• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.4
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• pp.343-352
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• 2019

Abnormal orofacial functions such as lip incompetency in the period of growth and development can cause morphological anomalies of the craniofacial complex. Therefore, it is crucial to make an early diagnosis based on the evaluation of the myofunctional conditions, and to make appropriate treatment plans. The objectives of this study were to quantitatively evaluate the standard lip closing force (LCF) of each age in the elementary school children, and to evaluate the relationships between LCF and affecting factors. The sample consisted of 765 children who were 7 - 12 years old in Jeonju city. Clinical examination about occlusal conditions and lip competency, and LCF measurement were performed by a single examiner. LCF was measured three times for each children with the LCF measuring device. The LCF was correlated positively with age in both sexes. The distribution of LCF groups was correlated significantly with Angle's classes and lip competency (p = 0.016, 0.004). The proportion of children with high LCFs was greater in the "competent lip" group, whereas the proportion of those with low LCFs was greater in the "incompetent lip" group.

• Journal of the Korean association of regional geographers
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• v.19 no.1
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• pp.97-110
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• 2013

The purpose of this study is to investigate the change of spacial structure from rural space to urban space and to examine the characteristic of spacial restructure, focusing on the Hwamyeong-Dong of Buk-gu in Busan. Hwamyeong-Dong has changed from rural area to urban area because of spacial expansion owing to industrialization and urbanization. The unique natural environment, rural village, etc. were disappeared and instead the apartment complex, commercial building, and so on were built. For this reason, historic and concrete place were vanished and so the spacial homogenization and uniformization were formed centering around apartment complex. But the singularity of Hwamyeong-Dong exposes in the way that unique history, custom and memory, trace of Hwamyeong-Dong preserved through the support and effort of the residents and that the Daechen stream changed to ecological stream. In addition, Hwamyeong-Dong altered heterogeneous, multi-layered urban space from homogeneous rural space in terms of the apartment supply sectors and scale, the distribution and kind of commercial facility, residents's composition. This has brought about the subdivision, hierarchization of the space as well as the residence, education, culture. Especially, Hwamyeong3-Dong that built to large scale apartment complex are significantly different from Hwamyeong2-Dong. Hwamyeong2-Dong is marginalizing step by step. However, It is found that the residents in Hwamyeong2-Dong are making an effort for liveable place with ecological residential community and educational cultural community as the center.

• Korean Journal of Soil Science and Fertilizer
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• v.36 no.5
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• pp.263-271
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• 2003

Effects of the existence of $CO_2$ gas and pH on the silica surface characteristics at silica/Pb(II) and sodium dodecyl sulfonate (SDS, $C_{12}H_{25}SO_3Na$) solution interface were studied. The hydrophobic characteristics of silica surface was delineated by contact angle measurement and surface force measurement using atomic force microscopy (AFM). In $CO_2$ free condition provided by purging $N_2$ gas, the contact angle of fused silica surface in $10^{-4}M$ Pb(II) and SDS solution increased greatly up to $90^{\circ}$ compared with $40^{\circ}$ in atmospheric condition. It was due to the precipitation of $PbCO_3$ in atmospheric condition. In $CO_2$ free condition the change of contact angle and adhesion force ($F_{ad}$) in AFM, affected by pH change, was similar to the distribution of $PbOH^+$ ion in speciation diagram corresponding to $10^{-4}M$ total Pb(II). Therefore, it was convinced that the $PbOH^+$ ion among Pb(II) species would be the main adsorbing type on silica surface. Both of contact angle measurement and surface force measurement using AFM showed that the Pb only treatment made the silica surface hydrophobic. However, it could not be explained theoretically by current knowledge, and required further study in atomic level to solve the problem.

• Journal of Adhesion and Interface
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• v.22 no.4
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• pp.136-143
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• 2021

Polyurea has been investigated as a polymer matrix for composite materials because of its high mechanical strength. Although polyurea has a similar chemical structure to polyurethane, it has much higher strength and durability. In this study, the fabrication of polyurea composites reinforced with carbon nanotube (CNT) and graphene oxide (GO) is demonstrated to enhance the tensile strength of the glass fibers composite. Using FTIR and Raman spectroscopies, the chemical structures of polyurea, CNT, and GO are investigated. As a result, spectroscopy analysis reveals that the chemical structure of CNT, GO, and polyurea is maintained during the fabrication of the composite structure. Scanning electron microscopy reveals the uniform distribution of CNT and GO across the polyurea matrix. The reinforcement of 1 wt% CNT in polyurea enhances the tensile strength of CNT/polyurea composites. In contrast, the reinforcement of GO in polyurea induces the degradation of the tensile strength of GO/polyurea composites.

