• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.3
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• pp.42-55
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• 2021

In this study, the effect of nozzle performance according to the selection of the center line equation. Three of S-type nozzles and three of double S-type nozzles were designed using the curve equation and design parameters, and the nozzle shielding performance was evaluated using the shielding ratio definition. In order to analyze the internal flow of the nozzle, the characteristics of the velocity distribution and pressure distribution were studied, and the nozzle performance was evaluated through the total thrust ratio(f) and the nozzle insulation efficiency coefficient(η). On the other hand, the centerline with a sharply change in curvature at the entrance has a low nozzle performance and a high shielding rate. The double S-type nozzle is excellent nozzle performance and shielding rate by using a smooth centerline at the first curvature.

• Journal of Advanced Navigation Technology
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• v.28 no.2
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• pp.232-237
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• 2024

In this paper, a broadband double dipole quasi-Yagi antenna using a 4×2 meander line array structure for maintaining 8 dBi gain was studied. The 4×2 meanderline array structure consists of a unit cell in the shape of a meanderline conductor, and it was placed above the second dipole antenna of the double dipole quasi-Yagi antenna. A double dipole quasi-Yagi antenna with generally used multiple strip directors was designed on an FR4 substrate with the same size, and the input reflection coefficient and gain characteristics were compared. Comparison results showed that the impedance frequency bandwidth increased by 6.3% compared to when using the multiple strip directors, the frequency bandwidth with a gain of 8 dBi or more increased by 10.1%, and average gain also slightly increased. The frequency band of the fabricated antenna for a voltage standing wave ratio less than 2 was 1.548-2.846 GHz(59.1%), and gain was measured to be more than 8 dBi in the 1.6-2.8 GHz band.

• Journal of Fashion Business
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• v.9 no.4
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• pp.127-144
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• 2005

The aim of this study is to find out the symbol of clothing decorations in Elsa Schiaparalli's design works and there are four major points due to the aim of this study. Firstly, a fantasy is represented through Surrealistic Arts which creates mysterious, secrete, and surprising spirits. In Surrealistic Arts, the fashion of schiaparelli demonstrates a fantasy spirit by using the methods like metaphor, transformation, and re-positioning. Secondly, In Surrealistic paintings, normally double image or different image from symbol immanent were expressed. However, Elsa Schiaparelli used double and multi-image decorations instead that has well-organized formative effect. The mixture of double images can be separated as symbolic mixture, design mixture and expressive mixture. Thirdly, the body parts has represented symbolism and sensuality in Surrealism Arts. Elsa Schiaparelli has demonstrated the expression of modern clothing as passionate, desirable, and powerful. This is the reason why her designs were absolutely different from the previous sihouette-focused clothing. Fourth, there are lots of intentional decoration that are different from actual images, such as transformation, exaggeration, minimization and repettion, as well as, re-location, re-arrangement, line-up arrangement, collage and odd materials.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.251-257
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• 1998

Spherical space frame structure with triangular network pattern, which has the various characteristics for the mechanic property, a funtional property, an aesthetic property and so on, has often been used as one of the most efficient space structures. It is expected that this type will be used widely in large-span structural roofs. But because this structure is made of network by combination of line elements there me many nodes therefore, the structure behavior is very complicated and there can be an overall collapse of structure by buckling phenomenon if the external force reaches a limitation. This kind of buckling is due to geometric shape, network pattern, the number of layer and so on, of structure. Therefore spherical space frame with triangle network pattern have attracted many designers and researchers attention all over the world. The number of layer of space frame is divided in to the simgle, double, multi layer. That is important element which is considered deeply in the beginning of structural design. The buckling characteristics of single-layer model and double-layer model for the spherical space frame structure with triangular network pattern are evaluated and the buckling loads of these types are compared with investigation their structural efficiency in this study.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2309-2311
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• 1998

