• Journal of Information Processing Systems
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• 제2권2호
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• pp.76-81
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• 2006

A PDA is used mainly for downloading data from a stationary server such as a desktop PC in an infrastructure network based on wireless LAN. Thus, the overall performance depends heavily on the performance of such downloading with PDA. Unfortunately, for a PDA the time taken to receive data from a PC is longer than the time taken to send it by 53%. Thus, we measured and analyzed all possible factors that could cause the receiving time of a PDA to be delayed with a test bed system. There are crucial factors: the TCP window size, file access time of a PDA, and the inter-packet delay that affects the receiving time of a PDA. The window size of a PDA during the downstream is reduced dramatically to 686 bytes from 32,581 bytes. In addition, because flash memory is embedded into a PDA, writing data into the flash memory takes twice as long as reading the data from it. To alleviate these, we propose three distinct remedies: First, in order to keep the window size at a sender constant, both the size of a socket send buffer for a desktop PC and the size of a socket receive buffer for a PDA should be increased. Second, to shorten its internal file access time, the size of an application buffer implemented in an application should be doubled. Finally, the inter-packet delay of a PDA and a desktop PC at the application layer should be adjusted asymmetrically to lower the traffic bottleneck between these heterogeneous terminals.

• 한국콘텐츠학회논문지
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• 제10권1호
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• pp.78-86
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• 2010

스펙트럼 센싱 기술은 차세대 무선통신 기술들 중 하나인 Cognitive Radio (CR) 시스템에서의 핵심 기술이다. 본 논문은 CR 기술 기반의 효율적인 스펙트럼 센싱을 위하여 대상 신호의 시간-주파수 측면의 분석을 위한 알고리즘인 Short Time Fourier Transform을 적용하는 방법을 제안하였다. STFT에 적용된 윈도우는 Kaiser Window이며, 그 중첩 정도는 50%로 규정하였다. 시뮬레이션을 위해 6MHz 대역폭을 가진 DVB-H 신호를 입력 신호로 하였으며, Modified Periodogram Method, Welch's Method와의 비교를 통하여 제안한 알고리즘의 성능을 확인하였다. 또한, 임베디드 보드를 통하여 스펙트럼 센싱 모듈을 구현하였다.

• 대한산업공학회지
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• 제27권1호
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• pp.18-24
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• 2001

This paper presents a model and a heuristic algorithm for the Traveling Salesman Problem with Time Windows(TSPTW). The main difference of our model compared with the previous ones lies in that the time windows we are concerned are more flexible and realistic than the previous ones. In the typical TSPTW, the service at a node must begin within the time grid called the time window that is defined by the earliest and the latest time to start the service at each node. But, in real business practice, a lateness cost is usually penalized rather than the service is prohibited at all when a vehicle arrives after the latest time. Considering this situation, we develop a model with a new time window that allows an arrival after the latest time and penalizes the late arrival by charging a lateness cost. A two-phased heuristic algorithm is proposed for the model and is extensively tested to verify the accuracy and efficiency of the algorithm.

• 산업경영시스템학회지
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• 제22권53호
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• pp.13-22
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• 1999

This paper presents a model and dynamic programming based algorithm for the Traveling Salesperson Problem with Time Windows (TSPTW). The main difference of our model compared with the previous ones lies in that the time windows we are concerned are far more flexible and realistic. In the typical TSPTW, the service at a node must begin within the time grid called the time window that is defined by the earliest and the latest time to start the service at the node. But, in real business practices, a lateness cost is usually penalized rather than the service is prohibited at all when a vehicle arrives after the latest time. Considering this situation, we propose a model with a new time window that allows an arrival after the latest time and penalizes the late arrival by charging a lateness cost. An algorithm introduced for the model is extensively tested to verify the accuracy and efficiency.

• 한국콘텐츠학회논문지
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• 제9권7호
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• pp.276-284
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• 2009

본 연구는 부산광역시의 15개 자치구에 대한 2003년부터 2007년까지의 5년간 자료를 가지고 DEA 와 DEA/Window 분석을 적용하여 자치구의 단일기간의 효율성 및 시대별 효율성 변동을 분석하였다. 분석을 위해 투입요인으로 공무원 수, 인건비, 인구수, 주민 세출액을 선정하였으며, 산출요인으로 민원처리건수, 지방세 정수액, 그리고 재정자립도를 선정하였다. 본 연구는 서로 다른 자치구의 효율성이 시대별로 어느 정도 변동하고 있는지를 분석할 수 있는 평가 모형을 제시하고 있으며, 분석결과로는 자치구의 효율성이 2003년부터 줄어들고 있음을 보여주고 있다. 실증분석은 비효율성이 일부 자치구의 특정 시점에서 존재하고 있음을 밝히고 있으며, DENWindow 분석의 필요성을 보여주고 있다. DENWindow 분석은 윈도우 1에서 윈도우 3으로 갈수록 자치구의 효율성이 점차 낮아지고 있음을 보여주고 있다.

