• Journal of the Society of Naval Architects of Korea
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• v.37 no.1
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• pp.67-81
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• 2000

An accurate and efficient numerical method for two-dimensional nonlinear radiation problem has been developed. The wave motion due to a moving body is described by the assumption of ideal fluid flow, and the governing Laplace equation can be effectively solved by the higher-order boundary element method with the help of the GMRES (Generalized Minimal RESidual) algorithm. The intersection or corner problem is resolved by utilizing the so-called discontinuous elements. The implicit trapezoidal rule is used in updating solutions at new time steps by considering stability and accuracy. Traveling waves caused by the oscillating body are absorbed downstream by the damping zone technique. It is demonstrated that the present method for time marching and radiation condition works efficiently for nonlinear radiation problem. To avoid the numerical instability enhanced by the local gathering of grid points, the regriding technique is employed so that all the grids on the free surface may be distributed with an equal distance. This makes it possible to reduce time interval and improve numerical stability. Special attention is paid to the local flow around the body during time integration. The nonlinear radiation force is calculated by the "acceleration potential technique". Present results show good agreement with other numerical computations and experiments.

• KIEAE Journal
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• v.11 no.6
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• pp.19-28
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• 2011

This study examines the current status on the supply of community facilities based on the supply criteria of present welfare facilities. Analyzing satisfaction of residents about community facilities based on physical supply criteria. The study sets up the concept and proposed trend of the related studies and distinction through the examination of previous researches. Next, the present systematical supply criteria, was used to make indication in order to propose the promotion of improvement on supply criteria for community facilities. Multi dimensional analyzing system and the satisfaction level of the community facility was used to analyze the relationship between the two. The direction of policy improvement according to the analysis is as per the following. First, it is necessary to improve supply criteria of household to guarantee the minimal amount of space. Second, specification of the minimum distance of community facility to residential area in the complex is needed. Also, the presentation of bottom boundary line of the formation area size to expand the size up to minimal level of size is needed. Third, resident exercise facility supply criteria among the community facility supply criteria need to be improved from the number of household base to the size for each household base. Forth, resident resting facility criteria among the community facility supply criteria should be changed from the present criteria of one facility per five hundred households.

• The KSFM Journal of Fluid Machinery
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• v.17 no.6
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• pp.59-63
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• 2014

Object of this study is to see whether the arc-groove on a D-shape bluff body effects the drag reduction or not. To this end, the changes of the boundary layer on the surface of the object, the downstream flow field and wake flow were found by experiments. The experiments are conducted by changing number and depth of the groove, angle of the first groove and Reynolds number(Re). Groove did not effect on the surface in the downstream boundary layer of the object and was minimal impact on the time mean velocity recovery of the wake flow. Also the effects of Groove did not have a significant impact on the structure of the wake and the wake frequency. Therefore it is found that the arc-groove of the drag reduction effect on the D-shape bluff body was smaller.

• Phonetics and Speech Sciences
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• v.5 no.4
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• pp.129-136
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• 2013

This study investigated how acoustic characteristics (i.e., duration, F1, F2) of English high front vowels /i, ɪ/ are modulated by boundary- and prominence-induced strengthening in native vs. non-native (Korean) speech production. The study also examined how the durational difference in vowels due to the voicing of a following consonant (i.e., voiced vs. voiceless) is modified by prosodic strengthening in two different (native vs. non-native) speaker groups. Five native speakers of Canadian English and eight Korean learners of English (intermediate-advanced level) produced 8 minimal pairs with the CVC sequence (e.g., 'beat'-'bit') in varying prosodic contexts. Native speakers distinguished the two vowels in terms of duration, F1, and F2, whereas non-native speakers only showed durational differences. The two groups were similar in that they maximally distinguished the two vowels when the vowels were accented (F2, duration), while neither group showed boundary-induced strengthening in any of the three measurements. The durational differences due to the voicing of the following consonant were also maximized when accented. The results are discussed further in terms of phonetics-prosody interface in L2 production.

• Proceedings of the KSPS conference
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• 2007.05a
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• pp.240-242
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• 2007

The goal of this paper is to investigate effects of three prosodic factors, such as phrasal accent (accented vs. unaccented), prosodic boundary (IP-initial vs. IP-medial) and coda voicing (e.g., bed vs. bet), on acoustic realization of English vowels (/i, $_I/$, $/{\varepsilon}$, ${\ae}/$) as produced by native (Canadian) and nonnative (Korean) speakers. The speech corpus included 16 minimal pairs (e.g., bet-bat, bet-bed) embedded in a sentence. Results show that phonological contrast between vowels are maximized when they were accented, though the contrast maximization pattern was not the same between the English and Korean speakers. However, domain-initial position do not affect the phonetic manifestation of vowels. Results also show that phonological contrast due to coda voicing is maximized only when the vowels are accented. These results propose that the phonetic realization of vowels is affected by phrasal accent only, and not by the location within prosodic position.

