• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.9
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• pp.527-535
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• 2009

The aim of this study is to investigate the daily heating performance of ground source multi-heat pump system with vertical single U-tube type GLHXs, which were installed in a school building located in Cheonan. Daily average COP of heat pump unit on Jan. 12th, 2009 at heating mode was lower than it on Nov. 10th, 2008 and Dec. 15th, 2008, because of lower EWT of the outdoor heat exchanger and relatively smaller size of condenser and evaporator. But, the system COP on the former was higher than it on the latter because ground loop circulating pump was operated in rated speed. It is suggested that the new algorithms to control the flow rate of secondary fluid for GLHX according to load change have to be developed in order to enhance the performance of the system COP.

• Korean Journal of Bronchoesophagology
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• v.14 no.2
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• pp.57-63
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• 2008

Hypopharyngeal perforation secondary to tracheal intubation is rare, but may result in severe airway complications that include retropharyngeal abscess, pneumothorax, pneumonia, mediastinitis and death. The most common site of hypopharyngeal perforation is the pyriform sinus and the region of the cricopharyngeus muscle. We report a 62-year old man with intubation-induced hypopharyngeal injury presenting as deep neck infection. The patient presented with dyspnea and pain on the neck. Neck CT scan identified fluid and air collection on the neck from the hyoid bone to the thoracic inlet level. Despite of delayed diagnosis, we successfully operated him by using strap muscle myofascial transposition flap. The patient was followed up for 3 months without any complications.

• International Journal of Aeronautical and Space Sciences
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• v.3 no.1
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• pp.95-104
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• 2002

Numerical solution of the full Navier-Stokes equation as well as the energy equation has been obtained for the unsteady natural convection in a rectangular enclosure. One side wall was maintained at very high temperature simulating fires. Especially the effect of surface radiation was taken into account. While the enclosed air was assumed to be transparent, the internal walls directly interacted one another through the surface radiation. Due to a significant temperature difference in the flow field, the equation of state was used instead of the Boussinesq approximation. It was found that the rapid heating of the adiabatic ceiling and floor by the incoming radiation from the hot wall made the evolution at thermo-fluid field highly unstable in the initial period. Therefore, the secondary cells brought about at the floor region greatly affected the heat transfer mechanism inside the enclosure. The heat transfer rate was augmented by the radiation, resulting in requiring less time for the flow to reach the steady state. At the steady state neglecting radiation two internal hydraulic jumps were clearly observed in upper/left as well as in lower/right comer. However, the hydraulic jump in the lower/right comer could not be observed for the case including radiation due to its high momentum flow over the bottom wall. Radiation resulted in a faster establishment of the steady state phenomena.

• Nuclear Engineering and Technology
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• v.19 no.3
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• pp.198-204
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• 1987

A plant simulation code, MCSIM (Micro-Computer SIMulator), has been developed to simulate plant transient accidents for pressurized water reactors. Reactor coolant system is modeled using decoupled energy and momentum equations, drift flux two-phase flow model and integral momentum equation. A two-fluid pressurizer model is used to simulate the pressurizer dynamics. Pot Boiler model is used for steam generator, steady-state decoupled energy and momentum equations for secondary side system, and point kinetics equations for nuclear power calculation. For test of the present version of MCSIM, complete loss of flow and RCCA withdrawal accidents are calculated with MCSIM. The results are compared with those in FSAR of KNU 5 & 6.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.1044-1051
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• 1989

A numerical calculation is carried out for the analysis of 3-dimensional compressible flow field in axial-flow rotating blades by using finite element method. The calculation of flow in impellers plays a dominant role in the theoretical research and design of turbomachines. Three-dimensional flow fields can be obtained by the quasi-three-dimensional iterative calculation of the flows both on blade-to-blade stream surfaces and hub-to-shroud stream surfaces with the introduction of viscous loss model in order to consider a loss due to viscosity of fluid. In devising the loss model, four primary sources of losses were identified: (1) blade profile loss (2) end wall loss (3) secondary flow loss (4) tip-leakage loss. For the consideration of an axially parabolic distribution of loss, the results of present calcullation are well agreed with the results by experiment, thus the introduction of loss model is proved to be valid.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.5
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• pp.633-641
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• 1999

