http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Dong-Eok Kim,Namhun Cho 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.2
In this paper, we propose a method to search candidates of network reconfiguration to restore distribution system with distributed energy resources using a level-based tree search algorithm. First, we introduce a method of expressing distribution network with distributed energy resources for fault restoration, and to represent the distribution network into a simplified graph. Second, we explain the tree search algorithm, and introduce a method of performing the tree search on the basis of search levels, which we call a level-based tree search in this paper. Then, we propose a candidate search method for fault restoration, and explain it using an example. Finally, we verify the proposed method using computer simulations.
Kim, Dong-Eok,Cho, Namhun,Yang, Seung-Kwon Korea Electric Power Corporation 2016 KEPCO Journal on electric power and energy Vol.2 No.4
In this paper, we propose a method to develop a static equivalent model of an inverter-based distributed energy resource (DER), where the model is used for a steady-state fault analysis of a power grid. First, we introduce the characteristics of an inverter-based DER as well as its general configuration. Then, we derive the equivalent model of the DER on the basis of the characteristics. Last, the performance of the proposed method is proven by the results of computer simulations.
Kim, Jeong-Yeon,Park, Jong-Ho,Jeong, Sang-Wuk,Schellingerhout, Dawid,Park, Jin-Eok,Lee, Dong Kun,Choi, Won Jun,Chae, Seok-Lae,Kim, Dong-Eog 대한신경과학회 2011 Journal of Clinical Neurology Vol.7 No.4
<P><B>Background and Purpose</B></P><P>Remnant lipoproteins (RLPs) are products of partially catabolized chylomicrons and very-low-density lipoprotein, from which some triglycerides have been removed. These particles are smaller and denser than the parent particles and are believed to be strongly atherogenic. We explored the association between RLP cholesterol (RLP-C) and ischemic stroke, including stroke subtypes.</P><P><B>Methods</B></P><P>A cohort of 142 ischemic stroke patients (90 men and 52 women; age, 65.2±12.8 years, mean±SD) was enrolled; all had acute infarcts confirmed by diffusion-weighted MRI, and had fasting lipograms. A full stroke-related evaluation was conducted on each patient. An outpatient population of 88 subjects without a history of cerebrovascular or cardiovascular disease served as a control group. Serum RLP fractions were isolated using an immunoaffinity gel containing specific antiapolipoprotein (anti-apo)B-100 and anti-apoA-I antibodies. RLP-C values were considered to be high when they were in the highest quartile of all values in the study.</P><P><B>Results</B></P><P>High RLP-C values were more common in stroke patients than in control patients (31.0% vs. 14.8%, <I>p</I>=0.01), when 5.6 mg/dL (>75th percentile) was used as the cutoff value. Multivariable analyses indicated that RLP-C was a risk factor for stroke, with an odds ratio of 2.54 (<I>p</I>=0.045). The RLP-C level was higher in the large artery atherosclerosis subgroup (5.7±3.9 mg/dL) than in any other stroke subgroup (small vessel occlusion, 4.9±5.9 mg/dL; cardioembolism, 1.8±2.3 mg/dL; stroke of undetermined etiology, 3.1±2.9 mg/dL).</P><P><B>Conclusions</B></P><P>We have found an association between high RLP-C levels and ischemic stroke, and in particular large artery atherosclerotic stroke.</P>
Kim, Dong-Eok,Cho, Namhun The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.2
In this paper, we propose a method to search candidates of network reconfiguration to restore distribution system with distributed energy resources using a level-based tree search algorithm. First, we introduce a method of expressing distribution network with distributed energy resources for fault restoration, and to represent the distribution network into a simplified graph. Second, we explain the tree search algorithm, and introduce a method of performing the tree search on the basis of search levels, which we call a level-based tree search in this paper. Then, we propose a candidate search method for fault restoration, and explain it using an example. Finally, we verify the proposed method using computer simulations.
Fault Analysis Method for Power Distribution Grid with PCS-based Distributed Energy Resources
Kim, Dong-Eok,Cho, Namhun The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.2
In this study, we propose a fault analysis method for a power distribution grid with PCS-based DERs. We first explain the characteristics of a PCS-based DER. According to the characteristics, the DER is considered as a current-controlled voltage source, which produces varying voltages within a certain limit so that currents equal to given references flowing from the DER to the grid (currents controlled). So, we introduce the symmetrical equivalent models in the form of varying voltage source for fault analysis and then, construct a convex optimization problem to solve the fault problem associated with the equivalent models and grid conditions. Thus, the proposed method enables to perform a proper fault analysis considering the characteristics of the DER, which are currents controlled, voltage limited, and unity power factor achievement. To verify the validity of the proposed method, we perform computer simulations with the proposed method and with MATLAB Simulink, and the results are compared.