• Journal of Korean Medical classics
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• v.32 no.3
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• pp.47-57
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• 2019

Objectives : We aim to assist in choosing an appropriate method for word extraction when analyzing East Asian Traditional Medical texts based on unsupervised learning. Methods : In order to assign ranks to substrings, we conducted a test using one method(BE:Branching Entropy) for exterior boundary value, three methods(CS:cohesion score, TS:t-score, SL:simple-ll) for interior boundary value, and six methods(BExSL, BExTS, BExCS, CSxTS, CSxSL, TSxSL) from combining them. Results : When Miss Rate(MR) was used as the criterion, the error was minimal when the TS and SL were used together, while the error was maximum when CS was used alone. When number of segmented texts was applied as weight value, the results were the best in the case of SL, and the worst in the case of BE alone. Conclusions : Unsupervised-Learning-Based Word Extraction is a method that can be used to analyze texts without a prepared set of vocabulary data. When using this method, SL or the combination of SL and TS could be considered primarily.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.5
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• pp.747-754
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• 2023

Energy-efficient routing protocol is an important task in a wireless sensor network that is used for monitoring and control by wirelessly collecting information obtained from sensor nodes deployed in various environments. Various routing techniques have been studied for this, but it is also necessary to consider WSN environments with specific situations and conditions. In particular, due to topographical characteristics or specific obstacles, a hole where sensor nodes are not deployed may exist in most WSN environments, which may result in inefficient routing or routing failures. In this case, the geographical routing-based hall bypass routing method using GPS functions will form the most efficient path, but sensors with GPS functions have the disadvantage of being expensive and consuming energy. Therefore, we would like to find the boundary node of the hole in a WSN environment with holes through minimal sensor function and propose hole bypass routing through boundary line formation.

• 한국전산유체공학회:학술대회논문집
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• 2000.10a
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• pp.129-134
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• 2000

An efficient numerical method to solve the unsteady incompressible Navier-Stokes equations is developed. A fully implicit time advancement is employed to avoid the CFL(Courant-Friedrichs-Lewy) restriction, where the Crank-Nicholson discretization is used for both the diffusion and convection terms. Based on a block LU decomposition, velocity-pressure decoupling is achieved in conjunction with the approximate factorization. Main emphasis is placed on the additional decoupling of the intermediate velocity components with only n th time step velocity The temporal second-order accuracy is Preserved with the approximate factorization without any modification of boundary conditions. Since the decoupled momentum equations are solved without iteration, the computational time is reduced significantly. The present decoupling method is validated by solving the turbulent minimal channel flow unit.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1128-1128
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• 2001

We have developed a probe for measuring the light levels inside illuminated fruit. The probe has minimal effect on the light levels being measured and enables the sampling of the light flux at any point within the fruit. We present experimental light extinction rates within apple, nashi, kiwifruit, and mandarin fruit. Moving from the illuminated side to the far side of the fruit, the extinction level follows an initial power law decay as the light diffuses into the fruit then reduces to an exponential decay through the rest of the fruit. Significant variations in the rates of light extinction are found in the core, skin and differing flesh regions. Monte Carlo simulations of the light distribution in fruit, which use scattering and absorption coefficients for the diffusely scattering tissue, and boundary conditions for the skin effects, produce results that follow the experimental results closely.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.71-74
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• 2002

A higher-order zig-zag theory is developed to refine the predictions of natural frequency and mode shape of laminated composite plates with multiple delaminations. By imposing top and bottom surface transverse shear stress-free and interface continuity conditions of transverse shear stresses including delaminated interfaces, the displacement field with minimal degree-of-freedoms are obtained. This displacement field can systematically handle the number, shape, size, and locations of delaminations. Through the dynamic version of variational approach, the dynamic equilibriums and variationally consistent boundary conditions are obtained. Through the numerical example of natural frequency analysis, the accuracy and efficiency of present theory are demonstrated. The present theory is suitable as an efficient tool to analyze the static and dynamic behavior of the composite plates with multiple delaminations.