최근 시멘트 콘크리트 포장의 아스팔트 덧씌우기 포장을 유지보수 공법으로 채택할 경우 반사균열이 다수 발생하여 유지보수 비용 증가로 이루어지고 있다. 반사균열 발생일 지연시키기 위하여 다양한 재료 및 공법을 사용하고 있으나 이에 대한 효과를 정확하게 평 가하는 시험방법 및 평가기준이 미비한 상태이다. 미국에서도 반사균열 문제로 인하여 유지보수 비용이 급격히 증가하고 있으며, 아스 팔트 함량을 높게 하고 개질제 및 그리드를 사용하여 반사균열 발생을 지연시키려는 노력을 하고 있다. 미국 및 선진국에서는 반사균열 평가 시험법으로 Texas Overlay Tester를 범용으로 사용하고 있으며, 반사균열 저항성 평가에 유일무 이한 장비로 알려져 있다. 최근 93%에 이르는 하중 감소율에 도달하는 하중 재하횟수 시험에 시간적 노력과 편차가 크다는 논란이 재 기되어 1000회 까지만 수행하여 균열발생(crack initiation)과 균열전파(crack propagation) 특성울 계산하여 보다 역학적인 방법에 의한 반 사균열 저항성 평가가 시도되고 있다. 밀입도, PSMA, 구스, 그리드 보강 아스팔트 혼합물에 대한 Overlay Tester를 이용하여 반사균열 수행을 수행하였으며, 이에 대한 균 열발생과 균열 전파 특서을 정량화 하여 비교 분석을 실시하였다.

The laser power has been continually increased since the laser was developed in the mid-20th century. Achieving higher laser power requires not only enhancing the cooling performance of laser systems but also addressing the potential degradation of optical characteristics due to thermal deformation induced by laser beam absorption in a mirror. This study delves into the thermal deformation characteristics of mirrors in high-power laser systems. To minimize thermal deformation by heat absorption, Zerodur, known for its low coefficient of thermal expansion, was employed as the mirror material. Various configurations including circular, rectangular, and spline shapes were implemented on a solid mirror structure. Furthermore, two different diameter of a mirror, 300mm and 400mm, were considered to investigate the size effect of the high-power laser beams. Also, three different transmitted beam power were adopted: 50W, 250W, and 500W. Based on the finite element analysis for the thermal deformation, the deformation characteristics of the different types of mirror structures were investigated and analyzed for high-power laser systems.

본 논문은 서해 군산분지 퇴적층 내에서 발견되는 다양한 화성암들을 탄성파 반사상에 따라 분류하고 그 공간 적 분포 양상을 도시하는 과정에 대해 상술한다. 연구지역인 서해 대륙붕 군산분지의 북동소분지, 남서소분지, 남동소분 지 내에서 총 6종류의 분출 화성암 반사상과 3종류의 관입 화성암 반사상이 중생대 후기 백악기, 신생대 에오세 및 전 기 마이오세, 신생대 제4기 층에서 발견되었다. 분출 화성암은 그 크기, 외형, 내부 층리구조에 따라 (1) 높이 200 m 이 하의 고깔형 화산체들로 1회성 단성화산 분화를 통해 형성된 것으로 추정되는 단성화산체(E.mono), (2) 단성화산체들이 모여 높이 500m 이내의 하나의 화산체를 형성하는 단성화산복합체(E.comp), (3) 높이 1 km 이상 직경 15 km 이상으 로 내부에 복수의 층이 인지되는 성층화산체(E.strato), (4) 기반암 저지대의 정단층 주변에서 고반사 특성을 보이는 열 극 분출암(E.fissure), (5) 저각 사면부와 내부에 직경 약 2 km 화도 구조를 보여주는 마르-다이아트림(E.maar), (6) 퇴적 층을 교란하는 직경 1 km 이내 파이프형 구조를 갖는 열수분출공(E.vent)으로 구성된다. 관입 화성암은 상부 퇴적층의 변형구조를 통해 인지되며, (1) 수평형, 계단형, 종지형 등 다양한 수직/수평 관입 기하를 나타내는 암맥 및 암상(I.dike/ sill), (2) 직경 1-3 km의 뿔 또는 기둥 모양 관입암체인 화성암주(I.stock), (3) 상부 퇴적층을 광범위하게 변형시키는 폭 10 km 이상의 관입암체인 저반/병반(I.batho/lac)으로 구성된다. 분출 화성암은 주로 군산분지 남서소분지 내 백악기 및 신생대 고제3기 에오세 층 내에서 인지되며, 관입암체는 주로 남동 및 남서 소분지 내에서 발견된다. 열수분출공은 군 산분지 전역에서 발견되며 활동시기는 전반적으로 중기 마이오세 이후로 일부는 현재까지 활동중인 것으로 보인다.

