• Journal of Mechanical Science and Technology
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• v.19 no.5
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• pp.1158-1168
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• 2005

A shunt from the left ventricle to the left anterior descending artery is being developed for coronary artery occlusive disease, in which the shunt or conduit connects the the left ventricle (LV) with the diseased artery directly at a point distal to the obstruction. To aid in assessing and optimizing its benefit, a computational model of the cardiovascular system was developed and used to explore various design conditions. Computational fluid dynamic analysis for the shunt hemodynamics was also done using a commercial finite element package. Simulation results indicate that in complete left anterior descending artery (LAD) occlusion, flow can be returned to approximately 65% of normal, if the conduit resistance is equal for forward and reverse flow. The net coronary flow can increase to 80% when the backflow resistance is infinite. The increases in flow rate produced by asymmetric flow resistance are enhanced considerably for a partial LAD obstruction, since the primary effect of resistance asymmetry is to prevent leakage back into the ventricle during diastole. Increased arterial compliance has little effect on net flow with a symmetric shunt, but considerably augments it when the resistance is asymmetric. The computational results suggest that an LV-LAD conduit will be beneficial when the resistance due to artery stenosis exceeds 27 PRU, if the resistance is symmetric. Fluid dynamic simulations for the shunt flow show that a recirculating region generated near the junction of the coronary artery with the bypass shunt. The secondary flow is induced at the cutting plane perpendicular to the axis direction and it is in the attenuated of coronary artery.

• Journal of the Korean Society of Safety
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• v.15 no.3
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• pp.66-70
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• 2000

In order to cope with environmental problems caused by harmful gases emitted from various industrial sources, a new technology which employs discharge plasma formed in ordinary atmospheric pressure has been intensively investigated in many industrialized nations. Although a plenty of useful outcomes and suggestions have been made public by scientists in this field, few commercial products which effectively decompose pollutant gases have appeared as yet. This is partly because that the energy efficiency of a most effective plasma reactor has not reached a satisfactory level in comparison with those of devices using conventional technologies. In an attempt to solve the problem mentioned above, we noticed to combine heterogeneous electrical discharges. This concepts is based on that each plasma reactor has its specific spatial region in which chemical reaction are active and by electrically affected with another reactor of different type, the activated region would increase - which may lead to cutting down the energy consumption. To prove this concept experimentally, two different discharge equipments, a plane ceramic-based surface discharge electrode and a corona electrode with tungsten needle may, are selected and combined to fabricate a hybrid plasma reactor. The results are summarized as follows; (1) Ozone concentration generated in the plasma region drastically increases when the positive corona discharge is added to the surface discharge. The rate of increase of ozone depends on the frequency of the surface discharge. The negative corona, however, does not contribute to the improvement of the ozone generation. (2) NO(nitrogen monoxide) decomposition rate also improves by simultaneously applying the surface and the positive corona discharges. The effect of the corona superposition is more evident when the level of the surface discharge is moderate. (3) By adjusting the corona level, the net energy efficiency during NO decomposition improves in comparison with the simple surface discharge reactor.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3292-3297
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• 2014

The vehicle wiper blade(W/B) to lower the friction coefficient of the rubber surface after the surface treatment with chlorine were investigated. IR spectrum from W/B was used to determine the extent of chlorination of the rubber surface. Coefficient of friction is significantly reduced by the treatment with chlorine. In particular, the more sensitive influence on the initial chlorination. Rubber surface properties with respect to the longitudinal direction of the cutting plane were obtained by EPMA line analysis results. Penetration depth by EPMA chlorine concentration($20.0{\ell}$ of water for 35.0% hydrochloric acid(HCl) $300m{\ell}$ with 5.25% sodium hypochlorite(NaOCl) $400m{\ell}$), the chlorine treatment for 5 minutes was conducted to find that after 1.2 ${\mu}m$.

• Journal of dental hygiene science
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• v.9 no.2
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• pp.153-160
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• 2009

The purposed of this study was to investigate the effect of Gold bonding agent as intermediate layer between metal substrate and ceramic coating. Gold bonding agent used to seal off any surface porosity, to mask the greyish color of the metal, and to provide an underlying bright golden hue to the ceramic coverage. The adhesion between metal substrate and ceramic is related to diffusion of oxygen during ceramic firing. The oxide layer produced on non-precious alloy anti titanium was considered to have a potentially adverse effect on metal-ceramic bonding. The oxidation characteristics of titanium and non-precious alloys are the main problem. Every group were divided into test and control groups. Control groups are carried out process of degassing for product oxide layer. Au coating was applied on each Ni-Cr, Co-Cr alloys and cp-Ti specimens with difference surface condition or degassing. Specimens surfaces and cutting plane was characterized by SEM/EDS. Results suggested that Au coating is effective barriers to protect metal oxidation during ceramic firing.

