• Advances in nano research
• /
• v.16 no.2
• /
• pp.111-125
• /
• 2024

Recently, a lot of research has been done on the analysis of axial vibrations of homogeneous and FG nanotubes (nanorods) with various aspects of vibrations that have been fully mentioned in history. However, there is a lack of investigation of the dynamic internal resonances of FG nanotubes (nanorods) between them. This is one of the essential or substantial characteristics of nonlinear vibration systems that have many applications in various fields of engineering (making actuators, sensors, etc.) and medicine (improving the course of diseases such as cancers, etc.). For this reason, in this study, for the first time, the dynamic internal resonances of FG nanorods in the simultaneous presence of large-amplitude size dependent behaviour, inertial and shear effects are investigated for general state in detail. Such theoretical patterns permit as to carry out various numerical experiments, which is the key point in the expansion of advanced nano-devices in different sciences. This research presents an AFG novel nano resonator model based on the axial vibration of the elastic nanorod system in terms of derivation from large-amplitude size dependent internal modals interactions. The Hamilton's Principle is applied to achieve the basic equations in movement and boundary conditions, and a harmonic deferential quadrature method, and a multiple scale solution technique are employed to determine a semi-analytical solution. The interest of the current solution is seen in its specific procedure that useful for deriving general relationships of internal resonances of FG nanorods. The numerical results predicted by the presented formulation are compared with results already published in the literature to indicate the precision and efficiency of the used theory and method. The influences of gradient index, aspect ratio of FG nanorod, mode number, nonlinear effects, and nonlocal effects variations on the mechanical behavior of FG nanorods are examined and discussed in detail. Also, the inertial and shear traces on the formations of internal resonances of FG nanorods are studied, simultaneously. The obtained valid results of this research can be useful and practical as input data of experimental works and construction of devices related to axial vibrations of FG nanorods.

• Journal of Technology Innovation
• /
• v.32 no.1
• /
• pp.1-25
• /
• 2024

Countries around the world are making active efforts to reduce greenhouse gas emissions. Korea is also pursuing a policy of abolishing aging coal power and converting it to LNG power generation. However, in Korea, gas turbine manufacturing technology has not been localized, so all of it is imported and installed from overseas manufacturers. Therefore, this paper examines the domestic and foreign environment of the gas turbine power generation industry and proposes a strategy to develop and expand the supply of Korean gas turbine technology by applying the PEST-SWOT-AHP methodology. As a result of the research, the strategy to develop and expand the supply of Korean gas turbine technology can be summarized as 1) strengthening the role of power generation public enterprises to develop and promote commercialization of gas turbine technology, 2) expanding the proportion of LNG power generation to reduce greenhouse gases, 3) the government's active efforts to create an ecosystem for the gas turbine industry, and 4) forming a public consensus on the construction of LNG power plants.

• Composites Research
• /
• v.37 no.3
• /
• pp.226-231
• /
• 2024

Coal ash has been used as a sand replacement in the construction industry. Due to the use of bituminous coal as a result of anthracite depletion, and quicklime as an air purifier in the desulfurization process, pop-out defects have recently occurred in concrete using coal ash, severely limiting the recycling of coal ash into concrete. In this study, the components that cause the pop-out problem of the coal ash filled concrete were identified and a pretreatment method to fully expand the expansive components in advance was proposed as a solution to this problem. By treating water twice for 10 min, allowing the CaO mixed in the coal ash to fully expand, the problems of pop-out and reduced compressive strength of the concrete were overcome. The cost and time efficient water treatment method proposed in this study is expected to promote the recycling of coal ash into concrete.

• The Journal of the Convergence on Culture Technology
• /
• v.10 no.1
• /
• pp.565-570
• /
• 2024

Recently, due to adjacent excavation work such as new buildings and common tunnel expansion concentrated around the urban railway, deformation of the underground box and tunnel structure of the urban railway built underground has occurred, and as a result, repair and reinforcement work is frequently carried. In addition, the subway is responsible for large-scale transportation, so ensuring the safety and drivability of underground structures is very important. Accordingly, an automated measurement system is being introduced to manage the safety of underground box structures. However, there is no analysis of structural damage vulnerabilities caused by subsidence or uplift of underground box structures. In this study, we aim to analyze damage vulnerabilities for safety monitoring of underground box structures. In addition, we intend to analyze major core monitoring locations by modeling underground box structures through numerical analysis. Therefore, we would like to suggest sensor installation locations and damage vulnerable areas for safety monitoring of underground box structures in the future.

