Recently, the demand for shape memory alloys in the biomedical industry is increasing. Nitinol alloy, which accounts for most of the shape memory alloy market, occupies most of the biomedical field. Nitinol for biomaterials requires a clean surface without sub-micron surface integrity and surface defects in order to be used more safely in a living body. Among them, new technologies such as polishing using MR fluid are being studied, but there is a disadvantage in that it takes a long time for processing due to a low material removal rate. In this study, material removal studies were conducted for effective polishing, and excellent polishing properties of MR fluid were confirmed.

This study performed the seismic response analysis of an LNG storage tank supported by a disconnected piled raft foundation (DPRF) with a load transfer platform (LTP). For this purpose, a precise analytical model with simultaneous consideration of Fluid-Structure Interaction (FSI) and Soil-Structure Interaction (SSI) was used. The effect of the LTP characteristics (thickness, stiffness) of the DPRF system on the seismic response of the superstructure (inner and outer tanks) and piles was analyzed. The analytical results were compared with the response of the piled raft foundation (PRF) system. The following conclusions can be drawn from the numerical results: (1) The DPRF system has a smaller bending moment and axial force at the head of the pile than the PRF system, even if the thickness and stiffness of the LTP change; (2) The DPRF system has a slight stiffness of the LTP and the superstructure member force can increase with increasing thickness. This is because as the stiffness of the LTP decreases and the thickness increases, the natural frequency of the LTP becomes closer to the natural frequency of the superstructure, which may affect the response of the superstructure. Therefore, when applying the DPRF system, it is recommended that the sensitivity analysis of the seismic response to the thickness and stiffness of the LTP must be performed.

Passengers on public buses operating in the metropolitan area are exposed to the closed indoor air for minutes to hours. The indoor air quality of buses is mostly controlled through ceiling-mounted ventilation and filtration devices. A simulation study using a commercial code was conducted for fluid flow analysis to evaluate the potential effectiveness of an air purifier that can be inserted into bus windows to supply clean air from the outside to the inside. As a result of field measurements, the average CO2 concentration inside the bus during morning and evening rush hours ranged from 2,106±309 ppm to 3,308 ± 255 ppm depending on the number of passengers on board. This exceeded the Guideline for Public Transportation. The optimal installation position of an air purifier appeared to be the front side of the bus. In fact, even a low diffusing flow velocity of 0.5m/s was effective enough to maintain a low concentration of CO2 throughout the indoor space. Based on numerical analysis predictions with 45 passengers on board, the maximum CO2 concentration in the breathing zone was 2,203 ppm with the operation of an air purifier.

Owing to the great demand for portable and wearable chemical sensors, the development of all-solid-state potentiometric ion sensors is highly desirable considering their simplicity and stability. However, most ion sensors are challenged by the penetration of water and gas molecules into ion-selective membranes, causing unstable and undesirable sensing performances. In this study, a hydrophobic ionic liquid-modified graphene (Gr) sheet was prepared using a fluid dynamics-induced exfoliation and functionalization process. The high hydrophobicity and electrical double-layer capacitance of Gr make it a potential solid-state ion-to-electron transducer for the development of potentiometric sodium-ion ( Na+) sensors. The as-prepared Na+ sensors effectively prevented the formation of the water layer and penetration of gas species, resulting in stable and high sensing performances. The Na+ sensors showed a Nernstian sensitivity of 58.11 mV/[Na+] with a low relative standard deviation (0.46), fast response time (5.1 s), good selectivity (K < 10− 4), and good durability. Furthermore, the Na+ sensor demonstrated its feasibility in practical applications by measuring accurate and reliable ion concentrations of artificial human sweat and tear samples, comparable to a commercial ion meter.

