동공 조사를 위한 GPR 장비의 주파수 선정에 관한 기초 연구

김제원,김연태,김부일,박희문 한국도로학회 2015 한국도로학회 학술발표회 논문집 Vol.2015 No.10

안테나 기술 및 데이터 처리 기술의 발전으로 인하여 비파괴 시험 장비인 GPR(Ground Penetration Radar; 지표투과탐사장비) 장비의 적용이 확대되고 있다. GPR 장비는 송신기에서 지표면으로 전자기파 를 송출하고, 송출된 전자기파가 매질의 유전율에 따라 수신기로 반사되거나 회절 또는 산란되어 돌아오 는 시간 영역에서의 특성에 기초하여 지표 하부의 층구조 및 매설물을 조사할 수 있는 장비이다. 이러한 GPR 장비는 현재 포장층 두께조사, 지하 동공 및 지질조사, 터널 라이닝 및 구조조사 등 여러 분야에서 적용되고 있다. 외국에서는 GPR 장비의 적용분야 가운데 도로포장분야에서 GPR 장비를 포장층 두께 측정, 박리의 위 치조사, 포장층 밀도예측, 다우웰바 탐지 등에 적용할 수 있다고 알려져 있으나 아직 많이 활성화되어 있 지는 않은 상황이다. 국내에서는 일반국도 도로포장관리시스템(Pavement Management System; PMS) 에서 주로 포장층 두께 측정을 위해 GPR 장비를 활용하면서 그 적용범위를 확대하고자 노력하고 있으며, 500MHz 주파수의 접촉식 GPR 장비와 1.0GHz 주파수의 비접촉식 GPR 장비가 사용되고 있다. 최근 사회적으로 이슈화되고 있는 도로함몰 예방을 위한 동공 조사에 현재 도로포장분야에서 활용중인 GPR 장비를 적용하기 위해서는 먼저 각 주파수별 측정 깊이의 파악이 필요하다. 왜냐하면 측정 주파수가 높으면 해상도는 좋아지지만 전자기파의 측정 깊이가 작아지고, 측정 주파수가 낮으면 해상도는 낮아지지 만 전자기파의 측정 깊이가 커지기 때문이다. 따라서 주파수별로 어느 정도 깊이까지 전자기파가 침투할 수 있는지, 측정된 데이터의 해상도가 어떻게 나타나는지 확인하여 사용목적에 적합하게 사용할 필요가 있다. 본 연구에서는 포장표면에서부터 깊이별로 스티로폼으로 모사한 동공을 설치하고 250MHz, 500MHz, 800MHz 주파수의 접촉식 GPR 장비와 1.0GHz 주파수의 비접촉식 GPR 장비를 사용하여 동일한 구간을 측정한 후, 각각의 B-scan 결과를 비교하였다. 그 결과, 포장층 두께 정도의 깊이를 조사하기 위해서는 1.0GHz 주파수의 비접촉식 안테나를 사용하는 것이 가능하지만, 1.5m 깊이 부근까지의 동공 여부를 조 사하기 위해서는 500MHz 주파수 정도의 접촉식 안테나를 사용해야 하는 것으로 나타났다.

국내 폐아스팔트 콘크리트의 특성에 관한 연구

김제원,김영민 한국도로학회 2019 한국도로학회 학술대회 발표논문 초록집 Vol.2019 No.09

분자선증착법으로 성장된 AlGaN 에피층의 표면 형상 분석

김제원,최인훈,박영균,김용태,Kim, Je-Won,Choe, In-Hun,Park, Yeong-Gyun,Kim, Yong-Tae 한국재료학회 1999 한국재료학회지 Vol.9 No.9

분자선증착법으로 (0001) 사파이어 기판 위에 $Al_xGa_1-_xN$ 에피층을 AlN 몰비를 변화시키면서 성장시켰다. AlN 몰비는 0.16에서 0.76까지 변화시켰으며 X선의 회절 실험과 Rutherford backscattering spectroscopy 방법을 이용하여 AlN 몰비를 결정하였다. $Al_xGa_1-_xN$ 에피층의 깊이 방향의 조성 변화를 관찰하였으며 스퍼터 시간에 대해 각 원소가 일정한 원자 농도를 가짐을 알 수 있었다. AlN 몰비의 증가에 따른 표면 특성의 변화를 관찰하기 위하여 atomic force microscopy 측정을 수행하였다. 표면에서의 입자 모양이 AlN 몰비가 변화함에 따라 원형에서 침상형태로 변화함을 알 수 있었다. 표면 입자에 대한 root mean square 값과 average roughness 값을 구하였으며 AlN 몰비를 바꿈에 따라 나타나는 변화를 관찰하였다. Structural properties of $Al_xGa_1-_xN$ epilayers grown on (0001) sapphire substrate by plasma induced molecular beam epitaxy are investigated in the range of AlN molar fraction from 0.16 to 0.76. The AlN molar fraction estimated by X-ray diffraction agrees well with that of Rutherford backscattering spectroscopy, showing a good linear relationship. The uniform Auger electron microscopy depth profile and linear dependence of average atomic concentration of all the constituents of AlGaN epilayers on AlN molar fraction imply that the epitaxial growth of $Al_xGa_1-_xN$ layers with variation of AlN molar fraction is well controlled without the compositional fluctuation in depth of the epilayer. It is observed by atomic force microscopy that the surface grain shape of $Al_xGa_1-_xN$ epilayer changes from roundish to coalesced one with increasing AlN molar fraction.