• Structural Engineering and Mechanics
• /
• v.91 no.3
• /
• pp.315-324
• /
• 2024

An expansive soil in 4970 special railway line in Dangyang City, China, has encountered a series of landslides due to the expansion characteristics of expansive soil over the past 50 years. Thereafter, a sheet-pile retaining structure was adopted to fortify the expansive soil slope after a comprehensive discussion. In order to evaluate the efficacy of engineering measure of sheet-pile retaining structure, the field test was carried out to investigate the lateral pressure and pile bending moment subjected to construction and service conditions, and the local daily rainfall was also recorded. It took more than 500 days to carry out the field investigation, and the general change laws of lateral pressure and pile bending moment versus local daily rainfall were obtained. The results show that the effect of rainfall on the moisture content of backfill behind the wall decreases with depth. The performance of sheet-pile retaining structure is sensitive to the intensity of rainfall. The arching effect is reduced significantly by employing a series of sheet behind piles. The lateral pressure behind the sheet exhibits a single-peak distribution. The turning point of the horizontal swelling pressure distribution is correlated with the self-weight pressure distribution of soil and the variation of soil moisture content. The measured pile bending moment is approximately 44% of the ultimate pile capacity, which indicates that the sheet-pile retaining structure is in a stable service condition with enough safety reserve.

• Advances in concrete construction
• /
• v.17 no.2
• /
• pp.93-110
• /
• 2024

The process of concrete production consumes an immense volume of water, with approximately one billion metric tons of freshwater being utilized for tasks such as aggregate washing, fresh concrete production, and concrete curing. The accessibility of clean water for the public is hindered by the limited availability of water resources, primarily due to the rapid expansion of industries such as tanneries, stone quarries, and concrete manufacturing. These industries not only consume substantial amounts of freshwater but also generate significant volumes of various types of waste. Therefore, the use of fresh water in concrete production should be minimized. Few studies have reviewed the production of concrete using wastewater to derive practical and applicable findings for the industry. Thus, this study thoroughly explores the physical and chemical effects of wastewater on concrete, examining aspects like durability, hardened properties, and rheological characteristics. It identifies key factors that can compromise concrete properties when exposed to wastewater. The scarcity of research on integrating wastewater into concrete production underscores the urgent necessity for innovative approaches and methodologies in this field. While the inclusion of wash water typically reduces the workability of fresh concrete, it often enhances its compressive strength. Notably, significant improvements have been observed when using tertiary processed wastewater, wash water, polyvinyl alcohol-based wash water (PVAW), and reclaimed water in the concrete mixing process. The application of tertiary treatment to wastewater resulted in a notable enhancement of compressive strength, showing increases of up to 7%. In contrast, wastewater treated through secondary methods experienced a decline in strength ranging from 9% to 18% over a period of six months. However, the use of reclaimed wastewater demonstrated an improvement in strength by 8% to 17%, depending on the concentration level ranging from 25% to 100%. In contrast, the utilization of secondary processed wastewater and industrial water has a minimal impact on the concrete's strength.

• The Journal of Engineering Geology
• /
• v.19 no.4
• /
• pp.433-439
• /
• 2009

The compressed packer device is designed to improve the underground contamination prevention facilities of ground water wells. As for the device, the installation is simple because of the safety lock device and the compression of the casing are simple the installation is simple. There is no leakage of ground water because the pressure resistance with $4.5\;kg/cm^2$ makes it equipped with the watertightness The single casing is installed and the reaming for grouting is possible with 300 mm excavation so that installation cost can be saved. Silicon rubber is used for the compressed packer so that the extension rate is 590%. In terms of environmental pollution, it is an environmental friendly product which does not contain harmful ingredients such as Pb, Cd, and phenol. below the standard or undetectable level Furthermore, the installation costs are 35 to 62% or lower than the conventional grouting construction method and are 87% or lower than the expansion packer construction method, the new environmental technology No.47 Also, the device is designed to meet the relevant regulations such as Rules on Preserving the Ground Water Quality, The Standard on Jeju Island Ground Water Development and Facility Installation and Management, and The Plan and Guideline on Operating and Managing the Small-Scale Tap Water Facilities of Ministry of Environment and Ministry of Food, Agriculture, Forestry and Fisheries.

