• The Journal of the Acoustical Society of Korea
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• 제19권1E호
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• pp.27-37
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• 2000

This paper presents a simplified analytical formulation for computing acoustic power radiation from a rectangular plate exposed to random forces such as turbulent boundary layer pressure fluctuations and arbitrary mechanical force in a subsonic flow field. The expression for the acoustic power is derived using modal expansion method and light fluid loading is assumed on the plate. In order to simplify the formulation for acoustic power due to combined excitations of mechanical forces and turbulent pressures, it is assumed that the structural damping of the plate is small and excitations are broadband random forces having frequency spectra above the convective coincidence. Under these assumptions, an approximate solution for the broadband acoustic power radiation from a plate excited by both turbulent pressures and arbitrary mechanical forces is obtained and evaluated considering the effect of modal coupling on the radiated acoustic power. An efficient method is also suggested to compute modal acoustic impedance in a moving fluid medium by using averaged Green function.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2012년도 추계학술대회
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• pp.793-796
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• 2012

최근 에너지 소비의 지속적 증가 및 에너지 가격의 급격한 상승으로 그린 IT 도입 운영이 필수적인 요소로 인식됨에 따라 서버 발열 및 데이터센터 에너지 절감을 위해 IT 인프라는 클라우드 컴퓨팅 플랫폼으로 대체 되어가고 있다. 본 연구에서는 일반 저비용 웹서비스 인프라를 오픈소스 기반 클라우드 플랫폼으로 변환하고 Linux Virtual Server 로드 밸런싱을 구현하여 그 성능을 분석하였다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2003년도 추계학술발표논문집 (중)
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• pp.781-784
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• 2003

본 논문은 Directory Service(white page, yellow page, green page)를 분산환경에 적합하고 시스템 유연성을 고려하기 위해서 EJB(Enterprise Java Bean)기반 Webservice로 구현한 방법론 및 그 시스템에 관한 논문이다. 기존 개발된 Directory Service가 대부분 폐쇄적 네트워크를 사용하고 있으므로 시스템 자체에 유연성이 없는 정적인 시스템으로 구현이 되어있고, 플랫폼에 의존하는 아키텍쳐로 설계 되었다. 따라서 본 논문은 이러한 서비스 비개방 특성을 극복하기 위해서 개발 아키텍쳐를 웹서비스(Web Service)환경을 기본으로 하고 분산컴퓨팅환경(Distributed Computing Environment)의 특성을 고려하기 위해서 EJB로 개발이 되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권8호
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• pp.1825-1842
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• 2013

Rapid growth of the IT industry has led to significant energy consumption in the last decade. Data centers swallow an enormous amount of electrical energy and have high operating costs and carbon dioxide excretions. In response to this, the dynamic consolidation of virtual machines (VMs) allows for efficient resource management and reduces power consumption through the live migration of VMs in the hosts. Moreover, each client typically has a service level agreement (SLA), this leads to stipulations in dealing with energy-performance trade-offs, as aggressive consolidation may lead to performance degradation beyond the negotiation. In this paper we propose a heuristic based resource allocation of VM selection and a VM allocation approach that aims to minimize the total energy consumption and operating costs while meeting the client-level SLA. Our experiment results demonstrate significant enhancements in cloud providers' profit and energy savings while improving the SLA at a certain level.

• 디지털산업정보학회논문지
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• 제7권3호
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• pp.43-53
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• 2011

The many cities are changing in the city form where the person and nature are mixed. Namely, the government invests many expense in tree field of distance space for the change in the green city. In this paper, we design and implement a tree growth management system using PDA built in 13.56MHz RFID reader and CBD(Component Based Development) for ubiquitous computing environments. Our system provides history management to increase business efficiency for location coordinate of tree and history information of tree which using RFID, the RFlD tag is attaching the new tree and that is inputting GPS location information in PDA and provides tree information of tree by location coordinate to history management. Finally, we show from a performance analysis that our system achieves about 85% average tree read rate of RFID under test scenario environments.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.613-616
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• 1998

In this paper, a model of a Eddy-current probe coil with a ferrite core in the presence of a half-space with a layer is developed. The half-space with a layer is accounted for by computing the appropriate Green's function by using Bessel transforms. Upon introducing equivalent Amperian currents within a core to explain effect to a impedance change in the coil due to a (ferrite) core, we derive a volume integral equation, The integral equation is transformed via the method of moments into a vector-matrix equation, which is then solved using a linear equation solver. Through the above processing, we computed impedance value in a Eddy-current probe coil due to a conductivity change of layer.

