• Journal of Korea Water Resources Association
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• v.42 no.9
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• pp.759-771
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• 2009

The electricity cost of pumping system accounts for a large part of the total operating cost for long distance water supply networks. This study presents a method based on dynamic programming for establishing an joint optimal operation of pumps and storages system on a hourly basis. Analysis is taken of the relative efficiencies of the available pumps, the structure of the electricity tariff, the consumer-demand pattern, and the storage characteristics and operational constraints of the pipe. The possible system objectives and constraints are described. An application of the method to the existing Yangju Water Supply System consisted of two pump station and 5 storage pools under the condition of expanding pumping facility in the part of the Capital Area Water Supply System is presented, showing that considerable electricity cost savings are remarkable. The approach was found to be implementable in real system operation and large-scale water supply system design in respect of minimizing life-cycle total cost.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.10
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• pp.1261-1267
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• 2013

In multibody mechanical systems, low-degree-of-freedom (DOF) joints such as revolute and translational joints are much more frequently used than high-DOF joints. In order to formulate kinematic constraint equations, especially for low-DOF joints, in an efficient and systematic manner, this paper presents a parametric generalized coordinate formulation as a new approach for describing constraint equations. In the proposed approach, joint constraint equations are formulated in terms of a mixed set of Cartesian and parametric generalized coordinates, which drastically reduces the complexity and computational cost of the partial derivatives of the constraints such as the constraint Jacobian. The proposed formulation is validated using a simple cylinder-crank system with an implicit integrator.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.44.1-44.1
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• 2015

We present joint constraints on the number of effective neutrino species $N_{eff}$ and the sum of neutrino masses ${\Sigma}m_{\nu}$, based on a technique which exploits the full information contained in the one-dimensional Lyman-${\alpha}$ forest flux power spectrum, complemented by additional cosmological probes. In particular, we obtain $N_{eff}=2.91{\pm}0.22$ (95% CL) and ${\Sigma}m_{\nu}$ < 0.15 eV (95% CL) when we combine BOSS Lyman-${\alpha}$ forest data with CMB (Planck+ACT+SPT+WMAP polarization) measurements, and $N_{eff}=2.88{\pm}0.20$ (95% CL) and ${Sigma}m_{\nu}$ < 0.14 eV (95% CL) when we further add baryon acoustic oscillations. Our results tend to favor the normal hierarchy scenario for the masses of the active neutrino species, provide strong evidence for the Cosmic Neutrino Background from $N_{eff}{\approx}3$($N_{eff}=0$ is rejected at more than $14{\sigma}$), and rule out the possibility of a sterile neutrino thermalized with active neutrinos (i.e., $N_{eff}=4$) - or more generally any decoupled relativistic relic with $${\Delta}N_{eff}{\sim_=}1$$ - at a significance of over $5{\sigma}$, the strongest bound to date, implying that there is no need for exotic neutrino physics in the concordance ${\Lambda}CDM$ model.

• Journal of the Korean Society of Industry Convergence
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• v.20 no.4
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• pp.299-305
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• 2017

This study proposes a new technique to design and control of robot hand gripper for assembling and disassembling of a machine parts. The motion equation describing dynamics of the manipulators and object together with geometric constraint is formulated by Lagrange-Euler's equation. And the problems of controlling both the grasping force and the rotation angle of the grasped object under the constraints are analyzed. The effect of geometric constraints and a method of computer simulation for overall system is verified. Finally, it is illustrated that even in case of there exists a sensory feedback from sensing data of the rotational angle of the object to command inputs control of joint and this feedback connection from sensing data to control grasping of machinery parts.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.78-86
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• 1998

This paper presents a numerical method of the minimum-time trajectory planning for a robot manipulator amid obstacles. Each joint displacement is represented by the linear combination of the finite-term quintic B-splines which are the known functions of the path parameter. The time is represented by the linear function of the same path parameter. Since the geometric path is not fixed and the time is linear to the path parameter, the coefficients of the splines and the time-scale factor span a finite-dimensional vector space, a point in which uniquely represents the manipulator motion. The displacement, the velocity and the acceleration conditions at the starting and the goal positions are transformed into the linear equality constraints on the coefficients of the splines, which reduce the dimension of the vector space. The optimization is performed in the reduced vector space using nonlinear programming. The total moving time is the main performance index which should be minimized. The constraints on the actuator forces and that of the obstacle-avoidance, together with sufficiently large weighting coefficients, are included in the augmented performance index. In the numerical implementation, the minimum-time motion is obtained for a planar 3-1ink manipulator amid several rectangular obstacles without simplifying any dynamic or geometric models.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.11
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• pp.5253-5270
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• 2016