Kim, Hyungdae,Park, Youngjae,Kim, Hyungmo,Lee, Chan,Jerng, Dong Wook,Kim, Dong Eok Pergamon Press 2017 International journal of heat and mass transfer Vol. No.
<P><B>Abstract</B></P> <P>This study reports the results of critical heat flux (CHF) enhancements by using single-layered metal wire mesh with micro/nano-sized pore structures with no modification of the original heating surface. Pool boiling tests with the wire mesh showed a significant CHF increment of up to 84% compared with that recorded on a bare surface. And, we investigated the dynamic behavior of the liquid and vapor phases on the boiling surfaces using an IR thermometry technique. From the quantitative measurements of liquid–vapor-solid phase distribution on the heating surface, it was revealed that the presence of the wire mesh and its hydrophilic nature play a role in sustaining a liquid phase inside the heating area that prevents the excessive expansion of the dry spot, and strongly disseminates thermal energy generated by the heater. In other words, the thermal energy generated inside the heater is dispersed more uniformly under the existence of the wire mesh. Using this type of mesh with the micro-sized pore structures for CHF enhancement intrinsically can mitigate changes in thermos-physical and chemical properties, and losses in structural durability for original heating surface. We expect that the meshes can be exploited in applications to several thermal systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pool boiling tests were conducted by using metal wire mesh on heating surface. </LI> <LI> The wire mesh showed a significant CHF enhancement compared to a bare surface. </LI> <LI> IR thermometry was utilized for detecting phase distribution on boiling surface. </LI> <LI> Capillary wicking through wire mesh significantly can reduce dry spot diameter. </LI> </UL> </P>
Power Flow Study of Low-Voltage DC Micro-Grid and Control of Energy Storage System in the Grid
Dong-Eok Kim 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.2
DC distribution has several differences compared to AC distribution. DC distribution has a higher efficiency than AC distribution when distributing electricity at the same voltage level. Accordingly, power can be transferred further with low-voltage DC. In addition, power flow in a DC grid system is produced by only a voltage difference in magnitude. Owing to these differences, operation of a DC grid system significantly differs from that of an AC system. In this paper, the power flow problem in a bipolar-type DC grid with unbalanced load conditions is organized and solved. Control strategy of energy storage system on a slow time scale with power references obtained by solving an optimization problem regarding the DC grid is then proposed. The proposed strategy is verified with computer simulations.
Fault Analysis Method for Power Distribution Grid with PCS-based Distributed Energy Resources
Dong-Eok Kim,Namhun Cho 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.2
In this study, we propose a fault analysis method for a power distribution grid with PCSbased DERs. We first explain the characteristics of a PCS-based DER. According to the characteristics, the DER is considered as a current-controlled voltage source, which produces varying voltages within a certain limit so that currents equal to given references flowing from the DER to the grid (currents controlled). So, we introduce the symmetrical equivalent models in the form of varying voltage source for fault analysis and then, construct a convex optimization problem to solve the fault problem associated with the equivalent models and grid conditions. Thus, the proposed method enables to perform a proper fault analysis considering the characteristics of the DER, which are currents controlled, voltage limited, and unity power factor achievement. To verify the validity of the proposed method, we perform computer simulations with the proposed method and with MATLAB Simulink, and the results are compared.
Measurement of Water Stress for Cucumber Seedlings using Infrared Thermography
( Dong-eok Kim ),( Kwang-soo Bae ),( Youn-ah Shin ),( Shin-hee Han ),( Dong-hyeon Kang ),( Young-hoe Woo ) 한국농업기계학회 2018 한국농업기계학회 학술발표논문집 Vol.23 No.1
The purpose of this study was to evaluate the moisture stress of cucumber seedlings by measuring the leaf temperature of cucumber seedlings using a thermal imaging camera. The change of leaf temperature of cucumber seedlings by the soil water content was continuously observed. Water stress of cucumber seedlings was estimated by the difference between leaf temperature and temperature. The leaf temperature of cucumber seedlings were measured using the thermal image camera. Leaf temperature of cucumber seedlings was changed continually with time. Leaf temperature of cucumber seedlings was lower at high soil water content. In the case of lack of soil water content, it was found that the leaf temperature was higher than the air temperature and it means that cucumber seedlings is under water stress. There were significant differences in the leaf temperature of stressed plants and non-stressed plants.