• 한국통신학회논문지
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• 제29권2B호
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• pp.263-271
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• 2004

본 논문에서는 perVC-Queuing 기반의 버퍼관리알고리즘을 제안한다. 제안된 알고리즘은 서비스 율 측정과 동적 VC 임계치를 사용하여 GFR VC에 네트워크 자원을 공정하게 분배하고 모든 VC가 요구하는 MCR을 보장한다. 컴퓨터 시뮬레이션결과 제안된 알고리즘이 GFR 서비스 클래스가 요구하는 QoS를 보장하고 TCP의 성능을 향상하였다.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.385-388
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• 2008

Recently, occurrence frequency of natural disaster decrease but scale of damage increase remarkably by the Climate change due to global warming. Especially, extreme heat become more critical wether problem in the Korean Peninsula. But, we don't have exact threshold about extreme heat. Therefore, to assess the influences by the extreme heat on personal injury, we analyzed statistics on the causes of the daily mortality. And we developed a threshold for extreme heat health watch warning system.

• East Asian Economic Review
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• 제28권2호
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• pp.175-219
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• 2024

This study investigates the impact of inflation rate fluctuations on economic growth in China, with a particular focus on potential non-linear characteristics. The global economic impact of the COVID-19 pandemic notably heightens the study's relevance. The research that the unidirectional causal relationship from inflation to economic growth in China first strengthens and then weakens over time. Furthermore, there is an inflation rate threshold effect on economic growth, identified at 2%. Below this threshold, inflation positively influences economic growth, whereas above it, the impact turns negative. This finding underscores the importance of balancing economic growth with inflation control in the formulation of monetary policy.

• Journal of applied mathematics & informatics
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• 제29권5_6호
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• pp.1097-1115
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• 2011

We consider the global stability of a general tuberculosis model with two differential infectivity, n classes of latent individuals and mass action incidence. This system exhibits the traditional threshold behavior. There is always a globally asymptotically stable equilibrium state. Depending on the value of the basic reproduction ratio $\mathcal{R}_0$, this state can be either endemic ($\mathcal{R}_0$ > 1), or infection-free ($\mathcal{R}_0{\leq}1$). The global stability of this model is derived through the use of Lyapunov stability theory and LaSalle's invariant set theorem. Both the analytical results and numerical simulations suggest that patients should be strongly encouraged to complete their treatment and sputum examination.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제23권1호
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• pp.39-63
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• 2019

In this paper, we study the effect of Cytotoxic T Lymphocyte (CTL) and antibody immune responses on the virus dynamics with both virus-to-cell and cell-to-cell transmissions. The infection rate is given by Holling type-II. We first show that the model is biologically acceptable by showing that the solutions of the model are nonnegative and bounded. We find the equilibria of the model and investigate their global stability analysis. We derive five threshold parameters which fully determine the existence and stability of the five equilibria of the model. The global stability of all equilibria of the model is proven using Lyapunov method and applying LaSalle's invariance principle. To support our theoretical results we have performed some numerical simulations for the model. The results show the CTL and antibody immune response can control the disease progression.

• 한국지능시스템학회논문지
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• 제20권3호
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• pp.368-374
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• 2010

영상 분할 (Image Segmentation)은 패턴 인식, 환경 인식, 문서 분석을 위한 영상 처리 과정에서 가장 기본적인 단계이다. 영상 분할 방법들 중 Otsu의 영상의 정규화된 히스토그램의 분포 정보를 이용하여 클래스 간의 분산을 최대화 시키는 임계치값을 결정하는 자동 임계치값 선정방법이 가장 잘 알려진 방법이다. Otsu의 방법은 영상의 전 영역에 대한 히스토그램을 분석함으로써 영상의 부분적인 특성을 반영하여 임계치값을 결정하기는 어렵다. 본 논문에서는 이 어려움 해소하기 위하여 Context Fuzzy c-Means 알고리즘을 이용하여 영상을 여러 개의 부분 영역으로 나누고, 정의된 부 영역에 영상 분할 기법을 적용함으로써 부 영역들에 적합한 여러 개의 임계치값을 계산함으로써 영상 분할 성능을 개선하고자 하였다.

