• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.44 no.10
• /
• pp.843-852
• /
• 2016

The autorotative flight of maple seeds(Acer palmatum) is numerically simulated based on the 3D geometry and the motion parameters of real seeds. The nominal values of the motion parameters are 1.26 m/s for descent velocity, 133.6 rad/s (1,276 rpm) for spinning rate, $19.4^{\circ}$ for coning angle, and $-1.5^{\circ}$ for pitch angle. A compact leading-edge vortex (LEV) positioned at the inner span of the seed blade causes a large suction pressure on its leeward surface. The suction pressure peaks occur near the leading region of inner span sections. The flow pattern characterized by the prominent LEV and the values of aerodynamic force coefficients obtained in the present study are in good agreement with experimental data measured for a dynamically-scaled robot maple seeds. A spiraling vortex developed in the leeward region advances toward the seed tip and merges with the tip-passing flow, which is considered to be a mechanism of maintaining stable and attached LEV for the autorotating maple seeds.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.12
• /
• pp.1059-1066
• /
• 2007

An experimental study has been conducted to investigate the flow separation control effects of a blowing jet on an elliptic airfoil at a Reynolds number of 7.84×105 based on the chord length. A blowing jet was obtained by pressing a plenum inside the airfoil and ejecting flow out of a thin jet slot that located in leading edge or trailing edge. The experimental results have shown that the blowing jet had an effect of suppressing the flow separation, resulting in the higher suction pressure distribution and higher normal force. The increase in Cn was more pronounced at higher incidence, whereas the effectiveness of the blowing jet reduced at lower incidences. The leading edge pulsating blowing with 90° was the most effective in controlling the flow separation than other types of blowing jet configuration tested in this research. Moreover, when the pulsating blowing was applied, the stall angle was postponed about 2°-3°. The continuous and pulsating blowing jet is a direct and effective flow separation control for improving the aerodynamic characteristics and performances of airfoil.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.32 no.6
• /
• pp.56-63
• /
• 2004

In this study, dynamic aeroelastic analyses of the canard with oscillating flap are conducted considering the effect of aerodynamic compressibility. The canard model considered herein is an all-movable type with a pitching axis on a canard-rotor-wing aircraft which was considered as one of the major UAV candidates under developing in Korea. The equivalent structural model is constructed based on the initial design data by the Korea smart UAV development center. Both the frequency and the time-domain aeroelastic analyses have been applied to practically conduct parametric studies on the effects of equivalent torsional stiffness. In the case of all-movable control surface with oscillating flap, the equivalent rotational stiffness of the pitch axes are important design parameters. The parametric results for the aeroelastic instability are practically presented.

• Journal of the Society of Naval Architects of Korea
• /
• v.39 no.1
• /
• pp.8-15
• /
• 2002

A two-dimensional higher order panel method using B-splines has been developed to overcome the disadvantages of the low order panel method and to obtain more accurate solution. The sources and the normal dipoles are distributed on both the body and the free surface. Instead of applying the upwind finite difference schemes to satisfy the linearized free surface and the radiation condition, the derivatives of the basis functions of the B-splines are directly applied to the linearized free surface condition. Numerical damping in the Dawson's method are avoided in the Present computations. In order to validate the present method, numerical computations are carried out for a submerged cylinder and a two-dimensional hydrofoil steadily moving beneath a free surface. The numerical results show that fast convergence and better accuracies have been achieved by the present method.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2002.11a
• /
• pp.95-100
• /
• 2002

The wing in ground effect (WIG) ship is an energy saying vessel that uses the lift from its air-wing along with the lift increase from the ground effect by flying low above the sea surface. The WIG Ship should consist of thin plate in order to float on the sea and to fly in the air. Therefore, the structure of WIG, Ship has very thin and light shell plate and stiffener like stringer and frame has comparatively large cross section area. This structure makes shell plate nearly pure shear field when shell plate is pressed by in-plane load. This complex thin plate structure of WIG Ship can he considered as a closed section beam which makes it possible to analyze structure response of WIG Ship affected by shear load and bending load. In this respect, the present study will show basic theory for analysing shear stress and focus on the analysis of structure strength of model WIC Ship's wing.

