• Aerospace Engineering and Technology
• /
• v.1 no.2
• /
• pp.105-112
• /
• 2002

In this paper, a servo filter design for the gimbal engine actuator system of KSR-III(Korea Sounding Rocket-III) is considered. A reasonable filter structure is determined based on the actuator analytic models. The servo filter consists of a 2-nd order lowpass filter and a 1-st order compensator. The lowpass filter is required to protect the actuator from high frequency vibration, and the compensator to enhance the resulting stability. A Butterworth type servo filter is considered as the simplest one. The final servo filter type is determined by evaluating simultaneously both high frequency gain reduction performance and the corresponding KSR-III stability margin. Consequently it is revealed that a notch type servo filter located on the error between command signal and feedback signal in the control loop is very effective. Later, based on the proposed servo filter type, an onboard servo filter hardware of KSR-III will be designed and tested.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.9 no.2
• /
• pp.243-248
• /
• 2014

The permanent magnet linear synchronous motors facilitate maintenance, for it is structurally simple compare to rotating machine and has lots of advantage such as a precision control, high speed, high thrust and so on. However, it causes an increase of material cost because of structural characteristics that need to arranges the armature on the full length of transportation lines. Thus, in order to resolve this problem, we propose the discontinuous arrangement method of the armature but the edge always exists due to the structure when the armature is arranged discontinuously. Due to this edge, the cogging force is greatly generated and it causes thrust force ripple generating noise, vibration and decline of performance. Therefore, in this paper, we examined the characteristic of end edge according to the skew angle through 3-D numerical analysis using finite element method(FEM) and improved the operation characteristics.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.23 no.4
• /
• pp.435-443
• /
• 2010

This study presents key parameters for the structure installed with MR controller in reducing its responses. MR controller is regarded as Bingham model of which control forces are frictional and viscous ones. The parameters are identified as friction force ratios, $R_f$ and $R_h$ which are, respectively, ratio of MR controller friction force to static restoring force for free vibration and ratio of the friction force to amplitude of harmonic force. Structure-MR controller system shows nonlinear response behavior due to friction force. Energy balance strategy is adopted to transform the behavior to linear one with equivalent damping ratio. Finally, proposed equivalent linear process is compared to the nonlinear one, which turns out to give acceptably good results.

• Journal of Dental Anesthesia and Pain Medicine
• /
• v.23 no.6
• /
• pp.317-325
• /
• 2023

Background: Local anesthetic injections may induce pain in children, leading to fear and anxiety during subsequent visits. Among the various approaches recommended to reduce pain, one is the use of a Buzzy Bee^TM device that operates on the concept of gate control theory and distraction. The literature regarding its effectiveness during the deposition of local anesthesia remains limited; hence, the aim of the present study was to determine the efficacy of extraoral cold and vibrating devices in reducing pain perception during the deposition of local anesthesia. Methods: A split-mouth crossover study in which 40 children aged 3-12 years requiring maxillary infiltration or inferior alveolar nerve block for extractions or pulp therapy in the maxillary or mandibular posterior teeth were included. The control intervention involved the application of topical anesthetic gel for one minute (5% lignocaine gel), followed by the administration of local anesthetic (2% lignocaine with 1:80,000 adrenaline) at a rate of 1 ml/ minute. Along with the control protocol, the test intervention involved using the Buzzy Bee^TM device for 2 minutes before and during the deposition of the local anesthetic injection. The heart rate and face, legs, arms, cry, and consolability revised (FLACC-R) scale scores were recorded by the dentist to assess the child's pain perception. Results: The mean age of the participants in Group A and Group B was 7.050 ± 3.12 years and 7.9 ± 2.65 years respectively. A reduction in the mean heart rate and FLACC-R score was observed during the deposition of local anesthetic solution in the tissues when the Buzzy Bee^TM was used in both groups at different visits in the same subjects (P < 0.05) The Buzzy Bee^TM device was effective in reducing the heart rate and FLACC-R scores when used during maxillary infiltration and inferior alveolar nerve block local anesthesia techniques (P < 0.05). Conclusion: The use of extraoral cold and vibrating devices significantly reduces pain perception during local anesthetic deposition in pediatric patients. Considering the results of this study, the device may be incorporated as an adjunct in routine dental practice while administering local anesthesia in children.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2004.03b
• /
• pp.433-441
• /
• 2004

