• Korean Journal of Head & Neck Oncology
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• v.23 no.1
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• pp.9-14
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• 2007

Background and Objectives：The prevalence rate of laryngeal cancer, the cancer known as good prognosis in comparison to other malignancy, accounts for 1% of all malignancy in Korea(Korea Central Cancer Registry, 2002). The purpose of this study is to review the treatment experiences of our hospital and find prognostic factors in laryngeal cancer patients. Materials and Method：A retrospective study was conducted on 244 laryngeal cancer patients between January 1987 through December 2003. Age, sex, TNM stage, 5 year survival rate, prognostic factors were analyzed. Results：The overall 5 year survival rate was 57.8%. The 5 year survival rate according to primary site and treatment method showed supraglottis 49.5%, glottis 79.2%, transglottis 28.2% and surgery only 71.4%, radiotherapy only 58.1%, post operative radiotherapy 47.2%, salvage operation 52.0%. There was no statistically significant difference among the results obtained by 4 different methods of treatment. but in supraglottis, surgery only has good 5 year survival rate(75.8%) compare to radiotherapy only(38.3%), postoperative radiotherapy(20.0%), salvage operation(43.7%) and there was statistically significant difference. The 5 year survival rate according to clinical stage and T status showed 84.1%, 37.2%, in stage I & II, III & IV respectively, 72.9%, 37.5% in stage T1 & T2, T3 & T4 respectively. The 5 year survival rate according to nodal status showed N(-)77.1%, N(+)35.6%. Conclusion：Those patient with early T stage, early clinical stage, glottic cancer, negative neck node and surgery only patient in supraglottis showed good treatment results in univariate analysis. The clinical stage and primary site of laryngeal cancer were found to be significant prognostic factors in laryngeal cancer patients in multivariate analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.4
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• pp.109-122
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• 1983

An accurate thick beam element (TB4) which includes the effects of the shear deformation and rotatory inertia has been degenerated from the three dimensional continuum by employing the Timoshenko beam assumptions. The proposed TB4 element has four nodes and two degrees of freedom at each node, totally eight degrees of freedom. The transverse deflection W and plane rotation ${\theta}$ with the cubic interpolation functions are selected as nodal variables. The element characteristics are formulated by discretizing the beam equations of motion, using the Galerkin weighted residual method, and are numerically integrated by the reduced shear integration technique, using the three-point Gauss quadrature with the various shear coefficients. Several numerical examples are analyzed to demonstrate the accuracy and the monotonic convergence behavior of the proposed TB4 beam element. The result indicates that the TB4 element shows the more excellent performance and the monotonic convergence behavior than the other existing Timoshenko beam type elements for the whole range of the beam aspect ratios, in both static and free vibration analyses.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.395-399
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• 2017

The LPI fuel filter housings used in automobiles were made from conventional die castings but have recently been developed by cold forging to improve the weight and durability. On the other hand, a sink may develop at the core of the forged product due to the resulting T-shape, which not only reduces the aesthetics, but also increases the post-processing cost of the product. Therefore, this research focused on methods to predict and mitigate sink development and progression during the T-shape forging process. Finite element analysis of the forging process was first performed to determine the optimal initial workpiece devoid of burrs and underfills. An accurate sink prediction was then obtained via metal flow analysis, which was a result of the finite element simulation. Through finite element analysis, it was confirmed that sink development is a product of the differences in nodal velocities arising from the T-shaped forging process. Consequently, a pad was inserted beneath the sink to minimize these velocity differences. The results yielded significant improvement with regard to the sink defect. This method was practically applied to an industrial site to validate the sink improvement.

• The Journal of Engineering Geology
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• v.18 no.4
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• pp.381-391
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• 2008

The eigenvalue technique is introduced to overcome the problem of truncation errors caused by temporal discretization of numerical analysis. The eigenvalue technique is different from simulation in that only the space is discretized. The spatially discretized equation is diagonized and the linear dynamic system is then decoupled. The time integration can be done independently and continuously for any nodal point at any time. The results of eigenvalue technique are compared with the exact solution and FEM numerical solution. The eigenvalue technique is more efficient than the FEM to the computation time and the computer storage in the same conditions. This technique is applied to the solute transport analysis in nonuniform flow fields around underground storage caverns. This method can be very useful for time consuming simulations. So, a sensitivity analysis is carried out by using this method to analyze the safety of caverns from nearly located contaminant sources. According to the simulations, the reaching time from source to the nearest cavern may takes 50 years with longitudinal dispersivity of 50 m and transversal dispersivity of 5 m, respectively.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.143-150
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• 1996

