• Wind and Structures
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• 제23권4호
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• pp.351-366
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• 2016

Nowadays, wind energy is the most rapidly developing technology and energy source and it is reusable. Due to its cleanliness and reusability, there have been rapid developments made on transferring the wind energy systems to electric energy systems. Converting the wind energy to electrical energy can be done only with the wind turbines. So installing a wind turbine depends on the wind speed at that location. The expected wind power can be estimated using a perfect probability distribution. In this paper Weibull and Weibull distribution with multiple parameters has been used in deriving the mathematical expression for estimating the wind power. Statistically the parameters of Weibull and Weibull distribution are estimated using the maximum likelihood techniques. We derive a probability distribution for the power output of a wind turbine with given rated wind speeds for the regions where the wind speed histograms present a bimodal pdf and compute the first order moment of this distribution.

• 한국언어정보학회지:언어와정보
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• 제14권1호
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• pp.145-163
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• 2010

This paper aims to propose that Benford's Law, non-uniform distribution of the leading digits in lists of numbers from many real-life sources, also appears in linguistic texts. The first digits in the frequency lists of morphemes from Sejong Morphologically Analyzed Corpora represent non-uniform distribution following Benford's Law, but showing complexity of numerical sources from complex systems like earthquakes. Benford's Law in texts is a principle reflecting regular distribution of low-frequency linguistic types, called LNRE(large number of rare events), and governing texts, corpora, or sample texts relatively independent of text sizes and the number of types. Although texts share a similar distribution pattern by Benford's Law, we can investigate non-uniform distribution slightly varied from text to text that provides useful applications to evaluate randomness of texts distribution focused on low-frequency types.

• 한국물환경학회지
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• 제23권1호
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• pp.1-11
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• 2007

The low nutrient environment in drinking water treatment plants and distribution systems cannot to be a good environment for bacterial growth. However, biofilms can be frequently found submerged surface in treatment plants and distribution system. Biofilms in distribution system are harmful, in that they can release organisms, and may cause problems in taste and odor of water. Control of these Biofilms is difficult, and disinfection alone is usually ineffective. Biofilms will not be eliminated from distribution systems by any contemporary technology available now or in the future. Therefore reduction of organic matter, improved disinfection, or a combination of these methods can be useful in controlling distribution system biofilms.

• 한국환경보건학회지
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• 제28권5호
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• pp.42-52
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• 2002

배수관망에서의 박테리아 재 증식은 큰 현안문제로 대두되고 있으며 이를 억제하기 위한 염소소독 또한 발암성의 부산물인 THMs(trihalomethanes)등을 생성시킬 우려 때문에 미국에서는 오존살균처리 또는 나노여과 (nanofiltration) 법으로 대체해 오고 있다. 그러나 종래의 많은 bench scale 실험결과를 통해 이러한 처리 이후에 잔존하는 미량의 유기물(assimilable organic carbon)이 박테리아 재 증식에 계속하여 영향을 주고 있다는 결과가 AOC(assimilable organic carbon)와 박테리아 재증식의 상관관계를 통하여 밝혀지고 있다. 그러나 현재까지 이러한 연구결과를 full-scale규모의 현장시설에서 직접 검토한 예는 없다. 따라서 본 실험은 미국플로리다주에 위치한 두 지역의 full-scale배수관망 시설을 선정하여 실시하였다. 첫 번째 시설은 오존 살균처리를 그리고 다른 한곳은 나노여과와 석회 연수법 (lime softening)을 병행한 처리법을 사용하고 있다. 박테리아 증식은 R2A 배지를 사용하는 HPC(heterotrophic plate counts)법으로 평가했으며 오존이 공급된 배수관망에서의 HPC 는 각 셈플링 지점의 AOC값을 이용한 지수모델과 높은 상관관계가 있음이 판명되었다($R^2$=0.97). 또한 오존처리는 100%이상의 AOC 농도증가를 나타냈다. 나노여과법과 석회연수법을 병행하고 있는 시설에서도 AOC에 근거한 지수모델과 상관관계를 나타냈다($R^2$=0.75). 그러나 BDOC(biodegradable dissolved organic carbon)는 박테리아 증식에 있어 매우 낮은 상관관계 값을 표시했다($R^2$=0.11). 결과적으로 종래의 많은 bench scale실험결과와 같이 AOC는 배수관망에서의 박테리아 증식과 크게 상관관계를 갖고 있는 것으로 밝혀졌다.

