• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.34 no.1
• /
• pp.91-98
• /
• 2016

In order to apply Kriging methods for geostatistics of spatial data, an estimation of spatial coherency functions is required priorly based on the spatial distance between measurement points. In the study, the typical coherency functions, such as semi-variogram, homeogram, and covariance function, were estimated using the national geoid model. The test area consisting of 2°×2° and the Unified Control Points (UCPs) within the area were chosen as sampling measurements of the geoid. Based on the distance between the control points, a total of 100 sampling points were grouped into distinct pairs and assigned into a bin. Empirical values, which were calculated with each of the spatial coherency functions, resulted out as a wave model of a semi-variogram for the best quality of fit. Both of homeogram and covariance functions were better fitted into the exponential model. In the future, the methods of various Kriging and the functions of estimated spatial coherency need to be studied to verify the prediction accuracy and to calculate the Mean Squared Prediction Error (MSPE).

• Proceedings of the Korean Information Science Society Conference
• /
• 2002.04a
• /
• pp.40-42
• /
• 2002

캐쉬 일관성 유지 프로토콜은 공유 메모리 다중 프로세서 시스템의 정확하고 효율적인 작동에 중요하다. 시스템이 점점 복잡해짐에 따라 시뮬레이션 방법만으로는 프로토콜의 정확성을 확인하기는 어렵다. 본 논문에서는 CC-NUMA용 디렉토리 기반 캐쉬 일관성 프로토콜인 RACE 프로토콜을 정형기법 도구인 ESTEREL을 이용하여 프로토콜이 안정적으로 동작함을 검증하였다.

• Proceedings of the KIEE Conference
• /
• 1999.11b
• /
• pp.273-275
• /
• 1999

This paper presents a dynamic equivalencing method in large electric power system for stability analysis. This method of modeling simplified equivalents for parts of the network outside the study area is to evaluate the stability of a study area modeled in detail. Generators are closely coupled in an electrical sense tend to swing together in groups during disturbances, and this behavior can be exploited to reduce the size of the power system model. The characteristics of generators swing together are referred to as coherency Coherency groups whose generators state trajectory are similar to the other generators state trajectory in the same coherency group by a certain disturbance. In this paper, procedures for forming dynamic equivalents of control devices of coherency-based generating units are proposed and the aggregation of the control devices such as excitation system and governor-turbine system is accomplished by this method. This method can deal with the aggregation of the same type of control devices and combination of hydro and steam unit or the many types of excitation systems. etc. This method is shown to be efficient in reducing the number of control device of generating units with small error in the study group by result of case study presented latter part of this paper.

• Geophysics and Geophysical Exploration
• /
• v.4 no.3
• /
• pp.89-95
• /
• 2001

The final goal of the seismic method is to verify the spatial characteristic of subsurface media. For this purpose, professional interpreters interprete the discontinuities of seismic events from seismic image. This paper introduces a method for automatic discontinuity extraction from 3D seismic image. The method consists of three steps. The first step is for estimating coherency of seismic events from seismic data. The second step is to express the potential region where discontinuities may exist in the form of binary image. The third step is to locate the discontinuities by thining the region found in the second step.

• Proceedings of the KIEE Conference
• /
• 1993.11a
• /
• pp.3-5
• /
• 1993

This paper presents a identification techniques of coherent generators for dynamic equivalents using artificial neural networks. In the developed neural network, inputs are the power system parameters which have a property of coherency. Outputs of the neural network are coherency and error indices which are derived from density measure concept. The learning of developed neural network is carried out by means of error back-propagation algorithm. Identification of coherent generators are implemented by proposed grouping algorithm using coherency and error indices. The proposed method is confirmed by simulations for 39-bus New England system.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.50 no.1
• /
• pp.6-12
• /
• 2001

This paper deals with the development of dynamic equivalents of the Korea Electric Corporation (KEPCO) systems. The weak coupling method is chosen for the most suitable coherency identification to represent the characteristics of the KEPCO system by the dynamic characteristic comparison of several coherency identification methods. Also, this paper shows the detail aggregation of generator groups makes a better representation of the dynamic and static characteristics of the original system than the classical aggregation. The simulation results of the developed KEPCO equivalent system are presented in comparison with the original system to illustrate the validity of the equivalent system are presented in comparison with the original system to illustrate the validity of the equivalent system.

• KIEE International Transactions on Power Engineering
• /
• v.12A no.1
• /
• pp.1-5
• /
• 2002

This paper presents the procedure to construct equivalent model of large power system based on nonlinear time simulation responses. It consists of coherency identification, generator aggregation and network reduction. Coherency index that can be directly implemented to this procedure is proposed. Generator aggregation based on detailed model is performed. This procedure can be used to construct equivalent model in PSS/E. It is also possible to reduce the large power system directly from the nonlinear time responses. This procedure is applied to the transient stability analysis of Korea power system that now experiences rapid changes. The equivalent model is compared with the original model in its size, accuracy, speed and performance. This paper shows that the developed equivalent model is a good estimate of the original system.

• ETRI Journal
• /
• v.10 no.3
• /
• pp.62-72
• /
• 1988

HARP(High-performance Architecture for Risc-type Processor)는 한국전자통신연구소에서 개발하고 있는 고유 모델의 RISC형 32비트 CPU이다. HACAM은 HARP의 캐쉬 메모리 및 MMU를 1칩의 VLSI로 구현한 것으로서 virtual cache 구조를 갖는다. Virtual cache 시스팀에서는 synonym문제가 수반되는데, 이 문제는 multitasking을 하는 single CPU 시스팀에서도 발생하지만, multiprocessor 시스팀에서는 데이터 coherency 문제와 함께 해결하여야 되기 때문에 더욱 어렵다. 본 논문에서는 HACAM이 virtual cache 구조로 구현하게 된 배경 및 이의 타당성을 논하였고, 아울러 virtual cache 구조를 갖기 때문에 발생하는 synonym 문제를 설명하고, 이의 해결 방안을 제시하였다.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.32 no.2
• /
• pp.227-242
• /
• 2022

This paper presents a Cache-Coherency Interconnect(CCI)-based Android pattern screen lock(PSL) attack on modern ARM processors. CCI has been introduced to maintain the cache coherency between the big core cluster and the little core cluster. That is, CCI is the central interconnect inside SoC that maintains cache coherency and shares data. In this paper, we reveal that CCI can be a side channel in security, that an adversary can observe security-sensitive operations. We design and implement a technique to compromise Android PSL within only a few attempts using the information of CCI in user-level applications on Android Nougat. Further, we analyzed the relationship between the pattern complexity and security. Our evaluation results show that complex and simple patterns would have similar security strengths against the proposed technique.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.53 no.8
• /
• pp.59-65
• /
• 2016

Performance optimization of applications with massive stream data processing has been performed by considering I/O data coherency problem where a memory is shared between processors and hardware accelerators. A formula for performance analyses is derived based on profiling results of system-level simulations. Our experimental results show that overall performance was improved by 1.40 times on average for various image sizes. Also, further optimization has been performed based on the parameters appeared in the derived formula. The final performance gain was 3.88 times comparing to the original design and we can find that the performance of the design with cacheable shared memory is not always.