• Title/Summary/Keyword: reflection model

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Electromagnetic Traveltime Tomography with Wavefield Transformation (파동장 변환을 이용한 전자탐사 주시 토모그래피)

  • Lee, Tae-Jong;Suh, Jung-Hee;Shin, Chang-Soo
    • Geophysics and Geophysical Exploration
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    • v.2 no.1
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    • pp.17-25
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    • 1999
  • A traveltime tomography has been carried out by transforming electromagnetic data in frequency domain to wave-like domain. The transform uniquely relates a field satisfying a diffusion equation to an integral of the corresponding wavefield. But direct transform of frequency domain magnetic fields to wave-field domain is ill-posed problem because the kernel of the integral transform is highly damped. In this study, instead of solving such an unstable problem, it is assumed that wave-fields in transformed domain can be approximated by sum of ray series. And for further simplicity, reflection and refraction energy compared to that of direct wave is weak enough to be neglected. Then first arrival can be approximated by calculating the traveltime of direct wave only. But these assumptions are valid when the conductivity contrast between background medium and the target anomalous body is low enough. So this approach can only be applied to the models with low conductivity contrast. To verify the algorithm, traveltime calculated by this approach was compared to that of direct transform method and exact traveltime, calculated analytically, for homogeneous whole space. The error in first arrival picked by this study was less than that of direct transformation method, especially when the number of frequency samples is less than 10, or when the data are noisy. Layered earth model with varying conductivity contrasts and inclined dyke model have been successfully imaged by applying nonlinear traveltime tomography in 30 iterations within three CPU minutes on a IBM Pentium Pro 200 MHz.

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Solitary Wave-like Ship Induced Waves and Its Associated Currents in a Water Channel of Narrow Width (협수로에서 생성되는 고립파 형태의 항주파와 항주파류)

  • Cho, Yong Jun;Choi, Han Rim
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.27 no.4
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    • pp.202-216
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    • 2015
  • In the narrow water channel, which has been frequently deployed in the artificial canal in the South Korea due to the lack of available land, solitary wave type ship induced waves can occur. In order to test this hypothetical view, we carried out the numerical simulation. Numerical model consists of Navier-Stokes Equations and VOF, and the verification is implemented using the data by PIANC (1987) and the analytical model derived in this study. It was shown that numerically simulated front wave height are much larger than the one by PIANC (1987), and the fluctuation of free surface near the channel bank persists much longer (around 20s). For the case of stern waves, numerically simulated wave height are somewhat smaller than the data by PIANC (1987). These results seriously deviates from the general characteristics of ship induced waves observed in the wide water channels, and leads us to conclude that ship induced waves is severely affected by the width of water channel. It was also shown that the currents from the channel banks toward a ship, and currents from the ship toward the channel banks are alternatively occurring due to reflection at the channel banks. The velocity of currents reaches its maximum at 0.90 m/s, and these values are sustained through the entire depth. which implies that severe scourings at the channel bottom can be underway.

Fusion of 3D seismic exploration and seafloor geochemical survey for methane hydrate exploration (메탄 하이드레이트 탐사를 위한 3 차원 탄성파 탐사와 해저면 지구화학탐사의 융합 기술)

  • Nagakubo, Sadao;Kobayashi, Toshiaki;Fujii, Tetsuya;Inamori, Takao
    • Geophysics and Geophysical Exploration
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    • v.10 no.1
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    • pp.37-43
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    • 2007
  • The MH21 Research Consortium has conducted a high-resolution 3D seismic survey and a seafloor geochemical survey, to explore methane hydrate reservoirs in the eastern Nankai Trough, offshore Japan. Excellent geological information about shallow formations was obtained from the high-resolution 3D seismic survey, which was designed to image the shallow formations where methane hydrates exist. The information is useful in constructing a geological and geochemical model, and especially to understand the complex geology of seafloor, including geochemical manifestations and the structure of migration conduits for methane gas or methane-bearing fluid. By comparing methane seep sites observed by submersibles with seismic sections, some significant relationships between methane hydrate reservoirs, free gas accumulations below the seafloor, and seafloor manifestations are recognised. Bathymetric charts and seafloor reflection amplitude maps, constructed from seismic reflections from the seafloor, are also useful in understanding the relationships over a vast area. A new geochemical seafloor survey targeted by these maps is required. The relationships between methane hydrate reservoirs and seafloor manifestations are becoming clearer from interpretation of high-resolution 3D seismic data. The MH21 Research Consortium will continue to conduct seafloor geochemical surveys based on the geological and geochemical model constructed from high-resolution 3D seismic data analysis. In this paper, we introduce a basis for exploration of methane hydrate reservoirs in Japan by fusion of 3D seismic exploration and seafloor geochemical surveys.

