• The Journal of Korean Academy of Prosthodontics
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• v.51 no.4
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• pp.245-251
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• 2013

Purpose: This study was conducted to compare in vivo biofilm formation on titanium surface and zirconia surface. Materials and methods: For biofilm formation on titanium and zirconia in oral cavity, after producing oral appliances using acrylic resin and orthodontic wire tailored to 9 subjects, we made titanium and zirconia specimens ($6mm{\times}6mm{\times}2mm$), fixed them on oral appliances and maintained them in oral cavity of test subjects for 24 and 72 hours. Test subjects who have equipped two pairs of specimens maintained oral hygiene not by using toothpaste but only by tooth brushing. After 24 and 72 hours, we removed and observed specimens through scanning electron microscopy (SEM). Results: Biofilm formation showed large deviation depending on individuals. For formation comparison between titanium and zirconia for 24 hours, zirconia showed less biofilm formation than titanium. Biofilm formation showed large deviation depending on individuals. As for formation comparison between zirconia and titanium, the degree of biofilm formation in zirconia was less than it was in titanium after a lapse of 24 hours. The result of biofilm formation in 72 hours trial show that zirconia has an inclination to formate less biofilm than it was in titanium. Conclusion: Based on the above results, we can conclude that early biofilm formation in oral cavity was influenced by difference of abutment materials.

• The korean journal of orthodontics
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• v.22 no.4 s.39
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• pp.881-920
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• 1992

This study was designed to assess profile preferences among Korean youths in the year 1992. Facial esthetics was evaluated by means of silhouette profiles, eliminating the influence of a number of aspects that may affect judgment when normal lateral photographs are used. The main points of preference to be clarified here are as follows. First, on facial convexity, Second, on nasion depth, Third, on mentolabial sulcus depth, Fourth, on the position of upper and lower lips, Fifth, on facial type according to Angle's classification of malocclusion, Sixth, on Song's tangents. The 54 subjects printed in questionnaire as black and white silhouettes were selected from 300 tracings from cephalometric radiographs of people whose age ranging from 11 to 20 years. Photographs of six female subjects were retouched by computer graphic software and printed in color and black/white photographs which were used for adaptation of eyes of participants in selecting profiles in silhouette. They constitute 2 questions. The 54 subjects were grouped as 22 questions, each of them composed of 6 subjects, according to the aspects to be clarified. Twenty four questions in total were asked to assess profile preferences. For the assessment, the profile line, the facial esthetic triangle, Song's tangents, and Angle's classification of malocclusion were introduced. The profile line is composed of 11 component points which are Trichion, Glabella, Nasion, Pronasale, Subnasale, Labrale superius, Stomion, Labrale inferius, Supramentale, Pogonion, and Gnathion. The facial esthetic triangle is composed of 3 tangents: A-tangent which is the tangent of dorsum of nose, B-tangent which is the line passing through Sn and Ls, and C-tangent which is drawn on the turning point of the curve which lies between mentolabial sulcus (Sm) and pogonion (Pg). Angle's classification has 3 types of malocclusion which are Class I, Class II, and Class III. Class II malocclusion is subdivided into Division 1 and Division 2. The participants of the survey were composed of 861 college students (448 male students, 413 female students) whose majors grouped as Fine Arts. Liberal Arts, and Natural Sciences, and whose mean age 21.8 years. The statistics program SPSS/PC + of SPSS Inc. was used to analyze answers of participants. Crosstabulation, Chi-square test, and Kendall test were done. The conclusions are as follows: First, Korean youths have a tendency to prefer the slightly convex face to the flat or concave face. Second, they prefer a moderately deep nasion. Third, they prefer a moderately deep mentolabial sulcus. Fourth, they prefer the position of lips which are near to Ricketts' E-line. The position of the upper lip which is slightly posterior to E-line is preferred. The upper lip which lies too far anterior or posterior to the lower lip is not perferred. Fifth, they prefer most, according to Angle's Classification of Malocclusion, Class I facial profile which has a slight inclination to Class II division 2. The order of preference is Class I, Class II division 2, Class III, and Class II division 1. Sixth, they prefer the type 2 and 3 of Song's tangents. The facial profile within which A-and B-tangent meet is preferred. The facial profile which has Cotangent that .meets with A-tangent slightly posterior to the crossing point of A-and B-tangent or that parallels with B-tangent is preferred.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.307-313
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• 2014

In order to predict the post-cracking tensile behavior of fiber reinforced concrete, it is necessary to evaluate the fiber orientation factor which indicates the number of fibers bridging a crack. For investigation of fiber orientation factor on a circular cross-section, in this paper, cylindrical steel fiber reinforced concrete specimens were casted with the variables of concrete compressive strength, circular cross-section size, fiber type, and fiber volumetric ratio. The specimens were cut perpendicularly to the casting direction so that the fiber orientation factor could be evaluated through counting the number of fibers on the circular cross-section. From the test results, it was investigated that the fiber orientation factor on a circular cross-section was lower than 0.5 generally adopted, as fibers tended to be perpendicular to the casting direction. In addition, it was observed that the fiber orientation factor decreased with an increase of the number of fibers per unit cross-section area. For rational prediction of the fiber orientation factor on a circular section, a rigorous model and a simplified equation were derived through taking account of a possible fiber inclination angle considering the circular boundary surface. From the comparison of the measured data and the predicted values, it was found that the fiber orientation factor was well predicted by the proposed model. The test results and the proposed model can be useful for researches on structural behavior of steel fiber reinforced columns with a circular cross-section.

