• Journal of the Korean Wood Science and Technology
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• v.44 no.3
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• pp.415-423
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• 2016

Cylindrical laminated veneer lumber (LVL) is produced by winding the veneer tape on a circular cylinder. The veneer tape was produced by cutting the veneer into a rectangular shape and sewing it in a vertical direction to the fiber. The tensile strength test was carried out by producing the veneer tape specimen with different species of veneer, types and combinations of sewing yarn. The Radiata pine veneer tape produced with three sewing lines using the reinforced sewing thread had the best tensile strength. Also, the separation and snapping problems of the veneer tape were improved, resulting in the improvement in the workability of cylindrical LVL. The bending strength of various cylindrical LVL produced with different types of veneer tape and a different number of lamination layers and the application of reinforcement with glass fiber cloth was compared with that of Larix log. Bending MOR of cylindrical LVL reinforced with glass fiber cloth at the volume ratio of 11% was improved by 65% in comparison to the non-reinforced cylindrical LVL. In the case of the cylindrical LVL produced with 2 sewing lines of veneer tape, a fracture occurred at the butt joint between the veneer tapes. However, in the case of the cylindrical LVL produced with 3 sewing lines of veneer tape a fracture occurred in the fiber direction.

• Journal of Digital Contents Society
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• v.15 no.3
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• pp.327-338
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• 2014

This study proposes the evolution model of emerging media platform including smart media (M-IPTV, Smart TV) and IPTV, through a spiral evolution model based on the theory of the exploration & the exploitation. Authors suppose that the IP media evolved from IPTV technology, evolution of which has come through the development model of serial circular process. For explanation of this evolution, we propose the research model integrating the spiral model and the exploration & exploitation theory. Researchers define the smart media as the evolved media from IPTV, through this proposed model. We expect this model to be the theoretical base of media regulation and setting direction of future media service. Thus, this research are summed up as follows. To begin with, we classify the evolutionary stage of IPTV from the view points of service feature, regulation frame and technological characters. Secondly, we organize and confirm the research model of IPTV evolution through case analysis of the 3 cycles of each evolutionary stage. As a result, discussion of this study helps understanding mobile IP media and smart media as a post IPTV and leads the solution of various regulation issues and the development of the innovative media service and content. In addition, it can guide the government for the evolutionary direction to promote the media and the content industry.

• Journal of Science Education
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• v.41 no.1
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• pp.152-165
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• 2017

The magnetic field due to a current is one of the core concepts in electromagnetism which has been taught in secondary science education. In addition, it is a representative example of using visual representations to explain the relation between invisible physical quantities; current and magnetic field. In this study we investigated middle school students' representational competence into three components; interpretation, construction, and application of visual representations. According to the analysis, more than 75 % of the respondents interpreted the meaning of the arrows for current and magnetic field correctly. However, half of them confused the movement of electric charges with the direction of magnetic field. Over 60 % of the students constructed the magnetic field representation as circular closed curves, but many of them could not express the density of field lines properly. In application of visual representations, more than half failed to draw the direction of compass needle correctly. The scores were in order of interpretation, construction and application. There were also significant correlations among three components of representational competence. More attention and research on students' representational competence and effective use of visual representations is needed to better support science learning and teaching.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.4
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• pp.526-552
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• 1994

The extent and direction of movement of removable partial dentures during function are influenced by the nature of the supporting structures and and the design of the prosthesis. Since forces are transmitted to the abutment teeth through occlusal rests, guide planes and direct retainers during functional movements, proper design based on the avaialble research data will maintain the health of abutment teeth and their supporting structures. The purpose of this in vitro study is evaluating stress distribution clinically around the abutment teeth prepared following 4-type clasping systems for unilateral free-end removable partial dentures. Three-Dimensional Photoelastic Stress Analysis method was used because it shows a visual display of stresses of the simulated abutment teeth and residual ridges and reveals stress concentration that can be read at any given points in terms of direction and magnitude. For this study, the author fabricated 4 mandibular photoelastic epoxy models missing left 1st and End molar. Epoxy models were duplicated and 4 unilateral removable partial dentures were construe- ted in accordance with 4-type direct retainers. Unilateral free-end removable partial dentures were positioned on their own models. 6kg force was loaded on the every removable partial dentures of the epoxy model on the central fossa of mandibular left 1st molar vertically by the loading device. After the stress was frozen in a stress freezing furnace, 6 specimens of 6-mm thickness were made from every epoxy model and examined with the circular polariscope. The results were as follows : 1. Generally I-bar clasp revealed the most favorable stress distribution around the abutment teeth. 2. At the end portion of the free-end ridge, Back action clasp showed the highest stress concentration at the bucco-lingual and top portions of the residual alveolar ridge. 3. At the distal area of the abutment teeth, Akers clasp and Roach clasp showed higher stress concentration bucco-lingually and apically than the others. 4. To the abutment tooth, I-bar clasp showed the least stress distribution bucco-lingually but the others showed irregular stress distribution. 5. At the mesial area of the abutment teeth, the order of effective stress distribution was I-bar clasp, Back-action clasp, Akers clasp and Roach clasp. There was big difference of stress distribution between them. 6. At the right 2nd premolar and 1st molar, the stress concentration of Akers clasp was a little high but that of I-bar clasp was low.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.2
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• pp.148-154
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• 2014

Photoelasticity is a useful technique for obtaining the differences and directions of principal stresses in a model. In conventional photoelasticity, the photoelastic parameters are measured manually point by point. Identifying and measuring photoelastic data is time-consuming and requires skill. The fringe phase shifting method was recently developed and has been found to be convenient for measuring and analyzing fringe data in photo-mechanics. This paper presents an experimental study on the stress distribution along a horizontal line that passes the central point of a rhombus plate made of Photoflex (i.e., type of urethane rubber). The isoclinic fringe and/or principal stress direction is constant on this horizontal line, so a four-bucket phase shifting method can be applied. The method requires four photoelastic fringes that are obtained from a circular polariscope by rotating the analyzer at $0^{\circ}C$, $45^{\circ}C$, $90^{\circ}C$ and $135^{\circ}C$. Experimental measurements using the method were quantitatively compared with the results from FEM analysis; the results from the two methods showed comparable agreement.

