream, although flood routing is not considered in this study.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.757-759
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• 2005

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.5
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• pp.1383-1393
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• 2014

Recently, with rapid improvement in computer hardware and theoretical development in the field of computational fluid dynamics, high-order accurate schemes also have been applied in the realm of computational hydraulics. In this study, numerical solutions of 1D shallow water equations are presented with TVD Runge-Kutta discontinuous Galerkin (RKDG) finite element method. The transcritical flows such as dam-break flows due to instant dam failure and transcritical flow with bottom elevation change were studied. As a formulation of approximate Riemann solver, the local Lax-Friedrichs (LLF), Roe, HLL flux schemes were employed and MUSCL slope limiter was used to eliminate unnecessary numerical oscillations. The developed model was applied to 1D dam break and transcritical flow. The results were compared to the exact solutions and experimental data.

• Speech Sciences
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• v.14 no.4
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• pp.65-80
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• 2007

This experimental study is designed to investigate the acoustic cues produced by English native speakers in order to disambiguate the ambiguous sentences. This study also investigates whether Korean learners of English and English native speakers can perceive the appropriate meanings from the sentences produced with those acoustic cues. In the perception test, English native speakers successfully found out the proper meaning, utilizing the intonational cues, while Korean learners had difficulties in distinguishing the differences in meaning. The break interval was manipulated in order to see whether the pause duration facilitates or interferes with disambiguation. Though phrasing played an important role in disambiguation, the break interval itself did not have influence on it. The result, therefore, suggests that the tonal realization of phrasal accents and boundary tones seem to be more significant than the break interval in the perception of phrasing.

• Journal of Biomedical Engineering Research
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• v.22 no.2
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• pp.205-210
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• 2001

The effectiveness of extracorporeal shock wave lithotripter for the therapy of calculus has been well known in the field of urology. There are many studies about the performance of that and the influence into human body. Among them, it is an impertant issue that cavitation is always deal with shock wave. A medium of the shock wave is related to the cavitation phenomenon. In this paper, therefore, we analysis the spectra of radiated sounds and the break efficiency on focal region due to the medium of shock wave. The results show that the cavitation bubbles produce a harmful on the break efficiency and the stability of the radiated sounds due to the ESWL.

• Journal of Sericultural and Entomological Science
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• v.14 no.2
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• pp.105-112
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• 1972

The effects of the stretching speed and the swelling degree of cocoon filaments on load-elongation curve were tested by tensilon with special attachments. The values of breaking strength, elongation at break and initial tensile strength obtained from load elongation curves are summarized as follows; 1. The breaking strength of the swollen cocoon filament appeared to increase at the high stretching speed, while elongation at break decreased. 2. Load-elongation curve became crinkled at the low speed of stretching. It suggests that both slip and break of the macrofibrils may occur in swelling of cocoon bave. 3. Breaking strength appeared to considerably decrease and elongation at break not to increase in swelling test at 9$0^{\circ}C$ for 60 min. 4. The initial tensile strength was influenced by the stretching speed and swelling degree of cocoon filaments.