Improvement of osteogenic potential of biphasic calcium phosphate bone substitute coated with two concentrations of expressed recombinant human bone morphogenetic protein 2

  • Choi, Hyun-Min;Park, No-Je;Jamiyandorj, Otgonbold;Choi, Kyung-Hee;Hong, Min-Ho;Oh, Seung-Han;Park, Young-Bum;Kim, Sung-Tae
    • Journal of Periodontal and Implant Science
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    • v.42 no.4
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    • pp.119-126
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    • 2012
  • Purpose: The aim of this study was to determine whether biphasic calcium phosphate (BCP) bone substitute with two different concentrations of Escherichia coli-expressed recombinant human bone morphogenetic protein 2 (ErhBMP-2) enhances new bone formation in a standardized rabbit sinus model and to evaluate the concentration-dependent effect of ErhBMP-2. Methods: Standardized, 6-mm diameter defects were made bilaterally on the maxillary sinus of 20 male New Zealand white rabbits. Following removal of the circular bony windows and reflection of the sinus membrane, BCP bone substitute without coating (control group) was applied into one defect and BCP bone substitute coated with ErhBMP-2 (experimental group) was applied into the other defect for each rabbit. The experimental group was divided into 2 subgroups according to the concentration of ErhBMP-2 (0.05 and 0.5 mg/mL). The animals were allowed to heal for either 4 or 8 weeks and sections of the augmented sinus and surrounding bone were analyzed by microcomputed tomography and histologically. Results: Histologic analysis revealed signs of new bone formation in both the control and experimental groups with a statistically significant increase in bone formation in experimental group 1 (0.05 mg/mL ErhBMP-2 coating) after a 4-week healing period. However, no statistically significant difference was found between experimental group 1 and experimental group 2 (0.5 mg/mL ErhBMP-2 coating) in osteoinductive potential (P<0.05). Conclusions: ErhBMP-2 administered using a BCP matrix significantly enhanced osteoinductive potential in a standardized rabbit sinus model. A concentration-dependent response was not found in the present study.

Land Prices, Exchange Rates and Bubbles (지가(地價), 환율(換率)과 거품)

  • Park, Won-am
    • KDI Journal of Economic Policy
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    • v.14 no.4
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    • pp.27-49
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    • 1992
  • This paper stresses the role of market fundamentals rather than bubbles in explaining Korea's recent experience of large fluctuations of stock and real estate prices. The bubble story that emphasizes the self-fulfilling prophecies of investors seems to be inappropriate to explain the recent changes of assets prices in Korea. Those who argue for bubble phenomenon in Korea tend to interpret the volatile movements of assets prices as some form of bubbles, but without implementing a rigorous test on the presence of bubbles. Even when some bubble tests are carried out, such studies exhibit various econometric problems in testing. More seriously, they suffer from the misspecification problems in setting up a market model. This paper has shown that Korea's recent changes in assets prices could be explained by changes in market fundamentals according to the emergence and the subsequent fading of 'three lows'. First, it tried to explain changes in assets prices by changes in such market fundamentals as real interest rates and economic growth. Second, it showed that the real estate prices overshoot when the liquidity and exchange rates change, using the two-sector general equilibrium portfolio balance model. It is argued that the rapid rise in real estate prices during 1986-89 stems from Yen's and Won's appreciation $vis-{\grave{a}}-vis$ the U.S. dollar and liquidity expansion (or decreases in real interest rates), while the downturn in real estate prices since 1990 is associated with Yen's and Won's depreciation $vis-{\grave{a}}-vis$ the U.S. dollar and rises in real interest rates in reflection of the excess demand for liquidity.

