• Textile Coloration and Finishing
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• v.34 no.3
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• pp.207-216
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• 2022

Hydrogels have gained considerable attention in various fields due to their easily transformative ability by different stimulation. In addition, metal-based conductive additives can enable the hydrogels to be conductive with dimension change. Although the development of the additives offered enhanced electrical properties to the hydrogels, correspondingly enhanced mechanical properties may limit the volume and electrical properties switching after stimulation. Here we prepared poly(N-isopropylacrylamide) (PNIPAM) thermo-responsive hydrogel that has a 32℃ of low critical solution temperature and added liquid metal particles (LMPs) as conductive additives, possessing soft and stretchable benefits. The LMPs enabled PNIPAM (PNIPAM/LMPs) hydrogels to be constricted over 32℃ with a high volume switching ratio of 15.2 when deswelled. Once the LMPs are spontaneously oxidized in hydrogel culture, the LMPs can release gallium ions into the hydrogel nature. The released gallium ions and oxidized LMPs enhanced the modulus of the PNIPAM/LMPs hydrogel, triggering high mechanical stability during repeated swelling/deswelling behavior. Lastly, highly constricted PNIPAM/LMPs hydrogel provided a 5x10⁶ of electrical switching after deswelling, and the switching ratio was closely maintained after repeated swelling/deswelling transformation. This study opens up opportunities for hydrogel use requiring thermo-responsive and high electrical switching fields.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.1
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• pp.25-33
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• 2008

This paper presents a new approach of a evaluation of location marginal prices(LMPs) considering demand response resources in the competitive electricity market. The stabilization of the electric power supply and demand balance has been one of the major important activities in electric power industry. Recently, much attention is paid to the demand-side resources which are responsive to incentives or time-varying prices and existing power system planning and operation activities are incorporated with the so-called demand response resources. In this paper, we first present an analytical method for calculation of LMPs considering demand response resources and then break down the LMPs into three components. In this study, we assume that Korean power system consists of two major regions, one which is the metropolitan and the other is non-metropolitan region. In the case study, we have considered several LMPs cases with different use of locational demand response resource and we can obtain a locational signal to demand response resources. Also, the economics of demand response resources are evaluated, compared with the increase of transmission line capacity and of generation capacity.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1157-1166
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• 2008

This paper presents a new approach for the evaluation of location marginal prices (LMPs) considering demand-side bidding (DSB) in a competitive electricity market. The stabilization of the electric power supply and demand balance is one of the major important activities in electric power industry. In this paper, we present an analytical method for calculation of LMPs considering DSB, which has opportunity to compete with generating units, as England & Wales Pool's DSB scheme[1]. Also, we propose a new approach that LMP considering DSB is divided into three components. The proposed approach can be used for the evaluation of demand-side bidding into the electricity market and the assessment of the influence of DSB on total production costs and LMPs as well as three components.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1480-1491
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• 2015

In new deregulated electricity market, short-term price forecasting is key information for all market players. A better forecast of market-clearing price (MCP) helps market participants to strategically set up their bidding strategies for energy markets in the short-term. This paper presents a new prediction strategy to improve the need for more accurate short-term price forecasting tool at spot market using an artificial neural networks (ANNs). To build the forecasting ANN model, a three-layered feedforward neural network trained by the improved Levenberg-marquardt (LM) algorithm is used to forecast the locational marginal prices (LMPs). To accurately predict LMPs, actual power generation and load are considered as the input sets, and then the difference is used to predict price differences in the spot market. The proposed ANN model generalizes the relationship between the LMP in each area and the unconstrained MCP during the same period of time. The LMP calculation is iterated so that the capacity between the areas is maximized and the mechanism itself helps to relieve grid congestion. The addition of flow between the areas gives the LMPs a new equilibrium point, which is balanced when taking the transfer capacity into account, LMP forecasting is then possible. The proposed forecasting strategy is tested on the spot market of the Nord Pool. The validity, the efficiency, and effectiveness of the proposed approach are shown by comparing with time-series models

• Coupled systems mechanics
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• v.12 no.6
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• pp.503-517
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• 2023

Standard Digital Volume Correlation (DVC) approaches are based on pattern matching between two reconstructed volumes acquired at different stages. Such frameworks are limited by the number of scans (due to acquisition duration), and time-dependent phenomena can generally not be captured. Projection-based Digital Volume Correlation (P-DVC) measures displacement fields from series of 2D radiographs acquired at different angles and loadings, thus resulting in richer temporal sampling (compared to standard DVC). The sought displacement field is decomposed over a basis of separated variables, namely, temporal and spatial modes. This study utilizes an alternative route in which spatial modes are con-structed via scan-wise DVC, and thus only the temporal amplitudes are sought via P-DVC. This meth-od is applied to a glass fiber mat reinforced polymer specimen containing a machined notch, subjected to in-situ cyclic tension, and imaged via X-Ray Computed Tomography. Different temporal interpolations are exploited. It is shown that utilizing only one DVC displacement field (as spatial mode) was sufficient to properly capture the complex kinematics up to specimen failure.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.193-198
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• 1997

