• The Journal of the Acoustical Society of Korea
• /
• v.20 no.1
• /
• pp.68-76
• /
• 2001

Sonar is the system that detects objects and finds their location in water by using the echo ranging technique. In order to have excellent performance in variable environment, acoustic characteristics of this system must be analyzed accurately. In this paper, based on the finite element analysis, modeling and analysis of acoustic characteristics of underwater acoustic sensors are preformed. Couplings between piezoelectric and elastic materials, and fluid and structure systems associated with the modeling of piezoelectric underwater acoustic sensors are formulated. In the finite element modeling of unbounded acoustic fluid, IWEE (Infinite Eave Envelop Element) is adopted to take into account the infinite domain. When an incidence wave excites the surface of Tonpilz underwater acoustic sensor, the scattered wave on the sensor is founded by satisfying the radiation condition at the artificial boundary approximately. Based on this scattering analysis, the electrical response of the underwater acoustic sensor under incidence, so called RVS (Receiving Voltage Signal) is founded accurately. This will devote to design Sonar systems accurately.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2021.06a
• /
• pp.102-102
• /
• 2021

광양만의 해수교환은 주로 여수해만을 통해 이루어지고, 만의 동측에는 노량수로를 통해 진주만으로의 해수교환이 일어나고 있으며, 만의 북측에는 섬진강을 끼고 있다. 광양항 건설 전 만내의 수심은 약 10 m 이내로 얕았으며, 만의 입구인 여수해만과 노량수로에서의 수심은 약 20 m 이상이었다. 광양만은 1982년 광양제철소의 건설을 시점으로 하여 광양항의 확장 개발, 폐기물처리장 건설 등으로 인한 매립이 진행되었다. 특히, 섬진강 하구는 광양만 개발 전에는 넓은 조간대 퇴적층의 발달로 다양한 생태계환경을 유지하고 있었으나, 광양항 건설 및 하구에서 모래 준설 등으로 인해 근래에 와서는 해수의 역류가 심각한 상태이다. 1982년 광양제철소 건설이후 계속적으로 광양만을 개발함으로써 해양환경에 큰 변화가 발생하였다. 따라서, 본 연구에서는 광양만 개발 전·후의 조석 및 해수유동의 변화특성을 해석하기 위해 조석 및 조류에 대한 현장관측과 3차원 해수유동 수치모형실험을 수행한 후 남해도를 둘러싸고 있는 광양만, 진주만 등의 조석 및 조류의 변동특성을 해석하였다. 광양만 개발 전·후의 해수유동의 변동특성을 해석하기 위해 김 등(1999)에 의해 개발된 3차원 layer·level 혼성 해수유동 모델을 광양만, 진주만을 포함하는 남해도 주변해역에 적용하여 30일간의 수치계산결과를 이용하여 해수유동의 변동특성을 해석하였다. 모델에서 격자간격은 동서-남북방향 동일하게 200 m, 시간간격은 20 sec, 계산영역은 동서방향으로 52 km, 남북방향으로 65 km인 260×325 격자체계로 구성 운영하였다. 외해 개방경계에서 조위는 수로국에서 관측한 조위와 본 연구에서 관측한 조위를 보간하여 사용하였다. 광양만 개발전·후의 조류의 변동특성을 수치해석한 결과 여수해만에서는 광만만 개발전이 개발 후보다 유속이 강하게 나타났으나, 노량수로에서는 개발 후가 개발전보다 유속이 훨씬 강하게 나타났다. 이와 같은 현상은 광양만 개발로 광양만으로 유입되는 조량이 감소함으로 인해 여수해만에서는 유속이 감소한 것으로 생각된다. 노량수로에서 개발 후가 개발전보다 유속이 증가한 것은 여수해만을 통해 유입한 해수가 개발 후에는 광양만의 해수면적 감소로 광양만의 서측으로 유입하는 조량이 감소한 반면에 광양만의 북측(섬진강 하구) 또는 동측(노량수로)으로 유입하는 조량이 많기 때문인 것으로 사료된다.

• Industry Promotion Research
• /
• v.8 no.4
• /
• pp.163-176
• /
• 2023

Through a literature review, this study examined the concept of slow learners and the lifelong learning characteristics of slow learners, and sought ways to achieve successful lifelong learning by utilizing grit and growth mindset among non-cognitive characteristics. Slow learners were experiencing difficulties in cognitive, academic, linguistic, social and emotional, and behavioral characteristics. For successful lifelong learning of slow learners, it was necessary to set long-term goals rather than short-term goals and to maintain effort and consistency of interest to achieve the goals. In addition, it was confirmed that in order to achieve long-term goals, it is necessary to believe that change can be achieved through effort and learning. In other words, the need for learning using grit and growth mindset was confirmed. Based on these previous research results, it was presented as a lifelong learning strategy for slow learners that applied grit and growth mindset, which are non-cognitive characteristics, rather than cognitive characteristics such as intelligence.