• Korean Journal of Child Education & Care
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• v.18 no.4
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• pp.65-89
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• 2018

Objective: The purpose of this study is to analyze the science concepts and teaching and learning methods presented in the science education-related activities of the Nuri Curriculum teacher guidebooks for ages 3-5. Methods: The research data included 772 activities related to science education in the teachers' guidebook. The analysis of science concepts was based on physical science (force and motion, physical structure, electricity and magnetism, light and shadow, sound properties), chemistry (material properties, material reaction), life science (organizational structure, growth and change, heredity and evolution, animal plant and human relationships), earth science (earth system interaction, earth system structure, and universe), engineering (designed world, engineering design, engineering, technology and society) and ecology (environment preservation). Teaching and learning methods were analyzed according to the types of small and large group activities and of free play activities. Results: Science concepts were mainly presented in the fields of engineering, chemistry, and life science commonly among children aged 3-5, whereas the concepts of physical science were lowly presented in all ages. Science concepts appeared mainly in the daily subjects of 'animal plant and nature', 'life tools', 'environment and life', and 'spring, summer, autumn and winter'. As the teaching and learning method, free paly activities (science area, free outdoor selection activity, math and manipulative activity) were mostly used for the ages of 3 and 4, and small and large group activities (cooking, story sharing, music activity) were for the age of 5. Conclusion/Implications: It is necessary to select the level of science area and concept that can be taught according to the age of children and the timing of the teaching.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.841-848
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• 2006

There is a complex variation of stress in PSC anchorage zones and box girder diaphragms because of large concentrated load by prestress. According to the AASHTO LFRD design code, three-dimensional effects due to concentrated jacking loads shall be investigated using three-dimensional analysis procedures or may be approximated by considering separate submodels for two or more planes. In this case, the interaction of the submodels should be considered, and the model loads and results should be consistent. However, box girder diaphragms are 3-dimensional disturbed region which requires a fully three-dimensional model, and two-dimensional models are not satisfactory to model the flow of forces in diaphragms. In this study, the strengths of the prestressed box girder diaphragms are predicted using the 3-dimensional grid strut-tie model approach, which were tested to failure in University of Texas. According to the analysis results, the 3-dimensional strut-tie model approach can be possibly applied to the analysis and design of PSC box girder anchorage zones as a reasonable computer-aided approach with satisfied accuracy.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.2
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• pp.109-123
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• 2009

The aim of the study was to assess the influence of insertion torque of bone quality and to compare axial force, moment and von Mises stress using finite element analysis of plastoelastic property for bone stress and strain by dividing bone quality to its thickness of cortical bone, density of trabecular bone and existence of lower cortical bone when implant inserted to mandibular premolar region. The $Br{\aa}nemark$ MKIII. RP implant and cylindrical bone finite model were designed as cortical bone at upper border and trabecular bone below the cortical bone. 7 models were made according to thickness of cortical bone, density of trabecular bone and bicortical anchorage and von Mises stress, axial force and moment were compared by running time. Dividing the insertion time, it seemed 300msec that inferior border of implant flange impinged the upper border of bone, 550msec that implant flange placed in middle of upper border and 800msec that superior border of implant flange was at the same level as bone surface. The maximum axial force peak was at about 500msec, and maximum moment peak was at about 800msec. The correlation of von Mises stress distribution was seen at both peak level. The following findings were appeared by the study which compared the axial force by its each area. The axial force was measured highest when $Br{\aa}nemark$ MKIII implant flange inserts the cortical bone. And maximal moment was measured highest after axial force suddenly decreased when the flange impinged at upper border and the concentration of von Mises stress distribution was at the same site. When implant was placed, the axial force and moment was measured high as the cortical bone got thicker and the force concentrated at the cortical bone site. The influence of density in trabecular bone to axial force was less when cortical bone was 1.5 mm thick but it might be more affected when the thickness was 0.5 mm. The total axial force with bicortical anchorage, was similar when upper border thickness was the same. But at the lower border the axial force of bicortical model was higher than that of monocortical model. Within the limitation of this FEA study, the insertion torque was most affected by the thickness of cortical bone when it was placed the $Br{\aa}nemark$ MKIII implant in premolar region of mandible.

• Progress in Medical Physics
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• v.23 no.4
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• pp.269-278
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• 2012

Aquaplast Thermoplastic (AT) is a tissue-equivalent oral compensator that has been developed to improve dose uniformity at the common boundary and around the treated area during radiotherapy in patients with head and neck cancer. In order to assess the usefulness of AT, the degree of improvement in dose distribution and physical properties were compared to those of oral compensators made using paraffin, alginate, and putty, which are materials conventionally used in dental imprinting. To assess the physical properties, strength evaluations (compression and drop evaluations) and natural deformation evaluations (volume change over time) were performed; a Gafchromic EBT2 film and a glass dosimeter inserted into a developed phantom for dose verification were used to measure the common boundary dose and the beam profile to assess the dose delivery. When the natural deformation of the oral compensators was assessed over a two-month period, alginate exhibited a maximum of 80% change in volume from moisture evaporation, while the remaining tissue-equivalent properties, including those of AT, showed a change in volume that was less than 3%. In a free-fall test at a height of 1.5 m (repeated 5 times as a strength evaluation), paraffin was easily damaged by the impact, but AT exhibited no damage from the fall. In compressive strength testing, AT was not destroyed even at 8 times the force needed for paraffin. In dose verification using a glass dosimeter, the results showed that in a single test, the tissue-equivalent (about 80 Hounsfield Units [HU]) AT delivered about 4.9% lower surface dose in terms of delivery of an output coefficient (monitor unit), which was 4% lower than putty and exhibited a value of about 1,000 HU or higher during a dose delivery of the same formulation. In addition, when the incident direction of the beam was used as a reference, the uniformity of the dose, as assessed from the beam profile at the boundary after passing through the oral compensators, was 11.41, 3.98, and 4.30 for air, AT, and putty, respectively. The AT oral compensator had a higher strength and lower probability of material transformation than the oral compensators conventionally used as a tissue-equivalent material, and a uniform dose distribution was successfully formed at the boundary and surrounding area including the mouth. It was also possible to deliver a uniformly formulated dose and reduce the skin dose delivery.

