• 대한방사선방어학회:학술대회논문집
• /
• 2009.11a
• /
• pp.158-159
• /
• 2009

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.5
• /
• pp.171-179
• /
• 2003

An Amplitude Proportional Friction Damper (APFD) is considered in order to improve the characteristics of Coulomb friction damper. The frictional force is proportional to the amplitude in APFD system and the system is non-linear as is Coulomb damper system. A free vibration analysis on the 1-DOF system has made to demonstrate the characteristics of the APFD system. The results show that APFD system has similar damping characteristics to the viscous damper. Also, the solution for the response of a base-excited system with APFD is developed through the application of a Fourier series to represent the frictional force of APFD. It is assumed that no stick-slips occur during any portion of the steady-state oscillation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1995.10a
• /
• pp.241-248
• /
• 1995

본 연구에서 얻어진 주된 결과를 요약하면 다음과 같다. 1) 모달필터의 오차로 인해 모달상태 추정에 오차가 발생할 때, 폐루프 진동제어계가 Lyapunov 점근 안정성을 갖기 위한 필요충분 조건식(26)을 유도하였다. 2) 모달필터의 오차가 클수록 폐루프 진동제어계의 안정성은 점점 나빠지게 된다. 3) 모달필터의 오차 .DELTA.D가 존재할 때, L$_{\infty}$-놈 이론을 적용하여 진동제어 응답성능의 오차의 상한, 식(32)를 유도하였다. 4) 응답성능 오차의 상한은 모달필터 오차 .DELTA.D의 크기에 비례하고 있으며, 비례계수는 모달공간에서의 제어기법이 종류에 따라 다르다.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.5
• /
• pp.377-384
• /
• 2004

An Amplitude Proportional Friction Damper (APFD), in which the friction force is proportional to the system displacement, has been introduced and mathematically modeled. To understand the damping characteristics of APFD, analytical solutions for the impulse response has been derivedand compared to the viscous damper. It is found that APFD system has very similar damping characteristics to viscous damper even though it is a friction damper. APFD may be used as a cost-effective substitution for the viscous damper and could also be used to improve the simple friction or Coulomb dampersince APFD works with no stick-slip and always returns to original position when external disturbance is disappeared.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.717-720
• /
• 2002

An Amplitude Proportional Friction Damper (APFD) system is considered in order to improve the stick-slip characteristics of Coulomb friction damper. The frictional force is proportional to the amplitude in APFD system and the system is non-linear as is Coulomb damper system. The free vibration analysis on an 1-DOF system has conducted to demonstrate the characteristics of the APFD system and the results show that the APFD system has similar damping characteristics to the viscous damper system. It is concluded that the APFD system may become a cost effective substitution for the viscous damper and it also has certain advantages over Coulomb damper system since the APFD system can be designed to work with no stick-slip.

• School Mathematics
• /
• v.18 no.4
• /
• pp.819-838
• /
• 2016

This research analyzed proportional reasoning abilities of the 5th grade students who learned only the basis of ratio and rate and 6th grade students who also learned proportion and cross product strategy. Data were collected through the proportional reasoning tests and the interviews, and then the achievement of the students and their proportional reasoning strategies were analyzed. In the light of such analytical results, the conclusions are as follows. Firstly, there is not much difference between 5th and 6th grade students in the achievement scores. Secondly, both 5th and 6th graders are less familiar with the geometric, qualitative and comparisons tasks than the other tasks. Thirdly, not only 5th graders but also 6th graders used informal strategies much more than the formal strategy. Fourthly, some students can't come up with other strategies than the cross product strategy. Finally, many students have difficulties in discerning proportional situation and non-proportional situations. This study provided suggestions for improving teaching proportional reasoning in elementary schools in Korea as follows: focusing on letting students use their informal strategies fluently in geometric, qualitative, and comparisons tasks as well as algebraic, quantitative, and missing value tasks focusing on the concept of ratio and proportion instead of enforcing the formal strategy.

• Journal of the Korean School Mathematics Society
• /
• v.23 no.1
• /
• pp.25-44
• /
• 2020

This study investigated the representation and algorithms of western mathematics reflected on the algebra domains of Chosun-Sanhak in the 18th century. I also analyzed the co-occurrences and replacement phenomenon between western algorithms and traditional algorithms. For this purpose, I analyzed nine Chosun mathematics books in the 18th century, including Gusuryak and Gosasibijip. The results of this study are as follows. First, I identified the process of changing to a calculation by writing of western mathematics, from traditional four arithmetical operations using Sandae and the formalized explanation for the proportional concept and proportional expression. Second, I observed the gradual formalization of mathematical representation of the solution for a simultaneous linear equation. Lastly, I identified the change of the solution for square root from traditional Gaebangsul and Jeungseunggaebangbeop to a calculation by the writing of western mathematics.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.15 no.2
• /
• pp.74-83
• /
• 2011

For launcher applications, different from other applications, very high flow rate is required which can lead to supply pressure drop against required setting pressure. The supply pressure decrease is closely related to regulator characteristics. In this paper, supply pressure offset is investigated considering regulators as kinds of control systems. Pressure offset of self-operated regulator is analyzed with sensitive parameter defined as the ratio of valve travel to pressure offset. It is shown that pressure offset of self-operating regulator can be improved by incorporating proportional and integral controls and they can be materialized with pilot regulator systems.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.23 no.12
• /
• pp.41-47
• /
• 2009

In this paper, authors performed improvement of control characteristics of an attraction type magnetic levitation system. The attraction type magnetic levitation system has an inherent instability in the system, therefore its controller must have not only proportional-integral gain but also differential gain additionally. In this paper, authors were proposed control algorithm using disturbance observer(DOB) on feedback signal. The computer simulation and experiments were performed for its verification.

• Geotechnical Engineering
• /
• v.14 no.4
• /
• pp.103-116
• /
• 1998

To estimate pure shear strength, 150 sets of triaxial test data were analyzed. The proportional coefficient of shear strength($I_c$) at zero normal stress was nonlinearly decreased as failure coefficient m increases, while the internal friction $\phi_0$ at zero normal stress was nonlinearly increased. The ratio of shear strength $(c/\phi_0)$was inversely proportional to the ratio of the internal friction angles$(\phi/phi_0)$ The shear strength decreased as m increased, while internal friction angle increased. And uniaxial strength was proportional to $c,\phi$ Regression analysis showed that shear strength strongly affects m and $\sigma_c$ The proportional coefficient of shear strength was nonlinearly increased with RMR, while the internal friction angle $(\phi}$was linearly decreased.