• Journal of the Korean Geotechnical Society
• /
• v.27 no.10
• /
• pp.35-43
• /
• 2011

The area to be studied is the place where the main line rail way will be constructed in accordance with the scheduled construction project of Yeongju dam, and is a fold and mylonite zone over several km that is formed by ductile-shearing effect. The ductile shear zone, which has been transformed by faulting for long geological time, shows a complicated geological structure. Due to the recrystallization of mineral caused by transformation in deep underground (>8km), a mylonite zone with lamellar structure has properties distinguished from other fault zones formed by transformation near earth surface <2km). To see the properties of mylonite, this study analyzed the transformation rate of sample rocks and the shape of constriction structure accompanied with transformation. While the transformation of fault zone shows a round oblate, the mylonite zone shows a prolate form. Transformation rate in fault zone was measured to be less than 1.2 compared to the state before transformation while the measured rate in mylonite zone was 2.5 at most. Setting the surface of discontinuity as the base, the unconfined compressive strength of slickenside can be categorized in sedimentary rocks, and a change of strength was observed after water soaking over certain time. Taking into account that the weathering resistance of the rock based on mineral and chemical organization is relatively higher, its engineering properties seems to result from the shattered crack structure by crushing effect. When undertaking tunnel construction in mylonite zone, there should be a special care for the expansion of shattered cracks or the fall of strength by influx of ground water.

• The Journal of Sustainable Design and Educational Environment Research
• /
• v.16 no.1
• /
• pp.1-11
• /
• 2017

The purpose of this study is to present the number of necessary facilities for the establishment of safety education facility for students through the analysis of situation and demand of safety experience education facilities so as to effectively implement safety education based on 7 standards of school safety education. 7 standards of school safety education and experience programs of the existing safety experience center were analyzed and the experience program was extracted based on the analysis. Based on the derived program, the experience space was set up, and the existing safety experience facility was analyzed accordingly. Based on this, the number of necessary facilities was suggested by using the calculation formula derived to estimate the scale of the facility expansion. This is the result of estimating the required number of facilities based on the 2015 school age population. In the long run, it is necessary to calculate the appropriate ratio by actually comparing the unit construction costs of the facilities and the vehicles. In consideration of this, it is necessary to plan for the long-term necessary facilities and vehicles for the construction plans.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.8 no.2
• /
• pp.68-80
• /
• 2005

Parks became a matter of concerned among urban planning facilities that have not been executed for a long time because of the judgement of constitutional disagreement. This study deals with actual condition of constructing neighborhood park at the level of urban planning. In order to enhance the coefficient of citizens' utilization of parks. This study analyzes current situation of neighborhood parks and developing condition in Busan, revealing problems by investigating types of facilities under construction as well as by comparing size and progress of the parks under construction. This study tries different kind of access to the problems with the emphasis on estimation of planning and establishing neighborhood parks on the basis of the coefficient of citizens' utilization. Through the various examinations, this study brings into relief the problems being created in the course of establishment of parks which functions only as green tracts of land at present. As a result, the following conclusions could be made. First, from the viewpoint of location the parks, Busan parks are mostly located in the mountain areas adjacent to urban districts. Secondly, establishment of neighborhood parks is usually for development projects and the facilities introduced in them are monotonous. Thirdly, there is a tendency towards expansion of size and standardization of facility. Forthly, establishment plan of parks lacks profitability. Lastly, there is serious limitation in the size of land for developing neighborhood parks, and what is worse, there is no management of them.