• Advances in concrete construction
• /
• v.6 no.6
• /
• pp.645-658
• /
• 2018

Despite being one of the most abundantly used construction materials because of its exceptional properties, concrete is susceptible to deterioration and damage due to various factors particularly corrosion, improper loading, poor workmanship and design discrepancies, and as a result concrete structures require retrofitting and strengthening. In recent times, Fiber Reinforced Polymer (FRP) composites have substituted the conventional techniques of retrofitting and strengthening of damaged concrete. Most of the research studies related to concrete strengthening using FRP have been performed on undamaged test specimens. This contribution presents the results of an experimental study in which concrete specimens were damaged by mechanical loading and elevated temperature in laboratory prior to application of Carbon Fiber Reinforced Polymer (CFRP) sheets for strengthening. The test specimens prepared using concrete of target compressive strength of 28 MPa at 28 days were subjected to compressive and splitting tensile testing up to failure and the intact pieces of the failed specimens were collected for the purpose of repair. In order to induce damage as a result of elevated temperature, the concrete cylinders were subjected to $400^{\circ}C$ and $800^{\circ}C$ temperature for two hours duration. Concrete cylinders damaged under compressive and split tensile loads were re-cast using concrete and rich cement-sand mortar, respectively and then strengthened using CFRP wrap. Concrete cylinders damaged due to elevated temperature were also strengthened using CFRP wrap. Re-cast and strengthened concrete cylinders were tested in compression and splitting tension. The obtained results revealed that re-casting of specimens damaged by mechanical loadings using concrete & mortar, and then strengthened by single layer CFRP wrap exhibited strength even higher than their original values. In case of specimens damaged by elevated temperature, the results indicated that concrete strength is significantly dropped and strengthening using CFRP wrap made it possible to not only recover the lost strength but also resulted in concrete strength greater than the original value.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.18 no.1
• /
• pp.24-30
• /
• 2019

The deck floor of a the cargo truck becomesis damaged and aged due to the continuous loading of the loading cargo and external environmental factors. Floor boards made of wood and metal are often used. In the case of wood, the cost is high due to the use of imported wood, and the strength is easily deterioratesd due to environmental factors. In the case of metal materials, the durability is higher than that of wood, but problems are raised due to the effect of major factors that hinder the weight reduction, and the effects of corrosion. In order to replace this stucturestructural design, this study proposed a wood fiber composite using natural raw materials. Woody composites are being used as environmentally and friendly exterior materials with the combined advantages of plastic, and wood,; low cost and low density. However, due to the nature of the woody composites, the properties are differentdiffer depending on the contents of the matrix, reinforcing agent, additives, compatibilizer, etc. In this study, we investigate these problems through analysis of the microstructure and mechanical properties according to proper content and injection molding conditions. As a result, it is considered that the wood deck composite can replaced the current Deck Floor Boardreplace current deck floor boards through continuous continued research and results of this study.

• Asia-Pacific Journal of Business
• /
• v.11 no.4
• /
• pp.189-203
• /
• 2020

Purpose - This study aims in analyzing the dynamic relationship between household loans and housing prices according to the characteristics of depository institutions after the financial crisis, identifying the recent trends between them, and making policy suggestions for stabilizing house prices. Design/methodology/approach - The monthly data used in this study are household loans, household loan interest rates, and housing prices ranging from January 2012 to May 2020, and came from ECOS of the Bank of Korea and Liiv-on of Kookmin Bank. This study used vector auto-regression, generalized impulse response function, and forecast error variance decomposition with the data so as to yield analysis results. Findings - The analysis of this study no more shows that the household loan interest rates in both deposit banks and non-bank deposit institutions had statistically significant effects on housing prices. Also, unlike the previous studies, there was statistically significant bi-directional causality between housing prices and household loans in neither deposit banks nor non-bank deposit institutions. Rather, it was found that there is a unidirectional causality from housing prices to household loans in deposit banks, which is considered that housing prices have one-sided effects on household loans due to the overheated housing market after the financial crisis. Research implications or Originality - As a result, Korea's housing market is closely related to deposit banks, and housing prices are acting as more dominant information variables than interest rates or loans under the long-term low interest rate trend. Therefore, in order to stabilize housing prices, the housing supply must be continuously made so that everyone can enjoy housing services equally. In addition, the expansion and reinforcement of the social security net should be realized systematically so as to stop households from being troubled with the housing price decline.

