• Journal of the KSME
• /
• v.17 no.1
• /
• pp.28-31
• /
• 1977

유압밸브의 스푸울(spool)에 작용하는 유동력을 정확하게 기술하는 것은 일반적으로 매우어렵고, 실험에 의존하는 경우가 많다. 수푸울의 형상이 비교적 간단한 경우에 대해서는, 적절한 가정하에 서 유동력의 크기를 계산할 수 있고, 그 결과를 설계에 이용할 수 있다. 많은 유압교과서에서 유 동력의 기술을 다루고 있으나 기술방법에 있어서 명확성이 결여된 느낌을 주는 경우가 많고, 가 끔 학생들이나 현장의 기술자들이 유동력의 개년메 대해서 혼돈하는 수가 있다. 이 글의 내용은 본인의 유압공학 강의에서 발춰, 정리한 것이고, 유압백브에 작용하는 유동력의 명확한 이해를 주 기 위해서 쓴 것이므로 앞으로 이 분야에 종사하는 사람들에게 참고가 되기를 희망한다. 여기서 다루는 문제는 유압밸브의 스푸울에 작용하는 반경방향의 유동력(Iateral forces)과 축방향의 힘 (axial forces), 포펫트형(popet type) 밸브에 미치는 유동력, 후렛퍼형(flapper) 밸브에 작용하는 힘 등이고 기하학적 형태가 간단한 경우에 대해서 논의한다.

• Journal of Drive and Control
• /
• v.16 no.1
• /
• pp.29-35
• /
• 2019

The control performance of hydraulic systems is basically influenced by the performance of electrohydraulic servo valve incorporated in a hydraulic control system. In this study, a control design was proposed to improve the control performance of a servo valve with a non-contact eddy current type position sensor. A mathematical model for the valve was obtained through an experimental identification process. A PI-D control together with a feedforward (FF) control was applied to the valve. To further improve the dynamic response of the servo valve, an input shaping filter (ISF) was incorporated into the valve control system. Finally, the effectiveness of the proposed control system was verified experimentally.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.37 no.4
• /
• pp.267-274
• /
• 2001

A prototype experiment on the anchovy boat seine was carried out in the southern sea of korea to analyze the vertical opening and the underwater geometry. The vertical opening and the underwater geometry of the prototype net were determined by distance of Minilog position with the combinations of the distance between paired boats and the towing speed. The results osbtained can be summarized as follows; 1. Vertical opening of the protype net was gradually lowered according to the increase of the distance between paired beats and the towing speed. 2. Vertical opening of Wing net, Inside wing net, Square, Fore bag net, Flapper and After bag net of the prototype net according to the distance between paired boats were varied in the range of 8.4~9.0, 15.7~17.4, 12.9~17.9, 13.6~19.0, 8.3~8.4, 11.1~14.7m respectively, varied in the range of 12~16, 22~24, 27~38, 59~83, 92~93, 41~54% of the normal opening respectively. 3. Vertical opening of Wing net, In side wing net, Square, Fore bag net, Flapper and After bag net of the prototype net according to the towing speed were varied in the range of 7.7~10.5, 19.6~21.6, 12.2~16.9, 15.4~17.1, 8.0~8.2, 13.7~14.7m respectively, varied in the range of 14~19, 27~30, 32~36, 67~74, 89~91, 51~54% of the normal opening respectively. 4. Prototype net was appeared apparent the pocket shape, because Wing net and Inside wing net was opened 20% of the normal opening. 5. Working depth of the prototype net was gradually shallow according to the increase of the distance between paired boats and the towing speed.

• Structural Engineering and Mechanics
• /
• v.75 no.3
• /
• pp.327-337
• /
• 2020

The stability and dynamic performance of a flapper-nozzle servo valve depend on several factors, such as the motion of the armature component and the deformation of the spring tube. As the only connection between the armature component and the fixed end, the spring tube plays a decisive role in the dynamic response of the entire system. Aiming at predicting the vibration characteristics of the servo valves to combine them with the control algorithm, an innovative dynamic stiffness based on a distributed parameter model (DPM) is proposed that can reflect the dynamic deformation of the spring tube and a suitable discrete method is applied according to the working condition of the spring tube. With the motion equation derived by DPM, which includes the impact of inertia, damping, and stiffness force, the mathematical model of the spring tube dynamic stiffness is established. Subsequently, a suitable program for this model is confirmed that guarantees the simulation accuracy while controlling the time consumption. Ultimately, the transient response of the spring tube is also evaluated by a finite element method (FEM). The agreement between the simulation results of the two methods shows that dynamic stiffness based on DPM is suitable for predicting the transient response of the spring tube.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.6
• /
• pp.982-990
• /
• 1987

In previous modeling of Helmholtz-type pulse combustion water heater, muffler and the motion of the flapper valve were omitted. In present work, these have been included in modeling for providing more accurate information regarding the thermal and dynamic behavior of the water heater. In addition, a computer simulation based on the modeling was developed. The comparison of computer predictions with available experimental data shows that the simulation is satisfactory in predicting the nature of operating behavior, amplitudes of the pressure oscillations, and the magnitude of the frequency. But the predicted time-averaged axial temperature of the flue gas along the flue tube length is somewhat below the previous experimental results. The temperature pulsation of the combustion chamber and the velocity pulsation of the flue gas were predicted which have never been measured in previous studies. In particular, the latter is of importance for a valid determination of the heat transfer enhancement due to the gas flow pulsation. Heat transfer results in flue tube were presented and discussed. Also the effects on the installation of the muffler were investigated.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.1 s.94
• /
• pp.42-48
• /
• 1999

A control method for a robot hand grasping a object in a partially unknown environment will be proposed, where a proximate sensor detecting the distance between the fingertip and object was used. Particularly, the finger joints were driven servo-pneumatically in this study. Based on the proximate sensor signal the finger motion controller could plan the grasping process divided in three phases ; fast aproach, slow transitional contact and contact force control. That is, the fingertip approached to the object with full speed, until the output signal of the proximate sensor began to change. Within the perating range of the proximate sensor, the finger joint was moved by a state-variable feedback position controller in order to obtain a smooth contact with the object. The contact force of fingertip was then controlled using the blocked-line pressure sensitivity of the flow control servovalve for finger joint control. In this way, the grasping impact could be reduced without reducing the object approaching speed. The performance of the proposed grasping method was experimentally compared with that of a open loop-controlled one.

