• Journal of Mechanical Science and Technology
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• 제20권11호
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• pp.2002-2009
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• 2006

This paper is primarily focused on the safe navigation between overtaking and overtaken vessels in restricted waterways under the external forces, such as wind and current. The maneuvering simulation between two ships was conducted to find an appropriate safe speed and distance, which is required to avoid collision. From the viewpoint of marine safety, a greater transverse distance between two ships is more needed for the smaller vessel. Regardless of external forces, the smaller vessel will get a greater effect of hydrodynamic forces than the bigger one. In the case of close navigation between ships under the forces of wind and current, the vessel moving at a lower speed is potentially hazardous because the rudder force of the lower speed vessel is not sufficient for steady-state course-keeping, compared to that of the higher speed vessel.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.89-93
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• 2006

This paper is primarily focused on the safe navigation between overtaking and overtaken vessels in restricted waterways under the external forces, such as wind and current. The maneuvering simulation between two ships was conducted to find an appropriate safe speed and distance, which is required to avoid collision. From the viewpoint of marine safety, a greater transverse distance between two ships is more needed for the smaller vessel. Regardless of external forces, the smaller vessel will get a greater effect of hydrodynamic forces than the bigger one. In the case of close navigation between ships under the forces of wind and current, the vessel moving at a lower speed is potentially hazardous because the rudder force of the lower speed vessel is not sufficient for steady-state course-keeping, compared to that of the higher speed vessel.

• 대한조선학회지
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• 제12권1호
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• pp.83-90
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• 1975

In order to establish a stability and buoyancy criteria of a floating vessel, the geometrical property as well as external forces and moments be dealt with. This paper discusses in general terms hidden but more salient factors of forces and moments of both natural and artificial origin, particularly wind, with regard to vessels of more general type such as oil drilling rigs.

• Tribology and Lubricants
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• 제22권6호
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• pp.342-349
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• 2006

In this study, a dynamic behavior of rotor-bearing system used in CNG compressor has been investigated using the combined methodologies of finite elements and transfer matrices. The finite element is formulated including the field element for a shaft section and the point element for roller bearings. The Houbolt method is used to consider the time march for the integration of the system equations. The transient whirl response of rotating shaft supported on roller bearings is obtained, considering compression forces and unbalance forces at eccentric crank-pin part. And, the steady state displacements of the rotor are compared with a variation in stiffness coefficient of roller bearings. Results show that the loci of crankshaft considering unbalance forces and external compression forces are more severe in whirl motion than with only unbalance forces.

• 한국가금학회지
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• 제50권1호
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• pp.23-30
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• 2023

본 연구는 농장 내 계란 이송시스템에서 발생하는 충격 정도를 파악하고 파란 발생률과 비교하여 문제점을 개선하기 위해 무창계사 12개 농장을 대상으로 하여 무선 전자계란(Wireless Egg Node II)를 활용하여 조사하였다. 전체적으로 충격 크기는 세척기와 건조기 연결 부분, 컨베이어 연결부분, 트랜스퍼, 정렬기, 집란 엘리베이터, 팩커, 계란 이송 연결부분, 알받이 순으로 나타났으나 농장에 따라 충격정도 및 충격발생 지점에 많은 차이가 있었다. 계란의 충격강도와 파란 발생률은 높은 정(+)의 상관관계가 나타났으며 일회성 충격보다는 누적된 충격의 양에 따라 파각발생이 높았고, 조사 지점에 따라 5~38 G까지 다양하며 총 파각란 발생률도 3.2%~14.5%로 나타났다. 파각 발생률을 낮추기 위해서는 난각 품질이 높은 계란을 생산하고자 하는 노력도 중요하지만 난각강도가 우수해도 최종제품에 난각이 파손되는 상황을 고려할 때 실금란 발생을 초래하는 계란이송라인 개선이 절대적으로 필요한 것으로 조사되었다.

• Transactions on Control, Automation and Systems Engineering
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• 제4권1호
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• pp.2-8
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• 2002

This paper discusses haptic display for grasping a virtual object by two fingers. Much research has been done on fundamental analysis for stability of haptic display. But it is difficult to apply the results immediately to grasping situations by two fingers, since the studies usually deal with a single device and a single object and the fingertip force in grasping situations has two components, internal and external components. The conventional methods, which specify the coupling impedance at each contact point separately, have no other alternative but to specify the impedance for the sum of the internal and external components. So even if only the impedance for the external force should be changed, the impedance for the internal force is also changed at the same time. In this paper, a new method, in which the coupling impedance is specified separately for the internal and external forces, is proposed and the stability of the proposed method is discussed using passivity analysis for 1 -DOF(Degree-Of-Freedom) system. Finally, some experiments are performed to study the effects of the proposed method.