With device-to-device (D2D) communications, an inactive user terminal can be utilized as a relay node to support multi-hop communication so that connective experience of the cell-edge user as well as the capacity of the whole system can be significantly improved. In this paper, we investigate the spectrum sharing for a cooperative relay assisted D2D communication underlying a cellular network. We formulate a joint relay selection and channel assignment problem to maximize the throughput of the system while guaranteeing the quality of service (QoS) requirements of cellular users (CUs) and D2D users (DUs). By exploiting coalition formation game theory, we propose two algorithms to solve the problem. The first algorithm is designed based on merge and split rules while the second one is developed based on single user's movement. Both of them are proved to be stable and convergent. Simulation results are presented to show the effectiveness of the proposed algorithms.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.96-111
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• 1995

A bellows is a component installed in the automobile exhaust system to reduce the impact from an engine. It's stiffness has a great influence on the natural frequency of the system. Therefore, it must be designed to keep the specified stiffness that requires in the system. This study present the finite element analysis of U-typed bellows using a curved conical frustum element and the shape optimal design with specified stiffness. The finite element analysis is verified by comparing with the experimental results. In the shape optimal design, the weight is considered as the cost function. The specified stiffness from the system design is transformed to equality constraints. The formulation has inequality constraints imposed on the fatigue limit, the natural frequencies, the buckling load and the manufacturing conditions. A procedure for shape optimization adopts a thickness, a corrugation radius, and a length of annular plate as optimal design variables. The external loading conditions include the axial and lateral loads with a boundary condition fixed at an end of the bellows. The recursive quadratic programming algorithm is selected to solve the problem. The result are compared with the existing bellows, and the characteristics of the bellows is investigated through the optimal design process. The optimized shape of the bellows are expected to give quite a good guideline to the practical design.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.3
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• pp.70-78
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• 1989

In the control of the robot system using the variable structure control(VSC) method, up to these days the advantage of the VSC method has not been applied effectively because the parameters are selected arbitrarily by the existence condition of sliding mode without a precise analysis about the VSC parameters. This paper reveals the relation between dynamic constraints and the VSC parameters of robot system, and analyzes the effect on the trajectory of the joint angle and the hand when the analytical result of the relation is applied to the robot system control. The result of the analysis in this paper is applied effectively to the path tracking control and the trajectory planning using the VSC method.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.43.5-44
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• 2021

In the local Universe, the gravitational effects of mass density fluctuations exert perturbations on galaxies' redshifts on top of Hubble's Law, called 'peculiar velocities'. These peculiar velocities provide an excellent way to test the cosmological model in the nearby Universe. In this talk, we present new cosmological constraints using peculiar velocities measured with the 2MASS Tully-Fisher survey (2MTF), 6dFGS peculiar-velocity survey (6dFGSv), the Cosmicflows-3 and Cosmicflows-4TF compilation. Firstly, the dipole and the quadrupole of the peculiar velocity field, commonly named 'bulk flow' and 'shear' respectively, enable us to test whether our cosmological model accurately describes the motion of galaxies in the nearby Universe. We develop and use a new estimators that accurately preserves the error distribution of the measurements to measure these moments. In all cases, our results are consistent with the predictions of the Λ cold dark matter model. Additionally, measurements of the growth rate of structure, fσ8 in the low-redshift Universe allow us to test different gravitational models. We developed a new estimator of the "momentum" (density weighted peculiar velocity) power spectrum and use joint measurements of the galaxy density and momentum power spectra to place new constraints on the growth rate of structure from the combined 2MTF and 6dFGSv data. We recover a constraint of fσ8=0.404+0.082-0.081 at an effective redshift zeff=0.03. This measurement is also fully consistent with the expectations of General Relativity and the Λ Cold Dark Matter cosmological model.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.3 s.303
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• pp.1-10
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• 2005

This paper proposes a novel fault-tolerant gait planning of a hexapod robot considering kinematic constraints. The failure concerned in this paper is a locked joint failure for which a joint in a leg cannot move and is locked in place. It is shown that the conventional fault-tolerant gait of a hexapod robot for forward walking on even terrain may be fallen into deadlock, depending on the configuration of the failed leg. For coping with such deadlock situation, a novel fault-tolerant gait planning is proposed. It can avoid deadlock by adjusting the position of the foot trajectory, and has the same leg sequence and stride length as those of the conventional fault-tolerant gait. To demonstrate the superiority of the proposed scheme, a case study is presented in which a hexapod robot, having walked over even terrain before a locked joint failure, could avoid deadlock and continue its walking by the proposed fault-tolerant gait planning.