• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.2
• /
• pp.217-222
• /
• 2006

To find a location, GPS has been wildly used. But, it is hard to use in indoor because of very weak signal level. To meet indoor requirements, there have been many studies applying wireless communication networks such as WLAN, UWB and ZigBee. Among these, ZigBee is widely adopted in many WSN applications because it has an advantage of low-power and low-cost. In ZigBee, the RSSI is used as range measurement for ad-hoc network. The RSSI are converted to ranges using the signal attenuation model and these ranges become inputs of positioning methods. The obtained position with RSSI has large error because of its poor accuracy. To overcome this problem, ultrasonic sensors are added in many researches. By measuring the arrival time difference of ZigBee and ultrasound as a range measurement, the precise position can be found. However, there are still many problems: scheduling of beacons to transmit signals in a correct order, addition and synchronization of beacons and low-rate positioning rate. At this paper, an efficient method to solve these problems is proposed. In the proposed method, a node transmits ZigBee and ultrasound signal simultaneously. And beacons find the range with the received signals and send it back to a node with ZigBee. The position is computed in a node with the received ranges. In addition, a new positioning algorithm to solve the risk of the divergence in the linearization method and the singularity problem in the Savarese method is presented. Both static and dynamic experimental results show 0.02m RMS errors with high output rate.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.11
• /
• pp.1066-1072
• /
• 2009

A panel method based on potential flow theory is developed for the steady/unsteady aerodynamic analysis of arbitrary three-dimensional Blended Wing Body aircraft. The panel method uses the piecewise constant source and doublet singularities as a solution. This potential based panel method is founded on the Dirichlet boundary condition and coupled with the time-stepping method. The present method uses the time-stepping loop to simulate the unsteady motion of the aircraft. The present method can solve the three-dimensional flow over the complex bodies with less computing time and provide various aerodynamic derivatives to secure the stability of Blended Wing Body aircraft. That will do much for practical applications such as aerodynamic designs and analysis of aircraft configurations and flight simulation.

• Journal of Welding and Joining
• /
• v.24 no.3
• /
• pp.27-33
• /
• 2006

Structural stress approach is well known as a mesh-size insensitive fatigue assessment method by using finite element analyses. It is, however, difficult to estimate the structural stress (SS) at weld end points due to stress singularities when shell elements are used. In this study, fatigue evaluations with longitudinal load carrying box fillet weldment under out-of-plane bending load have been performed by using virtual node method (VNM) in order to avoid the problem, which is called the weld end effect. Various combinations of virtual node parameters, such as reference point and virtual node locations, are investigated for the estimation of proper structural stress values applying VNM in a systematic manner. The appropriate guidance of virtual node parameter has been offered for the fillet weldment considered in the study. The structural stress values obtained by VNM have also been validated by comparing the result with finite element model including weld bead. Moreover, the fatigue strength of the fillet weldment based on the equivalent structural stress is shown to be consistent with the master S-N curve.

• The Journal of the Korea Contents Association
• /
• v.21 no.5
• /
• pp.170-181
• /
• 2021

The purpose of this study is to produce the results of the cultural aspects of the Honam region and present the aesthetic specificity of the traditional dances inherited in the Yehyang Honam region. The research method examined the regional characteristics of Honam dance and the form of Lee Mae-bang, Choi Seon, Jang Geum-do, and Cho Gap-nyeo Salpuri dance, and analyzed the authenticity and dance tendencies of Honam dance through the analysis.The work of understanding the background of local culture and creating cultural values through these representative salpuri dances in Honam region is an attempt to reflect on the essential value of the region as an intangible heritage of the region.

• Korean Journal of Pharmacognosy
• /
• v.50 no.3
• /
• pp.205-218
• /
• 2019

This study was conducted to investigate the toxicity symptoms and approximate lethal dose (ALD) of Oplopanax elatus (Nakai) Nakai hydrothermal extract powder by single oral dose toxicity and 4 weeks of repeated oral dose determination. The Sprague-Dawley (SD) male and female rats were treated with 1,250 (low- dosage group), 2,500 (medium- dosage group) and 5,000 (high- dosage group) mg/kg. In the single oral dose toxicity test, no dead animals and toxic symptoms were observed during the experiment. And there were no related with anomalies in normal weight changes and autopsy results. In the four-week repeated oral dose determination test, no death animals and toxicity symptoms were observed during the experiment, and there were no abnormal results in weight changes, feed and negative intake measurements. Results of eye examination, urinalysis, hematological values and serum biochemical values, gross findings and absolute organ were not of singularity. These result demonstrated that no toxic symptoms were observed by the test substance Oplopanax elatus (Nakai) Nakai hydrothermal extract powder under this test condition, and the non-toxic content is determined to be 5,000 mg/kg/day.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.32 no.3
• /
• pp.183-190
• /
• 2019

