• Journal of The Korean Society of Agricultural Engineers
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• v.65 no.4
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• pp.25-32
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• 2023

KDS (Korean Design Standard) for agricultural drainage is a planning standard that helps determine the appropriate capacity and type of drainage facilities. The objective of this study was to analyze the inundation of the agricultural basin considering the current design standard and the critical rainfall duration. This study used the rainfall durations of 1-48 hour, and the time distribution method with the Chicago and the modified Huff model. For the runoff model, the NRCS (Natural Resources Conservation Service) unit hydrograph method was applied, and the inundation depth and duration were analyzed using area-elevation data. From the inundation analysis using the modified Huff method with different rainfall durations, 4 hours showed the largest peak discharge, and 11 hours showed the largest inundation depth. From the comparison analysis with the current method (Chicago method with a duration of 48 hours) and the modified Huff method applying critical rainfall duration, the current method showed less peak discharge and lower inundation depth compared to the modified Huff method. From the simulation of changing values of drainage rate, the duration of 11 hours showed larger inundation depth and duration compared to the duration of 4 hours. Accordingly, the modified Huff method with the critical rainfall duration would likely be a safer design than the current method. Also, a process of choosing a design hydrograph considering the inundation depth and duration is needed to apply the critical rainfall duration. This study is expected to be helpful for the theoretical basis of the agricultural drainage design standards.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.1
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• pp.11-17
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• 2010

This study investigates the non-traditional manufacturing process of dry wire electrical discharge machining (EDM) in which liquid dielectric is replaced by a gaseous medium. Wire EDM experiments of thin workpieces were conducted both in wet and dry EDM conditions to examine the effects of spark cycle (T), spark on-time ($T_{on}$), thickness of work pieces, and work material on machining performance. The material removal rate (MRR) in the dry wire EDM case was much lower than that in the wet wire EDM case. In addition, the thickness of workpiece and work-material were found to be critical factors influencing the MRR for dry EDM process. The relative ratios of spark, arc and short circuit were also calculated and compared to examine the effectiveness of processes of dry and wet wire EDM.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1691-1693
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• 2002

Acoustic partial discharge detection has been used on GIS testing for more than 10 years. Sensitivities show that most of critical defect types can be detected with a reasonable signal-to-noise ratio. The paper reports on acoustic partial discharge detection comparable to sensitive electrical PD(partial discharge) measuring method.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.131-134
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• 2002

Compressible gas flow through a convergent-divergent nozzle is choked at the nozzle throat under a certain critical pressure ratio, and then being no longer dependent on the pressure change in the downstream flow field. In practical, the flow field at the divergent part of the critical nozzle can affect the effective critical pressure ratio. In order to investigate details of flow field through a critical nozzle, the present study solves the axisymmetric, compressible, Wavier-Stokes equations. The diameter of the nozzle throat is D=8.26mm and the half angle of the diffuser is changed between $2^{\circ}\;and\;10^{\circ}$ Computational results are compared with the previous experimental ones. The results obtained show that the divergence angle is significantly influences the critical pressure ratio and the present computations predict the experimented discharge coefficient and critical pressure ratio with a good accuracy. It is also found that a nozzle with the half angle of $4^{\circ}$ nearly predicts the theoretical critical pressure ratio.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.73-88
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• 2014

Various studies on the critical flow models for sub-cooled and/or saturated water were reviewed, especially on Fauske, Moody, and Henry for basic theoretical models; Zaloudek for insight into physical phenomena for a critical flow in an orifice type flow path; Sozzi & Sutherland for a critical flow test of saturated and sub-cooled water at high pressure for orifice and nozzles; and a Marviken test on a full-scale critical flow test. In addition, critical flow tests of sub-cooled water for the break simulators in integral effect test (IET) facilities were also investigated, and a hybrid concept using Moody's and Fauske's models was considered by the authors. In the comparison of the models for the selected test data, discussions of the effect of the diameters, predictions of the critical flow models, and design aspects of break simulator for SBLOCA scenarios in the IET facilities were presented. In the effect of diameter on the critical flow rate with respect to all dimensional scales, it was concluded that the effect of diameter was found irrespective of diameter sizes. In addition, the diameter effect on slip ratio affecting the critical flow rate was suggested. From a comparison of the critical flow models and selected test data, the Henry-Fauske model of the MARS-KS code was found to be the best model predicting the critical flow rate for the selected test data under study.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.49-53
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• 2009

The paper presents the results of the experimental study about flow discharge characteristics of double swirl coaxial injectors for a liquid rocket engine. Flow discharge characteristics of injectors become one of critical design issues for LRE combustion devices. Tap water and liquid oxygen/kerosene were used for ambient and hot firing tests, respectively. A combustion discharge coefficient varies depending on a mixture ratio and a recess ratio, and magnitudes of the variations are different with respect to injector shapes and operating conditions. The variation of a combustion discharge coefficient with a LOx injector is considered to result from flame structure changes due to physical property changes.

