• The Journal of Korea Robotics Society
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• v.11 no.4
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• pp.217-225
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• 2016

Dynamic Positioning (DP) is used to automatically maintain the position and heading of a floating structure subjected to environmental disturbances. A DP control system is composed of a motion controller to compute the desired force and moment and a thrust allocator to distribute the computed force and moment to multiple thrusters considering mechanical and operational constraints. Among various thruster configurations, azimuth thrusters or propeller/rudder pairs tend to make the allocation problem difficult to solve, because these types of propulsion systems include nonlinear constraints. In this paper, a dynamic positioning strategy for a twin-thruster ship that is propelled by two azimuthing thrusters is addressed, and a thrust allocation method which does not require a numerical optimization solver is proposed. The applicability of the proposed method is demonstrated with an experiment using an autonomous boat.

• Journal of the Korea Society for Simulation
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• v.20 no.4
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• pp.127-138
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• 2011

Certified Missile Round Concepts that is one-shot device use the periodic inspection policy to improve the continuously deteriorated reliability. In this paper, we suggest dormant reliability prediction model by simulation with real operational environment. The suggested prediction model is based on optimal inspection period decision model and additionally considers various constraints; moving, inspection or repair service time. The simulation results show the constraints affect dormant reliability and missile availability. Lastly, we suggest building up a depot to resolve the above problems by the suggested simulation model.

• Journal of Korean Institute of Industrial Engineers
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• v.35 no.1
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• pp.73-86
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• 2009

This paper discusses a method of determining the optimal design of a block. A horizontal layout of blocks is assumed in which transfer points are located at a side of the block. Each block has several transfer points (TPs) each of which is assigned to a group of adjacent bays and located at the center of the assigned group. The goal is to find the optimal size of a block and the optimal number of TPs while minimizing the total cost consisting of the fixed and operational cost of yard cranes (YCs), the operational cost of internal trucks, and the installation cost of TPs. Constraints on the maximum expected system time of trucks are imposed for the optimization. Formulas for estimating handling operation cycle times of a YC are derived analytically. Numerical experiments are conducted to illustrate optimal block designs for a given set of data.

• Aerospace Engineering and Technology
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• v.6 no.1
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• pp.92-96
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• 2007

The conventional commands & telemetry system of Korean low-earth orbiting satellites has certain limitations in accommodating various missions. As the payload becomes complex, it requires very complicated operational concepts in terms of commands and telemetry. With the current design, commands and telemetry formats have to be rebuilt whenever new payloads or operation concepts are involved, and many constraints in operation shall be produced due to the lacks of its flexibility. In this paper, a new strategy for commands & telemetry development partially derived from PUS (Packet Utilization Standard) of European Space Agency, which provides enhanced features for the accommodation of payloads & operational requirements, is presented.

• Korean System Dynamics Review
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• v.11 no.2
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• pp.119-138
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• 2010

This study introduces the system dynamics model that simulate total operational availability when 10 equipments made of 3 major components are serviced under the constrains of the maintenance capacity level and the number of spare parts. This simulation is designed on the base of reliability engineering concept so failures of components happens with the rule of engineering factors like the mean time between failure(MTBF) of component and the next failure time of one component is effected by the conditions of other components. We analysed availability of 10 equipments under 121 constrains and executed multiple regression analysis with the simulation result. The analysis provide the managerial insight in the service fields with operation many equipments.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.5
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• pp.882-889
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• 2010

This paper presents a method of finding the optimal operating point minimizing a given objective function with 3 phase power flow equations and operational constraints, called 3 phase optimal power flow (3POPF). 3 phase optimal power flow can provide operation and control strategies for the distribution systems with distributed generation assets, which might be frequently in unbalanced conditions assuming that high penetration rate of renewable energy sources in the systems. As the solution technique for 3POPF, this paper adopts a simulation-based method of particle swarm optimization (PSO). In the PSO based 3POPF, a utility function needs to be defined for evaluation of the degree in operational improvement of each particle's current position. To evaluate the utility function, in this paper, NR-based 3 phase power flow algorithm was developed which can deal with looped distributed generation systems. In this paper, illustrative examples with a 5-bus and a modified IEEE 37-bus test systems are given.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.4
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• pp.334-345
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• 1997

Reliability-based design approaches are needed for cylindrical shell structure whose design and operational experiences are few and which are subjected to external loads of random loads. In designing new type of structure, it is very difficult to evaluate the safety factors due to lack of previous design data and operational experience. To solve the above mentioned problem, much attention is being focussed on rational reliability based design approaches. This paper deals with weight-optional reliability-based design of cylindrical shell structure subjected to structural reliability constraints taking into account of the effect of local buckling and interactive behavior between local and global buckling. Present mentioned is compared with the exiting optional design method based only on safety factors. Numerical simulation reveals that the present method leads to lighter structure (4% reduction in weight compared to the existing optimal design) with the same reliability index. For larger structures with more number of structural members and possible failure modes, the present W0RBD procedure will be an efficient tool in designing cost-effective rationalized economic design.

• Journal of the Korean Society for Railway
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• v.9 no.1 s.32
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• pp.50-56
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• 2006

This paper presents a mathematical model of the long-term track tamping scheduling problem in the Korean highspeed railway system. The presented model encompasses various operational field constraints, moreover improves a state-of-the-art model in extending the feasible space. We show the model is sized up to intractable scale, then propose another approximation model that is possible to handle with the present computer system and commercial optimization package, directly. The aggregated index, lot, is selected, considering the resolution of the planning horizon as well as scheduling purpose. Lastly, this paper presents two test results for the approximation model. The results expose the approximation model to quite promising in deploying it into an operational software program for the long-term track tamping scheduling problem.

• Management & Information Systems Review
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• v.15
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• pp.37-50
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• 2004

Internet commerce has the potential to propel a company to 'break out' of existing strategic constraints and radically alter business processes, strengthen customer and supplier ties, and open up new markets. Therefore, many firms have rushed into internet commerce to conduct business more efficiently, create new business opportunities, and generate business value. The purpose of this study is to examine the relationship between the sales promotional functionality of internet shopping mall and its performance considering the characteristics of internet shopping mall's operational form as moderating variables. The results showed that the price functionality affects positive effects on the performance of shopping mall, and the characteristics of operational form can be considered as a significant moderating variables between the sales promotional functionality of shopping mall and the performance.

• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.143-153
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• 1996

Shutdown of boiler plants is a dynamic, complicated, and hazardous operation. Operational error is a major contributor to danserous situations during boiler plant shutdowns. It is important to develop an automatic system which synthesizes operating procedures to safely go from normal operation to complete shutdown. Knowledge representation for automatic shutdown of boiler plants makes use of the hierarchical, rule-based framework for heuristic knowledge, the semantic network, frame for process topology, and AI techniques such as rule matching, forward chaining, backward chaining, and searching. This knowledge representation and modeling account for the operational states, primitive operation devices, effects of their application, and planning methodology. Also, this is designed to automatically formulate subgoals, search for positive operation devices, formulate constraints, and synthesize shutdown procedures in boiler plants.