• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.2
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• pp.177-188
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• 2001

The paper presents the method to estimate the bottom shear stress driven by waves and current on rough turbulent flow. Parameter adjusting technique is suggested for the computation of bed shear stress driven by uni-directional flow, and the value ofpararneter is determined by comparing the computational results against Bijker's laboratory data. For the computation of combined flow bottom shear stress, two methods are presented; one is the modified Bijker approach (BYO Model) and the other is the modified Fredsoe approach (FY Model), both of which are refined by the present writers. BYO model is again refined in the computation of maximum shear stress, and the final version is tested against Bijkcr's laboratory data.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.3
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• pp.257-264
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• 1995

Various factors are investigated on the bed load transport driven by waves and current, and proper forms of bed load transport formulas mainly used in river hydraulics are chosen for the estimation of combined flow bed load transport after considering the additional factors. The BYO Model is employed for the computation of maximum bed shear stress and mean bed shear stress of the combined flow. The friction factor of uni-directional flow is estimated by using modified Keulegan equation, and equivalent roughness height is determined by obtaining correct answer for the bed shear stress of uni-directional flow. Empirical constant in each bed load formula is determined by applying it to Bijker's laboratory data of bed load transport by waves and current and the formulas obtained are discussed on their final forms with the values of empirical constants.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.178-181
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• 2011

본 연구에서는 광섬유센서를 내장한 스마트강연선을 이용하여 초고성능콘트리트로 제작된 하이브리드 사장교 세그먼트의 횡방향 도입 긴장력을 계측하고 세그먼트 내부의 프리스트레스를 계측하여 즉시손실에 해당하는 정착장치 활동에 의한 손실과 마찰손실을 도로교설계기준(2005)의 설계 마찰손실과 비교하였다. 제작된 2개의 UHPC 사장교 세그먼트는 횡방향 길이 16.7m, 종방향 길이 1.75m, 높이 1.5m이며 각 시험체의 1/4, 1/2, 3/4지점에 긴장력을 계측하기 위해 3개의 FBG센서를 배치하였다. 긴장력은 유압잭을 이용하여 5개의 강연선에 동시에 순차적으로 도입되었으며, 단부에서 최대 도입 긴장력은 세그먼트 1은 734kN, 세그먼트 2는 639kN이었다. 도로교설계기준에 제시된 마찰계수의 중간값(파상마찰계수=0.00405, 곡률마찰계수=0.20)을 사용하여 FBG센서 위치에서 계산된 긴장력은 계측치와 5% 이내의 차이를 보였으며, 정착장치 활동에 의한 순간손실은 긴장단에서 최대 12.8%로 계측되었다. 이로부터 이 연구에서 제시하는 긴장력계측방법의 적용성을 입증할 수 있었으며, 향후 이 방법은 프리스트레스트 콘크리트 교량의 설계기준 마찰계수 개정을 위한 연구에 좋은 도구로 활용될 수 있을 것으로 기대된다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.10a
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• pp.159-163
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• 2001

마찰구동은 다른 구동방식에 비하여 구조가 간단하고, 기계적인 정도를 얻기 쉬우며, 백래쉬 등에 기인하는 비선형 요소인 로스트모션이 없고 관성이 작아 구동력이 작은 이점이 있다. 그 반면에 접촉부에서 미끄럼이 발생하여 큰 구동력을 얻기 어렵고 마찰저항에 의하여 마멸이 생기는 결점이 지적되고 있다. 본 연구에서는 초정밀가공기용 위치결정기구로 마찰구동기구를 사용하기 위하여 위치 결정도에 관한 설계, 구동력의 설계 및 재료의 선택에 관하 여 분석하고 시작품을 제작하여 특성을 연구하였다.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.770-772
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• 1999

본 논문은 마찰력을 갖는 기계시스템에 대한 시간최적제어문제의 엄밀한 해를 제시한다. 특히 최적제어입력을 되먹임 형태로 구한다. 기존의 연구들에서 미리 보상되거나 무시되던 Coulomb 마찰력까지 완전히 고려하여 빠른 응답을 얻는데 제어입력을 최대한 활용할 수 있게 한다.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.183-184
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• 2018