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An Effect on Mathematical Preference and Learning Attitude of the Application of Designing for Portfolio using Mathematical History (수학사를 이용한 Portfolio 제작물 구안 적용이 수학적 성향 및 학습태도에 미치는 영향)

  • Shin, Jae-Yon;Park , Jun-Seok
    • Journal of the Korean School Mathematics Society
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    • v.7 no.2
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    • pp.1-20
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    • 2004
  • The purpose of this study is to suggest the new way about performance assessment through analyzing about what changes are occurred on mathematical attitude and interest by performance assessment as comparing and analyzing the effect on learners' mathematical preferences and learning attitudes through the application of teaching and evaluating model utilizing portfolio products using mathematical history which is one of the various ways of performance assessment. That can satisfy the feature of performance assessment that realizes instruction and assessment simultaneously on the first grade at high school. Also, it can reduce the teachers' works, search the potential ability of students, realize level type curriculum, and draw out the learners' interests because it is a self-leading instruction that consists of student-centered learning. For the purpose of this study, the role of mathematical history and its advantage and the way of utilizing it in mathematical history by referring to sundry records were studied. Evaluation, the way of performance assessment and scoring were also considered to design portfolio teaching and evaluating model using mathematical history. To solve the another tasks for this study, mathematical preference factors and mathematical learning attitude factors are used. Mathematical preference factors divide into confidence, flexibility, will, curiosity, reflection, and value and then make 4 questions each factor. And mathematical learning attitude factors divide into self-esteem, attitude, and learning habit and then make 10 questions each factor. These factors need to be reorganized the materials which are made by Korean Education Development Institute(1992) to be agreed with the purpose of this study.

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A Grounded Theory Approach to the Experience of Leaders in Self-help Group for Parents of Children with Cancer. (소아암 부모모임 리더들의 자조집단 참여 경험)

  • Kim, Jin-Sook
    • Korean Journal of Social Welfare
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    • v.57 no.2
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    • pp.405-434
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    • 2005
  • This study has been performed to analyze the experience of parents who had led a parents-group of children with cancer. For this study, fifteen participants were selected for an in-depth interview and the personal experiences of each participant had been interviewed in person until data were saturated. This study employed the grounded theory approach of Strauss and Corbin(1998). With the qualitative constant comparative analysis, ninty four concepts, twenty six subcategories, and seventeen categories were generated. In the axial coding, a paradigm model was proposed as follows: The central phenomenon of the leaders' experiences was that they had been 'Pushed Back' to lead the groups. The causal conditions were 'A Sense of Solidarity', 'Regaining Self-possession', and 'Feeling a Necessity of Parents Group'. The contextual conditions were 'Want to Help', 'A Sense of Mission', and 'Discontent with the Cure Environment'. The intervening conditions were 'Self-reflection of Leadership', 'Reaction of Their Own Family', 'Hope to Have an Expanded Group'. The action/interaction strategies were 'Assuming All Field Work', 'Accumulation of Experiences', 'Recognition of a Role Scope'. The consequences were 'Being Comforted', 'Positive Self-awareness', 'a Sense of Worthiness', and 'Desire to Quit'. In the selective coding, the core category was 'Pushed to Lead a Group'. Based on the core category, four types and five stages in the leaders' experiences were identified. The types include 'a Devoted Family Type', 'a Volunteer Type', 'a Role Model Type', and 'a Activist Type': the stages consist of 'Stage of Maintain Identity as a parent of a child with cancer', 'Stage of Questioning', 'Stage of Active Participation', 'Stage of Experience Accumulation', and 'Stage of Progressive Change'. The result of this study presents some implications and suggestions for social work services and theories with respect to the self-help group of pediatric cancer by attempting to understand more about the experiences of leaders' in such groups.