• Journal of the Korean GEO-environmental Society
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• v.20 no.1
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• pp.35-42
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• 2019

Various development works inevitably increase cutting slopes due to land use, and many of trails managed by different authorities are being deteriorated by long-term weathering. Collapse of slopes causes unavoidable damage of property and loss of lives because of its uncertainty and difficulty in predicting its occurrence. In order to overcome the unavoidability, America, Japan, and several European nations analyze the kinetic energy and moving distance when rocks of upper slope move along the inclined plane, via field tests and computerized interpretation of the test results. Also, they are making efforts to develop measures with which the kinetic energy of the rocks moving along the slope is absorbed and fails to reach to specific structures. However, domestic researches just focus on fragmentary prediction of rockfall using existing programs, and there have been few approaches to identify interpretation methods appropriate for domestic cases or determination of parameters. In this context, we in this study defined rockfall types and affecting factors and analyzed effects of parameters using a general-purpose rockfall simulation program to understand principles of rockfall and to estimate effects of various parameters.

• Journal of dental hygiene science
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• v.23 no.1
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• pp.1-12
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• 2023

Background: This study aimed to identify the present level and needs of clinical dental hygienists and to present the Borich needs assessment and the locus for focus model as integrated priorities. Methods: The participants of this study were dental hygienists working in dental clinics (hospitals). The final data of the 194 participants were analyzed using frequency analysis and a paired sample t-test. To analyze the need for clinical dental hygienists to perform work, the Borich priority determination formula was used. The x-y plane consisting of four quadrants was used to analyze the need using the locus for focus model, which helps to determine the priority while showing visual effects. Results: "Scaling" was the highest required level for clinical dental hygienists, and "panorama taking" was the highest present level. The priorities of educational needs were systematically and visually derived from dental hygienists who were currently working through the Borich needs assessment and the locus for focus model for each task performed in the clinical field. Through the priorities of these two models, a total of 13 items appeared in the common high-level area; "oral health care (disability)," "oral health care (systemic disease)," "applying a rubber dam," "professional mechanical tooth cleaning," "root planing," "taking vital signs," "medication counseling," "wire cutting," "removing cement after removing band/bracket," "delivering bracket," "preparing mini-screw implantation," "dental insurance claim," and "patient reception." Conclusion: Based on the results, the department of dental hygiene should maintain and improve the standardized clinical practice curriculum and clinical dental hygienists' practical skills and contribute to the realization of the legal scope of dental hygienists, reflecting the requirements of clinical fields.

• Geomechanics and Engineering
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• v.34 no.4
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• pp.409-424
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• 2023

Response of the pipeline crossing fault is considered as the large strain problem. Proper estimation of the pipeline response plays important role in mitigation studies. In this study, an advanced continuum modeling including material non-linearity in large strain deformations, hardening/softening soil behavior and soil-pipeline interaction is applied. Through the application of a fully nonlinear analysis based on an explicit finite difference method, the mechanics of the pipeline behavior and its interaction with soil under large strains is presented in more detail. To make the results useful in oil and gas engineering works, a continuous pipeline of two steel grades buried in two clayey soil types with four different crossing angles of 30°, 45°, 70° and 90° with respect to the pipeline axis have been considered. The results are presented as the fault movement corresponding to different damage limit states. It was seen that the maximum affected pipeline length is about 20 meters for the studied conditions. Also, the affected length around the fault cutting plane is asymmetric with about 35% and 65% at the fault moving and stationary block, respectively. Local buckling is the dominant damage state for greater crossing angle of 90° with the fault displacement varying from 0.4 m to 0.55 m. While the tensile strain limit is the main damage state at the crossing angles of 70° and 45°, the cross-sectional flattening limit becomes the main damage state at the smaller 30° crossing angles. Compared to the stiff clayey soil, the fault movement resulting 3% tensile strain limit reach up to 40% in soft clayey soil. Also, it was seen that the effect of the pipeline internal pressure reaches up to about 40% compared to non-pressurized condition for some cases.

