• Title/Summary/Keyword: phase field model

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Flow-Induced Noise Prediction for Submarines (잠수함 형상의 유동소음 해석기법 연구)

  • Yeo, Sang-Jae;Hong, Suk-Yoon;Song, Jee-Hun;Kwon, Hyun-Wung;Seol, Hanshin
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.24 no.7
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    • pp.930-938
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    • 2018
  • Underwater noise radiated from submarines is directly related to the probability of being detected by the sonar of an enemy vessel. Therefore, minimizing the noise of a submarine is essential for improving survival outcomes. For modern submarines, as the speed and size of a submarine increase and noise reduction technology is developed, interest in flow noise around the hull has been increasing. In this study, a noise analysis technique was developed to predict flow noise generated around a submarine shape considering the free surface effect. When a submarine is operated near a free surface, turbulence-induced noise due to the turbulence of the flow and bubble noise from breaking waves arise. First, to analyze the flow around a submarine, VOF-based incompressible two-phase flow analysis was performed to derive flow field data and the shape of the free surface around the submarine. Turbulence-induced noise was analyzed by applying permeable FW-H, which is an acoustic analogy technique. Bubble noise was derived through a noise model for breaking waves based on the turbulent kinetic energy distribution results obtained from the CFD results. The analysis method developed was verified by comparison with experimental results for a submarine model measured in a Large Cavitation Tunnel (LCT).

Ionosphere Modeling and Estimation Using Regional GPS Data (지역적인 GPS 관측 데이터를 이용한 이온층 모델링 및 추정)

  • 황유라;박관동;박필호;임형철;조정호
    • Korean Journal of Remote Sensing
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    • v.19 no.4
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    • pp.277-284
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    • 2003
  • We present a GPS-derived regional ionosphere model, which estimates Total Electron Content (TEC) in a rectangular grid on the spherical shell over Korea. After dividing longitude and latitude over Korea with 1$^{\circ}$$\times$1$^{\circ}$ spatial resolution, the TEC at the vertex of the grid was estimated by the Kalman filter. The GPS data received from nine nationwide GPS stations, operated by Korea Astronomy Observatory (KAO), were used for this study. To reduce inherent noises, the pseudorange data were phase-leveled by a linear combination of pseudoranges and carrier phases. The solar-geomagnetic reference frame, which is less variable to the ionosphere movement due to the Sun and the geomagnetic field than an Earth-fixed frame, was used. During a quiet time of solar activity, the KAO's regional ionosphere map indicated 30-45 Total Electron Content Unit at the peak of the diurnal variation. In comparison with the Global ionosphere Map of the Center for Orbit Determination in Europe, RMS differences were at the level of 4-5 TECU for five days.

Development of Three-dimensional Inversion Algorithm of Complex Resistivity Method (복소 전기비저항 3차원 역산 알고리듬 개발)

  • Son, Jeong-Sul;Shin, Seungwook;Park, Sam-Gyu
    • Geophysics and Geophysical Exploration
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    • v.24 no.4
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    • pp.180-193
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    • 2021
  • The complex resistivity method is an exploration technique that can obtain various characteristic information of underground media by measuring resistivity and phase in the frequency domain, and its utilization has recently increased. In this paper, a three-dimensional inversion algorithm for the CR data was developed to increase the utilization of this method. The Poisson equation, which can be applied when the electromagnetic coupling effect is ignored, was applied to the modeling, and the inversion algorithm was developed by modifying the existing algorithm by adopting comlex variables. In order to increase the stability of the inversion, a technique was introduced to automatically adjust the Lagrangian multiplier according to the ratio of the error vector and the model update vector. Furthermore, to compensate for the loss of data due to noisy phase data, a two-step inversion method that conducts inversion iterations using only resistivity data in the beginning and both of resistivity and phase data in the second half was developed. As a result of the experiment for the synthetic data, stable inversion results were obtained, and the validity to real data was also confirmed by applying the developed 3D inversion algorithm to the analysis of field data acquired near a hydrothermal mine.

