• Journal of KIISE:Computer Systems and Theory
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• v.26 no.8
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• pp.930-938
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• 1999

미래의 통합 이동 통신망은 멀티미디어 데이터 서비스를 하기 위해 작은 셀로 망이 구성될 것이다. 셀이 작은 경우, 이동 호스트의 셀간 이동이 상대적으로 증가해서 잦은 핸드오프 처리로 서비스 중단이 빈번히 발생할 수 있을 뿐만 아니라 자원의 낭비도 많아지게 된다. 따라서 이런 문제를 해결하기 위해 이동 호스트의 이동성을 예측해서 멀티캐스트 연결을 구성해서 사전 핸드오프 처리를 하는 SGMH방법을 제안한다. SGMH방법의 성능 평가를 위해 핸드오프 처리과정의 데이터 및 제어 정보의 흐름을 분석하고, 망 종속 인자들을 도입해서 버퍼 오버헤드와 서비스 중단 시간 면에서 기존 핸드오프 방법들과 비교했다. 비교 분석한 결과는 제안한 방법이 기존의 방법보다 기지국에서의 버퍼 오버헤드뿐만 아니라 서비스 중단 시간을 줄일 수 있음을 보였다.Abstract For mobile multimedia data services, future mobile communication networks will consist of small cells. In case of smaller cell size, the number of user movements between cells will increase and more network resources will be consumed for processing frequent handoffs. This processing delay will cause frequent connection service disruptions. To solve these problems, a multicast-based handoff method ,called SGMH(Sub-Group Multicast-based Handoff), is suggested. SGMH method estimates future movements of mobile hosts and setups a dynamic multicast connection tree for procesing handoffs. For performance evaluation, we represent flows of data and control messages as timing diagrams and introduce several network related factors. In terms of buffer overhead and service disruption time we compared the SGMH method to other methods. The results show that SGMH method has better performance in that it can reduce consumption of network resources and minimize service disruption time.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.389-394
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• 2008

The purpose of this research was to develop a methodology to determine whether conjunctive surface water and groundwater management could significantly reduce deficits in a river basin with a relatively limited alluvial aquifer. The Geum River basin is one of major river basins in South Korea. The upper region of the Geum River basin is typical of many river basins in Korea where the shape of river basin is narrow with small alluvial aquifer depths from 10m to 20m and where most of the groundwater pumped comes quickly from the steamflow. The basin has two surface reservoirs, Daecheong and Yongdam. The most recent reservoir, Yongdam, provides water to a trans-basin diversion, and therefore reduces the water resources available in the Geum River basin. After the completion of Yongdam reservoir, the reduced water supply in the Geum basin resulted in increasing conflicts between downstream water needs and required instream flows, particularly during the low flow season. Historically, the operation of groundwater pumping has had limited control and is administered separately from surface water diversions. Given the limited size of the alluvial aquifer, it is apparent that groundwater pumping is essentially taking its water from the stream. Therefore, the operation of the surface water withdrawals and groundwater pumping must be considered together. The major component of the conjunction water management in this study is a goal-programmin g based optimization model that simultaneously considers surface water withdrawals, groundwater pumping and instream flow requirements. A 10-day time step is used in the model. The interactions between groundwater pumping and the stream are handled through the use of response and lag coefficients. The impacts of pumping on streamflow are considered for multiple time periods. The model is formulated as a linear goal-programming problem that is solved with the commercial LINGO optimization software package.

• Korea-Australia Rheology Journal
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• v.16 no.2
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• pp.63-73
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• 2004

Flow in a channel with an obstruction at the entry can be reverse, stagnant or forward depending on the position of the obstruction. These flow phenomena have potential applications in the control of energy and various flows in process engineering. Parameters that affect this flow inside and around the test channel are the gap (g) between the obstruction geometry and the test channel, the Reynolds number (Re) and the length (L) of the test channel. The influence of these parameters on the flow behavior was investigated using a flat plate obstruction at the entry of the channel. A low concentration polyacrylamide solution (0.018% by weight) showing a powerlaw fluid behavior was used as the fluid in this investigation. The flow phenomena were investigated by the velocity measurement and the flow visualization and their results were compared with numerical simulation. These results of low concentration polyacrylamide solution are also compared with the results of water published elsewhere (Kabir et al., 2003). The maximum reverse flow inside the test channel observed was 20% - 30% of the outside test channel velocity at a g/w (gap to width) ratio of 1 for Reynolds numbers of 1000 to 3500. The influence of the test channel length (L) and the Reynolds number (Re) on the velocity ratio ($V_i$/$V_o$: inside velocity/outside velocity in the test channel) are also presented and discussed here.

• The Journal of the Acoustical Society of Korea
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• v.23 no.5
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• pp.390-399
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• 2004

In this paper, we design and implement a multiple-view VoiceXML editor to improve editing efficiency of the VoiceXML. The VoiceXML multiple-view Editor uses a MVC framework to support multiple views and paradigm. Our multiple-view editor consists of Model. View and Controller using MVC framework. A model, core data structure. is constructed of abstract syntax tree and abstract grammar. A view. user interface. is formalized in unparsing rules and unparser. A controller. to control model and view. is made of command interpreter and tree handler. The VoiceXML multiple-view editor overcomes a drawbacks of existing XML editors by showing document structure and context concurrently. as well as document flows. Our VoiceXML multiple-view editor. which MVC framework has been applied, provides various editing views concurrently to users. Thereby. it supports efficient and convenient editing environments for voice-web documents to users and it guarantees transparency of editors. as various views have a same consistent model.

