• Nuclear Engineering and Technology
• /
• v.31 no.5
• /
• pp.486-497
• /
• 1999

The local heat transfer coefficient is experimentally investigated for the reflux condensation in a countercurrent flow between the steam-air mixture and the condensate, A single vertical tube has a geometry which is a length of 2.4m, inner diameter of 16.56mm and outer diameter of 19.05mm and is made of stainless steel. Air is used as a noncondensible gas. The secondary side has a shape of annulus around vertical tube and the lost heat by primary condensation is transferred to the coolant water. The local temperatures are measured at 11 locations in the vertical direction and each location has 3 measurement points in the radial direction, which are installed at the tube center, at the outer wall and at the coolant side. In three different pressures, the 27 sets of data are obtained in the range of inlet steam flow rate 1.348∼3.282kg/hr, of inlet air mass fraction 11.8∼55.0%. The investigation of the flooding is preceded to find the upper limit of the reflux condensation. Onset of flooding is lower than that of Wallis' correlation. The local heat transfer coefficient increases as the increase of inlet steam flow rate and decreases as the increase of inlet air mass fraction. As an increase of the system pressure, the active condensing region is contracted and the heat transfer capability in this region is magnified. The empirical correlation is developed by 165 data of the local heat transfer. As a result, the Jacob number and film Reynolds number are dominant parameters to govern the local heat transfer coefficient. The rms error is 17.7% between the results by the experiment and by the correlation.

• Archives of Plastic Surgery
• /
• v.34 no.4
• /
• pp.461-465
• /
• 2007

Purpose: Nasal bone fracture may be the most common fracture among facial trauma. However, diagnosis and treatment tend to be overlooked while the reduction and maintenance of fragments remain complicated. Thus, the results are plagued with high rate of nasal deformity which leads cosmetic and functional discomfort. We took advantage of the fact that the nasal bone is one of the thinnest facial bone while at the same time being located close to the skin and utilized ultrasound in performing reduction of nasal bone. Methods:This method was performed on 25 patients with nasal bone fracture. The CL 15-7 linear array transducer (10-15MHz) ultrasound which provides a total of 7 views (3 axial views and 4 transverse views) of the elevator under the bony fragments was enough for the surgeon to accurately perform the reduction. Results: In our class, an accurate and precise reduction has been made possible by real time images before, during, and after the procedure with the help of ultrasound while reducing the exposure to radiation. Conclusion: Compared to previous methods, satisfaction of patients has increased in the nasal tip, minimal fracture of the side wall and secondary reduction cases. Therefore, the incorporation of ultrasound in the closed reduction of nasal bone may prove to be a useful method.

• Korea-Australia Rheology Journal
• /
• v.12 no.1
• /
• pp.55-67
• /
• 2000

In this paper, an experimental study of the rheological behavior of granular flow in a new type of storage silo is presented. The main characteristic of the new design is a hexagonal shape chosen with the objective of minimizing the stresses applied to the stored grains, and to reduce grain damage during the filling and emptying processes. Measurements of stress distribution and flow patterns are shown for a variety of granular materials. Because of the design of the silo, the granular material adopts its natural rest angle at all times eliminating collisional stresses and impacts between grains. A homogeneous, low friction flow is naturally achieved which provides a controlled stress distribution throughout the silo during filling and emptying. Secondary dynamic stresses, which are responsible for wall failure in conventional silos of the vertical type, are completely eliminated. A comparison between the two geometries is presented with data obtained for these silos and a number of granular materials. The discharge pattern inhibits powder formation in the silo and the filling system virtually eliminates unwanted material packing. Finally, notwithstanding the rheological advantages of this new design, the hexagonal cells that constitute the silo have many other advantages, such as the possible use of solar energy to control the humidity inside them. The cell type design allows for versatile storage capabilities and the elevation above the ground provides unlimited transportation facilities during emptying.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2000.02a
• /
• pp.180-180
• /
• 2000

