• Journal of Communications and Networks
• /
• 제11권4호
• /
• pp.416-427
• /
• 2009

Domain name system (DNS) is a primary identification mechanism for Internet applications. However, DNS resolutions often take an unbearably long time, and this could seriously impair the consistency of the service quality of Internet applications based on DNS such as World Wide Web. Several approaches reduce DNS resolution time by proactively refreshing expired cached records or prefetching available records beforehand, but these approaches have an inherent problem in that they cause additional DNS traffic. In this paper, we propose a DNS resolution time reduction scheme, named renewal using piggyback (RUP), which refreshes expired cached records by piggybacking them onto solicited DNS queries instead of by issuing additional DNS queries. This method decreases both DNS resolution time and DNS traffic since it reduces the number of queries generated to handle a given DNS resolution without generating additional DNS messages. Simulation results based on two large independent DNS traces show that our proposed approach much reduces not only the DNS resolution time but also the DNS traffic.

• 한국지리정보학회지
• /
• 제15권3호
• /
• pp.36-51
• /
• 2012

생태환경모델링, 수문모델링, 기후변화 영향평가 등 다양한 분야에서 정규 격자 형태의 기후자료에 대한 요구가 증가하고 있다. PRISM(Precipitation-Elevation Regressions on Independent Slopes Model)은 다양한 격자형태의 기후자료 생산방법 중 고지대의 강수량 추정에 유용한 방법이다. 그러나 국내에서는 이 모델의 매개변수 및 모델에 사용되는 수치표고모형의 공간해상도 최적화에 대한 논의가 충분하지 않았다. 이에 본 연구에서는 PRISM을 개발하였다. 그리고 SCE-UA(Shuffled Complex Evolution-University of Arizona) 기법을 이용하여 2000-2005년 1km 공간해상도의 남한 연평균 강수 격자자료를 생산하는 데 필요한 PRISM 매개변수 최적값 및 DEM의 적정 공간해상도를 추정하였다. 아울러 매개변수와 수치표고모형에 대한 PRISM의 민감도 분석을 수행하였다. 그 결과 PRISM 모델에서 관측소 최대 탐색반경(67km)과 최소반경(31km), 지형고도-강수량의 선형회귀식 산정에 필요한 최소 관측소 개수(4개), 수치표고모형의 적정 공간해상도($1{\times}1km$) 등을 결정하였다. 그리고 PRISM 모의 결과가 수치표고모형의 공간해상도에 매우 민감하다는 것을 확인하였다. 본 연구결과는 PRISM 기법을 국내에 적용할 때 정확도를 향상시키는데 기여할 것으로 기대된다.

• 대기
• /
• 제26권4호
• /
• pp.697-709
• /
• 2016

This study estimates and evaluates the extreme value of 30 m-resolution daily maximum and minimum temperatures over South Korea, using inverse distance weighting (IDW), parameter-elevation regression on independent slopes model (PRISM) and generalized extreme value (GEV) method. The three experiments are designed and performed to find the optimal estimation strategy to obtain extreme value. First experiment (EXP1) applies GEV firstly to automated surface observing system (ASOS) to estimate extreme value and then applies IDW to produce high-resolution extreme values. Second experiment (EXP2) is same as EXP1, but using PRISM to make the high-resolution extreme value instead of IDW. Third experiment (EXP3) firstly applies PRISM to ASOS to produce the high-resolution temperature field, and then applies GEV method to make high resolution extreme value data. By comparing these 3 experiments with extreme values obtained from observation data, we find that EXP3 shows the best performance to estimate extreme values of maximum and minimum temperatures, followed by EXP1 and EXP2. It is revealed that EXP1 and EXP2 have a limitation to estimate the extreme value at each grid point correctly because the extreme values of these experiments with 30 m-resolution are calculated from only 60 extreme values obtained from ASOS. On the other hand, the extreme value of EXP3 is similar to observation compared to others, since EXP3 produces 30m-resolution daily temperature through PRISM, and then applies GEV to that result at each grid point. This result indicates that the quality of statistically produced high-resolution extreme values which are estimated from observation data is different depending on the combination and procedure order of statistical methods.

• 한국측량학회:학술대회논문집
• /
• 한국측량학회 2004년도 춘계학술발표회논문집
• /
• pp.383-388
• /
• 2004

The fusion of a different kind sensor is fusion of the obtained data by the respective independent technology. This is a important technology for the construction of 3D spatial information. particularly, information is variously realized by the fusion of LiDAR and mobile scanning system and digital map, fusion of LiDAR data and high resolution, LiDAR etc. This study is to generate union DEM and digital ortho image by the fusion of LiDAR data and high resolution image and monitor precisely topology, building, trees etc in urban areas using the union DEM and digital ortho image. using only the LiDAR data has some problems because it needs manual linearization and subjective reconstruction.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 1999년도 Proceedings of International Symposium on Remote Sensing
• /
• pp.19-24
• /
• 1999

This paper addresses a new project being carried out at Satellite Technology Research Center. The purpose of the project is to implement a system which receives, processes and stores 1m resolution satellite image transmitted at over 300Mbps down link data rates. In order to develop such a system, a system operational concept design and a requirements study were being carried out As a result of the operational concept design, system objectives, system context and system functions were defined. The system shall be operated according to the philosophy of maximum automation. rapid processing, reliability, integrity, cost effectiveness, and expandability. The system is divided into twelve independent processes and its behavior is modeled by operational scenario, which are combinations of independent processes. Process information and logs generated by the system shall be stored in databases and data received and generated be automatically archived and managed in a hierarchical storage device. The system shall have redundant components in order to be ready for recovering from sudden system failures. This paper will describe in detail the system operational concept design and the system requirements derived from the operational concept design.