This is an explicit-Implicit, finite element analysis for linear as well as nonlinear hygrothermal stress problems. Additional features, such as moisture diffusion equation, crack element and virtual crack extension(VCE ) method for evaluating J-integral are implemented in this program. The Linear Elastic Fracture Mechanics(LEFM) Theory is employed to estimate the crack driving force under the transient condition for and existing crack. Pores in materials are assumed to be saturated with moisture in the liquid form at the room temperature, which may vaporize as the temperature increases. The vaporization effects on the crack driving force are also studied. The Ideal gas equation is employed to estimate the thermodynamic pressure due to vaporization at each time step after solving basic nodal values. A set of field equations governing the time dependent response of porous media are derived from balance laws based on the mixture theory Darcy's law Is assumed for the fluid flow through the porous media. Perzyna's viscoplastic model incorporating the Von-Mises yield criterion are implemented. The Green-Naghdi stress rate is used for the invariant of stress tensor under superposed rigid body motion. Isotropic elements are used for the spatial discretization and an iterative scheme based on the full newton-Raphson method is used for solving the nonlinear governing equations.

• Journal of Chest Surgery
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• v.31 no.9
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• pp.855-860
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• 1998

Background: Adequate exposure of the mitral valve is a prerequisite for mitral procedures including the repair. An extended transseptal approach in mitral valvular operations is known to have certain technical advantages in recent years because of the anatomic posterior location of the mitral valve, especially in reoperations and in the presence of the small atrium in spite of the possibility of arrhythmia due to injury of sinus nodal artery. Material and Method: We compared the preoperative status, operative, and postoperative factors among patients in two study groups, transseptal only (Group I, n=10) and extended transseptal approach(Group II, n=25). Result: There were no differences in age, sex, NYHA functional class, left atrial size, and left ventricular function. The incidence of the redo-operation was high and early postoperative arrhythmia, which was improved later, appeared in 3 patients in Group II, but not in Group I. Conclusion: We believe that atrial septal incision could be extended up to the atrial roof whenever exposure of the mitral valve during a transseptal approach is inadequate because the late results were similar.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.115-130
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• 2013

The sectional methods of current design codes have been broadly used for the design of various kinds of reinforced concrete pile caps. Lately, the strut-tie model approach of current design codes also became one of the attracting methods for pile caps. However, since the sectional methods and the strut-tie model approach of current design codes have been established by considering the behaviors of structural concrete without D-regions and two-dimensional concrete structures with D-regions, respectively, it is inappropriate to apply the methods to the pile caps dominated by 3-dimensional structural behavior with disturbed stress regions. In this study, the refined 3-dimensional strut-tie models, which consider the strength characteristics of 3-dimensional concrete struts and nodal zones and the load-carrying capacity of concrete ties in tension regions, are proposed for the rational analysis and design of pile caps. To examine the validity of the proposed models and to verify the necessity of appropriate constituent elements for describing 3-dimensional structural behavior and load-transfer mechanism of pile caps, the ultimate strength of 78 reinforced concrete pile caps tested to failure was examined by the proposed models along with the sectional and strut-tie model methods of current design codes.

• Journal of Chest Surgery
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• v.31 no.3
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• pp.271-278
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• 1998

In order to access the value of computed tomography in mediastinal LN staging of NSCLCa, 581 LN stations of 77 patients were selected from 552 patients who were diagnosed as Lung Ca and operated in Seoul National University Hospital from 1992 to 1995. The selection criteria were as follows ; the patients 1) whose preoperative chest CTs were available; 2) underwent curative resection (lobectomy or more) with complete lymph node dissection; 3) whose final pathologic diagnosis were proven to be non-small cell lung cancer. We adopted Receiver Operating Characteristic curve method to determine a proper size criterion for diagnosing malignant mediastinal adenopathy. From curve analysis, we decided the size criterion of lymph node to 1 cm in their short axis. Using this size criterion, it's sensitivity was 43.9%, specificity was 87.4%, and accuracy was 83.1%. Eventhough we couldn't determine the precise size criterion for the adenoca, it seemed that shorter than 1 cm size criterion should be applied in that particular cell type. Lymph node stations associated with the tuberculosis or bronchiectasis tend to be overestimated in nodal staging and have relatively high false positive rate. The low sensitivity of CT scan suggest that radical and complete dissection or precise mediastinal lymph node evaluation through the surgical approach is mandatory.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.30 no.4
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• pp.331-338
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• 2004