• Journal of Navigation and Port Research
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• v.37 no.5
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• pp.551-557
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• 2013

In this paper, we manufactured portable inflatable kayak using ultra high pressure drop stitch. by improving inflatable kayaks' performance with a design using the extra-high-voltage special space paper, they were manufactured to go near to performance of hard shell kayaks. The kayaks were manufactured having all merits of the performance of hard shell kayaks and functionality and portability of the inflatable kayaks, and through performance evaluation of test products, the performance was compared with previous hard shell kayaks. About 6 knot of target speed in the verification result of resistance performance, the developed kayak was more excellent than the HOBIE-KONA kayak by 12.33%. In case of same displacement in a result of inclination test, the centroid of the developed kayak was less distributed by 22.7% than the HOBIE-KONA kayak, based on the bottoms of the ships. This makes the difference for righting arm (GZ) lessened to some degree because the developed kayak is lower than the HOBIE-KONA kayak in the centroid. In the dynamic stability of ship bodies, the HOBIE-KONA kayak showed a little excellent performance. However, in rudder force and resistance factor, the developed kayak was more outstanding than the HOBIE-KONA kayak.

• 대한공업교육학회지
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• v.33 no.1
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• pp.23-43
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• 2008

The purpose of this study is to provide some necessary baseline data to the information prodigy related research through the study on the brain left/right tendency of information prodigies. Subjects were 298 gifted students(59 information, 79 mathematics, 80 science, 40 invention, 40 social science) and 114 general students summing up 412 in the schools of Daejeon metropolitan area. 'Brain Tendency Test' developed by Torrance and modified by Ko in Korean was used as a tool to measure the prodigies' brain tendencies. Data analysis has been done with the $x^2$ test of frequency with the alpha = .05. The results of this study are as follows. 1) The information gifted students have tendencies of utilizing right brain hemisphere at the most, both left/right brain(whole brain) utilization at the second, and left brain utilization at the last. 2) There was statistically no difference between information prodigies and general students in the left/right brain tendency. 3) There was statistically mild evidence to support the notion that there are some differences in the brain tendency between the group of information prodigies and the group of other area of the prodigies. The degree of inclination to utilize the whole brain hemisphere for the prodigies of the other area was the highest compare to other left/right brain utilization while the information prodigies tend to utilize the right brain hemisphere at the most. 4) The female information prodigies have tendencies of utilizing while brain area at the most, right brain utilization at the second, and left brain utilization at the last contrary to the brain utilization tendencies in the male information prodigies which are the same as the brain utilization tendencies of the information prodigies. However there was no difference in brain tendencies statistically between the two groups since the female subjects were too small.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.2
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• pp.122-130
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• 2016

The past few decades of industrialization enabled human-centered stream developments, which in turn resulted in constructing straight or covered streams, which are used only for sewage disposal purpose. However, these types of streams have become the cause of flood damages such as localized heavy rain. In response, various construction methods have been implemented to prevent stream and embankment damages. However, regulations regarding these measures only lay out minimum standards such as the height of slopes and the minimum angle of inclination. Moreover, examination of tractive force, the most crucial factor in preventing flood damage, is nonexistent. Therefore, this study evaluates various tractive forces by implementing a porous concrete tetrapod at a full scale artificial stream for experiment, controlling the rate of inflow, and measuring the velocity and depth of the stream under different experiment conditions. The test results of the compressive strength, and porosity and density of rock of the porous concrete tetrapod was between 16.6 and 23.2 MPa, and the actual measurement of air void was 10.1%, thus satisfying domestic standard. The result of tractive force experiment showed a limiting tractive force of $47.202N/m^2$, not satisfying the tractive force scope of $67N/m^2$ the stream design working expertise proposes. However, there was neither damage nor loss of blocks and hardpan. Based on previous researches, it can be expected that there will be resistance against a stronger tractive force. Therefore, it is necessary to conduct another experiment on practical limiting tractive force by adjusting some experimental conditions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.407-416
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• 2023

Demand for leisure facilities such as mooring facilities for berthing leisure vessels and floating pensions based on floating bodies is increasing owing to the rapid growth of the population and related industries for marine leisure activities. Owing to its relatively light weight as a fluid, inclination is easily generated by waves and surcharges flowing to the coast, resulting in frequent safety accidents because of the low stability. As a solution to this problem, a motion reduction device for floating bodies is proposed in this study. The device (motion reduction device based on the air pressure dif erence) was attached to a floating body and the effect was analyzed by comparing the results with those of a floating body without motion reduction. The effect analysis was further analyzed using a computer analysis test, and the method for increasing the stability of the floating body was studied, and its the effect was verified. Based on the analysis of the test results, the stability of the floating body increased with a motion damping device is higher than that of the floating body without a motion reducing device as the wave momentum reduces, owing to the air pressure difference. Therefore it was concluded that the use of such a device for reducing motion a floating body is useful not only for non-powered ships but also for powered and semi-submersible ships, and further research should be conducted by applying it to various fields.