• 대기
• /
• 제18권1호
• /
• pp.71-81
• /
• 2008

In this study, in order to estimate high resolution precipitation with monthly time scales, Parameter-elevation Regressions on Independent Slopes Model (PRISM) was modified and configured for Korean precipitation based on elevation, distance, topographic facet, and coastal proximity. Applying this statistical downscaling model to Korean precipitation for 5 years from 2001 to 2005, we have compiled monthly grid data with a horizontal resolution of 5-km and evaluated the model using bias, root mean square error (RMSE), and correlation coefficient between the observed and the estimated. Results show that bias, RMSE, and correlation coefficient of the estimated value have a range from 0.2% to 1.0%, 19.6% (June) to 43.9% (January), and 0.73 to 0.84, respectively, indicating that the modified Korean PRISM (K-PRISM) is reasonably worked by weighting factors, i.e., topographic effect and rain shadow effect.

• 디지털융복합연구
• /
• 제18권2호
• /
• pp.127-138
• /
• 2020

본 연구는 강원지역에 거주하는 베트남과 캄보디아 출신 결혼이주여성의 분쟁해결 대처방식을 연구하였다. 본 연구는 두 번의 세부 연구로 나누어 진행하였다. 첫 번째 연구는 폐쇄형 설문지를 통하여 12명의 베트남과 캄보디아 결혼이주여성을 대상으로 분석하였으며 두 번째 연구는 5명의 베트남과 캄보디아 출신 결혼이주여성들을 대상으로 개방형 설문지에 대한 응답과 면접을 통하여 진행하였다. 연구결과 상당수 결혼이주 여성들은 분쟁이 발생할 때 주로 모국인과 상담을 하는 것으로 나타나고 있으며 주로 부부 자체적으로 분쟁을 해결하고 있는 것으로 나타났다. 베트남 캄보디아 결혼이주여성들은 분쟁이 발생할 때 주로 갈등회피 형 전략을 사용하는 것으로 나타나고 있다. 또한 다문화가족지원 센터가 분쟁해결에 도움이 될 가능성을 보여주고 있다.

• 한국CDE학회논문집
• /
• 제10권6호
• /
• pp.432-443
• /
• 2005

Recent three-dimensional feature-based CAD systems based on solid or non-manifold modelling functionality have been widely used for product design in manufacturing companies. When product models associated with features are used in various downstream applications such as analysis, however, simplified and abstracted models at various levels of detail (LODs) are frequently more desirable and useful than the full detailed model. To provide multi-resolution models, the features need to be rearranged according to a criterion that measures the significance of the feature. However, if the features are rearranged, the resulting shape is possibly different from the original because union and subtraction Boolean operations are not commutative. To solve this problem, in this paper, the new concept of the effective zone of a feature is defined and identified using Boolean algebra. By introducing the effective zone, an arbitrary rearrangement of features becomes possible and arbitrary LOD criteria may be selected to suit various applications. Besides, because the effective zone of a feature is independent of the data structure of the model, the multi-resolution modelling algorithm based on the effective zone can be implemented on any 3D CAD system based on conventional solid representations as well as non-manifold topological (NMT) representations.

• 대한의용생체공학회:의공학회지
• /
• 제31권6호
• /
• pp.456-463
• /
• 2010

In the present study, we proposed a new subspace scanning algorithm to enhance the spatial resolution of electroencephalography (EEG) and magnetoencephalography(MEG) source localization. Subspace scanning algorithms, represented by the multiple signal classification (MUSIC) algorithm and the first principal vector (FINE) algorithm, have been widely used to localize asynchronous multiple dipolar sources in human cerebral cortex. The conventional MUSIC algorithm used principal component analysis (PCA) to extract the noise vector subspace, thereby having difficulty in discriminating two or more closely-spaced cortical sources. The FINE algorithm addressed the problem by using only a part of the noise vector subspace, but there was no golden rule to determine the number of noise vectors. In the present work, we estimated a non-orthogonal signal vector set using independent component analysis (ICA) instead of using PCA and performed the source scanning process in the signal vector subspace, not in the noise vector subspace. Realistic 2D and 3D computer simulations, which compared the spatial resolutions of various algorithms under different noise levels, showed that the proposed ICA-MUSIC algorithm has the highest spatial resolution, suggesting that it can be a useful tool for practical EEG/MEG source localization.

• IEIE Transactions on Smart Processing and Computing
• /
• 제4권5호
• /
• pp.311-317
• /
• 2015

The aim of this study is to develop a 3D registration algorithm for positron emission tomography/computed tomography (PET/CT) and magnetic resonance (MR) images acquired from independent PET/CT and MR imaging systems. Combined PET/CT images provide anatomic and functional information, and MR images have high resolution for soft tissue. With the registration technique, the strengths of each modality image can be combined to achieve higher performance in diagnosis and radiotherapy planning. The proposed method consists of two stages: normalized mutual information (NMI)-based global matching and independent component analysis (ICA)-based refinement. In global matching, the field of view of the CT and MR images are adjusted to the same size in the preprocessing step. Then, the target image is geometrically transformed, and the similarities between the two images are measured with NMI. The optimization step updates the transformation parameters to efficiently find the best matched parameter set. In the refinement stage, ICA planes from the windowed image slices are extracted and the similarity between the images is measured to determine the transformation parameters of the control points. B-spline. based freeform deformation is performed for the geometric transformation. The results show good agreement between PET/CT and MR images.