• Journal of Astronomy and Space Sciences
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• 제27권1호
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• pp.1-10
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• 2010

The distance distribution in our planetary system has been a controversial matter. Two kinds of important issues on Titius-Bode's relation have been discussed up to now: one is if there is a simple mathematical relation between distances of natural bodies orbiting a central body, and the other is if there is any physical basis for such a relation. We have examined, by applying it to exo-planetary systems, whether Titius-Bode's relation is exclusively applicable to our solar system. We study, with the $X^2$ test, the distribution of period ratios of two planets in multiple planet systems by comparing it with that derived from not only Titius-Bode's relation but also other forms of it. The $X^2$ value between the distribution of the orbital period derived from Titius-Bode's relation and that observed in our Solar system is 12.28 (dof=18) with high probability, i.e., 83.3 %. The value of $X^2$ and probability resulted from Titius-Bode's relation and observed exo-planetary systems are 21.38 (dof=26) and 72.2 %, respectively. Modified forms we adopted seem also to agree with the planetary system as favorably as Titius-Bode's relation does. As a result, one cannot rule out the possibility that the distribution of the ratio of orbiting periods in multiple planet systems is consistent with that derived from Titius-Bode's relation. Having speculated Titius-Bode's relation could be valid in exo-planetary systems, we tentatively conclude it is unlikely that Titius-Bode's relation explains the distance distribution in our planetary system due to chance. Finally, we point out implications of our finding.

• 신재생에너지
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• 제10권3호
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• pp.47-54
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• 2014

Recently, BESS is considered as one of essential countermeasure for demand side management. However, an economic evaluation is critical issue for the introduction of power system because the cost of BESS is very high in present stage. Therefor, this paper presents economic evaluation method for customer use case by considering peak shaving function based on the real time price. From the case study on the model power system and educational customer, it is confirmed that the proposed method is a practical tool for the economic analysis of BESS. and analytical approach for the reliability assessment in radially operated distribution systems. The approach can estimate the expected reliability performance of distribution systems by a direct assessment of the configuration of the systems using the reliability indexes such as NDP (Non-Delivery Power) and NDE (Non-Delivery Energy). The indexes can only consider the number and configuration of the load, but can not consider the characteristics of the load which is the one of the most important factor in the investment cost for the distribution systems. Therefore, this paper presents the new performance indexes for the investment of the distribution facilities considering both the expected interruption cost for the load section and the operation characteristics of Energy Storage System. The results from a case study show that the proposed methods can be a practical tool for the reliability management in distribution systems including Energy Storage System.

• 전기학회논문지
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• 제65권5호
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• pp.753-759
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• 2016

Power automation system to operate power distribution systems can be distinguished by distribution SCADA with remote monitoring and control; and distribution automation system with basic functions such as service restoration to the distribution SCADA; and distribution management system which is operated by various applications in order to enhance distribution system operation performance based on the distribution automation system. In the technological change, a technical boundary of information technology (IT) and operation technology (OT) is being blurred by that new concepts such as interoperability. In addtion, IT/OT convergence has been proposed by the improvement of ICT and power system technology. At the viewpoint, advanced distribution management system (ADMS) to have the new concepts and to increase distribution system operation efficiency through global information and functions from the other systems has been proposed. In order to implement the ADMS, IT and OT have to be employed together on the ADMS; and the concept-based IT/OT convergence concept has been presented. Therefore, this paper introduces ADMS and IT/OT convergence and proposes a design of IT/OT convergence based ADMS system design with configurations and functions.

• 전기학회논문지
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• 제56권3호
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• pp.472-480
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• 2007

This paper analyzes overvoltage on testing line for various parameter effect examination. Model systems consist of overhead line and underground cable. The model considered actual characteristic data of distribution lines. and will be constructed at testing yard. The simulations were performed under various line configuration such as cable kinds, cable length, lightning wave, lightning wave time, transformer and branch circuits. The simulation models are established by EMTP/ATPDraw and Line Constants are calculated by ATP_LCC. When lightning surge strikes on conductor of overhead line, EMTP/ATPDraw calculates overvoltage in many cases. Simulation results will be compared with real testing results at testing yard. The compared results will be used to establish protection methods in actual underground distribution systems.

• 한국조명전기설비학회지:조명전기설비
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• 제9권5호
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• pp.64-70
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• 1995

This paper presents a practical approach to evaluate the reliability indices of electric distribution systems. The use of reliability evaluation is placed with framework of distribution system planning and operation. In this paper, the reliability model is based on an analytical method, connecting component failure to load point outage in each section. Five cases are reported in the paper to study the effect of varying failure rates and repair times on real distribution systems. Simulations are preformed by the developed reliability evaluation program.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.147-149
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• 2000

This paper describes a power flow method for distribution systems, applying the method of symmetrical component to back/forward sweep method. The proposed algorithm is effective for unbalanced radial distribution system, with process of distributed resource(PQ & PV node), AVR(Auto Voltage Regulator), shunt capacitor. This proposed method compared conventional back/forward sweep method with the using three phase unbalanced distribution systems with 34 nodes.