• Korean Journal of Plant Resources
• /
• v.8 no.3
• /
• pp.223-235
• /
• 1995

Comparative studies on external morphology and anatomical characters were conducted understand the interspecific relationships and possibly to identify the position of Hanabusaya asiatica as an endemic genus among 4 genera and 9 species in H. asiatica and its allied groups. Such morphological characteristics as root shape, leaf size, presence or absence of wings in petiole, corolla and calyx shape, and inflorescence and stigma shape were useful qualitative characters. The morphology of stem, peduncle, calyx lobe, leaf, petiole, and ovary were also good characters to be included in this identification study. In the anatomical observations in these organs, projecting degree of epidermis and number of projecting area rather than cross-sectioned internal structures were found to be valuable index for the classification among species. External morphology and anatomical characters support the position of H. asiatica as an endemic genus very well. Known as the most important external characters to taxonomists(Fedorov, 1957: Nakai, 1952: Hong, 1983), leaf arrangement, inflorescence, and corolla shape were also preven to be very useful characters to identify the genera and species in the H. asiatica and its allied groups.

• Cartoon and Animation Studies
• /
• s.41
• /
• pp.107-131
• /
• 2015

This study is on the modification of characters' role and personality between spin-off animation and original works. For this, one of box office hits, (2011) and (2015) have been analyzed with Enneagram and Greimas' Actantial model. The result shows, firstly, the protagonist of spin-off work plays subject role in a new narrative comparing that he/she plays faithful helper's role in original work. Secondly, the protagonist's personality does not show big difference between in spin-off and in original. But, anyway, there's a small change that the secondary personality in original stands out as a primary personality in spin-off. Finally, the standing out personality of the protagonist tends to be 'achiever' or 'loyalist', those of stereotype successful animation characters. In conclusion, the role change according to new narrative seems to be unavoidable. And, the personality change is, too. However, the personality change is partial and it has continuity from the original considering the potential audiences' expectation.

• Korean journal of applied entomology
• /
• v.42 no.2
• /
• pp.125-132
• /
• 2003

Seasonal fluctuations in density of mosquito species were investigated at two cow sheds near to a large, reedy marsh with fairly polluted brackish water near the coast of Yongam-ri, Cheongryang-myon, Ulsan, Korea. Female mosquitoes were collected biweekly using Nozawa light traps from March to September, from 1999 to 2001. On average, 4,416.1, 5,505.9 and 6,863.8 females per trap night were collected from 10 species in 5 genera in 1999, 2000 and 2001, respectively. Among them, An. sinensis was most abundant (53.4% in species ratio), followed by Cx. tritaeniorhynchus (43.0%), Cx. inatomii (1.6%), Ochlerotatus dorsalis (1.3%) and Cx. pipiens pallens (0.5%). A malaria vector, An. sinensis and a Japanese encephalitis vector, Cx. tritaeniorhynchus were collected 3,663.3 females and 3,142.5 females per trap night from June to September for the years, respectively. According to the biweekly population changes at the area, Cx. inatomii which was dominant species in 1997, was the most abundant in the early July during 1999-2001.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.11 no.5
• /
• pp.681-688
• /
• 2000

In this paper, a planar antenna that is small and light, is designed and analyzed aiming handset antenna of IMT-2000. Employing the Ensemble simulator based on a MoM, design-parameters are found to determine a resonant frequency. Therefore, it is analyzed with the Ensemble simulation and FDTD numerical for resonating at the allocated frequency for IMT-2000 in the fixed antenna dimension of 21$^{\circ}$wing angle that is a design parameter. Analyzing with FDTD method, Though the results of FDTD are very exact, this analysis introduces errors due to the staircasing approximation in the slope of bowtie. To reduce this error, it is divided to 4-ranges where the cell contains the boundary of perfect conductor/free space. Then, each range is calculated by different by different equation, which modify the H-field to add the component of the area and length of the cell filled with free space. Therefore, the modified FDTD algorithm provided with a narrow bandwidth of return loss calculated with a standard FDTD algorithm that can be extended to the desired ranges.

• Tunnel and Underground Space
• /
• v.20 no.1
• /
• pp.65-72
• /
• 2010

Crack-controlled blasting method which utilizes notched charge hole has been proposed in order to achieve smooth fracture plane and minimize the excavation damage zone. In this study, the blast models, which have a notched charge hole, were analyzed using dynamic fracture process analysis software to investigate the effect of the geometry of a notched charge hole and decoupling indexes of the charge hole on crack growth control in blasting. As a result, crack extension increased and damage crack decreased with the notch length. Ultimately, stress increment factors and resultant fracture patterns with different notch length and width were analyzed in order to examine the effect factors on the crack growth controlling in rock blasts using a notched charge hole.