• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1154-1162
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• 2014

In the restructured electricity market, Performance-Based Regulation (PBR) regime has been introduced to the distribution network. To ensure the network stability, this regime is used along with quality regulations. Quality regulation impose new financial risks on distribution system operators (DSOs). The poor quality of the network will result in reduced revenues for DSOs. The mentioned financial risks depend on the quality indices of the system. Based on annual variation of these indices, the cost of quality regulation will also vary. In this paper with regard to reclosing fault in distribution network, we develop a risk-based method to assess the financial risks caused by quality regulation for DSOs. Furthermore, in order to take the stochastic behavior of the distribution network and quality indices variations into account, time-sequential Monte Carlo simulation method is used. Using the proposed risk method, the effect of taking reclosing time into account will be examined on system quality indicators and the cost of quality regulation in Swedish rural reliability test system (SRRTS). The results show that taking reclosing fault into consideration, affects the system quality indicators, particularly annual average interruption frequency index of the system (SAIFI). Moreover taking reclosing fault into consideration also affects the quality regulations cost. Therefore, considering reclosing time provides a more realistic viewpoint about the financial risks arising from quality regulation for DSOs.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.191-196
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• 2007

The enhancement of flame stability in coflow jets has been investigated experimentally by observing the liftoff behaviors of nonpremixed propane and methane flames in the electric fields. The liftoff or blowoff velocities has been measured in terms of the applied AC voltages and frequency. The experimental results showed that the liftoff velocity could be extended significantly just by applying the high voltage to the central fuel nozzle both for propane and methane. As increasing the applied voltage, the liftoff velocity increases almost linearly with the applied voltage and have its maximum value at certain applied voltage. After that, the liftoff velocity showed decrease with the applied voltage. Through the experimental observation, we found that the liftoff velocity could be correlated well with the applied voltage and frequency in the linearly increasing regime. And after having maximum in the liftoff velocity, it was observed that the liftoff velocity decreases with the applied voltage irrespective of AC frequencies. To visualize the change of flame structure with electric fields, planar laser induced fluorescence technique was adopted, and the enhancement of flame stability has been explained based on the flame structural change in electric fields.

• Nuclear Engineering and Technology
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• 제33권4호
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• pp.409-422
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• 2001

The dynamic character of a system of the governing differential equations for the one- dimensional two-fluid model, where the momentum flux parameters are employed to consider the velocity and void fraction distribution in a flow channel, is investigated. In response to a perturbation in the form of a＇traveling wave, a linear stability analysis is peformed for the governing differential equations. The expression for the growth factor as a function of wave number and various flow parameters is analytically derived. It provides the necessary and sufficient conditions for the stability of the one-dimensional two-fluid model in terms of momentum flux parameters. It is demonstrated that the one-dimensional two-fluid model employing the physical momentum flux parameters for the whole range of dispersed flow regime, which are determined from the simplified velocity and void fraction profiles constructed from the available experimental data and $C_{o}$ correlation, is stable to the linear perturbations in all wave-lengths. As the basic form of the governing differential equations for the conventional one-dimensional two-fluid model is mathematically ill posed, it is suggested that the velocity and void distributions should be properly accounted for in the one-dimensional two-fluid model by use of momentum flux parameters.s.

• The Journal of Asian Finance, Economics and Business
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• 제9권2호
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• pp.29-36
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• 2022

This study uses the panel probit model to investigate and evaluate the relationship between exchange rate regimes, political stability, and carbon dioxide during currency crises. To understand currency crisis times, we study a panel dataset of seven South Asian nations that contain annual observations from 1996 to 2020. Furthermore, we created the EMPI exchange market pressure indicator to detect crises. Our results strongly suggested that fixed exchange rate is negatively associated with currency crises, with good regulatory quality and better effective governments. Simultaneously, the floating exchange rate is positively related to the currency crises in those countries where the rule of law has less adequately flowed. However, CO₂, exports, and interest rates are buoyantly associated with crises. The floating exchange rate, the rule of law, exports, and interest rate are associated positively and contribute more prone to the crisis episodes. Negatively associated variables contributed less amid crises episodes: fixed exchange rate regime, government effectiveness, and regulatory quality. Meanwhile, CO₂ has a positive relationship with a currency crisis and contributes more likelihood to the probability of a currency crisis. Countries that adopted the fixed exchange rates with effective governments and regulatory quality faced more minor currency crises.