Stress transfer to the surrounding tissues is one of the factors involved in the design of dental implants. Unfortunately, insufficient data are available for stress transfer within the regenerated bone surrounding dental implants. The purpose of this study was to investigate the concentration of stresses within the regenerated bone surrounding the implant using three-dimensional finite element stress analysis method. Stress magnitude and contours within the regenerated bone were calculated. The $3.75{\times}10-mm$ implant (3i, USA) was used for this study and was assumed to be 100% osseointegrated, and was placed in mandibular bone and restored with a cast gold crown. Using ANSYS software revision 6.0, a program was written to generate a model simulating a cylindrical block section of the mandible 20 mm in height and 10 mm in diameter. The present study used a fine grid model incorporating elements between 165,148 and 253,604 and nodal points between 31,616 and 48,877. This study was simulated loads of 200N at the central fossa (A), at the outside point of the central fossa with resin filling into screw hole (B), and at the buccal cusp (C), in a vertical and $30^{\circ}$ lateral loading, respectively. The results were as follows; 1. In case the regenerated bone (bone quality type IV) was surrounded by bone quality type I and II, stresses were increased from loading point A to C in vertical loading. And stresses according to the depth of regenerated bone were distributed along the implant evenly in loading point A, concentrated on the top of the cylindrical collar loading point B and C in vertical loading. And, In case the regenerated bone (bone quality type IV) was surrounded by bone quality type III, stresses were increase from loading point A to C in vertical loading. And stresses according to the depth of regenerated bone were distributed along the implant evenly in loading point A, B and C in vertical loading. 2. In case the regenerated bone (bone quality type IV) was surrounded by bone quality type I and II, stresses were decreased from loading point A to C in lateral loading. Stresses according to the depth of regenerated bone were concentrated on the top of the cylindrical collar in loading point A and B, distributed along the implant evenly in loading point C in lateral loading. And, In case the regenerated bone (bone quality type IV) was surrounded by bone quality type III, stresses were decreased from loading point A to C in lateral loading. And stresses according to the depth of regenerated bone were distributed along the implant evenly in loading point A, B and C in lateral loading. In summary, these data indicate that both bone quality surrounding the regenerated bone adjacent to implant fixture and load direction applied on the prosthesis could influence concentration of stress within the regenerated bone surrounding the cylindrical type implant fixture.

• Clinical and Experimental Pediatrics
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• v.46 no.1
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• pp.51-55
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• 2003

Purpose : We intended to find out the role of transesophageal atrial pacing in evaluation of infants and children with palpitation of unknown origin. Methods : We tried transesophageal atrial pacing study in 69 infants and children with palpitation, in whom tachycardia wasn't documented in electrocardiogram and reviewed retrospectively the records of transesophageal pacing and medical records of theses patients to find out the induction rate of tachycardia by transesophageal atrial pacing and the possible mechanism of tachycardia if induced. Results : In 70.1% infants and children with palpitation, tachycardia was induced, so we could conclude that tachycaridia was the cause of palpitation in these cases. In most cases, tachycardia was induced by rapid atrial pacing, and in 21% by using isoproterenol. Tachycardia induction rate was higher in <6-year-old children than ${\geq}6$-year-old children(P<0.05). In cases of the induced, we reviewed the mechanism of tachycardia. Of these induced tachycardias, 53.2% is atrioventricular reentry tachycardia, 34.0% were atrioventricular nodal reentry tachycardia, and 12.8% were idiopathic left ventricular tachycardia. Invasive electrophysiologic study was done to 10 patients of those induced. The results of electrophysiologic study and transesophageal pacing and recording were the same except for one patient. Conclusion : Transesophageal atrial pacing and recording is a less invasive, safe and useful method to find out the cause of palpitation and the mechanism of tachycardia in infants and children.