• Journal of the Korean Society of Visualization
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• v.21 no.2
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• pp.83-90
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• 2023

The shape of an airfoil is a critical factor in determining aerodynamic characteristics such as lift and drag. Aerodynamic properties of an airfoil have a decisive impact on the performance of various engineering applications, including airplane wings and wind turbine blades. Therefore, it is essential to analyze the aerodynamic characteristics of airfoils. Various analytical tools such as experiments, computational fluid dynamics, and Xfoil are used to perform these analyses, but each tool has its limitation. In this study, airfoil parameterization, image recognition, and artificial intelligence are combined to overcome these limitations. Image and coordinate data are collected from the UIUC airfoil database. Airfoil parameterization is performed by recognizing images from image data to build a database for deep learning. Trained model can predict the aerodynamic characteristics not only of airfoil images but also of sketches. The mean absolute error of untrained data is 0.0091.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.1146-1153
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• 2022

As the population is aging, accidents involving elderly people are also increasing (2014:11,667 persons; 2018: 11,797 persons). In the case of the elderly population, falling accidents are the primary direct or indirect causes of death; in particular, they face an elevated risk of staircase falls. This study proposes a method of evaluating the safety of staircases using Building Information Modeling (BIM)-based virtual simulation. By making a virtual user with the behavioral characteristics of the elderly respond to a staircase in a BIM model, its safety performance can be evaluated. The evaluation criteria were derived from regulations, elements, and characteristics relevant to the safety of staircases. To validate the proposed method, safety evaluation tests were simulated on actual staircases. The evaluation result of the test simulation shows the safety scores of 1.97 points for the elderly user and 2.95 points for the average male adult user against a required safety score of a minimum of 2 points. That is, safety is relative to users as the safety of the same staircase can be different depending upon the different behavioral characteristics of users. The study suggests that the risk of staircase-related fall accidents to the elderly can be reduced by improving staircase designs through the proposed method.

• Wind and Structures
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• v.39 no.1
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• pp.15-30
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• 2024

In this paper, detailed wind field data of the full path of typhoon "Bailu" were obtained based on site measurements. Typhoon "Bailu" made first landfall southeast of the Taiwan Strait with a wind speed of approximately 30 m/s near the center of the typhoon eye and a second landfall in Dongshang County in Fujian Province. The moving process is classified into 3 regions for analysis and comparison. Detailed analyses of wind characteristics including wind profile, turbulence intensity, gust factor, turbulence integral scale and wind power spectral density function at the full process of the typhoon are conducted, and the findings are presented in this paper. Wind speed shows significant dependence on both the direction of the moving path and the distance between the typhoon center and measurement site. Wind characteristics significantly vary with the moving path of the typhoon center. The relationship between turbulence intensity and gust factor at different regions is investigated. The integral turbulence scales and wind speed are fitted by a Gaussian model. Such analysis and conclusions may provide guidance for future bridge wind-resistant design in engineering applications.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.784-788
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• 1999

In this work, we analyzed the viscoelastic characteristics of electrochemically polymerized polypyrrole(PPy) thin film in various electrolyte solutions, $Na_2SO_4,\;Na_2CO_3$ and SDS + $NaClO_4$, using QCA. The characteristics of redox reaction of electrochemically polymerized PPy thin film for 180 sec in each electrolyte, was investigated in 0.1 M $NaClO_4$ electrolyte solution by cyclic voltammetry method. We used one side of quartz crystal electrode as a working electrode and measured the resonant frequency, resonant resistance and current as analytical parameters. As the results, we suggest that electrochemically polymerized PPy thin film in various electrolyte solutions shows tendency changing from elastic characteristics to viscoelastic one in the order of $ClO_4{^{-}}\;+\;DS^-,\;SO_4{^{-2}}$ and $CO_3{^{-2}}$.

• Geomechanics and Engineering
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• v.20 no.2
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• pp.155-164
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• 2020

In recent years, the stability, safety and comfort of trains has received increased attention. The mechanical characteristics and differential settlement of the foundation are the main problems studied in high-speed railway research. The mechanical characteristics and differential settlement of the foundation are greatly affected by the ground treatment. Additionally, the effects of train load and earthquakes have a great impact. The dynamic action of the train will increase the vibration acceleration of the foundation and increase the cumulative deformation, and the earthquake action will affect the stability of the substructure. Earthquakes have an important practical significance for the dynamic analysis of the railway operation stage; therefore, considering the impact of earthquakes on the railway substructure stability has engineering significance. In this paper, finite element model of the CFG (Cement Fly-ash Gravel) pile + cement-soil compacted pile about composite foundation is established, and manual numerical incentive method is selected as the simulation principle. The mechanical characteristics and differential settlement of CFG pile + cement-soil compacted pile about composite foundation under train load are studied. The results show: under the train load, the neutral point of the side friction about CFG pile is located at nearly 7/8 of the pile length; the vertical dynamic stress-time history curves of the cement-soil compacted pile, CFG pile and soil between piles are all regular serrated shape, the vertical dynamic stress of CFG pile changes greatly, but the vertical dynamic stress of cement-soil compacted pile and soil between piles does not change much; the vertical displacement of CFG pile, cement-soil compacted pile and soil between piles change very little.

