• Bulletin of the Korean Chemical Society
• /
• v.30 no.2
• /
• pp.429-434
• /
• 2009

The OH($X^2{\Pi},\;{\nu}$"=0, 1) internal state distributions from the reaction of electronically ground state oxygen atoms with HSi$Cl_3$ were measured using laser-induced fluorescence. The ground-state O$(^3P_J)$ atoms with kinetic energies above the reaction barrier were produced by photolysis of N$O_2$ at 355 nm. The OH product revealed strong vibrational population inversion, P(${\nu}$"=1)/P(${\nu}$"=0) = 4.0 ${\pm}$ 0.6, and rotational distributions in both vibrational states exhibit substantial rotational excitations to the limit of total available energy. However, no preferential populations in either of the two $\Lambda$ doublet states were observed from the micropopulations, which supports a mechanism involving a direct abstraction of hydrogen by the atomic oxygen. It was also found that the collision energy between O and HSi$Cl_3$ is effectively coupled into the excitation of the internal degrees of freedom of the OH product ($$ = 0.62, and $<\;f_{rot}>$ = 0.20). The dynamics appear consistent with expectations for the kinematically constrained reaction which supports the reaction type, heavy + light-heavy $\rightarrow$ heavy-light + heavy (H + LH′ $\rightarrow$ HL + H′). The dynamics of oxygen atom collision with HSi$Cl_3$ are discussed in comparison to those with Si$H_4$.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.41 no.6
• /
• pp.507-515
• /
• 2017

Flexible multibody simulations are widely used in the industry to design mechanical systems. In flexible multibody dynamics, deformation coordinates are described either relatively in the body reference frame that is floating in the space or in the inertial reference frame. Moreover, these deformation coordinates are generated based on the discretization of the body according to the finite element approach. Therefore, the formulation of the flexible multibody system always deals with a huge number of degrees of freedom and the numerical solution methods require a substantial amount of computational time. Parallel computational methods are a solution for efficient computation. However, most of the parallel computational methods are focused on the efficient solution of large-sized linear equations. For multibody analysis, we need to develop an efficient formulation that could be suitable for parallel computation. In this paper, we developed a subsystem synthesis method for a flexible multibody system and proposed efficient parallel computational schemes based on the OpenMP API in order to achieve efficient computation. Simulations of a rotating blade system, which consists of three identical blades, were carried out with two different parallel computational schemes. Actual CPU times were measured to investigate the efficiency of the proposed parallel schemes.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• v.12 no.2
• /
• pp.121-130
• /
• 2012

This paper proposes an intuitive real-time robot control system using human body movement. Recently, it has been developed that motion generation for humanoid robots with reflecting human body movement, which is measured by a motion capture. However, in the existing studies about robot control system by human body movement, the detailed structure information of a robot, for example, degrees of freedom, the range of motion and forms, must be examined in order to calculate inverse kinematics. In this study, we have proposed Associative Motion Generation as humanoid robot motion generation method which does not need the detailed structure information. The associative motion generation system is composed of two neural networks: nonlinear principal component analysis and Jordan recurrent neural network, and the associative motion is generated with the following three steps. First, the system learns the correspondence relationship between an indication and a motion using training data. Second, associative values are extracted for associating a new motion from an unfamiliar indication using nonlinear principal component analysis. Last, the robot generates a new motion through calculation by Jordan recurrent neural network using the associative values. In this paper, we propose a real-time humanoid robot control system based on Associative Motion Generation, that enables user to control motion intuitively by human body movement. Through the task processing and subjective evaluation experiments, we confirmed the effective usability and affective evaluations of the proposed system.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.11
• /
• pp.1207-1214
• /
• 2014

Under excessive plasticity, the fracture toughness of a material depends on its size and geometry. Under fully yielded conditions, the stresses in a material near its crack tip are not unique but rather depend on the geometry. Therefore, the single-parameter J-approach is limited to a high-constraint crack geometry. The JQ theory has been proposed for establishing the crack geometry constraints. This approach assumes that the crack-tip fields have two degrees of freedom. In this study, the crack-tip stress field of a fully circumferential surface-cracked pipe under combined loads is investigated on the basis of the JQ theory by using finite element analysis. The combined loads are a tensile axial force and the thermal gradient in the radial direction. Q-stresses of the crack geometry and its loading state are used to determine the constraint effects. The constraint effects of secondary loading are found to be greater than those of primary loading. Therefore, thermal shock is believed to be the most severe loading condition of constraint effects.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.5
• /
• pp.597-604
• /
• 2010

