• Journal of Advanced Marine Engineering and Technology
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• v.19 no.2
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• pp.1-9
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• 1995

The processing paper has devoted to the theory of the flow equations, the basic derivative procedure, the meaning of a valve flow coefficient $C_v$, the valve Reynolds R$R_{ev}$ and its application for liquid control valves, which applicable under the condition of a non-critical flow and the case of piping geometry factor $F_p$=1.0. However there is no information on the effects of fittings, a critical flow and the flow resistance coefficient of a valve equivalent to that of pipe which is conveniently used in the piping design. Since the piping systems of plants or ships generally contain various fittings such as expanders and reducers due to different size between pipes and valves and there may occur a critical flow, that a mass flowrate is maintained to be constant, due to the pressure drop in a piping when a liquid is initially maintainder ar a saturated temperature or at nearby corresponding to upstream pressure, system designer should have a knowledge of the effect to flow due to fittings and the critical flow phenomenon of a liquid. This study is performed to inform system designers with the critical flow phenomenon of a liquid, a valve resistance coefficient, a valve geometry factor and their applications.

• Nuclear Engineering and Technology
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• v.52 no.11
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• pp.2638-2651
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• 2020

Nozzle corner cracks present at the intersection of reactor pressure vessels (RPVs) and inlet or outlet nozzles have been a persistent problem for a number of years. The fracture analysis of such nozzle corner cracks is very important and critical for the efficient design and assessment of the structural integrity of RPVs. This paper aims to perform an engineering critical assessment of RPVs with nozzle corner cracks subjected to several transients accompanied by pressurized thermal shocks. The critical crack size of the RPV model with nozzle corner cracks under transient loading is evaluated on failure assessment curve. In particular, the influence of cladding on the crack initiation of nozzle corner crack under thermal transients is studied. The influence of primary internal pressure and secondary thermal stress on the stress field at nozzle corner and SIF at crack front is analyzed. Finally, the influence of different crack size and crack shape on the final critical crack size is analyzed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1134-1139
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• 2011

When the aspect ratio of a magnet varies, the magnetic field in the magnet also varies. The critical current of a tape-shaped HTS wire varies with the direction and magnitude of applied magnetic field. Consequently when the aspect ration of a HTS magnet varies, the critical current of a HTS magnet varies. This paper shows the relation between the aspect ratio of a magnet and the energy and inductance of a HTS magnet. The critical current is also shown at various aspect ratio of the magnet. The length of the HTS wire, inner diameter of the magnet, and number of pancake are chosen to be variables which varies the shape of the magnet. For a HTS magnet consisting of pancake windings, calculation results show the number of pancake windings are the prime factor which varied the energy and inductance of the magnet. The inner diameter of the magnet varies the energy and inductance of the magnet a little.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.6
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• pp.770-777
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• 1999

In this study a phase diagram has been used to investigate the unsteadiness of two-dimensional lid-driven closed flows within a square cavity for twelve Reynolds numbers; $7.5{\times}10^3,\; 8{\times}10^3,\; 8.5{\times}10^3,\; 9{\times}10^3,\; 9.5{\times}10^3,\; 10^4,\;1.5{\times}10^4,\;2{\times}10^4,\; 3{\times}10^4,\; 7.5{\times}10^4$ and $10^5$. The results indicate that the first critical Reynolds number at which the flow unsteadiness of sinusoidal fluctuation appears from the temporal variation of total kinetic energy curves is assumed of sinusoidal fluctuation appears form the temporal variation of total kinetic energy curves is assumed to be in the neigh-bourhood of $Re=8.5{\times}10^3$ The second critical Reynolds number where the periodic amplitude and frequency collapse to random disturbance being existed around $Re=1.5{\times}10^4$ The exponentially decreasing vortices formed at the lower two corners are found commonly at the time-mean flow pattern of $Re=3{\times}10^4$.

• Journal of Korean Critical Care Nursing
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• v.2 no.2
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• pp.42-55
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• 2009

Purpose: Despite numerous evidence based preventive strategies of ventilator associated pneumonia (VAP) have been introduced, the incidence rate of VAP continues in an unacceptable range. The purposes of this review were to identify risk factors and diagnosis of VAP and to introduce current evidence based preventive strategies of VAP. Methods: A comprehensive literature search using keywords, including ventilator associated pneumonia were entered into a search engine. A number of highly pertinent papers relevant to the purpose of the review were identified. The papers that discussed specific preventive strategies of VAP were selected for analysis and inclusion in this review. Results: A number of evidence based preventive strategies that nurses can implement in their clinical practice to prevent VAP were identified. Such strategies include hand washing, use of protective gloves and gowns, oral care, stress ulcer prophylaxis, avoidance of unnecessary intubation, weaning protocol, sedation vacation, use of non-invasive ventilation, semi-recumbent position, continuous aspiration of subglottic secretions, and maintenance of proper endotracheal tube cuff pressure. Staff education is essential in preventing VAP. Conclusion: Preventive strategies of VAP should be applied to daily nursing care and each critical nurse should play a functional role in preventing VAP.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.61-65
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• 2012