algorithms for deriving and analyzing retroreflectivity influence factors through regression analysis. METHODS : An experimental road lane was created to examine the trends of retroreflectivity and LiDAR intensity values, and a controlled indoor experiment was conducted to identify influencing factors. The optimal algorithm was developed by regression analysis of the experimental data. RESULTS : The significance probability (P-value) through SPSS linear regression analysis was 0.000 for measured height, 0.001 for perpendicular angle, 0.157 for vertical angle, and 0.000 for LiDAR intensity, indicating that measured height, vertical angle, and LiDAR intensity are significant factors because the significance probability is less than 0.05, and vertical angle is not significant. The NNR regression model performed the best, so the measurement data with height (1.2m, 2m, 2.2m) and vertical angle (11.3°, 12.3°, 13.5°) were analyzed to derive the optimal LiDAR Intensity measurement height and vertical angle. CONCLUSIONS : For each LiDAR measurement height and vertical angle, the highest correlation between LiDAR Intensity and retroreflectivity was found at a measurement height of 1.2 meters and a vertical angle of 12.3°, where the model learning accuracy (R2) was the highest.

PURPOSES : The purpose of this study is to verify the effect of improving the retroreflectivity of pavement marking by increasing the refractive index of glass bead. METHODS : Pavement marking test-beds has been installed in National Highway 19, 42 and KICT Yeoncheon SOC Center. In testbeds several marking sections were installed for each type of marking materials and glass beads. In this test-beds initial dry and wet retroreflectivity were measured and analyzed. RESULTS : When the refractive index of glass bead was adjusted upward in water based paint(glass bead No.1→ No.2), dry retroreflectivity increased by about 30 to 70%, and wet retroreflectivity slightly increased by about 10 to 40%. When using glass bead No. 2 in water based paint, it was found to meet the standards of the Road Traffic Act. However, since wet retroreflectivity of water based paint slightly exceeds the standard value, a follow-up investigation is needed to determine how long this performance can be maintained. When using glass bead No.1 in MMA(methyl methacrylate), the average wet retroreflectivity was evaluated to be 128 to 150 mcd/lx/m2, and when using glass bead No.2, the average wet retroreflectivity was evaluated to be about 200 to 270 mcd/lx/m2. Accordingly, MMA showed the best performance compared to other paints. CONCLUSIONS : When using glass bead No.1 in water-soluble paints and thermoplastic, it did not meet the wet retroreflectivity standards of the Road Traffic Act. But when using glass bead No.2, it met the wet retroreflectivity standards. As a result of analyzing the road marking budget according to the upward adjustment of the refractive index of glass bead, it was analyzed that if only the material class was adjusted upward, the cost would increase by more than twice the current budget. In order to decrease this budget increase rate(to increase service life), it is necessary to strengthen quality control standards for pavement marking and develop scientific-systematic quality control techniques.

With the advancement of optical design and manufacturing technology, optical components have found diverse applications, spanning from semiconductors to the aerospace industry. A reflective mirror is a basic component in optics and plays a crucial role as the medium to reflect light. In this paper, a large mirror with a 700mm diameter was designed as a primary mirror using fused silica. The rear side of the mirror was subdivided into several equal angles, and neighboring vertices on the circumference were connected to establish a polygon. Accordingly, the geometric shapes of triangle, square, pentagon, and hexagon were formed. Furthermore, the mirror structure was strengthened by employing straight lines passing the vertices and the center of the circle. Based on the finite element analysis, deformations of the mirrors caused by the gravitational force were evaluated. Weight and deformation of the mirror structures were compared and analyzed to find a proper structure to reduce weight and deformation. This paper, therefore, presents a structural solution aimed at reducing the weight and deformation of a large aperture mirror induced by gravitational forces, thereby suggesting a geometric shape based structure to reduce surface deformation of a mirror.

