• Tribology and Lubricants
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• 제36권3호
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• pp.147-152
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• 2020

This paper is within the framework of an adhered complete contact problem wherein the contact between a half plane and sharp edged indenter, both of which are elastic in character, is constituted. The eigensolutions of the contact shear and normal stresses, σ_rq and σ_q, respectively, are evaluated via asymptotic analysis. The ratio of σ_rq/σ_qq is investigated and compared with the coefficient of friction, μ, of the contact surface to observe the propensity to slip on the contact surface. Interestingly, there exists a region of |σ_rθ/σ_θθ| ≥ |μ|. Thus, slipping can occur, although the problem is solved under the condition of an adhered contact without slipping. Given that a tribological failure potentially occurs at the slipping region, it is important to determine the size of the slipping region. This aspect is also factored in the paper. A simple example of the adhered contact between two elastically dissimilar squares is considered. Finite element analysis is used to evaluate generalized stress intensity factors. Furthermore, it is repeatedly observed that slipping occurs on the contact surface although the size of it is extremely small compared with that of the contacting squares. Therefore, as a contribution to the field of contact mechanics, this problem must be further explained logically.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.41-41
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• 2000

biped robots are expected to robustly traverse terrain with various unknown surfaces. The robot will occasionally encounter the unexpected events in made-for human environments. The slipping is a very real and serious problem in the unexpected events. The robot system must respond to the unexpected slipping after it has occurred and before control is lost. This paper proposes a reflex control method for biped robots to recover from slipage. Computer simulations with the 6-DOF environment model which consists of nonlinear dampers, nonlinear springs, and linear springs, show that the proposed method is effective in preventing fall-down due to slippage.

• 한국전문물리치료학회지
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• 제10권1호
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• pp.97-108
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• 2003

Slipping during various kinds of movement often leads to potentially dangerous incidents of falling. The purpose of this paper was to review some of the research performed in the field including such topics as rating scales for balance, kinematics and kinetics of slipping, adaptation to slippery conditions, postural and balance control, and protective movement during falling. Controlling slipping and fall injuries requires a multifaceted approach. Environmental conditions (state of floor surface, tidiness, lighting, etc), work task (walking, carrying, pushing, lifting, etc), and human behavior (anticipation of hazards, adaptation to risks, risk taking, etc) must be accounted for in the assessment of slip and fall-related risks. Future directions of research must deal with modeling of basic tribophysical, biomechanical, and postural control process involved in slipping and falling.

• Structural Engineering and Mechanics
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• 제4권5호
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• pp.469-484
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• 1996

Green's functions are obtained in exact closed-forms for the elastic fields in bi-material elastic solids with slipping interface and differing transversely isotropic properties induced by concentrated point and ring force vectors. For the concentrated point force vector, the Green functions are expressed in terms of elementary harmonic functions. For the concentrated ring force vector, the Green functions are expressed in terms of the complete elliptic integral. Numerical results are presented to illustrate the effect of anisotropic bi-material properties on the transmission of normal contact stress and the discontinuity of lateral displacements at the slipping interface. The closed-form Green's functions are systematically presented in matrix forms which can be easily implemented in numerical schemes such as boundary element methods to solve elastic problems in computational mechanics.

• 제어로봇시스템학회논문지
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• 제16권1호
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• pp.5-11
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• 2010

An adaptive formation control approach is proposed for nonhonolomic multiple mobile robots considering unknown slipping and skidding. It is assumed that unknown slipping and skidding effects are bounded by unknown constants. Under this assumption, the adaptive technique is employed to estimate the bounds of unknown slipping and skidding effects of each mobile robot. To deal with the skidding effect included in kinematics, the dynamic surface design approach is applied to design a local controller for each mobile robot. Using Lyapunov stability theorem, the adaptation laws for tuning bounds of slipping and skidding are induced and it is proved that all signals of the closed-loop system are bounded and the tracking errors and the synchronization errors of the path parameters converge to an adjustable neighborhood of the origin. Finally, simulation results are provided to verify the effectiveness of the proposed approach.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회(2)
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• pp.902-903
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• 2005