• Journal of Mechanical Science and Technology
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• 제16권6호
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• pp.810-818
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• 2002

When the contribution of lightweight components to the total energy of a system is small, tole inertia effects are sometimes ignored by replacing them to massless links. For example, a revolute-spherical massless link generates two kinematic constraint equations between adjacent bodies and allows four relative degrees of freedom. In this paper, to implement a massless link systematically in a computer program using the velocity transformation technique, the velocity transformation matrix of massless links is derived and numerically implemented. The velocity transformation matrix for a revolute-spherical massless link and a revolute-universal massless link are appeared as a 6$\times$4 matrix and a 6$\times$3 matrix, respectively. A massless link model in a suspension composite joint transmitting external forces is also developed and the numerical efficiency of the proposed model is compared to a conventional multibody model. For a massless link transmitting external forces, forces acting on links are resolved and transmitted to the attached points with a quasi-static assumption. Numerical examples are presented to verify the formulation.

• Smart Structures and Systems
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• 제24권6호
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• pp.693-707
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• 2019

This paper proposes an integrated safety assessment method that can take multiple sources data into consideration based on a data fusion approach. Data cleaning using the Kalman filter method (KF) was conducted first for monitoring data from each sensor. The inclination data from the four tilt sensors of the same monitoring section have been associated to synchronize in time. Secondly, the finite element method (FEM) model was established to physically correlate the external forces with various structural responses of the shield tunnel, including the measured inclination. Response surface method (RSM) was adopted to express the relationship between external forces and the structural responses. Then, the external forces were updated based on the in situ monitoring data from tilt sensors using the extended Kalman filter method (EKF). Finally, mechanics parameters of the tunnel lining were estimated based on the updated data to make an integrated safety assessment. An application example of the proposed method was presented for an urban tunnel during a nearby deep excavation with multiple source monitoring plans. The change of tunnel convergence, bolt stress and segment internal forces can also be calculated based on the real time deformation monitoring of the shield tunnel. The proposed method was verified by predicting the data using the other three sensors in the same section. The correlation among different monitoring data has been discussed before the conclusion was drawn.

• 대한인간공학회:학술대회논문집
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• 대한인간공학회 1992년도 추계학술대회논문집
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• pp.46-53
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• 1992

Finger movements in the sagittal plane mainly consist of flexion and extension about the metacarpophalangeal(MCP) and proximal interphalangeal(PIP) joints. A kinematic finger model was developed with the assumption of constant tendon moment arms. Equations of static equilibrium were derived for the finger model using the principle of virtual work. Equations of static equilibrium for the finger model were indeterminate since only three equations were available for five unknown variables(forces). The number of variables was reduced based on information on muscular activities in finger movements. Then the amounts of forces which muscles exerted to maintain static equilibrium against external loads were computed from the equilibrium equations. The muscular forces were expressed mathematically as functions of finger positions, tendon moment arms, lengths of phalanges, and the magnitude and direction of external load. The external finger strength were computed using the equations of muscular forces and anatomical data. Experiments were performed to measure finger strengths. Measurements were taken in combinations of four finger positions and four directions of force exertions. Validation of the finger models and of procedure to estimate finger strengths was done by comparing the results of computations and experiments. Significang differences were found between the predicted and measured finger strengths. However, the trends of finger strengths with respect to finger positions were similar inboth the predicted and measured. These findings indicate that the finger model and the procedure to predict finger strengths were correctly developed.

• Geomechanics and Engineering
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• 제6권5호
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• pp.503-515
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• 2014

On the basis of Hoek-Brown failure criterion, a numerical solution for the shape of collapsing block in the rectangular cavity subjected to seepage forces is obtained by upper bound theorem of limit analysis. The seepage forces obtained from the gradient of excess pore pressure distribution are taken as external loadings in the limit analysis, and the pore pressure is easily calculated with pore pressure coefficient. Thus the seepage force is incorporated into the upper bound analysis as a work rate of external force. The upper solution of the shape of collapsing block is derived by virtue of variational calculation. In order to verify the validity of the method proposed in the paper, the result when the pore pressure coefficient equals zero, and only hydrostatic pressure is taken into consideration, is compared with that of previous work. The results show good effectiveness in calculating the collapsing block shape subjected to seepage forces. The influence of parameters on the failure mechanisms is investigated.