• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.799-803
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• 2008

The possibility of manufacturing titanium hollow cylinder tank for ramjet engine was demonstrated with superplastic forming of subscale article. An innovative manufacturing method to produce complex configuration from titanium multi-sheets by low hydrostatic pressure was presented. Finite element analysis on superplastic blow forming process has been carried out in order to improve the forming process when manufacturing subscale hollow cylinder structure using Ti-6Al-4V multi-sheets. The simulation focused on the reduction of forming time and obtaining finally required shape throughout investigating the deformation mode of sheet according to the forming conditions and die geometry. From pre-sized titanium sheets, near net shape of hollow cylinder tank is obtained by superplastic blow forming conducted using gas pressure of 15bar at 1148K. The result shows that the manufacturing method with superplastic forming of multi-sheets of titanium alloy has been successful for near net shape forming of subscale hollow cylinder tank of ramjet engine.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.36 no.6
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• pp.273-279
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• 2014

Purpose: This study assessed the association between eye symptoms (enophthalmos or diplopia) and site of damage, volume, deviated inferior rectus muscle (IRM) and type of fracture with computed tomography (CT). The intent is to anticipate the prognosis of orbital trauma at initial diagnosis. Methods: Forty-five patients were diagnosed with fractures of the inferior wall of one orbit. Fracture area, volume of displaced tissue, deviated IRM, and type of fracture were evaluated from coronal CT by one investigator. The association of those variables with the occurrence of eye symptoms (diplopia and enophthalmos) was assessed. Results: Of 45 patients, 27 were symptom-free (Group A) and 18 had symptoms (Group B) of enophthalmos and/or diplopia. In Group B, 12 had diplopia, one was enophthalmos, and five had both. By CT measurement, group A mean area was $192.6mm^2$ and the mean volume was $673.2mm^3$. Group B area was $316.2mm^2$ and volume was $1,710.6mm^3$. The volume was more influential on symptom occurrence. Each patient was categorized into four grades depending on the location of IRM. Symptom occurrence and higher grade were associated. Twenty-six patients had trap-door fracture (one side, attached to the fracture), and 19 had punched-out fracture (both sides detached). The punched-out fracture was more strongly associated with symptoms and had statistically significantly higher area and volume. Conclusion: In orbital trauma, measurement of fracture area and volume, evaluation of the deviated IRM and classification of the fracture type by coronal CT can effectively predict prognosis and surgical indication.

• Journal of ILASS-Korea
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• v.25 no.4
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• pp.162-169
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• 2020

The worldwide focus on reducing the emissions, fuel and lubricant consumption in T-GDI engines is leading engineers to consider the crankcase ventilation and oil mist separation system as an important means of control. In today's passenger cars, the oil mist separation systems mainly use the inertia effect (e.g. labyrinth, cyclone etc.). Therefore, this study has investigated high efficiency cylinder head-integrated oil-mist separator by using a compact multi-impactor type oil mist separator system to ensure adequate oil mist separation performance. For this purpose, engine dynamometer testing with oil particle efficiency measurement equipment and 3D two-phase flow simulation have been performed for various engine operating conditions. Tests with an actual engine on a dynamometer showed oil aerosol particle size distributions varied depending on operating conditions. For instance, high rpm and load increases bot only blow-by gases but the amount of small size oil droplets. Submicron-sized particles (less than 0.5 ㎛) were also observed. It is also found that the impactor type separator is able to separate nearly no droplets of diameter lower than 3 ㎛. CFD results showed that the complex aerodynamics processes that lead to strong impingement and break-up can strip out large droplets and generate more small size droplets.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.595-598
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• 2011

Supersonic combustion phenomena in the main combustor of a dual combustion ramjet (DCR) engine are studied numerically. Since the supersonic combustion is affected significantly by the compressibility effects parametric studies have been carried out for the constant are length and the divergence angle. Numerical studies with fixed inflow condition for different geometric configurations reveals that the supersonic combustion in DCR combustor has the characteristics of lifting flame, where the lifting flame is maintained near the injector tip for the case of long combustor length with small divergence angle, but the lifting height is significantly increase for large divergence angle resulting flame blow-out of the combustor. Therefore, it is concluded that flame stability should be considered sufficiently in the design o DCR combustor.

