• Steel and Composite Structures
• /
• v.39 no.4
• /
• pp.401-417
• /
• 2021

This study experimentally reveals the influence of welding on grade S690Q high strength steel (HSS) butt joints from both micro and macro levels. Total eight butt joints, taking plate thickness and welding heat input as principal factors, were welded by shielded metal arc welding. In micro level, the microstructure transformations of the coarse grain heat affected zone (CGHAZ), the fine grain heat affected zone (FGHAZ) and the tempering zone occurred during welding were observed under light optical microscopy, and the corresponding mechanical performance of those areas were explored by micro-hardness tests. In macro level, standard tensile tests were conducted to investigate the impacts of welding on tensile behaviour of S690Q HSS butt joints. The test results showed that the main microstructure of S690Q HSS before welding was tempered martensite. After welding, the original microstructure was transformed to granular bainite in the CGHAZ, and to ferrite and cementite in the FGHAZ. For the tempering zone, some temper martensite decomposed to ferrite. The performed micro-hardness tests revealed that an obvious "soft layer" occurred in HAZ, and the HAZ size increased as the heat input increased. However, under the same level of heat input, the HAZ size decreased as the plate thickness increased. Subsequent coupon tensile tests found that all joints eventually failed within the HAZ with reduced tensile strength when compared with the base material. Similar to the size of the HAZ, the reduction of tensile strength increased as the welding heat input increased but decreased as the thickness of the plate increased.

• Computers and Concrete
• /
• v.33 no.5
• /
• pp.621-630
• /
• 2024

This study presents novel electromagnetic wave-based methods for evaluating the integrity of cement-based structures using time domain reflectometry (TDR). Two cement-based plates with embedded rebars are prepared under sound and defective conditions. TDR tests are carried out using transmission lines with various numbers of artificial joints, and electromagnetic waves are measured to assess the integrity of the plates. The experimental results show that the travel time of electromagnetic waves is consistently longer in sound plates than in defective ones, and an increase in the reflection coefficients is observed in the defect zone of the defective plates. Electromagnetic wave velocities are higher in the defective plates, especially when connectors are present in the transmission line. A novel approach based on the area of the reflection coefficient provides larger areas in the defective plates, and the attenuation effect of the electromagnetic waves induces a difference in the areas of the reflection coefficient between the two defect conditions. An alternative method using the centroid of the defect zone slightly overestimates the location of the defect zone. The length of the defect zone is estimated using the defect ratio and wave velocities of cement, air, and plate. The length of the defect zone can also be calculated using the travel times within the plate, total measured length of the plate, and wave velocities in the cement and air. Therefore, the electromagnetic wave-based methods proposed in this study may be useful for estimating the location and length of defect zones by considering attenuation effects.

• Journal of Korean Society of Disaster and Security
• /
• v.16 no.4
• /
• pp.137-145
• /
• 2023

Accidents involving deaths of children and pedestrians continue to occur in child protection zones, also known as school zones. Over the three years from 2019 to 2021, 11 child deaths occurred in school zones in Korea. In December 2022, a fatal accident occurred among an elementary school student in a school zone near an elementary school in Gangnam-gu, Seoul. In April 2023, an accident occurred in which an elementary school student died in a school zone near Seo-gu Middle School in Daejeon and an elementary school in Yeongdo-gu, Busan. Until recently, child deaths continued to occur on sidewalks in child protection zones. It is time to closely review the status of safety facilities installed in school zones and related regulations. We investigated and analyzed the current status of safety facilities and related regulations installed on sidewalks in child protection zones in Korea, and identified matters necessary for institutional improvement regarding safety facilities for sidewalks in child protection zones.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.24 no.2
• /
• pp.39-56
• /
• 2021

The seed zone is a map that describes the areas where plant material can be transferred with little risk for properly adapting to a new location. The seed zone study is largely divided into studies based on genetic data and studies based on climatic data. Can be. This study was conducted to establish a temporary domestic seed zone applicable to the entire Korean Peninsula and evaluate its possibility based on the US climate-based seed zone establishment methodology. The temporary seed zone was constructed in the same way as the US case by superimposing the data obtained by dividing the winter minimum temperature into 12 grades and the data obtained by dividing the annual heat: moisture index into 6 grades. As a result of the analysis, 65 temporary seed zones were formed throughout the Korean Peninsula, and the areas of the seed zones representing the smallest and largest areas were 3.0km² and 29,423.0km², respectively, and it was confirmed that they had an average size of about 5,064.9km². Temporary seed zones applied in Korea show a pattern of changes in temperature according to the relatively horizontal forest zone, and it was confirmed that the area where the Baekdu-daegan ecological axis is located has a tendency to show lower dryness than other areas. This study applied the US climate-based seed zone methodology in Korea as a pilot, and confirmed the climatic similarity across the Korean Peninsula. Furthermore, it is expected to provide an optimal seed map that improves the success rate of restoration in the future by revising the seed zone grade suitable for the domestic environment in consideration of the results of this study and the possibility of seed adaptation to the field survey and environmental space.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.18 no.3
• /
• pp.241-250
• /
• 2006

In the present study, a beach survey such as sand sizes, swim zone widths, and slopes of swash zone has been accomplished for 39 beaches along the Gangwon coastline. The data analysis presents that the swim zone width has a strong correlation with the sand size, showing that the swim zone width is reversely proportional to the 1.1 power of a grain size. The profile factor A has been analyzed using the beach profile form of $h=Ay^{2/3}$, where A was resulted to be proportional to the 0.77 power of a gram size.