• Journal of the Korean Magnetics Society
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• v.26 no.1
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• pp.19-23
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• 2016

In this study, we have constructed a measuring system to investigate tensile stress measurement of tendons, which is employed in bridges, by means of the non-destructive and non-contact method. The measuring system consists of tensile stress applying apparatus up to 2 GPa, and power supply for ac and dc current to tendon directly to magnetize tendon in circular direction and to coil wound on yoke to magnetize tendon in axial direction. We have used two kinds of tendon, which were produced by different companies, using the measuring system constructed in this work. Two kinds of experiments are carried out in this work; $1^{st}$ experiment : ac current was applied to the tendon and dc current was applied to coil wound on the yoke, and voltage induced from search coil wound on yoke (SCY) was measured and $2^{nd}$ experiment : dc current was applied to the tendon and ac current was applied to coil wound on the yoke, and voltage induced from search coil on tendon (SCT) was measured. In case of $1^{st}$ experiment, voltage induced from SCY was changed below 200MPa tensile stress but the voltage was not increased above 200 MPa. In case of $2^{nd}$ experiment, voltage induced from SCT was decreased up to 1.5 GPa linearly. We expect that $2^{nd}$ experiment could be applied to the non-destructive testing of tensile stress measurement of tendon.

• Geophysics and Geophysical Exploration
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• v.27 no.2
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• pp.108-118
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• 2024

In this study, expressions for the magnetic field and magnetic gradient tensor due to an elliptical disk were derived. Igneous intrusions and kimberlite structures often have elliptical cylinders with axial symmetry and elliptical cross sections. An elliptical cylinder with varying cross-sectional areas was approximated using stacks of elliptical disks. The magnetic fields of elliptical disks were derived using the Poisson relation, which includes the direction of magnetization in the gravity gradient tensor, as described in a previous study (Rim, 2024). The magnetic gradient tensor due to an elliptical disk is derived by differentiating the magnetic fields, which is equivalent to obtaining ten triple-derivative functions acquired by differentiating the gravitational potential of the elliptical disk three times in each axis direction. Because it is possible to exchange the order of differentiation, the magnetic gradient tensor is derived by differentiating the gravitational potential of the elliptical disk three times, which is then converted into a complex line integral along the closed boundary curve of the elliptical disk in the complex plane. The expressions for the magnetic field and magnetic gradient tensor derived from a complex line integral in complex plane are perfectly consistent with those of the circular disk derived from the Lipschitz-Hankel integral.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2402-2407
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• 2007

Heat transfer distributions and friction factors in square channels (3.5 ${\times}$ 3.5 cm) with twisted tape inserts and with twisted tape inserts plus interrupted ribs are respectively investigated. Tests are performed for Reynolds numbers ranging from 8,900 to 29,000. The rib height-to-channel hydraulic diameter, e/Dh, is kept at 0.057 and test section length-to-hydraulic diameter, L/Dh is 30. The twisted tape is 0.1 mm thick carbon steel sheet with diameter of 3.3cm, length of 90cm, and 2.5 turns. The square ribs are arranged to follow the trace of the twisted tape and along the flow direction defined as axial interrupted ribs. Each wall of the square channel is composed of isolated aluminum sections. The following conclusions from the experimental study were drawn as: 1) In the 4 heating wall channel with twisted tape inserts, Nusselt number based on bottom wall temperature is enhanced by 1.2 - 1.6 times if adding the axial interrupted ribs on the bottom wall only. 2) The twisted tape with interrupted ribs under the two-sided heating condition produces the highest heat transfer performance. 3) Friction factor data obtained for the square channel with twisted tape inserts plus axial interrupted ribs are less than those in the past publications for circular tubes with axial interrupted ribs and twisted tape inserts.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1171-1176
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• 2014

The eye-tracking [ET] is used on the human computer interaction [HCI] analysing the movement status as well as finding the gaze direction of the eye by tracking pupil's movement on a human face. Nowadays, the ET is widely used not only in market analysis by taking advantage of pupil tracking, but also in grasping intention, and there have been lots of researches on the ET. Although the vision based ET is known as convenient in application point of view, however, not robust in changing environment such as illumination, geometrical rotation, occlusion and scale changes. This paper proposes two steps in the ET, at first, face and eye regions are discriminated by Haar classifier on the face, and then the pupils from the discriminated eye regions are tracked by CAMShift as well as Template matching. We proved the usefulness of the proposed algorithm by lots of real experiments in changing environment such as illumination as well as rotation and scale changes.

• Journal of Digital Convergence
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• v.11 no.12
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• pp.417-422
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• 2013

In this paper, the implementation of a null-steering antenna array using GPS patch antennas is suggested. The antenna array consists of five patch antenna elements fabricated on the ceramic substrate. The antenna element proposed here is a typical circular polarization patch and a prototype patch array antenna is manufactured on the PCB. The antenna has one reference element located at the center and other four elements are placed at the corners. A null in the direction of the jamming signal can be produced by changing the phases of 4-elements. Simulation results of the array antenna by CST MWS are presented and discussed. The basic performances are measured and the results are shown. The results show that the antenna presented here can be used to remove the signals from the directions of any jammers.