An Interpretive Analysis of Magnetotelluric Response for a Three-dimensional Body Using FDM (FDM을 이용한 MT 탐사의 3차원 모형 반응 연구)

  • Han Nuree;Lee Seong Kon;Song Yoonho;Suh Jung Hee
    • Geophysics and Geophysical Exploration
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    • v.7 no.2
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    • pp.136-147
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    • 2004
  • In this study, the characteristics of magnetotelluric (MT) responses due to a three-dimensional (3-D) body are analyzed with 3-D numerical modeling. The first model for the analysis consists of a single isolated conductive body embedded in a resistive homogeneous half-space. The second model has an additional conductive overburden while the other conditions remain the same as the first one. The analysis of apparent resistivities shows well that the 3-D effects are dominant over some frequency range for the first model. Two mechanisms, current channeling and induction, for secondary electric fields due to the conductive body are analyzed at various frequencies: at high frequencies induction is more dominant than channeling, while at low frequencies channeling is more dominant than induction. Tippers have a strong relation to the position of anomalous body and the real and imaginary parts of induction vector also indicate the position of anomalous body. off-line conductive anomaly sometimes causes severe problem in 2-D interpretation. In such case, induction vector analysis can give information on the existence and location of the anomalous body. Each parameter of the second model shows similar responses as those of the first model. The only difference is that the magnitude of all parameters is decreased and that the domain showing the 3-D effects becomes narrower. As shown in this study, the analysis of 3-D effects provides a useful and effective means to understand the 3-D subsurface structure and to interpret MT survey data.

MT Response of a Small Island Model with Deep Sea and Topography (깊은 바다와 지형을 고려한 소규모 섬 모델의 MT 반응 연구)

  • Kiyeon Kim;Seong Kon Lee;Seokhoon Oh;Chang Woo Kwon
    • Geophysics and Geophysical Exploration
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    • v.27 no.1
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    • pp.37-50
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    • 2024
  • The magnetotelluric (MT) survey can be affected by external environmental factors. In particular, when acquiring MT data in islands, it is essential to consider the combined effect of topography and sea to understand the results and make accurate interpretations. To analyze the MT response (apparent resistivity, phase) with consideration of the effect of topography and sea, a small cone-shaped island model surrounded by deep sea was created. Two-dimensional (2-D) and three-dimensional (3-D) forward modeling were performed on the terrain model considering topography and the island model considering both topography and sea. The 2-D MT response did not reflect the topographic and sea effect of the direction orthogonal to the 2-D profile. The 3-D MT response included topographic and sea effects in all directions. The XY and YX components of the apparent resistivity were separated on undulating topography, such as a hill. A conductor at 1 km below sea level could be distinguished from topographic and sea effects in the MT response, and low resistivity anomaly was attenuated at greater depths. This study will facilitate understanding of field data measured on small islands.

A Case Study and Development of Computing System of Construction Waste for an Apartment by Using the Estimating Waste Units (원단위를 활용한 공동주택의 건설폐기물 산정 자동화 시스템 개발 및 사례분석)

  • Kim, Chang Hak;Kim, Hyo Jin
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.32 no.6D
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    • pp.607-614
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    • 2012
  • The importance of demolition industry is becoming lager because of reusing and recycling of construction waste in current trend to pursue for sustainable development. As considering situation of the domestic housing construction and existing house, a scale of demolition industry is expecting to be increased continually. Therefore, for sustainable development is needed forecasting and managing rightly demolition waste to be producted at demolition phase. But, The development of model for estimating demolition waste is not sufficient in the country, also, the development of computer system for managing it rightly has not yet been created. In this study developed the estimating waste units for estimating demolition waste of an apartment and a house. A regression model for quantifying demolition waste easily is developed to do simulation again after making the estimating waste units through analyzing draws. This model is developed as a computer system for increasing application and then verified the reliability through field application. this regression model can quantify a sort of 22 demolition waste easily based on the size of the floor area and a number of units. This system is expected to quantify demolition waste easily which is producted during redevelopment and remodeling of existing house.