반도체 조명 및 AVR 디스플레이 광원 적용을 위한 나노 구조 및 공정 개발

김제원 한국조명.전기설비학회 2018 조명·전기설비학회논문지 Vol.32 No.12

The purpose of this study is to produce the three-dimensional structure with the application of nano-mold process. The three-dimensional structure and growth will be more appropriately provided through nano manufacturing process using mask patterning and etching process. This study will show multiple wavelength of light emitting diodes different from the single wavelength of existing ones through formation of nano-mold with uniformity and reproducibility. This study will show the characteristics of various wavelengths beyond blue and green through newly developed nano-mold and its nanorod array. This research will also prove the feasibility of the white light emitting diode without phosphor as multiple wavelength in a single chip can be realized. This kind of study about the light emitting diode with nano structure is actively being conducted to develop the next generation technology for semiconductor lighting, AVR and wearable displays. This study is aimed at forming new nano-mold applied with semiconductor's manufacturing process, suggesting the new characteristics of nano structure by the way of realizing the light emitting diode of three-dimensional structure by this mold.

유연 디스플레이 및 조명용 광반도체를 위한 나노 칼럼 구조 개발

김제원 조선대학교 공학기술연구원 2022 공학기술논문지 Vol.15 No.3

The luminous efficiency of a light-emitting diode-based semiconductor light source applied as a flexible display and lighting source is an essential characteristic. In order to improve luminous efficiency, various research methods, including light emitting and current injection layers, have been proposed. However, since this efficiency improvement is based on a planar structure, it is not easy to improve the optical properties. In this study, the nano-patterned column integrated structures were formed through the reactive etching process. In addition, a semiconductor light source having a light emitting structure by depositing multi-quantum healthy layers on the nano-sized column structure can be realized through the etched nano frame and hole structure.

국내 아스팔트 혼합물 품질인자의 매개변수에 따른 PWL 기준 연구

김제원,김동혁,황성도,권수안,정규동 한국아스팔트학회 2022 한국아스팔트학회지 Vol.12 No.2

The objective of this study is to determine the major quality factors in the asphalt mixture production process, and to compare and evaluate the correlation and difference according to the PWL values of each item, assuming the average and standard deviation using quality standards in Korea. We determined the main variables for PWL, and performed PWL analysis according to the change in mean and standard deviation, and then proposed improvement of PWL analysis. When the standard deviation of the test results is 1/5s (limit) ~ 4/5s (limit), the closer the sample mean is to the center, the higher the PWL, and the further the sample mean is from the median, the lower the PWL. When the standard deviation of the test results was more than s (limit), the PWL rather decreased when the sample mean was closer to the center. This occurs because PWL is the sum of PWLL according to the lower limit and PWLU according to the upper limit. When considering the purpose of PWL, improvement is needed. Therefore, it is proposed to calculate the maximum value of the PWL obtained by substituting a virtual average value that is farther away from the average of the test results or a virtual standard deviation value that is greater than the standard deviation of the test results, as the modified PWLadjusted (Adjusted PWL) of the lot. PWL is an efficient evaluation method that can analyze the effectiveness and risk of quality by statistically combining the mean, standard deviation, and sample size of test results. The modified PWLadjusted is difficult to apply in practice because it is necessary to calculate PWL by substituting countless imaginary averages and standard deviations. In the future, it is necessary to develop calculation procedures using diagrams, algorithm diagrams, and programs to increase the practical applicability of the modified PWLadjusted.