Experiments were carried out to investigate the condensation heat transfer characteristics for R22 and its alternatives, R407C (R32/125/134a, 23/25/52wt%) and R410A (R32/125, 50/50wt%). A concentric tube heat exchanger was made to conduct condensation heat transfer tests. Mass flux and saturation temperature of refrigerants at the test section inlet were varied to get the corresponding heat transfer coefficients. Serial and parallel input of secondary fluid (water) were applied to the test subsections. Compared with existing correlations of condensation heat transfer, experimental heat transfer coefficients obtained in this study were generally higher than the predicted values, and mean absolute deviations from several correlations were shown. Wall subcooling was introduced to get a new correlation for condensation heat transfer coefficients by modifying Shah's equation. The RMS deviation of the measured heat transfer coefficients from the new correlation in this study for R22 is 9.9% and that for R407C and R410A are 10.2% and 14.6%, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.11
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• pp.874-880
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• 2006

The power density and heat dissipation rate per unit area of the telecommunication equipment have been increased with the technology development in the footprint of telecommunication hardware. A proper heat dissipation method from the PCB module is very important to allow reliable operation of its electronic component. In this study, a hybrid air-conditioner for the telecommunication equipment room was designed to save energy and obtain system reliability. For high outdoor temperatures, the hybrid system operates in the vapor compression cycle, while, for low outdoor temperatures, the hybrid system works in the secondary fluid cooling cycle with no operation of the compressor. The performance of the hybrid air-conditioner was measured by varying outdoor and indoor temperatures. The hybrid air-conditioner yielded 50% energy saving compared with the conventional refrigeration system when the mode switch temperature was $8.3^{\circ}C$.

• Nuclear Engineering and Technology
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• v.50 no.7
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• pp.1173-1183
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• 2018

Transient fluid velocity and pressure fields in a pressurized water reactor (PWR) steam generator (SG) secondary side during the blowdown period of a feedwater line break (FWLB) accident were numerically simulated employing the saturated water flashing model. This model is based on the assumption that compressed water in the SG is saturated at the beginning and decompresses into the two-phase region where saturated vapor forms, creating a mixture of steam bubbles in water by bulk boiling. The numerical calculations were performed for two cases of which the outflow boundary conditions are different from each other; one is specified as the direct blowdown discharge to the atmosphere and the other is specified as the blowdown discharge to an extended calculation domain with atmospheric pressure on its boundary. The present simulation results obtained using the two different outflow boundary conditions were discussed through a comparison with the predictions using a simple non-flashing model neglecting the effects of phase change. In addition, the applicability of each of the non-flashing water discharge and saturated water flashing models for the confirmatory assessments of new SG designs was examined.

• Journal of Korean Neurosurgical Society
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• v.65 no.6
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• pp.868-874
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• 2022

Spontaneous intracranial hypotension (SIH) most commonly manifests as bilateral subdural hematoma (SH). SIH cases mostly resolve spontaneously but further treatment would be needed via blind epidural blood patch (EBP). Cerebrospinal fluid (CSF) leakage in EBP-refractory cases can be treated surgically only if the localization of CSF leakage is detectable but it cannot be possible in most of the cases. Also surgical evacuation of SH secondary to SIH (SH-SIH) is not favorable without blocking the CSF leakage. Thus the management of these patients is a challenge and alternative treatment options are needed. Although middle meningeal artery embolization (MMAE) is an effective treatment option in non-SIH SH, there is no report about its application in the treatment of SH-SIH. We present two cases of SH-SIH which their clinical and radiological findings were completely resolved by bilateral MMAE treatment.

• Journal of Veterinary Clinics
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• v.39 no.5
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• pp.253-257
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• 2022

A 5-year-old castrated male Golden Retriever dog weighing 15 kg presented with evidence of intestinal intussusception. The patient had cachexia and severe dehydration before being referred to our department. Ultrasound imaging revealed a target sign indicative of intestinal intussusception. Emergency surgery was performed shortly after diagnosis. After a successful surgery, the patient was hospitalised for postoperative care. Initial treatment was aimed at the reversion of dehydration and the provision of adequate nutrition. Fluid therapy and central parenteral nutrition were administered via the peripheral and central venous catheters, respectively. Ten days postoperatively, swelling and edema were observed in the head and neck. Ultrasound and computed tomography confirmed complete blockage of the cranial vena cava due to thrombosis, which consequently obstructed both the left and right jugular veins. For treatment, dalteparin and tissue plasminogen activator were administered. However, the patient lost all of its vital function on the daybreak of postoperative day 11. Venous thrombus formation secondary to central parenteral nutrition application via the central line is a rare but possible complication. Veterinarians who are concerned about taking care of patients receiving CPN through the central line should keep the possibility of venous thrombus formation in mind.