• Journal of Drive and Control
• /
• v.15 no.1
• /
• pp.16-27
• /
• 2018

Hydraulic torque load simulator is essential to test and qualify the performance of various angle control systems. Typically a flapper-type second stage servovalve is applied to the load simulator, but here the direct drive servovalve, which is a kind of one-stage valve and affected by the large flow force, is applied. Since the torque load is applied not to the stationary shaft but to the rotating shaft of the angle control system, the controlled torque of load simulator is not accurate due to the rotating speed of the angle control system. A feedforward compensator is designed and applied to minimize the disturbance-like effect. A mathematical model is derived and linearized to analyze the stability, accuracy and responsiveness of the torque load simulator. The parameter effects of a controller, servovalve, hydraulic motor, rotating spring shaft are analyzed and summarized. The goodness of the linear analysis is verified by the digital computer simulations using both the linear and nonlinear mathematical models.

• Journal of Fashion Business
• /
• v.12 no.2
• /
• pp.12-27
• /
• 2008

The purpose of this study is to study main characters' (Roxie Hart, Velma Kelly) costumes and color images in the movie "Chicago". First, regarding the costumes and color images in characters, Roxie's straight silhouette slip in skin tone reflected her frailty and monotonous routines in reality. On the other hand, a white beaded dress showed her fame-hungry and self-absorption in fantasy. Also, a low waistline blue dress and a see-through black dress with a white collar were to disguise her guilt and draw sympathy to win a suitcase. Black and contrasting colors of red and blue body-suit style dresses expressed Velma's sensual attraction, aggressiveness, and desperation. Second, these images were reinforced by color images in the backgrounds in the film. On the scene of Velma's 'cell block tango', black and red showed her strong character. Contrasting colors of the red and blue expressed Velma's desire and despair in her act of 'the desperation'. As for images of black color on Roxie's stages, they represented her self-absorption and frustration of failing to attract public attention. On the ending of duet performance of Roxie and Velma, the yellow of the background expressed success and joy in life.

• The Research Journal of the Costume Culture
• /
• v.16 no.2
• /
• pp.249-262
• /
• 2008

The purpose of this study is to contemplate evening dress in contemporary fashion, thereby to analyze aesthetic characteristics of evening dress. For such purposes, this thesis first provides the historical survey of evening dresses, and to conduct a case study of survey of fashion photographs covering $pr{\hat{e}}t-{\acute{a}}t$-porter design products from 2000 to 2007 presented by Valentine. Based upon the historical survey, there are five representative styles in evening dress. Flapper chic looks could be characterized by frequent usage of sleeveless straight silhouette with long or mini hemlines, expressing sensuality, luxury, and ethnicity. Satin Siren looks were characterized by bias-cut, slim, long silhouette, expressing sensuality and luxury. Feminine Ideal looks were characterized by hourglass silhouette and decolltage with feminine details such as bow, pleats and frills, expressing historicism, luxury and sensuality. Freedom and fantasy looks were characterized by ethnic details or modern silhouette with transparent, printed materials, expressing ethnicity, sensuality, and luxury. Finally, postmodern glamourous looks were characterized by body-conscious silhouette with transparent, shiny, or stretch materials, expressing sensuality, experimentalism and luxury.

• Journal of Fashion Business
• /
• v.18 no.4
• /
• pp.80-96
• /
• 2014

The purpose of this study is to consider the expression of costume through the review of cinema costumes and to provide the model of cooperation between fashion and movie industry by analysis of collaboration with fashion brands in the movie . The subjects are the 1974 film directed by Jack Clayton and the 2013 version by Baz Luhrmann. Cinema Fashion was studied by analyzing the costumes of the two main characters, Gatsby and Daisy, in each scene. Gatsby's costume appeared as a model of traditional American classic suit, sensitive G-G look that symbolizes social success and traditional casual style that reflects upper-class life style. Daisy's costume expressed pastel toned luxury flapper look, oriental art deco style, and prestigious jewelry representing high class. The collaborations with fashion brands were carried out with Ralph Lauren and Cartier in 1974 film, and Brooks Brothers, Prada, and Tiffany in 2013. The value of prestige brands that matched the images of the movie was utilized, but marketing strategies for the promotion of fashion goods were not enough in 1974 version. On the other hand, in 2013 film, the effects of collaboration of the movie and fashion brands were forecasted sufficiently and marketing campaigns for promotion were performed in a various ways. The characteristics of collaborations were as follows: (1) the usage of prestige brands value, (2) collections planning and promotion using the stories of a movie, (3) the usage of multidirectional digital media, and (4) multi-dimensional promotion using entertainment factors. In collaborations with the movie, fashion brands could make cooperative relationship to produce the positive effects for promotion and prestige image strategies and draw attention of the people to the movie and fashion.