본 논문의 목적은 현재 사용중인 원자력발전소내 금속파편 감시계통 (LMPS: Loose Part Monitoring System)에서 금속파편의 발생위치 평가시 온라인화된 방식을 제안하고 그 효용성을 알아보는 것이다. 현재 사용중인 LMPS들은 센서들을 통해서 기준 진폭수준 이상의 신호가 입력될 때 경보음이 울리고 신호가 기록되도록 되어있다. 이렇게 기록된 신호를 전문가가 분석함으로써 발생한 금속파편 위치 및 계통손상 가능성 등을 평가한다. 그러나 이러한 방법에 의한 신호평가시 경험이 풍부한 전문가에 의해 파편위치 및 손상부위를 평가해야 하므로 많은 시간이 소요되고 금속파편에 의한 손상 잠재성이 큰 경우 즉각적인 조치를 취할 수가 없어 방사능 누출 등의 위험한 상황에 처할 수 있다. 따라서 본 논문에서는 이러한 점에 착안하여 센서로부터의 입력신호 분석 및 평가를 위한 온라인 기법을 제안하고 구조물 모형을 이용한 실험결과를 통하여 그 효용성을 입증한다.

• Environmental and Resource Economics Review
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• v.11 no.1
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• pp.57-79
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• 2002

동 연구는 미국 캘리포니아주 San Joaquin Valley의 고정오염원들로부터 발생되는 ROG(Reactive Organic Gases) 배출량을 저감하기 위하여 명령통제방식(CAC)과 경제적 유인제도를 적용할 경우의 비용효과성을 비교 분석하였다. 경제적 유인제도로서는 UMPS(uniform marketable permit system)와 LMPS(localized marketable permit system) 배출권거래제도를 적용하였다. 분석결과 배출권거래제도(UMPS, LMPS)를 이용한 ROG 배출량 저감이 명령통제방식보다 비용이 적게 드는 것으로 나타났다. 한편, one-to-one permits trading이 허용되는 UMPS의 경우에는 일부 특정 지역에 대한 환경질이 악화되는 결과를 초래하는 경우가 발생하여, 궁극적으로 San Joaquin Valley의 ROG 배출량 저감을 위해서는 UMPS 방식의 배출권거래제도 도입이 보다 바람직한 것으로 나타났다.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.4
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• pp.156-162
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• 2006

Transmission zones can be defined based on LMPs. Each zone consists of nodes with similar LMPs, and zonal price is determined by average nodal prices in each zone.[1] Network reduction is still important for the analysis of zonal systems under electricity market environments, even though the computing capability of computer system can deal with entire power systems. The Similarity Index is a good performance measure for the network reduction.[2] It can be applied to the network reduction between zones categorized by the nodal prices. This paper deals with a novel network reduction method between zones based on the similarity Index. Line admittances of reduced network were determined by using the least square method. The proposed method was verified by IEEE 39 bus test system.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.153-154
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• 2008

This paper presents a window-based software package for the education and training for the reduction of power system by using locational marginal price (LMP), clustering, and similarity indices of each bus. The developed package consists of three modules: 1) the LMP module, 2) the Clustering module and 3) the Reduction module. Each module has a separated and interactive interface window. First of all, LMPs are created in the LMP module, and then the Clustering module carries out clustering based on the results of the LMP module. Finally, groups created in this Clustering module are reduced by using the similarity indices of each bus. The developed package displays a variety of tables for results of the LMPs of base network, voltages, phases and power flow of reduced network so that the user can easily understand the reduction of network. To demonstrate the performance of the developed package, it is tested for the IEEE 39-bus power system.

• Computers and Concrete
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• v.31 no.5
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• pp.395-403
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• 2023

The paper investigates the effect of two parameters - sand content (SC) and grain migration during shearing - on the mechanical properties of gravel-sand mixtures. Consolidated undrained (CU) triaxial tests were carried out on eight series of mixtures containing gravel (1<d<16 mm) and sand (0.1<d<1 mm). The prepared mixtures have sand contents of 0, 10, 15, 20, 40, 54, 94 and 100%, and a relative density of 60%. The transition sand content (TSC) is experimentally defined and marks the transition from gravel-driven to sand-driven behavior. For SC<TSC, the dry density of the mixture increases with SC. This induces an increase in undrained peak strength and dilative trend. The slope and position of the critical state line (CSL) are also deeply dependent on SC. At SC=TSC, the mixtures exhibit the largest dry density and yield the highest undrained peak strength and the largest dilative trend. During shearing, large internal migration of grains was observed at the TSC, causing heterogeneity in the sample. Analysis of the CSL deduced from the final points of the triaxial tests shows that, at the TSC, failure appears to correspond to the behavior of the coarsest fraction of the soil. This fraction is located in the upper part of the sample, where the sand particles had been eliminated by suffusion. On the other hand, in the more stable materials, the CSL is consistent with the bulk grain size distribution of the soil.