In general, a large mirror without weight reduction in large optical or space telescope systems can increase the system’s weight or lead to significant deformation of the mirror surface. Thus, it is imperative to pursue lightweight design strategies. In this paper, the structure design of a spherical mirror, a diameter of 600mm and a mirror radius of 2,000mm, was investigated to reduce weight and minimize deformation. To establish load paths for internal and external loads, stiffeners were added across the lateral supports. This approach effectively reduced both weight and deformation caused by gravity. Weight reduction and reduction percentages were quantified, and the mirror deformation was evaluated by using finite element analysis (FEA). The proposed structures were compared with honeycomb structures for weight reduction. This evaluation allowed to assess the deformation characteristics and the potential advantages of the proposed structures for lightweight mirrors.

Zerodur, one of the optical materials, was used for large spherical mirrors in this study. For weight reduction, several types of honeycomb structures were investigated. The finite element simulation was used for deformation and mode analysis. It was revealed that the weight reduction rate and maximum deflection due to the gravity effect vary depending on the honeycomb structures. Additionally, this study highlights the potential of spline-shaped honeycomb structures as an alternative for weight reduction, and triangular honeycomb structures demonstrated the less deformation by the gravity effect. The findings from this study provide valuable insights for designing lightweight and high-performance spherical mirrors in optical systems.

PURPOSES : A mechanistic-empirical (ME) predictive design logic that can compute the reflective cracking life of hot-mix asphalt (HMA) overlaid on top of a composite pavement is proposed herein. METHODS : The overlay thickness design and analysis logic of the HMA were formulated based on the ME concept of reflection crack propagation. Climate data, traffic load data, the pavement material properties, and the thickness of each layer of the pavement are the main inputs for the ME-Reflective Cracking Rate (RCR) prediction algorithm. An Microsoft Excel Virtual Basic for Application (VBA) program was created to aid designers in assessing the expected performance of an HMA overlay design. Calibration was done using data from the Long-Term Pavement Performance (LTPP) sections. Sensitivity analysis was conducted to compare the results yielded by the program and data from a report by the Texas Transportation Institute. RESULTS : The predictive model performance effectively generates the dynamic and relaxation modulus curves. The correlation value of the calibration factors, R2, is 0.79. The calibration factors used for the Asphalt Overlay Thickness Design (AOTD) program and the sensitivity analysis, i.e., k1, k2,, and k3,, are set to 5, 5, and 150, respectively. The sensitivity of the AOTD program affords reasonable results. Additionally, the program yields results similar to the trends presented in a report by the Federal Highway Administration. CONCLUSIONS : The proposed ME design logic is successfully translated into an Excel VBA program, AOTD, which can perform routine assessments of laboratory tests for HMA overlays. The program can effectively perform numerous iterations and computations to predict an HMA overlay. The predictive model can generate reasonable dynamic modulus and relaxation modulus curves for the characterization of HMA overlays. Under the same asphalt binder grade and HMA type, doubling the HMA overlay thickness yields three times the expected reflective cracking service life.

We explored the frequency response of krill target strength (TS) to understand the Antarctic krill (Euphausia superba) and ice krill (Euphausia crystallorophias) using the stochastic distorted-wave Born approximation (SDWBA) model. The results showed that the distribution of orientation and the fatness factor could significantly impact on the frequency response of TS. Krill TS is clearly depended on acoustic properties, which could affect to estimate the biomass of two krill species. The results provide insight into the importance of understanding TS variation to estimate the Antarctic krill and ice krill biomass, and their ecology related to the environmental features in the Southern Ocean.

