• Journal of the Korean Solar Energy Society
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• v.35 no.2
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• pp.43-52
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• 2015

The performance of a photovoltaic array is affected by temperature, solar insolation, partial shading effect, and array configuration. Maximum power point tracking(MPPT) techniques are employed in photovoltaic systems to make full utilization of the PV array output power which depends on solar irradiation and ambient temperature. As much as MPPT is important in photovoltaic systems, many MPPT techniques have been developed. In this paper, several major existing MPPT methods are comparatively analyzed and novel hybrid MPPT algorithm is proposed. The proposed hybrid MPPT algorithm is developed in combination with traditional MPPT methods to complement each other for improving performance and mitigating partial shading effects. The proposed algorithm is implemented and validated using MATLAB/Simulink simulation tool.

• Journal of KIISE:Databases
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• v.32 no.2
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• pp.151-160
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• 2005

As web pages are created, destroyed, and updated frequently, web databases should be updated to keep up-to-date web pages. In order to keep web databases fresh effectively, we need to understand the change of real web pages. Previous researches on the change of the web pages have directed their efforts on the contents modification of web pages only, and have not taken into account the factors of creation and destruction of web pages In their research. This paper investigates the web page changes, which include contents modification, page creation, and page destruction. We introduce three metrics, namely DR (Download Rate), MR (Modification Rate), and CAV (Coefficient of Age Variation) to represent the change of the web pages. We have monitored three million web pages collected from the famous and random sites every other day for one hundred days. With the Download Rate and the Modification Rate, we learned that the download success and the modification depends on the past change of them, and proposes two estimation formulae that predict the download success and modification. With the Coefficient of Age Variation, we show how web pages do not change periodically.