• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.328-331
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• 2008

많은 양의 이미지를 포함하고 있는 대용량 데이터베이스에 대한 이미지 검색에서 보다 짧은 시간에 적은 양의 검색공간을 사용하면서 원하는 결과를 얻을 수 있는 이미지 인덱싱 기법에 대한 다양한 연구가 진행되어 왔다. 본 논문에서는 외형 기반의 이미지 검색에서 기존의 인덱싱 기법보다 빠른 검색을 지원할 수 있는 해시 기반의 새로운 인덱싱 기법을 제안한다. 기존의 해시 기반 인덱싱 기법에서는 해시 주소 계산을 위해 인덱스 값의 범위가 미리 정해져야 하기 때문에 색상 정보 등 소수의 특징 정보를 제외하고는 인덱싱에 널리 사용되지 못하고 있다. 한편, 제안된 해시 구조는 값의 범위가 정해지지 않은 정수형의 인덱스 값을 기반으로 효과적으로 이미지 인덱스를 구축할 수 있다. 효과적인 이미지 검색을 위해 제안된 인덱스를 기반한 범위검색(Range Search) 기법을 제안하였으며, 실험을 통해 제안된 인덱스 구조에서의 범위 검색이 기존의 인덱스 구조에 비해 보다 효과적임을 보인다.

• Journal of the Korean Association of Geographic Information Studies
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• v.21 no.2
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• pp.94-106
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• 2018

The epidemiological model is useful for creating simulation and associated preventive measures for disease spread, and provides a detailed understanding of the spread of disease space through contact with individuals. In this study, propose an agent-based spatial model(ABM) integrated with spatial big data to simulate the spread of MERS-CoV infections in real time as a result of the interaction between individuals in space. The model described direct contact between individuals and hospitals, taking into account three factors : population, time, and space. The dynamic relationship of the population was based on the MERS-CoV case in Seoul Metropolitan Government in 2015. The model was used to predict the occurrence of MERS, compare the actual spread of MERS with the results of this model by time series, and verify the validity of the model by applying various scenarios. Testing various preventive measures using the measures proposed to select a quarantine strategy in the event of MERS-CoV outbreaks is expected to play an important role in controlling the spread of MERS-CoV.

• Journal of KIISE:Databases
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• v.28 no.3
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• pp.512-527
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• 2001

In a client-server spatial database, it is desirable to maintain the cached data in a client side to minimize the communication overhead across a network. This paper deals with the issues of concurrency and consistency of map updates in this environment. A client transaction to update map data is an interactive work and takes a long time to complete it. The map update in a client site may affect the other sites'updates because of dependencies between spatial data stored at different sites. The concurrent updates should be propagated to the other clients as well as the server to keep the consistency of map replicated in a client cache, and also the communication overhead of the update propagation should be minimized not to lose the benefit of caching. The newly proposed cache region locking with CR lock and CX lock controls the update dependency due to spatial relationships. CS lock and COD lock are suggested to use optimistic detection-based approaches for guaranteeing the consistency of cached client data. The cooperative update protocol uses these extended locking primitives and Spatial Relationship-based 2PC (SR-based 2PC). This paper argues that the concurrent updates of cached client spatial data can be achieved by deciding on collaborative updates or independent updates based on spatial relationships.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2009.04a
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• pp.449-453
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• 2009

기존 주택 및 고층건물화재에서 발생하는 화재 폭발 사고에 대해서는 많은 연구가 이루어지고 있으나, 이천 냉동창고 화재와 같이 많은 인명피해가 발생되는 작업환경에서의 화재 특히 밀폐공간에서의 화재 폭발 위험성 및 특성은 주택 및 고층건물화재에 비교하여 높은 폭발위험성 및 빠른 화염전파 특성을 보이나 이에 관한여 구체적인 연구는 미비한 실정이다. 본 연구는 밀폐공간 작업환경에서의 화재 폭발 위험성 특성 분석을 위하여 밀폐공간에서 작업 시 발생되어지는 가연성 가스의 확산 특성 분석 및 폭발 위험성 분석 방법에 관한 연구와 밀폐공간에서의 화염 확산 특성에 관한 연구논문 이다.

• Tunnel and Underground Space
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• v.11 no.4
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• pp.362-367
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• 2001

The stiff top layer in a soil profile, which can happen in winter, may change the isolation effect of the wave barrier. The research scope of this paper is the investigation of the propagation of surface waves in layered soil with a stiff layer on its top, and the isolation effect of the solid stiff wave barrier. The investigations have been performed numerically by the Boundary-Element Method as a two-dimensional problem. A strip foundation vibrated harmonically in vertical direction was considered as the vibration source. Three soil profiles, a homogeneous half-space, two profiles with different thickness of stiff top layer, with two different types of wave barriers were investigated. The profiles with a stiff top layer show considerable reductions of the amplitude of the vibration in comparison to the homogeneous soil profile. The layered soil profiles with a stiff top layer do not show wave propagation velocities as high as they are expected from the material properties. Furthermore the vibration amplitudes in a frozen soil are much smaller with distance than in a non-frozen soil.