• Journal of Biosystems Engineering
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• v.29 no.4
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• pp.329-334
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• 2004

This study was conducted to investigate the characteristics of transmittance spectrum of Korean red ginseng using VIS/NIR spectroscopy. The results of this study were as follows; Light intensity affected the characteristics of the spectrum. For over 40% light intensity, the first and second peaks appeared at 700nm and 1,100nm, respectively. For the 20% light intensity, the first and second peaks appeared at 800nm and 1,100nm, respectively. Thus, the typical color characteristics of halogen lamp were similar to each other if over 40% of maximum light intensity power, otherwise it was not. Transmittance spectrum showed different characteristics at different portions of red ginseng. Normal red ginseng showed strong intensity at the first peak around 700nmbecause of reddish internal tissue. However, an internal white core red ginseng showed weak peak-intensity due to whitish internal tissue. There was no significant difference in the second peak at 800nm for the different internal qualities. Third peak at 900nm showed somewhat difference by internal qualities but it was difficult to find significant trend. To separate the differences of the internal qualities, intensity differences between peaks were used. It was possible to classify normal red ginseng by the differences of "peak 1 -peak 2" and "peak 1 - peak 3". In addition, shift of the first and the third peaks in the spectrum could separate normal red ginseng from others.ginseng from others.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.566-574
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• 2023

Investigating the seepage characteristics of the leaching solution in the ore-bearing layer during the in situ leaching process can be useful for designing the process parameters for the uranium mining well. We prepared leaching solutions of four different viscosities and conducted experiments using a self-developed multifunctional uranium ore seepage test device. The effects of different viscosities of leaching solutions on the seepage characteristics of uranium-bearing sandstones were examined using seepage mechanics, physicochemical seepage theory, and dissolution erosion mechanism. Results indicated that while the seepage characteristics of various viscosities of leaching solutions were the same in rock samples with similar internal pore architectures, there were regular differences between the saturated and the unsaturated stages. In addition, the time required for the specimen to reach saturation varied with the viscosity of the leaching solution. The higher the viscosity of the solution, the slower the seepage flow from the unsaturated stage to the saturated stage. Furthermore, during the saturation stage, the seepage pressure of a leaching solution with a high viscosity was greater than that of a leaching solution with a low viscosity. However, the permeability coefficient of the high viscosity leaching solution was less than that of a low viscosity leaching solution.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.3
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• pp.39-51
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• 2019

This paper is an exploratory study to investigate the influence of characteristics of local government web-sites on user satisfaction and trust. The objective of this research is to identify the characteristics of local government web-sites influencing on user satisfaction and trust, and determine how they affect user satisfaction and trust. From the literature review, we identify four characteristics which are expected to influence on user satisfaction: technical, information, customer-oriented, and work-performing characteristics. In addition, we develop research model that the four characteristics are expected to affect user satisfaction and trust via users' perceived values. The results of the research are as follows. The technical, customer-oriented, and work-performing characteristics significantly affects perceived values, which significantly affected user satisfaction and trust. Perceived value is partially mediated by user satisfaction in affecting user trust. The characteristics of local government web-sites affecting perceived values differed partially by the purpose of visitor. As for the personal goal, the technical, customer-oriented, and work-performing characteristics significantly affect perceived values, with the technical and customer-oriented characteristics having more significant effects. As for the business goal, the technical, information, work-performing characteristics significantly affected perceived values, with information characteristics having more significant effects.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.94-100
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• 1998

Microstep characteristics largely depends on the variation of friction force induced by the geometric accuracy of ballscrew, guide rail and the control characteristics of servo unit. In this paper, for improving the microstep characteristics of hydrostatic table with ballscrew, microstep resolution according to the control mode of servo amplifier and response characteristic by the variation of integral gain are tested and compared. Relationship between micro motion behavior of hydrostatic table and the output torque is also tested for acquiring the effective variables on control characteristics. From the results. it is confirmed that the torque control mode has a advantage in microstep resolution, and more stable than velocity control mode in low feed rate, and by the increase of integral gain in the elastic motion realm, response characteristics can be improved.

• Journal of Mechanical Science and Technology
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• v.18 no.12
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• pp.2294-2302
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• 2004

The objective of this study is to obtain detailed information for the micro fabrication of lead frames by applying spray technology to wet etching process. Wet etching experiments were performed with different etching parameters such as injection pressure, distance from nozzle tip to etched substrate, nozzle pitch and etchant temperature. The characteristics of single and twin spray were measured to investigate the correlation between the spray characteristics and the etching characteristics. Drop size and velocity were measured by Phase-Doppler Anemometer (PDA). Four liquids of different viscosity were used to reveal the effects of viscosity on the spray characteristics. The results indicated that the shorter the distance from nozzle tip and the nozzle pitch, the larger etching factor became. The average etching factor had good positive correlation with average axial velocity and impact force. It was found that the etching characteristics depended strongly on the spray characteristics.