• Journal of Korea Foundry Society
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• v.41 no.2
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• pp.144-152
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• 2021

Based on the analysis of the current state of the world's foundry industry, we looked at the international competitiveness of Korea's foundry industry for the past 20 years. Korea's total foundry production is 2.52 million tons, and the production per company (so-called productivity) is 2,831 tons, which is the eighth largest in the world and down one position for the case of total foundry production, while productivity remains its position compared to three years ago. Korea is the only one of the top 10 foundry to see a decline in production. Similar to the global situation, Korean products consist of 38% of grey csat iron, 31% of ductile cast iron, 15% of aluminum, and 9% of cast steel. In order to obtain statistics on Korea's foundry industry, the survey conducted a service project for approximately nine months from April 2020. Various statistical surveys and sample in-depth surveys by the Korean standard industry class were evaluated for various contents of the domestic casting industry. We also looked at the number of companies, the distribution by region, the number of workers and the percentage of foreigners, and the distribution of each job, as well as the R&D investment status according to the size of the enterprise. Together, sales, exports, sales and various profit ratios were analyzed to measure the earning power of foundry industry. In addition, the classification by grouping the foundry industry according to the process utilized by focusing on each company, and to determine the sales, exports, and yield status for each process was also investigated on the basis. Based on these data, the domestic foundry industry has presented a variety of offers for the following issues for sustainable growth; global ranking, marginal corporate restructuring, training of domestic technical people, differentiated support policies by company size and process.

• Journal of Astronomy and Space Sciences
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• v.22 no.2
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• pp.147-174
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• 2005

To understand the physical processes that control the high-latitude lower thermospheric dynamics, we quantify the forces that are mainly responsible for maintaining the high-latitude lower thermospheric wind system with the aid of the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEGCM). Momentum forcing is statistically analyzed in magnetic coordinates, and its behavior with respect to the magnitude and orientation of the interplanetary magnetic field (IMF) is further examined. By subtracting the values with zero IMF from those with non-zero IMF, we obtained the difference winds and forces in the high-latitude 1ower thermosphere(<180 km). They show a simple structure over the polar cap and auroral regions for positive($B_y$ > 0.8|$\overline{B}_z$ |) or negative($B_y$ < -0.8|$\overline{B}_z$|) IMF-$\overline{B}_y$ conditions, with maximum values appearing around -80$^{\circ}$ magnetic latitude. Difference winds and difference forces for negative and positive $\overline{B}_y$ have an opposite sign and similar strength each other. For positive($B_z$ > 0.3125|$\overline{B}_y$|) or negative($B_z$ < -0.3125|$\overline{B}_y$|) IMF-$\overline{B}_z$ conditions the difference winds and difference forces are noted to subauroral latitudes. Difference winds and difference forces for negative $\overline{B}_z$ have an opposite sign to positive $\overline{B}_z$ condition. Those for negative $\overline{B}_z$ are stronger than those for positive indicating that negative $\overline{B}_z$ has a stronger effect on the winds and momentum forces than does positive $\overline{B}_z$ At higher altitudes(>125 km) the primary forces that determine the variations of tile neutral winds are the pressure gradient, Coriolis and rotational Pedersen ion drag forces; however, at various locations and times significant contributions can be made by the horizontal advection force. On the other hand, at lower altitudes(108-125 km) the pressure gradient, Coriolis and non-rotational Hall ion drag forces determine the variations of the neutral winds. At lower altitudes(<108 km) it tends to generate a geostrophic motion with the balance between the pressure gradient and Coriolis forces. The northward component of IMF By-dependent average momentum forces act more significantly on the neutral motion except for the ion drag. At lower altitudes(108-425 km) for negative IMF-$\overline{B}_y$ condition the ion drag force tends to generate a warm clockwise circulation with downward vertical motion associated with the adiabatic compress heating in the polar cap region. For positive IMF-$\overline{B}_y$ condition it tends to generate a cold anticlockwise circulation with upward vertical motion associated with the adiabatic expansion cooling in the polar cap region. For negative IMF-$\overline{B}_z$ the ion drag force tends to generate a cold anticlockwise circulation with upward vertical motion in the dawn sector. For positive IMF-$\overline{B}_z$ it tends to generate a warm clockwise circulation with downward vertical motion in the dawn sector.