• Journal of the Architectural Institute of Korea Planning & Design
• /
• v.35 no.1
• /
• pp.139-147
• /
• 2019

The purpose of this paper is to analyze the linkage between Si-Jeong-Chon (municipalities of Japan) catastrophic disaster recovery-regeneration plan (DRRP) and regional comprehensive plan (RCP), each of which was made after the Great East Japan Earthquake, and to make implications on establishment of a disaster recovery plan of Korea. In order to explore the relationship between the two plans, the DRRPs and RCPs of 30 municipalities are collected and categorized according to their characteristics. The results show that DRRPs of the municipalities are not always in a consistent form and contents because regulations and guidelines on DRRP are not definite and specific. The relationship between DRRP and RCP in terms of its form and contents can be divided into 3 categories; Reflective Type (RT), Complementary Type (CT), and Substitutive Type (ST). The 22 RT plans as the majority of those DRRPs appear to reflect the development strategies of municipalities' RCPs. Both 3 CT plans and 5 ST plans seem to be integrated with RCPs in some way. The plan in CT of a municipality supplements its RCP by adding some new strategies to its recovery section and the plan in ST of a municipality appears to replace its RCP. Finally the influential factors which are considered to determine linkage type are identified as remaining time which is legally required to re-establish its RCP, the extent of damage, and socioeconomic condition changes.

• Journal of the Architectural Institute of Korea Planning & Design
• /
• v.35 no.11
• /
• pp.117-128
• /
• 2019

The necessity of the Toi-Maru has increased greatly in order to enter to the building or to move conveniently in the building after the mid-Joseon period, when the combination of On-dol Ma-ru began to be universally used. According to this process, the 3-Dori type upper structure is thought to have undergone the typological changed by securing a more stable space of Toi-Maru In cases where a relatively large girder was used, it is often the case that the space is divided using a pillar to place a Toi-Maru on the front. However, it is difficult to find a case where the width of the Toi-Maru exceeds 1meter due to its structural limit. The type that made additional Toi-girder to overcome the spatial constraint of this structure and replaced the method of former typology after Mid-Jpseon period. In case of 5-Dori type, Toi-Maru installed in between high post and Toi post in early period. In these type, the width of Toi-Maru was subordinated by the location of milled Dori of roof structure and sometimes it became too excessive. 5-Dori type with Pyon-ju occurred to overcome these restriction between the width of Toi-Maru and the location of milled Dori of roof structure. Not a few remains of Mid-Jpseon period keeping the evidences of changing process of roof structure provoked by Toi-Maru installation. The consistent process of Toi-Maru installation and structural adjustment will be focused to consider the attempt to spatial requirement and architectural reaction in Mid-Joseon perid.

• Journal of the Architectural Institute of Korea Planning & Design
• /
• v.36 no.3
• /
• pp.69-78
• /
• 2020

This study is designed to find out the role and relation of the Nemok-dori support members in order to clearly specify the structure of the Dapogye architecture which adopts the Nemok-dori. The dori at the eaves in the Dapogye architecture was expanded to include Oemok-dori, Jusim-dori and Nemok-dori in cooperation with the bracket. The Oemok-dori is used to lengthen the eaves and the Jusim-dori makes the reasonable transfer of loads while the Namok-dori contributes to the stability of the building through the balancing of the bracket. Nemok-dori is located higher than Oemok-dori or Jusim-dori, depending on the slope of Jangyeon and the distance of Chulmok. But as it is not directly supported by bracket or beam, it needs an independent support. The vertical support of Nemok-dori is selectively involved with Cheomcha, lower Jangyeo, support Wall and upper Jangyeo. As the time went by, the vertical height increased, thus making the omitted members less. The horizontal support of Nemok-dori is made in various ways. There are also special cases such as the Nemok-dori □ type chain structure for small rectangular buildings, the 'Nemok-dori = Jung-dori' type for the buildings having small sides and the 'Nemok-dori = Meongechangbang' type appearing on the lower part of the Bankanmulrim type middle height buildings. The horizontal support of Nemok-dori usually uses either the support of the Toeryang type member, the support of beam directed Hwaban or the support through overlaying of internal Jegong. As the time went by and the number and distance of Chulmok increased, the multiple support structures acted together rather than as one support structure. Nemok-dori got stabilized as it has both the vertical and horizontal supports and this support structure also has he role of decoration.

