• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1166-1167
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• 2008

풍력 발전기의 계통 연계 기준에서 Fault Ride Through 규정은 사고 시 계통의 응동 특성을 결정하기 때문에 해당 계통의 특징을 반영하여 결정되어야 한다. 이에 여기에서는 세계 각국의 풍력발전기에 적용되는 Grid code에 대해 분석하고, 이를 바탕으로 FRT 규정의 수립에 필요한 기술적 요건에 대해 검토한 후, 해당 규정 수립을 위한 방법론을 제시한다. 이때, 구체적인 parameter 설정은 제주계통을 대상으로 PSS/E를 이용한 안정도 모의 결과에 따라 사고 시 계통의 전압 특성을 반영할 수 있도록 하였다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.2
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• pp.75-83
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• 2003

Recently, the machine tools have been needed for high speed and accuracy to increase productivity. The most Important thing to get a more stabilized machine is to know the frequency response which has an effect on manufacture a lot. This problem should be considered seriously by many researchers. There are many application programs about FEM but Just using FEM program to get information of the object is not enough to put our confidence in the stability of the machine tool design. Therefore, the purpose of this research is to make a study for proving one of the ways to design to produce stabilized a machine more efficiently by comparing FRT method and FEM. At these two tests, we can learn about the frequency response area causing resonance and we can reconfirm the result to trust.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.1
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• pp.98-104
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• 2014

This paper presents the performance analysis of a sliding mode based hybrid controller for three phase voltage source inverter. The main objective of this analysis is to observe the effectiveness of the controller for fault ride through (FRT) capability improvement of the distributed generations (DG). The performance of the conventional PI based cascaded controller is also presented for comparison purpose.

• Journal of Power Electronics
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• v.15 no.1
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• pp.235-245
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• 2015

This paper proposes a reactive current assignment and control strategy for a doubly-fed induction generator (DFIG) based wind-turbine generation system under generic grid voltage sag or swell conditions. The system's active and reactive power constrains during grid faults are investigated with both the grid- and rotor-side convertors (GSC and RSC) maximum ampere limits considered. To meet the latest grid codes, especially the low- and high-voltage ride-through (LVRT and HVRT) requirements, an adaptive reactive current control scheme is investigated. In addition, a torque-oscillation suppression technique is designed to reduce the mechanism stress on turbine systems caused by intensive voltage variations. Simulation and experiment studies demonstrate the feasibility and effectiveness of the proposed control scheme to enhance the fault ride-through (FRT) capability of DFIG-based wind turbines during violent changes in grid voltage.

• Journal of Crop Science and Biotechnology
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• v.11 no.2
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• pp.141-150
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• 2008

The response of grain yield(GY) and milled-rice protein content(PC) to crop growth status and nitrogen(N) rates at panicle initiation stage(PIS) is critical information for prescribing topdress N rate at PIS(Npi) for target GY and PC. Three split-split-plot experiments including various N treatments and rice cultivars were conducted in Experimental Farm, Seoul National University, Korea in 2003-2005. Shoot N density(SND, g N in shoot $m^{-2}$) and canopy reflectance were measured before N application at PIS, and GY, PC, and SND were measured at harvest. Data from the first two years(2003-2004) were used for calibrating the predictive models for GY, PC, and SND accumulated from PIS to harvest using SND at PIS and Npi by multiple stepwise regression. After that the calibrated models were used for calculating N requirement at PIS for each of nine plots based on the target PC of 6.8% and the values of SND at PIS that was estimated by canopy reflectance method in the 2005 experiment. The result showed that SND at PIS in combination with Npi were successful to predict GY, PC, and SND from PIS to harvest in the calibration dataset with the coefficients of determination ($R^2$) of 0.87, 0.73, and 0.82 and the relative errors in prediction(REP, %) of 5.5, 4.3, and 21.1%, respectively. In general, the calibrated model equations showed a little lower performance in calculating GY, PC, and SND in the validation dataset(data from 2005) but REP ranging from 3.3% for PC and 13.9% for SND accumulated from PIS to harvest was acceptable. Nitrogen rate prescription treatment(PRT) for the target PC of 6.8% reduced the coefficient of variation in PC from 4.6% in the fixed rate treatment(FRT, 3.6g N $m^{-2}$) to 2.4% in PRT and the average PC of PRT was 6.78%, being very close to the target PC of 6.8%. In addition, PRT increased GY by 42.1 $gm^{-2}$ while Npi increased by 0.63 $gm^{-2}$ compared to the FRT, resulting in high agronomic N-use efficiency of 68.8 kg grain from additional kg N. The high agronomic N-use efficiency might have resulted from the higher response of grain yield to the applied N in the prescribed N rate treatment because N rate was prescribed based on the crop growth and N status of each plot.

