• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.267-277
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• 1997

The purpose of this study was to evaluate the shear bond strength of light-cured glass ionomer cements to dentin surface according to curing time induced by argon laser. In this study, 160 extracted human molars with sound crown were used. The dentin surface of these teeth were exposed with high speed diamond bur under water spray and polished with 120, 320, 400, 800, 1200 grits sand paper. 160 extracted human molars were randomly assigned into four groups (control, experimental 1, 2 & 3) with 40 teeth each. Control group used a visible light curing unit, XL 1000(3M Co., U.S.A) and experimental groups used argon laser($SPECTRUM^{TM}$). And then each group subdivided into two groups (A, B) according to filling materials. Subdivided A group used Fuji II LC(GC Co., Japan), B group used Vitremer(3M Co., U.S.A). The curing units and curing time of each group were as follows : Control group : visible light, 40 seconds Experimental group 1 Experimental group 2 Experimental group 3 : argon laser, 10 seconds : argon laser, 20 seconds : argon laser, 30 seconds The glass ionomer cements were bonded to dentin surface of each specimen. The specimens were stored in 100% relative humidity at 37"c for 7days. And then, the shear bond strength were measured by universal testing machine(Shimatzu Co. Japan) at crosshead speed of 5mm/min and 100kg in full scale and analyzed statistically. The following results were obtained : 1. Experimental group 2-A showed the highest shear bond strength with $9.87{\pm}1.24$ kgf and control group B showed the lowest shear bond strength with $4.08{\pm}0.78$ kgf(P<0.01). 2. The Fuji II LC showed higher shear bond strength with $9.49{\pm}1.24$ kgf than that of the Vitremer with $4.23{\pm}1.24$ kgf. There was significant difference between Fuji II LC and Vitremer(p<0.01). 3. There was no significant differences among experimental groups according to curing time induced by argon laser. 4. There was no significant differences between control group and experimental groups according to curing units.

• Journal of the Korean Society of School Health
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• v.8 no.2
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• pp.293-303
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• 1995

Health has occupied a position of importance in the human history, whether it be in the East or in the West, and it is a subject in which people have been constantly interested. The concept of health has changed continuously as the society has developed, industrialized and become more structured. The perception of health concept can be an esential factor which is to determine the health behaviors. This study is a descriptive inquiry done to identity high school students' perception of health and what they do as health behaviors. The subject consisted of 503 voctional high school seniors, 129 boys and 374 girls, from a school located in An-san Si, kyong-gi Do. The instruments used for this study were open-ended questionnaires and data were collected by having the students fill out the questionnaires which took 10 minutes, in their first class, April 6, 1995. The collected materials were classified and recorded on the cards according to each question using the terms which students had written. After putting statements which had common meanings together, the representative categories were labelled. The results obtained are as follows. 1. Categorizing and labelling of health concepts What high school students descripted as health concepts were classified as the absence of illness, physical comfort, strong physical strength and physique, not having a deformity, resisting power, self control mental-rest(or psychological comfort), wholesome ideas, self-control, harmony in body and in mind, maintenace of daily life, pleasant life, good friends, peaceful family life and realizing objectives. 2. Categorizing and labelling of health behaviors These were classified as preventive life, good dietary habits and regimen, maintenance of clean body, exercises, preventing obesity, rest, environmental balance or control of environment, limit one's tastes, making use of leisure, peaceful mind, sound thought and regular living habits. The result indicates that the health concepts were positive and included not only absence of illness but also harmony in body and in mind and pleasant life; health behaviors which had high frequency were good dietary habits and regimen, exercises and sound thought. It is hoped that these findings well serve as practical references for teachers when they counsel with, and provide the students with guidance programs which include health care.

