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Sangheon Yi,Seong-Joong Kim 한국지질과학협의회 2010 Geosciences Journal Vol.14 No.1
Age-controlled pollen record from wetland sediments of Hanam, western central Korean Peninsula (KP), reveals vegetation dynamics response to climate changes during the last glacial,26.1−20.1 cal kyr BP. The Hanam pollen assemblages are dominated by conifers, Picea and Pinus and cold tolerant deciduous broadleaved Betula, together with common xerophytic herb like Artemisia and Gramineae. Principal taxa are similar to those of subalpine forest in modern vegetation of KP. Humidity variation reconstructed by semi aridity index (AI) indicates that, during 26.1−22.7 cal kyr BP, cold and dry conditions were prevailed with an expansion of subalpine coniferous forest and high value of AI. From 22.5 to 20.5 cal kyr BP, cool and wet conditions were reconstructed with low value of AI due to climatic amelioration, enhanced conifers and temperate deciduous broadleaved mixed forests flourished. Between 20.3 and 20.1 cal kyr BP, an abundance of Picea and Betula associated with high value of AI infers that subalpine conifers forest colonized again in hinterland montane along with open, low grassland under colder and drier conditions owing to climatic deterioration. The principal pollen taxa suggest that prevailing climate conditions were annual mean temperature about 5−6 ℃ colder and annual mean precipitation 40% drier than today.
Sangheon Han,Hyoungtae Kim,Sungwoo Lee,Wook Kim 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.2
In order for the optimal solution of generators’ annual maintenance scheduling to be applicable to the actual power system it is crucial to incorporate the constraints related to the equivalent operation hours (EOHs) in the optimization model. However, most of the existing researches on the optimal maintenance scheduling are based on the assumption that the maintenances are to be performed periodically regardless of the operation hours. It is mainly because the computation time to calculate EOHs increases exponentially as the number of generators becomes larger. In this paper an efficient algorithm based on demand grouping method is proposed to calculate the approximate EOHs in an acceptable computation time. The method to calculate the approximate EOHs is incorporated into the optimization model for the maintenance scheduling with consideration on the EOHs of generators. The proposed method is successfully applied to the actual Korean power system and shows significant improvement when compared to the result of the maintenance scheduling algorithm without consideration on EOHs.
Sangheon Yi,Yoshiki Saito,Zhongyuan Chen,Dong Yoon Yang 한국지질과학협의회 2006 Geosciences Journal Vol.10 No.1
The wel-defined pollen record in massive marineclay deposits from the subaqueous Changjiang (Yangtze River)delta reveals changes in vegetation and inferred climate during thelast about 1600 years. Climatic periods inferred from the pollentively warm/wet conditions comparable to Medieval Warm Period(AD 9101085) with a strengthen summer monsoon, (3) a relativelycool and wet conditions possibly corresponding to Little Ice Age(LIA; AD 10851815) with a weaken summer monsoon, and finally(4) the present warm period, since AD 1815. The pollen aridityindex based on variations in humidity suggests that thre subpe-riods within the LIA can be identified: wet LIA-1 (AD 10851170),dry LIA-2 (AD 11701330), and wet LIA-3 (AD 13301815).
Adam Smith in the Tradition of Natural Law Philosophy
Sangheon Lee 서울대학교 경제연구소 1998 經濟論集 Vol.37 No.3
Smith's notion of an invisible hand comes from the discussion of 17th century natural law philosophers and Scottish moral philosophers. Natural jurists argued that social norms are immanent in human nature, but it should be explicated by reasons and upheld by social enforcement. Scottish moral philosophers argued that self-interested individuals spontaneously adopted social norms, once they are explicated by reasons. Smith rejected the necessity of reasons to identify social norms, and argued that spontaneous activities of self-interested individuals bring forward social norms immanent in human nature. Smith also argued that politics of creating social institutions is beyond moral judgement and would provide solutions to the systematic breakdown of a free commercial society.
Call Setup Latency Analysis in SIP-Based Voice over WLANs
Sangheon Pack,Hojin Lee IEEE 2008 IEEE COMMUNICATIONS LETTERS Vol.12 No.2
<P>In this letter, we consider session initiation protocol (SlP)-based voice over wireless local area networks (VoWLANs). We derive the analytical expression for the average call setup latency, and we observe the impact of the number of contending mobile nodes in a WLAN. Extensive simulation results are given to validate the analytical results.</P>
Bundling and Subsidy Competition in the Mobile Telecommunications Market
Sangheon Lee,Minsoo Park 한국경제연구학회 2016 Korea and the World Economy Vol.17 No.2
In this paper, we analyze the impact of handset subsidies on demand for bundles of mobile telecommunications service and handsets and evaluate the effects of subsidies and bundling regulations on social welfare using a counterfactual simulation analysis. By estimating a structural model that explicitly considers the demand for bundles and the profit maximization of mobile operators and handset manufacturers separately, we find that mobile carriers indeed offer a discriminatory subsidy for handsets depending on a consumers’ choice of service plans. Results of the simulation show that the ban of or putting a ceiling on handset subsidies reduces social welfare because, as the handset subsidy is regulated, consumers have to pay more for handsets or give up purchasing new products and service, and profits of providers are also reduced due to the decrease in demand. If the bundling of mobile carriers is prohibited, then price competition between handset manufacturers occurs, but the social welfare will not improve because the competition will not reduce handset prices as much as the price with the current subsidy level. Thus, in this paper, we argue that the most effective way to improve social welfare is to let the market decide.
모래주머니를 이용한 팔목과 몸통의 무게 증가가 만성 뇌졸중 환자들의 보행에 미치는 영향
( Sangheon Park ),( Hee Sung Lim ),( Sukhoon Yoon ) 한국운동역학회 2021 한국운동역학회지 Vol.31 No.1
Objective: This study aimed to determine the effect of wrist and trunk weight loading using sandbags in stroke patients in order to provide the quantitative data for enhancement of gait movement. Method: Twelve stroke patients, who have been diagnosed with hemiplegia over a year ago, were participated in this study. All subjects were asked to perform normal walking [N], wrist sandbag walking [W], wrist & trunk sandbag walking [WT], and both wrist sandbag walking [B] and both wrist & trunk sandbag walking [BT], respectively. Eight infrared cameras were used to collect the raw data. Gait parameters, arm swing, shoulder-pelvic kinematics, and lower extremity joint angle were calculated to examine the differences during walking. Results: As a result, there were no significant differences in the gait parameters, shoulder-pelvis, and lower extremities joint angles, but significant differences were found in the range of motion and the anteversion in arm swing. Conclusion: Wrist and trunk weight loading using sandbags affected the movement of the upper extremities only while it did not affect the movement of the lower extremities. It implies that it can reduce the risk of falling caused by a sudden movement change in lower extremities. In addition, the wrist and trunk weight loading using sandbags can induce changes in movement of the upper extremities independently and contribute to functional rehabilitation through resistance training.