• Journal of dental hygiene science
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• v.15 no.3
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• pp.318-324
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• 2015

The purpose of this study is to provide the basic date which is increase the number of revisits for scaling after analyzing factors that influence trend of dental revisits for 7 years. Research data was about 1,471 patients who visited S dental clinic in Seoul at 2007 for scaling. Data from January 2007 to December 2013 was collected. The subjects were divided into 3 groups by their trend in number of dental revisits for scaling: once, 2 times, 3~7 times. The data were analyzed using the chi-squire, independent-samples t-test and one-way ANOVA, binary logistic regression analysis. As a result, the trend of dental revisit for scaling is significantly decreased from first time to second time, and after 3rd time dental revisits were steadily continued. Factors affecting dental revisits for scaling are distance, family hospital, systemic disease, presence or absence of periodontal therapy. According to the results of the study, providing dental service in accordance with the patients' characteristics and increasing the dental revisits for scaling could give a positive influence to improvement of oral health.

• Journal of Korean Society of Forest Science
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• v.102 no.2
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• pp.176-181
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• 2013

The impacts of habitats changes of benthic macroinvertebrae species and individuals of the torrents due to construction of torrent structures can be summarized as follows. Approximately 16 to 40 species and 352 to 4,333.3 individuals of benthic macroinvertebrae were found around the local position of the torrent structures. Construction of torrential structures can increases the stability in the riverbed by preventing vertical corrosion and reducing the flow rate. However, if pond is created due to increase flow rate of rainfall, the temporal confusion of micro-habitats may lead to decrease in the number of species and induce reduced number of diversity as well as cause simplification in the community structure. Therefore, erosion control structures in torrent cause influence on the habitual ecosystem, though there are differences in the degree per distance depending on the types and heights of the structure. Before establishing torrent erosion control structure in mountainous torrent area, ecosystem status should be studied carefully from the planning stage and torrent habitats should be protected by deciding type, height and scale of structure, to minimize the influence on local habitants.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2D
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• pp.295-302
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• 2011

Ubiquitous is an information communication environment which peoples could connect on network without being conscious of the network and computer condition at anytime and anywhere. Presently, advanced technology, digital cities and eco-friendly cities using Ubiquitous technology are being focused through out the world. As recent information industry and communication technology have developed remarkably, studies on intelligent structures and structural maintenance methods by combining a general idea of connecting all objects on network by interpolating computers which is called Ubiquitous Computing, and USN(Ubiquitous Sensor Network) are being attempted. In this paper, a basic experiment on penetration of RF(Radio Frequency) sensor nodes using an experimental sample setting concrete and reinforcing bar as variables is studied to estimate the possibility of applying wireless sensor networks in structures. The spring of reinforcing bars, concrete thickness, intensity of radio frequency were set up as variables, transmitting and receiving distance were checked vertically and horizontally. Moreover, Spectrum Analyzer was used for checking the magnitude of the frequency used in order to measure the reduction of radio wave exactly. The radio wave reduction was numerically analyzed, and the influence of the wavelength was analysed as well. As a result, the penetration depth in concrete without reinforcing bars was 45cm, and in reinforced concretes which reinforcing bars placed at spacing of 5cm and 15cm, the penetration depth were 37cm and 45cm each. No influence on radio wave penetration depth were found when the spacing of reinforcing bars in the reinforced concrete structures becomes over 15cm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.186-194
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• 2016

This study was conducted to determine whether if the emotional response of participants influences senior citizens at a senior citizen center and to develop the qualities and skills of the instructors of the senior citizens. Not only will we provide effective materials but also provide basic materials as well. The emotional response of interpersonal relationships, achievement goal of ability to performance, and influence of orientating themselves. Additionally, the emotional response of interpersonal relationships, ability to concentrate, and confidence. Finally, the achievement goal of task orientation, concentration of ability to performance on orientating oneself, as well as confidence. Therefore, we will be able to determine if the emotional response of a participant influences achievement of a goal and of the effectiveness of senior citizen instructors. This will not only help with practical and cultural issues, but will close the distance between the instructors participants based on consideration of their situational aspects. Furthermore, the sports activities and continued participation of the elderly. Always need to be ready mentally, and rather than the consideration of others as well as the game results, it is important to have an interest in achieving their own standards. Instructors toned to lend support while setting goals for the participants so that they contribute to the personal development and overall quality of life of the participants.