• Korean Institute of Interior Design Journal
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• v.25 no.5
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• pp.42-54
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• 2016

The purpose of this study is to provide a reference for stage planning by analyzing current state of major theaters' stage space and understanding feedback from directors belonged to theaters. Each room in total 18 theaters' stage facilities was measured and their usage and requirements were analyzed on the spot. In addition, each director provided their experiential knowledge about appropriate stage composition for musical performance. The findings are as follow: under stage machinery is not needed for musical. Tour teams prefer to use their own show-deck for set conversion. On the other hand, over stage flying system needs to be able to deal with dense, fast, and accurate scene change. The size and location of the motor room needs to be carefully considered. The number of set battens is directly linked up with the size of the motor room, which should be located lower than the gridiron. As stage sets get bigger and complicated, the number of works at the gridiron is also increasing. The grating floor has to have enough strength coping with machines lifting heavy sets. Most sound control for musical performance is being done at F.O.H. these days rather that in the sound control room. It should equip enough work area and related infra especially for tour teams. 1st gallery needs to have enough effective width, power infra for lighting fixture, and strong guardrail. Lastly, the whole process of parking-unloading-transporting equipments and sets from loading dock to stage and vice versa needs to be efficient, and this has to be carefully considered from early stage of planning.

• Journal of the Korean Wood Science and Technology
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• v.33 no.6 s.134
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• pp.8-16
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• 2005

Fire-killed trees of Korean red pine are valuable resources for industrial uses. It is common only believed that fire-killed trees are too weak and brittle to use in construction purposes. The misunderstandings of fire-killed trees lead these valuable resources abandonment. The purposes of this research are focused on scrutinization of material properties of fire-killed trees to facilitate industrial uses of these resources. The sample logs were collected from the forest fire site of the eastern coast area in which the most catastrophic wild fire had taken place in 2000. Fire-killed Korean red pines were classified into 3 levels by the degree of fire damage so called light, medium and heavy, then their physical, mechanical and chemical properties were compared with sound trees. No significant difference in physical appearances were found in the cross sections by degree of damage compared to sound tree but bark char. Investigation on mechanical and chemical properties indicates that forest fire did not impact significantly in lowering the strength of damaged trees. It was concluded that there was any limitation of forest fire-killed trees of Korean red pine in industrial utilization.

• Journal of Biomedical Engineering Research
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• v.25 no.2
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• pp.145-150
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• 2004

In this study for the prosthesis of the spatial and directional sensation for the blind, an ultrasonic scale system and an electronic compass system were developed. The ultrasonic scale utilizes 40 ㎑ sound for the detection of distance to the barrier and the spatial information is transferred to the blind by various sound interval, which is proportional to the distance. The electronic compass utilizes a magnetoresistor bridge for the detection of the magnetic field strength of earth in horizontal plane. The information for the direction of the earth's north is transferred by tactile stimuli by a vibrating motor band around upper head. Detection distance of the ultrasonic scale is ranged from 0.065 to 3.26 meters, and the detection angle resolution of the electronic compass is about 22.5 degrees. The integrated system of the ultrasonic scale and the electronic compass was developed. Distance information is converted to the location of the tactile stimulation along the clockwise direction by a vibrating motor according to the distance installed around upper head of the blind. The intent of this article is to provide an practical prosthetic tool of spatial and directional sensation for the blind. Daily practice of this system will improve the usefulness of this system.

• Journal of the Korea Institute of Building Construction
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• v.19 no.2
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• pp.105-112
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• 2019

Fine aggregate made of ferronickel slag(FNS) is similar to natural fine aggregates and is used in concrete structures both domestically and abroad, but its applications and research areas are limited. In this research, in order to expand the availability of FNS and improve the performance of cement mortar products, the applicability of FNS on dry mortar for floor was examined. Experimental results show that FNS improves flow of cement mortar because it has low absorption rate, spherical shape, and glassy surface. Also, the high stiffness of the FNS aggregate itself is considered to contribute to the improvement of cement mortar quality such as crack reduction by improving the compressive strength and shrinkage reducing. In addition, when FNS fine aggregate is applied, it was possible to secure the impact sound insulation performance equal to or higher than that of mortar using natural fine aggregate.

