• Journal of Chest Surgery
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• v.29 no.5
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• pp.504-509
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• 1996

When a valve prosthesis is to be implanted in the aortic position, simple interrupted suture, figure-of- eight suture, or horizontal mattress suture technique is used as a suture method. However, the suture techniques may be unacceptable for aortic valve replacement in patients with friable annulus caused by some lesions, such as endocarditis and degenerative change. We used an alternative technique for the aortic vlave replacement in 4 patients with valve endocarditis, ) patients with degenerative valvular lesion, and 1 with rheumatic valvular disease. Mattress sutures through the annulus were placed with pledgets on the ventricular side of the annulus, whi h resulted in implantation of the prosthesis at a supra-annular level. Mechanical valves of 21 mm or larger were implanted in the supra-annular position in all patients and there was no impeded motion of leaflets during the follow-up period of mean 13.3 mouths. The transvalvular pressure gradient was less than 6 mm Hg in 3 patients and 20 to 40 mm Hg in 5 patients. The supra-annular implantation of mechanical aortic valve using a vertical mattress suture technique may be a useful alternative method of aortic valve replacement for the selected patients with friable or destroyed aortic annulus.

• Journal of the Korea Institute of Building Construction
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• v.10 no.2
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• pp.41-50
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• 2010

This study presented a model that can enable a reliability analysis for the repair and replacement cycle of a building by using background repair and replacement data and expert opinion as foundation data and applying Monte Carlo Simulation. The presented model offers the time of the repair and replacement of building elements for the period of a year, and supports the prediction of repair and replacement and expenses demand in advance while planning the maintenance of a building. In addition, the model will significantly reduce the risks to the building owner with regard to maintenance decisions. In addition, when a person in charge of the maintenance of large-scale building assets is having difficulties making decisions regarding the repair and replacement of existing building elements due to a lack of background data to support a long-term policy on the repair and replacement requirements, an engineering solution that can ensure the adequacy of this is provided. In summary, it can be largely divided into three study results. First, a method of estimating the repair and replacement cycle that can deal with the development of a construction system was developed. Second, a probabilistic methodology that can quantify the risk of the repair and replacement cycle was proposed. Third, the proposed model can be used as a means of supporting designer and constructor in making decisions for the life cycle plan of a building during a construction project.

• Journal of the Korean GEO-environmental Society
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• v.11 no.7
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• pp.57-63
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• 2010

The necessity of effective and economical improvement for soft ground is required more and more as mountains form 70% of country. The soft ground improvement methods for ocean development are sand compaction pile method, displacement method are applied to the soft ground improvement from ocean development pre-loading method, air pressure method, well point method, pack drain method, quicklime pile method etc. Among them, the sand compaction pile method, has many problems such as the economical problem on importing materials due to the lack of sand and destroying the nature while collecting sand. To replace the sand with other alternative materials, a study on the bottom ash compaction pile method because the bottom ash has the similar engineering properties with sand. Therefore, in this study, after compose the complex soil with a replacement rate of 10~80% and a large direct shear test, shear test, consolidation test with replacement rates of bottom ash are performed to estimate whether its shear and consolidation characteristics are suitable for the alternative material of compaction pile method. As a result of test, Shear Strength Parameters tend to be increased in accordance with the increase of replacement ratio of bottom compaction pile, and Settlement Reduction Factor and $t_{90}$ tend to be decreased.

• Journal of Chest Surgery
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• v.38 no.11 s.256
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• pp.783-787
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• 2005

Eight patients underwvnt reoperation after valve replacement surgery with a mechanical valve from January, 1992 to December, 2003. Among the various indications for reoperation, there were 4 patients with paravalvular leakage; 3 patients underwent resuturing of the area of leakage and one patient underwent redo valve replacement. Among the three patients with stenosis due to thrombosis of the valve, 2 patients underwent redo valve replacement and one patient underwent thrombectomy. In one patient, the valve functioned normally, but stenosis was caused by overgrowth of the patient and redo valve replacement was done 123 months later. There was no postoperative mortality or morbidity. After an average of 51 months ($2\~134$ months) of postoperative follow up, the patients were in good condition and were able to maintain a NYHA functional class of I or II. The operative method used, whether it be a redo valve replacement or valve sparing method, depends upon the type of lesion and the anatomic structure.

• Journal of Chest Surgery
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• v.40 no.12
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• pp.817-824
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• 2007