• Journal of the Korean Society for information Management
• /
• v.37 no.4
• /
• pp.151-179
• /
• 2020

This study explores the potential of using a library chatbot to improve the non-face-to-face digital reference services for academic library users by designing and implementing a library chatbot. Through data analysis, user needs and library services were analyzed, and a scenario was designed by selecting an appropriate development method. For user-friendly interaction, the personality of the chatbot and user interface was designed to evaluate its usability. In addition, the accuracy was verified through the response accuracy evaluation and performance evaluation of the chatbot, and the effectiveness of the chatbot was evaluated through a user satisfaction survey. In order to manage the operation and maintain service quality, the chatbot is improved by monitoring user-chatbot conversations and reflecting user feedback. Based on these findings, recommendations for designing and implementing a library chatbot were made to help improve library reference services.

• Design & Manufacturing
• /
• v.15 no.4
• /
• pp.65-71
• /
• 2021

In the early days of laser invention, it was simply used as a measuring tool, but as lasers became more common, they became an indispensable processing tool in the industry. Short-wavelength lasers are used to make patterns on wafers used in semiconductors depending on the wavelength, such as CO2 laser, YAG laser, green laser, and UV laser. At first, the hole of the PCB board mainly used for electronic parts was not thin and the hole size was large, so a mechanical drill was used. However, in order to realize product miniaturization and high integration, small hole processing lasers have become essential, and pattern exposure for small hole sizes has become essential. This paper intends to analyze the characteristics through patterns by exposing the PCB substrate through DMD and polygon scanner, which are different optical systems. Since the optical systems are different, the size of the patterns was made the same, and exposure was performed under the optimal conditions for each system. Pattern characteristics were analyzed through a 3D profiler. As a result of the analysis, there was no significant difference in line width between the two systems. However, it was confirmed that dmd had better pattern precision and polygon scanner had better productivity.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.16 no.6
• /
• pp.1311-1316
• /
• 2021

In this paper, we present a bifocal stereo camera system combining two cameras with different focal length cameras to generate stereoscopic image and their corresponding depth map. In order to obtain the depth data using the bifocal stereo camera system, we perform camera calibration to extract internal and external camera parameters for each camera. We calculate a common image plane and perform a image rectification for generating the depth map using camera parameters of bifocal stereo camera. Finally we use a SGM(Semi-global matching) algorithm to generate the depth map in this paper. The proposed bifocal stereo camera system can performs not only their own functions but also generates distance information about vehicles, pedestrians, and obstacles in the current driving environment. This made it possible to design safer autonomous vehicles.

• Journal of Koreanology Reviews
• /
• v.1 no.1
• /
• pp.37-49
• /
• 2022

The purpose of this study is to discuss how Dongi People in ancient societies resided in the region including the Korean Peninsula shaped its economy, what kind of currency was used, and their economic activities using this currency. This study started from a skeptical point of view that the Dongi People were conducting economic activities with the currency used in the country made by the Jina People before and after the Gojoseon society. Currently, in China, all currencies issued in China are treated as their own currency. It is due to subjective interpretation from a nationalist point of view. Japan subjectively interprets and judges from a Japanese point of view and North Korea judges from the central point of view on the Korean Peninsula. This difference is due to the subjective interpretation from the researcher which has been affected by their associating academic area. This has caused the lack of objectivity. In other words, it means that there is a big difference in the perception of the interpretation of history between different academic areas. This study, therefore, tried to avoid the application of biased concept or academic research in order to define the distribution economics more objectively by conducting the study based on the literature sources from Chinese ancient books and field research materials as much as possible, as the study and research conducted based on the domestic sources are insufficient in the sense that there is a gap between different perceptions and interpretations. As a conclusion of this study, the excavation area of Myeong-do-jeon is perfectly consistent with the old river area of Gojoseon, and in particular, considering Gojoseon was in the hostile relationship with Yan, it was found that only Myeong-do-jeon was used without using any other Chinese currency in the entire Gojoseon area, not just some areas. It is also a decisive clue to prove that it is not the Yan currency. The limitation of this study in developing the discussion different from the current research and study is that there was a lack of exploration and investigation of various documents and relics. For future research, this study will become more meaningful when it is conducted simultaneously with the discovering of new documents as well as the relics.