• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.8 s.239
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• pp.895-902
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• 2005

Lock-on characteristics of flow around a circular cylinder oscillating rotationally with a relatively high forcing frequency have been investigated experimentally. Dominant governing parameters are Reynolds number (Re), angular amplitude of oscillation (${\theta}_A$), and frequency ratio $F_R=f_f/f_n,\;where\;f_f$ is a forcing frequency and $f_n$ is a natural frequency of vortex shedding. Experiments were carried out under the conditions of $Re=4.14{\times}10^3,\;{\pi}/90{\leq}{\theta_A}{\leq}{\pi}/3,\;and\;F_R=1.0$. The effect of this active flow control technique on the lock-on flow characteristics of the cylinder wake was evaluated with wake velocity measurements and spectral analysis of hot-wire signals. The rotational oscillation modifies the flow structure of near wake significantly. The lock-on phenomenon always occurs at $F_R=1.0$, regardless of the angular amplitude ${\theta}_A$. In addition, when the angular amplitude is less than a certain value, the lock-on characteristics appear only at $F_R=1.0$,. The range of lock-on phenomena expands and vortex formation length is decreased, as the angular amplitude increases. The rotational oscillation create a small-scale vortex structure in the region just near the cylinder surface. At ${\theta}_A=60^{\circ}$, the drag coefficient was reduced about $43.7\%$ at maximum.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.5
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• pp.73-79
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• 2014

In this paper, we proposed the mechanism which can measure traffic flow and vehicle speed on the highway as well as road by using the video and image processing to detect and track cars in a video sequence. The proposed mechanism uses the first few frames of the video stream to estimate the background image. The visual tracking system is a simple algorithm based on the sum of absolute frame difference. It subtracts the background from each video frame to produce foreground images. By thresholding and performing morphological closing on each foreground image, the proposed mechanism produces binary feature images, which are shown in the threshold window. By measuring the distance between the "first white line" mark and the "second white line"mark proceeding, it is possible to find the car's position. Average velocity is defined as the change in position of an object divided by the time over which the change takes place. The results of proposed mechanism agree well with the measured data, and view the results in real time.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.4
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• pp.235-246
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• 2012

Typhoon induced surge simulations are done to make an establishment of coastal disaster prevention plan. To apply efficient run-up and overtopping on vertical harbor docks, in which prevailing wet-dry scheme cannot be satisfied due to infinite steepness, an imaginary internal barrier concept introduced and analyzed. Before real application on the Mokpo harbor area, feasibility tests are done on an idealized simple geometry and as a result it is found that the moderate width of the barrier might be 1 m. The threshold value of the minimum wet depth $H_{min}$ for land area, which behaves sensitive role in inundation area and depth, depends on grid size. However it is revealed that 0.01 m is adequate value in this fine finite element with 10 m spacing. A hypothetical typhoon of 100 years return period in central pressure and maximum velocity is generated based on historical tracks. Simulation of possible inundation on Mokpo area is performed with asymmetrical vortex of hypothetical typhoon and wave coupling. Model results show general agreement in pattern compared to other's prediction, however possibility of inundation enlargement is expected in harbor area.

• Korean journal of applied entomology
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• v.31 no.4
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• pp.492-495
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• 1992

Life cycle of the mirid predator, Cyrtorhinus lividipennis, was observed on the constant temper¬ature. Egg periods were 14.43, 9.33 and 6.94 days at $20^{\circ}C$, $25^{\circ}C$ and $30^{\circ}C$, respectively. Nymph periods were 24.3, 14.42, and 11.90 days at $20^{\circ}C$, $25^{\circ}C$ and $30^{\circ}C$, respectively and fe¬male longevity was 11.20, 11.93 and 11.87 days at above temperatures. Relationships between constant temperature and the developmental velocity of egg, nymph and egg-nymph were lin¬ear over temperatures tested. The calculated threshold temperatures of development were $10.7^{\circ}C$ in egg, $9.8^{\circ}C$ in nymph and $10.2^{\circ}C$ in egg-nymph. Total effective day-degrees were 133.9 in egg, 235.8 in nymph and 368.0 in egg-nymph. Number of eggs laid was 26.0 and 22.4 at $24^{\circ}C$ and $30^{\circ}C$, respectively.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.277-282
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• 2006

