• Journal of Korea Multimedia Society
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• v.12 no.3
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• pp.362-371
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• 2009

The key technology for developing high quality LCDs is about manufacturing BLUs with homogeneous dot distributions. Commonly, homogeneous dot distributions are obtained by the halftoning methods which convert a gray-scale image to a binary image. Among many halftoning algorithms, the error-diffusion technique based on the principle distance is known to show homogeneous dot distributions. However, this technique has a drawback; the extent of the principle distance at each pixel with respect to those of the neighboring pixels can be too small or big creating a gap or overlap. In this paper, we propose a new error diffusion algorithm based on the variable principle distance which improves the existing error diffusion technique based on the principle distance. The variable principle distance at a given pixel is calculated with gray-scale values of the pixel and its neighbors and thus the principle distance value is variable depending on the direction from that pixel. This variable principle distance technique helps BLUs obtain homogeneous dot distributions.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.293-296
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• 1998

본 논문에서는 다양한 멀티미디어 서비스를 위해 가변율 half rate 음성 부호화기를 설계하였다. 유, 무성음과 묵음의 구분을 위해 본 논문에서는 프레임 에너지와 음성 파라메터들을 이용한 효과적인 voicing 결정 알고리즘을 사용하였다. 유성음을 위한 half rate 음성 부호화기는 저속에서 좋은 특성을 보이는 generalized AbS구조를 이용하였다. LPC 계수는 LSP 계수로 변환한 후 predictive 2-stage VQ를 통해서 양자화하며, 여기 신호는 음질저하를 최소화하며 복잡도를 감소시킨 shift 방식의 대수적 고정 코드북 구조를 사용하고, 적응코드북과 여기코드북의 이득은 VQ로 양자화 하였다. 무성음을 위한 부호화기는 대부분이 유성음을 위한 부호화기와 동일하지만, 무성음에서는 피치간 상관도가 매우 낮으므로 피치 보간 방법을 사용하지 않고 개루프로 피치 lag를 찾은 후 전체 프레임에 사용한다. 1 kb/s 부호화기는 묵음 구간과 주변소음 구간에 사용되며 이 구간의 신호를 피치 성분이 미약한 주변소음들로 제한하고 이에 최적인 부음성 부호화기를 설계하였다. 최종적으로 완성된 가변율 half rate 부호화기는 voice activity factor(VAF)가 0.47인 시험음성에서 약 2.6 kb/s의 평균 전송률을 보였다. 주관적 음질 평가의 일환으로 IS-96 표준 코덱인 가변율 8 kb/s QCELP와 A-B preference 시험을 실시하였다. 시험 결과 평균전송률이 약 2배인 가변율 8 kb/s QCELP 보다 우수한 음질 성능을 보였다.

• The Korean Journal of Applied Statistics
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• v.21 no.5
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• pp.727-738
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• 2008

If a cointegrating relation is affected by important economic and political events occurred in the sample period, the assumption of the time-invariant cointegrating vector is violated, which leads to the misrep-resentation of the actual relations between the variables. From such a viewpoint, this study utilizes the recursive estimation process in testing for the stability of the long-run equilibrium of the domestic stock market system and then attempts to develop the framework for stabilizing time-variant cointegraing relations by introducing the dummy variables where the structural changes are found to exist.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12C
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• pp.1280-1287
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• 2006

We propose a modified stochastic gradient-based (MSGB) filter showing that the filter is the solution to an optimization problem. This paper analyzes the properties of the MSGB filter that corresponds to the nonlinear adaptive filter with additional update terms, parameterized by the variable scaling factor. The variably parameterized MSGB filter plays a role iii connecting the fixed parameterized MSGB filter and the null parameterized MSGB filter through variably scaling parameter. The stability regions and misadjustments are shown. A system identification is utilized to perform the computer simulation and demonstrate the improved performance feature of the MSGB filter.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04b
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• pp.619-622
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• 2001

실시간 응용 프로그램은 미디어 데이터간에 만족되어야 할 동기화 제약조건(synchronization constraints)을 가지고 있다. 이러한 제약조건은 프리젠테이션 되어야 할 미디어 데이터간의 지연시간 및 서비스 품질을 나타낸다. 미디어 데이터간의 지연시간 및 서비스 품질을 효율적으로 표현하기 위해서는 이에 적합한 새로운 동기화 기법이 요구된다. 제안된 논문은 가변적 전송 지연 시간을 흡수하면서 미디어 데이터간의 동기화를 수행하는 동적 동기화이다. 즉, 최대 지연 지터 시간을 이용한 동기화 구간 조정과 지연시간의 변화에 따른 가변적 대기 시간을 융통성 있게 처리하여 미디어 데이터간의 동기화 요구를 만족시킬 수 있는 기법이다. 본 논문은 동기화 구간 조정을 처리하기 위해 지연 지터를 적용함으로써 트래픽 증가로 인한 미디어 데이터의 손실 시간 및 지연시간의 변화로 인한 데이터 손실을 감소시켰다. 그리고 스무딩 버퍼의 대기 시간을 가변으로 처리함으로써 지연시간의 변화로 인한 불연속을 감소시켰다. 제안된 논문은 고품질 서비스의 보장을 요구하는 시스템에 적합하며 재생율 증가와 손실율 감소 등 서비스 품질을 향상시켰다.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.1
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• pp.33-38
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• 2012