Plasma source ion implantation is a new doping technique for the formation of shallow junction with the merits of high dose rate, low-cost and minimal wafer charging damage. In plasma source ion implantation process, the wafer is placed directly in the plasma of the appropriate dopant ions. Negative pulse bias is applied to the wafer, causing the dopant ions to be accelerated toward the wafer and implanted below the surface. In this work, inductively couples plasma was generated by anodized Al antenna that was located inside the vacuum chamber. The outside wall of Al chamber was surrounded by Nd-Fe-B permanent magnets to confine the plasma and to enhance the uniformity. Before implantation, the wafer was pre-sputtered using DC bias of 300B in Ar plasma in order to eliminate the native oxide. After cleaning, B2H6 (5%)/H2 plasma and negative pulse bias of -1kV to 5 kV were used to form shallow p+/n junction at the boron dose of 1$\times$1015 to 5$\times$1016 #/cm2. The as-implanted samples were annealed at 90$0^{\circ}C$, 95$0^{\circ}C$ and 100$0^{\circ}C$during various annealing time with rapid thermal process. After annealing, the sheet resistance and the junction depth were measured with four point probe and secondary ion mass spectroscopy, respectively. The doping uniformity was also investigated. In addition, the electrical characteristics were measured for Schottky diode with a current-voltage meter.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.11a
• /
• pp.299-304
• /
• 2008

Starting characteristics of the axi-symmetric second throat exhaust diffuser (STED) with zero-secondary flows are numerically investigated. Renolds-Average Navier-Stokes equations with a standard ${\kappa}-{\varepsilon}$ turbulence model incorporated with enhanced wall treatment are solved to simulate the diffusing evolutions of the nozzle plume. Minimum (optimum) starting pressure difference of 20$\sim$25% between 1-D theory and the measured data validated from previous results[5] is also applied to predict the range of an effective diffuser expansion ratio (Ad/At) in this system.

• The Journal of Korean Institute of Information Technology
• /
• v.16 no.11
• /
• pp.43-49
• /
• 2018

Computer simulation was performed using the SIMION program to develop an electron gun for MCP cleaning. The target, MCP, is located 180mm from the source of the electron gun, and the diameter of the MCP is approximately 20mm. Therefore, we tried to find the condition that the beam diameter of electrons reaching the MCP is to be 20mm using four variables such as E, ${\phi}$, d1, d2, where the E is the energy of the electron reaching the MCP, the ${\phi}$ is the diameter of the extractor, and the d1 and the d2 are the distance from the electron source to the end of the extractor tube, and to the wall of chamber, respectively. As a result of simulation, we figuried out that the E and the d2 have little effect on the beam diameter. On the other hand, we also found that the beam diameters were very sensitive to the d1 and varied relatively large with respect to the ${\phi}$, and the d1 was the secondary order function of the ${\phi}$. Therefore we found that this function will allow us to design electron guns that are suitable for the purposes of this study.

• Korean Journal of Heritage: History & Science
• /
• v.48 no.4
• /
• pp.44-61
• /
• 2015

Mural tomb in Goa-ri(Goryeong) built in the 6th Century Gaya period investigated precisely by the scientific method. They were used to optical equipments for investigation and made a damage map according to the damaging types. The mortar layer was mostly exfoliated from the rest of the wall except for the burial chamber ceiling and corridor ceiling. Also painting layers rarely not observed. Most of the paintings were damaged except lotus painting in burial chamber ceiling. Various damage types that exfoliation, earthen dirt, film coating were found in murals. Damage factors of mural were the porous characteristics of mortar layer and the movement of moisture in the murals. They were caused physical damage such as crack, exfoliation. It was getting worse and causing to secondary damage like earthen dirt, film coating.