An Investigation on the Periodical Transition of News related to North Korea using Text Mining (텍스트마이닝을 활용한 북한 관련 뉴스의 기간별 변화과정 고찰)

  • Park, Chul-Soo
    • Journal of Intelligence and Information Systems
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    • v.25 no.3
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    • pp.63-88
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    • 2019
  • The goal of this paper is to investigate changes in North Korea's domestic and foreign policies through automated text analysis over North Korea represented in South Korean mass media. Based on that data, we then analyze the status of text mining research, using a text mining technique to find the topics, methods, and trends of text mining research. We also investigate the characteristics and method of analysis of the text mining techniques, confirmed by analysis of the data. In this study, R program was used to apply the text mining technique. R program is free software for statistical computing and graphics. Also, Text mining methods allow to highlight the most frequently used keywords in a paragraph of texts. One can create a word cloud, also referred as text cloud or tag cloud. This study proposes a procedure to find meaningful tendencies based on a combination of word cloud, and co-occurrence networks. This study aims to more objectively explore the images of North Korea represented in South Korean newspapers by quantitatively reviewing the patterns of language use related to North Korea from 2016. 11. 1 to 2019. 5. 23 newspaper big data. In this study, we divided into three periods considering recent inter - Korean relations. Before January 1, 2018, it was set as a Before Phase of Peace Building. From January 1, 2018 to February 24, 2019, we have set up a Peace Building Phase. The New Year's message of Kim Jong-un and the Olympics of Pyeong Chang formed an atmosphere of peace on the Korean peninsula. After the Hanoi Pease summit, the third period was the silence of the relationship between North Korea and the United States. Therefore, it was called Depression Phase of Peace Building. This study analyzes news articles related to North Korea of the Korea Press Foundation database(www.bigkinds.or.kr) through text mining, to investigate characteristics of the Kim Jong-un regime's South Korea policy and unification discourse. The main results of this study show that trends in the North Korean national policy agenda can be discovered based on clustering and visualization algorithms. In particular, it examines the changes in the international circumstances, domestic conflicts, the living conditions of North Korea, the South's Aid project for the North, the conflicts of the two Koreas, North Korean nuclear issue, and the North Korean refugee problem through the co-occurrence word analysis. It also offers an analysis of South Korean mentality toward North Korea in terms of the semantic prosody. In the Before Phase of Peace Building, the results of the analysis showed the order of 'Missiles', 'North Korea Nuclear', 'Diplomacy', 'Unification', and ' South-North Korean'. The results of Peace Building Phase are extracted the order of 'Panmunjom', 'Unification', 'North Korea Nuclear', 'Diplomacy', and 'Military'. The results of Depression Phase of Peace Building derived the order of 'North Korea Nuclear', 'North and South Korea', 'Missile', 'State Department', and 'International'. There are 16 words adopted in all three periods. The order is as follows: 'missile', 'North Korea Nuclear', 'Diplomacy', 'Unification', 'North and South Korea', 'Military', 'Kaesong Industrial Complex', 'Defense', 'Sanctions', 'Denuclearization', 'Peace', 'Exchange and Cooperation', and 'South Korea'. We expect that the results of this study will contribute to analyze the trends of news content of North Korea associated with North Korea's provocations. And future research on North Korean trends will be conducted based on the results of this study. We will continue to study the model development for North Korea risk measurement that can anticipate and respond to North Korea's behavior in advance. We expect that the text mining analysis method and the scientific data analysis technique will be applied to North Korea and unification research field. Through these academic studies, I hope to see a lot of studies that make important contributions to the nation.

