• Journal of the Korean Society of Safety
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• v.32 no.3
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• pp.34-40
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• 2017

The catastrophic collapse of the in-boiler scaffolding system in the two thermal power plants occurred in March and April 2012. After site investigation and document review, it was found that the specialized scaffolding system was imported for overhaul & maintenance and that the system did not get the safety certification at the import. In this regard, this study developed & proposed an access platform and a support for the vertical tube section of the super heat as well as a variable-length platform for the horizontal tube section, satisfying the domestic certification standards. The access platform was developed to be easy to handle by the worker with a weight of about 0.069 kN, which could reduce the risk of falling accidents and workers' musculoskeletal diseases. For the variable-length platform, it is possible to cope with various changes in length between the horizontal tubes associated with the increase of rigidity in the overlapping and the elimination of the protrusion.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.2
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• pp.138-144
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• 2006

Kinematic and dynamic characteristics of a Stewart platform based parallel manipulators are fixed once they are constructed. Thus parallel manipulators with various configurations are required to meet a variety of applications. In this research a parallel manipulator with variable platform (PMVP) has been developed, in which the length of the arm linking the platform center to the platform-leg contact point can be varied by an actuator. The workspace of the PMVP is larger than that of a traditional Stewart platform and especially the range in which the maximum orientation angles can be maintained is significantly expanded. Furthermore, the characteristics of force and moment transmission between the legs and platform can be adjusted to meet the requirements of various tasks. Kinematic and dynamics analysis was performed to verify the usefulness of the PMVP and the actual hardware was built to demonstrate the feasibility.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.9
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• pp.2854-2865
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• 1996

The concept of variable-geometry truss structure(VGTS) is introduced as a class of actively controlled adaptive structure. VGTS can purposefully vary its geometric configurations by changing the lengths of some members of the structure. General kinematics and inverse kinematics of a statically determinate VGTS(variable geometry truss structure) are studied. The solution technique is based on the Jacobian matrix obtained via joint equilibrium equations. Pseudoinverse control method is applied to resolve the redundancy of a large VGTS. two types of actuator layout of octahedral type VGTS, VG truss and Stewart platform, are compared. Introducing the concept of performance index, Stewart platform based layout was found to has less consumption energy and manipulation time. A functional VGTS model with 3 octahedral modules is designed and manufactured for the labaratory demonstration. Six vertically located length-variable members are used to create general 6 d.o.f. motions.

• Geomechanics and Engineering
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• v.14 no.1
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• pp.91-98
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• 2018

Length of a vehicle is an important variation to generate different variants of an automotive platform. This parameter is usually adjusted by embedding dimensional flexibility into different components of the Body in White (BIW) including the floor pan. Due to future uncertainties, it is not necessarily possible to define certain values of wheelbase for the future products of a platform. This work is performed to add flexibility into the design process of a length-variable floor pan. By means of this analysis, the cost and time consuming process of optimization is not necessary to be performed for designing the different variants of a product family. Stiffness and mass of the floor pan are two important functional requirements of this component which directly affect the occupant comfort, dynamic characteristics, fuel economy and environmental protection of the vehicle. A combination of Genetic algorithm, GMDH-type of artificial neural networks and TOPSIS methods is used to optimally design the floor pan associated with arbitrary length of the variant in the defined system range. The correlation between the optimal results shows that for a constant mass of the floor pan, the first natural frequency decreases by increasing the length of this component.

• Wind and Structures
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• v.20 no.6
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• pp.751-761
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• 2015

A multi-platform offshore wind farm is receiving the worldwide attention for the sake of maximizing the wind power capacity and the dynamic stability at sea. But, its wind power efficiency is inherently affected by the interference of wake disturbed by the rotating blades, so its layout should be appropriately designed to minimize such wake interference. In this context, the purpose of this paper is to introduce a layout optimization for multi-platform offshore wind farm consisted of 2.5MW spar-type floating wind turbines. The layout is characterized by the arrangement type of wind turbines, the spacing between wind turbines and the orientation of wind farm to the wind direction, but the current study is concerned with the spacing for a square-type wind farm oriented with the specific angle. The design variable and the objective function are defined by the platform length and the total material volume of the wind farm. The maximum torque loss and overlapping section area are taken as the constraints, and their meta-models expressed in terms of the design variable are approximated using the existing experimental data and the geometry interpretation of wake flow.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.2
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• pp.156-163
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• 2002