The importance of urban green space creation is increasingly recognized as the most realistic and efficient approach for fine dust mitigation in urban areas. Particularly considering the characteristics of domestic cities, the application of buffer green spaces along roads can maximize the efficiency of fine dust reduction without the need for separate green space creation. Accordingly, this study analyzed the fine dust mitigation effects based on the types of plantings in the central dividers and roadside trees in Jeonju City, Jeollabuk-do. To do this, we controlled various external variables of urban space and considered the planting arrangement types in the central dividers, carrying out the analysis using a CFD simulation. The simulation results confirmed that the central dividers with plantings demonstrated more effective ultrafine dust reduction than those without. Moreover, the arrangement of roadside trees showed a greater ultrafine dust reduction effect when adopting a multilayered structure compared to a single layer. Based on these findings, we concluded that installing both trees and shrubs simultaneously in the central dividers and along roads was effective for ultrafine dust mitigation. On this basis, we quantified the dust reduction effects of plants in urban street environments and proposed planting guidelines for roadside green spaces to improve air quality.

In the fluid-structure interaction analysis, the finite element formulation is performed for the wave equation for dynamic fluid pressure, and the dynamic pressure is defined as a degree of freedom at the fluid nodes. Therefore, to connect the fluid to the structure, it is necessary to connect the degree of freedom of fluid dynamic pressure and the degree of freedom of structure displacement through an interface element derived from the relationship between dynamic pressure and displacement. The previously proposed fluid-structure interface elements use conformal finite element meshes in which the fluid and structure match. However, it is challenging to construct conformal meshes when complex models, such as water purification plants and wastewater treatment facilities, are models. Therefore, to increase modeling convenience, a method is required to model the fluid and structure domains by independent finite element meshes and then connect them. In this study, two fluid-structure interface elements, one based on constraints and the other based on the integration of nonsmooth functions, are proposed in nonconformal finite element meshes for structures and fluids, and their accuracy is verified.

This study analyzed the flow inside floating seedling equipment for Scapharca subcrenata. Due to the aging society of fishing villages, it is impossible to continuously input the labor force. Therefore, it is necessary to improve efficiency. Scapharca subcrenata has high per capita consumption. It serves as an important aquatic food resource. Scapharca subcrenata culture tends to be highly dependent on the natural environment. Production of Scapharca subcrenata is difficult to predict with low stability. In the past, manpower directly installed bamboo nets in mudflats. The seedling equipment devised in this study is a floating type and can be freely moved on the sea according to the prediction of Scapharca subcrenata generation. The flow around the floating seedling equipment was analyzed by numerical analysis. The physical phenomena of the flow around the net inside the floating seedling equipment were visualized. As a result, the space between the floating seedling equipment and the bottom net and the space between the net groups showed a lower flow rate than the inlet flow rate. It is expected that the low flow rate of the floating seedling equipment will have a positive effect on the attachment of Scapharca subcrenata.

Microclimate analysis was conducted through actual measurement according to land use status in urban, and CFD analysis was conducted to analyze and predict the microclimate characteristics of urban, and compared and analyzed with the actual measurement results. It was measured in high-rise areas and parks, and the temperature of the park area was 0.4 to 0.6℃ lower, and the relative humidity was 1.0 to 3.0% higher. The correlation coefficient was obtained by comparing the results of the computational fluid analysis with the results of the computational fluid analysis at the actual location located within the CFD analysis area for validation. The seasonal correlation coefficients are all higher than 0.8, so it is judged that they can be applied to microclimate analysis in urban area. The computational fluid analysis was divided into three areas (low-rise, low and high-rise, and high-rise) centered on the A2 point. On average, the low-rise area was 0.1 to 0.4% higher than the high-rise area. In the low and high-rise area and high-rise area, the pith of buildings are wide, so the airflow is smooth, so it is judged that the temperature is relatively low.