The Concept Analysis of Ego-integrity in the Elderly (노인의 자아통합감 개념 분석)

  • Chang Sung Ok;Kong Eun Sook;Kim Kwuy Bun;Kim Nam Cho;Kim Ju Hee;Kim Chun Gill;Kim Hee Kyung;Song Mi Soon;Ahn Soo Yeon;Lee Kyung Ja;Lee Young Whee;Chon Si Ja;Cho Nam Ok
    • Journal of Korean Academy of Nursing
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    • v.34 no.7
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    • pp.1172-1183
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    • 2004
  • Purpose: Ego-integrity in Erikson's stage theory is used frequently among health team members related to the care of the elderly and has specific meanings within the context of quality of life in later life. However, the concept of ego-integrity in the elderly has not been well articulated in the literature. This study was conducted clarify and conceptualize the phenomena of ego-integrity in the elderly. Method: A Hybrid Model of concept development was applied to develop a concept of ego-integrity, which included a field study carried out in Seoul, South Korea using in-depth interviews with old adults who were admitted as a right person for research subject according to attributes of ego-integrity analysed in the theoretical phase. Results: The concept of ego-integrity emerged as a complex phenomenon having meanings in several different dimensions which encompassed several attributes. Conclusions: Ego-integrity is a concept having needs that should be treated in a specific way and it is possible to enrich the meaning and methods to manage ego-integrity in nursing interventions for promoting quality of life so that its application may have effects that have positive impacts on the elderly's well being.

Effect of homogenization models on stress analysis of functionally graded plates

  • Yahia, Sihame Ait;Amar, Lemya Hanifi Hachemi;Belabed, Zakaria;Tounsi, Abdelouahed
    • Structural Engineering and Mechanics
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    • v.67 no.5
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    • pp.527-544
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    • 2018
  • In this paper, the effect of homogenization models on stress analysis is presented for functionally graded plates (FGMs). The derivation of the effective elastic proprieties of the FGMs, which are a combination of both ceramic and metallic phase materials, is of most of importance. The majority of studies in the last decade, the Voigt homogenization model explored to derive the effective elastic proprieties of FGMs at macroscopic-scale in order to study their mechanical responses. In this work, various homogenization models were used to derive the effective elastic proprieties of FGMs. The effect of these models on the stress analysis have also been presented and discussed through a comparative study. So as to show this effect, a refined plate theory is formulated and evaluated, the number of unknowns and governing equations were reduced by dividing the transverse displacement into both bending and shear parts. Based on sinusoidal variation of displacement field trough the thickness, the shear stresses on top and bottom surfaces of plate were vanished and the shear correction factor was avoided. Governing equations of equilibrium were derived from the principle of virtual displacements. Analytical solutions of the stress analysis were obtained for simply supported FGM plates. The obtained results of the displacements and stresses were compared with those predicted by other plate theories available in the literature. This study demonstrates the sensitivity of the obtained results to different homogenization models and that the results generated may vary considerably from one theory to another. Finally, this study offers benchmark results for the multi-scale analysis of functionally graded plates.

A Study of the Properties of Magnetic Particles in Medicinal Ointments (의학용 연고제에 포함된 자성물질 입자들의 성질에 대한 연구)

  • Do, Tae-Sung;Nam, Hyo-Duk;Park, Se-Gon;Hwang, Hyeun-Gook;Hwang, Yong-Soon;Kim, Eng-Chan;Park, Eun-Jung;V. I. Nikolaev;A. V. Bykov
    • Progress in Medical Physics
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    • v.8 no.1
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    • pp.69-79
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    • 1997
  • Stability of the properties of magnetite particles in novel medicinal magnetic ointments of multipurpose application has been studied by M ssbauer spectroscopy. It has been found that the comparative analysis of the results obtained by model fitting of $^{57}$ Fe nuclei spectra with those known for the system Fe$_3$O$_4$-${\gamma}$-Fe$_2$O$_3$ allows to identify the phase composition of the particles. It is noted that this composition, as well as that of the initial pure component in the form of a highly dispersed fraction (~100$\AA$), differs noticeably from the stoichiometric one. From the magnetic hyperfine field despite small particle sizes, the particles exhibit no superparamagnetism (in the temperature range from 95 to 300K). Radiative sterilization of the ointments has no effect on the magnetic component composition.

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