This paper presents a new formulation to simplify the three resulting constraint equations of the direct kinematics of the 3-6 (Stewart-Gough) Platform. The conventional direct kinematics of the 3-6 Platform has been formulated through complicated steps with trigonometric functions in three angle variables and thus results in the computational burden. In order to reduce the formulation complexity, we replace an angle variable into a length one and express three connecting joints on the moving platform in the same frame. The proposed formulation yields considerable abbreviation of the number of the calculation terms involved in the direct kinematics. It is verified through a series of simulation results.

• The Journal of Economics, Marketing and Management
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• v.2 no.1
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• pp.1-17
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• 2014

In today's highly competitive and fast changing business environment, key account management-a supplier company initiated relationship marketing approach targeted at the most important customers to solve their complex requirements with special treatment that eventually ensures both parties' financial and nonfinancial objectives- has regarded as a strategic weapon of many companies' sales efforts to manage their strategically important customers. On the basis of the existing studies, this research introduces a theoretical model highlighting the hypothetical relationship between key account management performance and repeat order. In addition, moderating effect of length of relationship on the relationship between key account management performance and repeat order is also introduced. We theorize the conditions under which key account management performance influences key customer repeat order behavior as well as the influence of moderating variable of length of relationship on key account management performance-repeat order relationship. Theoretical and managerial implications are provided along with suggestions to isolate a platform for future empirical research.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.5
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• pp.458-465
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• 2011

UAV-UGV teaming concept has been proposed that can compensate for weak points of each platform by providing carrying, launching, recovery and recharging capability for the VTOL-UAV through the host UGV. The teaming concept can expand the observation envelop of the UGV and extend the operational capability of the UAV through mechanical combination of each system. The spherical-shaped coaxial rotorcraft UAV is suggested to provide flexible and precise interface between two systems. Hybrid navigation solution that included vision-based target tracking method for precision landing is investigated and its experimental study is performed. Feasibility study on length-variable rotor to provide the compact configuration of the loaded rotorcraft platform is also described.

• The Journal of Korean Physical Therapy
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• v.14 no.2
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• pp.74-85
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• 2002

The purpose of this study was to investigate the effect of static balance performance on gait in elderly. Subjects were twenty four members living in Gwangju(12males, 12females), between 65 and 81 years of age. The Force platform was used to measured static balance performance and gait analyzed the 3-D Motion Analysis The results of this study were as follow ; 1. The postural sway showed, The mean value of toe-heel was $1.41\pm0.51cm$ and left-right was $063\pm0.20cm$. In gait analysis, the mean value of each variable were swing phase $40.5\pm9.65\%$, stance phase $59.5\pm9.65\%$, stride length 0.79m, cadence $0.83\pm0.44step/sec$, velocity $0.57\pm0.32m/sec$, Knee up $34.7\pm31.0^{\circ}$, Knee down $-53.6\pm40.14^{\circ}$. Ankle up $12.14\pm13.94^{\circ}$, Ankle down $-16.8\pm25.0^{\circ}$ showed. 2. The correlation matrix between L-R sway and Toe-heel sway and gait variables was not showed. 3. In multiple regression test, there were no related variable.

• Bulletin of the Korean Mathematical Society
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• v.46 no.4
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• pp.673-689
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• 2009

We analyze $MAP_1,\;MAP_2$/G/1 finite queues with service scheduling function dependent upon queue lengths. The customers are classified into two types. The arrivals of customers are assumed to be the Markovian Arrival Processes (MAPs). The service order of customers in each buffer is determined by a service scheduling function dependent upon queue lengths. Methods of embedded Markov chain and supplementary variable give us information for queue length of two buffers. Finally, the performance measures such as loss probability and mean waiting time are derived. Some numerical examples also are given with applications in telecommunication networks.