Background: There are two choices for heart valve replacement-the use of a tissue valve and the use of a mechanical valve. Using a tissue valve, additional surgery will be problematic due to valve degeneration. If the risk of additional surgery could be reduced, the tissue valve could be more widely used. Therefore, we analyzed the risk factors and mortality of patients undergoing repeated heart valve replacement and primary replacement. Material and Method: We analyzed 25 consecutive patients who underwent repeated heart valve replacement and 158 patients who underwent primary heart valve replacement among 239 patients that underwent heart vale replacement in out hospital from January 1995 to December 2004. Result: There were no differences in age, sex, and preoperative ejection fraction between the repeated valve replacement group of patients and the primary valve replacement group of patients. In the repeated valve replacement group, the previously used artificial valves were 3 mechanical valves and 23 tissue valves. One of these cases had simultaneous replacement of the tricuspid and aortic valve with tissue valves. The mean duration after a previous operation was 92 months for the use of a mechanical valve and 160 months for the use of a tissue valve. The mean cardiopulmonary bypass time and aortic cross clamp time were 152 minutes and 108 minutes, respectively, for the repeated valve replacement group of patients and 130 minutes and 89 minutes, respectively, for the primary valve replacement group of patients. These results were statistically significant. The use of an intra aortic balloon pump (IABP) was required for 2 cases (8%) in the repeated valve replacement group of patients and 6 cases (3.8%) in the primary valve replacement group of patients. An operative death occurred in one case (4%) in the repeated valve replacement group of patients and occurred in nine cases (5.1%) in the primary valve replacement group of patients. Among postoperative complications, the need for mechanical ventilation over 48 hours was different between the two groups. The mean follow up period after surgery was $6.5{\pm}3.2$ years. The 5-year survival of patients in the repeated valve replacement group was 74% and the 5-year survival of patients in the primary valve replacement group was 95%. Conclusion: The risk was slightly increased, but there was little difference in mortality between the repeated and primary heart valve replacement group of patients. Therefore, it is necessary to reconsider the issue of avoiding the use of a tissue valve due to the risk of additional surgery, and it is encouraged to use the tissue valve selectively, which has several advantages over the use of a mechanical valve. In the case of a repeated replacement, however, the mortality rate was high for a patient whose preoperative status was not poor. A proper as sessment of cardiac function and patient status is required after the primary valve replacement. Subsequently, a secondary replacement could then be considered.

• The KIPS Transactions:PartD
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• v.18D no.1
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• pp.1-8
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• 2011

The cache structure, which is designed for assuring fast accesses to frequently accessed data, resides on the various levels of computer system hierarchies. Many studies on this cache structure have been conducted and thus many page-replacement algorithms have been proposed. Most of page-replacement algorithms are designed on the basis of heuristic methods by using their own criteria such as how recently pages are accessed and how often they are accessed. This data-retrieval process in computer systems is analogous to human memory retrieval process since the retrieval process of human memory depends on frequency and recency of the retrieval events as well. A recent study regarding human memory cognition revealed that the possibility of the retrieval success and the retrieval latency have a strong correlation with the frequency and recency of the previous retrieval events. In this paper, we propose a novel page-replacement algorithm by utilizing the knowledge from the recent research regarding human memory cognition. Through a set of experiments, we demonstrated that our new method presents better hit-ratio than the LRFU algorithm which has been known as the best performing page-replacement algorithm for DBMS caches.

• Structural Engineering and Mechanics
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• v.86 no.1
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• pp.49-68
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• 2023

This study investigates the static and dynamic structural analysis of symmetrical and asymmetrical coupled shear walls using the continuous and modified transfer matrix methods by idealizing the coupled shear wall as a three-field CTB-type replacement beam. The coupled shear wall is modeled as a continuous structure consisting of the parallel coupling of a Timoshenko beam in tension (with axial extensibility in the shear walls) and a shear beam (replacing the beam coupling effect between the shear walls). The variational method using the Hamilton principle is used to obtain the coupled differential equations and the boundary conditions associated with the model. Using the continuous method, closed-form analytical solutions to the differential equation for the coupled shear wall with uniform properties along the height are derived and a numerical solution using the modified transfer matrix is proposed to overcome the difficulty of coupled shear walls with non-uniform properties along height. The computational advantage of the modified transfer matrix method compared to the classical method is shown. The results of the numerical examples and the parametric analysis show that the proposed analytical and numerical model and method is accurate, reliable and involves reduced processing time for generalized static and dynamic structural analysis of coupled shear walls at a preliminary stage and can used as a verification method in the final stage of the project.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.2
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• pp.185-190
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• 2013

The previous steganographic methods by using the interpolation were difficult to estimate the distortion because the size of cover image is extended by interpolation algorithms. In this paper, to solve the problems of previous methods proposed the improved steganographic method based on the pixel replacement algorithms. In our method, we cannot extend a cover image, but also can estimate exactly the distortion of the stego-images. In the experimental results, the estimated distortion and embedding capacity of stego-image are shown on three pixel replacement methods.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.2
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• pp.142-147
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• 2009

Conventional HP(high pressure) sodium or Metal-halide lamps have a life span of around one year requiring at least annual replacement and maintenance. High Power LED lights require no regular maintenance further increasing savings on replacement bulbs, access equipment and labour costs. New installations benefit from a substantial reduction in the cost of expensive heavy duty cable required for sodium lighting. Especially, LED light can achieve variable color temperature, high functional performance in the field of street light. There are two main method to achieve variable color temperature function of the street light. one method is using RGB multi-chip LED, the other is using Orange-White LED method. In this paper, it was compare RGB Multi-chip LED with white-orange LED for there characteristics performance.

• Journal of Biomedical Engineering Research
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• v.31 no.6
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• pp.449-455
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• 2010

A ceramic articulating system in total hip replacement thought to be superior to metal-on-polyethylene due to its extremely low coefficient of friction and potential for high resistance to wear. But ceramic is brittle, which makes it mechanically and theoretically susceptible to fracture under certain mechanical conditions. In the current study, nine different models of ceramic ball heads were mechanically evaluated using 3D finite element(FE) analyses. It was found that the maximum stress in all ceramic models was lower than ceramic flexural strength, and it satisfied the requirements of the FDA Gaudience for artificial hip implant. Thus, ceramic ball head models introduced in the current study could be mechanically safe for clinical applications.