• 한국안전학회지
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• 제27권5호
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• pp.1-8
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• 2012

The purpose of this study were to evaluate the dynamic characteristics of the portable slipmeters with respect to actual slipping and to compare their output with those of force platform. The selected slipmeters were commonly used devices for slipperiness measurement in situ floors. Their output quantity represented force (BOT-3000), loss of energy(British pendulum striker) and angle of inclination(English XL). The validity of these devices was studied with respect to actual slipping using a force platform. The precision of these devices was also evaluated with force platform. Based on dynamics of human subject behavior when slipping during normal walking, the all devices tested in this study showed poor performances: low built up ratio, low normal pressure, and long contact time prior to slip. Nevertheless, their results reasonably correlated with those calculated from the ground reaction forces generated by the operation of the selected slipmeters on the force platform although the absolute values of COF from these three devices could be quite different. Also the results showed good repeatability under the some test conditions.

• 한국정보과학회논문지:정보통신
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• 제32권4호
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• pp.525-534
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• 2005

본 논문은 무선 센서 네트워크에 있어서 궤도 기반 매취메이킹 서비스를 위한 질의 이탈 및 이의 방지에 관한 것이다. 이러한 문제는 정보 구독 궤도를 따라 전파되는 질의가 정보 발간 궤도와 기하학적으로는 겹침에도 불구하고 정보를 획득하지 못할 때 발생한다 이에 따라 질의를 재 제출하거나 새로운 구독 궤도를 시작함으로 인한 시간 지연이 초래되어 최악에는, 궤도내의 루핑이나 네트워크 전체로의 메시지 범람을 야기한다. 이 문제를 정형적으로 다루고 그 해결책을 제시한다. 먼저, 노드들이 존재하는 영역을 논리적으로 작은 그리드들로 분할하고, 그리드 기반 멀티캐스트 다음-흡 선택 알고리즘을 제안한다. 제안 알고리즘은 궤도 설정을 직선형태로 유지하도록 시도함은 물론 수신 노드들의 분포 및 틈새 없는 그리드 단위의 멀티캐스트를 고려한다 이러한 알고리즘에 의거하여 정보 발간 및 구독을 시행하는 경우 질의 이탈이 궁극적으로 방지됨을 증명한다. 제안 알고리즘이 탐욕적 송출과 같은 비 그리드 기반 알고리즘과 GAE와 같은 고정 크기의 그리드 접근법 보다 이웃 노드들의 전력을 더 적게 소모함을 알 수 있다.

• Fibers and Polymers
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• 제5권1호
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• pp.25-30
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• 2004

The present paper reports the impact of thermal treatment on the characteristics of core-sheath type hybrid technical yarns. The core-sheath type hybrid yams are prepared using DREF-III technology. Polyester and glass multifilaments are used as core components whereas the cotton and polyester staple fibers are the sheath components wrapped around the core filament with different proportions to form a hybrid structure. The thermal treatment is carried out both in dry and in wet state under relaxed condition and the thermal shrinkage, sheath-slipping resistance and tensile and bending properties of hybrid yarns have been studied. Thermal treatment markedly increases the thermal shrinkage and sheath-slipping resistance of hybrid yarns with polyester multifilament in core, but insignificant effect for yarns with glass multifilament in core. Breaking elongation of hybrid yams with polyester multifilament in core increases with treatment temperature. The hybrid yarns with glass multifilament in core are least affected by thermal treatment.

• 소음진동
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• 제6권6호
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• pp.819-825
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• 1996

Nonlinear dynamic characteristics of rubbing phenomenon in rotor dynamics are investigated experimentally and numerically. Rubbing phenomenon occurs when rotor contacts with stator during whirling and causes the large amplitude of vibration, high whirl frequencies, and possibly catastrophic failure. Rubbing has various types of forward whirl, backward rolling, backward slipping, and partial rub depending on the system parameters of rotating machinery and running speed. Experiments are performed for forward whirl and backward whirl. And numerical analysis are conducted to explain the changes between backward rolling and backward slipping. Experimental and numerical results show that the types of whirling motion depends on the friction coefficient between rotor and stator and the eccentricity of rotor.