• Geomechanics and Engineering
• /
• v.24 no.3
• /
• pp.253-266
• /
• 2021

The sufficient early strength of primary support is crucial for stabilizing the surroundings, especially for the tunnels constructed in soil. This paper introduces the Steel-Concrete Composite Support System (SCCS), a new support with high bearing capacity and flexible, rapid construction. The bearing characteristics and construction performance of SCCS were systematically studied using a three-dimensional numerical model. A sensitivity analysis was also performed. It was found that the stress of a π-shaped steel arch decreased with an increase in the thickness of the wall, and increased linearly with an increase in the rate of stress release. In the horizontal direction of the arch section, the nodal stresses of the crown and the shoulder gradually increased in longitudinally, and in the vertical direction, the nodal stresses gradually decreased from top to bottom. The stress distribution at the waist, however, was opposite to that at the crown and the shoulder. By analyzing the stress of the arch section under different installation gaps, the sectional stress evolution was found to have a step-growth trend at the crown and shoulder. The stress evolution at the waist is more likely to have a two-stage growth trend: a slow growth stage and a fast growth stage. The maximum tensile and compressive stresses of the secondary lining supported by SCCS were reduced on average by 38.0% and 49.0%, respectively, compared with the traditional support. The findings can provide a reference for the supporting technology in tunnels driven in loess.

• Journal of Trauma and Injury
• /
• v.34 no.4
• /
• pp.299-304
• /
• 2021

Atypical hemolytic uremic syndrome (aHUS) is a rare, progressive, life-threatening condition of thrombotic microangiopathy characterized by thrombocytopenia, microangiopathic hemolytic anemia, and renal impairment. The mechanisms underlying aHUS remain unclear. Herein, we present the first case in the literature of aHUS after a traumatic injury. A 55-year-old male visited the emergency department after a traumatic injury caused by a tree limb. Abdominal computed tomography revealed a rectal wall defect with significant air density in the perirectal space and preperitoneum, implying rectal perforation. Due to the absence of intraperitoneal intestinal perforation, we performed diverting sigmoid loop colostomy. An additional intermittent simple repair was performed due to perianal and anal injuries. One day postoperatively, his urine output abruptly decreased and serum creatinine level increased. His platelet level decreased, and a spiking fever occurred after 2 days. The patient was diagnosed with acute renal failure secondary to aHUS and was treated with fresh frozen plasma replacement. Continuous renal replacement therapy (CRRT) was also started for oliguria and uremic symptoms. The patient received CRRT for 3 days and intermittent hemodialysis thereafter. After hemodialysis and subsequent supportive treatment, his urine output and renal function improved. The hemolytic anemia and thrombocytopenia also gradually improved. Dialysis was terminated on day 22 of admission and the patient was discharged after recovery. This case suggests that that a traumatic event can trigger aHUS, which should be considered in patients who have thrombocytopenia and acute renal failure with microangiopathic hemolytic anemia. Early diagnosis and appropriate management are critical for favorable outcomes.

• Nuclear Engineering and Technology
• /
• v.54 no.5
• /
• pp.1914-1928
• /
• 2022

To improve the heat transfer efficiency of the reactor fuel assembly, it is necessary to accurately calculate the two-phase flow boiling characteristics and the critical heat flux (CHF) in the fuel assembly. In this paper, a Eulerian two-fluid model combined with the extended wall boiling model was used to numerically simulate the 5 × 5 fuel rod bundle with spacer grids (four sets of mixing vane grids and four sets of simple support grids without mixing vanes). We calculated and analyzed 11 experimental conditions under different pressure, inlet temperature, and mass flux. After comparing the CHF and the location of departure from the nucleate boiling obtained by the numerical simulation with the experimental results, we confirmed the reliability of computational fluid dynamic analysis for the prediction of the CHF of the rod bundle and the boiling characteristics of the two-phase flow. Subsequently, we analyzed the influence of the spacer grid and mixing vanes on the void fraction, liquid temperature, and secondary flow distribution. The research in this article provides theoretical support for the design of fuel assemblies.