It is well known that Kalman filtering is an optimal real-time data fusion method for GPS/INS integration. However, it has some limitations in terms of stability, adaptability and observability. A Kalman filter can perform optimally only when its dynamic model is correctly defined and the noise statistics for the measurement and process are completely known. It is found that estimated Kalman filter states could be influenced by several factors, including vehicle dynamic variations, filter tuning results, and environment changes, etc., which are difficult to model. Neural networks can map input-output relationships without apriori knowledge about them; hence a proper designed neural network is capable of learning and extracting these complex relationships with enough training. This paper presents a GPS/INS integrated system that combines Kalman filtering and neural network algorithms to improve navigation solutions during GPS outages. An Extended Kalman filter estimates INS measurement errors, plus position, velocity and attitude errors etc. Kalman filter states, and gives precise navigation solutions while GPS signals are available. At the same time, a multi-layer neural network is trained to map the vehicle dynamics with corresponding Kalman filter states, at the same rate of measurement update. After the output of the neural network meets a similarity threshold, it can be used to correct INS measurements when no GPS measurements are available. Selecting suitable inputs and outputs of the neural network is critical for this hybrid method. Detailed analysis unveils that some Kalman filter states are highly correlated with vehicle dynamic variations. The filter states that heavily impact system navigation solutions are selected as the neural network outputs. The principle of this hybrid method and the neural network design are presented. Field test data are processed to evaluate the performance of the proposed method.

• Restorative Dentistry and Endodontics
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• v.17 no.1
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• pp.1-9
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• 1992

The intradental nerve activity was recorded from single pulp nerve unit dissected from the inferior alveolar nerve in canine teeth of anesthetized cats. The effects of various test solutions on intradental nerve activity evoked by 4M NaCl applied to the deep dentinal cavities were investigated. 1. Total 15 single pulp nerve units were recorded. Of these 9 were Mi - fibers and 6 were C -fibers. The mean conduction velocity and electrical threshold of $A{\delta}$ - fiber were $6.3{\pm}3.7m/sec$, $1.2{\pm}0.7V$ and those of C - fiber were $1.0{\pm}0.2m/sec$, $2.3{\pm}1.3V$, respectively. The response to cold stimuli of $A{\delta}$ - fiber began immediately and that of C - fiber began after a latency. 2. When applied to deep dentinal cavity, 4M NaCl induced irregular bursts of action potential in 4 $A{\delta}$ - fibers and 3 C - fibers, which continued until the solution was washed away. 3. In the $A{\delta}$ - fiber, histamine failed to induce any nerve acitivity and did not produce an increase in intradental nerve activity evoked by 4M NaCl. However following the application of 1M KCl, the response to 4M NaCl was eliminated. 4. In the C - fiber, histamine generated some nerve activity and produced a significant increase in intradental nerve activity evoked by 4M NaCl, but 5M $CaCl_2$ did not abolish this enhandced response.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.157-163
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• 2011

In this study, after the target basin was divided into both overland and channel grids, the travel time from center of each grid cell to watershed's outlet was calculated based on the manning equation. Through this process, volumetric discharge was calculated according to the isochrones and finally, the direct runoff hydrograph was estimated considering watershed's hydrodynamic characteristics. Sanseong subwatershed located in main stream of Bocheong basin was selected as a target basin. The model parameters are only two: area threshold and channel velocity correction factor; the optimized values were estimated at 3,800 and 3.3, respectively. The developed model based on the tuned parameters led to well-matching results between observed and calculated hydrographs (mean of absolute error of peak discharge: 3.41%, mean of absolute error of peak time: 0.67 hr). Moreover, the analysis results regarding histogram of travel time-contribution area demonstrates that the proposed model characterizes relatively well hydrodynamic characteristics of the catchment due to effective rainfall.