• Physical Therapy Korea
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• v.21 no.3
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• pp.45-54
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• 2014

Fall is one of the most intimidating health conditions in elders. Comprehensive assessment is necessary to understand the individual and environmental aspects of the falls such as balancing abilities, depression, and quality of life. The purpose of this study was to compare the balancing ability, depression, and quality of life between elderly fallers and elderly non-fallers. Thirty-two community-dwelling elders (fifteen males and seventeen females between 65 and 83 years old), who have experienced fall on walking during last twelve months, were involved in the elderly fallers group. And twenty-four males and twenty-two females between 65 and 83 years old of community-dwelling elders, who have no experienced fall on walking during last twelve months, were involved in the elderly non-fallers group. Berg balance scale (BBS), timed up and go test (TUG), and functional reach test (FRT), were used to evaluate the ability of the physical balance. 'Beck depression scale in Korean' questionnaire was used to assess the depression. 'Korean version of World Health Organization Quality of Life Assessment Instrument-Bref' questionnaire was used to assess the quality of life. The results were as follows: 1) Balancing abilities measured by the BBS, TUG in the elderly fallers group were meaningfully lower than that of the elderly non-fallers group (p<.05), whereas no significant difference in the FRT was found (p>.05). 2) Depression level in the elderly fallers group was significantly higher than that of the elderly non-fallers group (p<.05). 3) Quality of life in the elderly fallers group was significantly lower than that of the elderly non-fallers group, excluding environment domain (p<.05). Therefore, in order for clinical evaluation of the community-dwelling elders those with reduced balancing ability, it is necessary to evaluate and understand the fall experience, depression, and quality of life.

• Journal of National Security and Military Science
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• s.5
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• pp.1-45
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• 2007

Reserved forces of ROKA are in charge of replacement of TOE in the wartime and mission of rear area operation. But there is institutional inertia in the law and organization oriented to fill human resources rather than take mission. We need to prepare for the investment and arrangement of reserved forces as military power that would be replaced standing forces. In this portion, to reinforce reserve forces elite, First, efficient mobilization regulations and systems are suggested. I covered a maintenance of relevant mobilization ordinances which need to legislated and approved by national assembly for wartime and development of mobilization system which might lose the appropriate time for mobilization due to complicated declaration procedures and measures to overcome the panic at the initial stage of the war and organization and employment of nationwide transportation system and mobilization center. To ensure efficient resource management and mobilization of reserve forces with a number of approximately 3 million, there's a necessity of organization for integration and conciliation. To make it real, I suggested establishing and employing the mobilization center, on first phase, employ the mobilization center focusing on homeland divisions, on second phase, it is advisable to convert to national level mobilization system and develop to central mobilization center focusing on national emergency planning committee. During peacetime, in conjunction with Mobilization Cell, mobilization center can conduct resource survey and integrate and manage mobilization resources and take charge of mobilization training of subordinate units, and during wartime, in conjunction with mobilization coordination team and Cell, can ensure the execution of mobilization. Second, Future oriented reserve forces management system such as service system of reserve forces and support system of homeland defense operations. Current service and trainings of reserve forces by the year have very low connection, as it is very complex to manage the resources and trainings, and service and training lack the equity, re-establishment of service system is required. Also in an aspect of CSS and cultivation support for reserve forces, as the scope and limitation of responsibility between the armed forces and autonomous organization is obscure, conditions to conduct actual-fighting exercises are limited. Concentrated budgetting is extremely difficult because reserve forces training fields are scattered nationwide, and facilities and equipments are rapidly getting older. To improve all these, I suggest the organization of homeland defense battalion with a unit of "City-Gun-District" and supporting the local reserve forces. Conduct unit replacement or personal replacement for those who have finished their 1 or 2 years and homeland defense operation duty for those with 3-5 years for consistency and simplification. Third, I suggest Future oriented Reserved Training(FRT) and Training Center oriented training management to establish a reliable reserve training. Reserves carry out expansion of unit, conventional combat mission, homeland defense and logistics support during wartime, and actual-fighting exercise, and disaster relief, peace keeping activities. Despite diverse activities and roles, their training condition still stays definitely poor. For these reasons, Modernization of weapons and facilities through gradual replacement and procurement is essential to enhance mobilization support system.