This paper proposes a method to evaluate the structural safety of a large wide-width greenhouse structure against wind load caused by a typhoon through a fluid structure interaction analysis technique. The conventional method consisted of roughly estimating the wind load based on the relevant laws and regulations, and determining safety through structural analysis. However, since the wind load changes nonlinearly according to the wind speed distribution and wind direction around the greenhouse and the external shape of the structure, there are many uncertainties in the existing structural safety evaluation method, and it is difficult to accurately determine the design margin. In this study, a systematic method was developed to accurately calculate the wind load acting on a greenhouse structure and evaluate structural safety by considering the characteristics of wind through a fluid structure interaction analysis using coupled computational fluid dynamics and computational structural mechanics. Using the proposed method, it is possible to significantly reduce the manufacturing cost because it is possible to obtain an optimal design that reduces the over-conservative design margin while securing the structural strength of the greenhouse.

A facile and efficient method was developed to prepare highly stretchable and conductive graphene conductors with wrinkled structures by the mechanical stretching and shrinking of elastomeric substrates, in which graphene inks were printed on a prestretched elastomeric substrate. Stretchable and exfoliated graphene inks were prepared by mixing graphite and Ecoflex in a shear-assisted fluid dynamics reactor. The resultant graphene conductor exhibited excellent stretchability at 150% strain and high electrical conductivity of 64 ± 1.2 S m− 1. The resistance of the conductor did not change in bent, twisted, and stretched states. The resistance did not change during 10,000 cycles of stretching/releasing, with a maximum strain of 150%. Based on the graphene conductor, a stretchable conductometric sensor with a two-electrode configuration was fabricated to measure impedance changes at different concentrations of electrolyte ions. This sensor exhibited a good and linear sensitivity curve (298.61 Ω mM− 1, R2 = 0.999) in bent and stretched states.

Given the domestic situation, all nuclear power plants are located at the seaside, where interim storage sites are also likely to be located and maritime transportation is considered inevitable. Currently, Korea does not have an independently developed maritime transportation risk assessment code, and no research has been conducted to evaluate the release rate of radioactive waste from a submerged transportation cask in the sea. Therefore, secure technology is necessary to assess the impact of immersion accidents and establish a regulatory framework to assess, mitigate, and prevent maritime transportation accidents causing serious radiological consequences. The flow rate through a gap in a containment boundary should be calculated to determine the accurate release rate of radionuclides. The fluid flow through the micro-scale gap can be evaluated by combining the flow inside and outside the transportation cask. In this study, detailed computational fluid dynamic and simplified models are constructed to evaluate the internal flow in a transportation cask and to capture the flow and heat transfer around the transportation cask in the sea, respectively. In the future, fluid flow through the gap will be evaluated by coupling the models developed in this study.

Micro-climate measurements and computational fluid analysis were conducted to use it as basic data for the preservation and management of the old house of Kim Myung-kwan, a traditional building that is National Folk Cultural Property No. 26. As a result of the actual measurement, the temperature and humidity are relatively evenly distributed indoors unlike outdoors, but the temperature and humidity vary depending on the time change and the installation location in the outdoors. It was found that the temperature increases after dawn and the temperature varies depending on the installation position around 14:00–15:00, when the temperature becomes the highest. In particular, the temperature was high at the outdoor measurement point adjacent to the building and the fence. As a result of the computational fluid analysis, the temperature was high in the buildings and fences in the old house or in the area adjacent to the building, and it was about 1℃ higher than the surrounding area. In this area, it is judged that the thickening of wood will occur more severely than in other locations, and special preservation management is required.

In this paper, numerical simulations were conducted to secure both flow distribution and uniform flow discharge through a wall mount type air sterilizer. In order to increase the reliability of the simulation results where there is no well-known validation case for air sterilizer, mesh sensitivity study was performed under the constraint that y+ set to one for k-w SST turbulent modeling for both the air sterilizer and the fan. The installation of various guides and structures was reviewed in the point of flow distribution and pressure drop inside the sterilizer, and the exhaust pressure conditions were predicted to secure uniform flow discharge at outlets. This study has been done based on the computational analysis during the development stage of the air sterilizer, and the results will be verified through physical testing after production of prototype.