• Journal of Korean Association for Spatial Structures
• /
• v.3 no.4 s.10
• /
• pp.1-10
• /
• 2003

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.27 no.6B
• /
• pp.579-585
• /
• 2002

The investigation into the effect of various feedback errors on system performance can help the robust feedback channel design and transmission of exact feedback channel information as well. In this paper, we address the algorithm that determines space combining weight vector maximizing received signal power at mobile on frequency flat fading channel and investigate the performance degradation by feedback channel delay in the FDD/CDMA systems employing transmit beamforming. We observe the effect of feedback channel delay corresponding to the number of transmit antennas and the temporal/spatial correlation of channel. The results show that performance is more sensitive to feedback delay with the larger number of antennas when fadings at transmit antennas are not spatially correlated.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
• /
• 2008.06a
• /
• pp.159-163
• /
• 2008

현재 우리나라 국토공간자료의 이용은 자료에 대한 낮은 접근성, 분석방법의 일관성 유지의 곤란, 결과의 미공유에 따른 중복작업, 자료의 분산에 따른 즉각적인 의사결정의 지연 등의 문제를 지니고 있다. 이를 위하여 다양한 국토모니터링 정보를 통합, 처리하여 효율적으로 제공하는 시스템 개발이 요구되고 있다. 이 연구에서는 현재까지 구축된 국토모니터링과 관련된 공간정보시스템의 사례를 조사하고, 특성을 정리하여 국토모니터링을 위한 통합된 공간정보시스템이 갖추어야할 내용과 설계전략을 제시하였다.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.41 no.2
• /
• pp.29-36
• /
• 2004

This paper deals with a fractional model reduction for linear systems with time varying delayed states. A contractive coprime factorization of linear time delayed systems is defined and obtained by solving linear matrix inequalities. Using generalize controllability and observability gramians of tile contractive coprime factor, a balanced state space realization of the system is derived. The reduced model will be obtained by truncating states in the balanced realization and an upper bound of model approximation error is also presented. In order to demonstrate efficacy of the suggested method, a numerical example is illustrated.

• The Journal of the Acoustical Society of Korea
• /
• v.17 no.8
• /
• pp.19-24
• /
• 1998

이 논문에서는 능동 소음 제어 시스템을 구성하는 요소들인 증폭기와 저주파 필터 와 같은 소자들의 비선형 특성과 공간에서의 주파수 대역에 따른 비선형 특성을 보상하여, 보다 효과적인 능동 소음 제어기를 설계하기 위해 시간 지연 신경 회로망을 이용하는 새로 운 방법을 제안한다. 공간을 포함한 2차 경로 함수를 모델링하여 보다 나은 성능을 갖는 능 동 소음 제어기를 구성하기 위한 기존의 최소 자승 오차 알고리듬에 기반한 filtered-x least mean square(LMS) 알고리듬과 오차 역전달 학습 알고리듬을 갖는 시간 지연 다층 구조 인 식자를 이용한 결과를 간단한 실험을 통하여 그 성능을 비교 분석한다.

• Annual Conference of KIPS
• /
• 2004.05a
• /
• pp.101-104
• /
• 2004

R-Tree 색인은 기존의 공간 데이터베이스관리시스템에서 공간 데이터 검색을 위하여 많이 사용되고 있는 공간 색인기법이다. 하지만 R-Tree 색인에서 기존의 잠금(Lock) 기반 동시성 제어는 갱신연산의 잠금으로 인해 검색연산의 블록킹 오버헤드(blocking overhead)가 발생한다. 본 논문에서는 R-Tree 색인에서 검색연산의 블록킹 오버헤드의 주요 원인이 되는 노드 분할 연산과 MBR(Minimum Bounding Rectangle) 갱신연산에 대해 각각 노드단위와 노드엔트리 단위의 버전(Version)을 생성하고 유지하여 동시에 발생하는 검색연산이 갱신연산으로 인한 지연이 없이 자신에 알맞은 버전을 읽음으로써, 검색성능을 높일 수 있는 버전 기반의 동시성 제어 기법을 제안한다.

• Journal of KIISE
• /
• v.43 no.4
• /
• pp.399-403
• /
• 2016

Deferred Shading is a shading technique that postprocesses pixels in the screen space, following geometry-only rendering passes with depth buffering. Unlike typical shadow mapping techniques, this technique allows us to render shadows from multiple light sources without changing the structure of the rendering pipelines. This paper presents a deferred shadow mapping technique and its extension to soft shadows using mipmapping. Our technique first generates visibility maps from light sources, and blurs the visibility maps for deferred shading. This strategy leads to efficient soft-edged shadows, but does not incorporate depth variation, producing light bleeding to some extent. In order to suppress the light-bleeding artifacts, we also propose a depth-adaptive mipmap sampling technique in the screen space.

• Journal of Advanced Navigation Technology
• /
• v.24 no.6
• /
• pp.549-556
• /
• 2020

This paper proposes several suboptimal methods of designing a controller for a networked control system with state feedback where delay due to transmission error and transmission delay is modeled as a Markov process. A stability condition for a control system with Markov delay is found through an equivalent relationship that corresponding delay-dependent Lyapunov-Krasovskii functional has the same form of the Lyapunov function of an augmented control system. Several suboptimal methods of designing a controller from the stability condition are proposed to reduce complexity. A simple numerical experiment shows that a restricted subspace method which limits the search space of a matrix variable to a block diagonal form provides the best tradeoff between the complexity and performance.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.3 no.1
• /
• pp.51-62
• /
• 2001

In-situ stress measurement using AE (Acoustic Emission) and DRA (Deformation Rate Analysis) is usually carried out under uniaxial loading in the laboratory and it consumes delay time from drilling to testing. Therefore, it should be considered how the lateral stress and delay time influence on the test results for the in-situ stress determination. As the delay time increased, the accuracy of estimating the pre-stress decreased. The pre-stress of the specimen loaded only axially was determined within an error of less than 9% (using AE) and 4% (using DRA). And the specimen on which axial pre-stress and the confining pressure were loaded had an error of less than 17% (using AE) and 14% (using DRA). The results of AE and DRA for field specimens were very similar with each other but smaller than those of hydraulic fracturing method.

• Journal of the Korea Society for Simulation
• /
• v.20 no.1
• /
• pp.19-28
• /
• 2011

The safety applications based on the IEEE 802.11p, periodically transmit the safety-related information to all surrounding vehicles with high reliability and a strict timeline. However, due to the high vehicle mobility, dynamic network topology and limited network resource, the fixed beacon scheduling scheme excess delay and packet loss due to the channel contention and network congestion. With this motivation, we propose a novel beacon scheduling algorithm referred to as spatial-aware(SA) beacon scheduling based on the spatial context information, dynamically rescheduling the beaconing rate like a TDMA channel access scheme. The proposed SA beacon scheduling algorithm was evaluated using different highway traffic scenarios with both a realistic channel model and 802.11p model in our simulation. The simulation results showed that the performance of our proposed algorithm was better than the fixed scheduling in terms of throughput, channel access delay, and channel load. Also, our proposed algorithm is satisfy the requirements of vehicular safety application.