• Journal of the Korean GEO-environmental Society
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• v.16 no.12
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• pp.45-52
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• 2015

With the rising interest in the environment, more attention on ecological restoration for damaged slope surface to restore its original state has been drawn. Generally, the most useful method is vegetation based spray work. This method uses green soil including sewage sludge, sawdust, paper sludge, and weathered granite soil. However, because there are neither accurate information nor test values about green soil, green soil is often lost by environmental factors such as rainfalls and strong winds. To solve the problem of green soil, it is necessary to prepare design standards about green soil, and conduct studies to deal with green soil loss in consideration of various variables including basic material property, soil quality of slope surface, and weather. This study was conducted in the mixture of green soil and eco-friendly soil stabilizer. With green soil, basic material property test and compaction test were conducted for the analysis on the basic characteristics of green soil. In the mixture with soil stabilizer at a certain ratio, we conducted shear strength test depending on the ratio in order to analyze the maximum shear strength, cohesion and the change in internal friction angles. Furthermore, in the mixture ratio of green soil and soil stabilizer, which is the same as the ratio in the shear strength test, an inclination of slope surface was made in laboratory for the analysis on erosion and germination rate. Finally, this study evaluated the most effective and economic mixing ratio of soil stabilizer to cope with neighboring environmental factors. According to the test, the shear strength of green soil increased up to 51% rely onto the mixing ratio of and a curing period, and its cohesion and internal friction angle also gradually increases. It is judged that the mixture of soil stabilizer was effective in improving shear strength and thereby increased the stability of green soil.

• Journal of the Korean Applied Science and Technology
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• v.37 no.6
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• pp.1556-1566
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• 2020

The purpose of this study was to investigate the effect of Nurida-Ball exercise on isokinetic muscle function, spinal alignment, and dynamic balance capacity in middle-aged men. All middle-aged men(n=16) were divided into 2 groups: Ball exercise(BE, n=8) and control(CON, n=8) group. BE group performed the Nurida-Ball exercise(30 min/day, 3 days/week, 8 weeks) and isokinetic knee and trunk muscle function, spinal alignment, and dynamic balance capacity were measured. All of the measured variables calculated the mean and standard deviation and verified normality using the Shapiro-Wilk test. The independent t-test method and the Paired t-test method were then analyzed to identify differences between groups. This study found that isokinetic knee and trunk muscle function was significantly strengthened in the BE compared with CON group by increasing peak torque(PT) of right and left knee extension(60°/sec, p<0.01, respectively), average power(AP) of right and left knee extension(60°/sec, p<0.05, p<0.01, respectively), and PT of right knee flexion(180°/sec, p<0.05) and AP of right knee extension(180°/sec, p<0.05). In the change of isokinetic trunk muscle function, only PT of trunk extension(180°/sec) was increased in the BE compared with the CON group(p<0.05). In addition, Nurida-ball exercise can improve the spinal alignment by reducing the trunk inclination(p<0.05) in the BE compared with the CON group. Finally, dynamic balance capacity was also enhanced in the BE compared with the CON group by decreasing the score of overall balance index(OBI, p<0.01) and Antero-posterior balance index(p<0.05) in the Stage-6, and OBI(p<0.05) in the Stage-1. This result demonstrated that Nurida-ball exercise may improve spinal alignment, dynamic balance capacity, and isokinetic muscle function, which might be an effective way for the improvement of health-related fitness in middle-aged men.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.4
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• pp.344-350
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• 2009

This paper proposes a hybrid antenna with novel beam steering scheme. The antenna have a cassegrain structure composed of two reflectors. The main reflector is designed for high gain performance using parabola curvature, and the sub-reflector is plate and can be rotated by ${\pm}3^{\circ}$. Thus proposed antenna can steer a antenna beam using the inclination of sub-reflector. A feed array composed of 20 elements is adapted as a feeder for electrical beam steering, and the antenna can be possible to steer the beam by the feed array with sub-reflector. Proposed antenna was fabricated to be operated in Ka-band(30.085$\sim$30.885 GHz) for TX and K-band(20.355$\sim$21.155 GHz), which are the operation frequencies of the Korean satellite, Mugunhwa, to provide satellite multi-media service to vehicles. By the performance test, it can be known that the antenna has minimum gain of 47 dBi for TX and 44.4 dBi for TX and can steer the beam by ${\pm}2^{\circ}$ with sub-reflector.