PURPOSES : This study aims to analyze and summarize test results related to permeable blocks used for sidewalks and roadways as an alternative to conventional urban road pavement technology, specifically focusing on low-impact development (LID) techniques. Furthermore, it aims to provide reference data on the feasibility of current policy implementation and future policy directions through a longterm analysis of the performance and durability of permeable blocks in sidewalk and roadway construction. METHODS : The research methodology involves (1) conducting a survey on the status and actual conditions of permeability sustainability tests based on the results of permeability persistence tests conducted in Seoul over nine years, from 2013 to 2021; (2) analyzing the differences between the permeability block rating system of Seoul City and that employed by the Ministry of Environment; (3) analyzing the permeability of graded pavement sections in permeable blocks for sidewalks after three years of public use and deriving a regression analysis formula to estimate the maintenance period; (4) analyzing the permeability of pavement sections in permeable blocks for roadways after five years of public use and deriving a regression analysis formula to estimate the maintenance period. RESULTS : This study revealed significant improvements in the performance and quality control of permeable blocks since the implementation of the permeability sustainability test in Seoul in 2013. An analysis of the differences in the permeability coefficient and distribution based on the rating systems of Seoul City and the Ministry of Environment showed that rating system of Seoul City has approximately twice the permeability coefficient quality standard compared to that of the Ministry of Environment. Regression analysis indicated that the firstgrade permeable block was predicted to maintain its permeability for approximately 5.1 years, whereas the third-grade permeable block was predicted to maintain its permeability for approximately 3.1 years. In roadway-permeable block pavements, the first-grade sections maintained excellent quality conditions even after five years, and regression analysis predicted a permeability maintenance period ranging from eight to 17 years. CONCLUSIONS : The correlation analysis of the permeability coefficients based on the common usage period of permeable blocks for sidewalks and roadways presented in this study can provide more accurate estimations of commonality. However, further research under various environmental conditions is required to supplement these findings. Considering the lack of studies on permeable block commonality analysis in Korea, this study highlights the significance of conducting long-term experimental follow-up research to establish commonality prediction formulas for different usage scenarios.

PURPOSES : The increasing heat wave warnings during the summer season in Korea have significant impacts on daily life and industry as a whole, especially in urban areas (such as areas with asphalt and sidewalk pavements). Heat waves directly affect urban heat island and heat dome phenomena. Various urban temperature reduction measures are being discussed to reduce urban heat islands and heat dome phenomena and to improve citizen safety against summer heat waves; suggestions include thermal packaging, rooftop greening, and expansion of vegetation areas. There is a lack of analysis on the methodology for increasing the road spraying effect during summer heat waves (e.g., there is no systematic engineering study on the effect from reducing the temperature of the road spraying during a heat wave in the city) and on the types of road pavements in the city. In addition, as the asphalt pavements of roadways and block pavements installed in sidewalks account for a considerable portion of all pavements, this study provides a more systematic and scientific approach and procedures for reducing temperatures through road spraying in the city by tracking the effects of heat waves. METHODS : In this preliminary experiment, four types of road pavement materials were selected as test specimens: asphalt test specimens (AP- 300 mm × 300 mm × 50 mm), concrete test specimens (CP-300 mm × 300 mm × 50 mm), impermeable blocks (IB-200 mm × 200 mm × 60 mm), and self-permeable blocks (PB-200 mm × 200 mm × 60 mm). As a test method to evaluate the size and duration of each spray effect package type, the surface temperature of each specimen was measured using thermal imaging cameras every 20 min after spraying at the maximum temperature point of each specimen, and the average surface temperature was analyzed based on the collected temperature data. In addition, to conduct a quantitative analysis of the effect of reducing the surface temperature of road pavements by road spraying in summer, field tests were conducted on asphalt roads and watertight blocks for sidewalks. RESULTS : As a result of the comparative analysis of the spray effect under a 36 ℃ air temperature based on a heat wave warning, the surface temperatures were, from high to low, the asphalt (68.8 ℃), concrete (59.1 ℃), impermeable block (57.3 ℃), and permeable block (58.7 ℃). The asphalt pavement had the greatest effect on the heat island and heat dome phenomena. From measuring the temperature reduction effect and sustainability of each type of road pavement, the surface temperature reduction effects were ranked in the following order: water-permeable block (Δ18.0 ℃), asphalt test piece (Δ17.5 ℃), concrete test piece (Δ12.2 ℃), and water-permeable block (over 240 min). In the report pitching block, the average road surface temperature reduction between the pore recovery and treatment was expected to continue to decrease by approximately -4.3 ℃ on the day of work and approximately -2.4 ℃ on the next day. The expected effect of the temperature reduction owing to simple spraying on the surface of the pore block was evaluated to be limited to the day. CONCLUSIONS : In the road spray effect analysis conducted on the common asphalt road, there was a slight difference in the initial temperature reduction size as the test specimen was measured, but the surface temperature difference between the non-spray section and spray section tended to be approximately Δ3°C after 140 minutes of spraying. Therefore, it was determined that the asphalt pavement temperature reduction plan through road spraying in urban areas in summer would be the most effective if it was repeated twice or more in an hour (between 13:00 and 14:00) on the day of the heat wave.

Recently, products that a have 3-dimensional(3D) micro structure have been in wide use. To fabricate these 3D micro structures, several methods, such as stereo lithography, reflow process, and diffuser lithography, have been used. However, these methods are either very complicated, have limitations in terms of patterns dimensions or need expensive components. To overcome these limitations, we fabricated various 3D micro structures in one step using a pair of diffusers that diffract the incident beam of UV light at wide angles. In the experiment, we used positive photoresist to coat the Si substrate. A pair of diffusers(ground glass diffuser, opal glass diffuser) with Gaussian and Lambertian scattering was placed above the photomask in the passage of UV light in the photolithography equipment. The incident rays of UV light diffracted twice at wider angles while passing through the diffusers. After exposure, the photoresist was developed fabricating the desired 3D micro structure. These micro structures were analyzed using FE-SEM and 3D-profiler data. As a result, this dual diffuser lithography(DDL) technique enabled us to fabricate various microstructures with different dimensions by just changing the combination of diffusers, making this technology an efficient alternative to other complex techniques.

To fabricate a precise micro metal mold, the electrochemical etching process has been researched. We investigated the electrochemical etching process numerically and experimentally to determine the etching tendency of the process, focusing on the current density, which is a major parameter of the process. The finite element method, a kind of numerical analysis, was used to determine the current density distribution on the workpiece. Stainless steel(SS304) substrate with various sized square and circular array patterns as an anode and copper(Cu) plate as a cathode were used for the electrochemical experiments. A mixture of H2SO4, H3PO4, and DIW was used as an electrolyte. In this paper, comparison of the results from the experiment and the numerical simulation is presented, including the current density distribution and line profile from the simulation, and the etching profile and surface morphology from the experiment. Etching profile and surface morphology were characterized using a 3D-profiler and FE-SEM measurement. From a comparison of the data, it was confirmed that the current density distribution and the line profile of the simulation were similar to the surface morphology and the etching profile of the experiment, respectively. The current density is more concentrated at the vertex of the square pattern and circumference of the circular pattern. And, the depth of the etched area is proportional to the current density.