국내 발파 현장에서 사용되고 있는 폭약류에 강력한 폭굉력을 충분하게 발휘하기 위해서는 뇌관(Blasting cap, Detonator)의 역할이 중요하다. 그리고 이 뇌관의 정밀성에 따라 발파 효율의 차이가 있게된다. 초기의 도화선 및 공업뇌관에서 시작하여 현재 정밀성 면에서는 MS(Milli Second)뇌관의 경우 20ms또는 25ms의 정밀한 시차로 순차적으로 기폭함으로써 발파효과의 극대화와 소음 및 진동제어에 큰 효과를 이루었으나, 최근 개발된 진자뇌관의 경우 자체 IC회로를 내징하여 $1{\sim}2ms$의 초정밀시차(오차범위 $0.1{\sim}0.2ms$이내)의 구현이 가능해짐에 따라 이를 적절히 조합하여 설계함으로써 각종 제어발파, 파쇄도 향상, 암손상영역 저감 등의 효과에 대해 국외에서 연구가 진행되고 있는 것으로 알려지고 있다. 그러나 우리나라와 같이 도심지 발파 및 터널이나 노천 현장 근거리에 보안물건이 위치해 있어 진동제어가 절실히 필요한 상황에서 진동제어에 효과가 있는 것으로 알려진 전자뇌관에 대한 연구가 이루어지고 있지 않은 상황에서 본 연구는 앞으로 이루어질 전사뇌관에 대한 수많은 연구에 기초자료를 제공하고자 실시하였다. 본 연구에서는 이를 위해 국내에서 최초로 2003년 9월 23일 강원도 양구 지역읜 00터널에 전자뇌관을 이용한 시험발파를 실시하였고, 발파에 의한 진동 등을 조사하여 그 효율성을 검토하였다. 이를 위해 전자뇌관의 특성과 장점을 최대한 살리기 위하여 각공을 발파하는 방식, 즉 1지발에 1공을 발파하는 방식을 채택하고 비전기 뇌관과 전자뇌관으로 설계를 하여 각각의 발파효율을 비교하여 보았다. 그 결과 발파신동의 경우 비전기뇌관을 이용하여 1공씩을 1지발로 발파를 한 경우에는 18${\sim}$56%의 진동저감 효과가 있었고, 번 설계에 의해 진해오딘 발파에 비하여는 최대 70% 이상의 진동저감 효과가 있는 것으로 나타났다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.42 no.6
• /
• pp.815-824
• /
• 2022

Among the main facilities of the power plant, the circulating water used for cooling the power generation system is supplied through the Circulation Water Intake Basin (CWIB). The vortexes of various types generated in the Pump Sump (PS) of CWIB adversely affect the Circulation Water Pump (CWP) and pipelines. In particular, the free surface vortex accompanied by air intake brings about vibration, noise, cavitation etc. and these are the causes of degradation of CWP performance, damage to pipelines. Then power generation is interrupted by the causes. Therefore, it is necessary to investigate the hydraulic characteristics of CWIB through the hydraulic model experiment and apply an appropriate Anti Vortex Device (AVD) that can control the vortex to enable smooth operation of the power plant. In general, free surface vortex is controlled by Curtain Wall (CW) and the submerged vortex is by the anti vortex device of the curtain wall. The detailed specifications are described in the American National Standard for Pump Intake Design. In this study, the circulating water intake part of the Tripoli West 4×350 MW power plant in Libya was targeted, the actual operating conditions were applied, and the vortex reduction effect of the anti vortex device generated in the suction tank among the circulating water intake part was analyzed through a hydraulic model experiment. In addition, a floor splitter was basically applied to control the submerged vortex, and a new type of column curtain wall was additionally applied to control the vortex generated on the free surface to confirm the effect. As a result of analyzing the hydraulic characteristics by additionally applying the newly developed Column Curtain Wall (CCW) to the existing curtain wall, we have found that the vortex was controlled by forming a uniform flow. In addition, the vortex angle generated in the circulating water pump pipeline was 5° or less, which is the design standard of ANSI/HI 9.8, confirming the stability of the flow.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.26 no.1
• /
• pp.93-100
• /
• 2008

The parameters of lens such as focal length, focus, and aperture stop changes while shooting the scenes with zoom lens. Especially, zooming action dramatically changes the geometry of lens system that causes significant change of lens model. We investigated how the lens model changes while zooming in general shooting condition. Each parameters of lens model was estimated and checked whether they can be modeled well in the condition of auto-controlling focus, aperture and vibration reduction. In order to do this, calibration images were taken, modeled in different fecal length setting. And changing patterns of models were inspected to find out if there is some elements that have some particular pattern in changing with respect to focal length. The result showed us that although we didn't control the focus and aperture setting, there's specific changing patterns in radial and do-centering distortion. Especially, the strong linear correlation was found between coefficient of $r^2$ and focal length. It is expected that many parts of distortion can be eliminated without additional self calibration even if zoom operation is done when shooting the scenes if we know its fecal length and model of this coefficient.