• Journal of IKEEE
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• v.10 no.1 s.18
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• pp.10-15
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• 2006

In this paper, a clock and data recovery (CDR) circuit for a serial link with a half rate 4x oversampling phase and frequency detector structure without a reference clock is described. The phase detector (PD) and frequency detector (FD)are designed by 4X oversampling method. The PD, which uses bang-bang method, finds the phase error by generating four up/down signal and the FD, which uses the rotational method, finds the frequency error by generating up/down signal made by the PD output. And the six signals of the PD and the FD control an amount of current that flows through the charge pump. The VCO composed of four differential buffer stages generates eight differential clocks. Proposed circuit is designed using the 0.18um CMOS technology and operating voltage is 1.8V. With a 4X oversampling PD and FD technique, tracking range of 24% at 3.125Gbps is achieved.

• Journal of Korea Water Resources Association
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• v.48 no.11
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• pp.957-967
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• 2015

It was reviewed for the 2D numerical simulations to evaluate the effects of flood control by detention basin, even if stage-discharge relationships for the side weir were not known. A 2D depth-integrated numerical model was constructed by the application of the finite volume method to the shallow water equations as a numerical method and the introduction of an approximate Riemann solver for the accurate calculation of fluxes. Results by the model were compared with those by the laboratory test for the cases of free overflow and submerged flow over a side weir between the channel and storage. The difference between simulated and measured discharge coefficients for the case of free overflow is very small. In addition, the results by simulations were in good agreement with those by experiments for the submerged flow over a side weir and its mechanism was reproduced well. Through this study the discharge coefficients of side weirs can be accurately determined by the 2D numerical model and a considerable degree of accuracy can be achieved to evaluate the effect of flood defenses by detention basins. Thus, it will be expected to apply this model practically to the plan of detention basins, the evaluation of design alternatives, or the management of the existing ones.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11B
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• pp.1234-1244
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• 2009

Nowadays, the traffic type and behavior are extremely diverse due to the appearance of various services and applications on Internet, which makes the need of application-level traffic classification important for the efficient management and control of network resources. Although lots of methods for traffic classification have been introduced in literature, they have some limitations to achieve an acceptable level of performance in terms of accuracy and completeness. In this paper we propose an application traffic classification method using statistic signatures, defined as a directional sequence of packet size in a flow, which is unique for each application. The statistic signatures of each application are collected by our automatic grouping and extracting mechanism which is mainly described in this paper. By matching to the statistic signatures we can easily and quickly identify the application name of traffic flows with high accuracy, which is also shown by comprehensive excrement with our campus traffic data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.4
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• pp.266-278
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• 2013

In this paper, to manage the efficient control of IP packet flows crossing multi-provider networks such as Internet, we propose a SDN(Software Defined Networking)-based policy controller. The proposed policy controller leverages the visibility of underlying network and manages both virtual links and ports to inter-connect networking elements. The controller is capable of quickly composing multiple on-demand virtual networks and dynamically managing the composed networks, thus it can provide more flexible and optimized overlay networking environment to end-user applications. More specifically, we first look into the proposed structure and features of policy controller. With two kinds of service applications, we then verify the applicability of the proposed controller by evaluating its service composition time.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.6
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• pp.637-647
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• 2010

Recent embedded systems are being more complicated due to their hierarchical software architecture including operating systems. The performance of such complicated software architecture could not be well analyzed through separate analysis of each software layer; the combined effect and the interactions among the whole software layers should be considered. In this paper, we show the design and implementation of a performance analysis framework that enables hierarchical analysis of performance of Linux-based embedded systems considering interactions among the software layers. By using the proposed framework, we can obtain useful run-time information about a hierarchical software structure which usually consists of user-defined function layer, library function layer, system call layer, and kernel events layer. Experimental results reveal that the proposed framework could accurately identify the performance bottlenecks with the corresponding software layers during executions of target applications through the accompanying sub-steps of the analysis: the actual execution paths, the execution time of each observed event in each software layer, and the control flows across the software layers.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.5
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• pp.551-557
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• 2015

The TMDL (Total Maximum Daily Load) has been used to determine the water quality target. LDC (Load Duration Curve) based on hydrology has been used to support water quality assessments and development of TMDL. Also FDC (Flow Duration Curve) analysis can be used as a general indicator of hydrologic condition. The LDC is developed by multiplying FDC with the numeric water quality target of the factor for the pollutant of concern. Therefore, this study was to create LDC using the stream flow data and numeric water quality target of BOD and T-P in order to evaluate the pollutant load characterization by flow conditions in Heukcheon stream. When it is to be a high-flows condition, BOD and T-P are necessary to manage. BOD and T-P did not satisfy the numeric water quality target for both seasons (spring and summer). In order to meet the numeric water quality target in Heukcheon stream, management of non point source pollutant is much more important than that of point source pollutant control.