• Journal of the Korean earth science society
• /
• v.35 no.6
• /
• pp.484-497
• /
• 2014

This study aimed to investigate high school students' conceptions of plate tectonics. Seventy students (N=70) in their 2 year of high schools in the province of Chungcheong-do participated in this study, and they took a conception test of visual representation. We conducted a semi-structured interview with 10 volunteering participants out of seventy. After learning about the concept of plate tectonics, this study found that participants ended up having alternative conceptions relating to terminology, meaning of colors, plates' movement, plates' boundaries, position and cause of melting, mantle's physical conditions, and driving forces of plate motion. The conceptions that the participants held after class were organically related, which included the meaning of colors, mantle's physical characteristic, and driving forces of plate movement. In addition, the visual representation used for teaching plate tectonics influenced the students' understanding about terminologies, plates' boundaries, position of melting, and the physical characteristic of mantle. The study found that there were the factors of visual representation that caused the learners to create alternative conceptions in learning about plate tectonics.

• Journal of Korea Multimedia Society
• /
• v.16 no.2
• /
• pp.169-179
• /
• 2013

Change detection algorithms take two image frames and return the locations of newly introduced objects which cause differences between the images. This paper presents a new change detection method, which classifies intensity changes due to introduced objects, reflected light and shadow from the objects to their neighborhood, and the noise, and exactly localizes the introduced objects. For classification and localization, first we analyze the histogram of the intensity difference between two images, and estimate multiple threshold values. Second we estimate candidate object boundaries using the gradient difference between two images. Using those threshold values and candidate object boundaries, we segment the frame difference image into multiple regions. Finally we classify whether each region belongs to the introduced objects or not using textures in the region. Experiments show that the proposed method exactly localizes the objects in various scenes with different lighting.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.8 no.4
• /
• pp.71-80
• /
• 2005

As local flash flood exceeding planned capacity occurs frequently, localized preparedness and response to flood inundation are increasingly important. Using XP-SWMM model and GIS techniques, this study analyzes inundation areas by local flash flood and develops rainfall standards for evacuation with the case of Sadang-Cheon area, a local stream and its nearby highly populated watershed in the southern part of metropolitan Seoul, Flood inundation areas overflowed from drainage systems are analyzed and mapped by amount of rainfall that is derived from reference levels of stream flow. Rainfall standards for evacuation are comprised of 'watch' (40mm/hr) in preparing for near-future inundation and 'evacuation' (65mm/hr) in responding to realized inundation. The methods suggested by this case study may be applied to other urban areas for sound flood prevention policy measures and thus risk minimization.

• Journal of Digital Convergence
• /
• v.16 no.9
• /
• pp.383-390
• /
• 2018

The purpose of this study is to find out how the evolution of digital play in virtualization and digital play tools are combined with and stereotyping the properties of traditional play. Virtualization characteristics and play theory were examined and the case was derived in four types and analyzed in four play properties with Roser Cailliois. In the case of Agon, the targets of mutual competition are expanded to singular and plural, computer and oneself of the future, and Mimicry showed the ambiguity of the segments and boundaries crossing the on-off line boundary, and in the case of Alea, the diversity of accident occurrence by immediacy and simultaneity has been strengthened, and in the case of Ilinx, the maximization of immersion has been developed and experimented with a variety of techniques for the utilization of senses and tools and the virtuality for this. As a result, play is developing due to the tendency to expand and coexist in time and space by various fusion combinations.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.8 no.3
• /
• pp.1-10
• /
• 2005

The purpose of this paper is to conduct an experimental measurement and analysis of cities' morphology. Fractal theory that is an effective tool for evaluating self-similarity and complexity of objects was applied. For the comparative analysis of fractailities and computational verification, two totally different cities in Japan were selected. They are Kitakyushu City, which is a big and fully developed city, and Jinguu Machi of which almost all the area is covered with agricultural land use. After converting vector data to raster data within GIS, fractal dimensions of two cases in Kitakyushu City and one case in Jinguu Machi were calculated. The calculation showed that two parts of Kitakyushu City were already fractal. Jinguu Machi, however, was difficult to find fractality. As a conclusion, fractal was proved to be an useful tool to estimate the shape of cities reflecting their internal spatial structure, that is self-similarity and complexity.

• The Journal of the Convergence on Culture Technology
• /
• v.4 no.3
• /
• pp.75-86
• /
• 2018

Desktop Documentary is a new documentary mode which uses a screen capture technology to complete the multitasking process of the creator who searches in the Internet Open Archive instead of shooting with a camera and remixes the selected multimedia contents using a computer interface. In this paper, we explore the desktop documentary that transforms potential archives into database narratives in the new media environment, converts cinematic mise-en-$sc{\grave{e}}ne$ into computational mise-en-interface, and transcends the boundaries between creation and criticism through creative mechanism as curation through stream of consciousness. We also examine the concept, type and characteristics of the desktop documentary which emerges since 2010s as an experimental attempt of new media art, a new hybrid genre of mainstream horror film, a new mode of fiction film, a new mockumentary style, and a new form of video essay and audiovisual critique.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.12
• /
• pp.8654-8664
• /
• 2015

Beam-type structures with non-uniform cross sections are widely used in mechanical, architectural, and civil engineering fields. This paper deals with dynamic characteristics and vibration problems. Governing equations are first derived by using local coordinates. Their solutions are then assumed by using Galerkin's mode summation method. Bisection method is also applied in solving the determinant of the matrix which can provide natural frequencies. Whereas finite element methods adopt admissible functions satisfying only geometric boundary condition, in this study we apply Galerkin's mode summation method which uses eigen-functions satisfying both governing equations and boundary conditions. Modal analysis and experimental tests are finally performed using simply-supported beams with four different non-uniform cross-sections. Our analytical results then show good agreement with experimental ones.