• Tribology and Lubricants
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• 제30권3호
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• pp.189-198
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• 2014

This paper presents the results of an experimental investigation of the correlation between the lubrication characteristics of an engine and its fuel economy. Improving the lubrication characteristics of the engine oil is one of the most efficient ways to improve a car's fuel economy. The methods to accomplish this include lowering the viscosity, adding a friction modifier and optimizing the shear stability index of a viscosity index improver. In addition, it is necessary to use different methods to reduce the friction to individual lubrication areas, because different lubrication regimes are used for different engine parts. The experimental investigation in this study is based on design of experiments ; this paper presents the results of a modified Sequence VID test, which is an ASTM standard test used to measure the effects of automotive engine oils on the fuel economy of passenger cars. The results demonstrate the effects of the following lubrication factors on the fuel economy : the low temperature cranking viscosity, high-temperature high shear (HTHS) viscosity, friction modifier, polymer type and shear stability index of the viscosity index improver. Moreover, this study involves an analysis of variance based on design of experiments. The test results show that the HTHS viscosity, friction modifier and shear stability index of the viscosity index improver are more effective than the other factors. Therefore, lowering the viscosity, adding a friction modifier and optimizing the shear stability index of a viscosity index improver should be considered to improve fuel economy.

• Animal Bioscience
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• 제36권5호
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• pp.785-796
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• 2023

Objective: We aimed to evaluate the color and oxidative stability of beef gluteus medius (GM) from cattle raised in organic and non-organic production systems. Methods: The GM samples (n = 10) were obtained from organic (ORG; n = 5) or nonorganic (NORG; n = 5) beef samples, sliced into 2.54-cm steaks, packaged in aerobic conditions, and stored for nine days at 4℃. ORG and NORG steaks were compared regarding myoglobin concentration, pH, instrumental color, delta E (ΔE), metmyoglobin reducing activity (MRA), and lipid oxidation on days 0, 5, and 9. Results: Feeding system did not influence (p>0.05) the myoglobin concentration. ORG steaks exhibited greater (p<0.05) meat pH, yellowness, and MRA, whereas NORG steaks exhibited greater (p<0.05) redness, chroma, R630/580, delta E, and lipid oxidation. ORG and NORG steaks exhibited similar (p>0.05) lightness and hue angle. During storage, ORG and NORG exhibited an increase in muscle pH, hue angle, and lipid oxidation; and a decrease (p<0.05) in redness, yellowness, chroma, and color stability (R630/580). Both samples exhibited a stable (p>0.05) pattern for lightness and MRA. Conclusion: Therefore, the production system can affect beef color and lipid stability during storage.

• KDI Journal of Economic Policy
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• 제32권2호
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• pp.1-26
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• 2010

본 논문은 한국이 1997년 외환위기 이후 변동환율제 도입과 더불어 자본자유화로 자본시장이 글로벌화된 상황에서 외부로부터 독립적인 통화정책을 유지할 수 있었는지를 자본자유화 이전 기간과 비교하여 분석했다. 트릴레마 이론에 비추어보면, 자본자유화 이전에는 환율시장에 적극적으로 개입을 해도 이론적으로 독립적인 통화정책을 유지할 수 있는 여지가 있었으며, 자본자유화 이후에는 환율제도가 자유변동환율제도로 전환함에 따라 독립적인 통화정책을 유지할 수 있는 여지가 있었다. 하지만 한국과 같은 소규모 개방경제의 경우 자본시장이 완전히 개방되어 국가 간 연계성이 증가하고, 막대한 양의 국제자본 유출입이 발생하여 환율과 자산 시장의 심각한 불안정성을 초래할 수 있으므로 외국의 통화정책과 자본 흐름으로부터 완전히 자유로운 통화정책을 집행하기 어려울 수 있다. 본 논문의 실증분석에서는 부를 미국으로 국한하여 한국의 통화정책이 미국의 통화정책으로부터 독립적인지 블록 외생성 구조 VAR 모형을 이용하여 자세히 분석하였다. 그 결과 한국의 통화정책이 자본자유화 이전과 이후 두 기간 모두에서 미국의 통화정책으로부터 완전히 독립적으로 운용되지 못하였던 것으로 보인다. 자본자유화 이후 기간의 경우 완전한 변동환율제를 실제로 운용하기는 쉽지 않았고, 이로 인해 필연적으로 한국의 통화정책은 외부의 충격으로부터 완전히 독립적이지 못했던 것으로 보인다. 또한 자본자유화 이후 기간에는 포트폴리오 자본의 유출입이 자본자유화 이전 기간에 비해 매우 민감하게 변화하여 독립적인 통화정책의 운영에 어려움을 초래한 것으로 보인다. 따라서 향후 자본의 글로벌화에 효과적으로 대응하면서 통화정책을 독립적으로 유지할 수 있는 정책의 틀을 개발하는 것이 시급하다고 하겠다.