• 대한교통학회지
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• 제18권2호
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• pp.73-89
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• 2000

본 연구에서는 평균차량통행량 대신 매주기마다 입력되는 대기차량, 차량도착율을 기초로 대기차량을 최소화하는 동적신호시간 결정모형을 개발하였다. 본 모형은 각 진입로에서의 대기차량예측모델을 기초로 하여 다음 주기에서의 대기차량을 예측한 후 유전자 알고리즘을 적용하여 신호시간을 산출하였다. 본 모형에서 산출된 신호주기와 녹색시간은 대기차량길이를 최소화하는 신호시간으로서 교차로간의 연동효과를 고려하여 실시간 교통 상황에 따라 주기별로 변화한다. 본 모형은 3개의 교차로로 구성되어 있는 간선도로를 대상으로 적용하였다. 이 모형은 MATLAB으로 구현하였으며, 동일한 조건 하에서 정주기식으로 신호시간을 주었을 때의 통과차량, 주기, 현시, 대기차량 등을 구하여 본 모형의 결과와 비교 및 평가를 실시하였다. 실험결과 포화상태나 포화상태의 경우 모두 정주기식보다는 동적으로 신호를 계산하는 본 모형이 더 좋은 결과를 나타내었다. 또한. 적합도 함수를 변형하여 Inbound, Balanced, Outbound 연동상황을 설정하여 수행한 경우 주방향의 대기차량이 상대적으로 다른 방향에 비해 감소하였으며, 주방향에 대한 연동효과를 나타내었다.

• 한국정보통신학회논문지
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• 제15권6호
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• pp.1391-1396
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• 2011

노동 집약적인 농업의 생산성을 높일 수 있는 방법은 IT 기술을 접목시키는 것이다. 유비쿼터스 컴퓨팅의 대표적인 기술은 교통, 자동차, 건설, 군방, 헬스, 농업, 의료 서비스 등 사회 전 분야에 적용되고 있다. 이러한 IT 기술은 전통산업 간의 융합기술 개발이 새로운 화두로 부상하고 있다. 유비쿼터스 농업 환경을 성공적으로 구축하기 위해서는 센서노드 H/W, 센서노드 미들웨이 플랫폼, 라우팅 프로토콜, 농업환경 응용 서비스 등 농업에 최적화된 핵심기술 개발이 필요하다. 본 논문에서는 정밀한 식물 생장환경관리를 위해서 재배온실에 환경요인 모니터링 센서 및 생체 정보 센서들을 이용하여 그린 생장환경 관리 시스템을 제안했다. 제안한 시스템을 이용하면 사용자는 저비용으로 특화된 융복합 농업을 실현할 수 있을 것으로 사료된다.

• Journal of Communications and Networks
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• 제18권4호
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• pp.540-550
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• 2016

Since energy efficiency has become a significant concern for network infrastructure, next-generation network devices are expected to have embedded advanced power management capabilities. However, how to effectively exploit the green capabilities is still a big challenge, especially given the high heterogeneity of devices and their internal architectures. In this paper, we introduce a hierarchical power management architecture (HPMA) which represents physical components whose power can be monitored and controlled at various levels of a device as entities. We use energy aware state (EAS) as the power management setting mode of each device entity. The power policy controller is capable of getting information on how many EASes of the entity are manageable inside a device, and setting a certain EAS configuration for the entity. We propose the optimal local control policy which aims to minimize the router power consumption while meeting the performance constraints. A first-order Markov chain is used to model the statistical features of the network traffic load. The dynamic EAS configuration problem is formulated as a Markov decision process and solved using a dynamic programming algorithm. In addition, we demonstrate a reference implementation of the HPMA and EAS concept in a NetFPGA frequency scaled router which has the ability of toggling among five operating frequency options and/or turning off unused Ethernet ports.

• 한국농공학회논문집
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• 제63권4호
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• pp.87-96
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• 2021

Determining design rainfall is the first step to plan an agricultural drainage facility. The objective of this study is to evaluate whether the current method for parameter estimation is reasonable for computing the design rainfall. The current Gumbel-Kendall (G-K) method was compared with two other methods which are Gumbel-Chow (G-C) method and Probability weighted moment (PWM). Hourly rainfall data were acquired from the 60 ASOS (Automated Synoptic Observing System) stations across the nation. For the goodness-of-fit test, this study used chi-squared (𝛘²) and Kolmogorov-Smirnov (K-S) test. When using G-K method, 𝛘² statistics of 18 stations exceeded the critical value (𝑥²_a=0.05,df=4=9.4877) and 10, 3 stations for G-C method, PWM method respectively. For K-S test, none of the stations exceeded the critical value (D^a=0.05_n=0.19838). However, G-K method showed the worst performances in both tests compared to other methods. Subsequently, this study computed design rainfall of 48-hour duration in 60 ASOS stations. G-K method showed 5.6 and 6.4% higher average design rainfall and 15.2 and 24.6% higher variance compared to G-C and PWM methods. In short, G-K showed the worst performance in goodness-of-fit tests and showed higher design rainfall with the least robustness. Likewise, considering the basic assumptions of the design rainfall estimation, G-K is not an appropriate method for the practical use. This study can be referenced and helpful when revising the agricultural drainage standards.