• Journal of Ginseng Research
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• v.45 no.1
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• pp.66-74
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• 2021

Background: Abnormal chloride (Cl-) transport has a detrimental impact on mucociliary clearance in both cystic fibrosis (CF) and non-CF chronic rhinosinusitis. Ginseng is a medicinal plant noted to have anti-inflammatory and antimicrobial properties. The present study aims to assess the capability of red ginseng aqueous extract (RGAE) to promote transepithelial Cl- secretion in nasal epithelium. Methods: Primary murine nasal septal epithelial (MNSE) [wild-type (WT) and transgenic CFTR-/-], fisher-rat-thyroid (FRT) cells expressing human WT CFTR, and TMEM16A-expressing human embryonic kidney cultures were utilized for the present experiments. Ciliary beat frequency (CBF) and airway surface liquid (ASL) depth measurements were performed using micro-optical coherence tomography (μOCT). Mechanisms underlying transepithelial Cl- transport were determined using pharmacologic manipulation in Ussing chambers and whole-cell patch clamp analysis. Results: RGAE (at 30㎍/mL of ginsenosides) significantly increased Cl- transport [measured as change in short-circuit current (ΔISC = ㎂/㎠)] when compared with control in WT and CFTR-/- MNSE (WT vs control = 49.8±2.6 vs 0.1+/-0.2, CFTR-/- = 33.5±1.5 vs 0.2±0.3, p < 0.0001). In FRT cells, the CFTR-mediated ΔISC attributed to RGAE was small (6.8 ± 2.5 vs control, 0.03 ± 0.01, p < 0.05). In patch clamp, TMEM16A-mediated currents were markedly improved with co-administration of RGAE and uridine 5-triphosphate (8406.3 +/- 807.7 pA) over uridine 5-triphosphate (3524.1 +/- 292.4 pA) or RGAE alone (465.2 +/- 90.7 pA) (p < 0.0001). ASL and CBF were significantly greater with RGAE (6.2+/-0.3 ㎛ vs control, 3.9+/-0.09 ㎛; 10.4+/-0.3 Hz vs control, 7.3 ± 0.2 Hz; p < 0.0001) in MNSE. Conclusion: RGAE augments ASL depth and CBF by stimulating Cl- secretion through CaCC, which suggests therapeutic potential in both CF and non-CF chronic rhinosinusitis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.6 s.177
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• pp.1499-1512
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• 2000

The dynamic explicit finite element method and the static implicit finite element method are applied effectively to analyze total auto-body panel stamping processes, which include the forming stage , the trimming stage and the spring-back stage.\The explicit time integration method has better merits in the forming stage including highly complicated three-dimensional contact conditions. On the contrary, the implicit time integration method is better for analyzing spring-back since the complicated contact conditions are removed and the computing time to get the final static state is short. In this work, brief descriptions of the formulation and the factor study are presented. Further, the simulated results for the total auto-body panel stamping processes are shown and discussed. The formability and the weld line movement in stamping with Tailor Welded Blanks were investigated through QTR-OTR-FRT.

• Journal of the Korean Society of Physical Medicine
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• v.12 no.4
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• pp.61-71
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• 2017

PURPOSE: The purpose of the present study was to investigate the effects of whole body vibration exercise on balance, muscle strength and falls efficacy in the elderly. METHODS: In this blinded randomized allocation study, 27 elderly were assigned to a whole-body vibration exercise group (n=14), consisting of 25 min structured exercises for 2 days per week for 6 weeks and a control group (n=13) performing the same program without vibration. At baseline and after the 6-week intervention, balance was measured using the Korean version of the Berg balance scale (K-BBS), timed up and go (TUG) test and functional reach test (FRT). Muscle strength was determined using the 30-s chair stand test (CST). Fear of falling was assessed using the Korean version of falls efficacy scale (K-FES). Paired t-test and independent t-test were used for within and between group comparisons, respectively. RESULTS: After the intervention, the experimental group showed significantly higher changes in all the parameters (K-BBS score, TUG test, CST, K-FES score) (p<.05) compared with the control group. However, there was no significant change in all parameters in the control group (p>.05). CONCLUSION: The whole-body vibration exercise program may be helpful to improve balance, mobility, muscle performance and fear of falling in the elderly.