• 융합보안논문지
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• 제18권3호
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• pp.113-122
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• 2018

한반도는 안보문제에 있어서 2018년에 남북 및 북미 정상회담을 계기로 최대의 격변을 겪고 있다. 북한은 정상회담을 통해 기존의 군사와 경제를 병행하여 발전시키려는 노선을 핵 포기를 통한 경제 중심의 노선으로 변경하여 추진하고 있으며, 이는 정상회담을 통해 자국의 경제적인 이득을 확보하기 위한 전략의 핵심이다. 이러한 노선의 변화는 리비아의 핵 포기 상황과 유사하게 흘러가고 있으며, 리비아의 사례(모델)을 교훈으로 왜 북한의 노선 변화가 있었고, 이후 북한의 핵 정책을 포함한 국가전략이 어떻게 변화될 것인가에 대해 전망이 필요한 시기이다. 리비아 모델은 국제적, 국내적, 국가 지도부의 정세 인식 측면으로 구분하여 분석/구축되었으며, 이를 기반으로 북한의 핵 정책 노선을 평가하였다. 또한 리비아의 핵 포기 이후 국가 상황을 북한과 비교하여 일부 전망해 보았다. 리비아 및 북한에게 핵 개발은 국제사회의 외교적, 경제적 압박은 체제의 불안정성을 가져오게 되었고, 이를 타개하기 위해 핵을 포기하고 경제적인 이득을 추구하도록 하였다. 하지만 리비아는 경제적 실리와 체제의 안정성은 일부 보장받았지만, 유입된 해외자본 및 사상/문화로 인해 민주주의의 물결 속에서 카다피 정권이 무너지는 결과가 있었다. 북한은 이러한 리비아의 사례를 기반으로 외교적, 경제적인 실리는 추구하겠지만, 부수적으로 유입될 수도 있는 민주주의 문화, 자유시장의 완전한 개방논리는 최대한 제한하려고 노력할 것이다.

• Korea-Australia Rheology Journal
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• 제14권1호
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• pp.33-45
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• 2002

Recent results obtained for the port-pom model and the constitutive equations with time-strain separability are examined. The time-strain separability in viscoelastic systems Is not a rule derived from fundamental principles but merely a hypothesis based on experimental phenomena, stress relaxation at long times. The violation of separability in the short-time response just after a step strain is also well understood (Archer, 1999). In constitutive modeling, time-strain separability has been extensively employed because of its theoretical simplicity and practical convenience. Here we present a simple analysis that verifies this hypothesis inevitably incurs mathematical inconsistency in the viewpoint of stability. Employing an asymptotic analysis, we show that both differential and integral constitutive equations based on time-strain separability are either Hadamard-type unstable or dissipative unstable. The conclusion drawn in this study is shown to be applicable to the Doi-Edwards model (with independent alignment approximation). Hence, the Hadamardtype instability of the Doi-Edwards model results from the time-strain separability in its formulation, and its remedy may lie in the transition mechanism from Rouse to reptational relaxation supposed by Doi and Edwards. Recently in order to describe the complex rheological behavior of polymer melts with long side branches like low density polyethylene, new constitutive equations called the port-pom equations have been derived in the integral/differential form and also in the simplifled differential type by McLeish and carson on the basis of the reptation dynamics with simplifled branch structure taken into account. In this study mathematical stability analysis under short and high frequency wave disturbances has been performed for these constitutive equations. It is proved that the differential model is globally Hadamard stable, and the integral model seems stable, as long as the orientation tensor remains positive definite or the smooth strain history in the flow is previously given. However cautious attention has to be paid when one employs the simplified version of the constitutive equations without arm withdrawal, since neglecting the arm withdrawal immediately yields Hadamard instability. In the flow regime of creep shear flow where the applied constant shear stress exceeds the maximum achievable value in the steady flow curves, the constitutive equations exhibit severe instability that the solution possesses strong discontinuity at the moment of change of chain dynamics mechanisms.

• Strategy21
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• 통권33호
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• pp.148-177
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• 2014

The regional security and stability in Northeast Asia has become more complicated because of a sudden establishment of China's Air Defense Identification Zone (ADIZ) on 23 November 2013. One dimensional conflicts on the territorial sovereignty over the islands between the regional States has developed into the two dimensional conflicts like maritime delimitations among the States concerned since they have all ratified the 1982 United Nations Convention on the Law of the Sea which adopts the 200 nautical mile Exclusive Economic Zone regime. Moreover, due to the notion of the outer limit of the continental shelf, the conflicts have developed into three dimensional ones in order to acquire more natural resources even in the seabed. To make matters worse, such three dimensional conflicts have expanded to the airspace as well. The paper will analyze what implications the sudden declaration of China's ADIZ have for the regional security in Northeast Asia from the perspectives of public international law. To this end, the paper 1) starts with the debates on the legal nature of the ADIZ, 2) identifies the Chinese government's political motives for the establishment of the ADIZ over the East China Sea, 3) assesses the responses of the regional States and the USA to the China's establishment of the ADIZ, and then 4) discuss what implications the overlapped ADIZ of the three key States in the region have for the regional security and stability.