• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.2
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• pp.73-84
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• 2004

In general, static firing test is conducted before flight in order to obtain data such as thrust. pressure, temperature and strain, which show the characteristics of rocket motors. But the measured thrust of the obtained data is especially distorted by the effects of dynamic characteristics of thrust stand so that it is difficult for us to determine the exact value of peak thrust and rising time etc., which represent the performance of rocket motor. This paper, therefore. verified the causes of distortion of measured thrust, and proposed the theoretical method to estimate the true thrust from the distorted thrust. And also the proposed method was applied to virtual thrust stand using computer simulation, and showed good result. As a result of that, the proposed method was proven to be valid and applicable to estimate distorted thrust.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.9-15
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• 2004

The measured thrust could be distorted because of the transient response of thrust stand during combustion of rocket motor. As a result of the distorted thrust, it is not easy for us to know the values of thrust peak and thrust duration time. Therefore, it is of great importance to compute the true thrust from the measured thrust. In this study the method to eliminate the transient response from the measured thrust using only the measured thrust was Proposed, and also experimental data were used to approve the proposed method. The result showed that the proposed method would be available to compute the true thrust.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.6
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• pp.655-667
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• 2017

The results of a numerical study on the performance of a propeller operating near a free surface are presented. The numerical simulations were performed for the various advance coefficients and the submergence depths of the model propeller. The effects of the model propeller size were investigated using two different model propeller sizes for all cases. The wave pattern of the free surface and the flow structure around the propeller as well as the hydrodynamic characteristics of the propeller were investigated through simulation results. The thrust and torque fluctuated and the trajectory of the tip vortex was distorted due to the interaction with the free surface. The wave pattern of the free surface was related to the tip vortex of the propeller. The decreases in thrust and torque at the small model propeller were greater than those of the large model propeller. The reduction rate of the thrust and torque increased with the advance coefficient.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.18-21
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• 2001

This paper describes the method of vibration supprssion on a control algorithm using Neuro-Fuzzy Theory in Linear Pulse Motor (LPM). The total thrust force Is distorted by magnetic and coil flux, and we classify the harmonic parts of it. A modulated current from harmonic components of static thrust characteristics of LPM compensates with reference current to total thrust force. Low vibration is obtatained by the method of current compensation using ANFIS.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.7
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• pp.789-795
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• 2011

In elliptical vibration cutting (EVC), cutting performance is largely affected by the shape of an elliptical path of the cutting tool. In this study, two parallel piezoelectric actuators were used to make an elliptical vibration cutting device. When harmonic voltages of $90^{\circ}$ out-of-phase are supplied to the EVC device, creation of an ideal elliptical trajectory whose major and minor axes are parallel to the cutting and thrust directions is anticipated from a kinematic analysis of the EVC device, however, the paths we experimentally observed showed significant distortions in its shape ranging from skew to excessive elongation of the major axis of the ellipse. To compensate distortions, an analytical model describing the elliptical path of the cutting tool was developed and verified with experimental results, and based on the analytical model, the distorted elliptical paths created at 100 Hz, 1 kHz, and 16 kHz were corrected for skew and elongation.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.8
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• pp.413-424
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• 2002

Recently, in the linear motion system, high performances are required In dynamic characteristics. Vector control method is capable of instantaneous thrust control can meet these high performance requirements. Linear induction motor(LIM) have static and dynamic end effects due to its finite core length, so that per-phase impedances are asymmetric and an air gap flux distribution is distorted. These points of the d-q axis equivalent circuit model considering both end effects is more complicated. This paper proposes the d-q axis equivalent circuit and the vector control method considering both static and dynamic end effects of the LIM. As a result, it is shown that the results of the equivalent circuit method(ECM) have a good agreement with those of the finite element method(FEM).

• Journal of the Korean Society of Costume
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• v.30
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• pp.275-294
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• 1996

In fashion there was a move away from the ascetic of the Gothic according to the appear-ance of a new spirit at the beginning of the fourteenth centuries initially in Italy. The new spirit Humanism applied their interest not to the universal but to the individual and particular. The Renaissace costume style based on the Humanism was sharp angled and curvy and had a grotesque silhouette with the exaggerated and tense decorations. The purpose of this study is researching the background led to the balanced costume style characterized by unique details. out of the tastte for luxury and beauty grew a new style known as slashing in which seams were left open and colored linigs thrust through or cuts were made in an entire cos-tume and contrasting material puffed out of the cuts. With the slashes another element was characterized in the high Renaissance cos-tume style that was the use of points or lace to hold a costume together. For the masculint costumes pads became into a fashion and were used for forming the antinatural artificial and bulky silhouettes. The body was distorted and tensed by putting the pads into the sleeves and bodice. The jacket with a full rounded bodice like a bow known as peascod belly and haut de chausses a onion-shaped trunk hose with a codipiece ap-peared and grew one of the most characteristic of Renaissance style. According to these sociological changes the view of the beauty based on the human body and in both of men and women the costume style was changed very much to emphasixed their physical beauty and finally it grew a grotesque style and even more a exposed style that exposed a part of their body. Those backgrounds as were stated above can be said to lead to the appearance of the grotesque style in the Renaissance Age.

• Journal of Korea Multimedia Society
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• v.9 no.9
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• pp.1131-1138
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• 2006

This paper proposes a novel method for grading of underground communication conduits by laser projection image analysis. The equipment thrust into conduit consists of a laser diode, a light emitting diode and a camera, the laser diode is utilized for generating projection image onto pipe wall, the light emitting diode for lighting environment and the image of conduit is acquired by the camera. In order to segment profile region, we used a novel color difference model and multiple thresholds method. The shape of profile ring is represented as a minimum diameter and the Fourier descriptor, and then the pipe status is graded by the rule-based method. Both local and global features of the segmented ring shaped, the minimum diameter and the Fourier descriptor, are utilized, therefore injured and distorted pipes can be correctly graded. From the experimental results, the classification is measured with accuracy such that false alarms are less than 2% under the various conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.10
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• pp.761-769
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• 2013

Effects of helicopter wakes on helicopter aerodynamics are serious, but the wake configuration is very complicated and hard to predict. The purpose of this study is the detailed observation of wake using numerical methods. Vortex lattice method and freewake method are used to track the vortices in the wake. In this paper, the wake configuration is observed during hovering flight. In the case of hovering flight at the moderate thrust level, besides tip vortex, counter-rotating vortex can be observed at the inboard part of blade. When the vortices move downward, tip vortex and counter-rotating vortex get close and influence to each other. Therefore, vortices are highly distorted due to their own instability.