시간영역반사계(TDR)는 케이블의 물리적 결함을 검사하는 기법이며 누수 탐지 분야로의 응용영역을 확대하고 있다. 본 연구는 시간영역반사계 기법을 활용하여 선박 기관실 해수 배관의 누설 감지용 케이블형 센서를 개발하였다. 케이블 센서의 형상은 꼬임형상과 흡습부재를 이용하여 제작하였으며 개발된 센서의 누수 감지 여부와 위치 탐지 가능성을 확인하였다. 개발된 센서는 실제 배관 시험 장치 에 부착하여 평가하였으며 해수 누설에 따른 다양한 TDR 신호를 취득하였다. 센서는 꼬임횟수, 피복 두께를 변수로 하여 제작하였으며 TDR 신호에 미치는 효과를 분석하였다. 실험 결과, 꼬임형 센서는 평행한 띠 형상의 센서에 비해 평활한 신호 취득이 가능하였으며 최적 꼬임 횟수는 단위길이 당 10회 이상인 것으로 나타났다. 절연 피복두께의 경우 적정 민감도 확보가 가능한 절연 피복부재의 두께는 도선 직경의 80%~120%로 확인되었다. 누수 위치 추정을 위해 회귀분석 실시 결과, 결정계수는 0.9998로 실제 누설 위치와 높은 상관관계를 나타 내었다. 결과적으로 제안된 TDR 기반의 누수 감지용 꼬임형 센서는 해수 배관 시스템의 누수 감시 센서로의 충분한 적용성을 확인하였다.

위성신호 반사계측(GNSS-Reflectometry) 기술은 위성으로부터 전송되는 신호의 지표면 혹은 해수면에 반사되는 신호를 측정하여 분석하는 기법으로서, 해수면 높이측정, 태풍 및 기상이변, 그리고 토양의 수분 및 적설량 측정 등에 활용되고 있다. 본 논문에서는 GNSS-R 기술의 해양 활용확대와 그 가능성을 살펴보기 위하여, 위성신호의 신호대잡음비를 이용하는 GNSS-R 기술의 개념과 측정원리에 대해 설명하고, 국제적인 활용 사례를 조사하여 제시하였다. 특히 GNSS-R 기술을 기존 DGNSS 기준국 및 상시관측소 인프라를 이용하여 해양안전 및 환경 모니터링에 활용 가능할 뿐만 아니라, 지상 및 해양기준국, 위성기반, 해상선박 탑재 측면에서의 해양 응용 가능분야를 조사하여 제안하였다.

PURPOSES : The retroreflectivity of pavement markings for road safety was evaluated. METHODS : Field tests of pavement markings, which are characters, symbols, crosswalks, and stop lines, but do not include line markings, were conducted using a portable retroreflectometer with the purpose of evaluating the retroreflectivity according to the type of pavement markings and roads. Furthermore, changes in retroreflectivity due to wheel passing and wet conditions were evaluated. Here, 192 test points for evaluating the retroreflectivity of pavement markings, 5 test points for evaluating reductions in retroreflectivity during conditions of wetness, and 28 test points for checking variability due to type of testing device were selected on major and minor arterial roads in Seoul. RESULTS : The average retroreflectivity of pavement markings measured in this study was 115.7 (mcd/m2·lux), which is lower than the minimum retroreflectivity required six months after installation but higher than the minimum remarking retroreflectivity required by Seoul city. The retroreflectivity of pavement markings measured on minor arterial roads was 69.1% of that on major arterial roads. The average retroreflectivity of pavement markings was reduced to 43.1% by wheel passing, which is below the remarking criterion. The average retroreflectivity measured on wet pavement markings was 43.7 (mcd/m2·lux), which is a ninth of that under dry conditions. The test results showed that retroreflectivity in the rain was much lower than the required value in the case of rain, which is 175 mcd/m2·lux, as issued by Seoul city. Compared with mobile retroreflectometers, a portable retroreflectometer produced 17% higher retroreflectivity based on the results of 28 test points. CONCLUSIONS : Based on the field tests, the retroreflectivity of pavement markings, i.e., characters, symbols, crosswalks, and stop lines, was higher than the average remarking criterion. However, the retroreflectivities of pavement markings passed by the wheel or in rain were lower than the remarking criteria. Considering that the remarking criteria in Seoul city are higher than those in Europe and the test results in this study indicate much lower values than those required in Seoul, further study is necessary to be able to properly modify the criteria for retroreflectivity.