• Journal of the Korea Institute of Building Construction
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• v.23 no.5
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• pp.629-638
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• 2023

This study introduces an innovative approach to monitor the whereabouts of workers within indoor construction settings. While traditional modalities such as GPS and NTRIP have demonstrated efficacy for outdoor localizations, their precision dwindles in indoor environments. In response, this research advocates for the adoption of Aruco markers. Leveraging computer vision technology, these markers facilitate the quantification of the distance between a worker and the marker, subsequently pinpointing the worker's instantaneous location with heightened accuracy. The methodology's efficacy was rigorously evaluated in a real-world construction scenario. Parameters including system stability, the influence of lighting conditions, the extremity of measurable distances, and the breadth of recognition angles were methodically appraised. System stability was ascertained by maneuvering the camera at a uniform velocity, gauging its marker recognition prowess. The impact of varying luminosity on marker discernibility was scrutinized by modulating the ambient lighting. Furthermore, the camera's spatial movement ascertained both the upper threshold of distance until marker recognition waned and the maximal angle at which markers remained discernible.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.4 s.37
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• pp.307-313
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• 2005

Electromigration behavior in the Sn96.5Ag3.0Cu0.5 solder lines was investigated and compared Sn96.5Ag3.0Cu0.5 with eutectic SnPb. Measurements were made for relevant parameters for electromigration of the solder, such as drift velocity, threshold current density, activation energy, as well as the product of diffusivity and effective charge number (DZ$\ast$). The threshold current density were measured to be $2.38{\times}10^4A/cm^2$ at $140^{\circ}C$ and the value represented the maximum current density which the SnAgCu solder can carry without electromigration damage at the stressing temperatures. The electromigration energy was measured to 0.56 eV in the temperature range of $110-160^{\circ}C$. The measured products of diffusivity and the effective charge number, DZ$\ast$ were $3.12{\times}10^{-10} cm^2/s$ at $110^{\circ}C$, $4.66{\times}10^{-10} cm^2/s$ at $125^{\circ}C$, $8.76{\times}10^{-10} cm^2/s$ at $140^{\circ}C$, $2.14{\times}10^{-9}cm^2/s$ at $160^{\circ}C$ SnPb solder existed incubation stage, while SnAgCu did not have incubation stage. It was thought that the diffusion mechanism of SnAgCu was different from that of SnPb.

• Journal of Bio-Environment Control
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• v.24 no.3
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• pp.226-234
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• 2015

To provide the data necessary to determine exposure coefficients used for calculating the snow load acting on a greenhouse, we compared the exposure coefficients in the greenhouse structure design standards for various countries. We determined the exposure coefficient for each region and tried to improve on the method used to decide it. Our results are as follows: After comparing the exposure coefficients in the standards of various countries, we could determine that the main factors affecting the exposure coefficient were terrain roughness, wind speed, and whether a windbreak was present. On comparing national standards, the exposure coefficients could be divided into three groups: exposure coefficients of 0.8(0.9) for areas with strong winds, 1.0(1.1) for partially exposed areas, and 1.2 for areas with dense windbreaks. After analyzing the exposure coefficients for 94 areas in South Korea according to the ISO4355 standard, all of the areas had two coefficients (1.0 and 0.8), except Daegwallyeong (0.5) and Yeosu (0.6), which had one coefficient each. In South Korea, the probability of snow is greater inland than in coastal areas and there are fewer days with a maximum wind velocity > $5m{\cdot}s^{-1}$ inland. When determining the exposure coefficients in South Korea, we can subdivide the country into three regions: coastal areas with strong winds have an exposure coefficient of 0.8; inland areas have a coefficient of 1.0; and areas with dense windbreaks have an exposure coefficient of 1.2. Further research that considers the number of days with a wind velocity > $5m{\cdot}s^{-1}$ as the threshold wind speed is needed before we can make specific recommendations for the exposure coefficient for different regions.