The attitude control of a double inverted pendulum with a periodical disturbance at link top is dealt in this paper. The proposed system is consisted of the double inverted pendulum and a disturbance link. The lower link is hinged on the plate to free for rotation in the vertical plane. The upper link is connected to the lower link through a DC motor. The DC motor is used to control the posture of the pendulum by adjusting the position of the upper link. The periodical disturbance can be generated by the additional link attached at the end of link 2 through another DC motor, which is the modeling of a posture for a biped supporting with one leg. The motor for the joint simulates the knee joint(or hip joint) and the disturbance for the legs moving in air. The algorithm for controlling a proposed inverted pendulum is consisted of a state feedback control and a fuzzy logic controller. The fuzzy controller keeps the center of gravity of the biped within the specified range through the nonlinear feedback compensator. The state feedback control takes over the role to maintain a desired posture regardless the disturbance at the link top. In these case, the change of the angle and COG of an upper link is compensated with on-line. Simulations with a mathematical model are conducted to show the validity of the proposed controller.

• Journal of Power Electronics
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• v.15 no.3
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• pp.695-701
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• 2015

Uninterruptible Power Supplies (UPSs) can be largely divided into the passive-standby, line-interactive and double-conversion methods. This paper proposes a double-conversion UPS with a low cost and high performance. This single phase UPS uses a single-loop robust voltage controller and 1-switch voltage doubler strategy PFC. The proposed UPS is composed of a single phase PFC, a half-bridge inverter, a battery charger and a battery discharger. Finally, the validity of proposed UPS was verified by various experimental tests.

• Journal of electromagnetic engineering and science
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• v.16 no.3
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• pp.159-163
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• 2016

In this paper, a frequency tunable double band-stop resonator (BSR) with voltage control by varactor diodes is suggested. It makes use of a half-wavelength shunt stub as its conventional basic structure, which is replaced by the distributed LC block. Taking advantage of the nonlinear relationship between the frequency and electrical length of the distributed LC block, a dual-band device can be designed easily. With two varactor diodes, the stop-band of the resonator can be easily tuned by controlling the electrical length of the resonator structure. The measurement results show the tuning ranges of the two operating frequencies to be 1.82 GHz to 2.03 GHz and 2.81 GHz to 3.03 GHz, respectively. The entire size of the resonator is $10mm{\times}11mm$, which is very compact.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.4
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• pp.491-500
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• 2014

Due to rapid urbanization and industrialization, water supply and sewer line systems are also developed relevantly. Manhole is an essential component structure of the pipeline system. Manhole is a structure constructed to accommodate the direction, dimension, differences in level, and easy of maintenance in the pipeline system. In this paper we present the result of investigations pertaining to the structural behavior of PVC sewer manhole buried underground. In the paper mechanical properties of PVC material are reported. In addition, by the finite element analysis (FEA), we confirmed that a PVC double-wall corrugated pipe manhole, when it is buried underground, is safe for the stress as well as buckling strength if the manhole is constructed within the suggested limit of buried depth.

• International Journal of Aeronautical and Space Sciences
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• v.8 no.2
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• pp.98-106
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• 2007

The vortex flow characteristics of a double-delta wing, which can change the incidence angle of its apex strake was investigated through the wing-surface pressure measurement and the particle image velocimetry(PIV) measurement of the wing-leeward flow region. The apex strake has sharp edges and can change its incidence angle with a hinge line at the 23% chord position measured from the apex of the main wing. The present study revealed that the incidence-angle change of the apex strake could greatly alter the vortex flow pattern around the double-delta wing and the wing-surface pressure distribution, which suggested that the apex strake could be used as an effective device for the active control of delta-wing vortex flow.

• Journal of Multimedia Information System
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• v.5 no.3
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• pp.179-188
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• 2018

In order to overcome the problems of contact palmprint recognition, a non-contact palmprint recognition system is developed on personal computer (PC) platform. Three methods, namely "double-line-single-point" (DLSP), "double-assistant-crosshair" (DAC) and "none-assistant-graphic" (NAG), are implemented for the palmprint localization to solve the severe technical challenges, including the complex background, variant illuminations, uncontrollable locations and gestures of hands. In NAG, hand segmentation and the cropping of region of interest are performed without any assistant graphics. The convex hull contour of hand helps detect the outside contour of little finger as well as the valley bottom between thumb and index finger. The three methods of palmprint localization have good operating efficiency and can meet the performance requirements of real-time system. Furthermore, an attendance system on PC platform is designed and developed based on non-contact palmprint recognition.