This paper introduces a near-tip grid refinement and explores its usefulness in the crack analysis by the natural element method(NEM). As a sort of local h-refinement in finite element method(FEM), a NEM grid is locally refined around the crack tip showing high stress singularity. This local grid refinement is completed in two steps in which grid points are added and Delaunay triangles sharing the crack tip node are divided. A plane strain rectangular plate with symmetric edge cracks is simulated to validate the proposed local grid refinement and to examine its usefulness in the crack analysis. The crack analysis is also simulated using a uniform NEM grid for comparison. Unlike the uniform grid, the refined grid provides near-tip stress distributions similar to the analytic solutions and the fine grid. In addition, the refined grid shows higher convergence than the uniform grid, the global relative error to the total number of grid points.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.47 no.4
• /
• pp.289-299
• /
• 2019

Attitude control modeling and simulation (M&S) can be extensively applied in overall development process, from simple algorithm design to on-board software verification. This paper introduces CMG-based attitude control M&S software, which consists of 6-DOF modeling (CMG and space environments modeling), and attitude control algorithm. The M&S software is divided into three modules, from an inner CMG motor control module to an outer earth observation mission module. While an application of this developed software is currently limited to the initial-phase attitude controller development, its application area can be extended to the later-phases by considering sophisticated model information in future.

• (The)Study of the Eastern Classic
• /
• no.37
• /
• pp.161-188
• /
• 2009

How did Japanese who surrender to Joseon reflect in old proses / Seo, Shin-hye This paper is focus on Japanese who surrender to Joseon. I researched how were these people to live through old novel, old tale and old biography. And I researched how these works reflected these people. Usually Japanese who surrender to Joseon were butchers. They were loyal to Joseon and their higher officer to a fare-thee-well. In old proses, writters compared these surrender with Joseon's general. People expect the general loyalty, but he didn't. Because of surrender's loyalty, Joseon's general was seen as an abject coward. This form came out in common in the biography of Gim Yeongcheol, the biography of Gang Hongrip and the biography of Gim Chungseon. But this fact was biased. All of Japanese surrender was not loyal, and they liked fighting in the battle. The singularity of the biography of the butcher who is Buddhist monk attracted our attention. In this work, we can see the surrender's mental conflict. We can realized the people is equal with Joseon's people.

• Wind and Structures
• /
• v.34 no.1
• /
• pp.43-58
• /
• 2022

The BARC flow is studied via Direct Numerical Simulation at a relatively low turbulent Reynolds number, with focus on the geometrical representation of the leading-edge (LE) corners. The study contributes to further our understanding of the discrepancies between existing numerical and experimental BARC data. In a first part, rounded LE corners with small curvature radii are considered. Results show that a small amount of rounding does not lead to abrupt changes of the mean fields, but that the effects increase with the curvature radius. The shear layer separates from the rounded LE at a lower angle, which reduces the size of the main recirculating region over the cylinder side. In contrast, the longitudinal size of the recirculating region behind the trailing edge (TE) increases, as the TE shear layer is accelerated. The effect of the curvature radii on the turbulent kinetic energy and on its production, dissipation and transport are addressed. The present results should be contrasted with the recent work of Rocchio et al. (2020), who found via implicit Large-Eddy Simulations at larger Reynolds numbers that even a small curvature radius leads to significant changes of the mean flow. In a second part, the LE corners are fully sharp and the exact analytical solution of the Stokes problem in the neighbourhood of the corners is used to locally restore the solution accuracy degraded by the singularity. Changes in the mean flow reveal that the analytical correction leads to streamlines that better follow the corners. The flow separates from the LE with a lower angle, resulting in a slightly smaller recirculating region. The corner-correction approach is valuable in general, and is expected to help developing high-quality numerical simulations at the high Reynolds numbers typical of the experiments with reasonable meshing requirements.

• Journal of Digital Convergence
• /
• v.20 no.2
• /
• pp.63-75
• /
• 2022

In this study, the smart docent interface provided at 25 exhibition halls at domestic and foreign were compared and analyzed based on affordance. Heuristic evaluation techniques were adopted, centered on a small number of experienced people, and six research participants were selected based on Jacob Nielsen's guidelines that five to eight people per set of research can achieve sufficient results. As a result of comparative analysis of affordance, smart docent used in the Oriental showed a higher average value than smart docent used in the Western, but a lower value for sensory affordance alone. In addition, the categories were subdivided to derive the affordance values for each country, and a singularity was found that the sensory affordance of smart docents used in the United States represents the highest value compared to other countries. In conclusion, this study was able to compare the four affordances of smart docents used in domestic and foreign exhibition halls while presenting directions for future behavioral improvement, which could provide practical implication for smart docent interface design and exhibition hall service strategies.