• Magazine of the Korean Society of Agricultural Engineers
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• v.28 no.1
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• pp.51-59
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• 1986

Through the hydraulic model test, a more convenient and accurate method of deter- mining discharge coefficients in the sluice type of tide gates can be derived by the use of aubmergence ratio as a parameter. The results obtained are summarized as follows; 1. Discharge coefficients under submerged flow conditions can be obtained by the application of sutmergerice ratio (S) to the free flow equation of the broad-erested we r. 2. The critical submergence ratios (Scr) for the flat basin and the broad-crested types of sill have the same value of 0.8. 3. Under free flow conditions, the discharge coefficient (m) are 0.37 and 0. 35 for the flat basin and the broad-crested types of sill respectively. However, when submerged flow condition exists, the discharge coefficients for both types of sill is given by a regression equation of discharge coefficients (IL) on submergence ratios (8) expressed as; m 1.3- 1. 17S. 4. The relationships between S and Froude number (Fr), for the flat basin and the broad-crested types of sill are Fr=2. 79-2.495 and Fr2.5=5. 7-6.16S respectively. From the above relationships, it can be concluded that m can also be expressed in terms of the Froude number which is a very relevant hydraulic parameter of the open channel hydraulics.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3221-3224
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• 2010

This study investigates the requirements of lithium-air cathodes, which directly influence discharge capacity. The cathodes of Li-air cell are made by using five different carbon materials, such as Ketjen black EC600JD, Super P, Ketjen black EC300JD, Denka black, and Ensaco 250G. The Ketjen black EC600JD provides discharge capacity of 2600 mAh/g per carbon weight, while that of Ensaco 250G shows only 579 mAh/g. To figure out the differences of discharge capacity from carbon materials, their surface area and pore volume are analyzed. These are found out to be the critical factors in determining discharge capacity. Furthermore, carbon loading on Ni foam and amounts of electrolyte are significant factors that affect discharge capacity. In order to investigate catalyst effect, electrolytic manganese dioxide (EMD) is incorporated and delivered 4307 mAh/g per carbon weight. This infers that EMD facilitates to break $O_2$ interactions and leads to enhance discharge capacity.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.2
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• pp.55-61
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• 1986

This paper describes the generation region and suppression effect of the abnormal field voltage induced when the synchronous generator is switched to the infinite bus, the critical value of negative field current is calculated by simmulation which has parameters of the phase difference and voltatge ratio between the bus and the generator. The suppression effect of discharge resistance connected in parallel with the field circuit is also investigated. According to this study, the optimal value of discharge resistance which can suppress effectively the abnormal field voltage may be calculated.

• Quality Improvement in Health Care
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• v.30 no.1
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• pp.15-32
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• 2024

Purpose: The number of severely ill patients requiring post-acute care has been increasing. Careful discharge planning minimizes unplanned emergency room visits and readmissions. This study aimed to survey the knowledge, experience, confidence, and obstacles faced by medical residents and fellows regarding the discharge process of severely ill patients. Methods: A survey consisting of 27 questions was sent electronically to residents and fellows who had experience in discharging severely ill patients from a tertiary hospital in Korea. The survey was conducted over a two-week period from September 29, 2022. Results: A total of 98 residents and fellows responded to the survey. Of these, 94% experienced difficulties related to the discharge process. The main obstacle was changes in the patient's condition during discharge planning (92.3%). Although 95% of the respondents acknowledged the need for providing discharge information, only 53.1% of the residents and fellows practiced this. Only 42.9% of the respondents and 20.4% of residents and fellows explained local community healthcare and welfare resources to patients because of a lack of relevant knowledge (69.7%) and feeling no responsibility to explain (40.4%). Conclusion: This study revealed that residents and fellows experienced difficulties in devising discharge plans and providing post-acute care related information, despite recognizing the importance of these. These gaps result from the lack of a discharge planning curriculum regarding critically ill patients and appropriate training in the discharge process. This suggests that an integrated discharge planning curriculum should be developed and adopted in residents' training programs for the differentiated treatment of critically ill patients.