• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.12
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• pp.1343-1351
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• 2010

In this paper, a novel patch antenna based on the metamaterial CRLH(Composite Right- and Left-Handed) structure is designed, implemented, and measured. Contrary to the standard microstrip patch's fundamental resonance mode of half-wavelength or its positive multiple, the proposed antenna shows the in-phase electric field over the entire antenna. The proposed antenna has a desired omni-directional field pattern which is typical characteristic of $\lambda/4$ monopole antenna, and also shows the merit of low profile. HFSS(High Frequency Structure Simulator) of Ansoft which is based on the FEM(Finite Element Method) is used to simulate the proposed antenna. FR-4 substrate of thickness 1.6 mm and relative permitivity 4.4 is used for the proposed antenna implementation. The implemented antenna showed VSWR (Voltage Standarding Wave Ratio)$\leq$2 for the frequency band from 2.63 GHz to 2.655 GHz which is used for S-DMB (Satellite-Digital Multimedia Broadcasting) service. And measured peak gain and efficiency are 2.65 dBi and 81.14 %, respectively.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.4
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• pp.462-466
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• 2010

The purpose of this study is to evaluate the safety of a wire connector fabricated for the effective installation of a lighting fixture including its contact resistance, insulation resistance, withstanding voltage characteristics, etc., and to provide the basis for the analysis and judgment of PL(Product Liability) dispute by presenting a damage pattern due to a general flame and overcurrent. This study applied the Korean Standard (KS) for the incombustibility test of the connector using a general flame and performed an overcurrent characteristics test of the connector using PCITS (Primary Current Injection Test System). The contact resistance of the housing connector was measured using a high resistance meter and the insulation resistance was measured using a multimeter. In addition, a supply voltage of AC 1,500V for testing the withstanding voltage characteristics was applied to both ends of the connector. Measurement was performed on 5 specimens and the measured values were used as a basis for judgment. Since the connector is fabricated in the form of a housing, it can be connected and separated easily and has a structure that allows no foreign material to enter. In addition, since it has a structure that allows wires to be connected only when their polarity is identical, any misconnection that may occur during installation can be prevented. When the incombustibility test was performed by applying a general flame to the connector, it showed outstanding incombustibility characteristics and the blade and blade holder connected to the housing remained firmly secured even after the insulation sheath (PVC) was completely destroyed by fire. In addition, the mechanism of the damaged connecting wire showed a comparatively uniform carbonization pattern and it was found that some residual melted insulation material was attached to both ends. In the accelerated life test (ALT) to which approximately 500% of the rated current was applied, the connector damage proceeded in the order of white smoke generation, wire separation, spark occurrence and carbonization. That is, it could be seen that the connector damaged by overcurrent lost its own metallic color with traces of discoloration and carbonization. The contact resistance of the connector at a normal state was 2.164mV/A on average. The contact resistance measured after the high temperature test was 3.258mV/A. In addition, the insulation resistance after the temperature test was completed was greater than $10G\Omega$ and the withstanding voltage test result showed that no insulation breakdown occurred to all specimens showing stable withstanding voltage and insulation resistance characteristics.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.1
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• pp.57-64
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• 2021

The speed change lane is installed at the point where the roads are connected on the urban roads, reducing the relative speed to facilitate traffic communication. However, in the case of the speed limit of 30 km/h in accordance with the implementation of the safe speed "5030" in the city, the standard is ambiguous, and there are criticisms about the installation of the transmission lane. This study conducted a pilot study on the traffic patterns of the speed change lanes, focusing on the section where the safe speed "5030" policy was scheduled to be implemented after theoretical consideration of the speed change lanes. After on-site investigation, as a result of analyzing the traffic pattern according to the travel speed of the main road according to road conditions and traffic conditions, the effectiveness of the speed change lane according to the safety speed "5030" was analyzed. In this study, the installation criteria for speed change lane by speed were presented. The criteria is that "speed change lanes should not be installed when the speed limit is 30 km/h, and speed change lanes should be installed when the speed limit is 50 km/h." The criteria will be considered as a reference when establishing engineering standards for connection of other facilities in urban areas in the future. It is expected that unnecessary restrictions on individuals' exercise of private property rights will be minimized, smooth traffic flow and secure safety by the installation of speed change lanes and expansion of turning radius.