• 응용통계연구
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• 제26권2호
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• pp.291-305
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• 2013

네트워크상에서 분산 서비스 거부(DDoS) 공격 탐지를 위해 수집되는 트래픽 자료(BPS, PPS 등)는 시간 순서대로 발생하는 대용량 자료이다. 대용량 자료에서 공격 탐지를 위한 변화점 탐지 알고리즘은 정확성 뿐 아니라 시간과 공간적인 계산 수행의 효율성이 확보되어야 한다. 본 연구에서는 대용량자료에서 변화점 탐지에 대한 Ross 등(2011)이 연구한 순차적인 Sliding Window and Discretization(SWD) 방법을 확장하였다. 그리고 경험적 분포함수와 순위를 이용한 다섯 종류의 검정방법을 사용하면서 자료의 분포에 대한 가정없이 DDoS 공격을 탐지할 수 있도록 새로운 비모수 모형을 제안한다. 다양한 확률밀도 함수와 이에 대응하는 모평균과 분산을 변화시키면서 모의실험하여 본 연구에서 제안한 비모수적 검정방법을 SWD 방법에 적용하여 모형의 효율성을 탐색하고 토론한다. 그리고 실증 분석을 통해 공격 탐지율 및 공격 탐지의 정확성을 기준으로 성능을 측정하고 비교하였다.

• 한국안전학회지
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• 제27권5호
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• pp.229-234
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• 2012

Operator's action time is evaluated from MAAP4 analysis used in conventional probabilistic safety assessment(PSA) of a nuclear power plant. MAAP4 code which was developed for severe accident analysis is too conservative to perform a realistic PSA. A best-estimate code such as RELAP5/MOD3, MARS has been used to reduce the conservatism of thermal hydraulic analysis. In this study, operator's action time of core cooling recovery operation is evaluated by using the MARS code, which its Fussell-Vessely(F-V) value was evaluated as highly important in a small break loss of coolant(SBLOCA) event and loss of component cooling water(LOCCW) event in previous PSA. The main conclusions were elicited : (1) MARS analysis provides larger time window for operator's action time than MAAP4 analysis and gives the more realistic time window in PSA (2) Sufficient operator's action time can reduce human error probability and core damage frequency in PSA.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.614-618
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• 2003

This paper presents a system identification (SI) scheme in time domain using measured acceleration data. The error function is defined as the time integral of the least square errors between the measured acceleration and the calculated acceleration by a mathmatical model. Damping parameters as well as stiffness properties of a structure are considered as system parameters. The structural damping is modeled by the Rayleigh damping. A new regularization function defined by the L$_1$-norm of the first derivative of system parameters with respect to time is proposed to alleviate the ill-posed characteristics of inverse problems and to accommodate discontinuities of system parameters in time. The time window concept is proposed to trace variation of system parameters in time.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2001년도 춘계학술대회 학술발표 논문집
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• pp.211-214
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• 2001

In this paper, we interpret a score as a time series and deal with the fuzzy logic-based modeling of it. The musical notes in a score represent a lot of information about the length of a sound and pitches, etc. In this paper, using melodies, tones and pitches in a score, we transform data on a score into a time series. Once more, we form the new time series by sliding a window through the time series. For analyzing the time series data, we make use of the Box-Jenkinss time series analysis. On the basis of the identified characteristics of time series, we construct the fuzz model.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.758-761
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• 2003

This paper introduces a method that can detect obstacles and corridor environments from the images captured by a CCD camera in an automobile or mobile robot is proposed. Processing the input dynamic images in real time requires high performance hardware as well as efficient software. In order to relieve these requirements for detecting the useful information from the images in real time, a "Moving Window" scheme is proposed. Therefore, detecting the useful information, it becomes possible to search the obstacles within the driving corridor of an automobile or mobile robot. The feasibility of the proposed algorithm is demonstrated through the simulated experiments of the corridor driving.