• Steel and Composite Structures
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• v.50 no.3
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• pp.347-362
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• 2024

Controlling vibrations and noise in steel box girders is important for reducing noise pollution and avoiding discomfort to residents of dwellings along bridges. The fundamental approach to solving this problem involves first identifying the main path of transmission of the vibration energy and then cutting it off by using targeted measures. However, this requires an investigation of the characteristics of flow of vibration energy in the steel box girder, whereas most studies in the area have focused on analyzing its single-point frequency response and overall vibrations. To solve this problem, this study examines the transmission of vibrations through the segments of a steel box girder when it is subjected to harmonic loads through structural intensity analysis based on standard finite element software and a post-processing code created by the authors. We identified several frequencies that dominated the vibrations of the steel box girder as well as the factors that influenced their emergence. We also assessed the contributions of a variety of vibrational waves to power flow, and the results showed that bending waves were dominant in the top plate and in-plane waves in the vertical plate of the girder. Finally, we analyzed the effects of commonly used stiffened structures and steel-concrete composite structures on the flow of vibration energy in the girder, and verified their positive impacts on energy regionalization. In addition to providing an efficient tool for the relevant analyses, the work here informs research on optimizing steel box girders to reduce vibrations and noise in them.

• Journal of The Korean Association of Information Education
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• v.5 no.1
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• pp.33-45
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• 2001

In order to adapt ourselves to the Informationalization Society of twenty-first century, it is required to have ability to find quickly the necessary information and solve the problem of our own. In the field of school, it should be educated to develop learner's ability that can cope with the Informationalization Society. When a learner can study in such direction, he or she will be able to plan the learning of his own as the subject of education, and develop his ability to solve the problem by collecting and examining various information. It is self-leading learning that can make education like this possible. Through computer, especially Web site, self-directed learning can develop can develop the individuality and creativity of learners. They can collect and utilize autonomously information and knowledge. To do such an education, the program that can work out self-directed learning is needed. Therefore the program I want to develop is to reconstruct the 'figure' part of mathematics in elementary school into five steps by utilizing Web site. In the first step is to learn the concept of various shape. This step enable learners to know what figure is and how it can be utilized in our real life. The second step of dot, line and angle makes it possible that learners can consolidate the foundation of the study about figure and recognize the relation between angle and figure. In the third step of plane figure, we can study how to calculate the relation of plane figures and the area of figure with various shapes by cutting and adding them. The fourth step is about congruence and symmetry. Learners can learn to know the figure in congruence, reduction and enlargement and how it is used in our real life. In the fifth step of solid figure, we can learn the relation among the plane figure, solid figure, the body of revolution, corn and pyramid etc. controling the speed of learning on the basis of his ability. In the process of the program, it is also possible to develop learner's ability of self-leading learning by solving the problem by himself. Because this program is progressed on the Web site, it is possible to learn anytime and anywhere. In addition to it, a learner can learn beyond the grade as well as do the perfect learning by controling the pace of learning on the basis of his ability. In the process of the program, it is also possible to develop learner's ability of self-leading learning by solving the problem by himself.

• Journal of Korean Society of Steel Construction
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• v.22 no.1
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• pp.33-42
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• 2010

Patterning with a geodesic line is essential for economical or efficient usage of membrane materialsin fabric tension membrane structural engineering and analysis. The numerical algorithm to determine the geodesic line for membrane structures is generally classified into two. The first algorithm finds a non-linear shape using a fictitious geodesic element with an initial pre-stress, and the other algorithm is the geodesic line cutting or searching algorithm for arbitrarily curved 3D surface shapes. These two algorithms are still being used only for the three-node plane stress membrane element, and not for the four-node element. The lack of a numerical algorithm for geodesic lines with four-node membrane elements is the main reason for the infrequent use of the four-node membrane element in membrane structural engineering and design. In this paper, a modified numerical algorithm is proposed for the generation of a geodesic line that can be applied to three- or four-node elements at the same time. The explicit non-linear static Dynamic Relaxation Method (DRM) was applied to the non-linear geodesic shape-finding analysis by introducing the fictitiously tensioned 'strings' along the desired seams with the three- or four-node membrane element. The proposed algorithm was used for the numerical example for the non-linear geodesic shape-finding and patterning analysis to demonstrate the accuracy and efficiency, and thus, the potential, of the algorithm. The proposed geodesic shape-finding algorithm may improve the applicability of the four-node membrane element for membrane structural engineering and design analysis simultaneously in terms of the shape-finding analysis, the stress analysis, and the patterning analysis.