• Journal of Dental Rehabilitation and Applied Science
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• v.37 no.4
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• pp.232-243
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• 2021

Purpose: The purpose of this study was to evaluate the shear bond strength of various 3D printed denture base resins and the conventional denture base resin to various denture relining materials. Materials and Methods: For denture base materials, a heatcured (Vertex RS) and two types of 3D printed DENTCA Denture base II, NextDent^TM Base) were used. And 4 types denture relining materials (Tokuyama Rebase II fast, Kooliner, Denture Liner, Denture Liner, Lang Jet Denture Repair Kit) with different components were used. It was classified into 12 groups. Adhesion was performed between the resin base and the relining materials in accordance with ISO/TS 11405 standard. The shear bonding strength was measured, and then the adhesion interface was observed with a stereoscopic microscope and a scanning electron microscope. The fracture pattern was investigated through the analysis of the fragment. Results: In the 3D printed denture resin group, the shear bonding strength with relining materials was significantly lower than that of the heat-cured resin group (P < 0.05). The group of polymethyl methacrylate -based relining materials, high shear bonding strength was shown regardless of the type of denture. As for the fracture pattern, adhesive fracture appeared in most groups, and cohesive, mixed fracture appeared in some groups. Conclusion: The polymethyl methacrylate -based denture relining materials showed high shear bonding strength values compared to other denture relining materials. But, for direct methods, it is considered advantageous in terms of shear bonding strength to use a isobutyl methacrylate-based denture relining materials.

• Journal of the Korean Geotechnical Society
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• v.37 no.11
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• pp.23-36
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• 2021

In this paper, the effect of shear rate on internal friction angle and unconfined compressive strength of non-cemented and cemented sand was investigated. A dry Jumunjin sand was prepared at loose, medium, and dense conditions with a relative density of 40, 60 and 80%. Then, series of direct shear tests were conducted at shear rates of 0.32, 0.64, and 2.54 mm/min. In addition, a cemented sand with cement ratio of 8% and 12% was compacted into a cylindrical specimen with 50 mm in diameter and 100 mm in height. Unconfined compression tests on the cemented sand were performed with various shear rates such as 0.1, 0.5, 1, 5 and 10%/min. Regardless of a degree of cementation, the unconfined compressive strength of the cemented sand and the angle of internal friction of the non-cemented sand tended to increase as the shear rate increased. For the non-cemented sand, the angle of internal friction increased by 4° at maximum as the shear rate increased. The unconfined compressive strength of the cemented sand also increased as the shear rate increased. However, its increasing pattern declined after the standard shear rate (1 mm/min). A discrete element method was also used to analyze the crack initiation and its development for the cemented sand with shear rate. Numerical results of unconfined compressive strength and failure pattern were similar to the experimental results.

• Journal of the Korean Society of Radiology
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• v.15 no.5
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• pp.697-704
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• 2021

It is hard to get Filaments which are materials of the 3D printing Fused Deposition Modeling(FDM) method as radiation shielding in Korea. and also related research is insufficient. This study aims to provide basic data for the development of radiation shields using 3D printing by evaluating the physical properties and radiation shielding capabilities of filaments containing metal particles. after selecting five metal filaments containing metal particle reinforcement materials, the radiation shielding rate was calculated according to the Korean Industrial Standard's protective equipment test method to evaluate physical properties such as tensile strength, density, X-ray Diffraction(XRD), and weight measurement using ASTM's evaluation method. In the tensile strength evaluation, PLA + SS was the highest, ABS + W was the lowest, and ABS + W is 3.13 g/cm³ which value was the highest among the composite filaments in the density evaluation. As a result of the XRD, it may be confirmed that the XRD peak pattern of the particles on the surface of the specimen coincides with the pattern of each particle reinforcing material powder metal, and thus it was confirmed that the printed specimen contained powder metal. The shielding effect for each 3D printed composite filament was found to have a high shielding rate in proportion to the effective atomic number and density in the order of ABS + W, ABS + Bi, PLA+SS, PLA + Cu, and PLA + Al. In this study, it was confirmed that the metal particle composite filament containing metal powder as a reinforcing material has radiation shielding ability, and the possibility of using a radiation shielding filament in the future.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.41 no.1
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• pp.21-34
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• 2023