• The Journal of the Acoustical Society of Korea
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• v.21 no.3
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• pp.213-220
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• 2002

The sound wave in the sea propagates under the effect of water depth, sound velocity structure, sea surface and bottom roughness, and bottom sediment distribution. In particular the sound velocity structure in shallow water varies with time and space, an? the sediment distributes very variedly with place. In order to investigate the seasonal variation of low-frequency sound propagation in the Yellow Sea, the propagation experiments were conducted along the same track in the middle part of the Yellow Sea at various seasons of spring. summer, and autumn. In this paper we consider the measurement results on the propagation loss with the sound velocity structure, and investigate the seasonal variation of the propagation loss. As a result, the propagation losses measured in summer were larger than the losses in spring and autumn. And the propagation losses measured in autumn were smaller than the losses in spring. The seasonal change of the propagation loss increased with the rise of sound frequency and the propagation range.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.8
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• pp.1595-1611
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• 1994

In this paper, the numerical wave propagation properties of the finite difference-time domain(FD-TD) method is investigated as a discrete model describing electromagnetic(EM) wave propagation phenomena. The leap-frog approximation of Maxwell's curl equations in time-space simulates EM wave propagation in terms of the numerical characteristic and the domain of dependence. A geometrical interpretation of the FD-TD numerical procedure is presented. The numerical dispersion error due to the leap-frog approximation and its dependence on the stability factor are illustrated. The FD-TD method using the leap-frog approximation is inherently a descriptive model. Thus, not only any physical picture about EM wave propagation phenomena can be drawn through this model, but also physical or engineering parameters in the frequency domain can be extracted from descriptive results. E-plane filter characteristics in the WR-28 rectangular waveguide and reflection property of an inductive iris in the WR-90 rectangluar waveguide extracted from simulation of the FD-TD model is included.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5A
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• pp.696-701
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• 2000

Electronic Toll Collection (ETC) System makes the telecommunication possible between the Beacon and the On Board Unit(OBU) for automatic toll collection. In this paper, the propagation path of microwave is modelled and the induced voltage of receiving antenna is analyzed numerically according to multi-path fading effect. In our modelling, we consider frequency, weather condition, polarization and antenna radiation pattern. Also, we suggest the diversity technique in order to reduce the fading effect. In the resuts, the fading effect is reduced significantly in case of the vertical polarization at the rain condition. In general the circular polarization is the most desirable in this application. The antenna which has the high directivity, is also desirable. Using the space and frequency diversity technique at the Beacon, the fading effect is reduced effectively. These results are compared with our experimental data.

• Tunnel and Underground Space
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• v.11 no.3
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• pp.217-224
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• 2001

Rock masses are usually discontinuous in nature due to various geological processes and contain rock joints and bridges. Crack propagation and coalescence processes in rock bridge mainly cause rock failures in slopes, foundations, and tunnels. In this study, we focused on the crack initiation, propagation and coalescence process of rock materials containing two pre-existing open cracks arranged in different geometries. Specimens of 120${\times}$60${\times}$25 mm in size, which were made of Yeoman Marble, were prepared. In the specimens, two artificial cracks were cut with pre-existing crack angle ${\alpha}$, bridge angle ${\beta}$, pre-existing crack length 2c and bridge length 2b. Wing crack initiation stress, wing crack propagation angle, and crack coalescence stress were measured and crack initiation, propagation and coalescence processes were observed during uniaxial compression. Crack coalescence types were classified and analytical study using Ashby and Hallam model (1986) was performed to be compared with the experimental results.

• Geophysics and Geophysical Exploration
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• v.20 no.2
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• pp.72-77
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• 2017

We calculated 3D frequency- and Laplace-domain wavefields using time-domain modeling and Fourier transform or Laplace transform. We adopted OpenACC and GPU for an efficient parallel calculation. The OpenACC makes it easy to use GPU accelerators by adding directives in conventional C, C++, and Fortran programming languages. Accordingly, one doesn't have to learn new GPGPU programming languages such as CUDA or OpenCL to use GPU. An OpenACC program allocates GPU memory, transfers data between the host CPU and GPU devices and performs GPU operations automatically or following user-defined directives. We compared performance of 3D wave propagation modeling programs using OpenACC and GPU to that using single-core CPU through numerical tests. Results using a homogeneous model and the SEG/EAGE salt model show that the OpenACC programs are approximately 53 and 30 times faster than those using single-core CPU.