This study focuses on the design of a mechanical joint for a zero moment crane (ZMC), which is a specialized loading/unloading system used in a mobile harbor (MH). The mechanical joint is based on the concept of zero moment point (ZMP), and it plays an important role in stabilizing a ZMC. For effective stabilization, it is necessary to ensure that the mechanical joint is robust to a wide variety of loads; further, the joint must allow the structures connected to it to perform rotational motion with two degrees of freedom By adopting a traditional design process, we designed a new mechanical joint; in this design, a universal joint is coupled with a spherical joint, and then, deformable rolling elements are incorporated. The rolling elements facilitate load distribution and help in decreasing power loss during loading/unloading. Because of the complexity of the proposed system, Kriging-based approximate optimization method is used for enhancing the optimization efficiency. In order to validate the design of the proposed mechanical joint, a structural analysis is performed, and a small-scale prototype is built.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.3 no.4
• /
• pp.11-22
• /
• 1999

In this study, the validity of the currently used seismic regulations for seismic isolated building structures is investigated, and a new formula for vertical distribution of seismic load is proposed. The distribution formula in UBC-91 did not provide sufficient safety, and thus revised in 1994. However it is pointed out that the revised formula overestimates the seismic load because of its similarity to that of the fixed-base structure. Therefore, in the proposed approach, it is intended to satisfy safety, economy, and applicability by combining the mode shapes of the seismic isolated structure idealized as two degrees of freedom system and those of fixed-base structure. For verification of the proposed formula, both a moment resisting frame and a shear wall system are analyzed. The results obtained from the proposed method turn out to be close to the results from a dynamic analysis.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.19 no.4
• /
• pp.451-456
• /
• 2009

In this paper, a virtual force is generated and fed back to the operator to make the teleoperation more reliable, which reflects the relationship between a slave robot and an uncertain remote environment as a form of an impedance. In general, for the teleoperation, the teleoperated mobile robot takes pictures of the remote environment and sends the visual information back to the operator over the Internet. Because of the limitations of communication bandwidth and narrow view-angles of camera, it is not possible to watch certain regions, for examples, the shadow and curved areas. To overcome this problem, a virtual force is generated according to both the distance between the obstacle and the robot and the approaching velocity of the obstacle w.r.t the collision vector based on the ultrasonic sensor data. This virtual force is transferred back to the master (two degrees of freedom joystick) over the Internet to enable a human operator to estimate the position of obstacle at the remote site. By holding this master, in spite of limited visual information, the operator can feel the spatial sense against the remote environment. It is demonstrated by experiments that this collision vector based haptic reflection improves the performance of teleoperated mobile robot significantly.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.8 no.2
• /
• pp.185-196
• /
• 1988

In this study, a method of nonlinear dynamic analysis of suspension bridges subjected to random wind loads is pre.sented. The nonlinearity considered is the one due to the interaction between the motion of the bridge girder and the tertsion variation of the main cables. The equation of motion is formulated using a continuum approach. The coupling between the vertical and torsional motions are included in the analysis. The equation of motion is solved by using the mode superposition method. The analysis is carried out in the frequency domain utilizing the stochastic linearization technique on to the modal equations. In the linearization procedure, the nonlinear terms are approximated as linear ones with constant terms. The verification of the method has been performed on a case with four modal degrees of freedom. Example analyses are carried out on two suspension bridges for various wind speeds and wind force parameters. Numerical results indicate that, by including the nonlinearity into the analysis, the dynamic responses of the bridges, particularly in the vertical direction, change considerably.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.13 no.1
• /
• pp.75-85
• /
• 2000

When applying a system identification technique, which incorporates an experimental model to a corresponding finite element model of a structure, one of the major problems is the large difference in the numbers of degrees of freedom (dof) between the two models. While there are large number of dofs in a finite element model, the number of measurement points is practically limited. So it is very difficult to incorporate them. Especially rotational dofs are hard to measure. In this study a method is presented for estimating structural dynamic responses at unmeasurable locations in frequency domain. The proposed method is tested numerically and the feasibility for practical application has been demonstrated through an example structure under moving loads, where translational and rotational dofs of beam at a center point are estimated from the partial measurements of responses at accessible points.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.15 no.3
• /
• pp.481-490
• /
• 2002

The purpose of this paper is to evaluate the efficiency of various solution techniques and propose new efficient solution techniques for space trusses. Solution techniques used in this study are three load control methods (Newton-Raphson Method, modified Newton-Raphson Method, Secant-Newton Method), two load-displacement control methods(Arc-length Method, Work Increment Control Method) and three combined load-displacement control methods(Combined Arc-length Method I , Combined Arc-length MethodⅡ, Combined Work Increment Control Method). To evaluate the efficiency of these solution techniques, we must examine accuracy of their solutions, convergences and computing times of numerical examples. The combined load-displacement control methods are the most efficient in the geometric nonlinear solution techniques and in tracing post-buckling behavior of space truss. The combined work increment control method is the most efficient in tracing the buckling load of spate trusses with high degrees of freedom.