• Archives of Plastic Surgery
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• v.36 no.4
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• pp.428-431
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• 2009

Purpose: Blow out fracture resulting from facial trauma is of high frequency among facial bone fractures, and can cause severe complications. So, proper management and close observation after operation are needed. So far, Computed tomography has been the best choice in the evalution following orbit wall reconstruction. However, cost - effectiveness, accessibility to patients and hazard of radiation exposure of computed tomography require supplementary measure for the evaluation following orbit wall reconstruction. This study was performed to describe the effectiveness of ultrasonography in the evalution following orbit wall reconstruction. Methods: A retrospective study was performed on 40 patients who underwent orbit wall reconstruction from June, 2008 to July, 2008. The patients' ages ranged from 13 to 65 years (mean 27.5 years), and this group was compsoed of 27 male and 13 female patients. The follow up period ranged from 2 weeks to 28 weeks (mean 11weeks). Preoperatively, all fractures were diagnosed using computed tomography. Ultrasonography for all cases, and computed tomography for 2 cases were performed for evaluation following orbit wall reconstruction. Results: Reduction of herniated orbital soft tissue and orbit implant was identified by using ultrasonography in 38 cases out of 40 cases. In other cases which we could not identify the orbit implant, computed tomography was performed. Con clusion: Compared to computed tomography, ultrasonography is simple, inexpensive and convenient method. Ultrasonography can be used as supplementary measure to computed tomography in the evaluation following orbit wall reconstruction for elective patients.

• Archives of Plastic Surgery
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• v.37 no.1
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• pp.99-103
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• 2010

Purpose: Blow-out fractures are reduced through transcutaneous or transconjunctival incisions. But the field of orbital surgery is difficult due to lack of visualization of fracture site, blind dissection of orbital floor, susceptibility of injury of orbital structures. In these situations, the former technique of using an antral balloon catheter has advantages over other methods for reconstruction because of its rapidity, simplicity, and inexpensiveness. Furthermore, the antral balloon catheter allows not only elevation of the orbital bone fragment but also expansion of the maxillary sinus in cases where there is a fracture of its walls. But postoperative follow-up method using computed tomography is expensive. Hence, we report a simple and inexpensive follow-up method using radiopaque dye inflation. Methods: We performed endoscopic transantral approach in 5 cases of blow-out fracture under general anesthesia. To accomplish this technique, a rigid 4 mm, 0 or 30 degree angled endoscopy was inserted into the maxillary sinus. Inflation of the catheter started gradually, with 10 to 15 mL of saline mixed radiopaque dye (saline: dye, 5 : 1) by syringe and while observing the elevation of the fracture site with endoscope until a proper contour was reached. For the maintain of the position of fractured site, 12 French urinary balloon foley catheter were used in fracture site for 7 - 10 days. Results: Postoperative assessment was performed by means of clinical and simple radiographic examination to secure the catheter under the inferior orbital wall and in the maxillary sinus. No specific complications occurred related to this procedure. Results of the surgery and follow-up in all cases were satisfactory. Conclusion: It may be a better alternative to the conventional follow-up method, with less cost and effectiveness of the catheter patency. The advantages of using the urinary balloon foley catheter with the radiopaque dye include the following : it is safe, efficacy, simple, and especially low cost. On drawback of this method is the discomfort to the patient caused by the catheter during the treatment.

• Journal of the Korean GEO-environmental Society
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• v.11 no.11
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• pp.77-85
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• 2010

Unconfined compressive strength tests were performed to evaluate curing characteristics of controlled low strength material(CLSM) made with coal ashes. It is found that unconfined compressive strength normalized by curing times, increases as decreasing the water contents of CLSM particularly during first three days. Dynamic cone penetrometer tests were also carried out to evaluate cost-effective CLSM lump strength characteristics with time. It takes around 10 days to reach target strength, 500kPa (penetration rate, 20mm/blow). Curing rate significantly decreases after 10 days elapsed regardless of CLSM formulation.