The onset of convection in a mushy layer is analyzed by using linear stability theory in time-dependent solidification of a binary melt. A simplified model of a near-eutectic mush, in which the mush is assumed to be a porous block, is used and the propagation theory is applied to determine the critical conditions for the onset of convection. The present critical Rayleigh number is higher than the existing experimental result and also theoretical results obtained by considering the mushy layer with an overlying liquid layer. The constant pressure (permeable) condition applied on the mush-liquid interface produces a lower critical Rayleigh number, which is closer to the experimental results of aqueous ammonium chloride solution, compared with the impermeable condition.

• Journal of Chest Surgery
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• v.55 no.4
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• pp.265-273
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• 2022

Lung transplantation is considered a viable treatment option for patients with end-stage lung disease. Recent decades have seen a gradual increase in the number of lung transplantation patients worldwide, and in South Korea, the case number has increased at least 3-fold during the last decade. Furthermore, the waiting list time is becoming longer, and more elderly patients (>65 years) are undergoing lung transplantation; that is, the patients placed on the waiting list are older and sicker than in the past. Hence, proper management during the pre-transplantation period, as well as careful selection of candidates, is a key factor for transplant success and patient survival. Although referring and transplant centers should address many issues, the main areas of focus should be the timing of referral, nutrition, pulmonary rehabilitation, critical care (including mechanical ventilation and extracorporeal membrane oxygenation), psychological support, and the management of preexisting comorbid conditions (coronary artery disease, diabetes mellitus, gastroesophageal reflux disease, osteoporosis, malignancy, viral infections, and chronic infections). In this context, the present article reviews and summarizes the pre-transplantation management strategies for adult patients listed for lung transplantation.

• Journal of the Korean Society of Visualization
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• v.21 no.1
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• pp.67-73
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• 2023

In the study, pool boing critical heat flux (CHF) was experimentally investigated depending on the length of heaters. A smooth silicon oxide surfaces are used as the boiling surfaces. As the results of pool boiling experiments based on distilled water in ambient pressure condition, the CHF decreased as the length of the heater increased. By the high speed imaging, it was shown that the number of vapor columns increased as the length of the heater increased. Comparing the number of vapor columns and the CHF according to the heater length, the change in the CHF according to the heater length was analyzed based on the hydrodynamic instability.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.141-141
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• 2021

This study proposed an equation for Rainfall Threshold for Flood Warning (RTFW) for urban areas based on computer simulations. First, a coupled 1D-2D dual-drainage model was developed for nine watersheds in Seoul, Korea. Next, the model simulation was repeated for a total of 540 combinations of the synthetic rainfall events and watershed imperviousness (9 watersheds × 4 NRCS Curve Number (CN) values × 15 rainfall events). Then, the results of the 101 simulations with the critical flooded depth (0.25m-0.35m) were used to develop the equation that relates the value of RTFW to the rainfall event temporal variability (represented as coefficient of variation) and the watershed Curve Number. The results suggest that 1) the rainfall with greater temporal variability causes critical floods with less amount of total rainfall; and that 2) the greater imperviousness requires less rainfall to have critical floods. For validation, the proposed equation was applied for the flood warning system with two storm events occurred in 2010 and 2011 over 239 watersheds in Seoul. The results of the application showed high performance of the warning system in issuing the flood warning, with the hit, false and missed alarm rates at 68%, 32% and 7.4% respectively for the 2010 event and 49%, 51% and 10.7% for the event in 2011.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3033-3038
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• 2007

In this research, Rayleigh instability of gas-liquid flow in annular pipe is studied in film boiling using viscous potential flow. Viscous potential flow is a kind of approximation of gas-liquid interface considering velocity field as potential including viscosity. A dispersion relation is obtained including the effect of heat and mass transfer and viscosity. New expression for dispersion relation in film boiling and critical wave number is obtained. Viscosity and heat and mass transfer have a stabilizing effect on instability and its effect appears in maximum growth rate and critical wave number. And the existence of marginal stability region is shown.