This study identified the materials and construction methods of 'Old Wall' in 13 villages which were designated as National Registered Cultural Heritage at the time of designation and examined the their structural changes based on field survey. The results are as follows: First, the 'Old Wall' consisted of 10 Soil-Stone Wall and 5 Stone Wall. At the time of designation, Stone Wall, which was built irregularly by dry-construction of natural stones, is similar in shape, but Soil-Stone Wall showed difference by the construction method of making used stones, joints, and faces. Second, the study extracted the changes of 'Old Wall' by repair and examined the changes of construction methods as well as the substitution and addition of materials of structure. The wall-roof was built with cement roof-tile and asbestos slate which have the advantage improve durability and cost-effectiveness. In addition, tile-mouth soil was added to korean traditional roof-tile to prevent rainwater from flowing in. Besides, to improve constructional convenience, the natural stone of the wall-body was replaced with blast stone, float stone and cut stone. Cement block, cement brick and cement mortar were frequently used to repair as well. As Soil-Stone Wall was transformed from irregular pattern-construction to comb pattern-construction and wet-construction was changed to dry-construction, it caused landscape and structural problems. Also, the layer of cement mortar applied to wall-foundation blocked the flow of rainwater that was induced by dry-construction of natural stones. Third, the study regarded that the problem with the repair of 'Old Wall' may occur as it is located in living space, because the owner of the wall could repair for the minor damages without technical knowledge. In addition, it is difficult for repair companies in charge of maintenance of Cultural Heritage to supply local materials, and it is differential construction specifications are not applied.

• The Journal of the Society of Stroke on Korean Medicine
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• v.9 no.1
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• pp.14-18
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• 2008

Objectives : This study was done to investigate the relationship of differentiation of the patten identification in stroke patients between acute and convalescent stage. Methods : In the time of period Apr. 1st 2007 to Sep. 29th 2008, 903 patients with stroke admitted in the department of Internal Medicine of Kyungwon University Oriental Medical Hospital, Kyunghee University Oriental Medical Hospital, Dongguk University Oriental Medical Hospital were included. Patients were hospitalized within a month after the onset of stroke. Stroke patients were interviewed by doctors who studied standard operation procedures. A questionnaire was completed by a question-and-answer form between patients and doctors after explanation details to patients and the agreement of patients. Results : The frequency of fire-heat patten was the highest in acute stage of stroke and the one of deficiency of Yin group was the highest in convalescent stage of stroke. This result doesn't have statistical significance. (p<0.05) Conclusions : In this study, we found the relationship of differentiation of the patten identification in stroke patients between acute and convalescent stage. Further, we have concluded that this difference should be considered in the management for stroke patients.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.296-296
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• 2022

This study was investigated to compare the milling and physicochemical characteristics of six Korean wheat cultivars (Keumkang, KK; Jokyung, JK; Goso, GS; Joongmo2008, JM; Baekkang, BK; Saekeumkang, SKK) and five foreign wheat classes (Australian standard white wheat, ASW; Australian hard, AH; US northern spring, NS; US hard red winter, HRW; Soft wheat, SW). Korea and foreign wheat grains were milled using a Buhler MLU-202. Flour moisture, ash, protein, gluten, sedimentation, particle size, solvent retention capacity (SRC) and dough properties of flour were analyzed. Results showed that the hard wheats had a greater total flour yield and reduction fraction yield than the soft wheats regardless of the country. However, there were in the milling characteristics between the US and Korean soft wheats. GS, a soft wheat in Korea, had the lowest flour yield (59.6%) and the highest bran fraction yield (21.4%). The particle sizes of flour by milling fraction were B1>B2>B3 for the largest, and the R1〈R2〈R3 for the smallest. Particle size, ash, protein contents and the values of lactic acid SRC showed highly correlated with flour yield. The gluten-performance-index (GPI) is the ratio of the lactic acid SRC value to the sum of sodium carbonate and sucrose SRC values, and it has been used as a quality indicator for overall performance potential of flour. GPI values differed depending on the wheat variety or class, JM (0.82) was the highest value, and SKK (0.56) and SW (0.59) were low. The curve pattern of the Mixolab result also gives a quality indication of the flour sample. JM and NS flour had similar pattern at water absorption and gluten strength parameters and BK and HRW had similar viscosity patterns. These results will enable further study for blending Korean wheat cultivar to improve the flour quality.

• Phonetics and Speech Sciences
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• v.16 no.1
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• pp.49-55
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• 2024

This study aims to develop a three-sentence speech screening test to evaluate speech development in 4-year-old children and provide standards for comparison with peers. Screening tests were conducted on 24 children each in the first and second halves of 4 years old. The screening test results showed a correlation of .7 with the existing speech disorder evaluation test results. We compared whether there was a difference between the two groups of 4-year-old in the phonological development indicators and error patterns obtained through the screening test. The developmental indicators of the children in the second half were high, but there were no statistically significant differences. The Korean Speech Sound Analysis Tool (KSAT) was used for all analyses, and the automatic analysis results and contents of the clinician's manual analysis were compared. The degree of agreement between the automatic and manual error pattern analyses was 93.63%. The significance of this study is that the standard of speech of a 4-year-old child of the speech screening test according to three sentences at the level of elicited sentences, and the applicability of the KSAT were reviewed in both clinical and research fields.