• Archives of Craniofacial Surgery
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• v.10 no.2
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• pp.81-85
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• 2009

Purpose: The inferior orbital wall is the most vulnerable to injury and inadequate reconstruction of inferior orbital fracture result in postoperative complications include enophthalmos, ocular dystopia and diplopia. Although the anatomical reconstruction of the inferior orbital wall is necessary to prevent these complications, the complexity of inferior orbital wall makes it difficult. We fabricated and remodeled the titanium micro-mesh plate for the anatomical reconstruction of inferior orbital wall. Methods: Twenty-nine patients with inferior orbital wall blow-out fracture were operated and twelve of them presented large extensive fracture. We intraoperatively fabricated and remodeled the Titanium-micro mesh to angulated lazy S shape similar to contralateral uninjured orbit. The preoperative and postoperative facial CT scan verified the 3-dimensional and anatomical reconstruction of the fractures. The mean follow-up was 19.7 months and postoperative complications was evaluated. Results: All cases showed the exact anatomical reconstruction, but there were minor complications in two cases. one patient had postoperative diplopia until 3months after surgery and the other patient had persistent enophthalmos (2 mm), but no further surgical correction was required. Conclusion: The comprehensive understanding of orbital convexity is the most important factor for anatomical reconstruction of inferior orbital fracture. We could prevent postoperative complications after inferior orbital wall reconstruction by intraoperative fabrication and anatomical remodeling of Titanium micro-mesh.

• Archives of Craniofacial Surgery
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• v.16 no.3
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• pp.114-118
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• 2015

Background: The reduction of orbital blowout fracture primarily aims to normalize the extra-ocular movement by returning the herniated orbital soft tissue into the original position, and to prevent enophthalmos by normalizing the orbital cavity volume. We introduce a balloon catheter-assisted orbital floor reduction technique. Methods: A retrospective review was performed for all patients with orbital floor fracture who underwent the technique described in the main body of this text. Medical records were reviewed for demographic data, clinical presentation and course, degree of enophthalmos, intraorbital volume on computed tomography scan, and postoperative outcomes. The enophthalmos and intraorbital volume of the injured site were compared to the uninjured eye and orbit. Results: The review identified 14 patients (11 male, 3 female). The mean preoperative difference in en-exopthalmos was 2.13 mm, while the mean orbital volume was 116%. The mean postoperative difference in en-exophthalmos had improved to 0.61 mm with a mean orbital volume of 101.85%. At the time of catheter removal at 10 days, three patients experienced diplopia (n=1), extra-ocular movement disorder (1), or enophthalmos (1). All of these had resolved by the 6-month follow-up visit. Conclusion: Balloon catheter-assisted reduction of the orbital floor fractures was associated with improvements in intraorbital volume and enopthalmos in the 14 patients. Notable complications included diplopia, enophthalmos, and limited extra-ocular movement, all of which were transient in the early postoperative period and had resolved by 6-month follow up.

• Archives of Craniofacial Surgery
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• v.17 no.3
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• pp.146-153
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• 2016

Background: Restoring the orbital cavity in large blow out fractures is a challenge for surgeons due to the anatomical complexity. This study evaluated the clinical outcomes and orbital volume after orbital wall fracture repair using a rapid prototyping (RP) technique and intraoperative navigation system. Methods: This prospective study was conducted on the medical records and radiology records of 12 patients who had undergone a unilateral blow out fracture reconstruction using a RP technique and an intraoperative navigation system from November 2014 to March 2015. The surgical results were assessed by an ophthalmic examination and a comparison of the preoperative and postoperative orbital volume ratio (OVR) values. Results: All patients had a successful treatment outcome without complications. Volumetric analysis revealed a significant decrease in the mean OVR from $1.0952{\pm}0.0662$ (ranging from 0.9917 to 1.2509) preoperatively to $0.9942{\pm}0.0427$ (ranging from 0.9394 to 1.0680) postoperatively. Conclusion: The application of a RP technique for the repair of orbital wall fractures is a useful tool that may help improve the clinical outcomes by understanding the individual anatomy, determining the operability, and restoring the orbital cavity volume through optimal implant positioning along with an intraoperative navigation system.