• Tunnel and Underground Space
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• v.27 no.3
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• pp.146-160
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• 2017

$CO_2$ sequestration for alleviating global warming is a hot issue in the world. In this study, TOUGH2 and FLAC3D were combined for analyzing the hyro-mechanical coupling behaviors expected in $CO_2$ sequestration and applied it to Sleipner project carried out in Norway. In the analysis, the influence of pore pressure on in situ stress was considered and the influence of caprock permeability on hydro-mechanical behaviors was analyzed. In the condition of constant injection rate, pressure and saturation at the injection well, liquid and gas saturation in rock, major and minor stress variations with time and distance from the injection well, and horizontal and vertical displacements after injection could be investigated. The major principal stress was quickly increased in the early stage and then slowly decreased to a stable value, which was higher than the initial value. In contrast, the minor principal stress returned to initial value after some increase in the early stage. Surface upheaval was steadily increased and it was up to 15mm in 2 years after injection. When the caprock's permeability was changed from $3e-15m^2{\sim}3e-18m^2$, it was found that the injection well pressure and surface upheaval were inversely propotional to the permeability.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1105-1123
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• 2018

The main risk factors of tunnel excavation through urban areas are ground settlement and surface sink which caused by ground conditions, excavation method, groundwater condition, excavation length, support method, etc. In the process of ground settlement assessment, the numerical analysis should be conducted considering the displacement and stress due to tunnel excavation. Therefore a technique that can simplify such process and easily evaluate the influence of tunnel excavation is needed. This study focused on the tunnelling-induced ground settlement which is main consideration of underground safety impact assessment. The parametric numerical analyses were performed considering such parameters as ground conditions, tunnel depth, and lateral distance from tunnel center line, etc. A simplified ground settlement evaluation chart was suggested by analyzing tendency of ground subsidence, lateral influence area and character by depth. The applicability of the suggested settlement evaluation chart was verified by comparative numerical analysis of settlement characteristics.

• Journal of the Korean Geotechnical Society
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• v.39 no.5
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• pp.27-40
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• 2023

A pile is a structural element that is used to transfer external loads from superstructures and has been widely utilized in construction fields all over the world. The method of installing a pile into the ground should be selected based on geotechnical conditions, location, site status, environmental factors, and construction costs, among others. It can be divided into two types: direct hammering and preboring. The direct hammering method installs a pile into the bearing layer, such as rock, using a few types of hammer, generating a considerable amount of pile driving-induced vibration. The vibration from pile driving influences adjacent structures and the ground; therefore, quantitatively investigating the effects of vibration is inevitably required. In this study, two-dimensional dynamic numerical modeling and analysis are performed using the finite difference method to investigate the influence on the adjacent slope, including temporary supporting system. Time-dependent loading induced by pile driving is estimated and used in the numerical analysis. Consequently, large surface displacement is estimated due to surface waves and less wave deflection, and refraction at the surface. The total displacement decreases with the increase of the distance from the source. However, lateral displacement at the top of the slope shows a larger value than vertical displacement, and the overall displacement tends to be concentrated near the face of the slope.

• Applied Chemistry for Engineering
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• v.21 no.2
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• pp.183-187
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• 2010

Activated carbons (ACs) have been prepared from pitch by the combination of a chemical oxidation with different $H_2O_2$ concentrations i.e., 5, 15, and 25 wt% and a chemical activation with KOH at a constant KOH/pitch ratio of 3/1. The influence of $H_2O_2$ solution on the microporous properties of the pitch and the final activated carbons were invested using XRD, FT-IR, XPS, $N_2$-adsorption, and SEM. XRD indicated that the value of interplanar distance $d_{002}$ increased by chemical oxidation. FT-IR and XPS results showed that the chemical oxidation promoted the formation of surface oxygen functionalities. Also, the specific surface area of the resulting ACs was increased with increasing the concentration of $H_2O_2$ chemical oxidation and showed a maximum value of $2111m^2/g$ at 25 wt% $H_2O_2$ concentration.

• Explosives and Blasting
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• v.30 no.2
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• pp.9-20
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• 2012

These days, mining industry prefers underground development for large mining because of exhaustive minning resources and large drafts and mining cavities thanks to extensive distribution of heavy excavation machines. In a mining design, to control collapse of cavities and secure stability, design of cavities and pillars are considered as very important. Therefore, this study obtained a prediction equation of blasting vibration through instrumentation for underground cavities. And we obtained theoretical shock vibration imposed on pillar through fragmentation analysis and measurement of flyrock distance. To examine the influence of pillar in underground mining blasting, we carried a finite element analysis and compared the result with prediction equation of blasting vibration, and shock vibration of flyrock when a impact was imposed on pillar and theoretical shock vibration.

• Journal of Navigation and Port Research
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• v.38 no.1
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• pp.19-27
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• 2014

When a ship operates in a shallow water and channel, the hull sinkage and asymmetrical force generated around the ship by the influence of sea bottom and bank walls are caused collision with sea bottom, other ships or the bank itself. Especially, the shipping company and pilots navigating the area of Europe and North America with many channels are deal with it as a important matter to prevent collision. In this paper, hydrodynamic force generated between the ship and bank using the numerical analysis for the safe navigation of ship, that is, sway force and yaw moment should be presumed qualitatively. It makes a program for fluid analysis of the shallow water and bank effect. Analyses are carried out for three kind of parameter, that is, ship's speed, water depth and ship-bank distance for crude oil carriers. The numerical analysis results are compared with results of the experiments and the previous published papers.