• Journal of Communications and Networks
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• 제10권2호
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• pp.213-220
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• 2008

This paper analyzes a broadcasting technique for wireless multi-hop sensor networks that uses a form of cooperative diversity called opportunistic large arrays (OLAs). We propose a method for autonomous scheduling of the nodes, which limits the nodes that relay and saves as much as 32% of the transmit energy compared to other broadcast approaches, without requiring global positioning system (GPS), individual node addressing, or inter-node interaction. This energy-saving is a result of cross-layer interaction, in the sense that the medium access control (MAC) and routing functions are partially executed in the physical (PHY) layer. Our proposed method is called OLA with a transmission threshold (OLA-T), where a node compares its received power to a threshold to decide if it should forward. We also investigate OLA with variable threshold (OLA-VT), which optimizes the thresholds as a function of level. OLA-T and OLA-VT are compared with OLA broadcasting without a transmission threshold, each in their minimum energy configuration, using an analytical method under the orthogonal and continuum assumptions. The trade-off between the number of OLA levels (or hops) required to achieve successful network broadcast and transmission energy saved is investigated. The results based on the analytical assumptions are confirmed with Monte Carlo simulations.

• 한국정보통신학회논문지
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• 제9권5호
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• pp.1102-1110
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• 2005

본 논문에서는 기존 복셀 칼라링 기법에서의 색상 일관성에 대한 문턱값 문제를 해결하기 위한 개선된 복셀 칼라링 기법을 제안하였다. 제안 기법에서는 표면 복셀에 대한 색상 일관성의 문턱값을 내부 복셀의 색상 일관성 값으로 대체함으로써 복셀 칼라링의 반복 회수가 증가함에 따라 개별 표면 복셀에 대한 최적의 문턱값을 찾아가도록 하였다. 또한 그래프 절단 기법을 적용하여 주위 복셀을 제거 판단에 함께 고려함으로써 표면 잡음을 감소시켰다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권8호
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• pp.1843-1859
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• 2013

The continuous increase of the spatial resolution of remote sensing images brings great challenge to image analysis and processing. Traditional prior knowledge-based region detection and target recognition algorithms for processing high resolution remote sensing images generally employ a global searching solution, which results in prohibitive computational complexity. In this paper, a more efficient region of interest (ROI) detection algorithm based on visual attention and threshold segmentation (VA-TS) is proposed, wherein a visual attention mechanism is used to eliminate image segmentation and feature detection to the entire image. The input image is subsampled to decrease the amount of data and the discrete moment transform (DMT) feature is extracted to provide a finer description of the edges. The feature maps are combined with weights according to the amount of the "strong points" and the "salient points". A threshold segmentation strategy is employed to obtain more accurate region of interest shape information with the very low computational complexity. Experimental statistics have shown that the proposed algorithm is computational efficient and provide more visually accurate detection results. The calculation time is only about 0.7% of the traditional Itti's model.

• Journal of Power Electronics
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• 제19권6호
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• pp.1566-1574
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• 2019

Maximum power point tracking (MPPT) under the partial shading condition is a challenging research topic for photovoltaic systems. Shaded photo-voltaic module result in complex peak patterns on the power versus voltage curve which can misguide classical MPPT algorithms. Thus, various kinds of global MPPT algorithms have been studied. These have typically consisted of partial shading detection, global peak search and MPPT. The conventional partial shading detection algorithm aims to detect all of the occurrences of partial shading. This results in excessive execution of global peak searches and discontinuous operation of the MPPT. This in turn, reduces the achievable power for the PV module. Based on a theoretical investigation of power verse voltage curve patterns under various partial shading conditions, it is realized that not all the occurrences of partial shadings require a global peak search. Thus, an intelligent partial shading detection algorithm that provides exact identification of global peak search necessity is essential for the efficient utilization of solar energy resources. This paper presents a new partial shading determinant algorithm utilizing adaptive threshold levels. Conventional methods tend to be too sensitive to sharp shading patterns but insensitive to smooth patterns. However, the proposed algorithm always shows superb performance, regardless of the partial shading patterns.