본 논문에서는 능동댐핑을 이용하여 영구자석 동기전동기(PMSM)의 회생 제동 시 기계적 마찰력을 이용한 브레이크와 같은 제동특성을 얻으면서도 최대한의 회생에너지를 얻을 수 있는 기법에 대하여 제안한다. 능동댐핑의 이득 값을 조정하여 가상으로 마찰력을 조정하였으며 최대회생이 가능한 이득 값의 기준을 정의하고, 시뮬레이션을 통해 가상 마찰력의 변화에 따른 감속 궤적 및 PMSM의 출력전력 변화를 확인하였다.

• Korean Journal of Applied Biomechanics
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• v.18 no.1
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• pp.117-127
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• 2008

The purpose of this study was to investigate the relationship between research of mechanical friction and Taekwondo kick performance. For this a Taekwondo kick performance test, A.F.T.S.(Automated Footwear Testing System) and survey about fitting was used. There was a statistically significant difference between all the Taekwondo shoe types. While performing the roundhouse kick there were statistically significant differences in the peak free moment(p=.01) and peak plantar pressure between type A and B. Comfort testing revealed that there were statistically significant difference between type A and B in the five comfort variables tested but not between type B and Type C. There was statistically significant differences between each of the Taekwondo shoes but there was no relationship between the performance and the results of the survey.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2000.09a
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• pp.133-139
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• 2000

일방향흐름의 해류나 천해파에 의한 파운동이나 해저면 가까이 경계층흐름은 주로 난류특성을 갖고 있으며, 난류특성은 완난류, 천이난류, 전난류 등 세 가지 증류로 대별된다. 그 중 완난류와 전난류로 대별하여 합성류 조건은 두 가지로 분류할 수 있다. 즉, 천해파와 해류가 합성될 때 해저면 가까이 난류특성 조건은 Table 1에 제시된 바와 같다. (중략)

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.1 s.41
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• pp.9-16
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• 2005

The purpose of this paper is to present a design procedure of a friction damper for controlling elastic and inelastic responses of building structures under earthquake excitation. The equivalent damping and period increased by the friction damper are estimated using ATC-40 and ATC-55 procedures which provide equivalent linear system for bilinear one, and then a design formula to achieve target performance response level by the friction damper is presented. It is identified that there exists error between the responses obtained by this formula and by performing nonlinear analysis and the features of the error vary according to the hardening ratio, yield strength ratio, and structural period. Equations for compensating the error are proposed based on the least square method, and the results from numerical analysis indicate that the error is significantly reduced. The proposed formula can be used without much error for designing a friction damper for retrofitting a structure showing elastic or inelastic behavior.

• The korean journal of orthodontics
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• v.28 no.1 s.66
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• pp.123-133
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• 1998

The effectiveness of TiN ion-plating was examined with TiN ion-plated Co-Cr wires(.016“, .016”x.022“) on three different types of bracket(TiN ion-plated metal bracket ceramic bracket and plastic bracket). Maximum static frictional forces and characteristic curves obtained from the frictional characteristic graph, were compared and surface roughness of wires and bracket slots before and after friction experiment was observed by SEM. The obtained results were as follows $\cdot$The frictional forces of TiN ion-plated wires were significantly lower than those of non ion-plated wires(p<0.05). $\cdot$On the effect of wire shape, the frictional forces of round wires were significantly lower than those of rectangular wires(p<0.05) $\cdot$As the result of the SEM observation on the wires and bracket slots after the friction experiment the surface of non ion-plated wires was rougher than that of TiN ion-plated ones. $\cdot$The difference between the static frictional forces and the kinetic frictional forces was not significant in case of the TiN ion-plated round ins, but the static frictional forces were a little higher than the kinetic frictional forces in the TiN ion-plated rectangular wires. $\cdot$The static frictional forces were much higher than the kinetic frictional forces in the case of non ion-plated wires.