지표투과레이더를 이용한 아스팔트 혼합물의 공극률 예측에 관한 연구

김제원,김연태,김부일,박희문 한국도로학회 2016 한국도로학회논문집 Vol.18 No.4

PURPOSES: The objective of this study was to determine the relationship between the dielectric characteristics of asphalt mixtures and the air voids present in them using ground penetrating radar (GPR) testing. METHODS : To measure the dielectric properties of the asphalt mixtures, the reflection coefficient method and the approach based on the actual thickness of the asphalt layer were used. An air-couple-type GPR antenna with a center frequency of 1 GHz was used to measure the time for reflection from the asphalt/base layer interface. A piece of aluminum foil was placed at the interface to be able to determine the reflection time of the GPR signal with accuracy. An asphalt pavement testbed was constructed, and asphalt mixtures with different compaction numbers were tested. After the GPR tests, the asphalt samples were cored and their thicknesses and number of air voids were measured in the laboratory. RESULTS: It was found the dielectric constant of asphalt mixtures tends to decrease with an increase in the number of air voids. The dielectric constant values estimated from the reflection coefficient method exhibited a slight correlation to the number of air voids. However, the dielectric constant values measured using the approach based on the actual asphalt layer thickness were closely related to the asphalt mixture density. Based on these results, a regression equation to determine the number of air voids in asphalt mixtures using the GPR test method was proposed. CONCLUSIONS: It was concluded that the number of air voids in an asphalt mixture can be calculated based on the dielectric constant of the mixture as determined by GPR testing. It was also found that the number of air voids was exponentially related to the dielectric constant, with the coefficient of determination, R2, being 0.74. These results suggest that the dielectric constant as determined by GPR testing can be used to improve the construction quality and maintenance of asphalt pavements.

순환골재를 이용한 칩실 공법의 현장 적용성에 관한 연구

김제원,황성도 한국도로학회 2018 한국도로학회논문집 Vol.20 No.5

PURPOSES : The objective of this study was to evaluate the field applicability of chip seals using recycled aggregates by comparing performance between natural aggregates and recycled aggregates for chip seals. METHODS : In order to check the performance of chip seals using recycled and natural aggregates, Bitumen Bond Strength (BBS) test, Vialit and bleeding tests were carried out. Cationic emulsions (RS(C)-2 and latex modified RS(C)-2L) were used in the tests. Granite aggregates were used as the natural aggregate and recycled aggregate from road wastes were used as the recycled aggregate. The aggregate was used with uniform gradation between 10 mm and 4.75 mm to clearly compare the performance difference between natural and recycled aggregates. RESULTS : Test results showed that the aggregate retention was low for both natural and recycled aggregates when applying RS(C)-2 (unmodified emulsion), but there was almost no difference between them when applying RS(C)-2L and RS(C)-2L-1 (modified emulsion) in the Vialit test results. In the bleeding tests, there was no bleeding for both natural and recycled aggregates when applying RS(C)-2 and RS(C)-2L. CONCLUSIONS: It was possible to apply chip seals using recycled aggregates in the field because the chip seals with recycled aggregates and RS(C)-2L (modified emulsion) showed aggregate retention similar to that of natural aggregates, and there was no bleeding.

Trackless형 유화 아스팔트 개발을 위한 기초연구

김제원,김영민 한국도로학회 2019 한국도로학회 학술대회 발표논문 초록집 Vol.2019 No.09

칼라 아스팔트 콘크리트 혼합물의 시인성 비교 연구

김제원,염우성,정규동 한국도로학회 2021 한국도로학회논문집 Vol.23 No.1

PURPOSES : The objective of this study is to quantitatively evaluate the visibility of a mixed-color asphalt pavement. METHODS : The visibility was compared and evaluated using a color pavement specimen, i.e., a pigment was added to the asphalt binder, which was used to fabricate a color pavement specimen, with red aggregate as the coarse aggregate, and the resultant difference in visibility was quantitively evaluated. The color asphalt mixture to which the pigment was added was prepared by varying the amount of pigment added — i.e., 3 %, 5 %, and 7 % of the total weight of the mixture — to confirm the change in visibility according to the amount of pigment added. For the color asphalt mixture with color aggregates, red-colored mudstone coarse aggregates(13mm and 10mm) were used. It is assumed that the surface of the produced specimen simulates the initial performance periods and the cut section of the specimen simulates the state of completion of the performance periods. RESULTS : The initial ΔE for the colored pavement exhibited the best visibility of WC-2-R. However, when considering the value of a in the red color pavement, the visibility of SMA13-R and WC-2-R was assessed as best; this is because SMA13-R exhibits a lower color difference than WC-2-R at the beginning of the performance periods but the red color is better. Upon completion of the colored pavement performance periods, the ΔE of each specimen using the SMA13-0C specimen as the reference specimen was high in SMA13-RC and ΔE using the WC-2-0C specimen as the reference specimen was also high in SMA13-RC. In addition, the a value is also higher than that of other mixtures so it is judged that the visibility of SMA13-RC is best when the performance periods are completed. CONCLUSIONS : The a value tended to increase with the increasing amount of pigment added at the beginning of the performance; however, it was found to decrease rapidly as the performance was completed. However, in the case of using SMA13-RC as the colored aggregate, since the color of the aggregate itself is red, it exhibits a constant value of 5.67 from the performance start to completion. Therefore, it is judged that a constant red color can be expressed during the performance period when the colored pavement using red colored aggregate is applied to the exclusive bus lane.