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Numerical Study based on Three-Dimensional Potential Flow in Time-Domain for Effect of Wave Field Change due to Coastal Structure on Hydrodynamic Performance of OWC Wave Energy Converter (연안 구조물로 인한 파동장의 변화가 진동수주 파력발전장치 유체성능에 미치는 영향에 관한 3차원 시간영역 포텐셜 유동 기반의 수치 연구)

  • Kim, J.S.;Nam, B.W.;Park, S.;Kim, K.H.;Shin, S.H.;Hong, K.
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2019.11a
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    • pp.150-152
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    • 2019
  • In this study, the effects of the wave field changes due to the coastal structure on the hydrodynamic performance of the OWC wave energy, converter are analyzed using a three-dimensional numerical wave tank technique (NWT). The OWC device is simulated numerically by introducing a linear pressure drop model, considering the coupling effect between the turbine and the OWC chamber in the time domain. The flow distribution around the chamber is different due to the change of reflection characteristics depending on the consideration of the breakwater model. The wave energy captured from the breakwater is spatially distributed on the plane of the front of the breakwater, and the converted pneumatic power increased when concentrated in front of the chamber. The change of the standing wave distribution is repeated according to the relationship between the incident wavelength and the length of the breakwater, and the difference in energy conversion performance of the OWC was confirmed.

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Case Study for Information Quality Maturity Model (정보 품질 성숙도 모델에 관한 연구)

  • Kim Chang-Jae;Choi Yong-Rak;Rhew Sung-Yul
    • The KIPS Transactions:PartD
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    • v.13D no.4 s.107
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    • pp.557-564
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    • 2006
  • Information is used effectively and contributes in profit creation and not only support management judgment quick but important resource to be possible recycled. The recent information systems improve enterprise's competitive power by reflection of user's various requirements and becoming big and complex for adaptation of rapidly circumstance change. Also it is trend that importance of information quality is emphasized gradually. The biggest problem in user requirement that is based on low quality data support. In case of business management is achieved by low quality information, company can not help dropping their competitive power such as company's strategy establishment, strategy achievement and management concentration breakup against competitor. Information of low quality increase time and expense to improve inaccurate data or revise and it is hard to accept correct information from specific situation. To solve these problems, we have to gain high quality data through definite comprehension, data management system establishment, and systematic data management achievement etc. Up to now, information quality and connected study were developed partially, but systematic methodology of information quality management's whole condition was not existed. Therefore, in this paper can show you how to extract process for information quality management & related evaluate factor with CMM (Capacity Maturity Mode]) 5 steps that is information warranty of quality process step. This paper whishes to contributes in competitive company or organization activity through information quality improvement management process.

Numerical Simulation of Irregular Airflow within Wave Power Converter Using OWC by Action of 3-Dimensional Irregular Waves (3차원불규칙파동장하의 진동수주형 파력발전구조물에서 불규칙공기흐름의 수치시뮬레이션)

  • Lee, Kwang-Ho;Park, Jung-Hyun;Kim, Do-Sam
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.24 no.3
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    • pp.189-202
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    • 2012
  • An Oscillating Water Column (OWC) wave generation system uses the air flow induced by the vertical motion of water column in the air chamber as a driving force of turbine. It is well known that OWC is one of the most efficient devices to harness wave power. This study estimated the air flow velocity from the time variation of the water level fluctuation in the air chamber under regular wave conditions using 3-dimensional numerical irregular wave tank (3D-NIT) model that can simulate the 3-dimensional irregular wave field. The applicability of the 3D-NIT model was validated by comparing numerically predicted air flow velocities with hydraulic experimental results. In addition, the characteristics of air flow frequency spectrum variation due to the incident frequency spectrum change, and the variations of frequency spectrum and wave reflection due to the existence of converter inside the air chamber were discussed. It is found that the phase difference exists in between the air flow velocity and the water level fluctuation inside the air chamber, and the peak frequency of the spectrum in water level fluctuation is amplified by the resonance in the air chamber.