• Laser Solutions
• /
• v.7 no.3
• /
• pp.25-36
• /
• 2004

This study was performed to clarification of the formation of weld discontinuities in the dissimilar laser fusion zone. Welding parameters were beam power of 1300, 1430, 1560, and 1700 W and travel speed of 1, 1.3, and 1.7 m/min. Most cavities in the fusion zone were observed near the tip. Cavities in the fusion zone observed to be formed and grown from pores in the tip. More cavities were formed as the beam position moves to the tip side. Small cavities were decreased but large cavities were increased when the energy input increased. W content in the fusion zone was increased with heat input and as the beam position close to the tip. In the fusion zone, W content in the dendrite boundary was increased with heat input. Considering the propagation path and fracture morphology, cracks were solidification cracking, and were initiated and propagated along the dendrite boundaries. The formation of cracks might be related with the W rich ${\mu}$ phase which was formed in the grain boundaries and dendrite boundaries.

• The Journal of Asian Finance, Economics and Business
• /
• v.9 no.2
• /
• pp.15-27
• /
• 2022

The paper addresses the importance of redesigning strategies for resilient and sustainable regional economic development - by applying strategic approaches to free economic zones for the digital economy. The purpose of the paper is to provide a broad comparative perspective on developed versus developing country efforts to use free economic zone programs to enhance various economic and social objectives. First, the paper introduces the chronicle experiences of free economic zone programs in South Korea and mainland China - developed versus developing economies. The main results of the analysis indicate that (1) achieving the goals and objectives of free economic zones is challenging over time; (2) trying to upgrade the technical component, develop knowledge-based and eco-friendly new industries, or value-added to the economy through free economic zone policies is even challenging; and (3) incentives and other program-specific variables are highly context-specific and not structurally correlated with free economic zone performance. In addition, the paper shows that the initial conception of the role of free economic zones has undergone significant change as individual countries have tried to enhance the contributions and avoid damages from incorporating free economic zones into their development strategy respectively, over time.

• The Journal of Asian Finance, Economics and Business
• /
• v.9 no.7
• /
• pp.41-52
• /
• 2022

This paper analyzes the advantages and opportunities of regional development prospects of the China (Anhui) Pilot Free Trade Zone. In addition, it provides suggestions for the future development of the Anhui Pilot Free Trade Zone. The establishment of the Anhui Pilot Free Trade Zone is a major platform for Anhui Province, China, to serve the nation's opening-up strategy to the world and an opportunity for the Anhui region to enhance the level of an open economy. The development plan points out that the Anhui Pilot Free Trade Zone 1) takes institutional innovation as the core, 2) complies with the requirements of the innovation-driven development and promotion of the Yangtze River Delta regional integration development strategy, and 3) plays a vital node role in promoting the construction of the Belt and Road Initiative, and 4) accelerates the construction of scientific and technological innovation sources, advanced manufacturing and strategic emerging industries. The findings of this study highlight three critical achievements as follows: 1) optimization and improvement of the business environment have progressed, 2) the conversion rate of scientific and technological innovation achievements has increased, and 3) advanced high-tech manufacturing and strategic emerging industries are clustered and developed.

• Journal of the Korean Institute of Educational Facilities
• /
• v.15 no.3
• /
• pp.31-36
• /
• 2008

• Journal of Korean Society of Transportation
• /
• v.26 no.5
• /
• pp.29-40
• /
• 2008

Police agency is indicated that the number of children's traffic accident is tending downwards, however about one child is dead every day due to traffic accident. Major parts of the accidents happen during walking; among the rest, jaywalking is the biggest reason. Many accidents take plate on the road to school or near the home so government legislate children safeguard zone at 1995. According to the legislation, drivers have to reduce speed and there are safety facilities for children at children safeguard zone. This study finds the problems of children safeguard zone and suggest more effective and quantitative method for children safeguard zone. Firstly this study grasps the characters of children's pattern movement and children's traffic accident at children safeguard zone and then divides specific danger factors of children's traffic accident at children safeguard zone. Secondly, each factor is given danger level depending on danger degree and suggests effective method for assignment standard of children safeguard zone using all of these things.