As underwater channel is very complex and time-varying, don't supports good-quality for communication service. In this paper, a multi-carrier CDMA(MC-CDMA) system for the reliability and robust service in the underwater acoustic channel is proposed and analyzed for its performance. Applied variable rate algorithm to the proposed system gets a channel state information from relationship between SINR and user data-rate. Using channel state information make spectrum usage more efficient and overall system performance improved. In this paper, the performance of proposed system analyzed by simulation. And Pseudo-Random spread codes used in the system are discussed.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.185-193
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• 2011

As a Lift axle is an additional axle installed mostly in heavy freight truck, It"s introduced for the purpose of cost saving, such as logistics, fuel, tire wear and prevention of the pavement damage. However, the Effects of a lift axle are anecdotal and they have occurred often that a lift axle is used improperly by expectations of some drivers. For these reasons, this study conducts a field experiment in order to identifying the change rate of fuel consumption due to an a Lift axle using, develops the fuel consumption model of field data, and then compares the effects of a Lift axle using through application of the model. As a result, fuel consumption decreased in loading conditions that are both empty and full when not using a lift axle.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.1
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• pp.16-26
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• 2011

Variable speed limit(VSL) is one of the highway ITS techniques designed to prevent accidents and traffic slow down by reducing congestion or speed variation between vehicles and lanes prior to arrive at the accident location by limiting speed. In Korea, while people have recognized the need for variable speed limit beginning with Seoul's urban expressway and installed facilities in order to provide guide for speed limit per lane and lane use, there has not been enough development of algorithm for internal administration as well as research on the basic principles behind administering variable speed limit. This study is for modeling and evaluating the VSL strategies based on the traffic flow theory. Supply-Demand method of the Cell Transmission Model is applied to demonstrate the traffic features and shockwaves to upstream of the bottleneck with/without VSL. We verified the explanation of Cell Transmission Model for the numerical example. and as the result, it is found that VSL strategies can reduce the total travel time in the congested section and variation of the speed. It means VSL is useful to improve the traffic condition and the safety on highway

• Journal of KIISE:Databases
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• v.33 no.4
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• pp.372-383
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• 2006

Among the approaches to image database management, content-based image retrieval (CBIR) is viewed as having the best support for effective searching and browsing of large digital image libraries. Typical CBIR systems allow a user to provide a query image, from which low-level features are extracted and used to find 'similar' images in a database. However, there exists the semantic gap between human visual perception and low-level representations. An effective methodology for overcoming this semantic gap involves relevance feedback to perform feature re-weighting. Current approaches to feature re-weighting require the number of components for a feature representation to be the same for every image in consideration. Following this assumption, they map each component to an axis in the n-dimensional space, which we call the metric space; likewise the feature representation is stored in a fixed-length vector. However, with the emergence of features that do not have a fixed number of components in their representation, existing feature re-weighting approaches are invalidated. In this paper we propose a feature re-weighting technique that supports features regardless of whether or not they can be mapped into a metric space. Our approach analyses the feature distances calculated between the query image and the images in the database. Two-sided confidence intervals are used with the distances to obtain the information for feature re-weighting. There is no restriction on how the distances are calculated for each feature. This provides freedom for how feature representations are structured, i.e. there is no requirement for features to be represented in fixed-length vectors or metric space. Our experimental results show the effectiveness of our approach and in a comparison with other work, we can see how it outperforms previous work.

• Journal of Korean Society of Transportation
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• v.26 no.3
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• pp.155-167
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• 2008

This paper studies a multiple user class variable demand user equilibrium and system optimal condition, and then establishes solution algorithms for them. The traffic network equilibrium is accomplished with basis on following assumptions. For considering heterogeneous road user, several user classes have discrete set of VOTs and the travel demand of each user classes varies according to generalized travel cost. this paper specifically investigates following question on multi-class variable demand: Are user equilibrium flows pattern dependent on the unit (time or money) perceived by road user classes? What is system optimal condition according to the unit used in measuring the travel cost or disutility? Finally, using this network equilibrium condition, The traffic assignment algorithm of each equilibrium condition are established.