• The Journal of the Acoustical Society of Korea
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• v.32 no.1
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• pp.14-21
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• 2013

The erosion, suspension, and transport of sediment frequently occur in the coastal waters and estuarine. These processes often generate the so-called fluid mud layer, which is defined as a high-concentration aqueous suspension of fine grained sediment (> 10 g/l), consisting mainly of silt and clay-size particles. Therefore the high-resolution ultrasound is mostly used to detect or monitor the fluid mud layer. Because the sound attenuation tends to increase rapidly with the suspended sediment concentration, it is necessary to consider the accurate attenuation correction to estimate the backscattering strengths from the suspended sediment layers. In this paper, the volume backscattering strengths with various suspended sediment concentrations were measured using 5-MHz ultrasound signal in a small-scale water tank. The sound attenuation due to the viscosity and scattering from suspended sediment particles was predicted by the Richard's model and applied to the sonar equation to estimate the volume backscattering strengths from the suspended sediment concentrations. For the case that the additional attenuation was not considered, the volume backscattering strengths increased to the concentration of 20 g/l, and over this point, the backscattering strengths were roughly constant. However, for the case that the attenuation due to the suspended sediment concentration was considered, the backscattering strengths increased with the concentration.

• Journal of the Korea Society of Computer and Information
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• v.14 no.9
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• pp.95-104
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• 2009

This paper proposes the noise robust algorithm to detect the starting point of music. Detection of starting point of music is necessary to solve computational-waste problem and retrieval-comparison problem with inconsistent input data in music content based retrieval system. In particular, such detection is even more necessary in time sequential retrieval method that compares data in the sequential order of time in contents based music retrieval system. Whereas it has the long point that the retrieval is fast since it executes simple comparison in the order of time, time sequential retrieval method has the short point that data starting time to be compared should be the same. However, digitalized music cannot guarantee the equity of starting time by bit rate conversion. Therefore, this paper ensured that recognition rate shall not decrease even while executing high speed retrieval by applying time sequential retrieval method through detection of music starting point in the pre-processing stage of retrieval. Starting point detection used minimum wave model that can detect effective sound, and for strength against noise, the noises existing in mute sound were swapped. The proposed algorithm was confirmed to produce about 38% more excellent performance than the results to which starting point detection was not applied, and was verified for the strength against noise.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6C
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• pp.407-419
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• 2006

Situations where support is provided solely in shaft resistance of drilled shafts are where the base of the drilled hole cannot be cleaned so that it is uncertain that any end bearing support will be developed. Alternatively, where sound bed rock underlies low strength overburden material, it may be possible to achieve the required support in end bearing on the rock only, and assume that no support is developed in the overburden. However, where the drilled shaft is drilled some depth into sound rock, a combination of side wall resistance and end bearing can be assumed. Both theoretical and field studies of the performance of rock socketed drilled shafts show that the major portion of applied load is usually carried in side wall resistance. Normal stress at the rock-concrete interface is induced by two mechanisms. First, application of a compressive load on the top of the pile results in elastic dilation of the concrete, and second, shear displacement at the rough surface of the drilled hole results in mechanical dilation of the interface. If the stiffness of the material surrounding the socket with respect to normal displacement is constant, then the normal stress will increase with increasing applied load, and there will be a corresponding increase in the shear strength. In this study, the numerical analyses are carried out to investigate the behavioral characteristics of side of rock socketed drilled shafts. The cause of non-linear head load-settlement relationship and failure mechanism at side are also investigated properly and the design charts are suggested and verified for the leading to greater efficiency and reliability in the pile design.

• The korean journal of orthodontics
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• v.40 no.2
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• pp.87-94
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• 2010

Objective: Many studies have carried out research on comparisons between laser etching and conventional etching systems to investigate methods of reinforcing shear bond strength. The purposes of this study were to assess the efficiency of bonding with erbium, chromium doped: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser etching combined with the conventional etching technique. Methods: Sixty-four sound premolars, extracted for orthodontic purposes, were randomly divided into 4 groups and treated in the following manner. First group, conventional etching of 37% phosphoric acid for 15 seconds (control); second group, 1.5 W laser etching for 10 seconds followed by conventional etching; third group, conventional etching followed by 1.5 W laser etching; fourth group, 1.5 W laser etching for 15 seconds only. We assessed the shear bond strength, the surface characteristics, and the adhesive remnant index scores between all groups. Results: Experimental groups showed higher shear bond strength than the control group. But no statistically significant differences were found between the second and third groups. Adhesive remnant scores were compared with the Kruskal-Wallis test, and no statistically significant differences were found between all groups. Conclusions: To obtain maximum shear bonding strength, a combined technique of Er,Cr:YSGG and 37% phosphoric acid is useful even though it may be inconvenient.